JP6488502B2 - Gasket, manufacturing method thereof, sealing method and sealing structure using the same - Google Patents

Description

  The present invention relates to a gasket formed by crosslinking a rubber composition containing acrylic rubber and a method for producing the same. The present invention also relates to a sealing method and a sealing structure using the gasket.

  Acrylic rubber is excellent in oil resistance and heat resistance, and is widely used for automobile parts and the like. For example, it is suitably used as a gasket or the like for fastening members around the engine that reach a high temperature. At this time, in many cases, a gasket is inserted into a groove provided on the sealing surface of one member, and then the sealing surfaces of the other member are opposed to each other, and both members are fastened and sealed. . By fixing the gasket in a groove provided in one member in advance, it is possible to position the gasket and securely seal between the two members.

  However, the surface of the acrylic rubber gasket has a high frictional resistance, and it was not easy to insert it into the groove. In particular, when a gasket having a complicated shape, such as an engine head cover gasket or an oil pan gasket, is inserted into the groove, the workability is inevitably lowered.

  For this reason, it has been widely practiced to apply silicone oil to the surface of the molded rubber gasket and then insert it into the groove. However, in this case, since the silicone oil is simply attached to the surface, there is a possibility that the periphery of the gasket may be contaminated or foreign matter may adhere to the gasket after insertion. In addition, when exposed to high temperatures in an environment where electrical equipment is located in the vicinity, silicone oil decomposes and low molecular weight siloxane is generated and volatilized, which adheres to electrical contacts such as relays and causes poor contact. It was also pointed out that there is a risk of it happening.

  As a measure other than the application of silicone oil, Patent Document 1 discloses a polyvalent metal salt of a higher fatty acid, an alkali metal salt of a higher fatty acid, and a tackifier for vulcanized rubber in which a higher fatty acid is dispersed in a paraffinic organic solvent. Has been. By applying this to vulcanized acrylic rubber, it is said that a rubber molded product that is thermally stable and free from defects adhering to equipment is obtained. However, a coating operation using an organic solvent must be performed, and there is no description that frictional resistance is improved.

Japanese Patent Laid-Open No. 10-30084

  The present invention has been made to solve the above problems, and provides an acrylic rubber gasket capable of reducing the coefficient of friction without separately applying a release agent and reducing compression set at high temperatures. It is for the purpose. Moreover, it aims at providing the suitable manufacturing method of the said gasket. Furthermore, it aims at providing the sealing method and sealing structure using the said gasket.

The above-mentioned problem is a gasket formed by crosslinking a rubber composition containing acrylic rubber (A), process oil (B) and crosslinking agent (C),
The acrylic rubber (A) is a polymer containing 90 to 99% by mass of an acrylate unit and 1 to 10% by mass of a crosslinkable monomer unit having a carboxyl group,
The crosslinking agent (C) is a polyamine compound;
Including 100 parts by mass of acrylic rubber (A), 1-10 parts by mass of process oil (B) and 0.1-3 parts by mass of crosslinking agent (C),
It is solved by providing a gasket characterized in that 98% by mass or more of the total polymer component contained in the rubber composition is acrylic rubber (A).

At this time, the process oil (B) is preferably a paraffinic process oil. It is also preferable that the aniline point of the process oil (B) is 100 ° C. or higher. Moreover, it is also preferable that the kinematic viscosity in 40 degreeC of process oil (B) is 100-1000 mm < ² > / s.

  A preferred embodiment of the gasket of the present invention is an engine head cover gasket, an oil pan gasket or an O-ring.

  The above problem is that after acrylic rubber (A), process oil (B), and cross-linking agent (C) are kneaded to obtain the rubber composition, the mold is filled and heated in the mold for crosslinking. It is also solved by providing a method for manufacturing the gasket, characterized in that it is removed from the mold.

  Further, the above-mentioned problem is a sealing method for sealing between two members via a gasket, and the gasket manufactured by the above method is removed from the mold without applying a lubricant, and the inside of the two members. The problem can also be solved by providing a sealing method characterized by inserting into a groove provided on the sealing surface of one member and subsequently fastening the two members with the sealing surface of the other member facing each other.

  Furthermore, the above-described problem is a sealing structure in which two members are sealed through the gasket, wherein the gasket is inserted into a groove provided on a sealing surface of one of the two members, and the other It is also solved by providing a sealing structure characterized in that the two members are fastened with the sealing surfaces of the members facing each other.

  According to the acrylic rubber gasket of the present invention, the coefficient of friction can be reduced without separately applying a release agent, and the compression set at a high temperature can also be reduced. Further, according to the sealing method using the gasket, even a gasket having a complicated shape can be easily inserted into the groove provided on the sealing surface. Therefore, it is preferably used as a gasket having a complicated shape, such as an engine head cover gasket or an oil pan gasket, which is used at a high temperature.

  The present invention relates to a gasket obtained by crosslinking a rubber composition containing acrylic rubber (A), process oil (B) and a crosslinking agent (C). Here, it is a great feature of the present invention that the rubber composition contains the process oil (B).

  Process oil is an oil formulated to improve the properties of rubber. By adding it, it is possible to improve the plasticity of rubber and improve processability, or to lower the hardness of rubber. . When the process oil is blended, it is considered that the oil molecules contained in the process oil enter between the polymer chains of the rubber and exert a lubricating action, thereby achieving the above effect. Therefore, in order to achieve the blending effect, it is necessary that the affinity between the process oil and the rubber is high. Process oil is derived from minerals such as petroleum and coal, and is a hydrophobic oil mainly composed of hydrocarbons. Therefore, it is usually used only for hydrophobic rubber with good affinity with it. . Specifically, natural rubber (NR), isoprene rubber (IR), styrene / butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), ethylene / propylene rubber (EPM), It is blended with a hydrophobic rubber such as ethylene / propylene / diene rubber (EPDM). The acrylic rubber (ACM), which is a polar rubber, and hydrophobic process oil have low affinity, so the above effect cannot be expected, and it has been thought that there is no significance in blending.

  However, in the present invention, a hydrophobic process oil (B) is intentionally blended with the acrylic rubber (A) which is a polar rubber. As a result, a crosslinked rubber molded product having a low static friction coefficient could be obtained. This is presumably because a small amount of process oil (B) bleeds out uniformly on the surface of the crosslinked rubber molded product, and there is almost no possibility of contaminating the periphery with oil. Moreover, despite the addition of oil with low affinity, the mechanical properties and heat aging resistance were not reduced. Such a phenomenon has been found for the first time by the present inventor through intensive studies.

  The acrylic rubber (A) used in the rubber composition of the present invention is a polymer containing 90 to 99% by mass of an acrylate unit and 1 to 10% by mass of a crosslinkable monomer unit having a carboxyl group.

Here, it is important that the acrylic rubber (A) contains 90 to 99% by mass of an acrylate unit. When the content of the acrylate unit is less than 90% by mass, the resulting gasket has insufficient heat aging resistance. The content of the acrylate unit is more preferably 95% by mass or more. For example, when ethylene-methyl acrylate copolymer rubber (AEM) containing an ethylene unit greatly exceeding 10% by mass is used, the resulting gasket has insufficient heat aging resistance and a high static friction coefficient. On the other hand, when the content of the acrylate unit exceeds 99% by mass, the strength of the obtained gasket becomes insufficient. The content of the acrylate unit is more preferably 98% by mass or less. Examples of the acrylate ester unit contained in the acrylic rubber (A) include an ethyl acrylate unit, a butyl acrylate unit, a methoxyethyl acrylate unit, and a methyl acrylate unit. The acrylic rubber (A) preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 20 to 50.

  It is also important that the acrylic rubber (A) contains 1 to 10% by mass of a crosslinkable monomer unit having a carboxyl group. By crosslinking such an acrylic rubber (A) with a polyamine compound, the resulting gasket has good heat aging resistance and a low static friction coefficient. When the content of the crosslinkable monomer unit having a carboxyl group is less than 1% by mass, the strength of the obtained gasket becomes insufficient. The content of the crosslinkable monomer unit is more preferably 2% by mass or more. On the other hand, when the content of the crosslinkable monomer unit having a carboxyl group exceeds 10% by mass, the resulting gasket has insufficient heat aging resistance. The content of the crosslinkable monomer unit is more preferably 5% by mass or less.

