JPH11254513A - Method for molding blastic bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for molding a bottle by uniformly heating an overall preform port by a frictional heat by rotatably driving a cylindrical rotor, and crystallizing the port. SOLUTION: A space 13 is formed between a core mold 2 and a mold 11a. After a melted resin is injected in the space, a cavity 11 is cooled, a resin of a body is cooled, solidified to mold a body 32a and a bottom 32b. Then, a preform 32 having a port 32c and a threaded part 32d is molded. A cylindrical rotor 5 is rotatably driven to heat resin of the port 32c by a frictional heat with an inner surface of the port 32c. the rotation is stopped, resin of the port is cooled to the ambient temperature, solidified, crystallized to mold a port and not crystallized to form the body. The preform 32 is charged in a temperature regulating pot, and heated to a blow molding temperature. This is expanded in a bottom molding mold 21a to mold a bottle P, cooled and solidified. The cavity 21 and the neck mold 3 are opened to complete molding of the bottle P.

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. 4 (a) to 4 (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. Examples of the method of strengthening the heating include JP-A-57-189824 and JP-A-1-189824.
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 heating the opening of a preform (parison) for plastic bottle blow molding by a heating means, the entire mouth is uniformly attached to the preform molding die. An object of the present invention is to provide a method for molding a plastic bottle in which a mouth is crystallized by heating to form a bottle.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to injection molding using a preform molding die composed of a core mold 2 of a preform molding core mold portion A and a preform molding cavity B. In a plastic bottle molding method in which the mouth of a plastic bottle obtained by blow molding a preform is heated and crystallized by heating, the molten resin is injected into a preform molding die to mold the preform. Then, a cylindrical rotating body 6 rotatable in contact with the inner periphery of the preform opening provided on the outer periphery of the neck 2a of the core mold 2 in the preform molding die.
Is a method for molding a plastic bottle, characterized in that the preform mouth is heated and crystallized by the frictional heat generated by driving and rotating the preform.

In the present invention, the resin used for injection-molding the preform is mainly a polyethylene terephthalate resin or a polyethylene terephthalate containing a small amount of polyethylene isophthalate. This is a method for molding a plastic bottle which is a resin or a resin mainly composed of polyethylene terephthalate containing a small amount of polyethylene naphthalate.

Further, the present invention is the plastic bottle molding method according to the above invention, wherein the heating temperature for heating the mouth of the preform by the frictional heat is 170 ± 20 ° C.

[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.

The neck portion 2a of the core mold 2 has a cylindrical shape rotatable in contact with the inner periphery of the preform mouth with a shaft 2b supporting the core mold 2 extending from the support portion 1 as a support shaft. A rotating body 6, which is integrally provided with a drive transmission gear 7, and a drive gear 8 meshes with the transmission gear 7,
The drive gear 8 is driven and rotated by an electric motor 9 at an appropriate rotation speed.

As shown in FIG. 1 (a), the preform molding cavities B (outer die portions) face each other and open and close to each other.
And a preform mold portion 11a formed inside the cavities 11, 11, a supply path 11b for molten resin, and an injection nozzle 11c.

FIG. 2 shows a preform molding core mold part A.
FIG. 2 is an enlarged sectional side view of the (inner mold portion), wherein 1 is a support portion, 2 is a core type, 2a is a neck portion, 2b is a support shaft, and 6 is a cylindrical rotating body supported by the support shaft 2b and rotatable. , 6a is a needle bearing, 7 is a transmission gear, 7a is a thrust bearing of the transmission gear 7, 8 is a drive gear meshing with the transmission gear 7, 9 is a drive gear 8 attached to the support 1 for driving at an appropriate rotation speed. An electric motor that rotates.

FIG. 3 is an enlarged side sectional view showing a state in which the preform molding core mold part A is mounted in the preform molding cavity B, and 11 is a cavity (outer mold).
It is.

The plastic bottle molding method of the present invention comprises:
This will be described in detail below with reference to FIGS.

