JPH01275966A - Gasket - Google Patents

Abstract

PURPOSE:To make a gasket for each passage so as to be unnecessary to form it into a separate body by mixing a high water absorptive polymer in the specified nitrile content of stock rubber as much as a specific quantity. CONSTITUTION:A gasket consists of a rubber vulcanizate of nitrile rubber compounds, and this rubber vulcanizate is 15-45% in nitrile content of stock rubber, and it is mixed with a high water absorptive polymer 10-40pts. to a material 100pts. When a water system fluid has been flowing out between stationary member mutual joining surfaces from a water system passage, the gasket itself expands and seal pressure is increased because the high water absorptive polymer is mixed therein. On the other hand, when a fluid has been flowing out between these stationary members themselves from an oil system passage, the gasket itself expands and the seal pressure glows large as well because of low in the nitrile content.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is used between joint surfaces of stationary members having both water-based channels and oil-based channels, and is used for rubber vulcanization of nitrile rubber compounds. Concerning gaskets made of material.

<Prior Art> Here, as an example of the above-mentioned type of gasket G, a gasket G used between the joint surface of the head 3 of the engine 1 and the intake manifold 5 as shown in FIG. 2 will be explained. It is not limited to this. A cooling water flow path as a water flow path and a gasoline flow path as an oil flow path are provided between the head 3 and the intake manifold 5.

The structure of the gasket used in the above areas is as follows:
Normally, each channel was configured with a different material (metal or rubber) that corresponded to the channel.

<Problems to be Solved by the Invention> For this reason, gaskets had to be molded separately for each flow path, which increased the number of man-hours for molding as a whole, and also increased the number of man-hours for assembly.

In view of the above, an object of the present invention is to provide a gasket that does not require separate formation of gaskets for each flow path and can significantly reduce the number of man-hours for molding and assembly.

<Means for Solving the Problems> As a result of intensive development efforts by the present inventors in order to solve the above problems, the present inventors were able to come up with a gasket having the following configuration.

A gasket made of a rubber vulcanizate of a nitrile rubber compound, which is used between the joint surfaces of stationary members having both a water-based flow path and an oil-based flow path, the compounding formulation of the nitrile rubber compound being: 4) The raw rubber has a nitrile content of 15 to 45%, and 10 to 40 parts by weight of a super absorbent polymer is blended with 100 parts by weight of the raw rubber. gasket.

Detailed explanation of the solution> The solution will be explained in detail below. In the following description, "parts" indicating a blending unit means "parts by weight" unless otherwise specified.

FIG. 1 is a plan view showing an example of a gasket G to which the present invention is applied.

This gasket is made of a rubber vulcanizate of a nitrile rubber compound, and the rubber vulcanizate has the following requirements.

■Nitrile content of raw rubber = 15 to 45%. Here, if it is less than 15%, the swelling due to oil becomes too large, and if it exceeds 45%, it is difficult to obtain a predetermined oil interstitial property, that is, a self-sealing property against oil.

■10 to 10 parts of super absorbent polymer per 100 parts of the raw material rubber
Contains 40 parts.

Here, if it is less than 10 parts, the predetermined water swelling property h (h) cannot be obtained, and if it exceeds 40 parts, the physical properties of the vulcanized rubber deteriorate, which is not desirable.

Here, superabsorbent polymers have the property of absorbing water tens to nearly 1,000 times their own weight, and once they absorb water and swell to form a hydrogel, they do not release water even under slight pressure. (do something that has)

Specific superabsorbent polymers include polyacrylate-based (ex, sodium/potassium polyacrylate), polyvinyl alcohol-cyclic anhydride graft copolymer, isobutylene-maleic acid copolymer, and starch-polyacrylic acid. Salt graft copolymerization, vinyl acetate-acrylic acid ester copolymer, vinyl acetate-unsaturated dicarboxylic acid copolymer, polyethylene oxide type, carboxymethyl cellulose type (ex, carboxymethyl cellulose sodium), starch-polyacrylonitrile graft copolymer etc. can be mentioned.

These forms are usually used in the form of powder or granules, which are kneaded with raw rubber.

