Polymer foam insulation structure having a facing of a multi-layer sheet that contains a heat resistant polymer layer and a polylactide resin layer
Thermal insulation structures include a polymer foam layer adhered to a multi-layer sheet having a non-cellular layer of a heat-resistant thermoplastic and a second non-cellular layer of a polylactide resin. The polylactide resin is a surprisingly good barrier to the diffusion of atmospheric gases into the foam layer and of blowing agents out of the foam layer. Accordingly, the diffusion of atmospheric gases and blowing agents is retarded substantially. This greatly reduces the loss of thermal insulation capacity of the structure due to the replacement of the blowing agent with atmospheric gases. The multi-layer sheet exhibits excellent thermal stability, even when the polylactide in the polylactide layer is highly amorphous.
1. A method that comprises applying a foam precursor mixture containing at least one polyisocyanate, water, and a physical hydrocarbon blowing agent having 3 to 8 carbon atoms to a surface of a first non-cellular layer of a multi-layer sheet, which multi-layer sheet includes i) the first non-cellular layer, which contains at least 50 weight % of one or more thermoplastic resins, wherein the one or more thermoplastic resins is not a polylactide resin and has a Vicat softening temperature (ASTM D1525, 50° C./hr, 1 kg) of at least 70° C., said first non-cellular layer being sealingly affixed to ii) a second non-cellular layer containing at least 50 weight % of a polylactide resin and (2) curing the foam precursor mixture while in contact with the first non-cellular layer of the multi-layer sheet to form a polymer foam layer adhered to the first non-cellular layer of the multi-layer sheet.
2. The method of claim 1 , wherein the one or more thermoplastic resins has a Vicat softening temperature (ASTM D1525, 50° C./hr, 1 kg) of at least 100° C.
3. The method of claim 2 , wherein the one or more thermoplastic resins are a homopolymer of methyl methacrylate or a copolymer containing at least 70 weight % polymerized methyl methacrylate.
4. The method of claim 2 , wherein said first non-cellular layer constitutes at least 10% of the total thickness of the multi-layer sheet.
5. The method of claim 2 , wherein the second non-cellular layer contains less than 25 J of polylactide crystallites per gram of polylactide resin in said second non-cellular layer.
6. The method of claim 2 , wherein the foam precursor mixture is dispensed into a cavity formed by the multi-layer sheet and a second layer and cured within the cavity to form a polymer foam layer adhered to the multilayer sheet and the second layer.