Rubber composition and conveyor belt

Abstract

Provided are: a rubber composition which has excellent processability and is capable of maintaining a vulcanization rate within an appropriate range while giving consideration to both excellent wear resistance and flame retardancy; and a conveyor belt. A rubber composition and a conveyor belt manufactured using the same, the rubber composition containing a diene-based rubber including natural rubber and butadiene rubber, a flame retardant including chlorinated paraffin and antimony trioxide, carbon black, sulfur, a vulcanization accelerator including a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator, the content of natural rubber is 20-50 mass%, the content of butadiene rubber is 50-80 mass%, the content of chlorinated paraffin is 20-35 parts by mass and the content of antimony trioxide is 5-12 parts by mass with respect to 100 parts by mass of the diene rubber, and the mass ratio of (the total content of sulfenamide vulcanization accelerator and guanidine vulcanization accelerator) / (the content of sulfur) is 1.00 or more. And the mass ratio of (the content of guanidine vulcanization accelerator) / (the content of sulfenamide vulcanization accelerator) is 0.20-0.60.

Description

Technical Field

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

[0002] Conventionally, in order to obtain a conveyor belt having excellent low loss properties while maintaining high strength and high flame retardancy as a rubber product, a rubber composition for a conveyor belt has been proposed. The rubber composition comprises a rubber component including natural rubber and butadiene rubber, a vulcanizing agent, a vulcanization accelerator, carbon black, chlorinated paraffin, and antimony trioxide, wherein the ratio of the natural rubber content to the butadiene rubber content (natural rubber content:butadiene rubber content) is 25:75 to 45:55 by mass (Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] [Patent Document 1] International Publication No. 2016 / 056219 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] On the other hand, rubber compositions for conveyor belts are required not only to have flame retardancy in the cured product obtained by curing the rubber composition, but also to have excellent processability from the viewpoint of preventing rubber scorch. From the viewpoint of excellent productivity of rubber products, the vulcanization rate of the rubber composition is required to be within an appropriate range, and the cured product obtained by curing the rubber composition is also required to have excellent wear resistance.

[0008] The present inventors have studied the rubber composition disclosed in Patent Document 1 and have found that the rubber composition may have poor processability, vulcanization rate, or wear resistance or flame retardancy of a cured product obtained by curing the rubber composition.

[0009] It should be noted that, in this specification, the processability of a rubber composition, considered from the perspective of preventing rubber scorch, is also referred to simply as "processability." Furthermore, the vulcanization rate of a rubber composition is also referred to simply as "vulcanization rate." The wear resistance of a cured product obtained by curing a rubber composition is also referred to simply as "wear resistance." The flame retardancy of a cured product obtained by curing a rubber composition is also referred to simply as "flame retardancy."

[0010] Therefore, an object of the present invention is to provide a rubber composition that can achieve both excellent wear resistance and flame retardancy while keeping the vulcanization rate within an appropriate range and having excellent processability.

[0011] Another object of the present invention is to provide a conveyor belt.

[0012] Technical means to solve the problem

[0013] The present inventors have conducted intensive studies to solve the above-mentioned problems and have found that the above-mentioned problems can be solved by making the rubber composition contain a diene rubber including natural rubber and butadiene rubber, a flame retardant including chlorinated paraffin and antimony trioxide, carbon black, sulfur, and a vulcanization accelerator including a sulfenamide vulcanization accelerator and a guanidine vulcanization accelerator, and by making the natural rubber content, the butadiene rubber content, the chlorinated paraffin content, the antimony trioxide content, the mass ratio of (the sum of the content of the sulfenamide vulcanization accelerator and the content of the guanidine vulcanization accelerator) / (the content of the sulfur), and the mass ratio of (the content of the guanidine vulcanization accelerator) / (the content of the sulfenamide vulcanization accelerator) all within predetermined ranges.

[0014] That is, specifically, the present invention solves the above-mentioned problems by the following configurations.

[0015] [1] A rubber composition comprising: a diene rubber comprising natural rubber and butadiene rubber, a flame retardant comprising chlorinated paraffin and antimony trioxide, carbon black, sulfur, and a vulcanization accelerator comprising a sulfenamide vulcanization accelerator and a guanidine vulcanization accelerator, and

[0016] The content of the natural rubber is 20 to 50% by mass of the total amount of the diene rubber.

[0017] The content of the butadiene rubber is 50 to 80% by mass of the total amount of the diene rubber.

[0018] The content of the chlorinated paraffin is 20 to 35 parts by mass relative to 100 parts by mass of the diene rubber.

[0019] The content of the antimony trioxide is 5 to 12 parts by mass relative to 100 parts by mass of the diene rubber.

[0020] The mass ratio of (the total content of the sulfenamide vulcanization accelerator and the guanidine vulcanization accelerator) / (the sulfur content) is 1.00 or more,

[0021] The mass ratio of (the content of the guanidine vulcanization accelerator) / (the content of the sulfenamide vulcanization accelerator) is 0.20 to 0.60.

[0022] [2] The rubber composition according to [1], wherein the content of the natural rubber is 25 to 45% by mass of the total amount of the diene rubber.

[0023] The content of the butadiene rubber is 55 to 75% by mass of the total amount of the diene rubber.

[0024] [3] The rubber composition according to [1] or [2], wherein the carbon black has a nitrogen adsorption specific surface area exceeding 100 m 2 / g and the oil absorption of dibutyl phthalate is 100~140cm 3 / 100g of carbon black 1.

[0025] [4] The rubber composition according to any one of [1] to [3], wherein the content of the chlorinated paraffin is 20 to 30 parts by mass per 100 parts by mass of the diene rubber, and the content of the antimony trioxide is 5 to 10 parts by mass per 100 parts by mass of the diene rubber.

[0026] [5] The rubber composition according to any one of [1] to [4], which is used for a conveyor belt.

[0027] [6] A conveyor belt manufactured using the rubber composition described in any one of [1] to [5].

[0028] Effects of the Invention

[0029] According to the present invention, a rubber composition can be provided which can achieve both excellent wear resistance and flame retardancy while keeping the vulcanization rate within an appropriate range and has excellent processability.

[0030] In addition, the present invention can also provide a conveyor belt. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a cross-sectional view of one embodiment of the conveyor belt of the present invention.

[0032] Figure 2 This is a cross-sectional view of another embodiment of the conveyor belt of the present invention. DETAILED DESCRIPTION

[0033] Hereinafter, the present invention will be described in detail.

[0034] Although the description of the constituent elements described below may be based on representative embodiments of the present invention, the present invention is not limited to such embodiments.

[0035] In this specification, the numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0036] In the present specification, each component can be used alone or in combination of two or more.

[0037] In this specification, when two or more components are used in combination, the "content" of the component refers to the total content of the two or more components unless otherwise specified.

[0038] In this specification, unless otherwise specified, the production method of each component is not particularly limited, and examples thereof include conventionally known methods.

[0039] In this specification, at least one of abrasion resistance, flame retardancy, a vulcanization rate within an appropriate range, and processability being excellent is also referred to as "making the effects of the present invention more excellent."

[0040] [Rubber composition]

[0041] Next, the rubber composition of the present invention will be described.

[0042] The rubber composition of the present invention contains:

[0043] A diene rubber comprising natural rubber and butadiene rubber, a flame retardant comprising chlorinated paraffin and antimony trioxide, carbon black, sulfur, and a vulcanization accelerator comprising a sulfenamide vulcanization accelerator and a guanidine vulcanization accelerator, and

[0044] The content of the natural rubber is 20 to 50% by mass of the total amount of the diene rubber.

[0045] The content of the butadiene rubber is 50 to 80% by mass of the total amount of the diene rubber.

[0046] The content of the chlorinated paraffin is 20 to 35 parts by mass relative to 100 parts by mass of the diene rubber.

[0047] The content of the antimony trioxide is 5 to 12 parts by mass relative to 100 parts by mass of the diene rubber.

[0048] The mass ratio of (the total content of the sulfenamide vulcanization accelerator and the guanidine vulcanization accelerator) / (the sulfur content) is 1.00 or more,

[0049] The mass ratio of (the content of the guanidine vulcanization accelerator) / (the content of the sulfenamide vulcanization accelerator) is 0.20 to 0.60.

[0050] [Diene rubber]

[0051] The rubber composition of the present invention contains a diene rubber including natural rubber and butadiene rubber.

[0052] In the present invention, the diene rubber contained as the rubber component is a polymer formed from monomers containing a conjugated diene compound.

[0053] In the present invention, the diene rubber includes natural rubber and butadiene rubber.

[0054] [Natural rubber]

[0055] In the present invention, the natural rubber (NR) contained as the diene rubber is not particularly limited, and examples thereof include conventionally known ones.

[0056] [Butadiene rubber]

[0057] In the present invention, the butadiene rubber (BR) contained as the diene rubber is not particularly limited, and examples thereof include conventionally known ones.

[0058] As one preferred embodiment of BR, for example, butadiene rubber that is solid at 23° C. BR may be either unmodified or modified.

[0059] The weight average molecular weight of BR may be 200,000 to 1,000,000.

[0060] In the present specification, the weight average molecular weight (Mw) of BR may be a standard polystyrene conversion value obtained by gel permeation chromatography (GPC) measurement under the following conditions.

[0061] Solvent: Tetrahydrofuran

[0062] Detector: RI detector

[0063] [Natural rubber content]

[0064] In the present invention, the content of natural rubber is 20 to 50% by mass of the total amount of the diene rubber.

[0065] From the viewpoint of achieving more excellent effects of the present invention, the content of the natural rubber is preferably 25 to 45% by mass of the total amount of the diene rubber.

[0066] [Butadiene rubber content]

[0067] In the present invention, the content of the butadiene rubber is 50 to 80% by mass of the total amount of the diene rubber.

[0068] From the viewpoint of further improving the effects of the present invention, the content of the butadiene rubber is preferably 55 to 75% by mass of the total amount of the diene rubber.

