JPS5941855B2 - Manufacturing method of synthetic resin board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a rigid plate-shaped polyurethane foam, and more particularly, to a method for producing a rigid plate-shaped polyurethane foam whose back surface has a good foaming state.

Conventionally, in the production of plate-shaped rigid polyurethane foam, the Japanese Patent Publication No. 49 was developed as an excellent method for removing air pockets on the back side.
-48176 is known.

In this method, a rigid polyurethane foam stock solution is injected into a flat mold in which a desired statue has been engraved, and a flexible polyurethane foam sheet having a thickness that allows the rigid urethane foam to be completely impregnated by the foaming pressure of the stock solution is placed on the mold surface. It is characterized in that the mold is sealed in a state where it is stretched along the line to complete the foaming of the stock solution. The main effect of this method is to improve the dimensional stability of the molded product, but in addition to this, when molding ordinary plate-shaped rigid polyurethane foam, the molded product due to air pockets inside the mold. It shows an excellent effect in preventing the occurrence of boards. However, even with this method, when it comes to manufacturing plate-shaped molded products, there are drawbacks such as dents on the back side of the molded product due to the formation of air pockets between the mold and the upper mold in the areas where the timing of foaming due to reaction is delayed. (see Figure 2), and a solution was requested. Conventionally, a known method for preventing such dents on the back surface is to make air vent holes in the upper die of the mold.

However, this method cannot be used in the molding of a highly viscous liquid in which the volume of the reaction liquid increases, as in the present invention, because the level of the reaction liquid is difficult to equalize. In the present invention, after pouring a rigid polyurethane raw foam liquid into the lower mold, it is covered with a sheet of flexible polyurethane foam having open air cells, which is then cut so as to cross the thickness step of the lower mold and communicate with both sides. A mold upper mold having grooves with a width of 1.5 irises or less and a depth of at least twice the width is bonded so that the grooves are in contact with a flexible polyurethane foam having open cells with a cell diameter of 500 μ or less during the foaming reaction. By molding, it attempts to solve the defects of molded products all at once.

The flexible polyurethane foam used in the present invention must have a cell diameter of 500 μm or less and a high open cell ratio because it is necessary to allow only available air to pass through and to prevent liquid seepage as much as possible.

The material of the flexible urethane foam may be polyether, polyester, or any other material, but the thickness is preferably in the range of 0.5 mm or more and 5.0 mm or less.

In the present invention, the width and depth of the groove cut into the upper mold in contact with the flexible polyurethane foam are limited by the flow characteristics of the reaction liquid during molding, and the shape is square, round, or triangular depending on the flow characteristics. etc.

As the reaction progresses, the viscosity of the raw solution of rigid polyurethane foam rapidly increases and its fluidity becomes plug-like.
Therefore, as the foaming reaction progresses, the rigid polyurethane foam stock solution increases in volume while decreasing its fluidity, and is first removed by passing through the soft polyurethane foam sheet and the air remaining in the mold. Next, when the sheet is lifted and brought into close contact with the mold, a difference in the timing of contact may occur due to, for example, a difference in plate thickness.If the center of the mold rises later than the periphery of the mold at this timing, air will be left behind in the mold. . In order to prevent this air from remaining, an air escape groove is cut in the upper mold, but the inside of this groove becomes clogged, preventing air from flowing out. As mentioned above, the fluidity of the liquid during the reaction that seeps out from the sheet is reduced, so by making the width of the groove less than 1.5 WLm and the depth more than twice the width, clogging of the groove can be avoided. It is possible to shift the reaction until approximately the end of the reaction.

However, the apparent specific gravity of the molded product is 0.8g/c! If it exceeds 1, the grooves will be clogged by the pressure during reaction, so it is excluded from the present invention.

The shape of the groove is rectangular or trapezoidal with a narrow entrance and a wide bottom. The end of the groove must be opened to the outside at the side end of the upper mold, and if the upper mold is cut halfway or is closed at the side when assembling the mold, the outflow of air will cause illumination. It will be done. Examples using the production method of the present invention are shown below.

Example size width 7001! m x length 500mI! X thickness 20m1 (
A plate-shaped rigid polyurethane foam with a peripheral thickness of 5 m0 is manufactured.

As shown in Figure 3 A, the mold consists of a clay mold and a lower mold.
The clay mold (made of aluminum) 1 has a width of 1.0 and a depth of 2 cut across the plate thickness step in the lower mold 2 so as to communicate with both ends.
．． A groove 3 is provided, and a silicone rubber mold 4 engraved with the shape of the product is incorporated into the lower mold (made of aluminum) 2.

As shown in Figure 3, first, a hard polyurethane foam stock solution 5 was poured into the lower mold, and then a soft polyurethane foam sheet (bubble diameter 480μ, thickness 2) with the same area as the product was poured on top of the hard polyurethane foam stock solution 5.

06, and as shown in Figure 3 C, join the upper mold 2.
Leave for 0 minutes to foam and harden.

After finishing, the upper mold 1 is removed and the product 7 is taken out from the lower mold 2 (Fig. 3 D). In this case, the groove 3 of the upper mold is on the back side of the product 7.
The mark 8 remains in a convex shape. (Figure 4). The clearer the convex shape, the more smoothly the air trapped inside the mold was discharged out of the mold. As mentioned above, by using the manufacturing method of the present invention, the drawback of causing dirt on the back side of the product can be completely solved, especially in the case of plate-shaped rigid polyurethane foams having a structure in which a thicker part is surrounded by a thinner part. This has completely eliminated product defects due to this type of defect.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of a product manufactured using the method of the present invention, and FIG. 2 is a cross-sectional view and back view of a product manufactured using a conventional method. Show trash. FIGS. 3A to 3B are cross-sectional views showing the steps in the manufacturing method of the present invention, and FIG. 4 is a cross-sectional view and a back view of a product manufactured by the manufacturing method of the present invention. [Explanation of symbols of main parts]
, A... Garbage on the back of the product, 1... Upper die, 2... Lower die, 3... Groove, 4...
... Silicone rubber mold, 5 ... Hard polyurethane foam stock solution, 6 ... Soft polyurethane foam sheet, 7 ... Product, 8 ...
・Convex groove marks.

Claims (1)

[Claims] 1 In the manufacturing method of plate-shaped rigid polyurethane foam with an apparent specific gravity of 0.8 g/cm^3 or less, after pouring the rigid urethane foam stock solution into the lower mold, the diameter of the bubbles is 500 μm.
Cover with a sheet of flexible polyurethane foam with open air cells as shown below, and cut it so that it crosses the plate thickness step of the lower mold and communicates with both ends, with a width of 1.5 mm or less and a depth of 2 mm A method for producing rigid polyurethane foam in the form of a plate, which is characterized by bonding a mold upper mold with grooves of twice the size or more and performing foam molding.