Hollow sphere organic pigment for paper or paper coatings

• US 6,139,961 A
• Filed: 05/06/1999
• Issued: 10/31/2000
• Est. Priority Date: 05/18/1998
• Status: Active Grant

• Current Assignee: Rohm and Haas Company (Dow, Inc.)
• Original Assignee: Rohm and Haas Company (Dow, Inc.)
• Inventors: Mlynar, Lubomir, Schultz, Barbara Jean, Blankenship, Robert Mitchell, Finch, William Christopher
• Primary Examiner(s): Mullis, Jeffrey C.
• Application Number:
  US09/306,488
• Time in Patent Office: 544 Days
• Field of Search: 428/402, 521/56, 521/59, 521/60, 521/65, 525/243
• US Class Current: 428/402
• CPC Class Codes: C08F 265/04 on to polymers of esters
• CPC Class Codes: C08F 265/06 Polymerisation of acrylate or methacrylate esters on to polymers thereof
• CPC Class Codes: C08F 285/00 Macromolecular compounds obtained by polymerising monomers on to preformed graft polymers
• CPC Class Codes: C08F 291/00 Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds according to more than one of the groups C08F251/00 - C08F289/00
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C09D 151/003 grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds C09D151/04, C09D151/06 take precedence
• CPC Class Codes: D21H 19/42 at least partly organic
• CPC Class Codes: D21H 21/18 Reinforcing agents
• CPC Class Codes: D21H 21/285 insoluble
• CPC Class Codes: D21H 21/54 being spherical, e.g. microcapsules, beads
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

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° C., the first shell having polymerized thereon a second shell polymer having a glass transition temperature of -15° C. to -50° 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.

Claims

1. 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°

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°

C. to -50°

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.

2. A waterborne paper or paperboard coating composition comprising the hollow sphere organic pigment of claim 1.

3. The coating composition of claim 2 which further comprises at least one pigment and from 2% to 25% by weight, based on the weight of pigment, of said hollow sphere organic pigment.

4. A method for improving the strength and opacity of a paper or paperboard coating comprising applying the coating composition of claim 2 or claim 3 to paper or paperboard and drying said coating composition.

5. A coated paper or paperboard bearing the dried coating composition of claim 2 or claim 3.

6. The coated paper or paperboard of claim 5 wherein said coating is applied by a size press.

7. 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°

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°

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.