As the process oil (B) used in the rubber composition of the present invention, those commercially available for rubber addition and the like can be used. Specific examples include paraffinic process oil, naphthenic process oil, and aromatic process oil. These may be used alone or in combination of two or more. Of these, paraffinic process oil is preferably used. Since the paraffinic process oil has low polarity and low affinity with the acrylic rubber (A), it can be sufficiently bleed out on the surface of the crosslinked rubber molded product. Here, the paraffinic process oil has a ratio of paraffinic carbon (% C _P ) of 60% or more when subjected to ring analysis (ndM method), and a ratio of naphthenic carbon (% C _N ) to aroma. It means that the total of the proportion of group carbon (% C _A ) is 40% or less.

  The aniline point of the process oil (B) is preferably 100 ° C. or higher. A process oil having a high aniline point has a low affinity for polar rubber. However, in the present invention, it is preferable to add a process oil having such a high aniline point to the acrylic rubber (A). Thereby, the process oil (B) can be sufficiently bleed out on the surface of the crosslinked rubber molded product. The aniline point is more preferably 120 ° C. or higher, and further preferably 130 ° C. or higher. On the other hand, the aniline point is usually 160 ° C. or lower. The aniline point is measured based on JIS K2256.

The kinematic viscosity at 40 ° C. of the process oil (B) is preferably 100 to 1000 mm ² / s. By using a process oil having a kinematic viscosity in this range, the amount of process oil that bleeds out to the surface of the crosslinked rubber molded product can be made an appropriate amount. If the kinematic viscosity is less than 100 mm ² / s, the amount of process oil that bleeds out on the surface of the crosslinked rubber molded product may be excessive, and the surface of the molded product may become sticky. The kinematic viscosity is more preferably 200 mm ² / s or more, and even more preferably 300 mm ² / s or more. On the other hand, if the kinematic viscosity exceeds 1000 mm ² / s, the amount of process oil that bleeds out to the surface of the crosslinked rubber molded product becomes insufficient, the coefficient of static friction increases, and the insertability of the gasket into the groove may deteriorate. is there. The kinematic viscosity is more preferably 500 mm ² / s or less. The kinematic viscosity is measured based on JIS K2283.

  The pour point of the process oil (B) is preferably 20 ° C. or lower. By having fluidity at room temperature, the gasket can be easily inserted into the groove. The pour point is preferably 10 ° C. or less, and more preferably 0 ° C. or less. On the other hand, the pour point is usually −50 ° C. or higher. The pour point is measured based on JIS K2269. The flash point of process oil (B) is preferably 240 ° C. or higher. When the flash point is 240 ° C. or higher, the safety of the gasket used in places exposed to high temperatures such as around the engine is improved. The flash point is more preferably 260 ° C. or higher, and even more preferably 280 ° C. or higher. On the other hand, the flash point is usually 360 ° C. or lower. The flash point is measured based on JIS K2265-4. Paraffinic process oils have a higher flash point than naphthenic process oils and aromatic process oils, and are highly safe for use in high-temperature atmospheres.

  It is known that various types of lubricants are usually used when molding acrylic rubber. However, when these lubricants are used, the static friction coefficient of the gasket cannot be sufficiently reduced as shown in a later comparative example, and the insertability into the groove is poor. For this reason, silicone oil has been applied after molding, but by adding process oil (B) to the rubber composition, it is excellent in insertability into the groove without applying silicone oil after molding. A gasket could be obtained.

  It is important that the crosslinking agent (C) used in the rubber composition of the present invention is a polyamine compound. By cross-linking the acrylic rubber (A) containing a crosslinkable monomer having a carboxyl group with a polyamine compound, the resulting molded article has good heat aging resistance.

The polyamine compound used in the present invention is not particularly limited as long as it is a compound having two or more amino groups or can be in the form of a compound having two or more amino groups at the time of crosslinking. A compound in which a plurality of hydrogen atoms of an aliphatic hydrocarbon or an aromatic hydrocarbon is substituted with an amino group or a hydrazide group (—CONHNH ₂ ) is preferable. Specific examples of the polyamine compound include aliphatic polyamine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, tetramethylenepentamine, hexamethylenediamine-cinnamaldehyde adduct, hexamethylenediamine-dibenzoate salt; Aromatic polyamines such as bis {4- (4-aminophenoxy) phenyl} propane, 4,4'-methylenedianiline, m-phenylenediamine, p-phenylenediamine, 4,4'-methylenebis (o-chloroaniline) And compounds having two or more hydrazide structures such as isophthalic acid dihydrazide, adipic acid dihydrazide, and sebacic acid dihydrazide. Among these, aliphatic polyamine compounds are preferable, and hexamethylenediamine carbamate is particularly preferable.

  The rubber composition of the present invention contains 1 to 10 parts by mass of process oil (B) with respect to 100 parts by mass of acrylic rubber (A). When the content of the process oil (B) is less than 1 part by mass, the static friction coefficient on the surface of the molded product is not sufficiently lowered, and the lubricity is not sufficiently improved. The content of the process oil (B) is preferably 1.5 parts by mass or more. On the other hand, when the content of the process oil (B) exceeds 10 parts by mass, the process oil (B) may be bleed out and contaminate the surroundings, and the mechanical strength also decreases. The content of the process oil (B) is preferably 5 parts by mass or less.

  Moreover, the rubber composition of this invention contains 0.1-3 mass parts of crosslinking agents (C) with respect to 100 mass parts of acrylic rubber (A). When the content of the crosslinking agent (C) is less than 0.1 parts by mass, sufficient crosslinking density cannot be obtained, and only a crosslinked rubber molded product having low strength can be obtained. The content of the crosslinking agent (C) is preferably 0.2 parts by mass or more. On the other hand, when the content of the crosslinking agent (C) exceeds 3 parts by mass, waste is increased. The content of the crosslinking agent (C) is preferably 2 parts by mass or less.

  Of all the polymer components contained in the rubber composition of the present invention, 98% by mass or more needs to be acrylic rubber (A). That is, it is preferable that the rubber composition of the present invention contains almost no polymer component other than the acrylic rubber (A). For example, if a hydrophobic rubber is included in addition to the acrylic rubber (A), the process oil is taken in and not only the lubricity is lowered, but also the mechanical strength is lowered. Moreover, there exists a possibility of impairing the oil resistance and heat resistance which acrylic rubber (A) has originally. Of all the polymer components, 99% by mass or more is preferably the acrylic rubber (A), and more preferably substantially composed of the acrylic rubber (A).

  The rubber composition of the present invention may contain components other than the acrylic rubber (A), process oil (B), and crosslinking agent (C) as long as the effects of the present invention are not impaired. Various additives, such as a vulcanization accelerator, a vulcanization aid, an acid acceptor, a colorant, a filler, and a plasticizer, which are usually used in rubber compositions can be included.

  The rubber composition of the present invention is produced by mixing the above components. The mixing method is not particularly limited, and kneading can be performed using an open roll, a kneader, a Banbury mixer, an intermixer, an extruder, and the like. Especially, it is preferable to knead | mix using an open roll or a kneader. The temperature of the rubber composition during kneading is preferably 20 to 120 ° C.

  The rubber composition thus obtained is filled into a mold, heated and crosslinked in the mold, and then removed from the mold to obtain the gasket of the present invention. Examples of the molding method of the rubber composition include injection molding, extrusion molding, compression molding and roll molding. Of these, injection molding and compression molding are preferred. At this time, it may be crosslinked after being molded in advance, or may be crosslinked simultaneously with the molding. The molding temperature is usually 10 to 200 ° C, preferably 25 to 120 ° C. The crosslinking temperature is usually 100 to 220 ° C, preferably 130 to 200 ° C, more preferably 150 to 200 ° C. The crosslinking time is usually from 10 seconds to 3 hours, preferably from 30 seconds to 1 hour, more preferably from 30 seconds to 30 minutes. Further, depending on the shape and dimensions of the gasket, even if the surface is cross-linked, there is a case where the surface is not fully cross-linked, so that secondary cross-linking may be performed by heating. As a heating method for crosslinking, general methods used for crosslinking of rubber, such as compression heating, steam heating, oven heating, hot air heating, and the like are used.

