JPS6058012B2 - Molding method of thermoplastic resin foam sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a thermoplastic resin foam sheet, and more particularly to a method for manufacturing a thermoplastic resin foam molded article for a container having a large drawing ratio using the foam sheet.

Conventionally, deep drawing of thermoplastic resin sheets, for example, sheets with a drawing ratio of about 1.2 to 15, can be easily formed in the case of non-foamed sheets, but this has not been easy in the case of foamed sheets.

This is because non-foamed sheets have a wide temperature range before they are damaged by heat, and can be softened sufficiently to allow molding with a drawing ratio of 1 or more. (Hereafter P.S.
(referred to as P), the surface cells are easily destroyed by heating.
Since it is not possible to soften the inside sufficiently, and the surface skin layer itself is weak, a drawing ratio of only about 0.2 to 0.3 can be obtained.In order to increase the drawing ratio, one side of the PSP is unfoamed. Even for laminated PSP backed with a sheet, the aperture ratio was limited to about 0.5.

In addition, the difficulty in deep drawing of foam sheets lies not only in the drawing ratio mentioned above, but also in the shape of the molded product, especially as the inclination angle θ of the female die is smaller, as shown in Figure 5, and in the case of a multi-cavity die. The smaller the mold spacing 1, the more difficult the molding becomes. In general, the drawing ratio of a molded product is required to be 1 to 1.2 for commercial value when targeting beverage storage containers, and the angle θ of the molded product is
Smaller molds are preferable in terms of capacity and stability when left standing.Also, the smaller the mold interval 1, the higher the yield of molded products and the smaller the amount of scrap, which is advantageous in terms of cost. As shown in FIG. 1, the molding method is to first bring a female die 11 into contact with a heated foam sheet 4, and at the same time press the foam sheet 4 with a male die 2 to open the external vacuum holes 13 and the female die. A common method is to apply vacuum suction through internal vacuum holes 12. In this method, the foam sheet 4 is squeezed by the female mold corner 16, and the surface of the foam sheet 4 is cooled and solidified the moment it comes into contact with the female mold 11. It becomes difficult to stretch.

As a result, the foamed sheet 4 has uneven elongation and cracks in defective areas 17.
, and a molded product with a drawing ratio of only about 0.5 can be obtained.Also, even with Temine day P, which has good elongation, the drawing ratio is about 0.7, and the mold angle θ shown in Fig. 5 is more than 100. In addition, even in a multi-cavity mold, the interval 1 between the molds is 0.4 to 0.5 relative to the mold diameter D, and the current situation is that around 50% of the original foam sheet is discarded as scrap. . The present invention solves these drawbacks, and it is possible to deep-draw a thermoplastic resin foam sheet to a drawing ratio of 1 or more, which was difficult with conventional methods, and to form a thermoplastic resin foam sheet with a drawing ratio of 0.5 to 1.0. For molded products, it is possible to improve the yield compared to the conventional method, to mold the wall thickness of the molded product uniformly, to improve the buckling strength and lateral pressure strength of the molded product, and to improve the shape of the molded product as shown in Figure 5. The purpose of this invention is to provide a method of molding a thermoplastic resin foam sheet that makes it possible to change the mold angle from 0 to a small angle that is highly difficult.

That is, in the present invention, after heating a thermoplastic resin foam sheet, a male mold is pressed onto the sheet to a predetermined position while the sheet is held between upper and lower clamp frames, and the clamp frame, male mold, male mold mounting base, and The space surrounded by the thermoplastic resin foam sheet is vacuumed, the sheet is brought into close contact with the surface of the male mold, the female mold and the male mold are brought into close contact via the sheet, and then the female mold is It is characterized by setting the outer mold of the foam molded product into a female mold shape by suctioning from the side.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram of a conventional example, and FIGS. 2, 3, 4, and 5 are explanatory diagrams of the present invention. The figure is a cross-sectional view of the foam sheet pressed by the male mold, Figure 3 is a cross-sectional view of the device with the foam sheet in close contact with the male mold, Figure 4 is a cross-sectional view of the device after molding is completed, and Figure 5 The figure shows a cross-sectional view of a multi-cavity mold.

1 is a clamp frame, 2 is a male mold, 3 is a male mold mounting base, 4 is a foam sheet, 5 is a space, 6 is an air escape hole, 7 is a seal, 8, 12 are Internal vacuum hole, 9,1
3 is an external vacuum hole, 10 and 15 are pistons, 14 is
A female mounting base, 16 a female corner, and 17 a defective part. In FIG. 2, the added thermoplastic resin foam sheet (hereinafter referred to as foam sheet) is sandwiched from above and below by a clamp frame 1, and then pressed by a male mold 2 fixed to a piston 10. . At this time, the male mounting base 3 and the clamp frame 1 should be in contact with each other, and the contact area should be sealed with the seal 7.
, to ensure complete sealing and prevent air leakage. As a result, a closed space 5 surrounded by a clamp frame 1, a male mold 2, a male mold mounting base 3, a seal 7, and a foam sheet
will occur. This space is evacuated through an internal vacuum hole 8 provided in the male mold 2 and an external vacuum hole 9 leading to an external vacuum line, not shown. As a result, the foamed sheet member comes into close contact with the male mold 2, as shown in FIG. After molding the male mold 2 with the foam sheet 4 in close contact with it in advance in this way, the female mold 1 is attached to the female mold mounting base 14 as shown in FIG.
1 with a piston 15 to regulate the wall thickness of the molded product, and at the same time, the inner vacuum hole 12 and the outer vacuum hole 13 suck the corner part to completely set the outer mold of the foam sheet 4 into the shape of the female mold 11. do.

