Adhesive compositions, adhesive articles and methods for making the same

Abstract

Adhesive compositions comprising a high molecular weight acrylic copolymer and a low molecular weight copolymer are disclosed. Adhesive articles and methods of making adhesive compositions and articles are also described.

1 . An adhesive article comprising a layer of an adhesive composition comprising a blend of:
 (i) a first acrylic copolymer resulting from polymerization of one or more monomers A and one or more monomers B, wherein the first acrylic copolymer has a number average molecular weight, M n , ranging from about 150,000 to about 600,000; and   (ii) a second acrylic copolymer resulting from polymerization of one or more monomers C and one or more monomers D, wherein the second acrylic copolymer has a number average molecular weight, M n , ranging from about 10,000 to about 70,000;   wherein monomers B and monomers D have at least one reactive group that is capable of hydrogen bonding; the second acrylic copolymer comprises greater than about 10 total parts by weight of the monomers D based a total weight of the second acrylic copolymer; and the total parts by weight of the monomers D in the second acrylic copolymer is greater than the total parts by weight of the monomers B in the first acrylic copolymer,   and further wherein the adhesive composition is a cured, foam layer, and wherein the foam layer comprises microspheres.   
     
     
         2 . The adhesive article of  claim 1 , wherein the adhesive composition has a stress relaxation ratio G(300)/G(0.1) as measured by a Stress Relaxation Test at 70° C. of from about 0.10 to about 0.30 after exposure to electron beam radiation. 
     
     
         3 . The adhesive article of  claim 1 , wherein the adhesive article passes a static shear test by maintaining a hanging load of 500 g for at least 10,000 minutes at 70° C. 
     
     
         4 . The adhesive article of  claim 1 , wherein the adhesive article has a density of from about 0.30 g/cc to about 0.80 g/cc. 
     
     
         5 . The adhesive article of  claim 1 , further comprising a first adhesive layer on a first outer surface of the layer of the adhesive composition and a second adhesive layer on a second outer surface of the layer of the adhesive composition opposite the first adhesive layer. 
     
     
         6 . The adhesive article of  claim 1 , further comprising a controlled degree of crosslinking between the first acrylic copolymer and the second acrylic copolymer. 
     
     
         7 . A method of making an adhesive article, said method comprising:
 providing an electron beam generating apparatus having a first control for an accelerating voltage and a second control for a dose;   providing a material to be cured having a composition, a thickness, and a density;   determining one or more desired properties capable of resulting from a controlled amount of crosslinking using the electron beam generating apparatus; and   using a Minimum Calculated Core Cure value of the material based on dose-depth profile calibration curves for the electron beam generating apparatus and for the material to be cured, crosslinking the material at a voltage and dose that results in the one or more desired properties.   
     
     
         8 . The method of  claim 7 , further comprising:
 preparing the dose-depth profile calibration curves for the electron beam generating apparatus and for the material to be cured based on the composition, thickness, and density of the material; and   determining the Minimum Calculated Core Cure value based on the dose-depth profile calibration curves.   
     
     
         9 . The method of  claim 7 , wherein the one or more desired properties comprise stress relaxation, shear strength, or a combination thereof 
     
     
         10 . The method of  claim 7 , wherein the material after curing exhibits a cure gradient through a cross section of the thickness of the material. 
     
     
         11 . The method of  claim 7 , wherein the material comprises a blend of:
 (i) a first acrylic copolymer resulting from polymerization of one or more monomers A and one or more monomers B, wherein the first acrylic copolymer has a number average molecular weight, M n , ranging from about 150,000 to about 600,000; and   (ii) a second acrylic copolymer resulting from polymerization of one or more monomers C and one or more monomers D, wherein the second acrylic copolymer has a number average molecular weight, M n , ranging from about 10,000 to about 70,000;   wherein monomers B and monomers D have at least one reactive group that is capable of hydrogen bonding; the second acrylic copolymer comprises greater than about 10 total parts by weight of the monomers D based a total weight of the second acrylic copolymer; and the total parts by weight of the monomers D in the second acrylic copolymer is greater than the total parts by weight of the monomers B in the first acrylic copolymer.