Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Patent
1995-09-19
1998-12-15
Yoon, Tae
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
428221, 428323, B32B 502, B32B 516, C08L 900
Patent
active
058494049
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a sheet material as well as to a process for production thereof. More particularly, the present invention relates to a sheet material which exhibits excellent flexibility, sealing property, strength, chemical resistance and heat resistance without using an asbestos fiber and which can be used as a gasket having excellent resistance particularly to fluoro carbon refrigerants and oils used in the apparatuses using said refrigerants; as well as to a process which can produce said sheet material easily, continuously and at a low cost.
BACKGROUND ART
An asbestos sheet is known as a sheet material used in gasket, etc. This asbestos sheet as a conventional sheet material is generally made of asbestos as a base material fiber, a rubber as a binder and a filler in order to have flexibility, sealing property, heat resistance and strength. With respect to asbestos, however, there have arisen in recent years problems such as exhaustion of asbestos resource, resultant difficulty in asbestos procurement, and adverse effect on human health; accordingly, the use of asbestos is under restudy.
Because of the above mentioned problems of asbestos, active researches have been conducted in the sheet material field in order to develop an asbestos sheet substitute by the use of a fibrous basic material other than asbestos. As asbestos substitutes, there have been proposed inorganic fibers such as glass fiber, rock wool, ceramic fiber, carbon fiber and the like, as well as organic fibers such as aramid fiber, polyester fiber, polyacrylonitrile fiber, phenolic resin fiber and the like.
However, none of these inorganic and organic fibers has yet shown fully satisfactory sealing property because their diameters are large as compared with those of asbestos and are disadvantageous to produce a sheet material of dense structure.
In order to overcome the drawback, it was proposed to use a thermoplastic polyolefin fiber or the like and melt bond the fiber to obtain improved sealing property. However, such a fiber generally causes remelting at a temperature of 1800.degree. C. or less and accordingly has insufficient heat resistance.
It was also proposed to increase the addition amount of a rubber to produce a sheet material of improved strength and sealing property. Such a sheet material, however, has low heat resistance and is easy to be flattened. In order to solve these problems, it was proposed to increase the amount of curing (crosslinking) agent for rubber. However, since the curing (crosslinking) agent is composed generally of sulfur or a peroxide, the proposal poses a new problem of metal corrosion and makes the approach of increasing the addition amount of rubber substantially meaningless.
Meanwhile, Japanese Patent Application Kokai (Laid-Open) No. 62814/1991 discloses a polycarbodiimide pulp obtained by converting an organic diisocyanate into a quaternary ammonium salt and then converting the salt into a polycarbodiimide. According to the literature, the polycarbodiimide pulp has heat resistance and can be used as a sheet material. It is feared, however, that the pulp, depending upon the application, generates an amine owing to the partial decomposition of the quaternary ammonium salt contained therein and the amine may pose an odor problem.
Recently, a need has increased for a gasket material which has durability to flon substitutes (these substitutes have come to be used in place of flon which causes the destruction of ozone layer) such as chlorofluorocarbons, hydrochlorofluorocarbons and hydrofluorocarbons, or to oils of polyalkylene glycol type or ester type used in the apparatuses using said refrigerants. Hence, it is desired to develop a sheet material having sufficient durability to said flon substitutes or said oils.
The objects of the present invention are to provide a sheet material which is free from the problems of the prior art, which exhibits excellent flexibility, sealing property, strength, chemical resistance and heat resistance without using an asbestos fiber
REFERENCES:
patent: 3963801 (1976-06-01), Su
patent: 4548999 (1985-10-01), Steinberger et al.
patent: 4718889 (1988-01-01), Blasius, Jr. et al.
patent: 4861828 (1989-08-01), Waggoner
patent: 4977218 (1990-12-01), Gardner et al.
patent: 5180631 (1993-01-01), Amano
Amano Satoshi
Ito Takahiko
Nisshinbo Industries Inc.
Yoon Tae
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