Rubber composition and conveyor belt

Abstract

To provide a rubber composition having excellent flame retardancy, ozone resistance, power saving properties, and abrasion resistance when cured, and a conveyor belt.SOLUTION: The rubber composition contains a rubber component including a diene rubber, a flame retardant including a halogen-based 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 halogen elements contained in the halogen-based flame retardant is 9 mass% or more of the total amount of the rubber composition, the mass ratio of the total content of divalent metals contained in the divalent metal compound to the content of halogen elements contained in the halogen-based flame retardant is 0.05 or more, and the total number of carbon atoms per one carboxylic acid molecule constituting the carboxylate is 6 to 12. The conveyor belt is manufactured using the rubber composition.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Conventionally, efforts have been made to make rubber flame retardant (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5768408 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to maintain the flame retardancy of rubber after aging during long-term use, it is usually necessary to pre-blend a considerable amount of a flame retardant into the rubber composition. In light of the above, the present inventors have studied the rubber composition disclosed in Patent Document 1 and have found that as the amount of flame retardant added to the rubber composition increases, the ozone resistance, power saving properties, and abrasion resistance of the cured product (vulcanized rubber) obtained from the rubber composition may deteriorate.

[0005] Therefore, an object of the present invention is to provide a rubber composition which, when cured, has excellent flame retardancy, ozone resistance, power saving properties, and abrasion resistance. Another object of the present invention is to provide a conveyor belt. [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the problems can be solved by the following configuration.

[0007] [1] A rubber composition comprising a rubber component including a diene rubber, a flame retardant including a halogen-based flame retardant, a filler, a divalent metal compound including a divalent metal carboxylate, an antioxidant, a vulcanization accelerator, and sulfur; The content of halogen elements contained in the halogen-based flame retardant is 9% by mass or more based on the total amount of the rubber composition, the mass ratio of the total content of divalent metals contained in the divalent metal compound to the content of halogen elements contained in the halogen-based flame retardant is 0.05 or more; A rubber composition in which 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 [1], wherein the diene rubber comprises natural rubber and / or butadiene rubber. [3] The divalent metal constituting the carboxylate is Zn 2+ The rubber composition according to [1] or [2], [4] The divalent metal constituting the above divalent metal compound is Zn 2+ The rubber composition according to any one of [1] to [3], [5] The rubber composition according to any one of [1] to [4], wherein the divalent metal compound further contains a divalent metal oxide. [6] The diene rubber contains a natural rubber and a butadiene rubber, and a mass ratio of the natural rubber / the butadiene rubber is 30 / 70 to 80 / 20; The rubber composition according to any one of [1] to [5], wherein the mass ratio of the total content of divalent metals contained in the divalent metal compound to the content of halogen elements contained in the halogen-based flame retardant is 0.2 to 0.3. [7] The rubber composition according to any one of [1] to [6], wherein a part or all of the halogen-based flame retardant is a bromine-based flame retardant, and the flame retardant further contains antimony trioxide. [8] The rubber composition according to any one of [1] to [7], which is for a conveyor belt. [9] A conveyor belt produced using the rubber composition according to any one of [1] to [8]. Effect of the Invention

[0008] According to the present invention, it is possible to provide a rubber composition which, when cured, exhibits excellent flame retardancy, ozone resistance, power saving properties, and abrasion resistance. The present invention also provides a conveyor belt. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of one embodiment of a conveyor belt of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of another embodiment of the conveyor belt of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. The following description of the configuration may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "~" means a range including the numerical values ​​written before and after "~". In this specification, each component contained in the rubber composition of the present invention can be used alone or in combination of two or more kinds. In this specification, when the rubber composition of the present invention uses two or more kinds of a certain component in combination, the "content" of the component means the total content of those two or more kinds, unless otherwise specified. In the present specification, the method for producing each component is not particularly limited unless otherwise specified. For example, a conventionally known method may be used.

[0011] [Rubber composition] The rubber composition of the present invention comprises: The rubber composition contains a rubber component including a diene rubber, a flame retardant including a halogen-based 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 halogen elements contained in the halogen-based flame retardant is 9% by mass or more based on the total amount of the rubber composition of the present invention, the mass ratio of the total content of divalent metals contained in the divalent metal compound to the content of halogen elements contained in the halogen-based flame retardant is 0.05 or more; The rubber composition has a total of 6 to 12 carbon atoms per molecule of the carboxylic acid constituting the carboxylate.

[0012] The reason why the rubber composition of the present invention having the above-mentioned configuration can solve the problems of the present invention is not necessarily clear, but the present inventors speculate as follows. The mechanism by which the effects are obtained is not limited by the following speculation. In other words, even if the effects are obtained by a mechanism other than the following, it is included in the scope of the present invention. In the rubber composition of the present invention, the content of halogen elements contained in the halogen-based flame retardant contained in the flame retardant, and the content of divalent metal contained in the divalent metal compound / content of the above-mentioned halogen elements are each within a specific range, and it is believed that by adding a carboxylate of a divalent metal to the rubber composition, flame retardancy is imparted to the obtained cured product, and power saving properties can be improved while maintaining required levels of rubber properties such as ozone resistance and abrasion resistance. It is speculated that the above-mentioned rubber properties are maintained and power saving is improved because the above-mentioned carboxylate functions as a scavenger that captures radicals that may be generated by decomposition of vulcanized rubber and / or halogens that may be generated from halogen-based flame retardants. The above speculation is considered to be evidenced by the fact that 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 a rubber composition that does not contain a carboxylate of a divalent metal. Hereinafter, in this specification, the "carboxylate of a divalent metal" is also referred to as the "specific carboxylate". In addition, when the rubber composition of the present invention becomes a cured product, at least one of flame retardancy, ozone resistance, power saving properties, and abrasion resistance is excellent, which is also referred to as "the effect of the present invention being superior."

[0013] [Rubber component] The rubber composition of the present invention contains a rubber component containing a diene rubber.

[0014] [Diene rubber] 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. Examples of diene rubbers include natural rubber, butadiene rubber, and styrene-butadiene rubber.

[0015] From the viewpoint of achieving superior effects of the present invention, the diene rubber preferably contains natural rubber and / or butadiene rubber, and more preferably contains natural rubber and butadiene rubber.

[0016] (Natural rubber) In the present invention, the natural rubber (NR) that can be contained as the diene rubber is not particularly limited, and examples thereof include those that are conventionally known.

[0017] (Butadiene rubber) In the present invention, the butadiene rubber (BR) that can be contained as the diene rubber is not particularly limited, and examples thereof include those that are conventionally known. In one preferred embodiment, the BR is, for example, polybutadiene that is solid at 23° C. In addition, the BR may be unmodified or modified.

[0018] From the viewpoint of obtaining superior effects of the present invention (particularly power saving properties and abrasion resistance), the weight average molecular weight of BR is preferably 200,000 or more, and more preferably 300,000 to 1,000,000. In this specification, the weight average molecular weight (Mw) of BR can be a value calculated as a standard polystyrene equivalent obtained by gel permeation chromatography (GPC) measurement under the following conditions. Solvent: Tetrahydrofuran Detector: RI detector

[0019] (mass ratio of natural rubber to butadiene rubber) When the diene rubber contains natural rubber and butadiene rubber, the mass ratio of natural rubber / butadiene rubber is preferably 30 / 70 to 80 / 20, and more preferably 50 / 50 to 75 / 25, from the viewpoint of obtaining better effects of the present invention (particularly, power saving properties and abrasion resistance).

[0020] (Total content of natural rubber and butadiene rubber) When the diene rubber contains a natural rubber and a butadiene rubber, the total content of the natural rubber and the butadiene rubber is preferably 80 to 100 mass % of the total amount of the rubber component, and more preferably 100 mass %, from the viewpoint of obtaining better effects of the present invention (particularly, power saving property and abrasion resistance).

[0021] [Flame retardant] The rubber composition of the present invention contains a flame retardant containing a halogen-based flame retardant. Flame retardants are compounds that impart flame retardancy to the resulting cured product.

[0022] [Halogen-based flame retardants] In the present invention, the halogen-based flame retardant is a flame retardant containing a halogen element. The halogen element contained in the halogen-based flame retardant is not particularly limited, and examples thereof include bromine and chlorine. Examples of halogen-based flame retardants include bromine-based flame retardants and chlorine-based flame retardants.

[0023] (Chlorine-based flame retardants) An example of a chlorine-based flame retardant is chlorine-based paraffin (paraffin containing chlorine). The chlorine content of the chlorine-based flame retardant is not particularly limited, but from the viewpoint of obtaining superior effects of the present invention (particularly flame retardancy), it is preferably 60 to 80 mass % in the chlorine-based flame retardant.

[0024] (Brominated flame retardants) From the viewpoint of achieving superior effects of the present invention (particularly power saving), it is preferable that a part or all of the halogen-based flame retardants are bromine-based flame retardants, and it is more preferable that all of the halogen-based flame retardants are bromine-based flame retardants.

[0025] A compound represented by formula (1) From the viewpoint of achieving superior effects of the present invention (particularly flame retardancy), the bromine-based flame retardant preferably contains a compound represented by the following formula (1). [ka] In formula (1), R represents an aliphatic hydrocarbon group which may contain an unsaturated bond.

[0026] In formula (1), the aliphatic hydrocarbon group which may contain an unsaturated bond as R may be linear, branched, cyclic, or a combination thereof, with a preferred embodiment being linear. The number of carbon atoms in the aliphatic hydrocarbon group is not particularly limited and can be, for example, 1 to 10. The number of carbon atoms is preferably 2 to 8.

[0027] In addition, the aliphatic hydrocarbon group which may contain an unsaturated bond may be either a saturated aliphatic hydrocarbon group which does not contain an unsaturated bond, or an unsaturated aliphatic hydrocarbon group which contains an unsaturated bond, with a preferred embodiment being a saturated aliphatic hydrocarbon group. Examples of the saturated aliphatic hydrocarbon group include a methylene group, an ethylene group, a trimethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, and an octylene group. 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. 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.

[0028] An example of the compound represented by formula (1) is bis(pentabromophenyl)ethane. From the viewpoint of obtaining superior effects of the present invention (particularly flame retardancy and power saving), it is preferable that the halogen-based flame retardant contains bis(pentabromophenyl)ethane.

[0029] From the viewpoint of obtaining superior effects of the present invention (particularly flame retardancy and power saving), it is preferable that the halogen-based flame retardant contains a bromine-based flame retardant having a melting point of 300° C. or higher. Bis(pentabromophenyl)ethane is a bromine-based flame retardant having a melting point of 300° C. or higher.

[0030] (Antimony Trioxide) From the viewpoint of achieving better effects of the present invention (particularly flame retardancy and power saving), it is preferable that the flame retardant further contains antimony trioxide, and when part or all of the above-mentioned halogen-based flame retardant is a bromine-based flame retardant, it is more preferable that the flame retardant further contains antimony trioxide. In the present invention, there is no particular limitation on the antimony trioxide (Sb2O3) that can be contained as a flame retardant. Antimony trioxide can function as a flame retardant assistant, and in the present invention, antimony trioxide is treated as a flame retardant.

[0031] (Halogen-based flame retardant content) From the viewpoint of obtaining superior effects of the present invention (particularly flame retardancy and power saving), the content of the halogen-based flame retardant is preferably 10 to 40 parts by mass, and more preferably 15 to 30 parts by mass, per 100 parts by mass of the rubber component.

[0032] (Antimony trioxide content) When the flame retardant further contains antimony trioxide, the content of antimony trioxide is preferably 3 to 12 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the above-mentioned rubber component, from the viewpoint of obtaining better effects of the present invention (particularly, flame retardancy and power saving).

[0033] (Total content of halogen flame retardants and antimony trioxide in total flame retardants) When the flame retardant further contains antimony trioxide, the total content of the halogen-based flame retardant (e.g., bromine-based flame retardant) and antimony trioxide is preferably 80 to 100 mass%, and more preferably 100 mass%, of the total amount of the flame retardant, from the viewpoint of obtaining better effects of the present invention (particularly, flame retardancy and power saving properties).

[0034] (Total content of halogen-based flame retardants and antimony trioxide per 100 parts by mass of rubber component) When the flame retardant further contains antimony trioxide, the total content of the halogen-based flame retardant and antimony trioxide is preferably 15 to 50 parts by mass, more preferably 20 to 45 parts by mass, and even more preferably 25 to 40 parts by mass, per 100 parts by mass of the rubber component described above, from the viewpoint of obtaining better effects of the present invention (particularly, flame retardancy and power saving).

[0035] [Filler] The rubber composition of the present invention contains a filler. Note that the filler does not contain a flame retardant. The rubber composition of the present invention contains a filler, and thus the resulting cured product has excellent ozone resistance, flame retardancy, and power saving properties. Examples of the filler include white fillers such as carbon black and silica. From the viewpoint of achieving better effects of the present invention (particularly power saving) and improved mechanical strength of the resulting cured product, the filler preferably contains carbon black and / or silica, and more preferably contains carbon black and silica.

[0036] (Carbon Black) When the rubber composition of the present invention contains carbon black (CB) as a filler, the carbon black has a nitrogen adsorption specific surface area of ​​20 to 100 m 2 / g and / or dibutyl phthalate oil absorption of 70 to 120 cm 3 It is preferable that the carbon black has a nitrogen adsorption specific surface area of ​​20 to 100 m / 100 g. 2 / g, and the dibutyl phthalate oil absorption is 70 to 120 cm 3 It is preferred that the carbon black content is 1 / 100g. The nitrogen adsorption specific surface area (N2SA) of carbon black can be measured in accordance with JIS K6217-2:2017. The dibutyl phthalate oil absorption (DBP) of carbon black can be measured in accordance with JIS K6217-4:2017.

[0037] (silica) When the rubber composition of the present invention contains silica as a filler, the silica is not particularly limited. For example, conventionally known silica may be used. Specific examples include wet silica, dry silica, and fumed silica.

[0038] (Filler content) The content of the filler is preferably 20 to 50 parts by mass, and more preferably 20 to 40 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of achieving better power saving properties and improved mechanical strength of the resulting cured product. When the filler contains carbon black and silica, it is preferred that at least half of the total amount of the filler is carbon black and the other half is silica.

[0039] [Divalent metal compounds] The rubber composition of the present invention contains a divalent metal compound including a carboxylate of a divalent metal (specific carboxylate). In the present invention, the divalent metal compound is a compound having a divalent metal. Divalent metals (divalent metals) include, for example, Zn 2+ , Ca 2+ , Mg 2+ Examples include:

[0040] The divalent metal constituting the above divalent metal compound is preferably Zn from the viewpoint of the effect of the present invention being more excellent. 2+ It is preferred that the compound contains

[0041] Examples of the divalent metal compound include specific carboxylates and divalent metal oxides.

[0042] [Divalent metal carboxylates] The rubber composition of the present invention contains a carboxylate of a divalent metal (specific carboxylate), and in the present invention, the specific carboxylate has 6 to 12 carbon atoms in total per carboxylic acid molecule. The rubber composition of the present invention contains the specific carboxylate, and thus has excellent ozone resistance, power saving properties, and abrasion resistance.

