JP2000159935A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for tire tread simultaneously satisfying wear resistance and wet skid performance at high temperature range by including aluminum hydroxide or the like in a specific ratio to a specific rubber component. SOLUTION: This composition comprises 100 pts.wt. of the rubber component comprising 20 to 80 wt.% of an elastic copolymer of an aromatic vinyl compound and conjugated diene compound having glass transition temperature of -70 to 0 deg.C obtained by solution polymerization comprising 20 to 60 wt.% of styrene and 15 to 70 wt.% of 1,2-diene unit, and 20 to 80 wt.% of one or more kinds of components selected from butyl rubber, halogenated butyl rubber or the like and 5 to 30 pts.wt. of aluminum hydroxide, 40 to 150 pts.wt. of silica having 100 to 300 m2/g of specific surface area observed by nitrogen absorption, 0 to 100 pts.wt. of carbon black having 70 to 300 m2/g of specific surface area observed by nitrogen absorption (in proviso that the sum of the silica and the carbon black is 45 to 165 pts.wt.), 50 to 200 pts.wt. of softening agent for rubber and 3-20% of silica coupling agent based on silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rubber composition for a tire tread. More specifically, the present invention relates to a rubber composition for a tire tread capable of producing a tire having significantly improved braking performance and handling stability not only on a general pavement road but also on a wet road surface of a circuit.

[0002]

2. Description of the Related Art With the recent increase in the speed of automobiles, the characteristics required for tires have become stricter year by year, and various performances on wet road surfaces during high-speed running are one of them. can give.

In order to improve braking performance and steering stability (hereinafter, also referred to as wet skid performance) on a wet road surface at the time of high-speed running, it is necessary to increase the grip force with the road surface and to increase the block rigidity of the tire tread pattern. Increasing the size to prevent block deformation at the time of cornering and improve cornering characteristics, and also prevent deformation of a groove formed in the tire tread to smoothly drain water and prevent hydroplaning, etc.

[0004] Therefore, conventionally, silica is blended with high styrene SBR having excellent mechanical properties to enhance gripping power.

[0005] However, the rubber composition for a tire tread as described above can enhance the grip force in a low temperature region where the road surface temperature is 15 ° C or less, but can be used on a wet road surface or a semi-wet surface in a high temperature region exceeding 15 ° C. It has been found that on a (semi-dry) road surface, a sufficient grip force cannot be exhibited, and that when the vehicle is repeatedly driven, the rigidity of the rubber is reduced and the grip force is greatly reduced.

[0006] Generally, when the grip force is improved,
There is also a problem that abrasion resistance, which is a property contradictory to grip force, is reduced.

Various proposals have conventionally been made to solve these problems, but at present, a rubber composition satisfying both wet skid performance at high temperature and abrasion resistance has not yet been developed. .

[0008]

Means for Solving the Problems The present inventors have intensively studied to improve these problems, and as a result, have developed a method for simultaneously satisfying wear resistance and wet skid performance in a high temperature range. Reached.

That is, according to the present invention, the glass transition temperature is-
At 70 to 0 ° C., the styrene unit content is 20 to 60% by weight (hereinafter referred to as “%”), 1,2-diene unit (a diene unit having a 1,2-bond and having a C 結合 C bond such as a vinyl group) 20-80% of a solution-polymerized elastic copolymer of an aromatic vinyl compound having an amount of 15-70% and a conjugated diene, butyl rubber, halogenated butyl rubber and isobutylene, and p
5 to 30 parts of aluminum hydroxide, based on 100 parts by weight (hereinafter referred to as "parts") of a rubber component comprising 20 to 80% of at least one selected from the group consisting of bromides of a copolymer with methylstyrene; Nitrogen adsorption specific surface area (hereinafter,
N ₂ SA) of 100 to 300 m ² / g silica 40
To 150 parts, carbon black having an N ₂ SA of 70 to 300 m ² / g 0 to 100 parts, provided that the total amount of silica and carbon black is 45 to 100 parts by weight of the rubber component.
165 parts, a rubber composition for a tire tread comprising 50 to 200 parts of a rubber softener and 3 to 20% of a silane coupling agent with respect to silica (Claim 1); Diameter 0.1-8 μm, BET
It has a specific surface area of at least 30 m ² / g and a pore size distribution of 5
The composition of claim 1 having a maximum value at ~ 100 nm (claim 2) and a silane coupling agent is of the formula _{(1): Y 3 -Si-} C n H 2n A (1) ( in the formula, Y is alkyl group having 1 to 4 carbon atoms, an alkoxy group or a chlorine atom, three of Y may be the same or different, n represents an integer from 1 to 6, a is -S _m C _n H _2n -S
i-Y ₃ group (m is an integer from 1 to 9, n represents the same), a nitroso group, a mercapto group, an amino group, an epoxy group, a vinyl group, a group that is selected from the group consisting of a chlorine atom and an imide group The composition according to claim 1, which is a compound represented by the following formula:

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the present invention comprises:
The glass transition temperature is -70 to 0 ° C and the styrene unit amount is 2
0 to 60% and 1,2-diene unit amount is 15 to 70%
A solution-polymerized elastic copolymer of an aromatic vinyl compound and a conjugated diene (hereinafter referred to as S-SDR; a unit other than a styrene unit and a 1,2-diene unit is generally a 1,4-diene unit ( 1,4-linked diene units) 20-80%, preferably 30-70%
Butyl rubber, halogenated butyl rubber, and at least one (hereinafter also simply referred to as another elastomer) selected from a bromide of a copolymer of isobutylene and p-methylstyrene in an amount of 20 to 80%, preferably 30 to 70%. And a component consisting of

The S-SDR is obtained by subjecting an aromatic vinyl compound such as styrene and a conjugated diene such as butadiene and isoprene to solution polymerization in a conventional manner.

If the styrene unit amount and the 1,2-diene unit amount in the S-SDR are smaller than the lower limits, sufficient grip performance cannot be obtained. It becomes too hard and the grip performance decreases. It is preferable that the styrene unit amount is 25 to 60% and the 1,2-diene unit amount is 18 to 65% from the viewpoint of achieving both grip performance and wear resistance.

The Mooney viscosity of the S-SDR (＠
(130 ° C.) is preferably from 30 to 80 from the viewpoint of workability.

The butyl rubber is not particularly limited as long as it is generally used for rubber compounding.

The Mooney viscosity of the butyl rubber (# 130
C) is preferably from 30 to 100 from the viewpoint of workability.

The halogenated butyl rubber is not particularly limited as long as it is generally used for rubber compounding, and the halogen content is 1.
Preferably, the content is 1 to 1.3%, and the brominated butyl rubber is 1.8 to 2.4%.

The Mooney viscosity (＠ 130 ° C.) of the halogenated butyl rubber is preferably 30 to 100 from the viewpoint of processability.

The bromide of the copolymer of isobutylene and p-methylstyrene is as follows: isobutylene unit amount /
The amount of p-methylstyrene unit is 90/10 to 98 by weight.
/ 2, the bromine content is preferably 5 to 1% from the viewpoint of co-crosslinkability. Preferred specific examples include, for example, EXXPRO (trade name) manufactured by Exxon Chemical Co., Ltd.

Among the other elastomers, bromide of a copolymer of isobutylene and p-methylstyrene,
For example, the above-mentioned EXXPRO is preferable from the viewpoint of achieving both wet skid performance and wear resistance.

If the amount of the other elastomer is less than 20% in the rubber component, a sufficient effect on the wet performance cannot be obtained, and if it exceeds 80%, the abrasion resistance decreases.

The aluminum hydroxide compounded in the rubber composition of the present invention is used to balance wet skid performance and abrasion resistance in a high temperature range and to suppress a change in wet grip performance over time. Component.

The aluminum hydroxide has an average particle diameter of 0.1 to 8 μm, more preferably 0.1 to 5 μm, and a BE
T specific surface area is 30 m ² / g or more, and more preferably 30 to 500
m ² / g, is to be 50~350m ² / g, in particular 10
0 to 350 m ² / g and a pore size distribution of 5 to 10
0 nm, even 8 to 80 nm, especially 10 to 80 n
m is preferably in the range. The average particle diameter is 0.
When the thickness is less than 1 μm, the kneading workability is reduced while grip performance cannot be expected to be improved. When the thickness is more than 8 μm, the elastic modulus tends to decrease, and the abrasion resistance tends to decrease. In addition, B
If the ET specific surface area is less than 30 m ² / g, the effect of improving grip performance is small, and if it exceeds 350 m ² / g, the dispersibility tends to decrease. Further, when the maximum value of the pore size distribution is out of the range of 5 to 100 nm, the effect of improving grip performance and the like tends to decrease.

The amount of the aluminum hydroxide is 5 to 30 parts, preferably 10 parts, per 100 parts of the rubber component.
~ 25 parts. If the amount is less than 5 parts, the effect of using aluminum hydroxide cannot be sufficiently obtained. If the amount is more than 30 parts, the abrasion resistance decreases, which is not preferable.

The silica compounded in the rubber composition of the present invention is a component used for improving wet grip performance and the like.

The silica has an N ₂ SA of 100 to 300.
m ² / g, more preferably from 130~280m ² / g. If N ₂ SA is smaller than the lower limit, sufficient reinforcing effect cannot be obtained, and if N ₂ SA exceeds the upper limit, dispersibility decreases and heat generation increases.

Examples of the silica include dry silica (silicic anhydride) and wet silica (hydrous silicic acid), but are not particularly limited. Of these, wet process silica is preferred. Preferred specific examples of the wet process silica include Nipsil VN manufactured by Nippon Silica Co., Ltd.
3AQ (product name) and the like.

The carbon black compounded in the rubber composition of the present invention is a component used for improving strength such as abrasion resistance.

The carbon black has an N ₂ SA of 70.
~300m ² / g, more preferably from 100 to 250 m ² / g. If the N ₂ SA is smaller than the lower limit, the dispersibility improving effect and the reinforcing effect are reduced, and if it exceeds the upper limit, the dispersibility is reduced, the heat generation is increased, and the wear resistance is reduced.

Examples of the carbon black include, for example, HAF, ISAF, SAF, etc., but there is no particular limitation.

The mixing amount of the silica and carbon black is 40 to 40 parts with respect to 100 parts of the rubber component, respectively.
150 parts, preferably 50-130 parts and 0-100
Parts, preferably 0 to 80 parts, and the total amount thereof is 45 to 165 parts, preferably 50 to 150 parts, per 100 parts of the rubber component. If the amount of silica is less than 40 parts, the gripping force on a wet road surface will be insufficient, and if it exceeds 150 parts, workability (workability) will decrease. If the amount of carbon black exceeds 100 parts, the effect of improving wet performance is reduced. If the total amount of the silica and carbon black is less than 45 parts, sufficient grip force and abrasion resistance cannot be obtained, and 165
Exceeding the portion is not preferable because the kneading workability is reduced although improvement in grip force and wear resistance cannot be expected.

The silane coupling agent blended in the rubber composition of the present invention is a component used to strengthen the bond between silica and the rubber component and to improve wear resistance.

As the silane coupling agent, for example, a compound represented by the following general formula (1): Y ₃ —Si—C _n H _2n A (1) (where Y is an alkyl group having 1 to 4 carbon atoms, an alkoxy group or a chlorine atom) represent the atoms, three of Y may be the same or different, n represents an integer from 1 to 6, a is -S _m C _n H _2n -S
i-Y ₃ group (m is an integer from 1 to 9, n represents the same), a nitroso group, a mercapto group, an amino group, an epoxy group, a vinyl group, a group that is selected from the group consisting of a chlorine atom and an imide group Are preferred.

Specific examples of the silane coupling agent include, for example, bis (3-triethoxysilylpropyl)
Tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercapto Propyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-
Nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2
-Chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane and the like. Of these, bis (3-triethoxysilylpropyl) tetrasulfide and the like are preferable from the viewpoint of achieving both the effect of adding the coupling agent and the cost.

The amount of the sila coupling agent is 3 to 20% based on silica. If the amount is less than 3%, the effect obtained by adding the silane coupling agent cannot be sufficiently obtained, and even if the amount is more than 20%, the effect corresponding to the cost is not obtained. From the viewpoint of the dispersing effect of silica, the amount of the silane coupling agent is preferably 4 to 15% based on silica.

The rubber composition of the present invention contains a rubber softener in order to improve processability and promote dispersion of other components.

As the rubber softener, any one which has been conventionally used in the field of rubber compositions can be used without particular limitation. For example, paraffin-based process oil, naphthene-based process oil, aromatic-based process oil, special process oil, and the like can be given. These can be used alone or in any combination.

The amount of the rubber softener is from 50 to 200.
Department. If the compounding amount is less than 50 parts, the effect of improving wet performance such as the intended grip cannot be sufficiently obtained,
If the amount exceeds 200 parts, workability is reduced.

The method for producing the rubber composition of the present invention is not particularly limited, and may be carried out by a usual method. At this time, in addition to the above components, vulcanizing agents such as sulfur that are commonly used in the rubber industry, various vulcanization accelerators, various antioxidants, zinc oxide,
Additives such as stearic acid, antioxidants and antiozonants can be added.

[0039]

EXAMPLES Next, the rubber composition of the present invention will be specifically described 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.

S-SDR: TUF manufactured by Asahi Kasei Corporation
DENE-3330 (styrene-butadiene copolymer,
Oil (rubber softener) 3 per 100 parts of rubber component
Exxpro: Exxpro manufactured by Exxon Chemical Co., Ltd.
(Bromide of copolymer of isobutylene and p-methylstyrene) BR150B: UBEPOL BR manufactured by Ube Industries, Ltd.
150B (95% of 1,4-butadiene units (referring to cis-1,4 bonded butadiene units) amount) 95% Aluminum hydroxide A: Hygilite H-43 manufactured by Showa Denko KK (average particle diameter: 0) 0.6 μm, BET specific surface area: 6.5 m ² / g, maximum of pore diameter distribution: 300 nm) Aluminum hydroxide B: UF- manufactured by Sumitomo Chemical Co., Ltd.
ATH 250 (average particle diameter: 2.5 μm, BET specific surface area: 250 m ² / g, maximum of pore diameter distribution: 12 nm) Silica: Ultrasil VN3 (N manufactured by Degussa Co., Ltd.)
₂ SA: 210 m ² / g) Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa Aroma oil: JOMO process X140 (softening agent for rubber) manufactured by Japan Energy Co., Ltd. Anti-aging agent: Nocrack 6 manufactured by Ouchi Shinko Chemical Co., Ltd.
C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) Stearic acid: Zinc flower stearic acid manufactured by NOF Corporation: Zinc flower No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (Zinc oxide) Sulfur: Powder sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator A: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur accelerator B: Noxeller D (N, N'-diphenyl guanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

(Lambourn abrasion test) 10 ° C. and 40
℃, load 2kg, slip rate 20%, sandfall 2
The measurement was performed using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho under the measurement conditions of 0 g / min and a test time of 5 minutes. The volume loss of each compound was calculated, and the loss amount of Comparative Example 1 was set to 100, and the result was indicated by an index using the following formula. A larger index indicates better wear resistance.

Abrasion index = Loss of Comparative Example 1 / Loss of each formulation × 100

(Wet skid performance) ASTM E3 using a portable skid tester manufactured by Stanley
Measured at 10 ° C and 40 ° C according to the method of 03-83. The numerical values were indicated by exponents using the following formula. A higher index indicates better wet skid performance.

Wet skid index = measured value of each formulation /
Measurement value of Comparative Example 1 × 100

(Actual Vehicle Test) A 225 / 45R 17-size passenger car tire was prototyped, and the running time (3 hours) on a wet handling road (asphalt road surface) of 800 m per lap.
(Laps 10 and 10) and the wear appearance after running were checked. The test was performed at low temperature (10-15 ° C) and high temperature (30-3
5 ° C), and the wear appearance was evaluated by the 5-point method (5 (good) → 1).
(Poor)).

Examples 1 and 2 and Comparative Examples 1 to 4 Compositions containing the main components shown in Table 1 (components other than sulfur, vulcanization accelerator A and vulcanization accelerator B) in the amounts shown in Table 1 were prepared. The mixture was kneaded in a Banbury at about 150 ° C. for 5 minutes. 1.5 parts of sulfur, 2 parts of vulcanization accelerator A and 0.5 part of vulcanization accelerator B were added to the obtained kneaded product, and the mixture was kneaded with a biaxial open roller at 60 ° C. for about 3 minutes (tire). The green rubber composition for tread) was vulcanized at 170 ° C. for 20 minutes to obtain a vulcanized rubber, and a Lambourn abrasion test and an evaluation of wet skid performance were performed.

Further, vulcanization is performed using the green rubber composition for a tire tread to produce a predetermined tire.
An actual vehicle test was performed.

The results are shown in Tables 1 to 3.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

From the comparison between the results of Examples 1 and 2 and the results of Comparative Examples 1 to 4, in Examples 1 and 2, the abrasion performance and the wet skid performance were all lower in both the low temperature range and the high temperature range. It can be seen that the balance is good and the balance is good. Also,
In particular, it can be seen that the performance of Example 2 in which aluminum hydroxide B was blended was excellent.

[0054]

By using the rubber composition of the present invention, both wet skid performance at high temperature and abrasion resistance can be achieved, and the change over time in wet grip performance is reduced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/541 C08K 5/54 A 5/544 F 5/548 L C08L 15/02 C08L 15/02 23 / 22 23/22 25/16 25/16 F term (reference) 4J002 AC08W AC12X AE05Y BB18X DA038 DE146 DJ017 EX039 EX079 EX089 FD02Y FD030 FD070 FD140 FD150 GN01

Claims (3)

[Claims] 1. A solution of an aromatic vinyl compound having a glass transition temperature of -70 to 0 ° C., a styrene unit content of 20 to 60% by weight and a 1,2-diene unit amount of 15 to 70% by weight, and a conjugated diene. 20 to 80% by weight of a polymerized elastic copolymer, butyl rubber, halogenated butyl rubber, isobutylene and p-
Aluminum hydroxide 5 to 100 parts by weight of a rubber component consisting of 20 to 80% by weight of at least one selected from the group consisting of brominated copolymers of methyl styrene.
30 parts by weight, specific surface area of nitrogen adsorption is 100 to 300 m ²
/ G silica 40-150 parts by weight, nitrogen adsorption specific surface area 70-300 m ² / g carbon black 0-100
Parts by weight, provided that the total amount of silica and carbon black is 45 to 165 parts by weight, 100 to 200 parts by weight of the rubber component, 50 to 200 parts by weight of a rubber softener, and 3 to 20% by weight of silica. A rubber composition for a tire tread, comprising a coupling agent. 2. The aluminum hydroxide according to claim 1, wherein the aluminum hydroxide has an average particle diameter of 0.1 to 8 μm, a BET specific surface area of 30 m ² / g or more, and a pore diameter distribution having a maximum value of 5 to 100 nm. Composition. 3. The silane coupling agent is represented by the general formula (1): Y ₃ —Si—C _n H _2n A (1) (in the formula, Y represents an alkyl group having 1 to 4 carbon atoms, an alkoxy group or a chlorine atom. the stands, three Y may be the same or different, n represents an integer from 1 to 6, a is -S _m C _n H _2n -S
i-Y ₃ group (m is an integer from 1 to 9, n represents the same), a nitroso group, a mercapto group, an amino group, an epoxy group, a vinyl group, a group that is selected from the group consisting of a chlorine atom and an imide group The composition according to claim 1, which is a compound represented by the following formula: