JP2015030802A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition having excellent processability, scorching resistance and extrusion skin property and a low extruder pressure.SOLUTION: The rubber composition comprises a diene rubber, silica, a mercapto silane coupling agent, and a titanium compound having an alkoxy group and/or an acylate group. The silica shows a nitrogen adsorption specific surface area of 180 m/g or more, and is included by 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber. The content of the mercapto silane coupling agent is 0.1 to 20 mass% with respect to the content of the silica; and the content of the titanium compound is 0.1 to 20 mass% with respect to the content of the silica.

Description

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

  In recent years, there has been a demand for reducing tire rolling resistance in order to improve fuel efficiency during vehicle travel. Therefore, a method is known in which silica is added to the diene rubber constituting the tread portion of the tire to reduce hysteresis loss (particularly, tan δ at high temperatures), thereby reducing heat generation and reducing tire rolling resistance. Yes.

  For example, Claim 1 of Patent Document 1 discloses a rubber composition for a tire tread containing a diene rubber and silica. Patent Document 1 describes that the rolling resistance of a tire can be lowered by adopting the configuration of claim 1.

  On the other hand, rubber compositions for tires and the like are required to have excellent processability and scorch resistance. Moreover, the surface after extrusion molding is calculated | required from the viewpoint of design property and quality control. That is, it is required to have excellent extruding skin properties. Further, since the extrusion amount decreases when the extruder pressure is high, the extruder pressure is required to be low from the viewpoint of productivity. In addition, when an extruder pressure is high, extrusion skin property may deteriorate.

JP 2010-270247 A

Under these circumstances, the present inventor examined a rubber composition containing a diene rubber, silica and a silane coupling agent based on Patent Document 1, and found that the extruder pressure was high and the level required recently has been satisfied. It became clear that there was no. In addition, when a mercapto-based silane coupling agent is used as the silane coupling agent, it has also been clarified that processability, scorch resistance and extrusion skin property do not satisfy the levels required recently.
Therefore, in view of the above circumstances, an object of the present invention is to provide a rubber composition having excellent processability, scorch resistance and extrusion skin property and having a low extruder pressure.

As a result of intensive studies on the above problems, the present inventors have used silica having a nitrogen adsorption specific surface area of a specific value or more, a mercapto-based silane coupling agent, and a titanium compound having an alkoxy group and / or an acylate group in combination. The present inventors have found that a rubber composition excellent in processability, scorch resistance and extrusion skin property and having a low extruder pressure can be obtained, and has led to the present invention.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) containing a diene rubber, silica, a mercapto silane coupling agent, and a titanium compound having an alkoxy group and / or an acylate group,
The nitrogen adsorption specific surface area of the silica is 180 m ² / g or more,
The content of the silica is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber, and the content of the mercapto silane coupling agent is 0.1 with respect to the content of the silica. A rubber composition wherein the content of the titanium compound is 0.1 to 20% by mass with respect to the content of the silica.
(2) The rubber composition according to (1), wherein the titanium compound is a titanium compound represented by the formula (1) described later.
(3) A pneumatic tire using the rubber composition according to the above (1) or (2) for a tire tread.

  As shown below, according to the present invention, it is possible to provide a rubber composition which is excellent in processability, scorch resistance and extrusion skin property and has a low extruder pressure.

It is a partial section schematic diagram of the tire showing an example of the embodiment of the pneumatic tire of the present invention.

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

[Rubber composition]
The rubber composition of the present invention (hereinafter also referred to as the composition of the present invention) contains a diene rubber, silica, a mercapto silane coupling agent, and a titanium compound having an alkoxy group and / or an acylate group. .
Here, the nitrogen adsorption specific surface area of the silica is 180 m ² / g or more. The content of the silica is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber, and the content of the mercapto silane coupling agent is 0 with respect to the content of silica. 0.1 to 20% by mass, and the content of the titanium compound is 0.1 to 20% by mass with respect to the content of the silica.
Since the composition of this invention takes such a structure, it is thought that it becomes a rubber composition which is excellent in workability, scorch resistance, and extrusion skin property, and has a low extruder pressure.

The reason is not clear, but it is presumed that it is as follows.
Generally, when a silane coupling agent is blended with diene rubber together with silica, the silane coupling agent is bonded to both the diene rubber and silica, and the dispersibility of the silica in the diene rubber is increased.
On the other hand, as described above, when the silane coupling agent is blended with the diene rubber together with the silica, the problem of an increase in the extruder pressure arises from the study by the present inventors. This is presumably because the flexibility of the rubber composition is reduced because the silane coupling agent bonded to silica causes a crosslinking reaction with the diene rubber. Furthermore, this phenomenon is remarkable in the case of a mercapto-based silane coupling agent. The mercapto group of the mercapto-based silane coupling agent becomes a radical generating source, and the mercapto-based silane coupling agent and the diene rubber or between the diene rubbers Cross-linking proceeds. Therefore, workability and scorch resistance are deteriorated, and the extrusion skin property is also deteriorated.

As described above, the composition of the present invention has a diene rubber, silica having a nitrogen adsorption specific surface area greater than a specific value (hereinafter also referred to as specific silica), a mercapto silane coupling agent, an alkoxy group and / or an acylate group. A titanium compound (hereinafter also referred to as a specific titanium compound). Here, the specific titanium compound strongly binds to silica, hydrophobizes the silica surface, and increases the affinity with the polymer. That is, the specific titanium compound functions as a component that further improves the dispersibility of silica.
Furthermore, the specific titanium compound bonded to silica efficiently captures a radical derived from the mercapto group of the mercapto silane coupling agent and stabilizes the mercapto silane coupling agent. Therefore, the crosslinking between the mercapto silane coupling agent and the diene rubber as described above is suppressed. As a result, it is considered that a highly flexible composite is formed, the pressure of the extruder is lowered, and the workability, scorch resistance and extrusion skin property are ensured.
Further, the specific titanium compound is used as a surface treatment agent in the field of coating and film (Japanese Patent Laid-Open No. 7-89016). The specific titanium compound in the material forms a film on the surface and changes the chemical properties of the material surface. Therefore, it is thought that releasability and lubricity are imparted. The specific titanium compound is considered to function in the rubber composition as well, and the resistance between the rubber composition and the metal (metal in the extruder such as a die or die) is lowered by imparting lubricity to the material surface. It is thought that the extruder pressure is lowered.
In addition, since a mercapto-based silane coupling agent having high affinity with silica reacts preferentially with respect to silica, when the nitrogen adsorption specific surface area of silica is not more than a specific value, the specific titanium compound is difficult to react with silica. . As a result, it is difficult to form a structure in which the specific titanium compound is bonded to silica, and it is considered that the effect of reducing the extruder pressure as described above cannot be obtained.
As described above, as shown in Comparative Examples described later, when the specific titanium compound is not contained (Comparative Examples 1 and 2), the extruder pressure is high, and in particular, the silane coupling agent is a mercapto-based silane coupling agent. (Comparative Example 1), the workability and scorch resistance are low, and even when a specific titanium compound is blended, a non-mercapto silane coupling agent is used as a silane coupling agent (Comparative Examples A3 and B3). ) And when the nitrogen adsorption specific surface area of silica is not more than a specific value (Comparative Example A4), it is presumed from the high extruder pressure. In particular, when a non-mercapto-based silane coupling agent is used even if a specific titanium compound is blended (Comparative Examples A3 and B3), the extruder pressure is high. This stabilization is presumed to be a phenomenon unique to mercapto silane coupling agents that does not occur with non-mercapto silane coupling agents.

  Hereinafter, each component contained in the composition of this invention is explained in full detail.

<Diene rubber>
The diene rubber contained in the composition of the present invention is not particularly limited, and specific examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer. Examples include coal rubber, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). The diene rubber may be a single diene rubber or a combination of two or more diene rubbers.

  The diene rubber is preferably a modified rubber. Among these, a modified rubber modified with a hydroxy group is preferable, and a modified rubber whose terminal is modified with a hydroxy group is more preferable.

As the diene rubber, aromatic vinyl-conjugated diene copolymer rubber (especially one having a terminal modified with a hydroxy group) is preferably used because of the excellent rigidity of the resulting tire, and aromatic vinyl-conjugated. It is more preferable to use butadiene rubber (BR) together with the diene copolymer.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene butadiene rubber (SBR) and styrene isoprene copolymer rubber. Among these, styrene butadiene rubber (SBR) is preferable because the rigidity of the obtained tire is excellent.

The aromatic vinyl content (for example, styrene content) of the aromatic vinyl-conjugated diene copolymer is preferably 20 to 45 mass%, more preferably 23 to 42 mass%.
Further, the vinyl bond content in the conjugated diene of the aromatic vinyl-conjugated diene copolymer is preferably 10 to 50%, and more preferably 25 to 48%. 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.

The said aromatic vinyl-conjugated diene copolymer is not specifically limited about the manufacturing method, It can manufacture by a conventionally well-known method.
Moreover, the aromatic vinyl and conjugated diene as a monomer used when manufacturing the said aromatic vinyl-conjugated diene copolymer are not specifically limited.
Here, 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.
On the other hand, examples of the aromatic vinyl monomer include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, Examples include 4-tert-butylstyrene, divinylbenzene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl) dimethylaminoethyl ether, N, N-dimethylaminoethylstyrene, and vinylpyridine.

The content in the case of using the aromatic vinyl-conjugated diene copolymer is preferably 50 to 100% by mass of the diene rubber, and is preferably 55 to 95% by mass, because the rigidity of the obtained tire is excellent. More preferably, it is more preferably 60 to 90% by mass.
Further, when the butadiene rubber (BR) is used in combination with the aromatic vinyl-conjugated diene copolymer, the content of the butadiene rubber (BR) is determined from the viewpoint of wet performance and wear resistance of the obtained tire. It is preferably 5 to 50% by mass of the diene rubber, more preferably 10 to 45% by mass, and still more preferably 20 to 40% by mass.

  The weight average molecular weight of the diene rubber is preferably 100,000 to 1,500,000 from the viewpoint of the toughness of the obtained tire and the handling of the composition of the present invention, and 600,000 to 1,300,000. More preferably, it is 000. The weight average molecular weight (Mw) of the diene rubber is measured by standard polystyrene conversion by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

<Specific silica>
The composition of the present invention contains silica (specific silica) having a nitrogen adsorption specific surface area (N ₂ SA) of 180 m ² / g or more.
As described above, since the mercapto-based silane coupling agent having high affinity with silica reacts preferentially with respect to silica, the specific titanium compound to be described later has a nitrogen adsorption specific surface area of less than 180 m ² / g. Does not easily react with silica. As a result, it is difficult to form a structure in which both the mercapto silane coupling agent and the specific titanium compound are bonded to silica, and the extruder pressure is increased.

The specific silica is not particularly if N ₂ SA is 180 m ² / g or more restrictions, and specific examples thereof, it is N ₂ SA is 180 m ² / g or more, wet silica, dry silica, fumed silica, diatomaceous earth Etc.
The N ₂ SA of the specific silica is preferably 190 m ² / g or more. The upper limit is not particularly limited, but is preferably 300 m ² / g or less, and more preferably 250 m ² / g or less.
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”.
As the specific silica, one type of silica may be used alone, or two or more types of silica may be used in combination.

  In the composition of the present invention, the content of the specific silica is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber. Especially, it is preferable that it is 20-150 mass parts, and it is more preferable that it is 50-100 mass parts.

<Mercapto silane coupling agent>
The mercapto silane coupling agent contained in the composition of the present invention is not particularly limited as long as it is a silane compound having a mercapto group (—SH) and a hydrolyzable group.
The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferable. When the hydrolyzable group is an alkoxy group, the alkoxy group preferably has 1 to 16 carbon atoms, more preferably 1 to 4 carbon atoms. As a C1-C4 alkoxy group, a methoxy group, an ethoxy group, a propoxy group etc. are mentioned, for example.

The mercapto-based silane coupling agent may have an organic functional group other than a mercapto group.
Such an organic functional group is not particularly limited, and examples thereof include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, and an amino group.

  A mercapto silane coupling agent may be used individually by 1 type, and may use 2 or more types together.

  Specific examples of the mercapto-based silane coupling agent include mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane.

The mercapto silane coupling agent is preferably a mercapto silane coupling agent having a polyether chain.
Here, the polyether chain is a side chain having two or more ether bonds, and examples thereof include a side chain having two or more structural units —R ^a —O—R ^b — in total. Here, in the structural unit, R ^a and R ^b are each independently a linear or branched alkylene group, a linear or branched alkenylene group, a linear or branched alkynylene group, Alternatively, it represents a substituted or unsubstituted arylene group. Of these, a linear alkylene group is preferable.

  As a suitable aspect of the mercapto type | system | group silane coupling agent which has the said polyether chain | strand, the compound represented by following formula (2) is mentioned, for example.

In the above formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms, among them, preferably an alkoxy group having 1 to 3 carbon atoms. Examples of the alkoxy group having 1 to 3 carbon atoms include a methoxy group and an ethoxy group. A plurality of R ²¹ when l is 2 may be the same or different.
In the formula (2), R ²² represents a straight-chain polyether group having 4 to 30 carbon atoms. The polyether group is a group having two or more ether bonds, and specific examples thereof include a group having two or more structural units —R ^a —O—R ^b — in total. Definitions and preferred embodiments of R ^a and R ^b are the same as R ^a and R ^b as described above. When m is 2, the plurality of R ²² may be the same or different.
As a suitable aspect of a C4-C30 linear polyether group, group represented by following formula (3) is mentioned, for example.

In the above formula (3), R ³¹ represents a linear alkyl group, a linear alkenyl group, or a linear alkynyl group, and among them, a linear alkyl group is preferable. As the linear alkyl group, a linear alkyl group having 1 to 20 carbon atoms is preferable, and a linear alkyl group having 8 to 15 carbon atoms is more preferable. Specific examples of the linear alkyl group having 8 to 15 carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group and the like, and tridecyl group is particularly preferable.
In the above formula (3), R ³² represents a linear alkylene group, a linear alkenylene group, or a linear alkynylene group, and among these, a linear alkylene group is preferable. As said linear alkylene group, a C1-C2 linear alkylene group is preferable and an ethylene group is more preferable.
In said formula (3), p represents the integer of 1-10 and it is preferable that it is 3-7.
In the above formula (3), * indicates a bonding position.

In the formula (2), R ²³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
In the above formula (2), R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, among them preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms. Specific examples of the alkylene group having 1 to 5 carbon atoms include a methylene group, an ethylene group, and a propylene group.
In said formula (2), l represents the integer of 1-2 and it is preferable that it is 1. In said formula (2), m represents the integer of 1-2 and it is preferable that it is 2. n represents an integer of 0 to 1, and is preferably 0. l, m, and n satisfy the relationship of l + m + n = 3.

  In the composition of the present invention, the content of the mercapto-based silane coupling agent is 0.1 to 20% by mass with respect to the content of the specific silica. Especially, it is preferable that it is 5-10 mass%.

<Specific titanium compounds>
The composition of the present invention contains a titanium compound (specific titanium compound) having an alkoxy group and / or an acylate group (-OCOR: R is a hydrocarbon group).
The specific titanium compound is preferably a titanium compound having an alkoxy group, and more preferably a titanium compound having an alkoxy group and an acylate group because of excellent dispersibility of silica.

  As a suitable aspect of a specific titanium compound, the titanium compound represented by following formula (1) is mentioned, for example.

In the above formula (1), R ¹¹ and R ¹² each independently represent a linear or branched alkyl group having 1 to 20 carbon atoms. A plurality of R ¹¹ and R ¹² may be the same or different.
In the above formula (1), R ¹¹ is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms. R ¹¹ is preferably a branched alkyl group.
In the above formula (1), R ¹² is preferably an alkyl group having 8 to 20 carbon atoms, and more preferably an alkyl group having 12 to 20 carbon atoms. R ¹² is preferably a linear alkyl group.
In said formula (1), a and b represent the integer of 0-4 each independently, and satisfy | fill the relational expression of a + b = 4. a is preferably an integer of 1 or more. b is preferably an integer of 1 or more, more preferably 3, for the reason that the dispersibility of silica is excellent.

In the composition of the present invention, the content of the specific titanium compound is 0.1 to 20% by mass with respect to the content of the silica. Especially, it is preferable that it is 0.5-15 mass% because the extruder pressure becomes lower.
When the content of the specific titanium compound is less than 0.1% by mass with respect to the content of the silica, processability, scorch resistance and extrusion skin property are insufficient, and the extruder pressure is increased. Moreover, when content of a specific titanium compound exceeds 20 mass% with respect to content of the said silica, extrusion skin property will become inadequate and an extruder pressure will become high.

  The content of the specific titanium compound with respect to the mercapto-based silane coupling agent is not particularly limited, but is preferably 10% by mass or more.

<Optional component>
If necessary, the composition of the present invention may further contain an additive within a range not impairing its effects and purposes.
Examples of the additive include fillers other than silica (for example, carbon black), silane coupling agents other than mercapto-based silane coupling agents (for example, Si69 manufactured by Evonik Degussa), zinc oxide (zinc white), stearin Various commonly used rubber compositions such as acids, antioxidants, processing aids, process oils, liquid polymers, terpene resins, thermosetting resins, vulcanizing agents (eg, sulfur), vulcanization accelerators, etc. An additive is mentioned.

<Method for producing rubber composition>
The method for producing the rubber composition of the present invention is not particularly limited, and specific examples thereof include, for example, kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). The method of doing is mentioned. When the composition of the present invention contains sulfur or a vulcanization accelerator, components other than sulfur and the vulcanization accelerator are first mixed at a high temperature (preferably 140 to 160 ° C.) and cooled, and then sulfur or It is preferable to mix a vulcanization accelerator.
The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire manufactured using the composition of the present invention described above. Especially, it is preferable that it is a pneumatic tire which used the composition of this invention for the tire tread.
FIG. 1 shows a schematic partial sectional view of a tire representing an example of an embodiment of the pneumatic tire of the present invention, but the pneumatic 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 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.

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

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 with the obtained master batch to obtain a rubber composition.
In Table 1, regarding the amount of SBR, the upper value is the amount of SBR (oil-extended product) (unit: parts by mass), and the lower value is the net amount of SBR contained in SBR (unit: parts by mass) It is.

<Mooney viscosity>
For the prepared rubber composition (unvulcanized), Mooney viscosity 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. Was measured.
The results are shown in Table 1. The results were expressed as an index with Comparative Example 1 as 100. The smaller the index, the lower the viscosity and the better the workability.

<Mooney coach>
About the prepared rubber composition (unvulcanized), the scorch time was measured according to JIS K6300-1: 2001 using an L-shaped rotor at a test temperature of 125 ° C.
The results are shown in Table 1. The results were expressed as an index with Comparative Example 1 as 100. The larger the index, the longer the scorch time and the better the scorch resistance.

<Extruder pressure>
About the prepared rubber composition (unvulcanized), the extruder pressure (test pressure at a constant volume flow rate) was measured under the condition of 120 ° C. according to JIS K7199: 1999.
The results are shown in Table 1. The results were expressed as an index with Comparative Example 1 as 100. A smaller index indicates a lower extruder pressure.

<Extruded skin properties>
The prepared rubber composition (unvulcanized) was extruded using a garbage die in accordance with ASTM D2230. The appearance of the obtained extrusion-molded product was visually observed and evaluated as follows. Practically, it is preferably A or B, more preferably A.
-A: The surface has no irregularities and is smooth.
B: Fine irregularities of less than 1 mm are observed on the surface.
C: Large irregularities of 1 mm or more are observed on the surface.

<Pain effect>
The prepared rubber composition (unvulcanized) was vulcanized at 170 ° C. for 10 minutes using a strain shear stress measuring machine (RPA2000, manufactured by α-Technology Co., Ltd.), and then the strain shear modulus G having a strain of 0.28%. ′ And the strain shear modulus G ′ of 30.0% strain were measured, and the difference G′0.28 (MPa) −G′30.0 (MPa) was calculated as the Payne effect.
The results are shown in Table 1. The results were expressed as an index with the Payne effect of Comparative Example 1 as 100. A smaller index means a smaller Pain effect and better silica dispersibility.

Details of each component shown in Table 1 are as follows.
Diene rubber 1: E581 (oil-extended product (including 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR. The net content of SBR in SBR is 72.7% by mass), styrene content: 40% by mass, Vinyl bond amount: 44%, weight average molecular weight: 1,260,000, manufactured by Asahi Kasei Corporation)
・ Diene rubber 2: BR1220 (manufactured by Nippon Zeon)
Silica: Ultrasil 9000GR (N ₂ SA: 235 m ² / g, manufactured by Evonik Degussa)
Comparative silica: Zeosil 1165MP (N ₂ SA: 165 m ² / g, manufactured by Rhodia)
Carbon black: Show black N339 (N ₂ SA: 90 m ² / g, manufactured by Cabot Japan)
Silane coupling agent: VP Si363 (manufactured by Evonik Degussa) (compound represented by the above formula (2). Here, R ²¹ : —OC ₂ H ₅ , R ²² : —O (C ₂ H ₄ O) _{) 5 -C 13 H 27, R} 24 :-( CH 2) 3 -, l = 1, m = 2, n = 0).
Comparative silane coupling agent: Si69 (Evonik Degussa) (bis (3-triethoxysilylpropyl) tetrasulfide)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Stearic acid YR (manufactured by NOF Corporation)
Antiaging agent: Santoflex 6PPD (manufactured by Solutia Europe)
・ Process oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
Titanium compound 1: Titacoat S-151 (manufactured by Nippon Soda Co., Ltd.) (titanium compound represented by the above formula (1). Here, R ¹¹ : -i-C ₃ H ₇ (isopropoxy group), R ¹² : _{-C 17 H 35, a = 1} , b = 3)
-Titanium compound 2: Tetrabutoxy titanium-Sulfur: Oil-treated sulfur (manufactured by Karuizawa Smelter)
・ Vulcanization accelerator 1: Noxeller CZ-G (Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: Perkacit DPG (manufactured by Flexsys)

As can be seen from Table 1, compared with Comparative Example 1 containing a mercapto-based silane coupling agent but not containing a specific titanium compound, the present embodiment containing a mercapto-based silane coupling agent and a specific titanium compound is All were excellent in workability, scorch resistance and extrusion skin property, and the extruder pressure was low. Among them, Examples A1 to A3, in which the specific titanium compound is a titanium compound having an alkoxy group and an acylate group, showed superior silica dispersibility.
From the comparison of Examples A1 to A3 and B1 to B3, Examples A1, A2, B1 and B2 in which the content of the specific titanium compound is 0.5 to 15% by mass with respect to the content of silica are extruded. The mechanical pressure was lower.

On the other hand, Comparative Examples A1 and B1, which contain a mercapto-based silane coupling agent and a specific titanium compound, but the content of the specific titanium compound is less than 0.1% by mass with respect to the content of silica, Scorch resistance and extrusion skin resistance were insufficient, and the extruder pressure was high.
In addition, Comparative Examples A2 and B2, which contain a mercapto-based silane coupling agent and a specific titanium compound, but the content of the specific titanium compound exceeds 20% by mass with respect to the content of silica, have insufficient extrusion skin properties. And the extruder pressure was high.
Moreover, although the specific titanium compound was contained, Comparative Example A3 and B3 which used the non-mercapto type | system | group silane coupling agent as a silane coupling agent had high extruder pressure.
Further, although containing a mercapto-based silane coupling agent and a specific titanium compound, Comparative Example A4 in which the nitrogen adsorption specific surface area of silica is not more than a specific value is insufficient in workability, scorch resistance and extrusion skin property, And the extruder pressure was high.

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 (3)

Containing a diene rubber, silica, a mercapto silane coupling agent, and a titanium compound having an alkoxy group and / or an acylate group,
The nitrogen adsorption specific surface area of the silica is 180 m ² / g or more,
The content of the silica is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber, and the content of the mercapto silane coupling agent is 0.1 with respect to the content of the silica. A rubber composition, which is ˜20% by mass, and wherein the content of the titanium compound is 0.1 to 20% by mass with respect to the content of the silica. The rubber composition according to claim 1, wherein the titanium compound is a titanium compound represented by the following formula (1).
(In Formula (1), R ¹¹ and R ¹² each independently represents a linear or branched alkyl group having 1 to 20 carbon atoms. A and b are each independently an integer of 0 to 4) And satisfies the relational expression of a + b = 4.)   A pneumatic tire using the rubber composition according to claim 1 or 2 for a tire tread.