JPS58220713A - Foam molding of plastics - Google Patents

Abstract

PURPOSE:To mold the titled foamed object of a large size and a light weight, by pouring a foaming plastic stock liquid in a closed mold and foaming it, reducing the pressure inside the mold. CONSTITUTION:By putting a rubber packing 3 between the peripheral parts of a bottom force 1 and the top force 2 of a foam molding mold 10 and clamping them by clamping jaws 5 the closed space of a fixed form is shaped between the bottom and top forces 1 and 2. The predetermined amount of a liquid isocyanate component and that of a liquid polyol component are supplied from material supply pipes 8 and 9 respectively, mixed in a mixing head 4 and poured from a stock liquid pouring port 7 into the mold. The pressure in the mold is reduced by a vacuum pump via an air aspirating pipe 6 and when a poured stock liquid begins to foam, the constant pressure is maintained by aspirating an air correspondingly and a foamed object is molded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a plastic foam molding method.

Conventionally, the foaming rate of plastic foam materials used for floating bodies and the like has been nominally expressed in terms of specific gravity. This specific gravity value is not the actual specific gravity value of each product, but indicates the specific gravity value of a reference product manufactured under the same conditions.

This standard product is made by free foaming an extremely small block of, for example, 200 x 200 x 151:1 m. However, if you make a large foam under the same conditions, for example, if the size is about 2X2X1FF1,
The specific gravity value will be about twice as high. Further, even if foamed into a predetermined shape in a mold, the product will similarly have a specific gravity higher than the nominal value. It is also possible to adjust the stock solution when foaming, but there is a problem that foaming will not be uniform when producing large blocks or molded products with low specific gravity. For this reason, a foam that is sufficiently lightweight to be used as a large foam for use in floating bodies of ships, etc., has not been manufactured in the past.

For example, if a product with a nominal specific gravity of 0.02 is manufactured using the same amount of stock solution, the actual product will have a specific gravity of about 0.04, and the amount of stock solution will be reduced to allow foaming in the mold. The foam did not conform to the shape of the mold or was not foamed uniformly.

This invention has been made to solve these conventional drawbacks, and it is possible to obtain a product with a foaming rate close to the nominal value by using the current stock solution even in in-mold foaming. That is, in this invention, a predetermined amount of a plastic foaming stock solution is injected into a sealed mold, and the foaming is caused while the pressure inside the mold is reduced.

Embodiments of the present invention will be described below with reference to the drawings. The foam molding mold 10 consists of a lower mold 1 and an upper mold 2, which are tightened by a rubber gasket 3 interposed on the periphery of the two.
By tightening the upper and lower molds 1 and 2, a sealed space of a predetermined shape is formed between the upper and lower molds 1 and 2. An air suction pipe 6 and a stock solution injection lower are formed in the upper mold 2, and a mixing head 4 is connected to the stock solution injection lower. Raw material supply pipes 8 and 9 are connected to.

In this apparatus, for example, to produce a urethane foam material, a predetermined amount of isocyanate component liquid is supplied from the raw material supply pipe 8 and a polyol component liquid is supplied from the raw material supply pipe 9, and these are fed into the mixing head 4. Mix and inject into the mold from the stock solution injection lower. Inside the mold, 1. The pressure is reduced by a vacuum pump through the air suction pipe 6, and when the injected stock solution starts to foam, air is sucked in accordingly to keep the pressure inside the mold constant. When foaming is carried out while maintaining the inside of the mold under a constant reduced pressure condition, the expansion ratio becomes sufficiently large, and a foam conforming to the shape inside the mold is formed in a uniformly foamed state. In the case of urethane foam materials, carbon dioxide gas and chlorofluorocarbon gas are generated by the reaction between isocyanate and polyol, and a foam is formed by encapsulating these gases in the urethane bond. If the volume of the contained gas such as carbon dioxide gas is increased by reducing the pressure inside the mold, the total volume of the foam will be increased, and a light foam will thereby be obtained.

As explained above, the present invention allows foaming to be carried out under reduced pressure in a sealed mold, thereby making it possible to form a large and lightweight foam.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of an apparatus for carrying out the present invention. 1...Lower mold, 2...Upper mold, 6...Air suction pipe, 7
...Still solution injection port.

Claims (1)

[Claims] 1. A method for foaming plastics, which comprises injecting a predetermined amount of a plastic foaming stock solution into a sealed mold and foaming while reducing the pressure inside the mold.