JPS5921780B2 - Method for improving vulcanization speed of elastomer articles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for increasing the vulcanization rate of elastomeric articles to be vulcanized and molded.

Generally, in order to improve the vulcanization speed and shorten the vulcanization time of elastomer articles, such as tires, the amount of vulcanizing agent or vulcanization accelerator in the rubber compound is increased, or the vulcanization is accelerated. There are ways to prevent rubber burning or reduce the amount of tartar blended, but rubber products such as tires that normally go through a kneading process, molding process, and vulcanization process are particularly difficult to apply after kneading and extrusion. , calendering, etc., each of the above methods is limited by the problem that rubber scorch occurs before the vulcanization step.

Therefore, in reality, there is a limit to how much the vulcanization rate can be improved by each of the above methods.

The present invention was made in view of such conventional problems, and basically, organic short fibers that cause capillarity are mixed into the elastomer material in the kneading process, and further The object of the present invention is to provide a novel method for improving the vulcanization rate, which is characterized in that a vulcanization accelerator is infiltrated into an elastomer material in a state where it is not subjected to thermal history.

In addition to the tires mentioned above, the elastomer articles include rubber hoses, rubber belts, rubber mats, etc., but this does not preclude application to other rubber products.

Examples of vulcanization accelerators that are normally liquid include sodium di-normal butyl dithiocarbamate.

Examples of substances that are normally gaseous include carbon disulfide.

Normally in powder form, cyclohexylbendothiazyl sulfenamide, enuoxydiethylene-2
- Pendothiazole, sulfenamide, etc.

Super accelerators in the vulcanization accelerator category include tetramethylthiuram disulfide, mercaptobenzothiazole, etc., which are normally in powder form.

Note that tetramethylthiuram, disulfide, and mercaptobenzothiazole can all be made into a solution.

To make it into a solution, use a solvent such as acetone, carbon cyanide, or chloroform.

In this case, the solution concentration is suitably about 5% or less.

In order to infiltrate the elastomer material with the vulcanization accelerator, the elastomer material may be immersed in a solution of the vulcanization accelerator for a certain period of time or placed in an atmosphere.

Alternatively, mechanical methods such as direct injection into the elastomeric article, such as with a syringe, can be employed.

Furthermore, a powder may be sprinkled on the surface of the elastomer material and covered with another elastomer material.

The vulcanization accelerator may be used in gas or powder form as described above, but liquid form is preferred from the standpoint of uniform and rapid permeability and dispersion and absorption.

In order to reduce the concentration difference in the diffusion direction (thickness direction) of the vulcanization accelerator into the elastomer material, the thinner the elastomer material is, the better, for example, 0.1 to 5 mm, preferably about 1 to 2 mm. It is.

In the case of a vulcanization accelerator solution, adding a small amount of a solvent that dissolves rubber, such as benzene or toluene, to the solution will cause the rubber compound to swell, resulting in a uniform concentration of dispersed absorption (soakability).
This further improves the density and eliminates the difference in density.

The soaking time of the elastomeric material varies depending on the type of elastomeric material, but ranges from a few minutes to several tens of hours.

It is preferable to mix short fibers into the elastomer material during the kneading process in order to promote the permeability of the vulcanization accelerator using capillary action.

The short fibers are preferably organic fibers (nylon, rayon, polyester, etc.), and are preferably continuous fibers, which are more likely to cause capillary action than single fibers.

For example, the length of short fibers is 5Wtm in the case of solid tires.
The thickness of ~6cm1 is 840~1500d/2 strands, and the mixing ratio in the rubber compound is 5~30%, and the key is to mix it to an extent that does not adversely affect the physical properties.

Next, an example will be described in which the vulcanization rate of an elastomer article immersed in a vulcanization accelerator solution was determined.

Example 1 Examples of rubber compounds for solid tires Two types of rubber compounds A and B shown in Table 1 were combined with 2 types of rubber compounds shown in Table 2.
After immersing each type of vulcanization accelerator solution and drying the solvent, vulcanization rate tester (Monsanto rheometer)
The vulcanization rate was determined.

The vulcanization rate is expressed by the scorch time at a constant temperature of 150°C, and a shorter scorch time indicates a faster vulcanization rate.

