US 7,320,739 B2
Sound absorptive multilayer composite
Delton R. Thompson, Jr., Woodbury, Minn. (US); and Xiaohe Liu, Woodbury, Minn. (US)
Assigned to 3M Innovative Properties Company, St. Paul, Minn. (US)
Filed on Jul. 01, 2004, as Appl. No. 10/884,545.
Application 10/884545 is a continuation in part of application No. 10/335752, filed on Jan. 02, 2003.
Prior Publication US 2004/0231915 A1, Nov. 25, 2004
Int. Cl. B32B 37/00 (2006.01)
U.S. Cl. 156—308.2  [156/196; 181/286; 181/291] 17 Claims
OG exemplary drawing
 
1. A method for making a multilayer sound absorptive composite comprising:
a) providing a stack of layers comprising in order an air-impermeable barrier, an air-permeable reinforcing core comprising a foam and having an airflow resistance of at least about 100 miks Rayls and a thickness at least about ⅓ the final composite thickness, an air-permeable open cell foam or fibrous pad having an airflow resistance less than about 2000 miks Rayls and a thickness at least about 1/10 the final composite thickness, and a semipermeable airflow-resistive membrane having an airflow resistance of about 500 to about 4000 miks Rayls, and
b) laminating the stack of layers together under sufficient heat and pressure to form a unitary sound absorptive multilayer composite.