U.S. patent application number 11/087953 was filed with the patent office on 2006-09-28 for pigment dispersant, method of making coating compositions, and coating compositions.
This patent application is currently assigned to BASF Corporation. Invention is credited to Sergio Balatan, Nicholas Caiozzo, Clair J. Certo, Zenon Paul Czornij, Janice E. Echols, Walter H. Ohrbom.
Application Number | 20060217485 11/087953 |
Document ID | / |
Family ID | 36643397 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060217485 |
Kind Code |
A1 |
Ohrbom; Walter H. ; et
al. |
September 28, 2006 |
Pigment dispersant, method of making coating compositions, and
coating compositions
Abstract
A coating composition comprises at least one pigment dispersed
in an acrylic polymer, wherein the acrylic polymer is polymerized
from a mixture of ethylenically unsaturated monomers comprising:
(a) one or more monomers having active hydrogen functionality; (b)
at least about 5% by weight of one or more monomers selected from
the group consisting of monomers having a carboxylic acid group in
which the carbonyl carbon is separated from the closest
ethylenically unsaturated carbon by at least four atoms,
.omega.-methyloxy-polyoxyethylene(meth)acrylates,
.omega.-methyloxy-poly(oxyethylene-co-oxypropylene)(meth)acrylates,
and combinations thereof; (c) optionally hydroxyethylene ethyl urea
(meth)acrylate; and (d) up to about 50 percent by weight of one or
more monomers selected from the group consisting of aromatic
polymerizable monomers, wherein the monomers (b) and (c) combined
are from about 5 to about 45 percent by weight of the mixture of
ethylenically unsaturated monomers.
Inventors: |
Ohrbom; Walter H.; (Hartland
Township, MI) ; Caiozzo; Nicholas; (St.Clair Shores,
MI) ; Balatan; Sergio; (West Bloomfield, MI) ;
Czornij; Zenon Paul; (Brighton, MI) ; Certo; Clair
J.; (Dearborn Heights, MI) ; Echols; Janice E.;
(Detroit, MI) |
Correspondence
Address: |
BASF CORPORATION
1609 BIDDLE AVENUE
WYANDOTTE
MI
48192
US
|
Assignee: |
BASF Corporation
Southfield
MI
|
Family ID: |
36643397 |
Appl. No.: |
11/087953 |
Filed: |
March 23, 2005 |
Current U.S.
Class: |
524/556 |
Current CPC
Class: |
C09D 5/027 20130101 |
Class at
Publication: |
524/556 |
International
Class: |
C08L 31/00 20060101
C08L031/00 |
Claims
1. A coating composition comprising at least one pigment dispersed
in an acrylic polymer, wherein the acrylic polymer is polymerized
from a mixture of ethylenically unsaturated monomers comprising:
(a) one or more monomers having active hydrogen functionality; (b)
at least about 5% by weight of one or more monomers selected from
the group consisting of monomers having a carboxylic acid group in
which the carbonyl carbon is separated from the closest
ethylenically unsaturated carbon by at least four atoms,
.omega.-methyloxy-polyoxyethylene (meth)acrylates,
.omega.-methyloxy-poly(oxyethylene-co-oxypropylene)
(meth)acrylates, and combinations thereof; (c) optionally
hydroxyethylene ethyl urea (meth)acrylate; and (d) up to about 50
percent by weight of one or more monomers selected from the group
consisting of aromatic polymerizable monomers, wherein the monomers
(b) and (c) combined are from about 5 to about 45 percent by weight
of the mixture of ethylenically unsaturated monomers.
2. A coating composition according to claim 1, wherein monomer (a)
is selected from the group consisting of acrylamide,
methacrylamide, beta-hydroxycarbamate acrylate,
beta-hydroxycarbamate methacrylate, hydroxyalkyl(meth)acrylates,
hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate,
hydroxybutyl(meth)acrylate, esters of epsilon caprolactone and
hydroxyalkyl(meth)acrylates, mono(meth)acrylates of polyethylene
glycols, and combinations thereof.
3. A coating composition according to claim 1, wherein the acrylic
polymer has a weight average molecular weight of from about 8,000
to about 70,000.
4. A coating composition according to claim 1, wherein the acrylic
polymer has a carboxylic acid equivalent weight of from about 800
to about 2000.
5. A coating composition according to claim 1, wherein the acrylic
polymer has an active hydrogen group equivalent weight of from
about 400 to about 2000.
6. A coating composition according to claim 1, wherein monomer (b)
comprises a .beta.-carboxyethyl acrylate.
7. A coating composition according to claim 1, wherein monomer (b)
comprises an .omega.-methyloxy-polyoxyethylene (meth)acrylate.
8. A coating composition according to claim 1, wherein the mixture
of ethylenically unsaturated monomers comprises from about 1 to
about 10 weight percent of hydroxyethylene ethyl urea
(meth)acrylate.
9. A coating composition according to claim 1, wherein the mixture
of ethylenically unsaturated monomers comprises from about 5 to
about 50 weight percent of styrene.
10. A coating composition according to claim 1, wherein the coating
composition is a solventborne coating composition.
