A method for producing a low viscosity, nitrogen-containing polyol suitable for use in sprayed, high density, rigid polyurethane foam, comprising the steps of
- a. mixing nonylphenol and diethanolamine, the molar ratio of nonylphenol to diethanolamine being about 1:2;
- b. adding formaldehyde to the mixture in proportions such that the molar ratio of formaldehyde to nonylphenol is in the range of about 1.25:1 to about 1.75:1;
- c. heating the resulting mixture at a temperature within the range of from about 50.degree. to 150.degree. C. for a period of time sufficient to reduce the formaldehyde content to no more than about 1 wt.%;
- d. stripping the water from the reaction product;
- e. adding propylene oxide and ethylene oxide separately or together to said stripped reaction product at a temperature within the range of about 30.degree. to 200.degree. C.;
- and
- f. recovering a nitrogen-containing polyol having a hydroxyl number of from about 250 to about 900, a nitrogen content of from about 1 to about 15 wt.% and a viscosity of 15,000 centipoise or less at 25.degree. C.