WO2015098339A1

WO2015098339A1 - Method for manufacturing cross-linked rubber molding

Info

Publication number: WO2015098339A1
Application number: PCT/JP2014/080028
Authority: WO
Inventors: 直樹大住; 清華戸田
Original assignee: 日本バルカー工業株式会社
Priority date: 2013-12-27
Filing date: 2014-11-13
Publication date: 2015-07-02
Also published as: TW201529647A; JP6403246B2; JP2015127358A

Abstract

Provided is a method for manufacturing cross-linked rubber moldings, the method comprising: a first cross-linking step for partially cross-linking a rubber composition containing cross-linkable rubber components to obtain a moldable first cross-linked product; and a second cross-linking step for cross-linking the first cross-linked product using ionizing radiation to obtain a second cross-linked product. Also including a molding step for molding the first cross-linked product between the first cross-linking step and the second cross-linking step is preferable. Said molding can be extrusion molding, injection molding, etc. The cross-linked rubber molding obtained can be used favorably as, for example, a sealing material.

Description

Method for producing crosslinked rubber molding

The present invention relates to a method for producing a crosslinked rubber molded body represented by a sealing material.

Generally, an elastomer having a crosslinked structure (hereinafter, also referred to as “crosslinked rubber”) is used as a sealing material such as a gasket and packing used in various applications. This is because the heat resistance usually required for a sealing material is excellent. In particular, fluororubber and the like are excellent in heat resistance. For example, JP 2005-113035 A (Patent Document 1) discloses a fluororubber seal material for semiconductor manufacturing equipment. The cross-linked rubber is a rubber that expresses rubber elasticity by causing a cross-linking reaction between molecular chains of a rubber component (elastomer-forming component) using a cross-linking agent or the like to give a cross-linked structure.

On the other hand, there are elastomers called “thermoplastic elastomers” in addition to crosslinked rubber. For example, Japanese Patent Application Laid-Open No. 2009-138158 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2002-173543 (Patent Document 3) disclose a method for producing a molded body made of a fluorine-based thermoplastic elastomer. In general, thermoplastic elastomers include blends of resin and rubber, dynamically cross-linked resin and rubber, block copolymers of resin component and rubber component, etc. The resin component is below the melting point of the resin. Working as a pseudo-crosslinking site, the shape is fixed and rubber elasticity is developed.

JP 2005-113035 A JP 2009-138158 A JP 2002-173543 A

For the production of a molded body made of crosslinked rubber,
a) Since a cross-linking reaction is essential for molding into a predetermined shape, it is not suitable for extrusion molding or injection molding, and it is difficult to continuously produce molded bodies by continuously molding.
b) Once the cross-linked structure is formed and the shape is fixed, the cross-linking reaction is irreversible, and even when heated, the shape is irreversible, so even if there is any defect in the shape after molding, The molding process cannot be performed again by reusing the molded material.
It has been recognized that it is difficult to improve production efficiency.

In contrast, thermoplastic elastomers are suitable for extrusion molding and injection molding because the resin part melts above the melting point of the resin that composes it, and the shape is fixed below the melting point. Therefore, the molded material can be reused and re-molded.

However, a thermoplastic elastomer containing a resin component that is thermally melted is inferior in heat resistance as compared with a crosslinked rubber having a similar structure, and in particular, compression set characteristics showing distortion due to thermal deterioration are greatly inferior. Patent Documents 2 and 3 describe that a radiation-based crosslinking is performed after molding on a fluorine-based thermoplastic elastomer, but it can also be used as a sealing material used in a high-temperature environment by using such radiation crosslinking. The compression set characteristics cannot be improved to a certain extent. In particular, a thermoplastic elastomer having a fluororesin described in Patent Document 2 as a continuous phase and a cross-linked fluororubber particle as a dispersed phase has a higher hardness and flexibility than a cross-linked rubber when subjected to radiation cross-linking after molding. Inferior to

Patent Document 1 describes that after heat-pressure molding (one type of thermal crosslinking) of the fluororubber composition, a thermal crosslinking treatment and a radiation crosslinking treatment are performed. It does not provide a method for producing a crosslinked rubber molded product that allows reuse of the material after molding.

