JPS63303719A - Hot molding method of laminated molded product of thermoplastic resin - Google Patents

Abstract

PURPOSE:To obtain easily and reliably a hot molded product which is free from a defect of a blister and well-balanced, by a method wherein after the fringe part of a resin sheet has been clamped by a clamp of a molding machine, deaeration through vacuum drawing between both the resin sheets is begun about synchronously with starting of heating. CONSTITUTION:A vinyl chloride resin sheet (PVC sheet) 1 and PVC sheet 2 are put between a top and bottom pair of clamps 6, 7 for a hot molded film and fixed under a state where an air suction frame 3 of a rectangular cross section is interposed between the fringe parts of the sheets. Then after starting of deaeration operation through suction between both the PVC sheets 1, 2 through a suction hole 5 of the air suction frame 3, the same is heated by a top and bottom heaters 8, 9. Consequently, the PVC sheets 1, 2 becomes a state where they adhere closely to each other due to softening of them and a laminated material 10 is formed by performing hot fusion. Therefore, the laminated material 10 which is heated and under a softened state is set up onto a mold 12 of an air-pressure forming machine 11. Simultaneously with sending in of compressed air (a) through the upper part ventilation (b) is performed through the lower part, molding is performed at 4 development magnifications and then a molded product A which is free from a defect of a blister in a box-like state is obtained by performing cooling and demolding.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a synthetic resin molded product used for, for example, a lighting cover, an outer shell of an attache case, a casing/cover of a computer, etc. The present invention relates to a thermoforming method for producing a laminate molded product made of a laminate of resin sheets.

Conventional technology Resin molded products for the above-mentioned purposes are often molded in order to improve the design by making the front and back sides different colors, or to add decorations such as back print patterns or designs to the surface. A laminated layer of synthetic resin sheets (including films) of different colors or different types that are layered on each other for various purposes such as improving the strength and heat resistance by supplementing the rigidity, impact resistance, and heat deformation resistance of the material. It may be thermoformed with material. Conventionally, the manufacturing of molded products using such laminated materials involves first manufacturing a laminated material by bonding multiple resin sheets together using heat-pressing or adhesive, and then using pressure forming or vacuum forming. , or a combination thereof, by pneumatic molding. However, with this manufacturing method, a wide variety of laminates can be produced depending on the purpose of the molded product, the type of design, etc. ! 91F4, material management is very difficult, and there is a problem that it is not suitable for manufacturing a wide variety of molded products in small quantities. For example, when trying to obtain various molded products with different color combinations on the front and back sides, it is necessary to prepare in advance various types of laminates corresponding to the types, and material management is required. was really troublesome.

As one means to solve these problems, the present applicant's earlier application, JP-A-59-1856, has been proposed.
As shown in No. 74, a thermoforming method was proposed in which the lamination operation and thermoforming operation of thermoplastic synthetic resin sheets are performed in a series of continuous steps. This thermoforming method basically consists of two thermoplastic resin sheets (21) (22) that are to be laminated together, and a breathable member (20) placed between their peripheral edges, as shown in Figure 7. In the interposed state, the resin sheets (21) (22) are clamped and fixed by the upper and lower clamps (23) (24) of the thermoforming machine, and then both resin sheets (21) (22
) is heated with the upper and lower heaters (25) and (26) to soften it, and the softening causes the resin sheet to stretch and the air to escape between the sheets (21) and (22) from the breathable member (20). After bringing them into close contact, thermoforming such as air pressure forming or vacuum forming is performed.

However, when using the above thermoforming method, as shown in Figure 8, a residual air layer (27) is often formed between the two resin sheets (21) and (22), resulting in so-called blistering defects in the molded product. There was a problem that this could occur.

This defect tends to occur more easily as the resin sheet becomes thinner. For this reason, as described in the above publication, after the resin sheets (21)' (22) are heated and softened, the air between the resin sheets (20) is actively sucked out before molding. Attempts have also been made to solve the problem, but a complete solution to the above problem has not been achieved.

The present inventors conducted various investigations into the causes of this, and found that while the resin sheet (21) (22) elongates itself as shown in Figure 8 when it is heated and softened, it also elongates inside the sheet during sheet molding. Residual stress causes irregular and complex wavy deformation, so even if the above-mentioned active suction and air removal is performed in this state, a sealed space is still formed between both sheets and some of the remaining air escapes. The passage was lost, but it remained intact,
As a result, it was found that the above-mentioned residual air portion (27) causes blistering defects in the molded product.

Means for Solving the Problems This invention solves the above problems by adjusting the relative timings of the starting points of heating and suction air removal based on the above-mentioned findings and as a result of further research. We have discovered that it is possible to easily and reliably obtain a well-proportioned thermoformed product without any blistering defects, and have completed this process.

Therefore, in this invention, when two thermoplastic resin sheets are superimposed and joined together under heat-softened conditions, and then pneumatically formed into a desired shape, the two resin sheets are An air suction frame connected to a vacuum pump is interposed between the peripheral edges of the resin sheets, and after the peripheral edges are clamped and fixed by the clamps of the molding machine, the suction frame is used to apply suction between the two resin sheets at least before the start of heating. A venting operation is started, and heating is performed while the suction venting operation is continued to heat and soften both resin sheets to form a tight bonding unit, and then the pneumatic molding is performed. The summary is a thermoforming method for thermoplastic resin laminate molded products.

In the above, "pneumatic forming" refers to pressure forming,
This includes vacuum forming and pressure/vacuum combined forming methods.

In addition, "before the start of heating" is used not only before the start of heating, but also includes the case where suction air removal is started at the same time as the start of heating. '' is used to include not only the exact same point in time, but also the point in time before the resin sheet is substantially affected by heating. Therefore, the scope of the present invention also includes a case where suction and air removal is started after a slight time lag after heating is started using a heating heater.

The material of the thermoplastic resin sheet used for molding generally includes, for example, vinyl chloride resin, methyl methacrylate resin, acrylonitrile-butadiene-styrene resin, polycarbonate resin, and the like. The thickness of the resin sheet is not particularly defined in this invention, but if it is a thick resin sheet, there is little advantage in applying this invention (especially if it is a thin resin sheet with a thickness of about 0.5 to 5aI11). It is generally applied when thermoforming is performed using resin sheets.In addition, the resin sheets to be laminated together are often one thick and the other thin. As mentioned above, the purpose of this is not only when two colored sheets of different colors are used in combination to make the front and back sides of the molded body different colors, but also when one of the colored sheets is used to form a printed pattern, etc. In some cases, a printed film is used on a resin sheet and laminated onto the other resin sheet, which serves as a substrate.Furthermore, in order to improve the physical properties of one resin sheet, a different material is added to it. In some cases, resin sheets are combined to improve rigidity, impact resistance, heat deformation resistance, etc.

When both resin sheets are to be laminated together, they are often bonded tightly using their own thermal adhesion properties, but if necessary, at least one resin sheet may be coated with a heat-activated adhesive, that is, heated. In some cases, an adhesive that softens and melts to exhibit tackiness is applied, and is activated by heating to bond and integrate both resin sheets.

Effects of the Invention As described above, the present invention includes a lamination operation in which two resin sheets are heated and softened to join them together;
Since the thermoforming operation into the desired shape is performed continuously in a series of steps, the desired laminate molded product can be obtained by arbitrarily combining individual resin sheets of individual materials during molding. , as in the case proposed by the prior application, it is possible to simplify material management, conveniently cope with the molding of a wide variety of molded products in small quantities, and achieve effects such as reducing manufacturing costs by simplifying the process. In addition to this, it also has the following unique functions and effects.

That is, in this invention, after the periphery of the resin sheet is clamped together with the air suction frame in the clamp of the molding machine, the vacuum suction and extraction between the two resin sheets is performed before heating them with a heater or synchronously with the start of heating. The above-mentioned heating is performed while the suction and air removal is continued, and both resin sheets are brought into close contact with each other and are integrated and laminated, so that the resin sheet becomes soft due to heating. At the stage when the process begins, a reduced pressure state is already maintained between the two resin sheets. Therefore, as the resin sheets soften, as shown in FIG. 3, they begin to become denser from the center, and the adhesion area gradually expands toward the periphery, and finally, as shown in FIG. 4. A perfect tight bonding state can be obtained over the entire predetermined area.

Therefore, there is no residual air between the two sheets, and even if the resin sheet is quite thin and is prone to waving deformation as it softens, the vacuum suction force Good complete adhesion with the resin sheet can be obtained. For this purpose, when a molded product is subsequently subjected to thermoforming, that is, pneumatic forming such as pressure forming or vacuum forming, it is possible to obtain a well-proportioned, high-quality molded product without any blistering defects caused by internal residual air layers. is possible,
As a result, the product yield can be improved.

Examples Example 1 As shown in Figure 2, the thickness is 0.5 ms, the width is 300, and the length is 7.
00m blue vinyl chloride resin sheet (hereinafter referred to as PvC sheet) (1), and a white PVC sheet (2) with a thickness of 2.0 mm and the same size as the sheet (1) above,
A pair of upper and lower clamps (6
) and (7) were clamped and fixed in between. Here is the air suction frame (3)
As shown in Fig. 1, it can be divided into two diagonally, and a large number of vent holes (4) are bored at predetermined intervals on the inner surface of the hollow peripheral frame. , each of the divided frames (3a) (3b) is connected to a vacuum pump (path shown) via a suction port (5).

Then, operate the vacuum pump to remove the air suction frame (3).
l: After starting the suction and air removal operation between the two PvC sheets (1) and (2), after a slight time delay, while continuing the above suction and air removal, both the upper and lower heaters (8) attached to the molding machine are activated. (9
), the upper PVC sheet (1) is heated to 180°C by the upper heater (8), and the lower heater (8) is heated to 180°C.
9), the lower PVC sheet (2) was heated to 190°C, respectively. As a result, PvC sheets (1) (2)
As the PVC sheets soften, they come into close contact with each other from the center as shown in Figure 3, and this close contact region gradually expands toward the periphery until the two PVC sheets reach a position near the periphery as shown in Figure 4. (1) and (2) were brought into close contact and thermally fused to form a laminate (10).

Therefore, the laminated material (10) in the heated and softened state was immediately set on the mold (12) of the pressure forming machine (11) as shown in FIG.
) from the mold (12).
After exhausting from the side (b) and molding to a 4x expansion magnification,
The mold was cooled and demolded to obtain a box-shaped molded product (A).

This molded product (A) has a blue color on the inner surface and a white color on the outer surface, and is coated with both PvC sheets (1
) (2) was completely adhered and was in good condition with no blistering defects due to residual air.

Example 2 In this example, an attempt was made to bond both resin sheets together using a heat-activated adhesive.

The upper PvC sheet (1) is transparent with a thickness of 0.5 m and has a printed pattern layer formed on one side.
The C sheet (2) is white and has a thickness of 2.0M.
I used one with an adhesive layer on one side of which a thin layer of heat-activated adhesive was applied.

Therefore, these two sheets (1) and (2) were placed with their printed surfaces and adhesive layer surfaces facing each other, and their peripheral edges were clamped (as in Example 1) via an air suction frame (3). 6) It was clamped and fixed between (7).

Thereafter, in the same manner as in Example 1, the suction and air removal operation was performed first, and heating was performed while continuing the suction and air removal to obtain the laminated material (10), which was then used as is as shown in FIG. 6. Place it on the mold (12'') of a vacuum forming machine (11'') and forcefully apply vacuum suction (B) to form the product at a development magnification of 4 times to obtain the desired box-shaped molded product (A'). ) was obtained.

This molded product (A゛) has a printed PvC sheet (1
), the outer surface was white, and the surface was smooth with no blistering defects on either the inner or outer surfaces.

Example 3 In this example, one resin sheet (1) has a thickness of 3.
A 0ag+ white PvC sheet was used, and a black heat-resistant PVC sheet with a thickness of 2.0 was used as the other resin sheet (2). Then, air pressure forming was carried out in the same manner as in Example 1, except that the vacuum suction degassing operation and the heating operation were started at the same time, and the heating temperature was 190°C.

It was confirmed that the obtained molded product was white on the inner surface and black on the outer surface, had excellent heat resistance on the outer surface, and had good adhesion without any blistering defects over the entire surface. I was able to do it.

Comparative Example 1 Using the same materials and molding equipment as in Example 1, each resin sheet (1) (2) was heated to 180°C using both upper and lower heaters (8) and (9).
After softening by heating to 190° C., suction and air removal between both sheets was performed using an air suction frame under this heated and softened state to obtain a laminate, followed by air pressure forming in the same manner as in Example 1. However, the obtained product was found to have blistering defects due to poor adhesion, especially on the inner surface side.

[Brief explanation of the drawing]

1 to 6 show embodiments of this invention,
Fig. 1 is a perspective view showing both resin sheets and the air suction frame in a separated state, Figs. 2 to 4 are cross-sectional views showing the lamination operation of both resin sheets in order of process, and Fig. 5 is a diagram showing the air pressure forming process. 6 is a cross-sectional view of the vacuum forming process. FIGS. 7 and 8 are cross-sectional views showing the deformed state of the resin sheet during the lamination process in the conventional thermoforming method. (1)(2)...Resin sheet, (3)...Air suction frame, (4)...Vent hole, (6)(7)...Clamp, (8)(9)...・Heater, (lO)...Laminated material,...Pressure forming machine, (11-)...Vacuum forming machine, (
A) (A'')... Molded product. Above Figure 5 Figure 6 Figure 7 Figure 8

Claims (3)

[Claims] (1) After two thermoplastic resin sheets are overlapped and joined together under heat-softening conditions, when pneumatically forming them into the desired shape, there is a gap between the peripheral edges of the two resin sheets. After clamping and fixing the peripheral edge with the clamp of the molding machine with an air suction frame connected to a vacuum pump interposed, the suction frame starts a suction air extraction operation between both resin sheets at least before the start of heating. Thermoplastic resin laminate molding, characterized in that heating is carried out while this suction and air extraction operation is continued to heat and soften both resin sheets to form a tight bonding unit, and then the pneumatic molding is performed. Method of thermoforming products. (2) A method for thermoforming a thermoplastic resin laminate molded product according to claim 1, wherein both resin sheets are joined and integrated by utilizing their own thermal adhesive properties. (3) Claim 1, wherein a heat-activated adhesive is applied in advance to the surface of at least one resin sheet, and the adhesive layer is activated by heating to join and integrate both resin sheets. A thermoforming method for thermoplastic resin laminate molded products.