Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1996-09-13
2001-03-06
Yoon, Tae (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S431000, C524S556000, C524S559000, C526S272000, C526S318200, C526S318250, C526S318300, C526S318450, C526S318600
Reexamination Certificate
active
06197879
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polymers useful in preparing inorganic pigment dispersions and methods of preparing such polymers, methods of preparing inorganic pigment dispersions useful in the manufacture of latex paints, and latex paints prepared therewith.
BACKGROUND OF THE INVENTION
Paint coatings are protective surface coatings applied to substrates and cured to form dry continuous films for decorative purposes as well as to protect the substrate. Consumer latex paint coatings are air-drying aqueous coatings applied primarily to architectural interior or exterior surfaces, where the coatings are sufficiently fluid to flow out, form a continuous paint film, and then dry at ambient temperatures to form continuous films.
A paint coating is ordinarily comprised of an organic polymeric binder, pigments, and various paint additives. The polymeric binder acts as a fluid vehicle for the pigments and imparts rheological properties to the fluid paint coating. In dried paint films, the polymeric binder functions as a binder for the pigments and provides adhesion of the dried paint film to the substrate. The pigments may be organic or inorganic and functionally contribute to opacity and color in addition to durability and hardness.
The manufacture of paint coatings involves the preparation of a polymeric binder, mixing of component materials, grinding of pigment in the presence of a pigment dispersant, mixing the pigment grind with the polymeric binder, and thinning to commercial standards. High speed dispersers or dissolvers are used in the grinding step to disperse the pigments into the polymeric binder solution.
Considerable research effort has been directed toward eliminating volatile organic compounds (VOC) from consumer paints and especially from latex paints to eliminate emission problems as well as the odor problems. (VOC is a measure of volatile organic compounds in a paint composition according to U.S. EPA Rule 24. See also ASTM Manual Series MNL4 and ASTM D-3960 and ASTM D-2369-87.) Thus, an urgent need exists to eliminate consumer VOC problems with air drying paints.
Polyacrylic acid in its neutralized form has been used to prepare aqueous pigment dispersions, particularly dispersions of titanium dioxide. Polyacrylic acid disperses the pigment well and contributes little, if at all, to the VOC of the latex paint into which the pigment dispersion is incorporated. However, polyacrylic acid also tends to contribute to water sensitivity of the dried paint coating. For example, an exterior paint coating is more susceptible to water damage as a result of precipitation and an interior paint coating may be damaged when scrubbed with aqueous liquids, e.g. soap and water. A pigment dispersant with a reduced contribution to the water sensitivity of the dried paint coating is therefore desirable.
SUMMARY OF THE INVENTION
This invention relates to a polymer useful as an inorganic pigment dispersant, said polymer being derived from monomers consisting essentially of an ethylenically unsaturated aromatic monomer, an ethylenically unsaturated dicarboxylic acid monomer, and an ethylenically unsaturated monocarboxylic acid monomer, wherein the total amount of said ethylenically unsaturated dicarboxylic acid monomer and said ethylenically unsaturated monocarboxylic acid monomer is sufficient to permit said polymer to associate with an inorganic pigment in an aqueous medium in a manner which disperses said inorganic pigment in said aqueous medium to form a stable aqueous dispersion of said inorganic pigment, and wherein the amount of said ethylenically unsaturated aromatic monomer is sufficient to reduce the water sensitivity of a dried coating of a latex paint comprised of said stable aqueous dispersion of said inorganic pigment.
This invention also relates to a process of preparing a polymer useful as an inorganic pigment dispersant, said process comprising dissolving monomers consisting essentially of an ethylenically unsaturated aromatic monomer, an ethylenically unsaturated dicarboxylic acid monomer, and an ethylenically unsaturated monocarboxylic acid monomer in a solvent consisting essentially of a major amount by weight of a water-miscible organic solvent having chain transfer activity and a minor amount by weight of water and polymerizing said monomers in said solution.
This invention also relates to a method of preparing an inorganic pigment dispersion useful in the preparation of latex paints, said method comprising dispersing an inorganic pigment in an aqueous medium further comprised of a dispersing polymer, said aqueous medium being essentially free of volatile organic solvents, and said dispersing polymer being derived from monomers consisting essentially of an ethylenically unsaturated aromatic monomer, ethylenically unsaturated dicarboxylic acid monomer, and an ethylenically unsaturated monocarboxylic acid monomer, wherein the amount of said ethylenically unsaturated acid monomer is sufficient to permit said polymer to associate with an inorganic pigment in an aqueous medium in a manner which disperses said inorganic pigment in said aqueous medium to form a stable aqueous dispersion of said inorganic pigment, and wherein the amount of said ethylenically unsaturated aromatic monomer is sufficient to reduce the water sensitivity of a dried coating of a latex paint comprised of said stable aqueous dispersion of said inorganic pigment. This invention also relates to an inorganic pigment dispersion comprising an inorganic pigment and a dispersing polymer as described above in an aqueous medium.
This invention also relates to latex paints comprising the inorganic pigment dispersion composition of this invention and to a method of coating a substrate comprising contacting a surface of a substrate with a composition comprising a latex paint binder and an inorganic pigment dispersion of this invention and drying said surface to form a film of said composition in contact with said surface.
With respect to certain embodiments, this invention relates to a polymer produced by the process of polymerizing monomers consisting essentially of:
(i) an aromatic monomer having the formula CH
2
═C(R
1
)(R
2
) wherein R
1
is an aromatic group having from 6 to 10 carbon atoms, and R
2
is hydrogen or methyl,
(ii) a di-acid monomer selected from the group of compounds having the formula R
3
R
4
C═C(R
5
)(C(O)OH) wherein R
3
, R
4
, and R
5
are hydrogen, carboxyl, lower alkyl, or carboxyl-substituted lower alkyl, provided that one of R
3
, R
4
, and R
5
must be carboxyl or carboxyl-substituted lower alkyl, one of R
3
, R
4
, and R
5
must be hydrogen said di-acid monomer having from 4 to 6 carbon atoms, and anhydrides of said compounds, and
(iii) an mono-acid monomer having the formula CH
2
═C(R
6
)(C(O)OH) wherein R
6
is hydrogen or methyl, or mixtures thereof. Said polymer is typically produced by polymerization of the monomers while in an aqueous alcohol solution. As used herein, the term “lower alkyl” refers to alkyl groups having from 1 to 4 carbon atoms, typically methyl and ethyl.
In typical embodiments, the monomers consist essentially of one or more of said aromatic monomers in an amount of from about 30% to about 50% by weight, and one or more of said di-acid monomers in an amount of from about 20% to about 40% by weight, and one or more of said mono-acid monomers in an amount of from about 20% to about 40% by weight. The polymer typically has a molecular weight (e.g. weight average) of from about 1,000 to about 20,000.
Certain of the polymers of this invention can also be represented by the formula:
wherein R
1
, R
2
, R
3
, R
4
, R
5
, and R
6
are as defined above, and the total of y and z is sufficient to permit said polymer to associate with an inorganic pigment in an aqueous medium in a manner which disperses said inorganic pigment in said aqueous medium to form a stable aqueous dispersion of said inorganic pigment, and wherein x is sufficient to reduce the water sensitivity of a dried coating of a latex paint comprised of said stable aqu
Fischer Stephen A.
Matta Bruce
Nowicki Eric
Wiggins Michael S.
Drach John E.
Henkel Corporation
Millson, Jr. Henry E.
Wood John Daniel
Yoon Tae
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