Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2002-03-14
2004-05-25
Robertson, Jeffrey B. (Department: 1712)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S364000, C428S375000, C428S421000, C428S447000, C428S450000, C524S588000, C492S056000, C525S478000, C528S015000, C528S031000, C528S032000
Reexamination Certificate
active
06740405
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid form addition curing type silicone rubber composition for forming rollers used in devices such as copiers, laser printers and facsimiles. Specifically, the present invention relates to a liquid form addition curing type silicone rubber composition for forming the roller used as a fixing roller, a developing roller or a paper supply roller in the above devices, and particularly to a liquid form addition curing type silicone rubber composition which displays good stability and undergoes almost no variation in viscosity at room temperature, and yet displays excellent curability at high temperature, as well as a roller comprising a layer of a silicone rubber elastic body formed from such a composition provided around the periphery of a metal core.
2. Description of the Prior Art
Liquid form addition curing type silicone rubber compositions are widely used for the fixing rollers, developing rollers and paper supply rollers used in devices such as copiers, laser printers and facsimiles. The reason for their use is that in comparison with other rubber materials, silicone rubber displays superior properties of releasability relative to toner, heat resistance and compression set. The formation of this type of roller usually involves either separating the constituents of the liquid form addition curing type silicone rubber composition into two parts, mixing them separately in a static mixer, and then combining the two parts at the time of use, or alternatively mixing all of the constituents together using the screw rotation action of a dynamic mixer. The thus obtained mixed product is then injected into a roll forming mold, cured under heat, and the cured roller then removed from the mold.
However, the time taken from preparation of the composition through to completion of the filling of the roll forming mold is considerably longer than typical injection molding, and because the mixed silicone rubber composition gradually begins to cure even at room temperature, problems such as thickening of the composition and gelling within the mold increase the likelihood of an unsatisfactory molding process. As a result, a composition which offers good stability and very little variation in viscosity over time at room temperature has been keenly sought. In contrast, once injected into the mold, the silicone rubber composition also needs to cure promptly under heating.
SUMMARY OF THE INVENTION
The present invention is the result of intensive research aimed at resolving the issues described above, and has an object of providing a liquid form addition curing type silicone rubber composition for roll forming purposes which displays little variation in viscosity at room temperature, and yet displays excellent curability at high temperature.
The inventors of the present invention discovered they could achieve this object with a liquid form addition curing type silicone rubber composition for roll forming purposes comprising:
(a) 100 parts by weight of an organopolysiloxane with at least two alkenyl groups bonded to non-terminal silicon atoms within the molecular chain of each molecule;
(b) 1 to 300 parts by weight of an inorganic filler;
(c) an effective quantity of a platinum based catalyst; and
(d) an organohydrogenpolysiloxane represented by a general formula (2),
wherein, R
3
represents an unsubstituted or a halogen-substituted monovalent hydrocarbon group with no aliphatic unsaturated double bonds, each R
4
represents, independently, either an unsubstituted or a halogen-substituted monovalent hydrocarbon group with no aliphatic unsaturated double bonds or a hydrogen atom, and x represents an integer of 2 or greater,
with at least two silicon atom-bonded hydrogen atoms (in other words, SiH groups) within a single molecule, in a sufficient quantity to produce a molar ratio of silicon atom-bonded hydrogen atoms within the constituent (d) relative to the alkenyl groups bonded to silicon atoms within the constituent (a) of 0.1 to 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As follows is a more detailed description of the present invention. First, each of the constituents of a silicone rubber composition of the present invention are described.
Constituent (a): Organopolysiloxane
Constituent (a), which is one of the essential constituents of a composition of the present invention, is an organopolysiloxane with at least two alkenyl groups bonded to non-terminal silicon atoms within the molecular chain (in other words, alkenyl groups bonded to the silicon atoms of bifunctional siloxane units (i.e., diorganosiloxane units) or trifunctional siloxane units (i.e., organosilasesquioxane units) represented by the formulas R
2
SiO
2/2
or RSiO
3/2
(wherein R is an unsubstituted or halogen-substituted monovalent hydrocarbon group, as described below) to form so-called pendent substituent groups). The molecular structure of this organopolysiloxane should preferably be essentially a straight chain, although a molecular structure with some minor branching is also acceptable.
This organopolysiloxane should preferably be of a structure represented by a general formula (1) shown below.
(wherein, R represents an unsubstituted or halogen-substituted monovalent hydrocarbon group, R
1
represents an unsubstituted or a halogen-substituted monovalent hydrocarbon group with no aliphatic unsaturated double bonds, R
2
represents an alkenyl group, n represents an integer of 2 or greater, and m represents 0, or an integer of 1 or greater).
Suitable examples of the unsubstituted or halogen-substituted monovalent hydrocarbon groups represented by R in the general formula (1) typically include hydrocarbon groups of 1 to 10, and preferably 1 to 6, carbon atoms, including alkyl groups such as methyl groups, ethyl groups, propyl groups, isopropyl groups, butyl groups, isobutyl groups, tert-butyl groups, pentyl groups, hexyl groups and cyclohexyl groups; alkenyl groups such as vinyl groups, allyl groups, propenyl groups and butenyl groups; aryl groups such as phenyl groups, tolyl groups and xylyl groups; aralkyl groups such as benzyl groups and phenylethyl groups; and halogenated alkyl groups such as 3-chloropropyl groups and 3,3,3-trifluoropropyl groups. Suitable R
1
groups include the same unsubstituted or halogen-substituted monovalent hydrocarbon groups mentioned above but excluding those groups with aliphatic unsaturated double bonds such as the alkenyl groups including vinyl groups and allyl groups. Amongst the groups listed above, both the R groups and the R
1
groups should preferably be methyl groups. The R
2
groups represent alkenyl groups such as vinyl groups, allyl groups, propenyl groups and butenyl groups. n represents an integer of 2 or greater, and m represents either 0, or an integer of 1 or greater, and m+n is typically an integer of 20 to 2000, and preferably an integer of 50 to 1000. Furthermore, n/(m+n) should preferably be a number from 0.001 to 0.2, with values from 0.002 to 0.1 being particularly preferred.
The viscosity of the constituent (a) at 25° C. should preferably be at least 1000 mPa·s (milliPascal·seconds), with values within a range from 1000 to 1,000,000 mPa·s being particularly preferred.
Specific examples of the constituent (a) include copolymers of dimethylsiloxane and methylvinylsiloxane with both terminals blocked with trimethylsiloxy groups, copolymers of dimethylsiloxane and methylvinylsiloxane with both terminals blocked with dimethylvinylsiloxy groups, copolymers of methylvinylsiloxane and diphenylsiloxane with both terminals blocked with trimethylsiloxy groups, copolymers of methylvinylsiloxane and diphenylsiloxane with both terminals blocked with dimethylvinylsiloxy groups, copolymers of dimethylsiloxane, methylvinylsiloxane and diphenylsiloxane with both terminals blocked with trimethylsilyl groups, copolymers of dimethylsiloxane, methylvinylsiloxane and diphenylsiloxane with both terminals blocked with dimethylvinylsiloxy groups, and copolymers of methylvinylsiloxane and
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Robertson Jeffrey B.
Shin-Etsu Chemical Co. , Ltd.
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