Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1993-10-28
2001-12-25
Gallagher, John J. (Department: 1733)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C156S330000, C428S317100, C428S414000, C525S452000, C525S528000, C525S907000
Reexamination Certificate
active
06333101
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of adhering adherends. More particularly, the present invention relates to a method of adhering adherends using; an adhesive composition superior in thermal stability of adhesive strength, which is suitably used in production of gasket materials, electromagnetic interference shield materials, electric appliances, civil engineering and construction materials, household appliances, etc., all employing flexible material such as expanded graphite at least as one adherend.
BACKGROUND OF THE INVENTION
Expanded graphite sheets have flexibility and are obtained by subjecting a graphite of highly developed crystal structure, such as natural graphite, kish graphite, pyrolytic graphite or the like to an acid treatment with a strongly oxidizing solution such as concentrated sulfuric acid-nitric acid mixture, concentrated sulfuric acid-potassium permanganate mixture or the like to form a graphite intercalation compound, subjecting the graphite intercalation compound to water washing and then to rapid heating to convert it into a graphite powder which is expanded in the C axis direction of graphite crystal, and subjecting the graphite powder to cold processing.
Above-mentioned expanded graphite sheets are superior in heat resistance, chemical resistance, sealing property, stress relaxation, etc. and are therefore in wide use as a gasket material or an electromagnetic interference shield material for automobile engine, atomic reactor, ship building or general industrial use.
As the performance requirements for the above applications have become higher, the performance requirements for the expanded graphite sheet used therein have become higher as well. Expanded graphite sheets are considered to have problems particularly in mechanical properties (bending and tensile strengths) as well as in leakage and significant strength reduction both caused by the infiltration of liquid thereinto.
In order to solve these problems, use of reinforcing material for expanded graphite sheet was proposed. As the reinforcing material, there are used a metal plate, a metal foil, a metal net, a high-strength fiber and a fabric made of said fiber; and gaskets, etc. are in actual production by attaching such a reinforcing material to an expanded graphite sheet with an adhesive. As this adhesive, there have been mainly used those of rubber type, epoxy resin type, acrylic resin type, phenolic resin type or polyamide type. As the performance requirements for expanded graphite sheet have become higher as mentioned above, however, it has come to be pointed out that the above conventional adhesives are not sufficient in heat resistance, adhesive strength, chemical resistance, etc.
Meanwhile, adhesives of polyimide type or polybenzimidazole type with excellent heat resistance have been developed in recent years. These adhesives, however, have problems in that they contain a particular high-boiling solvent, must satisfy severe (high temperature and high pressure) adhesion conditions owing to the physical properties, are expensive, and are used in limited applications.
In order to solve these problems, modification of epoxy resin was attempted. For example, Japanese Patent Application Kokai (Laid-Open) No. 260669/1985 proposes a heat-resistant epoxy resin type adhesive, for example, comprising polyfunctional epoxy resin as triglycidyl ether of triphenol, an aromatic diamine as curing agent and an inorganic filler. Also, Japanese Patent Application Kokai (Laid-Open) Nos. 89380/1984 and 79079/1985 propose epoxy resin type adhesive compositions each comprising an epoxy resin and a rubber component dispersed therein.
These conventional compositions, however, are solid and have a short pot life, and are inferior in workability and insufficient in heat resistance. Further, Japanese Patent Application Kokai (Laid-Open) No. 30122/1987 describes a composition obtained by adding a thermosetting bismaleimide compound to a polyimide resin to achieve improved thermal stability of adhesive strength. This composition, however, has a high curing temperature of 275° C. and is far from practical applicability in production of gasket, etc.
The present invention is intended to provide a heat-resistant adhesive composition which can be used in adhesion of flexible material such as expanded graphite, etc. under mild conditions and which is superior in heat resistance, chemical resistance, and adhesive strength particularly at high temperatures.
SUMMARY OF THE INVENTION
The present invention provides a method of adhering adherends, at least one of which is made of a flexible material, using a heat-resistant adhesive composition comprising mainly a polycarbodiimide resin and an epoxy resin, wherein the proportion of the epoxy resin is 1 part by weight or more per 100 parts by weight of the polycarbodiimide resin.
The present invention provides a method of adhering adherend, at least one of which is made of a flexible material, using a heat-resistant adhesive composition comprising mainly a polycarbodiimide resin, an epoxy resin and a curing agent for the polycarbodiimide resin, wherein the proportions of the epoxy resin and the curing agent for the polycarbodiimide resin are 1 part by weight or more and 0.1 part by weight of more, respectively, per 100 parts by weight of the polycarbodiimide resin.
The present invention further provides a method of adhering adherends, at least one of which is made of a flexible material, using a heat-resistant adhesive composition comprising mainly a polycarbodiimide resin, an epoxy resin and a curing agent for the epoxy resin, wherein the proportion of the epoxy resin is 1 part by weight or more per 100 parts by weight of the polycarbodiimide resin and the proportion of the curing agent for the epoxy resin is 0.1 part by weight of more per 100 parts by weight of the epoxy resin.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is hereinafter described in detail.
The polycarbodiimide resin used in a heat-resistant adhesive composition of the present invention can be produced by, for example, a process disclosed in Japanese Patent Application Kokai (Laid-Open) No. 61599/1976, a process by L. M. Alberino et al. [J. Appl. Polym. Sci., 21, 1999 (1977)] or a process disclosed in Japanese Patent Application Kokai (Laid-Open) No. 292316/1990. That is, it can be produced by using an organic polyisocyanate as starting material and a catalyst which promotes the carbodiimidization of said isocyanate. As the organic polyisocyanate, there can be mentioned, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, crude tolylene diisocyanate, crude methylene diphenyl diisocyanate, 4,4′,4″-triphenylmethylene triisocyanate, xylene diisocyanate, hexamethylene-1,6-diisocyanate, lysine diisocyanate, hydrogenated methylene diphenyl diisocyanate, m-phenyl diisocyanate, naphthylene-1,5-diisocyanate, 4,4′-biphenylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethoxy-4,4′-biphenyl diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, isophorone diisocyanate and their mixtures.
The polycarbodiimide resin may be a polycarbodiimide having a controlled molecular weight, produced by, for example, using in the production, at least one monoisocyanate to terminate polycondensation at a certain stage. As such a monoisocyanate for blocking the terminals of the formed polycarbodiimide to control the molecular weight thereof, there can be mentioned, for example, phenyl isocyanate, o-, m-or p-tolyl isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate and methyl isocyanate. As is easily inferred, the terminal-blocking agent may also be a derivative of an isocyanate-terminated compound easily obtained by reacting about 1 mole of a compound having a —OH, —NH
2
, —COOH, —SH or —NH-alkyl terminal, with 2 moles of an aromatic diisocyanate.
The catalyst for promoting the carbodiimidization of isocyanate, used in the p
Amano Satoshi
Imashiro Yasuo
Itoh Takahiko
Saito Kazuo
Takahashi Ikuo
Gallagher John J.
Kubovcik & Kubovcik
Nisshinbo Industries Inc.
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