JP5944764B2 - Tire rubber composition and heavy duty tire - Google Patents

Description

The present invention relates to a tire rubber composition and a heavy duty tire having a tread produced using the rubber composition.

In recent years, due to soaring fuel costs and the introduction of environmental regulations, there has been a strong demand for lower fuel consumption of vehicles, and among the tires, particularly excellent treads with a high occupation ratio are required. Traditionally, for treads, etc., carbon black, which can easily interact with rubber components and has excellent reinforcing effects, has been used as a filler, but silica is used instead to improve fuel efficiency. It has come to be.

In order to improve fuel economy in tires, particularly heavy-duty tires, it is common to use natural rubber or butadiene rubber as a rubber component, and a method of using silica as a method for further improving fuel economy, A method for reducing the amount of filler is known. However, these methods may reduce rubber strength and maintain good wear resistance. In particular, heavy duty tires require high rubber strength and require good chipping resistance. Therefore, it is difficult to use the above method.

As a method for solving this problem, it has been proposed to use a silane coupling agent having reactivity with a rubber component or silica, but it is difficult to sufficiently advance the reaction with silica, and unreacted silica. May remain poorly dispersed and the desired performance may not be exhibited. Furthermore, in order to prevent this, if a large amount of silane coupling agent is blended, due to the residual silane coupling agent, rubber burn during processing, wear resistance of vulcanized rubber and mechanical strength may be reduced. is there.

Patent Document 1 discloses a tire rubber composition containing a basic aqueous solution having a pH of 8 to 12 and silica for the purpose of enhancing the compatibility between silica and rubber, but the interaction between rubber and silica is disclosed. Cannot be sufficiently obtained, and the improvement effect such as low fuel consumption is not satisfactory. Therefore, it is desired to provide a silica-containing rubber that can improve fuel economy, wear resistance, chipping resistance, and processability in a well-balanced manner.

JP 2000-219779 A

An object of the present invention is to solve the above-described problems and provide a rubber composition for a tire that improves fuel economy, wear resistance, chipping resistance, and workability in a well-balanced manner, and a heavy-duty tire using the same. And

The present invention includes 5 to 200 parts by mass of silica and 0.1 to 40 parts by mass of cyclized rubber with respect to 100 parts by mass of the rubber component, and the content of natural rubber in 100% by mass of the rubber component is 5 parts by mass. % Of the rubber composition for tires.

The cyclization rate of the cyclized rubber is preferably 0.1 to 40%.
The cyclized rubber is preferably at least one selected from the group consisting of cyclized natural rubber, cyclized isoprene rubber, and cyclized butadiene rubber.

It is preferable that 1-100 mass parts of carbon black is included with respect to 100 mass parts of said rubber components.
It is preferably used for a tread.

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

According to the present invention, with respect to 100 parts by mass of the rubber component, 5 to 200 parts by mass of silica and 0.1 to 40 parts by mass of cyclized rubber are contained, and the content of natural rubber in 100% by mass of the rubber component is Since the tire rubber composition is 5% by mass or more, low fuel consumption, wear resistance, chipping resistance, and processability can be improved in a well-balanced manner.

The rubber composition for tires of the present invention is obtained by blending a predetermined amount of silica and cyclized rubber with a rubber component containing a predetermined amount of natural rubber.

A compounded rubber in which silica is blended with natural rubber is generally low in dispersibility of silica and it is difficult to obtain desired performance, but in the present invention, a rubber component such as silica and natural rubber is obtained by blending cyclized rubber. Interaction with is increased. Accordingly, the dispersibility of silica is improved, and the fuel economy, wear resistance, and chipping resistance are improved at the same time, and good processability is also obtained, and the balance of these performances can be improved synergistically.

Further, by using a cyclized rubber having a predetermined cyclization rate, the dispersibility of silica is dramatically improved, and the performance balance can be remarkably improved.

Natural rubber (NR) is not particularly limited, and for example, SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), high-purity natural rubber (HPNR), etc., which are common in the tire industry can be used.

The content of NR in 100% by mass of the rubber component is 5% by mass or more, preferably 10% by mass or more, more preferably 30% by mass or more, and further preferably 50% by mass or more. If it is less than 5% by mass, the wear resistance tends to decrease. The upper limit of the NR content is not particularly limited, and may be 100% by mass, but is preferably 90% by mass or less, and more preferably 80% by mass.

Other rubber components that can be used in the present invention include epoxidized natural rubber (ENR), styrene butadiene rubber (SBR), butadiene rubber (BR), diene rubber such as butadiene isoprene rubber, and butyl rubber such as chlorinated butyl rubber. Moreover, what condensed these rubber | gum, the modified thing, etc. can be used. Of these, it is preferable to use BR in addition to NR in order to improve fuel efficiency and improve the performance balance. These rubber components may be used alone or in combination of two or more.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd. Commonly used in the tire industry such as BR containing syndiotactic polybutadiene crystals can be used.

When the rubber composition of the present invention contains BR, 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. . If it is less than 5% by mass, the fuel efficiency tends to decrease. The BR content is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 30% by mass or less. When it exceeds 60 mass%, there exists a tendency for abrasion resistance to fall.

In the present invention, from the viewpoint of the performance balance, the total content of NR and BR in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. .

The silica used in the present invention is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid) and the like, but because of the large number of silanol groups, wet process silica. Is preferred.

Nitrogen adsorption specific surface area of the silica _(N 2 SA) of preferably at least ^{40 m} 2 / g, more preferably at least ^{50m 2 / g, 100m 2 /} g or more, and particularly preferably equal to or greater than 150m ² / g. If it is less than 40 m < ² > / g, there exists a tendency for the fracture strength after vulcanization to fall. Also, _N 2 SA of the silica is preferably not more than 500 meters ² / g, more preferably at most 300m ² / g. When it exceeds 500 m ² / g, there is a tendency that low heat build-up and rubber processability are lowered.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 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. If it is less than 5 parts by mass, the low heat build-up may be insufficient. Moreover, this content is 200 mass parts or less, Preferably it is 150 mass parts or less, More preferably, it is 80 mass parts or less. When it exceeds 200 parts by mass, it becomes difficult to disperse the filler into the rubber, and the processability of the rubber tends to deteriorate.

The rubber composition of the present invention may contain a silane coupling agent.
The silane coupling agent is not particularly limited, and conventionally known silane coupling agents can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-tri Methoxysilylpropyl) sulfide type such as tetrasulfide; mercapto type such as 3-mercaptopropyltrimethoxysilane; vinyl type such as vinyltriethoxysilane; amino type such as 3-aminopropyltriethoxysilane; γ-glycidoxypropyl Examples thereof include glycidoxy type such as triethoxysilane; nitro type such as 3-nitropropyltrimethoxysilane; chloro type such as 3-chloropropyltrimethoxysilane.

The content of the silane coupling agent is preferably 0 to 20 parts by mass with respect to 100 parts by mass of the rubber component. If the amount exceeds 20 parts by mass, the effect of dispersing the filler cannot be obtained for an increase in cost, and further, the reinforcing property and wear resistance may be lowered, and unreacted silane coupling agent remains. As a result, there is a risk that the rubber will be burned during processing and the breaking performance of the rubber after vulcanization may be reduced. The lower limit is more preferably 1 part by mass or more, still more preferably 2 parts by mass or more, and the upper limit is more preferably 12 parts by mass or less, still more preferably 9 parts by mass or less.

It is preferable that carbon black is blended in the rubber composition of the present invention. Thereby, the outstanding reinforcement property is obtained, abrasion resistance and chipping resistance improve, and the said performance balance can be improved notably. Carbon black is not particularly limited, and examples thereof include SAF, ISAF, HAF, FF, and GPF.

Carbon black having an average particle size of 31 nm or less and / or a DBP oil absorption of 100 ml / 100 g or more is preferable. By blending such carbon black, necessary reinforcing properties are imparted, block rigidity, uneven wear resistance, and fracture strength are ensured, and wear resistance and chipping resistance are improved. Remarkably obtained.

If the average particle size of the carbon black exceeds 31 nm, the breaking strength is greatly deteriorated, and it may be difficult to ensure wear resistance. The average particle diameter is more preferably 25 nm or less, and further preferably 23 nm or less. The average particle size is preferably 15 nm or more, and more preferably 19 nm or more. If it is less than 15 nm, the viscosity of the blended rubber is significantly increased, and the processability may be deteriorated. In the present invention, the average particle diameter is a number average particle diameter and is measured by a transmission electron microscope.

When the DBP oil absorption amount (dibutyl phthalate oil absorption amount) of carbon black is less than 100 ml / 100 g, the reinforcing property is low, and it may be difficult to ensure wear resistance. The DBP oil absorption is more preferably 105 ml / 100 g or more, and even more preferably 110 ml / 100 g or more. The DBP oil absorption is preferably 160 ml / 100 g or less, and more preferably 150 ml / 100 g or less. If it exceeds 160 ml / 100 g, it is difficult to produce carbon black itself. The DBP oil absorption of carbon black is measured according to JIS K6217-4: 2001.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, and more preferably 110 m ² / g or more. If it is less than 80 m ² / g, the breaking strength is greatly deteriorated, and it may be difficult to ensure wear resistance. Also, _N 2 SA of the carbon black is preferably not more than 200 meters ² / g, more preferably at most 150m ² / g. When it exceeds 200 m ² / g, the viscosity of the blended rubber is significantly increased, and the processability may be deteriorated. The N ₂ SA of carbon black is measured according to JIS K 6217-2: 2001.

The content of carbon black is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, the reinforcing property may be inferior. The content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 40 parts by mass or less. If it exceeds 60 parts by mass, the fuel efficiency tends to deteriorate.

The carbon black content (content) in the total of 100% by mass of silica and carbon black is preferably 35% by mass or more, more preferably 50% by mass or more, and still more preferably 53% by mass or more. If it is less than 35% by mass, the chipping resistance tends to decrease. In addition, the content is preferably 90% by mass or less, and more preferably 80% by mass or less. If it exceeds 90% by mass, the fuel efficiency and wear resistance are lowered, and the effects of the present invention may not be sufficiently exhibited.

The rubber composition of the present invention may contain other fillers, and examples include, but are not limited to, calcium carbonate, aluminum hydroxide, montmorillonite, cellulose, various short fibers, glass balloons and eggshells. It is not something.

As the cyclized rubber, compounds having various chemical structures have been proposed, but the cyclized rubber in the present invention is not limited to any of them, and any compound can be used. In the present invention, the cyclized rubber is not a rubber component but an additive (silica dispersion improver) having an action of improving the compatibility between silica and the rubber component and improving the silica dispersibility.

The cyclization rate of the cyclized rubber is preferably 0.1% or more, more preferably 1% or more, and further preferably 3% or more. If it is less than 0.1%, sufficient interaction with silica cannot be obtained, and the fuel efficiency may be deteriorated. The cyclization rate is preferably 40% or less, more preferably 35% or less, and still more preferably 30% or less. If it exceeds 40%, the cyclized rubber may gel or adhere to the kneader.

The cyclization rate is the ratio of double bonds reacted by the cyclization reaction to the number of double bonds of the raw rubber component (conjugated diene polymer) before the cyclization reaction. For example, by measuring the peak areas of protons derived from double bonds before and after the cyclization reaction of the conjugated diene polymer used as a raw material by ¹ H-NMR analysis, the cyclization reaction when the pre-cyclization reaction is 100 The ratio of the double bond remaining in the subsequent cyclized product is obtained, and can be measured as a value (%) represented by the calculation formula = (100−the ratio of the double bond remaining in the cyclized product).

