JP2010285611A - Rubber composition for sealing material and sealing material - Google Patents

Abstract

Provided is a rubber composition for a sealing material which is excellent in stress relaxation properties and permanent compression strain characteristics and has high sealing performance.
A rubber composition for a sealing material includes a rubber and a co-crosslinking agent, and the proportion of the co-crosslinking agent may be about 5 to 25 parts by weight with respect to 100 parts by weight of the rubber. The rubber may be at least one rubber selected from olefin rubber, diene rubber, and acrylic rubber, and the co-crosslinking agent is a compound having three (meth) acryloyl groups in one molecule. Also good. This rubber composition does not need to contain a fiber substantially, and can exhibit high sealing performance over a long period of time.
[Selection figure] None

Description

  The present invention relates to a rubber composition and a sealing material used for a sealing material (particularly, a sheet gasket used for a pipe joint portion such as a pipe).

  A sheet-like gasket member is used in a pipe joint portion of piping for transferring various fluids. Seat gaskets need to maintain water leakage prevention performance for a long period of time. Especially, the seat gaskets, etc. provided in the secondary piping equipment of nuclear power plants that are continuously operated have high reliability for preventing water leakage. Is required.

  Conventionally, a sheet gasket mainly composed of rubber has a large stress relaxation property, permanent compression strain, and a long-term sealability is insufficient. Therefore, a fabric is laminated on rubber, asbestos, aramid fiber, etc. Fiber was blended as a filler.

  For example, in JP 2008-239766 (Patent Document 1), at least selected from the group consisting of reinforcing fibers excluding asbestos, rubber, rubber chemicals, molasses, oligosaccharides, lignins and imide resins. A joint sheet obtained by heating and compressing a rubber composition containing a kind of component is disclosed, and JP 2006-194295 A (Patent Document 2) includes a base fiber having an organic fiber as a main fiber, A non-asbestos-based sheet-like gasket containing rubber, graphite, and rubber chemicals, and containing 15 to 30% by weight of organic fiber in the composition is disclosed in Japanese Patent Application Laid-Open No. 2006-71012. In Patent Document 3, a compound fiber containing base fiber and / or an inorganic filler, a rubber material, and a rubber chemical is filled in a space of a porous fiber sheet in which a large number of fibers are combined. The sheet gasket is disclosed.

  However, these sheet gaskets have exposed fiber cross sections on the inner and outer diameter surfaces of the gasket, so when used for a long period of time, the liquid penetrates the gaps and interfaces between the fibers inside the gasket due to capillary action, The internal fluid can easily leak. Therefore, when using a sheet gasket, it is necessary to use the gasket after sealing the inner and outer cross sections of the gasket, which complicates the gasket manufacturing process. Accordingly, there is a demand for a gasket that does not require a sealing process, has excellent stress relaxation properties and permanent compression strain characteristics, and has high sealing properties.

JP 2008-239766 A (Claim 1) JP 2006-194295 A (Claim 1) JP 2006-71012 A (Claim 1)

  Accordingly, an object of the present invention is to provide a rubber composition for a sealing material and a sealing material (for example, a sheet gasket) which are excellent in stress relaxation properties and permanent compression strain characteristics and have high sealing performance.

  Another object of the present invention is to provide a rubber composition for a sealing material and a sealing material (for example, a sheet gasket) that can exhibit high sealing performance over a long period of time.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have blended a rubber with a co-crosslinking agent (for example, polyol tri (meth) acrylate) at a specific ratio, so that the properties as a sealing material can be obtained. As a result, it was found that a rubber composition excellent in the above was obtained, and the present invention was completed.

  That is, the rubber composition of the present invention is a crosslinkable rubber composition for a sealing material containing a rubber and a co-crosslinking agent. The proportion of the co-crosslinking agent may be about 5 to 25 parts by weight (for example, 5 to 20 parts by weight) with respect to 100 parts by weight of the rubber.

  The rubber may be at least one rubber selected from olefin rubber, diene rubber, and acrylic rubber (particularly, rubber composed of olefin units or (meth) acrylic units and diene units). . The co-crosslinking agent may be a compound having at least one functional group selected from a (meth) acryloyl group and an alkenyl group, or may be a compound having a total of three or more functional groups in one molecule. Alternatively, it may be a compound having three (meth) acryloyl groups in one molecule. The rubber composition of the present invention may be substantially free of fibers.

  The present invention also includes a sealing material (particularly, a sheet gasket) formed from the rubber composition.

  In the present specification, acrylate and methacrylate are collectively referred to as (meth) acrylate, and cyanurate and isocyanurate are collectively referred to as (iso) cyanurate.

