JP3240770B2 - Method for producing rubber composition - 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 having excellent processability and vulcanizate properties. And a method for producing a rubber composition for tire treads.

[0002]

2. Description of the Related Art Conventionally, polybutadiene-based synthetic rubbers, particularly cis-1,4-polybutadiene rubber, have good abrasion resistance,
Utilizing features such as high rebound resilience, good low-temperature properties, good bending resistance, and low heat build-up, it is widely used as a blend with natural rubber and / or isoprene rubber, especially for tire applications.

[0003] Recently, from the viewpoint of reducing fuel consumption and weight without impairing the safety of the automobile, particularly without reducing the wet skid of the tread of the automobile tire, the rebound resilience which is an index of the fuel economy is improved, and the tread of the tread is improved. There is a strong demand for improvements in tensile properties and abrasion resistance so that the weight of the tire can be reduced by reducing the thickness.

In general, it is considered that the characteristics of these tires largely depend on the wear resistance and dynamic viscoelasticity of the tire tread rubber material. However, it is known that safety and low fuel consumption are properties of rubber materials that conflict with each other, and it has been difficult to improve the rebound resilience without dropping a wet skid. Here, the index of the wet skid is 0
Tanδ at 15 ° C and 15 Hz is well known.

In order to improve the tensile properties and abrasion resistance of polybutadiene rubber, a method for reducing the low molecular weight component in the molecular weight distribution of polybutadiene is known as a method for improving the molecular design. There was a problem that the Mooney viscosity increased and the processability deteriorated.

In the method using 1,2-polybutadiene rubber or cis-1,4-polybutadiene rubber and natural rubber and / or polyisoprene rubber as raw rubbers, rebound resilience is improved without dropping wet skids. There was no effect of improving the tensile properties and wear resistance.

[0007] Japanese Patent Publication No. 59-694 / 1984 and Japanese Patent Application Laid-Open No. 55-104343 disclose an improved mixing method using a rubber obtained by blending 1,2-polybutadiene rubber with natural rubber and / or isoprene rubber. As a method, a method of improving the rebound resilience without dropping the wet skid of the rubber composition has been proposed, but there is no effect of simultaneously improving the tensile properties and the wear resistance.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to devise a process for producing a compounded rubber in the use of a blend of polybutadiene rubber, preferably cis-1,4-polybutadiene rubber, and natural rubber and / or polyisoprene rubber. An object of the present invention is to provide a rubber composition which improves rebound resilience while maintaining a wet skid and lowers the Mooney viscosity of a compounded rubber to improve tensile properties and wear resistance.

[0009]

Means for Solving the Problems The present inventors have conducted various studies in order to solve the above-mentioned object, and as a result, the combination of raw rubbers is a combination of natural rubber and / or polyisoprene rubber and polybutadiene rubber. The kneading and mixing method of the raw rubber and the filler is a conventional method. After mechanically kneading and mixing the natural rubber and / or polyisoprene rubber as the raw rubber and the polybutadiene rubber, the filler and the rubber chemicals are mechanically mixed. It is not a one-stage kneading mixing method of kneading and mixing

A specific amount of a filler is mechanically kneaded with a specific amount of a natural rubber and / or a polyisoprene rubber, and a specific amount of the filler is specified by a specific amount. The rubber composition obtained by mechanically kneading and mixing the polybutadiene rubber of the present invention and the two-stage kneading and mixing method of mechanically kneading and mixing the two rubber compositions are used. In particular, it improves rebound resilience while maintaining an unexpected wet skid compared to the conventional one-stage kneading and mixing method, and lowers the Mooney viscosity of the compounded rubber to improve tensile properties and wear resistance. A rubber composition having an effect was obtained and solved.

