Rubber composition and conveyor belt

Abstract

The present invention addresses the problem of providing: a rubber composition having excellent flame retardancy, ozone resistance, power saving properties, and wear resistance when formed into a cured product; and a conveyor belt. [Solution] A rubber composition containing a rubber component containing a diene rubber, a flame retardant containing a halogen flame retardant, a filler, a divalent metal compound containing a carboxylic acid salt of a divalent metal, an anti-aging agent, a vulcanization accelerator, and sulfur, and a conveyor belt manufactured using the rubber composition, the content of a halogen element contained in the halogen-based flame retardant is 9% by mass or more relative to the total amount of the rubber composition, the mass ratio of the total content of the divalent metal contained in the divalent metal compound to the content of the halogen element contained in the halogen-based flame retardant is 0.05 or more, and the total number of carbon atoms per molecule of the carboxylic acid constituting the carboxylate is 6-12.

Description

Technical Field

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

[0002] Conventionally, flame retardancy of rubber has been studied (for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 5768408 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Generally, in order to maintain the flame retardancy of aged rubber during long-term use, a relatively large amount of a flame retardant needs to be compounded in advance into the rubber composition.

[0008] Based on the above situation, the inventors have studied the rubber composition disclosed in Patent Document 1 and found that, sometimes, as the amount of flame retardant added to the rubber composition increases, the ozone resistance, power saving, and wear resistance of the cured product (vulcanized rubber) obtained from the rubber composition deteriorate.

[0009] Therefore, an object of the present invention is to provide a rubber composition which, when formed into a cured product, is excellent in flame retardancy, ozone resistance, power saving, and wear resistance.

[0010] In addition, the present invention also aims to provide a conveyor belt.

[0011] Means for solving problems

[0012] The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the problems can be solved by the following configuration.

[0013] [1] A rubber composition comprising: a rubber component comprising a diene rubber, a flame retardant comprising a halogen flame retardant, a filler, a divalent metal compound comprising a divalent metal carboxylate, an antioxidant, a vulcanization accelerator, and sulfur;

[0014] The content of the halogen element in the halogen flame retardant is 9% by mass or more of the total amount of the rubber composition.

[0015] The mass ratio of the total content of the divalent metal in the divalent metal compound to the content of the halogen element in the halogen flame retardant is 0.05 or more.

[0016] The total number of carbon atoms per molecule of the carboxylic acid constituting the carboxylate is 6 to 12.

[0017] [2] The rubber composition according to [1], wherein the diene rubber includes natural rubber and / or butadiene rubber.

[0018] [3] The rubber composition according to [1] or [2], wherein the divalent metal constituting the carboxylate contains Zn 2+ .

[0019] [4] The rubber composition according to any one of [1] to [3], wherein the divalent metal constituting the divalent metal compound contains Zn 2+ .

[0020] [5] The rubber composition according to any one of [1] to [4], wherein the divalent metal compound further contains a divalent metal oxide.

[0021] [6] The rubber composition according to any one of [1] to [5], wherein the diene rubber comprises natural rubber and butadiene rubber, and the mass ratio of the natural rubber to the butadiene rubber is 30 / 70 to 80 / 20.

[0022] The mass ratio of the total content of the divalent metal contained in the divalent metal compound / the content of the halogen element contained in the halogen flame retardant is 0.2 to 0.3.

[0023] [7] The rubber composition according to any one of [1] to [6], wherein part or all of the halogen-based flame retardant is a bromine-based flame retardant, and the flame retardant further contains antimony trioxide.

[0024] [8] The rubber composition according to any one of [1] to [7], which is used for a conveyor belt.

[0025] [9] A conveyor belt produced using the rubber composition according to any one of [1] to [8].

[0026] Effects of the Invention

[0027] According to the present invention, a rubber composition can be provided which, when formed into a cured product, is excellent in flame retardancy, ozone resistance, power saving, and wear resistance.

[0028] Furthermore, the present invention may also provide a conveyor belt. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a cross-sectional view of one embodiment of the conveyor belt of the present invention.

[0030] Figure 2 It is a cross-sectional view of another embodiment of the conveyor belt of the present invention. DETAILED DESCRIPTION

[0031] Hereinafter, the present invention will be described in detail.

[0032] The description of the constituent elements described below may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0033] In the present specification, a numerical range expressed using "to" means a range including the numerical values ​​described before and after "to".

[0034] In the present specification, each component contained in the rubber composition of the present invention can be used alone or in combination of two or more.

[0035] In the present specification, when two or more components of the rubber composition of the present invention are used in combination, the "content" of the components means the total content of the two or more components unless otherwise specified.

[0036] In the present specification, the production method of each component is not particularly limited unless otherwise specified, and examples thereof include conventionally known methods.

[0037] [Rubber composition]

[0038] The rubber composition of the present invention contains:

[0039] A rubber component including a diene rubber, a flame retardant including a halogen flame retardant, a filler, a divalent metal compound including a carboxylate of a divalent metal, an antioxidant, a vulcanization accelerator, and sulfur,

[0040] The content of the halogen element in the halogen flame retardant is 9% by mass or more of the total amount of the rubber composition of the present invention.

[0041] The mass ratio of the total content of the divalent metal in the divalent metal compound to the content of the halogen element in the halogen flame retardant is 0.05 or more.

[0042] The total number of carbon atoms per molecule of the carboxylic acid constituting the carboxylate is 6 to 12.

[0043] The reason why the rubber composition of the present invention having the above-mentioned structure can solve the problems of the present invention is not necessarily clear, but the present inventors presume it as follows.

[0044] In addition, the mechanism of obtaining the effect is not limited to the following speculation. In other words, even if the effect is obtained by a mechanism other than the following, it is also included in the scope of the present invention.

[0045] It is considered that the rubber composition of the present invention has the halogen element content of the halogen flame retardant contained in the flame retardant and the divalent metal content of the divalent metal compound / the above-mentioned halogen element content in a specific range, and a divalent metal carboxylate is added to the rubber composition, thereby imparting flame retardancy to the obtained cured product, ensuring rubber properties such as ozone resistance and wear resistance at the required level, and improving power saving.

[0046] It is speculated that the above-mentioned rubber properties are ensured and the power saving is improved because the above-mentioned carboxylate acts as a scavenger for scavenging free radicals that may be generated by the decomposition of the vulcanized rubber and / or halogens that may be generated by the halogen-based flame retardant. It is believed that the above-mentioned speculation is confirmed by the following situation: in this example, the 50% modulus (M50) of the cured product obtained by overvulcanizing the rubber composition of the present invention is superior to that of the rubber composition not containing the carboxylate of a divalent metal.

[0047] Hereinafter, in this specification, "a carboxylate of a divalent metal" is also referred to as "a specific carboxylate".

[0048] Furthermore, when the rubber composition of the present invention is formed into a cured product and at least one of flame retardancy, ozone resistance, power saving, and wear resistance is excellent, it is also referred to as "the effect of the present invention is more excellent".

[0049] [Rubber ingredients]

[0050] The rubber composition of the present invention contains a rubber component comprising a diene rubber.

[0051] [Diene rubber]

[0052] In the present invention, the diene rubber contained as the rubber component is not particularly limited as long as it is a polymer formed from a monomer containing a diene compound.

[0053] Examples of the diene rubber include natural rubber, butadiene rubber, and styrene-butadiene rubber.

[0054] From the viewpoint of achieving more excellent effects of the present invention, the diene rubber preferably includes natural rubber and / or butadiene rubber, and more preferably includes natural rubber and butadiene rubber.

[0055] (Natural Rubber)

[0056] In the present invention, the natural rubber (NR) that can be included as the diene rubber is not particularly limited, and examples thereof include conventionally known ones.

[0057] (Butadiene rubber)

[0058] In the present invention, the butadiene rubber (BR) that can be included as the diene rubber is not particularly limited, and examples thereof include conventionally known ones.

[0059] As one of the preferred embodiments of BR, for example, polybutadiene which is solid at 23° C. BR may be unmodified BR or modified BR.

[0060] From the viewpoint of achieving more excellent effects of the present invention (particularly power saving and wear resistance), the weight average molecular weight of BR is preferably 200,000 or more, and more preferably 300,000 to 1,000,000.

[0061] 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.

[0062] Solvent: Tetrahydrofuran

[0063] Detector: RI detector

[0064] (Mass ratio of natural rubber to butadiene rubber)

[0065] When the diene rubber includes natural rubber and butadiene rubber, the mass ratio of natural rubber / butadiene rubber is preferably 30 / 70 to 80 / 20, more preferably 50 / 50 to 75 / 25, from the viewpoint of achieving better effects of the present invention (particularly power saving and wear resistance).

[0066] (Total content of natural rubber and butadiene rubber)

[0067] When the above-mentioned diene rubber includes natural rubber and butadiene rubber, from the viewpoint of better effects of the present invention (especially power saving and wear resistance), the total content of natural rubber and butadiene rubber is preferably 80 to 100% by mass, more preferably 100% by mass, of the total amount of the rubber component.

[0068] [Flame retardant]

[0069] The rubber composition of the present invention contains a flame retardant including a halogen-based flame retardant.

[0070] The flame retardant is a compound that imparts flame retardancy to the obtained cured product.

[0071] [Halogen flame retardants]

[0072] In the present invention, the halogen-based flame retardant is a flame retardant having a halogen element.

[0073] The halogen element contained in the halogen flame retardant is not particularly limited, and examples thereof include bromine and chlorine.

[0074] Examples of the halogen-based flame retardant include bromine-based flame retardants and chlorine-based flame retardants.

[0075] (Chlorine flame retardant)

[0076] Examples of the chlorine-based flame retardant include chlorinated paraffin (paraffin containing chlorine).

[0077] The chlorine content of the chlorine-based flame retardant is not particularly limited, but is preferably 60 to 80% by mass in the chlorine-based flame retardant from the viewpoint of achieving more excellent effects of the present invention (particularly flame retardancy).

[0078] (Brominated flame retardants)

[0079] From the viewpoint of achieving more excellent effects of the present invention (particularly power saving), it is preferred that part or all of the halogen flame retardant be a bromine flame retardant, and it is more preferred that all of the halogen flame retardant be a bromine flame retardant.

[0080] The compound represented by formula (1)

[0081] From the viewpoint of achieving more excellent effects of the present invention (particularly flame retardancy), the brominated flame retardant preferably contains a compound represented by the following formula (1).

[0082]

[0083] In formula (1), R represents an aliphatic hydrocarbon group which may contain an unsaturated bond.

[0084] In formula (1), the aliphatic hydrocarbon group which may contain an unsaturated bond as R may be linear, branched, cyclic, or a combination thereof, and a linear one is a preferred embodiment.

[0085] The number of carbon atoms in the aliphatic hydrocarbon group is not particularly limited, and may be, for example, 1 to 10. Preferably, the number of carbon atoms in the aliphatic hydrocarbon group is 2 to 8.

[0086] Furthermore, the aliphatic hydrocarbon group which may contain an unsaturated bond may be any of a saturated aliphatic hydrocarbon group not containing an unsaturated bond and an unsaturated aliphatic hydrocarbon group containing an unsaturated bond, and a saturated aliphatic hydrocarbon group can be mentioned as a suitable embodiment.

[0087] Examples of the saturated aliphatic hydrocarbon group include a methylene group, an ethylene group, a 1,3-propylene group, a 1,2-propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, and an octylene group.

[0088] Examples of the unsaturated bond that the aliphatic hydrocarbon group may have include a vinyl group, a vinylene group, an ethynyl group, and an ethynylene group.

[0089] When the aliphatic hydrocarbon group which may contain an unsaturated bond is an unsaturated aliphatic hydrocarbon group, examples of the unsaturated aliphatic hydrocarbon group include a combination of the above-mentioned saturated aliphatic hydrocarbon group and the above-mentioned unsaturated bond.

[0090] Examples of the compound represented by formula (1) include bis(pentabromophenyl)ethane.

