JP2011088983A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire capable of improving rigid touch, damping performance, and gripping performance, particularly rigid touch, damping performance, and gripping performance under a high temperature condition, and to provide a pneumatic tire using the rubber composition. <P>SOLUTION: This rubber composition for a tire is a rubber composition for a tire containing a rubber component and a polyurethane having a softening point of 40°C or lower, preferably a rubber composition for a tire in which the above polyurethane is a urethane oligomer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

In recent years, along with the improvement in performance of passenger cars and motorcycles, the ability to travel safely at high speeds with respect to tires has been demanded. A rubber composition for high-performance tires (especially tires used in racing and off-road) used in high-performance passenger cars and motorcycles needs to have high rigidity, damping performance, and grip performance.

As a method for obtaining a high rigidity feeling and damping performance in a tire, for example, it is known to use, as a rubber composition for a tire, a composition in which a filler component such as carbon black is increased or a plasticizer component is decreased. ing. Further, as a method for obtaining high grip performance in a tire, for example, it is known that a rubber component having a high glass transition temperature, carbon black having a large surface area, or a resin is blended in a tire rubber composition. However, tires tend to generate heat as they travel and become high temperature. However, the above method has a problem that the rigidity, damping performance, and grip performance are degraded under high temperature conditions.

On the other hand, Patent Document 1 discloses a rubber composition containing a granular material composed of an antioxidant and a thermoplastic resin such as polyurethane, and Patent Document 2 discloses a rubber composition containing urethane-based particles. Discloses a rubber composition containing thermoplastic polyurethane.

However, the softening point of polyurethane has not been studied in detail, and there is room for improvement in improving rigidity, damping performance, and grip performance under high temperature conditions.

JP 2001-348463 A JP 2002-97303 A JP 2008-50571 A

The present invention solves the above-mentioned problems, and provides a rubber composition for tires that can improve rigidity, damping performance, and grip performance, particularly rigidity, damping performance, and grip performance under high temperature conditions, and the rubber composition. An object is to provide a used pneumatic tire.

The present inventors have found that the above-mentioned problems can be solved by generating an energy loss (tan δ) in a rubber composition using a polyurethane having a softening point below a specific temperature, and have completed the present invention.
That is, this invention relates to the rubber composition for tires containing the rubber component and the polyurethane whose softening point is 40 degrees C or less.

The polyurethane is preferably a urethane oligomer.

The polyurethane is preferably urethane (meth) acrylate.

The rubber component preferably contains at least one rubber selected from the group consisting of styrene butadiene rubber, natural rubber, and butadiene rubber.

The rubber composition preferably contains carbon black.

The rubber composition is preferably used for a tread, a sidewall, or an inner liner.

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

According to the present invention, since it is a rubber composition for tires containing a polyurethane having a rubber component and a softening point of a specific temperature or less, energy loss can be caused in the rubber composition, and the rigidity, damping performance, and grip It is possible to improve performance, particularly rigidity at high temperature conditions, damping performance, and grip performance. Therefore, it is possible to provide a pneumatic tire that can provide excellent rigidity, damping performance, and grip performance even when the temperature of the vehicle or motorcycle is increased due to tire heat generation or the like. In the present invention, since the softening point of the polyurethane is below a specific temperature, the polyurethane has fluidity in the rubber composition, and it is assumed that energy loss occurs in the rubber composition by blending the polyurethane. Is done.

The rubber composition for tires of the present invention contains a polyurethane having a rubber component and a softening point equal to or lower than a specific temperature.

Examples of the rubber component used in the present invention include diene rubbers and butyl rubbers that are generally used in rubber compositions for tires. Examples of the diene rubber include natural rubber (NR); styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile. -Diene type synthetic rubbers such as butadiene rubber (NBR). Examples of the butyl rubber include halogenated butyl rubber (X-IIR) such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR), and butyl rubber (IIR). These may be used alone or in combination of two or more. Among them, it is preferable to use SBR as a tread because it has excellent grip performance. Moreover, as a side wall use, it is preferable to use NR and BR together for the reason of excellent crack growth resistance. In addition, as an inner liner application, it is preferable to use NR and a butyl rubber (preferably X-IIR) in combination because of excellent gas barrier properties.

In the rubber composition of the present invention, usable SBR is not particularly limited, and emulsion polymerization SBR (E-SBR), solution polymerization SBR (S-SBR) and the like can be used. Further, the NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, and TSR20 can be used. Also, the BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B and other high cis content BR, VCR412 manufactured by Ube Industries, Ltd., VCR617, etc. BR containing a syndiotactic polybutadiene crystal can be used.
The cis content of BR is preferably 95% by mass or more. Moreover, it does not specifically limit as a butyl-type rubber, The said IIR, Br-IIR, Cl-IIR, etc. can be used.

The styrene content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more. If it is less than 10% by mass, there is a tendency that sufficient grip performance under high temperature conditions cannot be obtained. Moreover, this styrene content becomes like this. Preferably it is 60 mass% or less, More preferably, it is 50 mass% or less. When it exceeds 60 mass%, there exists a possibility of showing embrittlement by use temperature.

When using the rubber composition of this invention for a tread, content of SBR in 100 mass% of rubber components becomes like this. Preferably it is 80 mass% or more, More preferably, it is 90 mass% or more, More preferably, it is 100 mass%. If it is less than 80% by mass, there is a tendency that sufficient grip performance under high temperature conditions cannot be obtained.

When the rubber composition of the present invention is used for sidewalls and inner liners, the content of NR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass. % Or more. If it is less than 10% by mass, the breaking strength may be inferior. The NR content is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. If it exceeds 90 mass%, the weather resistance may be inferior.

When using the rubber composition of this invention for a side wall and an inner liner, content of BR in 100 mass% of rubber components becomes like this. Preferably it is 10 mass% or more, More preferably, it is 30 mass% or more. If it is less than 10% by mass, the crack growth resistance may be poor. The BR content is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. When it exceeds 80 mass%, there exists a possibility that breaking strength may be inferior.

When the rubber composition of the present invention is used for the inner liner, the content of butyl rubber in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, and further preferably 50% by mass. That's it. If it is less than 30% by mass, the air permeation resistance tends to be insufficient. The content of the butyl rubber is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. If it exceeds 90 mass%, the durability (cracking performance) may be inferior.

When the rubber composition of the present invention is used for a side wall and an inner liner and NR and BR are used in combination, the total content of NR and BR in 100% by mass of the rubber component is preferably 80% by mass or more. Preferably it is 90 mass% or more, More preferably, it is 100 mass%. There exists a possibility that it may be inferior to durability (crack performance) as it is less than 80 mass%.

When the rubber composition of the present invention is used for an inner liner and NR and butyl rubber are used in combination, the total content of NR and butyl rubber in 100% by mass of the rubber component is preferably 60% by mass or more, More preferably, it is 70 mass% or more, More preferably, it is 75 mass% or more. There exists a possibility that it may be inferior to durability (crack performance) as it is less than 60 mass%.

In the present invention, a polyurethane having a softening point below a specific temperature is used. Thereby, energy loss can be caused in the rubber composition, and rigidity, damping performance, and grip performance, particularly rigidity, damping performance, and grip performance under high temperature conditions can be improved. Moreover, it is preferable to mix | blend the polyurethane whose softening point is below a specific temperature as a substitute for softeners, such as oil (a part or all amount of oil is substituted).

The polyurethane is not particularly limited as long as it is a polymer in which a monomer is polymerized by a urethane bond formed by condensation of an isocyanate group and a hydroxyl group. For example, polyisocyanate, polyol, thermoplastic polyurethane elastomer produced from a chain extender if necessary, polyisocyanate, hydroxy (meth) acrylate, urethane produced from a polyol, chain extender, etc. if necessary ( And (meth) acrylate. Especially, the urethane oligomer which is a polyurethane with which a viscosity satisfy | fills the following numerical range is preferable from the reason that it uses as a softening agent. Moreover, urethane (meth) acrylate is preferable because it is used as a softening agent, and a urethane (meth) acrylate oligomer that is a urethane (meth) acrylate whose viscosity satisfies the following numerical range is preferable.

Urethane (meth) acrylate can be synthesized by a known method. For example, a method of reacting a polyisocyanate, a polyol and a hydroxy (meth) acrylate having one or more hydroxyl groups, a method of reacting a polyisocyanate and a hydroxy (meth) acrylate having two or more hydroxyl groups, a diisocyanate A method of reacting a polyhydroxy (meth) acrylate having one or more hydroxyl groups with both end isocyanate groups of the compound, reacting an excess amount of a polyisocyanate compound with a polyhydric alcohol, and leaving one or more hydroxyl groups on the remaining isocyanate groups And a method of reacting a hydroxy (meth) acrylate having a hydrogen atom.

The polyisocyanate is not particularly limited as long as it has two or more isocyanate groups. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate can be used. Mixture (TDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3′-vitrylene-4,4′-diisocyanate (TODI), xylylene diisocyanate (XDI) , Tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisocyanate (PPDI), 4,4'-methylene-bis (phenylisocyanate) and other aromatic polyisocyanates; 4,4'-dicyclohexylmethane diisocyanate _(H 12 MDI), hydrogenated xylylene diisocyanate _(H 6 XDI), hexamethylene diisocyanate (HDI), alicyclic polyisocyanates or aliphatic polyisocyanates such as isophorone diisocyanate (IPDI) and the like.

Polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), polyoxytetramethylene glycol (PTMG); polyethylene adipate (PEA), polybutylene adipate (PBA), polyhexamethylene Examples include condensed polyester polyols such as adipate (PHMA); lactone polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; acrylic polyols and the like. Among these, PEG is preferable because it is easily available.

Examples of the hydroxy (meth) acrylate having one or more hydroxyl groups include 2-hydroxyethyl acrylate, 4-hydroxycyclohexyl acrylate, 5-hydroxycyclooctyl acrylate, pentaerythritol triacrylate, 2-hydroxyethyl methacrylate, 4-hydroxy Examples include cyclohexyl methacrylate, 5-hydroxycyclooctyl methacrylate, pentaerythritol trimethacrylate, trimethylolpropane diacrylate, dipentaerythritol pentaacrylate, and the like.

Commercial products of urethane (meth) acrylate include Art Range UN-1000PEP, Art Range UN-9000PEP, Art Range UN-9200A, Art Range UN-2500, Art Range UN-5200, Art Range manufactured by Negami Kogyo Co., Ltd. UN-llO2, Art Range UN-380G, Art Range UN-500, Art Range UN-9832; Aronix M-1200 manufactured by Toa Gosei Co., Ltd .; Chemlink 9503, Chemlink 9504, Chemlink 9505 manufactured by SARTOMER; Nippon Synthetic Chemical A trade name “Shikou” series manufactured by Kogyo Co., Ltd. can be mentioned.

The softening point of polyurethane is 40 ° C. or lower, preferably 30 ° C. or lower, more preferably 20 ° C. or lower. When the softening point of polyurethane exceeds 40 ° C., energy loss cannot be sufficiently generated in the rubber composition, rigidity, damping performance, and grip performance, particularly rigidity at high temperatures, damping performance, In addition, the grip performance may not be sufficiently improved. The softening point of polyurethane is preferably −50 ° C. or higher. When the softening point of polyurethane is less than −50 ° C., sufficient rigidity may not be obtained.
The softening point of polyurethane is a value measured by the ring and ball method (JIS K2207).

The viscosity of the polyurethane at 60 ° C. is preferably 300 cps or more, more preferably 400 cps or more. If it is less than 300 cps, sufficient rigidity may not be obtained.
The viscosity is preferably 100,000 cps or less, more preferably 80000 cps or less. If it exceeds 100000 cps, the energy loss cannot be sufficiently exhibited, and the rigidity, damping performance, and grip performance may be inferior.

When the rubber composition of the present invention is used for treads and sidewalls, the polyurethane content is preferably 3 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts per 100 parts by mass of the rubber component. More than part by mass. When the amount is less than 3 parts by mass, energy loss cannot be sufficiently generated in the rubber composition, and rigidity, damping performance, and grip performance, particularly rigidity, damping performance, and grip performance under high temperature conditions. May not be sufficiently improved. The polyurethane content is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. If it exceeds 60 parts by mass, bleeding out may occur and adhesion failure may occur.

When the rubber composition of the present invention is used for the inner liner, the polyurethane content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass with respect to 100 parts by mass of the rubber component. That's it. If it is less than 1 part by mass, energy loss cannot be sufficiently generated in the rubber composition, and there is a possibility that the rigidity feeling, particularly the rigidity feeling under high temperature conditions, cannot be sufficiently improved. The content of the polyurethane is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, still more preferably 80 parts by mass or less, particularly preferably 70 parts by mass or less, and most preferably 60 parts by mass or less. If it exceeds 100 parts by mass, there is a risk of blooming (coming out from the surface).

The rubber composition of the present invention preferably contains carbon black. Thereby, the reinforcement property with respect to rubber | gum is obtained and a rigidity feeling, damping performance, and grip performance, especially the rigidity feeling in high temperature conditions, damping performance, and grip performance can be improved. As carbon black, SAF, ISAF, HAF, FF, FEF, GPF and the like generally used in the tire industry can be used. Carbon black may be used alone or in combination of two or more.

When the rubber composition of the present invention is used for treads and sidewalls, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 60 m ² / g or more. When N ₂ SA of carbon black is less than 50 m ² / g, there is a possibility that sufficient grip performance and rigidity cannot be obtained. Also, _N 2 SA of carbon black is preferably 200 meters ² / g, more preferably at most 190 m ² / g. If N ₂ SA of the carbon black exceeds 200 m ² / g, the abrasion resistance may be deteriorated due to deterioration of dispersion.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

When the rubber composition of the present invention is used for an inner liner, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 20 m ² / g or more, more preferably 30 m ² / g or more. When N ₂ SA of carbon black is less than 20 m ² / g, durability may be reduced. The N ₂ SA of the carbon black is preferably 150 m ² / g or less, more preferably 140 m ² / g or less, still more preferably 100 m ² / g or less, particularly preferably 75 m ² / g or less, and most preferably 50 m ^2. / G or less. If N ₂ SA of carbon black exceeds 150 m ² / g, heat generation may be increased.

When the rubber composition of the present invention is used for treads and sidewalls, the content of carbon black is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, further preferably 100 parts by mass of the rubber component. It is 40 parts by mass or more. If the amount is less than 20 parts by mass, sufficient grip performance and damping performance may not be obtained. The carbon black content is preferably 200 parts by mass or less, more preferably 190 parts by mass or less, still more preferably 180 parts by mass or less, particularly preferably 120 parts by mass or less, and most preferably 80 parts by mass or less. . If it exceeds 200 parts by mass, the dispersibility may be deteriorated and the wear resistance may be deteriorated.

When the rubber composition of the present invention is used for the inner liner, the carbon black content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass with respect to 100 parts by mass of the rubber component. Part or more, particularly preferably 30 parts by weight or more. There exists a possibility that breaking strength may fall that it is less than 5 mass parts. The carbon black content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and still more preferably 80 parts by mass or less. If it exceeds 100 parts by mass, the heat generation may increase.

The rubber composition of the present invention may contain silica. By containing silica, tan δ can be lowered and rolling resistance can be improved.
The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process 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 preferably 50 m ² / g or more, more preferably 100 m ² / g or more, and still more preferably 125 m ² / g or more. There exists a possibility that sufficient reinforcement may not be shown as it is less than 50 m < ² > / g. Further, N ₂ SA of silica is preferably 250 m ² / g or less, more preferably 200 m ² / g or less. If it exceeds 250 m ² / g, the processability tends to deteriorate.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

When the rubber composition contains carbon black and silica, the total content of carbon black and silica is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 100 parts by mass of the rubber component. Is 30 parts by mass or more. If it is less than 10 parts by mass, sufficient breaking strength may not be obtained. The total content is preferably 200 parts by mass or less, more preferably 190 parts by mass or less. If it exceeds 200 parts by mass, the dispersibility is poor and the wear resistance may be deteriorated.

In the present invention, when silica is used, it is preferable to use a silane coupling agent together with silica.
As the silane coupling agent, conventionally known silane coupling agents can be used, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxy). Silylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxy Silylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate Sulfide type such as sulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, etc. mercapto type, vinyltriethoxysilane, vinyltrimethoxy Vinyl type such as silane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, etc. Glyci such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, etc. Doxy, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane and other nitro, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloro Examples include chloro-based compounds such as ethyltriethoxysilane. In addition, said silane coupling agent may be used independently and may be used in combination of 2 or more type. Of these, bis (3-triethoxysilylpropyl) tetrasulfide is preferable because of processability.

The content of the silane coupling agent is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 2 parts by mass, the fracture strength may decrease. Moreover, 20 mass parts or less are preferable with respect to 100 mass parts of silica, and, as for content of this silane coupling agent, 17 mass parts or less are more preferable. If it exceeds 20 parts by mass, the rolling resistance reduction effect may not be sufficiently obtained.

In addition to the components described above, the rubber composition of the present invention includes compounding agents conventionally used in the rubber industry, for example, inorganic and organic fillers such as clay, softeners such as oil, and vulcanization acceleration aids such as stearic acid. Agents, various anti-aging agents, ozone degradation inhibitors, vulcanizing agents such as wax, zinc oxide, sulfur or sulfur compounds, vulcanization accelerators, and the like can be appropriately blended as necessary.

As described above, in the present invention, since a polyurethane having a softening point of a specific temperature or lower can be blended instead of a softener such as oil, the amount of softener used can be reduced.
When the rubber composition of the present invention is used for a tread, the content of the softening agent is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, and still more preferably 160 parts by mass with respect to 100 parts by mass of the rubber component. Hereinafter, it is particularly preferably 100 parts by mass or less, and most preferably 60 parts by mass or less. When it exceeds 200 mass parts, there exists a possibility that abrasion resistance may fall.

When the rubber composition of the present invention is used for sidewalls and inner liners, the content of the softening agent is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably with respect to 100 parts by mass of the rubber component. Is 0.1 part by mass or less, particularly preferably 0 part by mass (not contained). If it exceeds 50 parts by mass, sufficient rigidity may not be obtained.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The rubber composition of the present invention can be suitably applied to each member of a pneumatic tire. In particular, it can be suitably used for treads, sidewalls, and inner liners of pneumatic tires.

The inner liner is a member formed so as to form a tire lumen surface, and by this member, the air permeation amount can be reduced and the tire internal pressure can be maintained. Specifically, it is a member shown in FIG. 1 of JP 2008-291091 A, FIGS. 1-2 of JP 2007-160980 A, and the like.

The pneumatic tire of the present invention can be produced by a usual method using the rubber composition. That is, the rubber composition is extruded in accordance with the shape of each member (for example, tread, sidewall, inner liner, etc.) at an unvulcanized stage, molded by a normal method on a tire molding machine, etc. The tire members are bonded together to form an unvulcanized tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce a tire.

The pneumatic tire of the present invention is suitably used as a passenger car tire, truck / bus tire, motorcycle tire and the like.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: RSS # 3, TSR
SBR: Toughden 4350 manufactured by Asahi Kasei Co., Ltd. (oil-containing SBR, SBR containing 100 parts by mass of solid, 50 parts by mass of oil, styrene content: 40% by mass)
BR (1): Nippon 1220 manufactured by Nippon Zeon Co., Ltd. (Hicis BR, cis content: 96.5% by mass)
BR (2): BR150B manufactured by Ube Industries, Ltd. (High cis BR, cis content: 97% by mass)
Chlorobutyl rubber: HT-1068 (chlorinated butyl rubber) manufactured by ExxonMobil
Polyurethane (1): Aliphatic urethane acrylate (trade name: CN9178) manufactured by SARTOMER (liquid urethane oligomer, softening point: −35 ° C., viscosity: 21000 cps (60 ° C.))
Polyurethane (2): Aromatic urethane acrylate (trade name: CN9782) manufactured by SARTOMER (liquid urethane oligomer, softening point: −32 ° C., viscosity: 42000 cps (60 ° C.))
Polyurethane (3): aliphatic urethane acrylate (trade name: CN965) manufactured by SARTOMER (liquid urethane oligomer, softening point: -37 ° C, viscosity: 998 cps (60 ° C))
Carbon Black (1): Show Black N220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan
Carbon Black (2): Show Black N550 manufactured by Cabot Japan (N ₂ SA: 42 m ² / g)
Silica: Ultrasil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Wax: Sunnock wax manufactured by Ouchi Shinsei Chemical Co., Ltd. Anti-aging agent: Nocrack 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylene manufactured by Ouchi Shinsei Chemical Co., Ltd.) Diamine)
Stearic acid: Zinc stearate oxide manufactured by NOF Corporation: Zinc Hua No. 1 oil manufactured by Mitsui Kinzoku Mining Co., Ltd .: Aroma process oil X-140 manufactured by Japan Energy
Sulfur: Powder sulfur vulcanization accelerator made by Tsurumi Chemical Co., Ltd. (1): Noxeller NS made by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (2): Noxeller DM manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples 1-12 and Comparative Examples 1-4
According to the contents 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 to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes at 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition.

