JP6153853B2 - Rubber composition and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  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 that a thiosulfuric acid compound having a specific structure is blended with a rubber composition to improve the viscoelastic properties of the vulcanized rubber and improve the low heat generation performance. .

  On the other hand, Patent Document 2 discloses that in a rubber composition for a belt such as a conveyor belt, a hydrazide compound having a specific structure is blended together with a terminal-modified butadiene rubber in order to reduce energy loss. However, this document does not disclose the point of incorporating a thiohydrazide compound.

  Patent Documents 3 and 4 disclose that a compound having a thiohydrazide structure is blended in a rubber composition. However, in Patent Document 3, a —C (═NH) — group bonded to a thiohydrazide group is essential, and in Patent Document 4, a carbonyl group bonded to a thiohydrazide group, that is, —C (═O). -Is essential, and a specific hydrazide compound described later is not disclosed. Moreover, these literatures use the said compound as an anti-aging agent, and are not mentioned about the low heat_generation | fever performance.

JP 2012-107232 A JP 2006-104372 A JP 2001-139728 A Japanese Patent Laid-Open No. 11-228737

  The present inventor has previously proposed a rubber composition containing a thiohydrazide compound having a specific structure in Japanese Patent Application No. 2013-122044. Although the low exothermic performance of the rubber composition can be improved by blending the thiohydrazide compound with a filler, a new problem has been found that the scorch property deteriorates. When a vulcanization retarder such as phthalic anhydride is added to the deterioration of the scorch property, the deterioration of the scorch property can be suppressed, but the appearance is impaired by blooming.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a rubber composition that can improve the low heat generation performance without suppressing deterioration of scorch properties and without impairing the appearance. To do.

The rubber composition according to the present invention is at least 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) with respect to 100 parts by mass of the diene rubber. 0.1-5.0 parts by mass of one type, 0.1-2.0 parts by mass of at least one selected from the group consisting of metal hydrogensulfate and metal dihydrogen phosphate, and fillers 30-150 It contains mass parts.

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 15 carbon atoms, and X represents a hydrogen atom or an amino group. , A hydroxyl group, a hydrocarbon group having 1 to 15 carbon atoms, or a group represented by the following formula (3) or formula (4).

(Y in the formula represents a divalent hydrocarbon group having 1 to 15 carbon atoms.)]

  According to the present invention, low heat generation performance can be improved by blending a thiohydrazide compound having a specific structure into a rubber composition together with a filler. Further, by blending a specific inorganic acid metal salt with the thiohydrazide compound, it is possible to suppress the deterioration of the scorch property without impairing the appearance.

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

  The rubber composition according to this embodiment includes a diene rubber, at least one thiohydrazide compound selected from the group consisting of compounds represented by the general formula (1) or (2), and a specific inorganic acid. A metal salt and a filler are blended.

  The diene rubber as the 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 rubber component is basically composed only of diene rubber, but non-diene rubber may be blended within a range that does not impair the effect (for example, 20% by mass or less).

  As one embodiment, it is preferable to use natural rubber as the diene rubber. For example, in 100 parts by mass of the diene rubber, 10 parts by mass or more of natural rubber may be contained, 50 parts by mass or more of natural rubber may be contained, or natural rubber alone may be used.

  The thiohydrazide compound used in the present embodiment is a thiohydrazide derivative represented by the above formula (1) or (2), and may be a compound represented by the formula (1) alone or represented by the formula (2). The compounds may be used alone or in combination.

In the above formula (1) and ^(2), R 1, ^{R 2} and ^{R 3} each independently represent a hydrogen atom or an optionally substituted hydrocarbon group of 1 to 15 carbon atoms. The hydrocarbon group is preferably a saturated or unsaturated linear or branched alkyl group, a saturated or unsaturated cycloalkyl group, or an aromatic hydrocarbon group. As a substituent, what contains hetero atoms, such as an oxygen atom and a nitrogen atom, is mentioned, Preferably they are a hydroxyl group and / or an amino group. As an alkyl group, it is preferable that it is C1-C10, More preferably, it is 1-6, More preferably, it is 1-4. Specific 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. The cycloalkyl group preferably has 3 to 15 carbon atoms, and more preferably 3 to 10 carbon atoms. Specific examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, and the like, and an alkyl group bonded to a ring carbon atom such as a 2-methylcyclopropyl group. And the like. The cycloalkyl group is not limited to a monovalent group obtained by removing a hydrogen atom from a ring carbon atom, and may be a group formed by removing a hydrogen atom from a side chain such as a cyclopropylmethyl group. . The aromatic hydrocarbon group preferably has 6 to 15 carbon atoms, and more preferably 6 to 10 carbon atoms. Specific examples of the aromatic hydrocarbon group include an aryl group such as a phenyl group, a naphthyl group, a tolyl group, a xylyl group, a mesityl group, a cumenyl group, and an anthryl group, and an aralkyl group such as a benzyl group and a phenethyl group. Can be mentioned.