11. A waterborne basecoat composition, comprising an aqueous
dispersion having at least one pigment dispersed by an acrylic
polymer, wherein the acrylic polymer is polymerized from a mixture
of ethylenically unsaturated monomers comprising: (a) one or more
monomers having active hydrogen functionality; (b) at least about
5% by weight of one or more monomers selected from the group
consisting of monomers having a carboxylic acid group in which the
carbonyl carbon is separated from the closest ethylenically
unsaturated carbon by at least four atoms,
.omega.-methyloxy-polyoxyethylene (meth)acrylates, and combinations
thereof; (c) optionally hydroxyethylene ethyl urea (meth)acrylate;
and (d) up to about 50 percent by weight of one or more monomers
selected from the group consisting of aromatic polymerizable
monomers, wherein the monomers (b) and (c) combined are from about
5 to about 45 percent by weight of the mixture of ethylenically
unsaturated monomers.
12. A waterborne basecoat composition according to claim 11,
further comprising a film-forming polymer other than the acrylic
polymer dispersing the pigment.
13. A waterborne basecoat composition according to claim 12,
further comprising a crosslinking agent.
14. A waterborne basecoat composition according to claim 12,
wherein monomer (a) is selected from the group consisting of
acrylamide, methacrylamide, beta-hydroxycarbamate acrylate,
beta-hydroxycarbamate methacrylate, hydroxyalkyl(meth)acrylates,
hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate,
hydroxybutyl (meth)acrylate, esters of epsilon caprolactone and
hydroxyalkyl(meth)acrylates, mono(meth)acrylates of polyethylene
glycols, and combinations thereof.
15. A waterborne basecoat composition according to claim 12,
wherein the acrylic polymer has a weight average molecular weight
of from about 8,000 to about 70,000.
16. A waterborne basecoat composition according to claim 12,
wherein the acrylic polymer has a carboxylic acid equivalent weight
of from about 800 to about 2000.
17. A waterborne basecoat composition according to claim 12,
wherein the acrylic polymer has an active hydrogen group equivalent
weight of from about 400 to about 2000.
18. A waterborne basecoat composition according to claim 12,
wherein monomer (b) comprises a .beta.-carboxyethyl acrylate.
19. A waterborne basecoat composition according to claim 12,
wherein monomer (b) comprises an .omega.-methyloxy-polyoxyethylene
(meth)acrylate.
20. A waterborne basecoat composition according to claim 12,
wherein the mixture of ethylenically unsaturated monomers comprises
from about 1 to about 10 weight percent of hydroxyethylene ethyl
urea (meth)acrylate.
21. A waterborne basecoat composition according to claim 12,
wherein the mixture of ethylenically unsaturated monomers comprises
from about 5 to about 50 weight percent of styrene.
Description
FIELD OF THE INVENTION
[0001] The invention relates pigment dispersants and methods of
making coating compositions with pigment dispersants.
BACKGROUND OF THE INVENTION
[0002] Coating finishes, particularly exterior coating finishes in
the automotive industry, are generally applied in two or more
distinct layers. One or more layers of primer coating composition
may be applied to the unpainted substrate first, followed by one or
more topcoat layers. Basecoat-clearcoat composite coatings are
particularly useful as topcoats for which exceptional gloss, depth
of color, distinctness of image, or special metallic effects are
desired. The basecoat layer contains the colorants that provide the
color for the topcoat, while the clearcoat layer provides a smooth,
glossy finish. The automotive industry has made extensive use of
these coatings for automotive body panels.
[0003] The colorants in automotive basecoat compositions are
typically one or more dispersed pigments. Pigment dispersion in the
composition must accomplish at least two objectives. First, the
pigment should be as fully wet-out as possible for optimum color
development in the coating layer. Secondly, the pigment should be
stabilized against hard settling and re-agglomeration of the
pigment particles so that the basecoat composition will have a
reasonably long shelf-life. Many types of dispersants have been
suggested for solventborne compositions. The options for waterborne
compositions has been more limited, as the dispersant must itself
be water-dispersible. Nonetheless, waterborne basecoat compositions
are in need of the same good color development and stability as
solventborne basecoat compositions. A pigment dispersant useful in
both solventborne and waterborne compositions would simplify
manufacturing and storage because the same dispersant intermediate
could be synthesized and used to made pigment dispersions for
either solventborne or waterborne compositions.
SUMMARY OF THE INVENTION
[0004] The present invention provides pigment dispersions offering
excellent color development in coating compositions, particularly
for basecoat coating compositions.
[0005] A pigmented coating composition of the invention comprises
at least one pigment dispersed in an acrylic polymer, wherein the
acrylic polymer is polymerized from a mixture of ethylenically
unsaturated monomers comprising: (a) one or more monomers having
active hydrogen functionality; (b) at least about 5% by weight of
one or more monomers selected from the group consisting of monomers
having a carboxylic acid group in which the carbonyl carbon is
separated from the closest ethylenically unsaturated carbon by at
least four atoms, .omega.-methyloxy-polyoxyethylene
(meth)acrylates, co-methyloxy-poly(oxyethylene-co-oxypropylene)
(meth)acrylates, and combinations thereof; (c) optionally
hydroxyethylene ethyl urea (meth)acrylate; and (d) up to about 50
percent by weight of one or more monomers selected from the group
consisting of aromatic polymerizable monomers, wherein the monomers
(b) and (c) combined are from about 5 to about 45 percent by weight
of the mixture of ethylenically unsaturated monomers. The
composition may be solventborne or waterborne.
