Vulcanizing agent, rubber composition, and vulcanized rubber

Abstract

To provide a vulcanizer that has excellent dispersibility in a rubber composition and allows the production of a rubber product having excellent elongation at break, thermal aging resistance and wear resistance and also provide a rubber composition containing the vulcanizer, and a vulcanized rubber prepared by using the same.SOLUTION: A vulcanizer is a product from the reaction that occurs, in the presence of a vulcanization accelerator, among a resin containing at least one of an unsaturated double bond and an aromatic ring and having a weight average molecular weight of 500 or more, an olefin compound having a weight average molecular weight of less than 500, and sulfur.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a vulcanizing agent, a rubber composition, and a vulcanized rubber. [Background technology]

[0002] Compositions containing diene rubber and sulfur are known, and these compositions can be rapidly crosslinked (vulcanized) by heating to form desired rubber products (vulcanized rubbers). For example, Patent Document 1 discloses a rubber composition containing a rubber component containing a diene rubber, silica and / or carbon black, and a masterbatch of sulfur and a resin having an acid value of 5 or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-182983 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors evaluated rubber compositions containing a masterbatch as a vulcanizing agent as described in Patent Document 1 and found that the dispersibility of the vulcanizing agent in the rubber composition may be insufficient, and that the rubber product (vulcanized rubber) obtained using the same may have insufficient performance in at least one of the following properties: elongation at break, heat aging resistance, and abrasion resistance.

[0005] Therefore, an object of the present invention is to provide a vulcanizing agent that has excellent dispersibility in a rubber composition and that can produce a rubber product that is excellent in elongation at break, heat aging resistance, and abrasion resistance. Another object of the present invention is to provide a rubber composition containing the vulcanizing agent and a vulcanized rubber obtained using the same. [Means for solving the problem]

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

[0007] [1] A vulcanizing agent obtained by reacting a resin having at least one of an unsaturated double bond and an aromatic ring and a weight-average molecular weight of 500 or more with an olefin compound having a weight-average molecular weight of less than 500, and sulfur in the presence of a vulcanization accelerator. [2] The vulcanizing agent according to [1], wherein the olefin compound contains at least one compound selected from the group consisting of limonene, pinene, and isoprene. [3] The vulcanizing agent according to [1] or [2], wherein the amount of sulfur used in the reaction is 30 to 90 mass % based on the total amount of sulfur used and the amount of the olefin compound used. [4] The vulcanizing agent according to any one of [1] to [3], wherein the reaction is carried out at a temperature of 100 to 180°C. [5] A diene rubber and a vulcanizing agent according to any one of [1] to [4], A rubber composition comprising 0.5 to 10 parts by mass of the vulcanizing agent per 100 parts by mass of the diene rubber, A rubber composition that satisfies the following requirement A or B. Requirement A: The rubber composition does not contain sulfur. Requirement B: The rubber composition further contains more than 0 part by mass and not more than 10 parts by mass of sulfur per 100 parts by mass of the diene rubber. [6] A vulcanized rubber obtained using the rubber composition described in [5]. [Effects of the Invention]

[0008] According to the present invention, there is provided a vulcanizing agent that has excellent dispersibility in a rubber composition and that can produce a rubber product that is excellent in elongation at break, heat aging resistance, and abrasion resistance. The present invention also provides a rubber composition containing the vulcanizing agent and a vulcanized rubber obtained using the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram showing an endothermic curve obtained by measuring vulcanizing agent 2 produced in an example using a differential scanning calorimeter. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, unless otherwise specified, each component may be used alone or in combination of two or more substances. When a component contains two or more substances, the content of the component means the total content of the two or more substances.

[0011] In this specification, the weight average molecular weight (Mw) is a value converted into standard polystyrene based on a measurement value obtained by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0012] [Vulcanizing agent] The vulcanizing agent of the present invention is obtained by reacting a resin having at least one of an unsaturated double bond and an aromatic ring and a weight-average molecular weight of 500 or more (hereinafter also referred to as a "specific resin"), an olefin compound having a weight-average molecular weight of less than 500 (hereinafter also referred to as a "specific olefin compound"), and sulfur in the presence of a vulcanization accelerator.

