| 摘要 |
<p>A release material suitable for coating the inside of ovens consists essentially of a mixture of (A) 15 to 95% by weight of a diorganopolysiloxane: Rn(OH)mSi 4-n-m/2 ; R is a monovalent alkyl, alkenyl or aryl radical, n has an average value of 1.98-2.0024, m has an average value not > 0.02 and m+n is not > 2.0024; the polymer has a viscosity of at least 50,000 c.s. at 25 DEG C.; at least 90% of the R's are methyl and not more than 2% are alkenyl, together with (B) from 5 to 85% by weight of a block copolymer consisting essentially of: (i) polymer blocks: [(CH3)2SiO]s[R12SiO]t [R1SiO1.5]u, each R1 is Me, Et, vinyl or phenyl, s+t+u has an average value of 6 to 100 and t and u each has a value up to 10% of s+t+u, and (ii) polymer blocks: (C6H5)q(CH3)w SiO 4-w-q/2 , w has an average value up to 0.25 and q from 1 to 1.25; q+w is not > 1.25. The siloxane units (i) comprise 10 to 75 mol per cent and the siloxane units (ii) from 25 to 90 mole per cent of the block copolymer. In preferred examples the diorganopolysiloxane (A) is either a hydroxyl or trimethysiloxy terminated dimethylpolysiloxane. In the block copolymer, units (i) are preferably dimethylsiloxane units and units (ii) are mainly monophenylsiloxane units with up to 25 mol per cent of other units such as phenylmethylsiloxane, monomethylsiloxane and diphenylsiloxane. The release material may be applied from an aerosol package when it is dissolved in an organic halogenated solvent (e.g. chloroelcane, CFCl3 or CF2Cl2) in an amount of 0.1 to 20% by weight together with an aerosol propellant. It may also be supplied as an aqueous emulsion.ALSO:A release material which is coated on the inside surface of ovens e.g. of enamel consists essentially of a mixture of (A) 15 to 95% by weight of a diorganopolysiloxane: Rn (OH)m Si4-n-m/2; R is a monovalent alkyl, alkenyl or aryl radical, n has an average value 1.98-2.0024, m has an average value not > 0.02 and m +n is not > 2.0024; the polymer has a viscosity of at least 50,000 c.s. at 25 DEG C; at least 90% of the R1S are methyl and not more than 2% are alkenyl, together with (B) from 5 to 85% by weight of a block copolymer consisting essentially of: (i) polymer blocks: [(CH3)2SiO]s [R1SiO]t [R1SiO1,5]u each R1 is Me, Et, vinyl or phenyl, s + t + u has an average value of 6 to 100 and t and u each has a value up to 10% of s + t + u, and (ii) polymer blocks: (C6H5)q(CH3)wSiO (C6H5) (CH3) SiO.4-w-a/2 w has an average value up to 0.25 and a from 1 to 1.25; q + w is not > 1.25. The siloxane units (i) comprise 10 to 75 mol % and the siloxane units (ii) from 25 to 90 mole % of the block copolymer. In preferred examples the diorganopolysiloxane (A) is either a hydroxyl or trimethylsiloxy terminated dimethylpolysiloxane. In the block copolymer, units (i) are preferably dimethylsiloxane units and units (ii) are mainly monophenylsiloxane units with up to 25 mol % of other units such as phenylmethylsiloxane, monomethylsiloxane and diphenylsiloxane. The release material may be applied from an aerosol package when it is dissolved in an organic halogenated solvent (e.g. chloroelcane, CFCl3 or CF2Cl2) in an amount of 0.1 to 20% by weight together with an aerosol propellant. It may be applied as an aqueous emulsion. It may also be applied from a pretreated cloth.</p> |
