Patent ID: 7018700

Claim:
A method for making cellular acoustic absorption polymer foam having improved thermal insulating performance comprising: (A) Providing a polymer foam having an average cell size in the range from 1.5 mm to 4 mm and an open cell content not greater than 40 percent measured according to ASTM D2856, Procedure A, and (B) Perforating the polymer foam provided in step (A) at a surface of the polymer foam to form a multiplicity of perforation channels extending from that surface into the polymer foam such that the open cell content of the foam measured according to ASTM D2856, Procedure A, is increased relative to the step (A) polymer foam by at least 10 percent to obtain a perforated polymer foam having an open cell content of at least 20 percent, measured according to ASTM D2856, Procedure A, wherein the perforating step (B) is carried out such that the number of perforation channels per square centimeter formed by step (B), “PD”, has a value defined by equation (I): PD≧X /( ACS ) 2 (I) wherein “ACS” represents the average cell size of the polymer foam provided in step (A) measured in millimeters according to ASTM D3576 and “X” equals 4, wherein PD is at least 30 perforation channels per 10 square centimeters and/or ACS is at least 3 mm.