JP2020090640A - Rubber composition and pneumatic tire - Google Patents

Abstract

To provide a rubber composition containing an odor-less natural rubber that conveniently reduces an odor of natural rubber made from cup lump while preventing deterioration of physical properties such as thermal aging resistance, and a pneumatic tire including the same.SOLUTION: A rubber composition contains a rubber component containing an odor-less natural rubber with an odorous component index of 0.1×10-2.0×10, and a filler.SELECTED DRAWING: None

Description

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

Natural rubber (NR), which is widely used as a material for a rubber composition, is a solidified sap (latex) collected from a rubber tree called Hevea brasiliensis cultivated in a tropical region. As a method of solidifying, a method of coagulating with an acid such as formic acid, a method of producing by drying, crushing a cup lamp obtained by naturally coagulating in a cup for latex collection in a rubber plantation, and repeating washing, There is a method of manufacturing by pressing after drying.

Since it is produced by the method as described above, natural rubber contains many non-rubber components such as proteins, lipids and sugars in addition to the polyisoprene component. Therefore, these components are putrefaction during the storage period before the drying, which causes the malodor. In particular, cup lamps contain a very large amount of non-rubber components, and have a long storage period due to storage in farms, storage/transportation in processing plants, etc., and odor problems are likely to occur. However, from the viewpoint of easiness of production and cost, in recent years, a large amount of natural rubber using cup lamps as raw materials has been used for tire applications. The putrefactive odor of natural rubber has become a problem not only in natural rubber processing plants, but also in rubber product manufacturing plants such as tires, where the working environment of the factory deteriorates and the environment around the factory is affected.

In order to solve the problem of odor of natural rubber, odor is reduced by adding proteolytic enzymes and surfactants to natural rubber latex and reacting them to remove proteins that are one of the causes of decay. The rubber odor is reduced by the method (see, for example, Patent Document 1) or by adding an inorganic salt and a proteolytic enzyme to a serum produced when concentrating and purifying natural rubber from natural rubber latex to prepare fine particle natural rubber. A method (see Patent Document 2, for example) is disclosed.

Further, Patent Document 3 discloses a method of adding an antioxidant to natural rubber latex and further reducing the drying temperature to reduce odor. In addition, a method of diminishing an odor component by immersing a coagulated product of natural rubber latex in an alkaline solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is also disclosed (see, for example, Patent Documents 4 and 5).

Japanese Patent No. 3654934 Japanese Patent No. 3750100 Japanese Patent No. 5312439 Japanese Patent No. 3573498 JP, 2013-249411, A

As described above, various studies have been conducted to remove the odor of natural rubber. For example, as in Patent Documents 1 and 2, a method for removing proteins from natural rubber latex or serum by a proteolytic enzyme treatment. Can be applied only when a liquid raw material such as latex or serum is used, and cannot reduce the odor of solid natural rubber such as cup lamp. Similarly, Patent Document 3 can be applied only when latex is used as a raw material, and odor cannot be reduced for solid natural rubber such as a cup lamp. On the other hand, the odor can be reduced by the method of treating the coagulated rubber with a strong alkaline solution such as an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide as in Patent Documents 4 and 5, but as a result of the study by the present inventors, after treatment, It was found that the rubber deteriorates during the drying, and it was found that the reduction of odor and the maintenance of natural rubber properties cannot be achieved at the same time.
Thus, there has not yet existed a technique for easily reducing the odor and maintaining the physical properties of a rubber composition using a cup lamp that is easily and inexpensively available.

The present invention solves the above problems, easily reduces the odor of natural rubber using a cup lamp as a raw material, and a rubber composition containing an odor-reduced natural rubber that does not reduce physical properties such as heat aging resistance, and the like. It is intended to provide a used pneumatic tire.

The present invention relates to a rubber composition containing a rubber component containing an odor-reducing natural rubber having an odor component index of 0.1×10 ^{6 to} 2.0×10 ⁶ , and a filler.

The odor component index of the rubber composition is preferably 1.0×10 ^{5 to} 5.0×10 ⁵ .

The odor-reduced natural rubber is obtained by crushing a cup lamp and crushing and washing the cup lamp to crush it, and reducing the moisture content of the cup lamp crushed and washed by the crushing and washing treatment to obtain a moisture-reduced natural rubber. It is preferably obtained through a dehydration treatment and a drying treatment of drying the moisture-reduced natural rubber.

The moisture content of the moisture-reduced natural rubber is preferably 30% or less.
The drying temperature in the drying treatment is preferably 140° C. or lower.

Furthermore, it is preferable to include a base treatment of bringing the natural rubber with reduced moisture content into contact with a basic solution before the drying treatment.
It is preferable that the basic solution further contains a surfactant.

It is preferable that 5 to 100 parts by mass of the filler is contained with respect to 100 parts by mass of the rubber component.

The present invention also relates to a pneumatic tire having a tire member using the rubber composition.
It is preferable that the tire member is a tire outer layer member.

According to the present invention, a rubber composition containing a filler and a rubber component containing an odor-reducing natural rubber having an odor component index of 0.1×10 ^{6 to} 2.0×10 ⁶ , and thus the odor of natural rubber can be easily In addition, the physical properties such as heat aging resistance can be maintained without deteriorating. Therefore, it is possible to provide a rubber composition containing such an odor-reducing natural rubber, which reduces odor and does not deteriorate physical properties such as heat aging resistance.

[Rubber composition]
The rubber composition of the present invention contains a rubber component containing a odor reducing natural rubber having an odor component index of 0.1×10 ^{6 to} 2.0×10 ⁶ , and a filler. Since the odor reducing natural rubber is included, the odor of the rubber composition can be reduced. Further, deterioration of physical properties such as heat aging resistance can be suppressed.

The odor reducing natural rubber has an odor component index of 0.1×10 ^{6 to} 2.0×10 ⁶ , but the lower limit is preferably 0.3×10 ⁶ or more, more preferably 0.5×10 ⁶ or more. is there. The upper limit is preferably 1.5×10 ⁶ or less, and more preferably 1.0×10 ⁶ or less from the viewpoint of odor control. The odor component index of the odor-reduced natural rubber is the sum of all the peak area ratios of the main causative substances of the odor of natural rubber detected using GCMS, corrected by the olfactory threshold of each component, It can be measured by the method described in Examples below.

The odor-reducing natural rubber having an odor component index of 0.1×10 ^{6 to} 2.0×10 ⁶ is, for example, a crushing washing treatment for crushing a cup lamp and washing the crushed cup lamp, crushing and washing by the crushing washing treatment. The odor-reduced natural rubber can be produced through a dehydration treatment for reducing the moisture content of the cup lamp thus obtained to obtain a moisture-reduction natural rubber, and a drying treatment for drying the moisture-reduction natural rubber. The odor-reducing natural rubber may include other treatments such as a base treatment, a pH adjusting treatment, and a washing treatment described below, as long as the above-mentioned treatments are included, and each treatment may be performed once or plural times. It may be repeated several times. Among them, it is preferable to carry out the dehydration treatment after performing the crushing and washing treatment a plurality of times, because the above effect can be obtained more suitably. It is also preferable to perform "crushing cleaning treatment and dehydration treatment" again after "crushing cleaning treatment and dehydration treatment", and to perform a plurality of series of "crushing cleaning treatment and dehydration treatment". More preferably, it is performed once.

The odor of natural rubber is that the non-rubber components of natural rubber, such as proteins, lipids and sugars, are decomposed during storage or decomposed during drying to generate lower fatty acids, which are the odor-causing substances. Is thought to be the cause. Therefore, by reducing the water content of the crushed and washed cup lamp, it is possible to suppress spoilage during storage and suppress the generation of lower fatty acids, which are odor-causing substances, even when the cup lamp is stored later. Can be reduced. It is considered that crushing improves the air flow during storage and can suppress the progress of putrefaction. Furthermore, since only crushing, washing, dehydration and drying are performed, physical properties such as heat aging resistance can be maintained without being deteriorated. Therefore, it is possible to provide a rubber composition containing an odor-reduced natural rubber produced through these treatments and having a reduced odor.

