JPH11179794A - Molding method of plastic bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method for a plastic bottle, in which the bottle is molded by crystallizing its mouth part by rotating a heating means so as to relatively approach to along the outer periphery of the mouth part, which is made to be allow to rotate along a guide at the heating operation with a heating means to the mouth part made of a pre-form (or a parison) for blow- molding a plastic bottle or to the mouth part of the plastic bottle after blow molding, for uniformly heating the whole mouth part. SOLUTION: In the molding method of a plastic bottle, in which the mouth part of the plastic bottle obtained by blow-molding a pre-form 32 is crystallization-treated so as to be strengthened by heating, the mouth part 32c of the pre-form 32 or the mouth part of the bottle after blow-molded is charged between a guide abutting against the inner peripheral surface of the mouth part and a heating body 51 near the outer peripheral surface of the mouth part, the mouth part 32c is rotatingly moved relative to the guide and the heating body 51 and heated so as to crystallize the mouth part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a plastic bottle in which the mouth of a plastic bottle obtained by blow molding a preform is strengthened by crystallization treatment by heating.

[0002]

2. Description of the Related Art Generally, a plastic bottle (commonly referred to as a PET bottle) made of polyethylene terephthalate is formed by a process shown in FIGS. 6 (a) to 6 (g). A pair of opposing neck dies 3 and 3 having a semicircular shape are attached to the neck 2a of the core dies 2 (inner dies) mounted and supported on the support portions 1 of the core dies A by arrows in the drawing (the actual arrow directions are as follows). (In the vertical direction) with a predetermined gap therebetween, and then, the core mold 2 is loaded into the mold part 11a provided in the cavity 11 (outer mold) of the preform molding cavity B as shown in FIG. Then, the core mold 2 and the mold portion 11a
And a space 31 is formed between them.

[0003] Next, in (c), a molten resin (polyethylene terephthalate) is injected from the injection nozzle 11c into the space 31 between the core mold 2 and the mold part 11a of the cavity 11, and the flow path 1 is formed.
After injection through 1b, the mold is cooled and the resin is solidified to form a body 32a, a bottom 32b, a mouth 32c,
A preform 32 having a threaded portion 32d is formed. Subsequently, in (d), the preform 32 (parison) together with the core mold 2 is pulled out from the inside of the mold portion 11a of the cavity 11, and then attached to the support portion 1. The core mold 2 is also pulled out of the preform 32 held by the neck molds 3 and 3.

Next, the preform 32 (parison) held by the neck dies 3 and 3 is loaded into a temperature adjusting pot (not shown), and the preform 32 is heated to a blow molding temperature. As shown in (e), the preform 32 held by the neck dies 3 and 3 is loaded into the bottle molding die 21a provided in the cavity 21 (outer die) of the blow molding cavity C. Then, the blow assist plug 5 attached to the blow device support portion 4 is loaded into the preform 32, and the neck mold 3,
After fixing the support plug 4 and the support 4, blow air is blown from the blow air nozzle 4 a while blowing the assist plug 5 from the blow air nozzle 4 a while pushing the inner bottom of the preform 32 at the tip while extending the assist plug 5 in (f). 32, and the preform 32 is inserted into the bottle mold 21.
a to form a bottle P by inflating the bottle P in close contact with the inner surface of the bottle P.
And finally opening the cavities 21, 21 and the neck molds 3, 3, as shown in (g),
The molding of is completed.

[0005] By the way, conventionally, in the plastic bottle forming process, a heat strengthening treatment for increasing the strength by heating and crystallizing the mouth 32c of the bottle P has been performed. As a method of strengthening by heating, JP-A-57-189824,
No. 258929.

The above method comprises the steps of heating the mouth, inserting a mold pin having an outer diameter slightly smaller than the diameter of the mouth into the heated mouth, and arranging the inside and outside of the mouth with the mold pin and cold air from outside. And whitening (crystallization) by the step of slow cooling.

In addition, for example, Japanese Patent Application Laid-Open No. Sho 62-28472
No. 3 discloses a method in which thermal crystallization is performed while heating the mouth of the preform from the outside, and a heating nozzle is closely fitted into the mouth and the inside of the mouth is also heated from the inside to form a thermal crystallization. In addition, the opening is pushed out from the inside and the mouth is gradually cooled after the heating nozzle is pulled out.

[0008] In addition, Japanese Patent Application Laid-Open No. 62-284724
This heat-crystallizes while heating the mouth of the preform from the outside, and closely inserts a heating nozzle into the mouth to heat the mouth from the inside to promote thermal crystallization. After the opening is pushed out from the inside and the heating nozzle is pulled out, the mouth is gradually cooled while being pressed in the inner radial direction by a jig fitted from the outside.

In addition to the above-mentioned conventional crystallization method for the mouth, for example, as disclosed in Japanese Patent Application Laid-Open No. 55-51525,
There is also a method of heating the mouth while rotating the bottle (bottle) for crystallization.

[0010]

However, the heat treatment of the mouth in the crystallization of the mouth of the plastic bottle as described above is performed using a heating means such as a heater, and the mouth is heated unevenly. When this occurs, the mouth is easily deformed or distorted by the heat, and the crystallization becomes unstable due to the uneven heating of the mouth, resulting in insufficient strength. There are cases.

According to the present invention, when a mouth of a plastic bottle blow molding preform (parison) or a mouth of a plastic bottle after blow molding is heated by a heating means, it can be rotated along a guide. A plastic bottle that forms a bottle by uniformly heating the entire mouth while rotating the heating means relatively close to the mouth along the outer periphery of the mouth to crystallize the mouth and form a bottle. A molding method is provided.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a method for molding a plastic bottle obtained by blow molding a preform and strengthening the mouth of the plastic bottle by crystallization treatment by heating. After loading the mouth of the bottle after molding, between the guide in contact with the inner peripheral surface of the mouth and the heating body close to the outer peripheral surface of the mouth, the mouth is moved with respect to the guide and the heating body. This is a method for molding a plastic bottle, characterized in that crystallization is performed by heating while relatively rotating and moving.

Further, according to the present invention, in the method for molding a plastic bottle according to the present invention, the guide which comes into contact with the inner peripheral surface of the mouth and the outer surface which is close to the outer peripheral surface of the mouth are rotated while moving the mouth of the bottle. This is a method for molding a plastic bottle in which a heating element is fixed in place and heated.

According to the present invention, in the method for molding a plastic bottle according to the present invention, the mouth of the bottle is fixed at a fixed position, and the guide contacting the inner peripheral surface of the bottle and the outer peripheral surface of the mouth are brought into close proximity. This is a method for forming a plastic bottle in which the heating body is rotated and heated to heat.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for molding a plastic bottle according to the present invention will be described in detail below with reference to an embodiment of a molding step shown in FIGS.

FIGS. 1A to 1D show a preform molding step, in which a preform is molded by a core mold part A and a preform molding cavity B. FIG.

As shown in FIG. 1A, a core mold part A (inner mold part) includes a movable core mounting support part 1 (movable block) and a preform molded support mounted on the support part 1. Core mold 2 (inner mold) and neck 2a of core mold 2
The opening and closing type semi-circular opening and closing neck dies 3 and 3 and the threaded portions 3a screwed to the opposing inner surfaces of the neck dies 3 and 3 are provided.

As shown in FIG. 1, the preform molding cavity B (outer die) has cavities 11 and 11 (outer die) which open and close opposing each other, and the cavities 11 and 11 respectively. A preform mold portion 11a formed therein, a supply path 11b for molten resin, and an injection nozzle 11
c.

First, in FIG. 1 (a), a pair of opposed semicircular neck dies 3, 3 are attached to a neck 2a of a core die 2 (inner die) mounted and supported on a support portion 1 of a core die portion A. Are placed close to each other with a predetermined gap as shown by an arrow, and then, as shown in FIG. 1B, the core mold is placed in a mold portion 11a provided in the cavity 11 (outer mold) of the preform molding cavity portion B. 2, and a space portion 31 is formed between the core mold 2 and the mold portion 11a.

Next, in FIG. 1 (c), a molten resin (polyethylene terephthalate) is injected from an injection nozzle 11c into a core mold 2.
After injecting through the flow path 11b into the space 31 between the cavity 11 and the mold 11a of the cavity 11, cold water is sent into the structure of the cavity 11 to cool the cavity 11 and solidify the resin. 32a, bottom 32b, mouth 3
2c, a preform 32 having a threaded portion 32d is formed. Subsequently, the preform 32 (parison) is pulled out from the mold portion 11a of the cavity 11 together with the core mold 2 in FIG.

Then, as shown in FIG. 1 (e), the neck dies 3, 3 on the outer periphery of the opening 32c of the preform 32 pulled out are released and separated, and the preform 32 is
Pull out more.

FIGS. 1 (f) to 1 (g) show a mouth strengthening step for heating and crystallizing the mouth 32c of the molded preform 32 to strengthen the mouth 32c. It is carried out by mounting and heating the mouth 32c.

The mouth heating guide means D includes a support block 41.
A rotary shaft 42 for mounting the preform 32 mounted on and supported by the support block 41; and a guide 44 for guiding the inner periphery of a mouth 32c provided along the periphery of the base of the rotary shaft 42. And

The rotating shaft 42 is shaped like a shaft.
If necessary, a holding body 43 may be provided at the distal end thereof, and may be provided so as to be freely rotatable with respect to the support block 41 or rotatably driven by a motor.
A holding member 43 that stands upright and fixed to the support block 41 and that can freely rotate with respect to the tip of the rotating shaft portion 42 may be provided.

The guide portion 44 may be provided integrally or in contact with the base of the rotating shaft portion 42 as shown in the figure, or may be provided at a predetermined interval. Good.

Outside the guide portion 44, one to two portions or a plurality of portions facing the outer periphery of the rotating shaft portion 42, or in a continuous annular shape, are opposed to the guide portion 44. A heating unit 51 using a hot air heating method or the like is provided.

First, as shown in FIG. 1 (f), the rotating shaft 42 of the mouth heating guide means D is connected to the mouth 3 of the preform 32.
2c, and then, as shown in FIG. 1 (g), the distal end (or the holder 43) of the rotating shaft 42 is attached to the preform 32.
While pressing against the inner surface of the bottom 32b, and fitting the guide 44 tightly or with a predetermined clearance into the mouth 32c of the preform 32.

Next, as shown in FIG. 1 (g), the preform 3 is pressed by pressing a rotatable rotary support 61 from the outside of the bottom 32b of the preform 32 toward the rotary shaft 42.
2 is rotatably held. The rotation support 61 may be simply a shaft tip portion, a plate-shaped portion attached to the shaft tip portion, or a concave shape corresponding to the outer shape of the bottom 32b of the preform 32. Department or the like.

Next, the rotating shaft 42 side or the rotating support 6
The preform 32 is rotated by driving and rotating the first side by a motor, and the opening 32 of the preform 32 is rotated.
c is rotated so that the inner periphery thereof and the guide portion 44 are relatively in sliding contact with each other, and at the same time, the opening 32c is heated by the heating element 51, and then the opening 32c is gradually cooled by air blowing at room temperature or cold temperature. The crystallization is performed by cooling or quenching to enhance the strength of the mouth portion 32c of the preform 32 and the screw portion 32d formed on the outer periphery of the mouth portion 32c.

The heating temperature for crystallization of the mouth 32c by the heating element 51 is 70 ° C. or more and 140 ° C. to 170 ° C., which is the glass transition point of the mouth 32c, and the heating time is 40 seconds to 180 seconds. More than 4 minutes to 10 minutes is appropriate.

Thus, the opening 3 of the preform 32
After crystallizing and strengthening the 2c, as shown in FIG. 6 (e) in the related art, after the neck molds 3 and 3 are fitted and closed to the screw portions 32d on the outer periphery of the mouth 32c of the preform 32, After heating the preform 32 to a blow molding temperature in a temperature adjustment pot (not shown), the cavity 21 (outer die) of the blow molding cavity portion C is heated.
The blow assist plug 5 attached to the blow device support 4 is loaded into the preform 32, and the neck dies 3, 3 and the support 4 are loaded. And fix.

In FIG. 6 (f), while the assist plug 5 is extended, the blow air is blown while pushing the inner bottom of the preform 32 at the tip.
From the assist plug 5 to the preform 32, the preform 32 is expanded so as to be in close contact with the inner surface of the bottle forming mold 21a to form a bottle P, and then the bottle forming mold 21a Is cooled to solidify the bottle P, and finally, as shown in FIG.
The molds 1, 21 and the neck molds 3, 3 are opened to complete the molding of the bottle P.

In the plastic bottle molding method of the present invention, in addition to the above, the mouth of the bottle P after the plastic bottle is molded is heated and strengthened by using the above-described mouth heating guide means D of the present invention. It is possible to process.

FIGS. 2 to 5 show an example of a mouth heating guide means D for strengthening the heating of the mouth used in the plastic bottle molding method of the present invention.

The mouth heating guide means D shown in FIG. 2 is used in a system in which the mouth side of a preform or a bottle is rotated and moved with respect to a heating body 51 fixed at a fixed position to perform a heating enhancement process. In the mouth heating guide means D, a rotation shaft 42 is erected in a fixed state with respect to a support block 41 fixed at a fixed position, and at least around a base of the rotation shaft 42 in a virtual circle in a plan view. A guide portion 44 is provided integrally with the outer edge inscribed continuously (cylindrically) or intermittently at equal intervals, and a free-rotatable holder 43 is provided at the tip of the rotary shaft portion 42.

The preform 32 faces the holding member 43.
The support 61 for pressing and holding the bottom 32b of the bottle P or the bottom of the bottle P after molding is composed of a block 62 mounted and supported on a shaft 64 driven and rotated by a motor.
2 includes a concave portion 63 corresponding to the outer shape of the bottom 32b of the preform 32 or the bottom of the bottle P after molding, and the concave portion 63 includes an air suction hole 62a for suction and fixing;
Air is sucked from the air passage 64a in the shaft portion 64, and sucks and holds the bottom 32b of the preform 32 or the bottom of the bottle P after molding.

By driving and rotating the shaft portion 64 and the block body 62, the mouth portion is uniformly heated by the heating element 51 while rotating the mouth portion by sliding the inner periphery thereof into contact with the guide portion 44. .

In contrast to the method shown in FIG. 2, the support 61 and the preform 32 or the bottle P after molding are fixed in place, and the support block 41, the rotary shaft 42 and the heating element 51 are connected to each other. You may make it drive-rotate around the trunk | drum of the reform 32 or the trunk | drum of the bottle P after shaping | molding.

The mouth heating guide means D shown in FIG.
In the same manner as described above, the preform or the bottle is used for a method in which the mouth side of the preform or the bottle is rotated and moved with respect to the heating body 51 fixed at the fixed position to perform the heating strengthening process. On the other hand, the rotating shaft portion 42 is erected in a fixed state, and the guide portion 44 is integrally attached around the base of the rotating shaft portion 42 in a dome shape (or a spherical shape) in a side view,
The rotating shaft 42 has a free end rotatable holder 43 at its tip.

By driving and rotating the shaft portion 64 and the block body 62, the mouth portion 32c is rotated while the inner periphery thereof is in sliding contact with the dome-shaped (or spherical) guide portion 44.
The heating portion 51 uniformly heats the mouth 32c.

In contrast to the method shown in FIG. 3, the support 61 and the preform 32 or the bottle P after molding are fixed at fixed positions, and the support block 41, the rotating shaft 42 and the heating element 51 are fixed to each other. You may make it drive-rotate around the trunk | drum of the reform 32 or the trunk | drum of the bottle P after shaping | molding.

The mouth heating guide means D shown in FIG. 4 strengthens the heating by rotating the mouth side of the preform or bottle with respect to the heating body 51 fixed at a fixed position as in FIGS. Although it is used for the processing method, a rotation shaft portion 42 is provided rotatably with respect to a support block 41 fixed at a fixed position, and the support block 41 is provided close to the periphery of the base of the rotation shaft portion 42. A pin-shaped (cylindrical) guide portion 44 is attached, and a holding member 43 is integrally attached and fixed to the tip of the rotating shaft portion 42.

By rotating the rotating shaft 42 or the shaft 64 and the block 62, the opening 32c is formed into a pin-shaped guide 44 with its inner periphery as shown in the LL sectional view of FIG. The mouth 32c is uniformly heated by the heating element 51 while being slid and rotated.

In contrast to the method shown in FIG. 4, the support 61 and the preform 32 or the bottle P after molding are fixed in place, and the support block 41, the rotating shaft 42 and the heating element 51 are connected to each other. You may make it drive-rotate around the trunk | drum of the reform 32 or the trunk | drum of the bottle P after shaping | molding.

[0045]

According to the plastic bottle molding method of the present invention, the mouth heating guide means described above is used for the mouth of a plastic bottle blow molding preform (parison) or the mouth of a plastic bottle after blow molding. The entire mouth can be heated uniformly while rotating the heating element relatively along the guide, enabling uniform crystallization of the bottle mouth due to heating, and stabilizing the strength of the mouth. There is an effect that can be implemented.

[Brief description of the drawings]

FIG. 1 is a molding process diagram showing an embodiment of a plastic bottle molding method of the present invention.

FIG. 2 is a side sectional view showing an example of a mouth heating guide means used for crystallization treatment of a bottle mouth in the plastic bottle molding method of the present invention.

FIG. 3 is a side sectional view showing another example of the mouth heating guide means used for the crystallization treatment of the bottle mouth in the plastic bottle molding method of the present invention.

FIG. 4 is a side sectional view showing another example of the mouth heating guide means used for the crystallization process of the bottle mouth in the plastic bottle molding method of the present invention.

FIG. 5 is a partial plan sectional view of a mouth heating guide means used for crystallization of the mouth of the bottle in the plastic bottle molding method of the present invention.

FIG. 6 is a molding process diagram for explaining a general plastic bottle molding method.

[Explanation of symbols]

A: Core mold part B: Preform molding cavity part C: Blow molding cavity part D: Mouth heating guide means 1 ... Support part 2 ... Core mold 3 ... Neck mold 11 ... Preform molding cavity 21 ... Blow molding Cavity 31 ... molding space 32 ... preform 32a ... trunk 32b ... bottom 32c ... mouth 32d ... screw 41 ... support 42 ... rotating shaft 43 ... holder 44 ...
Mouth guide section 51: heating body 61: support

Claims (3)

[Claims] 1. A method for molding a plastic bottle in which a mouth of a plastic bottle obtained by blow molding a preform is strengthened by crystallization treatment by heating, wherein the mouth of the preform or the mouth of a bottle after blow molding is strengthened. To
After being loaded between the guide in contact with the inner peripheral surface of the mouth and the heating body close to the outer peripheral surface of the mouth, heating is performed while rotating the mouth relatively with respect to the guide and the heating body. A method for molding a plastic bottle, characterized in that the plastic bottle is crystallized. 2. While rotating the mouth of the bottle,
2. The method for molding a plastic bottle according to claim 1, wherein the guide in contact with the inner peripheral surface of the mouth portion and the heating body close to the outer peripheral surface of the mouth portion are fixed at a fixed position and heated. ing 3. The bottle is fixed at a fixed position, and the guide is brought into contact with an inner peripheral surface of the bottle and the heating element close to the outer peripheral surface of the bottle is rotated to heat the bottle. 1
A method for molding the plastic bottle according to the above.