Rubber composition, vulcanized molded article, and rubber roll

Abstract

The present invention provides a rubber composition that can produce vulcanized molded articles having excellent water resistance and alkali resistance. [Solution] According to the present invention, a rubber composition containing a rubber component, wherein when a laminate is made by stacking test vulcanized molded bodies 1 of the rubber composition until it reaches a thickness of 6.0 mm or more, the hardness measured with a Type A durometer based on JIS K 6253-3:2023 is X, and when the heat generated by evaluating the test vulcanized molded body 2 of the rubber composition using a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute, based on JIS K 6265:2018, the hardness X and heat generated Y satisfy the following formula (1), and the test vulcanized molded body 1 contains the rubber composition as specified in JIS K A rubber composition is provided, which is a sheet-like vulcanized molded body with a thickness of 2 mm obtained by press vulcanization at 170°C for 20 minutes in accordance with 6299:2012, and the test vulcanized molded body 2 is a cylindrical vulcanized molded body with a diameter of 15 mm and a height of 25 mm obtained by press vulcanization of the rubber composition at 170°C for 20 minutes. 1.4XY>45.0 (1)

Description

[Technical Field]

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

[0002] Rubber products are widely used as materials for general industrial applications such as power transmission belts and conveyor belts, automotive air springs, vibration damping rubber, hoses, wipers, immersion products, sealing components, adhesives, boots, rubberized fabrics, and rubber rolls.

[0003] For example, Patent Document 1 discloses an invention relating to a sulfur-modified chloroprene rubber composition comprising sulfur-modified chloroprene rubber, a vulcanization accelerator, zinc oxide, and magnesium oxide, wherein the amount of the vulcanization accelerator is 0.1 to 5 parts by weight, and the amounts of zinc oxide and magnesium oxide are specified by a predetermined relationship between their respective amounts and the Mooney scorch time t. Furthermore, Patent Document 2 discloses an invention relating to a copolymer of a chloroprene monomer and an unsaturated nitrile compound having a Mooney viscosity ML(1+4)100℃ of 20 to 80 and a functional group of a specific structure. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-209522 [Patent Document 2] International Publication No. 2020 / 044899 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, conventional rubber compositions had room for improvement in terms of water resistance and alkali resistance in vulcanized molded articles of the composition.

[0006] This invention has been made in view of these circumstances, and provides a rubber composition that can produce a vulcanized molded article having excellent water resistance and alkali resistance. [Means for solving the problem]

[0007] According to the present invention, a rubber composition containing a rubber component, wherein when a laminate of test vulcanized molded articles 1 of the rubber composition is stacked until it reaches a thickness of 6.0 mm or more, the hardness measured with a Type A durometer according to JIS K 6253-3:2023 is X, and when the heat generated by evaluating a test vulcanized molded article 2 of the rubber composition using a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute according to JIS K 6265:2018 is Y, then the hardness X and the heat generated Y satisfy the following formula (1), and the test vulcanized molded article 1 contains the rubber composition according to JIS K A rubber composition is provided, which is a sheet-like vulcanized molded body with a thickness of 2 mm obtained by press vulcanization at 170°C for 20 minutes in accordance with 6299:2012, and the test vulcanized molded body 2 is a cylindrical vulcanized molded body with a diameter of 15 mm and a height of 25 mm obtained by press vulcanization of the rubber composition at 170°C for 20 minutes. 1.4XY>45.0 (1)

[0008] Through diligent research, the inventors discovered that by adjusting the formulation of the rubber composition so that the hardness X of the test vulcanized molded body 1 of the rubber composition and the heat generated Y of the test vulcanized molded body 2 of the rubber composition satisfy a specific relationship, it is possible to obtain a rubber composition that can produce vulcanized molded bodies with excellent water resistance and alkali resistance, thus completing the present invention.

[0009] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other.

[0010] [1] A rubber composition containing a rubber component, wherein the hardness of a laminate obtained by stacking test vulcanized molded bodies 1 of the rubber composition until a thickness of 6.0 mm or more is measured with a Type A durometer according to JIS K 6253-3:2023 is X, and the heat generated by evaluating the test vulcanized molded body 2 of the rubber composition with a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute according to JIS K 6265:2018 is Y, such that the hardness X and heat generated Y satisfy the following formula (1), and the test vulcanized molded body 1 contains the rubber composition according to JIS K A sheet-like vulcanized molded body with a thickness of 2 mm obtained by press vulcanization at 170°C for 20 minutes in accordance with 6299:2012, wherein the test vulcanized molded body 2 is a cylindrical vulcanized molded body with a diameter of 15 mm and a height of 25 mm obtained by press vulcanization of the rubber composition at 170°C for 20 minutes. 1.4XY>45.0 (1) [2] The rubber composition according to [1], wherein the hardness X is 40 or more and 98 or less. [3] The rubber composition according to [1] or [2], wherein the rubber component comprises a chloroprene polymer. [4] The chloroprene polymer comprises 80 to 100% by mass of chloroprene monomer units with respect to 100% by mass of the chloroprene polymer, the rubber composition according to [3]. A vulcanized molded article of a rubber composition described in any of [5][1] to [4]. [6] A rubber roll comprising a core metal and a surface layer provided on the circumferential surface of the core metal, wherein the surface layer includes the vulcanized molded body described in [5], and the rubber roll is used in at least one of an acid cleaning line and an alkaline cleaning line. [7]A vulcanized molded body containing a rubber component, when the vulcanized molded body is a test vulcanized molded body 1' with a thickness of 6.0 mm or more, the hardness measured with a Type A durometer based on JIS K 6253-3:2023 is X', and when the vulcanized molded body is a cylindrical test vulcanized molded body 2' with a diameter of 15 mm and a height of 25 mm, based on JIS K 6265:2018, at 40 °C, a strain of 0.175 inches, a load of 55 pounds, and a vibration frequency of 1,800 times per minute, when the heat generation obtained by evaluation in a constant strain flexometer test is Y', a vulcanized molded body in which the hardness X' and the heat generation Y' satisfy the following formula (2). 1.4X' - Y' > 45.0 (2)

Advantages of the Invention

[0011] According to the rubber composition of the present invention, a vulcanized molded body having excellent water resistance and alkali resistance can be obtained. Further, since the vulcanized molded body according to the present invention has excellent water resistance and alkali resistance, by taking advantage of these properties, it can be used as various members that require water resistance and / or alkali resistance, for example, as a rubber roll. The rubber roll according to one embodiment of the present invention is excellent in water resistance and alkali resistance, and can be used, for example, as at least one rubber roll in a pickling line and an alkali cleaning line.

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be exemplified and the present invention will be described in detail. The present invention is not limited in any way by these descriptions. Each feature of the embodiments of the present invention shown below can be combined with each other. Also, an invention can be established independently for each feature.

[0013] 1. Rubber composition The rubber composition according to the present invention contains a rubber component.

[0014] 1.1 Rubber component The rubber component according to the present invention may include at least one selected from chloroprene rubber, natural rubber (NR), hydrogenated acrylonitrile butadiene rubber (H-NBR), acrylonitrile butadiene rubber (NBR), and chlorosulfonated polyethylene (CSM). The rubber component preferably includes at least one selected from chloroprene rubber and natural rubber (NR), and the rubber composition according to one embodiment of the present invention preferably includes chloroprene rubber, that is, preferably includes a chloroprene polymer.

[0015] 1.1.1 Chloroprene-based rubber The chloroprene-based rubber according to the present invention refers to a rubber containing a chloroprene-based polymer having chloroprene (2-chloro-1,3-butadiene) as a monomer unit (monomer unit = structural unit). Examples of chloroprene-based polymers include chloroprene homopolymers and chloroprene copolymers (polymers of chloroprene and monomers copolymerizable with chloroprene). The polymer structure of the chloroprene-based polymer is not particularly limited.

[0016] It should be noted that commercially available 2-chloro-1,3-butadiene may contain small amounts of 1-chloro-1,3-butadiene as an impurity. Such 2-chloro-1,3-butadiene containing small amounts of 1-chloro-1,3-butadiene can also be used as the chloroprene monomer in this embodiment.

[0017] A chloroprene polymer according to one embodiment of the present invention may have monomer units derived from monomers other than chloroprene monomers. Examples of monomers other than chloroprene monomers are not particularly limited as long as they are copolymerizable with chloroprene monomers, but include unsaturated nitriles, esters of (meth)acrylic acid (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.), hydroxyalkyl (meth)acrylates (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, sulfur, etc. A chloroprene polymer according to one embodiment of the present invention may contain at least one monomer unit selected from 2,3-dichloro-1,3-butadiene and unsaturated nitrile monomers. A chloroprene polymer according to one embodiment of the present invention may contain unsaturated nitrile monomer units.

[0018] In the chloroprene polymer according to one embodiment of the present invention, when the chloroprene polymer is considered as 100% by mass, the content of unsaturated nitrile monomer units can be 25% by mass or less, preferably 20% by mass or less, and more preferably less than 20% by mass. The content of 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, 25% by mass, and may be within the range of any two of the values ​​exemplified here. By keeping the content of unsaturated nitrile monomer units in the rubber composition below the above upper limit, the water resistance and cold resistance of the vulcanized molded article of the rubber composition are further improved. In addition, the inclusion of unsaturated nitrile monomer units improves the oil resistance of the vulcanized molded article of the rubber composition.

[0019] Examples of unsaturated nitriles include acrylonitrile, methacrylonitrile, ethacrylonitrile, and phenylacrylonitrile. Unsaturated nitriles can be used individually or in combination of two or more. From the viewpoint of easily obtaining excellent moldability and easily obtaining excellent tensile strength, elongation at break, hardness, tear strength, and oil resistance in vulcanized molded articles, it is preferable that the unsaturated nitrile includes acrylonitrile.

[0020] The content of unsaturated nitrile monomer units in chloroprene rubber can be calculated from the nitrogen atom content in the chloroprene rubber. Specifically, the nitrogen atom content in 100 mg of chloroprene rubber can be measured using an elemental analyzer (Sumigraph 220F: manufactured by Sumika Analysis Center Co., 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 temperature is set to 900°C for the reactor, 600°C for the reduction furnace, 70°C for the column, and 100°C for the detector, with 0.2 mL / min of oxygen as the combustion gas and 80 mL / min of helium as the carrier gas flowing. A calibration curve can be created using aspartic acid (10.52%), which has a known nitrogen content, as a standard substance.

[0021] The chloroprene polymer according to one embodiment of the present invention preferably contains 75 to 100% by mass of chloroprene monomer units, and more preferably 80 to 100 parts by mass, when the chloroprene polymer is considered to be 100% by mass. The content of chloroprene monomer units in the chloroprene polymer is, for example, 75, 80, 85, 90, 95, 99, or 100% by mass, and may be within the range of any two of the values ​​exemplified herein. By setting the content of chloroprene monomer units within the above numerical range, a rubber composition can be obtained that yields a molded article with an excellent balance of hardness, tensile strength, and cold resistance.

[0022] The chloroprene polymer according to one embodiment of the present invention may contain 0 to 20% by mass of monomer units other than chloroprene monomer units and unsaturated nitrile monomer units when the chloroprene polymer is considered to be 100% by mass. The content of monomer units other than chloroprene monomer units and unsaturated nitrile monomer units in the chloroprene polymer may be, for example, 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, or 20% by mass, and may be within the range of any two of the values ​​exemplified here. By adjusting the copolymerization amount of monomers other than chloroprene monomers and unsaturated nitrile monomers to the above range, the effects of copolymerizing these monomers can be expressed without impairing the properties of the resulting rubber composition.

[0023] The chloroprene-based rubber according to one embodiment of the present invention may include at least one polymer selected from a chloroprene homopolymer, a copolymer containing chloroprene monomer units and unsaturated nitrile monomer units, and a copolymer containing chloroprene monomer units and 2,3-dichloro-1,3-butadiene monomer units.

[0024] The rubber component according to the present invention can be a chloroprene-based rubber, either alone or in combination of two or more types. In the case of a rubber composition according to one embodiment of the present invention that contains two or more types of chloroprene rubber, it is preferable that the content rate based on the total amount of each monomer unit contained in the two or more chloroprene polymers is within the above numerical range, relative to 100% by mass of the total of the two or more types of chloroprene polymers contained in the rubber composition.

[0025] The chloroprene polymer (chloroprene homopolymer, chloroprene copolymer, etc.) contained in the chloroprene rubber according to the present invention may be sulfur-modified chloroprene polymer, mercaptan-modified chloroprene polymer, xanthogene-modified chloroprene polymer, dithiocarbonate-based chloroprene polymer, trithiocarbonate-based chloroprene polymer, carbamate-based chloroprene polymer, etc.

[0026] 1.1.2 Method for manufacturing chloroprene rubber The method for producing chloroprene rubber according to the present invention is not particularly limited, but it can be obtained by a production method that includes an emulsion polymerization step in which raw material monomers containing chloroprene monomers are emulsion polymerized. In the emulsion polymerization process according to one embodiment of the present invention, a chloroprene monomer, or a raw material monomer containing a chloroprene monomer and other monomers, is emulsion polymerized using an emulsifier, dispersant, catalyst, chain transfer agent, etc. as appropriate, and when the desired final conversion rate is reached, a polymerization termination agent 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 in the emulsion polymerization process. The method for this is not particularly limited, and for example, a steam stripping method can be used. After that, the pH is adjusted, and a chloroprene rubber containing a chloroprene polymer can be obtained by going through processes such as conventional freeze-coagulation, water washing, and hot air drying.

[0027] There are no particular restrictions on the polymerization initiator used in emulsion polymerization; known polymerization initiators commonly used in the emulsion polymerization of chloroprene can be used. Examples of polymerization initiators include potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and organic peroxides such as t-butyl hydroperoxide.

[0028] There are no particular restrictions on the emulsifier used in emulsion polymerization, and any known emulsifier commonly used in the emulsion polymerization of chloroprene can be used. Examples of emulsifiers include alkali metal salts of saturated or unsaturated fatty acids having 6 to 22 carbon atoms, alkali metal salts of rosinic acid or disproportionated rosinic acid (e.g., potassium rosinate), and alkali metal salts of formalin condensates of β-naphthalenesulfonic acid (e.g., sodium salt).

[0029] There are no particular restrictions on the molecular weight modifier used in emulsion polymerization, and known molecular weight modifiers commonly used in the emulsion polymerization of chloroprene can be used, such as mercaptan compounds, xanthogene compounds, dithiocarbonate compounds, trithiocarbonate compounds, and carbamate compounds. In one embodiment of the present invention, xanthogene compounds, dithiocarbonate compounds, trithiocarbonate compounds, and carbamate compounds can be suitably used as molecular weight modifiers for chloroprene-based rubber.

[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. Polymerization may be carried out so that the final conversion rate of the monomer falls within the range of 40 to 95% by mass. To adjust the final conversion rate, a polymerization inhibitor can be added to stop the polymerization reaction when the desired conversion rate is reached.

[0031] There are no particular restrictions on the polymerization inhibitor; any known polymerization inhibitor commonly used in the emulsion polymerization of chloroprene can be used. Examples of polymerization inhibitors include phenothiazine (thiodiphenylamine), 4-t-butylcatechol, and 2,2-methylenebis-4-methyl-6-t-butylphenol.

[0032] A chloroprene-based rubber according to one embodiment of the present invention can be obtained, for example, by removing unreacted monomers by steam stripping, adjusting the pH of the latex, and then following conventional freeze-solidification, water washing, and hot-air drying processes.

[0033] Chloroprene-based rubbers are classified into mercaptan-modified type, xanthogene-modified type, sulfur-modified type, dithiocarbonate type, trithiocarbonate type, and carbamate type, depending on the type of molecular weight modifier used.

[0034] 1.2 Organic peroxides The rubber composition according to the present invention may contain organic peroxides. One or more organic peroxides may be freely selected and used.

[0035] 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. (sil) 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-tetramethylbutyl peroxy-2-ethylhexanoate, disuccinate peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane, t-hexyl peroxide Oxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, t-butylperoxy-2-ethylhexanoate, di(3-methylbenzoyl)peroxide, benzoyl(3-methylbenzoyl)peroxide, dibenzoylperoxide, 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-butylperoxy2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-di-methyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, 2,Examples include 2-di-(t-butylperoxy)butane, t-butylperoxybenzoate, n-butyl4,4-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)hexyn-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide. Among these, it is preferable that at least one is 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)hexyn-3, and particularly preferable is 1,4-bis[(t-butylperoxy)isopropyl]benzene.

[0036] The rubber composition according to the present invention preferably contains 0 to 5 parts by mass of organic peroxide relative to the rubber components, from the viewpoint of ensuring processing safety and obtaining a good vulcanized molded article. The organic peroxide content is, for example, 0, 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 the range of any two of the values ​​exemplified here. Furthermore, in the rubber composition according to one embodiment of the present invention, the hardness X and heat generation Y, and the relationship between hardness X and heat generation Y, can also be adjusted by adjusting the types and amounts of other components without incorporating organic peroxide.

[0037] 1.3 Vulcanizing agent The rubber composition according to the present invention can contain a vulcanizing agent. The type of the vulcanizing agent is not particularly limited as long as the effects of the present invention are not impaired. The vulcanizing agent is preferably a vulcanizing agent that can be used for vulcanizing chloroprene rubber. The vulcanizing agent can be freely selected and used singly or in combination of two or more. Examples of the vulcanizing agent include zinc oxide.

[0038] From the viewpoint of ensuring processing safety and obtaining a sufficiently vulcanized vulcanized molded body, the rubber composition according to the present invention preferably contains 1 to 15 parts by mass of a vulcanizing agent with respect to the rubber component contained in the rubber composition. The content of the vulcanizing agent is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 parts by mass with respect to 100 parts by mass of the rubber component contained in the rubber composition, and may be within the range between any two of the numerical values exemplified herein.

[0039] 1.4 Acid acceptor The rubber composition according to an embodiment of the present invention can contain an acid acceptor. The acid acceptor can contain at least one selected from the group consisting of hydrotalcite compounds, magnesium-aluminum solid solutions, magnesium oxide, lead oxide, red lead, iron trioxide, titanium dioxide, and calcium oxide, and can contain at least one selected from the group consisting of hydrotalcite compounds, magnesium-aluminum solid solutions, and magnesium oxide, and preferably contains magnesium oxide. The acid acceptor can be used singly or in combination of two or more.

[0040] As the hydrotalcite, those represented by the following formula can be used. [M x 1-x M 3+ x (OH)2] x+ [A n-x / n ·mH2O] x-

[0041] In the above formula, M 2+ :Mg 2+ 、Zn2+ at least one divalent metal ion selected from the above. M 3+ :Al 3+ Fe 3+ at least one trivalent metal ion selected from the above. A n- :Co3 2- Cl ― NO3 2- at least one n-type anion selected from the above. X:0 <X≦0.33とすることができる。

[0042] Hydrotalcite is 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 Examples include CO3·1,7H2O, and particularly preferably Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 It is CO3·3H2O.

[0043] The amount of acid acceptor added can be 0.1 to 15 parts by mass per 100 parts by mass of rubber components contained in the rubber composition. The amount of acid acceptor added can 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, and may be within the range of any two of the values ​​exemplified here.

[0044] 1.5 Maleimide Compounds A rubber composition according to one embodiment of the present invention may contain a maleimide compound. The maleimide compound can be used alone or in combination of two or more.

[0045] Maleimide compounds can contribute to the vulcanization of rubber compositions as co-crosslinking agents. Examples of maleimide compounds include N,N'-o-phenylenebismaleimide, N,N'-m-phenylenebismaleimide, N,N'-p-phenylenebismaleimide, N,N'-(4,4'-diphenylmethane)bismaleimide, 2,2-bis-[4-(4-maleimoidphenoxy)phenyl]propane, bis(3-ethyl-5-methyl-4-maleimoidphenyl)methane, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylenebismaleimide, and 1,6'-bismaleimide-(2,2,4-trimethyl)hexane. From the viewpoint of improving the heat resistance of the resulting vulcanized product and vulcanized molded article, it is particularly preferable to use N,N'-m-phenylenebismaleimide (also known as m-phenylenedimaleimide).

[0046] The rubber composition according to one embodiment of the present invention may contain 0 to 10 parts by mass of a maleimide compound per 100 parts by mass of rubber components. The content of the maleimide compound may be, for example, 0, 0.1, 0.2, 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and may be within the range of any two of the values ​​exemplified here. By setting the content of the maleimide compound to above the lower limit, the vulcanization of the resulting rubber composition proceeds more sufficiently, and a vulcanized molded article with good mechanical properties and heat resistance can be obtained. Furthermore, by setting the content of the maleimide compound to below the upper limit, the rubber elasticity of the resulting vulcanized molded article can be sufficiently maintained. In addition, the rubber composition according to one embodiment of the present invention can also be adjusted by adjusting the types and amounts of other components without incorporating a maleimide compound, thereby adjusting the relationship between hardness X and heat generation Y, as well as the relationship between hardness X and heat generation Y.

[0047] 1.6 Filling material The rubber composition according to one embodiment of the present invention may contain a filler and may contain carbon black. Examples of carbon black include furnace carbon black such as SAF, ISAF, HAF, EPC, XCF, FEF, GPF, HMF, and SRF; modified carbon black such as hydrophilic carbon black; channel black, fume black, thermal carbon such as FT and MT; acetylene black; and Ketjen black.

[0048] The rubber composition according to the present invention may contain 0 parts by mass or more and less than 100 parts by mass of carbon black per 100 parts by mass of rubber component. The carbon black content may be, for example, 0, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 parts by mass, and may be within the range of any two of the values ​​exemplified herein.

[0049] Furthermore, the rubber composition according to the present invention may also contain fillers other than carbon black, to the extent that they do not impair the effects of the present invention. Examples of fillers other than carbon black include silica such as wet silica filler (hydrated silica), dry silica filler (anhydrous silica), and colloidal silica filler, as well as clay, talc, and calcium carbonate. These can be used individually or in combination of two or more.

[0050] In one embodiment of the present invention, when the rubber component is 100 parts by mass, it is preferable that the total amount of carbon black and fillers (reinforcements) other than carbon black contained in the rubber composition is 0 to 100 parts by mass. In one embodiment of the present invention, when the total amount of carbon black and fillers (reinforcements) other than carbon black contained in the rubber composition is 100% by mass, the content of fillers and reinforcements other than carbon black can be 50% by mass or less. The content of fillers and reinforcements other than carbon black can be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50% by mass, and may be within the range of any two of the values ​​exemplified here. In one embodiment of the present invention, the rubber composition may also not contain fillers (reinforcements) other than carbon black. Furthermore, in one embodiment of the present invention, the rubber composition may not contain carbon black and fillers other than carbon black, and the relationship between hardness X and heat generation Y and hardness X and heat generation Y can be adjusted by adjusting the types and amounts of other components.

[0051] 1.7 Silane coupling agents A rubber composition according to one embodiment of the present invention may contain a silane coupling agent if it contains silica as a filler. There are no particular restrictions on the silane coupling agent, and those used in commercially available rubber compositions can be used, for example, vinyl coupling agents, epoxy coupling agents, styryl coupling agents, methacrylic coupling agents, acrylic coupling agents, amino coupling agents, polysulfide coupling agents, and mercapto coupling agents. In particular, vinyl coupling agents, methacrylic coupling agents, and acrylic coupling agents that initiate the reaction under high-temperature conditions during crosslinking are preferred from the viewpoint of scorch resistance and reinforcing effect.

[0052] A rubber composition according to one embodiment of the present invention may contain 0.5 to 10 parts by mass of a silane coupling agent per 100 parts by mass of silica contained in the rubber composition. The content of the silane coupling agent may be, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass per 100 parts by mass of silica, and may be within the range of any two of the values ​​exemplified herein. Silica can be used alone or in combination of two or more types. By including the above-mentioned silane coupling agent and setting the content of the silane coupling agent within the above-mentioned numerical range, the dispersibility of silica fillers in the rubber and the reinforcing effect between the rubber and silica fillers can be improved, and the occurrence of scorch can be suppressed.

[0053] 1.8 Lubricants and processing aids The rubber composition according to the present invention may further contain a lubricant and / or processing aid. The lubricant and processing aid are added mainly to improve processability, such as making it easier for the rubber composition to peel off rolls, molds, 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 Factis. These can be used individually or in combination of two or more. The rubber composition according to the present invention may contain 0.1 to 15 parts by mass of lubricants and processing aids per 100 parts by mass of rubber components, and may also contain 1 to 10 parts by mass. The content of lubricants and processing aids may be, for example, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0054] 1.9 Vulcanization accelerator The rubber composition according to the present invention may contain a vulcanization accelerator, and when the total rubber composition contained in the composition is 100 parts by mass, it may contain 0 to 5.0 parts by mass of the vulcanization accelerator. The content of the vulcanization accelerator may be, for example, 0, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass, and may be within the range of any two of the values ​​exemplified here. Furthermore, the rubber composition according to the present invention may not contain a vulcanization accelerator. In one embodiment of the present invention, the rubber composition may also be made without a vulcanization accelerator, and the relationship between hardness X and heat generation Y, as well as hardness X and heat generation Y, may be adjusted by adjusting the types and amounts of other components.

[0055] The type of vulcanization accelerator is not particularly limited as long as it does not impair the effects of the present invention. Preferably, the vulcanization accelerator is one that can be used for vulcanizing chloroprene rubber. One or more types of vulcanization accelerators can be freely selected and used. Examples of vulcanization accelerators include sulfur, thiram-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, thiourea-based vulcanization accelerators, guanidine-based vulcanization accelerators, xanthogenic acid-based vulcanization accelerators, and thiazole-based vulcanization accelerators.

[0056] Examples of thiram-based vulcanization accelerators include tetramethylthiram disulfide (TMTD), tetraethylthiram disulfide, tetrabutylthiram disulfide, tetrakis(2-ethylhexyl)thiram disulfide, tetramethylthiram monosulfide, and dipentamethylenethiram tetrasulfide. Examples of dithiocarbamate-based 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-based vulcanization accelerators include thiourea compounds such as ethylenethiourea, diethylthiourea (N,N'-diethylthiourea), trimethylthiourea, diphenylthiourea (N,N'-diphenylthiourea), and 1,3-trimethylene-2-thiourea. Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salts of dicatecholborate. Examples of xanthogenic acid-based vulcanization accelerators include zinc butylxanthonate and zinc isopropylxanthonate. Examples of thiazole-based 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 can be used individually or in combination of two or more types.

[0057] 1.10 Other The rubber composition according to the present invention may further contain, in addition to the above-mentioned components, components such as antioxidants, antioxidants, flame retardants, and vulcanization retardants, to the extent that they do not impair the effects of the present invention. Examples of antioxidants and antioxidants include ozone antioxidants, phenolic antioxidants, amine antioxidants, acrylate antioxidants, imidazole antioxidants, metal carbamate salts, waxes, phosphorus antioxidants, and sulfur antioxidants. Examples of imidazole antioxidants include 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and zinc salts of 2-mercaptobenzimidazole. The rubber composition according to the present invention may contain a total of 0.1 to 10 parts by mass of antioxidants and antioxidants per 100 parts by mass of rubber components contained in the rubber composition.

[0058] In one embodiment of the present invention, by arranging the types and contents of components in the rubber composition as described above, the hardness X of the test vulcanized molded body 1 of the rubber composition and the heat generated Y of the test vulcanized molded body 2 of the rubber composition are more likely to satisfy the relationship of formula (1).

[0059] 2. Method for producing rubber composition A rubber composition according to one embodiment of the present invention is obtained by kneading a rubber component and other required components at a temperature below the vulcanization temperature. A method for producing a rubber composition according to one embodiment of the present invention may include a mixing step of mixing a rubber component and other required components at a temperature below the vulcanization temperature.

[0060] A manufacturing method according to one embodiment of the present invention may include a first mixing step, a standing step, and a second mixing step. In the first mixing step, raw materials containing rubber components and compounding components for the first mixing step are mixed to obtain a rubber composition precursor. In the standing step, the rubber composition precursor is left to stand at 23°C or below for 12 hours or more. In the second mixing step, compounding components for the second mixing step are added to the standing rubber composition precursor and mixed to obtain a rubber composition.

[0061] In the first mixing step, raw materials containing rubber components and compounding components for the first mixing step are mixed to obtain a rubber composition precursor. The compounding components for the first mixing step may not contain vulcanizing agents, vulcanization accelerators, organic peroxides, or maleimide compounds. Preferably, the compounding components for the first mixing step do not contain components that contribute to vulcanization and crosslinking. The compounding components for the first mixing step may contain at least one, two, three, four, five, or six of the following: carbon black, acid acceptors, lubricants, processing aids, plasticizers, and antioxidants, and may contain all of these.

[0062] In the standing process, the rubber composition precursor is left to stand at 23°C or below for 12 hours or more. The standing temperature can be, for example, 5 to 23°C, such as 5, 8, 11, 14, 17, 20, or 23°C, and may be within the range of any two of the values ​​exemplified here. The standing time can be, for example, 12 to 24 hours, such as 12, 14, 16, 18, 20, 22, or 24 hours, and may be within the range of any two of the values ​​exemplified here. In one embodiment of the present invention, hardness X and heat generation Y can be adjusted by going through a settling process.

[0063] In the second mixing step, the rubber composition precursor, after standing, is mixed with the compounding components for the second mixing step to obtain the rubber composition. The compounding components for the second mixing step may include a vulcanizing agent, a vulcanization accelerator, an organic peroxide, and a maleimide compound. The compounding components for the second mixing step may also include carbon black, a lubricant, a processing aid, a plasticizer, an acid acceptor, an antioxidant, etc.

[0064] Examples of kneading devices used in each mixing process include conventionally known mixers, Banbury mixers, kneader mixers, and open roll mixers.

[0065] 3. Properties of rubber compositions In one embodiment of the present invention, when a rubber composition is formed by stacking test vulcanized molded articles 1 of the rubber composition until a thickness of 6.0 mm or more is reached, and the hardness measured using a Type A durometer according to JIS K 6253-3:2023 is X, and the heat generated by evaluating the test vulcanized molded article 2 of the rubber composition using a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute, according to JIS K 6265:2018, then, The hardness X and heat generation Y satisfy the following equation (1). 1.4XY>45.0 (1)

[0066] Here, the test vulcanized molded article 1 is a 2 mm thick sheet-like vulcanized molded article obtained by press vulcanizing a rubber composition at 170°C for 20 minutes, in accordance with JIS K 6299:2012. Furthermore, the test vulcanized molded body 2 is a cylindrical vulcanized molded body with a diameter of 15 mm and a height of 25 mm, obtained by press vulcanizing the rubber composition at 170°C for 20 minutes.

[0067] The rubber composition according to the present invention is a rubber composition that can be obtained in which a vulcanized molded article with excellent water resistance and alkali resistance can be obtained by adjusting the hardness X and heat generation Y of the vulcanized molded article of the rubber composition so that the relationship between the hardness X and heat generation Y of the vulcanized molded article of the rubber composition satisfies the relationship of formula (1). Hardness X can be controlled by adjusting the manufacturing conditions described later, for example, by changing the amounts of filler and plasticizer. Similarly, heat generation Y can be controlled by adjusting the manufacturing conditions described later, for example, in relation to the type and amount of filler, the crosslink density of the resulting vulcanized molded article, and the type and amount of plasticizer. It is believed that increasing the amount of filler increases heat generation Y, increasing the crosslink density decreases heat generation Y, and increasing the amount of plasticizer increases heat generation Y. Here, by adjusting the relationship between hardness X and heat generation Y to satisfy equation (1), the amount of filler, the amount of plasticizer, the crosslink density, etc. at hardness X can be adjusted, and it is presumed that a rubber composition capable of obtaining a vulcanized molded article with excellent water resistance and alkali resistance can be obtained. The value of (1.4XY) can be greater than 45.0 and less than or equal to 100.0. For example, it could be 45.5, 50.0, 55.0, 60.0, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, 95.0, or 100.0, and it may also be within the range of any two of the numbers exemplified here.

[0068] In one embodiment of the present invention, the rubber composition preferably has a hardness X of 40 to 98, measured using a Type A durometer based on JIS K 6253-3:2023, in a laminate obtained by stacking test vulcanized molded bodies 1 of the rubber composition until the thickness reaches 6.0 mm or more. The hardness X may be, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 98, and may be within the range of any two of the values ​​exemplified here.

[0069] Hardness X can be controlled by adjusting the manufacturing method of the rubber composition, for example, the presence, type, and amount of each component blended into the rubber composition, particularly the type and amount of fillers and plasticizers, as well as the manufacturing conditions of the rubber composition (in particular, the presence, temperature, and duration of the settling process).

[0070] In one embodiment of the present invention, the rubber composition preferably has a heat generation Y of 85°C or less, which is determined by evaluating a test vulcanized molded body 2 of the rubber composition using a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute, in accordance with JIS K 6265:2018. The heat generation Y is, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85°C, and may be within the range of any two of the values ​​exemplified here.

[0071] The heat generated Y can be controlled by adjusting the method of manufacturing the rubber composition, particularly by adjusting the presence, type, and amount of each component blended into the rubber composition, such as the presence, type, and amount of fillers and components that contribute to vulcanization and crosslinking, as well as the manufacturing conditions of the rubber composition (particularly the presence, temperature, and duration of the settling process).

[0072] Hardness X and heat generation Y can be evaluated specifically by the method described in the examples.

[0073] In one embodiment of the present invention, the rubber composition preferably has a volume change rate ΔV calculated according to JIS K 6258 when a test vulcanized molded body 1 and / or test vulcanized molded body 2 of the rubber composition is immersed in water at 70°C for 144 hours, which is less than 9%, and more preferably less than 6%. The volume change rate ΔV when immersed in water at 70°C for 144 hours may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8%, or less than 9%, and may be within the range of any two of the values ​​exemplified herein.

[0074] In one embodiment of the present invention, the rubber composition preferably has a volume change rate ΔV calculated according to JIS K 6258 when a test vulcanized molded body 1 and / or test vulcanized molded body 2 of the rubber composition is immersed in 10% sodium hydroxide at 70°C for 144 hours, which is less than 10%, and more preferably less than 7%. The volume change rate ΔV when immersed in water at 70°C for 144 hours may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9%, or less than 10%, and may be within the range of any two of the values ​​exemplified herein.

[0075] The water resistance and alkali resistance of vulcanized molded articles of rubber compositions can be measured specifically by the method described in the examples.

[0076] 6. Unvulcanized molded articles, vulcanized articles, and vulcanized molded articles 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 of the rubber composition (unvulcanized state) according to one embodiment of the present invention. A method for manufacturing an unvulcanized molded article according to one embodiment of the present invention comprises a step of molding the rubber composition (unvulcanized state) according to one embodiment of the present invention. An unvulcanized molded article according to one embodiment of the present invention consists of the rubber composition (unvulcanized state) according to one embodiment of the present invention.

[0077] A vulcanized product according to one embodiment of the present invention is a vulcanized product of a rubber composition according to one embodiment of the present invention. A method for producing a vulcanized product according to one embodiment of the present invention comprises the step of vulcanizing a rubber composition according to one embodiment of the present invention.

[0078] 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. A vulcanized molded article according to one embodiment of the present invention uses a vulcanized product according to one embodiment of the present invention and is a molded article (molded product) of a vulcanized product according to one embodiment of the present invention. A vulcanized molded article according to one embodiment of the present invention consists of a vulcanized product according to one embodiment of the present invention.

[0079] A vulcanized molded article according to one embodiment of the present invention can be obtained by molding a vulcanized product obtained by vulcanizing a rubber composition (unvulcanized state) according to one embodiment of the present invention, or by vulcanizing a molded article obtained by molding a rubber composition (unvulcanized state) according to one embodiment of the present invention. A vulcanized molded article according to one embodiment of the present invention can be obtained by vulcanizing a rubber composition according to one embodiment of the present invention after molding or during molding. A method for manufacturing a vulcanized molded article according to one embodiment of the present invention comprises the steps of molding a vulcanized product according to one embodiment of the present invention, or vulcanizing an unvulcanized molded article according to one embodiment of the present invention.

[0080] In one embodiment of the present invention, when the vulcanized molded body is defined as a test vulcanized molded body 1' with a thickness of 6.0 mm or more, and its hardness measured with a Type A durometer in accordance with JIS K 6253-3:2023 is defined as X', and when the vulcanized molded body is defined as a cylindrical test vulcanized molded body 2' with a diameter of 15 mm and a height of 25 mm, and its heat generation obtained by evaluating it with a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute in accordance with JIS K 6265:2018, It is preferable that the hardness X' and heat generation Y' satisfy the following equation (2). 1.4X'-Y'>45.0 (2) Furthermore, the test vulcanized molded body 1' with a thickness of 6.0 mm or more may be a laminate formed by stacking multiple vulcanized molded bodies with a thickness of less than 6.0 mm. The test vulcanized molded body 1' has a thickness of 6.0 mm or more, and can be 7.0 mm or less.

[0081] The value of (1.4XY) is greater than 45.0, for example, 45.5, 50.0, 55.0, 60.0, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, 95.0, 100.0, and may also be within the range of any two of the numbers exemplified here.

[0082] The hardness X' of the test vulcanized molded article 1' according to one embodiment of the present invention is, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 98, and may be within the range of any two of the values ​​exemplified herein.

[0083] The heat generated Y' of the test vulcanized molded body 2' according to one embodiment of the present invention is, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85°C, and may be within the range of any two of the values ​​exemplified herein.

[0084] The vulcanized molded article according to one embodiment of the present invention preferably has a volume change rate ΔV of less than 9%, and more preferably less than 6%, when immersed in 70°C water for 144 hours, calculated according to JIS K 6258. The volume change rate ΔV when immersed in 70°C water for 144 hours may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8%, or less than 9%, and may be within the range of any two of the values ​​exemplified herein.

[0085] The vulcanized molded article according to one embodiment of the present invention preferably has a volume change rate ΔV of less than 10%, and more preferably less than 7%, when immersed in 10% sodium hydroxide at 70°C for 144 hours, calculated according to JIS K 6258. The volume change rate ΔV when immersed in water at 70°C for 144 hours may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9%, or less than 10%, and may be within the range of any two of the values ​​exemplified herein.

[0086] The hardness, heat generation, water resistance, and alkali resistance of the vulcanized molded article can be measured specifically by the method described in the examples. Furthermore, the hardness, heat generation, water resistance, and alkali resistance of the vulcanized molded article can be controlled by adjusting the method of manufacturing the rubber composition, for example, the presence, type, and amount of each component blended into the rubber composition, in particular the presence, type, and amount of fillers and components that contribute to vulcanization and crosslinking, as well as the manufacturing conditions of the rubber composition (in particular, the presence, temperature, and time of the settling process).

[0087] An 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 water resistance and alkali resistance, and can therefore be used as various components where these properties are required. The rubber composition, 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, and can be used for rubber parts such as automotive rubber components (e.g., automotive sealing materials), hose materials, rubber molds, gaskets, rubber rolls, industrial cables, industrial conveyor belts, and sponges. In particular, it can be used as a power transmission belt, conveyor belt, hose, wiper, immersion product, sealing part, adhesive, boot, rubber-coated fabric, rubber roll, vibration-damping rubber, or sponge product.

[0088] (Rubber components for automobiles) Automotive rubber components include gaskets, oil seals, and packings, which are parts used in machinery and equipment to prevent leakage of liquids and gases, and to prevent the intrusion of dirt and foreign matter such as rainwater and dust. Specifically, there are gaskets used for fixed applications, and oil seals and packings used in moving parts. For gaskets where the sealing part is fixed with bolts, various materials are used depending on the purpose, as opposed to soft gaskets such as O-rings and rubber sheets. Packings are used in rotating parts such as the shafts of pumps and motors and the movable parts of valves, reciprocating parts such as pistons, coupler connections, and water-stopping parts of water faucets. The rubber composition of the present invention can enhance water resistance and alkali resistance. This makes it possible to manufacture automotive parts with excellent oil resistance, which was difficult with conventional rubber compositions.

[0089] (Hose material) Hose materials are flexible tubes, and specifically include high and low-pressure hoses for water, oil, air, steam, and hydraulics. The rubber composition of the present invention can improve the water resistance and alkali resistance of hose materials while maintaining the processability of the unvulcanized material. This makes it possible to manufacture hose materials with excellent water resistance and alkali resistance, which was difficult to achieve with conventional rubber compositions.

[0090] (Rubber molded object) Rubber-shaped products include vibration-damping rubber, vibration-damping materials, and boots. Vibration-damping rubber and vibration-damping materials are rubber that prevents the transmission and propagation of vibrations. Specifically, they include torsional dampers, engine mounts, and muffler hangers for automobiles and various other vehicles that absorb vibrations during engine operation and prevent noise. The rubber composition of the present invention can improve the water resistance and alkali resistance of vibration-damping rubber and vibration-damping materials. This makes it possible to manufacture vibration-damping rubber and vibration-damping materials with excellent water resistance and alkali resistance, which was difficult with conventional rubber compositions. Furthermore, boots are bellows-shaped components whose outer diameter gradually increases from one end to the other. Specifically, examples include constant velocity joint cover boots, ball joint cover boots (dust cover boots), and rack and pinion gear boots for protecting drive components such as automobile drive systems. The rubber composition of the present invention can enhance water resistance and alkali resistance. This makes it possible to manufacture boots that can be used in harsher environments than conventional rubber compositions.

[0091] (Gaskets, etc.) Gaskets, oil seals, and packings are components used in machinery and equipment to prevent leakage of liquids and gases, as well as the intrusion of dirt and foreign matter such as rainwater and dust. Specifically, there are gaskets used for fixed applications and oil seals and packings used in moving and movable parts. In gaskets where the sealing portion is fixed with bolts or the like, various materials are used depending on the purpose, as opposed to soft gaskets such as O-rings and rubber sheets. Packings are used in rotating parts such as the shafts of pumps and motors and the movable parts of valves, reciprocating parts such as pistons, coupler connections, and water-stopping parts of water faucets. The rubber composition of the present invention can improve the water resistance and alkali resistance of these components. This makes it possible to manufacture sealing components with excellent water resistance and alkali resistance, which was difficult to achieve with conventional rubber compositions.

[0092] (Rubber roll) Rubber rolls are manufactured by bonding and covering a metal core, such as an iron core, with rubber. Generally, they are manufactured by spirally winding a rubber sheet around a metal core. Rubber rolls use various rubber materials such as NBR, EPDM, and CR, depending on the required characteristics of various applications, including papermaking, various metal manufacturing, film manufacturing, printing, general industrial use, agricultural machinery such as rice hulling machines, 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. Furthermore, rubber rolls that convey heavy objects have the problem of deforming under load, and improvements are needed. The rubber composition of the present invention can improve the water resistance and alkali resistance of rubber rolls. This makes it possible to manufacture embossing rubber rolls with excellent water resistance and alkali resistance, which was difficult with conventional rubber compositions. The rubber composition according to one embodiment of the present invention can be used for rubber rolls used in at least one of an acid washing line and an alkali washing line.

[0093] A rubber roll according to one embodiment of the present invention comprises a core metal and a surface layer provided on the circumferential surface of the core metal, wherein the surface layer includes the vulcanized molded body described above, and the rubber roll is used in at least one of an acid cleaning line and an alkaline cleaning line.

[0094] (Industrial cables) Industrial cables are linear components used to transmit electrical and optical signals. They consist of good conductors such as copper or copper alloys, or optical fibers, covered with an insulating coating layer. 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 and alkali resistance of industrial cables. This makes it possible to manufacture industrial cables with superior water resistance and alkali resistance, which was difficult to achieve with conventional rubber compositions.

[0095] (Industrial conveyor belt) Industrial conveyor belts are made of rubber, resin, or metal, and are selected according to a wide variety of applications. Among these, rubber conveyor belts are inexpensive and widely used, but they are prone to deterioration and damage, especially in environments with high friction and collision with conveyed materials. The rubber composition of the present invention can improve the water resistance and alkali resistance of industrial conveyor belts. This makes it possible to manufacture industrial conveyor belts with excellent water resistance and alkali resistance for use in harsh environments, which was difficult with conventional rubber compositions.

[0096] (sponge) Sponge is a porous material with countless fine pores inside, and is specifically used in vibration damping components, sponge seal parts, wetsuits, shoes, and the like. The rubber composition of the present invention can improve the acid resistance and water resistance of sponge. Furthermore, because it uses chloroprene-unsaturated nitrile copolymer rubber, it can also improve the flame retardancy of sponge. This makes it possible to manufacture sponges with excellent water resistance and alkali resistance, as well as sponges with excellent flame retardancy, that can be used in harsh environments, which was difficult with conventional rubber compositions. In addition, the hardness of the resulting sponge can be adjusted as appropriate by adjusting the content of the foaming agent, etc.

[0097] Methods for forming a rubber composition (unvulcanized) and a vulcanized product according to one embodiment of the present invention include press molding, extrusion molding, and calendering. The temperature for vulcanizing the rubber composition can be set appropriately according to the composition of the rubber composition and can be 140 to 220°C. For example, the vulcanization temperature can be 140, 150, 160, 170, 180, 190, 200, 210, or 220°C, and may be within the range of any two of the values ​​exemplified here. The vulcanization time for vulcanizing the rubber composition can be set appropriately according to the composition of the rubber composition, the shape of the unvulcanized molded product, etc., and can be 10 to 300 minutes. For example, these could be 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, and 300 minutes, or they could be within the range of any two of the numbers exemplified here. [Examples]

[0098] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0099] <Method for manufacturing chloroprene-based rubber (A-2)> In a 3L polymerization vessel equipped with a heating / cooling jacket and a stirrer, 24 parts by mass of chloroprene (monomer), 24 parts by mass of acrylonitrile (monomer), 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, 5.00 parts by mass of potassium rosinate (manufactured by Harima Chemicals, Inc.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation) were added. Next, 0.1 parts by mass 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 atmosphere. The chloroprene was added in small amounts starting 20 seconds after the start of polymerization, and the addition flow rate was adjusted using a solenoid valve based on the change in the heat quantity of the refrigerant during the first 10 seconds of polymerization, and then readjusted every 10 seconds thereafter to continue the process. When the polymerization rate reached 50% of the total amount of chloroprene and acrylonitrile, 0.02 parts by mass of phenothiazine, a polymerization inhibitor, was added to stop the polymerization. Subsequently, unreacted monomers were removed from the reaction solution under reduced pressure to obtain a chloroprene-based latex containing a chloroprene-acrylonitrile copolymer.

[0100] The polymerization rate [%] of chloroprene latex mentioned above was calculated from the dry mass of the chloroprene latex after air drying. Specifically, it was calculated using the following formula (A). In the formula, "solid content concentration" is the concentration of solids [mass %] obtained by heating 2 g of sampled chloroprene latex at 130°C and removing volatile components such as solvent (water), volatile chemicals, and raw materials. "Total amount charged" is the total amount [g] of raw materials, reagents, and solvent (water) charged into the polymerization tank from the start of polymerization to a certain time. "Evaporation residue" is the mass [g] of chemicals [g] that remain as solids with the polymer without volatilizing under 130°C conditions, out of the chemicals and raw materials charged from the start of polymerization to a certain time. "Amount of monomer charged" is the sum of the amount [g] of monomers initially charged into the polymerization tank and the amount of monomers added from the start of polymerization to a certain time. Here, "monomer" refers to the total amount of chloroprene and acrylonitrile. Polymerization rate = {[(Total amount charged × Solid content concentration / 100) - Evaporation residue] / Amount of monomer charged} × 100 ... (A)

[0101] The pH of the chloroprene latex (R-2) described above was adjusted to 7.0 using acetic acid or sodium hydroxide. A sheet was then obtained by emulsifying and destroying the chloroprene latex by freezing and solidifying it on a metal plate cooled to -20°C. After washing this sheet with water, a solid chloroprene rubber (A-2) was obtained by drying it at 130°C for 15 minutes.

[0102] The monomer content of acrylonitrile in chloroprene-based rubber (A-2) was calculated from the nitrogen atom content in the chloroprene-acrylonitrile copolymer rubber. Specifically, the nitrogen atom content in 100 mg of chloroprene-based rubber (A-2) was measured using an elemental analyzer (Sumigraph 220F: manufactured by Sumika Analysis Center Co., Ltd.), and the monomer content of acrylonitrile was calculated. The monomer content of acrylonitrile was 10.0% by mass.

[0103] The elemental analysis described above 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 at 80 mL / min as the carrier gas. A calibration curve was created using aspartic acid (10.52%) with a known nitrogen content as the standard substance. The monomer content of acrylonitrile in the chloroprene-based rubber (A-2) obtained by the above manufacturing method was 10.0% by mass.

[0104] <Method for manufacturing chloroprene rubber (A-1)> By changing the amount of acrylonitrile monomer added during the polymerization process, a chloroprene-based rubber (A-1) was obtained in which the acrylonitrile monomer unit content in the chloroprene-based rubber was 5.0% by mass.

[0105] (Examples 1-19, Comparative Examples 1-13) <Preparation of rubber composition> From the components listed in Tables 1 to 4, all components except for the organic peroxide, vulcanization accelerator, maleimide compound, and vulcanizing agent were mixed in an 8-inch open roll to obtain a rubber composition precursor that does not contain the vulcanizing agent, etc. (first mixing step). Subsequently, the obtained rubber composition precursor was left to stand at 23°C for 12 hours. After that, the rubber composition precursor was kneaded with the organic peroxide, vulcanization accelerator, maleimide compound, and vulcanizing agent in an 8-inch open roll (second mixing step) to obtain the rubber compositions of the examples and comparative examples.

[0106] (Comparative Examples 14-17) <Preparation of rubber composition> Of the components listed in Table 4, all components except the organic peroxide, vulcanization accelerator, maleimide compound, and vulcanizing agent were mixed in an 8-inch open roll to obtain a rubber composition precursor that does not contain the vulcanizing agent, etc. (first mixing step). Subsequently, without going through a standing step, the rubber composition precursor was kneaded with the organic peroxide, vulcanization accelerator, maleimide compound, and vulcanizing agent in an 8-inch open roll (second mixing step) to obtain the comparative example rubber composition.

[0107] The components used to obtain the composition are as follows: Rubber components: Chloroprene-based rubber A-1: ​​Chloroprene-acrylonitrile copolymer, AN (acrylonitrile monomer unit) content 5% by mass Chloroprene-based rubber A-2: Chloroprene-acrylonitrile copolymer, AN (acrylonitrile monomer unit) content 10% by mass. Chloroprene-based rubber A-5: Mercaptan-modified chloroprene rubber (chloroprene homopolymer), manufactured by Denka Co., Ltd., S-40V • Natural rubber, manufactured by HB Chemical, SMR-CV60

[0108] Carbon black: Asahi Carbon Co., Ltd. "Asahi #70", HAF Organic peroxide: 1,4-bis[(t-butylperoxy)isopropyl]benzene, Nippon Oil & Fats Co., Ltd., Perbutyl P-40

[0109] vulcanization accelerator: • Noxellar TMU: Trimethylthiourea, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. • Sulfur: Sulfur, manufactured by Hosoi Chemical Industry Co., Ltd., finely powdered sulfur, 200 mesh. • Noxellar TT: Tetramethylthiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Noxellar TT • Noxellar CZ: N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Noxellar CZ

[0110] Maleimide compound: m-phenylenedimaleimide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Valnock PM Plasticizer: Ether ester compound, manufactured by ADEKA Corporation, ADEKA Sizer RS-700 Vulcanizing agent: Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., two types of zinc oxide. Acid acceptor: Magnesium oxide, manufactured by Kyowa Chemical Industry Co., Ltd., Kyowa Mag 150 Anti-aging agents: • Nocrack CD: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Nocrack CD • Nocrack 6C: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Nocrack 6C Processing aid: Stearic acid, manufactured by Shin Nippon Rika Co., Ltd., Stearic acid 50S

[0111] <Preparation of test vulcanized molded body 1> The obtained rubber composition was press-vulcanized at 170°C for 20 minutes according to JIS K 6299:2012 to produce a 2 mm thick sheet-like vulcanized molded article (test vulcanized molded article 1).

[0112] (Hardness) A vulcanized molded test body 1 was stacked to form a laminate with a thickness of 6.0 mm or more. The hardness of the laminate was measured using a Type A durometer in accordance with JIS K 6253-3:2023. The thickness of the laminate was set to 6.0 to 7.0 mm.

[0113] (Water resistance (volume change rate after immersion in 70°C water for 144 hours)) A test specimen measuring 25 mm in length and 20 mm in width was punched out from the above-mentioned vulcanized molded test body 1 to obtain a test specimen. The obtained test specimen was immersed in 70°C water for 144 hours. The volume change rate ΔV was calculated according to JIS K 6258. The obtained volume change rate ΔV was evaluated according to the following criteria. A: Less than 3% B: 3% or more, less than 6% C: 6% or more, less than 9% D: 9% or more

[0114] (Alkali resistance (volume change rate after immersion in 10% sodium hydroxide at 70°C for 144 hours)) A test specimen measuring 25 mm in length and 20 mm in width was punched out from the above-mentioned vulcanized molded body 1 to obtain a test specimen. The obtained test specimen was immersed in 10% sodium hydroxide at 70°C for 144 hours. The volume change rate ΔV was calculated according to JIS K 6258. The obtained volume change rate ΔV was evaluated according to the following criteria. A: Less than 4% B: 4% or more, less than 7% C: 7% or more, less than 10% D: 10% or more

[0115] (Fever) A cylindrical vulcanized molded body (test vulcanized molded body 2) with a diameter of 15 mm and a height of 25 mm was obtained by press vulcanization of the rubber composition at 170°C for 20 minutes. Based on JIS K 6265:2018, the heat generation was evaluated by a constant strain flexometer test using a Goodrich Flexometer. The constant strain flexometer test is a test method for evaluating the fatigue characteristics due to heat generation inside a test piece by applying a dynamic repeated load to a test piece such as vulcanized rubber. Specifically, a static initial load is applied to the test piece under constant temperature conditions, and then a sinusoidal vibration of constant amplitude is applied, and the amount of heat generation and creep of the test piece that changes over time is measured. The test method was carried out based on JIS K 6265:2018 under conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 times per minute, and the heat generation (°C) was measured.

[0116] Table 1

[0117] Table 2

[0118] Table 3

[0119] Table 4

Claims

1. A rubber composition containing rubber components, The hardness of a laminate obtained by stacking test vulcanized molded articles 1 of the rubber composition until it reaches a thickness of 6.0 mm or more, measured with a Type A durometer according to JIS K 6253-3:2023, is defined as X. When the heat generated by evaluating the test vulcanized molded body 2 of the rubber composition using a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute, based on JIS K 6265:2018, is denoted as Y, The hardness X and heat generation Y satisfy the following equation (1): The vulcanized molded body 1 for testing is a sheet-like vulcanized molded body with a thickness of 2 mm, obtained by press-vulcanizing the rubber composition at 170°C for 20 minutes in accordance with JIS K 6299:2012. The test vulcanized molded body 2 is a cylindrical vulcanized molded body with a diameter of 15 mm and a height of 25 mm, obtained by press vulcanizing the rubber composition at 170°C for 20 minutes. Rubber composition. 1.4X-Y>45.0 (1)

2. The rubber composition according to claim 1, wherein the hardness X is 40 or more and 98 or less.

3. The rubber composition according to claim 1 or claim 2, wherein the rubber component comprises a chloroprene polymer.

4. The rubber composition according to claim 3, wherein the chloroprene polymer contains 80 to 100% by mass of chloroprene monomer units based on 100% by mass of the chloroprene polymer.

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

6. It is a rubber roll, It comprises a core metal and a surface layer provided on the circumferential surface of the core metal, The surface layer comprises the vulcanized molded body described in claim 5, The rubber roll is a rubber roll used in at least one of an acid cleaning line and an alkaline cleaning line.

7. A vulcanized molded article containing a rubber component, When the aforementioned vulcanized molded body is designated as a test vulcanized molded body 1' with a thickness of 6.0 mm or more, the hardness measured with a Type A durometer in accordance with JIS K 6253-3:2023 is defined as X'. When the aforementioned vulcanized molded body is a cylindrical test vulcanized molded body 2' with a diameter of 15 mm and a height of 25 mm, and the heat generated by evaluating it using a constant strain flexometer test under the conditions of 40°C, strain of 0.175 inches, load of 55 pounds, and vibration frequency of 1,800 cycles per minute, according to JIS K 6265:2018, then Y' is the amount of heat generated. A vulcanized molded body whose hardness X' and heat generation Y' satisfy the following equation (2). 1.4X'-Y'>45.0 (2)

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