JPS591226A - Formation of biaxially oriented saturated polyester resin made bottle - Google Patents

Abstract

PURPOSE:To make the parting of a bottle wall easy in a mold release, by raising the bottom wall shaping face of a mold hill like, also providing an open hole blowing a high pressure air nearly in the center of the top part of the bottom wall shaping face and blowing an air after molding a biaxially oriented bottle. CONSTITUTION:A compressed air is blown into an intermediate stock 1 and its the bottom 4 is biaxially oriented, being pushed down by a stretching rod 10 at same time as being expanded. A high pressure air hole 11 is drilled at the axial line of the stretching rod 10 and the blowing ports 12 are opened at its bottom and side face. After a biasically oriented bottle is molded, a mold is opened and in that time the mold release of the bottle bottom wall 14 contacted to the bottom wall shaping face 6a of the mold is done by blowing an air from a high pressure air blowing hole 8 and raising the central part of the bottom wall 14 and making air flow in between the bottom wall 14 and the bottom wall shaping face 6a. The bottle bottom wall 14 can be parted and a molding cycle is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a biaxially stretched saturated polyester resin bottle.

Bottles made of saturated polyester resin have recently been attracting attention because they do not exude solvents and do not emit toxic gas when incinerated after disposal, but the bottles are usually biaxially stretched to improve their mechanical properties. It is considered to be elevated. However, it is difficult to biaxially stretch the bottom of the bottle to a degree that satisfies the strength, compared to the body and the like, and various efforts have therefore been made in this regard. The present applicant previously proposed biaxial stretching of the bottle bottom by forming a mold so that the bottle bottom protrudes inward inward, but even with this method, there are still problems. was to remain. In other words, in this case, the bottom part of the bottle is difficult to come off during mold release, resulting in a delay in the molding cycle.

The present invention eliminates the above drawbacks and will be described below with reference to the drawings.

First, an intermediate material l made of saturated polyester resin as shown in FIG. 1 is provided. The material is in the shape of a tube with a bottom and an open top, and the mouth portion 2 may be provided in the same manner as the widened neck portion of the final product. 3 is a screw for screwing the cap. The intermediate material is molded by injection molding or the like, but if it is slowly cooled from the molding temperature, it will whiten, so if the bottle is to be made transparent, it can be rapidly cooled to prevent whitening.

The intermediate material 1 is heated to a temperature suitable for stretching, and then placed in a blow molding mold 6 having a cavity 5 for additional molding.
Set it inside. The mold has a bottom formed, and the bottom wall forming surface 7, which is the upper surface of the bottom wall forming portion, is raised in a mountain shape. A hole 8 for blowing high-pressure air is bored in the center. Note that 9 is a cooling water flow hole for cooling the mold.

Next, compressed air is blown into the intermediate material 1, and at the same time as it expands, the bottom portion 4 of the intermediate material is pushed down by the stretching rod 10 to biaxially stretch it. In the illustrated example, a high-pressure air hole 11 is formed on the axis of the stretching rod, and a blow-off port 12 is opened at the lower end and side surface of the high-pressure air hole 11.

After forming the biaxially stretched bottle in this way, the mold is opened and released, but the bottle bottom wall 14 that is in close contact with the bottom wall forming surface 6a
The mold release is carried out by blowing air through the high-pressure air blowing hole 8 to push up the center portion of the bottom wall 14 and causing air to flow between the bottom wall and the bottom wall forming surface.

The method of the present invention is carried out as described above, and since the bottle bottom wall 14 is released from the mold by blowing air from the high-pressure air blowing hole 8, the bottle bottom wall 1 is in close contact with the bottom wall forming surface.
4 can be easily released from the mold, and the molding cycle can be improved. The biaxially stretched saturated polyester resin bottle is
When whitening is filled with high-temperature liquid, it tends to shrink due to heat and reduce the eye opening (capacity), and to prevent this, that is, to increase the heat distortion temperature, the mold temperature is often set to about 100 C. Since the molded bottle is molded in such a mold, the temperature of the molded bottle is high, and therefore it is easily deformed by external pressure, so the above-mentioned mold release cannot be performed by protruding pins, etc. However, in the present invention, the mold can be released by high pressure air. As a result, the bottle will not deform even at high temperatures. By setting the high-pressure air used for mold release at a low temperature, it is possible to lower the temperature of the bottle and eliminate the possibility of its deformation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the intermediate material, and FIG. 2 is a sectional view of the intermediate material in a state where it is expanded and formed into a bottle. 1...Intermediate material 6...Mold 6a...Bottom wall forming part 8...High pressure air blowing hole Patent applicant Yoshino Kogyosho Co., Ltd.-13 (

Claims (1)

[Claims] A preformed intermediate material made of saturated polyester is set in a mold having a cavity for molding, a stretching rod is inserted into the material, and compressed air is supplied through a passage provided in the rod. A method for producing a saturated polyester bottle by biaxially stretching the polyester so as to bring it into close contact with the inner surface of a blowing cavity, the method comprising: raising the entire bottom wall forming surface formed by the upper surface of the bottom wall forming portion of the mold into a mountain shape; A hole for blowing high-pressure air is made in the bottom wall forming part by making a hole approximately at the center of the top of the bottom wall forming surface, and after forming the biaxially stretched bottle, air is blown from the hole for blowing high-pressure air. 1. A method for molding a biaxially stretched saturated polyester resin bottle, which comprises releasing the bottom portion of the bottle that is in close contact with the bottom wall forming surface.