JP2018080754A - Gasket around engine and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gasket around an engine excellent in acid resistance under high temperature, and a manufacturing method thereof.SOLUTION: A rubber composition is a rubber composition for a gasket around an engine, and contains 100 pts.mass of rubber (A) selected from fluororubber or hydrogenated nitrile rubber, and 5-60 pts.mass of clay (B). Also, a rubber molding is manufactured by a manufacturing method comprising: a kneading step of kneading the rubber (A) and the clay (B) to obtain a rubber composition; and a vulcanization process of vulcanizing the rubber composition. The obtained rubber molding is suitably used as a gasket for an intake manifold of an engine.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gasket around an engine. The present invention also relates to a method for manufacturing the gasket.

  Rubber compositions are used in a wide range of applications by taking advantage of their elastic properties. Among them, it is widely used as a gasket for sealing a fluid. Examples of the rubber composition containing talc and clay used in the gasket include the rubber compositions described in Patent Documents 1 to 3.

Patent Document 1 discloses that 100 parts by weight of tetrafluoroethylene / vinylidene fluoride / hexafluoropropene terpolymer rubber having a fluorine content of 64% by weight or more and (A) a specific surface area of 5 to ²⁰ m ² / 5 to 90 parts by weight of carbon black, (B) 5 to 40 parts by weight of bituminous fine powder, (C) 1 to 30 parts by weight of hydrophilic imparting talc, and 1 to 20 parts by weight of at least one kind of hydrophilic imparting clay; (D) A fluororubber composition containing 0.5 to 6 parts by weight of an organic peroxide and used as a molding material for a fuel oil-based sealing material that comes into contact with fuel oil is described.

  In Patent Document 2, it was treated with 10 to 150 parts by weight of carbon black and 10 to 150 parts by weight of a silane coupling agent per 100 parts by weight of a rubber component composed of one or both of hydrogenated nitrile rubber or nitrile rubber. A rubber composition characterized by blending 1 to 10 parts by weight of clay and an organic peroxide is described.

  Patent Document 3 describes a rubber composition characterized in that, in a rubber composition containing NBR or a main component thereof, zinc oxide is added to 10 PHR or more and silane-treated clay as a main component with respect to 100 PHR of rubber. ing.

  However, the gasket around the engine formed by vulcanizing the rubber composition described in Patent Documents 1 to 3 has not had sufficient acid resistance at high temperatures.

International Publication No. 2012/137724 Japanese Patent Application Laid-Open No. 11-100144 JP 2007-269856 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gasket around an engine having excellent acid resistance at high temperatures and a method for producing the same.

  The above-mentioned subject is a rubber molding formed by vulcanizing a rubber composition containing 100 parts by mass of rubber (A) selected from fluorine rubber or hydrogenated nitrile rubber and 5-60 parts by mass of silylated clay (B). It is solved by providing a gasket around the engine with a product.

  At this time, it is preferable that the surface of the clay (B) is silylated with alkoxysilane. It is also preferred that the alkoxysilane is a silane coupling agent. Moreover, it is preferable that the said rubber composition does not contain carbon black substantially.

  Further, in the hardness test of the rubber molded product performed using an aqueous acetic acid solution having a pH of 3 as a test liquid according to JIS K 6258 (2003), the difference in hardness before and after the test (durometer type A) was 6 The following is preferable. According to JIS K 6258 (2003), in the volume change rate test of the rubber molded product performed using an aqueous acetic acid solution having a pH of 3 as a test liquid, the volume change rate is preferably 7% or less.

  The subject is a method for producing the gasket, comprising a kneading step of kneading rubber (A) and clay (B) to obtain a rubber composition, and a vulcanizing step of vulcanizing the rubber composition. This problem can also be solved by providing a manufacturing method.

  In a preferred embodiment of the present invention, the gasket is an intake manifold gasket.

  According to the present invention, it is possible to provide a gasket around an engine having excellent acid resistance at high temperatures and a method for producing the gasket.

It is sectional drawing which shows the example which mounted | wore the engine with the gasket 1 for intake manifolds.