  The sealing method for sealing between the two members through the gasket thus obtained is not particularly limited. The gasket can be inserted into a groove provided on the sealing surface of one of the two members, and the two members can be fastened with the sealing surface of the other member facing each other. At this time, the gasket of the present invention can be easily inserted into the groove without applying a lubricant after removing the molded product from the mold. Since no lubricating oil such as silicone oil is applied, the process is simplified, and contamination around the gasket caused by the application can also be prevented. The gasket of the present invention is particularly useful when required to be inserted into a complex shaped groove. Further, in the sealing structure using the gasket of the present invention, the gap between the two members is sealed through the gasket, and the gasket is inserted into the groove provided on the sealing surface of one of the two members. The two members are fastened with the sealing surfaces of the other member facing each other.

  Since the gasket of the present invention has good heat aging resistance, it is suitable for applications exposed to high temperatures. Among them, it is particularly suitable for use around the engine of an automobile that requires oil resistance, heat resistance, and heat aging resistance. Particularly suitable applications are engine head cover gaskets and oil pan gaskets. These gaskets are assembled by inserting a gasket into a complex-shaped groove formed on the sealing surface. Therefore, it is significant to use the gasket of the present invention that can be easily inserted into the groove without applying silicone oil. Moreover, it is not limited to a gasket having a complicated shape, and it is easy to handle and is preferably used as a general O-ring.

    The raw materials used in the following examples are as follows.

・ Acrylic rubber (carboxyl group-containing ACM)
“Nipol AR22” manufactured by Nippon Zeon Co., Ltd.
Mooney viscosity (ML _{1 + 4} , 100 ° C.): 47
・ Acrylic rubber (active chlorine group-containing ACM)
“NIPOL AR72LS” manufactured by Nippon Zeon Co., Ltd.
Mooney viscosity (ML _{1 + 4} , 100 ° C.): 33
・ Ethylene-acrylate copolymer rubber (AEM)
"VAMAC G" made by DuPont
Mooney viscosity (ML _{1 + 4} , 100 ° C.): 15

・ Carbon black (filler)
“Seast G116” manufactured by Tokai Carbon Co., Ltd.
・ Stearic acid (lubricant)
"Stearic acid" manufactured by NOF Corporation
・ 4,4'-bis (α, α-dimethylbenzyl) diphenylamine (anti-aging agent)
“Nowguard 445” manufactured by Shiraishi Calcium Co., Ltd.

The following four types of process oil were used. Details thereof are summarized in Table 1.
・ Paraffinic process oil “Diana Process Oil PW-380” manufactured by Idemitsu Kosan Co., Ltd.
・ Paraffinic process oil “Diana Process Oil PW-90” manufactured by Idemitsu Kosan Co., Ltd.
・ Naphthenic process oil “Diana Process Oil NS-90S” manufactured by Idemitsu Kosan Co., Ltd.
・ Aromatic process oil “Diana Process Oil AC-12” manufactured by Idemitsu Kosan Co., Ltd.

・ Fatty acid amide (lubricant)
Kao Wax EB-FF manufactured by Kao Corporation
・ Solid paraffin (lubricant)
"Paraffin wax" manufactured by Nippon Seiwa
・ Fatty acid ester (lubricant)
"TE-58A" manufactured by Technical Processing
・ Organic silicone compounds (lubricants)
"Stractor WS280" manufactured by S & S Japan Co., Ltd.

・ Hexamethylenediamine carbamate (vulcanizing agent)
"Diak No. 1" made by DuPont
・ Sulfur (vulcanizing agent)
"Salfax" manufactured by Tsurumi Chemical Co., Ltd.
・ Sodium stearate (vulcanizing agent)
“NS Soap” manufactured by Kao Corporation
・ Di-o-tolylguanidine (vulcanization accelerator)
"Noxeller DT" made by Ouchi Shinsei Chemical Co., Ltd.

