JP2981074B2 - Gasket material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasket material mainly used for a cylinder head gasket of an internal combustion engine and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, this type of gasket is a steel type gasket formed by stacking a plurality of metal sheets or a steel type gasket coated with rubber, synthetic resin or lead. BACKGROUND ART A metal gasket, a gasket made of an aromatic polyamide fiber (aramid fiber) and a synthetic resin, a flexible graphite sheet material made of expanded graphite in a sheet shape, and the like are known.
Metal-based gaskets such as the steel-type gaskets have a low restoration ratio after compression. Therefore, a process called beating is performed to improve the sealability, and the restoring force required for sealing is obtained in this processed portion. However, this beat has a drawback that it is unreliable because it becomes prone to prolonged use. Further, since the metal gasket is composed of a plurality of sheets, the manufacturing process is complicated, and there is a disadvantage that it is expensive. In addition, the coating material made of only rubber or synthetic resin of a metal gasket only has a role of compensating for the unevenness of the mating material, and has a low heat resistance and cannot cope with a high load and a high temperature of an engine. No sealing property is obtained. Also, in a cylinder head gasket having a coating layer of lead plating, the restoring force after compression is small and the sealing property is not good. On the other hand, a gasket made of aramid fiber and a synthetic resin provides good sealing properties, but is insufficient in heat resistance and cost. When a flexible graphite sheet material is used as a gasket, it is inevitably thick because it is in the form of a sheet. In addition, Tokiko Sho 57
Japanese Patent No. 25383 discloses a carbon-metal composite material having excellent contact resistance and impermeability obtained by bonding a sheet formed of expanded graphite to one or both surfaces of a metal. It is not used as a gasket for an internal combustion engine. Accordingly, the applicant of the present invention has
No. 33181, the disadvantages of a metal-based gasket are complemented by the advantages of expanded graphite sheet material, the restoring force after compression is high, the gasket characteristics such as friction coefficient and stress relaxation rate are good, such as coating or print printing. A gasket for an internal combustion engine having excellent sealing properties obtained by a simple process has been proposed. However, even with such a gasket, if the thickness of the coating layer becomes thin, especially in the case of 100 μm or less, there is still a problem in the strength of the coating layer, and improvement thereof has been desired.

[0003]

In order to solve the above-mentioned problems, a gasket material according to the present invention is composed of expanded graphite containing 20 to 33% by weight of carbon black and fluororubber, and the carbon black is mixed. A coating layer having a weight ratio of expanded graphite to fluororubber of 10: 100 to 50: 100 is provided on at least one surface of the substrate. Further, the method for producing a gasket material of the present invention comprises expanded graphite mixed with 20 to 33% by weight of carbon black and fluororubber, and the ratio of expanded graphite mixed with carbon black to fluororubber is 1%.
A compound having a weight ratio of 0: 100 to 50: 100 is screen-printed on at least one surface of the substrate, and then the compound is cured.

In the present invention, the expanded graphite refers to graphite which expands in the C-axis direction by a factor of 10 or more in a graphite layer structure, and is obtained as follows. That is, natural graphite,
Treat graphite such as pyrolytic graphite and quiche graphite with concentrated sulfuric acid, concentrated nitric acid, strong oxidizing agents such as concentrated nitric acid and potassium chlorate, concentrated sulfuric acid and potassium nitrate or potassium permanganate, or halides such as bromine or aluminum chloride. By rapidly heating the graphite particles on which the intercalation compound is formed,
For example, a decomposition gas is generated by treating at a high temperature of 1000 ° C. or more for 1 to 10 seconds, and the graphite layer is expanded by the gas pressure to obtain expanded graphite particles. In this case, the processing methods of the pretreatment and the heat treatment are adjusted to obtain expanded graphite having a specific volume of 10 to 300 cc / g (expanded to 10 to 300 times). The expanded graphite used in the present invention needs to have a specific volume of 10 to 300 cc / g. However, if the specific volume is less than 10 cc / g, the compression recovery ratio is low and it is not suitable for gaskets. This is because it is difficult to industrially obtain one exceeding 300 cc / g. Also,
The mixture of the expanded graphite and the carbon black and the fluororubber were blended so that the weight ratio in the compound was 10 to 50 for the latter and 100 for the latter, but when the former was less than 10, the compression recovery rate was insufficient. This is because, when it exceeds 50, swelling of the surface is observed.
By curing such a compound on a substrate, it is composed of expanded graphite mixed with 20 to 33% by weight of carbon black and fluororubber, and the ratio of expanded graphite mixed with carbon black to fluororubber is 10%. : 1
A coating layer having a weight ratio of 00 to 50: 100 is formed.

The method of manufacturing the gasket material of the present invention will be described in detail. First, it is composed of expanded graphite mixed with 20 to 33% by weight of carbon black and fluoro rubber, and expanded graphite mixed with the carbon black. Prepare a compound in which the weight ratio of the rubber and the fluoro rubber is adjusted to 10: 100 to 50: 100.
Adjust to a sheet. At this time, it is preferable to add an acid acceptor to the fluororubber for curing. Next, a solvent is added to the preparation to make it into an enamel. In the solvent,
For example, a weight ratio of carbitol acetate to methanol of 1
Use a mixture of about 0: 1. The weight ratio between the sheet and the solvent is, for example, about 40:60. Next, after mixing the enamel-like material with a mixer to prepare an ink, the substrate is screen-printed and finally cured. At this time, it is preferable that the substrate is subjected to a surface treatment and a primer treatment before printing. Further, the thickness of the coating layer is preferably about 10 to 300 μm in terms of application. In addition, for example, after curing at 120 ° C. for 30 minutes,
For 2 hours to cure. In the present invention, the base of the gasket may be a metal such as iron, copper, copper alloy, aluminum, aluminum alloy, or stainless steel, or a non-metal such as asbestos, ceramics, paper, aramid fiber, synthetic resin, graphite, rubber, or a composite material thereof. Metal.

[0006]

The carbon black has a structured structure, and therefore enters between the expanded graphites and becomes entangled with each other. Therefore, the strength is increased, and a thin coating layer having good compression recovery can be formed. Fluororubber is also known to have excellent heat resistance and high strength, but it is very well compatible with expanded graphite mixed with carbon black, so that a particularly strong coating layer can be obtained. It became clear. The gasket of the present invention obtained as described above has a high restoring force after compression, has a good gasket characteristic such as a friction coefficient and a stress relaxation rate, improves overall strength, and has basic characteristics such as oil resistance. Good.

[0007]

The present invention will be described below based on examples and comparative examples. (Examples 1-3, Comparative Examples 1-2) (a) A mixture of 100 parts by weight of expanded graphite having a specific volume of 200 cc / g and 30 parts by weight of carbon black, and (b) fluororubber (Florel FC2170, manufactured by Sumitomo 3M) Were mixed at various ratios shown in Table 1 and dispersed with a rubber roll to prepare a sheet. A solvent in which carbitol acetate and methanol were added at a weight ratio of 10: 1 was added thereto to obtain a compound adjusted to an ink having a viscosity of 150 to 500 poise. Next, a stainless steel (SUS-304) plate having a thickness of 0.25 mm was prepared as a substrate, subjected to a surface treatment by trichlene washing, and then subjected to a primer treatment. Primer treatment is Dynamar 5150 (Sumitomo 3M)
Was applied with a brush and dried at room temperature for 10 minutes. On this substrate, the above-prepared compound prepared in the form of ink was screen-printed on both sides of the substrate to obtain gasket materials having coating layers of various thicknesses shown in Table 1. In addition, the obtained gasket material was evaluated, and the evaluation results are shown in Table 1.

[0008]

[Table 1]

The test methods and evaluation methods in Table 1 are as follows. (1) Appearance The appearance of the obtained gasket was visually observed, and the appearance was extremely good, "◎", good thing "O", slightly swelling "△", swelling severe. Was evaluated as "x". (2) Adhesiveness The coating layer was scratched off with a knife and peeled off, and those with extremely strong adhesion were marked with “◎”, those with strong adhesion as “○”, those with relatively strong adhesion as “△”, and those with relatively strong adhesion as “×”. Was evaluated. (3) Compression / decompression rate The test was performed according to ASTM F36 method A. (4) Oil resistance The gasket material is JIS No. After immersion in the test oil specified as No. 3, the thickness increase rate, weight increase rate, and compression / restoration rate of the sample were determined. (5) Stress relaxation rate According to ASTM F36 method B, the ambient temperature is 150
The test was performed with the temperature set to ° C. (6) Coefficient of friction The pull-out force was measured by an autograph, and the maximum coefficient of static friction was determined. The fastening chuck used was one polished with abrasive paper # 1000, and a fastening force of 60 kg / cm ² was applied. still,
In the tests of (3) to (6), extremely good samples were evaluated as “◎”, good samples were evaluated as “” ”, normal samples were evaluated as“ △ ”, and poor samples were evaluated as“ × ”.

(Examples 4-5, Comparative Examples 3-6) Using the same expanded graphite, carbon black and fluororubber as in the above Examples and Comparative Examples, the mixing ratio of expanded graphite and carbon black and (a): The gasket material was obtained by changing the ratio of (b) variously as shown in Table 2. Table 2 shows the results of evaluating the other conditions under the same conditions.

[0011]

[Table 2]

Comparative Examples 7 to 9 A gasket material was obtained in the same manner as in Examples 1 to 3, except that a binder made of a phenol resin was used instead of the fluororubbers of Examples 1 to 3. The obtained gasket material was evaluated in the same manner as described above, and the results are shown in Table 3.

[0013]

[Table 3]

[0014]

As described above, according to the present invention, the restoring force after compression is high, the gasket characteristics such as the coefficient of friction and the stress relaxation rate are improved, the overall strength is improved, and the oil resistance and the like are improved. A gasket material having good basic characteristics can be provided.

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09K 3/10 C01B 31/04 C01B 35/54 C08K 3/00-3/04

Claims (4)

(57) [Claims] 1. An expanded graphite mixed with 20 to 33% by weight of carbon black and fluororubber, wherein the ratio of expanded graphite mixed with carbon black to fluororubber is 10: 100 to 50: 100 by weight. A gasket material, comprising a coating layer having a ratio on at least one surface of a substrate. 2. The gasket material according to claim 1, wherein the base is any one of iron, copper, copper alloy, aluminum, aluminum alloy, and stainless steel. 3. The non-metallic material of any one of asbestos, ceramics, paper, aromatic polyamide fiber (aramid fiber), synthetic resin, graphite, rubber, and a composite material thereof. The gasket material described. 4. The method for producing a gasket material according to claim 1, wherein the expanded graphite is a mixture of 20 to 33% by weight of carbon black and fluororubber, and the expanded graphite is a mixture of the carbon black. A compound having a weight ratio of 10: 100 to 50: 100 with fluororubber is screen-printed on at least one surface of the substrate,
Then, the compound is cured to produce a gasket material.