JP6627276B2 - Rubber composition and pneumatic tire - Google Patents

Description

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

Conventionally, a rubber composition used for a tire tread (tread portion) of a pneumatic tire has been known. In such a rubber composition, an ionic surfactant may be added for the purpose of improving the dispersibility of silica.
For example, Patent Literature 1 states that “5 to 100 parts by weight of silica, 1 to 20% by weight of silica silane coupling agent based on the weight of silica, and 100 parts by weight based on 100 parts by weight of diene rubber component, and. Rubber composition characterized by containing a hydrophilic surfactant "([Claim 1]). The “cationic surfactant” in Patent Document 1 is a specific quaternary ammonium salt ([0025]).

JP 2007-238682 A

The present inventors have, was examined vulcanized tire rubber composition containing an ionic surfactant, in some cases the low heat buildup and the elongation at break (E _B) is insufficient.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a rubber composition and a pneumatic tire using the rubber composition, which have low heat buildup and excellent elongation at break when vulcanized. I do.

  As a result of intensive studies by the present inventors, they have found that the above objects can be achieved by using a specific amount of an ionic surfactant and a nonionic surfactant as surfactants. Was completed.

That is, the present invention provides the following [1] to [7].
[1] A diene rubber, silica, a silane coupling agent, and a surfactant are contained, and the content of the silica is 50 to 200 parts by mass based on 100 parts by mass of the diene rubber. The content of the silane coupling agent is 0.1 to 20% by mass based on the content of the silica, and the content of the surfactant is 0.1 to 20% by mass based on the content of the silica. 10% by mass, wherein the surfactant contains an ionic surfactant and a nonionic surfactant, and the content of the ionic surfactant in the surfactant is 10 to 50 mol%. There is a rubber composition.
[2] The rubber composition according to the above [1], wherein the nonionic surfactant has an unsaturated carbon bond.
[3] The above [1] or [2], wherein the nonionic surfactant is at least one selected from the group consisting of carboxylic acids, carboxylic esters, ketones, alcohols, aldehydes, amines, and amides. The rubber composition according to the above.
[4] The rubber composition according to the above [3], wherein the nonionic surfactant is glycerol carboxylate.
[5] Any of the above [1] to [4], wherein the ionic surfactant is at least one selected from the group consisting of ammonium salts, pyridinium salts, imidazolium salts, sulfate salts and carboxylate salts. A rubber composition according to any one of the above.
[6] The rubber composition according to any one of the above [1] to [5], which is a rubber composition for a tire.
[7] A pneumatic tire using the rubber composition according to any one of the above [1] to [6] for a tire tread.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition which is excellent in low heat build-up and the elongation at the time of cutting | disconnection when made into a vulcanizate, and a pneumatic tire using the same can be provided.

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

[Rubber composition]
The rubber composition of the present invention contains a diene rubber, silica, a silane coupling agent, and a surfactant, and the content of the silica is 50 to 100 parts by mass of the diene rubber. 200 parts by mass, the content of the silane coupling agent is 0.1 to 20% by mass relative to the content of the silica, and the content of the surfactant is relative to the content of the silica. 0.1 to 10% by mass, the surfactant contains an ionic surfactant and a nonionic surfactant, and the content of the ionic surfactant in the surfactant is 10% by mass. ~ 50 mol% of the rubber composition.

The rubber composition of the present invention is excellent in low heat buildup and elongation at break (E _B ) when vulcanized. The reason is not clear, but is presumed as follows.
First, a rubber composition containing only an ionic surfactant as a surfactant is considered. The ionic surfactant strongly interacts with the silica and contributes to an improvement in the dispersibility of the silica. By improving the dispersibility of silica, the vulcanized product of the rubber composition has low heat build-up.
By the way, since the ionic surfactant has a large polarity and is easily aggregated in the diene rubber, the efficiency of improving the dispersibility of silica may not be said to be better than the mixing amount. In addition, the vulcanized product of the rubber composition tends to be broken starting from an aggregate (micelle) of the ionic surfactant in the diene rubber, and may have poor elongation at break.
At this time, it is conceivable to reduce the polarity of the ionic surfactant. In this case, the aggregation of the surfactant is suppressed and the elongation at break is improved, but the interaction with the silica is weakened, the dispersibility of the silica is reduced, and the low heat buildup may be insufficient. .
In contrast, in the rubber composition of the present invention, as the surfactant, an ionic surfactant and a nonionic surfactant having a smaller polarity than the ionic surfactant are used in a specific amount. Thereby, aggregation of the surfactant is suppressed. As a result, breakage starting from the surfactant aggregates (micelles) is suppressed, and the elongation at break is improved. It should be noted that the nonionic surfactant has a weaker interaction with silica than the ionic surfactant. However, by suppressing the aggregation of the ionic surfactant, the efficiency of improving the dispersibility of silica per compounding amount is improved, and as a result, low heat build-up is also improved.
Note that the above mechanism is presumed, and even when an effect is exhibited by a mechanism other than the above mechanism, the mechanism is within the scope of the present invention.

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

(Diene rubber)
The diene rubber is not particularly limited as long as it is a vulcanizable diene rubber. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber ( IIR), styrene / butadiene rubber (SBR), acrylonitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), ethylene / propylene / diene rubber (EPDM), and the like. Well, two or more kinds may be used in combination.
Among these, at least one selected from the group consisting of styrene-butadiene rubber (SBR) and butadiene rubber (BR) is preferable.

〔silica〕
The silica is not particularly limited, and conventionally known silicas used in rubber compositions for use in tires and the like can be used.Examples include wet silica, dry silica, fumed silica, diatomaceous earth, and the like. One type may be used alone, or two or more types may be used in combination.
Nitrogen adsorption specific surface area of the silica is preferably from ^{100~230m 2 / g, 150~185m 2 /} g is more preferable. The nitrogen adsorption specific surface area of silica is determined based on the BET method of ASTM D3037-81.

  The content of the silica is 50 to 200 parts by mass, preferably 55 to 150 parts by mass, more preferably 60 to 120 parts by mass with respect to 100 parts by mass of the diene rubber.

〔Silane coupling agent〕
The silane coupling agent is not particularly limited, and a conventionally known silane coupling agent can be used. Specifically, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilyl) Propyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetra Sulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl Trasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3- Triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethylsilylpropyl-N, N -Dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide and the like, and these may be used alone. At best, it may be used in combination of two or more thereof.

  Specific examples of the silane coupling agent other than the above include, for example, γ-mercaptopropyltriethoxysilane, 3- [ethoxybis (3,6,9,12,15-pentaoxaoctacosan-1-yloxy). ) Silyl] -1-propanethiol or other mercapto-based silane coupling agent; 3-octanoylthiopropyltriethoxysilane or other thiocarboxylate-based silane coupling agent; 3-thiocyanatepropyltriethoxysilane or other thiocyanate-based silane cup A ring agent; and these may be used alone or in combination of two or more.

  The content of the silane coupling agent is 0.1 to 20% by mass, preferably 1 to 18% by mass, and more preferably 3 to 15% by mass, based on the content of the silica.

(Surfactant)
In the rubber composition of the present invention, the content of the surfactant is 0.1 to 10% by mass based on the content of the silica, and the surfactant is an ionic surfactant or a nonionic surfactant. A surfactant, wherein the content of the ionic surfactant in the surfactant is 10 to 50 mol%. Thereby, as described above, the rubber composition of the present invention is excellent in low heat buildup when formed into a vulcanized product and elongation at break (E _B ).

<Ionic surfactant>
The ionic surfactant is a surfactant having a hydrophobic group and a hydrophilic group that is an ionic group. As the hydrophobic group, a saturated or unsaturated aliphatic hydrocarbon group (for example, having 5 to 20 carbon atoms). And preferably 10 to 20).
As the ionic surfactant, for example, at least one selected from the group consisting of a cationic surfactant and an anionic surfactant is preferably exemplified.

  Examples of the cationic surfactant that is the ionic surfactant include an ammonium salt, a pyridinium salt, and an imidazolium salt.

  Examples of the ammonium salt include quaternary ammonium salts. Specific examples thereof include hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium iodide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide. Octadecyltrimethylammonium iodide, dimethylethylhexadecylammonium chloride, dimethylethylhexadecylammonium bromide, dimethylethylhexadecylammonium iodide, dimethylethyloctadecylammonium chloride, dimethylethyloctadecylammonium bromide, dimethylethyloctadecylammonium iodide, benzyldimethyl Hexadecylua Moniumukurorido, benzyl dimethyl hexadecyl ammonium bromide, benzyl dimethyl hexadecyl ammonium iodide, benzyl dimethyl Okuda decyl ammonium chloride, benzyl dimethyl Okuda decyl bromide, and the like benzyl dimethyl Okuda decyl ammonium iodide is.

  Specific examples of pyridinium salts include tetradecyl pyridinium chloride, tetradecyl pyridinium bromide, tetradecyl pyridinium iodide, hexadecyl pyridinium chloride, hexadecyl pyridinium bromide, hexadecyl pyridinium iodide, 1-tetradecyl-4-methylpyridinium chloride, 1-tetradecyl-4-methylpyridinium bromide, 1-tetradecyl-4-methylpyridinium iodide, 1-hexadecyl-4-methylpyridinium chloride, 1-hexadecyl-4-methylpyridinium bromide, 1-hexadecyl-4-methylpyridinium iodide And the like.

  Specific examples of the imidazolium salt include 1-dodecyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium bromide, 1-dodecyl-3-methylimidazolium iodide, 1-methyl-3-dodecyl Imidazolium chloride, 1-methyl-3-dodecylimidazolium bromide, 1-methyl-3-dodecylimidazolium iodide, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1-dodecyl-2-methyl- 3-benzylimidazolium bromide, 1-dodecyl-2-methyl-3-benzylimidazolium iodide, 1-tetradecyl-3-methylimidazolium chloride, 1-tetradecyl-3-methylimidazolium bromide, 1-tetradecyl-3 -Methylimidazolium iodide, 1 Methyl-3-tetradecylimidazolium chloride, 1-methyl-3-tetradecylimidazolium bromide, 1-methyl-3-tetradecylimidazolium iodide, 1-hexadecyl-3-methylimidazolium chloride, 1-hexadecyl- 3-methylimidazolium bromide, 1-hexadecyl-3-methylimidazolium iodide, 1-hexadecyl-4-methylimidazolium chloride, 1-hexadecyl-4-methylimidazolium bromide, 1-hexadecyl-4-methylimidazolium Examples thereof include iodide, 1-methyl-3-hexadecylimidazolium chloride, 1-methyl-3-hexadecylimidazolium bromide, and 1-methyl-3-hexadecylimidazolium iodide.

  Examples of the anionic surfactant that is the ionic surfactant include a sulfonate, a sulfate, and a carboxylate (fatty acid salt).

  Specific examples of the sulfonate include alkyl diphenyl ether disulfonates such as sodium dodecyl diphenyl ether disulfonate and calcium dodecyl diphenyl ether disulfonate; alkylbenzene sulfonates such as sodium dodecyl benzene sulfonate;

  Specific examples of the sulfate ester salt include sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium hexadecyl sulfate, and sodium octyl sulfate.

  Specific examples of the carboxylate (fatty acid salt) include sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, potassium oleate, calcium oleate, and the like.

  The ionic surfactant is preferably at least one selected from the group consisting of an ammonium salt, a pyridinium salt, an imidazolium salt, a sulfate salt and a carboxylate (fatty acid salt), and an ammonium salt, a pyridinium salt And at least one member selected from the group consisting of sulfate salts, and more preferably a pyridinium salt from the viewpoint of low heat build-up and more excellent elongation at break.

<Nonionic surfactant>
The nonionic surfactant is a surfactant having a hydrophobic group and a hydrophilic group that is a nonionic group. As the hydrophobic group, a saturated or unsaturated aliphatic hydrocarbon group (having a carbon number of 5 -20, preferably 10-20).

The nonionic surfactant preferably has an unsaturated carbon bond (for example, has an unsaturated aliphatic hydrocarbon group as a hydrophobic group).
Thereby, the vulcanized product of the rubber composition of the present invention has good elongation at break after the heat aging test, and is excellent in heat aging resistance. Although the reason for this is not clear, for example, the sulfur reacts with the unsaturated carbon bond to increase the strength of the rubber component, or if unsaturated, the carbon bond is bent, so that the surfactant is not aligned and hardly aggregates. It is supposed to be.

  The nonionic surfactant preferably includes, for example, at least one selected from the group consisting of carboxylic acids, carboxylic esters, ketones, alcohols, aldehydes, amines, and amides.

As the carboxylic acid as the nonionic surfactant, a saturated or unsaturated fatty acid (monovalent linear carboxylic acid) is preferable, and specific examples of such a fatty acid include stearic acid, palmitic acid, and lauric acid. , Oleic acid, linoleic acid, linolenic acid and the like.
Of these, higher fatty acids having an unsaturated carbon bond (eg, oleic acid, linoleic acid, linolenic acid, etc.) are preferred for the reasons described above.

Examples of the carboxylic acid ester which is the nonionic surfactant include esters of the above-mentioned saturated or unsaturated fatty acids and polyhydric alcohols. Examples of the polyhydric alcohol include glycerin, polyglycerin, sorbitan, propylene glycol, and sucrose.
Examples of such carboxylic acid esters include glycerin carboxylate (monoglyceride), and specific examples thereof include glycerin laurate, glyceryl stearate, and glycerin linolenate.

Examples of the nonionic surfactant ketone include so-called higher ketones, and specific examples thereof include 2-pentadecanone, 2-hexadecanone, 2-heptadecanone, 2-octadecanone, and 2-nonadecanone.
Examples of the alcohol that is the nonionic surfactant include so-called higher alcohols, and specific examples thereof include myristyl alcohol, cetyl alcohol, stearyl alcohol, palmityl alcohol, oleyl alcohol, and lauryl alcohol.
Examples of the aldehyde that is the nonionic surfactant include lauryl aldehyde, myristyl aldehyde, cetyl aldehyde, stearyl aldehyde, oleyl aldehyde, and the like.
Examples of the amine that is the nonionic surfactant include laurylamine, dilaurylamine, lauryldimethylamine, stearylamine, distearylamine, and stearyldimethylamine.
Examples of the amide that is the nonionic surfactant include so-called higher fatty acid amides, and specific examples thereof include stearamide, oleic amide, lauric amide, ethylenebisstearamide, and methylenebisstearamide. , Ethylenebislauroamide, stearooleoamide and the like.

  As the above-mentioned nonionic surfactant, the above-mentioned carboxylic acid or carboxylic ester is preferable, and carboxylic acid ester is more preferable because of low heat build-up and more excellent elongation at break.

  The ionic surfactant and the nonionic surfactant described above may be used alone or in combination of two or more.

<Content>
The content of the surfactant is 0.1 to 10% by mass based on the content of the silica. However, when the rubber composition of the present invention is vulcanized, it has low heat buildup and elongation at break. Is more preferably 2.0 to 10% by mass, and more preferably 3.0 to 10% by mass.

  The content of the ionic surfactant in the surfactant is 10 to 50 mol%, which is why the rubber composition of the present invention is more excellent in low heat buildup when it is vulcanized. From 20 to 50 mol% is preferable, and 35 to 50 mol% is more preferable.

[Other additives]
The rubber composition of the present invention can further contain an additive, if necessary.
Examples of the additives include fillers other than silica (eg, carbon black), zinc oxide, stearic acid, an antioxidant, processing aids, various oils, plasticizers, liquid polymers, terpene resins, and thermosetting. Examples include various additives generally used in rubber compositions such as a conductive resin, a vulcanizing agent, and a vulcanization accelerator, and the content thereof is not particularly limited and can be appropriately selected.

(Production method of rubber composition)
The method for producing the rubber composition of the present invention is not particularly limited. For example, each of the above-mentioned components may be mixed at a temperature of 60 to 145 ° C. with a known method and apparatus (for example, Banbury mixer, kneader, roll, etc.). A method of kneading for up to 30 minutes is exemplified.
Further, the rubber composition of the present invention can be vulcanized under conventionally known vulcanization conditions to obtain a vulcanized product.

[Application]
The use of the rubber composition of the present invention is not particularly limited, but since the vulcanizate has low heat buildup and excellent elongation at break, for example, a rubber composition for a tire, more specifically, a rubber composition for a tire tread It can be preferably applied to objects.

[tire]
The tire (pneumatic tire) of the present invention is a pneumatic tire manufactured using the above-described rubber composition of the present invention. Above all, a pneumatic tire manufactured by using the rubber composition of the present invention for a tire tread is preferable.
FIG. 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the pneumatic tire of the present invention. However, 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.
A carcass layer 4 in which a fiber cord is embedded is mounted between the pair of right and left bead portions 1, and the end of the carcass layer 4 is turned around the bead core 5 and the bead filler 6 from the inside of the tire to the outside. Rolled up.
In the tire tread 3, a belt layer 7 is arranged outside the carcass layer 4 over one circumference of the tire.
In the bead portion 1, a rim cushion 8 is arranged at a portion in contact with the rim.

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

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

(Preparation of rubber composition)
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below.
Specifically, first, the components excluding sulfur and the vulcanization accelerator among the components shown in Table 1 below were mixed for 5 minutes using a Banbury mixer at 80 ° C. Next, using a roll, the sulfur and the vulcanization accelerator were mixed to obtain a rubber composition.

(Preparation of vulcanized rubber sheet)
Each of the obtained rubber compositions (unvulcanized) was press-vulcanized in a mold (15 cm × 15 cm × 0.2 cm) at 160 ° C. for 15 minutes to produce a vulcanized rubber sheet.

[Tan δ (60 ° C)]
For each of the obtained vulcanized rubber sheets, a loss tangent (tan δ (60 ° C.) was measured with a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho) under the conditions of initial strain 10%, amplitude ± 2%, frequency 20 Hz, and temperature 60 ° C. )) Was measured. The results are shown in Table 1 below. The result was represented by an index with tan δ (60 ° C.) of Standard Example 1 being 100. The smaller the value, the better the low heat generation.

[E _B (normal)]
For each of the obtained vulcanized rubber sheets, a tensile test was performed at a tensile speed of 500 mm / min in accordance with JIS K6251, and the elongation at break (E _B ) was measured at room temperature (E _B (normal state) [%]. ). The results are shown in Table 1 below. The result was represented by an index with the value of Standard Example 1 being 100. The larger the value, the better the elongation at break.

[E _B (after heat aging) / E _B (normal)]
After performing a heat aging test (100 ° C., 168 hours) on each of the obtained vulcanized rubber sheets, the elongation at break (E _B ) was measured at room temperature in the same manner as described above (E _B ( After heat aging) [%]). Then, to determine the E _B for E shows the elongation at break before heat aging test _B (normal) ratio (after heat aging) (E _B (after heat aging) / E _B (normal)). The results are shown in Table 1 below. The result was represented by an index with the value of Standard Example 1 being 100. The larger the value, the better the elongation at break after the heat aging test. That is, it is excellent in heat aging resistance.

The details of each component shown in Table 1 are as follows.
-SBR: Nipol 1723 (oil extension amount per 100 parts by mass of rubber: 37.5 parts by mass, manufactured by Zeon Corporation)
・ BR: NIPOL BR 1220 (manufactured by Zeon Corporation)
・ Silica: Zeosil 1165mp (nitrogen adsorption specific surface area: 165m ² / g, manufactured by Rhodia)
-Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide, manufactured by Evonik Degussa)
-Ionic surfactant 1: ammonium salt (hexadecyltrimethylammonium bromide, manufactured by Tokyo Chemical Industry Co., Ltd.)
・ Ionic surfactant 2: pyridinium salt (hexadecylpyridinium bromide, manufactured by Tokyo Chemical Industry Co., Ltd.)
-Ionic surfactant 3: sulfate salt (sodium hexadecyl sulfate, manufactured by Wako Pure Chemical Industries, Ltd.)
-Nonionic surfactant 1: unsaturated carboxylic acid (linolenic acid, manufactured by Tokyo Chemical Industry Co., Ltd.)
-Nonionic surfactant 2: unsaturated carboxylic acid (oleic acid, manufactured by Tokyo Chemical Industry Co., Ltd.)
-Nonionic surfactant 3: unsaturated carboxylic acid glycerin ester (linolenic acid glycerin (monoglyceride))
・ Nonionic surfactant 4: Saturated carboxylic acid (stearic acid, manufactured by Tokyo Chemical Industry Co., Ltd.)

・ Carbon black: Show black N339 (nitrogen adsorption specific surface area: 90 m ² / g, manufactured by Cabot Japan)
・ Process oil: Extract 4S (Showa Shell Sekiyu KK)
・ Anti-aging agent: SANTOFLEX 6PPD (manufactured by Saltia Europe)
・ Wax: Suntight (manufactured by Seiko Chemical Co., Ltd.)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Co., Ltd.)
・ Sulfur: Oil treated sulfur (Karuizawa Refinery)
-Vulcanization accelerator 1: Noxeller CZ-G (Ouchi Shinko Chemical Co., Ltd.)
・ Vulcanization accelerator 2: Perkacit DPG (manufactured by Flexsys)

As is clear from the results shown in Table 1 above, Examples 1 to 9 were excellent in low heat build-up and elongation at break as compared with Standard Example 1.
When Examples 1 to 6 were compared, Examples 1 to 5 using nonionic surfactants 1 to 3 having an unsaturated carbon bond showed that nonionic surfactants 4 having no unsaturated carbon bond were used. than in example 6 using the value of E _B (after heat aging) / E _B (normal) is large, and was excellent in heat aging resistance.

Further, when Example 1, Example 7, and Example 8 are compared, the content of the surfactant with respect to the content of the silica (described as “surfactant / silica” in Table 1) is 1.4% by mass. Example 7 having the same content of 2.9% by mass and Example 8 having the same content of 8.6% by mass have low heat build-up and good elongation at break. there were.
Further, when Example 1 and Example 9 are compared, the content of the ionic surfactant in the surfactant (indicated as “Ionic surfactant ratio” in Table 1) is 20 mol%. Example 1 in which the content was 43 mol% had better low heat buildup than Example 9.

On the other hand, Comparative Example 1 using only the nonionic surfactant 1 and Comparative Example 2 using both the nonionic surfactant 1 and the nonionic surfactant 2 have low heat build-up. Was not enough.
In Comparative Example 3 in which the amount of the surfactant (ionic surfactant and nonionic surfactant) to silica was small, the low heat build-up was insufficient.
Comparative Example 4 in which the amount of the surfactant (ionic surfactant and nonionic surfactant) to silica was large was insufficient in the low heat buildup.
In Comparative Example 5 in which the amount of the ionic surfactant in the surfactant was small, the low heat build-up was insufficient.
Comparative Example 6, in which the amount of the ionic surfactant in the surfactant was large, had low heat build-up and insufficient elongation at break.

1: bead portion 2: sidewall portion 3: tire tread portion 4: carcass layer 5: bead core 6: bead filler 7: belt layer 8: rim cushion

Claims (5)

Containing a diene rubber, silica, a silane coupling agent, and a surfactant,
The content of the silica is 50 to 200 parts by mass with respect to 100 parts by mass of the diene rubber,
The content of the silane coupling agent is 0.1 to 20% by mass relative to the content of the silica,
The content of the surfactant is 0.1 to 10% by mass relative to the content of the silica,
Wherein the surfactant comprises an ionic surfactant and a non-ionic surfactant,
The ionic surfactant is at least one selected from the group consisting of quaternary ammonium salts, pyridinium salts and sulfate salts ;
The nonionic surfactant is at least one selected from the group consisting of carboxylic acids and carboxylic esters,
A rubber composition, wherein the content of the ionic surfactant in the surfactant is 10 to 50 mol%.   The rubber composition according to claim 1, wherein the nonionic surfactant has an unsaturated carbon bond. Wherein the nonionic surfactant is a carboxylic acid glycerol ester, the rubber composition according to claim 1 or 2. The rubber composition according to any one of claims 1 to 3 , which is a rubber composition for a tire. A pneumatic tire using the rubber composition according to any one of claims 1 to 4 for a tire tread.