JP2014196385A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition exerting excellent wet performance and scorch resistance when formed into a tire.SOLUTION: A rubber composition contains diene rubber (A), silica (B), a specific mercapto silane coupling agent (C), and a tryptophane derivative (D). The content of the silica (B) is 5-150 pts.mass with respect to 100 pts.mass of the diene rubber (A). The content of the mercapto silane coupling agent (C) is 0.5-20 pts.mass with respect to the content of the silica (B). A ratio (p/q) of the number (p) of moles of the tryptophane derivative (D) to the number (q) of moles of a mercapto group contained of the mercapto silane coupling agent (C) is 1-1,000 mol%.

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 diene rubber constituting the tread portion of the tire is mixed with silica to reduce hysteresis loss (particularly tan δ at high temperature) to reduce heat generation and reduce tire rolling resistance. Yes.
However, since silica has low affinity with diene rubbers and high cohesiveness between silicas, silica is not dispersed even if silica is simply blended with diene rubbers, reducing the rolling resistance of tires. There was a problem that could not be obtained sufficiently.

As means for solving such a problem, the present applicant, in Patent Document 1, described, “In addition to blending 5 to 100 parts by weight of silica with 100 parts by weight of diene rubber, a specific mercaptosilane (1) is added to the silica. 0.5 to 4.0% by weight of the blending amount and 0.5 to 10% by weight of the silica blending amount of the specific mercaptosilane (2) are blended at a temperature of 145 to 185 ° C. "Method for producing tire rubber composition" has been proposed ([Claim 1]).
Patent Document 1 shows that by using the rubber composition for tires manufactured by the above method, the tire hysteresis loss can be reduced and the rolling resistance can be sufficiently reduced.

JP 2010-270247 A

On the other hand, the rubber composition for tires is required to have less cross-linking (rubber burn) in the storage stage and the stage before the vulcanization process. That is, excellent scorch resistance (workability) is required.
Moreover, with the improvement of the required safety level, it is required to exhibit excellent wet performance when used as a tire.

Under these circumstances, the present inventors examined a rubber composition for tires containing a diene rubber, silica and mercaptosilane based on Patent Document 1, and found that the scorch resistance and wet performance when made into a tire were high. It turns out that it does not meet the level required recently.
In view of the above circumstances, an object of the present invention is to provide a rubber composition having excellent wet performance and excellent scorch resistance when used as a tire.

As a result of intensive studies on the above-mentioned problems, the present inventors have used a specific mercapto-based silane coupling agent and a tryptophan derivative (D) in combination, so that they have excellent wet performance when made into a tire, and have scorch resistance. The present inventors have found that a rubber composition excellent in the above can be obtained, and have reached the present invention.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) Contains a diene rubber (A), silica (B), a mercapto silane coupling agent (C), and a tryptophan derivative (D),
The mercapto-based silane coupling agent (C) is represented by a compound represented by the following formula (2) and / or a repeating unit represented by the following formula (3) and a formula (4) described later. A copolymer having a repeating unit of
Content of the said silica (B) is 5-150 mass parts with respect to 100 mass parts of said diene rubber (A),
The content of the mercapto-based silane coupling agent (C) is 0.5 to 20% by mass with respect to the content of the silica (B),
The ratio (p / q) between the number of moles (p) of the tryptophan derivative (D) and the number of moles (q) of the mercapto group of the mercapto-based silane coupling agent (C) is 1-1000 mol%. Rubber composition.
(2) The rubber composition according to (1), wherein the tryptophan derivative (D) is a 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 excellent in wet performance when made into a tire and excellent in scorch resistance and a pneumatic tire using the rubber composition for a tire tread. .

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 (A), silica (B), a mercapto silane coupling agent (C), and a tryptophan derivative (D). The mercapto-based silane coupling agent (C) is represented by a compound represented by the formula (2) described below and / or a repeating unit represented by the formula (3) described below and a formula (4) described below. The mercapto-based silane coupling agent, wherein the content of the silica (B) is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber (A). The content of (C) is 0.5 to 20% by mass with respect to the content of the silica (B), the number of moles (p) of the tryptophan derivative (D) and the mercapto-based silane coupling agent ( C) The ratio of the moles of mercapto groups (q) having (p / q) is a 1~1000mol%.

  As described above, the composition of the present invention uses a specific mercapto silane coupling agent and a tryptophan derivative in combination. Here, as will be described later, the specific mercapto-based silane coupling agent contains a mercapto group and a polyether chain or a polysiloxane structure (—Si—O—).

Since the composition of this invention takes such a structure, it is thought that the outstanding wet performance and scorch resistance are shown. The reason is not clear, but it is presumed that it is as follows.
Generally, in a composition containing a polymer such as a rubber composition, the polymer is cleaved by an action such as heat or mechanical shearing force to generate a carbo radical. The generated carbo radical reacts with oxygen in the system to form a peroxide radical, and the peroxide radical extracts hydrogen from the polymer and changes to a peroxide. Further, it is considered that the generated peroxide is decomposed to generate new radicals, and as a result, radicals are generated in a chain.
When a radical is generated in this way, in the case of a polymer having a double bond such as a diene rubber, the cross-linking of the polymers proceeds due to the reaction between the radical and the double bond, and as a result, the scorch time is shortened. That is, the scorch resistance is reduced.

As described above, since the composition of the present invention contains a tryptophan derivative, the nitrogen atom of the pyrrole ring in the tryptophan derivative captures and stabilizes the radical generated in the rubber composition.
Here, it can be said that the composition of the present invention is characterized in that a specific mercapto silane coupling agent and a tryptophan derivative are used in combination. That is, silane coupling occurs when the mercapto group of a specific mercapto-based silane coupling agent and the polyether chain or polysiloxane structure (—Si—O—) interact with the nitrogen atom of the pyrrole ring in the tryptophan derivative. Both the silica dispersing ability of the agent and the radical scavenging ability of the nitrogen atom are improved. As a result, it is considered that excellent wet performance is exhibited when the dispersibility of silica is improved to form a tire. Moreover, it is thought that the scorch resistance which was excellent by the improvement of radical scavenging ability is shown. This is because, as shown in the comparative examples described later, when a specific mercapto silane coupling agent is contained but a tryptophan derivative is not contained (Comparative Example 1), or when a tryptophan derivative is contained but a specific mercapto silane cup is contained. It is also inferred from the fact that the desired effect cannot be obtained in the case of containing no ring agent (containing a mercapto silane coupling agent other than the specific mercapto silane coupling agent (C)) (Comparative Example 4). The

  The diene rubber (A), silica (B), mercapto silane coupling agent (C) and tryptophan derivative (D) and other components that may be optionally contained are described in detail below.

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

In the present invention, as the diene rubber (A), it is preferable to use an aromatic vinyl-conjugated diene copolymer rubber from the viewpoint of wear resistance of the obtained tire, and an aromatic vinyl-conjugated diene copolymer is preferably used. It is more preferable to use butadiene rubber (BR) together.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene copolymer rubber (SBR) and styrene-isoprene copolymer rubber. Especially, it is preferable that it is a styrene-butadiene copolymer rubber (SBR) from a viewpoint of the abrasion resistance of the tire obtained.

The aromatic vinyl content (for example, styrene content) of the aromatic vinyl-conjugated diene copolymer is preferably 20 to 45% by mass from the viewpoint of the balance between wear resistance and toughness of the obtained tire. It is more preferable that it is 23-42 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.
Furthermore, the weight average molecular weight of the aromatic vinyl-conjugated diene copolymer is preferably 100,000 to 1,500,000 from the viewpoint of the balance between processability and the toughness of the resulting tire, More preferably, it is 000-1,300,000. The weight average molecular weight (Mw) of the aromatic vinyl-conjugated diene copolymer is measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

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.

In the present invention, the content when the aromatic vinyl-conjugated diene copolymer is used is preferably 50% by mass or more of the diene rubber (A) from the viewpoint of wear resistance of the obtained tire. , 55% by mass or more, more preferably 60% by mass or more.
When the butadiene rubber (BR) is used in combination with the aromatic vinyl-conjugated diene copolymer, the content of the butadiene rubber (BR) is less than 50% by mass of the diene rubber (A). Is preferable, it is more preferable that it is less than 45 mass%, and it is further more preferable that it is less than 40 mass%.

<Silica (B)>
The silica (B) used in the composition of the present invention is not particularly limited, and any conventionally known silica that is blended in a rubber composition for uses such as tires can be used.
Examples of the silica (B) include wet silica, dry silica, fumed silica, and diatomaceous earth. As the silica (B), one type of silica may be used alone, or two or more types of silica may be used in combination.
In the present invention, the silica (B) is preferably wet silica from the viewpoint of rubber reinforcement.

The silica (B), from the viewpoint of balance between processability and low rolling resistance, it is preferable that the nitrogen adsorption specific surface area (N ₂ SA) is 100 to 300 m ² / g, in 140~200m ² / g More preferably.
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”.

  In the composition of the present invention, the content of the silica (B) is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber (A), and a balance between workability and low rolling resistance is achieved. From the viewpoint, it is preferably 20 to 140 parts by mass, and more preferably 35 to 130 parts by mass.

<Mercapto silane coupling agent (C)>
The mercapto-based silane coupling agent (C) used in the composition of the present invention is a compound represented by the following formula (2) and / or a repeating unit represented by the following formula (3) and the following formula (4). It is a copolymer having a repeating unit represented by:
The mercapto-based silane coupling agent (C) is preferably a compound represented by the following formula (2) because it is excellent in reactivity with silica or diene rubber and more excellent in wet performance.

In the formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms, among them, from the viewpoint of low rolling resistance of the tire obtained, it is 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. In the case where l is 2, the plurality of R ²¹ 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. Here, in the above structural unit, R ^a and R ^b each independently represent a linear alkylene group, a linear alkenylene group, or a linear alkynylene group, and in particular, low rolling A linear alkylene group is preferable because a tire excellent in resistance can be obtained. When m is 2, the plurality of R ²² may be the same or different.
As a suitable aspect of the said C4-C30 linear polyether group, group represented by following formula (5) is mentioned.

In the above formula (5), R ⁵¹ 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 (5), R ⁵² represents a linear alkylene group, a linear alkenylene group or a linear alkynylene group, and among them, 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 (5), p represents the integer of 2-10 and it is preferable that it is 3-7.
In the above formula (5), * 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 10 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 above formulas (3) and (4), R ³¹ and R ⁴¹ each independently represent an alkylene group having 1 to 5 carbon atoms, and specific examples thereof include a methylene group, an ethylene group, and a propylene group. It is done. Of these, a propylene group is preferred. When the mercapto silane coupling agent (C) has a plurality of repeating units, the plurality of R ³¹ and R ⁴¹ may be the same or different.
In the above formulas (3) and (4), R ³² and R ⁴² are each independently a linear or branched alkylene group having 1 to 30 carbon atoms, or a linear or branched carbon group having 2 to 30 carbon atoms. The alkenylene group or the linear or branched alkynylene group having 2 to 30 carbon atoms is preferable, and those having 3 to 20 carbon atoms are preferable. When R ³² is a terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight chain. It represents a chain or branched alkynyl group having 2 to 30 carbon atoms, and among them, those having 3 to 20 carbon atoms are preferable. If R ⁴² is terminated, the definition of R ^42, specific examples and preferred embodiments are the same as above R ^32. When the mercapto silane coupling agent (C) has a plurality of repeating units, the plurality of R ³² and R ⁴² may be the same or different.
In the above formulas (3) and (4), R ³³ and R ⁴³ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched group. A alkenyl group having 2 to 30 carbon atoms, a linear or branched alkynyl group having 2 to 30 carbon atoms, a linear or branched alkyl group having 1 to 30 carbon atoms, and a hydroxyl group or a carboxyl group at the terminal Or a linear or branched alkenyl group having 2 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the terminal. R ⁴³ is preferably a group having a hydroxyl group at the terminal. R ³² and R ³³ may form a ring with R ³² and R ³³ . R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ . When the mercapto silane coupling agent (C) has a plurality of repeating units, the plurality of R ³³ and R ⁴³ may be the same or different.
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms, and among them, an alkyl group having 3 to 10 carbon atoms is preferable. Specific examples of the alkyl group having 3 to 10 carbon atoms include a hexyl group, a heptyl group, and an octyl group. When the mercapto silane coupling agent (C) has a plurality of repeating units, the plurality of R ³⁴ may be the same or different.

  In the composition of the present invention, the content of the mercapto-based silane coupling agent (C) is 0.5 to 20% by mass with respect to the content of the silica (B), and processability and low rolling resistance. From the viewpoint of the balance, it is preferably 1 to 18% by mass, and more preferably 2 to 16% by mass.

<Tryptophan derivative (D)>
The composition of the present invention contains a tryptophan derivative (D). Here, the tryptophan derivative (D) is tryptophan (a compound represented by the following formula (6)) or a derivative of tryptophan. Tryptophan has optical isomers (L-form, D-form), but may be L-form or D-form. Especially, it is preferable that it is a L-form.

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

In said formula (1), X represents a hydrogen atom or a substituent.
The substituent is not particularly limited as long as it is a monovalent substituent. For example, a halogen atom, hydroxy group, nitro group, carboxy group, alkoxy group, amino group, mercapto group, acyl group, imide group, phosphino group , A phosphinyl group, a silyl group, a hydrocarbon group optionally having a hetero atom, and the like.
As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom etc. are mentioned, for example.
Examples of the hetero atom of the hydrocarbon group that may have a hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom.
Examples of the hydrocarbon group that may have a hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group obtained by combining these.
The aliphatic hydrocarbon group may be linear, branched or cyclic. Specific examples of the aliphatic hydrocarbon group include a linear or branched alkyl group (particularly having 1 to 30 carbon atoms), a linear or branched alkenyl group (particularly having 2 to 30 carbon atoms), Examples thereof include a linear or branched alkynyl group (particularly having 2 to 30 carbon atoms).
Examples of the aromatic hydrocarbon group include an aryl group and a naphthyl group. As said aryl group, C6-C18 aryl groups, such as a phenyl group, a tolyl group, a xylyl group, etc. are mentioned, for example.

  Plural Xs may be the same or different.

In the above formula (1), R ₁₁ represents a hydrogen atom or a substituent. Specific examples and preferred embodiments of the substituent are the same as those of X described above. R ₁₁ is preferably a hydrogen atom.

The formula (1), R ₁₂ represents a hydrogen atom or a substituent. Specific examples and preferred embodiments of the substituent are the same as those of X described above.
Suitable embodiments where R ₁₂ is a substituent, include groups represented by the following formula (7).

In the above formula (7), R ₇₁ represents a divalent aliphatic hydrocarbon group (for example, an alkylene group, preferably 1 to 8 carbon atoms), a divalent aromatic hydrocarbon group (for example, an arylene group, preferably 6-12 carbon atoms), —O—, —S—, —SO ₂ —, —N (R) — (R: alkyl group), —CO—, —NH—, —COO—, —CONH—, or Examples include a combination of these (for example, an alkyleneoxy group, an alkyleneoxycarbonyl group, an alkylenecarbonyloxy group, and the like). Among these, an alkylene group, —O—, —COO—, or a group obtained by combining these is preferable.

In said formula (7), _R72 represents an aromatic hydrocarbon group. Specific examples of the aromatic hydrocarbon group are the same as X described above. Of these, an aryl group is preferable.

  In the above formula (7), * represents a bonding position.

A plurality of R ₁₂ may be the same or different.

Of the plurality of R ₁₂ , at least one is preferably a hydrogen atom or a group represented by the above formula (7).

  In the composition of the present invention, the ratio (p / q) between the number of moles (p) of the tryptophan derivative (D) and the number of moles (q) of the mercapto group (—SH) of the mercapto silane coupling agent (C). ) Is 1-1000 mol%. p / q is preferably 10.0 mol% or more, and more preferably 50.0 mol% from the reason that the scorch resistance of the composition of the present invention is more excellent and a tire excellent in wet performance is obtained. Is more preferably 100.0 mol% or more, and particularly preferably 200.0 mol% 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 a silane coupling agent other than the mercapto-based silane coupling agent (C) contained in the composition of the present invention, a filler other than silica (B) (for example, carbon black), and zinc oxide. , Various additives commonly used in rubber compositions such as stearic acid, anti-aging agent, processing aid, aroma oil, liquid polymer, terpene resin, thermosetting resin, vulcanizing agent, vulcanization accelerator Is mentioned.

<Method for producing rubber composition>
The production method of the 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 etc. are mentioned.
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 using the above-described composition of the present invention for a tire (preferably a 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 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.
In Table 1, “tryptophan / mercapto group” means the ratio (p) of the number of moles (p) of the tryptophan derivative (D) to the number of moles (q) of the mercapto group possessed by the mercapto-based silane coupling agent (C). / Q).

<Mooney scorch> (index for scorch resistance)
With respect to the prepared rubber composition (unvulcanized), the scorch time was measured in accordance with 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 the scorch time of Comparative Example 1 as 100. The larger the index, the longer the scorch time and the better the scorch resistance (workability).

<Tan δ (−10 ° C.)> (Index of wet performance)
The prepared rubber composition (unvulcanized) was press vulcanized at 160 ° C. for 20 minutes in a mold (15 cm × 15 cm × 0.2 cm) to prepare a vulcanized rubber sheet.
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.), conditions of stretch deformation strain rate 10% ± 2%, frequency 20 Hz, temperature −10 ° C. Then, tan δ (−10 ° C.) was measured.
The results are shown in Table 1. The results were expressed as an index with tan δ (−10 ° C.) of Comparative Example 1 as 100. The larger the index, the larger the tan δ (−10 ° C.), and the better the wet performance when made into a tire.

Details of each component shown in Table 1 are as follows.
Diene rubber A1 (SBR): 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 (Mass%, vinyl bond amount: 44%, weight average molecular weight: 1,260,000, manufactured by Asahi Kasei Corporation)
-Diene rubber A2 (BR): Nipol BR1200 (manufactured by Nippon Zeon)
Silica B1: Zeosil 1165GR (CTAB adsorption specific surface area = 160 m ² / g, manufactured by Rhodia)
Carbon black: Show black N339 (CTAB adsorption specific surface area = 90 m ² / g, manufactured by Cabot Japan)
Silane coupling agent C1: 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.)
Silane coupling agent C2: NXT-Z45 (manufactured by Momentive) (a copolymer having a repeating unit represented by the above formula (3) and a repeating unit represented by the above formula (4). The proportion of the repeating unit represented by (3) is 55 mol%, and the proportion of the repeating unit represented by the above formula (4) is 45 mol%.) (Mole number of mercapto group contained in 1 g: 7 .0x10 ^-4 mol)
Silane coupling agent X1: VP Si69 (Evonik Degussa) (bis (3-triethoxysilylpropyl) tetrasulfide)
Silane coupling agent X2: KBM-803 (manufactured by Shin-Etsu Chemical) (γ-mercaptopropyltrimethoxysilane)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Stearic acid YR (manufactured by NOF Corporation)
Anti-aging agent: Santoflex 6PPD (manufactured by Solutia Europe)
・ Process oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
Tryptophan D1: L-tryptophan Tryptophan D2: N-carbobenzoxy-tryptophan Sulfur: Oil-treated sulfur (manufactured by Karuizawa Smelter Co., Ltd.)
・ 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, Comparative Example 1 containing a specific mercapto silane coupling agent (C) but no tryptophan derivative (D), or a specific mercapto silane containing a tryptophan derivative (D) Compared with Comparative Examples 4 to 6 which do not contain a coupling agent (C), all of the present Examples using a specific mercapto-based silane coupling agent (C) and a tryptophan derivative (D) have excellent resistance to resistance. Scorch and / or wet performance was exhibited.
From the comparison of Examples 1 to 5, the ratio (p / q) between the number of moles (p) of the tryptophan derivative (D) and the number of moles (q) of the mercapto group possessed by the mercapto-based silane coupling agent (C) is Examples 2 to 5, which are 10.0 mol% or more, showed better scorch resistance and wet performance. Especially, Examples 2-4 whose p / q is 50.0 mol% or more showed the further outstanding scorch resistance and wet performance. Among them, Examples 3 and 4 in which p / q is 100.0 mol% or more showed further superior scorch resistance and wet performance. Among them, Example 4 in which p / q is 200.0 mol% or more showed particularly excellent scorch resistance and wet performance.
From the comparison of Examples 1 to 6, Examples 1 to 5, in which the mercapto-based silane coupling agent (C) is a compound represented by the above formula (2), showed better wet performance.

  Although the specific mercapto silane coupling agent (C) and the tryptophan derivative (D) are used in combination, the comparative example 2 in which p / q is less than 1 mol% is more resistant to scorch and wet performance than the examples of the present application. Was inferior. Moreover, although the specific mercapto type | system | group silane coupling agent (C) and tryptophan derivative (D) are used together, although the comparative example 3 in which p / q exceeds 1000 mol% is excellent in scorch resistance, the wet performance is an Example of this application. It was inferior compared with.

  As can be seen from the comparison with Comparative Examples 5 and 6, when a non-mercapto silane coupling agent is used as the silane coupling agent, the scorch resistance and wet performance are improved even when tryptophan derivative (D) is blended. Was not seen.

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 (A), silica (B), a mercapto silane coupling agent (C), and a tryptophan derivative (D);
The mercapto-based silane coupling agent (C) is a compound represented by the following formula (2) and / or a repeating unit represented by the following formula (3) and a repeating unit represented by the following formula (4). A copolymer having
The content of the silica (B) is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber (A),
The content of the mercapto silane coupling agent (C) is 0.5 to 20% by mass with respect to the content of the silica (B),
The ratio (p / q) of the number of moles (p) of the tryptophan derivative (D) and the number of moles (q) of the mercapto group of the mercapto-based silane coupling agent (C) is 1-1000 mol%. Rubber composition.

(In formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms. R ²² represents a linear polyether group having 4 to 30 carbon atoms. R ²³ represents a hydrogen atom or a carbon atom. Represents an alkyl group having 1 to 8. R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, l represents an integer of 1 to 2, m represents an integer of 1 to 2, and n represents 0 to 1. Represents an integer, and l, m, and n satisfy the relationship of l + m + n = 3, and when R is 2, a plurality of R ²¹ may be the same or different, and m is 2. The plurality of R ²² may be the same or different.)

(In formulas (3) and (4), R ³¹ and R ⁴¹ each independently represents an alkylene group having 1 to 5 carbon atoms.
R ³² and R ⁴² are each independently a linear or branched alkylene group having 1 to 30 carbon atoms, a linear or branched alkenylene group having 2 to 30 carbon atoms, or a linear or branched group. Represents a alkynylene group having 2 to 30 carbon atoms. When R ³² is a terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight chain. A chain or branched alkynyl group having 2 to 30 carbon atoms is represented. When R ⁴² is a terminal, R ⁴² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight A chain or branched alkynyl group having 2 to 30 carbon atoms is represented.
R ³³ and R ⁴³ each independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, A linear or branched alkynyl group having 2 to 30 carbon atoms, a linear or branched alkyl group having 1 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the terminal, or linear or branched A alkenyl group having 2 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at its terminal.
R ³² and R ³³ may form a ring with R ³² and R ³³ .
R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ .
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms.
A plurality of R ³¹ , R ³² , R ³³ , R ³⁴ , R ⁴¹ , R ⁴² and R ⁴³ may be the same or different. ) The rubber composition according to claim 1, wherein the tryptophan derivative (D) is a compound represented by the following formula (1).

(In formula (1), X represents a hydrogen atom or a substituent. Plural Xs may be the same or different.
R ₁₁ represents a hydrogen atom or a substituent.
R ₁₂ represents a hydrogen atom or a substituent. A plurality of R ₁₂ may be the same or different. )   A pneumatic tire using the rubber composition according to claim 1 or 2 for a tire tread.