JPH08216241A - Sheet blow molding method and member therefor - Google Patents

Abstract

PURPOSE: To eliminate the contact trouble between sheets at the time of a molding air nozzle piercing process by preliminarily arranging a space member constituted so as not to obstruct the penetration of a nozzle tip and blow moldability to the nozzle insertion corresponding region in a first closed space. CONSTITUTION: A space member 8 constituted so as not to substantially obstruct the penetration of a nozzle tip and blow moldability is preliminarily arranged to the nozzle insertion corresponding region P in a first closed space S1. The peripheral edge parts of a sheet 1 and a sheet 1' having the spacer member 8 temporarily bonded thereto at a predetermined position by an acrylic rubber soln. are held under pressure by spacers 2 and clampers 3 to form the first closed space S1 and the sheets are heated and softened by a moving type infrared panel heater and, after the heater is removed, a pre-stretching air nozzle 4 is operated. Continuously, the sheets are pinched off by molds 6, 6' and, at the same time, a molding nozzle 7 is allowed to fall. By this constitution, the contact of the thermally softened sheets 1, 1' is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet blow molding method, and is useful for manufacturing a variety of hollow molded products, particularly heat insulating panels, advertising panels, thin containers, and other relatively large and flat hollow molded products. The present invention relates to a suitable sheet blow molding method and a member therefor.

[0002]

2. Description of the Related Art A method of reheating a preformed thermoplastic sheet, sandwiching it between a pair of molds, and pinching it off for blow molding is a well-known technique as one of sheet blow molding methods. (Plastic Processing Technology Handbook
Nikkan Kogyo Shimbun Ltd., published in 1979, Illustrated Dictionary of Plastic Molding Processing Terms, published by Industry Research Institute in 1990

6 to 8 illustrate a conventional method.
It First of all, as shown in FIG.
(Hereinafter abbreviated as sheet) 1, 1'peripheral edge is a continuous strip
Similarly, through the spacer 2 of
Clamping at 3, first closed space S Move after forming 1
Far infrared panel heater (hereinafter abbreviated as heater) 5,
Sheets 1 and 1'are softened by heating at 5 ', followed by FIG.
At the same time as removing the heater, a pair of dies (6,
 6 ') and pinch it off.
Penetrate the a nozzle into one sheet (sheet 1 in this example)
Through the second closed space S in the mold cavity Insert in 2
Then, as shown in FIG. 8, as shown in FIG.
Actuating the mold, seamless molding on the inner surface of the mold cavity
Form the body wall 9. FIG. 5 is obtained in this way
A sheet blow molded product is shown.

For the purpose of assisting the blow molding by the molding air nozzle, a plurality of pores communicating with the decompression line are provided on the inner surface of the mold cavity, and the sheet under blow molding is suctioned under reduced pressure to form the molded body wall 9. Techniques for promoting are also known.

[0005]

However, in the conventional sheet blow molding method, as shown in FIG. 7, in the step of inserting the molding air nozzle into the sheet and inserting it into the second closed space S2, as shown in FIG. The nozzle does not penetrate the sheet well, and as shown in FIG. 9, the portion of the heat-softening sheet that receives the tip of the nozzle is pushed down as the forming air nozzle descends, and the sheet 1, 1 ′ is pushed before the nozzle penetrates the sheet. However, even if heat fusion occurs at that portion, or even if fusion does not occur, the sheet is pulled at that portion and smooth blow molding is not performed, resulting in a defective product. Such inconveniences are likely to occur frequently when a large and thin molded product is molded or when the sheet is not pretensioned because the sheet gap is considerably smaller than the sheet area used for molding. The present inventor has conducted various researches on means for preventing such sheet-to-sheet contact trouble as much as possible, and as a result, has developed the method of the present invention and members for use in the method.

