JPS6213168B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a stretch-molded polyethylene terephthalate resin bottle.
The object of the present invention is to provide a method for forming a stretch-molded bottle made of polyethylene terephthalate resin, which has excellent mechanical strength and durability, and has a freely shaped neck portion with high molding accuracy.

Polyethylene terephthalate resin has come to be used in a wide range of fields due to its excellent physical properties and durability.

However, the excellent physical properties and durability of this polyethylene terephthalate resin are often only exhibited after a polyethylene resin molded product is stretch-molded.

For this reason, in order to stretch the material, the bottle structure is first molded into a bottomed cylindrical piece as a primary molded product by injection molding, and then this piece is stretch-blow molded using so-called in-jet extension blow molding. It was supposed to be molded using a molding method.

However, in injection blow molding, the neck of the piece must be immovably held in the blow mold during blow molding, so while the body of the bottle is fully stretched and molded, There was a problem in that the neck remained completely unstretched.

In this way, the neck of the molded bottle is not stretched, so it has inferior physical properties and durability compared to the body.For example, the body does not have any disadvantages when exposed to high concentration alcohol. On the other hand, alcohol penetrates into the neck, causing whitening and making it mechanically brittle, resulting in the serious inconvenience of a large number of thin cracks forming and a complete loss of sealing effect.

A concrete way to prevent this problem is to stretch-mold the neck together with or separately from the body, but stretching and molding the neck is quite troublesome, and the cap is attached to the bottle. The molding dimensions of the neck, which ensures the sealing of the body, require considerably higher precision than the body, and sufficient mechanical strength is also required for the cap assembly, so stretch-molding of the neck and stretch-molded neck are required. has many unresolved issues.

The present invention was devised to smoothly eliminate the inconveniences and problems in the conventional examples described above.
The neck of the bottle is stretch-formed by the simplest method of stretching, and the mouth piece is immovably fixed to the neck, thereby increasing the dimensional accuracy and mechanical strength of the neck as a bottle.

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

FIG. 1 is a partial longitudinal cross-sectional view of the main part of the bottle molded according to the present invention, and P' in the figure is the body part _P1.
The main body of _the bottle is made of polyethylene terephthalate resin and is stretch-molded.

The body _P1 of the bottle body P' is stretch-molded by ordinary stretch blow molding, but the neck _P2 is suitably stretch-molded separately from the body _P1 .

As a means for stretching the neck portion _P2 , tension stretch molding or punch stretch molding can be considered, but tension stretch molding is more advantageous in terms of ease of stretching operation.

A mouth piece K made of an appropriate material and having a cylindrical shape with an inner diameter into which the neck portion P ₂ fits snugly is fitted and fixed to the stretch-molded neck portion P ₂ .

This mouth piece K is provided mainly to increase the mechanical strength of the neck including the mouth edge of the bottle, but it is also used as an assembly part of the cap that is assembled to seal the bottle. In addition, in place of the neck _P2 , which cannot be formed with a thread due to stretch molding, a thread _K1 is formed on the outer peripheral surface so that a screw cap can be used. You can also do that.

The means for fitting and fixing the mouth piece K onto the neck P ₂ differs depending on the molding material of the mouth piece K, but for example, the mouth piece K is made of the same polyethylene terephthalate resin that forms the bottle body P'. In the case of a similar type of resin material, adhesion using an adhesive or the like, welding using ultrasonic waves, etc. are effective.

In addition, when the mouth piece K is molded from another material, for example, metal, there is a neck part P ₂ on each of the inner surface of the mouth piece K and the outer peripheral surface of the neck part P ₂ that contacts this inner surface.
An engaging part is provided to prevent the mouth piece K from idling against the neck part P2, and an appropriate means is provided to prevent the mouth piece K from slipping out of the neck part _P2 .

In any case, in order to more securely attach the mouth piece K to the neck part _P2 , the mouth edge part _P3 ', which is the upper edge of the neck part _P2 , is attached to the mouth piece K as shown in the figure. It is preferable to bend it outward so as to cover the upper surface of K.

It goes without saying that by bending the mouth edge portion P ₃ ′ outward in a manner that covers the upper surface of the mouth piece K, the assembly of the mouth piece K to the neck portion P ₂ is strengthened.
Since the stretched polyethylene terephthalate resin forming the bottle main body P' is located up to the end surface of the mouth part of the bottle, the mouth piece K does not come into contact with the liquid inside, and therefore the molding of the mouth piece K is prevented. The material can be freely selected, and since the liquid content does not penetrate into the joint surface between the mouth piece K and the neck part P ₂ , the strength of the assembly of the mouth piece K to the neck part P ₂ is reduced. There's no fear of letting it happen.

As described above, since the bottle molded according to the present invention is entirely stretch-molded, it can fully exhibit the excellent physical properties and durability of polyethylene terephthalate resin. The mouth piece K is molded separately, and this is made into the neck part _P2 .
Since the neck part is fitted and fixed, the dimensional accuracy of the neck part, which has been degraded due to stretch molding, can be improved.

Furthermore, since the neck part of the bottle is reinforced by the mouth piece K, the neck part _P2 can be sufficiently stretched without worrying about its wall thickness, making it possible to achieve a better stretching effect and to improve the stretch-molding operation. becomes easier.

Although various methods can be considered for forming this bottle, the most effective forming method according to the present invention will be explained next with reference to FIGS. 2 to 6.

