JPS61291121A - Method and apparatus for manufacturing stretched polyester bottle - Google Patents

Abstract

PURPOSE:To manufacture a stretched polyester bottle with a comparatively high production speed by a method in which a bottomed polyester parison is heated to a draw molding temperature and molded by blow molding to form a stretched bottle, and the bottle is put in cooling molds and a pressure gas is blown into the bottle for final molding. CONSTITUTION:Since a heated parison 6 is put into heating moles 18 and molded by draw blowing molding, the stretched bottle 22 so molded is heat-set during the period when it is touched by the molds 18. While the bottle 22 subjected to the heat setting is immediately held under a positive inner pressure to keep its shape, the bottle 22 is taken out of the molds 18 and put into cooling molds 23. A pressure gas 27 is blown into the bottle 22 kept at high temperatures for final molding, whereupon the bottle 22 in contact with the molds 23 is cooled to temperatures lower than the glass transition temperature. No deformation occurs in the bottle 22 taken out of the molds 23, and a normal shape of the bottle 22 can thus be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method and apparatus for producing a stretched polyester bottle, and more particularly to a method and apparatus for producing a heat-set stretched polyester bottle. In books, tettles made of saturated polyester such as polyethylene terephthalate are called polyester bottles.

(Prior art) Stretched polyester bottles with bottoms and formed by stretch blow molding, preferably biaxial stretch blow molding, are containers with transparency, impact resistance, gas barrier properties, strength, etc. Due to its excellent properties, it has recently been widely used as containers for carbonated drinks, soy sauce, edible oil, etc. However, stretched polyester ytP) produced by conventional methods has shrinkage internal strain, so during or after filling,
When heated to about 60°C or higher, thermal contraction occurs due to relaxation of the internal strain, so hot filling of juices, hot water sterilization of Japanese sake, retort heat sterilization of coffee, soup, etc. It is unsuitable for storing the contents.

As a countermeasure, stretch blow molding is performed in a mold whose inner surface is heated to a temperature slightly higher (e.g., approximately 10 to 40°C higher) than the hot filling temperature or retort heat sterilization temperature. After that, the mold is cooled, and cooling air is introduced into the bottle to bring the bottle to the mold release temperature (the temperature at which the bottle does not deform during mold release). A method has been proposed and adopted in which the bottle is cooled to a temperature of, for example, 50 to 70° C., and then the bottle is removed from the mold.

(Problems to be Solved by the Invention) In the case of the conventional heat setting method, the heat setting by heating the mold and the cooling of the bottle by cold air are performed at the same station, so the residence time at the same station is relatively long. Therefore, a problem arises in that the overall production speed decreases. For example, in the case of heat setting at 130 DEG C., after heat setting at 130 DEG C. for about 10-15 seconds, cooling is performed with cold air, so it takes about 15 to 20 seconds to release the mold.

Further, by using a type of apparatus as disclosed in Japanese Patent Application Laid-Open No. 52-109565, in which a parison injection molding stage, a parison heating steno, a stretch blow molding stage, and a mold release stake are arranged on all sides of the machine, When manufacturing a heat-set stretched bottle by the conventional method using the so-called hot parison method, especially when the preform, that is, the parison, is thick, there is a problem in the injection molding process. It may take a longer time (e.g., about 35 seconds or more) than the torque molding and heat setting processes, and in this case, the injection molding process becomes the production rate limiting factor.
There is a risk that the overall production speed will decrease.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a method and apparatus for producing heat-set stretched bottles from polyester bottomed parisons at relatively slow production rates.

(Structure of the Invention) The present invention transfer-heats a polyester bottomed parison to a stretch-molding temperature, charges the heated parison into a heating mold, performs stretch-blow molding, and produces a heat-set stretched bottle. After forming, the bottle is held at a positive internal pressure that allows it to maintain its shape. 1. It is taken out of the heating mold, placed in a cooling mold, and pressurized gas is introduced into the bottle to finalize the bottle. The present invention provides a method for manufacturing a stretched polyester bottle, which is characterized by molding.

Here, transfer heating refers to heating the molded part of the preformed bottomed parison (see 6C in FIG. 1) by transferring the bottomed parison and preferably rotating it around the axis while heating it with infrared rays. It refers to heating by irradiation, hot air blowing, or other appropriate heating means.

Furthermore, the present invention includes a transfer heating device and a bottle molding device that heat the polyester bottomed parison to a stretch molding temperature while being held hanging and transported by a conveying mold,
The bottle forming equipment includes a NoeIJson loading station, a stretch blow molding station, a final forming station,
and a device for transferring the following transport mold holding bars to each station in the above order, and the parison mounting station is a transporter that engages and holds the transport mold that holds the noclison sent from the transfer heating device. Complete with mold holding bars, the stretch blowing station includes a heated mold for stretch blow molding the parison to form a stretched bottle and heat setting the bottle, and the final forming station processes the heat set bottle. The present invention provides an apparatus for manufacturing a stretched polyester bottle, which is equipped with a cooling mold that performs final molding by blowing pressurized gas and cools at a temperature 1 at which it can be taken out.

(Means and effects for solving the problem) In the present invention, a pre-formed polyester bottomed parison is stretched at a temperature lower than the glass transition temperature of the resin, one or more times lower than the crystallization temperature. For example, in the case of polyethylene terephthalate, transfer heating is performed to a temperature within the range of about 80 to 110°C. Therefore, injection molding process and stretch blow molding
The heat setting process can be separated in terms of process time.

Therefore, the residence time in other steps is not restricted by the time required for injection molding.

Since the heated parison is charged into a heating mold and stretch blow molding is performed, the formed stretched bottle is heat set while in contact with the heating mold. The heat-set bottle is immediately maintained at a positive internal pressure that can maintain its shape [L is taken out from the heating mold and placed into a cooling mold. As mentioned above, if the bottle is taken out without being held at a positive internal pressure, it will be at a temperature above the glass transition point, so it will shrink and deform when taken out, which is undesirable. In this state, put the bottle, which is 1 degrees higher in temperature, into the cooling mold.
When the bottle is finally formed by blowing pressurized gas into the bottle, the bottle in contact with the cooling mold is cooled to a temperature below the glass transition point.

Therefore, there is no risk that the bottle will be deformed when it is taken out from the cooling bottle, and a bottle with a normal shape can be obtained. Furthermore, unlike conventional methods, after the bottle is formed in a heating mold and heat set, the bottle is not cooled (to a temperature lower than the glass transition point) in the mold, which ultimately shortens the residence time in the heating mold. , the prenatal rate increases.

(Example) Examples will be described below with reference to the drawings.

I shown in FIG. 1 is a parison injection molding apparatus, which has a water-cooled hole 2 and is composed of a water-cooled lower molding die 3a and a half-split mold, and an upper molding part for forming a threaded part 6a and a retaining ring 6b. A fixing plate 5 for fixing the molds 3b, b and the soil molding mold 3b is provided. Fixed plate 5 should be formed with a bottom 1? It is provided with a hollow core part 7 that defines an inner surface 6X of the litho 6. The parison 6 includes a threaded portion 6a, a holding cylinder 6b, 1. - and a bottomed cylindrical molded part 6c (slightly curved toward the bottom of the flexible cage) below the retaining ring 6b.

Molten polyester 9 injected from an injection device (not shown) passes through the hot runner nozzle 8 and the case 10 of the lower mold 3a, and enters the cavity 11 of the lower mold 3a and the upper mold 3b. Injected, a bottomed Rison 6 is formed. In particular, the molded part 6C is rapidly cooled by the water-cooled lower molding die 3a, so that it becomes a transparent amorphous structure.

The parison 6 formed as described above is extracted from the lower molding die 3a by pulling up the fixed plate 5 and the upper molding die 3b, and the resin of the case 10 is usually cut and removed. Immediately or after being stocked, the parison 6 is suspended in the holding ring 6b by the conveyance mold 4 (Fig. 3), and is rotated around the axis by a rotation mechanism (not shown), while being transferred heated as shown in Fig. 2. The device 12 is transferred by, for example, a chain 13, and the forming portion 6C thereof is heated to the stretch forming temperature at the center of the wall thickness.

As the heating device 12, a red IA line type, a hot air blowing type, or other appropriate type is adopted. The molding part 6e is normally heated uniformly in the height direction, but if you want to make the bottle thicker near a predetermined height, for example, the height near the corresponding height of the bottle 6 may be heated lower than other parts. May be heated to temperature.

The bottle forming apparatus 14 shown in FIG. 2 includes a parison mounting station A, a stretch blowing station B, a final forming station C, and a bottle unloading station D surrounding the four sides of a machine stand 15.

In addition, each station A, B, C,
Four transport mold holding bars 1 are placed above D.
7 is installed.

After exiting the heating device 12, the conveying mold 4 on which the crisscross 6 is suspended is moved by a feeding mechanism (not shown) to the holding bar 17 stopped at the mounting station A, as shown in FIG.
A plurality of pieces (seven pieces in the case of FIG. 2) are attached to. Immediately, the rotating shaft 16 rotates and the holding bar 17 stops at the stretch blow molding station B. Immediately hold bar 1
7 is lowered, and each noclison 6 is placed in a corresponding heating mold 18, as shown in FIG.

