JP2015044904A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire which is excellent in grip performance and blowout resistance when formed into a tire.SOLUTION: There are provided a rubber composition for a tire which comprises: 100 pts.mass of a diene-based rubber A; 60 to 150 pts.mass of carbon black; and 1 to 30 pts.mass of a liquid, modified polyisoprene and/or modified polybutadiene having a number average molecular weight of 800 to 60000, with both terminals of which are modified with an isocyanate group. In the rubber composition, a part or the whole of the diene-based rubber A is a diene-based rubber a having an active hydrogen group reactive with the isocyanate group, and the amount of the diene-based rubber a is 5 to 100 mass% of the amount of the diene-based rubber A. There is also provided a pneumatic tire using the rubber composition for a tire.

Description

  The present invention relates to a tire rubber composition and a pneumatic tire suitable for a racing tire.

  In competition tires, both grip performance and blowout resistance are major issues. In general, the above two performances are in a trade-off relationship. The applicant of the present application has proposed a rubber composition for a tire tread containing sulfur, sulfide, etc. for the purpose of improving dry grip performance and blowout resistance (for example, Patent Document 1).

JP 2010-235661 A

The inventor of the present application considered that the above-mentioned trade-off relationship was caused by the fact that the rubber was crosslinked only by sulfur crosslinking.
Therefore, the present invention provides a novel crosslinking agent, a rubber composition containing the same, and a rubber composition that can provide a rubber composition for a tire that is excellent in grip performance and blowout resistance when used as a tire. The purpose is to provide pneumatic tires.

  As a result of intensive studies on the above problems, the present inventors have sufficiently increased the crosslinking density by using a specific liquid polymer having an isocyanate group as a novel crosslinking agent for a diene rubber having an active hydrogen group. The present inventors have found that a rubber composition for a tire excellent in grip performance and blowout resistance can be obtained when it is made into a tire without increasing the flexibility of the rubber while increasing the flexibility.

The invention according to the present application is as follows.
1. Liquid modified polyisoprene and / or modified polybutadiene 1 having 100 parts by weight of diene rubber A, 60 to 150 parts by weight of carbon black, and a number average molecular weight of 800 to 60,000 and both ends modified with isocyanate groups Containing 30 parts by mass,
A part or all of the diene rubber A is a diene rubber a having an active hydrogen group capable of reacting with the isocyanate group,
A rubber composition for tires, wherein the amount of the diene rubber a is 5 to 100% by mass of the amount of the diene rubber A.
2. 2. The rubber composition for tires according to 1 above, wherein the active hydrogen group is at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a silanol group.
3. The modified polyisoprene or the modified polybutadiene is obtained by reacting a liquid raw material polyisoprene or raw material polybutadiene having active hydrogen groups capable of reacting with isocyanate groups at both ends and a polyisocyanate compound. Or the rubber composition for tires of 2.
4). 4. The rubber composition for tires according to any one of 1 to 3 above, wherein the carbon black has a nitrogen adsorption specific surface area of 90 to 400 m ² / g.
5. 5. The tire rubber composition according to any one of 1 to 4 above, which is used for a racing tire.
6). A pneumatic tire manufactured using the tire rubber composition according to any one of 1 to 5 above.
7). The pneumatic tire according to 6 above, which is a racing tire.

  ADVANTAGE OF THE INVENTION According to this invention, the tire rubber composition excellent in grip performance and blowout resistance when it is used as a tire, and a pneumatic tire using the tire rubber composition of the present invention can be provided.

FIG. 1 is a partial cross-sectional schematic view of a tire representing an example of an embodiment of the pneumatic tire of the present invention.

  Below, the rubber composition for tires of this invention and the pneumatic tire using the rubber composition for tires of this invention are demonstrated.

[Rubber composition for tire]
The rubber composition for tires of the present invention,
Liquid modified polyisoprene and / or modified polybutadiene 1 having 100 parts by weight of diene rubber A, 60 to 150 parts by weight of carbon black, and a number average molecular weight of 800 to 60,000 and both ends modified with isocyanate groups Containing 30 parts by mass,
A part or all of the diene rubber A is a diene rubber a having an active hydrogen group capable of reacting with the isocyanate group,
A tire rubber composition in which the amount of the diene rubber a is 5 to 100% by mass of the amount of the diene rubber A.

