Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-01-16
2003-09-23
Dawson, Robert (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C428S405000, C528S031000, C528S034000, C528S042000, C528S015000, C524S588000, C525S431000
Reexamination Certificate
active
06624231
ABSTRACT:
This invention relates to curable compositions which cure into parts having good solvent resistance, chemical resistance, heat resistance, low-temperature properties, mold release, water and oil repellency and weather resistance and more particularly, to curable compositions which cure into fluorinated elastomers having significantly improved mechanical strength and compression set as well as the foregoing properties and thus suitable as O-rings and sealing members.
BACKGROUND OF THE INVENTION
Curable fluorinated elastomer compositions utilizing addition reaction between alkenyl and hydrosilyl radicals are well known in the art. The applicant (assignee) previously proposed in Japanese Patent Application No. 11-53543 (U.S. Ser. No. 09/517,056 and EPA 00301722.5) to add microparticulate silica surface treated to be hydrophobic and having a specific surface area of at least 50 m
2
/g to such a composition whereby a cured product is improved in mechanical strength and compression set. The composition can be cured by brief heating. The cured product has good solvent resistance, chemical resistance, heat resistance, low-temperature properties, mold release, water and oil repellency and weather resistance and is useful in sealing applications where such properties are required.
However, the composition of the preceding application has the problem that mechanical strength sometimes declines as compression set lowers. With respect to the compression set itself, there is still left room for improvement, as compared with other fluoro-rubbers. Automotive parts such as O-rings and diaphragms and semiconductor parts are required to have long-term reliability although the service conditions under which they are used become increasingly strict. It is thus strongly desired to improve the compression set.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved curable composition which cures into a fluorinated elastomer that has good solvent resistance, chemical resistance, heat resistance, low-temperature properties, mold release, water and oil repellency and weather resistance as well as improved mechanical strength and compression set.
The present invention is predicated on the following discovery. It is directed to an addition reaction type curable composition based on (A) a fluorinated amide compound having at least two alkenyl radicals in a molecule, to which (B) a fluorinated organohydrogensiloxane is compounded as a crosslinker and chain extender, and (C) a platinum group compound is added as a curing catalyst. To the composition are added (D) silica powder as a reinforcing filler, and (E) a fluorinated organosilane or organosiloxane and (F) an alkenyl-bearing fluorinated organosilane or organosiloxane as a surface treating agent for the silica powder. The curable composition thus formulated cures into a fluorinated elastomer having good solvent resistance, chemical resistance, heat resistance, low-temperature properties, mold release, water and oil repellency and weather resistance as well as improved mechanical strength and compression set.
Specifically, the invention provides a curable composition comprising as essential components,
(A) a fluorinated amide compound having at least two alkenyl radicals in a molecule,
(B) a fluorinated organohydrogensiloxane having at least two hydrogen atoms attached to silicon atoms in a molecule,
(C) a catalytic amount of a platinum group compound,
(D) a silica powder having a BET specific surface area of at least 50 m
2
/g,
(E) an organosilane or organosiloxane having in a molecule at least one monovalent perfluorooxyalkyl, monovalent perfluoroalkyl, divalent perfluorooxyalkylene or divalent perfluoroalkylene radical and at least one hydroxy and/or alkoxy radical directly attached to a silicon atom, and
(F) an organosilane or organosiloxane having in a molecule at least one alkenyl radical, at least one monovalent perfluorooxyalkyl, monovalent perfluoroalkyl, divalent perfluorooxyalkylene or divalent perfluoroalkylene radical, and at least one hydroxy and/or alkoxy radical directly attached to a silicon atom.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Briefly stated, the curable composition of the invention contains (A) a fluorinated amide compound having at least two alkenyl radicals in a molecule as a base polymer, (B) a fluorinated organohydrogensiloxane as a crosslinker and chain extender, (C) a platinum group compound as a curing catalyst, (D) silica powder as a reinforcing filler, (E) a fluorinated organosilane or organosiloxane as a surface treating agent for the silica powder, and (F) an alkenyl radical-bearing fluorinated organosilane or organosiloxane as a surface treating agent for the silica powder and compression set reducing agent.
Component (A) is a fluorinated amide compound which should have at least two alkenyl radicals in a molecule, and preferably at least one alkenyl radical at each of opposite ends. In the compound, fluorine is preferably contained as a monovalent perfluorooxyalkyl, monovalent perfluoroalkyl, divalent perfluorooxyalkylene or divalent perfluoroalkylene radical. Preferably the compound has the following linkage.
Herein R
2
is hydrogen or a substituted or unsubstituted monovalent hydrocarbon radical having 1 to 10 carbon atoms, especially 1 to 8 carbon atoms, and preferably free of aliphatic unsaturation.
Further, the compound may have the following linkage.
Herein R
2
is as defined above; R
3
is a substituted or unsubstituted divalent hydrocarbon radical which may be separated by at least one atom of oxygen, nitrogen and silicon atoms; R
4
and R
5
each are a substituted or unsubstituted divalent hydrocarbon radical.
The fluorinated amide compound (A) is preferably of the following general formula (1).
Referring to formula (1), R
1
stands for substituted or unsubstituted monovalent hydrocarbon radicals preferably of 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and also preferably free of aliphatic unsaturation. Examples include alkyl radicals such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl and decyl; cycloalkyl radicals such as cyclopentyl, cyclohexyl and cycloheptyl; alkenyl radicals such as vinyl, allyl, propenyl, isopropenyl, butenyl, and hexenyl; aryl radicals such as phenyl, tolyl, xylyl and naphthyl; aralkyl radicals such as benzyl, phenylethyl and phenylpropyl; and substituted ones of these radicals in which some or all of the hydrogen atoms are replaced by halogen atoms or the like, typically fluorinated alkyl radicals such as chloromethyl, chloropropyl, bromoethyl, 3,3,3-trifluoropropyl, and 6,6,6,5,5,4,4,3,3-nonafluorohexyl.
R
2
stands for hydrogen or substituted or unsubstituted monovalent hydrocarbon radicals preferably of 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and also preferably free of aliphatic unsaturation, as defined above for R
1
. Examples of the monovalent hydrocarbon radicals are as exemplified above for R
1
, for example, alkyl radicals such as methyl, ethyl, propyl, and isopropyl; cycloalkyl radicals such as cyclohexyl; alkenyl radicals such as vinyl and allyl; aryl radicals such as phenyl and tolyl; and substituted ones of these radicals in which some hydrogen atoms are replaced by halogen atoms or the like, typically fluorinated alkyl radicals such as chloromethyl, chloropropyl, 3,3,3-trifluoropropyl, and 6,6,6,5,5,4,4,3,3-nonafluorohexyl.
Q is a radical of the following general formula (2) or (3).
R
2
in formula (2) is as defined above. R
3
may be selected from substituted or unsubstituted divalent hydrocarbon radicals, preferably from divalent hydrocarbon radical of 1 to 20 carbon atoms, especially 2 to 10 carbon atoms. Examples include alkylene radicals such as methylene, ethylene, propylene, methylethylene, butylene and hexamethylene; cycloalkylene radicals such as cyclohexylene; arylene radicals such as phenylene, tolylene, xylylene, naphthylene and biphenylene; substituted ones of these radicals in which some hydrogen atoms are replaced by halogen atoms or the lik
Birch & Stewart Kolasch & Birch, LLP
Dawson Robert
Shin-Etsu Chemical Co. , Ltd.
Zimmer Marc S.
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