JPH11348100A - Preform molding method for plastic bottle molding and plastic bottle molding method - Google Patents

Abstract

(57) [Summary] [Problem] To blow a preform after a stretching process by increasing the overall stretching ratio of the preform while suppressing the stretching ratio in the longitudinal direction (depth direction) of the preform as much as possible. The amount of heat shrinkage (shrinkage) in the longitudinal direction during molding is reduced as much as possible, and a heat-resistant bottle is molded by stable blow molding. A screw shaft (42), which is screwed to a support block (41) in a preform (32), is driven and rotated, and is capable of extending and shortening operation, is inserted into the preform (32). The preform is twisted by rotating the screw shaft while pinching the preform bottom by the rotatable rotary support 51 pressed against the tip of the spindle 42 from the outside of the preform bottom from the outside of the preform. And stretch molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for stretching a preform for blow molding a plastic bottle and a method for molding a plastic bottle using the stretched preform.

[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. 5 (a) to 5 (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.

By the way, conventionally, in the blow molding of the plastic bottle, a preform 32
The preform 32 is stretched by a predetermined length in the vertical direction (depth direction) while heating, and the body of the preform 32 is crystallized to enhance heat resistance. Thereafter, the stretched preform 32 is removed. It is blow-molded and subjected to a heat strengthening treatment for increasing the heat resistance of the body of the plastic bottle.

In the above-mentioned conventional heating and stretching treatment method, the preform 32 is stretched in the longitudinal direction over a predetermined length while being heated. Therefore, it is necessary to stretch the preform 32 in the longitudinal direction by the stretched length. The stretching process required a stretching stroke length for the stretching length.

[0007] Therefore, in order to increase the draw ratio in the heat drawing process as required, it is necessary to make the drawing stroke length longer, which results in an increase in the size of the drawing apparatus or in the drawing process. 2
It was time-consuming and costly to perform the stretching process at different times.

Further, the preform after the stretching treatment in which the stretching ratio in the longitudinal direction of the preform is made higher, the amount of heat shrinkage (shrinkage) in the longitudinal direction at the time of blow molding becomes larger corresponding to the stretching ratio. Therefore, quality control at the time of bottle molding becomes difficult and does not have a good influence on molding quality.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a preform for molding a plastic bottle, which suppresses the stretching ratio in the longitudinal direction (depth direction) of the preform as much as possible while reducing the overall stretching ratio of the preform. By increasing the height, the amount of heat shrinkage (shrinkage) in the vertical direction during blow molding of the preform after the stretching treatment is reduced as much as possible, so that a heat-resistant bottle can be molded by stable blow molding. is there.

[0010]

Means for Solving the Problems A first invention of the present invention is:
The preform is injection-molded with a preform molding die having a preform opening molding die portion and a preform body molding die portion, and then screwed into a support block in the preform. Inserting a screw shaft that can be extended and shortened while driving and rotating, and with the preform opening fixed, a rotation pressed against the shaft end from the tip of the screw shaft and the outside of the bottom of the preform. A preform stretching method for molding a plastic bottle, characterized in that the preform is stretched while being rotated while rotating a screw shaft while holding the preform bottom portion between the preform and a preform and twisting and stretching the preform.

Next, a second invention is characterized in that the preform obtained by the plastic bottle molding preform stretching method of the first invention is loaded into a blow molding cavity and blow-molded. This is a plastic bottle molding method.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a preform stretching method for forming a plastic bottle according to the first invention.
(A) to (e), a preform molding step, and FIG.
This will be described in detail below according to the preform stretching steps shown in (f) to (h).

FIGS. 1A to 1E 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 mounted on the support part 1 and supported. 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, 11 (outer die) which open and close opposing each other, and the cavities 11, 11 A preform mold portion 11a formed therein, a supply path 11b for molten resin, and an injection nozzle 11
c.

First, in FIG. 1A, a neck 2a of a core mold 2 (inner mold) mounted and supported on a support portion 1 of a core mold portion A has a pair of opposed semicircular neck molds 3,3. As shown by an arrow with a predetermined gap.

Subsequently, as shown in FIG. 1B, the core mold 2 is loaded into a mold portion 11a provided in the cavity 11 (outer mold) of the cavity portion B for preform molding.
A space portion 31 is formed between the mold and the mold portion 11a.

Next, in FIG. 1 (c), molten resin (polyethylene terephthalate) is injected from the injection nozzle 11c into the 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 screw portion 32d is molded.

Subsequently, in FIG. 1D, the preform 32 (parison) together with the core mold 2 is pulled out from the mold portion 11a of the cavity 11.

Then, as shown in FIG. 1E, the core mold 2 is pulled out from the preform 32 pulled out.

FIGS. 1 (f) to 1 (h) show a preform stretching step in which the formed preform 32 is subjected to a heat stretching treatment to strengthen the crystal.
2 is mounted on a stretching means D to perform a stretching process.

As shown in FIG. 1 (f), the stretching means D includes a support block 41, and a screw shaft 42 for mounting the preform 32 screwed to and supported by the support block 41. The tip of the shaft 42 is provided with a contact portion 43 (tip) having a shape corresponding to the shape of the inner bottom surface of the preform 32 as necessary.

The screw shaft 42 is shown in FIG.
As shown in FIG. 3 (f) and FIG. 3, a male screw portion 42a is screwed into the shaft 42, and is screwed to a female screw portion 41a which is screwed in the support block 41 in the vertical direction. By rotating in the reverse direction, it is possible to protrude and retreat with respect to the support block 41 and to retreat.

As shown in FIG. 3, the shaft 42 is rotated by a driving rotator 45 rotatably supported by a support block 41 via a bearing 45a such as a metal bearing or a bearing.

The shaft 42 is spline-fitted to the driving rotator 45, and is inserted through a fitting hole 45b for tightly fitting the shaft 42 formed in the driving rotator 45. A groove-shaped guide portion 42b formed linearly in the shaft 42 along the longitudinal direction thereof and a convex guide portion 45c of a fitting hole 45b formed in the drive rotating body 45 are fitted to each other. The shaft 42 and the driving rotator 45 rotate integrally with each other, and
Numeral 2 slides in the shaft (longitudinal) direction with respect to the driving rotary body 45 so that it can move forward and backward.

The driving rotator 45 is rotatable via an electric motor and a transmission gear (not shown), and the screw shaft 42 is integrally driven and rotated by the forward or reverse rotation of the driving rotator 45 and supported. It moves forward and backward with respect to the block 41.

First, as shown in FIG.
Of the screw shaft 42 by another heating
Mouth part 3 of preform 32 heated to about 121 ° C. to 121 ° C.
Load from 2c.

Then, as shown in FIG. 1 (g), the tip 43 of the screw shaft 42 of the stretching means D abuts against the inner bottom surface of the bottom 32b of the preform 32, and the outer bottom surface of the bottom 32b of the preform 32. Abuts the support body 51,
The bottom 32b of the preform 32 is held, and a pair of opposed neck dies 3, 3 that open and close in the left and right directions are brought into contact with and fixed to the lower surface of the support block 41.

As shown in FIGS. 1 (g) and 3, the support 51 corresponds to the block 52 and the bottom 32b of the preform 32 or the bottom of the bottle P after molding. The block body 52 is provided at the tip of a vertical rotation support shaft 54 which can be freely rotated or driven and rotated at the same rotation speed as the rotation of the screw shaft 42 by an electric motor. Installed.

As shown in FIG. 4, the support 51 is provided with a body 32 of the preform 32 above the block 52.
The block body 52 is integrally provided with a cylindrical (or cup-shaped) holder portion 55 capable of inserting and holding a, and an air suction hole 52a for suction fixing is provided below the concave portion 53 of the block body 52 as necessary. The air is sucked from the air passage 64a in the support shaft portion 54, and the preform 32 can be suction-held at the bottom portion 32b.

The vertical rotation support shaft 54 for mounting and supporting the support body 51 can move up and down in the vertical direction, and at the same speed corresponding to the lowering speed of the tip of the screw shaft 42 due to the rotation of the screw shaft 42. Drive down operation (drive by electric motor) or follow down operation (spring,
A follow-up operation can be performed by a vertically upward elastic urging force of a spring or the like.

Then, the driving rotator 45 on the side of the support block 41 is driven to rotate, and as shown in FIG. 1 (h), the screw shaft 42, the block body 52 facing the screw shaft, and the pinching and fixing between the shaft 42 and the block body 52. The lower part 32b of the preform 32 is vertically moved while rotating, so that the preform 3
The stretching process is performed while twisting 2 in the rotation direction.

The heating operation in the twist stretching process is as follows.
63 ° C. to 121 ° C. or glass transition temperature or higher, for example, 70 ° C. or higher and 140 ° C. to 170 ° C. or lower,
The stretching time is, for example, preferably from 40 seconds to 180 seconds or more and from 4 minutes to 10 minutes.

After the preform 32 is twisted and stretched for crystal strengthening in this manner, the pair of opposing neck portions 3, 3 are separated from the lower surface of the support block 41 as shown in FIG. At the same time, the preform 32 that has been subjected to the twist-stretching process shown in FIG. 1H is detached from the shaft 42 after the support body 51 is moved down and removed from the stretching means D. When performing the twist stretching process, a blow molding die may be arranged from the lower side of the preform 32, and primary molding may be performed while blowing air from the mouth of the preform 32.

FIG. 2 shows another embodiment of the preform stretching method for plastic bottle molding of the first invention.
(A) to (e) shown in FIG.
This will be described in detail below according to the preform stretching steps shown in (f) to (h).

2 (a) to 2 (e) 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. 2A, 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.

Further, as shown in the figure, the preform molding cavity B (outer mold portion) has cavities 11 and 11 (outer mold) which open and close to face 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. 2 (a), a pair of opposed semicircular neck dies 3, 3 is 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. As shown by an arrow with a predetermined gap.

Subsequently, as shown in FIG. 2B, the core mold 2 is loaded into a mold part 11a provided in the cavity 11 (outer mold) of the preform molding cavity part B.
A space portion 31 is formed between the mold and the mold portion 11a.

Next, in FIG. 2C, the molten resin (polyethylene terephthalate) was injected from the injection nozzle 11c into the 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 screw portion 32d is molded.

Subsequently, in FIG. 2D, the preform 32 (parison) together with the core mold 2 is pulled out from the mold portion 11a of the cavity 11.

Then, as shown in FIG. 2 (e), the neck dies 3, 3 on the outer periphery of the opening 32 c of the preform 32, which have been pulled out, are released and separated, and the preform 32 is pulled out from the core die 2.

FIGS. 2F to 2H show a preform stretching step in which the formed preform 32 is subjected to a heat stretching treatment to strengthen the crystal.
2 is mounted on a stretching means D to perform a stretching process.

As shown in FIG. 2 (f), the stretching means D includes a support block 41, and a screw shaft 42 for mounting the preform 32 which is screwed and supported on the support block 41. The tip of the shaft 42 is provided with a contact portion 43 having a shape corresponding to the shape of the inner bottom surface of the preform 32 as necessary.

The screw shaft 42 is shown in FIG.
As shown in FIG. 3 (f) and FIG. 3, a male screw portion 42a is screwed into the shaft 42, and is screwed to a female screw portion 41a which is screwed in the support block 41 in the vertical direction. By rotating in the reverse direction, it is possible to protrude and retreat with respect to the support block 41 and to retreat.

As shown in FIG. 3, the shaft 42 is rotated by a driving rotator 45 rotatably supported by a support block 41 via a bearing 45a such as a metal bearing or a bearing.

The shaft 42 is spline-fitted to the driving rotator 45, and is inserted through a fitting hole 45b for tightly fitting the shaft 42 provided in the driving rotator 45. A groove-shaped guide portion 42b formed linearly in the shaft 42 along the longitudinal direction thereof and a convex guide portion 45c of a fitting hole 45b formed in the drive rotating body 45 are fitted to each other. The shaft 42 and the driving rotator 45 rotate integrally with each other, and
Numeral 2 slides in the shaft (longitudinal) direction with respect to the driving rotary body 45 so that it can move forward and backward.

The driving rotator 45 can be driven and rotated via an electric motor and a transmission gear (not shown), and the screw shaft 42 is integrally driven and rotated by the forward or reverse rotation of the driving rotator 45 and supported. It moves forward and backward with respect to the block 41.

First, as shown in FIG.
Of the screw shaft 42 by another heating
Mouth part 3 of preform 32 heated to about 121 ° C. to 121 ° C.
Load from 2c.

Then, as shown in FIG. 2 (g), the tip 43 of the screw shaft 42 of the stretching means D abuts against the inner bottom surface of the bottom 32b of the preform 32, and the outer bottom surface of the bottom 32b of the preform 32. Abuts the support body 51,
Holding the bottom 32b of the preform 32 and closing the pair of mouth fixing parts 46, 46 provided on the lower side of the support block 41 and opening and closing left and right by opening and closing the mouth 3 of the preform 32.
2c is fixed and held.

As shown in FIGS. 2 (g) and 3, the support 51 corresponds to the block 52 and the bottom 32b of the preform 32 or the external shape of the bottom of the bottle P after molding. The block body 52 is provided at the tip of a vertical rotation support shaft 54 which can be freely rotated or driven and rotated at the same rotation speed as the rotation of the screw shaft 42 by an electric motor. Installed.

As shown in FIG. 4, the support 51 is provided on the upper side of the block body 52 with the body 32 of the preform 32.
The block body 52 is integrally provided with a cylindrical (or cup-shaped) holder portion 55 capable of inserting and holding a, and an air suction hole 52a for suction fixing is provided below the concave portion 53 of the block body 52 as necessary. The air is sucked from the air passage 64a in the support shaft portion 54, and the preform 32 inserted in the holder portion 55 can be suction-held at the bottom portion 32b.

The vertical rotation support shaft 54 for mounting and supporting the support body 51 can move up and down in the vertical direction, and at the same speed corresponding to the lowering speed of the tip of the screw shaft 42 due to the rotation of the screw shaft 42. Drive down operation (drive by electric motor) or follow down operation (spring,
A follow-up operation can be performed by a vertically upward elastic urging force of a spring or the like.

Then, the drive rotating body 45 on the support block 41 side is driven to rotate, and as shown in FIG. 2 (h), the screw shaft 42, the block body 52 facing the screw shaft 42, and the pinching and fixing between the shaft 42 and the block body 52. The lower part 32b of the preform 32 is vertically moved while rotating, so that the preform 3
The stretching process is performed while twisting 2 in the rotation direction.

The heating operation in the twist stretching process is as follows.
63 ° C. to 121 ° C. or glass transition temperature or higher, for example, 70 ° C. or higher and 140 ° C. to 170 ° C. or lower,
The stretching time is, for example, preferably from 40 seconds to 180 seconds or more and from 4 minutes to 10 minutes.

After the preform 32 has been twisted and stretched for crystal strengthening in this manner, the mouth fixing portions 46, 46
2F is opened as shown in FIG. 2F, and the preform 32 that has been subjected to the twist-stretching process shown in FIG.
After the lowering member 1 is moved down, it is detached from the shaft 42 and detached from the stretching means D.

The plastic bottle forming method of the second invention is the same as the conventional one shown in FIGS. 5 (e) to 5 (g) in which the preform 32 subjected to the twisting and stretching treatment is loaded into a blow molding die. The plastic bottle is molded by the following blow molding method.

The above-mentioned preform 3 subjected to twist stretching
2, the screw portion 32d is fitted and held in the neck molds 3 and 3, and then the preform 32 (parison) is loaded into a temperature adjustment pot (not shown) and the preform 32 is heated to the blow molding temperature. I do.

Subsequently, as shown in FIG. 5 (e), the preform 32 subjected to the torsion stretching process while being held by the neck molds 3, 3 is placed in the cavity 21 (outside) of the blow molding cavity C. Mold part 21 provided in the mold)
a, and then the blow assist plug 5 attached to the blow device support 4 is inserted into the preform 32.
Then, the neck dies 3 and 3 and the support portion 4 are fixed.

Subsequently, as shown in FIG. 5 (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 thereof.
From the assist plug 5 and the preform 32, and the preform 32 is inflated by blow air so as to be in close contact with the inner surface of the bottle forming mold portion 21a.
Then, the bottle forming mold part 21a is cooled to solidify the bottle P.

Finally, as shown in FIG. 5 (g), the cavities 21, 21 and the neck dies 3, 3 are opened to complete the molding of the plastic bottle P.

In the plastic bottle molding method according to the second aspect of the present invention, in addition to the above, the mouth of the bottle P after molding of the plastic bottle is provided with a mouth 32c using a mouth heating means (not shown). Can be heat-strengthened.

[0064]

The preform stretching method for plastic bottle molding and the plastic bottle molding method of the present invention are as follows.
Since the preform (parison) for plastic bottle blow molding is twisted and stretched, the stretch ratio of the preform can be increased as compared with the conventional method of stretching only in the longitudinal direction (longitudinal direction). In addition, the length of stretching in the longitudinal direction can be reduced while maintaining the conventional stretching ratio. In addition, the stretching ratio in the heating stretching process can be increased without increasing the length of the stretching stroke.

Further, the amount of heat shrinkage (shrinkage) in the longitudinal direction of the preform at the time of blow molding can be suppressed as much as possible, and the quality control at the time of bottle blow molding can be easily performed, so that the better blow molding quality of the bottle can be achieved. Has the effect of being able to hold

In addition, the size of the stretching apparatus can be made compact, and the labor and cost for performing the stretching process by dividing the conventional stretching process into two can be reduced.

[Brief description of the drawings]

FIGS. 1A to 1H are process diagrams illustrating an embodiment of a molding step and a stretching step in a preform stretching method for plastic bottle molding of the present invention.

FIGS. 2A to 2H are process diagrams for explaining another embodiment of a molding step and a stretching step in a method for stretching a preform for molding a plastic bottle according to the present invention.

FIG. 3 (a) is a side sectional view showing an example of a stretching means in the preform stretching method for molding a plastic bottle of the present invention, and FIG. 3 (b) is a top view of its rotating body.

FIG. 4 is a side sectional view showing another example of the support of the stretching means in the preform stretching method for molding a plastic bottle of the present invention.

FIG. 5 is a process diagram illustrating a general plastic bottle molding method.

[Explanation of symbols]

A: Core mold part B: Cavity part for preform molding C: Cavity part for blow molding D ... Mouth heating guide means 1 ... Support part 2 ... Core mold 3 ... Neck mold 4 ... Support block 5 ... Assist plug 11 ... Reform molding cavity 21 Blow molding cavity 31 Molding space 32 Preform 32a Body 32b Bottom 32c Mouth 32d Screw 41 41 Support block 42 Screw shaft 42
b: Spline groove part 45: Drive rotating body 45c: Spline convex part 51: Support body 54: Vertical rotation support shaft

Claims (2)

[Claims] 1. A preform is injection-molded in a preform molding die having a preform opening molding die portion and a preform body molding die portion. A screw shaft capable of being extended and shortened while being driven and rotated by being screwed to the support block is inserted, and in a state where the preform mouth portion is fixed, the screw shaft tip portion and the shaft tip portion direction from the outside of the preform bottom portion are fixed. A preform stretching method for plastic bottle molding, wherein the preform is stretched while rotating a screw shaft while holding the preform bottom by a rotating support pressed against the preform and twisting and stretching the preform. 2. A method for molding a plastic bottle, comprising: loading a preform obtained by the method for stretching a preform for molding a plastic bottle according to claim 1 into a blow molding cavity and performing blow molding.