Carbon black, zinc white, processing aids, anti-aging agents, sulfur vulcanizing agents, etc. are kneaded into the raw material rubber, similar to the usual nitrile rubber formulation. is made by transfer molding, press molding, etc.
It is vulcanized and formed into a gasket.

<Operations and Effects of the Invention> The gasket of the present invention is a gasket made of a rubber vulcanizate of a nitrile rubber compound, and is used between joint surfaces of stationary members having both a water-based flow path and an oil-based flow path. There it is,
The formulation of the nitrile rubber compound meets the following requirements: (1) the nitrile content of the raw rubber is 15 to 45%, (2) 10 to 40 parts by weight of a super absorbent polymer is blended with 100 parts by weight of the raw rubber. This configuration provides the following functions and effects.

When water-based fluid flows out from the water-based flow path between the joint surfaces of the stationary members, 1. As the superabsorbent polymer absorbs water and swells, the gasket itself expands, increasing the sealing pressure and exhibiting a self-sealing effect. On the other hand, if the oil-based fluid flows out between the stationary members from the oil-based flow path, the nitrile content of the raw rubber constituting the gasket is low;
The gasket swells with oil, and the gasket itself expands, increasing the sealing pressure and exhibiting a self-sealing effect.

Therefore, with the gasket of the present invention, there is no need to separately form a gasket for each flow path, and the number of man-hours for molding and assembly can be significantly reduced.

Test Example> Hereinafter, a trial drive conducted to confirm the effects of the present invention will be explained.

In the following compounding recipe, as shown in Table 1, raw rubbers with different nitrile contents are used, and after kneading raw rubbers containing various amounts of super absorbent polymer, the rubbers are press-molded (molding conditions: 170″cxlo min). Each rubber vulcanizate in the form of a sheet was obtained.

Blend Prescription Raw material rubber 100 parts Super absorbent polymer Variable carbon black 40 parts Processing aid
10 parts anti-aging agent
6 parts zinc white 5
Part sulfur vulcanizing agent 4.5 parts The following tests were conducted on each of the rubber vulcanizates.

(1) Normal physical properties: The physical properties of hardness CHs: JIS-^), tensile strength (T11), and elongation (E, ) were measured based on JIS-6301.

(2) Compression set: Based on JIS-6301, compression was performed at 100° C. for 70 hours.

(3) Swelling rate after immersion in aqueous fluid: According to JIS-6301, LLC/water = 50150
immersed in an aqueous fluid at 100°C for 70 hours,
The volume change rate was determined.

(4) Swelling rate after immersion in oil-based fluid: According to JIS-6301, the sample was immersed in Tsuyuel C (oil-based fluid) at 60° C. for 48 hours to determine the volume change rate.

The above test results are shown in Table 1, and each example within the scope of the technical idea of the present invention has almost no difference in normal state physical properties from Comparative Example 3, which is a conventional example, and has a volumetric expansion coefficient of
It can be seen that it is large for both water-based and oil-based fluids.

In contrast, Comparative Example 2, which has a high nitrile content, has a small swelling ratio with respect to oil-based fluids even though it contains a superabsorbent polymer, whereas Comparative Example 1, which has a superabsorbent polymer content exceeding 40 parts It can be seen that the reduction rate is large in normal state physical properties, etc. Furthermore, it can be seen that Comparative Example 3, which does not contain a superabsorbent polymer, has a much smaller expansion coefficient with respect to aqueous fluids than Examples and other Comparative Examples in which a superabsorbent polymer is blended.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a gasket to which the present invention is applied, and FIG. 2 is a schematic front view of an automobile engine showing parts to which the gasket of the present invention can be applied. 1...Engine, 3...Engine head, 5...Intake manifold G...Gasket. Patent applicant Figure 1 Figure 2

Claims (1)

[Scope of Claims] A gasket made of a rubber vulcanizate of a nitrile rubber compound, which is used between joint surfaces of stationary members having both a water-based flow path and an oil-based flow path; The compounding recipe meets the following requirements: (1) the nitrile content of the raw rubber is 15 to 45%, and (2) 10 to 40 parts by weight of the superabsorbent polymer is blended to 100 parts by weight of the raw rubber. A gasket characterized by: