JP6147585B2 - Rubber composition and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition, a method for producing the same, and a pneumatic tire using the rubber composition.

  Conventionally, for example, in rubber compositions used in pneumatic tires, in order to reduce rolling resistance, it has been required to make it difficult to generate heat, that is, to improve low heat generation performance, and various studies have been made. Yes.

  For example, Patent Document 1 discloses 2,2 ′ as a coupling agent for rubber-carbon black that improves the dispersibility of carbon black in a rubber composition and strengthens the chemical bond between carbon black and rubber molecules. It is disclosed that a sulfide compound such as bis (benzimidazolyl-2) ethyl disulfide is blended. However, it has been found that a sulfide compound in which an alkylene group is interposed between a sulfide group and an aromatic condensed heterocyclic ring has low reactivity with rubber molecules, and a sufficient effect cannot always be obtained.

  In Patent Document 2, in a silica-containing diene rubber composition, a polyfunctional group-containing disulfide compound is premixed with a diene rubber in order to improve processability, low heat generation performance, and wear resistance performance. Mixing silica into the mixture is disclosed. In this document, an aromatic ring-containing disulfide compound is also disclosed as a disulfide compound, but a compound containing a heterocyclic ring is not disclosed, and since an aromatic ring and a sulfide group are directly bonded, The bond is not considered strong.

  In Patent Document 3, in order to improve the low heat generation performance of the rubber composition, a disulfide compound having a specific functional group such as 4,4′-dipyridyl disulfide is premixed with diene rubber together with sulfur. It is disclosed to mix carbon black into the prepared premix. However, since the heterocycle and the sulfide group are directly bonded, it is considered that the bond with the rubber is not strong.

  Patent Document 4 discloses that a diene rubber is mixed with a mercapto group-containing silane coupling agent and an imidazole compound such as 2-mercaptobenzimidazole to form a master batch, and then kneaded with silica in the master batch. ing. However, the imidazole compound has a structure different from that of the sulfur compound used in the present invention, and is added as a radical scavenger that caps radicals generated in the diene rubber and traps radicals generated from the silane coupling agent. I'm just there.

JP 2013-23610 A JP 2010-18691 A JP 2010-18715 A JP 2012-153865 A

  By the way, in the rubber composition, it may be required to improve the wear resistance. Increasing the compounding amount of reinforcing fillers such as carbon black to improve wear resistance generally impairs low heat generation performance, so it is required to improve wear resistance without impairing low heat generation performance. .

  In view of the above points, an object of the present invention is to provide a rubber composition that can improve low heat generation performance and wear resistance performance.

The rubber composition according to the present invention comprises 0.01 to 3 parts by mass of a radical generator, a compound represented by the following general formula (1), and the following general formula (2) with respect to 100 parts by mass of the diene rubber. 0.1 to 10 parts by mass of at least one sulfur compound selected from the group consisting of the represented compounds are premixed, and the resulting premix is at least one selected from the group consisting of carbon black and silica 10 to 120 parts by mass of the reinforcing filler is added and mixed .

In the formula, R ¹ represents an alkylene group having 1 to 6 carbon atoms, R ² represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic group having 3 to 6 carbon atoms. A represents NH, NR ³ , O or S, R ³ represents a linear or branched alkyl or alkenyl group having 1 to 6 carbon atoms, or 3 to 6 carbon atoms. A cyclic alkyl group or an alkenyl group. x shows the integer of 1-4.

The method for producing a rubber composition according to the present invention is selected from the group consisting of a diene rubber, a radical generator, a compound represented by the general formula (1) and a compound represented by the general formula (2). A step of premixing the at least one sulfur compound formed, and a step of adding and mixing at least one reinforcing filler selected from the group consisting of carbon black and silica to the obtained premix. Is included. And in invention of Claim 1 , the said sulfur compound is a compound represented by the said General formula (1). In the invention described in claim 2 , the radical generator is at least one selected from the group consisting of o, o'-dibenzamide diphenyl disulfide, zinc salt of o-benzamidothiophenol, xylyl mercaptan, and β-naphthyl mercaptan. It is a seed. In the invention according to claim 3 , in the preliminary mixing, the mixing is performed by a kneader until the temperature of the preliminary mixture reaches a temperature of 90 ° C or higher and lower than 140 ° C.

  The pneumatic tire according to a preferred embodiment of the present invention uses the rubber composition for at least a part thereof.

  According to the present invention, a sulfur compound having a specific structure is premixed with a diene rubber together with a radical generator, and a reinforcing filler is mixed with the obtained premixture, whereby low heat generation performance, wear resistance performance and Aging resistance can be improved in a well-balanced manner.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition according to this embodiment is obtained by premixing a diene rubber with a specific sulfur compound together with a radical generator, and adding and mixing a reinforcing filler to the obtained premix.

  In the rubber composition, the diene rubber as a rubber component is not particularly limited. Examples of usable diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber, butadiene-isoprene rubber, and styrene-butadiene. -Isoprene rubber, nitrile rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like can be mentioned, and these can be used alone or in combination of two or more. More preferably, it is NR, SBR, BR, or a blend rubber of two or more thereof.

The diene rubber was also selected from the group consisting of an amino group, a hydroxyl group, an epoxy group, an alkoxy group, an alkylsilyl group, an alkoxysilyl group, and a carboxyl group at the molecular terminal or molecular chain of those listed above. A modified diene rubber modified with the functional group by introducing at least one functional group may be used. These functional groups interact with the functional groups on the surface of particles such as silica and carbon black (for example, silanol groups on the silica surface, carboxyl groups, phenolic hydroxyl groups, and quinone groups on the carbon black surface) (reactivity and affinity). ) And the dispersibility of the reinforcing filler can be improved. Here, the amino group may be not only a primary amino group but also a secondary or tertiary amino group. In the case of a secondary or tertiary amino group, the total number of carbon atoms of the hydrocarbon groups that are substituents is preferably 15 or less. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group represented as -OR (where R is an alkyl group having 1 to 4 carbon atoms, for example). Examples of the alkylsilyl group include a trimethylsilyl group, a triethylsilyl group, and a tert-butyldimethylsilyl group represented by —SiR ₃ (wherein R is an alkyl group having 1 to 4 carbon atoms, for example). Examples of the alkoxysilyl group include those in which at least one of the three alkyl groups of the alkylsilyl group is substituted with the alkoxy group, such as trialkoxysilyl group, alkyldialkoxysilyl group, dialkylalkoxysilyl group, etc. Is mentioned. As the modified diene rubber, modified SBR and / or modified BR are preferable.

  In the rubber composition of this embodiment, the diene rubber may be a modified diene rubber alone or a blend of a modified diene rubber and an unmodified diene rubber. The modified diene rubber can be used at 1 to 100 parts by mass, preferably 10 to 80 parts by mass, more preferably 20 to 50 parts by mass, out of 100 parts by mass of the diene rubber.

The sulfur compound used in the present embodiment is at least one selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following general formula (2). The compound represented by the formula (1) is a thiol compound in which an aromatic condensed heterocycle is bonded to a mercapto group via an alkylene group, and the compound represented by the formula (2) is present at both ends of the sulfide group. It is a sulfide compound having a structure in which an aromatic condensed heterocycle is bonded via an alkylene group (bis structure).

In these formulas (1) and (2), R ¹ represents an alkylene group having 1 to 6 carbon atoms (that is, an alkanediyl group), and may be linear or branched. Specific examples of R ¹ include a methylene group, an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, and a hexamethylene group. Preferably, R ¹ is a linear alkylene group represented by — (CH ₂ ) _n —, where n is an integer of 1 to 6 (preferably an integer of n = 1 to 3).

R ² in the formulas (1) and (2) is a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. Indicates. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, and an n-hexyl group. Are those having 1 to 4 carbon atoms. As an alkenyl group, a vinyl group, an allyl group, etc. are mentioned, for example, Preferably it is a C1-C4 thing. Examples of the cyclic alkyl group or alkenyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like, and an alkyl group bonded to a ring carbon atom such as a 2-methylcyclopropyl group. It may have a substituent, and further may be a group formed by removing a hydrogen atom from a side chain, such as a cyclopropylmethyl group.

A in the formulas (1) and (2) represents NH, NR ³ , O or S. In the case of NH or NR ³ , the heterocyclic ring is a benzimidazolyl group, and in the case of O, the heterocyclic ring is a benzoxazolyl. In the case of S, the heterocyclic ring is a benzthiazolyl group. Among these, NH is particularly preferable from the viewpoint of physical bonding to the silanol group on the silica surface. R ³ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. Specific examples and preferred carbon numbers thereof are those described above for R Same as ² .

  X in Formula (2) is an integer of 1-4, More preferably, it is an integer of 2-4.

