Patent GB-899098-A (GB)
Title: Vulcanisable silicone rubber-forming compositions
Filed: 1959-09-14
Abstract: Natural or synthetic aluminium silicates, e.g. natural and synthetic zeolites (the latter being described and claimed in Specification 773,233), permutite, heulandite, natrolite, thomsonite, analcime, kaolinite, montmorillonite, bentonite, floridine, commercial clays and bleaching earths, having absorbed therein a cross-linking agent and/or a non-peroxidic curing catalyst for silicone rubbers (see Group IV(a)), may be coated with a hydrophobic material, e.g. a triorganosilyl- or hydroxy-terminated-silicone oil, paraffin oil or a softener.  In Example (5) particles of "Linde's Molecular Sieve" containing absorbed therein hexaethoxydisiloxane and dibutyl tin dilaurate, were coated with a silicone oil.  In Example (3) sandblasted and degreased sheet iron and masonry were coated by spraying with a composition comprising a liquid hydroxy-terminated dimethylpolysiloxane, quartz meal and a synthetic zeolite having absorbed therein tetraethyl silicate and dibutyl tin dilaurate and hydrophobed with a coating of a dimethylsilicone oil, and the coatings were cured to rubbers at room temperature by atmospheric humidity (which drives the curing system out of the zeolite).ALSO:A silicone rubber-forming composition consists essentially of (1) an organopolysiloxane of the general formula XO(R2SiO)nX, wherein X is H or an alkyl radical, each R is an alkyl, alkenyl, aryl or halo-alkyl or halo-aryl radical and n has an average value of at least 50, (2) a filler, (3) a cross-linking agent, (4) a nonperoxidic curing catalyst, and (5) a porous aluminium silicate having absorbed therein (3) and/or (4).  Ingredients specified are:-fillerssilicas, C blacks, quartz meal, asbestos meal, titania, the oxides of Zn, Fe and Mg, CaCO3, glass frit, cork powder and sawdust; cross-linking agentsethyl ortho- and polysilicates, hexabutoxy disiloxane, methyltriethoxysilane, phenyltripropoxysilane, phenylsilane-triol, triethoxysilane, tetra- and hexa-ethoxydisiloxanes, methyldibutoxysilane, tetramethylcyclotetrasiloxane, tetrabutyl titanate, polymeric butyl titanate, aluminium isopropylate, boric acid triallyl ester and butyl metaborate; catalysts-stearic, trifluoracetic and perchloric acids, dibutylamine, piperidine, tetramethylammonium hydroxide, lead octoate, tin ricinoleate, cobalt hexoate, aluminium acetyl acetonate, zirconium acetoacetate, dibutyl tin dilaurate and dioctyl tin dimaleate; aluminium silicatesnatural and synthetic zeolites (as described and claimed in Specification 773,233), permutite, heulandite, natrolite, thomsonite, analcime, kaolinite, montmorillonite, bentonite, floridine, commercial clays and bleaching earths.  The silicate itself may act as a filler.  The compositions can be stored at room temperature and vulcanized simply by expelling the absorbed cross-linking agent and/or catalyst from the silicate, e.g. by heating to at least 50 DEG C. or by using polar liquids, e.g. water, alcohols or nitriles, which will effect vulcanization at room temperature.  The silicate containing (3) and/or (4) may be provided with a hydrophobic coating, e.g. a siloxane oil, paraffin oil or a softener. Examples are given.