U.S. patent application number 10/868967 was filed with the patent office on 2004-12-23 for particulate wood preservative and method for producing same.
Invention is credited to Hodge, Robert L., Richardson, H. Wayne.
Application Number | 20040258768 10/868967 |
Document ID | / |
Family ID | 34084833 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040258768 |
Kind Code |
A1 |
Richardson, H. Wayne ; et
al. |
December 23, 2004 |
Particulate wood preservative and method for producing same
Abstract
A wood preservative includes injectable particles comprising one
or more sparingly soluble copper salts. The copper-based particles
are sufficiently insoluble so as to not be easily removed by
leaching but are sufficiently soluble to exhibit toxicity to
primary organisms primarily responsible for the decay of the wood.
Exemplary particles contain for example copper hydroxide, basic
copper carbonate, copper carbonate, basic copper sulfates including
particularly tribasic copper sulfate, basic copper nitrates, copper
oxychlorides, copper borates, basic copper borates, and mixtures
thereof. The particles typically have a size distribution in which
at least 50% of particles have a diameter smaller than 0.25 .mu.m,
0.2 .mu.m, or 0.15 .mu.m. At least about 20% and even more than 75%
of the weight of the particles may be composed of the substantially
crystalline copper salt. Wood or a wood product may be impregnated
with copper-based particles of the invention.
Inventors: |
Richardson, H. Wayne;
(Sumter, SC) ; Hodge, Robert L.; (Sumter,
SC) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Family ID: |
34084833 |
Appl. No.: |
10/868967 |
Filed: |
June 17, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60478822 |
Jun 17, 2003 |
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60478827 |
Jun 17, 2003 |
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60478825 |
Jun 17, 2003 |
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60478820 |
Jun 17, 2003 |
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60571535 |
May 17, 2004 |
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Current U.S.
Class: |
424/630 ;
106/15.05; 106/18.3; 106/18.31 |
Current CPC
Class: |
B27K 3/52 20130101; B27K
3/007 20130101; A01N 25/26 20130101; A01N 59/20 20130101; A01N
59/20 20130101; A01N 25/12 20130101; B27K 3/32 20130101; A01N 25/34
20130101; A01N 25/04 20130101; A01N 25/00 20130101; A01N 2300/00
20130101; C09D 15/00 20130101; A01N 59/20 20130101; B27K 3/22
20130101; B27K 3/005 20130101 |
Class at
Publication: |
424/630 ;
106/015.05; 106/018.3; 106/018.31 |
International
Class: |
C09D 005/14; C09D
005/16; C09D 005/18; A01N 059/20 |
Claims
1. A wood preservative composition comprising: a plurality of first
particulates comprising at least 20% by weight of a sparingly
soluble copper salt, wherein greater than 98% by weight of the
particulates have a diameter less than 0.5 microns as determined by
the settling velocity of the particle in water, and at least 50%
have a diameter greater than 40 nanometers.
2. The wood preservative of claim 1, wherein greater than 98% by
weight of the particulates have a diameter less than about 0.3
microns, and less than 0.5% by weight have a diameter greater than
1.5 microns.
3. The wood preservative of claim 1, wherein greater than 98% by
weight of the particulates have a diameter less than about 0.2
microns and greater than 80% by weight of the particulates have a
diameter greater than 0.01 microns.
4. The wood preservative of claim 1, wherein the particulates
comprise at least 50% by weight of a sparingly soluble copper salt,
and at least 50% of the particulates have a diameter greater than
80 nanometers.
5. The wood preservative of claim 1, wherein the preservative is
substantially free of particulates having a diameter less than 5
nanometers.
6. The wood preservative of claim 1, wherein at least 99% of the
particulates, and aggregates of particulates, have a diameter less
than 0.35 microns.
7. The wood preservative of claim 1, wherein there is less than 10%
amines based on the weight of the particulates.
8. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper(II) borate.
9. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises basic copper carbonate.
10. The wood preservative claim 1, wherein the sparingly soluble
copper salt comprises tribasic copper sulfate.
11. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper hydroxide.
12. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper oxychloride.
13. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises alkaline copper nitrate.
14. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper ferricyanide, copper ferricyanate, or
mixture thereof.
15. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper fluorosilicate.
16. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper thiocyanate.
17. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper diphosphate.
18. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper borate, basic copper borate, or
mixture thereof.
19. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper carbonate, copper boride, copper(I)
carbonate, or copper phosphate.
20. The wood preservative of claim 1, wherein at least a portion of
the particulates comprise Cu.sub.2O.
21. The wood preservative of claim 1, wherein the sparingly soluble
copper salt is substantially crystalline.
22. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper/magnesium hydroxide, and wherein there
are between 6 parts and 20 parts magnesium per 100 parts
copper.
23. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper/magnesium/zinc hydroxide, and wherein
there are between 6 parts and 20 parts total of magnesium and zinc
per 100 parts copper.
24. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises basic copper/magnesium carbonate, and wherein
there are between 6 parts and 20 parts magnesium per 100 parts
copper.
25. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises basic copper/magnesium/zinc carbonate, and
wherein there are between 6 parts and 20 parts total of magnesium
and zinc per 100 parts copper.
26. The wood preservative of claim 1, further comprising a
plurality of second particulates comprising at least 20% by weight
of a sparingly soluble zinc salt, wherein greater than 98% by
weight of the second particulates have a diameter less than 0.5
microns as determined by the settling velocity of the particle in
water.
27. The wood preservative of claim 26, wherein the sparingly
soluble zinc salt comprises zinc borate, basic zinc borate, or
mixture thereof.
28. The wood preservative of claim 1, further comprising a
plurality of second particulates comprising at least 20% by weight
of a metallic copper, metallic zinc, or mixture thereof, wherein
greater than 98% by weight of the second particulates have a
diameter less than 0.3 microns as determined by the settling
velocity of the particle in water.
29. The wood preservative of claim I, further comprising a
plurality of second particulates comprising at least 20% by weight
of a sparingly soluble tin salt, wherein greater than 98% by weight
of the second particulates have a diameter less than 0.5 microns as
determined by the settling velocity of the particle in water.
30. The wood preservative of claim 1, wherein at least a portion of
the particulates comprise a copper phosphate coating thereon.
31. The wood preservative of claim 1, further comprising at least
one organic biocide.
32. The wood preservative of claim 31, wherein at least a portion
of the organic biocide is coated on the particulates.
33. The wood preservative of claim 1, wherein at least a portion of
the particulates comprise an organic coating.
34. The wood preservative of claim 1, wherein at least a portion of
the particulates comprise a dispersing agent attached thereon.
35. The wood preservative of claim 1, wherein the first
particulates comprise at least 50% by weight of a sparingly soluble
copper salt.
36. The wood preservative of claim 1, wherein at least a portion of
the particulates comprise between 0.001% to 0.5% silver, based on
the weight of the particulates.
37. The wood preservative of claim 1, wherein at least a portion of
the first particulates comprise a coating of copper
8-quinolinolate.
38. The wood preservative of claim 1, wherein the first
particulates comprise at least 50% of a substantially crystalline
sparingly soluble copper salt.
39. The wood preservative of claim 1, further comprising a
plurality of second particulates comprising a carrier having an
organic biocide associated associated thereon, wherein greater than
98% by weight of the second particulates have a diameter less than
0.3 microns as determined by the settling velocity of the particle
in water.
40. The wood preservative of claim 1, wherein at least a portion of
the first particulates comprise an organic coating and an organic
biocide disposed thereon.
41. The wood preservative of claim 1, wherein the preservative
further comprises an anionic surfactant.
42. The wood preservative of claim 1, wherein the first
particulates comprise less than 30 ppm lead based on the weight of
the particulates.
43. The wood preservative of claim 1, further comprising a
plurality of second particulates comprising a copper oxide, wherein
greater than 98% by weight of the second particulates have a
diameter less than 0.3 microns as determined by the settling
velocity of the particle in water.
44. The wood preservative of claim 1, further comprising a
plurality of second particulates comprising a copper oxide, wherein
greater than 98% by weight of the second particulates have a
diameter less than 0.3 microns as determined by the settling
velocity of the particle in water.
45. The wood preservative of claim 1, wherein the first
particulates comprise less than 35% by weight polymers.
46. The wood preservative of claim 1, wherein the first
particulates comprise less than 15% by weight polymers.
47. The wood preservative of claim 1, wherein the first
particulates comprise polymers, wherein the weight ratio of
polymers to copper is between 1:1 and about 1:10.
48. The wood preservative of claim 1, wherein the at least 30% by
weight of the first particulates have a diameter between 0.07
microns and 0.5 microns.
49. The wood preservative of claim 1, wherein the at least 30% by
weight of the first particulates have a diameter between 0.07
microns and 0.5 microns.
50. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises copper borate and at least one of copper
hydroxide and basic copper carbonate.
51. The wood preservative of claim 1, wherein the sparingly soluble
copper salt comprises a sparingly soluble copper/zinc salt.
52. The wood preservative of claim 1, further comprising between
about 0.1 to about 1 mole phosphonate-based scale inhibitors per kg
of particulates.
53. The wood preservative of claim 52, wherein the scale inhibitor
comprises hydroxyethylidene diphosphonic acid.
54. The wood preservative of claim 1, further comprising a wetting
agent.
55. The wood preservative of claim 1, further comprising a
moldicide.
56. A method of manufacturing the wood preservative composition of
claim 1, comprising the steps of: 1) providing particulates
comprising sparingly soluble copper salts, wherein at least 2% by
weight of the particulates have a diameter greater than 1 micron;
and 2) wet milling the particulates with a milling medium
comprising zirconium and having a diameter between about 0.1 mm and
about 1 mm.
57. The method of claim 56 wherein the milling media has a diameter
between about 0.3 mm and 0.7 mm.
58. The method of claim 56 wherein a wetting fluid or a rinsing
fluid used in wet milling comprises between 0.1% phosphate to 6%
phosphate.
59. The method of claim 56 wherein the step of providing
particulates comprising sparingly soluble copper salts comprises:
providing a an aqueous copper-alkanolamine complex solution; adding
acid to adjust the pH to between about 4 and about 7.5; and
recovering the copper hydroxide particulates that form.
60. The method of claim 59 wherein the acid comprises phosphoric
acid.
61. The method of claim 56 wherein the step of providing
particulates comprising sparingly soluble copper salts comprises:
providing an aqueous solution of copper ions and magnesium ions,
wherein the solution comprises about 0.2 to about 3.5 parts by
weight magnesium per 22.5 parts by weight copper; adding a base to
reduce the pH of the composition to above about 7; and recovering
the copper-containing particulates that form.
62. The method of claim 56 wherein the step of providing
particulates comprising sparingly soluble copper salts comprises:
providing an aqueous solution of copper ions, zinc ions, and
magnesium ions, wherein the solution comprises about 0.1 to about 3
parts by weight zinc and 0.25 to about 5 parts by weight magnesium
per 22.5 parts by weight copper; adding a base to reduce the pH of
the composition to above about 7; and recovering the
copper-containing particulates that form.
63. The wood preservative of claim 1, wherein the first
particulates are suspended in a aqueous carrier, and wherein the
preservative further comprises a dispersing agent, an
anti-aggregation agent, a wetting agent, or any combination
thereof.
64. The wood preservative of claim 63, wherein the aqueous carrier
comprises less than 1% by weight alkanolamines and less than 1% by
weight ammonia.
65. The wood preservative of claim 63, wherein the aqueous carrier
comprises less than 0.1% by weight alkanolamines and less than 0.1%
by weight amines, based on the weight of the suspension.
66. The wood preservative of claim 63, wherein the aqueous carrier
pH is between 7.5 and 9.5, and less than about 0.5% by weight of
the particulates have an average diameter greater than 1
micron.
67. The wood preservative of claim 63, wherein the aqueous carrier
comprises between about 5 ppm and about 500 ppm soluble
phosphate.
68. The wood preservative of claim 63, wherein at least 60% by
weight of the first particulates in the slurry are
mono-disbursed.
69. The wood preservative of claim 63, further comprising a
water-insoluble organic biocide, wherein a portion of the biocide
adheres to the first particulates.
70. The wood preservative of claim 63, further comprising a
corrosion inhibitor.
71. The wood preservative of claim 63, further comprising a pH
buffer.
72. The wood preservative of claim 63, wherein the slurry comprises
between about 15% and 40% by weight of first particulates.
73. The wood preservative of claim 1, wherein the preservative is a
dry mix further comprising a wetting agent and a dispersing
agent.
74. The wood preservative of claim 73, further comprising a
plurality of second particulates comprising a carrier having an
organic biocide associated thereon, wherein greater than 98% by
weight of the second particulates have a diameter less than 0.3
microns as determined by the settling velocity of the particle in
water.
75. The wood preservative of claim 73, further comprising a
granulating agent, wherein the preservative is a granular material
that is dispersible in water.
76. The wood preservative of claim 75, further comprising an
organic biocide.
77. The wood preservative of claim 75, comprising about 50% to
about 70% of sparingly soluble copper salts; about 10% to about 25%
of a dispersing agent; about 1 to about 8% of a wetting agent; and
about 10% to about 30% filler and/or moisture.
78. The wood preservative of claim 75, comprising about 40% to
about 80% by weight of a sparingly soluble copper salt, about 5% to
about 30% of a dispersing agent, about 1% to about 10% of a wetting
agent, , and about 5% to about 30% of a inert particulate
filler.
79. The wood preservative of claim 78, wherein the inert
particulate filler further comprises an organic biocide associated
therewith.
80. The wood preservative of claim 75, further comprising between
about 0.1 to about 1 mole phosphonate-based scale inhibitors per kg
of granular material.
81. The wood preservative of claim 80, wherein the scale inhibitor
comprises hydroxyethylidene diphosphonic acid.
82. The wood preservative of claim 75, wherein the granular
material comprises A) about 30% to about 70% by weight of slightly
soluble copper salt; B) about 10% to about 35% by weight of at
least one dispersing agent; C) between about 2.5% to about 20% by
weight of at least one wetting agent; D) between about 5% to about
25% by weight of at least one diluent, granulating agent, and/or
inert particulate carrier; and E) between about 0.05% to about 7.5%
by weight of at least one antifoam agent.
83. A method of preserving wood comprising: providing an aqueous
suspension of the wood preservative of claim 1; providing a wood
having open porosity therein; and injecting the suspension into
wood.
84. A preserved wood prepared by the method of claim 83.
85. A wood preservative composition comprising: a plurality of
first particulates comprising at least 30% by weight of a sparingly
soluble substantially crystalline copper salt, wherein greater than
98% by weight of the particulates have a diameter less than 0.5
microns as determined by the settling velocity of the particle in
water, and wherein the average particle diameter is between about
50 nanometers and about 250 nanometers.
86. A wood preservative composition comprising: a plurality of
particulates comprising at least 20% by weight of a sparingly
soluble zinc salt, wherein greater than 98% by weight of the
particulates have a diameter less than 0.5 microns as determined by
the settling velocity of the particle in water, and at least 50%
have a diameter greater than 40 nanometers.
87. The wood preservative of claim 86, wherein the sparingly
soluble copper salt comprises zinc carbonate; zinc chloride; zinc
cyanide; zinc diphosphate; zinc fluoride; zinc fluoride.times.4
water; zinc hydroxide; zinc oxide; zinc phosphate; or zinc
sulfate.
88. A method for preserving wood comprising: impregnating wood with
a wood preservative comprising a liquid carrier and one or more
injectable particulates comprising a sparingly soluble copper salt,
sparingly soluble zinc salt, or mixtures thereof.
89. The method of claim 88, wherein the sparingly soluble copper
salt is a substantially crystalline copper salt.
90. The method of claim 88, wherein one or more injectable
particulates comprise one or more organic biocides coated or
absorbed thereon.
91. The method of claim 88, wherein the sparingly soluble copper
salt comprises copper hydroxides; copper carbonates, basic copper
carbonates; basic copper sulfates; basic copper nitrates; copper
oxychlorides; copper borates, basic copper borates, and mixtures
thereof.
92. Wood impregnated with the method of claim 88.
Description
[0001] This application claims priority to the following U.S.
Provisional applications: Nos. 60/478,822, 60/478,827, 60/478,825,
and 60/478,820, all of which were filed on Jun. 17, 2003, and also
to U.S. Provisional application No. 60/571,535 filed on May 17,
2004, each of which is incorporated herein by reference.
[0002] The present invention relates to wood preservatives,
particularly wood preservatives comprising particles including one
or more copper compounds. More particularly, the invention relates
to a wood preservative comprising injectable particles of sparingly
soluble copper salts, as well as methods to prepare the wood
preservative, and methods of preserving wood using the wood
preservatives.
[0003] The production of wood which has been treated to inhibit
biological decomposition is well known. Decay is caused by fungi
that feed on cellulose or lignin of wood. Such organisms causing
wood decomposition include: basidiomycetes such as Gloeophyllum
trabeum (brown rot), Trametes versicolor (white rot), Serpula
lacrymans (dry rot) and Coniophora puteana. Soft rot attacks the
surface of almost all hard and softwoods, and it favors wet
conditions. Most of these fungi require food and moisture, e.g.,
moisture contents in wood of greater than 20% are conducive to
fungal growth. Dry rot is tenacious, as it can grow in dry wood.
Insects are also major causes of wood deterioration. Exemplary
organisms causing wood decomposition include coleopterans such as
Anobium punctatum (furniture beetle), Hylotrupes bajulus (house
longhorn) and Xestobium rufovillorum (death watch beetle);
hyrnenopterans such as termites and carpenter ants; and also by
marine borers and/or wasps. Finally, termites are ubiquitous, and
termite damage is estimated in the United States alone to be about
$2 billion per year
[0004] The production of wood based composite products has
increased dramatically in recent years. Oriented strandboard (OSB)
production exceeded that of plywood in 2000. The use of medium
density fiberboard and hardboard panel products likewise has
increased dramatically over the last couple of decades. However,
these products are typically used in interior applications where
attack from insects or decay fungi is limited, because it has been
found that these products are particularly susceptible to attack by
biological agents such as decay fungi and termites.
[0005] Preservatives are used to treat wood to resist insect attack
and decay. The commercially used preservatives are separated into
three basic categories, based primarily on the mode of
application--waterborne, creosote, and oil borne preservatives.
Waterborne preservatives include chromated copper arsenate (CCA),
ammoniacal copper quat (ACQ, which is believed to be
Copper-MEA-Carbonate and a quaternary amine), ammoniacal copper
zinc arsenate (ACZA), and ammoniacal copper arsenate (ACA). Wood
treated with these chemicals sometimes turns green or grey-green
because of a chemical reaction between copper in the preservative
and the sun's ultraviolet rays. The preservatives leach into the
soil over time, especially those made without chromium, when
exposed to weather. Creosote does not easily leach into soil, and
it is not corrosive to metals, but it can not be painted and it
leaves a dark, oily surface that has a strong odor. Oil borne
preservatives are made of certain compounds dissolved in light
petroleum oils, including pentachlorophenol (commonly known as
"penta"), copper naphthenate, and copper-8-quinolinolate. These
preservatives leave a surface that often is non-paintable, and the
surface of the wood can be dark and unnaturally colored.
[0006] Modern organic biocides are considered to be relatively
environmentally benign and not expected to pose the problems
associated with CCA-treated lumber. Biocides such as tebuconazole
are quite soluble in common organic solvents, while others such as
chlorothalonil possess only low solubility. The solubility of
organic biocides affects the markets for which the biocide-treated
wood products are appropriate. Biocides with good solubility can be
dissolved at high concentrations in a small amount of organic
solvents, and that solution can be dispersed in water with
appropriate emulsifiers to produce an aqueous emulsion. The
emulsion can be used in conventional pressure treatments for lumber
and wood treated in such a manner, and can be used in products such
as decking where the treated wood will come into contact with
humans. Biocides which possess low solubility must be incorporated
into wood in a solution of a hydrocarbon oil, such as AWPA P9 Type
A, and the resulting organic solution is used to treat wood
directly. Wood treated in this way can be used only for industrial
applications, such as utility poles and railway ties, because the
oil is irritating to human skin.
[0007] The primary preserved wood product has historically been
southern pine lumber treated with chromated copper arsenate (CCA).
Most of this treated lumber was used for decks, fencing and
landscape timbers. There has recently been raised concerns about
the safety and health effects of CCA as a wood preservative,
primarily relating to the arsenic content but also to the chromium
content. In 2003/2004, due in part to regulatory guidelines and to
concerns about safety, there has been a substantial cessation of
use of CCA-treated products. A new generation of copper containing
wood preservatives uses a form of copper that is soluble. Known
preservatives include copper alkanolamine complexes, copper
polyaspartic acid complex, alkaline copper quaternary, copper
azole, copper boron azole, copper bis(dimethyldithiocarbamate),
ammoniacal copper citrate, copper citrate, and the copper
ethanolamine carbonate. In practice, the principal criterion for
commercial acceptance, assuming treatment efficacy, is cost. Of the
many compositions listed above, only two soluble copper containing
wood preservatives have found commercial acceptance: 1) the copper
ethanolamine carbonate manufactured for example according to the
process disclosed in U.S. Pat. No. 6,646,147 and 2) copper boron
azole. There are, however, several problems with these new
copper-containing preservatives.
[0008] The soluble copper containing wood preservatives are very
leachable, compared to CCA. One study has shown that as much as 80
percent of the copper from a copper amine carbonate complex is
removed in about 10 years under a given set of field conditions.
Under severe conditions, such as the those used for the American
Wood Preserving Association's standard leaching test, these
products are quickly leached from the wood. For example, we found
that 77% by weight of a Cu-monoethanolamine preservative was
leached from the preserved wood in 14 days. This leaching is of
concern for at least two reasons: 1) removal of the copper portion
of the pesticide from the wood by leaching will compromise the long
term efficacy of the formulation and 2) the leached copper causes
concern that the environment will be contaminated. While most
animals tolerate copper, copper is extremely toxic to certain fish
at sub-part per million levels. Common ranges for EC.sub.50 for
copper are between 2 and 12 micrograms per liter. Another study
reported following the Synthetic Precipitation Leaching Procedure.
The study results showed that the leachate from CCA-treated wood
contained about 4 mg copper per liter; leachate from copper boron
azole-treated wood contained about 28 mg copper per liter; leachate
from copper bis(dimethyldithiocarbamate) treated wood had 7 to 8 mg
copper per liter; leachate from alkaline copper quaternary treated
wood had 29 mg copper per liter; and leachate from copper citrate
treated wood had 62 mg copper per liter. However, copper
concentrations depend in part on copper concentration, and CCA had
about 7% of total copper leach, the alkaline copper quaternary
preservative had about 12% of the total copper leach, while the
copper boron azole had about 22% of the total copper leach during
the Synthetic Precipitation Leaching Procedure. Copper leaching is
such a problem that some states do not allow use of wood treated
with the soluble copper containing wood preservatives near
waterways.
[0009] Another concern with soluble copper preservative products
generally is that most preservative materials are manufactured at
one of several central locations but are used in disparate areas
and must be shipped, sometimes substantial distances. The cost of
providing and transporting the liquid carrier for these soluble
products can be considerable, and the likelihood of an extreme
biological impact is very high if transported soluble copper wood
preservative material is spilled or accidentally released near a
waterway.
[0010] Further, unlike CCA, all of these soluble copper containing
wood preservatives require a second organic biocide to be effective
against some biological species. Therefore, wood preserved with
these soluble copper containing wood preservatives also contains a
second biocide that is efficacious against one or more particularly
troublesome species. Oil-soluble biocides such as a
copper(II)-sulfited tannin extract complex (epicatechins) can be
dissolved in light oils, emulsified in water, and injected into the
wood, as is disclosed in U.S. Pat. No. 4,988,545. Alternatively,
the second biocide is often slightly water soluble or emulsified,
and may be composed of a triazole group or a quaternary amine group
or a nitroso-amine group, and this biocide can be simply added to
the fluid used for pressure treating the wood.
[0011] One attempt to improve soluble copper containing wood
preservatives was to incorporate other salts. PCT patent
application WO 92/19429, published Nov. 12, 1992, in Example 2,
describes a method of treating an article of prepared wood by
immersing it for 20 minutes in a bath of 180.degree. C. linseed oil
containing a drying agent, or drier, of 0.07% lead, 0.003%
manganese and 0.004% calcium naphthenate, 0.3% copper naphthenate,
and 0.03 zinc naphthenates as an insecticide and fungicide. Others
have tried alternative metal-compounds, including silver. None of
these have found commercial acceptance.
[0012] Fojutowski, A.; Lewandowski, 0, Zesz. Probl. Postepow Nauk
Roln. No. 209: 197-204 (1978), describes fungicides comprising
fatty acids with copper compounds, applied by dipping hardboard
heated to 120.degree. C. into a bath of the fungicide, also
maintained at 120.degree. C. This is not practicable for a variety
of reasons. In "A New Approach To Non-Toxic, Wide-Spectrum,
Ground-Contact Wood Preservatives, Part I. Approach And Reaction
Mechanisms,"HOLZFORSCHUNG Vol. 47, No. 3, 1993, pp. 253-260, it is
asserted that copper soaps, made with the carboxylic acid groups
from unsaturated fatty acids of non-toxic vegetable oils, rosin,
and from synthetic unsaturated polyester resins have effectiveness
and long-term durability as ground contact wood preservatives for
use against termites and fungal attack. These are not yet in
widespread use, and are expected to have high leach rates and the
bio-available fatty acids are expected to encourage some molds.
[0013] The solubility of copper preservatives can be controlled by
using, for example, an oil barrier. But these oils can unfavorably
change the color, appearance, and burning properties of the wood,
and can be strong irritants. Oil-soaked wood containing oil-soluble
biocides like chlorothalonil, e.g., utility poles, are highly
resistant to leaching and biological attack, but the appearance of
this wood is not acceptable for most uses. Japanese Patent
Application 08-183,010 JP, published in 1996, describes a modified
wood claimed to have mildew-proofing and antiseptic properties and
ant-proofing properties, made by treating wood with a processing
liquid containing a copper salt and linseed oil or another liquid
hardening composition. U.S. Pat. No. 3,837,875 describes as a
composition for cleaning, sealing, preserving, protecting and
beautifying host materials such as wood a mixture of boiled linseed
oil, turpentine, pine oil, a dryer and 28 parts per million of
metallic copper. Feist and Mraz, Forest Products Lab Madison Wis.,
Wood Finishing: Water Repellents and Water-Repellent Preservatives.
Revision, Report Number-FSRN-FPL-0124-Rev (NTIS 1978) discloses
preservatives containing a substance that repels water (usually
paraffin wax or related material), a resin or drying oil, and a
solvent such as turpentine or mineral spirits. Addition of a
preservative such as copper naphthenate to the water repellent is
asserted to protect wood surfaces against decay and mildew
organisms. Soviet Union Patent No. SU 642166 describes a wood
surface staining and preservation treatment, carried out by
impregnating wood with an aqueous copper salt solution, followed by
thermal treatment in boiling drying oil containing
8-hydroxyquinoline dye. U.S. published application 20030108759
describes injecting a copper ammonium acetate complex and a drying
oil as a wood preservative. Again, oil is not favored as it can
alter burning characteristics of wood, can be staining and/or
discoloring, and can be an irritant. It is also difficult to work
with and to inject into wood. None of the above methods of
preserving wood have met commercial acceptance.
[0014] U.S. Pat. No. 6,521,288 describes adding certain organic
biocides to polymeric nanoparticles (particles), and claims
benefits including: 1) protecting the biocides during processing,
2) having an ability to incorporate water-insoluble biocides, 3)
achieving a more even distribution of the biocide than the prior
art method of incorporating small particles of the biocide into the
wood, since the polymer component acts as a diluent, 4) reducing
leaching with nanoparticles, and 5) protecting the biocide within
the polymer from environmental degradation. The application states
that the method is useful for biocides including chlorinated
hydrocarbons, organometallics, halogen-releasing compounds,
metallic salts, organic sulfur compounds, and phenolics, and
preferred embodiments include copper naphthenate, zinc naphthenate,
quaternary ammonium salts, pentachlorophenol, tebuconazole,
chlorothalonil, chlorpyrifos, isothiazolones, propiconazole, other
triazoles, pyrethroids, and other insecticides, imidichloprid,
oxine copper and the like, and also nanoparticles with variable
release rates that incorporate inorganic preservatives as boric
acid, sodium borate salts, zinc borate, copper salts and zinc
salts. The only examples used the organic biocides tebuconazole and
chlorothalonil incorporated in polymeric nanoparticles. There is no
enabling disclosure relating to any metal salts. While data was
presented showing efficacy of tebuconazole/polymeric nanoparticle
formulations and chlorothalonil/polymeric nanoparticle formulations
in wood, the efficacy of these treatments was not compared to those
found when using other methods of injecting the same biocide
loading into wood. Efficacy/leach resistance data was presented on
wood product material, where it was found that the
nanoparticle/biocide treated wood had the same properties as the
wood product treated with a solution of the biocide, i.e., the
polymeric nanoparticles had no effect. Finally, it is known in the
art that transport of preservative material is a large cost item,
and diluents will merely exacerbate this problem.
[0015] We have discussed the problems with current systems, e.g.,
they add undesired oil; they increase corrosion; they are dilute;
they are expensive, especially when the metal-based biocides must
be combined with large quantities of organic biocides; the high
copper leach rates are both a serious environmental problem in
itself and will almost certainly decrease the longevity of
treatment below that obtained with CCA. However, cost is a primary
factor in the selection of a wood preservative. The market is
accustomed to the low cost and effectiveness of CCA, and the market
is not ready to bear the incremental costs of large amounts of
expensive biocides and other materials such as polymeric
nanoparticles.
[0016] The principal aspect of the invention is the copper-based
particulate preservative treatment for wood and wood products. One
embodiment of this invention is an effective, long-lasting,
environmentally responsible, non-staining/coloring, inexpensive,
non-corrosion-inducing, injectable, substantially crystalline (or
amorphous sparingly soluble), copper-based particulate preservative
treatment for wood and wood products that is substantially free of
hazardous material. Yet another embodiment of the invention is an
effective, long-lasting, environmentally responsible,
non-staining/coloring, inexpensive, non-corrosion-inducing,
injectable, substantially crystalline (or amorphous sparingly
soluble), zinc-based particulate preservative treatment for wood
and wood products that is substantially free of hazardous material.
This zinc-based particulate composition can be used independently
of the copper-based particulates, but in preferred embodiments is
used in combination with one or more copper-based particulates. In
preferred embodiments, the substantially crystalline (or amorphous
sparingly soluble) copper- and/or zinc-based particulates are
injected in a formulation comprising one or more organic biocides.
As used herein, the term "organic biocide" also includes
organometallic biocides.
[0017] One aspect of the present invention relates to a
preservative that may be used to preserve wood and wood products.
In one embodiment, a preservative of the invention is a
copper-based preservative. In a preferred embodiment, the
copper-based preservative comprises copper-based particles.
Exemplary particles comprise, for example, copper hydroxide, a
copper salt, and a copper oxide.
[0018] In one embodiment, the copper-based particles comprise a
substantially crystalline copper compound. At least about 20%, 30%,
50%, or 75% of the weight of the copper-based particles may be
composed of the substantially crystalline copper compound. In
another embodiment, essentially all of the weight of the
copper-based particles is composed of substantially crystalline
copper compound. The substantially crystalline copper compound may
comprise, for example, at least one of copper hydroxide (such as
Cu(OH).sub.2), a copper salt, and a copper oxide (such as CuO).
[0019] Exemplary copper-based particles of the invention are
sufficiently small to be present within wood without a substantial
reduction in the original strength of the wood. For example,
substantially all of the copper-based particles may be sized to
occupy pores or vesicles of wood. In one embodiment, wood or a wood
product may be impregnated with copper-based particles of the
invention.
[0020] Copper or copper-based particles present within wood or wood
products is preferably less mobile than copper present in a liquid
without copper-based particles of the invention. Preferably, the
copper-based particles are sufficiently insoluble so as to not be
easily removed by leaching but are sufficiently soluble to exhibit
toxicity to primary organisms primarily responsible for the decay
of the wood. Exemplary copper-based particles of the invention are
sufficiently small to be present within wood without a substantial
reduction in the original strength of the wood. For example,
substantially all of the copper-based particles may be sized to
occupy pores or vesicles of wood. In one embodiment, exemplary wood
preservatives comprise copper-based particles having a size
distribution in which at least 50% of particles have a diameter
smaller than 0.25 .mu.m, 0.2 .mu.m, or 0.15 .mu.m. A preferred
particle sizing technique is a sedimentation or centrifugation
technique based on Stoke's Law.
[0021] Another embodiment of this invention is an effective,
long-lasting, environmentally responsible, non-staining/coloring,
inexpensive, less-corrosion-inducing, injectable, sparingly soluble
copper salt-containing particulate preservative treatment for wood
and wood products that is substantially free of hazardous material.
Generally, crystalline salts are preferred because they have lower
rates of dissolution than do their amorphous analogs. However,
amorphous salts are equally effective, and particulates made from
amorphous salts can be treated with one or more coatings, or can be
made of a particular size, such that the amorphous material may
easily have release and leach characteristics like the
substantially crystalline salts. Substantially crystalline salts
should be considered a preferred variant of the invention, as the
same disclosure is generally equally applicable to amorphous
sparingly soluble copper salts, or substantially amorphous
sparingly soluble copper salts. A "sparingly soluble salt" has, for
example, a K.sub.sp less than about 1 E-8, preferably between about
1 E-10 to about 1 E-21.
[0022] The copper-based particulates can comprise or consist
essentially of any sparingly soluble substantially crystalline (or
sparingly soluble amorphous) copper salts. In one embodiment the
substantially crystalline (or amorphous sparingly soluble) copper
salts in the copper-based particulates comprise or consist
essentially of one or more copper salts selected from copper
hydroxides; copper carbonates (e.g., "yellow" copper carbonate);
basic (or "alkaline") copper carbonates; basic copper sulfates
including particularly tribasic copper sulfate; basic copper
nitrates; copper oxychlorides (basic copper chlorides); copper
borates; basic copper borates; copper ferricyanate; copper
fluorosilicate; copper thiocyanate; copper diphosphate or copper
pyrophosphate, copper cyanate; and mixtures thereof. In one
embodiment, the copper-based particles comprise a substantially
crystalline copper compound. At least about 20%, 30%, 50%, or 75%
of the weight of the copper-based particles may be composed of the
substantially crystalline copper compound(s).
[0023] In a preferred embodiment the substantially crystalline (or
amorphous sparingly soluble) copper salts in the copper-based
particulates comprise or consist essentially of one or more copper
salts selected from copper hydroxides; copper carbonates, basic (or
"alkaline") copper carbonates; basic copper sulfates including
particularly tribasic copper sulfate; basic copper nitrates; copper
oxychlorides (basic copper chlorides); copper borates, basic copper
borates, and mixtures thereof. In one embodiment, the copper-based
particles comprise a substantially crystalline copper compound. At
least about 20%, 30%, 50%, or 75% of the weight of the copper-based
particles may be composed of the substantially crystalline copper
compound.
[0024] In another embodiment the substantially crystalline (or
amorphous sparingly soluble) copper salts in the copper-based
particulates in a wood preservative formulation can comprise or
consist essentially of a plurality of sparingly soluble
substantially crystalline (or amorphous sparingly soluble) copper
salts selected from copper oxide, copper hydroxides; copper
carbonates, alkaline (or "basic") copper carbonates; alkaline
copper sulfates; alkaline copper nitrates; copper oxychlorides;
copper borates, basic copper borates, and mixtures thereof, with
the proviso that at least one of the substantially crystalline (or
amorphous sparingly soluble) copper salts is not a copper oxide. Of
the copper oxides, Cu.sub.2O is preferred over CuO. In a variant of
this, the copper-based particulate material can comprise or consist
essentially of one or more sparingly soluble substantially
crystalline copper salts selected from copper hydroxides; copper
carbonates, alkaline (or "basic") copper carbonates; alkaline
copper nitrates; alkaline copper sulfates; copper oxychlorides;
copper borates, basic copper borates, and mixtures thereof. In one
embodiment, the copper-based particles comprise a substantially
crystalline copper compound. At least about 20%, 30%, 50%, or 75%
of the weight of the copper-based particles may be composed of the
substantially crystalline copper compound(s).
[0025] In any of the above, the substantially crystalline (or
amorphous sparingly soluble) copper composition can have a
substantial amount of one or more of magnesium, zinc, or both,
wherein these cations are either dispersed within the substantially
crystalline (or amorphous sparingly soluble) copper composition or
a separate phase within a particulate. In preferred embodiments of
the invention, at least some particulates comprise copper
hydroxide, basic copper carbonate, or both. In more preferred
embodiments, the copper hydroxide comprises between 6 and 20 parts
of magnesium per 100 parts of copper, for example between 9 and 15
parts of magnesium per 100 parts of copper. Alternatively, in
another more preferred embodiments, the copper hydroxide comprises
between 6 and 20 parts total of magnesium and zinc per 100 parts of
copper, for example between 9 and 15 parts total of magnesium and
zinc per 100 parts of copper. In some embodiments, the basic copper
carbonate comprises between 6 and 20 parts of magnesium per 100
parts of copper, for example between 9 and 15 parts of magnesium
per 100 parts of copper, or alternatively between 6 and 20 parts
total of magnesium and zinc per 100 parts of copper, for example
between 9 and 15 parts total of magnesium and zinc per 100 parts of
copper. Alternatively or additionally, in a preferred embodiment,
the copper hydroxide and/or basic copper carbonate comprises
between about 0.01 and about 5 parts of phosphate per 100 parts of
copper, for example between 9 and 15 parts of phosphate per 100
parts of copper.
[0026] In another preferred embodiment, the slurry comprises
sparingly soluble copper salt particulates and also comprises zinc
borate particulates. Preferably, at least some of the sparingly
soluble copper salt-based particulates comprise copper borate. It
is known to use a two stage process where a zinc or copper salt is
injected into the wood followed by a second step wherein the borax
is injected and the insoluble metal borate is formed in situ. Such
a complicated, time-consuming, and therefore expensive process in
not sufficiently cost-effective. As the solubility of copper borate
is very pH sensitive, in a preferred embodiment the sparingly
soluble copper salts comprise an alkaline material, e.g., copper
hydroxide or copper carbonate, to reduce the solubility of the
copper borate. The zinc borate loading can range from 0.025% to
0.5%, for example, independent of the copper loading in the
wood.
[0027] In any of the above-described embodiments, the substantially
crystalline copper composition in copper-based particulates and/or
copper-based particulate material can further comprise one or more
soluble substantially crystalline copper salts, for example copper
sulfate, copper fluoroborate; copper fluoride, or mixtures thereof,
where the soluble substantially crystalline copper salts phase is
stabilized against dissolution.
[0028] In any of the above-described embodiments, the substantially
crystalline copper composition in copper-based particulates and/or
copper-based particulate material can further comprise the
substantially insoluble copper salt copper phosphate,
Cu.sub.3(PO.sub.4).sub.2. In any of the above-described
embodiments, the copper composition in copper-based particulates
and/or copper-based particulate material can further comprise the
insoluble copper salt copper 8-quinolinolate. In any of the
above-described embodiments, the composition can further comprise
copper quinaldate, copper oxime, or both in particulate form. If
there are copper-based-particulates substantially comprising
Cu.sub.3(PO.sub.4).sub.2 and/or copper oxide and/or copper
8-quinolinolate, the particulates should be exceedingly small,
e.g., less than about 0.07 microns, preferably less than about 0.05
microns, to provide maximum surface area to help dissolution of the
particles, and the wood treatment should contain another type of
substantially crystalline (or amorphous sparingly soluble)
copper-based particulates, e.g., basic copper carbonate, basic
copper borate, tribasic copper sulfate, copper hydroxides, and the
like.
[0029] The zinc analogs of the above are useful for the zinc-based
particulates of the alternate embodiments of the invention. In one
embodiment the copper-based particulate material can further
comprise one or more of crystalline zinc salts selected from zinc
hydroxide; zinc oxides; zinc carbonate; zinc oxychloride; zinc
fluoroborate; zinc borate, zinc fluoride, or mixture thereof. The
zinc salts may be in a separate salt phase, or may be mixed Cu/Zn
salts, or combinations thereof. In preferred embodiments the
particle comprises at least about 40%, preferably at least about
60%, and more preferably at least about 80% by weight of one or
more substantially crystalline (or amorphous sparingly soluble)
copper salts, crystalline zinc salts, or mixtures or combinations
thereof.
[0030] In one embodiment the copper-based particulate preservative
treatment for wood can further comprise zinc-based particulates
comprising one or more of crystalline zinc salts selected from zinc
hydroxide; zinc oxides; zinc carbonate; zinc oxychloride; zinc
fluoroborate; zinc borate, zinc fluoride, or mixture thereof. The
preferred zinc-based substantially crystalline material are zinc
hydroxide, zinc borate, zinc carbonate, or mixture thereof, which
may be doped with other cations, e.g., from 0.1 to 10% copper, from
0.1 to 10% magnesium, or both, for example, based on the total
weight of the cations in the substantially crystalline (or
amorphous sparingly soluble) material. In preferred embodiments the
particle comprises at least about 40%, preferably at least about
60%, and more preferably at least about 80% by weight of one or
more crystalline zinc salts.
[0031] Preferred embodiments of the invention comprise particles
comprising one or more of copper hydroxide, alkaline copper
carbonate, alkaline copper oxychloride, tribasic copper sulfate,
copper borate, or mixtures thereof. The most preferred embodiments
of the invention comprise particles comprising copper hydroxide,
alkaline copper carbonate, copper borate, alkaline copper borate,
or mixtures thereof.
[0032] Metal salt-based preservatives require added organic
biocides to have the efficacy of the traditional CCA treatments. It
is believed that certain organic biocides are very effective
against most (but not all) undesired bio-organisms, and is also
long-lasting. A principal function of the copper in such a system
is to inhibit growth of those bio-organisms that degrade the
organic biocides and/or that are resistant to the organic biocides.
The most preferred embodiments of this invention have copper-based
particulates and optionally one or more of zinc-based particulates
and tin-based particulates, and further comprise between about
0.01% to about 20% by weight total of one or more organic biocides.
In addition, in some embodiments, the particulates provide a
carrier to carry the organic biocides into the wood and help ensure
the biocide is well-distributed throughout the wood. Preferred
embodiments of the invention are an injectable copper-based
particulate preservative treatment for wood that further comprises
one or more injectable organic biocides attached to
particulates.
[0033] Other aspects of this invention include methods to prepare
the copper-based particulates, methods of formulating the
injectable wood treatment compositions that comprise the
copper-based particulates and optionally one or more organic
biocides, methods of transporting the injectable wood treatments,
methods of mixing and injecting the copper-based particulate wood
preservative composition, and also wood and wood products treated
with the copper-based particulate preservative treatment
compositions.
[0034] We believe our combination of manufacture, pretreatment,
formulation and injection into wood of basic ("sparingly soluble")
crystalline copper compounds injected as particulates represent a
significant discovery. The slurries of this invention are
essentially unaffected by the use of hard water in the application.
The CMC material used in the prior art precipitates an
objectionable residue of calcium and magnesium carbonates onto the
surface of the wood. Injection of the present formulation uses the
standard operating procedure that is commonly practiced in the
industry. No changes are needed. The present formulation eliminates
the nitrogen content of the prior art products; and we believe the
nitrogen is associated with the enhanced rate of sapstain growth
which presently necessitates the use of expensive sapstain control
agents. Removal of the fraction of particles having a diameter
greater than 1 micron (1000 nanometers), accomplished with a
component of this technology, means the slurries are stable--slurry
particles settle over the course of days or even weeks. This is a
desirable application feature. The copper should be relatively
non-leachable, being comparable with the rates associated with the
CCA products. Due to lower leach rates, the product should be
usable underground, near waterways, and also in marine
applications. The cost per pound of copper is estimated to be
between $0.20 to $0.50 less than present copper-MEA-carbonate
products. We believe that corrosivity of the product will be less
than that associated with the copper-MEA-carbonate products.
Freight should be only one third that associated with the
copper-MEA-carbonate products.
[0035] Unless otherwise specified, all compositions are given in
"percent", where the percent is the percent by weight based on the
total weight of the entire component, e.g., of the particle, or to
the injectable composition. In the event a composition is defined
in "parts" of various components, this is parts by weight, wherein
the total number of parts in the composition is between 90 and
110.
[0036] Effective--By "effective" we mean the preservative treatment
is sufficiently distributable through the wood product, and is
sufficiently soluble and available so as to provide a bio-active
concentration of copper ions in the wood matrix. By "bio-active" we
mean the preservative treatment is sufficiently biocidal to one or
more of fungus, mold, insects, and other undesired organisms which
are normally the target of copper-containing wood preservatives
such that these organisms avoid and/or can not thrive in the
treated wood. It is known that copper arsenate
(Cu.sub.3(AsO.sub.4).sub.2) injected as a molecular layer is an
effective biocide. Therefore, the particulate preservative
treatment should provide a copper concentration roughly similar
(for example, about the same to about two times as high) as that
provided by the chromated copper arsenate (CCA) treatment. Too low
a solubility, and the copper is not bioactive. At the same time,
the injectable copper-based wood preservative treatment of this
invention is intended to have one or more organic-based biocides
incorporated therewith in amounts the same as are currently being
used with soluble copper preservatives, and efficacy is based on
the combination of the copper (and/or zinc) component in
combination with the organic biocides.
[0037] Long-lasting--By "long-lasting" we mean the preservative
treatment has an effective life of at least about the same as a
traditional CCA-treated product, alternatively, the treatment lasts
at least about 20 years under normal outdoor ground-contact use,
for example. Too high a solubility of the particulates, and the
copper is leached out of the wood at too fast a rate. Such fast
leaching creates environmental problems, i.e., the leached copper
contaminates the environment, and also longevity problems, i.e., so
much copper may be leached from the wood that the remaining
treatment can no longer provide a bio-active concentration of
copper ions.
[0038] Leaching is a function of particle size and the solubility
of the substantially crystalline (or amorphous sparingly soluble)
copper-containing material. Larger size particles have lower leach
rates, while particles in a size range from 1 to 10 nanometers
under certain circumstances will not have a leach rate much
different than that of an injected copper salt solution. In
preferred embodiments of this invention, at least 50% by weight of
the copper-containing particulates have a size greater than 40
nanometers. In more preferred embodiments, at least 50% by weight
of the copper-containing particulates have a size greater than 80
nanometers. In one preferred embodiment, at least 80% by weight of
the copper-containing particulates have a size between 0.05 microns
and 0.4 microns.
[0039] Leaching is not the only mechanism whereby material can be
flushed from wood. Because the material is in particulate form,
there is a possibility that particulates will be flushed from the
wood. Evidence suggests that very small substantially spherical
nanoparticles, i.e., spherical particles of size 5 to 20
nanometers, can migrate freely through a wood matrix. United States
Patent Application 20030077219 teaches a variant of the
precipitation method of forming nanoparticles from micro-emulsions,
the invention apparently relating to a block polymer used to
stabilize the micro-emulsions. This publication claims that
nanoparticles penetrate more easily and more deeply into the wood
layers under treatment due to their "quasi atomic size," thus
eliminating or reducing the need for pressure impregnation.
Immersion of wood into a copper hydroxide micro-emulsion showed the
copper hydroxide penetrated to a depth of more than 10 to 298 mm.
However, while said particles are easy to inject, they are also
clearly easily transported through wood and would be easily flushed
from the wood. These wood preservative treatments would not be
long-lasting. Therefore, in preferred embodiments of the invention
the material is substantially free of substantially spherical
particulates, wherein the size of the spherical particulates is
less than about 20 nanometers, particularly less than 15
nanometers.
[0040] Generally, the leaching rate from dispersed particulates is
controlled by 1) diffusion and boundary layer effects around the
limited surface area available to water; 2) the activation energy
needed to disrupt the crystal and to thereby cause dissolution, and
3) the absolute solubility of the material. Solubility is not an
easy parameter to control; the solubility of copper itself in
compositions containing hydroxyl groups and carbonates is about
0.01 ppm at pH 10, 2 ppm at pH 7, but is 640 ppm at pH 4. Wood
itself has a "pH" between 4 and 5, but there is essentially no
buffering capacity. Therefore, copper hydroxides are a component of
the preferred substantially crystalline (or amorphous sparingly
soluble) copper material, as the hydroxides will raise the pH of
the water in the wood.
[0041] Leaching will be discussed extensively infra.
Advantageously, the particulates of the present invention provide
at 240 hours into an AWPA E 11-97 leach test a total leached copper
value that is within a factor of two above, to within a factor of
five below, preferably within a factor of three below, the total
leached copper value obtained by a wood sample treated with CCA and
subjected to the same test.
[0042] Substantially free of hazardous material--By "substantially
free of hazardous material" we mean the preservative treatment is
substantially free of materials such as lead, arsenic, chromium,
and the like. By substantially free of lead we mean less than 0.1%
by weight, preferably less than 0.01% by weight, more preferably
less than 0.001% by weight, based on the dry weight of the wood
preservative. By substantially free of arsenic we mean less than 5%
by weight, preferably less than 1% by weight, more preferably less
than 0.1% by weight, for example less than 0.01% by weight, based
on the dry weight of the wood preservative. By substantially free
of chromium we mean less than 0.5% by weight, preferably less than
0.1% by weight, more preferably less than 0.01% by weight, based on
the dry weight of the wood preservative.
[0043] Environmentally responsible--By "environmentally
responsible" we mean the wood preservative (including co-biocide)
has a bioactive effectiveness that is at least about one half that
of CCA, preferably at least three quarters of that of CCA, for
example, about equal to that of CCA, for specified organism based
on the weight percent of the wood preservative material in the
wood. If, for instance, the wood preservative has a bioactive
effectiveness equal to that of CCA, then wood treated with a
selected concentration of the wood preservative will have
substantially similar bioactivity as wood treated with the same
concentration of CCA.
[0044] Additionally, the environmentally responsible material is
substantially free of small nanoparticles which can be readily
flushed from wood. Therefore, in preferred embodiments of the
invention the environmentally responsible material is substantially
free of substantially spherical particulates, wherein the size of
the spherical particulates is less than about 20 nanometers,
particularly less than 5 nanometers. More preferably, in preferred
embodiments of the invention the environmentally responsible
material is substantially free of particulates having a size less
than about 20 nanometers, particularly less than 5 nanometers.
Nanoparticle-sized metal particulates may be toxic to certain
aquatic life, though the data is very preliminary.
[0045] Additionally, environmentally responsible wood preservatives
are beneficially substantially free of organic solvents. By
substantially free we mean the treatment comprises less than 10%
organic solvents, preferably less than 5% organic solvents, more
preferably less than 1% organic solvents, for example free of
organic solvents, based on the weight of the copper in the wood
preservative.
[0046] Injectable--By "injectable" we mean the wood preservative
particulates are able to be pressure-injected into wood, wood
products, and the like to depths normally required in the industry,
using equipment, pressures, exposure times, and procedures that are
the same or that are substantially similar to those currently used
in industry. Pressure treatment is a process performed in a closed
cylinder that is pressurized, forcing the chemicals into the wood.
Copper loading, also called copper retention is a measure of the
amount of preservative that remains in the wood after the pressure
is released. It is given as "pcf," or pounds of preservative per
cubic foot of wood. Retention levels that must be reached are
dependent on three variables: the type of wood used, the type of
preservative used, and the use of the wood after treatment. The
sparingly soluble copper-salt particulates of this invention are
typically expected to be added to wood in an amount equal to or
less than 0.25 pounds as copper per cubic foot. In preferred
embodiments of the invention incising is not expected to be
required to inject the slurries of the present invention into
lumber having thicknesses of 6 to 10 inches.
[0047] Injectability requires the particulates be substantially
free of the size and morphology that will tend to accumulate and
form a filter cake, generally on or near the surface of the wood,
that results in undesirable accumulations on wood in one or more
outer portions of the wood and a deficiency in an inner portion of
the wood. Injectability is generally a function of the wood itself,
as well as the particle size, particle morphology, particle
concentration, and the particle size distribution.
[0048] The requirements of injectability for substantially round,
e.g., the diameter is one direction is within a factor of two of
the diameter measured in a different direction, rigid particles
generally are 1) that substantially all the particles, e.g.,
greater than 98% by weight, have a particle size with diameter
equal to or less than about 0.5 microns, preferably equal to or
less than about 0.3 microns, for example equal to or less than
about 0.2 microns, and 2) that substantially no particles, e.g.,
less than 0.5% by weight, have a diameter greater than about 1.5
microns, or an average diameter greater than about 1 micron, for
example. We believe the first criteria primarily addresses the
phenomena of bridging and subsequent plugging of pore throats, and
the second criteria addresses the phenomena of forming a filter
cake. Once a pore throat is partially plugged, complete plugging
and undesired buildup generally quickly ensues.
[0049] However, there are minimum preferred particulate diameters
for the wood treatment, which depend somewhat on the copper salt(s)
that are in the particulates. If the salts have a high solubility,
very small particulates having a large surface to mass ratio will
result in too high a copper ion concentration, and too fast a
copper leaching, compared to preferred embodiments of this
invention. Further, very small particulates, especially for example
small spherical particles of diameter between about 0.003 to about
0.02 microns, are readily flushed from the wood. Generally, it is
preferred that at least 80% by weight of the particles be above
0.01 microns in diameter, preferably greater than 0.03 microns, for
example greater than 0.06 microns in diameter.