[0006]

SUMMARY OF THE INVENTION One of the present inventions comprises two sheets.
The thermoplastic sheet (1, 1 ') is attached to the peripheral portion.
The first closed space (S After forming 1),
A pair of molds with or without heat softening and pre-expansion
It is sandwiched between (6, 6 ') and pinched off.
The shape air nozzle (7) penetrates one sheet,
Insert into the second enclosed space (S2) in the bitty, then
In the sheet blow molding method for blow molding,
Construction that does not substantially interfere with the entry of the tip and blow moldability
The space member (8) that becomes
The seal placed in the nozzle insertion corresponding part (P) in (S1)
Toblow molding method, the other two of the present invention,
It presents a suitable configuration of the space member used for the law.
is there.

As the thermoplastic sheet used in the molding method of the present invention, any material can be selected according to the intended use of the molded product. Generally, for example, vinyl chloride resin, acrylic resin, A thermoplastic sheet having a thickness of about 1 to 10 mm made of polycarbonate resin or the like is used. The two sheets 1, 1'may be made of different materials or different colors.

The space member used in the molding method of the present invention is arranged in advance in the nozzle insertion corresponding portion (P) in the first closed space (S1), and the molding air nozzle is inserted through the one side heating and softening sheet. At this time, the sheet acts as a separator that prevents the sheet from being pressed by the tip of the nozzle or being subject to its own weight, and the distance between the two sheets is significantly narrowed. It has a structure that does not substantially hinder blowing and smooth blow molding.

The elements constituting the space member are roughly classified into a shape structure and a material. One type of shape structure suitable for the above requirements is a hollow trapezoid having a plurality of openings, and as illustrated in FIGS. 4A to 4D, the main part has a plurality of openings. It is a hollow trapezoid, the other type is
As exemplified in (e) and (e), the principal part is a continuous porous trapezoid.

In addition to this, the material suitable for the above requirements is
It is excellent in heat resistance (synonymous with heat distortion resistance) in contact with a heat-softening sheet during a series of molding steps. Since the heat resistance of the space member is better than that of the sheet to be molded, various molding materials can be selected according to the material of the sheet to be molded.

Further, from the viewpoint of material, a molding material that does not cause sticking or adhesion to the molding air nozzle or the heat-softened sheet to be molded. However, even a molding material that easily sticks or contacts can be used by providing a peeling film or layer in the main part. From the above points, when enumerating the types of molding materials that can be used in terms of the material of the space member, the thermoplastic materials include highly filled resin compositions, fiber reinforced plastics, engineering plastics, high molecular weight polyolefin silicones and / or fluoropolymers. Examples of the cross-linked molding material include unfilled or filled thermosetting resins, fiber reinforced plastics, various rubber materials, cross-linked polyolefins, and the like, and other open-cell materials. Further, molded products of fibers and papers can also be used.

Among these, particularly preferable materials include ultrahigh molecular weight polyethylene, crosslinked polyethylene, highly filled polypropylene, ethylene-propylene crosslinked products, polyethylene terephthalate, polyamide, polyphenylene oxad, polyphenylene sulfide, etc. A molding material with excellent properties. Further, a highly foamed open-cell body such as a phenol resin, a urea resin, or polyurethane can also be suitably used as the space member.

When the space member 8 of the present invention is arranged in advance in the insertion-corresponding portion P of the molding air nozzle 7 in the first closed space S1, it is temporarily fixed in advance to a predetermined position of the sheet 1'with an adhesive material. Alternatively, it may be arranged at a predetermined position between the two sheets 1 and 1'just before forming the closed space S1. As an adhesive material for temporarily fixing the space member to the sheet, a polymer-based adhesive material having excellent thermal stability and elongation, for example, a solution type adhesive material such as acrylic rubber or silicon rubber is suitable.

[0014]

【Example】

Molding target: a rectangular thin hollow molding M having a width B of 350 mm, a length L of 240 mm, a thickness T of 20 mm, and a wall thickness t ₁ of 2 mm. Sheet to be molded: Extrusion molded hard impact resistant vinyl chloride resin sheet having a thickness of 2 mm Test space member; Shape and structure for each test NO are as follows.

