JPH0760825A - Manufacture of resin hollow vessel - Google Patents

Abstract

PURPOSE:To obtain a resin hollow vessel which has excellent heat resistance, a small capacity change at the time of molding and excellent shaping properties by releasing a residual stress in heating molds and cooling inner and outer walls of the vessel by using cooling medium of the ordinary temperature or lower. CONSTITUTION:A previously molded parison is heated to a temperature capable of orientating, disposed in heated molds 3, and a hollow vessel 1 is molded by biaxial orientation blow molding. The vessel 1 is held in heated blow molds 3, and its residual stress is released. In order to cool the vessel 1 in the heated molds 3, cooling medium is injected from a cooling medium injection hole 11 connected to a cooling medium feed tube 8 of a hollow part provided in an orientation and cooling rod 6 to cool the vessel 1. The medium is injected into a gap between the heated molds 3 and an outer wall of the vessel 1 to cool the vessel 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a saturated polyester resin container obtained by biaxial stretch blow molding, which has good heat resistance, a small capacity change during molding, and a good container shape. The present invention relates to a method for manufacturing a hollow container.

[0002]

2. Description of the Related Art Conventionally, as a method for molding a biaxially stretched hollow container, a preformed bottomed parison is heated to a temperature at which it can be stretched, and this is inserted into a blow molding die, and a stretching rod is used to form the parison. Stretching in the longitudinal direction by moving in contact with the bottom, then eject the compressed fluid from the blow molding mandrel inserted in the mouth and neck of the parison,
A method of manufacturing a biaxially stretched blow container in which the parison is stretched in the horizontal direction is known.

The container thus obtained is usually used as a container for heat-sterilized drinks such as carbonated drinks, fruit drinks and black tea. When used as a container for heat sterilization, it is required to have good heat resistance and good container shape.

As a concrete method corresponding to this, after stretch blow molding in a heated blow mold,
A method for cooling the hollow container by cooling the mold to prevent thermal deformation of the container and then taking it out (JP-A-54-6696).
No. 8), the residual stress is removed in a state where the internal pressure is kept inside the hollow container in the blow molding die, and then the hollow container is transferred to another cooling die and the internal pressure is applied to the hollow container again. A method of solidifying by cooling in close contact with the inside of a mold (Japanese Patent Laid-Open No. 62-
No. 33622), a hollow container is held in a heated blow mold to be heat-fixed, and then a liquid substance of nitrogen or carbon dioxide is diffused and injected into the inside of the hollow container to cool the hollow container (Japanese Patent Laid-Open No. 59-93330). Issue gazette).

[0005]

However, Japanese Unexamined Patent Application Publication No. Sho.
According to the method of Japanese Patent No. 4-66968, the mold is heated to a high temperature or cooled to a low temperature to mold, heat-fix and cool the container with the same mold, so that the molding time of the hollow container is extremely long. Therefore, there is a drawback that the molding efficiency is lowered. The method disclosed in Japanese Patent Laid-Open No. 62-33622 has a mold for molding and heat-fixing the container and a mold for cooling the container, but the cooling of the container is performed by the heat transmitted from the mold. In addition, similarly, there is a drawback that the molding time of the hollow container becomes long and the molding efficiency is lowered.

Further, as shown in JP-A-59-93330, a method of introducing liquefied nitrogen or carbon dioxide into a hollow container for direct cooling is excellent in cooling efficiency. Due to the extremely low temperature, these liquefactions are deformed due to the difference in cooling rate unless the container is cooled uniformly in the hollow container in the state where there is no time difference, and the liquefaction is extremely low temperature. In addition, since the water content of the air accumulated in the container is frozen, there is a drawback that the water content must be removed again.

The present invention solves the above-mentioned drawbacks by releasing residual stress of a biaxially stretch blow-molded hollow container, then ejecting a cooling medium into the hollow container, and at the same time, the hollow container. The present invention has been completed by finding a molding method in which the step of discharging the cooling medium from the inside and the step of ejecting the cooling medium into the gap between the outer wall surface of the hollow container and the mold wall surface are found.

[0008]

Means for Solving the Problems That is, according to the present invention, a premolded parison made of a thermoplastic resin is heated to a temperature at which it can be stretched, placed in a heated mold, and biaxially stretch blow molded to form a hollow container. After releasing the residual stress of the hollow container in the mold, the treatment (A) below is performed at the same time or before or after the treatment (B) is performed, and the internal pressure of the hollow container is released. The present invention provides a method for manufacturing a resin-made hollow container, which comprises taking out the hollow container from a mold. (A) A cooling medium is jetted into the hollow container, while the cooling medium is discharged from the hollow container. (B) A cooling medium is jetted into the gap between the outer wall surface of the hollow container and the mold wall surface.

The present invention will be described in detail below with reference to the drawings. In FIG. 1, a pre-injection-molded parison of a thermoplastic resin according to the present invention is blow-molded to form a hollow container, and after releasing residual stress, a cooling medium is further ejected into the hollow container and gold FIG. 6 is a partial cross-sectional view showing a mold part of a blow molding device used for cooling by ejecting a cooling medium into a gap between a mold and a hollow container.

The bottomed parison to be blow-molded is moved to the blow-molding die 3 after being heated in a state in which the blow-molding mandrel 7 is inserted into the parison opening which becomes the container neck 2 as shown in FIG. After closing the mold 3, the drawing / cooling rod 6 contained in the blow molding mandrel 7 is brought into contact with the bottom of the bottomed parison and drawn in the longitudinal direction to form a cavity in the blow molding mold 3. The bottom of the molded body is brought into close contact, and further, the high-pressure air sent from the pressure fluid passage 9 provided in the blow molding mandrel 7 laterally stretches and makes close contact with the cavity of the blow molding die 3 to form a molded body. Mold a hollow container.

Next, the hollow container 1 is held in the heated blow molding die 3 to release the residual stress. In order to cool the hollow container 1 in the heated mold 3, the cooling medium is ejected from the cooling medium ejection hole 11 connected to the cooling medium feeding pipe 8 in the hollow portion provided in the drawing / cooling rod 6. Are jetted to cool the hollow container 1. Further, the cooling medium is jetted into the gap between the heated mold 3 and the outer wall surface of the hollow container 1 to cool the hollow container 1.

The cooling medium is discharged from the blow high pressure gas inlet / outlet pipe 10 through the pressure fluid passage 9 provided in the blow molding mandrel 7. Further, the cooling medium sent to the outer wall surface of the hollow container is discharged from the gap provided on the mold parting surface. The above cooling medium may be ejected onto the inside and the outer wall surface of the hollow container at the same time or before or after, and it is particularly preferable that the cooling medium is ejected at the same time and the ejection to the outer wall surface is slightly delayed.

Although the cooling medium ejection holes 11 provided in the stretching / cooling rod 6 differ depending on the inner volume of the hollow container, it is preferable to provide the cooling medium ejection holes 11 at intervals such that the jetted cooling mediums intersect with each other. It is preferable to provide 2 to 7 locations in the axial direction of the working rod 6 and about 4 to 8 locations in the circumferential direction. Moreover, the cooling gas ejection hole 11 is
The container is arranged so that the cooling gas is uniformly brought into contact with the body part that is connected to the bottom part from the shoulder part of the container where residual stress is likely to occur during stretching.

The cooling medium ejection hole 12 provided in the cavity surface of the heated blow molding die 3 is in the shape of a hollow container,
Although it depends on the internal volume, it is preferable that the cooling medium be provided in a gap between the wall surface of the mold and the outer wall surface of the hollow container so that the cooling medium flows, for example, the side surface of the bottom of the hollow container, the circumference of the recessed portion of the center of the hollow container It is preferably provided at a plurality of positions in the direction.

The cooling medium is preferably a gas such as air, nitrogen or carbon dioxide, and the medium temperature is room temperature or lower,
It is preferably in the range of 10 to -50 ° C.

The resin used in the container of the present invention is preferably a thermoplastic polyester resin whose main repeating unit is ethylene terephthalate, and the thermoplastic polyester resin contains a homopolymer of polyethylene terephthalate as a main component.

In the thermoplastic polyester resin, a part of the terephthalic acid component is used as an aromatic dicarboxylic acid such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid or diphenyl sulfone dicarboxylic acid. Acids, alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid and azelaic acid; P-β
A copolymer of at least one other difunctional carboxylic acid such as hydroxyoxybenzoic acid or oxyacid such as ε-oxycaproic acid can be used.

In the thermoplastic polyester resin, a part of the ethylene glycol component is, for example, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene glycol, diethylene glycol, 1.1-cyclohexanedimethylol. , 1.4-cyclohexanedimethylol, 2.2 (4'-β-hydroxyethoxyphenyl)
It may be copolymerized by substituting with one or more polyfunctional compounds of other glycols such as sulfonic acid and functional derivatives thereof.

The thermoplastic polyester resin used for molding the hollow container of the present invention has an intrinsic viscosity in the range of 0.6 to 1.1, preferably 0.75.
It is 0.80.

Further, the thermoplastic polyester resin of the present invention may appropriately contain additives such as a colorant, a heat deterioration preventing agent, an antioxidant, an ultraviolet absorber, an antistatic agent, an antibacterial agent and a lubricant.

[0021]

The present invention will be described in detail with reference to the following examples.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.78 (trade name: RT543, manufactured by Nippon Unipet Co.) was injection-molded to obtain a bottomed parison. Next, after preheating the parison to 100 ° C., the parison is inserted into a blow molding mold heated to 140 ° C. by oil temperature control and stretched in the longitudinal direction by a stretching / cooling rod, and at the same time, a blow molding mandrel. High-pressure air was blown in through the resin to perform stretching in the transverse direction as well, and biaxial stretching blow molding was performed. Then, it was held in the mold for 10 seconds to release the residual stress.

After releasing the residual stress of the hollow container, stretching
High-pressure air at 5 ° C. was jetted for 5 seconds from a cooling medium jet hole connected to a cooling gas inlet pipe provided on the cooling rod. The high-pressure air was discharged from the pressure fluid passage provided in the blow molding mandrel and the blow high-pressure gas inlet / outlet pipe to cool the hollow container.

Simultaneously with the ejection of the above-mentioned high-pressure air, high-pressure air at 5 ° C. was ejected to the outer wall surface of the hollow container for 5 seconds from ejection holes for cooling provided in the inner wall of the mold to cool the hollow container. Then, after releasing the pressure in the hollow container, the hollow container was taken out from the mold to obtain a hollow container having a filling capacity of 1.5 liters. The total molding time was 45 seconds.

The characteristics of the 1.5-liter hollow container obtained above are as follows. Full capacity: The hollow container of the present invention showed almost no heat shrinkage during molding, and the full capacity was 1530 cm ³ . Heat resistance: The hollow container was filled with hot water of 87 ° C., and after cooling with water, the capacity decrease was 0.4%. Vessel wall density (gradient tube method): 1.370 to 1.374 g /
It was cm ³ . Haze (based on JIS K 7105): 1.5%
(A test piece was taken from the body of the container, and the thickness was 0.3m.
m)

Comparative Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.78 (manufactured by Nippon Unipet Co .: trade name, RT543) was injection-molded to obtain a bottomed parison. Next, the parison was preheated to 100 ° C. and then heated to 140 ° C. by adjusting the oil temperature, and the cooling medium ejection hole 12 was installed in the blow molding die having the same shape as that used in Example 1. The film was inserted into a non-mold and stretched in the longitudinal direction by a stretching / cooling rod, and at the same time, high-pressure air was blown through the blow molding mandrel to perform stretching in the transverse direction as well, thereby biaxially stretching. And 10 in the mold
Hold for seconds to release residual stress.

After releasing the residual stress of the hollow container, stretching
High-pressure air at 5 ° C. is jetted for 10 seconds from a cooling jet hole connected to a cooling gas inlet pipe provided on a cooling rod, and the high-pressure air is a pressure fluid passage and blow high-pressure gas provided in a blow molding mandrel. The hollow container was cooled by discharging it from the inlet / outlet pipe. However, the step of ejecting the cooling high-pressure air from the cooling medium ejection hole 12 to the outer wall surface of the hollow container was not performed. After releasing the internal pressure, the hollow container was taken out from the mold. The total molding time was 50 seconds.

The characteristics of the hollow container for 1.5 liter obtained as described above are as follows. Full capacity: The hollow container of the comparative example had a large heat shrinkage during molding, and the full capacity was 1500 cm ³ . Heat resistance: The hollow container was filled with hot water of 87 ° C., and after cooling with water, the capacity decrease was 0.4%. Container wall density (gradient tube method): 1.369 to 1.374 g /
cm ³ Haze (according to JIS K 7105): 1.5% (a test piece was sampled from the body of the container, the thickness was 0.3 mm)

[0029]

As described above, a hollow container is molded by the biaxial stretch blow molding of the present invention, residual stress is released in a heating mold, and a hollow medium is cooled in the same mold using a cooling medium at room temperature or lower. Due to the manufacturing method of cooling the inner wall surface and the outer wall surface of the container, the heat resistance is good, the volume change during molding is small, and
It is possible to obtain a resin hollow container having a good shape-imparting property, and it is possible to shorten the molding time of the hollow container.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a mold portion of a blow molding apparatus of the present invention.

[Explanation of symbols]

 1 Hollow Container 2 Container Mouth Neck 3 Blow Molding Die 4 Temperature Control Pipe (Body and Bottom) 5 Temperature Control Pipe (Mouth) 6 Stretching / Cooling Rod 7 Blow Molding Mandrel 8 Cooling Medium Inlet Pipe 9 Pressure fluid passage 10 Blow high pressure gas inlet / outlet pipe 11 Cooling medium ejection hole (stretching / cooling rod) 12 Cooling medium ejection hole (blow molding die)

Claims (1)

[Claims] 1. A premolded parison made of a thermoplastic resin is heated to a temperature at which it can be stretched, placed in a heated mold, and a hollow container is molded by biaxial stretch blow molding.
After releasing the residual stress of the hollow container in the mold, the process (A) below is performed at the same time, before or after the process (B), and the hollow container is hollowed after the internal pressure of the hollow container is released. A method for producing a resin hollow container, characterized in that the container is taken out. (A) A cooling medium is jetted into the inside of the hollow container, while the cooling medium is discharged from the inside of the hollow container. (B) A cooling medium is jetted into the gap between the outer wall surface of the hollow container and the mold wall surface.