U.S. patent application number 11/566662 was filed with the patent office on 2007-06-07 for stable, thin-film organic passivates.
Invention is credited to Brian D. Bammel, Thomas W. Cape, Gregory T. Donaldson, John D. McGee, Steven R. Smith, Thomas S. II Smith, Jasdeep Sohi.
Application Number | 20070125451 11/566662 |
Document ID | / |
Family ID | 39492543 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070125451 |
Kind Code |
A1 |
Smith; Steven R. ; et
al. |
June 7, 2007 |
STABLE, THIN-FILM ORGANIC PASSIVATES
Abstract
An aqueous liquid passivate composition for treating metal
surfaces having dispersed therein solid particles which result in a
transparent or translucent, preferably colorless, corrosion
resistant coating, upon drying of the aqueous liquid passivate
composition, the coating providing better resistance to heating by
solar energy than the untreated metal surface at lower coating
thicknesses than paint.
Inventors: |
Smith; Steven R.; (Troy,
MI) ; Cape; Thomas W.; (West Bloomfield, MI) ;
Sohi; Jasdeep; (Shelby Township, MI) ; Donaldson;
Gregory T.; (Sterling Heights, MI) ; McGee; John
D.; (Troy, MI) ; Smith; Thomas S. II; (Novi,
MI) ; Bammel; Brian D.; (Rochester Hills,
MI) |
Correspondence
Address: |
HENKEL CORPORATION
THE TRIAD, SUITE 200
2200 RENAISSANCE BLVD.
GULPH MILLS
PA
19406
US
|
Family ID: |
39492543 |
Appl. No.: |
11/566662 |
Filed: |
December 4, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11330869 |
Jan 12, 2006 |
|
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11566662 |
Dec 4, 2006 |
|
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60644191 |
Jan 14, 2005 |
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Current U.S.
Class: |
148/247 ;
148/251 |
Current CPC
Class: |
C23C 22/44 20130101;
C09D 5/084 20130101; C23C 22/361 20130101 |
Class at
Publication: |
148/247 ;
148/251 |
International
Class: |
C23C 22/26 20060101
C23C022/26 |
Claims
1. A composition useful for passivating a metal surface, said
composition comprising water and: (A) dispersed solid particles of
metal and/or metalloid oxide, desirably the metal and/or metalloid
oxide is a powder the particles preferably having a mean particle
size of less or equal to 100 nm, and (B) dissolved, dispersed, or
both dissolved and dispersed hexavalent chromium that is not part
of immediately previously recited component (A); (C) dissolved,
dispersed, or both dissolved and dispersed organic film-forming
resin; and, optionally, one or more of the following components:
(D) dissolved, dispersed, or both dissolved and dispersed pH
adjusting agent that is not part of any one of immediately
previously recited components (A) through (C); (E) dissolved,
dispersed, or both dissolved and dispersed trivalent chromium that
is not part of any one of immediately previously recited components
(A) through (D); (F) dissolved, dispersed, or both dissolved and
dispersed wax that is not part of immediately previously recited
component (A) through (E); (G) at least one dissolved, dispersed,
or both dissolved and dispersed surfactant and/or antiblocking
agent that is not part of any of immediately previously recited
components (A) through (F); (H) dissolved organic solvent that is
not part of any of immediately previously recited components (A)
through (G); (I) dissolved, dispersed, or both dissolved and
dispersed material selected from the group consisting of (i)
reducing agents that are capable, at a specified temperature, of
reducing hexavalent chromium in the composition to trivalent
chromium and (ii) oxidation products from a reducing agent that has
reduced some initially hexavalent chromium in the composition to
trivalent chromium, said dissolved, dispersed, or both dissolved
and dispersed material not being part of any of immediately
previously recited components (A) through (H); and (J) dissolved,
dispersed, or both dissolved and dispersed colorant that is not
part of any of immediately previously recited components (A)
through (I); wherein said composition comprises less than 0.04 wt %
chromium and dries to a transparent or translucent coating having
an emittance of at least 0.60 and a reflectance of at least
0.60.
2. The composition of claim 1, wherein the total concentration of
the complex fluoride is at least 0.5 g/L and is not more than 100
g/L.
3. The composition of claim 1, wherein the at least one complex
fluoride is a titanium and/or zirconium complex fluoride.
4. The composition of claim 1, wherein said composition is
essentially free of chromium, the resin comprises a non-ionic or
non-ionically stabilized acrylic and/or acrylic copolymer resin in
dispersed form, said composition comprising at least one pH
adjusting component.
5. The composition of claim 1, wherein the pH of the composition is
within a range of from about 1 to about 5 and the composition is
storage stable at 100 deg. F. for at least 3 months.
6. The composition of claim 1, comprising at least one component
that comprises vanadium.
7. The composition of claim 1, comprising at least one wax,
selected from the group of waxes stable in strong acidic solutions
having an average particle size less than about 1 micron and a
melting point of from about 50 to about 175 degrees C.
8. The composition of claim 1, containing: (A) 25-75 weight % of at
least one inorganic oxide in dispersed form, the particles
preferably having a mean particle size of less than 100 nm; (B)
0.05-5 weight % of at least one complex fluoride of an element
selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge
and B; preferably Ti and/or Zr; (C) 10-50 weight % of a non-ionic
or non-ionically stabilized resin in dispersed form selected from
the group consisting of acrylic, polyurethane, vinyl, and polyester
resins, and mixtures thereof; (D) optionally, dissolved phosphate
anions; (E) 0.1 to 7 weight % of at least one component comprising
vanadium; (F) 0.05-20 weight % of at least one wax in dispersed
form; (G) and optionally, at least one further additive selected
from the group consisting of a sequestrant, a wetting agent, a
defoamer, and a pH adjusting component; said composition comprising
less than 0.04 wt % chromium.
9. A process of treating a ferriferous, aluminiferous or
zinciferous metal substrate comprising: optionally, cleaning a
surface of said metal substrate to be passivated; contacting the
metal substrate surface to be passivated with a passivating
composition for a time sufficient to form a coating on said metal
surface, wherein the passivating composition comprises water and:
(A) at least one inorganic oxide in dispersed form, the particles
preferably having a mean particle size of less than 100 nm; (B) at
least one complex fluoride of an element selected from the group
consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti
and/or Zr; (C) a non-ionic or non-ionically stabilized resin in
dispersed form selected from the group consisting of acrylic,
polyurethane, vinyl, and polyester resins, and mixtures thereof;
(D) optionally, dissolved phosphate anions; (E) optionally, at
least one component comprising vanadium; (F) optionally, at least
one wax in dispersed form; (G) and optionally, at least one further
additive selected from the group consisting of a sequestrant, a
wetting agent, a defoamer, and a pH adjusting component; said
composition comprising less than 0.04 wt % chromium; and drying to
form a transparent or translucent passivate coating having an
emittance of 0.60 and a reflectance of 0.60, on the metal
surface.
10. The process of claim 14 further comprising the step of coating
the metal substrate with a dissimilar metal, thereby creating a
metal substrate surface to be passivated, prior to contacting with
the passivating composition.
11. A uniform and stable liquid composition of matter comprising
water and the following components: (A) dispersed solid particles
of metal and/or metalloid oxide having a mean particle size of less
or equal to 100 nm, and (B) dissolved, dispersed, or both dissolved
and dispersed hexavalent chromium that is not part of immediately
previously recited component (A); (C) dissolved, dispersed, or both
dissolved and dispersed organic film-forming resin; and,
optionally, one or more of the following components: (D) dissolved,
dispersed, or both dissolved and dispersed pH adjusting agent that
is not part of any one of immediately previously recited components
(A) through (C); (E) dissolved, dispersed, or both dissolved and
dispersed trivalent chromium that is not part of any one of
immediately previously recited components (A) through (D); (F)
dissolved, dispersed, or both dissolved and dispersed wax that is
not part of immediately previously recited component (A) through
(E); (G) at least one dissolved, dispersed, or both dissolved and
dispersed surfactant and/or antiblocking agent that is not part of
any of immediately previously recited components (A) through (F);
(H) dissolved organic solvent that is not part of any of
immediately previously recited components (A) through (G); (I)
dissolved, dispersed, or both dissolved and dispersed material
selected from the group consisting of (i) reducing agents that are
capable, at a specified temperature, of reducing hexavalent
chromium in the composition to trivalent chromium and (ii)
oxidation products from a reducing agent that has reduced some
initially hexavalent chromium in the composition to trivalent
chromium, said dissolved, dispersed, or both dissolved and
dispersed material not being part of any of immediately previously
recited components (A) through (H); and (J) dissolved, dispersed,
or both dissolved and dispersed colorant that is not part of any of
immediately previously recited components (A) through (I); wherein
said composition dries to a transparent or translucent coating
having an emittance of at least 0.60 and a reflectance of at least
0.60.
12. The composition of claim 11, wherein the dispersed solid
particles of metal and/or metalloid oxide are selected from oxides
of Ti, Zn, Zr, Sb, Al, Hf, and V.
13. The composition of claim 11, wherein the dispersed solid
particles of metal and/or metalloid oxide are present in an amount
of about 10.0 to about 80.0 weight %.
14. The composition of claim 11, wherein the dispersed solid
particles of metal and/or metalloid oxide are selected such that
the as-dried coating a clear, colorless coating after not more than
60 days.
15. The composition of claim 11, wherein the dispersed solid
particles of metal and/or metalloid oxide are selected such that
the coating has emittance of at least 0.60 at wavelengths of about
250 to about 2500 nm.
16. The composition of claim 11, wherein the dispersed solid
particles of metal and/or metalloid oxide have a mean particle size
range from about 1 to about 50 nanometers.
17. The composition of claim 11, wherein the dispersed solid
particles of metal and/or metalloid oxide have a mean particle size
range from about 5 to about 35 nanometers.
18. The composition of claim 11, wherein the dispersed solid
particles of metal oxide are selected from oxides of Ti, Zn, Zr,
Sb, Al, Hf, and V.
19. A process of treating a ferriferous, aluminiferous or
zinciferous metal substrate comprising: optionally, cleaning a
surface of said metal substrate to be passivated; contacting the
metal substrate surface to be passivated with a passivating
composition for a time sufficient to form a coating on said metal
surface, wherein the passivating composition comprises water and:
(A) dispersed solid particles of metal and/or metalloid oxide
having a mean particle size of less or equal to 100 nm, and (B)
dissolved, dispersed, or both dissolved and dispersed hexavalent
chromium that is not part of immediately previously recited
component (A); (C) dissolved, dispersed, or both dissolved and
dispersed organic film-forming resin; and, optionally, one or more
of the following components: (D) dissolved, dispersed, or both
dissolved and dispersed pH adjusting agent that is not part of any
one of immediately previously recited components (A) through (C);
(E) dissolved, dispersed, or both dissolved and dispersed trivalent
chromium that is not part of any one of immediately previously
recited components (A) through (D); (F) dissolved, dispersed, or
both dissolved and dispersed wax that is not part of immediately
previously recited component (A) through (E); (G) at least one
dissolved, dispersed, or both dissolved and dispersed surfactant
and/or antiblocking agent that is not part of any of immediately
previously recited components (A) through (F); (H) dissolved
organic solvent that is not part of any of immediately previously
recited components (A) through (G); (I) dissolved, dispersed, or
both dissolved and dispersed material selected from the group
consisting of (i) reducing agents that are capable, at a specified
temperature, of reducing hexavalent chromium in the composition to
trivalent chromium and (ii) oxidation products from a reducing
agent that has reduced some initially hexavalent chromium in the
composition to trivalent chromium, said dissolved, dispersed, or
both dissolved and dispersed material not being part of any of
immediately previously recited components (A) through (H); and (J)
dissolved, dispersed, or both dissolved and dispersed colorant that
is not part of any of immediately previously recited components (A)
through (I); drying to form a passivate coating having an emittance
of 0.60 and a reflectance of 0.60 and a thickness of 12 microns or
less, on the metal surface.
20. The process of claim 19 further comprising the step of coating
the metal substrate with a dissimilar metal, thereby creating a
metal substrate surface to be passivated, prior to contacting with
the passivating composition.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation in part of U.S.
application Ser. No. 11/330869, filed 12 Jan. 2006, which claims
priority to U.S. Provisional Application Ser. No. 60/644,191, filed
14 Jan. 2005, each of which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to compositions and processes
for passivating, i.e., forming a corrosion resistant surface layer,
on metal surfaces preferably predominantly of aluminum and/or zinc,
which also improves the metal surface's resistance to heating by
electromagnetic radiation (hereinafter EMR), in particular solar
radiation or energy. A wide variety of such surfaces are in normal
use, including many kinds of galvanized and/or aluminized steel,
and the invention is applicable to aluminiferous and/or zinciferous
surfaces which differ from the underlying metal, as well as to
solid alloys of aluminum and/or zinc which include zinc, such as
hot-dip and electro-galvanized, zinc alloys, aluminum, aluminum
alloys and mixtures thereof, as well as steel coated with these
metals (hereinafter referred to as zinc- and/or aluminum-containing
metal surfaces).
BACKGROUND OF THE INVENTION
[0003] Zinc (zinciferous) and zinc alloy (such as aluminiferous)
coatings are frequently used to protect steel from corrosion. Two
common types of metal-coated steel typically used are galvanized
steel (zinc), such as hot-dip, electrogalvanized and
Galvanneal.RTM., as well as zinc aluminum alloys such as
Galfan.RTM. and Galvalume.RTM. (55% Al, 43.5% Zn, 1.5% Si). The
thus coated steels have long service lifetimes as a result of
galvanic and/or sacrificial corrosion protection of the underlying
substrate afforded by the coatings. While the underlying steel
substrate is protected, the aluminum and zinc coating are sometimes
susceptible to corrosion that can result in surface staining and
white corrosion.
[0004] A variety of treatments can be used to prevent corrosion of
ferriferous, zinciferous and aluminiferous surfaces. These include
phosphate conversion coating followed by application of an oil,
which provides some short term protection, but requires removal of
the oil prior to painting. Also, well known in the industry are
phosphate conversion coatings, with or without a subsequent
painting step. Inorganic passivates, typically using chromium,
provide excellent passivation but have the drawbacks of poor paint
adhesion and adverse environmental impact.
