Foam wall structures and methods for their manufacture

A wall structure comprising:

• (a) a frame comprising:
• (i) a first member;
• (ii) a second member spaced apart from the first member;
• and (iii) connecting members extending between the first member and the second member, wherein the first member, the second member, and the connecting members each comprise a front surface and a rear surface that form a front frame surface and a rear frame surface;
• (b) a foam panel overlying the front frame surface, wherein at least one of:
• (i) the foam panel abuts the front frame surface such that the foam panel, the first member, the second member, and the connecting members define a cavity, or (ii) a non-foam sheathing abuts the front frame surface between the front frame surface and the foam panel, such that the non-foam sheathing, the first member, the second member, and the connecting members define the cavity;
• and
• (c) a polyurethane foam layer disposed within the cavity, wherein the polyurethane foam layer:
• (i) adheres to a rear surface of at least one of the foam panel or, if present, a rear surface of the non-foam sheathing,
• (ii) has a density, as determined by ASTM D1622-14, of 44 kg/m3 (2.75 lb/ft3) to 160 kg/m3 (10.0 lb/ft3) and exhibits a Class A rating according to ASTM E84-16, and
• (iii) is a cured reaction product of a polyurethane foam-forming composition comprising:
• (1) a polyisocyanate present in an amount by weight;
• (2) an aromatic polyester polyol having a functionality of greater than 2.5 and an OH number of 300 to 400 mg KOH/g, which is present in an amount of at least 50% by weight, based on total weight of the polyurethane foam-forming composition less the weight of the polyisocyanate;
• (3) a catalyst;
• and
• (4) a blowing agent composition comprising water and a hydrofluoroolefin, wherein the hydrofluoroolefin is present in an amount of 1 to 6% by weight, based on the total weight of the polyurethane foam-forming composition, less the weight of the polyisocyanate.