U.S. patent application number 11/817511 was filed with the patent office on 2008-10-09 for production of moulded bodies from lignocellulose-based fine particle materials.
This patent application is currently assigned to Basf Aktiengesellschaft. Invention is credited to Ulf Baus, Andreas Krause, Holger Militz, Gunter Scherr, Falko Wepner.
Application Number | 20080246177 11/817511 |
Document ID | / |
Family ID | 36499429 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080246177 |
Kind Code |
A1 |
Baus; Ulf ; et al. |
October 9, 2008 |
Production of Moulded Bodies From Lignocellulose-Based Fine
Particle Materials
Abstract
The present invention relates to a process for the production of
moldings from finely divided materials based on lignocellulose, and
the moldings obtainable thereby. The invention also relates to the
use of aqueous compositions which comprise at least one
crosslinkable urea compound for the preparation of finely divided
materials based on lignocellulose and treated with this composition
for the production of moldings.
Inventors: |
Baus; Ulf; (Dossenheim,
DE) ; Scherr; Gunter; (Ludwigshafen, DE) ;
Militz; Holger; (Bovenden, DE) ; Krause; Andreas;
(Gottingen, DE) ; Wepner; Falko; (Gottingen,
DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Basf Aktiengesellschaft
Ludwigshafen
DE
|
Family ID: |
36499429 |
Appl. No.: |
11/817511 |
Filed: |
March 3, 2006 |
PCT Filed: |
March 3, 2006 |
PCT NO: |
PCT/EP2006/001979 |
371 Date: |
August 31, 2007 |
Current U.S.
Class: |
264/128 ;
523/200 |
Current CPC
Class: |
B27N 1/006 20130101 |
Class at
Publication: |
264/128 ;
523/200 |
International
Class: |
D04H 1/64 20060101
D04H001/64 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2005 |
DE |
10 2005 010 042.2 |
Claims
1. (canceled)
2. The process according to claim 9, wherein the crosslinkable urea
compound is selected from
1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one,
1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one which is
modified with a C.sub.1-C.sub.6-alkanol, a C.sub.2-C.sub.6-polyol
or an oligo- or a polyethylene glycol, 1,3-bis(hydroxymethyl)urea,
1,3-bis(methoxymethyl)urea; -1-hydroxymethyl-3-methylurea,
1,3-bis(hydroxymethyl)imidazolidin-2-one,
1,3-bis(hydroxymethyl)-1,3-hexahydropyrimidin-2-one,
1,3-bis(methoxymethyl)-4,5-dihydroxyimidazolidin-2-one,
tetra(hydroxymethyl)acetylenediurea.
3. The process according to claim 9, wherein the crosslinkable urea
compound is 1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one
or a 1,3-bis(hydroxymethyl-4,5-dihydroxyimidazolidin-2-one modified
with a C.sub.1-C.sub.6-alkanol, a C.sub.2-C.sub.6-polyol or an
oligo- or a polyethylene glycol.
4-5. (canceled)
6. The process according to claim 9, wherein the catalyst K is
selected from metal salts from the group consisting of the metal
halides, metal sulfates, metal nitrates, metal phosphates, metal
tetrafluoroborates; boron trifluoride; ammonium salts from the
group consisting of the ammonium halides, ammonium sulfate,
ammonium oxalate and diammonium phosphate; organic carboxylic
acids, organic sulfonic acids, boric acid, sulfuric acid and
hydrochloric acid.
7. The process according to claim 9, wherein the catalyst K is
magnesium chloride.
8. The process according to claim 9, wherein the concentration of
the catalyst in the aqueous composition is in the range from 0.1 to
20% by weight, based on the total weight of the composition.
9. A process for the production of moldings from finely divided
materials based on lignocellulose, comprising i) provision of a
finely divided material based on lignocellulose and treated with a
curable, aqueous composition, the curable aqueous composition
comprising: a) at least one crosslinkable urea compound from the
group consisting of the urea compounds H which have at least one
N-bonded group of the formula CH.sub.2OR, where R is hydrogen or
C.sub.1-C.sub.4-alkyl, and/or a 1,2-bishydroxyethane-1,2-diyl group
bridging the two nitrogen atoms of the urea, precondensates of the
urea compound H, and reaction products or mixtures of the urea
compound H with at least one alcohol which is selected from
C.sub.1-C.sub.6-alkanols, C.sub.2-C.sub.6-polyols and oligoethylene
glycols, and b) at least one catalyst K effecting crosslinking of
the urea compound; ii) glue-coating of the finely divided material
based on lignocellulose and obtained in step i) or of a mixture
thereof with other finely divided materials with a liquid or
pulverulent formulation of a binder; and iii) shaping and curing of
the glue-coated finely divided material to give a molding, or ii')
mixing of the finely divided material based on lignocellulose and
obtained in step i) with a thermoplastic polymer and iii') shaping
of the mixture to give a molding.
10. The process according to claim 9, wherein the treated material
based on lignocellulose is prepared by impregnating an untreated,
finely divided material based on lignocellulose with the aqueous
composition and, if appropriate, carrying out a drying and/or
curing at elevated temperature.
11. The process according to claim 9, wherein the finely divided
material is dried to a residual moisture content of less than 30%,
based on the dry matter, before the glue-coating in step ii).
12. The process according to claim 10, wherein drying and/or curing
is carried out at temperatures in the range from 50 to 220.degree.
C.
13. The process according to claim 9, wherein, in step i), a
treated finely divided material based on lignocellulose is prepared
by impregnation with the curable, aqueous composition, and the
substantially uncured material is glue-coated in step ii).
14. The process according to claim 9, wherein the curable, aqueous
composition is used in an amount such that the curable components
absorbed by the finely divided material are in the range from 1 to
60% by weight, based on the dry matter of the untreated, finely
divided material.
15. The process according to claim 9, wherein the untreated finely
divided material based on lignocellulose is selected from wood
fibers, wood chips and wood shreds.
16. The process according to claim 9, wherein the finely divided
material based on lignocellulose accounts for at least 80% by
weight, based on the total weight of the finely divided materials
forming the molding.
17. The process according to claim 9, wherein the binder used in
step ii) comprises at least one heat-curable binder.
18. The process according to claim 17, wherein the heat-curable
binder is used in the form of an aqueous formulation.
19. The process according to claim 17, wherein the heat-curable
binder is selected from aminoplast resins, phenol resins,
isocyanate resins and polycarboxylic acid resins.
20. The process according to claim 9, wherein, based on the solid
binder components, the binder is used in an amount of from 0.5 to
20% by weight, based on the total weight of the materials forming
the molding.
21. The process according to claim 9, wherein, in step i), a drying
and curing step is carried out, and the finely divided material
thus obtainable is mixed with at least one thermoplastic polymer
and the mixture is subjected to a shaping process.
22. The process according to claim 21, wherein the thermoplastic
polymer accounts for from 20 to 90% by weight, based on the total
amount of thermoplastic polymer and molding.
23. The process according to claim 21, wherein the thermoplastic
polymer is selected from poly-C.sub.2-C.sub.6-olefins,
poly-C.sub.2-C.sub.4-haloolefins and a mixture thereof.
