Rubber composition and conveyor belt

Abstract

To provide a rubber composition and a conveyor belt exhibiting superior processability, ensuring superior adhesion of a resulting cured product to canvas, and delivering superior heat resistance.SOLUTION: A rubber composition contains a rubber component including 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 one 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 pt.mass or more and less than 5 pts.mass with respect to 100 pts.mass of the rubber component; and a conveyor belt having cover rubber, canvas, and coat rubber covering the canvas, the coat rubber being a cured product of the rubber composition.SELECTED DRAWING: None

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-194232 Summary of the Invention [Problem to be solved by the invention]

[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. Furthermore, rubber compositions for use as coating rubbers for covering canvas on conveyor belts are required to have excellent processability in an unvulcanized state and excellent heat resistance in 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 of the resulting cured product, and heat resistance. Another object of the present invention is to provide a conveyor belt. [Means for solving the problem]

[0006] As a result of intensive research into solving 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 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. Specifically, the present invention solves the above 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 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 [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 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 [1] to [3], further comprising carbon black, the content of the carbon black being 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 contains a dimethacrylic acid compound. [6] The rubber composition according to any one of [1] to [5], which is used for bonding canvas of a conveyor belt. [7] The rubber composition according to [6], wherein the canvas includes 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, a 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]. [Effects of the Invention]

[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 also provides a conveyor belt. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of one embodiment of the conveyor belt of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of the adhesive test specimen. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The following description of the components 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 the present specification, each component can be used alone or in combination of two or more kinds. In this specification, when two or more types of a certain component are used in combination, the "content" of the component means the total content of those two or more types, unless otherwise specified. In the present specification, the method for producing each component is not particularly limited unless otherwise specified, and may be, for example, a conventionally known method. 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 contains 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 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] The reason why the rubber composition of the present invention having the above-mentioned configuration can solve the problems of the present invention is not entirely clear, but the present inventors speculate as follows. That is, it is presumed that the rubber composition of the present invention, which contains ethylene propylene rubber, exhibits excellent tensile properties after heat aging and the resulting cured product has excellent heat resistance. It is presumed that the rubber composition of the present invention contains ethylene propylene diene rubber, which gives the composition an appropriate Mooney viscosity in an unvulcanized state and excellent processability. It is presumed that the rubber composition of the present invention contains the sulfur-containing silane coupling agent in a specific amount, and thus the resulting cured product has excellent adhesion to canvas. The above speculation does not limit the mechanism by which the effect is obtained. In other words, even if the effect is obtained by a mechanism other than the above, it is included in the scope of the present invention.

[0013] [Rubber component] The rubber composition of the present invention contains a rubber component, and the rubber component contains an ethylene propylene rubber and an ethylene propylene diene rubber. The total content of the rubber components can be set to 30 to 60% by 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 the rubber component. Ethylene propylene rubber is a copolymer of ethylene and propylene. Note that ethylene propylene rubber does not include ethylene propylene diene rubber, which will be described later. Ethylene propylene rubber also does not contain chlorine. One of the preferred embodiments is that 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 the product "EPT0045" (ethylene content 51.0% by mass, manufactured by Mitsui Chemicals, Inc.).

[0016] (Ethylene propylene rubber content) 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, from the viewpoint of achieving better effects of the present invention.

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

[0018] (Diene compounds) Examples of diene compounds constituting the ethylene propylene diene rubber include non-conjugated diene compounds, and specific examples include dicyclopentadiene, 5-ethylidene-2-norbornene, 1,4-hexadiene, vinylidene norbornene, etc. 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 contains 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) The diene content of the ethylene propylene diene rubber is preferably 1.0 to 10% by mass in the ethylene propylene diene rubber, from the viewpoint of achieving better effects of the present invention.

[0021] Commercially available ethylene propylene diene rubbers include, for example, EPT4021 (ethylene propylene diene rubber with an ethylene content of 51.0% by mass and a diene content of 8.1% by mass, manufactured by Mitsui Chemicals, Inc.) and EPT2060M (ethylene content of 55.0% by mass and a diene content of 2.3% by mass, manufactured by Mitsui Chemicals, Inc.).

[0022] (Ethylene propylene diene rubber content) The content of the ethylene propylene diene rubber is preferably 10 to 30% by mass, and more preferably 13 to 25% by mass, of the total amount of the rubber component, from the viewpoint of achieving better effects of the present invention.

[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% by mass of the total amount of the chlorinated polyethylene.

[0024] (chlorinated polyethylene content) The content of the chlorinated polyethylene can 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 the chlorinated polyethylene may be, for example, more than 0 part by mass in the total amount of the rubber component, and can be 3.0 to 10% by mass.

[0025] (mass ratio of ethylene propylene rubber / ethylene propylene diene rubber / chlorinated polyethylene content) 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, from the viewpoint of achieving better effects of the present invention. The above mass ratio is based on the above content (mass %) of each component in the total amount of the rubber component.

[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, and examples thereof include conventionally known silica. Examples of silica include wet silica, fumed silica, pyrogenic silica, precipitated silica, ground silica, fused silica, and colloidal silica.

[0027] (Silica content) The content of silica 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, from the viewpoint of achieving better effects of the present invention.

[0028] [Sulfur-containing silane coupling agents] 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 sulfurs] In the present invention, the number of sulfur (sulfur atoms) contained in one molecule of the sulfur-containing silane coupling agent is not more than 2. Note that the sulfur-containing silane coupling agent contains one or more sulfur (sulfur atoms) per molecule. The sulfur-containing silane coupling agent preferably contains two sulfur atoms (sulfur atoms) per molecule, from the viewpoint of achieving better effects of the present invention.

[0030] (disulfide bond) When the sulfur-containing silane coupling agent contains two 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, when the rubber composition of the present invention is cured, the disulfide bond is decomposed between sulfur atoms by heating, and the sulfur contained in the decomposition product reacts with the rubber component and / or canvas, which is presumed to result in better effects of the present invention (especially adhesion).

[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 may have one or two hydrolyzable silyl groups per molecule. In one preferred embodiment, the sulfur-containing silane coupling agent has two hydrolyzable silyl groups per molecule.

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

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

[0034] [Sulfur-containing silane coupling agent content] In the present invention, the content of the 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. 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, from the viewpoint of achieving better effects of the present invention.

[0035] [Peroxide] The rubber composition of the present invention contains a peroxide, which is a compound having a peroxy group (—OO—). 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 better effects of the present invention, it preferably contains an organic peroxide having multiple 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) The content of the peroxide is preferably 1.0 to 5.0 parts by mass, more preferably 1.0 to 3.0 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention.

[0038] The peroxide may be a mixture of peroxide and calcium carbonate. Commercially available products of the mixture of peroxide and calcium carbonate include Perkadox 14-40C (manufactured by Kayaku Akzo Co., Ltd.). In the present invention, when the above mixture is used as the peroxide, the content of the peroxide contained in the rubber composition of the present invention refers to the net content of the 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 above-mentioned ethylene propylene diene rubber and / or ethylene propylene diene rubber. In a preferred embodiment, the co-crosslinking agent contains a compound having a plurality of α,β-unsaturated bonds. Examples of the co-crosslinking agent include dimethacrylic acid compounds, triallyl isocyanurate, and diallyl compounds.

[0040] (Dimethacrylic acid compounds) The dimethacrylic acid compound refers to a compound having multiple methacryloyl groups (CH2=C(-CH3)-C(=O)-) per molecule. The linking group connecting the two methacryloyl groups is not particularly limited. Examples of dimethacrylic acid compounds include compounds having two methacryloyloxy groups (CH2=C(-CH3)-C(=O)-O-) per molecule, and specific examples include ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, and polypropylene glycol dimethacrylate. The number of repeating units of the oxyethylene group in the polyethylene glycol dimethacrylate can be, for example, 2 to 10. The same applies to the number of repeating units of the oxypropylene group in the polypropylene glycol dimethacrylate.

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

[0042] (diallyl compounds) The diallyl compound is not particularly limited as long as it is a compound having two allyl groups (CH2=CH-CH2-), and examples thereof include aromatic compounds having two allyl groups such as diallyl phthalate.

[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 the oxyethylene group is, for example, 2 to 10), and further preferably contains diethylene glycol dimethacrylate (structure shown below). [ka]

[0044] (Co-crosslinking agent content) 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, from the viewpoint of achieving better effects of the present invention.

[0045] (carbon black) From the viewpoint of achieving better effects of the present invention, the rubber composition of the present invention preferably further contains carbon black. From the viewpoint of obtaining a more excellent effect of the present invention, the carbon black has a nitrogen adsorption specific surface area (N2SA) of 20 to 100 m 2 / g, and N2SA is 50 to 90m 2 More preferably, the carbon black contains 0.1g of carbon black. The nitrogen adsorption specific surface area of ​​carbon black can be measured by measuring the amount of nitrogen adsorbed to the carbon black surface in accordance with JIS K6217-2:2017 "Carbon black for rubber use - Basic 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 amount of carbon black can be set to 0 to 60 parts by mass based on 100 parts by mass of the rubber component. When the rubber composition of the present invention further contains carbon black, the content of carbon black 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. The content of sulfur (simple substance) is preferably 0 part by mass per 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention. The above-mentioned sulfur (elemental substance) means sulfur (elemental sulfur) that can be generally contained in a rubber composition as a vulcanizing agent, and does not include sulfur contained in the above-mentioned sulfur-containing silane coupling agent.

[0050] (Manufacturing method) The method for producing the rubber composition of the present invention is not particularly limited, and examples thereof include a method for producing the rubber composition of the present invention 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] (hardening) 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] (Application) The rubber composition of the present invention can be used, for example, as a rubber composition for conveyor belts, and specifically, as a rubber composition for coating rubber of conveyor belts. Another preferred embodiment is that the rubber composition of the present invention is used to adhere canvas to a conveyor belt (i.e., the rubber composition of the present invention is used as a coating rubber for the canvas of a conveyor belt having canvas).

[0053] (Canvas) In a preferred embodiment, the canvas of the conveyor belt includes canvas that has been surface-treated with a latex of a styrene-butadiene-vinylpyridine copolymer, from the viewpoint of having better adhesion to the cured product obtained from the rubber composition of the present invention. 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). The surface treatment may be, for example, 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 comprises 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 a rubber composition for coating rubber, which has excellent processability, adhesion of the resulting cured product to canvas, and heat resistance, and therefore has excellent processability, adhesion between the coating rubber and canvas, and heat resistance of the coating rubber (and therefore heat resistance of the conveyor belt of the present invention).

[0055] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of a conveyor belt according to the present invention with reference to the accompanying drawings, but the present invention is not limited to the drawings. (Figure 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 sheets of canvas 1, and a coating rubber 2 covering the two sheets of canvas 1. The coating rubber 2 is also present between the two sheets of canvas 1. The coating rubber 2 is a cured product of the rubber composition of the present invention. The coating rubber 2 is covered with the cover rubber 3. The thicknesses T1 and T2 of the cover rubber 3 can each be, for example, about 1.5 to 20 mm. 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 is not particularly limited in terms of, for example, the number of canvas sheets, the thickness of the cover rubber (T1 and T2 in FIG. 1), the overall thickness of the coating rubber covering the canvas, the overall thickness of the conveyor belt of the present invention, and the belt 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 can 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 coating rubber covering the canvas is disposed between the upper cover rubber and the lower cover rubber (i.e., the sides of the coating rubber covering the canvas do not have to be covered by the cover rubber). The cover rubber may cover the entire coating 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 cover rubber in a general conveyor belt. Examples of the rubber composition for the cover rubber that can be used include rubber compositions containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), etc. as rubber components. 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 comprises canvas. 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 latex of a styrene-butadiene-vinylpyridine copolymer. The styrene-butadiene-vinylpyridine copolymer latex, surface treatment, and materials of the canvas itself are the same as those described above.

[0059] [Coated rubber] The conveyor belt of the present invention has a coating rubber, and the coating rubber covers the canvas. The coated rubber may cover the entire canvas. When there are two or more canvases, it does not matter whether there is a coated rubber between the canvases, but it is preferable to have a coated rubber 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) The conveyor belt of the present invention can be manufactured, for example, by preparing a laminate in which canvas surface-treated with the latex is placed between uncured rubber sheets molded from the rubber composition of the present invention, and then placing the laminate between rubber sheets of the rubber composition for cover rubber (uncured) to prepare an uncured conveyor belt, and then 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. [Example]

[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 following examples.

[0064] [Production of rubber composition] Each rubber composition was produced by mixing the components in the composition (parts by mass) shown in Table 1 below with a stirrer. The amounts shown in the peroxide column in Table 1 are the amounts of commercially available peroxides used.

[0065] [evaluation] The rubber compositions produced as described above were subjected to the following evaluations, and the results are shown in Table 1. [Peel strength, adhesiveness] (Preparation of adhesive test specimens) Each of the rubber compositions prepared as described above was used as a coating rubber. A five-layer laminate was prepared 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) prepared as described above as the coating rubber composition. The laminate was then vulcanized at 148°C for 120 minutes to prepare an adhesion test specimen (size: width 2.5 cm x depth 15 cm x height 0.5 cm).

[0066] (Figure 2) The above-mentioned adhesive test specimen will be described below with reference to the accompanying drawings. Figure 2 is a schematic cross-sectional view of an adhesion test specimen 30. In Figure 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] (Peeling strength in two-layer peeling test, with rubber) Using each of the adhesive specimens prepared as described above, a two-layer peel test (a T-shaped peel was performed at the center of the five coated rubber layers of the adhesive specimen) was conducted in accordance with JIS K6256-1:2013 "Peel strength from fabric" to measure the peel strength (N / mm). The results are shown in the "Peel strength from canvas" column in Table 1. After the two-layer peel test, the rubber remaining on the canvas surface was visually inspected on both sides of the peeled surface, and the percentage of the area of ​​rubber remaining on the canvas surface was calculated. When the failure mode due to peeling (cohesive failure) occurred over the entire surface of the coated rubber, the rubber was considered to be 100% attached. The percentage of rubber attached to the canvas surface is shown in the "Adhesion (rubber attached after peeling)" column in Table 1.

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

[0069] (Peeling force 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 above 11 N / mm, the stronger the adhesive strength between the canvas and the coating rubber, which is preferable. When the evaluation of the adhesiveness to the canvas is of the same level, the larger the peel force measured as described above, the more preferable it is.

[0070] (tensile strength, elongation at break) (Preparation of initial test specimen) Each rubber composition produced 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 2 mm thick crosslinked sheet. JIS No. 3 dumbbell-shaped test pieces conforming to JIS K6251 were punched out from each of the crosslinked sheets to prepare initial test pieces. (Preparation of heat aging test specimens) The initial test piece prepared as described above was subjected to a heat aging test in which it was placed under a condition of 150°C for 168 hours, and a test piece after the heat aging test (heat aging test piece) was prepared.

[0071] (Tensile test) Using the above initial test specimens and heat-aged test specimens, tensile tests were conducted 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 specimen) The initial test piece preferably has a tensile strength at break of 9 MPa or more. The higher the tensile strength at break, the more preferable the tensile strength of the resulting cured product in its normal state.

[0073] (Evaluation criteria for initial test piece elongation) 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 resulting 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 produced 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 Lübke sample (a cylindrical sample having a thickness of 12.5 mm and a diameter of 29 mm). (Hardness measurement) Using each of the Lupke samples 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] (Hardness evaluation criteria) The hardness is preferably 60 to 70.

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

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

[0079] [Table 1] [Table 2] [Table 3]

[0080] Details of each component shown in Table 1 are as follows: EPDM_EPT4021: Ethylene propylene diene rubber with 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 with an ethylene content of 51.0% by mass. Product name: EPT0045 (Mitsui Chemicals, Inc.) EPDM_EPT2060M: Ethylene propylene diene rubber with 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 Co., Ltd.). Chlorine content: 30 to 33% by mass CB(HAF): HAF grade carbon black. Vulcan 3D, manufactured by Cabot Japan. N2SA: 74m 2 / g, DBP: 101 cm 3 / 100g

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

[0083] Paraffin oil: Product name "SUNPAR2280" (manufactured by Japan Sun Oil Co., Ltd.) Zinc oxide: Product name "Zinc oxide type 3" (manufactured by Seido Chemical Industry Co., Ltd.) Stearic acid: Product name "Stearic Acid 50S" (manufactured by Nisshin Rika Co., Ltd.)

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

[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-treated 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 meet the above evaluation criteria in terms of adhesion to canvas, processability, or heat resistance. [Explanation of symbols]

[0088] 1 canvas 2 coated rubber 3 Cover rubber 4. Conveyor belt 11 Coated Rubber 12 Canvas 30 Adhesion test specimens

Claims

1. A rubber composition comprising: 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.

2. 2. The rubber composition according to claim 1, wherein a 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, wherein the content of the silica is 5 to 15 parts by mass based on 100 parts by mass of the rubber component.

4. 2. The rubber composition according to claim 1, further comprising carbon black, the amount 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 claim 1 , wherein the co-crosslinking agent comprises a dimethacrylic acid compound.

6. The rubber composition according to claim 1, 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 a styrene-butadiene-vinylpyridine copolymer.

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

9. A conveyor belt comprising a cover rubber, a 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 claims 1 to 8.

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