JP7091716B2 - Rubber composition for tires - Google Patents

Description

The present invention relates to a rubber composition for tread and a studless tire having a tread composed of the rubber composition.

One of the important performances required for studless tires is, for example, braking performance on ice. Adhesive friction, hysteresis friction, scratching (digging up) friction and the like are known as factors that control the friction between the tread rubber and the road surface, which affect the performance of the tire on ice.

Conventionally, as a method of improving the frictional force between the tread rubber and the road surface on ice, the method of focusing on adhesive friction to lower the hardness of the rubber at low temperature and increasing the contact area with the road surface, and focusing on hysteresis friction. A method of increasing the hysteresis loss of rubber and a method of improving the frictional force of rubber itself by blending a material having a moth hardness higher than that of ice have been studied, paying attention to scratch friction.

Since grip performance on icy and snowy roads is the highest priority for studless tires, the mainstream technology is to use butadiene rubber and natural rubber, which are more flexible in low temperature environments than styrene butadiene rubber. Therefore, it is difficult to secure the grip performance (wet grip performance) on a wet road surface when it is not snowing. Therefore, in passenger car tires, there is known a technique of ensuring wet grip performance while maintaining wear resistance by changing carbon black contained as a reinforcing agent to silica (Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 5-51484 Japanese Unexamined Patent Publication No. 9-87427

If the hardness of the rubber at a low temperature is lowered by increasing the amount of oil in order to improve the adhesive friction, the hysteresis friction also tends to decrease. Therefore, there is a problem that the braking performance on ice is deteriorated due to the decrease of the hysteresis friction in the vicinity of 0 ° C. where the temperature is relatively high and water is generated.

An object of the present invention is to provide a rubber composition for a tire capable of improving on-ice performance and a studless tire having a tire member composed of the rubber composition.

As a result of diligent studies, the present inventor has found that the above problems can be solved by blending a predetermined terpene resin and silica with highly purified natural rubber. In a more preferred embodiment, they have found that wear resistance and fracture properties can also be improved, and have completed the present invention.

That is, the present invention
[1] The weight average molecular weight (Mw) is 500 to 1500 with respect to 100 parts by mass of a rubber component containing 30% by mass or more of natural rubber having a nitrogen content of 0.30% by mass or less and 30% by mass or more of butadiene rubber. It contains 3 to 40 parts by mass of the terpene-based resin and 5 to 60 parts by mass of silica having a BET specific surface area of 50 to 300 m ² / g, and the content of silica with respect to the content of the terpene-based resin (silica content). / Rubber composition having a terpene resin content) of 0.1 to 50,
[2] The present invention relates to a studless tire having a tire member composed of the rubber composition according to [1].

A tire having a rubber composition containing the highly purified natural rubber of the present invention, a predetermined terpene resin and silica, and a tire member made of the rubber composition is excellent in on-ice performance.

The rubber composition according to an embodiment of the present invention is based on 100 parts by mass of a rubber component containing 30% by mass or more of natural rubber having a nitrogen content of 0.30% by mass or less and 30% by mass or more of butadiene rubber. Contains 3 to 40 parts by mass of a terpene resin having a weight average molecular weight (Mw) of 500 to 1500 and 5 to 60 parts by mass of silica having a BET specific surface area of 50 to 300 m ² / g. The content of silica (content of silica / content of terpene-based resin) is 0.1 to 50. In this specification, when a numerical range is indicated by using "-", the numerical values at both ends thereof are included.

<Rubber component>
As the rubber component used in the present embodiment, natural rubber having a high purity and a nitrogen content of 0.30% by mass or less (hereinafter, referred to as "modified natural rubber" may be described in the present specification. There is) is preferably used. Since the modified natural rubber is soft, the complex elastic modulus (0 ° C.E *) at low temperature is lowered, the hysteresis loss is improved, and the performance on ice is also improved. Furthermore, by combining a natural rubber-based resin and a terpene-based resin with high compatibility, the performance on ice is synergistically improved. In addition, silica softens the rubber in the low temperature range and increases its followability to ice, and the terpene resin contributes to the improvement of on-ice performance by increasing the adhesiveness of the rubber to the ice surface in the low temperature range. It is thought that. The modified natural rubber can be used alone or in combination of two or more.

(Modified natural rubber)
As used herein, "purification" means removing impurities such as phospholipids and proteins other than the natural polyisoprenoid component. Since the natural rubber has a structure in which the isoprenoid component is covered with an impurity component, the structure of the isoprenoid component is changed by removing the impurity component. When the structure of the isoprenoid component changes in this way, the state of interaction with the compounding agent also changes, resulting in a reduction in energy loss and an improvement in durability, resulting in a better modified natural rubber. Is thought to be possible.

The method for purifying the substance is not particularly limited, but specifically, (1) a method for saponifying natural rubber latex and (2) a method for aggregating natural rubber latex, which is then crushed and washed. (3) After the saponification treatment, a washing treatment is performed, and a method of treating with an acidic compound and the like can be mentioned. Of course, the method for purifying the modified natural rubber is not particularly specified, and known methods such as mechanical methods such as ultrasonic waves and centrifugation, and methods for decomposing impurities such as proteins by enzymes are used without limitation. However, from the viewpoint of removing impurities and improving fuel efficiency, a method of saponification treatment, cleaning treatment, and treatment with an acidic compound is preferable, and production efficiency, cost, dispersibility of white filler, etc. are preferable. From the viewpoint, the cleaning treatment is preferable. Specifically, the purification of natural rubber can be performed by the method described in International Publication No. 2014/125700 or the like.

Natural rubber latex includes raw latex (field latex) collected by tapping Hebea tree, and concentrated latex (purified latex, high ammonia latex to which ammonia is added by a conventional method) obtained by concentrating raw latex by centrifugation or creaming method. , LATZ latex stabilized by zinc flower, TMTD (tetramethylthium disulfide) and ammonia) and the like. Among them, it is preferable to use field latex because it is easy to purify by pH control.

The rubber component (solid rubber content) in the natural rubber latex is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, from the viewpoint of stirring efficiency and the like.

Examples of the saponification treatment method include the methods described in JP-A-2010-138359 and JP-A-2010-174169. Specifically, it can be carried out by adding an alkali and, if necessary, a surfactant to the natural rubber latex and allowing it to stand at a predetermined temperature for a certain period of time. Further, stirring or the like may be performed as needed. According to the above-mentioned production method, the phosphorus compound separated by saponification is removed, so that the phosphorus content of the natural rubber can be suppressed. Furthermore, since the protein in the natural rubber is decomposed by the saponification treatment, the nitrogen content of the natural rubber can be suppressed. By using the natural rubber latex, the saponification treatment can be efficiently performed.

Examples of the alkali used for the saponification treatment include sodium hydroxide, potassium hydroxide, calcium hydroxide, an amine compound and the like, and from the viewpoint of the effect of the saponification treatment and the influence on the stability of the natural rubber latex, hydroxylation is particularly high. It is preferable to use sodium or potassium hydroxide.

The amount of alkali added is not particularly limited, but the lower limit is preferably 0.1 part by mass or more, and more preferably 0.3 part by mass or more with respect to 100 parts by mass of the solid content of the natural rubber latex. The upper limit of the addition amount is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less. By setting the amount of alkali added to 0.1 parts by mass or more, the saponification treatment tends to be smoothly performed. On the contrary, by setting the addition amount of alkali to 10 parts by mass or less, it tends to be possible to prevent the natural rubber latex from becoming unstable.

As the surfactant, at least one of anionic surfactant, nonionic surfactant and amphoteric surfactant can be used. Among these, examples of the anionic surfactant include carboxylic acid-based, sulfonic acid-based, sulfate ester-based, and phosphoric acid ester-based anionic surfactants. Examples of the nonionic surfactant include nonionic surfactants such as polyoxyalkylene ester type, polyoxyalkylene ester type, polyhydric alcohol fatty acid ester type, glycolipid ester type, and alkyl polyglycoside type. Examples of the amphoteric tenside include amino acid type, betaine type, amine oxide type and the like. Of these, anionic surfactants are preferable, and sulfonic acid-based anionic surfactants are more preferable.

The amount of the surfactant added is not particularly limited, but the lower limit is preferably 0.01 part by mass or more, and more preferably 0.10 part by mass or more with respect to 100 parts by mass of the solid content of the natural rubber latex. .. The upper limit of the addition amount is preferably 5.00 parts by mass or less, more preferably 3.00 parts by mass or less. By adding the surfactant to 0.01 parts by mass or more, there is a tendency that destabilization of the natural rubber latex during the saponification treatment can be prevented. On the contrary, by setting the addition amount of the surfactant to 5.00 parts by mass or less, it tends to be possible to prevent the natural rubber latex from becoming too stable and becoming difficult to coagulate.

The temperature of the saponification treatment can be appropriately set within a range in which the saponification reaction with an alkali can proceed at a sufficient reaction rate and a range in which the natural rubber latex does not cause deterioration such as coagulation, but is usually 30 to 80 ° C. It is preferable to have it. In addition, the treatment time depends on the temperature of the treatment when the natural rubber latex is allowed to stand still, but considering that sufficient treatment and improvement of productivity are taken into consideration, 3 It is preferably about 24 hours.

The cleaning treatment can be performed by aggregating the natural rubber latex and then crushing and cleaning the agglomerated rubber. Examples of the aggregation method include a method of adding an acid such as formic acid, adjusting the pH, and further adding a polymer flocculant as needed. Further, as the polymer flocculant, a cationic polymer flocculant such as a polymer of a quaternary salt of methyl chloride of dimethylaminoethyl (meth) acrylate (for example, polymethacrylic acid ester-based agglomerate manufactured by MT Aqua Polymer Co., Ltd.) Agents, etc.), anionic polymer flocculants such as acrylate polymers, nonionic polymer flocculants such as acrylamide polymers, and methyl quaternary chloride salt of dimethylaminoethyl (meth) acrylate-acrylic acid salts. Examples thereof include an amphoteric polymer flocculant such as a polymer. The amount of the polymer flocculant added can be appropriately selected. Further, as a cleaning treatment, for example, a method of diluting the rubber component with water, cleaning the rubber component, and then performing a centrifugal separation process to remove the rubber component can be mentioned. When centrifuging, first, the natural rubber latex is diluted with water so that the rubber content is 5 to 40% by mass, preferably 10 to 30% by mass. Then, centrifugation may be performed at 5000 to 10000 mp for 1 to 60 minutes, and washing may be repeated until the desired phosphorus content is reached. After the cleaning treatment is completed, the modified natural rubber according to the present embodiment is obtained by drying.

The nitrogen content in the modified natural rubber according to the present embodiment is 0.30% by mass or less, preferably 0.20% by mass or less, more preferably 0.15% by mass or less, and 0.10% by mass or less. Is more preferable, and 0.05% by mass or less is particularly preferable. By setting the nitrogen content in the natural rubber to 0.30% by mass or less, the on-ice performance and the fracture characteristics can be remarkably improved. Further, when the nitrogen content exceeds 0.30% by mass, the gel content in the carbon black tends to decrease, and the fracture characteristics tend to decrease. Nitrogen is thought to be derived from proteins and amino acids. The nitrogen content can be measured by a conventional method such as the Kjeldahl method or a trace nitrogen meter. Since the modified natural rubber has the natural anti-aging agent component that is said to be originally possessed by the natural rubber removed, there is a risk of deterioration due to long-term storage. Therefore, an artificial anti-aging agent may be added. In such a case, the nitrogen content of the modified natural rubber is immersed in acetone at room temperature (25 ° C.) for 48 hours and extracted with acetone. The value is measured after removing the artificial antiaging agent in the rubber.

From the viewpoint of processability, the phosphorus content in the modified natural rubber according to the present embodiment is preferably 500 ppm or less, more preferably 200 ppm or less, still more preferably 100 ppm or less. Phosphorus is considered to be derived from phospholipids contained in natural rubber. The phosphorus content can be measured by a conventional method such as ICP emission spectrometry.

The gel content in the modified natural rubber according to the present embodiment is preferably 30% by mass or less, more preferably 25% by mass or less. By setting the gel content to 30% by mass or less, the physical characteristics of rubber such as fuel efficiency tend to be improved. The gel content means a value measured as an insoluble content in toluene which is a non-polar solvent, and may be simply referred to as "gel content" or "gel content" in the following. The method for measuring the gel content is as follows. First, a natural rubber sample is immersed in dehydrated toluene, shaded in a dark place and left for 1 week, and then the toluene solution is centrifuged at 1.3 × ¹⁰⁵ rpm for 30 minutes to obtain an insoluble gel component and a toluene-soluble component. To separate. Methanol is added to the insoluble gel to solidify it, and then it is dried. The gel content is determined from the ratio of the mass of the gel to the original mass of the sample.

The content of the modified natural rubber in 100% by mass of the rubber component is 30% by mass or more, preferably 35% by mass or more, more preferably 40% by mass or more, still more preferably 45% by mass or more. If the content of natural rubber is less than 30% by mass, the fracture characteristics tend to deteriorate. The content of the modified natural rubber in 100% by mass of the rubber component is preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less.

(Other rubber components)
In the present embodiment, the other rubber components that can be used other than the modified natural rubber are not particularly limited, and natural rubber other than the modified natural rubber, synthetic isoprene rubber (IR), butadiene rubber (BR), and the like. Examples thereof include diene rubber components such as styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR), and butyl rubber such as chlorinated butyl rubber. Further, these hydrogenated rubbers and modified rubbers may be used. Above all, it is preferable to use BR as another rubber component from the viewpoint of wear resistance.

Natural rubber other than modified natural rubber includes non-modified natural rubber (NR), epoxidized natural rubber (ENR), hydrided natural rubber (HNR), deproteinized natural rubber (DPNR), and high-purity natural rubber (UPNR). ), Modified natural rubber such as grafted natural rubber and the like. These rubbers may be used alone or in combination of two or more.

The NR is not particularly limited, and a tire that is common in the tire industry can be used, and examples thereof include SIR20, RSS # 3, and TSR20.

The BR is not particularly limited, and for example, BR (low cis BR) having a cis 1,4 bond content of less than 50%, BR (high cis BR) having a cis 1,4 bond content of 90% or more, and rare earths. Rare earth-based butadiene rubber (rare earth-based BR) synthesized using an elemental catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-sys-modified BR, rosis-modified BR), etc. Can be used. Among them, it is preferable to use at least one selected from the group consisting of high-cis BR, low-cis BR and low-cis modified BR, and it is more preferable to use high-cis BR.

Examples of the HISIS BR include HISIS BR manufactured and sold by JSR Corporation, ZEON Corporation, Ube Kosan Co., Ltd., and the like. Among the high cis BRs, those having a cis 1,4-bonding content of 95% or more are more preferable. These may be used alone or in combination of two or more. By containing HISIS BR, low temperature characteristics and wear resistance can be improved. Examples of the Rosis BR include BR1250 manufactured by Rosis BR manufactured and sold by Nippon Zeon Corporation and the like. These may be used alone or in combination of two or more. The cis 1,4-bond content in BR is a value calculated by infrared absorption spectrum analysis.

When BR is contained, the content in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more from the viewpoint of low temperature characteristics and wear resistance. Further, the content of BR in the rubber component is preferably 70% by mass or less, more preferably 65% by mass or less, still more preferably 60% by mass or less, from the viewpoint of fracture characteristics.

The total content of the modified natural rubber and BR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and consists only of 100% by mass (that is, modified natural rubber and butadiene rubber). That) is more preferable.

<Resin component>
As the resin component used in the present embodiment, terpene-based resins such as polyterpene resin, terpene phenol resin, and terpene styrene resin are preferably used, and polyterpene resin is more preferable.

(Terpene resin)
The terpene resin has a lower SP value than other adhesive resins such as an aliphatic petroleum resin, an aromatic petroleum resin, a phenol resin, a Kumaron inden resin, and a rosin resin, and the SP value is NR (SP value). : Since it is close to 8.1), it has excellent compatibility with the rubber component according to the present embodiment. The SP value of the terpene resin is preferably 8.60 or less, more preferably 8.50 or less, because the water repellency of the rubber composition can be further improved. The SP value of the terpene resin is preferably 7.5 or more from the viewpoint of compatibility with the rubber component.

The polyterpene resin is a resin made from at least one selected from terpene compounds. Specific examples of the terpine compound include, for example, α-pinene, β-pinene, 3-calene (δ-3-calene), dipentene, limonene, myrcene, aloosimene, osimene, α-ferrandrene, α-terpinene, γ-. Examples thereof include terpinene, terpineol, 1,8-cineole, 1,4-cineol, α-terpineol, β-terpineol, γ-terpineol and the like. Among them, α-pinene, β-pinene, 3-carene (δ-3-carene), dipentene and limonene are preferable, and α-pinene and limonene are more preferable, from the viewpoint of improving grip performance and durability in a well-balanced manner. Here, limonene may include any of d-form, l-form, and d / l-form. These terpene compounds may be used alone or in combination of two or more.

The terpene phenol resin is a resin made from the terpene compound and the phenol-based compound. The terpene styrene resin is a resin made from the terpene compound and styrene. The polyterpene resin, the terpene phenol resin, and the terpene styrene resin may be resins (hydrogenated polyterpene resin, hydrogenated terpene styrene resin) obtained by hydrogenating them.

The hydrogenation treatment to the terpene-based resin can be performed by a known method, or a commercially available hydrogenated resin can also be used. From the viewpoint of grip performance, the hydrogenation rate of the double bond is preferably 5% or more, more preferably 7% or more, further preferably 10% or more, and particularly preferably 15% or more. The hydrogenation rate of the double bond is preferably 80% or less, more preferably 60% or less, further preferably 40% or less, and particularly preferably 30% or less. The hydrogenation rate (hydrogenation rate) is a value calculated by the following formula from each integral value of the double bond-derived peak by 1H-NMR (proton NMR). In the present specification, the hydrogenation rate (hydrogenation rate) means the hydrogenation rate of a double bond.
(Hydrogenation rate [%]) = {(AB) / A} x 100
A: Integral value of double bond peak before hydrogenation B: Integral value of double bond peak after hydrogenation

The weight average molecular weight (Mw) of the terpene resin is 500 to 1500, preferably 600 to 1400. By using a terpene resin having Mw within the above range, compatibility with natural rubber is improved, and on-ice performance, wear resistance performance and fracture performance can be improved.

The glass transition temperature (Tg) of the terpene resin is preferably 20 ° C. or higher, more preferably 25 ° C. or higher, still more preferably 30 ° C. or higher. If the temperature is lower than 20 ° C., the wet grip performance tends to deteriorate. The Tg of the terpene resin is preferably 75 ° C. or lower, more preferably 70 ° C. or lower, and further preferably 65 ° C. or lower. If the temperature exceeds 75 ° C., the resin dispersion deteriorates, the viscoelastic property at low temperature deteriorates, and the wet grip performance tends to deteriorate. In the present specification, Tg is a value measured under the condition of a heating rate of 10 ° C./min using an automatic differential scanning calorimeter (DSC-60A) manufactured by Shimadzu Corporation in accordance with JIS K 7121. be.

The softening point of the terpene resin is preferably 130 ° C. or lower, more preferably 125 ° C. or lower, and further preferably 120 ° C. or lower. If it exceeds 130 ° C., it tends to be difficult to disperse during kneading. The softening point of the terpene resin is preferably 60 ° C. or higher, more preferably 65 ° C. or higher, still more preferably 70 ° C. or higher. If the temperature is lower than 40 ° C., the work efficiency tends to deteriorate. In the present invention, the softening point was determined by using a flow tester (CFT-500D, manufactured by Shimadzu Corporation) and using a plunger while heating 1 g of the resin as a sample at a heating rate of 6 ° C./min. A load of 96 MPa was applied, and the sample was extruded from a nozzle having a diameter of 1 mm and a length of 1 mm.

The content of the terpene resin with respect to 100 parts by mass of the rubber component is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and further preferably 8 parts by mass or more because the effect of the present invention can be obtained satisfactorily. The content of the terpene resin is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and 30 parts by mass or less from the viewpoint of appropriately ensuring the hardness, molding processability, and viscosity of the rubber composition. More preferred.

As the terpene resin, any one of the above-exemplified ones may be used alone, or two or more thereof may be used in combination. Commercially available products may be used as the terpene-based resin in the present embodiment. Examples of such commercially available products are those manufactured and sold by Arizona Chemical Co., Ltd., Yasuhara Chemical Co., Ltd., and the like.

(Resin other than terpene resin)
In the rubber composition according to the present embodiment, one or more adhesive resins other than the terpene-based resin can be used in combination as the resin component. As the adhesive resin other than the terpene-based resin, a petroleum-based resin or the like that is widely used in rubber compositions for tires can be used. Specifically, an aliphatic petroleum resin, an aromatic petroleum resin, or a phenol-based resin can be used. Examples thereof include resins, Kumaron inden resins, rosin-based resins, styrene resins, acrylic resins, cyclopentadiene-based resins and the like. Among them, it is preferable to use a phenol-based resin, a Kumaron inden resin, a terpene-based resin, a styrene resin, an acrylic resin, and a cyclopentadiene-based resin because of their excellent grip performance. Further, the cyclopentadiene resin is more preferable because the SP value is low and the compatibility with NR is excellent.

The cyclopentadiene-based resin includes a dicyclopentadiene resin (DCPD resin), a cyclopentadiene resin, a methylcyclopentadiene resin, and a hydrogenated cyclopentadiene-based resin (hydrogen-added cyclopentadiene-based resin). Can be mentioned. Of these, hydrogenated DCPD resin is preferable. The hydrogenation treatment to the cyclopentadiene resin can be performed by a known method.

Examples of the phenolic resin include kolesin (manufactured by BASF) and tackyrol (manufactured by Taoka Chemical Industry Co., Ltd.). Examples of the Kumaron inden resin include Esclon (manufactured by Nippon Oil & Sumikin Chemical Co., Ltd.) and Neopolymer (manufactured by JX Nikko Nisseki Energy Co., Ltd.). Examples of the styrene resin include Sylvatraxx 4401 (manufactured by Arizona chemical) and the like. Examples of the cyclopentadiene resin include opera (manufactured by ExxonMobil Corporation) and the like. These adhesive resins may be used alone or in combination of two or more.

When an adhesive resin other than the terpene resin is contained, the content with respect to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, because the effect of the present invention can be obtained satisfactorily. More than 5 parts by mass is more preferable. Further, from the viewpoint of appropriately ensuring the hardness, molding processability, and viscosity of the rubber composition, 20 parts by mass or less is preferable, and 15 parts by mass or less is more preferable.

<Filler>
The filler used in the present embodiment is characterized by containing silica as an essential component. Further, silica is preferably used in combination with a silane coupling agent.

(silica)
The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), and the like, which are common in the tire industry, can be used. Of these, hydrous silica prepared by a wet method is preferable because it has a large number of silanol groups. Silica may be used alone or in combination of two or more.

From the viewpoint of grip performance, the BET specific surface area of silica is preferably 50 m ² / g or more, more preferably 75 m ² / g or more, and even more preferably 100 m ² / g or more. The BET specific surface area of silica is preferably 300 m ² / g or less, more preferably 250 m ² / g or less, and even more preferably 200 m ² / g or less, from the viewpoint of fuel efficiency and workability. The BET specific surface area of silica in the present specification is a value measured by the BET method according to ASTM D3037-93.

The silica content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of silica is less than 5 parts by mass, silica tends to self-aggregate, and fracture characteristics such as fracture strength and elongation at break and low fuel consumption performance tend to deteriorate. The silica content is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and further preferably 50 parts by mass or less with respect to 100 parts by mass of the rubber component. By setting the silica content to 60 parts by mass or less, deterioration of the dispersibility of silica in rubber is suppressed, better fuel efficiency and workability tend to be obtained, and better wear resistance can be obtained. Tend.

The silica content (silica content / terpene resin content) with respect to the terpene resin content is preferably in the range of 0.1 to 50, more preferably in the range of 0.2 to 20, and more preferably 0.5. The range of 10 to 10 is more preferable, and the range of 1.0 to 4.0 is particularly preferable.

(Silane coupling agent)
Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. Examples of such a silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, and bis ( 3-Trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2- Triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxy) Cyrilbutyl) 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, 3-triethoxysilylpropyl-N, N- Dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl Silane coupling agents having sulfide groups such as tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropylmethacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, silane coupling agent having a mercapto group such as NXT-Z100, NXT-Z45, NXT manufactured by Momentive; vinyltriethoxysilane, vinyltrimethoxysilane, etc. Sulfide coupling agent with vinyl group; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, Silane coupling agents having an amino group such as 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane; γ-glycidoxypropyltriethoxysilane, γ- Glycydoxy-based silane coupling agents such as glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane; 3-nitropropyltrimethoxysilane, 3-nitropropyl Nitro-based silane coupling agents such as triethoxysilane; chloro-based silanes such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. Coupling agent; etc. These silane coupling agents may be used alone or in combination of two or more. Of these, sulfide-based and mercapto-based materials are preferable because they have a strong bond with silica and are excellent in fuel efficiency. Further, it is preferable to use the mercapto system from the viewpoint that the fuel efficiency performance and the wear resistance performance can be suitably improved.

The content of the silane coupling agent when it is contained is preferably 1% by mass or more, more preferably 2% by mass or more, based on the mass of silica, because effects such as silica dispersibility and viscosity reduction can be obtained. 4% by mass or more is more preferable. Further, 20% by mass or less is preferable, 18% by mass or less is more preferable, and 15% by mass is preferable with respect to the mass of silica, for the reason of efficiently obtaining a sufficient coupling effect and silica dispersion effect and ensuring reinforcing property. % Or less is more preferable.

When the silane coupling agent is contained, the content of the rubber component with respect to 100 parts by mass is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 4 parts by mass or more. The content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, and further preferably 15 parts by mass or less.

(Other fillers)
As the filler, other fillers may be used in addition to silica. The filler is not particularly limited, and any filler generally used in this field such as carbon black, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, talc, and clay is used. be able to. These fillers may be used alone or in combination of two or more. When a filler other than silica is used, carbon black is preferable from the viewpoint of rubber strength. That is, the filler preferably contains silica and carbon black, or is preferably composed only of silica and carbon black.

As the carbon black, a general one for rubber can be appropriately used. Examples of carbon black include furnace black, acetylene black, thermal black, channel black, graphite and the like, and specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N535, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787 N908, N990, N991 and the like can be preferably used, and in-house synthesized products and the like can also be preferably used. These carbon blacks may be used alone or in combination of two or more.

The BET specific surface area of carbon black is preferably 110 m ² / g or more, preferably 120 m ² / g or more, and more preferably 130 m ² / g or more. By containing a predetermined amount of carbon black having a BET specific surface area of 110 m ² / g or more, the carbon black is dispersed near the boundary between each phase of BR and SBR, and the contact area between SBR and carbon black is increased. From this, since the bond between each phase of BR and SBR is strengthened, the reinforcing effect on the rubber composition is improved, and the rubber composition having excellent wear resistance can be obtained. The upper limit of the BET specific surface area is not particularly limited, but is preferably 180 m ² / g or less, more preferably 160 m ² / g or less, and even more preferably 150 m ² / g or less from the viewpoint of processability. The BET specific surface area of carbon black in the present specification is measured according to JIS K 6217-2 "Basic characteristics of carbon black for rubber-Part 2: How to obtain the specific surface area-Nitrogen adsorption method-Single point method". Value.

When carbon black is contained, the content of the rubber component with respect to 100 parts by mass is preferably 1 part by mass or more, preferably 3 parts by mass or more, and more preferably 5 parts by mass or more from the viewpoint of wear resistance. The upper limit of the carbon black content is not particularly limited, but from the viewpoint of fuel efficiency and workability, 100 parts by mass or less is preferable, 95 parts by mass or less is more preferable, and 90 parts by mass or less is further preferable.

From the viewpoint of breaking characteristics, the content of the entire filler with respect to 100 parts by mass is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, and further preferably 50 parts by mass or more. Further, from the viewpoint of dispersibility and processability of silica, 150 parts by mass or less is preferable, 140 parts by mass or less is more preferable, and 130 parts by mass or less is further preferable.

The content of silica in the filler is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, from the viewpoint of fuel efficiency and wet grip performance.

<Other ingredients>
In addition to the above rubber components and fillers, the rubber composition according to the present embodiment includes compounding agents and additives conventionally used in the tire industry, such as waxes, oils, antioxidants, stearic acid, and zinc oxide. , Vulcanization agent, vulcanization accelerator and the like can be appropriately contained as needed.

When wax is contained, the content of the rubber component with respect to 100 parts by mass is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of rubber. Further, from the viewpoint of whitening the tire by bloom, 10 parts by mass or less is preferable, and 5 parts by mass or less is more preferable.

When oil is contained, the content of the rubber component with respect to 100 parts by mass is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, from the viewpoint of ensuring good wear resistance. Further, from the viewpoint of processability, 5 parts by mass or more is preferable, and 10 parts by mass or more is more preferable. The processability can also be ensured by adding a surfactant, a liquid resin, a liquid polymer, or the like.

The antiaging agent is not particularly limited, and those used in the rubber field can be used, and examples thereof include quinoline-based, quinone-based, phenol-based, and phenylenediamine-based antiaging agents.

When the anti-aging agent is contained, the content of the rubber component with respect to 100 parts by mass is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of ozone crack resistance of the rubber. Further, from the viewpoint of wear resistance and grip performance, 10 parts by mass or less is preferable, and 5 parts by mass or less is more preferable.

When stearic acid is contained, the content of the rubber component with respect to 100 parts by mass is preferably 0.2 parts by mass or more, and more preferably 1 part by mass or more from the viewpoint of processability. Further, from the viewpoint of the vulcanization rate, 10 parts by mass or less is preferable, and 5 parts by mass or less is more preferable.

When zinc oxide is contained, the content of the rubber component with respect to 100 parts by mass is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more from the viewpoint of processability. Further, from the viewpoint of wear resistance, 10 parts by mass or less is preferable, and 5 parts by mass or less is more preferable.

Sulfur is preferably used as the vulcanizing agent. As the sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used.

When sulfur is contained as a vulcanizing agent, the content with respect to 100 parts by mass of the rubber component is 0.5 parts by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction and obtaining good grip performance and wear resistance. It is preferably 1.0 part by mass or more, more preferably 1.0 part by mass or more. From the viewpoint of deterioration, 3.0 parts by mass or less is preferable, and 2.5 parts by mass or less is more preferable.

Examples of sulfides other than sulfur include Tackilol V200 manufactured by Taoka Chemical Industry Co., Ltd., DURALINK HTS (1,6-hexamethylene-sodium dithiosulfate / dihydrate) manufactured by Flexis, and Rankses. Examples thereof include a sulfurizing agent containing a sulfur atom such as KA9188 (1,6-bis (N, N'-dibenzylthiocarbamoyldithio) hexane) and an organic peroxide such as dicumyl peroxide.

Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xantate-based vulcanization accelerators. And so on. These vulcanization accelerators may be used alone or in combination of two or more. Among them, a sulfenamide-based vulcanization accelerator, a thiazole-based vulcanization accelerator, and a guanidine-based vulcanization accelerator are preferable, and a sulfenamide-based vulcanization accelerator is more preferable. Further, a combination of a sulfenamide-based vulcanization accelerator and another vulcanization accelerator (preferably a thiazole-based vulcanization accelerator and / or a guanidine-based vulcanization accelerator) can also be mentioned as a preferred embodiment.

Examples of the sulfenamide-based vulcanization accelerator include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N, N. -Dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS) and the like can be mentioned. Of these, N-tert-butyl-2-benzothiazolyl sulphenamide (TBBS) and N-cyclohexyl-2-benzothiazolyl sulphenamide (CBS) are preferable.

Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide and the like. Of these, 2-mercaptobenzothiazole is preferable.

Examples of the guanidine-based vulcanization accelerator include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salt of dicatecholbolate, 1, Examples thereof include 3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine and the like. Of these, 1,3-diphenylguanidine is preferable.

When the vulcanization accelerator is contained, the content with respect to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, from the viewpoint of vulcanization promotion. Further, from the viewpoint of processability, 5 parts by mass or less is preferable, and 3 parts by mass or less is more preferable.

<Manufacturing of rubber compositions and tires>
The rubber composition according to this embodiment can be produced by a known method. For example, each of the above components can be kneaded using a rubber kneading device such as an open roll, a Banbury mixer, or a closed kneader, and then vulcanized.

Another embodiment of the present invention is a tire having a tire member made of the above rubber composition. Examples of the tire member made of the rubber composition include tire members such as treads, undertreads, carcass, sidewalls, and beads. Among them, the tread is preferable because it is excellent in wet grip performance, wear resistance performance and ablation performance.

The tire according to the present embodiment can be manufactured by a usual method using the above rubber composition. That is, an unvulcanized rubber composition obtained by kneading each of the above components is extruded according to the shape of a tire member such as a tread, and a member is bonded together with other tire members on a tire molding machine, and is usually used. An unvulcanized tire can be formed by molding by a method, and the unvulcanized tire can be manufactured by heating and pressurizing in a vulcanizer.

The tire according to the present embodiment is suitable for competition tires, passenger car tires, large passenger car tires, large SUV tires, and motorcycle tires, and can be used as summer tires, winter tires, and studless tires, respectively.

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

Hereinafter, various chemicals used in the production examples are collectively shown.
Emulbin W (surfactant): Emulbin W (aromatic polyglycol ether) manufactured by LANXESS.
Tamor NN9104 (surfactant): BASF's Tamor NN9104 (naphthalene sulfonic acid / sodium salt of formaldehyde)
Van gel B (surfactant): Van gel B (hydrate of magnesium aluminum silicate) manufactured by Vanderbilt.
Wingstay L (anti-aging agent): Wingstay L (a compound obtained by butylating a condensate of ρ-cresol and dicyclopentadiene) manufactured by ELIOKEM.
Emar E-27C (surfactant): Emar E-27C manufactured by Kao Corporation (polyoxyethylene lauryl ether sodium sulfate, active ingredient 27% by mass)
NaOH: Sodium hydroxide formic acid manufactured by Wako Pure Chemical Industries, Ltd .: Formic acid-cationic polymer flocculant from Kanto Chemical Industries, Ltd .: Polymethacrylic acid ester-based flocculant

(Preparation of anti-aging agent dispersion)
12.5 g of Emalbin W, 12.5 g of Tamor NN9104, 12.5 g of Van gel B, and 500 g of Wingstay L (total 1000 g) were mixed with 462.5 g of water in a ball mill for 16 hours to prepare an antiaging agent dispersion.

(Manufacturing Example 1)
After adjusting the solid content concentration (DRC) of natural rubber latex (field latex obtained from Titex) to 30% (w / v), 25 g of 10% Emar E-27C aqueous solution and 25% NaOH are added to 1000 g of the latex. 60 g of an aqueous solution was added, and a saponification reaction was carried out at room temperature for 24 hours to obtain a saponified natural rubber latex. Then, 6 g of the antioxidant dispersion was added, the mixture was stirred for 2 hours, and then water was further added to dilute the rubber until the rubber concentration reached 15% (w / v). Then, formic acid was added with slow stirring to adjust the pH to 4.0, and then a cationic polymer flocculant was added, and the mixture was stirred for 2 minutes to aggregate. The diameter of the agglomerates (aggregated rubber) thus obtained was about 0.5 to 3 mm. The obtained agglomerates were taken out and immersed in 1000 mL of a 2% by mass sodium carbonate aqueous solution at room temperature for 4 hours, and then the rubber was taken out. To this, 1000 mL of water was added and stirred for 2 minutes, and the work of removing water as much as possible was repeated 7 times. Then, 500 mL of water was added, 2% by mass formic acid was added until the pH reached 4, and the mixture was stirred for 30 minutes. This rubber was made into a sheet while being sprinkled with water with a scraper, and dried at 90 ° C. for 4 hours to obtain natural rubber 1.

(Manufacturing Example 2)
In addition to repeating the work of removing the water as much as possible by adding 1000 mL of water as it is and stirring for 2 minutes without treating the agglomerates obtained by adding the cationic polymer flocculant in Production Example 1 with the aqueous sodium carbonate solution. Obtained natural rubber 2 by the same procedure.

(Manufacturing Example 3)
Commercially available high ammonia latex (manufactured by Muhiba Latex of Malaysia, solid rubber content 62.0%) is diluted with a 0.12% aqueous solution of sodium naphthenate to make the solid rubber content 10%, and further diphosphate diphosphate. The pH was adjusted to 9.2 by adding sodium hydrogen hydrogen. Then, a proteolytic enzyme (Alkalase 2.0M) was added at a ratio of 0.87 g to 10 g of rubber, and the pH was readjusted to 9.2 and then maintained at 37 ° C. for 24 hours.
Next, a 1% aqueous solution of a nonionic surfactant (trade name: Emargen 810 manufactured by Kao Corporation) was added to the latex that had been subjected to the enzyme treatment to adjust the rubber concentration to 8%, and 11,000 r. p. m. Centrifugation was carried out for 30 minutes at the rotation speed of. Next, the creamy fraction generated by centrifugation was dispersed in a 1% aqueous solution of Emargen 810 to adjust the rubber content concentration to 8%, and then again, 11,000 r. p. m. Centrifugation was carried out for 30 minutes at the rotation speed of. 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%. 2% by mass formic acid was added to this latex until the pH reached 4, and a cationic polymer flocculant was further added to obtain rubber particles having a thickness 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 the pH reached 3. After 30 minutes, the rubber was pulled up, made into a sheet with a scraper, and then dried at 90 ° C. for 4 hours to obtain natural rubber 3.

(Manufacturing Example 4)
Water is added to natural rubber latex (field latex obtained from Titex) to dilute it to DRC 15% (w / v), and then formic acid is added while stirring slowly to adjust the pH to 4.0-4. It was adjusted to 5 and aggregated. The agglomerated rubber was pulverized, washed repeatedly with 1000 mL of water, and then dried at 110 ° C. for 120 minutes to obtain natural rubber 4.

(Measurement of nitrogen content)
The nitrogen content of the obtained modified natural rubbers 1 to 3 was measured using CHN CORDER MT-5 (manufactured by Yanaco Analytical Industry Co., Ltd.). For the measurement, first, using antipyrine as a standard substance, a calibration curve for determining the nitrogen content was prepared. Next, about 10 mg of the natural rubber sample obtained in Production Example 1 was weighed, and the average value was obtained from the results of three measurements to determine the nitrogen content of the sample.

(Measurement of phosphorus content)
The phosphorus content was determined using an ICP emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation). For 31P-NMR measurement of phosphorus, an NMR analyzer (400MHz, AV400M, manufactured by Nippon Bruker Co., Ltd.) was used, and the measurement peak of the P atom of the 80% phosphoric acid aqueous solution was set as a reference point (0 ppm) by chloroform. The component extracted from raw rubber was purified, dissolved in CDCl3, and measured.

(Measurement of gel content)
A 70.00 mg sample of raw rubber cut into 1 mm × 1 mm was weighed, 35 mL of toluene was added thereto, and the mixture was allowed to stand in a cool and dark place for 1 week. Then, it was subjected to centrifugation to precipitate an insoluble gel component in toluene, the soluble component in the supernatant was removed, only the gel component was solidified with methanol, and then dried and the mass was measured. The gel content (% by mass) was determined by the following formula.
Gel content (% by mass) = [mass after drying mg / first sample mass mg] x 100

Hereinafter, various chemicals used in Examples and Comparative Examples are collectively shown.
Natural rubber 1-4: Modified natural rubber BR of Production Example 1: UBEPOL BR150B manufactured by Ube Kosan Co., Ltd. (Mw: 440,000, HISIS BR, SIS-1,4 bond content: 96%)
Carbon Black: Show Black N220 (BET: 111m ² / g) manufactured by Cabot Japan Co., Ltd.
Silica: Ultrasil VN3 manufactured by Evonik Degussa (BET: 175m ² / g, average primary particle size: 15nm)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
Terpene resin 1: YS resin PX1150N manufactured by Yasuhara Chemical Co., Ltd. (polyterpene resin, Mw: 1350, SP value: 8.4, softening point: 115 ° C, Tg: 65 ° C)
Terpene resin 2: Clearon P125 manufactured by Yasuhara Chemical Co., Ltd. (hydrogenated polyterpene resin, hydrogenation rate: 100 mol%, Mw: 700, SP value: 8.36, softening point: 125 ° C, Tg: 74 ° C )
Petroleum resin: Petrotac 100V manufactured by Tosoh Corporation (C5C9 polymerized petroleum resin, Mw: 3800, softening point: 96 ° C)
Wax: Ozoace 355 manufactured by Nippon Seiro Co., Ltd.
Anti-aging agent: Nocrack 6C (N- (1,3-dimethylbutyl) -N-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Co., Ltd.
Stearic acid: Stearic acid "Camellia" manufactured by NOF CORPORATION
Zinc oxide: "Ginmine R" manufactured by Toho Zinc Co., Ltd.
Oil: Diana Process NH-70S manufactured by Idemitsu Kosan Co., Ltd.
Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd.
Vulcanization accelerator: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

Examples and Comparative Examples According to the formulation shown in Table 2, chemicals other than sulfur and vulcanization accelerator were kneaded for 5 minutes until the discharge temperature reached 170 ° C. using a 1.7 L closed-type Banbury mixer, and kneaded. I got a thing. Further, the obtained kneaded product was kneaded again with the Banbury mixer at a discharge temperature of 150 ° C. for 4 minutes (remil). Next, using a twin-screw open roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded for 4 minutes until the temperature reached 105 ° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized at 170 ° C. for 12 minutes to prepare a test rubber composition.

Further, the unvulcanized rubber composition is extruded into the shape of a tire tread by an extruder equipped with a base having a predetermined shape, and bonded together with other tire members to form an unvulcanized tire, under the condition of 170 ° C. Test tires (size: 195 / 65R15, studless tires) were produced by press vulcanization underneath for 12 minutes.

The obtained unvulcanized rubber composition, vulcanized rubber composition and test tire were evaluated as follows. The evaluation results are shown in Table 2.

<Low temperature ice performance (0 ° C start performance)>
A vehicle equipped with test tires on the drive shaft was started from a state where it was stopped on the front road surface, and the mileage when the speed reached 10 km / h was measured. The results are shown as an index, and the larger the index, the better the performance on low temperature ice. The index was calculated by the following formula.
(Low temperature ice performance index) = (mileage reaching 10 km / h in Comparative Example 1) / (mileage reaching 10 km / h in each compounding example) × 100

<Abrasion resistance>
Each test tire was attached to all wheels of a vehicle (domestic FF2000cc), and the groove depth of the tire tread portion after a mileage of 8000 km was measured to determine the mileage when the tire groove depth was reduced by 1 mm. The results are expressed as an index, and the larger the index, the better the wear resistance. The index was calculated by the following formula.
(Abrasion resistance performance index) = (mileage when the tire groove of each compounding example is reduced by 1 mm) / (mileage when the tire groove of Comparative Example 1 is reduced by 1 mm) × 100

<Destruction characteristics>
A No. 3 dumbbell test piece was prepared from each vulcanized rubber composition according to JIS K 6251, and a tensile test was carried out. The elongation at break (EB) was measured and displayed as an index with the value of Comparative Example 1 as 100. The larger the index, the higher the rubber strength and the better the fracture characteristics.

From the results shown in Table 2, a tire having a rubber composition obtained by blending a predetermined terpene resin and silica with highly purified natural rubber and a tire member composed of the rubber composition has excellent on-ice performance and is a preferable embodiment. It can be seen that the wear resistance and the fracture characteristics are also improved.

Claims (2)

With respect to 100 parts by mass of the rubber component containing 30% by mass or more of natural rubber having a nitrogen content of 0.30% by mass or less and 30% by mass or more of butadiene rubber.
It contains 8 to 40 parts by mass of a terpene resin having a weight average molecular weight (Mw) of 500 to 1500 and 5 to 55 parts by mass of silica having a BET specific surface area of 50 to 300 m ² / g.
A tire having a tread composed of a rubber composition having a silica content (silica content / terpene resin content) of 0.2 to 4.0 with respect to the content of the terpene resin. The tire according to claim 1, wherein the tire is a studless tire.