[0069] (Total content of natural rubber and butadiene rubber)

[0070] The total content of natural rubber and butadiene rubber may be 70 to 100% by mass of the total amount of the diene rubber.

[0071] As one preferred embodiment of the above-mentioned diene rubber, only natural rubber and butadiene rubber can be cited.

[0072] When the total content of natural rubber and butadiene rubber is less than 100% by mass of the total amount of the diene rubber, the diene rubber may further contain diene rubber (other diene rubber) in addition to natural rubber and butadiene rubber without any particular limitation.

[0073] (Total content of diene rubber)

[0074] The content of the diene rubber may be 30 to 80% by mass of the total amount of the rubber composition of the present invention.

[0075] [Flame retardant]

[0076] The rubber composition of the present invention contains a flame retardant comprising chlorinated paraffin and antimony trioxide.

[0077] [Chlorinated paraffin]

[0078] In the present invention, the chlorinated paraffin contained as the flame retardant is a paraffin containing chlorine.

[0079] (Ratio of chlorine in chlorinated paraffin)

[0080] The proportion of chlorine in the chlorinated paraffin is not particularly limited, but is preferably 40 to 90% by mass, more preferably 60 to 90% by mass, in the chlorinated paraffin from the viewpoint of further improving the effects of the present invention (particularly flame retardancy).

[0081] [Content of chlorinated paraffin]

[0082] In the present invention, the content of the chlorinated paraffin is 20 to 35 parts by mass relative to 100 parts by mass of the diene rubber.

[0083] From the viewpoint of further improving the effects of the present invention, the content of the chlorinated paraffin is preferably 20 to 30 parts by mass relative to 100 parts by mass of the diene rubber.

[0084] [Antimony trioxide]

[0085] In the present invention, antimony trioxide (Sb2O3) contained as a flame retardant is not particularly limited.

[0086] [Antimony trioxide content]

[0087] In the present invention, the content of antimony trioxide is 5 to 12 parts by mass based on 100 parts by mass of the diene rubber.

[0088] From the viewpoint of further improving the effects of the present invention, the content of antimony trioxide is preferably 5 to 10 parts by mass relative to 100 parts by mass of the diene rubber.

[0089] [Carbon black]

[0090] The rubber composition of the present invention contains carbon black.

[0091] The carbon black is not particularly limited, and examples thereof include ISAF-grade carbon black and HAF-grade carbon black.

[0092] (Carbon Black 1)

[0093] From the viewpoint of achieving a more excellent effect of the present invention, the carbon black preferably contains a nitrogen adsorption specific surface area exceeding 100 m 2 / g and the oil absorption of dibutyl phthalate is 100~140cm 3 / 100g of carbon black 1, more preferably ISAF grade carbon black. The upper limit of the nitrogen adsorption specific surface area of ​​carbon black 1 may be 130m 2 / g or less.

[0094] The nitrogen adsorption specific surface area (N2SA) of carbon black can be measured in accordance with JIS K6217-2:2017.

[0095] The dibutyl phthalate oil absorption (DBP) of carbon black can be measured in accordance with JIS K6217-4:2017.

[0096] (Carbon black content)

[0097] From the viewpoint of further improving the effects of the present invention (particularly maintaining initial wear resistance and physical properties after aging), the content of carbon black is preferably 40 to 60 parts by mass per 100 parts by mass of the diene rubber.

[0098] When the carbon black includes the carbon black 1, the content of the carbon black 1 may be at least a portion of the content of the carbon black, and the total amount of the carbon black may be the carbon black 1.

[0099] [sulfur]

[0100] The rubber composition of the present invention contains sulfur.

[0101] The sulfur is not particularly limited as long as it can be used for vulcanization of rubber, and examples thereof include conventionally known sulfur.

[0102] (Sulfur content)

[0103] From the perspective of achieving even greater effects of the present invention, the sulfur content is preferably 0.5 to 3.0 parts by mass, more preferably 1.1 to 1.5 parts by mass, and even more preferably 1.2 to 1.4 parts by mass per 100 parts by mass of the diene rubber. It should be noted that the sulfur content refers to the net sulfur content.

[0104] [Vulcanization accelerator]

[0105] The rubber composition of the present invention contains a vulcanization accelerator comprising a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator.

[0106] [Sulfenamide vulcanization accelerator]

[0107] The sulfenamide vulcanization accelerator is a compound having a sulfenamide skeleton (eg, -S-NH-) and capable of accelerating sulfur vulcanization.

[0108] Examples of the sulfenamide vulcanization accelerator include N-cyclohexyl-2-benzothiazolesulfenamide, N-tert-butyl-2-benzothiazolesulfenamide, N-oxydiethylene-2-benzothiazolesulfenamide, and N,N′-dicyclohexyl-2-benzothiazolesulfenamide.

[0109] From the perspective of achieving a more excellent effect of the present invention, the sulfenamide vulcanization accelerator preferably contains N-alkyl-2-benzothiazole sulfenamide, and more preferably contains N-tert-butyl-2-benzothiazole sulfenamide. (Content of sulfenamide vulcanization accelerator)

[0110] From the viewpoint of achieving more excellent effects of the present invention, the content of the sulfenamide vulcanization accelerator is preferably 1.0 to 1.5 parts by mass, more preferably 1.05 to 1.15 parts by mass, relative to 100 parts by mass of the diene rubber.

[0111] [Guanidane vulcanization accelerator]

[0112] The guanidine vulcanization accelerator is a compound having a guanidine skeleton (for example, -NH-C(=NH)-NH-) and capable of accelerating sulfur vulcanization.

[0113] Examples of the guanidine-based vulcanization accelerator include diphenylguanidine and tolylguanidine.

[0114] The guanidine-based vulcanization accelerator preferably contains diphenylguanidine, and more preferably contains 1,3-diphenylguanidine, because the effects of the present invention are more excellent.

[0115] (Content of guanidine vulcanization accelerator)

[0116] From the viewpoint of achieving more excellent effects of the present invention, the content of the guanidine vulcanization accelerator is preferably 0.20 to 0.70 parts by mass, more preferably 0.35 to 0.44 parts by mass, relative to 100 parts by mass of the diene rubber.

[0117] [Mass ratio of the sum of the content of the sulfenamide vulcanization accelerator and the content of the guanidine vulcanization accelerator) / (sulfur content)]

[0118] In the present invention, the mass ratio of (the total content of the sulfenamide vulcanization accelerator and the guanidine vulcanization accelerator) / (the sulfur content) is 1.00 or more.

[0119] The “content of the sulfenamide vulcanization accelerator” in the above-mentioned mass ratio refers to the content of the sulfenamide vulcanization accelerator relative to 100 parts by mass of the diene rubber.

[0120] The “content of the guanidine vulcanization accelerator” in the above-mentioned mass ratio refers to the content of the guanidine vulcanization accelerator relative to 100 parts by mass of the diene rubber.

[0121] The “sulfur content” in the above-mentioned mass ratio refers to the sulfur content relative to 100 parts by mass of the diene rubber.

[0122] From the viewpoint of further improving the effects of the present invention, the mass ratio of (the total content of the sulfenamide vulcanization accelerator and the guanidine vulcanization accelerator) / (the sulfur content) is preferably 1.00 to 2.00, more preferably 1.00 to 1.60.

[0123] [Mass ratio of (content of guanidine vulcanization accelerator) / (content of sulfenamide vulcanization accelerator)]

[0124] In the present invention, the mass ratio of (the content of the guanidine vulcanization accelerator) / (the content of the sulfenamide vulcanization accelerator) is 0.20 to 0.60.

[0125] The “content of the sulfenamide vulcanization accelerator” in the above-mentioned mass ratio refers to the content of the sulfenamide vulcanization accelerator relative to 100 parts by mass of the diene rubber.

[0126] The “content of the guanidine vulcanization accelerator” in the above-mentioned mass ratio refers to the content of the guanidine vulcanization accelerator relative to 100 parts by mass of the diene rubber.

[0127] From the viewpoint of further improving the effects of the present invention, the mass ratio of (the content of the guanidine vulcanization accelerator) / (the content of the sulfenamide vulcanization accelerator) is preferably 0.25 to 0.55, and more preferably 0.30 to 0.40.

[0128] (Total content of sulfenamide vulcanization accelerator and guanidine vulcanization accelerator)

[0129] The total amount of the sulfenamide vulcanization accelerator and the guanidine vulcanization accelerator may be 80 to 100% by mass of the total amount of the vulcanization accelerator.

[0130] As one preferred embodiment of the vulcanization accelerator, only sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators can be cited.

[0131] When the sum of the content of the sulfenamide vulcanization accelerator and the content of the guanidine vulcanization accelerator is less than 100% by mass of the total amount of the vulcanization accelerator, the vulcanization accelerator may contain, in addition to the sulfenamide vulcanization accelerator and the guanidine vulcanization accelerator, any other vulcanization accelerators that may be contained are not particularly limited.

[0132] (Other vulcanization accelerators)

[0133] Examples of the other vulcanization accelerators include thiuram-based vulcanization accelerators such as tetrakis(2-ethylhexyl)thiuram disulfide, and sulfide-based vulcanization accelerators such as dibenzothiazyl disulfide (DM) and 4,4′-dimorpholine disulfide.

[0134] (Anti-aging agent)

[0135] The rubber composition of the present invention preferably further contains an antioxidant.

[0136] The anti-aging agent does not contain the above-mentioned amine compounds.

[0137] The anti-aging agent is not particularly limited, but preferably includes an amine anti-aging agent, and more preferably includes N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6C).

[0138] The content of the antioxidant is preferably 0.5 to 8.0 parts by mass relative to 100 parts by mass of the diene rubber.

[0139] (additive)

[0140] The rubber composition of the present invention may contain additives in addition to the above-mentioned components. Examples of the additives include wax, zinc oxide, stearic acid, oil, and a vulcanization retarder (eg, N-cyclohexylthiophthalimide).

[0141] (Manufacturing Method)

[0142] The method for producing the rubber composition of the present invention is not particularly limited, but an example thereof includes mixing the essential components and, if necessary, additives at 90 to 180° C. using a Banbury mixer or the like.

