JPS6016327B2 - How to manufacture molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a method of manufacturing a molded article using a thermoplastic resin sheet as a raw material by a ripening method.

``Substructure technology'' In general, when producing a desired molded product using a thermoplastic resin sheet as a raw material by the ripening method, a flat sheet with smooth surfaces on both sides is used as the raw material sheet. However, when manufacturing a molded product using a flat sheet by vacuum forming or aging molding such as pressure forming, for example, if the molded product obtained is a pyramid-shaped container with a wide entrance and a narrow bottom, There were drawbacks such as the wall thickness at the green checkpoint being thick and the elongated bottom and corner portions becoming thinner, resulting in so-called uneven thickness, and the strength of the bottom and corner portions becoming extremely weak. Therefore, when manufacturing deep-drawn molded products to improve the drawback of uneven thickness in molded products, it is necessary to adopt the plug assist method or use a mold with a special rib design. Methods such as the above have been attempted, but all of these methods require high mold costs and are not necessarily good means. "Problems to be Solved by the Invention" The present inventors aim to improve the above-mentioned drawbacks and produce molded products with a unique appearance, superior decorative effects, and high strength in an industrially advantageous manner. As a result of intensive study to develop the method, we decided to use a sheet with continuous convex parts vertically and horizontally on one or both sides as the sheet used for ripening, and mold it with a normal molding machine. They found a way to eliminate the above drawbacks and completed the present invention.

``Means for Solving the Problems'' An object of the present invention is to provide an industrially advantageous method for producing molded articles with excellent strength and decorative effects.

However, the gist of this is that when a thermoplastic resin sheet is matured to produce a molded product, a sheet with continuous convex portions vertically and horizontally provided on one or both surfaces is used to form the molded product. The temperature at which the thermoplastic resin sheet is ripened is such that the convex portions provided on the sheet surface disappear.
None, manufacturing a molded product from a thermoplastic resin sheet, characterized in that the thermoplastic resin sheet is molded with the surface provided with the convex portion facing the mold surface side in a temperature range. It lies in the method. To explain the present invention in detail below, the thermoplastic resins used in the present invention include general purpose polystyrene, high-impact polystyrene, styrene-acrylonitrile copolymer, styrene resin such as Amo resin, vinyl chloride resin, etc. Examples include resins, olefin resins such as polyethylene and polypropylene, polyamides, polycarbonates, polyacetals, and polyphenylene oxides. In the present invention, a molded article is manufactured by a ripening method using a sheet of the above-mentioned resin as a raw material. In the method of the present invention, it is necessary to use a sheet having continuous convex portions vertically and horizontally provided on one or both surfaces as the thermoplastic resin sheet used for ripening.

Examples of continuous convex portions provided on one or both of the sheets include those shown in perspective views in FIGS. 1, 2, and 3. FIG. 1 shows an example in which the convex portions are provided in a grid pattern, and FIG. 2 shows an example in which the convex portions are provided randomly. FIG. 3 shows an example in which grid-like convex portions are provided on both sides of the sheet. In the figure, 1, 11, and 21 are thermoplastic resin sheets; 2, 12, and 22 are convex portions provided on one side of the sheet; 23 are convex portions provided on the other side of the sheet; , 13, 24, and 25 are concave portions surrounded by convex portions provided on the sheet surface, respectively.

As long as the convex portions are provided continuously in the vertical and horizontal directions on one surface of the sheet, any pattern may be created by the convex portions.
If the convex portions are provided on both sides of the sheet, they may be provided continuously in the vertical and horizontal directions on both sides, or the convex portions may be provided on one side with a pattern that is continuous in the vertical and horizontal directions and the other side is provided with convex portions that are not continuous in the vertical and horizontal directions. It's okay. If the thickness of the portion of the sheet where the recess is located (corresponding to FIG. 1 3, FIG. 2 13, and FIG. 3 24) is 1, the thickness of this convex portion is 1.1 to 4. The thickness can be increased to .0 times. If the thickness of the convex portion is smaller than the above ratio, the object of the present invention will not be achieved, which is undesirable.On the other hand, if the thickness is larger than the above ratio, the recessed portion of the sheet will become too thin, which is undesirable. Such a thermoplastic resin sheet having convex portions formed on one or both surfaces is manufactured by a known molding method such as a press molding method, a continuous press molding method, a continuous injection molding method, an extrusion molding method, etc. However, from the viewpoint of cost, the most advantageous method is to form the sheet by extrusion and then mold it with a roll.

In this case, the thermoplastic resin sheet is extruded while being kept at a temperature higher than the ripening temperature by the temperature required for boiling, and is shaped using a shaping roll. The temperature of the molding roll at this time is preferably slightly lower than the thermoforming temperature. In the present invention, the thus-obtained thermoplastic resin sheet in which convex portions are continuously provided on one or both surfaces is used as a raw material, and a desired molded product is manufactured by an aging molding method.
The reason for providing a convex portion on one or both sides of the thermoplastic resin sheet to be aged is that when the resin sheet is stretched by the ripening, if there is a convex portion, this convex portion will be removed from other concave portions. (3 in Fig. 1, 13 in Fig. 2, or 24 in Fig. 3) is stretched in the same way, but the convex part is grounded against the molding die during molding and is cooled, so that it is lower than the concave part. It is difficult to stretch and remains on the final molded product without being extended much, and since it is thicker than the recess, even if it is stretched, it remains thicker than the recess, and this part reinforces the molded product. This is to perform a rib-like function and to obtain a molded product with high strength.

In the present invention, thermoforming (claw e-skin forming) refers to heating and softening a thermoplastic resin sheet by a normal method,
A molding method that uses vacuum forming, pressure forming, or a combination of both to produce a desired molded product.

In order to effectively achieve the object of the present invention, the raw material sheet is molded with the surface on which the convex portions are provided facing the surface of the mold.

For example, when manufacturing a molded product using only a female mold, the surface with the convex portion should be fixed facing the female mold surface, and only the male mold would be used. In this case, the surface with the convex portion is fixed facing the male mold surface and molding is performed. When a molded product is manufactured using a match mold, a sheet having convex portions on both sides is used as the raw material sheet. Of course, when using the female mold or the male mold described above, a sheet having convex portions on both sides can be used. In the present invention, during ripening, the surface of the raw material sheet with the convex portions is fixed to the molding die with the surface facing the molding die surface when applying vacuum, compressed air, etc. to the raw material sheet. The raw material sheet comes into contact with the molding die, but only the convex part of the raw material sheet contacts the mold surface, and since this contact surface is small, it easily slides on the mold surface, so it can easily spread even at the edge of the container entrance. This is to help ensure that both the convex and concave portions of the raw material sheet have substantially uniform thickness throughout the container.

In order to effectively achieve the object of the present invention, it is further necessary to set the heating temperature condition of the raw material sheet to the thermoforming temperature of the thermoplastic resin sheet to be molded, and the convex portions provided on the sheet surface. The temperature must be within a temperature range that does not cause loss of temperature.

If the sheet to be formed is overheated during thermoforming,
This is because the convex portions provided on the sheet will disappear, and the object of the present invention will no longer be achieved. Specifically, the lower limit of this temperature is 203° higher than the glass transition temperature (also called glass transition point or second-order transition point) of the thermoplastic resin constituting the sheet, and the sheet having convex portions is The temperature range is defined as an upper limit of 2000 degrees lower than the sheet temperature during manufacturing (temperature during sheet manufacturing). The preferred temperature is determined by the type of resin that makes up the sheet, the difference in thickness between the convex and concave parts of the sheet, the area ratio of the convex parts to the entire sheet, the shape of the convex parts, the size of the molded product, etc. It is best to choose a temperature within the above temperature range. Normally, the temperature is 5 to 150 degrees higher than the aging temperature of a flat sheet made of the same type of resin and having approximately the same thickness.
It is better to set the temperature to 0.0. "Effects of the Invention" The method of the present invention and the molded articles produced by the method of the present invention have the following excellent characteristics and have extremely high industrial utility value.

1. According to the method of the present invention, a deep drawn product can be manufactured without using a molding die with plug assist or a special curved design, and the cost of the die does not increase.

2 The convex portions provided on the surface of the sheet improve the sheet's slippage on the mold surface and delay cooling and solidification, so the sheet can be stretched sufficiently compared to the conventional method using a flat sheet. It is possible to produce molded products that are stretched relatively uniformly.

3. Since the convex portion provided on the surface of the sheet functions as a lip for the molded product, when using the method of the present invention, a deep drawing molded product can be produced extremely easily.

4. Convex portions provided vertically and horizontally on the surface of the thermoplastic resin sheet to be molded remain on the final molded product,
Since this functions as an IJ block for the molded product, a molded product with high strength can be manufactured.

