JPS625779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing bottles, and more particularly to a method for manufacturing stretch-blown polyethylene terephthalate bottles having a gas barrier plastic film coated on the outer surface.

Polyethylene terephthalate bottles (herein, polyethylene terephthalate copolymers containing ethylene terephthalate as a main component and blends containing polyethylene terephthalate as a main component) are formed from a bottomed parison by biaxial stretching and blow molding. Terephthalate (called terephthalate) has excellent container properties such as gas barrier properties, transparency, and impact resistance, and has recently been put into practical use for storing various contents. However, when filled with contents containing pressurized carbon dioxide such as beer or carbonated drinks,
When sealed, a small amount of carbon dioxide is lost over time through the thin walls of the shoulders and body, while a small amount of oxygen enters through the walls. The flavor of the contents is likely to be lost.

As a countermeasure, a method has been proposed in which a coating film with excellent barrier properties against carbon dioxide gas and oxygen, such as a coating film made of vinylidene chloride copolymer, is formed on the inner and/or outer surface of the Pasolin or bottle. It requires large and complicated equipment to apply, dry, and collect the paint, and it also causes problems such as a long time required for drying. Furthermore, since the coating film formed by one application is thin, several applications are required to ensure sufficient gas barrier properties, which causes the problem of reduced productivity.

It is an object of the present invention to solve the problems of the prior art described above.

In order to achieve the above object, the present invention loosely inserts a tube made of a heat-shrinkable plastic film having gas barrier properties into at least the body wall of a bottomed parison made of polyethylene terephthalate, and then at least the body wall of the bottomed parison. The tube is heated to a stretching temperature, the tube is brought into close contact with at least the outer surface of the body wall part by heat shrinking as the heating is performed, and then biaxial stretching and blow molding is performed, at least on the shoulder part and the outer surface of the body part. The present invention provides a method for manufacturing a polyethylene terephthalate bottle coated with the gas barrier plastic film.

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

In FIG. 1, 1 is a bottomed parison made of polyethylene terephthalate, which is usually formed by injection molding. 2 is a gas barrier plastic film (for example, a polyvinylidene chloride film with a thickness of 10 to 50 μm; a unit thickness of carbon dioxide gas,
A seamless long tube made of a plastic film whose barrier properties against oxygen gas, etc. It is cut to a length approximately equal to the height of the Its inner diameter is slightly larger than the outer diameter of the trunk wall portion 1a.

FIG. 1 shows a state in which the tube 2 is loosely inserted into the outer surface of the body wall portion 1a of the inverted parison 1 and placed on the neck ring 1b. Next, this parison 1 is stretched and blow molded at a stretching temperature of about 80 to 100.
It is heated to a predetermined temperature within the range of 0.degree. C. by infrared irradiation or passing through an oven. At this time, the tube 2 is thermally shrunk and comes into close contact with the outer surface of the body wall portion 1a of the parison 1, as shown in FIG. It is extremely difficult to tightly insert a flexible tube made of thin plastic film into the body wall by making the inner diameter of the tube substantially equal to the outer diameter of the body wall 1a from the beginning. However, as described above, it is relatively easy to slowly insert the tube even if the tube is easily bent. Then, by the usual method,
The parison 1 with the tube 2 in close contact therewith is subjected to biaxial stretching and blow molding to form a bottle 3 as shown in FIG. 3.

At this time, the tube 2 is also deformed at the same time, and the plastic film 2' forming the tube 2 deforms from the relatively thin (usually about 0.2 to 0.3 mm) body 3 of the bottle 3.
a and shoulder portion 3b in close contact with each other.

As the surface area increases during this molding, the thickness of the film 2' decreases by about 1/10 of the thickness of the tube 2. However, by appropriately determining the thickness of the tube 2, the thickness of the film 2' It can be made as thick as necessary (for example, about 10 to 50 μm) to ensure gas barrier properties. In some cases, tube 2
It may be formed in double or triple layers. bottom of bottle 3c
It is not necessarily necessary to cover it with a film 2', since it is usually relatively thick.

The tube 2 is made by rolling up a cut sheet of gas barrier film and joining the seams with a suitable adhesive (for example, polyester hot melt adhesive), or by heat fusion method, ultrasonic method, etc. It's okay.

According to the present invention, a tube made of a heat-shrinkable plastic film having gas barrier properties is loosely inserted into at least the body wall portion of a bottomed parison, and then at least the body wall portion is heated to a stretching temperature; In conjunction with this, the tube is brought into close contact with at least the outer surface of the body wall by heat shrinkage, and then biaxial stretching/blow molding is performed to manufacture the bottle, so the close contact of the tube is incidental to the heating process to the stretching temperature. Therefore, it is possible to produce a polyethylene terephthalate bottle with excellent gas barrier properties at low cost and high productivity by simply adding the simple operation of slowly inserting the tube to the conventional technique.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing a state in which a gas barrier plastic tube is loosely inserted into a parison for carrying out the present invention, and Fig. 2 shows a state in which the tube shown in Fig. 1 is tightly attached to the parison due to heat shrinkage. 3 is a partially cutaway front view of a row of bottles formed from the parison of FIG. 2; FIG. 1... Bottomed parison, 1a... Body wall part, 2...
Tube made of gas barrier plastic film, 2'... Gas barrier plastic film, 3... Polyethylene terephthalate bottle, 3a... Body, 3b... Shoulder.

Claims (1)

[Claims] 1. A tube made of a heat-shrinkable plastic film with gas barrier properties is loosely inserted into at least the body wall of a bottomed parison made of polyethylene terephthalate, and then at least the body wall is heated to a stretching temperature. At the same time, the tube is brought into close contact with at least the outer surface of the body wall by heat shrinking, and then biaxial stretching and blow molding is performed, so that at least the shoulder and the outer surface of the body are coated with the gas barrier plastic film. Method of manufacturing polyethylene terephthalate bottles.