Rubber composition, vulcanizate, and vulcanized molded article

Abstract

Provided is a rubber composition which can attain an improved balance among the scorch time of the unvulcanized form and the hardness, tensile strength, and freeze resistance of the vulcanizate. The rubber composition comprises a chloroprene-based rubber having a content of unsaturated nitrile monomer units of less than 25 mass% and an epoxy compound having a weight-average molecular weight higher than 100 but less than 900, wherein the epoxy compound is contained in an amount of 0.1-25 parts by mass per 100 parts by mass of the chloroprene-based rubber.

Description

[Technical Field]

[0001] The present invention relates to a rubber composition, a vulcanizate, a vulcanized molded article, and the like. [Background technology]

[0002] Chloroprene rubber has various excellent properties, and by utilizing these properties, it is used in a wide range of fields such as automobile parts, adhesives, various industrial rubber parts, etc. As technologies that enable the use of chloroprene rubber, the rubber compositions described in the following Patent Documents 1 to 3 are known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-23191 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-111899 [Patent Document 3] Japanese Patent Application Publication No. 9-268239 Summary of the Invention [Problem to be solved by the invention]

[0004] For rubber compositions containing chloroprene rubber, it is sometimes required that various properties be achieved at a high level in a vulcanized molded product of the rubber composition. However, it has been difficult to obtain a rubber composition that can improve the scorch time of an unvulcanized product and the hardness, tensile strength, and cold resistance of a vulcanized product in a well-balanced manner.

[0005] The present invention has been made in view of the above circumstances, and provides a rubber composition that can improve the scorch time of an unvulcanized product, and the hardness, tensile strength, and cold resistance of a vulcanized product in a well-balanced manner. [Means for solving the problem]

[0006] According to the present invention, there is provided a rubber composition comprising a chloroprene rubber having an unsaturated nitrile monomer unit content of less than 25% by mass and an epoxy compound having a weight average molecular weight of more than 100 and less than 900, the rubber composition containing 0.1 to 25 parts by mass of the epoxy compound per 100 parts by mass of the chloroprene rubber.

[0007] According to another aspect of the present invention, there is provided a vulcanizate of the above-described rubber composition. According to another aspect of the present invention, there is provided a vulcanized molded article using the vulcanizate described above.

[0008] As a result of extensive research, the present inventors have found that a rubber composition containing a specific type of chloroprene rubber and an epoxy compound having a specific molecular weight, and specifying the blending amount of the epoxy compound, can provide a rubber composition that can improve the scorch time of an unvulcanized product and the hardness, tensile strength, and cold resistance of a vulcanized product in a well-balanced manner, thereby completing the present invention.

[0009] Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other. [1] A rubber composition comprising a chloroprene rubber having an unsaturated nitrile monomer unit content of less than 25% by mass and an epoxy compound having a weight average molecular weight of more than 100 and less than 900, wherein the rubber composition contains 0.1 to 25 parts by mass of the epoxy compound per 100 parts by mass of the chloroprene rubber. [2] The rubber composition according to [1], wherein the unsaturated nitrile monomer is acrylonitrile. [3] The rubber composition according to [1] or [2], wherein the epoxy compound is at least one epoxy compound selected from an alicyclic epoxy compound, an epoxy resin composed of a copolymer of epichlorohydrin and bisphenol, and an epoxidized unsaturated fatty acid ester. [4] The rubber composition according to any one of [1] to [3], which contains 20 to 80 parts by mass of a filler per 100 parts by mass of the chloroprene rubber. [5] The rubber composition according to any one of [1] to [4], which contains 5 parts by mass or more of a curing agent per 100 parts by mass of the epoxy compound. [6] The rubber composition according to any one of [1] to [5], wherein the vulcanizate obtained by molding the rubber composition in accordance with JIS K6299 has a Type A durometer hardness of 80 or more as measured in accordance with JIS K6253. [7] A vulcanizate of the rubber composition according to any one of [1] to [6]. [8] A vulcanized molded article using the vulcanizate described in [7]. [Effects of the Invention]

[0010] The rubber composition according to the present invention can provide vulcanizates and vulcanized molded articles having a sufficient scorch time and excellent hardness, tensile strength, and cold resistance. Furthermore, the resulting vulcanizates and vulcanized molded articles have excellent processability and storage stability due to their sufficient scorch time. Furthermore, the resulting vulcanizates and vulcanized molded articles have improved hardness, tensile strength, and cold resistance in addition to the excellent mechanical strength, weather resistance, chemical resistance, and heat resistance that chloroprene-based rubbers possess, and can therefore be used in a variety of components requiring these properties. Examples of such components include rubber components for automobiles (e.g., automotive seals), hose materials, rubber molds, gaskets, rubber rolls, industrial cables, industrial conveyor belts, sponges, and other rubber components. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below by illustrating embodiments of the present invention. The present invention is not limited by these descriptions. The features of the embodiments of the present invention described below can be combined with each other. Furthermore, each feature can be an invention independently.

[0012] 1. Rubber composition The rubber composition according to the present invention contains a chloroprene rubber having an unsaturated nitrile monomer unit content of less than 25% by mass, and an epoxy compound having a weight average molecular weight of more than 100 and less than 900, and contains 0.1 to 25 parts by mass of the epoxy compound per 100 parts by mass of the chloroprene rubber. According to the present invention, by containing a specific type of chloroprene rubber and an epoxy compound having a specific molecular weight and specifying the amount of the epoxy compound, it is possible to improve the scorch time of the unvulcanized product and the hardness, tensile strength, and cold resistance of the vulcanized product in a well-balanced manner.

[0013] 1.1 Chloroprene rubber The chloroprene rubber according to the present invention refers to a rubber containing a chloroprene polymer having chloroprene (2-chloro-1,3-butadiene) as a monomer unit (a monomer unit of chloroprene; a monomer unit = a structural unit). Examples of the chloroprene polymer include a chloroprene homopolymer and a chloroprene copolymer (a copolymer of chloroprene and a monomer copolymerizable with chloroprene). The polymer structure of the chloroprene polymer is not particularly limited.

[0014] Commercially available 2-chloro-1,3-butadiene may contain a small amount of 1-chloro-1,3-butadiene as an impurity. 2-chloro-1,3-butadiene containing such a small amount of 1-chloro-1,3-butadiene can also be used as the chloroprene monomer of this embodiment.

[0015] The chloroprene rubber according to one embodiment of the present invention includes a chloroprene rubber having an unsaturated nitrile monomer unit content of less than 25% by mass. In the chloroprene rubber according to one embodiment of the present invention, when the rubber is taken as 100% by mass, the content of unsaturated nitrile monomer units is less than 25% by mass, and the content of unsaturated nitrile monomer units is preferably 1% by mass or more and less than 25% by mass. The content of unsaturated nitrile monomer units in the chloroprene-based rubber according to one embodiment of the present invention is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24% by mass, or less than 25% by mass, and may be within a range between any two of the values ​​exemplified here. By making the content of unsaturated nitrile monomer units less than 25% by mass, the resulting rubber composition has sufficient cold resistance. In particular, by making the content of unsaturated nitrile monomer units 1% by mass or more, the resulting rubber composition has sufficient oil resistance, and a vulcanized molded article having an excellent balance of hardness, tensile strength, and cold resistance can be obtained.

[0016] Examples of unsaturated nitriles include acrylonitrile, methacrylonitrile, ethacrylonitrile, and phenylacrylonitrile. The unsaturated nitriles can be used alone or in combination of two or more. The unsaturated nitrile preferably contains acrylonitrile, from the viewpoint of easily obtaining excellent moldability and easily obtaining excellent breaking strength, breaking elongation, hardness, tear strength, and oil resistance in a vulcanized molded product.

[0017] The content of unsaturated nitrile monomer units in chloroprene-based rubber can be calculated from the nitrogen atom content in the chloroprene-based rubber. Specifically, the nitrogen atom content of 100 mg of chloroprene-based rubber is measured using an elemental analyzer (Sumigraph 220F, manufactured by Sumika Chemical Analysis Center, Ltd.), and the content of structural units derived from unsaturated nitrile monomers can be calculated. Elemental analysis can be performed under the following conditions. For example, the electric furnace temperatures are set to 900°C for the reactor, 600°C for the reduction furnace, 70°C for the column, and 100°C for the detector. Oxygen is used as the combustion gas at a flow rate of 0.2 mL / min, and helium is used as the carrier gas at a flow rate of 80 mL / min. A calibration curve can be created using aspartic acid (10.52%), which has a known nitrogen content, as a standard substance.

[0018] The chloroprene rubber according to one embodiment of the present invention preferably contains 60 to 100% by mass of chloroprene monomer units when the rubber is taken as 100% by mass. The content of chloroprene monomer units in the chloroprene rubber is, for example, 60, 65, 70, 75, 80, 85, 90, 95, 99, or 100% by mass, and may be within a range between any two of the values ​​exemplified here. By ensuring that the content of chloroprene monomer units falls within the above range, a rubber composition can be obtained that can give a molded article with an excellent balance of hardness, tensile strength, and cold resistance.

[0019] The chloroprene-based rubber according to one embodiment of the present invention may also have a monomer unit other than the chloroprene monomer and the unsaturated nitrile monomer. The monomer unit other than the chloroprene monomer and the unsaturated nitrile monomer is not particularly limited as long as it is copolymerizable with the chloroprene monomer or the chloroprene monomer and the unsaturated nitrile monomer, and examples thereof include (meth)acrylic acid esters (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.), hydroxyalkyl (meth)acrylates (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, sulfur, etc.

[0020] A chloroprene-based rubber according to one embodiment of the present invention may contain 0 to 20 mass% of monomer units other than chloroprene monomer and unsaturated nitrile monomer when the rubber is taken as 100 mass%. The content of monomer units other than chloroprene monomer and unsaturated nitrile monomer in the chloroprene-based rubber may be, for example, 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, or 20 mass%, and may be within a range between any two of the values ​​exemplified here. By adjusting the copolymerization amount of monomers other than chloroprene monomer and unsaturated nitrile monomer within this range, the effects of copolymerizing these monomers can be achieved without impairing the properties of the resulting rubber composition. Furthermore, the chloroprene-based rubber according to one embodiment of the present invention may be composed only of chloroprene monomer units and unsaturated nitrile monomer units, or may be composed only of chloroprene monomer units.

[0021] In the rubber composition according to the present invention, the chloroprene rubber may be used alone or in combination of two or more kinds. When the rubber composition according to one embodiment of the present invention contains two or more types of chloroprene-based rubbers, it is preferable that the content of unsaturated nitrile monomer units contained in the two or more types of chloroprene-based rubbers contained in the rubber composition is less than 25 mass%.

[0022] The chloroprene polymer (chloroprene homopolymer, chloroprene copolymer, etc.) contained in the chloroprene rubber according to the present invention may be a sulfur-modified chloroprene polymer, a mercaptan-modified chloroprene polymer, a xanthogen-modified chloroprene polymer, a dithiocarbonate-based chloroprene polymer, a trithiocarbonate-based chloroprene polymer, a carbamate-based chloroprene polymer, etc.

[0023] The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (polydispersity of molecular weight, Mw / Mn) of the chloroprene rubber may be in the following ranges, from the viewpoint of easily obtaining excellent hardness, tensile strength, and cold resistance in a well-balanced manner.

[0024] The weight average molecular weight of chloroprene rubber is 10 × 10 3 g / mol or more, 50×10 3 g / mol or more, 100×10 3 g / mol or more, 300×10 3 g / mol or more, 400×10 3 g / mol or more, or 450 x 10 3 The weight average molecular weight of the chloroprene rubber may be 5000×10 g / mol or more. 3 g / mol or less, 3000×10 3 g / mol or less, 2000×10 3g / mol or less, 1000×10 3 g / mol or less, 800×10 3 g / mol or less, or 500 x 10 3 From these viewpoints, the weight average molecular weight of the chloroprene rubber may be 10×10 3 ~5000×10 3 g / mol, 100 × 10 3 ~2000×10 3 g / mol, or 300 x 10 3 ~1000×10 3 It may be in g / mol.

[0025] The number average molecular weight of chloroprene rubber is 1 x 10 3 g / mol or more, 5×10 3 g / mol or more, 10×10 3 g / mol or more, 50×10 3 g / mol or more, 100×10 3 g / mol or more, or 130×10 3 The number average molecular weight of the chloroprene rubber may be 1000×10 g / mol or more. 3 g / mol or less, 800×10 3 g / mol or less, 500×10 3 g / mol or less, 300×10 3 g / mol or less, 200×10 3 g / mol or less, or 150 x 10 3 From these viewpoints, the number average molecular weight of the chloroprene rubber may be 1×10 3 ~1000×10 3 g / mol, 10 × 10 3 ~500×10 3 g / mol or 50×10 3 ~300×10 3 It may be in g / mol.

[0026] The molecular weight distribution of the chloroprene rubber may be 1.0 or more, 1.5 or more, 2.0 or more, 2.5 or more, 3.0 or more, 3.2 or more, or 3.4 or more. The molecular weight distribution of the chloroprene rubber may be 10 or less, 8.0 or less, 5.0 or less, 4.0 or less, 3.8 or less, 3.5 or less, or 3.4 or less. From these viewpoints, the molecular weight distribution of the chloroprene rubber may be 1.0 to 10, 2.0 to 5.0, or 2.5 to 4.0.

[0027] The weight average molecular weight (Mw) and number average molecular weight (Mn) of the chloroprene rubber can be measured by gel permeation chromatography (GPC) and converted into polystyrene equivalents, and specifically, can be measured by the method described in the examples.

[0028] 1.2 Chloroprene rubber manufacturing method The method for producing the chloroprene rubber according to the present invention is not particularly limited, but the rubber can be obtained by a production method including an emulsion polymerization step of emulsion polymerizing raw material monomers including a chloroprene monomer. In the emulsion polymerization step according to one embodiment of the present invention, a chloroprene monomer or a monomer containing a chloroprene monomer and an unsaturated nitrile monomer is emulsion-polymerized using an emulsifier, a dispersant, a catalyst, a chain transfer agent, etc., as appropriate, and when a target final conversion rate is reached, a polymerization terminator is added to obtain a latex containing a chloroprene-based polymer containing chloroprene monomer units. Next, unreacted monomers can be removed from the polymerization solution obtained by the emulsion polymerization step by any method, including, but not limited to, steam stripping. Thereafter, the pH is adjusted, and the mixture is subjected to conventional steps such as freezing and coagulating, washing with water, and hot air drying, to obtain a chloroprene rubber containing a chloroprene polymer.

