Rubber composition, vulcanizate, and vulcanized molded article

Abstract

Provided is a rubber composition with which it is possible to obtain a vulcanizate and a vulcanized molded body that is exceptional in terms of both elongation at break and compression permanent set after heating. According to the present invention, there is provided a rubber composition containing 100 parts by mass of chloroprene rubber, 2-100 parts by mass of silica having a BET specific surface area of 10-120 m2 / g, 0.1-8 parts by mass of a maleimide compound, 0.1-5 parts by mass of an organic peroxide, and 1-15 parts by mass of a silane coupling agent per 100 parts by mass of the silica.

Description

[Technical Field]

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

[0002] Chloroprene rubber has excellent mechanical strength, weather resistance, chemical resistance, heat resistance, cold resistance, and oil resistance, and is therefore widely used as a material for general industrial transmission belts and conveyor belts, automotive air springs, vibration-proof rubber, hoses, wipers, immersion products, sealing parts, adhesives, boots, rubber-coated fabric, rubber rolls, and more.

[0003] For example, Patent Document 1 discloses a rubber composition containing 100 parts by mass of chloroprene rubber, 20 to 80 parts by mass of silica filler, 0.5 to 4 parts by mass of a maleimide compound, and 0.1 to 3 parts by mass of an organic peroxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-95493 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional chloroprene-based rubber compositions have room for improvement in the heat resistance and compression set of vulcanized molded articles of the rubber composition containing the chloroprene-based rubber. Specifically, it has been difficult to obtain a rubber composition that can give vulcanizates and vulcanized molded articles that are excellent in both elongation at break and compression set after heating.

[0006] The present invention has been made in view of the above circumstances, and provides a rubber composition from which a vulcanizate and a vulcanized molded article can be obtained that are excellent in both elongation at break and compression set after heating. [Means for solving the problem]

[0007] According to the present invention, a mixture of 100 parts by mass of chloroprene rubber and a rubber composition having a BET specific surface area of ​​10 to 120 m 2 The rubber composition contains 2 to 100 parts by mass of silica having a viscosity of 10 ...

[0008] The present inventors have conducted extensive research and have found that the rubber composition contains 100 parts by mass of chloroprene rubber and a rubber composition having a BET specific surface area of ​​10 to 120 m 2 The present inventors have found that by blending 2 to 100 parts by mass of silica having a viscosity of 1 / g, 0.1 to 8 parts by mass of a maleimide compound, 0.1 to 5 parts by mass of an organic peroxide, and 1 to 15 parts by mass of a silane coupling agent per 100 parts by mass of the silica, it is possible to obtain a rubber composition from which a vulcanizate and a vulcanized molded article excellent in both elongation at break and compression set after heating can be obtained, and have thus completed the present invention.

[0009] According to another aspect of the present invention, there is provided a vulcanizate of the rubber composition described above. According to another aspect of the present invention, there is provided a vulcanized molded article of the above-described rubber composition. Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other.

[0010] [1] A rubber composition comprising 100 parts by mass of chloroprene rubber, 2 to 100 parts by mass of silica having a BET specific surface area of ​​10 to 120 m / g, 0.1 to 8 parts by mass of a maleimide compound, 0.1 to 5 parts by mass of an organic peroxide, and 1 to 15 parts by mass of a silane coupling agent relative to 100 parts by mass of the silica. [2] The rubber composition according to [1], wherein the chloroprene-based rubber comprises a homopolymer of 2-chloro-1,3-butadiene or a copolymer of 2-chloro-1,3-butadiene and at least one monomer selected from 2,3-dichloro-1,3-butadiene and an unsaturated nitrile monomer. [3] The rubber composition according to [1] or [2], wherein the silane coupling agent comprises at least one selected from a silane coupling agent having a double bond in its structure, a silane coupling agent having an amino group, and a silane coupling agent having a double bond and an amino group. [4] The rubber composition according to any one of [1] to [3], wherein the silane coupling agent is at least one silane coupling agent selected from vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. [5] The rubber composition according to any one of [1] to [4], further comprising 0.1 to 20 parts by mass of a hydrotalcite compound per 100 parts by mass of the chloroprene rubber. [6] The maleimide compound is N,N'-o-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-(4,4'-diphenylmethane) bismaleimide, 2,2-bis-[4-(4-maleimidophenoxy)phenyl]propane, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, N,N'-( 4-methyl-1,3-phenylene ) Bismaleimide, 1, 6- The rubber composition according to any one of [1] to [5], wherein the maleimide compound is at least one selected from bismaleimide-(2,2,4-trimethyl)hexane. [7] The rubber composition according to any one of [1] to [6], wherein the organic peroxide is at least one organic peroxide selected from dicumyl peroxide, 1,4-bis[(t-butylperoxy)isopropyl]benzene, tert-butyl-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne, and 4,4-bis[(t-butyl)peroxy]butyl pentanoate. [8] The rubber composition according to any one of [1] to [7], further comprising 1 to 30 parts by mass of a compound having a thioether structure per 100 parts by mass of the chloroprene rubber. [9] A vulcanizate of the rubber composition according to any one of [1] to [8].

