JPS608017B2 - Polyisoprene rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixed rubber composition of a synthetic cis-1,4-polyisoprene rubber and a ring-related polymer of a norbornene derivative.

More specifically, a ring-linked polymer of a norporene derivative having a molecular weight of several hundred thousand or more, which has been softened in advance with process oil, is mixed with 95 to 7% by weight of synthetic cis-1,4-polyisoprene rubber.
A rubber composition obtained by mixing 5 to 3% by weight in terms of polymer, or a rubber composition in which carbon black, a vulcanizing agent, etc. The present invention relates to a rubber compounded composition that provides a vulcanizate with a high tensile stress and abrasion resistance. Synthetic cis-1,4-polysoprene rubber has almost the same molecular structure as natural rubber and its properties are similar to natural rubber, but its green strength and the tensile stress of the vulcanizate are lower, so it is more similar to natural rubber. There are problems when using it as a substitute for rubber. Carbon black blends of synthetic cis-1,4-polysoprene rubber are used in the manufacture of industrial products such as tires and belts;
Since polyisoprene rubber has low green strength, it may not be able to replace natural rubber in the molding process. Furthermore, when used as a rubber compound for tires, particularly for steel radial tires, the vulcanizate is required to have high tensile stress, and even natural rubber compounds do not yet have sufficient tensile stress. Further improvements are needed in the case of synthetic cis-1,4-polysoprene rubber, which exhibits lower tensile stress than natural rubber. Several methods have been proposed to improve the green strength of synthetic cis-1,4-polyisoprene rubber, such as partially crosslinking rubber molecules using peroxides or radiation, and There is a method of blending thermoplastic resins such as soprene and polyethylene.

The former often impairs the processability of rubber compounds due to partial gel introduction, and has little effect on improving the tensile stress of vulcanizates containing carbon black. On the other hand, in the latter case, the green strength and tensile stress of the vulcanizate may be increased, but the Mooney viscosity of the compound generally increases and processability is often impaired. The present inventors have synthesized cis-
While investigating various ways to improve the green strength of 1,4-polyisoprene rubber compounds and the tensile stress of vulcanizates, we found that norbornene, which has moderate compatibility with synthetic cis-1,4-polyisoprene rubber, was developed. It was discovered that by mixing a derivative ring-opening polymer with ease of mixing and dispersibility into the rubber, it was possible to improve the green strength and the tensile stress of the vulcanizate without changing the Mooney viscosity of the compound. This has led to the present invention.

That is, in the present invention, a synthetic cis-1,4-polyisoprene rubber 95 to 7
The green strength of the rubber compound composition and the tensile stress of the vulcanizate are improved by mixing 5 to 30% by weight in terms of polymer compared to 0% by weight.

At the same time, an improvement in the wear resistance of the vulcanizate was also observed. The synthetic cis-1,4-polyisoprene rubber used in the present invention is a polyisoprene rubber containing 90% or more of cis-104 bonds, which is synthesized using a Ziegler catalyst or an alkyl lithium catalyst.

On the other hand, the Kan ring of the norbornene derivative used in the present invention (
The co)polymer is represented by the general formula 2 (wherein R and R' are hydrogen, C, ~4 alkyl groups,
(lower aromatic hydrocarbon residue) monomer, for example,
It can be obtained by ring-opening polymerization according to the method described in JP-A-3580.

Specific examples of the above-mentioned norbornene derivatives used as monomers include 5-norbornene and 5-norbornene-2.
-methyl, 5-norbornene-2-ethyl, 5-norbornene-2-butyl, 2,3-dimethyl-5-norbornene, or mixtures thereof, but are not limited thereto. Opening of the above fist mass body (co)
All polymers are high molecular weight polymers with a glass transition temperature of 0° C. or higher and a molecular weight of several hundred thousand or more, preferably 100 or more, and are commonly used in the rubber industry, such as mixing rolls,
When mixed with synthetic cis-1,4-polyisoprene rubber using a mixer such as a Banbury mixer, poor dispersion occurs, so in order to improve the mixing and dispersibility, a foam is commonly used in the rubber industry. The following method is simple and preferred, in which the mixture is pre-softened with process oil to facilitate mixing. That is, naphthenic or aromatic process oil is added to the weight part of the related ring polymer 10 of norbornene derivative at the glass transition temperature of the polymer,
10-20 parts by weight depending on the molecular weight, preferably 30-20 parts by weight
If a pre-mixed and softened 10 parts by weight is mixed in a predetermined amount in terms of polymer into synthetic cis-114-polyisoprene rubber, the dispersibility will be good and the processability of the resulting rubber compounded composition will also be impaired. It won't happen.

Addition of process oil involves adding a ring-opened polymer of norbornene conductor moistened with the process oil to be used in advance at 60 to 60%.
This can be easily achieved by kneading in a mixing roll heated to 100 qo. The mixing ratio of the ring-opening polymer of norbornene derivative to the synthetic cis-1,4-polyisoprene rubber is 3 to 3 to 97 to 70% by weight of the rubber.
If it is less than 3% by weight, the effect of the present invention will not be significant, and if it is more than 30% by weight, the elasticity of the vulcanizate will be impaired, which is not preferable. This compound contains additives commonly used in the rubber industry, such as carbon black, sulfur, and vulcanization accelerators.
Vulcanization can be carried out by adding a vulcanization aid or an organic peroxide. In either case, the green strength and the tensile stress of the vulcanized rubber can be significantly improved compared to the case where the rubornene-related ring polymer is not added. Next, the present invention will be specifically explained with reference to Examples.

Example: To 10 parts by weight of norbornene ring polymer (NORSOREX, manufactured by France's Chibi Co., Ltd., with a molecular weight of 200 or more), 60 parts by weight of naphthenic process oil (CircoLight, manufactured by SunOil, Inc., USA) and [b] were added.
After absorbing 18 parts by weight at 50 to 6000 for 2 hours,
The oil-containing norbornene-related ring polymer was mixed on a mixing roll heated to 80 to 90q0, and then the synthetic cis-1
・4-Polyisoprene rubber (Nipol IR2200)
(1) 10% by weight and (1) 20% by weight were mixed in a Type B Banbury, and at the same time, various compounding agents shown in Table 1 were added to 100 parts by weight of this oil-containing rubber mixture to form a rubber compound composition. Obtained.

The stress/strain curve (green strength) of this unvulcanized rubber compound at room temperature is shown in FIG. Table 2 shows the yield stress (maximum stress), the blended Mooney viscosity, and the tensile strength, tensile stress, and Akron abrasion test results of the 14,500×2 press fillet of the above blended composition. Next, a blended composition * using norbornene ring-opening polymer powder in place of the oil-impregnated norbornene-related ring polymer 'a} was similarly prepared.
Note that an amount of oil corresponding to the amount of oil in the oil-containing polymer was added during mixing. The properties of the vulcanizate of this composition are also listed in Table 2. Table 1 1) N-oxodiethylene-2-penzothiazole sulfenamide 2) Phenyluknaphthylamine 3) Oil-containing norbornene ring-opening polymer (An amount of oil corresponding to the amount of oil in the polymer was added during mixing.

4) Oil-containing polymer (oil in the amount of oil in 0 was added at the time of mixing).

By incorporating a second oil-impregnated/lubornene ring-opening polymer, the green strength (maximum stress) is improved without increasing the compounded Mooney viscosity and the vulcanizate is 100% and 30%
It can be seen that 0% tensile stress and wear resistance are improved.

However, when the polymer was used in powder form without being softened beforehand, the polymer was not dissolved and mixed into the composition, but was mixed mostly in the form of particles, and properties other than tensile stress were significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the unvulcanized stress-strain curve (green strength) of a synthetic cis-1,4-polyisoprene rubber composition mixed with a norbornene ring-opening polymer according to an example of the present invention. . Many 1 drawings

Claims (1)

[Claims] 1 Synthetic cis-1,4-polyisoprene rubber 95-70
General formula ▲Mathematical formula, pre-softened with 10 to 200 parts by weight of process oil per 100 parts by weight of the polymer
There are chemical formulas, tables, etc. ▼ (In the formula, R and R' are hydrogen, C_
A ring-opened polymer having a molecular weight of several hundred thousand or more obtained by polymerizing at least one type of norbornene derivative represented by 1_ to _4 alkyl group, representing a lower aromatic hydrocarbon residue, has a molecular weight of 5 to 30 in terms of polymer. A rubber composition formed by mixing weight percent.