Pressure-sensitive adhesives based on emulsion polymers

A pressure-sensitive adhesive comprising:

• (a) from about 80 to about 90% by weight of total polymers of a first emulsion polymer having a glass transition temperature less than about -10.degree. C. and a gel content greater than about 50% by weight and comprising:
• i. at least one alkyl ester of acrylic acid containing from 1 to about 10 carbon atoms in the alkyl group, the total alkyl ester present in a total amount of from about 95 to about 97.5% by weight of the polymer, and
• ii. a mixture of acrylic acid and methacrylic acid present in a total amount of from about 2.5% to about 5% by weight of the first polymer and wherein the weight ratio of acrylic acid to methacrylic acid is from about 1:1 to about 1:3;
• b. an anionic surfactant system comprising, based on the weight of the anionic surfactant system and the first polymer:
• i. from about 1% to about 2% by weight of a sodium alkyl ether sulfate of the formula:
• CH.sub.3 --(CH.sub.2)--.sub.n CH.sub.2 O(C.sub.2 CH.sub.2 O)SO.sub.3 Na
• wherein N is from 6 to about 12 and x is from 20 to about 30,
• ii. from about 0.15 to about 0.3% by weight, disodium ethoxylated alkyl alcohol half ester of sulfosuccinic acid wherein the alkyl group contains from 10-12 carbon atoms, and
• iii. from about 0.1 to about 0.2% by weight, of a sodium dialkyl sulfosuccinate of the formula:
• ##STR3## wherein each Y is independently from about 6 to about 18;
• and (c) from about 20 to about 10% by weight of total polymers of a second tackifying emulsion polymer formed from about 55 to 90% by weight of a first monomer which is at least one alkyl acrylate containing from 4 to about 8 carbon atoms in the alkyl group, from 10 to about 20% by weight of a compound selected from the group unsaturated carboxylic acids, and hydroxy ethyl methacrylate, from 0 to about 15% by weight of at least one vinyl ester, and from 0% to about 15% by weight methyl acrylate, said mixture of emulsion polymer and said second tackifying polymer having a glass transition temperature of about -15.degree. to about -50.degree. C., said second tackifying emulsion polymer formed in the presence of anionic and nonionic surfactants, and a chain transfer agent.

A pressure-sensitive adhesive comprising:

• (a) from about 70 to about 95% by weight of total polymers of a first emulsion polymer having a glass transition temperature less than about -10.degree. C. and a gel content greater than about 50% by weight and comprising:
• i. butyl acrylate present in a total amount of from about 95 to about 97.5% by weight of the first emulsion polymer, and
• ii. a mixture of acrylic acid and methacrylic acid present in a total amount of from about 2.5 to about 5% by weight of the first polymer and wherein the weight ratio of acrylic acid to methacrylic acid is from about 1:1 to about 1:3;
• (b) an anionic surfactant system comprising, based on the weight of the anionic surfactant system and the first polymer:
• i. from about 1 to about 2% by weight of a sodium alkyl ether sulfate of the formula:
• CH.sub.3 --(CH.sub.2)--.sub.n CH.sub.2 O(CH.sub.2 CH.sub.2 O)SO.sub.3 Na
• wherein N is from 6 to about 12 and x is from 20 to about 30,
• ii. from about 0.15% to about 0.3% by weight, disodium ethoxylated alkyl alcohol half ester of sulfosuccinic acid wherein the alkyl group contains from 10-12 carbon atoms, and
• iii. from about 0.1% to about 0.2% by weight, of a sodium dialkyl sulfosuccinate of the formula:
• ##STR4## wherein each Y is independently from about 6 to about 18;
• and (c) from about 5 to about 30% by weight of total polymers of a second tackifying emulsion polymer formed from about 55 to 90% by weight of a blend of butyl acrylate and 2-ethyl hexyl acrylate, from 10 to about 20% by weight of a blend of methacrylate acid and acrylic acid, said first emulsion polymer and said second tackifying emulsion polymer having a glass transition temperature of about -15.degree. to about -50.degree. C., said second emulsion polymer formed in the presence of anionic and nonionic surfactants, and a chain transfer agent.