JPH0420844B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing oil-treated insoluble sulfur with improved fluidity. The insoluble sulfur produced by the method of the present invention is
It is insoluble in carbon disulfide and can prevent sulfur bloom during the rubber vulcanization process.
It is a substance particularly useful as a vulcanizing agent for radial tires. Prior Art Insoluble sulfur is generally produced by pouring sulfur vapor or liquid into a cold solvent such as carbon disulfide, and separating the soluble sulfur by dissolving the coexisting carbon disulfide. The insoluble sulfur produced in this way usually consists of fine particles around tens of microns or smaller, and it is easy to scatter dust and be charged with static electricity during handling, which can cause various troubles during work. Because it is easy to use, it is often used as so-called oil processing insoluble sulfur mixed with a certain amount of rubber processing oil. Problems to be Solved by the Invention Oil-treated insoluble sulfur is improved in that it does not cause the above-mentioned dust scattering and has fewer problems due to static electricity than untreated insoluble sulfur, but it has poor fluidity and is not suitable for industrial use. The problem remains that it tends to adhere to various equipment and containers during handling, causing problems with assembly line operations at factories. A method of compressing and granulating insoluble sulfur powder has been proposed as a means to solve these problems, but while this method can improve fluidity, it has problems with the dispersibility of insoluble sulfur inside the rubber when mixed with rubber. There was still a problem with the decline. As mentioned above, insoluble sulfur is mainly used as a vulcanizing agent for rubber, but the amount used is usually 100%
It is necessary to mix and disperse it as microscopically as uniformly as possible inside the rubber during kneading with the rubber, at an amount of about 3 to 5 parts by weight. To achieve this, the insoluble sulfur must return to its original shape of several tens of microns or less during kneading with rubber, but this cannot be done satisfactorily in the compression granulated products as the breaking strength of the particles is high. As a result, there is a problem of poor dispersibility in rubber. Furthermore, JP-A-49-93294 discloses a method for producing granular oil-treated insoluble sulfur by mixing oil whose surface tension has been reduced by mixing a surfactant with insoluble sulfur powder using a high-speed mixer. It is shown. The granules made by this method have good fluidity, and the breaking strength of the particles is not as great as the compression granules mentioned above, so they easily return to the primary particles before granulation during kneading with rubber, and therefore the rubber However, there are problems such as a decrease in the thermal stability of insoluble sulfur, which is the most important vulcanizing agent for rubber vulcanizing agents, and especially for radial tires, and a decrease in the adhesion between steel cord and rubber. Ta. Means to Solve the Problems The present inventors found that the cause of these problems was the surfactant, and as a result of researching various ways to improve it, we found that In the case of insoluble sulfur treated with α-methylstyrene, no surfactant is required and the insoluble sulfur and oil are mixed together using conventional rubber processing oil and then the insoluble sulfur is added to this. Fine-grained oil-treated insoluble sulfur has improved fluidity through two-stage high-speed mixing, and is easily broken down into original insoluble sulfur particles when kneaded with rubber, resulting in good dispersibility in rubber. The present invention was achieved by discovering that it could be manufactured. That is, the method of the present invention (1) uses a dry powder of insoluble sulfur purified with carbon disulfide containing α-methylstyrene, and (2) uses a high-speed mixer to combine the dry powder of insoluble sulfur with a rubber process. Oil weight ratio: 1:
After mixing at a ratio of 0.3 to 0.5 and making the mixture into fine particles, (3) then add dry powder of insoluble sulfur to this, and (4) adjust the mixing ratio of the rubber processing oil to 17 to 17% of the total weight. The intended purpose was achieved by adjusting it to 22%. Insoluble sulfur essentially has the property of converting into normal soluble sulfur over time, and this tendency is accelerated by increasing temperature. Insoluble sulfur, which is used as a rubber vulcanizing agent, does not convert to normal soluble sulfur depending on the kneading temperature with rubber and the storage time after kneading until the vulcanization process, which causes the bloom phenomenon. necessary to suppress it. For this reason, many substances are known as stabilizers for insoluble sulfur, but surprisingly, insoluble sulfur purified with carbon disulfide dissolved in α-methylstyrene, which is extremely effective as a stabilizer. found that it has a remarkable effect on maintaining the particle breaking strength of fine particles produced by high-speed mixing with oil within a suitable range. In order to improve the fluidity of oil-treated insoluble sulfur powder and reduce its adhesion to containers, etc., the fine powder is aggregated or granulated to lower the surface area of each particle and to reduce the particle's own weight. As mentioned above, it is known that the larger the particle size, the better, but what is important in this case is that the breaking strength of each agglomerated or granulated particle should be adjusted within a relatively narrow range of about 5 to 15 g. . If the breaking strength is higher than this, as mentioned above, the dispersibility into the rubber after being kneaded with rubber will decrease, and if the strength is lower, the particles will break into the original powder during transportation or handling, and the fluidity will decrease again. Both of these are not practical. In carrying out the method of the present invention, if the amount of rubber processing oil added to the insoluble sulfur powder exceeds a predetermined range, the insoluble sulfur powder may become sticky, inhibiting mixing, or oil may ooze out onto the surface of the product. This will cause problems with adhesion to containers, etc. The present invention will be specifically explained below using Examples and Reference Examples. The breaking strength of the product in these tests is
