Technics
Manufacturing Method for Non-Crosslinked PP Foamed Sheet
As a manufacturing method for foam products, chemical foaming method has been used, which suppressing foaming in the cylinder by maintaining high pressure with foaming agent.However, It is difficult to get high expanded products even though increasing the volume of agents as gases can be leaked out in the hopper and cannot maintain it in the cylinder.
There is also a physical foaming method that infusing organic compounds such as butane, pentane into the melted resin and foaming by increasing pressure upto downstream parts of extruder.
This method is possible to obtain more expanded products because organic compounds have high chemical affinity and solubility with resin, However, because of high inflammability and explosiveness, its method is dangerous and requires careful operation of the facility.
On account of this reason Preon-family gas and inactivated gases such as CO2 and N2 had been used instead of such organic compounds. However, these kinds of gases have less chemical affinity and solubility than those organic compounds, so it is not likely to get evenly dispersed foam either proper cell size.
The purpose of our business is blowing with a cocktail of physical blowing agents-mostly CO2 plus a blend of butane. As far as we experienced,it is different with chemically blown foams or using one of organic agents. It makes cell more stiff and tends to less collapse when thermoformed.
