# US 5,352,731 A · Thermally conductive silicone rubber composition containing organo polysiloxanes with high and low polymerization degrees and spherical aluminum oxide powder > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,352,731 A - Document ID: US5352731A - Status: Granted - Kind: A - Application number: 08/114,227 - Filed: 1993-09-01 - Granted: 1994-10-04 - Earliest claimed: 1991-04-26 - Assignees: Shin-Etsu Chemical Co., Ltd. - Inventors: Akio Nakano; Tsutomu Yoneyama; Nobumasa Tomizawa - Web page: https://patentgrep.com/patent/US5352731A ## CPC - C08K 3/22: of metals - C08L 83/04: Polysiloxanes - C08G 77/20: containing silicon bound to unsaturated aliphatic groups - C08G 77/24: halogen-containing groups - C08G 77/70: {Siloxanes defined by use of the MDTQ nomenclature} - C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09) - C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06) - C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS ## Abstract A silicone rubber composition having thermal conductivity higher than 5.times.10.sup.-3 cal/cm.multidot.sec.multidot..degree.C. and excellent workability in various molding processes, which comprises A) 95-50 parts by weight of an organopolysiloxane having an average polymerization degree of 6,000-12,000, B) 5-50 parts by weight of an organopolysiloxane having an average polymerization degree of 200-2,000, C) 500-1,200 parts by weight of a spherical aluminum oxide powder and D) a curing agent ample for curing the composition consisting of A) to C) . ## Claims ### Claim 1 A thermally conductive silicone rubber composition having thermal conductivity of 5.times.10.sup.-3 .multidot.cal/cm.multidot.sec.multidot..degree.C. or higher which consists essentially of A 95-50 parts by weight of a gummy organopolysiloxane having an average polymerization degree of 6,000-12,000, B) 5-50 parts by weight of an oily organpolysiloxane having an average polymerization degree of 200-2,000 and a viscosity of 600 to 120,000 centistokes, C) 500-1,200 parts by weight of a spherical aluminum oxide powder having an average particle size of 50 .mu.um or less and an average major axis diameter/minor axis diameter ratio of 1.0 to 1.4, and D) a curing agent in an amount sufficient to cure the composition. ### Claim 2 (depends on 1) The thermally conductive silicone rubber composition of claim 1, wherein said organopolysiloxane of component A) is represented by an average compositional formula, R.sub.n Si O .sub.(4-n)/z, wherein R is a monovalent substituted or unsubstituted hydrocarbon residue, and n is an positive number ranging from 1.95 to 2.05. ### Claim 3 (depends on 2) The thermally conductive silicone rubber composition of claim 2, wherein the main chain of said organopolysiloxane comprises dimethylsiloxane units. ### Claim 4 (depends on 3) The thermally conductive silicone rubber composition of claim 3, wherein part of the methyl groups of said main chain are replaced by vinyl groups, phenyl groups, trifluoropropyl groups or combinations thereof. ### Claim 5 (depends on 2) The thermally conductive silicone rubber composition of claim 2, wherein said monovalent hydrocarbon residue represented by R is an unsubstituted alkyl group, a halogenated alkyl group, an unsubstituted cycloalkyl group, a halogenated cycloalkyl group, an unsubstituted alkenyl group, a halogenated alkenyl group, an unsubstituted aryl group, a halogenated aryl group or combinations thereof. ### Claim 6 (depends on 5) The thermally conductive silicone rubber composition of claim 5, wherein said alkyl group is methyl, ethyl or propyl, said cycloalkyl group is cyclopentyl or cyclohexyl, said alkenyl group is vinyl or allyl, and said aryl group is phenyl or tolyl. ### Claim 7 (depends on 5) The thermally conductive silicone rubber composition of claim 5, wherein the halogen of said halogenated groups is chlorine or fluorine. ### Claim 8 (depends on 1) The thermally conductive silicone rubber composition of claim 1, wherein said organopolysiloxane of component B) is represented by an average compositional formula, R.sub.n Si O .sub.4-n)/z wherein R is a monovalent substituted or unsubstituted hydrocarbon residue, and n is a positive number ranging from 1.95 to 2.05. ### Claim 9 (depends on 8) The thermally conductive silicone rubber composition of claim 8, wherein the main chain of said organopolysiloxane comprises dimethylsiloxane units. ### Claim 10 (depends on 3) The thermally conductive silicone rubber composition of claim 3, wherein part of the methyl groups of said main chain are replaced by vinyl groups, phenyl groups, trifluoropropyl groups or combinations thereof. ### Claim 11 (depends on 2) The thermally conductive silicone rubber composition of claim 2, wherein said monovalent hydrocarbon residue represented by R is an unsubstituted alkyl group, a halogenated alkyl group, an unsubstituted cycloalkyl group, a halogenated cycloalkyl group, an unsubstituted alkenyl group, a halogenated alkenyl group, an unsubstituted aryl group, a halogenated aryl group or combinations thereof. ### Claim 12 (depends on 11) The thermally conductive silicone rubber composition of claim 11, wherein said alkyl group is methyl, ethyl or propyl, said cycloalkyl group is cyclopentyl group or cyclohexyl, said alkenyl group is vinyl or allyl, and said aryl group is phenyl or tolyl. ### Claim 13 (depends on 11) The thermally conductive silicone rubber composition of claim 11, wherein the halogen of said halogenated groups is chlorine or fluorine. ### Claim 14 (depends on 1) The thermally conductive silicone rubber composition of claim 1, wherein the mixing ratio of said component A) to said component B) ranges from 95/5 to 50/50. ### Claim 15 (depends on 1) The thermally conductive silicone rubber composition of claim 1, wherein said spherical aluminum oxide powder of component C) is an aluminum oxide powder prepared by process comprising a step of melting metallic aluminum and a step of oxidizing molten metallic aluminum with oxygen. ### Claim 16 (depends on 1) A curable silicone rubber article produced by molding a thermally conductive silicone composition of claim 1. ### Claim 17 (depends on 16) A cured silicone rubber article produced by heat curing an article of claim 16. ### Claim 18 (depends on 17) The silicone rubber article of claim 17 in the form of a sheet.