Aqueous dispersion of composite particles

Abstract

A stable aqueous dispersion including certain composite particles and a method for forming the stable aqueous dispersion is provided. The composite particles include a pigment particle, the pigment particle having disposed thereon a certain water-soluble polymer including copolymerized carboxylic acid monomer and N-containing monomer and the pigment particle bearing the water-soluble polymer having disposed on it a plurality of water-insoluble polymer particles. Also provided is a dry coating formed from the aqueous dispersion.

Claims

1. A stable aqueous dispersion comprising composite particles, said composite particles comprising: a pigment particle, said pigment particle having disposed thereon a water-soluble polymer, said water-soluble polymer comprising, as copolymerized units, from 10% to 30%, by weight based on the weight of said water-soluble polymer, ethylenically unsaturated carboxylic acid monomer when said ethylenically unsaturated carboxylic acid monomer has a molecular weight of from 70 to 100; or from 15% to 40%, by weight based on the weight of said water-soluble polymer, ethylenically unsaturated carboxylic acid monomer when said ethylenically unsaturated carboxylic acid monomer has a molecular weight of from greater than 100 to a molecular weight of 500; and from 5% to 95%, by weight based on the weight of said water-soluble polymer, ethylenically unsaturated N-containing monomer selected from the group consisting of: ##STR00017## wherein R.sub.0 is H, CH.sub.3, or CH.sub.2CH.sub.3; R.sub.1 is CH.sub.2CH.sub.2, CH.sub.2CH(CH.sub.3), or CH.sub.2CH.sub.2CH.sub.2, or CH(CH.sub.3)CH.sub.2CH.sub.2, CH.sub.2CH.sub.2CH.sub.2CH.sub.2, CH(CH.sub.2CH.sub.3)CH.sub.2, CH(CH.sub.3)CH(CH.sub.3); R.sub.2 and R.sub.3 are, independently, H, CH.sub.3, CH.sub.2CH.sub.3, or C.sub.3-C.sub.12 and selected from the group consisting of: linear, branched, alkyl, aromatic, and cyclic structures; or quaternary ammonium analogues of Structure I; ##STR00018## wherein R.sub.0 is H, CH.sub.3, CH.sub.2CH.sub.3; and R.sub.1 is CH.sub.2CH.sub.2, CH.sub.2CH(CH.sub.3), or CH.sub.2CH.sub.2CH.sub.2; R.sub.2 and R.sub.3 are, independently, H, CH.sub.3, CH.sub.2CH.sub.3, or C.sub.3-C.sub.12 selected from the group consisting of: linear: branched, alkyl, aromatic, and cyclic structures; or quaternary ammonium analogues of Structure II; ##STR00019## wherein R is C.sub.1-C.sub.4 alkyl and n is 0 to 4; ##STR00020## and mixtures thereof; wherein the molar ratio of carboxylic acid to N-functionality is from 0.1 to 4; and from 0% to 50%, by weight based on the weight of said water-soluble polymer, (meth)acrylic ester of a linear or branched monohydroxyl or amide of a monoamine compound having from 1 to 4 carbon atoms; or vinyl ester of a linear, branched, cyclic, or aromatic monocarboxylic acid having from 1 to 9 carbon atoms; and wherein the calculated M.sub.n of said water-soluble polymer is from 1,000 to 25,000; and said pigment particle bearing said water-soluble polymer having disposed thereon a plurality of water-insoluble polymer particles in an amount of from 5 to 50% by weight, based on the weight of the composite particles.

2. The stable aqueous dispersion of claim 1 wherein said ethylenically unsaturated N-containing monomer is selected from the group consisting of Structure I.

3. The stable aqueous dispersion of claim 1 wherein said pigment particle is an inorganic pigment particle having an average particle diameter of from 0.05 microns to 10 microns.

4. The stable aqueous dispersion of claim 1 wherein said inorganic pigment particle comprises TiO.sub.2.

5. The stable aqueous dispersion of claim 1 wherein said ethylenically unsaturated carboxylic acid monomer is (meth)acrylic acid or a salt thereof.

6. The stable aqueous dispersion of claim 1 further comprising at least one thickener selected from the group consisting of: hydrophobically modified ethoxylated urethanes (HEUR), hydroxyethyl cellulose (HEC), alkali-soluble emulsions (ASE), hydrophobically modified alkali-soluble emulsions (HASE), and hydrophobically modified hydroxyethyl cellulose (HMHEC) thickeners.

7. A method for forming a stable aqueous dispersion comprising composite particles comprising: a) dispersing a pigment particle in an aqueous medium in the presence of from 0.1% to 20%, by weight based on the weight of pigment, of a water-soluble polymer, said water-soluble polymer comprising, as copolymerized units, from 10% to 30%, by weight based on the weight of said water-soluble polymer, ethylenically unsaturated carboxylic acid monomer when said ethylenically unsaturated carboxylic acid monomer has a molecular weight of from 70 to 100; or from 15% to 40%, by weight based on the weight of said water-soluble polymer, ethylenically unsaturated carboxylic acid monomer when said ethylenically unsaturated carboxylic acid monomer has a molecular weight of from greater than 100 to a molecular weight of 500; and from 5% to 95%, by weight based on the weight of said water-soluble polymer, ethylenically unsaturated N-containing monomer having the structure: ##STR00021## wherein R.sub.0 is H, CH.sub.3, or CH.sub.2CH.sub.3; R1 is CH.sub.2CH.sub.2, CH.sub.2CH(CH.sub.3), or CH.sub.2CH.sub.2CH.sub.2, or CH(CH.sub.3)CH.sub.2CH.sub.2, CH.sub.2CH.sub.2CH.sub.2CH.sub.2, CH(CH.sub.2CH.sub.3)CH.sub.2, CH(CH.sub.3)CH(CH.sub.3); R.sub.2 and R.sub.3 are, independently, H, CH.sub.3, CH.sub.2CH.sub.3, or C.sub.3-C.sub.12 selected from the group consisting of: linear, branched, alkyl, aromatic, and cyclic structures; or quaternary ammonium analogues of Structure I; ##STR00022## wherein R.sub.0 is H, CH.sub.3, CH.sub.2CH.sub.3; and R.sub.1 is CH.sub.2CH.sub.2, CH.sub.2CH(CH.sub.3), or CH.sub.2CH.sub.2CH.sub.2; R.sub.2 and R.sub.3 are, independently, H, CH.sub.3, CH.sub.2CH.sub.3, or C.sub.3-C.sub.12 and may be linear, branched, alkyl, aromatic, or cyclic; or quaternary ammonium analogues of Structure II; ##STR00023## wherein R is C.sub.1-C.sub.4 alkyl and n is 0 to 4; ##STR00024## and mixtures thereof; wherein the molar ratio of carboxylic acid to N-functionality is from 0.1 to 4; and from 0% to 50%, by weight based on the weight of said water-soluble polymer, (meth)acrylic ester of a linear or branched monohydroxyl or amide of a monoamine compound having from 1 to 4 carbon atoms; or vinyl ester of a linear, branched, cyclic, or aromatic monocarboxylic acid having from 1 to 9 carbon atoms; and wherein the M.sub.n of said water-soluble polymer is from 1,000 to 25,000; and (b) contacting said dispersed pigment particle with an aqueous dispersion of water-insoluble polymer particles in an amount of from 5% to 300% by weight, based on the weight of the composite particles.

8. The method of claim 7 wherein said ethylenically unsaturated N-containing monomer is selected from the group consisting of Structure I.

9. The method of claim 7 wherein said contacting step (b) is conducted for a period of less than 30 minutes at a temperature of from 5 to 50 C.

10. A dry coating formed by the method comprising: a) forming an aqueous coating composition comprising the stable aqueous dispersion comprising composite particles of claim 1; b) applying said aqueous coating composition to a substrate; and c) drying, or allowing to dry, said aqueous coating composition.

Description

EXAMPLES 1-3 AND COMPARATIVE EXAMPLES A-H

Formation of Aqueous Coating Compositions

(1) Stable aqueous coating compositions, Examples 1-3 were made according to the process shown in Table 1.1. The pigment was dispersed with the water-soluble polymer indicated in Table 1.2, and the same or different dispersant was added later to make up the desired total dispersant level. The grind pH was adjusted to 9. Grind and binder were combined and mixed for about 30 min; the volume solids of this stage was made as high as practical. Surfactants and thickeners were added after the grind was combined with the binder(s). The volume solids (VS) was 35% and the pigment volume concentration (PVC) was 16% TiO.sub.2.

(2) TABLE-US-00001 TABLE 1.1 Aqueous composition formation (all amounts in g) Grind Water-soluble polymer (50%) 1.12 Water 7.93 TI-PURE R-706 37.53 Grind Sub-total 46.58 Water 5.00 Grind Sub-total 51.58 TAMOL SG-10M 111.54 Mixed 5 min; let stand 25 for total 30 minutes LetDown 163.12 TEXANOL 4.28 Water 29.03 ACRYSOL RM-2020 E 4.50 ACRYSOL RM-825 0.12 TERGITOL 15-S-9 0.40 Totals 201.45 TI-PURE and VAZO are trademarks of E. I. DuPont de Nemours and Co.; TAMOL, ACRYSOL and TERGITOL are trademarks of The Dow Chemical Co.; TEXANOL is a trademark of Eastman Chemical Co.

(3) TABLE-US-00002 TABLE 1.2 Evaluation of dry coatings for hiding efficacy % Carboxylic % N- Calc. acid containing Mole ratio Hiding Water-soluble polymer M.sub.n monomer monomer acid/amine* S/mil Comp A (80 MAA/20 DMAEMA) 3000 80 20 7.3 4.60 Comp B 40 MAA/60 DMAEMA 3100 40 60 1.2 5.05 Comp. C (60 MAA/20 DMAEMA/20 MMA) 3000 60 20 5.5 5.50 Comp D (60 MAA/40 DMAEMA) 3100 60 40 2.7 5.60 Comp E (51 BZMA/7 DMAEMA/15 BMA/ 3000 12 7 3.2 6.00 10 MMA/5 HEMA/12 MAA) per US 20040250735 Comp F 40 MAA/40 DMAEMA/20 MMA 3000 40 40 1.8 6.00 Comp G 40 MAA/20 DMAEMA/40 MMA 3000 40 20 3.7 6.20 Comp H 20 MAA/20 DMAEMA/60 MMA 2900 20 20 1.8 6.29 Ex. 1 20 MAA/60 DMAEMA/20 MMA) 3000 20 60 0.6 7.04 Ex. 2 20 MAA/80 DMAEMA 3000 20 80 0.5 7.21 Ex. 3 30 MAA/45 DMAEMA/25 MMA 3000 30 45 1.2 7.81 *mole ratio acid/amine ignores any other monomers. Compositions given in monomer w/w percent.

(4) Examples 1-3 of the present invention containing composite particles exhibit hiding properties superior to those of Comparative Examples A-H.