[0043] (Carboxylic acid constituting specific carboxylate) The carboxylic acid constituting the specific carboxylate is not particularly limited as long as the total number of carbon atoms per carboxylic acid molecule is 6 to 12. In the above carboxylic acid, the hydrocarbon group to which the carboxy 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 total number of carbon atoms includes the carbon atoms constituting the carboxy group. In a preferred embodiment, the carboxylic acid constituting the specific carboxylate has one carboxy group per carboxylic acid molecule. A preferred embodiment of the carboxylic acid constituting the specific carboxylate includes a fatty acid having a total of 6 to 12 carbon atoms per carboxylic acid molecule. The total number of carbon atoms in one molecule of the carboxylic acid (for example, the above-mentioned fatty acid) constituting the specific carboxylate is preferably 8 to 10, from the viewpoint of obtaining superior effects of the present invention. 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. From the viewpoint of achieving superior 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.

[0044] (Divalent metals constituting specific carboxylates) Examples of the divalent metal constituting the specific carboxylate include Zn. 2+ , Ca 2+ , Mg 2+ Examples include:

[0045] The divalent metal constituting the specific carboxylate is preferably Zn, from the viewpoint of providing a more excellent effect of the present invention. 2+ It is preferred that the compound contains

[0046] From the viewpoint of achieving superior effects of the present invention, the specific carboxylate preferably contains a divalent metal salt of a fatty acid having a total of 6 to 12 carbon atoms per molecule and one carboxy group, more preferably contains a zinc salt of a fatty acid having a total of 6 to 12 carbon atoms per molecule and one carboxy group, even more preferably contains zinc 2-ethylhexanoate and / or zinc neodecanoate, and even more preferably contains zinc 2-ethylhexanoate.

[0047] (Specific carboxylate content) 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, per 100 parts by mass of the rubber component, from the viewpoint of achieving superior effects of the present invention.

[0048] (Divalent metal oxides) From the viewpoint of achieving superior effects of the present invention, it is preferred that the divalent metal compound further contains a divalent metal oxide. The divalent metal constituting the divalent metal oxide is the same as the divalent metal constituting the divalent metal compound. From the viewpoint of obtaining a superior effect of the present invention, Zn 2+ It is preferred that the compound contains When the divalent metal compound further contains a divalent metal oxide, the divalent metal oxide preferably contains zinc oxide, from the viewpoint of achieving better effects of the present invention. When the divalent metal compound further contains a divalent metal oxide, 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, per 100 parts by mass of the above-mentioned rubber component, from the viewpoint of better effects of the present invention.

[0049] [Anti-aging agent] The rubber composition of the present invention contains an antioxidant. In one preferred embodiment, the antioxidant contains an amine-based antioxidant, which is an antioxidant having an amino group (-NH2) or an imino group (-NH-). Examples of the amine-based antiaging agent include phenylenediamine-based compounds and quinoline-based compounds. From the viewpoint of achieving superior 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.

[0050] (Phenylenediamine compounds) The phenylenediamine compound is a compound having a phenylenediamine skeleton. The two nitrogen atoms in the phenylenediamine skeleton can each independently form an amino group or an imino group, and it is preferable that at least one of the nitrogen atoms is an imino group, and it is more preferable that both of the nitrogen atoms are imino groups. Examples of the phenylenediamine compounds 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).

[0051] Quinoline compounds Quinoline compounds are compounds having a quinoline skeleton, such as a 2,2,4-trialkyl-1,2-dihydroquinone skeleton. Specific examples of quinoline compounds include 2,2,4-trimethyl-1,2-dihydroquinone and polymers thereof.

[0052] From the viewpoint of achieving superior effects of the present invention (particularly ozone resistance), the antioxidant preferably contains a polymer of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and / or 2,2,4-trimethyl-1,2-dihydroquinone, and more preferably contains a polymer of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinone.

[0053] [Anti-aging agent content] In the rubber composition of the present invention, the content of the antioxidant is preferably 2.5 to 10.0 parts by mass, and more preferably 3.0 to 5.0 parts by mass, per 100 parts by mass of the above-mentioned rubber component, from the viewpoint of achieving better effects of the present invention (particularly ozone resistance). When the antioxidant contains a phenylenediamine compound and a quinoline compound, from the viewpoint of achieving better effects of the present invention (particularly ozone resistance), it is preferable that the content of the phenylenediamine compound is 50 mass % or more of the total amount of the antioxidant, and the content of the quinoline compound is 50 mass % or less of the total amount of the antioxidant.

[0054] [Vulcanization accelerator] The rubber composition of the present invention contains a vulcanization accelerator. The vulcanization accelerator is not particularly limited as long as it is used for vulcanization of rubber. Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CZ) and N-tert-butyl-2-benzothiazolylsulfenamide (NS); thiuram vulcanization accelerators such as tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); and guanidine vulcanization accelerators such as diphenylguanidine (DPG). From the viewpoint of obtaining superior effects of the present invention (particularly flame retardancy and / or power saving resistance), the vulcanization accelerator preferably contains a sulfenamide-based vulcanization accelerator. The content of the vulcanization accelerator is preferably 0.5 to 8.0 parts by mass based on 100 parts by mass of the above-mentioned rubber component, from the viewpoint of obtaining better effects of the present invention (particularly flame retardancy and / or power saving resistance).

[0055] [sulfur] The rubber composition of the present invention contains sulfur. The sulfur is not particularly limited as long as it is used in vulcanization of rubber, and examples thereof include conventionally known sulfur. The content of sulfur is preferably 0.5 to 5.0 parts by mass based on 100 parts by mass of the rubber component described above, from the viewpoint of obtaining better effects of the present invention (particularly flame retardancy and / or power saving resistance).

[0056] [Halogen content in halogen flame retardants] In the present invention, the content of the halogen element contained in the above-mentioned halogen flame retardant is 9% by mass or more based on the total amount of the rubber composition of the present invention. By having the content of the halogen element contained in the halogen flame retardant be 9% by mass or more based on the total amount of the rubber composition of the present invention, the cured product obtained from the rubber composition of the present invention has excellent flame retardancy. From the viewpoint of obtaining superior effects of the present invention (particularly, ozone resistance, power saving, and abrasion resistance), the content of the halogen element in the halogen flame retardant is preferably 20 mass% or less, more preferably 9.0 to 12.0 mass%, and even more preferably 9.5 to 11.0 mass%, of the total amount of the rubber composition of the present invention.

[0057] [Mass ratio of total divalent metal content in divalent metal compounds to halogen element content in halogen-based flame retardants] In the present invention, the mass ratio of the total content of divalent metals contained in the above-mentioned divalent metal compound / the content of halogen elements contained in the above-mentioned halogen-based flame retardant is 0.05 or more. The mass ratio is (the total content of divalent metals contained in the divalent metal compound) / (the content of halogen elements contained in the halogen-based flame retardant). When the above mass ratio is 0.05 or more, the rubber composition of the present invention, when cured, has excellent flame retardancy, ozone resistance, power saving properties, and abrasion resistance. In the above mass ratio, the total content of divalent metals in the divalent metal compounds is the total content of divalent metals in the divalent metal compounds contained in the rubber composition of the present invention. The total content of divalent metals in the divalent metal compounds includes the content of divalent metals in the specific carboxylate. In addition, when the divalent metal compound further contains a divalent metal oxide (e.g., zinc oxide), the total content of divalent metals in the divalent metal compounds further includes the content of divalent metals in the divalent metal oxide. 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 divalent metal oxide reacts with the fatty acid to produce a divalent metal carboxylate, the amount of divalent metal contained in the divalent metal carboxylate produced within the rubber composition as described above is not included in the total divalent metal content of the divalent metal compound in the present invention.

[0058] The mass ratio of the total content of divalent metals contained in the above divalent metal compound to the content of halogen elements contained in the above halogen-based flame retardant is preferably 0.2 to 0.3, from the viewpoint of achieving superior effects of the present invention.

[0059] (Additives) The rubber composition of the present invention may further contain additives in addition to the above-mentioned components, such as fatty acids (e.g., stearic acid), vulcanization retarders (e.g., N-cyclohexylthiophthalimide), oils, and waxes. ·fatty acid 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 per 100 parts by mass of the above-mentioned rubber component. ·Vulcanization retarder 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 per 100 parts by mass of the above-mentioned rubber component.

[0060] (Manufacturing method) The method for producing the rubber composition of the present invention is not particularly limited, and may be, for example, a method in which the above-mentioned essential components and additives that may be further used as necessary are mixed under conditions of 120 to 180° C. using a Banbury mixer or the like.

[0061] (Vulcanization) The rubber composition of the present invention can be vulcanized under ordinary conditions. The vulcanization temperature can be, for example, 120 to 180° C. Pressure may be applied during vulcanization.

[0062] (Application) The rubber composition of the present invention may be used, for example, as a rubber composition for conveyor belts.

[0063] [Conveyor belt] The conveyor belt of the present invention is a conveyor belt formed using the rubber composition of the present invention.

[0064] The rubber composition used in the conveyor belt of the present invention is not particularly limited as long as it is the rubber composition of the present invention. The conveyor belt of the present invention is not particularly limited, except that it is formed using the rubber composition of the present invention. The conveyor belt of the present invention is formed using the above-mentioned rubber composition of the present invention, and therefore has excellent flame retardancy, ozone resistance, abrasion resistance, and power saving properties.

[0065] There is no particular limitation as to which of the components constituting the conveyor belt of the present invention the rubber composition of the present invention is applied to. All or a part of the rubber constituting the conveyor belt of the present invention may be formed from the rubber composition of the present invention.

[0066] The cured product obtained from the rubber composition of the present invention has excellent ozone resistance, abrasion resistance, flame retardancy, and power saving properties, and therefore, one of the preferable aspects of the conveyor belt of the present invention is that it has a cover rubber formed using the rubber composition of the present invention.

[0067] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a conveyor belt according to the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the accompanying drawings. Fig. 1 is a cross-sectional view of one embodiment of the conveyor belt of the present invention. One embodiment of the conveyor belt of the present invention shown in Fig. 1 (herein also referred to as a first embodiment of the conveyor belt of the present invention) is a conveyor belt 4 in which a fabric layer 1 is covered with a coating rubber (bonded rubber) 2 to form a core layer, and the outer periphery of the core layer is covered with a cover rubber 3. The cover rubber 3 is preferably formed using the rubber composition of the present invention. In FIG. 1, a conveyor belt 4 has a fabric layer 1 as a core material, and the number of layers of the fabric layer 1, the thickness of the cover rubber 3, the belt width, etc. can be appropriately determined depending on the purpose of use. The fabric layer may be, for example, canvas made of woven synthetic fibers such as nylon, vinylon, or polyester. The thicknesses T1 and T2 of the cover rubber 3 can usually be set to about 1.5 to 20 mm.

[0068] Also, a coating rubber used in a known conveyor belt can be used as the coating rubber 2. As the coating rubber, for example, a rubber composition containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), ethylene-propylene rubber (EPT), ethylene-propylene-diene rubber (EPDM), or the like as a rubber component can be used.

[0069] Next, a second embodiment of the conveyor belt of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view of another embodiment of the conveyor belt of the present invention. As shown in Fig. 2, the second embodiment of the conveyor belt of the present invention is a conveyor belt 8 in which a steel cord 5 is covered with a cushion rubber (adhesive rubber) 6 to form a core layer, and the outer periphery of the core layer is covered with a cover rubber 7. The cover rubber 7 is preferably formed using the rubber composition of the present invention. The conveyor belt 8 may have a core material of, for example, about 50 to 230 parallel steel cords 5 each having a diameter of about 2.0 to 9.5 mm, each of which is made by twisting together a plurality of wires each having a diameter of about 0.2 to 0.4 mm. In general, the total thickness T of the conveyor belt 8 may be about 10 to 50 mm. Also, for example, adhesive rubber that can be adhered to galvanized steel cords used in known steel conveyor belts can be used as the cushion rubber 6. Specifically, for example, a rubber composition containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), or the like as a rubber component can be used as the cushion rubber.

[0070] The conveyor belt of the present invention can be produced, for example, by interposing a fabric layer, a steel cord, or a core layer, etc., which will be the core material, between unvulcanized rubber sheets formed from the rubber composition of the present invention, and vulcanizing the mixture by applying heat and pressure according to a conventional method. The vulcanization conditions can be, for example, about 120 to 180°C, about 0.1 to 4.9 MPa, and about 10 to 90 minutes.

[0071] The conveyor belt of the present invention can be used under temperature conditions of, for example, -30 to +60°C. EXAMPLES

[0072] The present invention will be described in further detail below with reference to examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0073] <Production of Rubber Composition> Each rubber composition (unvulcanized) was produced by mixing the components in the compositions (parts by mass) shown in Tables 1 and 2 below in a Banbury mixer at 120 to 180° C.

[0074] (Preparation of vulcanized rubber sheets) - Preparation of vulcanized rubber sheet 1 under normal vulcanization conditions Each rubber composition (unvulcanized) produced as described above was vulcanized under normal vulcanization conditions for 30 minutes using a press molding machine at 148°C under a surface pressure of 3.0 MPa to produce a vulcanized rubber sheet 1 measuring 150 mm in length, 150 mm in width and 2 mm in thickness. - Preparation of vulcanized rubber sheet 2 under overvulcanization conditions Each rubber composition (unvulcanized) produced as described above was vulcanized under overvulcanization conditions for 90 minutes using a press molding machine at 148°C under a surface pressure of 3.0 MPa to produce a vulcanized rubber sheet 2 measuring 150 mm in length, 150 mm in width and 2 mm in thickness. In this specification, the vulcanized rubber sheet 2 produced under over-vulcanization conditions is intended to reproduce the decomposition of vulcanized rubber that can occur simultaneously with vulcanization due to a longer than normal thermal history (vulcanization time), the resulting radicals, and / or the generation of halogens from halogen-based flame retardants.

[0075] <Evaluation> The vulcanized rubber sheets prepared as described above were subjected to the following evaluations, and the results are shown in the tables.

[0076] (Ozone resistance) In accordance with 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% elongation to conduct an ozone resistance test (accelerated test). After the ozone resistance test, the surface of the vulcanized rubber sheet was visually observed. If the vulcanized rubber sheet had no cracks after the ozone resistance test at each time point, this was indicated as "NC." Evaluation criteria for ozone resistance In the present invention, when no cracks were observed in the vulcanized rubber sheet after the ozone resistance test, the obtained vulcanized rubber was evaluated as having excellent ozone resistance. On the other hand, when cracks occurred in the vulcanized rubber sheet after the above ozone resistance test, the ozone resistance of the obtained vulcanized rubber was evaluated as poor. If cracks were found in the vulcanized rubber sheet, the level of the cracks was evaluated in accordance with JIS K6259-1:2015 and indicated by a combination of letters and numbers such as the above levels "A5" and "C1". In the present invention, if cracks were found in the vulcanized rubber sheet after the ozone resistance test, levels "B" and "C" are considered to have worse ozone resistance than level "A". In addition, when the level letters are the same, the larger the number following the letter, the worse the ozone resistance.

[0077] (50% modulus after overvulcanization) A JIS No. 3 dumbbell-shaped rubber sheet piece was punched out from each of the vulcanized rubber sheets 2 prepared as described above to prepare a test specimen. Using this test specimen, 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].

[0078] (Power saving: RRF) Dynamic viscoelasticity measurement Using each vulcanized rubber sheet 2 produced as described above, dynamic viscoelasticity measurements were performed using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) under measurement conditions of a chuck distance of 10 mm, dynamic strain of 2%, and a frequency of 20 Hz. The loss tangent (tan δ) and dynamic modulus of elasticity E' (N / mm) were measured at 0°C and 20°C, and the obtained loss tangent (tan δ) and dynamic modulus of elasticity E' were applied to the following equation to calculate the rolling resistance factor (RRF).

number

[0079] Energy saving evaluation criteria In the present invention, a device was evaluated as having excellent power saving properties when both the RRF indexes at 0° C. and 20° C. were less than 100. The smaller the RRF index, the more excellent the power saving properties. On the other hand, when at least one of the indices at 0° C. and 20° C. was 100 or more, the power saving performance was evaluated as poor.

[0080] (Wear resistance) Using each vulcanized rubber sheet 1 manufactured as described above, an abrasion test (Method B) was carried out at 23°C using a DIN abrasion tester in accordance with JIS K6264-2:2005 under the conditions of rotation speed [40 rpm], load [9.8 N], and abrasion type [511XP60], and the amount of abrasion [mm 3 ] was measured.

[0081] -Abrasion resistance evaluation criteria In the present invention, the wear amount is 150 mm 3 When the wear amount was 150 mm or less, the abrasion resistance was evaluated as excellent. 3 The smaller the value, the better the abrasion resistance. On the other hand, the wear amount is 150 mm 3When the value exceeded this range, the abrasion resistance was evaluated as poor.

[0082] (Flame retardant) - Preparation of test specimens Using each rubber composition produced as described above, test pieces (6 for each test piece) were produced in accordance with JIS K6324:2013 "Flame retardant performance conveyor belt - Grade and test method" 7.2.1 for fabric layer conveyor rubber. The vulcanization during the above production was carried out under normal vulcanization conditions for 30 minutes under a surface pressure of 3.0 MPa using a press molding machine at 148°C, in the same manner as in the production of vulcanized rubber sheet 1, to obtain a BL sample (blank sample). An aging test was carried out on three of the six BL samples obtained as described above at 100° C. for 168 hours to obtain samples after the aging test.

[0083] Evaluation method The flame duration (unit: seconds) of the BL sample and the sample after the aging test was measured in accordance with JIS K6324:2013 "Flame retardant performance conveyor belts - Grades and test methods."

[0084] Evaluation criteria If the material met the JIS Class 3 flame retardancy test standard (flame duration of less than 60 seconds (flame duration is the average value of three test pieces) and there is no re-ignition), it was evaluated as having excellent flame retardancy, and this was marked as "O". If the JIS Class 3 flame retardancy test standard was not met, the flame retardancy was evaluated as poor and this was marked with an "X". The evaluation results of the flame retardancy of the BL samples are shown in the "Flame retardancy BL" column of each table. The evaluation results of the flame retardancy of the samples after the aging test are shown in the "Flame retardancy 100℃ 168H" column of each table. In the present invention, when the evaluation results of the flame retardancy of both the BL sample and the sample after the aging test were "◯", the flame retardancy was evaluated as excellent. On the other hand, if any of the flame retardancy evaluation results of the BL sample and the sample after the aging test was "x", the flame retardancy was evaluated as poor.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] In each table, "Metal (Zn) content (mass%) *1 " is the proportion (mass %) of the total content of divalent metals contained in the divalent metal compounds in the total amount of the rubber composition. Halogen content (mass%) *2 " is the percentage (mass %) of the content of the halogen element contained in the halogen-based flame retardant in the total amount of the rubber composition. Metal (Zn) / halogen mass ratio *3 " is the mass ratio of the total divalent metal content in the divalent metal compound to the halogen element content in the halogen-based flame retardant. In Table 1, Comparative Example 1 is used as the power saving index standard. In Table 2, Comparative Example 6 is used as the power saving index standard.

[0089] Details of each component shown in each table are as follows. (Rubber component, diene rubber) NR: Natural rubber. RSS#3 BR: Butadiene rubber. Product name: Nipol BR1220 (weight average molecular weight: 460,000, manufactured by Zeon Corporation)

[0090] (Divalent metal compounds) Specific carboxylate 1: Manufactured by Sil+Zailach, product name "Stractol" ZEH-75. The above product used as specific carboxylate 1 is a mixture containing 75% by mass of zinc 2-ethylhexanoate (structure below) as an active ingredient, and 25% by mass of silica. The zinc content in the mixture is 17% by mass. The "Specific carboxylate 1" column in each table indicates the content as the mixture. [ka] Zinc oxide: zinc oxide (ZnO 81.41g / mol). Zn content 80% by mass. Product name: "Zinc Oxide Type 3" (manufactured by Seido Chemical Industry Co., Ltd.). Zinc oxide is a divalent metal oxide. Zinc stearate (for comparison): The zinc content in zinc stearate is 10% by mass. Manufactured by Seido Chemical Co., Ltd. Zinc stearate does not fall under the category of specific carboxylates because the total number of carbon atoms per molecule of stearic acid that constitutes zinc stearate exceeds 12. Specific carboxylate 2: Zinc neodecanoate. The zinc content in zinc neodecanoate is 8% by mass. Manufactured by Nippon Chemical Industry Co., Ltd., product name: Zinc neodecanoate

[0091] (Filler) Silica: Product name "Nipsil AQ" (manufactured by Tosoh Silica Corporation) CB: GPF grade carbon black. Product name: Niteron #GN, manufactured by Shin-Nichika Carbon Co., Ltd. N2SA: 32m 2 / g, DBP: 91 cm 3 / 100g In the "Silica / CB" column in each table, the value to the left of the " / " indicates the amount of silica added, and the value to the right of the " / " indicates the amount of carbon black added. The same applies to the indications of antioxidants, vulcanization accelerators, etc. below. When the specific carboxylate is specific carboxylate 1, the amount of silica in the "Silica / CB" column does not include the amount of silica contained in specific carboxylate 1.

[0092] (Anti-aging agent) Antioxidant 6C: Amine-based antioxidant. N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (structure shown below). Product name: Ozonone 6C (manufactured by Seiko Chemical Co., Ltd.) [ka] Anti-aging agent RD: Polymer of 2,2,4-trimethyl-1,2-dihydroquinone (structure below). Product name: Nonflex RD (manufactured by Seiko Chemical Co., Ltd.) [ka]

[0093] (Flame retardant) Antimony trioxide: PATOX-M (product name) manufactured by Nihon Seiko Co., Ltd. (Halogen-based flame retardants) Brominated flame retardant: Bis(pentabromophenyl)ethane. Product name: "SAYTEX8010" (manufactured by ALBEMARLE CORPORATION). Br content: 82% by mass. Melting point: 300°C or higher. Chlorinated paraffin: Empara 70S (trade name) manufactured by Dover Chemical Co. Chlorine content: 68-72% by mass. Average Cl content: 70% by mass. The above average Cl content of 70% by mass was used to calculate the content of chlorine element in the chlorinated paraffin.

[0094] (Vulcanization accelerator) Vulcanization accelerator NS: N-tert-butyl-2-benzothiazolylsulfenamide (product name: Noccela NS, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0095] - Vulcanization retarder PVI: N-cyclohexylthiophthalimide. Product name: Retarder CTP, manufactured by Toray Fine Chemicals Co., Ltd.

[0096] (sulfur) Insoluble sulfur: Shikoku Chemical Industry Co., Ltd. (product name) Myucron OT-20

[0097] (Additives) Aroma oil: Product name A-OMIX (manufactured by Sankyo Yuka Kogyo) WAX: Wax. Product name: OZOACE-0037 (Nippon Seiro Co., Ltd.) Stearic acid: Product name "Stearic Acid 50S" (manufactured by Chiba Fatty Acid Co., Ltd.)

[0098] From the results in Tables 1 and 2, it was confirmed that the rubber composition of the present invention exhibits the desired effects.

[0099] On the other hand, in Table 1 (containing a bromine-based flame retardant as a halogen-based flame retardant), Comparative Example 1 not containing the specific carboxylate was poor in ozone resistance, power saving properties, and abrasion resistance. In Comparative Example 2, in which the content of halogen elements contained in the halogen-based flame retardant in the total amount of the rubber composition was less than 9 mass %, the flame retardancy was poor. Comparative Example 3, in which the mass ratio of the total content of divalent metals in the divalent metal compound to the content of halogen elements in the halogen-based flame retardant was less than 0.05, had poor ozone resistance and power saving properties. Comparative Example 4, which did not contain the specific carboxylate but contained zinc stearate instead, had poor ozone resistance, power saving properties, and abrasion resistance. In addition, in Table 1, the rubber composition of the present invention had a superior 50% modulus after overvulcanization to Comparative Example 1 which did not contain the specific carboxylate, and Comparative Example 4 which contained zinc stearate as described above.

[0100] In addition, in Table 2 (containing a chlorine-based flame retardant as a halogen-based flame retardant), Comparative Example 6, which did not contain the specific carboxylate, had poor ozone resistance, power saving properties, and abrasion resistance (the same trends as Comparative Example 1 in Table 1). Comparative Example 5, which did not contain the specific carboxylate and in which the content of halogen elements in the halogen-based flame retardant in the total amount of the rubber composition was less than 9 mass %, had poor abrasion resistance and flame retardancy. In addition, in Table 2, the rubber composition of the present invention had a superior 50% modulus after overvulcanization to Comparative Examples 5 and 6 which did not contain the specific carboxylate. [Explanation of symbols]

[0101] 1: Cloth layer 2:Coated rubber 3, 7: Cover rubber 4, 8: Conveyor belt 5: Steel cord 6: Cushion rubber

Claims

1. The rubber composition contains a rubber component including a diene rubber, a flame retardant including a halogen-based 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 halogen elements contained in the halogen-based flame retardant is 9% by mass or more based on the total amount of the rubber composition, a mass ratio of the total content of divalent metals contained in the divalent metal compound to the content of halogen elements contained in the halogen-based flame retardant is 0.05 or more; The rubber composition has a total of 6 to 12 carbon atoms per molecule of the carboxylic acid constituting the carboxylate.

2. The rubber composition according to claim 1 , wherein the diene-based rubber comprises natural rubber and / or butadiene rubber.

3. The divalent metal constituting the carboxylate is Zn. ２＋ The rubber composition according to claim 1 , comprising:

4. The divalent metal constituting the divalent metal compound is Zn ２＋ The rubber composition according to claim 1 , comprising:

5. The rubber composition according to claim 1 , wherein the divalent metal compound further contains a divalent metal oxide.

6. the diene rubber contains a natural rubber and a butadiene rubber, and a mass ratio of the natural rubber / the butadiene rubber is 30 / 70 to 80 / 20; 2. The rubber composition according to claim 1, wherein the mass ratio of the total content of divalent metals contained in the divalent metal compound to the content of halogen elements contained in the halogen-based 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 contains antimony trioxide.

8. 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 any one of claims 1 to 8.

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