That is, the present invention relates to (A) 30 to 70 parts by weight of a natural rubber and / or a polyisoprene rubber and (B) 70 to 30 parts by weight of a polybutadiene rubber; Fillers and rubber chemicals 3
In preparing a rubber composition by mixing 0 to 70 parts by weight, 1) A) 30 to 70 parts by weight of natural rubber and / or polyisoprene rubber, C) rubber excluding a filler and a vulcanization active component A rubber composition obtained by mechanically kneading and mixing 10 to 60% by weight of a chemical,

2) B) 70 to 30 parts by weight of polybutadiene rubber, C) 90 to 40% by weight of a rubber chemical excluding a filler and a vulcanizing active component, and mechanically kneading and mixing the rubber composition. D) 0 to 40 parts by weight of a softening agent with respect to 100 parts by weight of the raw rubber, and mechanically kneading and mixing the rubber composition of 1) and 2) with a vulcanizing active rubber chemical. This is a method for producing a characteristic rubber composition.

The natural rubber of component A) used in the present invention is a commercially available natural rubber, and polyisoprene rubber is a cis-1,4-polystyrene obtained by solution polymerization of isoprene using a transition metal catalyst. It is a polyisoprene rubber having a binding unit content of 90 mol% or more. And
Either natural rubber or polyisoprene rubber or a blend thereof is used.

The amount of the natural rubber and / or isoprene rubber used as the component A) in the present invention is 30 to 70 parts by weight, preferably 40 to 60 parts by weight. If it exceeds 70 parts by weight, the rebound resilience decreases.

The polybutadiene rubber of component B) used in the present invention is preferably a cis-1,4-polybutadiene rubber, which is obtained by polymerizing 1,3-butadiene using a transition metal catalyst. The amount of the polybutadiene rubber of the component B) used in the present invention is as follows:
The amount is 70 to 30 parts by weight, preferably 60 to 40 parts by weight. If it exceeds 70 parts by weight, the strength is poor, and if it is less than 30 parts by weight, the rebound resilience decreases.

The filler of the component C) used in the present invention is as follows:
There are carbon black, calcium carbonate, silica, magnesium carbonate and clay, but mainly carbon black. The carbon black is not particularly limited as long as it is generally used for an automobile tire tread, and includes various grades of ISAF, HAF, and the like. Other non-active rubber chemicals include zinc white, stearic acid and antioxidants commonly used in the rubber industry.

The amount of the filler (C) used in the present invention and the amount of the rubber chemical are 3 parts per 100 parts by weight of the raw rubber.
It is preferable to add 0 to 70 parts by weight, and if it is 30 parts by weight or less, there is a problem that the wear resistance is deteriorated, and if it is 70 parts by weight or more, the resilience decreases. In component C), the filler is usually 8
0 to 90% by weight.

The softening agent of component D) used in the present invention is
Aromatic, naphthenic and paraffinic oils usually used for rubber. Its usage is 0-40
Parts by weight, and if it exceeds 40 parts by weight, the wear resistance deteriorates.

As the vulcanizing active rubber chemical used in the present invention, vulcanizing agents and vulcanizing accelerators usually used in the rubber industry are used.

In order for the rubber composition comprising the combination of the raw rubber components and the filler as described above to exhibit the effects of the present invention, 1) the raw rubber composed of natural rubber and / or polyisoprene rubber and the filler Kneading and mixing, 2) preparing a rubber composition obtained by mechanically kneading and mixing the polybutadiene rubber and the filler, and adding a softening agent if necessary,
It is necessary to carry out a two-stage kneading method of mechanically kneading and mixing the rubber composition of 1) and 2).

This is because the present invention relates to A) natural rubber and / or
Or C) 30 to 70 parts by weight of carbon black and rubber chemicals as fillers with respect to 100 parts by weight of a raw rubber component composed of 30 to 70 parts by weight of polyisoprene rubber and 70 to 30 parts by weight of B) polybutadiene rubber. In the preparation of a rubber composition by compounding the above, 1) A) 30 to 70 parts by weight of natural rubber and / or polyisoprene rubber, C) rubber chemicals excluding carbon black as a filler and vulcanization active components A rubber composition obtained by mechanically kneading and adding 10 to 60% by weight of zinc white, stearic acid, an antioxidant, etc.

2) B) 70 to 30 parts by weight of polybutadiene rubber and C) 90 to 40% by weight of zinc black, stearic acid and an antioxidant which are rubber chemicals excluding fillers such as carbon black and vulcanizing active ingredients. To obtain a rubber composition which is mechanically kneaded and mixed, and D) a softening agent is added to 0 to 40 parts by weight with respect to 100 parts by weight of the raw rubber, and to the rubber compositions of 1) and 2). This is a two-stage kneading and mixing method in which a sulfur-active rubber chemical is mechanically kneaded and mixed.

The component (1) is 10 to 60 parts by weight of A) 30 to 70 parts by weight of natural rubber and / or polyisoprene rubber, and C) 30 to 70 parts by weight of rubber chemicals excluding filler and vulcanization active ingredient. % And mechanically kneaded and mixed to obtain a rubber composition. Here, the amount of the rubber chemicals excluding the filler and the vulcanization active component to be added is 10 to 60% by weight, preferably 20 to 45% by weight. And the effect of the present invention is not obtained.

Component 2) is B) polybutadiene rubber 7
To 0 to 30 parts by weight, C) 90 to 40% by weight of 30 to 70 parts by weight of the rubber chemicals excluding the filler and the vulcanizing active ingredient are added, and a rubber composition is kneaded and mixed mechanically. Rubber chemicals excluding fillers and vulcanization active ingredients to be added are 9
0 to 40% by weight, preferably 80 to 55% by weight;
If it exceeds 90% by weight or less than 40% by weight, the abrasion resistance deteriorates and the effect of the present invention is not obtained.

When mechanically kneading and mixing the rubber composition of 1) and 2) with a vulcanizing active rubber chemical, if necessary, D) a softener is added in an amount of 0 to 100 parts by weight of the raw rubber.
The kneading and mixing operation can be easily carried out by adding in the range of 40 parts by weight.

The feature of the present invention resides in that the above-mentioned special two-stage kneading method is carried out, and the rubber composition comprising the specific rubber component and the filler obtained by the method of the present invention has the same final composition as the one-stage kneader. The rebound resilience is improved while maintaining a wet skid equal to or higher than that of the rubber composition prepared by the kneading method, and the rubber Mooney viscosity is reduced to improve tensile properties and wear resistance.

The rubber composition thus obtained is vulcanized by a usual vulcanization method. The vulcanizate of the rubber composition of the present invention is mixed with the vulcanizate of the present invention obtained by a conventional one-stage kneading method. The vulcanizates of the rubber composition having the same composition as those described above are, in addition to having excellent rebound resilience, tensile properties and abrasion resistance, which are the effects of the present invention, as well as tear strength, electrical properties, and unvulcanized rubber compositions. Can be easily distinguished from the Mooney viscosity or the like.

[0028]

EXAMPLES The present invention will be described in detail with reference to examples.
Various measurements on the rubber compositions of Examples and Comparative Examples of the present invention were performed as follows. Measurement of Mooney Viscosity Mooney viscosity (MV) was measured according to a measurement method defined in JIS-K-6300. Measurement of tensile, rebound resilience and hardness The tensile test, rebound resilience and hardness of the vulcanizate are determined by JIS-K
It was measured according to the measurement method specified in -6301. The measurement of abrasion resistance and the abrasion resistance of the temperature-dispersed vulcanizate were performed using Lambourn abrasion (manufactured by Shimada Giken).
Was measured at room temperature under a slip ratio of 60%. The temperature dispersion of the vulcanized product was measured using RDA (manufactured by Rheometrics).

Kneading Method The kneading of the examples and comparative examples was carried out using a small Banbury mixer (1.8 L capacity). The kneading conditions were as follows: the initial Banbury control temperature was 60 ° C., the rotor speed was 40 rpm, and the oil temperature in the jacket was controlled so that the kneading temperature was 100 to 110 ° C.

Examples 1 to 4 and Comparative Examples 2 to 7 The cis-1,4-polybutadiene rubber in parts by weight shown in Tables 2 and 3 and the filler shown in Table 1 were added to the weight% shown in Tables 2 and 3 in advance.
Together with the rubber composition, kneaded in 5 minutes, the rubber composition kneaded in 5 minutes, 50 parts by weight of natural rubber and / or polyisoprene rubber in parts by weight shown in Tables 2 and 3, and the remaining filler were added, and in 2 minutes A kneaded rubber composition was prepared.
The two kneading compositions thus prepared, the vulcanization accelerator and sulfur were again charged into the Banbury mixer and kneaded for 3 minutes to complete the kneading. The Mooney viscosity was measured for the unvulcanized product, and press vulcanization was performed at 150 ° C. for 20 minutes in order to measure the vulcanized physical properties.

Comparative Examples 1 and 8 The kneading method of Comparative Examples 1 and 8 is the usual one-stage kneading method.
The parts by weight of cis-1,4-polybutadiene rubber and natural rubber shown in Tables 2 and 3 were simultaneously charged into a Banbury mixer,
After kneading for 30 seconds, all the compounding agents except for the vulcanization accelerator and sulfur were added and kneading was performed for 3 minutes and 30 seconds. The kneading composition, the vulcanization accelerator and sulfur thus prepared were again charged into the Banbury mixer, kneaded for 1 minute, and the same operation as above was performed.

Table 1 shows fillers other than the vulcanization active component. Tables 2 and 3 show the compounding ratio (parts by weight), filler type and distribution ratio, compounded rubber properties and vulcanized properties of Examples and Comparative Examples. From Examples 1 and 2 and Comparative Example 1, the present invention improves the rebound resilience while maintaining the wet skid and improves the tensile properties and abrasion resistance by lowering the blended rubber Mooney viscosity, despite the same blending. It turns out that there is an effect to do.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

According to Examples 1 and 2 and Comparative Examples 1 to 3, the filler and compounding chemical added to the polybutadiene rubber were 40 to 9
When the content exceeds 0% by weight (the filler and compounding chemicals added to the natural rubber are 60 to 10% by weight), the abrasion resistance and the tensile properties are inferior, and the effect of the present invention is reduced.

According to Example 3 and Comparative Examples 4 and 5, the filler was 3%.
At less than 0 parts by weight, the tensile strength decreases and the wear resistance deteriorates,
It can be seen that at 70 parts by weight or more, the tensile properties and the rebound resilience are reduced. From Example 3 and Comparative Examples 6 and 7, when the polybutadiene rubber exceeds 70 parts by weight, the tensile strength decreases,
It can be seen that when the amount is less than 30 parts by weight, the rebound resilience and the wear resistance are reduced.

From Example 4 and Comparative Example 8, even when polybutadiene rubber and isoprene rubber were used, the rebound resilience was improved while the wet skid of the vulcanized rubber was maintained, and the Mooney viscosity of the compounded rubber was lowered to vulcanize. The rubber has improved tensile properties and abrasion resistance, indicating that the present invention is effective.

[0039]

The rubber composition of the present invention improves the rebound resilience while maintaining the wet skid of the vulcanized rubber, and lowers the blended rubber Mooney viscosity to improve the tensile properties and wear resistance of the vulcanized rubber. A rubber composition can be provided.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kazumasa Hirose 2--11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) References JP-A-56-64849 (JP, A) JP-A Sho 61-64738 (JP, A) JP-A-57-143338 (JP, A) JP-A-56-106937 (JP, A) JP-A-55-104343 (JP, A) (58) Fields investigated (Int. Cl. ^7, DB name) C08L 7/00 C08J 3/20 C08L 9/00

Claims (1)

(57) [Claims] (1) 100 parts by weight of a raw rubber component comprising A) 30 to 70 parts by weight of natural rubber and / or polyisoprene rubber and B) 70 to 30 parts by weight of polybutadiene rubber, and C) a filler and a rubber. In preparing a rubber composition by mixing 30 to 70 parts by weight of a chemical, 1) A) 30 to 70 parts by weight of natural rubber and / or polyisoprene rubber, C) excluding a filler and a vulcanization active ingredient 2) B) 70 to 30 parts by weight of polybutadiene rubber, and C) a rubber composition obtained by mechanically kneading and mixing 10 to 60% by weight of a rubber chemical.
90 to 40 of rubber chemicals excluding filler and vulcanization active ingredient
% By weight and mechanically kneaded and mixed to prepare a rubber composition, and D) a rubber composition of 1) and 2) with 0 to 40 parts by weight of a softening agent based on 100 parts by weight of the raw rubber. And vulcanizing active rubber chemicals are mechanically kneaded and mixed.