24. A molding comprising finely divided materials based on
lignocellulose, obtainable by a process according to claim 9.
25. A finely divided material based on lignocellulose, obtainable
by treating an untreated finely divided material based on
lignocellulose with an aqueous composition, or by impregnating a
wood body with a curable, aqueous composition comprising: a) at
least one crosslinkable urea compound from the group consisting of
the urea compounds H which have at least one N-bonded group of the
formula CH.sub.2OR, where R is hydrogen or C.sub.1-C.sub.4-alkyl,
and/or a 1,2-bishydroxyethane-1,2-diyl group bridging the two
nitrogen atoms of the urea, precondensates of the urea compound H,
and reaction products or mixtures of the urea compound H with at
least one alcohol which is selected from C.sub.1-C.sub.6-alkanols,
C.sub.2-C.sub.6-polyols and oligoethylene glycols, and, if
appropriate, b) at least one catalyst K effecting crosslinking of
the urea compound.
Description
[0001] The present invention relates to a process for the
production of moldings from finely divided materials based on
lignocellulose, and the moldings obtainable thereby. The invention
also relates to the use of aqueous compositions which comprise at
least one crosslinkable urea compound for the preparation of finely
divided materials treated with this composition and based on
lignocellulose for the production of moldings.
[0002] Moldings based on finely divided materials based on
lignocellulose (also referred to below as moldings based on
lignocellulose particles), such as, for example, based on wood
particles, are widely used as construction materials in the
construction and furniture sectors. They are produced, as a rule,
by glue-coating of the lignocellulose particles with a liquid,
usually aqueous composition of binder polymers, shaping of the
materials thus glue-coated and curing. During the curing, adhesive
bonding of the finely divided materials takes place, if appropriate
with crosslinking of the binder, with the result that the molding
retains its stability. In the case of wood-plastic composites
(WPC), the finely divided materials are embedded in a plastic
matrix. An overview of the customary types of moldings based on
lignocellulose particles and the processes for their production is
given by H. H. Nimz et al, "Wood--Wood-based Materials", in
Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed. on CD-ROM,
Wiley-VCH, Weinheim 1997. As mass-produced goods, moldings based on
finely divided lignocellulose particles are subject to immense cost
pressure.
[0003] A key problem in the case of moldings based on
lignocellulose particles is their frequently only moderate to low
stability to water. This results from the property of the
lignocellulose particles to incorporate water, for example into the
cell walls, on contact with water or in a humid atmosphere. As a
result, the moldings swell and their mechanical strength is
reduced. Moreover, moldings based on lignocellulose particles, in
particular in the moist state, are attacked by wood-degrading or
wood-discoloring organisms, in particular microorganisms,
necessitating the treatment of the moldings with corresponding
fungicides and biocides. This in turn is a not inconsiderable cost
factor and is also disadvantageous from environmental points of
view.
[0004] For improving the stability, wood and comparable
lignocellulose-based materials are frequently rendered water
repellent, for example by treatment with wax-containing
impregnating agents. This makes it more difficult for water to
penetrate into the pores of the material.
[0005] It was proposed to improve the dimensional stability of
wood-base materials, such as particle boards and fiberboards, and
their stability to wood-destroying organisms by acetylating the
wood particles with the aid of anhydrides, such as acetic anhydride
(cf. EP-A 213252 and literature cited therein and Rowell et al.,
Wood and Fiber Science, 21 (1), pages 67-79). The high costs of the
treatment and the unpleasant intrinsic odor of the material thus
treated are disadvantageous, so that these measures have not become
established on the market.
[0006] Other chemicals too, such as isocyanates, siloxanes and
acrylamide, were proposed for the modification of lignocellulose
fibers (J. Appl. Polym Sci., 73 (1999) 2493-2505). However, these
measures too are as a whole unsatisfactory.
[0007] WO 2004/033170 and WO 2004/033171 describe the use of
impregnating agents based on hydroxymethyl- or
alkoxymethyl-modified urea derivatives, such as
1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one,
bis(hydroxymethyl)-4,5-dihydroxyimidazolidinone modified with
alkanols, 1,3-bis(hydroxymethyl)urea, 1,3-bis(methoxymethyl)urea,
1-hydroxymethyl-3-methylurea,
1,3-bis(hydroxymethyl)-imidazolidin-2-one,
1,3-dimethyl-4,5-dihydroxyimidazolidin-2-one or
tetra(hydroxy-methyl)acetylenediurea, for improving the durability,
dimensional stability and surface hardness of wood bodies
comprising solid wood. The problem of the dimensional stability of
moldings based on finely divided lignocellulose materials is not
discussed.
[0008] Accordingly, it is the object of the present invention to
provide a finely divided material based on lignocellulose, from
which material moldings having improved dimensional stability under
the action of moisture can be produced. The finely divided material
should moreover be economical to produce with regard to the use in
the production of mass-produced products, such as fiberboards and
particle boards.
[0009] It was surprisingly found that this and further objects can
be achieved by finely divided materials based on lignocellulose
which were treated with an aqueous composition which comprises at
least one crosslinkable urea compound, the crosslinkable urea
compound being selected from urea compounds H which have at least
one N-bonded group of the formula CH.sub.2OR, where R is hydrogen
or C.sub.1-C.sub.4-alkyl, and/or a 1,2-bishydroxyethane-1,2-diyl
group bridging the two nitrogen atoms of the urea, precondensates
of the urea compound H, and reaction products or mixtures of the
urea compound H with at least one alcohol which is selected from
C.sub.1-C.sub.6-alkanols, C.sub.2-C.sub.6-polyols and oligoethylene
glycols.
[0010] Below, finely divided materials based on lignocellulose are
also referred to as finely divided lignocellulose materials or
lignocellulose particles for short. Accordingly, finely divided
materials treated according to the invention and based on
lignocellulose are also referred to as treated lignocellulose
materials or finely divided lignocellulose materials according to
the invention or as treated lignocellulose particles or
lignocellulose particles according to the invention, and untreated
finely divided materials based on lignocellulose are also referred
to as untreated finely divided lignocellulose materials or
untreated lignocellulose particles.
[0011] Treatment is understood as meaning impregnation or soaking
of the untreated finely divided lignocellulose materials with the
aqueous composition and, if appropriate, drying and/or curing of
the impregnated material or the curable components absorbed by the
impregnated material.
[0012] Finely divided lignocellulose materials which were
impregnated with the aqueous composition of the crosslinkable urea
compounds and which were treated in a manner such that the
crosslinking of the urea compounds (curing) has taken place give,
on customary further processing, moldings which are distinguished
by superior mechanical properties, in particular by improved shape
stability or dimensional stability, i.e. less swelling on contact
with moisture, and by a higher surface hardness. Moreover, the
moldings are less susceptible to attack by wood-destroying
microorganisms, such as harmful wood-destroying fungi and
wood-destroying bacteria, with the result that the application of
corresponding fungicides and biocides can be reduced and frequently
even avoided. The crosslinking of the crosslinkable urea compounds
of the aqueous composition is effected after the impregnation,
optionally in a separate drying/curing step at elevated temperature
and/or during the subsequent shaping process after the glue-coating
with a binder customary for the production of moldings, if
appropriate by addition of a catalyst promoting the curing of the
urea compounds.
[0013] Accordingly, the present invention firstly relates to the
use of an aqueous composition, comprising at least one
crosslinkable urea compound from the group consisting of the urea
compounds H which have at least one N-bonded group of the formula
CH.sub.2OR, where R is hydrogen or C.sub.1-C.sub.4-alkyl, and/or a
1,2-bishydroxyethane-1,2-diyl group bridging the two nitrogen atoms
of the urea, precondensates of the urea compound H, and reaction
products or mixtures of the urea compound H with at least one
alcohol which is selected from C.sub.1-C.sub.6-alkanols,
C.sub.2-C.sub.6-polyols and oligoethylene glycols, for the
preparation of finely divided materials treated with this
composition and based on lignocellulose for the production of
moldings.
[0014] The invention furthermore relates to the treated
lignocellulose materials thus obtainable and their use for the
production of moldings. The invention also relates to the moldings
produced using such impregnated lignocellulose materials.
[0015] Aqueous compositions of crosslinkable urea compounds of the
type under discussion are disclosed, for example, in WO 2004/033170
and WO 2004/033171 cited at the outset and in K. Fisher et al.
"Textile Auxiliaries--Finishing Agents" Section 7.2.2 in Ullmann's
Encyclopedia of Industrial Chemistry, 5th Ed. on CD-ROM, Wiley-VCH,
Weinheim 1997, and literature cited there, e.g. U.S. Pat. No.
2,731,364 and U.S. Pat. No. 2,930,715, and are usually used as
crosslinking agents for textile finishing. Reaction products of
urea compounds with alcohols, for example modified
1,3-bis(hydroxymethyl)-4,5-dihydroxy-imidazolidin-2-one (mDMDHEU),
are disclosed, for example, in U.S. Pat. No. 4,396,391 and WO
98/29393. In addition, urea compounds H and their reaction products
and precondensates are commercially available, for example under
the trade names Fixapret.RTM. CP and Fixapret.RTM. ECO from BASF
Aktiengesellschaft.
[0016] The urea compounds present in the aqueous compositions are
low molecular weight compounds or oligomers having a low molecular
weight which as a rule are present completely dissolved in water.
The molecular weight of the urea compounds is usually below 400
dalton. It is assumed that, owing to these properties, the
compounds can penetrate into the cell walls of the lignocellulose
particles and, on curing, improve the mechanical stability of the
cell walls and reduce their swelling caused by water.
[0017] Examples of a crosslinkable urea compound of the curable,
aqueous composition are the following, without being restricted
thereto: [0018]
1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one (DMDHEU),
[0019] 1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one which
is modified with a C.sub.1-C.sub.6-alkanol, a
C.sub.2-C.sub.6-polyol or an oligoethylene glycol (modified DMDHEU
or mDMDHEU), [0020] 1,3-bis(hydroxymethyl)urea, [0021]
1,3-bis(methoxymethyl)urea; [0022] 1-hydroxymethyl-3-methylurea,
[0023] 1,3-bis(hydroxymethyl)imidazolidin-2-one
(dimethylolethyleneurea), [0024]
1,3-bis(hydroxymethyl)-1,3-hexahydropyrimidin-2-one
(dimethylolpropyleneurea), [0025]
1,3-bis(methoxymethyl)-4,5-dihydroxyimidazolidin-2-one (DMeDHEU)
and [0026] tetra(hydroxymethyl)acetylenediurea.
[0027] In a preferred embodiment of the invention, the
crosslinkable urea compound is selected from
1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one and a
1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one modified
with a C.sub.1-C.sub.6-alkanol, a C.sub.2-C.sub.6-polyol or an
oligoethylene glycol.
[0028] mDMDHEU are reaction products of
1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one with a
C.sub.1-C.sub.6-alkanol, a C.sub.2-C.sub.6-polyol, an oligoethylene
glycol or mixtures of these alcohols. Suitable C.sub.1-6-alkanols
are, for example, methanol, ethanol, n-propanol, isopropanol,
n-butanol and n-pentanol, methanol being preferred. Suitable
polyols are ethylene glycol, diethylene glycol, 1,2- and
1,3-propylene glycol, 1,2-, 1,3- and 1,4-butylene glycol and
glycerol. Suitable oligoethylene glycols are in particular those of
the formula HO(CH.sub.2CH.sub.2O).sub.nH, where n is from 2 to 20,
among which diethylene glycol and triethylene glycol are preferred.
For the preparation of mDMDHEU, DMDHEU are mixed with the alkanol,
the polyol or the polyethylene glycol. Here, the monohydric
alcohol, the polyol or oligo- or polyethylene glycol is usually
used in a ratio of from 0.1 to 2.0, in particular from 0.2 to 2,
mole equivalents each, based on DMDHEU. The mixture of DMDHEU and
the polyol or the polyethylene glycol is usually reacted in water
at temperatures of, preferably, from 20 to 70.degree. C. and a pH
of, preferably, from 1 to 2.5, the pH being adjusted as a rule to a
range of from 4 to 8 after the reaction.
[0029] In addition to the urea compounds H or the reaction products
or precondensates thereof (component A), the curable aqueous
compositions may also comprise one or more of the abovementioned
alcohols, C.sub.1-C.sub.6-alkanols, C.sub.2-C.sub.6-polyols,
oligoethylene glycols or mixtures of these alcohols (component C).
Suitable C.sub.1-6-alkanols are, for example, methanol, ethanol,
n-propanol, isopropanol, n-butanol and n-pentanol, methanol being
preferred. Suitable polyols are ethylene glycol, diethylene glycol,
1,2- and 1,3-propylene glycol, 1,2-, 1,3- and 1,4-butylene glycol
and glycerol. Suitable oligoethylene glycols are in particular
those of the formula HO(CH.sub.2CH.sub.2O).sub.nH, where n is from
2 to 20, among which diethylene glycol and triethylene glycol are
preferred.
[0030] The concentration of urea compound H or the reaction product
or precondensate thereof in the aqueous composition is usually in
the range from 1 to 60% by weight, frequently in the range from 10
to 60% by weight and in particular in the range from 15 to 50% by
weight, based on the total weight of the composition. If the
curable, aqueous composition comprises one of the abovementioned
alcohols, the concentration thereof is preferably in the range from
1 to 50% by weight, in particular in the range from 5 to 40% by
weight. The total amount of component A) and component C) usually
accounts for from 10 to 60% by weight and in particular from 20 to
50% by weight of the total weight of the aqueous composition.
[0031] In addition to the components A) and, if appropriate, C),
the aqueous composition may also comprise a catalyst K which
effects crosslinking of the urea compound H or of its reaction
product or precondensate. As a rule, metal salts from the group
consisting of the metal halides, metal sulfates, metal nitrates,
metal phosphates and metal tetrafluoroborates; boron trifluoride,
ammonium salts from the group consisting of the ammonium halides,
ammonium sulfate, ammonium oxalate and diammonium phosphate; and
organic carboxylic acids, organic sulfonic acids, boric acid,
sulfuric acid and hydrochloric acid are suitable as catalyst K.
[0032] Examples of metal salts suitable as catalysts K are in
particular magnesium chloride, magnesium sulfate, zinc chloride,
lithium chloride, lithium bromide, aluminum chloride, aluminum
sulfate, zinc nitrate and sodium tetrafluoroborate.
[0033] Examples of ammonium salts suitable as catalysts K are in
particular ammonium chloride, ammonium sulfate, ammonium oxalate
and diammonium phosphate.
[0034] Water-soluble organic carboxylic acids, such as maleic acid,
formic acid, citric acid, tartaric acid and oxalic acid, and
furthermore benzenesulfonic acid and p-toluene-sulfonic acid, but
also inorganic acids, such as hydrochloric acid, sulfuric acid,
boric acid or mixtures thereof, are in particular also suitable as
catalysts K.
[0035] The catalyst K is preferably chosen from magnesium chloride,
zinc chloride, magnesium sulfate, aluminum sulfate and mixtures
thereof, magnesium chloride being particularly preferred.
[0036] The catalyst K is usually added to the aqueous composition
only shortly before the impregnation of the lignocellulose
material. It is usually used in an amount of from 1 to 20% by
weight, in particular from 2 to 10% by weight, based on the total
weight of the components A) and, if appropriate, C) present in the
curable, aqueous composition. The concentration of the catalyst is
usually in the range from 0.1 to 10% by weight and in particular in
the range from 0.5 to 5% by weight, based on the total weight of
the curable, aqueous composition.
[0037] Furthermore, the aqueous composition used for the
impregnation may comprise a part or the total amount of the binders
which are required for the production of the moldings and which are
explained in more detail further below. If desired, the
concentration of the binder in the aqueous composition is usually
in the range from 0.5 to 25% by weight, frequently in the range
from 1 to 20% by weight and in particular in the range from 5 to
15% by weight, based on the total weight of the aqueous composition
and calculated as dry glue components (i.e. without any solvent or
diluent components of the binder).
[0038] It is assumed that the binder components of the glue
composition, in contrast to crosslinkable urea compounds, the
catalyst K and any alcohols of component C) which are present are
not absorbed or are absorbed only to a small extent by the cell
walls of the lignocellulose particles and remain substantially on
the surface of the particles and they are therefore available as
binder in the subsequent shaping process of the production of the
moldings.
[0039] The preparation of the finely divided materials impregnated
with the aqueous composition and based on lignocellulose can in
principle be effected by two different methods.
[0040] Thus, according to a first embodiment of the invention, a
coarse-particled, untreated material based on lignocellulose, e.g.
wood blocks, can be treated with the aqueous compositions which
comprise a catalyst K in the manner described in WO 2004/033170 or
WO 2004/033171 and then comminuted, for example by conversion into
chips, defibering or milling, or the treated wood chips or wood
fibers obtained on processing or recycling of the materials thus
obtained can be recovered.
[0041] Preferably, however, an untreated, finely divided material
based on lignocellulose is impregnated with the curable aqueous
composition and the catalyst K and then exposed to conditions which
effect crosslinking of the urea compounds present in the
composition and hence curing of the composition. The aqueous
composition and the catalyst K can be applied together in one
composition or in two separate compositions to the untreated finely
divided material based on lignocellulose. Usually, however, the
catalyst K is incorporated into the aqueous composition before the
application. However, it is also conceivable to impregnate the
finely divided material based on lignocellulose simultaneously or
in succession with a first aqueous formulation which comprises the
catalyst K in dissolved form, and a second aqueous composition
which comprises the crosslinkable urea compound and, if
appropriate, the alcohol component C).
[0042] The type of untreated finely divided lignocellulose material
depends in a known manner on the molding to be produced. Examples
of suitable finely divided lignocellulose materials comprise,
without being restricted thereto, finely divided materials
comprising wood, such as, for example, wood chips, for example from
chipped round wood and logs, chipped industrial wood and residual
industrial wood, sawmill and veneer wastes, chips from
thermomechanically digested wood, shavings from planing and
peeling, wood chips and wood shreds, and furthermore
lignocellulose-containing raw materials differing from wood, such
as bamboo, bagasse, cotton stalks, jute, sisal, straw, flax,
coconut fibers, banana fibers, reeds, e.g. Chinese silvergrass,
ramie, hemp, Manila hemp, esparto (alfa grass), rice husks and
cork.
[0043] The untreated finely divided lignocellulose materials may be
present in the form of granules, powder or preferably chips,
including sawdust and planing shavings, fibers and/or shreds. Among
these, materials comprising wood and bamboo, such as wood fibers,
wood chips and wood shreds or bamboo fibers, bamboo shreds and
bamboo chips and mixtures thereof, are particularly preferred.
These are in particular finely divided materials comprising wood.
The wood species of which the finely divided materials consist
comprise, for example, softwood, such as douglas fir, spruce, pine,
larch, stone pine, fir, cedar and Swiss stone pine, and hardwood,
such as maple, acacia, birch, beech, oak, alder, ash, aspen, hazel,
hornbeam, cherry, lime, poplar, locust, elm, walnut, willow,
adriatic oak and the like.
[0044] The dimensions, i.e. the measurements (length, thickness),
which at least 90% of the finely divided lignocellulose materials
have is usually in the range from 0.1 to 20 mm, in particular from
0.5 to 10 mm, and especially from 1 to 5 mm, it being possible for
the length which at least 90% of the particles have also to exceed
10 mm and be up to 200 mm in the case of elongated finely divided
materials having a length/width ratio>5. The average width or
thickness of elongated particles is typically in the range from 0.1
to 10, in particular in the range from 0.2 to 5, mm and especially
in the range from 0.3 to 3 mm.
[0045] The impregnation or soaking, respectively, of the untreated
finely divided materials based on lignocellulose can be carried
out, for example, by immersing the fibers in the aqueous
composition, by applying reduced pressure, if appropriate in
combination with pressure, or by spraying. The conditions are as a
rule chosen so that the amount of curable components of the aqueous
composition which are absorbed is at least 1% by weight, based on
the dry matter of the untreated material. The amount of curable
components which is absorbed may be up to 100% by weight, based on
the dry matter of the untreated lignocellulose materials and is
frequently in the range from 1 to 60% by weight, preferably in the
range from 5 to 50% by weight and in particular in the range from
10 to 30% by weight, based on the dry matter of the untreated
material used. Usually, the impregnation is effected at ambient
temperature, typically in the range from 15 to 40.degree. C.
[0046] The moisture of the untreated lignocellulose materials used
for the impregnation is not critical and may be, for example, up to
100% by weight. Here and below, the term "moisture" is synonymous
with the term residual moisture content according to DIN 52183.
Frequently, it is in the range from 1 to 80% and in particular from
5 to 50%.
[0047] On immersion, the untreated finely divided lignocellulose
materials, which advantageously have a moisture content in the
range from 1% to 100%, are immersed for a period of from a few
seconds to 12 h, in particular from 1 min to 60 min, in the aqueous
composition in a container or are suspended therein. The finely
divided lignocellulose material absorbs the aqueous impregnating
composition during this, it being possible for the amount of
curable components which is absorbed by the finely divided
lignocellulose material to be controlled by the concentration of
curable components (i.e. components A) and C)) in the aqueous
composition, by the temperature and by the duration of treatment.
The amount of curable components which is actually absorbed can be
determined by the person skilled in the art in a simple manner from
the weight increase of the finely divided lignocellulose material
and the concentration of the aqueous composition.
[0048] The impregnation can also be achieved by applying reduced
pressure, it being possible, if appropriate, for a phase of
elevated pressure to follow. For this purpose, the finely divided
lignocellulose material is brought into contact with the aqueous
composition under reduced pressure, which is frequently in the
range from 10 to 500 mbar and in particular in the range from 50 to
100 mbar, for example by immersion or suspension in the curable
aqueous composition. The time span is usually in the range from 1
min to 1 h. If appropriate, a phase at elevated pressure, for
example in the range from 1 bar to 20 bar, follows. The duration of
this phase is usually in the range from 1 min to 6 h, in particular
from 5 min to 1 h. During this, the finely divided lignocellulose
material absorbs the aqueous impregnating composition, it being
possible for the amount of curable components which is absorbed by
the finely divided lignocellulose material to be controlled by the
concentration of curable components in the aqueous composition, by
the pressure applied, by the temperature and by the duration of
treatment. Here too, the amount actually absorbed can be calculated
from the weight increase of the finely divided lignocellulose
material.
[0049] In a further embodiment of the invention, the impregnation
is effected by spraying the untreated lignocellulose particles with
the aqueous composition. The lignocellulose particles
advantageously have a moisture content of not more than 50%, for
example in the range from 1% to 30%. The spraying is usually
effected at temperatures in the range from 15 to 50.degree. C. The
amount of curable components which is absorbed by the finely
divided lignocellulose material can be controlled by the
concentration of curable components in the aqueous composition, by
the amount applied, by the temperature and by the duration of
spraying. The amount of curable components which is actually
absorbed results directly from the amount of aqueous composition
sprayed on. The spraying can be carried out in a conventional
manner in all apparatuses suitable for the spraying of solids, for
example in spray towers, fluidized-bed apparatuses and the
like.
[0050] The impregnation can also be effected by means of
ultrasound.
[0051] The impregnated finely divided lignocellulose particles thus
obtained are further processed to give moldings, if appropriate
after a drying step and/or a curing step.
[0052] In many cases, the further processing comprises glue-coating
of the treated finely divided material with a liquid or pulverulent
formulation of a binder and shaping and curing of the treated
material to give a molding. In other cases, for example in the
production of WPCs, the further processing comprises mixing of the
material obtained in step i) with a thermoplastic polymer and
shaping of the mixture. In this case, the production in step i)
usually comprises an impregnation and a drying or curing step.
[0053] The invention therefore also relates to a process for the
production of moldings from finely divided lignocellulose-based
materials, comprising [0054] i) provision of a lignocellulose-based
finely divided material which is impregnated with the curable,
aqueous composition described here and is, if appropriate, cured,
[0055] ii) glue-coating of the finely divided lignocellulose-based
material obtained in step i) or a mixture thereof with other finely
divided materials with a liquid or pulverulent formulation of a
binder; and [0056] iii) shaping and curing of the glue-coated
finely divided material to give a molding, or [0057] ii') mixing of
the treated, preferably dried and/or cured finely divided
lignocellulose-based material obtained in step i) with a
thermoplastic polymer and [0058] iii') shaping of the mixture to
give a molding.
[0059] The invention also relates to the moldings obtainable by the
process.
[0060] If the provision of the treated finely divided
lignocellulose materials comprises the impregnation of untreated
lignocellulose materials, a drying step, also predrying step below,
can be carried out after the impregnation in step i) and before the
glue-coating in step ii). During this, the volatile components of
the aqueous composition, in particular the water and excess organic
solvents which do not react in the curing/crosslinking of the urea
compounds, are partly or completely removed. In addition, depending
on the chosen drying temperature, partial or complete
curing/crosslinking of the curable components present in the
formulation may take place. The predrying/curing of the impregnated
materials is usually effected at temperatures of from 50.degree. C.
to 220.degree. C., in particular in the range from 80 to
200.degree. C. If curing is desired, the drying is preferably
effected at above 100.degree. C. The curing/drying can be carried
out in a conventional fresh air/exhaust air system, for example a
drum drier. The predrying is preferably effected in a manner such
that the moisture content of the finely divided lignocellulose
materials after the predrying is not more than 30%, in particular
not more than 20%, based on the dry matter. It may be advantageous
to carry out the drying/curing to a moisture content of <10% and
in particular <5%, based on the dry matter. The moisture content
can be controlled in a simple manner by the temperature, the
duration and the pressure chosen in the predrying.
[0061] However, a predrying step is in principle not necessary, and
removal of volatile components and crosslinking of the curable
components of the aqueous composition can also be effected after
the glue-coating in step ii) or can be carried out in the shaping
and curing step iii). Such a procedure not only has the advantage
of simplifying the process but permits shorter glue-coating and
shaping times. In a preferred embodiment, therefore, preferably no
separate drying step is carried out and the glue-coating is
effected immediately after the impregnation or simultaneously
therewith.
[0062] If the aqueous composition already comprises an amount of
binder which is sufficient for the production of the molding,
treatment step i) and glue-coating ii) take place at the same time,
and the removal of the volatile components and the crosslinking of
the curable components of the aqueous composition are carried out
in the shaping and curing step iii).
[0063] If the aqueous composition used for the impregnation in step
i) does not comprise an amount of binder which is sufficient for
the production of the moldings, the impregnated and, if
appropriate, predried and cured lignocellulose particles are then
glue-coated in a conventional manner with the binder required for
the production of the moldings.
[0064] The glue-coating can be effected in a conventional manner.
If appropriate, further finely divided materials forming the
molding, additives, catalysts or assistants are added at this
stage.
[0065] The type of binder depends in a known manner on the type of
molding to be produced. Suitable binders are described, for
example, in A. Pizzi (editor): Wood Adhesives, Marcel Dekker, New
York 1983. Examples of binders are: [0066] i) heat-curable binders
(reactive binders), such as aminoplast resins, phenol resins,
isocyanate resins, epoxy resins and polycarboxylic acid resins;
[0067] ii) thermoplastic materials, such as polyethylene,
polypropylene, polystyrene resins, polysulfones and polyester
resins; and [0068] iii) film-forming polymers, for example aqueous
polymer dispersions based on styrene-acrylates, polyacrylates
(acrylic ester/methacrylic ester copolymers), vinyl acetate
polymers (polyvinyl acetate), styrene-butadiene copolymers and the
like.
[0069] Preferred binders are the heat-curable binders mentioned in
group i) and mixtures thereof with film-forming polymers of group
iii), the heat-curable binders preferably being used in the form of
aqueous formulations.
[0070] Preferred binders are aminoplast resins, phenol resins,
isocyanate resins, polyvinyl acetate and polycarboxylic acid
resins.
[0071] Particularly suitable aminoplast resins are formaldehyde
condensates of urea (urea-formaldehyde condensates) and of melamine
(melamine-formaldehyde condensates). They are commercially
available as aqueous solutions or powders with the names
Kaurit.RTM. and Kauramin.RTM. (produced by BASF) and comprise urea-
and/or melamine-formaldehyde precondensates. Typical phenol resins
are phenol-formaldehyde condensates, phenol-resorcinol-formaldehyde
condensates and the like. Cocondensates of aminoplast resins and
phenol resins are also suitable. Examples of cocondensates of
aminoplast resins and phenol resins are urea-melamine-formaldehyde
condensates, melamine-urea-formaldehyde-phenol condensates and
their mixtures. Their preparation and use for the production of
moldings from finely divided lignocellulose materials are generally
known. Urea-formaldehyde resins are preferred, and among these in
particular those having a molar ratio of 1 mol of urea to 1.1 to
1.4 mol of formaldehyde.
[0072] In the processing of aminoplast resins and phenol resins,
there is a transition from the soluble and fusible precondensates
to infusible and insoluble products. In this process designated as
curing, complete crosslinking of the precondensates is known to
occur, which as a rule is accelerated by curing agents. Curing
agents which may be used are the curing agents known to the person
skilled in the art for urea-, phenol- and/or melamine-formaldehyde
resins, such as acidic and/or acid-eliminating compounds, e.g.
ammonium or amine salts. As a rule, the proportion of curing agent
in an adhesive resin liquor is from 1 to 5% by weight, based on the
proportion of liquid resin.
[0073] Suitable isocyanate resins are all conventional resins based
on methylenediphenylene isocyanates (MDI). As a rule, they consist
of a mixture of monomers and oligomeric di- or polyisocyanates, the
so-called precondensates, which are capable of reacting with the
cellulose, the lignin and the moisture content of the
lignocellulose particles. Suitable isocyanate resins are
commercially available, for example, as Lupranate brands
(Elastogran).
[0074] Examples of reactive polycarboxylic acid resins are
compositions comprising [0075] i) a polymer P of ethylenically
unsaturated monomers which is composed of from 5 to 100, preferably
from 5 to 50, % by weight of an ethylenically unsaturated acid
anhydride or of an ethylenically unsaturated dicarboxylic acid
whose carboxyl groups can form an anhydride, or the reaction
products thereof with alkanolamines (monomers a)), and from 0 to
95% by weight, preferably from 50 to 95% by weight, of monomers b)
which differ from the monomers a); and [0076] ii) at least one
alkanolamine A-(OH).sub.2 having at least two hydroxyl groups
and/or an alkoxylated polyamine and [0077] iii) if appropriate, a
water-insoluble, water-dispersible film-forming polymer P'.
[0078] Reactive polycarboxylic acid resins are known to the person
skilled in the art and are described in, for example, EP-A-882 093,
WO 97/45461, WO 99/09100, WO 99/02591, WO 01/27163 and WO
01/27198.
[0079] Polymers P which comprise maleic acid and/or maleic
anhydride as monomers a) are particularly preferred.
[0080] Preferred monomers b) are ethylenically unsaturated
C.sub.3-C.sub.6-monocarboxylic acids, such as acrylic acid or
methacrylic acid, olefins, such as ethene, propene, butene,
isobutene, cyclopentene or diisobutene, vinylaromatics, such as
styrene, alkyl vinyl ethers, e.g. methyl vinyl ether or ethyl vinyl
ether, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, vinyl
acetate, butadiene, acrylonitrile or mixtures thereof. Particularly
preferred monomers b) are acrylic acid, methacrylic acid, ethene,
acrylamide, styrene and acrylonitrile or mixtures thereof.
[0081] Polymers P in which the monomer b) comprises at least one
C.sub.3-C.sub.6-monocarboxylic acid, preferably acrylic acid, as
comonomer b) are particularly preferred.
[0082] Alkanolamines having at least two OH groups, such as
diethanolamine, triethanolamine, diisopropanolamine,
triisopropanolamine, methyldiethanolamine, butyldiethanolamine and
methyldiisopropanolamine, are mentioned as component A-(OH).sub.2.
Triethanolamine is preferred. Component A-(OH).sub.2 furthermore
includes alkoxylated, in particular ethoxylated, polyamines, as
described in WO 97/45461, for example compounds of the formulae I
and in particular Ia, Ie and If described there.
[0083] All water-insoluble polymers which are film-forming and are
dispersible in water are in principle suitable as component P' and
as a binder of group iii). These include in particular emulsion
polymers and the powders prepared therefrom, such as those referred
to as polymers A1, for example, in WO 01/27198. The polymers P'
frequently have a glass transition temperature in the range from
-10 to +150.degree. C. and in particular in the range from +20 to
+120.degree. C. They are in particular copolymers based on
styrene/butadiene, based on styrene/alkyl acrylate and those based
on alkyl methacrylate/alkyl acrylate.
[0084] For the preparation of the polycarboxylic acid resins, the
polymer P and the alkanolamine A-(OH).sub.2 are preferably used in
a ratio relative to one another such that the molar ratio of
carboxyl groups of the component P and of the hydroxyl groups of
the component A-(OH).sub.2 is from 20:1 to 1:1, preferably from 8:1
to 5:1 and particularly preferably from 5:1 to 1.7:1 (the anhydride
groups are calculated here as 2 carboxyl groups).
[0085] The binder is usually used in amounts of from 0.5 to 30% by
weight, frequently from 1 to 20% by weight, in particular in
amounts from 5 to 15% by weight, based on the treated
lignocellulose materials.
[0086] Preferred binders of group i) can of course also be used as
mixtures with one another or as mixtures with binders of groups ii)
and in particular iii).
[0087] In addition, conventional assistants and additives can be
used for the production of the moldings, such as the abovementioned
curing agents, i.e. catalysts, which result in more rapid
crosslinking of the binder.
[0088] The assistants include, for example, bactericides or
fungicides and water repellents for increasing the water resistance
of the moldings. Suitable water repellents are conventional aqueous
paraffin dispersions or silicones. Furthermore, wetting agents,
thickeners, plasticizing agents and retention aids can be used in
the production. These are frequently added to the binder
composition. The binder compositions frequently also comprise
coupling reagents, such as alkoxysilanes, for example
3-aminopropyltriethoxysilane, soluble or emulsifiable oils as
lubricants and dust-binding agents and wetting assistants.
[0089] Conventional additives comprise inert fillers, such as
aluminum silicates, quartz, precipitated or pyrogenic silica,
gypsum and barytes, talc, dolomite or calcium carbonate;
color-imparting pigments, such as titanium white, zinc white, iron
oxide black, etc.
[0090] Finally, conventional fireproofing agents, such as, for
example, aluminum silicates, aluminum hydroxides, borates and/or
phosphates, can be used in the production of the moldings.
[0091] The glue-coating is effected by the methods customary for
this purpose, for example by mixing the finely divided, impregnated
lignocellulose materials with the binder in conventional mixing
apparatuses for mixing liquid with solid materials, by fluidizing
the lignocellulose materials in an air stream and spraying the
binder, preferably in the form of a liquid binder composition, into
the fiber stream thus produced ("blow-line" method).
[0092] The glue-coated mixture of lignocellulose-containing
materials and the binder composition can be predried at elevated
temperature, for example at temperatures of from 10 to 200.degree.
C., for removal of volatile components prior to shaping. Depending
on the type of binder composition, however, the removal of volatile
components can also be dispensed with or can be carried out during
the shaping step.
[0093] After the glue-coating and, if appropriate, predrying, a
shaping step is effected, which is carried out in a manner known
per se, as a rule at elevated temperature, for example at
temperatures of from 50 to 300.degree. C., preferably from 100 to
250.degree. C. and particularly preferably from 140 to 225.degree.
C., and usually at elevated pressures of, in general, from 2 to 200
bar, preferably from 5 to 100 bar, particularly preferably from 20
to 50 bar.
[0094] Suitable methods of shaping are familiar to the person
skilled in the art and comprise, for example, extrusion methods,
thermoforming and in particular hot pressing, it being possible for
these methods to be batchwise or continuous, for example as roller
pressing, gliding film pressing, calender pressing, extrusion
pressing or steam injection pressing. An overview of conventional
methods is to be found, for example, in Ullmann's Encyclopedia of
Industrial Chemistry, "Wood--Wood based Materials", Sections 2.3.1,
2.3.2 and 2.3.3, 5th Edition on CD-ROM, Wiley-Verlag-Chemie,
Weinheim 1997.
[0095] At the temperatures prevailing during the shaping and the
pressure, adhesion of the lignocellulose particles and, depending
on the type of binder, melting and/or crosslinking of the binder
components takes place so that a stable molding forms on cooling
and removal of the mold.
[0096] The moldings may be shaped in any desired manner and
comprise sheet-like moldings, such as boards or mats, or have a
3-dimensional form, for example specially shaped articles. Examples
of sheet-like moldings comprise OSB boards (oriented structural
board), particle boards, wafer boards, insulating panels, medium
density fiberboards (MDF) and high density fiberboards (HDF). The
moldings according to the invention also include OSL boards and OSL
shaped articles (oriented strand lumber) and PSL boards and PSL
shaped articles (parallel strand lumber). The moldings also include
shaped articles comprising WPC (wood-plastic composites).
[0097] The process according to the invention is particularly
suitable for the production of moldings wherein the lignocellulose
material is wood. Here, depending on the size of the
lignocellulose-containing particles used, a distinction is made
between OSB boards (oriented structural boards), particle boards,
wafer boards, OSL boards and OSL shaped articles (oriented strand
lumber), PSL boards and PSL shaped articles (parallel strand
lumber), insulating panels and medium density fiberboards (MDF) and
high density fiberboards (HDF) and the like.
[0098] The process according to the invention is also particularly
suitable for the production of so-called WPC (wood-plastic
composites), as described, for example, in WO 96/34045, and the
literature cited there and in a general manner in Oster.
Kunststoffzeitschrift 35, 2004, 10-13 and in Klauditzforum 5th
Edition 6/2004. The processes known for the production of WPC can
be carried out in an analogous manner with the lignocellulose
materials treated according to the invention.
[0099] For the production of the WPCs, the finely divided
lignocellulose material treated according to the invention, after a
drying/curing step has been carried out beforehand, is mixed with
at least one thermoplastic material, for example thermoplastic
polymers based on poly-C.sub.2-C.sub.6-olefins, such as
polyethylene, polypropylene and the like, or based on
poly-C.sub.2-C.sub.4-haloolefins, such as polyvinyl chloride,
polyvinylidene chloride or copolymers of vinyl chloride with
vinylidene chloride, vinyl acetate and/or C.sub.2-C.sub.6-olefins,
and then subjected to a shaping process, as a rule an injection
molding or extrusion process. The amount of thermoplastic polymer
generally accounts for from 20 to 90% by weight and in particular
from 30 to 80% by weight, based on the total mass. Accordingly, the
proportion of finely divided lignocellulose material treated
according to the invention is in the range from 10 to 80% by weight
and in particular from 20 to 70% by weight, based on the total
weight of the WPC. In addition, conventional additives, such as
adhesion promoters (e.g. organosilanes, maleic anhydride,
isocyanates), pigments, light stabilizers, lubricants or
fire-retardant components, can be added to the WPCs. The addition
of biocides is on the other hand not required.
[0100] The finely divided lignocellulose materials treated
according to the invention are particularly suitable for the
production of wood-base materials, such as wood particle boards and
wood fiberboards, including HDF, MDF, OSB, OSL and PSL (cf.
Ullmann's Encyclopedia of Industrial Chemistry, loc. cit.), which
are produced by gluing of comminuted wood, such as, for example,
wood chips, wood shreds and/or wood fibers.
[0101] The production of particle boards is generally known and is
described, for example, in H. J. Deppe, K. Ernst Taschenbuch der
Spanplattentechnik, 2nd Edition, Verlag Leinfelden 1982, and can be
used analogously in the process according to the invention.
[0102] In the production of particle board, the glue-coating of the
previously dried chips is effected in continuous mixers. In
general, different chip fractions are differently glue-coated in
separate mixers and then poured separately (multilayer boards) or
together. Chips whose average chip thickness is from 0.1 to 2 mm,
in particular from 0.2 to 0.5 mm, and which comprise less than 6%
by weight of water are preferably used. The binder composition is
applied as uniformly as possible to the wood chips, for example by
spraying the binder composition in finely divided form onto the
chips. The glue-coated wood chips are then scattered to form a
layer having a surface which is as uniform as possible, the
thickness of the layer depending on the desired thickness of the
final particle board. The scattered layer is, if appropriate,
precompressed while cold and pressed to give a dimensionally
accurate board at a temperature of, for example, from 100 to
250.degree. C., preferably from 140 to 225.degree. C. by
application of pressures of, usually, from 10 to 750 bar. The
required pressing times may vary within a wide range and are in
general from 15 second to 30 minutes.
[0103] The wood fibers of suitable quality which are required for
the production of medium density wood fiberboards (MDF) can be
produced from bark-free wood shreds by grinding in special mills or
so-called refiners at temperatures of about 180.degree. C. In the
case of MDF and HDF board production, the fibers are glue-coated in
the blow-line after the refiner. For glue-coating, the wood fibers
are generally fluidized in an air stream, and the binder
composition is sprayed into the fiber stream thus produced
("blow-line" method). The glue-coated fibers then pass through a
drier in which they are dried to moisture contents of from 1 to 20%
by weight. In a few cases, the fibers are also first dried and
subsequently glue-coated in special continuous mixers. A
combination of blow-line and mixer glue-coating is also possible.
The ratio of wood fibers to binder composition, based on the dry
content or solids content, is usually from 40:1 to 3:1, preferably
from 20:1 to 4:1. The glue-coated fibers are dried in the fiber
stream at temperatures, of, for example, from 130 to 180.degree.
C., scattered to give a fiber mat, if appropriate precompressed
while cold and compressed at pressures of from 20 to 40 bar to give
boards or moldings.
[0104] In the case of OSB production, the wood chips (strands), if
appropriate after drying, are separated into middle and outer layer
material and glue-coated separately in continuous mixers. For
completion of the boards, the glue-coated wood chips are then
poured to give mats, if appropriate precompressed while cold and
pressed with heated presses at temperatures of from 170 to
240.degree. C. to give boards.
[0105] The glue-coated wood fibers can also be processed to give a
transportable fiber mat, as described, for example, in DE-A 2 417
243. This semifinished product can then be further processed in a
second spatially separate step carried out at a different time to
give boards or shaped articles, such as, for example, interior
trims of doors of motor vehicles.
