JP3080779B2 - Hard rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hard rubber composition, and more particularly to a hard rubber composition suitable for bead apex or clinch apex.

[0002]

2. Description of the Related Art Generally, in a radial tire, the cords of a carcass ply are arranged so as to be substantially parallel to each other at a right angle to the tire equatorial plane, and both ends thereof are folded around a bead wire. A bead apex extending in the sidewall direction is disposed inside the carcass, and a clinch apex is disposed outside the ply turn-up and adjacent to the rim flange. A tire having such a radial structure has a drawback in that a step of rigidity is generated at the folded end portion of the ply, so that damage is likely to occur at this portion, and that the radial structure is essentially inferior in lateral rigidity. for that reason,
A bead apex or a clinch apex having a particularly high hardness (or dynamic elastic modulus) has been proposed (JP-A-53-4059).

[0003] Therefore, as a method for producing a vulcanized rubber having a high rigidity or a complex elastic modulus, the amount of the thermosetting resin or carbon is increased, or the crosslink density is increased by using a large amount of sulfur or a vulcanization accelerator. Is being increased. However, the former is highly exothermic when kneading rubber with a Banbury mixer, so that the rubber scorches, or because the composition itself has a high viscosity, kneading, generates an excessive load during extrusion. . In the latter, when the composition is processed, sulfur blooms to impair the adhesiveness of the rubber, and also has a problem of deteriorating the physical properties of the vulcanized rubber.

[0004]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to solve the above problems, and as a result, have used syndiotactic 1,2-polybutadiene as a rubber component and further used a thermosetting resin. It has been found that by mixing the rubber composition, a rubber composition having an extremely high hardness excellent in workability and processability can be obtained, and the present invention has been completed.

[0005]

According to the present invention, syndiotactic 1,2-polybutadiene is added to raw rubber in an amount of 5%.
Rubber component containing 10 to 100% by weight and the rubber component 10
There is provided a hard rubber composition containing 2 to 40% by weight of a thermosetting resin with respect to 0 parts by weight.

[0006] Syndiotactic 1,2-polybutadiene is 5 to 100% by weight, preferably 1 to 100% by weight of the whole rubber component.
It is preferable to use 5 to 100% by weight. If it is less than 5% by weight, the effect of increasing the hardness is not sufficient, and the workability is poor. The syndiotactic 1,2-polybutadiene preferably has a crystallinity of 10% or more.
If it is less than 0%, the effect of increasing hardness and improving workability is small. Examples of the rubber component other than the syndiotactic 1,2-polybutadiene include diene rubbers such as natural rubber (polyisoprene rubber), styrene-butadiene copolymer rubber, and 1,4-polybutadiene rubber.

In the present invention, a thermosetting resin and a curing agent are blended in addition to the syndiotactic 1,2-polybutadiene. As the thermosetting resin to be used, a phenol resin, a cresol resin or a modified resin thereof,
For example, heat-modified resins such as cashew varnish-modified resins, oil-modified resins modified with oils such as linoleic acid, linolenic acid, and oleic acid, alkylbenzene-modified phenols modified with alkylbenzene such as xylene, epoxy-modified resins, aniline-modified resins, and melamine-modified resins Resins, which are used singly or as a mixture of two or more kinds in an arbitrary ratio. The thermosetting resin is used in an amount of 2 to 40 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the rubber component. If the amount is less than 2 parts by weight, the reinforcing effect is not sufficient, and if it exceeds 40 parts by weight, the kneading workability is significantly impaired.

[0008] The rubber composition of the present invention usually contains a curing agent for curing the thermosetting resin. The curing agent used is for curing the thermosetting resin, and is a compound that provides a methylene group when vulcanized under normal vulcanization conditions at 40 to 200 ° C., a so-called methylene donor. Examples include hexamethylenetetramine, polyvalent methylol, melamine derivatives, oxazolidine, bis (1,3 oxaziridine) derivatives, and the like. Although the amount of the curing agent needs to be adjusted according to the amount of the thermosetting resin, the amount is usually 0.5 to 7 parts by weight based on 100 parts by weight of the rubber component. By blending the thermosetting resin and the curing agent with the raw rubber containing syndiotactic 1,2-polybutadiene, the hardness and complex modulus of the vulcanized rubber can be further increased.

Further, the composition of the present invention can be appropriately compounded with commonly used additives such as fillers such as carbon and silica, vulcanizing agents, softening agents, antioxidants, vulcanization accelerators, plasticizers and the like. .

By kneading the above components, the hard rubber composition of the present invention can be obtained. The kneading is performed by a usual mixer. The rubber composition of the present invention can be further improved in kneading workability and extrusion workability while maintaining characteristics such as low heat build-up and high hardness by vulcanization molding by a conventional method.

[0011]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. Examples 1 to 5 and Comparative Examples 1 to 5 Using a Banbury mixer, a rubber composition having the composition shown in Table 1 was prepared by a conventional method, and these rubber compositions were mixed with 170 parts.
The sample was vulcanized at 15 ° C. for 15 minutes to obtain a sample for measuring hardness and viscoelasticity. The processability of the prepared unvulcanized rubber and the physical properties of the vulcanized rubber were examined by the following methods.

(1) Processability of unvulcanized rubber: Mooney Viscocity ML (1 + 4) (130) indicating the reversibility of the unvulcanized rubber
° C). The smaller the value, the better the workability. (2) Hardness of vulcanized rubber: Measured with a JISA type hardness meter. The larger the value, the better the rubber physical properties. (3) Complex elastic modulus and loss coefficient: Measured under the conditions of a dynamic strain of 2% and a temperature of 70 ° C. using an elasticity measuring device manufactured by Iwamoto Seisakusho. The larger the value of the complex modulus, the better the rubber properties. In addition, the smaller the value of the loss coefficient, the lower the heat generation of the rubber, and the better the physical properties of the rubber.

[0013]

[Table 1]

[0014]

[Table 2]

Table 2 shows the unvulcanized rubber properties and vulcanized rubber properties of the rubber compositions shown in Table 1.

[0016]

[Table 3]

[0017]

[Table 4]

As is apparent from Table 2, when both syndiotactic 1,2-polybutadiene and a thermosetting resin are blended, processability and physical properties of vulcanized rubber are improved. further,
As the blending amount of syndiotactic 1,2-polybutadiene increases and as the crystallinity increases, the processability and vulcanized rubber properties become better. It has been found that such an effect of improving processability and rubber properties is specific to syndiotactic 1,2-polybutadiene, and is not found in other 1,4-polybutadiene or atactic 1,2-polybutadiene. .

[0019]

As described above, according to the present invention, an extremely hard rubber composition having excellent workability and processability can be obtained.

Continuation of front page (56) References JP-A-4-63847 (JP, A) JP-A-4-95509 (JP, A) JP-A-2-114002 (JP, A) JP-A-1-109104 (JP) JP-A-63-99248 (JP, A) JP-A-59-122531 (JP, A) JP-A-57-119938 (JP, A) JP-A-59-68353 (JP, A) 4-362403 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 9/00 C08L 21/00 C08L 61/06 B60C 1/00

Claims (3)

(57) [Claims] 1. Syndiotactic 1,2 in raw rubber
A rubber component containing 5 to 100% by weight of polybutadiene and a thermosetting resin 2 based on 100 parts by weight of the rubber component;
A hard rubber composition containing up to 40% by weight. 2. The hard rubber composition according to claim 1, wherein the syndiotactic 1,2-polybutadiene has a crystallinity of 10% or more. 3. The hard rubber composition according to claim 1, wherein the thermosetting resin is a phenol resin, a cresol resin, or a modified resin thereof.