[0013] The mechanism by which the problem of the present invention is solved by adopting such a configuration is not entirely clear, but the present inventors speculate as follows. First, the vulcanizing agent of the present invention is a mixture of organosulfur compounds having complex and diverse structures, and it is impossible or impractical to directly identify it by structure or properties. Even under such circumstances, the present inventors assume that the vulcanizing agent synthesized in the presence of a vulcanization accelerator has a sulfur atom, a structure derived from the specific resin, and a structure derived from the specific olefin compound, specifically, a structure in which a sulfur atom has reacted with a specific resin and a specific olefin compound. It is presumed that the presence of a specific olefin compound having a molecular weight smaller than that of the specific resin during the production of the vulcanizing agent of the present invention improves the reactivity with the specific resin and sulfur in the system. As a result, the amount of unreacted components in the vulcanizing agent is reduced, improving the compatibility between the vulcanizing agent and other components in the rubber composition and resulting in good dispersion of the vulcanizing agent in the rubber composition. It is also presumed that when a rubber product is produced using the vulcanizing agent of the present invention, structures derived from the specific resin and the specific olefin compound are incorporated into the polymer of the rubber product, resulting in improved elongation at break, heat aging resistance, and abrasion resistance of the rubber product. Hereinafter, the superiority of at least one of the dispersibility of the vulcanizing agent in the rubber composition produced, and the elongation at break, heat aging resistance, and abrasion resistance of the rubber product produced, is also referred to as the superior effect of the present invention.

[0014] <Sulfur> Examples of sulfur used in preparing the vulcanizing agent of the present invention include powdered sulfur, precipitated sulfur, highly dispersible sulfur, insoluble sulfur, etc. The sulfur may be surface-treated. In order to obtain better effects of the present invention, the content of sulfur (sulfur atoms) relative to the total mass of the vulcanizing agent of the present invention is preferably 10 to 95 mass%, more preferably 30 to 90 mass%, even more preferably 30 to 80 mass%, and particularly preferably 35 to 70 mass%. The content of sulfur (sulfur atoms) relative to the total mass of the vulcanizing agent may include sulfur atoms derived from a vulcanization accelerator, which will be described later. Furthermore, in order to obtain better effects of the present invention, the content of sulfur is preferably 10 to 95 mass%, more preferably 30 to 90 mass%, even more preferably 30 to 80 mass%, and particularly preferably 35 to 70 mass%, relative to the total mass of a mixture containing sulfur, a specific resin, a specific olefin compound, and a vulcanization accelerator, which is prepared to produce the vulcanizing agent of the present invention (hereinafter, the mixture may be referred to as a "composition for forming a vulcanizing agent").

[0015] <Specific resin> The specific resin used to prepare the vulcanizing agent of the present invention is a resin having at least one of an unsaturated double bond and an aromatic ring, and having a weight average molecular weight of 500 or more.

[0016] The specific resin may have at least one of an unsaturated double bond and an aromatic ring, and from the viewpoint of achieving better effects of the present invention, it is preferable that the specific resin has an unsaturated double bond, and it is more preferable that the specific resin has both an unsaturated double bond and an aromatic ring. Unless otherwise specified, the unsaturated double bond in the present invention does not include a carbon-carbon double bond constituting an aromatic ring. Specific examples of the unsaturated double bond include a vinyl structure, an allyl structure, a propenyl structure, an isoprene structure, and a cycloalkene structure. Specific examples of the aromatic ring include a benzene ring and a naphthalene ring, with a benzene ring being preferred in terms of achieving better effects of the present invention.

[0017] The weight average molecular weight (Mw) of the specific resin is 500 or more. The lower limit of the specific Mw is preferably 700 or more, more preferably 900 or more, in terms of achieving better effects of the present invention. The upper limit of the Mw is preferably 2800 or less, more preferably 2400 or less, and even more preferably 2000 or less, in terms of achieving better effects of the present invention.

[0018] The specific resin is preferably a thermoplastic resin. Examples of the thermoplastic resin include natural resins such as terpene resins and rosin resins, petroleum resins, coal resins, phenol resins, styrene resins, indene resins (homopolymers of indene, copolymers of styrene compounds and indene, copolymers of coumarone and indene), and synthetic resins such as xylene resins. Among these, terpene resins and indene resins are preferred, and terpene resins are more preferred, because they provide better effects of the present invention. Examples of terpene resins include α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene phenol resin, terpene styrene resin, aromatic modified terpene resin, hydrogenated terpene resin, etc. Among these, aromatic modified terpene resin is preferred because it provides better effects of the present invention.

[0019] In order to obtain better effects of the present invention, the content of the partial structure derived from the specific resin is preferably 5 to 90 mass%, more preferably 10 to 70 mass%, still more preferably 20 to 70 mass%, and particularly preferably 30 to 65 mass%, relative to the total mass of the vulcanizing agent of the present invention. Furthermore, in order to obtain better effects of the present invention, the content of the specific resin is preferably 5 to 90 mass%, more preferably 10 to 70 mass%, even more preferably 20 to 70 mass%, and particularly preferably 30 to 65 mass%, relative to the total mass of the vulcanizing agent-forming composition.

[0020] In the vulcanizing agent of the present invention, the content of sulfur (sulfur atom) relative to the total content of sulfur (sulfur atom) and the partial structure derived from the specific resin is preferably 10 to 95 mass%, more preferably 30 to 90 mass%, still more preferably 30 to 80 mass%, and particularly preferably 35 to 70 mass%. In the reaction for producing the vulcanizing agent of the present invention, the amount of sulfur used relative to the total amount (total mass) of sulfur and the specific resin used is preferably 10 to 95 mass%, more preferably 30 to 90 mass%, still more preferably 30 to 80 mass%, and particularly preferably 35 to 70 mass%. Note that the amount used corresponds to the content of sulfur or the specific resin relative to the total amount of sulfur and the specific resin used in the vulcanizing agent-forming composition.

[0021] <Specific olefin compounds> The specific olefin compound used to prepare the vulcanizing agent of the present invention is an olefin compound having a weight average molecular weight of less than 500. In the present invention, the olefin compound refers to a hydrocarbon compound having at least one unsaturated double bond. Specific examples of the unsaturated double bond are the same as those of the specific resin described above.

[0022] The weight average molecular weight (Mw) of the specific olefin compound is less than 500. The upper limit of the Mw is preferably 400 or less, more preferably 300 or less, and even more preferably 200 or less, in terms of achieving better effects of the present invention. The lower limit of the specific Mw is preferably 30 or more, more preferably 40 or more, and even more preferably 50 or more, in terms of achieving better effects of the present invention.

[0023] Examples of the specific olefin compounds include cyclic olefin compounds such as limonene and pinene (α-pinene, β-pinene), and chain olefin compounds such as isoprene, butadiene, and piperylene. Among these, the specific olefin compound preferably contains at least one compound selected from the group consisting of limonene, pinene, and isoprene, in view of the superior effects of the present invention.

[0024] In order to obtain better effects of the present invention, the content of the partial structure derived from the specific olefin compound is preferably 2 to 20 mass%, more preferably 3 to 18 mass%, even more preferably 4 to 15 mass%, and particularly preferably 5 to 12 mass%, relative to the total mass of the vulcanizing agent of the present invention. In addition, in order to obtain better effects of the present invention, the content of the specific olefin compound is preferably 2 to 20 mass%, more preferably 3 to 18 mass%, even more preferably 4 to 15 mass%, and particularly preferably 5 to 12 mass%, relative to the total mass of the vulcanizing agent forming composition.

[0025] In the vulcanizing agent of the present invention, the content of sulfur (sulfur atom) relative to the total mass of sulfur (sulfur atom) and the partial structure derived from the specific olefin compound is preferably 10 to 95 mass%, more preferably 30 to 90 mass%, still more preferably 30 to 80 mass%, and particularly preferably 35 to 70 mass%. In the reaction for producing the vulcanizing agent of the present invention, the amount of sulfur used relative to the total amount (total mass) of sulfur used and the specific olefin compound used is preferably 10 to 95 mass%, more preferably 30 to 90 mass%, still more preferably 30 to 80 mass%, and particularly preferably 35 to 70 mass%. Note that the amount used corresponds to the content of sulfur or the specific olefin compound relative to the total amount of sulfur and the specific olefin compound used in the vulcanizing agent-forming composition.

[0026] In the vulcanizing agent of the present invention, the content of the partial structure derived from the specific olefin compound relative to the total mass of the partial structure derived from the specific olefin compound and the structure derived from the specific resin is preferably 2 to 20 mass%, more preferably 3 to 18 mass%, even more preferably 4 to 15 mass%, and particularly preferably 5 to 12 mass%. In the reaction for producing the vulcanizing agent of the present invention, the amount of the specific olefin compound used relative to the total amount (total mass) of the specific olefin compound and the specific resin used is preferably 2 to 20 mass%, more preferably 3 to 18 mass%, still more preferably 4 to 15 mass%, and particularly preferably 5 to 12 mass%. Note that the amount used corresponds to the content of the specific olefin compound or the specific resin relative to the total amount of the specific olefin compound and the specific resin used in the vulcanizing agent-forming composition.

[0027] <Vulcanization accelerator> In producing the vulcanizing agent of the present invention, the sulfur, the specific resin, and the specific olefin compound are reacted in the presence of a vulcanization accelerator. In order to obtain better effects of the present invention, the vulcanization accelerator is preferably a sulfur-containing vulcanization accelerator containing one or more (preferably 1 to 10) sulfur atoms in one molecule. In order to obtain better effects of the present invention, it is also preferable that the vulcanization accelerator contains one or more (preferably 1 to 3) metal atoms (zinc, tellurium, copper, and / or sodium, etc.) in one molecule. Examples of the vulcanization accelerator include dithiocarbamate vulcanization accelerators, sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, guanidine vulcanization accelerators, and thiuram vulcanization accelerators. Among them, the vulcanization accelerator is preferably a dithiocarbamate vulcanization accelerator, since it provides better effects of the present invention.

[0028] Examples of dithiocarbamate vulcanization accelerators include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dibenzyldithiocarbamate, tellurium diethyldithiocarbamate, copper dimethyldithiocarbamate, and sodium diethyldithiocarbamate.

[0029] Examples of sulfenamide vulcanization accelerators include N-cyclohexylbenzothiazole sulfenamide, Nt-butylbenzothiazole sulfenamide, N-oxydiethylenebenzothiazole sulfenamide, N,N-dicyclohexylbenzothiazole sulfenamide, and (morpholinodithio)benzothiazole.

[0030] Examples of thiazole vulcanization accelerators include di-2-benzothiazolyl disulfide, mercaptobenzothiazole, benzothiazyl disulfide, zinc salt of mercaptobenzothiazole, (dinitrophenyl)mercaptobenzothiazole, and (N,N-diethylthiocarbamoylthio)benzothiazole.

[0031] Examples of the guanidine vulcanization accelerator include diphenylguanidine, di(o-tolyl)guanidine, and o-tolylbiguanide.

[0032] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, tetrakis(2-ethylhexyl)thiuram disulfide, and tetrabenzylthiuram disulfide.

[0033] A part or all of the vulcanization accelerator may be incorporated into the vulcanizing agent of the present invention. In order to obtain better effects of the present invention, the total content of the partial structures derived from the vulcanization accelerator is preferably 0.1 to 10 mass%, more preferably 1 to 8 mass%, and even more preferably 2 to 5 mass%, based on the total mass of the vulcanizing agent of the present invention. In addition, in order to obtain better effects of the present invention, the content of the vulcanization accelerator is preferably 0.1 to 10 mass%, more preferably 1 to 8 mass%, and even more preferably 2 to 5 mass%, relative to the total mass of the vulcanizing agent forming composition.

[0034] When synthesizing the vulcanizing agent of the present invention, components other than those described above may be added to the system (to the vulcanizing agent-forming composition) within a range that does not impair the performance of the vulcanizing agent to be synthesized.

