Patent GB-841825-A (GB)
Title: Process for the manufacture of elastomeric organo-polysiloxane products
IPC: A61K6/896
Filed: 1956-07-30
Abstract: An elastomeric product is made by vulcanising e.g. at room temperature or below 100 DEG C., (A) a predominantly difuctional, linear siloxane convertible to the solid, elastic state, and having the general formula XO-Si(R2)-[O-Si(R)2-]nO-Si(R2)-OX, wherein each R is an alkyl, aryl or halogenated hydrocarbon radical, X is H or R and n is an integer of at least 50, by the addition of (B) a cross-linking agent and (C) a condensation catalyst other than an organic peroxide or per-salt.  The siloxane (A) may contain monoorganosiloxy units provided the R/Si ratio is within the range 1,9 to 2,1.  The cross-linking agents (B) are:-(a) silanes of the formula Rm Si Y4-m, in which Y is, e.g. H, OH, alkoxy, aryloxy or amino and m is O, or where a mixture of silanes is used, has an average value below 2, the preferred silanes being ethoxy silane, methyltriethoxy-silane and phenyltributoxysilane; (b) di-, tri- or tetra-siloxanes obtained by hydrolysis of silanes (a), e.g. di-methyltetraethoxydisiloxane and dimethyldiphenylhexa-ethoxytetrasiloxane; (c) organopolysiloxane resins having a functionality greater than 2, e.g. methyl or ethyl siloxanes having a R/Si ratio of 1,4 to 1 and containing 15% (by weight) of butoxy groups or having a R/Si ratio of 1,1:1 and containing 10% methoxy groups; (d) siloxane resins of the formula RmHSiO3-m/2, where m is less than 2, e.g. a siloxane of the formula <FORM:0841825/IV(a)/1> in which Y1 and Y2 are non-acidic terminal radicals e.g. OH, OR or -OSi(CH3)3; (e) polysilicates, which are used with thoroughly dried fillers; (b) reactive silicic acids, i.e. silicic acids containing surface Si-bonded H atoms, OH or OR groups; or (g) titanium esters, e.g. butyl titanate, or polymers thereof. Condensation catalysts (C), known to cure siloxane resins, are:-metal soaps, e.g. tin ricinoleate and cobalt naphthenate-though some metal carboxylates, e.g. zinc-2ethylhexoate, act too slowly, some are unsatisfactory physiologically, e.g. lead hexoate, and some cause discolouration, e.g. iron and cobalt-2-ethylhexoates; metal chelates, e.g. chromium acetylacetonate; metal salts of thiols or dithiocarbamic acids, e.g. Pb salt of mercaptobenzthiazole and Zn ethylphenyldithio-carbamate; metal oxides, e.g. HgO, PbO and CdO; organometal compounds, e.g. phenyl mercury acetate and dibutyltin-dilaurate; organic bases, e.g. triethanolamine and polyethyleneimine; basic fillers, e.g. asbestos; and acids, e.g. boric and oleic acids.  Fillers, antioxidants and extenders, e.g. P.V.C., may also be added.  The composition can be made immediately before use from separately packaged components.  In typical Examples, a linear hydroxy-terminated dimethylpoly-siloxane was mixed on a roller mill with (1) calcined diatomaceous earth, a methylsiloxane resin containing ethoxy groups and dibutyltindilaurate and vulcanised at various temperatures, (8) siliceous chalk, methylhydrogen -siloxane and zinc octoate, and spread on a glass fabric and cold-cured.  (10) A linear hydroxyterminated methylphenyl siloxane was emulsified with water and triethanolamine oleate to form a latex to which methylsiloxane and dibutyl tin di-maleate were added before being used to impregnate a cotton fabric.  The subject matter of Specification 764,246 is disclaimed.  Uses: for impregnating paper and textiles; as casting compositions for casting round or embedding electrical windings, for making laminated products, electrical insulating material such as tapes and for making moulds for moulding ethoxyline or polyester resins; as dispersions in water, alcohols, ethers, esters or ketones for use as paints or coating compositions; as body fitting converings of leg and arm prostheses, for making casts of living or dead bodies of human beings or animals, or parts thereof, and for bandaging and dental purposes; for sealing joints between slabs, pipes etc., made of stone, concrete, mortar or ceramics.  In Example (18) a liquid hydroxy-terminated linear dimethylpolysiloxane was mixed with calcined diatomaceous earth and then with a paste of:-powdered P.V.C., diamylphthalate and dibutyl-tin-dilaurate.  This mixture vulcanised in 6 minutes after the addition of methyl-hydrogen -polysiloxane.  Specification 729,202 and 765,744 also are referred to.ALSO:A composition, convertible at room temperature or below 100 DEG C to the solid elastic state, comprising (A) a predominantly linear siloxane containing terminal OR groups, in which R is H or a hydrocarbon or halogenated hydrocarbon radical, (B) a cross-linking agent which is a functional organosilicon compound, a reactive silicic acid or a titanium ester, and (C) a condensation catalyst other than an organic peroxide or persalt (see Group IV(a)), is used as a coating composition or paint, if desired in the form of a dispersion which has been stabilized with an alcohol, ether, ester or ketone.  In Examples, (2) a spool was covered with a liquid mixture of a hydroxy-terminated linear dimethylsiloxane, siliceous chalk, phenyltributoxy silane and lead oxide, in a sheet metal mould; after standing for 3 days at room temperature an elastic, bubble-free coating was formed; (26, 27) a cleaned and degreased metal sheet, lacquered with a solution of (26) a silicone resin (obtained as described in Specification 729,202), or (27) a methyl ethoxy polysiloxane resin, was coated by spreading thereon a composition of (26) a hydroxyterminated dimethylsiloxane liquid asbestos, Kieselguhr, methylhydrogen polysiloxane and dibutyl-tin dilaurate, or (27) a hydroxyterminated dimethylsiloxane liquid, Kieselguhr, cork meal, methylhydrogen siloxane, dibutyltin dilaurate and triethanolamine.  The compositions vulcanised at room temperature.ALSO:In Examples, (9) a mixture of 100 grams of a hydroxy-terminated linear dimethylpolysiloxane, 100 grams of Champagne chalk, 5 p  grams of methyl-hydrogen-polysiloxane and 5 grams of dibutyl-tin dilaurate, was poured into a metal mould to form, on standing at room temperature for 2 hours, a block of foamed silicone rubber; (24) 10 kg. of siliceous chalk and 20 grams of methyl-hydrogen-polysiloxane were mixed with 10 Kg. of a hydroxy-terminated dimethyl-polysilozane, and the resulting mass when mixed with dibutyl-tin dilaurate was used for sealing joints between concrete pipes; and (27) a composition for coating sheet metal consists of 100 grams of the above dimethylsiloxane, 30 grams of cork meal, 50 grams of Kieselguhr, 50 grams of methyl-hydrogen-polysiloxane, 0,2 gram of dibutyl-tin dilaurate and 0,2 gram of triethanolamine.  It is stated that if a larger amount of methyl-hydrogen-polysiloxane is used, the mass foams slightly.ALSO:A composition, convertible at room temperature or below 100 DEG C to the solid elastic state, comprising (A) a predominately linear siloxane containing terminal OR groups, in which R is hydrogen or a hydrocarbon or halogenated hydrocarbon radical, (B) a cross-linking agent which is a functional organosilicon compound, a reactive silicic acid or a titanium ester, and (C) a condensation catalyst other than an organic peroxide or per salt (see Group IV(a)), is used for making body fitting coverings of leg and arm prostheses, casts of living or dead bodies (human and animal), for bandaging and for dental purposes, such as a moulding composition for making casts of the mouth and teeth and as root fillings for decayed teeth.  In Examples (19) a mixture of hydroxy-terminated linear dimenthylpolysiloxane, kieselguhr, powdered mica and tetraethylsilicate, is allowed to thicken and the resulting thickened mass is then used for taking a dental impression; (20) the mass of (19) was mixed with methylhydrogenpoly-siloxane and butylamine, and vulcanised in 3 minutes at room temperature.