JPH09277366A - Method for crystallizing mouth neck part of preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat only the mouth neck part of a preform obtained by injection blow molding in order to produce a heat-resistant hollow container made of polyethylene terephthalate by using microwaves to crystallize and thermally strengthen the same. SOLUTION: A preform molded into a definite shape by injection molding is supplied to a preform holding jig 3 holding the body part of the preform in such a state that only the mouth neck part of the preform is exposed from the opening end of the cylindrical member of the holding jig 3 in a heatable manner to be introduced into a tunnel-shaped heating apparatus 6 through the feed chain 4 connected to the bottom part of the holding jig 3 and only the mouth neck part of the preform is irradiated with microwaves from a microwave generator 9 while the flange 3a of the holding jig 3 is supported on the surface of a guide rail 7 to be fed so that the body part of the preform held within the cylindrical member is passed through a lower shielding chamber 6B protected by a gate-shaped microwave shielding member 7 composed of an electromagnetic absorbing material and the mouth neck part 2 exposed from the opening end of the cylindrical member is passed through an upper heating chamber 6A to be subjected to heat treatment to be crystallized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of heat-treating a preform for producing a hollow container by blow molding and crystallizing the preform. More specifically, the invention relates to a hollow container produced using a polyethylene terephthalate resin. The present invention relates to a method of crystallizing and strengthening the mouth and neck.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Hollow containers made by biaxially stretch-blow molding of resin are lightweight and have excellent transparency, impact resistance, gas barrier properties, etc., so that they have been widely used in recent years as containers for filling and storing various contents. became. Generally used hollow containers made of PET resin are roughly classified into heat resistant containers that can be filled at high temperature and non-heat resistant containers that cannot be filled at high temperature. But,
Even in a heat-resistant container, a hollow container simply formed by a normal biaxial stretch blow molding method has low strength because the mouth-neck portion is not biaxially molecularly oriented like the body portion. When filling high temperature contents or sterilizing the filled container at high temperature, the mouth or neck of the container may be deformed, the sealing performance may be impaired, or the appearance may be significantly deteriorated. was there.

Therefore, in order to impart rigidity and heat resistance to the mouth and neck of a container formed by biaxially stretch-blow molding of PET resin,
A hollow container reinforced by whitening the mouth and neck by heat treatment to increase the crystallinity has come to be used.
(Refer to Japanese Utility Model Application Laid-Open No. 59-172113) In order to strengthen the mouth / neck portion of such a hollow container, only the mouth / neck portion of the preform is heated to a crystallization temperature before blow molding the injection-molded preform. And crystallize, and then blow molding into a hollow container (Japanese Patent Laid-Open No. 58-18 / 1983).
No. 5227), and a method of blow-molding an injection-molded preform into a hollow container and then heat-treating the mouth-neck portion of the container to crystallize it (see JP-A-2-67119). Is generally used.

However, in the latter method in which the mouth and neck of the container is heat-treated and crystallized after blow molding, the opening end of the mouth and neck is heated by a heating device using an electric heater or an infrared heater. When whitening from the head to the head, the heat rays are also radiated under the head to make the boundary between the part that you want to whiten and the part that you do not want to whiten blur, and the appearance will be impaired. . Therefore, in such a blow-molded container, in order to make the boundary portion between the whitened portion of the crystallized mouth-neck portion and the non-whitened portion of the non-crystallized main body portion clear, heat whitening treatment is performed. Since it is necessary to provide the device part with a shielding means for protecting the main body part of the container which is not desired to be whitened from the heat rays, the molding device inevitably becomes complicated and large.
(See Japanese Patent Publication No. 7-80236)

On the other hand, in the former method in which the mouth and neck of the preform is crystallized by heat treatment before blow molding, the preform has a smaller shape than that of the blow molded container. Since the shielding means for protecting the body of the preform from the heat rays is small, the whitening treatment device can be easily incorporated inline into the conventional molding device (see Japanese Patent Publication No. 5-9261). ,
Generally, this method is widely used.

