New Catalyst and Surfactant Additives Developed for Microcellular Polyurethane Foam Systems Used in Shoe Soling Applications

摘要

In the marketplace there has been a significant driving force for density reduction and improvement in the physical and processing properties of polyurethane microcellular foams used in shoe soling systems. Crompton Corporation has developed new polyurethane catalyst and surfactant additives that help meet these high-performance requirements. Some of the advantages that these new catalysts give are improved foam flowability, reduced part density, and increased foam openness. Catalysts that can give foam systems faster cure times with extended cream times are discussed. Novel catalysts that moderate the gelling reaction and allow for cell-opening have also been developed. It was found in this research that the catalyst package in a foam system must be tailored for the application and can be especially critical in low-density systems. This paper describes the use and advantages of these new catalysts and explains how catalyst package balance is important in obtaining desired system performance. High performance silicone surfactants with various degrees of stabilization have been developed for polyester-based and polyether-based systems. Our studies have demonstrated that surfactants for low-density systems, such as those used for making insoles and midsoles, must not only provide a fine cell-structure and good shear stability, but also allow for cell-opening. Without some cell-opening, low-density foams may be "tight" or closed-cell, causing dimensional instability resulting in either post expansion set or excessive shrinkage. High compression sets in low-density foams can also be related to dimensional instability caused by foam "tightness". This paper explains how proper surfactant selection is important for system performance and the choice of surfactant is dependent upon the base polyol type, molded density of the system, and the type of shoe soling application.