JPH05301231A - Method for heating rubber article having double-layered structure by microwave - Google Patents

Abstract

PURPOSE:To enhance the productivity at the time of preheating by adding a polar substance having a high loss factor to the layer having a low loss factor of a solid tire having a double-layered structure to average the loss factor of the tire and subsequently irradiating the tire with a microwave to average preheating. CONSTITUTION:A solid tire 5 having a double-layered structure is constituted of an outer peripheral rubber layer 5-1 and an inner peripheral rubber layer 5-2. A polar substance having a high loss factor is added to the inner peripheral robber layer 5-2 having a low loss factor among the rubber layers 5-1, 5-2 to average the loss factors of the layers 5-1, 5-2. By this constitution, the power concn. of a microwave is eliminated and the respective layers 5-1, 5-2 can be uniformly heated and the productivity at the time of preheating is enhanced.

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]

The microwave heating method for a multilayer rubber article according to the present invention is a microwave heating method for a multilayer rubber article having a loss coefficient different for each layer. It is characterized in that a microwave is irradiated after adding a polar substance having a high loss coefficient and averaging the loss coefficients.

[0007]

In the above-mentioned constitution, before performing microwave heating, the polar substance having a high loss factor is added to the layer having a low loss factor in advance at the compounding stage of each layer, and the loss factor of each layer is averaged. By doing so, the concentration of microwave power can be eliminated and the multi-layered rubber article can be heated uniformly. Since the polar substance is used only for controlling the loss coefficient, other characteristics hardly change even if the polar substance is added.

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 added needs to be determined according to the difference in the loss coefficient of each layer of the rubber article to be heated by microwave.

[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 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. Tire, 6 is a stirrer (rotary blade reflector) for stirring the electric field in the applicator 3 to make it uniform.
Is.

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 on the outer circumference and a rubber layer 5-2 on the inner circumference, and the loss coefficient between the rubber layer 5-1 and the rubber layer 5-2 is For example, by adding a predetermined amount of a polar material having a high loss coefficient to the rubber layer 5-2 having a low loss in the mixing stage of each layer, the rubber layers 5-2 are made to have substantially the same content.

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. At this time, in the present invention, since the loss coefficient of each layer is averaged as described above, it is possible to eliminate the concentration of microwave power that tends to concentrate in the layer of high loss factor, and as a result, a uniform multilayer structure. Preheating of the solid tire 5 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, when a microwave was applied to a multi-layer structure solid tire to which a polar substance was not added for 10 minutes, as shown in Table 1 below as a comparative example, only the outer peripheral rubber layer 5-1 having a high loss coefficient was The temperature was raised, and the result was that the inner peripheral rubber layer 5-2 having a low loss coefficient hardly heated. On the other hand, when 3 parts by weight of polyethylene glycol (PEG) was added to the inner rubber layer 5-2 having a low loss coefficient, as shown in Example 1 of Table 1, the inner rubber layer was exposed to microwave irradiation for 10 minutes. The temperature rise of the layer 5-2 was accelerated, and the result was able to eliminate the temperature rise imbalance between the outer peripheral rubber layer 5-1 and the inner peripheral rubber layer 5-2. In addition, in Example 2 in which 1 part by weight of polyethylene glycol (PEG) and 7 parts by weight of silica were added, almost the same result that the temperature rising imbalance could be eliminated was obtained. In Table 1, the position where the temperature was measured corresponds to the position indicated by the number in FIG. 2 (b).

[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, 3 parts by weight of polyethylene glycol as a polar substance was added to the layer having a low loss coefficient. However, when the difference in loss coefficient is large, the amount of polyethylene glycol added may be increased or polyethylene glycol and other materials may be added. A polar substance such as silica can also be used in combination. Furthermore,
It goes without saying that the polar substance can be selected and adopted from the above examples according to the purpose.

[0015]

As is apparent from the above description, according to the present invention, since a polar substance having a high loss coefficient is added to a layer having a low loss coefficient of a rubber article having a multi-layer structure, for example, about 10 minutes. With the microwave irradiation, it becomes possible to uniformly preheat to a preheating temperature which 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

Claims (1)

[Claims] 1. A microwave heating method for a rubber article having a multi-layer structure having a different loss coefficient for each layer, wherein a polar substance having a high loss coefficient is added to a layer having a low loss coefficient, and the loss coefficient is averaged. A microwave heating method for a rubber article having a multilayer structure, which comprises irradiating waves.