  Even if the sealing material formed of the rubber composition of the present invention does not substantially contain fibers, it has excellent stress relaxation properties and permanent compression strain characteristics and excellent sealing performance. In addition, high sealing performance can be exhibited over a long period of time.

FIG. 1 is a graph showing the relationship between surface pressure and time when a stress relaxation test is performed at an ambient temperature of 100 ° C. for the sheet gasket of the example. FIG. 2 is a graph showing the relationship between the surface pressure and time when a stress relaxation test is performed at an atmospheric temperature of 150 ° C. for the sheet gasket of the example. FIG. 3 is a graph showing the relationship between the surface pressure and strain when the stress relaxation test is performed at an ambient temperature of 100 ° C. for the sheet gasket of the example. FIG. 4 is a graph showing the relationship between surface pressure and strain when a stress relaxation test is performed at an atmospheric temperature of 150 ° C. for the sheet gasket of the example. FIG. 5 is a plan view showing the shape of the sheet gasket after the stress relaxation test at an atmospheric temperature of 150 ° C. in Example 4. 6 is a plan view showing the shape of a sheet gasket after a stress relaxation test at an ambient temperature of 150 ° C. in Comparative Example 1. FIG.

[Rubber composition for sealing material]
The rubber composition for a sealing material of the present invention is a composition that contains a rubber and a co-crosslinking agent and can be crosslinked.

(Rubber)
Examples of the rubber include olefin rubber, diene rubber, acrylic rubber, urethane rubber, silicone rubber, fluorine rubber, epichlorohydrin rubber, and polysulfide rubber.

  Examples of the olefin rubber include ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), polyoctenylene rubber, ethylene-vinyl acetate copolymer rubber, chlorosulfonated polyethylene rubber (CSM) (for example, Hyperon ( Registered trademark)), and chlorinated polyethylene rubber (CM).

  Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butyl rubber (IIR), butadiene rubber (BR), 1,2-polybutadiene rubber (1,2-BR), chloroprene rubber (CR), etc. Polymer rubber of diene monomer; acrylonitrile-diene copolymer rubber such as acrylonitrile butadiene rubber (NBR), nitrile chloroprene rubber (NCR), nitrile isoprene rubber (NIR); styrene-butadiene rubber (SBR), styrene chloroprene Styrene-diene copolymer rubber (random or block copolymer) such as rubber (SCR) and styrene isoprene rubber (SIR) can be exemplified. The diene rubber includes hydrogenated rubber (for example, hydrogenated nitrile rubber (HNBR)).

Acrylic rubbers include rubbers mainly composed of alkyl acrylates (for example, copolymer rubbers (ACM) of acrylic acid alkyl esters and chlorine-containing crosslinkable monomers (such as 2-chloroethyl vinyl ether), acrylic Copolymer rubber (ANM) of acid alkyl ester and acrylonitrile, copolymer rubber of alkyl acrylate ester and alkyl methacrylate, copolymer of alkyl acrylate ester and carboxyl group and / or epoxy group-containing monomer Polymer rubber, etc.]. Examples of the acrylic acid alkyl ester constituting the acrylic rubber include acrylic acid C _1-10 alkyl esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate (particularly, acrylic acid C _{2-2 8} alkyl ester).

  Examples of the urethane rubber include polyester type urethane elastomer and polyether type urethane elastomer.

  Examples of the silicone rubber include vinyl silicone rubber (VMQ) in which a part of methyl group of polydimethylsiloxane is substituted with vinyl group, and a phenyl silicone rubber (PMQ) in which part of methyl group of polydimethylsiloxane is substituted with phenyl group. ), Rubber (PVMQ) in which a part of methyl group of vinyl silicone rubber is substituted with phenyl group, and fluorinated silicone rubber (FVMQ) in which a fluorinated alkyl group is introduced into the side chain of vinyl silicone rubber.

  Fluororubber includes copolymer rubber (FKM) of vinylidene fluoride and perfluoropropene, copolymer rubber (FFKM) of tetrafluoroethylene and perfluoromethyl vinyl ether, alternating of tetrafluoroethylene and propylene Examples thereof include copolymer rubber.

  Examples of the epichlorohydrin rubber include a homopolymer rubber (CO) of epichlorohydrin, a copolymer rubber (ECO) of epichlorohydrin and ethylene oxide, and a copolymer weight of epichlorohydrin and allyl glycidyl ether. An example is a united rubber.

  Examples of the polysulfide rubber include a condensate rubber of alkylene dichloride (for example, ethylene dichloride) and sodium polysulfide.

  These rubbers can be used alone or in combination of two or more. Among these rubbers, at least one kind of rubber selected from olefin rubber, diene rubber, and acrylic rubber is preferable from the viewpoint that both elasticity and durability required for the sealing material can be achieved. Furthermore, from the viewpoint of excellent durability as a sealing material, a polymer rubber of an olefin unit (for example, ethylene-propylene rubber), a copolymer rubber of an olefin unit or an acrylic unit and a diene unit is preferable, and a diene unit is particularly preferable. Particularly preferred are rubbers such as ethylene-propylene-diene rubber and acrylonitrile-diene rubber. Since vinylidene fluoride-based fluororubber generally has a problem in compression set, when used as a sheet gasket, it is necessary to retighten the gasket.

  In the ethylene-propylene-diene rubber, the ratio (molar ratio) of ethylene units to propylene units is the former / the latter = 50/50 to 90/10, preferably 55/45 to 85/15, more preferably 60/40 to It may be about 80/20. Examples of the diene component constituting the ethylene-propylene-diene rubber include conjugated dienes such as butadiene, isoprene and 1,4-hexadiene, and alicyclic diene compounds such as ethylidene norbornene and dicyclopentadiene. Of these diene components, alkylidene norbornene such as ethylidene norbornene is preferred. The iodine value of the ethylene-propylene-diene rubber may be about 10 to 50, preferably about 15 to 45, and more preferably about 20 to 40. Of these ethylene-propylene-diene rubbers, ethylene-propylene-ethylidene norbornene rubber is widely used.

  In the acrylonitrile-diene rubber, the acrylonitrile content may be about 10 to 50 mol% with respect to the whole rubber. Examples of the diene component include conjugated dienes such as butadiene and isoprene. These diene components can be used alone or in combination of two or more. Of these diene components, butadiene is preferred. Further, the acrylonitrile-diene rubber may contain a copolymerizable component such as divinylbenzene, vinylpyridine, or acrylic acid. Of these acrylonitrile-diene rubbers, acrylonitrile butadiene rubber is widely used.

(Co-crosslinking agent)
A co-crosslinking agent (or a co-vulcanizing agent) is usually used together with a crosslinking agent, and is interposed between the main chain or side chain of rubber and has a function of connecting crosslinking points.

  The co-crosslinking agent is not particularly limited as long as the crosslinking points are linked, and is a compound having a polymerizable functional group, a maleimide compound [for example, an aromatic bismaleimide (for example, N, N′-1,3-phenylene diene). Maleimide etc.), aliphatic bismaleimide (eg N, N′-1,2-ethylene bismaleimide etc.)], ketoxime compounds (eg quinonedioxime, dibenzoylquinonedioxime etc.) and the like. Among these co-crosslinking agents, the viewpoint of improving sealability and durability (especially, sealability of rubbers containing diene components such as conjugated dienes such as butadiene and isoprene and alicyclic diene compounds such as ethylidene norbornene). Therefore, a compound having a polymerizable functional group is preferable.

Examples of the polymerizable functional group (group having an ethylenically unsaturated double bond) include C _{2 −} such as vinyl group, allyl group, 1-propenyl group, 1-butenyl group, and 2-butenyl group (crotyl group). Examples include C _2-4 alkenylene groups such as ₆ alkenyl groups, vinylene groups, and propenylene groups, or functional groups containing these polymerizable functional groups (for example, (meth) acryloyl groups, maleoyl groups, fumaroyl groups, etc.). Of these polymerizable functional groups, an alkenyl group and a (meth) acryloyl group are preferable.

That is, the compound having a polymerizable functional group has at least one functional group selected from an alkenyl group {for example, a C _2-4 alkenyl group (particularly, a vinyl group or an allyl group)} and a (meth) acryloyl group. Is preferred.

  The number of polymerizable functional groups may be 2 or more (for example, 2 to 8), preferably 3 or more (for example, 3 to 6), more preferably about 3 to 4 in one molecule.

  The compound having an alkenyl group (vinyl group or allyl group) may be, for example, a compound having one alkenyl group (vinyl group or allyl group) in one molecule (for example, styrene, vinylpyridine, etc.) Preferably, it is a compound having a plurality of alkenyl groups in one molecule or two or more (for example, about 2 to 6, preferably about 2 to 4, more preferably about 2 to 3). Examples of the compound having a plurality of alkenyl groups in one molecule include compounds having two alkenyl groups in one molecule [aromatic compounds having a vinyl group (for example, divinylbenzene); compounds having an allyl group (for example, , Aliphatic dicarboxylic acid diallyl esters such as diallyl fumarate; aromatic dicarboxylic acid diallyl esters such as diallyl phthalate], etc.], compounds having three alkenyl groups in the molecule [eg triallyl (iso) cyanurate, etc.] Etc.].

As a compound having a (meth) acryloyl group, for example, a compound having one (meth) acryloyl group in one molecule (for example, (meth) acrylic acid, (meth) acrylic acid sodium, (meth) acrylic acid alkyl ester However, a compound having 2 or more (for example, 2 to 6, preferably 2 to 4, more preferably about 2 to 3) (meth) acryloyl groups in one molecule is preferable. As such a compound, for example, a compound having two (meth) acryloyl groups in one molecule {for example, (meth) acrylic acid metal salt [for example, zinc (meth) acrylate, magnesium (meth) acrylate, etc. ] Alkanediol di (meth) acrylate [eg, ethylene glycol di (meth) acrylate (ie, ethylene di (meth) acrylate), propylene glycol di (meth) acrylate (ie, propylene di (meth) acrylate), 1,4 -C _2-10 alkanediol di (meth) acrylate such as butanediol di (meth) acrylate, hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate], alkane polyol di (meth) acrylate [for example , Glyceri C _3-10 alkane polyol di (meth) acrylates such as di (meth) acrylate, trimethylolethane di (meth) acrylate], dialkylene glycol di (meth) acrylates [for example, diethylene glycol di (meth) acrylate, dipropylene Di-C _2-4 alkylene glycol di (meth) acrylate such as glycol di (meth) acrylate], polyalkylene glycol di (meth) acrylate [eg, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) poly C _2-4 alkylene glycol di (meth) acrylates such as acrylate etc.], bisphenols (meth) acrylic acid esters [e.g., bi C _2-4, such as di- or polyol di (meth) acrylates such as di alkylene oxide adduct (meth) acrylate, etc.]} phenol A; compound having three (meth) acryloyl groups in one molecule {e.g., an alkane Triol tri (meth) acrylate [C _3-10 alkanetriol tri (meth) acrylate such as glycerin tri (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate)], pentaerythritol tri Polyol tri (meth) acrylate such as (meth) acrylate}; a compound having 4 or more (meth) acryloyl groups in one molecule {for example, alkanetetra to hexaoltetra to hexa (meth) acrylate [for example, pe Pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, C _4-20 alkane tetracarboxylic to hexanol tetra to hexa (meth) acrylates such as dipentaerythritol hexa (meth) acrylate, diglycerol tetra (meth ) Acrylates, polyol tetra to hexa (meth) acrylates such as polyglycerin tetra (meth) acrylate} and the like.

  Examples of the compound having an alkenyl group (vinyl group or allyl group) and a (meth) acryloyl group include allyl (meth) acrylate.

  These co-crosslinking agents can be used alone or in combination of two or more. The liquid co-crosslinking agent may be used in a powdered form by being adsorbed on silica or the like from the viewpoint of handleability.

Among these co-crosslinking agents, three or more polymerizable functional groups (the alkenyl group and (meth) acryloyl group) are included in one molecule because vulcanized rubber can be provided with appropriate elasticity and strong sealing properties and durability. Group), preferably a compound having three (meth) acryloyl groups in one molecule, especially a polyol tri (meth) acrylate [for example, alkanetriol (meth) acrylate such as trimethylolpropane tri (meth) acrylate) (For example, C _3-10 alkanetriol (meth) acrylate and the like) and the like] are preferable. When a plurality of co-crosslinking agents are used in combination, the average number of polymerizable functional groups (particularly (meth) acryloyl groups) per weighted average molecular weight (weighted average 1 mol) is, for example, 2.5-4. The co-crosslinking agent composition may be used by adjusting the degree, preferably 3 or more (for example, about 3 to 3.5).

  The ratio of the co-crosslinking agent is 5 to 25 parts by weight (for example, 5 to 20 parts by weight), preferably 6 to 24 parts by weight (for example, 6 to 20 parts by weight, particularly 7 to 7 parts by weight based on 100 parts by weight of the rubber. 15 parts by weight), more preferably about 8 to 22 parts by weight (for example, 10 to 20 parts by weight). Usually, a co-crosslinking agent (particularly a co-crosslinking agent having three or more polymerizable functional groups such as triallyl (iso) cyanurate and trimethylolpropane tri (meth) acrylate) is used as a vulcanization accelerating aid for organic peroxides. It has been known that it is used in a small amount of about 0.5 to 2 parts by weight with respect to 100 parts by weight of rubber, and even if the proportion is increased, no improvement in characteristics is observed. However, in the present invention, by using a large amount of the co-crosslinking agent in excess of a common amount, particularly excellent properties (stress relaxation property, permanent compression strain property, sealing property, etc.) as a rubber composition for a sealing material are obtained. It can be expressed. However, when the ratio of the co-crosslinking agent is larger than the above range, it becomes difficult to form the rubber composition into a sheet shape. On the other hand, when the proportion of the co-crosslinking agent is smaller than the above range, characteristics such as permanent compression strain cannot be sufficiently improved.

(Crosslinking agent)
The rubber composition of the present invention usually contains a crosslinking agent (or vulcanizing agent). The crosslinking agent can be classified into a sulfur-based crosslinking agent and a non-sulfur-based crosslinking agent.

Sulfur-based crosslinking agents include sulfur (eg, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, etc.), sulfur chloride (eg, sulfur monochloride, sulfur dichloride, etc.), sulfur-containing organic compounds { Thiurams [eg, tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), dipentamethylenethiuram tetrasulfide (DPTT), etc., dithiocarbamine acid salts [e.g., dimethyl dithiocarbamate, salt of a di-C _1-4 alkyl dithiocarbamic acid, such as diethyldithiocarbamate, sodium, potassium, iron, copper, zinc, lead, tellurium, or selenium (e.g., dimethyldithiocarbamate Acid salt (NaMDC), zinc dimethyldithiocarbamate (ZnMDC) etc.)], thiazoles [eg 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS) etc.], thioureas [eg ethylenethiourea (eg EU), diethylthiourea (DEU), trimethylthiourea (TMU), etc.], guanidines [for example, diphenylguanidine (DPG), diortolylguanidine (DOTG), orthotolylbiguanide (OTBG), etc.] etc.] .

  Non-sulfur crosslinking agents include organic peroxides {eg, diacyl peroxides [eg, lauroyl peroxide, benzoyl peroxide, 4-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide], dialkyl peroxides, etc. Oxides [e.g., di-t-butyl peroxide, 2,5-di (t-butylperoxy) -2,5-dimethylhexane, 2,5-di (t-butylperoxy) -2,5- Dimethyl-3-hexene, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxyisopropyl) benzene, dicumyl peroxide, etc.], hydro Peroxides [eg t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexene -2,5-dihydroperoxide, diisopropylbenzene hydroperoxide, etc.], ketone peroxides [eg, ethyl methyl ketone peroxide, cyclohexanone peroxide, etc.], peroxyesters [t-butyl peracetate, perpivalin] Acid t-butyl etc.]}, radical generators (radical-generating compounds) such as azo compounds (eg azobisisobutylnitrile), organic polyvalent amines (eg triethylenetetraamine, hexamethylenediamine carbamate, 4,4'-methylenebis-ortho-chloroaniline), metal soap (fatty acid salts such as sodium stearate and potassium stearate) and the like.

  These crosslinking agents can be selected according to the type of rubber and can be used alone or in combination of two or more. Of these cross-linking agents, non-sulfur cross-linking agents are preferable, and dialkyl such as organic peroxides (for example, 1,1-bis (t-butylperoxyisopropyl) benzene) from the viewpoint of excellent sealing properties and heat resistance. Particularly preferred are peroxides).

  The ratio of the crosslinking agent is 0.1 to 10 parts by weight, preferably 0.2 to 8 parts by weight, more preferably 0.4 to 6 parts by weight (for example, 0.5 to 5 parts by weight) with respect to 100 parts by weight of rubber. Part by weight).

  The ratio (weight ratio) between the co-crosslinking agent and the crosslinking agent is the former / the latter = 30/70 to 99/1, preferably 40/60 to 95/5, more preferably 50/50 to 90/10 (for example, 60/40 to 85/15). A large ratio of the co-crosslinking agent to the cross-linking agent is preferable from the viewpoint of heat resistance.

(Crosslinking aid)
The rubber composition of the present invention may contain a crosslinking aid (or vulcanization aid). Examples of the crosslinking aid include metal oxides (such as zinc oxide (zinc white), magnesium oxide, lead oxide), fatty acids (for example, C _8-24 fatty acids such as stearic acid), and the like. These crosslinking aids can be used alone or in combination of two or more. Of these crosslinking aids, metal oxides (for example, a combination of zinc white and magnesium oxide) are preferable.

  The ratio of the crosslinking aid may be about 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, and more preferably about 1 to 5 parts by weight with respect to 100 parts by weight of the rubber.

  The ratio of the crosslinking assistant may be 10 to 90 parts by weight, preferably 30 to 80 parts by weight, and more preferably about 50 to 70 parts by weight with respect to 100 parts by weight of the co-crosslinking agent.

(Other optional ingredients)
The rubber composition of the present invention may be substantially free of fibers as a reinforcing material. For this reason, the sealing material formed from the rubber composition of the present invention does not require the sealing treatment of the end fibers and can prevent deterioration of the sealing performance, so that high sealing performance can be exhibited over a long period of time.

  Further, the rubber composition of the present invention may contain other optional components as long as the effects of the present invention are not impaired. Other optional components include fillers [eg, carbon black, graphite, silica (anhydrous silicic acid, hydrous silicic acid, etc.), clay, talc, calcium sulfate, barium sulfate, calcium carbonate, magnesium carbonate, magnesium silicate, zeolite Etc.], plasticizers [for example, process oils and vegetable oils, factis (sub), aromatic carboxylic acid esters (for example, di- (2-ethylhexyl) phthalate, etc.), alkyl alkanedicarboxylates such as octyl adipate, butyl sebacate, etc. Esters, etc.], foaming agents (for example, nitroso compounds, azo compounds, sulfonyl hydrazides, etc.), coupling agents (silane-based, aluminum-based, titanate-based coupling agents, etc.), dispersants (paraffin and hydrocarbon resins, fatty acids, Fatty acid amide, fatty acid ester, fat ), Tackifiers (coumarone resins, coumarone indene resins, phenolic terpene resins, petroleum cyclocarbon resins such as dicyclopentane resins, rosin derivatives such as rosin esters), defoamers and moisture absorbents ( Oleic acid potassium soap, castor oil acid potassium soap, calcium oxide, etc., flame retardant (phosphorus compounds such as phosphate esters, nitrogen compounds such as urea or melamine or their derivatives, chlorine compounds and bromine compounds (bromination) Halogen compounds such as bisphenol A and brominated epoxy resins), antimony trioxide, aluminum hydroxide, magnesium hydroxide, zinc stannate compounds, expanded graphite, and the like, and colorants (eg, titanium oxide, carbon black, and other inorganic pigments) And organic pigments). These optional components can be used alone or in combination of two or more.

  Among these optional components, it is preferable to use a combination of a filler, a plasticizer, a colorant and the like. The ratio of the filler may be about 10 to 500 parts by weight, preferably 50 to 200 parts by weight, and more preferably about 80 to 120 parts by weight with respect to 100 parts by weight of the rubber. The proportion of the plasticizer may be about 0.1 to 20 parts by weight, preferably 1 to 15 parts by weight, and more preferably about 5 to 10 parts by weight with respect to 100 parts by weight of the rubber. The ratio of the colorant may be 1 to 30 parts by weight, preferably 5 to 25 parts by weight, and more preferably about 10 to 20 parts by weight with respect to 100 parts by weight of the rubber.

[Sealant]
The rubber composition for sealing material of the present invention is excellent in stress relaxation and permanent compression strain, and therefore has high compression adhesion to piping and the like, and is suitably used for various sealing materials (especially sheet gaskets, packings, etc.). it can. The rubber composition of the present invention can be prepared as a kneaded dough after a kneading step after mixing a rubber raw material kneading step and additives by a conventional method.

  The sealing material of the present invention also includes a step of molding the rubber composition prepared by the above method into various shapes by a conventional rubber processing method, a step of vulcanizing (crosslinking) the rubber molded product, and a vulcanized rubber molded product. It is obtained through a finishing process. Examples of the molding step before vulcanization include calendar processing, extrusion processing, and raw manufacturing processing. In particular, in the case of a sheet gasket, the rubber composition is formed into a sheet having a predetermined thickness by dispensing by roll rolling, dispensing by calendering, and raw manufacturing using extrusion molding (particularly dispensing by roll rolling). May be dispensed.

  In the vulcanization step, as a vulcanization method, a conventional method such as molding vulcanization using a mold, vulcanization can vulcanization, continuous vulcanization, or the like can be used. When using molding vulcanization with a mold, the kneaded dough may be directly put into the mold and vulcanized without passing through the molding process before the vulcanization process.

  The vulcanization (crosslinking) temperature can be appropriately selected according to the type of rubber and the like, and is, for example, about 80 to 250 ° C, preferably 100 to 230 ° C, more preferably 120 to 200 ° C (particularly 130 to 180 ° C). . The vulcanization time is, for example, about 5 minutes to 5 hours, preferably about 10 minutes to 3 hours, and more preferably about 15 minutes to 1 hour. During vulcanization, pressure may be applied.

  In the finishing process, tools such as knives and scissors, a method using a high-speed rotating grinder, a method of press punching with a punching die combined up and down, and the like can be used. The shape of the sealing material can be selected depending on the application, but particularly in the case of a sheet gasket, it may be punched into a ring shape (for example, punching using a blade).

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

  The contents of the components used in the examples and comparative examples and the method for evaluating the properties of the compositions are shown below.

(1) Content of each component Rubber A: EPDM (ethylene propylene ethylidene norbornene copolymer, manufactured by Mitsui Petrochemical Industries, EPT3045H)
Rubber B: NBR (butadiene acrylonitrile copolymer, manufactured by JSR Corporation, N230S)
Co-crosslinking agent A: trimethylolpropane trimethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., light ester TMP)
Co-crosslinking agent B: ethylene glycol dimethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., light ester EG)
Cross-linking agent A: 0.8 part by weight of sulfur (manufactured by Hosoi Chemical Co., Ltd., HK200-1), 0.9 weight by weight of di-2-benzothiazyl disulfide (manufactured by Ouchi Shinsei Chemical Co., Ltd., Noxeller DM) Parts, 1,3-diphenylguanidine (Ouchi Shinsei Chemical Co., Ltd., Noxeller D) 0.2 parts by weight, dibutyldithiocarbamate zinc (Ouchi Shinsei Chemical Co., Ltd., Noxeller BZ) 1.6 wt. Part, a mixture with 1.1 parts by weight of tetraethylthiuram disulfide (Ouchi Shinsei Chemical Co., Ltd., Noxeller TET) Crosslinker B: 1,1-bis (t-butylperoxyisopropyl) benzene (NOF Corporation ) Peroximon F40)
Filler A: Talc (Sanyo Clay Industry Co., Ltd., SMT)
Filler B: Silica (manufactured by Tokuyama Corporation, Tokuseal, average agglomerated particle size 7 to 10 μm, SiO ₂ : 93 to 96%)
Filler C: anhydrous clay (average particle size 1 μm, SiO ₂ : 51 to 53%, Al ₂ O ₃ : 42 to 44%, TiO ₂ : 1.6 to 2.5%)
Colorant: Titanium oxide (Furukawa Machine Metal Co., Ltd., FA-55W)
Plasticizer A: Paraffinic process oil (Fujiko Sangyo Co., Ltd., Fukkor P-200)
Plasticizer B: Di- (2-ethylhexyl) phthalate (DOP, manufactured by J-Plus)
Crosslinking aid A: Zinc flower (manufactured by Shodo Chemical Industry Co., Ltd., activated zinc flower AZO)
Crosslinking aid B: Magnesium oxide (Kyowa Chemical Industry Co., Ltd., Kyowamag # 150).

(2) Evaluation method of each characteristic Using the test samples of the sheet gaskets manufactured by the rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2, the gasket test made by Amtec, Germany, which received TA-LUFT certification Using a machine, a stress relaxation test and a leak test based on the test standard: EN13555 were performed and evaluated.

  In the stress relaxation test, the test sample is compressed at a surface pressure of 10 MPa, compressed at an ambient temperature of 100 ° C. or 150 ° C. for 4 hours, and then the surface pressure, strain, and deformation amount are recorded, and the stress relaxation rate and permanent compression are recorded. The strain rate was calculated. Further, the amount of change in the inner and outer diameters of the gasket before and after the test was measured. Tables 1 and 2 show the results at an atmospheric temperature of 100 ° C and an atmospheric temperature of 150 ° C. The test was conducted at a pressurization speed of 0.5 MPa / sec.

  In the leak test, the test sample is set in a testing machine, the seal surface pressure is changed from 5 MPa to 10 MPa, and further changed to 5 MPa, the leak amount is measured, and the final leak amount is measured by the differential pressure method. Measured and recorded. The results are shown in Table 3. The test was performed using helium gas as the pressurized fluid under conditions of normal temperature (23 ° C. ± 5 ° C.) and internal pressure of 1 MPa.

Examples 1-7 and Comparative Examples 1-5
Rubber compositions were prepared as test samples for sheet gaskets according to the formulations shown in Tables 1 and 2, respectively. Furthermore, after kneading the prepared rubber composition, it was dispensed by roll rolling to form an uncrosslinked rubber sheet, which was crosslinked by press crosslinking at 170 ° C. for 20 minutes to obtain a crosslinked rubber sheet. The obtained crosslinked rubber sheet was punched out by Thomson punching to obtain a ring-shaped sheet gasket having a thickness of 3 mm, an outer diameter of 88 mm, and an inner diameter of 43 mm.

  In Tables 1 and 2, those for which sheet processing was successfully performed are indicated by ○, and those for which sheet processing was not possible are indicated by ×. As is clear from Tables 1 and 2, in Comparative Example 3, the co-crosslinking agent was excessive, so that even when kneaded with a roll, an unvulcanized rubber fabric could not be uniformly kneaded and could be formed into a sheet shape. There wasn't. About Examples 1-7, it was able to process into a sheet form without a problem in particular.

