JP5887709B2 - Rubber composition - Google Patents

Description

  The present invention relates to a rubber composition. More specifically, the present invention relates to a rubber composition for tires.

  As a technique for reducing the rolling resistance of tires, it is known to use a rubber composition blended with silica, but in contrast to carbon black, silica does not have a high affinity for rubber molecules, so it has reinforcement and wear resistance. Inferior.

  Therefore, in order to increase the affinity of silica for rubber molecules and improve the dispersibility of silica, it is common to use a silane coupling agent in combination.

  However, if the coupling reaction (silanization) between the silica and the silane coupling agent is insufficient, good dispersibility of the silica cannot be obtained, and if the coupling reaction is excessive, the rubber burns. There has been a problem that the quality (particularly the reinforcing property) is reduced.

  In order to solve such a problem, a rubber composition in which dispersibility of silica is improved by blending an amino acid has been proposed (Patent Document 1).

JP 2009-19098 A

  However, there has been a demand for a rubber composition in which dispersibility of silica is further improved and rolling resistance is reduced, and a pneumatic tire using the rubber composition as a tread rubber of a tire.

  Therefore, an object of the present invention is to provide a rubber composition in which the dispersibility of silica is improved and the rolling resistance is reduced, and a pneumatic tire using the rubber composition for a tread rubber of a tire.

  As a result of intensive studies to solve the above problems, the present inventors have further included an amino acid and urea in a rubber composition containing a diene rubber, silica, and a sulfur-containing silane coupling agent. When the rubber is mixed in the state of an aqueous solution, it is possible to provide a rubber composition in which the dispersibility of silica is improved and the rolling resistance is reduced, and a pneumatic tire using the rubber composition for a tread rubber of a tire. I learned that I can do it.

That is, this invention provides the pneumatic tire which uses the rubber composition hung up below and its rubber composition for the tread rubber of a tire.
(1) A diene rubber, silica, a sulfur-containing silane coupling agent, an amino acid, and urea,
The amino acid is at least one selected from the group consisting of L-glutamic acid, L-aspartic acid and their enantiomers and salts thereof, and hydrates thereof;
20 to 120 parts by mass of the silica is contained with respect to 100 parts by mass of the diene rubber,
3 to 15 parts by mass of the sulfur-containing silane coupling agent, 0.5 to 10 parts by mass of the amino acid, and 0.25 to 5.0 parts by mass of urea with respect to 100 parts by mass of the silica. ,And,
A rubber composition in which 0.5 to 10 parts by mass of the urea is mixed with 100 parts by mass of silica as a 0.5 to 50% by mass urea aqueous solution.
(2) A pneumatic tire using the rubber composition according to (1) as a tire tread rubber.

  According to the present invention, it is possible to provide a rubber composition in which dispersibility of silica is improved and rolling resistance is reduced, and a pneumatic tire using the rubber composition as a tread rubber of a tire.

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

[Rubber composition]
The rubber composition of the present invention includes “(1) a diene rubber, silica, a sulfur-containing silane coupling agent, an amino acid, and urea, and the silica is contained in 100 parts by mass of the diene rubber. 20 to 120 parts by mass, 3 to 15 parts by mass of the sulfur-containing silane coupling agent, 0.5 to 10 parts by mass of the amino acid, and 0.25 of the urea with respect to 100 parts by mass of the silica. It is a rubber composition containing 0.5 to 10 parts by mass and mixed with 0.5 to 10 parts by mass of the urea as a 0.5 to 50% by mass urea aqueous solution with respect to 100 parts by mass of the silica. .

  Although the details of the mechanism by which the effect of the present invention is exerted by the combined use of amino acid and urea are unclear, there is a limit to the silanization promoting effect at the isoelectric point inherent to the amino acid. When combined with it, it reacts with the carboxy group or hydroxy group of the amino acid, neutralizes the acid, increases the apparent isoelectric point, accelerates the hydrolysis of the silane coupling agent, and disperses the silica. I think that it is promoting. Moreover, even if urea is mixed independently, there is no effect, and it is thought that the effect of this invention can be achieved by mixing as urea aqueous solution. However, the function and effect of the present invention are not limited to this mechanism.

Hereinafter, each component will be described in detail.
<Diene rubber>
The diene rubber contained in the rubber composition of the present invention is not particularly limited as long as it has a double bond in the main chain. Specific examples thereof include natural rubber (NR), isoprene rubber (IR), styrene.・ Butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene-propylene-diene copolymer rubber (EPDM), styrene-isoprene rubber, isoprene-butadiene rubber, nitrile Examples thereof include rubber and hydrogenated nitrile rubber. These may be used alone or in combination of two or more.

  Of these, styrene-butadiene rubber (SBR) and butadiene rubber (BR) are preferably used, and more preferably used in combination, because the wet performance and the reinforcing performance can be balanced.

  When styrene-butadiene rubber (SBR) and butadiene rubber (BR) are used in combination as the diene rubber, SBR is preferably 50 to 90 parts by mass, and 60 to 85 parts by mass in 100 parts by mass of the diene rubber. It is more preferable that Within this range, the general physical properties of the rubber composition after vulcanization will be better.

<silica>
The silica contained in the rubber composition of the present invention is not particularly limited, and any conventionally known silica compounded in the rubber composition for uses such as tires can be used.

  Specific examples of the silica include fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, colloidal silica, and the like. These may be used alone or in combination of two or more. You may use together.

  In the present invention, the content of the silica is 20 to 120 parts by mass of silica with respect to 100 parts by mass of the diene rubber, and the resulting tire has good wear resistance and has a reinforcing index, that is, rolling resistance performance. It is more preferable that the amount is 40 to 100 parts by mass.

<Sulfur-containing silane coupling agent>
The sulfur-containing silane coupling agent contained in the rubber composition of the present invention is not particularly limited, and any conventionally known silane coupling agent blended in the rubber composition for applications such as tires can be used.

  Specific examples of the silane coupling agent include 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, and triethoxysilylpropyl-methacrylate. Monosulfide, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, bis- [3- (triethoxysilyl) -propyl] tetrasulfide, bis- [3- (trimethoxysilyl) -propyl] tetra Examples include sulfide, bis- [3- (triethoxysilyl) -propyl] disulfide, 3-mercaptopropyl-trimethoxysilane, 3-mercaptopropyl-triethoxysilane, and the like. Well, it may be used in combination of two or more thereof.

  In the present invention, the content of the sulfur-containing silane coupling agent is 3 to 15 parts by mass with respect to 100 parts by mass of the silica, and the resulting tire has good wear resistance and a reinforcing index, that is, rolling resistance. Since the balance of performance will become favorable, it is more preferable that it is 5-10 mass parts.

<amino acid>
The amino acid that can be used in the rubber composition of the present invention includes one or more amino groups (groups represented by —NRR ′ (R and R ′ are each independently a hydrogen atom or a monovalent group) in one molecule. And / or an imino group (= NR ″ or> NR ″ (R ″ represents a hydrogen atom or a monovalent organic group)); There is no particular limitation as long as it is an organic compound having one or more carboxy groups.

  In this invention, content of the said amino acid is 0.5-10 mass parts with respect to 100 mass parts of said silicas, 0.5-5.0 mass parts is preferable, 1.0-3.0 masses Part is more preferred. Moreover, the said amino acid can be used individually by 1 type or in combination of 2 or more types.

  In the amino acid, the amino group or imino group and the carboxy group may be bonded to the same carbon atom or may be bonded to different carbon atoms. Further, the different carbon atoms may be adjacent carbon atoms or non-adjacent carbon atoms.

  Moreover, when the enantiomer exists in the said amino acid, the enantiomer can also be used. One of the amino acids in the enantiomeric relationship may be used, the other may be used, or both may be used in combination.

  Moreover, when the diastereomer exists in the said amino acid, the diastereomer can also be used. Any one of the diastereomeric amino acids may be used, or two or more amino acids may be used in combination.

Moreover, the said amino acid can be used also with the form of a salt. Examples of the salt form include metal salts such as lithium salt, sodium salt, potassium salt, magnesium salt, calcium salt, and barium salt; inorganic acid salts such as hydrochloride and nitrate; aliphatic carboxylates such as acetate; An aromatic carboxylate such as o-acetylsalicylate; an aromatic sulfonate such as p-toluenesulfonate; and the like. Examples of such metal salts of amino acids include sodium L-glutamate, and examples of inorganic acid salts include L-lysine hydrochloride.
The amino acid can also be used in the form of an ester with an alcohol. When the amino acid has a hydroxyl group, it can be used in the form of an ester with an oxo acid such as phosphoric acid. Examples of such phosphates of amino acids include O-phosphoserine.

  The amino acids and their salts and esters can also be used in the form of hydrates.

  Examples of the amino acid include α-amino acids such as glycine and alanine; β-amino acids such as β-alanine (3-aminopropanoic acid); γ-amino acids such as γ-aminobutyric acid (GABA);

As the α-amino acid, those represented by the following formula (i) or (ii) are preferable.

^[Wherein, R ^1, R 2, ^{R 3} and ^{R 4} are each independently a hydrogen atom or an organic group, ^{R 1} and ^{R 2} may form a ring together, ^{R 3} and R ⁴ may form a ring together. ]

  Specific examples of the α-amino acid represented by the above formula (i) or (ii) include glycine, L-alanine, L-arginine, L-asparagine, L-aspartic acid, L-cysteine, L -Glutamine, L-glutamic acid, L-histidine, L-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine L-valine, L-pyrrolysine, L-selenocysteine, L-cystine, L-hydroxylysine, L-hydroxyproline, O-phospho-L-serine, thyroxine, L-pyroglutamic acid, L-citrulline and L-ornithine As well as their enantiomers (excluding glycine) (for example, the D form) At least one selected from the group consisting of can be mentioned.

As the α-amino acid, those represented by the following formula (iii) or (iv) are more preferable.

[Wherein R ⁵ and R ⁶ each independently represents a hydrogen atom or an organic group. ]

  Specific examples of the α-amino acid represented by the above formula (iii) or (iv) include glycine, L-alanine, L-arginine, L-asparagine, L-aspartic acid, L-cysteine, L -Glutamine, L-glutamic acid, L-histidine, L-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-serine, L-threonine, L-tryptophan, L-tyrosine, L-valine , L-pyrrolysine, L-selenocysteine, L-cystine, L-hydroxylysine, O-phospho-L-serine, thyroxine, L-pyroglutamic acid, L-citrulline and L-ornithine and these (excluding glycine). At least one selected from the group consisting of enantiomers (for example, D-form) And the like.

  More preferable α-amino acids include glycine, L-alanine, L-arginine, L-asparagine, L-aspartic acid, L-cysteine, L-glutamine, L-glutamic acid, L-histidine, L-isoleucine, L-leucine. , L-lysine, L-methionine, L-phenylalanine, L-serine, L-threonine, L-tryptophan, L-tyrosine and L-valine and enantiomers of these (excluding glycine) (for example, D-form) And at least one selected from the group consisting of:

  More preferable α-amino acids include at least one selected from the group consisting of glycine, L-arginine, D-arginine, L-glutamic acid, D-glutamic acid, L-serine and D-serine.

  The α-amino acid preferably has an isoelectric point of 3.0 to 11.0, more preferably an isoelectric point of 5.0 to 11.0.

  Examples of the α-amino acid having an isoelectric point of 3.0 to 11.0 include, for example, L-alanine (isoelectric point 6.0), L-arginine (isoelectric point 10.76), L-asparagine (isoelectric). Point 5.41), L-cysteine (isoelectric point 5.05), L-glutamine (isoelectric point 5.65), L-glutamic acid (isoelectric point 3.22), glycine (isoelectric point 5.97). ), L-histidine (isoelectric point 7.59), L-isoleucine (isoelectric point 6.05), L-leucine (isoelectric point 5.98), L-lysine (isoelectric point 9.75), L-methionine (isoelectric point 5.74), L-phenylalanine (isoelectric point 5.48), L-proline (isoelectric point 6.30), L-serine (isoelectric point 5.68), L- Threonine (isoelectric point 6.16), L-tryptophan (isoelectric point 5.89), L-tyrosine Isoelectric point 5.66) and L-valine (isoelectric point 5.96) and at least one selected from the group consisting of these (excluding glycine) (for example, D-form). The above amino acids are mentioned.

<urea>
Urea is not particularly limited, and conventionally known urea can be used. The grade is not particularly limited, and various grades such as for general organic synthesis and biochemistry can be used.

  Content of the urea is 0.25 to 5.0 parts by mass with respect to 100 parts by mass of the silica, preferably 0.5 to 4.0 parts by mass, and more preferably 1.0 to 3.0 parts by mass. preferable. Moreover, 0.5-10 mass parts is mixed with diene rubber and other components with respect to 100 mass parts of silica as said 0.5-50 mass% aqueous solution of urea. Water for making urea into an aqueous solution is not particularly limited, and tap water, pure water (ion exchange water, distilled water, RO water, etc.), ultrapure water (Milli Q water, etc.) and the like can be used.

<Ingredients other than the above>
In addition to the above components, the rubber composition of the present invention includes a filler other than silica (for example, carbon black), a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, zinc oxide, a softening agent (oil), and aging. Various other additives generally used in tire rubber compositions such as an inhibitor and a plasticizer can be blended. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

[Method for producing rubber composition]
The rubber composition of the present invention can be produced by mixing and kneading the aforementioned components.
Among the components described above, urea is mixed in an amount of 0.5 to 50 parts by mass as an aqueous solution of 0.5 to 50% by mass with 100 to 10 parts by mass of silica and other components of diene rubber. When urea is mixed as an aqueous solution, the dispersibility of urea in the rubber composition of the present invention is improved, and the mixing property of urea and amino acid is also improved.
Also, among the components described above, components other than the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator are mixed and kneaded to prepare a master batch, and the vulcanization (crosslinking) agent and vulcanization are added to this master batch. It is preferable to produce a rubber composition by mixing a (crosslinking) accelerator and kneading using an open roll or the like. In this way, a masterbatch composed of components other than the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator is prepared, and the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator are mixed into the masterbatch. When kneaded, the vulcanization (crosslinking) rubber and the vulcanization (crosslinking) accelerator can be mixed to shorten the kneading time, resulting in non-uniform vulcanization (crosslinking). The physical properties of the composition can be prevented from being lowered, and vulcanization (crosslinking) can be easily controlled.

[Pneumatic tire]
The pneumatic tire of the present invention (hereinafter also simply referred to as “the tire of the present invention”) is a pneumatic tire using the above-described rubber composition of the present invention.
FIG. 1 shows a schematic partial sectional view of a tire representing an example of an embodiment of the tire of the present invention, but the 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 tire of the present invention is vulcanized or cured at a temperature corresponding to, for example, the diene rubber, vulcanizing agent or crosslinking agent, vulcanization accelerator or crosslinking accelerator contained in the rubber composition of the present invention, and the blending ratio thereof. It can manufacture by bridge | crosslinking and forming a tread part, a side wall part, etc.

  In the present invention, silica dispersibility is improved and rolling resistance is reduced. In addition, wear resistance and reinforcement are excellent. Therefore, it is preferable to form a tire tread portion having a larger amount of silica than other members with the rubber composition of the present invention.

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

[Rubber composition]
<Standard example, Example 1 , Reference example 2-4 , Comparative example 1-8>
The rubber compositions according to the standard example, the example 1 , the reference examples 2 to 4 and the comparative examples 1 to 8, as shown in the standard example column, the example column , the reference example column and the comparative example column in Table 1. Were prepared by blending the components shown in Table 1 in the amounts shown in Table 1.

[Test evaluation method]
<G'0.28 (indicator of silica dispersibility)>
Vulcanization was carried out at 160 ° C. for 20 minutes using unvulcanized rubber, and strain shear stress G ′ having a strain rate of 0.28% to 30.0% was measured (unit: MPa). For the measurement, a viscoelasticity measuring device RPA2000 (manufactured by Alpha Technologies) was used. Difference ΔG ′ = (G′0.28−G′30) between G ′ (G′0.28) at a strain rate of 0.28% and G ′ (G′30.0) at a strain rate of 30.0% 0.0), and the measured values of Example 1 , Reference Examples 2 to 4, and Comparative Examples 1 to 8 were expressed as indices using the measured value of the standard example as the reference (100). The smaller the index, the better the silica dispersibility.

<M300 / M100 (reinforcing index)>
The obtained rubber composition was press vulcanized at 160 ° C. for 20 minutes using a 150 × 150 × 2 mm mold to form a vulcanized rubber sheet having a thickness of 2 mm.
A No. 3 dumbbell-shaped test piece was punched from this vulcanized rubber sheet, 100% modulus (M100) and 300% modulus (M300) were measured according to JIS K 6251: 2004, and a value of M300 / M100 was obtained. . The value of M300 / M100 of Example 1 , Reference Examples 2 to 4, and Comparative Examples 1 to 8 was expressed as an index using the value of the standard example as the reference (100). This was used as an index of reinforcement. The greater the index, the better the reinforcement.

<Rebound resilience (40 ° C) (index of rolling resistance)>
The vulcanized rubber was subjected to a Rupke-type rebound resilience test in a constant temperature bath at 40 ° C. according to JIS K 6255: 1996, and the rebound resilience at a temperature of 40 ° C. was measured. Using the value of the standard example as a reference (100), the measured values of the resilience of Example 1 , Reference Examples 2 to 4, and Comparative Examples 1 to 8 were expressed as an index. This was used as an index of rolling resistance. The larger the index, the better the rolling resistance performance.

<Abrasion resistance (index of wear resistance)>
About vulcanized rubber, using Lambourne Abrasion Tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K 6264-2: 2005, load 5 kg (= 49 N), slip rate 25%, time 4 minutes, room temperature Wear loss was measured under the conditions. Using the value of the standard example as a reference (100), the measured values of wear loss in Example 1 , Reference Examples 2 to 4, and Comparative Examples 1 to 8 were expressed as an index. This was used as an index of wear resistance. The higher the index, the better the wear resistance.

Each component shown in Table 1 is listed below. Moreover, the compounding quantity of each component is represented by the mass part unit.
(1) Diene rubber SBR: Styrene butadiene rubber (BUNA VSL 5025-1 HM, manufactured by LANXESS; oil exhibition, Table 1 shows net mass of styrene butadiene rubber excluding 28.1 parts by mass of developed oil Part)
BR: Butadiene rubber (Nipol (R) 1220, manufactured by Nippon Zeon)
(2) Silica, silane coupling agent / Silica 1: precipitated silica (Zeosil® 1165MP, manufactured by Rhodia)
Silane coupling agent 1: sulfur-containing silane coupling agent (Si69 (R), manufactured by Evonik Degussa; 3,3'-bis (triethoxysilylpropyl) tetrasulfide)
(3) Amino acid / amino acid 1: L-glutamic acid / amino acid 2: glycine / amino acid 3: L-arginine (4) Urea, urea aqueous solution / urea aqueous solution 1: 50 mass% urea aqueous solution (prepared from urea and distilled water below)
-Urea aqueous solution 2: 0.1 mass% urea aqueous solution (prepared from urea and distilled water below)
・ Urea 1: Urea (manufactured by Tokyo Chemical Industry Co., Ltd.)
-Water 1: Distilled water (5) Softener-Softener 1: Aroma oil (Process X-140, manufactured by Japan Energy)
(6) Vulcanizing agent, vulcanization accelerator, vulcanization acceleration aid / vulcanizing agent 1: sulfur (oil-treated sulfur, manufactured by Hosoi Chemical Co., Ltd.)
Vulcanization accelerator 1: thiazole vulcanization accelerator (CBS, Flexsys Corporation; N- cyclohexyl-2-benzothiazolyl sulfenamide)
・ Vulcanization accelerator 2: Guanidine vulcanization accelerator (DPG, manufactured by Flexis Corp .; diphenylguanidine)
・ Vulcanization accelerating aid 1: Zinc oxide (3 types of zinc white, manufactured by Shodo Chemical)
・ Vulcanization acceleration aid 2: stearic acid (bead stearic acid YR, manufactured by NOF Corporation)

[Explanation of test results]
<Example 1 , Reference Examples 2 to 4>
(1) G′0.28, which is an index of silica dispersibility, is in the range of 52 to 63 with respect to 100 of the standard example, and a remarkable improvement was recognized.
(2) M300 / M100, which is an index of reinforcement, is in the range of 113 to 116 with respect to 100 of the standard example, and a remarkable improvement was recognized.
(3) Rebound resilience (40 ° C.), which is an index of rolling resistance, is in the range of 104 to 109 with respect to 100 of the standard example, and a marked improvement was observed.
(4) The abrasion resistance was in the range of 117 to 125 with respect to 100 of the standard example, and a marked improvement was observed.

<Comparative Examples 1-8>
<< Comparative Example 1 >>
This is a comparative example in which an amino acid was blended but no urea aqueous solution was blended.
Although improvement was recognized in G′0.28 which is an index of silica dispersibility, M300 / M100 which is an index of reinforcement, rebound resilience (40 ° C.) and an abrasion resistance which are indexes of rolling resistance, Even worse than the standard case.

<< Comparative Example 2 >>
It is the comparative example which mix | blended water, without mix | blending an amino acid and urea aqueous solution.
G′0.28, which is an index of silica dispersibility, and M300 / M100, which is an index of reinforcement, were recognized to be improved from the standard examples, but the resilience (40 ° C.), which is an index of rolling resistance, was improved. In addition, the wear resistance was deteriorated.

<< Comparative Example 3 >>
This is a comparative example in which an amino acid and a urea aqueous solution are not blended, and urea is blended in a powder state.
G′0.28, which is an index of silica dispersibility, and M300 / M100, which is an index of reinforcement, were recognized to be improved from the standard examples. However, the resilience (40 ° C.) and the abrasion resistance, which are indicators of rolling resistance There was no improvement.

<< Comparative Example 4 >>
It is a comparative example which mix | blended each component as shown in Table 1 .
G'0.28, which is an index of silica dispersibility, M300 / M100, which is an index of reinforcement, and abrasion resistance were improved from the standard examples, but rebound resilience (40 ° C), which is an index of rolling resistance. There was no improvement.

<< Comparative Example 5 >>
It is the comparative example which mix | blended urea aqueous solution, without mix | blending an amino acid.
G'0.28, which is an index of silica dispersibility, M300 / M100, which is an index of reinforcement, and abrasion resistance were improved from the standard examples, but rebound resilience (40 ° C), which is an index of rolling resistance. There was not enough improvement.

<< Comparative Example 6 >>
It is the comparative example which mix | blended urea aqueous solution, without mix | blending an amino acid. The concentration of the urea aqueous solution is different from that of Comparative Example 5, and this Comparative Example is thinner.
G'0.28, which is an index of silica dispersibility, M300 / M100, which is an index of reinforcement, rebound resilience (40 ° C), which is an index of rolling resistance, and wear resistance are improved from the standard examples. I couldn't.

<< Comparative Example 7 >>
This is a comparative example in which amino acids were blended, but urea aqueous solution was not blended, and urea and water were blended separately.
G'0.28, which is an index of silica dispersibility, M300 / M100, which is an index of reinforcement, and abrasion resistance were improved from the standard examples, but rebound resilience (40 ° C), which is an index of rolling resistance. There was not enough improvement.

<< Comparative Example 8 >>
This is a comparative example in which an amino acid was blended, but no urea aqueous solution was blended, and no silane coupling agent was blended.
G'0.28, which is an index of silica dispersibility, M300 / M100, which is an index of reinforcement, and abrasion resistance were improved from the standard examples, but rebound resilience (40 ° C), which is an index of rolling resistance. There was not enough improvement.

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 (2)

Including a diene rubber, silica, a sulfur-containing silane coupling agent, an amino acid, and urea;
The amino acid is at least one selected from the group consisting of L-glutamic acid, L-aspartic acid and their enantiomers and salts thereof, and hydrates thereof;
20 to 120 parts by mass of the silica is contained with respect to 100 parts by mass of the diene rubber,
3 to 15 parts by mass of the sulfur-containing silane coupling agent, 0.5 to 10 parts by mass of the amino acid, and 0.25 to 5.0 parts by mass of urea with respect to 100 parts by mass of the silica. ,And,
A rubber composition in which 0.5 to 10 parts by mass of the urea is mixed with 100 parts by mass of silica as a 0.5 to 50% by mass urea aqueous solution.   A pneumatic tire using the rubber composition according to claim 1 for a tread rubber of a tire.