[0106] Other lignocellulose materials, for example natural fibers,
such as sisal, jute, hemp, ramie, straw, flax, coconut fibers,
banana fibers and other natural fibers, can also be processed with
the use of binders known per se to give boards and moldings. The
natural fibers can also be used as mixtures with plastics fibers,
for example polypropylene, polyethylene, polyester, polyamides or
polyacrylonitrile. These plastics fibers may also act as cobinders
in addition to the abovementioned binder composition. The
proportion of the plastics fibers is preferably less than 50% by
weight, in particular less than 30% by weight and very particularly
preferably less than 10% by weight, based on all chips, shreds or
fibers. The processing of the fibers can be effected by methods
practiced in the case of the wood fiberboards. However, preformed
natural fiber mats can also be impregnated with the binders
according to the invention, if appropriate with addition of a
wetting assistant. The impregnated mats are then pressed in the
binder-moist or predried state, for example at temperatures of from
100 to 250.degree. C. and pressures of from 10 to 100 bar, to give
boards or shaped articles.
[0107] Owing to their high stability, the moldings according to the
invention are suitable for a multiplicity of different
applications, in particular for applications in which they are
exposed to weathering and moisture, for example as a base for
structural components in house building and in shipbuilding, for
example for interior and exterior walls, floor construction, for
the production of claddings in house building, shipbuilding and
automotive construction, for example as exterior trims, interior
trims, trunk and engine space linings, as a substrate for
decorative panels, such as ceiling, wall and prefabricted parquet
panels, as components and boards in the furniture industry and for
the do-it-yourself sector, etc.
[0108] The following examples are intended merely to explain the
examples according to the invention and are not to be understood as
being limiting.
[0109] The stated moisture contents were determined according to
DIN 52183.
EXAMPLE 1
[0110] The impregnating agent used was a 50% strength aqueous
solution of a DMDHEU modified with diethylene glycol and methanol
(mDMDHEU), which solution was mixed with 1.5% of
MgCl.sub.2.6H.sub.2O.
[0111] Thermomechanically digested spruce wood chips having an
average fiber length (90% value) and a moisture content of 11% were
introduced into an impregnating unit by means of a metal basket.
The impregnating unit was subjected to a reduced pressure of 100
mbar absolute for 30 minutes and then flooded with the impregnating
agent. A pressure of 10 bar was then applied for one hour. The
pressure phase was terminated and the residual liquid was removed.
The chips thus obtained were then dried in a drier for 4 h at
50.degree. C.
EXAMPLE 2
[0112] In a manner analogous to example 1, planing shavings of
pinewood having average dimensions of 0.5 mm.times.5 mm.times.100
mm were impregnated and then dried.
EXAMPLE 3
[0113] The impregnated pinewood shavings obtained in example 2 were
heated to 130.degree. C. in a drying oven for 1 h, cured pinewood
shavings being obtained.
EXAMPLE 4
Production of a Particle Board
[0114] 5400 g of dried chips from example 1 were sprayed with 1628
g of the composition stated in table 1, and 3370 g thereof were
poured into a mold (56.5 cm.times.44 cm). The material was pressed
in a press at 190.degree. C. up to a thickness of 18 mm in 230 s to
give a particle board.
[0115] The particle board comprised 14% of solid resin/absolutely
dry chips, 0.5% of solid wax/absolutely dry chips (absolutely dry=%
by weight, based on dry chips).
TABLE-US-00001 TABLE 1 Urea-formaldehyde resin, 68% strength 100.0
p Paraffin emulsion, 60% strength 6.3 p Ammonium nitrate solution,
52% strength 4.0 p p = parts by weight
EXAMPLE 5
Production of an MDF Board
[0116] 1000 g of absolutely dry fibers from example 3 were sprayed
with the glue batch stated in table 2 and dried to a moisture
content of 8%. 920 g thereof were poured into a mold (30
cm.times.30 cm). The material was pressed in a press at 190.degree.
C. to a thickness of 12 mm in 300 s to give an MDF board.
[0117] The MDF board comprised 14% of solid resin/absolutely dry
fibers and 0.5% of solid wax/absolutely dry fibers.
TABLE-US-00002 TABLE 2 Urea-formaldehyde resin, 68% strength 100.0
g Paraffin emulsion, 60% strength 3.2 g Water 11.8 g
EXAMPLE 6
[0118] In each case 70 g of wood fibers from example 3 were
thoroughly mixed with 13.2 g of a pulveruient composition according
to example P2 to P6 of WO 01/27198.14 g of water were then also
sprayed onto this fiber-binder mixture with continued mixing. The
glue-coated fibers were dried at 70.degree. C. to a residual
moisture content of 10% (absolutely dry) and scattered to give a
19.times.19 cm fiber mat.
[0119] These fiber mats were compressed using a hydraulic press
(manufacturer Wickert Maschinenbau GmbH, Landau, model WKP
600/3.5/3) at a pressing temperature of 220.degree. C. for 120 sec
between two metal plates with 2 mm spacers. For this purpose, a
press pressure of 50 bar was first established. After the pressure
had been relieved for 10 sec, a pressure of 200 bar was then
maintained for a further 90 sec.
[0120] The fiberboards obtained were stored for 24 h under standard
temperature and humidity conditions at 23.degree. C. and 65%
relative humidity and then tested. The water absorption was
determined from the weight increase (in %, based on the original
weight). The swelling, based on thickness, of the wood fiberboards
was determined as a relative increase in the thickness of 2.times.2
cm test specimens after storage for 24 h in demineralized water
analogously to DIN 52351.
EXAMPLE 7
[0121] Shavings, prepared by chipping pine panels modified with
DMDHEU, prepared according to WO 2004/033170, by analogy to example
2, were pressed with the glues given in Table 3 by analogy to
example 4 at 190.degree. C. for 230 s to give particle boards
(density 650 kg/m.sup.3). Likewise, non-modified pinewood shavings
were pressed under similar conditions to give particle boards. The
thus prepared particle boards were stored in demineralised water at
ambient temperature for 24 h and the swelling was determined as a
relative increase in the thickness.
TABLE-US-00003 TABLE 7 Swelling after 24 h Shavings [%] Kaurit
.RTM. 418.sup.1) [% b.w.].sup.2) 8 non-modified 25.7 10
non-modified 19.5 8 modified 14.1 10 modified 10.5 Kauramin .RTM.
620.sup.3) [% b.w].sup.2) 8 non-modified 20.4 10 non-modified 16.3
8 modified 11.9 10 modified 9.1 Kaurit .RTM. 347.sup.4) [%
b.w.].sup.2)) 6 non-modified 35.9 8 non-modified 22.1 6 modified
19.5 8 modified 15.4 Kaurit .RTM. 350.sup.5) [% b.w.].sup.2)) 6
non-modified 29.4 8 non-modified 22.3 6 modified 19.5 8 modified
15.4 .sup.1),4),5)aqueous urea resin glues, brands of BASF AG,
Ludwigshafen .sup.2)resin components, based on shavings (absolute
dry) .sup.3)aqueous melamine resin glue, brand of BASF AG,
Ludwigshafen
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