JP7006046B2 - Rubber composition and pneumatic tires - Google Patents

Description

The present invention relates to rubber compositions and pneumatic tires.

In recent years, it has been required to reduce the heat generation (hysteresis loss) of a tire from the viewpoint of low fuel consumption when the vehicle is running. On the other hand, a method of blending silica with a rubber component constituting a tread portion of a tire to reduce heat generation of the tire is known.
However, since silica has a low affinity with the rubber component and has high agglomeration between silicas, even if silica is simply mixed with the rubber component, the silica does not disperse and the effect of reducing heat generation is sufficiently obtained. There was a problem that it could not be done.

Under such circumstances, for example, Patent Document 1 discloses an organosilicon compound preferably used as a compounding agent for a rubber composition containing a filler such as silica, and a rubber composition containing the above-mentioned organosilicon compound. There is. According to Patent Document 1, it is described that a rubber composition containing the organosilicon compound has a low hysteresis loss and can realize a fuel-efficient tire.

Japanese Unexamined Patent Publication No. 2016-191040

In recent years, due to environmental problems and resource problems, it is required to further reduce the heat generation property of the tire, and accordingly, the rubber composition for tires containing silica is required to further improve the dispersibility of silica (silica dispersibility). ing. Further, in recent years, as the demand for automobile safety has increased, it is desired to further improve the wet grip performance of tires.

By the way, from the study of the present inventor, in a rubber composition containing butadiene rubber (BR), styrene-butadiene rubber (SBR) and silica, silica is an SBR phase (SBR phase) rather than a BR phase (BR phase). It is known that such a bias in the distribution of silica is one of the factors for the deterioration of the dispersibility of silica.
Further, when the ratio of the vinyl structure of SBR is high, the wet grip performance when the tire is made as compared with the case where the ratio of the vinyl structure is low due to the high compatibility with BR (hereinafter, also simply referred to as "wet grip performance"). ) Will be low. Since SBR having a high proportion of vinyl structure has advantageous properties such as excellent workability, even in a rubber composition using such SBR, the dispersibility of silica is further improved and the wet grip performance is improved. Is desirable.

Under such circumstances, when the present inventor blended BR, SBR having a high proportion of vinyl structure, silica, and the organosilicon compound described in Patent Document 1, the silica dispersibility is at the level required these days. It became clear that it does not necessarily satisfy. It has also become clear that the wet grip performance does not always meet the level required these days.

Therefore, in view of the above circumstances, the present invention uses a rubber composition using SBR having a high proportion of vinyl structure, which is excellent in silica dispersibility and wet grip performance, and the rubber composition. The purpose is to provide the pneumatic tires that have been used.

As a result of diligent studies on the above problems, the present inventor has found that the above problems can be solved by blending BR, SBR having a high proportion of vinyl structure, silica and a specific organosilicon compound in a specific amount ratio, and the present invention. It came to.
That is, the present inventor has found that the above problem can be solved by the following configuration.

(1) A diene-based rubber containing butadiene rubber and solution-polymerized styrene-butadiene rubber, silica, and an organosilicon compound represented by the formula (I) described later are contained.
The solution-polymerized styrene-butadiene rubber has a vinyl structure ratio of more than 40 mol%.
The content of the butadiene rubber in the diene rubber is 10 to 50% by mass, and the content of the solution-polymerized styrene-butadiene rubber is 50 to 90% by mass.
The silica content is 60 to 200 parts by mass with respect to 100 parts by mass of the diene rubber.
A rubber composition in which the content of the organosilicon compound is 10.0 to 150.0% by mass with respect to the content of the butadiene rubber.
(2) The rubber composition according to (1) above, wherein the silica has a CTAB adsorption specific surface area of 180 to 280 m ² / g.
(3) A pneumatic tire using the rubber composition according to (1) or (2) above.

As shown below, according to the present invention, a rubber composition using SBR having a high proportion of vinyl structure, which is excellent in silica dispersibility and wet grip performance, and the above rubber composition are used. It is possible to provide the pneumatic tires that have been used.

It is a partial cross-sectional schematic diagram which shows an example of embodiment of the pneumatic tire of this invention.

Hereinafter, the rubber composition of the present invention and a pneumatic tire using the rubber composition will be described.
The numerical range represented by using "-" in the present specification means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
In addition, each component contained in the rubber composition of the present invention may be used alone or in combination of two or more. Here, when two or more kinds of each component are used in combination, the content of the component means the total content unless otherwise specified.

[1] Rubber Composition The rubber composition of the present invention (hereinafter, also referred to as “the composition of the present invention”) includes a diene-based rubber containing a butadiene rubber and a solution-polymerized styrene-butadiene rubber, silica, and a formula (I) described later. ) Contains an organic silicon compound.
Here, the solution-polymerized styrene-butadiene rubber has a styrene unit content of 40% by mass or less and a vinyl structure ratio of more than 40 mol%.
Further, in the diene-based rubber, the content of the butadiene rubber is 10 to 50% by mass, and the content of the solution-polymerized styrene-butadiene rubber is 50 to 90% by mass.
The silica content is 60 to 200 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the organosilicon compound is 10.0 to 150.0% by mass with respect to the content of the butadiene rubber.

Since the composition of the present invention has such a structure, it is considered that the above-mentioned effects can be obtained. The reason is not clear, but it is presumed to be as follows.
As described above, from the study of the present inventor, in a rubber composition containing butadiene rubber (BR), styrene butadiene rubber (SBR) and silica, silica is in the SBR phase (SBR) rather than the BR phase (BR phase). It is easy to distribute to the phase), and it is known that such a bias in the distribution of silica is one of the factors for the deterioration of the dispersibility of silica. Further, when the proportion of the vinyl structure of the SBR is high, the initial dispersibility of silica is relatively high due to the high compatibility with BR, but the reaggregation of silica occurs, and as a result, the dispersibility of silica occurs. Is known to be at a low level.
Here, as described later, the specific organosilicon compound contained in the composition of the present invention has a skeleton portion having a structure of butadiene rubber and a side chain portion having a structure of alkoxysilane. The skeleton portion has a high affinity with butadiene rubber, and the side chain portion has a high affinity with silica. Therefore, it is considered that the specific organosilicon compound functions as a coupling agent for binding butadiene rubber and silica, enhances the distribution of silica to the BR phase, and improves the dispersibility of silica.
On the other hand, from the study of the present inventor, it is known that the effect of the coupling by the above-mentioned specific organosilicon compound changes significantly depending on the amount ratio with the butadiene rubber, and the criticality is observed.
The composition of the present invention contains BR, SBR, silica, and a specific organosilicon compound, and the content of the specific organosilicon compound is in a specific range with respect to BR, so that the composition exhibits extremely high silica dispersibility. it is conceivable that.

Hereinafter, each component contained in the composition of the present invention will be described.

[Diene rubber]
The diene-based rubber contained in the composition of the present invention includes a butadiene rubber and a solution-polymerized styrene-butadiene rubber.
Here, the solution-polymerized styrene-butadiene rubber has a styrene unit content of 40% by mass or less and a vinyl structure ratio of more than 40 mol%.
Further, in the diene-based rubber, the content of the butadiene rubber is 10 to 50% by mass, and the content of the solution-polymerized styrene-butadiene rubber is 50 to 90% by mass.

[Butadiene rubber]
As described above, the diene-based rubber includes butadiene rubber (hereinafter, also referred to as “BR”).

<Contents>
As described above, the content of butadiene rubber in the diene rubber is 10 to 50% by mass. Among them, it is preferably 15 to 45% by mass, more preferably 20 to 40% by mass, for the reason that the effect of the present invention is more excellent.

[Solution-polymerized styrene-butadiene rubber]
As described above, the diene-based rubber includes solution-polymerized styrene-butadiene rubber (hereinafter, also referred to as “solution-polymerized SBR” or simply “SBR”).
The SBR is not particularly limited as long as it is a styrene-butadiene rubber obtained by polymerizing styrene (or a derivative thereof) and butadiene by solution polymerization, and in addition to styrene (or a derivative thereof) and butadiene, yet another It may be a polymer of a monomer (for example, isoprene or acrylonitrile).

<Styrene unit content>
As described above, the SBR has a styrene unit content of 40% by mass or less. Above all, it is preferably 5 to 40% by mass because the effect of the present invention is more excellent.
The styrene unit content is intended to be the content of styrene units (repeating units derived from styrene (or a derivative thereof)) with respect to SBR.

<Micro structure>

(Vinyl structure)
As described above, the SBR has a vinyl structure ratio of more than 40 mol%. Among them, for the reason that the effect of the present invention is more excellent, it is preferably 45 mol% or more, more preferably 50 mol% or more, further preferably 55 mol% or more, and 60 mol% or more. It is particularly preferable to have. The upper limit is not particularly limited, but it is preferably 80 mol% or less, more preferably 70 mol% or less, for the reason that the effect of the present invention is more excellent.
The ratio of the vinyl structure is the ratio of the repeating units having a vinyl structure (for example, 1,2-vinyl structure when butadiene is 1,3-butadiene) among all the repeating units derived from butadiene (for example). Mol%) says.

(1,4-Transformer structure)
In the above SBR, the ratio of the 1,4-transformer structure is not particularly limited.
The ratio of the 1,4-trans structure means the ratio (mol%) of the repeating units having the 1,4-trans structure among all the repeating units derived from butadiene.

(1,4-cis structure)
In the above SBR, the ratio of the 1,4-cis structure is not particularly limited.
The ratio of the 1,4-cis structure is the ratio (mol%) of the repeating units having the 1,4-cis structure among all the repeating units derived from butadiene.

<Preferable aspect>
The SBR is preferably a terminal-modified SBR (terminally modified SBR), and more preferably a terminal-modified SBR having a hydroxy group at the terminal, for the reason that the effect of the present invention is more excellent.