[0050] By injectable, unless otherwise specified, we mean
injectable into normal southern pine lumber. This invention also
encompasses injecting the particulates into other woods as well as
into for example heartwood. Selected other woods and heartwood may
require a smaller substantially lower criteria on particle
dimensions for injectability, and such formulations can be made as
discussed herein, but the formulation most of interest is a
commercially operative formulation developed for normal Southern
Pine. Such a formulationn will typically be useful for all other
woods, with the possible exception of selected heartwood. Such
problems with heartwood are normally not a substantial concern, as
the injected particulate material may form a partial protective
filter cake around heartwood that protects the heartwood without
causing unsightly accumulations of preservative on the wood, and
also heartwood is naturally substantially resistant to attack by
many bioorganisms and therefore may require less copper to
constitute sufficient protection.
[0051] We have found three methods to improve injectability and/or
to maintain injectability of particulates. These methods improve
particle size distribution and/or morphology by wet milling, and
chemically and physically stabilize the particulates by coating the
particulates with selected materials.
[0052] Non-staining/Non-coloring--By "non-staining/non-coloring" we
mean the wood preservative does not impart undesired color to the
wood. Large particulates, or large agglomerations of smaller
particulates, impose a visible and undesired color to the treated
wood, which is generally bluish or greenish. Surprisingly, coloring
is usually indicative of poor injectability. Individual particles
of diameter less than about 1 micron, preferably less than 0.5
microns, that are widely dispersed in a matrix do not color a wood
product to any substantial degree. Filter cake forms unsightly
coloring. An aggregation of particles, similar to filter-cake,
could contribute un-wanted color. Preferably 100% by weight of the
particles have an average diameter of less than 1 micron, where an
average diameter is the diameter measured by Stokes law settling
(which may be assisted by centrifugation), or by preferably by
dynamic light (X-ray) scattering or by Doppler light scattering.
Even particulates having a size greater than 0.5 microns can impart
very visible color, and agglomerates of similar size have the same
effect as do large particles. In a preferred embodiment of the
invention, at least about 95%, e.g., at least about 99% by weight
of the particulates/aggregates are smaller than 0.5 microns in
average diameter. More preferably, at least about 95%, e.g., at
least about 99% by weight of the particulates/aggregates are
smaller than 0.35 microns in average diameter. Even more
preferably, at least about 95%, e.g., at least about 99% by weight
of the particulates/agreggates are smaller than 0.3 microns in
average diameter. Generally, it is preferred that at least 90% by
weight of the particles be above 0.01 microns in diameter,
preferably greater than 0.03 microns, for example greater than 0.06
microns. Certain compounds, particularly basic copper carbonate,
copper hydroxide, and copper oxychloride are preferred because they
impart less color than do other particles of comparable size.
Additionally, the presence of a zinc salt, a magnesium salt, or
both either as a separate phase or as a mixed phase may also reduce
color.
[0053] Inexpensive--By "inexpensive" we mean the wood preservative
is prepared using techniques so that the cost of the wood treatment
is competitive with, for example, copper-ethanolamine-complex
treatments and other commonly used treatments. As the cost of
copper is substantially constant regardless of the source,
inexpensive relates primarily to the costs of manufacture,
separation, sizing, and preservation of the particulate material.
There are many techniques to create very small nanoparticles, but
most of these processes are far too costly to be useful in the mass
production of a copper-based wood preservative treatment.
Generally, the term "inexpensive" means at a processed cost less
than or equal to the current costs of the soluble copper-co-biocide
treatments, alternately within about 20% of the cost of prior art
CCA treatments.
[0054] The preferred method of production is a precipitation
process, in the absence of organic solvents and the like.
Preferably the reactants are of standard industrial quality, as
opposed to higher levels of purity. The particles start with
certain characteristics including size distribution and morphology,
e.g., at least 2% by weight of the particles have a diameter
greater than 1 micron, usually greater than 1.5 microns, and
generally must undergo subsequent treatment, e.g., milling, to make
sure the particle size and particle size distribution are favorable
for injection. Particles made by other processes, particularly
emulsion precipitation processes and fuming processes, are not
sufficiently cost effective to manufacture commercially acceptable
copper particulates for wood preservation.
[0055] It is known that nanoparticles can be formed for example by
micro-emulsion (or micelle) precipitation, and the like. The
micelle system, where emulsions of small and uniformly sized
micelles are used as nanoreactors in which the deposition of the
metal salt is carried out, are known in the art. For example, it is
known to make nickel and nickel/copper (7/3) carbonate particles
via water in oil (hexane/hexanol) microemulsions. Two separate
microemulsions with the metal salt and ammonium bicarbonate,
respectively, were prepared and mixed rapidly to form metal
carbonate nanoparticles of 6 to 7 nm diameter with a small diameter
distribution. Such processes, while useful in forming very small
particulates, are not useful in forming commercially acceptable
wood preservative. The associated costs of adding and removing the
solvents used to form the emulsions makes these processes
economically un-usable for the purpose of forming a
copper-containing injectable particulate wood preservation
material.
[0056] It is known that nanoparticles can be formed for example by
forming fumed copper salts via a vapor process or an aerosol
oxidiation process. The authors of Copper and Copper Oxide
Nanoparticle Formation by Chemical Vapor Nucleation From Copper
(II) Acetylacetonate by Albert G. Nasibulin, P. Petri Ahonen,
Olivier Richard, Esko I describe methods of forming e.g., 2 nm to
20 nm in diameter nanoparticles. Generally, fuming processes are
limited to producing the oxides of copper, as these authors
produced. Again, the cost of obtaining such small size (and narrow
particle distribution) is not justified by any increase in efficacy
of the particles for most copper salts of this invention.
[0057] The cost of polymeric nanoparticles to act as a carrier for
the copper salts is similarly not justifiable.
[0058] Less-Corrosion-Inducing--The commercial soluble copper
containing wood preservatives often result in increased metal
corrosion, for example of nails within the wood. Preserved wood
products are often used in load-bearing out-door structures such as
decks. Traditional fastening material, including aluminum and
standard galvanized fittings, are not suitable for use with wood
treated with these new preservatives. Many regions are now
specifying that hardware, e.g., fittings, nails, screws, and
fasteners, be either galvanized with 1.85 ounces zinc per square
foot (a G-185 coating) or require Type 304 stainless steel.
Generally, the presence of any salt will induce corrosion. By
"less-corrosion-inducing" we mean the wood preservative has a
reduced tendency, compared to a similar concentration of copper
obtained from the soluble copper treatments such as the
amine-copper-complex treatments and alkanolamine-copper-complex
treatments in use today, to corrode metal that contacts the wood.
The degree of corrosion will depend in large part on the salts
selected, as well as on adjuvants, in particular amines.
[0059] We believe that the amines present in the treatments used in
soluble copper treatments--alkanolamines, ammonia, and the
like--are corrosive to metals. We also believe that another problem
with the new soluble complexed copper preservatives is that they
are, or they eventually turn into, biodegradable material that can
encourage certain biological attacks, particularly mildew. The
commonly used soluble copper compounds provide nitrogen-containing
nutrients (amines) which are believed to act as food-stuff and
causes an increase in the presence of sapstain molds, therefore
requiring additional biocides effective on sapstain molds to be
added to protect the external appearance of the wood. When there is
also bio-available carbon sources, in addition to bio-available
nitrogen, the problem is made worse. Advantageously, the wood
preservative is substantially free of any amines other than certain
selected amines that may be used as a supplemental biocide. By
substantially free we mean the treatment comprises less than 10%
amines, preferably less than 5% amines, more preferably less than
1% amines, for example free of amines, based on the weight of the
copper in the wood preservative. Alternatively, the term means
there is less than one amine molecule or moiety per four copper
atoms, preferably less than one amine molecule or moiety per ten
copper atoms. Again, amines that are used as supplemental biocides,
if any, are excluded from this limitation. While basic copper
nitrate is a useful sparingly soluble copper salt for use in this
invention, in most embodiments of the invention the wood
preservative is also substantially free of nitrates.
[0060] In other embodiments of the invention an injectable
copper-based particulate preservative treatment for wood that is
substantially free of bio-available nitrogen, and even more
preferably substantially free of bio-available nitrogen and
bio-available carbon is provided. By substantially free of
bio-available nitrogen we mean the treatment comprises less than
10% of nitrates and organic nitrogen, preferably less than 5% of
nitrates and organic nitrogen, more preferably less than 1% of
nitrates and organic nitrogen, for example less than 0.1% of
nitrates and organic nitrogen, based on the weight of the copper in
the wood preservative. In most of the soluble or complexed copper
treatments, there are between 1 and 4 atoms of organic nitrogen
that act as a complexer or carrier for one atom of copper. In the
preferred embodiments of this invention, there is less than 0.3
atoms, preferably less than 0.1 atoms, for example less than 0.05
atoms of organic nitrogen per atom of copper in the wood
preservative treatment. Again, organic nitrogen-containing
compounds that are used specifically as supplemental biocides are
excluded from this limitation. By substantially free of
bio-available carbon we mean the treatment comprises less than 30%
of bio-available organic material (defined as material that is
degradable or that will during the lifespan of the treatment will
become degradable), preferably less than 10% of bio-available
organic material, more preferably less than 1% of bio-available
organic material, based on the weight of the copper in the wood
preservative. Again, organic compounds that are used as
supplemental biocides, if any, are excluded from this limitation.
It is believed that the presence of bio-available organic carbon
may encourage the growth of certain molds.
[0061] In one embodiment, the copper-based particles are
substantially free of polymers, such as organic polymers. For
example, copper-based particles of the invention may be
substantially free of one or more of polyvinylpyridine,
polymethacrylate, polystyrene, polyvinylpyridine/styre- ne
copolymers, polyesters, polyethylene, polypropylene,
polyvinylchloride, blends of the above homopolymers with acrylic
acid and the like. By substantially free, it is meant that the
copper-based particles are less than about 50% by weight polymer.
The copper-based particles may be less than about 35% by weight
polymer, for example, less than 25% by weight polymer, such as less
than 15% by weight polymer. In one embodiment, the copper-based
particles are essentially free of polymer, by which it is meant the
copper-based particles comprise less than about 5% by weight
polymer. In one embodiment, the copper-based particles comprise
less than about 2.5% by weight polymer. In one embodiment, the
copper-based particles are free of polymer.
[0062] In one embodiment of the invention, the copper-based
particles may comprise a polymer. In this embodiment, the ratio of
the weight of copper present in the particles to polymer present in
the particles may be at least about 1 to 1, for example at least
about 2 to 1, 4 to 1, 5 to 1, 7 to 1, or at least about 10 to 1.
For example, if ratio of the weight of copper present in the
particles to the weight of polymer present in the particles is at
least about 2 to 1, the particles comprise at least about twice as
much copper by weight as polymer.
[0063] Substantially crystalline--By "substantially crystalline" we
mean, for example, greater than about 30%, preferably greater than
about 50%, by weight of the material of interest (copper salt, zinc
salt, and the like) is crystalline. A material is substantially
crystalline if the material gives the distinctive X-ray diffraction
patterns of the crystalline entity (relating to d spacing, not
present in the amorphous material). A convenient technique for
assessing the crystallinity relative to the crystallinity of known
crystalline salts is the comparison of the relative intensities of
the peaks of their respective X-ray powder diffraction patterns.
The degree of crystallinity can be determined by, for example,
determining the sum of the X-ray diffraction peak heights (for the
same sample size), in terms of arbitrary units above background,
and comparing the summed peak heights of the substantially
crystalline material in, for example, the copper-based particulates
with the corresponding peak heights of the known crystalline
material. This procedure utilizes, for example, only the strongest
4 peaks. When, for example, the numerical sum of the peak heights
of the material in a particulate is 30 percent of the value of the
sum of the peak heights of the same known crystalline copper salt,
then the product is 30 percent crystalline and is substantially
crystalline. The preferred method for determining crystallinity is
by calorimetry, by measuring the heat of dissolution of the sample
in a solvent and comparing this heat with the measured heats of
amorphous and crystalline standard of the same salt, provided the
dissolution of the crystalline salt is substantially different than
the dissolution of the corresponding amorphous salt.
[0064] As crystallinity is difficult to measure, the following
exemplary compounds meet the requirements for substantially
crystalline copper compounds: copper(II) borate; copper boride
(Cu.sub.3B.sub.2); yellow copper(I) carbonate; basic copper
carbonate; copper(II) carbonate dihydroxide
(CuCO.sub.3.times.Cu(OH).sub.2); copper(II) carbonate dihydroxide
(2CuCO.sub.3.times.Cu(OH).sub.2); copper (I and II) chloride;
copper(II) chloride.times.2H.sub.2O; copper oxychloride
(CuCl.sub.2.times.Cu(OH).sub.2); copper(I and II) cyanide; copper(I
and II) fluoride; copper(II) formate; copper(I and II) oxide;
copper phosphate.times.3 water; copper(I and II) sulfate; tribasic
copper sulfate; and copper(I) thiocyanate. The term (I and II)
means the copper(I) salt and the copper(II) salt. These salts are
considered substantially crystalline with as much as 20% by weight
based on the weight of the copper being substituted with magnesium,
zinc, or both. The following exemplary compounds meet the
requirements for substantially crystalline zinc compounds: zinc
carbonate; zinc chloride; zinc cyanide; zinc diphosphate; zinc
fluoride; zinc fluoride.times.4 water; zinc hydroxide; zinc oxide;
zinc phosphate; and zinc sulfate. These salts are typically
substantially crystalline with as much as 20% by weight based on
the weight of the zinc being substituted with magnesium, copper, or
both. The following exemplary compounds meet the requirements for
substantially crystalline tin compounds: tin(II) chloride; tin(II)
chloride.times.2 water; tin(II and IV) oxide; tin(II) diphosphate
(pyrophosphate); tin(II) phosphate (Sn.sub.3(PO.sub.4).sub.2); and
tin(II) sulfate.
[0065] In preferred embodiments, at least about 20%, 30%, 50%, or
75% of the weight of the copper-based particles may be composed of
the substantially crystalline (or amorphous sparingly soluble)
copper compound. The substantially crystalline (or amorphous
sparingly soluble) copper compound may comprise, and in preferred
embodiments does comprise, one or more cations in addition to
copper, for example, magnesium and/or zinc. In another embodiment,
essentially all of the weight of the copper-based particles is
composed of substantially crystalline (or amorphous sparingly
soluble) copper compound.
[0066] Several of the copper salts described herein are available
in crystalline and in amorphous phases. Generally crystallinity is
preferred, as the lattice energy of the crystal is expected to slow
down dissolution. However, amorphous copper salts are useful in the
invention, and for the less soluble salts the amorphous phases may
be preferred over crystalline phases. Phosphate-stabilized copper
hydroxide, a preferred sparingly soluble copper salt used in
embodiments of this invention, is typically substantially
amorphous. One embodiment of this invention is an effective,
long-lasting, environmentally responsible, non-staining/coloring,
inexpensive, non-corrosion-inducing, injectable, amorphous or
substantially amorphous copper-based, zinc-based, or tin-based
particulate preservative treatment for wood and wood products that
is substantially free of hazardous material. Amorphous sparingly
soluble salts are equally effective, and they can be treated with
one or more coatings, or can be made of a particular size, or of
more insoluble salts, such that the amorphous material may easily
have release and leach characteristics like the substantially
crystalline salts. Substantially crystalline sparingly soluble
salts should be considered a preferred variant of the invention, as
the same disclosure is generally equally applicable to amorphous
material, or substantially amorphous material.
[0067] Copper-Based Particulate--As used herein, the term
"copper-based particulate" means a particle having a size between
about 0.7 microns and about 0.01 microns that comprises at least
one substantially crystalline (or amorphous sparingly soluble)
copper salt. The term "particle" is used interchangably with the
term "particulate," while the term "nanoparticle" refers to
particles having a size less than about 0.01 microns in diameter.
The term "copper" includes, unless specifically stated otherwise,
the cuprous ion, the cupric ion, or mixtures thereof, or
combinations thereof. The term "copper-based" means the particle
comprises at least about 20%, 30%, 50%, or 75% by weight of one or
more substantially crystalline (or amorphous sparingly soluble)
copper compounds. In another embodiment, essentially all (e.g.,
more than 95%) of the weight of the copper-based particles is
composed of substantially crystalline (or amorphous sparingly
soluble) copper compound.
[0068] Zinc-Based Particulate--As used herein, the term "zinc-based
particulate" means a particle having a size between about 0.5
microns and about 0.01 microns that comprises at least one
substantially crystalline (or amorphous sparingly soluble) copper
salt. The term "particle" is used interchangably with the term
"particulate." The term "zinc-based" means the particle comprises
at least about 20%, 30%, 50%, or 75% by weight of one or more
substantially crystalline (or amorphous sparingly soluble) zinc
compounds. In another embodiment, essentially all (e.g., more than
95%) of the weight of the zinc-based particles is composed of one
or more substantially crystalline (or amorphous sparingly soluble)
zinc compounds. The preferred substantially crystalline
zinc-containing materials are zinc hydroxide, zinc borate
(Zn(BO.sub.2).sub.2.times.H.sub- .2O), and zinc carbonate. As for
the copper-based particles and the tin-based particles, if the
borate is used as the anion, preferably the composition also
comprises one or more salts of carbonate or hydroxide (or
hydroxide-containing) salts to maintain a slightly elevated pH
within the wood matrix, to slow dissolution of the borate salts. If
zinc-based particulates are used, they are advantageously used with
copper-based particulates.
[0069] Tin-based particulate--As used herein, the term "tin-based
particulate" means a particle having a size between about 0.5
microns and about 0.01 microns that comprises at least one
substantially crystalline (or amorphous sparingly soluble) tin
salt. The term "particle" is used interchangably with the term
"particulate." The term "tin-based" means the particle comprises at
least about 20%, 30%, 50%, or 75% by weight of one or more
substantially crystalline (or amorphous sparingly soluble) tin
compounds. In another embodiment, essentially all (e.g., more than
95%) of the weight of the tin-based particles is composed of one or
more substantially crystalline (or amorphous sparingly soluble) tin
compounds. Generally, tin-based particulates are not preferred
because tin does not have the desired bio-activity. Tin oxides are
believed to be particularly inert, though Nanophase Technologies in
February 2004 claimed, in "Nanotechnology in brief" available on
www.nanotechweb.org/articles/news/- 3/2/12/1, making pilot
quantities of 30 nm silver-doped nanocrystalline tin oxide for use
in wood preservatives, speciality paints, polymer additives,
conductive coatings, and electronic materials. The preferred
substantially crystalline tin material are tin hydroxides,
Sn(OH).sub.2 and Sn(OH).sub.4. If tin-based particulates are used,
they are advantageously used with copper-based particulates.
[0070] It is recognized that some embodiments encompassed by this
invention may not meet all of the objects or characteristics of the
preferred embodiments of the invention as described above. In
preferred embodiments of the invention, the injectable material
will meet any and preferably most of the criteria listed above for
the effective, long-lasting, environmentally responsible,
non-staining/coloring, inexpensive, non-corrosion-inducing,
injectable, substantially crystalline (or amorphous sparingly
soluble), copper-based particulate preservative treatment for wood
and wood products that is substantially free of hazardous
material.
[0071] In preferred embodiments of the invention, the injectable
copper-based particulates will meet any and preferably most of the
criteria listed above for the effective, long-lasting,
environmentally responsible, non-staining/coloring, inexpensive,
less-corrosion-inducing, injectable, substantially crystalline (or
amorphous sparingly soluble), copper-based particulate preservative
treatment for wood and wood products that is substantially free of
hazardous material.
[0072] The Substantially Crystalline Copper Composition in the
Copper-Based Particulates.
[0073] The copper-based particulates can have a substantially
homogenous substantially crystalline (or amorphous sparingly
soluble) copper composition within each particle. Alternatively,
the particles can comprise two or more separate substantially
crystalline (or amorphous sparingly soluble) copper phases.
Preferred particles comprise at least 30%, preferably at least 50%,
more preferably at least 70%, for example between about 80% and
about 98% by weight of total of copper hydroxides, copper oxides,
basic copper carbonates, copper carbonates, copper oxychloride,
tribasic copper sulfate, alkaline copper nitrate, copper borate, or
mixtures thereof. Most comprise a basic copper salt, with the
exception of copper borate and copper oxides. As a high pH
suppresses the solubility of copper borate, advantageously,
treatments that comprise particulates of copper borate also
comprise a basic substantially crystalline (or amorphous sparingly
soluble) copper-containing salts. Copper carbonate is a most
preferred compound, as it is less visible than some other salts,
and has excellent solubility characteristics.
[0074] In another embodiment of the invention, the various
particles within a wood preservative can comprise different
substantially crystalline (or amorphous sparingly soluble) copper
compositions. For example, a treatment may contain particles that
comprise crystalline copper borate, other particles that comprise
alkaline copper carbonate, and even other particles that comprise
copper oxide. The particles having different phases may in
preferred embodiments be of different sizes, porosity, or
morphology, depending on the crystalline copper material
present.
[0075] In one embodiment, exemplary wood preservatives comprise
copper-based salt particles having a size distribution in which at
least 50% of particles have a diameter smaller than 0.5 .mu.m, 0.25
.mu.m, 0.2 .mu.m, or 0.15 .mu.m. A preferred particle sizing
technique is a sedimentation or centrifugation technique based on
Stoke's Law. An exemplary preservative of the invention comprises
particles comprising a sparingly soluble copper salt, e.g., copper
hydroxide, having an average particle diameter of less than about
500 nanometers, for example less than about 250 nanometers, or less
than about 200 nanometers. In one embodiment, the average particle
diameter is at least 25 nanometers, for example, at least 50
nanometers.
[0076] Method Of Manufacture of Substantially Crystalline
Copper-Containing Particles
[0077] Exemplary copper-based particles comprise one or more of
copper metal, a copper oxide, a copper hydroxide, copper carbonate,
and a copper salt that is sparingly soluble. Preferred wood
preservatives comprise copper-based particles that comprise at
least about 20%, for example, at least about 50%, 60%, 70%, or 75%
by weight copper, based on the weight of the particle. An exemplary
copper-based particle comprises about twice as much copper by
weight as oxygen.
[0078] There are a large number of references describing how to
make copper-containing "nanoparticles." These references generally
can not be used to manufacture the particulates at the desired
cost. The formation of 7 nanometer particles of any of CuO,
Cu.sub.2O, or mixed phase CuO/Cu.sub.2O is described for example in
"Copper and Copper Oxide Nanoparticle Formation by Chemical Vapor
Nucleation From Copper(II) Acetacetonate" was described in Journal
of Nanoparticle Research, 3(5-6): 383-398, December 2001. Such
particles are, or course, readily injectable into wood, and if
injected they may provide a degree of biological activity. But they
can not be used for the process because such particles are too
expensive for use in wood treatment. R. L. Hamilton and O. K.
Cosser described using 35 nm CuO or 10 nm Cu metal particles to
enhance thermal conductivity of antifreeze in "Thermal Conductivity
of Heterogenous Two-Component Systems", Ind. & Engr. Chem.
Fund., 1, 187-191 (1962). Such particles would also be expected to
be injectable into wood. U.S. Patent Application 20030077219
describes a method for producing copper salts from at least one
cupriferous reactant and one additional reactant, where
micro-emulsions are prepared from two reactants while employing at
least one block polymer to obtain intermediate products with a
particle size of less than 50 nm, preferably 5 to 20 nm. Material
can be adjusted to specific applications through the appropriate
doping of foreign ions. This application teaches wood treatment
applications, stating copper compounds that have been produced
pursuant to the present invention can penetrate more easily and
more deeply into the wood layers under treatment due to their quasi
atomic size. These improved properties can eliminate or reduce the
need for pressure impregnation while ensuring prolonged protection
against various organisms. Agglomerates characterized by a size of
about 200 nanometers consist of a multitude of primary particles
characterized by a size range of 5 to 20 nm. Example particle sizes
were between 10 and 50 nm and agglomerate sizes between 100 and 300
nm. During the immersion of equivalent wood into the copper
hydroxide micro-emulsion prepared pursuant to the invention, the
copper hydroxide was not limited to the surface, but instead
penetrated to a depth of more than 10 to 298 mm. The use of
solvents makes such processes generally too expensive for use in
wood preservatives, though this process can be useful provided the
solvent serves a subsequent purpose of solvating one or more
organic biocides, to partially bind the organic biocides to the
particulate by partially or completely removing the solvent by
evaporation. Modifying the process of this application to make
particulates greater than 50 nanometers in diameter, for example
between about 100 and about 200 nanometers in diameter, can be
useful provided the solvent serves a subsequent purpose of
solvating one or more organic biocides, to partially bind the
organic biocides to the particulate by partially or completely
removing the solvent by evaporation.
[0079] The method of U.S. Pat. No. 6,596,246 which requires
rigorous removal of iron to make a copper hydroxide can be
utilized. Such a process increases the cost of the product,
however.
[0080] In one embodiment of the invention, copper-based particles
are prepared, such as by precipitation, from a mixture comprising
copper and an amine. The copper and amine may be present in the
form of a copper-amine complex. The mixture may comprise at least
one of copper monoethanolamine, copper diethanolamine,
copper-ammonia, and/or copper ethylenediamine. The copper-amine
complex is usually in an aqueous solution. Preferred precipitates
comprise copper hydroxides. The particles may be prepared by
modifying a pH of the mixture comprising copper and the amine. For
example, the pH of a mixture comprising copper and an amine may be
reduced to value sufficient to precipitate copper-based particles.
In any event, the mixture comprising copper and the amine may be
diluted with water to have a copper concentration of at least about
0.25, for example, at least about 0.5, such as at least about 1% by
weight. The copper concentration may be less than about 2%, for
example, less than about 1.5%. The pH of the mixture comprising
copper and the amine, such as the diluted mixture, may be reduced
using acid to prepare a precipitate comprising copper-based
particles. The particles may comprise copper hydroxide. A
dispersant may be added to the mixture, such as before obtaining
the precipitate, upon obtaining the precipitate, or thereafter. A
stable aqueous copper-amine complex solution may have a pH of 8 to
13. One method for preparing the precipitate comprises adjusting
the pH of an aqueous mixture of the copper-amine complexes. In one
embodiment, the pH is adjusted so that the pH is at least about 4,
for example, at least about 5.5. The pH of the mixture may be
adjusted to less than about 8, for example, to less than about 7.5,
such as less than about 7. The pH may be adjusted to about 7. The
pH is adjusted by adding an acid to the mixture. Alternatively, the
pH may be adjusted by adding the mixture to acid. The solution of
copper-amine complex may be prepared in the presence of acid.
Suitable acids for adjusting the pH include, for example, sulfuric
acid, nitric acid, hydrochloric acid, formic acid, boric acid,
acetic acid, carbonic acid, sulfamic acid, phosphoric acid,
phosphorous acid, and/or propionic acid. The anion of the acid used
may be partially incorporated in the precipitated salt.
[0081] One embodiment of a method for preparing copper-based
particles comprises precipitation of copper-based particles from a
solution comprising (a) copper, such as in the form of a copper
salt, and (b) a pH modifying agent, such as a hydroxide. Exemplary
hydroxides may be selected from hydroxides of group 1a and/or group
2a elements, such as sodium and potassium hydroxide.
[0082] Copper salts useful in preparing copper-based particles of
the invention preferably comprise water soluble salts of copper and
another material. An exemplary copper salt may include at least one
of a copper sulfate, a halogen-containing copper salt, such as
copper chloride or copper bromide, a copper nitrate, a copper
acetate, a copper formate, and a copper propionate. The one or more
copper salts may be provided in the form of a solution, such as an
aqueous solution, of a liquid and the copper salt.
[0083] U.S. Pat. No. 4,808,406, the disclosure of which is
incorporated by reference, describes a useful method for producing
finely divided stable cupric hydroxide compositions of low bulk
density comprising contacting solutions of an alkali metal
carbonate or bicarbonate and a copper salt, precipitating a basic
copper carbonate-basic copper sulfate to a minimum pH in the range
of greater than 5 to about 6, contacting the precipitate with an
alkali metal hydroxide and converting basic copper sulfate to
cupric hydroxide. Another method of manufacturing the copper
compounds is the method described in U.S. Pat. No. 4,404,169, the
disclosure of which is incorporated by reference. This patent
describes a process of producing cupric hydroxides having stability
in storage if phosphate ions are added to a suspension of copper
oxychloride in an aqueous phase. The copper oxychloride is then
reacted with alkali metal hydroxide or alkaline earth metal
hydroxide, and the cupric hydroxide precipitated as a result of the
suspension is washed and then re-suspended and subsequently
stabilized by the addition of acid phosphate to adjust a pH value
of 7.5 to 9. The suspended copper oxychloride is preferably reacted
in the presence of phosphate ions in an amount of 1 to 4 grams per
liter of the suspension and at a temperature of 20.degree. to
25.degree. C. and the resulting cupric hydroxide is stabilized with
phosphate ions.
[0084] There are numerous methods of preparing very small particles
of copper salts, and the above list is exemplary and not complete.
The simplest and by far the least expensive method of producing
small particles is a standard precipitation of admixing two
solutions, one containing soluble copper and one containing the
desired anion, and some particles resulting from slightly modified
precipitation processes are of a size that may be injected into the
wood. The most useful modification is simply adding small
quantities of anion to a concentrated solution of the cation, or
vice versa, with vigorous stirring. Examples in the prior art show
an average particle size as low as 0.3 microns was obtainable. Such
processes are also desirable because the cost of counter-ions
(those ions that form the salts that are admixed, but that are not
incorporated into the substantially crystalline (or amorphous
sparingly soluble) copper material) is negligible. Standard
materials such as chlorides, sulfates, ammonia, and the like are
common counterions. Further, the material need not be ultra-pure.
Indeed, it is desirable to have one or more "contaminants" in the
precipitating solutions. Smaller diameters are obtained when the
concentration of impurities such as Mg, Ca, Zn, Na, Al and Fe in
the suspension is high. Fe present in the suspension acts
especially strongly to prevent formation of large-diameter cuprous
hydroxide particles. Fe concentration is preferably greater than 70
ppm to obtain smaller particles.
[0085] In one embodiment, copper and a hydroxide are combined to
prepare a precipitate comprising copper. The copper and hydroxide
may be combined with the copper in the form of a copper salt. For
example, a solution comprising at least one copper salt and a
solution comprising at least one hydroxide may be combined to
precipitate copper-based particles. In one embodiment, the method
includes precipitating copper-based particles from a solution
comprising at least one other metal, such as a salt of at least one
other metal. For example, copper-based particles of the invention
may be precipitated from a solution comprising at least one of one
or more group 2a metals such as magnesium or salts thereof. The
metal or salt of the metal may be zinc. In one embodiment, (a) a
solution comprising a copper salt and at least one other metal,
which may be in the form of one or more salts, and (b) a solution
comprising a hydroxide are combined in amounts sufficient to
precipitate copper-based particles, such as particles comprising
copper hydroxide.
[0086] In one embodiment, particles are prepared by adding a copper
salt solution to a hydroxide solution comprising about 20%
hydroxide by weight. The copper salt solution is added until a
desired amount of copper-based particles are obtained. For example,
the copper salt solution may be added until the pH of the hydroxide
solution falls to at least about 11.5, 11, 10.5, or about 10. The
precipitate comprising the precipitated copper-based particles may
be used directly to protect wood or wood products, but are
beneficially milled to reduce the fraction of particulates having a
diameter above 1 micron.
[0087] Copper hydroxide is not particularly stable. Hydroxides can
be changed to oxides by for example, a quick and exothermic
reaction by exposure of the copper hydroxide particles to aqueous
solution of glucose. Copper hydroxide may react with air, sugars,
or other compounds to partially or completely form copper oxide.
While this is generally of less concern with foliar fungicides, the
conditions for conversion are highly favored during kiln-drying
treated wood, which contains gluconuronic acids, which are
sugar-like molecules, and heat and a dehydrating condition, create
a high probability of such transformation occurring within the
wood.
[0088] However, as taught by U.S. Pat. No. 3,231,464, the
disclosure of which is incorporated herein by reference thereto,
the presence of magnesium or magnesium and zinc can help stabilize
cupric hydroxide from converting to copper oxide via the loss of a
water molecule. The preferred copper hydroxide particles used in
this invention are stabilized. U.S. Pat. No. 3,231,464 teaches
stabilizing the copper hydroxide with added magnesium zinc, or
both, at a Cu:Mg and/or Cu:Zn weight ratio of 8:1. Copper hydroxide
prepared in a manner so as to contain significant magnesium and/or
zinc hydroxides are more stable and resistant to degradation to
copper oxides. The preferred copper hydroxide particles comprise
between 50% and 90% copper hydroxide, with the remainder comprising
zinc hydroxide, magnesium hydroxide, or both. The process described
in U.S. Pat. No. 3,231,464 is inexpensive, and with modifications
produces particulates with a particle size distribution with a
median particle size of a few tenths of a micron.
[0089] While such methods can provide small particles of selected
substantially crystalline (or amorphous sparingly soluble) salts,
these processes usually have a small fraction of particles that are
unacceptably large. Generally, however, a few particles from a
normal precipitation process are too big to be injectable. A very
small fraction of particles having a particle size above about 1
micron causes, in injection tests on wood specimens, severely
impaired injectability. Large particles, e.g., greater than about 1
micron in diameter, should be removed. Removal via filtering is not
effective, as a large fraction of injectable particles will be
caught on filters designed to remove the bigger particles. We have
surprisingly found that milling, for example wet-milling, can
advantageously modify particle size and morphology. Particles can
be smoothed and large particles removed by continuous-process
centrifuging. Alternately, as described above, we have surprisingly
found that substantially crystalline (or amorphous sparingly
soluble) copper-based particulates that are manufactured by a
precipitation process, using conditions known in the art to produce
small particles, can be readily milled into an injectable material
by wet milling with a milling material such as 0.5 mm diameter
zirconium silicate in a matter of minutes.
[0090] In another embodiment, the copper-based particulates can
have a substantial amount, e.g., at least 0.5% by weight, for
example at least 2% by weight, but less than 50% by weight based on
the weight of copper of one or more other cations, either dispersed
within the substantially crystalline (or amorphous sparingly
soluble) copper composition or substantially as a separate phase
within the particulate. In a preferred embodiment, the copper-based
particulates can have a substantial amount of one or more of
magnesium, zinc, or both, wherein these cations are either
dispersed within the substantially crystalline (or amorphous
sparingly soluble) copper composition or be a separate phase within
a particulate. The weight ratio of copper to zinc may range between
99.9:0.1 to 1:1, but is preferably between 99.5:0.5 to 90:10, for
example between 99:1 and 94:6. The weight ratio of copper to
magnesium may range between 99.9:0.1 to 1:1, but is preferably
between 99.5:0.5 to 85:15, for example between 95:5 and 90:10.
[0091] In one embodiment of the invention, copper-based particles
are precipitated from a mixture of a copper salt solution and a
hydroxide (and optionally other anions) in the presence of at least
one group 2a metal or salt thereof, such as magnesium or a
magnesium salt. In one embodiment, the copper-based particles are
precipitated from a mixture comprising at least about 0.05 parts
magnesium, for example at least about 0.1 parts magnesium per 9
parts copper. The mixture may comprise at least about 0.25 parts
magnesium per 9 parts copper. The mixture may comprise less than
about 1.5 parts magnesium, for example, less than about 1.0 parts,
or less than about 0.75 parts magnesium per 9 parts copper.
[0092] Copper-based particles prepared in accordance with the
present invention will comprise a group 2a metal or zinc if such
materials (metal ions) were used in preparation of the particles.
In another embodiment, the copper-based particles are precipitated
from a mixture comprising at least about 0.2 parts magnesium, for
example, at least about 0.25 parts magnesium per 22.5 parts copper.
The mixture may comprise at least about 0.5 parts magnesium per
22.5 parts copper. The mixture may comprise less than about 3.5
parts magnesium, for example, less than about 2.5 parts magnesium,
or less than about 2 parts magnesium per 22.5 parts copper. The
parts here merely reflect weight ratios of the cations in the
solution to be precipitated, and the parts do not imply
concentration.
[0093] Alternately, or in combination with the group 2a metal or
salt thereof, the copper-based particles may be precipitated from a
solution comprising zinc metal or salt thereof. For example, the
mixture may comprise at least about 0.1 parts zinc, for example, at
least about 0.25 parts zinc, at least about 1.0 parts zinc, or at
least about 2.0 parts zinc per 22.5 parts copper. The mixture may
comprise less than about 3.0 parts zinc, for example, less than
about 2.5 parts zinc, or less than about 1.5 parts zinc per 22.5
parts copper. Preferably, the mixture additionally comprises at
least about 0.25 parts magnesium, for example, at least about 0.5
parts magnesium, at least about 1.0 parts magnesium, or at least
about 2 parts magnesium per 22.5 parts copper. The mixture may
comprise less than about 5.0 parts magnesium, for example, less
than about 2.5 parts magnesium, or less than about 2 parts
magnesium per 22.5 parts copper. Table I sets forth exemplary
ratios of zinc, magnesium, and copper in accordance with the
present invention.
1TABLE I Exemplary Formulations To Precipitate Mg/Zn-Stabilized
Copper Hydroxide Formulation Parts Zinc Parts Magnesium Parts
Copper 1 0.5 0.5 22.5 2 0.75 0.75 22.5 3 1.5 1.5 22.5 4 2.5 1.0
22.5 5 2.5 2.5 22.5
[0094] Such mixtures can be used to precipitate copper hydroxides,
basic copper carbonate, copper oxychloride, copper borate, and any
of the substantially crystalline (or amorphous sparingly soluble)
salts described herein.
[0095] In alternative embodiments, the particulates can comprise
particles that contain a substantially crystalline (or amorphous
sparingly soluble) copper composition with between 0.001% and 3%,
preferably 0.005% to 0.5%, for example 0.01% to 0.1% by weight of
silver, based on the weight of copper, and also optionally the
other cations. Silver is expensive but is efficacious against some
bio-oganisms in very small amounts, and therefore silver is a
useful co-cation in a substantially crystalline (or amorphous
sparingly soluble) copper-based particulate. A wood treatment
containing 0.25 pounds copper per cubic foot would comprise, at a
0.04% silver loading relative to copper, less than 0.2 ounces of
silver per one hundred cubic feet of wood. Generally, if silver is
incorporated into the substantially crystalline (or amorphous
sparingly soluble) copper phase, the substantially crystalline (or
amorphous sparingly soluble) copper phase is preferably a copper(I)
salt and the silver ions are disposed homogenously through the
substantially crystalline (or amorphous sparingly soluble) copper
phase, to prevent the minute quantities of silver from being
prematurely leached from the wood.
[0096] Yet another embodiment of the invention is an effective,
long-lasting, environmentally responsible, non-staining/coloring,
inexpensive, non-corrosion-inducing, injectable, substantially
crystalline (or amorphous sparingly soluble), zinc-based
particulate preservative treatment for wood and wood products that
is substantially free of hazardous material. This composition can
be used independently of the copper-based particulates, but in
preferred embodiments is used in combination with one or more
copper-based particulates. Modification of the above processes to
produce substantially crystalline (or amorphous sparingly soluble)
zinc-containing particulates is within the ability of one of
ordinary skill in the art, and such modifications will not be
described here.
[0097] Similarly, modifications of the above processes to produce
substantially crystalline (or amorphous sparingly soluble)
zinc-containing particulates are within the ability of one of
ordinary skill in the art, and such modifications will not be
described here.
[0098] Milling--Generally, the simple, inexpensive copper salt
precipitation processes provide particles with a size too great for
injection. Even for processes that provide very small median
diameter particles, such as, a few tenths of a micron in diameter,
the precipitation process seems to result in a small fraction of
particles that are larger than about 1 micron, and these particles
plug up pores and prevent acceptable injectability. The size
distribution of the injectable particles must have the vast
majority of particles, for example at least 95% by weight,
preferably at least 99% by weight, more preferably at least 99.5%
by weight, be of an average diameter less than about 1 micron, and
advantageously the particles are not rod-shaped with a single long
dimension. Average particle diameter is beneficially determined by
Stokes Law to a size down to about 0.2 microns. Smaller sizes are
beneficially determined by, for example, a dynamic light scattering
method or laser scattering method or electron microscopy.
Generally, such a particle size and particle size distribution can
be achieved by mechanical attrition of particles.
[0099] Attrition can be obtained for example 1) by use of a
pressure homogenizer such as that manufactured by SMT Ltd. having
400 kg/cm.sup.2 of pressure at a flow rate of 1 l/min., though such
a system often requires the slurry be processed overnight; by
processing in an ultrasonic homogenizer such as is manufactured by
Nissei Ltd., though such a method is energy intensive; by wet
milling in a sand grinder charged with for example partially
stabilized zirconia beads with diameter 0.5 mm; alternately wet
milling in a rotary sand grinder with partially stabilized zirconia
beads with diameter 0.5 mm and with stirring at for example 1000
rpm; or by use of a wet-ball mill, an attritor (e.g., manufactured
by Mitsui Mining Ltd.), a perl mill (e.g., manufactured by Ashizawa
Ltd.,), or the like. Attrition can be achieved to a lesser degree
by centrifugation, but larger particles can be simply removed from
the composition via centrifugation. Removing the larger
particulates from a composition can provide an injectable
formulation. Said particulates can be removed by centrifugation,
where settling velocity substantially follows Stokes law. While
this process provides injectable slurries, a fraction of the
copper-containing particulates that are separated thereby include
both large particles as well as a portion of the injectable
particles, and generally this material would be recycled by being
dissolved and precipitated. Such a process adds an additional cost
to forming the injectable copper-containing particulate wood
treatment.
[0100] The most effective method of modifying the particle size
distribution is wet milling. Beneficially all injectable
formulations for wood treatment should be wet-milled, even when the
"mean particle size" is well within the range considered to be
"injectable" into wood. Traditional precipitation techniques are
known to produce particles with a median particle size between
about 0.2 and 6 microns, depending on the salts used as well as on
various reaction conditions. For example, a commercially available
copper-based particulate product, a magnesium stabilized form of
copper hydroxide (available from Phibro-Tech., Inc.) has a mean
particle size of about 200 nm. However, when this material was
slurried and injected into wood, there was unacceptable plugging on
the face of the wood. Careful examination found the precipitation
process used by Phibro-Tech., Inc. resulted in a few weight percent
of particles with a size over 1 micron, and this small amount of
material was hypothesized to form the start of the plug (where
smaller, normally injectable particles were subsequently caught by
the plug). Wet milling with 2 mm zirconium silicate media had no
effect--wet milling for days resulted in only a marginal decrease
in particle size, and the material was still not injectable in
commercial quantities.
[0101] However, we surprisingly found that a milling process using
0.5 mm high density zirconium silicate grinding media provides
further efficient attrition, especially for the removal of
particles greater than about 1 micron in the commercially available
copper-based particulate product available from Phibro-Tech., Inc.
The milling process usually takes on the order of minutes to
achieve almost complete removal of particles greater than 1 micron
in size. This wet milling process is inexpensive, and all of the
precipitate can be used in the injectable copper-containing
particulate wood treatment. The selection of the milling agents is
not critical, and can be zirconia, partially stabilized zirconia,
zirconium silicate, and yttrium/zirconium oxide, for example,
recognizing that the more dense materials give faster particle size
attrition. The size of the milling material is believed to be
important, even critical, to obtaining a commercially acceptable
process. The milling agent material having a diameter of 2 mm or
greater are ineffective, while milling agent material having a
diameter of 0.5 mm is effective typically after 15 minutes of
milling. We believe the milling agent is advantageously of a
diameter less than 1.5 mm, preferably is less than 1 mm in
diameter, for example between about 0.1 mm and about 1 mm, or
alternately between about 0.3 mm and 0.7 mm.
[0102] The original focus on injectability focused on the magnesium
stabilized copper hydroxide product available from Phibro-Tech.,
Inc., as this material started (and ended) with a material that had
a median diameter of 0.2 microns. While we originally believed that
the milling broke aggregates, possibly fused aggregates, of smaller
particles that formed the "greater than about 1 micron fraction" of
the above-described product, the milling process was surprisingly
equally effective on larger mean diameter particles.
[0103] We have surprisingly found that copper-based particulates
that are manufactured by a straightforward precipitation process,
using conditions known in the art to produce small particles, e.g.,
particles having a size less than 10 microns, can be readily milled
into an injectable material. Therefore, milling other precipitate
material with 0.5 mm diameter zirconium silicate (or any comparable
product, e.g., a 0.1 mm to 1 mm sized zirconium silicate or
zirconium oxide) can mill in a matter of minutes a substantially
crystalline (or amorphous sparingly soluble) powder material having
a larger initial average size into a product that can be readily
injected into wood. Milling with 0.5 mm zirconium silicate media
not only quickly reduced further the magnesium stabilized copper
hydroxide product, but this grinding medium was also found to be
effective on other forms of basic copper compounds such as other
stabilized copper hydroxides, copper carbonate, tribasic copper
sulfate, copper oxychloride, and copper oxides. The results of
milling of a variety of materials with the 0.5 mm milling material
described above for 15 minutes are shown in Table 2. Copper
hydroxide material with an initial median size of 2.5 microns was
quickly milled to an injectable material having a median particle
size of 0.3 microns. Additional milling time would doubtless
further reduce the median and average particle size. A copper
carbonate material having a median size of 3.4 microns was milled
to a material having a median size of less than 0.2 microns. FIG. 1
shows the face of wood injected with unmilled product and the face
of wood injected with the milled product. In the color photographs
the plugging is especially visible. A tribasic copper sulfate
material having a median size of 6.2 microns was milled to a
material having a median size of less than 0.2 microns. A copper
oxychloride material having a median size of 3.3 microns was milled
to a material having a median size of 0.4 microns.
[0104] Milling is believed to break up larger particles. It would
also break particles having one large dimension, e.g., rod-like
particles, which are know to have injection problems. Milling can
be combined with, for example, centrifugation to create a more
uniform product. Alternatively, milling can be combined with a
coating process to form a more stable material.
[0105] Specific substantially crystalline (or amorphous sparingly
soluble) copper-containing materials and other copper-containing
materials useful in embodiments of this invention will be described
below. In each instance, the zinc analog is useful for zinc-based
particulates. Generally, the tin analogs can also be useful for
tin-based particulates.
[0106] Copper Oxides--In one embodiment, the substantially
crystalline copper composition in a plurality of copper-based
particulates can comprise one or more copper oxides. Of the copper
oxides, Cu.sub.2O is preferred over CuO, as the Cu.sub.2O is
subject to oxidation by oxygen dissolved in water which appears to
increase the kinetics of dissolution. If the copper-based
particulate material consists essentially of one or more copper
oxides, however, the material will not be sufficiently bioactive.
In one variant, the copper oxide material can have a substantial
amount of one or more of magnesium, zinc, or both, wherein these
cations are either dispersed within the substantially crystalline
(or amorphous sparingly soluble) copper composition or be a
separate phase within a particulate. Generally, magnesium and zinc
co-cations can help stabilize copper hydroxide and prevent its
natural transition to copper oxide. We believe if substantial
amounts of zinc and especially magnesium are included in the
crystalline copper oxide material, it will partially disrupt the
crystal and therefore encourage solubility. Copper oxides are less
preferred than other substantially crystalline (or amorphous
sparingly soluble) copper compounds, because the rate of
dissolution is so slow. If the crystalline copper in the particles
is more than 60% copper oxide, then preferably the particles have a
maximum size of about 50 nanometers, or have a BET surface area of
at least 300 m2/gm, or both. The particulates may need special
treatments and/or properties to provide a bio-active copper
concentration, and are more easily flushed from the wood.
[0107] In any of the below-described embodiments, the substantially
crystalline (or amorphous sparingly soluble) copper composition in
copper-based particulates and/or copper-based particulate material
can further comprise one or more copper oxides. Of the copper
oxides, CuO is preferred over Cu.sub.2O.
[0108] Copper hydroxides--In a preferred embodiment the
substantially crystalline (or amorphous sparingly soluble) copper
composition in a plurality of copper-based particulates can
comprise or consist essentially of copper hydroxides. In a variant
of this, the copper-based particulate material can comprise or
consist essentially of copper hydroxides. Of the copper hydroxides,
copper hydroxide including CuOH (usually not stable) and/or
Cu(OH).sub.2 can be used, though Cu(OH).sub.2 is preferred over
CuOH. In a preferred embodiment of any of the above, the
substantially crystalline (or amorphous sparingly soluble) copper
composition can have a substantial amount of one or more of
magnesium, zinc, or both, wherein these cations are either
dispersed within the substantially crystalline (or amorphous
sparingly soluble) copper composition or be a separate phase within
a particulate.
[0109] Basic Copper Carbonate--In another preferred embodiment the
substantially crystalline copper composition in a plurality of
copper-based particulates can comprise or consist essentially of
alkaline (or "basic") copper carbonates. While various compositions
comprising copper hydroxide and copper carbonate are envisioned,
typically alkaline copper carbonate
is[CUCO.sub.3.times.Cu(OH).sub.2]. In a variant of this, the
copper-based particulate material can comprise or consist
essentially of alkaline copper carbonate. In a preferred embodiment
of any of the above, the substantially crystalline (or amorphous
sparingly soluble) copper composition can have a substantial amount
of one or more of magnesium, zinc, or both, wherein these cations
are either dispersed within the substantially crystalline (or
amorphous sparingly soluble) copper composition or be a separate
phase within a particulate.
[0110] Copper Carbonate--In another embodiment the substantially
crystalline copper composition in a plurality of copper-based
particulates can comprise or consist essentially of copper
carbonate, e.g., CuCO.sub.3. In a variant of this, the copper-based
particulate material can comprise or consist essentially of
alkaline copper carbonate. In a preferred embodiment of any of the
above, the substantially crystalline (or amorphous sparingly
soluble) copper composition can have a substantial amount of one or
more of magnesium, zinc, or both, wherein these cations are either
dispersed within the substantially crystalline (or amorphous
sparingly soluble) copper composition or be a separate phase within
a particulate. Copper carbonate is less preferred than basic copper
carbonate, as the OH groups in the latter help keep the pH
elevated, thereby reducing copper mobility.
[0111] Tribasic Copper Sulfates--In another preferred embodiment
the substantially crystalline copper composition in a plurality of
copper-based particulates can comprise or consist essentially of
basic copper sulfates. In a variant of this, the copper-based
particulate material can comprise or consist essentially of basic
copper sulfates. While various compositions comprising copper
hydroxide and copper sulfate are envisioned, typically alkaline
copper sulfate is [CuSO.sub.433 3Cu(OH).sub.2]. If tribasic copper
sulfate is used, the substantially crystalline (or amorphous
sparingly soluble) copper composition can additionally
advantageously have a substantial amount of one or more of
magnesium, zinc, or both, wherein these cations are either
dispersed within the substantially crystalline (or amorphous
sparingly soluble) copper composition or be a separate phase within
a particulate.
[0112] Alkaline Copper Nitrates--In another embodiment the
substantially crystalline copper composition in a plurality of
copper-based particulates can comprise or consist essentially of
alkaline copper nitrates. In a variant of this, the copper-based
particulate material can comprise or consist essentially of
alkaline copper nitrates. While various compositions comprising
copper hydroxide and copper nitrate are envisioned, typically
alkaline copper nitrate is [Cu(NO.sub.3).sub.2.time-
s.3Cu(OH).sub.2]. If alkaline copper nitrate is used, the
substantially crystalline (or amorphous sparingly soluble) copper
composition can additionally advantageously have a substantial
amount of one or more of magnesium, zinc, or both, wherein these
cations are either dispersed within the substantially crystalline
(or amorphous sparingly soluble) copper composition or be a
separate phase within a particulate. In the most preferred
embodiments of this invention, the wood preservative is
substantially free of copper nitrates, as the nitrogen, may during
the degradation process, eventually act as foodstuff for one or
more bio-organisms.
[0113] Copper Oxychlorides--In another preferred embodiment the
substantially crystalline copper composition in a plurality of
copper-based particulates can comprise or consist essentially of
copper oxychlorides. In a variant of this, the copper-based
particulate material can comprise or consist essentially of copper
oxychlorides. While various compositions comprising copper
hydroxide and copper chloride are envisioned, typically copper
oxychloride is [CuCl.sub.2.times.3Cu(OH).sub- .3]. In a preferred
embodiment of any of the above, the substantially crystalline (or
amorphous sparingly soluble) copper composition can have a
substantial amount of one or more of magnesium, zinc, or both,
wherein these cations are either dispersed within the substantially
crystalline (or amorphous sparingly soluble) copper composition or
be a separate phase within a particulate.
[0114] Copper Borate--In another preferred embodiment the
substantially crystalline copper composition in a plurality of
copper-based particulates can comprise or consist essentially of
copper borate. Copper borate includes basic copper borate. In a
variant of this, substantially crystalline (or amorphous sparingly
soluble) copper composition can have a substantial amount of one or
more of magnesium, zinc, or both, wherein these cations are either
dispersed within the substantially crystalline (or amorphous
sparingly soluble) copper composition or be a separate phase within
a particulate. Generally, the copper borate is advantageously
included in a composition that also comprises copper hydroxide or
one or more of the basic copper anion salts, to help moderate pH
and reduce solubility of the copper borate.