[0006] A waterborne basecoat composition of the invention comprises
an aqueous dispersion having at least one pigment dispersed by an
acrylic polymer, wherein the acrylic polymer is polymerized from a
mixture of ethylenically unsaturated monomers comprising: (a) one
or more monomers having active hydrogen functionality; (b) at least
about 5% by weight of one or more monomers selected from the group
consisting of monomers having a carboxylic acid group in which the
carbonyl carbon is separated from the closest ethylenically
unsaturated carbon by at least four atoms,
.omega.-methyloxy-polyoxyethylene (meth)acrylates, and combinations
thereof; (c) optionally hydroxyethylene ethyl urea (meth)acrylate;
and (d) up to about 50 percent by weight of one or more monomers
selected from the group consisting of aromatic polymerizable
monomers, wherein the monomers (b) and (c) combined are from about
5 to about 45 percent by weight of the mixture of ethylenically
unsaturated monomers. Preferably, the waterborne basecoat
composition also comprises a film-forming polymer other than the
acrylic polymer dispersing the pigment, and preferably a
crosslinking agent.
[0007] The coating compositions of the invention exhibit excellent
color development, humidity resistance, and adhesion.
[0008] As used herein, "(meth)acrylate" refers to both the acrylate
and methacrylate compound. "A" and "an" as used herein indicate "at
least one" of the item is present; a plurality of such items may be
present, when possible. "About" when applied to values indicates
that the calculation or the measurement allows some slight
imprecision in the value (with some approach to exactness in the
value; approximately or reasonably close to the value; nearly). If,
for some reason, the imprecision provided by "about" is not
otherwise understood in the art with this ordinary meaning, then
"about" as used herein indicates a possible variation of up to 5%
in the value.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0010] The coating composition includes at least one pigment
dispersed in an acrylic polymer. The acrylic polymer is polymerized
from a mixture of ethylenically unsaturated monomers comprising:
(a) one or more monomers having active hydrogen functionality; (b)
at least about 5% by weight of one or more monomers selected from
the group consisting of monomers having a carboxylic acid group in
which the carbonyl carbon is separated from the closest
ethylenically unsaturated carbon by at least four atoms,
.omega.-methyloxy-polyoxyethylene (meth)acrylates,
.omega.-methyloxy-poly(oxyethylene-co-oxypropylene)
(meth)acrylates, and combinations thereof; (c) optionally
hydroxyethylene ethyl urea (meth)acrylate; and (d) up to about 50
percent by weight of one or more monomers selected from the group
consisting of aromatic polymerizable monomers, wherein the monomers
(b) and (c) combined are from about 5 to about 45 percent by weight
of the mixture of ethylenically unsaturated monomers
[0011] Suitable examples of ethylenically unsaturated monomers
having active hydrogen functionality (a) include, without
limitation, acrylamide, methacrylamide, beta-hydroxyalkyl carbamate
(meth)acrylates such as beta-hydroxypropyl carbamate methacrylate,
carbamate alkyl(meth)acrylates, carbamyloxyalkyl(meth)acrylates
such as 2-carbamyloxyethyl methacrylate and 4-carbamyloxybutyl
acrylate, beta- and gamma-carbamyloxyhydroxyalkyl(meth)acrylates
such as 2-carbamyloxy-3-hydroxypropyl methacrylate and
3-carbamyloxy-2-hydroxypropyl methacrylate,
hydroxyalkyl(meth)acrylates such as hydroxyethyl (meth)acrylate,
hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, esters of
epsilon caprolactone and hydroxyalkyl(meth)acrylates such as the
commercially available Tone 100M monomer (from Dow Chemical),
mono(meth)acrylates of polyethylene glycols, and combinations of
these. Hydroxyl and carbamate functionalities are preferred. The
acrylic polymer preferably has an active hydrogen group equivalent
weight of from about 400 to about 2000, more preferably from about
400 to about 1000.
