JP2011052090A - Rubber composition for tire and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tires enhancing the reaction rate of silica, alkoxyalkylsilane and a silica coupling agent and improving rolling resistance, aging resistance and scorch resistance, and a pneumatic tire using it. <P>SOLUTION: In the rubber composition for tires, 40 pts.mass or more of silica and 100 pts.mass of a diene-based rubber are formulated, 2-10 mass% of one kind or more of alkoxyalkylsilane selected from dialkoxyalkylsilane and trialkoxyalkylsilane is formulated relative to the amount of silica, 0.5-3 pts.mass of a carboxylic acid amine salt is formulated, and a silane coupling agent is also formulated. In the pneumatic tire, the rubber composition for tires is used for cap treads. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tire rubber composition and a pneumatic tire using the same, and more particularly, to a tire rubber composition having improved rolling resistance, aging resistance, and scorch resistance, and a pneumatic tire using the same. It relates to tires.

The tire tread rubber is required to have wet performance and rolling resistance, and silica is blended in order to achieve both of these performances. However, when a large amount of silica is blended, there is a problem that the dispersibility, abrasion resistance, and workability of silica deteriorate.
Therefore, a technique for improving the dispersibility and processability of silica by blending a trialkoxyalkylsilane with a rubber composition containing silica has been disclosed (see, for example, Patent Document 1).
However, when a trialkoxyalkylsilane is compounded with a rubber composition containing silica, the reaction rate between silica and a silica coupling agent is reduced, or silica and an unreacted trialkoxyalkylsilane migrate to another member. A new problem has been found that the aging resistance deteriorates due to volatilization.

JP 2007-204684 A

  Accordingly, an object of the present invention is to improve the reaction rate of silica with an alkoxyalkylsilane and a silica coupling agent to improve rolling resistance, aging resistance, and scorch resistance, and a pneumatic composition using the same. To provide tires.

As a result of intensive studies, the present inventors have found that the above problem can be solved by blending a specific amount of alkoxyalkylsilane and carboxylic acid amine salt into a rubber composition containing silica and a silica coupling agent. The present invention has been completed.
That is, the present invention is as follows.
1. 40 parts by mass or more of silica, 100% by mass of diene rubber, 2 to 10% by mass of one or more alkoxyalkylsilanes selected from dialkoxyalkylsilane and trialkoxyalkylsilane based on the silica, carboxylic acid A tire rubber composition comprising 0.5 to 3 parts by mass of an amine salt and a silane coupling agent.
2. 2. The rubber composition for tire according to 1 above, wherein the alkoxyalkylsilane is a trialkoxyalkylsilane, and the trialkoxyalkylsilane is represented by the following formula 1.

(In Formula 1, R ₁ , R ₂ , R ₃ , R ₄ each independently represents an alkyl group.)
3. (B / A) is 0.1 to 0.3, where A is the number of moles of the alkoxy group of the trialkoxyalkylsilane and B is the number of moles of the amine of the carboxylic acid amine salt. The rubber composition for tires according to 2 above.
4). 4. The rubber composition for tire according to 2 or 3 above, wherein R ₁ of the trialkoxyalkylsilane has 8 to 15 carbon atoms.
5). 5. The rubber composition for tires according to any one of 2 to 4 above, wherein the trialkoxyalkylsilane is trialkoxyoctylsilane.
6). 5. The rubber composition for tire according to any one of 1 to 4, wherein the carboxylic acid amine salt is a succinic acid amine salt.
7). A pneumatic tire using the tire rubber composition according to any one of 1 to 6 as a cap tread.

  According to the present invention, since a specific amount of alkoxyalkylsilane and carboxylic acid amine salt is blended in a rubber composition containing silica and a silica coupling agent, the reaction rate between silica, alkoxyalkylsilane and silica coupling agent. The rolling resistance, aging resistance and scorch resistance can be improved. The rubber composition for tires of the present invention is particularly useful for cap treads.

It is a fragmentary sectional view of an example of a pneumatic tire.

  Hereinafter, the present invention will be described in more detail.

FIG. 1 is a partial cross-sectional view of an example of a pneumatic tire for a passenger car.
In FIG. 1, the pneumatic tire is composed of a pair of left and right bead portions 1 and sidewalls 2, and a tread 3 connected to both sidewalls 2, and a carcass layer 4 in which fiber cords are embedded between the bead portions 1 and 1 is mounted. Then, the end portion of the carcass layer 4 is turned up around the bead core 5 and the bead filler 6 from the tire inner side to the outer side. Further, in the tread 3, a belt layer 7 is disposed over the circumference of the tire outside the carcass layer 4.
The rubber composition for tires of the present invention described below is useful for various members for tires as described above, and particularly useful for cap treads.

(Diene rubber)
As the diene rubber component used in the present invention, any diene rubber that can be blended in the rubber composition for tires can be used. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and the like. These may be used alone or in combination of two or more. These rubber components are not particularly limited in molecular weight or microstructure, for example, and may be terminal-modified with amine, amide, silyl group or the like.
Among these diene rubbers, BR and SBR are preferable as the diene rubber from the viewpoint of the effect of the present invention.

(silica)
The silica used in the present invention is not particularly limited, and those usually blended in a rubber composition can be used. Examples thereof include wet method silica, dry method silica, and surface-treated silica. . Among them, those having a CTAB adsorption specific surface area (measured according to JIS K6217) of 50 to 250 m ² / g are preferable.

(Alkoxyalkylsilane)
The alkoxyalkylsilane used in the present invention is at least one selected from dialkoxyalkylsilane and trialkoxyalkylsilane.

  The dialkoxyalkylsilane is represented by the following formula 2.

In Formula 2, R ₅ , R ₆ , R ₇ and R ₈ each independently represents an alkyl group. Preferably, R ₅ and R ₆ are alkyl groups having 8 to 15 carbon atoms. Preferably, R ₇ and R ₈ are alkyl groups having 1 to 15 carbon atoms.
When the number of carbon atoms of R ₅ and R ₆ is less than 8, the desired effect is small. On the other hand, if it exceeds 15, the hardness is lowered, which may adversely affect the handling stability.

  The trialkoxyalkylsilane is represented by the following formula 1.

In Formula 1, R ₁ , R ₂ , R ₃ and R ₄ each independently represents an alkyl group. Preferably, R ₁ is an alkyl group having 8 to 15 carbon atoms. Moreover, Preferably, R < ₂ >, R < ₃ >, R < ₄ > is an alkyl group which has 1-15 carbon atoms.
If the carbon number of R ₁ is less than 8, the desired effect is small. On the other hand, if it exceeds 15, the hardness is lowered, which may adversely affect the handling stability.

  In the present invention, trialkoxyalkylsilane is preferable as the alkoxyalkylsilane from the viewpoint of the effect, and trialkoxyoctylsilane is more preferable.

(Carboxylic acid amine salt)
The carboxylic acid amine salt used in the present invention is a salt of an aliphatic or aromatic mono- or polyvalent carboxylic acid and an aliphatic or aromatic amine compound.
The carbon number of the aliphatic or aromatic mono- or polyvalent carboxylic acid is preferably 2-30. In the polyvalent carboxylic acid, the number of carboxyl groups in one molecule is preferably 2 to 4.
As carbon number of an aliphatic or aromatic amine compound, 2-30 are preferable.
Examples of the aliphatic or aromatic mono- or polyvalent carboxylic acid include succinic acid, tartaric acid, salicylic acid, malic acid, and the like. Of these, succinic acid is preferred.
Examples of the aliphatic or aromatic amine compound include cyclohexylamine, t-butylamine, and benzylamine.

(Silane coupling agent)
The silica coupling agent used in the present invention is not particularly limited, but a sulfur-containing silane coupling agent is preferable. For example, 3-octanoylthiopropyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, bis- (3 -Bistriethoxysilylpropyl) -tetrasulfide, bis- (3-bistriethoxysilylpropyl) -disulfide, 3-mercaptopropyltrimethoxysilane and the like.

(filler)
The tire rubber composition of the present invention may contain various fillers. The filler is not particularly limited and may be appropriately selected depending on the application site of the tire, and examples thereof include carbon black and inorganic filler. Examples of the inorganic filler include clay, talc, and calcium carbonate. Of these, carbon black is preferred.
Carbon black can be blended, for example, 60 to 120 parts by mass, preferably 80 to 110 parts by mass with respect to 100 parts by mass of diene rubber. When the blending ratio of carbon black is 60 parts by mass or more, the elastic modulus is improved. Moreover, abrasion resistance and workability improve by being 120 mass parts or less.

(Combination ratio of tire rubber composition)
In the tire rubber composition of the present invention, 40 parts by mass or more of silica, and one or more alkoxyalkylsilanes selected from dialkoxyalkylsilane and trialkoxyalkylsilane are used for the silica with respect to 100 parts by mass of the diene rubber. On the other hand, 2-10 mass%, 0.5-3 mass parts of carboxylic acid amine salt are mix | blended, and a silane coupling agent is mix | blended.
If the silica is less than 40 parts by mass, the desired effect cannot be achieved. In addition, it is not preferable to add more than 100 parts by mass of silica because processability deteriorates.
If the alkoxyalkylsilane is less than 2% by mass with respect to silica, the desired effect cannot be obtained. Conversely, if it exceeds 10% by mass, the aging resistance and scorch resistance deteriorate.
If the amount of the carboxylic acid amine salt is less than 0.5 parts by mass, the desired effect cannot be obtained. Conversely, if it exceeds 3 parts by mass, the scorch resistance deteriorates and bloom occurs, resulting in a poor appearance.

In the tire rubber composition of the present invention, the more preferable blending ratio of silica is 50 to 80 parts by mass.
The said more preferable mixture ratio of alkoxyalkylsilane is 3-9 mass% with respect to a silica.
The said more preferable mixture ratio of carboxylic acid amine salt is 1-2 mass parts.
A preferable blending ratio of the silane coupling agent is 4 to 15% by mass with respect to silica, and a more preferable blending ratio is 6 to 10% by mass.

In the tire rubber composition of the present invention, when the number of moles of the alkoxy group of the trialkoxyalkylsilane is A and the number of moles of the amine of the carboxylic acid amine salt is B, (B / A) is 0.00. It is especially preferable that it is 1-0.3. According to this embodiment, the rolling resistance, aging resistance, and scorch resistance, which are the effects of the present invention, can be further improved. When the (B / A) is less than 0.1, the effect of improving the effect is small. When (B / A) exceeds 0.3, the scorch resistance tends to deteriorate.
More preferably, the (B / A) is 0.1 to 0.2.
Here, the number of moles of the alkoxy group of the trialkoxyalkylsilane is the number of moles of the OR ₂ group + the number of moles of the OR ₃ group + the number of moles of the OR ₄ group in the above formula 1. The number of moles of amine of the carboxylic acid amine salt is the number of moles of amine groups contained in one molecule of the carboxylic acid amine salt.

In the tire rubber composition of the present invention, when a guanidine or thiuram vulcanization accelerator is used, the sum of the guanidine or thiuram vulcanization accelerator and the carboxylic acid amine salt is a diene type. The amount is preferably set in the range of 0.8 to 3 parts by mass, more preferably 0.8 to 2 parts by mass with respect to 100 parts by mass of rubber. If less than 0.8 part by mass, the desired effect cannot be obtained, and if it exceeds 3 parts by mass, problems such as deterioration of rubber appearance due to blooming, deterioration of scorch resistance, deterioration of wear resistance due to increase in crosslinking density, etc. May occur.
Examples of the guanidine-based vulcanization accelerator include diphenylguanidine, and examples of the thiuram-based vulcanization accelerator include tetramethylthiuram disulfide, tetrabenzylthiuram disulfide, and tetrakis (2-ethylhexyl) thiuram disulfide.

  In addition to the above-described components, the tire rubber composition of the present invention is generally used for tire rubber compositions such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, and plasticizers. Various additives blended in the above can be blended, and such additives can be kneaded by a general method to form a composition, which can be used for vulcanization or crosslinking. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated.

  The rubber composition of the present invention is particularly useful for cap treads among members used for tires.

  The rubber composition of the present invention can be used for producing a pneumatic tire according to a conventional method for producing a pneumatic tire.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Conventional example, Examples 1-4 and Comparative Examples 1-6
Preparation of sample In the composition (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were kneaded for 5 minutes with a 1.7 liter closed Banbury mixer, and then released outside the mixer. And cooled to room temperature. Subsequently, the composition was put into the Banbury mixer again, and a vulcanization system was added and kneaded to obtain a tire rubber composition. Next, the obtained rubber composition for tire was press vulcanized at 170 ° C. for 10 minutes in a predetermined mold to prepare a vulcanized rubber test piece. The physical properties of the obtained vulcanized rubber specimens were measured by the following test methods.

tan δ (60 ° C.): Measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho. The value of the conventional example was set to 100 and displayed as an index. Smaller values mean lower heat generation and better rolling resistance.
Aging resistance: Hardness was measured at 23 ° C. according to JIS K6253 (hardness @ standard). Separately, the test piece was left in a drying oven at 80 ° C. for 96 hours, and the hardness was measured at 23 ° C. (hardness @ aging). Calculate (hardness @ aging) / (hardness @ standard) × 100. The value of the conventional example was set to 100 and displayed as an index. A smaller value means better aging resistance.
Scorch resistance: Based on JIS K6300, the time for the viscosity to rise by 5 Mooney units at a temperature of 125 ° C. was measured, and the reciprocal thereof was used as an index. The value of the conventional example was set to 100 and displayed as an index. Smaller values mean better scorch resistance.
The results are also shown in Table 1.

Examples 5-7
Example 1 was repeated except that the value of (B / A) was variously changed when the number of moles of the alkoxy group of the trialkoxyalkylsilane was A and the number of moles of the amine of the carboxylic acid amine salt was B. Tan δ (60 ° C.), aging resistance and scorch resistance were evaluated. The results are shown in Table 2.

Examples 8-10
Example 1 was repeated except that the carbon number of the alkyl group in the trialkoxyalkylsilane was changed variously, and tan δ (60 ° C.), hardness and aging resistance were evaluated. The results are shown in Table 3.
Hardness: measured at 23 ° C. according to JIS K6253.

Examples 11-12
Example 1 was repeated except that various carboxylic acid amine salts were used in place of succinic amine, and tan δ (60 ° C.) and aging resistance were evaluated. The results are shown in Table 4.

* 1: SBR (Nippon Zeon Co., Ltd., Nipol NS460, 37.5 phr oil exhibition)
* 2: BR (manufactured by ZEON Corporation, Nipol BR1220)
* 3: Carbon black (Toast Carbon Co., Ltd., Seast KH)
* 4: Silica (Nippon Silica Industry Co., Ltd., nip seal VN3)
* 5: Silica coupling agent (Degussa, Si69)
* 6: ZnO (manufactured by Shodo Chemical Industry Co., Ltd., 3 types of zinc oxide)
* 7: Stearic acid (manufactured by NOF Corporation, beads stearic acid NY)
* 8: Aroma oil (made by Showa Shell Co., Ltd., Desolex No. 3)
* 9: 6C (SANTOFLEX 6PPD manufactured by Flexis, an anti-aging agent)
* 10: RD (Ouchi Shinsei Chemical Co., Ltd. Nocrack 224. Anti-aging agent)
* 11: Higher fatty acid salt (Kawaguchi Chemical Co., Ltd., Exton L-2-G)
* 12: Sulfur (manufactured by Hosoi Chemical Co., Ltd., oil-treated sulfur)
* 13: CZ (vulcanization accelerator manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller CZ-G)
* 14: DPG (vulcanization accelerator manufactured by Sumitomo Chemical Co., Ltd., trade name: Soxinol DG)
* 15: Octylsilane (Tokyo Chemical Industry Co., Ltd., n-octyltriethoxysilane)
* 16: Hexylsilane (Tokyo Chemical Industry Co., Ltd., n-hexyltriethoxysilane)
* 17: Dodecylsilane (Tokyo Chemical Industry Co., Ltd., n-dodecyltriethoxysilane)
* 18: Octadecylsilane (manufactured by Tokyo Chemical Industry Co., Ltd., n-octadecyltriethoxysilane)
* 19: Amine succinate (150 ml of acetone is put into a 1 liter stoppered round flask, then 60 g (0.508 mol) of succinic acid and 100.7 g (1.016 mol) of cyclohexylamine are reacted at room temperature for 5 minutes. The precipitate was filtered, and the precipitate remaining on the filter paper was washed twice with acetone and dried under reduced pressure to give 159.1 g (yield of cyclohexylamine succinate salt as a white powder product). 99%) was obtained.
* 20: Amine tartrate (Add 300 ml of acetone to a 1 liter stoppered round flask, then add 42 g (0.28 mol) of tartaric acid and 55.5 g (0.56 mol) of cyclohexylamine, and react at room temperature for 5 minutes to precipitate. The precipitate was filtered, and the precipitate remaining on the filter paper was washed twice with acetone and dried under reduced pressure to give 95.6 g (98% yield) of cyclohexylamine tartrate salt as a white powder product. )was gotten.
* 21: Amine salicylate (200 ml of acetone was placed in a 1 liter stoppered round flask, and then 40 g (0.29 mol) of salicylic acid and 30.1 g (0.34 mol) of cyclohexylamine were reacted at room temperature for 5 minutes. The precipitate was filtered and the precipitate remaining on the filter paper was washed twice with acetone and dried under reduced pressure to give 67.4 g (0.284 mol) of cyclohexylamine salicylate as a white powder product. (Yield 98%) was obtained.

As apparent from Table 1 above, the tire rubber compositions prepared in Examples 1 to 4 were prepared by adding an alkoxyalkylsilane and a carboxylic acid amine salt to a rubber composition containing silica and a silica coupling agent. Since a specific amount is blended, the reaction rate between silica, alkoxyalkylsilane and silica coupling agent is improved, and rolling resistance (tan δ (60 ° C.)), aging resistance and scorch resistance are improved compared to typical conventional examples. It has been improved.
On the other hand, since Comparative Example 1 does not contain an alkoxyalkylsilane, the rolling resistance (tan δ (60 ° C.)), aging resistance, and scorch resistance are not improved. In Comparative Example 2, the mixing ratio of the alkoxyalkylsilane is less than the lower limit specified in the present invention, so that rolling resistance (tan δ (60 ° C.)), aging resistance, and scorch resistance are not improved. In Comparative Example 3, since the compounding ratio of the alkoxyalkylsilane exceeds the upper limit defined in the present invention, the aging resistance and scorch resistance are not improved. In Comparative Example 4, the mixing ratio of the carboxylic acid amine salt is less than the lower limit specified in the present invention. Therefore, even when a large amount of DPG is added, the rolling resistance (tan δ (60 ° C.)), aging resistance, and scorch resistance are high. Not improved. In Comparative Example 5, since the mixing ratio of the carboxylic acid amine salt exceeded the upper limit specified in the present invention, the scorch resistance was deteriorated. In Comparative Example 6, since the blending ratio of silica was less than the lower limit specified in the present invention, desired rolling resistance (tan δ (60 ° C.)) and scorch resistance were not obtained.
As apparent from Table 2 above, when the number of moles of the alkoxy group of the trialkoxyalkylsilane is A and the number of moles of the amine of the carboxylic acid amine salt is B, the value of (B / A) is 0.00. When it is in the range of 1 to 0.3, the rolling resistance (tan δ (60 ° C.)) and the aging resistance are further improved without deteriorating the scorch resistance.
Further, as apparent from Table 3 above, the hardness is lowered when the carbon number of R ₁ of the trialkoxyalkylsilane is in the range of 8 to 15, particularly when the trialkoxyalkylsilane is trialkoxyoctylsilane. Without further improvement, rolling resistance (tan δ (60 ° C.)) and aging resistance are further improved.
Further, as apparent from Table 4 above, when the succinic acid amine salt is used, rolling resistance (tan δ (60 ° C.)) and aging resistance are further improved.

1 Bead part 2 Side wall 3 Tread 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer

Claims (7)

  40 parts by mass or more of silica, 100% by mass of diene rubber, 2-10% by mass of one or more alkoxyalkylsilanes selected from dialkoxyalkylsilane and trialkoxyalkylsilane based on the silica, carboxylic acid A tire rubber composition comprising 0.5 to 3 parts by mass of an amine salt and a silane coupling agent. 2. The tire rubber composition according to claim 1, wherein the alkoxyalkylsilane is a trialkoxyalkylsilane, and the trialkoxyalkylsilane is represented by Formula 1 below.

(In Formula 1, R ₁ , R ₂ , R ₃ , R ₄ each independently represents an alkyl group.)   (B / A) is 0.1 to 0.3, where A is the number of moles of the alkoxy group of the trialkoxyalkylsilane and B is the number of moles of the amine of the carboxylic acid amine salt. The tire rubber composition according to claim 2. The tire rubber composition according to claim 2 or 3, wherein R ₁ of the trialkoxyalkylsilane has 8 to 15 carbon atoms.   The tire rubber composition according to any one of claims 2 to 4, wherein the trialkoxyalkylsilane is trialkoxyoctylsilane.   The tire rubber composition according to any one of claims 1 to 4, wherein the carboxylic acid amine salt is a succinic acid amine salt.   The pneumatic tire which used the rubber composition for tires in any one of Claims 1-6 for cap tread.

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