JP7231813B2 - Tire rubber composition and pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition for tires and a pneumatic tire.

Tires are usually made of a vulcanized rubber composition and have a characteristic odor. Therefore, when the tire is displayed indoors at a tire store, the tire may be filled with an unpleasant odor.

Patent Literature 1 discloses that odor is suppressed by blending a fragrance into a rubber composition. However, there is a demand for further improvement in the odor suppressing effect.

JP-A-2004-203954

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for a tire which is remarkably suppressed in odor and improved in processability, and a pneumatic tire produced using the rubber composition. and

The present invention contains a rubber component and at least one fragrance selected from the group consisting of cedren, cedrol, cedrenol, methyl jasmonate, methyl dihydrojasmonate, and anethole, and 100% by mass of the rubber component contains natural The present invention relates to a rubber composition for tires having a rubber content of 40% by mass or more.

The rubber composition preferably contains a sulfenamide vulcanization accelerator and/or a thiazole vulcanization accelerator.

The rubber composition preferably contains sulfur.

The natural rubber is preferably a modified natural rubber having a phosphorus content of 500 ppm or less.

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

According to the present invention, there is provided a rubber composition containing a predetermined amount of natural rubber and at least one fragrance selected from the group consisting of cedren, cedrol, cedrenol, methyl jasmonate, methyl dihydrojasmonate and anethole. Therefore, odor is suppressed and workability is also improved.

The rubber composition for a tire of the present invention contains a rubber component and at least one fragrance selected from the group consisting of cedrene, cedrol, cedrenol, methyl jasmonate, methyl dihydrojasmonate and anethole, and the rubber component The content of natural rubber is 40% by mass or more in 100% by mass.

Cedrene, cedrol, cedrenol, methyl jasmonate, methyl dihydrojasmonate and anethole have structures that easily disperse with natural rubber (NR). is remarkably suppressed, and workability is also improved.

The rubber composition contains NR.
As NR, those commonly used in the tire industry, such as SIR20, RSS3, TSR20, and TSS8, can be used. These may be used individually by 1 type, and may use 2 or more types together.

As NR, modified natural rubber (high-purity natural rubber (UPNR)) that has been highly purified by removing non-rubber components such as proteins and phospholipids and adjusted to a pH of 2 to 7 is used. It is preferable to use As a result, the effect of suppressing odor and the effect of improving workability are improved, and the effect of improving fuel efficiency is also obtained.

In this specification, the phrase "the non-rubber component is removed" means that even a small amount of the non-rubber component is removed, and does not mean that all the non-rubber component is removed.
Further, high purification means removing impurities such as phospholipids and proteins other than natural polyisoprenoid components. Natural rubber has a structure in which the isoprenoid component is covered with the impurity component, and by removing the component, the structure of the isoprenoid component changes, and the interaction with the compounding agent changes to generate energy. It is presumed that loss can be reduced, durability can be improved, and a better rubber composition can be obtained.

The modified natural rubber that has been highly purified and adjusted to a pH of 2 to 7 may be a modified natural rubber that has been highly purified by reducing the amount of non-rubber components and has a pH of 2 to 7. Specifically, (a) a modified natural rubber obtained by removing non-rubber components from natural rubber and then treating it with an acidic compound and having a pH of 2 to 7; (c) a modified natural rubber obtained by washing deproteinized natural rubber latex and further treating it with an acidic compound and having a pH of 2 to 7; modified natural rubber having a pH of 2 to 7; (d) aggregating (coagulating) natural rubber latex; modified natural rubber of No. 7, and the like.

As described above, the modified natural rubber can be prepared by washing saponified natural rubber latex or deproteinized natural rubber latex with distilled water or the like and further treating with an acidic compound. It is important to lower the pH value by shifting it to the acidic side by treatment with an acidic compound. Normally, the pH of distilled water is not 7.00, but about 5 to 6. In this case, it is important to lower the pH value from 5 to 6 to the acidic side by treating with acidic compounds. Become. Specifically, it is preferable to lower the pH value by 0.2 to 2 from the pH value of water used for washing by treatment with an acidic compound.

The modified natural rubber has a pH of 2-7, preferably 3-6, more preferably 4-6. By adjusting the amount within the above range, deterioration of heat aging resistance can be prevented, and the above various performances can be significantly improved.

The pH of the modified natural rubber was determined by cutting the rubber into pieces within 2 mm square on each side, immersing them in distilled water, extracting them at 90°C for 15 minutes while irradiating them with microwaves, and measuring the immersed water with a pH meter. Specifically, it is measured by the method described in Examples below. Here, as for the extraction, since it is not possible to completely extract the water-soluble components from the inside of the rubber even if it is extracted for 1 hour using an ultrasonic cleaner or the like, it is not possible to accurately know the internal pH. Extracting it makes it possible to know the substance of the rubber.

The modified natural rubber is highly purified by various methods such as the above (a) to (d). For example, the phosphorus content in the modified natural rubber is preferably 500 ppm or less, more preferably It is 400 ppm or less, more preferably 300 ppm or less, particularly preferably 200 ppm or less, and most preferably 150 ppm or less. Thereby, an effect is obtained more suitably.

The phosphorus content can be measured by a conventional method such as ICP emission spectrometry. Phosphorus is believed to be derived from phospholipids contained in natural rubber.