Measurements were made by placing a sample on an electronic balance and pressing it with a glass rod. Example 1 Insoluble sulfur powder with a purity of 90% is dispersed in carbon disulfide containing 0.2% α-methylstyrene, stirred well at room temperature, filtered, and further washed thoroughly with carbon disulfide containing α-methylstyrene. After that, about 65℃
The mixture was kept in a nitrogen stream for about 1 hour to vaporize and dry the carbon disulfide content, thereby preparing an insoluble sulfur powder with a purity of 98%. Next, 12 kg of this dry powder of insoluble sulfur was charged into a high-speed mixer with a total capacity of 70 (trade name: "Spartani user PMO-50H type" manufactured by Fuji Paudal Co., Ltd.), and at the same time naphthenic aromatic and a small amount of paraffin were added. 5 kg of rubber process oil consisting of a system was charged. Note that the temperature of the rubber processing oil used was 20°C. Next, the rotation speed of the main shaft of the mixer was set to 2500 R.PM, and mixing was continued for 10 minutes. Next, the operation of the high-speed mixer was temporarily stopped, and 8 kg of the above-mentioned insoluble sulfur powder containing α-methylstyrene purified with carbon disulfide was added, and the rotation speed of the main shaft was set to 800 R.PM, and the mixture was mixed again for 30 seconds. The products treated in this way become fine particles with a uniform particle size of around 0.2 m/m containing 20% rubber processing oil, and most of the products have a breaking strength of 8 to 8.
It was in the 12g range. Example 2 134 kg of insoluble sulfur powder with a purity of 98% obtained by refining with carbon disulfide containing α-methylstyrene in the same manner as in Example 1 and the rubber processing oil used in Example 1 were placed in a 300-capacity Leday game mixer. 50 kg was charged, and the spindle rotation speed was set to 115 R.PM and mixed for 5 minutes. Next, the operation of the mixer was temporarily stopped, 66 kg of the above-mentioned insoluble sulfur powder was added, and the mixer was mixed again for 30 seconds at the same rotation speed. As a result, the product obtained in this way is
A uniform fine particle product with a particle size range of 0.5 to 1.0 m/m containing 20% rubber processing oil was obtained. The breaking strength of each particle ranged from 5 to 15 g. Reference Example 1 Using the same insoluble sulfur powder with a purity of 98% as used in Example 1, rubber processing oil, and a high-speed mixer, in Example 1, the insoluble sulfur powder was added in two stages, whereas We investigated whether a suitable fine grain product could be produced by step-by-step mixing. That is, 20 kg of insoluble sulfur powder and 5 kg of oil were charged at once into the high-speed mixer mentioned above, and the mixture was mixed at a rotation speed of 2500 R.PM.
Although the mixture was mixed for 10 minutes, the mixture remained powdery and no fine particles were obtained. Furthermore, the rotation speed was changed to a range of 800 to 3000 R.PM, but fine particles with good fluidity could not be obtained. Reference Example 2 The same procedure as in Example 1 was repeated except that insoluble sulfur powder with a purity of 90% was purified using carbon disulfide containing no α-methylstyrene. The resulting mixture has a particle size of 0.1 to 2 m/m compared to that of Example 1.
m and the fracture strength of the particles is 3 to 20.
There was a large variation in g. Reference Example 3 The adhesion of the oil-treated insoluble sulfur produced in each of the above Examples and Reference Examples to a stainless steel container was investigated. That is, 100 g of each sample was placed in a stainless steel round-bottomed cylindrical container (diameter 100 mm, height 60 mm). , put this container in a shaker (product name "SA-31 type" Yamato Scientific Co., Ltd.)
After shaking for 10 minutes at a vibration width of 30 mm and a frequency of 240 cycles/min, each container was gently removed from the shaker, tilted at 180°C to allow the sample to drain naturally, and then placed in the container. The amount of oil-treated insoluble sulfur that remained attached was measured. The results were as follows.

[Table] Reference Example 4 The thermal stability of the oil-treated insoluble sulfur produced in each of the above Examples and Reference Examples was investigated. That is, 1.2 g of each sample was allowed to stand for 35 minutes in a thermostatic chamber at a temperature of 100°C, and then thoroughly washed with carbon disulfide to completely dissolve the soluble sulfur in the carbon disulfide, filtered and dried to remove the remaining insoluble sulfur. Weighed the minutes. The results were as follows.

【table】

Claims (1)

[Claims] 1 To dry powder of insoluble sulfur purified by carbon disulfide containing α-methylstyrene, add 0.3 to 0.3 to 1 part by weight of rubber processing oil to 1 part by weight of the insoluble sulfur.
Add 0.5 parts by weight of the insoluble sulfur powder to the first stage of mixing using a high-speed mixer, and then add the dry powder of insoluble sulfur to the rubber processing oil at a mixing rate of 17 to 22% of the total.
1. A method for producing oil-treated insoluble sulfur with improved fluidity, characterized by performing a second stage of mixing by adding the sulfur in a proportion such that: