Polymer polyol quality

A process for preparing a stable, low viscosity polymer polyol having a solids content of at least about 30% by weight, based on the total weight of the polymer polyol, comprising:

• (1) free-radically polymerizing:
• (A) one or more base polyols;
• (B) one or more pre-formed stabilizers;
• and
• (C) one or more ethylenically unsaturated monomers;
• in the presence of
• (D) one or more free-radical polymerization initiators;
• and, optionally,
• (E) one or more polymer control agents;
• wherein the process is restarted after being stopped by (I) restarting the feed of said one or more base polyols and said one or more initiators, in which (a) the feed of said one or more base polyols and said one or more initiators is restarted simultaneously or (b) the feed of said one or more base polyols is restarted first, followed by restarting the feed of said one or more initiators;
• (II) continuing the polyol and initiator feed or feeds until the total feed amounts to at least 5% of the total reactor volume;
• and (III) restarting the feed of said one or more ethylenically unsaturated monomers wherein the ratio of monomers to total feed is ramped up to its final value over a period of not less than 25% of the reactor residence time.