Preventing the danger of explosion in e.g. polyurethane foam moulding when using pentane foaming agent

摘要

This new method prevents danger of explosion during the filling of a foam moulding cavity, when a potentially explosive foaming agent is used to expand the plastic. It is particularly suited for filling the moulds forming double walled refrigerators or freezer casings, when using pentane-foamed polyurethane. In the new procedure, the quantity of plastic introduced into the closed cavity is measured. When underfilling by the foam is anticipated from this quantity, such that an explosive mixture could fill the cavity, a pressurised flushing gas is introduced. Also claimed is plant to carry out the procedure. The mould has a guide fixed to the machine frame, carrying a driven carriage with a lance-like injection needle (8). The mould end- or side wall has a penetration aligning with the path of motion of the needle.