JPH0811198A - Apparatus and method for crystallizing bottom part of resin bottle - Google Patents

Abstract

PURPOSE:To heat the bottom part of a resin bottle after blow molding without collapsing the shape of the bottle to crystallize the same. CONSTITUTION:A bottom part crystallizing apparatus consists of a bottom mold 1 having the same mold shape as the bottom mold at the time of the blow molding of a resin bottle and a high pressure air supply device 2 and the resin bottle is received in the bottom mold 1 while the inner pressure thereof is held to 2-40kgf/cm<2> by the high pressure air supply device 2 to be heated to 100-200 deg.C to crystallize the bottom part of the bottle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for crystallizing the bottom of a pressure-resistant plastic container having a so-called petaloid bottom and capable of standing upright without using a base cup.

[0002]

A biaxially stretched blow molded container made of a saturated polyester resin represented by polyethylene terephthalate has a very excellent transparency and surface gloss, and is beautiful and has a gas barrier. Excellent in water resistance, water impermeability, content resistance, and storage stability. In addition, it has many advantages such as low heat generation during combustion and easy disposal because it does not damage the furnace. Therefore, it is widely used for various drinking water, seasonings, containers for liquor and other foods.

When such a biaxially stretched blow molded container (bottle) is used as a container for fruit juice or milky carbonated beverage, it is obliged to carry out heat sterilization. The heat sterilization is usually performed for 10 minutes or more under the condition that the cold spot becomes 65 ° C., and is called a past-riding process. In order to prevent deformation even after this past-riding step, the bottom of the container must be sufficiently stretched. For this reason, biaxially stretched blow-molded containers whose bottoms are stretched spherically are widely used. In the case of a biaxially stretch blow molded container having such a spherical bottom, a so-called base cup is attached to the bottom in order to impart self-supporting property to the container.

The above-mentioned container with a base cup is excellent in self-sustaining stability, and the bottom is reinforced, but since the process of mounting the base cup in a separate process and then attaching it to the container body increases, the productivity is improved. Inferior. In addition, since the base cup is usually molded with a resin different from that of the container body, the container equipped with the base cup is inferior in recyclability.

Therefore, a container having a structure in which various irregularities are formed on the bottom of the container to reinforce the bottom of the container and at the same time, self-standing stability is ensured without a base cup, has been developed and put into practical use. The self-supporting stable biaxially stretch blow molded container has a so-called petaloid-shaped bottom portion, and the bottom portion includes a central portion, a plurality of legs, and a valley portion existing between the legs.

However, in the case of a self-standing container, it is difficult to uniformly stretch the bottom portion, and unstretched portions or insufficiently stretched portions are likely to remain in the central portion and the valley portions. When this unevenly stretched portion or unstretched portion is exposed to a high temperature in the pasteurizing step, it swells due to insufficient heat resistance and causes uneven deformation in the ground contact portion, impairing the self-supporting stability of the container. .

Therefore, in a pressure resistant container of integral molding type which does not use a base cup, it has been proposed that after blow molding, the bottom part of the bottle is heated and held to crystallize the bottom part to improve heat resistance. However, if the material is heated enough to crystallize it, the material softens, and there is a problem that the shape of the bottom part of the material collapses during heating and the self-sustained stability is lost.

Accordingly, it is an object of the present invention to provide an apparatus and method for crystallizing the bottom of a bottle after blow molding so as not to disturb the shape of the bottle.

[0009]

As a result of earnest research to solve the above problems, the present inventors have found that the internal pressure of the bottle is maintained while the bottom of the bottle is held in the bottom mold cavity having the same shape as the bottom of the bottle. The present invention has been completed based on the idea that it is possible to crystallize while maintaining the shape of the bottom of the bottle by heating with the temperature raised.

That is, the bottom crystallization apparatus for a resin bottle of the present invention has a bottom mold having the same shape as the blow mold bottom mold of the resin bottle and having a heater, and the pressure inside the bottle is kept high. And a high-pressure gas supply device that operates.

In the bottom crystallization method of the present invention, the bottom mold is held in close contact with the bottom mold, and the pressure inside the bottle is adjusted to 2 to 10.
It is characterized in that the bottle is heated to 100 to 180 ° C. with a bottom mold equipped with the heater while being raised and maintained at 40 kgf / cm ² .

[0012]

The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a partial sectional front view of a bottom crystallization device for a resin bottle according to a first embodiment of the present invention. The bottom crystallization device for a resin bottle according to this embodiment comprises a bottom mold 1 equipped with a heater and a high-pressure gas supply device 2. The cavity 1a of the bottom mold 1 has the same shape as the bottom mold at the time of blow molding of the bottle. The high pressure gas supply device 2 includes a mouth tightening jig 21, a gas introduction pipe 23, a valve 25, a valve 27, and a regulator 26.
And a high pressure gas supply source 28, and an exhaust pipe 23 equipped with a valve (not shown) is attached to the jig 21. A gas flow passage 22 is formed inside the mouth tightening jig 21, and the gas supplied from the high-pressure gas supply source 28 is supplied to the inside of the bottle 3 via the gas introduction pipe 23 and the gas flow passage 22. To be done.

The bottom part of the resin bottle is crystallized by the following steps using the above-mentioned bottom part crystallization device for the resin bottle. (a) The bottle 3 is housed in the bottom mold 1 equipped with a heater and fixed by an appropriate means. (b) Fix the mouth tightening jig 21 to the mouth of the bottle 3 in an airtight state. (c) The gas from the high pressure gas supply source 28 is adjusted by the valves 25 and 27,
The internal pressure of the bottle 3 is maintained at ² to 40 kgf / cm ² . It is preferably maintained at ² to 10 kgf / cm ² . (d) Heat the bottom of the bottle closely accommodated in the bottom mold 1. The bottom mold 1 equipped with a heater is kept at an optimum crystallization temperature, specifically 100 to 200 ° C, preferably 120 to 180 ° C.
To The holding time may be 1 to 2 minutes. (e) After the crystallization is completed, the valve of the exhaust pipe 29 is opened, and the cooling blow gas is blown into the bottle from the high pressure gas supply source 28.
The heating gas and the cooling gas may be supplied from different devices, and may be switched by an appropriate valve. Due to the cooling blow, heat remains at the bottom of the heat-treated bottle,
It can be prevented from being deformed after being taken out of the mold. (f) After completion of the cooling blow, the bottle 3 is taken out from the bottom mold 1.

In the method of this embodiment, since the inside of the bottle is positive pressure during heating, the bottom portion is pressed against the bottom mold 1 and is kept in the shape at the time of molding even if the material is softened. Is prevented.

FIG. 2 is a front view of a bottom crystallization apparatus for a resin bottle according to a second embodiment of the present invention, which has the same mold shape as the bottom mold at the time of blow molding of the bottle as in the first embodiment. It comprises a bottom mold 1 equipped with a heater and a high-pressure gas supply device 2. Here, the high pressure gas supply device 2 is a mouth tightening jig.
21, a gas introduction pipe 23, an exhaust pipe 24, and a high-pressure gas supply source 28. The gas introduction pipe 23 includes a valve 25, and the exhaust pipe 24 includes a valve 27 and a regulator 26. Using the bottom crystallization device for a resin bottle, the bottle is heated in the same steps and conditions as the steps (a) to (d) of the first embodiment. The values in parentheses show the opened / closed states of the valves 25 and 27 in the process. (a) Fixing the bottle. (b) Fix the mouth tightening jig 21 to the bottle 3. (c) The internal pressure of the bottle is increased and maintained under the same conditions as in the first embodiment. (Opening-side valve 25 open, exhaust-side valve 27 closed) (d) The bottle is housed in the bottom mold 1. (e) The bottom of the bottle is heated under the same conditions as in the first example.
(Open the inlet valve 25 and close the exhaust valve 27) (f) After heating, release the internal pressure of the bottle. (Introduction valve
25 Closed, exhaust side valve 27 open) (g) When the bottle reaches a certain pressure, introduce air into the bottle and let it flow. (Inlet valve 25 open, Exhaust valve 27
Open) At this time, the air pressure on the inlet side is set to be higher than the pressure on the exhaust side. (h) When the bottle is sufficiently cooled, take it out from the bottom mold 1.

According to the method of this embodiment, the deformation of the bottle during heating can be prevented as in the first embodiment, and the deformation of the bottle due to the residual heat after taking out the bottle from the bottom mold can be prevented.

In the third embodiment of the present invention, a device for carrying and appropriately fixing the bottle 3 and a device for separately raising and lowering the bottom mold 1 having the mouth tightening jig 21 and the heater are added to the second embodiment. The temperature condition, the pressure condition, and the valve operation are the same as those in the second embodiment. In this example, crystallization can be continuously performed in the following steps. (a) Bring in and fix the bottle. (b) The mouth tightening jig 21 descends and is fixed to the bottle 3. (c) Increase and maintain the internal pressure of the bottle 3. (d) Raise the bottom mold 1 to accommodate the bottom of the bottle. (e) Heat the bottom of the bottle. (f) Release the bottle pressure. (g) Cool the bottle by passing air through it. (h) Lower the bottom mold 1. (i) Remove the mouth tightening jig 21 from the bottle and raise it. (j) Remove the bottle and bring in the next bottle.

According to the method of this embodiment, similarly to the second embodiment, the deformation of the bottle during heating and the deformation of the bottle due to the residual heat after taking out the bottle from the bottom mold can be prevented, and the crystallization can be continuously performed. Can be done.

The present invention has been described above with reference to the accompanying drawings. However, the present invention is not limited to this, and various modifications can be made without departing from the idea of the present invention.

[0020]

As described above in detail, in the bottom crystallization apparatus for a resin bottle and the bottom crystallization method using the same according to the present invention, the internal pressure of the bottle is raised during the heating of the bottom of the bottle, and the bottom crystallization at the time of blow molding of the bottle is performed. Since the bottom die having the same shape as the bottom die holds the outer periphery of the bottom portion in close contact, deformation of the bottle during heating can be prevented. Further, in a preferred embodiment of the present invention, after the bottom of the bottle is heated, a gas is caused to flow inside the bottle for cooling, so that the deformation due to the residual heat after taking out the bottle can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic front view showing the structure of a bottom crystallization device for a resin bottle according to a first embodiment of the present invention.

FIG. 2 is a schematic front view showing the structure of a bottom crystallization device for a resin bottle equipped with a bottle cooling means according to a second embodiment of the present invention.

[Explanation of symbols]

 1 ... Bottom type with heater 2 ... High-pressure gas supply device 21 ... Mouth tightening jig 23 ... Gas introduction pipe 28 ... High-pressure gas supply source 3 ... Bottle

Claims (6)

[Claims] 1. A bottom crystallization device for a resin bottle, the bottom mold having the same mold shape as the blow mold bottom mold for the resin bottle and having a heater, and raising and maintaining the pressure inside the bottle. A bottom crystallization device for a resin bottle, comprising a high-pressure gas supply device. 2. A method for crystallizing a bottom part of a resin bottle using the bottom part crystallizing device for a resin bottle according to claim 1, wherein the bottom part of the bottle is closely held in the bottom mold, and a pressure inside the bottle is maintained. 100 to 20 by holding the bottle up to ² to 40 kgf / cm ² and holding it with a bottom mold equipped with the heater.
A method for crystallizing a bottom portion of a resin bottle, which comprises heating to 0 ° C. 3. A method for crystallizing a bottom portion of a resin bottle using the apparatus according to claim 1, wherein the bottom portion of the bottle is closely held in the bottom mold, and the pressure inside the bottle is 2 to 10 kgf /.
A method for bottom crystallization, characterized in that the bottle is heated to 120 to 180 ° C. by a bottom mold equipped with the heater while being raised and held at cm ² . 4. The bottom crystallization device for a resin bottle according to claim 1, wherein the high-pressure gas supply device is provided with a plurality of gas circulation paths into the bottle, thereby increasing the pressure inside the bottle. A bottom crystallization device for a resin bottle, which is characterized by holding and introducing gas into the bottle or discharging the gas to the outside of the bottle. 5. A method for crystallizing a bottom part of a resin bottle using the bottom part crystallizer for a resin bottle according to claim 4, comprising: (a) closely holding the bottom part of the bottle in the bottom mold;
(B) The pressure inside the bottle is raised and maintained at ² to 40 kgf / cm ² , (c) The bottom of the bottle is heated to 100 to 200 ° C. by the bottom mold equipped with the heater, and (d) the inside of the bottle is heated after the heating is completed. After lowering the pressure of (1), the bottle is cooled by flowing a gas inside the bottle using the high-pressure gas supply device, and (e) the bottle is taken out. 6. A method for crystallizing a bottom part of a resin bottle using the bottom part crystallizing device for a resin bottle according to claim 4, comprising: (a) closely holding the bottle bottom part in the bottom mold;
(B) The internal pressure of the bottle is raised and maintained at ² to 10 kgf / cm ² , (c) The bottom of the bottle is heated to 120 to 180 ° C. by the bottom mold equipped with the heater, and (d) the inside of the bottle is heated after the heating is completed. After lowering the pressure of (1), the bottle is cooled by flowing a gas inside the bottle using the high-pressure gas supply device, and (e) the bottle is taken out.