In the rubber composition, the content of the odor reducing natural rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 25% by mass or more, further preferably 35% by mass or more. The upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less. When the content is within the above range, the odor of the rubber composition is suppressed and the required characteristics of the tire member tend to be secured.

[Manufacture of odor reducing natural rubber]
The odor-reducing natural rubber can be produced, for example, through the crushing washing treatment, the dehydration treatment and the drying treatment.

(Crushing and washing process)
The crushing and washing process is a process of crushing a cup lamp and washing the crushed cup lamp to obtain a crushed and washed cup lamp (crushing and washing process).

A cup lamp is provided for the crushing and washing process. A cup lamp is obtained by naturally coagulating natural rubber latex in a latex collecting cup in a rubber farm or the like, and by coagulating the natural rubber latex with an acid such as formic acid and drying to solidify it. Compared to other solid natural rubber such as latex coagulated rubber produced, it contains a lot of non-rubber components such as proteins, lipids, sugars, etc. other than polyisoprene components. It is a material that is prone to odor problems because it has a long storage period due to storage and transportation periods. In the present invention, even when a cup lamp which is apt to cause such an odor problem is used as a rubber raw material, the odor can be easily reduced and the physical properties such as heat aging resistance can be maintained without being deteriorated. It is possible to produce odor-reduced natural rubber.

In the crushing and washing process, the cup lamp is crushed.
The cup lamp may be crushed by using a known crusher (crusher) or a crusher. As the crusher, a hammer crusher (hammer mill), a prebreaker or the like is used, and as the crusher, a plastic crusher, a slab cutter, a rotary cutter, a shredder or the like is used.

In the crushing and washing process, after the cup lamp is crushed, the crushed cup lamp is washed.
The method for washing the crushed cup lamp is not particularly limited, for example, a method of diluting the crushed cup lamp with water and then centrifuging, leaving the crushed cup lamp in a water bath to float, and only the aqueous phase And a crushed cup lamp is removed, and a crushed cup lamp is washed with stirring in a water bath, and only a water phase is discharged to remove the crushed cup lamp.

The average diameter of the cup lamp after crushing and washing is preferably 5 cm or less, more preferably 3 cm or less, still more preferably 1 cm or less. The lower limit of the average diameter is not particularly limited, but is preferably 3 mm or more, more preferably 5 mm or more. When the average diameter of the cup lamp after crushing and washing is within the above range, the above effect can be more suitably obtained.
In the present specification, the average diameter of the crushed and washed cup lamps is arbitrarily selected from the 20 crushed and washed cup lamps, and the frequency of the equivalent volume sphere equivalent diameter is determined for these 20 cup lamps. It means the mode diameter calculated from the particle size distribution.

As the cup lamp to be subjected to the crushing and washing treatment, it is preferable to use one having a natural rubber latex within 2 weeks after coagulation, more preferably within 1 week, particularly preferably within 3 days. This can effectively prevent the generation of odor due to putrefaction during storage.

(Dehydration treatment)
The dehydration treatment is a step (dehydration step) of reducing the water content of the cup lamp that has been crushed and washed by the above crushing and cleaning treatment to obtain natural rubber with reduced water content. By this step, it becomes possible to remove the substance causing the odor from the natural rubber together with the water content.

In the above dehydration treatment, the method of reducing the moisture content of the cup lamp is not particularly limited as long as a moisture content-reduced natural rubber having a reduced moisture content can be obtained. A natural rubber having a reduced moisture content and a reduced moisture content can be obtained. Among them, the method of squeezing the cup lamp is preferable, and the method of squeezing the cup lamp is more preferable, because the water contained in the cup lamp can be removed and the above effect can be obtained more suitably. Examples of the method of squeezing the cup lamp include a method of squeezing the cup lamp by passing it through a roll. A creeper may be used as a device for squeezing the cup lamp through a roll.

When the cup lamp is passed through a roll and squeezed, the moisture-reduced natural rubber has a relatively flat shape.
The thickness of the natural rubber with reduced moisture content is preferably 3 mm or more, more preferably 5 mm or more, still more preferably 8 mm or more. Thereby, the natural rubber can be produced with higher productivity. On the other hand, the thickness is preferably 3 cm or less, more preferably 2 cm or less. Thereby, the effect of performing the dehydration treatment can be more suitably obtained.

The water content of the water content-reduced natural rubber is preferably 30% or less, more preferably 25% or less, still more preferably 15% or less. When the moisture content of the natural rubber having a reduced moisture content obtained by the dehydration treatment is within such a range, it is possible to suppress the progress of putrefaction during storage. On the other hand, the lower limit of the water content is not particularly limited, and the lower the better, the better, but from the viewpoint of the efficiency of adjusting the water content, 3% or more is preferable, 5% or more is more preferable, and 10% or more is further preferable. ..
The water content can be obtained from the difference in weight before and after sufficiently drying the water content-reduced natural rubber, as will be carried out in Examples described later.

The moisture content of the moisture content-reduced natural rubber may not be within the above range by performing only one dehydration treatment depending on the state of the cup lamp used for the dehydration treatment. The above range can be obtained by repeating the process once.
The moisture content of the moisture content-reduced natural rubber may be that measured immediately after the moisture content-reduced natural rubber is obtained by dehydration treatment.

In the production of the odor-reducing natural rubber, a dehydration treatment is carried out. Therefore, even if the dehydration treatment is carried out for a long period of time, the progress of putrefaction is suppressed and the odor can be reduced. Therefore, when the moisture-reduced natural rubber is stored for a long period of time after the dehydration treatment, the above-mentioned effects are more remarkably exhibited.

(Drying process)
In the production of the odor-reduced natural rubber, a drying process (drying step) for drying the moisture-reduced natural rubber is performed.

The method for drying is not particularly limited, and a method usually used for drying natural rubber can be used.

The drying temperature in the above drying treatment is preferably 145° C. or lower, more preferably 140° C. or lower, further preferably 135° C. or lower, particularly preferably 130° C. or lower, further 125° C. or lower, 120° C. or lower, 115° C. or lower. Is preferred. By setting the drying temperature in such a range, the generation of lower fatty acids due to the decomposition of the non-rubber component can be suppressed, and the odor can be reduced. On the other hand, the lower limit of the drying temperature is not particularly limited, but as the temperature is lowered, it takes more time to obtain a dried state of the same degree. Therefore, from the viewpoint of efficiency and productivity, 75° C. or higher is preferable. It is preferably 80°C or higher, more preferably 100°C or higher.

Surprisingly, in the production of the odor-reduced natural rubber, both the production of a moisture-reduced natural rubber having a low moisture content and the drying of the moisture-reduced natural rubber at a constant temperature or lower (125° C. or lower) are performed. By virtue of this, that is, by carrying out dehydration treatment and drying treatment at a drying temperature of a certain temperature or less, the above effects obtained by adding the effects of performing each independently with respect to odor reduction (so-called synergistic effect) The present inventors have for the first time found that the following is obtained. That is, by performing the dehydration treatment and then setting the drying temperature in the drying treatment to 125° C. or lower (preferably 120° C. or lower, more preferably 115° C. or lower), the odor component ratio can be significantly reduced synergistically. Also, in the rubber composition using the odor-reduced natural rubber obtained in this way, the odor component rate can also be significantly reduced synergistically.

The drying time in the above-mentioned drying treatment can be appropriately set according to the above-mentioned drying temperature, and is preferably as short as possible if the water can be removed sufficiently (completely).

(Base treatment)
The production of the odor-reduced natural rubber preferably further includes a base treatment (base treatment step) of bringing the moisture-reduced natural rubber into contact with a basic solution before the drying treatment. That is, after the dehydration treatment, it is preferable to perform a base treatment in which the moisture-reduced natural rubber obtained by the dehydration treatment is brought into contact with a basic solution. In the production of the odor-reduced natural rubber, by performing the above dehydration treatment, even when the moisture content-reduced natural rubber is stored, it is possible to suppress the spoilage during storage and suppress the generation of lower fatty acids that are odor-causing substances. Although it is possible to reduce the odor, it is still not possible to completely suppress the generation of lower fatty acids.However, by contacting the natural rubber with a reduced moisture content after storage with a basic solution, a small amount is generated. The odor can be further reduced by neutralizing and removing the lower fatty acid that has gone away.
When contacting the moisture-reduced natural rubber with a basic solution in the above-mentioned base treatment, the moisture-reduced natural rubber may be used as it is, or may be appropriately cut into a desired size and then treated. Good.

In the above base treatment, as a method for bringing the moisture content reduced natural rubber into contact with a basic solution, for example, a moisture content reduced natural rubber is coated with a basic solution, sprayed by a spray, a shower or the like, or a moisture content reduced natural rubber is used. It can be carried out by immersing the rubber in a basic solution, but from the viewpoint of deodorizing effect and efficiency, the method of immersing the natural rubber having a reduced water content in the basic solution is preferable.

When adopting a method of immersing the moisture content reduced natural rubber in a basic solution as a method of bringing the moisture content reduced natural rubber into contact with a basic solution, the moisture content reduced natural rubber is left in the basic solution. Although it can also be carried out by placing it, it is preferable to carry out stirring and/or microwave irradiation during the immersion, because the deodorizing effect is further promoted.

The contact time (treatment time) between the moisture-reduced natural rubber and the basic solution in the base treatment is not particularly limited, but is preferably 5 minutes or longer, more preferably 10 minutes or longer, still more preferably 30 minutes or longer, 3 hours or more is particularly preferable. By contacting for 5 minutes or more, the above effect can be obtained better. The upper limit of the contact time between the moisture-reduced natural rubber and the basic solution depends on the pH and concentration of the basic solution and is not particularly specified, but from the viewpoint of productivity, it is preferably 48 hours or less, and 24 hours or less. Is more preferable, and 16 hours or less is further preferable.

The contact temperature (treatment temperature) between the moisture-reduced natural rubber and the basic solution in the base treatment is not particularly limited, but is preferably 10 to 50° C., more preferably 15 to 35° C., for example. Especially, room temperature (20-30 degreeC) is especially preferable.

The basic solution is preferably a solution containing at least one basic inorganic substance selected from the group consisting of metal carbonates, metal hydrogen carbonates, metal phosphates, and ammonia. By using such a basic solution as a basic solution that is brought into contact with a moisture-reduced natural rubber, it is possible to further neutralize and remove odor components, thereby further reducing the odor of the moisture-reduced natural rubber. It is also possible to maintain the physical properties such as heat aging resistance without deteriorating.
Examples of the basic solution include an aqueous solution containing the basic inorganic substance and an alcohol solution containing the basic inorganic substance. An aqueous solution containing the basic inorganic substance is preferable.
The basic solution can be prepared by diluting and dissolving the basic inorganic substance with a solvent such as water or alcohol.

Examples of the metal carbonate include alkali metal carbonates such as lithium carbonate, sodium carbonate and potassium carbonate; alkaline earth metal carbonates such as magnesium carbonate, calcium carbonate and barium carbonate; and the like.
Examples of the metal hydrogencarbonate include alkali metal hydrogencarbonates such as lithium hydrogencarbonate, sodium hydrogencarbonate and potassium hydrogencarbonate.
Examples of the metal phosphate include alkali metal phosphates such as sodium phosphate and sodium hydrogenphosphate.
These basic inorganic substances may be used alone or in combination of two or more.

Among the above basic inorganic substances, metal carbonates, metal hydrogen carbonates, and ammonia are preferable, and alkali metal carbonates, alkali metal hydrogen carbonates, and ammonia are more preferable, and sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and carbonic acid are preferable. Potassium hydrogen is more preferable, and sodium carbonate and sodium hydrogen carbonate are particularly preferable.

The concentration of the basic inorganic substance in the basic solution is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass or more in 100% by mass of the basic solution. preferable. When it is 0.1% by mass or more, the odorous components can be more sufficiently neutralized and removed. Further, the concentration is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5.0% by mass or less, particularly preferably 3.0% by mass or less in 100% by mass of the basic solution. .. When the amount is 20% by mass or less, the amount of the odorous component is reduced in accordance with the amount of the basic inorganic substance used, and the efficiency corresponding to the cost can be obtained. Further, the physical properties of the rubber after the treatment (heat aging resistance, etc.) can be maintained.

The basic solution preferably further contains a surfactant. Thus, by including a surfactant together with the basic inorganic substance, it is easy to extract the odor-causing component in the moisture content-reduced natural rubber, or to facilitate the penetration of the basic inorganic substance into the moisture content-reduced natural rubber. It is possible to neutralize and remove odorous components more efficiently.

As the surfactant, at least one selected from the group consisting of anionic surfactants, nonionic surfactants, and amphoteric surfactants can be used. Examples of the anionic surfactants include carboxylic acid-based, sulfonic acid-based, sulfate ester-based, phosphoric acid ester-based anionic surfactants and the like.
Examples of the nonionic surfactant include polyoxyalkylene ester-based, polyhydric alcohol fatty acid ester-based, glycolipid ester-based, and alkyl polyglycoside-based nonionic surfactants.
Examples of the amphoteric surfactant include amphoteric surfactants of amino acid type, betaine type, amine oxide type and the like. Among these, an anionic surfactant is preferably used.
These surfactants may be used alone or in combination of two or more.

As the anionic surfactant, for example, alkyl sulfate ester salt, polyoxyethylene alkyl ether sulfate ester salt, alkylbenzene sulfonate, alkylnaphthalene sulfonate, and fatty acid salt can be preferably used. Examples of these salts include alkali metal salts (sodium salts and the like), ammonium salts, amine salts (alkanolamine salts such as monoethanolamine, diethanolamine, triethanolamine salts).
Among these, polyoxyethylene alkyl ether sulfate ester salt is particularly preferable.

As the alkyl sulfate ester salt, higher alkyl sulfate ester salt (higher alcohol sulfate ester salt) is preferable, and alkali metal salt such as sodium salt is preferable. The alkyl group in the alkyl sulfate ester salt preferably has 10 to 20 carbon atoms, and more preferably 10 to 16 carbon atoms. Specific examples of the alkyl sulfate ester salt include sodium lauryl sulfate (sodium dodecyl sulfate), potassium lauryl sulfate, ammonium lauryl sulfate, triethanolamine lauryl sulfate, sodium myristyl sulfate, potassium myristyl sulfate, sodium cetyl sulfate, and potassium cetyl sulfate. Can be mentioned. Among them, sodium lauryl sulfate is preferable because it has an excellent effect of reducing the amount of protein.

As the polyoxyethylene alkyl ether sulfate ester salt, a polyoxyethylene alkyl ether sulfate ester salt having an alkyl group having 10 to 18 carbon atoms is preferable, an amine salt and a sodium salt are more preferable, and a sodium salt is still more preferable. The carbon number is preferably 10 to 14. The average degree of polymerization of the oxyethylene group is preferably 1-10, more preferably 1-5. Specific examples of the polyoxyethylene alkyl ether sulfate ester salts include sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene myristyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate such as sodium polyoxyethylene oleyl ether sulfate, and polyoxyethylene Examples thereof include ethylene alcohol ether triethanolamine sulfate. Among them, sodium polyoxyethylene lauryl ether sulfate is preferable because it is excellent in the effect of reducing the amount of protein.

Examples of the alkylbenzene sulfonate include alkylbenzene sulfonate having an alkyl group having 3 to 20 carbon atoms, and alkali metal salts are preferable. Specific examples of the alkylbenzene sulfonate include dodecylbenzene sulfonic acid, pentadecyl benzene sulfonic acid, decyl benzene sulfonic acid, sodium salt of cetyl benzene sulfonic acid, potassium salt, ammonium salt, triethanolamine salt, calcium salt and the like. Can be mentioned. Among them, sodium dodecylbenzene sulfonate is preferable because it is excellent in the effect of reducing the amount of protein.

Examples of the alkylnaphthalene sulfonate include sodium mono-, di- or tri-isopropyl naphthalene sulfonate, potassium mono-, di- or tri-isopropyl naphthalene sulfonate, sodium octyl naphthalene sulfonate, potassium octyl naphthalene sulfonate, sodium dodecyl naphthalene sulfonate. Alkyl naphthalene sulfonic acid alkali metal salts such as potassium dodecyl naphthalene sulfonate. Of these, sodium alkylnaphthalene sulfonate is preferable because it is excellent in the effect of reducing the amount of protein.

The fatty acid salt is preferably a higher fatty acid salt having 10 to 20 carbon atoms, and examples thereof include sodium salt and potassium salt. Specific examples of the fatty acid salt include oleic acid, stearic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, docosanoic acid, linoleic acid, 2-ethylhexanoic acid, 2-octylundecanoic acid. And sodium salts such as palm oil; palm oil, palm oil, castor oil, palm kernel oil, sodium salts such as mixed fatty acids derived from beef tallow, potassium salts (castor oil potassium soap, etc.) and the like. Among them, potassium oleate soap is preferable because it has an excellent effect of reducing the amount of protein.

The concentration of the surfactant in the basic solution is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and further preferably 0.05% by mass or more in 100% by mass of the basic solution. preferable. When it is 0.01% by mass or more, the odorous components can be more sufficiently neutralized and removed. Further, the concentration is preferably 5.0% by mass or less, and more preferably 3.0% by mass or less in 100% by mass of the basic solution. When the content is 5.0% by mass or less, the amount of the odorous component is reduced depending on the amount of the surfactant used, and the efficiency corresponding to the cost can be obtained.

(Washing process)
After the base treatment in which the moisture-reduced natural rubber is brought into contact with a basic solution, a washing treatment (washing step) for washing the basic solution remaining on the surface of the obtained treated natural rubber is preferably performed.

The above washing treatment is particularly performed if the basic solution remaining on the surface of the treated natural rubber (also referred to as “base-treated natural rubber”) obtained as a result of the base treatment can be washed and removed. Although not limited, for example, a method of diluting the treated natural rubber with water and then centrifuging, a method of leaving the treated natural rubber in a water bath to float, and discharging only the aqueous phase to take out the natural rubber can be mentioned. Be done.

(PH adjustment treatment)
The production of the odor-reduced natural rubber may further include a pH adjusting treatment for adjusting the pH of the base-treated natural rubber obtained by the base treatment to 2 to 7. That is, after the treatment with the basic solution, the washing treatment is optionally performed, and then the pH of the obtained treated natural rubber is adjusted to 2 to 7 to obtain a deodorized natural rubber. it can. Especially, as a pH range to be adjusted, 3 to 6 is preferable, and 4 to 6 is more preferable. By adjusting the pH of the base-treated natural rubber within such a range, the deodorizing effect can be maintained for a long period of time, and the deterioration of heat aging resistance can be further prevented.
In addition, the above-mentioned pH is obtained by cutting the above-mentioned base-treated natural rubber into a size within 2 mm square on each side and immersing in distilled water, extracting at 90° C. for 15 minutes while irradiating microwaves, and measuring the immersed water with a pH meter. Is the value measured using.
Here, regarding the above-mentioned extraction, since the water-soluble component cannot be completely extracted from the inside of the rubber even if it is extracted with an ultrasonic cleaner for 1 hour, the internal pH cannot be accurately known. The substance (pH) of the natural rubber after the treatment can be known by performing the extraction using the wave.

In the pH adjustment treatment, the method of adjusting the pH of the base-treated natural rubber to 2 to 7 is not particularly limited, but, for example, exposing the base-treated natural rubber to an acidic atmosphere or adding an acidic compound to the base-treated natural rubber and It can be carried out by applying an acidic solution, spraying an acidic compound and/or an acidic solution on the base-treated natural rubber with a shower or a shower, or immersing the base-treated natural rubber in the acidic solution. , A method of contacting the base-treated natural rubber with the acidic solution, such as applying an acidic solution to the base-treated natural rubber, spraying the acidic solution on the base-treated natural rubber, or immersing the base-treated natural rubber in the acidic solution. preferable. Among them, the method of immersing the base-treated natural rubber in the acidic solution is particularly preferable from the viewpoint of work efficiency. By performing this treatment, the deodorizing effect can be maintained for a long period of time, and the deterioration of heat aging resistance can be further prevented.

As the acidic solution, it is preferable to use one whose pH is adjusted to 6 or less. By contacting the base-treated natural rubber with such an acidic solution, a long-term deodorizing effect and excellent heat aging resistance can be obtained. The upper limit of the pH of the acidic solution is more preferably 5 or less, further preferably 4.5 or less. The lower limit is not particularly limited, but is preferably 1 or more, more preferably 2 or more, because depending on the contact time, if the acidity is too strong, the rubber deteriorates or waste water treatment takes time.

When a method of immersing the base-treated natural rubber in an acidic solution is adopted as a method for adjusting the pH of the base-treated natural rubber to 2 to 7, by leaving the base-treated natural rubber in the acidic solution, However, it is preferable to perform stirring and/or microwave irradiation at the time of immersion because the treatment efficiency is further improved.

The contact time between the base-treated natural rubber and the acidic solution in the pH adjustment treatment is not particularly limited, but is preferably 3 seconds or longer, more preferably 10 seconds or longer, further preferably 30 seconds or longer, and more preferably 5 minutes or longer. More preferably, 10 minutes or more is particularly preferable, and 30 minutes or more is most preferable. When it is 3 seconds or more, it is sufficiently neutralized, and the above effect can be more favorably obtained. The upper limit of the contact time between the base-treated natural rubber and the acidic solution depends on the pH and concentration of the acidic solution and is not particularly specified, but in terms of productivity and work efficiency, 48 hours or less is preferable, and 24 hours or less is more preferable. It is preferably 10 hours or less, more preferably 5 hours or less.

The contact temperature (treatment temperature) between the base-treated natural rubber and the acidic solution in the pH adjustment treatment is not particularly limited, but may be, for example, 10 to 50°C. It is preferably 15 to 35°C. Especially, room temperature (20-30 degreeC) is especially preferable.

The acidic solution is preferably an acidic compound solution. Examples of the acidic compound solution include an aqueous solution of an acidic compound and an alcohol solution of an acidic compound, and an aqueous solution of an acidic compound is preferable.
The acidic solution can be prepared by diluting and dissolving the acidic compound described below with a solvent such as water or alcohol.

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 and sulfamic acid; formic acid, acetic acid, glycolic acid, oxalic acid , Propionic 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, methanesulfone 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, amino Benzoic acid, naphthalenedisulfonic acid, hydroxybenzenesulfonic acid, toluenesulfinic acid, benzenesulfinic acid, α-resorcinic acid, β-resorcinic acid, γ-resorcinic acid, gallic acid, phloroglysin, sulfosalicylic acid, ascorbic acid, erythorbic acid, Examples thereof include organic acids such as bisphenolic acid. The above acidic compounds may be used alone or in combination of two or more. Of these, sulfuric acid, formic acid, and acetic acid are preferable as the acidic compound.

The concentration of the acidic compound in the acidic solution is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, in 100% by mass of the acidic solution. It is particularly preferably 0.0% by mass or more. Further, the concentration is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5.0% by mass or less, and particularly preferably 3.0% by mass or less in 100% by mass of the acidic solution. When the concentration of the acidic compound in the acidic solution is within the above range, better heat aging resistance can be obtained.

After the pH adjustment treatment for adjusting the pH of the base-treated natural rubber to 2 to 7, a treatment for washing the acidic solution remaining on the surface of the obtained deodorized natural rubber may be performed. The method of performing the cleaning process is as described above.

As the rubber component that can be used in addition to the odor-reducing natural rubber, isoprene-based rubber other than the odor-reducing natural rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), Examples thereof include butyl rubber (IIR) and styrene-isoprene-butadiene copolymer rubber (SIBR). These diene rubbers may be used alone or in combination of two or more. Of these, isoprene rubber and BR are preferable.

When the rubber composition contains an isoprene-based rubber other than the odor-reduced natural rubber, the total content of the isoprene-based rubber in 100% by mass of the rubber component (the total content of the odor-reduced natural rubber, other natural rubber, isoprene rubber, etc. The amount) is preferably 10% by mass or more, more preferably 25% by mass or more, and further preferably 35% by mass or more. The upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less. Within the above range, the required characteristics of the tire member tend to be secured.

Examples of the isoprene-based rubber include natural rubber (NR) other than the odor-reducing natural rubber, isoprene rubber (IR), modified NR, modified NR, modified IR, and the like. As the NR, for example, those commonly used in the tire industry such as SIR20, RSS#3 and TSR20 can be used. The IR is not particularly limited and, for example, IR2200 or the like which is commonly used in the tire industry can be used. The modified NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR), and the modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

When the rubber composition contains BR, the content (total content) of BR in 100% by mass of the rubber component is preferably 20% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more. is there. The upper limit of the content is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less. When the content is within the above range, the odor of the rubber composition is suppressed and the required characteristics of the tire member tend to be secured.

In the rubber composition, the total content of isoprene-based rubber and BR in 100% by mass of the rubber component is preferably 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. The upper limit of the content is not particularly limited and is preferably 100% by mass. When the content is within the above range, the odor of the rubber composition is suppressed and the required characteristics of the tire member tend to be secured.

The BR is not particularly limited, and BR having a high cis content, BR containing syndiotactic polybutadiene crystals, rare earth-based BR, and the like can be used. As commercial products, products of Ube Industries, Ltd., JSR Corp., Asahi Kasei Corp., Nippon Zeon Corp., etc. can be used. BR may be either unmodified BR or modified BR, and examples of the modified BR include modified BR having the above-mentioned functional group introduced therein. These may be used alone or in combination of two or more. Among them, BR having a high cis content and BR having a rare earth content are preferable. The cis content (cis-1,4-bond amount) of the high cis content BR is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more.

The modified BR may be a BR having a functional group that interacts with a filler such as silica. For example, at least one terminal of BR is modified with a compound having the above functional group (modifying agent). BR (end modified BR having the above functional group at the end), main chain modified BR having the above functional group in the main chain, main chain end modified BR having the above functional group in the main chain and at the end (for example, in the main chain A main chain terminal-modified BR having the above-mentioned functional group and at least one end thereof being modified with the above-mentioned modifier, or a polyfunctional compound having two or more epoxy groups in the molecule (coupling) to form a hydroxyl group. And terminally modified BR having an epoxy group introduced therein.

Examples of the functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfides. 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 and the like. .. In addition, these functional groups may have a substituent. Among them, an amino group (preferably an amino group in which a 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 ( Alkoxysilyl groups having 1 to 6 carbon atoms are preferable.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一又は異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一又は異なって、水素原子又はアルキル基を表す。Ｒ^４及びＲ^５は結合して窒素原子と共に環構造を形成してもよい。ｎは整数を表す。） As the modified BR, BR modified with a compound (modifying agent) represented by the following formula is particularly preferable.

(In the formula, R ¹ , R ² and R ³ are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH) or a derivative thereof. R ⁴ and R ⁵ are the same or different and each represent a hydrogen atom or an alkyl group, R ⁴ and R ⁵ may combine with each other to form a ring structure together with a nitrogen atom, and n represents an integer.)

An alkoxy group is suitable as R ¹ , R ² and R ³ (preferably an alkoxy group having 1 to 8 carbon atoms, and more preferably an alkoxy group having 1 to 4 carbon atoms). As R ⁴ and R ⁵ , an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is preferable. n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. Further, when R ⁴ and R ⁵ are bonded to each other to form a ring structure together with the nitrogen atom, it is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group and the like) and an aryloxy group (phenoxy group, benzyloxy group and the like).

Specific examples of the modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane and 2-diethylaminoethyltrimethoxysilane. Examples thereof include methoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. Among them, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane and 3-diethylaminopropyltrimethoxysilane are preferable. These may be used alone or in combination of two or more.

As the modified BR, a modified BR modified with the following compound (modifying agent) can also be preferably used. Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; two or more diglycidylated bisphenol A and the like. Polyglycidyl ethers of aromatic compounds having phenol groups; 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxy compounds such as polyepoxidized liquid polybutadiene, 4,4'-diglycidyl-diphenyl Epoxy group-containing tertiary amines such as methylamine and 4,4′-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N′-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidyl metaxylenediamine Diglycidylamino compounds such as tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane and tetraglycidyl-1,3-bisaminomethylcyclohexane;

Amino group-containing acid chloride such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholine carbonyl chloride, 1-pyrrolidine carbonyl chloride, N,N-dimethylcarbamic acid chloride, N,N-diethylcarbamic acid chloride; 1 Epoxy group-containing silane compounds such as 3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;

(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (Trimethylsilyl)[3 -(Tributoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldi) A sulfide group-containing silane compound such as propoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide;

N-substituted aziridine compounds such as ethyleneimine and propyleneimine; alkoxysilanes such as methyltriethoxysilane; 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N, N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, N,N,N',N' (Thio)benzophenone compounds having an amino group and/or a substituted amino group such as -bis-(tetraethylamino)benzophenone; 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N, Benzaldehyde compounds having an amino group and/or a substituted amino group such as N-divinylaminobenzaldehyde; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl- N-substituted pyrrolidone such as 2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone N-substituted piperidone such as N-methyl-2-piperidone, N-vinyl-2-piperidone and N-phenyl-2-piperidone N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, N-phenyl -N-substituted lactams such as -β-propiolactam;

N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5 -Triazine-2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3 -Diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenyl) Amino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone and the like can be mentioned. Among them, modified BR modified with alkoxysilane is preferable.
The modification with the above compound (modifying agent) can be carried out by a known method.

The rubber composition preferably contains a filler from the viewpoint of ensuring the required characteristics of the tire member.

In the rubber composition, the content of the filler is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more with respect to 100 parts by mass of the rubber component. When it is at least the lower limit, a good reinforcing effect is obtained, and the required characteristics of the tire member tend to be secured. The content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 80 parts by mass or less. When it is at most the upper limit, good filler dispersibility tends to be obtained.

As the filler, organic filler such as carbon black; silica, alumina, hydrated alumina, aluminum hydroxide, magnesium hydroxide, magnesium oxide, talc, titanium white, titanium black, calcium oxide, calcium hydroxide, magnesium aluminum oxide, Inorganic fillers such as clay, pyrophyllite, bentonite, aluminum silicate, magnesium silicate, calcium silicate, calcium aluminum silicate, magnesium silicate, zirconium, and zirconium oxide; Among them, carbon black and silica are preferable from the viewpoint of ensuring the required characteristics of the tire member. These may be used alone or in combination of two or more.

