JPH0786154B2 - Method for producing insoluble sulfur composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an insoluble sulfur composition, and more particularly to a method for producing an insoluble sulfur composition having excellent dispersibility in rubber. .

The term "insoluble sulfur" as used herein refers to polymeric sulfur having a property of not dissolving in carbon disulfide.
In general, insoluble sulfur generally has the property of changing to normal carbon disulfide-soluble sulfur over time. Therefore, commercially available insoluble sulfur contains normal sulfur in the range of 10% or less. However, in the present specification, it will be simply referred to as insoluble sulfur hereinafter.

In the rubber industry, as a rubber vulcanizing agent,
Insoluble sulfur is desired over normal sulfur in the sense of preventing rubber scorch. Since insoluble sulfur has a relatively excellent ability to prevent scorch, it is used for clear rubber products that should not have scorch, and vivid colored rubber products, and rubber products that particularly require adhesion with metal parts. For example, insoluble sulfur has been favored as a vulcanizing agent for tires and the like.

<Prior Art> It is known that insoluble sulfur is a polymeric sulfur and has poor dispersibility in rubber. Therefore, conventionally. It was used as a fine particulate material mainly for the purpose of improving dispersibility. However, there are many problems from the viewpoints of workability and pollution prevention, such as being easily scattered as dust at the time of handling, and expected to be charged and cause an accident such as dust explosion.

Further, since insoluble sulfur does not have good fluidity, there are problems during storage, transportation and working.

Therefore, it has been proposed to add process oil for rubber to insoluble sulfur for the purpose of preventing dust of insoluble sulfur and preventing charging. However, in this case, the dispersibility of insoluble sulfur in rubber cannot be said to be sufficient as it is. Therefore, various proposals have been made in the past in order to improve these physical properties, particularly dispersibility in rubber. However, none of them have necessarily improved the above physical properties. That is, according to JP-A-49-93294, an example in which a treated oil obtained by mixing an oil and a surfactant is added to insoluble sulfur to form granules, and in US Pat. An example in which ethylene glycol ether, which is a nonionic surfactant, is added is disclosed. Both of these have improved the dispersibility of insoluble sulfur in rubber, but due to the use of a surfactant, there are problems in terms of price, and the dispersibility in rubber itself is not very satisfactory. There wasn't.

<Problems to be Solved by the Invention> An object of the present invention is to provide a simple method for producing an insoluble sulfur composition which prevents dust of insoluble sulfur and also prevents electrification, and is excellent in dispersibility in rubber and storage stability. It is to manufacture and provide at low cost.

<Means for Solving the Problems> The insoluble sulfur composition of the present invention which achieves the above object is produced by using a process oil for rubber, a rubber and an organic solvent which are widely used in the rubber industry.

Specifically, the method for producing an insoluble sulfur composition according to the present invention comprises dissolving rubber in a process oil in the presence or absence of an organic solvent, mixing the dissolved product with the insoluble sulfur in the presence of an organic solvent, After that, the organic solvent is removed, and the mixture of the rubber and the process oil is coated on the surface of insoluble sulfur. More specifically, the rubber is uniformly dissolved in the rubber process oil, and the rubber is mixed with the insoluble sulfur by simultaneously adding the organic solvent and / or the organic solvent. Then, the system is uniformly stirred and mixed to be uniformly mixed with the insoluble sulfur, and then the organic solvent is distilled off or volatilized to form a coating on the surface of the insoluble sulfur to form an insoluble sulfur composition. It is a thing.

Both rubbers and process oils for rubbers are commonly used in the rubber industry and have no adverse effect on the physical properties of vulcanized rubber. According to the present invention, an insoluble sulfur composition having excellent rubber dispersibility can be obtained by simply mixing the insoluble sulfur with a rubber and a process oil for rubber in the presence of an organic solvent, and the insoluble sulfur composition Has good fluidity and stability per se, and the significance of the present invention lies here.

The above-mentioned insoluble sulfur and other components can be mixed by using an arbitrary mixer such as a kneader or a blender.

In addition, the insoluble sulfur composition produced by the production method of the present invention can be widely used as a vulcanizing agent for rubber, like commercial insoluble sulfur.

<Operation> Although the action and principle of improving the dispersibility of the insoluble sulfur composition produced by the method of the present invention in rubber are not clear, the mixture of the rubber and the process oil for rubber is lipophilic to insoluble sulfur. It is presumed that micelles are formed, which seems to make the miscibility with rubber good when the insoluble sulfur composition acts as a vulcanizing agent.

Furthermore, when the insoluble sulfur composition is compared with conventional commercially available insoluble sulfur, the adhesiveness and the secondary agglomeration are small, and therefore,
Does not solidify when transferred. Therefore, it is possible to obtain an insoluble sulfur composition having good fluidity and excellent storage stability. As in the above case, it seems that lipophilic micelles are also formed, so that the insoluble sulfur composition itself has an effect of reducing the friction coefficient and suppressing static electricity.

As will be apparent from the following examples, the present invention exhibits effects by pre-treating insoluble sulfur on the surface, and dispersibility and the like even when a process oil for rubber or rubber is added during rubber vulcanization. Cannot be expected to improve.

Examples will be described below, but it should be understood that the present invention is not limited to the following examples.

<Example> (Method for adjusting coating oil, etc.) Rubber is added to naphthene-based, paraffin-based, or aromatic-based process oil, which is a process oil for rubber, and stirred as necessary. The mixture was heated to ℃ and stirred until the rubber was completely dissolved, and then cooled to room temperature to obtain a coating oil composition.

(Example 1) 850 g of powdery insoluble sulfur having a purity of 97% was placed in a stainless steel ribbon blender 2 and stirred, and 150 g of a coating oil composition comprising 70% by weight of paraffinic process oil and 30% by weight of ethylene propylene rubber. And 200 g of carbon disulfide were added dropwise, and after the addition was completed, the mixture was stirred and mixed for 60 minutes to complete the coating. Then, the organic solvent was removed to obtain 984 g of an insoluble sulfur composition containing 83% insoluble sulfur.

(Example 2) 1200 g of wet cake-like insoluble sulfur containing 22% of carbon disulfide during the usual synthesis of insoluble sulfur was put in a ribbon blender and stirred, and 95% by weight of naphthenic oil and 5% by weight of natural rubber were used. 70 g of the coating oil composition was mixed and homogenized to complete the coating. Then, carbon disulfide was removed to obtain 1001 g of an insoluble sulfur composition containing 92% of insoluble sulfur content.

(Example 3) 1100 g of the wet cake-like insoluble sulfur described in Example 2 was placed in a ribbon blender with stirring, and 150 g of a coating oil composition consisting of 80% by weight of naphthenic oil and 20% by weight of natural rubber and 300 g of xylene. Were added at the same time to mix and homogenize, and the coating was completed. Then, the organic solvent was removed to obtain 1003 g of an insoluble sulfur composition containing 85.1% of insoluble sulfur.

Comparative Example 1 800 g of powdery insoluble sulfur and 200 g of naphthenic oil were used for synthesis in the same manner as in Example 1 to obtain 990 g of oil-insoluble sulfur.

Comparative Example 2 1100 g of the wet cake-like insoluble sulfur described in Example 2 above, 150 g of aromatic oil and 300 g of toluene were simultaneously put in a ribbon blender and mixed. After that, the organic solvent was removed and the oil-only coating of insoluble sulfur 1002
got g.

(Rubber Dispersion Test Example) 100 g of commercially available polybutadiene rubber was wrapped around a roll at 50 ° C. ± 5 ° C., and 5 g of insoluble sulfur prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was gradually added over 1 minute, and 2 It turned over in minutes. Sheet thinly 5 times,
The number of poorly dispersed particles was counted and judged visually. The results are shown in Table 1 below.

<Effects of the Invention> As is clear from the above Examples and Comparative Examples, according to the insoluble sulfur composition synthesized by the production method of the present invention,
It can be seen that the dispersibility of insoluble sulfur in rubber is greatly improved.

Claims (5)

[Claims] 1. Dissolving rubber in a process oil in the presence or absence of an organic solvent, mixing the dissolved product with insoluble sulfur in the presence of the organic solvent, and then distilling or volatilizing the organic solvent. A method for producing an insoluble sulfur composition, characterized in that the surface of the insoluble sulfur is coated with the mixture of the rubber and the process oil described above. 2. The production method according to claim 1, wherein the organic solvent is one kind or two or more kinds selected from carbon disulfide and aromatic hydrocarbons. 3. The method according to claim 1, wherein the rubber is natural rubber and / or synthetic rubber. 4. The method according to claim 1, wherein the rubber is natural rubber and / or polybutadiene rubber. 5. The method according to claim 1, wherein the process oil is one kind or a mixture of two or more kinds selected from naphthene type, paraffin type and aromatic type process oils for rubber.