JP2003012863A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which has tan δ of improved temperature dependency, is excellent is abrasion resistance, tensile strength and elongation at break, and is suitably applicable, for example, to a tire tread use. SOLUTION: (A) 40-120 pts. of a SBR-CB rubber composition comprising SBR and carbon black (CB) having N2 SA (N2 specific surface area) of >=70 m<2> /g and (B) 40-120 pts. of a NR-CB rubber composition comprising NR and CB having N2 SA of >=70 m<2> /g, are added and mixed with (C) a material rubber of BR and/or SBR having Tg higher than that of SBR contained in the SBR-CB rubber composition (A) by >=10 deg.C, by an amount to obtain the rubber composition containing <=80 pts. of a total softener amount based on 100 pts. of the total rubber amount. In the rubber composition, the ratio of FMB which is an average CB concentration in relation to the rubber amount in the CB-containing rubber compositions (A) and (B), to FCOM which is a CB concentration in relation to the rubber amount in the rubber composition obtained by mixing using an internal mixer, is 1.2-3.0.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a styrene-butadiene copolymer rubber (SBR) -carbon black (CB).
A rubber composition obtained by mixing a raw material rubber having a Tg higher than that of SBR with a masterbatch composed of and a natural rubber (NR) -carbon black (CB) masterbatch in a specific ratio in an internal mixer, and more specifically, t
A rubber composition having improved temperature dependence of an δ and having significantly improved abrasion resistance, tensile strength, elongation at break, etc., which cannot be obtained by a conventional master batch of SBR system alone, and is suitable for pneumatic tires, for example. Regarding things.

[0002]

2. Description of the Related Art Conventionally, various proposals have been made for compounding carbon black with rubber by various methods to obtain a rubber composition having improved physical properties such as viscoelasticity. For example, Japanese Patent Application Laid-Open No. 9-67469 discloses a method in which carbon black is dividedly added to a terminal-modified rubber having a low Tg and a rubber having a high Tg. JP-A-9-324077 discloses the use of a wet masterbatch of carbon black and solution-polymerized SBR. JP-A-10
No. 237230 discloses a method using a wet masterbatch of carbon black and emulsion-polymerized SBR. JP-A 2000-336208 discloses that carbon black and SBR having a low viscosity and a low Tg are used for mixing.

[0003]

As described above, it has been proposed to improve the balance of tan δ of the tire tread rubber in order to reduce the fuel consumption of automobiles.
Specifically, it has been proposed to combine the compounding components, mix and mix, and further use a terminal-modified rubber. However, such a proposal is still insufficient, and further improvement is desired. Here, the temperature dependence of tan δ is improved at 0 ° C.
It means that the temperature dependence of tan δ at 60 ° C. increases. For example, the split mixing improves fuel economy, temperature dependence of tan δ, and wear resistance, but at the same time, causes an inconvenience to the process due to an increase in mixing steps. In addition, when silica or rubber having a high molecular weight is used in the divided mixing, the workability and the load on the process are further increased.

Therefore, an object of the present invention is to overcome the above-mentioned problems of the prior art, improve the temperature dependence of tan δ of vulcanized rubber, and have excellent wear resistance, tensile strength, elongation at break, etc. It is to provide a rubber composition that can be suitably used for a tire tread.

[0005]

According to the present invention, (A)
SBR-CB rubber compositions 40 to 12 in which the weight ratio of carbon black (CB) to at least one styrene-butadiene copolymer rubber (SBR) is 0.4 to 1.
0 parts by weight and NR-C in which the weight ratio of carbon black (CB) to (B) natural rubber (NR) is 0.4 to 1.
40 to 120 parts by weight of the B rubber composition, and (C) the SBR.
-Butadiene rubber (BR) and / or styrene-butadiene copolymer rubber (SBR) having a Tg higher than the Tg of the SBR raw material rubber in the CB rubber composition (A) by 10 ° C or more
A rubber composition (C obtained by adding a raw material rubber consisting of 100 parts by weight and a total amount of the softening agent of 80 parts by weight or less and mixing them in an internal mixer.
OM), which is the average value F of the CB concentration with respect to the total amount of rubber in the CB-containing rubber compositions (A) and (B).
Carbon black (C) based on the amount of rubber in the rubber composition (COM) obtained by mixing _MB with an internal mixer
B) A rubber composition having a concentration F _COM of a ratio F _MB / F _COM of 1.2 to 3.0 is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the constitution, operation and effect of the present invention will be described in detail. According to the invention, firstly the SBR
To the carbon black having a nitrogen specific surface area (N ₂ SA) of 70 m ² / g or more, preferably 90 m ² / g or more, is 0.4 to 1, preferably 0.6 to 1, and if necessary. A SBR-CB rubber composition (A) is obtained by mixing process oil, a plasticizer, an antioxidant, and the like. The SBR used here includes any SBR (emulsion polymerization or solution polymerization) conventionally used for a rubber material member used in a pneumatic tire, particularly a cap tread portion, and preferably contains styrene contained in the SBR. 10% by weight or more,
The SBR has a vinyl content of 20 mol% or more and a weight average molecular weight of 100,000 or more. Carbon black having a nitrogen specific surface area of 70 m ² / g or more, preferably 90 m ² / g or more can be used. As the method for producing the SBR-CB rubber composition (A) in the present invention, for example, the method disclosed in JP-A-10-237230 may be used.

According to the invention, the weight ratio of carbon black to NR is 0.4 to 1, preferably 0.6 to 1,
Further, if necessary, a process oil, a plasticizer, an antioxidant and the like are mixed to obtain an NR-CB rubber composition (B). Here, carbon black has a nitrogen specific surface area of 70 m ² /
It is possible to use those having a weight of at least g, preferably at least 90 m ² / g. The method for producing the NR-CB rubber composition (B) in the present invention is described in, for example, JP-A 2000-5078.
The method disclosed in Japanese Patent Publication No. 92 may be used.

According to the present invention, 40 to 120 parts by weight, preferably 49 to 11 parts by weight of the SBR-CB rubber composition (A).
6 parts by weight and 40 to 1 of the NR-CB rubber composition (B)
20 parts by weight, preferably 116 to 49 parts by weight, is mixed with the raw material rubber (C) in an amount such that the total rubber amount is 100 parts by weight and the total softening agent amount is 80 parts by weight or less.

The softening agent used in the present invention can be any softening agent conventionally blended in a rubber composition, and specifically, aromatic process oil, paraffin oil and the like can be mentioned. . The compounding amount thereof is 80 parts by weight or less, preferably 10 to 50 parts by weight, per 100 parts by weight of the total rubber. If the blending amount is too large, the reinforcing property of the rubber composition is deteriorated, which is not preferable.

According to the present invention, the Tg of the raw material SBR in the SBR-CB rubber composition (A) is higher by 10 ° C. or more,
Preferably, a raw rubber (C) made of BR and / or SBR having a Tg higher than 20 ° C. is added and mixed in an internal mixer such as a Banbury mixer to obtain a rubber composition (COM). If the difference in Tg is less than 10 ° C, tan δ
It is not preferable because the desired effect may not be obtained in the temperature dependence of.

As the raw rubber (C), there is no particular problem as long as the glass transition temperature is satisfied, and for example, any emulsion-polymerized or solution-polymerized polybutadiene and styrene-butadiene copolymer can be used.

The compounding amount of these raw material rubbers is 100 parts by weight as the total amount of rubber and 80 parts by weight or less of the softening agent, and the desired rubber composition is obtained by kneading in a closed mixer. be able to.

According to the present invention, the average value F of the CB concentration with respect to the total amount of rubber in the rubber compositions (A) and (B) is F.
Rubber composition (COM) after kneading with _MB and internal mixer
Ratio F of carbon black concentration F _COM to rubber in F
_MB / F _COM is preferably 1.2 to 3.0.
More preferably, it is 3 to 2.0. If this ratio is too small, the desired effect may not be obtained in the temperature dependence of tan δ, which is not preferable, and conversely, if it is too large, the workability deteriorates, which is not preferable.

The SBR in the SBR-CB rubber composition (A) of the present invention has a styrene content of 30% by weight or less and is emulsion polymerized S.
BR is preferred. If this styrene content is too high, SBR
It is not preferable because the Tg of itself increases and the difference in Tg becomes less than 10 ° C.

The carbon blacks used in the rubber compositions (A) and (B) of the present invention may be the same or different, and any carbon black conventionally used in rubber compositions for tires can be used. .

On the other hand, SBR in the rubber composition (C) of the present invention
Has a styrene content of 20 to 50% by weight, preferably 30
~ 50% by weight. If the styrene content is low, SB
This is not preferable because the Tg of R itself decreases and the difference in Tg becomes less than 10 ° C. On the other hand, when the amount of styrene is large, the rigidity of the rubber molecule is increased, and the balance of elongation and strength of the rubber material is deteriorated, which is not preferable. Further, in the case of SBR in the rubber composition (C) of the present invention, particularly in the case of SBR by the solution polymerization method, the vinyl content in the rubber is 1 in the butadiene site:
It is 0 to 70 mol%, preferably 30 to 70 mol%. If the vinyl content is low, the Tg of SBR itself will decrease,
The Tg difference is less than 70 ° C, which is not preferable. On the other hand, if the amount of vinyl is large, SBR, which is originally incompatible with NR, is compatible, and the tan δ temperature dependence is deteriorated, which is not preferable.

