Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1994-05-24
1996-06-18
Thibodeau, Paul J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
277277, 277235R, 277235B, 4273722, 4273855, 427387, 4273898, 428290, 4283077, 4283111, 4283115, 4283191, 4283197, 4283202, 428426, 428432, 428450, 428454, 428461, 428463, 428500, F16J 1500, B05D 302, B32B 306
Patent
active
055275990
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to non-asbestos flexible sheet material suitable for use in gaskets operating at high temperature, such as those for the exhaust manifold of an internal combustion engine.
DESCRIPTION OF THE PRIOR ART
Flexible sheet material having a basis of asbestos is made of fibers of asbestos bound together with a binder (often starch) and is made with the use of conventional paper-making machinery such as a Fourdrinier machine. In the manufacture of exhaust manifold gaskets, asbestos paper is drawn from a reel and, with a sheet of the metal (e.g. tinplate) which is to form the support element of the gasket, is passed between rollers which urge the two sheets into engagement with one another, as by pushing shallow tangs on the metal sheet into the paper. Additionally, before passage of the sheets between the rollers, adhesive may be applied to the metal sheet or to the paper to improve bonding after engagement. From the composite sheet thus formed blanks are cut in the desired shape. Composite sheet as just described is usually made in three forms: single-sided (one layer of metal support, and one layer of paper); double-sided paper; and double-sided metal. The paper employed is ordinarily made so that it will serve for all three forms of gasket.
SUMMARY OF THE INVENTION
The present invention is concerned to provide flexible sheet material not having a basis of asbestos, but with the properties required for use in exhaust manifold and like gaskets, and in particular the flexibility and tensile strength to withstand being made up into gaskets without losing its integrity, the ability to withstand temperatures of 500.degree.-700.degree. C., and the ability to retain its sealing capacity despite the constant fluctuations in temperature to which it may be subjected in use.
It is already known, e.g. from our GB 2 138 854 A, to make such non-asbestos flexible sheet material by a paper-making procedure. We now provide an alternative process, which utilizes non-woven web of glass (such as is now commercially available for the manufacture of glass-reinforced plastic articles) or like fiber stable at 700.degree. C.
The method of the invention can be employed to produce composite sheet having a sealing performance superior to that of sheet utilizing a non-asbestos paper, as in its better stress-retention under clamping bolt pressure or its improved resistance to loss of integrity during prolonged use.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention provides a method of making non-asbestos flexible sheet material suitable for use in gaskets operating at high temperature, in which a non-woven web of inorganic fibers stable at 700.degree. C. is impregnated with an aqueous slurry of inorganic filler, said aqueous slurry including a dispersed elastomeric binder and a dispersed or dissolved binder which is essentially inorganic and is effective above 300.degree. C.; and the impregnated web is then dried.
The inorganic fibre may be mineral or carbon fiber, but is preferably glass fiber.
The inorganic filler is the major weight component of the slurry, and may be chosen from materials commonly used in papermaking e.g. barytes, mica, talc, limestone. A mixture of materials may be used. Preferably the inorganic filler is predominantly a clay, such as ball clay, china clay or calcined china clay, for clays help to confer a desirable thixotropy which makes for stability and homogeneity in the slurry, with the suspended solids showing little tendency to settle out, and enables a smooth surface finish to be readily obtained on the impregnated web.
The elastomeric binder which is dispersed in the aqueous slurry provides flexibility and compressibility in the sheet material produced, and acts as a binder at temperatures up to about 300.degree. C. It is, of course, an ingredient which is useful in the manufacture stage but quickly becomes destroyed when the gasket product is used at temperatures of 500.degree.-700.degree. C. Suitable elastomers are of the acrylic or nitrile b
REFERENCES:
patent: 2360830 (1944-10-01), Denman
patent: 3914490 (1975-10-01), Fusiek
patent: 4786670 (1988-11-01), Tracy et al.
Hall David G.
Kennerley Jonathan R.
Sand Stephen
T&N Technology Limited
Thibodeau Paul J.
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