Annular sealing material and manufacturing method

Abstract

To provide an annular seal material capable of being mass-produced using different materials for a middle core and an outer layer, and a method for manufacturing the annular seal material.SOLUTION: An annular seal material comprises a middle core, and an outer layer surrounding the middle core. The middle core and the outer layer comprise crosslinked products of crosslinkable rubber compositions that have mutually different colors after hot press molding and / or after secondary crosslinking.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to annular sealing materials, and more particularly to a method for manufacturing them. [Background technology]

[0002] Patent Document 1 describes a method for manufacturing a composite O-ring, which involves cutting a composite structural material made by inserting a string-shaped inner layer into the internal space of a tubular outer layer, setting it in an O-ring mold, and then setting a string-shaped piece of material to be used for the outer layer into the gap between the cut surfaces of the composite structural material, and then pressurizing and heating it.

[0003] Patent Document 2 describes a method for manufacturing a composite O-ring structure in which two covering materials are pre-formed using a core material and a core material that is substantially the same shape, the core material is removed, and a supercritical extraction-treated O-ring-shaped rubber core material is inserted into the resulting cavity and integrally molded together with the covering material.

[0004] Patent Document 3 describes a method for manufacturing a two-layer O-ring, characterized by extruding a string-like body composed of an outer layer and an inner layer, and simultaneously vulcanizing the inner and outer layers by heat pressing.

[0005] Patent Document 4 describes a method for manufacturing an O-ring having a two-layer structure, which involves wrapping an outer layer material containing a perfluoroelastomer in the shape of a ribbon around a core material and then heating and pressurizing it, and a method in which the outer layer material is freeze-pulverized to form particles, which are then attached to the core material and then heated and pressurized. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4148493 [Patent Document 2] Japanese Patent Publication No. 10-323847 [Patent Document 3] Japanese Patent Publication No. 10-52885 [Patent Document 4] Japanese Patent Application Publication No. 10-329271 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the manufacturing method described in Patent Document 1, the outer layer material may rupture when the outer layer is inflated. Furthermore, because a connecting member made of the outer layer material is placed at the joint, the joint does not have a two-layer structure. Moreover, the process is complex and costly.

[0008] In the manufacturing method described in Patent Document 2, the core material may protrude from the gap between the upper and lower outer layers during integral molding in the mold.

[0009] In the manufacturing method described in Patent Document 3, the inner layer may protrude from the parting line and seams during molding with a mold.

[0010] In the manufacturing method described in Patent Document 4, simply wrapping the material in a ribbon shape makes it difficult to insert the material into the mold because wrinkles form in the curved part of the inner diameter of the O-ring. Furthermore, there is a high possibility that the core material will protrude through the gaps in the ribbon, and it is difficult to take countermeasures against this. Moreover, when the outer layer material is freeze-dried and pulverized to form particles, and these particles are then attached to the core material, the particles do not adhere to the core material, making it difficult to completely cover the core.

[0011] When manufacturing annular sealing material having a two-layer structure using different materials for the core and outer layer, the core may sometimes protrude from the outer layer at the joint and parting line. However, since the core and outer layer have the same or similar colors, it is often difficult or impossible to detect this protrusion.

[0012] The object of the present invention is to provide an annular sealing material having a two-layer structure using different materials for the core and outer layer, in which the protrusion of the core from the outer layer at the joint and parting line is easily recognizable, and a method for manufacturing the same.

[0013] [Means for Solving the Problem]

[0014] The present invention provides the following annular sealing material and a method for manufacturing the same. [1] An annular sealing material including a core and an outer layer covering the periphery of the core, wherein the core and the outer layer include a crosslinked product of a crosslinkable rubber composition having different colors from each other either after thermocompression molding or after secondary crosslinking or both. [2] The annular sealing material according to [1], wherein the average ratio of the thickness of the outer layer to the total thickness in the cross section is 1 / 35 to 1 / 4. [3] The annular sealing material according to [1] or [2], wherein at least one of the core and the outer layer contains a colorant. [4] The annular sealing material according to [3], wherein the core contains a colorant and the outer layer does not contain a colorant. [5] The annular sealing material according to [3] or [4], wherein the colorant is at least one selected from the group consisting of inorganic pigments and organic pigments. [6] The annular sealing material according to any one of [1] to [5], wherein the outer layer includes a crosslinked product of at least one selected from the group consisting of perfluoroelastomers and fluororubbers, and the core includes a crosslinked product of at least one selected from the group consisting of perfluoroelastomers, fluororubbers, silicone rubbers, and fluorosilicone rubbers. [7] A method for manufacturing the annular sealing material according to [1], comprising: preparing a preform including an uncrosslinked core made of a crosslinkable rubber composition for the core and an uncrosslinked outer layer made of a crosslinkable rubber composition for covering the periphery of the uncrosslinked core; installing the preform in a mold and performing thermocompression molding; [[ID=二十七]]including a method for manufacturing an annular sealing material, wherein the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer have different colors either after thermocompression molding or after secondary crosslinking or both. [8] The step of preparing the preform includes an extrusion molding step using the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer, which is the manufacturing method of the annular seal material according to [7]. [9] The preform is in a rope shape, which is the manufacturing method according to [7] or [8].

Advantages of the Invention

[0015] According to the present invention, when manufacturing an annular seal material having a two-layer structure using different materials for the core and the outer layer, it is possible to provide an annular seal material in which the protrusion of the core from the outer layer at the joint and the parting line is easily recognizable, and a manufacturing method thereof.

Brief Description of the Drawings

[0016] [Figure 1] A schematic cross-sectional view of an annular seal material according to one aspect of the present invention is shown. [Figure 2] A schematic cross-sectional view of an annular seal material according to one aspect of the present invention is shown.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the following drawings, the scale is appropriately adjusted for easy understanding of each component, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component. <00001'13> <Annular Seal Material> An annular seal material according to one aspect of the present invention includes a core and an outer layer covering the periphery of the core, and the core and the outer layer include crosslinked products of crosslinkable rubber compositions having different colors from each other in either or both of after hot press molding and after secondary crosslinking. The annular seal material will be described while referring to the drawings.

[0019] Figure 1 shows a cross-section of an annular sealing material. The annular sealing material 1 shown in Figure 1 includes a core 2 and an outer layer 3 that covers the periphery of the core 2. As shown in Figure 1, the annular sealing material 1 preferably has a circular cross-sectional shape, but may have other cross-sectional shapes depending on the application.

[0020] The annular sealant 1 preferably has an average ratio of the thickness of the outer layer 3 to the total thickness in the cross-section (hereinafter also referred to as the average ratio) of 1 / 50 to 1 / 3, and more preferably 1 / 35 to 1 / 4. The average ratio is the average of the ratios measured at two or more randomly selected cross-sections other than the joints in the annular sealant. The ratio is, for example, in Figure 2, the ratio T / D of the thickness T of the outer layer 3, which is the largest thickness in the cross-section of the annular sealant 1, and the diameter D of the cross-section of the annular sealant 1 that includes that thickness.

[0021] The thickness T of the outer layer 3 may be, for example, 0.1 to 10 mm, and preferably 0.2 to 3 mm. The diameter D of the cross-section of the sealing material 1 may be, for example, 3 to 50 mm, and preferably 3 to 15 mm.

[0022] The crosslinkable rubber composition for forming the core 2 (hereinafter also referred to as the crosslinkable rubber composition for the core) and the crosslinkable rubber composition for forming the outer layer 3 (hereinafter also referred to as the crosslinkable rubber composition for the outer layer) have different colors from each other after either or both of the following: after hot press molding and / or after secondary crosslinking, it becomes easier to check for overflow from the outer layer 3 of the core 2 at the joints and parting lines after at least one of the following: this tends to improve productivity.

[0023] The core 2 and the outer layer 3 can have different colors from each other after hot press molding and / or after secondary crosslinking, for example, by selecting the types of raw materials contained in the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer (hereinafter, when referring to both, they are also called the crosslinkable rubber composition), or by adjusting the mixing ratio of the raw materials.

