JPH0220325A - Flammable foamed polystyrene - Google Patents

Abstract

PURPOSE:To prevent smoke or soot from being generated at the time of pouring a molten metal and prevent smoke or soot from being generated upon combustion of the title material in the atmosphere by lowering the pressures in primary and secondary foaming devices to expel air therefrom, and introducing oxygen into the foaming devices. CONSTITUTION:A primary foaming device is charged with a polystyrene material for foaming, then the pressure inside the device lowered to 50Torr by a vacuum pump, and oxygen is introduced into the device to the atmospheric pressure. Next, water vapor is introduced into the device, and the polystyrene material is foamed to about 10 times the original volume thereof. The foamed polystyrene is then loaded into a predetermined metallic mold, which is placed into a secondary foaming device. The pressure inside the secondary foaming device is lowered to 50Torr by a vacuum pump, and oxygen is introduced into the device to the atmospheric pressure. After such a process, water vapor is introduced into the device to foam the polystyrene at an expansion ratio of about 45. The oxygen-enriched foamed polystyrene thus obtained is coated with a slurry of a high melting point refractory having excellent gas permeability. After drying, the coated foamed polystyrene is set in a flask, which is filled with dried molding sand, a polyethylene film is placed on the top surface of a mold, and after reducing the pressure inside the mold, molten cast iron is poured into the mold through a pouring gate part. Upon such a process, the resultant cast part contained no soot.

Description

[Detailed Description of the Invention] [Industrial Application Field] In recent years, the disappearing model casting method using expanded polystyrene has become popular. When the expanded polystyrene disappears in this casting method, soot is generated, which often gets mixed into the casting.
This has become an issue in the industry.

The present invention relates to a smoke-free process for expanded polystyrene.

[Conventional technology]

Polystyrene is usually foamed using water vapor in the air, so expanded polystyrene contains air and a small amount of water. Therefore, it has poor combustibility and tends to generate soot and smoke.

[Problem to be solved by the invention]

In the vanishing model casting method using expanded polystyrene, no soot or smoke is generated when pouring molten metal, and no soot or smoke is generated when expanded polystyrene waste is burned in the atmosphere.

[Means for Solving the Problems] Foamed polystyrene is generally produced by foaming polystyrene raw materials in the air to about 10 times the original size, filling this primary foam into a mold, and then blowing water vapor in the air to expand the original foam to about 10 times the original size. 50
The product is foamed twice as much.

In the method of the present invention, primary foaming and secondary foaming are carried out in an oxygen-enriched atmosphere. That is, the pressure inside the primary foaming device and the secondary foaming device is reduced to expel air, and then oxygen is injected. Polystyrene is foamed with water vapor in this oxygen-enriched atmosphere.

[Effect]

It has been found that expanded polystyrene enriched with oxygen produces almost no soot when burned.

〔Example〕

The polystyrene raw material for foaming is put into the primary foaming device, and after reducing the pressure to 50 Torr with a vacuum pump, oxygen is injected to return it to atmospheric pressure, and then water vapor is injected into the device to foam the polystyrene to about 10 times its original size. I let it happen.

Next, the foamed polystyrene was filled into a predetermined mold, put into a secondary foaming device, and heated to 50°C using a vacuum pump as described above.
After reducing the pressure to 45 Torr, oxygen was injected to return it to atmospheric pressure, and then water vapor was injected into the device to reduce the polystyrene to about 45 Torr.
Foamed twice as much.

This oxygen-enriched expanded polystyrene is coated with a highly breathable, high melting point refractory slurry (thickness: approx. 3 mm).
After drying, it was placed in a flask, filled with dried foundry sand, a polyethylene film was placed on the top of the mold, the entire mold was depressurized, and cast iron was poured into the sprue. The casting did not contain any soot.

When this expanded polystyrene was burned in a commercially available incinerator, no soot was generated.

〔Effect of the invention〕

The oxygen-enriched polyethylene foam of the present invention makes it possible to produce sound castings without soot and smoke in the investment casting method. Furthermore, since no soot is produced even when burned in the atmosphere, it has become possible to use it as a fuel.

Now □

Claims (1)

[Claims] Expanded polystyrene is made by foaming polystyrene in an oxygen-enriched atmosphere and trapping a large amount of oxygen within the polystyrene.