Patent GB-1484816-A (GB)
Title: Surface treating compositions
IPC: B05D5/08
Filed: 1975-01-28
Abstract: 1484816 Organopolysiloxane compositions IMPERIAL CHEMICAL INDUSTRIES Ltd 16 Dec 1975 [28 Jan 1975 23 July 1975] 3592/75 and 30843/75 Heading C3T [Also in Divisions B5 and B2] An organopolysiloxane composition suitable for conferring release properties on substrates comprises 100 p.b.w. of a diorganopolysiloxane in the form of a curable release composition consisting essentially of a linear diorganopolysiloxane capable of being cured to an elastomer and such crosslinking and/or curing agent as may be necessary, and 0À1 to 50 p.b.w. of a copolymer of the average general formula where A is selected from R, R<SP>1</SP>Q, alkenyl, OH and hydrogen, Q is oxygen or sulphur, R is selected from (a) alkyl, aryl, alkaryl, aralkyl and cycloalkyl groups, (b) -R<SP>2</SP>QR<SP>3</SP> where R<SP>2</SP> is a divalent organic group having at least 2 carbon atoms and is joined to silicon by a C-Si linkage and R<SP>3</SP> is a monovalent hydrocarbon group and (c) hydrocarbonoxy groups joined to silicon by a C-Si linkage, R<SP>1</SP> is a hydrocarbon or hydrocarbonoxy group, a and d, which will not normally be the same, are 0-950, b is 0-999, c is 1-1000, a+b+c+d is 20-1000, (b+c)/(a+b+c+d) is not less than 0À05, at least one of the groups R<SP>1</SP> having not less than 6 carbon atoms when b is 0 and, when b is not 0, 'at least one of the groups R having not less than 4 carbon atoms and/or at least one of the groups R<SP>1</SP> having not less than 6 carbon atoms, the proportion of said copolymers also being such that the ratio of R<SP>1</SP>Q groups in which R<SP>1</SP> has at least 6 carbon atoms plus R groups having at least 4 carbon atoms to total silicon atoms in the composition is not less than 1 : 2000. Preferably a/(a+b+c+d) is not less than 0À1:1, and d/(a+b+c+d) is not greater than 0À3 : 1. The curable release composition may comprise (1) a linear diorganopolysiloxane containing Si-OH groups, a crosslinking agent selected from polysiloxanes containing silicon-bonded hydrogen, alkyl polysilicates, trialkoxyorganosilanes and partial hydrolysates thereof and organotriacyloxysilanes, and a curing catalyst; or (2) a linear diorganopolysiloxane containing silicon-bonded vinyl groups and either (a) a peroxide catalyst or (b) a polysiloxane containing silicon-bonded hydrogen and a Pt catalyst. The compositions may comprise other components, e.g. abrasion resistant additives and bath stabilizers. The compositions may be used with or without an organic solvent, or in the form of aqueous dispersions or emulsions. The compositions preferably cure in less than 2 minutes at 70-200‹ C. Suitable substrates are glass, stone, ceramics, plastics, e.g. polypropylene and polyethylene terephthalate films and fabrics, cellulosic materials, e.g. films and fabrics of wood, cotton and paper, and aluminium foils. In the examples coating compositions are prepared from (1) a linear OH-ended dimethylpolysiloxane (10<SP>7</SP> cP), (2) a linear trimethylsilyl - ended methylhydrogen polysiloxane (20 cP), optionally (3) or tetra - (2 - methoxyethoxy)silane or 3- aminopropyltriethoxysilane, (4) dibutyltin diacetate, or 1,3 - diacetyl - 1,1,3,3 - tetrabutyldistannoxane or dibutyltin di-(2-ethylhexoate or bis - (butyraldoximo)distannoxane or dibutyl bis - (benzaldoximo)stannane or dibutyltin diethoxide or bis - (diethylsulphide)platinous chloride; optionally (5) acetic acid, (6) solvents selected from toluene, methyl ethyl ketone and an aliphatic solvent of B.Pt. 110-135‹ C., and (7) any one of the following copolymers Coating compositions are also prepared from a linear trimethylsilyl-ended methylvinyl polysiloxane, a linear (CH 3 ) 3 Si-ended methylhydrogenpolysiloxane, bis-(diethylsulphide)platinous chloride, optionally an aliphatic solvent, and either copolymer (i) or (vii) above. The above compositions are each coated on to vegetable parchment paper, cured at elevated temperature, then coated with an aggressive SBR pressure sensitive adhesive, and label paper is then applied to the adhesive surface.