[0024] When selecting raw material types so that the core 2 and outer layer 3 exhibit different colors after hot press molding or secondary crosslinking, a colorant can be included in at least one of the crosslinkable rubber compositions. Therefore, at least one of the core 2 and outer layer 3 may contain a colorant. When a colorant is included in at least one of the crosslinkable rubber compositions, it is preferable that the core 2 contains the colorant and the outer layer 3 does not. When both the core 2 and outer layer 3 contain a colorant, it is preferable that the core 2 and outer layer 3 contain different types of colorants. It is also possible to make the core 2 and outer layer 3 exhibit different colors after hot press molding or secondary crosslinking without incorporating pigments into the crosslinkable rubber composition.

[0025] The crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer may be the same color or different colors before hot press molding or secondary crosslinking. Furthermore, the colors of the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer may be the same or different after hot press molding or secondary crosslinking compared to before hot press molding or secondary crosslinking.

[0026] The coloring agent may be any coloring agent that has been conventionally used in sealing materials. Examples of coloring agents include at least one selected from the group consisting of inorganic pigments and organic pigments. Examples of inorganic pigments include white pigments (e.g., silica, zinc oxide, lead white, lithopon, titanium dioxide, precipitated barium sulfate, and barite powder), red pigments (e.g., red lead, iron oxide), yellow pigments (e.g., lead yellow, zinc yellow), blue pigments (e.g., ultramarine blue, Prussian blue, YInMn blue), and black pigments (e.g., carbon black). Examples of organic pigments include azo pigments (azo lake pigments, insoluble azo pigments, condensed azo pigments, etc.); anthraquinone pigments, thioindigo pigments, perinone pigments, perylene pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, dioxazine pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, and other polycyclic pigments; phthalocyanine pigments, etc. Organic pigments classified as pigments in the color index can be used. Preferably, the pigments used are organic pigments that do not contain metal elements. Organic pigments that do not contain metal elements do not pose a risk of scattering of metal-derived substances even if the sealing material is used in harsh ozone environments such as semiconductor applications and the cyclic sealing material is etched.

[0027] The amount of colorant in the crosslinkable rubber composition may be, for example, 0.01 parts by mass or more and less than 2 parts by mass per 100 parts by mass of the crosslinkable rubber component described later. From the viewpoint of ease of checking for overflow from the outer layer 3 of the core 2 at joints and parting lines, it is preferably 0.05 parts by mass or more and 1.5 parts by mass or less, and more preferably 0.1 parts by mass or more and 1 part by mass or less.

[0028] A crosslinkable rubber composition may contain a crosslinkable rubber component. The crosslinkable rubber component is capable of forming an elastomer (crosslinked rubber) having the above-described crosslinked structure through a crosslinking reaction. The crosslinkable rubber component may have crosslinkable sites such as carbon-carbon unsaturated groups, nitrile groups, hydroxyl groups, amino groups, carbonyl groups, and halogen groups.

[0029] Specific examples of crosslinkable rubber components include perfluoroelastomers (FFKM), fluororubber (FKM), silicone rubber, fluorosilicone rubber, 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), and acrylic rubber. Among these, perfluoroelastomers, fluororubber, silicone rubber, and fluorosilicone rubber are preferably used. In a crosslinkable rubber composition, one of the above crosslinkable rubber components may be used alone, or a polymer blend containing two or more of the above may be used.

[0030] The outer layer 3 preferably contains at least one crosslinked material selected from the group consisting of perfluoroelastomers and fluororubber, and the core 2 preferably contains at least one crosslinked material selected from the group consisting of perfluoroelastomers, fluororubber, silicone rubber, and fluorosilicone rubber. Therefore, the crosslinkable rubber component in the crosslinkable rubber composition for the outer layer is preferably at least one selected from the group consisting of perfluoroelastomers and fluororubber, and more preferably a perfluoroelastomer. The crosslinkable rubber component in the crosslinkable rubber composition for the core is preferably at least one selected from the group consisting of perfluoroelastomers, fluororubber, silicone rubber, and fluorosilicone rubber. The outer layer 3 preferably contains a crosslinked perfluoroelastomer from the viewpoint of radical resistance. The core 2 preferably contains at least one crosslinked material selected from the group consisting of fluororubber, silicone rubber, and fluorosilicone rubber from the viewpoint of material cost.