[0115] Copper ferricyanate--In any of the above-described
embodiments, the substantially crystalline (or amorphous sparingly
soluble) copper composition in copper-based particulates and/or
copper-based particulate material can further comprise copper
ferricyanate. This embodiment includes less preferably copper
ferricyanide. Alternatively, the substantially crystalline (or
amorphous sparingly soluble) copper composition in the copper-based
particulates can comprise or consist essentially of copper
ferricyanate, Cu.sub.2[Fe(CN).sub.6]. In another embodiment, the
copper-based particulate material can comprise or consist
essentially of copper ferricyanate.
[0116] Copper Fluorosilicate--The substantially crystalline (or
amorphous sparingly soluble) copper composition in copper-based
particulates and/or copper-based particulate material can comprise
copper fluorosilicate. Alternatively, the substantially crystalline
(or amorphous sparingly soluble) copper composition in the
copper-based particulates can comprise or consist essentially of
copper fluorosilicate. In another embodiment, the copper-based
particulate material can comprise or consist essentially of copper
fluorosilicate.
[0117] Copper Thiocyanate--In any of the above-described
embodiments, the substantially crystalline copper composition in
copper-based particulates and/or copper-based particulate material
can further comprise copper thiocyanate, though it is generally
difficult to manufacture crystalline copper thiocyanate.
Alternatively, the copper composition in the copper-based
particulates can comprise or consist essentially of CuSCN. In
another embodiment, the copper-based particulate material can
comprise or consist essentially of CuSCN.
[0118] Copper diphosphate or Copper pyrophosphate--In any of the
above-described embodiments, the substantially crystalline copper
composition in copper-based particulates and/or copper-based
particulate material can further comprise copper pyrophosphate,
Cu.sub.2P.sub.2O.sub.7. Alternatively, the substantially
crystalline (or amorphous sparingly soluble) copper composition in
the copper-based particulates can comprise or consist essentially
of copper pyrophosphate. In another embodiment, the copper-based
particulate material can comprise or consist essentially of copper
pyrophosphate.
[0119] Copper Cyanate and/or Copper Cyanate--Copper cyanide,
Cu(CN).sub.2, and copper cyanate, Cu(CNO).sub.2, are each a
sparingly soluble copper salt, but they are too dangerous to be
useful for copper-based wood preservative treatments. When even a
small quantity of copper cyanate and/or copper cyanide is used, the
formulation must be basic, that is, contained in an alkaline
formulation.
[0120] The copper-based particulates can comprise or consist
essentially of any of the above listed sparingly soluble copper
compounds. In another preferred embodiment the substantially
crystalline (or amorphous sparingly soluble) copper composition in
the copper-based particulates in a wood preservative formulation
can comprise or consist essentially of a plurality of sparingly
soluble substantially crystalline (or amorphous sparingly soluble)
copper salts selected from copper oxide, copper hydroxides; copper
carbonates, alkaline (or "basic") copper carbonates; alkaline
copper sulfates; alkaline copper nitrates; copper oxychlorides;
copper borates, and mixtures thereof, with the proviso that at
least one of the substantially crystalline (or amorphous sparingly
soluble) copper salts is not a copper oxide. In a variant of this,
the copper-based particulate material can comprise or consist
essentially of one or more sparingly soluble substantially
crystalline copper salts selected from copper hydroxides; copper
carbonates, alkaline (or "basic") copper carbonates; alkaline
copper nitrates; alkaline copper sulfates; copper oxychlorides;
copper borates, and mixtures thereof. In any of the above, the
substantially crystalline (or amorphous sparingly soluble) copper
composition can have a substantial amount of one or more of
magnesium, zinc, or both, wherein these cations are either
dispersed within the substantially crystalline (or amorphous
sparingly soluble) copper composition or be a separate phase within
a particulate.
[0121] In preferred embodiments of the invention, at least some
particulates comprise copper hydroxide, basic copper carbonate, or
both. In more preferred embodiments, the copper hydroxide comprises
between 6 and 20 parts of magnesium per 100 parts of copper, for
example between 9 and 15 parts of magnesium per 100 parts of
copper. Alternatively, in another more preferred embodiments, the
copper hydroxide comprises between 6 and 20 parts total of
magnesium and zinc per 100 parts of copper, for example between 9
and 15 parts total of magnesium and zinc per 100 parts of copper.
In some embodiments, the basic copper carbonate comprises between 6
and 20 parts of magnesium per 100 parts of copper, for example
between 9 and 15 parts of magnesium per 100 parts of copper, or
alternatively between 6 and 20 parts total of magnesium and zinc
per 100 parts of copper, for example between 9 and 15 parts total
of magnesium and zinc per 100 parts of copper. Alternatively or
additionally, in a preferred embodiment, the copper hydroxide
and/or basic copper carbonate comprises between about 0.01 and
about 5 parts of phosphate per 100 parts of copper, for example
between 9 and 15 parts of phosphate per 100 parts of copper.
[0122] In another preferred embodiment, slurry comprises a
sparingly soluble copper salt particulates and also comprises zinc
borate particulates. Preferably at least some of the sparingly
soluble copper salt-based particulates comprise copper borate. It
is known to use a two stage process where a zinc or copper salt is
injected into the wood followed by a second step wherein the borax
is injected and the insoluble metal borate is formed in situ. Such
a complicated, time-consuming, and therefore expensive process is
not sufficiently cost-effective. As the solubility of copper borate
is very pH sensitive, in a preferred embodiment the sparingly
soluble copper salts comprise an alkaline material, e.g., copper
hydroxide or copper carbonate, to reduce the solubility of the
copper borate.
[0123] Soluble Substantially Crystalline Copper Salts--In any of
the above-described embodiments, the substantially crystalline
copper composition in copper-based particulates and/or copper-based
particulate material can further comprise one or more soluble
substantially crystalline copper salts, for example copper sulfate,
copper fluoroborate; copper fluoride, or mixtures thereof, where
the soluble substantially crystalline copper salts phase is
stabilized against dissolution. Alternatively, the substantially
crystalline copper composition in the copper-based particulates can
comprise or consist essentially of one or more soluble
substantially crystalline copper salts, for example, copper
fluoroborate; copper sulfate, copper fluoride, or mixtures thereof,
where the soluble substantially crystalline copper salts phase is
stabilized against dissolution. Such protection may be provided by
encasing the soluble copper salts in a shell or a matrix of
sparingly soluble copper salts or in insoluble copper salts, such
as copper phosphate.
[0124] In another embodiment, the copper-based particles may be
essentially free of halogen, which means that the weight percent of
halogen in the particles is less than about 2.5%. Preferably, the
weight percent of halogen in copper-based particles that are
essentially free of halogen is less than about 1%. The copper-based
particles may be free of halogen.
[0125] Copper Phosphate--In any of the above-described embodiments,
the substantially crystalline copper composition in copper-based
particulates and/or copper-based particulate material can further
comprise the substantially insoluble copper salt copper phosphate,
Cu.sub.3(PO.sub.4).sub.2. Alternatively, the substantially
crystalline (or amorphous sparingly soluble) copper composition in
the copper-based particulates can comprise or consist essentially
of Cu.sub.3(PO.sub.4).sub.2. Generally, in preferred embodiments,
if Cu.sub.3(PO.sub.4).sub.2 is present it is a coating over other
sparingly soluble copper salts, wherein the
Cu.sub.3(PO.sub.4).sub.2 provides a fairly inert coating for a
period of time before it dissolves or partially dissolves. If there
are copper-based-particulates substantially comprising
Cu.sub.3(PO.sub.4).sub.2 and/or copper oxide, the particulates
should be exceedingly small, e.g., less than about 0.05 microns,
preferably less than about 0.04 microns, to provide maximum surface
area to help dissolution of the particles, and the wood treatment
should contain another type of substantially crystalline (or
amorphous sparingly soluble) copper-based particulates, e.g., basic
copper carbonate, copper borate, tribasic copper sulfate, copper
hydroxides, and the like.
[0126] Copper 8-Quinolinolate--In any of the above-described
embodiments, the copper composition in copper-based particulates
and/or copper-based particulate material can further comprise the
insoluble copper salt copper 8-quinolinolate. Alternatively, the
copper composition in the copper-based particulates can comprise or
consist essentially of copper 8-quinolinolate. Generally, in
preferred embodiments, if copper 8-quinolinolate is present it is a
coating over other sparingly soluble copper salts, wherein the
copper 8-quinolinolate provides a fairly inert coating for a period
of time before it dissolves or partially dissolves. If there are
copper-based-particulates substantially comprising copper
8-quinolinolate, the particulates should be exceedingly small,
e.g., less than about 0.01 microns, preferably less than about
0.005 microns, to provide maximum surface area to help dissolution
of the particles.
[0127] In any of the above-described embodiments, the composition
can further comprise copper quinaldate, copper oxime, or both in
particulate form.
[0128] In one embodiment, the copper-based particles comprise a
substantially crystalline copper compound. At least about 20%, 30%,
50%, or 75% of the weight of the copper-based particles may be
composed of the substantially crystalline copper compound. In
another embodiment, essentially all (e.g., more than 90%, for
example more than 95%) of the weight of the copper-based particles
is composed of substantially crystalline copper compound. In
preferred embodiments the particle comprises at least about 20%,
preferably at least about 30%, and more preferably at least about
50%, for example at least about 75% by weight of one or more
sparingly soluble copper salts. In another embodiment, essentially
all (e.g., more than 90%, for example more than 95%) of the weight
of the copper-based particles is composed of substantially
crystalline copper compound(s).
[0129] In one embodiment of the invention, the copper-based
particles are substantially free of at least one of the halogens,
for example, at least one of fluorine, chlorine, bromine, and
iodine. Preferably, the weight percent of the at least one halogen
in particles that are substantially free of the at least one
halogen is less than about 25%, for example, less than about 20%,
15%, 10%, or 5%.
[0130] In one embodiment, the copper-based particles are
essentially free of at least one of the halogens, for example at
least one of fluorine, chlorine, bromine, and iodine. Particles
that are essentially free of at least one halogen have less than
about 2.5% of the at least one halogen. Preferred particles have
less than about 1% of the at least one halogen. In one embodiment,
the copper based particles are free of at least one of the
halogens.
[0131] In another embodiment, the copper-based particles may be
substantially free of halogen. Preferably, the weight percent of
halogen in copper-based particles that are substantially free of
halogen is less than about 25%, for example, less than about 20%,
15%, 10%, or 5%.
[0132] Again, the zinc analogs of the above are useful for the
zinc-based particulates of the alternate embodiments of the
invention. In one embodiment the copper-based particulate material
can further comprise one or more of crystalline zinc salts selected
from zinc hydroxide; zinc oxides; zinc carbonate; zinc oxychloride;
zinc fluoroborate; zinc borate, zinc fluoride, or mixtures thereof.
The zinc salts may be in a separate salt phase, or may be mixed
Cu/Zn salts, or combinations thereof. In preferred embodiments the
particle comprises at least about 40%, preferably at least about
60%, and more preferably at least about 80% by weight of one or
more substantially crystalline (or amorphous sparingly soluble)
copper salts, crystalline zinc salts, or mixtures or combinations
thereof.
[0133] In one embodiment the copper-based particulate preservative
treatment for wood can further comprise zinc-based particulates
comprising one or more of crystalline zinc salts selected from zinc
hydroxide; zinc oxides; zinc carbonate; zinc oxychloride; zinc
fluoroborate; zinc borate, zinc fluoride, or mixtures thereof. The
preferred zinc-based substantially crystalline material are zinc
hydroxide, zinc borate, zinc carbonate, or mixture thereof, which
may be doped with other cations, e.g., from 0.1 to 10% copper, from
0.1 to 10% magnesium, or both, for example, based on the total
weight of the cations in the substantially crystalline (or
amorphous sparingly soluble) material. In preferred embodiments the
particle comprises at least about 40%, preferably at least about
60%, and more preferably at least about 80% by weight of one or
more crystalline zinc salts.
[0134] Preferred embodiments of the invention comprise particles
comprising one or more of copper hydroxide, alkaline copper
carbonate, alkaline copper oxychloride, tribasic copper sulfate,
copper borate, or mixtures thereof. The most preferred embodiments
of the invention comprise particles comprising copper hydroxide,
alkaline copper carbonate, copper borate, or mixtures thereof.
[0135] Coatings for the Copper-Based And Zinc-Based
Particulates.
[0136] In any of the above-described embodiments, the substantially
crystalline copper composition in copper-based particulates and/or
copper-based particulate material can further comprise one or more
materials disposed on the exterior of the particles to inhibit
dissolution of the underlying substantially crystalline (or
amorphous sparingly soluble) copper material at least for a time
necessary to prepare the formulation and inject the prepared wood
treatment composition. Over time, however, there is unfavorable
particle growth via dissolution and precipitation processes and
also particle growth via agglomeration. Also, the particulates are
very susceptible to premature dissolution if the slurry is formed
with an acidic water. In preferred embodiments, either the
particulates containing, for example, alkaline copper carbonate,
copper hydroxide, copper borate, alkaline copper nitrate, copper
oxychloride, tribasic copper sulfate. Additionally or alternatively
the acid-soluble particles are coated with a substantially inert
coating, for example a trace outer coating of e.g. copper phosphate
or copper sulfide, or a coating of a polymeric material such as
dispersants, or with a thin hydrophobic coating, or any combination
thereof. In one embodiment the particles are treated with a
dispersing material which is substantially bound to the
particles.
[0137] The milled copper-based, zinc-based, and/or tin-based
particles described above are readily slurried and injected into
wood after the milling process. Generally, however, milling is done
well before the particles are slurried and injected. The particles
may be shipped in a dry form or in a wet form. The milled particles
may be transported to a site as a dry mix or as a concentrated
slurry, which is then formed into an injectable slurry, and then
after some indeterminate storage time the particles may be injected
into wood. Particulates in solution have a tendency to grow over
time by 1) the thermodynamically driven tendency of sub-micron
particles in solution to grow by a dissolution/reprecipitation
process, where there is a greater tendency for small particles to
slowly dissolve and for the salts to reprecipitate on the larger
crystals. It is not uncommon, in unstabilized slurries, for the
median particle size to increase by 50% over a period of a day or
two. The goal is to simultaneously achieve the critical particle
size, particle size distribution, and particle stability at a cost
where the material can be commercially used and at the point where
the material will be commercially used. Therefore, it is
advantageous to have a coating on the particle to substantially
hinder dissolution of the particle while the particle is slurried.
However, the coating should not overly hinder dissolution of the
particle in the wood matrix. Further, no coating to hinder
dissolution is desirable for copper oxides particulates.
[0138] Inorganic Coating--Generally, the discussion focuses on the
preferred copper-based particulates, but the compositions and
methods are equally applicable to the zinc-based and tin-based
particulates. The substantially crystalline (or amorphous sparingly
soluble) copper-based material, zinc-based material, and/or
tin-based material can be stabilized by a partial or full coating
of an inorganic salt. The manufacturing process is amenable to the
formation of a substantially inert inorganic coating on the
particle that will be of such low thickness that the coating will
not substantially hinder particle dissolution in the wood. The
preferred coatings are very low solubility metal salts of the
underlying metal cations, e.g., copper, zinc, or tin. Exemplary
very low solubility salts include copper sulfide (Ksp=6 E-36),
copper(II) phosphate (Ksp=1 E-37), and copper 8-quinolinolate
(Ksp=2 E-30). The selection between sulfide, 8-quinolinolate, and
phosphate generally depends on which coating shows the greatest
protection for the particular substantially crystalline (or
amorphous sparingly soluble) material, at the particular size
distribution and particle morphology that may exist. A coating of a
very low solubility salt can substantially arrest the
dissolution/reprecipitation process by severely limiting the amount
of copper that can dissolve. The coating, however, is mechanical
protection only. Exposed portions of the underlying substantially
crystalline (or amorphous sparingly soluble) copper-, zinc-, or
tin-based particulates are subject to dissolution. Further, the
inorganic coating is generally at most a few atoms to a few
nanometers in depth.
[0139] An inorganic coating can be formed during and immediately
after the particulate precipitation process, for example by adding
after admixing the dissolved copper solution and the dissolved
anion solution together to form the "precipitation solution", e.g.,
after precipitation of the substantially crystalline (or amorphous
sparingly soluble) particulates has begun. In one embodiment, the
admixed copper-anion solution has a small excess of anions.
Precipitation of the desired copper salts is generally fast, but
adding a phosphate composition (as acid phosphate, or as a
partially neutralized acid phosphate) in an amount to give a
concentration between a few hundred ppm and a few percent by weight
will cause a layer of copper sulfate to form, for example, between
crystals or even over the crystals of the substantially crystalline
copper material. Alternately, a source of sulfide or
8-quinolinolate can be added to the precipitation solution. The
advantage is the newly formed substantially crystalline (or
substantially amorphous) material is fresh and therefore more
reactive toward the added phosphate ions than would be an aged
precipitate. This is not a preferred mechanism, however, because
during milling some of the coating will be abraded away, and some
previously unexposed substantially crystalline (or amorphous
sparingly soluble) material will now be exposed. Additionally, the
amount of material used to get the required concentration of anions
in the precipitation solution is much more than is needed to form a
coating on particulates.
[0140] The particles may be wet-milled using a very fine milling
material and a fluid containing a source of sulfate ions, phosphate
ions, or less preferably (because of odor and handling problems)
sulfide ions. In one preferred embodiment, the wet milling process
uses as the milling fluid a composition comprising between a few
hundred ppm of phosphate to about 6% phosphate, for example between
0.1% phosphate to 3% phosphate. Small amounts of phosphate will
take hours or days to form a completely protective coating, while a
more concentrated solution may form a protective coating in
minutes. Advantageously the milling liquid has a pH between about 6
and about 9.5, for example between about 7 and about 8.5. This high
concentration of phosphate is not wasteful because the milling
fluid can be re-used, and also because the milling fluid is a
relatively small volume. Such milling in the phosphate-containing
milling fluid, for example for a time ranging from 5 minutes to 4
hours, typically from 10 minutes to 30 minutes, will promote the
formation of a thin coating of copper phosphate over the
substantially crystalline (or amorphous sparingly soluble) copper
material. As the coating is probably only a few atoms in thickness,
the coating will dissolve in good time within the wood so as not to
impair exposure of the underlying substantially crystalline copper
material in the wood. Alternatively, a source of sulfide or
8-quinolinolate can be added to the milling liquid. Sulfide is
again not preferred, for safety reasons. If sulfide is added the pH
should be above 8, preferably above 9. The addition of the
8-quinolinolate is not an inorganic coating, and the adherence of a
coating of an organic nature may be beneficial.
[0141] In another embodiment, the copper-based particles after
milling can be exposed to a rinse solution that contains between a
few hundred ppm of phosphate to about 6% phosphate, for example
between 0.1% phosphate to 3% phosphate. U.S. Pat. No. 4,404,169
describes a process of producing phosphate-stabilized particulates.
Phosphate ions are added to a suspension of copper oxychloride in
an aqueous phase. The copper oxychloride is then reacted with
alkali metal hydroxide or alkaline earth metal hydroxide, and the
cupric hydroxide precipitated as a result of the suspension is
washed and then re-suspended and subsequently stabilized by the
addition of acid phosphate to adjust a pH value of 7.5 to 9. The
suspended copper oxychloride is reacted in the presence of
phosphate ions in an amount of 1 to 4 grams per liter of the
suspension and at a temperature of 20.degree. C. to 25.degree. C.
and the resulting cupric hydroxide is stabilized with phosphate
ions in an amount of 3 to 6 grams per liter of the suspension.
Advantageously, the rinse liquid has a pH between about 6 and about
9.5, for example between about 7 and about 8.5. After contacting
the particles, advantageously for at least a minute or more, this
rinse solution can itself be rinsed away with fresh water.
Alternatively, a source of sulfide or 8-quinolinolate can be added
to the rinse liquid. If sulfide is added, the pH should be above 8,
preferably above 9.
[0142] In another embodiment, the copper-based particles after
milling can be exposed to a rinse solution that contains between a
few hundred ppm of phosphate to about 1% phosphate, for example
between 0.1% phosphate to 0.5% phosphate ions (by weight of the
rinse). After contacting the particles, advantageously, for at
least a minute or more, this rinse solution can itself be rinsed
away with fresh water, and the particles can be rinsed with a
solution comprising a few hundred ppm of soluble copper to about 1%
soluble copper, for example between 0.1% phosphate to 0.5% soluble
copper ions. This copper-containing solution can be rinsed off with
a minimum quantity of water, and the rinsed particulates can be
re-exposed to a rinse solution that contains between a few hundred
ppm of phosphate to about 1% phosphate, for example, between 0.1%
phosphate to 0.5% phosphate ions. Advantageously the fluids have a
pH between about 6 and about 9.5, for example between about 7 and
about 8.5.
[0143] In some embodiments some copper-containing particulates are
stabilized with a coating, and some particulates are not subject to
such stabilization. For example, advantageously only the very small
particulates, e.g., smaller than about 0.05 microns in diameter,
are stabilized by a low-solubility covering layer.
[0144] The invention also embraces embodiments where particles are
substantially free of an inorganic coating.
[0145] Organic Coating--Copper-based particles (or zinc-based
particles, or tin-based particles, or mixtures thereof) of the
invention may be used directly to preserve wood or wood products.
The copper-based, zinc-based, or tin-based particles or mixtures
thereof may additionally comprise an organic coating, e.g., an
organic layer that partially or completely covers the exterior
surface area of the particulates. The protective organic layer may
additionally function as one or more other active agents, as
discussed infra. This organic coating can comprise a variety of
materials having a variety of functions over and above being an
organic layer acting as a protective layer temporarily isolating
the sparingly soluble salt from the aqueous carrier to slow
dissolution of particulates in the slurry, including: 1) an organic
biocide carrier, 2) a dispersing/anti-aggregation/wettability
modifying agent, 3) one or more biocides, or any combinations
thereof. The oil coating can comprise for example light oils,
dehydrating oils, polymeric films, organic biocides, disbursing
agents, anti-coagulating agents, or mixtures thereof.
[0146] In one embodiment, at least some of the particulates are
coated with an organic protective coating. The particulates may
have been previously coated with an inorganic coating. The organic
coating should provide a thin layer of organic material that at
least partially coats the particulate and for a period of time
reduces the tendency of the sparingly soluble copper, zinc, and/or
tin salts in the particulates to dissolve in the slurry.
[0147] Generally such coatings are extremely thin, with a
particulate comprising, for example, between about 0.1% to about
50% by weight, more typically from about 0.5% to about 10%, of the
weight of the above-mentioned sparingly soluble salts. The coating
may cover only a portion of the exterior surface area, for example
only 50% of the external surface area of a particulate.
[0148] The hydrocarbon composition can include one or more
hydrophobic oils, and/or may comprise an organic compound having
one or more polar functional groups which increase adherence of,
for example, mono- and/or poly-carboxylic acids that may be at
least partially neutralized with a metal such as a fatty acid or a
polycarylic polymer, a surfactant and/or a disbursing agent,
amphoteric agents, an organic biocide including an amine, azole,
triazole, or any other organic biocides, a film-forming polymer
such as a sulfonated ionomer, or mixtures thereof. These and other
organic and/or organometallic components that form an organic layer
will generally be referred to as a "hydrocarbon layer" or
"hydrocarbon composition."
[0149] An organic coating may be formed by contacting particulates
with a hydrocarbon composition containing the materials to be
deposited onto the exterior surface of the particle. The contacting
may occur in a slurry or may be done with a paste of water-wetted
particulates or may be done with dried particulates. The less free
water, the easier it is to promote adherence between the
hydrocarbon composition to the particulates.
[0150] Heating a mixture of particulates and the hydrocarbon
composition will also help the hydrocarbon composition wet and
adhere to the particulates. Advantageously, in one embodiment most
of the solvent of the hydrocarbon composition is volatile and is
removed prior to injection of the particulates into the wood. This
will leave a thin layer of a more concentrated biocide in heavier
oils and/or binders than was found in the hydrocarbon/biocide
composition. The organic coating generally becomes more adherent if
the coated particulates are allowed to age, and/or are subjected to
heat, for example, to 35.degree. C. or above for a period of an
hour, for example.
[0151] Incorporating some solvents, typically polar solvents, e.g.,
at least 10%, for example, at least 30% or at least 50% by weight
of solvents such as one or more of alcohols, amides, ketones,
esters, ethers, glycols, and such into the particulates may help
the hydrocarbon layer composition wet the particulates, and will
allow thinner hydrocarbon layers to be deposited. Solvents are
lower molecular weight and higher volatility than oils, and
solvents may be stripped from the organic coating before slurrying
the particles or during kiln drying of the wood. The hydrocarbon
composition may therefore comprise optional solvents and/or
diluents, for example, a mixture of an oily or oil-type
organochemical compound and a solvent of low volatility and/or a
polar organochemical solvent or solvent mixture. Organochemical
oils which are preferably employed are oily or oil-type solvents
with an evaporation number of above 35 and a flash point of above
30.degree. C., preferably above 45.degree. C. Such water-insoluble,
oily and oil-type solvents of low volatility which are used are
suitable mineral oils or their aromatic fractions or
mineral-oil-containing solvent mixtures, preferably white spirit,
petroleum and/or alkyl benzene. Mineral oils include those with a
boiling range of from 170 to 220.degree. C., spindle oil with a
boiling range of from 250 to 350 C, petroleum and aromatics with a
boiling range of from 160 to 280.degree. C., oil of turpentine and
the like. In one embodiment, liquid aliphatic hydrocarbons with a
boiling range of from 180 to 210.degree. C. or high-boiling
mixtures of aromatic and aliphatic hydrocarbons with a boiling
range of 180 to 220.degree. C. and/or spindle oil and/or
monochloronaphthalene are used, for example, a
monochloronaphthalene. The organic oily or oil-type solvents of low
volatility and with an evaporation number of above 35 and a flash
point of above 30.degree. C., preferably above 45.degree. C., can
be replaced in part by organochemical solvents of high or medium
volatility, with the proviso that the preferred solvent mixture
also has an evaporation number of above 35 and a flashpoint of
above 30.degree. C., preferably 45.degree. C., and that the
biocides and/or other compounds are soluble or emulsifiable in this
solvent/oil mixture. In one embodiment, aliphatic organochemical
solvents which contain hydroxyl and/or ester and/or ether groups
are used, such as, for example, glycol ethers, esters or the like.
Advantageously the hydrocarbon mixture comprises binders to wet and
adhere to the particulate, for example, synthetic resins binding
drying oils including linseed oil, and also binders comprising, an
acrylate resin, a vinyl resin, for example polyvinyl acetate,
polyester resin, polycondensation or polyaddition resin,
polyurethane resin, alkyd resin or modified alkyd resin, preferably
of medium oil length, phenol resin, hydrocarbon resin such as
indene/coumarone resin, silicone resin, drying vegetable and/or
drying oils and/or physically drying binders based on a natural
and/or synthetic resin. Pertinent agricultural drying oils include
linseed, soybean, canola, rapeseed, sunflower, tung and castor
oils.