The heating mold (metal mold) 18 is a half mold 18a.

18a, and by the heating medium passing through the heating medium passage I9, the inner surface 20a of the cavity 20 is heated to the temperature at which the contents are filled into a bottle (e.g., 80°C) or the retort heating temperature (e.g., 120°C). It is heated to a slightly higher temperature (preferably 10° C. or higher).

Immediately after the parison 6 is loaded into the heating mold 18 as described above, the hollow stretching rods 21 of the first stretching rod row
is pushed into the parison 6 through the insertion hole 17a of the holding bar 17, and the plug 26 is fitted into the insertion hole 17a.

At the same time, pressurized gas 21a (usually air) is blown out from the stretching rod 21, and the molded part 6c of the parison 6 is biaxially stretched and blow molded, and the shoulder part 22a, body part 22b and bottom part 22
A stretched bottle 22 in which c is molecularly oriented is formed.

The formed shoulder portion 22a1, body portion 22b and bottom portion 22c come into contact with the heated cavity inner surface 20&, and are heated and heat set. Immediately after removing the heat, the heating mold 18 is opened, the holding bar 17 rises together with the stretching rod 21, and the heat-set stretched bottle 22 is taken out from the heating mold 18 while still at a high temperature.

The rotating shaft 16 then rotates and the holding bar 17 together with the stretching rod 21 stops at the final forming station C. During this time, in order to minimize the deformation of the relatively hot bottle 22, that is, to maintain the shape of the bottle 22, preferably the bottle 22 is
The internal pressure of 2 is slightly higher than atmospheric pressure (for example, about O1 to 1
kg/cm), the valve of the gas piping to the stretching rod 21 (not shown) is stopped, and the bottle 2
The internal pressure of No. 2 is maintained at the above value (see Fig. 6).

The final molding station C has a half mold 23a.

A cooling mold 23 made of 23a is provided. As shown in FIG. 7, the inner surface 24a of the cavity 24 of the cooling mold 23 is cooled by the cooling medium flowing through the cooling medium passage 25, and even after the comparatively high temperature bottle 22 is inserted, the inner surface 24a of the cavity 24 The temperature is kept below 30°C. Note that the cavity inner surface 24a of the cooling mold has substantially the same shape as the cavity inner surface 20a of the heating mold.

After the holding bar 17 is lowered together with the stretching rod 21 with the cooling mold 23 open, the cooling mold 23 is closed and the bottle 22 is inserted into the cooling mold 23. Immediately, the plug 26 inserted into the extension rod insertion hole 17aK of the holding bar 17 is removed, and at the same time, a switching valve (not shown) operates to supply pressurized gas 27 from the extension rod 21 into the bottle 22.
(Usually air at or below room temperature) is supplied, and while cooling the bottle 2270 from the inside, the gas is discharged to the outside from the insertion hole 17a from which the gold plate 25 was removed. .

The shoulder 22a, body 22b, and bottom 22c of the bottle 22 are cooled by the pressurized gas 27.
a, and the slight thermal deformation that occurred during the transfer from the heating mold 18 to the cooling mold 23 is corrected. At the same time, the body 22b and the like of the bottle 22 are rapidly cooled from the inner and outer surfaces to a temperature lower than the glass transition point by the pressurized gas 27 and the cavity inner surface 24a. During this final forming operation, the parisons 6 of the subsequent parison row are formed into bottles 22 at stretch blow molding station B using the stretch rods 21 of the second stretch rond row.

Thereafter, the supply of pressurized gas 27 by the stretching rod 21 is stopped, the cooling mold 23 is opened, and the holding bar 17 is
The bottle 22 rises together with the cooling mold 23.
taken out from Next, due to the rotation of the rotary shaft 16, the holding bar 17 moves together with the bottle 22 to the unloading station D, where, as shown by the dashed line in FIG. Take it out and send it to the next process. The open conveyance mold 4 is also held by the holding bar 1
7 and sent to the inlet side of the heating device 12 by a feeding mechanism (not shown) for reuse. On the other hand, the stretching rod 21 pulled up in the final forming stage C
is shown; A mechanism returns it to the stretch blow molding station B for waiting.

As shown in FIG. 9, the parison mounting station A and the bottle unloading station D are common and surround three sides of the triangular machine base 28. - The parison mounting station A, the stretch blow molding A bottle forming device 29 similar to the bottle forming device 14 may be used except that station B, final forming station C, and bottle removal station D are arranged.

(Specific example) Using the type 9 IJson injection molding apparatus 1 shown in FIG. .8m (
7:) A bottomed parison 6 made of polyethylene terephthalate was produced.

K-) After cutting and removing the 10 resins, as shown in FIG. While conveying the metal mold 6 with the conveying mold 4 by a mechanism not shown, the RIJ son 6 is placed around the circumference 9 of the axis by 20°.
After heating the molding section 6C to 100° C. substantially uniformly in the height direction by passing it through an infrared heating type heating device 12 while rotating at a speed of rpm, the bottle molding of the type shown in FIG. 2 is performed. iRIJson loading station A of device 14
In the process, eight conveyance molds (4) were simultaneously engaged with the holding bar 17.

Immediately, the holding bar 17 is transferred to the stretch molding station B, and the parison 6 is placed in a heating mold 18 of the type shown in FIG. The bottle 22 was heat set. At this time, the temperature of the inner surface 20a of the cavity of the heating mold 18 is 200°C, the pressure of the pressurized air is 25kg/m 2 , the total height of the bottle 22 is 305m, the outer diameter of the body 22b is 95mm, and the average wall thickness is 0.5mm. It was 4+nm. The stretch blow molding time was 5 seconds, and the heat setting time was 5 seconds.

Immediately, the bottle 22 is taken out from the heating mold 18 and placed into the cooling mold 23 whose cavity inner surface 24a has been cooled to 15° C. while the internal pressure is maintained at 0.1 to 0.5 kg/m2 (Goodes pressure). and pressurized air (pressure 25
kg/■) was corrected by blowing. The pressurized air blowing time was 5 seconds. Next, the bottle 22 was taken out from the cooling mold 23 and moved to the bottle removal station D, where it was removed from the conveying mold 4 and sent to the next process. Each station A, B, of the holding bar 17
C. The residence time for Dvck was 15 seconds. In other words, the rotating shaft 16 was rotated every 15 seconds.

The resulting stretched bottle is transparent and has a predetermined shape, and even when filled with Orange North at 85-90°C,
There was no deformation.

(Effects of the Invention) According to the present invention, a heat-set stretched bottle can be manufactured at a relatively higher production rate than a polyester bottomed parison.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an example of an apparatus for forming a bottomed parison;
FIG. 2 is an explanatory plan view of a first example of an apparatus for carrying out the method of the present invention, and FIG. 3 is a longitudinal cross-sectional view taken along the line ■-■ in FIG. 2, in which the bottomed parison is Drawings showing the state of transfer heating, FIG. 4 is a longitudinal sectional view taken along the line ■-■ in FIG. 2, and FIG. 5 is a longitudinal sectional view taken along the line ■-■ in FIG. Drawings showing the process of stretch blow molding a tZ parison, FIG. 6 is a side view of the formed bottle being transferred from a heating mold to a cooling mold, and FIG. 8 is a view showing ■-■ in FIG. 2. 9 is an illustrative plan view of a second example of an apparatus for carrying out the method of the invention; FIG. 4... Conveyance mold, 6... Bottomed parison, 12...
Transfer heating device, 14...bottle forming device,
17... Transfer mold holding bar, 18... Heating mold, 22... Stretching bottle, 23... Cooling mold, 2
7... Pressure body, A... parison mounting station, B... stretch blow molding station, C... final molding station f'-john 0 1') n-

Claims (2)

[Claims] (1) Transfer heating a polyester bottomed parison to a stretch molding temperature, charging the heated parison into a heating mold and performing stretch blow molding to form a heat-set stretched bottle; is taken out from the heating mold while being maintained at a positive internal pressure that can maintain its shape, placed in a cooling mold, and pressurized gas is fed into the bottle to final shape the bottle. Method for manufacturing stretched polyester bottles. (2) Equipped with a transfer heating device and a bottle molding device that heat the polyester bottomed parison to a stretch molding temperature while being suspended and transported by a conveying mold, and the bottle molding device includes a parison mounting station, a stretch blowing The parison mounting station includes a molding station, a final molding station, and a device for transferring the following transport mold holding bars to each station in the above order, and the parison mounting station supports the transport mold holding the parison sent from the transfer heating device. a transfer mold holding bar for engaging and holding the parison, the stretch blowing station includes a heated mold for stretch blow molding the parison to form a stretched bottle, and a heated mold for heat setting the bottle; 1. An apparatus for manufacturing a stretched polyester bottle, comprising a cooling mold for final shaping the bottle by blowing pressurized gas and cooling it to a temperature at which it can be taken out without deformation.