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Flame Retardant For Use in Rigid Polyurethane Foams

Novel flame retardant compositions, which are useful in the preparation of rigid polyurethane foams, comprise a sucrose polyol, an aromatic polyester polyol, and a brominated, hydroxyl-containing pentaerythritol.


Flame Retardant For Use in Rigid Polyurethane Foams, E. J. Termine and S. P. Ginter, United States Patent No. 4,511,688.
Available at: http://terminegroup.com/archives/166


This invention relates to a polyol composition and to rigid polyurethane foams prepared therefrom. More specifically, the invention relates to a flame retardant, halogen-containing polyol composition.

Long standing technical concerns and recent changes in the flame retardant market as related to rigid polyurethane foams have generated a need for new products that will enable the producers of polyurethane foam to meet stringent municipal building codes and insurance company fire regulations. Historically, several approaches have been taken to reduce flammability of rigid polyurethane foams. These approaches fall into two main categories: (1) the use of polyurethane-modified isocyanurates which require minimal levels of flame retardants, and (2) the use of rigid polyurethanes, which require relatively higher levels of flame retardant materials. Each approach has been applied successfully to specific applications, but both suffer from processing constraints and/or shortcomings in foam physical properties. The major advantage realized from polyurethane-modified isocyanurate technology is that foams prepared by this method have inherent thermal stability and can easily pass ASTM E-84 requirements. However, a major disadvantage associated with the use of polyurethane-modified isocyanurates is that large exotherms are produced causing fast reactivities which lead to processing difficulties. For rigid polyurethanes, reactive and additive flame retardants (bromine; chlorine; and phosphorus-containing compounds are most common) are used for pour-in-place, spray, and, to a lesser extent, boardstock applications. Of these two types of flame retardants, reactive compounds generally are preferred because they are nonfugitive after incorporation into the foam.

The most commonly used reactive flame retardant product was THERMOLIN RF-230 chlorinated polyol. Formulations with RF-230 flame retardant retained normal processing characteristics of conventional urethanes, did not require phosphorus additives, produced foam with adequate physical properties, and achieved low flame spread and smoke ratings. An example of the use of RF-230 is disclosed in U.S. Pat. No. 4,223,068. Unfortunately, RF-230 flame retardant was withdrawn from the market. The removal of this product has created a need for a replacement flame retardant in the rigid polyurethane market, especially for pour-in-place panel applications.

In general, halogenated flame retardants tend to be solids or high viscosity liquids. Polyurethane foamers generally do not have solids handling capability and can only manipulate high viscosity products with difficulty, hence foamers actively seek new reactive flame retardant products which are low viscosity liquids that can be easily incorporated into their current processing equipment. Thus, a reactive flame retardant product that produces ASTM E-84 rated foam with good physical properties and without adverse processing constraints is needed for the rigid polyurethane industry.


The present invention is a novel, low viscosity, reactive flame retardant polyol composition comprising:
(a) a sucrose polyol;
(b) an aromatic polyester polyol; and
(c) an amount of a halogenated, hydroxy-containing derivative of pentaerythritol which is sufficient to impart a degree of flame retardancy to a rigid polyurethane foam prepared using said composition, such that the polyurethane can achieve a Class I or Class II rating according to the ASTM E-84 test of the American Society for Testing and Materials (hereinafter “ASTM”) for determining surface burning characteristics of building materials.

The rigid foams produced with the polyol composition of the present invention are useful in many applications including, for example, in pour-in-place panels which are used for commercial coolers, walk-in freezers, refrigerators, and the like. Surprisingly, polyurethane-containing rigid foams prepared
using said compositions do not require phosphorus-containing flame retardants to achieve Class I or Class II ratings.

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