Patent ID: 7208531

Claim:
A viscoelastic polyurethane foam comprising a reaction product of: (A) an isocyanate component; (B) a first polyether polyol having; (i) a hydroxyl number of from 20 to 60 mg KOH/g, (ii) a plurality of internal blocks formed from oxyalkylene monomers comprising a random heteric mixture of ethylene oxide and propylene oxide with said internal blocks having at most 20% by weight ethylene oxide based on a total weight of said oxyalkylene monomers in said internal blocks, and (iii) a plurality of terminal caps attached to said plurality of internal blocks and comprising at most 25% by weight ethylene oxide based on a total weight of said first polyether polyol; (C) a second polyether polyol having; (i) a hydroxyl number of from 20 to 200 mg KOH/g, (ii) a plurality of internal blocks formed from oxyalkylene monomers, (iii) a plurality of terminal caps attached to said plurality of internal blocks, and (iv) at least 50% by weight ethylene oxide based on the total weight of the second polyether polyol; wherein said first polyether polyol (B) is reacted in an amount of from 50 to 65% by weight, and said second polyether polyol (C) is reacted in an amount of from 35 to 50% by weight, both based on the total weight of the first and the second polyether polyols; (D) a chain extender present in an amount of from 3 to 20 parts by weight based on the total weight of (A), (B), (C), and (D) and having; (i) a backbone chain with from two to eight carbon atoms, and (ii) a weight-average molecular weight of from 25 to 250; and said foam having a density of from 1 to 20 pounds per cubic foot and having a first glass transition temperature greater than zero degrees Celsius and a second glass transition temperature less than zero degrees Celsius and having a tan delta peak ratio of said first glass transition temperature to said second glass transition temperature less than 2.2.