JPH11269331A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of improving the wet-grip performance of a tire and realizing excellent high-speed stability by compounding a rubber component containing a brominated isobutylene/p- methylstyrene copolymer with a specific wet-process silica. SOLUTION: The objective composition is produced by compounding (A) 100 pts.wt. of a polymer containing >=30 wt.% of a brominated isobutylene/p- methylstyrene copolymer with (B) 50-200 pts.wt. of wet-process silica having a BET specific surface area of 100-250 m<2> /g after leaving in nitrogen atmosphere at 150 deg.C for 0.5 hr and (C) 1-15 wt.% (based on the component B) of a silane compound of formula Z-R-Sn -R-Z [R is a bivalent group of a 1-18C hydrocarbon; Z is a group of formula Si (R<1> )2 R<2> (R<1> is a 1-4C alkyl or the like; R<2> is a 1-8C alkoxy or the like) or the like; (n) is 2-8], formula Z-R-SH, formula Z-R-NH2 , formula Z-CH=CH2 or formula Z-R-X (X is a halogen).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition suitable for a tire tread excellent in wet grip performance.

[0002]

2. Description of the Related Art Due to the recent development of a highway network, tires are required to have a high level of high-speed stability, and there is a need to improve grip characteristics particularly on wet road surfaces.

Here, for example, Japanese Patent Application Laid-Open No. H6-11882,
JP-A-6-240050, JP-A-9-241430 and JP-A-9-241426 disclose halogenated rubber as a rubber component mainly from the viewpoint of improving wet skid characteristics, ozone resistance and bending fatigue resistance. It uses butyl rubber or a bromide of a copolymer of isomonoolefin and paramethylstyrene, and contains carbon black as a reinforcing material.

However, in recent years, silica has been compounded in place of part or all of carbon black from the viewpoint of improving wet grip properties.

[0005] In this case, the rubber composition containing silica is inferior in silica dispersibility, so that the silica characteristics such as improvement of abrasion resistance and wet gripping property cannot be sufficiently exhibited. There was a problem.

[0006]

Accordingly, an object of the present invention is to provide a rubber composition comprising a rubber component containing bromide of isobutylene / paramethylstyrene copolymer and a specific wet silica, An object of the present invention is to provide a rubber composition for a tire tread having improved wet grip properties.

[0007]

According to the present invention, a bromide of isobutylene / paramethylstyrene copolymer is contained in an amount of 30% by weight.
With respect to 100 parts by weight of the polymer contained above, 0.1 at 150 ° C.
Wet silica having a BET specific surface area of 100 to 250 m ² / g after being left in a nitrogen atmosphere for
00 parts by weight, and formula (1): Z—R—S _n —R—
Z, Formula (2): ZR-SH, Formula (3): ZR-NH
_3, equation (4): Z-CH = CH 2 or formula (5): Z-R
-X (wherein, R is a divalent hydrocarbon group having 1 to 18 carbon atoms,
n is an integer of 2 to 8, Z is —Si (R ¹ ) ₂ R ² , —SiR ¹
(R ² ) ₂ or —Si (R ² ) ₃ (where R ¹ is an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group or a phenyl group, R ² is an alkoxy group having 1 to 8 carbon atoms, 5 carbon atoms) Is a cycloalkoxy group or an aryloxy group having 6 to 8 carbon atoms, X is a halogen atom), and a silane compound in an amount corresponding to 1 to 15% by weight of the wet silica amount of The present invention relates to a rubber composition for a tread.

In this case, tan δ (10 Hz, 0 ° C.,
0.5%) is 0.5 or more, and the shear modulus G is 5%, 25%, 50% under the conditions of a frequency of 10 Hz and a temperature of 70 ° C.
Shear modulus G (5%) at the time of the third 5% displacement when measured three times at each of the dynamic shear displacements of 100% and 150%.
And the shear modulus G (100%) at the time of 100% displacement are as follows: Formula (I): G (5%) / G (100%) ≦ 1.6 and Formula (II): G (100%) ≧ 0. 6 is preferably satisfied.

When the wet silica is heated from 20 ° C. to 500 ° C. at a rate of 5 ° C./min, the ratio of weight loss at 400 ° C. to 100 ° C. is 0.70% by weight or less. It is preferred that

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer component in the present invention comprises:
It contains at least 30% by weight of a bromide of isobutylene / paramethylstyrene copolymer, but preferably contains 50 to 100% by weight, more preferably 70 to 100% by weight, in order to sufficiently exhibit the properties of each component. Is particularly preferred.

The polymer component other than the bromide of the isobutylene / paramethylstyrene copolymer may be any one which exhibits elasticity at room temperature after vulcanization. For example, styrene butadiene rubber (SBR), natural rubber (N
R), isoprene rubber (IR), butadiene rubber (B
R), diene rubbers such as acrylonitrile butadiene rubber (NBR), ethylene propylene rubber (EPPM), chloroprene rubber (CR), butyl rubber (II)
R), fluorine rubber (FKM), epichlorohydrin rubber, etc., and one or more of them. Among them, styrene-butadiene rubber (SBR), natural rubber is preferable from the viewpoint of excellent mechanical strength characteristics and fatigue resistance and heat resistance. Rubber (NR),
It is preferable to use one or more kinds such as butyl rubber (IIR).

Next, the rubber composition for a tire tread of the present invention contains wet silica having a BET specific surface area of 100 to 250 m ² / g after being left in a nitrogen atmosphere at 150 ° C. for 0.5 hour. The BET specific surface area is from 150 to 150 from the viewpoint of improving the mechanical strength of the rubber composition after vulcanization.
It is preferably 250 m ² / g. In particular, in a rubber composition containing a relatively large amount of silica, the BET
If the specific surface area exceeds 250 m ² / g, the rubber composition becomes too hard when compounding silica with the polymer, resulting in poor processability.

As such silica, Nippon Silica Co., Ltd.
“Nipsil VN3” manufactured by Degussa, “Tokusil V” manufactured by Tokuyama Corporation, and “Carl Rex XR” manufactured by Shionogi & Co., Ltd.

Further, the wet silica according to the present invention comprises 5
When the temperature was raised from 20 ° C. to 500 ° C. at a temperature rising rate of ° C./min, the ratio of weight loss at 400 ° C. to weight at 100 ° C. (hereinafter also referred to as “weight loss ratio”) was 0.70 weight. % Or less. Furthermore, the weight loss ratio is preferably 0.20 to 0.70% by weight because a small amount of water is required when the silane compound chemically bonds to silica.

The wet silica having a weight loss ratio of 0.70% by weight or less can be obtained by the method described in Japanese Patent Application No. 9-345972. Specifically, a wet silica having a BET specific surface area within the above range can be obtained. The silica may be heat-treated at 130 to 180 ° C. under a pressure of 5 to 20 mmHg for 60 to 120 minutes.

In the present invention, the amount of silica is as follows:
The amount may be 50 to 200 parts by weight based on 100 parts by weight of the polymer component, but is preferably 50 to 150 parts by weight from the viewpoint that the strength of the vulcanized rubber is maintained and the processability during kneading is good. And more preferably 60 to 120 parts by weight.

Next, in the present invention, the formula (1): Z
-R-S _n -R-Z, wherein (2): Z-R- SH, wherein (3): Z-R- NH 3, equation (4): Z-CH = CH 2 or formula (5): Z—R—X (wherein, R represents 1 to 18 carbon atoms)
A is a divalent hydrocarbon group, n is an integer of 2 to 8, and Z is -Si
(R ¹ ) ₂ R ² , —SiR ¹ (R ² ) ₂ , or —Si (R
² ) ₃ (where R ¹ is an alkyl group having 1 to 4 carbon atoms, cyclohexyl group or phenyl group, R ² is 1 to 8 carbon atoms)
Is an alkoxy group, a cycloalkoxy group having 5 to 8 carbon atoms or an aryloxy group having 6 to 8 carbon atoms, and X is a halogen atom).

In the rubber composition of the present invention, the silane compound serves as a coupling agent to chemically bond to both the silica and the polymer, and to function to bond the silica to the polymer.

In the above formulas (1) to (5), Z is -Si (R
¹ ) ₂ R ² , —SiR ¹ (R ² ) ₂ , or —Si (R ² ) ₃ , where R ¹ is an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl, butyl, etc., cyclohexyl R ² is a C 1-8 alkoxy group such as methoxy, ethoxy, butoxy, a C 5-8 cycloalkoxy group such as cyclohexyloxy or a C 6-8 carbon atom such as phenoxy, benzyloxy, etc. 8 is an aryloxy group. R is a divalent hydrocarbon group having 1 to 18 carbon atoms such as ethylene and propylene.

As the silane compound represented by the formula (1), for example,

[0021]

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And the like. Examples of commercially available products include Si69 (3,3'-bis (triethoxysilylpropyl) tetrasulfide) manufactured by Degussa.

The silane compound represented by the formula (2) includes, for example,

[0024]

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And the like. Examples of commercially available products include TSL8380 manufactured by Toshiba Silicone Co., Ltd. and KBM803 (3-mercaptopropyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.

As the silane compound represented by the formula (3), for example,

[0027]

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Examples of commercially available products include KBM903 (γ-aminopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.

As the silane compound represented by the formula (4), for example,

[0030]

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Examples of commercially available products include KBM1003 (vinyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.

Examples of the silane compound represented by the formula (5) include, for example,

[0033]

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Examples of commercially available products include KBM703 (γ-chloropropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.

Of these, rubber scorch (scorch)
In view of this, it is preferable to use 3,3'-bis (triethoxysilylpropyl) tetrasulfide.

The compounding amount of the silane compound may be an amount corresponding to 1 to 15% by weight of the hydrated silica. However, the phenomenon that an excessive coupling agent is precipitated on the rubber surface is prevented, and the material cost is reduced. In terms of preventing the rise, 1
Preferably, the amount corresponds to 10 to 10% by weight.
It is particularly preferred that the amount corresponds to% by weight.

In the rubber composition of the present invention, in addition to the above-mentioned components, white fillers such as silica, talc, clay and the like other than the above-mentioned wet silica, fillers such as carbon black, paraffin-based, aroma-based, and naphthene-based Softeners such as process oils, tackifiers such as coumarone indene resins, rosin resins, cyclopentadiene resins, vulcanizing agents such as sulfur and peroxides, vulcanization accelerators, stearic acid, zinc oxide, etc. A vulcanization aid, an antioxidant, and the like can be appropriately compounded as needed as long as the effects of the present invention are not impaired.

In particular, the filler other than the wet silica is 2
It is preferable to mix and select 0 to 200 parts by weight, 10 to 200 parts by weight of the softener and 5 to 50 parts by weight of the tackifier. Further, the vulcanizing agent, the vulcanization accelerator and the vulcanization aid are added in an amount of 4 to 15 parts by weight in view of adjusting the vulcanization rate to an appropriate value, and the antioxidant has aging resistance properties and excessively. From the viewpoint of not blending, it is preferable to appropriately select and blend within the range of 1 to 10 parts by weight.

The rubber composition of the present invention can be obtained by a conventional method using a Banbury mixer, an open roll or the like.

The rubber composition of the present invention obtained as described above has a tan δ (10 Hz, 0 ° C., 0.5%) of 0.5.
The shear modulus G is 5%, 25%, 50%, 100%, 150 at a frequency of 10 Hz and a temperature of 70 ° C.
% When measured three times at each dynamic shear displacement, the ratio of the shear modulus G (5%) at the third 5% displacement to the shear modulus G (100%) at the 100% displacement is: It is preferable to satisfy the formula (I): G (5%) / G (100%) ≦ 1.6 and the formula (II): G (100%) ≧ 0.6.

Here, tan δ (1
(0 Hz, 0 ° C., 0.5%) is used for evaluation of wet grip properties, and the larger the value, the better the wet grip properties, and the more preferable it is, especially, 0.5 or more.

Next, the shear modulus G measured under the conditions of a frequency of 10 Hz and a temperature of 70 ° C. is measured as close to actual running as possible with an actual test machine, taking into account the heat generation phenomenon caused by running of the tire. It shows the hardness of rubber under the conditions. Above all, when the dynamic shear displacement is measured at 5% and 100%, the shear modulus G is 5%, and when 5%, the rubber hardness at the moment when the tire is in contact with the ground (micro strain) is 100%.
% Indicates the hardness of the rubber when the tire subsequently rotates and undergoes large deformation.

In the present invention, the rubber that is soft when subjected to small deformation and hardens when subjected to large deformation improves wet grip.
When measured three times, the shear modulus G (5%) at the third 5% displacement and the shear modulus G (100%) at the 100% displacement are measured.
%) Preferably satisfies the formula (I): G (5%) / G (100%) ≦ 1.6 and the formula (II): G (100%) ≧ 0.6.

By kneading the components at the above-described mixing ratios under the following kneading conditions, a vulcanized rubber having such properties can be obtained.

A method of kneading in two stages using a closed kneader as follows:
And kneading for 5 minutes or more at a temperature of not more than 90 ° C.
By a method of kneading at 40 ° C. for 5 minutes or more, G (5
%), G (100%), and tan δ can be controlled to fall within the above ranges.

The rubber composition of the present invention can be suitably applied to a tread of a tire.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0048]

EXAMPLES First, the components used in the examples are shown in Table 1.

Examples 1 to 6 First, according to the mixing ratios shown in Table 2, components other than sulfur and a vulcanization accelerator were mixed in a 3-liter kneader manufactured by Moriyama Seisakusho Co., Ltd. After mixing 1 part by weight of sulfur, 1.5 parts by weight of vulcanization accelerator A and 2 parts by weight of vulcanization accelerator B with an open roll,
By vulcanizing at 70 ° C. for 30 minutes, rubber compositions 1 to 6 of the present invention after vulcanization were obtained.

Incidentally, in all rubber compositions, 1.5 parts by weight of wax, 2 parts by weight of antioxidant A, and antioxidant B
1 part by weight, zinc white 4 parts by weight, and stearic acid 2 parts by weight.

[Test Method] Tensile test: M100, according to JIS K6301
M300, was measured T _B and E _B. M300 is 4.1
It suffices if it is at least MPa.

Viscoelasticity test of micro-strain: Using a DVA-200 dynamic visco-elasticity tester manufactured by Shimadzu Corporation, frequency: 10 Hz, temperature: 0 ° C., dynamic strain: 0.5% (pre-expansion 1
0%), tan δ (10H
z, 0 ° C., 0.5%). tan δ (10H
(z, 0 ° C., 0.5%) is preferably 0.5 or more.

Large deformation viscoelasticity test: Using a 1.5-ton dynamic shear tester manufactured by Tokyo Koki Co., Ltd.
5%, 25%, 50%, 100% at a temperature of 70 ° C.
%, 150% each time the shear modulus G is changed three times at each dynamic shear displacement.
Was measured. The shear modulus G (5
%) And the shear modulus G at 100% displacement (100%), G (100%) and G (5%) / G (100
%), And the wet grip property was evaluated. Was.
G (100%) is 0.6 or more, and G (5%) / G
(100%) is preferably 1.6 or less.

Grip property on wet road surface: A tire having a tread made of the rubber composition was prepared by a conventional method, and the tire was driven by a car. The dry grip property was evaluated based on time and driver's feeling. In the driving test, the same driver measures the time for each lap of the tire for each lap of a fixed distance course of five laps, calculates the average value of three short times for each tire, and calculates the average value of Comparative Example 1 described later. It was indicated by an index as 100. The higher the index, the better the dry grip characteristics. In addition, the driver's feeling was evaluated on a scale of 5 such that the number of the driver felt better than that of Comparative Example 1 was 2, and the value of the driver felt lower than that of Comparative Example 1 was smaller.

The results of the above test are summarized in Table 2.

Comparative Examples 1 to 6 Comparative rubber compositions 1 and 6 were produced in the same manner as in Example 1 except that the mixing ratios were changed as shown in Table 2, and the same tests as those in Examples were performed. Table 2 shows the results.

[0057]

[Table 1]

[0058]

[Table 2]

From Examples 1 to 4 and Comparative Examples 1 to 4, tires having a tread made of the rubber composition within the scope of claim 1 have extremely excellent grip characteristics on wet road surfaces. The rubber composition within the scope of claim 1 also exhibits a viscoelastic property (tan δ) and a strain dependence of shear modulus (G (5%) / (G400%)) as described in claim 2 (G (5%) / (G400%)). Examples 1 and 2) prove to be particularly good.

Example 1 and Comparative Example 5, Example 5 and Comparative Example 6
From the comparison of the above, when carbon black was blended in place of silica, tan δ was reduced, the elastic modulus of micro-strain (= G (5%)) was increased, and the strain dependence of shear modulus (= G (5 %) / G (100%)). That is, the elastic modulus of micro strain is large and tan δ
Since (10 Hz, 0 ° C., 0.5%) is small, it can be seen that grip performance is reduced.

Further, Example 6 is a tire having a tread made of the rubber composition according to claim 1 when silica in the range described in claim 3 is used, but has a grip characteristic on a wet road surface. It turns out that it is the best.

[0062]

According to the present invention, there is provided a rubber composition comprising a rubber component containing a bromide of isobutylene / paramethylstyrene copolymer and a specific wet silica, which has improved wet grip properties. A rubber composition for a tire tread can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // (C08K 13/02 3:36 5:54)

Claims (3)

[Claims] 1. A BET specific surface area of 100 parts by weight of a polymer containing 30% by weight or more of a bromide of isobutylene / paramethylstyrene copolymer after leaving the mixture at 150 ° C. for 0.5 hours in a nitrogen atmosphere. ~250m ² / g
50 to 200 parts by weight of wet silica is as well, equation (1): Z-R- S n -R-Z, wherein (2): Z-R- S
H, Formula (3): ZR-NH ₃ , Formula (4): Z-CH =
CH ₂ or formula (5): Z—R—X (where R is a divalent hydrocarbon group having 1 to 18 carbon atoms, n is an integer of 2 to 8, and Z is —Si (R ¹ ) ₂ R ² , -SiR ¹ (R ² ) ₂ , or -S
i (R ² ) ₃ (where R ¹ is an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group or a phenyl group, R ² is an alkoxy group having 1 to 8 carbon atoms, a cycloalkoxy group having 5 to 8 carbon atoms or carbon Is an aryloxy group of the formulas 6 to 8, and X is a halogen atom).
A rubber composition for a tire tread, comprising a silane compound in an amount corresponding to 15% by weight. 2. Tan δ (10 Hz, 0 ° C., 0.5%)
Is 0.5 or more, and the shear modulus G is 5%, 25%, 50%, 100% under the conditions of a frequency of 10 Hz and a temperature of 70 ° C.
When measured three times at each dynamic shear displacement of 150%,
Shear modulus G (5%) at the time of the third 5% displacement and 100%
The shear modulus G (100%) at the time of displacement satisfies the formula (I): G (5%) / G (100%) ≦ 1.6 and the formula (II): G (100%) ≧ 0.6. The rubber composition for a tire tread according to claim 1. 3. The wet silica is heated at a rate of 5 ° C./min.
When the temperature is raised from 0 ° C to 500 ° C, the ratio of the weight loss at 400 ° C to the weight at 100 ° C is
The rubber composition for a tire tread according to claim 1, which is not more than 0.70% by weight.