[0012] The dispersant acrylic polymer also includes at least about
5% by weight of one or more polymerized monomers (b) selected from
the group consisting of monomers having a carboxylic acid group in
which the carbonyl carbon is separated from the closest
ethylenically unsaturated carbon by at least four atoms,
.omega.-methyloxy-polyoxyethylene (meth)acrylates,
.omega.-methyloxy-poly(oxyethylene-co-oxypropylene)
(meth)acrylates, and combinations of these. Preferred examples of
ethylenically unsaturated monomer having a carboxylic acid group in
which the carbonyl carbon is separated from the closest
ethylenically unsaturated carbon by at least four atoms are
oligomers of (meth)acrylic acid, particularly .beta.-carboxyethyl
acrylate. Other examples of ethylenically unsaturated monomers
having a carboxylic acid group in which the carbonyl carbon is
separated from the closest ethylenically unsaturated carbon by at
least four atoms are the reaction products of hydroxyalky
(meth)acrylates (e.g., hydroxyethyl methacrylate, hydroxypropyl
acrylate) with cyclic carboxylic acid anhydrides (e.g., succinic
anhydride, isophthalic anhydride), such as monomethacryloyloxyethyl
hexahydrophthalate. Preferred examples of
.omega.-methyloxy-polyoxyethylene (meth)acrylates and
.omega.-methyloxy-poly(oxyethylene-co-oxypropylene) (meth)acrylates
are those having molecular weights of at least about 750, more
preferably at least about 1000, and those having molecular weights
of up to about 4500, more preferably up to about 3000, and still
more preferably up to about 2500. Particularly preferred,
especially for waterborne compositions, are
.omega.-methyloxy-polyoxyethylene (meth)acrylates of those
molecular weights. The mixture of ethylenically unsaturated monomer
used to prepare the dispersing acrylic polymer preferably includes
one or more monomers having a carboxylic acid group in which the
carbonyl carbon is separated from the closest ethylenically
unsaturated carbon by at least four atoms in an amount sufficient
so that the acrylic polymer has an acid equivalent weight of 800 or
more grams per equivalent, more preferably an equivalent weight of
about 2000 or less and from about 1000 or more grams per
equivalent. The mixture of ethylenically unsaturated monomer used
to prepare the dispersing acrylic polymer preferably includes up to
about 20 percent by weight of one or more
.omega.-methyloxy-polyoxyethylene (meth)acrylates, more preferably
up to about 15% by weight of one or more
.omega.-methyloxy-polyoxyethylene (meth)acrylates, and also
preferably at least about 5% by weight of the one or more
.omega.-methyloxy-polyoxyethylene (meth)acrylates.
[0013] Optionally, the mixture of ethylenically unsaturated
monomers used to prepare the dispersing acrylic polymer includes
(c) hydroxyethylene ethyl urea methacrylate and/or hydroxyethylene
ethyl urea acrylate The mixture of ethylenically unsaturated
monomer used to prepare the dispersing acrylic polymer includes
preferably up to about 10 percent by weight, more preferably up to
about 7% by weight hydroxyethylene ethyl urea (meth)acrylate, and
also preferably includes at least about 1% by weight, more
preferably at least about 2% by weight, and still more preferably
at least about 3% by weight hydroxyethylene ethyl urea
(meth)acrylate.
[0014] Together the monomers (b) selected from the group consisting
of monomers having a carboxylic acid group in which the carbonyl
carbon is separated from the closest ethylenically unsaturated
carbon by at least four atoms,
.omega.-methyloxy-polyoxyethylene(meth)acrylates,
.omega.-methyloxy-poly(oxyethylene-co-oxypropylene)
(meth)acrylates, and combinations of these and the monomer (c)
hydroxyethylene ethyl urea (meth)acrylate comprise at least about 5
weight percent, more preferably at least about 15 weight percent of
the mixture of ethylenically unsaturated monomers polymerized to
form the acrylic polymer. It is also preferred that together the
monomers (b) selected from the group consisting of monomers having
a carboxylic acid group in which the carbonyl carbon is separated
from the closest ethylenically unsaturated carbon by at least four
atoms, .omega.-methyloxy-polyoxyethylene(meth)acrylates,
.omega.-methyloxy-poly(oxyethylene-co-oxypropylene)(meth)acrylates,
and combinations of these and the monomer (c) hydroxyethylene ethyl
urea (meth)acrylate comprise up to about 45 weight percent, more
preferably up to about 35 weight percent of the mixture of
ethylenically unsaturated monomers polymerized to form the acrylic
polymer.
[0015] The mixture of ethylenically unsaturated monomers
polymerized to form the acrylic polymer preferably includes one or
more aromatic polymerizable monomers. Suitable examples of aromatic
polymerizable monomers include, without limitation, styrene,
.alpha.-methyl styrene, vinyl toluene, tert-butyl styrene, and
combinations of these. The mixture of ethylenically unsaturated
monomer used to prepare the dispersing acrylic polymer preferably
includes at least about 5 percent, more preferably at least about
15 percent by weight of one or more aromatic polymerizable
monomers. The mixture of ethylenically unsaturated monomer used to
prepare the dispersing acrylic polymer includes up to about 50
percent, preferably up to about 30 percent, and more preferably up
to about 25 percent by weight of one or more aromatic polymerizable
monomers.
[0016] The mixture of ethylenically unsaturated monomers may
include other polymerizable monomers, such as, for example and
without limitation, esters of .alpha.,.beta.-ethylenically
unsaturated monocarboxylic acids containing 3 to 5 carbon atoms
such as acrylic, methacrylic, and crotonic acids; mono- and
di-esters of .alpha.,.beta.-ethylenically unsaturated dicarboxylic
acids containing 4 to 6 carbon atoms; vinyl esters, vinyl ethers,
vinyl ketones, and heterocyclic aliphatic vinyl compounds.
