Rubber composition and conveyor belt

Abstract

The present invention aims to provide a rubber composition and a conveyor belt, wherein the vulcanized rubber obtained from the rubber composition exhibits excellent energy-saving properties at the ambient temperature of use, durability relative to deformed vulcanized rubber, ozone resistance, and flame retardancy after aging. The solution is a rubber composition containing a diene rubber, a flame retardant, carbon black, sulfur, an anti-aging agent, and a vulcanization accelerator. The diene rubber comprises natural rubber and butadiene rubber, wherein in 100 parts by weight of the diene rubber, natural rubber comprises 20-70 parts by weight, and butadiene rubber comprises 30-80 parts by weight. The carbon black contains dibutyl phthalate with an oil absorption of 100 ml / 100g or more and less than 150 ml / 100g, and a nitrogen adsorption specific surface area of ​​60-100 m². 2 / g of carbon black has a nitrogen adsorption specific surface area of ​​20-50m². 2 The carbon black 2 is in a mass ratio of 1.0 to 2.0, and the total content of carbon black 1 and carbon black 2 is 40 to 70 parts by mass relative to 100 parts by mass of diene rubber. The vulcanization accelerator contains an alkaline vulcanization accelerator, and the content of the alkaline vulcanization accelerator is 0.1 to 1.0 parts by mass relative to 100 parts by mass of diene rubber.

Description

Technical Field

[0001] This invention relates to rubber compositions and conveyor belts. Background Technology

[0002] Rubber compositions for conveyor belts containing natural rubber, butadiene rubber, vulcanizing agent, vulcanization accelerator, carbon black, chlorinated paraffin, antimony trioxide, etc. are known in the past (e.g., Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 6620105 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Conveyor belts are required to have excellent energy-saving properties at ambient operating temperatures, durability relative to the deformation of the vulcanized rubber (examples of such deformation include, for instance, the elongation of the conveyor belt during startup. In this specification, these durability properties can be observed from the resulting tensile properties. The same applies below), ozone resistance, and flame retardancy after aging under the assumption of long-term use.

[0008] After studying the rubber composition containing flame retardants and the like disclosed in Patent Document 1, the inventors found that the vulcanized rubber obtained by curing such rubber composition has low energy-saving properties and other properties at its service environment temperature (0-20°C).

[0009] Furthermore, it was found that when adjusting the amount of rubber components and fillers added to the rubber composition as a countermeasure to this problem, the tensile properties, ozone resistance, durability relative to deformed vulcanized rubber, and flame retardancy after aging of the obtained vulcanized rubber tend to deteriorate.

[0010] Here, the subject of the present invention is to provide a rubber composition, wherein the vulcanized rubber obtained therefrom exhibits excellent energy-saving properties at ambient temperature, durability relative to deformed vulcanized rubber, ozone resistance, and flame retardancy after aging.

[0011] In addition, another objective of the present invention is to provide a conveyor belt.

[0012] Methods for solving problems

[0013] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that the above-mentioned problems can be solved by the following configuration.

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

[0015] [1] A rubber composition comprising a diene rubber, a flame retardant, carbon black, sulfur, an anti-aging agent, and a vulcanization accelerator, wherein the diene rubber comprises natural rubber and butadiene rubber.

[0016] Of the aforementioned diene-based rubbers, the content of natural rubber is 20-70 parts by weight, and the content of butadiene rubber is 30-80 parts by weight.

[0017] The carbon black mentioned above contains dibutyl phthalate with an oil absorption capacity of more than 100 ml / 100g and less than 150 ml / 100g, and a nitrogen adsorption specific surface area of ​​60-100 m². 2 / g of carbon black has a nitrogen adsorption specific surface area of ​​20-50m². 2 / g of carbon black 2,

[0018] The mass ratio of carbon black 1 to carbon black 2 is 1.0 or more and less than 2.0, and...

[0019] Relative to 100 parts by weight of the aforementioned diene rubber, the total content of carbon black 1 and carbon black 2 is 40 to 70 parts by weight.

[0020] The above-mentioned vulcanization accelerator contains an alkaline vulcanization accelerator, and the content of the alkaline vulcanization accelerator is 0.1 to 1.0 parts by weight relative to 100 parts by weight of the diene rubber.

[0021] [2] The rubber composition as described in [1], wherein the cis-1,4 bond content of the butadiene rubber is 97 mol% or more, and the Mooney viscosity (ML) at 100°C is... 1＋4 The viscosity of a 5% by mass toluene solution is above 40, and the viscosity (T-cp) of a 5% by mass toluene solution at 25°C is above 100 cps.

[0022] [3] The rubber composition as described in [2], wherein the Mooney viscosity (ML) of the butadiene rubber at 100°C is as described above. 1＋4 The viscosity of the 5% by mass toluene solution at 25°C is 45 or higher, and the viscosity (T-cp) of the solution is 115 cps or higher.

[0023] [4] The rubber composition as described in any one of [1] to [3] further contains antimony trioxide.

[0024] The above flame retardants contain chlorinated paraffin.

[0025] Relative to 100 parts by weight of the aforementioned diene-based rubber, the content of the aforementioned chlorinated paraffin is 20-35 parts by weight.

[0026] The content of antimony trioxide is 5 to 12 parts by mass relative to 100 parts by mass of the diene rubber mentioned above.

[0027] [5] The rubber composition as described in [4] has an average particle size of 1.5 μm or less for the antimony trioxide.

[0028] [6] The rubber composition as described in any one of [1] to [5] is used in a conveyor belt.

[0029] [7] A conveyor belt made using any one of the rubber compositions described in [1] to [6].

[0030] Invention Effects

[0031] According to the present invention, a rubber composition can be provided, wherein the vulcanized rubber obtained therefrom exhibits excellent energy-saving properties at the service ambient temperature, durability properties relative to deformed vulcanized rubber, ozone resistance, and flame retardancy after aging.

[0032] In addition, the present invention also provides a conveyor belt. Attached Figure Description

[0033]

Figure 1

[0034]

Figure 2

[0035] The present invention will now be described in detail.

[0036] The following description of the constituent elements is sometimes based on representative embodiments of the present invention, but the present invention is not limited to these embodiments.

[0037] In this specification, the numerical range represented by “~” refers to the range including the values ​​recorded before and after “~” as the lower and upper limits.

[0038] In this instruction manual, each ingredient can be used individually or in combination of two or more.

[0039] In this specification, when a component is used in combination with two or more other components, unless otherwise stated, the “content” of that component refers to the total content of the two or more components.

[0040] Unless otherwise stated, there are no limitations on the manufacturing methods of the components in this specification. For example, existing well-known methods can be listed.

[0041] In this specification, the statement that "the present invention is superior" refers to at least one of the following properties: energy saving at ambient temperature, durability relative to deformed vulcanized rubber, ozone resistance, and flame retardancy after aging.

[0042] [Rubber Composition]

[0043] The rubber composition of the present invention will be described below.

[0044] The rubber composition of the present invention contains diene rubber, flame retardant, carbon black, sulfur, anti-aging agent, and vulcanization accelerator, wherein the diene rubber contains natural rubber and butadiene rubber.

[0045] Of the aforementioned diene-based rubbers, the content of natural rubber is 20-70 parts by weight, and the content of butadiene rubber is 30-80 parts by weight.

[0046] The carbon black mentioned above contains dibutyl phthalate with an oil absorption capacity of more than 100 ml / 100g and less than 150 ml / 100g, and a nitrogen adsorption specific surface area of ​​60-100 m². 2 / g of carbon black has a nitrogen adsorption specific surface area of ​​20-50m². 2 / g of carbon black 2,

[0047] The mass ratio of carbon black 1 to carbon black 2 is 1.0 or more and less than 2.0, and...

[0048] Relative to 100 parts by weight of the aforementioned diene rubber, the total content of carbon black 1 and carbon black 2 is 40 to 70 parts by weight.

[0049] The above-mentioned vulcanization accelerator contains an alkaline vulcanization accelerator, and the content of the alkaline vulcanization accelerator is 0.1 to 1.0 parts by weight relative to 100 parts by weight of the diene rubber.

[0050] The reason why the rubber composition of the present invention having the above-described structure can solve the problem of the present invention is not necessarily clear, but the inventors speculate that it is for the following reasons. Furthermore, the following speculation does not limit the mechanism by which the effect is obtained. In other words, cases where the effect is obtained through mechanisms other than those described below are also included within the scope of the present invention.

[0051] In this invention, it is believed that by containing specific carbon blacks 1 and 2, and by ensuring that the content of natural rubber, the content of butadiene rubber, the total content of carbon blacks 1 and 2, their mass ratio, and the content of alkaline vulcanization accelerator are all within specific ranges, the energy-saving properties at the service environment temperature, the durability characteristics relative to the deformed vulcanized rubber, the ozone resistance, and the flame retardancy after aging of the obtained vulcanized rubber can be balanced at an excellent level.

[0052] [Diene-based rubber]

[0053] In this invention, the diene-based rubber contains natural rubber and butadiene rubber.

[0054] In this invention, the diene rubber contained as a rubber component is a polymer formed from monomers containing conjugated diene compounds.

[0055] [Natural rubber]

[0056] In this invention, there are no particular limitations on the natural rubber (NR) contained as a diene-based rubber. Examples of known natural rubbers can be cited as examples.

[0057] Butadiene rubber

[0058] In this invention, there are no particular limitations on the butadiene rubber (BR) contained in the diene-based rubber. Examples of existing and well-known butadiene rubbers can be cited as examples.

[0059] As a preferred embodiment, BR can be, for example, polybutadiene that is solid at 23°C. Furthermore, BR can be unmodified BR or modified BR.

[0060] (Content of cis-1,4 bonds in butadiene rubber)

[0061] From the viewpoint of achieving better results with the present invention, the cis-1,4 bond content of butadiene rubber is preferably 97 mol% or more.

[0062] There is no particular limit to the upper limit of the cis-1,4 bond content in butadiene rubber, which can be less than 100 moles.

[0063] The microstructure of butadiene rubber can be analyzed using infrared absorption spectroscopy with a 0.4% (w / w) carbon disulfide solution containing butadiene rubber, starting from 740 cm⁻¹. -1 (Vertical), 967cm -1 (Reverse style), 910cm -1 The absorption strength ratio of (vinyl) is calculated. As calculated above, the 740cm strength of butadiene rubber... -1 The (cis) absorption strength is higher than the cis-1,4 bond content of the corresponding butadiene rubber.

[0064] (Mounney viscosity of butadiene rubber)

[0065] From the viewpoint of achieving superior results in this invention, the Mooney viscosity (ML) of butadiene rubber at 100°C is [value missing]. 1＋4 The value is preferably 40 or higher, and more preferably 45 or higher.

[0066] For butadiene rubber at 100°C Mooney viscosity (ML)1＋4 There is no particular limit to the upper limit of ), but for reasons such as the good processability of uncured rubber, it can be below 100.

[0067] Regarding the Mooney viscosity (ML) of butadiene rubber 1＋4 The Mooney viscosity (100°C) was determined according to JIS K 6300-1:2013, using an L-shaped rotor, preheated at 100°C for 1 minute, and then measured after 4 minutes.

[0068] (Viscosity of butadiene rubber at 25°C with 5% by mass toluene solution (T-cp))

[0069] From the viewpoint of achieving better results with the present invention, the viscosity (T-cp) of the butadiene rubber at 25°C at 5% by mass of toluene solution is preferably 100 cps or more, more preferably 115 cps or more, and even more preferably 125 cps or more.

[0070] There is no particular upper limit to the viscosity (T-cp) of butadiene rubber at 25°C for a 5% by mass toluene solution. Based on the good processability of uncured rubber, it can be, for example, below 180 cps.

[0071] The viscosity (T-cp) of a 5% by mass toluene solution of butadiene rubber at 25°C is an indicator of the linearity (degree of linearity) of butadiene rubber, i.e., the degree of branching of its molecular structure. For the same molecular weight, the higher the viscosity (T-cp) of a 5% by mass toluene solution at 25°C, the more linear the butadiene rubber is.

[0072] Regarding the viscosity (T-cp) of a 5% by mass toluene solution of butadiene rubber, 2.28 g of the polymer (butadiene rubber) was dissolved in 50 ml of toluene, and then measured using a Canon-Fensk viscometer No. 400 at 25°C. Additionally, a standard solution for viscometer calibration (JIS Z8809) was used as the standard solution.

[0073] From the viewpoint of achieving superior effects of the present invention, it is preferable that the butadiene rubber has a cis-1,4 bond content of 97 mol% or more and a Mooney viscosity (ML) at 100°C. 1＋4 The content of the toluene solution is 40 or higher, and the viscosity (T-cp) of a 5% by mass toluene solution at 25°C is 100 cps or higher. More preferably, the content of cis-1,4 bonds is 97 mol% or higher, and the Mooney viscosity (ML) at 100°C is [missing value]. 1＋4 The viscosity of a 5% by mass toluene solution is 45 or higher, and the viscosity (T-cp) of a 5% by mass toluene solution at 25°C is 115 cps or higher.

[0074] (Weight-average molecular weight of butadiene rubber)

[0075] From the viewpoint of achieving better results with the present invention, the weight-average molecular weight of BR is preferably 200,000 or more, and more preferably 300,000 to 1,000,000.

[0076] In this specification, the weight-average molecular weight (Mw) of BR can be a standard polystyrene equivalent value obtained by gel permeation chromatography (GPC) under the following conditions.

[0077] • Solvent: Tetrahydrofuran

[0078] • Detector: RI detector

[0079] As a preferred embodiment, the diene-based rubbers mentioned above are only natural rubber and butadiene rubber.

[0080] Polymers other than diene rubbers

[0081] The rubber composition of the present invention, as a rubber component, may also contain polymers other than diene rubbers. The total content of natural rubber and butadiene rubber is preferably 80-100% by mass of the total content of diene rubbers and other polymers (i.e., the total amount of rubber components), more preferably 90-100% by mass, and even more preferably 100% by mass. Furthermore, the polymers other than diene rubbers do not contain the trimethyldihydroquinoline compounds described later.

[0082] [Content of natural rubber and butadiene rubber]

[0083] In this invention, of the 100 parts by weight of the diene rubber, the content of the natural rubber is 20 to 70 parts by weight, and the content of the butadiene rubber is 30 to 80 parts by weight.

[0084] By keeping the content of natural rubber and butadiene rubber within the above-mentioned range, the rubber composition of the present invention exhibits excellent flame retardancy after aging.

[0085] From the viewpoint of achieving better results with the present invention, the content of the above-mentioned natural rubber in 100 parts by weight of the diene rubber is preferably 20 to 40 parts by weight.

[0086] From the viewpoint of achieving better results with the present invention, the content of butadiene rubber in 100 parts by weight of the diene rubber is preferably 60 to 80 parts by weight.

[0087] [Flame retardant]

[0088] The rubber composition of the present invention contains a flame retardant.

[0089] There are no particular limitations on the flame retardants contained in the rubber compositions of the present invention, as long as they are compounds capable of imparting flame retardancy to vulcanized rubber.

[0090] The rubber composition of the present invention, by containing a flame retardant, can impart flame retardancy to vulcanized rubber obtained by vulcanizing the rubber composition of the present invention.

[0091] Examples of flame retardants mentioned above include halogenated flame retardants such as chlorine-based and bromine-based flame retardants.

[0092] The aforementioned chlorine-based flame retardants are flame retardants containing chlorine. Examples of such chlorine-based flame retardants include chlorinated paraffin.

[0093] The aforementioned brominated flame retardants are flame retardants containing bromine. Examples of such brominated flame retardants include, for instance, di(pentabromophenyl)ethane.

[0094] From the viewpoint that the effects of the present invention are superior (especially in terms of durability characteristics relative to deformed vulcanized rubber), the above-mentioned flame retardant preferably contains chlorinated paraffin.

[0095] (Chlorinated paraffin)

[0096] Chlorinated paraffins that can be used as flame retardants are paraffins containing chlorine.

[0097] (The proportion of chlorine in chlorinated paraffin)

[0098] There is no particular limitation on the proportion of chlorine in chlorinated paraffin. From the viewpoint of achieving better results in this invention, the proportion of chlorine in chlorinated paraffin is preferably 40-90% by mass, and more preferably 60-80% by mass.

[0099] (Flame retardant additives)

[0100] The rubber composition of the present invention preferably further contains a flame retardant additive. By using the flame retardant additive in combination with the aforementioned flame retardant, the flame retardancy imparted by the aforementioned flame retardancy can be further improved. Examples of such flame retardant additives include, for instance, antimony trioxide.

[0101] (Antimony trioxide)

[0102] In this invention, there are no particular restrictions on antimony trioxide (Sb2O3) that can be contained as a flame retardant additive.

[0103] From the viewpoint of achieving better results in this invention, the average particle size of antimony trioxide is preferably 1.5 μm or less.

[0104] There is no particular limitation on the lower limit of the average particle size of antimony trioxide; for example, it can be above 0.02 μm, based on the reason of its excellent dispersibility during mixing.

[0105] The average particle size of antimony trioxide can be determined according to JIS Z8825:2022 (particle size analysis - laser diffraction and scattering method).

[0106] (Content of flame retardants, etc.)

[0107] From the viewpoint of achieving better results with the present invention, the content of the flame retardant (excluding flame retardant additives) is preferably 20 to 35 parts by weight relative to 100 parts by weight of the diene rubber.

[0108] From the viewpoint of achieving better results with the present invention, the content of the flame retardant additive is preferably 0 to 12 parts by mass, more preferably 5 to 12 parts by mass, relative to 100 parts by mass of the diene rubber.

[0109] From the viewpoint of achieving better results, the rubber composition of the present invention preferably contains chlorinated paraffin as the flame retardant and antimony trioxide as the flame retardant additive.

[0110] In the case where the rubber composition of the present invention contains chlorinated paraffin and antimony trioxide, from the viewpoint of having better effects of the present invention, the content of chlorinated paraffin is preferably 20 to 35 parts by weight relative to 100 parts by weight of the diene rubber, and the content of antimony trioxide is preferably 5 to 12 parts by weight relative to 100 parts by weight of the diene rubber.

[0111] [Carbon black]

[0112] The rubber composition of the present invention contains carbon black.

[0113] In this invention, the carbon black contains dibutyl phthalate with an oil absorption capacity of 100 ml / 100 g or more but less than 150 ml / 100 g, and has a nitrogen adsorption specific surface area of ​​60–100 m². 2 / g of carbon black has a nitrogen adsorption specific surface area of ​​20-50m². 2 / g of carbon black 2.

[0114] The rubber composition of the present invention contains carbon black 1 and carbon black 2 in a specific range of total content and mass ratio, thereby exhibiting excellent energy saving at ambient temperature, durability relative to deformed vulcanized rubber, and ozone resistance.

[0115] In addition, in this specification, carbon black 1 is sometimes referred to as "CB1". In addition, carbon black 2 is sometimes referred to as "CB2".

[0116] In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black can be determined according to JIS K6217-2:2017. Additionally, the dibutyl phthalate oil absorption (DBP) of carbon black can be determined according to JIS K6217-4:2017.

[0117] [Carbon Black 1]

[0118] In this invention, carbon black 1 (CB1) has an oil absorption capacity of dibutyl phthalate of 100 ml / 100 g or more but less than 150 ml / 100 g, and a nitrogen adsorption specific surface area of ​​60-100 m². 2 / g of carbon black.

[0119] As for carbon black 1, examples include HAF grade carbon black.

[0120] From the viewpoint that the effects of the present invention are superior (especially the durability characteristics relative to deformed vulcanized rubber), carbon black 1 preferably contains HAF grade carbon black.

[0121] [Carbon Black 2]

[0122] In this invention, carbon black 2 has a nitrogen adsorption specific surface area of ​​20-50 m². 2 / g of carbon black.

[0123] Examples of carbon black 2 include, for example, GPF grade carbon black, FEF grade carbon black, and SRF-LM grade carbon black.

[0124] There are no particular restrictions on the oil absorption of dibutyl phthalate in carbon black 2 as long as it is below 150ml / 100g, for example, it can be 30 to 150ml / 100g.

[0125] From the viewpoint of superior performance of the present invention (especially energy saving at ambient temperature), carbon black 2 preferably contains a nitrogen adsorption specific surface area of ​​20-35 m². 2 / g of carbon black, preferably containing nitrogen adsorption specific surface area of ​​25-35m². 2 / g of carbon black, further preferably containing GPF grade carbon black.

[0126] (A combination of carbon black 1 and carbon black 2)

[0127] From the viewpoint of achieving better results with the present invention, the combination of carbon black 1 and carbon black 2 is preferably a combination of HAF grade carbon black as carbon black 1 and GPF grade carbon black as carbon black 2.

[0128] [The total content of carbon black 1 and carbon black 2]

[0129] In this invention, relative to 100 parts by weight of the diene rubber mentioned above, the total content of carbon black 1 and carbon black 2 is 40 to 70 parts by weight.

[0130] From the viewpoint of achieving better results with the present invention, the total content of carbon black 1 and carbon black 2 is preferably 40 to 60 parts by mass relative to 100 parts by mass of the diene rubber mentioned above.

[0131] [The mass ratio of carbon black 1 content to carbon black 2 content]

[0132] In this invention, the mass ratio (CB1 / CB2) of the content of carbon black 1 to the content of carbon black 2 is 1.0 or more and less than 2.0.

[0133] Furthermore, the content of carbon black 2 in the above mass ratio refers to the content of carbon black 2 relative to 100 parts by mass of the diene rubber mentioned above. The content of carbon black 1 in the above mass ratio is also the same.

[0134] From the viewpoint of achieving better results from the present invention, the above-mentioned mass ratio (CB1 / CB2) is preferably 1.0 to 1.8.

[0135] [Sulfur]

[0136] The rubber composition of the present invention contains sulfur.

[0137] There are no particular restrictions on the sulfur used in the vulcanization of rubber. For example, some well-known sulfur species can be listed.

[0138] (Sulfur content)

[0139] From the viewpoint of achieving better results with the present invention, the content of sulfur is preferably 0.5 to 5.0 parts by weight, more preferably 1.0 to 3.0 parts by weight, relative to 100 parts by weight of the diene rubber mentioned above.

[0140] [Anti-aging agents]

[0141] The rubber composition of the present invention contains an anti-aging agent.

[0142] There are no particular limitations on the anti-aging agents mentioned above. Examples of existing, well-known anti-aging agents can be listed.

[0143] From the viewpoint of achieving better results with the present invention, the above-mentioned anti-aging agent preferably contains an amine-based anti-aging agent. The amine-based anti-aging agent is an anti-aging agent having an amino group (-NH2) and / or an imino group (-NH-).

[0144] (Amine-based anti-aging agents)

[0145] As amine-based anti-aging agents, examples include:

[0146] diamine compounds such as p-phenylenediamine compounds;

[0147] Monoamine compounds such as p,p'-dioctyldiphenylamine;

[0148] Trimethyldihydroquinoline compounds.

[0149] (p-phenylenediamine compounds)

[0150] p-Phenylenediamine compounds are compounds having a p-phenylenediamine skeleton. The two nitrogen atoms in the p-phenylenediamine skeleton can independently form amino or imino groups, with at least one of the nitrogen atoms preferably being an imino group, and more preferably both being imino groups.

[0151] Examples of p-phenylenediamine compounds include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-dinaphthyl-p-phenylenediamine (DNPD), and N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD).

[0152] (Trimethyldihydroquinoline compounds)

[0153] Examples of the above-mentioned trimethyldihydroquinoline compounds include polymers of 2,2,4-trimethyl-1,2-dihydroquinoline (compounds with structures within [ ] in the following formula). Additionally, compounds shown within [ ] below are represented in monomer form. A polymer of 2,2,4-trimethyl-1,2-dihydroquinoline refers to a polymer of two or more monomers of 2,2,4-trimethyl-1,2-dihydroquinoline. n (number of repeating units) in the following formula is 2 or more. There is no particular upper limit to n; it can be a value corresponding to the weight-average molecular weight of the trimethyldihydroquinoline compounds described later.

[0154]

[0155] • Weight-average molecular weight of trimethyldihydroquinoline compounds

[0156] The weight-average molecular weight of trimethyldihydroquinoline compounds is preferably 300 or higher. The upper limit of the above weight-average molecular weight is preferably 1000 or lower.

[0157] In this specification, the weight-average molecular weight (Mw) of trimethyldihydroquinoline compounds can be converted to standard polystyrene values ​​obtained by gel permeation chromatography (GPC) under the following conditions.

[0158] • Solvent: Tetrahydrofuran

[0159] • Detector: RI detector

[0160] From the viewpoint of achieving better results with the present invention, the above-mentioned anti-aging agent preferably contains a p-phenylenediamine-based compound and / or a trimethyldihydroquinoline-based compound, more preferably a polymer containing N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and / or 2,2,4-trimethyl-1,2-dihydroquinoline, and even more preferably a polymer containing N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline.

[0161] (Content of anti-aging agents)

[0162] From the viewpoint of achieving better results with the present invention, the content of the anti-aging agent (the total content of two or more anti-aging agents when used together) is preferably 1.0 to 6.0 parts by weight, more preferably 2.0 to 5.0 parts by weight, relative to 100 parts by weight of the diene rubber described above.

[0163] When p-phenylenediamine compounds and trimethyldihydroquinoline compounds are used as the above-mentioned anti-aging agents, from the viewpoint of achieving better results according to the present invention, the content of p-phenylenediamine compounds in the total amount of the above-mentioned anti-aging agents is 50% by mass or more and less than 100% by mass, and the content of trimethyldihydroquinoline compounds in the total amount of the above-mentioned anti-aging agents is preferably greater than 0% by mass and less than 50% by mass.

[0164] [Vulcanization accelerator]

[0165] The rubber composition of the present invention contains a vulcanization accelerator.

[0166] In this invention, the above-mentioned vulcanization accelerator contains an alkaline vulcanization accelerator.

[0167] Furthermore, in this invention, the content of the alkaline vulcanization accelerator is 0.1 to 1.0 parts by mass relative to 100 parts by mass of the diene rubber described above.

[0168] [Alkaline vulcanization accelerator]

[0169] There are no particular limitations on the alkaline vulcanization accelerator contained in the rubber composition of the present invention, as long as it is an alkaline vulcanization accelerator.

[0170] Examples of alkaline vulcanization accelerators include guanidine-based vulcanization accelerators and aldehyde-amine-based vulcanization accelerators.

[0171] From the viewpoint of achieving better results with the present invention, the alkaline vulcanization accelerator preferably contains a guanidine-based vulcanization accelerator.

[0172] Examples of guanidine-based vulcanization accelerators include, for example, N,N'-diphenylguanidine (D and DPG) and N,N'-di-o-tolylguanidine (DT).

[0173] Examples of aldehyde-amine sulfidation accelerators include, for instance, hexamethylenetetramine (H).

[0174] [Content of alkaline vulcanization accelerator]

[0175] As described above, in this invention, the content of the alkaline vulcanization accelerator is 0.1 to 1.0 parts by mass relative to 100 parts by mass of the diene rubber.

[0176] From the viewpoint of achieving better results with the present invention, the content of the alkaline vulcanization accelerator is preferably 0.2 to 0.8 parts by weight relative to 100 parts by weight of the diene rubber.

[0177] (Vulcanization accelerators other than basic vulcanization accelerators)

[0178] The rubber composition of the present invention may also contain vulcanization accelerators other than basic vulcanization accelerators (other vulcanization accelerators).

[0179] Other examples of vulcanization accelerators besides basic vulcanization accelerators include, for instance, benzothiazole sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide (CZ) and N-tert-butyl-2-benzothiazole sulfenamide (NS); thiuram-based vulcanization accelerators such as tetra(2-ethylhexyl)thiuram disulfide (TOT-N); and sulfide-based vulcanization accelerators such as dibenzothiazole disulfide (DM) and 4,4'-dithiomorpholine.

[0180] In cases where the rubber composition of the present invention also contains other vulcanization accelerators, the other vulcanization accelerators are preferably benzothiazole sulfenamide-based vulcanization accelerators.

[0181] In cases where the rubber composition of the present invention also contains other vulcanization accelerators, from the viewpoint of achieving better results, the content of other vulcanization accelerators is preferably 1.0 to 3.0 parts by weight relative to 100 parts by weight of the diene rubber described above.

[0182] (additive)

[0183] In addition to the components described above, the rubber composition of the present invention may also contain additives. Examples of additives include, for example, oils such as aromatic oils, waxes, zinc oxide, stearic acid, and vulcanization retarders (e.g., N-cyclohexylthiophthalimide).

[0184] • Vulcanization delay agent

[0185] When the rubber composition of the present invention further contains a vulcanization retarder, the content of the vulcanization retarder is preferably 0.1 to 1.0 parts by weight relative to 100 parts by weight of the diene rubber described above.

[0186] As a preferred embodiment, the rubber composition of the present invention does not contain hydrazine compounds. There is no particular limitation on the type of hydrazine compound, as long as it is a compound having a group represented by -CO-NHN.

[0187] As a preferred embodiment, the rubber composition of the present invention is substantially free of silica. In this specification, "substantially free of silica" means that the silica content is 0 parts by mass or more and less than 1 part by mass relative to 100 parts by mass of diene rubber.

[0188] (Manufacturing method)

[0189] There are no particular limitations on the method for manufacturing the rubber composition of the present invention. For example, a method in which the above-mentioned essential components, and additives that may be used further as needed, are mixed in a Banbury mixer or the like at a temperature of 90 to 180°C.

[0190] (vulcanization)

[0191] The vulcanization of the rubber composition of the present invention can be carried out under normal conditions. The vulcanization temperature can be, for example, 120–180°C. Pressure can be applied during vulcanization.

[0192] (use)

[0193] Examples of applications of the rubber compositions of the present invention include, for instance, rubber compositions for conveyor belts.

[0194] [conveyor]

[0195] The conveyor belt of the present invention is a conveyor belt manufactured using the rubber composition of the present invention.

[0196] There are no particular limitations on the rubber composition used in the conveyor belt of the present invention, as long as it is the rubber composition of the present invention.

[0197] The conveyor belt of the present invention is not particularly limited except for being manufactured using the rubber composition of the present invention.

[0198] The conveyor belt of the present invention is manufactured using the rubber composition of the present invention described above. Therefore, the conveyor belt of the present invention has excellent energy saving at ambient temperatures (e.g., 0 to 20°C), durability relative to deformed vulcanized rubber, ozone resistance, and flame retardancy after aging.

[0199] There are no particular limitations on the application of the rubber composition of the present invention to any component constituting the conveyor belt of the present invention. All or part of the rubber constituting the conveyor belt of the present invention can be manufactured using the rubber composition of the present invention.

[0200] The vulcanized rubber obtained by curing the rubber composition of the present invention exhibits excellent energy-saving properties at the service environment temperature, durability relative to deformed vulcanized rubber, ozone resistance, and flame retardancy after aging. Therefore, as a preferred embodiment, the conveyor belt of the present invention has a cover rubber formed using the rubber composition of the present invention.

[0201] The embodiments of the 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.

[0202] Figure 1 A cross-sectional view of one embodiment of the conveyor belt of the present invention. Figure 1 One embodiment of the conveyor belt of the present invention shown (also referred to herein as the first embodiment of the conveyor belt of the present invention) is a conveyor belt 4 obtained by covering a cloth layer 1 with a coated rubber (adhesive rubber) 2 to form a core layer, and covering the outer periphery of the core layer with a covering rubber 3. The covering rubber 3 is preferably formed using the rubber composition of the present invention.

[0203] exist Figure 1 In the conveyor belt 4, the fabric layer 1 is used as the core material. The number of layers of fabric layer 1, the thickness of the covering rubber 3, the width of the conveyor belt, etc. can be appropriately determined according to the purpose of use.

[0204] As a fabric layer, examples include canvas made of synthetic fibers such as nylon, vinylon, and polyester.

[0205] The thicknesses T1 and T2 of the covering rubber 3 are typically around 1.5 to 20 mm.

[0206] Alternatively, the coated rubber 2 can be a known type of coated rubber used in conveyor belts. As the aforementioned coated rubber, a rubber composition containing, for example, natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), ethylene-propylene rubber (EPT), ethylene-propylene-diene rubber (EPDM) as rubber components can be used.

[0207] The following uses Figure 2 A second embodiment of the conveyor belt of the present invention will be described.

[0208] Figure 2 This is a cross-sectional view of another embodiment of the conveyor belt of the present invention.

[0209] like Figure 2 As shown, a second embodiment of the conveyor belt of the present invention is a conveyor belt 8 obtained by covering the steel cord 5 with a cushioning rubber (adhesive rubber) 6 to form a core material layer, and covering the outer periphery of the core material layer with a covering rubber 7. The covering rubber 7 is preferably formed using the rubber composition of the present invention.

[0210] The conveyor belt 8 can, for example, be made by arranging approximately 50 to 230 steel cords 5 with a diameter of approximately 2.0 to 9.5 mm side by side to form the core material. The steel cords 5 are formed by twisting and combining multiple baselines with a diameter of approximately 0.2 to 0.4 mm. Typically, the total thickness T of the conveyor belt 8 can be approximately 10 to 50 mm.

[0211] Alternatively, the cushioning rubber 6 can be, for example, an adhesive rubber capable of bonding with galvanized steel cords used in known steel conveyor belts. Specifically, as the cushioning rubber, a rubber composition containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), etc., as rubber components can be used.

[0212] The conveyor belt of the present invention can be manufactured, for example, by conventional methods, by sandwiching an uncured rubber sheet formed from the rubber composition of the present invention between layers of cloth, steel cord, or core material, and then subjecting it to heating, pressure, and vulcanization. Vulcanization conditions can be, for example, at approximately 120–180°C and approximately 0.1–4.9 MPa for approximately 10–90 minutes.

[0213] The conveyor belt of the present invention can be used, for example, at temperatures of -50 to +60°C, and preferably at temperatures of 0 to 20°C.

[0214] Example

[0215] The present invention will be further described in detail below based on embodiments.

[0216] The materials, amounts, proportions, processing contents, and processing steps shown in the following embodiments can be appropriately modified without departing from the spirit of the invention. Therefore, the scope of the invention should not be construed as limited to the embodiments shown below.

[0217] <Preparation of Rubber Compositions>

[0218] Using the components listed in Table 1 below, mix them in a Banbury mixer at 90–180°C to produce various rubber compositions (unvulcanized).

[0219] <Evaluation>

[0220] The following evaluations were conducted using the various rubber compositions prepared as described above. The results are shown in Table 1.

[0221] (Energy saving)

[0222] • Production of test films

[0223] The rubber compositions (uncured) manufactured as described above are vulcanized for 30 minutes under normal vulcanization conditions using a compression molding machine at 148°C and a surface pressure of 3.0 MPa to produce a vulcanized rubber sheet 1 (initial) with a length of 150 mm, a width of 150 mm, and a thickness of 2 mm.

[0224] From each vulcanized rubber sheet 1 (initial) prepared as described above, vulcanized sheets are punched out with dimensions of 40 mm in length, 5 mm in width, and 2 mm in thickness, thereby producing test pieces for evaluating energy-saving performance.

[0225] Evaluation Methods

[0226] Using test pieces prepared as described above, dynamic viscoelasticity was measured using a viscoelastic spectrometer (manufactured by Toyo Seiki Co., Ltd.) under the conditions of a fixture distance of 10 mm, dynamic strain of 2%, and frequency of 20 Hz. The loss tangent (tanδ) and dynamic elastic modulus E' (N / mm) at 0°C and 20°C were measured. The obtained loss tangent (tanδ) and dynamic elastic modulus E' were substituted into the following formula to calculate the RRF (Rolling Resistance Factor). In this invention, RRF is used to evaluate energy saving performance.

[0227]

[0228] • Energy-saving performance evaluation criteria under ambient temperature

[0229] The relationship between the RRF values ​​at 0℃ and 20℃ and the energy-saving judgment mark is shown in Table 2 below.

[0230]

[0231] In this invention, the energy-saving performance of the obtained vulcanized rubber at the ambient temperature is evaluated as excellent when the RRF at 0°C is less than 0.120 and the RRF at 20°C is less than 0.105.

[0232] Under the above conditions, the smaller the RRF ratio at 0°C is (0.120) and / or the smaller the RRF ratio at 20°C is (0.105), the better the energy saving performance.

[0233] (Durability characteristics relative to deformed vulcanized rubber)

[0234] • Determination of tensile properties

[0235] Using a compression molding machine at 148°C, each rubber composition (uncured) manufactured as described above is vulcanized for 30 minutes under normal vulcanization conditions at a surface pressure of 3.0 MPa to produce a vulcanized rubber sheet 1 (initial) with a length of 150 mm, a width of 150 mm, and a thickness of 2 mm.

[0236] Each vulcanized rubber sheet 1 (initial) obtained as described above is punched into a JIS 3 dumbbell-shaped test piece, and the tensile properties of the obtained test pieces are evaluated.

[0237] Using the test pieces obtained as described above, tensile tests were conducted at 23℃±2℃ and a tensile speed of 500 mm / min according to JIS K6251:2017 to determine the tensile strength (TB) [unit: MPa] and elongation at break (EB) [unit: %].

[0238] Calculate their product (TB×EB) based on the TB and EB values ​​measured as described above.

[0239] • Evaluation criteria for durability properties relative to deformed vulcanized rubber

[0240] In this invention, when the value of the product (TB×EB) calculated as described above is 9500 or higher, the durability characteristics relative to the deformed vulcanized rubber are evaluated as excellent.

[0241] The larger the value of the above product compared to 9500, the better the durability characteristics relative to the deformed vulcanized rubber.

[0242] (Ozone resistance)

[0243] Using a compression molding machine at 148°C, each rubber composition (unvulcanized) manufactured as described above is vulcanized for 30 minutes under normal vulcanization conditions at a surface pressure of 3.0 MPa, thereby producing a vulcanized rubber sheet 1 (initial) with a length of 150 mm, a width of 150 mm, and a thickness of 2 mm.

[0244] According to JIS K6259-1:2015, each vulcanized rubber sheet 1 (initial) prepared as described above was placed in an ozone bath (40°C, 50 pphm) and subjected to an ozone resistance test (accelerated test) for 168 hours with 20% elongation. After the ozone resistance test, the surface of the vulcanized rubber sheet was visually observed.

[0245] If the vulcanized rubber sheet does not crack after the above ozone resistance test, it is recorded as "NC".

[0246] • Evaluation criteria for ozone resistance

[0247] In this invention, if the vulcanized rubber sheet does not crack after the above ozone resistance test, the ozone resistance of the obtained vulcanized rubber is evaluated as excellent.

[0248] Furthermore, if the vulcanized rubber sheet cracks after the aforementioned ozone resistance test, the level of cracking is evaluated according to JIS K6259-1:2015, expressed using a combination of letters and numbers, similar to level "C2" mentioned above. Compared to level "A", levels "B" and "C" exhibit worse ozone resistance. Additionally, when the letters in the levels are the same, a larger number after the letter indicates poorer ozone resistance.

[0249] (Flame retardancy after aging)

[0250] • Production of test films

[0251] Using the rubber compositions manufactured as described above, test pieces (six of each type) were prepared for the fabric conveyor belt rubber according to JIS K6324:2013 "Flame retardant properties of conveyor belts - grades and test methods" 7.2.1. Regarding the vulcanization during the preparation process, a compression molding machine at 148°C was used, and the samples were vulcanized for 30 minutes under normal vulcanization conditions at a surface pressure of 3.0 MPa to obtain BL samples (blank samples).

[0252] Using three of the six BL samples obtained as described above, an aging test was conducted by placing them at 100°C for 168 hours to obtain the samples after the 168-hour aging test.

[0253] • Evaluation method for flame retardancy

[0254] For BL specimens (3 specimens) and specimens after 168 hours of aging test (3 specimens), the flame duration (in seconds) was determined according to JIS K6324:2013 "Flame retardant performance of conveyor belts - grades and test methods".

[0255] • Evaluation criteria for the flame retardancy of BL specimens and specimens after aging tests

[0256] In this invention, if the above-mentioned BL sample meets the JIS Class 3 flame retardant test standard [flame duration less than 1 minute (flame duration is the average of 3 test pieces), and there is no reignition], it is represented as "0". The evaluation results of the flame retardancy of the BL sample are shown in the "Flame Retardancy BL" column of the table.

[0257] The evaluation criteria for the flame retardancy of the specimens after the 168-hour aging test are the same as those for the BL specimens. If a specimen does not meet the JIS Class 3 flame retardancy test standard after the 168-hour aging test, it is marked as "×". The evaluation results of the flame retardancy of the specimens after the 168-hour aging test are shown in the "Flame Retardancy AG" column of the table.

[0258] • Evaluation criteria for flame retardancy after aging

[0259] In this invention, when the initial flame retardancy is excellent (the "Flame Retardancy BL" column in the table is marked as "○") and the "Flame Retardancy AG" column in the table is marked as "○", the flame retardancy evaluation after aging is excellent.

[0260]

[0261]

[0262]

[0263]

[0264]

[0265]

[0266] The detailed information for each component shown in each table is as follows.

[0267] (Diene-based rubber)

[0268] • NR: Natural Rubber. RSS #3

[0269] •BR1~3: Detailed information on BR1~3 as butadiene rubber is shown in Table 3 below.

[0270]

[0271] (Carbon black)

[0272] (Carbon Black 1)

[0273] • CB1 (HAF grade CB): Trade name Seast N, manufactured by Tokai Carbon. N2SA: 74m 2 / g, DBP: 101ml / 100g

[0274] The HAF grade CB mentioned above belongs to carbon black 1 in this invention.

[0275] (Carbon Black 2)

[0276] • CB2 (GPF grade CB): Trade name Niteron #55S, manufactured by Nippon Steel Chemical & Material Co., Ltd. N2SA: 26m 2 / g, DBP: 88ml / 100g

[0277] The aforementioned GPF grade CB belongs to carbon black 2 in this invention.

[0278] • CB2 (FEF grade CB): Product name HTC #100, manufactured by Shin-Nichika Carbon. N2SA: 40m 2 / g, DBP: 106ml / 100g

[0279] The aforementioned FEF grade CB belongs to carbon black 2 in this invention.

[0280] • SRF-LM grade CB: Trade name HTC#SL, manufactured by Nippon Steel Chemical & Material Co., Ltd. N2SA: 24m 2 / g, DBP: 54ml / 100g

[0281] The SRF-LM grade CB mentioned above belongs to carbon black 2 in this invention.

[0282] (Carbon black other than Carbon Black 1 and 2)

[0283] • ISAF grade CB: Trade name Niteron #300, manufactured by Nippon Steel Chemical & Material Co., Ltd. N2SA: 115m 2 / g, DBP: 116ml / 100g

[0284] The aforementioned ISAF grade CB does not belong to either carbon black 1 or 2 in this invention.

[0285] • SRF-H grade CB: Trade name Asahi #50, manufactured by Asahi Carbon. N2SA: 19m 2 / g, DBP: 61ml / 100g

[0286] The SRF-H grade CB mentioned above does not belong to either carbon black 1 or 2 in this invention.

[0287] (Flame retardant)

[0288] • Chlorinated paraffin: Empara 70S, manufactured by Dover Chemical Co., Ltd. Chlorine content 68–72% by mass. Average Cl content 70% by mass. The chlorine content in chlorinated paraffin is calculated using the aforementioned average Cl content of 70% by mass.

[0289] • Bromine-based flame retardant: Di(pentabromophenyl)ethane. Trade name "SAYTEX 8010" (manufactured by ALBEMARLE CORPORATION).

[0290] (Flame retardant additives)

[0291] • Antimony trioxide 1-2: Detailed information on antimony trioxide 1-2 is shown in Table 4 below.

[0292]

[0293] (Anti-aging agent)

[0294] • 6C: Amine-based anti-aging agent. N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (structure below). Trade name: Ozonone 6C (manufactured by Seiko Chemical Co., Ltd.). 6C has the following structure. (Molecular weight: 268)

[0295]

[0296] • RD: A polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (structure described below). Trade name: Non-Flex RD (manufactured by Seiko Chemical Co., Ltd.). Weight average molecular weight: 400–600

[0297]

[0298] (additive)

[0299] • Wax: Solid paraffin wax. Trade name OZOACE-0015 (Japan Fine Wax Co., Ltd.).

[0300] • Zinc white: Zinc oxide. Trade name "Zinc Oxide 3 Types" (manufactured by Zhengtong Chemical Industry Co., Ltd.)

[0301] • St: Stearic acid. Trade name "Stearic Acid 50S" (Chiba Fatty Acid Co., Ltd.)

[0302] (Vulcanization accelerator)

[0303] • Vulcanization accelerator NS: N-tert-butyl-2-benzothiazole sulfenamide (trade name Noccela NS, manufactured by Ouchi Shinshin Chemical Co., Ltd.)

[0304] • Vulcanization accelerator D: Diphenylguanidine (trade name Noccela D, manufactured by Ouchi Shinshin Chemical Co., Ltd.)

[0305] The aforementioned vulcanization accelerator D is an alkaline vulcanization accelerator.

[0306] • Curing delay agent PVI: N-cyclohexylthiophthalimide. Trade name: Retarder CTP, manufactured by Toray Fine Chemicals.

[0307] (Vulcanizing agent)

[0308] • Sulfur: Insoluble sulfur. Manufactured by Shikoku Chemical Industry Co., Ltd. (trade name) Myucron OT-20S. Sulfur concentration 80% by mass. The content shown in the "Sulfur" column of Table 1 refers to the amount of the aforementioned insoluble sulfur.

[0309] The results in Table 1 confirm that the rubber composition of the present invention exhibits the desired effect.

[0310] On the other hand, in Comparative Examples 1 and 2 where the content of natural rubber and butadiene rubber is outside the specified range, Comparative Example 3 where carbon black 2 is not contained, Comparative Examples 4 and 15 where carbon black 1 is not contained, Comparative Examples 12 and 13 where carbon black other than carbon black 1 and 2 is not contained, Comparative Example 14 where carbon black other than carbon black 1 is not contained, Comparative Examples 5, 6, 9 to 11, 17 and 18 where the mass ratio of CB1 / CB2 is outside the specified range, Comparative Examples 7 and 8 where the content of alkaline vulcanization accelerator is outside the specified range, and Comparative Example 16 where the total content of carbon black 1 and 2 is outside the specified range, at least one of the following aspects of the obtained vulcanized rubber is insufficient: energy saving at the service environment temperature, durability characteristics relative to deformed vulcanized rubber, ozone resistance, and flame retardancy after aging.

[0311] Explanation of reference numerals in the attached figures

[0312] 1: Fabric layer

[0313] 2: Coated rubber

[0314] 3, 7: Covering rubber

[0315] 4, 8: Conveyor belt

[0316] 5: Steel cord

[0317] 6: Cushioning rubber

Claims

1. A rubber composition comprising a diene rubber, a flame retardant, carbon black, sulfur, an anti-aging agent, and a vulcanization accelerator, wherein the diene rubber comprises natural rubber and butadiene rubber. In 100 parts by weight of the diene-based rubber, the content of natural rubber is 20-70 parts by weight, and the content of butadiene rubber is 30-80 parts by weight. The carbon black contains dibutyl phthalate with an oil absorption capacity of more than 100 ml / 100g and less than 150 ml / 100g, and a nitrogen adsorption specific surface area of ​​60-100 m². 2 / g of carbon black has a nitrogen adsorption specific surface area of ​​20-50m². 2 / g of carbon black 2, The mass ratio of carbon black 1 to carbon black 2 is 1.0 or more and less than 2.0, and... Relative to 100 parts by weight of the diene rubber, the combined content of carbon black 1 and carbon black 2 is 40-70 parts by weight. The vulcanization accelerator contains an alkaline vulcanization accelerator, and the content of the alkaline vulcanization accelerator is 0.1 to 1.0 parts by weight relative to 100 parts by weight of the diene rubber.

2. The rubber composition of claim 1, wherein the butadiene rubber has a cis-1,4 bond content of 97 mol% or more, and a Mooney viscosity (ML) at 100°C. 1＋4 The viscosity of a 5% by mass toluene solution is above 40, and the viscosity (T-cp) of the solution at 25°C is above 100 cps.

3. The rubber composition of claim 2, wherein the butadiene rubber has the Mooney viscosity (ML) at 100°C. 1＋4 The viscosity of the 5% by mass toluene solution at 25°C is 45 or higher, and the viscosity (T-cp) of the solution is 115 cps or higher.

4. The rubber composition according to claim 1 or 2, further comprising antimony trioxide. The flame retardant contains chlorinated paraffin. The content of chlorinated paraffin is 20-35 parts by weight relative to 100 parts by weight of the diene rubber. The content of antimony trioxide is 5 to 12 parts by mass relative to 100 parts by mass of the diene rubber.

5. The rubber composition according to claim 4, wherein the average particle size of the antimony trioxide is less than 1.5 μm.

6. The rubber composition as described in claim 1 or 2, used in a conveyor belt.

7. A conveyor belt manufactured using the rubber composition according to any one of claims 1 to 6.

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