JP3874033B2 - Preform heat treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for heat-treating a preform for producing a hollow container by blow molding a thermoplastic synthetic resin. More specifically, the mouth-and-neck portion of a blow-molding preform made of polyethylene terephthalate resin is microwaved. It is related with the heating apparatus which heat-processes and crystallizes.
[0002]
[Prior art]
Hollow containers made of biaxially stretched polyethylene terephthalate (PET) resin are lightweight and have excellent transparency, impact resistance, gas barrier properties, etc., and as a container for filling and storing various contents in recent years. Widely used, among others, a heat-resistant hollow container made of PET resin capable of high-temperature filling has been demanded.
However, in a heat-resistant hollow container in which PET resin is simply produced by a normal biaxial stretch blow molding method, the neck and neck portions are not biaxially oriented like the body portion, so the strength is low. If this is filled with hot contents, or if the container filled with contents is sterilized under high temperature, the neck and / or thread of the container will be deformed and the sealing performance will be impaired, There were problems such as significantly reducing the appearance.
[0003]
Therefore, in order to make a heat-resistant hollow container made of biaxially stretched blow molded PET resin having a rigid and heat-resistant neck and neck, the neck and neck are heat-treated and whitened to obtain a crystallinity degree. It is necessary to increase the temperature, and thus a heat-enhanced hollow container has been used. (See Japanese Utility Model Publication No.59-172113)
In order to heat strengthen the neck and neck of the hollow container in this way, the injection molded preform is crystallized by heating only the neck and neck of the preform to the crystallization temperature before blow molding, and then the hollow A method of blow molding into a container (see JP-A-58-185227 and JP-A-62-284724), and after the injection-molded preform is blow-molded into a hollow container, the neck portion of the container is heated. Two methods of crystallization by treatment (see JP-A-2-67119 and JP-A-59-201824) are generally used.
[0004]
However, the latter method, in which the mouth and neck of the container is crystallized by heat treatment after blow molding, is heated by a heating device using an electric heater, an infrared heater, etc. When whitening is performed, heat rays are also irradiated below the buttock, so the boundary between the part that is desired to be whitened and the part that is not desired to be whitened is not clear and is blurred and the appearance is impaired. It is.
Therefore, in the method of blow molding a hollow container using such a heater heating device, the boundary portion between the whitened portion of the crystallized mouth and neck and the unwhitened portion of the non-crystallized main body is clarified. In order to achieve this, since it is necessary to provide a shielding means for protecting the main body portion of the container that is not desired to be whitened from heat rays in the heating device portion for whitening treatment, the molding device is Japanese Patent Publication No. 7-80236. As shown in the official gazette, it must inevitably become complicated and large.
[0005]
In contrast, the former method in which the neck of the preform is heated and crystallized before blow molding is performed, since the preform has a smaller shape than the blow molded container. Since the shielding means for protecting the body from heat rays can be made small, such a crystallization treatment apparatus can be easily incorporated in-line into a conventional molding apparatus as disclosed in JP-A-63-176129. In general, this method is often employed.
[0006]
By the way, in the conventional method as described above in which the neck and neck are heated and crystallized at the preform stage before blow molding, an apparatus as shown in FIG. 6 is used.
That is, the preform 1 preformed in a predetermined shape by injection molding is introduced into the heat treatment apparatus 6 while being supported by the preform holding jig 3, and the mouth of the preform is formed by the heater 4A and the reflector 5A. The neck 2 is heated and crystallized to be whitened. In such a type of heating device, means for heating by near infrared or far infrared using an electric heater made of quartz glass as the heater for heating is used. It is common.
[0007]
However, when the preform is heated by a heating device using an infrared heater as described above, it is difficult to control the heating section to an optimum heating temperature because of a temperature gradient, and if it is originally warmed I do not want to heat the surrounding air surrounding the preform in the heating device, and also the jigs and other device members that support the preform, and the upper part of the body near the mouth and neck is also crystallized. Therefore, the preform is easily broken in the next blow molding process.
Also, since electric heaters have a limited life span, the heating efficiency of the heaters gradually deteriorates with the time of use, and the quality starts to vary, resulting in frequent maintenance of defective electric heaters. Inspection is necessary, and this is a factor causing deterioration in workability and various other problems.
[0008]
Therefore, it is very difficult to crystallize by heating only the neck and neck of the preform locally to a predetermined temperature using a radiation heating device using an infrared heater or a heating device that blows hot air. As an alternative to such a heating device, as seen in Japanese Patent Application Laid-Open No. 58-217326, a method of locally heating only the neck and neck of a preform using a high frequency dielectric heating device has been attempted.
