JPH08187769A - Blow mold and production of hollow molded object - Google Patents

Abstract

PURPOSE: To simply close a blow hole in a blow molding process in the production of a hollow molded object using a blow mold. CONSTITUTION: A cavity 13 is provided between an outer mold 11 and a core mold 12 and a cylindrical member 2 is provided to the core mold 12 so as to freely advance and retreat between the surface of the cavity 13 and the interior thereof. A air venting needle 3 is provided to the cylindrical member 2 so as to freely advance and retreat from the leading end surface thereof to the cavity and a heating means for heating the leading end surface of the cylindrical member is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding die and a method for producing a hollow molding.

[0002]

2. Description of the Related Art Hollow molded articles obtained by a blow molding method may cause dust or water to enter through blow holes during transportation, storage, or use, which may cause dirt or reduce durability. Since it is easy, it is necessary to close the blow hole.

In view of this point, as a conventional method for closing a blow hole, for example, as described in Japanese Patent Publication No. 3-33088, the side wall of the open end of the blow hole of a hollow molded article formed by blow molding. A method has been proposed in which a heated and pressurized gas is blown onto the molten metal to melt and move the side wall of the opening end portion to close the blow hole.

[0004]

However, according to the conventional method as described above, after the molded body is molded in the blow mold, the molded body is taken out of the mold and the secondary processing is performed. Since it has to be stepped on, there is a problem that the process is complicated.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a blow molding die and a method for producing a hollow molding which can easily close a blow hole in a blow molding process. It was made.

[0006]

In a blow molding die of the present invention, a cavity is provided between an outer die and a core die, and a cylindrical body is provided in the core die so as to be able to advance and retreat from the cavity surface into the cavity. The tubular body is provided with a ventilating needle that can advance and retreat from the tip end surface into the cavity, and a heating means for heating the tip end surface of the tubular body.

The method for producing a hollow molded article of the present invention is a method for producing a hollow molded article using the blow molding die of the present invention, in which a side wall of the parison is penetrated into the parison supplied into the cavity. The ventilating needle is advanced and the pressurized gas is blown from its tip while the parison is pressed against the cavity surface for shaping, and the ventilating needle exhausts the inside of the parison and heats the tip surface of the tubular body. While heating by the means, the cylindrical body is advanced toward the cavity surface of the outer mold inside the cavity, and the side wall of the core mold side of the parison is heated to the melting point or higher so that the outer mold side of the opposite parison is heated. The method comprises a step of pressing against the wall portion to fuse them.

The blow mold of the present invention comprises an outer mold and a core mold, and a blow molding cavity is provided between them. A tubular body is provided in the core mold so as to be movable back and forth into the cavity from the cavity surface toward the cavity surface of the outer mold.

That is, before the parison is supplied into the cavity of the blow molding die, the core-shaped tubular body is retracted, and its tip portion forms a part of the cavity surface.
After the pressurized gas is blown into the parison to shape it and then the blow hole is closed, the parison can be advanced from the cavity surface of the core mold toward the cavity surface of the outer mold. A ventilating needle is provided on the tubular body so that the ventilating needle can move back and forth from the tip end surface into the cavity. Further, the cylindrical body is provided with heating means for heating the tip end surface.

As the material of the tubular body, for example, a material having a high thermal conductivity is preferable in order to quickly raise and lower the temperature. Examples of the heating means provided on the tubular body include a heat transfer wire and ultrasonic heating.

When the heating means is a heat transfer wire, the heat transfer wire is embedded in the wall of the cylindrical body near the tip surface thereof, and when the heating means is ultrasonic heating, the ultrasonic heating device is a cylindrical body. Connected to the rear end of the.

As the temperature control of the tubular body, for example, the temperature is kept lower than the fusion temperature of the resin before the pressurized gas is blown, and immediately after the blowing is completed, the temperature is raised to the fusion temperature of the resin. After advancing the shaped body into the cavity, the temperature may be lowered to the fusion temperature of the resin.

