US 6,139,961 AGranted

Hollow sphere organic pigment for paper or paper coatings

AssigneeRohm and Haas Company

InventorsRobert Mitchell Blankenship, William Christopher Finch, Lubomir Mlynar, Barbara Jean Schultz

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Abstract

A hollow sphere organic pigment in which a core containing a void is encapsulated by a first shell polymer having a glass transition temperature greater than 50.degree. C., the first shell having polymerized thereon a second shell polymer having a glass transition temperature of -15.degree. C. to -50.degree. C. is provided. Also provided is a paper or paperboard coating composition containing the hollow sphere organic pigment, a method for improving the strength and opacity of a paper or paperboard coating by using the coating composition dried, a coated paper or paperboard bearing the dried coating composition, and a method for improving the strength and opacity of paper or paperboard by incorporating a particular hollow sphere organic pigment into the formed wet sheet.

Claims7

Dependent claims

A hollow sphere organic pigment formed by

(a) forming emulsion-polymerized multistaged polymer particles comprising
(1) a hydrophilic core polymer formed from 5% to 100% by weight, based on the total weight of said core polymer, of a hydrophilic monoethylenically unsaturated monomer and from 0% to 95% by weight, based on the total weight of said core polymer, of at least one nonionic monoethylenically unsaturated monomer;
(2) a first shell polymer formed from 90% to 99.9% by weight, based on the total weight of said first shell polymer, of at least one nonionic monoethylenically unsaturated monomer and from 0.1% to 10% by weight, based on the total weight of said first shell polymer, of an acid functional monoethylenically unsaturated monomer, wherein said first shell polymer fully encapsulates said core polymer, wherein the ratio of the weight of said core polymer to the weight of said first shell polymer is from 1:2 to 1:100, and wherein said first shell polymer has a glass transition temperature greater than 50.degree. C.;
and
(3) a second shell polymer formed from 93% to 99.9% by weight, based on the total weight of said second shell polymer, of at least one nonionic monoethylenically unsaturated monomer and from 0.1% to 7% by weight, based on the total weight of said second shell polymer, of an acid functional monoethylenically unsaturated monomer, wherein said second shell polymer is formed in the presence of said first shell polymer, and wherein said second shell polymer has a glass transition temperature from -15.degree. C. to -50.degree. C., and wherein said second shell polymer is at least 15% by weight of the total weight of said first shell polymer and said second shell polymer;
and
(b) neutralizing said particles formed with a base so as to swell said core and form particles containing a void.

4 more elements

A method for improving the strength and opacity of paper or paperboard comprising incorporating a hollow sphere organic pigment into the formed wet sheet of paper or paperboard, the hollow sphere pigment formed by

(a) emulsion-polymerizing multistaged polymer particles comprising
(1) a hydrophilic core polymer formed from 5% to 100% by weight, based on the total weight of said core polymer, of a hydrophilic monoethylenically unsaturated monomer and from 0% to 95% by weight, based on the total weight of said core polymer, of at least one nonionic monoethylenically unsaturated monomer;
(2) a first shell polymer formed from 90% to 99.9% by weight, based on the total weight of said first shell polymer, of at least one nonionic monoethylenically unsaturated monomer and from 0.1% to 10% by weight, based on the total weight of said first shell polymer, of an acid functional monoethylenically unsaturated monomer, wherein said first shell polymer fully encapsulates said core polymer, wherein the ratio of the weight of said core polymer to the weight of said first shell polymer is from 1:2 to 1:100, and wherein said first shell polymer has a glass transition temperature greater than 50.degree. C.;
and
(3) a second shell polymer formed from 93% to 99.9% by weight, based on the total weight of said second shell polymer, of at least one nonionic monoethylenically unsaturated monomer and from 0.1% to 7% by weight, based on the total weight of said second shell polymer, of an acid functional monoethylenically unsaturated monomer, wherein said second shell polymer is formed in the presence of said first shell polymer, and wherein said second shell polymer has a glass transition temperature lower than 15.degree. C., and wherein said second shell polymer is at least 15% by weight of the total weight of said first shell polymer and said second shell polymer;
and
(b) neutralizing said particles formed with a base so as to swell said core and form particles containing a void;
and
(c) drying said sheet of paper or paperboard.

6 more elements

Dependencies are inferred from the claim text.