[0031] The perfluoroelastomer is not particularly limited, and examples thereof include tetrafluoroethylene (TFE)-perfluoro(alkyl vinyl ether) copolymers, TFE-perfluoro(alkoxyalkyl vinyl ether) copolymers, and the like. These copolymers may further contain structural units derived from other perfluoromonomers. According to the perfluoroelastomer composition containing a perfluoroelastomer, the ozone resistance can be further enhanced as compared with a crosslinkable rubber composition containing a fluorine elastomer containing hydrogen atoms. The crosslinkable rubber composition may contain only one kind of perfluoroelastomer or may contain two or more kinds thereof.

[0032] The perfluoro(alkyl vinyl ether) forming the tetrafluoroethylene (TFE)-perfluoro(alkyl vinyl ether) copolymer may have 1 to 5 carbon atoms in the alkyl group, and examples thereof include perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), and the like. Preferably, it is perfluoro(methyl vinyl ether).

[0033] The perfluoro(alkoxyalkyl vinyl ether) forming the TFE-perfluoro(alkoxyalkyl vinyl ether) copolymer may have 3 to 12 carbon atoms in the group bonded to the vinyl ether group (CF2 = CFO-), and for example CF2 = CFOCF2CF(CF3)OC n F 2n+1 、 CF2 = CFO(CF2)3OC n F 2n+1 、 CF2 = CFOCF2CF(CF3)O(CF2O) m C n F 2n+1 、または CF2 = CFO(CF2)2OC n F 2n+1 It can be. In the above formula, n is, for example, 1 to 5, and m is, for example, 1 to 3.

[0034] The perfluoroelastomer is preferably crosslinkable, and more specifically, it is preferably a copolymer of crosslinking site monomers (containing further constituent units derived from the crosslinking site monomers). The crosslinking site refers to a site that can undergo crosslinking reactions. Examples of crosslinking sites include nitrile groups, halogen groups (e.g., I groups, Br groups, etc.), and perfluorophenyl groups.

[0035] An example of a crosslinking monomer having a nitrile group as the crosslinking site is a nitrile group-containing perfluorovinyl ether. Examples of nitrile group-containing perfluorovinyl ethers include: CF2 = CFO(CF2) n OCF(CF3)CN(n is, for example, 2-4), CF2 = CFO(CF2) n CN(n is, for example, 2 to 12), CF2 = CFO[CF2CF(CF3)O] m (CF2) n CN(n is, for example, 2, m is, for example, 1 to 5), CF2 = CFO[CF2CF(CF3)O] m (CF2) n CN(n is, for example, 1 to 4, m is, for example, 1 to 2), CF2 = CFO[CF2CF(CF3)O] n CF2CF(CF3)CN(n is, for example, 0-4) Examples include:

[0036] An example of a crosslinking monomer having a halogen group as the crosslinking site is a halogen-containing perfluorovinyl ether. An example of a halogen-containing perfluorovinyl ether is the one described above, where the nitrile group is replaced with a halogen group.

[0037] A crosslinkable perfluoroelastomer may have a crosslinking structure that crosslinks two main chains.

[0038] In perfluoroelastomers, the ratio of TFE-derived constituent units / perfluoro(alkyl vinyl ether) or perfluoro(alkoxyalkyl vinyl ether)-derived constituent units / crosslinking site monomer-derived constituent units is typically 50-79.6% / 20-49.8% / 0.2-5% in molar ratio, and preferably 60-74.8% / 25-39.5% / 0.5-2%. The crosslinkable rubber composition may also contain two or more perfluoroelastomers with different ratios of the above constituent units.

[0039] Examples of fluororubbers include binary vinylidene fluoride rubbers such as vinylidene fluoride / hexafluoropropylene copolymer, ternary vinylidene fluoride rubbers such as vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, vinylidene fluoride / tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, vinylidene fluoride / tetrafluoroethylene / propylene copolymer, tetrafluoroethylene / propylene copolymer, ethylene / tetrafluoroethylene / perfluoromethyl vinyl ether copolymer, thermoplastic fluororubber, and liquid fluororubber with a perfluoropolyether backbone (for example, "SIFEL®" manufactured by Shin-Etsu Chemical Co., Ltd.). Fluororubber may be used individually or in combination of two or more types.

[0040] Fluororubber may contain functional groups. Functional groups can be introduced, for example, by copolymerizing a crosslinked monomer having the functional group. The crosslinked monomer may be a halogen-containing monomer.

[0041] The crosslinkable rubber composition may optionally contain a crosslinking agent, depending on the crosslinking system of the crosslinkable rubber component, together with a co-crosslinking agent (crosslinking aid). Examples of crosslinking systems for perfluoroelastomers include peroxide crosslinking systems, triazine crosslinking systems, oxazole crosslinking systems, imidazole crosslinking systems, thiazole crosslinking systems, and bisphenol crosslinking systems. Examples of crosslinking systems for vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber include peroxide crosslinking systems, polyamine crosslinking systems, and polyol crosslinking systems. The crosslinkable rubber composition may be crosslinked with one of these crosslinking systems, or with two or more crosslinking systems.

[0042] Examples of peroxide crosslinking agents include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (examples of commercially available products: NOF Corporation's "Perhexa 25B" and "Perhexa 25B-40"), dicumyl peroxide (example of commercially available product: NOF Corporation's "Permil D"), 2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, t-butyldicumyl peroxide, benzoyl peroxide (example of commercially available product: NOF Corporation's "Nipper B"), 2,5-dimethyl-2,5-(t-butylperoxy)hexyn-3 (example of commercially available product: NOF Corporation's "Perhexyn 25B"), 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, α,α'-bis(t-butylperoxy-m-isopropyl)benzene (example of commercially available product: NOF Corporation's "Perbutyl P"), t-butylperoxyisopropyl carbonate, and parachlorobenzoyl peroxide. Peroxide crosslinking agents may be used individually or in combination of two or more types.

[0043] Examples of co-crosslinking agents used in peroxide crosslinking systems include compounds (unsaturated polyfunctional compounds) that can be co-crosslinked by radicals, such as triallyl isocyanurate (example of a commercially available product: "TAIC" manufactured by Mitsubishi Chemical Corporation); triallyl cyanurate; triallyl formal; triallyl trimellitate; N,N'-m-phenylene bismaleimide; dipropagyl terephthalate; diallyl phthalate; and tetraallyl terephthalamide. One co-crosslinking agent may be used alone, or two or more may be used in combination. Among the above, from the viewpoint of reactivity and heat resistance (compression set characteristics), it is preferable that the co-crosslinking agent includes triallyl isocyanurate.

[0044] In triazine crosslinking systems, crosslinking catalysts such as organotin compounds, onium salts such as quaternary phosphonium salts and quaternary ammonium salts, urea, and silicon nitride are used.

[0045] Examples of crosslinking agents used in oxazol crosslinking systems include 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BOAP), 4,4'-sulfonylbis(2-aminophenol), and 9,9-bis(3-amino-4-hydroxyphenyl)fluorene. Preferably, BOAP is used.

[0046] Conventionally known crosslinking agents can be used in imidazole crosslinking systems and thiazole crosslinking systems. Examples of crosslinking agents used in imidazole crosslinking systems include 3,3',4,4'-tetraaminobenzophenone and 3,3'-diaminobenzidine.

[0047] The amount of crosslinking agent (total amount if two or more types are used) in the crosslinkable rubber composition is, for example, 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the total amount of crosslinkable rubber components.

[0048] The content of co-crosslinking agents (total amount if two or more are used) in the crosslinkable rubber composition is, for example, 0.5 to 10 parts by mass per 100 parts by mass of the total amount of crosslinkable rubber components, and preferably 1 to 8 parts by mass from the viewpoint of improving heat resistance.

[0049] The crosslinkable rubber composition may contain additives such as antioxidants, antioxidants, vulcanization accelerators, processing aids (e.g., stearic acid), stabilizers, tackifiers, silane coupling agents, plasticizers, flame retardants, mold release agents, waxes, and lubricants, as needed, for purposes such as improving processability and adjusting physical properties. Other examples of additives include tackiness reducing (preventing) agents such as fluorinated oils (e.g., perfluoroethers). Only one additive may be used, or two or more may be used in combination.

[0050] However, when the annular sealing material is used in a high-temperature environment, there is a risk of volatilization, leaching, or precipitation, so it is preferable to use as little additive as possible (for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the total amount of crosslinkable rubber components), and it is desirable to use no additive at all.

[0051] Furthermore, the crosslinkable rubber composition may optionally contain fillers (e.g., fluororesin, silica, alumina, zinc oxide, titanium oxide, clay, talc, diatomaceous earth, barium sulfate, calcium carbonate, magnesium carbonate, calcium oxide, mica, graphite, aluminum hydroxide, aluminum silicate, hydrotalcite, metal powder, glass powder, ceramic powder, etc.). Only one type of filler may be used, or two or more types may be used in combination. The filler content in the crosslinkable rubber composition (total amount if two or more types are used) is, for example, 0.1 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the total amount of the crosslinkable rubber component, preferably 1 part by mass or more and 30 parts by mass or less, and more preferably more than 1 part by mass and 30 parts by mass or less, from the viewpoint of improving mechanical strength. In this specification, fillers are distinguished from the organic pigments and inorganic pigments used as colorants as described above, and different types of fillers can be used.

[0052] When a crosslinkable rubber composition contains a fluororesin filler, the ozone resistance and mechanical strength of the crosslinked material can be further improved. The fluororesin can be included in the crosslinkable rubber composition, for example, as fluororesin particles.

[0053] The fluororesin used as a filler is a resin having fluorine atoms in its molecule, and can be, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride-hexafluoropropylene copolymer (PVF), vinylidene fluoride-hexafluoropropylene copolymer (VDF-HFP copolymer), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer (VDF-HFP-TFE copolymer), etc. A single fluororesin may be used alone, or two or more may be used in combination.

[0054] Among the above, it is preferable to use fluororesins with relatively high melting points, such as PFA and PTFE, from the viewpoint of preventing the resin from melting in a high-temperature environment and impairing properties such as compression set.

[0055] The fluororesin used as a filler may contain functional groups. Functional groups can be introduced, for example, by copolymerizing monomers having such functional groups. When the above-mentioned crosslinking site monomers are copolymerized as monomers having functional groups, the crosslinking between the fluororesin and the perfluoroelastomer also proceeds due to the crosslinking agent, which can further enhance the mechanical strength of the crosslinked product of the perfluoroelastomer composition. An example of a fluororesin containing functional groups is the nitrile group-containing polytetrafluoroethylene described in Japanese Patent Application Publication No. 2013-177631. Furthermore, the fluororesin can also be a modified fluororesin, such as "TFM-modified PTFE" (manufactured by Dyneon Corporation).

[0056] When a crosslinkable rubber composition contains a perfluoroelastomer and a fluororesin filler, for example, a fluororesin-containing perfluoroelastomer can be used, produced by 1) kneading perfluoroelastomer powder and fluororesin powder using a mixing roll, 2) melt-kneading perfluoroelastomer powder or pellets and fluororesin powder or pellets using equipment such as a mixer or twin-screw extruder, or 3) adding fluororesin during the perfluoroelastomer preparation stage.

[0057] The method described in 3) above includes a method in which an aqueous dispersion of perfluoroelastomer obtained by emulsion polymerization is mixed with an aqueous dispersion of fluororesin, and then a mixture of perfluoroelastomer and fluororesin is obtained by co-coagulation.

