| abstract |
This invention relates to the use of a C2-6 polyfluorocarbon compound containing no chlorine or bromine atoms as physical blowing agent in the preparation of rigid, closed-cell, polymer foams. Use of such blowing agents, especially 1,1,1,2-tetrafluoroethane (R-134a), in the preparation of polyurethane or polyisocyanurate foams provided for products in which the loss in thermal insulation performance with time compared to products prepared in absence of such blowing agents is reduced. |