Reduced Density Carbon Dioxide Blown Foam Based on a Novel Polyol Technology

Abstract

In view of increasing pressure to use environmentally acceptable, nonflammable blowing agents with zero ozone depletion potential in the manufacture of rigid polyurethane foams, there is greater interest in 100% carbon dioxide blown technology. When trichlorofluoromethane (CFC-11) or 1,1-dichloro-1-fluoroethane (HCFC-141b) is replaced by carbon dioxide as the cell gas, the resulting foam, in general, suffers from higher thermal conductivity (k-factor), poorer adhesion and worse flowability leading to higher density. The water level in the formulation can be increased to improve flowability of these systems, but foam with poorer dimensional stability is obtained due to rapid diffusion of carbon dioxide out of the foam. In order to maintain adequate dimensional stability, similar to what is achieved in CFC-11/HCFC-141b blown systems, the water level has to be reduced. This leads to unacceptably higher foam density. In addition, the higher k-factor of the foam is primarily due to higher gas k-factor of carbon dioxide compared to those of CFC-11 and HCFC-141b. This is partially offset by lower radiative contribution arising from finer cell structure of carbon dioxide blown foams. Certain applications, however, are less sensitive to the energy requirement, and a foam with higher k-factor may be acceptable.

This paper deals with a design of experiments to yield a foam with good processability and excellent dimensional stability in a variety of conditions, while maintaining the in-place density usually obtained with CFC-11/HCFC-141b blown systems. The key to the success was the development of a novel polyol that led to dimensionally stable foams at higher levels of water. The commercial viability of this technology has been demonstrated by producing actual parts without any equipment modifications.