[0015] As shown in FIG. 1, a sheet 1 and a sheet 1 ′ in which a test space member is temporarily fixed to a predetermined place with an acrylic rubber solution are squeezed by a spacer 2 and a clamper 3 at a peripheral edge portion,
The first closed space S1 is formed, and the moving infrared panel heater heats and softens the heater, and the heater is removed. At the same time, the pre-expansion air nozzle 4 is operated. Then, as shown in FIG. 2, when the sheet is pinched off by the molds 6 and 6 ′ and the molding nozzle 7 is lowered at the same time, the tip of the nozzle tries to push down the sheet 1, but the space member 8 has a heat resistance. Since it is a trapezoid, it can be restrained from being pushed down, preventing contact between the heat-softened sheets 1 and 1 ', and because the sheet 1'is fixed by a space member, it is easy to penetrate the nozzle. Become. In addition, the nozzle has entered due to the specific shape and structure of the space member, and the air blowing into the closed space S2 has been made extremely smooth. The blow molding shown in FIG. 3 was completed through the above steps. N
O. As a result of repeated molding tests for all of Nos. 1 to 4, there was no defective rate due to sheet contact.

[0016]

EFFECTS OF THE INVENTION Since the seed blow molding method of the present invention and the space member used therefor are configured as described above, it is possible to eliminate the contact trouble between sheets during the step of penetrating the molding air nozzle. It has become possible to significantly reduce the defect rate of. Further, the present invention can be effectively applied to various sheet blow moldings, but particularly when it is used for producing a large-sized thin hollow molding, it exhibits a remarkable effect.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention.

FIG. 2 is a view showing the insertion of a molding air nozzle according to an embodiment of the present invention,
It is a principal part sectional view which shows a blowing start state.

FIG. 3 is a sectional view of an essential part showing a state at the time of blow molding in the example of the present invention.

FIG. 4 is a perspective view illustrating the shape of a space member used in the present invention.

FIG. 5 is a perspective view illustrating a sheet blow-molded product.

FIG. 6 is a sectional view of an essential part showing a conventional method contrasting with FIG.

FIG. 7 is a cross-sectional view of essential parts showing a conventional method in contrast to FIG.

FIG. 8 is a cross-sectional view of essential parts showing a conventional method in contrast to FIG.

FIG. 9 is a cross-sectional view of a main part illustrating a trouble at the time of inserting a molding air nozzle in a conventional method.

[Explanation of symbols]

 1, 1'thermoplastic sheet 2 spacer 3 clamper 4 pre-tensioning air nozzle 5, 5'movable infrared heater 6, 6'mold 7 molding air nozzle 8 space member 9 molded body wall 10 molded product pinched off part S1 First closed space S2 Second closed space P Nozzle insertion corresponding part M Sheet blow molded product

Claims (3)

[Claims] 1. Two thermoplastic sheets
(1, 1 ') is squeezed by the peripheral portion to create a first closed space.
(S After forming 1), it is softened by heating and pre-tensioned again.
Is not pretensioned and is pinched between a pair of molds (6, 6 ')
Turn off the air nozzle (7) for molding
Through the sheet of the second closed space in the mold cavity
A seat tube to be inserted into (S2) and subsequently blow molded
In the low-molding method, the nozzle tip enters and blows
Space member (8) having a configuration that does not substantially interfere with formability
In advance for nozzle insertion in the first closed space (S1)
Nozzle penetrating body characterized in that it is placed in the part (P)
Sheet Blow Molding Method to Prevent Contact Problems between Sheets
Law. 2. A space member for a sheet blow molding method according to claim 1, wherein a main part thereof is a hollow heat-resistant trapezoidal body having a plurality of openings. 3. A space member for a sheet blow molding method according to claim 1, wherein a main part of the space member is made of a continuous porous heat-resistant trapezoidal body.