5. Since the convex portions provided on the sheet surface appear as they are on the surface of the molded product, by selecting and combining the patterns of the convex portions provided on the sheet surface, a molded product with an excellent decorative effect can be obtained.

"Examples" Hereinafter, the method of the present invention will be explained in more detail according to Examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded.

Example A sheet of Dialex HT516 (trade name of impact-resistant polystyrene manufactured by Mitsubishi Monsanto ■, glass transition temperature of approximately 90 points) was made by extrusion molding from a beret, and this sheet was used as a raw material, and one side was molded with a smooth surface. Using a molded plate with a lattice pattern on the other side, sheets of types A and B having convex portions on the surface as shown in FIG. 1 were prepared.

The temperature during sheet production was 200 pm. The sheets thus obtained have the grid pattern and thickness shown in Table 1 below.

Units in Table 1: m/m) From these sheets, the fourth
A container like the one shown in the front view was molded using a female mold.

This container has an opening diameter of 75 m/skin and a bottom diameter of 55 m.
The size of the enemy is 40m/m and the height is 40m/m. The molding conditions for molding this container using each of Sheet A and Sheet B as raw materials are as shown in Table 2 below. For comparison, a similar container was molded using the same air pressure molding machine used to mold Sheet A and Sheet B, using a flat sheet with a thickness of 0.71 m/cm and having smooth surfaces on both sides. The molding conditions are also shown in Table 2. The molded products obtained from the second table sheet A and sheet B have lattice-like convex portions on the inside of the molded product (before molding, the convex portions are on the mold side, but after molding, The mold surface became smooth.

), this resulted in a beautiful pattern. In addition, since there are continuous thick walls (ribs) on the molded product vertically and horizontally, the molded product
Even when the container was held in the hand and pressed with fingers, the wall did not deform much and was extremely strong. The strength and wall thickness distribution of the obtained molded article were measured as follows.

'1} Measurement of strength of molded product Place the obtained molded product between two compression plates as shown in Figure 5, and compress the container by moving the compression plate in the direction of the arrow in Figure 5. The load was measured when the amount of deformation reached 1% of the container depth.

The results are shown in Table 3 along with the loads for molded products made from flat films that were measured in the same manner. Table 3 From Table 3 above, when the weights of the molded products are approximately the same, the strength of the molded product obtained using the lattice sheet as the raw material is
It is clearly higher than that of molded products obtained using flat sheets as raw materials.

In addition, even though molded products made from lattice sheets are much lighter than molded products made from flat sheets, they can have the same strength as heavier flat sheet molded products, saving raw material thermoplastic resin. can do. ■ Measurement of wall thickness distribution of molded product Regarding the molded product obtained using the sheet B as a raw material, the wall thickness was measured at each of the parts corresponding to A, B, C, and D in Figure 4 and a total of 26 other parts. .

The results are shown in FIG. 6 together with the measurement results for the molded product obtained from the flat film. From FIG. 6, the molded product obtained from sheet B having a lattice-like convex portion on one side is
The difference in wall thickness between the top edge and the bottom of the molded product for both the convex and concave parts is 4 mm, whereas the difference in wall thickness between the top edge and the bottom of the molded product obtained from the flat sheet is 4 mm. It can be seen that the difference is large.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 show examples of sheets provided with convex portions used in the present invention. FIG. 1 shows an example in which a lattice pattern is provided on one side, FIG. 2 shows an example in which a random pattern is provided on one side, and FIG. 3 shows an example in which a lattice pattern is provided on both sides. FIG. 4 is a side view of a molded product manufactured according to an embodiment of the present invention, and FIG.
FIG. 6, an explanatory diagram of the molded article compression test, shows the wall thickness distribution of the molded article. In the figure, 1, 11 and 22 are resin sheets, 2
, 12, 22 and 23 are convex portions provided on the sheet;
3, 13, 24 and 25 respectively indicate the concave portions surrounded by the convex portions. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. When thermoforming a thermoplastic resin sheet to produce a molded product, use a sheet with continuous convex portions provided vertically and horizontally on one or both sides, and the thermoforming temperature of the thermoplastic resin sheet to be molded. In a temperature range in which the convex portions provided on the sheet surface do not disappear, the thermoplastic resin sheet is molded with the surface on which the convex portions are provided facing the mold surface side. A method for manufacturing a molded article from a thermoplastic resin sheet, characterized by: