Adhesive acrylic copolymers with a broad molecular weight distribution
AssigneeExxon Chemical Patents Inc.
InventorHenry W. Yang
Life of this patent
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Abstract
Acrylic copolymer PSA compositions having enhanced peel strength without substantially decreasing shear properties have been formulated by producing the copolymer with a broad molecular weight distribution such that the ratio M.sub.w /M.sub.n is above 6, preferably above 10. The alkyl (meth)acrylate and (meth)acrylic acid monomers are emulsion polymerized over a temperature profile wherein the difference between the maximum and minimum polymerization temperatures is at least about 40.degree. C. and less than about 70.degree. C., preferably using a redox initiator system such as bromate/bisulfite.
Claims24
A pressure sensitive adhesive comprising an acrylic copolymer comprising:
- from about 10 to about 50 percent by weight of lower alkyl acrylate, said lower alkyl having 1 to 4 carbon atoms, from about 25 to about 88 percent by weight of an upper alkyl acrylate, said upper alkyl having 5 to 14 carbon atoms, and from about 1 to about 15 percent by weight of a acrylic acid, said copolymer having a unimodal Gaussian type molecular weight distribution of at least about 6 with a minimum Mn of about 10,000.
A pressure sensitive adhesive latex emulsion, comprising:
- an acrylic copolymer comprising about 10 to about 50 percent by weight of a lower alkyl acrylate, said lower alkyl having 1 to 4 carbon atoms, from about 25 to about 88 percent by weight of an upper alkyl acrylate, said upper alkyl having 5 to 14 carbon atoms, and from about 1 to about 15 percent by weight of acrylic acid, said copolymer having an M.sub.w /M.sub.n ratio of at least about 6 defined by a Gaussian distribution curve, and having a Tg of from about -70.degree. C. to about 10.degree. C. and is essentially from of gel.
A pressure sensitive adhesive latex emulsion, comprising:
- an acrylic copolymer essentially free of gel, comprising:
- from about 10 to about 50 percent by weight of a lower alkyl acrylate, said lower alkyl having 1 to 4 carbon atoms, from about 25 to about 88 percent by weight of an upper alkyl acrylate, said upper alkyl having from 5 to 14 carbon atoms, and from about 1 to about 15 percent by weight of acrylic acid, said copolymer having an M.sub.w /M.sub.n defined by a Gaussian distribution curve of at least about 6, a Tg of from about -70.degree. C. to about 10.degree. C., said copolymer being produced under emulsion polymerization conditions in the presence of a redox polymerization initiator having an inititation temperature between about -40.degree. C. to about 80.degree. C.
An acrylic copolymer having an M.sub.w M.sub.n of at least 6, with a minimum M.sub.n of about 10,000, said acrylic copolymer being obtained by the polymerization of 10 to 50 percent by weight of a lower alkyl (meth) acrylate, from about 25 to 88 percent by weight of an upper alkyl (meth) acrylate and from about 1 to about 15 percent of a (meth) acrylic acid, said lower alkyl having from 1 to 4 carbon atoms, said upper alkyl having from 5 to 14 carbon atoms, with a temperature gradient during polymerization, wherein the difference between the minimum and maximum polymerization temperature is at least 40.degree. C.
An acrylic copolymer having an M.sub.w M.sub.n of at least 6, with a minimum M.sub.n of about 10,000, said acrylic copolymer being obtained by the polymerization of 10 to 50 percent by weight of a lower alkyl (meth) acrylate, from about 25 to 88 percent by weight of an upper alkyl (meth) acrylate and from about 1 to about 15 percent of a (meth) acrylic acid, said lower alkyl having from 1 to 4 carbon atoms, said upper alkyl having from 5 to 14 carbon atoms, with a polymerization temperature profile wherein the difference between the minimum and maximum polymerization temperature is at least 40.degree. C., wherein the polymerization takes place in the presence of a redox polymerization initiator, and initiator having an initiation temperature between about -40.degree. C. to about 80.degree. C.
An acrylic copolymer having an M.sub.w M.sub.n of at least 6, with a minimum M.sub.n of about 10,000, said acrylic copolymer being obtained by the polymerization of 10 to 50 percent by weight of a lower alkyl (meth) acrylate, from about 25 to 88 percent by weight of an upper alkyl (meth) acrylate and from about 1 to about 15 percent of a (meth) acrylic acid, said lower alkyl having from 1 to 4 carbon atoms, said upper alkyl having from 5 to 14 carbon atoms, under polymerization conditions in the presence of a redox polymerization initiator, said initiator having an initiation temperature between about -40.degree. C. to about 80.degree. C. and a temperature profile wherein the difference between the minimum an maximum polymerization temperature is at least 40.degree. C.
The acrylic copolymer of claim 22, having a T.sub.g from about -70.degree. C. to about 10.degree. C.
An acrylic copolymer latex wherein said copolymer has an M.sub.w /M.sub.n of at least 6, said M.sub.w /M.sub.n defined by an unimodal of Gaussian distribution curve, said acrylic copolymer latex being obtained by emulsifying monomers, said monomers comprising about 10 to about 50 percent by weight of a lower alkyl (meth) acrylate, from about 25 to about 88 percent by weight of an upper alkyl (meth) acrylate and from about 1 to about 15 percent by weight of (meth) acrylic acid in an aqueous medium, said lower alkyl having from 1 to 4 carbon atoms, said upper alkyl having from 5 to 14 carbon atoms, polymerizing the emulsified monomers in the presence of a redox polymerization initiator, said initiator having an initiation temperature between about -40.degree. C. to about 80.degree. C.
Dependencies are inferred from the claim text.