Patent GB-1055777-A (GB)
Title: Curable silicone compositions
IPC: H01B3/46
Filed: 1964-11-03
Abstract: A curable composition consists of (1) a siloxane polymer of viscosity greater than 500 c. composed of CH3RSiO units and an average of at least 2 <FORM:1055777/C3/1> units per molecule but not more than 2 mole per cent, where R is alkyl or aryl not more than 40% being aryl and a=0-2, (2) a polymer of general formula <FORM:1055777/C3/2> where R1 is a hydrogen atom or a hydrocarbon group, x is at least 4, y=0-3750, x+y is not more than 5000 and y is not more than 3x or a cyclic siloxane of formula (RHSiO)b where b is at least 4, (3) a liquid olefin of b.p. at least 100 DEG  C. and formula <FORM:1055777/C3/3> where Q is a hydrocarbon group and Q1 is hydrogen or, when Q is aryl, a lower alkyl radical and (4) a platinum catalyst, the amount of SiH groups being at least sufficient to react with the SiCH=CH2 groups and 1% of olefin (3) and the amount of (3) being 1-45% of the mixture and not more than 25% in excess of that required to react with the available SiH groups after their reaction with the SiCH=CH2 groups.  R groups specified are methyl, ethyl, phenyl and cyclohexyl.  R1 groups specified are methyl, octyl, octadecyl, isopropyl, vinyl, allyl, hexenyl, cyclohexyl, cyclohexenyl, cyclopentyl, phenyl, xenyl, tolyl, benzyl and b -phenylethyl. The quantity of olefin (3) may be no more than is required to react with the SiH groups.  Olefins specified are styrene, a -methyl styrene, vinyl toluene, 1-octene, 1-octadecene, a -isopropyl styrene, 4-methyl oct-1-ene, 8-phenyl oct-1-ene, 3-phenylpropylene, 2-methyl-3-phenyl-propylene and divinyl benzene. Catalysts specified are finely divided platinum, platinum dispersed on charcoal, chloroplatinic acid and complexes of platinic chloride with ethylene, propylene, butadiene and cyclohexene. 0.5-200 p.p.m. may be used.  Component (1) may also include up to 50% of a polymer of (CH3)3SiO 1/2 , SiO2 and (CH3)2CH2= CHSiO 1/2 units containing 1.5-3.5% of vinyl radicals the ratio of silicon end-groups to SiO2 groups being between 0.6:1 and 1:1. This may be prepared either by cohydrolysing a mixture of SiX4, Me3SiX and Me2ViSiX where X = halogen or alkoxyl or by treating SiO2 with Vi2SiCl or Vi2Me4Si2O simultaneously with or subsequent to Me3SiOSiMe3 or Me3SiCl.  The composition may contain up to 200% of a filler which may be treated with an organosiloxane to render them hydrophobic. Fillers specified are fume silica, aluminium silicate, quartz, CaCO3, zirconium silicate, alumina, ZnO, titania and ferric oxide. An antioxidant, e.g. N,N1-di-a -naphthyl-p-phenylene diamine, may be present.  The compositions which may be cured at 50-100 DEG  C. may be used to encase electronic circuits.  In examples, the following silicon containing polymers are used: a vinyl-ended dimethyl siloxane of viscosity 2000 c. (I, II, IV and V), Me3SiO(MeHSiO)60SiMe3 (I, II, IV and V), ViMePhSiO(Me2SiO)300SiPhViMe (III), Me3SiO (MeHSiO)45(Me2SiO)15SiMe3 (III), Et2ViSiO(Me EtSiO)300(EtViSiO)3SiViEt2 (VI), (SiO2)31(Me3 SiO 1/2 )18(Me2ViSiO 1/2 )2 (VI), (C18H37)3SiO(PhHSi O)50(Me2SiO)100Si(C18H37)3 VI) PhMeViSiO(Me2 SiO)500SiViMePh (VII), (SiO2)17(Me3SiO 1/2 )14(Me2\t ViSiO 1/2 )3 (VII), CH3C6H4(C6H11)2SiO(MeH <FORM:1055777/C3/4> ViSi[(OSiMe2)100OSiViMe2]3 (VIII), (MeHSiO)4 (VIII), ViSi[(OSiMe2)70(OSiPhMe)30OSiMe2Vi]3 (IX) and Pr2HSiO(MeHSiO)80PhMeSiO)2SiPr2 H (IX).