Process for production of low density water-blown rigid foams with flow and dimensional stability

A water-blown foam having a minimum in-place density of from about 1 to about 5 lbs./ft..sup.3, and the foam exhibiting less than a 5.5% volume change when stored at 158.degree. F. for 28 days, the foam being prepared by a method comprising the steps of:

• (a) preparing a polymer base to contain from about 5-8 parts by weight of water and at least about 60% by weight, based on the weight of the polymer base, of a polyester having a functionality of at least about 1.6;
• and
• (b) reacting the polymer base with an isocyanate in the presence of a tertiary amine.

A water-blown rigid foam comprising a mixture of polyols and an isocyanate, where at least about 60% by weight based on the weight of the polyols is a polyester having a functionality of from about at least about 1.6,

• the foam having a free rise density of from about 1 to about 2.5 pounds/ft.sup.3 and exhibiting less than a 5.5% volume change when stored at 158.degree. F. for 28 days, and
• the foam having a parallel compressive strength of about 25-30 psi and perpendicular compressive strength of about 15-20 psi, and a closed cell content of greater than about 95%.