GB2363172A - A process for preparing high sealing gaskets - Google Patents

Abstract

A process for coating gasket edges which surround an aperture in the gasket comprising placing a plurality of the sheets together so that a cavity is formed by the apertures, the sides of the cavity being the aperture edges to be coated. The sides of the cavity are the aperture edges to be coated. The coating material is introduced into the cavity and contacts the edges to be coated to form the coated edges. If there is any coating material left it is removed, and then the gasket edges are dried.

Description

2363172 HIGH SEALING GASKETS This invention relates to gaskets which have

good sealing properties even at low flange pressures. More particularly, the present invention relates to gaskets which can be used to seal fluids. The invention makes it possible to provide gaskets which, when positioned in a flange to seal against fluids, can seal against fluid leaks both through the gasket sheet internally and across the gasket face.

Gaskets are used, for example, to seal fluids in engines. A number of proposals have been made in order to obtain good sealability (sealing ability) in the gaskets.

Beading on the face of a gasket is known. Such beading is a raised area on the face; this beading, however, does not extend past the edge and further does not extend onto the edge. Such beading is used to enhance sealing.

A gasket material which can be used to give a good seal at high temperatures is described in U.S. 5,240,766. This reference describes a gasket sheet material comprising fibre, filler, and binder. According to the reference, the filler component provides desirable sealability.

Another reference which describes gasket sheet materials is U.S. 5,536, 565. This reference describes a gasket sheet material with fibre and filler. The filler component must include a gel-forming mineral. This filler gives the gasket good sealing properties, especially against polar liquids.

In spite of the wide use of gaskets to obtain a seal against fluids in engines, obtaining a good -seal continues to be a problem in gasket sheet materials. Many gaskets do not seal well at low flange pressures. Other gaskets are given coatings in order to obtain a gasket sheet which will seal well. Unfortunately, such coatings are then responsible for the gasket having poor compression failure resistance.

Gaskets according to the invention can provide good sealing ability even at low flange pressures. In some embodiments the gasket is not coated or has only a limited amount of a coating provided in order to obtain good sealability, thus allowing the gasket also to be compression failure resistant.

The present invention provides a gasket comprising a sheet with two faces, each face having a facial plane, the planes being substantially parallel to each other, the gasket having an aperture and an edge surface around the aperture, the edge surface having a comer abutting each face and being substantially perpendicular to the facial planes, the edge surface having a coating on it which is wider than the edge surface in a direction parallel to the edge surface so that the coating protrudes past at least one comer of the edge surface and forms a barrier against fluids to retard fluid from going from the aperture past the edge and across at least one of the faces, the barrier formed by the coating extending past the said comer by an amount which is effective to give the gasket a better sealing ability than the gasket would have if the coating was no wider than the edge surface and each comer of the edge abutting one face, the barrier formed by the coating extending at least about 1 mil (0.025 mm) past the said comer in a direction substantially perpendicular to the facial planes of the gasket, and the sheet being compressible and porous.

The sheet is compressible and porous. A sheet, for example, a metal sheet, that is not porous will not be compressible, as there is no pore space to allow the sheet material to contract under a load: a non-porous sheet will simply deform if the load is large enough, or resist the load if that load is not big enough.

Where a gasket has a coating on a gasket face, specific figures given herein for the extent to which an edge coating on a gasket protrudes (whether around an aperture, or at the gasket perimeter) indicate the extent to which the edge coating protrudes beyond the facial coating (the coating surface is the facial plane in this case).

The invention also provides a gasket comprising a sheet with two opposed faces, each face having a facial plane, said gasket having an aperture and an edge surface around the aperture, said surface being substantially perpendicular to the facial planes, the edge surface having a coating on it which is wider than the edge surface in a direction parallel to the edge surface so that the coating protrudes at least about 1 mil (0.025 mm) beyond the facial plane of at least one face and extends past the facial plane in a direction perpendicular to the plane, the sheet being compressible and porous.

The invention further provides a gasket comprising a sheet with two faces, each face having a facial plane, the planes being substantially parallel to each other, said gasket further having an aperture and an edge surface around the aperture, said edge surface being substantially perpendicular to the planes, the edge surface having a coating which is wider than the edge surface in a direction parallel to the edge surface so that the coating protrudes past a comer of the edge surface and forms a barrier against fluids, the coating extending past the comer in an amount which is effective to give the gasket a better sealing ability than the gasket would have if the coating was no wider than the edge surface, said comer being between the edge and one face, the barrier formed by the coating extending past the comer in a direction substantially perpendicular to the facial planes of the gasket, and the sheet being compressible and porous.

The invention also provides a gasket sheet comprising two opposed faces and an aperture in the sheet, the sheet being compressible and porous and having an edge around the aperture, the edge being substantially perpendicular to the opposed faces, the edge having a coating on it which forms a barrier to retard fluid from going from the aperture, past the edge and across either one of the gasket faces, wherein the edge has a comer abutting each face and the coating barrier further extends at least about 5 mils (0. 125 mm) past each comer of the edge in a direction substantially perpendicular to a facial plane of the gasket, the coating having a surface abutting each comer of the gasket, said coating surface forming an inclined plane on each side abutting the gasket sheet between the sheet and the aperture as a result of the coating on the edge getting gradually wider in a direction substantially perpendicular to the edge.

The invention further provides a gasket sheet comprising two faces, each face having a facial plane, the planes being substantially parallel to each other, said gasket having an outside edge around the gasket sheet forming a perimeter, the edge being substantially perpendicular to the facial planes and having two comers, each comer being between the edge and a face, the edge having a coating on it which forms a barrier to retard fluid from flowing past at least one gasket face, the barrier further extending past a corner of the edge in a direction substantially perpendicular to a facial plane of the gasket, the gasket sheet being compressible and porous.

The invention also provides a process for coating an aperture edge of a soft gasket sheet wherein the gasket sheet has two substantially opposed, facial surfaces and an aperture with the edge substantially perpendicular to the facial surfaces, the apertures of each gasket sheet being substantially identical in size and shape, comprising placing a plurality of the sheets together so that a cavity is formed by the apertures of the plurality of gasket sheets, and contacting the edges of the aperture on each gasket sheet with a coating material so that the edges become coated in an amount effective to achieve a substantial sealing of the gasket along the edge of the aperture where the edge is coated, and a gasket made by the process.

The invention further provides an article which includes a gasket according to the invention, and the use of a gasket according to the invention to enhance sealing in an article.

In another aspect, the invention provides gasket sheet comprising two opposed faces, and an aperture with a gasket sheet edge (also called the aperture's edge or the aperture's gasket sheet edge) which is preferably substantially perpendicular to the opposed faces. The sheet edge has at least one body which forms a barrier or dam to retard fluid from going from the aperture, past the edge and across a face of the gasket.

The barrier can protrude from the edge or from the gasket face. When the barrier protrudes from the edge it gets wider in a direction perpendicular to a facial plane of the gasket, and it protrudes past a comer plane at some point between the sheet edge and the aperture. The barrier is sufficiently wide to retard the flow of fluid from the aperture across the face of the gasket: thus the barrier protrudes a sufficient distance past the comer of the gasket sheet edge to be effective to give the gasket a better sealing ability than the gasket would have if the barTier stopped at a point in a plane going through the comer of the edge (stopped at the comer between the face and the edge).

Preferably, the barrier is formed by a coating that is wider than the thickness of the aperture's gasket sheet edge, measuring the width of the coating in a direction parallel to the sheet edge from one of the comers between the edge and one face through the other comer between the edge and the other face. The coating, at the edge, is thus sufficiently wide to extend past at least one of said comers in a direction parallel to the surface of the sheet edge. The coating on the edge of the gasket sheet at the aperture goes beyond one of said comers to an extent sufficient to give the gasket a better. sealing ability than the gasket would have if the coating was only as wide as the thickness of the gasket sheet edge and thus stopped at both comers. The coating, however, does not necessarily lap around the comer onto the face of the gasket, although, optionally, it can.

The coating on the sheet edge, going beyond at least one of the comers lying between a face and the aperture's gasket sheet edge (where the edge meets a gasket face), is herein referred to as a "wide edge coating" or a "protruding coating". A comer is located at each side of the edge where it abuts a face, at the point between the face and the edge; this point can be identified easily as the point where the cut, frequently porous, edge ends and the less porous, non-cut face of the gasket begins.

In some embodiments the gasket is provided with a protruding coating on the sheet edge which is around the outside of the gasket (coating C). This is a secondary sealing position which prevents fluid from leaking past the gasket and outside of the flange, and as such it is less preferred than the coatings on the aperture's edge which seals the gasket where the gasket is first and primarily exposed to fluid (giving a primary seal). The edge coating around the perimeter of the gasket (coating C), must protrude past at least one comer of the edge of the gasket sheet, and preferably, in embodiments where the facial plane does not go through the comer of the gasket edge, the coating protrudes past the facial plane.

The protruding coating applied to the gasket may extend onto either or both faces, and may extend so far as to completely cover one or both faces of the gasket: the coating must protrude to provide the barrier, and not be a level coating over the gasket. When the edge coating sticks up past the comer plane or facial plane at an edge, the coating provides a dam to retard fluids from going from the aperture past the edge and out onto the gasket face between the face and a flange; where the edge is a perimeter edge the coating protrusion will stop fluids from going past the gasket out of the flange.

A completely coated gasket can take advantage of the sealing made possible by the present invention, although in some embodiments, to preserve compression failure resistance, the amount of coating is preferably limited so that the coating covers only a portion of the gasket, the rest of the gasket being left uncoated. In such embodiments it is preferred to use a wide edge-coating to seal off the aperture's gasket sheet edge to fluids that go through the gasket itself. Preferably, to preserve compression failure resistance a coating will not cover more than about 50% of the gasket, and even more preferably it is limited to cover a maximum of about 30% of the gasket. In another preferred embodiment there is no coating on either face of the gasket so that the gasket has optimized compression failure resistance.

Compression failure resistance is the ability of a gasket structure to withstand pressure without the gasket being deformed to the point of failure. The crush test is an industry accepted measurement of compression failure resistance. The degree of compression failure resistance that a gasket must have is typically established by the load that it will experience in a particular application or a specific flange.

Suitably, the coating on the edge covers all of the portions of the edge which must be coated in order to give the gasket a good sealing ability. It may not be necessary, to have the coating on the edge at, for example, bolt areas, or at non-porous portions of the edge. The edge is coated to allow the gasket to provide a better seal. Acceptable embodiments include instances where the coating covers major portions of the edge. The gasket sheet edge can thus be coated to an extent effective to achieve a substantial sealing of the gasket along the edge of the aperture. The edge, for example, can be coated up to about 75 % of the aperture's gasket edge. Such embodiments can be used for good sealing ability, where the very best sealing ability (obtained from coating the entire edge of the gasket) does not have to be used. Preferably, however, the entire edge of the aperture is coated.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a photograph showing an enlargement of a cross-section through a portion of a gasket with an aperture having a coated edge. A portion of the coated aperture's gasket sheet edge is shown in the cross-section; this sheet edge is substantially perpendicular to opposed, parallel planes, one plane lying on each face of the gasket (a facial plane). In the photograph the gasket can be seen to have two faces which are substantially parallel. The comer between the coated sheet edge and face is seen in the photograph at the top and bottom of the gasket sheet. In a direction parallel to the coated edge of the gasket, the coating is wider than the edge and goes past the comer of the coated edge to thus protrude past the comer on the edge. Moreover, in fact, the coating is sufficiently wide so that the coating itself protrudes past the facial plane on at least one side of the gasket. The coating is a silicone rubber coating.

Fig. 2 is a photograph showing an enlargement of the cross-section through a portion of a gasket which has an aperture with a coated edge. A portion of the coated gasket edge is shown. The coated edge of the gasket sheet is seen and is substantially perpendicular to each face and to the opposed, parallel, facial planes that lie along each of the gasket's substantially parallel faces. In the photograph the comer between each face of the gasket and the coated edge of the gasket sheet is seen at the top and bottom of the gasket. In Fig. 2, going through the coating in a direction parallel to the edge of the gasket in the direction parallel to the edge of the gasket in the direction going from comer to comer, the coating is wider than the coated gasket sheet edge and in fact is sufficiently wide so that the coating itself protrudes past the comer on each side of the edge, and in this embodiment the coating also protrudes past the facial plane on both sides of the gasket. This gives the gasket a better sealing ability than it would have if the coating were level with the gasket on each face. It thus gives the gasket a barrier on the gasket sheet edge to retard the flow of fluids from the aperture across the face of the gasket sheet. In this embodiment the coating also extends out onto the gasket face on each side of the gasket. The coating is an acrylic latex.

Fig. 3 is a photograph showing an enlargement of a cross-sectional through a portion of a gasket having an aperture with a coated gasket sheet edge. The coated edge is substantially perpendicular to each gasket face and to each of the opposed, parallel, facial planes that contains each gasket face. The photograph shows a portion of the coated edge on the gasket sheet. Also, the comer between each face and the coated gasket sheet edge is seen at the top and bottom of the gasket in the photograph. In the direction from comer to comer parallel to the gasket sheet edge of the gasket, the coating is wider than the edge and goes past each comer and, in fact, the coating is sufficiently wide so that the coating itself goes past the facial plane on each side of the gasket. In this embodiment the coating does not extend out onto either one of the gasket faces. The coating on each side of the gasket gets gradually wider than the edge until the coating comes to a point (see also Fig. 4). The embodiment shown in this photograph provides a gasket with a sealing ability ranging from a good seal to a total seal and simultaneously provides the best (most optimized) compression failure resistance since neither of the gaskets faces has any coating to seal the gasket. The coating is an acrylic latex.