When the modified natural rubber contains an artificial antioxidant, the nitrogen content after immersion in acetone at room temperature (25°C) for 48 hours is preferably 0.15% by mass or less. , 0.10% by mass or less. Thereby, an effect is obtained more suitably.

Since the natural anti-aging component that is said to be originally present in natural rubber has been removed from highly purified natural rubber, there is a risk of deterioration during long-term storage. Therefore, artificial anti-aging agents are sometimes added. The above nitrogen content is measured after removal of the artificial anti-aging agents in the rubber by acetone extraction. The nitrogen content can be measured by a conventional method such as the Kjeldahl method or a trace nitrogen meter. Nitrogen is derived from proteins and amino acids.

The modified natural rubber preferably has a Mooney viscosity ML (1+4) at 130°C of 75 or less, more preferably 40 to 75, still more preferably 45 to 75, measured according to JIS K6300:2001-1. Especially preferably 50-70, most preferably 55-65. By being 75 or less, mastication normally required before rubber kneading becomes unnecessary. Therefore, the modified natural rubber produced without a mastication step can be suitably used as a compounding material for a rubber composition.

The modified natural rubber is preferably a rubber having a heat aging resistance index represented by the following formula of 75 to 120% with respect to the Mooney viscosity ML(1+4) of 130°C.

The heat aging resistance index represented by the above formula is more preferably 80 to 115%, still more preferably 85 to 110%. Various methods have been reported for evaluating the heat aging resistance of rubber. It is possible to accurately evaluate the heat aging resistance of time and tire use. Here, within the above range, excellent heat aging resistance can be obtained, and the performance balance of the above various properties can be remarkably improved.

The above-mentioned modified natural rubbers (a) to (d), which are highly purified and adjusted to a pH of 2 to 7, are produced by (manufacturing method 1) a step 1-1 of saponifying natural rubber latex; A production method comprising step 1-2 of washing saponified natural rubber latex and step 1-3 of treating with an acidic compound, (Production method 2) Step 2-1 of deproteinizing natural rubber latex, It can be prepared by a production method including step 2-2 of washing rubber latex and step 2-3 of treating with an acidic compound.

[Manufacturing method 1]
(Step 1-1)
In step 1-1, natural rubber latex is saponified. As a result, phospholipids and proteins in the rubber are decomposed to prepare a saponified natural rubber latex with reduced non-rubber components.

Natural rubber latex is collected as the sap of natural rubber trees such as the Hevea tree, and contains water, proteins, lipids, inorganic salts, etc. in addition to the rubber content, and the gel content in the rubber is based on the complex presence of various impurities. is considered a thing. In the present invention, as the natural rubber latex, raw latex (field latex) obtained by tapping Hevea trees, or concentrated latex (purified latex, high-ammonia Latex, such as LATZ latex stabilized with zinc white and TMTD and ammonia) can be used.

As a method of saponification treatment, for example, the methods described in JP-A-2010-138359 and JP-A-2010-174169 can be suitably performed, and specifically, the following method can be performed.

The saponification treatment can be carried out by adding an alkali and, if necessary, a surfactant to the natural rubber latex and allowing the mixture to stand at a predetermined temperature for a certain period of time.

Alkali used in the saponification treatment are preferably sodium hydroxide, potassium hydroxide, or the like, but are not limited to these. The surfactant is not particularly limited, and includes known anionic surfactants such as polyoxyethylene alkyl ether sulfate salts, nonionic surfactants, and amphoteric surfactants. Anionic surfactants such as polyoxyethylene alkyl ether sulfates are preferred because they can be saponified. In the saponification treatment, the amounts of alkali and surfactant to be added, and the temperature and time of saponification treatment may be appropriately set.

(Step 1-2)
In step 1-2, the saponified natural rubber latex obtained in step 1-1 is washed. The washing removes non-rubber components such as proteins.

In step 1-2, for example, the saponified natural rubber latex obtained in step 1-1 is coagulated to produce a coagulated rubber, and then the obtained coagulated rubber is treated with a basic compound and washed. can be implemented by Specifically, after preparing the flocculated rubber, it can be diluted with water to transfer the water-soluble components to the aqueous layer, and the non-rubber components can be removed by removing the water. Non-rubber components trapped within the rubber during aggregation can be redissolved. As a result, non-rubber components such as proteins strongly adhered to the aggregated rubber can be removed.

Examples of the flocculation method include a method of adding an acid such as formic acid, acetic acid, and sulfuric acid to adjust the pH and, if necessary, further adding a polymer flocculant. As a result, instead of large agglomerates, granular rubber having a diameter of several mm to 1 mm or less to about 20 mm is formed, and proteins and the like are sufficiently removed by treatment with a basic compound. The above pH is preferably adjusted in the range of 3.0 to 5.0, more preferably 3.5 to 4.5.

Examples of polymer flocculants include cationic polymer flocculants such as polymers of methyl chloride quaternary salt of dimethylaminoethyl (meth)acrylate, anionic polymer flocculants such as acrylate polymers, and acrylamide polymers. and amphoteric polymer flocculants such as a copolymer of methyl chloride quaternary salt of dimethylaminoethyl (meth)acrylate-acrylic acid salt. The amount of polymer flocculant to be added can be selected as appropriate.

The resulting coagulated rubber is then treated with a basic compound. Here, the basic compound is not particularly limited, but a basic inorganic compound is preferable from the viewpoint of the ability to remove proteins and the like.

Basic inorganic compounds include metal hydroxides such as alkali metal hydroxides and alkaline earth metal hydroxides; metal carbonates such as alkali metal carbonates and alkaline earth metal carbonates; alkali metal hydrogencarbonates and the like. metal phosphates such as alkali metal phosphates; metal acetates such as alkali metal acetates; metal hydrides such as alkali metal hydrides; and ammonia.

Alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Alkaline earth metal hydroxides include magnesium hydroxide, calcium hydroxide, barium hydroxide and the like. Alkali metal carbonates include lithium carbonate, sodium carbonate, potassium carbonate and the like. Alkaline earth metal carbonates include magnesium carbonate, calcium carbonate, barium carbonate and the like. Alkali metal hydrogencarbonates include lithium hydrogencarbonate, sodium hydrogencarbonate, potassium hydrogencarbonate and the like. Alkali metal phosphates include sodium phosphate, sodium hydrogen phosphate and the like. Alkali metal acetates include sodium acetate, potassium acetate and the like. Examples of alkali metal hydrides include sodium hydride and potassium hydride.

Among them, metal hydroxides, metal carbonates, metal hydrogencarbonates, metal phosphates and ammonia are preferred, alkali metal carbonates, alkali metal hydrogencarbonates and ammonia are more preferred, and sodium carbonate and sodium hydrogencarbonate are further preferred. preferable. The above basic compounds may be used alone or in combination of two or more.

The method of treating the coagulated rubber with a basic compound is not particularly limited as long as it is a method of bringing the coagulated rubber into contact with the basic compound. and a method of spraying an aqueous solution of a chemical compound. Aqueous solutions of basic compounds can be prepared by diluting and dissolving each basic compound in water.

The content of the basic compound in 100% by mass of the aqueous solution is preferably 0.1% by mass or more, more preferably 0.3% by mass or more. When it is 0.1% by mass or more, there is a tendency that proteins can be sufficiently removed. The content is preferably 10% by mass or less, more preferably 5% by mass or less. When it is 10% by mass or less, it is possible to efficiently perform the treatment without using an unnecessarily large amount of the basic compound.

The pH of the aqueous solution of the basic compound is preferably 9 to 13, more preferably 10 to 12 from the viewpoint of treatment efficiency.

The treatment temperature may be appropriately selected, but is preferably 10 to 50°C, more preferably 15 to 35°C. The treatment time is usually 1 minute or longer, preferably 10 minutes or longer, and more preferably 30 minutes or longer. When the time is 1 minute or more, the effect tends to be obtained more preferably. Although there is no upper limit, it is preferably 48 hours or less, more preferably 24 hours or less, still more preferably 16 hours or less from the viewpoint of productivity.

After treatment with the basic compound, a washing treatment is performed. The washing treatment sufficiently removes non-rubber components such as proteins entrapped in the rubber at the time of coagulation, and at the same time, makes it possible to sufficiently remove not only the surface of the coagulated rubber but also the basic compounds existing inside. . In particular, by removing the basic compounds remaining in the entire rubber in the washing process, it becomes possible to sufficiently apply the treatment with the acidic compound described later to the entire rubber, and not only the surface of the rubber but also the internal pH is 2. Can be adjusted from ~7.

As the washing method, a means capable of sufficiently removing non-rubber components and basic compounds contained in the entire rubber can be suitably used. There is a method in which the rubber is allowed to float by standing still, and only the water phase is discharged to extract the rubber. The number of times of washing can be any number that can reduce non-rubber components such as proteins and basic compounds to the desired amount. If the cycle is repeated, 3 times (3 cycles) or more is preferable, 5 times (5 cycles) or more is more preferable, and 7 times (7 cycles) or more is even more preferable.

The washing treatment is preferably carried out until the phosphorus content in the rubber is 500 ppm or less (preferably 200 ppm or less) and/or the nitrogen content is 0.15% by mass or less. By sufficiently removing phospholipids and proteins by the washing treatment, the above various performances are improved.

(Step 1-3)
In step 1-3, the washed rubber obtained in step 1-2 is treated with an acidic compound. As described above, the treatment adjusts the pH of the rubber as a whole to 2 to 7, making it possible to provide a modified natural rubber excellent in the various properties described above. The treatment with a basic compound tends to lower the heat aging resistance, but by further treating with an acidic compound, such problems can be prevented and good heat aging resistance can be obtained.

The acidic compound is not particularly limited, and inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, metaphosphoric acid, boric acid, boronic acid, sulfanilic acid, sulfamic acid; formic acid, acetic acid, glycolic acid, oxalic acid, propion acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, salicylic acid, methanesulfonic acid, Itaconic acid, benzenesulfonic acid, toluenesulfonic acid, naphthalenedisulfonic acid, trifluoromethanesulfonic acid, styrenesulfonic acid, trifluoroacetic acid, barbituric acid, acrylic acid, methacrylic acid, cinnamic acid, 4-hydroxybenzoic acid, aminobenzoic acid , Naphthalenedisulfonic Acid, Hydroxybenzenesulfonic Acid, Toluenesulfinic Acid, Benzenesulfinic Acid, α-Resorcinic Acid, β-Resorcinic Acid, γ-Resorcinic Acid, Gallic Acid, Phlologlycin, Sulfosalicylic Acid, Ascorbic Acid, Erythorbic Acid, Bisphenolic Acid and organic acids such as Among them, acetic acid, sulfuric acid, formic acid and the like are preferable. The above acidic compounds may be used alone or in combination of two or more.

The method of treating the coagulated rubber with an acid is not particularly limited as long as it is a method of bringing the coagulated rubber into contact with the above acidic compound. A spraying method and the like can be mentioned. Aqueous solutions of acidic compounds can be prepared by diluting and dissolving each acidic compound with water.

The content of the acidic compound in 100% by mass of the aqueous solution is not particularly limited, but the lower limit is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and the upper limit is preferably 15% by mass or less. It is more preferably 10% by mass or less, still more preferably 5% by mass or less. Favorable heat aging resistance is obtained as this content is in the said range.

The treatment temperature may be appropriately selected, but is preferably 10 to 50°C, more preferably 15 to 35°C. Also, the treatment time is generally preferably 3 seconds or longer, more preferably 10 seconds or longer, and still more preferably 30 seconds or longer. When it is 3 seconds or longer, there is a tendency that sufficient neutralization can be achieved and the effect can be preferably obtained. Although there is no upper limit, it is preferably 24 hours or less, more preferably 10 hours or less, and still more preferably 5 hours or less from the viewpoint of productivity.

In a treatment such as immersion in an aqueous solution of an acidic compound, it is preferable to adjust the pH to 6 or less.
Such neutralization provides excellent heat aging resistance. The upper limit of the pH is more preferably 5 or less, still more preferably 4.5 or less. Although the lower limit is not particularly limited and depends on the immersion time, it is preferably 1 or more, more preferably 2 or more because if the acid is too strong, the rubber deteriorates and waste water treatment becomes troublesome. Note that the immersion treatment can be carried out by leaving the coagulated rubber in an aqueous solution of an acidic compound.

After the treatment, after removing the compound used in the treatment of the acidic compound, the treated coagulated rubber may be appropriately washed. Examples of the washing treatment include methods similar to those described above. For example, the non-rubber components may be further reduced by repeating washing, and the content may be adjusted to a desired level. Alternatively, the coagulated rubber after the treatment with the acidic compound may be squeezed by a roll-type squeezer or the like to form a sheet or the like. By adding the step of squeezing the coagulated rubber, the pH of the surface and the inside of the coagulated rubber can be made uniform, and rubber with desired performance can be obtained. If necessary, after washing and squeezing, the rubber is passed through a creper, cut, and dried to obtain the modified natural rubber. The drying is not particularly limited, and can be carried out using a common dryer such as a trolley dryer, a vacuum dryer, an air dryer, a drum dryer, etc., which are used to dry the TSR.

[Manufacturing method 2]
(Step 2-1)
In step 2-1, natural rubber latex is deproteinized. As a result, a deproteinized natural rubber latex from which non-rubber components such as proteins have been removed can be prepared. Examples of the natural rubber latex used in step 2-1 are the same as those described above.

As the method for deproteinization, any known method capable of removing protein can be employed without particular limitation.

The proteolytic enzyme used for deproteinization is not particularly limited, and may be derived from bacteria, filamentous fungi, or yeast. Specifically, protease, peptidase, cellulase, pectinase, lipase, esterase, amylase and the like can be used singly or in combination.

The amount of the protease added is preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, and still more preferably 0.05 parts by mass or more with respect to 100 parts by mass of the solid content in the natural rubber latex. is. When it is at least the lower limit, there is a tendency that the protein decomposition reaction becomes sufficient.

In addition, in the deproteinization treatment, a surfactant may be added together with the protease. Examples of surfactants include anionic, cationic, nonionic and amphoteric surfactants.

(Step 2-2)
In step 2-2, the deproteinized natural rubber latex obtained in step 2-1 is washed. The washing removes non-rubber components such as proteins.

Step 2-2 can be carried out, for example, by flocculating the deproteinized natural rubber latex obtained in step 2-1 to prepare a coagulated rubber, and then washing the obtained coagulated rubber. As a result, non-rubber components such as proteins strongly adhered to the aggregated rubber can be removed.

Aggregation can be carried out in the same manner as in step 1-2 above. Furthermore, if necessary, it may be treated with a basic compound as described above. After the production of the coagulated rubber, a washing treatment is carried out. The washing treatment can be carried out in the same manner as in step 1-2 above, thereby removing non-rubber components such as proteins and basic compounds. For the same reason as described above, the cleaning treatment should be carried out until the phosphorus content in the rubber is 500 ppm or less (preferably 200 ppm or less) and/or the nitrogen content is 0.15% by mass or less. is preferred.

(Step 2-3)
In step 2-3, the washed rubber obtained in step 2-2 is treated with an acidic compound. Not only treatment with basic compounds, but also in acid coagulation, if the amount of acid is small, when the finally obtained rubber is extracted with water, it becomes alkaline to neutral, resulting in a decrease in heat aging resistance. Tend. Generally, an enzyme having an optimum pH in the alkaline region is used as a proteolytic enzyme for the reason that it can be suitably deproteinized, and the enzymatic reaction is performed under alkaline conditions according to the optimum pH. In many cases, in order to adjust the pH of the final rubber to 2 to 7, the deproteinization treatment of the natural rubber latex in step 2-1 is preferably performed at pH 8 to 11, and pH 8.5 to 11 is preferable. more preferred. After that, the rubber is coagulated under acidic conditions at the time of agglomeration, but if the rubber is only washed with water, the extraction described below raises the pH of the rubber to a level higher than that of the extract, and in this case, the deterioration of the heat aging resistance is particularly large. On the other hand, after solidification, if necessary, after treatment with a basic compound, treatment with an acidic compound can prevent such problems and obtain good heat aging resistance.

Examples of the acidic compound include those similar to those used in Step 1-3 above. The method of treating the coagulated rubber with an acid is not particularly limited as long as it is a method of bringing the coagulated rubber into contact with the above acidic compound. Examples include a method of spraying an aqueous solution. Aqueous solutions of acidic compounds can be prepared by diluting and dissolving each acidic compound with water.

The content of the acidic compound in 100% by mass of the aqueous solution is not particularly limited, but the lower limit is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and the upper limit is preferably 15% by mass or less. It is more preferably 10% by mass or less, still more preferably 5% by mass or less. Favorable heat aging resistance is obtained as this content is in the said range.

The treatment temperature and treatment time may be appropriately selected, and the same temperature as in step 1-3 may be employed. Further, in the treatment such as immersion in an aqueous solution of an acidic compound, it is preferable to adjust the pH to the same value as in step 1-3 above.

After the treatment, after removing the compound used in the treatment of the acidic compound, the treated flocculated rubber may be appropriately washed. Examples of the washing treatment include methods similar to those described above. For example, the non-rubber components may be further reduced by repeating washing, and the content may be adjusted to a desired level. After the washing treatment is completed, the modified natural rubber is obtained by drying. The method of drying is not particularly limited, and the above-described method or the like can be employed.

The content of NR in 100% by mass of the rubber component may be 40% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and preferably 95% by mass or less. Preferably, it is 85% by mass or less. Within the above range, the effect tends to be obtained more favorably.

Examples of rubber components that can be used in addition to NR include styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene - Diene rubber such as isoprene-butadiene copolymer rubber (SIBR). These may be used individually by 1 type, and may use 2 or more types together. Among them, BR is preferable.

The BR is not particularly limited, and BR with a high cis content, BR with a low cis content, BR containing syndiotactic polybutadiene crystals, and the like can be used. Examples of commercially available products include products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, and the like. These may be used alone or in combination of two or more.

The cis content of BR is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 98% by mass or more, and the upper limit is not particularly limited. Within the above range, the effect tends to be obtained more favorably.
The cis content of BR can be measured by infrared absorption spectroscopy.

BR may be either non-denatured BR or denatured BR.
Functional groups possessed by the modified BR include, for example, an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, and a sulfide group. group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. is mentioned. In addition, these functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), an alkoxysilyl group ( An alkoxysilyl group having 1 to 6 carbon atoms is preferable), and an amide group is preferable.

When BR is contained, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more, and preferably 60% by mass or less, more preferably 40% by mass. % or less, more preferably 30 mass % or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition contains at least one fragrance selected from the group consisting of cedren, cedrol, cedrenol, methyl jasmonate, methyl dihydrojasmonate and anethole.

Cedren, cedrol and cedrenol are the main components of cedar oil (cedarwood oil). When used in the rubber composition, each component may be isolated from cedar oil and used, or the cedar oil may be used as it is.
Methyl jasmonate and methyl dihydrojasmonate are aromatic components of jasmine and can be industrially produced by a general method.
Anethole is the main component of anise oil and fennel oil. When used in the rubber composition, anethole may be isolated from anise oil or fennel oil and used, or anise oil or fennel oil may be used as it is.

As a commercial product of the fragrance, products of Ogawa Koryo Co., Ltd., Takasago Koryo Kogyo Co., Ltd., etc. can be used.

Among the perfumes mentioned above, cedren, cedrol and cedrenol are preferred, and their combined use is more preferred. Since these are hydrocarbons (terpenes) having isoprene as a constituent unit, they can be well dispersed in NR and exhibit excellent odor suppressing effects and workability improving effects.

The content of the perfume is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and still more preferably 0.7 parts by mass or more with respect to 100 parts by mass of the rubber component. is 2.5 parts by mass or less, more preferably 1.5 parts by mass or less, and still more preferably 1.2 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain carbon black.
Examples of carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550 and N762. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can. These 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 20 m ² /g or more, more preferably 40 m ² /g or more, and is preferably 100 m ² /g or less, more preferably 80 m ² /g. It is below. Within the above range, the effect tends to be obtained more favorably.
The N ₂ SA of carbon black is a value measured according to JIS K6217-2:2001.

When carbon black is contained, the content of carbon black is preferably 10 parts by mass or more, more preferably 25 parts by mass or more, and still more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component, and It is preferably 80 parts by mass or less, more preferably 60 parts by mass or less. Within the above range, the effects of the present invention can be obtained more favorably.

The rubber composition may contain silica.
Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrated silicic acid), but wet silica is preferred because it contains many silanol groups. Commercially available products of Evonik Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

When silica is contained, the content of silica is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and preferably 150 parts by mass or less, more preferably It is 100 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

When the rubber composition contains silica, it preferably further contains a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3- sulfides such as triethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl-based such as methoxysilane; amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

When a silane coupling agent is contained, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 15 parts by mass with respect to 100 parts by mass of silica. Below, more preferably 10 mass parts or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain an adhesive resin.
Examples of adhesive resins include phenol-based resins, alkylphenol-based resins, terpene-based resins, coumarone-based resins, indene-based resins, coumarone-indene-based resins, styrene-based resins, acrylic-based resins, rosin-based resins, which are commonly used in the tire industry. Aromatic hydrocarbon-based resins such as dicyclopentadiene-based resins (DCPD-based resins), aliphatic hydrocarbon-based resins such as C5-based resins, C8-based resins, C9-based resins, C5/C9-based resins, and hydrogenation of these things, etc. Commercially available products include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nichinuri Chemical Co., Ltd., Japan. Catalysts, products of JX Nippon Oil & Energy Corporation, Zeon Corporation, Harima Kasei Co., Ltd., Toagosei Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., etc. can be used. These may be used alone or in combination of two or more.

When an adhesive resin is contained, the content of the adhesive resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 20 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain wax.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers of ethylene and propylene. As commercially available products, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

When wax is contained, the content of wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. Preferably, it is 3 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain oil.
Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, or the like can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. These may be used individually by 1 type, and may use 2 or more types together.

When oil is contained, the content of oil is preferably 3 parts by mass or more, more preferably 7 parts by mass or more, and preferably 30 parts by mass or less, more preferably 100 parts by mass of the rubber component. It is 15 parts by mass or less.

The rubber composition may contain an antioxidant.
Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; -Isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based antioxidants; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, monophenolic anti-aging agents such as styrenated phenol; inhibitors and the like. As commercially available products, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used. These may be used individually by 1 type, and may use 2 or more types together. Among them, p-phenylenediamine antioxidants and quinoline antioxidants are preferred.

When an anti-aging agent is contained, the content of the anti-aging agent is preferably 1 part by mass or more, more preferably 4 parts by mass or more, and still more preferably 5.5 parts by mass or more with respect to 100 parts by mass of the rubber component. Yes, preferably 10 parts by mass or less, more preferably 8 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain stearic acid.
As the stearic acid, conventionally known ones can be used, and commercially available products include NOF Corporation, NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd., and the like. Available. These may be used individually by 1 type, and may use 2 or more types together.

When stearic acid is contained, the content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain zinc oxide.
As zinc oxide, conventionally known ones can be used, and commercially available products are available from Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd. etc. products can be used. These may be used individually by 1 type, and may use 2 or more types together.

When zinc oxide is contained, the content of zinc oxide is preferably 1 part by mass or more, more preferably 4 parts by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. Preferably, it is 6 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly used in the rubber industry. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

When sulfur is contained, the content of sulfur is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 6 parts by mass or less, more preferably It is 4 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain a vulcanization accelerator.
Vulcanization accelerators include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis (2 -ethylhexyl) thiuram-based vulcanization accelerators such as thiuram disulfide (TOT-N); N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide ( TBBS), N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide and other sulfenamide additives. Sulfurization accelerator: Guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine and orthotolylbiguanidine can be mentioned. As commercially available products, products of Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and thiazole-based vulcanization accelerators are preferred.

When a vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. It is 8 parts by mass or less, more preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In addition to the above components, the rubber composition contains additives commonly used in the tire industry, such as organic peroxides; fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. ; and the like may be further added. The content of these additives is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

The above rubber composition can be produced, for example, by kneading each of the above components using a rubber kneading apparatus such as an open roll mixer or a Banbury mixer, followed by vulcanization.

As for the kneading conditions, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C in the base kneading step in which additives other than the vulcanizing agent and the vulcanization accelerator are kneaded. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. A composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to vulcanization treatment such as press vulcanization. The vulcanization temperature is generally 140-190°C, preferably 150-185°C. Vulcanization time is usually 5 to 15 minutes.

The rubber composition described above is preferably used for sidewalls, but is used for members other than sidewalls, such as tread (cap tread), base tread, undertread, clinch apex, bead apex, breaker cushion rubber, and carcass cord coating. It may also be used for rubbers, insulations, chafers, inner liners, etc., and side reinforcing layers of run-flat tires.

The pneumatic tire of the present invention is manufactured by a normal method using the rubber composition.
That is, the rubber composition blended with the above components is extruded in an unvulcanized stage according to the shape of each tire member such as the tread, and molded together with other tire members on a tire molding machine by an ordinary method. to form an unvulcanized tire. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire can be used as a tire for passenger cars, a tire for trucks and buses, a tire for two-wheeled vehicles, a high-performance tire, and the like, and can be particularly preferably used as a tire for trucks and buses.

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

Various chemicals used in the production examples are collectively described below.
Field latex: Field latex Emal E-27C (surfactant) obtained from Muhibaratex Co., Ltd.: Emal E-27C (sodium polyoxyethylene lauryl ether sulfate, active ingredient 27% by mass) manufactured by Kao Corporation
NaOH: NaOH manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.
Wingstay L (anti-aging agent): ELIOKEM Wingstay L (butylated compound of condensate of ρ-cresol and dicyclopentadiene)
Emulvin W (surfactant): Emulvin W (aromatic polyglycol ether) manufactured by LANXESS
Tamol NN9104 (surfactant): Tamol NN9104 from BASF (sodium salt of naphthalenesulfonic acid/formaldehyde)
Van gel B (surfactant): Van gel B (hydrate of magnesium aluminum silicate) from Vanderbilt

(Preparation of antioxidant dispersion)
462.5 g of water was mixed with 12.5 g of Emalvin W, 12.5 g of Tamol NN9104, 12.5 g of Van gel B, and 500 g of Wingstay L (1000 g in total) in a ball mill for 16 hours to prepare an antioxidant dispersion.

(Production example 1)
After adjusting the solid content concentration (DRC) of the field latex to 30% (w / v), 25 g of 10% Emal E-27C aqueous solution and 60 g of 25% NaOH aqueous solution were added to 1000 g of the latex, and the mixture was heated at room temperature (23 ° C.). A saponification reaction was carried out for 24 hours to obtain a saponified natural rubber latex. Then 6 g of the antioxidant dispersion was added and stirred for 2 hours, followed by further dilution with water to a rubber concentration of 15% (w/v). Then, while stirring slowly, formic acid was added to adjust the pH to 4.0, then a cationic polymer flocculant was added and stirred for 2 minutes to cause aggregation. The aggregate (aggregated rubber) thus obtained had a diameter of about 0.5 to 5 mm. The obtained agglomerate was taken out and immersed in 1000 ml of a 2% by mass sodium carbonate aqueous solution at normal temperature (23° C.) for 4 hours, and then the rubber was taken out. To this, 2000 ml of water was added, stirred for 2 minutes, and water was removed as much as possible, which was repeated 7 times. After that, 500 ml of water was added, and 2 mass % formic acid was added until the pH reached 4, and left for 15 minutes. Furthermore, after removing as much water as possible, adding water again and stirring for 2 minutes was repeated three times, after squeezing the water with a water squeeze roll to form a sheet, it was dried at 90 ° C. for 4 hours to form a solid rubber ( A modified natural rubber A) was obtained.

(Production example 2)
Commercially available high ammonia latex [manufactured by Muhibaratex of Malaysia, solid rubber content 62.0%] is diluted with 0.12% sodium naphthenate aqueous solution to make the solid rubber content 10%, and diphosphate diphosphate is added. Sodium hydride was added to adjust the pH to 9.2. Then, 0.87 g of proteolytic enzyme (Alcalase 2.0 M) was added to 10 g of the rubber content, and after readjusting the pH to 9.2, the mixture was maintained at 37° C. for 24 hours.
Next, a 1% aqueous solution of a nonionic surfactant (trade name Emulgen 810, manufactured by Kao Corporation) was added to the enzyme-treated latex to adjust the rubber concentration to 8%. Centrifuge for 30 minutes. Next, the creamy fraction produced by centrifugation was dispersed in a 1% aqueous solution of Emulgen 810 to adjust the rubber concentration to 8%, and then the mixture was again rotated at a rotational speed of 11,000 rpm for 30 minutes. Centrifuge for 1 minute. After repeating this operation twice, the resulting creamy fraction was dispersed in distilled water to prepare deproteinized natural rubber latex having a solid rubber content of 60%.
2 mass % formic acid was added to this latex until the pH reached 4, and a cationic polymer flocculant was further added to obtain rubber granules of 0.5 to 5 mm. Water was removed as much as possible, 50 g of water was added to 10 g of the rubber content, and 2 mass % formic acid was added until the pH reached 3. After 30 minutes, the rubber was pulled out, formed into a sheet by a creper, and dried at 90°C for 4 hours to obtain a solid rubber (modified natural rubber B).

(Production example 3)
After diluting the field latex with water to a DRC of 15% (w/v), formic acid was added with slow stirring to adjust the pH to 4.0-4.5 and coagulate. Aggregated rubber was pulverized, washed repeatedly with 1000 ml of water, and then dried at 110° C. for 120 minutes to obtain a solid rubber (modified natural rubber C).

The modified natural rubber obtained above was evaluated as follows, and the results are shown in Table 1. Only the modified natural rubbers A and B were measured for pH, nitrogen content and gel content.

<Measurement of rubber pH>
Cut 5 g of the obtained rubber into pieces with a total of three sides of 5 mm or less (about 1 to 2 x about 1 to 2 x about 1 to 2 (mm)), put it in a 100 ml beaker, and add 50 ml of distilled water at room temperature (23 ° C.). was added, the temperature was raised to 90°C in 2 minutes, and then microwaves (300 W) were irradiated for 13 minutes (total 15 minutes) while adjusting to keep the temperature at 90°C. Then, the immersion water was cooled in an ice bath to 25° C., and the pH of the immersion water was measured using a pH meter.

<Measurement of nitrogen content>
(Acetone extraction (preparation of test piece))
About 0.5 g of a sample was prepared by chopping each solid rubber into 1 mm square pieces. The sample was immersed in 50 g of acetone, and after 48 hours at room temperature (25° C.), the rubber was taken out and dried to obtain each test piece (antiaging agent extracted).

(measurement)
The nitrogen content of the obtained test piece was measured by the following method.
The nitrogen content was determined by decomposing and gasifying the acetone-extracted test pieces obtained above using a trace nitrogen carbon measuring device "SUMIGRAPH NC95A (manufactured by Sumika Chemical Analysis Service, Ltd.)". The nitrogen content was quantified by analyzing with a gas chromatograph “GC-8A (manufactured by Shimadzu Corporation)”.

<Measurement of phosphorus content>
The phosphorus content was determined using an ICP emission spectrometer (P-4010, manufactured by Hitachi Ltd.).

<Measurement of gel content>
About 70 mg of a raw rubber sample cut to 1 mm×1 mm was accurately weighed, 35 mL of toluene was added thereto, and the sample was allowed to stand in a cool and dark place for 1 week. Next, it was subjected to centrifugal separation to precipitate the gel content insoluble in toluene, the soluble content of the supernatant was removed, and only the gel content was solidified with methanol, dried, and the mass was measured. The gel content (% by mass) was determined by the following formula.
Gel content (% by mass) = [mg after drying/mg of initial sample] x 100

Various chemicals used in Examples and Comparative Examples will be collectively described.
NR1: TSR20 (phosphorus content: 572 ppm)
NR2: TSS8 (phosphorus content: more than 500 ppm)
Modified Natural Rubber A: Production Example 1
Modified Natural Rubber B: Production Example 2
Modified Natural Rubber C: Production Example 3
BR: BR150B (cis content: 98% by mass) manufactured by Ube Industries, Ltd.
Carbon black: Diablack N550 (N ₂ SA: 42 m ² /g) manufactured by Mitsubishi Chemical Corporation
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Antiaging agent 6C: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Antiaging agent RD: Nocrack 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Zinc oxide: Type 2 zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Beads stearic acid manufactured by NOF Corporation Tsubaki Oil: Diana Process NH-70S manufactured by Idemitsu Kosan Co., Ltd.
Perfume 1: Cedar oil manufactured by Ogawa Perfumery Co., Ltd. (main components: cedren, cedrol, cedrenol)
Fragrance 2: Methyl jasmonate manufactured by Ogawa Perfumery Co., Ltd. Perfume 3: Methyl dihydrojasmonate manufactured by Ogawa Perfumery Co., Ltd. Perfume 4: Anise oil (main component: anethole) manufactured by Ogawa Perfumery Co., Ltd.
Fragrance 5: Strawberry oil manufactured by Soda Aromatic Co., Ltd. (main component: propylene glycol)
Sulfur: powdered sulfur (containing 5% oil) manufactured by Tsurumi Chemical Industry Co., Ltd.
Vulcanization accelerator NS: Noxcellar NS (N-tert-butyl-2-benzothiazolylsulfenamide (TBBS)) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator CZ: Noxceler CZ (N-cyclohexyl-2-benzothiazylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator DM: Noxceler DM (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Examples and Comparative Examples)
According to the formulation shown in Table 2, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerator were kneaded at 150 ° C. for 5 minutes, and the kneaded product was obtained. Obtained. Next, sulfur and a vulcanization accelerator were added to the resulting kneaded material, and the mixture was kneaded at 80° C. for 5 minutes using an open roll to obtain an unvulcanized rubber composition.
The resulting unvulcanized rubber composition was molded into a sidewall shape, laminated with other tire members to form an unvulcanized tire, vulcanized at 150 ° C. for 12 minutes, and a test tire ( Size: 195/65R15) was manufactured.

The unvulcanized rubber composition and test tire thus obtained were used for the following evaluations. Table 2 shows the results.

(Odor evaluation index)
A vulcanized sample (2 mm in thickness, 150 mm in length and width) obtained by vulcanizing each unvulcanized rubber composition at 170° C. for 12 minutes was placed in a polyethylene bag, and the odor intensity after 24 hours was evaluated. For the evaluation, the odor intensity was ranked in the following 6 stages (0 to 5) based on the 6-stage odor intensity display method, and the average value of 3 monitors was adopted.
Intensity 0: No odor Intensity 1: Barely perceptible odor intensity 2: Weak odor intensity 3: Easily perceivable odor intensity 4: Strong odor intensity 5: Strong odor

(Workability index)
For each unvulcanized rubber composition, the Mooney viscosity was measured at 100° C. according to JIS K6300 (1994), and indexed with Comparative Example 2 being 100. The smaller the index, the lower the Mooney viscosity and the better the workability.

(Fuel efficiency index)
Using a rolling resistance tester, measure the rolling resistance when running each test tire with a rim (15 × 6 JJ), internal pressure (230 kPa), load (3.43 kN), speed (80 km / h), It is indicated as an index when Comparative Example 2 is set to 100. A larger index indicates lower rolling resistance and better fuel efficiency.

From Table 2, examples containing a predetermined amount of natural rubber and at least one fragrance selected from the group consisting of cedren, cedrol, cedrenol, methyl jasmonate, methyl dihydrojasmonate, and anethole have a pronounced odor. was suppressed, and workability was also improved.

Claims (5)

Containing a rubber component, at least one fragrance selected from the group consisting of cedren, cedrol, cedrenol, methyl jasmonate , and anethole, and sulfur,
The content of natural rubber is 40% by mass or more in 100% by mass of the rubber component,
A rubber composition for tires containing 2 to 6 parts by mass of sulfur per 100 parts by mass of the rubber component. A rubber component, at least one fragrance selected from the group consisting of cedren, cedrol, cedrenol, methyl jasmonate, methyl dihydrojasmonate and anethole, sulfur, and an antioxidant,
The content of natural rubber is 40% by mass or more in 100% by mass of the rubber component,
The sulfur content is 2 to 6 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for tires in which the content of an antioxidant is 4 to 8 parts by mass with respect to 100 parts by mass of the rubber component. 3. The rubber composition for tires according to claim 1, which contains a sulfenamide vulcanization accelerator and/or a thiazole vulcanization accelerator. The rubber composition for tires according to any one of claims 1 to 3, wherein the natural rubber is a modified natural rubber having a phosphorus content of 500 ppm or less. A pneumatic tire produced using the rubber composition according to any one of claims 1 to 4 .