In the rubber composition, the content of carbon black is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and further preferably 25 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 60 parts by mass or less. Within the above range, a good reinforcing effect can be obtained, and the required characteristics of the tire member tend to be secured.

From the viewpoint of ensuring the required characteristics of the tire member, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² /g or more, more preferably 80 m ² /g or more, and preferably 200 m ² /G or less, more preferably 150 m ² /g or less.
The nitrogen adsorption specific surface area of carbon black is measured according to ASTM D4820-93.

The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Examples of commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin Nihon Carbon Co., Ltd., and Columbia Carbon Co., Ltd. Can be used. These may be used alone or in combination of two or more.

In the rubber composition, the content of silica is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and further preferably 25 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 60 parts by mass or less. Within the above range, a good reinforcing effect can be obtained, and the required characteristics of the tire member tend to be secured.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² /g or more, more preferably 70 m ² /g or more, still more preferably 110 m ² /g or more. When it is at least the lower limit, a good reinforcing effect is obtained, and the required characteristics of the tire member tend to be secured. The N ₂ SA of silica is preferably 220 m ² /g or less, more preferably 200 m ² /g or less. When it is at most the upper limit, good dispersibility tends to be obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

Examples of silica include dry method silica (anhydrous silica) and wet method silica (hydrous silica). Among them, wet process silica is preferable because it has many silanol groups. Examples of commercially available products include products such as Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., and Tokuyama Corporation.

As other components of the rubber composition, for example, silane coupling agents, softeners, solid resins, waxes, various anti-aging agents, stearic acid, zinc oxide, processing aids, adhesives and the like used in the conventional rubber industry. Compounding agents.

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-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3- Sulfides such as triethoxysilylpropylmethacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercaptos such as NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, vinyltri Glycidoxy such as vinyl-based such as methoxysilane, amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and the like System, nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more. Of these, sulfide type and mercapto type are preferable. As commercial products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used.

When the rubber composition contains silica, it is preferable to further contain a silane coupling agent.
In the rubber composition, the content of the silane coupling agent is preferably 3 parts by mass or more and more preferably 5 parts by mass or more with respect to 100 parts by mass of silica. If it is 3 parts by mass or more, the effect of addition tends to be obtained. The content is preferably 25 parts by mass or less, more preferably 20 parts by mass or less. When the amount is 25 parts by mass or less, an effect commensurate with the blending amount is obtained, and good workability during kneading tends to be obtained.

The softening agent (hydrocarbon, resin, etc. in a liquid state at room temperature (25° C.)) is not particularly limited, but oil, liquid diene polymer, etc. are preferably used. By using the softening agent, good characteristics required for the tire member can be secured. Of these, oil is preferable.

In the rubber composition, the content of oil is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, still more preferably 1.5 parts by mass or more, based on 100 parts by mass of the rubber component. is there. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less. Within the above range, the required characteristics of the tire member tend to be secured.
The oil content also includes the amount of oil contained in rubber (oil-extended rubber).

Examples of oils include process oils, vegetable oils and fats, or mixtures thereof. As the process oil, for example, paraffin type process oil, aroma type process oil, naphthene type process oil and the like can be used. As vegetable oils and oils, 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, sesame oil, Beni flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. These may be used alone or in combination of two or more. Examples of commercially available oils include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., H&R Co., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu Co., Ltd. Products such as Fuji Kosan Co., Ltd. can be used.

The solid resin (resin in a solid state at room temperature (25° C.) (solid resin) is not particularly limited as long as it is widely used in the tire industry, and petroleum resin, styrene resin, coumarone indene resin, terpene. Examples of the resin include resin, pt-butylphenol acetylene resin, and acrylic resin. Among them, petroleum resin is preferable.

In the rubber composition, the content of petroleum resin is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and further preferably 3.0 parts by mass or more. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less. Within the above range, the required characteristics of the tire member tend to be secured.

Petroleum resin refers to a resin produced by the polymerization of a part of the by-product oil of naphtha cracking used in the petrochemical industry (C5 fraction, C9 fraction, etc.), and C5 obtained by cationically polymerizing a chain olefin mixture of C5. -Based petroleum resin, dicyclopentadiene-based petroleum resin thermally polymerized with dicyclopentadiene fraction, C9-based petroleum resin cationically polymerized with a mixture of C9 aromatic olefins, C5C9-based petroleum resin, and alphamethylstyrene contained in C9 fraction And a petroleum resin called pure monomer resin produced from pure alphamethylstyrene, and a resin obtained by hydrogenating these. Among them, C5 petroleum resin, C9 petroleum resin and C5C9 petroleum resin are preferable, and C5 petroleum resin and C5C9 petroleum resin are more preferable.

The weight average molecular weight (Mw) of the petroleum resin is preferably 1500 or more, more preferably 1700 or more. The Mw is preferably 5000 or less, more preferably 4500 or less, and further preferably 4000 or less. Within the above range, the required characteristics of the tire member tend to be secured.
In addition, in this specification, Mw of petroleum resin is a gel permeation chromatography (GPC) (Tosoh Corp. GPC-8000 series, a detector: differential refractometer, a column: Tosoh Corp. TSKGEL SUPERMALPTORE HZ. -M) can be obtained by standard polystyrene conversion based on the measured value.

The softening point of the petroleum resin is preferably 30° C. or higher, more preferably 60° C. or higher, even more preferably 80° C. or higher. The softening point is preferably 140°C or lower, more preferably 110°C or lower. Within the above range, the required characteristics of the tire member tend to be secured.
In the present specification, the softening point of the petroleum resin is the temperature at which the sphere has fallen when the softening point defined in JIS K 6220-1:2001 is measured with a ring and ball softening point measuring device.

The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant wax and animal wax; and synthetic waxes such as polymers such as ethylene and propylene. As commercial products, for example, products of Ouchi Shinko Chemical Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. can be used. These may be used alone or in combination of two or more. Among them, petroleum wax is preferable, and paraffin wax is more preferable.

In the rubber composition, the content of the wax is preferably 0.5 to 20 parts by mass, more preferably 1.0 to 10 parts by mass with respect to 100 parts by mass of the rubber component. Within the above range, the required characteristics of the tire member tend to be secured.

Examples of the antiaging agent include naphthylamine antiaging agents such as phenyl-α-naphthylamine; diphenylamine antiaging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; N -Isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. A p-phenylenediamine anti-aging agent; a quinoline anti-aging agent such as a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, Monophenolic antiaging agents such as styrenated phenols; bis, tris, polyphenolic aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane Examples include inhibitors. These may be used alone or in combination of two or more. Of these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1 A polymer of 2,2-dihydroquinoline is more preferable. Examples of commercially available products that can be used include products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Corporation.

In the rubber composition, the content of the antioxidant is preferably 1 to 10 parts by mass or more, and more preferably 2 to 7 parts by mass or more with respect to 100 parts by mass of the rubber component. Within the above range, the required characteristics of the tire member tend to be secured.

As stearic acid, conventionally known ones can be used, and products such as NOF CORPORATION, NOF Company, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. and the like can be used. As the zinc oxide, conventionally known ones can be used, for example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. Can be used.

In the rubber composition, the content of stearic acid is preferably 0.5 to 10.0 parts by mass, and more preferably 1.0 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component. Within the above range, the required characteristics of the tire member tend to be secured.

In the rubber composition, the content of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 7 parts by mass with respect to 100 parts by mass of the rubber component. Within the above range, the required characteristics of the tire member tend to be secured.

As a material to be blended with the rubber composition, for example, a vulcanizing agent, a vulcanization accelerator and the like can be preferably used. The vulcanizing agent is not particularly limited as long as it is a chemical capable of crosslinking the rubber component, and examples thereof include sulfur. Further, a hybrid crosslinking agent (organic crosslinking agent) can also be used as a vulcanizing agent. These may be used alone or in combination of two or more. Of these, sulfur is preferred.

In the rubber composition, the content of sulfur is preferably 0.1 to 10.0 parts by mass, more preferably 0.5 to 5.0 parts by mass, and still more preferably 0.1 to 100 parts by mass of the rubber component. It is 7 to 3.0 parts by mass. Within the above range, the required characteristics of the tire member tend to be secured.

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur that are generally used in the rubber industry. The organic cross-linking agent is not particularly limited, and examples thereof include maleimide compounds, alkylphenol/sulfur chloride condensates, organic peroxides, amine organic sulfides and the like. These may be used alone or in combination of two or more. Examples of commercially available products that can be used include products such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Japan Dry Storage Industry Co., Ltd., Hosoi Chemical Co., Ltd.

In the rubber composition, the content of the organic crosslinking agent is preferably 0.1 to 10.0 parts by mass, more preferably 0.5 to 5.0 parts by mass, and still more preferably 100 parts by mass of the rubber component. It is 0.7 to 3.0 parts by mass. Within the above range, the required characteristics of the tire member tend to be secured.

In the rubber composition, the content of the vulcanization accelerator is preferably 0.1 to 7.0 parts by mass, more preferably 0.3 to 5.0 parts by mass, further 100 parts by mass of the rubber component. It is preferably 0.5 to 3.0 parts by mass. Within the above range, the required characteristics of the tire member tend to be secured.

Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide and N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD). ), tetrabenzyl thiuram disulfide (TBzTD), tetrakis(2-ethylhexyl) thiuram disulfide (TOT-N), and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl- 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide, etc. Sulfenamide-based vulcanization accelerators such as diphenylguanidine, diortotolylguanidine, orthotolylbiguanidine, and other guanidine-based vulcanization accelerators. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferable.

[Production of rubber composition]
For example, after producing the odor-reducing natural rubber by the step of producing the odor-reducing natural rubber through the crushing washing treatment, the dehydration treatment, and the drying treatment, a rubber component and a filler containing the obtained odor-reducing natural rubber. The rubber composition can be produced through the step of kneading. The rubber composition produced by using the obtained odor-reducing natural rubber has a sufficiently reduced odor, even though it is made of cup lamp as a raw material. Further, it is possible to suppress deterioration of physical properties such as heat aging resistance.

The step of kneading the odor-reducing natural rubber and the filler is not particularly limited as long as it is a method of kneading the odor-reducing natural rubber and the filler, and for example, a rubber component containing the odor-reducing natural rubber, a filler, and optionally other components. An embodiment including a base kneading step of kneading the components, and a kneading product obtained in the base kneading step, a vulcanizing agent, and a final kneading step of kneading other components as required. For example, the rubber composition (vulcanized) can be produced by such a production method.

(Base kneading process)
The base kneading step can be carried out, for example, by kneading the odor-reducing natural rubber, a rubber other than the natural rubber, a filler (filler), and optionally other components. The kneading method in the base kneading step is not particularly limited, and for example, a known (closed type) kneader such as a Banbury mixer, a kneader or an open roll may be used for mixing.

In the base kneading step, the kneading temperature is usually 50 to 200° C., preferably 80 to 190° C., and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes.

(Finishing process)
The finish kneading step can be carried out, for example, by kneading the kneaded product obtained in the base kneading step, the vulcanizing agent, and, if necessary, other components. The kneading method in the finish kneading step is not particularly limited, and, for example, a known kneader such as an open roll can be used. The kneading temperature is usually 100° C. or lower, preferably room temperature to 80° C.

Examples of other components to be kneaded in the finish kneading step include a vulcanization accelerator and the like. In addition, when a part of the rubber component, the filler and the like is kneaded in the base kneading step, the remaining part is also included.

(Vulcanization process)
The unvulcanized rubber composition (kneaded material) obtained in the finishing kneading step is usually vulcanized thereafter. For example, it can be carried out by applying a known vulcanizing means to the unvulcanized rubber composition, and a rubber composition (vulcanized) can be produced. The vulcanization temperature in the vulcanization step is preferably 130 to 200°C, and the vulcanization time is preferably 5 to 15 minutes.

The rubber composition (vulcanized) preferably has an odor component index of 1.0×10 ^{5 to} 5.0×10 ⁵ from the viewpoint of odor control. The lower limit is more preferably 1.2×10 ⁵ or more, and further preferably 1.4×10 ⁵ or more. The upper limit is more preferably 4.5×10 ⁵ or less, still more preferably 4.0×10 ⁵ or less, from the viewpoint of odor control. The odor component index of the rubber composition (vulcanized) is the peak area ratio of the main causative substances of the odor of natural rubber detected by GCMS for the rubber composition (vulcanized) of each component. It is corrected by the olfactory threshold value and all are added, and it can be measured by the method described in Examples below.

The rubber composition, various tire members (tread (cap tread)), sidewalls, base tread, undertread, clinch apex, bead apex, breaker cushion rubber, carcass cord coating rubber, insulation, chafer, You may use it for an inner liner etc. and the side reinforcement layer of a run flat tire. Among them, from the viewpoint of reducing odor, it can be suitably used for tire outer layer members such as treads, sidewalls, clinches, and wings, and is particularly suitable for sidewalls.

The pneumatic tire is manufactured by a usual method using a rubber composition.
That is, a rubber composition (unvulcanized) containing the above components is extruded in accordance with the shape of each tire member at the unvulcanized stage, and is then subjected to a normal method on a tire molding machine together with other tire members. An unvulcanized tire is formed by molding. A tire is obtained by heating and pressing this unvulcanized tire in a vulcanizer.

The pneumatic tire is suitably used as a tire for passenger cars, a tire for heavy loads such as trucks and buses, a tire for two-wheeled vehicles, a tire for competition, and the like.

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

Various chemicals used in the natural rubber samples of Examples and Comparative Examples are shown below.
Basic substance: Sodium carbonate (Na ₂ CO ₃ ) (manufactured by Sigma-Aldrich)
Surfactant: Emal E-27C (polyoxyethylene lauryl ether sodium sulfate) manufactured by Kao Corporation

<Obtaining natural rubber samples>
I got a cup lamp made in a normal rubber plantation. Then, after treating the obtained cup lamp with a hammer mill made by Natural Rubber Machine and Equipment Co., Ltd., after finely pulverizing (pulverizing) with a rubber granulator, the pulverized cup lamp is washed while stirring in a water bath, It was washed by discharging only the phase and taking out the crushed cup lamp (crushing and washing treatment). The average diameter of the cup lamp after crushing and washing was 5 mm.

(Comparative Example 1)
The crushed and washed cup lamp was stored at room temperature (20 to 30° C.) for one month. The water content of the cup lamp before storage was measured by the following method and was as shown in Table 1.
After washing the cup lamp stored for 1 month as described above about 5 times with water, 100 g of the cup lamp was added to 1 L of the aqueous solution prepared at the concentration shown in Table 1 for 6 hours at room temperature (20 to 30° C.). Soaked in. An appropriate weight was placed so that the cup lamp did not float on the liquid surface of the aqueous solution during the immersion, and the cup lamp was placed so that the whole was submerged in the aqueous solution. The cup lamp was taken out, washed with water, and then dried at 135° C. for 4 hours to obtain a natural rubber sample (NR1).

(Comparative example 2)
A natural rubber sample (NR2) was prepared in the same manner as in Comparative Example 1 except that the moisture-reduced natural rubber stored for 1 month was washed with water and refined with a cutter 5 times, and then dried at 120° C. for 4 hours. Got

(Example 1)
The crushed and washed cup lamp was passed through a creeper (apparatus for squeezing using a roll) and squeezed to a thickness of 8 mm to prepare a moisture-reduced natural rubber (dehydration treatment). The obtained moisture-reduced natural rubber was stored at room temperature (20 to 30° C.) for 1 month. Moisture content reduction before storage The moisture content of the natural rubber was measured by the following method and was as shown in Table 1.
As described above, the moisture-reduced natural rubber stored for 1 month was washed with water about 5 times and then dried at 135° C. for 4 hours (drying treatment) to obtain a natural rubber sample (NR3).

(Example 2)
A natural rubber sample (NR4) was obtained in the same manner as in Example 1 except that the water content-reduced natural rubber stored for 1 month was washed with water about 5 times and then dried at 145° C. for 4 hours.

(Example 3)
The crushed and washed cup lamp is passed through a creeper (a device that squeezes using rolls) to squeeze to a thickness of 8 mm to prepare a moisture-reduced natural rubber (dehydration treatment), and this dehydration treatment is performed 5 times. went. The obtained moisture-reduced natural rubber was stored at room temperature (20 to 30° C.) for 1 month. Moisture content reduction before storage The moisture content of the natural rubber was measured by the following method and was as shown in Table 1.
After washing the moisture-reduced natural rubber stored for 1 month as described above with water about 5 times, 100 g of the moisture-reduced natural rubber was added to 1 L of the aqueous solution prepared at the concentration shown in Table 1 for 6 hours at room temperature. It was immersed at (20-30°C). An appropriate weight was placed so that the natural rubber with reduced water content did not float on the liquid surface of the aqueous solution during the immersion, and the whole was set so as to be submerged in the aqueous solution. The moisture-reduced natural rubber was taken out, washed with water, and then dried at 135° C. for 4 hours (drying treatment) to obtain a natural rubber sample (NR5).

Various chemicals used in the production of the test tire will be described collectively.
NR1 to 5: Natural rubber sample BR manufactured in the above Comparative Examples and Examples: BR150B manufactured by Ube Industries, Ltd. (cis content: 98% by mass)
Carbon black: Diablack N550 (N ₂ SA: 42 m ² /g) manufactured by Mitsubishi Chemical Corporation
Petroleum resin: PetroTac 100V manufactured by Tosoh Corporation (C5C9 series petroleum resin, Mw: 3800, softening point: 96° C.)
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Anti-aging agent 6C: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Co., Ltd.
Anti-aging agent RD: Nocrac 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Chemical Co., Ltd.
Stearic acid: beads made by NOF Corporation Stearic acid Tsubaki Zinc oxide: Zinc oxide type 2 oil made by Mitsui Mining & Smelting Co., Ltd.: VIVATEC 400 (TDAE oil) made by H&R
Sulfur: Powdered sulfur from Tsurumi Chemical Industry Co., Ltd. (containing 5% oil)
Vulcanization accelerator: Nocceller CZ (N-cyclohexyl-2-benzothiazylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

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

The cup lamp, the moisture-reduced natural rubber, the natural rubber samples obtained in Comparative Examples and Examples, and the test tires produced as described above were evaluated as follows. The results are shown in Tables 1-2.

(Measurement of water content)
A cup lamp or a moisture-reduced natural rubber (1 g) was accurately weighed (weight before drying), finely cut, dried at 70° C. for 14 hours, and then the weight after drying was measured. Then, the water content was determined by the following formula.
Moisture content (%)={(weight before drying (g)-weight after drying (g))/weight before drying (g)}×100

1. Analysis method of natural rubber (odor index of natural rubber)
The major causative agents of the odor of natural rubber include lower fatty acids such as acetic acid, valeric acid, isovaleric acid, isovaleric acid aldehyde, and butyric acid, and their aldehydes.
Therefore, the peak area of the above components detected using Head-Space GCMS (manufactured by Shimadzu Corporation, product name “GCMS-QP2010 Ultra”, and Shimadzu Corporation “HS-20” used as a headspace sampler) The ratio was corrected by the olfactory threshold of each component, and the sum was added to give the odor component index (natural rubber).

(Odor component ratio (%) of natural rubber)
With respect to the odor component index obtained above, the odor component ratio was evaluated by the following formula.
Odor component ratio (%) of natural rubber=(odor component index in natural rubber sample of each example/odor component index in natural rubber sample of Comparative Example 1)×100

(Evaluation of deterioration characteristics of natural rubber)
As for the deterioration characteristics of the natural rubber sample, the Mooney viscosity retention after aging at 80° C. for 72 hours was evaluated by the following formula. The larger the Mooney viscosity retention value, the better the natural rubber sample is in deterioration characteristics (heat aging resistance). Specifically, if the Mooney viscosity retention rate is 60% or more, it can be said that the deterioration characteristics are sufficiently excellent.
Mooney viscosity retention (%) = (mooney viscosity after aging/mooney viscosity before aging) x 100

2. Analysis method of rubber composition (odor component index of rubber composition)
A sample (rubber composition sample) was taken from the sidewall portion of the test tire, and the sample was measured in the same manner as in the analysis method of the odorous component of natural rubber, and the peak area ratio of the above-mentioned components detected was determined for each component. The odor component index (rubber composition) was obtained by correcting for the olfactory threshold value and adding all.

(Ratio of odor component of rubber composition (%))
With respect to the odor component index obtained above, the odor component ratio was evaluated by the following formula.
Odor component ratio (%) of rubber composition=(odor component index in rubber composition sample of each example/odor component index in rubber composition sample of Comparative Example 1)×100

(Evaluation of deterioration characteristics of rubber composition)
According to JIS K6251, a tensile test was carried out using a No. 3 dumbbell-shaped test piece consisting of a sample (rubber composition sample), and the breaking strength (TB) of each sample was measured. Next, TB was measured after heat aging the sample at 80° C. for 168 hours. The retention ratio of the breaking strength (TB) before and after aging was calculated by the following formula. The higher the number, the smaller the change in rubber physical properties due to heat aging, and the better the heat aging resistance. Specifically, it can be said that if the breaking strength retention rate is 70% or more, the deterioration characteristics are sufficiently excellent.
Retention rate (%)=TB after heat aging/TB before heat aging×100

From the results shown in Table 1, crushing and washing the cup lamp and washing the crushed cup lamp, and reducing the moisture content of the cup lamp crushed and washed by the pulverizing and cleaning treatment to obtain a moisture-reduced natural rubber. The rubber composition using the odor-reduced natural rubber produced through the dehydration treatment and the drying treatment for drying the moisture-reduced natural rubber has a reduced odor and is also excellent in heat aging resistance.

Further, it was also clarified that the odorous component can be significantly reduced by treating the moisture-reduced natural rubber with a basic solution.

Claims (10)

A rubber composition comprising a rubber component containing an odor reducing natural rubber having an odor component index of 0.1×10 ^{6 to} 2.0×10 ⁶ , and a filler. The rubber composition according to claim 1, wherein the odor component index of the rubber composition is 1.0×10 ^{5 to} 5.0×10 ⁵ . The odor-reduced natural rubber is obtained by crushing a cup lamp and crushing and washing the cup lamp to crush it, and reducing the moisture content of the cup lamp crushed and washed by the crushing and washing treatment to obtain a moisture-reduced natural rubber. The rubber composition according to claim 1 or 2, which is obtained through a dehydration treatment and a drying treatment for drying the moisture-reduced natural rubber. The rubber composition according to claim 3, wherein the natural rubber having a reduced water content has a water content of 30% or less. The rubber composition according to claim 3 or 4, wherein the drying temperature in the drying treatment is 140°C or lower. The rubber composition according to any one of claims 3 to 5, further comprising a base treatment in which the moisture-reduced natural rubber is brought into contact with a basic solution before the drying treatment. The rubber composition according to claim 6, wherein the basic solution further contains a surfactant. The rubber composition according to claim 1, which contains 5 to 100 parts by mass of a filler with respect to 100 parts by mass of the rubber component. A pneumatic tire having a tire member using the rubber composition according to claim 1. The pneumatic tire according to claim 9, wherein the tire member is a tire outer layer member.