  Specific examples of the thiol compound represented by the formula (1) include 2- (benzimidazolyl 2) ethane-1-thiol, 2- (5-methyl-benzimidazolyl-2) ethane-1-thiol, 2- (Benzimidazolyl-2) propane-1-thiol, 2- (5-methyl-benzimidazolyl-2) propane-1-thiol, 3- (benzimidazolyl-2) propane-1-thiol, 4- (benzimidazolyl- 2) Butane-1-thiol, 5- (benzimidazolyl-2) pentane-1-thiol, 6- (benzimidazolyl-2) hexane-1-thiol, 2- (benzoxazolyl-2) ethane-1- Thiol, 2- (benzoxazolyl-2) propane-1-thiol, 3- (benzoxazolyl-2) propane-1-thiol, 4- ( Nzoxazolyl-2) butane-1-thiol, 5- (benzoxazolyl-2) pentane-1-thiol, 6- (benzoxazolyl-2) hexane-1-thiol, 2- (benzthiazolyl-2) ethane -1-thiol, 2- (benzthiazolyl-2) propane-1-thiol, 3- (benzthiazolyl-2) propane-1-thiol, 4- (benzthiazolyl-2) butane-1-thiol, 5- (benzthiazolyl-2) ) Pentane-1-thiol, 6- (benzthiazolyl-2) hexane-1-thiol, and the like, and these may be used alone or in combination of two or more.

  Specific examples of the sulfide compound represented by the formula (2) include bis (benzimidazolyl-2) methyl sulfide, 2,2′-bis (benzimidazolyl-2) ethyl sulfide, and 2,2′-bis (benzimidazolyl). -2) Ethyl disulfide, 2,2'-bis (benzimidazolyl-2) ethyl trisulfide, 2,2'-bis (benzimidazolyl-2) ethyl tetrasulfide, 3,3'-bis (benzimidazolyl-2) Propyl disulfide, 4,4′-bis (benzimidazolyl-2) butyl disulfide, 5,5′-bis (benzimidazolyl-2) pentyl disulfide, 6,6′-bis (benzimidazolyl-2) hexyl disulfide, 2, 2′-bis (1-methylbenzimidazolyl-2) ethyl disulfide, 2,2 -Bis (benzoxazolyl-2) ethyl disulfide, 2,2'-bis (benzoxazolyl-2) ethyl tetrasulfide, 2,2'-bis (4-methylbenzoxazolyl-2) ethyl disulfide 2,2′-bis (benzthiazolyl-2) ethyl disulfide, 2,2′-bis (benzthiazolyl-2) ethyl tetrasulfide, and the like, which can be used alone or in combination of two or more. .

  Examples of the thiol compound represented by the formula (1) include a 1,2-diaminobenzene compound, a 2-aminothiophenol compound, a 2-aminophenol compound, a mercaptocarboxylic acid compound, and 4N It can synthesize | combine by making it react in hydrochloric acid. Examples of the sulfide compound represented by the formula (2) include a 1,2-diaminobenzene compound, a 2-aminothiophenol compound, or a 2-aminophenol compound, and a thiodicarboxylic acid compound as 4N. It can synthesize | combine by making it react in hydrochloric acid.

  Examples of the 1,2-diaminobenzene compounds include 1,2-diaminobenzene, 2,3-tolylenediamine, 1,2-diamino-3-ethylbenzene, 1,2-diamino-3-n-propylbenzene. 1,2-diamino-3-isopropylbenzene, 1,2-diamino-3-n-butylbenzene and the like. Examples of the 2-aminothiophenol compound include 2-aminothiophenol, 2-amino-3-methylthiophenol, 2-amino-3-ethylthiophenol, 2-amino-3-n-propylthiophenol, 2 -Amino-4-methylthiophenol, 2-amino-4-ethylthiophenol, 2-amino-4-n-propylthiophenol, 2-amino-5-methylthiophenol, 2-amino-5-ethylthiophenol, 2 -Amino-5-n-propylthiophenol, 2-amino-6-methylthiophenol, 2-amino-6-ethylthiophenol, 2-amino-6-n-propylthiophenol and the like. Examples of 2-aminophenol compounds include 2-aminophenol, 2-amino-3-methylphenol, 2-amino-3-ethylphenol, 2-amino-3-n-propylphenol, and 2-amino-4. -Methylphenol, 2-amino-4-ethylphenol, 2-amino-4-n-propylphenol, 2-amino-5-methylphenol, 2-amino-5-ethylphenol, 2-amino-5-n- Examples include propylphenol, 2-amino-6-methylphenol, 2-amino-6-ethylphenol, and 2-amino-6-n-propylphenol. Examples of mercaptocarboxylic acid compounds include thioglycolic acid, mercaptopropionic acid, mercaptobutanoic acid, mercaptopentanoic acid, mercaptohexanoic acid, and the like. Examples of the thiodicarboxylic acid compound include thiodiglycolic acid, dithiodiglycolic acid, tetrathiodiglycolic acid, thiodipropionic acid, dithiodipropionic acid, trithiodipropionic acid, tetrathiodipropionic acid, dithiodibutyric acid. Tetrathiodibutyric acid, dithiodipentylic acid, tetrathiodipentylic acid, dithiodihexylic acid, tetrathiodihexylic acid and the like.

