Cross-linked foamed pressure sensitive adhesive and method for preparing the same

The method of clam 1, wherein the pressure sensitive adhesive has a density of 0.1 to 3.0 g/cm3 .

A method for producing a pressure sensitive adhesive comprising:

• (a) rolling into a sheet or extruding a mixture comprising a tacky acrylic polymer having a weight average molecular weight of at least 100,000 g/mol, a heat cross-linking agent, and a heat foaming agent that decomposes to generate a gas upon heating, wherein the foaming temperature of the heat foaming agent is lower than the reaction start temperature of the heat cross-linking agent, and wherein the mixture is free of expandable, polymeric microspheres, and
• (b) heating the extruded mixture to a temperature higher than the activation temperatures of both the cross-linking agent and the heat foaming agent to cause foaming and cross-linking,
• wherein the resulting cross-linked foamed pressure sensitive adhesive has cells that are exposed on a surface of the pressure sensitive adhesive.

A method for producing a pressure sensitive adhesive comprising:

• (a) rolling into a sheet or extruding a mixture comprising a tacky acrylic polymer having a weight average molecular weight of at least 100,000 g/mol, a heat cross-linking agent, and a heat foaming agent that decomposes to generate a gas upon heating, wherein the foaming temperature of the heat foaming agent is lower than the reaction start temperature of the heat cross-linking agent, and wherein the mixture is free of expandable, polymeric microspheres and said rolling or extruding step is performed at a temperature lower than (i) the foaming temperature and (ii) the reaction start temperature of the heat cross-linking agent, and
• (b) heating the extruded mixture to a temperature higher than the activation temperatures of both the cross-linking agent and the heat foaming agent to cause foaming and cross-linking.