Flame-retardant polyurethane foams

In a crosslinked hydrophilic flame-retardant polyurethane foam prepared by reacting a hydrophilic polyoxyalkylene urethane prepolymer under foam-forming conditions with at least 20 moles of water for every mole of NCO groups in the prepolymer and in the presence of alumina hydrate having an average particle size of about 0.5 to about 120 microns and ammonium polyphosphate with said alumina hydrate carried in the water phase and said prepolymer being a mixture of a polyethylene glycol and a polyhydric alcohol containing 3 or 4 hydroxyl groups per mole, said hydroxyl groups of the glycol and polyol being reacted with sufficient polyisocyanate to cap all of said hydroxyl groups, the improvement comprising:

• incorporating wood cellulose into the water phase prior to contact with the prepolymer in the foam-forming reaction in an amount of from about 2 to about 5 parts by weight of wood cellulose based on 100 parts by weight of the prepolymer.

In a method for preparing a crosslinked hydrophilic foam-retardant polyurethane foam by reacting a hydrophilic polyoxyalkylene urethane prepolymer under foam-forming conditions with at least 20 moles of water for every mole of NCO groups in the prepolymer and in the presence of alumina hydrate and a phosphorous fire-retardant compound with said alumina hydrate carried in the water phase, the improvement comprising:

• incorporating into the foam-forming reaction from about 5 to about 30 parts, based on 100 parts by weight of the prepolymer, of a water-dispersible and combustible organic carbon compound selected from the group consisting of a phenol having at least 2 hydroxyl groups per mole, starch, lignin, and wood cellulose, said carbon compound providing an essentially neutral pH when dissolved or dispersed in water, said carbon compound being present from about 5 to about 30 parts by weight based on 100 parts by weight of the prepolymer, provided that when said carbon compound is wood cellulose it is present from about 2 to about 10 parts by weight based on 100 parts by weight of the prepolymer, and said carbon compound not functioning as a gellatinizing agent at the concentration employed.

In a method for preparing a crosslinked hydrophilic flame-retardant polyurethane foam by reacting a hydrophilic polyoxyalkylene urethane prepolymer under foam-forming conditions with at least 20 moles of water for every mole of NCO groups in the prepolymer and in the presence of alumina hydrate having an average particle size of about 0.5 to about 120 microns and ammonium polyphosphate with said alumina hydrate carried in the water phase and said prepolymer being a mixture of a polyethylene glycol and a polyhydric alcohol containing 3 or 4 hydroxyl groups per mole, said hydroxyl groups of the glycol and polyol being reacted with sufficient polyisocyanate to cap all of said hydroxyl groups, the improvement comprising:

• incorporating wood cellulose into the foam-forming reaction in an amount of from about 2 to about 5 parts, based on 100 parts by weight of the prepolymer.