The object of the present invention is to produce a crosslinked rubber molded article that can be continuously molded by melt molding as in the case of using a thermoplastic elastomer, and that the material can be reused in the molding process, and exhibits excellent compression set characteristics. It is to provide a method that can do this.

The present invention provides a method for producing a crosslinked rubber molded body shown below.
[1] A first crosslinking step in which a rubber composition containing a crosslinkable rubber component is partially crosslinked to obtain a moldable first crosslinked body;
A second crosslinking step of crosslinking the first crosslinked body with ionizing radiation to obtain a second crosslinked body;
A method for producing a crosslinked rubber molded body, comprising:

[2] The manufacturing method according to [1], further including a molding step of molding the first crosslinked body between the first crosslinking step and the second crosslinking step.

[3] The manufacturing method according to [2], wherein the first crosslinked body is formed by extrusion molding or injection molding.

[4] The production method according to any one of [1] to [3], wherein the rubber composition is crosslinked by heat in the first crosslinking step.

[5] The production method according to any one of [1] to [4], wherein the crosslinkable rubber component is at least one selected from the group consisting of fluorine rubber and ethylene propylene rubber.

[6] The manufacturing method according to any one of [1] to [5], wherein the crosslinked rubber molded body is a sealing material.

[7] The production method according to any one of [1] to [6], wherein the rubber composition further includes at least one selected from the group consisting of a thermoplastic resin and a thermoplastic elastomer.

According to the method of the present invention, it is possible to produce a crosslinked rubber molded body that can be continuously molded by melt molding and reuse of materials in the molding process, and exhibits excellent compression set characteristics. The obtained crosslinked rubber molded article can be suitably used as a sealing material such as packing or gasket.

The method for producing a crosslinked rubber molded body according to the present invention comprises:
(1) a first crosslinking step in which a rubber composition containing a crosslinkable rubber component is partially crosslinked to obtain a moldable first crosslinked body; and (2) the first crosslinked body is crosslinked with ionizing radiation. , Including a second crosslinking step for obtaining a second crosslinked body, preferably between the first crosslinking step and the second crosslinking step,
(3) It further includes a molding step of molding the first crosslinked body. Hereafter, each process is demonstrated in detail, showing embodiment.

(1) 1st bridge | crosslinking process The rubber composition provided to this process contains a crosslinkable rubber component. The crosslinkable rubber component is not particularly limited as long as it can form an elastomer (crosslinked rubber) having the above-mentioned crosslinked structure by a crosslinking reaction. Specific examples of the crosslinkable rubber component include, for example, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), nitrile rubber (NBR: acrylonitrile butadiene rubber), hydrogenated nitrile rubber (HNBR; hydrogenated acrylonitrile butadiene rubber). Butyl rubber (IIR), fluoro rubber (FKM), perfluoroelastomer (FFKM), acrylic rubber, and silicone rubber. Of these, fluoro rubber (FKM), perfluoroelastomer (FFKM), ethylene-propylene rubber (EPM), and ethylene-propylene-diene rubber (EPDM) are preferred because they have good properties as rubber for sealing materials. More preferably, fluorine rubber (FKM) or ethylene-propylene rubber (EPM) is used. As the crosslinkable rubber component, only one type may be used, or two or more types may be used in combination.

Specific examples of fluororubber (FKM) include, for example, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) polymer; vinylidene fluoride (VDF) -hexafluoropropylene (HFP) -tetrafluoroethylene (TFE). ) Polymer; tetrafluoroethylene (TFE) -propylene (Pr) polymer; vinylidene fluoride (VDF) -propylene (Pr) -tetrafluoroethylene (TFE) polymer; ethylene (E) -tetrafluoroethylene (TFE) -perfluoromethyl vinyl ether (PMVE) polymer; vinylidene fluoride (VDF) -tetrafluoroethylene (TFE) -perfluoromethyl vinyl ether (PMVE) polymer, vinylidene fluoride (VDF) -perful It can be exemplified b methyl vinyl ether (PMVE) polymer.

Examples of perfluoroelastomer (FFKM) include tetrafluoroethylene (TFE) -perfluoromethyl vinyl ether (PMVE) -based polymers.

The crosslinking system of the crosslinkable rubber component is not particularly limited. For example, in the case of fluoro rubber (FKM), a peroxide crosslinking system, a polyamine crosslinking system, and a polyol crosslinking system are ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber ( EPDM) is a peroxide cross-linking system, sulfur cross-linking system, quinoid cross-linking system, and resin cross-linking system, and perfluoroelastomer (FFKM) is a peroxide cross-linking system, bisphenol cross-linking system, triazine cross-linking system, oxazole cross-linking system, imidazole. Examples thereof include a crosslinking system and a thiazole crosslinking system. The crosslinkable rubber component may be cross-linked by any one cross-linking system, or may be cross-linked by two or more cross-linking systems.

The peroxide crosslinking agent (radical polymerization initiator) used in the peroxide crosslinking system is, for example, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (example of commercially available product: “Perhexa 25B manufactured by NOF Corporation”. Dicumyl peroxide (example of commercial product: “Parkmill D” manufactured by NOF); 2,4-dichlorobenzoyl peroxide; di-t-butyl peroxide; t-butyl dicumyl peroxide; benzoyl peroxide (commercially available) Example of product: NOIPA “NIPER B”); 2,5-dimethyl-2,5- (t-butylperoxy) hexyne-3 (example of commercial product: NOF “Perhexin 25B”); 2,5 -Dimethyl-2,5-di (benzoylperoxy) hexane; α, α'-bis (t-butylperoxy-m-isopropyl) benzene (example of commercially available product: NOF Corporation) “Perbutyl P”); t-butyl peroxyisopropyl carbonate; parachlorobenzoyl peroxide and the like. Only one peroxide crosslinking agent may be used, or two or more peroxide crosslinking agents may be used in combination.

As a co-crosslinking agent used in the peroxide crosslinking system, triallyl isocyanurate (example of commercially available product: “TAIC” manufactured by Nippon Kasei Co., Ltd.); triallyl cyanurate; triallyl formal; triallyl trimellitate; N, N ′ Examples include compounds (polyfunctional monomers) capable of co-crosslinking with radicals such as -m-phenylenebismaleimide; dipropargyl terephthalate; diallyl phthalate; tetraallyl terephthalamide. Only one type of co-crosslinking agent may be used, or two or more types may be used in combination. Among these, the co-crosslinking agent preferably contains triallyl isocyanurate from the viewpoint of reactivity and heat resistance of the obtained crosslinked rubber molded article.

The rubber composition used in this step is optionally filled with a filler (reinforcing agent), processing aid, anti-aging agent, antioxidant, vulcanization accelerator, stabilizer, silane coupling agent, flame retardant. Additives such as lubricants can be included. Specific examples of fillers include carbon black, silica, alumina, zinc oxide, titanium dioxide, clay, talc, diatomaceous earth, barium sulfate, silicate compounds (silicates, etc.), calcium carbonate, magnesium carbonate, calcium oxide, mica, Includes graphite, aluminum hydroxide, and resin fine particles. Specific examples of the processing aid include thermoplastic resin, liquid rubber, oil, plasticizer, softener, and tackifier. For example, when the crosslinkable rubber component is FKM or FFKM, a fluororesin or particles thereof may be contained as a filler, and liquid fluororubber may be contained as a processing aid. When the crosslinkable rubber component is EPM or EPDM, for example, paraffinic oil can be contained as a processing aid. Only 1 type may be used for said additive and it may use 2 or more types together.

Examples of commercially available liquid fluororubber products are, for example, “DAIEL G-101” manufactured by Daikin Industries, Ltd. and “SIFEL series” (SIFEL 8000 series, etc.) manufactured by Shin-Etsu Chemical Co., Ltd.

Also, in order to improve the moldability in the molding process described later, the rubber composition can also contain a thermoplastic resin or a thermoplastic elastomer. For example, when the crosslinkable rubber component is FKM or FFKM, blending a fluororesin or a fluoroplastic elastomer may be advantageous for moldability. Further, when the crosslinkable rubber component is EPM or EPDM, blending polyethylene or polypropylene may be advantageous for moldability. Only one type of thermoplastic resin or thermoplastic elastomer may be used, or two or more types may be used in combination. However, from the viewpoint of heat resistance (compression set) of the obtained crosslinked rubber molded product, when a thermoplastic resin or a thermoplastic elastomer is blended, the total amount is 300 weights with respect to 100 parts by weight of the crosslinkable rubber component. Part or less, preferably 200 parts by weight or less.

Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer. Polymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene A polymer (VDF-HFP copolymer), a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer (VDF-HFP-TFE copolymer), or the like can be used. A fluororesin may be used individually by 1 type and may use 2 or more types together.

In this step, the rubber composition is partially cross-linked by any one or more of the cross-linking systems to obtain a moldable first cross-linked body. “Partially crosslinked” means that the degree of crosslinking is higher than that in an uncrosslinked state, but the crosslinking agent (including a crosslinking aid such as a co-crosslinking agent) is insufficient, and the crosslinking agent (cross-linking such as a co-crosslinking agent). In a state where the degree of crosslinking required for the final product is not reached due to deactivation, crosslinking inhibition, ionizing radiation dose deficiency, etc., or a crosslinking agent (a crosslinking aid such as a co-crosslinking agent) )), Although it remains in the rubber composition, it does not reach the degree of crosslinking required for the final product even when further heat is applied or it is irradiated with ionizing radiation. .

More specifically, in this step, when a vulcanization curve of a rubber composition having a horizontal axis as a time and a vertical axis as a torque value is obtained by a curast meter (rheometer, vulcanization / curing characteristic tester). The rubber composition is preferably partially crosslinked so that the maximum torque value MH is 2 to 70% of the maximum torque value MH ₀ in the reference system. The maximum torque value MH is more preferably 3 to 40% of MH ₀ .

The reference system includes a crosslinking agent (including a crosslinking aid such as a co-crosslinking agent) in a sufficient amount, and when a sufficient amount of heat is applied, the maximum degree of crosslinking that can be developed. It refers to a rubber composition that can form a crosslinked product. More specifically, the cross-linked body refers to a cross-linked body in which the degree of cross-linking has progressed to a state where it does not melt even when the cross-linked body is heated to the decomposition temperature of the cross-linked portion in an air atmosphere. Regarding the reference system, a sufficient amount of the crosslinking agent in various crosslinking systems and a crosslinking temperature and a crosslinking time for achieving the maximum degree of crosslinking that can be expressed can be selected based on common technical knowledge in the field. The decomposition temperature of the crosslinked portion is, for example, about 200 ° C. in the case of fluorine rubber crosslinked by a peroxide crosslinking system, and about 230 ° C. in the case of fluorine rubber crosslinked by a polyol crosslinking system.

In this step, the uncrosslinked rubber composition is crosslinked until it can be molded. “Moldable” means that the molding process itself can be performed and the shape after molding can be maintained. If the rubber composition remains uncrosslinked, the fluidity is too high to be molded. On the other hand, if the degree of crosslinking is too high, shaping becomes difficult due to excessive progress of shape fixing by crosslinking, and melting by heat becomes impossible.

The cross-linking method in this step may be cross-linking by heat, cross-linking by ionizing radiation, or a combination thereof. In the case of cross-linking by heat, partial cross-linking is performed by reducing the amount of the cross-linking agent and / or cross-linking auxiliary agent from the above reference system, or by adding an additive that inhibits cross-linking to the rubber composition. Can do. The degree of crosslinking can be controlled by adjusting the blending amount of the crosslinking agent and / or crosslinking aid and the blending amount of the crosslinking inhibitor. When crosslinking is performed by irradiation with ionizing radiation, there is a tendency that partial crosslinking occurs even if the irradiation amount is sufficiently large. However, the degree of crosslinking can be controlled by adjusting the irradiation amount.

Examples of additives that inhibit crosslinking include 2,2-bis (4-hydroxyphenyl) hexafluoropropane; o-phenylphenol; hydroquinone; 2,4-diphenyl-4-methyl-1-pentene; -Bis (3-amino-4-hydroxyphenyl) hexafluoropropane; amine-ketone antioxidants (eg poly 2,2,4-trimethyl-1,2-dihydroquinoline); aromatic secondary amines Anti-aging agent (for example, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine); Monophenol type anti-aging agent (for example, 2,6-di-t-butyl-4-methylphenol); Bisphenol type Anti-aging agent (for example, 4,4′-thiobis (3-methyl-6-tert-butylphenol); benzimidazole anti-aging agent (eg, If, and 2-mercaptobenzimidazole).

In the cross-linking method in this step, cross-linking by heat is preferably used from the viewpoint of preventing an increase in manufacturing cost.

In the case of obtaining the first crosslinked body by ionizing radiation, an electron beam or γ-ray can be used as the ionizing radiation as in the second crosslinking step described later.

(2) Molding process The manufacturing method of the present invention preferably includes a molding process for molding the first crosslinked body. Since the first crosslinked body is partially crosslinked to the extent that it can be molded, it can be melted by heat, for example, continuous molding using melt molding such as extrusion molding or injection molding is possible. is there. This makes it possible to continuously produce a crosslinked rubber molded body, and thus to reduce manufacturing costs.

In the production method of the present invention, when the first crosslinked body is not further crosslinked by heat due to a lack of a crosslinking agent or a crosslinking aid, Unlike the manufacturing method, scorch in which cross-linking by heat is unlikely to occur, and this is also advantageous for continuous molding using melt molding such as extrusion molding or injection molding.

Since the first cross-linked body can be melted by heat, there is some problem in the shape after molding, especially when it is not cross-linked by heat due to factors such as lack of cross-linking agent or cross-linking aid. In this case, the molded material can be reused by re-melting the molded body and performing the molding process again. Reuse of such materials is also advantageous for reducing manufacturing costs.

The melt molding (extrusion molding or injection molding) of the first crosslinked body can be performed in the same manner as a general thermoplastic resin or thermoplastic elastomer. The molding temperature can be, for example, 150 to 320 ° C.

(3) Second cross-linking step In this step, the first cross-linked body or the molded body thereof is cross-linked by ionizing radiation to give a degree of cross-linking required as a final product, thereby obtaining a second cross-linked body. Although ionizing radiation is not particularly limited, electron beams and γ rays can be preferably used. The dose of ionizing radiation is preferably 10 to 500 kGy, more preferably 30 to 200 kGy. When the irradiation dose is less than 10 kGy, a sufficient degree of crosslinking cannot be obtained, and the desired mechanical strength tends to be not obtained. Moreover, when the irradiation amount exceeds 500 kGy, the second crosslinked body may be deteriorated by ionizing radiation.

After the second cross-linking step, heat treatment may be applied to the second cross-linked body using an oven (electric furnace, vacuum electric furnace) or the like, if necessary. The heat treatment conditions can usually be 100 to 320 ° C. (for example, about 170 to 230 ° C. or about 170 to 200 ° C.).

The crosslinked rubber molded body (second crosslinked body) obtained by the production method of the present invention exhibits excellent heat resistance (compression set properties) and has a rubber component as a continuous phase (thermoplastic to the rubber composition). When a resin is blended, a co-continuous phase can be taken.), Having a suitable hardness and excellent flexibility.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

<Example 1>
According to the compounding composition shown in Table 1 (the unit of the compounding amount in Table 1 is parts by weight), after kneading predetermined amounts of the crosslinkable rubber component, the crosslinking agent and the co-crosslinking agent with an open roll, the obtained kneading The product was thermally crosslinked at 200 ° C. for 15 minutes to obtain a first crosslinked product (first crosslinking step). Next, the first crosslinked body was extrusion molded at 230 ° C. to obtain a molded body having a sealing material (O-ring) shape (molding process). Extrusion molding (melt molding) into a sealing material shape was easy. Thereafter, radiation (γ rays; the same applies hereinafter) was applied at an irradiation dose of 80 kGy to obtain a sealing material (O-ring) which is a second crosslinked body (crosslinked rubber molded body) (second crosslinking step). The first cross-linked body exhibited heat melting property, and it was easy to heat melt the molded body and perform molding again. The obtained sealing material exhibited excellent compression set characteristics.

<Examples 2 to 8>
According to the composition shown in Table 1, after kneading a predetermined amount of the crosslinkable rubber component, the thermoplastic elastomer and the fluororesin at 230 ° C. with a kneader, the predetermined amount of the crosslinking agent and the co-crosslinking agent is kneaded into the kneaded product. Got. Using the obtained kneaded material, the 1st bridge | crosslinking process, the shaping | molding process, and the 2nd bridge | crosslinking process were performed similarly to Example 1, and the sealing material was obtained. Extrusion molding (melt molding) into a sealing material shape in the molding process was easy. In addition, the first crosslinked body exhibited heat melting property, and it was easy to heat-melt the molded body and perform molding again. The obtained sealing material exhibited excellent compression set characteristics.

<Comparative Example 1>
According to the composition shown in Table 1, predetermined amounts of thermoplastic elastomer, crosslinking agent and co-crosslinking agent were kneaded. The obtained kneaded product is subjected to press molding at 230 ° C. for 15 minutes to obtain a sealing material (O-ring) shaped molded body, and then irradiated with radiation at an irradiation dose of 80 kGy to obtain a sealing material. Obtained. Since the thermoplastic elastomer is used, the kneaded product can be melt-molded. Also, the molded product can be melted by heat after press molding, and molding can be performed again. It was inferior to the permanent set characteristics.

<Comparative example 2>
According to the composition shown in Table 1, the thermoplastic elastomer is extruded at 230 ° C. to obtain a molded material having a sealing material (O-ring) shape, and then irradiated with radiation at a dose of 80 kGy to obtain a sealing material. It was. The thermoplastic elastomer can be melt-molded, and it was possible to heat-mold and re-mold the molded body after extrusion molding, but the obtained sealing material was inferior in compression set characteristics. It was.

<Comparative Example 3>
According to the composition shown in Table 1, predetermined amounts of the crosslinkable rubber component, the crosslinking agent, and the co-crosslinking agent were kneaded with an open roll. The obtained kneaded product was subjected to press molding at 170 ° C. for 15 minutes, and then heat treated at 200 ° C. for 4 hours to obtain a sealing material (O-ring). The kneaded product can be melt-molded itself such as extrusion, but the melt-molding conditions are extremely limited due to the occurrence of scorch (a phenomenon in which crosslinking proceeds by heat). When scorching occurs during molding, 1) molding defects such as surface roughness occur during extrusion. 2) When crosslinking proceeds in a mold or an extruder, it becomes difficult to take out the molded product, and production must be stopped. 3) In the case of 2), a great deal of labor is required to restore the equipment, and in some cases, the equipment (mold, extruder screw, cylinder) is damaged.

The cross-linked rubber molded body (seal material) after press molding in this comparative example did not melt even when reheated, and it was impossible to re-mold by reusing it.

The details of each compounding agent used in Examples and Comparative Examples are as follows.
[1] FKM 1: Vinylidene fluoride (VDF) -hexafluoropropylene (HFP) -tetrafluoroethylene (TFE) polymer [“Daiel G912” manufactured by Daikin Industries, Ltd.].
[2] FKM 2: Tetrafluoroethylene (TFE) -propylene (Pr) polymer [Aflas 150P manufactured by Asahi Glass Co., Ltd.
[3] Thermoplastic Elastomer: A fluorinated thermoplastic elastomer that is a block polymer in which a fluororubber part and a fluororesin part are bonded (“Dai-L Thermoplastic T-530” manufactured by Daikin Industries, Ltd.).
[4] PVDF: polyvinylidene fluoride [“Kureha KF Polymer # 850” manufactured by Kureha Corporation].
[5] ETFE: Tetrafluoroethylene-ethylene copolymer ["Neofluon EP610" manufactured by Daikin Industries, Ltd.]
[6] Crosslinker: Perhexa 25B (2,5-dimethyl-2,5-di (t-butylperoxy) hexane) [“Perhexa 25B” manufactured by NOF Corporation].
[7] Co-crosslinking agent: triallyl isocyanurate [“TAIC” manufactured by Nippon Kasei Co., Ltd.].

The sealing material of Comparative Example 3 does not melt even when heated to 200 ° C. in an air atmosphere, and the kneaded material (material before press molding) contains a sufficient amount of a crosslinking agent and a co-crosslinking agent. Since sufficient heat is applied for crosslinking, the kneaded product can be regarded as the above-mentioned reference system. The vulcanization curve (200 ° C., 15 minutes) of this reference system and the vulcanization curves (200 ° C., 15 minutes) in the first crosslinking step of Examples 1 to 8 were used with a curast meter (Orientec). The maximum torque value MH ₀ in the reference system and the maximum torque value MH of each example were determined. Table 1 shows the maximum torque value MH (%) when the maximum torque value MH _{0 is set} to 100%.

In addition, Table 1 shows measured values of compression set of the sealing materials obtained in each of Examples and Comparative Examples. The compression set is the most important evaluation item for evaluating the life (heat resistance) of the rubber seal material. The compression set was measured as follows.

In accordance with JIS K 6262, a sample (AS214 O-ring) is sandwiched between iron plates at a compression rate of 25%, heated in an electric furnace at 200 ° C. for 72 hours, compressed and released, and allowed to cool for 30 minutes. The compression set of the following formula:
Compression set (%) = {(T0−T1) / (T0−T2)} × 100%
Calculated based on T0 is the height of the sample before the test, T1 is the height of the sample after being allowed to cool for 30 minutes, and T2 is the thickness (height) of the spacer.

Claims

A first crosslinking step in which a rubber composition containing a crosslinkable rubber component is partially crosslinked to obtain a moldable first crosslinked body;
A second crosslinking step of crosslinking the first crosslinked body with ionizing radiation to obtain a second crosslinked body;
A method for producing a crosslinked rubber molded body, comprising:
The manufacturing method according to claim 1, further comprising a molding step of molding the first crosslinked body between the first crosslinking step and the second crosslinking step.
The manufacturing method according to claim 2, wherein the first crosslinked body is formed by extrusion molding or injection molding.
The manufacturing method according to claim 1, wherein the rubber composition is crosslinked by heat in the first crosslinking step.
The production method according to claim 1, wherein the crosslinkable rubber component is at least one selected from the group consisting of fluorine rubber and ethylene propylene rubber.
The manufacturing method according to claim 1, wherein the crosslinked rubber molded body is a sealing material.
The production method according to claim 1, wherein the rubber composition further comprises at least one selected from the group consisting of a thermoplastic resin and a thermoplastic elastomer.