Thereafter, the male mold 2 and female mold 11 are opened by pistons 10 and 15, and the molded product is taken out. From the above molding methods, the first
As shown in the figure, the sheet ejected by the male mold is squeezed by the corner of the female mold, eliminating forced ejection of the foam sheet and local cooling of the foam sheet, allowing the foam sheet to be stretched uniformly. Moreover, since the occurrence of defective products is eliminated, it becomes possible to mold deep-drawn foam molded products with a drawing ratio of 1 or more, and in some cases close to 1.5, which could not be practically achieved using conventional methods. Ta.

Here, the thermoplastic resin foam sheet is a foam sheet that contains air bubbles in the sheet and softens when heated, and suitable materials include polyethylene, ABSl polypropylene, polyethylene, vinyl chloride, nylon resin, etc.

Examples will be described below, but the present invention is not limited thereto.

Example 1 Female mold diameter 83Tm depth 83TnIn (drawing ratio 1.0) angle θ = 7 molds, mold spacing 1 = 45T! r! n (including 9 molds arranged with clamp frame W = 579 mm, and as a foam sheet, 1 mm foam thickness is 0.15 to PSP in order of 2.5 mm)
A laminate PSP obtained by laminating impact-resistant styrene resin sheets of - was molded by the molding method of the present invention.

As a result, the upper wall thickness is 1.8WrIn1, the lower wall thickness is 1.6Trr.
! A molded product with an n1 bottom wall thickness of 1.5 wa was obtained. In this case, the weight yield of the molded product based on the original fabric was 55% or more. On the other hand, in the conventional molding method, from the bottom
A hole formed from the upper part of the 20Tn, making it impossible to mold. Example 2 Female diameter 837wt depth 77wt (aperture ratio 0.9
3), angle θ=100, mold spacing 30T! Using a mold in which 9 molds were arranged with Rln (of which the clamp frame width W = 3Tfn), a laminate Ps manufactured by U-Pearl Co., Ltd. was used as a foam sheet.
It was molded using pr trade name #L7O8J.

In this case, the thickness of the molded product is 1.9Tn at the top! R lower part 1.8
It was 1.777rm at the bottom of 7m.

Also, the buckling strength under the condition of DOwnspeed 2-/min is 1
5 to 20k9, and the lateral pressure strength required to distort the side surface of the molded product in a 10-order order was 0.8 to 1.2 kg, which was sufficient for practical use. In this case, the weight yield of the molded product is 6%
That's all. On the other hand, the wall thickness of the molded product molded using the conventional method is 2.1 mm at the top, 0.5 mm at the bottom, and 1.3 mm at the bottom.The buckling strength is 4 to 7k9, and the lateral pressure strength is 0.2. ~1
．． It was 3k9 and not suitable for practical use. Example 3 Female mold diameter 7, depth 105 (drawing ratio 1.5) angle θ = 8
．． 5 diameter, mold spacing 45W! E (including clamp frame W = 3T
! r! Using a mold with 9 pieces arranged in n), a polypropylene resin with 1.5 times the foam and a thickness of 2 gourds was used as a foam sheet.
Molding was carried out using the method and apparatus according to the invention.

As a result, the molded product yield was 50%. Also, although there were some difficulties in terms of strength, a molded product with a drawing ratio of 1.5 was obtained.
Example 4 Female diameter 83T! n1, depth 10.8 (aperture ratio 1.3)
Using a single-cavity mold with an angle of 0=100, we used Laminate Pspr manufactured by U-Pearl Co., Ltd., product name #L7, as a foam sheet.
O8J was vacuum formed.

As a result, a foamed molded product with no thickness deviation similar to that of Example 1 was obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional example, Fig. 2, Fig. 3, Fig. 4,
Fig. 5 is an explanatory diagram of the present invention, in which Fig. 1 is a sectional view showing the occurrence of defects, Fig. 2 is a sectional view of the foam sheet pressed by a male mold, and Fig. 3 is a sectional view of the foam sheet pressed by a male mold. FIG. 4 is a cross-sectional view of the device in a state where it is in close contact with a male mold, FIG. 4 is a cross-sectional view of the device in a state where molding is completed, and FIG. 5 is a cross-sectional view of a multi-cavity mold. Code, 1... Clamp frame, 2... Male type, 3... Male type mounting base, 4... Foam sheet, 5... Space Part, 6... Air escape hole, 7... Seal, 8, 12... Internal vacuum hole, 9
, 13... External vacuum hole, 10, 15...
Piston, 14...Female mounting base, 16...
...Female corner, 17...Defective part.

Claims (1)

[Claims] 1. After heating the thermoplastic resin foam sheet, press the male die onto the sheet to a predetermined position while holding the sheet between the upper and lower clamp frames, and press the male die onto the sheet to a predetermined position.
The space surrounded by the male mold mounting base and the thermoplastic resin foam sheet is vacuumed, the sheet is brought into close contact with the surface of the male mold, and then the female mold and the male mold are brought into close contact with each other via the sheet. 1. A method for molding a thermoplastic resin foam sheet, characterized in that the outer mold of the foamed molded product is set in the shape of the female mold by suction from the female mold side.