| 摘要 |
<p>IMPROVED FOAMING SYSTEM FOR RIGID URETHANE AND ISOCYANURATE FOAMS BASED ON POLYETHERS AND AROMATIC POLYESTER POLYOLS Improved fluorocarbon blowing agents composed of blends of (a) CFC-11, triclorofluoromethane, with (b) CFC-123 or CFC-123a, dichlorotrifluoroethane, have been found which impart significant improvement in the solubility characteristics of rigid urethane foam systems that contain significant amounts of aromatic polyester polyols. A substantial increase in the solubility of the CFC-11/CFC-123 or CFC-11/CFC-123a blends over CFC-11 alone in typical rigid urethane foam premix systems containing variable concentrations or aromatic polyester polyol is obtained. Preparation of rigid urethane foams have shown that improved solublity CFC-11 blends with CFC-123 or CFC-123a permit an increase in the amount of aromatic polyester polyol than can be used in the formulation without any significant differences in the physical characteristics of foams compared to those produced from CFC-11 without inclusion of aromatic polyester polyols. The solubility and compatibililty characteristics of the premixes which contain aromatic polyester polyols as substitutes for a portion of conventional polyols used in rigid urethane systems can be used effectively with the blend of CFC-11 and CFC-123 or CFC-123a blowing agent whereas use of CF-11 alone for such combinations of urethane polyol mixtures was heretofore substantially ineffective in regard to desireable solubility and compatibility characteristics. The aromatic polyester polyols impart the following desirable characteristics to rigid urethane foams: lower formulation costs, improved compressive strength properties, enhanced flame retardancy, and increased use-service temperature of low-density foams.</p> |