The number average molecular weight (Mn) of the cyclized rubber is preferably 1,000 to 1,000,000, more preferably 5,000 to 500,000, and 10,000 to 300,000. More preferably. If it is less than 1,000, the wear resistance and fuel efficiency may be deteriorated, and if it exceeds 1,000,000, the viscosity increases and the workability may be deteriorated.

The molecular weight distribution of the cyclized rubber, that is, the weight average molecular weight / number average molecular weight (Mw / Mn) is preferably 4 or less.
In addition, Mw / Mn is a standard polystyrene conversion value measured by GPC.

The glass transition temperature (Tg) of the cyclized rubber is not particularly limited and is usually −100 to 100 ° C., but preferably −90 to 80 ° C., more preferably −90 to 40 from the viewpoint of the effect of the present invention. ° C, particularly preferably -90 to 20 ° C, most preferably -90 to 5 ° C.

The gel amount of the cyclized rubber is preferably 10% by mass or less, more preferably 5% by mass or less from the viewpoint of the effect of the present invention, and a gel having substantially no gel is particularly preferable.

As the cyclized rubber, a conjugated diene polymer cyclized product can be preferably used. The conjugated diene polymer cyclized product is prepared by (co) polymerizing a conjugated diene monomer or a conjugated diene monomer and another monomer copolymerizable with the conjugated diene monomer by a known method. And the like obtained by cyclizing the conjugated diene polymer.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl- Examples include 1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, and the like. These monomers may be used alone or in combination of two or more.

Examples of other monomers copolymerizable with the conjugated diene monomer include styrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, and p-tert. -Butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, 2-methyl-1,4-dichlorostyrene, Aromatic vinyl monomers such as 2,4-dibromostyrene and vinylnaphthalene; Chain olefin monomers such as ethylene, propylene and 1-butene; Cyclic olefin monomers such as cyclopentene and 2-norbornene; 1,5 -Hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, 5-ethylidene-2-no Non-conjugated diene monomers such as rubornene; (meth) acrylic acid esters such as methyl (meth) acrylate and ethyl (meth) acrylate; (meth) acrylonitrile, (meth) acrylamide and the like. These monomers may be used alone or in combination of two or more.

The content of the conjugated diene monomer unit in the conjugated diene polymer may be appropriately selected within a range not impairing the effects of the present invention, but is preferably 40 mol% or more, more preferably 60 mol% or more, and still more preferably. Is 80 mol% or more.

As the cyclized rubber, the conjugated diene polymer cyclized product described above can be used. Among them, cyclized natural rubber, cyclized isoprene rubber, cyclized butadiene rubber and the like are particularly preferable from the viewpoint of the effect of the present invention.

As described above, the conjugated diene polymer cyclized product can be prepared by cyclizing the conjugated diene polymer, but this cyclization reaction can be carried out by a known method, for example, after the (co) polymerization reaction, one-pot reaction as it is. And a method of cyclization by adding a cyclization catalyst in (3), (co) polymerization, a method of re-creating a solution from a dried conjugated diene polymer, and the like.

Here, in the cyclization reaction, for example, a known cyclization catalyst is allowed to act directly on raw rubber or on a rubber solution, and a part of chain molecules in the rubber molecule is cyclized to reduce double bonds. Thereby obtaining a cyclized rubber. Examples of the cyclization catalyst include organic sulfonic acids such as sulfuric acid and p-toluenesulfonic acid, and chlorosulfonic acid.

The content of the cyclized rubber is 0.1 parts by mass or more, preferably 2 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content is 40 mass parts or less, Preferably it is 30 mass parts or less. If the amount is less than 0.1 parts by mass, the effect of silica dispersion is not sufficient, and the effect of improving fuel economy tends to be difficult to obtain. If it exceeds 40 parts by mass, the physical properties of the rubber are lowered and the cost tends to be high.

In addition to the above components, the rubber composition of the present invention includes oils, waxes, anti-aging agents, additives such as stearic acid and zinc oxide, vulcanizing agents such as sulfur, vulcanization accelerators, vulcanization acceleration aids, etc. May be appropriately blended.

The oil content is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, with respect to 100 parts by mass of the rubber component. When it exceeds 15 parts by mass, the wear resistance is lowered and the effects of the present invention tend not to be sufficiently obtained. The lower limit of the oil content is not particularly limited and may not include oil, but is preferably 2 parts by mass or more, more preferably 5 parts by mass or more from the viewpoint of workability.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading each of the above components with a kneader such as a Banbury mixer, a kneader, or an open roll, and then vulcanizing. The rubber composition can be used for each member of a tire and can be suitably used for a tread (particularly, a tread of a heavy load tire).

As kneading conditions, when additives other than the vulcanizing agent and the vulcanization accelerator are blended, the kneading temperature is usually 50 to 200 ° C., preferably 80 to 190 ° C., and the kneading time is usually 30 seconds. -30 minutes, preferably 1-30 minutes. Moreover, when mix | blending a vulcanizing agent and a vulcanization accelerator, kneading | mixing temperature is 100 degrees C or less normally, Preferably it is room temperature-80 degreeC. A composition containing a vulcanizing agent and a vulcanization accelerator is usually used after vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200 ° C, preferably 140 to 180 ° C.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, by extruding a rubber composition containing the above components in accordance with the shape of a tread or the like at an unvulcanized stage, and molding it with a tire molding machine by a normal method along with other tire members, Form an unvulcanized tire. The pneumatic tire of the present invention can be manufactured by heating and pressurizing the unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention can be used for passenger car tires, heavy duty tires (truck / bus tires), etc., and can be particularly suitably used for heavy duty tires that require high wear resistance.

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

(Production Example 1)
A pressure-resistant reactor equipped with a stirrer substituted with nitrogen was charged with 1400 g of dehydrated toluene and 18 mmol of n-butyllithium, and the internal temperature was maintained at 60 ° C. 487 g of isoprene was continuously added to the reactor over 15 minutes, and the internal temperature was controlled not to exceed 75 ° C. Thereafter, the mixture was reacted at 70 ° C. for 10.5 hours, and then 1.4 mmol of methanol was added as a polymerization terminator to terminate the polymerization reaction.
After stopping the polymerization reaction, the temperature was raised to 80 ° C., 4.24 g of p-toluenesulfonic acid was added, and the cyclization reaction was performed for 1 hour while maintaining the temperature at 80 ° C. Subsequently, an aqueous solution in which 1.70 g of sodium carbonate was dissolved in 5.1 g of water was added to stop the cyclization reaction, and the reaction solution was filtered to remove the catalyst residue. After adding 0.4 g of an anti-aging agent (Irganox 1010: manufactured by Ciba Specialty Chemicals) to this solution, toluene was distilled off and dried under reduced pressure to obtain a cyclized rubber 1.

(Production Example 2)
In a pressure vessel equipped with a stirrer substituted with nitrogen, 300 g of liquid polyisoprene (Kuraray LIR-30: Mn = 28,000) and 700 g of toluene were charged. The mixture was heated to 80 ° C. to completely dissolve polyisoprene, and then 2 g of p-toluenesulfonic acid was added to carry out a cyclization reaction while maintaining the internal temperature at 80 ° C. After reacting for 1 hour, a 25% aqueous solution of sodium carbonate containing 0.8 g of sodium carbonate was added to stop the reaction, stirred at 80 ° C. for 30 minutes, and then filtered to remove the catalyst residue. After adding 0.3 g of an anti-aging agent (Irganox 1010: manufactured by Ciba Specialty Chemicals) to this solution, toluene was distilled off and dried under reduced pressure to obtain a cyclized rubber 2.

(Production Example 3)
A cyclized rubber 3 was obtained in the same manner as in Production Example 2, except that liquid polybutadiene (manufactured by Sartomer, Rycon 150, Mn = 5,200) was used instead of liquid polyisoprene.

(Production Example 4)
Instead of liquid polyisoprene, polybutadiene (Ube Industries, UBEPOL 150L, Mn = 250,000) was used, and the cyclized rubber 4 was prepared in the same manner as in Production Example 2 except that the cyclization reaction time was changed to 3 hours. Obtained.

The physical properties of the obtained cyclized rubber were measured by the following methods, and the results are shown in Table 1.

(Cyclization rate of cyclized rubber)
The cyclization rate of the cyclized rubber was determined by the peak area ratio of protons in the polymer before and after the cyclization reaction by ¹ H-NMR measurement using an AV400 NMR apparatus manufactured by BRUKER, data analysis software TOP SPIN2.1. . In addition, the detailed cyclization rate calculation method is as having described in the following literature.
Y. Tanaka and H.M. Sato, J .; Polym. Sci: Poly. Chem. Ed. , 17, 3027 (1979)

(Number average molecular weight (Mn) and weight average molecular weight (Mw) of cyclized rubber)
The calibration curve obtained from the molecular weight distribution curve obtained by performing gel permeation (permeation) chromatography of cyclized rubber (GPC, manufactured by Tosoh Corporation) using polystyrene as a standard substance and tetrahydrofuran as a solvent at a temperature of 40 ° C. Mn and Mw were calculated.

(Glass transition temperature Tg of cyclized rubber)
The glass transition temperature of the cyclized rubber was measured using a differential scanning calorimeter (manufactured by Seiko Denshi Kogyo Co., Ltd .: SSC5200) under the conditions of a starting temperature of −100 ° C. and a heating rate of 10 ° C./min.

(Gel amount of cyclized rubber)
After 0.2 g of a sample cut to 2 mm square was immersed in 100 ml of toluene for 48 hours, the ratio of the dry weight of the gel remaining on the 80-mesh wire net was shown as a percentage.

The chemicals used in the examples and comparative examples are summarized below.
NR: RSS # 3
BR: UBEPOL BR150B manufactured by Ube Industries, Ltd. (cis 1,4 bond amount 97%, ML _{1 + 4} (100 ° C.) 40, Mw / Mn 3.3)
Cyclized rubber 1-4: Production Examples 1-4
Silica: Ultrasil VN3 (N ₂ SA: 175 m ² / g) manufactured by EVONIK-DEGUSSA
Carbon black: Dia Black I manufactured by Mitsubishi Chemical Corporation (ISAF carbon, average particle size 23 nm, DBP oil absorption 114 ml / 100 g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by EVONIK-DEGUSSA
Oil: Process X-140 (aromatic process oil) manufactured by Japan Energy Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Stearic acid “paulownia” manufactured by NOF Corporation
Zinc oxide: Zinc oxide type 2 anti-aging agent manufactured by Mitsui Mining & Smelting Co., Ltd .: NOCRACK 6C (N- (1,3-dimethylbutyl) -N-phenyl-p-phenylene) manufactured by Ouchi Shinsei Chemical Diamine)
Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Examples and Comparative Examples>
In accordance with the formulation of Table 2, using a 1.7L Banbury mixer manufactured by Kobe Steel Co., Ltd., chemicals other than sulfur and a vulcanization accelerator were filled to a filling rate of 58%, and 140 rpm at 140 rpm. A kneaded product was obtained by kneading until reaching 0C. Next, using an open roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded to obtain an unvulcanized rubber composition.
Further, the obtained unvulcanized rubber composition was molded into a predetermined size, and a vulcanized rubber composition was obtained by press vulcanization at 150 ° C. for 20 minutes, and a vulcanization of about 2 mm × 130 mm × 130 mm was obtained. A rubber slab sheet was prepared.

Further, the obtained unvulcanized rubber composition is molded into a tread shape, and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, which is vulcanized at 150 ° C. for 30 minutes, and tested. Tires (size: 11R22.5) were manufactured.

The following evaluation was performed about the obtained unvulcanized rubber composition, a vulcanized rubber slab sheet, and a test tire. The results are shown in Table 2.

(Processability)
Based on JIS K6300-1, Mooney viscosity (ML _{1 + 4} ) was measured at 130 ° C., and Comparative Example 1 was taken as 100, and the workability index was calculated from the following formula. The larger the index, the better the processability when unvulcanized.
(Processability index) = (Mooney viscosity of Comparative Example 1) / (Mooney viscosity of each formulation) × 100

(Viscoelasticity test)
Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho, the loss tangent (tan δ) of the vulcanized rubber slab sheet was measured under conditions of a temperature of 70 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. The rolling resistance index of Comparative Example 1 was set to 100, and the rolling resistance was indicated by an index according to the following formula. The larger the rolling resistance index, the lower the rolling resistance, which is preferable.
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Abrasion resistance)
A test tire is mounted on a domestic 2-D vehicle, the groove depth of the tire tread portion after a mileage of 50,000 km is measured, and the mileage when the tire groove depth is reduced by 1 mm is calculated. The travel distance when the tire groove depth was reduced by 1 mm was taken as 100 and indexed by the following formula. The higher the index, the better the wear resistance.
(Abrasion resistance index) = (travel distance when the tire groove depth of each compound is reduced by 1 mm) / (travel distance when the tire groove depth of Comparative Example 1 is reduced by 1 mm) × 100

(Chip resistance)
Chipping resistance was evaluated by performing the following measurements.
That is, the inner surface of a cylindrical iron container having an inner diameter of 155 mm and a height of 177 mm is formed by a needle mountain block in which three iron quenching pins having a diameter of 5 mm are embedded in each surface of an iron hexahedron having a regular triangle of 45 mm on one side. Further, a sample rubber (vulcanized rubber slab sheet) of 120 mm × 82 mm × 5 mm (thickness), which was vulcanized and molded using a molding frame and measured in advance, was fixed in a six-sheet drum. Then, after maintaining the temperature in the drum at about 70 ° C. and rotating at a speed of 36 rpm for 7 days, the needle block is taken out, the sample rubber is removed from the drum, and the attached rubber debris is completely removed. The volume change rate was calculated | required by measuring the weight and converting into volume from specific gravity. The larger the index, the better the chipping resistance.

In Comparative Example 2 in which the amount of oil was increased compared to Comparative Example 1, although the workability and fuel efficiency (rolling resistance) were improved, the wear resistance and chipping resistance were lowered, and a good improvement in performance balance was observed. There wasn't. On the other hand, in Examples 1 to 4 in which 10 parts of cyclized rubber was added to silica compounded rubber, processability, fuel efficiency, wear resistance, and chipping resistance could be improved at the same time, and these performance balances could be improved synergistically. Became clear. Further, even in Examples 5 to 6 in which the addition amount of the cyclized rubber was increased, while maintaining the workability indexes “98” and “96” within a practically no problem range, low fuel consumption, wear resistance, and chipping resistance were maintained. Sexually improved.

Claims (5)

5 to 200 parts by mass of silica and 0.1 to 40 parts by mass of cyclized rubber with respect to 100 parts by mass of the rubber component,
Ri Der content not less than 5 mass% of natural rubber wherein the rubber component in 100% by mass,
The cyclized rubber for cyclization ratio is a rubber composition for a tire Ru 0.1 to 40% der. The cyclized rubber, cyclized natural rubber, claim 1 tire rubber composition, wherein at least one member selected from the group consisting of cyclized isoprene rubber and cyclized butadiene rubber. The rubber composition for a tire according to claim 1 or 2, comprising 1 to 100 parts by mass of carbon black with respect to 100 parts by mass of the rubber component. The rubber composition for tires according to any one of claims 1 to 3 , which is used for a tread. Heavy duty tire having a tread produced from the rubber composition according to any one of claims 1-4.