JPH0687153A - Production of plastic molded object and device therefor - Google Patents

Abstract

PURPOSE:To obtain a method for producing a plastic molded object superior in rigidity without local wall thickness reduction in a plastic molded piece having a specific wall thickness or less and a device suitably used in this method CONSTITUTION:A peripheral edge part of a plastic sheet 1 is clamped by clamping/heating means 2, 3. The plastic sheet 1 is heated except at least a plastic sheet part 1a corresponding to the bottom of a recessed part 15. Therefore, if a force is applied to the plastic sheet part 1a corresponding to the bottom of the recessed part 15 in the forming of the recessed part 15, the plastic sheet part 1a is molded into the bottom of the recessed part 15 without a possibility of expansion, thus still having the same thickness as the plastic sheet 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a plastic molding having a recess and used as a container or the like.

[0002]

2. Description of the Related Art A concave molded body made of a plastic material is used as a container or the like. In general, injection molding is used when a three-dimensional molded body is manufactured using plastic. However, if a thin concave molded body having a thickness of 1 mm or less is to be manufactured by injection molding, it is difficult to mold the molten plastic material because the melted plastic material does not easily flow smoothly in the mold because the inside of the mold is narrow.

Therefore, the entire plastic thin plate is heated to a temperature at which it can be deformed, the inside of the mold is depressurized to bring the plastic thin plate into close contact with the inside of the mold by vacuum molding, or the plastic thin plate is pressed to mold the plastic thin plate into a metal mold. Pneumatic molding is performed in which a mold is pressed and molded.

[0004]

However, it is difficult to control the wall thickness of the molded body by these methods. For example,
2 is a perspective view, and FIG. 3 is a sectional view taken along the line AA ′, in the case of manufacturing a molded body having a truncated pyramidal recess, the ridges 21 and the corners 22 have different thicknesses. Since it is thinner than the portion, there are drawbacks such as poor rigidity of the molded body.

The present invention solves the above drawbacks,
The purpose is to obtain a plastic molded product having a thickness of 1 mm or less without locally reducing the thickness.
An object of the present invention is to provide a manufacturing method capable of manufacturing a plastic molded body having excellent rigidity and an apparatus preferably used for this manufacturing method.

Another object of the present invention is to provide a manufacturing method and a manufacturing apparatus capable of easily manufacturing the plastic molded body in a short time.

[0007]

In order to form a recess in a thin plate while avoiding local thinning, a deep drawing in which the thin plate is drawn into the mold and formed is effective. When a thin plastic plate is uniformly heated and deep-drawn, plastic is not work-hardened unlike metal, so if a force is applied by bringing it into contact with a punch having a ridge, it breaks at the ridge. The inventors have found that the thin plate can be partially softened by heating and deep-drawn to prevent breakage at the ridge.

That is, the present invention is a method for manufacturing a plastic molded body in which a recess is formed while leaving a peripheral edge of a plastic thin plate, and sandwiching the peripheral edge and at least a plastic thin plate portion corresponding to the bottom of the recess. Except for this, the step of heating and the step of applying a force to the thin plate portion to form the concave portion are performed, whereby the above object is achieved.

Further, the manufacturing apparatus of the present invention is a manufacturing apparatus of a plastic molded body in which a concave portion is formed by leaving a peripheral edge portion of a plastic thin plate, and the plastic material sandwiching the peripheral edge portion and corresponding to the bottom of the concave portion. The sandwiching / heating means for heating at least the thin plate portion and the force applying means for applying a force to the thin plate portion to form the concave portion are provided, thereby achieving the above object.

Preferably, in the above manufacturing apparatus, the sandwiching / heating means comprises a pair of sandwiching / heating members each having a through hole, and one sandwiching / heating member having a through hole has the other sandwiching / heating member. The diameter is larger than the through hole of the member.

Further, the force applying means comprises a punch,
The punch is configured to be inserted into the through hole of the other sandwiching / heating member.

Further, a cooling auxiliary die is provided on the side opposite to the force-applying means with the plastic molded body having the recess formed therebetween so as to be able to come into contact with and separate from the plastic molded body, and the cooling auxiliary die is approached. By so doing, it is preferable to contact the plastic molded body and cool the concave portion.

Further, the punch is provided with an outlet hole for cooling air flow in order to cool the side surface of the recess.

More preferably, cutting means for cutting off a part or all of the peripheral edge of the molded plastic is provided on the contact side of the cooling auxiliary die with the plastic molded body.

[0015]

Since the peripheral portion of the plastic thin plate is sandwiched by the sandwiching / heating means and the plastic thin plate portion corresponding to the bottom of the recess is removed at least for heating, it corresponds to the bottom of the recess when forming the recess. Even if a force is applied to the plastic thin plate portion, this thin plate portion does not expand, and a recess is formed while keeping the thickness of the plastic thin plate as it is.

When a plastic thin plate is sandwiched by a pair of sandwiching / heating members each having a through hole, the thin plate is heated at a portion other than the through hole. Since one of the sandwiching / heating members has a larger diameter than the other sandwiching / heating member, the thin plate portion on the through hole having the smaller diameter is not heated. This unheated portion becomes a thin plate portion corresponding to the bottom of the recess.

When the punch is inserted through the through hole of the other sandwiching / heating member, the upper surface thereof abuts the thin plate portion corresponding to the bottom, and a force is applied to the thin plate portion to form a recess.

Further, the cooling auxiliary die comes into contact with the concave portion formed by the force applying means, and contacts and cools the concave shape while maintaining the concave shape. At this time, when cooling air is jetted from the blowout holes provided in the punch, the concave portion is pressed against the cooling auxiliary die and is also cooled by the cooling air itself, so that the die holding and cooling are more effective. .

Further, the cutting means provided in the cooling auxiliary die cuts off a part or all of the peripheral edge of the plastic when the cooling auxiliary die is fitted with the recess, so that the molding can be cooled and trimmed at the same time. Done.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment to which the present invention is applied in the case of manufacturing a molded product having a flange portion and a frustoconical recess will be described below with reference to the drawings.

In this embodiment, a commercially available circular biaxially stretched polyethylene terephthalate thin plate (thickness 188 μm, diameter 90 mm) was used as the plastic thin plate.

As shown in FIG. 1A, the manufacturing apparatus used in this embodiment includes a heating die 2 supported by a die holder 5 via a heat insulating plate 6 and having a through hole 12, and a heating die. 2 is provided below the punch 4
And a holding plate 3 having a through hole 11 having a diameter smaller than the through hole of the heating die 2 and a columnar shape below the holding plate 3 and inserted into the through holes 11 and 12. And a cooling auxiliary die 10 provided at a position facing the punch 4 and capable of being inserted into the through hole 12 and having a truncated cone-shaped forming die.

Heaters 7 and 8 are embedded in the lower portion of the heating die 2 and the upper portion of the holding plate 3, respectively. The heating die 2 and the pressing plate 3 are configured such that a plastic thin plate (hereinafter referred to as a thin plate) 1 is sandwiched between them.

The punch 4 is provided with a blowout hole 9 for passing cooling air from the inside to the side surface, and the cooling air supplied to the inside from the outside of the punch 4 is jetted from the side surface. Is configured.

The cooling auxiliary die 10 is provided with a ventilation hole 14 penetrating from the outside into the mold.
Further, a knife 13 is provided as a cutting means on the edge thereof.

The details of each member of the manufacturing apparatus in this embodiment are as follows. The mold tool is tool steel SK3.
Is formed by.

Heating die 2: inner diameter of the inner space 12 is 60 m
m, shoulder radius 4 mm, presser plate 3: hole 11 inner diameter 30 mm, punch 4: diameter 28 mm, shoulder radius 4 mm, cooling auxiliary die 10: upper side 28 mm, lower side 60 mm, height 2
0 mm truncated cone shape.

A process for producing a plastic molded body using the above apparatus will be described.

First, the thin plate 1 is sandwiched between the heating die 2 and the holding plate 8 with a sandwiching force of 936 kgf, and heated at 230 ° C. for 40 seconds so that the thin plate 1 can be deformed. At this time, the portion 1a on the through hole 11 of the holding plate 8 of the thin plate 1
Is not heated. The thin plate 1 is the heating die 2 or the pressing plate 8
The portion 1b and the sandwiching portion 1c which are in contact with are heated, and the portion 1b and the sandwiching portion 1c become deformable.

After the portion of the thin plate 1 on the holding plate 3 is softened, as shown in FIG. 1 (b), punching is performed by a hydraulic press (not shown) of a container of 10 tons at a pushing speed of 15 mm / sec. 4 is raised and the through hole 11 of the restraining plate 3 is raised.
Of the thin plate 1 is brought into contact with the unheated portion 1a of the thin plate 1, and the thin plate 1 is pushed up while the heating die 2
It is inserted into the through hole 12. With the rise of the punch 4,
The thin plate 1 is drawn into the through hole 12 of the heating die 2, and the heated portion 1b is contracted in the circumferential direction of the punch 4 and is stretched in the radial direction to become the side wall of the concave portion 15, and the holding portion 1c is formed. It becomes the flange of the body. The portion 1 a that abuts the upper surface of the punch 4 becomes the bottom of the recess 15. Since the bottom portion is not softened, the wall thickness does not become thin. Also,
At this time, the thickness of the side wall of the recess 15 can be adjusted by adjusting the holding force between the heating die 2 and the pressing plate 3 and the rising speed of the punch 4. Thereby, the molding can be performed without locally reducing the wall thickness.

After the recess 15 is formed, as shown in FIG. 1 (c), compressed air (Bourdon tube pressure 5 kg / cm ² ) at room temperature is pressed into the recess 15 through the blowout hole 9 of the punch 4, While cooling the side surface of the concave portion 15, the lowered cooling auxiliary die 10 is brought into contact with the outer surface of the concave portion 15, and the concave portion 15 is forcedly cooled while being pressed against the cooling auxiliary die 10. Thereby, the recess 15 can be cooled in a short time. Further, by blowing air from the blowout holes 9 in this manner, the side wall of the concave portion 15 which is easily distorted inward can be completely brought into contact with the cooling auxiliary die 10 while being cooled.

By forced cooling as described above,
The recess 15 can be cooled rapidly. The mold holding time for fixing the shape of the molded body in this example was 10
It took about a second and could be cooled in a very short time.

Further, the concave portion 15 is cut at the flange portion by the knife 13 provided at the edge portion of the cooling auxiliary die 10 to form a molded body. Therefore, trimming can be performed at the same time as cooling, and the working time can be shortened. After trimming, the cooling auxiliary die 10 is moved from the inside of the heating die 2, pressurized air is introduced from the blower holes 14 thereof, and the molded product is taken out. As a result, the molded body after cooling can be quickly taken out.

In the manufacturing method of the present invention, cooling of the formed concave portion does not have to be performed rapidly as in this embodiment, and the cooling auxiliary die 10 and the blowout hole 9 of the punch 4 are essential. is not. However, if these forced cooling means are omitted, the mold holding time becomes long. In the above example, when the recess 15 was cooled using only the cooling auxiliary die 10, the mold holding time was about 25 seconds. Further, the concave portion 1 is used without using the cooling auxiliary die 10 or the like.
When 5 was naturally cooled, a mold holding time of 10 minutes or more was required after turning off the heater. If not sufficiently cooled, the side wall and flange of the molded product may warp, sag, and wrinkle due to residual heat, and the height of the molded product may decrease by 25 to 50% due to recovery of residual strain generated during deep drawing.

Whether the cooling is carried out by any of the above three methods, the obtained molded article is subjected to 1 ° C in an oven at 120 ° C.
Even after heating for 0 minutes, no change in shape was observed within a range that could be visually discerned. No shape change was observed in the flange.

The plastic thin plate used in the present invention is not limited to the one used in the above embodiment, and a film or sheet made of a thermoplastic polymer and having a thickness of about 25 to 1000 μm is used.

The above-mentioned thermoplastic polymer has a melting point of 1
A crystalline polymer having a temperature of 20 ° C. or higher is suitable. Examples thereof include polyethylene, polypropylene, polyethylene terephthalate, etc., but are not particularly limited thereto. A biaxially stretched film of polyethylene terephthalate or polypropylene is particularly preferable because it is lightweight, tough and has excellent heat resistance. In particular, polyethylene terephthalate has excellent heat resistance. For thin plastic plates, talc, mica,
Calcium carbonate, a pigment, particles made of an organic material, hollow fine particles, small voids and the like may be contained.

For example, a non-crystalline polystyrene film (thickness 350 μm, non-stretched product) is used and the heating temperature is 98.
The shape of the molded article obtained in the same manner as in the above-mentioned example except that the temperature was set to 0 ° C. was greatly broken when heated in an oven at 115 ° C.

If a thin plate thinner than 25 μm is used,
It becomes difficult to pinch with a uniform pressure, 1000 μm
When a thicker thin plate is used, the lightness of the molded product is poor.

Further, the molded body obtained by the manufacturing method of the present invention is not limited to the frustoconical shape with the flange of the above-mentioned embodiment, but the shape without the flange as shown in FIG. 4 and the pyramidal trapezoidal shape shown in FIG. 2 and FIG. It can also be applied to the case of producing a molded body such as a hemisphere. Further, a molded body having a shape in which a large number of recesses are formed in one thin plate, such as a blister package, may be used. Generally, when these molded bodies have ridges and corners, their radius of curvature R is 1 mm or more. The punch is selected according to the shape of the molded body.

Further, in the above-mentioned embodiment, an apparatus provided with a pair of sandwiching / heating means and one punch was used, and one thin plate was used as the material, but an apparatus provided with a plurality of sandwiching / heating means and punches. As shown in FIG. 5, a large thin plate 41 formed by punching a plurality of circular thin plates used in the above embodiment into the same thin plate material may be used to produce a plurality of molded bodies at one time. Is. In this thin plate 41, a molding portion 44 having a shape corresponding to the molding shape is punched except for the connecting portion 43. By forming the punched portion 42 in this manner, the forming portions 44 are not pulled during deep drawing, and do not affect each other. With such a configuration, it is possible to further improve the production efficiency.

[0042]

According to the present invention, it is possible to manufacture a thin plastic molded body using a simple manufacturing apparatus without locally reducing the wall thickness.

In this manufacturing apparatus, the die is simple and inexpensive. In addition, the time required for shaping can be extremely shortened, trimming can be performed at the same time as or immediately after molding, and automation of take-out of the molded body can be achieved. It is possible to produce a molded product.

According to the present invention, it is possible to inexpensively produce a tough molded article which is lightweight and has excellent heat resistance and rigidity.
It is possible to produce a molded article that can sufficiently withstand deformation even when heat sterilization is performed at a high temperature or when a microwave oven is used. This molded product can be suitably used as a food container or the like.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a process of a manufacturing method of the present invention.

FIG. 2 is a perspective view showing an example of a plastic molded body manufactured according to the present invention.

FIG. 3 is a sectional view taken along the line AA ′ in FIG.

FIG. 4 is a cross-sectional view showing another example of the plastic molded body manufactured by the present invention.

FIG. 5 is a plan view showing an example of a plastic thin plate used in the present invention.

[Explanation of symbols]

 1 Plastic Thin Plate 1a Unheated Part 2 Heating Die 3 Suppression Plate 4 Punch 7, 8 Heater 9 Blowout Hole 10 Cooling Aid Die 13 Knife 15 Recess

Claims (7)

[Claims] 1. A method for producing a plastic molded body in which a recess is formed by leaving a peripheral edge of a plastic thin plate, wherein the peripheral edge is sandwiched and heating is performed by removing at least the plastic thin plate portion corresponding to the bottom of the recess. And a step of applying a force to the thin plate portion to form a concave portion, the method for producing a plastic molded body. 2. An apparatus for producing a plastic molded body in which a concave portion is formed by leaving a peripheral edge portion of a plastic thin plate, wherein the peripheral edge portion is held and at least the plastic thin plate portion corresponding to the bottom of the concave portion is heated. An apparatus for manufacturing a plastic molded body, comprising: a sandwiching / heating means for forming a concave portion by applying a force to the thin plate portion. 3. The sandwiching / heating means comprises a pair of sandwiching / heating members each having a through hole, wherein the through hole of one sandwiching / heating member is more than the through hole of the other sandwiching / heating member. The apparatus for manufacturing a plastic molded body according to claim 2, wherein the plastic molded body has a large diameter. 4. The apparatus for manufacturing a plastic molded body according to claim 3, wherein the force applying means comprises a punch, and the punch is inserted through a through hole of the other sandwiching / heating member. 5. A cooling auxiliary die is provided on the opposite side of the force-applying means with the plastic molded body having the recess formed therebetween so as to be able to come into contact with and separate from the plastic molded body, and the cooling auxiliary die is approached. The apparatus for producing a plastic molded body according to claim 2, wherein the plastic molded body is brought into contact with the plastic molded body to cool the concave portion. 6. The plastic molded body according to claim 5, wherein cutting means for cutting off a part or all of the peripheral edge portion of the molded plastic is provided on the side of the cooling auxiliary die that contacts the plastic molded body. Manufacturing equipment. 7. The apparatus for manufacturing a plastic molded body according to claim 4, wherein the punch is provided with an outlet hole for cooling air flow for cooling the side surface of the recess.