To heat and crystallize the mouth and neck at the preform stage, conventionally, as shown in FIG.
The preform 1 preformed by injection molding is supported by the holding jig 3 with the mouth / neck portion 2 exposed and introduced into the heat treatment device 6, and then the heat ray from the heater 4A and the reflection plate 5A. In general, a method of heating the neck and neck portion 2 of the preform to whiten it is performed by such a conventional heating heater such as near infrared or far infrared heating using an electric heater made of quartz glass. The device is being used.

However, when such an infrared heater is used for heating, the ambient air surrounding the preform in the apparatus, which is not desired to be heated, as well as a jig or apparatus for supporting the preform, is used. The members are also heated together, and it is difficult to control the heating temperature, and the upper part of the body near the mouth and neck is also crystallized, making it easier to break during blow molding. Since the electric heater has a long life and the heating efficiency gradually deteriorates, it may cause variations in quality, replacement of defective heaters, deterioration of workability due to maintenance and inspection, and various other problems. ing.

Therefore, it is difficult to locally heat and crystallize only the mouth and neck of the preform to a predetermined temperature by a radiant heating method using an infrared heater or a hot air blowing heating method. Japanese Patent Laid-Open No. 58-
A method of heat treating the mouth and neck of the preform by high frequency dielectric heating as disclosed in Japanese Patent No. 217326 is considered. That is, the positive electrode fixed to the electrode holder is inserted and fixed in the mouth-neck portion of the preform held by the half-divided preform holder to be heat-treated with a slight gap, and Negative electrodes are provided opposite each other with the holding body sandwiched therebetween, and a high-frequency current is passed from the high-frequency oscillator to the positive electrode while the bottom of the preform is supported by a supporting body, so that the dielectric In this method, only the mouth and neck of the preform is whitened by heating.

However, the method using the heat treatment apparatus as described above is complicated because the holding structure of the preform and the electrode holding structure requires high precision and becomes expensive, and the current, frequency and other heating Strict control of the conditions is required, and in particular, at the same time as the control of turning on and off the high-frequency current, the positive electrode section and the heating section must be rapidly cooled. If it cannot be completed completely, it may be a cause of defective products in which crystallization varies.

[0010]

SUMMARY OF THE INVENTION The present invention uses an electric heater or dielectric heating as a heating source to locally heat only the mouth and neck of a preform or hollow container molded using PET resin. Instead, it provides a method of directly heating the mouth and neck using microwaves for uniform crystallization.

[0011]

Means for Solving the Problem A preform held by a preform jig is transferred into a microwave heating device while being held by a preform holding jig, and a collar portion of a mouth neck portion of the preform is transferred. The lower portion of the preform holding jig is shielded by a radio wave absorber so as not to be irradiated with microwaves, and only the mouth and neck of the preform is heat-treated by microwaves to be crystallized.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A PET resin is injection-molded into a preform having a shape that conforms to the final shape and size of a container except for the mouth and neck, by a commonly used known molding apparatus. The preform is supplied from the molding die to the preform holding jig connected to the transport chain by the preform supply device, and the mouth and neck of the preform is exposed and held so that it can be heated. The preform held by the preform holding jig is transferred to the heating device by the transfer chain.

In the preform transferred into the heating device, the body part held in the preform holding jig below the collar part of the mouth and neck part is introduced into the shielded chamber, and the preform is inserted from the collar part of the mouth and neck part. The mouth and neck exposed from the upper holding jig is introduced into the heating chamber and, while being transferred through the heating device, the mouth of the preform is irradiated by the microwave radiated from the microwave heating device provided on the ceiling. Only the neck is heat treated and crystallized.

[0014]

EXAMPLES In a known injection blow molding apparatus, a PET resin was injection-molded at a preform molding position to form a bottomed preform having a predetermined shape, and then the preform 1 released from the molding die was It is supplied to the preform holding jig 3 by the preform supply device. In the preform 1 supplied to the preform holding jig 3, only the mouth and neck is exposed from the open end of the cylindrical body of the holding jig so that the body can be transferred and held in the jig cylinder. . The preform 1 held by the holding jig 3 is transferred to a tunnel-type heating device 6 via a transfer chain 4 connected to the bottom of the holding jig and transferred to an inlet 6e of a heating chamber 6A. The door 6g that opens and closes in synchronization with the movement of the chain 4 is opened, and the mouth / neck portion 2 of the preform 1 is introduced into the heating device 6 while being exposed to the outside of the holding jig 3.

