Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-12-15
2002-07-16
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S036900, C428S036910
Reexamination Certificate
active
06420038
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a silicone rubber composition for fixing rolls used in copier machines, printers, fax machines, etc. and to a fluorocarbon resin-covered fixing roll. More specifically the present invention relates to a liquid silicone rubber composition for fixing rolls capable of forming silicone rubber of superior durability and hardness stability under high-temperature conditions and which exhibits practically no decrease in hardness after high-temperature treatment, and to a fluorocarbon resin-covered fixing roll of superior hardness stability and reliability during use.
BACKGROUND OF THE INVENTION
Fixing rolls produced by forming a low-hardness silicone rubber layer over the peripheral surface of a metal roll shaft and then coating this external layer with a fluorocarbon resin are called fluorocarbon resin-covered fixing rolls. They are widely used in electrophotographic copiers, printers, facsimile machines, etc. (refer to Japanese Publication No. Sho 53(1978)-74436, Japanese Publication No. Sho 57(1982)-89785, Japanese Publication No. Sho 59(1984)-74578, and Japanese Publication No. Sho 59(1984)-52269). Superior heat resistance is required of this type of fluorocarbon resin-covered fixing rolls because they are used for fixing toner at high temperatures in excess of 200° C. Because the silicone rubber of the underlayer portion is shielded from contact with the air by the fluorocarbon resin coating, this tends to cause depolymerization, brings about a decrease in hardness, generates non-uniformity in hardness, and other problems. In addition, when the process of providing a coating of fluorocarbon resin on the surface of a roll is based on methods involving application of a fluorocarbon resin latex and baking at a high temperature, the silicone rubber of the underlayer undergoes softening and degradation because during the high temperature baking step of about 220~350° C. When this type of silicone rubber is employed for fluorocarbon resin-covered fixing rolls, during paper-passing durability testing, toner residue adheres to the surface of the roll, or creasing develops in the fluorine material layer on the surface of the roll.
As a result of in-depth investigations directed to eliminating the problems of the above-described prior art, the authors of the present invention found that a liquid silicone rubber composition produced by the addition of a particulate hydroxide or oxide of an alkali metal or a particulate hydroxide or oxide of an alkaline earth metal is superior in heat resistance, and especially heat stability in the absence of air due to a fluorocarbon resin coating. It is an object of the present invention to provide a silicone rubber composition for fixing rolls capable of forming silicone rubber of superior durability and hardness stability that exhibits practically no decrease in hardness after high-temperature treatment in a fluorocarbon resin coating step, and to provide a fixing roll of superior hardness stability and reliability during use.
SUMMARY OF THE INVENTION
A liquid silicone rubber composition for fixing rolls comprising
(A) 100 parts by weight of a diorganopolysiloxane which has at least two silicon-bonded alkenyl groups in each molecule and is liquid at room temperature,
(B) 5~300 parts by weight of an inorganic filler,
(C) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in each molecule in a quantity that affords a value of from 0.3:1 to 5:1 for the ratio of the number of moles of silicon-bonded hydrogen atoms in the present component and silicon-bonded alkenyl groups in component (A),
(D) a platinum catalyst in a quantity that affords a value of from 0.1 part by weight to 500 parts by weight of platinum metal atoms per 1,000,000 parts by weight of component (A), and
(E) 0.01~10 parts by weight of a particulate hydroxide or oxide of an alkali metal, or a particulate hydroxide or oxide of an alkaline earth metal.
DESCRIPTION OF THE INVENTION
The present invention is a liquid silicone rubber composition for fixing rolls comprising
(A) 100 parts by weight of a diorganopolysiloxane which has at least two silicon-bonded alkenyl groups in each molecule and is liquid at room temperature,
(B) 5~300 parts by weight of an inorganic filler,
(C) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in each molecule in a quantity that affords a value of from 0.3:1 to 5:1 for the ratio of the number of moles of silicon-bonded hydrogen atoms in the present component and silicon-bonded alkenyl groups in component (A),
(D) a platinum catalyst in a quantity that affords a value of from 0.1 part by weight to 500 parts by weight of platinum metal atoms per 1,000,000 parts by weight of component (A), and
(E) 0.0110 parts by weight of a particulate hydroxide or oxide of an alkali metal, or a particulate hydroxide or oxide of an alkaline earth metal.
The diorganopolysiloxane of component (A), which has at least two silicon-bonded alkenyl groups in each molecule, is the principal component used to form silicone rubber by means of crosslinking the present composition. Component (A) is a substantially linear diorganopolysiloxane or a linear diorganopolysiloxane with some branching represented by average unit formula
R
n
SiO
(4-n)/2
,
where R is a monovalent hydrocarbon group exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, or other alkyl groups; vinyl, allyl, propenyl, hexenyl, or other alkenyl groups; phenyl, tolyl, or other aryl groups; or 3,3,3-trifluoropropyl, 3,3,3-trichloropropyl, or other halogen-substituted monovalent hydrocarbon groups; the subscript n is a value of 1.9~2.1. The viscosity of this type of diorganopolysiloxane is typically in the range of from 100 mPa·s to 1,000,000 mPa·s.
Component (A) is exemplified by dimethylvinylsiloxy-endblocked dimethylpolysiloxane, dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane copolymers, dimethylvinylsiloxy-endblocked dimethylsiloxane-methylphenylsiloxane copolymers, dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers, dimethylvinylsiloxy-endblocked dimethylsiloxane-diphenylsiloxane copolymers, dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymers, dimethylvinylsiloxy-endblocked dimethylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers, and dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers.
Any inorganic filler known in the past as reinforcing fillers or semi-reinforcing fillers can be used as the inorganic filler of component (B), which is used for regulating the viscosity of the present composition and for imparting mechanical strength to the silicone rubber. The reinforcing fillers are exemplified by dry process silicas, wet process silicas, and hydrophobic silicas obtained by surface treating these silicas with, for example, organochlorosilane, organoalkoxysilane, organopolysiloxane, or organosilazane. Silica micropowders with an average particle size of 50 &mgr;m or less and a specific surface area by the BET method of at least 100 m
2
/g are preferred. The semi-reinforcing fillers are exemplified by diatomaceous earth, quartz powder, mica, aluminum oxide, titanium oxide, and materials obtained by treating them with organosilanes, organopolysiloxanes, fatty acids, and the like. Component (B) is compounded into the composition at 5~300 parts by weight per 100 parts by weight of component (A).
The organohydrogenpolysiloxane of component (C), which has at least two silicon-bonded hydrogen atoms in each molecule, acts as a cross-linking agent for the present composition. The organohydrogenpolysiloxane is exemplified by methylhydrogenpolysiloxane having both terminal ends blocked by trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers having both terminal ends blocked by trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers having both terminal ends blocked by dimethylhydrogensiloxy
Oka Yutaka
Tsuji Yuichi
Yoshida Hiroaki
Dawson Robert
De Cesare Jim L.
Dow Corning Toray Silicone Co. Ltd.
Keehan Christopher M
Warren Jennifer S.
LandOfFree
Liquid silicone rubber composition for fixing rolls and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid silicone rubber composition for fixing rolls and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid silicone rubber composition for fixing rolls and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2846928