JPS63307928A - Heating method for high-molecular resin molded product - Google Patents

Abstract

PURPOSE:To heat uniformly in a short time by heating a substance to be heated with infrared rays before or after heating with micro-standing waves. CONSTITUTION:A preform 1 inserted into a mandrel 3 is rotated and conveyed inside a hollow resonance device 20. The preform 1 passes sections where an electric field of standing waves generated in the resonance device is strong and where the same is weak alternately and it is dielectrically heated. In order to correct the temperature unevenness of the preform, an infrared heating zone constituted of a heating unit 26 is provided. In the case when said infrared heating zone is provided in the pro-process of a dielectric heating zone, the same is easily heated in the following dielectric zone, while provided in the post-process, heated sections being insufficient because of the dielectric heating can be corrected, and the desired temperature distribution can be obtained. The heating unit 26 is constituted of an infrared heater 24 and a reflector 25, and the focus of infrared rays is adjusted on the sections insufficiently heated because of the dielectric heating by the reflector 25.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for heating a thermoplastic bottle or preform, and particularly to a heating method for heating a thermoplastic bottle or preform, and particularly for heating a thermoplastic bottle or preform consisting of a bottomed cylindrical body and a mouth. A method of uniformly heating the body of the preform when making a bottle by blow molding, and crystallizing the mouth of a thermoplastic bottle or preform so as to obtain dimensional stability at high temperatures. It relates to a method of heating for oxidation.

(Conventional Art) When a thermoplastic bottle is filled with contents at high temperature, the mouth part is heated and thermally deformed, making it impossible to seal it with a lid.

Therefore, it is common practice to crystallize the mouth of plastic bottles to prevent thermal deformation. Conventionally, the method for this purpose is to cover the mouth with a cap and heat the cap by induction heating (Japanese Patent Laid-Open No. 55-1998).
12031) A method of arranging a heating cover around the mouth and blowing hot air into the heating cover (Japanese Patent Application Laid-Open No. 61-79627)
Alternatively, electrodes are placed inside and outside the mouth, a high frequency voltage is applied to the electrodes, and heating is performed using high frequency dielectrics (Japanese Unexamined Patent Publication No. 58-2
17326) etc. are known.

Furthermore, when producing bottles by blow molding from a thermoplastic preform consisting of a bottomed cylindrical body and a mouth, it is necessary to heat the chest of the preform. An infrared heater was placed outside to heat the preform from the outside.

[Problem that the invention seeks to solve]

In order to crystallize the mouth of the plastic bottle, a cap is placed on the plastic bottle and the cap is heated by induction, a heating cover is placed around the mouth and hot air is blown into the heating cover, or the preform is heated with an infrared heater from the outside. In all of these heating methods, the body of the preform and the mouth of the plastic bottle are heated from the outside, and the heat is transmitted from the outside to the inside through the plastic resin pipe wall. In this case, the thermal conductivity of the plastic nuc resin is low, and it takes a long time to sufficiently raise the temperature inside. Furthermore, in order to rapidly raise the temperature of the inside to a desired temperature, the temperature of the outer surface must be increased, resulting in overheating of the outside and deterioration of the properties of the material. Furthermore, it is difficult to obtain a uniform temperature distribution inside and outside.

On the other hand, in the dielectric heating method, the heating rate of each part is determined by the shape of the electrode and the object to be heated, but it is difficult to make this uniform, and the parts where the temperature locally becomes high due to heating are As the heating rate increases and the temperature rises extremely, it is difficult to achieve uniform heating.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for uniformly heating a thermoplastic bottle or preform in a short time.

[Means for solving problems]

Microwaves are introduced into the cavity resonator, and the high electric field region and low electric field region of the standing wave existing in a resonant state within the cavity resonator are repeated while rotating the heated part of the polymer resin molded product. The polymer resin molded product is heated by passing it through. More uniform heating can be achieved by concentrating infrared rays on a specific location while rotating the object to be heated during the heating process using the micro standing waves or afterwards.

(Function) When creating a standing wave in a resonant state in the cavity resonator and passing it through the high electric field region and low electric field region while rotating the polymer resin molded product, the heated Objects are heated strongly at certain times and weakly heated at other times.

According to such a heating method, it is possible to prevent so-called thermal runaway, in which a certain part of the object to be heated is heated strongly, and that part is heated even more strongly. Furthermore, by irradiating the object with the focused infrared rays, the temperature distribution of the object can be effectively controlled. That is, if a part of the object to be heated that is to be heated strongly is irradiated with infrared rays in advance, the temperature of that part increases by one arm, making it easier to be heated by microwaves. Conversely, the temperature distribution can also be controlled by heating the object to be heated with microwaves and then irradiating the part of the object to be heated strongly with infrared rays.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the mandrels 3, 3, . . . supporting the preform 1 circulate between the rotating tables in the order indicated by the arrows. That is, from the preform delivery table 4 to the transfer table 5, the heating station table 6, the annealing station table 7.8, the transfer table 9,
Blow molding station table 10, transfer table 1
1, the preform transfer table 4 and the mandrels 3', 3, . Preforms 1.1... are mounted onto the mandrels 3.3... which are circulated in this manner from a conventionally known supply device 4 via a supply table 12.13. The preform 1 has the cross-sectional shape shown in FIG. 2, and consists of a bottomed cylindrical body 15 and a mouth 16 having a thread or an annular protrusion. While this preform 1 is mounted on the mandrel 3 and circulates through the above-mentioned route, the body is heated on the heating station table 6 and blow molded on the blow molding station table by a conventionally known method.
A thermoplastic bottle 2 shown in FIG. 3 is manufactured. The manufactured thermoplastic plastic bottle 2 is handled by a conventionally known device from a mandrel 3 held on a delivery table 4 and sent out via a delivery table 14.

The mandrel 3 has a cross-sectional shape shown in FIG. 4, and is integrally provided with circumferential grooves 17, 17 for holding on each table, and sprockets 18, 18 for rotationally driving. Chains are strung around the parts of the heating station table 6 and annealing station table 7.8 where the mandrels 3.3... pass through so that they are in different stages, and engage with the upper or lower subblocks 1-18, 18 and the mandrels. is driven to impart rotational motion to the

However, the chain is not shown.

Next, the device for bending the heating station table 6 and the heating operation will be explained with reference to FIGS. 2 to 7. Mandrel holding devices 19 are attached to the heating station table 6 at equal intervals, and arcuate cavity resonators 20 are arranged along the periphery of the table.

established and established. As shown in FIG. 5, the preform 1 inserted into the mandrel is rotated and conveyed within the cavity resonator 2o. In order to prevent radio wave leakage, both ends of the cavity resonator 20 have a rectangular cross section narrowed by at least one wavelength of the standing wave existing within the cavity resonator, as shown in FIG. The 'a' wavelength of the cross section is smaller than the wavelength of the standing wave existing within the cavity resonator. A slit is cut in the lower surface 21 of the resonator so that the preform 1 can pass through, but in order to prevent radio wave leakage from the lower surface, a ring-shaped collar 22 attached to the upper part of the mandrel is pressed against the lower surface of the resonator. It has a mechanism that moves while rotating. At this time, a thin Teflon sheet 23 is provided between the lower surface of the resonator and the ring-shaped brim to prevent discharge from occurring between the two. Further, a protrusion such as a post 27 may be provided inside the cavity resonance 520 so that the electric field can be controlled. The preform 1 is heated by dielectric heating as it passes alternately through the strong and weak electric fields of the standing wave generated in the resonator, but each part of the preform changes to a weak electric field immediately after passing through the strong electric field. The phenomenon of heat loss that occurs when a so-called uniform electric field is applied does not occur.

In order to correct temperature irregularities in the preform, an infrared heating zone consisting of a heating unit 26 as shown in FIG. 7 is provided. If this infrared heating zone is provided in the previous process of the dielectric heating zone, the area heated by infrared rays will be more easily heated in the next dielectric heating zone, and if it is provided in the second process, dielectric heating will be insufficient. This means that the heated portion can be corrected, and a desired temperature distribution can be obtained in either case. The heating unit 26 is composed of an infrared heater 24 and a reflecting mirror 25, and irradiates infrared rays toward the preform 1 that rotates together with the mandrel 3. The reflector 125 has an ellipsoidal surface, and is installed so as to focus the infrared rays on a portion that is insufficiently heated due to dielectric heating. The preform heated in the preform heating station table 6 in this manner is uniformly heated in the annealing station 7.8 and blow molding station 1.
Blow molded into bottles at 0. FIG. 8 is a sectional view showing another embodiment of the present invention, in which the mouth of the preform is crystallized. The preform is supported with its mouth facing upward, subjected to rotational motion, and dielectrically heated within the cavity resonator. A post 27 is erected inside the cavity resonator 20, and the electric field can be controlled by the shape and insertion depth of the post. A portion of the heating unit for heating the outside of the preform in the embodiment of FIG. 1 has been replaced with an infrared concentrator 26' of FIG. The infrared condensing device 26' is composed of a reflecting mirror 25' having a circular cross section and a linear infrared heater 24'. Concentrate on the protruding part of the mouth of the preform located at the focal point. In this way, the entire mouth of the preform is heated to the required temperature.

(Effects of the Invention) As explained above, since the mouth of a thermoplastic bottle or preform or the body of the preform is heated from the inside and outside, the opening time required for heating is shortened and productivity is improved. Moreover, uniform heating of each part becomes possible.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an outline of an embodiment of the present invention, FIG. 2 is a sectional view of a preform 1 heated in this embodiment,
FIG. 3 is a cross-sectional view of a thermoplastic bottle manufactured from preform 1 by blow molding, FIG. 4 is a cross-sectional view of mandrel 3 that supports preform 1, and FIG. 5 is a cross-sectional view taken along line AA in FIG. 6 is a schematic view showing the large end of the cavity resonator, FIG. 7 is a sectional view taken along line B-8 in FIG. 1, and FIG. 8 is a perspective view showing another embodiment of the present invention. FIG. 9 is a sectional view showing an infrared heating section in another embodiment of the present invention. 1... Preform, 2... Thermoplastic bottle, 3... Mandrel, 4... Delivery table,
5゜9.11... Transfer table, 6... Heating station table, 7, 8... Annealing station table, 10... Blow molding station table, 12.13... Supply table, 14... - Delivery table, 15...body, 16...mouth, 17...
Circumferential groove, 18... Sprocket, 19... Holding device,
20...Cavity resonator, 21...Resonator bottom surface, 22.
...Ring-shaped brim, 23...Insulating sheet, 24...
Infrared heater, 25...Reflector, 26...Heating unit, 27...Post. Applicant's agent Hiroshi Fujimoto Figure 3 Brown Figure 4 Figure 6 Figure 7 Figure 6 $ 9 Old

Claims (1)

[Claims] 1. Microwaves are introduced into a cavity resonator, and the high electric field region and low electric field region of a standing wave existing in a resonant state within the cavity resonator are transmitted to a polymer resin molded product. A method for heating a polymer resin molded product, which is characterized by passing the heated part repeatedly while rotating it. 2. Infrared rays are focused in advance on a specific part of the heated part of the polymer resin molded product to heat it, and then the high electric field region and low electric field region of the microwave standing wave that exists in a resonant state inside the cavity resonator is heated. A method for heating a polymer resin molded product, characterized in that the heating portion is repeatedly passed through the heated portion while rotating. 3. The high electric field region and the low electric field region of the microwave standing wave existing in a resonant state in the cavity resonator are repeatedly passed through the heated part of the polymer resin molded product while rotating, and then the heated part is A method for heating a polymer resin molded product, which is characterized by focusing infrared rays on a low-heating part and heating it while additionally rotating it.