JPH11222502A - Method for masticating natural rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for masticating a natural rubber while effectively preventing a malodor from being emitted. SOLUTION: Zine oxide is added to a natural rubber simultaneously with or after the addition of the natural rubber. The amount of the zinc oxide added is 1-20 pts.wt. per 100 pts.wt. natural rubber. When this amount is below 1 pt.wt., the effect of preventing a malodor is not sufficient. When it is above 20 pt.wt., the effect of preventing a malodor no longer increases with consequent economical disadvantage and consequent adverse effect on the properties of the natural rubber. Therefore, the amount should be limited within the above range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for masticating natural rubber which can effectively suppress generation of odor.

[0002]

2. Description of the Related Art Natural rubber is supplied to the market as a product having a wide range of applications by being subjected to a vulcanization step after addition of additives and the like, followed by molding mainly in combination with metals and fibers. A mastication step for making the rubber itself soft and uniform exists as a pre-process for adding an additive or the like to such natural rubber.

[0003] The mastication of natural rubber is usually carried out by putting a natural rubber cut into an appropriate size and a shuffling agent into a kneader, and kneading the mixture with the kneader. However, in such a mastication method, there is a problem that a plurality of components present in the natural rubber are volatilized during the mastication step and emit a bad smell to the surroundings to cause environmental deterioration.

[0004] As a regulated substance based on the Odor Control Law,
At present, 22 substances such as ammonia and butyl aldehyde are listed, but even if each of them is less than the amount prescribed by law, it becomes a complex odor and deteriorates the environment, often causing complaints to residents. . Recently, regulations have been tightened to judge the substantial effect of odor prevention by a sensory test by an odor judge who is certified by the Environment Agency.

[0005] Hitherto, as a method for preventing odors in the method of kneading natural rubber, a washing method, a masking method, a neutralization method, an adsorption method, a combustion method and the like have been performed. It has not been established yet.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for masticating natural rubber which can effectively prevent odors in view of the above-mentioned situation.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for masticating natural rubber, which comprises mixing natural rubber and other additives into a kneading machine and mixing the same. A method for masticating natural rubber, comprising adding 1 to 20 parts by weight of zinc oxide to 100 parts by weight. Hereinafter, the present invention will be described in detail.

In the method for masticating natural rubber of the present invention, a conventional mastication method in which natural rubber and other additives are charged into a kneader and mixed can be used. The above-mentioned other additives are not particularly limited, and for example, arbitrary ones such as a shuffling agent, carbon black, silica and the like can be added for accelerating shuffling.

The above kneader is not particularly limited, and its size, shape and the like can be arbitrarily selected according to the purpose of use of the natural rubber. Is also good. Further, the mixing method is not particularly limited, and the mixing speed and the rotation temperature can be appropriately selected according to the purpose of the rubber to be obtained.

In the present invention, zinc oxide is added at the same time as natural rubber or at a different timing. The amount of the zinc oxide is 1 to 100 parts by weight of natural rubber.
20 parts by weight. If the amount is less than 1 part by weight, the effect of preventing odor becomes insufficient, and if it exceeds 20 parts by weight, the effect of preventing odor does not change, so that it is economically disadvantageous and affects the properties of natural rubber. , Is limited to the above range.

The form of the zinc oxide is represented by the chemical formula Zn
There is no particular limitation as long as it is represented by O, and it may be a single substance, or a composite or a mixture with another substance. The zinc oxide is preferably in the form of particles, and the particle size is not particularly limited.
Those having a particle size of about μm are preferred. The zinc oxide can be added as zinc oxide alone in the method of the present invention, or can be added in a form mixed with other additives described above.

[0012]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

EXAMPLES AND COMPARATIVE EXAMPLES Natural rubber and other additives listed in Table 1 were all charged at once using an internal mixer with a volume of 180 L and mixed for 5 minutes to masticate natural rubber. Was. The rubber after mastication was discharged, the air containing odor components at the time of discharging was collected, and evaluated by measuring the dilution multiple by the following “air dilution method three-point comparison odor bag method”. The results are shown in Table 1.

In Table 1, the natural rubber was RSS # 3. Shattering agent is manufactured by Ouchi Shinko Chemical Co., Ltd., Noctizer S
D. As zinc oxide, three kinds of zinc oxide (JIS K
5102). The zinc oxide-containing agent was Meta ZL50 (containing 50% ZnO) manufactured by Inoue Lime Industry Co., Ltd.
The carbon black was N330. The silica was Nipsil VN-3 manufactured by Nippon Silica Co., Ltd.

Air dilution method Three-point comparison odor bag method A total of three sets of one odor bag and two odorless odor bags diluted with the odor of the sample were distributed to six panelists, and 3 odor bags were distributed.
Select a odor bag with a smell from each set. If there is a correct answer in this selection operation, the odor dilution factor of the sample is tripled, and the selection operation is performed by that person.
This test was repeated, and the number of dilutions at the time when there were no more correct answers (multiples from the original sample) was used as the evaluation score.

[0016]

[Table 1]

When the amount of zinc oxide was 1 part by weight to 30 parts by weight, only an odor of about 200 to 800 was evaluated in a dilution factor. Even when 5 parts by weight of meta ZL50 containing 50% of zinc oxide was used, the value was 500, which was a low value. When zinc oxide was used in an amount of 0.5 part by weight (Comparative Example 2), it was 3,500, and had an odor exceeding the practical range. Even worse results were obtained for those containing no zinc oxide.

[0018]

Since the method for masticating natural rubber according to the present invention has the above-mentioned constitution, the odor can be suppressed very efficiently and it is useful as a method for masticating natural rubber which does not cause environmental deterioration.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Koaise 3-2-15 Meiwadori, Hyogo-ku, Kobe Bando Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for masticating natural rubber, comprising mixing a natural rubber and other additives into a kneader and mixing them, wherein the additive is 1 to 100 parts by weight of the natural rubber. A method for masticating natural rubber, comprising adding 20 parts by weight of zinc oxide.