JP5767548B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

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

Conventionally, with regard to tread rubber, nitrogen compounds and acids are blended to form hydrogen bonds or compounds with ionic bonds to increase hysteresis loss (tan δ) and grip performance (grips on dry road surfaces) Performance) was improved (Patent Documents 1 to 5).

However, by blending a nitrogen compound and an acid and / or a compound having an ionic bond, the grip performance is improved, but there is a problem in that crosslinking is insufficient or blow occurs due to large heat generation. is there. Accordingly, it is desired to improve the grip performance and sufficiently crosslink to obtain desired rubber physical properties and at the same time to prevent blowout.

JP 2008-163108 A JP-A-2005-112922 JP 2006-124423 A JP 2008-163109 A JP 2007-138101 A

An object of the present invention is to solve the above problems and provide a rubber composition for a tire that can improve the grip performance, blow resistance, and wear resistance in a well-balanced manner, and a pneumatic tire using the same.

The present invention comprises a rubber component, an acid and a nitrogen compound, and / or at least one compound selected from the group consisting of an organic carboxylic acid metal salt, a thiocarboxylate and a phosphate,
The present invention relates to a tire rubber composition comprising fine zinc oxide having an average primary particle size of 300 nm or less and a complex obtained by mixing fatty acid at a temperature equal to or higher than the melting point of the fatty acid.

In the complex, the content of the fine particle zinc oxide in a total of 100% by mass of the fine particle zinc oxide and the fatty acid is preferably 10 to 90% by mass.
It is preferable that 0.1 to 20 parts by mass of the fine particle zinc oxide is included with respect to 100 parts by mass of the rubber component.
The rubber composition is preferably used as a tread rubber composition.

The present invention also relates to a pneumatic tire produced using the rubber composition.
The pneumatic tire is preferably a competition tire.

According to the present invention, the rubber component, the acid and the nitrogen compound, and / or at least one compound selected from the group consisting of an organic carboxylic acid metal salt, a thiocarboxylate and a phosphate, and the average primary particle size Is a rubber composition for tires containing a fine particle zinc oxide of 300 nm or less and a complex obtained by mixing the fatty acid at a temperature equal to or higher than the melting point of the fatty acid, so that the grip performance, blow resistance and wear resistance are well balanced. By applying the rubber composition to a tread or the like, it is possible to provide a pneumatic tire excellent in these performance balances.

It is a figure which shows the measurement result of FT-IR of the complex prepared in manufacture example 1.

The tire rubber composition of the present invention comprises a rubber component, an acid and a nitrogen compound, and / or at least one compound selected from the group consisting of organic carboxylic acid metal salts, thiocarboxylates and phosphates, And a complex obtained by mixing fine zinc oxide having an average primary particle size of 300 nm or less and a fatty acid at a temperature equal to or higher than the melting point of the fatty acid.

By adding fine zinc oxide to the compound, the vulcanization of the rubber composition is optimized, and the fracture nuclei of the rubber are also reduced, so that the blow resistance can be improved. However, there is a problem that it becomes difficult to disperse the fine zinc oxide. Therefore, when using fine particles having an average primary particle size of 300 nm or less, a high level of dispersion technique is required, and for example, a large number of kneading times are required, resulting in a decrease in productivity. On the other hand, if the kneading is insufficient, the blow resistance may be deteriorated due to poor dispersion.

In the present invention, a complex obtained by mixing finely divided zinc oxide and a fatty acid, which are difficult to disperse, at a temperature equal to or higher than the melting point of the fatty acid is used after being easily dispersed. That is, premixing makes a complex state of fatty acid zinc, which can be easily dispersed, so that it can be highly dispersed by kneading several times without increasing the number of times of special kneading. Therefore, it is possible to uniformly disperse the fine zinc oxide, and the blow resistance can be greatly improved while obtaining good productivity. In addition, since a good cross-linked state can be obtained, the wear resistance is excellent, and the grip performance is also excellent by adding the above compound. Therefore, in the present invention, it is possible to improve the grip performance, blow resistance, and wear resistance in a well-balanced manner while obtaining good productivity.