<Contents>
As described above, the content of the SBR in the diene rubber is 50 to 90% by mass. Among them, 55 to 85% by mass is preferable, and 60 to 80% by mass is more preferable, for the reason that the effect of the present invention is more excellent.

[Total content of BR and SBR]
The total content of BR and SBR in the diene rubber is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and 90 to 90 to 100% by mass, because the effect of the present invention is more excellent. It is more preferably 100% by mass.

[Other diene rubber]
The diene-based rubber contained in the composition of the present invention may further contain a diene-based rubber (other diene-based rubber) that does not fall under any of the above-mentioned BR and SBR. Examples of such diene-based rubbers include natural rubber (NR), isoprene rubber (IR), solution-polymerized styrene-butadiene rubber other than the above-mentioned solution-polymerized styrene-butadiene rubber, emulsified polymerized styrene-butadiene rubber, and acrylonitrile-butadiene copolymer rubber. (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like can be mentioned.
The content of the other diene-based rubber in the diene-based rubber is not particularly limited, but is preferably 0 to 30% by mass for the reason that the effect of the present invention is more excellent.

[Molecular weight]
The weight average molecular weight (Mw) of the diene-based rubber contained in the composition of the present invention is preferably 100,000 to 10,000,000, preferably 300,000 to 10,000, for the reason that the effect of the present invention is more excellent. More preferably, it is 3,000,000.
The number average molecular weight (Mn) of the diene-based rubber contained in the composition of the present invention is 50,000 or more. Among them, for the reason that the effect of the present invention is more excellent, it is preferably 5,000,000 or less, and more preferably 150,000 to 1,500,000.
It is preferable that the Mw and / or Mn of at least one diene rubber contained in the diene rubber is included in the above range, and the Mw and / or Mn of all the diene rubbers contained in the diene rubber is described above. It is more preferable to be included in the range.

The above Mw and Mn are standard polystyrene-equivalent values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
・ Solvent: Tetrahydrofuran ・ Detector: RI detector

[silica]
The silica contained in the composition of the present invention is not particularly limited, and any conventionally known silica can be used.
Examples of the silica include wet silica, dry silica, fumed silica, and diatomaceous earth. As the silica, one kind of silica may be used alone, or two or more kinds of silica may be used in combination.

The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area (hereinafter, “CTAB adsorption specific surface area” is also simply referred to as “CTAB”) of the silica is not particularly limited, but 100 to 300 m ² for the reason that the effect of the present invention is more excellent. It is preferably / g, more preferably 150 to 290 m ² / g, and even more preferably 180 to 280 m ² / g.
Here, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorbed on the silica surface according to JIS K6217-3: 2001 "Part 3: How to obtain the specific surface area-CTAB adsorption method".

In the composition of the present invention, the content of silica is 60 to 200 parts by mass with respect to 100 parts by mass of the above-mentioned diene rubber. Among them, 70 to 130 parts by mass is preferable, and 80 to 110 parts by mass is more preferable, for the reason that the effect of the present invention is more excellent.

[Specific organosilicon compound]
The specific organosilicon compound contained in the composition of the present invention is represented by the following formula (I).
As described above, it is considered that the specific organosilicon compound functions as a coupling agent for binding butadiene and silica, enhances the distribution of silica to the butadiene rubber phase, and improves the dispersibility of silica.

上記式（Ｉ）中、Ｒ^１は、炭素数１～１０のアルキル基又は炭素数６～１０のアリール基を表し、Ｒ^２は、炭素数１～１０のアルキル基又は炭素数６～１０のアリール基を表し、ｆは、０以上の数を表し、ｅ及びｇは、それぞれ独立して、０より大きい数を表し、ｍは、１～３の整数を表す。ただし、各繰り返し単位の順序は任意である。
Ｒ^１が複数存在する場合、複数存在するＲ^１は同一であっても異なっていてもよい。Ｒ^２が複数存在する場合、複数存在するＲ^２は同一であっても異なっていてもよい。

In the above formula (I), R ¹ represents an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms, and R ² is an alkyl group having 1 to 10 carbon atoms or 6 to 10 carbon atoms. Represents an aryl group, f represents a number greater than or equal to 0, e and g each independently represent a number greater than 0, and m represents an integer of 1 to 3. However, the order of each repeating unit is arbitrary.
When there are a plurality of R ^1s , the plurality of R ^1s may be the same or different. When there are a plurality of R ^2s , the plurality of R ^2s may be the same or different.

The alkyl group having 1 to 10 carbon atoms may be linear, cyclic or branched, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an i-propyl group and an n-. Butyl group, s-butyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, cyclopropyl group, cyclobutyl group, Cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group and the like can be mentioned. Among them, a linear alkyl group is preferable, and a methyl group or an ethyl group is more preferable, because the effect of the present invention is more excellent.
Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, an α-naphthyl group, a β-naphthyl group and the like. Among them, a linear alkyl group is preferable, and a methyl group or an ethyl group is more preferable, because the effect of the present invention is more excellent.

