Patent GB-1476657-A (GB)
Title: Mould release composition
IPC: B29C33/64
Filed: 1974-12-03
Abstract: 1476657 Mould release agents SWS SILICONES CORP 3 Dec 1974 [3 Dec 1973] 52317/74 Heading C5F [Also in Division C3] A process for the manufacture of a release composition comprises (i) mixing a diorganopolysiloxane fluid that is substantially of the general formula -[(R) 2 SiO-]- x , wherein the R/Si ratio varies from 1À75 to 2À25, and where R is a monovalent hydrocarbon or halohydrocarbon radical of up to 18 carbon atoms and x is greater than 20, and a diorganopolysiloxane gum having a plasticity value of up to 120 mm., in a gum to fluid weight ratio of from 1 : 3 to 1 : 25, with sufficient hydrocarbon or halohydrocarbon solvent to give a silicone dispersion having a viscosity of from 10<SP>4</SP> to 10<SP>5</SP> cP at 25‹ C.; (ii) mixing the resulting dispersion with an emulsifying agent in an emulsifying agent to silicone dispersion weight ratio of at least 1 : 25, and with sufficient water to form a waterin-oil emulsion of pasty consistency; (iii) adding further water to form an oil-in-water emulsion; and (iv) mixing the following components to form a release composition: (a) the silicone emulsion prepared under (iii) in an amount such that the composition contains up to 25% wt. of diorganopolysiloxane, (b) 20-60% wt. of a filler; (c) 0À1-5% wt. of a dispersing agent, (d) 0-25% wt. of a lubricant, (e) a suspending agent, and (f) if necessary or desired, further water such that the composition contains at least 20% wt. of water, all percentages being based on the total weight of the composition. The diorganopolysiloxane fluid is preferably a dimethylpolysiloxane having a viscosity of from 100-100,000 cP at 25‹ C. The diorganopolysiloxane gum preferably has the average unit formula R n SiO (4-n)/2  where n= 1À9-2À1, and preferably at least 75 mole per cent of its silicon atoms are substituted by alkyl radicals. The emulsifier may be anionic or non-ionic, e.g. polyoxyethylene alkylphenols, nonylphenoxypoly(ethyleneoxy)ethanols, polyoxyethylene sorbitol hexastearate or oleate, polyoxyethylene cetylether, trimethylnonylether of polyethylene glycol, sodium alkylaryl polyether sulphonate and a partial sodium salt of a phosphate ester of an ethyleneoxide adduct of nonyl phenol. The filler preferably has a particle size of 100-600 mesh and is preferably mica, other fillers include graphite, carbon black, alkaline earth metal silicates, aluminium silicates, vermiculite, talc and kaolin. The preferred dispersing agent is lecithin; others inelude alkylaryl sulphonates, sodium triphosphate and the anionic emulsifiers. Suitable lubricants are polyalkylene glycols having a molecular weight of from 400-4000, e.g. homopolymers or copolymers of ethylene glycol and propylene glycol. Suitable suspending agents are magnesium aluminium silicate, bentonite clay, and water soluble celluloses and are preferably used in an amount of from 0À02-1À5% wt. of the composition. Optional ingredients include preservatives, e.g. HCHO and 6-acetoxy - 2,4 - dimethyl - m - dioxane, antifoam agents, rust inhibitors, e.g. NaNO 2  or NaNO 3 , and colouring agents. In a typical example a release composition is prepared from a (i) silicone emulsion prepared as above from a diorganopolysiloxane gum (95-100 mm.), dimethylpolysiloxane fluids (60,000 cP and 350 cP), mineral spirits, water and nonylphenoxypoly(ethyleneoxy)ethanol, (ii) water, (iii) sodium carboxymethylcellulose, (iv) lecithin, (v) a copolymer of ethyleneglycol and propylene glycol, (vi) a mica. The compositions are particularly useful as mould release agents in the manufacture of tyres where they are sprayed on to green tyre carcasses.