JPS6213322A - Method for high frequency dielectric heating of synthetic resin plate - Google Patents

Abstract

PURPOSE:To attain to uniformize temp. by preventing the rising in the circumferential temp. of a synthetic resin plate, by heating the synthetic resin plate in such a state that a specific heat insulating plate is interposed between a dielectric pole and the synthetic resin plate. CONSTITUTION:In applying high frequency dielectric heating to the synthetic resin plate inserted between parallel flat electrodes constituted as the resonance capacitor of a high frequency oscillation circuit, a heat insulating plate, which as an area larger than the flat area of the synthetic resin plate and of which the side surface in the side opposite to the electrodes is partially covered with a radio wave shielding material, is interposed between the electrodes and the synthetic resin plate so that 2mm or more of the shielding material is present over the entire periphery of the synthetic resin plate so as to be directed at least to an external side from the part corresponding to the circumference of the synthetic resin plate to apply high frequency dielectric heating to the synthetic resin plate. The heat insulating plate is pref. similar to the flat shape of the synthetic resin plate. By this method, because the intensity of the electric field between the circumference of the synthetic resin plate and the peripheries of the parallel flat electrodes becomes almost same to that of the interior of the synthetic resin plate as compared with the peripheral part thereof, the peripheral temp. and internal temp. of the synthetic resin plate being an article to be heated become equal to uniformly heat the synthetic resin plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high frequency dielectric heating method for uniformly heating a synthetic resin sheet metal.

[Conventional technology]

Conventionally, as a method of heating a synthetic resin plate, a method is known in which a synthetic resin plate is inserted between parallel plate electrodes configured as a resonant capacitor of a high frequency oscillation circuit and subjected to high frequency dielectric heating.

However, this method is not completely satisfactory both technically and economically.

[Problem that the invention seeks to solve]

When a synthetic resin plate is inserted between parallel plate electrodes that are configured as a resonance capacitor for a high frequency oscillation circuit, and the synthetic resin plate is subjected to high frequency dielectric heating, the electric field strength is greater around the parallel plate electrodes than inside. Therefore, the temperature around the synthetic resin plate as the object to be heated increases.

[Means and effects for solving all the problems] As a result of intensive research to overcome the drawbacks of the conventional methods, the present inventors found that When a synthetic resin plate is inserted into a plastic plate and subjected to high-frequency dielectric heating, if a specific heat insulating plate is interposed between the dielectric electrode and the synthetic resin plate and heated, the surrounding temperature of the synthetic resin plate will not rise5. The present invention was completed by discovering that a resin plate can be obtained.

That is, the present invention provides a method for inserting a synthetic resin plate between parallel plate electrodes configured as a resonance capacitor of a high frequency oscillation circuit and performing high frequency dielectric heating. 1. Place a heat insulating board having a larger area than the original size and having the side opposite to the electrode partially covered with radio wave shielding material at least outwardly from the corresponding area around the synthetic resin board. Another object of the present invention is to provide a method for high-frequency dielectric heating of a synthetic resin plate, characterized in that high-frequency dielectric heating is performed with the heat insulating plate interposed so that two or more of the shielding materials are present over the entire circumference.

In general, high-frequency dielectric heating using parallel plate electrodes is independent of heat conduction, which is proportional to the high-frequency power.

It is used as a pre-molding heat treatment for synthetic resins because it can be heated rapidly using the molecular motion of the material itself. The temperature around the synthetic resin plate of the object to be heated will rise.1 Depending on the surrounding conditions, heat will be dissipated from the surface of the synthetic resin plate of the object to be heated, and the temperature increase will be greater inside the substance.6. Therefore, it is difficult to obtain a synthetic resin plate with a uniform temperature, and it cannot be applied to applications with strict quality requirements.

In the present invention, when a synthetic resin plate is inserted between parallel plate electrodes configured as a resonance capacitor of a high frequency oscillation circuit and subjected to high frequency dielectric heating, the area of the synthetic resin plate is A heat insulating plate having a large area and partially covered with a radio wave shielding material on the side opposite to the electrode is installed at least all the way outward from the area corresponding to the periphery of the synthetic resin plate. By interposing the heat insulating plate so that two or more of the shielding materials exist throughout the area, the electric field strength between the periphery of the synthetic resin plate and the periphery of the parallel plate electrode becomes approximately the same as that inside the periphery of the synthetic resin plate. So,
The surrounding temperature and the internal temperature of the synthetic resin plate of the object to be heated become equal, resulting in uniform heating.

Therefore, the structure of the heat insulating plate interposed between the parallel plate electrodes and the synthetic resin plate is important, and the first consideration is its shape.

It is preferable that the planar shape is similar to that of the synthetic resin plate and that it is larger than one synthetic resin plate.

In addition, the position of the radio wave shielding material covering at least 251 m outward from the corresponding part of the synthetic resin plate will only function as a part of the electrode if it covers the part on the electrode side. By covering the opposite side of the electrode, the electric field strength between the periphery of the synthetic resin plate and the periphery of the parallel plate electrode can be made almost the same between the periphery and the inside of the synthetic resin plate.

From the area corresponding to the periphery of the synthetic resin plate, towards the outside,
If the width of covering the opposite side of the electrode with the radio wave shielding material is less than 2 -, the electric field strength between the periphery of the synthetic resin plate 1 and the periphery of the parallel plate electrode will be larger at the periphery than inside the synthetic resin plate 1. Therefore, the temperature is preferably higher than the temperature of the peripheral part of the synthetic resin plate of the object to be heated.

In addition, in the case where at least two or more parts of the synthetic resin plate are coated with radio wave shielding material outward from the area corresponding to the periphery, the area inward from the area corresponding to the periphery of the synthetic resin plate is covered with radio wave shielding material. Although it varies depending on the size of the electrode plate and the synthetic resin plate, they may be coated with a radio wave shielding material to the extent that the object of the present invention is not impaired (for example, about IO-).

In order to equalize the peripheral temperature and internal temperature of the synthetic resin plate, it is more preferable that the width of the radio wave shielding material is 10 or more.

Regarding the relationship between the sizes of the parallel plate electrodes and the synthetic resin plates of the object to be heated, it is preferable for each synthetic resin plate to be smaller than the size of the parallel plate electrodes for uniform heating, but economically unfavorable.

Therefore, in general, the area of the synthetic resin plate is set to be 40% or more of the area of the parallel plate electrodes.

The above-mentioned area relationship that can fully exhibit the effects of the present invention is 5
It's more than a percentage of the time.

The material of the heat insulating board itself may be any non-dielectric heat insulating material with cushioning properties.

Examples include Teflon, silicone, glass fiber reinforced silicone, and polyethylene.

Examples of the radio wave shielding material include, but are not limited to, metal foils and thin plates of AA, Cu, etc., and thin plates of synthetic resin with vapor-deposited metal thin films.

The synthetic resin board can be any dielectric resin.

For example, PET, POM, Ny6. Ny6G, PMMA,
Examples include phenol, but polyolefins such as polyethylene and polypropylene, which inherently do not have polar groups and cannot be subjected to high-frequency dielectric heating, may also be used, in which polar molecules are preliminarily dispersed.

Furthermore, a non-dielectric synthetic resin mixed with conduction electrons such as carbon generates heat not due to dielectric loss but due to loss due to conduction current, and this type of synthetic resin is also applicable.

The laminated form of the synthetic resin plates is one synthetic resin plate or a synthetic resin sheet interposed between two synthetic resin plates to prevent thermal adhesion between the resin plates.

A laminate made of paper or other so-called interleaf paper.

Alternatively, a laminate of different types of synthetic resin plates that are not bonded together may be used.

Gold paper is generally a non-dielectric polyolefin sheet such as polyethylene or polypropylene, but PET',
A dielectric sheet 1 such as Ny6° paper may also be used.

A laminate consisting of a synthetic resin sheet and so-called gold paper such as paper, which is interposed between synthetic resin plates and prevents thermal adhesion between the resin plates, and the synthetic resin plate and the gold paper. Those with different coefficients of thermal expansion and contraction, specifically,
Although the linear expansion coefficient ratio between the synthetic resin board and gold paper is 2 or more or 0, although it is not limited to this as it varies depending on the processing conditions of the synthetic resin board or paper, high frequency dielectric heating conditions, etc.
．． If the heat shrinkage rate ratio is 1°5 or more or 0.67 or less, a part of the 8R laminate may be deformed or wrinkles may occur, which is undesirable. Although it is difficult to obtain a laminate, if the laminate is heated by high frequency dielectric under pressure, even if the coefficient of thermal expansion and thermal contraction of the synthetic resin plate and the mount which make up the laminate are different, the pressure will change depending on the applied pressure. Changes due to thermal expansion and thermal contraction of the laminate can be forcibly suppressed, so it is extremely unlikely that a part of the laminate to be heated will be deformed or wrinkled during high-frequency dielectric heating. This is preferable because a laminate with a smooth surface and a uniform temperature can be obtained.

The pressing force to prevent part of the laminate of the object to be heated from being deformed or wrinkled during heating varies depending on the type of laminate, but is at least 2 Kg/elJ or more,
The pressure must be within a range that does not cause the laminate to be compressed and stretched during heating.

If the pressing force is less than 2 Kf/-, it is not possible to sufficiently prevent a part of the laminate plate of the object to be heated from being deformed or wrinkled.

If heat dissipates from the surface of the synthetic resin board due to ambient conditions and the temperature rises larger inside the synthetic resin board, reheat the synthetic resin board using a heating press after high-frequency dielectric heating. good.

Furthermore, when performing high-frequency dielectric heating, heat dissipation may be reduced by blowing hot air into a heating chamber that uses parallel plate electrodes with heaters or parallel plate electrodes.

The oscillation frequency of the high frequency oscillation circuit is preferably selected to have a wavelength that is at least twice the maximum length of one synthetic resin plate in plan area.

When aiming at molecular cleavage or loosening of side chain bonds in a synthetic resin plate during heating, high frequency dielectric heating is preferably performed by applying high frequency energy greater than the respective bond energies.

[Example 1] 11 KVA, 62 MHz low pressure (s, 5oo
V),! : High voltage (a, 5oQV) switching type, output sKW,
Using a high-frequency dielectric heating device with parallel plate electrodes of size 36 x 363, P of size 21 m x 253 m and thickness of 40 w
As a result of heating the MMA plate under the conditions shown in Table 1, the temperature difference between the peripheral part of the plate (1 to 4 in Figure 1) and the center part of the plate (5 in Figure 1) is shown in Figure 1. It's extremely small.

The following margins [Comparative Example 1] Using the same equipment and synthetic resin plate as in Example 1, heating was performed under the conditions shown in Table 2.
There is a large temperature difference between 4) and the center of the plate (5 in Figure 2).

Table 2 [Example 2] Using the same equipment as in Example 1, HX Q of size 27
The results of heating a phenol plate of 7 cm- and thickness of 25M under the conditions shown in Table 3 are as follows:
) and the center of the plate (5 in Figure 3), the temperature at the foot of Ift & 1% is also 18 ~ [Comparative Example 2] Using the same equipment and synthetic resin plate as in Example 2, Table 4 shows The results of heating under the conditions shown in Figure 4 are as follows:
Table 4 [Example 3] 11 KVA, 62 MHz low pressure (5,500 V)
) High voltage (6,500V) switching type, output 5KW,
Using a high-frequency dielectric heating device with a parallel plate electrode size of 363 x 36 crII% and a maximum pressing force of 6 tons,
7tMX27m, 18 2+u OPMMA plates, 17 PP sheets (thickness 0.2 wf) interposed between them,
All laminates with a total thickness of 39.4 lJ were heated under the conditions shown in Table 5. The results for each board (1 to 18 in Fig. 5 are the floors of the laminates and are shown in order from the top) are as follows: The temperature difference between the plate (marked Δ in FIG. 5) and the center of the plate (marked ○ in FIG. 5) is extremely small.

The following margins [Comparative Example 3] Using the same equipment and laminated plates as in Example 3, heating was performed under the conditions shown in Table 6. The results for each plate (1 to 18 in Figure 6)
The peripheral part of the plate (marked with Δ in Figure 6) and the center of the plate (marked with O in Figure 6)
There is a large temperature difference between the

In addition, the PP sheet interposed between the PMMA plates was wrinkled, and some of the PMMA plates had slight marks.
18 25 cm, 2 mm thick OPMMA plates, 17 PP sheets with a thickness of 0°2 IIJII interposed between them, total 39.4. The results of heating a laminate of the thickness shown in Table 7 under the conditions shown in Table 7 and then reheating the laminate using a hot press at a temperature of 150° C. as shown in FIG. When reheated using a hot press for 1 to 5 minutes, the difference in temperature between the surface and center of the laminate is small.

The following margin [Example 5] When heating the laminate using the same equipment and conditions as Example 3,
Heating was carried out while blowing hot air at a temperature of 50°C into a heating chamber having parallel plate electrodes.

As a result, as shown in FIG. 8, the temperature difference between the surface and the inside of the laminate was significantly reduced by suppressing heat radiation from the parallel plate electrodes and the periphery of the laminate.

〔Effect of the invention〕

As explained above, according to the high frequency dielectric heating method for a synthetic resin board of the present invention, when heating a synthetic resin board, a synthetic resin board having a uniform temperature with no temperature difference between the periphery and the center of the board can be obtained. Furthermore, since the synthetic resin plate of the object to be heated does not partially deform or wrinkle during heating, it is possible to produce a synthetic resin plate with good appearance. 0

[Brief explanation of drawings]

Fig. 1.3.5.7.8 shows the results of the example of the present invention, and Fig. 2.4.6 shows the experimental results of the comparative example. 1st
．． Figure 3 shows the temperature at the center of the plate and the peripheral area of the plate in Example 1.2 and Figure 2.4 in Comparative Examples 1 and 2, respectively. FIG. 5.6 shows the temperature at the center and end of the plates of Example 3 and Comparative Example 3, respectively. FIG. 7 shows the temperature of the plate during hot pressing. Figure 8 shows the temperature of the plate when heated while blowing hot air. Patent Applicant: Asahi Kasei Kogyo Co., Ltd. Figure 1 + 234 5 Figure 2 + 234 5 IeL Figure 3 + 2345 Irachi! Figure 4: +2345 Figure 5: Figure 6: N1 grade upper r5 J sushi) Figure 8: 123456789101 Mortar 213141516171
82 middle school
Lower surface % 1 Surface 11 Bottle upper furnace 5th grade - Flea procedure amendment (voluntary) January 7, 1985

Claims (1)

[Claims] 1. When inserting a synthetic resin plate between parallel plate electrodes configured as a resonance capacitor of a high frequency oscillation circuit and performing high frequency dielectric heating, a synthetic resin plate is inserted between the electrode and the synthetic resin plate. A heat insulating board having an area larger than the planar area of Method 2 of high-frequency dielectric heating of a synthetic resin board, characterized in that high-frequency dielectric heating is performed with the insulation plate interposed so that the shielding material is present at least 2 mm over the entire circumference, a synthetic resin board is heated by high-frequency dielectric heating Claim 1, characterized in that high-frequency dielectric heating is performed in a pressurized state.
Heating method 3 described in section 3, when performing high frequency dielectric heating by inserting a synthetic resin plate between parallel plate electrodes configured as a resonance capacitor of a high frequency oscillation circuit, a synthetic resin plate is inserted between the electrode and the synthetic resin plate. A heat insulating plate having an area larger than a flat area and whose side surface opposite to the electrode is partially covered with a radio wave shielding material is placed at least outwardly from the area corresponding to the periphery of the synthetic resin plate. A synthetic resin board characterized in that the synthetic resin board is heated by high frequency dielectric with the heat insulating board interposed so that the shielding material is present at least 2 mm over the entire circumference, and then the synthetic resin board is subsequently reheated using a heating press. High frequency dielectric heating method