  The present invention relates to a gasket around an engine having a rubber molded product obtained by vulcanizing a rubber composition. Since the engine periphery is exposed to high-temperature combustion gas and deteriorated oil, the gasket used requires high acid resistance even at high temperatures. Since the gasket of the present invention is excellent in acid resistance at high temperatures, it is preferably used for a gasket around an engine. The gasket at this time may consist of only a rubber molded product obtained by vulcanizing the rubber composition, or may be bonded to a rubber molded product obtained by vulcanizing the rubber composition and another member such as a metal. And may be combined.

  Here, the gasket around the engine includes a fastening portion between the intake manifold and the cylinder head, a fastening portion between the cylinder head cover and the cylinder head, a fastening portion between the oil pan and the cylinder block, and a fastening portion between the air cleaner and the throttle body. It is the gasket used.

  In recent years, from the viewpoint of improving fuel efficiency, an engine that uses exhaust gas recirculation (ERG: Exhaust Gas Recirculation) and burns a mixed gas of intake air and EGR gas in a combustion chamber has been used. It has become. Since the gasket of the present invention has excellent acid resistance even under high temperatures, it is particularly suitably used as an intake manifold gasket.

  The rubber composition in the present invention contains 100 parts by mass of rubber (A) selected from fluorine rubber or hydrogenated nitrile rubber and 5 to 60 parts by mass of silylated clay (B). The rubber molded product in the present invention is obtained by vulcanizing the rubber composition.

  In the present invention, it is important to use silylated clay (B). As a result of intensive studies, the present inventors blended a specific amount of silylated clay (B) with rubber (A) and vulcanized the resulting rubber composition at a high temperature. It was found that a gasket excellent in acid resistance was obtained. Hereinafter, the rubber composition and rubber molded product of the present invention will be described.

[Rubber (A)]
(Fluoro rubber)
The type of fluororubber is not particularly limited. For example, fluoroolefins such as vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, and vinyl fluoride; perfluoromethyl vinyl ether, Examples include those obtained by polymerizing monomers such as fluoroalkyl vinyl ethers such as perfluoropropyl vinyl ether. Among these, binary fluororubber or ternary fluororubber containing a structural unit derived from vinylidene fluoride is preferable, and ternary fluororubber is more preferable from the viewpoint of excellent heat resistance.

  Examples of the binary fluororubber include vinylidene fluoride / hexafluoropropylene copolymer and tetrafluoroethylene / propylene copolymer. Examples of the ternary fluororubber include vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer and vinylidene fluoride / tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer.

  Further, the fluorine content in the fluororubber is not particularly limited, but from the viewpoint of heat resistance, the fluorine content is preferably 50% by mass or more, and more preferably 60% by mass or more. Although the upper limit of fluorine content is not specifically limited, Usually, it is 80 mass% or less.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the fluororubber is preferably 20 to 120. From the viewpoint of improving the mechanical properties of the obtained rubber molded article, the Mooney viscosity is more preferably 50 or more. On the other hand, the Mooney viscosity is more preferably 100 or less from the viewpoint of ease of kneading.

(Hydrogenated nitrile rubber)
The type of hydrogenated nitrile rubber used in the present invention (hereinafter, hydrogenated nitrile rubber may be abbreviated as HNBR) is not particularly limited, and a hydrogenated nitrile copolymer of 1,3-butadiene is used. Can be used. In the hydrogenation, hydrogen is added to the double bond remaining in the 1,3-butadiene unit after polymerization. The iodine value of HNBR is preferably 80 g / 100 g or less. If the iodine value is too large, heat aging resistance and chemical resistance may be lowered. The iodine value is more preferably 60 g / 100 g or less, and further preferably 30 g / 100 g or less.

  The content of acrylonitrile units in HNBR is preferably 15 to 50% by mass. Moreover, it is preferable that content of a 1, 3- butadiene unit is 50-85 mass% including what was hydrogenated. As long as the effect of the present invention is not impaired, it may contain a constitutional unit derived from another copolymerizable monomer, but its content is usually 10% by mass or less, preferably 5 It is below mass%.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of HNBR is preferably 20 to 120. From the viewpoint of improving the mechanical properties of the obtained rubber molded article, the Mooney viscosity is more preferably 50 or more. On the other hand, from the viewpoint of fluidity during molding, the Mooney viscosity is more preferably 100 or less.

  In the present invention, from the viewpoint of obtaining a gasket having excellent acid resistance at a higher temperature, it is preferable to use fluororubber, and HNBR is preferably used when the material cost is important.

[Clay (B)]
The clay (B) used in the present invention is a clay having a silylated surface. Clay is a powder composed of fine mineral particles mainly composed of hydrous aluminum silicate. The type of the clay is not particularly limited as long as the surface can be silylated, and examples thereof include kaolin, wax, sericite, talc, and montmorillonite. The clay used in the present invention may be a wet clay, a dry clay, or a fired clay obtained by firing these. Further, clays are generally classified into hard clays and soft clays depending on the hardness of the kneaded dough when blended with rubber, and any of them may be used. These clays can be appropriately used depending on the required performance of the rubber molded product to be obtained.

  In the present invention, it is preferable that the surface of the clay (B) is silylated with alkoxysilane. By reacting clay with alkoxysilane, a clay (B) having a silylated surface by reacting a hydroxyl group on the clay surface with an alkoxy group of the alkoxysilane can be obtained.

  At this time, it is preferable that the said alkoxysilane is a silane coupling agent from a miscibility viewpoint with rubber | gum (A). A silane coupling agent is an alkoxysilane to which an organic group having a reactive functional group is bonded. Examples of the reactive functional group include vinyl group, epoxy group, styryl group, methacryl group, acrylic group, amino group, isocyanurate group, ureido group, mercapto group, sulfide group, and isocyanate group. It is preferable to use a clay silylated with a coupling agent having a mercapto group or an amino group. From the viewpoint of improving tensile strength, it is preferable to use a clay silylated with a coupling agent having a mercapto group.

  The amount of the clay (B) is 5 to 60 parts by mass with respect to 100 parts by mass of the nitrile rubber (B). When the amount of clay (B) is less than 5 parts by mass, the effect of adding clay (B) becomes insufficient. The blending amount of clay (B) is preferably 10 parts by mass or more. On the other hand, if the amount of clay (B) exceeds 60 parts by mass, the moldability deteriorates. The blending amount of clay (B) is preferably 50 parts by mass or less. Moreover, it is preferable that the average particle diameter of clay (B) is 0.2-8.0 micrometers.

  It is preferable that the rubber composition in the present invention does not substantially contain carbon black. Acid resistance can also be improved by blending carbon black with the rubber composition. However, a rubber molded product obtained by vulcanizing a rubber composition containing carbon black is black. If a black rubber molded product is used around the engine, it may be indistinguishable from the components that make up the engine, and work efficiency may be reduced. Since the gasket substantially not containing carbon black can be colored in any color, it can be easily distinguished from the parts that constitute the engine.

  The rubber composition in the present invention preferably contains a vulcanizing agent (crosslinking agent). As the vulcanizing agent (crosslinking agent), those usually used for vulcanizing fluororubber and HNBR such as peroxide, sulfur, polyamine, polyol and the like can be adopted. The amount of the crosslinking agent is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber (A). When the content of the vulcanizing agent is less than 0.1 parts by mass, the vulcanization time becomes longer and the mechanical properties of the obtained rubber molded article may be deteriorated. The content of the vulcanizing agent is preferably 0.2 parts by mass or more. On the other hand, when the content of the vulcanizing agent exceeds 10 parts by mass, the mechanical properties of the resulting rubber molded product may be deteriorated. The content of the vulcanizing agent is preferably 2 parts by mass or less.

  The rubber composition in the present invention preferably contains a co-curing agent (co-crosslinking agent) such as triallyl isocyanurate. The amount of the co-crosslinking agent is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber (A). When the content of the co-vulcanizing agent is less than 0.1 parts by mass, the vulcanization time becomes longer and the mechanical properties of the obtained rubber molded article may be deteriorated. The content of the co-vulcanizing agent is preferably 1 part by mass or more. On the other hand, when the content of the vulcanizing agent exceeds 10 parts by mass, the mechanical properties of the resulting rubber molded product may be deteriorated. The content of the vulcanizing agent is preferably 5 parts by mass or less.

  The rubber composition may contain components other than the rubber (A) and the silylated clay (B) as long as the effects of the present invention are not inhibited. Examples of other components include various additives such as a vulcanization accelerator, a vulcanization retarder, an adhesive, an acid acceptor, a colorant, a filler, a plasticizer, a processing aid, and an antiaging agent.

  The method for producing the gasket of the present invention is not particularly limited, and suitable production methods thereof include a kneading step of kneading rubber (A) and clay (B) to obtain a rubber composition, and vulcanizing the rubber composition. And a vulcanization step.

  In the above method, the rubber (A) and the clay (B) may be those described above, and the blending amount thereof may also be the amount described above. In the kneading step, as long as the effect of the present invention is not hindered, other than rubber (A) and clay (B) can be added as described above.

  The method for mixing the above components in the kneading step is not particularly limited, and kneading can be performed using an open roll, a kneader, a Banbury mixer, an intermixer, an extruder, or the like. Especially, it is preferable to knead | mix using an open roll or a kneader. The temperature during kneading is preferably 60 to 150 ° C.

  The gasket of the present invention is obtained by molding the rubber composition thus obtained and vulcanizing it in the next vulcanization step.

  Vulcanization is performed by forming the rubber composition into a gasket shape and heating. Examples of the method for molding the rubber composition include extrusion molding, compression molding, and injection molding. Of these, compression molding is preferred. The vulcanization temperature is preferably 140 to 250 ° C. The vulcanization time is preferably 1 to 30 minutes. Further, depending on the shape and dimensions of the gasket, even if the surface is vulcanized, it may not be sufficiently vulcanized to the inside. Therefore, secondary vulcanization may be performed by further heating. As a heating method for vulcanization, general methods used for rubber vulcanization such as compression heating, steam heating, oven heating, hot air heating and the like are used, and compression heating is preferable.

  Moreover, it can also vulcanize | fill by filling a metal mold | die with the metal core and the rubber composition in this invention, and pressing. As a result, a gasket in which the surface of the metal core is covered with the rubber molded product can be obtained.

  Examples of the core bar used at this time include a metal plate made of iron, aluminum, or the like, or an alloy plate thereof. These core bars may be subjected to surface treatment such as plating. For example, SECC shown by JIS G3313, SUS301 shown by JIS G4305, SPCC shown by JIS G3141, etc. are mentioned. From the viewpoint of improving the adhesion between the rubber molded product and the cored bar, the cored bar may have an adhesive applied to the surface thereof. Examples of the adhesive include a phenol-based adhesive, an epoxy-based adhesive, and a silane coupling agent.

  The shape of the core metal is not particularly limited, but is usually annular. Further, the thickness of the metal core and the thickness of the rubber molded product are not particularly limited, and can be appropriately set according to the size of the gasket.

  According to JIS K 6258 (2003), the rubber molded product thus obtained has a difference in hardness (durometer type A) before and after the test in a hardness test performed using an aqueous acetic acid solution having a pH of 3 as a test liquid. It is preferable that it is 6 or less. Here, the difference in hardness before and after the test is the absolute value | α−β | of the difference between the hardness (α) after the test and the hardness (β) before the test. From the viewpoint of sealing properties, the difference in hardness before and after the test is more preferably 4 or less, and further preferably 3 or less.

  In a hardness test performed using a pH 3 aqueous nitric acid solution as a test liquid, the difference in hardness (durometer type A) before and after the test is preferably 6 or less. From the viewpoint of sealing properties, the difference in hardness before and after the test is more preferably 3 or less, and even more preferably 2 or less.

  In addition, the obtained rubber molded article has a volume change rate of 7% after the test in a volume change rate test performed using an aqueous acetic acid solution having a pH of 3 as a test liquid in accordance with JIS K 6258 (2003). The following is preferable. From the viewpoint of sealing properties, the volume change rate is more preferably 5% or less, and further preferably 4% or less.

  In the volume change rate test conducted using a pH 3 aqueous nitric acid solution as the test liquid, the volume change rate after the test is preferably 7% or less. From the viewpoint of sealing properties, the volume change rate is more preferably 4% or less.

  Next, an example of the gasket around the engine of the present invention is shown. FIG. 1 is a cross-sectional view showing an example in which an intake manifold gasket 1 is mounted between an intake manifold 2 and a cylinder head 3. The gasket 1 shown in FIG. 1 is composed only of a rubber molded product, and is formed in an O-ring shape having an oblong cross section. The intake manifold 2 has a groove 21, and the gasket 1 is inserted into the groove 21. The gasket 1 is provided with a plurality of protrusion-like gasket drop-off prevention means made of elastic bodies 22a and 22b at appropriate intervals in the circumferential direction. After the gasket 1 is inserted, the intake manifold 2 is fastened to the cylinder head 3 by being fastened in the directions of arrows 101 and 102 by a fastening tool such as a bolt.

  Since the gasket of the present invention is excellent in acid resistance at high temperatures, it can be suitably used as a gasket around an engine, particularly an intake manifold gasket as shown in FIG.

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

・ Fluoro rubber A
“Daiel G-952” manufactured by Daikin Industries, Ltd. (fluorine concentration (mass%) 68.5, specific gravity (23 ° C.) 1.84, Mooney viscosity (ML _{1 + 10} , 100 ° C.) 80)
The “DAIEL G-952” is a ternary fluororubber of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer.
・ Fluoro rubber B
“DAIEL LT-302” manufactured by Daikin Industries, Ltd. (fluorine concentration (mass%) 64.5, specific gravity (23 ° C.) 1.80, Mooney viscosity (ML _{1 + 10} , 100 ° C.) 68)
The “DAIEL LT-302” is a fluororubber made of a vinylidene fluoride / tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer.

・ Hydrogenated nitrile rubber Nippon Zeon Co., Ltd. “Zetpol 2020”
(Bound acrylonitrile content central value (%) 36.2, iodine value central value (mg / 100 mg) 28, Mooney viscosity (central value) 78

・ Clay A
Aminosilane-treated calcined kaolin “ST-100” manufactured by Shiraishi Calcium Co., Ltd.
pH: 7.8, average particle size: 3.5 μm
・ Clay B
Mercaptosilane-treated kaolin “ST-309” manufactured by Shiraishi Calcium Co., Ltd.
pH: 5.0, average particle size: 0.7 μm
・ Clay C
Non-silane treated clay “Opti White P” manufactured by Burgess Pigment
pH: 4.0, average particle size: 1.4 μm

・ Silica Tosoh ・ Silica manufactured by Silica Corporation “Nipsil ER”
Average particle diameter: 12.0 μm, BET specific surface area: 120 m ² / g, DBA value: ²⁰⁰ mmol / kg
The above “Nipsil ER” is one in which the hydrogen atom of the silanol group on the silica surface is not substituted with a silicon atom.

・ Triallyl isocyanurate (co-crosslinking agent)
“TAIC” manufactured by Nippon Kasei Co., Ltd.
・ 1,4-Bis [(t-butylperoxy) isopropyl] benzene (crosslinking agent)
“Perbutyl P” manufactured by Nippon Oil & Fats Co., Ltd.

Example 1
(Production of vulcanized rubber sheet)
A mixture having the composition shown below was kneaded for 30 minutes at a temperature of 80 ° C. using an open roll to prepare an unvulcanized rubber sheet having a thickness of 3 mm. The obtained unvulcanized rubber sheet was press vulcanized at 180 ° C. for 10 minutes to obtain a vulcanized rubber sheet having a length (long side) of 150 mm × width (short side) of 120 mm × thickness of 2 mm. Thereafter, secondary vulcanization was performed in an oven at 200 ° C. for 2 hours. The color of the obtained vulcanized rubber sheet was light brown.
Fluoro rubber A: 100 parts by mass Clay A: 30 parts by mass Co-crosslinking agent: 3 parts by mass Crosslinking agent: 1.5 parts by mass

(Production of intake manifold gasket)
The mixture used in “Preparation of Vulcanized Rubber Sheet” was mixed with a kneader to obtain a rubber composition. Next, a ring-shaped mold was prepared, the rubber composition was injected into the mold by an injection molding machine, and vulcanization molding was performed at 170 ° C. for 20 minutes. Thereafter, the rubber molded product was removed from the mold and subjected to secondary vulcanization at 170 ° C. for 4 hours in an oven to obtain a ring-shaped gasket. The basket color was light brown. This gasket can be mounted in the groove of the intake manifold of the engine.

[Evaluation]
(Tensile test)
A tensile test was performed according to JIS K6251. The obtained uncrosslinked rubber sheet was pressed and crosslinked at 180 ° C. for 3 minutes to obtain a crosslinked rubber sheet having a thickness of 2 mm. Using a dumbbell-shaped No. 3 test piece obtained by punching out the obtained crosslinked rubber sheet, the tensile strength (MPa) was obtained at a tensile rate of 500 mm / min at 23 ° C. and a relative humidity of 50%. Elongation (%) was measured. As a result, the tensile strength was 16.8 MPa and the elongation was 280%. These results are shown in Table 1.

(Measurement of hardness change and volume change rate)
As a test piece, a vulcanized rubber sheet having a length (long side) 30 mm × width (short side) 20 mm × thickness 2 mm was prepared, and the test piece was immersed in an acetic acid aqueous solution (pH 3) at 90 ° C. for 72 hours. The hardness change and the volume change rate were measured. Measured according to the method described in JIS K 6258 (2003), the hardness of the test piece (durometer type A) was measured, and the hardness was determined based on formula (11) of JIS K 6258 (2003) 5.6.8. The change in thickness was measured. The results are shown in Table 1. The hardness of the test piece before immersion is as shown in Table 1. As shown in Table 1, the absolute value of the difference in hardness before and after the test was 2. In addition, that a measured value is minus has shown having softened by being immersed in the acetic acid aqueous solution.

  Moreover, the volume change rate was measured based on Formula (2) of JIS K 6258 (2003) 5.6.1. The results are shown in Table 1. The volume change rate was + 2%. In addition, that the volume change rate is positive has shown that it expanded by being immersed in the acetic acid aqueous solution.

  The test liquid was changed to a nitric acid aqueous solution of pH 3, and the hardness change and the volume change rate were measured by the same method as described above. The results are shown in Table 1.

Examples 2-5 and Comparative Examples 1-4
A rubber sheet was obtained in the same manner as in Example 1 except that the types and amounts of the components were changed as shown in Table 1 in “Preparation of Vulcanized Rubber Sheet”. And evaluation similar to Example 1 was performed. The results are shown in Table 1.

1 Gasket for intake manifold 101, 102 Tightening direction 2 Intake manifold 21 Groove 22a, 22b Elastic body

Claims (8)

  Engine having a rubber molded article obtained by vulcanizing a rubber composition containing 100 parts by mass of rubber (A) selected from fluorine rubber or hydrogenated nitrile rubber and 5-60 parts by mass of silylated clay (B) Around the gasket.   The gasket according to claim 1, wherein the surface of the clay (B) is silylated with alkoxysilane.   The gasket according to claim 2, wherein the alkoxysilane is a silane coupling agent.   The gasket according to any one of claims 1 to 3, wherein the rubber composition does not substantially contain carbon black.   According to JIS K 6258 (2003), in a hardness test of the rubber molded product performed using an aqueous acetic acid solution having a pH of 3 as a test liquid, the difference in hardness (durometer type A) before and after the test was 6 or less. The gasket according to any one of claims 1 to 4.   The volume change rate is 7% or less in a test of the volume change rate of the rubber molded product, which was performed using an aqueous acetic acid solution having a pH of 3 as a test liquid in accordance with JIS K 6258 (2003). The gasket according to any one of the above.   It is a gasket for intake manifolds, The gasket in any one of Claims 1-6.   A method for producing a gasket according to any one of claims 1 to 7, wherein a kneading step of kneading rubber (A) and clay (B) to obtain a rubber composition, and a vulcanization for vulcanizing said rubber composition. A method for manufacturing a gasket comprising a sulfurating step.