GB1096898A - Improvements in or relating to acrylic polymers - Google Patents

Abstract

A copolyme which cures on exposure to moisture to form an elastomer consists of (a) 100 molar parts of <FORM:1096898/C3/1> (b) 1.0 to 8 molar parts of <FORM:1096898/C3/2> (c) 0 to 50 molar parts of CH2=CA2 and (d) 0.5 to 4 molar parts of HSR11 (Si Xy\ Z3- y)z, the molar quantity of (b) being 0.7 to 4 times the molar quantity of (d), wherein R is H or CH3, the majority of R's in (a) being H; R1 is an alkyl radical containing not more than 12 carbon atoms; Q is an alkylene radial; R11 is a mono- or divalent hydrocarbon radical free from aliphatic unsaturation, the adjacent S atom being bonded to an aliphatic carbon atom; X is a hydrolysable atom or group; Z is a monovalent hydrocarbon radical free from aliphatic unsaturation and containing not more than 7 carbon atoms; A is H, Cl or an acetate, phenyl, nitrile or vinyl radical, or least one A being H or Cl; x has an average value of 0 to 1 and y an average value of 1 to 3. Suitable R1, Q R11, X and Z radicals and compounds (a), (b), (c) and (d) are given, e.g. (a) may be ethyl, methyl, n-butyl or decyl acrylate, or methyl or n-butyl methacrylate, or mixtures thereof and (c) may be styrene, acrylonitrile, vinylidene chloride, vinyl chloride, butadiene or vinyl acetate or a mixture of monomers such as of styrene and vinylidene chloride. The polymerization may be carried out using 0.02 to 1 molar part of a free radical forming catalyst e.g. tertiary butyl perbenzoate, dibenzoyl peroxide, N,N1-azobis (isobutyronitrile), dicumyl peroxide, tertiary butyl peracetate, ammonium persulphate, 2,5-dimethyl - 2,5 - dihydroperoxyhexane or bis (2,4-dichlorobenzoyl) peroxide. On exposure to moisture, preferably at above 5 DEG C., the polymers yield infusible elastomers, curing being accelerated by silanol condensation catalysts. Cross-linking agents e.g. ethyl polysilicate and methyltriethoxy-silane may also be added to the copolymers, as can inorganic fillers. In Examples 1 to 3 ethyl acrylate is copolymerized in benzene, using benzoyl peroxide, as catalyst, with (1) vinyl trimethoxysilane (2) <FORM:1096898/C3/3> and (3) <FORM:1096898/C3/4> compound (d) being HS(CH2)3Si(OCH3)3 in each case. In Example 4, ethyl acrylate and acrylonitrile are copolymerized with the (b) monomer used in (2) in the presence of the same (d) compound, using N,N1-azobisisobutyronitrile as catalyst and benzene as solvent. The monomer in Example 5 are n-butyl acrylate, methyl methacrylate and <FORM:1096898/C3/5> (d) being 2-ethylhexyl mecaptan, the catalyst tertiary butyl perbenzoate and the solvent toluene. In Example 6, methyl acrylate, n-propyl methacrylate, vinyl chloride and the compound <FORM:1096898/C3/6> are copolymerized, (d) being 2-phenylpropyl mercaptan, the catalyst tert-butyl peracetate and the solvent cyclohexane. The copolymers of Examples 1 to 4 are cured using a catalyst selected from dibutyl tin dilaurate, tetraisopropyl titanate and Sn Cl4.