[0005] Thin-film organic passivates are used industrially to
provide corrosion protection to zinc- and/or aluminum-containing
metal surfaces, including zinc coated or zinc alloy coated steel.
In addition these coatings provide lubricity to facilitate roll
forming of steel coils. The thin-film organic passivates are
distinguished from typical phosphate conversion coatings by, for
example, the presence of organic film forming resin and the amount
of protection provided by the coating. Known phosphate conversion
coatings generally require an overcoating of paint to achieve
adequate corrosion resistance.
[0006] Traditionally, most zinciferous and/or aluminiferous
surfaces have been passivated by chemical treatment with aqueous
liquid compositions containing at least some hexavalent chromium.
Thin-film organic passivates generally comprise an organic film
forming resin, typically an aqueous dispersion or latex; a surface
passivating material, most often a hexavalent chromium containing
substance; water and optional additives.
[0007] Various attempts have been made to make alternatives to the
chromium-containing products by substituting other metals for the
chromium in the latex-based passivate treatment products. The
alternative products included various metal ions and tend to have a
very low pH, that is in the range of pH about 1-2. Many of these
attempts failed where the latex became unstable and the formulation
coagulated, due at least in part to the low pH and the presence of
other ingredients, such as metal ions. Often, even if the
formulation did not immediately coagulate, the chromium-free
products had little or no shelf life, either separating or
coagulating over a matter of days or even hours.
[0008] Another drawback of prior art organic passivating
compositions is their undesirable effects on the physical
attributes of coils of metal. In the coil industry, lengths of
sheet metal are typically galvanically coated and passivated in a
continuous process. The metal is then coiled for storage and
transport, ordinarily while still at elevated temperature. These
coils are later unwound as the sheet metal is introduced into a
metal forming operation, such as stamping. The metal is cut into
selected lengths and formed into component parts of, by way of
non-limiting example, appliances, automobiles, furniture. In this
industry, the nature of the passivate coating can have undesirable
effects of binding or slippage between metal surfaces in the coil.
Each undesirable effect causes problems in manufacture; binding
refers to the coils sticking together and interferes with
uncoiling, and slipping/sliding of the metal surfaces relative to
each other in a coil can cause coil collapse. The need to avoid
undue lubricity in a passivate coating must also be balanced
against the need to provide a formable surface. The passivate
coating on the lengths of sheet metal must be sufficiently
lubricious, formable and flexible to allow forming of the sheet
metal without galling or binding.
[0009] As a result of their excellent properties, zinc- and/or
aluminum-containing metal surfaces, more particularly aluminum-zinc
alloy coated steel sheets have found wide application as building
materials in the form of roofing and walling materials, in civil
engineering applications, e.g., as guard rails, sound insulating
barriers, anti-snow fencing, or drainage gullies, as materials for
automobiles, domestic appliances, and industrial machinery and,
after having been painted, as replacements for painted steel
sheets.
[0010] Zinc- and/or aluminum-containing metal surfaces,
particularly aluminum-zinc alloy coated steel sheets, are used
extensively in roofs and walls of commercial buildings.
Particularly in warmer climates, it has become increasingly
important to reduce the amount of solar energy retained by these
structural components, in part to reduce energy costs. When EMR,
such as solar energy, strikes a material, the EMR is absorbed,
reflected and/or transmitted (if the material is not opaque)
through the material. Absorbed EMR can be re-emitted at various
wavelengths or can remain as heat to raise the temperature of the
material. Interestingly, even a highly reflective material, such as
polished metal, e.g. a chrome car bumper, will get very hot in the
sun if the material does not re-emit the EMR it has absorbed. The
ability to re-emit absorbed EMR is known in the industry as
emittance, which ranges from zero to one; one being a theoretical
100% emittance. It has been demonstrated that emittance is a
property of the surface of an object rather than the underlying
material. For example, the emittance of a metal roof, newly painted
white, has been measured at about 0.83; in comparison, the
unpainted metal roof was found to have an emittance of only about
0.08 measured according to ASTM C1371-04a (1.0 being ideal
emittance). Aluminum-zinc alloy coated steel sheets have good solar
reflecting properties, but poor emittance of solar energy that is
not reflected. Such non-reflected energy is largely translated into
heat in the steel sheets and some of the heat is then transferred
to the interior of the building increasing the cost of cooling the
interior.
[0011] As energy costs increase, the demand for improvements in the
EMR reflecting and/or emitting properties of outdoor structures
made of zinc- and/or aluminum-containing metal surfaces, such as
aluminum-zinc alloy coated steel sheets, has increased. Typically,
the corrosion and lubricious coatings of the prior art deposited on
aluminum-zinc surfaces provide less than desirable resistance to
heating by the electromagnetic radiation of the sun (solar
radiation). One commercially available, chromium-containing
corrosion protective coating composition provides an emittance of
only 0.22 as measured by ASTM C1371-04a. This is better than the
untreated metal surface's emittance of 0.06, but still leaves room
for improvement.
[0012] Corrosion resistant coatings, such as inorganic chromium
passivates and organic thin film passivates do not substantially
improve emittance. Some non-white paints provide improvements in
emittance of solar energy, but at an insufficient rate with
increasing film build compared to their tendency to reduce the
solar reflectance of the coated surface. Overall, the non-white
paints offer a less than desirable trade-off between emittance and
reflectance. White paints initially have good solar reflectance and
provide improvements in emittance of solar energy, but white paints
have other drawbacks. White paints require a series of additional
processing steps and tend to highlight any dirt deposition, easily
becoming aesthetically displeasing and hiding the desirable
appearance of the metal coating. For at least the foregoing
reasons, white paint is not used in many market segments for
coating metal. Thus, there is a need for a protective coating for
aluminum and/or zinc coated steel sheets that improves emittance
while avoiding the limitations of paint.
[0013] A common means of increasing resistance to heating by the
sun is to deposit reflective coatings, such as white paint and the
like on the metal surfaces. Solar reflectance is a measure of the
solar reflectance of a surface. Solar reflectance is the ratio of
the reflected solar radiation flux to the incident flux. ASTM C1549
provides a scale of 0 to 1.0 of solar reflectance, 0 being
non-reflective and 1.0 being 100% reflective. Surfaces coated with
white paint have achieved a solar reflectance as measured by ASTM
C1549 of as high as 0.7, this is not as reflective as the uncoated
metal surface, which is about 0.78. The reflectivity of non-white
paints varies by color but is often substantially lower than for
white paints. A drawback of painting metal surfaces white to
improve resistance to electromagnetic heating is the limited life
of the paint and the tendency of the paint to stain and age, which
reduces solar reflectance. Another drawback of conventional paints
is the thickness required. Standard paint thicknesses in the
building material industry are about 25 microns. Over a large
expanse of surface, such as a roof, this thickness adds significant
weight that must be supported, which adds to the overall expense of
construction.
[0014] Thus there is a need for a corrosion resistant coating for
building materials, particularly aluminum-zinc roofing, that
reduces heating of the metal substrate by EMR, such as solar
energy, by improving emittance and/or solar reflectance. There is
also a need for a corrosion resistant coating that provides good
emittance and/or solar reflectance at a lower coating thickness
than conventional paints.
[0015] As such, there is a need for a composition and process for
passivating metal surfaces that overcomes at least one constraint
in the prior art.
SUMMARY OF THE INVENTION
[0016] This invention relates to treatment of a metal article with
an aqueous liquid composition that, before and/or during drying of
the liquid composition into place on the metal, spontaneously
reacts with the metal surface, without any application of
electromotive force from an external source, to produce on the
metal a coating providing corrosion resistance that is better than
the original untreated metal. The resulting coated surface has the
additional feature of improved resistance to heating by
electromagnetic radiation (EMR) than the original untreated metal
article by reflecting and/or re-emitting the energy. More
particularly, this invention is related to a composition and
process that provide a corrosion protective treatment which also
provides to the metal article improved emittance of EMR, such as
solar energy, while maintaining the solar reflectance of the
underlying metal, such that the surface and the underlying metal
remain cooler than the original untreated metal surface when
exposed to sunlight. Still more particularly, the metal surface
treated is a metal selected from zinc, zinc alloy, aluminum,
aluminum alloy, an alloy of zinc and aluminum, or ferrous metal
substrate coated with any of the foregoing metals.
[0017] It has been found that at least the major object of the
invention as stated above can be achieved by treating a substrate
having a metal surface with an aqueous liquid passivate composition
having dispersed, preferably homogeneously dispersed, therein solid
particles which result in a transparent or translucent, preferably
clear and colorless, passivate coating, upon drying of the aqueous
liquid passivate composition. Desirably, when deposited on a metal
surface, the solid particle-containing passivate coating exhibits a
solar reflectance that is not significantly reduced as compared to
the solar reflectance of the metal surface coated with a similar
passivate coating in the absence of the solid particles. In a
preferred embodiment, the passivate coating on the metal surface
has a solar reflectance of not less than, independently, in
increasing order of preference, 50, 55, 60, 65, 70, 75, 80, 85, 90,
95, 97 or 99 percent of the solar reflectance of the uncoated metal
surface.
[0018] It is also desirable that the passivate coating on the metal
surface exhibits an emittance of at least, independently, in
increasing order of preference, 0.70, 0.75, 0.80, 0.85, 0.90, or
0.95.
[0019] Suitable solid particles include those solid particles
having physical and chemical characteristics resulting in a
transparent or translucent passivate coating, which do not
interfere with the corrosion resistance provided by the passivate.
Preferred particles are oxides of metals and/or metalloids, defined
herein as Al, Ga, Ge, As, Se, In, Sn, Sb, Te, and IUPAC groups 2-12
of the periodic table of elements.
[0020] Desirably, the solid particles having a mean particle size
in nanometers of less than 250; preferred embodiments have particle
size of less than 100, particularly preferably less than 30, most
preferably less than 10 nm. Independently preferably, the mean
particle size ranges in nanometers are from 1-50, most preferably,
if only for economy, from 5-35. At least a portion of the
transparency of the passivate coating is due to the size of the
particles used.
[0021] Applicants have found that certain metal and/or metalloid
oxide particles that appear white in bulk, produce transparent,
colorless passivate coatings, by way of non-limiting example metal
and/or metalloid oxide powders. Without being bound by a single
theory, it is believed to be desirable that the passivate comprise
a metal and/or metalloid oxide powder selected from the group of
metal and/or metalloid oxide powders having high mean emittance of
EMR in the 250 to 2500 nm range.
[0022] While application of the invention may be through any
commercial passivate, Applicants preferred embodiments include
chrome (VI) based passivates and alternative embodiments which are
substantially chrome-free, as will be described in more detail
hereinafter.
FIRST EMBODIMENT
[0023] In a first embodiment of the invention, an essentially or
substantially chromium-free composition and process for passivating
metal surfaces has been developed that provides corrosion
resistance comparable to, i.e. about the same as, previously used
chromate-containing passivating agents. Another aspect of the first
embodiment of the invention provides a new thin organic coating
that reduces the tendency of surfaces of coiled or stacked metal
sheet metal that are in contact with each other to stick together,
i.e. reduces the tendency of the coil or stack to "bind". In
another aspect of first embodiment of the invention, thin organic
coating is provided that has sufficient lubricity to enhance
formability and prevent binding, but not so much that the lubricity
contributes to the tendency of coils of metal to collapse due to
sliding of metal surfaces, relative to each other within the
coil.
[0024] The compositions of the first embodiment of the invention
have been developed as chrome-free passivates that desirably
perform as well as, and in some aspects better than, chrome
containing passivates of the prior art. Although not preferred,
formulations according to the invention can be made including
chromium. Compositions according to the first embodiment of the
invention desirably contain less than 0.04, 0.02, 0.01, 0.001,
0.0001, 0.00001, 0.000001 percent by weight of chromium, most
preferably essentially no chromium. It is particularly preferred
that the compositions according to the first embodiment contain
less than 0.04, 0.02, 0.01, 0.001, 0.0001, 0.00001, 0.000001
percent by weight of hexavalent chromium, most preferably
essentially no hexavalent chromium. The amount of chromium present
in the compositions of the first embodiment of the invention is
desirably minimized and preferably only trace amounts are present,
most preferably no chromium is present.
[0025] In one aspect, the first embodiment of the invention
provides a composition useful for passivating a metal surface, that
includes less than 0.04 wt % chromium, preferably essentially no
chromium, most preferably in the absence of chromium, and
comprising, preferably consisting essentially of, most preferably
consisting of water and: [0026] (A) at least one inorganic oxide in
dispersed form, the particles preferably having a mean particle
size of less than 100 nm; [0027] (B) at least one complex fluoride
of an element selected from the group consisting of Ti, Zr, Hf, Si,
Sn, Al, Ge and B; preferably Ti and/or Zr; [0028] (C) a non-ionic
or non-ionically stabilized resin in dispersed form selected from
the group consisting of acrylic, polyurethane, vinyl, and polyester
resins, and mixtures thereof; [0029] (D) optionally, dissolved
phosphate anions; [0030] (E) optionally, at least one component
comprising vanadium; [0031] (F) optionally, at least one wax in
dispersed form; [0032] (G) and optionally, at least one further
additive selected from the group consisting of a sequestrant, a
wetting agent, a defoamer, and a pH adjusting component; wherein
said composition comprises less than 0.04 wt % chromium, and is
preferably essentially free of chromium.
[0033] In a further embodiment of the invention the total
concentration of the complex fluoride is at least 0.5 g/L and is
not more than 100 g/L. In a particular aspect of the first
embodiment, the composition is essentially free of chromium, (C)
comprises a non-ionic or non-ionically stabilized acrylic and/or
acrylic copolymer resin in dispersed form, said composition
comprising at least one pH adjusting component and/or dissolved
phosphate anions, alternatively, the non-ionic or non-ionically
stabilized resin is selected from acrylic resins and polyurethane
resins, and mixtures thereof.
[0034] In another aspect, the first embodiment of the invention
provides a composition having a pH within a range of from about 1
to about 5 and the composition is storage stable at 100 deg. F. for
at least 3 months, preferably at least 6 months.
[0035] In another aspect of the first embodiment, the composition
includes at least one wax, selected from the group of waxes stable
in strong acidic solutions having an average particle size less
than about 1 micron and a melting point of from about 50 to about
175 degrees C. In a yet further aspect of the first embodiment of
the invention, the concentration of wax ranges from about 0.05 to
about 6 weight percent.
[0036] In an alternative version of the first embodiment, the
composition includes at least one component that comprises
vanadium. In one aspect of this embodiment, a composition useful
for passivating a metal surface is provided comprising less than
0.04 wt % chromium and comprising: water; 0.05-10 weight % of at
least one complex fluoride of an element selected from the group
consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti
and/or Zr; a non-ionic or non-ionically stabilized resin in
dispersed form, said resin selected from the group consisting of
acrylic, polyurethane, vinyl, and polyester resins, and mixtures
thereof; 25 to 80 weight % of at least one inorganic oxide in
dispersed solid form, the solid particles preferably having a mean
particle size of less than 50 nm; 0.1 to 7 weight % of at least one
component comprising vanadium; 0.05-20 weight % of at least one wax
in dispersed form; and optionally, any one or more of the
following: dissolved phosphate anions; at least one further
additive selected from the group consisting of a sequestrant, a
wetting agent, a defoamer, and a pH adjusting component. It is
preferred that this coating, upon drying on a metal surface, forms
a transparent or translucent coating having an emittance of at
least 0.7 and a reflectivity that is at least 50% of the
reflectivity of the metal surface uncoated. In a further aspect of
this embodiment, (C) comprises 5-50 weight % of a non-ionic or
non-ionically stabilized resin in dispersed form selected from the
group consisting of acrylic resins and polyurethane resins, and
mixtures thereof.
SECOND EMBODIMENT
[0037] In a second embodiment the composition comprises, preferably
consists essentially of, or more preferably consists of, water and
the following components: [0038] (A) dispersed solid particles of
metal and/or metalloid oxide, desirably the metal and/or metalloid
oxide is a powder the particles preferably having a mean particle
size of less or equal to 100 nm, and [0039] (B) dissolved,
dispersed, or both dissolved and dispersed hexavalent chromium that
is not part of immediately previously recited component (A); [0040]
(C) dissolved, dispersed, or both dissolved and dispersed organic
film-forming resin; and, optionally, one or more of the following
components: [0041] (D) dissolved, dispersed, or both dissolved and
dispersed pH adjusting agent that is not part of any one of
immediately previously recited components (A) through (C); [0042]
(E) dissolved, dispersed, or both dissolved and dispersed trivalent
chromium that is not part of any one of immediately previously
recited components (A) through (D); [0043] (F) dissolved,
dispersed, or both dissolved and dispersed wax that is not part of
immediately previously recited component (A) through (E); [0044]
(G) at least one dissolved, dispersed, or both dissolved and
dispersed surfactant and/or antiblocking agent that is not part of
any of immediately previously recited components (A) through (F);
[0045] (H) dissolved organic solvent that is not part of any of
immediately previously recited components (A) through (G); [0046]
(I) dissolved, dispersed, or both dissolved and dispersed material
selected from the group consisting of (i) reducing agents that are
capable, at a specified temperature, of reducing hexavalent
chromium in the composition to trivalent chromium and (ii)
oxidation products from a reducing agent that has reduced some
initially hexavalent chromium in the composition to trivalent
chromium, said dissolved, dispersed, or both dissolved and
dispersed material not being part of any of immediately previously
recited components (A) through (H); and [0047] (J) dissolved,
dispersed, or both dissolved and dispersed colorant that is not
part of any of immediately previously recited components (A)
through (I).
[0048] In a different aspect of the invention, which applies to
both chrome and non-chrome embodiments, a process of treating a
ferriferous, aluminiferous or zinciferous metal substrate is
provided comprising: optionally, cleaning a surface of said metal
substrate to be passivated; contacting the metal substrate surface
to be passivated with a passivating composition as described herein
for a time sufficient to form a coating on said metal surface and
drying the coating. This process may include the step of coating
the metal substrate with a dissimilar metal, thereby creating a
metal substrate surface to be passivated, prior to contacting with
the passivating composition. Optionally, a process according to the
invention may include a step wherein the passivating coating on the
metal surface is overcoated with a protective layer comprising at
least one organic binder.
[0049] Various embodiments of the invention include working
compositions for direct use in treating metals, make-up
concentrates from which such working compositions can be prepared
by dilution with water, replenisher concentrates suitable for
maintaining optimum performance of working compositions according
to the invention, processes for treating metals with a composition
according to the invention, and extended processes including
additional steps that are conventional per se, such as cleaning,
rinsing, and subsequent painting or some similar overcoating
process that puts into place an organic binder-containing
protective coating over the metal surface treated according to one
embodiment of the invention. Articles of manufacture including
surfaces treated according to a process of the invention are also
within the scope of the invention.
[0050] Except in the operating examples, or where otherwise
expressly indicated, all numerical quantities in this description
indicating amounts of material or conditions of reaction and/or use
are to be understood as modified by the word "about" in describing
the broadest scope of the invention. Practice within the numerical
limits stated is generally preferred. Also, unless expressly stated
to the contrary: percent, "parts of", and ratio values are by
weight; the term "polymer" includes "oligomer", "copolymer",
"terpolymer", and the like; the description of a group or class of
materials as suitable or preferred for a given purpose in
connection with the invention implies that mixtures of any two or
more of the members of the group or class are equally suitable or
preferred; description of constituents in chemical terms refers to
the constituents at the time of addition to any combination
specified in the description, and does not necessarily preclude
chemical interactions among the constituents of a mixture once
mixed; specification of materials in ionic form implies the
presence of sufficient counter-ions to produce electrical
neutrality for the composition as a whole (any counter-ions thus
implicitly specified should preferably be selected from among other
constituents explicitly specified in ionic form, to the extent
possible; otherwise such counter-ions may be freely selected,
except for avoiding counter-ions that act adversely to the objects
of the invention); the first definition of an acronym or other
abbreviation applies to all subsequent uses herein of the same
abbreviation and applies mutatis mutandis to normal grammatical
variations of the initially defined abbreviation; the term "paint"
includes all like materials that may be designated by more
specialized terms such as lacquer, enamel, varnish, shellac,
topcoat, and the like; and the term "mole" and its variations may
be applied to elemental, ionic, and any other chemical species
defined by number and type of atoms present, as well as to
compounds with well defined molecules. For the purposes of this
description, unless specifically stated otherwise: [0051] a
"dissolved, dispersed, or both dissolved and dispersed film-forming
resin" means a material that satisfies the following condition:
when said liquid film is dried at at least one temperature that is
at least 40.degree. C., the resin forms a cohesive continuous solid
body at the temperature of drying after drying is complete; and
[0052] "wax" is defined as a substance that: (i) is a plastic solid
at 25.degree. C. under normal atmospheric pressure and (ii) melts
in contact with the natural ambient atmosphere without visually
evident decomposition at a temperature that is at least 55.degree.
C.
DETAILED DESCRIPTION OF THE INVENTION
[0053] Reference will now be made in detail to compositions and
methods of the invention, which constitute the best modes of
practicing the invention presently known to the inventors.
[0054] Applicants have developed a process for coating a substrate
having a metal surface with an aqueous liquid passivate composition
having dispersed, preferably homogeneously dispersed, therein solid
particles which result in a transparent or translucent, preferably
clear and colorless, passivate coating, upon drying of the aqueous
liquid passivate composition. The passivate coating provides
resistance to heating to the underlying metal surface by a two-fold
mechanism. First, the coating has high emittance in the EMR
wavelengths that are known in the art to cause the most heating,
namely about 250 to about 2500 nm. This range of wavelengths
includes light visible to humans and the near infrared spectrum.
The high emittance of the coating is important to heat resistance
particularly since metals tend to have high reflectance and poor
emittance. The second aspect of the mechanism uses the transparency
of the passivate coating to gain the benefit of the solar
reflectance of the underlying metal. Thus the coating improves the
emittance of the coated metal substrate while minimizing any
negative effect on the metal's solar reflectance. Preferably, the
passivate coating on the unpainted metal surface provides a
material that exhibits a solar reflectance of 0.65, 0.66, 0.67,
0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78,
0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89,
0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or 1.00.
and an emittance 0.55, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66,
0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77,
0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88,
0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or
1.00.
[0055] All embodiments of the passivate coatings described herein
comprise solid particles. Suitable solid particles include those
solid particles having physical and chemical characteristics
resulting in a transparent passivate coating, which do not
interfere with the corrosion resistance provided by the passivate.
Preferred particles are oxides of metals and/or metalloids, defined
herein as Al, Ga, Ge, As, Se, In, Sn, Sb, Te, and IUPAC groups 2-12
of the periodic table of elements. In a preferred embodiment, the
solid particles are selected from oxides of Ti, Zn, Zr, Sb, Al, Hf,
and V, most preferably Ti, Zr and Sb.
[0056] Desirably, the solid particles having a mean particle size
of less than or equal to, independently, in increasing order of
preference, of 100, 80, 60, 50, 40, 35, 30, 25, 20, 15, 10, or 6
nm. At least a portion of the transparent or translucent nature of
the passivate coating is due to the size of the particles used.
Significant quantities of particles larger than 100 nm, typically
used in conventional paints, result in an opaque surface that
interferes with the underlying metal surface's reflection of solar
energy out through the coating.
[0057] Typical substances useful as solid particle additives are
those oxides that are solid at ambient temperature and are
substantially insoluble in water, as will be understood by one of
skill in the art. Desirably, these substances are oxides of metals
and/or metalloids. In one embodiment, the raw material metal and/or
metalloid oxide particles in bulk have a white appearance to the
human eye.
[0058] Applicants have found that certain metal and/or metalloid
oxide particles produce transparent, colorless passivate coatings,
by way of non-limiting example metal and/or metalloid oxide
powders. Without being bound by a single theory, it considered
desirably, that the emittance of the bulk, dry raw material metal
and/or metalloid oxide powder also has a mean emittance of EMR in
the 250 to 2500 nm range that is at least, independently, in
increasing order of preference, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65,
0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76,
0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87,
0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98,
0.99 or 1.00.
[0059] Accordingly, one or more inorganic oxides are present in the
passivate composition, preferably in dispersed, fine particulate
form. Oxides of silicon, aluminum, zinc and the like may be used,
for example. In one embodiment, when one or more components
comprising inorganic oxides are used, independently of their
chemical nature, the total concentration of inorganic oxides in a
working composition according to the invention, preferably is at
least, with increasing preference in the order given, 10.0, 20.0,
25.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0 weight % of total
composition and independently preferably not more than, with
increasing preference in the order given, 80.0, 75.0, 74.0, 73.0,
72.0, 71.0, 70.0, or 65.0 weight %. In a preferred embodiment, the
weight percent of oxides is in the range of 20%-75%, most
preferably 30%-65%. LUDOX CL-P silica, available from W. R. Grace
& Co., Bonderite NT-1, available from Henkel Corporation, and
Nyacol DP 5370, a commercially available aqueous dispersion of
nanoparticulate zinc oxide, are illustrative inorganic oxides
suitable for use in the present invention.
[0060] In a preferred embodiment, the amount and particle size of
oxide component is selected such that the as-dried coating
according to the invention is a clear, colorless coating after not
more than, with increasing preference in the order given 60, 45,
30, 21, 14, 7, 5, 3, 2 or 1 days.
FIRST EMBODIMENT
[0061] Typically, thin-film organic passivates comprise an organic
film forming resin; a surface passivating material; water and
optional additives. One of the problems associated with
formulations with non-chrome passivating materials in such
formulations is the degree to which the non-chrome passivating
materials compromise stability in the formulated thin-film
passivating composition. Many alternative passivating materials,
such as organic and inorganic acids, are most effective when the
formulated thin-film passivating composition is at low pH. Under
these conditions most resin dispersions or latexes are
destabilized, i.e. the resin does not remain dispersed. Two
indicators of instability in the composition are phase separation,
including precipitation, which is not readily remixed, and
coagulation, where the composition may form a consistency similar
to, and known in the industry as, "cottage cheese". Prior art
approaches have not provided stable formulations. Such systems
either phase separated immediately upon mixing, or separated upon
aging at elevated temperature.
[0062] It has now been found that using a resin which is non-ionic
or non-ionically stabilized provides passivates according to the
invention which are stable both immediately after preparation at
room temperature, as well as after aging at elevated temperature
for several months. Moreover, such compositions can provide
corrosion protection to metal surfaces that is at least comparable
to that attained using chrome-containing passivates.
[0063] Storage-stable organic passivate formulations are obtained
when the organic film forming resin is non-ionic or is
non-ionically stabilized. The non-ionically stabilized resins of
the invention can be stabilized by conventional non-ionic
surfactant or by incorporating covalently-bound non-ionic
stabilizing groups into the polymer chain of the resin.
Compositions according to the invention are stable and do not
coagulate upon mixing of the components together. Desirably, the
compositions remain dispersed in a single phase, or if phase
separation occurs, can be readily remixed. It is preferred that the
compositions do not form precipitates or coagulate upon storage for
at least, with increasing preference in the order given, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or
24 weeks. It is independently preferred that the compositions do
not form precipitates or coagulate upon storage at ambient or
higher temperatures including, with increasing preference in the
order given, 80, 85, 90, 95, 100 and 110 degrees F. Particularly
preferred embodiments of the present invention are stable after
aging at elevated temperature, e.g. 100 degrees F., for at least
six months.
[0064] It has been found that one or more of the objects stated
above for the invention can be achieved by the use of a passivating
aqueous liquid composition, as described herein. The present
invention thus provides a composition useful for passivating a
metal surface, said composition comprising, preferably consisting
essentially of, most preferably consisting of water and: [0065] (A)
at least one inorganic oxide in dispersed form; [0066] (B) at least
one complex fluoride of an element selected from the group
consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; [0067] (C) a
non-ionic or non-ionically stabilized resin in dispersed form said
resin selected from the group consisting of acrylic, polyurethane,
vinyl, and polyester resins, and mixtures thereof; [0068] (D)
optionally, dissolved phosphate anions; [0069] (E) optionally, at
least one component comprising vanadium; [0070] (F) optionally, at
least one wax in dispersed form; [0071] (G) and optionally, at
least one further additive selected from the group consisting of a
sequestrant, a wetting agent, a defoamer, and a pH adjusting
component; wherein said composition comprises less than 0.04 wt %
chromium, and is preferably essentially free of chromium.
[0072] The compositions of the first embodiment of the invention
contain, in addition to water, at least one complex fluoride of an
element selected from the group consisting of Ti, Zr, Hf, Si, Sn,
Al, Ge and B (preferably, Ti, Zr and/or Si; most preferably, Ti).
The complex fluoride should be water-soluble or water-dispersible
and preferably comprises an anion comprising at least 4 fluorine
atoms and at least one atom of an element selected from the group
consisting of Ti, Zr, Hf, Si, Sn, Al, Ge or B. The complex
fluorides (sometimes referred to by workers in the field as
"fluorometallates") preferably are substances with molecules having
the following general empirical formula (I):
H.sub.pT.sub.qF.sub.rO.sub.s (I) wherein each of p, q, r, and s
represents a non-negative integer; T represents a chemical atomic
symbol selected from the group consisting of Ti, Zr, Hf, Si, Sn,
Al, Ge, and B; r is at least 4; q is at least 1 and preferably is
not more than, with increasing preference in the order given, 3, 2,
or 1; unless T represents B, (r+s) is at least 6; s preferably is
not more than, with increasing preference in the order given, 2, 1,
or 0; and (unless T represents Al) p is preferably not more than
(2+s), with all of these preferences being preferred independently
of one another. One or more of the H atoms may be replaced by
suitable cations such as ammonium, metal, or alkali metal cations
(e.g., the complex fluoride may be in the form of a salt, provided
such salt is water-soluble or water-dispersible).
[0073] The acids are usually preferred for economy and because a
net acidity of the compositions is preferable as considered further
below, and the entire stoichiometric equivalent as any of the above
recited fluorometallate ions in any source material as dissolved in
a composition according to the invention or a precursor composition
for it is to be considered as part of the fluorometallate
component, irrespective of the actual degree of ionization that may
occur. Independently of their chemical nature, the total
concentration of the fluorometallate anions dissolved in a working
treatment composition according to the invention preferably is at
least, with increasing preference in the order given, 0.5, 1.0,
2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.5, 8.5, 10.0, 11.0, 12.0 or 13.0
g/L and independently, primarily for reasons of economy, preferably
is not more than, with increasing preference in the order given,
400, 200, 100, 90, 80, 75, 65, 50, 45, 38, 37.5, 35.0, 32.5 30.0,
28.0, 27.0 or 26.0 g/L.
[0074] Illustrative examples of suitable complex fluorides include,
but are not limited to, H2TiF6 (which is especially preferred),
H2ZrF6, H2HfF6, H2SiF6, H2GeF6, H2SnF 6, H3AlF6, ZnSiF6, and HBF4
and salts (fully as well as partially neutralized) and mixtures
thereof. Examples of suitable complex fluoride salts include
SrSiF6, MgSiF6, Na2SiF6 and Li2SiF6.
[0075] The dissolved phosphate ions that comprise component may be
obtained from a variety of sources as known in the art. Normally
much of the phosphate content will be supplied by phosphoric acid
added to the composition, and the stoichiometric equivalent as
phosphate ions of all undissociated phosphoric acid and all its
anionic ionization products in solution, along with the
stoichiometric equivalent as phosphate ions of any dihydrogen
phosphate, monohydrogen phosphate, or completely neutralized
phosphate ions added to the composition in salt form, are to be
understood as forming part of phosphate ions, irrespective of the
actual degree of ionization and/or reaction to produce some other
chemical species that exists in the composition. If any
metaphosphoric acid, other condensed phosphoric acids, or salts of
any of these acids are present in the compositions, their
stoichiometric equivalent as phosphate is also considered part of
the phosphate component. Generally, however, it is preferred, at
least partly for reasons of economy, to utilize orthophosphoric
acid and its salts as the initial source for the phosphate
component.
[0076] In a working passivating aqueous liquid composition
according to this embodiment of the invention, the concentration of
phosphate ions and/or their stoichiometric equivalents as noted
above preferably is at least, with increasing preference in the
order given, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 9.0, 10.0, 12.0, 13.0,
14.0, 15.0, 16.0 or 17.0 grams per liter (hereinafter usually
abbreviated as "g/L") of total composition and independently
preferably is not more than, with increasing preference in the
order given, 400, 200, 100, 90, 80, 75, 70, 60, 50, 45, 40 or 34
g/L.
[0077] Furthermore, independently of their actual concentrations,
the concentrations of fluorometallate anions and phosphate ions
preferably are such that the ratio between them, in working
compositions and concentrated solutions used to prepare working
concentrations, is at least, with increasing preference in the
order given, 0.10:1.0, 0.15:1.0, 0.25:1.0, 0.35:1.0, 0.45:1.0,
0.50:1.0, 0.55:1.0, 0.60:1.0, 0.65:1.0, or 0.75:1.0 and
independently preferably is not more than, with increasing
preference in the order given, 5:1.0, 4:1.0, 3.5:1.0, 3.2:1.0,
2.0:1.0, 1.5:1.0, 1.0:1.0, or 0.9:1.0.
[0078] The resin used in the first embodiment may be either
non-ionic or non-ionically stabilized. "Non-ionically stabilized"
resins include resins that are stabilized (i.e., kept in dispersed
form) using a non-ionic surfactant as well as resins that are
stabilized by incorporating covalently-bound non-ionic stabilizing
groups onto the resin. Preferably, the number of anionic functional
groups on the resin is minimized, as this will tend to improve the
stability of the dispersed resin under acidic conditions. These
resins can be described as aqueous emulsions or dispersions. They
can be high molecular weight emulsions such as acrylic latex,
polyurethane dispersion, or vinyl latex or they can be low
molecular weight dispersions including water reducible polyester,
acrylic, or urethane. The resins may be copolymers or mixtures of
polymer chains having similar or different functional groups.
[0079] These resins can be either thermoplastic or thermosetting.
Reactive functionality is any functionality that can react with an
external curing agent (two component system) or internal curing
agents (one component system). Reactive functionality is acceptable
in resins useful in the invention provided that the amount of
reactive functionality does not adversely affect the stability of
the resulting composition.
[0080] The concentration of resin (measured on a solids basis) in
the passivate compositions of the first embodiment of the invention
preferably is at least, with increasing preference in the order
given, 4.0, 5.0, 6.0, 7.0, 9.0, 10.0, 12.0, 13.0, 14.0, 15.0, 16.0
or 17.0 weight % (hereinafter usually abbreviated as "g/L") of
total composition and independently preferably is not more than,
with increasing preference in the order given, 60, 50, 45, 40, 39,
38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22,
21 weight %. The optimal amount of resin depends in large part on
the desired end property of the coating. If relatively significant
corrosion protection is considered more important than ease of
coating removability, then a relatively higher amount of resin can
be used, however, if ease of coating removability is considered
more important than corrosion protection, then a relatively smaller
amount of resin can be used.
[0081] Furthermore, in the first embodiment, independently of their
actual concentrations, the concentrations of resin and phosphate
anions preferably are such that the ratio between them, in working
compositions and concentrated solutions used to prepare working
concentrations, is at least, with increasing preference in the
order given, 0.005:1.0, 0.01:1.0, 0.015:1.0, 0.02:1.0, 0.025:1.0,
0.03:1.0, 0.035:1.0, 0.04:1.0, 0.045:1.0 or 0.05:1.0, and
independently preferably is not more than, with increasing
preference in the order given, 3.:1.0, 2.5:1.0, 2.0:1.0, 1.5:1.0,
1.3:1.0, 1.2:1.0, 1.0:1.0, 0.90:1.0, 0.75:1.0, 0.60:1.0, 0.50:1.0,
0.45:1.0, 0.35:1.0, 0.25:1.0, 0.20:1.0, 0.10:1.0 or 0.07:1.0.
[0082] Preferred resins for use in the first embodiment include
acrylic resins and polyurethane resins. Acrylic resins are
well-known in the art and are thermoplastic synthetic organic
polymers made by the polymerization of ethylenically unsaturated
monomers selected from groups consisting of acrylates,
methacrylates, styrene, vinyl, or allylic monomers. Examples of
these include monomers such as acrylic acid, methacrylic acid,
alkyl esters of acrylates and methacrylates, and the like,
including copolymers of such monomers with non-acrylic monomers
such as olefins, vinyl compounds, styrene, and the like. Suitable
non-ionically stabilized acrylic resin dispersions and latexes are
available commercially or may be prepared by known techniques.
Suitable acrylic resin based materials include acrylic polymers and
acrylic copolymers comprising styrene, acrylates and/or
methacrylates. RHOPLEX HA-16 acrylic latex, available from Rohm
& Haas, is an example of a commercially available,
non-ionically stabilized acrylic resin latex useful in the present
invention. RHOPLEX HA-16 is believed to be a high molecular weight
copolymer of styrene and acrylates and methacrylates.
[0083] Polyurethane resins are also well-known in the art and are
resins obtained by reacting polyisocyanates with one or more active
hydrogen-containing compounds such as polyether, polyester,
polycarbonate, polyacrylic, or polyolefin glycols to form a
pre-polymer which can be dispersed in water followed by chain
extension with polyamines or polyalcohols. The nonionic
stabilization of the acrylic or urethane polymers can be achieved
by incorporating a reactive internal non-ionic monomer or by the
addition of non-ionic surfactant. Suitable non-ionic polyurethane
dispersions and latexes are available commercially or may be
synthesized using standard methods. PERMAX 120, 200 and 220
emulsions, available from Noveon, Inc., 9911 Brecksville Road,
Cleveland, Ohio 44141-3247, are examples of polyurethane resin
dispersions found to be especially useful in the present invention.
These materials are described by their supplier as aliphatic
polyether waterborne urethane polymers constituting about 35-44%
solids.
[0084] Generally speaking, the effectiveness of the passivate
composition in imparting corrosion resistance to a metal surface
will be influenced by the pH of the composition. One or more pH
adjusting components may be used in compositions according to the
invention. The pH of the treatment formulation according to the
first embodiment should be from 1.0 to 5.0, more preferably 1.2 to
4.5, and most preferably from 1.5 to 3.0. The pH can be adjusted
using a pH adjusting component such as an acid such as phosphoric
acid, or nitric acid, or a base such as sodium hydroxide, potassium
hydroxide, sodium carbonate, or ammonium hydroxide, with ammonium
hydroxide being the most preferred. Generally, acids are added to
the composition to lower pH and optimize its effectiveness.
Although both organic as well as inorganic acids can be used,
generally it will be preferred to use a mineral acid such as a
phosphorus-containing acid (e.g., phosphoric acid). The phosphate
ions included in certain aspects of the first embodiment of the
invention may be derived, in whole or in part from this
phosphorus-containing acid.
[0085] In one aspect of the first embodiment of the invention, the
composition comprises at least one component comprising vanadium.
When one or more components comprising vanadium are used,
independently of their chemical nature, the total concentration of
vanadium dissolved in a working composition according to the
invention, preferably is at least, with increasing preference in
the order given, 0.10, 0.20, 0.25, 0.30, 0.40, 0.50, 0.55, 0.60 or
0.65 weight % of total composition and independently preferably not
more than, with increasing preference in the order given, 5.0, 4.0,
3.0, 2.5, 2.0, 1.5, 1.0, 0.90, 0.80 or 0.75 weight %. Preferred
sources of vanadium include V.sub.2O.sub.5 and
NH.sub.4VO.sub.3.
[0086] The composition of the present invention also optionally
includes a lubricating agent. The lubricating agent is particularly
useful for providing lubrication to surfaces that are to be formed,
so as to prevent binding and galling. Lubricating agents that
improve lubricity of the coating during forming without increasing
water sensitivity of the composition and that are soluble and
stable in strong acidic solutions are preferred. Moreover, for use
in the coil industry it is desirable that the lubricity provided to
the surfaces for subsequent forming does not interfere with stable
coiling of the substrate for transport or storage. It is desirable
that the lubricating agent is a wax emulsion to aid in dispersal in
the composition. Such cares can function as a release aid in the
coating formed on the metal surface upon application of the
passivate composition, lower the coefficient of friction on the
metal surface, improve metal forming, and/or provide anti-block
properties. Examples of suitable waxes include Fischer Tropsch
waxes, polyethylene waxes (including LDPE and HDPE waxes), paraffin
waxes, montan waxes, carnauba wax, ethylene/acrylic acid copolymer
waxes, polypropylene waxes, microcrystalline waxes, and the like,
and combinations thereof. In one embodiment, polypropylene and
paraffin comprise the lubricating agent. Typically, the wax will
have an average particle size less than about 1 micron and a
melting point of from about 50 to about 175 degrees C.
[0087] The concentration of wax in a passivate composition
according to the invention preferably is at least, with increasing
preference in the order given, 0.5, 1.0, 2.0, 2.5, 3.0, 4.0, 5.0,
6.0, 7.5, 8.5, 10.0, 11.0, 12.0 or 13.0 g/L and independently,
primarily for reasons of economy, preferably is not more than, with
increasing preference in the order given, 200, 100, 90, 80, 75, 65,
50, 45, 38, 37.5, 35.0, 32.5 30.0, 28.0, 27.0 or 26.0 g/L.
[0088] The passivate composition may also comprise a sequestrant
(i.e., sequestering agent). Sequestrants containing two or more
phosphonic acid groups per molecule may be used, including, for
example, 1-hydroxy ethylidene-1,1-diphosphonic acid (available
commercially under the trademark DEQUEST 2010 from Solutia Inc.,
575 Maryville Centre Drive, St. Louis, Mo. The sequestrant
concentration in the passivate composition may range, for example,
from about 0.1 to about 10 weight percent, and preferably is at
least, with increasing preference in the order given, 2.0, 3.0,
4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 or 13.0, 14.0, 15.0,
16.0, 17.0, 18.0, 19.0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30
g/L and independently, primarily for reasons of economy, preferably
is not more than, with increasing preference in the order given,
90, 80, 75, 65, 64, 63, 62, 61, 60, 59, 58, 57.5, 55.0, 52.5, 50.0
g/L.