In the present invention, as the ventilating needle, the front end can be inserted through the side wall of the parison, and the parison has a narrow vent passage so that compressed air can be blown into the parison from the front end. Any material having a function can be appropriately used, and examples thereof include a hollow needle having an air passage open at the tip portion and a material entirely made of a porous member. In the present invention, an inert gas such as nitrogen gas or carbon dioxide gas is preferably used as the pressurized gas.

In the present invention, the resin usable for blow molding is, for example, polyethylene, polypropylene, polybutene, polycarbonate, polystyrene resin, acrylonitrile-butadiene-styrene copolymer, vinyl chloride resin, chlorinated vinyl chloride resin. , Polyphenylene ether, polyethylene terephthalate, polyphenylene sulfide, polyamide, polysulfone, polyether sulfone, polybutylene terephthalate, polyetherimide, polyether ether ketone, polyethylene ionomer, ethylene-vinyl acetate copolymer, vinylidene fluoride resin, Thermoplastic resins such as polytetrafluoroethylene may be mentioned.

These resins may be used alone or in combination of two or more kinds. If necessary, glass fibers, talc, stabilizers, lubricants, fillers such as flame retardants, modifiers, and the like may be added to the resin.

The present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a blow molding die of the present invention. Reference numeral 1 denotes a blow molding die, and a cavity 13 having an inner surface shape corresponding to the outer surface shape of a blow molded body to be blow molded is provided between an outer mold 11 and a core mold 12.

The core die 12 has an opening 1 on the cavity surface.
A through hole 121 having 21a is provided, and the inner diameter of the through hole 121 is enlarged. In the through hole 121,
A tubular body 2 is provided. The cylindrical body 2 has a tip portion 21 having a small diameter (diameter D ₁ ), and the gear portion 22 allows the tip portion 21 to pass through the opening 121 a to form a cavity from the cavity surface toward the cavity surface of the outer mold 11. It is possible to move back and forth within 13.

A central hole 23 having a diameter D ₂ is formed in the cylindrical body 2 along the axial direction, and the tip end surface is formed in a donut shape having a width w. The ventilating needle 3 is provided in the center hole 23 of the tubular body 2 by the cylinder 31 so as to be able to move back and forth from the tip end surface of the tubular body 2 into the cavity 13. A heating wire 24 is embedded in the wall of the distal end portion of the tubular body 2 so that the heating wire 24 can heat the distal end surface.

Next, an example of a method for manufacturing the hollow molded article of the present invention using the blow molding die shown in FIG. 1 will be described with reference to FIGS.

First, as shown in FIG. 2, the ventilation needle 3 is advanced into the hollow portion of the parison 4 supplied into the cavity 13 of the blow molding die 1 so as to pass through the core mold side wall 42 of the parison 4. The pressurized gas is blown into the parison 4 and the parison 4 is pressed against the cavity surface for a predetermined time to shape the parison 4.

Next, as shown in FIG. 3, the inside of the parison 4 is exhausted while the ventilating needle 3 is retracted into the central hole 23 of the cylindrical body 2. Then, as shown in FIG. 4, while heating the tip end surface of the tubular body 2 by the heating wire 24, the tubular body 2 is advanced toward the cavity surface of the outer mold 11 facing the same by a length A _1. Let
The core type side wall portion 42 of the parison 4 is heated to a melting point or higher, and pressed against the opposing cavity side wall portion 41 of the parison 4 to be fused.

As a result, the blow hole 43 is completely fused around and closed. Lastly, although not particularly shown, the blow molding die 1 is opened to obtain a hollow molded body in which the blow holes are closed.

FIG. 5 is a sectional view showing another example of the blow molding die of the present invention. Blow molding die 1'of this example
In the case of, in the core die 12, a protruding portion protruding by a height A _{2 in} the cavity surface direction of the outer die 11 is formed on the cavity surface around the through hole 121 provided so as to have the opening 121a in the cavity surface. 125 is provided. Except for the points other than the above, it is the same as that shown in FIG. 1, so the same reference numerals as in FIG. 1 are given in the figure, and detailed description thereof is omitted.

In the method of manufacturing a hollow molded body using this blow molding die 1 ', as shown in FIG.
The length for advancing toward the cavity surface of the outer mold 11 can be only A ₁ shown in the figure. Then, as shown in FIG. 7, it is possible to obtain a hollow molded body in which a plurality of blow holes 43 are completely fused around and closed.

FIG. 8 is a sectional view showing still another example of the blow molding die of the present invention. In this blow molding die 1 ″, except that the ultrasonic wave transmission device 5 is connected to the rear end of the tubular body 2 instead of the heating wire 24 in the blow molding die 1 shown in FIG. 1. And is the same as the blow molding die shown in FIG. In this case, the tip end surface of the tubular body 2 is vibrated and heated by the ultrasonic wave transmitting device 5, and the tubular body 2 is advanced toward the cavity surface of the outer mold 11 which faces the core body of the parison. The mold side wall is heated above the melting point and pressed against the cavity side wall facing the parison to fuse.

[0026]

In the blow molding die of the present invention, a cavity is provided between the outer die and the core die, and the tubular body is provided in the core die so as to be able to move back and forth from the cavity surface into the cavity. In the blow molding process, the ventilation needle is provided so that the tip surface of the hollow body can be moved back and forth into the cavity, and the heating means for heating the tip surface of the tubular body is provided to block the blow hole in the blow molding process. It can be used as a mold.

According to the method for manufacturing a hollow molded article of the present invention, the parison is passed through the side wall of the parison supplied into the cavity and the vent needle is advanced to blow pressurized gas from the tip of the parison to the cavity surface. The process of pressing to the shape and the exhaust of the parison from the ventilating needle, while heating the tip end surface of the tubular body with the heating means, the tubular body inside the cavity of the opposing outer cavity Of the core mold side of the parison and heating the side wall of the core side of the parison above the melting point to press against the wall of the outer mold side facing the parison to cause fusion. It is possible to completely close the periphery of the hole, and it is possible to easily obtain a hollow molded body in which the blow hole is closed.

[0028]

EXAMPLES Using the blow mold shown in Example 5, through the steps described with reference to FIG. 6, as shown in FIG. 7, five fully fused state around the blow hole Thus, a hollow molded body closed was obtained.

As the blow molding resin, polyethylene (manufactured by Showa Denko KK, trade name "SHOREX 555"
1 ”) was used. As the core mold 12, one having a protrusion 125 having a protrusion height A ₂ of 13 mm and a diameter D ₃ of 50 mm was used. As a cylindrical body, the outer diameter D ₁ is 3
5 mm, inner diameter D ₂ is 5 mm, protrusion length A ₁ is 30 mm,
The material used was aluminum and the heating wire was embedded in the wall of the tip. The outer diameter of the ventilation needle is 4.
A 5 mm one was used.

The tip of the cylindrical body 2 is advanced by 2 mm into the cavity 13 of the blow molding die 1 having a temperature of 20 ° C., and the parison 4 having a resin temperature of 210 ° C. is supplied into the cavity 13. The mold was closed while pre-blowing at a pressure of ² kg / cm ² . Immediately after closing the mold, parison 4
The vent needle 3 is advanced so that the tip portion of the core side wall 41 is inserted, and pressurized gas is blown into the hollow portion of the parison 4 at a pressure of 10 kg / cm ² to keep the parison 4 on the cavity surface for a predetermined time. Pressed and shaped.

30 seconds after the mold was closed, the parison was pulled from the ventilation needle 3.
The pressure in the hollow part of 4 is 5 kg / cm ²To lower
Then, continue to blow compressed gas while maintaining the pressure.
Was. 60 seconds after the mold is closed, the heating of the tip surface of the tubular body 3 is started.
90 seconds after closing the mold, raise the temperature of the tip surface to 180 ° C.
Allowed to warm and maintained at that temperature. 120 seconds after mold closing
While retracting the ventilation needle 3 into the tubular body 4, the parison 4
Exhaust was performed so that the internal pressure of the tank became atmospheric pressure.

135 seconds after the mold was closed, the wall 41 on the core mold side of the parison 4 was pressed while being heated by the front end surface of the heated cylindrical body 4, and the cylindrical body 3 was moved forward by 10 mm to move the parison. No. 4 was pressed against the opposing cavity-side wall 42 to fuse the two. At that time, heating of the tip surface of the tubular body 3 was stopped. 180 seconds after the mold was closed, the mold was opened while retracting the tubular body to obtain a container-shaped hollow product having a double wall and the periphery of the blow hole being fused. When the container-shaped hollow molded body thus obtained was filled with water, no water leakage occurred.

Comparative Example After the mold was closed for 135 seconds, the ventilating needle was retracted to release the pressure in the hollow part of the parison 4 to atmospheric pressure, and then the mold was opened without advancing into the cavity of the tubular body at all. Except for the above, a hollow molded article having a double wall and having blow holes was obtained in the same manner as in the example. With respect to this hollow molded article, the blow hole was closed in a separate step according to the method described in Japanese Patent Publication No. 3-33088. As a result, it took 150 seconds to close all the blow holes.

[0034]

Since the blow molding die of the present invention is constructed as described above, it can be used as a blow molding die for closing the blow hole in the blow molding step.

Since the method for producing a hollow molded article of the present invention is constructed as described above, in the blow molding step,
The periphery of the blow hole can be completely closed, and a hollow molded body with the blow hole closed can be easily obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a blow molding die of the present invention.

FIG. 2 is a cross-sectional view illustrating the first half of the steps of an example of the method for producing a hollow molded body of the present invention, which uses the blow molding die shown in FIG.

FIG. 3 is a cross-sectional view illustrating an intermediate step of an example of the method for producing a hollow molded body of the present invention using the blow molding die shown in FIG.

FIG. 4 is a cross-sectional view illustrating the latter half of the steps of an example of the method for producing a hollow molded body of the present invention using the blow molding die shown in FIG.

FIG. 5 is a cross-sectional view showing another example of the blow molding die of the present invention.

FIG. 6 is a cross-sectional view illustrating a step of another example of the method for producing a hollow molded body of the present invention, which uses the blow molding die shown in FIG.

FIG. 7 is a plan view showing an example of a hollow molded body obtained by the present invention.

FIG. 8 is a cross-sectional view showing still another example of the blow molding die of the present invention.

[Description of sign]

 1, 1 ′, 1 ″ Mold for blow molding 2 Cylindrical body 3 Venting needle 4 Parison 11 Outer mold 12 Core mold 13 Cavity 24 Heating wire

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Claims (2)

[Claims] 1. A cavity is provided between an outer die and a core die, and a tubular body is provided in the core die so as to be able to advance and retreat from the cavity surface into the cavity. A vent needle is provided to move back and forth,
A blow molding die, comprising a heating means for heating the tip end surface of the tubular body. 2. A method for manufacturing a hollow molded article using the blow molding die according to claim 1, wherein a vent needle is advanced through the side wall of the parison supplied into the cavity by advancing the vent needle. While blowing a pressurized gas from the tip, a step of shaping the parison by pressing it against the cavity surface, and exhausting the inside of the parison from the ventilation needle, while heating the tip surface of the tubular body by the heating means, The cylindrical body is advanced toward the cavity surface of the opposing outer mold in the cavity, and the side wall of the core side of the parison is heated above the melting point and pressed against the wall of the opposite outer mold side of the parison to fuse. The method for producing a hollow molded article, which comprises the step of: