Polyurethaneurea solutions and spandex therefrom

An improved solution of polyurethaneurea polymer in an inert organic solvent, the improvement comprising, for protection against viscosity changes during storage and processing, a 4,4'-biphenylenediphosphonite additive incorporated in the solution, the additive amounting to 0.05 to 1.5 percent of the weight of the polymer and having the following structural formula ##STR2## wherein the biphenylene unit is unsubstituted or substituted,

• R.sub.1, R.sub.2, R.sub.3 and R.sub.4, each independently is a mono-substituted, di-substituted or tri-substituted phenyl group or an alkyl group of 3 to 8 carbon atoms, and
• the substituents on the biphenylene or phenyl groups are lower alkyl of 1 to 4 carbon atoms.