GB2131325A

GB2131325A - Reinforced sheet material

Info

Publication number: GB2131325A
Application number: GB08328248A
Authority: GB
Inventors: Dr Hansgeorg Granle
Original assignee: LECHLER ELRING DICHTUNGSWERKE; Elring Dichtungswerke GmbH
Current assignee: LECHLER ELRING DICHTUNGSWERKE; Elring Dichtungswerke GmbH
Priority date: 1982-10-21
Filing date: 1983-10-21
Publication date: 1984-06-20
Also published as: DE3239010A1; ES526586A0; SU1598861A3; GB8328248D0; JPS6232108B2; GB2131325B; JPS5991056A; ES8505586A2

Abstract

A reinforced sheet or board material suitable for the fabrication of gaskets, heat insulating boards and the like comprising a support layer having a smooth surface which is coated with a vulcanisable soft material consisting partially of fibrous material and predominantly of asbestos free base mineral and containing a binder, wherein the powdered asbestos free base mineral consists of 55-80 parts by weight of chemically and thermally untreated material e.g. slate and 0-25 parts by weight of chemically and/or thermally treated material e.g. expanded graphite or expanded vermiculite. The soft material may consist of at least 80% of powdered base mineral constituents, 6% of binder and not more than 14% of asbestos free fibres. All percentages are by weight.

Description

SPECIFICATION Reinforced sheet material This invention relates to a reinforced sheet or board material suitable for the production of flat gaskets and also for the manufacture of heat insulating boards.

In our earlier British Patent Application, GB 2106012A, we disclosed a reinforced sheet or board material suitable for the fabrication of gaskets, heat-insulating boards and the like comprising a support layer having a smooth surface coated with a vulcanisable soft material consisting partially of fibrous material and predominantly of powdered asbestos-free base minerals, and containing a binder. In a preferred embodiment of this disclosure, the soft material of this sheet or board material consists of at least 80% of powdered base mineral constituents, about 6% of binder and not more than 14% of asbestos free fibres. All percentages herein are by weight.

The main properties of flat gaskets, such as cylinder head gaskets in internal combustion engines, which are subjected to high mechanical and thermal stress are as follows: a) adaptability b) pressure resistance c) resilience d) gas- and fluid-tightness e) temperature resistance f) longitudinal and transverse stability g) strength at the cut edges and h) corrosion resistance.

The aim of the invention is to improve the reinforced sheet or board material as disclosed in GB210601 2A in terms of the following properties: 1. Elasticity (resilience) and adaptability 2. Density of the soft material and 3. Reduction of the tendency to stick.

We have found that this objective can be achieved if the powdered asbestos-free base mineral consists of 55 to 80 parts by weight of chemically and themally untreated material, preferably powdered slate, and 0 to 25 parts by weight of chemically and/or thermally treated material. We have found that mica may also be used as the chemically and thermally untreated constituent of the powdered mineral asbestos-free base materal.

According to the present invention, therefore, we provided a reinforced sheet or board material suitable for the fabrication of gaskets, heat insulating boards and the like comprising a support layer having a smooth surface which is coated with a vulcanisable soft material consisting partially of fibrous material and predominantly of powdered asbestos-free base mineral and containing a binder, wherein the powdered asbestos-free base mineral consists of 55-80 parts by weight of chemically and thermally untreated material and 0-25 parts by weight of chemically and/or thermally treated material.

In a preferred embodiment of the invention, the soft material consists of at least 80% of the powdered asbestos-free base mineral constituents, about 6% of binder and not more than 14% of asbestos-free fibres. The composition of the binder and the fibrous material is preferably as disclosed in GB2106012A. Thus, for example, the binder may by synthetic rubber (latex) and the fibrous material preferably comprises organic fibres of natural or synthetic origin e.g. polyamide or cellulose.

In a further preferred embodiment of the invention, the chemically and thermally untreated material is powdered slate or mica. Powdered slate is particularly preferred.

In a still further preferred embodiment of the invention, expanded graphite is used as the chemically and thermally treated base material.

In a yet still further preferred embodiment of the invention, expanded vermiculite is used as a purely thermally treated base material.

Expanded graphite may be obtained from soft mineral natural graphite, i.e. pure carbon, by incorporating groups of foreign atoms between the planes ofthe graphite crystal lattice (chemical treatment) and subsequently thermally breaking it open (thermal treatment). The thermal treatment causes an enlargement in the distances between the planes of the graphite crystal lattice.

The term "vermiculite" is the geological name for a group of water-bound lamellar minerals with the appearance of mica. Crude vermiculite consists of laminae which contain crystalline water in microscopicfineness and underthe effect of a sudden temperature change from 800 to 1000 C expand, giving off steam, to a multiple of their original volume. This is a thermal treatment of crude vermiculite.

The above composition may then be formed into a sheet or board according to the procedure given in GB2106012, which may include vulcanisation of the binder.

