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US 6,576,051 B2Granted
Polymer-pigment composites
AssigneeRohm and Haas Company
InventorsJames Keith Bardman, Ward Thomas Brown, Kenneth Michael Donnelly, Wei Zhang, Bernhard Helmut Lieser
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Abstract
Composite particles and a method of preparing the composite particles are provided. The composite particles contain titanium dioxide particles with adsorbed two-phase polymer particles. The two-phase polymer particles have a soft polymer phase and a hard polymer phase in which the weight ratio of the hard polymer phase to the soft polymer phase is in the range of 10:1 to 1:5. The composite particles containing the two-phase polymer particles have improved aqueous stability and provide coatings with improved scrub resistance.
Claims14
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.
16 more elements
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.
15 more elements
Dependencies are inferred from the claim text.