JP2001026672A - Tire tread rubber composition and tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the vulcanization time of silica-compounded rubber compositions without changing the rubber properties to a great extent and further, without causing a problem from the standpoint of process. SOLUTION: Tire tread rubber compositions contain 100 pts.wt. at least one of a diene based rubber, a butyl rubber, and a halogenated butyl rubber, 20-100 pts.wt. silica, 3-80 pts.wt. carbon black, 0.5-12 pts.wt. silane coupling agent containing a sulfur atom in the molecule, and 0.5-5 pts.wt. zinc stearate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition for a tire tread and a tire using the same.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for reducing fuel consumption of automobiles for the purpose of suppressing carbon dioxide emission and preserving the global environment.

In order to achieve the above-mentioned object, a rubber composition in which part or most of carbon black is replaced with silica instead of carbon black which has been conventionally used has been used. It is well known that when silica is used in place of carbon black, it is possible to reduce hysteresis loss in rubber and to reduce fuel consumption of tires.

[0004] However, if silica is used alone in the rubber, process problems such as an increase in the viscosity of the kneaded rubber and deterioration of the extruded dough will arise.

[0005] By adding polyethylene glycol or the like in order to solve this problem, it is possible to solve the problems in the process, but it is known that the finished rubber composition has significantly poor reinforcing properties. I have.

A silane coupling agent such as Si-69 (manufactured by Degussa) as a silane coupling agent for bonding silica and rubber when compounding silica with rubber to cope with the problem of reinforcing property. It has been proposed to use together. It is also known that the use of these coupling agents can reduce the viscosity of the kneaded rubber, improve the extruded rubber material, and improve the wear resistance of the finished tire when used in a tread. ing.

[0007] However, by blending the silane coupling agent, the vulcanization rate of the rubber generally decreases,
The vulcanization time has to be extended, which reduces productivity.

[0008] To solve the above problems, the present inventors have
In order to increase the vulcanization rate of a rubber composition containing silica, a sulfenamide-based CB is used as a vulcanization accelerator.
S (N-cyclohexyl-2-benzothiazolesulfenamide) and TBBS (N-tert-butyl-2-
In addition to benzothiazolylsulfenamide), guanidine-based DPG (diphenylguanidine) and the like are blended to improve the vulcanization rate.

However, there is a limit in improving the vulcanization rate by changing these vulcanization accelerators or increasing the amount of vulcanization accelerator, and there are various problems such as changes in rubber properties of the tire after vulcanization.

[0010]

It is generally known that a rubber composition containing silica has a low vulcanization rate.
As a result of the study of the present inventors, the cause of the slow vulcanization rate,
It was found that the silane coupling agent had a sulfur atom in the molecule. Further, the present inventors have conducted various studies, and as a result, after adding the silane coupling agent, in place of the vulcanization aid such as stearic acid and zinc white, adding zinc stearate, the silane It has been found that the disadvantage that the vulcanization speed due to the coupling agent is reduced is improved, and that the vulcanization time can be shortened.

The present invention has been made based on the above-mentioned findings, and it has been found that the vulcanization time of a rubber composition containing silica can be reduced without significantly changing the physical properties of the rubber and without causing any problems in the process. And at least one of diene rubber, butyl rubber and halogenated butyl rubber in an amount of 100 parts by weight (hereinafter referred to as "parts").
20 to 100 parts of silica, 3 to 80 parts of carbon black,
Silane coupling agent containing a sulfur atom in the molecule 0.5
A rubber composition for a tire tread containing 1 to 12 parts of zinc stearate and 0.5 to 5 parts of zinc stearate (claim 1); The present invention relates to a tire (claim 3) using the rubber composition according to claim 1 or 2.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition for a tire tread used in the present invention is a composition containing at least one of diene rubber, butyl rubber and halogenated butyl rubber as a rubber component. Since one or more of diene rubber, butyl rubber and halogenated butyl rubber are used as a rubber component, a rubber composition for a tread that can produce a tire having excellent workability, low-temperature characteristics, and abrasion resistance and excellent grip performance. You can get things.

The diene rubber contains natural rubber or a diene monomer such as butadiene or isoprene, preferably butadiene, in an amount of 20 to 100% by weight (hereinafter referred to as%).
Butadiene rubber obtained by (co) polymerizing a monomer having copolymerizability with these, for example, an aromatic vinyl compound such as styrene, 0 to 80% such as isobutylene or acrylonitrile, and is generally used for tires. The weight average molecular weight is 10,000 to 5,000,000 and the molecular weight distribution (weight average molecular weight /
Those having a (number average molecular weight) of about 1.1 to 5 and a Tg of about −50 to 0 ° C. are preferred because of good workability and a good balance of performance.

Specific examples of the synthetic rubber among the diene rubbers include butadiene rubber (BR) (preferably solution-polymerized BR (S-BR)) and SBR (preferably solution-polymerized SBR (S-SBR)). , Isoprene rubber, chloroprene rubber, nitrile rubber and the like.

The butyl rubber is a copolymer of isobutylene and a small amount of isoprene, and the amount of isoprene relative to the whole butyl rubber is generally 1 to 3%. By using butyl rubber, aging resistance, weather resistance, wet performance, and the like can be improved.

The butyl rubber is not particularly limited,
For example, those having a Mooney viscosity of 40 to 60 are preferable from the viewpoint of processability.

The halogenated butyl rubber is a rubber obtained by halogenating the butyl rubber with chlorine or bromine. Halogenated butyl rubber is superior in vulcanizability and heat resistance as compared with butyl rubber, and can be easily blended with other unsaturated rubbers such as natural rubber and SBR.

Examples of the halogenated butyl rubber include chlorinated butyl rubber and brominated butyl rubber. The halogen content is generally 1.1 to 1.
3%, and 1.8 to 2.4% for brominated butyl rubber.

The halogenated butyl rubber is not particularly limited, but, for example, one having a Mooney viscosity of 50 to 60 is preferable from the viewpoint of processability.

The diene rubber, butyl rubber and halogenated butyl rubber may be used alone or in combination of two or more. There is no particular limitation on the combination method when two or more types are used in combination. For example, SBR (especially S-SBR), BR (especially S-B
R) or a mixture of one or more butadiene rubbers (particularly solution-polymerized butadiene rubber) and one or more other diene rubbers, butyl rubbers, halogenated butyl rubbers, or the like, or a butadiene rubber. It is preferable from the viewpoint of improvement. In that case, as the blend ratio,
The former is 40% or more and less than 100%, and the latter is more than 0% 60
% Or less.

The silica used in the present invention is a component used as a reinforcing agent. Among the various reinforcing agents, the use of silica in particular is because the rolling resistance in the case of a tire can be reduced.

As the silica, those generally used for compounding a general-purpose rubber are used. Specific examples include dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica disclosed in JP-A-62-62838. These silicas may be used alone or in combination of two or more.

The silica has, for example, a CTAB adsorption specific surface area (hereinafter referred to as CTAB) of 100 to 200.
m ² / g, BET nitrogen adsorption specific surface area (hereinafter, referred to as BET) is used. For 100 to 250 m ² / g.

Specific examples of the silica include, for example, Nipsil VN3 (manufactured by Nippon Silica Co., Ltd., CTAB 144).
m ² / g, BET 210 m ² / g), Nipsil AQ (manufactured by Nippon Silica Co., Ltd., CTAB 150 m ² / g, BET
227 m ² / g).

The amount of the silica used is 20 to 100 parts, preferably 30 parts, per 100 parts of the total amount of the rubber component.
~ 90 parts. If the amount is too small, the reinforcing properties are insufficient, and the wear resistance and strength are reduced. On the other hand, if the amount is too large, the viscosity of the composition becomes too high, and the processability decreases.

The carbon black used in the present invention is:
It is a component used as a reinforcing agent. By using carbon black as a reinforcing agent, the processability of the composition and the wear resistance of the tire can be improved.

The carbon black is used in an amount of 3 to 80 parts, preferably 20 to 80 parts, per 100 parts of the rubber component.
70 parts. If the amount is too small, the reinforcing properties are insufficient, and the wear resistance and strength are reduced. Conversely, if the amount is too large, the heat generation becomes high, which is disadvantageous for reducing fuel consumption.

The carbon black is not particularly limited, and any carbon black generally used for compounding a general-purpose rubber can be used. Specific examples include furnace black, acetylene black, thermal black, channel black, graphite, and the like.

The silane coupling agent containing a sulfur atom in the molecule used in the present invention enhances the dispersibility of silica in the rubber, so that the viscosity of the kneaded rubber containing silica increases and the extruded fabric becomes poor. In order to improve the abrasion resistance and reinforcement of the resulting tire by reducing the problems in the process such as, and by chemically bonding the rubber molecules and silica particles directly or via a vulcanizing agent. It is a component used for.

Since the silane coupling agent contains a sulfur atom, the silane coupling agent exhibits a coupling effect by, for example, crosslinking with a double bond in a polymer molecule. On the other hand, when the silane coupling agent is used, the vulcanization rate is reduced. Is delayed.

Specific examples of the silane coupling agent include bis- (3- (triethoxysilyl) propyl) tetrasulfide (for example, Si-6 manufactured by Degussa).
9), γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, γ-trimethoxysilylpropylbenzothiazyltetrasulfide and the like.

The amount of the silane coupling agent to be used is 0.5 to 12 parts, preferably 3 to 10 parts, per 100 parts of the rubber component. If the amount is too small,
If the wear resistance is lowered or sufficient wet performance cannot be obtained, and if it is too large, the cost increases.

The zinc stearate used in the present invention comprises:
It is a component used to prevent the vulcanization rate from being delayed when a silane coupling agent containing a sulfur atom in the molecule is used. After adding the silane coupling agent, the delay of the vulcanization rate can be prevented only by adding zinc stearate instead of the vulcanization aid such as stearic acid and zinc white. Moreover, the above effect can be obtained without increasing the amount of a vulcanization accelerator which greatly changes the rubber properties after vulcanization. Such an effect of preventing a delay in the vulcanization rate was first discovered by the present inventors.

Since the zinc stearate is a component used for obtaining a vulcanization delay preventing effect which cannot be obtained when a vulcanization aid such as stearic acid or zinc white is used, the rubber of the present invention is used. It is preferable that stearic acid and zinc white are not contained in the composition. When stearic acid or zinc white is contained together with zinc stearate, the vulcanization time tends to be long.

As the zinc stearate, any commercially available lubricant can be used without particular limitation.

The amount of the zinc stearate used is 0.5 to 5 parts, preferably 2 to 5 parts per 100 parts of the rubber component.
4 parts. When the amount is too small, the above-mentioned effects of using zinc stearate cannot be sufficiently obtained, and the vulcanization time is not shortened. When the amount is too large, the cost increases.

The composition of the present invention comprises the above rubber component, silica, carbon black, a silane coupling agent containing a sulfur atom in the molecule and zinc stearate, and, if necessary, generally contains an additive for a rubber composition for a tire tread. (However, it is better not to use stearic acid and zinc white) may be added in a range generally used.

Specific examples of the additives include process oils (paraffinic process oils, naphthenic process oils, aromatic process oils), vulcanizing agents (sulfur, sulfur chloride compounds, organic sulfur compounds, etc.), Sulfur accelerators (guadinine, aldehyde-amine, aldehyde-ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, xanthate compounds, etc.), reinforcing agents (high styrene resin, Phenol-formaldehyde resin, etc., antioxidants or antioxidants (diphenylamine-based, p-phenylenediamine-based amine derivatives, quinoline derivatives, hydroquinone derivatives, monophenols, diphenols, thiobisphenols, hindered phenols) , Sub-phosphorus And esters), wax, and vulcanizing agents and the like.

The method for producing the composition of the present invention is not particularly limited, and the composition may be produced by a conventional method using a rubber component having predetermined characteristics.

The rubber composition produced is used for forming a tread portion of a tire. At this time, a silane coupling agent containing a sulfur atom in the molecule is used as a component of the composition to reduce problems in the process and improve the reinforcing property of the rubber composition, and to use zinc stearate. Since the reduction in vulcanization rate is prevented by this, vulcanization can be performed at a high vulcanization rate without changing the rubber properties after vulcanization.

[0041]

EXAMPLES Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

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

Rubber component S-SBR (1): S-SBR having a styrene unit amount of 30% and a vinyl unit amount (1,2-butadiene unit amount) of 30%;
Oil content 37.5%, Tuf manufactured by Asahi Kasei Kogyo Co., Ltd.
den3330 S-SBR (2): S-SBR with styrene unit content of 40%, vinyl unit content of 50%, oil content of 37.5%, SE8529 carbon black manufactured by Sumitomo Chemical Co., Ltd .: iodine adsorption amount 180 m ² / g, 24
M4DBP is 100 ml / 100 g of carbon, HS-SAF manufactured by Mitsubishi Chemical Corporation Silica: Ultrasil VN3 manufactured by Degussa Sulfur atom-containing silane coupling agent: Si-69 manufactured by Degussa Process oil: Idemitsu Kosan Co., Ltd. Diana Process Wax: Sannoc N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant: Antigen 6c manufactured by Sumitomo Chemical Co., Ltd. Zinc flower: Zinc oxide manufactured by Toho Zinc Co., Ltd. Stearic acid: Nippon Yushi ( Co., Ltd. Stearic acid zinc stearate: Yoneyama Pharmaceutical Co., Ltd. zinc stearate Sulfur: Karuizawa sulfur Co., Ltd.

Vulcanization accelerator TBBS: Ouchi Shinko Chemical Co., Ltd. Vulcanization accelerator DPG: Sumitomo Chemical Co., Ltd.

(Scorch Time) Measured with a Mooney meter manufactured by Shimadzu Corporation.

(Vulcanization time) Measured with a curast meter manufactured by JSR Corporation.

(Spring hardness (Hs)) JIS K
Measured according to 6253.

(Viscoelasticity (E ^* )) Using a viscoelasticity measuring instrument manufactured by Iwamoto Seisakusho, 70 ° C., ± 1.0% strain, 10H
Measured at z.

(Tan δ) Measured at 70 ° C., ± 1.0% strain, 10 Hz using a viscoelasticity measuring device manufactured by Iwamoto Seisakusho Co., Ltd.

(Lambourn abrasion) Measured with a load of 2.0 kg and a slip ratio of 40% using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho. The evaluation was indicated by an index so that Comparative Example 1 was 100. The higher the number, the better the result.

Examples 1 to 3 and Comparative Examples 1 to 3 Base I and Base II each containing the components shown in Table 1 in the proportions shown in Table 1 were kneaded for 4 minutes with a 1.7 L Banbury manufactured by Kobe Steel, Ltd. did. Base I obtained, base
II and the components of the sawdust shown in Table 1 were mixed at the ratios shown in Table 1 and kneaded with an open roll for about 2 minutes to evaluate a rubber composition for a tire tread. Table 1 shows the results.

[0052]

[Table 1]

From the results of Examples 1 and 2 and Comparative Examples 1 and 2, it can be seen that there is not much difference in physical properties between the compositions. In other words, when zinc stearate is used, there is not much difference in physical properties,
This shows that the vulcanization time can be shortened. When Example 3 and Comparative Example 3 are compared, Comparative Example 3 does not contain the sulfur atom-containing silane coupling agent (Si-69), and thus Lambourn abrasion and vulcanization time are significantly inferior.

By comparing Example 3 and Comparative Example 3, it can be seen that Example 3 has a longer scorch time but a shorter vulcanization time than Comparative Example 3.

[0055]

According to the present invention, zinc vulcanization can be prevented by using zinc stearate instead of stearic acid and zinc white in a silica compound using a silane coupling agent having a sulfur atom in the molecule.

Claims (3)

[Claims] 1. 100 parts by weight of at least one of diene rubber, butyl rubber and halogenated butyl rubber, silica 20 to
100 parts by weight, carbon black 3 to 80 parts by weight, silane coupling agent containing a sulfur atom in the molecule 0.5 to 1
A rubber composition for a tire tread, comprising 2 parts by weight and 0.5 to 5 parts by weight of zinc stearate. 2. The rubber composition according to claim 1, wherein stearic acid and zinc white are not blended. 3. A tire using the rubber composition according to claim 1.