JPS5914401B2 - Method for manufacturing molded sulfur - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing molded sulfur having excellent dispersibility and useful as a rubber compounding agent.

Sulfur is used as a rubber compounding agent in diene rubbers, namely natural rubber or styrene-butadiene rubber, acrylonitrile-butadiene rubber, isoprene rubber, butadiene rubber,
In the vulcanization of synthetic rubbers such as butyl rubber, it is essentially the most important substance involved in the vulcanization reaction, along with accelerators and zinc white. However, the sulfur remains as a coarse particle,
If they are present in the rubber to be vulcanized, during vulcanization, the areas where coarse particles are present will locally become overvulcanized, and after vulcanization, post-recursion will proceed in these areas, resulting in aging of the rubber product5. It gets faster. Therefore, it is desirable that the sulfur be as fine a particle as possible, and currently, sulfur in the form of a fine powder of 200 to 300 mesh or more is normally used for dry rubber. Today, the most common method for producing powdered sulfur industrially is to grind bulk sulfur into powder using a crusher, and then classify the powder to collect a portion of a certain particle size.

A special method is to pressurize liquid sulfur, force it out of a nozzle to form a mist, and rapidly cool it in a large, cooled room. In these 15 methods, there is a risk of dust explosion, so in the former case, not only is it necessary to circulate an inert gas such as nitrogen or carbon dioxide in the chamber, but also a dust explosion is required in order to handle fine powder. Because of the risk of causing pollution, special consideration must be taken. The object of the present invention is to eliminate these drawbacks in the production of sulfur for rubber, and at the same time provide sulfur with excellent dispersibility, which has been long-awaited in terms of rubber processing technology.

25 In order to achieve this objective, as a result of intensive research, we discovered a method for producing molded sulfur by heating and melting sulfur and wax above the melting point of sulfur, stirring them to make them homogeneous, and then cooling and molding them, thus completing the present invention. .

30 Separately, the present inventors heated a wax that is solid at room temperature and a powdered rubber compounding agent having a higher melting point above the melting point of the wax, stirred it to make it uniform, and then cooled and molded it. Discovered a method for manufacturing molded rubber compounds,
I filed a patent application first (Publication 35 Patent Publication 1982-2259)
No. 3), but in the present invention, the above-mentioned wax is added to bulk sulfur instead of powdered sulfur, heated above the melting point of sulfur, and treated in the same manner, thereby creating a rubber that does not require a pulverization step and has excellent dispersibility. The present invention provides a method for producing sulfur for industrial use.

At this time, since it is necessary to heat and melt the bulk sulfur, it is of course possible to use liquid sulfur instead of the bulk sulfur. According to this method, there is no risk of causing dust pollution or dust explosion during manufacturing or use in a rubber factory, and there is no need to use auxiliary materials such as inert gas.
Furthermore, it is possible to economically produce sulfur that has better dispersibility than conventional powdered sulfur, is easy to handle, and has good fluidity (free-flow ink). The raw material sulfur used in the present invention may be distilled sulfur or sulfur recovered by petrochemistry, and any purity can be used as long as it has a purity comparable to conventionally used sulfur. In the present invention, the wax added to sulfur includes paraffin wax separated and refined from petroleum, microcrystalline wax, general valuable wax, animal wax,
In addition to mineral waxes, in some cases, synthetic waxes can be used, as long as they do not have an adverse effect on the vulcanization reaction or vulcanized rubber, but microcrystalline waxes are particularly preferred. Get results.

When adding wax to sulfur in a weight ratio of usually 5% or less, most preferably 0.1 to 3%, a product preferable as sulfur for rubber can be obtained. In carrying out the present invention, in order to mold into granules, for example, wax is added to liquid sulfur, stirred and cooled to a semi-molten state while maintaining a uniformly dispersed state, and then extruded and granulated.

A feature of the present invention is that it solves many problems in producing sulfur for rubber.

That is, in the past, a pulverization process was required to make it into a fine powder, but in the present invention, such a pulverization process is not required at all, so there is no fear of causing dust pollution, and it is hygienic.
In addition, when pulverizing sulfur, there is a risk of a dust explosion due to overheating of the pulverizer, so the pulverizer is cooled or an inert gas is used, but in the present invention, such considerations are unnecessary. Yes, there is no risk of fire or explosion. Moreover, the present invention can be easily implemented continuously. In other words, the liquid sulfur and wax that flow in a certain amount at a certain time from a metering pump are mixed in a mixer and cooled until it becomes a semi-molten state, and then fed to a granulator to be molded and cooled. Therefore, molded sulfur of constant quality can be produced continuously. Furthermore, in this continuous production method, molded sulfur can be obtained from liquid sulfur within 30 minutes, so the labor and utility costs are a fraction of that of normal rubber sulfur production, making it economically viable. is also advantageous. Additionally, the mechanical equipment required to carry out the present invention is much smaller than conventional powdered sulfur manufacturing equipment, which is advantageous in terms of the area required. Furthermore, when conventional powdered sulfur is used in the manufacturing process of rubber products, it is easy to cause dust pollution and adheres to the hopper and container, making the blending operation difficult and weighing difficult. Although errors are likely to occur, since the sulfur according to the present invention is in the form of free-flowing ink, such defects are not observed at all.

Furthermore, the sulfur produced by the present invention begins to melt at a lower temperature than simple sulfur and has a wider melting point range, so it can be dispersed into rubber at a lower temperature and in a shorter time than ordinary powdered sulfur, so it can be used without worrying about poor dispersion. It is the most suitable sulfur for rubber. As described above, the present invention enables liquid sulfur to be uniformly dispersed in rubber without being powdered by adding wax that does not adversely affect the vulcanization reaction or the properties of vulcanized rubber. This is a novel method for producing sulfur for rubber, which aims to produce sulfur for rubber in a form that is easy to handle safely, hygienically, and economically.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 Liquid sulfur 5009 preheated to about 120°C
Microcrystalline wax (melting point 55℃) 15f while stirring! was added, mixed and melted, and while stirring so that both were homogeneous, was cooled to a semi-molten state and granulated using an extrusion type granulator to obtain pellet-like sulfur 5079 that began to melt at 89°C.

Example 2 Solid sulfur 5009 and microcrystalline wax 5
9 are mixed and melted by heating to about 120°C, stirred so that both are uniform, cooled to a semi-molten state while continuing to stir, and extruded and granulated to form pellet-shaped sulfur 4909 that starts to melt at 109°C. I got it.

Example 3 Liquid sulfur was continuously supplied at a rate of 1.0 kg/Hr and microcrystalline wax at a rate of 0.5 kg/Hr to a continuous mixer (kneader 1) heated to about 120°C, and mixed and melted. The mixture is stirred until homogeneous, then introduced into a cooled continuous mixer, and extruded and granulated in a semi-molten state.

Continuous fluidized cooling yielded sulfur pellets that began to melt at 74°C. Unvulcanized natural rubber 1 was molded with the wax synthesized in Examples 1 to 3 to test the dispersibility of sulfur.
00g of sulfur was mixed in a roll for 5 minutes, and 1
After passing through the rubber several times, the number of poorly dispersed particles in the rubber was determined visually. The results are shown below.

From the above, it has been found that the present invention can produce molded sulfur having good dispersibility equivalent to that of powdered sulfur even though it is a molded product.

Claims (1)

[Claims] 1. A method for producing molded sulfur, which comprises heating sulfur and wax, which is solid at room temperature, above the melting point of sulfur, stirring the mixture to make it uniform, and then cooling and molding.