JPH0517020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a biaxially stretched blow-molded synthetic resin bottle, and its object is to obtain a wide-mouth bottle with excellent heat resistance.

Containers for storing products such as fruits and jams are preferably wide-mouthed so that the stored items can be easily taken out and filled, and the above-mentioned items should not be heated at high temperatures for sterilization. Generally, the wide-mouthed bottle is filled or subjected to high-temperature treatment after filling, and therefore the wide-mouthed bottle must have excellent heat resistance.

By the way, if the above-mentioned bottle is molded from a thermoplastic resin such as polyethylene terephthalate resin, molding is easy and excellent quality can be obtained.
In order to impart heat resistance to this thermoplastic resin bottle, there is a way to raise the mold temperature and perform biaxial stretch blow molding, but when the mold temperature is raised, the stretch ratio must be strictly controlled. If not selected, the so-called "sink mark" phenomenon will occur in the molded product, causing distortion and making it impossible to obtain a satisfactory product.

That is, in order to improve heat resistance, it is necessary to grow oriented crystals and remove residual strain. The number of oriented crystals increases as the stretching ratio increases and the biaxial stretching increases, but at the same time, the strain during stretching also increases.

However, since the wide-mouthed bottle has a large diameter relative to its depth, it has been difficult to obtain a sufficient stretching ratio, especially at the upper end of the body, and it has therefore been difficult to increase the mold temperature. In other words, in order to biaxially stretch blow mold a wide mouth bottle made of thermoplastic synthetic resin with excellent heat resistance,
There were various problems.

The present invention relates to a biaxial stretch blow molding method for heat-resistant wide-mouth bottles, which was developed to solve the above-mentioned conventional drawbacks. This is a method in which the remainder of the film and the peripheral edge of the bottom are biaxially stretched, and the bottom is sequentially stretched from biaxial to uniaxial stretching from the peripheral edge to the center.

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

First of all, FIG. 1 shows a wide-mouth bottle 1 molded according to the present invention, in which a ring-shaped mouthpiece 2 is followed by a cylindrical body portion with a diameter slightly larger than the diameter of this mouthpiece 2. 3 is arranged, and the bottom part 4 is placed at the lower end of the body part 3.
is continuous, but the center portion 5 of the bottom portion 4 is depressed inward. Then, the upper part of the body part 3 is the area A, the remaining part from the center to the lower part of the body part 3 and the peripheral edge part 6 of the bottom part 4.
and the center part 5 of the bottom part 4 are set as the B area, and the center part 5 of the bottom part 4 is set as the C area.

FIG. 2 shows a primary molded product 7 for molding the wide-mouth bottle 1 described above. It has a structure in which the mouth tube 2 is integrally provided, and the circumferential end 9 of the disc part 8 is thin, and the central part 10 is thick.

The above-mentioned primary molded product 7 is then placed in a predetermined mold 1.
1 and then biaxially stretched and blown.

The form of this biaxial stretching blow is as follows.

That is, a stretching pin is brought into contact with the center of the dish-shaped primary molded product 7, in which the mouthpiece 2 is assembled and fixed in a predetermined mold 11, and biaxial stretching blowing is performed. Therefore, area A is mainly 1
The area B is stretched biaxially and oriented in the axial direction, and the area C is stretched sequentially from the peripheral edge 6 of the bottom 4 to the center 5. The orientation direction is set by moving to axial stretching.

As for area A, its diameter is slightly larger than the diameter of mouth tube 2, so sufficient biaxial stretching cannot be performed, and molding distortion increases and "sink marks" are likely to occur due to distortion. In the invention, since the peripheral end 9 of the primary molded product 7, which is to be the area A, is made thin, sufficient stretching can be obtained in at least one axis direction, and it is possible to achieve the desired orientation.

Further, in area B, since the center portion 10 of the primary molded product 7 is stretched, sufficient stretching can be obtained in the biaxial directions.

Regarding area C, the center is non-oriented and the peripheral edge 6 is biaxially oriented, so it is the area where molding distortion is most likely to occur. Center part 5 of bottom part 4 to be formed
Since the shape is made to be depressed inward, the orientation can be made to decrease sequentially from the peripheral edge part 6 toward the center part 5, and if the boundary between the oriented part and the non-oriented part is not formed, , it is possible to prevent the occurrence of distortion.

As is clear from the above description, according to the molding method of the present invention, uniaxially oriented crystals can be grown without causing strain by mainly uniaxially stretching the upper part of the body 3. is completed, body 3
Biaxially oriented crystals can be grown by biaxially stretching from the remainder of the bottom part 4 to the peripheral edge 6 of the bottom part 4, and further, by sequentially biaxially stretching the bottom part 4 from the peripheral edge 6 to the center part 5. By changing the direction from uniaxial stretching to uniaxial stretching, desired oriented crystals can be grown.

Therefore, the molding method of the present invention can grow and form desired oriented crystals on the wall of the bottle, so the molded bottle has extremely excellent heat resistance, and therefore the contents can be kept at high temperatures. Since it can be sterilized, it is expected to be widely used as wide-mouthed bottles, and since distortions such as sink marks do not occur during molding, it has great commercial value, and is simple in structure and easy to mold. It has many excellent effects such as being easy to use.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a wide-mouth bottle molded according to the present invention. FIG. 2 is a sectional view showing a primary molded product of a wide mouth bottle. Explanation of symbols: 1; wide mouth bottle; 2; mouthpiece; 3; body; 4; bottom; 5; center; End portion, 10; center portion, 11; mold.

Claims (1)

[Claims] 1. A method for biaxial stretch blow molding of a wide-mouth bottle molded from a thermoplastic synthetic resin and having a large-diameter mouthpiece, a cylindrical body, and a bottom with an inwardly depressed center, comprising: The upper part of the body is mainly uniaxially stretched, and the remaining part of the body and the peripheral edge of the bottom are stretched in two directions.
A biaxial stretch blow molding method for a heat-resistant wide-mouth bottle body, which comprises axially stretching and then sequentially transitioning from biaxially stretching to uniaxially stretching the bottom portion from the circular end to the center.