JP3310365B2 - 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 for providing a rubber member having high hardness.

[0002]

2. Description of the Related Art In recent years, studies have been made to reduce the weight of automobiles from the viewpoint of energy saving. Its weight reduction is also strongly required for tires. In order to reduce the weight of the tire, it is conceivable to reduce the thickness of each component. However, simply reducing the thickness of the tire causes problems such as insufficient strength. In particular, the bead and its peripheral members are required to be made of a hard material because of the requirement of the running performance of the tire. In addition, there is a strong demand for weight reduction in various industrial rubber parts such as belts and hoses, and the situation is the same.

In order to increase the hardness of rubber, a large amount of a reinforcing agent such as carbon black is blended. However, when the blending amount of carbon black increases, the viscosity of the blend increases greatly, and the moldability decreases significantly. In order to improve molding processability, the use of softeners such as process oils and plasticizers is conceivable.However, when these softeners are used, processability such as extrusion is improved, but vulcanization is performed. The hardness of the later molded product is reduced, which is not suitable for the purpose of obtaining a member with high hardness. At present, in molded products, high hardness and sufficient moldability are not compatible.

[0004]

The object of the present invention is to provide a rubber composition which has sufficient molding processability and gives a vulcanized product having a high hardness when the obtained molded product is vulcanized. With the goal.

[0005]

According to the present invention, the above object is achieved by providing 95 to 40 parts by weight of a solid rubber, 2 to 50 parts by weight of a diene-based liquid rubber.
45 parts by weight, styrene thermoplastic elastomer 3 to 35
Ri Do the parts, total 100 parts by weight der of such components
This is achieved by providing a rubber composition characterized in that the composition comprises a base compound as a base polymer.

[0006] The solid rubber used in the present invention is:
A rubber containing a diene component, such as natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SB
R), butadiene rubber (BR), nitrile rubber (NB
Rubbers such as diene rubbers such as R), butyl rubber (IIR), and ethylene propylene rubber (EPDM) are exemplified.

The diene liquid rubber is a polymer of a diene monomer such as isoprene or butadiene, or a copolymer of a diene monomer and an aromatic vinyl compound such as styrene, having a number average molecular weight of 7000 to 7000. 50,000
Are used. When the molecular weight is smaller than the above range , the processability of the obtained rubber composition is improved, but when the molded body obtained from the composition is vulcanized , a sufficiently high hardness is obtained. Absent. Conversely, diene liquid
If the molecular weight of the rubber is too large, the effect of improving the processability cannot be sufficiently obtained.

When the diene liquid rubber is a copolymer of a diene monomer and an aromatic vinyl compound,
Any of a taper and a block can be used, but as the block copolymer, a block copolymer containing one block each based on a diene monomer and one block based on an aromatic vinyl compound is used. When the block copolymer contains three or more of these blocks, the effect of improving processability is poor. When the amount of the aromatic vinyl compound in the block copolymer exceeds 50/50 by weight with respect to the diene-based monomer, problems such as poor compatibility with the solid rubber may occur. For this reason, it is preferable to keep the content within the above range.

Such diene-based liquid rubbers can be obtained by known methods. Among them, the method of anion polymerization is easy to control the molecular weight, and the diene-based monomer
Has more than 70% of 1,4 bonds ,
It is most preferably used because it has good compatibility with solid rubber.

The styrene-based thermoplastic elastomer which is another important component of the present invention is a copolymer containing a polymer block composed of styrene and a polymer block composed of a diene monomer such as isoprene or butadiene. Yes, a block (A) made of styrene,
The block (B) composed of a diene monomer is represented by (A-
B) n-A, (B -A) n-B [n is an integer of 1 or more] those copolycondensation combined in the form is used. In order to improve the workability, which is the object of the present invention, and to express high hardness in the physical properties after vulcanization, a styrene-based thermoplastic elastomer is used.
And the molecular weight is 50,000 to 250,000 in number average molecular weight.
In the range of, and Weight ratio of the block consisting of styrene, a block consisting of a diene monomer is 5/95
It is preferable to use a block copolymer in the range of 40/60. Gore If the molecular weight is too small than the above range
When the molded body of the rubber composition is vulcanized, the effect of improving the hardness cannot be obtained, and when the molecular weight is too large, the compatibility with the solid rubber becomes poor, which is not preferable. Furthermore, in the block copolymer, the double bond in the block composed of the diene monomer may be hydrogenated.

Such a styrene-based thermoplastic elastomer can be easily obtained by a known anionic polymerization method. That is, using the anionic heavy GoHiraki initiator such as an alkyl lithium, by weight engaged styrene and diene monomers, the desired block copolymer is obtained.

In the present invention, the solid rubber is 95 to 40.
Parts by weight, 2 to 45 parts by weight of diene liquid rubber, and 3 to 35 parts by weight of styrene thermoplastic elastomer
It is being used. It mixing ratio of the diene-based liquid rubber can not be expected processability improving effect of the rubber composition is obtained when less than the above range, range mixing ratio of the reversed
Ri If too much pressure to the molded product obtained from a rubber composition
When sulfurated, the physical properties are not sufficient and are not preferred. Also,
The mixing ratio of the styrene thermoplastic elastomer is within the above range.
If less, the hardness of the molded product obtained from the rubber composition
When the improvement effect of
Has properties when vulcanized molded articles obtained from rubber composition
Is not sufficient and is not preferred.

The compositions of the present invention except that an essential the polymer component, used various additives usually used in rubber compounding is added. Particularly in the case of obtaining a high hardness rather preferred to use a reinforcing agent, carbon black, use of such silica
Is suitable for this purpose. Other calcium carbonate,
A filler such as clay, a crosslinking agent such as sulfur, peroxide, and phenol resin, an antioxidant, and the like are blended.

The rubber composition of the present invention is prepared by mixing the components by a processing method usually employed in the rubber industry .
And can be prepared in the rubber industry.
It is molded and vulcanized by a commonly used processing method before use.

Since the rubber composition of the present invention can exhibit high hardness by vulcanization, it is suitably used around beads of automobile tires, and is also used for industrial articles such as belts and hoses. Applied.

[0016]

The present invention will be described below in detail with reference to examples.

Examples 1 to 6 and Comparative Examples 1 to 3 Isoprene and styrene were sequentially polymerized using butyllithium as a catalyst to obtain a liquid rubber (LSI) in which isoprene and styrene were copolymerized in a block shape. The number average molecular weight of this liquid rubber is 29000, and the ratio of isoprene / styrene is 85/15 by weight. A number average molecular weight of 350 obtained by polymerizing only the isoprene monomer in the same manner.
Thus, a homopolymerized liquid rubber (LIR) of isoprene No. 00 was obtained. Further, as a thermoplastic elastomer, a block copolymer having a styrene-isoprene-styrene structure, a weight ratio of styrene / isoprene of 20/80, and a vinyl bond amount of a polyisoprene block of 70% [Hybler VS-1; Kuraray Co., Ltd.] also has a styrene-isoprene-styrene structure,
A block copolymer having a weight ratio of 14/86 and a vinyl bond amount of a polyisoprene block of 10% [Califlex TR-1107; manufactured by Shell Co., Ltd.], and a styrene-isoprene-styrene structure, wherein styrene / isoprene weight ratio is 13/87, the double bond 98% hydrogenated block copolymer of polyisoprene block [Septon 2043; manufactured by Kuraray Co., Ltd.] by the formulations shown in table 1 using the prepared formulations, Mooney viscosity And the physical properties of the vulcanizate were evaluated by the hardness and the workability of the compound. As shown in Table 1, it is understood that the composition according to the present invention can simultaneously exhibit improved processability and high hardness.

[0018]

[Table 1]

[0019]

According to the present invention, there is provided a rubber composition having improved processability and providing a vulcanizate of high hardness.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-206644 (JP, A) JP-A-57-70134 (JP, A) JP-A-61-28552 (JP, A) JP-A 51-206 12859 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 21/00 C08L 9/00 C08L 53/02

Claims (1)

(57) [Claims] 1. A solid rubber 95 to 40 parts by weight, the diene liquid rubber 2 to 45 parts by weight, Ri Do a styrene thermoplastic elastomer 3 to 35 parts by weight, the sum of such components is 100
A rubber composition characterized by containing a compound in parts by weight as a base polymer.