Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-08-17
2003-06-10
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C138S137000, C138S138000, C428S036800, C428S421000, C428S422000
Reexamination Certificate
active
06576311
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a rubber laminate and uses thereof, and more particularly to a rubber laminate having excellent heat resistance and rubber products prepared therefrom such as a hose, etc.
BACKGROUND ART
Fluororubbers are excellent in heat resistance, compression set, oil resistance and resistance to chemicals and are useful in the field of industrial materials and other fields. Nevertheless, it appears unlikely that these rubbers will be used in remarkably increased quantities in spite of their outstanding properties since economy is not negligible for prevalent use in these fields. Additionally, when fluororubbers are used as a material for an oil hose, they have the drawback of deteriorating markedly in the presence of additives contained in engine oils.
Other than fluororubbers, acrylic rubber and copolymer rubber of &agr;,&bgr;-unsaturated nitrile-conjugated diene monomer or its hydrogenated copolymer are relatively high in heat resistance and oil resistance, and are widely used as a material for an oil hose.
However, in recent years, an engine room reaches a high temperature increasingly in order to attain an improvement in performance and fuel consumption of automobiles. It is demanded for an oil hose as well to have more improved heat resistance, and conventional acrylic rubber and copolymer rubber of &agr;,&bgr;-unsaturated nitrile-conjugated diene monomer or its hydrogenated copolymer become insufficient in heat resistance.
In order to solve the above problem, it is investigated to laminate a fluororubber, and acrylic rubber, copolymer rubber of &agr;,&bgr;-unsaturated nitrile-conjugated diene monomer or its hydrogenated copolymer, and then to prepare a hose therefrom by molding (JP-A-169243/1986, JP-A-189934/1986, JP-A-51439/1987, JP-A-152060/1989, JP-A-159245/1989, U.S. Pat. No. 2,526,134). However, since the fluororubber is poor in affinity with other acrylic rubber, etc. and is different in cure formulation, there arises a problem that the laminate has a low adhesiveness between layers and is liable to separate. Further, an amount of the fluororubber is limited in view of cost, and it is difficult to improve sufficiently heat resistant temperature of a hose. Heat resistance herein includes for example excellent compression set which contributes to the hose being hardly separated from a metal pipe, in addition to resistance to oxidative-deterioration by high temperature air, resistance to swelling by high temperature oil, etc.
Although studies were also made on blends of acrylic rubbers and vinylidene fluoride resins (JP-A-39336/1988, JP-A-20341/1988, JP-A-19486/1988, JP-A-8447/1988, JP-A-236841/1987, JP-A-152133/1989 and JP-A-152016/1989), the products still remained to be improved in compression set because vinylidene fluoride resins can not be vulcanized and are crystalline.
An object of the present invention is to provide a rubber laminate which is excellent in heat resistance, compression set and oil resistance, and rubber products prepared therefrom.
DISCLOSURE OF THE INVENTION
The present invention provides a rubber laminate in which a rubber layer (1) containing the following rubber composition (A) is adhered by vulcanization to a rubber layer (2) containing another rubber composition (B).
Rubber composition (A): Composition comprising 100 parts by weight of a mixture and 0.1 to 15 parts by weight of a peroxide crosslinking agent admixed therewith, the mixture comprising 5 to 95 wt. % of a peroxide-crosslinkable fluororubber containing vinylidene fluoride copolymerized therein in a proportion of 45 to 88 mole % and having a number average molecular weight of 20,000 to 200,000, and 95 to 5 wt. % of an acrylic rubber containing 0.1 to 1.5 wt. % of a polyfunctional monomer copolymerized therein and having a functional group rendering the acrylic rubber peroxide-cocrosslinkable with the fluororubber and a functional group effecting the copolymerization of the monomer with an acrylic ester.
According to the rubber composition (A) of the invention, examples of peroxide-crosslinkable fluororubbers are vinylidene fluoride copolymers such as vinylidene fluoride/hexafluoropropylene, vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene and vinylidene fluoride/chlorotrifluoroethylene; copolymers such as tetrafluoroethylene/propylene, hexafluoropropylene/ethylene and fluoro(alkyl vinyl ether)/olefin (for example, vinylidene fluoride/tetrafluoroethylene/perfluoroalkyl vinyl ether), etc. Preferable among these are elastomers of vinylidene fluoride/hexafluoropropylene and vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene. The fluoro(alkyl vinyl ether) may contain a plurality of ether linkages. These fluororubbers are 20,000 to 200,000, preferably 20,000 to 100,000, more preferably 20,000 to 70,000, in molecular weight, i.e., in number average molecular weight. When to be used singly, fluororubbers are generally in excess of 200,000 in molecular weight to exhibit satisfactory characteristics. In contrast, the fluororubber to be compounded with the acrylic rubber for use in the invention fails to give satisfactory processability if exceeding 200,000 in molecular weight, while fully acceptable characteristics are unavailable after vulcanization if the molecular weight is lower than 20,000. The term processability means the viscosity of polymer at high temperatures, vulcanization characteristics and amenability to rolling process. The proportion of copolymerized vinylidene fluoride in the fluororubber is 45 to 88 mole %, preferably 55 to 65 mole % or 80 to 88 mole %, more preferably 55 to 63 mole % or 80 to 85 mole %.
When used singly, fluororubbers tend to lower in glass transition temperature with an increase in the proportion of copolymerized vinylidene fluoride. Fluororubbers also tend to exhibit higher compatibility with acrylic rubbers with an increase in this proportion. However, when compounded with acrylic rubber and if containing 65 to 80 mole % of copolymerized vinylidene fluoride, the fluororubber conversely tends to exhibit a higher glass transition temperature. Further the fluororubber containing 80 to 88 mole % of copolymerized vinylidene fluoride has poor rubber elasticity, is not usable singly as a rubber, but exhibits improved mechanical strength and higher compatibility with acrylic ubbers if compounded with acrylic rubbers. The fluororubber is then highly dispersible in alkyl (meth)acrylate polymers wherein the alkyl has at least 4 carbon atoms and which tend to exhibit lower compatibility with fluororubbers although having a low glass transition temperature. The fluororubber is low in compatibility with acrylic rubbers and encounters difficulty in giving higher dispersibility to polymers if less than 45 mole % in the proportion of copolymerized vinylidene fluoride. Impaired compression set will result if this proportion exceeds 88 mole %.
The fluororubbers of the invention include, for example, iodine-containing fluororubbers, which will be described below.
The preferred examples of iodine-containing fluororubbers include a readily curable fluororubber (see JP-A-125491/1978) which is obtained by polymerizing vinylidene fluoride (VdF) and at least one of monomers comprising a fluorine-containing ethylenically unsaturated compound having 2 to 8 carbon atoms (and when required, a fluorine-free ethylenically unsaturated compound having 2 to 4 carbon atoms) in the presence of a radical generator and an iodine compound represented by the formula RI
x
(wherein R is a saturated or unsaturated fluorohydrocarbon group having 1 to 16 carbon atoms, chlorofluorohydrocarbon group or hydrocarbon group having 1 to 3 carbon atoms, and x, which is the number of bonds of R, is an integer of not smaller than 1). Useful iodine-containing fluororubbers are copolymers containing 45 to 88 mole %, preferably 55 to 65 mole %, more preferably 55 to 63 mole %, of vinylidene fluoride (VdF) unit, 0 to 55 mole %, preferably 13 to 25 mole %, of tetrafluoroethylene (TFE) unit and 10 to 40 mole %, preferably 10 to 25 mole %, of hexafluoro
Kishine Mitsuru
Matsumoto Kazuhisa
Noguchi Tsuyoshi
Ono Tsuyoshi
Daikin Industries Ltd.
Kubovcik & Kubovcik
Nolan Sandra M.
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