Example 1
[Preparation of unvulcanized rubber sheet]
Carboxyl group-containing acrylic rubber “Nipol AR22” 100 parts by mass, carbon black (filler) 60 parts by mass, stearic acid (lubricant) 3 parts by mass, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine (anti-aging) Agent) 2 parts by mass and 3 parts by mass of paraffinic process oil “Diana Process Oil PW-380” were kneaded in a closed kneader, and hexamethylenediamine carbamate (polyamine crosslinking agent: HMDC) 0 was added to the resulting mixture. .6 parts by mass and 2 parts by mass of di-o-tolylguanidine (a vulcanization accelerator) were added, an unvulcanized rubber sheet was prepared using an open roll, and subjected to the following tests. The blending ratio is shown in Table 2.

[Hardness measurement]
It measured based on JISK6253-3. The obtained unvulcanized rubber sheet was press vulcanized at 170 ° C. for 20 minutes and then vulcanized in an oven at 170 ° C. for 4 hours to obtain a vulcanized rubber sheet having a thickness of 2 mm. Three obtained vulcanized rubber sheets were stacked and measured using a type A durometer at 23 ° C. and a relative humidity of 50%, and the peak value was read. As a result, the A hardness was 59. The results are shown in Table 2.

[Tensile test]
A tensile test was performed according to JIS K6251. Using a dumbbell-shaped No. 3 test piece obtained by punching out a vulcanized rubber sheet having a thickness of 2 mm produced in the same manner as in the hardness test, at a tensile rate of 500 mm / min at 23 ° C. and a relative humidity of 50%. The tensile strength (MPa) and elongation (%) were measured. As a result, the tensile strength was 9.5 MPa and the elongation was 220%. These results are shown in Table 2.

[Compression set]
The measurement was performed according to JIS K6262. The obtained unvulcanized rubber sheet was press vulcanized at 170 ° C. for 20 minutes and then vulcanized in an oven at 170 ° C. for 4 hours to obtain a vulcanized rubber test piece having a diameter of 29 mm and a thickness of 12.5 mm. After compressing the obtained test piece at a compression rate of 25%, it was taken out of the thermostatic bath after being put in a thermostatic bath at 150 ° C. for 70 hours, quickly removed from the compression apparatus, and the thickness of the test piece was measured after 30 minutes. However, the compression set was 10%. The results are shown in Table 2.

[Static friction coefficient]
Using a 2 mm thick vulcanized rubber sheet produced in the same manner as in the hardness test and using a surface property measuring machine manufactured by Shinto Chemical Co., Ltd., the static friction coefficient of the sheet was measured under the following conditions. It was. The results are shown in Table 2.
Measurement speed: 600 mm / min
Measuring distance: 20mm
Vertical load: 100g

[Insertion]
The obtained unvulcanized rubber sheet was used for press vulcanization at 170 ° C. for 20 minutes, and then vulcanized in an oven at 170 ° C. for 4 hours to obtain a gasket test piece having a length of 50 mm. The shape of the cross section perpendicular to the longitudinal direction of the test piece was an ellipse having a width of 5 mm and a height of 12 mm, in which a semicircle having a diameter of 5 mm was joined to the top and bottom of a rectangle having a width of 5 mm and a height of 7 mm. The test piece was manually inserted into a rectangular groove having a width of 5 mm and a depth of 10 mm, and the ease of insertion was evaluated in the following three stages. The results are shown in Table 2.
A: It was able to insert smoothly and in a short time with a light force.
B: It took time only to insert.
C: It was difficult to insert.

[Bleed-out amount]
The surface of a vulcanized rubber sheet having a thickness of 2 mm produced in the same manner as in the hardness test was rubbed with a finger to confirm the amount of bleed out of the process oil. The results are shown in Table 2.
A: An appropriate amount of process oil was bleeding out.
B: Excess process oil bleeded out and the surface was sticky.
None: Since the process oil was not blended, the surface of the molded product was dry.

Example 2 and Comparative Examples 8 and 9
In Example 1, an unvulcanized rubber sheet was prepared in the same manner as in Example 1 except that other process oils shown in Table 1 were used instead of the paraffinic process oil “Diana Process Oil PW-380”. . Then, vulcanization molding was performed in the same manner as in Example 1, and hardness measurement, tensile test, compression set, static friction coefficient, and insertability were evaluated. The results are shown in Table 2.

Comparative Example 1
In Example 1, an unvulcanized rubber sheet was produced in the same manner as in Example 1 except that the paraffinic process oil “Diana Process Oil PW-380” was not used. Then, vulcanization molding was carried out in the same manner as in Example 1, and hardness measurement, tensile test, compression set, static friction coefficient and insertability were evaluated. The results are shown in Table 2.

Comparative Examples 2-5
In Example 1, an unvulcanized rubber sheet was produced in the same manner as in Example 1 except that the lubricant shown in Table 2 was used instead of the paraffinic process oil “Diana Process Oil PW-380”. Then, vulcanization molding was performed in the same manner as in Example 1, and hardness measurement, tensile test, compression set, static friction coefficient, and insertability were evaluated. The results are shown in Table 2.

Comparative Example 6
In Example 1, instead of the carboxyl group-containing ACM “Nipol AR22”, an active chlorine group-containing ACM “Nipol AR72LS” was used, and a combination of 0.6 parts by mass of hexamethylenediamine carbamate and 2 parts by mass of di-o-tolylguanidine An unvulcanized rubber sheet was prepared in the same manner as in Example 1 except that a combination of 0.3 part by mass of sulfur “Sulfax” and 3 parts by mass of sodium stearate “NS soap” was used instead of using. Then, vulcanization molding was carried out in the same manner as in Example 1, and hardness measurement, tensile test, compression set, static friction coefficient and insertability were evaluated. The results are shown in Table 2.

Comparative Example 7
In Example 1, ethylene-acrylate copolymer rubber “VAMAC G” was used instead of carboxyl group-containing ACM “Nipol AR22”, and the blending amount of hexamethylenediamine carbamate was increased to 2 parts by mass, and di-o-tolyl was used. An unvulcanized rubber sheet was produced in the same manner as in Example 1 except that the amount of guanidine was increased to 4 parts by mass. Then, vulcanization molding was carried out in the same manner as in Example 1, and hardness measurement, tensile test, compression set, static friction coefficient and insertability were evaluated. The results are shown in Table 2.

Claims (8)

A gasket obtained by crosslinking a rubber composition containing acrylic rubber (A), process oil (B) and a crosslinking agent (C),
The acrylic rubber (A) is a polymer containing 90 to 99% by mass of an acrylate unit and 1 to 10% by mass of a crosslinkable monomer unit having a carboxyl group,
The kinematic viscosity at 40 ° C. of the process oil (B) is 100 to 1000 mm ² / s,
The crosslinking agent (C) is a polyamine compound;
Including 100 parts by mass of acrylic rubber (A), 1-10 parts by mass of process oil (B) and 0.1-3 parts by mass of crosslinking agent (C),
98% by mass or more of the total polymer component contained in the rubber composition is acrylic rubber (A).   The gasket according to claim 1, wherein the process oil (B) is a paraffinic process oil.   The gasket according to claim 1 or 2, wherein the aniline point of the process oil (B) is 100 ° C or higher. The flash point of process oil (B) is 240-360 degreeC , The gasket in any one of Claims 1-3.   An engine head cover gasket, an oil pan gasket, or an O-ring, comprising the gasket according to claim 1.   Acrylic rubber (A), process oil (B) and cross-linking agent (C) are kneaded to obtain the rubber composition, then filled into a mold, heated in the mold and cross-linked, then from the mold It removes, The manufacturing method of the gasket in any one of Claims 1-4 characterized by the above-mentioned. A sealing method for sealing between two members via a gasket,
The gasket manufactured by the method according to claim 6 is inserted into a groove provided on a sealing surface of one of the two members without applying a lubricant after being removed from the mold, and then the other A sealing method, wherein the two members are fastened with the sealing surfaces of the members facing each other. A sealing structure in which two members are sealed via a gasket,
The gasket is the gasket according to any one of claims 1 to 4,
The gasket is inserted into a groove provided on the sealing surface of one of the two members,
A sealing structure characterized in that the two members are fastened with the sealing surfaces of the other member facing each other.