[0143] (Curing)

[0144] The rubber composition of the present invention can be cured (vulcanized) under conventional conditions. The curing temperature can be, for example, 120 to 180° C. Pressurization can be applied during curing.

[0145] (use)

[0146] Examples of uses of the rubber composition of the present invention include rubber compositions for conveyor belts.

[0147] (cured material)

[0148] The cured product obtained by curing the rubber composition of the present invention can achieve both excellent wear resistance and flame retardancy while keeping the vulcanization rate within an appropriate range and has excellent processability.

[0149] (use)

[0150] Examples of uses of the cured product include conveyor belts.

[0151] [conveyor]

[0152] The conveyor belt of the present invention is a conveyor belt produced using the rubber composition of the present invention.

[0153] The conveyor belt of the present invention is produced using the rubber composition of the present invention. Therefore, the vulcanization rate can be adjusted to an appropriate range while achieving both excellent wear resistance and flame retardancy, and the processability is excellent.

[0154] [Rubber composition]

[0155] The rubber composition used in the conveyor belt of the present invention is not particularly limited as long as it is the rubber composition of the present invention.

[0156] The conveyor belt of the present invention is not particularly limited except that it is produced using the rubber composition of the present invention.

[0157] There is no particular limitation on which component of the conveyor belt of the present invention the rubber composition of the present invention is applied to, and all or part of the rubber constituting the conveyor belt of the present invention can be produced from the rubber composition of the present invention.

[0158] The rubber composition of the present invention can achieve both excellent wear resistance and flame retardancy while keeping the vulcanization rate within an appropriate range and having excellent processability. Therefore, one of the preferred embodiments of the conveyor belt of the present invention is one having a covering rubber formed using the rubber composition of the present invention.

[0159] Hereinafter, embodiments of the conveyor belt of the present invention will be described using the accompanying drawings. However, the present invention is not limited to the accompanying drawings.

[0160] Figure 1 This is a cross-sectional view of one embodiment of the conveyor belt of the present invention. Figure 1One embodiment of the conveyor belt of the present invention shown (herein also referred to as the first embodiment of the conveyor belt of the present invention) is a conveyor belt 4 having a core layer formed by covering a fabric layer 1 with a coating rubber (adhesive rubber) 2, and the outer periphery of the core layer is covered with a covering rubber 3. The covering rubber 3 is preferably formed using the rubber composition of the present invention.

[0161] exist Figure 1 In the embodiment, the conveyor belt 4 uses the fabric layer 1 as the core material. The number of layers of the fabric layer 1, the thickness of the covering rubber 3, the belt width, etc. can be appropriately determined according to the intended use.

[0162] Examples of the fabric layer include canvas made of woven fabrics of synthetic fibers such as nylon, vinylon, and polyester.

[0163] Typically, the thicknesses T1 and T2 of the cover rubber 3 are respectively about 1.5 to 20 mm.

[0164] The coating rubber 2 may be a coating rubber used in known conveyor belts. Examples of the coating rubber include rubber compositions containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), ethylene-propylene rubber (EPT), and ethylene-propylene-diene rubber (EPDM).

[0165] Next use Figure 2 A second embodiment of the conveyor belt of the present invention will be described.

[0166] Figure 2 This is a cross-sectional view of another embodiment of the conveyor belt of the present invention.

[0167] like Figure 2 As shown, a second embodiment of the conveyor belt of the present invention is a conveyor belt 8 having a core layer formed by covering steel cords 5 with cushion rubber (adhesive rubber) 6 and covering the outer periphery thereof with covering rubber 7. The covering rubber 7 is preferably formed using the rubber composition of the present invention.

[0168] The conveyor belt 8 may be formed by arranging 50 to 230 steel cords 5 with a diameter of about 2.0 to 9.5 mm, for example, by twisting a plurality of filaments with a diameter of about 0.2 to 0.4 mm. The conveyor belt 8 generally has a total thickness T of about 10 to 50 mm.

[0169] The cushion rubber 6 may be, for example, an adhesive rubber that can bond to galvanized steel cords used in known steel conveyor belts. Specifically, the cushion rubber may be a rubber composition containing, for example, natural rubber (NR), acrylonitrile-butadiene rubber (NBR), ethylene-butadiene copolymer rubber (SBR), or butadiene rubber (BR).

[0170] The conveyor belt of the present invention can be manufactured, for example, by sandwiching a core material, such as a cloth layer, steel cord, or core material layer, between unvulcanized rubber sheets molded from the rubber composition of the present invention according to conventional methods, and then vulcanizing the sheet by heating and pressing. Vulcanization conditions can be, for example, approximately 120 to 180°C and 0.1 to 4.9 MPa for approximately 10 to 90 minutes.

[0171] The conveyor belt of the present invention can be used at a temperature of -30 to +60°C, for example.

[0172] Example

[0173] Hereinafter, the present invention will be described in further detail based on examples.

[0174] The materials, usage amounts, ratios, treatment contents, and treatment sequences shown in the following examples may be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited to the following examples.

[0175] [Manufacturing of Rubber Composition]

[0176] Each rubber composition was produced by using the components shown in the following tables (parts by mass) and mixing them with a stirrer.

[0177] Sulfur in each table * The amount shown in the column represents the amount of sulfur used as a commercial product. Guanidine vulcanization accelerator 2 (DOPD) * Thiazole vulcanization accelerator * The same is true for the (compare DM) column.

[0178] The values ​​shown in the (sulfenamide vulcanization accelerator + guanidine vulcanization accelerator) / sulfur mass ratio column in each table are calculated based on the net contents of sulfur, sulfenamide vulcanization accelerator, and guanidine vulcanization accelerator. The same applies to the values ​​shown in the sulfenamide vulcanization accelerator / guanidine vulcanization accelerator / sulfur mass ratio column.

[0179] [evaluate]

[0180] The following evaluations were performed using each of the rubber compositions produced as described above. The results are shown in Table 1.

[0181] [Mooney scorch time @125℃]

[0182] (Determination of Mooney scorch time)

[0183] The Mooney minimum viscosity (minimum torque) and Mooney scorch time of each rubber composition (unvulcanized) produced as described above were measured at 125°C using a Mooney viscometer (L-type rotor) in accordance with the Mooney scorch test method specified in JIS K6300-1:2013, "Unvulcanized Rubber - Physical Properties - Part 1: Method for Determination of Viscosity and Scorch Time Using a Mooney Viscometer." The Mooney scorch time is indicated in the "Mooney Scorch Time (minutes) @ 125°C" column in each table as the time required for a 5-Mooney increase from the minimum torque (ML-5up, in minutes).

[0184] (Evaluation criteria for processability)

[0185] In the present invention, when the Mooney scorch time measured as described above is 25.0 to 35.0 minutes, the processability is evaluated as excellent. When the Mooney scorch time is within the above range, rubber scorch is less likely to occur, which is preferred.

[0186] When the Mooney scorch time is 25.0 to 35.0 minutes, a longer Mooney scorch time is more preferred from the viewpoint of being less likely to cause rubber scorch.

[0187] [Vulcanization time]

[0188] (Measurement of each vulcanization time T)

[0189] For each rubber composition (unvulcanized) produced as described above, the torque was measured at 148°C using a rotorless vulcanization tester as a vulcanizer in accordance with JIS K6300-2:2001 "Unvulcanized rubber - Physical properties - Part 2: Method for determining vulcanization characteristics using a vibrating vulcanization tester." A vulcanization curve was prepared with the torque obtained as described above as the vertical axis and the vulcanization time (minutes) as the horizontal axis. The maximum value MH and the minimum value ML of the torque were obtained from the vulcanization curve.

[0190] The difference between the maximum value MH and the minimum value ML obtained as described above is defined as ME.

[0191] The time to reach the torque ML+ME×0.05 (the time (in minutes) from the start of vulcanization until the torque measured by the vibration vulcanization tester reaches 5% of the difference ME between the maximum torque MH and the minimum torque ML of the vulcanization curve) is defined as T5.

[0192] The time to reach the torque ML+ME×0.30 is defined as T30 (the time (minutes) from the start of vulcanization until the torque measured by the vibration vulcanization tester reaches 30% of the difference ME between the maximum torque MH and the minimum torque ML of the vulcanization curve).

[0193] The time to reach the torque ML+ME×0.70 is defined as T70 (the time (minutes) from the start of vulcanization until the torque measured by the vibration vulcanization tester reaches 70% of the difference ME between the maximum torque MH and the minimum torque ML of the vulcanization curve).

[0194] The time to reach the torque ML+ME×0.95 is defined as T95 (the time (minutes) from the start of vulcanization until the torque measured by the vibration vulcanization tester reaches 95% of the difference ME between the maximum torque MH and the minimum torque ML of the vulcanization curve).

[0195] (T70-T30)

[0196] T70 and T30 obtained as described above are substituted into "T70-T30".

[0197] (T95-T5)

[0198] T95 and T5 obtained as described above were substituted into "T95-T5".

[0199] (Evaluation criteria for vulcanization speed)

[0200] In the present invention, when the value of T70-T30 obtained as described above satisfies the formula (1): 3.0 ≤ (T70-T30) ≤ 3.5, and the value of T95-T5 obtained as described above satisfies the formula (2): 15.0 ≤ (T95-T5) ≤ 18.0, the vulcanization rate is evaluated to be within the appropriate range. When the vulcanization rate is within the appropriate range, the productivity of the obtained rubber product is excellent, which is preferred.

[0201] The closer the value of T70-T30 is to 3.0 and / or the closer the value of T95-T5 is to 15.0, the more appropriate the vulcanization speed is evaluated.

[0202] [Abrasion resistance]

[0203] (Preparation of Vulcanization Test Specimen)

[0204] Each rubber composition produced as described above was vulcanized for 30 minutes at a surface pressure of 3.0 MPa using a press molding machine at 148° C. to produce a vulcanized test piece having a diameter of 16 mm and a thickness of 6 mm.

[0205] (DIN abrasion test)

[0206] Using each vulcanized test piece prepared as described above, a DIN abrasion test (Method A: non-rotating method in which the test piece is not rotated) was conducted at 23°C using a DIN abrasion tester in accordance with JIS K6264-2:2005, with the drum of the DIN abrasion tester rotating at 40 rpm and a load of 9.8 N. The wear amount [mm 3 ].

[0207] The wear amount measured as above is 40 mm 3 The following cases are indicated by "◎".

[0208] The wear amount measured as above exceeds 40 mm 3 And 70mm 3 The following situations are represented by "0".

[0209] The wear amount measured as above exceeds 70 mm 3 The case is indicated by “×”.

[0210] (Evaluation criteria for wear resistance)

[0211] In the present invention, when the wear amount measured as described above is 70 mm 3 When the value is less than 0.05, the wear resistance is evaluated as excellent.

[0212] The above wear is less than 70mm 3 , the better the wear resistance.

[0213] [Flame retardancy]

[0214] (Preparation of test pieces)

[0215] Using each of the rubber compositions produced above, test pieces (three for each test piece) were prepared in accordance with JIS K6324:2013, "Flame Retardant Conveyor Belts - Grades and Test Methods," Section 7.2.1. Vulcanization was performed using a press molding machine at 148°C for 30 minutes at a surface pressure of 3.0 MPa under standard vulcanization conditions.

[0216] (Evaluation method of flame retardancy)

[0217] The flame duration (unit: seconds) of the test piece prepared as described above was measured in accordance with JIS K6324:2013 “Flame retardant conveyor belts - Grades and test methods”.

[0218] (Evaluation criteria for flame retardancy)

[0219] In the present invention, when the test piece satisfies the JIS 3 grade flame retardancy test standard [flame duration is within 1 minute (flame duration is the average value of 3 test pieces), no repeated burning], it is evaluated as having excellent flame retardancy and is represented as "0".

[0220] When the test piece did not satisfy the flame retardancy test standard of JIS Class 3, it was evaluated as having poor flame retardancy and was indicated as "×".

[0221] [Table 1]

[0222]

[0223] [Table 2]

[0224]

[0225] [Table 3]

[0226]

[0227] [Table 4]

[0228]

[0229] Details of the components shown in Tables 1 to 4 are as follows.

[0230] (Diene rubber)

[0231] NR: Natural rubber. RSS#3

[0232] BR: Butadiene rubber. Trade name: Nipol BR1220 (weight average molecular weight: 460,000, manufactured by ZEON, Japan)

[0233] (Carbon Black)

[0234] CB (ISAF): Trade name SHOW BLACK N220, manufactured by Cabot Japan. N2SA: 111m 2 / g, DBP: 115cm 3 / 100g

[0235] CB (HAF): Trade name Seast N, manufactured by New Sun Chemical Carbon Co., Ltd. N2SA: 74m 2 / g, DBP: 101cm 3 / 100g

[0236] (flame retardant)

[0237] Chlorinated paraffin: manufactured by NEIMENGU XIHE CHEMICAL CO., LTD. (trade name): CHLORINATED PARAFFIN 70. Average chlorine content: 70% by mass.

[0238] Antimony trioxide: PATOX-M manufactured by Nippon Seiko Co., Ltd. (trade name)

[0239] Antiaging agent (6C): Amine-based antiaging agent. N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (structure shown below). Trade name: Ozonone 6C (manufactured by Seiko Chemical Co., Ltd.).

[0240]

[0241] Wax: Paraffin wax. Trade name: OZOACE-0037 (manufactured by Nippon Seira Co., Ltd.)

[0242] Zinc oxide: Trade name: "JIS #3 zinc oxide" (manufactured by Shodo Chemical Industry Co., Ltd.).

[0243] Stearic acid: Trade name "Stearic acid 50S" (manufactured by Nissin Rika Co., Ltd.)

[0244] (sulfur)

[0245] ·sulfur ＊ Oil-treated sulfur. Produced by Hosoi Chemical Industry Co., Ltd. Sulfur concentration: 95.24% by mass.

[0246] (Sulfenamide vulcanization accelerator)

[0247] Sulfenamide vulcanization accelerator 1 (CZ): N-cyclohexyl-2-benzothiazolesulfenamide (structure shown below) (trade name: Nocceler CZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0248]

[0249] Sulfenamide vulcanization accelerator 2 (NS): N-tert-butyl-2-benzothiazolesulfenamide (structure shown below) (trade name: Sanceler NS-G, manufactured by Sanshin Chemical Industry Co., Ltd.)

[0250]

[0251] (Guanidine vulcanization accelerator)

[0252] Guanidine vulcanization accelerator 1 (DPG): diphenylguanidine (structure shown below) (trade name: Soxinol DG, manufactured by Sumitomo Chemical Co., Ltd.)

[0253]

[0254] Guanidine vulcanization accelerator 2 (DOPG) ＊ : 1,3-di-o-tolylguanidine (structure shown below) (trade name Soxinol DT-O, manufactured by Sumitomo Chemical Co., Ltd.) having a 1,3-di-o-tolylguanidine concentration of 95% by mass or greater. It should be noted that when calculating the net content of 1,3-di-o-tolylguanidine contained in the commercially available product, the 1,3-di-o-tolylguanidine concentration in the commercially available product was set to 95% by mass.

[0255]

[0256] Thiuram vulcanization accelerator (Comparison TMTM): Tetramethylthiuram monosulfide (trade name Nocceler TS, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0257] Thiazole vulcanization accelerator ＊ (Comparative DM): Dibenzothiazole disulfide (trade name: Nocceler DM-PO, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) with a dibenzothiazole disulfide concentration of 95% by mass or greater. The net content of dibenzothiazole disulfide in the commercially available product was calculated based on the dibenzothiazole disulfide concentration in the commercially available product being 95% by mass.

[0258] From the results in Tables 1 to 4, it was confirmed that the rubber composition of the present invention exhibited the desired effects.

[0259] On the other hand, Comparative Examples 1 and 9, in which the mass ratio of (guanidine vulcanization accelerator content) / (sulfenamide vulcanization accelerator content) was less than the specified range, had poor processability. In addition, the vulcanization rate of Comparative Example 9 did not fall within the appropriate range.

[0260] Comparative Examples 2 and 10 to 12, where the mass ratio of (total content of sulfenamide vulcanization accelerator and guanidine vulcanization accelerator) / (sulfur content) was less than 1.00, had vulcanization rates that fell outside the appropriate range. Comparative Examples 2 and 11 also had poor processability.

[0261] Comparative Example 3, which did not contain a guanidine vulcanization accelerator but a thiuram vulcanization accelerator, Comparative Example 4, which did not contain a guanidine vulcanization accelerator but a thiazole vulcanization accelerator, and Comparative Example 5, which did not contain a guanidine vulcanization accelerator, did not achieve an appropriate vulcanization rate. Comparative Examples 4 and 5 also had poor processability.

[0262] In Comparative Examples 6 and 7, in which the natural rubber content and the butadiene rubber content exceeded the prescribed ranges, at least the vulcanization rate did not fall within the appropriate range.

[0263] Comparative Example 8, in which the content of chlorinated paraffin exceeded the prescribed range, had poor processability and abrasion resistance, and the vulcanization rate did not fall within the appropriate range.

[0264] In Comparative Example 13, in which the mass ratio of (the sum of the content of the sulfenamide vulcanization accelerator and the content of the guanidine vulcanization accelerator) / (sulfur content) was less than 1.00 and the mass ratio of (the content of the guanidine vulcanization accelerator) / (the content of the sulfenamide vulcanization accelerator) was outside the prescribed range, the vulcanization rate did not fall within the appropriate range.

[0265] In Comparative Example 14, in which the mass ratio of (content of guanidine-based vulcanization accelerator) / (content of sulfenamide-based vulcanization accelerator) exceeded the prescribed range, the vulcanization rate did not fall within the appropriate range.

[0266] Description of Reference Numerals

[0267] 1: cloth layer;

[0268] 2: Covering rubber;

[0269] 3, 7: Covering rubber;

[0270] 4, 8: conveyor belt;

[0271] 5: Steel cord;

[0272] 6: Buffer rubber.

Claims

1. A rubber composition comprising: a diene rubber comprising natural rubber and butadiene rubber, a flame retardant comprising chlorinated paraffin and antimony trioxide, carbon black, sulfur, and a vulcanization accelerator comprising a sulfenamide vulcanization accelerator and a guanidine vulcanization accelerator, and The content of the natural rubber is 20-50% by mass of the total amount of the diene rubber. The content of the butadiene rubber is 50-80% by mass of the total amount of the diene rubber. The content of the chlorinated paraffin is 20 to 35 parts by mass relative to 100 parts by mass of the diene rubber. The content of the antimony trioxide is 5 to 12 parts by mass relative to 100 parts by mass of the diene rubber. The mass ratio of (the sum of the content of the sulfenamide vulcanization accelerator and the content of the guanidine vulcanization accelerator) / (the content of sulfur) is 1.00 or more, The mass ratio of (the content of the guanidine vulcanization accelerator) / (the content of the sulfenamide vulcanization accelerator) is 0.20 to 0.

60.

2. The rubber composition according to claim 1, wherein The content of the natural rubber is 25-45% by mass of the total amount of the diene rubber. The content of the butadiene rubber is 55 to 75% by mass of the total amount of the diene rubber.

3. The rubber composition according to claim 1, wherein The carbon black comprises a nitrogen adsorption specific surface area exceeding 100 m 2 / g and the oil absorption of dibutyl phthalate is 100~140cm 3 / 100g of carbon black 1.

4. The rubber composition according to claim 1, wherein The content of the chlorinated paraffin is 20 to 30 parts by mass relative to 100 parts by mass of the diene rubber. The content of the antimony trioxide is 5 to 10 parts by mass relative to 100 parts by mass of the diene rubber. The rubber composition according to claim 1 , which is used for a conveyor belt. 6 . A conveyor belt produced using the rubber composition according to claim 1 .

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