JPH0115370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of applying relief-like unevenness to substantially the entire surface of a highly transparent acrylic resin plate by so-called embossing.

Injection molding is generally used as a method for applying unevenness to the surface of thermoplastic hard resin products, but this injection molding method can be used as a method for applying relief-like unevenness to almost the entire surface of a flat resin plate. It is practically impossible to use it.

Therefore, it seems that the most suitable method for carrying out the above method is stamping, but in the past, it has not been practical to apply unevenness to almost the entire surface of a thermoplastic hard resin board by so-called stamping. No attempt has been made.

There are various possible reasons for this, but when it comes to acrylic resin plates, the optimum processing temperature for thermoforming acrylic resin plates is
It was supposed to be between 150℃ and 160℃. If the temperature is higher than this, the transparency and surface smoothness of the acrylic resin board, which is the lifeblood of the acrylic resin board, will be lost due to the generation of bubbles and the progression of chemical changes, which will significantly reduce the commercial value of the acrylic resin board. On the other hand, under the heating conditions of about 150° C. to 160° C., it is almost impossible to mold a delicate uneven pattern that follows the uneven pattern on the mold surface. Furthermore, in conventional heat molding, when a molded product is subjected to secondary processing such as bending or fusing by heating, the molded uneven pattern returns to its original shape, making secondary processing impossible.

Further, the above-mentioned problems are almost the same for transparent hard vinyl chloride resin plates.

On the other hand, acrylic resin plates have excellent physical properties as described below.

Transparency It has excellent light transmittance, exceeding that of glass, and its surface is as smooth as a mirror and has a beautiful luster.

Weather resistance There is almost no deterioration in strength, decrease in transparency, or change in color even when used outdoors for a long period of time.

Being a thermoplastic resin, it can be molded and bent at temperatures of 150℃ to 160℃.

Combustibility It burns when it comes into contact with flame, but its speed is slow and comparable to that of hard wood, and it does not continue to smolder once the fire is extinguished.

The ignition temperature is 370°C to 500°C.

mechanical nature (a) Must be three times stronger than hard PVC board.

(b) It has a low specific gravity, about half that of ordinary glass.

(c) Impact resistance should be approximately 10 times higher.

(d) It has a physical property of having a high rate of change with respect to heat, but if the temperature is below 80°C, no deformation that would cause a practical problem will occur.

(e) Water resistance Although it has the property of absorbing water to a small extent, a very slight dimensional change occurs. However, the speed is slow and changes in mechanical properties are minimal.

In view of the above points, the present invention provides a method in which substantially the entire surface of the acrylic resin flat plate having the above-mentioned excellent physical properties can be subjected to secondary processing by heating without impairing the excellent physical properties of the resin plate. Moreover, the object of the present invention is to provide a method of applying relief-like unevenness processing by embossing molding, which can also express sufficiently delicate parts.

That is, the present invention includes a preheating step in which an acrylic resin board is preheated to soften the entire board into a soft rubber-like state, and a template is pressed against the surface of the resin board softened by this preheating step to apply high frequency to the resin board. A method for molding an acrylic resin plate, comprising: an embossing step of forming an uneven pattern along the shape of the mold surface on the surface of the mold.

Furthermore, the present invention includes a preheating step of preheating the acrylic resin plate and softening it into a soft rubber-like state as a whole;
With a silicone sheet interposed on the surface of the resin plate softened by this preheating process, a mold plate is pressed and high frequency is applied to form an uneven process on the surface of the resin plate that follows the shape of the mold surface. A method for molding an acrylic resin plate, comprising the steps of:

FIG. 1 is a perspective view of an embossing molding machine used to carry out the method of the present invention.

The embossing molding machine 1 is provided with a lower mold 2 and an upper mold 3 that rises and lowers in opposition to the lower mold 2 in the center thereof, and a material supply table 4 and a material take-out table 5 in front and behind the lower mold 2. and is provided. The upper die 3 is a template having a desired embossed concavo-convex pattern engraved on its surface, and has a structure as a high-frequency welder.

Next, an example of the method of the present invention carried out using this embossing molding machine will be described.

As an acrylic resin plate as a processing material, 3
A transparent acrylic resin flat plate with a wall thickness of mm was used.

First, place the resin plate above on the lower mold, and then
The resin plate was heated to 180°C, and 120 seconds elapsed after the temperature was raised to preheat the resin plate. Through this preheating process, the entire resin plate was softened into a soft rubber-like state. Also, during this preheating process, the upper mold was heated to 120°C by high frequency.

A silicone sheet was placed on the surface of the preheated resin plate, and the upper die was pressed at a high frequency temperature of 180° C. and a press pressure of 100 tons was applied for 20 seconds while the high frequency was being applied.

After the embossing process using pressure, a cooling process was performed for about 30 seconds, and the resin plate was allowed to cool naturally until the temperature of the resin plate dropped to 60° C. or lower with the resin plate placed on the lower mold.

As a result, a product 10 made of a transparent acrylic resin flat plate having an embossed uneven pattern 10a formed on substantially the entire surface as shown in FIG. 2 is obtained.

This product 10 does not impair the excellent physical properties of the above-mentioned acrylic resin plate, and moreover, it is possible to express the delicate uneven pattern 10a with high precision. In addition, in terms of products, it has become possible to mass-produce products as indoor equipment such as glazings, or as stained class products by painting a part of the pattern, making it possible to produce high-priced products that are dangerous due to conventional glass. This makes it possible to provide safe and affordable products to the masses, expanding the scope of their use.

The main functions or features of this embodiment method are as follows.

The uneven pattern can be applied uniformly without compromising the thickness of the resin board, and it is also possible to express delicate parts. Furthermore, even if secondary processing is performed by reheating, the uneven pattern will not return to its original state. This is due to the softening of the material resin plate during the preheating process and the vibration effect caused by high frequency waves, which is different from deformation due to simple heat pressing, and the molecules that make up the resin plate themselves easily flow from the compressed area of the uneven surface to the space area. This is thought to be because it adapts to the mold surface.

Conventionally, air bubbles appeared when heating acrylic resin plates above 160°C, but with this method, air bubbles could be removed using the oscillation effect and press pressure using high frequency waves following the preheating process.

The temperature conditions during the embossing process are adjusted to the surface of the resin plate.
The difference was made by setting the temperature to 120℃, the back side to 180℃, and the high frequency temperature to 180℃.

It was possible to maintain sufficient transparency and surface smoothness.

This is because the smooth surface unique to the silicone sheet was transferred to the surface of the product due to the use of the silicone sheet, and the heat from the upper mold was transferred to the surface of the resin plate in a somewhat relaxed manner due to the somewhat insulating effect of the silicone sheet. .

In the above examples, almost the same effect as above could be obtained even if the temperature conditions and time conditions were slightly changed.

For example, the temperature of the lower mold in the above preheating process is 165
It is sufficient that the temperature is within the range of ℃ to 210℃, and the temperature of the upper mold is also within the range of 100℃ to 160℃. Further, the preheating time can also be set to 90 seconds to 180 seconds. However, when using a resin plate of 3 mm or more as described above, it is not suitable to heat the plate with a direct heater or furnace because it causes temperature unevenness and only the surface temperature exceeds the measured value. Furthermore, in the embossing process, the high frequency temperature may be set at 160° C. to 200° C., and the time may also be set at 15 seconds to 5 seconds. The press pressure can be between 80 tons and 120 tons.

In the cooling process, the product is heated to 60℃ as mentioned above.
Cool gradually on the lower mold until the temperature below is reached. Uneven cooling leaves distortions in the molded product, causing the molded product to deform or warp during long-term use, or to cause differences in optical properties. Generally speaking, forced cooling is not a good idea. Furthermore, the above-mentioned molding time and molding temperature depend on the thickness of the resin plate, its shape, ambient temperature, and mold temperature. In extremely general molding, in the case of a 3 mm plate, as mentioned above, 30
Can be molded in seconds.

In the above examples, almost the same features as above were obtained even when embossing was performed without interposing a silicone sheet. However, there was some difficulty in the smoothness of the surface, but it is not a problem for normal products, and it is not a problem at all for products that are colored later, such as Stained Class. be.

According to the method of the present invention, as described above, by embossing molding, which enables mass production and low cost, it is possible to express delicate parts, and a uniform uneven pattern can be applied to almost the entire surface. , it is possible to obtain an embossed molded product of acrylic resin plate with excellent transparency, good surface finish, and whose uneven pattern does not disappear or deform even when subjected to secondary processing by heating. .

Furthermore, by interposing the silicone sheet, there is an effect that the smoothness and transparency of the resin plate surface can be further improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a stamping machine used in the method of this invention, and FIG. 2 is a perspective view of a product obtained by the method of this invention.

Claims (1)

[Scope of Claims] 1. A preheating process in which an acrylic resin plate is preheated to soften it into a soft rubber-like state as a whole, and a template is pressed against the surface of the resin plate softened by this preheating process to apply high frequency to the resin. A method for molding an acrylic resin board, comprising the steps of: forming an uneven pattern on the surface of the board in accordance with the shape of the mold surface. 2. The method for molding an acrylic resin plate according to claim 1, wherein the preheating temperature in the preheating step is 165°C to 210°C. 3. A preheating process in which the acrylic resin plate is preheated to soften it into a soft rubber-like state as a whole, and a silicone sheet is interposed on the surface of the resin plate softened by this preheating process, and a template is pressed to apply high frequency waves. 1. A method for molding an acrylic resin plate, the method comprising: forming an uneven pattern on the surface of the resin plate in accordance with the shape of the mold surface.