KR840000175B1 - Method injection flow molding - Google Patents

Abstract

No content.

Description

Injection Stretching and Blow Molding Method

1 is a vertical cross-sectional view of a basal parison in accordance with the present invention.

2 is a vertical cross-sectional view of a hollow molded article produced according to the present invention.

The present invention relates to an injection stretching and blow molding method, in particular a stretching and blow molding method of obtaining a hollow molded product by injection molding of two layers using a synthetic resin resistant to stretching and blow molding.

A method of blow molding a base injection molded Parison into a hollow molded product such as a bottle, and injecting molten resin into a closed mold including a core and a cavity forming mold and blowing the core together. Method of blow molding base-based flyson after moving to mold, injection molding base-based flyson and separating from injection core, moving to blow-molding mold and inserting into blown core equipped with drawing rod Next, methods for blow molding base-based Parisone while stretching in the axial direction in the blow molding die are known.

The former method is generally called injection blow molding and the latter is called injection stretching and blow molding. By the injection drawing and the blow molding method, a product having a thinner wall, higher transparency and higher strength than the product produced by the former method can be obtained.

However, the injection drawing and blow molding methods cannot be preferably applied to any resin. Of the stretchable and blowable resins, some resins cannot be easily molded. In particular, vinyl chloride resins can be stretched and molded very easily into blow molded products having various colors, but sometimes difficulties arise when molding them into blow molded products by injection stretching and blow molding methods. This is because the layer of resin is ruptured before the blow molding is sufficiently stretched or fully expanded, and it is very difficult to mold these resins into hollow molded products having a uniform wall thickness.

There may be various reasons for such low molding ability, but one of the reasons is that the injection molding of the resin is possible and the distribution of the wall thickness is not uniform in the products manufactured by the stretching and the blow molding method. Likewise, it is presumed that problems arise in maintaining the heat deflection temperature in the stretching and blow molding. As a result, many studies have been conducted to find a suitable method for maintaining the heat deflection temperature in drawing and blow molding. As a result, it has been found that the base has parison, which can be obtained from polyethylene terephthalate resin which can be easily stretched and blow molded. In comparison, it is very important to maintain optimum heat distortion temperature for base-side Parison, which is obtained by injection molding resins such as vinyl chloride resin, styrol resin, acrylic resin, acrylonitrile resin, ABS resin or AS resin. I found it difficult. Therefore, another method is needed to maintain the base Parish at a heat deflection temperature suitable for stretching and blow molding.

Therefore, the present inventors have studied a method of drawing and blowing a core capable of maintaining the flyson at a suitable temperature by inserting the temperature-controlled core into the base flyson. It has been found that this method is suitable for stretchable and blowable resins, for example polyethylene terephthalate, but it is relatively unsuitable for stretching and blow molding resins that are difficult to stretch and blow, namely vinyl chloride resins. . This is because, when the base-based flyson with the core inserted is axially drawn using a drawing rod in the center of the core, the inner surface of the flyson adheres tightly and partially adheres to the core heated by the tensile strength. This is because the parison cannot be expanded sufficiently when the air is blown in the mold.

Extensive studies of means for maintaining baseline parison at moderate temperatures have shown that resins that can be easily stretched and blow molded as a means of keeping parison at optimum temperature without the use of a heated core. We found that it is best to use.

It is therefore an object of the present invention to provide a drawing and blow molding method for maintaining a base with parison, especially a parison made of a resin which is difficult to stretch and blow molding at a suitable temperature. Another object of the present invention is to provide a drawing and blow molding method without using a heated core as a means for maintaining the base with parison at a suitable temperature.

It is a further object of the present invention to provide a stretching and blow molding method using a resin which can be easily stretched and blow molded as a means for maintaining the base parison at a suitable temperature.

The resin which can be easily stretched and blow molded as described above can be adjusted to the temperature most suitable for stretching and blow molding without taking any special method as long as it is molded immediately after controlling the temperature.

The temperature can be maintained to some extent even when the resin which can be easily stretched and blow-molded is brought into contact with other resins.However, maintaining the temperature of the resin which is difficult to stretch and blow-molding is a method of injection molding two layers of flyson. Can be adult using. Therefore, the blow molded product having the desired shape is injection-molded resin which is difficult to stretch and blow molding and resin which can be stretched and blow molded temporarily, and the resin is difficult to stretch and blow molding, and the other is easy to stretch and blow molding. The base layer is made of two-layer flyson, made of resin, and the temperature of the baseline flyson is adjusted to a temperature suitable for stretching and blow molding, while the base flyson is axially stretched in the blowing mold. It has been found that it is prepared by blowing air into the drawn parison.

The blow-molded product thus obtained is not satisfactory in terms of the distribution of the wall thickness, but the rupture caused by the use of resins that are difficult to stretch and blow molding does not occur, and the expansion by air blowing is effective for the entire surface.

The following examples are intended to illustrate the invention in detail and thus do not limit the scope of the invention.

EXAMPLE

First, polyethylene terephthalate resin is injection molded into an inner layer having a thickness of 2 mm. The outer vinyl chloride of the inner layer 1 is injection molded to form an outer layer 2 having a thickness of 3 mm. Thus prepared two-layer flyson 3 with a base part is heated to a heat deflection temperature suitable for drawing and blow molding, and then transferred to a blow molding mold, where the base piece is simultaneously drawn in the axial direction and blown with air. Make a blow molded article 4 of the layer. The heat deflection temperature may be preferably adjusted to a temperature most suitable for stretching and blowing the polyethylene terephthalate resin. Blow molding can be performed by stretching the outer layer 2 together with the inner layer 1 using a drawing rod. This method can use the inner layer 1 to maintain the heat deflection temperature in the outer layer 2 without a significant decrease in temperature during blow molding. In this way, a hollow molded product with no difference in stretching and expansion between the two layers after molding can be obtained, because the outer layer 2 can be stretched and blow molded temporarily and the inner layer 1 can be expanded uniformly. Because it expands together. Therefore, the manufactured blow molded product 4 has high strength and uniform thickness of the inner and outer layers.

In the above embodiment, polyethylene terephthalate resin was used as the inner layer 1, but vinyl chloride resin may be used instead of the tereethylene phthalate resin. In this case, the wall thickness of the inner layer may be nonuniform compared with the outer layer, but it is not a problem that the hollow product has such a degree of nonuniformity.

The wall thicknesses of the two layers in the base Parish are not necessarily the same, and from an economic point of view, it is desirable to make the cheaper resin layer thicker than the more expensive resin layer.

The following table shows the heat deformation temperatures of various resins that are difficult to stretch and blow, and the polyethylene terephthalate resin is used as a resin that can be easily stretched and blow molded.

PET 75-85 ℃ (inner layer)

PVC 84 ℃ (outer layer)

Styrol 82 ℃ (outer layer)

Acrylic 88 ℃ (outer layer)

ABS 82 ℃ (〃)

AS 85 ℃ (〃)

Acrylonitrile 74 ℃ (Outer Layer)

Claims (1)

Two layers with base, consisting of a resin that can be easily stretched and blow molded and a resin that is difficult to stretch and blow molded, one layer is a resin that can be easily stretched and blow molded, and the other layer is a resin that is difficult to stretch and blow molded. After injection molding with the fly's flyson, the thermal deformation temperature of resins that are difficult to stretch and blow molding can be easily adjusted within the heat deformation temperature range of resins that can be stretched and blow molded, and the resin layers difficult to stretch and blow are easily stretched An injection drawing and blow molding method characterized by drawing together with a resin layer which can be blow molded and blowing air into the base with Parison.

Images