In the preform 1 thus introduced into the heating device 6, the body portion 1a held in the cylindrical portion of the holding jig 3 below the flange portion of the mouth / neck portion 2 has a radio wave absorbing material. The mouth-neck portion 2 exposed from the open end of the cylindrical portion of the holding jig 3 above the flange portion passes through the inside of the heating chamber 6A in the shielding chamber 6B protected by the gate-shaped microwave shield 7 As described above, the flange 3a of the holding jig 3 slides on the guide rail 7a and conveys it in the tunnel-shaped heating device 6. Then, in the upper heating chamber 6A, the preform mouth / neck portion 2 exposed from the holding jig 3 is
The microwave is radiated from the microwave generator 9 provided on the ceiling part of the device, and only the mouth / neck part 2 is heated and crystallized while being conveyed. At this time, in the lower shield chamber 6B, the body portion 1a held in the cylindrical portion of the holding jig 3 is
Is protected by being covered with a gate-shaped microwave shield 7 made of a magnetic material such as ferrite, so that it is prevented from being heated by microwaves.

The supporting portion 3 provided at the bottom of the holding jig 3 is used when the heating device is supported by a carrying chain for transfer.
The mouth / neck portion 2 of the preform can be heated more uniformly if it is conveyed while being rotated by a rack or other known rotating means via the pinion gear 3c of b. Further, the heating time can be controlled to an optimum one in accordance with the crystallinity by adjusting the feed speed of the transport chain that transports the preform. Furthermore, if the tubular main body of the preform holder 3 is made of an electromagnetic wave absorber made of a magnetic material, the body of the preform can be protected more reliably from microwaves.

The preform 1 crystallized by the heat treatment in the heating chamber as described above is opened outside the heating chamber 6A by opening the shielding door 6h of the outlet 6f which opens and closes in synchronization with the transport chain 4. Be delivered to. In the preform thus heat-treated in the mouth and neck, the volume decreases as the density of the mouth and neck increases as the crystallizes,
Since the size of the caliber becomes smaller than the size of the original preform, and it becomes a factor of impairing the sealing property between the lid and the mouth and neck when closing the lid, see JP-A-62-284723. As described above, the preform carried out to the outside of the heating device is immediately crystallized by immediately inserting a core-shaped orthopedic body such as a support or core into the mouth and neck and then performing a quenching operation. Along with the correction of the deformation of the dimension of the mouth and neck, the preform is improved in rigidity and heat resistance of the mouth and neck. In this way, the preform whose mouth and neck is crystallized and has rigidity and heat resistance is sent to the next heating step and reheated to a temperature at which blow molding is possible, and then transferred to the blow molding step. It is molded into a hollow container with heat resistance and strength.

Since the present invention uses microwaves for heating as described above, it is necessary to prevent leakage of microwaves that adversely affect the human body and others. In view of this, in the present invention, the entire wall surface of the heating device is surrounded by a metal plate such as stainless steel that reflects electromagnetic waves, and a door that shields microwaves at the entrance and exit of the heating chamber conveys the preform holding jig. The safety can be maintained by the configuration provided so as to open and close in synchronization with. Further, instead of the metal plate, the shielding door has a deformable slit formed on a rubber plate capable of absorbing electromagnetic waves mixed with powder of magnetic material such as ferrite so that the preform holding jig can pass therethrough. It is also possible to prevent the microwave from leaking by using.