In addition to the above-mentioned essential components, the rubber composition according to the present invention is generally used as a vulcanizing agent such as sulfur, a vulcanization accelerator, a vulcanization retarder, an antiaging agent, a wax, and other rubber drugs. Ingredients can be used and the amounts used can be conventional.

[0018]

EXAMPLES The contents and effects of the present invention will be described more specifically below with reference to Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Examples 1 to 7, standard examples and comparative examples 1 to 4 Rubber compositions having the formulations shown in Table I were prepared and their physical properties were evaluated. The formulations of the master batches 1 to 6 used in the formulation of the standard examples, examples and comparative examples are as follows.

Compounding of Masterbatch 1 Raw rubber latex: styrene content 36%, vinyl content (in BR component) 16%, glass transition temperature -36
Emulsion-polymerized SBR latex carbon black N339 with a weight average molecular weight of 720,000: Tokai Carbon Co., Seast KH oil: aromatic process oil blending ratio: rubber latex / carbon black / oil =
70/65/30

Blending of Masterbatch 2 Raw material rubber latex: Natural rubber latex carbon black having a weight average molecular weight of 1 million N339: Tokai Carbon Co., Ltd., KIST oil: Aromatic process oil blending ratio: rubber latex / carbon black / oil =
70/65/30

Compounding of Masterbatch 3 Raw material rubber: styrene content 36%, vinyl content (in
BR component) 16%, glass transition temperature -36 ° C, weight average molecular weight 720,000, 37.5 phr oil-extended emulsion-polymerized SBR carbon black N339: Tokai Carbon Co., Shihto KH oil: aromatic process oil blending ratio: oil-extended rubber / Carbon black / oil = 96.
25/65 / 3.75

Compounding of Masterbatch 4 Raw material rubber: Natural rubber carbon black N339 having a weight average molecular weight of 1,000,000: Tokai Carbon Co., Shihto KH oil: Aromatic process oil compounding ratio: rubber / carbon black / oil = 70/65
/ 30

Compounding of Masterbatch 5 Raw rubber latex: styrene content 36%, vinyl content (in BR component) 16%, glass transition temperature -36
Emulsion-polymerized SBR latex carbon black N339 with a weight average molecular weight of 720,000: Tokai Carbon Co., Seast KH oil: aromatic process oil blending ratio: rubber latex / carbon black / oil =
90/65/30

Blending of Masterbatch 6 Raw rubber latex: Natural rubber latex carbon black having a weight average molecular weight of 1,000,000 N339: Tokai Carbon Co., Shist KH oil: Aromatic process oil blending ratio: Rubber latex / carbon black / oil =
90/65/30

Mixing master batches 1, 2, 5 and 6
Method A rubber latex aqueous solution, a carbon black suspension aqueous solution, and an oil soap emulsion are adjusted to a predetermined composition, and simultaneously mixed and stirred to uniformly disperse them. Then, the mixture is coagulated with an acid or the like, dehydrated and dried.

Mixing method of master batches 3 and 4 rubber, carbon black and oil are mixed in predetermined amounts,
Mix mechanically in an internal mixer. The mixture was rolled into a sheet.

Sample Preparation Each of the components shown in Table I, except for sulfur and vulcanization accelerator, was 1.
Knead with an 8 liter Banbury mixer for 3-5 minutes,
It was released when it reached 165 ± 5 ° C. Next, the vulcanization accelerator and sulfur were kneaded with an 8-inch open roll to obtain a rubber composition.

The sample composition obtained was treated with 15 × 15 ×
The target test pieces were prepared by press vulcanization at 160 ° C. for 20 minutes in a 0.2 cm mold, and the vulcanized physical properties were evaluated. The results are shown in Table I.

The test methods for the vulcanized physical properties of the compositions obtained in each example are as follows. 1) 300% deformation stress, breaking strength and breaking elongation: JIS
It measured based on K6251 (dumbbell-shaped No. 3 type). 2) tan δ: Measured with a viscoelastic device Rheographic Solid manufactured by Toyo Seiki Seisakusho at 20 Hz, initial elongation of 10% and dynamic strain of 2% (sample width 5 mm, temperature 0 ° C. and 60 ° C.)

