JPS5892535A - Plastic bottle - Google Patents

Abstract

PURPOSE:To obtain a plastic bottle of which neck is excellent in heat and shock resistance by such an arrangement wherein the neck part of the plastic bottle made of polyester is composed of internal and external surface layer which are crystallized to higher crystallinity and an intermediate layer which is crystallized to lower crystallinity. CONSTITUTION:In a plastic bottle composed of a bottom part 2, a barrel part 1, a shoulder part 3 and a neck part 4 which is formed by such a method whereby polyester parison is formed by 2-axes blow molding, the neck part 4 is composed of internal and external surface layers 9, 10 of higher crystallinity having a density higher than 1.36g/cc and a intermediate layer 11 of lower crystallinity with a density less than 1.35g/cc. To realize such crystallization, such a means is adopted wherein a temperature gradient is provided between outer and inner surface layers (outer and inner circumference parts) 10, 9 and the intermediate part 11 of the neck part, and it is heat treated and then cooled rapidly. Practically, only the neck part is held by a neck mold and a core mold heated up to 180 deg.C for a period of 30-60sec and then it is cooled rapidly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a biaxially stretched plastic bottle, and more particularly to a 92-axis honed plastic bottle with an excellent combination of heat resistance and impact resistance.

A plastic bottle is obtained by stretching a parison (preform) made of a saturated polyester resin such as polyethylene terephthalate in the axial direction and inflating it with a fluid within the amount of gold. It has excellent transparency, impact resistance, gas barrier properties, and light weight, and has become widely used.

When hot-filling plastic bottles with the contents in order to sterilize the contents and preserve them in good condition, there is a problem in that the bottles shrink and become warped or deformed. Regarding this problem, the dimensional stability at high temperatures can be improved by so-called heat setting in the body of the container, where molecular orientation occurs in biaxial directions; however, in the neck of the bottle, such molecular orientation does not occur. Therefore, the dimensional stabilizing effect of heat setting cannot be expected. However, if the bottle neck lacks heat resistance or dimensional stability at high temperatures, the mold may become deformed during hot overflow filling.
Alternatively, when the bottle cap is hammered, the threaded support ring may be deformed, making it difficult to ensure a secure seal.

As a means of improving the heat resistance of saturated polyester resin molded products, it is already well known that the molded products are heat treated to increase their crystallinity. It has already been proposed in KII that it be applied to the neck of “C”.
I/mru (Special Publication No. 54-68385).

However, when the neck of the bottle is crystallized by heat treatment, although the heat resistance is improved, there is a problem in that the neck becomes a mechanically brittle structure and the impact resistance etc. are significantly reduced.

Therefore, it is an object of the present invention to provide a neck tube made of 9 polyethylene terephthalate with an excellent combination of heat resistance and impact resistance.
We offer a wide range of axially stretched plastic bottles.

Another object of the present invention is to provide a lightweight, impact-resistant plastic bottle suitable for hot filling and forming a reliable seal with the bottle jar.

According to the present invention, there is provided a plastic bottle formed by biaxial stretch-forming of a polyester parison mainly containing ethylene terephthalate units, and comprising a nine-bottom portion, a body portion, a shoulder portion, and a bottom portion, the bottom portion Fi Wisdom is 1.561
Highly crystallized inner and outer surface layers with a density of /ct- or more and a density of 1
．． A plastic bottle is provided, characterized in that the bottle has a low crystallinity intermediate region of less than or equal to 35 f/ct.

The present invention will be explained in detail below based on specific examples shown in the accompanying drawings.

In FIG. 1 showing the overall structure of the plastic bottle of the present invention, the bottle is integrally molded from polyester and has a nine body part 1, a bottom part 2 that extends to the lower end of the body, and a frustum-shaped shoulder that extends to the upper end of the body. part 6 and the mold part 4 connected to the upper end of this shoulder part
It consists of This bottle is formed by biaxially stretch play-molding a parison of polyester mainly composed of ethylene terephthalate units. The molecules are oriented in the direction.

The neck 4 has a screw 6 or a stepped portion 7 for holding a rounded bottle cap (not shown) that is rounded to seal the bottle opening 5, or for holding the bottle tube when the bottle cap is sealed in engagement. A support ring 8 is provided.

In FIG. 2, which shows an enlarged view of the cross section of the bottle neck IB4, the plastic bottle of the present invention has a high crystalline material having a density of 1.36 f/cc or higher, particularly 1.37 F/cc or higher, in the neck 4. The inner and outer surface layers 9 and 1o have a density of 1.35
The remarkable feature is that it has a low crystallization intermediate 1B11 which is less than f/w and less than 1.345 f/cc in bone.

That is, in the present invention, when the above-mentioned highly crystallized inner and outer surface layers 9 and 10 and the low crystallized intermediate portion 11 are provided in the mold part of the bottle, the neck part has a thermally strong structure even during hot filling, and the crown part Alternatively, it is possible to obtain the heat deformation resistance, rigidity, etc. necessary to securely seal and engage the metal inner tube, and also completely eliminate the tendency of the neck to be damaged due to drop impact or tV @ shock when opening the cap. This is based on the knowledge that

Among the lids for bottles, the most reliable in terms of sealability over time are crowns and caps made of metal aO shells, but when using these metal caps, these Reliable sealing cannot be achieved unless the bottle is a dimensionally stable rigid body that engages with the crown cap. According to the present invention, the threaded portion 6 and the step portion 7III of the bottle neck portion 4 that engage with the crown middle cap! an outer periphery 9 provided with and an inner periphery 10t in contact with the actually hot contents.

By being composed of highly crystallized polyester,
Even when the contents are filled hot, thermal deformation of the above-mentioned parts is prevented, the product becomes dimensionally stable, and the rigidity of the outer periphery improves, resulting in a high degree of sealing reliability. Do it like this.

In addition, if the entire polyester constituting the neck 4 of the bottle is highly crystallized, the neck 4 will have a mechanically brittle structure, and the neck will be extremely easily damaged by drop impact or impact from time to time. There is. On the other hand, in the present invention, it does not engage with the crown middle cap,
In addition, since the middle W11t of the neck does not come into contact with the contents and is made of low-crystallization or unset ◆ polyester, the mold part 4 can be easily damaged by drop impact or impact during use without impairing sealing reliability. Tendency to breakage is prevented.

The crystallinity of saturated polyester O such as polyethylene terephthalate can be observed at 70°C. In the present invention, an outer surface layer (outer periphery) 9 and an inner surface layer (inner periphery)
It is important for the density of 10 to be 1.36 f / cc or more in terms of dimensional stability and sealing reliability of the neck, and if it is lower than this, dimensional stability and rigidity during hot filling will be lacking. As a result, the shelf life of the contents tends to decrease. In addition, the intermediate part 11 O'mFlk 1.35 f/
cc or less is important from the point of view of impact resistance, and if it is larger than this, the tendency of the neck to be damaged by impact cannot be ignored.

In the present invention, in order to give the plastic bottle OX part the crystallization characteristics described above, a temperature gradient is created between the outer surface layer (outer periphery) and inner surface layer (inner periphery) of the mold part and the intermediate part. A method is adopted in which the heat treatment is carried out, followed by rapid cooling.

A polyester two-wheel stretch-molded bottle is manufactured by mechanically stretching the polyester in the axial direction at the stretching temperature of the polyester parison, and expanding and stretching the polyester in the circumferential direction by blowing fluid in a cage. After molding the parison or at any stage after molding the polyester, heat treatment is carried out under the conditions described above.In other words, polyester crystallization occurs at temperatures ranging from just below its melting point to 100°C lower than its melting point. Specifically, crystallization progresses significantly in the temperature range of 140 to 230°C.In the present invention, the crystallization temperature of the outer circumference of the neck and the inner circumference of the tube is 10 to 60°C, particularly at a temperature of 160 to 200°C. Hold for a few seconds to allow crystallization.

The heat treatment is advantageously carried out by clamping the inner and outer periphery of the tube with a heat source.

The parison may be a bottomed parison manufactured by injection molding of polyester, or a pipe obtained by extrusion molding of polyester, cut to a specified size, one end closed by compression molding, and a nine-bottomed parison. . 1. The polyester parison is preheated to the stretching temperature prior to stretch blowing. This stretching temperature is a temperature lower than the crystallization temperature of the polyester used and at which the polyester parison can be stretched, and specifically, a temperature of 80 to 150°C, particularly 90 to 110°C is used. .

The preheated stretch blow molding of the parison tube may be carried out by means known per se, such as sequential stretch blow molding or simultaneous stretch blow molding. The container is abrasively stretched in the axial direction while being blown (pre-produced), and then stretched by expanding the container in the circumferential direction while being blown with fluid at a relatively high pressure. (9) In the latter case, stretching in the circumferential direction and stretching in the axial direction are performed simultaneously from the beginning by blowing fluid at a higher pressure. To stretch the parison in the axial direction, for example, the neck of the parison can be made into a metal part! This can be easily done by holding the paper between the handles, applying a stretching rod T- to the self-portion at the bottom of the parinon, and stretching the stretching rod.

The stretching ratios of the parison in the axial direction and the horse direction are each 1.5.
~2.5 times (axial direction) and 1.7~! It is desirable to set it to 4.0 times (circumferential direction).

The IjlIO plastic bottle of the present invention is particularly useful for hot filling and long-term storage of juices, mineral water, sauces, ketchup, various sauces, lactic acid bacteria drinks, and the like.

Example Polyethylene terephthalate with a density of 1.34 and an intrinsic viscosity of 0.75 is injection molded to have a height of 162+w and a body diameter of 2611.
M1% trunk average wall thickness 4wx% violet wall thickness 111I preform metal molding, no heat treatment is applied to the mold part Only the neck of the A1 V form is heated to t-180°C to create a nine-neck mold and core. After being held in the mold for 10 seconds, 60 seconds, and 1 minute, preforms B, C, and D were obtained by cooling.

In addition, a preform E of the same shape was heated and crystallized in a mold with only the neck heated to 180° C. during the injection molding process.

These A, B%C%D, and E preforms were heated to an appropriate stretching temperature and then stretch-play molded to an inner volume of 1000cc.
photokABcDE1 was obtained. The densities of the neck surface of this bottle ABCDE are 1.34.1 and 35.1, respectively.
57.1.69.1.40, and bottles A and B
The neck was transparent. Bottle C5DC) The neck part was crystallized on the inner and outer surfaces, but the middle part of the neck wall was not crystallized, but the neck part of bottle E was completely crystallized on both the surface and middle part, making it heat resistant as a bottle of 90 ABCDE. We evaluated the impact resistance and obtained the following results.

1) Heat Resistance Each bottle was filled up to the neck with hot water at 85°C and left to stand for 30 minutes, after which the amount of shrinkage in the radial direction of the metric screw portion was measured.

Table 1 JRl bottles with C, D%E showed good thermodynamic properties.

2) A shock-resistant bottle was filled with 110 water, coated with a metal medium, and then stored overnight at 5°C. Nine bottles were dropped to investigate the sound of breakage.

Falling conditions Falling height 1.8 Coastal falling direction
Inverted temperature: 5℃ If the neck part is completely crystallized like E, it will break.9.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially sectional front view showing the overall structure of the plastic bottle of the present invention, and FIG. 2 is an enlarged sectional view of the neck of the bottle shown in FIG. 1. Side light number 1 is the body, 2 is the bottom, 6 is the shoulder, 4 is III,
6 is a threaded portion, 7 is a step portion, 9 and 10 are highly crystallized inner and outer surface portions, and 11 is a low crystallized intermediate portion. Figure 1 Figure 2rlJ

Claims (1)

[Claims] A plastic bottle consisting of a bottom, a body, a shoulder, and a neck formed by biaxially stretching polyester parison mainly composed of ethylene tele 7 turret F units, the neck having a density of 1.36f. 1. A plastic bottle characterized by having highly crystalline inner and outer surface layers having a density of 1.35 t/cc or more and a low crystallization middle part having a density of 1.35 t/cc or less.