JPH081760A - Method for manufacturing biaxially stretched blow container - Google Patents

Abstract

(57) [Abstract] [Purpose] The shape of the secondary molded product molded by the free-blow molding method can be stabilized and made closer to the shape of the final molded product. An object of the present invention is to provide a manufacturing method capable of manufacturing a biaxially stretched blow container having excellent pressure characteristics. [Structure] In a method for manufacturing a biaxially stretched blow container, a mouth of a preform 1 heated to a stretching temperature is replaced with a mouth holder 2.
While holding the drawing rod 3 inserted into the preform and the pressing rod 4 outside the preform, the drawing rod 3 is driven in the bottom direction while the center of the bottom of the preform is sandwiched and the sandwiched state is maintained. Further, it is characterized in that the preform is free-blow-molded by blowing a fluid into the preform in a state where the periphery of the preform is not restrained to the final stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a biaxially stretched blow container, and more particularly to a biaxially blown container capable of providing a molded article excellent in heat resistance or heat and pressure resistance by utilizing a free blow molding method. The present invention relates to a method for manufacturing a stretch blow container.

[0002]

2. Description of the Related Art Conventionally, the two-stage blow molding method has been adopted for molding biaxially stretched plastic bottles, and usually a step of primary blow molding a preform molded product using a mold, and the resulting molded product. Is heated in an oven or the like to shrink and crystallize, so-called heat setting step, and the heat-shrinked molded article is subjected to secondary blow molding using a mold to obtain a final shape. In the two-stage blow molding method, the primary blow molding is sufficiently stretched at a draw ratio of about 2 to 5 times, and the stretched secondary molded article is sufficiently shrunk to about 60 to 90% by heat setting to give a bottle Since the rigidity can be improved and the heat resistance can be imparted by the intermediate heating method, it is suitable for a method for manufacturing a stretch blow-molded container for heat resistance.

As blow molding means, a die blow molding method using a die and a free blow molding method in which only the vicinity of the mouth of a preform molded article is constrained to perform blow molding without using a die are known. As a primary blow molding means for two-step blow molding, a mold blow molding method is generally adopted (Japanese Patent Laid-Open No. 63-189224, etc.), and two-step blow molding using a free blow molding method. There is not much molding. However, the free-blow molding method does not require the use of a mold, and therefore has the advantage that cooling of the molded product due to contact with the mold is prevented and that the heat setting process can be easily contacted.
There is a demand for two-step blow molding by adopting a free blow molding method.

[0004]

While the free-blow molding method has the above advantages, it is difficult to stabilize the shape of the secondary molded product obtained because a mold is not used. Especially, the shape near the neck is greatly bent, and the central axis When a secondary molded product with a deviation is formed, there is a problem that it is difficult to insert it because it does not match the shape of the secondary blow molding die. In addition, the bottom shape of the secondary molded product obtained by the free blow molding method is usually a dome shape, and when heat setting and heat shrinking are performed with the shape as it is, a concave bottom shape is formed in the next secondary blow molding process. In order to obtain the final molded product, the amount of secondary blow molding at the bottom becomes considerably large, and in the part where the stretch processing rate is large, such as the bottom corner, the wall thickness becomes locally thin and the strength decreases. Further, there is a problem that the crystallinity is lowered and the heat resistance is not obtained. Therefore, an object of the present invention is to provide a method for producing a biaxially stretched blow container capable of stabilizing the shape of a secondary molded product molded by a free blow molding method and approximating the shape of a final molded product. To provide.

According to the present invention, the mouth of the preform heated to the stretching temperature is held by the mouth holder, and the preform is inserted between the drawing rod and the pressing rod outside the preform. The center of the bottom of the preform is sandwiched and the stretched rod is driven toward the bottom while maintaining the sandwiched state, and a fluid is blown into the preform while the periphery of the preform is not constrained to the final stage, and the preform is free-blow molded. A method for producing a biaxially stretched blow container is provided, which comprises heat-shrinking the obtained secondary molded product, and then performing secondary blow molding in a blow mold to obtain a final container.

[0006]

In the method for producing a biaxially stretch blow-molded container according to the present invention, the preform is composed of a stretch rod inserted inside the preform molded article and a pressing rod placed at the center of the bottom outside the preform. Free blow molding is performed while driving the stretch rod in the bottom direction while sandwiching the bottom part and restraining the center part of the bottom part, so the center part of the bottom part is prevented from coming off the axis of the preform, and the vicinity of the neck part does not bend. It is possible to obtain a relatively stable shape.

In order to obtain a final molded product having excellent heat resistance and heat pressure resistance, it is necessary to reduce the processing rate in the secondary blow molding as much as possible, especially because the bottom has a large processing amount.
It is preferable that the secondary molded product to be subjected to the secondary blow molding has a shape close to the final molded product. Generally, in heat-resistant containers, the one with the center part of the bottom part dented inward is usually used, but in the conventional free blow molding method the bottom part becomes a dome shape, and such a shape changes from the final shape to the final shape. When secondary blow molding was performed up to this point, there were drawbacks such as an increase in the amount of processing especially at the bottom corners and a uniform wall thickness could not be obtained, but in the present invention, free blow molding is utilized to obtain such a shape. It is also possible to mold a secondary molded product.

That is, the drawing rod is raised by a driving means having a driving source such as pneumatic pressure or a motor in synchronism with blow molding, while the pressing rod is kept pressed down by air or the like. It rises according to the rise of the drawing rod,
The bottom shape having the above-described shape can be obtained because the stretching rod and the pressing rod expand while controlling the center of the bottom portion. In particular, in the free-blow molding of the bottom with the center of the bottom dented inward, the driving speed of the drawing rod at the final stage of free blow or in the vicinity of the final stage is set to a speed slightly lower than the axial expansion speed of the preform Due to this, since the degree of expansion of the bottom center sandwiched between the stretch rod and the pressing rod and the bottom portion other than that portion is different, it is possible to finally form the bottom center portion in which the bottom center is indented more inward than the bottom bottom portion. You can do it.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of the manufacturing process of the present invention. In FIG. 1, a preform molded product 1 (FIG. 1A) molded by injection molding or the like has its neck fixed by a fixture 2. The drawing rod 3 is inserted into the preform 1 from the lower side of the drawing, and its tip is in contact with the center of the bottom so as to pass through the axis of the preform 1. On the other hand, from the upper part of the drawing, the pressing rod 4 is raised in accordance with the rise of the stretch rod 3 in a state in which the center of the bottom portion of the preform is biased, and the center of the bottom portion of the preform 1 is the stretch rod 3 and the pressing rod 4. It is sandwiched between. The stretching rod 3 is provided with a pressing rod 4 so as to be synchronized with blow molding by a driving means (not shown) having a driving source such as pneumatic pressure or a motor.
Are arranged so as to be vertically movable by utilizing air pressure or springs. Moreover, the preform 1 is heated to a temperature (about 90 to 110 ° C.) at which it can be stretched.

FIG. 1 (B) is an enlarged view showing the vicinity of the bottom of the preform of FIG. 1 (A). In the example shown in FIG. 1, the pressing rod 4 has a convex tip portion and is heated to a temperature equal to or higher than the molding temperature of the preform molded product (about 80 to 1).
40 ° C.), on the other hand, the tip of the drawing rod 3 is made of a heat insulating material. Free-blow molding is performed by pressing the pressing rod 4 against the center of the bottom of the preform molded product 1 and biting the convex tip 5 into the center of the bottom. As a result, it is possible to surely prevent the runout of the molded product in the free blow molding.
In the secondary molded product 6 thus obtained, the restraint portion sandwiched by the stretch rod and the pressure rod at the center of the bottom remains almost unstretched, but can be thinned by the secondary blow molding. It is possible to reduce the wall thickness to the maximum extent equivalent to the stretched portion around it.

FIG. 1 (C) is a diagram showing a state in which a fluid is blown into the preform 1 from the state of FIG. 1 (A) and the stretching rod is raised to stretch the preform. When the stretching progresses, the blow pressure is released, the stretching rod and the pressing rod are removed, and the free-blow molding is finished, a secondary molded product 6 having a slightly dome-shaped bottom is obtained (FIG. 1 (D)). . At the time of primary blow molding, the thickness of the body and the bottom of the secondary molded product is substantially 0.6 mm or less, preferably 0.2 to 0.5, except for the unstretched portion at the center of the bottom and the vicinity of the neck.
When the thickness is set to mm, it becomes possible to perform the subsequent shrinkage heating and heating in the heat setting step in a short time. When the thickness of the heated portion exceeds 0.6 mm, the temperature distribution in the thickness direction becomes too large when heated for a short time, and it becomes difficult to keep the temperature within the preferable temperature range. In the primary blow molding, the axial draw ratio is 2 to 5 times, particularly 2.2 to 4 times, and the circumferential draw ratio is 2.5 to 6.6 times, especially 3 to 6 times. Good. In this case, the draw ratios in the axial direction and the circumferential direction are determined according to the shape and heating temperature of the preform molded product, and the blow conditions such as the blow molding pressure or the drawing form with the drawing rod. Further, it is preferable that the pressure of the fluid in the free blow molding is usually within the range of ^{2 to} 10 kg / cm ² .

Next, the secondary molded product thus obtained is heated and shrunk. In this case, the shape of the secondary molded product after heat shrinkage should be sufficiently housed in the next secondary blow molding die, and close to the final product shape so that the processing rate in the secondary blow molding should be as small as possible. Is important, and it is particularly preferable that the shape of the bottom is flat or concave to secure the bottom diameter to some extent. In the present invention, the dome-shaped bottom portion of the secondary molded product 6 obtained by free blow molding is shown in FIG.
As shown in (E), by providing a heating body 7 facing the bottom of the secondary molded product 6 to preferentially heat-shrink the bottom, the bottom has a flat plate shape and the bottom diameter is equal to that of the secondary molded product 6. It is possible to obtain the tertiary molded product 8 that hardly changes. Furthermore, FIG.
As shown in (F), by heating and shrinking the whole of the tertiary molded product 8 in the tunnel-shaped heating body 9, the bottom has a flat plate shape, and the quaternary shape is such that the trunk is mainly shrunk. A molded product 10 is obtained.

In these heating and shrinking steps, various means such as a heating method using hot air or a solid contact heating method in which a flat heating element is pressed by a dome-shaped top to heat it are used. However, the infrared heating method is particularly preferable in the present invention.
In the infrared heating method, compared to heating by heat conduction from the surface using hot air, part of infrared rays penetrates and is absorbed inside the plastic, so that heating can be performed relatively efficiently. In addition, the target heating can be carried out in a relatively short time of about 1 to 15 seconds by allowing the tertiary molded product to pass while rotating while passing through a tunnel-shaped heating body in which planar infrared radiators are combined.

The temperature at which shrinkage begins by heating depends on the stretching conditions of free blow molding, the temperature at the time when the internal pressure of the secondary molded product molded by free blow molding is released, etc., and is usually about 100 to 140 ° C. To start contraction. The molding temperature at which blow molding is possible in the secondary blow molding is usually 80 to 11.
The temperature is 0 ° C or higher, and the secondary molded product is heated to the shrinking temperature and the stretching temperature or higher. In the case of a heat-resistant container, it is preferable to finally heat the body and bottom of the secondary molded product to a temperature of about 130 to 220 ° C. and to perform a heat setting step of sufficiently performing thermal crystallization. On the other hand, in the heat-resistant pressure container, sufficient heat resistance can be secured by performing free blow molding, and in the secondary blow molding, stretch molding for adjusting the shape is sufficient. For this reason, in the heating step, the body may be held only at a temperature at which it can be stretched (about 90 to 140 ° C).

The heat-set quaternary molded product is crystallized and the residual stress is relaxed while the container is contracted. Further, the temperature is slightly cooled before the secondary blow molding process, and the temperature difference between the inner and outer surfaces is relaxed by the heat conduction effect in the thickness direction. Usually, a relaxation time of about 0.3 to 3 seconds is provided. In the secondary blow molding process, as shown in FIG.
As shown in (A), the quaternary molded product 10 that has been heated is stretch blow-molded using the mold 11. Such secondary blow molding is preferably performed using a gas pressure of 15 to 40 kg / cm ² . Furthermore, for containers that require heat resistance, maintain the mold temperature at about 70 to 130 ° C,
It is preferable to prevent rapid cooling of the molded product during the secondary blow molding. The obtained final molded product is shown in FIG.

FIG. 3 is a view showing an embodiment of an apparatus for producing a biaxially stretched blow container by the method of the present invention,
In the primary blow molding process by the free blow molding method indicated by 11 in its entirety, the preform 12 is supplied to the primary blow molding process 11 to perform blow molding. Next, the secondary molded product 13 is a pair of infrared heating members 14 facing the body.
a, 14b, and a heat setting step 15 including a tunnel-shaped heating device formed of a planar infrared heating element (not shown) facing the bottom. As a result, the secondary molded product 13 first shrinks in the form of a flat plate at the bottom, then the body shrinks in the height direction and in the radial direction, and is finally heated to the crystallization temperature to become the quaternary molded product 16. . Next, the quaternary molded product 16 is supplied to the secondary blow mold 18 in the secondary blow molding process indicated by 17 in its entirety, and is secondary blow molded to be taken out as the final molded product 19. In this device,
The above-mentioned first bottom heating (FIG. 1 (E)) and second body and bottom heating (FIG. 1 (F)) are tunnel-like in cross section similar to FIG. Infrared heating device 1
It is performed by moving the secondary molded product 13 in 5 while rotating. Each infrared heating element that constitutes the infrared heating device is divided into several parts on the circumference and the temperature can be adjusted, and the temperature rise of the bottom of the secondary molded product is higher than the temperature rise of the body. It is controlled to grow. As a result, firstly, the bottom portion shrinks into a flat plate shape, secondly the barrel portion shrinks, and finally the barrel portion and the bottom portion reach a predetermined crystallization temperature.

In the method of the present invention, various modifications can be added to the above-mentioned basic steps. FIG. 4 shows an example using a pressing rod having a concave tip. FIG. 4 (A)
FIG. 3 is an enlarged view showing the vicinity of the bottom portion of the preform, in which the center of the bottom portion of the preform 1 is sandwiched by the stretching rod 3 and the pressing rod 4. A recess 20 is formed at the tip of the pressing rod 4. From this state, free blow molding is performed while pressing the concave portion 20 of the pressing rod 4 to form a secondary molded product. As shown in FIG. 4 (B), the secondary molded product 6 has an unstretched thick portion 21 formed at the center of the bottom. In order to preferentially heat-shrink the bottom portion of the secondary molded product 6, the secondary molded product 6 is heated by the heating body 7 as shown in FIG.
When heating the bottom portion of the sheet, the bottom portion is kept sandwiched by the pressing rod 4 and the stretching rod 3, and the bottom portion is heated while pressing the center of the bottom portion with the pressing rod.
It is possible to mold a tertiary molded product 8 having a dented portion 1 and a flat bottom around its periphery (FIG. 4 (D)). Next, as shown in FIG. 4 (E), the body and the bottom of the tertiary molded product 8 are heated to crystallize. At this time, by heating while sandwiching the central portion of the bottom portion with the stretching rod 3 and the pressing rod 4, it is possible to effectively prevent the molded product from collapsing or bending during heating. In this case, following the contraction of the molded product, the pressing rod 4 is driven and lowered, while the stretching rod 3 is moved upward in a biased state in accordance with the movement of the pressing rod 4. The quaternary molded product 10 thus obtained is subjected to the same secondary blow molding as described above to obtain a final molded product.

Further, as shown in FIG. 5, in order to provide a recess at the center of the bottom of the secondary molded product in the free blow molding process, it can also be formed by controlling the driving speed of the pressing rod and the stretching rod. That is, by making the driving speed of the pressing rod and the stretching rod slightly slower than the ascending speed of the bottom peripheral portion by blow molding, it is possible to obtain a secondary molded product having a dent in the bottom central portion. In this case, if the upward driving speed of the stretching rod 3 and the pressing rod 4 is extremely slower than the blowing speed, the rising speed of the peripheral portion of the bottom is also restricted and the vicinity of the neck portion swells due to the action of the blowing pressure. Therefore, it is necessary to adjust the rising speed of the stretching rod 3 and the pressing rod 4 so that the vicinity 22 of the neck portion does not bulge too much (FIG. 5 (A)). Also, if the dent in the center of the bottom of the secondary molded product 6 is increased,
Since the difference in the thickness distribution of the bottom portion becomes large and a thin portion is easily formed, it is preferable to make the dent in the center portion of the bottom extremely small. In that case, as shown in FIG. 5 (B), by providing an unstretched thick portion 21 in the center of the bottom,
And, the crystallized quaternary molded product having a preferable shape can be obtained by the heating means shown in FIG.

FIG. 6 shows an example of the structure of the pressing rod. In this example, the pressing rod 4 is composed of the pressing rod 4 having a convex tip, a supporting plate 23 provided so as to surround the pressing rod 4, and a spring 24 for biasing the supporting plate downward. When the free-blow molding is performed while pressing the center of the bottom with the pressing rod, the convex portion of the peripheral portion of the bottom may bulge locally. However, as in the example shown in FIG.
In the case of being provided in the periphery of the, the support plate 23 lightly presses the convex portion, so that by raising the pressing rod 4 and the support plate 23, the convex portion in the peripheral portion of the bottom is circumferentially crossed. Can be uniform. The support plate 23 is usually maintained at a temperature at which blow molding can be performed (90 ° C. or higher), and it is also possible to heat the molded product component that comes into contact with the support plate 23. The secondary molded product 6 whose bottom has been heated can be contracted and crystallized by relatively uniform heating, and a crystallized tertiary molded product 8 having a preferable shape as shown in FIG. 6D is obtained. It becomes possible.

In the present invention, as the plastic,
Any plastic can be used as long as it can be stretch-blow molded and heat-set, but thermoplastic polyester, particularly ethylene terephthalate-based thermoplastic polyester, is advantageously used. Of course, polycarbonate, arylate resin, or the like can also be used. As the ethylene terephthalate thermoplastic polyester, ethylene terephthalate units occupy most of the ester repeating units, generally 70 mol% or more, and particularly 80 mol% or more,
Glass transition point (Tg) of 50 to 90 ° C, especially 55 to 80 ° C, and melting point (Tm) of 200 to 275 ° C, especially 2
Thermoplastic polyesters at 20 to 270 ° C. are preferred. Homopolyethylene terephthalate is preferable in terms of heat resistance, but a copolymerized polyester containing a small amount of ester units other than ethylene terephthalate units can also be used.

Dibasic acids other than terephthalic acid include aromatic dicarfonic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; succinic acid, adipic acid, sebacic acid and todecanedione. One or a combination of two or more kinds of aliphatic dicarboxylic acids such as acids, and examples of diol components other than ethylene glycol include propylene glycol, 1,4-butanediol, diethylene glycol,
One or two or more of 1,6-hexylene glycol, cyclohexanedimethanol, and an ethylene oxide adduct of bisphenol A can be used.

The ethylene terephthalate type thermoplastic polyester used should have at least a molecular weight sufficient to form a film, and an injection grade or an extrusion grade is used depending on the application. This intrinsic viscosity (IV) is generally from 0.6 to 1.4 dl / g, especially from 0.
Those in the range of 63 to 1.3 dl / g are preferable.

Injection molding can be used for molding the plastic preform. That is, the plastic is melt-injected into a cooled injection mold and cooled to form an amorphous plastic preform. An injection machine known per se equipped with an injection plunger or a screw is used, and the mixture is injected into an injection mold through a nozzle, a sprue, and a gate. As a result, polyester or the like flows into the injection mold cavity and is solidified into a preform for stretch blow molding. As the injection type, one having a cavity corresponding to the shape of the container is used, but it is preferable to use a one-gate type or multi-gate type injector. Injection temperature is 270 to 310
The temperature and pressure are preferably 28 to 110 kg / cm ² .

[0024]

EXAMPLE The outer diameter of the final molded product was 94 using the apparatus of FIG.
A heat-resistant polyethylene terephthalate (PET) bottle having a total height of 305 mm, a total height of 305 mm (heating part height of 280 mm), a capacity of 1500 ml, and a concave bottom portion was prepared as shown in FIG. 2 (B). A given preform is heated to 100 ° C, the preform mouth is fixed with a fixture, and the inside of the preform has a Teflon stretch rod and a convex tip.
A fluid having an internal pressure of 3 kg / cm ² was blown into the preform while sandwiching the center of the bottom of the preform with a pressing rod heated to 00 ° C. to perform free blow molding to obtain a secondary molded product. The obtained secondary molded product has a dome-shaped bottom shape with a relatively uniform thickness in which the center of the bottom is stretched,
It had a stable shape with substantially no neck bending and no axial misalignment.

The secondary molded product is divided into three zones on the circumference, and each part is allowed to pass for 6 seconds while rotating in a tunnel-shaped infrared heating body whose temperature is controlled within a surface temperature of 500 to 700 ° C. As a result, firstly a quaternary molded product in which the bottom part contracts into a substantially flat plate shape, secondly the body part contracts in the height and radial directions, and finally the temperature of the body part and the bottom part is about 180 ° C. Obtained. This quaternary molded product was subjected to secondary blow molding to obtain a final product. The final product was filled with hot water at 95 ° C., and heat resistance was evaluated from the rate of change in volume (good range: rate of change in volume of 2% or less), and good results were obtained.

[0026]

According to the present invention, when the primary blow molding is carried out by utilizing the free blow molding method, the obtained secondary molded article may be largely bent at the neck portion and the axis may be displaced. The secondary molded product can be heat-shrinked into a more preferable form without heat loss, and the heated secondary molded product (tertiary molded product or quaternary molded product) is subjected to secondary blow molding to provide heat resistance. It was possible to manufacture a biaxially stretched blow molded container having excellent properties and heat and pressure resistance. In addition, since the primary blow molding is based on the free blow molding method,
Since it is not necessary to use a mold, cooling of the molded product due to contact with the mold is prevented, and there is an advantage that the heat setting process can be easily contacted. Further, the strength in the vicinity of the bottom of the molded container is improved, and since there is no local thin wall portion and the wall thickness distribution is relatively uniform, it is possible to reduce the basis weight.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a molding process of the present invention.

FIG. 2 is a diagram for explaining an example of a secondary blow molding process that is a continuation of the molding process of FIG.

FIG. 3 is an overall layout diagram of an example of a manufacturing apparatus for carrying out the method of the present invention.

FIG. 4 is a diagram illustrating a molding process using another example of the pressing rod.

FIG. 5 is a diagram illustrating another example of the method of the present invention.

FIG. 6 is a diagram illustrating a molding process using another example of the pressing rod.

[Description of sign]

 1 Preform 2 Mouth Holder 3 Stretching Rod 4 Pressing Rod 5 Convex 6 Secondary Molded Product 7, 9 Heated Body 8 Tertiary Molded Product 10 Fourth Molded Product 11 Mold

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[Procedure amendment]

[Submission date] September 4, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

In order to obtain a final molded product having excellent heat resistance and heat pressure resistance, it is necessary to reduce the processing rate in the secondary blow molding as much as possible, especially because the bottom has a large processing amount.
It is preferable that the secondary molded product to be subjected to the secondary blow molding has a shape close to the final molded product. Generally, in heat-resistant containers, the one with the center part of the bottom part dented inward is usually used, but in the conventional free blow molding method the bottom part becomes a dome shape, and such a shape changes from the final shape to the final shape. until disadvantage of such processing amount can not be obtained a uniform thickness increases in particular the bottom corner when the secondary blow molding has occurred, by using a free blow molding in the present invention, the bottom central portion It is also possible to mold a secondary molded product having an inwardly concave shape.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Next, the secondary molded product thus obtained is heated and shrunk. In this case, the shape of the secondary molded product after heat shrinkage should be sufficiently stored in the next secondary blow molding die, and close to the final product shape so that the processing rate in the secondary blow molding is minimized. Is important,
In particular, it is preferable that the bottom portion has a flat plate shape or a concave shape to secure the bottom diameter to some extent. In the present invention, the dome-shaped bottom portion of the secondary molded product 6 obtained by free blow molding is provided with a heating body 7 facing the bottom portion of the secondary molded product 6 as shown in FIG. By heat-shrinking, it is possible to obtain a tertiary molded product 8 having a flat bottom and a bottom diameter which is almost the same as that of the secondary molded product 6. Furthermore, FIG.
As shown in (F), by causing heat shrinking the overall tertiary molded article 8 in the tunnel-like heating body 9, the bottom is flat, quaternary mainly shaped as the body portion is deflated A molded product 10 is obtained.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

The quaternary molded article heat set is completed, both the shrinkage of the container is being performed, is crystallized, residual stress is relaxed. Further, the temperature is slightly cooled before the secondary blow molding process, and the temperature difference between the inner and outer surfaces is relaxed by the heat conduction effect in the thickness direction. Usually, a relaxation time of about 0.3 to 3 seconds is provided. In the secondary blow molding process, as shown in FIG.
As shown in (A), the mold 18 is used to stretch blow mold the quaternary molded product 10 that has been heated. Such secondary blow molding is preferably performed using a gas pressure of 15 to 40 kg / cm ² . Furthermore, for containers that require heat resistance, maintain the mold temperature at about 70 to 130 ° C,
It is preferable to prevent rapid cooling of the molded product during the secondary blow molding. The obtained final molded product is shown in FIG.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

In the method of the present invention, various modifications can be added to the above-mentioned basic steps. FIG. 4 shows an example using a pressing rod having a concave tip. FIG. 4 (A)
FIG. 3 is an enlarged view showing the vicinity of the bottom portion of the preform, in which the center of the bottom portion of the preform 1 is sandwiched by the stretching rod 3 and the pressing rod 4. A recess 20 is formed at the tip of the pressing rod 4. From this state, free blow molding is performed while pressing the concave portion 20 of the pressing rod 4 to form a secondary molded product. As shown in FIG. 4B, the secondary molded product 6 has a substantially unstretched thick portion 21 formed at the center of the bottom. In order to preferentially heat-shrink the bottom of the secondary molded product 6, when the bottom of the secondary molded product 6 is heated by the heating body 7 as shown in FIG. By pressing the center of the bottom portion with the pressing rod while keeping the bottom portion sandwiched by 3 and heating the bottom portion, the unstretched portion 21 in the central portion is dented, and the periphery thereof has a flat bottom shape. 8 can be molded (FIG. 4 (D)).
Next, as shown in FIG. 4 (E), the body and the bottom of the tertiary molded product 8 are heated to crystallize. At this time, the drawing rod 3
Also, by heating while sandwiching the central portion of the bottom portion with the pressing rod 4, it is possible to effectively prevent the molded product from falling or bending during heating. In this case, following the contraction of the molded product, the pressing rod 4 is driven and lowered, while the stretching rod 3 is moved upward in a biased state in accordance with the movement of the pressing rod 4. The quaternary molded product 10 thus obtained is subjected to the same secondary blow molding as described above to obtain a final molded product.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Further, as shown in FIG. 5, in order to provide a recess at the center of the bottom of the secondary molded product in the free blow molding process, it can also be formed by controlling the driving speed of the pressing rod and the stretching rod. That is, by making the driving speed of the pressing rod and the stretching rod slightly slower than the ascending speed of the bottom peripheral portion by blow molding, it is possible to obtain a secondary molded product having a dent in the bottom central portion. In this case, if the upward driving speed of the stretching rod 3 and the pressing rod 4 is extremely slower than the blowing speed, the rising speed of the peripheral portion of the bottom is also restricted and the vicinity of the neck portion swells due to the action of the blowing pressure. Therefore, it is necessary to adjust the rising speed of the stretching rod 3 and the pressing rod 4 so that the vicinity 22 of the neck portion does not bulge too much (FIG. 5 (A)). Also, if the dent in the center of the bottom of the secondary molded product 6 is increased,
Since the difference in the thickness distribution of the bottom portion becomes large and a thin portion is easily formed, it is preferable to make the dent in the center portion of the bottom extremely small. In that case, by providing a substantially unstretched thick portion 21 in the central portion of the bottom as shown in FIG. 5B, the heating means shown in FIGS. It is possible to obtain a quaternized molded product.

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Settsuko Nakamaki 25 Sachigaoka, Asahi-ku, Yokohama-shi, Kanagawa (72) Inventor Kimio Takeuchi 2297-5 Nogawa, Misaki-ku, Kawasaki-shi, Kanagawa (72) Hideo Kurashima, Kanagawa 3-26-16 Iwato, Yokosuka City (72) Inventor Yoshitsugu Maruhashi 6-35-5 Hiyoshihoncho, Kohoku Ward, Yokohama City, Kanagawa Prefecture

Claims (3)

[Claims] 1. The mouth of a preform heated to a drawing temperature is held by a mouth holder, and the bottom center of the preform is held by a drawing rod inserted inside the preform and a pressing rod outside the preform. The stretch rod is driven in the bottom direction while being sandwiched and maintained in a sandwiched state, and a fluid is blown into the preform in a state where the periphery of the preform is not constrained to the final stage, and the preform is free-blow molded to obtain A method for producing a biaxially stretched blow container, which comprises heat-shrinking a next molded product, and then performing secondary blow molding in a blow mold to obtain a final container. 2. The drive speed of the draw bar at the final stage of free blow molding or in the vicinity of the final stage is set to a speed slightly lower than the axial expansion speed of the preform, whereby the bottom of the blow molded product is lower than the bottom bottom. The manufacturing method according to claim 1, wherein a center portion of the bottom that is recessed inward is formed. 3. A pressing rod having a convex tip and being heated to a temperature equal to or higher than the stretching temperature of the preform is used, and the convex tip is cut into the center of the bottom of the preform so that the center of the bottom is also The manufacturing method according to claim 1, wherein the manufacturing method is thin.