Shuichi Okuzono

An Insight into the Characteristics of a Nucleation Catalyst in CFC-Free Rigid Foam Systems

The establishment of CFC-free polyurethane foam systems, aimed at total CFC elimination by the year 1995, is of paramount importance in the present day polyurethane foam technology. Especially in rigid foam systems, the attempts to apply a variety of alternative blowing agents such as HCFC-22, -141b, and -142b, HFC-134a and -356, and hydrocarbons such as n-pentane, isopentane and cyclopentane, as well as all-water blown systems, are being examined. In all cases of alternative blown systems, however, there exist differences in foaming behavior as well as inferior foam properties compared to traditional CFC-11 blown systems. Especially in HCFC-141b and cyclopentane blown systems, which have gained the greatest interest among the above-mentioned options, the following three subjects are of major concern. The requirements involved in achieving the resolution of these problems are dependent not only on the development of major raw materials but also on the selection of suitable auxiliary intermediates such as catalysts and foam stabilizers. (1) Thermal Conductivity; HCFC-141b, cyclopentane and carbon dioxide, which is generated from the reaction of water and isocyanate, have high thermal conductivity compared to CFC-11, thereby causing inferior insulation performance of the foam. Fine cell technology is now being examined in order to improve the thermal conductivity. For the achievement of the fine cell structure, the selection of suitable amine catalyst systems is important, although the effect of foaming stabilizers has an especially large contribution. (2) Dimensional Stability; not only in all-water blown systems, but also in HCFC-141b and cyclopentane blown systems which use water in high concentration, dimensional stability becomes a large problem due to the diffusion of carbon dioxide gas from the foam cell. For the improvement of dimensional stability, there exists the option to increase the foam strength; moreover, it is important to improve the isotropy of cell structure by adjusting amine catalyst systems. (3) Foam density; since 141b and cyclopentane have relatively higher boiling points and less blowing efficiency, lowering the foam density becomes rather difficult. Moreover, lower foam density normally provides poor dimensional stability. It can be said that the catalytic activity ratio in blowing/gelling of amine catalysts play an important role for the lowering of foam density with improved dimensional stability. It is very difficult to improve these three factors simultaneously. In this report, however, the improvements of these subjects are discussed from a standpoint of amine catalysts; also special newly developed nucleation catalyst systems are introduced for cyclopentane and HCFC-141b blown systems.

New polyisocyanurate catalysts which exhibit high activity at low temperature

In polyisocyanurate foam production, alkali metal catalysts of organic carboxylic acids and hydroxyalkyltrimethyl quaternary ammonium salts are traditional standards as polyisocyanurate foam catalysts. The activity of these catalysts, however, is not efficient at low temperature. Therefore, the initiation reactions are extremely delayed, and the flowability of the foam system is far too inferior. In addition, the foam exhibits shrinkage when the thickness of the sprayed layer was thin and the temperature was low while applying the sprayed foams. The combination of other tertiary amine catalysts could improve the flowability; however, the flammability of the foam would be a hazard because the isocyanurate reaction has not fully progressed. For the improvement of the above-mentioned problems, Tosoh Corp. has developed several new quaternary ammonium salt compounds, such as Toyocat-TR20. TR20, however, should be used in conjunction with an alkali metal co-catalyst. Presently, Tosoh has succeeded in developing another new catalyst having even higher catalytic activity at low temperature, which can replace the use of the alkali metal catalyst. The new catalyst provides the low temperature dependency in the isocyanurate reaction activity compared to the traditional isocyanurate catalysts. The new catalyst provides the following advantages: 1. The catalytic activity is high. 2. The isocyanurate reaction activity at low temperature is high. 3. The initial foaming reaction is improved, thereby the rise profile is now smooth. In this report, new quaternary ammonium salts will be introduced with comparison data using the FT-IR analytical methods, as well as the evaluation in panel and sprayed foams.

Innovative Quaternary Ammonium and Metal Based Catalyst Systems for CFC Free Isocyanurate Foams

This paper explains and introduces novel quaternary ammonium and metal based catalyst systems in CFC free polyisocyanurate (PIR) rigid foam applications. CFC elimination in polyurethane (PUR) applications has successfully been achieved, in most cases, with the more environmentally acceptable HCFCs, hydrocarbons (HCs) and water (CO 2 ) blown systems. The survey of next generation HFC blowing agents still is expanding. In PIR foam applications, however, inferior foam properties, as well as the decline in flame resistance, in HCFCs, HCs and CO 2 blown systems, are major issues. In general, PIR foams are produced by complex reactions such as the trimerization of isocyanate, urethane and urea, which all proceed simultaneously. The catalyst plays an important role in the control of these reaction rates, foaming profiles and foam properties such as adhesive strength, dimensional stability and flammability resistance. A number of catalysts, such as alkali metals, quaternary ammonium compounds and tertiary amines, have been proposed and used in PIR rigid foam applications as trimerization catalysts. All catalysts cannot, however, always meet the present industrial requirements. For example, alkali metals exhibit high trimerization activity at high temperature but much less activity at lower temperature, which results in inadequate rise profiles and severe friability, namely inferior adhesive strength. Quaterary ammonium compounds and tertiary amine catalysts provide better rise profiles, flow properties and moldability, however, they exhibit lower trimerization activity products, less flame resistance property and strong odor. Tosoh Corporation has successfully developed several new innovations in quaternary ammonium, metal based catalysts, as well as a flowability analysis system, using a Long Range Laser Displacement (LLD) apparatus, which can be applied to HCFC-141b/CO 2 as well as all CO 2 blown PIR foam. This technology assists in the successful production of PIR foams with excellent physical properties, including high conversion of trimerization, as well as improved flame resistance, flowability and friability.

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

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.

Innovative Tertiary Amine Catalyst Systems for CFC Free All MDI Based HR Foam

Newly developed catalyst systems are discussed and examined in formulations containing a variety of water levels and isocyanate index in order to compare traditional systems to newly developed ones in hopes of finding the overall best combination for the production of an all MDI HR foam

Characterization of Innovative Tertiary Amine Catalyst Systems for All Water Blown Flexible Polyurethane Foams

J. Fis Union Carbide Chemicals and Plastics Company Inc. (Europe) S.A. The replacement of CFC-11 in rigid foams is, today, the polyurethane industry. The more promising candidates as regards to ozone depletion potential (ODP) or to global warming potential (GWP) are HFA-123 and HFA-141b. Nevertheless, HFA blown foams’ physical properties will be affected due to the plasticising effect of the HFAs. Following the observation that HFA-123 systems could not be properly stabilized with some commercial silicone surfactants, Union Carbide has undertaken an experimental design study to define the effect of the silicone copoly-