  As is clear from Tables 1 and 2, in Comparative Examples 1, 2, 4 and 5, the stress relaxation rate and the permanent compression strain rate were deteriorated, and a product that could perform sufficiently as a gasket was not obtained. When the stress relaxation rate exceeds 30, and when the permanent compression strain rate exceeds 40, the sealing performance of the gasket often becomes poor, and the performance as a sheet gasket becomes insufficient. On the other hand, in Examples 1 to 7, the stress relaxation rate and the permanent compression strain rate that can be judged to be sufficient performance as a gasket were measured.

  For Examples 1 and 4 and Comparative Example 1, FIG. 1 and FIG. 2 are graphs showing the relationship between surface pressure and time in the stress relaxation test, and FIG. 3 and FIG. The relationship is shown in a graph. 1 and 3 show the results when the ambient temperature is 100 ° C., and FIGS. 2 and 4 show the results when the ambient temperature is 150 ° C. Moreover, in FIGS. 1-4, the data of the rubber gasket (comparative example 6) of a commercial item are plotted as a comparison object.

  5 and 6 are plan views of the shape of the sheet gasket after the stress relaxation test in Example 4 and Comparative Example 1 at an atmospheric temperature of 150 ° C., respectively. As is apparent from the comparison of the plan views, in Example 4, no deformation was observed, and the inner and outer diameters of the ring-shaped gasket were substantially perfect circles, whereas in Comparative Example 1, the creep deformation was significant. Especially, the inner diameter is greatly deformed, and the circular shape is not maintained.

  Specifically, in the seat gaskets after the tests of Comparative Examples 1 and 2 (not shown), the traces of the mold when the gasket is attached to the flange and tightened are clearly left on the inner diameter side and the outer diameter side of the gasket. The traces of creep deformation were clearly recognized, and the creep deformation was larger than the comparison of gasket diameter change. On the other hand, in the sample of Example 2 (not shown), although the amount of change in dimensions of the gasket was close to that of Comparative Examples 1 and 2, the gaskets after the test were compared with Comparative Examples 1 and 2. Remarkable creep deformation traces were not clearly recognized, and the deformation was at an acceptable level for a sheet gasket. Note that the pressure loss of the fluid inside the pipe occurs in the sheet gasket whose inner diameter is greatly deformed as in Comparative Example 1.

As is clear from Table 3, the gasket of Comparative Example 1 has a large amount of leak and the sealing performance is not sufficient, but the gaskets of Examples 1 to 7 showed good sealing performance. In this test, it can be said that if the leak amount is less than the order of 10 −8, the sealing performance is sufficient as a gasket. The measurement lower limit value of the leak amount of the test machine used was 1.7 × 10 ⁻⁸ , and in Examples 1 and 3 to 7, the leak amount was not more than the measurement lower limit value. That is, in the leak test, the ratio of the co-crosslinking agent was particularly good at 10 parts by weight or more with respect to 100 parts by weight of rubber.

  Since the rubber composition for a sealing material of the present invention is excellent in stress relaxation and permanent compression strain properties and can maintain the sealing performance of the sealing material for a long period of time, various sealing materials {packing [for example, squeeze packing ( For example, O ring, X ring, D ring, T ring, etc.), lip packing (for example, U packing, V packing, L packing, J packing, etc.), gland packing, oil seal, diaphragm seal, etc.], gasket (for example, Sheet gasket, spiral gasket, etc.). In particular, since it has high sealing performance and durability, it can be suitably used for a sheet gasket used for a joint portion such as a pipe.

Claims (8)

  A rubber composition for a sealing material comprising a rubber and a co-crosslinking agent, wherein the ratio of the co-crosslinking agent is 5 to 25 parts by weight with respect to 100 parts by weight of the rubber.   The rubber composition according to claim 1, wherein the rubber is at least one rubber selected from olefin rubber, diene rubber, and acrylic rubber.   The rubber composition according to claim 1 or 2, wherein the co-crosslinking agent is a compound having at least one functional group selected from a (meth) acryloyl group and an alkenyl group.   The rubber composition according to any one of claims 1 to 3, wherein the co-crosslinking agent is a compound having a total of 3 or more of at least one functional group selected from a (meth) acryloyl group and an alkenyl group in one molecule.   The rubber composition according to any one of claims 1 to 4, wherein the co-crosslinking agent is a compound having three (meth) acryloyl groups in one molecule.   The rubber composition according to any one of claims 1 to 5, which is substantially free of fibers.   The sealing material formed with the rubber composition in any one of Claims 1-6.   The sealing material according to claim 7, which is a sheet gasket.

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