[0035] <Production of vulcanizing agent> The vulcanizing agent of the present invention is obtained by reacting the above-mentioned sulfur, the above-mentioned specific resin, and the above-mentioned specific olefin compound in the presence of the above-mentioned vulcanization accelerator. The reaction is preferably carried out under heating in order to obtain better effects of the present invention. The temperature in the reaction (i.e., the temperature of the vulcanizing agent-forming composition) is preferably 100 to 180° C., more preferably 110 to 170° C., and even more preferably 120 to 160° C. The heating is maintained for preferably 0.5 to 20 hours, more preferably 1 to 10 hours, and even more preferably 2 to 5 hours. The heating may be carried out continuously or intermittently.

[0036] The reaction may be carried out, for example, by mixing the sulfur, the specific resin, the specific olefin compound, and the vulcanization accelerator components used in the production of the vulcanizing agent together to obtain a vulcanizing agent-forming composition, and then reacting the resulting vulcanizing agent-forming composition. Alternatively, the vulcanizing agent-forming composition may be obtained by sequentially mixing some or all of the components, or by heating some or all of the components before the vulcanizing agent-forming composition is completed. For example, a heated (or unheated) portion of each of the components may be added to another heated (or unheated) portion of each of the components to complete the vulcanizing agent-forming composition, and then the sulfur and the specific resin in the completed vulcanizing agent-forming composition may be reacted. Before the vulcanizing agent-forming composition is completed, some of the components may have already started to react.

[0037] Alternatively, for example, the vulcanizing agent of the present invention may be obtained by adding the specific resin, the specific olefin compound, and the vulcanization accelerator to sulfur that has been heated to 116 to 200°C (preferably 120 to 180°C) and made liquid, and continuing to heat the obtained vulcanizing agent forming composition to react the sulfur with the specific resin and the specific olefin compound.

[0038] The obtained vulcanizing agent may be subjected to a washing treatment or the like to remove unreacted components (unreacted sulfur, unreacted specific resin, unreacted specific olefin compound, and / or unreacted vulcanization accelerator) from the vulcanizing agent.

[0039] [Rubber composition] The present invention also relates to a rubber composition. The rubber composition of the present invention contains the vulcanizing agent of the present invention. In order to obtain better effects of the present invention, the rubber composition preferably contains a diene rubber and the vulcanizing agent. In addition, in order to obtain better effects of the present invention, the rubber composition preferably contains 0.5 to 10 parts by mass, more preferably 0.6 to 8 parts by mass, and even more preferably 0.8 to 5 parts by mass of the vulcanizing agent per 100 parts by mass of the diene rubber. Furthermore, the rubber composition preferably satisfies the following requirement A or B. Requirement A: The rubber composition does not contain sulfur. Requirement B: The rubber composition further contains more than 0 parts by mass and not more than 10 parts by mass (preferably more than 0 parts by mass and less than 5 parts by mass, more preferably more than 0 parts by mass and less than 3 parts by mass) of sulfur per 100 parts by mass of the diene rubber. The sulfur in the requirements A and B is sulfur that is added to the rubber composition separately from the sulfur atoms contained in the vulcanizing agent.

[0040] <Diene rubber> As described above, the rubber composition preferably contains a diene rubber. The diene rubber is not particularly limited as long as it has a double bond in the main chain, and known diene rubbers can be used. Examples of diene rubbers include natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), aromatic vinyl-conjugated diene copolymer rubber (e.g., styrene-butadiene rubber (SBR), styrene-isoprene rubber, styrene-butadiene-isoprene rubber (SBIR)), styrene-isoprene rubber (SIR), and styrene-isoprene-butadiene rubber (SIBR). The diene rubber may also be a derivative in which a side chain, one end, or both ends are modified with at least one functional group selected from the group consisting of an alkyl group, an allyl group, an amino group, an isocyanate group, a hydroxyl group, a thiol group, a vinyl group, an epoxy group, a carboxy group, a carbonyl group-containing group, an amide group, an ester group, an imide group, a nitrile group, a thiocyanate group, an alkoxy group, a silyl group, an alkoxysilyl group, and a nitro group. Of these, the diene rubber is preferably NR or SBR. In order to obtain better effects of the present invention, the content of the diene rubber is preferably 20 to 90 mass %, more preferably 30 to 80 mass %, and even more preferably 40 to 70 mass %, based on the total mass of the rubber composition.

[0041] <Vulcanizing agent> The rubber composition contains the vulcanizing agent of the present invention, as described above. The vulcanizing agent of the present invention and the preferred content thereof are as described above.

[0042] <Sulfur> The rubber composition may contain sulfur. Examples of the sulfur contained in the rubber composition include the sulfur described above as the sulfur that can be used to prepare the vulcanizing agent of the present invention. The preferred content of sulfur in the rubber composition is as described above.

[0043] <Vulcanization accelerator> The rubber composition may contain a vulcanization accelerator. Examples of the vulcanization accelerator contained in the rubber composition include the vulcanization accelerators described as vulcanization accelerators that can be used to produce the vulcanizing agent of the present invention. In order to obtain better effects of the present invention, the content of the vulcanization accelerator in the rubber composition is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the diene rubber.

[0044] <Filler> The rubber composition may include a filler. The filler is not particularly limited and can be used without any particular limitation. Examples of fillers include carbon black and white fillers (excluding zinc oxide). White fillers include, for example, silica, calcium carbonate, talc, and mica. In order to obtain better effects of the present invention, the content of the filler in the rubber composition is preferably 0.1 to 350 parts by mass, more preferably 10 to 200 parts by mass, and even more preferably 20 to 90 parts by mass, per 100 parts by mass of the diene rubber.

[0045] <Other ingredients> The rubber composition may contain other components in addition to the above-mentioned components. The other components may further include additives such as zinc oxide, stearic acid, and / or antioxidants. The content of these additives can be determined appropriately within a range that does not impair the object of the present invention. For example, when the rubber composition contains zinc white (zinc oxide), the content thereof is preferably 0.5 to 20 parts by mass per 100 parts by mass of the diene rubber. When the rubber composition contains stearic acid, the content thereof is preferably 0.1 to 15 parts by mass per 100 parts by mass of the diene rubber.

[0046] <Method of manufacturing rubber composition> The method for producing the rubber composition is not particularly limited, and the rubber composition can be produced by a known method for producing a rubber composition. Examples of the method for producing the rubber composition include a method in which the above-mentioned components are kneaded using an apparatus (for example, a Banbury mixer, a kneader, or a roll). In this case, the components may be mixed simultaneously or stepwise.

[0047] [Vulcanized rubber] The present invention also relates to a vulcanized rubber. The vulcanized rubber of the present invention is a vulcanized rubber obtained using the above-mentioned rubber composition. The method for producing the vulcanized rubber is not particularly limited, and examples thereof include a method in which the rubber composition is heated. The heating temperature is not particularly limited, but is preferably 130 to 200° C. The vulcanization time is preferably 10 to 240 minutes. The vulcanized rubber can be used, for example, in tires (particularly pneumatic tires), conveyor belts, hoses, golf balls, civil engineering materials such as seismic isolation rubber, industrial sealing materials, fenders, medical equipment, and the like. [Example]

[0048] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0049] [Manufacturing of vulcanizing agents] <Production of vulcanizing agent 2> 75 g of sulfur (Tsurumi Chemical Industry Co., Ltd., finely divided sulfur with Kinkaji oil) was added to the flask, and the contents of the flask were heated to a temperature of 130°C. It was confirmed that all of the sulfur in the flask had become liquid. Next, 75 g of YS Resin TO125 (manufactured by Yasuhara Chemical Co., Ltd., aromatic modified terpene resin, Mw: 1300, specific resin, containing unsaturated double bonds and aromatic rings), 15 g of limonene (specific olefin compound, molecular weight: 136), and 3 g of zinc diethyldithiocarbamate (vulcanization accelerator) were added to the flask. The temperature of the contents of the flask was adjusted to 130°C, and the adjusted temperature was maintained for 3 hours, allowing the sulfur in the flask to react with the specific resin and specific olefin compound, yielding vulcanizing agent 2. The obtained vulcanizing agent 2 was measured by a differential scanning calorimeter (DSC), and the resulting endothermic curve is shown in Figure 1. The DSC measurement was carried out at a temperature rise rate of 10°C / min. In the endothermic curve of FIG. 1, the endothermic peaks corresponding to sulfur, the specific resin, and the specific olefin compound have disappeared, which indicates that a vulcanizing agent, which is a reaction product of sulfur with the specific resin and the specific olefin compound, has been produced.

[0050] <Other vulcanizing agents> Vulcanizing agents 1 and 3 to 4 were produced in the same manner as in "Production of vulcanizing agent 2," except that the type and amount of resin, and whether or not a vulcanization accelerator was used, were changed as shown in the table below. Vulcanizing agent 1 is produced using sulfur, a specific resin, and a vulcanization accelerator, but does not use a specific olefin compound, and therefore corresponds to a comparative vulcanizing agent. Vulcanizing agent 3 corresponds to the vulcanizing agent of the present invention because sulfur, a specific resin, a specific olefin compound, and a vulcanization accelerator were used in the production of the vulcanizing agent. Vulcanizing agent 4 is produced using sulfur, a specific resin, and a specific olefin compound, but does not use a vulcanization accelerator, and therefore corresponds to a comparative vulcanizing agent. In addition, in the production of any vulcanizing agent, the total mass of the added amount of sulfur and the added amount of resin was fixed to a constant amount (150 g). FMR0150: Mitsui Chemicals, Inc., 4-methyl-α-methylstyrene-indene copolymer, Mw: 2000, specific resin. Contains aromatic rings and no unsaturated double bonds.

[0051] [Production of rubber composition] The components shown in the tables below were mixed in a 1 L Banbury mixer to prepare rubber compositions for each Example or Comparative Example. In the tables, the content of each component is shown in parts by mass relative to 100 parts by mass of diene rubber.

[0052] [Manufacturing of vulcanized rubber] The obtained rubber composition was pressed in a predetermined mold at 160° C. for 20 minutes to obtain a rubber test piece (vulcanized rubber) of each example or comparative example.

[0053] [test] <Dispersibility> The rubber composition was visually observed and the dispersibility of the vulcanizing agent was evaluated according to the following evaluation criteria. Good: No vulcanizing agent particles were observed in the rubber composition. ×: Vulcanizing agent particles can be seen in the rubber composition.

[0054] <Elongation at break> For the rubber test pieces, the elongation at break (EB) was measured at room temperature (23 °C) in accordance with JIS K6251:2017 (Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Tensile Properties). And the elongation at break index was calculated from the following formula. Elongation at break index: (EB of each rubber test piece / reference EB) × 100 In the evaluations of Comparative Examples 1-1 to 1-6 and Examples 1-1 to 1-2, the EB of the rubber test piece of Comparative Example 1-1 was used as the reference EB. In the evaluations of Comparative Examples 2-1 to 2-6 and Examples 2-1 to 2-2, the EB of the rubber test piece of Comparative Example 2-1 was used as the reference EB. The larger the elongation at break index, the more difficult it is to break, meaning excellent elongation at break.

[0055] <M300 change rate index> For the rubber test pieces before heat aging without performing the heat aging treatment described later, the 300% modulus was measured at room temperature (23 °C) in accordance with JIS K6251 (Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Heat Aging Properties). Also, for the rubber test pieces after heat aging that were subjected to a heat aging treatment of leaving them in an oven heated to 70 °C for 96 hours, the 300% modulus was also measured at room temperature (23 °C) in the same manner as above, and the change rate of the 300% modulus (M300 change rate) was determined based on the formula shown below. M300 change rate (%): 100 × { (300% modulus of the rubber test piece before heat aging) - (300% modulus of the rubber test piece after heat aging)} / (300% modulus of the rubber test piece after heat aging) And in the evaluations of Comparative Examples 1-1 to 1-6 and Examples 1-1 to 1-2, it was expressed as an index (M300 change rate index) with the M300 change rate of the rubber test piece of Comparative Example 1-1 being 100. Also, in the evaluations of Comparative Examples 2-1 to 2-6 and Examples 2-1 to 2-2, it was expressed as an index (M300 change rate index) with the M300 change rate of the rubber test piece of Comparative Example 2-1 being 100. The smaller the M300 change rate index, the less heat aging and the better the heat aging resistance.

[0056] <Wear resistance index> The abrasion loss of the rubber test pieces (rubber test pieces before heat aging) was measured at a temperature of 20°C and a slip ratio of 50% using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264-1, 2:2005. The abrasion resistance index was then calculated using the following formula. Abrasion resistance index: (standard abrasion amount / abrasion amount of each rubber test piece) x 100 In the evaluation of Comparative Examples 1-1 to 1-6 and Examples 1-1 to 1-2, the amount of wear of the rubber test piece of Comparative Example 1-1 was used as the reference amount of wear. In the evaluation of Comparative Examples 2-1 to 2-6 and Examples 2-1 to 2-2, the wear amount of the rubber test piece of Comparative Example 2-1 was used as the reference wear amount. The larger the wear resistance index, the smaller the amount of wear and the better the wear resistance.

[0057] [result] The formulations of each rubber composition and the evaluation results are shown in Tables 1 and 2 below. In the table, the descriptions in parentheses in the columns for vulcanizing agents 1 to 4 indicate the characteristics of each vulcanizing agent at the time of production. For example, the description "(FMR0150 / sulfur = 5 / 5)" for vulcanizing agent 1 indicates that when vulcanizing agent 1 was synthesized, FMR0150 and sulfur were added so that the mass ratio of FMR0150 / sulfur was 5 / 5. For example, the description "(no vulcanization accelerator used)" for vulcanizing agent 4 indicates that no vulcanization accelerator was used when synthesizing vulcanizing agent 4. Note that all of the other vulcanizing agents use a vulcanization accelerator when synthesizing them.

[0058] [Table 1]

[0059] [Table 2]

[0060] Details of the components in each composition are as follows: NR:TSR20 SBR: Nipol1502 manufactured by Nippon Zeon CB: Cabot Japan Show Black N220 Zinc oxide: Zinc oxide type 3 manufactured by Seido Chemical Industry Co., Ltd. Stearic acid: Stearic acid manufactured by NOF CORPORATION Vulcanization accelerator: Noccela NS-P manufactured by Ouchi Shinko Chemical Co., Ltd. Sulfur: Tsurumi Chemical Industry Co., Ltd. Kinka-in oil-filled fine powder sulfur Resin 1: Yasuhara Chemical YS Resin TO125, aromatic modified terpene resin, Mw: 1300 Resin 2: Arakawa Chemical Co., Ltd. Chinese Gum Rosin WW, softening point 65°C, Mw: 1000 Resin 3: Mitsui Chemicals FMR0150 (4-methyl-α-methylstyrene-indene copolymer), Mw: 2000

[0061] From the results shown in Tables 1 and 2, it was confirmed that the use of the vulcanizing agent of the present invention enables the production of rubber products that have excellent dispersibility in rubber compositions and excellent elongation at break, heat aging resistance, and abrasion resistance. In particular, a comparison between Example 1-1 and Example 1-2, and a comparison between Example 2-1 and Example 2-2 confirmed that when a specific resin having both an unsaturated double bond and an aromatic ring is used (Example 1-1 and Example 2-1), rubber products with at least better abrasion resistance can be obtained.

Claims

1. A vulcanizing agent obtained by reacting a resin having at least one of an unsaturated double bond and an aromatic ring and a weight-average molecular weight of 500 or more with an olefin compound having a weight-average molecular weight of less than 500 and sulfur in the presence of a vulcanization accelerator, wherein the resin is an aromatic-modified terpene resin or a 4-methyl-α-methylstyrene-indene copolymer.

2. 2. The vulcanizing agent of claim 1, wherein the olefinic compound comprises at least one compound selected from the group consisting of limonene, pinene, and isoprene.

3. 3. The vulcanizing agent according to claim 1, wherein the amount of sulfur used in the reaction is 30 to 90 mass% based on the total amount of sulfur used and the amount of the olefin compound used.

4. A rubber composition comprising a diene rubber and the vulcanizing agent according to any one of claims 1 to 3, A rubber composition comprising 0.5 to 10 parts by mass of the vulcanizing agent per 100 parts by mass of the diene rubber, A rubber composition that satisfies the following requirement A or requirement B. Requirement A: The rubber composition does not contain sulfur. Requirement B: The rubber composition further contains more than 0 part by mass and not more than 10 parts by mass of sulfur per 100 parts by mass of the diene rubber.

5. A vulcanized rubber obtained using the rubber composition according to claim 4.

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