Preparation of low friability rigid polyurethane foam

In a process of preparing a rigid polyurethane foam from a reaction mixture comprised of a polyether polyol reactant, an organic polyisocyanate reactant, a reaction catalyst and a forming agent, said polyether polyol reactant having a hydroxyl number of about 150-800 and being the product of condensing 4,4,4-trichloro-1,2-epoxybutane with a mixture selected from the group consisting of a mixture of dextrose and water, a mixture of dextrose and an aliphatic diol or triol, and a mixture of dextrose, water and an aliphatic diol or triol, the improvement of including in said reaction mixture a second polyol, in a proportion which is effective in reducing the surface friability of said foam, said second polyol characterized by having a hydroxyl number of about 100-800 and being an adduct of ethylene oxide and an amine selected from the group consisting of an aliphatic amine having 1-8 carbon atoms, an aromatic primary amine having 6-8 carbon atoms, an alkanolamine in which each alkanol group contains 2-5 carbon atoms, and a mixture thereof.