The obtained unvulcanized rubber composition is molded into an inner liner shape, bonded to another tire member, molded into a tire, and vulcanized under conditions of 25 kgf for 35 minutes at 150 ° C. Size: 11 × 7.10-5) was produced.

The following tests were performed using the obtained vulcanized rubber composition and test tire. The results are shown in Tables 1-3.

<Evaluation of rubber composition for tread>
(Viscoelasticity test 1)
The obtained vulcanized rubber composition was subjected to a 10% initial strain using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho, and a dynamic strain of 2% was applied at 100 ° C. at a frequency of 5 Hz. Viscoelasticity (complex elastic modulus E ′ and loss coefficient tan δ) was measured. The value of Comparative Example 1 was set to 100, and each index was displayed. The larger the value of tan δ, the larger the grip when made into a tire and the better the grip performance. The larger the value of E ′, the higher the rigidity and the better the steering stability.

(Tensile test 1)
The obtained vulcanized rubber composition was tested with a dumbbell No. 3 sample at 70 ° C. based on JIS tensile test method K6251. The value of Comparative Example 1 was set to 100, and each index was displayed. It shows that abrasion resistance is so excellent that M300 (300% elongation stress) is large.

<Evaluation of rubber composition for sidewall>
(Viscoelasticity test 2)
When the obtained vulcanized rubber composition was subjected to 10% initial strain using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho, and 2% dynamic strain was applied at 70 ° C. at a frequency of 5 Hz. Viscoelasticity (complex elastic modulus E ′ and loss coefficient tan δ) was measured. The value of Comparative Example 2 was set to 100, and each index was displayed. The larger the value of tan δ, the greater the damping when the tire is made, and the better the damping performance. The larger the value of E ′, the higher the rigidity and the better the steering stability.

(Tensile test 2)
A No. 3 dumbbell-shaped rubber test piece was prepared from the obtained vulcanized rubber composition, and subjected to a tensile test at 70 ° C. based on JIS tensile test method K6251 to measure breaking strength (TB) and elongation at break (EB). did. The value of Comparative Example 2 was set to 100, and each index was displayed. It shows that it is excellent in a fracture | rupture characteristic, so that TB and EB are large.

<Evaluation of rubber composition for inner liner>
(Tensile test 3)
A No. 3 dumbbell-shaped rubber test piece was prepared from the obtained vulcanized rubber composition, and a tensile test was performed at 70 ° C. based on JIS tensile test method K6251 to measure the breaking strength (TB). The value of Comparative Example 3 was set to 100, and each index was displayed. It shows that it is excellent in durability, so that TB is large.

(Maneuvering stability)
The test tire was attached to the test cart, and the test course of 1 km 2 km was run 8 times. The steering stability of the tire of Comparative Example 3 was 3 points, and the test driver made a sensory evaluation with a maximum score of 5 points. The larger the value, the better the steering stability.

According to Table 1, in Examples including a polyurethane having a softening point equal to or lower than a specific temperature, the grip performance and the rigidity (steering stability) were excellent as compared with the Comparative Example, and the wear resistance was equivalent.

As shown in Table 2, in Examples including a polyurethane having a softening point equal to or lower than a specific temperature, the damping performance and rigidity (steering stability) were excellent as compared with the Comparative Example, and the fracture characteristics were equivalent.

According to Table 3, in an example including a polyurethane having a softening point equal to or lower than a specific temperature, compared to the comparative example (comparing examples 7 to 9 and comparative example 3, and examples 10 to 12 and comparative example 4), the steering stability. Excellent (rigidity).

Claims (7)

A tire rubber composition comprising a polyurethane having a rubber component and a softening point of 40 ° C or lower. The tire rubber composition according to claim 1, wherein the polyurethane is a urethane oligomer. The tire rubber composition according to claim 1 or 2, wherein the polyurethane is urethane (meth) acrylate. The tire rubber composition according to any one of claims 1 to 3, wherein the rubber component includes at least one rubber selected from the group consisting of styrene butadiene rubber, natural rubber, and butadiene rubber. The rubber composition for tires according to any one of claims 1 to 4 containing carbon black. The tire rubber composition according to any one of claims 1 to 5, which is used for a tread, a sidewall, or an inner liner. A pneumatic tire using the rubber composition according to claim 1.