JPH0363496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a heat-resistant bottle by biaxially stretching blow-molding a crystalline resin and then heat-treating the resin to crystallize it.

In recent years, containers made of crystalline resins such as polyethylene terephthalate that are biaxially stretched and blow-molded and further crystallized through heat treatment have been used as containers that can withstand temperatures such as high-temperature filling of fruit juice and the like. There is. One specific method is to perform biaxial stretch blow molding using pressurized fluid in a heated mold whose temperature is controlled to be above the crystallization start temperature of the crystalline resin, and then heat treatment by pressing the bottle wall against the inner surface of the mold using internal pressure. After that, a method has been proposed in which a refrigerant such as liquefied carbon dioxide gas is blown into the bottle to cool and solidify it, and then the bottle is removed from the mold. However, in this method in which molding and heat treatment are performed using one mold, the passage for the pressurized fluid for molding and the refrigerant passage are shared or provided together, so the pressure fluid passage is cooled and condensation does not occur on the surface. As a result, the friction coefficient of the stretching rod changes, causing unstable movement, and moisture adheres to the bottle during molding, resulting in variations in the quality of the molded product.

When a common passage for pressurized fluid and refrigerant is provided in the stretching rod, the diameter of the refrigerant passage cannot be increased, so there is a limit to the amount of refrigerant blown, which lengthens the cooling cycle and increases the amount of refrigerant consumed.

There were problems such as.

The present invention enables efficient and stable production of bottles by using separate molds and heating molds and combining with refrigerant cooling. Stretch blow molding is performed in a mold at a temperature below the crystallization temperature of the resin to form an intermediate bottle, and this intermediate bottle is loaded into a heating mold heated at a temperature above the crystallization start temperature of the resin to a melting point of -30°C or below. This method of molding a heat-resistant bottle is characterized in that the intermediate bottle wall is pressed against the inner surface of the mold by internal pressure and subjected to heat treatment, and then a refrigerant is blown into the bottle to cool it and then taken out from the heating mold.

The resin constituting the parison in the present invention may be any resin that can be oriented and crystallized by stretching and heating to improve heat resistance, physical properties, etc., such as polyester such as polyethylene terephthalate, polyvinylidene chloride, nylon, etc. Although crystalline resins can be used, polyethylene terephthalate (hereinafter simply referred to as PET) is particularly preferred because of its excellent heat resistance and strength. In order to manufacture a parison, these resins may be formed into a tubular shape by injection molding, extrusion molding, or the like.

Next, an example using a parison made of PET as an embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

FIGS. 1 to 3 are schematic diagrams showing the steps of carrying out the method for molding a heat-resistant bottle of the present invention.

As shown in Figure 1, a parison 2 made of PET heated to a stretching droplet temperature is fixed to a mold 1 whose temperature is below the crystallization temperature of PET, and a pressurized fluid is blown into the inside of the parison 2 to create a shape along the mold 1. Then, the intermediate bottle 21 is obtained by stretch-molding. The mold 1 is at a low temperature below the crystallization temperature of PET (120 to 130 °C), preferably below the glass transition temperature (65 to 75 °C), so after blow molding,
Since the intermediate bottle has been cooled and solidified to some extent,
There is no extreme thermal deformation even after removing from the mold 1.
Maintains approximately final shape. In this example, the stretch rod 3 pushes up the bottom of the parison 2 to stretch it in the longitudinal direction, and at the same time blows pressure fluid through a passage provided in the stretch rod.
This is biaxial stretch blow molding, which performs shaping in the lateral direction.

In this way, the intermediate bottle 21, which has been stretch-blow-molded into a shape close to the final shape, is molded into a heating mold 4 shown in FIG.
The intermediate bottle wall is again pressed against the inner surface of the heating mold 4 using a pressure fluid to heat-treat the bottle to form a heat-treated bottle 22. Thereafter, a refrigerant is blown into the heat-treated bottle from the refrigerant nozzle 5 inserted into the heat-treated bottle to cool the heat-treated bottle 22 from the inside in a short time, and the bottle 22 is immediately taken out from the heating mold 4 to form a heat-resistant bottle. Here, since the bottle 22 in the heating mold 4 has already been molded to almost the final shape,
Even if moisture adheres to the refrigerant nozzle 5, etc.
Unlike the molding process, there is no variation in the quality of the molded product.

In order to heat the heating mold 4, water vapor or the like can be passed through a heating medium channel 41 provided in the mold, for example. The temperature may be between the crystallization initiation temperature and (melting point -30°C). If the temperature is lower than the crystallization start temperature, there will be no heat treatment effect, and if the temperature is higher than the melting point -30°C, it will stick inside the heating mold and the surface will become rough. 120℃ to 220℃ for PET
is suitable. In addition, the heating time is 2 to 300 seconds, preferably 3 to 300 seconds, depending on the bottle wall thickness and heating temperature.
You can set it appropriately within 10 seconds.

The pressure of the pressurized fluid is 5 in absolute atmospheric pressure in the case of PET.
Kg/cm ² or more is preferable.

As the refrigerant used for cooling, liquefied carbon dioxide gas can be suitably used, but any refrigerant that is low temperature and easily vaporized, such as liquid nitrogen, may be used.

According to the method of molding a heat-resistant bottle of the present invention, first, an intermediate bottle in approximately the final shape is stretch-blow-molded in a relatively low-temperature mold, then transferred to a heating mold and heat-treated, and then cooled by blowing a refrigerant into it. As a result, a bottle with excellent heat resistance can be efficiently manufactured without causing variations in quality due to moisture adhesion during molding.

[Brief explanation of drawings]

FIGS. 1 to 3 are schematic diagrams showing the steps of carrying out the method for molding a heat-resistant bottle of the present invention. 1... Molding mold, 4... Heating mold, 21... Intermediate bottle.

Claims (1)

[Claims] 1. A parison heated to an appropriate stretching temperature is stretch-blow-molded in a mold at a temperature below the crystallization temperature of the resin constituting the parison to form an intermediate bottle, and this intermediate bottle is heated to a melting point of - 30
A heat-resistant bottle characterized in that it is loaded into a heating mold heated to below ℃ and subjected to heat treatment by pressing the intermediate bottle wall against the inner surface of the mold by internal pressure, and then cooled by blowing a refrigerant into the bottle before being taken out from the heating mold. molding method.