Rubber composition, vulcanized rubber molded body, and rubber roll

Abstract

To provide a rubber composition of which the unvulcanized material has a sufficiently low Mooney viscosity and of which the vulcanized material has excellent water resistance.SOLUTION: According to the present invention, provided is a rubber composition comprising a chloroprene-based rubber and an epoxy-based compound, in which the chloroprene-based rubber contains a chloroprene-based rubber having a content of an unsaturated nitrile monomer unit of less than 25 mass%, the epoxy-based compound contains an epoxy-based compound A which is an epoxy-based compound containing no ester bond, and the rubber composition contains 0.05-25.0 pts.mass of the epoxy-based compound A based on 100 pts.mass of the chloroprene-based rubber, and when a vulcanized molded body for test, obtained by press-vulcanizing the rubber composition under a condition of 160°C and 50 minutes, is stored under an environment of 40°C and humidity of 90% for 72 hours, moisture absorptivity M of the vulcanized molded body for test is 0.1-2.0 mass%, and the moisture absorptivity M is represented by the following formula, M=(B-A) / A×10, when a mass of the vulcanized molded body for test after storage is represented by Bg and a mass of the vulcanized molded body for test before storage is represented by Ag.SELECTED DRAWING: None

Description

[Technical Field]

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

[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. [Background technology]

[0003] For example, Patent Document 1 discloses an invention relating to a sulfur-modified chloroprene rubber composition comprising a sulfur-modified chloroprene rubber, a vulcanization accelerator, zinc oxide, and magnesium oxide, wherein the blending amount of the vulcanization accelerator is 0.1 to 5 parts by weight, and the blending amounts of zinc oxide and magnesium oxide are specified by a predetermined relational expression between each blending amount and the Mooney scorch time t. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-209522 Summary of the Invention [Problem to be solved by the invention]

[0005] 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 has a sufficiently low Mooney viscosity in the unvulcanized product and that has excellent water resistance in the vulcanized product of the rubber composition.

[0006] The present invention has been made in view of the above circumstances, and provides a rubber composition which has a sufficiently low Mooney viscosity in the unvulcanized state and which has excellent water resistance in the vulcanized state. [Means for solving the problem]

[0007] According to the present invention, there is provided a rubber composition comprising a chloroprene rubber and an epoxy compound, wherein the chloroprene rubber contains less than 25% by mass of unsaturated nitrile monomer units, and the epoxy compound contains epoxy compound A, which is an epoxy compound containing no ester bonds. The rubber composition contains 0.05 to 25 parts by mass of the epoxy compound A per 100 parts by mass of the chloroprene rubber. The rubber composition is press-vulcanized at 160°C for 50 minutes to obtain a vulcanized test molded article. When the test molded article is stored at 40°C and 90% humidity for 72 hours, the moisture absorption rate M of the test molded article is 0.1 to 2.0% by mass, and the moisture absorption rate M is expressed by the following formula, where Bg is the mass of the test molded article after storage and Ag is the mass of the test molded article before storage: M = (BA) / A × 100

[0008] The present inventors have conducted extensive research and have found that by combining a specific type of chloroprene rubber with an epoxy compound of a specific structure in the formulation of a rubber composition and controlling the moisture absorption rate of a vulcanized molded product of the rubber composition within a specific numerical range, a rubber composition can be obtained in which the Mooney viscosity of the unvulcanized product is sufficiently low and the vulcanized product of the rubber composition has excellent water resistance, which led to the completion of 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 and an epoxy compound, wherein the chloroprene rubber contains less than 25% by mass of unsaturated nitrile monomer units, and the epoxy compound contains an epoxy compound A which is an epoxy compound containing no ester bonds, and the rubber composition contains 0.05 to 25.0 parts by mass of the epoxy compound A per 100 parts by mass of the chloroprene rubber. The rubber composition is press-vulcanized at 160°C for 50 minutes to obtain a test vulcanized molded article. When the test vulcanized molded article is stored in an environment of 40°C and 90% humidity for 72 hours, the moisture absorption rate M of the test vulcanized molded article is 0.1 to 2.0% by mass, and the moisture absorption rate M is expressed by the following formula, where Bg is the mass of the test vulcanized molded article after storage and Ag is the mass of the test vulcanized molded article before storage: M = (BA) / A × 100 [2] The rubber composition according to [1], wherein the moisture absorption rate M is 0.1 to 0.6 mass %. [3] The rubber composition according to [1] or [2], wherein the epoxy compound A has an epoxy equivalent of 120 to 180. [4] The rubber composition according to any one of [1] to [3], wherein the epoxy compound A has a solubility parameter of 9.0 to 10.5. [5] The rubber composition according to any one of [1] to [4], wherein the content of the acid acceptor relative to the chloroprene rubber is less than 7 parts by mass. [6] A vulcanized molded article of the rubber composition according to any one of [1] to [5]. [7] A rubber roll comprising the vulcanized molded article according to [6]. [Effects of the Invention]

[0010] The rubber composition according to the present invention can provide a rubber composition having a sufficiently low Mooney viscosity in the unvulcanized form and excellent water resistance in the vulcanized form. Furthermore, the resulting vulcanized molded article has excellent water resistance and can be used as various components that require water resistance. Specifically, the vulcanized molded article according to one embodiment of the present invention can be suitably used as a material for, for example, general industrial power transmission belts and conveyor belts, automotive air springs, anti-vibration rubber, hoses, wipers, immersion products, sealing parts, adhesives, boots, rubberized fabrics, and rubber rolls. It can be particularly used as a component used in an environment that requires water resistance. For example, the vulcanized molded article according to one embodiment of the present invention can be suitably used as a rubber roll, particularly suitable for rubber rolls for steelwork (e.g., rubber rolls for cleaning steel plates) that require water resistance. Furthermore, the vulcanized molded article according to one embodiment of the present invention can be particularly suitably used as a rubber roll for papermaking that requires water resistance. 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 A rubber composition according to the present invention comprises a chloroprene rubber and an epoxy compound, wherein the chloroprene rubber contains less than 25% by mass of unsaturated nitrile monomer units, and the epoxy compound contains an epoxy compound A which does not contain an ester bond. The rubber composition contains 0.05 to 25.0 parts by mass of the epoxy compound A per 100 parts by mass of the chloroprene rubber. The rubber composition is press-vulcanized at 160°C for 50 minutes to obtain a vulcanized test molded article. When the test molded article is stored at 40°C and 90% humidity for 72 hours, the moisture absorption rate M of the test molded article is 0.1 to 2.0% by mass, and the moisture absorption rate M is expressed by the following formula, where Bg is the mass of the test molded article after storage and Ag is the mass of the test molded article before storage: M = (BA) / A × 100

[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 (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.

[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 the present invention includes a chloroprene rubber having an unsaturated nitrile monomer unit content of less than 25% by mass. The chloroprene-based rubber according to the present invention may contain one or more chloroprene-based rubbers. The chloroprene-based rubber according to one embodiment of the present invention may contain a chloroprene-based rubber containing one or more unsaturated nitrile monomer units. The chloroprene-based rubber according to one embodiment of the present invention may further contain a chloroprene-based rubber that does not contain one or more unsaturated nitrile monomer units.

[0016] The chloroprene-based rubber (the chloroprene-based rubber containing unsaturated nitrile monomer units and the chloroprene-based rubber not containing unsaturated nitrile monomer units) according to one embodiment of the present invention may contain monomer units derived from a monomer other than the chloroprene monomer and the unsaturated nitrile monomer. The monomer other than the chloroprene monomer and the unsaturated nitrile monomer is not particularly limited as long as it is copolymerizable with the chloroprene monomer, and examples thereof 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), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, and sulfur. For example, the chloroprene-based rubber according to one embodiment of the present invention may include 2,3-dichloro-1,3-butadiene monomer units.

[0017] The content of unsaturated nitrile monomer units in the chloroprene-based rubber according to the present invention, which has an unsaturated nitrile monomer unit content of less than 25% by mass, may be, 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, or 24% by mass, or may be within a range between any two of the values ​​exemplified herein. By keeping the content of unsaturated nitrile monomer units in the chloroprene-based rubber below the above upper limit, the Mooney viscosity of the unvulcanized product can be maintained sufficiently low, while the water resistance and heat resistance of the vulcanized product of the rubber composition can be improved. From the viewpoint of improving mechanical properties, dynamic properties, abrasion resistance, oil resistance, etc., the rubber composition according to one embodiment of the present invention more preferably contains a chloroprene-based rubber containing unsaturated nitrile monomer units.

[0018] When the chloroprene-based rubber according to one embodiment of the present invention contains two or more chloroprene-based rubbers, the content of unsaturated nitrile monomer units contained in the two or more chloroprene-based rubbers based on the total amount of the two or more chloroprene-based rubbers, relative to 100% by mass of the two or more chloroprene-based rubbers contained in the rubber composition, is preferably within the above-mentioned range. That is, in the chloroprene-based rubber according to one embodiment of the present invention, the content of unsaturated nitrile monomer units in the chloroprene-based rubber contained in the rubber composition is preferably less than 25% by mass based on 100% by mass of the chloroprene-based rubber contained in the rubber composition, and the content of the unsaturated nitrile monomer units may be within a range between any two of the above-mentioned numerical values. Furthermore, in the chloroprene-based rubber according to one embodiment of the present invention, the content of acrylonitrile monomer units in the chloroprene-based rubber contained in the rubber composition is preferably less than 25% by mass based on 100% by mass of the chloroprene-based rubber contained in the rubber composition, and the content of the acrylonitrile monomer units may be within a range between any two of the above-mentioned numerical values.

[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 70 to 100% by mass of chloroprene monomer units when the chloroprene rubber is taken as 100% by mass. The content of chloroprene monomer units in the chloroprene rubber is, for example, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the values ​​exemplified here. By setting the content of chloroprene monomer units within the above range, a rubber composition can be obtained that can give molded articles with excellent hardness, mechanical properties, etc.

[0022] 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 units and unsaturated nitrile monomer units, when the chloroprene-based rubber is taken as 100 mass%. The content of monomer units other than chloroprene monomer units and unsaturated nitrile monomer units 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 monomers and unsaturated nitrile monomers to fall within the above range, the effects of copolymerizing these monomers can be achieved without impairing the properties of the resulting rubber composition.

[0023] When a rubber composition according to one embodiment of the present invention contains two or more types of chloroprene-based rubber, it is preferable that the content based on the total amount of each monomer unit contained in the two or more types of chloroprene-based rubber falls within the above-mentioned numerical range relative to 100% by mass of the total of the two or more types of chloroprene-based rubber contained in the rubber composition.

[0024] 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.

[0025] 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 within the following ranges, from the viewpoint of easily obtaining well-balanced mechanical properties, etc.

[0026] The weight average molecular weight of the chloroprene rubber is, for example, 10 × 10 3 g / mol, 50 × 10 3 g / mol, 100 × 10 3 g / mol, 300 × 10 3 g / mol, 400 × 103 g / mol, 450 × 10 3 g / mol, 500 × 10 3 g / mol, 800 × 10 3 g / mol, 1000 × 10 3 g / mol, 2000 × 10 3 g / mol, 3000 × 10 3 g / mol, 5000 × 10 3 g / mol and may be within a range between any two of the values ​​exemplified herein.

[0027] The number average molecular weight of chloroprene rubber is, for example, 1 × 10 3 g / mol, 5 × 10 3 g / mol, 10 × 10 3 g / mol, 50 × 10 3 g / mol, 100 × 10 3 g / mol, 130 × 10 3 g / mol, 200 × 10 3 g / mol, 300 × 10 3 g / mol, 500 × 10 3 g / mol, 800 × 10 3 g / mol, 1000 × 10 3 g / mol and may be within a range between any two of the values ​​exemplified herein.

[0028] The molecular weight distribution of the chloroprene rubber is 1.0, 1.5, 2.0, 2.5, 3.0, 3.2, 3.4, 3.5, 3.8, 4.0, 5.0, 8.0, or 10, and may be within a range between any two of the numerical values ​​exemplified here.

[0029] 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.

[0030] 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 an emulsion polymerization process according to one embodiment of the present invention, raw material monomers containing a chloroprene monomer and, if necessary, an unsaturated nitrile monomer are emulsion-polymerized using appropriate emulsifiers, dispersants, catalysts, chain transfer agents, etc., and when the target final conversion rate is reached, a polymerization terminator is added to obtain a latex containing a chloroprene polymer containing chloroprene monomer units. Next, unreacted monomers can be removed from the polymerization solution obtained by the emulsion polymerization process. This method is not particularly limited, and examples include steam stripping. The pH is then adjusted, and the resulting mixture is subjected to conventional processes such as freeze coagulation, water washing, and hot air drying to obtain a chloroprene rubber containing a chloroprene polymer.

[0031] 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.

[0032] 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).

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 1.3 Other rubbers The rubber composition according to one embodiment of the present invention may contain rubbers other than chloroprene-based rubber. Examples of other rubbers include natural rubber (NR), hydrogenated acrylonitrile butadiene rubber (H-NBR), acrylonitrile butadiene rubber (NBR), chlorosulfonated polyethylene (CSM), butadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), isoprene rubber (IR), styrene-butadiene rubber (SBR), epoxidized natural rubber (ENR), acrylonitrile butadiene rubber (NBR), styrene-isoprene-butadiene copolymer rubber (SIBR), epichlorohydrin rubber (CO), acrylic rubber (ACM), urethane rubber (U), silicone rubber (Q), fluororubber (FKM), and polysulfide rubber (T).

[0039] A rubber composition according to one embodiment of the present invention preferably contains 50% by mass or more of chloroprene rubber when the rubber contained in the rubber composition is 100% by mass. The content of chloroprene rubber may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% 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 preferably contains 50% by mass or more of a chloroprene-based rubber having an unsaturated nitrile monomer unit content of 25% by mass, where the rubber contained in the rubber composition is taken as 100% by mass. The content of the chloroprene-based rubber having an unsaturated nitrile monomer unit content of 25% by mass may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the values ​​exemplified here. The rubber composition according to one embodiment of the present invention preferably contains 20% by mass or more of rubber when the rubber composition is taken as 100% by mass, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the numerical values ​​exemplified here. The rubber composition according to one embodiment of the present invention preferably contains 20% by mass or more of chloroprene rubber when the rubber composition is taken as 100% by mass, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0040] 1.4 Epoxy compounds The rubber composition according to the present invention contains an epoxy compound, and the epoxy compound contains an epoxy compound A which is an epoxy compound containing no ester bond. In the present invention, the epoxy compound means a compound having one or more epoxy groups. The rubber composition according to the present invention contains 0.05 to 25.0 parts by mass of epoxy compound A relative to 100 parts by mass of chloroprene rubber. The content of epoxy compound A relative to 100 parts by mass of chloroprene rubber is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, or 25.0 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0041] According to the present invention, by combining a specific type of chloroprene-based rubber with an epoxy-based compound having a specific structure in the formulation of a rubber composition and controlling the moisture absorption rate of a vulcanized product of the rubber composition within a specific range, it is possible to obtain a rubber composition having a sufficiently low Mooney viscosity in the unvulcanized state and excellent water resistance in the vulcanized product of the rubber composition. While the reason why the effects of the present invention are achieved by satisfying these requirements is unclear, it is believed that the epoxy-based compound in the rubber composition may exhibit an acid-accepting effect when heated, thereby preventing a decrease in various properties even when the amount of acid acceptor compounded is reduced compared to conventional methods. Furthermore, by adjusting the formulation of the rubber composition so that the moisture absorption rate falls within a specific range, it is believed that the acid-accepting capacity of the entire rubber composition can be highly controlled. As a result, it is believed that the use of specific types and amounts of epoxy-based compounds and chloroprene-based rubbers and the control of the moisture absorption rate lead to the production of a rubber composition having a sufficiently low Mooney viscosity in the unvulcanized state, excellent water resistance in the vulcanized product of the rubber composition, and excellent heat resistance in the vulcanized product of the rubber composition.

[0042] The epoxy compound A preferably has an epoxy equivalent of 120 to 180. The epoxy equivalent may be, for example, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180, or may be within a range between any two of the values ​​exemplified here. When the epoxy equivalent is within the above numerical range, the molecular weight of the epoxy compound A is adjusted, thereby adjusting the viscosity of the epoxy compound, resulting in a rubber composition with a sufficiently low Mooney viscosity of the unvulcanized product and superior processability. Furthermore, when the epoxy equivalent is within the above numerical range, the rubber composition can be used to obtain a vulcanized molded product with superior water resistance and heat resistance.

[0043] The epoxy compound A preferably has a solubility parameter of 9.0 to 10.5. The solubility parameter is, for example, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, or 10.5, and may be within a range between any two of the values ​​exemplified here. When the solubility parameter is within the above range, the rubber composition can be one that has excellent processability and can give a vulcanized molded product that is excellent in water resistance and heat resistance.

[0044] The epoxy compound A preferably has a viscosity of 10 to 200 cP at 25° C. The viscosity at 25° C. is, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 cP, and may be within a range between any two of the values ​​exemplified here. When the viscosity at 25° C. is within the above range, the rubber composition has better processability.

[0045] The rubber composition according to one embodiment of the present invention may contain an epoxy compound containing an ester bond. The content of the epoxy compound containing an ester bond per 100 parts by mass of the chloroprene rubber is, for example, 0.1, 0.2, 0.3, 0.4, 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 values ​​exemplified here. In a rubber composition according to one embodiment of the present invention, the content of epoxy compound A relative to 100 mass% of the epoxy compounds contained in the rubber composition may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0046] 1.5 Plasticizers and Softeners The rubber composition according to the present invention may contain a plasticizer and / or a softener. The plasticizer and softener may be 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 and softener, as long as they are compatible with rubber. Examples of 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 DUP (diundecyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DOTP (dioctyl terephthalate), DOS (dioctyl sebacate), DBS (dibutyl sebacate), DOA (dioctyl adipate), DINCH (diisononyl 1,2-cyclohexanedicarboxylate), TOP (trioctyl phosphate), and TBP (tributyl phosphate), ether ester compounds, thioether-based plasticizers, aromatic oils, naphthenic oils, lubricating oils, process oils, paraffin, liquid paraffin, petroleum asphalt, and other petroleum-based plasticizers. The plasticizers and softeners may be free of epoxy compounds. These may be used alone or in combination of two or more. The plasticizer and softener may not contain an epoxy compound.

[0047] A rubber composition according to one embodiment of the present invention may contain 5 to 50 parts by mass of a plasticizer and a softener, based on 100 parts by mass of the rubber contained in the rubber composition. The content of the plasticizer and the softener may be, for example, 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. In a rubber composition according to one embodiment of the present invention, the content of the plasticizer and softener containing an ester bond can be less than 10 parts by mass when the rubber contained in the rubber composition is taken as 100 parts by mass. The content of the plasticizer and softener containing an ester bond may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, or 9 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0048] 1.6 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.

[0049] 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.

[0050] 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 an epoxy-based compound. The amount of curing agent added per 100 parts by mass of an epoxy-based 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, and by containing the curing agent below the lower limit, shortening of scorch time can be prevented.

[0051] 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 curing agent preferably has a gelation time of 60 minutes or less at 160°C. The gelation 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 having a gelation time within the above range, it is possible to achieve both a sufficiently long scorch time of the unvulcanized product and excellent mechanical properties of the vulcanized product.

[0052] 1.7 Vulcanizing Agents 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 and organic peroxides.

[0053] 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.

[0054] From the viewpoint of ensuring processing safety and obtaining a good vulcanizate, the rubber composition according to the present invention may contain 10 parts by mass or less 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 may be, for example, 0, 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.

[0055] 1.8 Vulcanization accelerators The rubber composition according to the present invention may contain a vulcanization accelerator, and may contain 5.0 parts by mass or less of the vulcanization accelerator per 100 parts by mass of rubber contained in the rubber composition. The content of the 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. Note that the rubber composition according to the present invention may also be one that does not contain a vulcanization accelerator.

[0056] 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 vulcanization accelerators include thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, and thiazole-based accelerators.

[0057] 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.

[0058] 1.9 Acid acceptor In a rubber composition according to one embodiment of the present invention, the amount of acid acceptor per 100 parts by mass of the chloroprene rubber may be less than 7 parts by mass. The acid acceptor may include at least one selected from the group consisting of hydrotalcite compounds, magnesium and aluminum solid solutions, magnesium oxide, zinc oxide, lead oxide, trimelead tetroxide, iron trioxide, titanium dioxide, and calcium oxide, and may include at least one selected from the group consisting of hydrotalcite compounds, magnesium and aluminum solid solutions, magnesium oxide, and zinc oxide. The acid acceptors may be used alone or in combination of two or more.

[0059] As the hydrotalcite, one represented by the following formula can be used. [M 2+ 1-x M 3+ x (OH)2] x+ [A n-x / n mH2O] x-

[0060] In the above formula, M 2+ :Mg2+ , 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。

[0061] As for hydrotalcite, 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, etc., and particularly preferred is Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O.

[0062] The content of the acid acceptor relative to 100 parts by mass of the chloroprene polymer contained in the rubber composition can be less than 7 parts by mass. The content of the acid acceptor is, for example, 0.1, 0.2, 0.3, 0.5, 1, 2, 3, 4, 5, or 6 parts by mass, and may be within a range between any two of the values ​​exemplified here. The rubber composition according to one embodiment of the present invention has sufficiently excellent water resistance, or excellent water resistance and heat resistance, even when the content of the acid acceptor is reduced compared to conventional compositions.

[0063] 1.10 Fillers The rubber composition according to the present invention may contain a filler. Examples of fillers 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, silica, clay, talc, and calcium carbonate. These may be used alone or in combination of two or more.

[0064] A rubber composition according to one embodiment of the present invention may contain 20 to 80 parts by mass of a filler relative to 100 parts by mass of rubber contained in the rubber composition. The amount of filler may be, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. By containing the filler within the above numerical range, the rubber composition according to one embodiment of the present invention can improve the hardness of the vulcanizate and vulcanized molded article.

[0065] 1.11 Lubricants and processing aids The rubber composition according to the present invention may further contain a lubricant and a processing aid. The lubricant and the processing aid 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 according to the present invention may contain 1 to 15 parts by mass of the lubricant and the processing aid, or may be 1 to 10 parts by mass, based on 100 parts by mass of the rubber contained in the rubber composition. The content of the lubricant and the 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.

[0066] 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, a flame retardant, a silane coupling agent, etc., within a range that does not impair the effects of the present invention. 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 rubber contained in the rubber composition.

[0067] 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.

[0068] 2. Rubber composition characteristics (Mooney viscosity) The rubber composition according to one embodiment of the present invention preferably has a Mooney viscosity of 80 or less, measured in accordance with JIS K 6300-1 with an L-type rotor preheating time of 1 minute, a rotation time of 4 minutes, and a test temperature of 100°C. The Mooney viscosity may be, for example, 40, 45, 50, 55, 60, 65, 70, 75, or 80, or may be within a range between any two of the values ​​exemplified here.

[0069] (Moisture absorption rate (moisture absorption rate of test vulcanized molded body stored for 72 hours at 40°C and 90% humidity)) When a vulcanized test molded article is obtained by press-vulcanizing the rubber composition according to the present invention at 160°C for 50 minutes and then stored for 72 hours in an environment of 40°C and 90% humidity, the moisture absorption rate M of the vulcanized test molded article is 0.1 to 2.0% by mass, preferably 0.1 to 0.6% by mass. The moisture absorption rate M may be, for example, 0.1, 0.2, 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, 1.8, 1.9, or 2.0% by mass, or may be within a range between any two of the values ​​exemplified here.

[0070] The moisture absorption rate can be measured by the following method. 100 g of the rubber composition is press-vulcanized in accordance with JIS K 6299 at 160° C. for 50 minutes to prepare a sheet-like vulcanized molded product having a thickness of 2 mm. The above-mentioned 2 mm thick sheet-shaped vulcanized molding was punched out to a length of 25 mm, width of 20 mm, and thickness of 2 mm (surface area 1180 mm 2 ) is prepared as a vulcanized molded article for moisture absorption testing. The mass of the obtained vulcanized molded article for testing is measured and defined as Ag. Next, the vulcanized molded article for testing is stored in an environment of 90% humidity for 72 hours, and the mass after storage is measured and defined as Bg. The moisture absorption rate M is calculated using the following formula. M = (BA) / A × 100

[0071] The rubber composition according to the present invention is a rubber composition that combines a specific type of chloroprene rubber with an epoxy compound of a specific structure, and by adjusting the types and amounts of the rubber composition and controlling the moisture absorption rate of a vulcanized molded product of the rubber composition within a specific numerical range, the rubber composition has a sufficiently low Mooney viscosity in the unvulcanized product and excellent water resistance in the vulcanized product of the rubber composition. Furthermore, the rubber composition according to one embodiment of the present invention also has excellent heat resistance in the vulcanized product of the rubber composition.

[0072] The moisture absorption rate M of the test vulcanized molded article made from the rubber composition can be controlled by adjusting the production conditions of the rubber composition, in particular, the types and amounts of the acid acceptor, rubber, filler such as carbon, epoxy compound, etc.

[0073] (Water resistance (volume change rate after immersion in 70°C water for 336 hours)) In a rubber composition according to one embodiment of the present invention, when a vulcanized molded article obtained by molding based on JIS K 6299 is immersed in water at 70°C for 336 hours, the volume change ΔV calculated based on JIS K 6258 is preferably less than 6%. The volume change ΔV may be, for example, 0, 1, 2, 3, 4, or 5%, and may be within a range between any two of the values ​​exemplified here.

[0074] (Heat resistance (change in elongation at break after heating at 100°C for 96 hours)) In a rubber composition according to one embodiment of the present invention, a vulcanized molded article obtained by molding in accordance with JIS K 6299 is molded into a dumbbell No. 3 test piece, and the elongation at break is measured in accordance with JIS K 6251. Further, a dumbbell No. 3 test piece prepared in the same manner is heated at 100°C for 96 hours, and then the elongation at break is measured in accordance with JIS K 6251. It is preferable that the rate of change in elongation at break before and after heating is less than 30%. The rate of change in elongation at break before and after heating is, for example, 0, 5, 10, 15, 20, 25, or 29%, and may be within a range between any two of the values ​​exemplified here.

[0075] 1.4 Unvulcanized moldings, vulcanized products and vulcanized moldings An unvulcanized molded article according to one embodiment of the present invention uses a rubber composition according to one embodiment of the present invention, and is a molded article (molded product) of the rubber composition (unvulcanized state) according to one embodiment of the present invention. A method for producing an unvulcanized molded article according to one embodiment of the present invention includes a step of molding the rubber composition (unvulcanized state) according to one embodiment of the present invention. The unvulcanized molded article according to one embodiment of the present invention is made of the rubber composition (unvulcanized state) according to one embodiment of the present invention.

[0076] A vulcanizate according to one embodiment of the present invention is a vulcanizate of the rubber composition according to one embodiment of the present invention. A method for producing a vulcanizate according to one embodiment of the present invention includes a step of vulcanizing the rubber composition according to one embodiment of the present invention.

[0077] A vulcanized molded article according to one embodiment of the present invention is a vulcanized molded article of a rubber composition according to one embodiment of the present invention. The vulcanized molded article according to one embodiment of the present invention uses a vulcanizate according to one embodiment of the present invention and is a molded article (molded product) of the vulcanizate according to one embodiment of the present invention. The vulcanized molded article according to one embodiment of the present invention is made of a vulcanizate according to one embodiment of the present invention.

[0078] The vulcanized molded article according to one embodiment of the present invention can be obtained by molding a vulcanizate obtained by vulcanizing the rubber composition (unvulcanized state) according to one embodiment of the present invention, and can also be obtained by vulcanizing a molded article obtained by molding the rubber composition (unvulcanized state) according to one embodiment of the present invention. The vulcanized molded article according to one embodiment of the present invention can be obtained by vulcanizing the rubber composition according to one embodiment of the present invention after molding or during molding. A method for producing a vulcanized molded article according to one embodiment of the present invention comprises a step of molding a vulcanized article according to one embodiment of the present invention, or a step of vulcanizing an unvulcanized molded article according to one embodiment of the present invention.

[0079] (Moisture absorption rate of vulcanized molded products stored for 72 hours at 40°C and 90% humidity) When the vulcanized molded article according to the present invention is stored for 72 hours in an environment of 40°C and 90% humidity, the moisture absorption rate M of the test vulcanized molded article is preferably 0.1 to 2.0% by mass, and more preferably 0.1 to 0.6% by mass. The moisture absorption rate M may be, for example, 0.1, 0.2, 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, 1.8, 1.9, or 2.0% by mass, and may be within a range between any two of the values ​​exemplified here.

[0080] (Water resistance (volume change rate after immersion in 70°C water for 336 hours)) The vulcanized molded article according to one embodiment of the present invention is preferably immersed in water at 70°C for 336 hours and has a volume change ΔV of less than 6% as calculated in accordance with JIS K 6258. The volume change ΔV may be, for example, 0, 1, 2, 3, 4, or 5%, or may be within a range between any two of the values ​​exemplified here.

[0081] (Heat resistance (change in elongation at break after heating at 100°C for 96 hours)) A vulcanized molded product according to one embodiment of the present invention is molded into a dumbbell-shaped No. 3 test piece, and the elongation at break is measured according to JIS K 6251. Further, a dumbbell-shaped No. 3 test piece prepared in the same manner is heated at 100°C for 96 hours, and the elongation at break is measured according to JIS K 6251. It is preferable that the rate of change in elongation at break before and after heating is less than 30%. The rate of change in elongation at break before and after heating is, for example, 0, 5, 10, 15, 20, 25, or 29%, and may be within a range between any two of the values ​​exemplified here.

[0082] The unvulcanized molded article, vulcanized product, and vulcanized molded article 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. The rubber composition according to the present invention has excellent Mooney viscosity in the unvulcanized form and excellent water resistance in the vulcanized form, and can therefore be used as various components requiring these properties. Furthermore, the rubber composition according to one embodiment of the present invention has excellent Mooney viscosity in the unvulcanized form and excellent water resistance and heat resistance in the vulcanized form, and can therefore be used as various components requiring these properties. Specifically, the rubber composition according to one embodiment of the present invention 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, and can be particularly used as components used in environments requiring water resistance or water resistance and heat resistance. For example, the vulcanized molded article according to one embodiment of the present invention can be suitably used as a rubber roll, and particularly suitably used as a rubber roll for steelwork requiring water resistance (e.g., a rubber roll for cleaning steel plates). Moreover, the vulcanized molded article according to one embodiment of the present invention can be particularly suitably used as a rubber roll for papermaking, which is required to have water resistance.

[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 application, 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 enhance the water resistance, or water resistance and heat resistance, of these components while maintaining the processability of the unvulcanized product. This makes it possible to manufacture seals for use in harsh environments, which was previously difficult with conventional rubber compositions.

[0084] (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 improve the water resistance, or the water resistance and heat resistance, of hose materials while maintaining the processability of the unvulcanized product. This makes it possible to produce hose materials for use in harsh environments, which has been difficult with conventional rubber compositions.

[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 improve the water resistance, or the water resistance and heat resistance, 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 harsh environments, 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 improve the water resistance or the water resistance and heat resistance of boots. This makes it possible to produce boots that can be used in harsher environments than conventional rubber compositions.

[0086] (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 improve the water resistance, or water resistance and heat resistance, of these components. This makes it possible to manufacture seals that can be used in harsh environments, which was previously difficult with conventional rubber compositions.

[0087] (rubber roll) Rubber rolls are manufactured by adhesively coating a metal core, such as an iron core, with rubber. They 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 the friction of the objects being conveyed, making it widely used in rubber roll applications. However, rubber rolls used in environments that come into contact with oil and water, such as during the production of industrial materials and products for steelmaking and papermaking, lack sufficient oil and water resistance, and improvements are needed. Furthermore, rubber rolls are sometimes exposed to acids and alkalis during plating processes such as gold, silver, nickel, chromium, and zinc, and during product cleaning processes, so resistance to these conditions is also required. Furthermore, rubber rolls used to transport heavy loads are prone to deformation under load, and improvements are needed. The rubber composition of the present invention can improve the water resistance or the water resistance and heat resistance of a rubber roll, and thus can be particularly suitably used for rubber rolls that are in contact with water for a long period of time, such as rubber rolls for steel (e.g., rubber rolls for cleaning steel plates) and rubber rolls for papermaking.

[0088] (Industrial Cables) Industrial cables are linear components for transmitting electrical or optical signals. They are made of good conductors such as copper or copper alloys, or optical fibers, coated 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 improve the water resistance, or the water resistance and heat resistance, of industrial cables. This makes it possible to manufacture industrial cables that can be used in harsh environments, which has been difficult with conventional rubber compositions.

[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 materials, they have been prone to damage due to deterioration. The rubber composition of the present invention can improve the water resistance, or the water resistance and heat resistance, of industrial conveyor belts. This makes it possible to produce industrial conveyor belts that can be used in harsh environments, which has been difficult with conventional rubber compositions.

[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 improve the water resistance, or the water resistance and heat resistance, of the sponge. Furthermore, the use of chloroprene-based rubber also makes it possible to improve the flame retardancy of the sponge. This makes it possible to produce sponges that can be used in harsh environments, 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.

[0091] Methods for molding the rubber composition (unvulcanized state) and vulcanized product according to one embodiment of the present invention 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, for example, 140, 150, 160, 170, 180, 190, 200, 210, or 220°C, or may be within a range between any two of the values ​​exemplified here. 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, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 minutes, or may be within a range between any two of the values ​​exemplified here. [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] <Manufacturing method of chloroprene rubber (chloroprene-acrylonitrile copolymer AN content 10%)> 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 a chloroprene-based latex containing a chloroprene-acrylonitrile copolymer.

[0094] 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)

[0095] The pH of the above-mentioned chloroprene-based latex was adjusted to 7.0 using acetic acid or sodium hydroxide, and then the chloroprene-based 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-based rubber (chloroprene-acrylonitrile copolymer AN content: 10%).

[0096] 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.

[0097] 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

[0098] 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.

[0099] The content of acrylonitrile monomer units contained in the chloroprene-based rubber 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 chloroprene-based rubber was measured, and the content of acrylonitrile monomer units was calculated. The content of acrylonitrile monomer units was 10.0 mass%.

[0100] The above elemental analysis was carried out 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 prepared using aspartic acid (10.52%), which has a known nitrogen content, as the standard substance. The chloroprene-based rubber (chloroprene-acrylonitrile copolymer AN content: 10%) obtained by the above manufacturing method had an acrylonitrile monomer unit content of 10.0% by mass.

[0101] <Manufacturing method of chloroprene rubber (chloroprene-acrylonitrile copolymer AN content 5%, 25%)> The amount of acrylonitrile monomer added in the polymerization process was changed to obtain a chloroprene-based rubber having an acrylonitrile monomer unit content of 5.0 mass% (chloroprene-acrylonitrile copolymer AN content: 5%) and a chloroprene-based rubber having an acrylonitrile monomer unit content of 25.0 mass% (chloroprene-acrylonitrile copolymer AN content: 25%).

[0102] <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.

[0103] The components used to obtain the rubber composition are as follows: (chloroprene rubber) Chloroprene-acrylonitrile copolymer AN content 10%: A chloroprene-acrylonitrile copolymer having an acrylonitrile monomer unit content of 10.0% by mass. The above-mentioned chloroprene-acrylonitrile copolymer AN content 5%: the above-mentioned chloroprene-acrylonitrile copolymer having an acrylonitrile monomer unit content of 5.0% by mass The above-mentioned chloroprene-acrylonitrile copolymer AN content 25%: the above-mentioned chloroprene-acrylonitrile copolymer having an acrylonitrile monomer unit content of 25.0% by mass. Chloroprene rubber AN content 0%: Mercaptan-modified chloroprene rubber (chloroprene homopolymer), manufactured by Denka Co., Ltd., S-40V

[0104] (epoxy compounds) Epoxy compound A 1,6-Hexanediol diglycidyl ether (Denacol EX-212): Nagase ChemteX Corporation, Denacol EX-212, viscosity: 20 cP, epoxy equivalent: 151 g / eq., SP value: 9.37 Ethylene glycol diglycidyl ether (Epolite 40E): Kyoeisha Chemical Co., Ltd., Epolite 40E, viscosity: 15-35 cP, epoxy equivalent: 125-140 g / eq., SP value: 10.40 Cresyl glycidyl ether (ED-529): ADEKA Corporation, ED-529, viscosity: 20 cP, epoxy equivalent: 180 g / eq., SP value: 10.40 Trimethylolpropane triglycidyl ether (ED-505), viscosity: 150 cP, epoxy equivalent: 150 g / eq., SP value: 10.26 Dicyclopentadiene epoxy resin (EP-4088S): ADEKA Corporation, EP-4088S, viscosity: 230 cP, epoxy equivalent: 170 g / eq. 1,4-Butanediol diglycidyl ether (Denacol-214L): Nagase ChemteX Corporation, Denacol-214L, viscosity: 15 cP, epoxy equivalent: 115 g / eq., SP value: 10.40 High-purity ethylene glycol diglycidyl ether (Denacol EX-810P), viscosity: 10 cP, epoxy equivalent: 95 g / eq., SP value: 10.40 Other epoxy compounds Alicyclic epoxy resin (Celloxide 2021P)* containing ester bonds: Celloxide 2021P, manufactured by Daicel Corporation, represented by the following chemical formula:

[0105] [ka]

[0106] plasticizer Ether ester compound (RS-700) *Contains an ester bond and no epoxy group: ADEKA Cizer RS-700 manufactured by ADEKA Corporation Processing aids Stearic acid: New Japan Chemical Co., Ltd., Stearic acid 50S Heat-resistant antioxidant Nocrac CD: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, Ouchi Shinko Chemical Industry Co., Ltd., Nocrac CD Filler Carbon black (FEF): Asahi Carbon Co., Ltd., Asahi #60, FEF Acid acceptor ·ZHT-4A: Chemical formula Mg3ZnAl2(OH) 12 CO3·3H2O, Kyowa Chemical Industry Co., Ltd., ZHT-4A Zinc oxide: Sakai Chemical Industry Co., Ltd., zinc oxide type 2 Vulcanizing Agent Organic peroxide: 1,4-bis[(t-butylperoxy)isopropyl]benzene, NOF Corporation, Perbutyl P Vulcanization accelerator Noccela CZ: N-cyclohexylbenzothiazole-2-sulfenamide, Ouchi Shinko Chemical Industry Co., Ltd., Noccela CZ hardener Carboxylic acid dihydrazide: Otsuka Chemical Co., Ltd., isophthalic acid dihydrazide It was confirmed that when 5 parts by mass of carboxylic acid dihydrazide was added to 100 parts by mass of the epoxy compound A used in the examples, the compound cured within 40 minutes.

[0107] <Evaluation of rubber composition (unvulcanized)> (Mooney viscosity measurement) The Mooney viscosity of the rubber composition (unvulcanized) was measured in accordance with JIS K 6300-1, with an L-type rotor preheating time of 1 minute, a rotation time of 4 minutes, and a test temperature of 100°C. A: 65 or less B: More than 65, less than 70 C: Over 70, under 80 D: over 80

[0108] <Preparation of vulcanized molded body> 100 g of the obtained rubber composition was press-vulcanized in accordance with JIS K 6299 at 160°C for 50 minutes to prepare a vulcanized molded sheet having a thickness of 2 mm.

[0109] <Evaluation of vulcanized molded products> The vulcanized molded articles were evaluated as follows. The results are shown in Tables 1 and 2.

[0110] (Moisture absorption rate (moisture absorption rate of test vulcanized molded body stored for 72 hours at 40°C and 90% humidity)) The above-mentioned 2 mm thick sheet-shaped vulcanized molding was punched out to a length of 25 mm, width of 20 mm, and thickness of 2 mm (surface area 1180 mm 2 ) was prepared as a vulcanized molded article for moisture absorption testing. The mass of the obtained vulcanized molded article for testing was measured and recorded as Ag. Next, the vulcanized molded article for testing was stored in an environment of 90% humidity for 72 hours, and the mass after storage was measured and recorded as Bg. The moisture absorption rate M was calculated using the following formula. M = (BA) / A × 100

[0111] (Water resistance (volume change rate after immersion in 70°C water for 336 hours)) A test piece measuring 25 mm in length and 20 mm in width was punched out from the 2 mm-thick sheet-like vulcanized molding 1. The test piece was immersed in water at 70°C for 336 hours, and the volume change rate ΔV was calculated according to JIS K 6258. The volume change rate ΔV was evaluated according to the following criteria. A: Less than 2% B: 2% or more, less than 4% C: 4% or more, less than 6% D: 6% or more

[0112] (Heat resistance (change in elongation at break after heating at 100°C for 96 hours)) The above-mentioned 2 mm thick sheet-like vulcanized molded article was molded into a dumbbell No. 3 test piece, and the elongation at break was measured in accordance with JIS K 6251. In addition, a dumbbell No. 3 test piece prepared in the same manner was heated at 100°C for 96 hours, and then the elongation at break was measured in accordance with JIS K 6251, and the rate of change before and after heating was evaluated according to the following criteria. A: Less than 25% B: 25% or more, less than 28% C: 28% or more, less than 30% D: 30% or more

[0113]

Table 1

[0114]

Table 2

Claims

1. A rubber composition containing a chloroprene-based rubber and an epoxy-based compound, the chloroprene-based rubber includes a chloroprene-based rubber having an unsaturated nitrile monomer unit content of less than 25% by mass, The epoxy compound includes an epoxy compound A that does not contain an ester bond, the rubber composition contains 0.05 to 25.0 parts by mass of the epoxy compound A relative to 100 parts by mass of the chloroprene rubber, the rubber composition is press-vulcanized at 160°C for 50 minutes to obtain a vulcanized test molded article, and when the vulcanized test molded article is stored in an environment of 40°C and 90% humidity for 72 hours, the moisture absorption rate M of the vulcanized test molded article is 0.1 to 2.0% by mass; The moisture absorption rate M of the rubber composition is expressed by the following formula, where the mass of the test vulcanized molded article after storage is Bg and the mass of the test vulcanized molded article before storage is Ag. M=(B-A) / A×100

2. The rubber composition according to claim 1, wherein the moisture absorption rate M is 0.1 to 0.6 mass %.

3. 3. The rubber composition according to claim 1, wherein the epoxy compound A has an epoxy equivalent of 120 to 180.

4. 3. The rubber composition according to claim 1, wherein the epoxy compound A has a solubility parameter of 9.0 to 10.

5.

5. 3. The rubber composition according to claim 1, wherein the content of the acid acceptor is less than 7 parts by mass per 100 parts by mass of the chloroprene rubber.

6. A vulcanized molded article of the rubber composition according to claim 1 or 2.

7. A rubber roll comprising the vulcanized molded article according to claim 6.

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