JPS6139895B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for stretch-molding a neck portion of a piece for a biaxially stretched bottle, and its object is to reliably and easily stretch-mold the neck portion of a piece.

Polyethylene terephthalate resin products are becoming widely used due to the excellent physical properties and durability of polyethylene terephthalate resin. Many areas are exhibited when the product is stretch-molded.

For this reason, when a polyethylene terephthalate resin product has a bottle structure, first a piece in the shape of a cylinder with a bottom is formed as a primary molded product by injection molding, and then this piece is formed into a bottle by blow molding. The molding was performed by a so-called in-die extension blow molding method, and stretching was applied during the blow molding.

By the way, when blow molding the piece into a bottle,
Without exception, the neck of the piece is fixed in the blow mold,
Since the body (including the bottom) is blow molded, the body of the bottle is stretched, while the neck of the bottle is not stretched.

For this reason, while the body of the bottle can fully demonstrate the excellent physical properties and durability of polyethylene terephthalate resin, the neck cannot fully demonstrate its excellent physical properties and durability. For example, if a high concentration of alcohol is attached, this alcohol penetrates and whitens the neck, making it mechanically brittle, and many thin cracks are formed, causing a loss of sealing effect, which is a serious drawback. Ta.

The present invention was devised to eliminate the drawbacks of the above-mentioned polyethylene terephthalate resin bottle, and the present invention will be described below with reference to the drawings.

In the present invention, a piece P is held immovably by its body part _P1 and a bottom part, and the neck part _P2 of this immovably held piece P is heated to a temperature that produces a stretching effect, and the tip of the neck part _P2 is heated. The mouth edge P ₃ is held by the stretched pieces E with a substantially uniform force over the entire circumference, and this mouth edge P ₃
The neck portion P3 is stretched and formed by moving the stretched piece E along the central axis of the immovably held piece P while holding the piece _P3 between the legs.

The means for holding the piece P immobile is not particularly limited, but since the neck portion P ₂ is heated to a temperature that produces a stretching effect, in order to prevent uneven heating of the neck portion P ₂ , Neck P ₂ as much as possible
Therefore, it is desirable to hold the piece P in a portion from the lower end of the body _P1 to the bottom.

Furthermore, the holding of the mouth edge P ₃ by the stretched piece E does not necessarily have to be done uniformly over the entire circumference of the mouth edge P ₃ , but rather at as many equally spaced points as possible. It is sufficient if the tensile force acting on the neck _P2 is uniform over the entire circumference of the neck _P2 .

By the way, in the case of the illustrated embodiment, the neck part _P2 is formed thinner than the body part _P1 , and the wall thickness of the shoulder part, which is the boundary between the neck part _P2 of the body part _P1 , is smaller than that of the body part _P1 . The wall thickness gradually decreases as it approaches the neck _P2 , and this is done in order to ensure that the entire neck _P2 can be stretched uniformly and during blow molding. This is to ensure that even the shoulder portion, which has a relatively small amount of stretching, is stretched to a certain extent during stretch-forming of the neck portion _P2 .

However, if the amount of stretching of the neck P ₂ is large and a good heating state of the neck P ₂ can be achieved, it is not necessary to form the neck P ₂ thinly as in the illustrated embodiment; It may have the same wall thickness as part _P1 .

In particular, when the amount of stretching is large, the thickness of the neck P ₂ becomes even thinner due to this stretching, so it may be disadvantageous to form the neck P ₂ thin from the beginning as in the illustrated embodiment. be.

In this manner, the present invention heats the neck portion P ₂ to a temperature that produces a stretching effect and applies a tensile stretching force to the neck portion P ₂ , so that only the neck portion P ₂ can be reliably stretched and formed. The stretching operation is extremely simple and there is no possibility of making a mistake since it is sufficient to simply hold the mouth edge _P3 and pull it along the axis of the piece P.

Further, since the amount of stretching of the neck portion P ₂ is determined only by the amount of pulling movement of the stretching piece E, the amount of stretching of the neck portion P ₂ can be freely and easily set.

As is clear from the above description, the present invention
_P2 can be stretch-molded, so when it is formed into a bottle, it can exhibit the same excellent physical properties and durability as the body, and it is extremely easy to carry out, and it can be formed more reliably and freely. It has many excellent effects such as being able to be set and implemented.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the piece before the method of the present invention is carried out, and FIG. 2 is a longitudinal cross-sectional view showing the piece while the method of the present invention is being carried out. Explanation of symbols P: Piece, _P1 : Body, _P2 : Neck, _P3 : Mouth edge, E: Stretched piece.

Claims (1)

[Claims] 1. A method for stretching and molding a neck part _P2 of a bottomed cylindrical piece P that is injection molded as a primary molded product of a polyethylene terephthalate resin bottle that is biaxially stretched, the body part _P1 and the bottom part being The neck portion P ₂ of the piece P held immovably by is heated to a temperature that produces a stretching effect, and the mouth edge P ₃ , which is the tip of the neck portion P ₂ , is stretched by a stretching piece E with an almost uniform force over the entire circumference. A biaxially stretched molded bottle that is held in place and stretched by moving the stretched piece E along the central axis of the piece P while the temperature of the neck portion _P2 is within the temperature range where the stretching effect occurs. Stretch molding method for the neck of the piece.