# US 7,612,121 B2 · Cross-linked foamed pressure sensitive adhesive and method for preparing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,121 B2 - Document ID: US7612121B2 - Status: Granted - Kind: B2 - Application number: 10/363,447 - Filed: 2001-08-29 - Published: 2004-02-19 - Granted: 2009-11-03 - Earliest claimed: 2001-08-29 - Assignees: 3M Innovative Properties Company - Inventors: Yasuhiro Mino - Web page: https://patentgrep.com/patent/US7612121B2 ## CPC - C08J 9/32: from compositions containing microballoons, e.g. syntactic foams - C09J 5/08: using foamed adhesives - C09J 7/10: without carriers - C09J 11/02: Non-macromolecular additives - C08J 2203/22: Expandable microspheres, e.g. Expancel® - C08J 2207/02: Adhesive - C08J 2333/08: Homopolymers or copolymers of acrylic acid esters - C08L 33/00: Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers - C09J 2433/00: Presence of (meth)acrylic polymer - Y10T 428/249953: Composite having voids in a component [e.g., porous, cellular, etc.] - Y10T 428/249985: Composition of adhesive or bonding component specified - Y10T 428/31504: Composite [nonstructural laminate] - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - C09J: ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES (preparation of glue or gelatine C09H) - C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A cross-linked foamed pressure sensitive adhesive having excellent stress relaxing property, restoration property and solvent resistance brought forth by uniform and sufficient cross-linking and foaming irrespective of transmissibility of ultraviolet rays and electron beams to components, and free from drawbacks inherent to low molecular weight acrylic copolymers. A cross-linked foamed pressure sensitive adhesive having restoration property, prepared by heating a heat cross-linkable and heat foamable composition containing a tacky polymer having a molecular weight of at least 100,000, a heat cross-linking agent and a heat foaming agent to cause cross-linking and foaming. ## Claims ### Claim 1 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 mixture is free of expandable, polymeric microspheres, and (b) heating the 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 at substantially the same time, wherein the resulting cross-linked foamed pressure sensitive adhesive has a restorative property. ### Claim 2 (depends on 1) The method of claim 1, wherein when said pressure sensitive adhesive has an initial thickness of 10 mm and is compressed to 25 % of the initial thickness at a rate of 10 min/mm in a thickness-wise direction, a compressive load is 0.1 to 300 N/cm2. ### Claim 3 (depends on 1) The method of claim 1, wherein the tacky polymer is obtained by polymerizing a polymerizable precursor comprising a cross-linikable acrylic monomer. ### Claim 4 (depends on 1) The method of claim 1, wherein the mixture further comprises a radiation-impermeable component. ### Claim 5 The method of clam 1, wherein the pressure sensitive adhesive has a density of 0.1 to 3.0 g/cm3 . ### Claim 6 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. ### Claim 7 (depends on 1) The method of claim 1, wherein the tacky polymer is obtained by polymerizing a non-cross-likable acrylic monomer and a cross-likable acrylic monomer. ### Claim 8 (depends on 3) The method of claim 3, wherein the cross-likable acrylic monomer is present in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the polymerizable prepolymer. ### Claim 9 (depends on 7) The method of claim 7, wherein the cross-likable acrylic monomer is present in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the non-cross-likable acrylic monomer. ### Claim 10 (depends on 6) The method of claim 6, wherein said pressure sensitive adhesive has a thickness of up to 10 cm. ### Claim 11 (depends on 6) The method of claim 6, wherein said rolling or extruding step comprises rolling or extruding at a temperature lower than foaming temperature and the reaction start temperature of the heat cross-linking agent. ### Claim 12 (depends on 6) The method of claim 6, wherein said rolling or extruding step comprises an extruding step. ### Claim 13 (depends on 6) The method of claim 6, wherein said mixture further comprises a non-cross-linkable rubber, elastomer, or thermoplastic polymer. ### Claim 14 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. ### Claim 15 (depends on 14) The method of claim 14, wherein said heating step comprises heating the 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 at substantially the same time. ### Claim 16 (depends on 14) The method of claim 14, wherein said heating step comprises: heating to a temperature above the foaming temperature of the heat foaming agent but lower than the reaction start temperature of the heat cross-linking agent; and then heating to a temperature above the reaction start temperature of the heat cross-linking agent. ### Claim 17 (depends on 14) The method of claim 14, further comprising: co-extruding or laminating an additional layer to the pressure sensitive adhesive. ### Claim 18 (depends on 14) The method of claim 14, wherein said mixture further comprises a non-cross-linkable rubber, elastomer, or thermoplastic polymer. ### Claim 19 (depends on 6) The method of claim 6, wherein the mixture further comprises a radiation-impermeable component selected from a pigment, a colorant, a metal filler, an inorganic filler, or a combination thereof.