JP3410980B2 - Rubber composition for tire tread - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire tread having both high wet grip properties and low rolling resistance.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for a rubber composition for a tread which provides a tire with low rolling resistance in response to the demand for low fuel consumption of automobiles, and from the viewpoint of safety. There is a demand for a rubber composition for a tread that provides a tire having high grip performance on wet road surfaces, that is, high wet grip performance.

The rolling resistance and wet grip properties of these tires depend on the hysteresis loss (ta) of the tread rubber.
n.delta.), the smaller the tan.delta. at about 70.degree. C., the lower the rolling resistance, and the larger the tan.delta. at about 0.degree. C., the higher the wet grip property, and it was difficult to satisfy both.

As a technique for solving the above-mentioned problems, JP-A-8-283461, JP-A-8-283462 and JP-A-8-283464 disclose (a) an isobutylene unit, a paramethylstyrene unit and parabromo. When 10 to 50 parts by weight of a copolymer containing a methylstyrene unit (hereinafter referred to as “part”), (b) a natural rubber and / or a diene-based synthetic rubber are used, and the compounding amount of the copolymer is X. , (100-X) parts, (c) carbon black 20 to 150 parts, and (d) hydrazide compound 0.1 to 5.0 parts, thiazole compound 0.1 to 5.0 parts and 2 or more per molecule. Kneading a rubber composition containing any of 0.25 to 10 parts of the amine derivative having a nitro group, to which stearic acid, zinc white, an accelerator and sulfur are further added. Compounded, it is described that the use of those vulcanization (145 35 min at ° C.).

By using the composition described in the above publication, the effect of increasing the tan δ value at 0 ° C. while maintaining the tan δ value at 60 ° C. is achieved to some extent, but it is not yet satisfactory.

[0006] As another technique for solving the above-mentioned problem, Japanese Patent Publication No. 5-507517 discloses (a) C.
₄ -C ₁₇ iso halogen-containing copolymers of monoolefins and para-alkylstyrene, (b) natural rubber, styrene - butadiene rubber, polybutadiene rubber, ethylene, propylene, terpolymers of non-conjugated dienes, and mixtures thereof A tire tread composition containing the selected rubber, (c) carbon black, (d) plasticizer oil, and (e) curative is mixed at about 80-105 ° C. to evenly disperse the curative and then About 140-185 ° C
It is described that the vulcanized product is used for about 10 to 60 minutes.

The composition described in the above-mentioned publication describes that the curing agent is better dispersed without being reacted at the time of kneading in Banbury, and is vulcanized at the time of vulcanization. Since there is no process for selectively vulcanizing the rubber component of, the wet grip and extrusion processability are not sufficient.

Further, as another technique for solving the above-mentioned problems, Japanese Patent Laid-Open No. 10-81784 discloses that a low air permeability functional group vulcanizable rubber and the functional group vulcanizable rubber can be vulcanized. A curing agent and a functional group vulcanizable rubber are kneaded (preliminary kneading) in a temperature range in which they do not vulcanize, and a carbon-carbon double bond vulcanizable rubber is added to the resulting kneaded product at 90 to 140. Inner liner, case, tube of tire obtained by performing selective vulcanization of functional group vulcanizable rubber by kneading at ℃
A rubber composition used for applications such as a gas hose is disclosed.

The composition described in the above publication has low air permeability,
Although it is excellent in vulcanization adhesiveness with a diene rubber, it requires two steps to perform selective vulcanization, and therefore further improvement is desired.

[0010]

The present inventors have improved a rubber composition obtained by a method which requires two steps to carry out the selective vulcanization, and provide an excellent rubber composition for a tire tread. As a result of earnest research to obtain, by increasing the lower limit of the kneading temperature (110 ° C or higher) and appropriately selecting the curing agent, sufficient wet grip properties can be obtained without pre-kneading. It was found that extrusion processability is improved, and further, a bromide of a copolymer of isobutylene which is a functional group vulcanizable rubber and p-methylstyrene or a halogenated butyl rubber, a divalent metal oxide and a specific metal oxide When a rubber composition obtained by using a diene-based rubber and a specific manufacturing method was applied to a tread of a tire, the above-mentioned high wet grip property and low rolling resistance were obtained. Found that it is possible to stand,
The present invention has been completed.

That is, the present invention provides (A) a bromide or halogenated butyl rubber of a copolymer of isobutylene and p-methylstyrene, (B) a divalent metal oxide and (C) a natural rubber, an isoprene rubber, Butadiene rubber and
Fine styrene - butadiene rubber alone, or two or more of
The kneaded Risuruko in a temperature range of 10 to 150 ° C.,
A high viscosity product obtained by selectively vulcanizing the component (A) during kneading.
A rubber composition for tire treads ( et 1) having both et-grip properties and low rolling resistance , (A) a copolymer of isobutylene and p-methylstyrene.
Bromide or halogenated butyl rubber 100 parts by weight
(Hereinafter referred to as “part”), (B) 0.2 to 20 parts of a divalent metal oxide and (C) natural rubber, isoprene rubber, butadiene rubber and
And styrene-butadiene rubber alone or in combination of two or more 40
The rubber composition for a tire tread according to claim 1 (claim 2) , the components (A) to (C) in a temperature range of 110 to 150 ° C.
When kneading with the (A) component and (C) component
And kneading the compound in an amount of 20 to 80% by weight of the component (B).
The rubber composition for a tire tread according to claim 2.
Item 3), and an amount of 20 to 80% by weight of the component (B),
To 100 parts in total of the components (A) and (C),
The tire tread go according to claim 3, which is 0.5 to 8 parts.
System composition (claim 4) .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition for a tire tread of the present invention comprises (A) a bromide of a copolymer of isobutylene and p-methylstyrene or a halogenated butyl rubber,
(B) divalent metal oxide and (C) natural rubber, isop
Ren rubber, butadiene rubber and styrene-butadiene
It is obtained by kneading rubbers singly or in combination of two or more and selectively vulcanizing the component (A) during the kneading. In the present invention, the pre-kneading of the (A) component and the (B) component before performing selective vulcanization is not performed, but the (A) to (C) components are kneaded from the beginning to prepare the (A) component. Perform selective vulcanization. Therefore, it is possible to obtain a rubber composition for a tire tread that has both high wet grip properties and low rolling resistance, and it is possible to shorten the manufacturing process.

The component (A) is a component used to improve the wet grip by selectively vulcanizing during kneading.

The bromide of the copolymer of isobutylene and p-methylstyrene is not particularly limited,
From the viewpoint of co-crosslinkability, the isobutylene unit amount / p-methylstyrene unit amount is 90/10 to 98/2 by weight and the bromine content is 0.5 to 5% by weight (hereinafter referred to as%). preferable. Preferred specific examples include EXXPRO90-10 (trade name) manufactured by Exxon Chemical Co., Ltd. (Moonie viscosity ML (1 + 8) 125 ° C. = 45 ± 5).

The halogenated butyl rubber is not particularly limited as long as it is a compound generally used for rubber compounding, but the halogen content of chlorinated butyl rubber is 1.
It is preferably 1 to 1.3% and brominated butyl rubber is 1.8 to 2.4%. Further, the Mooney viscosity (@ 130 ° C.) of the halogenated butyl rubber is preferably 30 to 100 from the viewpoint of workability.

The bromide of the copolymer of isobutylene and p-methylstyrene and the halogenated butyl rubber may be used alone or in combination. Of these, EXXPRO90-10 is preferable because of its high crosslinking efficiency.

The component (B), that is, the divalent metal oxide plays a role of vulcanizing the component (A).

Examples of the metal forming the component (B) include Mg, Zn, Ca and Ba. That is, specific examples of the component (B) include MgO, ZnO, and Ca.
Examples include O and BaO. Of these, ZnO is preferable because of its high reactivity.

The kneading ratio of the component (B) to the component (A) is 0.2 to 20 with respect to 100 parts of the component (A).
The amount is preferably 0.5 part, more preferably 0.5 to 17 parts from the viewpoint of improving the physical properties of rubber, and particularly preferably 1 to 17 parts from the viewpoint of shortening the kneading time.

[0020] (C) is in minutes formation, natural are conventionally used for tire tread rubber (NR), isoprene
Rubber (IR), butadiene rubber (BR) and styrene
-One or more types of butadiene rubber (SBR) are used .
These are not vulcanized in the component (B) upon kneading, that obtained by vulcanizing by sulfur.

[0021] Of these, the viewpoint of improving the mechanical strength of the resulting tire tread, from the viewpoint of imparting tackiness to the resulting rubber composition, NR, to use SBR preferred.

The kneading ratio of the component (C) to the component (A) is 40 to 300 with respect to 100 parts of the component (A).
The amount is preferably 50 parts, more preferably 50 to 300 parts from the viewpoint of abrasion resistance, and particularly preferably 50 to 250 parts from the viewpoint of further improving wet grip properties.

In the rubber composition of the present invention, other components such as a vulcanization accelerator, an antioxidant, a process oil and a filler such as carbon black are generally used as long as the effects of the present invention are not impaired. You may add the component used for manufacture of the rubber composition for tire treads.

In the present invention, the components (A) to (C) and, if necessary, the above-mentioned other components are kneaded, and the component (A) is selectively vulcanized during the kneading.

When the components (A) to (C) are mixed,
Without pre-kneading the components (A) and (B),
First, the components (A) and (C) are kneaded, and then the component (B) is added. However, there may be some difference in the time of preparation within the range of common sense for those skilled in the art. Therefore, for example, the (A) component (or (C) component), the (C) component (or (A) component) and the (B) component may be charged simultaneously or sequentially into a container for kneading.

The selective vulcanization (kneading) may be carried out within a temperature range in which the component (A) can be vulcanized. It may be carried out within a temperature range in which the component (A) starts to be vulcanized and does not cause deterioration of the obtained rubber composition, but from the viewpoint of shortening the kneading time, it is 110 to 150 ° C, and further 115 to 140.
It is preferably carried out in the temperature range of ° C. Further, it is preferable to knead in an open roll from the viewpoint of stabilizing the physical properties, and kneading in a Banbury mixer from the viewpoint of improving workability and workability.

The kneading time required for the selective vulcanization is usually 3 to 30 minutes, more preferably 4 to 15 minutes.

The vulcanization of the diene rubber in the rubber composition (hereinafter also referred to as the rubber composition (I)) obtained by carrying out the selective vulcanization is carried out by, for example, sulfur which is a vulcanizing agent for the diene rubber. A predetermined amount (for example, rubber component ((A) component and (C) component
0.5 to 5 parts based on 100 parts of the total components) In addition to the rubber composition (I), if necessary, stearic acid, N-te
A vulcanization accelerator such as rt-butyl-2-benzothiazolyl sulfenamide (NS), a process oil, a filler such as carbon black and an antioxidant are appropriately blended and further kneaded at 40 to 100 ° C. , Rubber composition (I
It may be carried out by heating after molding as I).

The component (B) to be blended may be charged in its entirety from the beginning, or may be charged in two or more times. For example, (A) component and (C) component and a part of (B) component are initially charged and kneaded, and (A) component is selectively vulcanized to obtain a rubber composition (I). When a rubber composition (II) is compounded with sulfur or a vulcanization accelerator for vulcanizing the diene rubber, a part of the lumber may be charged. However, in the case where the component (B) is charged in two or more times, the amount of 20 to 80% of the total amount (for example, 100 parts of the total of the component (A) and the component (C)) is 0. 5 to 8 parts, and further 1 to 5 parts) are blended to obtain a rubber composition having good physical properties.

The rubber composition (II) is excellent in vulcanization adhesion with other diene rubber compositions, has good extrusion processability, and after molding, finally diene rubber is vulcanized. Then, by forming the tread, it is possible to obtain a tire having both high wet grip properties and low rolling resistance.

As a preferred embodiment of the present invention, for example, the following rubber composition and kneading conditions can be mentioned.

[0032] (Example 1) copolymer brominated 100 parts of isobutylene and p- methylstyrene (EXXPRO 90-10) divalent metal oxide (ZnO). 3 to 20 parts natural rubber 200 to 250 parts Kneading temperature 120 to 140 ° C. Kneading time 5 to 10 minutes (however, when ZnO is used in a large amount, 4 to 10
Part, after the selective vulcanization is performed, the rest is compounded)

[0033] (Example 2) isobutylene and p- methylstyrene, copolymers of brominated (EXXPRO 90-10) 100 parts accelerator EZ. 4 to 10 parts divalent metal oxide (ZnO). 3 to 20 parts heaven Natural rubber 200 to 250 parts Kneading temperature 120 to 140 ° C. Kneading time 5 to 10 minutes (however, when ZnO is used in a large amount, 4 to 10
Part, after the selective vulcanization is performed, the rest is compounded)

Example 3 Bromobutyl rubber 100 parts Divalent metal oxide (ZnO) 3 to 20 parts S BR 200 to 250 parts Kneading temperature 120 to 140 ° C. Kneading time 5 to 10 minutes (however, when ZnO is used in a large amount, 4 to 10
Part, after the selective vulcanization is performed, the rest is compounded)

[0035]

EXAMPLES Next, the rubber composition of the present invention will be specifically explained based on examples, but the present invention is not limited to these.

The raw materials used in the examples and comparative examples and the evaluation methods are summarized below.

EXXPRO 90-10: bromide brominated butyl rubber of a copolymer of isobutylene and p-methylstyrene manufactured by Exxon Chemical Co., Ltd .: bromobutyl 2255 HAF N330 manufactured by Exxon Chemical Co., Ltd .: Mitsubishi Chemical Co., Ltd. Made carbon black (diamond black H) Stearic acid: Zinc stearate No. 1 manufactured by NOF CORPORATION: Zinc oxide sulfur manufactured by Mitsui Mining & Smelting Co., Ltd .: Sulfur powder accelerator NS manufactured by Tsurumi Chemical Co., Ltd. : Ouchi Shinko Chemical Co., Ltd. N-tert-butyl-2-benzothiazyl sulfenamide (Nocceller NS) Accelerator EZ: Ouchi Shinko Chemical Co., Ltd. zinc diethyldithiocarbamate (Noccer EZ)

(Measurement of tan δ) With respect to a predetermined vulcanized rubber, VES-FIII2 manufactured by Iwamoto Seisakusho Co., Ltd. was used, and initial elongation was 10%, 10 Hz, and dynamic amplitude was ± 0.25%.
Under the conditions, tan δ at 0 ° C. and 70 ° C. was measured. A large tan δ at 0 ° C. is preferable in that the wet grip property becomes large, and a tan δ at 70 ° C.
Is preferable because the rolling resistance is reduced.

(Measurement of Lambourn Wear) A predetermined vulcanized rubber was subjected to a load of 1.5 using a Lambourn abrasion tester.
Lambourn abrasion was measured at a slip rate of 50% in kgf. The results are shown as an index with the value when the rubber composition of Comparative Example 1 described below is used as a reference being 100. The larger the index, the less wear and the better.

(Measurement of Wet Grip) A μ-s measuring vehicle equipped with a predetermined tire was run on a lubricated road surface at 40 km / h, and the brake was applied to lock the wheels until the measuring vehicle stopped. Was measured, and the maximum friction coefficient between them was measured. The result was shown as an index with the value of 100 when the rubber composition of Comparative Example 1 described later was used as a reference. The larger the index, the better the wet grip.

(Measurement of Rolling Resistance) A predetermined tire was rotated on a drum tester at 80 km / h under a load of 350 kgf to measure a rolling resistance coefficient. The result was shown as an index with the value of 100 when the rubber composition of Comparative Example 1 described later was used as a reference. The smaller the index, the smaller the rolling resistance and the better the fuel economy.

Examples 1 and 2 and Comparative Examples 1 and 2 The raw materials (a) shown in Table 1 were mixed in the proportions shown in Table 1, the mixer set temperature was 110 ° C., and the mixer indicated temperature was 13%.
The mixture was kneaded for about 8 minutes until it reached 0 ° C. The raw material (B) shown in Table 1 was added to the obtained kneaded product (rubber composition (I)) at a ratio shown in Table 1, and the mixture was kneaded with an open roll at 50 ° C. for 5 minutes to obtain a green rubber composition (rubber). A composition (II)) was obtained. That is, except that the method of adding Zinc Hua No. 1 (time of addition) is different, and that Comparative Examples 1 and 2 do not perform selective vulcanization during kneading, Examples 1 and 2 and Comparative Example 1 The same operation as in 2 was performed.

The obtained green rubber composition was treated at 170 ° C.
Vulcanized rubber was obtained by vulcanization under the condition of 15 minutes, and tan δ and Lambourn abrasion were measured. Further, the green rubber composition was applied to a tread to prepare a tire by a usual method, and wet grip and rolling resistance were measured. The green rubber compositions of Examples 1 and 2 were excellent in extrusion processability when producing tire treads, as compared with the green rubber compositions of Comparative Examples 1 and 2. The results are shown in Table 1.

[0044]

[Table 1]

As a result of the evaluation, when the contents were compared in the same compounding composition, Examples 1 and 2 in which selective vulcanization was performed during kneading in Banbury were compared with Comparative Examples 1 and 2, respectively.
The result was that tan δ at 0 ° C. increased and tan δ at 70 ° C. decreased. This suggests that both improvement of wet grip and reduction of rolling resistance can be achieved.
Lambourn wear did not deteriorate and tended to improve.

Also in the evaluation using a predetermined tire, Example 1 in which selective vulcanization was performed during kneading in Banbury,
It was found that No. 2 has better wet grip and less rolling resistance than Comparative Examples 1 and 2.

[0047]

EFFECT OF THE INVENTION By using the rubber composition for a tire tread of the present invention, it is possible to obtain a tire having both high wet grip properties and low rolling resistance.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI // B60C 1/00 B60C 1/00 A (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 1/00- 101/16 C08K 3/00-13/08 C08J 3/24

Claims (4)

(57) [Claims] 1. A bromide or halogenated butyl rubber of (A) a copolymer of isobutylene and p-methylstyrene, (B) a divalent metal oxide and (C) a natural rubber, an isoprene rubber, a butadiene rubber and
Fine styrene - butadiene rubber alone, or two or more of
By kneading in the temperature range of 10 to 150 ° C ,
A high viscosity product obtained by selectively vulcanizing the component (A) during kneading.
A rubber composition for a tire tread, which has both an et grip property and a low rolling resistance . 2. (A) Isobutylene and p-methylstyrene
Bromide or halogenated butyl rubber copolymer
For 100 parts by weight, (B) 0.2 to 20 parts by weight of a divalent metal oxide and (C) Natural rubber, isoprene rubber, butadiene rubber and
And styrene-butadiene rubber alone or in combination of two or more 40
2. The tire tray according to claim 1, wherein the kneading is performed in an amount of about 300 parts by weight.
Rubber composition for shoes. 3. The components (A) to (C) of 110 to 15 are added.
When kneading in the temperature range of 0 ° C, the component (A) and
20 to 80% by weight of the component (C) and the component (B)
The tire tread according to claim 2, wherein the compound of (1) is kneaded.
Rubber composition. 4. The amount of 20 to 80% by weight of the component (B) is
To 100 parts by weight of the total of the components (A) and (C),
The tire tray according to claim 3, which is 0.5 to 8 parts by weight.
Rubber composition for shoes.