JPH0788035B2 - Primary molded product made of synthetic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyethylene terephthalate resin (hereinafter, simply
It is referred to as PET) and relates to a primary molded product used for biaxially stretch blow molding a bottle body.

[Prior Art] Biaxially stretch blow-molded PET bottles have excellent content resistance, mechanical strength, and ease of molding.
It is widely used as a container for various contents because it is lightweight, easy to handle, and inexpensive to manufacture.

Since many excellent properties of this PET bottle are exhibited by the PET material being biaxially stretched and formed into the final shape, the structure and forming method of the PET bottle are It is considered that sufficient stretching can be given to each part of the.

In particular, the bottom of the PET bottle is the part that is stretched and deformed together with the body to be molded into the final shape,
Since the amount of stretching deformation received is small, it has a concave-convex wall structure so that it can be subjected to a large amount of stretching deformation as much as possible, and it has a shape that is largely curved and depressed in the bottle body and that it is provided with ribs for many reinforcements. As a result, the amount of stretching in the circumferential direction is increased.

[Problems to be solved by the invention]

In this way, by constructing the bottom structure of the bottle body so that more stretching deformation is given to this bottom part,
The mechanical strength of the bottom is improved, and in particular, it is possible to increase the internal pressure resistance, but when it is used as a storage container for contents that require heat treatment such as heat sterilization, this The low heat resistance of the bottom was a problem.

That is, PE that has been biaxially stretch blow molded as described above.
The bottom of the T bottle can be made highly resistant to internal pressure by devising its structure, but the central part of the bottom receives the structure of this bottom no matter how it is designed. Since the absolute amount of stretching is small, the heat resistance cannot be improved.

Especially in the case of a wide-mouth bottle, the stretching applied to each part to be molded is mostly the axial stretching, so the lack of the amount of stretching at the center of the bottom should be eliminated by devising the structure of this bottom. However, the stretching amount was insufficient in a relatively wide range.

As described above, the center portion of the bottom of the PET bottle that has been biaxially stretch-blow-molded lacks the amount of stretching deformation. Due to the effect of the above, there is a problem that it causes heat softening or heat shrinkage deformation, resulting in inconvenient deformation.

A heat setting means is generally known as a means for improving the heat resistance of the biaxially stretch blow-molded PET bottle body. The heat setting means is a bottle body that has been sufficiently stretched and formed. It can be effectively applied to the body and the peripheral edge part of the bottom part, but a sufficient effect can be obtained for the center part of the bottom part that has not been sufficiently or hardly stretched. In addition to being unable to do so, it sometimes caused inconvenience.

That is, when heat setting is applied, the heat shrinkage amount in the central portion of the bottom is larger than that in the other portions, and thus the shape of the bottom of the bottle is deformed illegally. However, a part of the central part of the bottom, particularly the outer surface part, is partially crystallized, which causes inconvenience such as irregular white turbidity.

Further, since the heat resistance is not sufficiently improved by the heat setting means, when the heat treatment is performed on the contents, the bottom center portion softened by the heating acts from the bottle body to the bottom center portion. When the force, for example, the weight of the contents or the action of internal pressure, causes large deformation, the internal volume of the bottle is greatly deformed, the internal pressure resistance strength of the entire bottom part is reduced, and when the deformation is large, , It was supposed to cause a serious inconvenience that the independence function of the bottle body would be lost.

The present invention was devised to solve the problems, drawbacks, and inconveniences in the above-described conventional example, and has the mechanical strength and heat resistance of the central portion of the bottom that is formed into the final shape with almost no stretching deformation. The purpose is to secure.

[Means for solving problems]

Hereinafter, a synthetic resin primary molded article according to the present invention will be described with reference to the drawings showing an embodiment of the present invention.

A synthetic resin primary molded article according to the present invention is a polyethylene terephthalate resin (hereinafter referred to as PET) biaxially stretched blow molded bottle body 1a in the shape of a bottomed cylinder, and is a bottle body 1a. The central portion 7 of the bottom portion 6 which is integrally connected to the lower end of the body portion 2 which is biaxially stretch-molded on the body portion 2a is made to have the same structure as the central portion 7 of the bottom portion 6a of the bottle body 1a which is a molding object. In addition, it is made to whiten and crystallize by heat treatment.

The structure of the central portion 7 that is whitened by crystallization by heat treatment is not specified, and the bottle body that is the molding target is used.
It is designed and set according to the shape, dimensions, usage conditions and handling conditions of 1a.

[Action]

The primary molded product 1 according to the present invention has the structure as described above, and the molding of the primary molded product 1 into the bottle body 1a is performed in exactly the same manner as the conventional biaxial stretch blow molding.

That is, the primary molded product 1 is uniformly heated to a temperature at which a stretching effect can be obtained, and the bottle 1a is biaxially stretch blow-molded in this heated state.

During the biaxial stretch blow molding from the primary molded product 1 to the bottle 1a, the whitened central portion 7 is a portion that is not stretched and deformed even when subjected to a stretching force. The force acts on the rest of the body portion 2 and the bottom portion 6, that is, the peripheral end portion of the bottom portion 6, and the peripheral end portion of the bottom portion 6 adjacent to the central portion 7 which is not stretched and deformed in particular receives a stronger stretching force. As a result, compared with the conventional case, that is, the case where the central portion is slightly stretched and deformed, the stretch and deformation is significantly increased.

Further, the central portion 7 is formed in the same shape as the central portion 7 of the bottle body 1a which is the molding object, that is, when it is molded into the primary molded product 1, it is a portion molded into the final shape. However, since the shape is not only the same as that of the central portion 7 of the bottle 1a but also whitening is caused by crystallization, special care is required for its molding.

That is, when the PET material is crystallized by heat treatment, its volume shrinks and changes at a constant rate. Therefore, when molding the central portion 7, the volume shrinkage caused by this whitening should be taken into consideration. Need to be implemented.

Since the contraction deformation generated in the central portion 7 due to whitening occurs in the height direction and the circumferential direction, the contraction deformation amount and the shape are predicted, and the shape after the contraction deformation is the bottle shape.
It should be designed to match the shape of the central portion 7 of 1a.

Thus, the primary molded product 1 according to the present invention has the bottom portion 1
The center portion 7 of the bottle 1a is molded into the same shape as the center portion 7 of the bottle 1a, and is crystallized. Therefore, the bottle 1a biaxially stretch-blow-molded from the primary molded product 1 has a bottom portion. The central portion 7 of 6a is whitened.

Since the central portion 7 of the molded bottle 1a is whitened,
Even if the bottle body 1a is subjected to heat treatment for sterilization or the like, the central portion 7 is not softened or contracted and deformed by heat, and exhibits extremely high heat resistance.

Further, since the central portion 7 is whitened, the rigidity thereof is significantly enhanced, so that the central portion 7 is not unnecessarily deformed by the force applied from the outside, and the bottom portion is accordingly increased.
The mechanical strength of 6a can be increased.

〔Example〕

In the illustrated embodiment, a mouth cylinder 3 having a screw 5 protruding from the outer peripheral surface is integrally connected to the upper end of a cylindrical body 2, and the mouth cylinder 3 and the body 2 are connected to each other. 2 has a general structure in which a flange 4 is provided around the outer circumference of the nozzle. The mouth tube 3 and the flange 4 are crystal-whitened.

Further, at the center of the lower surface of the crystallized white central portion 7, when the primary molding 1 is stretched along the axial direction of the bottle body 1a, the center of the central portion 7, that is, the stretching center, is not misaligned. In addition, a projecting piece 8 for holding the stretching center of the primary molded product 1 with respect to the mold for biaxial stretch blow molding is additionally provided.

That is, when the primary molded product 1 is stretched in the axial direction, the central portion 7 of the primary molded product 1 is sandwiched between the bottom die that has moved forward along the axial direction and the stretching pin. The projection piece 8 is fitted into the positioning recess provided in the center of the die surface of the bottom die, thereby reliably and strongly preventing the occurrence of an improper displacement of the extension center of the primary molded product 1 during the extension operation. Of.

Further, the central portion 7 has a spherical arc shell structure that is curved and depressed toward the inside of the primary molded product 1, and imparts a self-supporting function to the bottom portion 6a of the bottle body 1a which is the molding target.

The central portion 7 in the shape of a spherical arc shell is not whitened up to the peripheral end where the curvature of the wall structure is reversed, so most of the molded bottom portion 6a except the central portion 7 extends. It is deformed and molded into the final shape.

The embodiment shown in FIGS. 1 and 2 shows a bottle body 1a having a relatively wide mouth.
Since the body portion 2 and the bottom portion 6 are formed into the body portion 2a and the bottom portion 6a by receiving a relatively large amount of stretching in the axial direction and the circumferential direction,
The thickness is large and the body portion 2 is vertically long.

The embodiment shown in FIG. 3 and FIG. 4 is conveniently constructed for molding a wide mouth bottle 1a having a relatively high height. The portion 2 has a tapered cylindrical shape whose diameter decreases as it goes downward.

Further, the embodiment shown in FIG. 5 and FIG. 6 is conveniently constructed in the case of molding a wide mouth bottle 1a having a low height. The body 2 of the primary molded product 1 is stretched and deformed as much as possible. The height is suppressed to a low value so as to be stretch-molded on the body portion 2a and the bottom portion 6a, and a taper cylinder structure having a large inclination angle is formed.

〔The invention's effect〕

As is clear from the above description, the synthetic resin primary molded article according to the present invention hardly undergoes stretching deformation.
The center part of the bottom of the primary molded product that will be molded in the center part of the bottom of the axially stretched blow-molded product is crystallized in advance by heat treatment at the time of the primary molded product. There is no inconvenience related to heat resistance and mechanical strength due to insufficient stretching amount, and it is possible to make it extremely stable in terms of physical properties. Also, the heat treatment for whitening of the central portion is a primary molded product. Since the heat treatment on the central portion hardly affects other portions, the operation can be achieved easily and smoothly, and the central portion does not undergo stretching deformation at all. Since it is a portion, the peripheral portion of the bottom portion adjacent to this central portion is in a state where it is easily stretched and deformed, and therefore, the bottom portion can be sufficiently stretched and deformed, and many other advantages are obtained. It is intended to demonstrate the effect.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing one embodiment of the present invention configured to mold a bottle body having a relatively wide mouth and a vertically long shape. FIG. 2 is a partially cutaway view of a bottle body that has been biaxially stretch blow-molded based on the embodiment shown in FIG. FIG. 3 is a vertical cross-sectional view showing another embodiment of the present invention configured to mold a tall wide-bottle bottle. FIG. 4 is a partial cutaway view of a bottle body that has been biaxially stretch blow molded based on the embodiment shown in FIG. FIG. 5 is a vertical cross-sectional view showing yet another embodiment of the present invention configured to mold a low-height wide-mouth bottle. FIG. 6 is a partial cutaway view of a bottle body that has been biaxially stretch blow-molded based on the embodiment shown in FIG. DESCRIPTION OF SYMBOLS 1; Primary molded product, 1a; Bottle, 2, 2a; Body, 3; Mouthpiece, 6, 6a; Bottom, 7; Central part.

Claims (1)

[Claims] 1. A primary molded product (1) having a bottomed cylindrical shape of a biaxially stretch blow molded bottle body (1a) made of polyethylene terephthalate resin, wherein the body portion (2a) of the bottle body (1a) has two parts. The central portion (7) of the bottom portion (6) integrally connected to the lower end of the body portion (2) that is axially stretch-molded is the central portion (7a) of the bottom portion (6a) of the bottle body (1a) which is the molding object. A primary molded product made of synthetic resin, which is molded into the same structure as 7) and is whitened and crystallized by heat treatment.