In the formulas (1) and (2), X represents a hydrogen atom, an amino group, a hydroxyl group, a hydrocarbon group having 1 to 15 carbon atoms, or a group represented by the above formula (3) or formula (4). Show. The amino group includes a primary, secondary or tertiary amino group. In addition, in the case of a secondary or tertiary amino group, the number of carbon atoms of the hydrocarbon groups as substituents is preferably 15 or less in total. Examples of the hydrocarbon group having 1 to 15 carbon atoms include a saturated or unsaturated linear or branched alkyl group, a saturated or unsaturated cycloalkyl group, and an aromatic hydrocarbon group, and R ¹ , R same as the hydrocarbon groups mentioned in ² and R ³ may be mentioned as preferred. When X is a group represented by the formula (3) or (4), it is a bifunctionalized thiohydrazide structure. Usually, the group represented by the formula (3) is represented by the formula (1). The group represented by formula (4) is introduced as X of the compound represented by formula (2), and is introduced as X of the compound represented by formula (2).

  Y in the formulas (3) and (4) represents a divalent hydrocarbon group having 1 to 15 carbon atoms, for example, a divalent alkyl group, a divalent cycloalkyl group, or a divalent aromatic group. A hydrocarbon group is mentioned. The divalent alkyl group (that is, alkanediyl group) may be linear or branched, and preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. Specific examples of the divalent alkyl group include divalent groups generated by further removing one hydrogen atom from those listed as specific examples of the monovalent alkyl group. The divalent cycloalkyl group (that is, cycloalkanediyl group) preferably has 3 to 15 carbon atoms, and more preferably 3 to 10 carbon atoms. Specific examples of the divalent cycloalkyl group include divalent groups generated by further removing one hydrogen atom from those listed as specific examples of the monovalent cycloalkyl group. The divalent aromatic hydrocarbon group preferably has 6 to 15 carbon atoms, more preferably 6 to 10 carbon atoms. Specific examples of the divalent aromatic hydrocarbon group include divalent groups produced by removing one hydrogen atom from those listed as specific examples of the monovalent aromatic hydrocarbon group ( For example, an arylene group or an aralkyldiyl group) may be mentioned.

Incidentally, ^R 1, ^{R 2} and ^{R 3} in the formula (3) and (4) is the same as ^R 1, ^{R 2} and ^{R 3} in formula (1) and (2).

In the above formula, R ¹ , R ² and R ³ are each independently preferably a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, and X is preferably an amino group.

  Specific examples of the thiohydrazide compound include the following. These compounds can be used alone or in combination of two or more.

[Compound represented by Formula (1)]
Examples of X = amino group: acetone thiosemicarbazone, formaldehyde-3-thiosemicarbazone, acetaldehyde-3-thiosemicarbazone, heptaldehyde-3-thiosemicarbazone, cyclohexylmethylketone-3-thiosemi Carbazone, benzylmethylketone-3-thiosemicarbazone, p-hydroxybenzaldehyde-3-thiosemicarbazone, acetaldehyde-4-methyl-3-thiosemicarbazone, heptaaldehyde-4-methyl-3-thiosemi Carbazone, cyclohexyl methyl ketone-4-methyl-3-thiosemicarbazone, benzylmethylketone-4-methyl-3-thiosemicarbazone, p-hydroxybenzaldehyde-4-methyl-3-thiosemicarbazone, acetaldehyde -4-butyl-3-thiocete Carbazone, heptaldehyde-4-butyl-3-thiosemicarbazone, cyclohexylmethylketone-4-butyl-3-thiosemicarbazone, benzylmethylketone-4-butyl-3-thiosemicarbazone, p-hydroxybenzaldehyde -4-butyl-3-thiosemicarbazone, acetaldehyde-4-phenyl-3-thiosemicarbazone, heptaaldehyde-4-phenyl-3-thiosemicarbazone, cyclohexylmethylketone-4-phenyl-3-thio Semicarbazone, benzyl methyl ketone-4-phenyl-3-thiosemicarbazone, p-hydroxybenzaldehyde-4-phenyl-3-thiosemicarbazone;
Examples of X = hydrocarbon groups: N′-methylidenehexanoic acid-3-thiohydrazide, N′-ethylidenehexanoic acid-3-thiohydrazide, N ′-(1-methylethylidene) hexanoic acid-3-thiohydrazide :
Examples of X = hydrogen atom: N′-methylidenemethanoic acid-3-thiohydrazide, N′-ethylidenemethanoic acid-3-thiohydrazide, N′-heptylidenemethanoic acid-3-thiohydrazide, N ′-(1 -Methylethylidene) methanoic acid-3-thiohydrazide, N '-(1-cyclohexylethylidene) methanoic acid-3-thiohydrazide, N'-(1-phenylethylidene) methanoic acid-3-thiohydrazide, N '-( 4-hydroxyphenylmethylidene) methanoic acid-3-thiohydrazide;
Examples of X = hydroxyl group: N′-methylidenehydrazinecarbothio O-acid, N′-ethylidenehydrazinecarbothio O-acid, N′-heptylidenehydrazinecarbothio O-acid, N ′-(1- Methylethylidene) hydrazinecarbothio O-acid, N '-(1-cyclohexylethylidene) hydrazinecarbothio O-acid, N'-(1-phenylethylidene) hydrazinecarbothio O-acid, N '-(4-hydroxyphenyl) Methylidene) hydrazinecarbothio O-acid;
X = examples of groups represented by formula (3): N ′ (1), N ′ (5) -di (1-methylethylidene) pentanebis (thiohydrazide), N ′ (1), N ′ (3 ) -Di (1-methylethylidene) benzene-1,3-bis (thiohydrazide).

[Compound represented by Formula (2)]
Examples of X = amino group: thiosemicarbazide, 2-methyl-3-thiosemicarbazide, 4-methyl-3-thiosemicarbazide, 4-ethyl-3-thiosemicarbazide, 4-butyl-3-thiosemicarbazide, 4-tert -Butyl-3-thiosemicarbazide, 4-hexyl-3-thiosemicarbazide, 4-allyl-3-thiosemicarbazide, 4-phenyl-3-thiosemicarbazide, 4-benzyl-3-thiosemicarbazide, 2-ethyl-3- Thiosemicarbazide, 2-cyclohexyl-3-thiosemicarbazide, 2-phenyl-3-thiosemicarbazide, 2-methyl-4-ethyl-3-thiosemicarbazide, 2-ethyl-4-ethyl-3-thiosemicarbazide, 2-cyclohexyl -4-ethyl-3-thiosemicarbazide, 2-phenyl-4-ethyl Ru-3-thiosemicarbazide;
Examples of X = hydrogen atom: methanoic acid-3-thiohydrazide, N-methylmethanoic acid-3-thiohydrazide, N-ethylmethanoic acid-3-thiohydrazide, N-cyclohexylmethanoic acid-3-thiohydrazide, N- Phenylmethanoic acid-3-thiohydrazide;
Examples of X = hydrocarbon group: hexanoic acid-3-thiohydrazide, N-methylhexanoic acid-3-thiohydrazide, N-ethylhexanoic acid-3-thiohydrazide, N-cyclohexylhexanoic acid-3-thiohydrazide, Examples of N-phenylhexanoic acid-3-thiohydrazide X = hydroxyl group: hydrazine carbothio O-acid, N-methyl hydrazine carbothio O-acid, N-ethyl hydrazine carbothio O-acid, N-cyclohexyl hydrazine carbo Thio O-acid, N-phenylhydrazine carbothio O-acid;
X = examples of groups represented by formula (4): succinic acid dithiohydrazide, adipic acid dithiohydrazide, phthalic acid dithiohydrazide, isophthalic acid dithiohydrazide, terephthalic acid dithiohydrazide.

  The compounding amount of the thiohydrazide compound is preferably 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the diene rubber. By setting it as such a compounding quantity, the improvement effect of low heat generation performance can be heightened. The compounding amount of the thiohydrazide compound is more preferably 0.3 to 4.0 parts by mass, and still more preferably 0.5 to 3.0 parts by mass.

The inorganic acid metal salt used in the present embodiment is a hydrogen sulfate metal salt and / or a dihydrogen phosphate metal salt. More specifically, these alkali metal salts include sodium salts, potassium salts, lithium salts and the like. Among these, sodium hydrogen sulfate (NaHSO ₄ ) and / or sodium dihydrogen phosphate (NaH ₂ PO ₄ ) is particularly preferably used.

  The compounding amount of these inorganic acid metal salts is preferably 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the diene rubber. By setting it as such a compounding quantity, scorch property can be improved, without impairing the improvement effect of the low heat generation performance by having added the thiohydrazide compound. The compounding amount of the inorganic acid metal salt is more preferably 0.3 to 1.5 parts by mass.

  As the filler to be blended in this embodiment, carbon black and / or silica as a reinforcing filler is preferably used. More preferably, carbon black alone or a combination of carbon black and silica is used.

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. Specifically, SAF class (N100 series), 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.

  It is preferable that the compounding quantity of a filler is 30-150 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 30-100 mass parts, More preferably, it is 40-60 mass parts. It is preferable that the compounding quantity of carbon black is 5-150 mass parts, More preferably, it is 20-100 mass parts, More preferably, it is 30-60 mass parts. The amount of silica is preferably 100 parts by mass or less. When silica is used in combination, the blending amount is preferably 10 to 80 parts by mass, and more preferably 20 to 50 parts by mass.

  In addition, when mix | blending a silica as a filler, in order to improve the dispersibility of a silica, you may mix | blend a silane coupling agent. Although the compounding quantity of a silane coupling agent is not specifically limited, It is preferable that it is 2-25 mass parts with respect to 100 mass parts of silica. The silane coupling agent is not particularly limited, and various silane coupling agents such as sulfide silane and mercaptosilane can be used.

  In the rubber composition according to the present embodiment, in addition to the above components, oil, zinc white, stearic acid, 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 rubber composition can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. For example, in the first mixing stage, the diene rubber is added and mixed with a thiohydrazide compound, an inorganic acid metal salt and a filler together with other additives excluding a vulcanizing agent and a vulcanization accelerator, and then obtained. A rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator in the final mixing stage.

  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 tread rubber and / or sidewall rubber of a pneumatic tire, and rolling resistance can be reduced to produce a tire with excellent fuel efficiency. Examples of pneumatic tires include, but are not limited to, various types of tires such as radial tires for passenger cars and heavy duty tires used for large vehicles such as trucks and buses. One embodiment is used for tread rubber of heavy duty tires. May be.

In the rubber composition according to this embodiment, the thiohydrazide compound interacts with a functional group on the surface of the filler (for example, carbonyl or carboxyl on the surface of carbon black, or a silanol group on the surface of silica). The dispersibility can be improved, and therefore the loss factor tan δ at high temperature can be reduced and the low heat generation performance can be improved. More specifically, the thiohydrazide compound of the above formula (1) is considered to be physically bonded because of its close polarity to carbonyl and carboxyl on the surface of carbon black. In the thiohydrazide compound of the above formula (2), it is considered that the amino group (—NH ₂ ) reacts with the carbonyl on the surface of the carbon black to be chemically bonded. As a result, the surface of the carbon black is modified with a thiohydrazide compound, so that the dispersibility of the carbon black is improved.

  When natural rubber is used as the diene rubber, the natural rubber generally contains a protein or phospholipid at the terminal, and these carbonyls can react with the thiohydrazide compound. Therefore, since the polar group derived from the thiohydrazide compound is introduced at the end of the natural rubber, the dispersibility of the filler such as carbon black is further improved, and tan δ at high temperature can be reduced.

