Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-12-23
2001-02-20
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C526S248000, C526S261000, C522S167000
Reexamination Certificate
active
06191233
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fluorine-containing triallyl isocyanurate, a curing agent comprising a fluorine-containing triallyl isocyanurate, a curable elastomer composition comprising such a curing agent, and a method for the curing of such a composition.
PRIOR ART
Triallyl isocyanurate (hereinafter referred to as “TAIC”) is a symmetric polyfunctional triazine compound, and used as a reactive monomer, a crosslinking agent of various synthetic resins and synthetic rubbers, a crosslinking aid, and a modifier.
TAIC can greatly improve the heat resistance, mechanical properties, weather resistance, hydrolysis resistance, etc. of various polymer, by making effective use of good heat resistance of a triazine ring which forms a core structure of TAIC.
For example, when TAIC is used as a crosslinking aid in the peroxide curing of fluororubbers which are required to have very high heat resistance, it achieves high advantages that the fluororubbers can be very effectively cured, and the obtained cured materials have good mechanical properties. However, the heat resistance of the cured materials is not always satisfactory in comparison with the heat resistance of cured materials which are cured by other curing systems such as a polyol or polyamine curing system. Thus, it is desired to improve the heat resistance of cured materials of fluororubbers obtained by peroxide curing.
A proposal is made in U.S. Pat. No. 4,320,216 to replace a part of hydrogen atoms in the three allyl groups of TAIC with a fluorine atom which improves heat resistance. However, this U.S. patent describes the use of such a fluorine-substituted TAIC as a modifier to obtain gelled fluororubbers by copolymerization.
Klenovich, S. V. et al describe, in Zh. Prikl, Khim. (Leningrad) (1987), 60(3), 656-8, 1,3,5-tris(2-fluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione, which is a derivative of TAIC in which a part of hydrogen atoms in the three allyl groups of TAIC are replaced with fluorine atoms which improve heat resistance. However, this literature reports only that the replacement of a hydrogen atom at the 2-position of an allyl group retards the transfer from TAIC, but does not describe the use of such a compound as a crosslinking aid for fluororubbers.
PROBLEMS TO BE SOLVED BY THE INVENTION
The present invention intends to provide a derivative of TAIC, which has very good curing properties when used as a crosslinking aid for fluororubbers which are required to have high heat resistance, and which is useful as a crosslinking aid that can provide a cured material having excellent mechanical properties and also heat resistance.
MEANS TO SOLVE THE PROBLEMS
According to the first aspect, the present invention provides a fluorine-containing triallyl isocyanurate of the formula [I]:
wherein at least one of X and Y is a fluorine atom, and the other is a hydrogen atom or a fluorine atom.
According to the second aspect, the present invention provides a crosslinking aid comprising a fluorine-containing triallyl isocyanurate of the formula [II]:
wherein at least one of X, Y and Z is a fluorine atom, and the others are hydrogen or fluorine atoms.
According to the third aspect, the present invention provide a curable elastomer composition comprising a peroxide-curable elastomer, a fluorine-containing triallyl isocyanurate of the above formula [I] or [II] as a crosslinking aid, and an organic peroxide.
According to the fourth aspect, the present invention provides a method for the curing of a peroxide-curable elastomer comprising curing such an elastomer with an organic peroxide in the presence of a fluorine-containing triallyl isocyanurate of the above formula [I] or [II] as a crosslinking aid.
According to the fifth aspect, the present invention provides a shaped article, in particular, a sealing material, obtained by shaping the curable elastomer composition of the present invention.
One of the reasons for the low heat resistance of the organic peroxide-cured materials of fluororubbers using conventional fluorine-free triallyl isocyanurate may be the insufficient heat resistance of bonds (crosslinked sites) between the fluororubbers and the crosslinking aid. It may be assumed that the introduction of a fluorine atom or fluorine atoms into the allyl groups of TAIC can improve the heat resistance of crosslinked sites.
The fluorine-containing triallyl isocyanurate of the present invention can be prepared from a corresponding starting material by the same method as that for the preparation of conventional triallyl isocyanurate.
For example, diethyl azodicarboxylate is dropwise added into a solution of a fluorine-containing allyl alcohol, cyanuric acid and triphenylphosphine in, for example, dimethylacetamide, and stirred at room temperature for several hours. The solvent is evaporated off from the resulting reaction mixture, and the concentrated mixture is purified by silica gel chromatography. The details of such a method will be described in the Examples below.
Preferable examples of the fluorine-containing triallyl isocyanurate of the present invention are 1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione, and 1,3,5-tris(2,3-difluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione.
The fluorine-containing triallyl isocyanurate of the present invention is preferably used as a crosslinking aid when elastomers are cured with peroxides. When a fluorine-containing triallyl isocyanurate is used as a crosslinking aid, any known fluorine-containing isocyanurate may be suitably used.
The known fluorine-containing isocyanurates include 1,3,5-tris(2-fluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione, 1,3,5-tris(3-fluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione, 1,3,5-tris(3,3-difluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione, etc.
Elastomers which can be cured using a curing aid comprising the fluorine-containing triallyl isocyanurate of the present invention include the following elastomers which may have the crosslinking site of a halogen atom such as an iodine atom or a bromine atom:
vinylidene fluoride-hexafluoropropylene elastomers, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene elastomers, vinylidene fluoride-chlorotrifluoroethylene elastomers, tetrafluoroethylene-propylene elastomers, hexafluoropropylene-ethylene elastomers, perfluoro(alkyl vinyl ether)-tetrafluoroethylene elastomers, vinylidene fluoride-tetrafluoroethylene-perfluoro(alkyl vinyl ether) elastomer.
The above fluorine-containing elastomers may contain a copolymerized crosslinking-site monomer of the following formula, in place of or in addition to the crosslinking site of a halogen atom such as an iodine atom or a bromine atom:
X
1
CH
2
CF
2
CF
2
(OCH
2
CF
2
CF
2
)
m
(OCFY
1
CF
2
)
n
OCF═CF
2
wherein X
1
is a halogen atom, Y
1
is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 5, and n is an integer of 0 to 2;
and
BrCF
2
CF
2
O—CF═CF
2
In addition to the above-exemplified fluoroelastomers, the following hydrocarbon elastomers may be exemplified as peroxide-curable elastomers:
acrylic rubbers, natural rubbers, synthetic rubbers, ethylene-propylene rubbers, ethylene-propylene-third diene rubbers, butadiene-styrene rubbers, polybutadiene rubbers, halogenated butyl rubbers, chloroprene rubbers, isobutylene-isoprene rubbers, butadiene-acrylonitrile rubbers, chlorosulfonated polyethylene rubbers, epichlorohydrine rubbers, and epichlorohydrine-ethylene oxide rubbers.
The acrylic rubbers will be explained in detail.
A peroxide-curable acrylic rubber may be prepared by copolymerizing the combination of the following (meth)acrylate ester monomer and the following polyfunctional monomer by any conventional polymerization method.
A (meth)acrylate ester monomer is represented by the formula:
CH
2
═C(R
1
)COOR
2
wherein R
1
is a hydrogen atom or a methyl group, and R
2
is a C
1
-C
8
alkyl group which may be substituted with an alkoxy group. Specific examples of such an ester are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acr
Iseki Katsuhiko
Iwasaki Yasuji
Kishine Mitsuru
Mori Yoshiko
Oishi Satoshi
Asinossky Olga
Birch & Stewart Kolasch & Birch, LLP
Daikin Industries Ltd.
Seidleck James J.
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