JP2000071711A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an additive for substantially improving tanδ balance of a rubber composition for tire. SOLUTION: The rubber composition for tire contains (1) additive having specific surface area of nitrogen from 60 to 150 m2/g, and dibutyl phthalate oil absorption from 80 to 150 ml/100g in 30 to 100 parts by weight, and (2) at least one kind of ester having a melting point from 40 to 60 deg.C in 1 to 30 parts by weight, based on 100 parts by weight of a raw material rubber formed of at least one kind of diene-based rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rubber composition for a tire, and more particularly to a rubber composition useful for a tire tread in which the tan δ balance of rubber is significantly improved.

[0002]

2. Description of the Related Art Conventionally, a rubber obtained by adding palm oil to BR (butadiene rubber) or SBR (styrene-butadiene copolymer rubber) of tire rubber (Japanese Patent Laid-Open No. 58-747).
No. 31, JP-A-60-215, and those containing an ester-based or naphthenic-based or paraffin-based oil.
No. 403), those containing a neopentyl type polyol ester (Japanese Patent Application Laid-Open No. 62-253644), those containing a fatty acid metal salt (Japanese Patent Application Laid-Open No. 6-248114), and the like are known. However, the ester compounds described in these prior arts all have low melting points and are added for the purpose of acting as a plasticizer, so that tan δ on the high temperature side decreases but tan δ on the low temperature side simultaneously decreases. Is also reduced. Further, when solids such as wax and fatty acid zinc are added, tan δ on the low temperature side increases, but tan δ on the high temperature side also increases.
There is a problem that nδ also increases.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rubber composition for tires in which a tan δ balance of rubber is significantly improved by adding a fatty acid ester compound having a specific melting point to rubber. And

[0004]

According to the present invention, raw rubber 100 comprising at least one or more diene rubbers is provided.
(1) Nitrogen specific surface area 60 to 150 m ²
/ G, oil absorption of dibutyl phthalate 80-150 ml / 10
0 to 30 parts by weight of filler, (2) melting point of 40 to
At least one ester in the range of 60 ° C.
There is provided a rubber composition for a tire, comprising-30 parts by weight.

According to the present invention, the melting point is 40 to
The ester in the range of 60 ° C. is an ester of a polyhydric alcohol having 3 to 6 carbon atoms and a carboxylic acid having 14 to 18 carbon atoms and containing 60% by weight or more of a carboxylic acid having an iodine value of 10 or less, or Aromatic carboxylic acid and C12-
The rubber composition for a tire is provided as an ester with an alcohol containing 60% by weight or more of No. 18 higher alcohol.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention focuses on fatty acid derivatives having a specific melting point. Specifically, the melting point is 4
By adding a fatty acid ester compound at 0 to 60 ° C. to the rubber, the tan δ balance of the rubber has been significantly improved. More specifically, (A) an ester of a polyhydric alcohol having 3 to 6 carbon atoms and a carboxylic acid containing 14 to 18 carbon atoms and containing 60% by weight or more of a carboxylic acid having an iodine value of 10 or less, or (B) an aromatic compound A rubber composition for a tire tread, comprising at least one selected from an ester additive of a carboxylic acid and an alcohol containing 60% by weight or more of a higher alcohol having 12 to 18 carbon atoms. By blending this additive with rubber, the viscosity of the unvulcanized rubber is reduced, and
The effect is that the low-temperature side tan δ near ° C. increases, the high-temperature side tan δ above 40 ° C. decreases, and the tan δ gradient increases.

In the rubber composition for a tire of the present invention, the ester having the specific structure of the above (A) or (B) is compounded. C3, one of the components constituting the additive (A)
The polyhydric alcohols Nos. To 6 include, for example, trimethylolethane, trimethylolpropane, glycerin, 3-methyl-1,3,5-pentanetriol, pentaerythritol, diglycerin, erythritol, triglycerin, sorbitol, dipentaerythritol And the like, and as the other component, a saturated carboxylic acid having 14 to 18 carbon atoms, for example, myristic acid, palmitic acid,
Stearic acid or the like is used. Further, as the aromatic carboxylic acid which is one of the components constituting the additive (B), for example, benzenetricarboxylic acid, isophthalic acid, phthalic acid, benzoic acid, salicylic acid and the like are used, and the other component is the other component. As the higher alcohol having 12 to 18 carbon atoms, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol and the like are used.

As the ester of the additive (A) or (B) used in the present invention, those having a melting point in the range of 40 to 60 ° C. are used. When the melting point is lower than 40 ° C., the high temperature side tan δ of 40 ° C. or higher is reduced, and −
The low-temperature side tan δ around 10 to 0 ° C. also decreases. At the same time, the hardness near room temperature also decreases. When the melting point exceeds 60 ° C., the low-temperature side tan δ increases, but at the same time, the high-temperature side tan δ also increases.

The esters (A) and (B) as additives used in the present invention may be obtained by mixing the above-mentioned specific polyhydric alcohol with a saturated carboxylic acid or the above-mentioned specific aromatic carboxylic acid and a higher alcohol. It can be obtained by charging according to the desired composition ratio and performing esterification by a conventional esterification method. Melting point 40-60 ° C
Preferred examples of the ester include those called hydrogenated oils obtained by hydrogenating animal and vegetable oils.

In the rubber composition for a tire according to the present invention, the raw rubber 100 comprising at least one or more diene rubbers is used.
The nitrogen specific surface area is 60 to 150 m ² / g with respect to parts by weight.
And the dibutyl phthalate oil absorption is 80-150 ml / 100
g (carbon black, silica, etc.) of 30 to 1
00 parts by weight, and the above additive (A) or (B)
Needs to be used in an amount of 1 to 30 parts by weight. If the amount of the filler is less than 30 parts by weight, the effect as a filler is not exhibited, and if it exceeds 100 parts by weight, the mixing processability is deteriorated, which is not preferable.
If the amount of the ester of the additive (A) or (B) is less than 1 part by weight, the intended desired effect cannot be exhibited, and if it exceeds 30 parts by weight, the rubber hardness, It is not preferable because it causes a significant decrease in the physical properties of breakage and the like, and adversely affects the wear resistance.

The rubber component diene rubber used in the rubber composition for a tire of the present invention includes, for example, natural rubber (N
R), various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), polyisoprene rubber (IR), acrylonitrile butadiene rubber, chloroprene rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer Polymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber and the like are used.

The rubber composition for a tire of the present invention contains, in addition to the above-mentioned essential components, ordinary vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, various oils, antioxidants, plasticizers, softeners and the like. Various additives generally used for tires can be compounded, and the compound can be kneaded and vulcanized by a general method to produce various tire members. The amounts of these additives may be conventional general amounts as long as they do not contradict the purpose of the present invention.

[0013]

EXAMPLES The present invention will be described in more detail with reference to standard examples, examples and comparative examples, but it goes without saying that the technical scope of the present invention is not limited to these examples.

Table I shows the types and melting points of various esters, fatty acid metal salts and waxes used in the following Examples and Comparative Examples. The melting point is measured by DSC (Differencial
Using a Scanning Calorimeter)
The temperature was raised at a rate of 10 ° C./min. The melting point was determined from the temperature of the melting peak of the DSC curve obtained by DSC measurement.

[0015]

[Table 1]

The following commercially available products were used as the other components used in the formulations of the standard examples, examples and comparative examples. NR: SIR-20 SBR: Nipol 1702 (37.5 phr oil extension, styrene content 23.5%) (manufactured by Zeon Corporation) cis-BR: Nipol BR 1220 (manufactured by Zeon Corporation) HAF carbon black: SEAST KH (manufactured by Tokai Carbon Co., Ltd.) (N ₂ SA = 93 m ² / g, DBP = 1)
01ml / 100g) ISAF carbon black: DIA BLACK I
(Manufactured by Mitsubishi Chemical Corporation) (N ₂ SA = 142 m ² / g, D
BP = 98 ml / 100 g) Zinc oxide: three kinds of zinc oxide (manufactured by Seido Chemical Co., Ltd.) Antioxidant: VULKANOX 4020 (N-phenyl-N ′-(1,3-dimethyl) -p-phenylenediamine), (Sumitomo Chemical Co., Ltd.) Stearic acid: Beads stearic acid paulownia (Kao Corporation) Aroma oil: Process X-140 (Nippon Oil Co., Ltd.)
Sulfur: Oil-treated powdered sulfur (Karuizawa Smelting Co., Ltd.) Vulcanization accelerator NS: Noxeller NS-P (Nt-butyl-2-benzothiazolylsulfenamide) (Ouchi Shinko Chemical Co., Ltd.) Vulcanization accelerator CZ: VULKACIT CZ / EG (N-
Cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Akzo Chemicals)

Preparation of Sample The vulcanization accelerator and components other than sulfur are kneaded in a 1.8 liter closed mixer for 3 to 5 minutes, and the vulcanization accelerator is added to the masterbatch released when the temperature reaches 165 ± 5 ° C. And sulfur were kneaded with an 8-inch open roll to obtain a rubber composition. The unvulcanized property “ML _{1 + 4} ” (Mooney viscosity) of the obtained rubber composition was measured. Next, this composition was added to 15 × 15 ×
Press vulcanization in a 0.2 cm mold at 160 ° C for 20 minutes to prepare a target test piece (rubber sheet), and measure and evaluate “viscoelasticity” and “abrasion resistance” of vulcanization properties. did.

The test methods for unvulcanized properties and vulcanized properties of the rubber compositions obtained in the respective examples are as follows. Unvulcanized physical properties 1) Mooney viscosity (ML _{1 + 4} ): Measured at 100 ° C. based on JIS K6300. Vulcanization properties 1) Viscoelasticity tan δ (0 ° C., 60 ° C.): Using rheograph solid manufactured by Toyo Seiki Seisaku-sho, measure viscoelasticity at initial strain = 10%, dynamic strain = 2%, frequency = 20 Hz (test) (Width: 5 mm). The tan δ slope is defined as 0 ° C. tan δ value of 6
It is a value obtained by dividing by the 0 ° C. tan δ value. 2) Abrasion resistance: The wear loss was measured using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) at a temperature of 20 ° C. and a slip rate of 50%. The larger the value, the better the wear resistance.

Standard Examples 1-2, Examples 1-7 and Comparative Example
1-7 These examples, the rubber composition of the NR or SBR, Table I
1 shows the evaluation results of rubber compositions containing various esters shown in FIG. The formulations and results for each example are shown in Table II below.

[0020]

[Table 2]

[0021]

[Table 3]

According to the results shown in Table II, those of Examples in which the predetermined ester of the present invention is blended have improved processability of unvulcanized rubber and greatly improved tan δ balance (tan δ gradient). I understand.

Standard Example 3, Examples 8 to 12 and Comparative Example 8
To 13 Examples of these are the NR + BR rubber composition shows a tendency of the operation and effect in case of increasing the amount of the ester additives of the present invention. The results, as well as the results using conventional plasticizers, are shown in Table III below.

[0024]

[Table 4]

[0025]

[Table 5]

According to the results shown in Table III, as the amount of the ester additive of the present invention is increased, the viscosity of the unvulcanized rubber decreases and the tan δ balance (tan δ gradient) increases.
It can be seen that also significantly improved. However, it also shows that the wear resistance is greatly reduced. Further, it can be seen that the tan δ balance is poor in the comparative example containing the conventional plasticizer.

[0027]

As described above, by adding a predetermined ester to the rubber composition according to the present invention, the workability at the time of unvulcanization is increased, and the tan δ is greatly improved without changing the abrasion resistance. The balance can be improved. Therefore, a rubber composition containing this additive is extremely useful as a rubber composition for a tire, particularly a rubber composition for a tire tread.

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Claims (3)

[Claims] 1. A filler 30 having (1) a nitrogen specific surface area of 60 to 150 m ² / g and a dibutyl phthalate oil absorption of 80 to 150 ml / 100 g with respect to 100 parts by weight of a raw rubber composed of at least one or more diene rubbers. (2) A rubber composition for a tire comprising 1 to 30 parts by weight of (2) at least one ester having a melting point in the range of 40 to 60 ° C. 2. An ester whose melting point is in the range of 40 to 60 ° C. is a polyhydric alcohol having 3 to 6 carbon atoms and a polyhydric alcohol having 1 to 6 carbon atoms.
A carboxylic acid having an iodine value of 10 or less of 4 to 18 is 60% by weight.
The rubber composition for a tire according to claim 1, which is an ester with the carboxylic acid contained above. 3. The ester having a melting point in the range of 40 to 60 ° C. is an ester of an aromatic carboxylic acid and an alcohol containing 60% by weight or more of a higher alcohol having 12 to 18 carbon atoms. The rubber composition for a tire according to claim 1.