  On the other hand, when the thiohydrazide compound is added, the scorch property of the rubber composition is impaired, which becomes a factor of deteriorating the productivity of rubber products such as tires. On the other hand, according to this embodiment, by blending the specific inorganic acid metal salt, it is possible to suppress the deterioration of the scorch property without impairing the appearance.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, according to the composition (parts by mass) shown in Table 1 below, first, in the first mixing stage, components other than sulfur and vulcanization accelerator are added and mixed (discharge temperature = 160 ° C.), and then obtained. In the final mixing stage, sulfur and a vulcanization accelerator were added to and mixed with the resulting mixture (discharge temperature = 90 ° C.) to prepare a tire tread rubber composition. The details of each component in Table 1 are as follows.

・ NR: RSS # 3
・ Carbon black: ISAF, “Seast 6” manufactured by Tokai Carbon Co., Ltd.
・ Sodium hydrogen sulfate: Nacalai Tesque Co., Ltd. ・ Sodium dihydrogen phosphate: Wako Pure Chemical Industries, Ltd. ・ Zinc oxide: Mitsui Metal Mining Co., Ltd. “Zinc Hua 1”
・ Stearic acid: “Beadstearic acid” manufactured by NOF Corporation
Anti-aging agent: “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
・ Vulcanization accelerator: Sanshin Chemical Industry Co., Ltd. “Sunseller CM-G”
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.

-ATS: Acetone thiosemicarbazone, manufactured by Tokyo Chemical Industry Co., Ltd.-TS: Thiosemicarbazide, manufactured by Tokyo Chemical Industry Co., Ltd.-2-MTS: 2-Methyl-3-thiosemicarbazide, Sigma-Aldrich Japan

  About each obtained rubber composition, while scorching property was evaluated, the low heat-generating performance and the external appearance property were evaluated using the test piece which vulcanized-molded at 150 degreeC x 30 minutes. Each evaluation method is as follows.

-Scorch property: Mooney scorch test in accordance with JIS K6300-1 was performed using a rheometer (L-shaped rotor), t5 value (minute) at the time of measurement at a preheating of 1 minute and a temperature of 130 ° C was obtained. It was shown as an index with a value of 100. The larger the index, the longer the scorch time, that is, the less the scorch is, and the better the scorch property is.

Low heat generation performance: Using a viscoelastic spectrometer manufactured by UBM, the loss coefficient tan δ at a frequency of 10 Hz, a static strain of 15%, a dynamic strain of ± 2.5%, and a temperature of 60 ° C. was measured. It was shown as an index. The smaller the index, the smaller the tan δ at 60 ° C., and the lower the heat generation performance (that is, the lower fuel consumption).

Appearance: Leave the vulcanized rubber piece in the room (23 ° C), and visually observe the surface of the vulcanized rubber piece before standing (0 day in the room) and after 40 days (40 days in the room). The appearance was evaluated according to the criteria.
○: The surface is black and no discoloration is observed. ×: Discoloration is observed.

  The results are as shown in Table 1, and in Comparative Examples 2 and 3 in which a specific thiohydrazide compound represented by the above formula (1) or (2) was blended with respect to Comparative Example 1 as a control, Although the low heat generation performance was improved, the scorch property deteriorated. In Comparative Example 7, in which phthalic anhydride was blended as a vulcanization retarder with respect to the blend of Comparative Example 2 in order to improve the scorch property, although the scorch property was improved, the appearance was impaired.

  On the other hand, in Examples 1 to 5 in which the thiohydrazide compound and the inorganic acid metal salt are combined, the low heat generation performance is remarkably improved without deteriorating the scorch property without impairing the appearance. It was.

Claims (3)

0.1 to 5.0 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) with respect to 100 parts by mass of the diene rubber It contains at least one kind selected from the group consisting of parts by weight, metal hydrogensulfate and metal dihydrogen phosphate, and 0.1 to 2.0 parts by weight, and 30 to 150 parts by weight of filler. Rubber composition.

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 15 carbon atoms, and X represents a hydrogen atom or an amino group. , A hydroxyl group, a hydrocarbon group having 1 to 15 carbon atoms, or a group represented by the following formula (3) or formula (4).

(Y in the formula represents a divalent hydrocarbon group having 1 to 15 carbon atoms.)] The R ¹ , R ² and R ³ in the formula each independently represent a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, and X represents an amino group. Rubber composition.   A pneumatic tire comprising the rubber composition according to claim 1.