JP2000135734A - Blow molding method for hollow molded product and blow molding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the whole molded product to be cooled uniformly and in a short time by cooling the molded product with an indented hindrance part formed internally from the outer face of the molded product through cooling a mold and at the same time, spraying a cooling mist with a specified grain size toward the hollow part of the molded product from an air blowing aperture, while the inner pressure of the molded product is kept at a specified pressure level. SOLUTION: An air blowing nozzle 12 has an air supply path 14 and an air removal path 15 for blowing a blow air and a cooling air to a parison inside a mold 11. At the same time, a mist nozzle 13 for spraying a mist is fitted into the air supply path 14. Further a mist spray hole is biasedly arranged along with the conical shape of the tip of the mist nozzle 13 so that the jet direction of the mist is set in the hollow part direction of a molded product. Thus the mist with 200 μm or less, preferably 10 μm or less dia. is generated. After spraying the mist for a specified time, the air supplied/removed and also circulated and is blown to the parison further uniformly, while the inner pressure of the molded product is kept at a specified pressure level. The outer face of the molded product is cooled with the help of a coolant flowing through a coolant passage hole in the mold 11, while the inner face is also cooled simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for blow molding a hollow molded article made of a resin such as high-density polyethylene, low-density polyethylene, polypropylene, polyvinyl chloride, and ABS, and a blow molding apparatus used for the method.

[0002]

2. Description of the Related Art Conventionally, blow molding, which is known as a method for manufacturing bottles and containers, includes a parison molding step, a mold closing step, a blowing step, a cooling / solidifying / exhausting step,
It is a multi-stage complex molding method consisting of a mold opening process and a removal process. In order to perform optimal molding, studies are being conducted based on empirical rules as well as theoretical analysis and simulation of each process.

[0003] In the production of blow molded articles, it is generally important to shorten the molding time, improve the molding cycle efficiency, and improve the productivity. Since it is necessary to perform sufficient cooling in order to prevent the shrinkage deformation of the molded product when the molded product is removed from the mold by shortening the cooling and solidifying process in the evacuation / removal process, As a method of forcibly cooling a molded article blown in a mold, a cooling medium is supplied from a parison to the inside of the molded article to forcibly cool the molded article.

As a prior art relating to the forced cooling of the blow-molded product, a mold is provided with a gas inlet pipe for jetting a cooling gas toward a parison being formed and a gas discharge pipe for discharging the cooling gas. The method described in JP-A-3-222714 discloses a method in which a high-pressure air flow in which water is mixed into a parison is blown from below the mold to expand the parison.
The method described in Japanese Patent Publication No. Hei 6-365 for cooling the inner surface of the mold, and the opening of the mold is started while a cooling medium is ejected from a center extending rod to the periphery.
The method described in Japanese Patent Laid-Open No. 1 is known.

[0005]

However, the techniques for forced cooling of a molded product obtained by blow molding a parison described in the above publications have the following problems.

That is, in the blow molding method described in JP-A-3-222714, in which a cooling gas flows from a gas introduction pipe to a gas discharge pipe, when a cooling gas is blown into the parison from the gas introduction pipe. The part facing the tip of the gas introduction tube is easily preferentially cooled locally and
There is a problem that the parison shell wall is cooled non-uniformly as a whole and the molded container becomes non-uniform. Also, the cooling gas blown into the parison goes straight toward the gas discharge pipe having low pressure resistance without being circulated in the parison as a whole, and is discharged from the gas discharge pipe to the outside. There is a problem that the effect of shortening the cooling time cannot be sufficiently obtained because the sensible heat of the gas cannot be effectively used.

[0007] The blow molding method described in Japanese Patent Publication No. 6-365 is suitable for a blow pallet having a low blow ratio as a molded product, but water droplets remain on the inner surface of the molded product, and the final product is inevitable. There is a fear that a problem that a water droplet mark remains on the inner surface of the substrate may occur.

In the blow molding method described in Japanese Patent Application Laid-Open No. 3-9831, the stretching rod is arranged on the central axis of the molding container. Although there is no problem, in the case of a molded container such as a substantially rectangular parallelepiped or a substantially elliptical cylinder, or a container having an uneven obstacle inside the molded product, the position of the stretching rod serving as the cooling medium blowing port and the parison (preform) Since the distance from the inner surface varies depending on the location, the manner in which the cooling medium blown from the stretching rod hits the parison becomes uneven, and thus, as in the case described above, the shell wall of the parison becomes uneven as a whole. There is a problem that the molded container becomes inhomogeneous as a result of being cooled, and no method for improving this problem is disclosed.

As described above, in the above-described conventional methods of blowing the cooling medium into the blown parison to cool the parison for the purpose of shortening the molding time and improving the molding cycle, the shortening of the molding time is insufficient. In addition, there is a problem that the molded product is not uniformly cooled as a whole and becomes an inhomogeneous product due to injection of the cooling medium because the blow air blowing port is located at a biased position. Mouth (Air and cooling medium blowing port during blow molding.
After molding, it becomes a port for filling and discharging liquid inside the container) is a molded product that is horizontally displaced from the center of the figure of the container, and there are uneven obstacles inside the molded product In the case of a molded product in which the distance from the air inlet to each inner wall surface is not constant ("irregular shaped product"), the blowing of the cooling medium to promote cooling may cause defective products on the other hand. Problem.

[0010] The present invention has been made intensively in order to solve the problems of the prior art as described above.
For a hollow molded product to be blow-molded with a mold, a resin is formed using a mold whose opening communicating with the inside and outside (blow air blowing port) is shifted horizontally from a vertical line passing through the center of the figure of the mold cavity. In the case of blow-molding a molded product of (1), a blow molding method and a blow-molding apparatus used for the same in which cooling can be performed in a short time while allowing cooling to be performed as uniformly as possible for the entire blow-molded product. It was made to provide.

[0011]

A feature of the blow molding method according to claim 1 of the present invention which solves the above-mentioned problem is that a parison which is extruded into a tube shape from a die head and hangs down is blown in a hollow cavity of a mold to make a resin. Of hollow molded products of
In the blow molding method in which the blow molding to be cooled and taken out from the mold is performed by using a molding mold provided at a position where the blowing port of the blow air is horizontally shifted from a vertical line passing through the center of the figure of the hollow cavity, In order to cool the molded product in which the uneven part is present inside the blown part in the blowing process, the outer surface of the molded product is cooled by cooling the mold and the inside of the molded product is maintained at a predetermined pressure. While spraying a cooling mist of 200 μm or less from the position of the blow air blowing port toward the hollow portion of the molded product, and maintaining the pressure in the molded product as needed, the air in the molded product is discharged as needed. It is characterized in that the inside of the molded product is cooled by exhausting air.

In the method of the invention described above, the temperature of the parison when the blow air is blown for the blow molding is set at, for example, 18 degrees at which the resin to be molded is easily deformed.
Since the air temperature is about 0 ° C., the parison is easily deformed to the shape of the inner surface of the mold by this air blowing, and exhibits a shape following the inner surface of the mold. In the present invention, at the stage where the inside of the parison reaches a predetermined pressure by blowing the blow air and the parison is formed into a shape following the predetermined shape, the internal pressure is maintained, and the molded product is cooled by cooling the mold. While cooling the outer surface, the cooling mist is sprayed into the molded product to cool the inner surface. At this time, it is essential that the mist is sprayed toward the hollow portion of the molded product. By spraying the mist in this manner, the entire shell wall of the molded product is cooled to about 60 ° C. without causing large cooling unevenness. On the other hand, if the spraying direction is not directed toward the hollow portion of the molded article but is sprayed, for example, so as to spread vertically upward in a cone shape, the shell wall of the molded article is not uniformly cooled as a whole. It is not suitable because it becomes inhomogeneous.

In the above, mist spraying is generally performed by spraying mist at a pressure higher than the pressure in a molded product maintained at a constant pressure, so that the mist is conical toward a hollow portion of the molded product. Sprayed to spread out. The pressure in the molded product can be maintained at the above-mentioned predetermined pressure by, for example, a relief valve provided in an exhaust system. In addition, at the time of spraying mist, the relief valve may be closed.

According to the present invention, the parison (molded product) is formed by the cooling of the mold and the latent heat effect of vaporization by mist evaporation.
In a state in which the mold is deformed according to the shape of the cavity of the mold, forced cooling is quickly realized from the inner and outer surfaces of the hollow molded product and as uniform as possible over the entire shell wall of the molded product.

According to a second aspect of the present invention, in the above-mentioned invention,
After the cooling mist is blown into the inside of the molded article to cool the inner surface of the molded article, the spray of the mist is stopped, and then the blowing of the cooling air and the exhaust of the air in the molded article are performed in parallel through the position of the blow air inlet. To supply and exhaust cooling air into the molded product.
It is characterized in that it is circulated, whereby the molded article is cooled sufficiently.

The pressure increased by the blowing of the cooling air is exhausted to the outside through the pressure holding means such as the relief valve of the exhaust system in the same manner as described above, so that the supply and exhaust of the differential pressure is performed. Will be.

According to the present invention, the warmed air in the molded article is exhausted and the cooling air is blown, so that the cooling proceeds smoothly.

According to a third aspect of the present invention, in each of the above-mentioned inventions, the size of the cooling mist to be sprayed is 10 μm or less, which further reduces the possibility that water droplet marks remain on the inner surface of the hollow molded article. Reduced.

The blow molding apparatus according to claim 4 of the present invention is
What is claimed is: 1. A blow molding apparatus for blow molding a resin hollow molded article, comprising a hollow cavity having a shape of the hollow molded article, and a parison supplied from a blow die head being confined in the cavity. And a mold cooling means for cooling the mold, and a blow air blowing nozzle provided to face the inside of the mold to blow blow air for molding into the parison confined in the mold, The blow air blowing nozzle is provided at a position shifted in a horizontal direction from a vertical line passing through the center of the figure of the hollow cavity of the mold, and sprays a cooling mist of 200 μm or less toward the hollow portion of the molded product. Mist spray port, a blow-in port for cooling air into the blow-molded molded article, and an exhaust port for exhausting air in the molded article to the outside. Mouth, characterized in that it is connected to a pressure holding means for holding the air pressure in the molded article at a predetermined pressure.

The cooling means of the molding die is usually provided as a jacket-type cooling structure for circulating a cooling medium inside the wall, and water is generally used as a cooling medium.

In the above configuration, the air blowing nozzle is
It is provided to have a blow air blowing port, a cooling mist spraying port, and a cooling air blowing port and an air discharging port for supplying and exhausting cooling air. This is an unavoidable configuration when an air supply / discharge port with the outside cannot be provided in addition to the blow-in port for the product. The structure for providing the cooling mist spray port, the cooling air blow port, and the exhaust port in the air blowing nozzle for blow molding is not particularly limited. The inside of the nozzle is divided into an air supply path and an air exhaust path, and the air supply path is also used for blowing blow air and cooling air. An example of a configuration having an inlet and an outlet can be given. Further, the mist spray port can be exemplified by a configuration in which a mist spray nozzle is provided inside a blow air blowing nozzle. Also, the mist spray nozzle can be provided so as to be relatively movable in the axial direction with respect to the blow air blowing nozzle,
By doing so, the spray port of the spray mist can be inserted into the mold to preferably give mist spray toward the hollow portion of the molded article. The mist spray nozzle is not limited, but the tip of the nozzle is formed in a hemispherical, conical wall shape, and one or more of the small holes serving as the spray ports are biased to the tip wall in the spray direction to open. An example of a configuration having such a configuration can be given. Further, the wall surface of the nozzle tip may be an elliptical plane inclined in the spray direction with respect to the central axis, and one or more small holes serving as the spray ports may be opened in this plane.

In the present embodiment, the resin-made hollow molded product blow-molded is a vertical cylindrical shape (cylindrical, elliptical cylindrical, long cylindrical) having an uneven obstruction inside the upper and lower end closed molded product. ), A rectangular parallelepiped type, a cubic type, and the like, and are not particularly limited, but typically include tank-shaped blow molded articles such as gasoline tanks.

The progress of each process operation of blowing blow air, spraying mist, supplying and discharging cooling air, and discharging the internal pressure of a molded product is as follows.
It can be performed by sequence program control or the like using computer technology.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 This embodiment shows a typical embodiment of the method according to claims 1 to 3 and the apparatus according to claims 4 to 7.

The blow molding apparatus 10 of the present embodiment shown in FIGS. 1 to 3 is used for molding an irregularly shaped container main body and a hollow container having an opening deviated on one side of the upper surface thereof in an inverted state by using a mold 11. FIG. 1 is a longitudinal sectional view showing a closed state of a mold 11 composed of a pair of mold pieces for confining a parison (not shown) supplied from a blow die head (not shown). . In the mold 11, a cooling device is formed by forming a coolant flow passage in the thickness of the mold. However, the cooling device is omitted because the drawing becomes complicated.

Reference numeral 12 denotes an air supply / discharge type nozzle (hereinafter, referred to as an “air blowing nozzle”), and an air supply path 14 for blowing blow air and cooling air into the parison confined in the mold 11. An air exhaust path 15 for exhausting air from the molded article is provided, and a mist nozzle 13 for spraying mist is provided inside the air supply path 14.

The details of the air blowing nozzle 12 are shown in FIG. That is, the nozzle 12 of the present example is configured such that the inside of the nozzle cylinder 121 having the open end is formed by the partition wall 1 extending in the axial direction.
The cylindrical mist nozzle 22 is divided into an air supply passage 14 having a large cross-sectional area and an air exhaust passage 15 having a small cross-sectional area. 13 are installed. 141 is an opening at the end of the air supply path, which is also used as a blow-in port for blow air and a blow-in port for cooling air, and 151 is an opening at the end of the exhaust path 15 and constitutes an exhaust port.

In the mist nozzle 13, a plurality of small holes are provided as mist spray holes 132 on the conical tip closing wall surface 131.
Mist is sprayed from. In addition, these mist spray holes 132 are arranged so that the spray direction of the mist is directed toward the hollow portion of the molded product in combination with the conical shape of the front end closing wall 131 of the mist nozzle 13. The mist nozzle 13 is for generating a mist of 200 μm or less, preferably 10 μm or less.

The blow pressure and the blow time of blow molding using the apparatus of this embodiment differ depending on the capacity of the hollow molded product and the diameter of the air blowing nozzle 12, and are as follows, for example.

When the size of the mist is 10 μm, in order not to wet the inner surface of the hollow molded article,
The blow time is in the range of 5 to 30 seconds, and the mist spray time is 20
Up to 90 seconds, supply / discharge of cooling air after stopping mist spraying
As for the circulation time, it is preferable that the exhaust time is in the range of 20 to 90, and the exhaust time is in the range of 5 to 20 seconds.

Next, the procedure and operation of blow molding by the molding apparatus of this embodiment will be described.

First, the parison is extruded from the blow die head into the opened mold 11.

Next, the mold 11 is closed, the air blowing nozzle 12 is moved upward from below to the air blowing position, and air is blown from the air supply path 141 of the air blowing nozzle 12 into the parison housed in the hollow cavity. Blow molding. When the inside of the parison reaches a predetermined pressure, the shape of the parison follows the inner surface of the cavity of the mold (hereinafter, the parison in this state is referred to as “molded product 18”), blowing of blow air is stopped, and the mist nozzle is stopped. A mist of 200 μm or less, preferably 10 μm or less is sprayed from the tip of 13 toward the center of the figure of the parison so that the inner surface of the parison is brought into direct contact with the mist. By this mist spraying, the inner surface of the parison is rapidly cooled by a latent heat effect when the mist in contact with the inner surface of the parison evaporates and evaporates. When the mist to be sprayed is particularly 10 μm or less, the mist evaporates at the moment of contact with the inner surface of the hollow molded product. There is no.

After the mist spraying is performed for a predetermined time, the spraying is stopped, and then the supply and discharge and circulation of the air are performed while maintaining the internal pressure by the blowing pressure of the air, and the air is circulated inside the hollow molded article. The inner surface of the hollow molded article is further uniformly cooled by circulating air. Thereafter, the pressurized air in the molded product is exhausted to atmospheric pressure, the mold 11 is opened, and the molded product 18 is taken out. In addition, by connecting the exhaust path 151 to the relief valve 16 at the time of mist spraying and air supply / discharge / circulation,
The inside of the molded product is maintained at a predetermined pressure (generally, the pressure at the final stage of blowing the blow air) by the pressure detector 17.

In parallel with the cooling of the inner surface of the hollow molded article,
The outer surface of the molded article is cooled by the coolant flowing through the coolant passage hole (not shown) of the mold 11.

Thus, the blow molding of this embodiment is completed. FIG. 4 shows the procedure of air supply (blowing), mist supply (spraying), and exhaustion in this series of blow molding.

The mist nozzle 13 can be provided in a fixed relation to the air blowing nozzle 12, but can also be provided so as to be relatively movable in parallel. The mist nozzle 13 can also be made to project from the opening to a position suitable for mist spraying.

[0038]

EXAMPLES Using the apparatus of Embodiment 1, blow molding of a resin hollow molded product was conducted in the following Examples 1 and 2 and Comparative Examples 1 to 3 under the following conditions.

Target material: high-density polyethylene HDPE 8700 <manufactured by Tosoh Corporation> (melt index HLMI = 8.5 g / 10 min, density d = 0.949 g / cm ³ ) Blow molded product: tank with an inner volume of 20 liters (30 cm square, average wall thickness: 10 mm) Blow molding method: Lower blowing type Horizontal displacement of 125 mm from a vertical line passing through the center of the figure of the air blowing nozzle Molding conditions (based on air blow molding): Extrusion cylinder temperature 190 ° C Mold cooling temperature: 23 ° C. Injection time: 10 seconds Blow pressure: 4.5 kg / cm ² (Method of measuring the temperature of the inner surface of the blow molded product) At 90 seconds after the start of mold opening, the temperature of the inner surface of the blow molded product was measured by thermography (manufacturer). : Japan Avionics Co., Ltd., Model T
VS-2100MKIIST) at five points shown in FIG. 2, and the results of each example are shown in Table 1 below.

Example 1 15 seconds after the start of air blowing for blow molding, the air blowing was stopped, and a water mist (20 μm in size) was used as a cooling medium on the inner surface of the hollow molded product in the direction of the hollow portion of the molded product 18. (Diagonally upward (approximately 45 degrees elevation))
Spraying was performed for 0 seconds (mist spray amount: 5 ml / sec). After that, the mist spraying was stopped, circulation was performed for 10 seconds, and this operation was repeated four times, so that a cooling time of 100 seconds (a blow time of 15 seconds, a mist time of 10 seconds and a circulation time of 10 seconds were repeated four times, (A total of 5 seconds of evacuation time).

Example 2 After 15 seconds from the start of air blowing for blow molding, the air blowing was stopped, and a water mist (20 μm in size) was used as a cooling medium on the inner surface of the hollow molded product in the direction of the hollow portion of the molded product 18. (Diagonally upward (elevation angle about 45 degrees))
Spraying was performed for 0 seconds (mist spray amount: 5 ml / sec). After that, the mist spraying was stopped, the circulation was performed for 20 seconds, and this operation was repeated twice, so that the cooling time was 100 seconds (blow time 15 seconds, mist time 20 seconds and circulation time 20 seconds were repeated twice, (A total of 5 seconds of evacuation time).

COMPARATIVE EXAMPLE 1 Mist was not sprayed, and air was used as a cooling medium for the inner surface of the hollow molded article.
(Total of seconds and evacuation time of 5 seconds).

COMPARATIVE EXAMPLE 2 Mist was not sprayed, and air was used as a cooling medium for the inner surface of the hollow molded article.
(Total of 5 seconds and 5 seconds of evacuation time).

COMPARATIVE EXAMPLE 3 After the blowing of the blow air was stopped, the cooling medium on the inner surface of the hollow molded product was changed to a water mist (20 μm in size), which was generated so as to collide with the obstacle in a conical shape in the spraying direction. The molding was performed with a cooling time of 100 seconds (a blow time of 15 seconds, a mist time of 20 seconds, and a circulation time of 20 seconds were repeated twice, and the exhaust time was 5 seconds in total).

When the hollow molded article was taken out of the mold after molding, a large amount of water leaked from the inside.

[0046]

[Table 1]

As can be seen from this table, the temperature distribution of the cooling time of 100 seconds by the mist spraying shows almost the same distribution as that of the cooling time of 140 seconds by the usual air molding, and the cooling time is reduced by 30%. Have been.

Further, when the mist spray is not uniformly applied to the inner surface of the molded article, the cooling is locally uneven and the cooling time is not shortened.

[0049]

According to the blow molding method and the blow molding apparatus of the present invention, the outer surface is cooled by cooling the mold while the parison is deformed according to the shape of the cavity of the mold, and the inner surface is The sprayed mist of 200 μm or less comes into contact with the inner surface of the hollow molded product in a high temperature state and is evaporated, and is rapidly cooled by the action of latent heat of vaporization at the time of evaporation. Uniform and quick forced cooling. Therefore, the efficiency of the cooling process can be increased, the molding cycle time can be shortened, and high productivity can be obtained.

According to the invention of each claim, the following effects can be obtained.

According to the second aspect of the present invention, by supplying and discharging the cooling air following the spray of the mist, the heated air in the molded article can be quickly exhausted to the outside and replaced with the cooling air. As a result, the molded product can be cooled more smoothly. In addition, the amount of mist consumption can be reduced, the moisture content is not contained during reprocessing of burrs, the quality of the regenerating function can be improved, and the molded product can be cooled to an appropriate temperature, and burns can be caused when removing the molded product. Can be prevented.

According to the third or seventh aspect of the present invention, 10 μm
m, the mist evaporates instantaneously when it comes into contact with the inner surface of the hollow molded product, and no large water droplets are formed on the inner surface of the cooled hollow molded product. There is an effect that no uneven surface is formed on the hollow molded article at the time of collision.

According to the fifth aspect of the present invention, there is an effect that the spray direction of the mist can be adjusted by the mist nozzle having a simple structure.

According to the sixth aspect of the present invention, the means for maintaining the inside of the molded article at a predetermined pressure is operated by the relief valve, so that the heated air is quickly exhausted to the outside, and the pressure is maintained by holding the pressure. The effect that the cooling by a type | mold can be performed is produced.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing an outline of a configuration of a blow molding apparatus according to a first embodiment of the present invention, particularly showing a positional relationship between a mold and an air blowing nozzle.

FIG. 2 is a diagram showing a temperature measurement point on the inner surface of a blow molded product.

3A and 3B are diagrams for explaining the structure of an air blowing nozzle, wherein FIG. 3A is a perspective view of a tip portion of the air blowing nozzle, and FIG.
FIG. 3 is a front view of the tip of the mist nozzle, and FIG. 3C is a plan view of the tip of the mist nozzle.

FIG. 4 is a diagram showing an example of an operation procedure relationship of air supply and discharge and mist spraying during molding.

[Explanation of symbols]

 10: Blow molding apparatus 11: Die 12: Air blowing nozzle 121: Nozzle cylinder 122: Partition wall 13: Mist nozzle 131: Tip block 132: Mist spray hole 14: Air supply path 141: Blow air (cooling air) Entrance 15: Air exhaust path 151: Air exhaust port 16: Relief valve 17: Pressure detector 18: Molded product

Claims (7)

[Claims] 1. A blow molding in which a parison extruded into a tube shape from a die head and hung down is blown into a hollow cavity of a mold to form a resin hollow molded article, and then cooled and taken out of the mold. In the blow molding method using a molding die whose injection port is horizontally offset from the vertical line passing through the center of the figure of the hollow cavity, there are uneven obstacles inside the blow blow process In order to cool the molded product to be cooled in the molding die, the outer surface of the molded product is cooled by cooling the mold, and the molded product is cooled from the position of the blow air blowing port while maintaining the inside of the molded product at a predetermined pressure. Spraying a cooling mist of 200 μm or less toward the hollow portion, and evacuating air in the molded product as needed while keeping the inside of the molded product at the above pressure to cool the inner surface of the molded product. Blow molding of the resin hollow molded article, characterized in that. 2. A blow molding, wherein a parison extruded into a tube shape from a die head and hung down is blown into a hollow cavity of a mold to form a resin hollow molded article, and cooled and taken out of the mold. In the blow molding method using a molding die whose injection port is horizontally offset from the vertical line passing through the center of the figure of the hollow cavity, there are uneven obstacles inside the blow blow process In order to cool the molded product to be cooled in the molding die, the outer surface of the molded product is cooled by cooling the mold, and the molded product is cooled from the position of the blow air blowing port while maintaining the inside of the molded product at a predetermined pressure. Spraying a cooling mist of 200 μm or less toward the hollow portion, and evacuating air in the molded product as necessary while maintaining the inside of the molded product at the above-described pressure to cool the inner surface of the molded product. After that, the spraying of the mist is stopped, and then the blowing of the cooling air and the exhaust of the air in the molded product are performed in parallel through the position of the blow air blowing port to supply / discharge / circulate the cooling air in the molded product. A characteristic blow molding method. 3. The blow molding method according to claim 1, wherein the size of the cooling mist to be sprayed is 10 μm or less. 4. A blow molding apparatus for blow-molding a hollow molded article made of resin, comprising a hollow cavity having the shape of the hollow molded article, wherein a parison supplied from a blow die head is provided in the cavity. A mold to be confined in the mold, mold cooling means for cooling the mold, and blow air blowing provided to face the mold to blow blow air for molding into the parison confined in the mold. Nozzle, and the blow air blowing nozzle,
A mist spray port for spraying a cooling mist of 200 μm or less toward the hollow portion of the molded product, while being provided at a position shifted in the horizontal direction from a vertical line passing through the center of the figure of the hollow cavity of the mold, It has a blow-in port for cooling air into the blow-molded article and an exhaust port for exhausting the air inside the molded article to the outside. The exhaust port keeps the air pressure in the molded article at a predetermined pressure. Blow-molding apparatus connected to a pressure holding means for performing the blow-molding. 5. The mist spray port according to claim 4, wherein one or a plurality of small mist spray ports are arranged on a hemispherical or conical tip wall of the mist spray nozzle provided inside the blow-air blowing nozzle, and are skewed in the mist spray direction. A blow molding device characterized by being formed as a hole. 6. A pressure valve according to claim 4, wherein the pressure holding means for holding the inside of the blow-molded product at a predetermined pressure is a relief valve provided in an exhaust pipe connected to an exhaust port. Features blow molding equipment. 7. The blow molding apparatus according to claim 4, wherein the mist spray port sprays a mist of 10 μm or less.