JP2014111689A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire excellent in silica dispersibility and scorch property.SOLUTION: There is provided a rubber composition for a tire which comprises: a diene-based rubber (A); silica (B); a silane coupling agent (C) having a thiol group and/or a thiol ester group; and lecithin (D), wherein the content of the silica (B) is 5 to 150 pts.mass based on 100 pts.mass of the diene-based rubber, the content of the silane coupling agent (C) is 0.5 to 20 mass% based on the content of the silica (B) and the content of the lecithin (D) is 0.5 to 20 mass% based on the content of the silica (B).

Description

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

  Patent Document 1 discloses a method for producing a tire rubber composition in which silica is blended with a diene rubber and a specific mercaptosilane is blended. In the tire rubber composition produced by this method, It is described that silica dispersibility is improved.

JP 2010-270247 A

  When the present inventor examined a rubber composition for tires containing a diene rubber, silica and mercaptosilane based on Patent Document 1, although the silica dispersibility was relatively good, the scorch time was short, and the scorch It was found that the property (workability) was not sufficient.

  This invention is made | formed in view of the above point, and it aims at providing the rubber composition for tires which is excellent in a silica dispersibility and scorch property.

As a result of intensive studies to achieve the above object, the present inventors have found that not only silica dispersibility but also scorch properties are improved by using a specific silane coupling agent and lecithin in combination. The present invention has been completed.
That is, the present invention provides the following (i) to (iii).

  (I) A diene rubber (A), silica (B), a silane coupling agent (C) having a thiol group and / or a thiol ester group, and lecithin (D), and the silica (B ) Is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber (A), and the content of the silane coupling agent (C) is relative to the content of the silica (B). The tire rubber composition, wherein the content of lecithin (D) is 0.5 to 20% by mass relative to the content of silica (B).

  (Ii) The silane coupling agent (C) is represented by the compound represented by the following formula (2) and / or the repeating unit represented by the following formula (3) and / or the following formula (4). The tire rubber composition according to (i) above, which is a polymer having a repeating unit.

(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 3, m represents an integer of 0 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 hydroxy group or a carboxy group at the terminal, A branched alkenyl group having 2 to 30 carbon atoms and having a hydroxy group or a carboxy group at the end is represented.
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. )

  (Iii) A pneumatic tire using the tire rubber composition described in (i) or (ii) above in a tire tread.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for tires which is excellent in a silica dispersibility and a scorch property can be provided.

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

(Rubber composition)
The rubber composition for tires of the present invention (hereinafter also simply referred to as “the rubber composition of the present invention”) is a silane having a diene rubber (A), silica (B), a thiol group and / or a thiol ester group. The coupling agent (C) and lecithin (D) are contained, and 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 silane coupling agent (C) is 0.5 to 20% by mass with respect to the content of the silica (B), and the content of the lecithin (D) is the content of the silica (B). It is a rubber composition for tires which is 0.5-20 mass% to the quantity.

Generally, in a composition containing a polymer such as a rubber composition, the polymer generates radicals by the action of heat, mechanical shearing force, etc., and the generated radicals extract hydrogen from the polymer via peroxy radicals. It is thought that it changes to peroxide. Moreover, the produced | generated peroxide decomposes | disassembles and produces | generates a new radical, As a result, it is thought that a radical produces | generates 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, cross-linking of the polymers proceeds by a reaction between the radical and the double bond, resulting in a short scorch time and a scorch property. Is expected to decrease.

However, since the rubber composition of the present invention contains lecithin, the phosphate ester structure in lecithin captures and stabilizes the radicals generated in the rubber composition, resulting in chain formation of radicals. It is considered that the scorch property is improved.
On the other hand, when lecithin is simply blended, since the lecithin does not have a silica / polymer coupling function, silica dispersibility is lowered.
The rubber composition of the present invention contains a silane coupling agent having a thiol group and / or a thiol ester group together with lecithin. Therefore, the thiol group (including those obtained by hydrolysis of the thiol ester group) improves the affinity between the rubber component and silica, improves the silica dispersibility, and the thiol group of the silane coupling agent is contained in lecithin. By acting with the phosphate ester structure, it is presumed to exhibit excellent scorch properties.

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

<Diene rubber (A)>
The diene rubber (A) used in the rubber 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. Examples include diene 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, aromatic vinyl-conjugated diene copolymer rubber is preferably used as the diene rubber (A), and butadiene rubber (BR) can be used in combination with the aromatic vinyl-conjugated diene copolymer. More preferred.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene copolymer rubber (SBR) and styrene-isoprene copolymer rubber. Among them, styrene-butadiene copolymer is mentioned. Rubber (SBR) is preferred.

The aromatic vinyl content (for example, styrene content) of the aromatic vinyl-conjugated diene copolymer is preferably 20 to 45% by mass because it is more excellent in silica dispersibility, and is 23 to 42% by mass. It is more preferable that
Further, the vinyl bond amount in the conjugated diene of the aromatic vinyl-conjugated diene copolymer is preferably 10 to 50% because the extrusion processability of the rubber composition of the present invention is excellent. More preferably, it is 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, and more preferably 600,000 to 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), because it is superior in silica dispersibility. The content is more preferably at least mass%, and further preferably at least 60 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 superior in silica dispersibility, so that the diene rubber (A ) Is preferably less than 50% by mass, more preferably less than 45% by mass, and even more preferably less than 40% by mass.

<Silica (B)>
The silica (B) used in the rubber composition of the present invention is not particularly limited, and any conventionally known silica compounded in the rubber composition for use 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, it is preferable that the silica (B) contains wet silica from the viewpoint of rubber reinforcement.

In the present invention, the silica (B) is preferably cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of 100 to 300 m ² / g, more preferably 140~200m ² / g.
Here, the CTAB adsorption specific surface area is a surrogate property of the surface area that silica can be used for adsorption with the silane coupling agent, and the amount of CTAB adsorption on the silica surface is JIS K6217-3: 2001 “Part 3: Specific surface area of It is a value measured according to “How to obtain—CTAB adsorption method”.

  In the rubber composition of the present invention, 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), and the silica dispersibility is more excellent. It is preferably 20 to 140 parts by mass, and more preferably 35 to 130 parts by mass.

<Silane coupling agent (C)>
The silane coupling agent (C) of the present invention is a silane coupling agent having a hydrolyzable group, and further has a thiol group and / or a thiol ester group.
The thiol group is represented by the formula “—SH” and is also referred to as a “mercapto group”.
The thiol ester group is represented by the formula “—SC (═O) R” (wherein R represents a hydrocarbon group, for example, an alkyl group having 1 to 13 carbon atoms represented by R ³⁴ described later), Hydrolysis provides a thiol group (—SH) and a carboxylic acid (RCOOH).
Hereinafter, when the term “thiol group” is simply used, the “thiol ester group” may include a “thiol group” provided by hydrolysis.

  Since the rubber composition of the present invention contains the silane coupling agent (C), it is considered that the thiol group improves the affinity between the rubber component and silica and the silica dispersibility is improved as described above.

  Here, examples of the hydrolyzable group include an alkoxy group, a phenoxy group, a carboxy group, and an alkenyloxy group. Among these, an alkoxy group is preferable because silica dispersibility is more excellent. 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 silane coupling agent (C) has a polyether chain and / or has a polysiloxane structure (-Si-O-) because of its superior silica dispersibility and scorch properties. Is preferred.

Here, the polyether chain is a side chain having two or more ether bonds, and specific examples thereof include, for example, a side chain having two or more structural units —R ^a —O—R ^b — in total. Can be mentioned. 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. Among these, a linear alkylene group is preferable because it is superior in silica dispersibility.

  By the way, as said silane coupling agent (C), 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, and among these, an alkoxy group having 1 to 3 carbon atoms is preferable because it is superior in silica dispersibility. 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 (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 1-10 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 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 1-3 and it is preferable that it is 1. m represents an integer of 0 to 2, and is preferably 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 addition, as a suitable aspect of the silane coupling agent (C) which has the said polyether chain | strand, for example, it is a compound represented by the said Formula (2), Comprising: l represents the integer of 1-2, m is 1 A compound representing an integer of ˜2 and n represents an integer of 0 to 1 is exemplified.

  On the other hand, as a suitable aspect of the silane coupling agent (C) having the polysiloxane structure, for example, it has a repeating unit represented by the following formula (3) and / or a repeating unit represented by the following formula (4). Examples include polymers.

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. A 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. A 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. An 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 hydroxy group or carboxy at the terminal Or a linear or branched alkenyl group having 2 to 30 carbon atoms and having a hydroxy group or a carboxy 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 . A plurality of R ³³ and R ⁴³ may be the same or different.

In the case having both units the polymer is represented by the unit and the formula represented by (4) the formula (3), it is preferred that R ⁴³ is a group having a hydroxy group at the terminal.
Further, when the polymer does not have the unit represented by the above formula (4) but has only the unit represented by the above formula (3), R ³³ may be a group having a hydroxy group at the terminal. preferable.

In the above formula (3), R ³⁴ represents an alkyl group of 1 to 13 carbon atoms, among them, preferably an alkyl group having 3 to 10 carbon atoms. Specific examples of the alkyl group having 3 to 10 carbon atoms include a hexyl group, a heptyl group, and an octyl group. A plurality of R ³⁴ may be the same or different.

  As a polymer having such a unit represented by the above formula (3) and / or a unit represented by the above formula (4), from the viewpoint of a balance between good scorch properties and silica dispersibility, A copolymer having a unit represented by the formula (3) and a unit represented by the above formula (4) is preferable.

As said silane coupling agent (C), the thing which has the said polyether chain | strand is more preferable than the thing which has the said polysiloxane structure from the reason that a silica dispersibility is more excellent.
When the silane coupling agent (C) has a polyether chain, the polyether chain protects the silica, so that the radical scavenging ability of lecithin (D) due to the interaction with the silica is suppressed, and the silica dispersibility is reduced. It is considered excellent.

  Content of the said silane coupling agent (C) is 0.5-20 mass% with respect to content of the said silica (B), and is 1-18 mass% from the reason that it is excellent by a silica dispersibility. It is preferably 2 to 15% by mass.

<Lecithin (D)>
Next, lecithin (D) used in the rubber composition of the present invention will be described. In the present specification, the term lecithin is used as a general term for phospholipids.
The phospholipid is not particularly limited as long as it has a phosphate ester structure. The phosphate ester structure refers to a structure in which part or all of the three hydrogen atoms of phosphoric acid (O═P (OH) ₃ ) are substituted with an organic group.

  Since the rubber composition of the present invention contains the lecithin (D), as described above, radicals are stabilized by the phosphate ester structure in the lecithin (D), and chain generation of radicals is suppressed. I guess that. In addition, since the rubber composition of this invention contains the said silane coupling agent (C) with the said lecithin (D) as mentioned above, the thiol group (thiol ester group of the said silane coupling agent hydrolyzed. In the lecithin (D), the radical stabilizing ability of the lecithin (D) is improved, and the amount of lecithin (D) added to the rubber component Even in a small amount, it is estimated that excellent scorch properties are exhibited.

The lecithin (D) is not particularly limited. For example, glycerophospholipid having a basic skeleton such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol, diphosphatidylglycerol, and derivatives thereof; sphingo Sphingophospholipids based on sphingosine bases such as myelin and derivatives thereof; and the like.
The lecithin (D) may be enzyme-decomposed lecithin. Examples of the enzymatically decomposed lecithin include lysophosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylinositol, lysophosphatidylserine and the like obtained by limited hydrolysis of the fatty acid ester moiety.

  Among these, glycerophospholipid is preferable because scorch is more excellent, and phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and derivatives thereof are more preferable.

As said lecithin (D) which is glycerophospholipid, the compound represented by following formula (1) is mentioned, for example.

In the above formula (1), X represents a polar group such as choline, ethanolamine, inositol, or serine, and —C (O) R ¹¹ and —C (O) R ¹² are the same or different and are fatty acid residues. Represents.

The fatty acid of the fatty acid residue may be a saturated fatty acid or an unsaturated fatty acid, and the carbon number thereof is preferably 4 to 30, for example, and more preferably 12 to 22.
Examples of saturated fatty acids include n-butanoic acid, n-pentanoic acid, 3-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid (caprylic acid), n-nonanoic acid, and n-decanoic acid. (Capric acid), n-dodecanoic acid (lauric acid), n-tetradecanoic acid (myristic acid), n-pentadecanoic acid, n-hexadecanoic acid (palmitic acid), n-heptadecanoic acid, n-octadecanoic acid (stearic acid) N-icosanoic acid, n-docosanoic acid, n-tetracosanoic acid, n-hexacosanoic acid, n-octacosanoic acid, n-triacontanoic acid and the like.
Examples of unsaturated fatty acids include caproleic acid, sterling acid, 9-dodecenoic acid, palmitooleic acid, oleic acid, elaidic acid, ricinoleic acid, petrothelic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearin Acid, punicic acid, licanoic acid, parinaric acid, gadoric acid, arachidonic acid, 5-icosenoic acid, 5,8,11,14,17-eicosapentaenoic acid, 5-docosenoic acid, cetoleic acid, erucic acid, 5,13 -Docosadienoic acid, ceracholic acid (nervonic acid), etc. are mentioned.

  The content of lecithin (D) is 0.5 to 20% by mass with respect to the content of silica (B). It is preferable that it is 18 mass%, and it is more preferable that it is 6.5-15 mass%.

<Optional component>
If necessary, the rubber composition of the present invention may further contain an additive within a range that does not impair its effects and purposes.
Examples of the additive include a silane coupling agent other than the silane coupling agent (C) contained in the rubber composition of the present invention, a filler other than silica (B) (for example, carbon black), 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, etc. Can be 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.
The rubber 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 rubber composition of the present invention for 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 is not particularly limited except that the rubber composition of the present invention is used for a tread of a pneumatic tire, and can be produced, 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 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 coach>
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 result was expressed as an index with the scorch time of the standard example as 100. The larger the index, the longer the scorch time and the better the scorch property (workability).

<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 Paine effect of the standard example as 100. The smaller the index, the smaller the Pain effect and the better the silica dispersibility.

<Reinforcing index>
The rubber composition after vulcanization was subjected to a tensile test according to ASTM K6251 and the ratio (M300 / M100) of its 300% modulus (M300) to 100% modulus (M100) was calculated as the reinforcing index.
The results are shown in Table 1. The results were expressed as an index with the reinforcing index of the standard example as 100. A larger index means better silica dispersibility.

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)

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%.)
Silane coupling agent C3: NXT silane (manufactured by Momentive) (polymer having a repeating unit represented by the above formula (3). The proportion of the repeating unit represented by the above formula (3) is 100 mol%. .)

Silane coupling agent C4: γ-mercaptopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM803) (compound represented by the above formula (2). Here, R ²¹ : —OCH ₃ , R ²⁴ :-( _{CH 2) 3 -, l =} 3, m = 0, n = 0).

Silane coupling agent X1: VP Si69 (Evonik Degussa) (bis (3-triethoxysilylpropyl) tetrasulfide)
Additive D1: San lecithin L-61 (manufactured by Taiyo Kagaku) (refined soybean lecithin)
Additive X2: Sunsoft Q-185SP (manufactured by Taiyo Kagaku) (decaglyceryl pentastearate)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator: Mixture of Noxeller CZ-G (manufactured by Ouchi Shinsei Chemical Co., Ltd.) and Sunceller DG (manufactured by Sanshin Chemical Industry Co., Ltd.)

  As can be seen from Table 1, the implementation containing the silane coupling agent (C) and lecithin (D) compared to the standard example containing the silane coupling agent (C) but not containing lecithin (D). It turned out that all of Examples 1-7 are excellent in scorch property and silica dispersibility.

On the other hand, although the silane coupling agent (C) and the lecithin (D) are contained, the lecithin (D) amount is more than 20% by mass with respect to the silica (B) amount, and the scorch property is insufficient. I understood that.
It was found that Comparative Example 2 having the silane coupling agent (C) but not containing lecithin (D) has insufficient scorch and silica dispersibility.
Comparative Example 3 containing no silane coupling agent (C) and lecithin (D) was found to be inferior in silica dispersibility although the scorch property was good.
It was also found that Comparative Example 4 containing lecithin (D) but not containing the silane coupling agent (C) was inferior in silica dispersibility although the scorch property was good.

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)

A diene rubber (A), silica (B), a silane coupling agent (C) having a thiol group and / or a thiol ester group, and lecithin (D),
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),
Content of the said silane coupling agent (C) is 0.5-20 mass% with respect to content of the said silica (B),
A tire rubber composition, wherein the content of lecithin (D) is 0.5 to 20% by mass relative to the content of silica (B). The 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 / or a repeating unit represented by the following formula (4). The tire rubber composition according to claim 1, which is a polymer having
(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 3, m represents an integer of 0 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 hydroxy group or a carboxy group at the terminal, A branched alkenyl group having 2 to 30 carbon atoms and having a hydroxy group or a carboxy group at the end is represented.
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. )   A pneumatic tire using the tire rubber composition according to claim 1 for a tire tread.