Key Aspects of Novel Catalyst Systems in all-Water Blown Integral Skin Foams-Related Catalytic Activities in the Isocyanate Reaction

Abstract

This paper will focus on the generalization of catalytic activities of a variety of typical amine and tin catalysts in the isocyanate reaction of gelation, blowing and crosslinking Secondly the relationship between catalytic activities and foaming behavior, as well as foam properties, will be discussed from the stand-point of developing novel catalyst systems for all-water blown integral skin foams (ISF). Catalysts play an important role in the control and balance between the gelation and blowing reactions. Especially in ISF systems, this control becomes increasingly important for the improvement of surface skin formation in all-water blown systems, which are now required for eliminating CFC. That is to say, skin formation and cure become inferior when using water as a blowing agent, primarily because the role of CFC is to aid in skin formation. Moreover, other than the two primary reactions, it will be considered that the catalytic activity of the crosslinking reactions such as allophanate, biuret and isocyanurate formation will have some effect on foaming behavior as well as foam properties. Therefore, it will be important to know the crosslinking activities for the design of novel catalyst systems. Concerning the catalytic activities for the primary gelation and blowing reactions, many reports have been presented in the past where the relationships between catalytic activities and foaming behaviors, as well as foam properties, have been reported. On the other hand, several reports have been recently presented on the crosslinking activities, based on the method using HPLC analysis techniques in a model reaction. Few reports, however, describe the reaction kinetic analysis of the catalytic crosslinking activities and the systematic examination of its relation to foaming behavior and foam properties. In this paper, the catalytic activity of a variety of typical amine and tin catalysts will be generalized with a review on gelation and blowing activities and a reaction kinetic analysis of the crosslinking activities using HPLC analysis in a model reaction. In addition, the relationship between these catalytic activities and foaming behaviors, as well as foam properties, will be discussed in an all-water blown ISF system. As to the foaming reaction, the relationship between viscosity rise profiles, which may have a large relation to cure, will also be discussed. Concerning foam properties, the relation to cure and skin formation will be discussed. As a result, it will be shown that strong gelling catalysts with high crosslinking activities provide improvement in skin formation. This report will intro-duce novel catalyst systems in all-water blown ISF systems by suggesting the effectiveness of catalytic activities in the selection of a suitable catalyst system.