Rubber composition and conveyor belt

Abstract

The purpose of the present invention is to provide: a rubber composition that is excellent in processability and can be used to obtain a cured product that exhibits excellent heat resistance and adhesiveness to a canvas; and a conveyor belt. One aspect of the present invention is a rubber composition comprising: a rubber component containing an ethylene propylene rubber and an ethylene propylene diene rubber; silica; a sulfur-containing silane coupling agent containing sulfur; a peroxide; and a co-crosslinking agent, the number of sulfur atoms contained per molecule of the sulfur-containing silane coupling agent being 2 or less, and the content of the sulfur-containing silane coupling agent being from 0.5 parts by mass to less than 5 parts by mass per 100 parts by mass of the rubber component. Another aspect of the present invention is a conveyor belt comprising a cover rubber, a canvas, and a coating rubber covering the canvas, with the coating rubber being a cured product of the rubber composition.

Description

Rubber composition and conveyor belt

[0001] The present invention relates to a rubber composition and a conveyor belt.

[0002] Conventionally, compositions that can be used for conveyor belts and the like have been proposed, for example, in Patent Document 1.

[0003] JP 2013-194232 A

[0004] The present inventors have investigated the use of the composition disclosed in Patent Document 1 as a coating rubber for covering the canvas of a conveyor belt and have found that there is room for further improvement in the adhesion between the cured product obtained from the composition and the canvas. In addition, a rubber composition for use as a coating rubber for covering the canvas of a conveyor belt is required to have excellent processability in an unvulcanized state and excellent heat resistance of the resulting cured product.

[0005] Therefore, an object of the present invention is to provide a rubber composition that has excellent processability, adhesiveness to canvas when cured, and heat resistance. Another object of the present invention is to provide a conveyor belt.

[0006] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a rubber composition containing a rubber component containing ethylene propylene rubber and ethylene propylene diene rubber, silica, a sulfur-containing silane coupling agent containing sulfur, a peroxide, and a co-crosslinking agent, wherein the number of sulfur atoms contained per molecule of the sulfur-containing silane coupling agent is 2 or less, and the content of the sulfur-containing silane coupling agent is 0.5 parts by mass or more but less than 5 parts by mass per 100 parts by mass of the rubber component. That is, the present invention specifically solves the above-mentioned problems by the following configuration.

[0007] [1] A rubber composition comprising a rubber component containing an ethylene propylene rubber and an ethylene propylene diene rubber, silica, a sulfur-containing silane coupling agent containing sulfur, a peroxide, and a co-crosslinking agent, wherein the number of sulfur atoms contained per molecule of the sulfur-containing silane coupling agent is two or less, and the amount of the sulfur-containing silane coupling agent is 0.5 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the rubber component. [2] The rubber composition according to [1], wherein the mass ratio of the ethylene propylene rubber / the ethylene propylene diene rubber / chlorinated polyethylene is 10-90 / 10-30 / 0-10. [3] The rubber composition according to [1] or [2], wherein the amount of the silica is 5 to 15 parts by mass per 100 parts by mass of the rubber component. [4] The rubber composition according to any one of [1] to [3], further comprising carbon black, wherein the amount of the carbon black is 20 to 60 parts by mass per 100 parts by mass of the rubber component. [5] The rubber composition according to any one of [1] to [4], wherein the co-crosslinking agent comprises a dimethacrylic acid compound. [6] The rubber composition according to any one of [1] to [5], wherein the rubber composition is used for bonding canvas of a conveyor belt. [7] The rubber composition according to [6], wherein the canvas comprises canvas surface-treated with a latex of a styrene-butadiene-vinylpyridine copolymer. [8] The rubber composition according to [6] or [7], wherein the canvas is made of a polyamide having an aliphatic skeleton. [9] A conveyor belt having a cover rubber, canvas, and a coating rubber covering the canvas, wherein the coating rubber is a cured product of the rubber composition according to any one of [1] to [8].

[0008] According to the present invention, a rubber composition can be provided which has excellent processability, and the resulting cured product has excellent adhesion to canvas and heat resistance. The present invention can also provide a conveyor belt.

[0009] Fig. 1 is a cross-sectional view of an embodiment of the conveyor belt of the present invention, and Fig. 2 is a schematic cross-sectional view of an adhesion test specimen.

[0010] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, each component can be used alone or in combination of two or more. In this specification, when two or more components are used in combination, the "content" of that component refers to the total content of those two or more components, unless otherwise specified. In this specification, the manufacturing method of each component is not particularly limited unless otherwise specified. Examples include conventionally known methods. In this specification, "excellent effects of the present invention" refers to superior processability and at least one of the adhesiveness to canvas and heat resistance of the resulting cured product.

[0011] [Rubber Composition] The rubber composition of the present invention will be described below. The rubber composition of the present invention is a rubber composition containing a rubber component including an ethylene propylene rubber and an ethylene propylene diene rubber, silica, a sulfur-containing silane coupling agent containing sulfur, a peroxide, and a co-crosslinking agent, wherein the number of sulfur atoms contained per molecule of the sulfur-containing silane coupling agent is 2 or less, and the content of the sulfur-containing silane coupling agent is 0.5 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the rubber component.

[0012] Although the reason why the rubber composition of the present invention having the above-described configuration can solve the problems of the present invention is not entirely clear, the present inventors speculate as follows. That is, it is speculated that the rubber composition of the present invention contains ethylene propylene rubber, which results in excellent tensile properties after heat aging and excellent heat resistance of the resulting cured product. It is speculated that the rubber composition of the present invention contains ethylene propylene diene rubber, which results in an appropriate Mooney viscosity in the unvulcanized state and excellent processability. It is speculated that the rubber composition of the present invention contains a specific amount of the sulfur-containing silane coupling agent, which results in excellent adhesion of the resulting cured product to canvas. However, the above speculation does not limit the mechanism by which the effects are obtained. In other words, even if the effects are obtained by a mechanism other than those described above, it is within the scope of the present invention.

[0013] [Rubber Component] The rubber composition of the present invention contains a rubber component, and the rubber component includes an ethylene propylene rubber and an ethylene propylene diene rubber. The total content of the rubber components can be 30 to 60 mass % of the total amount of the rubber composition of the present invention.

[0014] [Ethylene Propylene Rubber] The rubber composition of the present invention contains ethylene propylene rubber (EPM) as a rubber component. The ethylene propylene rubber is a copolymer of ethylene and propylene. The ethylene propylene rubber does not contain the ethylene propylene diene rubber described below. The ethylene propylene rubber does not contain chlorine. In one preferred embodiment, the repeating units constituting the ethylene propylene rubber are only repeating units of ethylene and propylene.

[0015] (Ethylene Content of Ethylene Propylene Rubber) From the viewpoint of achieving superior effects of the present invention, the ethylene content of the ethylene propylene rubber is preferably 40 to 60 mass %, more preferably 40 mass % or more and less than 60 mass %, and even more preferably 45 to 55 mass %. An example of a commercially available ethylene propylene rubber is "EPT0045" (ethylene content 51.0 mass %, manufactured by Mitsui Chemicals, Inc.).

[0016] (Content of Ethylene Propylene Rubber) From the viewpoint of achieving superior effects of the present invention, the content of the ethylene propylene rubber is preferably 10 to 90 mass %, more preferably 70 to 83 mass %, of the total amount of the rubber component.

[0017] [Ethylene Propylene Diene Rubber] The rubber composition of the present invention contains ethylene propylene diene rubber (EPDM) as a rubber component. Ethylene propylene diene rubber is a copolymer of ethylene, propylene, and a diene compound.

[0018] (Diene Compound) Examples of the diene compound constituting the ethylene propylene diene rubber include non-conjugated diene compounds, and specific examples include dicyclopentadiene, 5-ethylidene-2-norbornene, 1,4-hexadiene, and vinylidene norbornene. These can be used alone or in combination of two or more. From the viewpoint of achieving better effects of the present invention, the diene compound constituting the ethylene propylene diene rubber preferably includes 5-ethylidene-2-norbornene.

[0019] (Ethylene Content of Ethylene Propylene Diene Rubber) From the viewpoint of achieving better effects of the present invention, the ethylene content of the ethylene propylene diene rubber is preferably 40 to 60 mass%, more preferably 40 mass% or more and less than 60 mass%, and even more preferably 45 to 55 mass%.

[0020] (Diene Content of Ethylene Propylene Diene Rubber) From the viewpoint of achieving superior effects of the present invention, the diene content of the ethylene propylene diene rubber is preferably 1.0 to 10% by mass in the ethylene propylene diene rubber.

[0021] Examples of commercially available ethylene propylene diene rubbers include those sold under the trade name EPT4021 (ethylene propylene diene rubber having an ethylene content of 51.0% by mass and a diene content of 8.1% by mass, manufactured by Mitsui Chemicals, Inc.) and those sold under the trade name EPT2060M (ethylene content of 55.0% by mass and a diene content of 2.3% by mass, manufactured by Mitsui Chemicals, Inc.).

[0022] (Content of Ethylene Propylene Diene Rubber) From the viewpoint of achieving superior effects of the present invention, the content of the ethylene propylene diene rubber is preferably 10 to 30 mass % of the total amount of the rubber component, and more preferably 13 to 25 mass %.

[0023] (Chlorinated Polyethylene) The rubber composition of the present invention may further contain chlorinated polyethylene as a rubber component. Chlorinated polyethylene refers to a compound whose main chain skeleton is polyethylene, in which some of the hydrogen atoms of the polyethylene are substituted with chlorine atoms. The chlorine content of the chlorinated polyethylene can be 20 to 50 mass% of the total amount of the chlorinated polyethylene.

[0024] (Content of Chlorinated Polyethylene) The content of chlorinated polyethylene may be, for example, 0 to 10% by mass of the total amount of the rubber component. When the rubber component further contains chlorinated polyethylene, the content of chlorinated polyethylene may be, for example, more than 0 parts by mass of the total amount of the rubber component, and may be, for example, 3.0 to 10% by mass.

[0025] (Mass Ratio of Ethylene Propylene Rubber / Ethylene Propylene Diene Rubber / Chlorinated Polyethylene Contents) From the viewpoint of achieving superior effects of the present invention, the mass ratio of the ethylene propylene rubber / ethylene propylene diene rubber / chlorinated polyethylene contents is preferably 10-90 / 10-30 / 0-10, and more preferably 70-83 / 13-25 / 0-8. The above mass ratio is a mass ratio based on the above content (% by mass) of each component in the total amount of rubber components.

[0026] [Silica] The rubber composition of the present invention contains silica. The silica contained in the rubber composition of the present invention is not particularly limited. For example, conventionally known silicas can be used. Examples of silica include wet silica, fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, and colloidal silica.

[0027] (Silica Content) From the viewpoint of achieving better effects of the present invention, the silica content is preferably 1 to 30 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the rubber component.

[0028] [Sulfur-Containing Silane Coupling Agent] The rubber composition of the present invention contains a sulfur-containing silane coupling agent containing two or less sulfur atoms per molecule. The sulfur-containing silane coupling agent is a compound having a sulfur atom and a hydrolyzable silyl group.

[0029] [Number of sulfur] In the present invention, the number of sulfur (sulfur atom) contained in each molecule of the sulfur-containing silane coupling agent is 2 or less. Note that, each molecule of the sulfur-containing silane coupling agent contains one or more sulfur (sulfur atom). From the viewpoint of achieving better effects of the present invention, it is preferable that each molecule of the sulfur-containing silane coupling agent contains two sulfur (sulfur atom).

[0030] (Disulfide bond) When the sulfur-containing silane coupling agent contains two sulfur atoms (sulfur atoms) per molecule, the two sulfur atoms preferably form a disulfide bond, from the viewpoint of achieving better effects of the present invention. When the sulfur-containing silane coupling agent has a disulfide bond, the disulfide bond is decomposed between sulfur atoms by heating when the rubber composition of the present invention is cured, and the sulfur contained in the decomposition product reacts with the rubber component and / or canvas, resulting in better effects of the present invention (particularly adhesiveness).

[0031] (Hydrolyzable Silyl Group) The hydrolyzable silyl group contained in the sulfur-containing silane coupling agent is not particularly limited. Examples include conventionally known hydrolyzable silyl groups. Specific examples include monoalkoxysilyl groups, dialkoxysilyl groups, and trialkoxysilyl groups. The alkoxy group contained in the monoalkoxysilyl group or the like is not particularly limited. Examples include methoxy groups, ethoxy groups, and propyloxy groups. When the hydrolyzable silyl group is a monoalkoxysilyl group or a dialkoxysilyl group, the substituent that the monoalkoxysilyl group or the dialkoxysilyl group can further have is not particularly limited. Examples include hydrocarbon groups. The sulfur-containing silane coupling agent can have one or two hydrolyzable silyl groups per molecule. One preferred embodiment of the sulfur-containing silane coupling agent is one in which the sulfur-containing silane coupling agent has two hydrolyzable silyl groups per molecule.

[0032] (Linking Group) In the sulfur-containing silane coupling agent, sulfur (sulfur atom) and the hydrolyzable silyl group can be bonded via a linking group. The linking group is not particularly limited.

[0033] Examples of the sulfur-containing silane coupling agent include bis[(alkoxysilyl)-alkyl]disulfides. In the bis[(alkoxysilyl)-alkyl]disulfides, the alkylene group linking the alkoxysilyl group and the disulfide is not particularly limited. Examples include alkylene groups having 1 to 10 carbon atoms, which may be linear, branched, or cyclic, or a combination thereof. Specific examples of the bis[(alkoxysilyl)-alkyl]disulfide include bis[(monoalkoxysilyl)-alkyl]disulfides, bis[(dialkoxysilyl)-alkyl]disulfides, and bis[(trialkoxysilyl)-alkyl]disulfides. From the viewpoint of achieving superior effects of the present invention, the sulfur-containing silane coupling agent preferably contains bis[(trialkoxysilyl)-alkyl]disulfides. The alkylene group linking the trialkoxysilyl group and disulfide contained in the bis[(trialkoxysilyl)-alkyl]disulfide is the same as that of the above-mentioned bis[(alkoxysilyl)-alkyl]disulfide. Examples of bis[(trialkoxysilyl)-alkyl]disulfides include bis[3-(triethoxysilyl)-propyl]disulfide and bis[3-(trimethoxysilyl)-propyl]disulfide. From the viewpoint of achieving superior effects of the present invention, the sulfur-containing silane coupling agent preferably contains bis[3-(triethoxysilyl)-propyl]disulfide.

[0034] [Content of Sulfur-Containing Silane Coupling Agent] In the present invention, the content of the sulfur-containing silane coupling agent (sulfur-containing silane coupling agent containing two or less sulfur atoms per molecule) is 0.5 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the rubber component. From the viewpoint of achieving better effects of the present invention, the content of the sulfur-containing silane coupling agent is preferably 0.5 to 2.0 parts by mass per 100 parts by mass of the rubber component.

[0035] [Peroxide] The rubber composition of the present invention contains a peroxide. The peroxide is a compound having a peroxy group (—O—O—). In a preferred embodiment, the peroxide is an organic peroxide. Examples of organic peroxides include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,3-bis(t-butylperoxypropyl)benzene, di(2-tert-butylperoxyisopropyl)benzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, and 1,1-dibutylperoxy-3,3,5-trimethylsiloxane.

[0036] The peroxide can also function as a crosslinking agent, and from the viewpoint of achieving superior effects of the present invention, it preferably contains an organic peroxide having a plurality of peroxy groups per peroxide molecule, and more preferably contains at least one selected from the group consisting of di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,3-bis(t-butylperoxypropyl)benzene, and di(2-tert-butylperoxyisopropyl)benzene.

[0037] (Peroxide Content) In order to obtain better effects of the present invention, the peroxide content is preferably 1.0 to 5.0 parts by mass, and more preferably 1.0 to 3.0 parts by mass, per 100 parts by mass of the rubber component.

[0038] The peroxide may be a mixture of peroxide and calcium carbonate. Commercially available mixtures of peroxide and calcium carbonate include, for example, Perkadox 14-40C (manufactured by Kayaku Akzo Co., Ltd.). When the above mixture is used as the peroxide in the present invention, the content of peroxide contained in the rubber composition of the present invention refers to the net content of peroxide in the above mixture.

[0039] [Co-crosslinking agent] The rubber composition of the present invention contains a co-crosslinking agent. The co-crosslinking agent is not particularly limited as long as it is a compound that can crosslink the ethylene propylene diene rubber and / or the ethylene propylene diene rubber. In a preferred embodiment, the co-crosslinking agent includes a compound having multiple α,β-unsaturated bonds. Examples of the co-crosslinking agent include a dimethacrylic acid compound, triallyl isocyanurate, and a diallyl compound.

[0040] (Dimethacrylic acid compound) Dimethacrylic acid compounds contain a methacryloyl group (CH ２ =C(-CH ３ The linking group connecting the two methacryloyl groups is not particularly limited. Examples of dimethacrylic acid compounds include compounds having a methacryloyloxy group (CH ２ =C(-CH ３ )-C(═O)-O-) per molecule, and specific examples thereof include ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, and polypropylene glycol dimethacrylate. The number of repeating units of the oxyethylene group in polyethylene glycol dimethacrylate can be, for example, 2 to 10. The same applies to the number of repeating units of the oxypropylene group in polypropylene glycol dimethacrylate.

[0041] (Triallyl isocyanurate) Triallyl isocyanurate is a compound having the following structure:

[0042] (Diallyl Compound) Diallyl compounds are compounds containing an allyl group (CH２ =CH-CH ２ There are no particular limitations on the compound as long as it has two allyl groups. For example, an aromatic compound having two allyl groups such as diallyl phthalate can be mentioned.

[0043] From the viewpoint of achieving better effects of the present invention, the co-crosslinking agent preferably contains a dimethacrylic acid compound, more preferably contains polyethylene glycol dimethacrylate (the number of repeating units of oxyethylene groups is, for example, 2 to 10), and further preferably contains diethylene glycol dimethacrylate (structure shown below).

[0044] (Content of Co-Crosslinking Agent) From the viewpoint of achieving superior effects of the present invention, the content of the co-crosslinking agent is preferably 0.05 to 10.0 parts by mass, and more preferably 1.0 to 5.0 parts by mass, per 100 parts by mass of the rubber component.

[0045] (Carbon Black) From the viewpoint of achieving superior effects of the present invention, the rubber composition of the present invention preferably further contains carbon black. From the viewpoint of achieving superior effects of the present invention, the carbon black preferably has a nitrogen adsorption specific surface area (N ２ SA) is 20 to 100 m ２ / g of carbon black, ２ SA is 50 to 90m ２ The nitrogen adsorption specific surface area of ​​the carbon black can be determined by measuring the amount of nitrogen adsorbed onto the surface of the carbon black in accordance with JIS K6217-2:2017 "Carbon black for rubber - Fundamental properties - Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0046] From the viewpoint of achieving better effects of the present invention, the carbon black preferably contains HAF, FEF, or GPF grade carbon black, and more preferably contains HAF grade carbon black.

[0047] (Carbon Black Content) The carbon black content can be 0 to 60 parts by mass per 100 parts by mass of the rubber component. When the rubber composition of the present invention further contains carbon black, the carbon black content is preferably 20 to 60 parts by mass per 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention.

[0048] (Additives) The rubber composition of the present invention may further contain additives in addition to the above-mentioned components, such as paraffin oil, zinc oxide, and stearic acid.

[0049] (Sulfur) In one preferred embodiment of the rubber composition of the present invention, the content of sulfur (simple substance) is 0 to 0.1 parts by mass per 100 parts by mass of the rubber component. From the viewpoint of achieving superior effects of the present invention, the content of sulfur (simple substance) is preferably 0 parts by mass per 100 parts by mass of the rubber component. The sulfur (simple substance) refers to sulfur (simple substance) that can be generally contained in a rubber composition as a vulcanizing agent. The sulfur (simple substance) does not include the sulfur contained in the sulfur-containing silane coupling agent.

[0050] (Production Method) The method for producing the rubber composition of the present invention is not particularly limited. For example, the rubber composition of the present invention may be produced by mixing the above-mentioned essential components, and carbon black and additives that may be further used as needed, in a Banbury mixer or the like under conditions of 90 to 180°C.

[0051] (Curing) The rubber composition of the present invention can be cured (crosslinked) under ordinary conditions. The curing temperature can be, for example, 120 to 180° C. Pressure may be applied during curing.

[0052] (Uses) The use of the rubber composition of the present invention can be, for example, a rubber composition for conveyor belts, specifically, a rubber composition for coating rubber of conveyor belts. In addition, a preferred embodiment of the rubber composition of the present invention is to use it for adhering a canvas of a conveyor belt (i.e., to use the rubber composition of the present invention as a coating rubber for the canvas of a conveyor belt having canvas).

[0053] (Canvas) In view of superior adhesion to the cured product obtained from the rubber composition of the present invention, a preferred embodiment of the canvas of the conveyor belt includes canvas surface-treated with a latex of a styrene-butadiene-vinylpyridine copolymer. The styrene-butadiene-vinylpyridine copolymer contained in the latex is not particularly limited as long as it is a copolymer of styrene, butadiene, and vinylpyridine. There are no particular limitations on the styrene, butadiene, and vinylpyridine. The latex may further contain resorcinol and formaldehyde. Examples of canvas (the material of the canvas itself) include canvas made of polyamide having an aliphatic skeleton (nylon canvas). Examples of polyamide having an aliphatic skeleton include polycaprolactam (nylon 6) and polyamide of hexamethylenediamine and adipic acid (nylon 6,6). Examples of the surface treatment include a dipping treatment in which the canvas is immersed in the latex. The canvas after the surface treatment with the latex can be used after, for example, curing, for example, by aging the canvas after the surface treatment with the latex at room temperature and then baking it at 190°C for 2 minutes.

[0054] [Conveyor Belt] The conveyor belt of the present invention has a cover rubber, a canvas, and a coating rubber covering the canvas, the coating rubber being a cured product of the rubber composition of the present invention. The conveyor belt of the present invention uses the rubber composition of the present invention as the rubber composition for the coating rubber, which has excellent processability, adhesion to the canvas of the resulting cured product, and heat resistance, and therefore has excellent processability, adhesion between the coating rubber and the canvas, and heat resistance of the coating rubber (and therefore heat resistance of the conveyor belt of the present invention).

[0055] An embodiment of a conveyor belt of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the accompanying drawings. (FIG. 1) FIG. 1 is a cross-sectional view of one embodiment of a conveyor belt of the present invention. In FIG. 1, a conveyor belt 4 has a cover rubber 3, two canvas sheets 1, and a coating rubber 2 covering the two canvas sheets 1. The coating rubber 2 is also present between the two canvas sheets 1. The coating rubber 2 is a cured product of the rubber composition of the present invention. The coating rubber 2 is covered with a cover rubber 3. The thickness T of the cover rubber 3 １ , T ２ The total thickness of the coating rubber 2 covering the two sheets of canvas 1 can be, for example, about 1.5 to 20 mm.

[0056] The conveyor belt of the present invention has, for example, the number of canvas sheets, the thickness of the cover rubber (T in FIG. 1), １ , T ２ There are no particular limitations on the thickness of the coating rubber covering the canvas, the thickness of the conveyor belt of the present invention, or the width of the conveyor belt of the present invention, and these can be determined appropriately depending on the intended use.

[0057] [Cover Rubber] The conveyor belt of the present invention has a cover rubber. The conveyor belt of the present invention may have an upper cover rubber and a lower cover rubber as the cover rubber. When the conveyor belt of the present invention has an upper cover rubber and a lower cover rubber, it is sufficient that the coated rubber covering the canvas is disposed between the upper cover rubber and the lower cover rubber (i.e., the sides of the coated rubber covering the canvas do not have to be covered by the cover rubber). The cover rubber may cover the entire coated rubber covering the canvas. The rubber composition used for the cover rubber is not particularly limited as long as it is a rubber composition used for the cover rubber of a general conveyor belt. As the rubber composition for the cover rubber, for example, a rubber composition containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), etc., as a rubber component can be used. The rubber composition of the present invention may be used as the rubber composition for the cover rubber.

[0058] [Canvas] The conveyor belt of the present invention has canvas. The canvas can function as a core material in the conveyor belt of the present invention. From the viewpoint of achieving superior effects of the present invention, the canvas of the conveyor belt of the present invention preferably includes canvas that has been surface-treated with a styrene-butadiene-vinylpyridine copolymer latex. The styrene-butadiene-vinylpyridine copolymer latex, the surface treatment, and the material of the canvas itself are the same as those described above.

[0059] [Coated Rubber] The conveyor belt of the present invention has a coated rubber, and the coated rubber covers the canvas. The coated rubber may cover the entire canvas. When there are two or more canvases, the coated rubber may or may not be present between the canvases, but it is preferable that the coated rubber be present between the canvases because this improves the strength of the conveyor belt.

[0060] [Rubber Composition] In the present invention, the coating rubber is a cured product of the rubber composition of the present invention. The rubber composition used to form the coating rubber is not particularly limited as long as it is the rubber composition of the present invention.

[0061] (Manufacturing Method) A method for manufacturing the conveyor belt of the present invention includes, for example, preparing a laminate in which canvas surface-treated with the latex is placed between uncured rubber sheets molded with the rubber composition of the present invention, placing the laminate between rubber sheets of the rubber composition for cover rubber (uncured) to prepare an uncured conveyor belt, and curing the uncured conveyor belt by heating and pressurizing. The curing conditions for the uncured conveyor belt can be, for example, about 120 to 180°C, about 0.1 to 4.9 MPa, and about 10 to 90 minutes.

[0062] The conveyor belt of the present invention can be used under temperature conditions of, for example, -30 to +60°C.

[0063] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0064] [Production of Rubber Compositions] Each rubber composition was produced by mixing the components shown in Table 1 below in the proportions (parts by mass) shown in the table using a mixer. The amount shown in the peroxide column in Table 1 is the amount of a commercially available peroxide used.

[0065] [Evaluation] The following evaluations were carried out using each of the rubber compositions produced as described above. The results are shown in Table 1. [Peel Force, Adhesion] (Preparation of Adhesion Test Specimen) Each of the rubber compositions produced as described above was used as the coating rubber. A five-layer laminate was produced using two sheets of 6,6-nylon canvas, each surface-treated with a styrene-butadiene-vinylpyridine copolymer latex, and each of the rubber compositions (three layers) produced as described above as the coating rubber composition. The laminate was vulcanized under vulcanization conditions of 148°C x 120 minutes to produce an adhesion test specimen (size: width 2.5 cm x depth 15 cm x height 0.5 cm).

[0066] (Fig. 2) The above-mentioned adhesion test specimen will be described below with reference to the accompanying drawing. Fig. 2 is a schematic cross-sectional view of the adhesion test specimen. In Fig. 2, the adhesion test specimen 30 is constructed by alternately laminating three layers of coating rubber 11 and two layers of canvas 12. The thickness of each coating rubber 11 is approximately 2 mm, and the thickness of each canvas 12 is approximately 0.5 mm.

[0067] (Peel Force in Two-Layer Peel Test, Rubber Attachment) Using each of the adhesion test specimens prepared as described above, a two-layer peel test (in the adhesion test specimen, the central coating rubber of the five layers was peeled in a T-shape) was performed in accordance with JIS K6256-1:2013 "Peel Strength from Fabric" to measure the peel force (N / mm). The results are shown in the "Peel Force from Canvas" column in Table 1. After the two-layer peel test, the rubber adhering to the canvas surface on both sides of the peeled surface after peeling was visually observed, and the percentage of the area (%) of rubber remaining on the canvas surface was calculated. When a failure mode due to peeling (cohesive failure) occurred over the entire surface of the coating rubber, the rubber attachment was considered to be 100%. The results of the percentage (%) of rubber attachment to the canvas surface are shown in the "Adhesion (rubber attachment after peeling)" column in Table 1.

[0068] [Evaluation Criteria for Adhesion to Canvas] In the present invention, when the rubber adhesion was 50% or more, the resulting cured product was evaluated as having excellent adhesion to canvas. The higher the rubber adhesion (%), the better the adhesion.

[0069] (Peel strength from canvas) When the peel strength measured as described above was 11 N / mm or more, the adhesive strength between the canvas and the coating rubber was evaluated as being strong. The greater the peel strength than 11 N / mm, the stronger and more preferable the adhesive strength between the canvas and the coating rubber. Note that when the evaluation of the adhesion to the canvas described above was the same, the greater the peel strength measured as described above, the more preferable.

[0070] (Tensile strength, elongation at break) (Preparation of initial test specimens) Each rubber composition prepared as described above was crosslinked for 45 minutes using a press molding machine at 160°C under a surface pressure of 3.0 MPa to prepare a crosslinked sheet having a thickness of 2 mm. JIS No. 3 dumbbell-shaped test specimens conforming to JIS K6251 were punched out from each of the crosslinked sheets to prepare initial test specimens. (Preparation of heat-aging test specimens) A heat-aging test was performed on the initial test specimens prepared as described above, in which the specimens were left at 150°C for 168 hours, to prepare test specimens after the heat-aging test (heat-aging test specimens).

[0071] (Tensile test) Using the above initial test specimens and heat-aged test specimens, a tensile test was performed in accordance with JIS K6251:2017 under conditions of 23°C and a tensile speed of 500 mm / min, and the tensile strength at break (Tb) [MPa] and elongation at break (Eb) [%] were measured. The results of the tensile strength at break (Tb) of the initial test specimens are shown in the initial Tb column of Table 1. The results of the elongation at break (Eb) of the initial test specimens are shown in the initial Eb column of Table 1. The results of the tensile strength at break of the heat-aged test specimens are shown in the heat resistance column of Table 1.

[0072] (Evaluation Criteria for Tensile Strength of Initial Test Piece) The tensile strength at break of the initial test piece is preferably 9 MPa or more. The higher the tensile strength at break, the more preferable the tensile strength of the obtained cured product in its normal state.

[0073] (Evaluation Criteria for Elongation of Initial Test Piece) The elongation at break of the initial test piece is preferably 300% or more. The greater the elongation at break, the more preferable the elongation of the obtained cured product in its normal state.

[0074] [Evaluation Criteria for Heat Resistance Using Heat-Aging Test Pieces] In the present invention, when the tensile strength at break of the heat-aging test piece was 3.0 MPa or more, the heat resistance was evaluated as excellent. The higher the tensile strength at break, the more excellent the heat resistance.

[0075] [Hardness] (Preparation of test specimens) Each rubber composition prepared as described above was crosslinked for 45 minutes using a press molding machine at 160°C under a surface pressure of 3.0 MPa to prepare a Lupke sample (a cylindrical shape with a thickness of 12.5 mm and a diameter of 29 mm). (Measurement of hardness) Using each Lupke sample prepared as described above, the rubber hardness was measured at a temperature of 23°C using a durometer type A in accordance with JIS K6253-3:2012.

[0076] (Evaluation Criteria for Hardness) The hardness is preferably 60 to 70.

[0077] [Processability (Mooney Viscosity)] (Measurement of Mooney Viscosity) In accordance with the Mooney viscosity test of JIS K6300-1:2013 "Unvulcanized rubber - Physical properties - Part 1: Determination of viscosity and scorch time using a Mooney viscometer," the Mooney viscosity at 125°C of each rubber composition (unvulcanized) produced as described above was measured using a Mooney viscometer (L-type rotor). The results are shown in the processability (Mooney viscosity) column.

[0078] (Evaluation Criteria for Processability) In the present invention, when the Mooney viscosity measured as described above is 38 or less, the canvas and the unvulcanized rubber composition have good compatibility and the processability is evaluated as excellent. The smaller the Mooney viscosity, the better the processability.

[0079]

[0080] Details of each component shown in Table 1 are as follows: EPDM_EPT4021: Ethylene propylene diene rubber having an ethylene content of 51.0% by mass and a diene content of 8.1% by mass. Product name "EPT4021" (manufactured by Mitsui Chemicals, Inc.) EPM_EPT0045: Ethylene propylene rubber having an ethylene content of 51.0% by mass. Product name "EPT0045" (manufactured by Mitsui Chemicals, Inc.) EPDM_EPT2060M: Ethylene propylene diene rubber having an ethylene content of 55.0% by mass and a diene content of 2.3% by mass. Product name "EPT2060M" (manufactured by Mitsui Chemicals, Inc.)

[0081] Chlorinated polyethylene: Trade name "Elaslen (registered trademark) 301AE" (manufactured by Resonac Corporation). Chlorine content: 30 to 33% by mass. CB (HAF): HAF-grade carbon black. Vulcan 3D, manufactured by Cabot Japan. N ２ SA: 74m ２ / g, DBP: 101cm ３ / 100g

[0082] Silica: wet silica, trade name Tokusil GU (Oriental Silicas Corporation)

[0083] Paraffin oil: Trade name "SUNPAR 2280" (manufactured by Nippon Sun Oil Co., Ltd.) Zinc oxide: Trade name "Zinc oxide 3 types" (manufactured by Seido Chemical Industry Co., Ltd.) Stearic acid: Trade name "Stearic acid 50S" (manufactured by Nisshin Rika Co., Ltd.)

[0084] Peroxide: organic peroxide. Trade name: "Perkadox 14-40C" (manufactured by Kayaku Nouryon Co., Ltd.). This commercially available product is a mixture of di(2-tert-butylperoxyisopropyl)benzene and calcium carbonate. The content of di(2-tert-butylperoxyisopropyl)benzene in the commercially available product is 37.5-42.5% by mass, and the content of calcium carbonate in the commercially available product is 57.5-62.5% by mass. In this specification, when calculating the content of di(2-tert-butylperoxyisopropyl)benzene in Perkadox 14-40C, the proportion of di(2-tert-butylperoxyisopropyl)benzene in Perkadox 14-40C was set to 40.0% by mass. Co-crosslinking agent 2EG: Trade name: Light Ester 2EG, manufactured by Kyoeisha Chemical Co., Ltd. Diethylene glycol dimethacrylate (structure shown below)

[0085] Sulfur-containing silane coupling agent Si75: Product name Si75, manufactured by EVONIK DEGUSSA GMBH. Bis(3-(triethoxysilyl)propyl)disulfide Silane coupling agent (comparison) Si69: Product name Si69, manufactured by EVONIK DEGUSSA GMBH. Bis(3-(triethoxysilyl)propyl)tetrasulfide Sulfur: Product name "Oil Treatment Sulfur", manufactured by Hosoi Chemical Industry Co., Ltd. Net sulfur content 95% by mass

[0086] From the results in Table 1, it was confirmed that the rubber composition of the present invention exhibits the desired effects.

[0087] On the other hand, Comparative Examples 1 and 2, which contained a larger amount of specific sulfur-containing silane coupling agent than specified, Comparative Example 3, which did not contain the specific sulfur-containing silane coupling agent but instead contained a silane coupling agent with four sulfur atoms per molecule, Comparative Example 4, which did not contain EPM, Comparative Example 5, which did not contain EPDM, and Comparative Example 6, which did not contain the specific sulfur-containing silane coupling agent, did not satisfy the above evaluation criteria in terms of adhesion to canvas, processability, or heat resistance.

[0088] REFERENCE SIGNS LIST 1 Canvas 2 Coating rubber 3 Cover rubber 4 Conveyor belt 11 Coating rubber 12 Canvas 30 Adhesion test specimen

Claims

1. A rubber composition comprising a rubber component containing ethylene propylene rubber and ethylene propylene diene rubber, silica, a sulfur-containing silane coupling agent containing sulfur, a peroxide, and a co-crosslinking agent, wherein the number of sulfur atoms contained per molecule of the sulfur-containing silane coupling agent is 2 or less, and the content of the sulfur-containing silane coupling agent is 0.5 parts by mass or more but less than 5 parts by mass per 100 parts by mass of the rubber component.

2. The rubber composition according to claim 1, wherein the mass ratio of the ethylene propylene rubber / the ethylene propylene diene rubber / chlorinated polyethylene is 10-90 / 10-30 / 0-10.

3. The rubber composition according to claim 1 or 2, wherein the content of the silica is 5 to 15 parts by mass per 100 parts by mass of the rubber component.

4. The rubber composition according to any one of claims 1 to 3, further comprising carbon black, the content of said carbon black being 20 to 60 parts by mass per 100 parts by mass of said rubber component.

5. The rubber composition according to any one of claims 1 to 4, wherein the co-crosslinking agent includes a dimethacrylic acid compound.

6. The rubber composition according to any one of claims 1 to 5, which is used for bonding canvas of a conveyor belt.

7. The rubber composition of claim 6, wherein the canvas comprises canvas surface-treated with a latex of styrene-butadiene-vinylpyridine copolymer.

8. The rubber composition according to claim 6 or 7, wherein the canvas is made of a polyamide having an aliphatic skeleton.

9. A conveyor belt comprising a cover rubber, canvas, and a coating rubber covering the canvas, the coating rubber being a cured product of the rubber composition according to any one of claims 1 to 8.

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