[0058] A crosslinkable rubber composition can be prepared by uniformly mixing a crosslinkable rubber component, a colorant, a crosslinking agent, a co-crosslinking agent (if necessary), a filler, and additives. Conventional mixing machines such as mixing rolls, pressure kneaders, and internal mixers (Banbury mixers) can be used. Each component may be mixed and kneaded all at once, or the components may be mixed in stages, such as first uniformly mixing the components excluding those that contribute to the crosslinking reaction (crosslinking accelerators, crosslinking retarders, crosslinking agents, etc.), and then mixing in the components that contribute to the crosslinking reaction.

[0059] <Method for manufacturing ring-shaped sealing material> A method for manufacturing an annular sealing material may include, for example, the following steps. 1) A step of preparing a pre-molded body comprising an uncrosslinked core made of a crosslinkable rubber composition for the core and an uncrosslinked outer layer made of a crosslinkable rubber composition for the outer layer that covers the periphery of the uncrosslinked core [hereinafter also referred to as step 1)]. 2) A step in which a pre-molded body is placed in a mold and hot press molding is performed [hereinafter also referred to as step 2)].

[0060] The above-described explanation for the annular sealing material applies to the annular sealing material, the crosslinkable rubber composition for the core, and the crosslinkable rubber composition for the outer layer.

[0061] Step 1) may include a step of extruding using a crosslinkable rubber composition for the core and a crosslinkable rubber composition for the outer layer. The pre-molded body prepared in Step 1) may be rope-shaped. A rope-shaped pre-molded body can be made, for example, as follows: First, the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer are formed into a sheet using a roll to produce a sheet-shaped molded product. The thickness of the sheet-shaped molded product may be, for example, 1 mm to 5 mm. Next, the sheet-shaped molded product is cut into a ribbon-shaped molded product, for example, with a width of 5 mm to 30 mm, using a cutting machine. After that, the ribbon-shaped molded products of the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer are fed into a screw-type extruder equipped with a crosshead and extruded into a rope shape to obtain a rope-shaped pre-molded body having a two-layer structure in which the outer layer is made of the crosslinkable rubber composition for the outer layer and the core is made of the crosslinkable rubber composition for the core. The extrusion speed into a rope shape may be, for example, 100 to 1000 mm / min.

[0062] The diameter of the cross-section of the rope-shaped preform may be, for example, 3 to 50 mm, preferably 3 to 15 mm. The outer layer thickness of the rope-shaped preform may be, for example, 0.1 to 10 mm, preferably 0.2 to 3 mm. The length of the rope-shaped preform may be, for example, 100 to 5000 mm.

[0063] In step 1), the ribbon-shaped molded product may be produced by extruding the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer into a ribbon shape using a plunger-type extruder, without producing a sheet-shaped molded product.

[0064] In step 2), the hot press forming may be a feed press forming method in which a linear or arc-shaped molded body is produced from a rope-shaped preform using a die having a linear or arc-shaped cavity, and the ends of these molded bodies are joined to form an annular sealing material, or an annular sealing material may be produced by placing a rope-shaped preform in a die having an annular cavity and performing a hot press. The heating temperature in the hot press forming may be, for example, around 110 to 220°C.

[0065] The method for manufacturing the annular seal material may include a secondary crosslinking step after step 2) for further crosslinking the crosslinkable rubber composition. The heating temperature in the secondary crosslinking step may be, for example, around 150 to 310°C.

[0066] In the method for manufacturing the annular sealing material of the present invention, the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer have different colors after heating, such as after hot pressing or secondary crosslinking. Therefore, after step 2), the overflow from the outer layer of the core at the joints and parting lines tends to be easier to recognize. [Examples]

[0067] The present invention will be described in more detail below with reference to examples. In the examples, "%" and "parts" refer to mass%, and parts, respectively, unless otherwise specified.

[0068] <Example 1> A crosslinkable rubber composition for the outer layer was prepared by kneading a perfluoroelastomer with Perhexa 25B as a crosslinking agent and TAIC as a crosslinking aid using a kneader. Next, a crosslinkable rubber composition for the core was prepared by kneading a fluororubber with 0.1 parts by mass of a coloring agent (Cromphtal Violet D5700) per 100 parts by mass of fluororubber, with Perhexa 25B as a crosslinking agent and TAIC as a crosslinking aid using a kneader. Next, the crosslinkable rubber composition for the outer layer and the crosslinkable rubber composition for the core were formed into sheets using a roll to a thickness of approximately 3 mm, and then cut into ribbons with a width of approximately 15 mm using a cutting machine. The ribbon-shaped crosslinkable rubber composition for the outer layer and the crosslinkable rubber composition for the core were fed into a screw-type extruder equipped with a crosshead, and five rope-like pre-molded bodies having a two-layer structure consisting of the outer layer being the crosslinkable rubber composition for the outer layer and the core being the crosslinkable rubber composition for the core were produced. The rope-like pre-molded body had a cross-sectional diameter of approximately 7 mm, an outer layer thickness of approximately 1 mm, and a length of 800 mm.

[0069] Next, annular sealing material was fabricated by press-molding five rope-like preforms at a temperature of 170°C. Subsequently, secondary crosslinking was performed on the obtained annular sealing material at a temperature of 200°C. It was confirmed that the obtained annular sealing material did not protrude from the outer layer of the core. The average ratio of the thickness of the outer layer to the diameter of the cross-section of the annular sealing material was 1 / 7. [Explanation of Symbols]

[0070] 1. Annular sealing material, 2. Core, 3. Outer layer, T. Thickness of the outer layer, D. Diameter of the cross-section.

Claims

1. An annular sealing material comprising a core and an outer layer covering the periphery of the core, wherein the core and the outer layer have different colors from each other after hot press molding and / or after secondary crosslinking, and comprises a crosslinked product of a crosslinkable rubber composition containing a crosslinkable rubber component. It has seams and parting lines, The outer layer includes a crosslinked perfluoroelastomer, The thickness of the outer layer is 0.1 to 10 mm. The average ratio of the thickness of the outer layer to the total thickness in the cross-section is 1 / 50 to 1 / 3. At least one of the core and the outer layer contains a coloring agent, The aforementioned coloring agent is an organic pigment that does not contain metal elements, and is a cyclic sealing material.

2. The annular sealing material according to claim 1, wherein the crosslinkable rubber composition comprises a peroxide crosslinking agent and a cocrosslinking agent.

3. The cyclic sealing material according to claim 2, wherein the cocrosslinking agent comprises triallyl isocyanurate.

4. The annular sealing material according to any one of claims 1 to 3, wherein the core contains a coloring agent and the outer layer does not contain a coloring agent.

5. The annular sealing material according to any one of Claims 1 to 4, wherein the content of the coloring agent in the crosslinkable rubber composition is 0.01 parts by mass or more and less than 2 parts by mass per 100 parts by mass of the crosslinkable rubber component.

6. The annular sealing material according to any one of claims 1 to 5, wherein the core comprises at least one crosslinked material selected from the group consisting of perfluoroelastomer, fluororubber, silicone rubber, and fluorosilicone rubber.

7. A method for manufacturing an annular sealing material according to claim 1, A step of preparing a pre-molded body comprising an uncrosslinked core made of a crosslinkable rubber composition for the core, and an uncrosslinked outer layer made of a crosslinkable rubber composition for the outer layer that covers the periphery of the uncrosslinked core, The process involves placing the aforementioned pre-molded body in a mold and performing hot press molding. Includes, A method for manufacturing an annular seal material, wherein the crosslinkable rubber composition for the core and the crosslinkable rubber composition for the outer layer have different colors from each other after hot press molding and / or after secondary crosslinking.

8. The method for manufacturing an annular seal material according to claim 7, wherein the step of preparing the pre-molded body includes a step of extruding the core crosslinkable rubber composition and the outer layer crosslinkable rubber composition.

9. The manufacturing method according to claim 7 or 8, wherein the pre-molded body is rope-shaped.

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