JPH0517018B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of molding a wide-mouth bottle using synthetic resin, and aims to obtain stability in the rigidity and dimensional accuracy of the mouth.

BACKGROUND ART Wide-mouth bottles are widely used as containers for storing certain foodstuffs, etc., and a technique has been developed for biaxially stretch blow-molding these wide-mouth bottles from thermoplastic synthetic resin.

Some caps for wide-mouthed bottles have a simple crimped cap structure, rather than a screw-on structure for the mouth part.When assembling this crimped cap, high rigidity and dimensional accuracy are required for the mouth part of the molded bottle body. stability is required.

In other words, in order for the crimped cap to have good opening and sealing properties, the opening must have high dimensional accuracy, and to prevent the opening from deforming, it must have high rigidity.

In addition, a thin plate-shaped structure with a short cylindrical opening around the periphery of the disc-shaped main body has been developed as a primary molded product for biaxial stretch blow molding of wide-mouthed bottles, but the bottle can be used as is. The mouth of the primary molded product, which becomes the mouth of the body, is not stretched; only the main body is stretched. Therefore, when the main body is stretched, the stretching force acting on the torso is It is fully predicted that this will affect the mouth and cause the mouth to become deformed.

The present invention relates to a method for forming a wide-mouth biaxially stretched blow-molded bottle, which was developed in view of the above-mentioned conventional demands and disadvantages. The rigidity of this mouth part is increased and then biaxial stretch blow molding is performed.

An embodiment of the present invention will be described below with reference to the drawings.

The primary molded product 1 is injection molded using thermoplastic synthetic resin such as polyethylene terephthalate resin.
It has a structure in which a short cylindrical mouth part 3 is integrally provided on the circumference of a disc-shaped main body part 2.

This mouth part 3 has a mouth part 5 which is connected to the diagonally outer upper part of a mouth part 4 having a thick short cylindrical shape. A curved surface with good sealability between the upper surface 7 and the gasket (not shown) of the caulking cap,
They each have a molded structure, and a stepped portion 8 is provided around the outer periphery of the continuous portion between the mouth tube portion 4 and the main body portion 2.

Prior to biaxial stretching blowing, the primary molded product 1 having such a configuration is placed on a predetermined jig 9 and the mouth portion 3 is heat treated.

This jig 9 has a cylindrical shape, for example, and holds the primary molded product 1 in such a manner that the stepped portion 8 of the primary molded product 1 is supported by the upper end of the jig 9, with the mouth 3 facing upward and outward ( It is heated further (as shown by the arrow in the drawing) and then slowly cooled to crystallize it.

Through this heat treatment, the mouth part 3 is sufficiently heated and crystallized, but if the main body part 2 is heated and crystallized together with the mouth part 3, It is necessary to prevent crystallization from occurring in the main body part 2 because it will not be possible to stretch and mold the main body part 2 in the next step.

Basically, as a means for preventing the occurrence of crystallization in the main body part 2, it is sufficient to prevent the main body part 2 from being heated to a temperature at which crystallization occurs.

As a specific means for preventing the heating of the main body part 2, it is preferable to use a jig 9 that blocks radiation of the heating hot wire to the main body part 2, as shown in the illustrated embodiment.

In the case of the embodiment shown in FIG. 1, only the cylindrical jig 9 whose upper end surface is in contact with the stepped portion 8 is shown as a device for blocking the radiation of heat rays to the main body portion 2. In addition to this jig 9, a flat disk-shaped shield that blocks heat rays from above may be placed directly above the main body 2 in the mouth 3.

In addition, the heat treatment for crystallizing the mouth part 3 softens the primary molded product 1, especially the entire mouth part 3 of the primary molded product 1, making it easy to deform under the action of gravity. Since the portion 3 is placed on the jig 9, there is no risk that the mouth portion 3 will be deformed due to the action of gravity, and therefore, even if the mouth portion 3 is heated to crystallize it, it will not be deformed. In this case, the mouth portion 3 is not subjected to improper deformation due to the heat treatment, and thereby the mouth portion 3 can be crystallized while maintaining its dimensions accurately during injection molding.

In this way, after the mouth portion 3 is crystallized by heat treatment, the entire primary molded product 1, especially the main body portion 2
is heated to a stretching temperature and biaxially stretched blow molded into a bottle 1'.

That is, as is clear from FIG. 2, in the wide-mouth bottle 1', the main body part 2 of the primary molded product 1 forms its body part 2' and bottom part 2'', and the mouth part 3' forms the body part 2' of the primary molded product 1.
The mouth part 3 remains as it is.

In the molding method of the present invention, the mouth part 3 of the primary molded product 1 is heat-treated to crystallize it white before biaxial stretching blowing.
Therefore, when the main body part 2 is biaxially stretched, the stretching force does not reach the mouth part 3, especially the mouth edge part 5, which requires high dimensional accuracy. There is no risk of distortion or other deformation occurring in the cap 5, and sufficient mechanical durability can be exerted against the tightening force of the crimping cap, so that stable sealing can be achieved by the crimping cap.

Moreover, since the mouth tube part 4 below the mouth edge part 5 is thick, the stretching force applied to the main body part 2 is also absorbed by this mouth tube part 4, and the influence of the stretching force on the mouth edge part 5 is completely eliminated. It will disappear.

Since the jig 9 is used for the heat treatment of the mouth part 3, the heating point is limited to the mouth part 3 and does not affect the main body part 2, so there is no problem in stretching the main body part 2, and Since the primary molded product 1 can be held by the jig 9, there is no need to worry about it losing its shape.

Therefore, according to the method of forming a wide-mouth bottle by biaxial stretch blow molding of the present invention, it is possible to ensure the rigidity of the mouth part and maintain the stability of dimensional accuracy, so that the opening and sealing properties of the crimped cap can be improved. It can be held at a high level, the configuration and process are simple, etc.
It has many excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention. FIG. 2 is a sectional view showing the wide mouth bottle after blow molding. Explanation of symbols: 1; Primary molded product; 2; Main body;
3; mouth part, 4; mouth barrel part, 5; mouth edge part, 8; step part,
9; Jig.

Claims (1)

[Claims] 1. On the diagonally outer upper side of the thick short cylindrical mouth part, the outer lower surface is formed with a curved surface that provides good opening performance, and the upper surface is formed with a curved surface that provides good sealing performance with the cap gasket. made of thermoplastic synthetic resin, in which a mouth part with continuous mouth rims is integrally provided on the periphery of the disc-shaped main body part, and a stepped part is molded on the outer peripheral surface of the connecting part between the mouth pipe part and the main body part. A method for forming a wide-mouth synthetic resin bottle, in which only the mouth part after primary molding is crystallized by heating from above and from the outside, and then the main body part is biaxially stretch blow molded into the bottle body.