JPH08244105A - Bottle molding method - Google Patents

Abstract

PURPOSE: To eliminate center shift and to prevent the irregularity of heat resistance or thickness by suppressing center shift by supporting the central part of the bottom part of a primary blow bottle by a support member and forcibly moving the support member. CONSTITUTION: The central part 21 of the bottom part of a primary blow bottle 2 is supported by a support member 3 to suppress center shift and the support member 3 is forcibly moved. The support member 3 is held from the inside and outside thereof by the support rod 31 supporting the central part 21 of the bottom part of the primary blow bottle from the inside and an outside support rod 32 to be certainly supported to suppress center shift. The support member 3 is forcibly moved by supporting the lower end 311 of the support rod 31 made slidable up and down within the mandrel 33 supporting a mouth plug part 22 by the cam surface 341 of a cam member 34. The mandrel 33, the support rod 31 and the outside support rod 32 are allowed to advance in the direction shown by an arrow 7 while rotated around the axis of them to generate heat shrinkage by uniform heating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a heat-treated bottle.

[0002]

2. Description of the Related Art In order to improve heat resistance of biaxially stretched blow bottles made of polyester resin such as polyethylene terephthalate, injection molded parison is blow molded to form primary blow bottles, and the primary blow bottles are heated. Then, while suppressing the heat shrinkage by adjusting the internal pressure,
We propose a molding method to obtain a heat-treated bottle by supporting it with a rod whose movement is controlled by elastic force such as a spring to suppress core misalignment, heat shrinking, and then blow molding again in the final mold. Has been done.

[0003]

However, in the above-described conventional bottle molding method, when the primary blow bottle is supported by the rod and thermally contracted while adjusting the internal pressure, the primary blow bottle is sufficiently shrunk. As a result, there was a problem that the heat-treated bottles obtained tended to have variations in heat resistance and thickness.

[0004]

The present invention relates to a method for molding a heat-treated bottle which has solved the above-mentioned problems, and its gist is to blow-mold an injection-molded parison to form a primary blow bottle. In heating and shrinking the primary blow bottle, and then performing blow molding in the final mold again, the center part of the bottom of the primary blow bottle is supported by a supporting member to suppress misalignment, and A bottle molding method is characterized in that a support member is forcibly moved.

The bottle molding method of the present invention can be obtained by supporting the central portion of the bottom of the primary blow bottle with a support member to prevent misalignment and forcibly moving the support member. The heat-treated bottle has no misalignment or the like and is excellent in appearance, and does not cause variations in heat resistance and thickness.

The reason for this is that in the conventional bottle molding method, when the primary blow bottle is heated and thermally contracted, the primary blow bottle is supported by a rod whose movement is controlled by the elastic force of a spring or the like to cause thermal contraction. Since it moves depending on the shrinkage force associated with, the degree of heat shrinkage and the speed of heat shrinkage vary due to fluctuations in internal pressure, fluctuations in temperature for heating the primary blow bottle, fluctuations in frictional resistance of the rod, etc. It is considered that in the present invention, by forcibly moving the support member, the above fluctuation does not affect the heat shrinkage.

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

FIG. 1 is a schematic sectional front view of an apparatus for carrying out the bottle molding method of the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG.

As shown in FIGS. 1 and 2, the present invention blow-molds an injection-molded parison 1 to form a primary blow bottle 2.
In order to heat-shrink the primary blow bottle 2 to cause heat shrinkage, and then to perform blow molding again in the final mold 4, the bottom central portion 21 of the primary blow bottle 2 is supported by the support member 3.
The method for forming a bottle is characterized in that the support member 3 is supported by the above-mentioned method to suppress misalignment, and the support member 3 is forcibly moved.

The injection-molded parison 1 is preferably made of a crystalline resin such as a polyester resin containing polyethylene terephthalate as a main component because the heat resistance thereof is improved by heat treatment.

In order to blow mold the parison 1 to form the primary blow bottle 2, the parison 1 is stretched at a temperature of 70 to 100 in the case of the parison 1 made of polyester resin.
It is heated to 0 ° C., stretched in the axial direction by the stretching rod 51 in the primary blow mold 5, and is also stretched in the radial direction by blowing a pressure gas.

The primary blow mold 5 is set to about 30 to 60 ° C., and the formed primary blow bottle 2 is brought into contact with the primary blow mold 5 to be cooled and solidified and taken out.

The primary blow mold 5 is preferably larger than the final mold 4 in both the radial direction and the axial direction, and is 5 to 40% in the radial direction and 5 to 60% in the axial direction. If it is also large, the heat resistance is significantly improved and 1
It is particularly preferable because there is no stress whitening due to the subsequent blow.

In order to heat the formed primary blow bottle 2, it can be passed through, for example, a hot air heating furnace 6 as shown in FIG. 2, and the heating temperature is 1 at the ambient temperature.
The range of 50 to 250 ° C. is 20 to 12 as the heating time.
0 second is preferable, and in short, heating may be performed until the primary blow bottle 2 is thermally contracted to 10 to 50% in the radial direction and 10 to 70% in the axial direction.

As the support member 3, for example, as shown in FIG. 1, a support rod 31 for supporting the bottom central portion 21 from the inside of the formed primary blow bottle 2 can be used. Further, by supporting the central portion 21 of the bottom portion from the outside of the primary blow bottle 2 by sandwiching it from both sides with the external support rod 32, it is possible to support more reliably and suppress misalignment, which is preferable.

In order to forcibly move the support member 3, as shown in FIG. 2, the plug portion 22 of the primary blow bottle 2 is used.
The lower end 311 of the support rod 31 that is vertically slidable inside the mandrel 33 that supports the cam is supported by a cam surface 341 having a predetermined pattern in the traveling direction indicated by the arrow 7 on the cam body 34. The adopted structure can be adopted.

While rotating the mandrel 33, the supporting rod 31, and the external supporting rod 32 around the shaft, the arrow 7
By advancing at a predetermined speed in the direction, heat contraction can be caused by uniform heating, and it can be forcibly moved along the cam surface 341. As a result, the support member 3 supports the bottom central portion 21. However, the support member 3 can be surely lowered according to the speed of this heat contraction, and a natural heat treatment can be realized.

When the discharge hole 35 can communicate with the outside with almost no resistance and the heat can be freely shrunk in the state where there is no difference between the internal pressure and the external pressure, the residual strain generated on the wall surface due to the primary blow is completely eliminated. It is preferable because it is removed and blow molding is performed uniformly during re-stretching.

The pattern of the cam surface 341 for forcibly moving may be set in advance so as to forcibly move downward in accordance with the contraction speed in the axial direction when freely heat-contracting. Not only does it not hinder the free thermal shrinkage, but it can maintain a constant movement pattern even if the shrinkage speed changes slightly due to variations in conditions, and the effects of variations in conditions are minimized. The primary blow bottle 2 that has been shrunk is obtained.

In this example, the primary blow bottle 2 is heated in the inverted state, but the supporting device or the like may be arranged so that the primary blow bottle 2 is heated in the upright state.

The primary blow bottle 2 which has undergone heat shrinkage is
It is inserted into the final mold 4 while maintaining the stretching temperature, and is stretched in the axial direction by the stretching rod 41, and is also stretched in the radial direction by blowing a pressure gas and blow-molded again to the final mold 4. The final product 20
Can be obtained.

[0022]

INDUSTRIAL APPLICABILITY The present invention blow-molds an injection-molded parison to form a primary blow bottle, heats the primary blow bottle to cause heat shrinkage, and then blow-molds it again in the final mold. According to the method for molding a bottle, the center part of the bottom of the primary blow bottle is supported by a support member to prevent misalignment, and the support member is forcibly moved. The center part of the bottom of the is supported by a support member to prevent misalignment, and by forcibly moving the support member, uniform heat shrinkage can be realized, and the resulting heat-treated bottle has no misalignment. It has an excellent appearance and has the effect of not causing variations in heat resistance and thickness.

[Brief description of drawings]

FIG. 1 is a schematic sectional front view of an apparatus for carrying out a bottle molding method of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

[Explanation of symbols]

 1 Parison 2 Primary blow bottle 21 Bottom center 3 Support member 4 Final type

Claims (1)

[Claims] 1. A primary blow bottle is formed by blow molding an injection-molded parison, the primary blow bottle is heated to cause heat shrinkage, and then blow molded again in a final mold. A bottle molding method characterized in that the center of the bottom of a blown bottle is supported by a support member to prevent misalignment and the support member is forcibly moved.