Sponge Slabstock Foaming Machine-Carbon Dioxide Foaming

This is a process technology that uses liquid carbon dioxide to replace chlorofluorocarbons (CFCs) or other low-boiling-point organic compounds as auxiliary blowing agents to produce low-density flexible foam blocks. The production process and corresponding equipment were successfully developed in the 1990s by companies such as Cannon Group (under the name Car Dio), Hennecke (under the name Nova Flex), and Beamech (under the name CO₂TM), and were commercialized in the mid-1990s.

Car Dio utilizes a valve on the connecting pipe between the mixing head and the distributor to depressurize the mixed material, which then flows out from the depressurizing distributor in a foamed state. Nova Flex, on the other hand, depressurizes and discharges the foamed material through a creamer connected to the bottom of the mixing head.

As shown in the process diagram, the mixing head operates under pressure conditions that maintain carbon dioxide in liquid form; therefore, all material systems entering the mixing head require high-pressure metering pumps.

Nova Flex Process Diagram

Carbon dioxide foaming technology is compatible with horizontal foaming machines employing various foaming processes. The modifications mainly involve the metering, mixing, and foamed material distribution devices. The conveying channels and cutting sections do not require changes.

As a component of air, carbon dioxide can be obtained from liquid air or as a byproduct of the construction materials and food industries. It is inexpensive, harmless to the ozone layer, has a high molar mass ratio, and provides a high foaming rate. Replacing auxiliary blowing agents like CFCs with carbon dioxide offers both environmental and economic benefits.

However, due to limitations on the mixing amount of carbon dioxide in polyether polyols, the minimum foam density currently achievable with CO₂ foaming is 13–14 kg/m³. When producing low-density products, defects such as pinholes may occur, indicating that the foaming technology still requires further improvement.

The use of carbon dioxide foaming on vertical foaming machines is currently still in the research and development stage.