JPS6255485B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a heat-resistant saturated polyester resin bottle, and more specifically,
The object of the present invention is to obtain a saturated polyester resin bottle that does not deform due to the heat of the high-temperature liquid when it is injected and filled with the high-temperature liquid.

Saturated polyester resin bottles are usually biaxially stretched in order to more effectively exhibit the excellent physical properties and characteristics of saturated polyester resin.

This biaxial stretch molding of saturated polyester resin bottles is based on general blow molding, and is performed by adding a stretching operation using a stretch pin to the blow molding operation, so it is inevitable that the inside of the wall that makes up the bottle will be stretched. , there will be relatively large residual strains within the wall, especially in the stretch-formed portion.

For this reason, when particularly high-temperature liquid is injected and filled into the bottle, thermal deformation is likely to occur due to the above-mentioned residual strain due to the influence of the heat of the liquid.

In particular, when filling bottles with juice or milk, the liquid content is heated to a high temperature for the purpose of sterilization, and after filling, the liquid must be sealed and cooled to room temperature or even lower temperature, the volume of the liquid may decrease. A fairly large negative pressure will be generated inside the bottle due to the dissolution of the vapor content in the head space, but due to this negative pressure inside the bottle and the distortion described above, the bottle may be greatly deformed. Moreover, this deformation is locally concentrated and causes cracks, which is a serious disadvantage.

In order to solve this problem, conventional methods have been to change the structure of the bottle itself by molding reinforcing ribs on the wall of the bottle, or to create a bottle with a shape that makes it difficult to notice the occurrence of deformation, that is, the appearance of the bottle is less likely to deteriorate due to deformation. However, all of these methods were extremely negative and could not provide a fundamental solution to thermal deformation.

The present invention was devised to solve the above-mentioned disadvantages of the conventional example, and it removes residual strain in the wall of a stretch-molded saturated polyester resin product by heat treatment, thereby preventing thermal deformation. In other words, a saturated polyester resin bottle with high heat resistance can be obtained.

The present invention will be explained below with reference to the drawings.

The method of molding a bottle according to the present invention involves in-die extension molding a piece 1 as a primary molded product in the shape of a straight cylinder with a bottom, using a saturated polyester resin, and molding the piece 1 and a desired diameter while heating it to a temperature that produces a stretching effect. Biaxial stretch blow molding is performed on an intermediate molded product 5 having a body 4 having a straight cylindrical shape, and this intermediate molded product 5 is
The final mold is reheated to a temperature not lower than 110 [°C], which is set as the mold temperature, which is sufficiently higher than the temperature at which the stretching effect occurs and the temperature at the time of filling the content liquid to be high-temperature sterilized. The bottle 6, which is a molded product, is stretch-blow molded.

The injection molded piece 1 is the first
As shown in the figure, it is preferable that the body part to be subjected to biaxial stretch blow molding has a wall thickness at the front corresponding to the amount of stretching.

In addition, the mouth barrel part 2 of this piece 1 becomes the mouth barrel part of the final molded product, the bottle body 6, without being subjected to stretch molding in many cases.
When molding the piece 1, it is preferable to mold it into the same shape and dimensions as the mouth barrel of the intended bottle body 6.

In addition, the thread 3 formed on the outer circumferential surface of the mouth tube part 2 is
This is to achieve sealing of the bottle 6 with a screw cap, and is not necessary if the bottle 6 is not sealed with a screw cap.

The injection-molded piece 1 is heated to a temperature that produces a stretching effect, and is biaxially stretched and blow-molded into an intermediate molded product 5 as shown in FIG.

The body 4 of this intermediate molded product 5 has a straight cylindrical shape, and the diameter of this body 4 is a size that does not exceed the minimum diameter of the body of the bottle 6 which is the final molded product. The value is set as close as possible to the minimum diameter of the body of No. 6.

In this way, the body part 4 of the intermediate molded product 5 is formed by simply extending the body part of the piece 1 in the radial and axial directions.
Residual strain generated within the wall of the body 4 due to axial stretching is uniform over the entire area of the body 4 and is extremely small.

This intermediate molded product 5 is heated from 110 [°C], which is the temperature of a mold (not shown) for molding the intermediate molded product 5 into a bottle 6, which is set according to the temperature of the content liquid to be subjected to high-temperature sterilization. Although not small, this 110
While heated to a temperature approximately equal to [° C.], stretch blow molding is performed to form a bottle 6, which is the final molded product.

In this way, since the intermediate molded product 5 is reheated to around 110 [°C] and stretch-molded into the bottle 6, the residual strain in the wall of the intermediate molded product 5 is removed by this reheating operation. It disappears completely.

At this time, if there are parts of the intermediate molded product 5 where the residual strain is locally large, it is almost impossible to eliminate all the residual strain by reheating the intermediate molded product 5 described above. Although it is possible, as mentioned above, the residual strain generated within the wall of the intermediate molded product 5 is almost uniform over the entire area of the body 4,
Moreover, since they are small, they can be completely eliminated by the above-mentioned reheating operation.

Furthermore, since the intermediate molded product 5 has been biaxially stretched and blow molded to dimensions that are approximately the same as the final molded product, the bottle 6, the stretching during the stretch molding operation from the intermediate molded product 5 to the bottle 6 is difficult. The amount is very small, and therefore, almost no residual strain is generated within the wall of the bottle 6 that is stretch-molded from the intermediate molded product 5.

Furthermore, the temperature of the liquid that is injected and filled after high-temperature sterilization is usually no more than 100 degrees Celsius.
On the other hand, the bottle 6 formed by the method of the present invention has an intermediate molded product 5 of at least 110
Since it is reheated to [℃] and then stretch-molded, a liquid content of about 100 [℃] is injected, and the heat of this liquid content acts.
The slight residual strain caused by stretch molding under heating to 110 degrees Celsius does not appear on the outside, and therefore the bottle can be made by filling the bottle with the usual high-temperature sterilized liquid. There is no fear of any inconvenience such as thermal distortion occurring in the body 6.

As is clear from the above description, the present invention makes it possible to minimize the residual strain generated within the wall of the bottle 6, which is the final molded product, and to reduce the residual strain generated within the wall of the bottle 6, which is the final molded product, from the content liquid that has undergone ordinary high-temperature sterilization. All distortions that may appear due to thermal effects are completely eliminated during the molding operation, so even if the content is injected and filled with normal high temperature sterilization at about 100 [℃] It is easy to carry out the process because it does not undergo thermal deformation, and conventional molding equipment can be used as is.
Since the amount of stretching can be set to a sufficient value, the excellent physical properties and characteristics of saturated polyester resin can be fully and effectively exhibited. It has various functions and effects.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a piece as a primary molded product in an embodiment of the method of the present invention. Figure 2 is a front view of an intermediate molded product biaxially stretch blown from the piece shown in Figure 1, and the two-dot chain line in Figure 2 indicates the outer shell line of the bottle, which is the final molded product. . FIG. 3 is a front view of a bottle as a final molded product obtained by stretch-blow molding the intermediate molded product shown in FIG. 2. Explanation of symbols: 1; Piece; 2; Mouth barrel; 3; Thread; 4; Body; 5; Intermediate molded product; 6; Bottle.

Claims (1)

[Scope of Claims] 1. A piece as a primary molded product made of saturated polyester resin that has been injection molded into the shape of a straight cylinder with a bottom is heated to a temperature that produces a stretching effect,
An intermediate molded product having a linear cylindrical body whose diameter is as close as possible to the minimum diameter of the final molded bottle body without exceeding the minimum diameter of the final molded product is biaxially stretch blow molded, and The intermediate molded product is at least 110
A method for forming a heat-resistant saturated polyester resin bottle, in which the final molded product, the bottle, is stretch-blow molded after being reheated to about [°C].