JP3054233B2 - Blow molding bottle manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for producing a bottle made of a thermoplastic polyester resin by blow molding.

[0002]

2. Description of the Related Art Bottles obtained from thermoplastic polyester resin such as polyethylene terephthalate by biaxial stretch blow molding are excellent in transparency, strength and hygiene and are widely used in various applications. However, when exposed to high temperatures, it has the disadvantage of causing thermal contraction. In order to solve this difficulty and increase the heat resistance and dimensional stability of the bottle, heat-treat (heat-fix) the blow-molded bottle at a high temperature, for example, by keeping the mold at the time of blow molding at a high temperature suitable for heat treatment. It is known that the wall surface of the bottle in contact with the mold is heated and fixed by heat.

However, when the molded bottle is taken out of the mold, shrinkage deformation occurs. To eliminate this inconvenience, a method of supplying a cooling medium into the molded bottle, for example, liquefied carbon dioxide or air containing water droplets is injected. Or enter
Alternatively, there has been proposed a method of cooling and fixing a molded bottle by blowing air at a low temperature, for example, room temperature.

[0003]

However, when the cooling medium is injected into the molding bottle as described above, since the molding bottle is in close contact with the mold wall kept at a high temperature, the cooling efficiency of the molding bottle is reduced. Poorly, it is difficult to remove the blow molded bottle without causing deformation. Also, sufficient cooling of the bottle is required to remove the bottle from the mold without causing deformation, but this requires a long cooling time, that is, a long molding cycle and is not suitable for commercial production. There is a problem.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems, efficiently cools a molded bottle with a cooling medium, shortens the molding cycle, and causes deformation when the bottle is removed from the mold. It is an object of the present invention to provide a method for producing a thermoplastic polyester resin bottle by biaxial stretch blow molding. While the internal pressure is applied to the molding bottle, the molding bottle is heated at a high temperature by holding the molding die at a high temperature, and thereafter, a high-pressure gaseous cooling medium is partially discharged while being blown into the bottle. While maintaining the inside of the bottle at a high pressure, the cooling medium is circulated to cool the inner wall of the bottle, and while the blowing of the cooling medium is continued, the cooling medium is discharged at once from the mouth of the molded bottle. Thereafter, to stop the blowing of the cooling medium, by opening the stop and substantially molding die at the same time,
The method comprises removing a bottle.

According to the present invention, a bottomed parison made of a polyester resin, particularly preferably polyethylene terephthalate (hereinafter abbreviated as PET) is used as a starting material, which is blow-molded by a blow-molding apparatus, and the mold is heated to a temperature suitable for heat treatment. The molded bottle is pressed against the blow molding mold and heat-treated, and thereafter, a cooling medium is introduced into the molded bottle to cool the bottle.
Operations up to the above-mentioned heat treatment may be performed according to a conventionally known method. And the method of the present invention is characterized by cooling the molded bottle with the subsequent cooling medium,
Hereinafter, this will be described with reference to the accompanying drawings.

FIG. 1 is an explanatory view showing an embodiment of the method of the present invention, in which a mold portion is shown in a schematic vertical sectional view. FIG.
FIG. 2 is an explanatory view showing a state in which the nozzle touch portion supporting the extension rod is lowered downward in the mold shown in FIG. 1 and is separated from the mold. In the figure, 1 and 2 are blow molds having a split mold structure, 3 is a bottom mold, 4 is a mandrel supporting a bottomed parison, 5 is a nozzle touch section, 6
Is a packing for sealing the front edge of the mouth of the parison, and is incorporated in the mandrel 4. Reference numeral 7 denotes a packing that seals a gap between the mandrel 4 and the nozzle touch unit 5, and is incorporated in the nozzle touch unit 5.

[0007] 8 is a tubular stretching rod, 9 is a compressed air tank,
10 is a conduit for sending compressed air from the compressed air tank 9 to the extension rod 8, 11 is an electromagnetic valve provided in the conduit 10, and 12 is a passage formed in the nozzle touch part 5, which is connected to a blow-formed parison. I have. 13 is a pipe leading to the passage 12, 14 is an exhaust pipe branched from the pipe 13, 15 is an electromagnetic valve, 16 and 17 are branch pipes each separated from the pipe 13, 18 is a valve, 19 is a pressure reducing valve, 20 is Valve, 21
Is a pressure reducing valve, 22 is a blow-molded bottle, 23 is a mouth of the bottle 22, 24 is a muffler, and 25 to 30 are refrigerant outlets provided on the extension rod 8.

Next, an embodiment for implementing the method of the present invention in the above apparatus will be described. The mold is not shown,
The heating medium is passed through a heating medium passage formed in the mold and heated to 80 to 250 ° C., preferably 120 to 190 ° C., while the bottomed parison supported by the mandrel 4 is at or above the glass transition temperature of the material (for example, 90 for PET
After being heated to about 110 ° C. and loaded into the mold, and the mold is closed, the nozzle touch unit 5 holding the stretching rod 8 is attached to the mold.

Next, the extension rod 8 is protruded into the parison to extend the parison in the vertical direction, and pressurized gas is blown into the parison. The blowing of the pressurized gas (normally, air at normal temperature) into the parison is performed at a relatively low pressure (for example, 10
A primary blow of ~ 15 kg / cm ² gauge pressure (hereinafter, gas pressure blown into the parison is indicated by gauge pressure) and a secondary blow of a higher pressure (for example, 25-60 kg / cm ² ) The high-pressure gas of the primary blow is supplied from the branch pipe 16 communicating with the compressed air tank 9, and the high-pressure gas of the secondary blow is supplied from the branch pipe 17 connected to the compressed air tank 9, respectively.
3, the passage 12 is introduced into the parison through a tubular gap sandwiched between the mandrel 4 and the extension rod 8, and blow molding is performed. The first blow blows the parison into a rough bottle shape, and the second blow increases the pressure to form details on the outer surface of the bottle.
In this blow, since the bottle in close contact with the mold is subjected to heat treatment, the time is set to include the time of this heat treatment.

When blow molding is completed, valves 18 and 20 are closed. Then, the solenoid valve 15 is opened, and the high-pressure gas in the bottle is discharged from the exhaust pipe 14. At the same time, the solenoid valve 11 opens, and a gaseous cooling medium is introduced into the bottle. That is,
In the case shown in the drawing, air at normal temperature in the compressed air tank 9 is used as a cooling medium. The cooling medium is jetted toward the inner wall surface of the bottle as a cooling medium from refrigerant outlets 25 to 30 provided in the stretching rod 8. The cooling medium spouted into the bottle enters the passage 12 formed in the nozzle touch portion 5 from the tubular gap between the mandrel 4 and the extension rod 8 and enters the pipe 1
3, and then discharged into the atmosphere via the exhaust pipe 14.

In FIG. 1, the jets of the refrigerant are jet ports 25 and 2.
From arrows 6, 27, 28, 29 and 30, arrows a
The operation is performed in the directions indicated by 1, a2, a3, a4, a5, and a6. And spouts 25 and 26, 27 and 2
8, 29 and 30 form a set and are installed at a position in the inner wall surface of the bottle where cold air is directed particularly to a place where cooling is desired immediately. In each set, for example, as shown in FIG.
The spout 5 and the spout 26 are arranged at positions slightly shifted in the length direction and 90 ° in the circumferential direction of the tube in the tubular body of the extension rod 8. Thus, the desired inner wall portions of the bottle can be intensively cooled without reducing the strength of the tubular stretching rod 8.

The gaseous cooling medium is blown into the bottle at a rate of usually 25 kg / cm ² or more, preferably 28 to 35 kg / c.
At a high pressure of m ² , the exhaust from the exhaust pipe 14 is squeezed and the inside of the bottle is kept at a high pressure to prevent deformation of the bottle. In this state, the cooling medium is continuously ejected, for example, for 1.0 to 3.0 seconds, and then the cooling medium is discharged at once from the mouth portion 23 of the bottle while continuing to press the cooling medium. This causes a rapid temperature drop due to the adiabatic expansion of the high-pressure cooling medium, and the bottle is effectively cooled.

FIG. 2 shows an embodiment in which the cooling medium is discharged at once from the mouth 23 of the bottle. That is, the molds 1 and 2 and the bottom mold 3 are closed, and the mounting of the mandrel 4 is maintained as it is, the nozzle touch part 5 is detached from the mandrel 4, lowered in the direction of arrow d, and the packing 7 and Open the seal at location 6. To do so,
The high-pressure gas in the bottle is discharged in the directions of the arrows b and c, the pressure in the bottle is rapidly reduced, and a cooling effect by adiabatic expansion is achieved.

As described above, the nozzle touch portion 5 is removed from the blow molding die to rapidly cool the bottle, for example, from 0.1 to
Immediately after 1.0 second, the passage of the cooling medium is stopped, and the blow mold is opened substantially simultaneously with the stop of the passage of the cooling medium, and the cooled molded bottle is heated again by the mold. Remove the bottle from the mold before

It is difficult to perform the above-mentioned stopping of the passage of the cooling medium and the opening of the blow molding mold substantially simultaneously at the same time in industrial production. It means that it cannot be removed and there is such a time lag. As a result of various attempts in the present invention, even with the same time lag,
It has been found that it is preferable that the stoppage of the cooling medium is more preceded than the opening of the mold, rather than the opening time of the cooling medium that extends after the opening of the blow mold. Specifically, it has been found that there may be a time lag of 0.2 seconds or less between the stoppage of the cooling medium and the opening of the mold.

FIG. 3 shows a chart (time chart) illustrating the time relationship of each step in the blow molding of the present invention. In the figure, A indicates a period during which the parison is mounted on the molding die and the die is closed. The dotted line e indicates the time when the mold is closed, and the dotted line f indicates the time when the closed mold is opened. B is a nozzle touch portion (a portion indicated by reference numeral 5 in FIG. 1).
Indicates a period during which the nozzle touch portion is attached to the blow mold, and the nozzle touch portion is removed from the mold as shown in FIG. 2 and a large amount of high-pressure gas in the bottle is discharged, as shown in FIG. Indicates a point in time. C indicates a period in which the stretching rod is projected into the bottle and the projected state is maintained. D indicates a blow period of the primary blow, E indicates a blow period of the secondary blow, and a dotted line g indicates a point in time when the blow is stopped. F indicates a period during which the blowing is stopped and the solenoid valve (15 in FIG. 1) of the exhaust pipe is opened to discharge the high-pressure gas in the bottle.
G indicates a period during which the gaseous cooling medium is blown into the bottle.

In FIG. 3, t1 to t9 attached to each of A to G are the time of each operation (t4 and t6).
Represents the time from the closing of the mold until the start of the primary blow and the secondary blow), and the respective times are as follows. This is an example in the case of manufacturing a 1.5 liter PET bottle having the shape shown in FIG. t1 = 5.0 to 12.5 seconds t2 = 5.0 to 11.0 seconds t3 = 5.5 to 13.0 seconds t4 = 0.05 to 0.25 seconds t5 = 0.5 to 5.0 seconds t6 = 0.5 to 3.0 seconds t7 = 2.0 to 5.0 seconds t8 = 1.0 to 3.0 seconds t9 = 0.1 to 1.0 seconds Exhaust period F and cooling medium blowing period G indicates the time before the nozzle touch portion is removed from the mold and the time after the nozzle touch portion is removed.

The gaseous cooling medium used in the method of the present invention includes air, nitrogen and the like, and these gases may contain mist. Generally, it is preferable to use room temperature air.

[0019]

【Example】

Example 1 and Comparative Example 1 In these examples and comparative examples, the apparatus shown in FIG. 1 was used, and the method described with reference to FIG. 1 was followed. According to this method, a parison having a weight of 60.5 g is heated to 90 ° C., and is heated to 30 ° C. in a molding die previously held at 145 ° C. as a cooling medium.
Table 1 below shows Example 1 and Comparative Example 1 in which the required time in each step was changed while using room temperature air of kg / cm ² . The items of t1 to t9 in Table 1 are A (t1) to G (t) in the time chart of FIG. 3 described above.
8, t9).

With respect to the containers obtained in Example 1 and Comparative Example 1, the full capacity at the time of removal (measured with water at 20 ° C.) and the displacement of the capacity (n = 10 pieces) were measured. Standard deviation σ _{n = 1} ) and deformation after filling with hot water were examined.
Deformation after filling with hot water means that a molding container is filled with a specified amount of hot water at 87 ° C., and then a cap (for example, 1.5 liters is filled in a container for 1.5 liters) is placed, and the container is turned sideways. After standing for 30 seconds and then for 2 minutes in an upright state, the sample was cooled with a shower and visually observed for deformation.

[0021]

[Table 1]

In Example 1, the stopping of the cooling medium blowing and the opening of the mold were performed substantially simultaneously. (When the points of both operations were precisely examined, after the stopping of the cooling medium blowing, There was an interval of 0.10 seconds before the opening of the mold, but from the point of view of action and effect, it is considered to be substantially simultaneous.) On the other hand, in Comparative Example 1, the time of t1 was longer than that of Example 1 by 0.3 second, and the mold was opened after a lapse of 0.3 second from the stoppage of the cooling medium blowing. Due to the above difference, in Example 1, the full filling capacity was as specified, the capacity deflection was as small as 2.72, and there was no deformation after filling with hot water. In contrast, in Comparative Example 1, the mold was opened 0.3 seconds after the stoppage of the cooling medium blowing as described above, whereby the bottle shrank due to the heat of the mold, and the full filling capacity was small. In addition, the capacity was large and 8.35, and when the bottle was taken out of the mold due to shrinkage, the bottle had already been deformed.

[0023]

According to the method of the present invention, in the production of a bottle by biaxial stretch blow molding, the molded bottle is efficiently cooled by a cooling medium, and the molding cycle is shortened.
Moreover, it is possible to prevent deformation when the bottle is removed from the mold after molding.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of the method of the present invention.

FIG. 2 is an explanatory view showing a state in which a nozzle touch portion is removed from a mold in the molding mold shown in FIG. 1 in order to discharge high-pressure gas in a bottle at a time.

FIG. 3 is a table illustrating a time relationship of each step in the method of the present invention.

[Explanation of symbols]

 1 and 2 Mold 3 Bottom mold 4 Mandrel 5 Nozzle touch part 8 Stretch rod 9 Compressed air tank 22 Blow molded bottle

Continuation of the front page (56) References JP-A-3-86518 (JP, A) JP-A-3-9831 (JP, A) JP-A-1-133716 (JP, A) JP-A-1-133714 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 49/00-49/80

Claims (2)

(57) [Claims] 1. A method for producing a thermoplastic polyester resin bottle by biaxial stretch blow molding, comprising: after blow molding, while continuously applying an internal pressure in the bottle, and maintaining a molding die at a high temperature. By heat-treating the molded bottle and then partially discharging the high-pressure gaseous cooling medium into the bottle while blowing it, the cooling medium is circulated while keeping the inside of the bottle at high pressure to cool the bottle inner wall, While continuing the blowing of the cooling medium, the cooling medium was discharged at once from the mouth of the molding bottle, and then the blowing of the cooling medium was stopped, and the molding die was opened substantially at the same time as the stop. And removing the bottle. 2. The gaseous cooling medium blown into the molded bottle has a high pressure of 25 kg / cm ² (gauge pressure) or more.
The described method.