JP2019056083A - Rubber composition for tire, and pneumatic tire - Google Patents

Abstract

To provide a rubber composition capable of improving wear resistance performance and fracture resistance performance while maintaining good processability, and a pneumatic tire using the rubber composition.SOLUTION: The present invention relates to a rubber composition for a tire, which contains carbon black (1) having a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 140-150 m/g, a nitrogen adsorption specific surface area of 140-150 m/g, an iodine adsorption (IA) of 120-135 mg/g, a ratio (CTAB/IA) of the CTAB to the IA of 1.10-1.20, a compressed dibutyl phthalate oil absorption of 110-120 mL/100 g, and a dibutyl phthalate oil absorption of 127-141 mL/100 g.SELECTED DRAWING: None

Description

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

Pneumatic tires are required to have excellent wear resistance and destructive performance from the viewpoint of safety, etc.In particular, high-load tires mounted on trucks and buses are used under severe conditions. Excellent wear resistance and fracture resistance are required. Conventionally, carbon black is blended in the tire rubber composition in order to obtain these performances (for example, Patent Document 1). However, in the conventional technique, wear resistance performance is maintained while maintaining good processing performance. And there is room for improvement in terms of improving fracture resistance.

JP 2011-140532 A

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition that can improve wear resistance and fracture resistance while maintaining good processing performance, and a pneumatic tire using the same.

The present invention has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 140 to 150 m ² / g, a nitrogen adsorption specific surface area of 140 to 150 m ² / g, an iodine adsorption amount (IA) of 120 to 135 mg / g, and a CTAB for IA. Tire rubber comprising carbon black (1) having a ratio of CTAB / IA of 1.10 to 1.20, a compressed dibutyl phthalate oil absorption of 110 to 120 ml / 100 g, and a dibutyl phthalate oil absorption of 127 to 141 ml / 100 g Relates to the composition.

In the rubber composition, the content of the carbon black (1) is preferably 20 to 70 parts by mass with respect to 100 parts by mass of the rubber component.

It is preferable to include a modified natural rubber having a phosphorus content of 500 ppm or less.

It is preferable that the content of isoprene-based rubber in 100% by mass of the rubber component is 60 to 90% by mass and the content of butadiene rubber is 10 to 40% by mass.

It is preferable to contain carbon black (2) having a nitrogen adsorption specific surface area of less than 140 m ² / g.

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

The pneumatic tire is preferably a truck / bus tire.

According to the present invention, since it is a rubber composition for tires containing specific carbon black, it is possible to improve wear resistance and fracture resistance while maintaining good processing performance, and excellent wear resistance and fracture resistance. A pneumatic tire can be provided.

The tire rubber composition of the present invention has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 140 to 150 m ² / g, a nitrogen adsorption specific surface area of 140 to 150 m ² / g, and an iodine adsorption amount (IA) of 120 to 135 mg. / G, carbon black having a ratio of CTAB to IA (CTAB / IA) of 1.10 to 1.20, compressed dibutyl phthalate oil absorption of 110 to 120 ml / 100 g, and dibutyl phthalate oil absorption of 127 to 141 ml / 100 g (1 )including. Thereby, wear resistance performance and fracture resistance performance can be improved while maintaining good processing performance.
The reason why such an effect can be obtained is not necessarily clear, but is presumed as follows.

Since carbon black (1) is highly activated, it is considered that the wear resistance and fracture resistance are improved, and the particle size is moderately large, so that good processing performance is maintained. Therefore, it is presumed that the wear resistance and fracture resistance can be improved while maintaining good processing performance.

(Rubber composition)
The rubber composition includes carbon black (1).

The carbon black (1) has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 140 to 150 m ² / g, preferably 143 to 147 m ² / g. The effect of this invention is suitably acquired as CTAB is in the said range.
In this specification, the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of carbon black is a value measured according to JIS K6217-3: 2001.

The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black (1) is 140 to 150 m ² / g, preferably 143 to 148 m ² / g. When N 2 _SA is within the above range, the effect of the present invention can be preferably obtained.
In the present specification, the nitrogen adsorption specific surface area of carbon black is a value measured according to JIS K6217-2: 2001.

The iodine adsorption amount (IA) of carbon black (1) is 120 to 135 mg / g, preferably 123 to 135 mg / g. When the iodine adsorption amount (IA) is within the above range, the effect of the present invention is suitably obtained.

The ratio (CTAB / IA) of cetyltrimethylammonium bromide adsorption specific surface area (CTAB) to iodine adsorption amount (IA) of carbon black (1) is 1.10 to 1.20 m ² / mg, preferably 1.10 to 1 .18 m ² / mg. When CTAB / IA is within the above range, the effects of the present invention are preferably obtained.
In the present specification, the iodine adsorption amount (IA) of carbon black is a value measured according to JIS K6217-1: 2008.

The surface activity index represented by CTAB / IA can be considered as an index of the crystallinity (graphitization rate) of carbon black. That is, as CTAB / IA is higher, crystallization is less advanced, and the interaction between carbon black and the rubber component tends to increase.
CTAB / IA is also positioned as a parameter for evaluating the amount of acidic functional groups present on the carbon black surface. The acidic functional group on the surface of carbon black contributes to the interaction with the rubber component, but the higher the CTAB / IA, the more acidic functional groups are present on the surface of the carbon black. Therefore, when CTAB / IA is within the above range, a more remarkable reinforcing effect can be exerted on the rubber component, and the effects of the present invention can be suitably obtained.

The compressed dibutyl phthalate oil absorption (24M4DBP) of carbon black (1) is 110 to 120 ml / 100 g, preferably 110 to 115 ml / 100 g. The effect of this invention is suitably acquired as 24M4DBP is in the said range.
In the present specification, the compressed dibutyl phthalate oil absorption (24M4DBP) of carbon black is a value measured in accordance with ASTM D3493-85a.

Carbon black (1) has a dibutyl phthalate oil absorption (DBP) of 127 to 141 ml / 100 g, preferably 129 to 135 ml / 100 g. The effect of this invention is suitably acquired as DBP is in the said range.
In addition, in this specification, DBP of carbon black is a value measured according to JIS K6217-4: 2001.

Carbon black (1) can be produced by a person skilled in the art by a known production method if the above target characteristics are determined. The production method is not particularly limited, but specifically, a method of producing carbon black by spraying raw material oil into combustion gas is preferably employed, and conventionally known, for example, furnace method and channel method. The method is used. Of these, the furnace method shown below is preferable.

The furnace method (oil furnace method) is, for example, as disclosed in Japanese Patent Application Laid-Open No. 2004-43598 and Japanese Patent Application Laid-Open No. 2004-277443. A process using a device having a reaction zone for introducing hydrocarbons and converting raw material hydrocarbons to carbon black by a pyrolysis reaction, and a reaction stop zone for quenching reaction gas to stop the reaction, combustion conditions, high temperature Carbon blacks having various characteristics can be produced by controlling various conditions such as the combustion gas flow rate, the conditions for introducing the raw material oil into the reaction furnace, and the time from the conversion of carbon black to the termination of the reaction.

In the combustion zone, air, oxygen or a mixture thereof and a gaseous or liquid fuel hydrocarbon are mixed and burned as an oxygen-containing gas to form a high-temperature combustion gas. As the fuel hydrocarbon, petroleum-based liquid fuel such as carbon monoxide, natural gas, coal gas, petroleum gas, heavy oil, and coal-based liquid fuel such as creosote oil are used. The combustion is preferably controlled so that the combustion temperature is in the range of 1400 ° C to 2000 ° C.

In the reaction zone, the raw material hydrocarbon is sprayed and introduced into the high-temperature combustion gas flow obtained in the combustion zone in a co-current flow or in a lateral direction, and the raw material hydrocarbon is thermally decomposed and converted to carbon black. Preferably, the feedstock oil is introduced by one or more burners into a high temperature combustion gas stream having a gas flow rate in the range of 100 to 1000 m / s. The feedstock oil is preferably divided and introduced by two or more burners. In order to improve the reaction efficiency, it is preferable to provide a throttle part in the reaction zone. The ratio of the diameter of the throttle part / the diameter of the upstream area of the throttle part is preferably 0.1 to 0.8.

In the reaction stop zone, water spray or the like is performed to cool the high temperature reaction gas to 1000 to 800 ° C. or less. The time from the introduction of the feedstock to the reaction stop is preferably 2 to 100 milliseconds. The cooled carbon black can be separated and recovered from the gas and then subjected to a known process such as granulation and drying.

Specific examples of raw material oils include: (1) aromatic hydrocarbons such as anthracene; coal-based hydrocarbons such as creosote oil; EHE oil (replicated oil during ethylene production), FCC oil (fluid catalytic cracking residue oil) And a raw material mixture of at least one selected from the group consisting of petroleum heavy oils such as ()) and (2) aliphatic hydrocarbons. These may be modified. Among these, a mixed raw material oil of coal-based hydrocarbon and aliphatic hydrocarbon is preferable.

As the aliphatic hydrocarbon, for example, petroleum-based aliphatic hydrocarbons typified by process oil, and animal and vegetable oils typified by fatty acids such as soybean oil, rapeseed oil, and palm oil can be used.
Here, animal and vegetable oils include fish oil (liver oil) obtained from fish liver, marine animal oil such as sea animal oil obtained from whales, and land animal oil such as beef tallow and pork fat, as well as plant seeds, fruits, and nuclei. It contains fats and oils and the like containing fatty acid glycerides collected from the above.

The content of carbon black (1) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, relative to 100 parts by mass of the rubber component. Most preferably, it is 35 parts by mass or more. The carbon black content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, particularly preferably 80 parts by mass or less, and most preferably 70 parts by mass or less. When the content of carbon black (1) is within the above range, the effects of the present invention are more suitably obtained.

The rubber composition preferably contains carbon black (1) and carbon black other than carbon black (1) (hereinafter also referred to as carbon black (2)). Thereby, the effect of this invention is acquired more suitably.

The carbon black (2) is not particularly limited as long as it is a carbon black other than the carbon black (1), and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, and the like. . These may be used alone or in combination of two or more. Among these, it is preferable to use carbon black (2) having a nitrogen adsorption specific surface area of less than 140 m ² / g. Thereby, the effect of this invention is acquired more suitably.

The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black (2) is less than 140 m ² / g, preferably 130 m ² / g or less, and more preferably 120 m ² / g or less. Further, the _N 2 SA is preferably at least ^{5 m} 2 / g, more preferably at least ^{50 m} 2 / g, more preferably not less than ^{80m 2 / g, 100m 2 /} g or more is particularly preferable. When the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black (2) is within the above range, the effects of the present invention are more suitably obtained.

Carbon black (2) has a dibutyl phthalate oil absorption (DBP) of 100 to 130 ml / 100 g, preferably 107 to 123 ml / 100 g. When the DBP of the carbon black (2) is within the above range, the effects of the present invention can be obtained more suitably.

As carbon black (2), for example, Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd. Etc. can be used.

When carbon black (2) is contained, the content of carbon black (2) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and still more preferably 9 parts by mass with respect to 100 parts by mass of the rubber component. That's it. The content is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 40 parts by mass or less, and particularly preferably 20 parts by mass or less. When the content of carbon black (2) is within the above range, the effects of the present invention are more suitably obtained.

The total content of carbon black (1) and carbon black (2) is preferably 5 to 250 parts by weight, more preferably 10 to 200 parts by weight, and still more preferably 15 to 150 parts by weight with respect to 100 parts by weight of the rubber component. Parts, particularly preferably 20 to 100 parts by mass, most preferably 30 to 80 parts by mass, and most preferably 40 to 60 parts by mass. When the total content of the carbon black (1) and the carbon black (2) is within the above range, the effects of the present invention are more suitably obtained.

The content of carbon black (1) in 100% by mass of carbon black is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, particularly preferably 40% by mass or more, and most preferably. Is 60% by mass or more, and most preferably 70% by mass or more. The content may be 100% by mass, but is preferably 95% by mass or less, and more preferably 90% by mass or less. When the content of carbon black (1) is within the above range, the effects of the present invention are more suitably obtained.

Examples of the rubber component that can be used in the present invention include diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), and styrene isoprene butadiene rubber (SIBR). A rubber component may be used independently and may use 2 or more types together. Among these, isoprene-based rubber and BR are preferable because the effects of the present invention can be more suitably obtained, and the combined use of isoprene-based rubber and BR is more preferable.

The BR is not particularly limited, and for example, BR having a high cis content, BR containing a syndiotactic polybutadiene crystal, and the like can be used. These may be used alone or in combination of two or more. Of these, the BR cis content is preferably 90% by mass or more because of its good wear resistance.

BR may be non-modified BR or modified BR. These may be used alone or in combination of two or more.
The modified BR may be any 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 a functional group (modifier). BR (terminal modified BR having the above functional group at the terminal), main chain modified BR having the above functional group at the main chain, and main chain terminal modified BR having the above functional group at the main chain and terminal (for example, in the main chain) Modified (coupled) with a polyfunctional compound having the above functional group and having at least one terminal modified with the above modifier with a main chain terminal modified BR) or a polyfunctional compound having two or more epoxy groups in the molecule. And terminal-modified BR having an epoxy group introduced therein. These may be used alone or in combination of two or more.

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, etc. . These functional groups may have a substituent. Among these, 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, because the effects of the present invention can be obtained more suitably. C1-C6 alkoxy group) and alkoxysilyl groups (preferably C1-C6 alkoxysilyl groups) are preferred.

As BR, for example, products such as Ube Industries, JSR, Asahi Kasei, Nippon Zeon, and the like can be used.

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 10% by mass or more, and further preferably 15% by mass or more. The content is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified natural rubber, modified NR, and modified IR. As the NR, for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20 and the like can be used. As IR, it is not specifically limited, For example, IR2200 etc. can use what is common in tire industry. High-purity natural rubber (UPNR), etc. as modified natural rubber, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. as modified NR, epoxidized as modified IR Examples include isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more. Of these, natural rubber (NR) and modified natural rubber (high purity natural rubber (UPNR)) are preferable, and modified natural rubber (high purity natural rubber (UPNR)) is more preferable. Modified natural rubber from which non-rubber components have been removed (high purity natural rubber (UPNR)) has good affinity with carbon black (particularly carbon black (1)), and modified natural rubber (high purity natural rubber) (UPNR)) and carbon black (1) can be used in combination to synergistically improve wear resistance and fracture resistance.

The modified natural rubber (high-purity natural rubber (UPNR)) is not particularly limited as long as it is a natural rubber that has been purified by removing non-rubber components such as proteins and phospholipids. Among these, modified natural rubber that is highly purified and has a pH adjusted to 2 to 7 is more preferable. The modified natural rubber may be used alone or in combination of two or more. In the present specification, the removal of the non-rubber component only requires removal of the non-rubber component as much as possible, and does not mean that all the non-rubber component has been removed.

The modified natural rubber, which removes non-rubber components such as proteins and phospholipids to be highly purified and controls the pH of the rubber to an appropriate value, has improved processing performance, wear resistance, and fracture resistance. In addition, the removal of non-rubber components and the rubber becomes basic or strongly acidic facilitates the deterioration of the rubber, but by adjusting the pH of the rubber to a predetermined range, a decrease in molecular weight during storage is suppressed. Therefore, good heat aging resistance is obtained. As a result, it is possible to prevent deterioration of the physical properties of rubber in the kneading step and to improve the dispersibility of the filler, thereby improving the performance balance of processing performance, wear resistance performance, and fracture resistance performance.

Here, 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. By removing the component, the structure of the isoprenoid component changes, and the interaction with the compounding agent changes, resulting in energy. It is speculated that loss can be reduced, durability can be improved, and a better rubber composition can be obtained.

The modified natural rubber having a high purity and a pH adjusted to 2 to 7 may be a modified natural rubber having a high purity by reducing the amount of non-rubber components and having a rubber pH of 2 to 7. Specifically, (a) a modified natural rubber having a pH of 2 to 7 obtained by treating with an acidic compound after removing non-rubber components of natural rubber, and (b) Ken The natural rubber latex is washed and further treated with an acidic compound, the modified natural rubber having a pH of 2 to 7, and (c) the deproteinized natural rubber latex is washed and further treated with an acidic compound. A modified natural rubber having a pH of 2 to 7, (d) obtained by agglomerating (coagulating) natural rubber latex, pulverizing the agglomerated (coagulated) rubber, and washing repeatedly with water; 7 modified natural rubber, and the like.

Thus, the modified natural rubber can be prepared by a method of 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 to the acidic side by treatment with an acidic compound. Usually, the pH of distilled water is not 7.00 and is about 5 to 6, but in this case, it is important to reduce the pH value to the acidic side from 5 to 6 by treatment with an acidic compound. Become. Specifically, it is preferable to lower the pH value by 0.2 to 2 by treatment with an acidic compound, rather than the pH value of water used for washing.

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

The pH of the modified natural rubber is cut into a size of 2 mm square or less on each side, soaked in distilled water, extracted at 90 ° C. for 15 minutes while irradiating with microwaves, and the soaked water was measured using a pH meter. Specifically, it is measured by the method described in the examples described later. Here, regarding extraction, even if it is extracted for 1 hour with an ultrasonic cleaner or the like, the water-soluble component cannot be completely extracted from the inside of the rubber, so the internal pH cannot be accurately determined. Extraction makes it possible to know the substance of rubber.

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

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

When the modified natural rubber contains an artificial anti-aging agent, the nitrogen content after being immersed in acetone at room temperature (25 ° C.) for 48 hours is preferably 0.15% by mass or less. More preferably, it is 0.10% by mass or less. Thereby, the effect of this invention is acquired more suitably.

Highly purified natural rubber may be deteriorated by long-term storage because the natural anti-aging component, which is said to be inherent to natural rubber, has been removed. Therefore, an artificial anti-aging agent may be added. The nitrogen content is a measured value after removing an artificial anti-aging agent in rubber by extraction with acetone. The nitrogen content can be measured by a conventional method such as Kjeldahl method or trace nitrogen meter. Nitrogen is derived from proteins and amino acids.

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

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

The heat aging 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. By using the method in which the Mooney viscosity ML (1 + 4) is evaluated at the rate of change before and after heat treatment at 80 ° C. for 18 hours at 130 ° C., tire production is performed. It is possible to accurately evaluate heat aging resistance at times and when using tires. Here, if it is within the above range, excellent heat aging resistance can be obtained, and the performance balance of the various performances can be remarkably improved.

The modified natural rubber having a high purity such as (a) to (d) and having a pH adjusted to 2 to 7 is (Production method 1) Step 1-1 of saponifying natural rubber latex; A production method comprising a step 1-2 for washing the saponified natural rubber latex and a step 1-3 for treating with the acidic compound; (Production method 2) a step 2-1 for deproteinizing the natural rubber latex; It can be prepared by a production method including a step 2-2 for washing rubber latex and a step 2-3 for treating with an acidic compound.

[Production method 1]
(Step 1-1)
In step 1-1, natural rubber latex is saponified. Thereby, saponified natural rubber latex in which phospholipids and proteins in the rubber are decomposed and non-rubber components are reduced is prepared.

Natural rubber latex is collected as sap of natural rubber trees such as Hevea, and contains rubber, water, proteins, lipids, inorganic salts, etc., and the gel content in rubber is based on the complex presence of various impurities. It is considered a thing. In the present invention, as natural rubber latex, raw latex (field latex) produced by tapping Hevea tree, or concentrated latex concentrated by centrifugal separation or creaming (refined latex, high ammonia to which ammonia is added by a conventional method) Latex, zinc oxide, TMTD, and LATZ latex stabilized with ammonia can be used.