The standard vulcanization conditions are 150° C. and 180 minutes.

As illustrated in the graph of Figure 1, 2% of the vulcanization accelerator M
The vulcanization time of rubber compound A, which was immersed in the acetone solution for 0.1 hour, was 120 minutes as shown in (b), whereas the vulcanization time of untreated rubber compound A was (a)
As shown, it is 180 minutes.

Therefore, the vulcanization time was reduced by about 30%.

Example 2 - Example of tread rubber compound for pneumatic tires The tread rubber compound C shown in Table 3 was immersed in the vulcanization accelerator solution shown in Table 4, and after drying the solvent, it was tested using a vulcanization rate tester. The vulcanization rate was determined using a rheometer manufactured by Monsanto.

The vulcanization rate is expressed by the scorch time at a constant temperature of 150°C, and a shorter scorch time indicates a faster vulcanization rate.

The standard vulcanization conditions are 150° C. and 50 minutes.

As shown in the graph of Table 2, the vulcanization time of rubber compound C immersed in a 2% acetone solution of vulcanization accelerator M for 18 hours was 35 minutes, as shown in (d). , the vulcanization time of untreated rubber compound C is 50 minutes as indicated at 0.

Therefore, the vulcanization time was reduced by about 30%.

In addition to the purpose of improving the vulcanization rate, the method of the present invention also has the purpose of preventing rubber burning in each step of kneading, extrusion, and calendering. For all of the above, the vulcanization accelerator is strained at the initial compounding stage, and in a state where the vulcanization accelerator is no longer subjected to any further heat history before vulcanization molding, the method of the present invention is used to apply the vulcanization accelerator to each rubber sheet 1 to 3. Each rubber sheet 1
It is also possible to readjust the vulcanization rate in steps .

To manufacture a solid tire according to the method of the present invention, a rubber sheet of a predetermined thickness is extruded and then dipped in a predetermined vulcanization accelerator solution, which is then rolled up on a drum using a conventional method to form a green tire. Complete with vulcanization.

Furthermore, the production of pneumatic tires according to the method of the present invention includes:
A stand tire (raw tire with only the tread not attached) is made in advance, and a rubber sheet of a predetermined thickness is extruded and dipped in a vulcanization accelerator solution, then wrapped around the stand tire to form a tread. The green tires are formed and then finished by vulcanization.

In addition, in FIG. 3, only the layer portion where the temperature rise is slowest during the vulcanization process, for example, the tread rubber sheet of layer 3, may be immersed in a vulcanization accelerator solution so that the vulcanization rate is the fastest. .

As is clear from the above description, the present invention mixes organic short fibers that cause capillary action into an elastomer material in the cross-wire process, and provides a state in which the elastomer material is not subjected to any further thermal history before the vulcanization process. Since the vulcanization accelerator is allowed to penetrate into the elastomer material, there is no need to worry about burning the elastomer material, and compared to conventional methods, the vulcanization speed is improved and the vulcanization time is significantly shortened. You will be able to do this.

Moreover, the organic short fibers promote the permeability of the vulcanization accelerator.

In the case of pneumatic tires, if the tread rubber vulcanization speed is increased by about 5 times (from 5.0 minutes to 1.0 minutes in terms of scorch time) using the method of the present invention, the tire vulcanization time can be reduced by about 10 to 50%. Can be shortened.

Furthermore, since the vulcanization time is shortened, the operating rate of the vulcanization equipment is improved, equipment costs are reduced, and furthermore, it is possible to contribute to energy saving.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between vulcanization time and degree of vulcanization for rubber compounds for solid tires, and Figure 2 is a graph showing the relationship between vulcanization time and degree of vulcanization for rubber compounds for pneumatic tires. The graph shown in FIG. 3 is a sectional view of a tread rubber sheet portion of a pneumatic ink tire. A, B, C...Rubber compound, 1 to 3...
・Tread rubber sheet.

Claims (1)

[Claims] 1. Organic short fibers that cause capillary action are mixed into the elastomer material in a cross-mixing process, and a vulcanization accelerator is infiltrated into the elastomer material in a state where it is not subjected to any further heat history before the vulcanization process. 1. A method for improving the vulcanization rate of an elastomer article, the method comprising: