JP6919210B2 - Rubber composition for tires - Google Patents

Description

The present invention relates to a rubber composition for a tire, which contains recycled rubber and has improved tensile fracture characteristics and low heat generation.

In recent years, from the viewpoint of resource conservation and environmental protection, recycled rubber has been blended into the rubber composition of pneumatic tires. Recycled rubber is defined in JIS K6313 and is a recycled product of used automobile tires, tubes and other rubber products, and is obtained by crushing or further desulfurizing the used rubber products. It is rubber. However, the rubber composition containing the recycled rubber has a problem that the physical properties are inevitably lowered, and in particular, the tensile breaking strength and the tensile breaking elongation are lowered, and the heat generation property is increased.

Patent Document 1 proposes to improve the heat aging prevention performance by using a rubber composition for tires in which a tea extract containing catechin is mixed with recycled rubber and diene-based rubber. However, the action of improving the tensile fracture property and the low heat generation property is not always sufficient, and further improvement is required.

Japanese Unexamined Patent Publication No. 2010-65103

An object of the present invention is to provide a rubber composition for a tire, which contains a recycled rubber and has improved tensile fracture characteristics and low heat generation properties to a level higher than the conventional level.

（式中、ｎは２〜１０の整数を表す。） The rubber composition for a tire of the present invention that achieves the above object has 100 parts by mass of natural rubber, 30 to 160 parts by mass of a reinforcing filler, 5 to 100 parts by mass of recycled rubber, and 0.1 parts by mass of a carbon coupling agent. It is characterized by blending up to 15.0 parts by mass, and the carbon coupling agent is S- (aminoalkyl) thiosulfuric acid represented by the following general formula (1) or a metal salt thereof .

(In the formula, n represents an integer of 2 to 10.)

The rubber composition for a tire of the present invention, together with natural rubber, recycled rubber, and a reinforcing filler, is a carbon coupling which is S- (aminoalkyl) thiosulfate represented by the general formula (1) or a metal salt thereof. Since the agent is blended, the tensile strength at break and the elongation at break can be maintained and improved, and the heat generation can be reduced to a level higher than the conventional level.

In the present invention, the recycled rubber is preferably a recycled rubber that has not been frozen and pulverized, and the action of the carbon coupling agent can be further enhanced.

Before Symbol quinones can be selected benzoquinone, naphthoquinone, anthraquinone.

The pneumatic tire made of the rubber composition for a tire having improved tensile fracture characteristics and low heat generation as described above can improve durability and fuel efficiency more than the conventional level while using a recycled material.

In the rubber composition for a tire of the present invention, the diene-based rubber means an unused diene-based rubber, and is different from the recycled rubber and the rubber component in the recycled rubber. Examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, and butyl halide rubber. Of these, natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and halogenated butyl rubber are preferable. These diene rubbers can be used alone or as an arbitrary blend.

The recycled rubber used in the present invention is not particularly limited, and is crushed rubber mechanically crushed at room temperature or in a frozen state, desulfurized rubber that has been desulfurized, and automobile tires and tubes specified in JIS K6313. And other rubber products such as used rubber, and recycled rubber having the same properties as this can be mentioned. Of these, recycled rubber that has not been frozen and crushed, that is, crushed rubber and desulfurized rubber that have been crushed at room temperature is preferable. When the recycled rubber that has not been frozen and crushed is used, the tensile fracture characteristics and the low heat generation property can be made more excellent than those in the case where the recycled rubber that has been frozen and crushed is used. The reason for this is that the frozen and crushed recycled rubber is considered to have less deterioration during freezing and crushing and is less likely to generate radicals, whereas the room temperature crushed rubber and desulfurized rubber are likely to be deteriorated during the regeneration process and have radicals. It is presumed that this radical promotes the reaction with the carbon coupling agent and facilitates the action of the carbon coupling agent. The crushed recycled rubber preferably has a mesh diameter of 60 mesh or more, more preferably 80 mesh or more. By setting the mesh diameter of the recycled rubber within such a range, the chances of contact with the carbon coupling agent during kneading are increased, and the tensile fracture characteristics and low heat generation can be further improved.

Further, the type of recycled rubber focusing on the raw material may be selected from tube recycled rubber, tire recycled rubber, and other recycled rubber, and a plurality of types can be combined. Of these, recycled tire rubber is preferable.

Recycled rubber comprises an organic component such as low molecular weight rubber that has been pulverized and / or desulfurized and an inorganic component such as carbon black. However, since the rubber component contained in the recycled rubber has a low molecular weight, the properties such as tensile fracture property and low heat generation property are inferior to those of the diene rubber. Therefore, in the present invention, a carbon coupling agent is blended together with the diene rubber and the recycled rubber, and by applying a shearing force and kneading, the recycled rubber and the diene rubber are bridged and the recycled rubber is blended. The accompanying disadvantages can be eliminated. In particular, by blending recycled rubber that has not been frozen and pulverized, tensile fracture characteristics and low heat generation can be further improved.

In the rubber composition for tires of the present invention, the recycled rubber is blended in an amount of 5 to 100 parts by mass, preferably 5 to 85 parts by mass, and more preferably 5 to 70 parts by mass with respect to 100 parts by mass of the diene rubber. If the blending amount of the recycled rubber is less than 5 parts by mass, it is not preferable from the viewpoint of the recycling rate. Further, if the blending amount of the recycled rubber exceeds 100 parts by mass, deterioration of tensile fracture characteristics and low heat generation cannot be tolerated.

In the present invention, the carbon coupling agent refers to a diene-based rubber and carbon black coupling agent. The carbon coupling agent is not particularly limited as long as it interacts with both the diene rubber and the carbon black, has a high affinity, and / or has a chemical bond property.

The carbon coupling agent is blended in an amount of 0.1 to 15.0 parts by mass, preferably 0.3 to 10 parts by mass, and more preferably 0.7 to 5 parts by mass with respect to 100 parts by mass of the diene rubber. If the blending amount of the carbon coupling agent is less than 0.1 parts by mass, the tensile fracture characteristics and low heat generation cannot be improved. Further, when the blending amount of the carbon coupling agent exceeds 15.0 parts by mass, the tensile breaking strength and the tensile breaking elongation deteriorate.

（式中、ｎは２〜１０の整数を表す。） Examples of the carbon coupling agent include S- (aminoalkyl) thiosulfuric acid represented by the following general formula (1) or a metal salt thereof. Here, the amino group portion can interact with carbon black, and the S-thiosulfate and S-thiosulfate portions can interact with diene rubber, particularly natural rubber.

(In the formula, n represents an integer of 2 to 10.)

In the above general formula (1), n represents an integer of 2 to 10, preferably an integer of 2 to 6, and more preferably an integer of 3 to 4. Examples of S- (aminoalkyl) thiosulfuric acid include S- (aminomethyl) thiosulfuric acid, S- (2-aminoethyl) thiosulfuric acid, S- (3-aminopropyl) thiosulfuric acid, and S- (4-aminobutyl). Thiosulfuric acid, S- (5-aminopentyl), S- (6-aminohexyl) thiosulfate, S- (7-aminopeptyl) thiosulfate, S- (8-aminooctyl) thiosulfate, S- (9-aminononyl) ) Thiosulfuric acid, S- (10-aminodecyl) thiosulfuric acid is exemplified. Of these, S- (3-aminopropyl) thiosulfate and S- (4-aminobutyl) thiosulfate are preferable.

The metal salt of S- (aminoalkyl) thiosulfate represented by the general formula (1) exemplifies, for example, lithium ion, sodium ion, potassium ion, cesium ion, cobalt ion, copper ion, and zinc ion as metal ions. be able to.

（式中、Ｒ¹は置換基を有してもよい炭素数６〜１２の２価の芳香族炭化水素基、Ｒ²，Ｒ³はそれぞれ独立に水素原子、ハロゲン原子、炭素数１〜６のアルキル基、炭素数６〜１２のアリール基、ヒドロキシ基または炭素数１〜６のアルコキシ基、Ｒ⁴はヒドロキシ基または−ＯＮａ、Ｘは−ＮＨ−または−Ｏ−を表す。） Further, as the carbon coupling agent, a compound having an alkanediyl group represented by the following general formula (2) can be mentioned. Here, the amino group portion can interact with carbon black, and the alkanediyl group portion can interact with diene rubber, particularly natural rubber.

(In the formula, R ¹ is a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms which may have a substituent, and R ² and R ³ are independently hydrogen atoms, halogen atoms and 1 to 6 carbon atoms, respectively. Alkyl group, aryl group having 6 to 12 carbon atoms, hydroxy group or alkoxy group having 1 to 6 carbon atoms, R ⁴ represents a hydroxy group or -ONa, and X represents -NH- or -O-).

In the general formula (2), R ¹ is a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms which may have a substituent. Examples of the divalent aromatic hydrocarbon group having 6 to 12 carbon atoms include a phenylene group, a naphthylene group, and a biphenylene group. Examples of the substituent include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxy group, a nitro group, a cyano group, a sulfo group, a halogen atom and the like. These substituents can optionally substitute 0 to 4 hydrogen atoms of the aromatic hydrocarbon group. R ¹ is preferably a phenylene group.

R ² and R ³ are independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxy group, or an alkoxy group having 1 to 6 carbon atoms. Examples of the halogen atom in R ² and R ³ include fluorine, chlorine, bromine and iodine. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group and an isopentyl group. Groups, n-hexyl groups and the like can be mentioned. Examples of the aryl group having 6 to 12 carbon atoms include a monocyclic or condensed polycyclic aromatic hydrocarbon having 6 to 12 carbon atoms, and examples thereof include a phenyl group, a naphthyl group, and a biphenyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group and an n-pentoxy group. , Isopentoxy group, n-hexyloxy group and the like.

As R ² and R ³ , ^{it is preferable that R 2} is a hydrogen atom, R ³ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably R ² and R ³ are hydrogen atoms.
R ⁴ is a hydroxy group or −ONa, preferably a hydroxy group.
X is -NH- or -O-. X is preferably −NH−.

Examples of the compound represented by the general formula (2) include (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid and (2Z) -4-[(3-amino). Phenyl) amino] -4-oxo-2-butenoic acid, (2Z) -4-[(4-aminophenyl) amino] -2-methyl-4-oxo-2-butenoic acid, sodium (2Z) -4- [(4-Aminophenyl) amino] -4-oxo-2-butenoic acid, sodium (2Z) -4-[(3-aminophenyl) amino] -4-oxo-2-butenoic acid, etc. can be exemplified. can. Among them, (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid, sodium (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2- Butenoic acid is preferable, and (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid is particularly preferable.

Further, the carbon coupling agent may include at least one structure selected from the group consisting of sulfonic acid, thiosulfuric acid and salts thereof, and a compound containing a quinone structure in the same molecule. Further, the quinones may be at least one selected from benzoquinone, naphthoquinone and anthraquinone. Here, the structural parts of quinones can interact with carbon black, and the structural parts of sulfonic acids, thiosulfates and salts thereof can interact with diene rubbers, especially natural rubbers.

Benzoquinone, naphthoquinone, and anthraquinone are compounds represented by the following chemical formulas, respectively.

（式中、Ｍ^r+はｒ価のカチオンであり、ｒは１または２である。また＊はキノン類の構造への結合手を表す。） The sulfonic acid and the salt of the sulfonic acid are represented by the following chemical formulas, respectively.

(In the formula, ^{Mr +} is an r-valent cation, r is 1 or 2, and * represents a bond to the structure of quinones.)

（式中、Ｍ^r+はｒ価のカチオンであり、ｒは１または２である。また＊はキノン類の構造への結合手を表す。） Thiosulfuric acid and salts of thiosulfuric acid are represented by the following chemical formulas, respectively.

(In the formula, ^{Mr +} is an r-valent cation, r is 1 or 2, and * represents a bond to the structure of quinones.)

The cation ^{Mr +} is not particularly limited, and examples thereof include sodium ion, potassium ion, lithium ion, calcium ion, barium ion, ammonium ion, and phosphonium ion.

The carbon coupling agent described above can be prepared and used by a usual method, or a commercially available one can be used.

In the present invention, a reinforcing filler can be blended. Examples of the reinforcing filler include carbon black, silica, clay, talc, mica, calcium carbonate and the like. Of these, carbon black and silica are preferable, and silica is particularly preferable. By blending silica, the tan δ at 60 ° C. can be made smaller and the low temperature heat generation can be made more excellent.

The reinforcing filler is blended in an amount of 30 to 160 parts by mass, preferably 35 to 140 parts by mass, and more preferably 40 to 130 parts by mass with respect to 100 parts by mass of the diene rubber. If the blending amount of the reinforcing filler is less than 30 parts by mass, the tensile breaking strength decreases. Further, when the blending amount of the reinforcing filler exceeds 160 parts by mass, heat generation becomes large and worsens.

The rubber composition for tires may contain various additives generally used in rubber compositions for tires, such as vulcanization accelerators, antiaging agents, kneading accelerators, various oils, and plasticizers. The additive can be kneaded in a conventional manner into a rubber composition for tires and used for vulcanization or cross-linking. The blending amount of these additives can be a conventional general blending amount as long as it does not contradict the object of the present invention. The rubber composition for a tire of the present invention can be produced by mixing each of the above components using a normal rubber kneading machine, for example, a Banbury mixer, a kneader, a roll, or the like.

Since the rubber composition for tires of the present invention comprises a rubber composition for tires having improved tensile fracture characteristics and low heat generation while using a recycled material, steering stability and durability can be improved while increasing the recycling rate of raw materials. And the fuel efficiency can be improved more than the conventional level.

Hereinafter, the present invention will be further described with reference to Examples, but the scope of the present invention is not limited to these Examples.

13 types of rubber compositions for tires having the common composition shown in Table 3 and having the composition shown in Tables 1 and 2 (Examples 1 to 4, 7, Reference Examples 5 and 8, Standard Examples 1 and 2, Comparative Example) In preparing 1 to 4), the components excluding sulfur and the vulcanization accelerator were weighed, kneaded with a 1.8 L closed mixer for 5 minutes, released and cooled to prepare a masterbatch. Thirteen types of rubber compositions for tires were prepared by adding sulfur and a vulcanization accelerator to the obtained masterbatch and mixing them with an open roll. Further, the blending amount of the common component in Table 3 is described as a mass part with respect to 100 parts by mass of the diene rubber shown in Tables 1 and 2.

The rubber composition for tires obtained above was vulcanized at 170 ° C. for 10 minutes in a mold having a predetermined shape to prepare a test piece, and the tensile fracture characteristics and tan δ at 60 ° C. were obtained by the methods shown below. Was evaluated.

Tensile breaking characteristics (tensile breaking strength and tensile breaking elongation)
Using the obtained test piece, a dumbbell JIS No. 3 type test piece was prepared in accordance with JIS K6251, and a tensile test was conducted under the conditions of 20 ° C. and a tensile speed of 500 mm / min to determine the tensile strength at break and the tensile elongation at break. It was measured. The results obtained are the "tensile fracture strength" and "tensile fracture" in Tables 1 and 2, with the respective values of Standard Example 1 as 100 in Table 1 and the respective values of Standard Example 2 as 100 in Table 2. Shown in the column of "elongation".

60 ° C tan δ
Using the obtained test piece, in accordance with JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, under the conditions of initial strain of 10%, dynamic strain of ± 2%, and frequency of 20 Hz, at a temperature of 60 ° C. tan δ (tangent loss) was measured. The obtained results are shown in the columns of "tan δ (60 ° C.)" in Tables 1 and 2 as an index in which the value of Standard Example 1 is 100 in Table 1 and the value of Standard Example 2 is 100 in Table 2. The smaller this index is, the smaller the heat generation is, which means that excellent fuel efficiency can be obtained when the tire is used.

The types of raw materials used in Tables 1 and 2 are shown below.
・ NR: Natural rubber, STR20
-Silica: ZEOSIL 1165MP manufactured by Rhodia
-Recycled rubber-1: Recycled rubber crushed by freezing, GF-80 manufactured by LEHIGH
-Recycled rubber-2: Recycled rubber that has not been frozen and crushed, 100MESH manufactured by China Rubber Migration Co., Ltd.
-Recycled rubber-3: Desulfurized recycled rubber, red line mark on tires manufactured by Muraoka Rubber Industries Co., Ltd.-Silane coupling agent: Si69 manufactured by Evonik Industries, Ltd.
-Carbon coupling agent-1: S- (3-aminopropyl) thiosulfate, Sumitomo Chemical Co., Ltd. Sumilink 100
Carbon coupling agent -2: (2Z) -4 - [ (4- aminophenyl) amino] -4-oxo-2-sodium butenoate, Sumitomo Chemical Co., Ltd. Sumi link 20 0

The types of raw materials used in Table 3 are shown below.
-Stearic acid: Stearic acid 50S manufactured by Nissin Rika Co., Ltd.
・ Zinc oxide: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. ・ Oil: Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.
・ Sulfur: Oil-treated sulfur manufactured by Hosoi Chemical Industry Co., Ltd. ・ Vulcanization accelerator-1: Noxeller NS-P manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
-Vulcanization accelerator-2: Soxinol DG manufactured by Sumitomo Chemical Co., Ltd.

As is clear from Tables 1 and 2 , the rubber compositions for tires of Examples 1 to 4 and 7 have conventional levels of tensile breaking strength, tensile breaking elongation and low heat generation (tan δ at 60 ° C.) while containing recycled rubber. It was confirmed that the above improvement was achieved.

As is clear from Table 1, since the tire rubber compositions of Comparative Examples 1 and 2 contained recycled rubber-1 and recycled rubber-2 in the tire rubber composition of Standard Example 1, the tensile strength at break and the tensile strength were increased. The elongation at break decreased and the tan δ at 60 ° C. increased.
In the rubber composition for tires of Comparative Example 3, since the blending amount of recycled rubber-1 exceeded 100 parts by mass, the tensile breaking strength and the tensile breaking elongation decreased, and the tan δ at 60 ° C. increased.

As is clear from Table 2, since the rubber composition for tires of Comparative Example 4 contains recycled rubber-3 in the rubber composition for tires of Standard Example 2, the tensile strength at break and the elongation at break are reduced, and 60 The tan δ at ° C increased.

Claims (3)

30 to 160 parts by mass of reinforcing filler, 5 to 100 parts by mass of recycled rubber, and 0.1 to 15.0 parts by mass of carbon coupling agent are blended with 100 parts by mass of natural rubber. A rubber composition for a tire, wherein the agent is S- (aminoalkyl) thiosulfuric acid represented by the following general formula (1) or a metal salt thereof.

(In the formula, n represents an integer of 2 to 10.) The rubber composition for a tire according to claim 1, wherein the recycled rubber is a recycled rubber that has not been frozen and crushed. A pneumatic tire comprising the rubber composition for a tire according to claim 1 or 2.