JP2018039917A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve wet grip performance and its operability at a higher level than a conventional one.SOLUTION: A rubber composition for tire is formed by blending 100-250 pts.mass of silica, a low temperature plasticizer, a tackifier resin, and a silane coupling agent with respect to 100 pts.mass of a diene rubber having an average glass transition temperature of -25 to -5°C, where the silane coupling agent is formed of polysiloxane having an average composition formula represented by general formula (1): (A)(B)(C)(D)(R)SiO, and an amount of the silane coupling to be blended is 1-30 mass% with respect to the silica amount. In formula (1), A is a divalent organic group containing a sulfide group, B is a monovalent hydrocarbon group having 5 to 10 carbon numbers, C is a hydrolyzable group, D is an organic group containing a mercapto group, Ris a monovalent hydrocarbon group having 1 to 4 carbon atoms, and a to e satisfy relational expressions of 0<a<1, 0<b<1, 0<c<3, 0<d<1, 0≤e<2 and 0<2a+b+c+d+e<4.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for tires that achieves both wet grip performance and operability.

  Competition tires for running on wet surfaces on a circuit are required not only to have excellent wet grip performance but also to exhibit excellent wet grip performance immediately after the start of running. In general, in order to obtain an excellent wet grip performance, a diene rubber having a high glass transition temperature is blended with a rubber composition for a tread, or a large amount of silica is blended as a reinforcing filler. However, when a diene rubber having a high glass transition temperature is blended, the operability until the wet grip performance is exhibited is remarkably lowered. Even if a large amount of silica is blended, the wet grip performance cannot be improved if the dispersibility is poor.

  Patent Document 1 proposes a rubber composition in which silica, a silane coupling agent having a mercapto group, a plasticizer, an oil, and a resin are blended with a diene rubber in order to improve grip performance. However, the level of wet grip performance and operability that consumers demand for racing tires for running on wet surfaces on the circuit is higher and further improvements are required.

JP 2006-3254 A

  An object of the present invention is to provide a rubber composition for a tire that achieves both wet grip performance and operability at a higher level than before.

The rubber composition for a tire according to the present invention that achieves the above object has 100 to 250 parts by mass of silica, a low-temperature plasticizer, and 100 parts by mass of a diene rubber having an average glass transition temperature of -25 ° C to -5 ° C. An adhesive resin and a silane coupling agent are blended, and the silane coupling agent is composed of polysiloxane having an average composition formula represented by the following general formula (1), and the blending amount is 1 to 1 of the silica amount. It is characterized by 30% by mass.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} (1)
(In the formula (1), A is a divalent organic group containing a sulfide group, B is a monovalent hydrocarbon group having 5 to 10 carbon atoms, C is a hydrolyzable group, and D is an organic containing a mercapto group. Group R ¹ is a monovalent hydrocarbon group having 1 to 4 carbon atoms, and a to e are 0 <a <1, 0 <b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4 is satisfied.)

  The rubber composition for tires of the present invention is a silane comprising a diene rubber having an average glass transition temperature of −25 ° C. to −5 ° C., a low temperature plasticizer, an adhesive resin, silica, and a polysiloxane having a specific average composition formula. Since the coupling agent is blended, the wet grip performance and the operability can be improved to the conventional level or higher.

  The low temperature plasticizer may have a glass transition temperature of −50 ° C. to −70 ° C., and the amount of the low temperature plasticizer may be 5 to 50 parts by mass with respect to 100 parts by mass of the diene rubber.

  The pneumatic tire using the tire rubber composition of the present invention in the tread portion can achieve both wet grip performance and operability at a higher level than before, and is a competitive pneumatic tire for wet road running. It is suitable as.

  In the rubber composition for tires of the present invention, the rubber component is a diene rubber having an average glass transition temperature of -25 ° C to -5 ° C. Examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, butyl rubber, and chloroprene rubber. Styrene butadiene rubber is preferable. These diene rubbers can be used alone or as any blend.

  The average glass transition temperature of the diene rubber is -25 ° C to -5 ° C, preferably -25 ° C to -10 ° C. By setting the average glass transition temperature of the diene rubber to −25 ° C. or higher, the wet grip performance can be enhanced. By setting the average glass transition temperature of the diene rubber to −5 ° C. or less, the operability of the wet grip performance can be improved. Here, the average glass transition temperature of the diene rubber is the glass transition temperature when the diene rubber is made of one rubber, and the glass transition temperature of the blended rubber when the diene rubber is made of a blend of a plurality of rubbers. . The glass transition temperature of the diene rubber is measured by a differential scanning calorimetry (DSC) under a heating rate condition of 20 ° C./min, and is set as the temperature at the midpoint of the transition region. When the diene rubber is an oil-extended product containing oil, the glass transition temperature of the diene rubber excluding the oil is used. The average glass transition temperature of the blended rubber can also be calculated as a weighted average from the glass transition temperature of the constituent diene rubber and the respective weight ratios.

  The rubber composition for tires of the present invention improves wet grip performance by blending silica. The compounding quantity of a silica is 100-250 mass parts with respect to 100 mass parts of diene rubbers, Preferably it is 110-240 mass parts, More preferably, it is 120-230 mass parts. When the amount of silica is less than 100 parts by mass, the wet grip performance cannot be sufficiently increased. Moreover, when the compounding quantity of a silica exceeds 250 mass parts, abrasion resistance will fall.

The silica used in the present invention preferably has a nitrogen adsorption specific surface area N ₂ SA of 140 to 250 m ² / g, more preferably 150 to 230 m ² / g. By making N ₂ SA in such a range, the wet grip performance can be made excellent. The N ₂ SA of silica is measured according to JIS K6217-2.

In the rubber composition for tires of the present invention, the dispersibility of silica can be improved by blending a silane coupling agent composed of polysiloxane having an average composition formula represented by the following general formula (1). The compounding quantity of a silane coupling agent is 1-30 mass% of the amount of silica, More preferably, it is good in it being 3-15 mass%. If the amount of the silane coupling agent is less than 1% by mass, the dispersibility of silica may not be improved. When the compounding amount of the silane coupling agent exceeds 30% by mass, the rubber composition is liable to cause early vulcanization and the molding processability may be deteriorated.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} (1)
(In the formula (1), A is a divalent organic group containing a sulfide group, B is a monovalent hydrocarbon group having 5 to 10 carbon atoms, C is a hydrolyzable group, and D is an organic containing a mercapto group. Group R ¹ is a monovalent hydrocarbon group having 1 to 4 carbon atoms, and a to e are 0 <a <1, 0 <b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4 is satisfied.)

  The mercaptosilane compound having the average composition formula represented by the general formula (1) has a siloxane skeleton as its skeleton. The siloxane skeleton can be linear, branched, three-dimensional structures, or a combination thereof.

  In the general formula (1), a, b, c, and d are greater than 0. Therefore, this polysiloxane necessarily contains a divalent organic group A containing a sulfide group, a monovalent hydrocarbon group B having 5 to 10 carbon atoms, a hydrolyzable group C, and an organic group D containing a mercapto group. .

  The silane compound comprising a polysiloxane having an average composition formula represented by the general formula (1) has a divalent organic group A containing a sulfide group, thereby improving wet grip performance and operability. Make things. For this reason, the subscript a of the divalent organic group A containing a sulfide group in the general formula (1) is preferably 0.01 ≦ a ≦ 0.50.

  The divalent organic group A containing a sulfide group can be a hydrocarbon group that may have a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom.

The divalent organic group A containing a sulfide group may be a group represented by the following general formula (2) from the viewpoint of improving the dispersibility of silica and further improving processability. preferable.
_{* - (CH 2) n -S} x - (CH 2) n - * (2)
In said general formula (2), n represents the integer of 1-10, and it is preferable that it is an integer of 2-4 especially. Moreover, x represents the integer of 1-6, and it is preferable that it is an integer of 2-4 especially. Note that * indicates a binding position.

Specific examples of the group represented by the general formula (2), for _{example, * - CH 2 -S 2 -CH} 2 - *, * - C 2 H 4 -S 2 -C 2 H 4 - *, * _{-C 3 H 6 -S 2 -C 3} H 6 - *, * - C 4 H 8 -S 2 -C 4 H 8 - *, * - CH 2 -S 4 -CH 2 - *, * - C 2 H ₄ —S ₄ —C ₂ H ₄ — *, * —C ₃ H ₆ —S ₄ —C ₃ H ₆ — *, * —C ₄ H ₈ —S ₄ —C ₄ H ₈ — *, and the like. .

  The mercaptosilane compound comprising a polysiloxane having an average composition formula represented by the general formula (1) has a monovalent hydrocarbon group B having 5 to 10 carbon atoms, thereby protecting the mercapto group and the Mooney scorch time. At the same time it becomes longer, it has excellent workability by having excellent affinity with rubber. Therefore, the subscript b of the hydrocarbon group B in the general formula (1) is preferably 0.10 ≦ b ≦ 0.89. Specific examples of the hydrocarbon group B preferably include monovalent hydrocarbon groups having 6 to 10 carbon atoms, more preferably 8 to 10 carbon atoms, such as hexyl group, octyl group, and decyl group. As a result, the mercapto group can be protected, the Mooney scorch time can be lengthened, the workability can be improved, and the wet grip performance and the operability can be improved.

The silane compound composed of the polysiloxane having the average composition formula represented by the general formula (1) has a hydrolyzable group C, so that it has excellent affinity and / or reactivity with silica. The subscript c of the hydrolyzable group C in the general formula (1) is preferably 1.2 ≦ c ≦ 2.0 because the wet grip performance is better and the dispersibility of silica is better. Specific examples of the hydrolyzable group C include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group, and the like. The hydrolyzable group C is preferably a group represented by the following general formula (3) from the viewpoint of improving the dispersibility of silica and further improving processability.
* -OR ² (3)
In the general formula (3), * indicates a bonding position. R ² represents an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 6 to 10 carbon atoms (arylalkyl group), or an alkenyl group having 2 to 10 carbon atoms, It is preferable that it is a C1-C5 alkyl group.

  Specific examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, and an octadecyl group. Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group and a tolyl group. Specific examples of the aralkyl group having 6 to 10 carbon atoms include a benzyl group and a phenylethyl group. Specific examples of the alkenyl group having 2 to 10 carbon atoms include a vinyl group, a propenyl group, and a pentenyl group.

The silane compound made of polysiloxane having the average composition formula represented by the general formula (1) can interact and / or react with the diene rubber by having the organic group D containing a mercapto group. , To improve wet performance and operability. The subscript d of the organic group D containing a mercapto group is preferably 0.1 ≦ d ≦ 0.8. The organic group D containing a mercapto group is preferably a group represented by the following general formula (4) from the viewpoint of improving the dispersibility of silica and further improving processability.
_{* - (CH 2) m -SH} (4)
In said general formula (4), m represents the integer of 1-10, and it is preferable that it is an integer of 1-5 especially. In the formula, * indicates a bonding position.

Specific examples of the group represented by the general formula (4) include * —CH ₂ SH, * —C ₂ H ₄ SH, * —C ₃ H ₆ SH, * —C ₄ H ₈ SH, * —C. _{5 H 10 SH, * - C} 6 H 12 SH, * - C 7 H 14 SH, * - C 8 H 16 SH, * - C 9 H 18 SH, * - C 10 H 20 SH and the like.

In the general formula (1), R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. Examples of the hydrocarbon group R ¹ include a methyl group, an ethyl group, a propyl group, and a butyl group.

  In the general formula (1), a to e are 0 <a <1, 0 <b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4. Satisfy the formula.

  The rubber composition for tires of the present invention can improve wet grip performance and improve the operability by blending a low temperature plasticizer. The blending amount of the low temperature plasticizer is not particularly limited, but is preferably 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, and more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the diene rubber. Good part. By setting the blending amount of the low temperature plasticizer within such a range, the wet grip performance and the operability can be improved.

  The glass transition temperature of the low-temperature plasticizer is preferably −50 ° C. to −70 ° C., more preferably −55 ° C. to −70 ° C. By setting the glass transition temperature of the low-temperature plasticizer within such a range, the wet grip performance and the operability thereof can be improved. The glass transition temperature of the low temperature plasticizer can be measured in the same manner as the glass transition temperature of the diene rubber.

  Examples of the low temperature plasticizer include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate ( DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP) ), Triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP) and the like, among others, DOS, TOP Is preferred.

  The rubber composition for tires of the present invention can improve wet grip performance by blending an adhesive resin. The compounding amount of the adhesive resin is not particularly limited, but is preferably 5 to 50 parts by mass, more preferably 10 to 60 parts by mass, and more preferably 15 to 50 parts by mass with respect to 100 parts by mass of the diene rubber. It is good to be. By setting the blending amount of the adhesive resin within such a range, the wet grip performance can be further improved.

  Examples of the adhesive resin include petroleum resins and aromatic resins. The petroleum-based resin is an aromatic hydrocarbon resin or a saturated or unsaturated aliphatic hydrocarbon resin produced by polymerizing components obtained by subjecting crude oil to treatment such as distillation, decomposition, and reforming. Examples of petroleum resins include C5 petroleum resins (aliphatic petroleum resins obtained by polymerizing fractions such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9 petroleum resins (α-methylstyrene, o -Aromatic petroleum resin obtained by polymerizing fractions such as vinyltoluene, m-vinyltoluene, p-vinyltoluene), C5C9 copolymerized petroleum resin, and the like.

  The aromatic resin is a polymer having at least one segment composed of an aromatic hydrocarbon, such as coumarone resin, phenol resin, alkylphenol resin, terpene resin, rosin resin, novolac resin, resole resin, etc. Can give. Of these, aromatic modified terpene resins are preferred. These resins can be used alone or as a blend. The C9 petroleum resin described above is an aromatic hydrocarbon resin, but is classified as a petroleum resin in this specification.

  The softening point of the adhesive resin is not particularly limited, but is preferably 130 to 200 ° C, more preferably 135 to 180 ° C. By setting the softening point of the resin within such a range, the wet grip performance can be improved. In this specification, the softening point of the resin is measured according to JIS K6220-1 (ring and ball method).

  In the present invention, other compounding agents other than those described above can be added. Other compounding agents are generally pneumatic, such as reinforcing fillers other than silica, vulcanization or crosslinking agents, vulcanization accelerators, anti-aging agents, liquid polymers, thermosetting resins, thermoplastic resins, etc. Various compounding agents used for a tire can be illustrated. The compounding amounts of these compounding agents can be conventional conventional compounding amounts as long as they do not contradict the purpose of the present invention. Moreover, as a kneading machine, a normal rubber kneading machine, for example, a Banbury mixer, a kneader, a roll or the like can be used.

  Examples of other reinforcing fillers include carbon black, clay, mica, talc, calcium carbonate, aluminum hydroxide, aluminum oxide, and titanium oxide. Of these, silica is preferable.

  The tire rubber composition of the present invention is preferably used for a pneumatic tire for competition running on a wet road surface, and can achieve both wet grip performance and operability at a higher level than ever before.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  Thirteen types of tire rubber compositions (Examples 1 to 6, Standard Examples and Comparative Examples 1 to 6) having the composition shown in Table 1 were mixed with components other than sulfur and a vulcanization accelerator using a 16 L Banbury mixer. The mixture was kneaded for minutes, and the master batch was discharged at a temperature of 160 ° C. and cooled at room temperature. This master batch was subjected to a 16 L Banbury mixer, and sulfur and a vulcanization accelerator were added and mixed to prepare a rubber composition for a tire. In addition, in the column of diene rubber-1 to -4 in Table 1, in addition to the blending amount of the product, the blending amount of the net diene rubber excluding the oil-extended component is shown in parentheses. Further, the average glass transition temperature of the blend, excluding the oil-extended components of these diene rubbers, is shown in the column of “Diene rubber Tg” in Table 1.

  A pneumatic tire for a race having a tire size of 195 / 55R15 in which a tire tread portion was constituted by the obtained 13 kinds of rubber compositions was manufactured. Each of the resulting pneumatic tires is rim-assembled at a rim size of 15 x 6 J at an air pressure of 150 kPa and mounted on a competition vehicle. Each lap when the test driver runs 10 laps on a circuit course under wet conditions (about 2 km per lap) The lap time was measured, the wet grip performance and the operability of the wet grip performance were evaluated by the following judgment method, and the obtained results are shown in Table 1.

Wet grip performance Measures the best time when running a circuit course under wet conditions for 10 consecutive laps, calculates the reciprocal of each, and uses the standard example value as 100 as an index in the “Wet performance” column of Table 1. Described. A larger wet performance index means faster best time and better wet grip performance.

Wet grip performance operability We measured the best times of 1 to 3 laps when running a circuit course under wet conditions for 10 laps continuously, calculated the reciprocals of each, and set the value of the standard example as 100 as an index. In the column “above-mentioned operability”. A larger index of “above-mentioned operability” means that the best time at the start of traveling is faster and the operability of wet grip performance is better.

In addition, the kind of raw material used in Table 1 is shown below.
-Diene rubber-1: styrene butadiene rubber, E581 manufactured by Asahi Kasei Co., Ltd., an oil-extended product in which 37.5 parts by mass of an oil component is blended with 100 parts by mass of styrene butadiene rubber, and a glass transition temperature is -30 ° C.
Diene rubber-2: styrene butadiene rubber, SE-6411 manufactured by Sumitomo Chemical Co., Ltd., oil-extended product in which 20 parts by mass of oil component is blended with 100 parts by mass of styrene butadiene rubber, glass transition temperature is -20 ° C
Diene rubber-3: Styrene butadiene rubber, SE-6233 manufactured by Sumitomo Chemical Co., Ltd., oil-extended product in which 37.5 parts by mass of oil component is blended with 100 parts by mass of styrene butadiene rubber, glass transition temperature is -10 ° C
Silica: 7000GR manufactured by Evonik, nitrogen adsorption specific surface area of 165 m ² / g
・ Carbon black: Tokai Carbon Co., Ltd. Seast 9M
-Low temperature plasticizer-1: TOP manufactured by Daihachi Chemical Co., Ltd., glass transition temperature -70 ° C
・ Low temperature plasticizer-2: DOP manufactured by Daihachi Chemical Co., Ltd., glass transition temperature of −50 ° C.
Coupling agent-1: Average composition formula (—C ₃ H ₆ —S ₄ —C ₃ H ₆ —) _0.071 (—C ₈ H ₁₇ ) _0.571 (—OC ₂ H ₅ ) _1.50 (—C ₃ H ₆ SH ) Sulfur-containing silane coupling agent represented by _0.286 SiO _0.75 , 9511D manufactured by Shin-Etsu Chemical Co., Ltd.
Coupling agent-2: sulfur-containing silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide, Si69 manufactured by Evonik
-Adhesive resin: aromatic modified terpene resin, YS resin TO125 manufactured by Yasuhara Chemical Co., Ltd., softening point 125 ° C
・ Stearic acid: NOF beads stearic acid YR
・ Zinc flower: 3 types of zinc oxide manufactured by Shodo Chemical Co., Ltd. ・ Anti-aging agent: Santoflex 6PPD manufactured by Flexis
・ Process oil: Extract No. 4 S manufactured by Showa Shell Sekiyu KK
・ Sulfur: Fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd. ・ Vulcanization accelerator 1: Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator 2: Noxeller D manufactured by Ouchi Shinsei Chemical Co., Ltd.

  As is clear from Table 1, it was confirmed that the rubber compositions for tires of Examples 1 to 7 were excellent in wet grip performance and operability.

  The rubber composition of Comparative Example 1 improves the wet grip performance by setting the average glass transition temperature of the diene rubber rubber to −15 ° C. with respect to the rubber composition of the standard example. The operability of grip performance deteriorates.

  Since the rubber composition of Comparative Example 2 has less than 100 parts by mass of silica, the wet grip performance is deteriorated.

  Since the rubber composition of Comparative Example 3 was blended with the coupling agent-2 not represented by the average composition formula represented by the formula (1) instead of the coupling agent-1, the wet grip performance and the operability thereof were Getting worse.

  Since the rubber composition of Comparative Example 4 does not contain an adhesive resin, wet grip performance and operability thereof are deteriorated.

  In the rubber composition of Comparative Example 5, since the average glass transition temperature of the diene rubber rubber is lower than −25 ° C., the wet grip performance is deteriorated.

Claims (4)

100 parts by mass of diene rubber having an average glass transition temperature of −25 ° C. to −5 ° C., 100 to 250 parts by mass of silica, a low temperature plasticizer, an adhesive resin and a silane coupling agent, A rubber composition for tires, wherein the coupling agent is made of polysiloxane having an average composition formula represented by the following general formula (1), and the blending amount thereof is 1 to 30% by mass of the silica amount.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} (1)
(In the formula (1), A is a divalent organic group containing a sulfide group, B is a monovalent hydrocarbon group having 5 to 10 carbon atoms, C is a hydrolyzable group, and D is an organic containing a mercapto group. Group R ¹ is a monovalent hydrocarbon group having 1 to 4 carbon atoms, and a to e are 0 <a <1, 0 <b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4 is satisfied.)   The rubber composition for tires according to claim 1, wherein the low temperature plasticizer has a glass transition temperature of -50 ° C to -70 ° C.   The tire rubber composition according to claim 1 or 2, wherein the amount of the low-temperature plasticizer is 5 to 50 parts by mass with respect to 100 parts by mass of the diene rubber.   The pneumatic tire which has a tread part which consists of a rubber composition for tires in any one of Claims 1-3.