[0091] From the viewpoint of achieving more excellent effects of the present invention (particularly flame retardancy and power saving), the halogen-based flame retardant preferably contains bis(pentabromophenyl)ethane.

[0092] Furthermore, from the viewpoint of achieving better effects of the present invention (particularly flame retardancy and power saving), the halogen flame retardant preferably includes a brominated flame retardant having a melting point of 300° C. or higher. Bis(pentabromophenyl)ethane is a brominated flame retardant having a melting point of 300° C. or higher.

[0093] (Antimony trioxide)

[0094] From the viewpoint of achieving better effects of the present invention (particularly flame retardancy and power saving), the flame retardant preferably further contains antimony trioxide. When part or all of the halogen-based flame retardant is a bromine-based flame retardant, the flame retardant more preferably further contains antimony trioxide.

[0095] In the present invention, antimony trioxide (Sb 2 O 3 ) that can be contained as a flame retardant is not particularly limited.

[0096] Antimony trioxide can function as a flame retardant aid. In the present invention, antimony trioxide is treated as a flame retardant.

[0097] (Content of halogen flame retardant)

[0098] From the viewpoint of achieving more excellent effects of the present invention (particularly flame retardancy and power saving), the content of the halogen flame retardant is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass, based on 100 parts by mass of the rubber component.

[0099] (Antimony trioxide content)

[0100] When the flame retardant further contains antimony trioxide, the content of antimony trioxide is preferably 3 to 12 parts by mass, more preferably 5 to 10 parts by mass, relative to 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention (particularly flame retardancy and power saving).

[0101] (Total content of halogen flame retardant and antimony trioxide in the total amount of flame retardant)

[0102] When the flame retardant further contains antimony trioxide, from the viewpoint that the effects of the present invention (especially flame retardancy and power saving) are better, the total content of the halogen flame retardant (for example, a bromine flame retardant) and antimony trioxide is preferably 80 to 100% by mass of the total amount of the flame retardant, and more preferably 100% by mass.

[0103] (Total content of halogen flame retardant and antimony trioxide relative to 100 parts by mass of rubber component)

[0104] When the flame retardant further includes antimony trioxide, from the viewpoint that the effects of the present invention (especially flame retardancy and power saving) are more excellent, the total content of the halogen flame retardant and antimony trioxide is preferably 15 to 50 parts by mass, more preferably 20 to 45 parts by mass, and further preferably 25 to 40 parts by mass relative to 100 parts by mass of the rubber component.

[0105] [Bulking Agent]

[0106] The rubber composition of the present invention contains a filler. In addition, the filler does not contain a flame retardant.

[0107] The rubber composition of the present invention contains a filler, so that the obtained cured product is excellent in ozone resistance, flame retardancy and power saving.

[0108] Examples of the filler include white fillers such as carbon black and silica.

[0109] From the viewpoint that the obtained cured product has more excellent effects of the present invention (particularly power saving) and improved mechanical strength, the filler preferably contains carbon black and / or silica, and more preferably contains carbon black and silica.

[0110] (Carbon Black)

[0111] When the rubber composition of the present invention contains carbon black (CB) as a filler, the carbon black preferably has a nitrogen adsorption specific surface area of ​​20 to 100 m 2 / g of carbon black, and / or dibutyl phthalate oil absorption of 70 to 120 cm 3 / 100g of carbon black, preferably containing a nitrogen adsorption specific surface area of ​​20 to 100m 2 / g, and the oil absorption of dibutyl phthalate is 70 to 120 cm 3 / 100g of carbon black.

[0112] The nitrogen adsorption specific surface area (N2SA) of carbon black can be measured in accordance with JIS K6217-2:2017.

[0113] The dibutyl phthalate oil absorption (DBP) of carbon black can be measured in accordance with JIS K6217-4:2017.

[0114] (Silicon Dioxide)

[0115] When the rubber composition of the present invention contains silica as a filler, the silica is not particularly limited and may be, for example, conventionally known materials. Specifically, for example, wet silica, dry silica, and fumed silica may be mentioned.

[0116] (Content of filler)

[0117] The content of the filler is preferably 20 to 50 parts by mass, more preferably 20 to 40 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of achieving better power saving and improved mechanical strength of the obtained cured product.

[0118] When the filler contains carbon black and silica, it is preferred that half or more of the total amount of the filler is carbon black and half or less of the total amount of the filler is silica.

[0119] [Divalent metal compound]

[0120] The rubber composition of the present invention contains a divalent metal compound including a divalent metal carboxylate (specific carboxylate).

[0121] In the present invention, the divalent metal compound is a compound containing a divalent metal.

[0122] Examples of the divalent metal include Zn 2+ , Ca 2+ Mg 2+ .

[0123] From the viewpoint of further improving the effect of the present invention, the divalent metal constituting the divalent metal compound preferably contains Zn. 2+ .

[0124] Examples of the divalent metal compound include divalent metal oxides in addition to specific carboxylates.

[0125] [Divalent metal carboxylates]

[0126] The rubber composition of the present invention contains a divalent metal carboxylate (specific carboxylate). In the present invention, the carboxylic acid constituting the specific carboxylate has a total carbon number of 6 to 12 per molecule.

[0127] The rubber composition of the present invention is excellent in ozone resistance, power saving and wear resistance by containing a specific carboxylate salt.

[0128] (Carboxylic acid constituting specific carboxylate)

[0129] The carboxylic acid constituting the specific carboxylate is not particularly limited as long as the total number of carbon atoms per molecule of the carboxylic acid is 6 to 12.

[0130] In the above carboxylic acids, the hydrocarbon group to which the carboxyl group is bonded is not particularly limited as long as the total number of carbon atoms per molecule of the above carboxylic acid is 6 to 12. The above total number of carbon atoms also includes carbon atoms constituting the carboxyl group.

[0131] As a preferred embodiment, the carboxylic acid constituting the specific carboxylate has one carboxyl group per one molecule of the carboxylic acid.

[0132] As the carboxylic acid constituting the specific carboxylate, a fatty acid having a total carbon number of 6 to 12 per molecule of carboxylic acid is preferably mentioned.

[0133] From the viewpoint of achieving more excellent effects of the present invention, the total number of carbon atoms per molecule of the carboxylic acid (for example, the above-mentioned fatty acid) constituting the specific carboxylate is preferably 8 to 10.

[0134] The aliphatic hydrocarbon group bonded to the fatty acid is not particularly limited. The aliphatic hydrocarbon group may be linear, branched, or cyclic, and may have an unsaturated bond.

[0135] From the viewpoint of achieving more excellent effects of the present invention, the aliphatic hydrocarbon group bonded to the fatty acid is preferably a branched saturated aliphatic hydrocarbon group, and more preferably a 1-ethylpentyl group.

[0136] (Divalent metal constituting specific carboxylate)

[0137] Examples of the divalent metal constituting the specific carboxylate include Zn 2+ , Ca 2+ Mg 2+ .

[0138] From the viewpoint of further improving the effect of the present invention, the divalent metal constituting the specific carboxylate preferably contains Zn. 2 + .

[0139] From the viewpoint of achieving a more excellent effect of the present invention, the specific carboxylate preferably comprises a divalent metal salt of a fatty acid having 6 to 12 total carbon atoms and one carboxyl group per molecule, more preferably comprises a zinc salt of a fatty acid having 6 to 12 total carbon atoms and one carboxyl group per molecule, further preferably comprises zinc 2-ethylhexanoate and / or zinc neodecanoate, and further preferably comprises zinc 2-ethylhexanoate.

[0140] (Content of specific carboxylate)

[0141] From the viewpoint of achieving more excellent effects of the present invention, the content of the specific carboxylate is preferably 0.1 to 5.0 parts by mass, more preferably 1.0 to 4.0 parts by mass, and even more preferably 1.2 to 2.5 parts by mass based on 100 parts by mass of the rubber component.

[0142] (Divalent Metal Oxide)

[0143] From the viewpoint of achieving more excellent effects of the present invention, the divalent metal compound preferably further contains a divalent metal oxide.

[0144] The divalent metal constituting the divalent metal oxide is the same as the divalent metal constituting the divalent metal compound. From the viewpoint of further improving the effect of the present invention, it is preferred that the divalent metal oxide contains Zn. 2+ .

[0145] When the divalent metal compound further contains a divalent metal oxide, the divalent metal oxide preferably contains zinc oxide from the viewpoint of achieving more excellent effects of the present invention.

[0146] When the divalent metal compound further contains a divalent metal oxide, from the viewpoint of further improving the effect of the present invention, the content of the divalent metal oxide is preferably 0.5 to 8.0 parts by mass, more preferably 1.0 to 6.0 parts by mass, and even more preferably 4.0 to 5.5 parts by mass based on 100 parts by mass of the rubber component.

[0147] [Antiaging agent]

[0148] The rubber composition of the present invention contains an antioxidant.

[0149] As one of the preferred embodiments, the antioxidant includes an amine antioxidant. The amine antioxidant is an antioxidant having an amino group (-NH2) or an imino group (-NH-).

[0150] Examples of the amine antioxidant include phenylenediamine compounds and quinoline compounds.

[0151] From the viewpoint of achieving more excellent effects of the present invention (particularly ozone resistance), the antioxidant preferably contains a phenylenediamine compound and / or a quinoline compound, and more preferably contains a phenylenediamine compound and a quinoline compound.

[0152] (Phenylenediamine compounds)

[0153] The phenylenediamine compound is a compound having a phenylenediamine skeleton. The two nitrogen atoms in the phenylenediamine skeleton may each independently form an amino group or an imino group, and preferably at least one of the nitrogen atoms is an imino group, and more preferably both are imino groups.

[0154] Examples of the phenylenediamine compound include p-phenylenediamine compounds such as N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), N,N′-dinaphthyl-p-phenylenediamine (DNPD), and N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD).

[0155] Quinoline compounds

[0156] The quinoline compound is a compound having a quinoline skeleton. Examples of the quinoline skeleton include a 2,2,4-trialkyl-1,2-dihydroquinone skeleton.

[0157] Specific examples of the quinoline compound include 2,2,4-trimethyl-1,2-dihydroquinone and polymers thereof.

[0158] From the viewpoint that the effects of the present invention (especially ozone resistance) are more excellent, the antioxidant preferably comprises a polymer of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and / or 2,2,4-trimethyl-1,2-dihydroquinone, and more preferably comprises a polymer of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinone.

[0159] [Content of antioxidant]

[0160] In the rubber composition of the present invention, the content of the antioxidant is preferably 2.5 to 10.0 parts by mass, more preferably 3.0 to 5.0 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention (particularly ozone resistance).

[0161] When the antioxidant contains a phenylenediamine compound and a quinoline compound, from the viewpoint that the effect of the present invention (especially ozone resistance) is more excellent, it is preferred that the content of the phenylenediamine compound is more than 50% by mass of the total amount of the antioxidant, and the content of the quinoline compound is less than 50% by mass of the total amount of the antioxidant.

[0162] [Vulcanization accelerator]

[0163] The rubber composition of the present invention contains a vulcanization accelerator.

[0164] The vulcanization accelerator is not particularly limited as long as it is a substance used for the vulcanization of rubber. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CZ) and N-tert-butyl-2-benzothiazolylsulfenamide (NS); thiuram-based vulcanization accelerators such as tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); and guanidine-based vulcanization accelerators such as diphenylguanidine (DPG).

[0165] The vulcanization accelerator preferably contains a sulfenamide-based vulcanization accelerator from the viewpoint of achieving more excellent effects of the present invention (particularly flame retardancy and / or power saving).

[0166] From the viewpoint of achieving more excellent effects of the present invention (particularly flame retardancy and / or power saving), the content of the vulcanization accelerator is preferably 0.5 to 8.0 parts by mass based on 100 parts by mass of the rubber component.

[0167] [sulfur]

[0168] The rubber composition of the present invention contains sulfur.

[0169] Sulfur is not particularly limited as long as it is a substance used for vulcanization of rubber, and examples thereof include conventionally known substances.

[0170] From the viewpoint of achieving more excellent effects of the present invention (particularly flame retardancy and / or power saving), the sulfur content is preferably 0.5 to 5.0 parts by mass based on 100 parts by mass of the rubber component.

[0171] [Content of halogen elements in halogen flame retardants]

[0172] In the present invention, the content of the halogen element in the halogen flame retardant is 9% by mass or more of the total amount of the rubber composition of the present invention. Since the content of the halogen element in the halogen flame retardant is 9% by mass or more of the total amount of the rubber composition of the present invention, the flame retardancy of the cured product obtained from the rubber composition of the present invention is excellent.

[0173] From the viewpoint of achieving better effects of the present invention (particularly ozone resistance, power saving, and wear resistance), the content of the halogen element in the halogen flame retardant is preferably 20% by mass or less, more preferably 9.0 to 12.0% by mass, and further preferably 9.5 to 11.0% by mass, based on the total amount of the rubber composition of the present invention.

[0174] [Mass ratio of total content of divalent metals in divalent metal compounds / content of halogen elements in halogen flame retardants]

[0175] In the present invention, the mass ratio of the total content of the divalent metals in the divalent metal compound / the content of the halogen element in the halogen flame retardant is 0.05 or more. In addition, the mass ratio is (the total content of the divalent metals in the divalent metal compound) / (the content of the halogen element in the halogen flame retardant).

[0176] When the mass ratio is 0.05 or more, the rubber composition of the present invention, when formed into a cured product, is excellent in flame retardancy, ozone resistance, power saving, and wear resistance.

[0177] In the above mass ratio, the total content of the divalent metals in the divalent metal compound is the total content of the divalent metals in the divalent metal compound contained in the rubber composition of the present invention. The total content of the divalent metals in the divalent metal compound includes the content of the divalent metals in the specific carboxylate. In addition, when the divalent metal compound further includes a divalent metal oxide (e.g., zinc oxide), the total content of the divalent metals in the divalent metal compound further includes the content of the divalent metals in the divalent metal oxide.

[0178] In addition, when the rubber composition of the present invention further contains a divalent metal oxide (e.g., zinc oxide) and a fatty acid (e.g., stearic acid), and the above-mentioned divalent metal oxide reacts with the above-mentioned fatty acid to generate a divalent metal carboxylate, the amount of the divalent metal contained in the divalent metal carboxylate generated in the rubber composition as described above is not included in the total content of the divalent metal contained in the divalent metal compound in the present invention.

[0179] From the viewpoint of achieving more excellent effects of the present invention, the mass ratio of the total content of the divalent metal in the divalent metal compound / the content of the halogen element in the halogen-based flame retardant is preferably 0.2 to 0.3.

[0180] (additive)

[0181] The rubber composition of the present invention may further contain additives in addition to the above-mentioned components. Examples of the additives include fatty acids (such as stearic acid), vulcanization retarders (such as N-cyclohexylthiophthalimide), oils, and waxes.

[0182] ·fatty acid

[0183] When the rubber composition of the present invention further contains a fatty acid (for example, stearic acid), the content of the fatty acid is preferably 0.5 to 5.0 parts by mass based on 100 parts by mass of the rubber component.

[0184] Vulcanization delay agent

[0185] When the rubber composition of the present invention further contains a vulcanization retarder (for example, N-cyclohexylthiophthalimide), the content of the vulcanization retarder is preferably 0.05 to 1.0 part by mass based on 100 parts by mass of the rubber component.

[0186] (Manufacturing method)

[0187] The method for producing the rubber composition of the present invention is not particularly limited, and one example includes a method in which the essential components and additives that may be further used as needed are mixed at 120 to 180° C. using a Banbury mixer or the like.

[0188] (vulcanization)

[0189] The vulcanization of the rubber composition of the present invention can be carried out under the conditions usually performed. The vulcanization temperature can be, for example, 120 to 180° C. During the vulcanization, pressure can be applied.

[0190] (use)

[0191] As an application of the rubber composition of the present invention, for example, a rubber composition for conveyor belts can be mentioned.

[0192] [conveyor]

[0193] The conveyor belt of the present invention is a conveyor belt formed using the rubber composition of the present invention.

[0194] The rubber composition used for the conveyor belt of the present invention is not particularly limited as long as it is the rubber composition of the present invention.

[0195] The conveyor belt of the present invention is not particularly limited except that it is formed using the rubber composition of the present invention.

[0196] Since the conveyor belt of the present invention is formed using the rubber composition of the present invention, it is excellent in flame retardancy, ozone resistance, abrasion resistance, and power saving.

[0197] There is no particular limitation on which component member constituting the conveyor belt of the present invention is applied to the rubber composition of the present invention. All or part of the rubber constituting the conveyor belt of the present invention may be formed by the rubber composition of the present invention.

[0198] Since the cured product obtained from the rubber composition of the present invention is excellent in ozone resistance, abrasion resistance, flame retardancy, and power saving, one of the preferred embodiments of the present invention is that the conveyor belt of the present invention has a covering rubber formed using the rubber composition of the present invention.

[0199] Embodiments of the conveyor belt of the present invention will be described below using the attached drawings. In addition, the present invention is not limited to the attached drawings.

[0200] 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 in which a fabric layer 1 is coated with a coating rubber (adhesive rubber) 2 to form a core material layer, and the outer periphery thereof is covered with a covering rubber 3. The covering rubber 3 is preferably formed using the rubber composition of the present invention.

[0201] exist Figure 1 In the embodiment, the conveyor belt 4 has the fabric layer 1 as the core material, and the number of laminated layers of the fabric layer 1, the thickness of the covering rubber 3, the belt width, etc. can be appropriately determined according to the purpose of use.

[0202] Examples of the cloth layer include canvas made of woven fabrics of synthetic fibers such as nylon, vinylon, and polyester.

[0203] The thicknesses T1 and T2 of the cover rubber 3 may be approximately 1.5 to 20 mm, respectively, under normal circumstances.

[0204] In addition, coating rubber 2 can use coating rubber used for known conveyor belts. As the coating rubber, for example, a rubber composition containing natural rubber (NR), nitrile rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), ethylene-propylene rubber (EPT), ethylene-propylene-diene rubber (EPDM), etc. as a rubber component can be used.

[0205] Next, use Figure 2 A second embodiment of the conveyor belt of the present invention will be described.

[0206] Figure 2 It is a cross-sectional view of another embodiment of the conveyor belt of the present invention.

[0207] like Figure 2 As shown, the second embodiment of the conveyor belt of the present invention is a conveyor belt 8 in which a steel cord 5 is coated with a cushion rubber (adhesive rubber) 6 to form a core layer, and the outer periphery thereof is covered with a covering rubber 7. The covering rubber 7 is preferably formed using the rubber composition of the present invention.

[0208] The conveyor belt 8 may be made of, for example, 50 to 230 steel cords 5 with a diameter of about 2.0 to 9.5 mm, which are formed by twisting a plurality of wires with a diameter of about 0.2 to 0.4 mm. Generally, the total thickness T of the conveyor belt 8 may be about 10 to 50 mm.

[0209] In addition, the buffer rubber 6 may use, for example, an adhesive rubber that can be bonded to the galvanized steel cord used in a known steel conveyor belt. Specifically, as the buffer rubber, for example, a rubber composition containing natural rubber (NR), nitrile rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), etc. as a rubber component may be used.

[0210] The conveyor belt of the present invention can be manufactured, for example, by placing a cloth layer, a steel cord, or a core material layer, etc., which is a core material, between unvulcanized rubber sheets molded from the rubber composition of the present invention according to a conventional method, and vulcanizing them by heating and pressing. The vulcanization conditions are, for example, about 120 to 180° C. and about 0.1 to 4.9 MPa for about 10 to 90 minutes.

[0211] The conveyor belt of the present invention can be used at a temperature of, for example, -30 to +60°C.

[0212] Example

[0213] The present invention will be described in further detail below based on examples.

[0214] The materials, usage amounts, ratios, processing contents, and processing steps shown in the following examples may be appropriately changed 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.

[0215] <Manufacturing of rubber composition>

[0216] The components shown in Tables 1 and 2 below were used in the compositions (parts by mass) shown in the tables, and these were mixed in a Banbury mixer at 120 to 180° C. to produce rubber compositions (unvulcanized).

[0217] (Production of vulcanized rubber sheets)

[0218] ·Preparation of vulcanized rubber sheet 1 under normal vulcanization conditions

[0219] Each rubber composition (unvulcanized) produced as described above was vulcanized for 30 minutes using a press molding machine at 148° C. and at a surface pressure of 3.0 MPa under normal vulcanization conditions to produce a vulcanized rubber sheet 1 having a length of 150 mm, a width of 150 mm, and a thickness of 2 mm.

[0220] Preparation of vulcanized rubber sheet 2 under over-vulcanization conditions

[0221] Each rubber composition (unvulcanized) produced as described above was vulcanized for 90 minutes under overvulcanization conditions at a surface pressure of 3.0 MPa using a press molding machine at 148°C to produce a vulcanized rubber sheet 2 having a length of 150 mm, a width of 150 mm, and a thickness of 2 mm.

[0222] In this specification, the vulcanized rubber sheet 2 under overvulcanization conditions is subjected to a longer thermal history (vulcanization time) during vulcanization than usual, thereby attempting to reproduce the decomposition of the vulcanized rubber that may occur simultaneously with the vulcanization, the free radicals that may be generated thereby, and / or the generation of halogens from the halogen-based flame retardant.

[0223] <Evaluation>

[0224] The following evaluations were performed using each vulcanized rubber sheet produced as described above. The results are shown in the tables.

[0225] (Ozone resistance)

[0226] According to JIS K6259-1:2015, each vulcanized rubber sheet 1 prepared as described above was placed in an ozone tank (40°C, 50 pphm) and left to stand for 168 hours under 20% stretching to perform an ozone resistance test (accelerated test). After the ozone resistance test, the surface of the vulcanized rubber sheet was visually observed.

[0227] When the vulcanized rubber sheet after the ozone resistance test after each time period had no cracks, this was indicated as "NC".

[0228] · Evaluation criteria for ozone resistance

[0229] In the present invention, when the vulcanized rubber sheet after the ozone resistance test has no cracks, it is evaluated that the obtained vulcanized rubber has excellent ozone resistance.

[0230] On the other hand, when cracks were generated in the vulcanized rubber sheet after the above-mentioned ozone resistance test, it was evaluated that the obtained vulcanized rubber had poor ozone resistance.

[0231] In addition, when the vulcanized rubber sheet has cracks, the level of the cracks is evaluated according to JIS K6259-1: 2015, and is represented by a combination of letters and numbers, such as the above-mentioned levels "A5" and "C1". In the present invention, when the vulcanized rubber sheet has cracks after the ozone resistance test, the ozone resistance of levels "B" and "C" is worse than that of level "A". In addition, when the letters of the levels are the same, the larger the number after the letter, the worse the ozone resistance.

[0232] (50% modulus after vulcanization)

[0233] A JIS No. 3 dumbbell-shaped rubber sheet was punched out from each vulcanized rubber sheet 2 prepared as described above to prepare a test piece. Using the test piece, a tensile test was performed at a tensile speed of 500 mm / min at 23° C. in accordance with JIS K6251:2017 to measure the 50% modulus (M50) [unit: MPa].

[0234] (Power saving: RRF)

[0235] Dynamic viscoelasticity measurement

[0236] Using each vulcanized rubber sheet 2 manufactured as described above, a dynamic viscoelasticity measurement was performed using a viscoelasticity spectrophotometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) under the measurement conditions of an inter-chuck distance of 10 mm, a dynamic strain of 2%, and a frequency of 20 Hz. The loss tangent (tan δ) and the dynamic elastic modulus E' (N / mm) at 0°C and 20°C were measured, and the obtained loss tangent (tan δ) and dynamic elastic modulus E' were substituted into the following formula to calculate RRF (Rolling Resistance Factor).

[0237] [Number 1]

[0238]

[0239] In the present invention, the power saving performance was evaluated by the above-mentioned RRF.

[0240] The RRF results are shown by RRF values ​​and RRF indices (indices when the result of Comparative Example 1 is set as an evaluation standard of 100 in Table 1, and indices when the result of Comparative Example 6 is set as an evaluation standard of 100 in Table 2).

[0241] ·Evaluation criteria for power saving

[0242] In the present invention, when the index of RRF at 0° C. and 20° C. is less than 100, it is evaluated that the power saving property is excellent. The smaller the index of the RRF is, the better the power saving property is.

[0243] On the other hand, when at least any one of the indices at 0° C. and 20° C. was 100 or more, the power saving was evaluated to be poor.

[0244] (Abrasion resistance)

[0245] Using each vulcanized rubber sheet 1 manufactured as described above, a wear test (B method) was carried out using a DIN wear tester at 23°C under the conditions of rotation speed [40 rpm], load [9.8 N], and abrasion type [511XP60] in accordance with JIS K6264-2:2005, and the wear amount [mm 3 ].

[0246] Evaluation criteria for wear resistance

[0247] In the present invention, when the wear amount is 150 mm 3 The wear resistance is evaluated as excellent when the wear amount is less than 150 mm.3 , the better the wear resistance.

[0248] On the other hand, when the wear exceeds 150 mm 3 In the case of , the wear resistance was evaluated to be poor.

[0249] (Flame retardancy)

[0250] ·Test piece preparation

[0251] Using each rubber composition produced as described above, test pieces (6 pieces for each test piece) were produced according to JIS K6324:2013 "Flame retardant performance Conveyor belt - Grades and test methods (Flame retardant performance conveyor belt - Grades and test methods)" 7.2.1. The vulcanization during the above production was similar to the production of the vulcanized rubber sheet 1, using a press molding machine at 148°C, and vulcanized for 30 minutes under a surface pressure of 3.0 MPa under normal vulcanization conditions to obtain a BL sample (blank sample).

[0252] Three of the six BL samples obtained as described above were used and left to stand at 100° C. for 168 hours to perform an aging test, thereby obtaining samples after the aging test.

[0253] Evaluation method

[0254] The duration of flame (unit: seconds) was measured for the BL sample and the sample after the aging test in accordance with JIS K6324:2013 “Flame retardant performance conveyor belts - Grades and test methods (Flame retardant performance conveyor belts - Grades and test methods)”.

[0255] Evaluation benchmark

[0256] When the flame retardancy test standard of JIS Class 3 [the duration of the flame is less than 60 seconds (the duration of the flame is the average value of 3 test pieces), and there is no re-burning] is satisfied, the flame retardancy is evaluated as excellent and indicated as "0".

[0257] When the flame retardancy test standard of JIS Class 3 was not satisfied, the flame retardancy was evaluated as poor and indicated as "×".

[0258] The evaluation results of the flame retardancy of the BL samples are shown in the "Flame retardancy BL" column of each table. In addition, the evaluation results of the flame retardancy of the samples after the aging test are shown in the "Flame retardancy 100°C 168H" column of each table.

[0259] In the present invention, when the evaluation results of the flame retardancy of the BL sample and the sample after the aging test are both "○", it is evaluated that the flame retardancy is excellent.

[0260] On the other hand, when any one of the evaluation results of the flame retardancy of the BL sample and the sample after the aging test was "×", the flame retardancy was evaluated to be poor.

[0261]

[0262]

[0263]

[0264] In each table, "Metal (Zn) content (mass%) ＊1 ” is the ratio (mass %) of the total content of the divalent metal contained in the divalent metal compound in the total amount of the rubber composition.

[0265] "Halogen content (mass %) ＊2 " is the ratio (mass %) of the content of the halogen element in the halogen flame retardant in the total amount of the rubber composition.

[0266] “Mass ratio of metal (Zn) / halogen ＊3 " is the mass ratio of the total content of the divalent metal in the divalent metal compound to the content of the halogen element in the halogen flame retardant.

[0267] In Table 1, the index criterion of power saving is set as Comparative Example 1. In Table 2, the index criterion of power saving is set as Comparative Example 6.

[0268] The details of each component shown in each table are as follows.

[0269] (Rubber component, diene rubber)

[0270] NR: Natural rubber. RSS#3

[0271] BR: Butadiene rubber. Trade name: Nipol BR1220 (weight average molecular weight: 460,000, manufactured by Nippon Zeon Co., Ltd.)

[0272] (Divalent Metal Compound)

[0273] · Specific carboxylate 1: manufactured by Sil + Syrha Co., Ltd., trade name "Strucktor" ZEH-75. The above-mentioned product used as specific carboxylate 1 is a mixture containing 75% by mass of zinc 2-ethylhexanoate (structure shown below) as an active ingredient and 25% by mass of silicon dioxide. The content of zinc in the above-mentioned mixture is 17% by mass. In addition, the "Specific Carboxylate 1" column of each table shows the content of the above-mentioned mixture.

[0274]

[0275] Zinc oxide: Zinc oxide (ZnO 81.41 g / mol). Zn content 80% by mass. Trade name "Oxidized lead 3" (manufactured by Shodo Chemical Industry Co., Ltd.). Zinc oxide corresponds to a divalent metal oxide.

[0276] Zinc stearate (comparative): The zinc content in zinc stearate is 10% by mass. Produced by Seido Chemical Co., Ltd. Zinc stearate does not correspond to a specific carboxylate because the total number of carbon atoms per molecule of stearic acid constituting zinc stearate exceeds 12.

[0277] · Specific carboxylate 2: zinc neodecanoate. The zinc content in zinc neodecanoate is 8% by mass. Made by Nippon Chemical Industry Co., Ltd., trade name: zinc neodecanoate

[0278] (Bulking Agent)

[0279] Silica: Trade name: "Nippsil AQ" (manufactured by Tosoh Silicon Co., Ltd.)

[0280] CB: GPF grade carbon black. Product name: Niteron #GN, manufactured by Shinjoy Chemical Co., Ltd. N2SA: 32m 2 / g, DBP: 91cm 3 / 100g

[0281] In the column "Silica / CB" in each table, the value on the left side of " / " indicates the amount of silica added, and the value on the right side of " / " indicates the amount of carbon black added. The same is true for the following displays in antioxidants, vulcanization accelerators, etc. In addition, when the specific carboxylate is specific carboxylate 1, the amount of silica in the column "Silica / CB" does not include the amount of silica contained in specific carboxylate 1.

[0282] (Antioxidant)

[0283] Antioxidant 6C: Amine antioxidant. N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (structure shown below). Trade name: Ozonone 6C (manufactured by Seiko Chemical Co., Ltd.)

[0284]

[0285] Antioxidant RD: A polymer of 2,2,4-trimethyl-1,2-dihydroquinone (the following structure). Trade name: Nonflux RD (manufactured by Seiko Chemical Co., Ltd.)

[0286]

[0287] (Flame Retardant)

[0288] · Antimony trioxide: PATOX-M manufactured by Nippon Seiko Co., Ltd. (trade name)

[0289] (Halogen flame retardant)

[0290] Brominated flame retardant: bis(pentabromophenyl)ethane. Trade name: "SAYTEX 8010" (manufactured by ALBEMARLE CORPORATION). Br content: 82% by mass. Melting point: 300°C or higher.

[0291] · Chlorinated paraffin: Enpara 70S manufactured by Dober Chemika Co., Ltd. (trade name). Chlorine content 68 to 72% by mass. Average Cl content 70% by mass. The chlorine content in the chlorinated paraffin was calculated using the average Cl content of 70% by mass.

[0292] (Vulcanization accelerator)

[0293] Vulcanization accelerator NS: N-tert-butyl-2-benzothiazolylsulfenamide (trade name: Noxelara NS, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0294] Vulcanization retarder PVI: N-cyclohexylthiophthalimide. Trade name: Retarder CTP, manufactured by Toray Film Chemical Co., Ltd.

[0295] (sulfur)

[0296] · Insoluble sulfur: Miukron OT-20 manufactured by Shikoku Chemical Industry Co., Ltd. (trade name)

[0297] (additive)

[0298] Aroma oil: Trade name A-OMIX (manufactured by Sankyo Yuka Kogyo)

[0299] ·WAX: wax. Trade name OZOACE-0037 (Nihon Fine Wax Co., Ltd.)

[0300] · Stearic acid: Trade name "Stearic acid 50S" (manufactured by Chiba Fatty Acid Co., Ltd.)

[0301] From the results in Tables 1 and 2, it was confirmed that the rubber composition of the present invention exhibited the desired effects.

[0302] On the other hand, in Comparative Example 1 in Table 1 (containing a brominated flame retardant as a halogen-based flame retardant), which does not contain a specific carboxylate, ozone resistance, power saving, and abrasion resistance are poor.

[0303] In Comparative Example 2, in which the content of the halogen element contained in the halogen flame retardant in the total amount of the rubber composition was less than 9 mass %, the flame retardancy was poor.

[0304] In Comparative Example 3, in which the mass ratio of the total content of the divalent metals in the divalent metal compound / the content of the halogen element in the halogen flame retardant was less than 0.05, ozone resistance and power saving were poor.

[0305] Comparative Example 4, which did not contain the specific carboxylate but contained zinc stearate instead, was inferior in ozone resistance, power saving, and abrasion resistance.

[0306] In Table 1, the rubber composition of the present invention is superior in 50% modulus after overvulcanization compared with Comparative Example 1 containing no specific carboxylate and Comparative Example 4 containing zinc stearate as described above.

[0307] In Table 2 (containing a chlorine-based flame retardant as a halogen-based flame retardant), Comparative Example 6 containing no specific carboxylate was inferior in ozone resistance, power saving, and abrasion resistance (the same tendency as Comparative Example 1 in Table 1).

[0308] In Comparative Example 5, which did not contain the specific carboxylate salt and in which the content of the halogen element in the halogen flame retardant in the total amount of the rubber composition was less than 9 mass %, the wear resistance and the flame retardancy were inferior.

[0309] In Table 2, the rubber composition of the present invention is superior in 50% modulus after overvulcanization compared with Comparative Examples 5 and 6 which do not contain a specific carboxylate salt.

[0310] Explanation of symbols

[0311] 1: Fabric layer

[0312] 2: Coating rubber

[0313] 3,7: Covering rubber

[0314] 4, 8: Conveyor belt

[0315] 5: Steel cord

[0316] 6: Buffer rubber.

Claims

1. A rubber composition comprising: a rubber component including a diene rubber, a flame retardant including a halogen flame retardant, a filler, a divalent metal compound including a carboxylate of a divalent metal, an antioxidant, a vulcanization accelerator, and sulfur, The content of the halogen element in the halogen flame retardant is 9% by mass or more of the total amount of the rubber composition. The mass ratio of the total content of the divalent metal in the divalent metal compound to the content of the halogen element in the halogen flame retardant is 0.05 or more. The total number of carbon atoms per molecule of the carboxylic acid constituting the carboxylate is 6 to 12. 2 . The rubber composition according to claim 1 , wherein the diene rubber comprises natural rubber and / or butadiene rubber.

3. The rubber composition according to claim 1, wherein the divalent metal constituting the carboxylate contains Zn 2+ .

4. The rubber composition according to claim 1, wherein the divalent metal constituting the divalent metal compound contains Zn 2+ . 5 . The rubber composition according to claim 1 , wherein the divalent metal compound further contains a divalent metal oxide.

6. The rubber composition according to claim 1, wherein the diene rubber comprises natural rubber and butadiene rubber, and the mass ratio of the natural rubber to the butadiene rubber is 30 / 70 to 80 / 20. The mass ratio of the total content of the divalent metal in the divalent metal compound to the content of the halogen element in the halogen flame retardant is 0.2 to 0.

3. 7 . The rubber composition according to claim 1 , wherein a part or all of the halogen-based flame retardant is a bromine-based flame retardant, and the flame retardant further comprises antimony trioxide. The rubber composition according to claim 1 , which is used for a conveyor belt. 9 . A conveyor belt produced using the rubber composition according to claim 1 .

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