JPH09295342A - Method and device for heating thermoplastic resin molded product - Google Patents

Abstract

(57) Abstract: To make microwave dielectric heating of a thermoplastic resin molded product suitable for mass production. SOLUTION: While heating and continuously transferring a large number of thermoplastic resin molded articles 5, the heated portion 5c is laterally irradiated with near-infrared rays, and the heated portion 5c is made of glass of the thermoplastic resin. The temperature is higher than the transition point and lower than the recrystallization temperature. After that, the path 5 through which the thermoplastic resin molded product 5 is sent
The cavity resonators 10a and 10 arranged in a skewed pattern with respect to x.
Microwaves are transmitted into b, and the heated portion 5c is dielectrically heated by passing only one high electric field region 36 for each of the cavity resonators 10a and 10b.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microwave dielectric heating method and apparatus for a thermoplastic resin molded article such as a preform for forming a plastic bottle formed by blow molding or stretch blow molding, and an infrared radiation heating method. Regarding

[0002]

In Japanese Patent Publication No. 6-22874, a polymer resin molded article is repeatedly passed through a high electric field region and a low electric field region of a microwave standing wave existing in a resonance state in a cavity resonator, A method of microwave dielectric heating a polymer resin molded article has been proposed. That is, as shown in FIG. 9, a microwave is transmitted in the direction of the arrow B to pass through the inside of the cavity resonator 100 in which the high electric field region 101 and the low electric field region 102 are alternately present, and the polymer resin molding is performed. The heated portion 103 of the article is passed in the direction of arrow A for microwave dielectric heating. However, according to the experience of the present inventor, in this method, two or more heated portions 103 are simultaneously formed in the cavity resonator 1.
It has been found that satisfactory heating cannot be achieved by passing through 00. Therefore, this method is not suitable for mass production, because the cavity resonator 100 having a relatively long length can heat only one by one.

The reason is considered as follows. If the receiving end 105 of the cavity resonator 100 of FIG. 9 is closed by the characteristic impedance, all the incident energy is absorbed by the receiving short 105 and there is no reflected wave. If the impedance of the receiving end 105 is different from the characteristic impedance, part or all of the incident energy is reflected by the receiving end 105 to generate a reflected wave. In this case, the electric field in the cavity resonator 100 is a combination of the incident wave and the reflected wave, and this combined wave is called a standing wave. As shown in FIG. 10 (when the cavity resonator is substantially closed except the entrance end 104), the standing wave has an antinode and a node of the wave at a certain position, and the electric field strength is sinusoidal between them. It is a wave that is distributed over time and changes at that position with time but does not progress at all. A slit (35 in FIG. 3) for allowing the heated portion 103 to pass through the bottom of the cavity resonator 100.
11) is formed, as shown in FIG. 11, there is more microwave leakage especially in the center in the length direction,
The electric field strength decreases. Therefore, in the central portion of the cavity resonator 100, the heating efficiency is low even if only one heated portion 103 passes through. In this state, when one heated portion 103, which is a dielectric, enters the cavity resonator 100,
When impedance matching is performed, as shown in FIG. 12, since the absorptance of the heated portion 103 is large, the reflected microwave power becomes small and the transmitted microwave power also becomes small. Therefore, the plurality of heated portions 103 are
When passing 0 in the direction of arrow A, the heated portion 1 on the incident side
Most of the microwave power is absorbed by 03, the transmitted microwave power to the heated portion 103 located downstream thereof is reduced, and the heating efficiency is further reduced.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a microwave dielectric heating method and apparatus for thermoplastic resin molded articles, which is suitable for mass production. Further, the present invention is
In order to crystallize the heated part of the thermoplastic resin molded product,
It is an object of the present invention to provide a method for uniformly and rapidly heating a heated portion to a temperature exceeding its recrystallization temperature.

