JPH06285961A - Preform for molding plastic bottle and molding method of bottle using the same - Google Patents

Abstract

PURPOSE:To prevent occurrence of buildup, burr or shrinkage mark in a part from under a neck ring over to a shoulder part in a plastic bottle after a preform is heated an blow-molded, by improving the shape of this preform. CONSTITUTION:A preform 1 of which a part 3 of a prescribed length under a neck ring of the part from under the neck ring to a shoulder part to be formed when the preform is molded as a plastic bottle is made a recessed curved surface is formed, and this preform 1 is softened by heating, blow-molded in a mold to be stretched, and formed into a bottle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preform for molding a plastic bottle and a bottle molding method using the same, and more particularly to a preform and a method for blow molding the preform to mold a plastic bottle.

[0002]

2. Description of the Related Art Conventionally, it is well known that, for example, a plastic bottle or the like is molded from polyethylene terephthalate resin or RAN resin by blow molding. Briefly explaining this blow molding, a resin material is heat-melted by an extruder to form a preform in a mold. Next, this preform is heated and softened by a heater, and air is blown into the preform in the blow molding die to stretch it to, for example, a double length to form a bottle, which is taken out from the blow molding die. .

[0003]

However, in particular,
When molding a plastic bottle from RAN resin by blow molding, it is known that when the preform is heated and softened for biaxial stretch blow molding, it contracts in the axial direction and expands in the radial direction. Therefore, when the blow mold (split mold) is closed, the bulging part under the neck ring contacts or is pinched by this mold to cool the preform, and as a result, the neck ring is molded as a plastic bottle. There was a problem in that a lump of meat was generated in a range of about 20 mm below, or when it was caught in a mold during blow molding, burrs and wrinkles were formed.

The object of the present invention is to solve the above-mentioned conventional problems, and to improve the shape of the preform to form a lump or a burr that occurs from under the neck ring to the shoulder after blow molding. The object of the present invention is to provide a plastic bottle molding method that prevents wrinkles.

[0005]

In order to solve such conventional problems, the present invention provides the following preform to mold a plastic bottle.

[0006] That is, the preform of the present invention is a bottomed tubular preform having a mouth tube portion opened at the upper end, a neck ring projecting around the lower portion thereof, and the lower end closed, and molded as a plastic bottle. The preform is characterized in that a portion of a predetermined length under the neck ring from a portion below the neck ring to a shoulder when formed is formed into a concave curved surface.

The plastic bottle molding method of the present invention comprises:
When formed on a plastic bottle, a preform is formed by forming a concave curved surface at a predetermined length under the neck ring, which is the part from the bottom of the neck ring to the shoulder, and heats this preform to soften it. It is blow-molded in a mold and stretched to form a bottle.

At this time, the concave curved surface under the neck ring in the preform has a radius of about 120 mm to 150 m.
It is formed by an arc of m, and it is particularly preferable that the concave curved surface is an arc having a radius of about 120 mm.

Further, in the plastic bottle molding method of the present invention, the wall thickness of the concave curved surface portion under the neck ring of the preform is made thinner and the clearance between this portion and the blow molding die is increased, and the concave curved surface portion is further formed. It is more preferable to lower the heating temperature to the part to heat and soften the preform.

In short, when the preform is heated, the expansion in the radial direction is suppressed as much as possible, and the predetermined length portion under the neck ring is prevented from coming into contact with the blow molding die. When molded into a bottle, it is possible to prevent the formation of meat folds and wrinkles from under the neck ring of the bottle to the shoulder.

[0011]

According to the plastic bottle molding method of the present invention, the resin material is heat-melted by the extruder to form the preform in the mold. At this time, the lower part of the neck ring of this preform is formed into a concave curved surface. This curved surface preferably has a radius of about 120 mm to 150 mm. As a result, it is possible to suppress the deformation under the neck ring after the preform is heated during blow molding, and it is not possible to cool the blow mold by contacting it, so that the buildup of meat is eliminated.

When the preform after heating is placed in the blow molding die, the bottom of the neck ring of the preform is not in contact with the blow molding die because the preform is sandwiched between the split blow dies. Therefore, burrs and wrinkles are not generated, and a plastic bottle having a smooth surface can be molded.

[0013]

EXAMPLES The plastic bottle molding preform of the present invention and the bottle molding method using the same will now be described in more detail with reference to Examples.

FIG. 1 shows a preform 1 formed by a plastic bottle molding method according to an embodiment of the present invention.
It is shown. The preform 1 is a bottomed tubular preform having a mouth tube portion 20 having an opening at the upper end, a neck ring 2 protrudingly provided around the lower portion thereof, and having a lower end closed.

In this preform 1, an outer surface of a predetermined length portion under the neck ring 2 is formed with a concave curved surface 3. The predetermined length portion below the neck ring 2 in the preform 1 is a portion from below the neck ring to the shoulder portion of the bottle when the preform 1 is subsequently molded into a plastic bottle.

In particular, the reason why the predetermined length portion under the neck ring is formed into the concave curved surface 3 is the most flesh in the portion extending from the neck ring bottom to the shoulder portion of the bottle when the preform is molded into a plastic bottle by blow molding. This is because there are many occurrences of balls, wrinkles, and burrs.

The preform 1 as described above is formed by molding a material by heat melting the material in an extruder according to a conventional method. At this time, the mold for preform molding is configured to form a concave curved surface 3 in a predetermined length portion below the neck ring 2 of the preform 1 when molded with this.

The preform 1 in which the lower portion of the neck ring 2 is formed with the concave curved surface 3 in this way is heated and softened by a heater. At that time, the preform 1 contracts in the axial direction and expands in the radial direction (in FIG. 1, the shape 4 in the heat-softened state is shown by a chain double-dashed line). Then, the heat-softened preform 1 is transferred into a blow molding die, and then air is blown into the preform to stretch it.
As a result, a plastic bottle having a predetermined shape is formed.

When a plastic bottle is molded by blow molding from the preform 1 having the above-mentioned shape, since the predetermined length portion below the neck ring 2 is formed into the concave curved surface 3, the blow molding die is used. When closing, the predetermined length under the neck ring does not come into contact with or get caught in the blow molding die, whereby the predetermined length under the neck ring of the preform 1 is cooled and molded into a plastic bottle. There is no possibility that flesh will be generated when struck, or burrs or wrinkles will be generated by being sandwiched between molds.

Further, in the plastic bottle molding method of the present invention, not only the predetermined length portion below the neck ring 2 of the preform 1 is made into the concave curved surface 3, but also the clearance with the blow molding die is increased, If the wall thickness of the concave curved surface portion 4 is made particularly thin, or if the heater temperature is slightly lowered only for this portion at the time of heating, these act synergistically to further suppress the radial expansion.

This makes it possible to avoid the contact of the predetermined length portion of the preform 1 below the neck ring with the blow molding die during blow molding. As a result, meat accumulates in the part from the neck ring under the plastic bottle blow molded from this preform to the shoulder.
It is possible to more effectively prevent the occurrence of burrs, wrinkles, and the like.

Example 1 With a conventional plastic bottle, 20 m below the neck ring
Up to about m, that is, there was a lump of meat on the neck of the bottle. Therefore, as shown in FIG. 2, the outer surface of the preform having a predetermined length below the neck ring from the neck ring to the shoulder portion of the plastic bottle has a radius of 1
A preform 11 formed into a concave curved surface of 50 mm having a small outer diameter and a substantially thin piece thickness at this portion 10 is formed.
The lower predetermined length portion 10 was prevented from bulging outward.

When this preform 11 is heated,
As shown in FIG. 3, the deformation of the lower predetermined length portion 10 of the neck ring after heating is shown by a solid line in comparison with the shape line 13 before improvement shown by a chain double-dashed line (a concave curved surface with a radius of 150 mm and The shape is slightly improved as can be seen from the shape line 14 of FIG. However, with this degree of improvement, the occurrence of flesh accumulation from the bottom of the neck ring to the shoulder after bottle formation was slightly improved, and the presence of flesh accumulation was still recognized. Further, there is a tendency that a predetermined length portion under the neck ring comes into contact with the blow mold at the time of mold clamping, and it is not completely solved.

Example 2 As described above, the cause of the buildup of meat is that the preform 1 is sandwiched or brought into contact with the blow mold during mold clamping due to the expansion of the preform 1 after heating, and the preform is It is cooled and does not stretch during blow molding. Therefore, in Example 2, the outer diameter of the neck ring of the preform 1 was made smaller by 0.7 mm, and conversely, the outer diameter of this portion in the bottle mold was made thicker by 0.9 mm, which is a total compared with the conventional one. With a large 1.6 mm clearance,
A predetermined length portion under the neck ring was formed into a concave curved surface with a radius of 120 mm, and the synergistic action of these conditions was used to further suppress the radial expansion after heating the preform. At the same time, the wall thickness of the preform underneath the neck ring was made as thin as possible, and the preset temperature of the heater was also lowered to suppress expansion of the preform.

As a result, the contact of the preform during the mold clamping of the blow molding die was eliminated, and as a result, the accumulation of meat from under the neck ring of the bottle to the shoulder was eliminated. However, on the other hand, the thickness of the neck ring was reduced from the bottom of the neck ring to the shoulder while the buckling strength was slightly reduced. Therefore, as a countermeasure against the above-mentioned flesh accumulation, it is necessary to make the preform body thicker on average by the weight corresponding to the thickness of the lower neck ring for adjustment.

[0026]

As described above, according to the plastic bottle molding preform of the present invention and the bottle molding method using the same, the outer surface of the predetermined length portion under the neck ring has a concave curved surface. By forming a reform, softening it by heating, and blow molding with a blow molding die to mold a plastic bottle, it is possible to suppress radial expansion at a predetermined length under the neck ring during preform heating. It is possible to prevent the contact of this part with the blow molding die.

As a result, when the preform is blow-molded into a plastic bottle, it is possible to prevent the accumulation of flesh, burrs or wrinkles in the portion from the bottom of the neck ring to the shoulder of the bottle. A high plastic bottle can be provided. In addition, conditions such as increasing the clearance between the blow molding die and the predetermined length under the neck ring of the preform, further reducing the wall thickness of this portion, and lowering the heating temperature to this portion should be added. Thus, radial expansion during heating of the preform can be further suppressed, and therefore, it is possible to more effectively prevent the accumulation of flesh or wrinkles from under the neck ring to the shoulder during molding of the bottle.

[Brief description of drawings]

FIG. 1 is a front view showing a preform used in a plastic bottle molding method of the present invention.

FIG. 2 is a partial cross-sectional view showing the shape of the preform in Example 1 according to the plastic bottle molding method of the present invention.

3 is a partial front view showing a degree of expansion in a predetermined length portion under a neck ring after heating the preform shown in FIG. 2. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preform 2 Neck ring 3 Concave curved surface part under neck ring 4 Shape line after preform heating 10 Preform concave curved surface part of one example 11 Preform 12 Neck ring 13 Conventional neck ring lower shape line 14 This example Neck ring bottom shape line

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[Procedure amendment]

[Submission date] April 20, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

Conventionally, for example, it is well known that plastic bottles are molded by blow molding of polyethylene terephthalate resin and P AN resin. Briefly explaining this blow molding, a resin material is heat-melted by an extruder to form a preform in a mold. Next, this preform is heated and softened by a heater, and air is blown into the preform in the blow molding die to stretch it to, for example, a double length to form a bottle, which is taken out from the blow molding die. .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

[0003]

However, in particular,
When molding a plastic bottle from a PAN resin by blow molding, it is known that when the preform is heated and softened for biaxial stretch blow molding, it contracts in the axial direction and expands in the radial direction. Therefore, when the blow mold (split mold) is closed, the bulging part under the neck ring contacts or is pinched by this mold to cool the preform, and as a result, the neck ring is molded as a plastic bottle. There was a problem in that a lump of meat was generated in a range of about 20 mm below, or when it was caught in a mold during blow molding, burrs and wrinkles were formed.

Claims (5)

[Claims] 1. A bottomed tubular preform having a mouth tube portion having an opening at the upper end, a neck ring projecting around the lower portion thereof, and a lower end closed, from the bottom of the neck ring when molded as a plastic bottle. A preform characterized in that a predetermined length portion below the neck ring of a portion which becomes a shoulder portion is formed into a concave curved surface. 2. The concave curved surface under the neck ring of the preform has a radius of about 120 mm to 150 m.
2. It is formed by an arc of m.
Preform described in. 3. A preform having a concave curved surface at a predetermined length below the neck ring from the bottom of the neck ring to a shoulder when molded as a plastic bottle is formed, and the preform is heated and softened. A plastic bottle molding method, which comprises blow molding and stretching in a mold to mold into a bottle. 4. The concave curved surface under the neck ring of the preform has a radius of about 120 mm to 150 m.
4. It is formed by an arc of m.
The method for molding a plastic bottle according to. 5. A heater for increasing the clearance between a portion formed by the concave curved surface and the blow molding die under the neck ring in the preform and thinning the thickness of this portion, and further heating this portion. The plastic bottle molding method according to claim 4, wherein the preform is heated to soften the preform and softened to form a bottle.