| 摘要 |
PROBLEM TO BE SOLVED: To provide a sound absorber whose sound absorbing property, specially, almost at 2000 Hz is improved and a duct which has the sound absorber. SOLUTION: The sound absorber is formed of a polyurethane foam obtained by subjecting polyol and polyisocyanate to reaction; and the polyol is polyol with a 2 to 3 mean functional group number and a 20 to 120 mean hydroxyl value or polyol having a 2 to 3 mean functional group number and a 20 to 120 mean hydroxyl value for 95 to 70 wt.% of the 100 wt.% polyol and a 1 functional group number and a 40 to 120 hydroxyl value for the rest, and the polyurethane foam is a closed mold molding. The polyurethane foam formed of the closed mold molding has a 60 to 200 kg/m<SP>3</SP>density, preferably, a density 1.5 to 5 times as large as a free foaming density. COPYRIGHT: (C)2004,JPO
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