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, in FIG. 1B, 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, and the core mold 2 and the mold are joined together. A space 31 is formed between the space 11a and the space 11a.

Next, in FIG. 1C, the molten resin (polyethylene terephthalate) is injected from the injection nozzle 11c into the core mold 2
After injecting into the space 31 between the mold 11a of the cavity 11 through the flow path 11b, cold water is sent into the structure of the cavity 11 to cool the cavity 11 and cool the resin of the preform body. The body 32 is solidified.
a, the bottom part 32b is molded, and the preform 32 having the preform mouth part 32c and the screw part 32d is molded.

On the other hand, in a state where the preform mouth 32c is mounted and held between the neck part 2a, which is the mold part of the preform mouth, and the neck molds 3, 3, the preform mouth 32c is brought into close contact with the inner surface of the mouth 32c. The rotating cylindrical body 6 is rotated,
It is driven and rotated at about 600 rpm to generate frictional heat between the inner surface of the opening 32c and the outer surface of the rotating body 6, thereby heating the resin of the preform opening 32c that is undergoing cooling and solidification.

FIG. 4A shows a cooling temperature curve of the resin at the mouth of the preform at that time (horizontal axis: time t, vertical axis: temperature T).
FIG. 4B shows a cooling temperature curve (horizontal axis: time t, vertical axis: temperature T) of the resin in the preform body at that time.

As shown in the graph of FIG. 4 (a), the temperature T ₂ of the molten resin at the mouth of the preform immediately after being injected into the cavity 11 is lowered by the cooling operation of the cavity 11 and after a predetermined time elapses. the T _1. The temperature T _{2 of the} molten resin is about 200 to 290 ° C., and the temperature T ₁ after a lapse of a predetermined time is around 170 ° C.
It is appropriate to set the temperature to about 20 ° C.

[0029] When the injected resin of the preform mouth portion has reached the temperatures T _1, by rotating the rotary member 6 of the neck portion 2a, a predetermined time held at temperatures T ₁ and then re-heating the resin of the mouth Then, the high frequency is stopped and the neck 2
The resin at the mouth of the preform between the a and the neck molds 3 and 3 is cooled and solidified to room temperature T ₀ (around 20 ° C. or room temperature) and crystallized, and a resin having a mouth 32 c and a screw portion 32 d is formed. The reform mouth is formed.

During this time, the molten resin in the preform body is:
By continuing cooling the cavity 11 by flowing feed cold water into the structure of the cavity 11, Fig. 4 as shown in the graph of (b), the resin of the preform mouth is normal temperature T ₀ (20
(Approx. Or near room temperature), the temperature is lowered from the temperature T ₂ to the normal temperature T ₀ , and is cooled and solidified and is not crystallized.
a, a preform body having a bottom 32b is molded.

Subsequently, the preform 32 (parison) is pulled out from the mold portion of the cavity 11 together with the core mold 2 and the neck molds 3 and 3, and the preform 32 (parison) held by the neck molds 3 and 3 is drawn. Is loaded into a temperature adjustment pot (not shown) and the preform 32 is heated to the blow molding temperature.

Thereafter, the preform 32 held by the neck dies 3 and 3 shown in FIG. 1 (e) is provided in the cavity 21 (outer die) of the blow molding cavity C and the bottle forming die. Then, the blow assist plug 5 attached to the blow device support portion 4 is loaded into the preform 32, and the neck dies 3, 3 and the support portion 4 are fixed.

Thereafter, as shown in FIG. 1 (f), the tip of the preform 32 is extended while the assist plug 5 is extended.
Blow air while pressing the inner bottom of the blow air nozzle 4
a into the space between the assist plug 5 and the preform 32 to expand the preform 32 so as to be in intimate contact with the inner surface of the bottle forming die 21a to form a bottle P. The bottle P is solidified by cooling 21a.

Finally, in FIG. 1 (g), the cavities 21, 21 and the neck molds 3, 3 are opened to complete the molding of the bottle P.

The heating temperature for crystallization of the mouth 32c is about 63 ° C. to 121 ° C. or 70 ° C. to 140 ° C. to 170 ° C., which is the glass transition point of the mouth 32c.
The heating time is suitably from 40 seconds to 180 seconds or more and from 4 minutes to 10 minutes.

FIG. 5 is a graph showing the relationship between the general crystallization speed v and the temperature T of polyethylene terephthalate resin, which is a resin for molding plastic bottles. The crystallization speed is highest when the resin temperature is around 170 ± 20 ° C. High, peaking around 170 ° C. In addition, resin temperature 170
The longer the temperature holding time at ± 20 ° C., the more crystallization proceeds.

[0037]

According to the plastic bottle molding method of the present invention, the mouth of a preform (parison) for plastic bottle blow molding can be crystallized by heating by frictional heat in a preform molding die. Without removing the preform from the molding die and crystallizing the mouth, crystallize in real time in the same molding die with the preform mouth attached and held in the molding die. It does not require a special mouth crystallization device in addition to the molding die, which is effective in increasing the efficiency of the crystallization process of the preform mouth, and the crystallization operation is attached to the molding die. Since the holding is carried out, the crystallization process can be performed stably while preventing deformation of the mouth during the crystallization operation, and the preform and the mouth of the plastic bottle obtained by blow molding the preform. It is effective in stabilizing reinforcement of shape and strength.

[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 an enlarged side sectional view of a preform molding core mold portion (inner mold portion) used in the plastic bottle molding method of the present invention.

FIG. 3 is an enlarged sectional side view showing a state in which a preform molding core mold used in the plastic bottle molding method of the present invention is mounted in a preform molding cavity.

FIG. 4 (a) is a graph showing a cooling curve of a molten resin in a crystallization process of a bottle mouth portion of the plastic bottle molding method of the present invention, and FIG. 4 (b) is a melting of a bottle body of the plastic bottle molding method of the present invention. 4 is a graph showing a cooling curve of a resin.

FIG. 5 is a graph showing the relationship between the crystallization speed and temperature of a general polyethylene terephthalate resin.

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

[Explanation of symbols]

A: Preform molding core mold part B: Preform molding cavity part C: Blow molding cavity part 1: Support part 2: Core mold neck part 2a 3: Neck mold 4: Support part 5: Blow assist plug 6 ... Cylindrical rotating body 7 ... Transmission gear 8 ... Drive gear 9 ... Electric motor 11 ... Preform molding cavity 21 ... Blow molding cavity 31 ... Molding space 32 ... Preform 32a ... Body 32b ... Bottom 32c ... Mouth 32d: Screw part

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI B29L 22:00

Claims (3)

[Claims] 1. A core mold 2 of a core mold part A for preform molding.
The mouth of a plastic bottle obtained by blow-molding a preform injection-molded using a preform-molding die composed of a preform-molding mold composed of a preform-forming cavity and a preform-molding cavity B is strengthened by crystallization treatment by heating. In the method for molding a plastic bottle, a molten resin is injected into a preform molding die to form a preform, and then the preform is molded around the neck portion 2a of the core die 2 in the preform molding die. A plastic bottle is formed by driving and rotating a rotatable cylindrical rotor 6 in contact with the inner periphery of the provided preform mouth to heat and crystallize the preform mouth by frictional heat. Method. 2. The resin used for injection molding of the preform is a polyethylene terephthalate resin, a resin mainly composed of polyethylene terephthalate containing a small amount of polyethylene isophthalate, or a polyethylene terephthalate containing a small amount of polyethylene naphthalate. The method for molding a plastic bottle according to claim 1, wherein the resin is mainly a resin. 3. The method for molding a plastic bottle according to claim 1, wherein the heating temperature for heating the mouth of the preform by the frictional heat is 170 ± 20 ° C.