JP2016003269A - Summer tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a summer tire that offers an excellent balance of fuel economy, wet grip performance and handling ability, and has a low discoloration of a tire surface.SOLUTION: This invention relates to a summer tire having a tread made using a rubber composition wherein, based on the rubber component 100 mass%, the content of farnesene resin with a weight average molecular weight of 1000-500000 is 1-50 pts. mass, and the content of silica with a nitrogen adsorption specific surface area of 40-400 m2/g is 10-150 pts.

Description

The present invention relates to a summer tire.

In recent years, from the standpoint of saving resources and protecting the environment, it has been required to improve fuel efficiency by improving rolling resistance of tires, and also to improve wet grip performance to improve safety during driving.

Hysteresis loss is required to improve fuel economy, and wet skid resistance is required to improve wet grip performance. However, low hysteresis loss and high wet skid resistance are contradictory, and it is difficult to improve the fuel economy and wet grip performance in a balanced manner.

As a method for improving fuel economy and wet grip performance in a well-balanced manner, there is a method using silica as a filler. Silica has strong self-aggregation property and there is room for improvement in that it is difficult to disperse.

In Patent Document 1, a styrene butadiene rubber terminal-modified with a specific compound containing a nitrogen atom and a silicon atom and an aliphatic carboxylic acid zinc salt are blended, and a rubber composition excellent in low fuel consumption and wet grip performance is obtained. Although the method of obtaining is described, the provision of other methods is also sought.

In addition, tires are known to deteriorate due to heat generated during running, ozone in the air, oxygen, ultraviolet rays, and the like, and in recent years, the amount of ozone has been increasing due to industrialization and the like. Therefore, it is required to further improve the ozone resistance, suppress the deterioration of the rubber, and extend the life of the tire.

As a method for enhancing ozone resistance, a method of blending an anti-aging agent or wax is known, but in such a method, the anti-aging agent and the wax are transferred to discolor the tire surface and impair the appearance. Such deterioration of aesthetics is a problem particularly in the sidewall, but it is also a problem in vehicles and the like that are less frequent in the tread.

JP 2010-111754 A

An object of the present invention is to solve the above-mentioned problems, and to provide a summer tire that is excellent in balance between fuel efficiency, wet grip performance and handling performance, and has less discoloration on the tire surface.

In the present invention, 1 to 50 parts by weight of farnesene resin having a weight average molecular weight of 1000 to 500,000 and 10 to 150 parts by weight of silica having a nitrogen adsorption specific surface area of 40 to 400 m ² / g with respect to 100 parts by weight of the rubber component. The present invention relates to a summer tire having a tread produced using the contained rubber composition.

The farnesene resin is preferably a farnesene homopolymer.

The farnesene resin is preferably a copolymer of farnesene and a vinyl monomer.

The vinyl monomer is preferably styrene.

The vinyl monomer is preferably butadiene.

The copolymerization ratio of the farnesene and the vinyl monomer in the copolymer is preferably farnesene / vinyl monomer = 99/1 to 25/75 on a mass basis.

The copolymer preferably has a melt viscosity at 38 ° C. of 1000 Pa · s or less.

The farnesene resin is preferably obtained by polymerizing farnesene prepared by culturing microorganisms using a carbon source derived from sugar.

According to the present invention, a rubber composition containing a specific amount of a specific farnesene resin having a weight average molecular weight within a specific range and a silica having a nitrogen adsorption specific surface area within a specific range, respectively, was prepared. Since it is a summer tire having a tread, it is possible to provide a summer tire that is excellent in the balance of fuel efficiency, wet grip performance and handling performance and has less discoloration on the tire surface.

The summer tire of the present invention was produced by using a rubber composition containing a predetermined amount of farnesene resin having a weight average molecular weight within a specific range and silica having a nitrogen adsorption specific surface area within a specific range. It has a tread. By blending the farnesene resin as a softening agent, a farnesene resin film is formed in the vicinity of the silica surface, and the dispersibility of the silica is improved. As a result, it is possible to obtain a tire with reduced hysteresis loss, good fuel economy, and improved wet grip performance and handling performance. At the same time, the bleeding of the farnesene resin and the accompanying oil, anti-aging agent, and wax bleeding are suppressed, so that discoloration (whitening, browning) of the rubber surface can be suppressed.

The rubber composition according to the present invention can use natural rubber (NR) or diene synthetic rubber as a rubber component. Examples of the diene synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), and styrene butadiene. Examples thereof include rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR). Of these, NR, BR, and SBR are preferable because they exhibit a good balance between low fuel consumption and wet grip performance. These rubber components may be used alone or in combination of two or more.
These rubber components are not particularly limited, and those generally used in the tire industry can be used.

The content of NR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more, and preferably 35% by mass or less, more preferably 25% by mass or less. Within this range, low fuel consumption and wet grip performance can be obtained with a better balance.

The cis content of BR is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 97% by mass or more. If it is in this range, the effect of the present invention can be obtained satisfactorily.
In the present specification, the cis content can be measured by infrared absorption spectrum analysis.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more, and preferably 35% by mass or less, more preferably 25% by mass or less, and still more preferably. 22% by mass or less. Within this range, low fuel consumption and wet grip performance can be obtained with a better balance.

The styrene content of SBR is preferably 15% by mass or more, more preferably 22% by mass or more, and further preferably 24% by mass or more. If it is less than 15% by mass, the effects of the present invention, particularly the wet grip performance improving effect, may not be sufficiently obtained. The styrene content is preferably 40% by mass or less, more preferably 30% by mass or less. If it exceeds 40% by mass, the fuel efficiency may be significantly deteriorated.

The content of SBR in 100% by mass of the rubber component is preferably 35% by mass or more, more preferably 45% by mass or more, still more preferably 55% by mass or more, and preferably 85% by mass or less, more preferably It is 75 mass% or less, More preferably, it is 65 mass% or less. Within this range, low fuel consumption and wet grip performance can be obtained with a better balance.

The rubber composition according to the present invention contains a farnesene resin. The farnesene resin means a polymer obtained by polymerizing farnesene as a monomer component. Farnesene includes α-farnesene ((3E, 7E) -3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1). , 6,10-dodecatriene) and the like, (E) -β-farnesene having the following structure is preferred.

In the present invention, by blending a farnesene resin having a weight average molecular weight within a specific range as a softening agent, the fuel economy, wet grip performance and handling performance are excellent. In addition, it is preferable to mix | blend farnesene-type resin, replacing with softeners, such as the oil currently mix | blended conventionally. Thereby, the effect of this invention is acquired more suitably.

The farnesene resin may be a farnesene homopolymer (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer). Examples of vinyl monomers include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5- t-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl) dimethylaminoethyl ether, N, N-dimethylaminoethyl Styrene, N, N-dimethylaminomethyl styrene, 2-ethyl styrene, 3-ethyl styrene, 4-ethyl styrene, 2-t-butyl styrene, 3-t-butyl styrene, 4-t-butyl styrene, vinyl xylene, Vinyl naphthale , Vinyl toluene, vinyl pyridine, diphenylethylene, and aromatic vinyl compounds such as tertiary amino group-containing diphenylethylene, butadiene, and the like conjugated diene compound such as isoprene. Of these, styrene and butadiene are preferable. That is, the farnesene-vinyl monomer copolymer is preferably a copolymer of farnesene and styrene (farnesene-styrene copolymer) or a copolymer of farnesene and butadiene (farnesene-butadiene copolymer). By blending the farnesene-styrene copolymer, the effect of improving wet grip performance can be enhanced, and by blending the farnesene-butadiene copolymer, the effect of improving fuel economy and wear resistance can be enhanced. it can.

The glass transition temperature (Tg) of the farnesene homopolymer is preferably −60 ° C. or lower, more preferably −70 ° C. or lower, preferably −120 ° C. or higher, more preferably −110 ° C. or higher. If it is in the said range, it can be used conveniently as a tire softener and a fuel-consumption agent.
For the same reason, the Tg of the farnesene-styrene copolymer is preferably −15 ° C. or lower, more preferably −30 ° C. or lower, preferably −80 ° C. or higher, more preferably −70 ° C. or higher.
For the same reason, the Tg of the farnesene-butadiene copolymer is preferably −60 ° C. or lower, more preferably −70 ° C. or lower, preferably −120 ° C. or higher, more preferably −110 ° C. or higher.
Tg is a value measured according to JIS-K7121: 1987, using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., under a temperature increase rate of 10 ° C./min. .

The weight average molecular weight (Mw) of the farnesene resin is 1000 or more, preferably 2000 or more, more preferably 3000 or more, still more preferably 5000 or more, and particularly preferably 8000 or more. If it is less than 1000, the handling performance and wear resistance tend to deteriorate. The Mw is 500,000 or less, preferably 300,000 or less, more preferably 150,000 or less, and particularly preferably 100,000 or less. If it exceeds 500,000, the viscosity of the compounded rubber tends to increase and the processability tends to deteriorate. The farnesene resin having Mw within the above range is in a liquid state at normal temperature and can be suitably used as a tire softener and a fuel economy agent.

The melt viscosity of the farnesene homopolymer is preferably 1000 Pa · s or less, more preferably 200 Pa · s or less, preferably 0.1 Pa · s or more, more preferably 0.5 Pa · s or more. If it is in the said range, it can be used conveniently as a softener for tires and a fuel-saving agent, and it is excellent also in bloom resistance.
For the same reason, the melt viscosity of the farnesene-vinyl monomer copolymer is preferably 1000 Pa · s or less, more preferably 650 Pa · s or less, further preferably 200 Pa · s or less, preferably 1 Pa · s or more, more Preferably, it is 5 Pa · s or more.
The melt viscosity is a value measured at 38 ° C. using a Brookfield viscometer (manufactured by BROOKFIELD ENGINEERING LAB. INC.).

In the farnesene homopolymer, the content of farnesene in 100% by mass of the monomer component is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

In the farnesene-vinyl monomer copolymer, the total content of farnesene and vinyl monomer in 100% by mass of the monomer component is preferably 80% by mass or more, more preferably 90% by mass or more, even if it is 100% by mass. Good. The copolymerization ratio of farnesene and vinyl monomer is preferably farnesene: vinyl monomer = 99/1 to 25/75 on a mass basis, and farnesene: vinyl monomer = 80/20 to 40/60. Is more preferable.

The synthesis of the farnesene resin can be performed by a known method. For example, in the case of synthesis by anionic polymerization, hexane, farnesene, sec-butyllithium and, if necessary, a vinyl monomer are charged into a pressure-resistant container sufficiently substituted with nitrogen, and then heated and stirred for several hours. The liquid farnesene resin can be obtained by performing vacuum treatment after the quenching treatment of the obtained polymerization solution.

In the polymerization for preparing the farnesene homopolymer, the polymerization procedure is not particularly limited. For example, all the monomers may be polymerized at once, or the monomers may be sequentially added and polymerized. In the copolymerization for preparing the farnesene-vinyl monomer copolymer, the polymerization procedure is not particularly limited. For example, all monomers may be randomly copolymerized at once, or a specific monomer (for example, , Farnesene monomer only, butadiene monomer only, etc.), then the remaining monomers may be added for copolymerization or block copolymerization of pre-copolymerized specific monomers. Also good.

The farnesene used in the farnesene resin may be prepared from petroleum resources by chemical synthesis, or may be extracted from insects such as aphids and plants such as apples, but is derived from sugar. It is preferably prepared by culturing a microorganism using a carbon source. By using the farnesene, a farnesene resin can be efficiently prepared.

The sugar may be a monosaccharide, a disaccharide, or a polysaccharide, or a combination thereof. Examples of monosaccharides include glucose, galactose, mannose, fructose, and ribose. Examples of the disaccharide include sucrose, lactose, maltose, trehalose, cellobiose and the like. Examples of the polysaccharide include starch, glycogen, cellulose, chitin and the like.

Suitable sugars for the production of farnesene can be obtained from a wide variety of materials, such as sugar cane, bagasse, miscantas, sugar beet, sorghum, sorghum, switchgrass, barley, hemp, kenaf, potato, sweet potato, cassava , Sunflower, fruit, molasses, whey, skim milk, corn, straw, cereal, wheat, wood, paper, straw, cotton and the like. In addition, cellulose waste and other biomass materials can be used. Among them, plants belonging to the genus Saccharum such as sugar cane (Saccharum officinarum) are preferable, and sugar cane is more preferable.

The microorganism is not particularly limited as long as it can be cultured to produce farnesene, and examples thereof include eukaryotes, bacteria, archaea, and the like. Examples of eukaryotes include yeast and plants.

The microorganism may be a transformant. A transformant is obtained by introducing a foreign gene into a host microorganism. The foreign gene is not particularly limited, but a foreign gene involved in farnesene production is preferable because the production efficiency of farnesene can be further improved.

The culture conditions are not particularly limited as long as the microorganism can produce farnesene. The medium used for culturing microorganisms may be any medium that is usually used for culturing microorganisms. Specifically, in the case of bacteria, examples include KB medium and LB medium. In the case of yeast, YM medium, KY medium, F101 medium, YPD medium, and YPAD medium are exemplified. In the case of plants, White medium, Heller medium, SH medium (Schench and Hildebrandt medium), MS medium (Murashige and Skoog medium), LS medium (Linsmaier and Skoog medium), Gamburg medium, B5 medium, Examples include basic media such as MB media and WP media (Wood Plant: for wood).

Although culture | cultivation temperature changes with kinds of microorganisms, it is preferable that it is 0-50 degreeC, it is more preferable that it is 10-40 degreeC, and it is still more preferable that it is 20-35 degreeC. The pH is preferably from 3 to 11, more preferably from 4 to 10, and even more preferably from 5 to 9. Moreover, culture | cultivation can be performed on both anaerobic conditions and aerobic conditions according to the kind of microorganism.

Microbial culture can be carried out by batch culture or continuous culture using a bioreactor. Specific culture methods include shaking culture, rotary culture, and the like. Farnesene can be accumulated in the cells of microorganisms and can also be produced and accumulated in the culture supernatant.

When obtaining farnesene from the cultured microorganism, the microorganism can be recovered by centrifugation, then the microorganism can be crushed and extracted from the crushed liquid using a solvent such as 1-butanol. In addition, a known purification method such as chromatography can be appropriately used in combination with the solvent extraction method. Here, the disruption of the microorganism is preferably performed at a low temperature such as 4 ° C. in order to prevent the denaturation / disintegration of farnesene. The microorganism can be crushed by, for example, physical crushing using glass beads.

In order to obtain farnesene from the culture supernatant, the cells are removed by centrifugation, and then extracted from the obtained supernatant with a solvent such as 1-butanol.

The farnesene resin obtained by using the above-mentioned farnesene derived from microorganisms can be obtained as a commercial product. Examples of farnesene homopolymers include KB-101 and KB-107 manufactured by Kuraray Co., Ltd. Examples of the farnesene-styrene copolymer include FSR-221, FSR-242, FSR-251 and FSR-262 manufactured by Kuraray Co., Ltd., and farnesene-butadiene copolymers include Kuraray Co., Ltd. Examples thereof include FBR-746, FB-823, and FB-884.

The content of the farnesene resin is 1 part by mass or more, preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, particularly preferably 15 parts by mass with respect to 100 parts by mass of the rubber component. More than a part. If it is less than 1 part by mass, the effect of improving the performance obtained by blending the farnesene resin tends to be insufficient. Moreover, this content is 50 mass parts or less, Preferably it is 40 mass parts or less, More preferably, it is 30 mass parts or less. When it exceeds 50 parts by mass, handling performance and wear resistance tend to deteriorate.

The rubber composition according to the present invention contains silica. By blending silica with the farnesene resin, the silica can be dispersed well. The silica is not particularly limited, and examples thereof include dry method silica (anhydrous silica), wet method silica (hydrous silica) and the like, and wet method silica is preferable because of its large number of silanol groups. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is 40 m ² / g or more, preferably 50 m ² / g or more, more preferably 60 m ² / g or more, still more preferably 100 m ² / g or more, particularly preferably 170 m ^2. / G or more. If it is less than 40 m ² / g, the reinforcing effect is small and the wear resistance tends to decrease. Further, the _N 2 SA is, 400 meters ² / g or less, preferably 360 m ² / g or less, more preferably 300 meters ² / g or less, more preferably 250 meters ² / g or less, particularly preferably at 200 meters ² / g or less . When it exceeds 400 m < ² > / g, it will become difficult to disperse | distribute a silica and there exists a tendency for low-fuel-consumption property and workability to deteriorate.
The N ₂ SA of silica is a value measured according to ASTM D3037-81.

The content of silica is 10 parts by mass or more, preferably 30 parts by mass or more, more preferably 45 parts by mass or more with respect to 100 parts by mass of the rubber component. When the amount is less than 10 parts by mass, the effect of blending silica cannot be sufficiently obtained, and wet grip performance, handling performance, and wear resistance tend to deteriorate, or discoloration of the tire surface tends not to be suppressed. Moreover, this content is 150 mass parts or less, Preferably it is 100 mass parts or less. When it exceeds 150 parts by mass, fuel economy and handling performance tend to deteriorate or discoloration of the tire surface cannot be suppressed.

A silane coupling agent may be used in combination with the silica. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl Trimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarb Moyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilyl Propyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide And dimethoxymethylsilylpropylbenzothiazole tetrasulfide. Of these, bis (3-triethoxysilylpropyl) tetrasulfide and 3-trimethoxysilylpropylbenzothiazole tetrasulfide are preferable from the viewpoint of reinforcing effect. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 1 part by mass, the viscosity of the unvulcanized rubber composition is high, and the processability tends to deteriorate. The content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When it exceeds 20 parts by mass, there is a tendency that an effect commensurate with the increase in cost cannot be obtained.

Known additives can be used, such as sulfur vulcanizing agents; thiazole vulcanization accelerators, thiuram vulcanization accelerators, sulfenamide vulcanization accelerators, guanidine vulcanization accelerators. Vulcanization accelerators such as stearic acid and zinc oxide; organic peroxides; fillers such as carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica; oils, etc. Examples of softeners include anti-aging agents.

Examples of the vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and thiazole vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram disulfide Thiuram vulcanization accelerators such as: N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N- Sulfenamide vulcanization accelerators such as oxyethylene-2-benzothiazole sulfenamide and N, N′-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, diortolylguanidine, orthotolylbiguanidine, etc. Can be mentioned guanidine vulcanization accelerator, its amount is preferably from 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component, more preferably 0.2 to 3 parts by weight.

Carbon black includes furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF; acetylene black (acetylene carbon black); FT and MT Thermal black (thermal carbon black) such as: Channel black (channel carbon black) such as EPC, MPC and CC; Graphite and the like. These can be used alone or in combination of two or more.

Nitrogen adsorption specific surface area _(N 2 SA) of carbon black is usually 5 to 200 m ² / g, the lower limit is preferably ^{50 m} 2 / g, more preferably ^{80 m} 2 / g, the upper limit is preferably 150 meters ² / G, more preferably 120 m ² / g, still more preferably 100 m ² / g. Carbon black has a dibutyl phthalate (DBP) absorption amount of usually 5 to 300 ml / 100 g, the lower limit is preferably 80 ml / 100 g, and the upper limit is preferably 180 ml / 100 g, more preferably 150 ml / 100 g. . If the N ₂ SA or DBP absorption amount of the carbon black is less than the lower limit of the above range, the reinforcing effect tends to be small and the wear resistance tends to decrease. If the upper limit of the above range is exceeded, dispersibility is poor and hysteresis loss increases. There is a tendency for fuel efficiency to decrease. The nitrogen adsorption specific surface area is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93.

The content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 1 part by mass, sufficient reinforcement may not be obtained. The content is preferably 60 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. If it exceeds 60 parts by mass, the rubber becomes too hard and the wet grip performance tends to deteriorate.

Examples of oils include aroma oil (viscosity specific gravity constant (VGC value) 0.900 to 1.049), naphthenic oil (VGC value 0.850 to 0.899), paraffin oil. (V.G.C. value 0.790 to 0.849) and the like may be used and may be blended if necessary.

As described above, the farnesene-based resin is preferably blended by replacing part or all of oil or the like conventionally blended as a softening agent. The content of the farnesene resin in 100% by mass of the softening agent is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, particularly preferably 60% by mass or more, and most preferably 80%. It may be 100% by mass or more. Moreover, the total content of softeners (including the content of farnesene resin) is preferably 1 to 100 parts by mass, more preferably 10 to 80 parts by mass, and still more preferably 15 to 100 parts by mass of the rubber component. -60 mass parts, Especially preferably, it is 20-40 mass parts.

As a method for producing the rubber composition according to the present invention, a known method, for example, a method of kneading each component with a known mixer such as a roll or a banbury can be used.

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.

When blending a vulcanizing agent and a vulcanization accelerator, the kneading temperature is usually 100 ° C. or lower, preferably room temperature to 80 ° C. 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 rubber composition according to the present invention is used for a tread (cap tread).

The summer tire of the present invention is produced by a usual method using the rubber composition. That is, the rubber composition blended with various additives as necessary, extruded according to the shape of the tread of the tire in the unvulcanized stage, and molded by a normal method on a tire molding machine, Bonding together with other tire members forms an unvulcanized tire. The unvulcanized tire can be heated and pressurized in a vulcanizer to produce the summer tire of the present invention.

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

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
NR: TSR20
BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
SBR: ASAPRENE 1205 manufactured by Asahi Kasei Corporation (styrene content: 25% by mass)
Silica: Ultrasil VN3-G (N ₂ SA: 175 m ² / g) manufactured by Degussa
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Carbon black: Dia Black N339 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 96 m ² / g, DBP absorption: 124 ml / 100 g)
Oil: X-140 (Aroma Oil) manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Antigen 3C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate Zinc oxide: Zinc flower No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Co., Ltd.
Farnesene homopolymer 1: KB-101 manufactured by Kuraray Co., Ltd. (Mw: 10,000, melt viscosity: 0.7 Pa · s, Tg: −72 ° C.)
Farnesene homopolymer 2: KB-107 manufactured by Kuraray Co., Ltd. (Mw: 135000, melt viscosity: 69 Pa · s, Tg: −71 ° C.)
Farnesene-styrene copolymer 1: FSR-221 manufactured by Kuraray Co., Ltd. (Mw: 10,000, copolymerization ratio based on mass: farnesene / styrene = 77/23, melt viscosity: 5.7 Pa · s, Tg: −54 ℃)
Farnesene-styrene copolymer 2: FSR-242 manufactured by Kuraray Co., Ltd. (Mw: 10000, copolymerization ratio based on mass: farnesene / styrene = 60/40, melt viscosity: 59.2 Pa · s, Tg: −35 ℃)
Farnesene-butadiene copolymer 1: FBR-746 manufactured by Kuraray Co., Ltd. (Mw: 100,000, copolymerization ratio based on mass: farnesene / butadiene = 60/40, melt viscosity: 603 Pa · s, Tg: −78 ° C.)
Farnesene-butadiene copolymer 2: FB-823 manufactured by Kuraray Co., Ltd. (Mw: 50000, copolymerization ratio based on mass: farnesene / butadiene = 80/20, melt viscosity: 13 Pa · s, Tg = −78 ° C.)
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. 1: Soxinol CZ manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator 2: Soxinol D manufactured by Sumitomo Chemical Co., Ltd.

(Examples and Comparative Examples)
In accordance with the composition shown in Tables 1 to 3, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., and mixed. A kneaded paste was obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 12 minutes to obtain a vulcanized rubber composition. 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 170 ° C. for 12 minutes, and tested. Tires (size: 195 / 65R15) were manufactured.

The following evaluation was performed about the obtained vulcanized rubber composition and the tire for a test. The results are shown in Tables 1-3.

<Test items and test methods>

(Low fuel consumption index)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), a sheet-like vulcanized rubber composition was measured for tan δ of each formulation under conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 1%. The tan δ of Comparative Example 1 was taken as 100, and the index was expressed by the following formula. The higher the index, the better the fuel efficiency.
(Low fuel consumption index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Wet grip performance index)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), a sheet-like vulcanized rubber composition was measured for tan δ of each formulation under the conditions of frequency 10 Hz, dynamic strain 0.1%, and temperature 0 ° C. The tan δ of Comparative Example 1 was taken as 100, and the index was expressed by the following formula. The larger the index, the better the wet grip performance.
(Wet grip performance index) = (tan δ of each formulation) / (tan δ of Comparative Example 1) × 100

(Blackness)
About the tire for a test after leaving to stand at ozone 50ppph and 40 degreeC for 1 week, the blackness was measured using the color difference meter, and the discoloration (white discoloration and brown discoloration) of the tire surface was evaluated on the following reference | standard.
5: No discoloration 4: Slight discoloration 3: Discolored part is less than half of the whole 2: Discolored part is more than half of the whole 1: Discolored entirely

(Handling performance index)
The test tire was mounted on a passenger car with a displacement of 2500 cc, and it traveled while meandering a course of 3 km per lap, and the handling performance was sensory evaluated according to the following criteria.
Based on 5 points,
6.5 points: good enough to detect clearly 6 points: good enough to detect enough 5.5 points: good enough to detect slightly 4.5 points: slightly perceptible bad 4 points: enough to detect Bad 3.5: Bad enough to be clearly detected

(Abrasion resistance index)
The amount of wear was measured at room temperature, a load of 1.0 kgf, and a slip rate of 30% using a Lambone-type wear tester. The reciprocal of the amount of wear was displayed as an index with Comparative Example 1 as 100. The larger the value, the higher the wear resistance.

From Tables 1 to 3, the examples in which a predetermined amount of silica having a nitrogen adsorption specific surface area within a specific range and a farnesene resin having a weight average molecular weight within a specific range are combined. In addition to excellent balance between performance and handling performance, discoloration of the tire surface was also suppressed. In particular, when a farnesene-butadiene copolymer was blended as the farnesene resin, the wear resistance was also improved.

Claims (8)

A rubber composition containing 1 to 50 parts by mass of a farnesene resin having a weight average molecular weight of 1000 to 500,000 and 10 to 150 parts by mass of silica having a nitrogen adsorption specific surface area of 40 to 400 m ² / g with respect to 100 parts by mass of the rubber component. A summer tire having a tread made from a product. The summer tire according to claim 1, wherein the farnesene resin is a homopolymer of farnesene. The summer tire according to claim 1, wherein the farnesene resin is a copolymer of farnesene and a vinyl monomer. The summer tire according to claim 3, wherein the vinyl monomer is styrene. The summer tire according to claim 3, wherein the vinyl monomer is butadiene. The summer tire according to any one of claims 3 to 5, wherein a copolymerization ratio of the farnesene and the vinyl monomer in the copolymer is farnesene / vinyl monomer = 99/1 to 25/75 on a mass basis. . The summer tire according to any one of claims 3 to 6, wherein the copolymer has a melt viscosity at 38 ° C of 1000 Pa · s or less. The summer tire according to any one of claims 1 to 7, wherein the farnesene resin is obtained by polymerizing farnesene prepared by culturing microorganisms using a carbon source derived from sugar.