JPH01257115A - Production of graphite gasket material - Google Patents

Abstract

PURPOSE:To obtain graphite gasket material having high strength, and excellent sealing property and liq. impermeability by arranging an expansive graphite sheet impregnated with resin on the inner layer of a metal thin plate and an expansive graphite sheet on the outer layer of the metal thin plate and by press-heating. CONSTITUTION:The graphic gasket is obtd. by laminating the expansive graphite sheet impregnated with resin as an inner layer and the expansive graphite sheet as an outer layer on both the surfaces of the metal plate having round- or square-shaped projections and by press-heating to harden the resin. As the impregnated resin, liq. thermosetting resin such as phenolic resin, furan resin, epoxy resin is pref. The proportion of the impregnated resin is preferably 0.2-10wt.%, as solid content, to the expansive graphite sheet. In the gasket, oil resistance is improved, and sealing property and stress relaxation are in creased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a graphite gasket material having excellent strength, sealing properties, stress relaxation properties, and compression recovery properties.

(Prior art) Graphite gasket materials are generally made of graphite with a highly developed crystal structure, such as natural graphite, Kish graphite, and pyrolytic graphite.
A graphite intercalation compound is generated by treatment with a mixture of concentrated sulfuric acid and a strong oxidizing agent such as nitric acid or potassium permanganate, which is then washed with water and then rapidly heated to produce a black material with a thickness of 0.5 mm and having two circular or square projections. It is formed by rolling an expanded graphite sheet onto both sides of a 15-0.25 mm metal reinforcing plate using the above protrusions, and is mainly used as a gasket material for internal combustion engines in automobiles and industrial machinery. has been done.

(Problems to be Solved by the Invention) However, when a single compact of # tension graphite is immersed in water, oil, or various inorganic or organic liquids at high temperature, the liquid penetrates and swells, resulting in a significant decrease in strength.

In particular, as modern automobile engines have become lighter, the load placed on the gaskets has increased, and engine oil has become heavier.

The above-mentioned problem is becoming more serious due to the requirement for sealing performance at high temperatures such as antifreeze.

This problem was solved by impregnating an expanded graphite sheet with a binder such as a resin, as shown in Japanese Patent Application Laid-open No. 191058/1983.
．． This can be resolved by increasing the number of points.

Expanded graphite's unique properties such as sealing properties and stress relaxation properties deteriorate, making it undesirable for use as a gasket.

An object of the present invention is to solve the above-mentioned problems and provide a method for producing a graphite gasket material that has high strength, excellent sealing performance, and liquid impermeability.

(Means for Solving the Problems) The present invention provides a resin-impregnated expanded graphite sheet on both sides of a thin metal plate having nine circular or square projections, and an expanded graphite sheet laminated on the outside of the resin-impregnated expanded graphite sheet. 121 to a method for producing a graphite gasket material by pressing and then heating.

In the present invention, the expanded graphite sheet constituting the graphite gasket material is obtained by a known method.2 For example, natural scale graphite is treated with a mixed solution of concentrated sulfuric acid and concentrated nitric acid, and then washed with water and dehydrated. By removing the superacid acid and the acid adhering to the surface of the graphite, and then performing an expansion treatment by rapid heating, expanded graphite is obtained in which the raw graphite is expanded to a ratio of 20 times or more in terms of Kaza density ratio. , an expanded graphite sheet that is pressure-molded is used.

As the resin to be impregnated into the expanded graphite sheet, phenolic resin is used due to its adhesive strength and liquid impermeability.

It is preferable to use a liquid thermosetting resin such as furan resin, epoxy resin, melamine resin, or polyimide resin.

The impregnation rate of the resin described above is preferably 0.2 to 10% by weight based on the solid content of the expanded graphite sheet. If the resin impregnation rate is low, the effect of improving strength and liquid impermeability will be small, and if it is too high, gasket properties such as sealing properties and stress relaxation properties will deteriorate.

The graphite gasket material of the present invention is made by sandwiching two metal thin plates that maintain mechanical strength, placing a resin-impregnated expanded graphite sheet in the inner layer and an expanded graphite sheet in the outer layer, and pressurizing them.

The resin is then cured by heating, and the inner layer has liquid impermeability and the outer layer has sealing properties. Further, due to the above heating, a portion of the resin penetrates into the vicinity of the boundary of the expanded graphite sheet of the outer layer and hardens, so that the inner layer and the outer layer are well bonded.

(Example) The present invention will be explained in detail below.

Example 1 A phenolic resin (
Expanded graphite 7-t (manufactured by Hitachi Chemical Co., Ltd.: product name Carbofit: plate thickness 1.1 rnvn) impregnated with 255ii solids of expanded graphite (manufactured by Hitachi Chemical Co., Ltd.: VP-231N)
, density: 0.7 g/cm''), the outer layer was a single expanded graphite sheet with the same thickness and density and not impregnated with resin, rolled at a pressure of 300 kg/an'', then rolled at 180°C. The material was cured for a period of time to obtain a graphite gasket material with a thickness of 1.2 mm.

Example 2 On both sides of the same reinforcing plate as in Example 1, epoxy resin (manufactured by Dainippon Ink Co., Ltd.: Evicron 1010) was used as the inner layer.
An expanded graphite sheet with the same thickness and density as Example 1 impregnated with 4.0% by weight of 5l-75 as a solid content was laminated as the outer layer, and the same expanded graphite sheet as in Example 1 was laminated as the outer layer. After rolling in the same manner as above, the material was cured at 160° C. for 1 hour to obtain a graphite gasket material with a thickness of 1.21 layers.

Comparative Example f Example 1 in which both sides of the same reinforcing plate as in Example 1 were impregnated with the same phenol resin as in Example 1 at a solid content of 1.3ii
Two layers of expanded graphite sheets with the same thickness and density were laminated and rolled in the same manner as in Example 1.
After time curing, a graphite gasket material having a plate thickness of 1.2 am was obtained.

Reference Example Two layers of the same expanded graphite sheet as in Example 1 were laminated on both sides of the same reinforcing plate as in Example 1, and after rolling in the same manner as in Example 1, the plate thickness was 1 or 2. A graphite gasket material was obtained.

Test Examples Example 1.2. The following tests were conducted on the graphite gasket materials prepared in Comparative Examples and Reference Examples.

(1) Compression rate and recovery rate Using a φ6.4 barrel penetrator, apply 7 to 9/d to the test piece.
The thickness of the compressed part when a preload is applied is T1゜350
The compression ratio and recovery ratio were determined using the following equations, where Ts is the thickness when a main load of 7 kg/cm'' is applied and then Ts is the thickness when a main load of 7 kg/cm'' is applied.

(2) Oil Resistance A 50x50 (Sono) rectangular test piece was immersed in ASTM Arashi 3 oil at 150°C for 5 hours, and the weight increase rate (%) and compressive fracture strength (ks/am'') were measured.

(3) LLC leak characteristics Test piece 1 with inner diameter d = 34 nm and outer diameter D = 50 m+ shown in Figure 1 is held between jig 2 and 60 kg with 9M10 bolt 3.
Tighten with a surface pressure of 10n'' and connect the liquid inlet 4 to the space 5.
An ethylene glycol aqueous solution of 0 volume was introduced, internal pressure was applied, and the internal pressure at which leakage or oozing of the ethylene glycol aqueous solution occurred was investigated.

(4) Stress relaxation properties The test was carried out in accordance with ASTM-38 table.

The test results are shown in Table 1.

Table 1 As is clear from Table 1, the graphite gasket material of the example has a smaller weight increase rate than that of the reference example that does not contain tat fat, has a higher compressive fracture strength, and has higher oil resistance than the comparative example. It has been improved to the same extent, and the LCIJ-resistance properties, which indicate stress relaxation properties and sealing properties, have also been significantly improved (comparative examples containing a large amount of resin).

The values for the reference example and the same hometown are shown.

(Effect of the invention)

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a method for testing LLCIJ characteristics. Explanation of symbols 1...Test piece 2...Jig 3...Bolt 4...Liquid inlet 5...Space

Claims (1)

[Claims] 1. Graphite characterized by laminating a resin-impregnated expanded graphite sheet on both sides of a thin metal plate having circular or square projections and an expanded graphite sheet on the outside of the resin-impregnated expanded graphite sheet, pressurizing the sheet, and then heating the sheet. Manufacturing method of quality gasket material.