JP3354642B2 - 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, and more particularly to a rubber composition for a tire tread having improved heat generation and abrasion resistance of a tire.

[0002]

2. Description of the Related Art In the rubber industry, especially in the tire industry, in recent years, fuel-efficient tires have been actively developed in order to meet the social demands for resource saving and energy saving. For the development of such fuel-efficient tires, the development of a low heat-generating rubber composition is indispensable, and many inventions belonging to this field have been recently proposed.

[0003] For example, Japanese Patent Application Laid-Open No. 55-12133,
JP-A-56-127650 discloses a high vinyl polybutadiene rubber (V-BR) disclosed in JP-A-57-5520.
No. 4, JP-A-57-73030 proposes a high vinyl styrene-butadiene copolymer rubber (V-SBR), and these rubbers are effective in improving grip performance and heat generation. Has been stated. However, in these cases, there is a problem that abrasion resistance is deteriorated because a polymer having a high glass transition temperature (Tg) is used.

Further, Japanese Patent Application Laid-Open No. Sho 59-117514,
JP-A-61-103902, JP-A-61-142
No. 14, JP-A-61-141741 discloses a method for reducing the heat build-up of a rubber composition by using a modified polymer in which a functional group such as benzophenone or isocyanate is introduced into the molecular chain of the polymer. ing.
However, even if these V-BR, V-SBR or modified polymers are used, the recent demand for low heat build-up has not yet been sufficiently satisfied, and a rubber composition having even lower heat build-up has been desired. .

On the other hand, as a method for obtaining a rubber composition having a low heat build-up, a method using carbon black having a large particle diameter and a method of reducing the blending amount of carbon black are generally known. Also, the breaking strength and abrasion resistance of the rubber are reduced, so that it is not practical. Conversely, in order to improve the wear resistance of the rubber composition for tire tread, a method of using carbon black having a small particle size and a large specific surface area or increasing the blending amount of carbon black is known. However, these methods have the drawback that the viscosity of the rubber composition is increased and the kneading workability is significantly reduced, and further, the dispersion of carbon black is further deteriorated, and at the same time, the exothermicity of the rubber composition is increased. .

For this reason, many attempts have been made to improve both the wear resistance and the heat build-up of rubber compositions for tire treads. For example, CTAB of carbon black, 24M4DBP oil absorption, and agglomeration of ISAF have been made. Methods for optimizing the particle size distribution of the gate, the transmittance of toluene coloring, and the like are described in JP-A-63-264647, JP-A-64-74242, and JP-A-1-14.
No. 4434, JP-A-2-22348, JP-A-2-286727, etc., a rubber composition for a tire tread having both sufficient abrasion resistance and low heat generation is obtained. In addition, when the above-described special carbon black is used, the kneading workability is often lowered and the dispersion of the carbon black is often deteriorated.

Further, Japanese Patent Application Laid-Open No. 63-101440,
JP-A-63-33436, JP-A-64-1684
No. 5, JP-A-1-197541 and JP-A-3-19741.
No. 28244 discloses an attempt to improve the balance between grip performance and abrasion resistance of a tire by using a low molecular weight polymer as a softener in a rubber composition for a tire.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a composition for a tire tread rubber which is excellent in abrasion resistance and grip performance and has low heat generation. .

[0009]

According to the present invention, (i)
(A) at least one of an alkali metal and alkaline earth addition rubbery polymer and an N-substituted aminoketone, an N-substituted thioaminoketone, an N-substituted aminoaldehyde, an N-substituted thioaminoaldehyde and a compound represented by the general formula (I) ):

[0010]

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(Wherein M represents an oxygen or sulfur atom)
Having a styrene content of 5 to 40% and a 1,2-vinyl bond amount of 10 to 75 obtained by reacting at least one organic compound selected from compounds having an atomic group represented by
% Styrene butadiene copolymer rubber (SBR)
100% by weight and (B) at least one other than (A)
(Ii) CTAB is 70 parts by weight based on 100 parts by weight of a raw rubber containing 70 to 0% by weight of a kind of diene rubber as a rubber component.
１６０160 m ² / g, 24M4DBP oil absorption of 110-14
0 ml / 100 g, 85% less light transmittance of toluene at a wavelength 420 mm, is at 120nm following aggregates Stokes equivalent system D _st by centrifugal sedimentation, the half width of aggregate distribution measured by the D _st and the centrifugal sedimentation method △ the ratio of the D _st △ D _st
30 to 100 parts by weight of carbon black having a property of / D _st of 0.60 to 0.90, and (iii) a liquid polybutadiene (BR) having a weight average molecular weight of 2,000 to 50,000, and a liquid styrene butadiene copolymer. Merging (SB
R), a rubber composition for a tire tread, comprising 3 to 35 parts by weight of at least one liquid polymer selected from the group of liquid polyisoprene (IR) and the like.

Here, as the liquid polymer, as in the case of the above-mentioned modified SBR, an N-substituted aminoketone, N-substituted
Substituted thioaminoketone, N-substituted aminoaldehyde, N
Those modified by reacting with a substituted thioaminoaldehyde and at least one organic compound carried from a compound having the atomic group represented by the above general formula (I) in the molecule are particularly preferable.

In the present invention, a specific carbon black and a specific liquid polymer are blended with the above-mentioned polymer having the specific characteristics, whereby an exothermic index is obtained as compared with a conventional rubber composition. Tan δ at 60 ° C. is remarkably improved (reduced), kneading workability is easy, carbon black dispersibility is excellent, and extremely excellent abrasion resistance can be secured.

Hereinafter, the configuration of the present invention will be described in detail. (1) Raw Rubber In the present invention, an alkali metal and / or alkaline earth metal addition rubber polymer, an N-substituted amino ketone,
Substituted thioaminoketone, N-substituted aminoaldehyde, N
Obtained by reacting thioaminoaldehyde and at least one organic compound selected from compounds having an atomic group represented by the above general formula (I) in a molecule,
Styrene content is 5 to 40%, 1,2-vinyl bond amount is 1
A raw rubber containing at least 30% by weight or more of 0 to 75% styrene butadiene copolymer rubber is used. If the content of the obtained polymer is less than 30% by weight, even if the above-mentioned carbon black and liquid rubber are blended, the heat generation is not sufficiently improved, which is not preferable.

In the present invention, examples of the alkali metal or alkaline earth metal-added rubber polymer modified with the organic compound include alkali metal catalysts (for example, metals such as lithium, sodium, rubidium and cesium, and hydrocarbon compounds thereof). A monomer system containing styrene and butadiene is polymerized by a general polymerization method such as solution polymerization or emulsion polymerization in the presence of a complex with a polar compound) or an alkaline earth metal catalyst (for example, a compound such as barium, strontium, or calcium). SBR can be mentioned.

Examples of the organic compound 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, 4-diethylaminoacetophenone,
1,3-bis (diphenylamino) -2-propanone,
N-substituted aminoketones such as 1,7-bis (methylethylamino) -4-heptanone and their corresponding N
-Substituted aminothioketones; 4-dimethylaminobenzaldehyde, 4-diphenylaminobenzaldehyde,
N-substituted aminoaldehydes such as 4-divinylaminobenzaldehyde and their 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, Nt-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-lauriloractam,
N-substituted lactams such as N-phenyl-ω-laurylolactam, Nt-butyl-laurylolactam, N-vinyl-ω-laurylolactam, N-benzyl-ω-laurylolactam and their counterparts Thiolactams;
1,3-dimethylethylene urea, 1,3-diphenylethylene urea, 1,3-di-t-butylethylene urea,
Examples include N-substituted ethylene ureas such as 1,3-divinyl ethylene urea and their corresponding N-substituted thioethylene ureas. The amount of these compounds to be used is generally 0.1 to 5 mol, preferably 0.1 to 5 mol per mol of the alkali metal and / or alkaline earth metal addition rubbery polymer.
It is in the range of 3 to 1.0 mole. The introduction of a functional group by this reaction can be easily performed by adding these compounds after the completion of the polymerization of the rubbery polymer, but may also be performed by a method such as performing polymerization using an initiator having a functional group. Any method may be used as long as a functional group is introduced into the polymer chain of the rubbery polymer.

In the raw rubber of the present invention, in addition to the organic compound-modified SBR (A), 0 to 70% by weight of a diene rubber other than (A) (eg, natural rubber, polybutadiene, polyisoprene, SBR, etc.) Can be blended.
However, the compounding amount of this diene rubber becomes too large and 70
When the content is more than 30% by weight, the amount of the organic compound-modified SBR (A) is less than 30% by weight, and the heat generation property is not sufficiently improved.

(2) Carbon black The carbon black used in the present invention is CTA
B is 70~110m ² / g, preferably 80~100m ² /
g, 24M4DBP oil absorption: 110-140 ml / 100
g, preferably 110-120 ml / 100 g, wavelength 42
85% or less light transmittance of toluene at 0 mm, the aggregate Stokes equivalent diameter D _st by centrifugal sedimentation method 120nm or less, and the half width △ D _st of aggregate distribution by the D _st and the centrifugal sedimentation method from 0.60 to 0 .90, preferably 0.65
It satisfies each characteristic of 〜0.85. That is,
The specified range for CTAB and 24M4DBP oil absorption of carbon black covers the general-purpose range of so-called carbon black for tire treads. Outside this specified range, even if the toluene coloring transmittance at a wavelength of 420 nm described below, D _st Even if the requirements of _{ΔD st} / D _st are satisfied, it is not preferable because one or both of abrasion resistance and heat generation tend to deteriorate.

The carbon black has a wavelength of 420.
The toluene coloring transmittance in nm is an indispensable condition especially for lowering the heat generation of the composition, and if it exceeds 85%, satisfactory low heat generation cannot be obtained. The toluene coloring transmittance is generally considered as a measure of the amount of organic substances on the surface of carbon black. The lower the toluene coloring transmittance of carbon black, the higher the interaction with rubber, the higher the reinforcing property and the lower the heat generation. It is thought that it will bring gender balance.

D _st is the maximum frequency equivalent Stokes diameter (nm) in the distribution of equivalent Stokes diameters by centrifugal sedimentation.
If this value is larger than 120 nm, satisfactory wear resistance cannot be obtained. Further, this D _st and the half width ΔD _st / D _{st of the} aggregate distribution measured by the centrifugal sedimentation method are 0.6.
If it is less than 0, the heat build-up deteriorates, while if it exceeds 0.90, the wear resistance decreases. Preferably it is 0.65-0.85. In addition, the centrifugal sedimentation method here is a method of measuring the aggregate distribution using a disc centrifuge manufactured by Joyce Reble Co., which utilizes the fact that particles having a larger Stokes diameter diffuse faster. And determining the size of the sedimented particles. The compounding amount of carbon black is in the range of 30 to 100 parts by weight, preferably 35 to 60 parts by weight, based on 100 parts by weight of the raw rubber. 30
When the amount is less than the weight part, the heat generation is improved, but the breaking strength and the abrasion resistance are inferior. On the other hand, if it exceeds 100 parts by weight, heat generation is not improved, so that it is not preferable.

(3) Liquid Polymer The liquid polymer used in the present invention has a weight average molecular weight of 2,000 to 50,000 and a styrene content of 0 to 35.
%, 1.2 low-molecular weight polymer such as liquid polybutadiene, liquid styrene butadiene copolymer, liquid polyisoprene, liquid acrylonitrile butadiene copolymer having a vinyl bond content of 10 to 70%. Further, it is more preferable to use a liquid polymer obtained by reacting the liquid polymer with various organic compounds described in the section of the raw rubber of (1) as the liquid polymer.

In the present invention, by mixing the above liquid polymer as a softening agent into the rubber composition, the kneading workability of the above specific polymer system and the specific carbon black is improved so that the obtained tire has abrasion resistance and low heat generation. Not only can it be improved while maintaining the properties, but also the dispersibility of the carbon black can be improved due to the improved kneading workability, and higher wear resistance can be obtained. If the amount of the liquid polymer is less than 3 parts by weight per 100 parts by weight of the raw rubber, the effect of improving the kneadability at the time of compounding the rubber is small, and if it exceeds 35 parts by weight, the abrasion resistance is insufficient, which is not preferable. The preferred compounding amount is 5 to 2 per 100 parts by weight of the raw rubber.
5 parts by weight.

The rubber composition for a tire tread of the present invention contains, in addition to the raw rubber, carbon black and liquid polymer, compounding agents usually used in the rubber industry, such as sulfur, a softener, an antioxidant, A tire tread can be manufactured by appropriately compounding a vulcanization accelerator, a filler, a plasticizer, and the like as needed within a range of a usual compounding amount, and vulcanizing by a general method. For example, the compounding amount of sulfur is preferably at least 1.2 parts by weight, more preferably 1.5 to 3.0 parts by weight, per 100 parts by weight.

[0024]

EXAMPLES The present invention will be further described with reference to the following examples, but it goes without saying that the scope of the present invention is not limited to these examples. Examples 1 to 4 and Comparative Examples 1 to 6 Ten kinds of rubber compositions were prepared by mixing and kneading with a Banbury mixer and a kneading roll machine according to a conventional method with the contents (parts by weight) shown in Table 1 (Comparative Example 1). To 6 and Examples 1 to
4). These rubber compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare target test pieces, and various tests were performed.
Its physical properties were measured. Table 1 shows the results. The test method is as follows.

1) 300% modulus, expansion force and elongation Measured according to JIS K6301 method.

2) Rebound resilience (Lupke) The rebound resilience was measured at 0 ° C. and 60 ° C. according to the method of JIS K6301. The smaller the value at 60 ° C., the smaller the exothermic property and the better. Also, the larger the value at 0 ° C., the better the wet grip property.

Abrasion resistance (pico abrasion) : Measured using a pico abrasion tester according to ASTM D2228. The index was expressed as (abrasion amount of Comparative Example 1) × 100 / (abrasion amount of sample). Therefore, the larger the value, the better the wear resistance.

The method for measuring the carbon black characteristics is as follows. CTAB : According to ASTM-D3765-80 method. 24M4DBP oil absorption : According to ASTM-D3493 method. Toluene coloring transmittance : Measured at 420 nm in JIS K6221 method. 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. Sample. Disc Centrifuge (Joice Loe, UK)
bl (manufactured by BL Co., Ltd.) at a rotation speed of 8000 rpm, 10 ml of spin solution (distilled water) is added, and then 0.5 ml of buffer solution (ethanol aqueous solution) is injected. Then, 0.5 ml of the sample solution is added by a syringe to start centrifugal sedimentation, and at the same time, the recorder is operated to optically produce a distribution curve of the aggregate Stokes equivalent diameter. The Stokes equivalent diameter of the maximum frequency in the obtained distribution curve is D _st (nm). Also, the aggregate distribution value at half the most frequent frequency is defined as a half width (ΔD _st ).

[0029]

[Table 1]

[0030]

As described in detail above, the rubber composition for a tire tread of the present invention has a heat buildup index of t.
An δ (60 ° C.) can be remarkably improved, and not only tan δ (0 ° C.), that is, wet grip can be maintained, but also extremely excellent wear resistance can be secured. As described above, the rubber composition of the present invention is particularly preferable for use as a tread for a tire because it has excellent wear resistance, heat generation properties, and wet grip properties.

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 15/00 C08K 3/00-3/04 C08L 21/00

Claims (2)

(57) [Claims] 1. (i) (A) at least one of an alkali metal and alkaline earth metal addition rubbery polymer, an N-substituted aminoketone, an N-substituted thioaminoketone, an N-substituted aminoaldehyde, an N-substituted thione Formula (I) in an aminoaldehyde and a molecule: (Wherein M represents an oxygen or sulfur atom) and has a styrene content of 5 to 4 obtained by reacting with at least one organic compound selected from compounds having an atomic group represented by the following formula:
0%, 1.2-30% by weight of a styrene butadiene copolymer rubber having a vinyl bond content of 10 to 75% and (B)
At least one diene rubber other than (A)
(Ii) CTAB of 70 to 160 m ² / g, 24M based on 100 parts by weight of raw rubber containing 0% by weight as a rubber component
4DBP oil absorption 110-140ml / 100g, wavelength 4
85% or less light transmittance of toluene at 20 mm, is at 120nm following aggregate Stokes equivalent diameter D _st by centrifugal sedimentation, the ratio of the half width △ D _st of the aggregate distribution measured by the D _st and the centrifugal sedimentation method ΔD _st / △ D _st is 0.60
Carbon black 30-100 having properties of 0.90
Parts by weight and (iii) a weight average molecular weight of 2,000 to 5
A rubber composition for a tire tread, comprising 3 to 35 parts by weight of at least one liquid polymer selected from the group consisting of 0000 liquid polybutadiene, liquid styrene butadiene copolymer and liquid polyisoprene. . 2. The liquid polymer having an amount of bound styrene of from 0 to 3
5%, 1.2 Vinyl bond content is 10 to 70%, and N-substituted aminoketone, N-substituted thioaminoketone,
N-substituted aminoaldehydes, N-substituted thioaminoaldehydes and the compound of the formula (I) in the molecule: The liquid styrene-butadiene copolymer or polybutadiene obtained by reacting at least one compound selected from compounds having an atomic group represented by the formula (wherein M represents an oxygen or sulfur atom). Rubber composition.