[0152] This organic coating can comprise a variety of materials
having a variety of functions, including, but not limited to,
surface-active agents and organic biocides.
[0153] Surface-Active Agents--Agents improving the suspension of
the particulates include dispersants such as phenyl sulfonates,
alkylnaphthalene sulfonates and polymerized naphthalene sulfonates,
polyacrylic acids and their salts, polyacrylamides,
polyalkoxydiamine derivatives, polyethylene oxides, polypropylene
oxide, polybutylene oxide, taurine derivatives and their mixtures,
and sulfonated lignin derivatives. Surfactants include anionic
surfactants, cationic surfactants, nonionic surfactants, or
combinations thereof. Polyethyleneimine can act as a surfactant or
a stabilizer and will also chelate copper. Dispersants can be used
at 0.1% to 50%, preferably 0.5% to 20% or 5-10% of the particulate
product.
[0154] Organic Biocides--As previously stated, the particles may be
combined with one or more additional moldicides or more generally
biocides, to provide added biocidal activity to the wood or wood
products. Preferred preservative treatments comprise copper-based
particles having one or more additional organic biocide(s) that are
bound, such as by adsorption, to a surface of the particles. Wood
and wood products may be impregnated substantially homogeneously
with (a) copper-based particles of the invention and (b) a material
having a preservative function, such as a material bound to the
surface of the copper-based particles. By substantially
homogeneously we mean averaged over a volume of at least one cubic
inch, as on a microscopic scale there will be volumes having
particulates disposed therein and other volumes within the wood
that do not have particulates therein. Thus, the distribution of
preservative function within the wood or wood product is preferably
not heterogeneous.
[0155] The absolute quantity of organic biocides is very low. In
general, the biocides are present in a use concentration of from
0.1% to 20%, preferably 1% to 5%, based on the weight of the copper
salts. The sparingly soluble copper-salt particulates of this
invention are typically expected to be added to wood in an amount
equal to or less than 0.25 pounds as copper per cubic foot. The
organic biocide(s) at a 4% loading relative to the copper are
present at about 0.16 ounces or about 3 to 4 milliliters of biocide
per cubic foot. The organic biocides are often insoluble in water,
which is the preferred fluid carrier for injecting the wood
preservative treatment into wood, so getting adequate distribution
of the biocide within the wood matrix is problematic. In prior art
formulations, the wood preservative may be, for example, admixed in
a large excess of oil, and the oil emulsified with water and
admixed with the soluble copper for injection into the wood.
Problems arise if the injection is delayed, or if the slurry has
compounds which break the emulsion, and the like.
[0156] The greatest benefit is that a portion or all of the organic
biocides incorporated into the wood preservative treatment can
advantageously be coated on to the particulates. By adhering the
biocides on particulates, a more even distribution of biocide in
ensured, and the copper is disposed with the biocide and therefore
is best positioned to protect the biocide from those bio-organisms
which may degrade or consume the biocide. Finally, a formulation
with biocide adhering to particulates does not face the instability
problems that emulsions face.
[0157] Generally, so little of the organic biocide is needed that
it is dissolved in and diluted with sufficient hydrocarbon material
to make the phase of appreciable size. The organic material/biocide
mixture can be contacted with particulates in a slurry, though it
may be difficult to have the hydrocarbon phase adhere to the
particulates. Pretreating the particulates with a coating of for
example 8-quinolinolate will greatly increase the likelihood of the
biocide absorbing on the particulate. The particulates may be
concentrated, for example, to an at least 40% by weight
particulates in water slurry before admixing in with the
hydrocarbon/biocide composition.
[0158] The biocides can be any of the known organic biocides.
Exemplary materials having a preservative function include
materials having at least one of one or more: azoles; triazoles;
imidazoles; pyrimidinyl carbinoles; 2-amino-pyrimidines;
morpholines; pyrroles; phenylamides; benzimidazoles; carbamates;
dicarboximides; carboxamides; dithiocarbamates;
dialkyldithiocarbamates; N-halomethylthio-dicarboximide- s; pyrrole
carboxamides; oxine-copper, guanidines; strobilurines; nitrophenol
derivatives; organo phosphorous derivatives; polyoxins;
pyrrolethioamides; phosphonium compounds; polymeric quaternary
ammonium borates; succinate dehydrogenase inhibitors;
formaldehyde-releasing compounds; naphthalene derivatives;
sulfenamides; aldehydes; quaternary ammonium compounds; amine
oxides, nitroso-amines, phenol derivatives; organo-iodine
derivatives; nitrites; quinolines such as 8-hydroxyquinoline
including their Cu salts; phosphoric esters; organosilicon
compounds; pyrethroids; nitroimines and nitromethylenes; and
mixtures thereof.
[0159] Exemplary biocides include Azoles such as azaconazole,
bitertanol, propiconazole, difenoconazole, diniconazole,
cyproconazole, epoxiconazole, fluquinconazole, flusiazole,
flutriafol, hexaconazole, imazalil, imibenconazole, ipconazole,
tebuoonazole, tetraconazole, fenbuconazole, metconazole,
myclobutanil, perfurazoate, penconazole, bromuconazole, pyrifenox,
prochloraz, triadimefon, triadlmenol, triffumizole or
triticonazole; pyrimidinyl carbinoles such as ancymidol, fenarimol
or nuarimol; chlorothalonil; chlorpyriphos;
N-cyclohexyldiazeniumdioxy; dichlofluanid; 8-hydroxyquinoline
(oxine); isothiazolone; imidacloprid;
3-iodo-2-propynylbutylcarbamate tebuconazole;
2-(thiocyanomethylthio) benzothiazole (Busan 30); tributyltin
oxide; propiconazole; synthetic pyrethroids; 2-amino-pyrimidines
such as bupirimate, dimethirimol or ethirimol; morpholines such as
dodemorph, fenpropidin, fenpropimorph, spiroxanin or tridemorph;
anilinopyrimdines such as cyprodinil, pyrimethanil or mepanipyrim;
pyrroles such as fenpiclonil or fludioxonil; phenylamides such as
benalaxyl, furalaxyl, metalaxyl, R-metalaxyl, ofurace or oxadixyl;
benzimidazoles such as benomyl, carbendazim, debacarb, fuberidazole
or thiabendazole; dicarboximides such as chlozolinate,
dichlozoline, iprdine, myclozoline, procymidone or vinclozolin;
carboxamides such as carboxin, fenfuram, flutolanil, mepronil,
oxycarboxin or thifluzamide; guanidines such as guazatne, dodine or
iminoctadine; strobilurines such as azoxystrobin, kresoxim-methyl,
metominostrobin, SSF-129, methyl
2-[(2-trifluoromethyl)pyrid-yloxymethyl]- -3methoxycacrylate or
2-[.alpha.{[(.alpha.-methyl-3-trifluoromethyl-benzyl-
)imino]oxy}-o-toly]glyoxylic acid-methylester-o-methyloxime
(trifloxystrobin); dithiocarbamates such as ferbam, mancozeb,
maneb, metiram, propineb, thiram, zineb, or ziram;
N-halomethylthio-dicarboximid- es such as captafol, captan,
dichlofluanid, fluorormide, folpet or tolfluanid; nitrophenol
derivatives such as dinocap or nitrothal-isopropyl; organo
phosphorous derivatives such as edifenphos, iprobenphos,
isoprothiolane, phosdiphen, pyrazophos or toclofos-methyl; and
other compounds of diverse structures such as aciberolar-S-methyl,
anilazine, blasticidin-S, chinomethionat, chloroneb,
chlorothalonil, cymoxanil, dichlone, dicomezine, dicloran,
diethofencarb, dimethomorph, dithianon, etridiazole, famoxadone,
fenamidone, fentin, ferimzone, fluazinam, flusuffamide, fenhexamid,
fosetyl-alurinium, hymexazol, kasugamycin, methasuifocarb,
pencycuron, phthalide, polyoxins, probenazole, propamocarb,
pyroquilon, quinoxyfen, quintozene, sulfur, triazoxide,
tricyclazole, triforine, validamycin, (S)-5-methyl-2-methylth-
io-5-phenyl-3-phenyl-amino-3,5-dihydroimidazol-4-one (RPA 407213),
3,5-dichloro-N-(3-chlro-1-ethyl-1-methyl-2-oxopropyl)-4-methylbenzamide
(RH7281),
N-alkyl-4,5-dimethyl-2-timethylsilylthiophene-3-carboxamide (MON
65500),
4-chloro-4-cyano-N,N-dimethyl-5-p-tolylimidazole-1-sulfonami- de
(IKF-916),
N-(1-cyano-1,2-dimethylpropyl)-2-(2,4dichlorophenoxy)-propio-
namide (AC 382042), or iprovalicarb (SZX 722). Also included are
the biocides including pentachlorophenol, petroleum oils,
phenothrin, phenthoate, phorate, as well as trifluoromethylpyrrole
carboxamides and trifluoromethylpyrrolethioamides described in U.S.
Pat. No. 6,699,818; Triazoles such as amitrole, azocylotin,
bitertanol, fenbuconazole, fenchlorazole, fenethanil,
fluquinconazole, flusilazole, flutriafol, imibenconazole, isozofos,
myclobutanil, metconazole, epoxyconazole, paclobutrazol,
(.+-.)-cis-1-(4-chlorophenyl)-2-(1H-1,2,4-triazol-1-yl)-cy-
cloheptanol, tetraconazole, triadimefon, triadimenol,
triapenthenol, triflumizole, triticonazole, uniconazole and their
metal salts and acid adducts; Imidazoles such as Imazalil,
pefurazoate, prochloraz, triflumizole,
2-(1-tert-butyl)-1-(2-chlorophenyl)-3-(1,2,4-triazol-1-yl)--
propan-2-ol, thiazolecarboxanilides such as
2',6'-dibromo-2-methyl-4-trifl-
uoromethoxy-4'-trifluoromethyl-1,3-thiazole-5-carboxanilide;
fungicides such as azaconazole, bromuconazole, cyproconazole,
dichlobutrazol, diniconazole, hexaconazole, metconazole,
penconazole, epoxyconazole, methyl
(E)-methoximino[.alpha.-(o-tolyloxy)-o-tolyl)]acetate, methyl
(E)-2-{2-[6-(2-cyanophenoxy)-pyrimidin-4-yl-oxy]phenyl}-3-methoxyacrylate-
, methfuroxam, carboxin, fenpiclonil,
4(2,2-difluoro-1,3-benzodioxol-4-yl)- -1H-pyrrole-3-carbonitrile,
butenafine, and 3-iodo-2-propynyl-n-butylcarba- mate (IPBC);
triazoles such as described in U.S. Pat. Nos. 5,624,916, 5,527,816,
and 5,462,931; the biocides described in U.S. Pat. No. 5,874,025;
5-[(4-chlorophenyl)methyl]-2,2-dimethyl-1-(1H-1,2,4-triazol-1--
yl-methyl)cyclopentanol;
Methyl(E)-2-[2-[6-(2-cyanophenoxy)pyrimidin-4-ylo-
xy]phenyl]3-methoxyacrylate;
methyl(E)-2-[2-[6-(2-thioamidophenoxy)pyrimid-
in-4-yloxy]phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[6-(2-fluorophenoxy)p-
yrimidin-4-yloxy]phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[6-(2,6-difluor-
ophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[3-(pyrimidin-2-yloxy)phenoxy]phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[3-(5-methylpyrimidin-2-yloxy)-phenoxy]phenyl]-3-methoxyac-
rylate;
methyl(E)-2-[2-[3-(phenylsulphonyloxy)phenoxy]phenyl]-3-methoxyacr-
ylate,
methyl(E)-2-[2-[3-(4-nitrophenoxy)phenoxy]phenyl]-3-methoxyacrylate-
; methyl(E)-2-[2-phenoxyphenyl]-3-methoxyacrylate;
methyl(E)-2-[2-(3,5-dim-
ethylbenzoyl)pyrrol-1-yl]-3-methoxyacrylate;
methyl(E)-2-[2-(3-methoxyphen- oxy)phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-(2-phenylethen-1-yl)-phenyl]- -3-methoxyacrylate;
methyl(E)-2-[2-(3,5-dichlorophenoxy)pyridin-3-yl]-3-me-
thoxyacrylate;
methyl(E)-2-(2-(3-(1,1,2,2-tetrafluoroethoxy)phenoxy)phenyl-
)-3-methoxyacrylate;
methyl(E)-2-(2-[3-(alphahydroxybenzyl)phenoxy]phenyl)-
-3-methoxyacrylate;
methyl(E)-2-(2-(4-phenoxypyridin-2-yloxy)phenyl)-3-met-
hoxyacrylate;
methyl(E)-2-[2-(3-n-propyloxyphenoxy)phenyl]-3-methoxyacryla- te;
methyl(E)-2-[2-(3-isopropyloxyphenoxy)phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[3-(2-fluorophenoxy)phenoxy]phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-(3-ethoxyphenoxy)phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-(4-tert-butylpyridin-2-yloxy)phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[3-(3-cyanophenoxy)phenoxy]phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[(3-methylpyridin-2-yloxymethyl)phenyl]-3-methoxyacrylate;
methyl(E)-2-[2-[6-(2-methylphenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacr-
ylate;
methyl(E)-2-[2-(5-bromopyridin-2-yloxymethyl)phenyl]-3-methoxyacryl-
ate;
methyl(E)-2-[2-(3-(3-iodopyridin-2-yloxy)phenoxy)phenyl]-3-methoxyacr-
ylate;
methyl(E)-2-[2-[6-(2-chloropyridin-3-yloxy)pyrimidin-4-yloxy]phenyl-
]-3-methoxyacrylate;
(E),(E)-methyl-2-[2-(5,6-dimethylpyrazin-2-ylmethoxim-
inomethyl)phenyl]-3-methoxyacrylate;
(E)-methyl-2-{2-[6-(6-methylpyridin-2-
-yloxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate;
(E),(E)-methyl-2-{2-[(3-methoxyphenyl)methyloximinomethyl]phenyl}-3-metho-
xyacrylate;
(E)-methyl-2-{2-[(6-(2-azidophenoxy)-pyrimidin-4-yloxy]phenyl}-
-3-methoxyacrylate;
(E),(E)-methyl-2-{2-[(6-phenylpyrimidin-4-yl)-methylox-
iminomethyl]phenyl}-3-methoxyacrylate;
(E),(E)-methyl-2-{2-[(4-chloropheny-
l)-methyloximinomethyl]phenyl}-3-methoxyacrylate;
(E)-methyl-2-{2-[6-(2-n--
propylphenoxy)-1,3,5-triazin-4-yloxy]phenyl}-3-methoxyacrylate;
(E),(E)-methyl-2-{2-[(3-nitrophenyl)methyloximinomethyl]phenyl}-3-methoxy-
acrylate; Succinate dehydrogenase inhibitors such as Fenfuram,
furcarbanil, cyclafluramid, furmecyclox, seedvax, metsulfovax,
pyrocarbolid, oxycarboxin, shirlan, mebenil (mepronil), benodanil,
and flutolanil; Benzimidazoles, such as carbendazim, benomyl,
furathiocarb, fuberidazole, thiophonatmethyl, thiabendazole or
their salts; Morpholine derivatives, such as tridemorph,
fenpropimorph, falimorph, dimethomorph, dodemorph; aldimorph,
fenpropidine and their arylsulphonates, such as, for example,
p-toluenesulphonic acid and p-dodecylphenylsulphonic acid;
Benzothiazoles, such as 2-mercaptobenzothiazole; Benzamides, such
as 2,6-dichloro-N-(4-trifluoromethylbenzyl)-benzamide; Formaldehyde
and formaldehyde-releasing compounds, such as benzyl alcohol
mono(poly)-hemiformal, oxazolidine, hexa-hydro-S-triazines,
N-methylolchloroacetamide, paraformadehyde, nitropyrin, oxolinic
acid, tecloftalam; Tris-N-(cyclohexyldiazeneiumdioxy)-aluminium;
N-(cyclohexyldiazeneiumdioxy)-tributyltin;
N-octyl-isothiazolin-3-one; 4,5-trimethylene-isothiazolinone;
4,5-benzoisothiazolinone; N-methylolchloroacetamide; Pyrethroids,
such as allethrin, alphamethrin, bioresmethrin, byfenthrin,
cycloprothrin, cyfluthrin, decamethrin, cyhalothrin, cypermethrin,
deltamethrin, alpha-cyano-3-phenyl-2-methylben- zyl
2,2-dimethyl-3-(2-chloro-2-trifluoro-methylvinyl)cyclopropane-carboxyl-
ate, fenpropathrin, fenfluthrin, fenvalerate, flucythrinate,
flumethrin, fluvalinate, permethrin, resmethrin and tralomethrin;
Nitroimines and nitromethylenes, such as
1-[(6-chloro-3-pyridinyl)-methyl]-4,5-dihydro-N--
nitro-1H-imidazol-2-amine (imidacloprid), and
N-[(6-chloro-3-pyridyl)methy-
l]-N.sup.2-cyano-N.sup.1-methylacetamide (NI-25); Quaternary
ammonium compounds, such as didecyldimethylammonium salts,
benzyldimethyltetradecy- lammonium chloride,
benzyldimethyldodecylammonium chloride, and
didecyldimethaylammonium chloride; Phenol derivatives, such as
tribromophenol, tetrachlorophenol, 3-methyl-4-chlorophenol,
3,5-dimethyl-4-chlorophenol, phenoxyethanol, dichlorophene,
o-phenylphenol, m-phenylphenol, p-phenylphenol,
2-benzyl-4-chlorophenol and their alkali metal and alkaline earth
metal salts; iodine derivatives, such as diiodomethyl p-tolyl
sulphone, 3-iodo-2-propynyl alcohol,
4-chloro-phenyl-3-iodopropargyl formal, 3-bromo-2,3-diiodo-2-pro-
penyl ethylcarbamate, 2,3,3-triiodoallyl alcohol,
3-bromo-2,3-diiodo-2-pro- penyl alcohol, 3-iodo-2-propynyl
n-butylcarbamate, 3-iodo-2-propynyl n-hexylcarbamate,
3-iodo-2-propynyl cyclohexyl-carbamate, 3-iodo-2-propynyl
phenylcarbamate; Microbicides having an activated halogen group,
such as chloroacetamide, bronopol, bronidox, tectamer, such as
2-bromo-2-nitro-1,3-propanediol, 2-bromo-4'-hydroxy-acetophenone,
2,2-dibromo-3-nitrile-propionamide, 1,2-dibromo-2,4-dicyanobutane,
.beta.-bromo-.beta.-nitrostyrene; and combinations thereof. These
are merely exemplary of a few classes of the known and useful
biocides, and the list could easily extend for pages.
[0160] The preferred biocides are oil-soluble, and include
quaternary ammonium compounds including, for example,
didecyldimethylammonium salts; azoles/triazoles including, for
example, N-alkylated tolytriazoles, metconazole, imidacloprid,
hexaconazole, azaconazole, propiconazole, tebuconazole,
cyproconazole, bromoconazole, and tridemorph tebuconazole;
moldicides; HDO available commercially by BASF, or mixtures
thereof. Biocides such as tebuconazole are quite soluble in common
organic solvents, while others such as chlorothalonil possess only
low solubility.
[0161] To apply the biocide to particulates, the
biocide/hydrocarbon composition is admixed, taking care that the
biocide is dispersed and preferably solubilized in the hydrocarbon
composition. The biocide/hydrocarbon composition can be prepared in
a manner known per se, for example, by mixing the active compounds
with the solvent or diluent, emulsifier, dispersant and/or binder
or fixative, water repellant, and, if appropriate, dyes and
pigments and other processing auxiliaries. Then, the
biocide/hydrocarbon composition is admixed with particulates, where
the particulates can be suspended in a slurry, be wet, or be dry.
The composition is mixed to aid the wetting of and distribution of
the biocide/hydrocarbon composition to particulates. The
composition may be heated, for example to about 40.degree. C., and
is also beneficially allowed to sit for a period ranging from
minutes to hours. The mixture can then be incorporated into a
slurry or be dried or formulated into a stable concentrated slurry
for shipping.
[0162] In an alternative embodiment, the biocide/hydrocarbon
composition is applied as a spray or aerosol onto individual
particles, such as particles suspended in a gas stream. These
coated particulates are then treated to prevent coalescence by, for
example, drying the oil to remove tackiness, or coating the
particle with other adjuvants such as anticoagulants, wettability
agents, dispersibility agents, and the like. Such a product can be
stored, shipped, and sold as a dry pre-mix.
[0163] In another embodiment, the particles are wetted with a light
hydrocarbon material, which may or may not contain biocide, and the
hydrocarbon material is then substantially removed by washing or
drying, leaving a very thin layer of hydrocarbon residue that may
range, for example, from 1 to 30 nanometers thick. Such a very thin
layer will have negligible tackiness and negligible weight, but
will protect the particulate from dissolution and will discourage
coagulation in the slurry.
[0164] Alternate Organic Biocide Carrier--In another embodiment,
only a fraction of the particulates, be they copper-based,
zinc-based, or tin-based, may be coated with the
hydrocarbon/biocide combination. Some precipitation techniques are
known to produce salts having high porosity, and these high
porosity salts can absorb a substantial quantity of the biocide
therein without forming a tacky coating.
[0165] In another embodiment, the organic biocide/hydrocarbon
composition is contacted with a porous inert particulate carrier,
for example 0.1 micron in diameter high porosity alumina, silica,
zeolites, diatomaceous earth, attapulgite clay, or the like. Such
material is readily available. For example, U.S. Pat. No. 5,527,423
disclosed alumina with a maximum particle size below 0.3 microns,
having high porosity as evidenced by a BET surface area of several
hundred square meters per gram, and shows this material can be made
into a stable slurry. Preferred zeolites include Ag, Zn or
Cu-containing zeolites, which themselves have a biocidal activity.
These carrier materials are inexpensive, they do not contribute
bio-nourishment as does the polymeric nanoparticles, and the rigid
alumina/silica/zeolite/diatom/clay particulates will hold the
biocides within the pores thereof during preparation of the slurry
and injection of the slurry, or for example during admixing with
glue and/or resins to make wood composites. Therefore, such inert
carrier/organic biocide particulates and, additionally or
alternatively, biocidal zeolite/organic biocide particulates would
be useful even with the soluble copper wood preservative treatments
in commercial use today. Such particulates advantageously have a
solid, typically insoluble, crystalline structure that is
advantageously between about 0.01 to about 0.3 microns in average
diameter, for example, between about 0.05 to about 0.2 microns in
average diameter. A method of manufacturing said particulates is to
pull a vacuum on a quantity of dry carrier material, and then
introduce thereto a composition comprising a major portion (e.g.,
50% to 90%) of solvent(s), advantageously a minor portion (e.g., 5%
to 48%) of oil(s), and including between 1% and 40% of organic
biocides. The composition is mixed with the inert carrier and
pressure may be exerted to fill the pores of the inert carrier
material with the composition. Then, the solvents and optionally
some of the oils may be removed by drying, heat, or by vacuum.
Assuming 30% effective porosity in an alumina carrier is filled to
one third with a hydrocarbon/biocide composition having 20% by
weight of biocide, the total amount of biocide carrier material
needed to treat 100 cubic feet of wood would be about 1 to 2 cups
of alumina. Beneficially, organic biocide is slowly leached from
the particulates. The biocide formulation in an inert particulate
carrier advantageously comprises oils to help transport biocide
from the center of the particulate to the exterior of the
particulate, and/or may include binders to increase the tenacity of
the biocide to the particulates. These particulates will protect
the biocide dispersed within the pores thereof, and will reduce the
leach rate of the biocide. These particulates are an improvement
over emulsions in that they ensure a stable formulation and uniform
dispersion of the organic biocides in wood. The carrier material,
for example alumina, can be milled with the same equipment used to
mill the copper salt containing particulates. These
biocide-containing polymers can then be slurried with the
copper-based particulates of the current invention and both solids
can be injected. The advantage of this process is that the carrier,
for example, alumina, can be separately prepared and treated so
that the alumina will not be tacky, by, for example, driving off
the lighter oils and leaving only a very thin layer of biocide
within the pores of the carrier. A second advantage is that the
alumina/biocide can be used as a filler in a premix, thereby
encouraging mixing properties.
[0166] An exemplary preservative of the invention comprises a
flowable material comprising copper-based particles of the
invention. Exemplary flowable materials include liquids, emulsions,
slurries, and suspensions.
[0167] In one embodiment, a preservative of the invention comprises
one or more materials additional to the copper-based particles, the
additional materials preferably also providing a preservative
function. For example, an exemplary preservative comprises an
emulsion comprising the copper-based particles, where at least one
phase of the emulsion may comprise one or more materials having a
preservative function. Exemplary materials having a preservative
function include materials having at least one of one or more
triazole groups, one or more quaternary amine groups, and one or
more nitroso-amine group. Mixtures of these materials may be used.
Preferred preservative materials inhibit organisms that may be
resistant to copper-based preservatives. Biocides useful in wood or
wood product preservation are preferred materials. Preferred
preservatives comprise copper-based particles comprising one or
more materials having a preservative function that are bound, such
as by adsorption, to a surface of the particles. Wood and wood
products may be impregnated substantially homogeneously with (a)
copper-based particles of the invention and (b) a material having a
preservative function, such as a material bound to the surface of
the copper-based particles. Thus, the distribution of preservative
function within the wood or wood product is made more heterogeneous
by being absorbed onto the particulates.
[0168] Finally, in one embodiment the wood preservative treatment
may comprise a portion of the organic biocide coated on the
copper-based particulates and another portion of the organic
biocide with a particulate inert carrier. The carrier particulates
containing organic biocides and/or the copper-based particulates
may be treated to reduce tackiness.
[0169] Injectable Slurry
[0170] In a variation of the invention, the slurry comprises: a
liquid carrier; injectable solid particulates comprising one or
more organic biocides; and one or more soluble copper salts or
complexes including the soluble copper treatments described in the
prior art. The injectable particulates can be copper-based
particulates, zinc-based particulates, tin-based particulates,
inert carrier-based particulates, bioactive zeolite-based
particulates, or mixtures thereof. The particulates in this variant
of the invention are primarily carriers for the organic biocides.
An exemplary particle comprises copper hydroxide having an average
particle diameter of less than about 500 nanometers, for example
less than about 250 nanometers, or less than about 200 nanometers,
as measured by Stokes Law. Preferably, the average particle
diameter is at least 25 nanometers, for example, at least 50
nanometers. In one embodiment of the invention, the particles have
a surface area of at least about 10 m.sup.2/gram of particles, for
example, at least about 40 m.sup.2/gram of particles, for example,
at least about 75 m.sup.2/gram of particles, for example about 80
m.sup.2/gram of particles. The particle size distribution of the
particulates in one embodiment is such that at least about 30% by
weight of the particulates have an average diameter between about
0.07 microns and about 0.5 microns, or preferably at least about
50% by weight of the particulates have an average diameter between
about 0.1 microns and about 0.4 microns.
[0171] In another variation of the invention the slurry comprises:
a liquid carrier; injectable solid particulates comprising a
slightly soluble copper salt; and particulates comprising metallic
copper and/or zinc. An exemplary particle having an average
particle diameter of less than about 500 nanometers, for example,
less than about 250 nanometers, or less than about 200 nanometers,
as measured by Stokes Law, and the average particle diameter is at
least 25 nanometers, for example, at least 50 nanometers. The
particle size distribution of the particulates in one embodiment is
such that at least about 30% by weight of the particulates have an
average diameter between about 0.02 microns and about 0.4 microns,
or preferably at least about 50% by weight of the particulates have
an average diameter between about 0.05 microns and about 0.3
microns. The metallic copper and/or metallic zinc particulates have
both a minor biocidal effect and also an anti-corrosion effect. The
amount of metal, either copper, zinc, or both, in the
anti-corrosion metallic particulates can range from about 1 part to
about 25 parts per 100 parts of particulates comprising slightly
soluble copper salts. The metal-containing particulates in this
variant of the invention are primarily anti-corrosion additives,
though they will have some biocidal effect. Further, organic
biocides can be readily coated onto these metal-containing
particulates. In one embodiment of this variant, the slurry
comprises: A) a liquid carrier; B) injectable solid particulates
comprising metallic copper and/or metallic zinc and also one or
more organic biocides, and either C-1) one or more soluble copper
salts or complexes including the soluble copper treatments
described in the prior art, C-2) one or more injectable
particulates comprising slightly soluble salts of copper and/or
zinc, or C-3) both.
[0172] The copper-based particulates can comprise or consist
essentially of any sparingly soluble substantially crystalline (or
sparingly soluble amorphous) copper salts. In one embodiment the
substantially crystalline (or amorphous sparingly soluble) copper
salts in the copper-based particulates comprise or consist
essentially of one or more copper salts selected from copper
hydroxides; copper carbonates (e.g., "yellow" copper carbonate);
basic (or "alkaline") copper carbonates; basic copper sulfates
including particularly tribasic copper sulfate; basic copper
nitrates; copper oxychlorides (basic copper chlorides); copper
borates; basic copper borates; copper ferricyanate; copper
fluorosilicate; copper thiocyanate; copper diphosphate or copper
pyrophosphate, copper cyanate; and mixtures thereof. In one
embodiment, the copper-based particles comprise a substantially
crystalline copper compound. At least about 20%, 30%, 50%, or 75%
of the weight of the copper-based particles may be composed of the
substantially crystalline copper compound(s).
[0173] In a preferred embodiment, the substantially crystalline (or
amorphous sparingly soluble) copper salts in the copper-based
particulates comprise or consist essentially of one or more copper
salts selected from copper hydroxides; copper carbonates, basic (or
"alkaline") copper carbonates; basic copper sulfates including
particularly tribasic copper sulfate; basic copper nitrates; copper
oxychlorides (basic copper chlorides); copper borates, basic copper
borates, and mixtures thereof. In one embodiment, the copper-based
particles comprise a substantially crystalline copper compound. At
least about 20%, 30%, 50%, or 75% of the weight of the copper-based
particles may be composed of the substantially crystalline copper
compound.
[0174] In another embodiment the substantially crystalline (or
amorphous sparingly soluble) copper salts in the copper-based
particulates in a wood preservative formulation can comprise or
consist essentially of a plurality of sparingly soluble
substantially crystalline (or amorphous sparingly soluble) copper
salts selected from copper oxide, copper hydroxides; copper
carbonates, alkaline (or "basic") copper carbonates; alkaline
copper sulfates; alkaline copper nitrates; copper oxychlorides;
copper borates, basic copper borates, and mixtures thereof, with
the proviso that at least one of the substantially crystalline (or
amorphous sparingly soluble) copper salts is not a copper oxide. Of
the copper oxides, Cu.sub.2O is preferred over CuO. In a variant of
this, the copper-based particulate material can comprise or consist
essentially of one or more sparingly soluble substantially
crystalline copper salts selected from copper hydroxides; copper
carbonates, alkaline (or "basic") copper carbonates; alkaline
copper nitrates; alkaline copper sulfates; copper oxychlorides;
copper borates, basic copper borates, and mixtures thereof. In one
embodiment, the copper-based particles comprise a substantially
crystalline copper compound. At least about 20%, 30%, 50%, or 75%
of the weight of the copper-based particles may be composed of the
substantially crystalline copper compound(s).
[0175] In any of the above, the substantially crystalline (or
amorphous sparingly soluble) copper composition can have a
substantial amount of one or more of magnesium, zinc, or both,
wherein these cations are either dispersed within the substantially
crystalline (or amorphous sparingly soluble) copper composition, or
be a separate phase within a particulate. In preferred embodiments
of the invention, at least some particulates comprise copper
hydroxide, basic copper carbonate, or both. In more preferred
embodiments, the copper hydroxide comprises between 6 and 20 parts
of magnesium per 100 parts of copper, for example between 9 and 15
parts of magnesium per 100 parts of copper. Alternatively, in
another more preferred embodiments, the copper hydroxide comprises
between 6 and 20 parts total of magnesium and zinc per 100 parts of
copper, for example between 9 and 15 parts total of magnesium and
zinc per 100 parts of copper. In some embodiments, the basic copper
carbonate comprises between 6 and 20 parts of magnesium per 100
parts of copper, for example between 9 and 15 parts of magnesium
per 100 parts of copper, or alternatively between 6 and 20 parts
total of magnesium and zinc per 100 parts of copper, for example
between 9 and 15 parts total of magnesium and zinc per 100 parts of
copper. Alternatively or additionally, in a preferred embodiment,
the copper hydroxide and/or basic copper carbonate comprises
between about 0.01 and about 5 parts of phosphate per 100 parts of
copper, for example between 9 and 15 parts of phosphate per 100
parts of copper.
[0176] In another preferred embodiment, the slurry comprises a
sparingly soluble copper salt particulates and also comprises zinc
borate particulates. Preferably, at least some of the sparingly
soluble copper salt-based particulates comprise copper borate. It
is known to use a two stage process where a zinc or copper salt is
injected into the wood followed by a second step, wherein the borax
is injected and the insoluble metal borate is formed in situ. Such
a complicated, time-consuming, and therefore expensive process in
not sufficiently cost-effective. As the solubility of copper borate
is very pH sensitive, in a preferred embodiment the sparingly
soluble copper salts comprise an alkaline material, e.g., copper
hydroxide or copper carbonate, to reduce the solubility of the
copper borate. The zinc borate loading can range from 0.025% to
0.5%, for example, independent of the copper loading in the
wood.
[0177] In any of the above-described embodiments, the substantially
crystalline copper composition in copper-based particulates and/or
copper-based particulate material can further comprise one or more
soluble substantially crystalline copper salts, for example copper
sulfate, copper fluoroborate; copper fluoride, or mixtures thereof,
where the soluble substantially crystalline copper salts phase is
stabilized against dissolution.
[0178] In any of the above-described embodiments, the substantially
crystalline copper composition in copper-based particulates and/or
copper-based particulate material can further comprise the
substantially insoluble copper salt copper phosphate,
Cu.sub.3(PO.sub.4).sub.2. In any of the above-described
embodiments, the copper composition in copper-based particulates
and/or copper-based particulate material can further comprise the
insoluble copper salt copper 8-quinolinolate. In any of the
above-described embodiments, the composition can further comprise
copper quinaldate, copper oxime, or both in particulate form. If
there are copper-based-particulates substantially comprising
Cu.sub.3(PO.sub.4).sub.2 and/or copper oxide and/or copper
8-quinolinolate, the particulates should be exceedingly small,
e.g., less than about 0.07 microns, preferably less than about 0.05
microns, to provide maximum surface area to help dissolution of the
particles, and the wood treatment should contain another type of
substantially crystalline (or amorphous sparingly soluble)
copper-based particulates, e.g., basic copper carbonate, basic
copper borate, tribasic copper sulfate, copper hydroxides, and the
like.
[0179] The zinc analogs of the above are useful for the zinc-based
particulates of the alternate embodiments of the invention. In one
embodiment the copper-based particulate material can further
comprise one or more of crystalline zinc salts selected from zinc
hydroxide; zinc oxides; zinc carbonate; zinc oxychloride; zinc
fluoroborate; zinc borate, zinc fluoride, or mixture thereof. The
zinc salts may be in a separate salt phase, or may be mixed Cu/Zn
salts, or combinations thereof. In preferred embodiments the
particle comprises at least about 40%, preferably at least about
60%, and more preferably at least about 80% by weight of one or
more substantially crystalline (or amorphous sparingly soluble)
copper salts, crystalline zinc salts, or mixtures or combinations
thereof.
[0180] In one embodiment the copper-based particulate preservative
treatment for wood can further comprise zinc-based particulates
comprising one or more of crystalline zinc salts selected from zinc
hydroxide; zinc oxides; zinc carbonate; zinc oxychloride; zinc
fluoroborate; zinc borate, zinc fluoride, or mixture thereof. The
preferred zinc-based substantially crystalline material are zinc
hydroxide, zinc borate, zinc carbonate, or mixture thereof, which
may be doped with other cations, e.g., from 0.1 to 10% copper, from
0.1 to 10% magnesium, or both, for example, based on the total
weight of the cations in the substantially crystalline (or
amorphous sparingly soluble) material. In preferred embodiments,
the particle comprises at least about 40%, preferably at least
about 60%, and more preferably at least about 80% by weight of one
or more crystalline zinc salts.
[0181] Preferred embodiments of the invention comprise particles
comprising one or more of copper hydroxide, alkaline copper
carbonate, alkaline copper oxychloride, tribasic copper sulfate,
copper borate, or mixtures thereof. The most preferred embodiments
of the invention comprise particles comprising copper hydroxide,
alkaline copper carbonate, copper borate, alkaline copper borate,
or mixtures thereof.
[0182] In preferred embodiments of this invention the slurry
comprises: a liquid carrier; sparingly soluble (and preferably
substantially crystalline) copper based particulates, sparingly
soluble (and preferably substantially crystalline) zinc-based
particulates, sparingly soluble (and preferably substantially
crystalline) tin-based particulates, or mixtures thereof; and
optionally the slurry also advantageously contains one or more
organic biocides, one or more corrosion inhibiting agents, and
optionally other ingredients including those discussed herein. The
particulates, and the sparingly soluble salts forming the core
thereof, have been previously discussed. The organic biocides can
be in the form of a solution with the carrier (for water-soluble
biocides); an emulsion; a coating on the sparingly soluble copper
based, zinc-based, and/or tin-based particulates; a coating on
and/or in other injectable solid particulates; or any combination
thereof. In one embodiment substantially all (e.g., greater than
99% by weight) of the copper-based, zinc-based particulates, and/or
tin-based particulates of preferred preservatives have a diameter
smaller than 0.4 microns (400 nanometers). Such particles may be
insufficiently large to scatter enough light to discolor wood or
wood products treated with the particles. In another embodiment,
exemplary wood preservatives comprise copper-based particles having
a size distribution in which at least 50% of particles have a
diameter smaller than about 0.5 .mu.m, 0.25 .mu.m, 0.2 .mu.m, or
0.15 .mu.m.
[0183] An exemplary preservative of the invention comprises
sparingly soluble copper salt (e.g., copper hydroxide) or sparingly
soluble zinc salt particles having an average particle diameter of
less than about 500 nanometers, for example less than about 250
nanometers, or less than about 200 nanometers. In a preferred
embodiment, the average particle diameter is at least 25
nanometers, for example, at least 50 nanometers. In a most
preferred embodiment, the sparingly soluble (and preferably
substantially crystalline) copper based particulates, sparingly
soluble (and preferably substantially crystalline) zinc-based
particulates, and/or sparingly soluble (and preferably
substantially crystalline) tin-based particulates advantageously
have a median particle size below about 0.6 microns, preferably
between about 0.1 and about 0.4 microns. The particle size
distribution of the particulates is such that less than about 1% by
weight, preferably less than about 0.5% by weight, of the
particulates have an average diameter greater than 1 micron.
Preferably, the particle size distribution of the particulates is
such that less than about 1% by weight, preferably less than about
0.5% by weight, of the particulates have an average diameter
greater than about 0.6 microns. In one embodiment the particle size
distribution of the particulates is such that at least about 30% by
weight of the particulates have an average diameter between about
0.07 microns and about 0.5 microns. In a preferred embodiment, the
particle size distribution of the particulates is such that at
least about 50% by weight of the particulates have an average
diameter between about 0.1 microns and about 0.4 microns.
[0184] In preferred embodiments of this invention, the slurry is
substantially free of alkanolamines, e.g., the slurry comprises
less than 1% alkanolamines, preferably less than 0.1%
alkanolamines, or is totally free of alkanolamines.
[0185] In preferred embodiments of this invention, the slurry is
substantially free of amines, e.g., the slurry comprises less than
1% amines, preferably less than 0.1% amines, or is totally free of
amines, with the proviso that amines whose primary function is as
an organic biocide are excluded.
[0186] In preferred embodiments of this invention, the slurry is
substantially free of ammonium compounds (e.g., ammonium
hydroxide), e.g., the slurry comprises less than 1% ammonia,
preferably less than 0.1% ammonia, or is totally free of ammonium
compounds, with the proviso that ammonium compounds whose primary
function is as an organic biocide are excluded. In another
embodiment, the composition comprises an amount of ammonium
hydroxide to keep the pH of the liquid carrier between about 7 and
about 10, for example between about 7.5 and 9, or between about 8
and about 8.5.
[0187] In preferred embodiments of this invention, the slurry is
substantially free of solvents, e.g., the slurry comprises less
than 1% organic solvents, preferably less than 0.1% organic
solvents, or is totally free of organic solvents.
[0188] The slurry contains sparingly soluble (and preferably
substantially crystalline) copper based particulates, sparingly
soluble (and preferably substantially crystalline) zinc-based
particulates, sparingly soluble (and preferably substantially
crystalline) tin-based particulates, or mixtures thereof. The
sparingly soluble materials may have a fraction of additional
cations, e.g., zinc and/or magnesium. The particulates may have an
organic coating covering at least a portion of the exterior of at
least a fraction of the particulates. For example, the particles
can be wetted with an oil or solvent comprising e.g., linseed oil,
turpentine, and/or pine oil, and typically the oil or solvent will
include at least a portion of the organic biocides. In another
embodiment, the slurry will alternately or additionally comprise
inert metal oxide carrier particulates having organic biocide
associated therewith. The particulates may have an inorganic
coating covering at least a portion of the exterior of at least a
fraction of the particulates. The inorganic coating in one
preferred embodiment comprises copper phosphate formed by having
phosphate absorb onto the sparingly soluble copper salt.
[0189] The loading of the particulates in the slurry will depend on
a variety of factors, including the desired copper loading in the
wood, the porosity of the wood, and the dryness of the wood.
Calculating the amount of copper-based particulates and/or other
particulates in the slurry is well within the skill of one of
ordinary skill in the art. Generally, the desired copper loading
into wood is between 0.025 and about 0.5 pounds copper per cubic
foot of wood.
[0190] In a preferred embodiment, the liquid carrier consists
essentially of water and, optionally, one or more additives to aid
particulate dispersion, pH maintenance, interfacial tension
(surfactants), and anticoagulants. In another embodiment, the
carrier consists essentially of water and, optionally, one or more
additives to aid particulate dispersion, pH maintenance,
interfacial tension (surfactants), anticoagulants, and oil-in-water
emulsion of oil containing organic biocides dissolved therein.
[0191] Advantageously, the pH of the liquid carrier is between
about 7 and about 9, for example, between about 7.5 to about 8.5.
The pH can be adjusted with sodium hydroxide, potassium hydroxide,
alkaline earth oxides, methoxides, or hydroxides; or less
preferably ammonium hydroxide. The pH of the injectable slurry is
typically between pH 6 and 11, preferably between 7 and 10, for
example, between 7.5 and about 9.5. Acidic pH slurries are not
preferred because several of the sparingly soluble copper salts of
this invention have a higher solubility at lower pH. Therefore,
delays in preparing the slurry, injecting the slurry, and removing
the water carrier may result in undesired dissolution of sparingly
soluble material from the particulates. The pH can be adjusted to
the desired pH with alkali or alkaline earth oxides, methoxides, or
hydroxides, or less preferably ammonium hydroxide. Alkaline earth
bases are less preferred because if carbon dioxide or carbonates
are present in solution, there is a possibility of precipitation,
for example, of calcite. Such precipitation may create undesired
plugging of the wood during injection. The preferred ingredients to
increase the pH is an alkali hydroxide, e.g., sodium hydroxide or
potassium hydroxide. The pH modifying agent may be provided in the
form of a preferably aqueous solution comprising at least one
hydroxide salt.
[0192] The slurry is beneficially buffered, by, for example, adding
phosphoric acid or salts thereof in an amount sufficient to give a
phosphate content of between about 5 ppm and about 500 ppm. An
alternative buffer comprises an alkali bicarbonate and alkali
carbonate. The higher concentrations of phosphates may be
beneficial if the particulates do not have any coatings formed
thereon, as the soluble phosphate ions will discourage dissolution
of the copper salts from the particulates into the liquid carrier.
The salts of metal phosphates are extremely insoluble, for example,
the solubility product constant of copper phosphate is about 1
E-37, so in pure water this amount of phosphate would limit the
copper ion concentration to a negligible quantity. The phosphate
ions would therefore discourage dissolution and re-precipitation of
the copper, zinc, tin, or any combination thereof. This phosphate
may also allow an existing phosphate-based coating to repair after
damage by for example abrasion with other particles or abrasion
while being handled. Finally, the presence of phosphate ions will
slow the leach rate of copper from the wood. On the other hand, the
bioactive efficacy of copper phosphate is probably very low, for
the same reasons that the efficacy of copper oxides is low. The
solubilized copper ions are believed to be bioactive and therefore
contribute to the bioactivity of the formulation, and the
solubility of copper phosphate is very low. Therefore, it is
desirable that any copper phosphate coating on the particulates be
so thin as to be short-lived in the wood. Excessive soluble
phosphate may not allow the phosphate coating to readily break down
in the wood, and this could impair the bioactivity of the
particulates. Also, if the mixing tank has, for example, a residual
salts from previous injection of soluble materials, then the
phosphates can result in unwanted precipitates forming. For this
reason the concentration of phosphates in the liquid carrier is
beneficially kept below 1000 ppm, for example below 500 ppm or
below 100 ppm.
[0193] In one embodiment the slurry comprises between 50 and 800
ppm of one or more scale precipitation inhibitors, particularly
organophosphonates. Alternately or additionally the slurry may
contain between about 50 and about 2000 ppm of one or more
chelators. Both of these additives are meant to inhibit
precipitation of salts such as calcium carbonate and the like,
where the source of calcium may be from the water used to make up
the slurry. The preferred inhibitors are hydroxyethylidene
diphosphonic acid (HEDP), diethylenetriamine-pentamethy-
lenephosphonic acid (DTPMP), and/or
2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC). If the
preservative is in a slurry concentrate, the slurry should comprise
between 10 mmoles and 100 mmoles/L of HEDP, or between 30 mmoles
and 170 mmoles/L of PBTC or DTPMP. Mixtures of inhibitors are
preferred, as concentrates may have more inhibitor than can readily
be solubilized therein. If the preservative is in a solid form, the
preservative should comprise between about 0.1 to about 1 mole HEDP
per kg of particulates, or between about 0.17 to about 2 mole PBTC
and/or DTPMP per kg of particulates.
[0194] In one embodiment of the invention, a precipitate comprising
copper-based particles is prepared in the presence of a material
that inhibits precipitation of at least one of calcium and
magnesium. Alternatively, a material that inhibits precipitation of
at least one of calcium and magnesium is added to a mixture
comprising copper-based particles of the invention. In one
embodiment, the precipitation inhibitor is a chelator comprising
having at least one ethylene diamine compound, such as an
ethylenediamine-tetramethylene compound or
ethylenediaminetetracetate compound. An acid, such as a phosphonic
or acetic acid, of the ethylenediamine compound may be used. Salts
of the ethylenediamine compound may also be used. In one
embodiment, the precipitation inhibitor comprises at least one and
preferably at least two phosphonic groups. The precipitation
inhibitor may comprise a phosphonic acid or salt of a phosphonic
acid. The precipitation inhibitor may comprise at least one of a
hydroxyethylidene diphosphonic acid and an aceto diphosphonic acid.
A suitable phosphonate may be synthesized from phosphorous acid by
reaction with formaldehyde and either ammonia or amines. A wood
preservative of the invention may include at least one of a
ethylenediamine tetra methylenephosphonic acid, a
hexamethylenediamine tetra methylenephosphonic acid, a
diethylenetriamine penta methylenephosphonic acid, and a 1-hydroxy
ethane diphosphonic acid.
[0195] In some embodiments of the invention, the sparingly soluble
(and preferably substantially crystalline) copper based
particulates, sparingly soluble (and preferably substantially
crystalline) zinc-based particulates, sparingly soluble (and
preferably substantially crystalline) tin-based particulates, or
mixtures thereof, are used in conjunction with a liquid carrier
comprising soluble copper, for example, any of the soluble copper
formulations discussed in the background, including, for example, a
copper monoethanolamine carbonate complex, copper monoethanolamine
borate complex, copper azole borate, or copper citrate.
Advantageously, this soluble copper material is kept separate from
the particulate slurry or paste of this invention until the
injectable slurry is formulated. If such material is admixed into a
concentrated slurry or paste for shipping and storage, then
beneficially the particulates have one or more protective coating
layers thereon to minimize copper dissolution of the
particulates.
[0196] In some embodiments of the invention, the sparingly soluble
(and preferably substantially crystalline) copper based
particulates, sparingly soluble (and preferably substantially
crystalline) zinc-based particulates, sparingly soluble (and
preferably substantially crystalline) tin-based particulates, or
mixtures thereof, are used in conjunction with a liquid carrier
comprising one or more soluble borate salts. Soluble borates can be
added in an amount from about 5 ppm to about 2000 ppm in the
slurry, where less than 5 ppm has little effect and more than 2000
ppm is cost-prohibitive. Borates have both a biocidal activity and
a fire-retardant activity.
[0197] In some embodiments of the invention, the sparingly soluble
(and preferably substantially crystalline) copper based
particulates, sparingly soluble (and preferably substantially
crystalline) zinc-based particulates, sparingly soluble (and
preferably substantially crystalline) tin-based particulates, or
mixtures thereof, are used in conjunction with a liquid carrier
comprising one or more soluble chromate salts. Soluble chromates
can be added in an amount from about 5 ppm to about 2000 ppm in the
slurry, where less than 5 ppm has little effect and more than 2000
ppm is cost-prohibitive. Chromates have both a biocidal activity
and may have a corrosion-reducing activity.
[0198] Increased corrosion of metal fillings has been observed in
formulations using soluble copper preservatives, as opposed to the
prior art CCA formulations. The slurry, having a slightly basic pH
and having very low amine content, is expected to reduce the
corrosion rate over that seen with soluble copper. There are
additional treatment that can help reduce corrosion. The presence
of small quantities of buffered phosphate may further reduce
corrosion. Eliminating certain sparingly soluble salts such as the
oxychlorides will remove chloride, which will reduce corrosion from
that source. Finally, some of the injectable particulates can
comprise at least a portion of reduced metallic zinc or copper. The
particulates are advantageously sized about the same as for the
injectable particulates comprising the sparingly soluble, usually
substantially crystalline copper salts. Indeed, in addition to
being useful in slurries of this invention, corrosion of metallic
fittings may be somewhat alleviated by incorporating metallic
copper and/or zinc particulates in the soluble copper solution
preservatives of the prior art. Metallic zinc and copper are not
considered to be substantially crystalline, nor are they considered
to be sparingly soluble salts. The amount of these anti-corrosion
metallic particulates can range from about 1 part to about 25 parts
per 100 parts of copper in the sparingly soluble copper salts.
[0199] Contact with air can facilitate oxidation of certain
sparingly soluble copper salts, for example, copper hydroxide
(especially in very small particulate form, and especially if not
coated and/or if not containing a stabilizer such as magnesium
ions, to form into copper oxides). This transition is generally not
preferred because copper oxide has such limited solubility that it
may not be sufficiently bioactive. The concentrated slurry or paste
may comprise one or more antioxidants. Soluble sulfite salts
between 5 ppm and 100 ppm in the liquid carrier is a useful
inexpensive antioxidant.
[0200] If the wood preservative treatment will comprise organic
biocides, these biocides may be partially or fully coated onto the
sparingly soluble (and preferably substantially crystalline) copper
based particulates, sparingly soluble (and preferably substantially
crystalline) zinc-based particulates, sparingly soluble (and
preferably substantially crystalline) tin-based particulates, or
mixtures thereof. Preferred preservative materials inhibit
organisms that may be resistant to copper-based preservatives.
Moldicides useful in wood or wood product preservation are also
preferred organic biocides. Alternatively or additionally, these
biocides may be partially or fully coated onto the available
surface area of an inert particulate carrier. If the biocides are
to be added to the slurries as an emulsion, the organic biocides
are beneficially kept separate from the concentrated slurry or
paste of this invention until the injectable slurry is
formulated.
[0201] The slurry can advantageously contain one or more additives
to aid wetting, for example surfactants. Surfactants may be in
solution, or alternatively may bind to the surface. When bound to
the surface these surfactants function as disbursing agents. A
dispersing agent may be combined with the precipitated copper-based
particles. Alternatively, copper-based particles may be formed in
the presence of the dispersing agent. Preferred dispersing agents
include a surface active portion that interacts with the
copper-based particle and a second preferably different portion,
which operates to inhibit irreversible agglomeration of the
copper-based particles. For example, a polyacrylate dispersing
agent may include at least one carboxyl group capable of
associating, such as electrostaticaly, with a copper-based particle
and a second, hydrophobic portion that may operate to inhibit the
permanent agglomeration of the copper-based particles. Exemplary
dispersing agents may include at least one of a surfactant, a
polyacrylate, a polysaccharide, a polyaspartic acid, a
polysiloxane, and a zwitterionic compound. Exemplary compounds
useful as dispersing agents are disclosed in for example,
Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, Vol.
22 (John Wiley & Sons, 1983); Napper, Polymeric Stabilization
of Colloidal Dispersion (Academic Press, 1983); and Rosen,
Surfactants & Interfacial Phenomena, 2nd edition (John Wiley
& Sons, 1989), all of which are incorporated herein by
reference. In one embodiment of the invention, the copper-based
particles may comprise a polymer. In this embodiment, the ratio of
the weight of copper present in the particles to polymer present in
the particles may be at least about 1 to 1, for example at least
about 2 to 1, 4 to 1, 5 to 1, 7 to 1, or at least about 10 to 1.
For example, if ratio of the weight of copper present in the
particles to the weight of polymer present in the particles is at
least about 2 to 1, the particles comprise at least about twice as
much copper by weight as polymer. Another aspect of the invention
relates to a preservative useful for wood or wood products, the
preservative preferably comprising a preferably aqueous suspension
of copper-based particles. If a dispersing agent is present in the
suspension, the ratio of the weight of copper present in the
copper-based particles of the suspension to the weight of
dispersing agent present in the suspension may be at least about 1
to 1, for example at least about 5 to 1, 10 to 1, 15 to 1, 20 to 1
or at least about 30 to 1.
[0202] In one embodiment, the dispersing agent is substantially
free of phosphate ion. For example, the dispersing agent may be
substantially free of trisodium phosphate. The dispersing agent may
be substantially free of silicates, sodium carbonate and ammonia.
By substantially free of one or more particular dispersing agents,
it is meant that the weight percent of the one or more dispersing
agent relative to the copper-based particles is less than 3%. In
one embodiment, the weight percent of the one or more particular
dispersing agents relative to the copper-based particles is less
than about 2%, such as less than about 1%, for example, less than
about 0.5%. In one embodiment, the dispersing agent is free of at
least one of phosphate ion, trisodium phosphate, silicates, sodium
carbonate, and ammonia.
[0203] Dispersing agents aid particulate dispersion and to prevent
aggregation of particulates. Sub-micron sized particulates have a
tendency to form much larger aggregates. Aggregates as used herein
are physical combinations of a plurality of similarly-sized
particles, often brought together by VanDerWaal's forces or
electrostatic forces. By similarly-sized we mean the particles
forming the aggregate have diameters that are generally within a
factor of five of each other. Such aggregates are not desired in
the compositions of this invention. If aggregates are allowed to
form, they often can age into a stable aggregate that can not be
readily broken up by mechanical agitation, for example by vigorous
stirring of a slurry. Such aggregates may grow to a size where the
aggregates are not readily injectable, or may be of a size to make
the aggregates visible, therefor giving undesired color. In
preferred embodiments of the invention at least 30%, preferably at
least 60%, more preferably at least 90% by weight of the
substantially crystalline copper-based particulates in a slurry are
mono-disbursed, e.g., are not in aggregates. To prevent
particulates from agglomerating, the concentrated slurry or paste
may comprise cationic, anionic, and/or non-ionic surfactants;
emulsifiers such as gelatine, casein, gum arabic, lysalbinic acid,
and starch; and/or polymers, such as polyvinyl alcohols, polyvinyl
pyrrolidones, polyalkylene glycols and polyacrylates, in quantities
of 0.1 to 20% by weight, based on the weight of the
particulates.
[0204] Another aspect of the invention relates to a preservative
useful for wood or wood products, the preservative preferably
comprising a preferably aqueous suspension of copper-based
particles. The suspension may be stabilized by a
suspension-stabilizing amount of a dispersing agent. Preferred
dispersing agents include a surface active portion that interacts
with the copper-based particle and a second, preferably different
portion, which operates to inhibit irreversible agglomeration of
the copper-based particles. For example, a polyacrylate dispersing
agent may include at least one carboxyl group capable of
associating, such as electrostatically, with a copper-based
particle and a second, hydrophobic portion that may operate to
inhibit the permanent agglomeration of the copper-based particles.
Exemplary dispersing agents may include at least one of a
surfactant, a polyacrylate, a polysaccharide, a polyaspartic acid,
a polysiloxane, or a zwitterionic compound. If a dispersing agent
is present in the suspension, the ratio of the weight of copper
present in the copper-based particles of the suspension to the
weight of dispersing agent present in the suspension may be at
least about 1 to 1, for example at least about 5 to 1, 10 to 1, 15
to 1, 20 to 1 or at least about 30 to 1.
[0205] The slurry formulations mentioned can be prepared in a
manner known per se, for example by mixing the active compounds
with the liquid carrier, and including emulsifier, dispersants
and/or binders or fixative, and other processing auxiliaries.
Particulates can be provided in a concentrated slurry, in a very
concentrated paste, as dry particulates, as coated dry
particulates, as part of a dry pre-mix, or any combination
thereof.
[0206] Slurry Concentrate--If the wood preservative is to be
manufactured, stored, or transported in a wetted form, it is
beneficial that it be in a concentrated form to minimize the volume
and increased handling expense. Preferably the concentrated slurry
or paste comprises between 5% and 80% by weight, for example
between about 15% and 40%, of sparingly soluble (and preferably
substantially crystalline) copper based particulates, sparingly
soluble (and preferably substantially crystalline) zinc-based
particulates, sparingly soluble (and preferably substantially
crystalline) tin-based particulates, or mixtures thereof, with the
remainder of the concentrated slurry or paste being a fluid
carrier. The concentrated slurry or paste may further comprise
solid particulates that are carriers for one or more organic
biocides, solid particulates comprising metallic copper and/or zinc
as corrosion inhibitors, or both. The fluid carrier beneficially
comprises one or more additives as discussed for the slurry,
including anti-oxidants; surfactants; disbursing agents; other
biocidal salts and compounds; chelators; corrosion inhibitors,
e.g., phosphates or metallic zinc or copper particulates; pH
modifiers and/or buffers; and the like. The concentration of these
additives will depend in part on the degree to which the slurry
concentrate is expected to be diluted to make a commercially useful
injectable slurry having the proper copper loading.
[0207] The moisture content of the copper-based particles of the
invention may be reduced, such as by drying. A dispersing agent may
be used to inhibit irreversible agglomeration of reduced moisture
particles of the invention. The reduced moisture particles may be
diluted, such as by hydration with water or combination with
another liquid. Generally, dilution is with water, beneficially
fresh water.
[0208] Another aspect of the invention relates to an agglomeration
comprising a plurality of copper-based particles and, optionally, a
dispersing agent. The agglomeration may also include one or more
materials in addition to the copper-based particles that also
provide a wood or wood product preservative function. The
agglomeration may have a liquid content (excluding any additional
preservative material that may be present) of less than about 75%
by weight, for example, of less than about 50%, less than about
25%, less than about 15%, or less than about 5% by weight. The
liquid may be water. The agglomeration may be diluted and/or
dispersed with mixing or agitation, such as mechanically or
ultrasonically.
[0209] As in the injectable slurry itself, the particle size
distribution of the particulates is such that less than about 1% by
weight, preferably less than about 0.5% by weight, of the
particulates have an average diameter greater than 1 micron.
Preferably the particle size distribution of the particulates is
such that less than about 1% by weight, preferably less than about
0.5% by weight, of the particulates have an average diameter
greater than about 0.6 microns. The particle size distribution of
the particulates is such that at least about 30% by weight of the
particulates have an average diameter between about 0.07 microns
and about 0.5 microns. In a preferred embodiment, the particle size
distribution of the particulates is such that at least about 50% by
weight of the particulates have an average diameter between about
0.1 microns and about 0.4 microns.
[0210] The pH of the wood preservative in the form of a concentrate
or paste is in general between pH about 6 and about 13, preferably
between about 7 and about 10.5, for example, between about 7.5 and
about about 9.5. The pH can be adjusted to the desired pH with
alkali or alkaline earth oxides, methoxides, or hydroxides; or less
preferably ammonium hydroxide. The preferred ingredient to increase
the pH is an alkali hydroxide such as sodium hydroxide. The
concentrated slurry or paste is beneficially buffered, for example,
by adding phosphoric acid in an amount sufficient to give a
phosphate content of between about 10 ppm and about 1000 ppm.
[0211] If the wood preservative comprises organic biocides, these
biocides may be partially or fully coated onto the sparingly
soluble (and preferably substantially crystalline) copper based
particulates, sparingly soluble (and preferably substantially
crystalline) zinc-based particulates, sparingly soluble (and
preferably substantially crystalline) tin-based particulates, or
mixtures thereof. Alternatively, or additionally, these orgnanic
biocides may be partially or fully coated onto the surface area of
an inert particulate carrier. If the organic biocides are to be
added to the slurries as an emulsion, the organic biocides are
beneficially kept separate from the concentrated slurry or paste of
this invention until the injectable slurry is formulated.
[0212] Dry Particulates and Dry Mix For Slurry--The particulates
are preferably sold as a dry component. The dry component can be
simply the copper-based, zinc-based, and/or tin-based particulates,
which may be coated or uncoated. If coated, the coating can be
inorganic, organic, or both. The particulates advantageously
comprise one or more additives such as are described as being
present in the slurry, including, for example, inert particulates
having organic biocides thereon; anti-oxidants; surfactants;
disbursing agents; other biocidal salts and compounds; chelators;
corrosion inhibitors, e.g., phosphates or metallic zinc or copper
particulates; pH modifiers; and/or buffers, such as carboxylic acid
salts, or inorganic salts, such as phosphate salts and the like.
The additives can be coated onto the sparingly soluble copper-based
particulates and/or can be a second particulate.
[0213] The dry-mix material advantageously has, in addition to dry
particulates discussed above, all necessary components in a single
mix, and each component is present in a range that is useful when
the dry mix is formed into an injectable slurry. The dry-mix
material may optionally, but preferably, incorporate a granulating
material, which is a material that, when wet, holds a plurality of
particulates together in the form of a granule, but that dissolves
and releases the individual particulates on being admixed with the
liquid carrier. Granules are preferred over sub-micron-sized
particulates because of dust problems and also the ease of
measuring and handling a granular mixture. Granulating agents can
be simple soluble salts, for example alkali carbonates, that are
sprayed onto or otherwise admixed with the particulate material.
Several additives to a slurry can be also used as granulating
agents.
[0214] One embodiment of the invention relates to a dry-mix
material having a copper content of at least about 8% by weight. A
preferred material includes a plurality of copper-based particles,
which may be in the form of granules. The material may be shipped,
such as in granular form, to a location where the material will be
prepared for use as a wood preservative. The dry-mix material may
also comprise at least one of a wetting agent; a dispersing agent;
a diluent, which may be a particulate comprising organic biocides
thereon; an antifoaming agent; and an additional material having a
biocide function.
[0215] One embodiment of the invention relates to a dry-mix
material having a copper content of at least about 15% by weight. A
preferred dry-mix material includes a plurality of copper-based
particles, which may be in the form of granules. The dry-mix
material also comprises at least one of a wetting agent, a
dispersing agent, a diluent, an antifoaming agent, or an additional
material having a biocide function. In one embodiment, the dry-mix
material is a granular material comprising about 50% to about 70%,
for example about 58%, copper hydroxide or other sparingly soluble
copper salts, about 10% to about 25%, for example about 18%, of a
dispersing agent, such as Borresperse NA, about 1% to about 8%,
e.g., about 4%, of a wetting agent, such as Morwet EP, and about
10% to about 30% filler, e.g., about 20% attapulgite clay, such as
Diluex A.
[0216] In one embodiment, the dry-mix material is a granular
material comprising about 40% to about 80% by weight of a sparingly
soluble copper salt, e.g., copper hydroxide, about 5% to about 30%
of a dispersing agent, such as Borresperse NA, about 1% to about
10% of a wetting agent, such as Morwet EP, and about 5% to about
30% of a inert particulate filler which may additionally comprise
organic biocides absorbed thereon, e.g., attapulgite clay, such as
Diluex A. In one embodiment, the dry-mix material is a granular
material comprising about 58% copper hydroxide, about 18% of a
dispersing agent, such as Borresperse NA, about 4% of a wetting
agent, such as Morwet EP, and about 20% attapulgite clay, such as
Diluex A.
[0217] Another aspect of the invention relates to dry-mix material
comprising a copper content of at least about 15%, for example, at
least about 20%, such as at least about 30% by weight. In one
embodiment, the dry-mix material may have a copper content of about
35% by weight. The dry-mix material has a copper content of less
than about 50%, for example, less than about 45%, such as less than
about 40% by weight. The dry-mix material may comprise a plurality
of granules each comprising a plurality of copper-based particles.
The copper-based particles may be associated with a dispersing
agent.
[0218] In one embodiment, the dry-mix material comprises A) about
30% to about 70% by weight of a slightly soluble copper salt, e.g.,
copper hydroxide, for example, about 35% to about 65%, such as
about 38% to about 61% of the slightly soluble copper salt; B)
about 10% to about 35% by weight, such as about 15% to about 30% of
at least one dispersing agent, e.g., lignosulfonates or
polyacrylates; C) about 2.5% to about 20% by weight, such as about
5% to about 15% of at least one wetting agent, for example, a
surfactant, e.g., Morwet EP available from Barton Solvents, Inc.;
D) about 5% to about 25% by weight, such as about 10% to about 20%
of at least one diluent, for example soluble and insoluble
diluents, such as those used in agricultural products, e.g., clay,
such as an attapulgite clay, or particulate carrier particles
comprising organic biocide; E) about 0.05% to about 7.5% by weight,
such as about 0.1% to about 5%, of at least one antifoam agent; and
optionally F) about 2.5% to about 25%, alternatively less than
about 7.5%, such as less than about 5% by weight, of water.
[0219] The dry-mix material may be shipped in granular form. The
dry-mix material of the invention offers reduced shipping costs and
improved ease of handling compared to known preservative materials.
A user may receive the dry-mix material as a flowable material
comprising a plurality of copper-based particles. The dry-mix
material may be diluted, for example, with water or another liquid.
The copper-based particles of the dry-mix material may be injected
into wood and/or wood materials as a preservative. Mechanical
agitation and/or mixing may be used to disperse the granules in the
liquid. Upon dispersing the material, wood or wood products may be
treated with the dispersed material, such as by subjecting the wood
or wood products to vacuum and or pressure in the presence of the
dispersed material. Upon dispersing granules of the material,
dispersed copper-based particles preferably remain suspended for at
least about 30 minutes without further agitation, preferably, even
in standard hard water having a hardness of about 342 ppm. Once
dispersed, about fifty percent of the dispersed copper-based
particles may have diameters less than about 1 micron, for example,
less than about 0.5 micron, such as less than about 0.25 micron. In
one embodiment, about 50% of the dispersed copper-based particles
have diameters less than about 0.2 micron, for example, about 50%
of the dispersed copper-based particles have diameters of about 0.1
micron.
[0220] The copper-based material may comprise additional material
providing a wood preservative and/or biocide function. For example,
in one embodiment, the additional material comprises a plurality of
copper-based particles and a co-biocide. Exemplary co-biocides may
include, for example, one or more of a triazole compound, a
quarternary amine, and a nitroso-amine.
[0221] Leaching Data
[0222] One object of the invention is to provide an effective,
injectable copper-based particulate preservative treatment that has
leaching characteristics similar to CCA. It is known that copper
arsenate (Cu.sub.3(AsO.sub.4).sub.2) injected as a molecular layer
is effectiveas a preservative. Therefore, the particulate
preservative should provide a copper concentration roughly similar
(for example, about the same to within a factor of three times) to
that provided by copper arsenate treatment. Generally, leach rate
tests involve high leaching medium flow rates so the leaching
medium can not easily dissolve the sparingly soluble salts, and
therefore measured leach rates of particulates are expected to be
low compared to leach rates from more soluble salts. By "leach rate
similar to CCA," we mean the leach rate using the AWPA Standard
Method E11-97(1997), determined as percent of copper leached per
hour. For a particulate inhibitor injected into wood is within a
factor of about 2 above, preferably within a factor of about 1.5
above, to within a factor of 5 below, preferably within a factor of
about 3 below, more preferably within a factor of about 2 below,
the percent of copper leached from CCA-treated wood at 240 hours
using the AWPA Standard Method E11-97 (1997), by using a test
extending to at least 300 hours duration. Another object of the
invention is to provide an effective, injectable copper-based
particulate preservative treatment that retains more than 94% of
the injected copper in a 14 day standard leach test.
[0223] Advantageously the copper-based particulate is an effective
preservative. To be effective, the copper-based particles comprise
one or more sparingly soluble copper salts that release a small but
effective concentration of soluble copper when wetted with water.
If the copper salts have too high a solubility, the copper is
quickly leached out of the wood and contaminates the environment
rather than protecting the wood. If the copper salts have too low a
solubility, the copper salts (and copper oxides) are not bioactive.
The dissolution rate/leach rate of the sparingly soluble copper
salts used in the particulates will be a function of 1) the
solubility of the sparingly soluble copper salt(s) in the leaching
medium; 2) the surface area of the sparingly soluble copper salts
available to contact the leaching medium; 3) the lattice energy of
the crystal which must be overcome to dissolve the crystal; and 4)
the flow characteristics of the leaching medium in the wood matrix,
especially boundary layer effects. Each of these properties plays a
role in every flowrate scenario, but some are more dominant than
others at certain times. We believe the leach rates will be
governed primarily by the solubility of the sparingly soluble salts
and by boundary layer effects of the copper and counterions
diffusing from the particulates in regimes where the leaching
medium is moving extremely slowly, e.g., less than a few
millimeters per day. At intermediate leachant flow rates, we
believe the leach rate of copper will depend primarily on the
available surface area. At higher rates, such as found in the
standard test methods typically used by industry, the leach rates
will be governed more by the available surface area of the
sparingly soluble salts and by the lattice energy of the
crystal.
[0224] Generally, surface area is known be an important factor.
This is because, as the sparingly copper salts exist as approximate
point sources within the wood matrix, the leaching medium typically
does not contact a sufficient amount of particulates for a
sufficient time to become saturated with the sparingly soluble
copper salts. Dissolution is a function not only of the pH of the
water within the wood and the solubility product of the particular
salts in water, but also of dynamic conditions. Since the copper is
present in the wood as particulates, dissolution of copper will
also be restricted by the low surface area of the particles. Larger
particulates will reduce the leaching rate in most leaching
regimes. The dissolution of larger particulates is more dependent
on surface effects than is the dissolution of smaller particulates,
in part because the available surface area is lower for larger
particulates. At low flow rates, boundary layer effects may
multiply the effects of lower surface area, but at typical leaching
regimes boundary layer effects may be minimized if the flow of the
leaching medium through the wood matrix is turbulent.
[0225] The easiest way to alter surface area is to change particle
size. In a simplistic model, reducing the average particle size by
one half will increase the available surface area by about a factor
of 2. If the particulates become too small, e.g., below about 0.02
microns (20 nanometers) in diameter or below about 10 nanometers in
diameter, for many of the sparingly soluble copper salts, we
believe the leaching medium will always approximate being saturated
by the sparingly soluble copper salts and the available surface
area will approach that of a monolayer, giving leaching properties
of an injected soluble copper. The crystals may then dissolve too
quickly if subjected to a high leaching regime for an extended
period of time. Further, we believe that high leachant flow rates
may dislodge and remove from the wood matrix very small
particulates. For this reason in preferred embodiments of the
invention at least about 30% or more of the sparingly soluble salts
are present as particulates having a diameter greater than about
0.1 microns.
[0226] Generally, the available surface area can be further reduced
by the presence of one or more coatings, be they organic,
inorganic, or both. The coatings must be designed to have a
coverage and efficiency such that at least a bioactive amount of
copper is leached from the sparingly soluble copper salts in the
particulates. In some embodiments, the coating is dissolved over a
period of time, thereby allowing the available surface area of the
sparingly soluble copper salts to increase with time. This is
advantageous because newly-installed wood generally does not need
biocides to be released until the bio-organisms invade or contact
the wood, and this usually takes some time.
[0227] The solubility of the sparingly soluble copper salts can be
estimated based on values of the solubility product constant.
However, the presence of ions such as phosphate in the wood matrix
will reduce solubility, while the presence of acids in the leachant
will greatly increase solubility of most of the preferred sparingly
soluble salts. At low flow rates, the pH of the leaching medium
will be modified by the dissolution of the copper hydroxides and
the copper carbonates. The isoelectric point of copper hydroxide is
at about pH 11, making copper hydroxide a very effective base. The
presence of other salts, for example phosphate ions, can further
hinder leach rates by temporarily holding the solubilized copper,
reducing the flow rate of copper through the wood matrix. At high
leaching medium flow rates, however, such as are used in standard
leaching tests, the flow rates are such that the presence of
hydroxides, phosphates, and the like are minimized.
[0228] Generally, the leach rate of copper from particulates of
sparingly soluble copper salts disposed in a wood matrix is
dependent on particle size (and hence particle size distribution),
leaching medium flow rates through the wood matrix, and a variety
of other factors. The copper-based particulates of the invention
advantageously have a low leach rate at both relatively high
leaching medium flow rates and at relateively low leaching medium
flow rates, because the copper-based particulates have 1) a wide
distribution of particle sizes, 2) sparingly soluble salts of
differing solubilities, or 3) both.
EXAMPLES
[0229] We have successfully injected slurries comprising
sub-micron-sized particles of various sparingly soluble copper
salts into standard 1 inch cubes of Southern yellow pine. Copper
development by calorimetric agents (dithio-oxamide/ammonia) showed
the copper to be fully penetrated across the block in the sapwood
portion. FIG. 3 shows the penetration of injected particulate
copper hydroxide developed with dithio-oxamide in the third
picture. The stain corresponds to copper. Subsequent acid leaching
and quantitative analysis of the copper from two blocks showed that
loadings of 95% and 104% of expectation, or essentially 100%
average of expectation had occurred. At 100% loading, values of
0.22 lbs of copper per cubic foot would be obtained.
[0230] Leaching data from wood preserved with a prior art soluble
solution of copper MEA and from a slurry of injected copper
hydroxide particulates of this invention was measured following the
AWPA Standard Method E11-97. The total copper leached from wood
preserved with copper-MEA-carbonate is 5.7% at 6 hours, 8.5% at 24
hours, 11% at 48 hours, 22% at 96 hours, 36% at 144 hours, 49% at
192 hours, 62% at 240 hours, 69% at 288 hours, and 76% at 336
hours. The amount of copper leached from copper hydroxide
particulates was 0.4% at 6 hours, 0.6% at 24 hours, 0.62% at 48
hours, 1.0% at 96 hours, 1.6% at 144 hours, 2.1% at hours, 3.2% at
240 hours, 3.4% at 288 hours, and 3.7% at 336 hours.
[0231] Leaching data from wood was measured using the AWPA Standard
Method E11-97 for the following preservative treatments, where
unless specified the tebuconazole (TEB) concentration was added as
an emulsion at 3% of the weight of the added copper: A) TEB and
injected basic copper carbonate particulates; B) traditionally
CCA-treated wood (as a control); C) TEB and copper methanolamine
carbonate (as a control, believed to approximate the currently
available Wolman E treatment); D) TEB and injected basic copper
carbonate particulates with sodium bicarbonate buffer; E) injected
basic copper carbonate particulates; F) TEB and injected copper
hydroxide particulates modified with zinc and magnesium; G) about
5% TEB and injected copper hydroxide particulates modified with
phosphate coating; and H) TEB and injected tribasic copper sulfate
particulates; I) TEB and injected copper oxychloride particulates.
The leaching data for the various particulate slurries and from two
controls are shown in FIG. 1.
[0232] Using the copper leach rate of CCA as a standard, and
viewing the total leached copper at 96 and 240 hours as
representative, the leach rate ratios given by the "total leached
copper to total CCA-leached copper" is given in Table 3 below:
2 96 hr. 240 hr. ratio ratio Ex. Description of Preservative System
to CCA to CCA A 3% TEB and basic copper carbonate particulates
0.67:1 0.51:1 C 3% TEB and copper MEA carbonate 5.2:1 3.85:1
(comparative) D 3% TEB and basic copper carbonate particulates
0.54:1 0.46:1 with sodium bicarbonate buffer E basic copper
carbonate particulates 0.77:1 0.63:1 F 3% TEB and copper hydroxide
with Zn and Mg 0.2:1 0.19:1 particulates G 5% TEB and copper
hydroxide particulates 1.0:1 0.88:1 modified with phosphate coating
H 3% TEB and tribasic copper sulfate particulates 0.96:1 0.88:1 I
3% TEB and copper oxychloride particulates 1.4:1 1.17:1
[0233] Of the sparingly soluble salts used, the leach rate in
decending order is copper MEA carbonate (comparative)>>copper
oxychloride>tribasic copper sulfate and/or copper hydroxide with
phosphate>basic copper carbonate>copper hydroxide with Zn and
Mg. The isoelectric point of copper oxychloride is about 5 to 5.5,
and the isoelectric point of tribasic copper sulfate is about 6 to
6.5. As these materials are very poor bases, the higher leach
rates, from the materials is consistent with expected higher
solubility at lower pH values.
[0234] The presence of TEB reduced leach rates from basic copper
carbonate by about 20%, most likely due to TEB partially coating
particulates.
[0235] A buffering system, sodium bicarbonate, reduced the leach
rates from TEB/basic copper carbonate by about 10% relative to a
preservative without the buffer.
[0236] Surprisingly, the phosphate material in the copper hydroxide
did not appear to show any protective value at all. The reason for
this is not clear. Copper hydroxide with magnesium and zinc ions
showed the lowest leach rates.
[0237] Method Of Preserving Wood
[0238] Another aspect of the invention relates to wood or a wood
product comprising copper-based particles and, optionally, one or
more additional materials having a preservative function, injected
into the wood or wood product. An exemplary piece of wood
comprising copper-based particles has a volume of at least about 6
cm.sup.3, for example, at least about 100 cm.sup.3, such as at
least about 1,000 cm.sup.3.
[0239] The material of this invention is useful for wood, and also
for wood composites. Preferred wood composites have the
preservatrive of this invention either mixed with the wood
particles before bonding, or preferably injected into the wood
particulates and dried prior to bonding. Exemplary wood products
include oriented strand board (OSB), particle board (PB), medium
density fiberboard (MDF), plywood, laminated veneer lumber (LVL),
laminated strand lumber (LSL), hardboard, and the like.
[0240] In one embodiment, the wood or wood product has a surface, a
thickness, a width, and a length. Preferably, the wood or wood
product comprises a homogenous distribution of copper-based
particles of the invention. In one embodiment, the volume number
density of the copper-based particles 5 cm from the surface, and
preferably throughout the interior of the wood or wood product, is
at least about 50%, for example, at least about 60%, at least about
70%, or at least about 75% of the volume number density of the
copper-based particles about 1 cm from the surface.
[0241] Wood or wood products comprising copper-based particles in
accordance with the present invention may be prepared by subjecting
the wood to vacuum and/or pressure in the presence of a flowable
material comprising the copper-based particles. A pre-injection of
carbon dioxide followed by vacuum and then injection of the slurry
is a preferred method of injecting the slurry into wood. Injection
of particles into the wood or wood product from a flowable material
comprising the particles may require longer pressure treatments
than would be required for liquids free of such particles.
Pressures of, for example, at least about 75 psi, 100 psi, or 150
psi may be used. Exemplary flowable materials include liquids
comprising copper-based particles, emulsions comprising
copper-based particles, and slurries comprising copper-based
particles.
* * * * *
References