JP2013224356A - Rubber composition for tire tread and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for tire treads capable of manufacturing a tire excellent in workability and rolling resistance, and a pneumatic tire using the same.SOLUTION: A rubber composition for tire treads includes a diene rubber, silica, a silane coupling agent and a plasticizer. A terminal-modified styrene-butadiene copolymer rubber produced by solution polymerization accounts for ≥30 mass% of the diene rubber. The plasticizer is a polymer or copolymer such as a polyether, and is an organic polymer containing a crosslinkable silyl group, which has at least one crosslinkable silyl group per molecule. The content of the silica is 5-150 pts.mass based on 100 pts.mass of the diene rubber. The content of the silane coupling agent is 0.5-20 mass% based on the mass of the silica. A content of the plasticizer is 1-20 pts.mass based on 100 pts.mass of the diene rubber.

Description

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

  It is known to use a rubber composition containing silica as a technique for improving the wet performance of a tire and reducing rolling resistance. From the viewpoint of further improving the performance, a rubber composition using a silane coupling agent together with silica. Things are also known.

  For example, in Patent Document 1, the present applicant states that “(A) 100 parts by weight of at least one rubber selected from natural rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, polyisoprene rubber and butyl rubber” (B) 5 to 100 parts by weight of carbon black and / or silica, and (C) a tread for a tire comprising 2 to 100 parts by weight of a compound having a main chain of polyisobutylene and having at least one alkoxysilyl group at the terminal. "A rubber composition" has been proposed ([Claim 2]), and it is further described that a predetermined amount of a sulfur-containing silane coupling agent can be blended ([Claim 3]).

  Further, in Patent Document 2, the present applicant states that “a tire tread rubber composition in which a diene rubber, silica and two or more silane coupling agents are blended, and at least one silane coupling agent”. Is a rubber composition for tire treads, wherein the main chain skeleton is polyethylene glycol or polypropylene glycol and has an alkoxysilyl group at the terminal. "[Claim 1]).

JP-A-11-91310 Japanese Patent Laid-Open No. 11-181160

  However, when the inventor has further studied the rubber compositions described in Patent Documents 1 and 2, depending on the type of diene rubber to be blended, the viscosity of the rubber composition when unvulcanized increases and processed. It became clear that the effect of improving tire rolling resistance could not be sufficiently achieved.

  Then, an object of this invention is to provide the rubber composition for tire treads which can produce the tire which was excellent in workability and excellent in rolling resistance, and a pneumatic tire using the same.

As a result of intensive studies to solve the above problems, the present inventor has formulated a polymer having a predetermined main chain skeleton and a crosslinkable silyl group together with a specific styrene-butadiene copolymer rubber. The inventors have found that a tire excellent in workability and rolling resistance can be produced, and completed the present invention.
That is, the present invention provides the following (1) to (11).

(1) containing a diene rubber, silica, a silane coupling agent and a plasticizer,
30% by mass or more of the diene rubber is a solution-polymerized styrene-butadiene copolymer rubber having a terminal modified,
The plasticizer is a polyether-based, polyester-based, polyolefin-based, polycarbonate-based, aliphatic-based, saturated hydrocarbon-based, acrylic-based or plant-derived polymer or copolymer, and has a crosslinkable silyl group. A crosslinkable silyl group-containing organic polymer having at least one molecule per molecule;
The content of the silica is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber,
Content of the said silane coupling agent is 0.5-20 mass% with respect to the mass of the said silica,
A rubber composition for a tire tread, wherein the content of the plasticizer is 1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber.

  (2) The rubber composition for a tire tread according to (1), wherein the solution-polymerized styrene-butadiene copolymer rubber has a styrene content of 38 to 48% by mass and a vinyl bond content of 20 to 45 mol%. .

  (3) The rubber composition for a tire tread according to the above (1) or (2), wherein the solution-polymerized styrene-butadiene copolymer rubber has a weight average molecular weight of 600,000 to 1,500,000.

  (4) The terminal-modified group of the solution-polymerized styrene-butadiene copolymer rubber is at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an alkoxy group, an epoxy group, a carbonyl group, and a carboxy group. The rubber composition for a tire tread according to any one of the above (1) to (3).

  (5) The rubber composition for a tire tread according to any one of (1) to (4), wherein the crosslinkable silyl group-containing organic polymer contains an alkylene oxide monomer unit in the main chain.

(6) The rubber composition for a tire tread according to (5), wherein the alkylene oxide monomer unit is a propylene oxide (—OCH (CH ₃ ) CH ₂ —) monomer unit.

(7) The rubber composition for a tire tread according to (6), wherein the crosslinkable silyl group-containing organic polymer is represented by the following formula (I) or (II).

(In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkylene group having 1 to 30 carbon atoms, a Represents an integer of 1 to 3, and n represents an integer of 2 to 450. When a is 2 or 3, a plurality of R ^{1 s} may be the same or different, and when a is 1, A plurality of R ¹ may be the same or different.)

  (8) The tire tread according to any one of (1) to (7), wherein the main chain of the crosslinkable silyl group-containing organic polymer and the crosslinkable silyl group are bonded via at least a urethane bond. Rubber composition.

  (9) The rubber composition for a tire tread according to any one of (1) to (8), wherein the crosslinkable silyl group of the crosslinkable silyl group-containing organic polymer is an alkoxysilyl group.

(10) The rubber composition for tire tread according to any one of (1) to (9), wherein the silica has a nitrogen adsorption specific surface area of 150 to 300 m ² / g.

  (11) A pneumatic tire using the tire tread rubber composition according to any one of (1) to (10) as a tire tread.

  As described below, according to the present invention, it is possible to provide a rubber composition for a tire tread capable of producing a tire having excellent workability and excellent rolling resistance, and a pneumatic tire using the rubber composition.

It is a typical fragmentary sectional view of the tire showing an example of the embodiment of the pneumatic tire of the present invention.

[Rubber composition for tire]
The rubber composition for tire treads of the present invention (hereinafter also simply referred to as “the rubber composition of the present invention”) contains a diene rubber, silica, a silane coupling agent, and a plasticizer. It is a solution-polymerized styrene-butadiene copolymer rubber having a terminal content modified by mass% or more, and the plasticizer is a polyether, polyester, polyolefin, polycarbonate, aliphatic, saturated hydrocarbon, acrylic or plant. It is a polymer or copolymer of a derived type, and is a crosslinkable silyl group-containing organic polymer having at least one crosslinkable silyl group per molecule, and the silica content is 100 parts by mass of the diene rubber. 5 to 150 parts by mass with respect to the mass of the silica, and the content of the silane coupling agent is 0.5 to 20% by mass with respect to the mass of the silica. The content of the plasticizer is a rubber composition for a tire tread is 1 to 20 parts by weight with respect to the diene rubber 100 parts by weight.
Below, each component which the rubber composition of this invention contains is demonstrated in detail.

<Diene rubber>
The diene rubber contained in the rubber composition of the present invention is a solution-polymerized styrene-butadiene copolymer rubber (hereinafter also referred to as “modified S-SBR”) in which 30% by mass or more thereof is terminal-modified.
By blending the modified S-SBR, the processability of the rubber composition is improved, and a tire excellent in rolling resistance can be produced. This is presumably because the dispersibility of silica in the rubber composition was improved by the interaction between the terminal modified group of the modified S-SBR and a silanol group present on the surface of the silica particles described later.
In addition, the content (ratio) of the modified S-SBR is preferably 30 to 60% by mass of the diene rubber because a tire excellent in wet performance and rolling resistance can be produced. More preferably, it is -55 mass%.

In the present invention, the styrene content of the modified S-SBR is preferably 38 to 48% by mass, and 40 to 48% by mass because the processability of the rubber composition becomes better. Is more preferable.
Further, the vinyl bond amount of the modified S-SBR is preferably 20 to 45 mol%, because the processability of the rubber composition becomes better and the dispersibility of silica is improved, and preferably 25 to 35 mol%. It is more preferable that Here, the amount of vinyl bonds refers to the ratio of 1,2-vinyl bonds among cis-1,4-bonds, trans-1,4-bonds and 1,2-vinyl bonds, which are conjugated dienes. Say.

In the present invention, the weight average molecular weight (Mw) of the modified S-SBR is preferably 600,000 to 1,500,000 because the processability of the rubber composition becomes better. More preferably, it is 800,000 to 1,200,000.
Here, the weight average molecular weight (Mw) is measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

Specific examples of the functional group (terminal modified group) used for terminal modification of the modified S-SBR include a hydroxyl group, an amino group, an alkoxy group, an epoxy group, a carbonyl group, and a carboxy group.
Of these, a hydroxyl group is preferred because the processability of the rubber composition is further improved.

In the present invention, when a diene rubber other than the above S-SBR is contained, the diene rubber is not particularly limited as long as it has a double bond in the main chain. Specific examples thereof include natural rubber. (NR), isoprene rubber (IR), butadiene rubber (BR), emulsion polymerized styrene-butadiene rubber (E-SBR), (unmodified) solution polymerized styrene-butadiene rubber (S-SBR), chloroprene rubber (CR) , Acrylonitrile butadiene rubber (NBR), ethylene-propylene-diene copolymer rubber (EPDM), styrene-isoprene rubber, isoprene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, etc., and these are used alone. Or two or more of them may be used in combination.
Among these, it is preferable to use E-SBR, S-SBR, NR, and BR because the processability of the rubber composition becomes better and a tire having excellent wear resistance can be produced.

<Silica>
The silica contained in the rubber composition of the present invention is not particularly limited, and any conventionally known silica compounded in the rubber composition for uses such as tires can be used.
Specific examples of the silica include wet silica, dry silica, fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, colloidal silica, and the like, and these may be used alone. In addition, two or more kinds may be used in combination.

In the present invention, the silica has a good wet performance and can produce a tire excellent in rolling resistance, so that the nitrogen adsorption specific surface area (N ₂ SA) is 150 to 300 m ² / g. Is more preferable, and it is more preferable that it is 160-270 m < ² > / g.
Here, N ₂ SA is a surrogate property of the surface area that silica can use for adsorption with rubber molecules, and the amount of nitrogen adsorbed on the silica surface is determined according to JIS K6217-2: 2001 “Part 2: Determination of specific surface area— It is a value measured according to the “nitrogen adsorption method—single point method”.

  Moreover, in this invention, content of the said silica is 5-150 mass parts with respect to 100 mass parts of said diene rubbers, and it is preferable that it is 30-120 mass parts.

<Silane coupling agent>
The silane coupling agent contained in the rubber composition of the present invention is not particularly limited, and any conventionally known silane coupling agent blended in the rubber composition for uses such as tires can be used.
As the silane coupling agent, a sulfur-containing silane coupling agent having a mercapto group is preferably used. Specific examples thereof include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and trimethoxysilylpropyl. -Mercaptobenzothiazole tetrasulfide etc. are mentioned, These may be used individually by 1 type and may use 2 or more types together.

  In this invention, content of the said silane coupling agent is 0.5-20 mass% with respect to the mass of the said silica, and it is preferable that it is 1-15 mass%.

<Plasticizer>
The plasticizer contained in the rubber composition of the present invention is a polyether-based, polyester-based, polyolefin-based, polycarbonate-based, aliphatic-based, saturated hydrocarbon-based, acrylic-based or plant-based polymer or copolymer. And a crosslinkable silyl group-containing organic polymer having at least one crosslinkable silyl group per molecule.

Here, examples of the polyether polymer or copolymer include polyethylene glycol, polypropylene glycol (PPG), polypropylene triol, ethylene oxide / propylene oxide copolymer, polytetramethylene ether glycol (PTMEG), and sorbitol. Based polyols and the like.
Examples of the polyester-based polymer or copolymer include low-molecular polyhydric alcohols (for example, ethylene glycol, diethylene glycol, propylene glycol) and polybasic carboxylic acids (for example, adipic acid, sebacic acid, Condensates with terephthalic acid, isophthalic acid and the like) (condensed polyester polyols); lactone polyols, and the like.
Examples of the polyolefin-based polymer or copolymer include polyethylene, polypropylene, ethylene-propylene copolymer (EPR, EPDM), polybutylene, polyisobutylene, and hydrogenated polybutadiene.
Examples of the polycarbonate-based polymer or copolymer include esters of polyol compounds (for example, 1,6-hexanediol, 1,4-butanediol, 1,5-pentanediol, etc.) and dialkyl carbonate. Examples thereof include those obtained by exchange reaction.
Examples of the acrylic polymer or copolymer include acrylic polyols; homopolymers of acrylates such as acrylates, methyl acrylates, ethyl acrylates, butyl acrylates, 2-ethylhexyl acrylates; acrylates combining two or more of these acrylates. Copolymer; and the like.
Examples of plant-derived polymers or copolymers include vegetable oils such as castor oil and soybean oil; various elastomers derived from polyester polyols modified from polylactic acid, and the like.

  Among these, the crosslinkable silyl group-containing organic polymer is preferably a polyether polymer or copolymer containing an alkylene oxide monomer unit in the main chain, and the proportion of the monomer unit is More than 50% by mass is more preferable, and 70% by mass or more is still more preferable.

Moreover, as said alkylene oxide monomer unit, specifically, for example, —CH ₂ CH ₂ O—, —CH ₂ CH (CH ₃ ) O—, —CH ₂ CH (C ₂ H ₅ ) O— _{, -CH (CH 3) CH 2} O -, - CH (C 2 H 5) CH 2 O -, - expressed CH ₂ CH ₂ CH ₂ O- or -CH ₂ CH ₂ CH ₂ CH ₂ O- in A repeating unit etc. are mentioned, It may consist only of 1 type of these repeating units, and may consist of 2 or more types.
Among these, it is a propylene oxide (—OCH (CH ₃ ) CH ₂ —) monomer unit because the processability of the rubber composition becomes better and a tire excellent in rolling resistance can be produced. Is preferred.

On the other hand, the crosslinkable silyl group of the crosslinkable silyl group-containing organic polymer has 1 to 3 hydroxy groups and / or hydrolyzable groups bonded to a silicon atom, and in the presence of moisture or a crosslinking agent, It is a silicon-containing group that can be crosslinked by causing a condensation reaction by using a catalyst or the like as necessary to form a siloxane bond.
Examples of the crosslinkable silyl group include an alkoxysilyl group, an alkenyloxysilyl group, an acyloxysilyl group, an aminosilyl group, an aminooxysilyl group, an oximesilyl group, an amidosilyl group, and the like.
Among these, an alkoxysilyl group is preferred because the processability of the rubber composition becomes better and a tire excellent in rolling resistance can be produced. Specifically, in the following formula (i) The alkoxysilyl group is more preferably represented by (di or tri) methoxysilyl group or (di or tri) ethoxysilyl group.

(In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, a represents an integer of 1 to 3. a is 2 or 3) In this case, the plurality of R ¹ may be the same or different, and when a is 1, the plurality of R ¹ may be the same or different.)

  Moreover, it is preferable to have the said crosslinkable silyl group in the terminal of a principal chain, and it is more preferable to have in both terminal.

In the present invention, the main chain of the crosslinkable silyl group-containing organic polymer (for example, the alkylene oxide monomer unit) and the crosslinkable silyl group, because a tire excellent in rolling resistance can be produced. Are preferably bonded via at least a urethane bond. This is presumably because the increase in the viscosity of the rubber composition was suppressed by the interaction between the urethane bond and the silanol group present on the surface of the silica particles.
Here, “bonded via at least a urethane bond” means, for example, an oxygen atom at a terminal of the alkylene oxide monomer unit (for example, propylene oxide) constituting the main chain and a silicon atom of the crosslinkable silyl group. Is in a state of being bonded by a covalent bond including a urethane bond.

  Specific examples of such crosslinkable silyl group-containing organic polymers include polymers represented by the following formula (I) or (II).

In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkylene group having 1 to 30 carbon atoms, and a represents Represents an integer of 1 to 3, and n represents an integer of 2 to 450. When a is 2 or 3, the plurality of R ¹ may be the same or different, and when a is 1, the plurality of R ¹ may be the same or different.
Here, R ³ is preferably an alkylene group having 2 to 20 carbon atoms, specifically, for example, specifically, for example, ethylene group, 1,3-propylene group, 2,2-dimethyl group. Propane-1,3-diyl group, 1,4-butylene group, 1,5-pentylene group, 1,6-hexylene group, 1,7-heptylene group, 1,8-octylene group, 1,9-nonylene group 1,10-decylene group, 1,11-undecylene group, 1,12-dodecylene group, 2,4-diethylpentane-1,5-diyl group, 3-methylpentane-1,5-diyl group and other alkylene Group: vinylene group; divalent alicyclic hydrocarbon group such as 1,4-cyclohexylene group; 1,4-phenylene group, 1,2-phenylene group, 1,3-phenylene group, 1,3- Divalent aromatic compounds such as phenylenebis (methylene) groups Family hydrocarbon group; and the like.
Moreover, it is preferable that n is an integer of 20-400.

  In this invention, content of the said plasticizer is 1-20 mass parts with respect to 100 mass parts of said diene rubbers, and it is preferable that it is 3-15 mass parts.

  In addition to the components described above, the rubber composition of the present invention includes fillers other than silica (for example, carbon black), vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, zinc oxide, oil, anti-aging agents, Various additives generally used in tire rubber compositions such as plasticizers other than the crosslinkable silyl group-containing organic polymer can be blended. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

The method for producing the rubber composition of the present invention is not particularly limited, and examples thereof include a method of kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). It is done.
The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

〔tire〕
The pneumatic tire of the present invention (hereinafter also simply referred to as “the tire of the present invention”) is a pneumatic tire using the rubber composition of the present invention described above.
FIG. 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention, but the tire of the present invention is not limited to the embodiment shown in FIG.

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 3, a belt layer 7 is disposed over the circumference of the tire on the outside of 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 tire of the present invention is vulcanized or cured at a temperature corresponding to, for example, the diene rubber, vulcanizing agent or crosslinking agent, vulcanization accelerator or crosslinking accelerator contained in the rubber composition of the present invention, and the blending ratio thereof. It can manufacture by bridge | crosslinking and forming a tread part, a side wall part, etc.

  Hereinafter, the present invention will be specifically described with reference to examples. The present invention is not limited to these.

(Examples 1-11 and Comparative Examples 1-3)
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below.
Specifically, when the components shown in Table 1 below, excluding sulfur and the vulcanization accelerator, were kneaded for 5 minutes with a 1.7 liter closed Banbury mixer and reached 150 ± 5 ° C. To obtain a master batch.
Next, sulfur and a vulcanization accelerator were kneaded with an open roll in the obtained master batch to obtain a rubber composition.

<Mooney viscosity (index of workability)>
For the prepared rubber composition (unvulcanized), Mooney was used in accordance with JIS K6300-1: 2001, using an L-shaped rotor, with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100 ° C. The viscosity was measured.
The measured values are represented by an index with the value of Comparative Example 1 being 100, and are shown in Table 1 below. A smaller index means a lower viscosity and better workability.

<Mooney scorch (index for scorch)>
About the prepared rubber composition (unvulcanized), scorch time was measured according to JIS K6300-1: 2001 under the same measurement conditions as Mooney viscosity.
The measured value was expressed as an index with the value of Comparative Example 3 being 100, and is shown in Table 1 below. The larger the index, the longer the scorch time and the better the scorch property.

<Tan δ (60 ° C.) (index of rolling resistance)>
About the vulcanized rubber sheet produced by the measurement of hardness, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho), initial strain 10%, amplitude ± 2%, frequency 20 Hz, temperature 60 Tan δ under the condition of ° C. was measured.
The obtained results were expressed as an index with the value of Comparative Example 1 being 100, and are shown in Table 1 below. The smaller the index, the smaller the tan δ and the better (smaller) the rolling resistance.

The following components were used as the components in Table 1.
・ Natural rubber: RSS # 1
E-SBR: emulsion polymerization SBR [Nipol 1712 (oil-extended product containing 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR), styrene content: 24% by mass, vinyl bond content: 18.9 mol%, Weight average molecular weight: 570,000, manufactured by Nippon Zeon Co., Ltd.]
Modified S-SBR1: hydroxyl group-modified solution polymerization SBR [E581 (oil-extended product containing 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR), styrene content: 40% by mass, vinyl bond content: 44 mol%, Weight average molecular weight: 1,260,000, manufactured by Asahi Kasei Corporation
Modified S-SBR2: hydroxyl group-modified solution polymerization SBR [NS616 (non-oil extended), styrene content: 23 mass%, vinyl bond content: 70 mol%, weight average molecular weight: 490,000, manufactured by Nippon Zeon Co., Ltd.]
S-SBR: Unmodified solution polymerization SBR [SLR6430 (oil-extended product containing 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR), styrene content: 28% by mass, vinyl bond content: 70 mol%, weight (Average molecular weight: 1,010,000, manufactured by Dow Chemical Company)

Silica: Zeosil 1165MP (N ₂ SA: 165 m ² / g, manufactured by Rhodia)
Carbon black: Seast 6 (N ₂ SA: 119 m ² / g, manufactured by Tokai Carbon Co., Ltd.)
Silane coupling agent: Si363 (Evonik Degussa)
Polypropylene glycol: PREMINOL S4012 (number average molecular weight: 10,000, manufactured by Asahi Glass Co., Ltd.)

Crosslinkable silyl group-containing organic polymer 1: polyether polymer [MS polymer represented by the following formula (1) S810 (main chain: propylene oxide monomer unit, crosslinkable silyl group: dimethoxysilyl group (both Terminal), weight average molecular weight: 35,000, urethane bond: none, manufactured by Kaneka Corporation)]

Crosslinkable silyl group-containing organic polymer 2: Polypropylene glycol (PREMINOL S4012, weight average molecular weight: 10,000, manufactured by Asahi Glass Co., Ltd.) and γ-isocyanatopropyltriethoxysilane (A-1310, manufactured by Momentive Performance Materials Co., Ltd.) ) 5 g and a polyether polymer represented by the following formula (2) synthesized by stirring at 80 ° C. for 20 hours under a nitrogen atmosphere (main chain: propylene oxide monomer unit, crosslinkable silyl group: tri (Ethoxysilyl group (both ends), weight average molecular weight: 45,000, urethane bond: yes)

  Crosslinkable silyl group-containing organic polymer 3: polyether polymer (Exester ES-S2420, weight average molecular weight: 24000, manufactured by Asahi Glass Co., Ltd.)

-Crosslinkable silyl group-containing organic polymer 4: Polyester polymer synthesized by the following method (Synthesis method)
Polymerization of propylene oxide was carried out using dehydrated polyoxypropylene diol (linear, weight average molecular weight: about 3000, number of hydroxy groups per molecule: 2) as an initiator, and hydroxyl-terminated polypropylene oxide (weight average molecular weight: about 20000). )
Subsequently, allyl chloride is further added to the hydroxyl group of the hydroxyl group-terminated polypropylene oxide to convert the terminal hydroxyl group into an allyl group, and a bifunctional allyl polypropylene oxide having a terminal allyl group (weight average molecular weight: about 20,000). )
With respect to 100 parts by mass of the obtained bifunctional allylpolypropylene oxide, 150 ppm of an isopropanol solution having a platinum content of 3% by mass of a platinum vinylsiloxane complex as a catalyst and a compound represented by HSi (OCH ₃ ) ₃ at 90 ° C. for 2 hours By reacting, a polyester polymer having a trimethoxysilyl group (weight average molecular weight: 20000, urethane bond: none) was obtained.

Crosslinkable silyl group-containing organic polymer 5: polycarbonate polymer synthesized by the following method (synthesis method)
236 g of polycarbonate diol (Duranol T5652, weight average molecular weight: 2000, hydroxyl value: 56, manufactured by Asahi Kasei Chemicals) and 61 g of 3-isocyanatopropyltriethoxysilane (A-1310, manufactured by Momentive Performance Materials Japan GK) Were put into a three-necked flask and stirred at 80 ° C. for 6 hours to obtain a polycarbonate-based polymer having a triethoxysilyl group (weight average molecular weight: 2000, urethane bond: present).

-Crosslinkable silyl group-containing organic polymer 6: Aliphatic polymer synthesized by the following method (Synthesis method)
Hydroxyl-terminated liquid polyisoprene (Poly ip, weight average molecular weight: 2500, hydroxyl value: 46.6, manufactured by Idemitsu Kosan Co., Ltd.) 120 g, 3-isocyanatopropyltriethoxysilane (A-1310, Momentive Performance Materials Japan) 24.7 g) (manufactured by Godo Kaisha) was put into a three-necked flask and stirred at 80 ° C. for 8 hours to obtain an aliphatic polymer having a triethoxysilyl group (weight average molecular weight: 2500, urethane bond: present).

Crosslinkable silyl group-containing organic polymer 7: saturated hydrocarbon polymer (Epion EP-505s, weight average molecular weight: 20000, urethane bond: none, manufactured by Kaneka Chemical Co., Ltd.)
Crosslinkable silyl group-containing organic polymer 8: Acrylic polymer (US-6110, weight average molecular weight: 3200, urethane bond: none, manufactured by Toagosei Co., Ltd.)

・ Zinc oxide: 3 kinds of zinc white (made by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
Anti-aging agent: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (Santflex 6PPD, manufactured by Flexis)
Aroma oil: Extract No. 4 S (manufactured by Showa Shell Sekiyu KK)
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator 1: N-cyclohexyl-2-benzothiazolylsulfenamide (Noxeller CZ-G, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: 1,3-diphenylguanidine (Soccinol DG, manufactured by Sumitomo Chemical Co., Ltd.)

From the results shown in Table 1, it can be seen that the rubber composition of Comparative Example 1 prepared by blending the terminal-unmodified solution-polymerized SBR is inferior in workability due to its high viscosity and inferior in rolling resistance. It was.
Further, even when an appropriate amount of the terminal-modified solution-polymerized SBR is blended, the rubber composition of Comparative Example 2 blended with polypropylene glycol as a plasticizer has improved processability than the rubber composition of Comparative Example 1. However, it was found that the rolling resistance was inferior.
Similarly, even when a suitable amount of terminal-modified solution-polymerized SBR is blended, the rubber composition of Comparative Example 3 prepared by blending a large amount of a crosslinkable silyl group-containing organic polymer as a plasticizer is a comparative example. Although the scorch property was improved as compared with the rubber composition of No. 1, it was found that the processability was inferior and the rolling resistance was also inferior.

In contrast, the rubber compositions of Examples 1 to 11 in which an appropriate amount of terminal-modified solution-polymerized SBR is blended and an appropriate amount of a crosslinkable silyl group-containing organic polymer is blended as a plasticizer are all excellent in processability. It turns out that it is excellent also in rolling resistance.
In particular, from the comparison between Example 1 and Example 3, when blended with a terminal-modified solution polymerization SBR having a styrene content of 38 to 48% by mass and a vinyl bond content of 20 to 45% by mol, processability and rolling It has been found that the resistance is better.
Further, from the comparison between Examples 3 and 5 to 11, it was found that when a polyether or aliphatic polymer was used, the balance between workability and rolling resistance was excellent.
Furthermore, from comparison between Example 3 and Example 5, it was found that when a crosslinkable silyl group-containing organic polymer into which a crosslinkable silyl group was introduced via a urethane bond was blended, the rolling resistance was further improved. .

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 (11)

Contains diene rubber, silica, silane coupling agent and plasticizer,
30% by mass or more of the diene rubber is a terminal-modified solution-polymerized styrene-butadiene copolymer rubber,
The plasticizer is a polyether-based, polyester-based, polyolefin-based, polycarbonate-based, aliphatic-based, saturated hydrocarbon-based, acrylic-based or plant-derived polymer or copolymer, and has a crosslinkable silyl group. A crosslinkable silyl group-containing organic polymer having at least one molecule per molecule;
The content of the silica is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber,
The content of the silane coupling agent is 0.5 to 20% by mass with respect to the mass of the silica,
A rubber composition for a tire tread, wherein the content of the plasticizer is 1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber.   The rubber composition for a tire tread according to claim 1, wherein the solution-polymerized styrene-butadiene copolymer rubber has a styrene content of 38 to 48 mass% and a vinyl bond content of 20 to 45 mol%.   The rubber composition for a tire tread according to claim 1 or 2, wherein the solution-polymerized styrene-butadiene copolymer rubber has a weight average molecular weight of 600,000 to 1,500,000.   The terminal-modified group of the solution-polymerized styrene-butadiene copolymer rubber is at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an alkoxy group, an epoxy group, a carbonyl group, and a carboxy group. The rubber composition for tire treads in any one of -3.   The rubber composition for a tire tread according to any one of claims 1 to 4, wherein the crosslinkable silyl group-containing organic polymer contains an alkylene oxide monomer unit in a main chain. The rubber composition for a tire tread according to claim 5, wherein the alkylene oxide monomer unit is a propylene oxide (—OCH (CH ₃ ) CH ₂ —) monomer unit. The rubber composition for a tire tread according to claim 6, wherein the crosslinkable silyl group-containing organic polymer is represented by the following formula (I) or (II).

(In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkylene group having 1 to 30 carbon atoms, a Represents an integer of 1 to 3, and n represents an integer of 2 to 450. When a is 2 or 3, a plurality of R ^{1 s} may be the same or different, and when a is 1, A plurality of R ¹ may be the same or different.)   The rubber composition for a tire tread according to any one of claims 1 to 7, wherein a main chain of the crosslinkable silyl group-containing organic polymer and the crosslinkable silyl group are bonded through at least a urethane bond.   The rubber composition for a tire tread according to any one of claims 1 to 8, wherein the crosslinkable silyl group of the crosslinkable silyl group-containing organic polymer is an alkoxysilyl group. The rubber composition for tire tread according to any one of claims 1 to 9, wherein the silica has a nitrogen adsorption specific surface area of 150 to 300 m ² / g.   The pneumatic tire which used the rubber composition for tire treads in any one of Claims 1-10 for tire tread.