JPS5914402B2 - Method for producing granular 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.

More specifically, sulfur and dibenzothiazyl disulfide in an amount of 0.1 to 5% by weight of sulfur are melted by heating to a temperature above the melting point of sulfur to make it homogeneous, and then cooled to a semi-molten state and extruded into granules. The present invention relates to a method for producing granular sulfur characterized by: Sulfur is used as a rubber compounding agent, together with accelerators and zinc white, in the vulcanization of diene rubber, that is, natural rubber or synthetic rubber products such as styrene-butadiene rubber, acrylonitrile-butadiene rubber, isoprene rubber, butadiene rubber, and butyl rubber.
5 Essentially the most important substance involved in the vulcanization reaction.

However, if sulfur is present in the rubber to be vulcanized as coarse particles, the area where the coarse particles are present will locally become overvulcanized during vulcanization, and after vulcanization, 0 will be post-vulcanized in this area. This progresses, causing the rubber products to age faster.

Therefore, it is desirable that sulfur be as fine a particle as possible, and currently, sulfur for dry rubber is
A fine powder of 200 to 300 mesh or more is used. 15 Today, the most common method for producing powdered sulfur industrially is to grind bulk sulfur into powder using a grinder.
This is a method of classifying this and collecting parts of a certain particle size.

A special method is to make it into a liquid and rapidly cool it in a large, cooled room. In both of these 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, but also the chamber is used to handle fine powder. To,
Since there is a risk of causing dust 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 to provide sulfur with excellent dispersibility, which has been long-awaited in terms of rubber processing technology.

30 In order to achieve this objective, the present inventors previously invented a method for producing molded sulfur in which sulfur and wax are melted by heating to a temperature above the melting point of sulfur, stirred to make it uniform, and then cooled and molded. As a result of further research, it was found that by mixing and melting sulfur with a small amount of dibenzothiazyl 35 disulfide, and then extruding and granulating it in a semi-molten state, molded sulfur that can be easily kneaded into rubber and has excellent dispersibility was created. It was discovered that =- could be obtained, and the present invention was completed.

Conventionally, there is an example of eutectic reaction of sulfur and dibenzothiacyl disulfide to form a molecular compound, as described in the Journal of the Japan Rubber Association, Vol. 25, p. 138, and furthermore, the resulting resinous eutectic product is blended into rubber as it is. and tested as a vulcanizing agent (
There is also a report on the plasticizing effect on rubber (p. 166). However, in this example, since the amount of dibenzothiacyl disulfide added is large, what is obtained by eutectic synthesis with sulfur is a resinous material, and it is impossible to granulate it as in the present invention. . The present invention differs from these known documents in that a small amount of dibenzothiacyl disulfide is added to sulfur in an amount of 0.1 to 5.0% by weight and then mixed and melted. This was done based on the knowledge that grains are possible.

This means that when the amount of dibenzothiacyl disulfide added to sulfur is large, when both are heated and melted, almost all of the sulfur reacts with dibenzothiacyl disulfide to form various polysulfides, resulting in resin However, when the amount added is small, part of the sulfur reacts with dibenzothiacyl disulfide to form a polysulfide, and then this polysulfide and sulfur form a eutectic product. It is thought to form a

Furthermore, during granulation, it is presumed that the polysulfide produced here acts effectively as if it were a binder. Moreover, surprisingly, the molded sulfur obtained in this way has the same or better dispersibility when blended into rubber than the conventionally used fine powder sulfur. found. Furthermore, the present invention is characterized by completely eliminating the need for a crushing process, which was an essential process in the production of powdered sulfur in the past, so there is no risk of dust explosion, and there is no risk of dust pollution, making it a hygienic process. can produce sulfur for rubber. Moreover, the molded sulfur obtained according to the invention has many advantages when used in the manufacturing process of rubber products.

In other words, when using conventional powdered sulfur, it is easy to cause dust pollution, and because it adheres to the hopper and container, not only is the mixing operation difficult, but it also tends to cause errors in weighing. Since the sulfur according to the invention is in the form of a free-flowing ink, no such drawbacks are observed. The raw material sulfur used in the present invention may be distilled sulfur or sulfur recovered through petrochemistry, as long as its purity is at the level conventionally used for rubber. In addition, it is of course possible to use liquid sulfur from the beginning since it is necessary to heat and melt it during production.

To carry out the invention advantageously, the sulfur
Add 5.0% by weight of an organic disulfide compound, heat to 120 to 140°C, mix and melt while stirring for 30 minutes to 1 hour, make it homogeneous, cool to a semi-molten state, and extrude. Extrusion and granulation are carried out using a granulator using a conventional method.

Next, the present statement will be explained by giving examples. Example 1 1 kg of solid sulfur was placed in a stainless steel mixer (kneader 1), heated to 120-125°C to melt it, added dibenzothiacyl disulfide 309 while stirring, mixed and melted at the same temperature for 30 minutes, and then heated to 120-125°C. When cooled to 100°C, granulated in a semi-molten state using an extrusion type granulator, and cooled with fluidization, granular sulfur 1010 melts at 95°C.
9 was obtained.

Example 2 100g of liquid sulfur preheated to about 130°C
Add benzothiacil disulfide 109 while stirring.
When added and melted by heating at the same temperature for 30 minutes, both forms a uniform liquid layer.

Next, add this to 900f1 of liquid sulfur, and add 3
After mixing and melting with stirring for 0 minutes, the mixture was allowed to cool to a semi-molten state, granulated using an extrusion type granulator, and fluidized and cooled to obtain granular sulfur 9909 that melted at 99°C. Comparative Example 1 The procedure of Example 1 was followed except that cybenzothiazyl disulfide was changed to 0.8 g.

Extrusion granulation was performed in a semi-molten state, but the sulfur was flabby. −
It turned into a square shape. Comparative Example 2 The procedure of Example 1 was followed except that the amount of dibenzothiacyl disulfide was changed to 90 g.

Although extrusion granulation was carried out in a semi-molten state, the sulfur did not become granulated, and the sulfur remained in a molten state and became agglomerated. Example. Comparative Example To test the dispersibility of sulfur, sulfur 51 was mixed into natural rubber 1009 in a roll for 5 minutes, passed through once, and then judged visually.

The results are described below. As described above, the present invention is a method for producing molded sulfur with good dispersibility, and even though it is a granular product, it can be produced with good dispersibility equivalent to that of powdered sulfur by adding the amount within the scope of the claims of the present patent. It turns out that sulfur can be obtained.

Claims (1)

[Claims] 1 Sulfur and dibenzothiazyl disulfide in an amount of 0.1 to 5% by weight based on the sulfur content are melted by heating to a temperature above the melting point of sulfur to make it homogeneous, and then cooled to a semi-molten state and extruded and granulated. Characteristic method for producing granular sulfur.