JPH1087887A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber compsn. excellent in the balance of tanδ and improved in abrasion resistance by compounding a specific rubber component with a carbon black and a softener. SOLUTION: This compsn. is prepd. by compounding 100 pts.wt. rubber component comprising 50-90 pts.wt. rubber (A) contg. 20-100wt.% soln.-polymerized diene rubber having molecular ends modified or coupled and 50-100 pts.wt. rubber (B) comprising a diene rubber having molecular ends neither modified nor coupled with 60-120 pts.wt. carbon black (X) having a nitrogen adsorption specific surface area of 130-200m<2> /g and a DBP absorption of 100-130ml/100g and 20-80 pts.wt. softener. The average glass transition point of rubber A (TgA deg.C) and that of rubber B (TgB deg.C) satisfy the relation represented by formula I. Rubber A, 80-100wt.% of ingredient X, and 50-100wt.% of the softener are first mixed in such amts. as to satisfy the relation represented by formula II at 135 deg.C or higher and then rubber B, the rest of component X, and the rest of the softener are added and mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition containing a specific carbon black, and more particularly to a rubber composition suitable for a pneumatic tire tread.

[0002]

2. Description of the Related Art It has been proposed to improve the balance of tan δ of tire tread rubber to reduce the fuel consumption of automobiles. Specifically, it has been proposed to divide and mix components and use a terminal-modified rubber. ing.

For example, Japanese Patent Publication No. 5-1298 discloses that
A rubber composition is described in which a vulcanizate containing a conjugated diene-based polymer having an aromatic tertiary amino group at a terminal portion of the conjugated diene-based polymer has improved rebound resilience and tensile strength.
On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 55-104343 discloses a raw rubber comprising an amorphous 1,2-polybutadiene rubber and a natural rubber and / or a polyisoprene rubber (which may further contain a conjugated diene rubber). When compounding carbon black to produce a rubber composition for a tire tread,
First, a raw rubber component containing at least 25% by weight of 1,2-polybutadiene is mixed with carbon black in a specific ratio, and then the remaining raw rubber components are added and mixed to improve fuel efficiency and safety of an automobile. Is described.
JP-A-2-129241 proposes to improve the tensile strength and abrasion resistance of a vulcanizate by blending a terminal-modified conjugated diene polymer with carbon black in an organic solvent. Further, the present inventors have disclosed in Japanese Patent Application No. Hei.
No. 54378 proposes to improve the balance of tan δ by a method in which a terminal-modified polymer and carbon black are mixed first and then an emulsion-polymerized polymer is added.

[0004]

However, the above-mentioned techniques such as the method of dividing and mixing the components and the use of a terminal-modified rubber have a problem that, for example, the effect is diminished in a high compounding system of oil and carbon black. There is still a need for improvement. In the case of split mixing, there is a problem that only a specific rubber combination is effective, and the usable range is limited. In addition, when a method in which the terminal-modified polymer and carbon black are mixed in advance and the emulsion-polymerized polymer is added later, the balance of tan δ is improved, but there is still a problem that abrasion resistance is reduced. . Accordingly, an object of the present invention is to provide a rubber composition for a tire tread in which a tan δ balance of a vulcanized rubber is excellent and abrasion resistance is improved.

[0005]

According to the present invention, terminal-modified and / or coupled diene rubbers 20 to 1 are provided.
50 to 90 parts by weight of a raw rubber (A) containing 00% by weight;
Raw rubber (B) 50 to 10 comprising at least one type of diene rubber which is not terminal-modified and / or coupled
Nitrogen adsorption specific surface area 130-200 m ² / g, DBP oil absorption 1
In a rubber composition obtained by mixing 60 to 120 parts by weight of carbon black (X) at 100 to 130 ml / 100 g and 20 to 80 parts by weight of a softening agent, the average glass transition temperature TgA (° C.) of the raw rubber (A) is determined. The average glass transition temperature TgB (° C.) of the raw rubber (B) is in the following relationship: TgA + 20>TgB> TgA-20, and the total amount of the raw rubber (A) and the carbon black is 80%.
-100% by weight and 50-100% by weight of the total amount of the softener are defined as follows.

(Equation 3) After mixing at a temperature of 135 ° C. or more, the raw rubber (B)
And a remaining carbon black and a softening agent.

According to a preferred embodiment of the present invention, the carbon black (X) has a nitrogen adsorption specific surface area of 90 to 120 m ² / g and a DBP oil absorption of 90 to 120 ml / g.
100 g of carbon black (Y) is mixed so that the total of the carbon blacks (X) and (Y) is 60 to 120 parts by weight, and carbon black (X),
(Y) Specific nitrogen adsorption specific surface areas S (X), S (Y)
Is the following relationship

(Equation 4) And the average glass transition temperature Tg of the raw rubber (A)
A and the average glass transition temperature TgB of the raw rubber (B) are
The following relationship is satisfied: 20 ° C.>TgA> −45 ° C., and the terminal-modified diene rubber of the raw rubber (A) is an alkali metal or a synthetic terminal of the rubber molecule of the solution-polymerized diene raw rubber. At least 20% of the alkaline earth metal is -CO-N <or -CS-N <in the molecule.
A styrene-butadiene copolymer rubber and / or a polybutadiene rubber obtained by reacting with a compound having a bond, while the diene rubber to which the raw rubber (A) is coupled is a solution-polymerized diene rubber. A styrene-butadiene copolymer rubber and / or polybutadiene rubber obtained by reacting at least 20% of the alkali metal or alkaline earth metal at the synthetic end of the rubber molecule of the raw rubber with tin halide or silicon halide, The rubber composition, wherein the raw rubber (A) comprises a styrene-butadiene copolymer rubber obtained by solution polymerization, and the raw rubber (B) comprises a styrene-butadiene copolymer rubber synthesized by emulsion polymerization. Provided.

Further, according to the present invention, there is provided a rubber composition for a tire obtained by using the above rubber composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the structure, operation and effect of the present invention will be described in detail. The present inventors have found that the tan δ of the rubber composition is almost independent of the rubber adsorbed phase near the filler such as carbon black, and is due to only the matrix phase. Tanδ by isolation
It has succeeded in improving the balance.

In addition, the present inventors have developed a tight network consisting of a polymer / carbon gel at the stage of pre-mixing with a polymer under specific conditions using at least one or more carbon blacks of a certain grade or higher. By forming, the abrasion resistance can be improved.

[0010] Therefore, in the first means, the raw material rubber having a high reactivity with the carbon black, including a terminal-modified and / or coupled diene rubber, is brought into contact with the carbon black so that the surface of the carbon black is reduced. Wrap,
Subsequently, by adding a raw material rubber composed of a diene-based rubber having low terminal modification and / or uncoupled with low reactivity, carbon used for obtaining a rubber composition for tire tread excellent in tan δ balance of vulcanized rubber is obtained. A black-containing rubber composition can be provided, and the abrasion resistance of the vulcanized rubber is improved by setting the relationship between the amounts of the raw rubber to be premixed, the carbon black, and the softener under specific conditions. A carbon black-containing rubber composition used for obtaining a composition for a tire tread can be provided.

The carbon black used in the present invention includes a nitrogen adsorption specific surface area (ASTM D 303).
7) 130-200 m ² / g, DBP oil absorption (measured in accordance with JIS K 6221) 100-
130 ml / 100 g of high-grade carbon black (X) alone or this carbon black (X) and a nitrogen adsorption specific surface area of 90 to 120 m ² / g, DB
Two types of carbon black mixtures with carbon black (Y) having a P oil absorption of 90 to 120 ml / 100 g are used in any case in a range of 60 to 120 parts by weight. When the latter is used in a mixed system of carbon blacks, the compounding ratio is appropriately selected and used, but in order to make the obtained vulcanized rubber composition have abrasion resistance, these carbon blacks (X), It is necessary that the composition of (Y) is determined so that the following relationship is satisfied when the respective nitrogen adsorption specific surface areas are S (X) and S (Y).

(Equation 5)

However, according to the present invention, diene rubbers synthesized by solution polymerization and terminal-modified and / or coupled (for example, polybutadiene rubber (BR),
Raw rubber (A) containing 20 to 100% by weight, preferably 20 to 80% by weight, and most preferably 50 to 80% by weight of styrene-butadiene copolymer rubber (SBR) and styrene-propylene-butadiene copolymer rubber (SIBR). ) 50
-90 parts by weight, preferably 50-80 parts by weight, and a raw material comprising at least one type of diene rubber (for example, emulsion- or solution-polymerized BR, SBR, SIBR) which has not been terminally modified and / or coupled. Rubber (B)
The nitrogen adsorption specific surface area is 130 to ²⁰⁰ m ² / g and the DBP oil absorption is 100 to 130 parts by weight with respect to 100 parts by weight of the raw rubber composed of 50 to 10 parts by weight, preferably 50 to 20 parts by weight.
ml / 100 g of carbon black (X) alone or this carbon black (X) and nitrogen adsorption specific surface area 9
0-120 m ² / g, DBP oil absorption 90-120 ml / 1
A mixture with 00 g of carbon black (Y) is 60 to 1
A rubber composition comprising 20 parts by weight, preferably 60 to 100 parts by weight, and 20 to 80 parts by weight, preferably 35 to 70 parts by weight of a softener (for example, an aromatic process oil or a naphthenic process oil). In the production of the raw rubber (A), the average glass transition temperature TgA (° C.) and the average glass transition temperature TgB (° C.) of the raw rubber (B) are as follows: TgA + 20>TgB> TgA-20, preferably 20>TgA> −45 and TgA + 20>TgB> TgA−10, and 80 to 100% by weight, preferably 85 to 100% by weight of the total amount of the raw rubber (A) and carbon black
And the softener with the following relationship:

(Equation 6) First, at a temperature of 135 ° C. or more, preferably 130 to 150 ° C., for example, mixed with a closed mixer such as a Banbury mixer, and then the raw rubber (B) and the remaining carbon black, a softener and other compounding agents are mixed. , Preferably 135
A desired rubber composition can be obtained by mixing at a temperature of not less than ° C.

The terminal-modified diene rubber used in the present invention may be, as described in JP-A-64-60604, an alkali metal (Sol, SBR, BR) or the like at the synthetic terminal of rubber molecules such as solution-polymerized SBR and BR according to a conventional method. For example, a compound having a -CO-N <or -CS-N <bond in a molecule (e.g., N, N
Amides such as -diethylformamide, N, N-dimethylacetamide, N, N-dimethylbenzamide;
Ureas such as N, N'-dimethylurea, N, N'-dimethylethyleneurea, ε-caprolactam, N-methyl-
ε-caprolactam, N-methyl-2-pyrrolidone, N
Lactams such as -vinyl-2-pyrrolidone; compounds described in JP-A-61-103904; 1,3-dimethyl-2-imidazolidin; and 1,3-dimethylethylenethiourea; And the like, compounds described in a gazette, etc.). At this time, the effect is higher as the modification rate of the synthetic terminal is higher, and usually, a modification rate of 20% or more is used.

The coupled diene rubber used in the present invention can be prepared by a conventional method, for example, by using an alkali metal or alkaline earth metal at the terminal of a rubber molecule of a solution-polymerized diene rubber (SBR, BR, etc.). Alternatively, the remaining terminal alkali metal or alkaline earth metal of the diene rubber terminal-modified by the above method is reacted with at least 20%, preferably 30 to 50%) of, for example, a tin halide or a silicon halide according to a conventional method. Can be obtained.

As described above, according to the present invention, in the first step, the specific diene-based raw rubber (A) and the specific carbon black are first mixed at a temperature of 135 ° C. or more, so that the terminal rubber is formed around the carbon black particles. Since a rubber-adsorbed phase such as a modified SBR is provided and the raw material rubber (B) serving as a matrix phase is blended therein, a desired vulcanized product can be obtained. If the mixing temperature is less than 135 ° C., the reaction between the carbon particles and the terminal-modified (and / or coupled) diene rubber (A) is insufficient, and the desired effect cannot be obtained.

The rubber composition of the present invention contains, in addition to the above-mentioned polymer component, reinforcing agent and softening agent, sulfur, a vulcanization accelerator, an antioxidant, other fillers, a plasticizer, and other additives for automobile tires. Various additives generally compounded in the rubber composition can be compounded, and the compound can be vulcanized by a general method. The amount of these additives is also
It can be a general amount. For example, the amount of sulfur is preferably 0.5 parts by weight or more, more preferably 1.0 to 2.5 parts by weight, per 100 parts by weight of the rubber component.
Vulcanization conditions are also in a general range. These additives are generally blended after the completion of the first and second steps, but are not limited thereto.

[0017]

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.

[Blending Components] The blending components used in the blending of each of the examples and comparative examples are as follows. SBR1: glass transition temperature -30 ° C., bound styrene content 20%, vinyl bound content 65%, weight average molecular weight 350,000,
Terminal modified / coupling-treated solution-polymerized styrene-butadiene copolymer having a coupling ratio of 75% SBR2: 33 having a glass transition temperature of -21 ° C, a bound styrene amount of 45%, a vinyl bond amount of 12%, and a weight average molecular weight of 1.2 million. 0.3% oil-extended emulsion-polymerized styrene-butadiene polymer SBR3: glass transition temperature -25 ° C, bound styrene content 15%, vinyl bonded content 75%, weight average molecular weight 350,000,
Copolymerized styrene-butadiene copolymer with terminal modification / coupling treatment solution having a coupling ratio of 70% carbon black 1: nitrogen adsorption specific surface area 150 m ² /
g, DBP oil absorption 127 ml / 100 g carbon black 2: nitrogen adsorption specific surface area 117 m ² /
g, DBP oil absorption 112 ml / 100 g zinc oxide: zinc white No. 3 stearic acid: industrial stearic acid antioxidant 6C: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine aroma oil: Aromatic process oil Powder sulfur: Powder sulfur treated with 5% oil Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazylsphenamide

[Preparation of Samples] The samples used in the measurements of the examples and comparative examples were prepared as follows.
In the case of the two-step mixing, the first step involves mixing the vulcanization accelerator and the components other than sulfur with a 1.8-liter closed mixer.
Knead for ~ 4 minutes and release the masterbatch when it reaches 150 ± 5 ° C with the remaining ingredients in the second step, 1.8.
Mix for 3-5 minutes with a closed liter mixer,
The vulcanization accelerator and sulfur were kneaded with an 8-inch open roll to the master batch of the second step released when the temperature reached ± 5 ° C., to obtain a rubber composition. In the case of one-step mixing, the vulcanization accelerator and components other than sulfur are kneaded in a 1.8-liter closed mixer for 3 to 4 minutes, and the masterbatch released when the temperature reaches 165 ± 5 ° C. The sulfur was kneaded with an 8-inch open roll to obtain a rubber composition. The composition was then placed in a 15 × 15 × 0.2 cm mold at 160 ° C. for 2 hours.
A test specimen was prepared by press vulcanization for 0 minutes to obtain a sample for evaluating vulcanization properties.

[Test Method] The test methods for vulcanizate properties of the compositions obtained in Examples and Comparative Examples are as follows. Vulcanization properties 1) 300% denaturing stress, breaking strength: JIS K 625
1 (measured in accordance with No. 3 dumbbell shape) 2) tan δ: Measured with a rheograph solid manufactured by Toyo Seiki Seisakusho at 20 Hz, initial elongation 10%, dynamic strain 2% (sample width 5 mm, temperature 0 ° C.) 3) Abrasion resistance: Measured with a Lambourn type abrasion tester, and the wear loss is displayed as an index. However, the reference test pieces were calculated as Comparative Examples 1 and 6 in Tables I and II, respectively.

Examples 1-4 and Comparative Examples 1-5 In Examples 1-4 and Comparative Examples 1-5, SBR1 (glass transition temperature -30 ° C, bound styrene content 20%, vinyl bound content 65%, weight Average molecular weight 350,000, coupling ratio 75
% Terminal modification / coupling treatment solution polymerized styrene-butadiene copolymer) and SBR2 (glass transition temperature-
21 ° C, bound styrene amount 45%, vinyl bound amount 12%,
A 33.3% oil-extended emulsion-polymerized styrene-butadiene polymer having a weight average molecular weight of 1.2 million) as a raw material rubber,
As shown in Table I, other components were blended and the vulcanization properties were evaluated. The results are shown in Table I below.

[0022]

[Table 1]

From the results in Table I, it is found that the rubber compositions of Examples 1-4 satisfying all the requirements specified in the present invention have the formulas I and
It is understood that the condition of II is satisfied, the balance of tan δ is good, and the wear resistance is excellent. On the contrary,
As in Comparative Examples 2 and 3, even if a predetermined amount of carbon black 1 is added to Comparative Example 1, if the rubber components of SBR 1 and 2 are not separately mixed and the condition of Formula 2 is not satisfied, This shows that the balance of tan δ is poor and the wear resistance is not improved. Also, as in Comparative Example 4, carbon black 1 which is a high-grade carbon black
Was not used, the conditions of the formulas I and II were not satisfied even when the split mixing of the rubber components of SBR1 and 2 was taken,
It shows that the balance of tan δ is excellent but there is no improvement in wear resistance. Further, as in Comparative Example 5, when carbon black 1, which is a high-grade carbon black, was not used, SBR1 and SBR2 were used in the first step, and the rubber component using SBR1 was divided and mixed in the second step. At times, the condition of Formula I is not satisfied, and as a result, tan δ
This shows that the balance and wear resistance are also inferior.

Examples 5 to 7 and Comparative Example 6 In Examples 5 to 7 and Comparative Example 6, SBR3 (glass transition temperature -25 ° C., bound styrene content 15%, vinyl bound content 7
5%, a weight-average molecular weight of 350,000, a terminal-modified / coupling-treated solution-polymerized styrene-butadiene copolymer having a coupling ratio of 70%) and SBR2 (glass transition temperature: -21)
° C, 45% bound styrene, 12% vinyl bound, 33.3% oil-extended emulsion-polymerized styrene-butadiene polymer having a weight average molecular weight of 1.2 million) as the raw material rubber and Table II
As shown in Table 2, other components were blended to evaluate the vulcanization properties. The results are shown in Table II below.

[0025]

[Table 2]

From the results in Table II, the rubber compositions of Examples 5 to 7 satisfying all the requirements specified in the present invention have the formulas I and
It is understood that the condition of II is satisfied, the balance of tan δ is good, and the wear resistance is excellent. On the contrary,
As in Comparative Example 6, SBR3 having good reactivity with carbon
Is used together with SBR2, and when carbon black 1, which is a high-grade carbon, is used, when these are mixed together with other components, the condition of Formula II is not satisfied, and the balance of tan δ is not satisfied. In addition, it shows that both the abrasion resistance and the abrasion resistance are inferior to those of the examples.

[0027]

As described above, according to the present invention,
It is possible to obtain a rubber composition having an improved balance of tan δ and also improved abrasion resistance, and by using this as a rubber composition for a tire tread, a tire having excellent performance with low fuel consumption. Is provided.

Claims (7)

[Claims] 1. A raw rubber (A) containing 20 to 100% by weight of a terminal-modified and / or coupled diene rubber.
Raw rubber 100 composed of 50 to 90 parts by weight and 50 to 10 parts by weight of raw rubber (B) composed of at least one type of diene rubber not subjected to terminal modification and / or coupling
The nitrogen adsorption specific surface area is 130 to ²⁰⁰ m ^{2 with} respect to parts by weight.
/ G, 60-120 parts by weight of carbon black (X) having a DBP oil absorption of 100-130 ml / 100 g and a softener 20
In a rubber composition obtained by mixing 80 parts by weight, the average glass transition temperature TgA (° C.) of the raw rubber (A) and the average glass transition temperature TgB (° C.) of the raw rubber (B) are as follows: TgA + 20>TgB> TgA-20, and the total amount of raw rubber (A) and carbon black is 80
１００100% by weight and 50-100% by weight of the total amount of the softener are defined as follows: After mixing at a temperature of 135 ° C. or more, the raw rubber (B)
And a remaining carbon black and a softening agent. 2. The carbon black (X)
Carbon black (Y) having a nitrogen adsorption specific surface area of 90 to 120 m ² / g and a DBP oil absorption of 90 to 120 ml / 100 g
When the sum of the carbon blacks (X) and (Y) is 6
0 to 120 parts by weight of carbon black (X) and (Y).
(X) and S (Y) have the following relationship: The rubber composition according to claim 1, which is: 3. The average glass transition temperature T of the raw rubber (A)
The rubber composition according to claim 1, wherein gA and the average glass transition temperature TgB of the raw rubber (B) satisfy the following relationship: 20 ° C.>TgA> −45 ° C. 4. 4. The diene-based rubber whose terminal rubber is modified from the raw rubber (A) is an alkali metal or alkaline earth metal of a synthetic terminal of rubber molecules of the diene-based raw rubber obtained by solution polymerization.
A styrene-butadiene copolymer rubber and / or polybutadiene rubber obtained by reacting 0% or more with a compound having a -CO-N <or -CS-N <bond in a molecule. 9. The rubber composition according to claim 1. 5. The diene rubber to which the raw rubber (A) has been coupled has a tin halide of 20% or more of the alkali metal or alkaline earth metal at the synthetic end of the rubber molecule of the diene raw rubber obtained by solution polymerization. The rubber composition according to any one of claims 1 to 4, which is a styrene-butadiene copolymer rubber and / or a polybutadiene rubber obtained by reacting with a silicon halide. 6. The raw rubber (B) wherein the raw rubber (A) comprises a solution-polymerized styrene-butadiene copolymer rubber.
Is a styrene-butadiene copolymer rubber synthesized by emulsion polymerization. The rubber composition according to any one of claims 1 to 5, wherein 7. A rubber composition for a tire, obtained by using the rubber composition according to any one of claims 1 to 6.