  In the present invention, the active hydrogen group of the diene rubber a and the isocyanate group of the modified polyisoprene and / or modified polybutadiene react with each other, so that crosslinking by polyisoprene and / or polybutadiene different from sulfur crosslinking is caused to the rubber. It is formed. By crosslinking, the crosslinking density increases from before crosslinking and blowout resistance is improved. In general, the grip performance, which is said to decrease as the blowout resistance is improved, maintains or improves the flexibility without hardening the rubber because the cross-linking is caused by polyisoprene and / or polybutadiene. Will not drop. On the contrary, it is possible to improve the grip performance which is deteriorated by sulfur crosslinking in the present invention. Note that the above mechanism is the inventor's inference, and even if the mechanism is different, it is within the scope of the present invention.

In the present invention, a part or all of the diene rubber A is a diene rubber a having an active hydrogen group capable of reacting with an isocyanate group.
The active hydrogen group is not particularly limited as long as it is a group having active hydrogen. For example, it can be at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a silanol group.
For example, the silanol group may be generated from an alkoxysilyl group or a phenoxysilyl group. When the silanol group has one or two OH groups on one silicon atom, the group bonded to the other silicon atom is not particularly limited. Examples thereof include a hydrocarbon group, an alkoxysilyl group, and a phenoxysilyl group.

  The main chain (part other than the active hydrogen group) of the diene rubber a is not particularly limited. For example, natural rubber (NR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber ( Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like.

  The diene rubber a and the active hydrogen group can be bonded directly or through an organic group. The organic group is not particularly limited. For example, the hydrocarbon group which may have a hetero atom like an oxygen atom, a nitrogen atom, and a sulfur atom is mentioned. Examples of the hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. The hydrocarbon group may be linear or branched, and may have an unsaturated bond.

The diene rubber a is preferably an aromatic vinyl-conjugated diene copolymer rubber from the viewpoint of better grip performance and blowout resistance.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene copolymer rubber (SBR) and styrene-isoprene copolymer rubber. Among these, styrene-butadiene copolymer rubber (SBR) is preferable because the grip performance and blowout resistance of the obtained tire are more excellent.
The weight average molecular weight Mw of the diene rubber a is preferably from 1 million to 2 million, more preferably from 1.1 million to 1.8 million, from the viewpoint of superior grip performance and blowout resistance. The weight average molecular weight (Mw) of the diene rubber is determined in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent (the same applies hereinafter).

The aromatic vinyl monomer and the conjugated diene monomer used when producing the aromatic vinyl-conjugated diene copolymer rubber are not particularly limited.
Examples of the aromatic vinyl monomer include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, and 4-tert. -Butylstyrene, divinylbenzene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl) dimethylaminoethyl ether, N, N-dimethylaminoethylstyrene, vinylpyridine and the like.
Examples of the conjugated diene monomer include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene. 1,3-pentadiene and the like.

The aromatic vinyl content (for example, styrene content) of the aromatic vinyl-conjugated diene copolymer rubber is 15 to 45% by mass of the aromatic vinyl-conjugated diene copolymer rubber from the viewpoint of better grip performance. Preferably there is.
The amount of vinyl bonds by the conjugated diene is preferably 10 to 75% by mass of the conjugated diene constituting the aromatic vinyl-conjugated diene copolymer rubber.

  The glass transition temperature of the diene rubber a is preferably −35 ° C. or higher, more preferably −30 ° C. to −10 ° C. As for the glass transition temperature, a thermogram is measured by differential scanning calorimetry (DSC) under a heating rate condition of 20 ° C./min, and the temperature is set at the midpoint temperature of the transition region. When the diene rubber a is an oil-extended product, the glass transition temperature of the raw rubber excluding the oil is used.

The diene rubber a is preferably an aromatic vinyl-conjugated diene copolymer rubber having a hydroxyl group, more preferably an SBR having a hydroxyl group, from the viewpoint of excellent grip performance and blowout resistance.
The production of the diene rubber a is not particularly limited. For example, a conventionally well-known thing is mentioned. The diene rubbers a can be used alone or in combination of two or more.

In the present invention, when the amount of the diene rubber a is less than 100% by mass of the diene rubber A, the diene rubber A can further contain a diene rubber other than the diene rubber a. Diene rubbers other than the diene rubber a are not particularly limited. The diene rubber other than the diene rubber a can be the same as the diene rubber a except that it does not have an active hydrogen group capable of reacting with an isocyanate group.
Examples of the diene rubber other than the diene rubber a include natural rubber (NR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber ( NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like. Of these, aromatic vinyl-conjugated diene copolymer rubber is preferable and SBR is more preferable from the viewpoint of excellent grip performance and blowout resistance.
The weight average molecular weight Mw of the diene rubber other than the diene rubber a is preferably 500,000 to 2,000,000, more preferably 700,000 to 1,500,000, from the viewpoint of superior grip performance and blowout resistance. preferable.
Diene rubbers other than the diene rubber a can be used alone or in combination of two or more.

In the present invention, the amount of the diene rubber a is 5 to 100% by mass of the amount of the diene rubber A. From the viewpoint of excellent grip performance and blowout resistance, the amount of the diene rubber a is preferably 5 to 90% by mass of the amount of the diene rubber A.
The amount of the diene rubber other than the diene rubber a is preferably 95 to 0% by mass of the amount of the diene rubber A from the viewpoint of excellent grip performance and blowout resistance. It is more preferable that it is 95-10 mass%.

The carbon black will be described below. The carbon black contained in the rubber composition for tires of the present invention is not particularly limited.
In the present invention, carbon black can be used even if it has a small particle size and generally causes the rubber to generate more heat when the vehicle is running. This is because according to the present invention, the heat generation is effectively suppressed and the blowout resistance is excellent.
In the present invention, the nitrogen adsorption specific surface area of carbon black can be 90 to 400 m ² / g, and a higher range of nitrogen adsorption specific surface area (for example, 130 to 350 m ² / g or 150 to 350 m ² / g) can do. In the present invention, the nitrogen adsorption specific surface area (N ₂ SA) was measured according to JIS K6217-2.
Carbon black is not particularly limited for its production. Carbon blacks can be used alone or in combination of two or more.

  In the present invention, the amount of carbon black is 60 to 150 parts by mass with respect to 100 parts by mass of the diene rubber A, and 90 to 150 parts by mass from the viewpoint of excellent grip performance and blowout resistance. Preferably, it is 100-130 mass parts.

The modified polyisoprene and modified polybutadiene will be described below. The modified polyisoprene contained in the tire rubber composition of the present invention is a liquid, modified polyisoprene having a number average molecular weight of 800 to 60,000 and having both ends modified with isocyanate groups. The modified polybutadiene is a liquid modified polybutadiene having a number average molecular weight of 800 to 60,000 and having both ends modified with isocyanate groups.
In the present invention, modified polyisoprene and modified polybutadiene are collectively referred to as “modified polymer”.

In the present invention, the number average molecular weight (Mn) of the modified polymer is 800 to 60,000, and is preferably 800 to 50,000 from the viewpoint of excellent grip performance and blowout resistance, and is preferably 800 to 30 More preferably, it is 1,000. The number average molecular weight of the modified polymer is determined in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.
Further, both ends of the modified polymer are modified with isocyanate groups.
The main chain of the modified polymer is polyisoprene or polybutadiene. The main chain of the modified polymer is mentioned as one of the preferred embodiments that is a homopolymer.
The main chain of the modified polymer and the isocyanate group can be bonded directly or via an organic group. The organic group is not particularly limited. For example, the hydrocarbon group which may have a hetero atom like an oxygen atom, a nitrogen atom, and a sulfur atom is mentioned. Examples of the hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. The hydrocarbon group may be linear or branched, and may have an unsaturated bond. The heteroatom may form a linking group such as a urethane bond, a urea bond, or an amide bond.

  The modified polymer is liquid. One of the preferred embodiments is that the modified polymer is liquid at 5 to 60 ° C. or room temperature.

As a modified polymer, the compound represented by following formula (1) is mentioned, for example.
^{OCN-R 1 -Y 1 -R-} Y 2 -R 2 -NCO (1)
In the formula, R is polyisoprene or polybutadiene, R ¹ and R ² are each independently an organic group, Y ¹ and Y ² are each independently a urethane bond, a urea bond, an amide bond, and —N—CO—. It is at least one linking group selected from the group consisting of O—Si— (O) _n —.
The polyisoprene or polybutadiene as R is the same as the main chain of the modified polymer. The organic groups as R ¹ and R ^{2 are} as defined above. In the —N—CO—O—Si— (O) _n —, a silicon atom can be bonded to R ³ and R ^4, and R ³ and R ⁴ are each independently —OH, an alkoxy group (for example, methoxy Group, ethoxy group, etc.), phenoxy group and hydrocarbon group. The hydrocarbon group is not particularly limited, and examples thereof are the same as described above. N is 0 or 1.

  The modified polymer (modified polyisoprene or modified polybutadiene) is not particularly limited for its production. For example, a method of producing by reacting a liquid raw material polyisoprene or raw material polybutadiene (these are collectively referred to as raw material polymers) having active hydrogen groups capable of reacting with isocyanate groups at both ends, and a polyisocyanate compound. Is mentioned.

  The active hydrogen group possessed by the raw polymer can be at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a silanol group.

  The main chain of the raw material polymer (part other than the active hydrogen group) is the same as the main chain of the modified polymer. The number average molecular weight of the raw material polymer can be obtained by subtracting the amount of the reacted polyisocyanate compound from the number average molecular weight of the modified polymer. The number average molecular weight of the raw material polymer can be set to, for example, 500 to 60,000. It is the same as that of the modified polymer that the raw material polymer is liquid.

The raw polymer and the active hydrogen group can be bonded directly or via an organic group. The organic group is not particularly limited. For example, the hydrocarbon group which may have a hetero atom like an oxygen atom, a nitrogen atom, and a sulfur atom is mentioned. Examples of the hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. The hydrocarbon group may be linear or branched, and may have an unsaturated bond.
The raw material polymer is preferably polyisoprene having a hydroxyl group or polybutadiene having a hydroxyl group from the viewpoint of excellent grip performance and blowout resistance.

The polyisocyanate compound used in producing the modified polymer is not particularly limited as long as it is a compound having two or more isocyanate groups in one molecule. For example, a low molecular weight polyisocyanate compound is mentioned.
A plurality of isocyanate groups are bonded through an organic group. The organic group is not particularly limited. For example, the hydrocarbon group which may have a hetero atom like an oxygen atom, a nitrogen atom, and a sulfur atom is mentioned. Examples of the hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. The hydrocarbon group may be linear or branched, and may have an unsaturated bond.

Examples of the polyisocyanate compound include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and modified products. Specifically, for example, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), aromatic polyisocyanates such as 1,5-naphthalene diisocyanate (NDI), triphenylmethane triisocyanate; hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate methyl ( NBDI) aliphatic polyisocyanates; transcyclohexane-1,4-diisocyanate Over DOO, isophorone diisocyanate (IPDI), bis (isocyanatomethyl) cyclohexane (H ₆ XDI), alicyclic polyisocyanates such as dicyclohexylmethane diisocyanate (H ₁₂ MDI); these modified products (e.g., carbodiimide-modified products, isocyanurate Modified body, adduct modified body, biuret modified body).
Polyisocyanate compounds can be used alone or in combination of two or more.

  The reaction between the raw material polymer and the polyisocyanate compound is not particularly limited. For example, 100 parts by mass of the raw material polymer, 5 to 30 parts by mass of the polyisocyanate compound, and a tin compound such as dibutyltin dilaurate as a catalyst can be mixed and reacted under stirring at 60 to 100 ° C. . Specifically, for example, when XDI (xylylene diisocyanate, molecular weight 188, NCO = 44.68%) is used as the polyisocyanate compound, 17.5 g of this is used, and the condition is about 80 ° C. for 12 hours. It can be carried out by reacting to some extent.

  In the present invention, the amount of the modified polymer is 1 to 30 parts by mass with respect to 100 parts by mass of the diene rubber A, and is 3 to 30 parts by mass from the viewpoint of excellent grip performance and blowout resistance. It is preferably 4 to 25 parts by mass.

[Optional ingredients]
The rubber composition for tires of the present invention can further contain an additive as long as the effect and the purpose are not impaired. Examples of additives include silane coupling agents, fillers other than carbon black (for example, silica), zinc oxide (zinc white), stearic acid, anti-aging agents, processing aids, aroma oils, process oils, and terpene resins. Generally used in rubber compositions for tires such as polyisocyanate compounds other than modified polymers, polysulfide compounds [for example, cyclic polysulfides represented by the following formula (I), thermosetting resins, vulcanizing agents, vulcanization accelerators, etc. And various additives to be used.

Wherein R is a substituted or unsubstituted alkylene group having 2 to 20 carbon atoms, a substituted or unsubstituted oxyalkylene group having 2 to 20 carbon atoms or an alkylene group containing an aromatic ring, and x is an average of 2 to 6 Number, n is an integer from 1 to 20.)

<Terpene resin>
The tire rubber composition of the present invention preferably further contains a terpene resin because the lip performance of the resulting tire is more excellent. The terpene resin is preferably an aromatic-modified terpene resin (particularly having a softening point of 60 to 180 ° C.).
The amount of the terpene resin is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the diene rubber A from the viewpoint that the grip performance is superior.

<Polyisocyanate compound>
Examples of the polyisocyanate compound (excluding the modified polymer) that can be further contained in the rubber composition for tires of the present invention include the same polyisocyanate compounds used in producing the modified polymer. Among these, hexamethylene diisocyanate, diphenylmethane diisocyanate, and toluene diisocyanate are preferable because the grip performance and blowout resistance of the tire are more excellent.
The amount of the polyisocyanate compound that can be further contained in the rubber composition for tires of the present invention is 0.05 to 10 parts by mass with respect to 100 parts by mass of the diene rubber A from the viewpoint of excellent grip performance and blowout resistance. It is preferable.

[Method for producing rubber composition for tire]
The manufacturing method of the rubber composition for tires of the present invention is not particularly limited, and specific examples thereof include, for example, each component described above using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). And a kneading method.
The tire rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.
Cross-linking of polyisoprene and / or polybutadiene by the reaction between the active hydrogen group of the diene rubber a and the isocyanate group of the modified polymer can be formed on the rubber simultaneously with sulfur vulcanization. The cross-linking structure is different from the sulfur cross-linking.

  The use of the rubber composition for tires of the present invention is not particularly limited except that it is for tires. For example, it is mentioned as one of the preferable aspects used for a competition tire. Moreover, it is mentioned as one of the aspects with preferable using, for example in a tire tread part in a tire.

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire manufactured using the tire rubber composition of the present invention.
The tire rubber composition used for the pneumatic tire of the present invention is not particularly limited as long as it is a tire rubber composition of the present invention.
In the pneumatic tire of the present invention, for example, it is mentioned as one of preferable embodiments that the tire tread portion is formed of the tire rubber composition of the present invention.
In FIG. 1, the partial cross-sectional schematic of the tire showing an example of the embodiment of the pneumatic tire of this invention is shown. The pneumatic tire of the present invention is not limited to the attached drawings.

In FIG. 1, reference numeral 1 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread portion.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end of the carcass layer 4 extends from the inside of the tire to the outside around the bead core 5 and the bead filler 6. Wrapped and rolled up.
In the tire tread portion 3, a belt layer 7 is disposed outside the carcass layer 4.
Moreover, in the bead part 1, the rim cushion 8 is arrange | positioned in the part which touches a rim | limb.

  The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  Since the pneumatic tire of the present invention is excellent in grip performance and blowout resistance, it is particularly suitable for a racing tire.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

<Manufacture of rubber composition>
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below.
Specifically, first, among the components shown in Table 1 below, the components excluding sulfur and the vulcanization accelerator were mixed for 5 minutes using a 1.7 liter closed Banbury mixer, and reached 150 ± 5 ° C. Was released and cooled to room temperature to obtain a masterbatch. Furthermore, using the Banbury mixer, sulfur and a vulcanization accelerator were mixed into the obtained master batch to produce a rubber composition.
In Table 1, the values of SBR1 and SBR2 are amounts (unit: parts by mass) of SBR (oil-extended product).
A rubber composition was produced in the same manner as in Table 1 with respect to Table 2 below.

<Manufacture of pneumatic tires>
A pneumatic tire having a tire size of 195 / 55R15 was manufactured using the rubber composition manufactured as described above for the tire tread portion.

<Evaluation>
The following evaluation was performed using the rubber composition and the pneumatic tire manufactured as described above. The results are shown in Tables 1 and 2.
・ Blowout resistance The rubber composition produced as described above was vulcanized at 150 ° C. for 30 minutes, and a cylindrical test piece having a diameter of 17.8 mm and a height of 25.0 mm was manufactured for evaluation of blowout resistance. did.
Using the test piece, blowout resistance was evaluated in accordance with JIS K6265 using a Flexometer made by Goodrich. In the test method, a dynamic repetitive load is applied to the test piece, and fatigue characteristics due to heat generation inside the test piece are evaluated. Specifically, a static initial load of 55 pounds was applied to the test piece at a temperature condition of 50 ° C., and the test time until bubbles were confirmed on the cut surface of the test piece (blowout) was measured.
In Table 1, the obtained results are displayed as an index with the test time of standard example 1 being blown out as 100. In Table 2, the test time for the blowout of the standard example 2 is expressed as an index of 100. The larger this value, the better the blowout resistance.

-Grip performance Pneumatic tires manufactured as described above are assembled on rims each having a size of 15 x 6 J, with an air pressure of 200 kPa and mounted on four wheels of a four-wheeled vehicle. The lap time for each lap when the lap was run 10 laps continuously was measured, and the grip performance was evaluated by the following determination method.

The average time of 1 to 10 laps when the circuit course under dry conditions was continuously run for 10 laps was measured and evaluated according to the following criteria. In Table 1, the average time of the pneumatic tire of Standard Example 1 was used as the reference time, and in Table 2, the average time of the pneumatic tire of Standard Example 2 was used as the reference time. The higher this score, the better the grip performance.
5: The average lap time is 0.5 seconds or more faster than the reference time.
4.5: The average lap time is 0.35 seconds or more and less than 0.5 seconds faster than the reference time.
4: The average lap time is 0.2 seconds or more and less than 0.35 seconds faster than the reference time.
3.5: The average lap time is 0.1 seconds or more and less than 0.2 seconds faster than the reference time.
3: The difference between the average lap time and the reference time is within a range of less than ± 0.1 seconds.
2.5: The average lap time is 0.1 second or more and less than 0.2 seconds later than the reference time.
2: The average lap time is 0.2 seconds or more and less than 0.35 seconds later than the reference time.
1.5: The average lap time is 0.35 seconds or more and less than 0.5 seconds later than the reference time.
1: The average lap time is 0.5 seconds or more and less than 0.65 seconds later than the reference time.
0.5: The average lap time is 0.65 seconds or more later than the reference time.

Details of each component shown in Table 1 and Table 2 are as follows.
-SBR1: OH terminal modified solution polymerized styrene butadiene rubber, trade name E581 (oil-extended product: 37.5 parts by mass of oil-extended oil to 100 parts by mass of SBR), styrene content: 37% by mass, derived from butadiene Vinyl bond amount: 42%, Tg: -27 ° C., weight average molecular weight: 1,260,000, manufactured by Asahi Kasei Co., Ltd. SBR2: unmodified solution polymerized styrene butadiene rubber, trade name JSR HP755 (aromatic oil based on 100 parts by weight of SBR) 37.5 parts by weight added oil), glass transition temperature −24 ° C., weight average molecular weight 980,000, manufactured by JSR ・ Carbon black 1: Dia Black N234 manufactured by Mitsubishi Chemical Corporation, nitrogen adsorption specific surface area (N ₂ SA) = 123m ² / g
Carbon black 2: Dia Black A manufactured by Mitsubishi Chemical Corporation, nitrogen adsorption specific surface area (N ₂ SA) = 142 m ² / g
・ Zinc flower: 3 types of zinc oxide (manufactured by Shodo Chemical Industries)
・ Stearic acid: Bead stearic acid YR (manufactured by NOF Corporation)
-Anti-aging agent: 6PPD manufactured by Flexis
・ Oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator 1: Vulcanization accelerator CBS (Noxeller CZ-G, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
-Vulcanization accelerator 2: Sunseller DG, manufactured by Sanshin Chemical Industry Co., Ltd.-Terpene resin: YS resin TO-125 (aromatic modified terpene resin, softening point: 125 ° C, manufactured by Yasuhara Chemical Co., Ltd.)
・ Liquid polyisoprene: Product name Kuraray Co., Ltd. LIR-50
-Modification IR1: Polyip (Hydroxyl-terminated liquid polyisoprene, Mn 2,500, hydroxyl value 47.0) 100 parts by mass made by Idemitsu Chemical Co., Ltd. Hexamethylene diisocyanate (HDI), manufactured by Showa Chemical Co., Ltd. The same applies below. Both ends were modified with isocyanate groups by reacting them at 80 ° C. for 12 hours in the presence of dibutyltin dilaurate (0.001 parts by mass) as a catalyst using 17.5 parts by mass). Polyisoprene (liquid) was produced. The produced polyisoprene is referred to as modified IR1. The number average molecular weight of the modified IR1 was 2800.
・ Modified IR2: 100 parts by mass of LIR-403 (carboxyl-terminated liquid polyisoprene, Mn = 34,000) manufactured by Kuraray Co., Ltd., using HDI (17.5 parts by mass) as a polyisocyanate and dibutyl as a catalyst In the presence of tin dilaurate (0.001 part by mass), polyisoprene (45 parts by mass, liquid) in which both ends were modified with an isocyanate group was produced by reacting at 80 ° C. for 12 hours. The produced polyisoprene is referred to as modified IR2. The number average molecular weight of the modified IR2 was 34300.
・ Isocyanate compound: Hexamethylene diisocyanate (HDI), manufactured by Showa Chemical Co., Ltd.

As is clear from the results shown in Table 1, Comparative Examples 1 and 2 in which the amount of sulfur was simply increased as compared with Standard Example 1 were lower in grip performance than Standard Example 1. In Comparative Example 3 containing unmodified liquid polyisoprene, the blowout resistance was lowered. The comparative example 4 which does not contain the diene rubber | gum which has an active hydrogen group which can react with an isocyanate group fell blowout resistance. In Comparative Example 5 in which the amount of the diene rubber a having an active hydrogen group capable of reacting with an isocyanate group was less than 5% by mass, the blowout resistance was lowered. In Comparative Example 6 which did not contain modified polyisoprene or the like but instead contained an isocyanate compound, grip performance and blowout resistance were lowered.
On the other hand, Examples 1-5 are excellent in grip performance and blowout resistance as compared with Standard Example 1.

As is clear from the results shown in Table 2, Example 6 is superior to Standard Example 2 in grip performance and blowout resistance.
Standard Example 1 and Standard Example 2 differ in the particle size of the carbon black used. The carbon black 2 used in the standard example 2 has a smaller particle size than the carbon black 1 used in the standard example 1. As the particle size of carbon black is smaller, the rubber is more likely to generate heat, so the rubber in Standard Example 2 is more likely to generate heat than in Standard Example 1.
However, for both grip performance and blowout resistance, when comparing the degree of improvement of Example 1 and Example 6 (difference between the standard example and the example) on the basis of the standard example corresponding to each example, The degree of improvement is greater in Example 6 than in Example 1.
Therefore, even when carbon black having a smaller particle size is used in the present invention and the rubber is more likely to generate heat, the tire rubber composition of the present invention exhibits extremely excellent grip performance and blowout resistance. be able to.

1 Bead part 2 Side wall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims (7)

Liquid modified polyisoprene and / or modified polybutadiene 1 having 100 parts by weight of diene rubber A, 60 to 150 parts by weight of carbon black, and a number average molecular weight of 800 to 60,000 and both ends modified with isocyanate groups Containing 30 parts by mass,
A part or all of the diene rubber A is a diene rubber a having an active hydrogen group capable of reacting with the isocyanate group,
A rubber composition for tires, wherein the amount of the diene rubber a is 5 to 100% by mass of the amount of the diene rubber A.   The tire rubber composition according to claim 1, wherein the active hydrogen group is at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a silanol group.   The modified polyisoprene or the modified polybutadiene is obtained by reacting a liquid raw material polyisoprene or raw material polybutadiene having active hydrogen groups capable of reacting with isocyanate groups at both ends and a polyisocyanate compound. The rubber composition for tires according to 1 or 2. The tire rubber composition according to any one of claims 1 to 3, wherein the carbon black has a nitrogen adsorption specific surface area of 90 to 400 m ² / g.   The tire rubber composition according to any one of claims 1 to 4, which is used for a racing tire.   The pneumatic tire manufactured using the rubber composition for tires in any one of Claims 1-5.   The pneumatic tire according to claim 6, which is a racing tire.