Examples of rubber components that can be used in the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber ( IIR) and diene rubbers such as styrene-isoprene-butadiene copolymer rubber (SIBR) may be used. These diene rubbers may be used alone or in combination of two or more. Among these, SBR is preferable because high tan δ can be obtained.

The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR) and the like can be used. Among these, S-SBR is preferable because blowout hardly occurs.

The styrene content of SBR is preferably 25% by mass or more, more preferably 30% by mass or more. If it is less than 25% by mass, sufficient grip performance may not be obtained. The styrene content is preferably 50% by mass or less, more preferably 45% by mass or less. When it exceeds 50 mass%, it tends to generate heat and blowout tends to occur.
Incidentally, styrene content ^is calculated by H 1 -NMR measurement.

The content of SBR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more. If it is less than 80% by mass, sufficient grip performance may not be obtained. Further, the SBR content is more preferably 100% by mass because it is excellent in grip performance, wear resistance, blow resistance, and vulcanization adhesion to members inside the tire.

In the present invention, (i) an acid and a nitrogen compound and / or (ii) at least one compound selected from the group consisting of an organic carboxylic acid metal salt, a thiocarboxylate and a phosphate is used.

It does not specifically limit as an acid, For example, carboxylic acid, a phenol derivative, a sulfonic acid etc. are mentioned. Of these, carboxylic acids and phenol derivatives are preferred because they are less likely to adversely affect the vulcanization characteristics.

Carboxylic acids include aliphatic monocarboxylic acids such as acetic acid, propionic acid and oleic acid, aliphatic dicarboxylic acids such as succinic acid and maleic acid, benzoic acid, benzoic acid derivatives, aromatic monocarboxylic acids such as cinnamic acid and naphthoic acid. Aromatic polycarboxylic acids such as carboxylic acid, phthalic acid, phthalic anhydride, trimellitic acid and pyromellitic acid can be mentioned. Of these, aromatic monocarboxylic acids are preferable, and benzoic acid and benzoic acid derivatives are more preferable. Examples of the benzoic acid derivative include those in which a functional group such as a hydrocarbon group (alkyl group, alkoxy group, etc.) or a hydroxyl group is introduced into benzoic acid. Specifically, p-methylbenzoic acid, p- Examples include methoxybenzoic acid, p-chlorobenzoic acid, p-nitrobenzoic acid, and salicylic acid.

Examples of the phenol derivative include compounds represented by the following general formulas (I) to (IV).

In the general formulas (I) to (IV), R ^{1 to} R ⁷ are the same or different and are each a hydrocarbon group having 1 to 10 (preferably 1 to 6) carbon atoms. As this hydrocarbon group, a C1-C10 (preferably 1-6) alkyl group and a C2-C10 (preferably 2-6) alkenyl group are preferable, for example, a methyl group, an ethyl group, n -Propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, n-pentyl group, i-pentyl group, n-hexyl group, i-hexyl group and the like can be mentioned.

n and n 'are the same or different, and are 0 or an integer of 1-3, and 1-2 are preferable respectively.
m and m ′ are the same or different and are integers of 1 or 2, each of which is preferably 1.
s is an integer of 1-3, and 1-2 are preferable.
t is 0 or an integer of 1-3, and 1-2 is preferable.

X is at least one atom selected from the group consisting of an oxygen atom, a sulfur atom and a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may contain the atom. Examples of the hydrocarbon group include divalent hydrocarbon groups, and examples thereof include saturated groups and unsaturated groups such as alkylene groups and cycloalkylene groups. For example, a saturated group such as methylene group, ethylene group, propylene group, n-butylene group, i-butylene group, pentylene group, hexylene group, heptylene group; vinylene group, propylidene group, isopropylidene group, butylidene group, isobutylidene group, Mention may be made of unsaturated groups such as ester bond-containing groups and aromatic groups. Preferred specific examples of X are the following (1) to (3). The ester bond-containing group is a group containing —CO—O—, and specific examples include those represented by the following (4) to (7).

Specific examples of the phenol derivatives represented by the general formulas (I) to (IV) include, for example, 2-tert-butylphenol; 2-ethyl-6-methylphenol; 2,6-di-tert-butylphenol; 3 -Methyl-2,6-bis (1-methylethyl) phenol; 4-methyl-2,6-di-tert-butylphenol; 3-methyl-2,6-bis (1-methylpropyl) phenol; 2-butyl -6-ethylphenol; 4-butyl-2,6-di-tert-butylphenol; 4-tert-butyl-2,6-dimethylphenol; 6-tert-butyl-2,3-dimethylphenol; 2-tert- Butyl-4-methylphenol; 2-cyclohexyl-6-tert-butylphenol; 2-cyclohexyl-6-tert- 2-tert-butyl-4,6-dimethylphenol; 4,4'-dihydroxybiphenyl; 4,4'-thiobisphenol; hydroquinone; 1,5-hydroxynaphthalene; 4,4'- Thiobis (3-methyl-6-tert-butylphenol); 4,4′-thiobis (2-methyl-6-tert-butylphenol); 4,4′-methylenebis (2,6-di-tert-butylphenol); 4 4,4′-ethylenebis (2,6-di-tert-butylphenol); 4,4′-propylidenebis (2-methyl-6-tert-butylphenol); 4,4′-bis (2,6-di-tert) -Butylphenol); 4,4'-bis (2-methyl-6-tert-butylphenol); 2,2'-methylenebi (4-ethyl-6-tert-butylphenol); 2,2′-methylenebis (4-methyl-6-tert-butylphenol); 4,4′-butylidenebis (3-methyl-6-tert-butylphenol); 4'-isopropylidenebis (2,6-di-tert-butylphenol); 2,2'-methylenebis (4-methyl-6-nonylphenol); 2,2'-isobutylidenebis (4,6-dimethylphenol) ); 2,2′-methylenebis (4-methyl-6-cyclohexylphenol) and the like. Among them, 2,2′-methylenebis (4-methyl-6-tert-butylphenol) and 4,4′-butylidenebis (3-methyl-6-tert-butylphenol) are preferred because they easily form hydrogen bonds with nitrogen compounds. ) Is preferred.

The said acid may be used independently and may be used in combination of 2 or more type.

The acid content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and still more preferably 3.0 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.5 parts by mass, hydrogen bonds cannot be sufficiently formed with the nitrogen compound, and the effect of improving the grip performance may not be sufficiently obtained. The acid content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less. When it exceeds 20 parts by mass, the wear resistance may be deteriorated due to crosslinking inhibition.

The nitrogen compound is preferably one capable of forming a hydrogen bond with an acid. By blending such a nitrogen compound in the rubber composition, the grip performance under intermediate temperature conditions (30 to 50 ° C.) can be improved. .

The nitrogen compound preferably has one or more cyclic structures containing nitrogen. If no annular structure containing nitrogen is included, high temperature grip performance tends not to be improved.

As such nitrogen compounds, piperidine derivatives, imidazoles, caprolactams and the like can be preferably used.

Examples of piperidine derivatives include 2,2,6,6-tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, and bis (1,2,2,6,6-). Pentamethyl-4-piperidyl) sebacate, 1- [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} ethyl] -4- {3- (3,5-di- t-butyl-4-hydroxyphenyl) propionyloxy} -2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 8-acetyl-3-dodecyl- 7,7,9,9-tetramethyl-1,3,8-triazaspiro [4,5] decane-2,4-dione, poly [{6- (1,1,3,3-tetramethylbutyl) amino -1, , 5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino }, 2,2,6,6-tetramethyl such as 1,2,2,6,6-tetramethyl-4-piperidyl-methacrylate, 2,2,6,6-tetramethyl-4-piperidyl-methacrylate Examples include piperidine and derivatives thereof. Of these, 2,2,6,6-tetramethylpiperidine or a derivative thereof is preferable, a derivative of 2,2,6,6-tetramethylpiperidine is more preferable, and bis (1,2,2,6,6-pentamethyl) is more preferable. -4-piperidyl) sebacate is more preferred.

Examples of imidazoles include imidazole, 1-methylimidazole, 2-methylimidazole, N-acetylimidazole, 2-mercapto-1-methylimidazole, benzimidazole, 2-mercaptobenzimidazole, 2-phenylimidazole, 1-benzyl. -2-methylimidazole and the like. Among them, 2-methylimidazole, imidazole, or 1-methylimidazole is preferable because the structure is simple, an acid approaches a nitrogen atom, and a hydrogen bond is easily formed.

Examples of caprolactams include ε-caprolactam.

Among the nitrogen compounds described above, piperidine derivatives and imidazoles are more preferable.

Nitrogen compounds may be used singly or in combination of two or more. However, combining two or more may reduce the effect and reduce wear resistance. Is preferred.

The content of the nitrogen compound is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and further preferably 3.0 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.5 parts by mass, sufficient hydrogen bonds cannot be formed with the acid compound, and the effect of improving the grip performance may not be sufficiently obtained. Content of a nitrogen compound becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 15 mass parts or less, More preferably, it is 10 mass parts or less. If it exceeds 20 parts by mass, the crosslinking becomes insufficient and the wear resistance may be lowered.

The total content of the acid and the nitrogen compound is preferably 1.0 parts by mass or more, more preferably 2.0 parts by mass or more, and still more preferably 6.0 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1.0 part by mass, the effect of improving the grip performance may not be sufficiently obtained. The total content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less. If it exceeds 40 parts by mass, the wear resistance may be deteriorated due to crosslinking inhibition.

In the present invention, at least one selected from the group consisting of (ii) a metal salt of an organic carboxylic acid, a thiocarboxylate, and a phosphate instead of or together with the mixture of the acid and nitrogen compound of (i) A compound is used. The said compound contains an ionic bond and can improve the grip performance under high temperature conditions (around 100 degreeC) by mix | blending in a rubber composition.

Examples of the organic carboxylic acid metal salt include: (A) aromatic carboxylic acid metal salt (benzoic acid metal salt, naphthoic acid metal salt, etc.); (B) carboxylic acid metal salt containing no aromatic ring (multiple bonds (carbon- And carboxylic acid metal salts not containing an aromatic ring (containing no aromatic ring) and carboxylic acid metal salts containing multiple bonds (containing no aromatic ring)). Examples of the carboxylic acid metal salt containing no multiple bond include organic monocarboxylic acid metal salts such as acetic acid metal salt and propionic acid metal salt; and organic dicarboxylic acid metal salts such as oxalic acid metal salt. Examples of the carboxylic acid metal salt containing multiple bonds include acrylic acid metal salts and methacrylic acid metal salts.

Examples of the metal contained in the organic carboxylic acid metal salt include alkali metals such as sodium and potassium, alkaline earth metals such as magnesium and calcium, transition metals such as zinc and nickel, and alkaline earth metals. preferable.

Examples of the organic carboxylic acid metal salt include magnesium acetate, calcium propionate, calcium acetate, magnesium propionate, etc., but since they are generally commercially available and easily available, magnesium acetate, calcium acetate, and calcium propionate are preferable.

Examples of the thiocarboxylate include thioacetate and thiopropionate.

Examples of the phosphate include metaphosphate.

Examples of substances that form salts with thiocarboxylic acid or phosphoric acid in thiocarboxylic acid salts and phosphates include metals and organic substances having positive charges such as amino acids. Examples of the metal include the same metals as those contained in the organic carboxylic acid metal salt.

As the organic carboxylic acid metal salt, thiocarboxylate and phosphate, the above compounds may be used alone or in combination of two or more, but the effect of combining two or more is difficult to obtain, Furthermore, since wear resistance is lowered and not preferred, it is preferably used alone.

The total content of the organic carboxylic acid metal salt, thiocarboxylate and phosphate is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.5 part by mass, the effect of improving the grip performance may not be sufficiently obtained. The total content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less. If it exceeds 20 parts by mass, the crosslinking becomes insufficient and the wear resistance may be lowered.

In the present invention, the complex is obtained by mixing fine zinc oxide having an average primary particle size of 300 nm or less and a fatty acid at a temperature equal to or higher than the melting point of the fatty acid, and can be used as a vulcanization aid.

The average primary particle diameter of the particulate zinc oxide is 300 nm or less, preferably 150 nm or less, more preferably 100 nm or less, and still more preferably 50 nm or less. The lower limit of the average primary particle diameter of the fine particle zinc oxide is not particularly limited, but is preferably 20 nm or more, more preferably 40 nm or more. Within the above range, excellent blow resistance and wear resistance can be obtained.
In addition, the average primary particle diameter of zinc oxide represents the average particle diameter (average primary particle diameter) converted from the specific surface area measured by the BET method by nitrogen adsorption.

The fatty acid is not particularly limited, and examples thereof include saturated fatty acids such as stearic acid, palmitic acid, myristic acid, and lauric acid, and unsaturated fatty acids such as oleic acid, linoleic acid, and linolenic acid. Of these, saturated fatty acids are preferred because of their good blow resistance and wear resistance, and those represented by the following formula are more preferred.
CH ₃ (CH ₂ ) _r COOH
(In the formula, r represents an integer of 10 to 30 (preferably 14 to 18).)
As such a fatty acid, stearic acid is preferable because it is obtained in a dimension having high resistance to blow and wear.

The complex can be prepared by mixing fine particle zinc oxide and a fatty acid at a temperature equal to or higher than the melting point of the fatty acid, for example, 40 to 100 ° C. for 1 to 30 minutes (preferably 69.6 to 80 ° C. for 3 to 10 minutes. More preferably, the mixing may be performed under conditions of 70 to 75 ° C. for 3 to 10 minutes. The mixing step can be performed using a known heating device or mixing device. For example, fine particles of zinc oxide and fatty acid are stirred and heated using a Henschel mixer, a water bath, an oil bath, etc., and the fatty acid is melted to form fine particles. Complexes can be prepared by mixing with zinc oxide.

The obtained complex is preferably in a solid state at normal temperature (23 ° C.). By kneading the solid state complex with the rubber component, the fine zinc oxide and the fatty acid can be well dispersed in the rubber component, and the blow resistance and wear resistance can be improved in a well-balanced manner.

In the above complex, the content of the fine zinc oxide in the total 100% by mass of the fine zinc oxide and the fatty acid is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 40% by mass or more. If the amount is less than 10% by mass, the effect of improving the blow resistance and wear resistance may not be sufficiently obtained. The content of fine zinc oxide is preferably 90% by mass or less, more preferably 70% by mass or less. When it exceeds 90 mass%, there is little fatty acid and there exists a possibility that the above-mentioned improvement effect cannot fully be acquired.

In the rubber composition of the present invention, the content of the fine zinc oxide is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, still more preferably 0.00 parts by mass with respect to 100 parts by mass of the rubber component. 5 parts by mass or more. If the amount is less than 0.1 parts by mass, sufficient crosslinking efficiency cannot be obtained, and sufficient wear resistance may not be obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 13 parts by mass or less. When the amount exceeds 20 parts by mass, the fine zinc oxide does not disperse, becomes a core of blow, and the blow resistance tends to deteriorate.

In the rubber composition of the present invention, the content of the fatty acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1 part by mass, the amount of fatty acid is small and dispersion tends to be poor. Moreover, this content becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 15 mass parts or less. If it exceeds 20 parts by mass, the wear resistance tends to deteriorate.

In addition, fine particle zinc oxide and a fatty acid may be blended separately in addition to the above complex, and in this case, each of the above contents means the total amount contained in the rubber composition.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions, such as reinforcing fillers such as carbon black and silica, silane coupling agents, stearic acid, various An antioxidant, an ozone degradation inhibitor, oil, wax, a vulcanizing agent, a vulcanization accelerator, and the like can be appropriately blended.

Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. Wear resistance can be improved by blending carbon black. Carbon black may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, more preferably 90 m ² / g or more, and still more preferably 120 m ² / g or more. If it is less than 80 m < ² > / g, there exists a possibility that sufficient grip performance may not be obtained. Further, the nitrogen adsorption specific surface area of the carbon black is preferably at most 200 meters ² / g, more preferably not more than 190 m ² / g, more preferably 160 m ² / g or less. When it exceeds 200 m ² / g, the dispersibility of the carbon black is deteriorated and the wear resistance may be deteriorated.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

Carbon black has a dibutyl phthalate (DBP) oil absorption of preferably 5 ml / 100 g or more, more preferably 10 ml / 100 g or more, and even more preferably 80 ml / 100 g or more. If it is less than 5 ml / 100 g, the wear resistance may be deteriorated. The DBP oil absorption of carbon black is preferably 300 ml / 100 g or less, more preferably 280 ml / 100 g or less, still more preferably 200 ml / 100 g or less, and particularly preferably 150 ml / 100 g or less. If it exceeds 300 ml / 100 g, the wear resistance may be deteriorated.
In addition, the DBP oil absorption amount of carbon black is calculated | required by the measuring method of JISK6217-4.

The content of carbon black is preferably 50 parts by mass or more, more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 50 parts by mass, sufficient grip performance may not be obtained. The carbon black content is preferably 200 parts by mass or less, more preferably 190 parts by mass or less, still more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less. If it exceeds 200 parts by mass, the dispersibility is low and the wear resistance may be reduced.

The rubber composition of the present invention may contain oil. By blending oil, processability can be improved. As the oil, for example, process oil, vegetable oil, or a mixture thereof can be used.
As the process oil, for example, a paraffin process oil, an aroma process oil, a naphthenic process oil, or the like can be used. Specific examples of the paraffinic process oil include PW-32, PW-90, PW-150, and PS-32 manufactured by Idemitsu Kosan Co., Ltd. In addition, as an aroma-based process oil, specifically, AC-12, AC-460, AH-16, AH-24, AH-58 made by Idemitsu Kosan Co., Ltd., Process X-260 made by Japan Energy, etc. Can be mentioned. As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Of these, an aroma-based process oil is preferably used.

When the rubber composition contains oil, the content of oil is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 25 parts by mass or more, particularly 100 parts by mass of the rubber component. Preferably it is 40 mass parts or more. If it is less than 10 mass parts, there exists a possibility that workability may deteriorate. The oil content is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, still more preferably 120 parts by mass or less, particularly preferably 100 parts by mass or less, and most preferably 80 parts by mass or less. When it exceeds 200 mass parts, there exists a possibility that abrasion resistance may deteriorate.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The rubber composition of the present invention can be suitably used for each member (particularly tread) of a tire.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, the rubber composition containing the above components is extruded in accordance with the shape of the tread at an unvulcanized stage and molded together with other tire members on a tire molding machine by a normal method. Form a vulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The pneumatic tire of the present invention is preferably used as a passenger tire, truck / bus tire, motorcycle tire, competition tire (cart tire, etc.), and particularly as a competition tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

酸：川口化学（株）製のアンテージＷ３００（４，４’−ブチリデンビス（３−メチル−６−ｔｅｒｔ−ブチルフェノール））
有機カルボン酸金属塩：キシダ化学（株）製の酢酸マグネシウム
硫黄：鶴見化学（株）製の粉末硫黄
加硫促進剤ＮＳ：大内新興化学工業（株）製のノクセラーＮＳ（Ｎ−ｔ−ブチル−２−ベンゾチアジルスルフェンアミド） Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
SBR: Toughden 4850 manufactured by Asahi Kasei Corporation (styrene content: 39% by mass, containing 50 parts by mass of oil with respect to 100 parts by mass of rubber solid content)
Carbon black: Dia Black A (N110, N ₂ SA: 142 m ² / g, DBP oil absorption: 116 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Anti-aging agent 6C: Santoflex 13 from Flexis
Anti-aging agent 224: NOCRACK 224 manufactured by Flexis
Stearic acid: Palmitic acid stearate manufactured by NOF Corporation: Zinc palmitate manufactured by Wako Pure Chemical Industries, Ltd .: Three types of zinc oxide manufactured by Hakusuitec Co., Ltd. (average primary particle size: 1.0 μm = 1000 nm) )
Fine zinc oxide 1: Zincock Super F-1 manufactured by Hakusuitec Co., Ltd. (average primary particle size: 100 nm)
Fine zinc oxide 2: Zinccock Super F-3 (average primary particle size: 50 nm) manufactured by Hakusui Tech Co., Ltd.
Aroma oil: Process X-260 manufactured by Japan Energy Co., Ltd.
Nitrogen compound: Sanol LS-765 (bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (compound represented by the following formula)) manufactured by Sankyo Co., Ltd.)

Acid: Antage W300 (4,4′-butylidenebis (3-methyl-6-tert-butylphenol)) manufactured by Kawaguchi Chemical Co., Ltd.
Organic carboxylate metal salt: Magnesium acetate sulfur manufactured by Kishida Chemical Co., Ltd .: Powder sulfur vulcanization accelerator NS manufactured by Tsurumi Chemical Co., Ltd. NS: Noxeller NS (N-t-butyl manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) -2-Benzothiazylsulfenamide)

(Production Example 1)
(Preparation of complex)
In accordance with the formulation shown in Table 1, using a Henschel mixer, stearic acid or palmitic acid was heated to a melting temperature (69-72 ° C.) or higher, and after confirming that stearic acid or palmitic acid had melted, various zinc oxides Was added. After stirring and mixing for 5 minutes, the complex was obtained by air cooling at room temperature.

(Confirmation of complex: FT-IR)
Regarding the complex of fine particle zinc oxide and stearic acid prepared in Production Example 1, and the complex of zinc oxide and stearic acid, the formation of the complex was confirmed using FT-IR. It was confirmed (FIG. 1). Complex formation was also confirmed with fine zinc oxide and palmitic acid.

(Examples and Comparative Examples)
According to the blending contents shown in Table 1, using a BP Banbury mixer, materials other than sulfur and vulcanization accelerator were kneaded for 3 minutes at 150 ° C. to obtain a kneaded product (base) Kneading). Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under a condition of 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition. In Comparative Examples 3 and 5, the base was kneaded twice.
The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 12 minutes to obtain a vulcanized rubber composition.

Further, the obtained unvulcanized rubber composition is molded into a tread shape, bonded to another tire member, molded into a tire, and press vulcanized at 170 ° C. for 15 minutes to test cart tires (tire size: 11 × 7.10-5) was produced.

The following evaluation was performed using the obtained vulcanized rubber composition and test cart tire. Each test result is shown in Table 1.
(Degree of crosslinking (SWELL))
The obtained vulcanized rubber composition was extracted with toluene, and the volume change rate (SWELL) before and after extraction was measured. In addition, it shows that the dispersion | variation in bridge | crosslinking can be suppressed and it is so preferable that SWELL is small.

(Viscoelasticity test)
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., viscoelasticity (complex elastic modulus E ′) of a vulcanized rubber composition at 40 ° C. under conditions of initial strain 10%, dynamic strain 2%, and vibration frequency 10 Hz. And loss tangent tan δ).
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., the viscoelasticity (complex elastic modulus E ′) of the vulcanized rubber composition at 100 ° C. under conditions of initial strain 10%, dynamic strain 2%, and vibration frequency 10 Hz. And loss tangent tan δ).
In the viscoelasticity test at 40 ° C., the larger the tan δ / E ′, the better the initial grip performance (grip performance under low temperature conditions).
In the viscoelasticity test at 100 ° C., the larger the tan δ / E ′, the better the latter half grip performance (grip performance under high temperature conditions).

(Tensile test)
According to JIS K 6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”, a tensile test was conducted using a No. 3 dumbbell-shaped rubber test piece made of a vulcanized rubber composition, and a stress at 300% elongation ( M300) was measured. And the tensile strength index | exponent of the comparative example 1 was set to 100, and M300 of each mixing | blending was displayed as an index | exponent with the following formula. In addition, it shows that it is excellent in abrasion abrasion resistance, so that a tensile strength index | exponent is large. However, when blow occurs, the abrasion wear resistance is reduced regardless of the tensile strength index.
(Tensile strength index) = (M300 of each formulation) / (M300 of Comparative Example 1) × 85

(Actual vehicle evaluation)
The test cart tire is mounted on the test cart, and the test course (DRY road surface) of 1 km 2 runs 8 laps. The initial grip performance and the second half grip performance of the tire of Comparative Example 1 are 3.0 points, and 5 points. The test driver made a sensory evaluation with a perfect score. The initial grip performance indicates the grip performance of the first to fourth laps (under a low temperature condition), and the latter half grip performance indicates the grip performance of the fifth to eighth laps (under a high temperature condition).
The test cart tire was attached to the test cart, and the test course (DRY road surface) of 1 lap 2 km was run 18 laps. After running, the wear appearance of the tire was observed, and the wear appearance of the tire of Comparative Example 1 was rated as 3.0 points, and was evaluated on a 5-point scale. It shows that it is excellent in abrasion resistance, so that a numerical value is large. Further, the tire after running was disassembled, the degree of blow of the tread cross section was observed, the comparative example 1 was set to 3.0 points, and the blow resistance was evaluated with a maximum of 5 points. Larger values indicate better blow resistance.

In the example using the complex of fine zinc oxide and stearic acid, the blow resistance was improved as compared with the comparative example in which the fine zinc oxide and stearic acid were simply kneaded. In addition, a good cross-linked state was obtained, and grip performance and wear resistance were also good. Furthermore, the kneadability was also good, and the fine zinc oxide could be sufficiently dispersed in a normal base kneading process, and desired rubber physical properties were obtained. On the other hand, when ordinary zinc oxide was used, no complex was formed, and the performance was not sufficiently improved (Comparative Example 7, FIG. 1). The same improvement effect was also obtained in Example 5 using a complex of fine zinc oxide and palmitic acid.

Claims (6)

After preparing a complex by mixing fine zinc oxide and fatty acid having an average primary particle size of 300 nm or less at a temperature equal to or higher than the melting point of the fatty acid, the prepared complex, a rubber component, an acid and a nitrogen compound, and / or Or the manufacturing method of the rubber composition for tires including the process of knead | mixing with the at least 1 sort (s) of compound selected from the group which consists of organic carboxylic acid metal salt, thiocarboxylate, and phosphate. 2. The method for producing a rubber composition for a tire according to claim 1, wherein a content of the fine zinc oxide in a total of 100 mass% of the fine zinc oxide and the fatty acid in the complex is 10 to 90 mass%. The tire rubber composition, a manufacturing method of the the rubber component 100 parts by weight, according to claim 1 or 2 tire rubber composition according comprising the 0.1 to 20 parts by mass of zinc oxide particles. The manufacturing method of the rubber composition for tires in any one of Claims 1-3 in which the said rubber composition for tires is used as a rubber composition for treads. After preparing a complex by mixing fine zinc oxide and fatty acid having an average primary particle size of 300 nm or less at a temperature equal to or higher than the melting point of the fatty acid, the prepared complex, a rubber component, an acid and a nitrogen compound, and / or Or the manufacturing method of a pneumatic tire including the process of knead | mixing with the at least 1 sort (s) of compound selected from the group which consists of organic carboxylic acid metal salt, thiocarboxylate, and phosphate. The method for manufacturing a pneumatic tire according to claim 5, wherein the pneumatic tire is a racing tire.

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