1. A reinforced sheet or board material suitable for the fabrication of gaskets, heat insulating boards and the like comprising a support layer having a smooth surface which is coated with a vulcanisable soft material consisting partially of fibrous material and predominantly of powdered asbestos-free base mineral and containing a binder, wherein the powdered asbestos-free base mineral consists of 55-80 parts by weight of chemically and thermally untreated material and 0-25 parts by weight of chemically and/or thermally treated material.

2. A sheet or board material as claimed in claim 1, wherein the soft material consists of at least 80% of the powdered asbestos-free base mineral constituents, about 6% of binder and not more than 14% of asbestos free fibres.

3. A sheet or board material as claimed in claim 1 or 2 wherein the binder consists of synthetic rubber (latex) and the fibres are organic material of natural or synthetic origin.

4. A sheet or board material as claimed in claims 1, 2 or 3 wherein the chemically and thermally untreated constituent of powdered asbestos-free base mineral is powdered slate.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Reinforced sheet material This invention relates to a reinforced sheet or board material suitable for the production of flat gaskets and also for the manufacture of heat insulating boards. In our earlier British Patent Application, GB 2106012A, we disclosed a reinforced sheet or board material suitable for the fabrication of gaskets, heat-insulating boards and the like comprising a support layer having a smooth surface coated with a vulcanisable soft material consisting partially of fibrous material and predominantly of powdered asbestos-free base minerals, and containing a binder. In a preferred embodiment of this disclosure, the soft material of this sheet or board material consists of at least 80% of powdered base mineral constituents, about 6% of binder and not more than 14% of asbestos free fibres. All percentages herein are by weight. The main properties of flat gaskets, such as cylinder head gaskets in internal combustion engines, which are subjected to high mechanical and thermal stress are as follows: a) adaptability b) pressure resistance c) resilience d) gas- and fluid-tightness e) temperature resistance f) longitudinal and transverse stability g) strength at the cut edges and h) corrosion resistance. The aim of the invention is to improve the reinforced sheet or board material as disclosed in GB210601 2A in terms of the following properties: 1. Elasticity (resilience) and adaptability 2. Density of the soft material and 3. Reduction of the tendency to stick. We have found that this objective can be achieved if the powdered asbestos-free base mineral consists of 55 to 80 parts by weight of chemically and themally untreated material, preferably powdered slate, and 0 to 25 parts by weight of chemically and/or thermally treated material. We have found that mica may also be used as the chemically and thermally untreated constituent of the powdered mineral asbestos-free base materal. According to the present invention, therefore, we provided a reinforced sheet or board material suitable for the fabrication of gaskets, heat insulating boards and the like comprising a support layer having a smooth surface which is coated with a vulcanisable soft material consisting partially of fibrous material and predominantly of powdered asbestos-free base mineral and containing a binder, wherein the powdered asbestos-free base mineral consists of 55-80 parts by weight of chemically and thermally untreated material and 0-25 parts by weight of chemically and/or thermally treated material. In a preferred embodiment of the invention, the soft material consists of at least 80% of the powdered asbestos-free base mineral constituents, about 6% of binder and not more than 14% of asbestos-free fibres. The composition of the binder and the fibrous material is preferably as disclosed in GB2106012A. Thus, for example, the binder may by synthetic rubber (latex) and the fibrous material preferably comprises organic fibres of natural or synthetic origin e.g. polyamide or cellulose. In a further preferred embodiment of the invention, the chemically and thermally untreated material is powdered slate or mica. Powdered slate is particularly preferred. In a still further preferred embodiment of the invention, expanded graphite is used as the chemically and thermally treated base material. In a yet still further preferred embodiment of the invention, expanded vermiculite is used as a purely thermally treated base material. Expanded graphite may be obtained from soft mineral natural graphite, i.e. pure carbon, by incorporating groups of foreign atoms between the planes ofthe graphite crystal lattice (chemical treatment) and subsequently thermally breaking it open (thermal treatment). The thermal treatment causes an enlargement in the distances between the planes of the graphite crystal lattice. The term "vermiculite" is the geological name for a group of water-bound lamellar minerals with the appearance of mica. Crude vermiculite consists of laminae which contain crystalline water in microscopicfineness and underthe effect of a sudden temperature change from 800 to 1000 C expand, giving off steam, to a multiple of their original volume. This is a thermal treatment of crude vermiculite. The above composition may then be formed into a sheet or board according to the procedure given in GB2106012, which may include vulcanisation of the binder. CLAIMS

5. A sheet or board material as claimed in claims 1,2 or 3 wherein the chemically and thermally untreated constituent of powdered asbestos-free base mineral is mica.

6. A sheet or board material as claimed in any of the preceding claims wherein the chemically and thermally treated constituent of the powdered asbestos-free base mineral is expanded graphite.

7. A sheet or board material as claimed in any of claims 1 to 5 wherein the thermally treated consti tuentofthe powdered asbestos-free mineral is expanded vermiculite.

8. A flat gasket fabricated from material as claimed in any of claims 1 to 7.

9. A reinforced sheet or board material substantally as herein described.

10. Asheet of board material suitable for the fabrication of gaskets, heat insulating boards and the like comprising a material as claimed in claim 1 in which the vulcanisable material has been vulcanised.