[0019]

As described above, according to the present invention, a tubular preform holding jig connected to a conveyor chain holds a preform with its caliber exposed and is introduced into a heating device. Since the mouth and neck of the preform is moved in the heating chamber and the body is moved in the shielded chamber, the body of the preform is protected by the shield that absorbs electromagnetic waves. Only the mouth and neck of the preform can be heated and crystallized by microwaves without being crystallized. The preform holding jig with only the mouth and neck of the preform exposed can be conveyed while rotating in the heating device, and the heating time can be easily controlled by adjusting the transfer speed of the transfer chain. Therefore, the mouth and neck can be uniformly heated by the microwaves that are scattered and reflected, and can be crystallized without variations. Further, since the heating is performed by microwaves, the heating device can be downsized and the heating temperature can be easily adjusted, and it can be easily incorporated inline into a conventional injection blow molding machine.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heating device of the present invention cut in a vertical direction.

FIG. 2 is a sectional view taken along line XX in FIG.

FIG. 3 is a vertical sectional view of a preform holding jig used in the present invention.

FIG. 4 is a cross-sectional view showing a conventional heating device.

[Explanation of symbols]

 1 Preform 2 Mouth neck of preform 3 Preform holding jig 4 Conveyor chain 5 Sprocket 6 Heating device 6A Heating chamber 6B Shielding chamber 6g Entrance door 8 Machine frame 9 Microwave generator

Claims (9)

[Claims] 1. A preform made of polyethylene terephthalate is introduced into a heating device while exposing the mouth and neck and holding the body below the mouth and neck in a tubular preform holding jig. A method of crystallizing the mouth and neck of a preform, which comprises irradiating microwaves in a heating device to heat and crystallize only the mouth and neck of the preform. 2. The preform held by the preform holding jig is introduced into a heating device configured by being divided into an upper heating chamber and a lower shielding chamber, and a microwave generator provided in the upper heating chamber is used. The method for crystallizing the mouth / neck portion of the preform according to claim 1, wherein the mouth / neck portion of the preform is heat-treated. 3. The preform is supported by a transport chain connected to a bottom support portion of a preform holding jig, introduced into a heating device, and subjected to heat treatment. A method to crystallize the mouth and neck of the preform. 4. The preform has a mouth-neck portion exposed from a tubular preform holding jig heated in an upper heating chamber of a heating device and a body portion held in the tubular preform holding jig heated. The method for crystallizing the mouth-neck portion of a preform according to any one of claims 1 to 3, wherein the method is introduced into the lower shielded chamber of the apparatus while being supported by a transport chain so as to be positioned and heat-treated. 5. The preform is protected by an electromagnetic wave shield provided in a lower shielded chamber of a heating device to protect the body of the preform held in a tubular preform holding jig. The method for crystallizing the mouth / neck portion of the preform according to claim 1, wherein the mouth / neck portion is heat-treated by microwave. 6. The preform protects a body portion held in a tubular preform holding jig in the inner cavity of the electromagnetic wave shield formed in a gate shape, and a mouth and neck is provided in an upper heating chamber. The method for crystallizing the mouth / neck portion of a preform according to claim 5, wherein the portion is heat-treated by microwave. 7. The preform held by the cylindrical preform holding jig is a gate-shaped electromagnetic wave formed so as to vertically cut a wall surface center that divides a heating device into an upper heating chamber and a lower shielding chamber. The guide rail surface provided on the top surface of the shield slidably supports the flange portion at the opening end of the holding jig, protects the body portion in the inner cavity of the electromagnetic wave shield body, and protects the mouth and neck portion from microwaves. Heat treatment is performed, The heat treatment of Claim 5 or 6 is carried out.
The method of crystallizing the mouth and neck of the preform according to 1. 8. The preform held by the tubular preform holding jig is heat-treated by microwaves on the mouth and neck while being supported and transferred by a transfer chain connected to a bottom support portion of the holding jig. Claim 1 characterized by the above.
A method for crystallizing the mouth and neck of the preform according to any one of items 1 to 7. 9. The preform held by the tubular preform holding jig is supported and transferred by a conveying chain connected to a bottom support portion of the holding jig, and at the same time, the preform is microwaved while rotating. 9. The method for crystallizing the mouth-neck portion of the preform according to claim 1, wherein the method is performed by heat treatment with.