Claims
- 1. A composition comprising at least one composite particle;wherein said composite particle comprises: a) a titanium dioxide particle; and b) two-phase polymer particles adsorbed on the surface of said titanium dioxide particle; wherein said composite particle is formed in an aqueous mixture consisting essentially of at least one said titanium dioxide particle, a multiplicity of said two-phase polymer particles, and optionally, dispersant, and the weight ratio of said multiplicity of said two-phase polymer particles to at least one said titanium dioxide particle in said aqueous mixture is in the range of 1:20 to 1:2; wherein each of said two-phase polymer particles, which contain ethylenically unsaturated monomer as polymerized units, comprises: i) a soft polymer phase with a glass transition temperature less than or equal to 40° C., and ii) a hard polymer phase with a glass transition temperature greater than 40° C.; wherein the difference between the glass transition temperature of said hard polymer phase and said soft polymer phase is at least 10° C.; wherein the average weight ratio of said hard polymer phase to said soft polymer phase is in the range of 10:1 to 1:5; and wherein A) each of said two-phase polymer particles includes at least one element selected from the group consisting of: at least one phosphorus functional monomer as a polymerized group, at least 5 weight % of at least one carboxylic acid monomer as a polymerized group, based on weight of said two-phase polymer particles, at least one acid macromonomer as a polymerized group, and a water soluble polymer chemically bonded to said two-phase polymer particles wherein said water soluble polymer has a molecular weight of at least 1500 prior to bonding to said two-phase polymer particles and contains at least one moiety adsorbable to said titanium dioxide particle; or B) said two-phase polymer particles and said titanium dioxide particle have opposite charges.
- 2. The composition according to claim 1 wherein said two-phase polymer particles comprise as polymerized units, at least one phosphorus functional monomer.
- 3. The composition according to claim 1 wherein said two-phase polymer particles comprise as polymerized units, at least 5% weight of at least one carboxylic acid monomer, based on weight of said two-phase polymer particles.
- 4. The composition according to claim 1 wherein said two-phase polymer particles are prepared by an aqueous emulsion polymerization process including at least two polymerization stages.
- 5. The composition according to claim 1 wherein said two-phase polymer particles have an average diameter in the range of 30 to 200 nm.
- 6. A process for preparing a stable aqueous dispersion of composite particles comprising the steps of:a) dispersing titanium dioxide particles in a first aqueous medium; b) preparing a dispersion or suspension of two-phase polymer particles in a second aqueous medium, wherein said two-phase polymer particles, which contain ethylenically unsaturated monomer as polymerized units, comprise: i) a soft polymer phase with a glass transition temperature less than or equal to 40° C., and ii) a hard polymer phase with a glass transition temperature greater than 40° C.; wherein the difference between the glass transition temperature of said hard polymer phase and said soft polymer phase is at least 10° C.; wherein the average weight ratio of said hard polymer phase to said soft polymer phase is in the range of 10:1 to 1:5; and wherein A) each of said two-phase polymer particles includes at least one element selected from the group consisting of: at least one phosphorus functional monomer as a polymerized group, at least 5 weight % of at least one carboxylic acid monomer as a polymerized group, based on weight of said two-phase polymer particles, at least one acid macromonomer as a polymerized group, and a water soluble polymer chemically bonded to said two-phase polymer particles wherein said water soluble polymer has a molecular weight of at least 1500 prior to bonding to said two-phase polymer particles and contains at least one moiety adsorbable to said titanium dioxide particle; or B) said two-phase polymer particles and said titanium dioxide particle have opposite charges; c) preparing a mixture consisting essentially of said first aqueous medium, said second aqueous medium, and optionally, dispersant, wherein the average weight ratio of said two-phase polymer particles to said titanium dioxide particles is in the range of 1:20 to 1:2; and d) permitting adsorption of said two-phase polymer particles to said titanium dioxide particles to form said stable aqueous dispersion of composite particles.
- 7. The process according to claim 6 wherein said two-phase polymer particles comprise as polymerized units, at least one phosphorus functional monomer.
- 8. The process according to claim 6 wherein said two-phase polymer particles comprise as polymerized units, at least 5% weight of at least one carboxylic acid monomer, based on weight of said two-phase polymer particles.
- 9. The process according to claim 6 wherein said two-phase polymer particles are prepared by an aqueous emulsion polymerization process including at least two polymerization stages.
- 10. The process according to claim 6 wherein said two-phase polymer particles have an average diameter in the range of 30 to 200 nm.
- 11. The composition according to claim 1 wherein said ethylenically unsaturated monomer is selected from the group consisting of monoethylenically unsaturated monomers, multiethylenically unsaturated monomers, functional monomers, and mixtures thereof.
- 12. The composition according to claim 1 wherein said two-phase polymer is prepared by emulsion polymerization of ethylenically unsaturated monomers.
- 13. The process of according to claim 6 wherein said ethylenically unsaturated monomer is selected from the group consisting of monoethylenically unsaturated monomers, multiethylenically unsaturated monomers, functional monomers, and mixtures thereof.
- 14. The process according to claim 6 wherein said two-phase polymer is prepared by emulsion polymerization of ethylenically unsaturated monomers.
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
This is a non-provisional application of prior pending U.S. provisional application serial No. 60/252,275 filed Nov. 21, 2000.
US Referenced Citations (19)
Foreign Referenced Citations (1)
Number |
Date |
Country |
WO9925780 |
May 1999 |
WO |
Provisional Applications (1)
|
Number |
Date |
Country |
|
60/252275 |
Nov 2000 |
US |