[0029] The polymerization initiator used in emulsion polymerization is not particularly limited, and any known polymerization initiator generally used in emulsion polymerization of chloroprene can be used. Examples of the polymerization initiator include potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and organic peroxides such as t-butyl hydroperoxide.

[0030] The emulsifier used in emulsion polymerization is not particularly limited, and any known emulsifier generally used in emulsion polymerization of chloroprene can be used. Examples of the emulsifier include alkali metal salts of saturated or unsaturated fatty acids having 6 to 22 carbon atoms, alkali metal salts of rosin acid or disproportionated rosin acid (e.g., potassium rosinate), and alkali metal salts of formalin condensates of β-naphthalenesulfonic acid (e.g., sodium salt).

[0031] The molecular weight modifier used in emulsion polymerization is not particularly limited, and any known molecular weight modifier commonly used in emulsion polymerization of chloroprene can be used, such as mercaptan compounds, xanthogen compounds, dithiocarbonate compounds, trithiocarbonate compounds, and carbamate compounds. Xanthogen compounds, dithiocarbonate compounds, trithiocarbonate compounds, and carbamate compounds are preferably used as molecular weight modifiers for the chloroprene rubber according to one embodiment of the present invention.

[0032] The polymerization temperature and the final conversion rate of the monomer are not particularly limited, but the polymerization temperature may be, for example, 0 to 50°C or 10 to 50°C. The polymerization may be carried out so that the final conversion rate of the monomer falls within the range of 40 to 95% by mass. In order to adjust the final conversion rate, a polymerization terminator that terminates the polymerization reaction may be added to terminate the polymerization when the desired conversion rate is reached.

[0033] The polymerization terminator is not particularly limited, and any known polymerization terminator commonly used in emulsion polymerization of chloroprene can be used, such as phenothiazine (thiodiphenylamine), 4-t-butylcatechol, and 2,2-methylenebis-4-methyl-6-t-butylphenol.

[0034] The chloroprene rubber according to one embodiment of the present invention can be obtained, for example, by removing unreacted monomers by a steam stripping method, adjusting the pH of the latex, and then performing conventional steps such as freeze coagulation, water washing, and hot air drying.

[0035] Chloroprene rubbers are classified into mercaptan-modified, xanthogen-modified, sulfur-modified, dithiocarbonate-based, trithiocarbonate-based and carbamate-based types depending on the type of molecular weight modifier.

[0036] 1.3 Epoxy compounds The rubber composition according to the present invention contains an epoxy compound, i.e., a compound having an epoxy group. The epoxy compound improves the fluidity of the unvulcanized product and, by curing during vulcanization, can function as a reactive plasticizer (curing plasticizer) that improves the mechanical properties, such as hardness and tensile strength, of the vulcanized product. Examples of the epoxy compound include an alicyclic epoxy compound, an epoxy resin composed of a copolymer of epichlorohydrin and bisphenol, an epoxidized unsaturated fatty acid ester, and a diene polymer having an epoxy group (excluding compounds corresponding to chloroprene polymers). The epoxy compound preferably contains at least one selected from the group consisting of an alicyclic epoxy compound, an epoxy resin composed of a copolymer of epichlorohydrin and bisphenol, and an epoxidized unsaturated fatty acid ester.

[0037] Examples of the alicyclic epoxy compound include compounds represented by the following formulas (1), (2), and (3).

[0038] [ka]

[0039] In formula (1), X can be any organic group, for example, a hydrocarbon group optionally having a substituent, such as an alkyl group or alkenyl group optionally having a substituent. The hydrocarbon group can include a carbonyl group, an ether group (ether bond), an epoxy group, or a group in which a plurality of these groups are linked together.

[0040] [ka]

[0041] In formula (2), Y represents any single bond or linking group (a divalent group having one or more atoms). Examples of the linking group include a divalent hydrocarbon group (e.g., an alkylene group), a carbonyl group, an ether group (ether bond), an epoxy group, and groups in which multiple of these groups are linked together.

[0042] [ka]

[0043] In equation (3), Z 1 and Z 2 can each independently be any organic group, for example, a hydrocarbon group optionally having a substituent, such as an alkyl group or alkenyl group optionally having a substituent. The hydrocarbon group can include a carbonyl group, an ether group (ether bond), an epoxy group, or a group in which a plurality of these groups are linked together.

[0044] Examples of alicyclic epoxy compounds include 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 1-vinyl-3,4-epoxycyclohexane, 4,5-epoxycyclohexane-1,2-dicarboxylate di-2-ethylhexyl, and 4,5-epoxycyclohexane-1,2-dicarboxylate di(9,10-epoxystearyl).

[0045] An epoxy resin made of a copolymer of epichlorohydrin and bisphenol is represented by formula (4).

[0046] [ka] (n in formula (4) is any integer that satisfies the molecular weight requirements below.)

[0047] In formula (4), n preferably satisfies 0≦n≦2.

[0048] Examples of the epoxidized unsaturated fatty acid ester include epoxidized fatty acid isobutyl and epoxidized fatty acid 2-ethylhexyl.

[0049] The diene polymer having an epoxy group is preferably liquid at room temperature (25° C.). Examples of diene polymers having epoxy groups include aliphatic conjugated diene polymers having epoxy groups, such as polybutadiene and polyisoprene; aromatic vinyl-aliphatic conjugated diene copolymers such as styrene-butadiene polymer (SBR); vinyl cyanide-conjugated diene copolymers such as acrylonitrile-butadiene polymer (NBR); hydrogenated SBR; hydrogenated NBR, etc. The diene polymer having epoxy groups may include, for example, a compound represented by the following formula (5):

[0050] [ka] (In formula (5), m and n are any integers that satisfy the molecular weight requirements below.)

[0051] The epoxy compound according to the present invention has a weight average molecular weight of more than 100 and less than 900. The weight average molecular weight of the epoxy compound according to the present invention is, for example, more than 100 and less than 110, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 890, or 900, and may be within a range between any two of the numerical values ​​exemplified here. By adjusting the molecular weight of the epoxy compound to the above upper limit or less, the scorch time of the unvulcanized product can be improved, and by adjusting the molecular weight of the epoxy compound to the above lower limit or less, the hardness, tensile strength, and cold resistance of the vulcanized product can be improved in a balanced manner. The weight average molecular weight can be obtained by measuring by gel permeation chromatography (GPC) and converting it into polystyrene equivalent, and can be measured in the same manner as the weight average molecular weight of a chloroprene polymer.

[0052] The epoxy equivalent of the epoxy compound can be 100 to 500 g / eq. The epoxy equivalent is, for example, 100, 150, 200, 250, 300, 350, 400, 450, or 500 g / eq, and may be within a range between any two of the values ​​exemplified here.

[0053] The rubber composition according to the present invention contains 0.1 to 25 parts by mass of an epoxy compound relative to 100 parts by mass of the chloroprene rubber. The content of the epoxy compound relative to 100 parts by mass of the chloroprene rubber is, for example, 0.1, 0.5, 1, 5, 10, 15, 20, or 25 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. By setting the content of the epoxy compound within the above range, a rubber composition can be obtained that can improve the scorch time of the unvulcanized product, and the hardness, tensile strength, and cold resistance of the vulcanized product in a well-balanced manner.

[0054] 1.4 Hardener The rubber composition according to one embodiment of the present invention may contain a curing agent. There are no particular limitations on the curing agent as long as it contributes to curing of the epoxy compound. Examples of the curing agent include carboxylic acid hydrazide curing agents, amine curing agents, phenolic curing agents, and acid anhydride curing agents. These may be used alone or in combination of two or more.

[0055] The curing agent according to one embodiment of the present invention preferably contains a carboxylic acid hydrazide curing agent. The carboxylic acid hydrazide curing agent preferably contains any one selected from the group consisting of carboxylic acid hydrazides and carboxylic acid dihydrazides. Specific examples of the carboxylic acid hydrazide curing agent include salicylic acid hydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, tetrahydrophthalic acid dihydrazide, phthalic acid dihydrazide, dodecanedioic acid dihydrazide, and isophthalic acid dihydrazide. The curing agent according to one embodiment of the present invention more preferably contains a carboxylic acid dihydrazide. More preferably, the curing agent according to one embodiment of the present invention includes any one selected from the group consisting of isophthalic acid dihydrazide, sebacic acid dihydrazide, adipic acid dihydrazide, and dodecanedioic acid dihydrazide.

[0056] A rubber composition according to one embodiment of the present invention may contain 5 or more parts by mass of a curing agent per 100 parts by mass of the epoxy compound. The amount of curing agent added per 100 parts by mass of the epoxy compound may be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 parts by mass, and may be within a range between any two of the values ​​exemplified here. By containing the curing agent in an amount equal to or greater than the lower limit, the rubber composition according to one embodiment of the present invention can further improve mechanical properties, while by containing the curing agent below the lower limit, shortening of scorch time can be prevented. A rubber composition according to one embodiment of the present invention may not contain a curing agent.

[0057] When 5 parts by mass of the curing agent according to one embodiment of the present invention is added to 100 parts by mass of the epoxy compound, the gel time at 160° C. is preferably 60 minutes or less. The gel time may be, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 minutes, or may be within a range between any two of the values ​​exemplified here. By selecting a curing agent whose gelation time is within the above range, it is possible to achieve both a sufficiently long scorch time for the unvulcanized product and excellent mechanical properties for the vulcanized product.

[0058] 1.5 Vulcanizing Agent The rubber composition according to the present invention may contain a vulcanizing agent. The type of vulcanizing agent is not particularly limited as long as it does not impair the effects of the present invention. The vulcanizing agent is preferably a vulcanizing agent that can be used to vulcanize chloroprene-based rubber. One or more vulcanizing agents can be freely selected and used. Examples of vulcanizing agents include sulfur, metal oxides, and organic peroxides.

[0059] Examples of metal oxides include zinc oxide, magnesium oxide, lead oxide, trimlead tetroxide, iron trioxide, titanium dioxide, calcium oxide, etc. The metal oxide preferably contains zinc oxide or magnesium oxide, and more preferably contains zinc oxide.

[0060] Examples of organic peroxides include dicumyl peroxide, benzoyl peroxide, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, diisobutyryl peroxide, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl) peroxydicarbonate, and di(2-ethylhexyl) peroxydicarbonate. C12-14C12-16 alkyl acrylate peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexyl peroxy Peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, t-butylperoxy-2-ethylhexanoate, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, dibenzoyl peroxide, 1,1-di(t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2, 2-Di(4,4-di-(t-butylperoxy)cyclohexyl)propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, 2,Examples include 2-di-(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl 4,4-di-(t-butylperoxy)valerate, 1,4-bis[(t-butylperoxy)isopropyl]benzene, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide. Among these, at least one selected from dicumyl peroxide, 1,4-bis[(t-butylperoxy)isopropyl]benzene, t-butyl-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3 is preferred, and 1,4-bis[(t-butylperoxy)isopropyl]benzene is particularly preferred.

[0061] From the viewpoint of ensuring processing safety and obtaining a good vulcanizate, the rubber composition according to the present invention preferably contains 3 to 15 parts by mass of a vulcanizing agent per 100 parts by mass of the rubber contained in the rubber composition. The content of the vulcanizing agent per 100 parts by mass of the rubber contained in the rubber composition is, for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0062] A rubber composition according to one embodiment of the present invention may contain a metal oxide and an organic peroxide. When an organic peroxide is used, the amount of the organic peroxide added may be 0.3 to 1.8 parts by mass per 100 parts by mass of the chloroprene rubber. The amount of the organic peroxide added may be, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or 1.8 parts by mass, and may be within a range between any two of the values ​​exemplified here.

[0063] 1.6 Hydrotalcite The rubber composition according to one embodiment of the present invention may contain hydrotalcite. As the hydrotalcite, one represented by the following formula (6) can be used.

[0064] [6] [M 2+ 1-x M 3+ x (OH)2] x+ [A n-x / n mH2O] x- (6)

[0065] In the above formula (5), M 2+ :Mg 2+ , Zn 2+ At least one divalent metal ion selected from M 3+ :Al 3+ , Fe 3+ At least one trivalent metal ion selected from A n- :Co3 2- , Cl ― , NO3 2- At least one n-type anion selected from X:0 <X≦0.33とすることができる。

[0066] As for hydrotalcite, Mg 4.3 Al2(OH) 12.6CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O, Mg 4.5 Al2(OH) 13 CO3·3.5H2O, Mg 4.5 Al2(OH) 13 CO3, Mg4Al2(OH) 12 CO3·3.5H2O, Mg6Al2(OH) 16 CO3·4H2O, Mg5Al2(OH) 14 CO3·4H2O, Mg3Al2(OH) 10 CO3·1.7H2O, etc., and particularly preferred is Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O.

[0067] When hydrotalcite is used, the amount of hydrotalcite added can be 1 to 10 parts by mass relative to 100 parts by mass of chloroprene rubber, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0068] 1.7 Plasticizers and softeners The rubber composition according to the present invention may contain a plasticizer / softener. The plasticizer / softener is added to adjust the processability of the unvulcanized rubber composition and the flexibility of the vulcanized product and vulcanized molded article after vulcanization. There are no particular restrictions on the plasticizer / softener, as long as it is compatible with rubber. Plasticizers and softeners include vegetable oils such as rapeseed oil, linseed oil, castor oil, and palm oil; phthalate-based plasticizers; ester-based plasticizers such as diundecyl phthalate (DUP), dioctyl phthalate (DOP), diisononyl phthalate (DINP), dioctyl terephthalate (DOTP), dioctyl sebacate (DOS), dibutyl sebacate (DBS), dioctyl adipate (DOA), diisononyl 1,2-cyclohexanedicarboxylate (DINCH), trioctyl phosphate (TOP), and tributyl phosphate (TBP); ether ester compounds; thioether-based plasticizers; aromatic oils, naphthenic oils, lubricating oils, process oils, paraffin, liquid paraffin, petrolatum, and petroleum asphalt. These can be used alone or in combination.

[0069] A rubber composition according to one embodiment of the present invention may contain 5 to 50 parts by mass of a plasticizer / softener, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts by mass, based on 100 parts by mass of rubber contained in the rubber composition, and may also be within a range between any two of the numerical values ​​exemplified here.

[0070] 1.8 Fillers (reinforcements) The rubber composition according to the present invention may contain a filler / reinforcing material. Examples of fillers and reinforcing materials include furnace carbon blacks such as SAF, ISAF, HAF, EPC, XCF, FEF, GPF, HMF, and SRF; modified carbon blacks such as hydrophilic carbon black; thermal carbons such as channel black, lamp black, FT, and MT; acetylene black, ketjen black, silica, clay, talc, and calcium carbonate. These may be used alone or in combination of two or more. The rubber composition according to the present invention preferably contains silica from the viewpoint of improving hardness.

[0071] A rubber composition according to one embodiment of the present invention may contain 20 to 80 parts by mass, and preferably 35 to 65 parts by mass, of a filler / reinforcing material or silica, based on 100 parts by mass of rubber contained in the rubber composition. The content of the filler / reinforcing material or silica may be, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80 parts by mass, or may be within a range between any two of the values ​​exemplified here. The rubber composition according to one embodiment of the present invention can further improve the hardness of the vulcanizate and vulcanized molded article by containing a filler / reinforcing material, particularly silica, in the above-mentioned range.

[0072] 1.9 Silane coupling agents The rubber composition according to one embodiment of the present invention may contain a silane coupling agent. The silane coupling agent is not particularly limited, and those used in commercially available rubber compositions can be used, such as vinyl coupling agents, epoxy coupling agents, styryl coupling agents, methacrylic coupling agents, acrylic coupling agents, amino coupling agents, polysulfide coupling agents, and mercapto coupling agents. In particular, from the viewpoint of scorch resistance and reinforcing effect, vinyl coupling agents, methacrylic coupling agents, and acrylic coupling agents are preferred, as they initiate reaction under high temperature conditions during crosslinking.

[0073] Specific examples of the silane coupling agent include bis-(3-triethoxysilylpropyl)tetrasulfide, bis-(3-trimethoxysilylpropyl)tetrasulfide, bis-(3-methyldimethoxysilylpropyl)tetrasulfide, bis-(2-triethoxysilylethyl)tetrasulfide, bis-(3-triethoxysilylpropyl)disulfide, bis-(3-trimethoxysilylpropyl)disulfide, bis-(3-triethoxysilylpropyl)trisulfide, 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, and 2-decanoylthioethyltriethoxysilane. Silane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 3-trimethoxysilylpropyl-N,Examples of suitable silanes include N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-trimethoxysilylpropyl methacryloyl monosulfide, methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, trimethylethoxysilane, trimethylmethoxysilane, isobutyltrimethoxysilane, n-decyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, hexyltrimethoxysilane, octadecylmethyldimethoxysilane, octadecyltrimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, triphenylchlorosilane, heptadecafluorodecylmethyldichlorosilane, heptadecafluorodecyltrichlorosilane, and triethylchlorosilane.

[0074] A rubber composition according to one embodiment of the present invention may contain 0.5 to 10 parts by mass of a silane coupling agent when the rubber contained in the rubber composition is 100 parts by mass, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. By including the above-mentioned silane coupling agent and by keeping the content of the silane coupling agent within the above-mentioned range, it is possible to improve the dispersibility of the silica filler in the rubber and the reinforcing effect between the rubber and the epoxy compound and the silica filler, and also to suppress the occurrence of scorch.

[0075] 1.10 Lubricants and processing aids The rubber composition of the present invention may further contain a lubricant or processing aid. Lubricants and processing aids are added primarily to improve processability, such as by making the rubber composition easier to release from rolls, molding dies, extruder screws, etc. Examples of lubricants and processing aids include fatty acids such as stearic acid, paraffin-based processing aids such as polyethylene, fatty acid amides, petrolatum, and factice. These may be used alone or in combination of two or more. The rubber composition of the present invention may contain 1 to 15 parts by mass of lubricant or processing aid, or may be 1 to 10 parts by mass, per 100 parts by mass of rubber contained in the rubber composition. The content of the lubricant or processing aid may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, or may be within a range between any two of the values ​​exemplified herein.

[0076] 1.11 Vulcanization accelerators The rubber composition according to the present invention may contain a vulcanization accelerator, and may contain 0.3 to 5.0 parts by mass of the vulcanization accelerator when the rubber contained in the rubber composition is taken as 100 parts by mass. The content of the vulcanization accelerator is, for example, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass, and may be within a range between any two of the values ​​exemplified here. The rubber composition according to the present invention may also be one which does not contain a vulcanization accelerator.

[0077] The type of vulcanization accelerator is not particularly limited as long as it does not impair the effects of the present invention. The vulcanization accelerator is preferably a vulcanization accelerator that can be used for vulcanizing chloroprene-based rubber. One or more vulcanization accelerators can be freely selected and used. Examples of the vulcanization accelerator include thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, and thiazole-based accelerators.

[0078] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, and dipentamethylenethiuram tetrasulfide. Examples of dithiocarbamate vulcanization accelerators include sodium dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, and tellurium diethyldithiocarbamate. Examples of thiourea vulcanization accelerators include thiourea compounds such as ethylene thiourea, diethyl thiourea (N,N'-diethyl thiourea), trimethyl thiourea, diphenyl thiourea (N,N'-diphenyl thiourea), and 1,3-trimethylene-2-thiourea. Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salts of dicatechol borate. Examples of xanthogenate-based vulcanization accelerators include zinc butylxanthogenate and zinc isopropylxanthogenate. Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, 2-mercaptobenzothiazole zinc salt, cyclohexylamine salt of 2-mercaptobenzothiazole, 2-(4'-morpholinodithio)benzothiazole, and N-cyclohexylbenzothiazole-2-sulfenamide. These may be used alone or in combination of two or more.

[0079] 1.12 Other In addition to the above-mentioned components, the rubber composition according to the present invention may further contain components such as an antioxidant, an antioxidant, and a flame retardant, within a range that does not impair the effects of the present invention. Examples of antioxidants and antioxidants include ozone antioxidants, phenolic antioxidants, amine antioxidants, acrylate antioxidants, imidazole antioxidants, carbamic acid metal salts, waxes, phosphorus antioxidants, sulfur antioxidants, etc. Examples of imidazole antioxidants include 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and zinc salt of 2-mercaptobenzimidazole. The rubber composition according to the present invention may contain 0.1 to 10 parts by mass of an antioxidant and an antioxidant, based on 100 parts by mass of the rubber contained in the rubber composition.

[0080] 2.Method for producing rubber composition The rubber composition according to one embodiment of the present invention can be obtained by kneading a chloroprene rubber, an epoxy compound, and other necessary components at a temperature equal to or lower than the vulcanization temperature. Examples of the device for kneading the raw material components include conventionally known kneading devices such as a mixer, a Banbury mixer, a kneader mixer, and an open roll.

[0081] 3. Rubber composition characteristics The rubber composition according to one embodiment of the present invention preferably has a scorch time of 7 minutes or more, more preferably 9 minutes or more, and even more preferably 11 minutes or more, as measured by a Mooney scorch test at 125°C in accordance with JIS K 6300-1. The scorch time may be, for example, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 minutes, or may be within a range between any two of the values ​​exemplified herein.

[0082] In the rubber composition according to one embodiment of the present invention, the vulcanizate obtained by molding in accordance with JIS K6299 preferably has a Type A durometer hardness measured in accordance with JIS K6253 of 80 or more, more preferably 85 or more, and even more preferably 90 or more. The Type A durometer hardness may be, for example, 80, 85, 90, 95, or 100, or may be within a range between any two of the values ​​exemplified here.

[0083] In a rubber composition according to one embodiment of the present invention, the tensile strength of a vulcanizate obtained by molding in accordance with JIS K6299, as measured in accordance with JIS K6251, is preferably 21 MPa or more, more preferably 23 MPa or more, and even more preferably 25 MPa or more. The tensile strength may be, for example, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 MPa, and may be within a range between any two of the values ​​exemplified here.

[0084] In a rubber composition according to one embodiment of the present invention, the T10 of a vulcanizate obtained by vulcanizing the rubber composition according to JIS K6299, as determined by a Gehman torsion test based on JIS K6261, is preferably less than −10° C., more preferably less than −20° C., and even more preferably less than −30° C. T10 may be, for example, −40, −35, −30, −25, −20, −15, or −10° C., and may be within a range between any two of the values ​​exemplified here.

[0085] 4. Unvulcanized molded products, vulcanized products, and vulcanized molded products The unvulcanized molded article according to this embodiment uses the rubber composition according to this embodiment, and is a molded article (molded product) of the rubber composition (unvulcanized state) according to this embodiment. The method for producing the unvulcanized molded article according to this embodiment includes a step of molding the rubber composition (unvulcanized state) according to this embodiment. The unvulcanized molded article according to this embodiment is made of the rubber composition (unvulcanized state) according to this embodiment.

[0086] The vulcanizate according to the present embodiment is a vulcanizate of the rubber composition according to the present embodiment. The method for producing the vulcanizate according to the present embodiment includes a step of vulcanizing the rubber composition according to the present embodiment.

[0087] The vulcanization molded article according to this embodiment is a vulcanization molded article of the rubber composition according to this embodiment. The vulcanization molded article according to this embodiment uses the vulcanizate according to this embodiment and is a molded article (molded product) of the vulcanizate according to this embodiment. The vulcanization molded article according to this embodiment is made of the vulcanizate according to this embodiment.

[0088] The vulcanized molded article according to this embodiment can be obtained by molding a vulcanized product obtained by vulcanizing the rubber composition according to this embodiment (unvulcanized state), and can also be obtained by vulcanizing a molded article obtained by molding the rubber composition according to this embodiment (unvulcanized state). The vulcanized molded article according to this embodiment can be obtained by vulcanizing the rubber composition according to this embodiment after molding or during molding. The method for producing the vulcanized molded article according to this embodiment includes a step of molding the vulcanized product according to this embodiment, or a step of vulcanizing the unvulcanized molded article according to this embodiment.

[0089] The unvulcanized molded article, vulcanized product, and vulcanized molded article according to this embodiment can be used as rubber parts in various industrial fields, such as buildings, structures, ships, railways, coal mines, and automobiles. The rubber composition according to this embodiment has excellent processability due to a sufficiently long scorch time of the unvulcanized product, and has a well-balanced hardness, tensile strength, and cold resistance of the vulcanized product, so it can be used as a variety of components requiring these properties. The rubber composition according to one embodiment of the present invention can be used as rubber parts in various industrial fields, such as buildings, structures, ships, railways, coal mines, and automobiles, and can be used as rubber parts such as automotive rubber components (e.g., automotive seals), hose materials, rubber molds, gaskets, rubber rolls, industrial cables, industrial conveyor belts, and sponges. The rubber composition according to one embodiment of the present invention is particularly suitable for use as a rubber roll, from the viewpoint of its high hardness.

[0090] (rubber components for automobiles) Automotive rubber components include gaskets, oil seals, and packings, which are used to prevent the leakage of liquids and gases and the intrusion of debris and foreign objects such as rainwater and dust into machinery and equipment. Specifically, there are gaskets used for fixed applications and oil seals and packings used for moving parts. Gaskets with sealed components fixed with bolts or other fasteners are made of various materials depending on the purpose, as opposed to soft gaskets such as O-rings and rubber sheets. Packings are also used for rotating parts such as pump and motor shafts, moving parts of valves, reciprocating parts such as pistons, coupler connections, and water stop parts of water faucets. The rubber composition of the present invention can increase the tensile strength and hardness of these components. This makes it possible to manufacture seals for high-load applications, which was previously difficult to achieve with conventional rubber compositions.

[0091] (hose material) Hose materials are flexible pipes, and specific examples include high- and low-pressure hoses for water, oil, air, steam, and hydraulic systems. The rubber composition of the present invention can increase the tensile strength of hose materials. This makes it possible to produce hose materials for use in high-load applications, which was difficult with conventional rubber compositions.

[0092] (rubber mold) Rubber molded products include vibration-isolating rubber, vibration-damping materials, boots, etc. Vibration-isolating rubber and vibration-damping materials are rubbers that prevent the transmission and spread of vibrations, and specific examples include torsional dampers, engine mounts, muffler hangers, etc. that absorb vibrations and prevent noise when the engine of an automobile or various vehicles is running. The rubber composition of the present invention can increase the tensile strength of vibration-isolating rubber and vibration-damping materials. This makes it possible to produce vibration-isolating rubber and vibration-damping materials that can be used in high-load applications, which was difficult with conventional rubber compositions. A boot is a bellows-shaped member whose outer diameter gradually increases from one end to the other, and specific examples include boots for constant velocity joint covers, boots for ball joint covers (dust cover boots), and boots for rack and pinion gears, which are used to protect drive parts such as those in automobile drive systems. The rubber composition of the present invention can increase the tensile strength of boots. This makes it possible to produce boots that can be used in applications where higher loads are applied than with conventional rubber compositions.

[0093] (gaskets, etc.) Gaskets, oil seals, and packings are components used in machinery and equipment to prevent the leakage of liquids and gases and the intrusion of debris and foreign objects such as rainwater and dust. Specifically, there are gaskets used for fixed applications and oil seals and packings used for moving parts. Gaskets whose sealing parts are fixed with bolts or other fasteners are made of various materials depending on the purpose, as opposed to soft gaskets such as O-rings and rubber sheets. Packings are also used for rotating parts such as pump and motor shafts, moving parts of valves, reciprocating parts such as pistons, coupler connections, and water stop parts of water faucets. The rubber composition of the present invention can increase the tensile strength and hardness of these components. This makes it possible to manufacture seals that can be used in high-load applications, which was previously difficult with conventional rubber compositions.

[0094] (rubber roll) Rubber rolls are manufactured by adhesively coating a metal core, such as an iron core, with rubber, and are generally manufactured by spirally winding a rubber sheet around a metal iron core. Rubber materials such as NBR, EPDM, and CR are used for rubber rolls depending on the required characteristics for various applications, such as papermaking, various metal manufacturing, film manufacturing, printing, general industrial use, agricultural machinery such as rice hullers, and food processing. CR has good mechanical strength that can withstand friction from the objects being conveyed, making it widely used in rubber roll applications. However, rubber rolls used in oily environments, such as during the manufacture of industrial materials and products for steelmaking and papermaking, lack sufficient oil resistance, and improvements are needed. Furthermore, products may be exposed to acids and alkalis during plating processes, such as gold, silver, nickel, chromium, and zinc, and resistance to these is also required. Furthermore, rubber rolls used to convey heavy loads have the problem of deformation under load, and improvements are needed. The rubber composition of the present invention can increase the tensile strength and hardness of rubber rolls. This makes it possible to produce a rubber roll that can be used under high tension, which was difficult to do with conventional rubber compositions.

[0095] (Industrial Cables) Industrial cables are linear components for transmitting electrical or optical signals. They are made by covering a good conductor such as copper or a copper alloy, or an optical fiber, with an insulating coating layer, and a wide variety of industrial cables are manufactured depending on their structure and installation location. The rubber composition of the present invention can increase the tensile strength of industrial cables. This makes it possible to manufacture industrial cables that can be used in high-load applications, which was difficult with conventional rubber compositions.

[0096] (industrial conveyor belts) Industrial conveyor belts are made of rubber, resin, and metal, and are selected to suit a wide variety of uses. Among these, rubber conveyor belts are inexpensive and widely used, but when used in environments where there is a lot of friction and collision with the conveyed materials, they have been prone to damage due to deterioration. The rubber composition of the present invention can increase the tensile strength of industrial conveyor belts. This makes it possible to produce industrial conveyor belts that can be used in high-load environments, which was difficult with conventional rubber compositions.

[0097] (sponge) Sponges are porous materials with countless fine pores inside, and are specifically used in vibration-damping materials, sponge sealing parts, wetsuits, shoes, etc. The rubber composition of the present invention can increase the tensile strength of the sponge. Furthermore, the use of chloroprene-based rubber can also increase the flame retardancy of the sponge. This makes it possible to produce sponges that can be used under high tension, which was difficult with conventional rubber compositions, and sponges with excellent flame retardancy. Furthermore, the hardness of the resulting sponge can be appropriately adjusted by adjusting the content of the foaming agent, etc.

[0098] Methods for molding the rubber composition (unvulcanized state) and vulcanizate according to this embodiment include press molding, extrusion molding, calendar molding, etc. The temperature for vulcanizing the rubber composition may be appropriately set depending on the composition of the rubber composition, and may be 140 to 220°C, or 160 to 190°C. The vulcanization time for vulcanizing the rubber composition may be appropriately set depending on the composition of the rubber composition, the shape of the unvulcanized molded product, etc., and may be 10 to 60 minutes. [Example]

[0099] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0100] <Method for producing chloroprene rubber A-2> A 3-L polymerization vessel equipped with a heating / cooling jacket and a stirrer was charged with 24 parts by weight of chloroprene (monomer), 24 parts by weight of acrylonitrile (monomer), 0.5 parts by weight of diethylxanthogen disulfide, 200 parts by weight of purified water, 5.00 parts by weight of potassium rosinate (Harima Chemicals Co., Ltd.), 0.40 parts by weight of sodium hydroxide, and 2.0 parts by weight of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation). Next, 0.1 parts by weight of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40°C under a nitrogen gas flow. The chloroprene was added in portions starting 20 seconds after the start of polymerization. The portion-by-portion addition flow rate was adjusted with a solenoid valve based on the change in the heat content of the refrigerant over the first 10 seconds of polymerization. The flow rate was then readjusted every 10 seconds thereafter for continuous polymerization. When the polymerization rate relative to the total amount of chloroprene and acrylonitrile reached 50%, 0.02 parts by mass of a polymerization terminator, phenothiazine, was added to terminate the polymerization. Thereafter, unreacted monomers in the reaction solution were removed under reduced pressure to obtain chloroprene-based latex A-2 containing a chloroprene-acrylonitrile copolymer.

[0101] The above-mentioned conversion rate [%] of the chloroprene latex was calculated from the dry mass of the air-dried chloroprene latex. Specifically, it was calculated using the following formula (A). In the formula, "solids concentration" refers to the concentration [mass %] of the solids obtained by heating 2 g of a sample of chloroprene latex at 130°C and removing volatile components such as the solvent (water), volatile chemicals, and raw materials. "Total charge amount" refers to the total amount [g] of raw materials, reagents, and solvent (water) charged into the polymerization vessel from the start of polymerization to a certain time. "Evaporation residue" refers to the mass [g] of chemicals and raw materials charged from the start of polymerization to a certain time that do not volatilize under conditions of 130°C and remain as solids together with the polymer. "Monomer charge amount" refers to the sum [g] of the amount of monomer initially charged into the polymerization vessel and the amount of monomer added in portions from the start of polymerization to a certain time. Note that "monomer" here refers to the total amount of chloroprene and acrylonitrile. Conversion rate = {[(total charge amount × solid concentration / 100) - evaporation residue] / charge amount of monomer} × 100 (A)

[0102] The pH of the chloroprene latex A-2 was adjusted to 7.0 using acetic acid or sodium hydroxide, and the chloroprene latex was demulsified by freezing and coagulating it on a metal plate cooled to -20°C to obtain a sheet. The sheet was washed with water and then dried at 130°C for 15 minutes to obtain a solid chloroprene rubber A-2.

[0103] The chloroprene rubber was dissolved in THF to a concentration of 0.1% by mass, and the weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the chloroprene rubber were measured (based on standard polystyrene standards) using a high-performance GPC system (TOSOH HLC-8320GPC, manufactured by Tosoh Corporation). A TSK guard column HHR-H was used as a precolumn, and three HSKgel GMHHR-H analytical columns were used. The sample was pumped at a pressure of 8.0 to 9.5 MPa, a flow rate of 1 mL / min, and 40°C, and detected with a differential refractometer.

[0104] The elution time and molecular weight were obtained using a calibration curve prepared by measuring nine standard polystyrene samples with known molecular weights listed below. Mw = 8.42 × 10 6 , 1.09×10 6 , 7.06×10 5 , 4.27×10 5 , 1.90×10 5 , 9.64 x 10 4 , 3.79 × 10 4 , 1.74×10 4 , 2.63 × 10 3

[0105] The weight average molecular weight (Mw) of chloroprene rubber is 473 x 10 3 g / mol, and the number average molecular weight (Mn) is 138 × 10 3 g / mol, and the molecular weight distribution (Mw / Mn) was 3.4.

[0106] The content of acrylonitrile monomer units contained in the chloroprene-based rubber A-2 was calculated from the content of nitrogen atoms in the chloroprene-acrylonitrile copolymer rubber. Specifically, using an elemental analyzer (Sumigraph 220F, manufactured by Sumika Chemical Analysis Center Co., Ltd.), the content of nitrogen atoms in 100 mg of the chloroprene-based rubber A-2 was measured, and the content of acrylonitrile monomer units was calculated. The content of acrylonitrile monomer units was 10.0 mass%.

[0107] The above elemental analysis was performed as follows. The electric furnace temperatures were set to 900°C for the reactor, 600°C for the reduction furnace, 70°C for the column, and 100°C for the detector. Oxygen gas was flowed at 0.2 mL / min as the combustion gas, and helium gas was flowed at 80 mL / min as the carrier gas. A calibration curve was created using aspartic acid (10.52%), which has a known nitrogen content, as the standard substance. The chloroprene rubber A-2 obtained by the above production method had an acrylonitrile monomer unit content of 10.0% by mass.

[0108] <Production Method of Chloroprene Rubbers A-1, A-3 to A-5> The amount of acrylonitrile monomer added in the polymerization process was changed to obtain chloroprene rubber A-1, in which the acrylonitrile monomer unit content in the chloroprene rubber is 5.0 mass%, chloroprene rubber A-3, in which the acrylonitrile monomer unit content is 15.0 mass%, chloroprene rubber A-4, in which the acrylonitrile monomer unit content is 20.0 mass%, and chloroprene rubber A-5, in which the acrylonitrile monomer unit content is 25.0 mass%.

[0109] <Preparation of Rubber Composition> The components were mixed as shown in Tables 1 and 2 and kneaded with an 8-inch open roll to obtain rubber compositions of Examples and Comparative Examples.

[0110] The components used to obtain the rubber composition are as follows: Chloroprene rubber: The above-mentioned chloroprene rubber A-1 (chloroprene-acrylonitrile copolymer AN (acrylonitrile monomer unit) content 5% by mass), Chloroprene rubber A-2 (chloroprene-acrylonitrile copolymer AN content 10% by mass), Chloroprene rubber A-3 (chloroprene-acrylonitrile copolymer AN content 20% by mass), Chloroprene rubber A-4 (chloroprene-acrylonitrile copolymer AN content 25% by mass), Chloroprene rubber A-5 (mercaptan-modified chloroprene rubber (chloroprene homopolymer), "S-40V" manufactured by Denka Co., Ltd.) Reactive plasticizer: Epoxy compound A (molecular weight 700), 4,5-epoxycyclohexane-1,2-dicarboxylic acid di(9,10-epoxystearyl), New Japan Chemical Co., Ltd., Sanso Cizer E-PO Reactive plasticizer: Epoxy compound B (molecular weight 370), condensation product of bisphenol A and epichlorohydrin, manufactured by Mitsubishi Chemical Corporation, JER-828 Reactive plasticizer: Epoxy compound C (molecular weight 250), 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, Daicel Corporation, Celloxide 2021P Reactive plasticizer: Epoxy compound D (molecular weight 125), 1-vinyl-3,4-epoxycyclohexane, Daicel Corporation, Celloxide 2000 Reactive plasticizer: Epoxy compound E (molecular weight Mw≧900), epoxy group-containing polybutadiene rubber, Nippon Soda Co., Ltd., JP-100 Plasticizer: Ether ester compound, manufactured by ADEKA Corporation, Adeka Cizer RS-700, Filler: Carbon black (HAF), Asahi Carbon Co., Ltd. "Asahi #70" Filler: Silica, Tosoh Silica Corporation, Nipsil AQ Silane coupling agent: methacryloxypropyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd., KBM-503 Hydrotalcite: Chemical formula Mg 4.3 Al2(OH)12.6 CO3·3.5H2O, Kyowa Chemical Industry Co., Ltd., DHT-4A Processing aid: Stearic acid: New Japan Chemical Co., Ltd., Stearic acid 50S Zinc oxide: Sakai Chemical Industry Co., Ltd., zinc oxide type 2 Organic peroxide: 1,4-bis[(t-butylperoxy)isopropyl]benzene, NOF Corporation, Perbutyl P Heat-resistant anti-aging agent: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, Ouchi Shinko Chemical Industry Co., Ltd., Nocrac CD Hardener: Carboxylic acid dihydrazide, Otsuka Chemical Co., Ltd., Isophthalic acid dihydrazide

[0111] When 5 parts by mass of carboxylic acid dihydrazide was added to 100 parts by mass of epoxy compound B, the gelation time was 28 minutes at 160° C. Furthermore, when 5 parts by mass of carboxylic acid dihydrazide was added to 100 parts by mass of epoxy compounds A to D used in the examples, it was confirmed that the compounds cured within 40 minutes.

[0112] <Evaluation of rubber composition (unvulcanized)> (Scorch Time) A Mooney scorch test was carried out using an L-type rotor at a test temperature of 125°C in accordance with JIS K 6300-1. The time required for the measured Mooney viscosity to increase by 5M was taken as the scorch time. The obtained scorch time was evaluated according to the following criteria. A: 11 minutes or more B: 9 minutes or more, less than 11 minutes C: 7 minutes or more, less than 9 minutes D: Less than 7 minutes

[0113] <Preparation of vulcanized molded body> The obtained rubber composition was press-vulcanized under conditions of 160°C x 40 minutes in accordance with JIS K6299 to produce a vulcanized molded sheet having a thickness of 2 mm.

[0114] <Evaluation of vulcanized molded products> The vulcanized molded articles were evaluated as follows. The results are shown in Tables 1 and 2.

[0115] (tensile strength) Based on JIS K 6251, the above-mentioned vulcanized molded sheet was molded into 2 mm thick dumbbell-shaped No. 3 test pieces, and five test pieces were prepared. The tensile strength of each test piece was measured at a tension speed of 500 mm / min using a long stroke tensile testing system for vulcanized rubber manufactured by Shimadzu Corporation. The obtained tensile strength was evaluated according to the following criteria. A:25MPa or more B: 23MPa or more, less than 25MPa C: 21 MPa or more, less than 23 MPa D: Less than 21 MPa

[0116] (Hardness (Type A durometer)) The above-mentioned sheet-like vulcanized molded article was measured for durometer hardness (Type A) as defined in JIS K 6253 using an Asker Rubber Hardness Tester Type A (Kobunshi Keiki Co., Ltd.). The obtained hardness was evaluated according to the following evaluation criteria (for details of durometer hardness measurement, see JIS K 6253-3). A: 90 or above B: 85 or above, less than 90 C: 80 or more, less than 85 D: Under 80

[0117] (cold resistance) Gehman torsion test was carried out based on JIS K 6261 to determine T10. For the above vulcanized molded article, the temperature (T10) at which the 180° torsion modulus became 10 times the 180° torsion modulus at room temperature was determined. The obtained T10 was evaluated according to the following criteria. A: Below -30°C B: -30℃ or higher, below -20℃ C: -20℃ or higher, below -10℃ D: -10℃ or more

[0118] [Table 1]

[0119]

Table 2

Claims

1. A rubber composition comprising a chloroprene rubber having an unsaturated nitrile monomer unit content of less than 25 mass % and an epoxy compound having a weight average molecular weight of more than 100 and less than 900, the rubber composition contains 0.1 to 25 parts by mass of the epoxy compound per 100 parts by mass of the chloroprene rubber, The rubber composition includes a metal oxide, an organic peroxide, and hydrotalcite, the rubber composition contains 0.3 to 1.8 parts by mass of the organic peroxide per 100 parts by mass of the chloroprene rubber, the rubber composition contains 1 to 6 parts by mass of the hydrotalcite per 100 parts by mass of the chloroprene rubber, the rubber composition is molded in accordance with JIS K6299 to produce a vulcanizate, which has a tensile strength of 21 MPa or more as measured in accordance with JIS K 6251; Rubber composition.

2. 2. The rubber composition according to claim 1, wherein the unsaturated nitrile monomer is acrylonitrile.

3. 2. The rubber composition according to claim 1, wherein the epoxy compound is at least one epoxy compound selected from the group consisting of an alicyclic epoxy compound, an epoxy resin composed of a copolymer of epichlorohydrin and bisphenol, and an epoxidized unsaturated fatty acid ester.

4. The rubber composition according to claim 1, further comprising 20 to 80 parts by mass of a filler relative to 100 parts by mass of the chloroprene rubber.

5. The rubber composition according to claim 1, further comprising 5 parts by mass or more of a curing agent relative to 100 parts by mass of the epoxy compound.

6. 2. The rubber composition according to claim 1, wherein a vulcanizate obtained by molding the rubber composition in accordance with JIS K6299 has a type A durometer hardness of 80 or more as measured in accordance with JIS K6253.

7. A vulcanizate of the rubber composition according to claim 1.

8. A vulcanized molded article using the vulcanizate according to claim 7.

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