First, as shown in FIG. 2, a bottomed cylindrical piece P, which is injection molded as a primary molded product from polyethylene terephthalate resin, is held immovably by its body part P ₁ and bottom part, and the neck part P ₂ is heated to a temperature that produces a stretching effect.

Since it is desirable to uniformly heat the entire neck portion _P2 , it is best to hold the piece P immovably at a location as far away from the neck portion _P2 as possible.
For this reason, as mentioned above, it is desirable to hold it in the area from the trunk _P1 to the bottom.

In addition, the mouth edge P ₃ which is the upper edge of the neck P ₂ is
In order to effectively apply the tensile force of the stretched piece E during the stretching process of _P2 , it is preferable to leave it in a slightly bulging state as in the illustrated embodiment.

Once the entire area of the neck P ₂ has been heated to a temperature that produces a stretching effect, the mouth edge P ₃ is held by a stretched piece E with a substantially uniform holding force over its entire circumference, and this stretched piece E is attached to the neck. While the temperature of P ₂ is still within the temperature range of the stretching effect, move the piece P along the central axis (upward movement in the case of the illustrated embodiment) to move the neck P ₂ by the amount of movement of this stretched piece E. Tensile stretch molding.

In this way, when the tension stretch forming of the neck part P ₂ is completed, a neck part of a predetermined length connected to the body part P ₁ is formed.
Cut off the tip of neck P ₂ leaving P ₂ (see Figure 4)
Then, a mouth piece K formed into a cylindrical shape whose inner circumferential surface contacts the outer circumferential surface of the neck _P2 over its entire area is fitted onto the neck _P2 from which the tip has been cut off using a suitable material. (see Figure 5) and secure it using appropriate means.

In this way, the piece P with the mouth piece K fixed to the neck part _P2 is assembled and held in a blow mold, and the body part _P1 of the piece P is stretch blow molded to form a bottle.

When this piece P is stretch-blow-molded using a blow mold, only the body P ₁ of the piece P is stretch-molded to become the bottle body P', but the neck part P ₂ of this bottle body P' is
Since it has already been stretch-molded, the main body of the bottle
All parts of P' are stretch-molded.

By the way, when fitting and fixing the mouth piece K to the neck part _P2 ,
As shown in FIG. 6, apart from the fixing means for the neck _P2 of the mouth piece K, the newly formed mouth edge _P3 ' is bent outward to cover the upper end surface of the mouth piece K. By doing so, the assembly of the mouth piece K to the neck part P ₂ can be strengthened, and the upper end surface of the mouth piece K can be covered with stretched polyethylene terephthalate resin having excellent physical properties and durability. .

In this molding method, the neck part P ₂ is stretched and molded, so a sufficient amount of stretching can be obtained for the neck part P ₂ .
Moreover, the apparatus and operation for carrying out this method are also simple.

Further, a mouth piece K is fitted and fixed to the neck part _P2 , and a stretch-molded mouth edge _P3 ' is folded to cover the upper end surface of the mouth piece K. It is desirable that the neck part P 2 be curved, and this requires that the length of the neck part P ₂ be longer than the mouth piece K, and that the mouth edge part P ₃ ' itself needs to be stretch-molded.
It has become extremely advantageous to stretch the P ₂ stretch.

As is clear from the above description, in the present invention, all parts of the bottle body P' can be stretch-molded, so the excellent physical properties and durability of polyethylene terephthalate resin can be fully exhibited. Furthermore, even if the dimensions of the neck _P2 are different from those during injection molding due to stretch molding, the mouth piece K is fitted and fixed, resulting in dimensional inconveniences in the neck as a bottle. It has many excellent effects, such as being completely fearless, simple, and extremely easy to implement.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a main part showing an embodiment of a bottle molded according to the present invention. 2 to 6 are longitudinal cross-sectional views at each step showing the method of forming the bottle shown in FIG. 1, FIG. 2 is a view before stretch forming, FIG. 3 is a view during stretch forming, FIG. 4 is a view when the upper end of the neck is cut off, FIG. 5 is a view when the mouth piece is fitted and fixed, and FIG. 6 is a view when the mouth edge is bent outward. Explanation of symbols, P; Piece, P′; Bottle body, P ₁ ;
Body, P ₂ ; Neck, P ₃ , P ₃ ′; Mouth edge, K; Mouth piece, K ₁ ; Thread, E: Stretched piece.

Claims (1)

[Claims] 1. A piece P, which has been injection molded as a primary molded product of the bottle main body P', is held immovably between the body part P1 and the bottom part, and the neck part P2 of the piece P is heated to a temperature that produces a stretching effect, and the neck part P2 is The mouth edge P3, which is the tip, is held by the stretched piece E with a substantially uniform force over the entire circumference, and the stretched piece E is held while the temperature of the neck part P2 is within the temperature range where the stretching effect is produced. The piece P is moved along the central axis to be stretched and formed, the upper end of the neck P2 that has been stretched and formed is cut off, and then the neck P2 is
A cylindrical mouth piece K made of an appropriate material is immovably fixed to the mouth piece K, and a mouth edge P3', which is the upper edge of the neck part P2, is bent outward to cover the upper end surface of the mouth piece K. A method for forming a stretch-molded bottle body, further comprising stretching and blow-molding the body portion P1.