Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-05-30
2002-10-29
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S015000, C528S031000, C528S032000, C524S588000
Reexamination Certificate
active
06472078
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a silicone rubber composition used for fixing rollers used in copying machines, laser beam printers, fax machines and so forth. More particularly, it relates to a liquid addition-curable silicone rubber composition used for a fixing roller having a silicone rubber surface layer, and a fixing roller produced using such a composition.
2. Description of the Prior Art
As fixing rollers used in copying machines, laser beam printers, fax machines and the like, conventionally used are those comprising a mandrel and a silicone rubber surface layer provided on the former's outer periphery (called silicone rubber rollers). The reason why silicone rubber is used in the surface layer is that the silicone rubber has physical and mechanical properties such as toner releasability, heat resistance, compression set and so forth which are superior to those of other rubber materials.
In recent years, however, as fixed images are required to be improved in sharpness and machinery has been made high-speed, toner releasability and mechanical strength are sought to be more improved. Also, some addition-curable silicone rubber compositions used to form silicone rubber layers are foamable. Such foamable compositions may damage the sharpness and so forth of fixed images, and hence it has been sought to provide a non-foamable addition-curable silicone rubber composition.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a substantially non-foamable, fixing roller purpose liquid addition-curable silicone rubber composition which has a good moldability and enables production of a fixing roller having a silicone rubber layer having superior toner releasability and mechanical strength; and a fixing roller obtained using such a composition.
To achieve the above object, the present invention provides a substantially non-foamable, fixing roller purpose liquid addition-curable silicone rubber composition comprising;
(A) 100 parts by weight of an organopolysiloxane having in one molecule at least two alkenyl groups bonded to silicon atoms;
(B) from 1 part by weight to 30 parts by weight of an organopolysiloxane having hydroxyl groups at both terminals of the molecular chain;
(C) an organohydrogenpolysiloxane having in one molecule at least two hydrogen atoms bonded to silicon atoms (SiH groups); the SiH groups in the component (C) being present in an amount of from 0.4 to 5.0equivalent weight (i.e., from 0.4 to 5.0 groups) per one alkenyl group in the component (A); and
(D) a platinum group metal compound in a catalytically effective quantity.
The present invention also provides a fixing roller comprising a mandrel and provided on the outer periphery thereof a silicone rubber layer comprising a cured product of the above composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The liquid addition-curable silicone rubber composition of the present invention is substantially non-foamable and is used for fixing rollers, which is constituted basically of an organopolysiloxane having in one molecule at least two alkenyl groups bonded to silicon atoms; (B) an organopolysiloxane having hydroxyl groups at both terminals of the molecular chain; (C) an organohydrogenpolysiloxane having in one molecule at least two hydrogen atoms bonded to silicon atoms (SiH groups); and (D) a platinum group metal compound.
The respective components used to make up the silicone rubber composition of the present invention will be described.
(A) Alkenyl Group-containing Organopolysiloxane
The component (A) organopolysiloxane having in one molecule at least two alkenyl groups bonded to silicon atoms is a known organopolysiloxane usually used as a base polymer for addition-curable silicone rubber compositions. This organopolysiloxane has a viscosity of from 100 to 1,000,000 cP (centipoise) at 25° C., and is a compound represented by the general compositional formula (I):
R
a
SiO
(4−a)/2
wherein R's each represent a substituted or unsubstituted monovalent hydrocarbon group bonded to a silicon atom, and a represents a number of from 1.9 to 2.4, and preferably from 1.95 to 2.05.
In the general compositional formula (I), as examples of the substituted or unsubstituted monovalent hydrocarbon group represented by R, it may include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group and a dodecyl group; cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group and a cycloheptyl group; alkenyl groups such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a hexenyl group, a cyclohexenyl group and a cycloheptenyl group; aryl groups such s a phenyl group, a tolyl group, a xylyl group, a naphthyl group and a biphenylyl group; aralkyl groups such as a benzyl group, a phenylethyl group, a phenylpropyl group and a methylbenzyl group; and halogen-substituted or cyano-substituted hydrocarbon groups such as a chloromethyl group, a 2-bromoethyl group, 3-chloropropyl group, a 3,3,3-trifluoropropyl group, a chlorophenyl group, a fluorophenyl group, a cyanoethyl group and a 3,3,4,4,5,5,6,6,6-nonafluorohexyl group. These substituted or unsubstituted monovalent hydrocarbon groups R's may preferably be those having 1 to 12 carbon atoms, and particularly 1 to 8 carbon atoms, and may be the same or different, provided that at least two alkenyl groups must be present in one molecule. These alkenyl groups may be those bonded to any of the silicon atom present at one molecular-chain terminal and a silicon atom present along the molecular chain, or may be those bonded to the both. They may preferably be alkenyl groups bonded at least to the silicon atoms present at both terminals of the molecular chain.
Among the alkenyl groups exemplified above, a vinyl group is preferred. Also, among monovalent hydrocarbon groups R's other than the alkenyl groups, a methyl group, a phenyl group and a 3,3,3-trifluoropropyl group are preferred.
This organopolysiloxane may be of a straight chain, or a branched chain containing an RSiO
3/2
unit [R is as defined in the general compositional formula (I)] or an SiO
4/2
unit. Usually, it may preferably be a straight-chain diorganopolysiloxane terminated with triorganosiloxyl groups at both molecular chain terminals and having a molecular backbone chain consisting basically of the repetition of diorganosiloxane units (i.e., R
2
SiO
2/2
units).
The component (A) organopolysiloxane can be produced by known processes. For example, it can be obtained by subjecting an organocyclopolysiloxane and a hexaorganodisiloxane to equilibration reaction in the presence of an acid catalyst.
As examples of the component (A), it may include
In the above formulas, R's are the same as the groups other than the alkenyl group represented by R in the general compositional formula (I); m is an integer of 1 or more, usually from 1 to 200, and preferably from 2 to 100; n is an integer of 0 or more, usually from 10 to 3,000, and preferably from 50 to 1,500; and a is 1, 2 or 3, and preferably 1.
The alkenyl group-containing organopolysiloxane as described above may be used alone or in combination of two or more types.
(B) Both-terminal Hydroxyl-group-containing Organopolysiloxane
The component (B) organopolysiloxane having hydroxyl groups bonded to silicon atoms (i.e., silanol groups) at both terminals of the molecular-chain is commonly a diorganopolysiloxane having basically a straight-chain structure whose molecular chain is terminated with a diorganohydroxysiloxyl group at both terminals and whose backbone chain consists basically of the repetition of a diorganosiloxane unit, i.e., R
1
2
SiO
2/2
unit where R
1
is as defined below. This compound may also have a branched-chain structure such as a monooroganosiloxane unit (trifunctional sil
Shudo Shigeki
Ubukata Shigeru
Moore Margaret G.
Pillsbury & Winthrop LLP
Shin-Etsu Chemical Co. , Ltd.
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