JPH05301232A - Method for heating rubber article having double layered structure by microwave - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a microwave heating method for a multi-layered rubber article capable of uniformly preheating even a multi-layered rubber article having a different loss coefficient for each layer. [Structure] In a microwave heating method for a multilayer-structured rubber article composed of a material having a different loss coefficient for each layer,
After applying a polar material having a high loss coefficient to a constituent sheet for producing a layer having a low loss coefficient, a rubber article having a multilayer structure is molded together with other constituent sheets to form a thin layer of the polar material between the sheets. After that, microwave irradiation is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a microwave heating method for a multi-layered rubber article, in particular a multi-layered solid tire, in which the loss coefficient is different for each layer.

[0002]

2. Description of the Related Art Conventionally, multi-layered rubber articles have been used in various fields. For example, as a tire used for a special vehicle such as a forklift truck, a multi-layered article in which rubber layers having different characteristics are laminated in a circumferential direction. Structural solid tires are known. When vulcanizing a thick-walled tire such as this multi-layer solid tire, when vulcanizing the tire at room temperature, in the heat conduction method from the surface, the central part where temperature rise is most difficult reaches the optimum vulcanized state. At times, there was a problem that the outer surface part was over-vulcanized. Therefore, before the vulcanization operation, a preheating operation is employed in which the tire is stored in a relatively low temperature greenhouse for a long time and the temperature inside the tire is raised on average.

Usually, this preheating operation requires a long time, and the storage space of the greenhouse is enormous. Therefore, the heat capacity of the greenhouse is large, and the heat dissipation to the outside air is also large, resulting in the problem that the heating efficiency has to remain at a low level. In order to solve this problem, for example, in Japanese Patent Publication No. 57-42501,
A method utilizing microwave heating has been disclosed in order to reduce the preheating time of the tire.

[0004]

In a normal preheating operation by microwave heating, when the solid tire has a multi-layer structure and the loss coefficients of the respective layers are different, the loss coefficient is proportional to the amount of heat generated. During heating, the microwave power concentrates on the layer having a high loss coefficient, and it is difficult to uniformly raise the temperature of the entire solid tire, resulting in a problem that an optimum preheating temperature cannot be obtained. It is also possible to separately heat each layer of a solid tire having a multi-layer structure with different loss factors and then form a solid tire having a multi-layer structure, but heat transfer to other layers that does not preheat during tire forming However, there is a problem that the preheating effect is deteriorated, and if the multi-layered rubber is to be preheated at the same time, a microwave heating device corresponding to the number is required.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a microwave heating method for a multi-layered rubber article capable of uniformly preheating even a multi-layered rubber article having a different loss coefficient for each layer.

[0006]

A microwave heating method for a multi-layered rubber article according to the present invention is a microwave heating method for a multi-layered rubber article composed of a material having a different loss coefficient for each layer. After applying a polar material having a high loss coefficient to a constituent sheet for producing a layer having a coefficient, after forming a rubber article having a multilayer structure with other constituent sheets to form a thin layer of polar material between the sheets, It is characterized by irradiation with microwaves.

[0007]

In the above structure, a thin layer of a polar substance is formed between the sheets by applying a polar substance having a high loss factor to a constituent sheet of a layer having a low loss factor in advance and performing molding before performing microwave heating. Since it is formed, the microwave absorptivity of the thin layer portion can be increased to heat the layer having the low loss coefficient by the heat conduction from the thin layer to the sheet, and as a result, the layer having the high loss coefficient and the low loss coefficient can be heated. It is possible to eliminate the temperature rise imbalance with the layer having the loss coefficient and perform uniform preheating.

As the polar substance, diethanolamine,
Amino alcohols such as triethanolamine, glycols such as diethylene glycol, polyethylene glycol, etc., factice, silica, magnesium carbonate, titanium oxide, lanolin, stearic acid, waxes individually or a mixture thereof, and further carbon black, accelerating vulcanization Agents and the like can be used, and those having a small influence on the vulcanization of the multilayer rubber article and the physical properties after vulcanization are preferable. Also,
The required amount of the polar substance to be formed into a thin layer needs to be determined according to the difference in the loss coefficient of each layer of the rubber article to be microwave-heated.

[0009]

FIG. 1 is a diagram showing an example of a state in which the microwave heating method for a multilayer rubber article of the present invention is carried out. The present invention is used for preheating a multilayer solid tire as a multilayer rubber article. The applied example is shown below. In FIG. 1, 1 is a microwave generator for generating microwaves, 2 is a waveguide for transmitting the microwaves generated from the microwave generator 1, and 3 is an application forming a chamber for preheating. 4 is a rotary type support stand provided in the applicator 3, which is preferably made of polypropylene, which is a microwave transmitting material, and 5 is an unvulcanized multi-layer structure solid placed on the support stand 4 to be preheated. A tire, 6 is a stirrer (rotating blade reflector) for stirring the electric field in the applicator 3 to make it uniform, and 7 is a thin layer made of a polar material having a high loss coefficient.

FIG. 2 is a diagram showing in detail a multi-layer structure solid tire 5 as an example of a multi-layer structure rubber article to be subjected to microwave heating of the present invention. FIG. 2 (a) is a perspective view thereof. FIG. 2B is a view showing a cross section taken along the line AA in FIG. In this embodiment, the solid tire 5 having a multi-layer structure is composed of a rubber layer 5-1 having a high loss coefficient on the outer circumference and a rubber layer 5-2 having a low loss coefficient on the inner circumference, and a rubber layer having a low loss coefficient. By applying the above-mentioned polar material having a high loss factor to the constituent sheet around 5-2, and molding it,
A thin layer 7 made of a polar material having a high loss coefficient is provided.

In the state shown in FIG. 1, the microwave generated by the microwave generator 1 is applied to the inside of the applicator 3 through the waveguide 2 to be mounted on the rotating support base 4. It is possible to preheat the multilayer solid tire 5 having the structure shown in FIG. According to the present invention, the thin layer 7 is made of a polar material having a high loss coefficient to increase the microwave absorptivity and has a low loss coefficient due to heat conduction from the thin layer 7 to the rubber layer 5-2. The temperature of 5-2 can be raised, and as a result, uniform preheating of the solid tire 5 having a multilayer structure can be performed.

An example in which preheating before vulcanization of the solid tire having the two-layer structure shown in FIG. 2 in the state shown in FIG. 1 is actually described below. First, microwave was applied to a conventional multi-layer solid tire without a thin layer of polar substance.
After irradiation for 0 minutes, as shown in Table 1 below as a comparative example, only the outer peripheral rubber layer 5-1 having a high loss coefficient is heated, and the inner peripheral rubber layer 5-2 having a low loss coefficient is heated. The result was that the temperature hardly increased. On the other hand, when a thin layer 7 made of polyethylene glycol (PEG) was provided around the inner rubber layer 5-2 having a low loss coefficient, as shown in Example 1 of Table 1, the inner layer was exposed to micro irradiation for 30 minutes. The temperature rise of the peripheral rubber layer 5-2 was accelerated, and the temperature imbalance between the outer peripheral rubber layer 5-1 and the inner peripheral rubber layer 5-2 could be eliminated. Further, even if the thin layer 7 made of a mixture of polyethylene glycol and silica was provided, the result that the temperature imbalance could be eliminated almost in the same manner as in Example 2 was obtained. In Table 1, the position where the temperature was measured is shown in FIG.
It corresponds to the position indicated by the number in.

[0013]

[Table 1]

The present invention is not limited to the above-mentioned embodiments, but various modifications and changes can be made. For example, in the above-mentioned embodiments, the example of the two-layer structure is shown as the multi-layer structure solid tire, but it is needless to say that the multi-layer structure is not limited to two layers and a multi-layer structure of two or more layers can be adopted. .. Further, the shape is not limited to the tire, and it goes without saying that a rubber article having a multi-layer structure may have any shape. Furthermore, in the above-mentioned examples, a thin layer of polyethylene glycol as a polar substance was provided in a layer having a low loss coefficient, but if the difference in loss coefficient is large, the amount of polyethylene glycol used may be increased,
It is also possible to employ a combination of polyethylene glycol and another polar substance such as silica. Furthermore, it goes without saying that the polar substance can be selected and adopted from the above-mentioned examples according to the purpose.

[0015]

As is apparent from the above description, according to the present invention, since a rubber article having a multi-layer structure is provided with a thin layer made of a polar material having a high loss coefficient on a layer having a low loss coefficient, for example, By microwave irradiation for about 30 minutes, it becomes possible to uniformly preheat to a preheating temperature that cannot be obtained by long-term storage in a greenhouse, and the following effects can be obtained. (1) A greenhouse is not required for long-term storage, resulting in significant space and energy savings. (2) Since the loss coefficient of each layer is averaged, high output
It can be heated for a short time, productivity during preheating can be greatly improved, and energy efficiency can be greatly improved. (3) Since the preheating temperature can be increased, the time for main vulcanization can be greatly shortened, and the productivity during vulcanization can be greatly improved.
Energy efficiency can also be significantly improved. (4) Since the time for main vulcanization can be shortened, the point where the tire surface was over-vulcanized compared to the center of the tire where conventional vulcanization is most delayed is eliminated, and a more uniform degree of vulcanization is obtained. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a state in which a microwave heating method for a multilayer rubber article of the present invention is carried out.

FIG. 2 is a diagram showing in detail a multi-layer structure solid tire 5 as an example of a multi-layer structure rubber article to be subjected to microwave heating of the present invention.

[Explanation of symbols]

 1 Microwave generator 2 Waveguide 3 Applicator 4 Support 5 Multi-layer solid tire 6 Stirrer 7 Thin layer

Claims (1)

[Claims] 1. A microwave heating method for a rubber article having a multi-layer structure having loss factors different from each other in each layer, wherein a polar material having a high loss factor is added to a constituent sheet for producing a layer having a low loss factor. After coating, a rubber article having a multilayer structure is molded together with other constituent sheets to form a thin layer of a polar substance between the sheets, and then microwave irradiation is performed, and microwave heating of the rubber article having a multilayer structure is characterized. Method.