Patent GB-797606-A (GB)
Title: Improvements relating to hydrocarbon rubber-vinyl containing organopolysiloxane compositions
IPC: C08L83/04
Filed: 1955-08-05
Abstract: A vulcanizable mixture comprises from 25 to 95 per cent (by weight) of a hydrocarbon gum and from 5 to 75 per cent of an organopolysiloxane gum having the formula <FORM:0797606/IV (a)/1> where a has a value of 0.0086 to 0.18, b has a value of 1.80 to 2.0014, a+b has a value of 1.98 to 2.01, and each R is an alkyl, aryl, cycloalkyl, aralkyl, alkaryl or haloaryl radical, at least 50 mol. per cent of the radicals being methyl radicals.  Siloxanes that may be used are disclosed in Specifications 586,187, [Group IV], 620,693, 785,384.  Gums specified are natural gum, butyl gum (i.e. a rubbery copolymer of a major proportion of a mono-olefin, e.g. isobutylene and 2-ethylbutene-1, and a low molecular weight conjugated diolefin, e.g. butadiene, isoprene, cyclopentadiene-1 : 3, and hexadiene-2 : 4), styrene-butadiene gum, butadiene-acrylonitrile gum, neoprene gum, polyacrylic ester gum, polysulphide gum and isobutylene gum.  The mixture, with or without inorganic fillers, e.g. carbon black, zinc oxide, clay, whiting, slate flour, silica, silica aerogel and diatomaceous earth, in amount up to 50 per cent by weight of the mixture, may be vulcanized in known manner with vulcanizing agents, e.g. sulphur, sulphur halides and sulphides and with or without (a) curing accelerators, e.g. mercaptobenzothiazole, diphenylguanidine, tetramethylthiuramdisulphide, zinc dimethyldithiocarbamate and benzothiazodisulphide, (b) acelerator activators, e.g. zinc oxide and stearic acid, and (c) additives such as softeners, odourants and pigments.  In examples, mixtures of a vinyl-containing organopolysiloxane and (1) pale natural crepe gum, carbon black and zinc oxide, (2, 8) butadiene-styrene gum, carbon black and (8) zinc oxide, (3) butadiene-acrylonitrile gum and carbon black, (4 to 7) butyl gum (isoprene-isobutylene copolymer) zinc oxide and carbon black with or without silica aerogel, or calcium carbonate and diatomacious earth, are vulcanized with sulphur and benzothiazodisulphide.  The mixtures are useful per se as dielectric material in transformers and capacitors, and the products are useful as gasket material, wire coating material, fillers for electric cables, encasing material for transformers, capacitators and for making tyres for aircraft, automotive vehicles and military equipment.  Specifications 794,119 also is referred to.ALSO:A vulcanizable mixture comprises from 25 to 95 per cent (by weight) of a natural hydrocarbon gum and from 5 to 75 per cent of an organopolysiloxane gum having the formula <FORM:0797606/V/1> where a has a value of 0,0086 to 0,18, b has a value of 1,80 to 2,0014, a + b has a value of 1,98 to 2,01, and each R is an alkyl, aryl, cycloalkyl, aralkyl, alkaryl or haloaryl radical, at least 50 mol per cent of the radicals being methyl.  Siloxanes that may be used are disclosed in Specifications 586,187 [Group IV], 620,693 and 785,384 [both in Group IV(a)].  The mixture with or without inorganic fillers, e.g., carbon black, zinc oxide, whiting, slate flour, silica aerogel and diatomaceous earth, in amount up to 50 per cent by weight of the mixture, may be vulcanized in known manner with vulcanizing agents, e.g., sulphur, sulphur halides and sulphides, and with or without (a) curing accelerators, e.g., mercaptobenzothiazole, diphenylguanidine, tetramethylthiuramdisulphide, zinc dimethyl dithiocarbamate and benzothiazodisulphide, (b) accelerator activators, e.g. zinc oxide and stearic acid, and (c) additives such as softeners, odourants and pigments.  In example (1) a mixture of vinyl-containing organopolysiloxane, pale natural crepe gum, carbon black and zinc oxide, is vulcanized with sulphur and benzothiazodisulphide.  The mixtures are useful per se as dielectric material in transformers and capacitors, and the products are useful as gasket material, wire-coating material, fillers for electric cables, encasing material for transformers, capacitors and for making tyres for aircraft, automotive vehicles and military equipment. Specification 794,119 [Group IV(a)] also is referred to.