[0089] The composition of the present invention also optionally
includes a wetting agent. The wetting agent is particularly useful
for wetting surfaces that are known to be somewhat difficult to
wet, such as Galvalume.RTM.. Wetting agents that improve coating
wetting without increasing water sensitivity of the composition and
that are soluble and stable in strong acidic solutions are
preferred. Examples of suitable wetting agents include, but are not
limited to, phosphate esters and silicon based wetting agents. Byk
348, a wetting agent commercially available from Byk Chemie, is a
silicon surfactant based on the polyether modified
poly-dimethyl-siloxane. Preferred phosphate esters include, but are
not limited to, substituted phosphate esters, and more preferably
substituted carboxylated phosphate esters.
[0090] When one or more wetting agents are used, independently of
their chemical nature, the total concentration of wetting agent
dissolved in a working composition according to the invention,
preferably is at least, with increasing preference in the order
given, 0.10, 0.20, 0.25, 0.30, 0.40, 0.50, 0.55, 0.60 or 0.65 g/L
of total composition and independently preferably not more than,
with increasing preference in the order given, 5.0, 4.0, 3.0, 2.5,
2.0, 1.5, 1.0, 0.90, 0.80 or 0.75 g/L.
[0091] The passivate composition may also comprise a defoamer, i.e.
a defoaming agent. Suitable defoamers are those known defoamers,
which do not adversely affect the stability of the composition. In
particular, the defoamer desirably is compatible with the resins
used. Defoamers containing hydrocarbons and/or non-ionic
surfactants may be used, including, for example, Foamaster.RTM. NDW
(available commercially from Cognis Inc. The defoamer concentration
in the passivate composition is not critical provided that
sufficient defoaming agent is provided to reduce foaming of the
composition, for example, from about 0.01 to about 0.4 weight
percent, preferred is 0.02%, depending on the process
conditions.
SECOND EMBODIMENT
[0092] In the second embodiment, a hexavalent chromium containing
passivate that provides both excellent corrosion resistance and
improved resistance to retention of solar radiation is described.
Accordingly, the second embodiment of the invention relates to
compositions and processes for passivating metal surfaces, which
also improves the metal surface's resistance to heating by
electromagnetic radiation (hereinafter EMR), in particular solar
radiation or energy. This embodiment is applicable to aluminiferous
and/or zinciferous surfaces which differ from the underlying metal,
as well as to solid alloys of aluminum and/or zinc which include
zinc, such as hot-dip and electro-galvanized, zinc alloys,
aluminum, aluminum alloys and mixtures thereof, as well as steel
coated with these metals.
[0093] The second embodiment comprises oxides of metals and/or
metalloids, as described herein, which provide a surprising benefit
of improved emittance of absorbed solar radiation while retaining
more than 50% of the reflectance of the uncoated metal. Preferred
embodiments of the passivate coating are transparent or translucent
and colorless.
[0094] Any water soluble source of hexavalent chromium atoms may be
used to provide component (B) according to the invention. Examples
include chromic acid (i.e., CrO3), ammonium bichromate, potassium
bichromate, sodium bichromate, ammonium chromate, potassium
chromate, sodium chromate, and the like. The use of ammonium salts
and/or chromic acid is preferred, in order to avoid the presence in
a composition according to the invention of any non-volatile alkali
component. Inasmuch as the pH value preferred for a working
composition according to the invention is at least slightly
alkaline, ammonium salts are preferred for at least part of
component (B), but they are, at least for economy, preferably
formed in situ by adding aqueous ammonia to an aqueous solution of
chromic acid. Accordingly, the concentration of chromium in a
composition according to the invention is usually measured as its
stoichiometric equivalent as CrO3, and this stoichiometric
equivalent preferably has a ratio to the concentration of component
(C) (on a dry basis) in the same composition that is at least, with
increasing preference in the order given, 0.0001:1.0, 0.0005:1.0,
0.0010:1.00, 0.0020:1.00, 0.0050:1.00, 0.0075:1.00, 0.0100:1.00,
0.0110:1.00, 0.0120:1.00, 0.0130:1.00, 0.0135:1.00, 0.0140:1.00,
0.0145:1.00, 0.0150:1.00, 0.0155:1.00, 0.0158:1.00, or 0.0162:1.00
and independently preferably is not more than, with increasing
preference in the order given, 0.50:1.00, 0.20:1.00, 0.10:1.00,
0.050:1.00, 0.040:1.00, 0.030:1.00, 0.025:1.00, 0.021:1.00, or
0.017:1.00. If the hexavalent chromium-containing material is too
low in ratio to organic film-forming resin, the treated material
usually has inadequate corrosion resistance and is often subject to
blackening, while if the ratio of hexavalent chromium to organic
film-forming resin is too large, the treatment composition may
become unstable, will definitely generate higher pollution and/or
pollution abatement costs if used in the large majority of
jurisdictions where chromium is considered polluting, and will
decrease the likelihood of achieving a transparent coating as is
usually desired.
[0095] Component (C) preferably is selected from resins that, after
drying from any solution/dispersion in which they may initially be
present, are not soluble in water at 25.degree. C. to an extent
greater than, with increasing preference in the order given, 1.0,
0.5, 0.20, 0.10, 0.050, 0.020, 0.010, 0.0050, 0.0020, 0.0010,
0.00050, 0.00020, or 0.00010 % of the resin in water.
[0096] Independently, component (C) preferably is selected from
organic film-forming polymers of vinyl monomers selected from the
group consisting of hydrocarbons, halohydrocarbons, acrylic acid,
methacrylic acid, maleic acid, and all esters, amides, and nitrites
of organic acids. (Whether before or after polymerization, salts of
any of these acids are to be understood as equivalent to the acids
themselves.) If these polymers, as is usually preferred, have as
low a solubility in water before drying as they are preferred to
have after drying, the resins will be predominantly dispersed
rather than dissolved in the treatment composition. In such
dispersions, a surfactant is normally used as a dispersing agent.
The surfactants commonly used for this purpose in some (but not
all) commercially supplied latexes, the preferred source for
component (C), have not been observed to have any harmful effect on
the properties of the compositions prepared with latexes containing
them and if present are part of optional component (G) as described
above, unless they are copolymerized into the polymer resin itself,
in which instance they are part of component (C).
[0097] More preferably, component (C) is selected from polymers of
monomers selected from the group consisting of acrylic acid,
methacrylic acid, maleic acid, the esters of all of these acids,
acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide
and still more preferably, in such polymers, the total number of
millimoles of carboxylic acid and carboxylate salt moieties per
gram of the dried resin is at least, with increasing preference in
the order given, 0.030, 0.040, 0.050, 0.070, 0.080, 0.090, 0.100,
0.110, 0.120, 0.130, 0.135, or 0.140 and independently preferably
is not more than, with increasing preference in the order given,
1.5, 1.0, 0.50, 0.40, 0.35, 0.30, 0.27, 0.24, 0.22, 0.200, 0.190,
0.180, 0.170, or 0.160.
[0098] Independently of other preferences, polymers of component
(C) preferably have a glass transition temperature that is not more
than, with increasing preference in the order given, 30, 27, 25,
23, 21, 19, 17, or 15.degree. C.
[0099] A working treatment composition according to the invention
preferably has a pH value that is at least, with increasing
preference in the order given, 5.0, 5.5, 6.0, 6.5, 7.0, 7.2, 7.4,
or 7.6, and independently preferably is not more than, with
increasing preference in the order given, 10.0, 9.6, 9.2, 9.0, 8.8,
8.6, 8.4, 8.2, 8.0, 7.8. If the pH is too high or too low, the
composition is likely to be unstable, because of precipitation
and/or coagulation of at least part of its constituents. If most or
all of the chromium present has been added as CrO3 and there is no
other alkaline constituent in the composition, an alkalinizing
agent will usually be required as optional component (D) in order
to achieve a pH value of 7.5 or more when that is desired. Any
alkaline material may be used, but volatile ones such as ammonia
and amines, for example, monoethylamine, diethylamine,
triethylamine, and the like, and alkanolamines such as
monoethanolamine, diethanolamine, and triethanolamine are
preferred. At least for economy, simple ammonia, usually added as a
concentrated solution in water, is most preferred.
[0100] Chemically, a wax to be used as optional component (F) in a
composition or process according to this invention preferably is
predominantly an organic substance selected from the group
consisting of hydrocarbons, halohydrocarbons, halocarbons,
alcohols, ethers, carboxylic acids, esters of carboxylic acids,
ketones, and aldehydes. Most if not all of the preferred waxes have
scant solubility in water, and therefore are preferably added as
dispersions to a mixture that constitutes, or after further
additions will constitute, a composition according to the
invention. Commercially available dispersions with fine dispersed
particle size are preferably used. More particularly, the average
particle size of a dispersion of wax that is part of component (F)
in a composition according to the invention preferably is not more
than, with increasing preference in the order given, 50, 40, 30,
20, 10, 5, 2, 1.0, 0.5, 0.20, 0.15, 0.12, 0.10, 0.08, or 0.06
micrometers. As with the organic film-forming resin polymers used
in the same compositions, there is usually a dispersing agent
required for a stable dispersion of this type; the dispersing
agents in some but not all commercially supplied dispersions do not
have any detrimental effect on a composition or process according
to the invention; and when a dispersing agent for the wax component
in a composition used according to the invention is present, this
dispersing agent usually forms part of optional component (G).
[0101] Independently of its chemical nature, the melting point of a
wax used in this invention preferably is at least, with increasing
preference in the order given, 57, 65, 75, 85, 95, 105, 110, 115,
120, 125, or 130.degree. C. and independently preferably is not
more than, with increasing preference in the order given, 400, 350,
300, 250 200, 180, 170, 160, 155, 150, 145, 140, or 135.degree.
C.
[0102] A wax component (F) may be used to obtain the maximum
resistance to damage in forming the finished product, but too large
a fraction of wax can be disadvantageous. For example, too much wax
may: reduce the corrosion resistance, if the wax by itself does not
form a continuous protective coating as component (C) does; make a
substrate surface so slippery that it is very difficult to keep it
coiled and/or to keep anything placed on an inclined surface of the
coated substrate from sliding off; and/or cause undesired adhesion
of the coated surface to another surface with which it is in
contact, especially if the wax is low in melting point and the
coated surface is exposed to heat while or shortly before it is in
contact with another surface from which it is desired later to
separate it. Specifically, the ratio by mass, on a dried basis, of
wax component (F) to component (C) preferably is at least, with
increasing preference in the order given, 0.020:1.00, 0.040:1.00,
0.050:1.00, 0.060:1.00, 0.065:1.00, 0.070:1.00, 0.075:1.00,
0.080:1.00, 0.085:1.00, 0.090:1.00, 0.095:1.00, 0.100:1.00, or
0.103:1.00 and independently preferably is not more than, with
increasing preference in the order given, 0.50:1:00, 0.40:1.00,
0.30:1.00, 0.25:1.00, 0.20:1.00, 0.15:1.00, 0.13:1.00, or
0.11:1.00.
[0103] As already noted above, some surfactant, part of optional
component (G), may be needed to disperse any insufficiently
water-soluble constituents of component (C). If the substrate to be
treated is exceptionally difficult to wet uniformly and/or if the
composition according to the invention contains preferred amounts
of solvent added to reduce the likelihood of cracks in the coating
formed, additional surfactant may be needed to assure adequately
uniform wetting. In such an instance, a fluorinated surfactant,
more preferably a fluorinated anionic surfactant, most preferably a
fluorinated alkyl carboxylate salt surfactant in which at least 80%
of the carboxylate groups have at least 8 carbon atoms, is
preferred. Independently, the concentration of fluorinated
surfactant in a working composition according to the invention
preferably is at least, with increasing preference in the order
given, 0.0010, 0.0020, 0.0030, 0.0040, 0.0050, 0.0060, or 0.0070%
of the total composition and independently preferably is not more
than, with increasing preference in the order given, 0.080, 0.060,
0.050, 0.040, 0.030, 0.020, 0.015, 0.010, 0.0090, or 0.0080% of the
total composition. A surfactant may also be needed in some
instances for abatement of foaming, particularly if preferred
amounts and types of component (G) as described below are present
in the working composition. If foam is a problem with a composition
according to the invention that does not contain an antifoam agent,
there should be present in the composition according to the
invention an amount of antifoam agent corresponding to a
concentration that is at least, with increasing preference in the
order given, 0.0020, 0.0040, 0.0050, 0.0060, 0.0070, 0.0080,
0.0090, 0.0100, 0.0110, 0.0120, 0.0130, or 0.0140% of the total
composition and independently preferably is not more than, with
increasing preference in the order given, 0.100, 0.080, 0.060,
0.050, 0.040, 0.030, 0.025, 0.020, 0.018, or 0.016% ofthe total
composition. Independently of its concentration, any antifoam agent
used preferably is a non-ionic surfactant and more preferably is
selected from the group consisting of poly(oxyalkylene) polymers,
ethoxylates of organic substances containing at least one phenol
moiety per molecule, and organo-siloxane polymers.
[0104] An antiblocking agent may be used to reduce spontaneous, at
least temporary adhesion between a surface treated according to the
invention and another surface, optionally also treated according to
the invention, which contacts the surface treated according to the
invention. (This phenomenon, often called "blocking", is
particularly troublesome when surfaces treated according to the
invention are wound into a coil that is later unwound before use.
The compression inherent in winding favors at least temporary
adhesion between the surfaces. If such adhesion occurs, unwinding
can cause transfer of coating from one portion of the treated
surface to some other surface, thereby producing unsatisfactory
coating uniformity. Even if such transfer does not occur,
"stick-slip" behavior of the coil can occur, resulting in uneven
tensions in various parts of the coil processing line and
consequent potential coil treatment and/or coil usage
irregularities that are undesirable.) It has been found that
blocking can be prevented by including in a composition according
to the invention at least one of the following types of
antiblocking agents: [0105] a silicone and/or ethoxylated silicone
polymer, preferably a siloxane, in an amount having a ratio to the
total solids content of the composition that is at least, with
increasing preference in the order given, 0.0010:1.00, 0.0020:1.00,
0.0030:1.00, 0.0040:1.00, 0.0050:1.00, 0.0080:1.00, 0.010:1.00,
0.015:1.00, 0.020:1.00, 0.023:1.00, or 0.025:1.0 and independently,
at least for economy, preferably is not more than, with increasing
preference in the order given, 1.0:1.00, 0.80:1.00, 0.60:1.00,
0.50:1.00, 0.45:1.00, 0.40:1.00, 0.35:1.00, 0.30:1.00, 0.25:1.00,
0.20:1.00, 0.15:1.00, 0.12:1.00, 0.10:1.00, or 0.075:1.00; and
[0106] a fluorinated organic surfactant, preferably an anionic
surfactant, in an amount having a ratio to the total solids content
of the composition that is at least, with increasing preference in
the order given, 0.0002:1.00, 0.0004:1.00, 0.0006:1.00,
0.0008:1.00, 0.0010:1.00, 0.0012:1.00, 0.0014:1.00, or 0.0016:1.0
and independently, at least for economy, preferably is not more
than, with increasing preference in the order given, 0.010:1.00,
0.0075:1.00, 0.0050:1.00, 0.0040:1.00, 0.0030:1.00, or
0.0025:1.00.
[0107] The fluorinated surfactants have the property that they do
not substantially reduce the static frictional properties of the
surfaces coated according to the invention, so that the undesired
"telescoping" of a coil of substrate treated according to the
invention is less likely to occur. Silicone polymers are more
consistent in preventing blocking but do cause reduced static
frictional properties of the surfaces coated with them. A choice
between these two types of blocking prevention may be made on this
basis.
[0108] Optional component (H) of organic solvent may not be needed
and when not needed is preferably omitted for economy and avoidance
of pollution problems and/or pollution abatement expense. There are
at least three reasons, however, why organic solvents may be needed
in a composition according to this invention in some instances.
First, desired constituents of component (C) may require the
presence of organic solvent as an aid in practical preparation of a
composition according to the invention. In any such instance, the
amount of organic solvent added for this purpose is preferably kept
to the minimum required. Secondly, an organic solvent may be useful
in removing contaminants from the substrate simultaneously with
forming the desired protective coating according to the invention,
but ordinarily better results will be achieved if the substrate is
conventionally cleaned before any contact with a composition
according to this invention. Thirdly and most frequently, component
(H) may be needed to avoid cracking of the coating formed in a
process according to the invention. Component (H) is unlikely to be
needed for this reason if the glass transition temperature of
component (C) is not more than 17.degree. C. and is likely to be
needed if the glass transition temperature of component (C) is more
than 30.degree. C.
[0109] When component (H) is included in a composition according to
the invention in order to avoid cracking of the coating formed,
this component is preferably selected from the group consisting of:
[0110] esters with a structure that can be made by completely
esterifying orthophosphoric acid or sulfuric acid with at least one
monoalcohol, which may include halogen atoms and/or ether oxygen
atoms in its molecules; and [0111] glycols, polyglycols, and the
ethers and esters of glycols and polyglycols, i.e., molecules that
conform to the general chemical formula (I):
R.sup.1-O--R.sup.2-(OR.sup.3).sub.n--O--R.sup.4 (I), wherein:
[0112] each of R.sup.1 and R.sup.4, which may be the same or
different, represents one of a hydrogen moiety, a monovalent
hydrocarbon, halohydrocarbon, or halocarbon moiety, and a
monovalent acyl or halo-substituted acyl moiety; [0113] each of
R.sup.2 and R.sup.3, which may be the same or different, represents
a divalent hydrocarbon, halohydrocarbon, or halocarbon moiety; n
represents zero or a positive integer; and [0114] the R.sup.3
moiety in any one of the n (OR.sup.3) moieties may be the same as
or different from the R.sup.3 moiety in any other distinct one of
these (OR.sup.3) moieties. Preferably, component (H) when present
to minimize cracking of the coating is selected from molecules that
conform to general formula (I) as given above, and more preferably,
independently for each preference stated, the molecules selected
conform to general formula (I) when: [0115] R.sup.1 represents a
hydrogen atom and R.sup.4 represents an alkyl moiety having a
number of carbon atoms that is at least, with increasing preference
in the order given, 2, 3, or 4 and independently preferably is not
more than, with increasing preference in the order given, 10, 8, 6,
5, or 4; [0116] each of R.sup.2 and R.sup.3 has at least 3 carbon
atoms and independently preferably has not more than, with
increasing preference in the order given, 10, 8, 6, 5, 4, or 3
carbon atoms; [0117] n is not more than, with increasing preference
in the order given, 4, 3, 2, or 1. Still more preferably, component
(H) when present to minimize cracking of coatings formed with it
comprises, preferably consists essentially of, or more preferably
consists of, two distinct subcomponents as follows: [0118]
subcomponent (H.1) is selected from molecules that preferably have
not more than, with increasing preference in the order given, 9, 8,
or 7 carbon atoms each; and [0119] subcomponent (H.2) is selected
from molecules that have at least 10 carbon atoms each and
independently preferably have not more than, with increasing
preference in the order given, 15, 14, 13, 12, 11, or 10 carbon
atoms each. Independently, when both subcomponents (0.1) and (0.2)
are present in a composition according to the invention, the mass
of (0.1) present has a ratio to the mass of (0.919 2) present that
is at least, with increasing preference in the order given,
1.0:1.00, 2.0:1.00, 3.0:1.00, 4.0:1.00, 5.0:1.00, 5.5:1.00,
6.0:1.00, 6.5:1.00, 7.0:1.00, or 7.5:1.00 and independently
preferably is not more than, with increasing preference in the
order given, 25:1.00, 20:1.00, 18:1.00, 16:1.00, 14:1.00, 12:1.00,
10:1.00, or 8.0:1.00.
[0120] Independently of all other preferences, when component (H)
is present in a composition according to the invention to minimize
crack formation, it preferably has the property that at least, with
increasing preference in the order given, 50, 60, 70, 80, 90, 95,
or 99% of the amount of component (H) present in a wet coating
formed in a process according to the invention is volatilized and
therefore not present in the dry coating eventually formed by the
process. If the temperature at which a composition according to the
invention is to be used is not known, preferably at least, with
increasing preference in the order given, 50, 60, 70, 80, 90, 95,
or 99% of the amount of component (H) present in a wet layer of a
working composition with a thickness of 1.0 millimeter will be
volatilized from said wet layer by heating the layer at 121.degree.
C. for at least 60 seconds.
[0121] Independently of all other preferences, when component (H)
is present in a composition according to the invention to minimize
cracking of coatings formed with the composition, preferably at
least part of it is emulsified into the composition rather than
dissolved in it. (The occurrence of emulsification may normally be
detected by a cloudy rather than a transparent appearance of the
composition when it is mixed.) In order to facilitate the optimal
degree of dispersion, preferably at least, with increasing
preference in the order given, 50, 60, 65, 70, 75, 80, 85, or 88%
of component (H) preferably consists of solvent(s) that have a
solubility in water at 25.degree. C. that is not greater than, with
increasing preference in the order given, 15, 13, 11, 9.0, 8.0,
7.5, 7.3, 7.1, 6.9, 6.7, or 6.5 grams of solvent per 100 grams of
water; and independently at least, with increasing preference in
the order given, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0,
or 11.0% of component (H) preferably consists of solvent(s) that
have a solubility in water at 25.degree. C. that is not greater
than, with increasing preference in the order given, 7.0, 6.8, 6.5,
6.2, 5.9, 5.6, 5.3, or 5.1 grams of solvent per 100 grams of
water.
[0122] Also independently of all other preferences, the
concentration of component (H) in a working composition according
to the invention in which component (H) is present preferably is at
least, with increasing preference in the order given, 0.5, 1.0,
1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 4.9% of the total working
composition and independently preferably is not more than, with
increasing preference in the order given, 30, 25, 20, 15, 10, 9.0,
8.0, 7.0, or 6.0% of the total working composition.
[0123] As is generally known in the art, the resistance to leaching
of a chromium containing protective coating can be increased by
converting part of the initially added hexavalent chromium to
trivalent chromium (or, of course, by otherwise supplying trivalent
chromium to the composition and correspondingly reducing the
content of hexavalent chromium). In general, no trivalent chromium
is needed for this purpose in a working composition according to
the invention, and if not needed is preferably omitted. In some
instances, however, even when no trivalent chromium is desired in
the working liquid composition as applied, it is advantageous for
some chromium to be converted to a trivalent form during drying of
the working composition into place on the substrate surface to be
treated. This result may be achieved by using a working composition
that contains an organic material that is not readily effective as
a reducing agent for hexavalent chromium under the conditions of
concentrations and storage and/or use temperature for the working
composition, but that is effective as such a reducing agent at
higher temperatures, higher concentrations, or both, which are
achieved during drying of the liquid coating of working
composition. For this purpose, it is preferable to utilize a
reducing agent that does not cause any deterioration in the
protective quality of the coatings formed. (It is widely believed,
although not known with certainty, that the major reaction product
from most of these reducing agents is carbon dioxide that escapes
as a gas from the liquid composition before the liquid composition
dries.) If preferred component (H) selected from molecules
conforming to general formula (I) as described above is present, no
other material is normally needed for component (I). If only
non-reducing solvents or none at all are otherwise present in a
composition according to the invention, it is preferred for such a
composition to include at least one reducing additive such as at
least one of various alcohols, such as by way of non-limiting
example glycerol, glycols, such as by way of non-limiting example
propylene glycol, sugars, starch, and like organic materials that
are suitable for this purpose, as known to those skilled in the
art.
[0124] When one of these reducing additives is present in a
composition according to the invention and all of the chromium
present in the composition is supplied to the composition as
hexavalent chromium, the mass of the reducing additive present in
the composition preferably has a ratio to total mass of chromium
present in the same composition that is at least, with increasing
preference in the order given, 0.30:1.00, 0.50:1.00, 0.70:1.00,
0.90:1.00, 1.10:1.00, 1.30: 1.00, 1.50:1.00, 1.70:1.00, 1.90:1.00,
2.10:1.00, 2.30:1.00, 2.40:1.00, 2.50:1.00, 2.60:1.00, 2.70:1.00,
2.80:1.00, or 2.86:1.00 and independently preferably is not more
than, with increasing preference in the order given, 10:1.0,
8.0:1.0, 6.0:1.0, 5.0:1.0, 4.5:1.0, 4.0:1.0, 3.5:1.0, or
3.0:1.0.
[0125] A liquid surface treatment composition according to the
invention may be coated onto the substrate by any effective method,
such as dipping, spraying, brushing, roll coating, or using an air
knife or an electrostatic coating technique, preferably after
removing any grease or other soil from the surface of the
substrate, to form a liquid coating over the substrate to be
treated according to the invention. The coating may be formed on
all surfaces of the substrate or on selected portions of the
surface only, depending on the positioning of the liquid film from
which the dry film is formed.
[0126] The passivate compositions of the present invention may be
used to treat any type of metal surface but are especially useful
for passivating the surface of iron-containing metals such as
steel, including zinc-coated and zinc alloy-coated steel such as
Galvalume.RTM. steel as well as hot dipped galvanized steel.
[0127] The passivate composition may be applied to the metal
surface using any suitable method such as dipping, rolling,
spraying, brushing or the like. The composition is kept in contact
with the metal surface for a period of time and at a temperature
effective to form the desired corrosion protective coating on the
surface. Typically, it will be desirable to apply a wet coating of
the passivate composition to the metal surface and then to heat the
metal surface to a temperature above room temperature to dry the
coating.
[0128] A process according to the invention in its simplest form
consists of bringing a metal surface to be passivated into physical
contact with a working composition according to the invention as
described above for a period of time, then discontinuing such
contact and drying the surface previously contacted. Preferred
metal surfaces include galvanized and/or aluminized steel, and
solid alloys of aluminum and/or zinc. Physical contact and
subsequent separation can be accomplished by any of the methods
well known in the metal treatment art, such as immersion for a
certain time, then discontinuing immersion and removing adherent
liquid by drainage under the influence of natural gravity or with a
squeegee or similar device; spraying to establish the contact, then
discontinuing the spraying and removing excess liquid as when
contact is by immersion; roll coating of the amount of liquid
followed by drying into place, and the like. Drying may be
accomplished at ambient temperature, but it is preferred that
drying take place at elevated temperatures, with the highest metal
temperature (peak metal temperature) achieved not exceeding 250
degrees F. to reduce drying time. Typical processes for use of the
invention are roll coating, for galvanized metal surfaces it is
preferred that passivation be performed immediately after
galvanizing. Roll coating is the preferred method of application in
the coil industry where the coil can be galvanized and passivated
in a continuous process.
[0129] Preferably in roll coating processes, the composition is
applied to strips of sheet metal from a coil and is then heated to
dry and coalesce the coating. The peak metal temperature reached by
the substrate during drying is desirably within the range of 150 to
250 degrees F. The quality of the passivation layer formed is not
known to be substantially affected by the temperature during
passivating if the temperature is within these preferred
limits.
[0130] The thickness of the coating is preferably at least 3, 3.5,
4, 4.5, 5, 5.5, 6.0 and is not more than 12, 11, 10 , 9, 8 microns.
Preferably, the thickness of the coating formed by the aqueous
liquid composition according to the invention corresponds to at
least, with increasing preference in the order given, 100, 150,
200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800,
850, 900 milligrams per square meter of the metal surface
passivated (hereinafter usually abbreviated as "mg/m2"), measured
as total weight of the coating, and independently, preferably is
not more than, with increasing preference in the order given, 1600,
1500, 1200, 1000 mg/m2 measured as total weight of the coating. The
desired coating weight varies with the application. The amount of
total coating weight added-on may conveniently be measured with
commercially available instruments, or by other means known to
those skilled in the art.
[0131] In certain embodiments, the passivating coating can act as a
temporary coating. In this temporary coating embodiment, the
passivating coating is intended to provide temporary corrosion
protection for preventing corrosion and staining during the time
period after galvanizing and prior to final finishing, i.e., during
storage and shipping. The passivating coating is then removed and
the substrate coated with a more permanent corrosion resistant
coating, as is known in the art. For instance, the more permanent
corrosion resistant coatings can be provided by a suitable
conversion coating process. Suitable conversion coating composition
and processes are disclosed in U.S. Pat. Nos. 4,961,794; 4,838,957;
5,073,196; 4,149,909; 5,356,490; 5,281,282; and 5,769,967, which
are hereby incorporated by reference. In this embodiment, if the
passivating coating is to be removed, it is presently contemplated
that this can be readily done by exposing the passivating coating
to a suitable alkaline cleaner solution.
[0132] Before passivating according to this invention is to be used
for any metal substrate, the substrate to be passivated may, but is
not necessarily, thoroughly cleaned by any of various methods well
known to those skilled in the art to be suitable for the particular
substrate to be coated.
[0133] Where galvanized metal surfaces are mentioned in connection
with the present invention, they are understood to be material
surfaces of electrolytically galvanized or hot-dip-galvanized or
even alloy-galvanized steel, preferably electrolytically galvanized
or hot-dip-galvanized steel strip. By steel is meant unalloyed to
low-alloyed steel of the type used, for example, in the form of
sheets for automotive bodywork. The use of galvanized steel,
particularly electrolytically galvanized steel in strip form, has
grown considerably in significance in recent years. The expression
"galvanized steel" in the context of the present invention is
understood to encompass electrolytically galvanized steel and also
hot-dip-galvanized steel and also applies generally to
alloy-galvanized steel, zinc/nickel alloys, zinc/iron alloys
(Galvaneal) an zinc/aluminum alloys (GALFAN.RTM., from Eastern
Alloys, Inc., of Maybrook, N.Y., Galvalume.RTM. .TM., from BIEC
International, Inc. of Vancouver, Wash.) playing a particularly
crucial role as zinc alloys.
[0134] The practice of this invention may be further appreciated by
consideration of the following, non-limiting examples, and the
benefits of the invention may be appreciated by the examples set
forth below.
EXAMPLES
Examples 1-5
[0135] Applicants prepared a series of latexes to assess stability
under low pH conditions, which are found in non-chrome thin-film
organic passivates.
[0136] Example 1 was a cationic latex stabilized by addition of a
non-ionic surfactant. This nonionically stabilized cationic latex
was prepared a ccording to the following procedure: TABLE-US-00001
TABLE 1 Part Ingredient Grams A) DI water 293.5 Triton X-305 7.4 B)
DI water 39.6 Triton X-305 9.1 butyl methacrylate 40.4 methyl
methacrylate 39.8 Styrene 13.5 2-ethylhexyl acrylate 37.1
Hexanediol diacrylate 1.2 C) DI water 102.9 Triton X-305 23.7 butyl
methacrylate 105.1 Hexanediol diacrylate 1.2 2-ethylhexyl acrylate
97.5 Styrene 35.0 methyl methacrylate 104.5 Dimethylaminoethyl
methacrylate 9.7 D1) 70% t-butyl hydroperoxide 0.22 DI water 2.50
D2) 1% Ferrous sulfate 0.50 D3) Sodium formaldehyde sulfoxylate
0.15 DI water 2.50 D4) 1% EDTA sodium salt 3.1 E) 70% t-butyl
hydroperoxide 2.75 DI water 65 F) Sodium formaldehyde sulfoxylate
0.65 DI water 65 G) DI water 22.4 Total 1126.0
[0137] To a 2 liter four-necked flask, equipped with stirrer,
condenser, and nitrogen inlet was added part (A). Stirring and
Nitrogen blanket were applied. Parts (B) and (C) were added to and
mixed by shaking in separate containers until uniform stable
dispersions were obtained. (E) and (F) were added to separate
beakers and stirred to form clear solutions. The flask was heated
to 40 degrees C. at which time (B) was added followed immediately
by addition of (D1) through (D4). The flask contents exothermed to
a temperature of 75 C over 30 minutes after which time (C), (E) and
(F) were added at a uniform rate over 2 hours. During the two-hour
addition, temperature was maintained at 65 degrees C. After
additions were complete, (G) was used to rinse (C) residues into
the flask. Temperature was maintained at 65 degrees C for a period
of 20 minutes at which time the polymerization was complete. The
flask contents were cooled and filtered. Final particle size was
173 nm and measured solids were 44.8%.
[0138] Example 2 was a cationic latex similar to Example 1, but the
amine monomer was not used. This nonionically stabilized cationic
latex was prepared according to the following procedure and
stabilized by an non-ionic surfactant: TABLE-US-00002 TABLE 2 Part
Ingredient Grams A) DI water 293.5 Triton X-305 7.4 B) DI water
142.5 Triton X-305 32.9 butyl methacrylate 155.2 methyl
methacrylate 144.3 Styrene 48.5 2-ethylhexyl acrylate 75.0 Butyl
acrylate 59.6 Hexanediol diacrylate 2.4 C1) 70% t-butyl
hydroperoxide 0.22 DI water 2.50 C2) 1% Ferrous sulfate 0.50 C3)
Sodium formaldehyde sulfoxylate 0.15 DI water 2.50 C4) 1% EDTA
sodium salt 3.1 D) 70% t-butyl hydroperoxide 2.75 DI water 65 E)
Sodium formaldehyde sulfoxylate 0.65 DI water 65 F) DI water 22.4
1126.0
[0139] To a 2 liter four-necked flask, equipped with stirrer,
condenser, and nitrogen inlet was added part (A). Stirring and
Nitrogen blanket were applied. Part (B) was added to and mixed by
shaking in a container until a uniform stable dispersion was
obtained. (D) and (E) were added to separate beakers and stirred to
form clear solutions. The flask was heated to 40 degrees C. at
which time 180.7 g of (B) was added followed immediately by
addition of (C1) through (C4). The flask contents exothermed to a
temperature of 75 degrees C. over 30 minutes after which time the
remainder of (B), (D) and (E) were added at a uniform rate over 2
hours. During the two hour addition, temperature was maintained at
65 degrees C. After additions were complete, (F) was used to rinse
(B) residues into the flask. Temperature was maintained at 65
degrees C. for a period of 20 minutes at which time the
polymerization was complete. The flask contents were cooled and
filtered. Final particle size was 148 nm and measured solids were
45.6%.
[0140] Example 3 and 4 were cationic latexes stabilized by the
incorporation of a polymerizable non-ionic surfactant into the
polymer chain and were prepared as follows: TABLE-US-00003 TABLE 3
Part Ingredient Grams A DI water 146.8 Noigen RN-20 2.6 B) DI water
71.3 Noigen RN-20 11.5 butyl methacrylate 77.6 methyl methacrylate
72.2 Styrene 24.3 2-ethylhexyl acrylate 67.3 Hexanediol diacrylate
1.2 C1) 70% t-butyl hydroperoxide 0.11 DI water 1.3 C2) 1% Ferrous
sulfate 0.25 C3) Sodium formaldehyde sulfoxylate 0.08 DI water 1.3
C4) 1% EDTA sodium salt 1.6 D) 70% t-butyl hydroperoxide 1.4 DI
water 33 E) Sodium formaldehyde sulfoxylate 0.33 DI water 33 F) DI
water 11.2 558.4
[0141] To a 2 liter four-necked flask, equipped with stirrer,
condenser, and nitrogen inlet was added part (A). Stirring and
Nitrogen blanket were applied. Part (B) was added to and mixed by
shaking in a container until a uniform stable dispersion was
obtained. (D) and (E) were added to separate beakers and stirred to
form clear solutions. The flask was heated to 40 degrees C. at
which time 90.3 g of (B) was added followed immediately by addition
of (C1) through (C4). The flask contents was heated to a
temperature of 65C over 30 minutes after which time the remainder
of (B), (D) and (E) were added at a uniform rate over 2 hours.
During the two hour addition, temperature was maintained at 65
degrees C. After additions were complete, (F) was used to rinse (B)
residues into the flask. Temperature was maintained at 65 degrees
C. for a period of 20 minutes at which time the polymerization was
complete. The flask contents were cooled and filtered. Final
particle size was 268 nm and measured solids were 45.5%.
[0142] Example 4 is an additional non-ionically stabilized latex
prepared using the formulation and procedure described by example
3. Final particle size was 217 nm and measured solids were
45.1%.
[0143] Example 5 is a Comparative Example using a cationic latex
typical of those used in the coil industry stabilized by use of a
polymerizable anionic surfactant. This cationic latex was prepared
according to the following procedure, and was stabilized by the
incorporation of the anionic stabilizing groups into the polymer
chain of the resin: TABLE-US-00004 TABLE 4 Part Ingredient Grams A)
DI water 293.6 B) butyl methacrylate 64.0 methyl methacrylate 59.5
Styrene 20.0 butyl acrylate 55.5 Hexanediol diacrylate 1.0 Hitenol
BC-10 6.0 C) Ammonium persulfate 0.4 DI water 5.0 D) DI water 105
Total 610.0
[0144] To a 2 liter four-necked flask, equipped with stirrer,
condenser, and nitrogen inlet was added part (A). Stirring and
Nitrogen blanket were applied. Part (B) was added to and mixed by
stirring in a separate container. (C) was added to a beaker and
stirred to form clear solution. The flask was heated to 80 degrees
C. after which time 41.2 g of (B) was added followed by addition of
(C). The flask contents were maintained at a temperature of 80 C
while the remainder of (B) was added over 3 hours. After additions
were complete, (D) was added to the flask. Temperature was
maintained at 80 degrees C. for a period of 30 minutes at which
time the polymerization was complete. The flask contents were
cooled and filtered. Final particle size was 95 nm and measured
solids were 33.4%.
[0145] Triton X-305 is a nonionic surfactant from Dow Chemical.
EDTA is ethylenediaminetetraacetic acid. Noigen RN-20 is a
polymerizable nonionic surfactant from DKS International, Inc.
Hitenol BC-10 is a polymerizable anionic surfactant from DKS
International, Inc.
Examples 6-18
[0146] Commercially available resins, as well as those of Examples
1-5, were utilized to make non-chrome, thin-film organic passivate
compositions, according to Tables 5 and 6, below. In Examples 6-12,
the ratio of Part A to Part B was 1:1 parts by volume. When the
resin of Example 5 was mixed with the other constituents, the
composition gelled and no further testing of Example 5 was done.
TABLE-US-00005 TABLE 5 COMPONENT A (grams) COMPONENT B (grams) %
H.sub.2O H.sub.3PO.sub.4 H.sub.2TiF.sub.6 H.sub.2O Dequest HA EX
Solids DI 75% 50% DI 2010 16 Lube APP* Ex 1 Ex 2 Ex 3 Ex 4 6 15.86
89.5 7 3.5 46.2 12 35.3 6.5 7 16.36 89.5 7 3.5 36.2 12 35.3 6.5 10
8 24.79 89.5 7 3.5 6.5 12 75 6.5 9 24.72 89.5 7 3.5 6.5 12 6.5 75
10 24.79 89.5 7 3.5 6.5 12 6.5 75 11 24.98 89.5 7 3.5 6.5 12 6.5 75
12 24.81 89.5 7 3.5 6.5 12 6.5 75 *Amino-phenolic polymer
[0147] Non-chrome, thin-film organic passivate compositions were
made as two pack compositions by first formulating Component A and
Component B as found in Table 5, and then combining the two
components. The passivate compositions were also formulated as one
pack compositions, as found in Table 6, below, by combining all
constituents of the composition in a single batch mix, rather than
formulating separate components. TABLE-US-00006 TABLE 6 H.sub.2O
H.sub.3PO.sub.4 H.sub.2TiF.sub.6 Dequest HA EX DI 75% 50% Bonderite
NT-1 2010 Lube Ex 1 Ex 2 16 13 44.75 3.5 1.75 6 6.5 37.5 14 45.45
3.5 1.75 6 6.5 36.8 15 45.45 3.5 1.75 6 6.5 36.8 16 38.75 3.5 1.75
6 6 6.5 37.5 17 39.45 3.5 1.75 6 6 6.5 36.8 18 39.45 3.5 1.75 6 6
6.5 36.8 Amounts are in grams
[0148] The pH of Examples 6-18 was 2.6. Bonderite NT-1 is a
phosphate free surface treatment containing inorganic oxide
particles and dissolved fluorometallate anions commercially
available from Henkel Corporation. Dequest 2010 is an aqueous
solution of phosphonic acids comprising approximately 60 wt %
1-hydroxyethylidene-1, 1-diphosphonic acid commercially available
from Solutia, Inc. The lubricant used for Examples 6-18 was ML160,
a waterborne wax emulsion commercially available from Michelman,
Inc.; it is described in product literature as a low VOC, anionic
carnauba wax having a particle size of 0.135 microns, a melting
point of 85.degree. C. and an ASTM D-5 hardness of 1. HA16 in
Tables 5 and 6 is Rhoplex HA-16, commercially available from Rohm
& Haas; it is described in product literature as a nonionic,
self cross-linking acrylic emulsion polymer having a pH of 2.6 and
a solids wt % of 45.5.
[0149] Variations of the compositions of Examples 13-18 were also
prepared. For Examples 13C, 14C and 15B, the formulations in Table
6 were made according to Examples 13,14 and 15, respectively, with
the exception that additional distilled water was used in place of
the Dequest 2010 to achieve 100 grams total weight. The remaining
variations of Examples 13-18 were made according to their
respective Examples 13-18, and additional components were
introduced, as recited in the Additives column of Table 7. The pH
of Examples 6-18 was 2.6, including the variations was 2.6.
[0150] The compositions were tested for phase stability, based on
phase separation or coagulation after mixing that was visible to
the unaided human eye, and storage stability, which was assessed by
aging the composition at 100.degree. F. for 6 months and observing
whether phase separation or coagulation, visible to the unaided
human eye, had taken place. TABLE-US-00007 TABLE 7 Stability
Testing Storage Stability Formulation Resin Additives Phase
Stability @ 100.degree. F. Example 6 Rhoplex HA16 pass fail Example
7 Rhoplex HA16 pass fail Example 8 Rhoplex HA16 pass fail Example 9
Example 1 pass Pass Example 10 Example 2 pass Pass Example 11
Example 3 pass Pass Example 12 Example 4 pass Pass Example 13A
Example 1 pass Pass Example 13B Example 1 0.02% Byk 348 pass Pass
Example 13C Example 1 w/o Dequest 2010 pass Pass Example 13D
Example 1 1% Nyacol DP 5370 pass Pass Example 14A Example 2 pass
Pass Example 14B Example 2 0.02% Byk 348 pass Pass Example 14C
Example 2 w/o Dequest 2010 pass Pass Example 14D Example 2 1%
Nyacol DP 5370 pass Pass Example 15A RHOPLEX HA 16 pass fail
Example 15B RHOPLEX HA 16 w/o Dequest 2010 pass fail Example 16A
Example 1 pass Pass Example 16B Example 1 1% Nyacol DP 5370 pass
Pass Example 17A Example 2 pass Pass Example 17B Example 2 1%
Nyacol DP 5370 pass Pass Example 18A RHOPLEX HA 16 fail Fail
Example 18B RHOPLEX HA 16 1% Nyacol DP 5370 fail Fail
[0151] Byk 348 is a wetting agent, commercially available from Byk
Chemie. Byk 348 is a silicon surfactant, based on the polyether
modified poly-dimethyl-siloxane. Nyacol DP 5370 is a commercially
available aqueous dispersion of nanoparticulate zinc oxide.
Examples 19-28
[0152] Non-chrome, thin-film organic passivate compositions
containing vanadium were formulated according to Table 8, below.
TABLE-US-00008 TABLE 8 Non-chrome thin film passivate formulations
containing Vanadium pbw Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24
Ex. 25 Ex. 26 Ex. 27 Ex. 28 DI Water 36.6 36.3 42.25 40.95 40.95
43.35 39.65 57.15 59.75 57.15 V.sub.2O.sub.5 1 1 1 1 1 1
NH.sub.4VO.sub.3 1.3 1.3 1.3 1.3 50% NaOH 2.3 2.3 2.3 2.3 2.3 2.3
2.3 45% KOH 3.6 28% NH.sub.4OH 3.6 LiOH.cndot.H.sub.2O 1.2 Dequest
6 6 6 6 6 6 6 6 6 6 2010 75% H.sub.3PO.sub.4 5.4 5.4 5.4 5.4 5.4
5.4 7 7 5.4 7 50% H.sub.2TiF.sub.6 1.75 1.75 1.75 1.75 1.75 1.75
1.75 1.75 1.75 1.75 Nyacol 1 BP 5370 Zinc Oxide 1 1 Permax 220 23.6
23.6 Permax 200 18.75 18.75 Resin 1 17.5 17.5 17.5 17.5 17.5 17 17
17 Resin 2 17.3 17.3 17.3 17.3 17.3 Lube 6.5 6.5 6.5 6.5 6.5 6.5
6.5 6.5 6.5 6.5
[0153] Permax 220 and 200 are nonionically stabilized urethane
resins available from Noveon Inc. and described as aliphatic
polyether waterborne urethane polymers constituting about 35-44%
solids. Resin 1 and 2 are nonionically stabilized acrylic resins
with a solids content of approximately 45-50%. The lubricant used
for Examples 19-28 was ML160, a waterborne wax emulsion
commercially available from Michelman, Inc.
[0154] Galvalume.RTM. and Hot Dip Galvanized (HDP) steel panels
were obtained from the National Steel, Trenton, Mich. The panels
were coated with the compositions as recited in Table 8 using a #3
drawbar and also with a laboratory scale roll coater designed to
approximate industrial roll coating conditions. All panels were
dried in an oven and reached a peak metal temperature (PMT) of
200.degree. F. TABLE-US-00009 TABLE 9 Corrosion results Ex. 19 Ex.
20 Ex. 21 Ex. 22 Ex. 23 Ex. 24 Ex. 25 Ex. 26 % % % % % % % %
Corrosion/ Corrosion/ Corrosion/ Corrosion/ Corrosion/ Corrosion/
Corrosion/ Corrosion/ Hrs Hrs Hrs Hrs Hrs Hrs Hrs Hrs Neutral Salt
5-648 5-936 5-1008 1-1008 2-1008 2-1008 3-1008 2-600 Spray on
Galvalume .RTM. Neutral Salt 7-312 7-432 5-420 3-168 10-336 10-168
10-336 3-264 Spray on HDG Stack Test 10-168 30-168 5-1008 10-1008
3-1008 10-840 10-840 3-1008 on Galvalume .RTM. Stack test 7-336
10-168 10-504 10-504 3-504 7-504 7-336 10-672 on Hot Dipped
Galvanized Butler 10-2016 10-1848 3-2016 5-1008 10-672 3-1008
0-1008 0-1008 Water Immersion test on Galvalume .RTM. Butler 3-168
7-168 5-504 3-336 10-1008 10-1008 7-336 7-336 Water Immersion test
on HDG Cleveland 10-672 100-360 7-1008 3-1008 3-1008 3-1008 3-672
3-672 Condensing on Galvalume .RTM. Cleveland 10-672 40-360 7-1008
10-1008 10-1008 3-1008 10-672 5-672 Condensing on Hot Dipped
Galvanized
Example 29
[0155] Formula Part (A), which was the same as the Control, was a
mixture of the substances recited in Table 10, added sequentially
with low speed agitation until uniform in consistency:
TABLE-US-00010 TABLE 10 Parts per Constituent hundred parts by
weight Acrylic emulsion resin 45.6 De-ionized water 39.1 Wax
emulsion 8.7 Ammonium dichromate (10% wt) intermediate 6.4 Silicone
anti-block 0.2
[0156] Formula Part (B) was a commercially available conventional
sized or nanoparticulate dispersion of metal and/or metalloid oxide
powder. A number of the dispersions include a stabilizer in small
amounts to aid in sustaining uniform dispersion of the
particles.
[0157] The candidate compositions were prepared by combining Part A
and Part B using one of the following alternative methods to
produce the particular Formula to be tested, as follows: [0158] I.
Direct addition using low-speed agitation of Part (B) to Part (A)
in relative amounts pre-calculated to achieve the targeted pigment
volume concentration, with subsequent maintenance of low-speed
agitation until uniform in consistency (Formulas 1, 2A-C, 3A-C, 4,
5, 6, & 12); [0159] II. Method I. modified by the application
of extended high-speed dispersion of initially mixed Parts (A) and
(B) until uniform in consistency (Formulas 7A-C, 8, & 9);
[0160] III. Pre-neutralization of Part (B) to pH.about.8.0,
followed by processing according to Method I. (Formulas 10A-D &
11A-D).
[0161] The composition of Formulas 1-12 is recited in Table 11.
TABLE-US-00011 TABLE 11 Mean Pigment diameter, Dry film % Pigment
Volume Concentration (PVC) type nm Stabilizer appearance* 5% 10%
15% 20% 30% 40% 50% SiO.sub.2 15 ammonia Initial light amber 1 --
-- -- -- -- -- fading to colorless, transparent, high gloss
SiO.sub.2 15 none Initial light amber -- -- -- 2A -- 2B 2C fading
to colorless, transparent, high gloss TiO.sub.2 250 Alumina Initial
light amber 3A 3B -- 3C -- -- -- zirconia fading to colorless,
sl.-mod. opaque, high gloss TiO.sub.2 250 Alumina Initial light
amber 4 -- -- -- -- -- -- silica fading to colorless, sl.-mod.
opaque, high gloss TiO.sub.2 25 proprietary Initial green-gray 5 --
-- -- -- -- -- organic fading to colorless, mod. opaque, high gloss
ZnO 100 none Initial light yellow- 6 -- -- -- -- -- -- green fading
to colorless, transparent, high gloss ZrO.sub.2 5-10 acetic acid
Initial light yellow- 7A 7B 7C -- -- -- -- green fading to
colorless, transparent, high gloss ZrO.sub.2 5-10 nitric acid
Initial light yellow- -- -- 8 -- -- -- -- green fading to
colorless, transparent, high gloss ZrO.sub.2 100 Nitric acid
Initial light yellow- -- -- 9 -- -- -- -- green fading to
colorless, sl. opaque, low gloss Sb.sub.2O.sub.5 5 TEA Initial
green-gray 10A 10B 10C 10D -- -- -- phosphate fading to colorless,
transparent, high gloss Sb.sub.2O.sub.5 35 TEA Initial green-gray
-- -- -- 11A 11B 11C 11D fading to colorless, transparent, high
gloss CeO.sub.2 20 proprietary Persistent medium -- -- 12 -- -- --
-- organic amber, sl.-mod. opaque, low gloss
[0162] The Formulas prepared according to Table 11 were tested for
their effect upon the emittance of a typical metal roofing
material. For each Formula, a series of Fairfield Galvalume.RTM.
panels was coated at different coating weights using a draw down
bar.
[0163] The progressive dissipation of initial color noted in panels
produced from all mixtures except Formula 12 was observed to be
dependent wholly or mostly on extended light, rather than heat,
exposure. In general, the progression from the initial residual
colored appearance to colorless was complete within about 24-48
hours under conditions of ambient indoor illumination.
[0164] The coated panels were evaluated for emittance and
reflectence of EMR as described in Table 12. Formula Part A was
used as the control. TABLE-US-00012 TABLE 12 Mean Pigment Diameter,
Coating Solar Formula ID type nm Stabilization wt, mg/ft.sup.2*
Emittance** Reflectance.dagger. Control none N/A N/A 0 0.06 0.78
117 0.22 0.69 129 0.34 -- 253 0.37 -- 310 0.36 -- 316 0.39 -- 369
0.41 0.64 385 0.42 -- 410 0.38 -- 1 SiO.sub.2 15 Ammonia 228 0.39
-- 300 0.45 -- 392 0.48 -- 2A SiO.sub.2 15 None 656 0.65 -- 2B
SiO.sub.2 15 None 688 0.66 -- 2C SiO.sub.2 15 None 712 0.67 -- 3A
TiO.sub.2 250 alumina/zirconia 234 0.37 -- 439 0.50 -- 3B TiO.sub.2
250 alumina/zirconia 267 0.42 -- 455 0.58 -- 3C TiO.sub.2 250
alumina/zirconia 296 0.55 -- 530 0.66 -- 4 TiO.sub.2 250
alumina/silica 272 0.37 -- 426 0.53 -- 5 TiO.sub.2 25 proprietary
168 0.44 -- organic 289 0.53 -- 411 0.61 -- 6 ZnO 100 none 174 0.24
-- 311 0.37 -- 408 0.45 -- 7A ZrO.sub.2 5-10 acetic acid 212 0.41
-- 313 0.52 -- 407 0.58 0.64 488 0.60 -- 623 0.62 -- 671 0.69 --
721 0.71 -- 803 0.71 -- 896 0.72 -- 931 0.72 -- 1053 0.74 0.62 7B
ZrO.sub.2 5-10 acetic acid 517 0.67 0.64 547 0.69 -- 560 0.70 --
633 0.74 0.62 7C ZrO.sub.2 5-10 acetic acid 476 0.67 -- 505 0.70 --
500 0.71 -- 542 0.72 -- 576 0.74 0.62 8 ZrO.sub.2 5-10 nitric acid
269 0.57 -- 298 0.64 -- 420 0.71 -- 502 0.74 -- 588 0.75 0.62 569
0.78 -- 9 ZrO.sub.2 100 Nitric acid 403 0.61 -- 10A Sb.sub.2O.sub.5
5 TEA phosphate 326 0.49 -- 464 0.53 -- 549 0.57 -- 699 0.61 -- 828
0.65 -- 986 0.67 -- 1091 0.70 -- 10B Sb.sub.2O.sub.5 5 TEA
phosphate 335 0.55 -- 485 0.61 -- 606 0.66 -- 671 0.68 -- 10C
Sb.sub.2O.sub.5 5 TEA phosphate 341 0.59 -- 525 0.66 -- 604 0.68 --
628 0.70 -- 10D Sb.sub.2O.sub.5 5 TEA phosphate 301 0.57 -- 323
0.61 -- 441 0.65 -- 482 0.69 -- 549 0.71 -- 642 0.73 -- 11A
Sb.sub.2O.sub.5 35 TEA 624 0.59 -- 11B Sb.sub.2O.sub.5 35 TEA 320
0.59 -- 424 0.63 -- 503 0.67 -- 539 0.67 -- 620 0.71 -- 659 0.73 --
703 0.75 0.60 11C Sb.sub.2O.sub.5 35 TEA 408 0.62 -- 338 0.62 --
476 0.69 -- 480 0.70 -- 492 0.70 -- 574 0.74 -- 664 0.77 -- 11D
Sb.sub.2O.sub.5 35 TEA 386 0.63 -- 416 0.66 -- 460 0.69 -- 528 0.73
-- 542 0.76 -- 593 0.77 -- 516 0.78 -- 12 CeO.sub.2 20 proprietary
.sup. 886.sup..dagger-dbl. 0.50 -- organic 1244.sup..dagger-dbl.
0.57 -- 1461.sup..dagger-dbl. 0.62 -- *Coating weight calculated
from XRF Cr analysis and known Cr composition of mixture, assuming
quantitative loss of volatiles. **Emittance measured per ASTM
C1371-04a using a Devices and Services Model AE/RD1 Emissometer.
.sup..dagger.Solar Reflectance measured per ASTM C1549 using a
Devices and Services Model SSR-E Solar Spectrum Reflectometer with
Air Mass 2 spectral weighting. .sup..dagger-dbl.Coating weight
skewed high due to spectral interference between Cr and Ce at the
analytical wavelength.
[0165] A series of Fairfield Galvalume.RTM. panels was coated at
the below coating weights using a draw down bar. TABLE-US-00013
Control Formula 7A Cr cwt, mg/ft.sup.2 applied: 1.6 10.7 Total cwt,
mg/ft.sup.2 applied: 120 1050
[0166] TABLE-US-00014 TABLE 13 ASTM D610 Corrosion Rating Test
Procedure Duration Control Formula 7A Neutral Salt Spray* 1000 hrs
9 10 Cleveland condensing humidity 1000 hrs 9 10 Butler water
immersion 1000 hrs 6 10 Stack 2000 hrs 7 8 *Rating on roll-formed
panels. Rating is exclusive of performance along the length of
convex ridges of the roll-formed profile, where localized corrosion
occurred due to film fracture during forming.
[0167] Although Formula 7A was not optimized for corrosion
resistance at the lowest possible chromate concentration, the
corrosion resistance was at least as good as the control at the
coating weight that provided emittance of 0.74.
[0168] Although the invention has been described with particular
reference to specific examples, it is understood that modifications
are contemplated. Variations and additional embodiments of the
invention described herein will be apparent to those skilled in the
art without departing from the scope of the invention as defined in
the claims to follow. The scope of the invention is limited only by
the breadth of the appended claims.
* * * * *