U.S. patent application number 13/249331 was filed with the patent office on 2013-04-04 for acid cleaners for metal substrates and associated methods for cleaning and coating metal substrates.
This patent application is currently assigned to PPG Industries Ohio, Inc.. The applicant listed for this patent is Susanna Fraley, Brian C. Okerberg, Terri Ziegler. Invention is credited to Susanna Fraley, Brian C. Okerberg, Terri Ziegler.
Application Number | 20130081950 13/249331 |
Document ID | / |
Family ID | 47010774 |
Filed Date | 2013-04-04 |
United States Patent
Application |
20130081950 |
Kind Code |
A1 |
Okerberg; Brian C. ; et
al. |
April 4, 2013 |
ACID CLEANERS FOR METAL SUBSTRATES AND ASSOCIATED METHODS FOR
CLEANING AND COATING METAL SUBSTRATES
Abstract
Disclosed are methods for cleaning and coating metal substrates,
and the coated substrate formed therein, that include contacting
the substrate with an acid and then contacting the cleaned
substrate with an electrodepositable coating composition comprising
a film forming polymer and a corrosion inhibitor.
Inventors: |
Okerberg; Brian C.;
(Gibsonia, PA) ; Fraley; Susanna; (Fenelton,
PA) ; Ziegler; Terri; (Cranberry Township,
PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Okerberg; Brian C.
Fraley; Susanna
Ziegler; Terri |
Gibsonia
Fenelton
Cranberry Township |
PA
PA
PA |
US
US
US |
|
|
Assignee: |
PPG Industries Ohio, Inc.
Cleveland
OH
|
Family ID: |
47010774 |
Appl. No.: |
13/249331 |
Filed: |
September 30, 2011 |
Current U.S.
Class: |
205/50 ;
205/211 |
Current CPC
Class: |
C09D 5/084 20130101;
C25D 13/20 20130101; C25D 13/04 20130101; C25D 13/10 20130101; C09D
5/448 20130101 |
Class at
Publication: |
205/50 ;
205/211 |
International
Class: |
C25D 5/34 20060101
C25D005/34 |
Claims
1. A method comprising: (a) contacting a substrate with an acid;
and then (b) contacting the substrate with an electrodepositable
coating composition comprising (i) a film-forming polymer; and (ii)
a corrosion inhibitor; with the proviso that the method does not
comprise contacting the substrate with a pretreatment composition
prior to step (b).
2. The method of claim 1, wherein said corrosion inhibitor
comprises a rare earth metal, a lanthanide, or combinations
thereof.
3. The method of claim 1, wherein said corrosion inhibitor
comprises a source of yttrium.
4. The method of claim 3, wherein said source of yttrium comprises
an yttrium compound.
5. The method of claim 1, wherein said corrosion inhibitor
comprises a source of cerium.
6. The method of claim 1, wherein said source of cerium comprises a
cerium compound.
7. The method of claim 1, wherein said corrosion inhibitor
comprises a source of yttrium and a source of cerium.
8. The method of claim 1, wherein said electrodepositable coating
composition further comprises (iii) a silane that does not contain
an ethylenically unsaturated double bond
9. The method of claim 1, wherein said acid comprises an organic
acid.
10. The method of claim 1, wherein said acid comprises a mineral
acid.
11. The method of claim 1, wherein said acid comprises an organic
acid, a mineral acid or mixtures thereof.
12. The method of claim 9, wherein said organic acid comprises a
carboxylic acid.
13. The method of claim 9, wherein said organic acid comprises
citric acid.
14. The method of claim 1 further comprising (c) contacting the
substrate with an alkaline cleaner prior to steps (a) and (b).
15. The method of claim 1 further comprising (c) contacting the
substrate with an alkaline cleaner prior to step (b) and after step
(a).
16. A coated substrate formed in accordance with the method of
claim 1.
17. A coated substrate formed in accordance with the method of
claim 8.
18. A method for coating a substrate comprising: (a) contacting the
substrate with an acid; (b) contacting the substrate with an
alkaline cleaner; and then (c) contacting the substrate with an
electrodepositable coating composition comprising (i) a
film-forming polymer; and (ii) a corrosion inhibitor; with the
proviso that the method does not comprise contacting the substrate
with a pretreatment composition prior to step (b).
19. The method of claim 1, wherein said corrosion inhibitor
comprises a rare earth metal, a lanthanide, or combinations
thereof.
20. A coated substrate formed in accordance with the method of
claim 19.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to acid cleaners for metal
substrates and associated methods for cleaning metal substrates
with the acid cleaners prior to application of a pretreatment
composition and/or an electrodepositable coating composition.
BACKGROUND INFORMATION
[0002] The use of protective coatings on metal substrates for
improved corrosion resistance and paint adhesion is common.
Conventional techniques for coating such substrates include
techniques that involve pretreating the metal substrate with a
pretreatment composition and/or with an electrodepositable coating
composition.
SUMMARY OF THE INVENTION
[0003] In certain embodiments, the present invention is directed to
a method comprising: (a) contacting a substrate with an acid; and
then (b) contacting the substrate with an electrodepositable
coating composition comprising (i) a film-forming polymer; and (ii)
a corrosion inhibitor; with the proviso that the method does not
comprise contacting the substrate with a pretreatment composition
prior to step (b).
DETAILED DESCRIPTION OF THE INVENTION
[0004] For purposes of the following detailed description, it is to
be understood that the invention may assume various alternative
variations and step sequences, except where expressly specified to
the contrary. Moreover, other than in any operating examples, or
where otherwise indicated, all numbers expressing, for example,
quantities of ingredients used in the specification and claims are
to be understood as being modified in all instances by the term
"about". Accordingly, unless indicated to the contrary, the
numerical parameters set forth in the following specification and
attached claims are approximations that may vary depending upon the
desired properties to be obtained by the present invention. At the
very least, and not as an attempt to limit the application of the
doctrine of equivalents to the scope of the claims, each numerical
parameter should at least be construed in light of the number of
reported significant digits and by applying ordinary rounding
techniques.
[0005] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
inherently contains certain errors necessarily resulting from the
standard variation found in their respective testing
measurements.
[0006] Also, it should be understood that any numerical range
recited herein is intended to include all sub-ranges subsumed
therein. For example, a range of "1 to 10" is intended to include
all sub-ranges between (and including) the recited minimum value of
1 and the recited maximum value of 10, that is, having a minimum
value equal to or greater than 1 and a maximum value of equal to or
less than 10.
[0007] In this application, the use of the singular includes the
plural and plural encompasses singular, unless specifically stated
otherwise. In addition, in this application, the use of "or" means
"and/or" unless specifically stated otherwise, even though "and/or"
may be explicitly used in certain instances.
[0008] Certain embodiments of the present invention are directed to
methods for cleaning a substrate by contacting the metal substrate
with an acid.
[0009] The acid cleaned substrate, in certain embodiments, may then
be contacted with a pretreatment composition. In certain of these
embodiments, the pretreatment composition includes a group IIIB
and/or IVB metal compound, wherein the citric acid cleaner acts to
provide increased deposition of the group IIIB and/or IVB metal
onto the metal substrate surface, wherein the increased metal
content acts to improve corrosion resistance.
[0010] In certain other embodiments, a film forming composition,
such as an electrodepositable coating composition, may be applied
over the acid cleaned and optionally pretreated substrate. In these
embodiments, the acid provides improved corrosion protection to the
coated substrate as compared with coated and uncleaned substrates
or substrates cleaned with alkaline cleaners and coated as
described above.
[0011] In certain other embodiments, a film forming composition,
such as an electrodepositable coating composition, may be applied
over the acid cleaned substrate without first contacting the
substrate with a pretreatment composition. In certain of these
embodiments, the acid acts to improve corrosion resistance of these
acid cleaned and electrocoated substrates as compared with coated
and uncleaned substrates or substrates cleaned with alkaline
cleaners and electrocoated as described above.
[0012] Each of these embodiments is described below:
Substrate
[0013] Suitable substrates that can be cleaned and coated in
accordance with the present invention include, without limitation,
metal substrates, metal alloy substrates, and/or substrates that
have been metallized, such as nickel plated plastic. In some
embodiments, the metal or metal alloy can be aluminum and/or steel.
For example, the steel substrate could be cold rolled steel,
electrogalvanized steel, and hot dipped galvanized steel. Moreover,
in some embodiments, the substrate may comprise a portion of a
vehicle such as a vehicular body (e.g., without limitation, door,
body panel, trunk deck lid, roof panel, hood, and/or roof) and/or a
vehicular frame. As used herein, "vehicle" or variations thereof
includes, but is not limited to, civilian, commercial, and military
land vehicles such as cars, motorcycles, and trucks.
Cleaning
[0014] In certain embodiments, the substrates may be contacted with
an acid prior to contacting the substrate with a pretreatment
composition and/or an electrodepositable coating composition.
[0015] While not wanting to be bound by any theory, it is believed
that the acid etches the substrate to provide increased surface
area to the substrate. Increased surface area is believed to
provide improved adhesion between the substrate and the
subsequently applied coating materials, which is believed to
improve corrosion resistance to the coated panels. In addition,
increased etching of the substrate material is believed to allow
for increased deposition of metal from the pretreatment
composition, when utilized, which also is believed to increase
corrosion resistance to the coated panels. Further, increased
etching of the substrate material is believed for increased
deposition of metal from the electrodepositable coating
composition, when utilized, at the interface between the
electrodepositable coating composition and the substrate, which may
provide even more corrosion resistance to the coated panels.
[0016] In certain embodiments, the acid comprises a single acid,
while in other embodiments the acid comprises a mixture of
acids.
[0017] In certain embodiments, the acid comprises a weak acid,
while in other embodiments the acid comprises a strong acid. A weak
acid, by definition, is an acid that dissociates incompletely (i.e.
it does not release all its hydrogens in solution), while a strong
acid is an acid that ionizes completely in an aqueous solution
(i.e. which release all of their hydrogen atoms when dissolved in
water).
[0018] In still other embodiments, the acid comprises an organic
acid. An organic compound, by definition, is an organic compound
having acidic properties. Exemplary organic acids include uric
acid, sulfonic acid, and carboxylic acids including lactic acid,
formic acid, citric acid, and oxalic acid, as well as mixtures
thereof.
[0019] In still other embodiments, the acid comprises a mineral
acid. A mineral acid, by definition, is an acid derived from an
inorganic compound. Exemplary mineral acids include hydrochloric
acid, sulfuric acid, boric acid, phosphoric acid, hydrofluoric
acid, hydrobromic acid, nitric acid, and mixtures thereof.
[0020] In still other embodiments, the acid may comprise any
combination of one or more organic acids and/or mineral acids.
