In the polyurethane field, increased interest is being shown in compounds which can be added to the polyurethane polymers to act as fire retardant agents. Particular interest is being shown in compounds which have functional groups reactive with the polyol or polyisocyanate used in preparing the polyurethane so that the fire retardant agent can be copolymerized into the polymer chain. One such group of compounds of this type are the polyalkylene glycol polyphosphites and phosphonates. In general, these materials are prepared by transesterifying a secondary phosphite with a polyalkylene glycol in the presence of an alkaline catalyst such as sodium phenolate or sodium methylate. However, many of these materials have relatively high acidity causing them to react with and thereby deactivate certain catalyst systems generally used in the formation of polyurethane polymers such, for example, as tertiary amine compounds. To alleviate this problem, the polyalkylene glycol phosphonates have heretofore been reacted with materials such as alkylene oxides in order to reduce the number of acid groups on the phosphorus. However, addition of the alkylene groups onto the phosphorus has decreased the relative flame retardancy of these compounds. Alternatively, secondary polyalkylene glycol phosphites have been reacted with carbon tetrachloride or chloral in order to add flame retardant chlorine atoms to the molecule. However, the phosphonates formed in this manner are still relatively high in acidity.
Therefore, it is an object of the present invention to produce a class of compounds which are compatible with polyurethane foams, which can be copolymerized therewith, which have a high degree of flame retardancy and which are relatively low in acidity. Various other objects and advantages of this invention will be apparent from a reading of the disclosure which follows hereinafter.