JPS588968B2 - Netsukaso Seijyuushiseikeihinno Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermoplastic resin molded article that has excellent decorative effects and has no mold marks caused by a mold and has a locally large curvature.

Various molding methods have been developed to obtain various molded products from sheets of thermoplastic synthetic resin such as acrylic resin, but generally a heated and softened resin sheet is pressed into a mold under air pressure or reduced pressure. After that, the molded product is cooled and hardened to obtain a predetermined molded product, or the molded product is molded by being sandwiched between male and female molds.

In these methods, the whole or part of the molded product is in close contact with the mold, and mold marks are left on the part that is in close contact.

In applications where a strong decorative effect is required, such as display equipment, lighting equipment, etc., such mold marks are easily visible, especially when the surface of a molded product made of a transparent plate is finished with a near-mirror finish. In addition to adjusting the temperature of the mold to make it difficult for mold marks to appear during molding, and polishing and repairing mold marks after molding by hand, both methods incur costs such as mold costs and labor costs.

In addition, if molding is performed without using such a mold and only by applying air pressure, the above problem will not occur, but there is a limit to the shape that can be obtained, and it is especially difficult to mold a molded product with a shape with a large sharp curvature. It is difficult to obtain.

In order to solve the above-mentioned problems, the inventor of the present invention has arrived at the present invention as a result of intensive studies.The present inventor uses molding using a mold together with molding using air pressure, and uses a part of the synthetic resin plate as the mold. , acts on the remaining material that does not form a molded product, causing a deformation that is larger than that caused by air pressure and has a large curvature.Then, the part that the mold contacted is cut out, but due to the pushing of the mold. By using the accompanying deformation as the shape of the molded product, we can obtain a molded product with a large decorative effect, without mold marks, and with a shape with a large curvature that cannot be expected from molding using air pressure alone. I found out that it can be done.

That is, the present invention applies air pressure to a thermoplastic synthetic resin plate to deform it, and also deforms a part of the plate by pushing a mold into the portion that is a part of the plate and will be left over when obtaining a molded product. The method consists of deforming the part to a greater extent than that caused by air pressure, and then cutting off the part that came in contact with the mold.

Further, to explain the present invention with reference to drawings, FIG. 1 shows a mode in which a hemisphere with one end is formed, and such a hemisphere is used as a display device.

Fig. 1A shows a state in which a thermoplastic synthetic resin plate 5 is attached to a molding device. an air box 2 equipped with a compressed air inlet 7;
It consists of an elevating device 4 like a hydraulic jack, which is equipped with a mold 3 capable of molding one eye part by pressure molding inside an air box 2.

The resin plate 5 is covered with a holding frame 1 and its ends are fixed with clamps 6.

The plate is heated to a predetermined temperature in advance, then mounted on a forming device and deformed by compressed air introduced from the air pipe 7.

Subsequently, as shown in FIG. 1B, the mold 3 attached to the lifting device 4 is lifted, thereby locally deforming the mold 3 with a larger curvature than the deformation caused by the air pressure.

After the molding is completed and the resin plate is cooled and hardened, the mold 3 is lowered, the pressure in the air box is lowered by exhaust, and the clamp is removed to take out the molded product.

The molded product is trimmed, in particular, the part that was in contact with the mold 3 is removed, and the deformation incidentally introduced by the pressing of the mold 3 is left behind, resulting in a product with the shape shown in Figure 1C. can be obtained.

FIG. 2 shows an example of a molded product used for the shade of a lighting device formed by the same method as in FIG. 1.

FIG. 2A shows the state before molding, FIG. 2B shows the state during molding, and FIG. 2C shows the shape of the obtained molded product.

In the case of Figure 1, the molded part introduced by the mold 3 has only a decorative effect, but the second
In the case shown in the figure, it has a practical shape as an umbrella, and can be molded without making mold marks, so it has a great decorative effect.

In the present invention, the thermoplastic synthetic resin plate is made of acrylic resin, vinyl chloride resin, etc., and has a thickness of about 3 to 20 mm.

During molding, the ends of the plate are fitted with restraint frames and fixed with clamps.

This is done by using a male and female type as a holding frame, or by using only either a male or a female.

Further, as shown in FIG. 2A, a frame having a specific shape such as a wave-like shape is also used, and the shape of the frame can be varied in accordance with the shape of the molded product.

The synthetic resin plate is heated appropriately and air pressure is applied to it.

Examples of the method of applying air pressure include conventional pressurization and vacuum methods.

Normally, a hemispherical deformation occurs due to the action of air pressure, but it is possible to change the shape by changing the holding frame, air flow, plate thickness, temperature, etc.

Thus, the mold is made to work together with the action of air pressure as described above.

Usually one mold is used for a synthetic resin plate, but more than one mold may be used if a complex shape is desired.

As the mold, a cylindrical or truncated pyramid shaped mold with a flat head of about 1 to 5 cm is used, but it goes without saying that various shapes can be used as required.

This mold is applied to a portion of the plate in order to locally apply large deformations to the plate that cannot be achieved by pneumatic deformation.

Therefore, the mold is usually pushed into the plate by h=10 cm or more from the original position of the plate, and the plate is deformed as shown in FIG.

The degree of deformation in this case is as shown in the figure, at an angle α = 90 ~
It is about 150°.

Such deformation cannot normally be achieved with pneumatic pressure.

The direction in which the mold is pushed and the direction in which the air pressure is applied are usually the same, but they may be pushed in the opposite direction.

The above-mentioned mold is applied to the remaining material of the synthetic resin plate and removed after molding, but the deformation caused by the pressing and the part not in contact with the mold is used as the shape of the molded product.

Materials for the mold include metal, corrosion-resistant synthetic resin, and FRP.
etc. are used.

When cutting off the contact portion of the mold, the method of cutting is selected depending on the shape of the molded product, as shown in FIGS. 1 and 2.

The present invention is carried out as described above, and the molded product obtained according to the present invention has no mold marks and has a shape with a locally large curvature, and can be used for various practical products.
It has a strong decorative effect.

Furthermore, since the portion that remains after the molded product is taken out is pressure-molded using a mold, mold marks, scratches, wrinkles, etc. that occur on this molded portion are not a problem.

Therefore, the mold used for pressure molding may be a wooden or metal plate cut out into the desired molding shape, and it is sufficient that the desired deformation occurs through pressure molding. The thickness is sufficient to withstand the load.

In addition, the surface of the mold can be simply finished to the extent that the thermoplastic resin plate will not be damaged during pressure molding, or it can be covered with flannel, etc., so the mold cost is higher than that of conventional three-dimensional molds. Since there is very little weight and the weight can be reduced, it is easy to attach and detach the mold.

In addition, in the present invention, since the mold does not come into contact with the part to be taken out as a molded product, there are no mold marks or scratches during molding, so the rework work that was conventionally done after molding is no longer necessary, and the cost of this work can be reduced. .

As described above, the present invention requires only a simple mold, so in the case of production of a wide variety of products in small quantities, molds can be easily supplemented, removed, etc., and various processing can be carried out quickly.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Molding was carried out by the method shown in FIGS. 1A and 1B to obtain a molded product shown in FIG. 1C.

In the forming device, the holding frame 1 is an iron plate, and has a diameter of 400 mm.
Two mm holes are drilled with a center spacing of 500 mm, and these holes are connected by a groove-like hole.

A lifting device 4 with a stroke of 200 mm was provided at the center of the bottom of the air box 2, and a mold 3 made of phenol resin was attached thereon.

The shape of the mold 3 is that the part in contact with the plate is flat, and the size is 80X1.
It is a truncated pyramid with a size of 5 mm, a periphery of about 5 mmH, and a slope of about 1/20.

Thickness L preheated to 160°C in such a forming device
Omm acrylic resin plate (size 500mmxiooo
mm) and fixed with a holding frame, compressed air (gauge pressure 0.7 to 0.8 kg/cm2) was introduced into the air box 2, and the mold 3 inside the air box was further raised.

When the blow molding of the hemisphere was completed, the mold 3 was pushed up until the top was almost at the same height as the top of the cow ball, and the molding was completed in about 2 minutes.

This molding resulted in a deformation of α110° at the end of h=150m.

After air-cooling this for 5 minutes, the resulting molded product was trimmed to obtain two molded products at once.

The molded product is a hemisphere with a diameter of 400 mm and a V with a depth of 150 mm.
It has a shaped opening.

Example 2 Molding was carried out by the method shown in FIGS. 2A and 2B to obtain a molded product shown in FIG. 2C.

As shown in FIG. 2A, a restraining frame 1 is made up of male and female rings having wavy cut ends and interlocking with each other, one of which is used as a restraining frame from above, and the other of which is attached to the top of the air box 2.

A lifting device 4 is placed in the center of the air box, and a mold 3 is attached to it.

The mold 3 has a truncated conical shape with an inclination of about 1/20, and its upper surface has a radius of 50 mm in diameter and a radius of 3 mm in circumference.

1 methacrylic resin plate with a diameter of about 600 mm and a thickness of 5 mm.
After heating to 60°C and fixing it between the holding frames 1, the gauge pressure inside the air box is set to 0.2 to 0. While applying an air pressure of 3 kg/cm2, push up the mold in the air box and complete the molding shown in Figure 2B in about 1 minute.The mold is air-cooled for about 3 minutes, and after being removed, the surrounding area is held down and the frame is closed. Cut along the inside and make a hole in the center to match mold 3 to a diameter of 500m.
A lighting umbrella with a height of 150 mm was obtained.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the method of the present invention and the shape of the molded product obtained, and in each figure A shows the state before molding when the thermoplastic synthetic resin plate is attached to the molding device. FIG. 2 is a cross-sectional view, B is a cross-sectional view showing an aspect during molding, and C is a perspective view showing the shape of a molded product obtained by molding. Further, FIG. 3 is a diagram showing a mode in which the thermoplastic synthetic resin plate is deformed by the mold K. In the figure, 1 holding frame, 2 air box, 3 mold, 4 lifting device, 5 synthetic resin plate, 6 clamp, 7 air pipe, α deformation angle formed by contact with mold, h moving distance of mold. show.

Claims (1)

[Claims] 1. A thermoplastic synthetic resin plate is deformed by applying air pressure, and a molded product is pushed into a portion that is a part of the plate and will be left over when obtaining a molded product. It has a shape that has no mold marks and has a locally large curvature. A method for producing thermoplastic resin molded products with excellent decorative effects.