That is, the positive electrode fixed to the electrode holder is inserted and fixed with a slight gap in the mouth-and-neck portion of the preform to be heat-treated, which is held by the half-shaped preform holder, and the mouth-and-neck portion A negative electrode is provided opposite to the outer side of the holding body, and a high-frequency current is applied to the positive electrode from a high-frequency oscillator with the bottom of the preform supported by a support body (not shown). In this device, only the mouth neck of the preform is heated and crystallized by dielectric heating.
[0009]
However, the dielectric heat treatment apparatus as described above has a complicated structure for holding the preform and the electrode, and requires high precision and is expensive, and the current, frequency, and other heating conditions are strict. Control is necessary, and in particular, the positive electrode must be cooled and the heating section must be cooled at the same time as the control to turn on and off the high-frequency current. Requires advanced technology and skill, and if the control cannot be performed completely, it is expected that crystallization will vary and cause defective products.
[0010]
[Problems to be solved by the invention]
Microwave heating instead of conventional techniques using an electric heater or dielectric heating means as a heating source to locally heat only the neck and neck in a preform or hollow container molded with PET resin The device is used to heat and crystallize the mouth and neck of the preform.
An example of an attempt to heat the mouth and neck of the preform using a microwave heating apparatus is described in the above-mentioned Japanese Patent Application Laid-Open No. 63-176129. As a result, non-uniformity occurs and the degree of crystallinity varies more than infrared heating.
Therefore, the present invention uses a microwave heating apparatus as a means for heating the preform so that the body of the preform is not heated so that such a defect does not occur, and only the mouth and neck portion is heated. It is an object of the present invention to provide a heating apparatus that can be directly heated locally, can be easily crystallized, and does not vary in crystallinity.
[0011]
A preform for holding a preform, which is preformed by injection molding, is connected to a transport chain to pull the preform in a state where the mouth and neck are exposed to be heated, and the preform holding jig is provided. The transport chain is stretched in a tunnel-type heating furnace so that it can be transported.
The heating furnace forms an upper heating chamber provided with a microwave generator on the ceiling, and a gate type made of an electromagnetic wave absorbing material provided with a rail for guiding the preform holding jig at the lower portion of the heating chamber. Forming a lower shielding chamber having a shielding body, and providing a holding jig holding the lower part of the neck portion of the preform neck and neck so as to convey the shielding chamber to shield from the microwave, Only the mouth / neck portion of the preform is heated by a microphone wave reflected and scattered to be crystallized locally.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
PET preform is injection-molded by a known injection molding device, and the preform 1 is preformed into a shape suitable for the final shape and dimensions of the container except for the neck and neck portion. It is supplied into the cylindrical preform holding jig 3 by the supply device, and the mouth / neck portion 2 of the preform is held so as to be exposed from the opening end of the holding jig 3 so as to be heatable.
The preform holding jig 3 whose bottom portion is connected to the transport chain 4 is driven via a sprocket and transported to the heating device 6, and a guide rail provided on an electromagnetic wave shield 7 provided in the heating device. The mouth flange 3a of the preform holding jig is slidably supported on 7b and introduced into the microwave heating chamber 6A.
[0013]
The preform 1 in which the body portion is held in the cylindrical body of the holding jig 3 introduced into the heating device 6, the body portion is in the lower shielding chamber 6B protected by the electromagnetic shielding body 7, The mouth and neck are transported through the upper heating chamber 6A by the transport chain.
Then, the mouth / neck portion conveyed in the heating chamber was exposed to the microwaves 9 reflected and scattered from the microwave generator 9 provided on the ceiling, and exposed to the outside of the holding jig. Only the mouth neck 2 of the preform is locally crystallized.
[0014]
【Example】
The heating device 6 of the present invention is disposed and fixed on a machine base 8 of a preform heating process section of a known injection blow molding device, and its outer wall 6c is entirely surrounded by a metal plate that can reflect electromagnetic waves such as stainless steel. And it is configured as a tunnel.
The heating device 6 includes an upper heating chamber 6A that heat-treats the neck 2 of the preform 1 by microwaves, and a body 1a of the preform 1 held in the preform holding jig 3 as an electromagnetic wave absorber. 7 has a structure partitioned into two upper and lower chambers with a lower shielding chamber 6B to be protected.
[0015]
In the upper heating chamber 6A, an inlet 6e and an outlet 6f of the preform 1 are formed on the front and rear wall surfaces thereof, and electromagnetic shielding doors 6g and 6h that open and close in synchronization with the movement of the transport chain 4 are rails, respectively. 6j is movably provided, and a microwave generator 9 for heating the mouth / neck portion 2 of the preform is provided on the ceiling.
In the lower shielding chamber 6B, the electromagnetic shielding body 7 formed of an electromagnetic wave absorbing material such as ferrite having a substantially gate-shaped cross section is divided into a top surface and a central portion of the partition wall in the vertical direction. It is provided so as to penetrate, and is provided so as to surround the preform holding jig 3 and the transport chain 4 in the lower cavity.
[0016]
The holding jig 3 includes a cylindrical main body portion, a flange portion 3a at an upper end opening portion thereof, a rotation support portion 3b at a lower end portion, and a rotating member such as a pinion 3c. A conveying chain 4 is provided at the lower end of the support portion. It is connected and stretched through the heating device 6 so as to pass through the inlet 6g to the outlet 6f.
A slit for guiding the upper part of the preform holding jig 3, that is, an opening passage 7 a is formed at the center of the top surface of the gate-shaped electromagnetic wave shield 7, and the preform holding jig is formed on the opening surface. A guide rail 7b that slidably supports a flange 3a provided at the opening end of the tool 3 is integrally provided, and a preform holding treatment is provided in a portal-shaped lumen 7c below the guide rail 7b. The tool 3 is continuously provided so as to be moved through the sprocket 5 by the transport chain 4 connected to the support portion 3b at the bottom.
[0017]
The present invention configured as described above is a predetermined one that corresponds to the final shape of a container by injection molding a thermoplastic resin such as PET resin in a preform molding process of a commonly used injection blow molding apparatus. The bottomed preform 1 formed into a shape is supplied to a preform holding jig 3 which is formed into a tubular shape by a preform supply device after the forming mold is opened. Only the body is exposed so that it can be heated, and the body portion is held in the jig cylinder so as to be transportable.
The preform held by the holding jig 3 is sprinkled by a sprocket 5 via a transport chain 4 connected to the bottom of the holding jig with the mouth and neck 2 exposed to the outside of the holding jig. It is transferred to the heating device 6, and the electromagnetic shielding door 6 g that can be opened and closed in synchronization with the movement of the transfer chain 4 is opened at the inlet 6 e of the heating chamber 6 </ b> A. It is introduced into the heating chamber while being exposed to the outside.
[0018]
In the preform 1 introduced into the heating chamber 6A, the trunk portion 1a existing in the holding jig 3 below the mouth and neck portion 2 is protected by a portal microwave shield 7 made of a radio wave absorber, It is guided so as to slide on the rail 7a integrally with the holding jig 3, and is conveyed in the tunnel type heating device 6.
The preform neck portion 2 exposed from the holding jig 3 is, if necessary, a rack body or the like provided in a shielding chamber or an electromagnetic shielding body via a pinion gear 3c provided on a support portion 3b at the bottom of the jig. Only the mouth-and-neck portion 2 exposed while being rotated by being irradiated with microwaves from the microwave generator 9 provided on the ceiling portion of the heating chamber 6A while being conveyed while being rotated by the known rotation means. Is crystallized by heat treatment.
The preform 1 thus crystallized by being heated in the heating chamber is carried out of the heating chamber 6A by opening the shielding door 6h of the outlet 6f that opens and closes in synchronization with the transfer chain 4. .
[0019]
Subsequently, as shown in JP-A-62-284723 and others, the carried-out preform is rapidly cooled by inserting a shaped body having a core shape such as a support or a core into the mouth and neck. In order to correct the deformation of the mouth and neck as the crystallizes, a preform with improved rigidity and heat resistance of the mouth and neck is formed.
The preform having the neck and neck crystallized in this way and having rigidity and heat resistance is sent to the next heating step, reheated to a temperature at which blow molding is possible, and then transferred to the blow molding step. And molded into a hollow container with heat resistance and strength.
[0020]
Since the present invention is heated using the microwave as described above, in order to prevent the microwave from leaking from the heating chamber so as not to adversely affect the human body and others, The entire wall is surrounded by a metal plate such as stainless steel that reflects and scatters electromagnetic waves, and the door that shields microwaves at the entrance and exit of the heating chamber is configured to open and close in synchronization with the transport chain that transports the preform holding jig. However, in place of such a door, as shown in FIG. 4, a rubber plate that absorbs electromagnetic waves mixed with powder of a magnetic material such as ferrite can be used to transform into a shielding plate suitable for the shape of the doorway. It is possible to prevent leakage of microwaves by using a shield or a shield 6k formed in a curtain or warm shape by providing a slit. Bayori is effective.
[0021]
If the entire cylindrical part holding the preform is made of an electromagnetic wave absorber made of ferrite or other magnetic material or a magnetic rubber body, the body of the preform can be more reliably protected from microwaves. Is possible.
Furthermore, if a swirling fan that stirs and reflects microwaves is provided on the inner wall surface of the microwave heating chamber, the mouth and neck can be heated more uniformly.
The output of the microwave generator can easily control the heating temperature by adjusting the power, and the heating time can be easily controlled by adjusting the transfer speed of the transport chain. Is possible.
From the above, according to the apparatus of the present invention, only the mouth and neck can be locally heat-treated at the optimum temperature for the optimum time, and controlled to the desired crystallinity. Easy to do.
[0022]
【The invention's effect】
As described above, the present invention uses a microwave to crystallize the mouth and neck of a preform, and the furnace wall of a tunnel-type heating device provided with a microwave generator on the ceiling reflects electromagnetic waves. A cylindrical preform holding jig formed of a plate and connected to a conveying chain in the heating device is provided to be able to convey while rotating into the heating furnace, and the preform holding jig is shielded to absorb electromagnetic waves. Since the body has a structure, only the mouth and neck of the preform are held at the optimum temperature by microwaves while the preform holding jig holding only the mouth and neck of the preform is exposed. Since it can be heated uniformly in an optimal time, it can be crystallized without variation.
In addition, since heating is performed with microwaves, the heating device can be reduced in size and can be easily incorporated in-line into a conventional injection blow molding machine.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a heating device of the present invention cut in a vertical direction.
FIG. 2 shows an XX cross section in FIG.
FIG. 3 is an enlarged view showing the front entrance portion of the embodiment of the heating device of the present invention.
FIG. 4 is an enlarged view showing the front inlet portion of another embodiment of the heating device of the present invention.
FIG. 5 is a longitudinal sectional view of a preform holding jig used in the present invention.
FIG. 6 is a cross-sectional view showing a conventional heating device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Preform 2 Mouth neck part of preform 3 Preform holding jig 4 Transport chain 5 Sprocket 6 Heating device 6A Heating chamber 6B Shielding chamber 6g Entrance door 6k Rubber shield 8 Machine base 9 Microwave generator

Claims (7)

  A heat treatment apparatus for holding a preform preformed with a thermoplastic resin on a preform holder and heating and crystallizing the mouth and neck, wherein the heat treatment apparatus heats the mouth and neck of the preform by microwaves. An upper heating chamber and a lower electromagnetic shielding chamber that protects the preform body from microwaves, and the preform is placed on a guide rail provided at a central portion of the partition wall that is divided into the upper and lower chambers. A preform heat treatment apparatus, wherein the preform heat treatment apparatus is formed in a linear tunnel shape that slidably supports the reform holder.   In the heat treatment apparatus, an inlet and an outlet are formed at the front end surface and the rear end surface, respectively, and a door for shielding microwaves is provided at the outlet and the inlet of the upper heating chamber, and the preform holder is a bottom support portion. The preform heat treatment apparatus according to claim 1, wherein a conveying chain is connected to the lower electromagnetic wave shielding chamber so as to be transportable through the doorway.   The electromagnetic shielding chamber is provided with an electromagnetic shield made of an electromagnetic wave absorber for protecting the preform body from microwaves, and a guide rail for supporting the preform holder is provided on the top surface of the shield. The preform heat treatment apparatus according to claim 1, wherein the heat treatment apparatus is a preform heat treatment apparatus.   The electromagnetic wave absorber is formed in a gate shape in a vertical direction through a central portion of a partition wall that partitions the heating chamber and the electromagnetic wave shielding chamber, and the guide for allowing the preform holder to pass through the top surface portion of the gate shape. 4. The preform heat treatment apparatus according to claim 3, wherein a slit is provided, and a guide rail is provided in parallel at an opening end of the guide slit.   The electromagnetic wave absorber is provided by slidably supporting the flange portion of the preform holder on the guide rail at the end surface of the guide slit, and the main body portion of the preform holder and the transport chain are provided in the portal cavity. 5. The preform heat treatment apparatus according to claim 4, wherein the preform heat treatment apparatus is transportable.   The microwave shielding door is formed of a metal plate capable of reflecting electromagnetic waves, and is formed to be opened and closed in synchronization with a preform holder or a conveyance chain. Preform heat treatment equipment.   The microwave shielding door is configured to form a slit capable of pressing opening in a rubber plate made of a magnetic material so that the flange portion of the preform holder and the preform mouth and neck portion can enter and exit. The preform heat treatment apparatus according to claim 2.

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