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

The saponification treatment can be performed by adding an alkali and, if necessary, a surfactant to natural rubber latex and allowing to stand at a predetermined temperature for a certain period of time. Stirring may be performed as necessary.

The alkali used for the saponification treatment is preferably sodium hydroxide or potassium hydroxide, but is not limited thereto. The surfactant is not particularly limited, and examples include 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 addition amount of alkali and surfactant, the temperature and time of the 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. By the washing, non-rubber components such as proteins are removed.

Step 1-2 includes, for example, aggregating the saponified natural rubber latex obtained in Step 1-1 above to produce an agglomerated rubber, and then treating the obtained agglomerated rubber with a basic compound and further washing. Can be implemented. Specifically, after the agglomerated rubber is produced, the non-rubber component can be removed by diluting with water and transferring the water-soluble component to the aqueous layer and removing the water, and further by treating with a basic compound after agglomeration. Non-rubber components confined in the rubber during agglomeration can be redissolved. Thereby, non-rubber components such as protein strongly adhered to the agglomerated rubber can be removed.

Examples of the aggregating method include a method of adjusting the pH by adding an acid such as formic acid, acetic acid or sulfuric acid, and further adding a polymer flocculant as necessary. Thereby, not a large aggregate but a granular rubber having a diameter of about 20 mm is formed from a diameter of several mm to 1 mm or less, and proteins and the like are sufficiently removed by the basic compound treatment. The 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 methyl chloride quaternary salt polymer of dimethylaminoethyl (meth) acrylate, anionic polymer flocculants such as acrylate polymer, and acrylamide polymer. Nonionic polymer flocculants such as, and amphoteric polymer flocculants such as dimethylaminoethyl (meth) acrylate methyl chloride quaternary salt-acrylate copolymer. The addition amount of the polymer flocculant can be selected as appropriate.

Next, the resulting agglomerated rubber is treated with a basic compound. Here, although it does not specifically limit as a basic compound, A basic inorganic compound is suitable from the point of removal performance, such as protein.

Examples of 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 hydrogen carbonates and the like Metal phosphates such as alkali metal phosphates; metal acetates such as alkali metal acetates; metal hydrides such as alkali metal hydrides; ammonia and the like.

Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Examples of the alkaline earth metal hydroxide include magnesium hydroxide, calcium hydroxide, and barium hydroxide. Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of the alkaline earth metal carbonate include magnesium carbonate, calcium carbonate, barium carbonate and the like. Examples of the alkali metal hydrogen carbonate include lithium hydrogen carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate. Examples of the alkali metal phosphate include sodium phosphate and sodium hydrogen phosphate. Examples of the alkali metal acetate include sodium acetate and potassium acetate. Examples of the alkali metal hydride include sodium hydride and potassium hydride.

Of these, metal hydroxides, metal carbonates, metal hydrogen carbonates, metal phosphates, and ammonia are preferable, alkali metal carbonates, alkali metal hydrogen carbonates, and ammonia are more preferable, and sodium carbonate and sodium hydrogen carbonate are more preferable. preferable. The said basic compound may be used independently and may use 2 or more types together.

The method for treating the agglomerated rubber with the basic compound is not particularly limited as long as the agglomerated rubber is brought into contact with the basic compound. For example, the method of immersing the agglomerated rubber in an aqueous solution of the basic compound, And a method of spraying an aqueous solution of the active compound. An aqueous solution of a basic compound can be prepared by diluting and dissolving each basic compound with 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. There exists a tendency which can fully remove protein as it is 0.1 mass% or more. The content is preferably 10% by mass or less, more preferably 5% by mass or less. When the content is 10% by mass or less, it is possible to efficiently perform the treatment without using an unnecessarily large amount of the basic compound.

As pH of the aqueous solution of the said basic compound, 9-13 are preferable and 10-12 are more preferable from the point of processing efficiency.

Although the said processing temperature should just be selected suitably, Preferably it is 10-50 degreeC, More preferably, it is 15-35 degreeC. Moreover, processing time is 1 minute or more normally, Preferably it is 10 minutes or more, More preferably, it is 30 minutes or more. There exists a tendency for the effect of this invention to be acquired more favorably as it is 1 minute or more. The upper limit is not limited, but is preferably 48 hours or less, more preferably 24 hours or less, and still more preferably 16 hours or less from the viewpoint of productivity.

After the basic compound treatment, a washing treatment is performed. By this washing treatment, it is possible to sufficiently remove non-rubber components such as proteins trapped in the rubber at the time of aggregation, and at the same time sufficiently remove not only the surface of the aggregated rubber but also the basic compounds present inside. . In particular, by removing the basic compound remaining in the entire rubber in the washing step, it becomes possible to sufficiently treat the entire rubber with an acidic compound described later, and not only the surface of the rubber but also the internal pH is 2 Can be adjusted to ~ 7.

As the washing method, a non-rubber component contained in the whole rubber, means capable of sufficiently removing the basic compound can be suitably used, for example, a method of diluting the rubber with water and washing, followed by centrifugation, There is a method in which the rubber is floated by standing, and the rubber component is taken out by discharging only the aqueous phase. The number of washings can be any number of times that can reduce the amount of non-rubber components such as proteins and basic compounds to a desired amount. However, washing is performed by adding 1000 mL of water to 300 g of dry rubber and stirring and dehydrating. If it is the method of repeating a cycle, 3 times (3 cycles) or more are preferable, 5 times (5 cycles) or more are more preferable, and 7 times (7 cycles) or more are still more preferable.

The washing treatment is preferably performed 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 mass% or less. The various performances are improved by sufficiently removing phospholipids and proteins by the washing treatment.

(Step 1-3)
In Step 1-3, the washed rubber obtained in Step 1-2 is treated with an acidic compound. As described above, by performing the treatment, the pH of the entire rubber is adjusted to 2 to 7, and a modified natural rubber having excellent various performances can be provided. In addition, although there exists a tendency for heat aging resistance to fall resulting from the process of a basic compound, such a problem is prevented by further processing with an acidic compound, and favorable heat aging resistance is 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 , Naphthalene disulfonic acid, hydroxybenze Examples include organic acids such as sulfonic acid, toluenesulfinic acid, benzenesulfinic acid, α-resorcinic acid, β-resorcinic acid, γ-resorcinic acid, gallic acid, phloroglicin, sulfosalicylic acid, ascorbic acid, erythorbic acid, and bisphenolic acid. It is done. Of these, acetic acid, sulfuric acid, formic acid and the like are preferable. The said acidic compound may be used independently and may use 2 or more types together.

The method of treating the agglomerated rubber with an acid is not particularly limited as long as the agglomerated rubber is brought into contact with the acidic compound. For example, a method of immersing the agglomerated rubber in an aqueous solution of the acidic compound, an aqueous solution of the acidic compound in the agglomerated rubber The method of spraying etc. are mentioned. An aqueous solution of an acidic compound 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. More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less. When the content is within the above range, good heat aging resistance can be obtained.

Although the said processing temperature should just be selected suitably, Preferably it is 10-50 degreeC, More preferably, it is 15-35 degreeC. The treatment time is usually preferably 3 seconds or more, more preferably 10 seconds or more, and further preferably 30 seconds or more. If it is 3 seconds or more, it can be sufficiently neutralized and the effects of the present invention tend to be obtained satisfactorily. Although there is no restriction | limiting in an upper limit, From the point of productivity, Preferably it is 24 hours or less, More preferably, it is 10 hours or less, More preferably, it is 5 hours or less.

In the treatment such as immersion of the acidic compound in an aqueous solution, the pH is preferably adjusted to 6 or less.
By such neutralization, excellent heat aging resistance is obtained. The upper limit of the pH is more preferably 5 or less, still more preferably 4.5 or less. The lower limit is not particularly limited, and although it 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 or the wastewater treatment becomes troublesome. The immersion treatment can be performed by leaving the agglomerated rubber in an acidic compound aqueous solution.

After the treatment, the compound used for the treatment of the acidic compound may be removed, and then the agglomerated rubber after the treatment may be appropriately washed. Examples of the cleaning treatment include the same methods as described above. For example, the non-rubber component may be further reduced by repeating the cleaning and adjusted to a desired content. Further, the agglomerated rubber after the treatment with the acidic compound may be squeezed with a roll type squeezer or the like to form a sheet. By adding a step of squeezing the agglomerated rubber, the pH of the agglomerated rubber surface and inside can be made uniform, and a rubber having a desired performance can be obtained. If necessary, the modified natural rubber can be obtained by carrying out a washing and squeezing step, then cutting through a creper and drying. In addition, drying is not specifically limited, For example, it can implement using normal dryers, such as a trolley-type dryer used in order to dry TSR, a vacuum dryer, an air dryer, and a drum dryer.

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

As a method for deproteinization, a known method capable of removing a protein can be used without particular limitation, and examples thereof include a method of degrading a protein by adding a proteolytic enzyme to natural rubber latex.

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

The amount of proteolytic enzyme added is preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, 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. It is. If it is at least the lower limit, the protein decomposition reaction tends to be sufficient.

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

(Process 2-2)
In step 2-2, the deproteinized natural rubber latex obtained in step 2-1 is washed. By the washing, non-rubber components such as proteins are removed.

Step 2-2 can be performed, for example, by aggregating the deproteinized natural rubber latex obtained in Step 2-1 to produce an aggregated rubber, and then washing the obtained aggregated rubber. Thereby, non-rubber components such as protein strongly adhered to the agglomerated rubber can be removed.

The aggregation method can be performed in the same manner as in Step 1-2 above. Furthermore, you may process with a basic compound as mentioned above as needed. After the production of the agglomerated rubber, a cleaning process is performed. The washing treatment can be carried out in the same manner as in Step 1-2 above, whereby non-rubber components such as proteins and basic compounds can be removed. The cleaning treatment is performed 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 mass% or less for the same reason as described above. Is preferred.

(Step 2-3)
In step 2-3, the washed rubber obtained in step 2-2 is treated with an acidic compound. When the acid amount is small in acid aggregation as well as in the treatment with a basic compound, the heat aging resistance is reduced due to the fact that the finally obtained rubber becomes alkaline to neutral when extracted with water. Tend. In general, an enzyme having an optimum pH in the alkaline region is used as a proteolytic enzyme because it can be suitably deproteinized, and the enzyme reaction is performed under alkaline conditions in accordance with the optimum pH. In many cases, in order to adjust the final rubber pH to 2-7, the deproteinization treatment of natural rubber latex in step 2-1 is preferably carried out at pH 8-11, and pH 8.5-11 is preferred. More preferred. Thereafter, it is coagulated under acidity at the time of agglomeration, but if the rubber is washed only with water, the pH will be higher than that of the extract by the extraction described later, and in this case, particularly the heat aging resistance is greatly reduced. On the other hand, such a problem can be prevented and good heat aging resistance can be obtained by treatment with an acidic compound after solidification, if necessary, after solidification.

Examples of the acidic compound include those similar to those in the above step 1-3. The method of treating the agglomerated rubber with an acid is not particularly limited as long as the agglomerated rubber is brought into contact with the acidic compound. For example, the method of immersing the agglomerated rubber in an aqueous solution of the acidic compound, Examples include a method of spraying an aqueous solution. An aqueous solution of an acidic compound 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. More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less. When the content is within the above range, good heat aging resistance can be obtained.

What is necessary is just to select the said process temperature and process time suitably, and should just employ | adopt the temperature similar to the said process 1-3. In the treatment such as immersion of the acidic compound in an aqueous solution, the pH is preferably adjusted to the same value as in Step 1-3.

After the treatment, the compound used for the treatment of the acidic compound may be removed, and then the agglomerated rubber after the treatment may be appropriately washed. Examples of the cleaning treatment include the same methods as described above. For example, the non-rubber component may be further reduced by repeating the cleaning and adjusted to a desired content. The modified natural rubber is obtained by drying after the washing treatment. In addition, drying is not specifically limited, The above-mentioned method etc. are employable.

When isoprene-based rubber is contained, the content of isoprene-based rubber (preferably modified natural rubber) in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70%. It is at least mass%. Moreover, this content becomes like this. Preferably it is 95 mass% or less, More preferably, it is 90 mass% or less, More preferably, it is 85 mass% or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The total content of isoprene-based rubber and BR in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. .

The rubber composition may contain a resin.
In the present invention, the resin means a polymer compound, more specifically, a polymer obtained by polymerizing monomer units, and may be solid or liquid.
The resin is not particularly limited as long as it is generally used in the tire industry. For example, polyalkylene resin, coumarone indene resin, α-methylstyrene resin, terpene resin, acrylic resin, C5 resin Examples thereof include resins and C9-based resins. These may be used alone or in combination of two or more. Of these, polyalkylene resins and terpene resins are preferred because they can plasticize rubber and promote the dispersion of fillers, and the effects of the present invention can be more suitably obtained.

The polyalkylene resin is not particularly limited as long as it has a unit derived from alkylene. For example, polyethylene resin, polypropylene resin, polybutylene resin, ethylene propylene resin, ethylene propylene styrene resin, ethylene styrene resin, propylene styrene resin, etc. Is mentioned. Of these, ethylene propylene resin and ethylene propylene styrene resin are preferable.

The terpene resin is not particularly limited as long as it is a resin having a unit derived from a terpene compound. For example, polyterpene (resin obtained by polymerizing a terpene compound), terpene aromatic resin (terpene compound and aromatic compound and Resin obtained by copolymerization), aromatic modified terpene resin (resin obtained by modifying terpene resin with an aromatic compound) and the like.

The terpene compound is a hydrocarbon represented by a composition of (C ₅ H ₈ ) _n and an oxygen-containing derivative thereof. Monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ) is a compound having a terpene as a basic skeleton. Terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol and the like can be mentioned. Examples of the terpene compound also include resin acids (rosin acid) such as abietic acid, neoabietic acid, parastrinic acid, levopimaric acid, pimaric acid, and isopimaric acid. That is, the terpene resin includes a rosin resin mainly composed of rosin acid obtained by processing pine resin. The rosin resins include natural rosin resins (polymerized rosin) such as gum rosin, wood rosin, tall oil rosin, modified rosin resins such as maleic acid modified rosin resin, rosin modified phenolic resin, rosin glycerin ester, etc. Examples thereof include rosin esters and disproportionated rosin resins obtained by disproportionating rosin resins.

The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring. For example, phenol compounds such as phenol, alkylphenol, alkoxyphenol, unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, Examples thereof include naphthol compounds such as saturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene. Of these, styrene is preferred.

The softening point of the resin is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, and further preferably 40 ° C. or higher. The softening point is preferably 160 ° C. or lower, more preferably 140 ° C. or lower, and further preferably 100 ° C. or lower. The effect of this invention is acquired more suitably as it is in the said numerical range.
In the present invention, the softening point of the resin is a temperature at which the sphere descends when the softening point defined in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring apparatus.

The resin may be hydrogenated, and from the reason that the effects of the present invention can be obtained more suitably, the resin is preferably a hydrogenated hydrogenated resin. The hydrogenation can be performed by a known method. For example, any of catalytic hydrogenation using a metal catalyst, a method using hydrazine, and the like can be preferably used (Japanese Patent Laid-Open No. 59-161415, etc.). For example, catalytic hydrogenation with a metal catalyst can be carried out by adding hydrogen under pressure in the presence of a metal catalyst in an organic solvent. As the organic solvent, any of tetrahydrofuran, methanol, ethanol, etc. is suitable. Can be used for These organic solvents can be used individually by 1 type or in mixture of 2 or more types. In addition, as the metal catalyst, for example, palladium, platinum, rhodium, ruthenium, nickel and the like can be preferably used. These metal catalysts can be used alone or in combination of two or more. . As a pressure at the time of pressurization, it is preferable that it is 1-300 kg weight / cm < ² >, for example.

In the above resin, the hydrogenation rate of the double bond is 1 to 100%, particularly preferably 2% or more, more preferably 5% or more, and further preferably 8% or more. . In addition, the upper limit of the hydrogenation rate of the double bond may be changed in the preferred range due to the pressurization and heating conditions in the hydrogenation reaction, progress in production technology such as a catalyst, improvement in productivity, etc. Although it has not been confirmed accurately at the present time, for example, it is preferably 80% or less, more preferably 60% or less, still more preferably 40% or less, and even more preferably 30% or less. 25% or less is particularly preferable.
In addition, this hydrogenation rate (hydrogenation rate) is a value calculated by the following formula from each integrated value of the double bond-derived peak by ¹ H-NMR (proton NMR). In the present specification, the hydrogenation rate (hydrogenation rate) means a hydrogenation rate of double bonds.
(Hydrogenation rate [%]) = {(A−B) / A} × 100
A: Integrated value of double bond peak before hydrogenation B: Integrated value of double bond peak after hydrogenation

Examples of the resin include Mitsui Chemicals, Stratol, Yashara Chemical, Arizona Chemical, Nikko Chemical, Rutgers Chemicals, Arakawa Chemical Co., Maruzen Petrochemical, Products such as Sumitomo Bakelite Co., Ltd., Tosoh Co., Ltd., Nippon Shokubai Co., Ltd., JX Energy Co., Ltd., Toagosei Co., Ltd. can be used.

When the resin is contained, the content of the resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 15 parts by mass or less. Thereby, the effect of this invention is acquired more suitably.

The rubber composition may contain silica.
Examples of the silica include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid) and the like, but wet process silica is preferred because of the large number of silanol groups. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 70 m ² / g or more, and more preferably 150 m ² / g or more. By setting it to 70 m ² / g or more, there is a tendency that the wear resistance and the like are further improved. _N 2 SA of the silica is preferably 500 meters ² / g or less, more preferably 200m ² / g. There exists a tendency for process performance to be improved more by setting it as 500 m < ² > / g or less.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

Examples of silica that can be used include products such as Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama.

When silica is contained, the content of silica is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and still more preferably 70 parts by mass or more with respect to 100 parts by mass of the rubber component. There exists a tendency for low-fuel-consumption performance to be improved more that it is 30 mass parts or more. Moreover, this content becomes like this. Preferably it is 200 mass parts or less, More preferably, it is 150 mass parts or less, More preferably, it is 100 mass parts or less. When the amount is 200 parts by mass or less, the balance between the processing performance and the low fuel consumption performance tends to be further improved.

The content of carbon black in 100% by mass of silica and carbon black is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and particularly preferably 40% by mass or more. It is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and may be 100% by mass. Thereby, the effect of this invention is acquired more suitably.

When the rubber composition contains silica, it is preferable to further contain a silane coupling agent.
The silane coupling agent is not particularly limited. For example, 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-trimethoxysilyl ester) 3) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3 -Sulphides such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, Momentive NXT, NXT-Z, etc. mercapto, vinyltriethoxysilane, vinyl Vinyl type such as trimethoxysilane, amino type such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycid Glycidoxy such as cyclopropyltrimethoxysilane, nitro such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane Etc. These may be used alone or in combination of two or more. Among these, a mercapto-based silane coupling agent is preferable because the effects of the present invention tend to be obtained better.

Examples of the silane coupling agent that can be used include Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Amax Co., Ltd., and Toray Dow Corning Co., Ltd.

When the silane coupling agent is contained, 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. There exists a tendency for the effect by addition to be acquired as it is 3 mass parts or more. The content is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less. When the amount is 20 parts by mass or less, an effect commensurate with the blending amount is obtained, and good workability during kneading tends to be obtained.

The rubber composition may contain oil.
Examples of the oil include process oil, vegetable oil and fat, or a mixture thereof. As the process oil, for example, a paraffin process oil, an aroma process oil, a naphthenic process oil, or the like can be used. As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut hot water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Among these, process oil is preferable and aroma-based process oil is more preferable because the effects of the present invention can be obtained satisfactorily.