As described above, in formula (I), e represents a number greater than 0 (preferably an integer greater than 0). Among them, for the reason that the effect of the present invention is more excellent, it is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. The upper limit is not particularly limited, but is preferably 100 or less, more preferably 50 or less, still more preferably 40 or less, for the reason that the effect of the present invention is more excellent.

As described above, in the formula (I), f represents a number of 0 or more (preferably an integer of 0 or more). The upper limit is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 20 or less, more preferably 10 or less, further preferably 5 or less, and particularly preferably 1 or less. preferable.

As described above, in formula (I), g represents a number greater than 0 (preferably an integer greater than 0). Among them, 5 or more is preferable, and 10 or more is more preferable, for the reason that the effect of the present invention is more excellent. The upper limit is not particularly limited, but is preferably 50 or less, more preferably 30 or less, still more preferably 20 or less, for the reason that the effect of the present invention is more excellent.

For e, f and g in the formula (I), e / (e + f + g) is preferably 0.50 to 0.90, preferably 0.60 to 0.85, for the reason that the effect of the present invention is more excellent. It is more preferably 0.70 to 0.80, more preferably 0.72 to 0.75, and particularly preferably 0.72 to 0.75.

For e, f and g in the formula (I), f / (e + f + g) is preferably less than 0.28, more preferably 0.20 or less, for the reason that the effect of the present invention is more excellent. It is more preferably 0.10 or less. The lower limit is not particularly limited and is 0.

For e, f and g in the formula (I), g / (e + f + g) is preferably 0.10 to 0.50, preferably 0.15 to 0.40, for the reason that the effect of the present invention is more excellent. It is more preferably 0.20 to 0.30, more preferably 0.25 to 0.25, and particularly preferably 0.25 to 0.25.

For f and g in the formula (I), g / (f + g) is preferably 0.30 or more, and more preferably 0.70 or more, for the reason that the effect of the present invention is more excellent. The upper limit is not particularly limited and is 1.

For e, f and g in the formula (I), (f + g) / (e + f + g) is preferably 0.05 to 0.50, and 0.10 to 0. It is more preferably 40, further preferably 0.20 to 0.30, preferably more than 0.20 and less than 0.30, and particularly preferably 0.25 to 0.25.

The number average molecular weight (Mn) of the specific organosilicon compound is less than 50,000. Among them, it is preferably 25,000 or less, and more preferably 10,000 or less, for the reason that the effect of the present invention is more excellent. The lower limit is not particularly limited, but is preferably 1,000 or more for the reason that the effect of the present invention is more excellent.

The Mn is a standard polystyrene-equivalent value obtained by gel permeation chromatography (GPC) measurement under the following conditions.
・ Solvent: Tetrahydrofuran ・ Detector: RI detector

[Manufacturing method of specific organosilicon compound]
The method for producing the specific organosilicon compound is not particularly limited, but for the reason that the effect of the present invention is more excellent, polybutadiene represented by the formula (II) and the organic represented by the formula (III) are shown in the following scheme. A method for producing a silicon compound by hydrosilylation in the presence of a platinum compound-containing catalyst, preferably in the presence of a platinum compound-containing catalyst and a co-catalyst is preferable.

In the above formulas (II) and (III), the definitions, specific examples and suitable embodiments of R ¹ , R ² , f, e, g and m are described in R ¹ , R ² and R 2 in the above formula (I), respectively. Same as f, e, g and m.

For e and f + g in the formula (II), e / (e + f + g) is preferably 0.50 to 0.90, preferably 0.60 to 0.85, for the reason that the effect of the present invention is more excellent. Is more preferable, 0.70 to 0.80 is further preferable, and 0.72 to 0.75 is particularly preferable.

For e and f + g in the formula (II), (f + g) / (e + f + g) is preferably 0.05 to 0.50, preferably 0.10 to 0.40, for the reason that the effect of the present invention is more excellent. It is more preferably 0.20 to 0.30, more preferably more than 0.20 and less than 0.30, and most preferably 0.25 to 0.28.

The number average molecular weight (Mn) of the polybutadiene represented by the formula (II) is preferably 25,000 or less, and more preferably 10,000 or less, for the reason that the effect of the present invention is more excellent. The lower limit is not particularly limited, but is preferably 1,000 or more for the reason that the effect of the present invention is more excellent.

The Mn is a standard polystyrene-equivalent value obtained by gel permeation chromatography (GPC) measurement under the following conditions.
・ Solvent: Tetrahydrofuran ・ Detector: RI detector

The polybutadiene represented by the formula (II) can also be obtained as a commercially available product, for example, NISSO-PB B-1000, NISSO-PB B-2000, NISSO-PB B-3000 (above, Nippon Soda Co., Ltd.). , Ricon130, Ricon131, Ricon134, Ricon142, Ricon150, Ricon152, Ricon153, Ricon154, Ricon156, Ricon157 (above, manufactured by CRAY VALLEY), LBR-302, LBR-307, LBR-305, LBR-300 , LBR-361 (all manufactured by Kuraray Co., Ltd.) are on the market.

On the other hand, examples of the organosilicon compound represented by the formula (III) include trimethoxysilane, methyldimethoxysilane, dimethylmethoxysilane, triethoxysilane, methyldiethoxysilane, and dimethylethoxysilane. Of these, triethoxysilane is preferable because the effect of the present invention is more excellent.

The platinum compound-containing catalyst used in the hydrosilylation reaction is not particularly limited, and specific examples thereof include platinum chloride, an alcohol solution of platinum chloride, and platinum-1,3-divinyl-1,1. , 3,3-Tetramethyldisiloxane complex in toluene or xylene, tetraxtriphenylphosphine platinum, dichlorobistriphenylphosphine platinum, dichlorobis acetonitrile platinum, dichlorobisbenzonitrile platinum, dichlorocyclooctadiene platinum, etc., platinum-carbon , Platinum-alumina, platinum-silica and other supported catalysts.
From the viewpoint of selectivity during hydrosilylation, a 0-valent platinum complex is preferable, and a toluene or xylene solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex is more preferable.
The amount of the platinum compound-containing catalyst used is not particularly limited, but from the viewpoint of reactivity, productivity, etc., 1 × of platinum atoms contained in 1 mol of the organosilicon compound represented by the formula (III). An amount of ^10-7 to 1 × 10 ⁻² mol is preferable, and an amount of 1 × ^10-7 to 1 × 10 ⁻³ mol is more preferable.

As the co-catalyst in the above reaction, it is preferable to use one or more selected from an ammonium salt of an inorganic acid, an acid amide compound and a carboxylic acid.
Specific examples of ammonium salts of inorganic acids include ammonium chloride, ammonium sulfate, ammonium ammonium sulfate, ammonium nitrate, monoammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium diaphosphate, ammonium carbonate, and hydrogen carbonate. Ammonium, ammonium sulfide, ammonium borate, ammonium borofluoride and the like can be mentioned. Among them, ammonium salts of inorganic acids having a pKa of 2 or more are preferable, and ammonium carbonate and ammonium hydrogencarbonate are preferable because the effect of the present invention is more excellent. Is more preferable.

Specific examples of the acid amide compound include formamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, propionamide, acrylamide, malonamide, succinamide, maleamide, fumalamide, benzamide, phthalamide, palmitate amide, stearate amide and the like. Can be mentioned.

Specific examples of the carboxylic acid include acetic acid, propionic acid, butyric acid, methoxyacetic acid, pentanoic acid, caproic acid, heptonic acid, octanoic acid, lactic acid, glycolic acid and the like, and among these, acetic acid, acetic acid and lactic acid are preferable. , Acetic acid is more preferred.

The amount of the co-catalyst used is not particularly limited, but 1 × 10 ^-5 to 1 × 10 ⁻ per 1 mol of the organosilicon compound represented by the formula (III) from the viewpoint of reactivity, selectivity, cost and the like. ¹ mol is preferable, and 1 × 10 ^-4 to 5 × 10 ^-1 mol is more preferable.

Although the above reaction proceeds without a solvent, a solvent can also be used.
Specific examples of the solvent that can be used include hydrocarbon solvents such as pentane, hexane, cyclohexane, heptane, isooctane, benzene, toluene and xylene; ether solvents such as diethyl ether, tetrahydrofuran and dioxane; ethyl acetate, butyl acetate and the like. Ester-based solvents; aprotonic polar solvents such as N, N-dimethylformamide; chlorinated hydrocarbon-based solvents such as dichloromethane and chloroform, and the like, even if one of these solvents is used alone, 2 A mixture of seeds or more may be used.

The reaction temperature in the hydrosilylation reaction is not particularly limited, and is preferably 0 to 200 ° C. for the reason that the effect of the present invention is more excellent.
In order to obtain an appropriate reaction rate, the reaction is preferably carried out under heating, and from such a viewpoint, the reaction temperature is more preferably 40 to 110 ° C, and even more preferably 40 to 90 ° C.
The reaction time is also not particularly limited and is usually about 1 to 60 hours, but 1 to 30 hours is preferable and 1 to 20 hours is more preferable because the effect of the present invention is more excellent.

〔Content〕
In the composition of the present invention, the content of the specific organosilicon compound is 10.0 to 150.0% by mass with respect to the content of the above-mentioned butadiene rubber. Hereinafter, the content of the specific organosilicon compound with respect to the content of the butadiene rubber is also referred to as "specific Si / BR".
The specific Si / BR is preferably 15.0 to 140.0% by mass, more preferably 40.0 to 135.0% by mass, for the reason that the effect of the present invention is more excellent.

In the composition of the present invention, the content of the specific organic silicon compound is preferably 1.0 to 20.0% by mass with respect to the above-mentioned content of silica for the reason that the effect of the present invention is more excellent. , 2.0 to 15.0% by mass, more preferably 5.0 to 10.0% by mass.

In the composition of the present invention, the content of the specific organosilicon compound is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the above-mentioned diene-based rubber, for the reason that the effect of the present invention is more excellent. Above all, it is preferable that the amount is 10 parts by mass or more because the effect of the present invention is more excellent.

[Arbitrary ingredient]
The composition of the present invention may contain components (arbitrary components) other than the above-mentioned components, if necessary, as long as the effects and purposes are not impaired.
Such components include, for example, fillers other than silica (eg, carbon black), silane coupling agents, terpene resins (preferably aromatic-modified terpene resins), thermosetting microcapsules, zinc oxide (zinc flower). ), Stealic acid, anti-aging agents, waxes, processing aids, process oils, liquid polymers, thermosetting resins, vulcanizing agents (eg sulfur), commonly used in rubber compositions such as vulcanization accelerators. Various additives and the like can be mentioned.

〔Carbon black〕
The composition of the present invention preferably contains carbon black because the effect of the present invention is more excellent. As the carbon black, one kind of carbon black may be used alone, or two or more kinds of carbon black may be used in combination.
The carbon black is not particularly limited, and for example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF and the like. Can be used.
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is not particularly limited, but is preferably 50 to 200 m ² / g, preferably 70 to 150 m ² / g, for the reason that the effect of the present invention is more excellent. Is more preferable.
Here, the nitrogen adsorption specific surface area (N ₂ SA) is the amount of nitrogen adsorbed on the carbon black surface according to JIS K6217-2: 2001 "Part 2: How to obtain the specific surface area-Nitrogen adsorption method-Single point method". It is a measured value.

In the composition of the present invention, the content of carbon black is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the above-mentioned diene-based rubber. More preferably, it is 2 to 10 parts by mass.

〔Silane coupling agent〕
The composition of the present invention preferably contains a silane coupling agent because the effect of the present invention is more excellent. The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional 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 because the effect of the present invention is more excellent. When the hydrolyzable group is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 to 16 and more preferably 1 to 4 for the reason that the effect of the present invention is more excellent. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, a propoxy group and the like.

The above organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound, for example, an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group, a mercapto group, or a block. Examples thereof include a mercapto group (protected mercapto group) (for example, an octanoylthio group), and among them, a sulfide group (particularly, a disulfide group and a tetrasulfide group), a mercapto group, and a block mercapto group for the reason that the effect of the present invention is more excellent. Is preferable.
One type of silane coupling agent may be used alone, or two or more types may be used in combination.

The silane coupling agent is preferably a sulfur-containing silane coupling agent because the effect of the present invention is more excellent.

Specific examples of the above silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and mercaptopropyltrimethoxy. Silane, mercaptopropyl triethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilyl Examples thereof include propyl-N, N-dimethylthiocarbamoyl-tetrasulfide, 3-octanoylthio-1-propyltriethoxysilane, etc., and one of them may be used alone or two or more thereof may be used in combination. ..

The silane coupling agent is preferably a compound represented by the following formula (S) because the effect of the present invention is more excellent.
(C _n H _{2n + 1} O) ₃ -Si-C _m H _2m -S-CO-C _k H _{2k + 1} formula (S)
In the formula (S), n represents an integer of 1 to 3, m represents an integer of 1 to 5 (preferably an integer of 2 to 4), and k represents an integer of 1 to 15 (preferably 5 to 10). Integer).

In the composition of the present invention, the content of the silane coupling agent is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 2 to 20% by mass with respect to the above-mentioned silica content. More preferably, it is 5 to 15% by mass.

[2] Pneumatic tire The pneumatic tire of the present invention is a pneumatic tire manufactured by using the composition of the present invention described above. Above all, it is preferable that the tire is a pneumatic tire using the composition of the present invention for the tire tread.
FIG. 1 shows a schematic partial cross-sectional view of a pneumatic tire showing 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 a fiber cord is embedded is mounted between the pair of left and right bead portions 1, and the end portion of the carcass layer 4 is located around the bead core 5 and the bead filler 6 from the inside to the outside of the tire. It is folded back and rolled up.
Further, in the tire tread portion 3, the belt layer 7 is arranged on the outside of the carcass layer 4 over one circumference of the tire.
Further, in the bead portion 1, the rim cushion 8 is arranged at a portion in contact with the rim.
The tire tread portion 3 is formed by the composition of the present invention described above.

The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Further, as the gas to be filled in the pneumatic tire, an inert gas such as nitrogen, argon or helium can be used in addition to normal air or air adjusted for oxygen partial pressure.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[Manufacturing of Specified Organosilicon Compounds]
In a 1 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer, Ricon130 (manufactured by Cray Valley, number average molecular weight: 2,500, polybutadiene represented by the above formula (II), formula ( II), (f + g) / (e + f + g) = 0.28) 100 g, toluene 200 g, toluene solution of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (0 as platinum atom) .52 × 10 ^-4 mol) and 0.31 g of acetic acid (0.52 × ^10-2 mol) were charged. To this, 85 g (0.52 mol) of triethoxysilane was added dropwise at an internal temperature of 75 to 85 ° C. over 2 hours, and then the mixture was stirred at 80 ° C. for 1 hour.
After the stirring is completed, the mixture is concentrated under reduced pressure and filtered to obtain a specific organosilicon compound (in formula (I), e = 33, f = 0, g = 13, viscosity: 2,000 mPa · s, number average molecular weight: 4,600). Obtained.

[Preparation of rubber composition]
Of the components shown in Table 1 below, the components excluding sulfur and the vulcanization accelerator were kneaded with a 1.7 L closed-type Banbury mixer, and after a lapse of a predetermined time, they were discharged from the mixer and cooled to room temperature. A rubber composition was prepared by putting this into a 1.7 L closed-type Banbury mixer, adding sulfur and a vulcanization accelerator, and mixing them.

The values of each component in Table 1 below are parts by mass.
When the diene-based rubber is an oil-extended product, the mass portion of the diene-based rubber in Table 1 below represents the net amount (mass portion) of the rubber excluding the oil-extended oil.

〔evaluation〕
The obtained rubber composition was evaluated as follows.

<Unvulcanized pane effect>
The obtained rubber composition (unsulfurized) was subjected to a strain shear stress measuring machine (RPA2000, manufactured by α-Technology) with a strain shear elastic modulus G'of 0.28% strain and strain shear of 30.0% strain. The elastic modulus G'was measured, and the difference G'0.28 (MPa) -G'30.0 (MPa) was calculated as the unsheared Pain effect.
The results are shown in Table 1. The results are expressed as an index with Comparative Example 1 as 100. The smaller the index, the better the silica dispersibility.

<Tanδ (0 ° C)>
The obtained rubber composition (unvulcanized) was press-vulcanized in a mold (15 cm × 15 cm × 0.2 cm) at 160 ° C. for 20 minutes to prepare a vulcanized rubber sheet.
The vulcanized rubber sheet produced was subjected to a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K6394: 2007 under the conditions of a stretch deformation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 0 ° C. , Tanδ (0 ° C.) was measured.
The results are shown in Table 1. The results are expressed as an index with Comparative Example 1 as 100. The larger the index, the better the wet grip performance.

The details of each component shown in Table 1 above are as follows. SBR1 to 3 are solution-polymerized SBRs having a styrene unit content of 40% by mass or less and a vinyl structure ratio of more than 40 mol%. On the other hand, SBR4 is a solution-polymerized SBR having a styrene unit content of 40% by mass or less but a vinyl structure ratio of 40 mol% or less. The number average molecular weight (Mn) of BR and SBR1 to 4 is 50,000 or more.
・ BR: Nipol BR1220 manufactured by Zeon Corporation
SBR1: TUFDENE E581 manufactured by Asahi Kasei Corporation (terminal modified solution polymerization SBR having a hydroxy group at the end, styrene unit content: 40% by mass, ratio of vinyl structure: 44 mol%)
SBR2: HPR850 manufactured by JSR (solution polymerization SBR, styrene unit content: 27.0% by mass, ratio of vinyl structure: 58.8 mol%)
SBR3: NS616 manufactured by Nippon Zeon Corporation (terminal modified solution polymerization SBR having a hydroxy group at the end, styrene unit content: 20.9% by mass, ratio of vinyl structure: 63.3 mol%)
SBR4: NS612 manufactured by Nippon Zeon (solution polymerization SBR, styrene unit content: 16% by mass, vinyl structure ratio: 31 mol%)
・ Silica 1: ZEOSIL 200MP manufactured by Rhodia, CTAB = 200m ² / g
-Silica 2: ZEOSIL 1165MP manufactured by Rhodia, CTAB = 155m ² / g
-Carbon black: Cabot Japan's show black N339, nitrogen adsorption specific surface area (N ₂ SA) = 90 m ² / g)
-Specific organosilicon compound: Specified organosilicon compound produced as described above-Silane coupling agent 1: NXT Silane manufactured by Momentive Performance Materials, 3-octanoylthio-1-propyltriethoxysilane, represented by the above formula (S). Compounds to be used ・ Silane coupling agent 2: Si69 manufactured by Ebonic Degussa, bis (3-triethoxysilylpropyl) tetrasulfide ・ Zinc oxide: Zinc oxide 3 manufactured by Shodo Chemical Industry Co., Ltd. ・ Steer acid: manufactured by Nichiyu Co., Ltd. YR stearate
-Anti-aging agent: Santoflex 6PPD manufactured by Solutia Europe
・ Process oil: Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.
・ Sulfur: Oil-treated sulfur manufactured by Karuizawa Smelter Co., Ltd. ・ Vulcanization accelerator CZ: Noxeller CZ-G manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
-Vulcanization accelerator DPG: Perkact DPG manufactured by Flexsys.

In Table 1, "specific Si / BR" represents the above-mentioned "specific Si / BR".

As can be seen from Table 1, Examples 1 to 13 containing the specific organosilicon compound showed excellent silica dispersibility and wet grip performance as compared with Comparative Example 2 containing no specific organosilicon compound.
On the other hand, Comparative Example 6 containing a specific organic silicon compound but having a “specific Si / BR” of less than 10.0% by mass, and a specific organic silicon compound containing a specific organic silicon compound but having a vinyl structure in an amount of more than 40 mol% as SBR. Comparative Example 1 which does not contain a certain solution-polymerized SBR (containing a solution-polymerized SBR having a vinyl structure ratio of 40 mol or less as SBR) and Comparative Example 3 which does not contain butadiene rubber have silica dispersibility and wet grip performance. Was inadequate.
Here, as can be seen from the comparison between Example 1, Examples 9 to 13, and Comparative Example 6, the silica dispersibility and wet grip performance are significantly improved by setting the “specific Si / BR” to 10.0% by mass or more. Improved to. That is, a remarkable criticality was found between "specific Si / BR" and silica dispersibility and wet grip performance.

From the comparison between Examples 1 and 9 to 13 (contrast between embodiments in which only the content of the specific organosilicon compound is different), Examples 1 and 10 to 13 in which "specific Si / BR" is 15.0% by mass or more. Showed better silica dispersibility. Among them, Examples 1 and 10 to 12 in which the "specific Si / BR" was 130.0% by mass or less showed better wet grip performance. Among them, Examples 1 and 11 to 12 in which "specific Si / BR" was 30.0% by mass or more showed further excellent silica dispersibility. Among them, Examples 1 and 11 in which "specific Si / BR" was 90.0% by mass or less showed further excellent wet grip property. Among them, Example 11 in which "specific Si / BR" was 60.0% by mass or more showed further excellent silica dispersibility and wet grip property.

From the comparison between Examples 1 and 2 (contrast between embodiments in which only the contents of BR and SBR 1 are different), Example 1 in which the content of butadiene rubber in the diene-based rubber is 20% by mass or less is more excellent. It showed silica dispersibility and wet grip performance.

From the comparison between Examples 1 and 3 and 4 (contrast between embodiments in which only the silica content is different), Examples 1 and 3 in which the silica content is 140 parts by mass or less with respect to 100 parts by mass of the diene-based rubber. Showed better silica dispersibility and wet grip performance. Among them, Example 1 in which the silica content was 100 parts by mass or less with respect to 100 parts by mass of the diene-based rubber showed further excellent silica dispersibility and wet grip performance.

From the contrast between Examples 1 and 5 and 6 (contrast between embodiments in which only the type of SBR is different), Examples 1 and 6 in which the SBR is a terminally modified SBR showed better silica dispersibility. Among them, Example 6 in which the ratio of the vinyl structure of SBR was 50 mol% or more showed better wet grip performance.

From the comparison between Examples 3 and 8 (contrast between embodiments in which only the types of silane coupling agents are different), Example 8 in which the silane coupling agent is a silane coupling agent having a tetrasulfide group is more excellent silica. It showed dispersibility and wet grip.

From the comparison between Examples 4 and 7 (contrast between modes having different types of silica), Example 4 in which the CTAB adsorption specific surface area of silica was 180 to 280 m ² / g showed better silica dispersibility. ..

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)

It contains a diene-based rubber containing butadiene rubber and solution-polymerized styrene-butadiene rubber, silica, and an organosilicon compound represented by the following formula (I).
The solution-polymerized styrene-butadiene rubber has a styrene unit content of 40% by mass or less and a vinyl structure ratio of more than 40 mol%.
The number average molecular weight of the diene rubber is 50,000 or more, and the diene rubber has a number average molecular weight of 50,000 or more.
The CTAB adsorption specific surface area of the silica is 180 to 280 m ² / g.
The number average molecular weight of the organosilicon compound is less than 50,000.
The content of the butadiene rubber in the diene rubber is 10 to 50% by mass, and the content of the solution-polymerized styrene-butadiene rubber is 50 to 90% by mass.
The silica content is 60 to 200 parts by mass with respect to 100 parts by mass of the diene rubber.
A rubber composition in which the content of the organosilicon compound is 10.0 to 150.0% by mass with respect to the content of the butadiene rubber.

In the above formula (I), R ¹ represents an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms, and R ² is an alkyl group having 1 to 10 carbon atoms or 6 to 10 carbon atoms. Represents an aryl group, f represents a number greater than or equal to 0, e and g each independently represent a number greater than 0, and m represents an integer of 1 to 3. However, the order of each repeating unit is arbitrary. The rubber composition according to claim 1, wherein e / (e + f + g) is 0.75 or less in the formula (I). A pneumatic tire using the rubber composition according to claim 1 or 2.

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