[10] A vulcanized molded article of the rubber composition according to any one of [1] to [8]. [Effects of the Invention]

[0011] The rubber composition according to the present invention can provide a vulcanizate and a vulcanized molded article that are excellent in both elongation at break and compression set after heating. Furthermore, the obtained vulcanizate and vulcanized molded article can be used to their full potential as various components that require excellent heat resistance and / or excellent compression set, and are particularly suitable for use as sealing materials, gaskets, packings, etc. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] 1. Rubber composition The rubber composition according to the present invention comprises 100 parts by mass of chloroprene rubber and a rubber composition having a BET specific surface area of ​​10 to 120 m 2 The rubber composition according to the present invention contains 2 to 100 parts by mass of silica having a molecular weight of 1 / g, 0.1 to 8 parts by mass of a maleimide compound, 0.1 to 5 parts by mass of an organic peroxide, and 1 to 15 parts by mass of a silane coupling agent per 100 parts by mass of the silica. The rubber composition according to the present invention is a rubber composition from which a vulcanizate and a vulcanized molded article excellent in both elongation at break and compression set after heating can be obtained.

[0014] 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 (monomer unit = 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.

[0015] 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.

[0016] A chloroprene-based rubber according to one embodiment of the present invention may contain a homopolymer of 2-chloro-1,3-butadiene (hereinafter referred to as chloroprene), or a copolymer of 2-chloro-1,3-butadiene and at least one monomer selected from 2,3-dichloro-1,3-butadiene and an unsaturated nitrile monomer. The chloroprene-based rubber according to one embodiment of the present invention may be made of a rubber containing a homopolymer of chloroprene and a copolymer of chloroprene and at least one monomer selected from 2,3-dichloro-1,3-butadiene and an unsaturated nitrile monomer, or may be made of a rubber containing a homopolymer of chloroprene, or may be made of a rubber containing a copolymer of chloroprene and at least one monomer selected from 2,3-dichloro-1,3-butadiene and an unsaturated nitrile monomer.

[0017] A chloroprene-based rubber according to one embodiment of the present invention may contain a copolymer containing 2,3-dichloro-1,3-butadiene monomer units and monomer units derived from an unsaturated nitrile monomer. When the chloroprene-based rubber according to one embodiment of the present invention is taken as 100% by mass, the total content of the 2,3-dichloro-1,3-butadiene monomer units and the unsaturated nitrile monomer units may be less than 25% by mass, and is preferably 1% by mass or more and less than 25% by mass. The content of 2,3-dichloro-1,3-butadiene monomer units and unsaturated nitrile monomer units in the chloroprene 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 mass%, less than 25 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0018] The chloroprene-based rubber according to one embodiment of the present invention preferably contains a copolymer containing monomer units derived from an unsaturated nitrile monomer. The content of the 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 setting the content of the unsaturated nitrile monomer units to less than 25% by mass, the resulting rubber composition has sufficient cold resistance. In particular, by setting the content of the unsaturated nitrile monomer units to 1% by mass or more, the resulting rubber composition has sufficient oil resistance, and a vulcanized molded article having an excellent balance between tensile strength and cold resistance can be obtained.

[0019] 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.

[0020] 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.

[0021] The chloroprene rubber according to one embodiment of the present invention preferably contains 60 to 100% by mass of chloroprene monomer units, assuming the chloroprene rubber to be 100% by mass. The content of chloroprene monomer units in the rubber may be, 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.

[0022] The chloroprene-based rubber according to one embodiment of the present invention may also have a monomer unit other than the chloroprene monomer, 2,3-dichloro-1,3-butadiene monomer, and unsaturated nitrile monomer. The monomer unit other than the chloroprene monomer, 2,3-dichloro-1,3-butadiene monomer, and unsaturated nitrile monomer is not particularly limited as long as it is copolymerizable with the chloroprene monomer, 2,3-dichloro-1,3-butadiene monomer, and unsaturated nitrile monomer. Examples of the monomer unit other than the chloroprene monomer, 2,3-dichloro-1,3-butadiene monomer, and unsaturated nitrile monomer include (meth)acrylic acid esters (e.g., methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate), hydroxyalkyl (meth)acrylates (e.g., 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate), 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, and sulfur.

[0023] 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 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.

[0024] 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 total content of unsaturated nitrile monomer units and 2,3-dichloro-1,3-butadiene contained in the two or more types of chloroprene-based rubbers contained in the rubber composition is less than 25 mass%.

[0025] 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.

[0026] 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 and, as necessary, monomers including 2,3-dichloro-1,3-butadiene and an unsaturated nitrile monomer are emulsion-polymerized using an emulsifier, a dispersant, a catalyst, a chain transfer agent, and the like, appropriately, 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.

[0027] 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.

[0028] 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).

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 1.3 Silica The rubber composition according to the present invention is a rubber composition having a BET specific surface area of ​​10 to 120 m per 100 parts by mass of chloroprene rubber. 2 The rubber composition contains 2 to 100 parts by mass of silica having a hydroxyl group content of 1 / g. Silica is generally added to rubber compositions as a filler. Silica forms a covalent bond with the chloroprene polymer via surface functional groups (e.g., OH groups) present on the surface of the silica and a silane coupling agent. This is thought to result in a stronger binding of the chloroprene polymer than with other fillers such as carbon, improving elasticity and compression set.

[0035] Although not particularly limited, examples of silica that can be used include wet silica filler (hydrated silicic acid), dry silica filler (anhydrous silicic acid), and colloidal silica filler, with wet silica filler being preferred. Surface-unmodified silica can also be used as silica. Surface-modified silica can also be used as silica.

[0036] The silica contained in the rubber composition according to the present invention has a BET specific surface area of ​​10 to 120 m 2The BET specific surface area is, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 m 2 / g, and may be within a range between any two of the values ​​exemplified herein. By controlling the BET specific surface area of ​​the silica within a specific range, the rubber composition according to the present invention can produce vulcanizates and vulcanized molded articles that are excellent in both elongation at break and compression set after heating. By controlling the BET specific surface area of ​​the silica to be equal to or less than the above upper limit, the number of surface functional groups present on the silica surface per unit mass is defined, which is presumably because the specific surface functional groups (e.g., OH groups) present on the silica surface increase the reactivity with chloroprene-based rubber during heating, reduce the compatibility between silica and chloroprene-based rubber, and suppress aggregation of silica particles. Furthermore, by controlling the BET specific surface area of ​​the silica to be equal to or less than the above upper limit, the amount of surface functional groups per silica particle increases, increasing the number of reaction sites with the silane coupling agent per silica particle. This allows the chloroprene-based polymer near the silica to be firmly bound, and is thought to improve compression set. Furthermore, by controlling the BET specific surface area of ​​the silica to be equal to or greater than the above lower limit, the processability of the rubber composition can be maintained.

[0037] The specific surface area of ​​silica can be measured by a gas phase adsorption method using nitrogen gas as the adsorbent gas, for example, with a rapid surface area measuring device SA-1000 manufactured by Shibata Chemical Instruments Co., Ltd.

[0038] The rubber composition according to the present invention contains 2 to 80 parts by mass of silica per 100 parts by mass of chloroprene rubber. The silica content may be, for example, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 parts by mass, or may be within a range between any two of the values ​​exemplified here. By adding silica in an amount equal to or greater than the upper limit, reinforcing effects and abrasion resistance can be maintained. Furthermore, by adding silica in an amount equal to or less than the upper limit, aggregation and scorch can be suppressed, and vulcanization can proceed sufficiently.

[0039] Silica can be used alone or in combination of two or more. When the rubber composition according to the present invention contains two or more types of silica, it is sufficient that the specific surface area of ​​the mixed silica contained in the rubber composition according to the present invention satisfies the above-mentioned numerical range.

[0040] 1.4 Silane coupling agents The rubber composition according to the present invention contains 1 to 15 parts by mass of a silane coupling agent relative to 100 parts by mass of silica. The silane coupling agent improves the dispersibility of silica in the rubber and the adhesion between the rubber and silica. It is added to improve the reinforcing effect of the

[0041] 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. The silane coupling agent according to one embodiment of the present invention preferably includes at least one selected from a silane coupling agent having a double bond in its structure, a silane coupling agent having an amino group, and a silane coupling agent having a double bond and an amino group. The silane coupling agents can be used alone or in combination of two or more.

[0042] The silane coupling agent having a double bond in its structure is not particularly limited except for having a double bond in its structure, and examples thereof include vinyl coupling agents, styryl coupling agents, methacrylic coupling agents, and acrylic coupling agents. In particular, vinyl coupling agents, methacrylic coupling agents, and acrylic coupling agents are preferred from the viewpoint of processability and reinforcing effect. The silane coupling agent having a double bond in its structure more preferably has a (meth)acrylic group in its structure, and even more preferably has a methacrylic group. Specific examples of silane coupling agents having a double bond in their structure include vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyltriethoxysilane, vinyltriacetoxysilane, and allyltrimethoxysilane.

[0043] The silane coupling agent having an amino group is not particularly limited as long as it has an amino group in its structure, and those used in commercially available rubber compositions can be used. The silane coupling agent having an amino group can be an amino-based coupling agent. The silane coupling agent having an amino group can be a silane coupling agent having a primary amino group and / or a secondary amino group, and a silane coupling agent having a secondary amino group is more preferred. Examples of silane coupling agents having an amino group include N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride.

[0044] The rubber composition according to one embodiment of the present invention may also contain a silane coupling agent having neither a double bond nor an amino group in its structure. The content of the silane coupling agent having neither a double bond nor an amino group in its structure is preferably less than the total content of the silane coupling agent having a double bond in its structure, the silane coupling agent having an amino group, and the silane coupling agent having a double bond and an amino group. In the rubber composition according to one embodiment of the present invention, when the total amount of the silane coupling agents contained in the rubber composition is taken as 100% by mass, the total content of the silane coupling agent having a double bond in its structure, the silane coupling agent having an amino group, and the silane coupling agent having a double bond and an amino group is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The rubber composition according to one embodiment of the present invention does not necessarily need to contain a silane coupling agent having neither a double bond nor an amino group in its structure.

[0045] The rubber composition according to the present invention contains 1 to 15 parts by mass of a silane coupling agent per 100 parts by mass of silica. The content of the silane coupling agent can be, for example, 1, 2, 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 values ​​exemplified here. By using the silane coupling agent within this range, necessary and sufficient effects can be obtained and the occurrence of scorch can be suppressed.

[0046] 5. Maleimide compounds The chloroprene rubber composition according to one embodiment of the present invention contains 0.1 to 8 parts by mass of a maleimide compound per 100 parts by mass of the chloroprene rubber. The maleimide compounds can be used singly or in combination of two or more.

[0047] The maleimide compound can contribute to the vulcanization of the rubber composition as a co-crosslinking agent. Examples of the maleimide compound include N,N'-o-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-(4,4'-diphenylmethane)bismaleimide, 2,2-bis-[4-(4-maleimidophenoxy)phenyl]propane, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, N,N'-( 4-methyl-1,3-phenylene ) Examples of suitable bismaleimide include bismaleimide and 1,6-bismaleimide-(2,2,4-trimethyl)hexane. From the viewpoint of improving the heat resistance and compression set resistance of the resulting vulcanized molded article, it is particularly preferable to use N,N'-m-phenylene bismaleimide (also known as m-phenylene dimaleimide).

[0048] A rubber composition according to one embodiment of the present invention contains 0.1 to 8 parts by mass of a maleimide compound per 100 parts by mass of chloroprene rubber. The content of the maleimide compound is, for example, 0.1, 0.2, 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, or 8 parts by mass, and may be within a range between any two of the values ​​exemplified herein. By setting the content of the maleimide compound to be equal to or greater than the above-mentioned lower limit, vulcanization of the resulting rubber composition proceeds more sufficiently, and a vulcanized molded article having excellent compression set resistance and elongation at break after heating can be obtained. Furthermore, by setting the content of the maleimide compound to be equal to or less than the above-mentioned upper limit, the rubber elasticity of the resulting vulcanized molded article can be sufficiently maintained, and a decrease in compression set resistance can be suppressed.

[0049] 1.6 Organic peroxides The rubber composition according to the present invention contains 0.1 to 5 parts by mass of an organic peroxide. The organic peroxides can be used as vulcanizing agents. The organic peroxides can be used alone or in combination of two or more.

[0050] 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, t-butyl hydroperoxide, 4,4-bis[(t-butyl)peroxy]butyl pentanoate, and 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne. Among these, at least one selected from dicumyl peroxide, 1,4-bis[(t-butylperoxy)isopropyl]benzene, tert-butyl-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne, and 4,4-bis[(t-butyl)peroxy]butyl pentanoate is preferred, and 1,4-bis[(t-butylperoxy)isopropyl]benzene is particularly preferred.

[0051] The rubber composition according to the present invention may contain 0.1 to 5 parts by mass of organic peroxide per 100 parts by mass of chloroprene rubber. The amount of organic peroxide added may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, or 5 parts by mass, and may be within a range between any two of the values ​​exemplified here. By keeping the content of organic peroxide within the above range, processing safety is ensured and a good vulcanizate can be obtained.

[0052] 1.7 Hydrotalcite compounds The rubber composition according to the present invention may contain 0.1 to 20 parts by mass of a hydrotalcite compound relative to 100 parts by mass of the chloroprene rubber, The hydrotalcite compound can function as an acid acceptor. As the hydrotalcite compound, compounds represented by the following formula can be used. [M 2+ 1-x M 3+ x (OH)2] x+ [A n-x / n mH2O] x-

[0053] In the above formula, 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。

[0054] Hydrotalcite compounds include Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, 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, Mg 0.7 Al 0.3 O1.15 Particularly preferred are Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O, Mg 0.7 Al 0.3 O 1.15 is.

[0055] When a hydrotalcite compound is used, the amount of the hydrotalcite compound added can be 0.1 to 20 parts by mass per 100 parts by mass of the chloroprene rubber. The amount of the hydrotalcite compound added is, for example, 0.1, 0.2, 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. The hydrotalcite compounds can be used alone or in combination of two or more.

[0056] 1.8 Compounds with thioether structures A chloroprene rubber composition according to one embodiment of the present invention may contain 1 to 30 parts by mass of a compound having a thioether structure per 100 parts by mass of the chloroprene rubber. By using a compound having a thioether structure in combination with an organic peroxide, vulcanization can be sufficiently progressed within a specified vulcanization time, resulting in a rubber composition from which a vulcanizate having excellent compression set resistance and heat resistance can be obtained. In addition, organic peroxide remaining after crosslinking and hydroperoxide produced by thermal degradation are decomposed, further improving the heat resistance of the resulting vulcanized molded article.

[0057] A compound having a thioether structure according to one embodiment of the present invention can be represented by, for example, the following formula (1), or can have a structural unit represented by formula (2): 1 , R 2 , R 3 , R 4 can be any organic group which may have a substituent.

[0058] [ka]

[0059] [ka]

[0060] When the compound having a thioether structure according to one embodiment of the present invention is represented by formula (1), the R 1 , R 2 Preferably, at least one of R 3 , R 4 It is preferable that at least one of the thioether structures has an ether structure. In formula (2), n is any natural number equal to or greater than 1. It is preferable that the compound having one or more thioether structures according to one embodiment of the present invention has two or more ether structures.

[0061] Also, in one aspect, R 1 , R 2 , R 3 , R 4 Preferably, R has an alkylene group having 2 to 20 carbon atoms, more preferably an alkylene group having 2 to 11 carbon atoms. 1 , R 2 , R 3 , R 4 may have a carbonyl group.

[0062] The amount of the compound having a thioether structure added can be 1 to 30 parts by mass per 100 parts by mass of chloroprene rubber. The amount of the compound having a thioether structure added can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, or 30 parts by mass, and may be within a range between any two of the values ​​exemplified herein. By setting the amount of the compound having a thioether structure at or above the lower limit, when an organic peroxide is added, the organic peroxide remaining after crosslinking and the hydroperoxide generated by thermal degradation are decomposed, resulting in a vulcanizate with better heat resistance. Furthermore, by setting the amount of the compound having a thioether structure at or below the upper limit, vulcanization proceeds more thoroughly, resulting in a rubber composition with sufficient moldability and a vulcanized molded product with better compression set resistance and heat resistance.

[0063] 1.9 Vulcanizing Agents The rubber composition according to one embodiment of the present invention may contain a vulcanizing agent in addition to the above compounds. Examples of the vulcanizing agent include metal oxides. Examples of the metal oxide include zinc oxide, magnesium oxide, lead oxide, trimelead tetroxide, iron trioxide, titanium dioxide, and calcium oxide. The metal oxide preferably contains at least one of zinc oxide and magnesium oxide, and may contain both zinc oxide and magnesium oxide, and preferably contains at least zinc oxide.

[0064] The rubber composition according to the present invention may contain 0.1 to 15 parts by mass of the vulcanizing agent relative to 100 parts by mass of the chloroprene rubber. The content of the vulcanizing agent may be, for example, 0.1, 0.2, 0.3, 0.5, 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 here. The vulcanizing agents may be used alone or in combination of two or more.

[0065] 1.10 Fillers (reinforcements) The rubber composition according to the present invention may also contain a filler (reinforcing material) other than silica. 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, channel black, lamp black, thermal carbons such as FT and MT, acetylene black, ketjen black, clay, talc, and calcium carbonate. These may be used alone or in combination of two or more.

[0066] In a rubber composition according to one embodiment of the present invention, the total amount of silica and fillers (reinforcing materials) other than silica contained in the rubber composition is preferably 2 to 100 parts by mass when the chloroprene rubber is taken as 100 parts by mass. In a rubber composition according to one embodiment of the present invention, the content of fillers / reinforcing materials other than silica may be 50% by mass or less when the total amount of silica and fillers (reinforcing materials) other than silica contained in the rubber composition is taken as 100% by mass. The content of fillers / reinforcing materials other than silica may be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50% by mass, and may be within a range between any two of the numerical values ​​exemplified here. A rubber composition according to one embodiment of the present invention may not contain fillers (reinforcing materials) other than silica. In the rubber composition according to one embodiment of the present invention, by setting the content of fillers other than silica within the above-mentioned range, the hardness of the vulcanizate and vulcanized molded article can be improved while maintaining the effects of the present invention.

[0067] 1.11 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 15 parts by mass or less of the lubricant or processing aid per 100 parts by mass of the chloroprene-based rubber contained in the rubber composition, and may also contain 10 parts by mass or less. The content of the lubricant or processing aid may be, for example, 0, 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. The rubber composition of the present invention may also be free of a lubricant or processing aid.

[0068] 1.12 Sulfur vulcanization accelerators The rubber composition according to the present invention may contain sulfur and a vulcanization accelerator. Alternatively, the rubber composition according to the present invention may contain neither sulfur nor a vulcanization accelerator. The rubber composition may contain 5.0 parts by mass or less of the sulfur vulcanization accelerator per 100 parts by mass of the chloroprene-based rubber. The content of the sulfur vulcanization accelerator may be, for example, 0, 0.1, 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, or may be within a range between any two of the values ​​exemplified here.

[0069] 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.

[0070] 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. Examples of triazine vulcanization accelerators include 2,4,6-trimercapto-s-triazine. These may be used alone or in combination of two or more.

[0071] 1.13 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; aromatic oils, naphthenic oils, lubricating oils, process oils, and petroleum-based plasticizers such as paraffin, liquid paraffin, petrolatum, and petroleum asphalt. These can be used alone or in combination.

[0072] A rubber composition according to one embodiment of the present invention may contain 50 parts by mass or less of a plasticizer / softener relative to 100 parts by mass of the chloroprene rubber contained in the rubber composition. The content of the plasticizer / softener may be, for example, 0, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts by mass, or may be within a range between any two of the values ​​exemplified here. A rubber composition according to one embodiment of the present invention may also be free of a plasticizer.

[0073] 1.14 Other In addition to the above-described components, the rubber composition according to the present invention may further contain components such as an antioxidant, an antioxidant, a stabilizer, a flame retardant, and a vulcanization retarder, as long as the effects of the present invention are not impaired. Examples of the antioxidants and antioxidants include ozone antioxidants, phenolic antioxidants, amine antioxidants, acrylate antioxidants, imidazole antioxidants, metal carbamates, waxes, phosphorus antioxidants, sulfur antioxidants, etc. Examples of the 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 chloroprene rubber contained in the rubber composition.

[0074] 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, silica, a maleimide compound, an organic peroxide, a silane coupling agent, and other necessary components at a temperature equal to or lower than the vulcanization temperature. Examples of devices for kneading the raw material components include conventionally known kneading devices such as mixers, Banbury mixers, kneader mixers, and open rolls.

[0075] 3. Rubber composition characteristics (Heat resistance of vulcanized molded products) The rubber composition according to one embodiment of the present invention is a rubber composition having an elongation at break EB0 measured in accordance with JIS K6251 of a vulcanized molded product molded in accordance with JIS K6299, and an elongation at break EB measured in accordance with JIS K6251 after heating the vulcanized molded product at 150°C for 144 hours. i When the above formula is satisfied, it is preferable that the change in elongation at break ΔEB calculated by the following formula is −68 or more. ΔEB=(EB i -EB0)÷EB0×100 The change in elongation at break ΔEB is, for example, −68, −67, −66, −65, −60, −55, −50, −45, or −40, and may be within a range between any two of the values ​​exemplified here.

[0076] (Compression set of vulcanized molded body) In the rubber composition according to one embodiment of the present invention, it is preferable that the compression set of a vulcanized molded product obtained by press-vulcanizing the rubber composition at 180°C for 30 minutes is 34 or less, as measured under test conditions of 150°C and 72 hours in accordance with JIS K 6262:2013. The compression set may be, for example, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, or within a range between any two of the values ​​exemplified herein.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The vulcanizate and vulcanized molded article according to one embodiment of the present invention preferably have a change in elongation at break ΔEB and a compression set within the above-mentioned ranges.

[0082] 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 vulcanized product made from the rubber composition according to one embodiment of the present invention is excellent in elongation at break after heating and compression set, and can therefore be used as various 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. Taking advantage of its properties, the rubber composition according to one embodiment of the present invention can be used as various components requiring excellent heat resistance and / or excellent compression set, and can be particularly suitably used as seals, gaskets, packing, and the like.

[0083] (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 secured by 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. A vulcanizate made from a rubber composition according to one embodiment of the present invention exhibits no observed bleeding and excellent elongation at break and compression set after heating, making it possible to manufacture seals that utilize these properties.

[0084] (hose material) Hose materials are flexible pipes, and specific examples include high- and low-pressure hoses for water supply, oil supply, air supply, steam supply, hydraulic pressure, etc. A vulcanizate made from the rubber composition according to one embodiment of the present invention is excellent in elongation at break and compression set after heating, and therefore can be used to manufacture hose materials that take advantage of these properties.

[0085] (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. Furthermore, 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), boots for rack and pinion gears, etc., which are used to protect drive parts such as automobile drive systems. The vulcanizate of the rubber composition according to one embodiment of the present invention is excellent in elongation at break and compression set, and therefore, for example, it is possible to manufacture boots that are used by taking advantage of these properties.

[0086] (gaskets, etc.) Gaskets, oil seals, and packings are components used in machinery and equipment to prevent leaks 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. A vulcanizate made from a rubber composition according to one embodiment of the present invention has excellent elongation at break and compression set, making it possible to manufacture seals that utilize these properties, for example.

[0087] (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 equipment such as rice hullers, and food processing. CR has good mechanical strength that can withstand the friction of the objects being conveyed, and is therefore used in a wide range of rubber roll applications. The rubber composition of the present invention has excellent elongation at break and compression set, making it possible to manufacture rubber rolls that utilize these properties.