  It is preferable that the compounding quantity of the sulfur compound represented by Formula (1) or (2) is 0.1-10 mass parts with respect to 100 mass parts of diene rubbers. By setting it as such a compounding quantity, the improvement effect of low heat generation performance, abrasion resistance performance, and anti-aging performance can be heightened. The amount of the sulfur compound is more preferably 0.5 to 5 parts by mass, still more preferably 1 to 4 parts by mass.

  As the radical generator used in the present embodiment, those capable of generating oxygen radicals, carbon radicals, or sulfur radicals during premixing with the diene rubber can be used, and are selected from peptizers and sulfur. It is preferable that it is at least one kind. In particular, it is more preferable to use a peptizer because it can generally exhibit an effect at a lower temperature than sulfur.

  Examples of the peptizer (peptizer) include o, o'-dibenzamide diphenyl disulfide, zinc salt of o-benzamidothiophenol, xylyl mercaptan, β-naphthyl mercaptan, and the like. These may be used alone or in combination of two or more.

  Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. These may be used alone or in combination of two or more.

  The blending amount of the radical generator is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 2 parts by mass, and still more preferably 0.1 to 100 parts by mass of the diene rubber. -1.0 mass part. Moreover, it is preferable that the compounding quantity of a radical generator is 20 mass parts or less with respect to 100 mass parts of sulfur compounds represented by Formula (1) or (2), More preferably, it is 5-15 mass parts. .

  The reinforcing filler used in the present embodiment is carbon black and / or silica, that is, carbon black alone, silica alone, or a combination of carbon black and silica may be used. More preferably, the reinforcing filler is made of carbon black or carbon black and silica.

Carbon black is not particularly limited, and various known varieties can be used. For example, when used for tire tread rubber, those having a nitrogen adsorption specific surface area (N ₂ SA) (JIS K6217-2) of 70 to 150 m ² / g are preferably used, and specifically, SAF class (N100 range). ISAF class (N200 series), HAF class (N300 series) (both ASTM grade) are preferably used.

The silica is not particularly limited, but wet silica such as wet precipitation silica or wet gel silica is preferably used. BET specific surface area of the silica (measured according to BET method according to JIS K6430) is not particularly limited, is preferably 90~250m ² / g, more preferably 150~220m ² / g.

  The compounding amount of the reinforcing filler is preferably 10 to 120 parts by mass, more preferably 20 to 120 parts by mass, and further preferably 30 to 100 parts by mass with respect to 100 parts by mass of the diene rubber. More preferably, it is 40-100 mass parts. The compounding amount of carbon black is preferably 3 to 120 parts by mass, more preferably 10 to 120 parts by mass, still more preferably 20 to 100 parts by mass, and in one embodiment, even 30 to 80 parts by mass. Good. It is preferable that the compounding quantity of a silica is 100 mass parts or less, for example, 10-80 mass parts may be sufficient, and 20-50 mass parts may be sufficient. In one embodiment, the compounding amount of carbon black may be more than the compounding amount of silica.

  When silica is blended as a reinforcing filler, a silane coupling agent may be blended in order to improve the dispersibility of silica. Although the compounding quantity of a silane coupling agent is not specifically limited, It is preferable that it is 2-20 mass% of the compounding quantity of a silica (namely, 2-20 mass parts of silane coupling agents with respect to 100 mass parts of silica), More preferably, it is 5-15 mass%. The silane coupling agent is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis Sulfide silane coupling agents such as (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide; 3-mercaptopropyltrimethoxysilane, 3- Mercaptosilane coupling agents such as mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane; Examples thereof include protected mercaptosilane coupling agents such as tanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane. These can be used alone or in combination of two or more.

  In the rubber composition according to the present embodiment, in addition to the above components, zinc oxide, stearic acid, oil, anti-aging agent, softener, wax, vulcanizing agent, vulcanization accelerator, etc. Various commonly used additives can be blended. Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount is 100 parts by mass of diene rubber. It is preferable that it is 0.1-10 mass parts with respect to it, More preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 0.5-5 mass parts.

  The method for producing a rubber composition according to the present embodiment includes a step of premixing a diene rubber with a radical generator and the specific sulfur compound (preliminary mixing step), and a reinforcing property to the premixture obtained thereby. And a step of adding and mixing a filler (usually a mixing step). These mixing can be performed using kneading machines, such as a Banbury mixer, a kneader, and a roll, which are generally used for mixing rubber compositions.

  In the preliminary mixing step (first step), 0.01 to 3 parts by mass of the radical generator and 0.1 to 10 parts by mass of the specific sulfur compound are added to 100 parts by mass of the diene rubber, and a kneader is added. The master batch which is a pre-mixture is produced by pre-mixing using. During the premixing, the sulfur compound can be reacted with the rubber molecules of the diene rubber by the action of radicals generated from the radical generator.

  In the preliminary mixing step, a silane coupling agent may be blended. By premixing together with the silane coupling agent, the effect of improving the low heat generation performance, wear resistance performance and fatigue resistance performance can be further enhanced. The compounding amount of the silane coupling agent is basically 2 to 20% by mass of the compounding amount depending on the compounding amount of the reinforcing filler usually added in the mixing step, so that the premixing step The ratio with respect to the diene rubber is not necessarily important, but is preferably 0.5 to 20 parts by weight, and more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the diene rubber.

  In the premixing step, a diene rubber, a radical generator, the specific sulfur compound, and a silane coupling agent are optionally mixed. Basically, other components (such as a vulcanization accelerator) The above various additives) are not mixed. Also, it is preferred that the reinforcing filler is not blended in the premixing step, and therefore the premix does not substantially contain the reinforcing filler. Here, substantially not containing means that the amount of the reinforcing filler is 20% by mass or less based on the total amount of the premix. More preferably, the amount of the reinforcing filler is 10% by mass or less, more preferably 5% by mass or less, based on the total amount of the premix.

  The premixing step is performed for reacting the diene rubber with the specific sulfur compound, and it is preferable to mix with a kneader until the temperature of the premix reaches 90 to 160 ° C. The rubber kneading in the closed kneader is usually started at 30 to 80 ° C., the temperature rises with the kneading, and is discharged when the temperature reaches a predetermined temperature (discharge temperature). In the premixing step, it is preferable that the discharge temperature is in the range of 90 to 160 ° C. When a peptizer is used as the radical generator, the above reaction can be performed by generating radicals at a lower temperature range, so by lowering the upper limit of the kneading temperature, the thermal degradation of the diene rubber can be suppressed and Abrasion performance and anti-aging performance can be improved. The discharge temperature is more preferably 90 ° C. or higher and lower than 140 ° C., and further preferably 100 to 130 ° C. The kneading time is basically controlled by the discharge temperature and is not particularly limited, but is preferably 30 to 300 seconds.

  In the normal mixing step, a rubber composition is prepared by adding and mixing a reinforcing filler composed of carbon black and / or silica to the premix obtained above. By adding and mixing the reinforcing filler to the pre-mixture obtained by reacting the sulfur compound with the diene rubber, the sulfur compound and the reinforcing filler are combined by interaction, resulting in low heat generation performance, wear resistance performance and resistance. Aging performance can be improved. The amount of the reinforcing filler that is usually added in the mixing step is the same as the blending amount of the reinforcing filler described above.

  In the normal mixing step, the above various additives can be blended together with the reinforcing filler. In the normal mixing step, other diene rubbers may be additionally blended in addition to the diene rubber blended as the premix within a range that does not impair the above-described effects.

  The normal mixing process can be further divided into two mixing processes. That is, a second step of mixing at least a reinforcing filler with the preliminary mixture, and then a third step of blending and mixing sulfur as a vulcanizing agent and a vulcanization accelerator into the obtained mixture (final mixing step). You may divide and implement. In this case, usually, in the second step, other additives such as a silane coupling agent, zinc white, oil, anti-aging agent and stearic acid are blended together with the reinforcing filler, and these are kneaded with the above premix. The And in the 3rd process, sulfur and a vulcanization accelerator are added and knead | mixed with respect to the obtained mixture, and the last rubber composition is prepared. The kneading temperature in the second step (i.e., the discharge temperature from the kneader) is not particularly limited, and can be set in accordance with normal non-pro kneading, for example, preferably 120 to 170 ° C. Preferably it is 130-160 degreeC. The kneading temperature in the third step (i.e., the discharge temperature from the kneader) is not particularly limited, and can be set according to ordinary professional kneading, for example, preferably 70 to 110 ° C, more Preferably it is 80-100 degreeC.

  The rubber composition according to this embodiment can be used for various rubber compositions that form rubber parts such as pneumatic tires, vibration-proof rubbers, and conveyor belts. Preferably, it is used for tires, and rubber parts of various pneumatic tires can be constituted by vulcanization molding at 140 to 180 ° C., for example, according to a conventional method. As one embodiment, it is preferably used for a tread rubber and / or sidewall rubber of a pneumatic tire, and a tire excellent in low fuel consumption performance by reducing rolling resistance and in wear resistance and fatigue resistance is manufactured. be able to.

  According to this embodiment, the following effects are exhibited. When the reinforcing filler contains carbon black, the aromatic condensed heterocycle of the sulfur compound interacts with carbon black, and the sulfur portion reacts with the rubber, thereby binding the carbon black and the rubber. Strengthens and improves low heat generation performance and wear resistance. Here, if the heterocyclic ring and sulfur are directly bonded, even if they are bonded to the rubber molecule, the cleavage is likely to occur at the same time, and the degree of bonding decreases. However, in the specific sulfur compound described above, there is a gap between the heterocyclic ring and sulfur. Since an alkylene group is inserted into the ring, cleavage of the bond with the rubber molecule is suppressed, so that the aging resistance can be improved. On the other hand, when the alkylene group is inserted, the reactivity to the rubber molecule is low. However, in the present embodiment, the reactivity can be increased by performing preliminary mixing using a radical generator. .

  Further, even when the reinforcing filler contains silica, when the specific sulfur compound is used, the amino group in the aromatic condensed heterocyclic ring and the surface silanol group of the silica are physically bonded, so that the silica and the rubber The bond can be enhanced to improve the low heat generation performance, wear resistance performance and aging resistance performance. Furthermore, since the heterocyclic ring of the sulfur compound is basic, it is considered that the hydrolysis of the alkoxy group in the silane coupling agent is promoted and the reactivity between silica and the silane coupling agent is improved. Therefore, the sulfur compound is effective both when silica is used as the reinforcing filler and when carbon black and silica are used in combination.

Examples of the present invention will be described below, but the present invention is not limited to these examples. Examples 3, 8, and 13 are reference examples. The raw materials used in the examples and comparative examples are as follows.

[raw materials]
・ NR: RSS3 ・ SBR: “VSL5025-0HM” manufactured by LANXESS
-Modified SBR: alkoxy group and amino group terminal modified solution polymerization SBR, "HPR355" manufactured by JSR Corporation
・ BR: “BR01” manufactured by JSR Corporation
-Modified BR: butadiene rubber with tin coupling and amino group introduced, "BR1250H" manufactured by Nippon Zeon Co., Ltd.
Carbon black: HAF, “Seast 3” manufactured by Tokai Carbon Co., Ltd. (N ₂ SA = 79 m ² / g)
・ Silica: “Ultrasil VN3” manufactured by Evonik Degussa
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik Degussa
-Oil: "Extract No. 4 S" manufactured by Showa Shell Sekiyu KK
・ Zinc flower: "Zinc flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: “Lunac S20” manufactured by Kao Corporation
Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Wax: Nippon Seiwa Co., Ltd. “OZOACE0355”
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator 1: “Sokushinol CZ” manufactured by Sumitomo Chemical Co., Ltd.
・ Vulcanization accelerator 2: “Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Compound A: 2-mercaptobenzimidazole, “NOCRACK MB” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Compound B: di-2-benzothiazolyl disulfide, “Noxeller DM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Compound C: 2,2′-bis (benzimidazolyl-2) ethyl disulfide (synthesized according to Reference Example 1 in paragraph 0033 in JP2013-23610)
Compound D: 2- (benzimidazolyl-2) ethane-1-thiol (Synthesis Example 1 below)
-Peptizer: o, o'-dibenzamide diphenyl disulfide, "Nokutizer SS" manufactured by Ouchi Shinsei Chemical Co., Ltd.

The chemical formulas of compounds C and D are as follows.

[Synthesis Example 1]
A reaction vessel was charged with 1000 mL of 4N hydrochloric acid, 108 g of 1,2-diaminobenzene, and 106 g of 3-mercaptopropionic acid, and allowed to react at 95 ° C. for 12 hours while stirring. Thereafter, 560 mL of 25% aqueous ammonia was added and stirred at room temperature, and then the precipitate was separated, washed and dried to obtain 150 g of a reaction product. The obtained reaction product was analyzed by ¹ H-NMR and ¹³ C-NMR, and confirmed to be 2- (benzimidazolyl-2) ethane-1-thiol.

[First embodiment]
Rubber compositions for tire treads of Examples and Comparative Examples were prepared using a Banbury mixer in accordance with the formulation shown in Table 1 below (parts by mass unless otherwise specified). Specifically, in Example 1, compound C and peptizer were added and kneaded to the diene rubber in the first step (starting kneading from 75 ° C. and discharging at 160 ° C.), and then to the resulting pre-kneaded product. In the second step, components other than sulfur and vulcanization accelerator are added and kneaded (discharge temperature = 160 ° C.), and then in the third step, sulfur and vulcanization accelerator are added and kneaded in the third step. (Discharge temperature = 90 ° C.) to prepare a rubber composition. In Examples 2 to 5, the components added in the first step are changed as shown in Table 1 with respect to Example 1, and in Examples 6 to 10, the exhaust temperature in the first step is compared to Examples 1 to 5. Was changed from 160 ° C to 120 ° C. Comparative Examples 1 to 6 are examples in which the first step is omitted. Comparative Examples 7 to 11 are examples prepared by changing the components to be blended in the first step and the other components in the same manner as in Example 1.

  About each obtained rubber composition, it vulcanized | cured at 150 degreeC x 30 minutes, the test piece was produced, and the low heat_generation | fever performance, abrasion resistance, and anti-aging performance were evaluated. Each evaluation method is as follows.

Low heat generation performance: According to JIS K6394, the loss factor tan δ was measured under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of 2%, and displayed as an index with the value of Comparative Example 1 being 100. . The smaller the index is, the smaller the tan δ is, and the lower the heat generation performance is, and the better the fuel efficiency is due to the reduction in rolling resistance.

・ Abrasion resistance performance: In accordance with JIS K6264, the wear amount was measured at a load of 3 kg, a slip rate of 20%, a temperature of 23 ° C., and a sandfall rate of 20 g / min using a Lambone abrasion tester, and the reciprocal of the wear amount was compared. Displayed as an index with the value of Example 1 as 100. Larger values indicate better wear resistance performance.

-Aging resistance performance: The test piece was heated in a gear oven adjusted to 90 ° C. for 168 hours to give a thermal history, then subjected to a tensile test according to JIS K6251 to measure the breaking strength, and before aging The retention rate of the rupture strength after aging with respect to the rupture strength was determined and expressed as an index with the value of Comparative Example 1 being 100. A larger index means higher retention and better aging resistance.

  The results are as shown in Table 1. Examples in which the sulfur compound represented by the above formula (1) or formula (2) was premixed in a diene rubber together with a radical generator with respect to Comparative Example 1 as a control. When it was 1 to 10, a remarkable improvement effect was obtained in low heat generation performance, wear resistance performance and aging resistance performance. Further, as is clear from the comparison between Examples 1 and 2 and Examples 3 and 4 and the comparison between Examples 6 and 7 and Examples 8 and 9, as the radical generator, peptizer is more preferable. It was more effective than sulfur. Further, as in Examples 6 and 7, when a peptizer is used as the radical generator, it is possible to process at a low temperature, so that the discharge temperature in the first step is reduced to 120 ° C. The effect of wear resistance and aging resistance was further improved by suppressing molecular degradation. Further, as in Examples 5 and 10, by using the modified diene rubber, a further improvement effect was obtained in terms of low heat generation performance, wear resistance performance and aging resistance performance.

  On the other hand, in Comparative Examples 4 and 5, the sulfur compound represented by Formula (1) or Formula (2) was used, but no premixing was performed. Not only slightly inferior, but also inferior in the effect of improving wear resistance and aging resistance. In Comparative Examples 8 and 9, since the compounds A and B in which the aromatic condensed heterocycle and sulfur were directly bonded were used, the effect of improving the low heat generation performance was obtained, but the bond between the compound and the rubber molecule was cleaved. It was easy and the effect of improving wear resistance and aging resistance was small. In Comparative Examples 10 and 11, since the radical generator was not added during the premixing, the improvement effect was insufficient.

[Second Embodiment]
Using a Banbury mixer, a rubber composition for a tire tread was prepared in the same manner as in the first example according to the formulation (parts by mass) shown in Table 2 below. The obtained rubber composition was vulcanized at 150 ° C. for 30 minutes to prepare a test piece, and the low heat generation performance, wear resistance performance and aging resistance performance were evaluated. Each evaluation method is the same as that of the first example, but all are shown as indexes with the value of Comparative Example 12 as 100.

  The results are as shown in Table 2. Even when carbon black and silica were used in combination, the sulfur compound represented by the above formula (1) or (2) was premixed in the diene rubber together with the radical generator. As a result, as shown in Examples 11 to 14, a remarkable improvement effect was obtained in low heat generation performance, wear resistance performance and aging resistance performance. Further, in the preliminary mixing step, by further adding a silane coupling agent, as shown in Examples 15 and 16, further improvement effects were obtained in low heat generation performance, wear resistance performance and aging resistance performance.

Claims (7)

A step of premixing a diene rubber with a radical generator and a sulfur compound represented by the following general formula (1);
Adding and mixing at least one reinforcing filler selected from the group consisting of carbon black and silica to the resulting premix; and
The manufacturing method of the rubber composition containing this.

(In the formula, R ¹ represents an alkylene group having 1 to 6 carbon atoms, R ² represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or 3 to 6 carbon atoms. A cyclic alkyl group or an alkenyl group, A represents NH, NR ³ , O or S, R ³ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or 3 to 3 carbon atoms 6 represents a cyclic alkyl group or an alkenyl group. Diene rubber, at least one radical generator selected from the group consisting of o, o′-dibenzamide diphenyl disulfide, zinc salt of o-benzamidothiophenol, xylyl mercaptan, and β-naphthyl mercaptan; A step of premixing at least one sulfur compound selected from the group consisting of a compound represented by the general formula (1) and a compound represented by the following general formula (2);
Adding and mixing at least one reinforcing filler selected from the group consisting of carbon black and silica to the resulting premix; and
The manufacturing method of the rubber composition containing this.

(In the formula, R ¹ represents an alkylene group having 1 to 6 carbon atoms, R ² represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or 3 to 6 carbon atoms. A cyclic alkyl group or an alkenyl group, A represents NH, NR ³ , O or S, R ³ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or 3 to 3 carbon atoms 6 represents a cyclic alkyl group or an alkenyl group of 6. x represents an integer of 1 to 4.) The diene rubber is premixed with a radical generator and at least one sulfur compound selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following general formula (2). Process,
Adding and mixing at least one reinforcing filler selected from the group consisting of carbon black and silica to the resulting premix; and
Including
A method for producing a rubber composition, wherein in the preliminary mixing, mixing is performed with a kneader until the temperature of the preliminary mixture reaches a temperature of 90 ° C or higher and lower than 140 ° C.

(In the formula, R ¹ represents an alkylene group having 1 to 6 carbon atoms, R ² represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or 3 to 6 carbon atoms. A cyclic alkyl group or an alkenyl group, A represents NH, NR ³ , O or S, R ³ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or 3 to 3 carbon atoms 6 represents a cyclic alkyl group or an alkenyl group of 6. x represents an integer of 1 to 4.) The method for producing a rubber composition according to claim 1 or 3, wherein the radical generator is a peptizer. The method for producing a rubber composition according to claim 1 or 3, wherein the radical generator is sulfur. A modified diene rubber wherein the diene rubber is modified with at least one functional group selected from the group consisting of an amino group, a hydroxyl group, an epoxy group, an alkoxy group, an alkylsilyl group, an alkoxysilyl group and a carboxyl group. It contains, The manufacturing method of the rubber composition of any one of Claims 1-5 characterized by the above-mentioned. The manufacturing method of the pneumatic tire which manufactures a rubber composition by the method of any one of Claims 1-6 , and manufactures a pneumatic tire using the obtained rubber composition .