JPH06200075A - Rubber composition for tire - Google Patents

Abstract

PURPOSE:To provide a compsn. improved in heat build-up resistance and abrasion resistance. CONSTITUTION:The compsn. is obtd. by compounding 100 pts.wt. natural and/or polyisoprene rubber or rubber component comprising such a rubber and 40 pts.wt. or lower another diene rubber, 30-65 pts.wt. carbon black having a CTAB of 100-150m<2>/g, a 24M4DBP of 115-140ml/100g, a toluene discoloration value at a wavelength of 342nm of 70% or lower, a Stokes equivalent diameter Dst of agglomerate by centrifugal precipitation of 100nm or lower, and a ratio (ADst/Dst) of the half-value width Dst of agglomerate distribution by centrifugal precipitation to Dst of 0.60-0.80, and 1-20 pts.wt. at least one liq. polymer having a number-average mol.wt. of 2.000-50,000 and selected from the group consisting of a liq. polybutadiene, a liq. polyisoprene, and a liq. styrene-butadiene copolymer rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a rubber composition for tires, and more particularly, to a rubber composition for tires having improved heat generation and abrasion resistance.

[0002]

As a rubber composition for a tire tread,
Natural rubber (NR), styrene-butadiene copolymer rubber
Blends of rubbers such as (SBR) and polybutadiene rubber (BR) with carbon black as a reinforcing filler for these rubbers have been widely used.
Then, by appropriately setting the type and molecular weight of the rubber, the type of carbon black, the characteristics and blending amount, and further the type and blending amount of oil to be blended, the mixing processability of the rubber composition for tire tread, the rubber Elasticity, heat generation,
Various properties such as wear resistance and mechanical properties have been improved.

By the way, conventionally, as a method for improving the wear resistance of a rubber composition for a tire tread, carbon black having a small particle size and a large specific surface area is used,
Methods for increasing the amount of carbon black compounded are known, but these methods increase the viscosity of the rubber composition, significantly reduce the kneading workability, and further deteriorate the dispersion of carbon black. . At the same time, there is a drawback that the exothermic property of the rubber composition is increased.

On the contrary, in order to improve the heat build-up of the rubber composition for tire tread, there is known a method of increasing the particle size of carbon black to be compounded or reducing the compounding amount of carbon black. However, in this method, even if the heat generation property is improved, there is a problem that the wear resistance is deteriorated. Therefore, in a rubber composition for a tire tread, abrasion resistance and heat build-up have an antinomic relationship, and it has been considered difficult to improve the two in a balanced manner.

Nevertheless, many attempts have been made to improve the wear resistance and heat buildup of rubber compositions for tire treads, for example, the particle size distribution of carbon black CTAB, 24M4DBP and ISAF aggregates. , And a method for optimizing toluene color transmission etc. are disclosed in JP-A-63-264647, JP-A-64-74242, JP-A-1-144434, JP-A-2-22348, and Although proposed by Kaihei 2-286727, etc.,
A rubber composition for a tire tread having both sufficient abrasion resistance and low heat buildup has not yet been obtained, and when such a special carbon black is used, the kneading workability is deteriorated and carbon black is reduced. Often deteriorates the dispersion of

[0006]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a rubber composition for tires having excellent wear resistance and low heat buildup.

[0007]

A rubber composition for a tire according to the present invention comprises a natural rubber and / or a polyisoprene rubber, or 100 parts by weight of a rubber component containing 40 parts by weight or less of another diene rubber. CTAB is 100-150m ² / g, 2
4M4DBP 115-140ml / 100g, toluene transmittance at wavelength 342nm is 70% or less, aggregate Stokes equivalent diameter D _st by centrifugal sedimentation method is 100nm or less, and aggregate distribution measured by this D _st and centrifugal sedimentation method FWHM of ΔD _st
30 to 65 parts by weight of carbon black satisfying the ratio ΔD _st / D _st of 0.60 to 0.80 is added, and liquid polybutadiene, liquid polyisoprene and liquid styrene having a number average molecular weight of 2000 to 50,000 are added. 1 to 20 of at least one liquid polymer selected from the group of butadiene copolymer rubber
It is characterized by being mixed in parts by weight.

As described above, in the present invention, since the carbon black having the above-mentioned specific characteristics and the liquid polymer are used in combination, as compared with the conventional rubber composition for tire tread, the tan at 60 ° C., which is an index of heat buildup, is used. significantly improved δ
(Lower size), easy kneading workability, excellent dispersion of carbon black, and extremely excellent abrasion resistance can be secured.

The structure of the present invention will be described in detail below. The rubber composition for a tire of the present invention, with respect to the rubber component,
It is characterized by being mixed with carbon black and a liquid polymer. Rubber component Use natural rubber and / or polyisoprene rubber,
Alternatively, 40 parts by weight or less, preferably 10 parts by weight or less of another diene rubber with respect to natural rubber and / or polyisoprene rubber.
30 parts by weight are compounded and used as 100 parts by weight of total rubber.

Here, the other diene rubbers are, for example, butadiene rubber and styrene-butadiene copolymer rubber. Carbon black CTAB 110-150m ² / g, 24M4DBP 115-140m
Toluene color transmission at l / 100g, wavelength 342nm is 70%
Hereafter, the aggregate Stokes equivalent diameter D _st by the centrifugal sedimentation method is
It satisfies the characteristics of 100 nm or less, and the full width at half maximum ΔD _st / D _st of the aggregate distribution by D _st and the centrifugal sedimentation method is 0.60 to 0.80.

The specified range for CTAB and 24M4DBP covers the general range of so-called carbon black for tire treads, and outside this specified range, the toluene colorant transmittance, D _st and Δ at the wavelength of 342 nm described below are obtained. Even if the specification of D _st / D _st is satisfied, one or both of the wear resistance and the heat generation property tends to deteriorate, which is not preferable.

The toluene coloring transmittance at a wavelength of 342 nm of carbon black is a condition indispensable for lowering the heat generation of the composition, and if it exceeds 70%, a satisfactory low heat generation property cannot be obtained. The toluene color transmission is generally considered as a scale showing the amount of organic substances on the surface of carbon black, and the JIS standard uses a measured value at a wavelength of 420 nm. It is considered that the lower the toluene coloring permeability of the carbon black, the higher the interaction with the rubber and the higher reinforceability and the lower heat generation property. However, according to the study by the present inventors, when the toluene coloring transmittance measured at a wavelength of 420 nm is simply low, the carbon black conversion is low and the yield is not only low, On the contrary, it was found that the interaction with rubber tends to be inhibited. Therefore, as a result of further studies on the surface properties of carbon black necessary for enhancing the interaction with rubber, the present inventors have found that the conventional wavelength of 420 nm.
Instead, use the toluene coloring transmittance measured under the condition of shorter wavelength of 342 nm as a scale, and the measured value is 70%.
It has been found that a rubber composition for tires having a sufficiently high interaction between rubbers and a significantly improved heat buildup can be obtained by the following stipulations, even if the transmittance of toluene coloring on the long wavelength side is high. However, even if the transmittance of toluene coloring measured under the condition of wavelength 342 nm is more than 70%, the exothermic property is not significantly reduced. Therefore, in the present invention, the value is 70% or less,
It is preferably 50% or less.

D_stIs the Stokes aggregate by centrifugal sedimentation
Maximum frequency of Stokes equivalent diameter in equivalent diameter distribution (nm)
And if this value is greater than 100 nm, satisfactory abrasion resistance is obtained.
Not wearable. Also, this D_stAnd by the centrifugal sedimentation method
Half-value of measured aggregate distribution ΔD_st/ D _stIs less than 0.60
Exothermicity deteriorates, while if it exceeds 0.80, wear resistance
descend. The centrifugal sedimentation method here is Joyce
・ Using the Rebel disk centrifuge
A method for measuring aggregate distribution, which uses Stokes
Sedimentation using the fact that larger particles diffuse faster
This is a method of obtaining the size of particles.

Liquid polymer It is at least one selected from the group consisting of liquid polybutadiene having a number average particle amount of 2000 to 50,000, liquid polyisoprene, and liquid styrene-butadiene copolymer rubber. The liquid styrene-butadiene copolymer rubber has a bound styrene content of 35% or less, preferably 10% to 30%, and a vinyl bond content of 65%.
% Or less, preferably 20% to 50%, and it is better that the molecular ends are modified with a modifying agent.

Examples of the modifier include N-substituted aminoketone, N-substituted thioaminoketone, N-substituted aminoaldehyde, N-substituted thioaminoaldehyde, and the following formula (wherein
M represents an oxygen or sulfur atom) is a compound having an atomic group represented by

[0016]

Examples of the modifier include 4-dimethylaminobenzophenone, 4-diethylaminobenzophenone, 4-di-t-butylaminobenzophenone, 4
-Diphenylbenzophenone, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone, 4,4'-bis (di-t-butylamino) benzophenone, 4,4'-bis ( Diphenylamino) benzophenone, 4,4'-bis (divinylamino)
Benzophenone, 4-dimethylaminoacetophenone,
N-substituted aminoketones such as 4-diethylaminoacetophenone, 1,3-bis (diphenylamino) -2-propanone, 1,7-bis (methylethylamino) -4-heptanone and corresponding N-substituted aminothioketones ; 4
-N-substituted aminoaldehydes such as dimethylaminobenzaldehyde, 4-diphenylaminobenzaldehyde, 4-divinylaminobenzaldehyde and the corresponding N-substituted aminothioaldehydes; N-methyl-β-propiolactam, Nt-butyl -Β-propiolactam, N-phenyl-β-propiolactam, N-methoxyphenyl-β-propiolactam, N-naphthyl-β
-Propiolactam, N-methyl-2-pyrrolidone, N
-T-butyl-2-pyrrolidone, N-phenyl-pyrrolidone, N-methoxyphenyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-benzyl-2-pyrrolidone, N-naphthyl-2-pyrrolidone, N- Methyl-5
Methyl-2-pyrrolidone, Nt-butyl-5-methyl-2-pyrrolidone, N-phenyl-5-methyl-2-pyrrolidone, N-methyl-3,3'-dimethyl-2-pyrrolidone, Nt -Butyl-3,3'-dimethyl-2-pyrrolidone, N-phenyl-3,3'-dimethyl-2-pyrrolidone, N-methyl-2-piperidone, Nt-butyl-2
-Pyrrolidone, N-phenyl-2-piperidone, N-methoxyphenyl-2-piperidone, N-vinyl-2-piperidone, N-benzyl-2-piperidone, N-naphthyl-2-piperidone, N-methyl-3, 3'-dimethyl-
2-piperidone, N-phenyl-3,3'-dimethyl-2
-Piperidone, N-methyl-ε-caprolactam, N-
Phenyl-ε-caprolactam, N-methoxyphenyl-ε-caprolactam, N-vinyl-ε-caprolactam, N-benzyl-ε-caprolactam, N-naphthyl-ε-caprolactam, N-methyl-ω-laurylolactam, N -Phenyl-ω-laurylolactam, Nt-
N such as butyl-lauryl lactam, N-vinyl-ω-lauryl lactam, N-benzyl-ω-lauryl lactam
-Substituted lactams and their corresponding thiolactams; 1,3-dimethylethylene urea, 1,3-diphenylethylene urea, 1,3-di-t-butylethylene urea, 1,3
-N-substituted ethylene ureas such as divinyl ethylene urea and the corresponding N-substituted thioethylene ureas.

In the present invention, 30 to 65 parts by weight of the carbon black and 1 to 20 parts by weight of the liquid polymer are blended with 100 parts by weight of the rubber component. If the content of carbon black is less than 30 parts by weight, the abrasion resistance will be insufficient, and if it exceeds 65 parts by weight, the kneading property will be significantly reduced, which is not preferable. When the amount of the liquid polymer is less than 1 part by weight, the effect of improving the kneading property is small, and when it exceeds 20 parts by weight, the abrasion resistance is insufficient. By blending the liquid polymer, not only the improvement of kneading workability of the specific rubber component and the specific carbon black can be achieved while maintaining wear resistance and low heat build-up, but also improvement of kneading workability can be achieved. Further, the dispersion of carbon black is improved, and higher abrasion resistance can be obtained.

The tire rubber composition of the present invention contains
A compounding agent usually used in the rubber industry, for example, a softening agent, an antioxidant, a vulcanization accelerator and the like can be appropriately compounded in a usual compounding amount range, if necessary.

[0020]

[Examples] Eight types of rubber compositions were prepared with the compounding contents (parts by weight) shown in Table 1 (Comparative Examples 1 to 5 and Examples 1 to 3).
. These rubber compositions were press-vulcanized at 150 ° C. for 30 minutes to prepare target test pieces, various tests were carried out, and the physical properties were measured. The results are shown in Table 1. The test method is as follows.

The types of carbon black used in this case are shown in Table 2. The method of measuring the carbon black characteristics is as follows. CTAB : According to ASTM-D3765-80. 24M4DBP oil absorption : According to ASTM-D3493. Toluene color transmission : Measurement wavelength in JIS K6221
342 nm. D _st , ΔD _st : A dry carbon black sample was mixed with a 20% by volume aqueous ethanol solution containing a small amount of a surfactant to prepare a dispersion having a carbon black concentration of 5 mg / 100 cc, which was sufficiently dispersed by ultrasonic waves. And use it as a sample. A disk centrifuge device (manufactured by Joice Loebl, UK) is set at a rotation speed of 8000 rpm, 10 ml of a spin solution (distilled water) is added, and then 0.5 ml of a buffer solution (ethanol aqueous solution) is injected. Then, 0.5 ml of the sample solution is added with a syringe to start centrifugal sedimentation, and at the same time, a recorder is operated to optically produce a distribution curve of the Stokes equivalent diameter of the aggregate. The maximum frequency of Stokes equivalent diameter in the obtained distribution curve is defined as D _st (nm). Further, the aggregate distribution value at 1/2 of the most frequent frequency is defined as the full width at half maximum (ΔD _st ). Mooney viscosity (ML _{1 + 4} , 100 ° C) : Measured according to JIS K6300. The smaller this value, the better the kneading workability,
The dispersibility of carbon black is also excellent. Abrasion resistance evaluation method : Lambourn abrasion tester
The test piece disc and the polishing disc are contact-rotated without making an angle, and 25% slip is generated between the test piece disc and the polishing disc at this time, and the result of measuring the wear amount of the test piece per unit time is an index. Evaluation (The larger the index, the better the abrasion resistance). Measuring method of tan δ : Using a viscoelasticity spectrometer (manufactured by Iwamoto Seisakusho), temperature 60 ° C, strain rate 10 ± 2%, frequency
Measured under the condition of 20Hz (The smaller the value, the better the heat generation).

[0022]

Note) (1) RSS # 1. (2) NIPOLE BR 1220 (manufactured by Zeon Corporation).

(3) Ceast 9 (made by Tokai Carbon). (4) LIR-30 (made by Kuraray), number average molecular weight: 2900
0. (5) Liquid SBR, number average molecular weight: 22000, bound styrene amount: 25%, vinyl amount: 35%, and 4-dimethylaminobenzophenone at the terminal portion. (6) Kyoseki Process X-140.

(7) Zinc Flower No. 3, manufactured by Shodo Kagaku. (8) Nt-butyl-2-benzothiazolylsulfenamide (Santocure NS manufactured by Monsanto). SBR content and 1,2-bond content of SBR : Infrared spectroscopy: LH Hampton, Analytical, Chem, 21 923 (19
Calculated by the method of 49).

[0026]

As is clear from the results shown in Table 1, the rubber composition for a tire of the present invention has excellent wear resistance, heat generation and kneading workability in balance.

[0028]

As described above in detail, the rubber composition for a tire of the present invention has a tan of 60 ° C., which is an index of exothermicity.
Not only can δ be remarkably improved (tan δ can be reduced), but also extremely excellent wear resistance can be ensured, and both wear resistance and heat generation are excellent, so of course it is not only used for tire treads, but also for carcass. It is also useful for forming parts such as breakers, side rubbers, bead fillers, and chafers.

Claims (2)

[Claims] 1. A CTAB of 100 to 150 m with respect to 100 parts by weight of a natural rubber and / or polyisoprene rubber, or 100 parts by weight of a rubber component containing 40 parts by weight or less of another diene rubber.
² / g, 24M4DBP 115-140ml / 100g, toluene coloring transmittance at wavelength 342nm is 70% or less, aggregate Stokes equivalent diameter D _st by centrifugal sedimentation method is 100nm or less, and measured by this D _st and centrifugal sedimentation method. that the ratio of the half width △ D _st of aggregate distribution △ D _st / D _st is blended 30-65 parts by weight of carbon black satisfying the characteristics of 0.60 to 0.80, further,
A rubber composition for a tire, comprising 1 to 20 parts by weight of at least one liquid polymer selected from the group consisting of liquid polybutadiene having a number average molecular weight of 2000 to 50000, liquid polyisoprene, and liquid styrene-butadiene copolymer rubber. . 2. A liquid styrene-butadiene copolymer rubber having a bound styrene content of 35% or less and a vinyl bond content of 65% or less, and having N-substituted aminoketone, N-substituted thioaminoketone, and N-substituted amino. The terminal of a molecule is modified with a modifier of an aldehyde, an N-substituted thioaminoaldehyde, or a compound having an atomic group represented by the following formula (wherein M represents an oxygen or sulfur atom). Rubber composition for tire.