[0088] (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. A vulcanizate made from the rubber composition according to one embodiment of the present invention is excellent in elongation at break and compression set after heating, and therefore can be used to manufacture industrial cables that utilize these properties, for example.

[0089] (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 goods, they have been prone to damage due to deterioration. A vulcanizate made from a rubber composition according to one embodiment of the present invention has excellent elongation at break and compression set after heating, and therefore can be used to produce industrial conveyor belts that take advantage of these properties.

[0090] (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, since a chlorine-based rubber is used, the flame retardancy of the sponge can also be increased. A vulcanizate made from the rubber composition according to one embodiment of the present invention has excellent elongation at break and compression set after heating, and therefore can be used to produce, for example, sponges that take advantage of these properties or 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.

[0091] 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]

[0092] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited to these examples.

[0093] <Method of manufacturing acrylonitrile-containing chloroprene rubber> 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 phenothiazine, a polymerization terminator, was added to terminate the polymerization. Thereafter, unreacted monomers in the reaction solution were removed under reduced pressure to obtain an acrylonitrile-containing chloroprene-based latex containing a chloroprene-acrylonitrile copolymer.

[0094] The above-mentioned conversion rate [%] of the acrylonitrile-containing 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 [% by mass] of 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 total amount [g] of monomers initially charged into the polymerization vessel and the amount of monomers added in portions from the start of polymerization to a certain time. The "monomer" referred to here is the total amount of chloroprene and acrylonitrile. Conversion rate = {[(total charge amount × solid concentration / 100) - evaporation residue] / charge amount of monomer} × 100 (A)

[0095] The pH of the above-mentioned acrylonitrile-containing chloroprene latex was adjusted to 7.0 using acetic acid or sodium hydroxide, and then the acrylonitrile-containing 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 acrylonitrile-containing chloroprene rubber.

[0096] The content of acrylonitrile monomer units contained in the acrylonitrile-containing chloroprene rubber was calculated from the content of nitrogen atoms in the chloroprene-acrylonitrile copolymer rubber. Specifically, the content of nitrogen atoms in 100 mg of chloroprene-based rubber was measured using an elemental analyzer (Sumigraph 220F, manufactured by Sumika Chemical Analysis Center Co., Ltd.), and the content of acrylonitrile monomer units was calculated.

[0097] 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 acrylonitrile-containing chloroprene rubber obtained by the above production method had an acrylonitrile monomer unit content of 10.0 mass %.

[0098] <Preparation of Rubber Composition> The components were mixed as shown in Tables 1 to 3 and kneaded with an 8-inch open roll to obtain rubber compositions of Examples and Comparative Examples.

[0099] The components used to obtain the rubber composition are as follows: <Chloroprene rubber> Acrylonitrile (AN)-containing chloroprene rubber: acrylonitrile-containing chloroprene rubber prepared by the above-mentioned manufacturing method. Mercaptan-modified chloroprene rubber: Mercaptan-modified chloroprene rubber, "S-40V" manufactured by Denka Co., Ltd.

[0100] Silica: "ULTRASIL360" manufactured by Evonik Industries AG BET specific surface area: 55 m 2 / g Silica: Tosoh Silica Corporation "Nipsil E-74P" BET specific surface area: 50 m 2 / g Silica: Tosoh Silica Corporation "Nipsil ER-R" BET specific surface area: 78 m 2 / g

[0101] Silane coupling agent: 3-methacryloxypropylmethoxysilane, Shin-Etsu Chemical Co., Ltd. "KBM-503" Silane coupling agent with a double bond

[0102] [ka] Silane coupling agent: N-phenyl-3-aminopropyltrimethoxysilane, "KBM-573" manufactured by Shin-Etsu Chemical Co., Ltd. Silane coupling agent containing a secondary amine

[0103] [ka] Silane coupling agent: (3-mercaptopropyl)trimethoxysilane, Toray Dow Corning "Z-6062" mercapto type

[0104] [ka]

[0105] Carbon black: FEF, Asahi Carbon Co., Ltd., "Asahi #60" Organic peroxide: 1,4-bis[(t-butylperoxy)isopropyl]benzene, NOF Corporation, "Perbutyl P-40" Organic peroxide: 4,4-bis[(t-butyl)peroxy]butylpentanoate, NOF Corporation, "Perhexa V-40" Vulcanization accelerator: Trimethylthiourea, Ouchi Shinko Chemical Industry Co., Ltd., "Noccela TMU" Maleimide compound (co-crosslinking agent): m-phenylenedimaleimide, Ouchi Shinko Chemical Industry Co., Ltd., "Balnoc PM" Compounds with a thioether structure: Thioether-based plasticizer, "Vulcanol OT" manufactured by LANXESS (a mixture mainly consisting of compound A containing one or more thioether structures and two or more ether structures, and compound B containing one or more thioether structures and three or more ether structures) Vulcanizing agent: Zinc oxide, Sakai Chemical Industry Co., Ltd. "Zinc oxide type 2" Hydrotalcite (acid acceptor): Mg 0.7 Al 0.3 O 1.15 , Kyowa Chemical Industry Co., Ltd. "KW-2100" Antioxidant: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, Ouchi Shinko Chemical Industry Co., Ltd., "Nocrac CD" Lubricants and processing aids: Stearic acid: "Stearic acid 50S" manufactured by New Japan Chemical Co., Ltd.

[0106] <Evaluation of vulcanized molded products> The above rubber compositions were used to prepare vulcanized molded articles, which were then evaluated as follows. The results are shown in Tables 1 to 3.

[0107] (Heat resistance (change in elongation at break after heating)) The obtained rubber composition was press-vulcanized under conditions of 180°C for 20 minutes in accordance with JIS K6299 to prepare a vulcanized molded sheet having a thickness of 2 mm. The obtained sheet was molded into a dumbbell-shaped No. 3 test piece, and the elongation at break EB0 was measured based on JIS K6251. Next, the vulcanized molded product was heated at 150°C for 144 hours, and then the elongation at break EB i The elongation at break EB0 before heating and the elongation at break EB after heating were measured. i The change in elongation at break ΔEB before and after the heat resistance test was calculated from the above. ΔEB=(EB i -EB0)÷EB0×100

[0108] (Compression set) The rubber composition was press-vulcanized at 180°C for 30 minutes to produce cylindrical vulcanized molded articles with a diameter of 29 mm and a height of 12.5 mm. The compression set of the vulcanized molded articles was measured at 150°C for 72 hours in accordance with JIS K 6262:2013.

[0109] [Table 1]

[0110] [Table 2]

[0111]

Table 3

Claims

1. 100 parts by mass of chloroprene rubber; BET specific surface area is 10 to 120 m ２ / g of silica, and 0.1 to 8 parts by mass of a maleimide compound; 0.1 to 5 parts by mass of an organic peroxide; 1 to 15 parts by mass of a silane coupling agent relative to 100 parts by mass of the silica A rubber composition comprising: The rubber composition further contains 0.1 to 9 parts by mass of a hydrotalcite compound per 100 parts by mass of the chloroprene rubber.

2. The rubber composition according to claim 1, wherein the chloroprene-based rubber comprises a homopolymer of 2-chloro-1,3-butadiene, or a copolymer of 2-chloro-1,3-butadiene and at least one monomer selected from 2,3-dichloro-1,3-butadiene and an unsaturated nitrile monomer.

3. 3. The rubber composition according to claim 1, wherein the silane coupling agent comprises at least one selected from a silane coupling agent having a double bond in its structure, a silane coupling agent having an amino group, and a silane coupling agent having a double bond and an amino group.

4. The rubber composition according to claim 1 or 2, wherein the silane coupling agent is at least one silane coupling agent selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

5. The rubber composition according to claim 1 or 2, wherein the maleimide compound is at least one maleimide compound selected from N,N'-o-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-(4,4'-diphenylmethane) bismaleimide, 2,2-bis-[4-(4-maleimidophenoxy)phenyl]propane, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, N,N'-(4-methyl-1,3-phenylene) bismaleimide, and 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

6. The rubber composition according to claim 1 or 2, wherein the organic peroxide is at least one organic peroxide selected from the group consisting of dicumyl peroxide, 1,4-bis[(t-butylperoxy)isopropyl]benzene, tert-butyl-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne, and 4,4-bis[(t-butyl)peroxy]butyl pentanoate.

7. The rubber composition according to claim 1 or claim 2, further comprising 1 to 30 parts by mass of a compound having a thioether structure per 100 parts by mass of the chloroprene rubber.

8. 100 parts by mass of chloroprene rubber; BET specific surface area is 10 to 120 m ２ / g of silica, and 0.1 to 8 parts by mass of a maleimide compound; 0.1 to 5 parts by mass of an organic peroxide; 1 to 15 parts by mass of a silane coupling agent relative to 100 parts by mass of the silica A rubber composition comprising: The rubber composition, wherein the silane coupling agent comprises at least one selected from a silane coupling agent having a double bond in its structure, a silane coupling agent having an amino group, and a silane coupling agent having a double bond and an amino group.

9. 100 parts by mass of chloroprene rubber; BET specific surface area is 10 to 120 m ２ / g of silica, and 0.1 to 8 parts by mass of a maleimide compound; 0.1 to 5 parts by mass of an organic peroxide; 1 to 15 parts by mass of a silane coupling agent relative to 100 parts by mass of the silica A rubber composition comprising: The rubber composition further contains 1 to 30 parts by mass of a compound having a thioether structure relative to 100 parts by mass of the chloroprene rubber.

10. A vulcanizate of the rubber composition according to claim 1, claim 2, claim 8, or claim 9.

11. A vulcanized molded article of the rubber composition according to claim 1, claim 2, claim 8, or claim 9.

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