Fig. 4 shows an enlarged schematic cross-section through a portion of a gasket having a coating on the gasket sheet edge 71, said edge being substantially perpendicular to the opposed planes 34 and 35 containing the gasket faces 15 and 30. The coating, in a direction parallel to the edge, is sufficiently wide so that the coating goes past the planes 34 and 35 on both sides of the gasket. Here, each of planes 34 and 35 is both a facial plane and a comer plane (going through the comer between the face and the coated gasket edge). The coating, which becomes gradually larger in a direction extending away from the gaskets edge 71, flares so that the surface of the coating forms an inclined plane up to its widest point. The coating forms a barrier against the passage of fluids across the face of the gasket This is a preferred embodiment of the present invention (also shown in Fig. 3).

Fig. 5 shows an enlarged schematic cross-section through a portion of a gasket having a coating on an aperturds gasket sheet edge 72, said edge being substantially perpendicular to opposed faces 17 and 31. The coating 18 is wide enough, in a direction parallel to the edge, to extend past the comer of the gasket at the top of edge 72, and past the facial plane 54. Here, the facial plane 54 is not the same as the comer plane (not indicated) which goes through the comer of the edge.

Fig. 6 shows an enlarged schematic cross-section through a portion of a gasket having a coating on an apertures gasket sheet edge 75. The edge (or edge surface) is substantially perpendicular to opposed faces 24 and 32. The coating 26 protrudes past "facial planes" or "comer planes" 37 and 38 on both sides of the gasket. Here, the facial plane and the comer plane are the same plane.

Fig. 7 is a plan view of a gasket 10 having a coated edge 12. A portion of the face of the gasket is also coated (11).

Fig. 8 shows an enlarged schematic cross-section through a portion of the gasket of Fig. 7, taken on the line 8-8. The coating 12 is indicated on the aperture's gasket sheet edge 76 and the extended portion 11 of the coating that laps onto face 25 is also indicated. Facial, comer planes 39 and 65 are shown. The coating protrudes past the planes, going in a direction parallel to edge 76. In more preferred embodiments the coating will protrude at least about 1 mil (0.025 mm) past that part of the coating that is on the face of the gasket, as is shown, for example, by Figs. 2 and Fig. 8. In Fig. 2 the coating is seen to extend out onto the face of the gasket, but the coating from side to side in a direction parallel to the edge is mfider than the distance from the surface of the coating passing through the gasket sheet and out to the surface of the coating on the other side. In Fig. 8 the barrier against fluids extends over the faces 25 and 33. In Fig. 2 on each side of the gasket the barrier against fluids rests on and inclines slightly over the gasket face.

Fig. 9 shows an enlarged schematic cross-section through a portion of a gasket having a coating 41 on the edge 77. The coating protrudes past the comer of the edge which lies between the face 40 and the edge 77. The coating extends past the comer plane 80 but does not extend past the facial plane 36. Such a coating provides a barrier, on one side of the gasket, against fluids that might otherwise go from the aperture across the face 40 of the gasket, although the barrier (dam) is not as high, i.e. does not extend as far past the relevant face 24 as does the coating of Fig. 6.

Fig. 10 shows an enlarged schematic cross-section through a gasket having an outer edge or perimeter 47 and having coating 48 on an gasket sheet edge 78 of an aperture. The gasket has beading 46 and surface areas which are lower 49 than the facial plane; these areas can be made by embossing. The coating 48 extends past the plane 60 which is both a facial plane and a comer plane. Faces 44 and 45 both have areas made by embossing and beading; the extension of the facial plane 60 is seen going through the gasket face, from one side of the gasket, across the gasket to the other side. It will be noted that the facial plane 60 contains the flat portions of the face 45 of the gasket and the comer between the coated edge 78 and the face 45.

Unless otherwise indicated, the following description is generally applicable, and does not relate solely to embodiments of the invention shown in the drawings.

A protruding coating can be effective to retard or to stop the flow of fluids across the face of gaskets which must seal against fluids. The coating does this by providing a dam on the edge of the gasket. This "dam" is the protruding portion of the edge coating and is a preferred barrier to the fluid.

A soft gasket material comprising a binder and fibre and/or filler can be given an edge seal on a aperture exposed to a fluid, thus giving a seal against the fluid. Surprisingly, there is no need to change the composition of the sheet material to obtain a significant improvement in sealing ability. The edge coating provides the seal. Surprisingly, in many cases there is no need for significant sealing ability in the base sheet. Furthermore, a base sheet with an edge seal can accommodate many different types of flanges without any change being made to the base sheet.

Any gasket material which seals against fluids can take advantage of the present invention. This includes coated or uncoated gaskets; soft gasket materials; and layered gaskets such as gaskets which have a compressible or non-compressible core between two layers or which have an incompressible substrate sheet on one side of the gasket. In embodiments where the gasket has more than one layer, a protruding coating on the edge of the aperture could be only on one layer. Preferably, however, the protruding coating would extend across the layers completely in a direction from one of the comers between a face and the edge to the other comer between the other face and the edge and would extend beyond at least one of the comers. Preferably the coating would penetrate and seal off any cracks present between the layers.

In some embodiments, the barrier extends in a direction perpendicular to at least one facial plane, past the comer between the gasket sheet edge and the face. Some embodiments have a barrier on the edge coating where the coating extends over the edge. Preferably the gasket will have barriers protruding past both comers of the aperture, such as in Fig. 6 and 8.

Some embodiments of the present invention, are ideally suited and especially preferred for gaskets which are compressible and porous and which must also seal against fluids going through the gasket. In such a case, a wide edge-coating on an gasket sheet edge which covers the edge from comer to comer and past the comer; protruding past the comer plane in a direction perpendicular to the facial plane, will give the gasket a better sealing ability, especially since it seals against two types of fluid flow; both through the gasket and across the gasket face. This is particularly true where the aperture has been cut in the gasket. The cut edge will have more pores than a surface which is not cut, even in porous and compressible gaskets. Coating the edge so that the coating penetrates or closes off the pores will be effective to seal off the pores to fluid which could seep through the gasket.

Soft gasket materials are preferred for use With the wide edge-coating of the present invention. Many types of soft gasket materials comprise fibre and a binder; other types of soft gasket materials comprise a binder and a filler, such as, for example, rubber and cork. Many soft gasket materials comprise fibre, binder, and filler. Such soft gasket materials, comprising a binder and fibre and/or filler, have pores along the sheet edge where the aperture has been cut. These pores are detrimental to the sealing ability of the gasket. Thus, it is preferred to have an edge coating on the aperture's gasket sheet edge which will penetrate or at least close off the pores. In some embodiments the aperture is a bolt hole.

When the gasket sheet material comprises fibre and binder, in most case, a filler is also present. The gasket sheet preferably comprises at least 1 % by wt. of binder and at least about 5 % by wt. of fibre. Filler can also be added at a preferred minimum level of about 1 %. Suitable ranges are from about 3 to about 40 % by wt. of binder, from about 5 to about 70 % by weight (wt.) of fibre, and from about 1 to about 92 % by wt. of filler.

Preferred gaskets that can make use of the present edge seal are gaskets for intake manifolds, oil pan gaskets (sealing against oil); cover gaskets such as a valve cover (which seals against oil) or an axle cover (which seals against gear lubricant); and compressor gaskets which are frequently exposed to refrigerants such as freon; gas meter gaskets, which seal gas; water pump gaskets, which seals against water and antif reeze; and gaskets for industrial flanges which will seal against steam and/or chemicals. The type of coating for each application is important for achieving advantageous results since some particular types of coatings will withstand particular fluids better than others. The wide edge sealing design has been found to be surprisingly suited for sealing oil pans of diesel engines and for sealing vacuum in intake manifolds against air and fuel mixtures. Chloroprene polymers and acrylonitrile polymers are the preferred coatings for embodiments with exposure to refrigerants and acrylic or acrylonitrile polymers are the preferred coatings for embodiments with exposure to oil or gear lubricants: these coatings have especially good resistance to exposure to the specified fluids.

On each end of the aperture's gasket sheet edge there is a comer which abuts a gasket face. Each comer can be considered to lie in two different parallel, infinite planes (such as, for example, in Fig. 8 having plane 39 and plane 65). The plane is a 'facial plane" when it goes through the substantially flat surface area of a gasket face. The facial plane thus contains the flat surface area of the gasket face. Generally, the edge of the gasket sheet around the aperture is substantially perpendicular to the facial plane. A plane is a "comer plane" when the infinite plane contains a comer between the face and the edge. In some cases the facial plane does not go through the comer so that there is both an infinite 'facial plane" and an infinite "comer plane" (such as in Fig. 5 which shows the facial plane 54 and Fig. 9 which shows comer plane 80 and facial plane 36. Whenthe facial plane goes through the comer between the face and an aperture's gasket sheet edge the plane is both a comer plane and a facial plane (a "comer, facial plane"). A coating which extends beyond the comer between the edge and the face will protrude past the comer plane as does coating 41 of Fig. 9. The coating should protrude past the comer plane in order to provide the seal against fluids which would otherwise seep onto the gasket face between the gasket face's surf-ace and the flange.

In some preferred embodiments the coating protrudes past both a comer plane and a facial plane (in embodiments where the facial plane does not go through the comer of the aperture's gasket sheet edge). Such embodiments provide an even befter barrier against fluids from going across the face of the gasket, between the face and the flange.

The "edge thickness" is the distance on the edge from one comer which lies between one face and the edge and the other comer which lies between the other face and the edge. In the present invention, to obtain sealing ability across the face of the gasket and through the gasket, the edge coating is wider than the edge thickness so that the edge coating extends beyond a comer plane on at least one side of the gasket.

In some cases the facial plane and the comer plane will be the same plane. In some cases, however, by using pressure, a facial area can be forced into a different plane from the rest of the face. When this is done abutting an aperture, the comer between the face and the edge may become rounded and it may be more difficult to identify the location of the comer plane. In such cases the comer plane is easily located by noting the point where the cut portion of the edge ends; this point is in the comer plane. The cut portion of the edge typically contains more pores than the surface of either gasket face and is also distinctive in appearance as it shows a cross-section of the materials inside the gasket.

The coating portion on the gasket edge, such as in Fig. 9, 10, 4, 6, and 3 can be referred to herein, for convenience, as coating A. Fig. 2 and 8 show embodiments where coating A is on the gasket material's edge, and since the coating also overlaps onto the face of the gasket, the gasket also has a coating B. Thus, where the coating extends onto the gasket face, the coating portion on the face can be referred to as coating B, such as is seen in Fig. 8 and Fig. 2; coating A is on the gasket edge. A coating like coating A but which is on the outside perimeter of the gasket sheet edge is herein referred to as coating C. Where coating C extends over the face of the gasket it is referred to as coating B. Preferably, coating A extends past coating B, protruding past the surface of coating B at least about 1 mil (0.025 mm) on at least one side of the gasket; more preferably coating A protrudes at least about 5 mils (0. 125 mm) past coating B, and most preferably coating A protrudes past coating B at least about 10 mils (0.255 mm) on at least one side of the gasket. The preferred embodiment has coating A protruding past coating B on both sides of the gasket. Where coating A extends past the gasket face at the comer of the edge (thus protruding past the facial, comer plane), or where coating A extends past coating B, this can be referred to as a "lip formation" or a "lip". This lip forms a dam or barrier against fluids on the aperture side of the coating.

At least one edge, which is around an aperture and is substantially perpendicular to the substantially opposed faces can be given a wide edgecoating which goes past at least one comer of the edge (protruding through the comer plane of that comer). In a direction from one of the comers between a face and the edge past the other comer between the other face and the edge and parallel to the edge, the protruding coating should be sufficiently wide to give the gasket a better sealing ability than the gasket would have with a coating which just extended from one of the comer planes to the other comer plane (merely touching the comer plane).

Suitably, in this direction, the aperture's gasket sheet edge has a barrier (such as a coating) that protrudes past the comer plane a distance of at least about 1 mil (0.025 mm). A coating from comer to comer will thus be at least about I mil wider than the edge is thick. Furthermore, it has been found that an even wider barrier coating will give an even better sealing ability. More preferably, therefore, the barrier protrudes at least about 5 mils (0.025 mm) beyond one comer plane. Suitably, the barrier extends from about 1 to about 80 mils (0.025 to 2.030 mm) past the comer plane. The wide edge-coating can thus extend past either or both comer planes a distance of from about 1 to about 80 mils. A more preferred range is from about 5 to about 80 mils (0. 125 to 2.030 mm) and, still more preferably the coating extends a distance of from about 10 to about 80 mils (0.255 to 2.030 mm) past the corner plane. Preferably, the wide edge-coating protrudes past at least one comer plane a distance of at least about 10 mils (0.255 mrn). More preferably the wide coating extends past each comer plane a distance of at least about 10 mils; gaskets with such coatings, in fact have been found to give a seal ranging from excellent to a total seal. This is true even with flange pressures of about 300 PSI (about 2070 kPa) or more, or about 25 PSI (about 170 kPa) or more. A total seal is found where the coating will completely prevent fluids from leaking past the aperture, across the face of the gasket and also through the gasket sheet. To achieve such a seal it is preferred that the wide edgecoating protrudes past each comer plane a distance of at least about 15 mils (0.380 mm).

For a gasket giving a total seal it is also preferred that from the edge surface, in a direction extending into the aperture parallel to the facial plane and away from the edge, the coating on the edge gets gradually wider (as seen in Fig. 2, 3, and 4) forming an inclined plane, until it comes to the coating's widest point at some distance from the edge. The distance from the edge that the coating extends and reaches its widest point is not critical. Suitably, however, in such an embodiment, the coating is at least 1 mil (0.025 mm) wider than the thickness of the gasket edge. Preferably the coating is at least 5 mils (0. 125 mm) wider than the thickness of the gasket edge. It is preferred that a "lip" is formed, such as in Fig. 6, or such as in Fig. 2, 3, and 4 (where the lip resembles an inclined plane and is formed by the coating getting gradually wider going away from the aperture's gasket sheet edge).

In embodiments where a face has a facial plane that does not go through a comer between the face and a plane, it is optionally preferred to have a barrier that protrudes beyond the facial plane. Suitably the barrier will protrude past the plane in an amount effective to give a better seal than the gasket would have if the barrier merely came up to the facial plane but did not go past it. The coating can protrude at least about 1 mil (0.025 mm) beyond such a facial plane; more preferably it extends at least about 5 mils (0. 125 mm) beyond such a facial plane and even more preferably it extends at least about 10 mils (0.255) beyond such a facial plane. Preferably, the barrier will extend at least about 1 mil past at least one facial plane; more preferably it will extend at least about 5 mils past at least one facial plane, and even more preferably the coating will extend at least about 10 mils past at least one facial plane; total seals have been achieved particularly when the coating protrudes at least about 15 mils (0.380 mm) past the facial plane; preferably the barrier will extend from about 5 to about 80 mils (about 0. 125 to about 2.030 mm) past at least one facial plane (including embodiments where the facial plane lies above or outside the comer plane on the face of the gasket as noted in Fig. 5 and Fig. 9). The more preferred embodiments have the barrier in the form of a coating extending beyond the facial plane on both faces of the gasket.

The coating can be applied in any film-forming manner such as, for example, dipping, melting or painting the exposed edge while protecting any gasket portions not to be coated. In one embodiment a coating can be applied to an aperture edge (the edge of the gasket sheet) by placing a plurality of gasket sheets together so that a cavity is formed from the apertures of the plurality of gasket sheets, and then contacting the edge of each gasket sheet along the cavity with a coating material so that the edges become coated in an amount effective to achieve a substantial sealing of the gasket along the edge of the gasket sheet at the aperture where the edge is coated. The sides of the cavity are the aperture edges to be coated. The coating material is introduced into the cavity and contacts the edges to be coated to form the coated edges. If there is any coating material left it is removed, and then the gasket edges are dried.

When the gasket sheets are placed together to form a cavity from the apertures and the coating contacts the surface of the cavity, separating the gaskets while the coating is viscous or elastic (before the coating cures or becomes hard) will stretch the coating so that it becomes wider than the aperture's gasket sheet edge. When the coating has partially cured or when it is plastic and moldable, separating the sheets can cause the coating on the edge to be more pointed and wider than the aperture's edge (this is shown by Fig. 2 and 3) forming an inclined plane. This technique is easily car6ed out, preferably with acrylic latex.

The gaskets can be aligned and placed together so that they abut, or, in some embodiments, it may be desirable to position other sheets (spacers) between two or more of the gasket sheets. One method which can be used to align the stack of gaskets or the stack of gaskets and spacers is to cut the sheets identically so that each has an aperture with the edge to be coated and also has at least one, preferably two, "rod-receiving apertures". A rod is put through these rod-receiving apertures to align the gaskets, or gaskets and spacers, and keep them aligned while the coating composition contacts the aperture edges to be coated. Bolts can be used at each end of the or each rod to secure the gasket stack and make sure that the gaskets are tightly held together.

The gaskets, or gaskets and spacers, are preferably aligned to form the cavity into which the coating must be introduced in order to contact the edge to be coated. In another preferred embodiment, when the sheets are secured together (with or without spacers) a holding container ("well") for the coating composition is attached or at least placed at one end of the cavity formed by the sheets. The stack of sheets together with this coating-filled well can be tipped so that the coating runs from the well and into the cavity along the sheet edges so that they are contacted and coated. Preferably the stack of sheets and well are rotated together so that the edges become completely coated. Using the coating-filled well in this method 1) minimizes the problem of trapping or forming air bubbles in the coating, 2) allows a maximum surface area to be coated with a minimum volume of coating, and 3) facilitates the edge-coating of a multiplicity of gaskets, all of which are advantageous.

Sheets placed between the gaskets are referred to as "spacers", and separate the gaskets from each other. The advantage of using spacers is that a spacer will allow more coating to be applied to the edge and will also allow the coating to contact the edge only in the exposed locations so that the resulting gasket coat has a particular configuration. Spacers, for example can be used to obtain coatings having the configuration of Fig. 4, 6, or Fig. 8.

The spacer sheets have apertures, but the apertures can be 1) the same size as, 2) wider than, or 3) smaller than the apertures of the gaskets. A particular spacer sheet will result in a coating configuration that is characteristically produced by that spacer. For example, when the spacer aperture is wider than the aperture of the gasket, a portion of the gasket sheet face is exposed, and the coating material contacts the gasket face around the edge and coats the face where it is exposed around the aperture. This type of spacer characteristically produces coatings that are wider than the gasket edge and thus protrude past the facial plane, but which also have the gasket face coated near the aperture as is indicated in Fig. 7 and 8.

When the spacer aperture is smaller, the gasket sheets will be separated from each other and the coating is prevented from overlapping the comer of the edge onto the face of the sheet. The coating, however may still be wider than the gasket edge in the direction parallel to the edge so that the coating protrudes past the face, if the spacers and gaskets are separated when the coat is liquid or plastic enough to stretch or flow into a lip formation. This type of spacer, however, could also be used to make gaskets which only have the coating on the edge of the gasket. Spacers can be coated for easy release of the gasket coating material. Spacers can also be used to form the protruding coating on an edge. In other embodiments the spacers can be configured to give the final wide edgecoating a different shape, particularly where the coating protrudes past the comer plane.

When a spacer has an aperture that is wider than the gasket aperture, the spacer aperture suitably has an aperture that is from about 5 to about 125 mils (0.125 to 3.175 mm) larger than the gasket aperture. This allows some of the coating to be deposited on the exposed gasket face. When the spacer must have an aperture that is smaller than the gasket aperture it is preferred that the spacer aperture be in the range of from about 3 to about 12 mils (0.075 to 0.305 mm) smaller than the gasket aperture. It is even possible to use spacers which have apertures that vary from being wider than the gasket aperture in some locations, the same size in other locations, and smaller than the gasket aperture in other locations. Thus the spacer aperture can be from about 5 to 125 mils (0. 125 to 3.175 mm) wider than the gasket aperture in some locations and from about 3 to about 12 mils (0.075 to 0.305 mm) smaller than the gasket aperture in other locations. A spacer can even have an aperture ranging from about 5 mils (0. 125 mm) wider to about 3 mils (0.075 mm) smaller than the gasket aperture.

The spacer sheets themselves must be thick enough to allow a separation of the gasket sheets, at least about 5 mils (0.125 mm) thick, which will position the gaskets 5 mils apart when their aperture edges are coated. The spacers can have a thickness in the range of from about 5 to about 150 mils (0. 125 to 3.810 mm). It is, however, preferred to use spacers with a thickness in the range of from about 10 to about 40 mils (0.255 to 1.015 MM).

It has also been discovered that highly porous spacers can be used. The highly porous spacers advantageously allow the liquid of the coating to be absorbed into the spacer. The absorption of the coating liquid will result in faster drying of the coating, allowing a solid coating to form faster on the edge of the gasket. A highly porous spacer has a minimum void volume of at least about 35 %. Preferably, a porous spacer has from about 35 to about 75 % void volume. A "non-porous" spacer has a maximum of about 15 % void volume, suitably from about 15 to about 0.01 % void volume.

In some embodiments of the invention, some of the aperture's gasket sheet edge can be protected from the coating material so that only a portion of each edge of the gasket sheet at the aperture is contacted with the coating!'naterial. This can be useful where the edge is close to a bolt area. Where the edge is within, for example, 3.5 cm of a bolt, it may be desired to preserve more compression resistance by not applying coating even to the edge. The extra pressure applied by the bolt will be effective to give some added sealing ability to the gasket, so that it may not be necessary or desired completely to coat the aperture's gasket sheet edge. To obtain such embodiments a spacer sheet can be configured to cover the portion of the edge which is not to be coated. (Where the gasket must seal against fluids that would go through the sheet of the gasket, however, the coating material should contact the edge portion to be coated so that the coating material covers the edge completely from one comer to the other comer.) A bolt area is an area near or under the bolt where higher pressure is put on the gasket than on areas further away from the bolt.

Any edge between the opposed faces of a gasket sheet material can be given a coating, including an edge which forms, or forms part of, the outer perimeter of the gasket. The coating can be organic or inorganic. When the edge is one which contacts fluids during use, however, a polymer coating is particularly useful and preferred.

Optionally, a coating (coating B) can be applied on one or both faces completely around an aperture so that it abuts the edge perpendicular to each face and also abuts or even joins with the coating on the aperture's gasket sheet edge (coating A). Such a coating, (which forms a coating strip) can be beneficially used where the flanges do not fit together fightly to form a tight seal against fluids. If, for example, a flange is warped even slightly so that it curves away from a planar (flat) surface, the coating strip can be useful in providing a better seal against fluid leakages. For such applications, the coating strip will preferably be put around the aperture where fluids are encountered in use.

The coating on the aperture's gasket sheet edge (coating A) can overlap onto either or both faces, forming coating B. The ovedap can extend for a very small a distance, less than 1 mil (0.025 mm), or can extend over the entire gasket surface. The edge coating on the vertical edge can lap over onto either or both faces of the gasket (such as is shown, for example, in Fig. 8). Preferably, the sealing coating can extend up to about 1.5 cm on the face of the gasket. More preferably, it extends a maximum of about 5 mm across the face of the gasket, and especially a maximum of about 1 mm; such embodiments (minimizing coating on the gasket faces) provide good compression resistance.

Optionally, each gasket face, or a portion thereof, can be given only a release coating, and not any coating for sealing the gasket. This will give the gasket more compression resistance. Release coatings, in general, do not substantially affect compression resistance. A release coating is normally less than 1 mil (0.025 mm) in thickness. Coatings to seal the gasket, however, are heavier, thicker, and generally penetrate more into the gasket and gasket pores than does a release coating; thus, coatings providing sealing ability are detrimental to compression resistance and their use is thus limited in embodiments where it is important to preserve compression resistance.

It has been found that a thick coating on the face of the gasket also will be detrimental to compression resistance. For this reason therefore, it is preferred that the overlap of the edge coating onto the face of the gasket is not more than about 11 mils (0.280 mm) thick in order to preserve compression resistance.

When a release coating is used, for best performance the release coating preferably does not penetrate the gasket structure. This will give the gasket more compression failure resistance than if the release coating penetrated the gasket structure. A suitable release coating is a fluoropolymer-containing polymer coating.

Practicality is the factor limiting the thickness of the coating on the vertical edge, that is thickness in both the direction parallel to the vertical edge and the direction perpendicular to the vertical edge. Very small thicknesses (perpendicular to the edge) have been found to be effective. Since a relatively thin coating is effective it will be cost effective to limit the thickness and width of the coating on the vertical edge of the gasket aperture.

The coating thickness, in the direction perpendicular to the vertical edge and parallel to the facial plane is thus not critical. The coating preferably is a minimum of at least about 0. 1 mm thick and preferably can be up to about 2 mm thick. The coating on the vertical edge is intended to seal the gasket against fluids both through the gasket sheet edge and across the surface of at least one gasket face. The coating should have a minimum thickness needed to seal the gasket against fluids from going through the aperture's edge. Suitably the sealing coating on the edge of a soft gasket sheet should be at least about I mil (0.025 mm) in thickness (extending in a direction perpendicular to the vertical edge). Preferred embodiments will have a protruding edge forming a barrier that goes beyond the comer plane a sufficient distance to give the gasket a seal against fluids from going across at least one gasket face, and preferably across both faces.

Inorganic materials which can be used as a coating include chemically delaminated vermiculite and mica. Preferred coatings comprise polymers. Polymeric material can be used to form coating A, coating B, and/or coating C. Suitable polymer materials include organic, inorganic, and inorganictorganic hybrid polymers, as well as filled polymers. Suitably the polymer coating materials are coatings selected from acrylic polymers, acrylonitrile polymers, polyvinylidene chloride, fluorosilicone polymers, polyurethanes, acrylonitrile butadiene rubbers (NBR), fluoro polymers, hydrogenated NBR, silicone rubber coatings (both UV curable and room temperature curable), styrene butadiene polymers, fluoroelastomer polymers, fluorosilicone polymers, acrylic-acrylonitrile polymers, carboxylated acrylonitrile polymers, carboxylated styrene butadiene polymers, chloroprene rubber polymers, ethylene propylene rubber polymers, ethylene/vinyl acetate, epoxy resins, and mixtures thereof. Any latex can be used. Also suitable as a coating material are polymer powders which are heated to melt them onto the surface of the gasket. In fact, any powder which can be fused can be used to seal and coat the gasket. Coatings A, B, and C can comprise different coating materials or they can comprise the same material.

The following Examples illustrate the invention. EXAMPLES Two identical annular gaskets were cut from a cellulose based paper gasket sheet material. Each gasket formed a ring and had the following measurements: inner diameter 0.515 inches (0.130 mm) (distance from the centre of the aperture to the inner edge of the ring); outer diameter 0. 95 inches (24.15 mm); ring width 0.2175 inches (5.525 mm). The gaskets each had two substantially flat, opposed faces and each ring aperture had an edge that was substantially vertical and substantially perpendicular to each face. The edge thickness (also the gasket thickness) was 32 mils (0.810 mm).

The gasket ring for sample A was left completely uncoated as the control. For sample B, an acrylic latex was used to coat the gasket ring on the inner vertical edge of the ring aperture. The coating was applied to the aperture's gasket sheet edge so that the coating was wider than the thickness of the aperture's edge (wider than the gasket thickness), and extended past each corner of the inner, vertical edge by approximately 27 mils (0.685 mm) on each side, measuring the coating at its widest point. The distance from the inner, vertical edge of the gasket to the surface of the coating at the centre of the gasket was about 0.9 mm. The coating on the edge of the gasket sheet at the aperture was like the coating shown in Fig. 4 and Fig. 3.

The gasket was tested in a cylinder which could be pressurized with nitrogen. The nitrogen pressure in the cylinder was brought up to 14 PSI (pounds per square inch) (about 97 kPa) and the number of minutes which elapsed while the pressure fell to 13 PSI (about 90 kPa) was measured. Each gasket was placed in the cylinder's flange and the flange was tightened. The test was carried out on a smooth flange having a roughness of 18 RaMS (Ra is the average roughness value and this is measured in micro-inches; MS indicates micro-inches). The flange was tightened and the pressure level of the flange was measured in pounds per square inch (PSI).

Sample A for this test held the pressure only for 1.5 minutes and required a flange pressure of 2100 PSI (about 14480 Wa). Sample B, the wide edge sealed gasket, gave a total seal (pressure did not decrease in the cylinder), and the flange pressure of the cylinder on the gasket of sample B was only 300 PSI (about 2070 Wa).

Claims (63)

-26CLAIMS:

1. A process for coating an aperture edge of a soft gasket sheet wherein the gasket sheet has two substantially opposed, facial surfaces and an aperture with the edge substantially perpendicular to the facial surfaces, the apertures of each gasket sheet being substantially identical in size and shape, comprising placing a plurality of the sheets together so that a cavity is formed by the apertures of the plurality of gasket sheets, and contacting the edges of the aperture on each gasket sheet with a coating material so that the edges become coated in an amount effective to achieve a substantial sealing of the gasket along the edge of the aperture where the edge is coated.

2. A process as claimed in claim 1, wherein each sheet also has a rodreceiving aperture, and wherein the gasket sheets are placed together and aligned by inserting a rod through the rod-receiving aperture of each sheet.

3. A process as claimed in claim 1 or claim 2, wherein a well holding the coating material is located at one end of the cavity formed by the apertures of the plurality of gasket sheets and wherein the edges of the aperture are contacted with the coating material by tipping the well and gasket sheets so that the coating runs from the well and into the cavity along the sheet edges so that they are contacted by the coating material and coated.

4. A process as claimed in any one of claims 1 to 3, wherein at least one pacer, also having an aperture, is located between at least two gasket sheets.

5. A process as claimed in claim 4, wherein the aperture of each gasket is identical in size and shape, and each spacer is either A) the same size as, B) wider than, or C) smaller than the aperture of the gasket sheets on each side of it.

6. A process as claimed in claim 5, wherein the aperture of each spacer is B) wider than the aperture of the gasket sheets on each side of it.

7. A process as claimed in claim 5, wherein the aperture of each spacer is from about 5 to about 125 mils (0. 125 to 3.175 mm) larger than the aperture of the gasket sheets on each side of it.

8. A process as claimed in claim 5, wherein the aperture of each spacer is from about 3 to about 12 mils (0.075 to 0.305 mm) smaller than the aperture of the gasket sheets on each side of it.

9. A process as claimed in any one of claims 4 to 8, wherein each spacer has a thickness of at least about 5 mils (0.125 mm).

10. A process as claimed in any one of claims 4 to 8, wherein each spacer has a thickness of from about 5 to about 150 mils (0.125 to 3.810 mm).

11. A process as claimed in any one of claims 4 to 8, wherein at least one spacer has a minimum void volume of at least about 35 %.

12. A process as claimed in any one of claims 4 to 8, wherein at least one spacer has a void volume in the range of from about 35 % to about 75 %.

13. A process as claimed in any one of claims 4 to 8, wherein at least one spacer has a maximum void volume of at about 15 %.

14. A process as claimed in any one of claims 4 to 8, wherein at least one spacer has a void volume in the range of from about 15 to about 0.01 %.

15. A process as claimed in claim 1, carried out substantially as described herein.

16. A gasket made by a process as claimed in any one of claims 1 to 15.

17. An article which includes a gasket as claimed in claim 16.

18. The use of a gasket as claimed in claim 16 to enhance sealing in an article.

19. A gasket comprising a sheet with two faces, each face having a facial plane, the planes being substantially parallel to each other, the gasket having an aperture and an edge surface around the aperture, the edge surface having a corner abutting each face and being substantially perpendicular to the facial planes, the edge surface having a coating on it which is wider than the edge surface in a direction parallel to the edge surface so that the coating protrudes past at least one corner of the edge surface and forms a barrier against fluids to retard fluid from going from the aperture past the edge and across at least one of the faces, the barrier formed by the coating extending past the said corner by an amount which is effective to give the gasket a better sealing ability than the gasket would have if the coating was no wider than the edge surface and each corner of the edge abutting one face, the barrier formed by the coating extending at least about 1 mil (0. 025 mm) past the said corner in a direction substantially perpendicular to the facial planes of the gasket, and the sheet being compressible and porous.

20. A gasket as claimed in claim 19, wherein at least one facial plane goes through said corner of the edge surface, and the coating extends at least about 1 mil (0.025 mm) past the corner that the facial plane goes through, the coating thereby forming the barrier against fluids, to retard the fluids from going past the edge at that corner.

21. A gasket as claimed in claim 19, wherein no facial plane goes through either corner of the edge.

22. A gasket as claimed in claim 21, wherein the barrier formed by the coating extends past at least one corner of the edge and also past at least one facial plane.

23. A gasket as claimed in any one of claims 19 to 22, wherein the barrier formed by the coating on the edge extends past the corner a distance in the range of from about 5 to about 80 mils (0.125 to 2.030 mm).

24. A gasket as claimed in any one of claims 19 to 23, wherein the barrier formed by the coating extends a distance in the range of from about 10 to about 80 mils (0.255 to 2.030 mm).

25. A gasket as claimed in any one of claims 19 to 24, wherein the barrier formed by the coating extends at least about 1 mil (0.025 mm) past each corner of the edge.

26. A gasket as claimed in claim 19 or claim 20, wherein each facial plane goes through one corner of the edge and abuts the said edge at the corner, and wherein the coating on the edge extends past each corner of the edge a distance of at least about 1 mil (0.025 mm) in a direction substantially perpendicular to the facial plane, the coating thereby forming the barrier against fluids from going past the edge at the corner.

27. A gasket as claimed in claim 25 or claim 26, wherein the barrier formed by the coating extends past each corner a distance of at least about 3 mils (0.075 mm).

28. A gasket as claimed in claim 25 or claim 26, wherein the barrier formed by the coating extends a distance in the range of from about 5 to about 80 mils (0. 125 to 2.030 mm).

29. A gasket as claimed in any one of claims 19 to 28, wherein the coating extends at least about 10 mils (0.255 mm) past the facial plane on both faces of the gasket to give the gasket the ability to have a total seal in a flange.

30. A gasket as claimed in any one of claims 19 to 28, wherein the coating extends at least about 10 mils (0.255 mm) past the facial plane on both faces of the gasket the ability to have a total seal in a flange with a flange pressure of about 25 PSI (about 172 kPa).

31. A gasket as claimed in any one of claims 19 to 22, wherein the coating has a surface abutting each corner of the edge of the aperture, said surface abutting the gasket sheet at each corner of the aperture edge, said coating surface forming an inclined plane on the coating as a result of the coating getting gradually wider in a direction going away from the corner.

32 A gasket as claimed in claim 31, wherein the coating on the edge is sufficiently wide so that the inclined plane of the coating surface extends at about 5 mils (0.125 mm), past each corner of the edge of the aperture in a direction substantially perpendicular to the facial planes of the gasket.

33. A gasket as claimed in claim 32, wherein the coating extends a distance in the range of from about 5 to about 80 mils (0.125 to 2.030 mm) past each corner.

34. A gasket as claimed in claim 31, wherein the coating on the edge is sufficiently wide that the inclined plane of the coating surface extends at least about 10 mils (0.255 mm) past each corner of the edge of the aperture in a direction that is substantially perpendicular to the facial plane on both faces of the gasket to give the gasket the ability to have a total seal in a flange.

35. A gasket as claimed in claim 34, wherein the coating extends a distance in the range of from about 10 to about 80 mils (0.255 to 2.030 mm) past each corner.

36. A gasket as claimed in any one of claims 19 to 35, where the coating is on only part of the edge.

37. A gasket as claimed in any one of claims 19 to 35, where the coating is on the entire edge surface.

38. A gasket as claimed in any one of claims 19 to 37, wherein the coating comprises a polymer.

39. A gasket as claimed in any one of claims 19 to 37, the coating comprises a coating material selected from the group consisting of acrylic polymers, acrylonitrile polymers, polyvinylidene chloride, fluorosilicone polymers, polyuretanes, acrylonitrile butadiene rubbers, fluoro polymers, hydrogenated NBR, silicone rubber coatings, styrene butadiene polymers, fluoroelastomer polymers, fluorosilicone polymers, acrylic-acrylonitrile polymers, carboxylated acrylonitrile polymers, carboxylated styrene butadiene polymers, chloroprene rubber polymers, ethylene propylene rubber polymers, ethylene/vinyl acetate, epoxy resins, and mixtures thereof.

40. A gasket as claimed in any one of claims 19 to 39, which is either an oil pan gasket, which must seal against oil, or a cover gasket which must seal against gear lubricant.

41. A gasket as claimed in claim 40, wherein the coating on the edge surface comprises an acrylic polymer or acrylonitrile polymer.

42. A gasket as claimed in any one of claims 19 to 39, which is a gasket for an intake manifold.

43. A gasket as claimed in any one of claims 19 to 39, which is a compressor gasket.

44. A gasket as claimed in any one of claims 19 to 39, which must seal against a refrigerant.

45. A gasket as claimed in claim 44, in which the coating on the edge surface comprises a chloroprene polymer.

46. A gasket as claimed in any one of claims 19 to 39, which is a gas meter gasket for sealing against gas.

47. A gasket as claimed in any one of claims 19 to 39, which is for an industrial flange to seal against steam and/or chemicals.

48. A gasket as claimed in any one of claims 19 to 39, wherein said gasket further has an outside edge around the gasket sheet forming a perimeter, the edge being substantially perpendicular to the facial planes and having two comers, each corner abutting one of the faces, the edge further having a coating on it which protrudes past at least one of the said corners of the said outside edge to form a barrier against fluids to retard fluid from flowing past at least one gasket face, the barrier further extending past the said corner of the edge for a distance of at least about 1 mil (0.025 mm).

49. A gasket as claimed in claim 48, wherein the coating is on the entire outside edge of the sheet.

50. A gasket as claimed in claim 48 or claim 49, wherein at least one facial plane goes through a corner of the outside edge.

51. A gasket as claimed in claim 50, wherein the coating on the outside edge extends past the corner that the facial plane goes through.

52. A gasket as claimed in claim 48 or claim 49, wherein the facial plane goes through either corner of the outside edge.

53. A gasket as claimed in any one of claims 48 to 52, wherein the coating on the outside edge comprises a polymer.

54. A gasket as claimed in any one of claims 48 to 52, wherein the coating comprises a coating material selected from the group consisting of acrylic polymers, acrylonitrile polymers, polyvinylidene chloride, fluorosilicone polymers, polyurethanes, acrylonitrile butadiene rubbers, fluoro polymers, hydrogenated NBR, silicone rubber coatings, styrene butadiene polymers, fluoroelastomer polymers, fluorosilicone polymers, acrylic-acrylonitrile polymers, carboxylated acrylonitrile polymers, carboxylated styrene butadiene polymers, chloroprene rubber polymers, ethylene propylene rubber polymers, ethylenelvinyl acetate, epoxy resins and mixtures thereof.

55. A gasket as claimed in any one of claims 48 to 54, which is either an oil pan gasket, which must seal against oil, or is a cover gasket which must seal against gear lubricant.

56. A gasket as claimed in claim 55, wherein the coating on the outside edge comprises either an acrylic polymer or an acrylonitriie polymer.

57. A gasket as claimed in any one of claims 48 to 54, which is a compressor gasket.

58. A gasket as claimed in any one of claims 48 to 54, which must seal against a refrigerant.

59. A gasket as claimed in claim 58, in which the coating on the outside edge surface comprises a chloroprene polymer.

60. A gasket as claimed in any one of claims 48 to 54, which is a gas meter gasket for sealing against gas.

61. A gasket as claimed in any one of claims 48 to 54, which is for an industrial flange to seal against steam and/or chemicals.

62. A gasket as claimed in any one of claims 48 to 61, in which the coating on the outside edge extends a distance in the range of from about 5 to about 80mils (0. 125 to 2.030 mm) past the corner.

63. A gasket as claimed in any one of claims 48 to 61, in which the coating on the outside edge extends a distance in the range of from about 10 to about 80 mils (0.255 to 2.030 mm) past the corner.