Water-based pressure-sensitive adhesive compositions

An emulsion composition comprising:

• a) water;
• b) a polymerizable surfactant having an unsaturated group that can undergo free radical polymerization;
• c) a first monomer composition comprising
• 1) an alkyl (meth)acrylate having an alkyl group with at least six carbon atoms;
• 2) a first acidic monomer having a glass transition temperature equal to at least 100° C. when measured as a homopolymer;
• and
• 3) a second acidic monomer having a glass transition temperature equal to no greater than 50° C. when measured as a homopolymer;
• and
• d) a second (meth)acrylate polymer in an amount of 0.5 to 15 weight percent based on a total weight of the first monomer composition, wherein
• the second (meth)acrylate polymer has a weight average molecular weight in a range of 3,000 to 150,000 Daltons,
• the second (meth)acrylate polymer has a glass transition temperature greater than −50° C., and
• the second (meth)acrylate polymer is formed from a second monomer composition comprising at least 10 weight percent of a non-acidic high Tg monomer based on a total weight of monomers in the second monomer composition, the non-acidic high Tg monomer having a glass transition temperature equal to at least 80° C. when measured as a homopolymer;
• wherein
• the emulsion has a first phase comprising water and a second phase dispersed as droplets within the first phase;
• and
• the droplets comprise a mixture comprising
• i) at least 85 weight percent of the first monomer composition;
• and
• ii) the second (meth)acrylate polymer, wherein the second (meth)acrylate polymer is not miscible with the first phase and wherein the second (meth)acrylate polymer is dissolved in the first monomer composition within the droplets.