Expandable microspheres and methods of making and using the same
First Claim
1. An expandable microsphere comprising:
- a gas impermeable shell encapsulating at least one blowing agent, said gas impermeable shell including;
a first polymeric layer surrounding said at least one blowing agent; and
a second polymeric layer at least substantially encapsulating said first polymeric layer,wherein said second polymeric layer includes a homo- and/or co-polymer of at least one monomer selected from the group consisting of a monomer having a weight average Tg of at least 85°
C. and a chemically reactive monomer;
wherein said at least one monomer is selected from the group consisting of acrylonitrile, vinylidene chloride, methyl methacrylate, tetraethylene glycol dimethacrylate, 2,3-epoxypropyl acrylate, methacrylonitrile, glycidyl methacrylate, methacrylic acid, and vinyl benzyl chloride;
and wherein said second polymeric layer has a weight average Tg that is greater than a weight average Tg of the first polymeric layer.
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Accused Products
Abstract
Expandable microspheres formed by suspension polymerization using a shot growth method are provided. The microspheres are formed of a continuous, gas impermeable shell surrounding a blowing agent. The shell includes a first polymer layer formed from primary monomers and a second layer that includes a chemically reactive monomer or a high Tg monomer. To form the microspheres, the primary monomers are polymerized in a reaction vessel to an approximate 90% polymerization, at which time a secondary monomer that is either a monomer having a Tg of at least 85° C. or a chemically reactive monomer, is added to the reaction vessel to drive the polymerization reaction to completion. The outer layer thus contains either a larger amount of the high Tg monomer or a chemically reactive monomer that possesses the ability to covalently bond a cationic species. The microspheres may be used in papermaking processes to increase the paper bulk.
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Citations
21 Claims
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1. An expandable microsphere comprising:
a gas impermeable shell encapsulating at least one blowing agent, said gas impermeable shell including; a first polymeric layer surrounding said at least one blowing agent; and a second polymeric layer at least substantially encapsulating said first polymeric layer, wherein said second polymeric layer includes a homo- and/or co-polymer of at least one monomer selected from the group consisting of a monomer having a weight average Tg of at least 85°
C. and a chemically reactive monomer;wherein said at least one monomer is selected from the group consisting of acrylonitrile, vinylidene chloride, methyl methacrylate, tetraethylene glycol dimethacrylate, 2,3-epoxypropyl acrylate, methacrylonitrile, glycidyl methacrylate, methacrylic acid, and vinyl benzyl chloride; and wherein said second polymeric layer has a weight average Tg that is greater than a weight average Tg of the first polymeric layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, 21)
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13. A method of forming an expandable microsphere comprising:
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mixing primary monomers selected from nitrile containing monomers, acrylic ester monomers, methacrylic ester monomers, vinyl esters, vinyl halide monomers and combinations thereof, at least one blowing agent, a crosslinking monomer, a polymerization initiator, and a stabilizer system in a reaction vessel for a period of time sufficient to achieve an approximate 90% polymerization of said primary monomers and form a first polymeric layer surrounding said blowing agent; and adding a secondary monomer selected from monomers having a weight average Tg of at least 85°
C. and chemically reactive monomers to said reaction vessel to form a second polymeric layer at least substantially surrounding said first polymeric layer and form an expandable microsphere;to form an expandable microsphere comprising; a gas impermeable shell encapsulating at least one blowing agent, said gas impermeable shell including; a first polymeric layer surrounding said at least one blowing agent; and a second polymeric layer at least substantially encapsulating said first polymeric layer, wherein said second polymeric layer includes a homo- and/or co-polymer of at least one monomer selected from the group consisting of a monomer having a Tg of at least 85°
C. and a chemically reactive monomer;wherein said at least one monomer is selected from the group consisting of acrylonitrile, vinylidene chloride, methyl methacrylate, tetraethylene glycol dimethacrylate, 2,3-epoxypropyl acrylate, methacrylonitrile, glycidyl methacrylate, methacrylic acid, and vinyl benzyl chloride; and wherein said second polymeric layer has a weight average Tq that is greater than a weight average Tg of the first polymeric layer. - View Dependent Claims (14, 15, 16, 17)
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19. A paper comprising:
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a web of cellulose fibers; and a plurality of expandable microspheres, said expandable microspheres including; a gas impermeable shell encapsulating at least one blowing agent, said gas impermeable shell including; a first polymeric layer surrounding said at least one blowing agent; and a second polymeric layer at least substantially encapsulating said first polymeric layer, wherein said second polymeric layer includes a homo- and/or co-polymer of at least one monomer selected from the group consisting of a monomer having a weight average Tg of at least 85°
C. and a chemically reactive monomer;wherein said at least one monomer is selected from the group consisting of acrylonitrile, vinylidene chloride, methyl methacrylate, tetraethylene glycol dimethacrylate, 2,3-epoxypropyl acrylate, methacrylonitrile, glycidyl methacrylate, methacrylic acid, and vinyl benzyl chloride; and wherein said second polymeric layer has a weight average Tg that is greater than a weight average To of the first polymeric layer. - View Dependent Claims (20)
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Specification