Silicone rubber-covered copier roll

Abstract

The silicone rubber obtained by curing in the presence of a platinum-containing catalyst a composition comprising an organopolysiloxane containing a plurality of lower alkenyl radicals and a organohydrogensiloxane consisting essentially of R 3 SiO 1/2 units, R 2 SiO units, RHSiO units, and RSiO 3/2 units in a specified molar ratio is uniquely suitable as the coating material for the press roll in the fixing assembly of an electrophotographic copier.

That which is claimed is: 
     
       1. In a silicone rubber-covered roll for use in an electrophotographic copier, said roll comprising a roll axle and a layer of silicone rubber obtained by curing a composition comprising (A) 100 parts by weight of an organopolysiloxane having at least 2 silicon-bonded lower alkenyl radicals in each molecule;   (B) an organohydrogensiloxane wherein each molecule contains at least two silicon-bonded hydrogen atoms, and the amount of said organohydrogensiloxane is equivalent to a molar ratio of silicon-bonded hydrogen atoms in (B) to lower alkenyl radicals in (A) of from 0.5 to 20; and   (C) a platinum-containing catalyst in a quantity providing 0.1 to 500 parts by weight of platinum metal for each 1 million weight parts of the total quantity of components (A) and (B),   the improvement characterized by (1) selecting said cured silicone rubber from those exhibiting a hardness value in the range of from 10 to 70 measured on the A scale in accordance with Japanese Industrial Standard C 2123 and a compression set of 10% or less, and (2) selecting said organohydrogensiloxane from organosiloxane copolymers comprising R 3  SiO 1/2   units, R 2  SiO units, RHSiO units, and RSiO 3/2  units, where each R is individually selected from monovalent hydrocarbon or halogenated hydrocarbon radicals free of ethylenic unsaturation, and where from 0.5 to 50 mol % of said copolymer consists of RSiO 3/2  units.   
     
     
       2. A roll according to claim 1 where said R radicals are lower alkyl, phenyl or 3,3,3-trifluoropropyl and said hardness value is from 10 to 30. 
     
     
       3. A roll according to claim 2 where said R radicals are methyl, said organopolysiloxane is a dimethylvinylsiloxy-terminated dimethylpolysiloxane, said hardness value is from 10 to 25, said molar ratio is from 1 to 3, and said layer of silicone rubber is cured at a temperature of from 100 to 170° C. 
     
     
       4. A roll according to claim 1 where said roll is a press roll. .Iadd.5. In an improved curable composition comprising (A) 100 parts by weight of an organopolysiloxane having at least 2 silicon-bonded lower alkenyl radicals in each molecule;   (B) an organohydrogensiloxane wherein each molecule contains at least two silicon-bonded hydrogen atoms, and the amount of said organohydrogensiloxane is equivalent to a molar ratio of silicon-bonded hydrogen atoms in (B) to lower alkenyl radicals in (A) of from 0.5 to 20; and   (C) a platinum-containing catalyst in a quantity providing 0.1 to 500 parts by weight of platinum metal for each 1 million weight parts of the total quantity of components (A) and (B),   where the improvement is characterized by selecting said organohydrogensiloxane from organosiloxane copolymers comprising R 3  SiO 1/2   units, R 2  SiO units, RHSiO units, and RSiO 3/2  units, where each R is individually selected from monovalent hydrocarbon radicals free of ethylenic unsaturation, and where from 0.5 to 50 mol % of   
     
     
        said copolymer consists of RSiO 3/2  units. .Iaddend. .Iadd.6.  A composition according to claim 5 where said R radicals are lower alkyl, phenyl or 3,3,3-trifluoropropyl. .Iaddend. .Iadd.7. A composition according to claim 6 where said organohydrogensiloxane is a methylhydrogenpolysiloxane having a silicon-bonded hydrogen content of 0.6 weight percent and containing 21 mole percent of Me 3  SiO 1/2  units, 21 mole percent of Me 2  SiO units, 47 mole percent of MeHSiO units and 11 mole percent of MeSiO 3/2  units, where Me represents a methyl radical. .Iaddend. .Iadd.8. An organosiloxane copolymer comprising R 3  SiO 1/2   units, R 2  SiO units, RHSiO units, and RSiO 3/2  units, where each R is individually selected from monovalent hydrocarbon radicals free of ethylenic unsaturation, and where from 0.5 to 50 mol % of said copolymer consists of RSiO 3/2  units. .Iaddend. .Iadd.9. A composition according to claim 8 where said R radicals are lower alkyl, phenyl or 3,3,3-trifluoropropyl. .Iaddend. .Iadd.10. A composition according to claim 9 where said copolymer is a methylhydrogenpolysiloxane having a silicon-bonded hydrogen content of 0.6 weight percent and containing 21 mole percent of Me 3  SiO 1/2  units, 21 mole percent of Me 2  SiO units, 47 mole percent of MeHSiO units and 11 mole percent of MeSiO 3/2  units, where Me represents a methyl radical. .Iaddend.