When oil is contained, the content of oil is preferably 1 part by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less.

The rubber composition may contain a wax.
The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers such as ethylene and propylene. These may be used alone or in combination of two or more. Of these, petroleum wax is preferable, and paraffin wax is more preferable.

As the wax, for example, products such as Ouchi Shinsei Chemical Co., Ltd., Nippon Seiwa Co., Ltd., Seiko Chemical Co., Ltd. can be used.

When the wax is contained, the content of the wax is preferably 0.3 to 20 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of the performance balance. .

The rubber composition may contain an anti-aging agent.
Examples of the antiaging agent include naphthylamine type antiaging agents such as phenyl-α-naphthylamine; diphenylamine type 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. P-phenylenediamine-based antioxidants; quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer; 2,6-di-t-butyl-4-methylphenol; Monophenolic antioxidants such as styrenated phenol; tetrakis- [methylene-3- (3 ', 5'-di-t-butyl- '- hydroxyphenyl) propionate] bis methane, tris, and the like polyphenolic antioxidants. These may be used alone or in combination of two or more. Of these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable.

As the anti-aging agent, for example, products such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Co., Ltd., and Flexis Co. can be used.

When the anti-aging agent is contained, the content of the anti-aging agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

The rubber composition preferably contains stearic acid.
A conventionally well-known thing can be used as a stearic acid, For example, products, such as NOF Corporation, NOF company, Kao Corporation, Wako Pure Chemical Industries, Ltd., and Chiba fatty acid company, can be used.

When stearic acid is contained, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

The rubber composition preferably contains zinc oxide.
Conventionally known zinc oxide can be used, for example, Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd. Can be used.

When zinc oxide is contained, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. If it is within the above numerical range, the effect of the present invention tends to be obtained better.

The rubber composition preferably contains sulfur.
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. These may be used alone or in combination of two or more.

As the sulfur, for example, products such as Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Nihon Kiboshi Kogyo Co., Ltd., Hosoi Chemical Co., Ltd. can be used.

When sulfur is contained, the content of sulfur is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less. If it is within the above numerical range, the effect of the present invention tends to be obtained better.

The rubber composition preferably contains a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), Tetrabenzylthiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N, N′-diisopropyl-2-benzothiazole sulfenamide, etc. Sulfena De-based vulcanization accelerator; diphenylguanidine, it may be mentioned di-ortho-tolyl guanidine, guanidine-based vulcanization accelerators such as ortho tri ruby guanidine. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred because the effects of the present invention can be obtained more suitably.

When the vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. If it is within the above numerical range, the effect of the present invention tends to be obtained better.

In addition to the above components, additives generally used in the tire industry can be added to the rubber composition. Organic peroxides: calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica And the like; and the like.

The rubber composition can be produced by, for example, a method of kneading the above components using a rubber kneading apparatus such as an open roll or a Banbury mixer and then vulcanizing.

Although the said rubber composition can be used for each member of a tire, it can be used conveniently for a tread, a base tread, a sidewall, a carcass, a clinch etc., and can be used suitably for a tread (cap tread).

(Pneumatic tire)
The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, the rubber composition containing the above components is extruded in accordance with the shape of each tire member such as a tread at an unvulcanized stage, and is molded together with the other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The pneumatic tire is suitable for use in passenger car tires, truck / bus tires, motorcycle tires, high-performance tires, etc., and has good wear resistance and fracture resistance. It can be suitably used as a tire for an automobile.

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

Hereinafter, various chemicals used in the production examples will be described together.
Field Latex: Field Latex Emar E-27C (surfactant) obtained from Muhiba Latex Co., Ltd .: Emar E-27C (Polyoxyethylene lauryl ether sodium sulfate, 27% by mass of active ingredient) manufactured by Kao Corporation
NaOH: NaOH manufactured by Wako Pure Chemical Industries, Ltd.
Wingstay L (anti-aging agent): WINGSTAY L (compound obtained by butylating the condensate of ρ-cresol and dicyclopentadiene) manufactured by ELIOKEM
Emulvin W (surfactant): Emalvin W (aromatic polyglycol ether) manufactured by LANXESS
Tamol NN9104 (surfactant): Tamol NN9104 manufactured by BASF (Naphthalenesulfonic acid / formaldehyde sodium salt)
Van gel B (surfactant): Van gel B (magnesium aluminum silicate hydrate) manufactured by Vanderbilt

(Preparation of anti-aging agent dispersion)
462.5 g of water was mixed with 12.5 g of Emulvin W, 12.5 g of Tamol NN9104, 12.5 g of Van gel B, and 500 g of Wingstay L (total of 1000 g) for 16 hours by a ball mill 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% Emar E-27C aqueous solution and 60 g of 25% NaOH aqueous solution were added to 1000 g of the latex, and at room temperature (23 ° C.). Saponification reaction was performed for 24 hours to obtain a saponified natural rubber latex. Next, 6 g of the anti-aging dispersion was added and stirred for 2 hours, and then further diluted with water to a rubber concentration of 15% (w / v). Next, formic acid was added with slow stirring to adjust the pH to 4.0, and then a cationic polymer flocculant was added and stirred for 2 minutes for aggregation. The diameter of the aggregate (aggregated rubber) thus obtained was about 0.5 to 5 mm. The obtained agglomerates were taken out and immersed in 1000 ml of a 2% by weight aqueous sodium carbonate solution at room temperature (23 ° C.) for 4 hours, and then the rubber was taken out. To this, 2000 ml of water was added and stirred for 2 minutes to remove water as much as possible 7 times. Thereafter, 500 ml of water was added, 2% by mass formic acid was added until pH 4 was reached, and the mixture was allowed to stand for 15 minutes. Further, after removing the water as much as possible, repeating the work of adding water again and stirring for 2 minutes three times, squeezing the water with a water squeezing roll to form a sheet, and then drying at 90 ° C. for 4 hours to solid rubber ( Modified natural rubber A) was obtained.

(Production Example 2)
Commercially available high-ammonia latex (manufactured by Mujiba Latex of Malaysia, solid rubber content 62.0%) is diluted with 0.12% sodium naphthenate aqueous solution to make the solid rubber content 10%, and dihydrogen phosphate. Sodium was added to adjust the pH to 9.2. And with respect to 10g of rubber | gum, after adding proteolytic enzyme (Alcalase 2.0M) in the ratio of 0.87g and adjusting pH again to 9.2, it maintained at 37 degreeC for 24 hours.
Next, 1% aqueous solution of nonionic surfactant [trade name Emulgen 810 manufactured by Kao Co., Ltd.] is added to the latex that has been subjected to the enzyme treatment to adjust the rubber concentration to 8%, and at a rotation speed of 11,000 rpm. Centrifuge for 30 minutes. Next, the cream-like fraction produced by centrifugation is dispersed in a 1% aqueous solution of the above Emulgen 810 and adjusted so that the rubber concentration is 8%, and then again at a rotational speed of 11,000 rpm. Centrifuged for minutes. After repeating this operation twice, the obtained creamy fraction was dispersed in distilled water to prepare a deproteinized rubber latex having a solid rubber content of 60%.
To this latex, 2% by mass formic acid was added until the pH reached 4, and a cationic polymer flocculant was further added to obtain rubber particles of 0.5 to 5 mm. The water was removed as much as possible, 50 g of water was added to 10 g of rubber, and 2% by mass formic acid was added until pH 3 was reached. After 30 minutes, the rubber was pulled up, formed into a sheet with a creper, and then dried at 90 ° C. for 4 hours to obtain a solid rubber (modified natural rubber B).

(Production Example 3)
Water was added to the field latex to dilute to DRC 15% (w / v), and then the formic acid was added with slow stirring to adjust the pH to 4.0 to 4.5 and agglomerate. The agglomerated 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.

<Measurement of pH of rubber>
5 g of the obtained rubber was cut into a total of 3 mm or less (about 1-2 × about 1-2 × about 1-2 (mm)) and placed in a 100 ml beaker, and 50 ml of distilled water at room temperature (23 ° C.) Was added, and the temperature was raised to 90 ° C. in 2 minutes. Thereafter, microwaves (300 W) were irradiated for 13 minutes (total 15 minutes) while maintaining the temperature at 90 ° C. Next, the immersion water was cooled with an ice bath to 25 ° C., and then the pH of the immersion water was measured using a pH meter.

<Measurement of nitrogen content>
(Acetone extraction (test piece preparation))
About 0.5 g of a sample obtained by chopping each solid rubber into 1 mm square was prepared. 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 (extracted with anti-aging agent).

(Measurement)
The nitrogen content of the obtained test piece was measured by the following method.
The nitrogen content was determined by decomposing and gasifying each of the acetone-extracted test pieces obtained above using a trace nitrogen carbon measuring device “SUMIGRAPH NC95A (manufactured by Sumika Chemical Analysis Center)”. 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 mixture was allowed to stand in a cool dark place for 1 week. Subsequently, centrifugation was performed to precipitate a gel component insoluble in toluene, the soluble component of the supernatant was removed, and only the gel component was solidified with methanol, and then dried and the mass was measured. The gel content (mass%) was determined by the following formula.
Gel content (mass%) = [mass mg after drying / mg of initial sample] × 100

Various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20 (phosphorus content: 572 ppm)
Modified natural rubber A: Modified natural rubber A obtained in Production Example 1
Modified natural rubber B: Modified natural rubber B obtained in Production Example 2
Modified natural rubber C: Modified natural rubber C obtained in Production Example 3
BR: BR150B manufactured by Ube Industries, Ltd. (cis content: 98% by mass)
Carbon Black N220: Diamond Black N220 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 114 m ² / g, DBP: 114 ml / 100 g)
Carbon blacks 1 to 6: carbon blacks 1 to 6 having the characteristics shown in Table 2 below
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate zinc oxide: Zinc oxide 2 types manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. (containing 5% oil)
Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Examples and Comparative Examples)
According to the blending contents shown in Table 3, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes under a condition of 150 ° C. using a Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is formed into a tread shape and bonded together with other tire members to form an unvulcanized tire, press vulcanized at 170 ° C. for 10 minutes, and a test tire ( Size: 195 / 65R15). The obtained unvulcanized rubber composition and the test tire were used for the evaluation shown below, and the results are shown in Table 3.

(Processing performance)
For each unvulcanized rubber composition, according to the Mooney viscosity measurement method according to JIS K 6300-1, “Unvulcanized rubber—physical properties—Part 1: Determination of viscosity and scorch time using Mooney viscometer” Mooney viscosity (ML1 + 4) was measured under a temperature condition of 130 ° C. The results were expressed as an index with the Mooney viscosity of Comparative Example 1 as 100 (working performance index). The larger the index, the lower the Mooney viscosity and the better the processing performance. When it was 95 or more, it was judged to be good.

(Abrasion resistance)
Each test tire was mounted on a domestic FF vehicle, the groove depth of the tire tread portion after a mileage of 8000 km was measured, and the mileage when the tire groove depth decreased by 1 mm was calculated. Expressed in hourly index (wear resistance performance index). The larger the index, the longer the travel distance when the tire groove depth is reduced by 1 mm, and the better the wear resistance.

(Destruction resistance)
Using a No. 3 dumbbell-shaped test piece made of rubber cut from the tread of each test tire, a tensile test was performed at room temperature according to JIS K 6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. The elongation at break EB (%) was measured and displayed as an index when the comparative example 1 was set to 100 (destructive performance index). It shows that it is excellent in fracture resistance, so that an index | exponent is large.

From Table 3, in the Example containing specific carbon black, it was able to improve wear resistance and fracture resistance while maintaining good processing performance.
In addition, by using the modified natural rubber (high-purity natural rubber (UPNR)) from which the non-rubber component was removed and carbon black (1) in combination with Examples 1 and 4 and Comparative Examples 1 and 2, It was found that the wear resistance and fracture resistance can be improved synergistically.

Claims (7)

Cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 140 to 150 m ² / g, nitrogen adsorption specific surface area of 140 to 150 m ² / g, iodine adsorption amount (IA) of 120 to 135 mg / g, ratio of CTAB to IA (CTAB) / IA) is a rubber composition for tires containing carbon black (1) having 1.10 to 1.20, compressed dibutyl phthalate oil absorption of 110 to 120 ml / 100 g, and dibutyl phthalate oil absorption of 127 to 141 ml / 100 g. The rubber composition for a tire according to claim 1, wherein the content of the carbon black (1) is 20 to 70 parts by mass with respect to 100 parts by mass of the rubber component. The tire rubber composition according to claim 1 or 2, comprising a modified natural rubber having a phosphorus content of 500 ppm or less. The rubber composition for tires according to any one of claims 1 to 3, wherein the content of isoprene-based rubber in 100% by mass of the rubber component is 60 to 90% by mass and the content of butadiene rubber is 10 to 40% by mass. The rubber composition for tires according to any one of claims 1 to 4, comprising carbon black (2) having a nitrogen adsorption specific surface area of less than 140 m ² / g. The pneumatic tire which has a tread produced using the rubber composition for tires in any one of Claims 1-5. The pneumatic tire according to claim 6, which is a truck / bus tire.