[0005]

A method for heating a thermoplastic resin molded article according to claim 1 is a method for continuously dielectrically heating a large number of thermoplastic resin molded articles by microwaves,
Microwaves are transmitted into one or a plurality of cavity resonators arranged in a skewed pattern with respect to the route through which the thermoplastic resin molded article is sent, and the heated portion of the thermoplastic resin molded article is transferred to each cavity resonator. It is characterized by allowing only one high electric field region to pass therethrough. The method for heating a thermoplastic resin molded article according to claim 2, wherein while rotating the thermoplastic resin molded article, a portion to be heated is irradiated with near-infrared rays from the side, and the portion to be heated is glass of the thermoplastic resin. The dielectric heating according to claim 1 is performed after heating to a temperature equal to or higher than the transition point and lower than the recrystallization temperature. A method for heating a thermoplastic resin molded article according to a third aspect is that, after performing the dielectric heating according to the first aspect, while irradiating the thermoplastic resin molded article, a portion to be heated is irradiated with near infrared rays from the side. Then, the heated portion is heated to a temperature exceeding the recrystallization temperature of the thermoplastic resin.
A method for heating a thermoplastic resin molded article according to claim 4, wherein while rotating the thermoplastic resin molded article, a portion to be heated is irradiated with near-infrared rays from a side, and the portion to be heated is glass of the thermoplastic resin. Heating to a temperature above the transition point and below the recrystallization temperature, then to a temperature near the recrystallization temperature by dielectric heating according to claim 1, and then heating the thermoplastic resin molding while rotating it. The part is irradiated with near infrared rays from the side to heat the part to be heated to a temperature exceeding the recrystallization temperature of the thermoplastic resin.

A heating device for a thermoplastic resin molded product according to a fifth aspect is a device for continuously dielectrically heating a large number of thermoplastic resin molded products by microwaves, the device comprising: One or more microwave cavity resonators arranged in a skewed pattern with respect to a route to be sent; a device for forming only one high electric field region in a portion of the cavity resonator along the route, and thermoplastic resin molding It is characterized by comprising a device for transferring an item along the path.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a method and an apparatus for improving the heat resistance etc. by crystallizing (whitening) the mouth and neck of a preform (made of a polyethylene terephthalate type polyester resin) by heating and hardening it will be described. FIG. 1 is a plan view for explaining the above-mentioned device, in which 1 is a pedestal, 2 is a drive sprocket, 3 is a guide sprocket, 4 is a drive sprocket 2 and a guide sprocket 3 and move in a direction indicated by an arrow at a constant speed. And a moving chain for transferring the preform 5. 6 and 7 are preform 5 respectively
And the sending section and the sending section. A first infrared preheating device 8a and a second infrared preheating device 8b are provided outside the guide sprocket 3 along the moving chain 4 on the feeding portion 6 side. Further, the third infrared preheating device 8c and the fourth infrared preheating device 8c are provided outside the first infrared preheating device 8a and the second infrared preheating device 8b along the moving chain 4, respectively. 8d is provided. An infrared post-heating device 9 is arranged outside the drive sprocket 2 along the moving chain 4 in the vicinity of the delivery portion 7 side. The cavity resonator set 10 is disposed on the downstream side of and close to the fourth infrared preheating device 8d. The cavity resonator set 10 is connected to the microwave oscillator 14 via the waveguide 12 and the isolator 13.
The isolator 13 protects the oscillator 14 by avoiding the reflected wave in the absorber 11. The absorber 11 is a water load that absorbs the reflected wave from the cavity resonator set 10.

As shown in FIG. 2, each link pin 15 of the movable chain 4 extends vertically upward, and a sleeve 17 is externally fitted to an upper portion 15a thereof via a ball bearing 16. A sprocket 18 is provided around the sleeve 17. Reference numerals 19 and 20 respectively denote an inner fixed chain and an outer fixed chain, which are provided in parallel along the straight path of the moving chain 4 and engage with the sprocket 18, and the sleeve 17 rotates as the moving chain moves. It is supposed to do. Reference numerals 21 and 22 are a side guide member and a lower guide member of the movable chain 4, respectively, and 23 is a roller attached to the lower portion of the movable chain 4. The lower guide member 22 is arranged along the entire path of the moving chain 4, and its upper surface 22a is located at a constant level over the entire length so that the preform 5 can always move at the same height. .

A cylindrical preform holder 24 extending in the vertical direction is mounted on the collar portion 17a of the sleeve 17. The preform holder 24 is made of metal such as aluminum. The bottom of the preform 5 is the pedestal 1
7b and the spring 17c, the collar portion 5a of the preform 5 has an upper thin portion 24 of the preform holder 24.
It floats 2 to 3 mm above the end face of a. The infrared pre-heating devices 8a, 8b, 8c, 8d and the infrared post-heating device 9 have a moving direction (longitudinal direction) of the preform 5 at a position facing the collar portion 5a of the preform 5 including the collar portion 5a and the screw portion 5b. The infrared reflecting mirror 26 having a U-shaped cross section extending in the (direction) is provided. Inside the infrared reflecting mirror 26, a near-infrared lamp 25 consisting of a set of upper and lower two is arranged in the longitudinal direction at a position where it can be focused on the mouth / neck portion 5c. Two
7 is an infrared shielding plate, 28 is a preform holder 2
4 is a guide plate.

As shown in FIGS. 3, 4 and 5, the cavity resonator set 10 includes two cavity resonators 10a and 10a.
0b is integrated, and is a metal plate as a whole (preferably made of aluminum or copper having high electric conductivity)
It is composed of a closed box (closed except for the slots 30a and 31a and the slit 35 described later) which has a uniform inner surface height H and is surrounded by. The cavity resonator 10a and the cavity resonator 10b are separated by a partition wall 29 starting from the rod 32 and extending perpendicularly to the end wall 33, and both are of the same size. It is determined that the electric field region 36 is formed. The path of the preform 5 is determined so that the locus 5x of the axis line of the moving preform 5 (that is, the locus of the axis line of the link pin 15) passes through the center O of the two independent high electric field regions 36. In this case, the distance between the trajectory 5x of the axis of the preform and the inner surface of the end wall 33 of the cavity resonator is (1/4) · λ.
(Λ is the wavelength of the microwave in the cavity resonator: see Fig. 10)
become. Since the end wall 33 of the cavity resonator is a short-circuit plate (sealing plate), the electric field at the end wall 33 becomes 0, and the distance of the center O of the high electric field region 36 from the inner surface of the end wall 33 is (1/4).・ Because it becomes λ. The partition wall 29, the inlet side wall portion 30 of the cavity resonator 10a and the outlet side wall portion 31 of the cavity resonator 10b are perpendicular to the moving direction of the preform 5, that is, the moving chain 4, and each of them has a rectangular slot. 29a, 30a and 31a are formed. The slots 29a, 30a and 31a are formed in the same size so that the center line (for example, 31a1 in FIG. 4) passes through the locus 5x of the axis line of the moving preform 5. The heights h and widths w of the slots 29a, 30a and 31a are set to be slightly larger than the height and the maximum diameter of the mouth / neck portion 5c of the preform 5, respectively. Microwaves are transmitted from the oscillator 14 to the cavity resonators 10a and 10b in the direction of arrow B. A slit 35 is formed in the bottom portion 34 of the cavity resonator set 10 by connecting the bottom portions of the slots 29a, 30a, and 31a at right angles to the arrow B direction, and the mouth / neck portion 5c of the preform 5 is changed from the inlet sidewall portion 30 to the outlet sidewall portion. You can pass through to 31. Thus, the cavity resonators 10a and 10b are
The preforms 5 are arranged in a skewed pattern with respect to the moving path. That is, the transmission direction of microwaves (direction of arrow B) to the cavity resonators 10a and 10b is perpendicular to the movement path.

The inlet side wall portion 30 is connected to a slant portion 38 extending obliquely inward. The inlet side wall portion 31 is also connected to the inclined portion 39 extending obliquely inward. The length of the partition wall 29, the inner surface of the inclined portion 38 and the inner surface of the inclined portion 39, and the rod 32.
The distance from the center of the cavity is the distance s between the inner wall of the side wall 30 of the end wall 33a of the cavity resonator 10a and the partition 29, or the distance s between the inner wall of the side wall 31 of the end wall 33b of the cavity resonator 10b and the partition 29. Almost equal. Further, the lengths of the inlet side wall portion 30 and the outlet side wall portion 31 are substantially equal to or slightly larger than the distance s. The distance s is set to an appropriate size of λ / 2 or more and λ or less. The height H is preferably about s / 2. Assuming that the wavelength of the microwave in the free space is λ0, λ is expressed by {1- (λ0 / s) ² x1
Equal to the value divided by the square root of / 4}. However, s ≠ λ0 /
2. The ramps 38 and 39 connect to the base 37 whose inner surface width is equal to the distance s. 40 is a flange portion for connecting the base portion 37 to the waveguide 12. 41 and 42 are
It is a stub tuner for adjusting the impedance of the cavity resonators 10a and 10b.

