this invention can be employed to produce a plexifilamentary product comprising only one of the polymers by selectively dissolving away one and leaving the other the product of example 10 for instance can be treated with trifluoroacetic acid at room temperature to dissolve away the poly pivalolactone component leaving the acrylic conversely it can be treated with dimethylformamide at 80 u00b0 90 u00b0 c to dissolve away the acrylic component leaving the poly pivalolactone component a polymer of 1 5 intrinsic viscosity consisting of 93 9 units derived from acrylonitrile 5 98 methylacrylate and 0 12 sodium styrenesulfonate 3 314 kg is charged into a 19 liter steam jacketed autoclave equipped with a stirrer and bottom outlet along with 17 440 kg of water the contents are agitated to form a slurry the autoclave is pressured to 105 kg cm 2 with nitrogen and the vessel and contents heated over the course of about 30 minutes to 170 u00b0 c to form a water dispersion of acrylonitrile polymer hydrate agitation is stopped for 5 minutes to allow settling of the hydrate to the bottom of the autoclave the hydrate is metered at a rate of 278 g min into a mixing chamber along with 317 g min of water the dispersion is forced through a 6 1 meter length of pressure tubing having.