[0021] In certain of these embodiments, the carboxylic acid
selected for use in the compositions described herein has a water
solubility of >1 g/L at 20.degree. C. Carboxylic acids suitable
for use include, for example, monocarboxylic acids, such as formic
acid, acetic acid, propionic acid, methylacetic acid, butyric acid,
ethylacetic acid, n-valeric acid, n-butanecarboxylic acid, acrylic
acid, propiolic acid, methacrylic acid, palmitic acid, stearic
acid, oleic acid, linolic acid, and linolenic acid; dicarboxylic
acids, such as oxalic acid, malonic acid, succinic acid, glutaric
acid, adipic acid, pimelic acid, suberic acid, azelaic acid,
lepargilic acid, sebacic acid, maleic acid, and fumaric acid;
aliphatic hydroxy acids, such as glycolic acid, lactic acid,
tartronic acid, glyceric acid, malic acid, tartaric acid,
citramalic acid, citric acid, isocitric acid, leucine acid,
mevalonic acid, pantoic acid, recinoleic acid, ricinelaidic acid,
cerebronic acid, quinic acid, and shikimic acid; aromatic hydroxy
acids, such as salicylic acid, creosote acid, vanillic acid,
syringic acid, pyrocatechuic acid, resorcylic acid, protocatechuic
acid, gentisic acid, orsellinic acid, gallic acid, mandelic acid,
benzilic acid, atrolactinic acid, melilotic acid, phloretic acid,
coumaric acid, umbellic acid, caffeic acid, ferulic acid, and
sinapic acid. Mixtures of any of the foregoing may also be
used.
[0022] In certain embodiments, the acid is incorporated into an
acid cleaner that also may include other components such as water,
surfactants and/or buffers, including commercially available
surfactants and/or buffers.
[0023] In certain other embodiments, the substrate to be treated in
accordance with the methods of the present invention may first be
cleaned to remove grease, dirt, or other extraneous matter. This is
often done by employing mild or strong alkaline cleaners, such as
are commercially available and conventionally used in metal
pretreatment processes. Examples of alkaline cleaners suitable for
use in the present invention include Chemkleen 163, Chemkleen 177,
Chemkleen 2010LP and Chemkleen 490MX, each of which are
commercially available from PPG Industries, Inc. In certain
embodiments, a surfactant may also be included in the alkaline
cleaner, such as 181LP, commercially available from PPG Industries,
Inc. Such cleaners are often followed and/or preceded by a water
rinse. After cleaning, the bare substrate materials may be rinsed
thoroughly with deionized water.
[0024] In certain of these embodiments, the alkaline cleaner is
applied to the substrate prior to the acid cleaner, while in other
embodiments the acid cleaner is applied to the substrate prior to
the alkaline cleaner.
Pretreatment
[0025] In certain embodiments of the methods of the present
invention, after the substrate is contacted with the acid, it may
then be contacted with a pretreatment composition. As used herein,
the term "pretreatment composition" refers to a composition that
upon contact with a substrate reacts with and chemically alters the
substrate surface and binds to it to form a protective layer.
[0026] In certain other embodiments of the present invention, the
pretreatment composition comprises a group IIIB and/or IVB metal
compound.
[0027] In certain embodiments, the pretreatment composition
comprises a carrier, often an aqueous medium, so that the
composition is in the form of a solution or dispersion of a group
IIIB or IVB metal compound in the carrier. In these embodiments,
the solution or dispersion may be brought into contact with the
substrate by any of a variety of known techniques, such as dipping
or immersion, spraying, intermittent spraying, dipping followed by
spraying, spraying followed by dipping, brushing, or roll-coating.
In certain embodiments, the solution or dispersion when applied to
the metal substrate is at a temperature ranging from 60 to
150.degree. F. (15 to 65.degree. C.). The contact time is often
from 10 seconds to five minutes, such as 30 seconds to 2
minutes.
[0028] As used herein, the term "group IIIB and/or IVB metal"
refers to an element that is in group IIIB or group IVB of the CAS
Periodic Table of the Elements as is shown, for example, in the
Handbook of Chemistry and Physics, 63.sup.rd edition (1983). Where
applicable, the metal themselves may be used. In certain
embodiments, a group IIIB and/or IVB metal compound is used. As
used herein, the term "group IIIB and/or IVB metal compound" refers
to compounds that include at least one element that is in group
IIIB or group IVB of the CAS Periodic Table of the Elements.
[0029] In certain embodiments, the group IIIB and/or IVB metal
compound used in the pretreatment composition is a compound of
zirconium, titanium, hafnium, yttrium, cerium, or a mixture
thereof. Suitable compounds of zirconium include, but are not
limited to, hexafluorozirconic acid, alkali metal and ammonium
salts thereof, ammonium zirconium carbonate, zirconyl nitrate,
zirconium carboxylates and zirconium hydroxy carboxylates, such as
hydrofluorozirconic acid, zirconium acetate, zirconium oxalate,
ammonium zirconium glycolate, ammonium zirconium lactate, ammonium
zirconium citrate, and mixtures thereof. Suitable compounds of
titanium include, but are not limited to, fluorotitanic acid and
its salts. A suitable compound of hafnium includes, but is not
limited to, hafnium nitrate. A suitable compound of yttrium
includes, but is not limited to, yttrium nitrate. A suitable
compound of cerium includes, but is not limited to, cerous
nitrate.
[0030] In certain embodiments, the group TIM and/or IVB metal
compound is present in the pretreatment composition in an amount of
at least 10 ppm metal, such as at least 100 ppm metal, or, in some
cases, at least 150 ppm metal. In certain embodiments, the group
IIIB and/or IVB metal compound is present in the pretreatment
composition in an amount of no more than 5000 ppm metal, such as no
more than 300 ppm metal, or, in some cases, no more than 250 ppm
metal. The amount of group IIIB and/or IVB metal in the
pretreatment composition can range between any combination of the
recited values inclusive of the recited values. The pH of the
pretreatment composition often ranges from 2.0 to 7.0, such as 3.5
to 5.5. The pH of the pretreatment composition may be adjusted
using, for example, any of the acids and bases identified earlier
with respect to cleaning the substrate.
[0031] In some embodiments, the pretreatment composition may be a
silane or a non-crystalline phosphate, such as iron phosphate,
containing pretreatment composition. Suitable silane containing
pretreatment compositions include, but are not limited to, certain
commercially available products, such as Silquest A-1100 Silane,
which is described in the Examples herein and which is commercially
available from Momentive Performance Materials. Suitable
non-crystalline phosphate containing pretreatment composition
include pretreatment composition that comprise, iron phosphate,
manganese phosphate, calcium phosphate, magnesium phosphate, cobalt
phosphate, or an organophosphate and/or organophosphonate, such as
is disclosed in U.S. Pat. No. 5,294,265 at col. 1, line 53 to col.
3, line 12 and 5,306,526 at col. 1, line 46 to col. 3, line 8, the
cited portions of which being incorporated herein by reference.
Suitable non-crystalline phosphate containing pretreatment
compositions are commercially available, such as Chemfos.RTM. 158
and Chemfos.RTM. 51, which are iron phosphate pretreatment
compositions commercially available from PPG Industries, Inc.
[0032] In certain embodiments, the pretreatment composition also
comprises an electropositive metal, such as copper. The source of
electropositive metal, such as copper, in the pretreatment
composition may comprise, for example, any of the materials
described earlier with respect to the plating solution. In certain
embodiments, the electropositive metal is included in such
pretreatment compositions in an amount of at least 1 ppm, such as
at least 5 ppm, or in some cases, at least 10 ppm of total metal
(measured as elemental metal). In certain embodiments, the
electropositive metal is included in such pretreatment compositions
in an amount of no more than 500 ppm, such as no more than 100 ppm,
or in some cases, no more than 50 ppm of total metal (measured as
elemental metal).
[0033] In certain embodiments, the pretreatment composition
comprises a resinous binder. Suitable resins include reaction
products of one or more alkanolamines and an epoxy-functional
material containing at least two epoxy groups, such as those
disclosed in U.S. Pat. No. 5,653,823. In some cases, such resins
contain beta hydroxy ester, imide, or sulfide functionality,
incorporated by using dimethylolpropionic acid, phthalimide, or
mercapto glycerine as an additional reactant in the preparation of
the resin. Alternatively, the reaction product is that of the
diglycidyl ether of Bisphenol A (commercially available from Shell
Chemical Company as EPON 880), dimethylol propionic acid, and
diethanolamine in a 0.6 to 5.0:0.05 to 5.5:1 mole ratio. Other
suitable resinous binders include water soluble and water
dispersible polyacrylic acids as disclosed in U.S. Pat. Nos.
3,912,548 and 5,328,525; phenol formaldehyde resins as described in
U.S. Pat. No. 5,662,746; water soluble polyamides such as those
disclosed in WO 95/33869; copolymers of maleic or acrylic acid with
allyl ether as described in Canadian patent application 2,087,352;
and water soluble and dispersible resins including epoxy resins,
aminoplasts, phenol-formaldehyde resins, tannins, and polyvinyl
phenols as discussed in U.S. Pat. No. 5,449,415.
[0034] In these embodiments of the present invention, the resinous
binder is present in the pretreatment composition in an amount of
0.005 percent to 30 percent by weight, such as 0.5 to 3 percent by
weight, based on the total weight of the ingredients in the
composition.
[0035] In other embodiments, however, the pretreatment composition
is substantially free or, in some cases, completely free of any
resinous binder. As used herein, the term "substantially free",
when used with reference to the absence of resinous binder in the
pretreatment composition, means that any resinous binder is present
in the pretreatment composition in an amount of less than 0.005
percent by weight. As used herein, the term "completely free" means
that there is no resinous binder in the pretreatment composition at
all.
[0036] The pretreatment composition may optionally contain other
materials, such as nonionic surfactants and auxiliaries
conventionally used in the art of pretreatment. In an aqueous
medium, water dispersible organic solvents, for example, alcohols
with up to about 8 carbon atoms, such as methanol, isopropanol, and
the like, may be present; or glycol ethers such as the monoalkyl
ethers of ethylene glycol, diethylene glycol, or propylene glycol,
and the like. When present, water dispersible organic solvents are
typically used in amounts up to about ten percent by volume, based
on the total volume of aqueous medium.
[0037] Other optional materials include surfactants that function
as defoamers or substrate wetting agents, such as those materials
and amounts described earlier with respect to the plating
solution.
[0038] In certain embodiments, the pretreatment composition also
comprises a reaction accelerator, such as nitrite ions, nitro-group
containing compounds, hydroxylamine sulfate, persulfate ions,
sulfite ions, hyposulfite ions, peroxides, iron (III) ions, citric
acid iron compounds, bromate ions, perchlorinate ions, chlorate
ions, chlorite ions as well as ascorbic acid, citric acid, tartaric
acid, malonic acid, succinic acid and salts thereof. Specific
examples of suitable materials and their amounts are described in
United States Patent Application Publication No. 2004/0163736 A1 at
[0032] to [0041], the cited portion of which being incorporated
herein by reference.
[0039] In certain embodiments, the pretreatment composition also
comprises a filler, such as a siliceous filler. Non-limiting
examples of suitable fillers include silica, mica, montmorillonite,
kaolinite, asbestos, talc, diatomaceous earth, vermiculite, natural
and synthetic zeolites, cement, calcium silicate, aluminum
silicate, sodium aluminum silicate, aluminum polysilicate, alumina
silica gels, and glass particles. In addition to the siliceous
fillers other finely divided particulate substantially
water-insoluble fillers may also be employed. Examples of such
optional fillers include carbon black, charcoal, graphite, titanium
oxide, iron oxide, copper oxide, zinc oxide, antimony oxide,
zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide,
barium sulfate, strontium sulfate, calcium carbonate, and magnesium
carbonate.
[0040] As indicated, in certain embodiments, the pretreatment
composition is substantially or, in some cases, completely free of
chromate and/or heavy metal phosphate. As used herein, the term
"substantially free" when used in reference to the absence of
chromate and/or heavy metal phosphate, such as zinc phosphate, in
the pretreatment composition means that these substances are not
present in the composition to such an extent that they cause a
burden on the environment. That is, they are not substantially used
and the formation of sludge, such as zinc phosphate, formed in the
case of using a treating agent based on zinc phosphate, is
eliminated.
[0041] Moreover, in certain embodiments, the pretreatment
composition is substantially free, or, in some cases, completely
free of any organic materials. As used herein, the term
"substantially free", when used with reference to the absence of
organic materials in the composition, means that any organic
materials are present in the composition, if at all, as an
incidental impurity. In other words, the presence of any organic
material does not affect the properties of the composition. As used
herein, the term "completely free" means that there is no organic
material in the composition at all.
[0042] In certain embodiments, the film coverage of the residue of
the pretreatment coating composition generally ranges from 1 to
1000 milligrams per square meter (mg/m.sup.2), such as 10 to 400
mg/m.sup.2. The thickness of the pretreatment coating can vary, but
it is generally very thin, often having a thickness of less than 1
micrometer, in some cases it is from 1 to 500 nanometers, and, in
yet other cases, it is 10 to 300 nanometers.
[0043] In certain other embodiments of the present invention, the
pretreatment composition comprises (a) a rare earth metal; and (b)
a zirconyl compound. These pretreatment compositions are applied
directly to the metal substrate without the prior application of an
electropositive metal (i.e. in a one-step pretreatment
process).
[0044] Often, the pretreatment composition comprises a carrier,
often an aqueous medium, so that the composition is in the form of
a solution or dispersion of the rare earth metal compound and/or
other pretreatment composition components in the carrier. In these
embodiments, the solution or dispersion may be brought into contact
with the substrate by any of a variety of known techniques, such as
dipping or immersion, spraying, intermittent spraying, dipping
followed by spraying, spraying followed by dipping, brushing, or
roll-coating. In certain embodiments, the solution or dispersion
when applied to the metal substrate is at a temperature ranging
from 60 to 150.degree. F. (15 to 65.degree. C.). The contact time
is often from 10 seconds to five minutes, such as 30 seconds to 2
minutes.
[0045] As defined by IUPAC and used herein, rare earth elements or
rare earth metals are a collection of seventeen chemical elements
in the periodic table, specifically the fifteen lanthanoids (the
fifteen elements with atomic numbers 57 through 71, from lanthanum
to lutetium) plus scandium and yttrium. Where applicable, the metal
themselves may be used. In certain embodiments, a rare earth metal
compound is used. As used herein, the term "rare earth metal
compound" refers to compounds that include at least one element
that is a rare earth element as defined above.
[0046] In certain embodiments, the rare earth metal compound used
in the pretreatment composition is a compound of yttrium, cerium,
praseodymium, or a mixture thereof. Exemplary compounds that may be
used include praseodymium chloride, praseodymium nitrate,
praseodymium sulfate, cerium chloride, cerium nitrate, cerium
sulfate, yttrium chloride, yttrium nitrate, yttrium sulfate.
[0047] In certain embodiments, the rare earth metal compound is
present in the pretreatment composition in an amount of at least 10
ppm metal, such as at least 100 ppm metal, or, in some cases, at
least 150 ppm metal. In certain embodiments, the rare earth metal
compound is present in the pretreatment composition in an amount of
no more than 5000 ppm metal, such as no more than 300 ppm metal,
or, in some cases, no more than 250 ppm metal. The amount of rare
earth metal in the pretreatment composition can range between any
of the recited values inclusive of the recited values.
[0048] As noted above, the pretreatment composition also comprises
a zirconyl compound. A zirconyl compound, as defined herein, refers
to a zirconium compound with an oxide or a hydroxide group on a
zirconium atom.
[0049] In certain embodiments, the zirconyl compound in the
pretreatment composition is zirconyl nitrate (ZrO(NO.sub.3).sub.2),
zirconyl acetate, zirconyl carbonate, zirconyl sulfate, or a
mixture thereof.
[0050] In certain embodiments, the ratio of zirconium (from the
zirconyl compound or compounds) to rare earth metal (from the rare
earth metal or rare earth metal compound) is between 200/1 and 1/1.
In other embodiments, the ratio is between 100/1 and 2/1. In
certain embodiments, the ratio is 20/1.
[0051] In certain embodiments, the pretreatment composition also
includes a group IIIB, group IVB, and/or group VB metal. As used
herein, the term "group IIIB, group IVB, and/or group VB metal"
refers to an element that is in group IIIB or group IVB or group VB
of the CAS Periodic Table of Elements as is shown, for example, in
the Handbook of Chemistry and Physics, 63.sup.rd edition (1983).
Where applicable, the metal themselves may be used. In certain
embodiments, a group IIIB, group IV and/or a group VB metal
compound is used. As used herein, the term "a group IIIB, group IV
and/or a group VB metal compound" refers to compounds that include
at least one element that is in the group IIIB or group IVB or
group VB of the CAS Periodic Table of Elements.
[0052] In certain embodiments, the group IIIB or group IVB or group
VB metal compound used in the pretreatment composition is a
compound of zirconium, titanium, hafnium, yttrium, cerium,
praseodymium, or a mixture thereof. Suitable compounds of zirconium
include, but are not limited to, hexafluorozirconic acid, alkali
metal and ammonium salts thereof, ammonium zirconium carbonate,
zirconyl nitrate, zirconium carboxylates and zirconium hydroxy
carboxylates, such as hydrofluorozirconic acid, zirconium acetate,
zirconium oxalate, ammonium zirconium glycolate, ammonium zirconium
lactate, ammonium zirconium citrate, and mixtures thereof. Suitable
compounds of titanium include, but are not limited to,
fluorotitanic acid and its salts. A suitable compound of hafnium
includes, but is not limited to, hafnium nitrate. A suitable
compound of yttrium includes, but is not limited to, yttrium
nitrate. A suitable compound of cerium includes, but is not limited
to, cerous nitrate.
[0053] In certain embodiments, the group IIIB or group IVB or group
VB metal compound is present in the pretreatment composition in an
amount of at least 10 ppm metal, such as at least 100 ppm metal,
or, in some cases, at least 150 ppm metal. In certain embodiments,
the group IIIB or group IVB or group VB metal compound is present
in the pretreatment composition in an amount of no more than 5000
ppm metal, such as no more than 300 ppm metal, or, in some cases,
no more than 250 ppm metal. The amount of group IIIB or group IVB
or group VB metal in the pretreatment composition can range between
any combination of the recited values inclusive of the recited
values.
[0054] In certain embodiments, the pretreatment composition also
comprises an electropositive metal. As used herein, the term
"electropositive metal" refers to metals that are more
electropositive than the metal substrate. This means that, for
purposes of the present invention, the term "electropositive metal"
encompasses metals that are less easily oxidized than the metal of
the metal substrate. As will be appreciated by those skilled in the
art, the tendency of a metal to be oxidized is called the oxidation
potential, is expressed in volts, and is measured relative to a
standard hydrogen electrode, which is arbitrarily assigned an
oxidation potential of zero. The oxidation potential for several
elements is set forth in the table below. An element is less easily
oxidized than another element if it has a voltage value, E*, in the
following table, that is greater than the element to which it is
being compared.
TABLE-US-00001 Element Half-cell reaction Voltage, E* Potassium
K.sup.+ + e .fwdarw. K -2.93 Calcium Ca.sup.2+ + 2e .fwdarw. Ca
-2.87 Sodium Na.sup.+ + e .fwdarw. Na -2.71 Magnesium Mg.sup.2+ +
2e .fwdarw. Mg -2.37 Aluminum Al.sup.3+ + 3e .fwdarw. Al -1.66 Zinc
Zn.sup.2+ + 2e .fwdarw. Zn -0.76 Iron Fe.sup.2+ + 2e .fwdarw. Fe
-0.44 Nickel Ni.sup.2+ + 2e .fwdarw. Ni -0.25 Tin Sn.sup.2+ + 2e
.fwdarw. Sn -0.14 Lead Pb.sup.2+ + 2e .fwdarw. Pb -0.13 Hydrogen
2H.sup.+ + 2e .fwdarw. H.sub.2 -0.00 Copper Cu.sup.2+ + 2e .fwdarw.
Cu 0.34 Mercury Hg.sub.2.sup.2+ + 2e .fwdarw. 2Hg 0.79 Silver
Ag.sup.+ + e .fwdarw. Ag 0.80 Gold Au.sup.3+ + 3e .fwdarw. Au
1.50
[0055] Thus, as will be apparent, when the metal substrate
comprises one of the materials listed earlier, such as cold rolled
steel, hot rolled steel, steel coated with zinc metal, zinc
compounds, or zinc alloys, hot-dipped galvanized steel, galvanealed
steel, steel plated with zinc alloy, aluminum alloys, aluminum
plated steel, aluminum alloy plated steel, magnesium and magnesium
alloys, suitable electropositive metals for deposition thereon in
accordance with the present invention include, for example, nickel,
copper, silver, and gold, as well mixtures thereof.
[0056] In certain embodiments, the source of electropositive metal
in the pretreatment composition is a water soluble metal salt. In
certain embodiments of the present invention, the water soluble
metal salt is a water soluble copper compound. Specific examples of
water soluble copper compounds, which are suitable for use in the
present invention include, but are not limited to, copper cyanide,
copper potassium cyanide, copper sulfate, copper nitrate, copper
pyrophosphate, copper thiocyanate, disodium copper
ethylenediaminetetraacetate tetrahydrate, copper bromide, copper
oxide, copper hydroxide, copper chloride, copper fluoride, copper
gluconate, copper citrate, copper lauroyl sarcosinate, copper
formate, copper acetate, copper propionate, copper butyrate, copper
lactate, copper oxalate, copper phytate, copper tartarate, copper
malate, copper succinate, copper malonate, copper maleate, copper
benzoate, copper salicylate, copper aspartate, copper glutamate,
copper fumarate, copper glycerophosphate, sodium copper
chlorophyllin, copper fluorosilicate, copper fluoroborate and
copper iodate, as well as copper salts of carboxylic acids in the
homologous series formic acid to decanoic acid, copper salts of
polybasic acids in the series oxalic acid to suberic acid, and
copper salts of hydroxycarboxylic acids, including glycolic,
lactic, tartaric, malic and citric acids.
[0057] When copper ions supplied from such a water-soluble copper
compound are precipitated as an impurity in the form of copper
sulfate, copper oxide, etc., it may be preferable to add a
complexing agent that suppresses the precipitation of copper ions,
thus stabilizing them as a copper complex in the solution.
[0058] In certain embodiments, the copper compound is added as a
copper complex salt such as K.sub.3Cu(CN).sub.4 or Cu-EDTA, which
can be present stably in the composition on its own, but it is also
possible to form a copper complex that can be present stably in the
composition by combining a complexing agent with a compound that is
difficultly soluble on its own. Examples thereof include a copper
cyanide complex formed by a combination of CuCN and KCN or a
combination of CuSCN and KSCN or KCN, and a Cu-EDTA complex formed
by a combination of CuSO.sub.4 and EDTA.2Na.
[0059] With regard to the complexing agent, a compound that can
form a complex with copper ions can be used; examples thereof
include inorganic compounds, such as cyanide compounds and
thiocyanate compounds, and polycarboxylic acids, and specific
examples thereof include ethylenediaminetetraacetic acid, salts of
ethylenediaminetetraacetic acid, such as dihydrogen disodium
ethylenediaminetetraacetate dihydrate, aminocarboxylic acids, such
as nitrilotriacetic acid and iminodiacetic acid, oxycarboxylic
acids, such as citric acid and tartaric acid, succinic acid, oxalic
acid, ethylenediaminetetramethylenephosphonic acid, and
glycine.
[0060] In certain embodiments, the electropositive metal, such as
copper, is included in the pretreatment compositions in an amount
of at least 1 ppm, such as at least 5 ppm, or in some cases, at
least 10 ppm of total metal (measured as elemental metal). In
certain embodiments, the electropositive metal is included in such
pretreatment compositions in an amount of no more than 500 ppm,
such as no more than 100 ppm, or in some cases, no more than 50 ppm
of total metal (measured as elemental metal). The amount of
electropositive metal in the pretreatment composition can range
between any combination of the recited values inclusive of the
recited values.
[0061] The pretreatment composition may optionally contain other
materials, such as nonionic surfactants and auxiliaries
conventionally used in the art of pretreatment. In an aqueous
medium, water dispersible organic solvents, for example, alcohols
with up to about 8 carbon atoms, such as methanol, isopropanol, and
the like, may be present; or glycol ethers such as the monoalkyl
ethers of ethylene glycol, diethylene glycol, or propylene glycol,
and the like. When present, water dispersible organic solvents are
typically used in amounts up to about ten percent by volume, based
on the total volume of aqueous medium.
[0062] Other optional materials include surfactants that function
as defoamers or substrate wetting agents, such as those materials
and amounts described earlier with respect to the plating
solution.
[0063] In certain embodiments, the pretreatment composition also
comprises a reaction accelerator, such as nitrite ions, nitro-group
containing compounds, hydroxylamine sulfate, persulfate ions,
sulfite ions, hyposulfite ions, peroxides, iron (III) ions, citric
acid iron compounds, bromate ions, perchlorinate ions, chlorate
ions, chlorite ions as well as ascorbic acid, citric acid, tartaric
acid, malonic acid, succinic acid and salts thereof. Specific
examples of suitable materials and their amounts are described in
United States Patent Application Publication No. 2004/0163736 A1 at
[0032] to [0041], the cited portion of which being incorporated
herein by reference.
[0064] In certain embodiments, the pretreatment composition also
comprises a filler, such as a siliceous filler. Non-limiting
examples of suitable fillers include silica, mica, montmorillonite,
kaolinite, asbestos, talc, diatomaceous earth, vermiculite, natural
and synthetic zeolites, cement, calcium silicate, aluminum
silicate, sodium aluminum silicate, aluminum polysilicate, alumina
silica gels, and glass particles. In addition to the siliceous
fillers other finely divided particulate substantially
water-insoluble fillers may also be employed. Examples of such
optional fillers include carbon black, charcoal, graphite, titanium
oxide, iron oxide, copper oxide, zinc oxide, antimony oxide,
zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide,
barium sulfate, strontium sulfate, calcium carbonate, and magnesium
carbonate.
[0065] As indicated, in certain embodiments, the pretreatment
composition is substantially or, in some cases, completely free of
chromate and/or heavy metal phosphate. As used herein, the term
"substantially free" when used in reference to the absence of
chromate and/or heavy metal phosphate, such as zinc phosphate, in
the pretreatment composition means that these substances are not
present in the composition to such an extent that they cause a
burden on the environment. That is, they are not substantially used
and the formation of sludge, such as zinc phosphate, formed in the
case of using a treating agent based on zinc phosphate, is
eliminated.
[0066] Moreover, in certain embodiments, the pretreatment
composition is substantially free, or, in some cases, completely
free of any organic materials. As used herein, the term
"substantially free", when used with reference to the absence of
organic materials in the composition, means that any organic
materials are present in the composition, if at all, as an
incidental impurity. In other words, the presence of any organic
material does not affect the properties of the composition. As used
herein, the term "completely free" means that there is no organic
material in the composition at all.
[0067] In certain embodiments, the film coverage of the residue of
the pretreatment coating composition generally ranges from 1 to
1000 milligrams per square meter (mg/m.sup.2), such as 10 to 400
mg/m.sup.2. The thickness of the pretreatment coating can vary, but
it is generally very thin, often having a thickness of less than 1
micrometer, in some cases it is from 1 to 500 nanometers, and, in
yet other cases, it is 10 to 300 nanometers.
[0068] Following contact with the pretreatment solution according
to any of the above embodiments, the substrate may be rinsed with
water and dried.
Additional Coating Composition or Compositions after
Pretreatment
[0069] In certain embodiments of the methods of the present
invention, after the substrate is contacted with the acid and
optional alkaline cleaner and optionally with a pretreatment
composition, it is then contacted with a coating composition
comprising a film-forming resin. Any suitable technique may be used
to contact the substrate with such a coating composition,
including, for example, brushing, dipping, flow coating, spraying
and the like. In certain embodiments, however, as described in more
detail below, such contacting comprises an electrocoating step
wherein an electrodepositable composition is deposited onto the
metal substrate by electrodeposition.
[0070] As used herein, the term "film-forming resin" refers to
resins that can form a self-supporting continuous film on at least
a horizontal surface of a substrate upon removal of any diluents or
carriers present in the composition or upon curing at ambient or
elevated temperature. Conventional film-forming resins that may be
used include, without limitation, those typically used in
automotive OEM coating compositions, automotive refinish coating
compositions, industrial coating compositions, architectural
coating compositions, coil coating compositions, and aerospace
coating compositions, among others.
[0071] In certain embodiments, the coating composition comprises a
thermosetting film-forming resin. As used herein, the term
"thermosetting" refers to resins that "set" irreversibly upon
curing or crosslinking, wherein the polymer chains of the polymeric
components are joined together by covalent bonds. This property is
usually associated with a cross-linking reaction of the composition
constituents often induced, for example, by heat or radiation.
Curing or crosslinking reactions also may be carried out under
ambient conditions. Once cured or crosslinked, a thermosetting
resin will not melt upon the application of heat and is insoluble
in solvents. In other embodiments, the coating composition
comprises a thermoplastic film-forming resin. As used herein, the
term "thermoplastic" refers to resins that comprise polymeric
components that are not joined by covalent bonds and thereby can
undergo liquid flow upon heating and are soluble in solvents.
[0072] As previously indicated, in certain embodiments, the
substrate is contacted with a coating composition comprising a
film-forming resin by an electrocoating step wherein an
electrodepositable composition is deposited onto the metal
substrate by electrodeposition. In the process of
electrodeposition, the metal substrate being treated, serving as an
electrode, and an electrically conductive counter electrode are
placed in contact with an ionic, electrodepositable composition.
Upon passage of an electric current between the electrode and
counter electrode while they are in contact with the
electrodepositable composition, an adherent film of the
electrodepositable composition will deposit in a substantially
continuous manner on the metal substrate.
[0073] Electrodeposition is usually carried out at a constant
voltage in the range of from 1 volt to several thousand volts,
typically between 50 and 500 volts. Current density is usually
between 1.0 ampere and 15 amperes per square foot (10.8 to 161.5
amperes per square meter) and tends to decrease quickly during the
electrodeposition process, indicating formation of a continuous
self-insulating film.
[0074] The electrodepositable composition utilized in certain
embodiments of the present invention often comprises a resinous
phase dispersed in an aqueous medium wherein the resinous phase
comprises: (a) an active hydrogen group-containing ionic
electrodepositable resin, and (b) a curing agent having functional
groups reactive with the active hydrogen groups of (a).
[0075] In certain embodiments, the electrodepositable compositions
utilized in certain embodiments of the present invention contain,
as a main film-forming polymer, an active hydrogen-containing
ionic, often cationic, electrodepositable resin. A wide variety of
electrodepositable film-forming resins are known and can be used in
the present invention so long as the polymers are "water
dispersible," i.e., adapted to be solubilized, dispersed or
emulsified in water. The water dispersible polymer is ionic in
nature, that is, the polymer will contain anionic functional groups
to impart a negative charge or, as is often preferred, cationic
functional groups to impart a positive charge.
[0076] Examples of film-forming resins suitable for use in anionic
electrodepositable compositions are base-solubilized, carboxylic
acid containing polymers, such as the reaction product or adduct of
a drying oil or semi-drying fatty acid ester with a dicarboxylic
acid or anhydride; and the reaction product of a fatty acid ester,
unsaturated acid or anhydride and any additional unsaturated
modifying materials which are further reacted with polyol. Also
suitable are the at least partially neutralized interpolymers of
hydroxy-alkyl esters of unsaturated carboxylic acids, unsaturated
carboxylic acid and at least one other ethylenically unsaturated
monomer. Still another suitable electrodepositable film-forming
resin comprises an alkyd-aminoplast vehicle, i.e., a vehicle
containing an alkyd resin and an amine-aldehyde resin. Yet another
anionic electrodepositable resin composition comprises mixed esters
of a resinous polyol, such as is described in U.S. Pat. No.
3,749,657 at col. 9, lines 1 to 75 and col. 10, lines 1 to 13, the
cited portion of which being incorporated herein by reference.
Other acid functional polymers can also be used, such as
phosphatized polyepoxide or phosphatized acrylic polymers as are
known to those skilled in the art.
[0077] As aforementioned, it is often desirable that the active
hydrogen-containing ionic electrodepositable resin (a) is cationic
and capable of deposition on a cathode. Examples of such cationic
film-forming resins include amine salt group-containing resins,
such as the acid-solubilized reaction products of polyepoxides and
primary or secondary amines, such as those described in U.S. Pat.
Nos. 3,663,389; 3,984,299; 3,947,338; and 3,947,339. Often, these
amine salt group-containing resins are used in combination with a
blocked isocyanate curing agent. The isocyanate can be fully
blocked, as described in U.S. Pat. No. 3,984,299, or the isocyanate
can be partially blocked and reacted with the resin backbone, such
as is described in U.S. Pat. No. 3,947,338. Also, one-component
compositions as described in U.S. Pat. No. 4,134,866 and DE-OS No.
2,707,405 can be used as the film-forming resin. Besides the
epoxy-amine reaction products, film-forming resins can also be
selected from cationic acrylic resins, such as those described in
U.S. Pat. Nos. 3,455,806 and 3,928,157.
[0078] Besides amine salt group-containing resins, quaternary
ammonium salt group-containing resins can also be employed, such as
those formed from reacting an organic polyepoxide with a tertiary
amine salt as described in U.S. Pat. Nos. 3,962,165; 3,975,346; and
4,001,101. Examples of other cationic resins are ternary sulfonium
salt group-containing resins and quaternary phosphonium salt-group
containing resins, such as those described in U.S. Pat. Nos.
3,793,278 and 3,984,922, respectively. Also, film-forming resins
which cure via transesterification, such as described in European
Application No. 12463 can be used. Further, cationic compositions
prepared from Mannich bases, such as described in U.S. Pat. No.
4,134,932, can be used.
[0079] In certain embodiments, the resins present in the
electrodepositable composition are positively charged resins which
contain primary and/or secondary amine groups, such as described in
U.S. Pat. Nos. 3,663,389; 3,947,339; and 4,116,900. In U.S. Pat.
No. 3,947,339, a polyketimine derivative of a polyamine, such as
diethylenetriamine or triethylenetetraamine, is reacted with a
polyepoxide. When the reaction product is neutralized with acid and
dispersed in water, free primary amine groups are generated. Also,
equivalent products are formed when polyepoxide is reacted with
excess polyamines, such as diethylenetriamine and
triethylenetetraamine, and the excess polyamine vacuum stripped
from the reaction mixture, as described in U.S. Pat. Nos. 3,663,389
and 4,116,900.
[0080] In certain embodiments, the active hydrogen-containing ionic
electrodepositable resin is present in the electrodepositable
composition in an amount of 1 to 60 percent by weight, such as 5 to
25 percent by weight, based on total weight of the
electrodeposition bath.
[0081] As indicated, the resinous phase of the electrodepositable
composition often further comprises a curing agent adapted to react
with the active hydrogen groups of the ionic electrodepositable
resin. For example, both blocked organic polyisocyanate and
aminoplast curing agents are suitable for use in the present
invention, although blocked isocyanates are often preferred for
cathodic electrodeposition.
[0082] Aminoplast resins, which are often the preferred curing
agent for anionic electrodeposition, are the condensation products
of amines or amides with aldehydes. Examples of suitable amine or
amides are melamine, benzoguanamine, urea and similar compounds.
Generally, the aldehyde employed is formaldehyde, although products
can be made from other aldehydes, such as acetaldehyde and
furfural. The condensation products contain methylol groups or
similar alkylol groups depending on the particular aldehyde
employed. Often, these methylol groups are etherified by reaction
with an alcohol, such as a monohydric alcohol containing from 1 to
4 carbon atoms, such as methanol, ethanol, isopropanol, and
n-butanol. Aminoplast resins are commercially available from
American Cyanamid Co. under the trademark CYMEL and from Monsanto
Chemical Co. under the trademark RESIMENE.
[0083] The aminoplast curing agents are often utilized in
conjunction with the active hydrogen containing anionic
electrodepositable resin in amounts ranging from 5 percent to 60
percent by weight, such as from 20 percent to 40 percent by weight,
the percentages based on the total weight of the resin solids in
the electrodepositable composition.
[0084] As indicated, blocked organic polyisocyanates are often used
as the curing agent in cathodic electrodeposition compositions. The
polyisocyanates can be fully blocked as described in U.S. Pat. No.
3,984,299 at col. 1, lines 1 to 68, col. 2, and col. 3, lines 1 to
15, or partially blocked and reacted with the polymer backbone as
described in U.S. Pat. No. 3,947,338 at col. 2, lines 65 to 68,
col. 3, and col. 4 lines 1 to 30, the cited portions of which being
incorporated herein by reference. By "blocked" is meant that the
isocyanate groups have been reacted with a compound so that the
resultant blocked isocyanate group is stable to active hydrogens at
ambient temperature but reactive with active hydrogens in the film
forming polymer at elevated temperatures usually between 90.degree.
C. and 200.degree. C.
[0085] Suitable polyisocyanates include aromatic and aliphatic
polyisocyanates, including cycloaliphatic polyisocyanates and
representative examples include diphenylmethane-4,4'-diisocyanate
(MDI), 2,4- or 2,6-toluene diisocyanate (TDI), including mixtures
thereof, p-phenylene diisocyanate, tetramethylene and hexamethylene
diisocyanates, dicyclohexylmethane-4,4'-diisocyanate, isophorone
diisocyanate, mixtures of phenylmethane-4,4'-diisocyanate and
polymethylene polyphenylisocyanate. Higher polyisocyanates, such as
triisocyanates can be used. An example would include
triphenylmethane-4,4',4''-triisocyanate. Isocyanate ( )-prepolymers
with polyols such as neopentyl glycol and trimethylolpropane and
with polymeric polyols such as polycaprolactone diols and triols
(NCO/OH equivalent ratio greater than 1) can also be used.
[0086] The polyisocyanate curing agents are typically utilized in
conjunction with the active hydrogen containing cationic
electrodepositable resin in amounts ranging from 5 percent to 60
percent by weight, such as from 20 percent to 50 percent by weight,
the percentages based on the total weight of the resin solids of
the electrodepositable composition.
[0087] In certain embodiments, the coating composition comprising a
film-forming resin also comprises yttrium. In certain embodiments,
yttrium is present in such compositions in an amount from 10 to
10,000 ppm, such as not more than 5,000 ppm, and, in some cases,
not more than 1,000 ppm, of total yttrium (measured as elemental
yttrium).
[0088] Both soluble and insoluble yttrium compounds may serve as
the source of yttrium. Examples of yttrium sources suitable for use
in lead-free electrodepositable coating compositions are soluble
organic and inorganic yttrium salts such as yttrium acetate,
yttrium chloride, yttrium formate, yttrium carbonate, yttrium
sulfamate, yttrium lactate and yttrium nitrate. When the yttrium is
to be added to an electrocoat bath as an aqueous solution, yttrium
nitrate, a readily available yttrium compound, is a preferred
yttrium source. Other yttrium compounds suitable for use in
electrodepositable compositions are organic and inorganic yttrium
compounds such as yttrium oxide, yttrium bromide, yttrium
hydroxide, yttrium molybdate, yttrium sulfate, yttrium silicate,
and yttrium oxalate. Organoyttrium complexes and yttrium metal can
also be used. When the yttrium is to be incorporated into an
electrocoat bath as a component in the pigment paste, yttrium oxide
is often the preferred source of yttrium.
[0089] The electrodepositable compositions described herein are in
the form of an aqueous dispersion. The term "dispersion" is
believed to be a two-phase transparent, translucent or opaque
resinous system in which the resin is in the dispersed phase and
the water is in the continuous phase. The average particle size of
the resinous phase is generally less than 1.0 and usually less than
0.5 microns, often less than 0.15 micron.
[0090] The concentration of the resinous phase in the aqueous
medium is often at least 1 percent by weight, such as from 2 to 60
percent by weight, based on total weight of the aqueous dispersion.
When such compositions are in the form of resin concentrates, they
generally have a resin solids content of 20 to 60 percent by weight
based on weight of the aqueous dispersion.
[0091] The electrodepositable compositions described herein are
often supplied as two components: (1) a clear resin feed, which
includes generally the active hydrogen-containing ionic
electrodepositable resin, i.e., the main film-forming polymer, the
curing agent, and any additional water-dispersible, non-pigmented
components; and (2) a pigment paste, which generally includes one
or more colorants (described below), a water-dispersible grind
resin which can be the same or different from the main-film forming
polymer, and, optionally, additives such as wetting or dispersing
aids. Electrodeposition bath components (1) and (2) are dispersed
in an aqueous medium which comprises water and, usually, coalescing
solvents.
[0092] As aforementioned, besides water, the aqueous medium may
contain a coalescing solvent. Useful coalescing solvents are often
hydrocarbons, alcohols, esters, ethers and ketones. The preferred
coalescing solvents are often alcohols, polyols and ketones.
Specific coalescing solvents include isopropanol, butanol,
2-ethylhexanol, isophorone, 2-methoxypentanone, ethylene and
propylene glycol and the monoethyl monobutyl and monohexyl ethers
of ethylene glycol. The amount of coalescing solvent is generally
between 0.01 and 25 percent, such as from 0.05 to 5 percent by
weight based on total weight of the aqueous medium.
[0093] In addition, a colorant and, if desired, various additives
such as surfactants, wetting agents or catalyst can be included in
the coating composition comprising a film-forming resin. As used
herein, the term "colorant" means any substance that imparts color
and/or other opacity and/or other visual effect to the composition.
The colorant can be added to the composition in any suitable form,
such as discrete particles, dispersions, solutions and/or flakes. A
single colorant or a mixture of two or more colorants can be
used.
[0094] Example colorants include pigments, dyes and tints, such as
those used in the paint industry and/or listed in the Dry Color
Manufacturers Association (DCMA), as well as special effect
compositions. A colorant may include, for example, a finely divided
solid powder that is insoluble but wettable under the conditions of
use. A colorant can be organic or inorganic and can be agglomerated
or non-agglomerated. Colorants can be incorporated by use of a
grind vehicle, such as an acrylic grind vehicle, the use of which
will be familiar to one skilled in the art.
[0095] Example pigments and/or pigment compositions include, but
are not limited to, carbazole dioxazine crude pigment, azo,
monoazo, disazo, naphthol AS, salt type (lakes), benzimidazolone,
condensation, metal complex, isoindolinone, isoindoline and
polycyclic phthalocyanine, quinacridone, perylene, perinone,
diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,
anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone,
dioxazine, triarylcarbonium, quinophthalone pigments, diketo
pyrrolo pyrrole red ("DPPBO red"), titanium dioxide, carbon black
and mixtures thereof. The terms "pigment" and "colored filler" can
be used interchangeably.
[0096] Example dyes include, but are not limited to, those that are
solvent and/or aqueous based such as phthalo green or blue, iron
oxide, bismuth vanadate, anthraquinone, perylene, aluminum and
quinacridone.
[0097] Example tints include, but are not limited to, pigments
dispersed in water-based or water miscible carriers such as
AQUA-CHEM 896 commercially available from Degussa, Inc., CHARISMA
COLORANTS and MAXITONER INDUSTRIAL COLORANTS commercially available
from Accurate Dispersions division of Eastman Chemical, Inc.
[0098] As noted above, the colorant can be in the form of a
dispersion including, but not limited to, a nanoparticle
dispersion. Nanoparticle dispersions can include one or more highly
dispersed nanoparticle colorants and/or colorant particles that
produce a desired visible color and/or opacity and/or visual
effect. Nanoparticle dispersions can include colorants such as
pigments or dyes having a particle size of less than 150 nm, such
as less than 70 nm, or less than 30 nm. Nanoparticles can be
produced by milling stock organic or inorganic pigments with
grinding media having a particle size of less than 0.5 min. Example
nanoparticle dispersions and methods for making them are identified
in U.S. Pat. No. 6,875,800 B2, which is incorporated herein by
reference. Nanoparticle dispersions can also be produced by
crystallization, precipitation, gas phase condensation, and
chemical attrition (i.e., partial dissolution). In order to
minimize re-agglomeration of nanoparticles within the coating, a
dispersion of resin-coated nanoparticles can be used. As used
herein, a "dispersion of resin-coated nanoparticles" refers to a
continuous phase in which is dispersed discreet "composite
microparticles" that comprise a nanoparticle and a resin coating on
the nanoparticle. Example dispersions of resin-coated nanoparticles
and methods for making them are identified in United States Patent
Application Publication 2005-0287348 A1, filed Jun. 24, 2004, U.S.
Provisional Application No. 60/482,167 filed Jun. 24, 2003, and
U.S. patent application Ser. No. 11/337,062, filed Jan. 20, 2006,
which is also incorporated herein by reference.
[0099] Example special effect compositions that may be used include
pigments and/or compositions that produce one or more appearance
effects such as reflectance, pearlescence, metallic sheen,
phosphorescence, fluorescence, photochromism, photosensitivity,
thermochromism, goniochromism and/or color-change. Additional
special effect compositions can provide other perceptible
properties, such as opacity or texture. In certain embodiments,
special effect compositions can produce a color shift, such that
the color of the coating changes when the coating is viewed at
different angles. Example color effect compositions are identified
in U.S. Pat. No. 6,894,086, incorporated herein by reference.
Additional color effect compositions can include transparent coated
mica and/or synthetic mica, coated silica, coated alumina, a
transparent liquid crystal pigment, a liquid crystal coating,
and/or any composition wherein interference results from a
refractive index differential within the material and not because
of the refractive index differential between the surface of the
material and the air.
[0100] In certain embodiments, a photosensitive composition and/or
photochromic composition, which reversibly alters its color when
exposed to one or more light sources, can be used. Photochromic
and/or photosensitive compositions can be activated by exposure to
radiation of a specified wavelength. When the composition becomes
excited, the molecular structure is changed and the altered
structure exhibits a new color that is different from the original
color of the composition. When the exposure to radiation is
removed, the photochromic and/or photosensitive composition can
return to a state of rest, in which the original color of the
composition returns. In certain embodiments, the photochromic
and/or photosensitive composition can be colorless in a non-excited
state and exhibit a color in an excited state. Full color-change
can appear within milliseconds to several minutes, such as from 20
seconds to 60 seconds. Example photochromic and/or photosensitive
compositions include photochromic dyes.
[0101] In certain embodiments, the photosensitive composition
and/or photochromic composition can be associated with and/or at
least partially bound to, such as by covalent bonding, a polymer
and/or polymeric materials of a polymerizable component. In
contrast to some coatings in which the photosensitive composition
may migrate out of the coating and crystallize into the substrate,
the photosensitive composition and/or photochromic composition
associated with and/or at least partially bound to a polymer and/or
polymerizable component in accordance with certain embodiments of
the present invention, have minimal migration out of the coating.
Example photosensitive compositions and/or photochromic
compositions and methods for making them are identified in U.S.
application Ser. No. 10/892,919 filed Jul. 16, 2004, incorporated
herein by reference.
[0102] In general, the colorant can be present in the coating
composition in any amount sufficient to impart the desired visual
and/or color effect. The colorant may comprise from 1 to 65 weight
percent, such as from 3 to 40 weight percent or 5 to 35 weight
percent, with weight percent based on the total weight of the
composition.
[0103] After deposition, the coating is often heated to cure the
deposited composition. The heating or curing operation is often
carried out at a temperature in the range of from 120 to
250.degree. C., such as from 120 to 190.degree. C., for a period of
time ranging from 10 to 60 minutes. In certain embodiments, the
thickness of the resultant film is from 10 to 50 microns.
Electrodepositable Coating Composition without Pretreatment
[0104] In certain embodiments of the methods of the present
invention, after the substrate is contacted with the acid and
without the subsequent contact with a pretreatment composition, it
may then be contacted with a electrodepositable coating composition
comprising (i) a film-forming compound and (ii) a source of
yttrium.
[0105] As defined herein, the term "without the subsequent contact
with a pretreatment composition" means that the substrate has not
been contacted with a composition that, upon contact with the
substrate, reacts with and chemically alters the substrate surface
and binds to it to form a protective layer. This specifically
includes any of the pretreatment compositions comprising a group
IIIB and/or group IVB metal as described above, and further
includes other known pretreatment compositions such as, for
example, zinc or iron phosphate-type conversion or pretreatment
coatings.
[0106] In certain embodiments, the electrodepositable coating
composition may be formed in accordance with U.S. patent
application Ser. No. 12/693,626, which is herein incorporated by
reference, and may also include (iii) a silane that does not
contain an ethylenically unsaturated double bond. In certain
embodiments, the coating composition may be formed in accordance
with U.S. patent application Ser. No. 12/693,626 and may further
also include (iii) an aminosilane, which could or could not contain
an ethylenically unsaturated double bond.
[0107] In some embodiments, when the film-forming polymer comprises
a reactive functional group, the coating composition further
comprises (iv) a curing agent that is reactive with a reactive
functional group of the film-forming polymer.
[0108] A wide variety of film-forming polymers, which are known in
the art, can be used as component (i) so long as the polymers are
"water dispersible." As used herein, "water dispersible" means that
a material is adapted to be solubilized, dispersed, and/or
emulsified in water. The film-forming polymers used in the present
invention are ionic in nature. Accordingly, in some embodiments,
the film-forming polymer is cationic. In other words, the
film-forming polymer comprises cationic salt groups, generally
prepared by neutralizing a functional group on the film-forming
polymer with an acid, which enables the film-forming polymer to be
electrodeposited onto a cathode.
[0109] Examples of film-forming polymers suitable for use in
cationic electrocoating coating compositions include, without
limitation, cationic polymers derived from a polyepoxide, an
acrylic, a polyurethane, and/or polyester. In certain embodiments,
the film-forming polymer comprises reactive functional groups. As
used herein, the phrase "reactive functional group" means hydroxyl,
carboxyl, carbamate, epoxy, isocyanate, aceto acetate, amine-salt,
mercaptan, or combinations thereof. It should be noted that in some
embodiments, the film-forming polymer is a copolymer of the
polymers listed in the preceding sentence. In some embodiments, the
cationic polymer can be derived by reacting a polyepoxide
containing polymer with a cationic salt group former. As used
herein, "cationic salt group former" means a material that is
reactive with epoxy groups and which can be acidified before,
during, or after reaction with the epoxy groups to form cationic
salt groups. Suitable materials that can be used as the cationic
salt group former include amines such as primary or secondary
amines, which can be acidified after reaction with the epoxy groups
to form amine salt groups, or tertiary amines, which can be
acidified prior to reaction with the epoxy groups and which after
reaction with the epoxy groups form quaternary ammonium salt
groups. Examples of other cationic salt group formers are sulfides
which can be mixed with acid prior to reaction with the epoxy
groups and form ternary sulfonium salt groups upon subsequent
reaction with the epoxy groups.
[0110] In certain embodiments, the film-forming polymer (i) that is
used in the present invention comprises the reaction product of an
epoxy functional compound (e.g., EPON 880) and a phenolic hydroxyl
group-containing material such as bisphenol A, which is a
polyhydric phenol. In some embodiments, the film-forming polymer
(i) described in the preceding sentence can be reacted with an
amine, such as aminopropyldiethanolamine (APDEA) and
dimethylaminopropylamine (DMAPA), in order to make the film-forming
polymer water dispersible. In certain embodiments, ketimine can be
reacted with the backbone of the film-forming polymer thereby
forming ketimine arms that extend pendant to the backbone. When the
polymer is dispersed in a water/acid mixture, the ketimine arms
will hydrolyze and form primary amines. Accordingly, in some
embodiments, the electrodepositable coating compositions that are
disclosed in U.S. Pat. Nos. 5,633,297, 5,820,987, and/or 5,936,012
can be used with the present invention.
[0111] Various corrosion inhibitors may be used as component (a) in
the present invention. Suitable corrosion inhibitors include,
without limitation, rare earth metals, bismuth, copper, zinc,
silver, zirconium, or combinations thereof. In certain embodiments,
an yttrium compound or a cerium compound, or a mixture of an
yttrium and cerium compound, may be used as the corrosion
inhibitor. Yttrium and cerium compounds, as defined herein, include
their respective salts and hereinafter may be referred to simply as
yttrium compounds or cerium compounds. They may also be included in
the list of potential compounds comprising a source or yttrium or a
source of cerium.
[0112] Various yttrium compounds may be used as component (ii) in
the present invention. For example, the yttrium compounds may
include, without limitation, yttrium formate, yttrium acetate,
yttrium lactate, yttrium sulfamate, yttrium methane sulfonate,
yttrium nitrate, or combinations thereof. In some embodiments,
yttrium comprises .ltoreq.5 weight % of the total resin solids of
the electrodepositable coating composition. In other embodiments,
yttrium comprises .gtoreq.0.15 weight % of the total resin solids
of the electrodepositable coating composition. In certain
embodiments, the amount of yttrium can range between any
combination of values, which were recited in the preceding
sentences, inclusive of the recited values. For example, in certain
embodiments, the amount of yttrium can range from 0.20 weight % to
2 weight % of the total resin solids of the electrodepositable
coating composition.
[0113] Various cerium compounds may be used as component (ii) in
the present invention. For example, the cerium compounds may
include ammonium cerium nitrate, ammonium cerium sulfate, cerium
acetate, cerium bromide, cerium carbonate, cerium chloride, cerium
fluoride, cerium iodide, cerium nitrate, cerium molybdate, cerium
oxide, cerium oxalate, cerium phosphate, and cerium sulfate. In
some embodiments, cerium comprises .ltoreq.5 weight % of the total
resin solids of the electrodepositable coating composition. In
other embodiments, cerium comprises .gtoreq.0.15 weight % of the
total resin solids of the electrodepositable coating composition.
In certain embodiments, the amount of cerium can range between any
combination of values, which were recited in the preceding
sentences, inclusive of the recited values. For example, in certain
embodiments, the amount of cerium can range from 0.20 weight % to 2
weight % of the total resin solids of the electrodepositable
coating composition.
[0114] Various combinations of yttrium compounds and cerium
compounds, as described in the previous paragraphs, may be used as
component (ii) in the present invention. In some embodiments, the
combination of yttrium and cerium comprises .ltoreq.5 weight % of
the total resin solids of the electrodepositable coating
composition. In other embodiments, the combination of yttrium and
cerium comprises .gtoreq.0.15 weight % of the total resin solids of
the electrodepositable coating composition. In certain embodiments,
the amount of yttrium and cerium can range between any combination
of values, which were recited in the preceding sentences, inclusive
of the recited values. For example, in certain embodiments, the
amount of yttrium and cerium can range from 0.20 weight % to 2
weight % of the total resin solids of the electrodepositable
coating composition.
[0115] If (i) the film-forming polymer comprises reactive
functional groups, such as those described above, then the
electrodepositable coating composition may further comprise (iv) a
crosslinking agent ("curing agent") that is reactive with the
reactive functional groups of the polymer. Suitable crosslinking
agents include, without limitation, aminoplasts, polyisocyanates
(including blocked isocyanates), polyepoxides,
beta-hydroxyalkylamides, polyacids, anhydrides, organometallic
acid-functional materials, polyamines, polyamides, cyclic
carbonates, siloxanes, or combinations thereof. In some
embodiments, the curing agent can comprise from 30 weight % to 40
weight % of the total resin solids of the coating composition.
[0116] In certain embodiments, the electrodepositable coating
composition may further comprise (v) a curing catalyst, which may
be used to catalyze the reaction between the crosslinking agent and
the reactive functional groups of the film-forming polymer.
Suitable curing catalysts that may be used as component (v)
include, without limitation, organotin compounds (e.g., dibutyltin
oxide, dioctyltin oxide) and salts thereof (e.g., dibutyltin
diacetate); other metal oxides (e.g., oxides of cerium, zirconium
and/or bismuth) and salts thereof (e.g., bismuth sulfamate and/or
bismuth lactate), bicyclic guanidine (as disclosed in U.S. patent
application Ser. No. 11/835,600), or combinations thereof.
[0117] The electrodepositable coating composition disclosed herein
is typically supplied as two components: (1) a main vehicle ("clear
resin feed") and (2) a grind vehicle ("pigment paste"). In general,
(1) the main vehicle comprises (a) a film-forming polymer ("an
active hydrogen-containing ionic salt group-containing resin"), (b)
a crosslinking agent, and (c) any additional water-dispersible,
non-pigmented components (e.g., catalysts, hindered amine light
stabilizers). In general, (2) the grind vehicle comprises (d) one
or more pigments (e.g., titanium dioxide, carbon black), (e) a
water-dispersible grind resin, which can be the same or different
from the film-forming polymer, and, optionally, (f) additives such
as catalysts, antioxidants, biocides, defoamers, surfactants,
wetting agents, dispersing aids, clays, hindered amine light
stabilizers, UV light absorbers and stabilizers, or combinations
thereof. An electrodeposition bath, which contains the
electrodepositable coating composition of the present invention,
can be prepared by dispersing components (1) and (2) in an aqueous
medium which comprises water and, usually, coalescing solvents. The
(ii) yttrium and/or the (iii) silane, which are used in the
electrodepositable coating composition of the present invention,
may be incorporated into the main vehicle, the grind vehicle, or
post-added to a bath that is prepared with components (1) and (2).
Alternatively, components (1) and (2) may also be provided as a
single component.
[0118] The electrodepositable coating composition described herein
may be applied alone or as part of a coating system that can be
deposited onto a number of different substrates. The coating system
typically comprises a number of coating layers. A coating layer is
typically formed when a coating composition that is deposited onto
the substrate is substantially cured by methods known in the art
(e.g., by thermal heating).
[0119] After the electrodepositable coating composition is cured, a
primer-surfacer coating composition is applied onto at least a
portion of the electrodepositable coating composition. The
primer-surfacer coating composition is typically applied to the
electrodepositable coating layer and cured prior to a subsequent
coating composition being applied over the primer-surfacer coating
composition.
[0120] The primer-surfacer layer that results from the
primer-surfacer coating composition serves to enhance chip
resistance of the coating system as well as aid in the appearance
of subsequently applied layers (e.g., color imparting coating
composition and/or substantially clear coating composition). As
used herein, "primer-surfacer" refers to a primer composition for
use under a subsequently applied coating composition, and includes
such materials as thermoplastic and/or crosslinking (e.g.,
thermosetting) film-forming resins generally known in the art of
organic coating compositions. Suitable primers and primer-surfacer
coating compositions include spray applied primers, as are known to
those skilled in the art. Examples of suitable primers include
several available from PPG Industries, Inc., Pittsburgh, Pa., as
DPX-1791, DPX-1804, DSPX-1537, GPXH-5379, OPP-2645, PCV-70118, and
1177-225A. Another suitable primer-surfacer coating composition
that can be utilized in the present invention is the
primer-surfacer described in U.S. patent application Ser. No.
11/773,482, which is incorporated in its entirety herein by
reference.
[0121] It should be noted that in some embodiments, the
primer-surfacer coating composition is not used in the coating
system. Therefore, a color imparting basecoat coating composition
can be applied directly onto the cured electrodepositable coating
composition.
[0122] In some embodiments, a color imparting coating composition
(hereinafter, "basecoat") is deposited onto at least a portion of
the primer surfacer coating layer (if present). Any basecoat
coating composition known in the art may be used in the present
invention. It should be noted that these basecoat coating
compositions typically comprise a colorant.
[0123] In certain embodiments, a substantially clear coating
composition (hereinafter, "clearcoat") is deposited onto at least a
portion of the basecoat coating layer. As used herein, a
"substantially clear" coating layer is substantially transparent
and not opaque. In certain embodiments, the substantially clear
coating composition can comprise a colorant but not in an amount
such as to render the clear coating composition opaque (not
substantially transparent) after it has been cured. Any clearcoat
coating composition known in the art may be used in the present
invention. For example, the clearcoat coating composition that is
described in U.S. Pat. Nos. 5,989,642, 6,245,855, 6,387,519, and
7,005,472, which are incorporated in their entirety herein by
reference, can be used in the coating system. In certain
embodiments, the substantially clear coating composition can also
comprise a particle, such as a silica particle, that is dispersed
in the clearcoat coating composition (such as at the surface of the
clearcoat coating composition after curing).
[0124] One or more of the coating compositions described herein can
comprise colorants and/or other optional materials, which are known
in the art of formulated surface coatings. As used herein, the term
"colorant" means any substance that imparts color and/or other
opacity and/or other visual effect to the composition. The colorant
can be added to the coating in any suitable form, such as discrete
particles, dispersions, solutions and/or flakes (e.g., aluminum
flakes). A single colorant or a mixture of two or more colorants
can be used in the coating composition described herein.
[0125] Example colorants include pigments, dyes and tints, such as
those used in the paint industry and/or listed in the Dry Color
Manufacturers Association (DCMA), as well as special effect
compositions. A colorant may include, for example, a finely divided
solid powder that is insoluble but wettable under the conditions of
use. A colorant can be organic or inorganic and can be agglomerated
or non-agglomerated. Colorants can be incorporated into the
coatings by use of a grind vehicle, such as an acrylic grind
vehicle, the use of which will be familiar to one skilled in the
art.
[0126] Example pigments and/or pigment compositions include, but
are not limited to, carbazole dioxazine crude pigment, azo,
monoazo, disazo, naphthol AS, salt type (lakes), benzimidazolone,
condensation, metal complex, isoindolinone, isoindoline and
polycyclic phthalocyanine, quinacridone, perylene, perinone,
diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,
anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone,
dioxazine, triarylcarbonium, quinophthalone pigments, diketo
pyrrolo pyrrole red ("DPPBO red"), titanium dioxide, carbon black
and mixtures thereof. The terms "pigment" and "colored filler" can
be used interchangeably.
[0127] Example dyes include, but are not limited to, those that are
solvent and/or aqueous based such as phthalo green or blue, iron
oxide, bismuth vanadate, anthraquinone, perylene, aluminum and
quinacridone.
[0128] Example tints include, but are not limited to, pigments
dispersed in water-based or water miscible carriers such as
AQUA-CHEM 896 commercially available from Degussa, Inc., CHARISMA
COLORANTS and MAXITONER INDUSTRIAL COLORANTS commercially available
from Accurate Dispersions division of Eastman Chemical, Inc.
[0129] As noted above, the colorant can be in the form of a
dispersion including, but not limited to, a nanoparticle
dispersion. Nanoparticle dispersions can include one or more highly
dispersed nanoparticle colorants and/or colorant particles that
produce a desired visible color and/or opacity and/or visual
effect. Nanoparticle dispersions can include colorants such as
pigments or dyes having a particle size of less than 150 nm, such
as less than 70 nm, or less than 30 nm. Nanoparticles can be
produced by milling stock organic or inorganic pigments with
grinding media having a particle size of less than 0.5 mm. Example
nanoparticle dispersions and methods for making them are identified
in U.S. Pat. No. 6,875,800, which is incorporated herein by
reference. Nanoparticle dispersions can also be produced by
crystallization, precipitation, gas phase condensation, and
chemical attrition (i.e., partial dissolution). In order to
minimize re-agglomeration of nanoparticles within the coating, a
dispersion of resin-coated nanoparticles can be used. As used
herein, a "dispersion of resin-coated nanoparticles" refers to a
continuous phase in which discreet "composite microparticles",
which comprise a nanoparticle and a resin coating on the
nanoparticle, is dispersed. Example dispersions of resin-coated
nanoparticles and methods for making them are identified in U.S.
Patent Publication No. 2005/0287348, filed Jun. 24, 2004, U.S.
Provisional Application No. 60/482,167 filed Jun. 24, 2003, and
U.S. patent application Ser. No. 11/337,062, filed Jan. 20, 2006,
which are also incorporated herein by reference.
[0130] Example special effect compositions that may be used include
pigments and/or compositions that produce one or more appearance
effects such as reflectance, pearlescence, metallic sheen,
phosphorescence, fluorescence, photochromism, photosensitivity,
thermochromism, goniochromism and/or color-change. Additional
special effect compositions can provide other perceptible
properties, such as opacity or texture. In a non-limiting
embodiment, special effect compositions can produce a color shift,
such that the color of the coating changes when the coating is
viewed at different angles. Example color effect compositions are
identified in U.S. Pat. No. 6,894,086, incorporated herein by
reference. Additional color effect compositions can include
transparent coated mica and/or synthetic mica, coated silica,
coated alumina, a transparent liquid crystal pigment, a liquid
crystal coating, and/or any composition wherein interference
results from a refractive index differential within the material
and not because of the refractive index differential between the
surface of the material and the air.
[0131] In certain non-limiting embodiments, a photosensitive
composition and/or photochromic composition, which reversibly
alters its color when exposed to one or more light sources, can be
used in the coating composition described herein. Photochromic
and/or photosensitive compositions can be activated by exposure to
radiation of a specified wavelength. When the composition becomes
excited, the molecular structure is changed and the altered
structure exhibits a new color that is different from the original
color of the composition. When the exposure to radiation is
removed, the photochromic and/or photosensitive composition can
return to a state of rest, in which the original color of the
composition returns. In one non-limiting embodiment, the
photochromic and/or photosensitive composition can be colorless in
a non-excited state and exhibit a color in an excited state. Full
color-change can appear within milliseconds to several minutes,
such as from 20 seconds to 60 seconds. Example photochromic and/or
photosensitive compositions include photochromic dyes.
[0132] In a non-limiting embodiment, the photosensitive composition
and/or photochromic composition can be associated with and/or at
least partially bound to, such as by covalent bonding, a polymer
and/or polymeric materials of a polymerizable component. In
contrast to some coatings in which the photosensitive composition
may migrate out of the coating and crystallize into the substrate,
the photosensitive composition and/or photochromic composition
associated with and/or at least partially bound to a polymer and/or
polymerizable component in accordance with a non-limiting
embodiment of the present invention, have minimal migration out of
the coating. Example photosensitive compositions and/or
photochromic compositions and methods for making them are
identified in U.S. patent application Ser. No. 10/892,919, filed
Jul. 16, 2004.
[0133] In general, the colorant can be present in any amount
sufficient to impart the desired visual and/or color effect. The
colorant may comprise from 1 to 65 weight percent of the present
compositions, such as from 3 to 40 weight percent or 5 to 35 weight
percent, with weight percent based on the total weight of the
compositions.
[0134] The coating compositions can comprise other optional
materials well known in the art of formulated surface coatings,
such as plasticizers, anti-oxidants, hindered amine light
stabilizers, UV light absorbers and stabilizers, surfactants, flow
control agents, thixotropic agents such as bentonite clay,
pigments, fillers, organic cosolvents, catalysts, including
phosphonic acids and other customary auxiliaries.
[0135] In addition to the materials described above, the coating
composition can also comprise an organic solvent. Suitable organic
solvents that can be used in the coating composition include any of
those listed in the preceding paragraphs as well as butyl acetate,
xylene, methyl ethyl ketone, or combinations thereof.
[0136] It will be further appreciated that one or more of the
coating compositions that form the various coating layers described
herein can be either "one component" ("1K"), "two component"
("2K"), or even multi-component compositions. A 1K composition will
be understood as referring to a composition wherein all of the
coating components are maintained in the same container after
manufacture, during storage, etc. A 2K composition or
multi-component composition will be understood as referring to a
composition wherein various components are maintained separately
until just prior to application. A 1K or 2K coating composition can
be applied to a substrate and cured by any conventional means, such
as by heating, forced air, and the like.
[0137] The coating compositions that form the various coating
layers described herein can be deposited or applied onto the
substrate using any technique that is known in the art. For
example, the coating compositions can be applied to the substrate
by any of a variety of methods including, without limitation,
spraying, brushing, dipping, and/or roll coating, among other
methods. When a plurality of coating compositions are applied onto
a substrate, it should be noted that one coating composition may be
applied onto at least a portion of an underlying coating
composition either after the underlying coating composition has
been cured or prior to the underlying coating composition being
cured. If the coating composition is applied onto an underlying
coating composition that has not been cured, both coating
compositions may be cured simultaneously.
[0138] The coating compositions may be cured using any technique
known in the art such as, without limitation, thermal energy,
infrared, ionizing or actinic radiation, or by any combination
thereof. In certain embodiments, the curing operation can be
carried out at temperatures .gtoreq.10.degree. C. In other
embodiments, the curing operation can be carried out at temperature
.ltoreq.246.degree. C. In certain embodiments, the curing operation
can carried out at temperatures ranging between any combination of
values, which were recited in the preceding sentences, inclusive of
the recited values. For example, the curing operation can be
carried out at temperatures ranging from 120.degree. C.-150.degree.
C. It should be noted, however, that lower or higher temperatures
may be used as necessary to activate the curing mechanisms.
[0139] In certain embodiments, one or more of the coating
compositions described herein is a low temperature, moisture
curable coating compositions. As used herein, the term "low
temperature, moisture curable" refers to coating compositions that,
following application to a substrate, are capable of curing in the
presence of ambient air, the air having a relative humidity of 10%
to 100%, such as 25% to 80%, and a temperature in the range of
-10.degree. C. to 120.degree. C., such as 5.degree. C. to
80.degree. C., in some cases 10.degree. C. to 60.degree. C. and, in
yet other cases, 15.degree. C. to 40.degree. C.
[0140] The dry film thickness of the coating layers described
herein can range from 0.1 micron to 500 microns. In other
embodiments, the dry film thickness can be .ltoreq.125 microns,
such as .ltoreq.80 microns. For example, the dry film thickness can
range from 15 microns to 60 microns.
[0141] While specific embodiments of the invention have been
described in detail, it will be appreciated by those skilled in the
art that various modifications and alternatives to those details
could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are
meant to be illustrative only and not limiting as to the scope of
the invention which is to be given the full breadth of the claims
appended and any and all equivalents thereof.
[0142] It will be appreciated by those skilled in the art that
changes could be made to the embodiments described above without
departing from the broad inventive concept thereof. It is
understood, therefore, that this invention is not limited to the
particular embodiments disclosed, but it is intended to cover
modifications which are within the spirit and scope of the
invention, as defined by the appended claims.
EXAMPLES
[0143] Coating compositions, panels, and testing methods used in
these Examples were prepared and described as follows:
[0144] Alkaline Cleaner 1: Chemkleen 2010LP/181ALP, a commercial
alkaline cleaner available from PPG Industries, Inc.
[0145] Alkaline Cleaner 1A: Experimental alkaline cleaner with a
composition similar to Chemkleen 166HP, commercially available from
PPG Industries, Inc.
[0146] Acid Cleaner 2--A citric acid cleaner prepared as follows.
First, 468.4 g of anhydrous citric acid was dissolved in 18,000 g
of water. Next, 103.4 g of a commercial surfactant package,
Chemkleen 171-12, was added to the mixture. Finally, potassium
hydroxide was added to the mixture to adjust the pH of the
resultant mixture to 4.5.
[0147] Pretreatment Composition 1: CHEMFOS 700, immersion applied
tricationic Zn phosphate (a commercial pretreatment product
available from PPG Industries, Inc.).
[0148] Electrodepositable Paint Composition 1: Enviro-prime.RTM.
7000P, a cationic electrocoat commercially available from PPG
Industries, Inc.
[0149] Electrodepositable Paint Composition 2: Yttrium-containing
Electrodeposiable Paint prepared in accordance with Paint 4 in
Table 1 (paragraph [0074]) of U.S. patent application Ser. No.
12/693,626.)
[0150] Phosphated panels were purchased from ACT.
[0151] Test 1: 40 cycles of GM9540P (Cycle B)
[0152] Test 2: 24 hours in a cathodic disbondment test. The test
involves a scribed panel submerged into a sodium sulfate solution
where a current of 10 mA is passed through the panel. After 24
hours, tape is used to remove delaminated paint and the width of
the delaminated area is measured.
Comparative Results
Experiment 1
Comparison of Corrosion Resistance on Cleaned Panels Subsequently
Coated with Electrodepositable Coating Composition 1--Alkaline
Cleaner 1 Vs. Acid Cleaner 2
[0153] Cold-rolled steel panels (ACT Panels) were cleaned using
Cleaner 1 or Cleaner 2, rinsed with deionized water, and dried
using forced hot air. The panels were electrocoated in
Electrodepositable Paint Composition 1 and cured for 25 minutes @
177.degree. C. in an electric oven. The dry film thickness was
0.0005-0.0010 inches. Samples were then scribed vertically and
placed in Test 1. Average scribe creep results are shown in Table 1
below.
TABLE-US-00002 TABLE 1 Cleaner Avg Scribe Creep (mm) #1 - 2' Spray
18.7 #2 - 4' Spray 7.6
Experiment 2
Comparison of Corrosion Resistance on Cleaned Panels Subsequently
Coated with Electrodepostable Coating Composition 2--Alkaline
Cleaner 1A Vs. Acid Cleaner 2
[0154] Cold-rolled steel panels (ACT Panels) were cleaned using
Alkaline Cleaner 1A or Acid Cleaner 2, rinsed with deionized water,
and dried using forced hot air. The panels were electrocoated in
Electrodepositable Paint Composition 2 and cured for 25 minutes @
177.degree. C. in an electric oven. The dry film thickness was
0.0005-0.0010 inches. Samples were then scribed vertically and
placed in Test 1. Average scribe creep results are shown in Table 2
below:
TABLE-US-00003 TABLE 2 Cleaner Avg Scribe Creep (mm) #1A - 2'
Immersion 9.5 #2 - 4' Spray 3.3
Experiment 3
Comparison of Yttrium Deposition on Cleaned Panels--Alkaline
Cleaner 1A Alone Vs. Alkaline Cleaner 1A Followed by Acid Cleaner
2
[0155] Cold-rolled steel panels (ACT Panels) were cleaned using
Alkaline Cleaner 1A alone, or Alkaline Cleaner 1A followed by Acid
Cleaner 2, and rinsed with deionized water. The panels were then
placed in a solution of yttrium sulfamate (800 ppm yttrium)
buffered to a pH of 5.5. 80 mA of current was passed through the
solution for 2 minutes at room temperature. Panels were then rinsed
with deionized water and dried using forced air. After drying, the
amount of yttrium deposited on the panels was measured by
wave-dispersive X-ray fluorescence. The results are shown in Table
3 below:
TABLE-US-00004 TABLE 3 Cleaner #1A Cleaner #2 Wt % Y 2' Spray --
0.82 1' Spray 2' Spray 1.5
Experiment 4
Comparison of Corrosion Resistance on Cleaned Panels Subsequently
Coated with Electrodepositable Coating Composition 2--Cleaner 1A
Vs. Cleaner 1A Followed by Cleaner 2 Vs. Cleaner 2 Followed by
Cleaner 1A--Ecoated Panels (with Corrosion Inhibitor)
[0156] Cold-rolled steel panels (ACT Panels) were cleaned using
Alkaline Cleaner 1A, Alkaline Cleaner 1A followed by Acid Cleaner
2, or Acid Cleaner 2 followed by Alkaline Cleaner 1A, and then
rinsed with deionized water. Panels were then dried using forced
air. After drying, the panels were electrocoated in
Electrodepositable Paint Composition 2 and cured for 25 minutes @
177.degree. C. in an electric oven. The dry film thickness was
0.0005-0.0010 inches.
[0157] Panels with Pretreatment 1 were purchased from ACT and
electrocoated with Electrodepositable Paint Composition 1 for
comparison.
[0158] Samples were then scribed vertically and placed in Test 2.
The results are shown Table 4 below:
TABLE-US-00005 TABLE 4 Scribe Creep Step 1 Step 2 (mm) Cleaner #1A
- 2' Spray -- 5.52 Cleaner #1A - 30 sec Spray Cleaner #2 - 3' Spray
3.03 Cleaner #2 - 3' Spray Cleaner #1A - 30 sec Spray 3.00
Phosphate (Pretreatment #1) 5.34
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