With the above apparatus, the mouth / neck portion 5c of the preform 5 is crystallized as follows. Before starting the work, the near-infrared lamp 25 is turned on, the microwave oscillator 14 is turned on, and the microwave is transmitted to the cavity resonators 10a and 10b in the direction of arrow B (FIGS. 1 and 3). The microwave standing wave is present in the resonators 10a and 10b in a resonance state, and the high electric field region 3 is formed in the cavity resonator corresponding to the slit 35 through which the preform 5 passes.
6 are formed. The drive sprocket 2 is driven to move the moving chain 4 in the arrow direction. After the above preparation is completed, an insertion device (not shown) is provided at the feeding unit 6.
Then, the preforms 5 are inserted into the preform holders 24 one after another as shown in FIG. The mouth / neck portion 5c of the preform 5 rotates while rotating infrared preheating devices 8a, 8b, 8
The glass transition point of the polyethylene terephthalate-based polyester (called Tg: 75-
80 ° C or higher, recrystallization temperature (called Tc: 155-1
It is heated to a temperature below 60 ° C. Preferably Tg and T
temperature between g + 50 ° C., more preferably Tg and Tg + 3
Heated to a temperature between 0 ° C.

The preheating of the mouth / neck portion 5c is as follows.
This is because when the temperature reaches the glass transition point or higher, the resin is rapidly dielectrically heated to raise the temperature. The reason is considered as follows. When the temperature of the resin is equal to or higher than the glass transition point, the bond between the polymer chains is weakened, and the polymer chains easily move. When the resin is placed in an electric field of microwaves in this state, the motion of the polymer chains due to the polarization action becomes vigorous, and the dielectric heating is promoted by heat generation due to the frictional force between the polymer chains at that time. Immediately, the mouth / neck portion 5c passes through the cavity resonators 10a and 10b while rotating on its axis. At this time, in each cavity resonator, microwave induction heating is performed by passing only one high electric field region 36. In this way, when a plurality of mouth / neck portions 5c (heated portions of the thermoplastic resin molded product) enter the high electric field region in a direction perpendicular to the microwave transmission direction (arrow B direction), each mouth / neck portion 5c The microwave power is evenly divided and absorbed. Therefore, paragraph numbers 0002 and 000
It does not occur that only one heated portion is satisfactorily heated and the other heated portions are not satisfactorily heated, as described in 3. When the mouth-neck portion 5c of the preform 5 is dielectrically heated in the cavity resonators 10a and 10b,
The temperature distribution in the height direction of the mouth / neck portion 5c changes depending on the insertion depth f of the jaw portion 5a in FIG. 4, and in the case of the example described later, good results were obtained when the insertion depth f was 4 mm. . Since the slit 35 of the cavity resonator has a considerably high electric field and may be discharged when it comes into contact with the preform holder 24,
It is preferable to cover the end surface of the slit 35 with an electric insulator having a small dielectric loss.

At the time of leaving the cavity resonator 10b, the mouth and neck 5
c is heated to a temperature near the recrystallization temperature Tc (155 to 160 ° C.) of the polyethylene terephthalate polyester. It is preferably heated to a temperature between Tc-10 ° C and Tc + 10 ° C. Immediately after that, the mouth / neck portion 5c passes through the infrared post-heating device 9 while rotating, and the whole is heated uniformly above the recrystallization temperature, preferably Tc + 5 ° C.
And Tc + 40 ° C., the recrystallization (whitening) begins. The preform 5 is an infrared post-heating device 9
Immediately after exiting the sheet, the sheet is taken out from the preform holder 24 by a delivery device (not shown) in the delivery section 7 and sent to the device for the next step. By the next process, mouth and neck 5c
Is allowed to cool slightly, and recrystallization is matured. At the same time, the metal mold is shaped to adjust the inner diameter and height of the mouth / neck portion 5c to predetermined values, and then rapidly cooled.

FIG. 6 shows the relationship between the temperature rising rate and the initial temperature of the neck portion of the preform in the near infrared lamp (4 kw) heating and the microwave (output 2.7 kw) heating. In the case of near-infrared lamp heating, the rate of temperature rise is high when the initial temperature is low (however, the temperature difference in the thickness direction is large), but in the case of microwave heating, the higher the initial temperature above the glass transition point, the higher the temperature. The rate of climb will be higher. In this way, it is possible to set the near infrared lamp output, the microwave heating output, the heating time, and the like from FIG. 6 to increase the heating efficiency.

[0016]

EXAMPLE Each of the infrared pre-heating devices 8a, 8b, 8c, 8d and the infrared post-heating device 9 has a length of 2 kw and a length of 3
One set (two) of near-infrared lamps 25 of 00 mm was arranged. As the microwave oscillator 14, one having a microwave frequency of 2,450 MHz and a rated output of 5 kW was used (the output during heating was 2.7 kW). Cavity resonators 10a, 1
0b has a distance s (FIG. 3) of 110 mm and a height H of 55 m.
m, height h of slot (31a etc.) is 40 mm, width w
Of 38 mm was used. Mouth neck 5 of preform 5 made of polyethylene terephthalate polyester
The height of c is 23 mm, and the diameter of the thread portion of the thread portion 5b is 2
7 mm. The center distance between the link pins 15 of the movable chain 4, and thus the center distance between the preforms 5 is 65 m.
and the moving speed of the moving chain 4 was set to 4.1 m / min. The heating rate at this time is about 63 pieces / minute. When the mouth and neck 5c of the preform was heated under the above conditions, the infrared preheating time was 20 seconds, 120 ° C, the microwave heating time was 3 seconds, 165 ° C, and the infrared postheating time was 5 seconds, 180 ° C. A satisfactory crystallization of 5c has taken place.

For comparison, the cavity resonators 100 of the type shown in FIG. 9 (the length r is 400 mm, the width p is 113 mm, and the height 60 mm) are provided at the positions where the cavity resonators 10a and 10b are located.
Was arranged such that the moving direction of the preform 5 (direction of arrow A) was the length direction. Three stub tuners (impedance matching devices) were inserted between the isolator 13 and the cavity resonator 100, and microwaves were transmitted in the arrow B direction. Except for this, heating was performed under the same conditions as above, but the temperature of the mouth / neck 5c after leaving the cavity resonator 100 was 130 ° C.
Therefore, crystallization was not performed even after the post heating.

The present invention is not limited to the above-described embodiment. For example, the mouth-neck portion of the preform 5 is assembled in a Y-shaped cavity resonator set 50 and 51 as shown in FIG. 5c may be passed. In FIG. 7, 50a and 50b are cavity resonators of the cavity resonator set 50, 51a and 51b are cavity resonators of the cavity resonator set 51, both of which have the same structure as the cavity resonator 10a shown in FIG. And has similar slots and slits. Reference numeral 52 is a portion formed with a slit through which the mouth / neck portion 5c passes. The microwave is transmitted in the direction of arrow B. Further, as shown in FIG. 8, the I-shaped cavity resonators 60 and 61 may be arranged in a skewer-like arrangement with respect to the path along which the thermoplastic resin molded product is fed.
Reference numerals 62 and 63 are slits, and microwaves are transmitted in the direction of arrow B. If the production rate (the number of heatings per minute) is small, only one cavity resonator may be used. In this case, the rod 32 of the cavity resonator set 10 and the base 3 of the inclined portion 39
A partition wall 53 may be provided between the end portions on the seventh side to block microwaves from being transmitted to the cavity resonator 10b. Alternatively, only one of the cavity resonators 60 or 61 in FIG. 8 may be used. During dielectric heating, the thermoplastic resin molded article does not have to rotate.

[0019]

EFFECTS OF THE INVENTION The inventions according to claims 1, 2 and 5 have the effect that the thermoplastic resin molding can be microwave-dielectrically heated in a mass-produced manner. The invention according to claim 3 has an effect that the heated portion of the thermoplastic resin molded article can be uniformly crystallized. The invention according to claim 4 has an effect that the heated portion of the thermoplastic resin molded product can be uniformly and rapidly crystallized.

[Brief description of drawings]

1 is a schematic plan view of an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a vertical sectional view taken along the line II-II in FIG.

3 is an enlarged plan view of the cavity resonator set shown in FIG. 1. FIG.

FIG. 4 is a side view of the cavity resonator set of FIG. 3, taken along line IV-IV.

FIG. 5 is a front view of the cavity resonator of FIG. 3 as seen from the line VV.

FIG. 6 is a diagram showing an example of a relationship between an initial temperature of a heated portion and a temperature rising rate in near-infrared heating and microwave heating.

FIG. 7 is a plan view of another example of the cavity resonator set used for implementing the present invention.

FIG. 8 is a plan view of still another example of the cavity resonator set used for implementing the present invention.

FIG. 9 is a plan view for explaining a conventional cavity resonator.

10 is a diagram showing a standing wave when the cavity resonator of FIG. 9 is in a substantially hermetically sealed state except for a microwave incident part.

FIG. 11 is a diagram showing an electric field strength distribution when the bottom portion of the cavity resonator shown in FIG. 9 has a slit and no heated portion (dielectric body) is included.

FIG. 12 is a diagram showing an electric field intensity distribution when one heated portion (dielectric material) is included in a case where a slit is provided at the bottom of the cavity resonator shown in FIG. 9.

[Explanation of symbols]

1 Moving Chain (Transfer Device) 5 Preform (Thermoplastic Resin Molded Product) 5c Mouth and Neck (Head to be Heated) 5x Preform Axis Trajectory (Route to which the Thermoplastic Resin Molded Product Is Sent) 8a Infrared Preheating Device ( 8b Infrared preheating device (device heating to glass transition temperature or higher) 8c Infrared preheating device (device heating to glass transition temperature or higher) 8d Infrared preheating device (Device for heating to a temperature above the glass transition point) 9 Infrared post-heating device (device for heating above recrystallization temperature) 10a Cavity resonator 10b Cavity resonator 12 Waveguide (device for forming high electric field) 14 Microwave oscillator (device for generating microwave electric field) 18 Sprocket (device for rotating thermoplastic resin molded product) 19 Internal fixed chain (Device for rotating thermoplastic resin molded product) 20 Outside fixed chain (Device for rotating thermoplastic resin molded product) 25 Near infrared lamp 35 Slit (Route to which thermoplastic resin molded product is sent) 36 High electric field region 50a Cavity resonance Device 50b Cavity resonator 51a Cavity resonator 51b Cavity resonator 52 Slit (path through which thermoplastic resin molded product is sent) 60 Cavity resonator 61 Cavity resonator 62 Slit (path through which thermoplastic resin molded product is sent) 63 Slit ( (Route through which the thermoplastic resin molded product is sent)

Claims (5)

[Claims] 1. A method for continuously dielectrically heating a large number of thermoplastic resin molded articles by microwaves, wherein the thermoplastic resin molded articles are arranged in a skewed pattern with respect to a route to which the thermoplastic resin molded articles are fed.
Transmitting microwaves in one or more cavity resonators,
A method for heating a thermoplastic resin molded article, which comprises allowing a heated portion of the thermoplastic resin molded article to pass through only one high electric field region for each cavity. 2. While rotating the thermoplastic resin molded article,
2. Near-infrared rays are radiated from the side to the heated portion to heat the heated portion to a temperature not lower than the glass transition point of the thermoplastic resin and lower than the recrystallization temperature, and then the dielectric heating according to claim 1. Method for heating thermoplastic resin molded product. 3. After performing the dielectric heating according to claim 1, while rotating the thermoplastic resin molded article, the portion to be heated is irradiated with near infrared rays from the side, and the portion to be heated is made of the thermoplastic resin. A method for heating a thermoplastic resin molded article, which comprises heating to a temperature exceeding the recrystallization temperature. 4. While rotating the thermoplastic resin molded article,
The portion to be heated is irradiated with near infrared rays from the side to heat the portion to be heated to a temperature not lower than the glass transition point of the thermoplastic resin and lower than the recrystallization temperature, and then by dielectric heating according to claim 1. While heating the thermoplastic resin molded article to a temperature near the recrystallization temperature, while irradiating the thermoplastic resin molded article, the heated portion is irradiated with near infrared rays from the side, and the heated portion is recrystallized at the thermoplastic resin temperature. A method for heating a thermoplastic resin molded article, which comprises heating to a temperature exceeding 100 ° C. 5. An apparatus for continuously dielectrically heating a large number of thermoplastic resin molded articles by microwaves, said apparatus comprising:
One or a plurality of microwave cavity resonators arranged in a skewed pattern with respect to a path through which the thermoplastic resin molded article is sent; a device for forming only one high electric field region in a portion of the cavity resonator along the path. And a device for transferring the thermoplastic resin molded product along the path, a heating device for the thermoplastic resin molded product.