JPH04299106A - Mold for induction heating - Google Patents

Abstract

PURPOSE:To increase the temp. rising speed of a heating body subjected to vulcanization or melt molding and to shorten the time required in vulcanization and melt molding in a dielectric heating apparatus using a high frequency electric field of 100MHz. CONSTITUTION:As the material quality of upper and lower molds 1, 2, a machinable ceramic material or an engineering plastic material having high heat-resistant temp. and high compressive strength is employed. Further, material quality of which the dielectric constant is 3.0 or more and the dielectric loss factor is smaller than that of a heating body is used as that of the molds. Therefore, the time required in the vulcanization or melt molding of the heating body can be shortened.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric heating mold for vulcanizing or melt-molding rubber or plastic by dielectric heating.

0002

2. Description of the Related Art There is a high-frequency dielectric heating device that vulcanizes or melts and molds, for example, rubber or plastic using a high-frequency electric field of 100 MHz or less. (Utility Model Hei 2-4830
(See Publication No. 3).

In contrast to this dielectric heating device that uses a high frequency electric field of 100 MHz or less, there is a microwave dielectric heating device that uses a magnetron to irradiate a heating element with microwaves of, for example, 2450 MHz (Japanese Patent Laid-Open No. 58-124629).
Publication No. 58-212928, Special Publication No. 2-
8887, JP-A-2-26710, JP-A-2-48413).

[0004] As mentioned above, this microwave dielectric heating is configured to irradiate the heating element with microwaves, so in order to generate heat while pressurizing the heating element, the structure of the mold is complicated. I end up.

On the other hand, the above-mentioned high-frequency dielectric heating device that uses a high-frequency electric field of 100 MHz or less has a configuration in which the high-frequency electric field is applied to the heating element by an electrode plate, so the mold has a simple structure. There is.

[0006]

By the way, if the mold in the above-mentioned high frequency dielectric heating device is made of a conductive material such as iron, the electric field becomes zero and the heating element cannot generate heat.

Therefore, for example, tetrafluoroethylene (dielectric loss factor 0.0004, dielectric constant 2.0, dielectric loss tangent 0.000
There are molds made of materials such as 2) that have a small dielectric loss factor, such as fluororesin or silicone resin. However, since fluororesin and silicone resin have low strength, the mold must be thick, and if the wall thickness is increased, the time it takes for the heating element to reach a predetermined temperature will be delayed. Also,
Since fluororesin and silicone resin have a low deformation temperature, a formwork is required to prevent deformation.

On the other hand, there is one in which the mold is made of a ceramic material. Ceramic materials have superior heat resistance and strength compared to fluororesins and silicone resins.

However, even when the mold is made of ceramic material, if the dielectric loss factor of the mold is larger than the dielectric loss factor of the heating element, the temperature of the mold will rise more than that of the heating element. As a result, the heating element could not be successfully vulcanized or melt-molded.

0010

[Means for Solving the Problems] In order to solve the above-mentioned problems, this invention is filled with a heat-generating material made of rubber or plastic, pressurizes the filled heat-generating material, and uses a high-frequency electric field of 100 MHz or less. In the dielectric heating mold for vulcanizing or melt-molding the heat-generating material by dielectric heating, the dielectric loss factor is smaller than the dielectric loss factor of the heat-generating material, and the dielectric constant is 3.0. It is characterized by the above.

[0011]

[Operation] The rate of temperature rise of the heating element is improved, and the time required for vulcanization or melt molding of the heating element is shortened.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic sectional view of an apparatus to which a dielectric heating mold according to an embodiment of the present invention is applied.

In the figure, 1 is an upper mold, and 2 is a lower mold, and the upper mold 1 and the lower mold 2 constitute a mold. A heating element 5 is then filled into the cavity formed by the upper mold 1 and the lower mold 2. Also, 3
is an upper electrode, and 4 is a lower electrode, and a constant high frequency current of 100 MHz or less is supplied to the upper electrode 3 and the lower electrode 4.

The dielectric constant of the mold consisting of the upper mold 1 and the lower mold 2 is 3.0 or more, and the dielectric loss factor is higher than that of the heating element 5.
This value is smaller than the dielectric loss factor of .

FIG. 2 is a diagram showing the characteristic values of four examples of the materials obtained by using the above-mentioned mold. however,
These four materials were selected from a machinable ceramic material called a free-cutting ceramic material that has pressure strength and an engineering plastic material that has pressure strength and heat resistance.

In FIG. 2, material A has a heat resistance temperature of 7.
00℃, compressive strength 22.0kgf/mm2, dielectric constant 6.
6, dielectric loss tangent 0.004, dielectric loss factor (permittivity x dielectric loss tangent) 0.026. In addition, material B has a heat resistance temperature of 100
0℃, compressive strength 35.0kgf/mm2, dielectric constant 5.9
2, dielectric loss tangent 0.003, dielectric loss factor 0.018. Material C has a heat resistance temperature of 260℃ and a compressive strength of 12.0kgf.
/mm2, dielectric constant 4.2, dielectric loss tangent 0.0012, and dielectric loss factor 0.005. Furthermore, material D has a heat resistance temperature of 5
00℃, compressive strength 19.4kgf/mm2, dielectric constant 3.
35, dielectric loss tangent 0.0011, dielectric loss factor 0.0037
It is.

When the above materials A to D are used as molds, the time required for the temperature of the heating element to rise to 150°C is 22 seconds for material A, 27 seconds for material B, 37 seconds for material C,
D was 42 seconds. However, the material shown in FIG. 3 is used as the heating element, and its dielectric constant is 5.6, dielectric loss tangent is 0.08, and dielectric loss factor is 0.448. Note that the above dielectric constant and dielectric loss tangent are measured at a measurement frequency of 1 MHz and a room temperature of 25
This is a value measured at ℃ and 50% humidity. Furthermore, we use a thermometer that is not affected by electromagnetic waves to measure the temperature rise of the heating element.
The sensor part was placed in the center of the heating element.

Further, FIG. 2 shows an example in which conventional fluororesin (tetrafluoroethylene) and silicone resin are used as the mold. The fluororesin has a heat resistance temperature of 260°C (heat distortion temperature of 121°C) and a compressive strength of 1.
2kgf/mm2, dielectric constant 2.0, dielectric loss tangent 0.000
2. The dielectric loss factor is 0.0004. In addition, silicone resin has a heat resistance temperature of 220°C, a dielectric constant of 3.0, and a dielectric loss tangent of 0.
001, and the dielectric loss factor is 0.003.

When the above fluororesin and silicone resin were used as molds, the time required for the temperature of the heating element to rise to 150°C was 65 seconds for the fluororesin and 47 seconds for the silicone resin.

FIG. 4 is a graph showing that the temperature rise of the heating element varies depending on the material of the mold.

In FIG. 4, A to D are the materials A to D mentioned above.
D, E represents silicone resin, and F represents fluororesin.

According to the embodiment of the present invention described above, the material of the mold is a dielectric material with a dielectric constant of 3.0 or more among machinable ceramic materials or engineering plastic materials with high heat resistance and high compressive strength. Since the material has a lower body loss rate than the heating element and the temperature rise rate of the heating element is improved, it is possible to perform hot-flow or melt molding of the rubber or plastic heating element while pressurizing it in a short time.

[0023] The material of the mold has a dielectric constant of 3.
．． A machinable ceramic material or an engineering plastic material having a dielectric loss factor of 0 or more and smaller than that of the heating element can also be used. For example, polyimide resin, polyetherketone, polyethersulfone, etc. can also be used.

[0024]

As described above, according to the present invention, a heat generating material made of rubber or plastic is filled, the filled heat generating material is pressurized, and dielectric heating is performed using a high frequency electric field of 100 MHz or less. , in the dielectric heating mold for vulcanizing or melt-molding the heat generating material, the dielectric loss factor of the mold is smaller than the dielectric loss factor of the heat generating material, and the dielectric constant of the mold is 3. Since the material is made of a material with a temperature of .0 or more, the temperature rise rate of the heating element is improved,
The time required for vulcanization or melt molding of the heating element can be shortened.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a device to which an embodiment of the present invention is applied.

FIG. 2 is a diagram showing characteristic values of examples of mold materials.

FIG. 3 is a diagram showing the blending ratio of heating elements.

FIG. 4 is a graph showing the difference in temperature rise rate of the heating element depending on the material of the mold.

[Explanation of symbols]

1... Upper mold, 2... Lower mold, 3... Upper electrode, 4... Lower electrode, 5
...Heating element, A, B, C, D...Mold material.

Claims (1)

[Claims] Claim 1: A heat-generating material made of rubber or plastic is filled, the filled heat-generating material is pressurized, and dielectric heating is performed using a high-frequency electric field of 100 MHz or less to vulcanize or melt mold the heat-generating material. A mold for dielectric heating, characterized in that the dielectric loss factor is smaller than the dielectric loss factor of the heat generating material, and the dielectric constant is 3.0 or more.