3) Abrasion resistance: Measured with a Lambourn type abrasion tester, and the abrasion loss was expressed as an index by the following method. Abrasion resistance (index) = [(weight loss in the test piece of Comparative Example 7) /
(Reduction in weight of each test piece)] × 100

[0032]

[Table 1]

Table I Footnote SBR 1: Styrene content 36%, vinyl content (in
BR component) 16%, glass transition temperature -36 ° C, weight average molecular weight 720,000, 50 phr oil extended emulsion polymerization SBR SBR2: styrene content 25%, vinyl content (in
BR component) 16%, glass transition temperature -51 ° C, weight average molecular weight 620,000, 37.5 phr oil extended emulsion polymerization SBR SBR3: styrene content 48%, vinyl content (in
BR component) 14%, glass transition temperature-21 ° C, weight average molecular weight 680,000, 50 phr oil-extended emulsion polymerization SBR

Carbon black N339: Tokai Carbon Co., Ltd., Seast KH, N ₂ SA = 92 m ² / g Zinc oxide: Zinc white No. 3 stearic acid: Industrial stearic acid antioxidant 6C: N-phenyl-N '-( 1,3-Dimethylbutyl) -p-phenylenediamine wax: Industrial paraffin wax Softener: Aromatic process oil Sulfur powder: 5% Oil-extended powder Sulfur vulcanization accelerator CZ: N-cyclohexyl-2-benzotidylsulfene Amide

The standard example is an example in which SBR1 and SBR2 and carbon black are mechanically mixed simultaneously in an internal mixer. Comparative Example 1 uses SBR2 in a masterbatch and S
This is an example of mixing with BR1. By mixing SBR2 in a masterbatch, ta at 0 ° C.
n δ was significantly improved, tan δ at 60 ° C. was decreased, and the tan δ gradient was increased. On the other hand, Examples 1 to 3 are examples in which the master batches of SBR and NR were used together according to the present invention. By replacing the master batch of NR, the breaking strength, breaking elongation, wear resistance and tan δ gradient were improved. Comparative Example 2 is an example of a master batch of NR. Compared with the present Examples 1 to 3, the fracture properties and the tan δ gradient were improved, but 0
The tan δ at ℃ and the wear resistance decreased.

Examples 4 to 6 are examples in which master batches obtained by mechanical mixing with an internal mixer were used. Although the physical properties at break, the tan δ gradient and the wear resistance were improved as compared with Comparative Example 1, the physical properties at break and the tan δ gradient were decreased as compared with Example 2.

Comparative Example 3 is an example in which the difference in Tg is less than 10 ° C. Tan δ at 60 ℃ decreased, but tan at 0 ℃
δ has also dropped significantly, and the slope has also deteriorated. vice versa,
Example 7 is an example in which the Tg difference is large, and a significant increase in tan δ at 0 ° C. and a significant improvement in the tan δ gradient were observed without lowering other physical properties.

Comparative Example 4 is an example in which the value of F _MAS / F _COM is 1.2 or less. A significant decrease in the tan δ slope was seen.

[0039]

As described above, according to the present invention, t
It is possible to maintain or improve the fracture properties, wear resistance and the like while improving the temperature dependence of an δ and the absolute value of tan δ.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C08L 91/00 C08L 91/00

Claims (5)

[Claims] 1. A weight ratio of (A) carbon black (CB) having a nitrogen specific surface area (N ₂ SA) of 70 m ² / g or more to at least one styrene-butadiene copolymer rubber (SBR) is 0.4 to. 40 to 120 parts by weight of the SBR-CB rubber composition which is 1, and (B) natural rubber (NR)
40 to 120 parts by weight of an NR-CB rubber composition in which the weight ratio of carbon black (CB) having a nitrogen specific surface area (N ₂ SA) of 70 m ² / g or more to 0.4 is 0.4 to 1, and (C)
A total of raw material rubbers made of butadiene rubber (BR) and / or styrene-butadiene copolymer rubber (SBR) having a Tg higher than that of the SBR raw material rubber in the SBR-CB rubber composition (A) by 10 ° C. or more. A rubber composition (COM) obtained by adding the rubber in an amount such that the amount of the rubber is 100 parts by weight and the total amount of the softening agent is 80 parts by weight or less, and mixing the mixture in an internal mixer. rubber composition (a) and the average value F _MB of CB concentration to the total amount of rubber in (B), an internal rubber composition obtained by mixing in a mixer carbon black to rubber content in (COM) (CB) Concentration F _COM ratio F _MB / F _COM is 1.2 to 3.0
A rubber composition. 2. The SBR-CB rubber composition (A) is S
The rubber composition according to claim 1, which is a rubber composition obtained by coagulating, dehydrating and drying a rubber latex mixture in which a weight ratio of carbon black (CB) to BR raw material latex (solid content) is 0.4 to 1. object. 3. The NR-CB rubber composition (B) is NR
The rubber composition according to claim 1 or 2, which is a rubber composition obtained by coagulating, dehydrating and drying a rubber latex mixture in which the weight ratio of carbon black (CB) to the raw material latex (solid content) is 0.4 to 1. Composition. 4. The rubber composition according to claim 1, wherein the raw rubber (C) is SBR produced by solution polymerization and / or emulsion polymerization. 5. A pneumatic tire having a cap tread portion made of the rubber composition according to any one of claims 1 to 4.