Representative examples of suitable esters of acrylic, methacrylic,
and crotonic acids include, without limitation, those esters from
reaction with saturated aliphatic alcohols containing 1 to 20
carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl,
isobutyl, tert-butyl, hexyl, 2-ethylhexyl, dodecyl, cyclohexyl,
alkyl-substituted cyclohexyl, alkanol-substituted cyclohexyl, such
as 2-tert-butyl and 4-tert-butyl cyclohexyl, 4-cyclohexyl-1-butyl,
and 3,3,5,5,-tetramethyl cyclohexyl; isobornyl, lauryl, and stearyl
acrylates, methacrylates, and crotonates. Representative examples
of other ethylenically unsaturated polymerizable monomers include,
without limitation, such compounds as fumaric, maleic, and itaconic
monoesters, and diesters with alcohols such as methanol, ethanol,
propanol, isopropanol, butanol, isobutanol, and tert-butanol.
Representative examples of co-polymerizable vinyl monomers include,
without limitation, such compounds as vinyl acetate, vinyl
propionate, vinyl ethers such as vinyl ethyl ether, vinyl and
vinylidene halides, vinyl ethyl ketone, and 2-vinyl
pyrrolidone.
[0017] The acrylic polymer is prepared according to usual methods,
such as by bulk or solution polymerization. The acrylic polymer
preferably has a weight average molecular weight of from about
8,000 to about 70,000.
[0018] After polymerization, any acid functionality may be salted,
preferably with an alkali or base, preferably an amine, even more
preferably a tertiary amine. Examples of suitable salting materials
include, without limitation, ammonia, monoethanolamine, ethylamine,
dimethylamine, diethylamine, triethylamine, propylamine,
dipropylamine, isopropylamine, diisopropylamine, triethanolamine,
butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine
propylenediamine, ethylethanolamine, dimethylethanolamine,
diethylethanolamine, 2-amino-2-methylpropanol, and morpholine.
Preferred salting materials include 2-amino-2-methylpropanol and
dimethylethanolamine.
[0019] The acrylic polymers may be prepared as solutions in an
organic solvent medium. For aqueous coating compositions, the
organic solvent or solvents are preferably selected from
water-soluble or water-miscible organic solvents, and after
polymerization the acrylic polymers are dispersed into water. After
dispersion into water, the organic solvent can be distilled from
the aqueous dispersion or emulsion.
[0020] The acrylic polymers may also be prepared by emulsion
polymerization. Preferably, a nonionic or an anionic surfactant is
used for the emulsion polymerization. Suitable surfactants include,
without limitation, polyoxyethylenenonylphenyl ethers,
polyoxyethylenealkylallyl ether sulfuric acid esters, amino and
alkali salts of dodecylbenzenesulfonic acid such as the
dimethylethanolamine salt of dodecylbenzenesulfonic acid and sodium
dodecylbenzenesulfonic acid, and sodium dioctylsulfosuccinate.
[0021] The polymerization may be carried out by free radical
polymerization. The free radical source is typically supplied by a
redox initiator or by an organic peroxide or azo compound. Useful
initiators include, without limitation, ammonium peroxydisulfate,
potassium peroxydisulfate, sodium metabisulfite, hydrogen peroxide,
t-butyl hydroperoxide, dilauryl peroxide, t-butyl peroxybenzoate,
2,2'-azobis(isobutyronitrile), and redox initiators such as
ammonium peroxydisulfate and sodium metabisulfite with ferrous
ammonium sulfate. Optionally, a chain transfer agent may be used.
Typical chain transfer agents include mercaptans such as octyl
mercaptan, n- or tert-dodecyl mercaptan, thiosalicylic acid,
mercaptoacetic acid, and mercaptoethanol; halogenated compounds;
and dimeric alpha-methyl styrene.
[0022] The coating compositions according to the invention further
include a pigment that may be selected from any organic or
inorganic compounds or colored materials. Examples of suitable
classes of organic pigments that may be used include, without
limitation, metallized and non-metallized azo pigments, azomethine
pigments, methine pigments, anthraquinone pigments, phthalocyanine
pigments, perinone pigments, perylene pigments,
diketopyrrolopyrrole pigments, thioindigo pigments,
iminoisoindoline pigments, iminoisoindolinone pigments,
quinacridone pigments such as quinacridone reds and violets,
flavanthrone pigments, indanthrone pigments, anthrapyrimidine
pigments, carbazole pigments, monoarylide and diarylide yellows,
benzimidazolone yellows, tolyl orange, naphthol orange, and
quinophthalone pigments. Examples of suitable inorganic pigments
include, without limitation, metal oxide pigments such as titanium
dioxide, iron oxides including red iron oxide, black iron oxide,
and brown iron oxide, and chromium oxide green; carbon black;
ferric ferrocyanide (Prussian blue); ultramarine; lead chromate;
and so on.
[0023] The color pigment or pigments are dispersed in the acrylic
polymer according to known methods. In general, dry pigment and the
acrylic polymer are brought into contact under a shear high enough
to break the pigment agglomerates down to the primary pigment
particles and to wet the surface of the pigment particles. The
breaking of the agglomerates and wetting of the primary pigment
particles are important for pigment stability and color
development. All of the pigments may be dispersed together in the
acrylic polymer or separate pigment dispersions may be made for one
or more pigments that are then combined in the coating
composition.
[0024] The coating composition may also include fillers and/or
metallic or other inorganic flake materials such as pearlescent
mica flake pigments or metallic flake pigments such as aluminum
flake. Metallic basecoat colors are produced using one or more
special flake pigments. Metallic colors are generally defined as
colors having gonioapparent effects. For example, the American
Society of Testing Methods (ASTM) document F284 defines metallic as
"pertaining to the appearance of a gonioapparent material
containing metal flake." Metallic basecoat colors may be produced
using metallic flake pigments like aluminum flake pigments, copper
flake pigments, zinc flake pigments, stainless steel flake
pigments, and bronze flake pigments and/or using pearlescent flake
pigments including treated micas like titanium dioxide-coated mica
pigments and iron oxide-coated mica pigments to give the coatings a
different appearance when viewed at different angles. Unlike the
solid color pigments, the flake pigments do not agglomerate and are
not ground under high shear because high shear would break or bend
the flakes or their crystalline morphology, diminishing or
destroying the gonioapparent effects. The flake pigments may be
dispersed with the acrylic polymer, but may also be dispersed with
the crosslinker or another film-forming resin or polymer, by
stirring under low shear.
[0025] When the coating composition is a basecoat composition, it
typically has a pigment to binder ratio of about 0.04 to about 1.0,
depending on the pigments used.
[0026] The coating compositions of the present invention preferably
also include a film-forming polymer or resin other than the acrylic
polymer dispersing the pigment. Suitable examples of such
film-forming polymers and resins include, without limitation,
acrylic polymers, polyesters, polyurethanes, and modified
polyurethanes such as graft copolymers. The film-forming polymers
and resins generally have reactive groups, such as active hydrogen
groups, particularly hydroxyl groups.
[0027] The coating compositions of the present invention preferably
also include a crosslinker component. The crosslinker component
includes one or more crosslinkers reactive with active hydrogen
functionality. Examples of crosslinkers reactive with active
hydrogen functionality include, without limitation, materials
having active methylol or methylalkoxy groups, including aminoplast
resins or phenol/formaldehyde adducts; blocked polyisocyanate
curing agents; tris(alkoxy carbonylamino)triazines (available from
Cytec Industries under the name TACT); and combinations thereof.
Suitable aminoplast resins are amine/aldehyde condensates,
preferably at least partially etherified, and most preferably fully
etherified. Melamine and urea are preferred amines, but other
triazines, triazoles, diazines, guanidines, or guanamines may also
be used to prepare the alkylated amine/aldehyde aminoplast resins
crosslinking agents. The aminoplast resins are preferably
amine/formaldehyde condensates, although other aldehydes, such as
acetaldehyde, crotonaldehyde, and benzaldehyde, may be used.
Non-limiting examples of preferred aminoplast resins include
monomeric or polymeric melamine formaldehyde resins, including
melamine resins that are partially or fully alkylated using
alcohols that preferably have one to six, more preferably one to
four, carbon atoms, such as hexamethoxy methylated melamine;
urea-formaldehyde resins including methylol ureas and siloxy ureas
such as butylated urea formaldehyde resin, alkylated
benzoguanimines, guanyl ureas, guanidines, biguanidines,
polyguanidines, and the like. Monomeric melamine formaldehyde
resins are particularly preferred. The preferred alkylated melamine
formaldehyde resins are water miscible or water soluble. Examples
of blocked polyisocyanates include isocyanurates of toluene
diisocyanate, isophorone diisocyanate, and hexamethylene
diisocyanate blocked with a blocking agent such as an alcohol, an
oxime, or a secondary amine such as pyrazole or substituted
pyrazole.
[0028] The crosslinker component preferably is from about 2% by
weight to about 40% by weight, and more preferably from about 15%
by weight to about 35% by weight, and particularly preferably about
20% to about 30% by weight of the combined nonvolatile weights of
the film-forming materials.
[0029] The coating compositions may include one or more catalysts.
The type of catalyst depends upon the particular crosslinker
component composition utilized. Useful catalysts include, without
limitation, blocked acid catalysts, such as para-toluene sulfonic
acid, dodecylbenzene sulfonic acid, and dinonylnaphthylene
disulfonic acid blocked with amines; phenyl acid phosphate,
monobutyl maleate, and butyl phosphate, hydroxy phosphate ester;
Lewis acids, zinc salts, and tin salts, including dibutyl tin
dilaurate and dibutyl tin oxide.
[0030] The coating compositions may be solventborne or waterborne.
Suitable solvents for solventborne compositions include, without
limitation, esters, alcohols, and substituted aromatic solvents.
Waterborne compositions may include, in addition to water, organic
cosolvents such as, without limitation, alkyl ethers of propylene
and ethylene glycol and dimmers thereof.
[0031] Other conventional materials, such as flow control or
rheology control agents, antioxidants, hindered amine light
absorbers, and other conventional coatings additives may be added
to the compositions.
[0032] The coating compositions of the present invention are
preferably applied as basecoats on automotive articles, such as
metal or plastic automotive bodies or elastomeric fascia. It is
preferred to have a layer of a primer surfacer before application
of the basecoat coating composition of the invention. A clearcoat
composition is preferably applied over the basecoat
composition.
[0033] A preferred composite coating of the invention has, as one
layer, a basecoat coating layer that is obtained from the basecoat
composition of the invention. The composite coating has a clearcoat
layer applied over the basecoat coating layer. Crosslinking
compositions are preferred for forming the clearcoat layer.
Coatings of this type are well-known in the art and include
waterborne compositions as well as solventborne compositions. For
example, the clearcoat according to U.S. Pat. No. 5,474,811 may be
applied wet-on-wet over a layer of the basecoat composition.
Polymers known in the art to be useful in clearcoat compositions
include, without limitation, acrylics, vinyl, polyurethanes,
polycarbonates, polyesters, alkyds, and polysiloxanes. Acrylics and
polyurethanes are preferred. Thermoset clearcoat compositions are
also preferred, and, to that end, preferred polymers comprise one
or more kinds of crosslinkable functional groups, such as
carbamate, hydroxy, isocyanate, amine, epoxy, acrylate, vinyl,
silane, acetoacetate, and so on. The polymer may be
self-crosslinking, or, preferably, the composition may include a
crosslinking agent such as a polyisocyanate or an aminoplast resin
of the kind described above. In one embodiment, waterborne
clearcoat compositions having low volatile organic content are
used. The waterborne clearcoat compositions preferably has a
volatile organic content of less than about 1.5, more preferably
less than about 1.3.
[0034] Each layer of the composite coatings of the invention can be
applied to an article to be coated according to any of a number of
techniques well-known in the art. These include, for example, spray
coating, dip coating, roll coating, curtain coating, and the like.
If an initial electrocoat primer layer is applied to a metallic
substrate, the electrocoat primer is applied by electrodeposition.
For automotive applications, the primer surfacer coating
composition, basecoat composition of the invention, and the
clearcoat composition layers are preferably applied by spray
coating, particularly electrostatic spray methods. Coating layers
of one mil or more are usually applied in two or more coats,
separated by a time sufficient to allow some of the solvent or
aqueous medium to evaporate, or "flash," from the applied layer.
The flash may be at ambient or elevated temperatures, for example,
the flash may use radiant heat. The coats as applied can be from
0.5 mil up to 3 mils dry, and a sufficient number of coats are
applied to yield the desired final coating thickness.
[0035] Basecoat-clearcoat topcoats are usually applied wet-on-wet.
The compositions are applied in coats separated by a flash, as
described above, with a flash also between the last coat of the
basecoat composition and the first coat the clearcoat composition.
The two coating layers are then cured simultaneously. Preferably,
the cured basecoat layer is 0.5 to 1.5 mils thick, preferably a
thickness at least to hiding, and the cured clear coat layer is 1
to 3 mils, more preferably 1.6 to 2.2 mils, thick.
[0036] The coating compositions described are preferably cured with
heat. Curing temperatures are preferably from about 70.degree. C.
to about 180.degree. C., and particularly preferably from about
170.degree. F. to about 200.degree. F. for a composition including
an unblocked acid catalyst, or from about 240.degree. F. to about
275.degree. F. for a composition including a blocked acid catalyst.
Typical curing times at these temperatures range from 15 to 60
minutes, and preferably the temperature is chosen to allow a cure
time of from about 15 to about 30 minutes. In a preferred
embodiment, the coated article is an automotive body or part.
[0037] The invention is further described in the following
examples. The examples are merely illustrative and do not in any
way limit the scope of the invention as described and claimed.
EXAMPLES
Example 1
Pigment Dispersant of the Invention
[0038] A suitable reactor was charged with 450 parts by weight of
propylene glycol monopropyl ether, which was heated under an inert
atmosphere to 140.degree. C. Then a mixture of 92 parts by weight
of Sipomer B-CEA (Rhodia, Cranbury, N.J.), 132.5 parts by weight of
2-hydroxyethyl acrylate, 32.5 parts by weight of methyl
methacrylate, 128.6 parts by weight of butyl methacrylate, 42.6
parts by weight of 2-ethylhexyl acrylate, 123.7 parts by weight of
styrene, 32.5 parts by weight of
1-(2-methacryloyloxyethyl)-2-imidazolidinone, 65 parts by weight of
M-230 (Kowa American Corp. NY, N.Y.), 8.3 parts by weight of
t-butyl peracetate, and 8.3 parts by weight of odorless mineral
spirits was added to the reactor over a 3-hour time period. Next 20
parts by weight of propylene glycol monopropyl ether were added and
the reaction mixture kept at 140.degree. C. for 50 minutes. The
reaction mixture was cooled to 110.degree. C., and a mixture of 9.7
parts by weight of t-butyl peroxy-2-ethylhexanoate and 20 parts by
weight of propylene glycol monopropyl ether was added over a
20-minute time period. Then 10 parts by weight of propylene glycol
monopropyl ether were added and the reaction mixture held at
110.degree. C. for 1 hour. The reaction mixture was then cooled.
167 parts of a 20% mixture of aminopropanol in deionized water was
added, followed by 346.4 parts of deionized water. The final resin
had a measured nonvolatile content of 41.2% by weight.
Example 2
Red Pigment Composition According to the Invention
[0039] A red pigment composition was prepared by adding 14.31 parts
by weight perylene pigment (C.I. Pigment Red 179) to a stirred
mixture of 33.48 parts by weight pigment dispersant resin prepared
in accordance with Example 1, 4.58 parts by weight propylene glycol
n-propyl ether, 45.71 parts deionized water, and 1.92 parts by
weight of a commercial polyalkylene additive. The resultant mixture
was stirred on a Cowles disperser for thirty minutes and milled in
an Eiger bead mill for two and a half hours.
Comparative Example A
Comparative Red Pigment Composition
[0040] A comparative red pigment composition was prepared by adding
14.31 parts by weight perylene pigment (C.I. Pigment Red 179) to a
stirred mixture of 16.74 parts by weight of an acrylic grind resin
that was not prepared according to the invention, 16.74 parts by
weight of a polyurethane resin, 4.58 parts by weight propylene
glycol n-propyl ether, 45.71 parts deionized water, and 1.92 parts
by weight of a commercial polyalkylene additive. The resultant
mixture was stirred on a Cowles disperser for thirty minutes and
milled in an Eiger bead mill for two and a half hours.
Example 3
Blue Pigment Composition According to the Invention
[0041] A blue pigment composition was prepared by adding 14.28
parts by weight indanthrone pigment (C.I. Pigment Blue 60) to a
stirred mixture of 19.04 parts by weight pigment dispersant resin
prepared in accordance with Example 1, 8.57 parts by weight
propylene glycol n-propyl ether, and 58.11 parts by weight
deionized water. The resultant mixture was stirred on a Cowles
disperser for thirty minutes and milled in an Eiger bead mill for
ten hours.
Comparative Example B
Comparative Blue Pigment Composition
[0042] A blue pigment paste was prepared by adding 14.28 parts by
weight indanthrone pigment (C.I. Pigment Blue 60) to a stirred
mixture of 19.04 parts by weight of an acrylic grind resin that was
not prepared according to the invention, 8.57 parts by weight
propylene glycol n-propyl ether, and 58.11 parts by weight
deionized water. The resultant mixture was stirred on a Cowles
disperser for thirty minutes and milled in an Eiger bead mill for
ten hours.
Example 4
Coating Composition According to the Invention
[0043] A coating composition was prepared that contained the red
pigment composition of Example 2 by combining with rapid stirring
79.94 parts by weight of an unpigmented basecoat mixture, 16.18
parts by weight of the red pigment composition of Example 2, 1.16
parts by weight of a black tinting paste (prepared by mixing an
anionic polyurethane resin with carbon black pigment, stirring the
mixture on a Cowles disperser for thirty minutes, and milling the
stirred mixture in an Eiger bead mill for two and one-half hours).
and 7.72 parts by weight of a mica pigment dispersion (prepared by
slurrying 2.20 parts by weight iron oxide coated mica in a
combination of 2.54 parts by weight of polyester resin and 2.54
parts by weight propylene glycol n-propyl ether, then adding 0.44
parts by weight of a 20% aqueous solution of amine). Stirring was
continued for about thirty minutes.
Comparative Example C
Comparative Coating Composition
[0044] A coating composition was prepared according to Example 4,
except that the 16.18 parts by weight of the red pigment
composition of Example 2 was replaced by 16.18 parts by weight of
the comparative red pigment composition of Comparative Example
A.
Example 5
Coating Composition According to the Invention
[0045] A coating composition was prepared that contained the blue
pigment composition of Example 3 by combining with rapid stirring
82.62 parts by weight of the unpigmented basecoat mixture used in
Example 4 and 7.83 parts by weight of the blue pigment composition
of Example 3 premixed with 9.55 parts by weight of an aluminum
pigment dispersion (prepared by slurrying 4.01 parts by weight
aluminum pigment in a combination of 2.55 parts by weight of
polyester resin and 2.55 parts by weight propylene glycol n-propyl
ether, then adding 0.44 parts by weight of a 20% aqueous solution
of amine). Stirring was continued for about thirty minutes.
Comparative Example D
Comparative Coating Composition
[0046] A coating composition was prepared according to Example 5,
except that the 7.83 parts by weight of the blue pigment
composition of Example 3 was replaced by 7.83 parts by weight of
the comparative blue pigment composition of Comparative Example
B.
Testing of Coating Compositions
[0047] The coating compostions of Examples 4 and 5 and Comparative
Examples C and D were applied as basecoats and cured according to
established procedures and equipment.
[0048] The color development in the coatings and stability of the
coating compositions were compared. The film derived from the
coating composition of Example 4 and Example 5 showed excellent
metallic effect as a result of good transparency in the red pigment
and blue pigment, respectively. The coating compositions of
Examples 4 and 5 showed no instability after makeup and
storage.
[0049] The basecoat coating colors were measured by a
goniospectrophotometer at 25 degrees from specular with results as
indicated below. TABLE-US-00001 a* (red Coating Composition L*
(brightness) index) b* (yellow index) Example 4 26.3 40.2 20.4
Comparative Example C 24.9 38.8 19.7 Example 5 67.05 -6.24 -40.03
Comparative Example D 65.10 -6.85 -42.52
[0050] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *