Molded body of thermoplastic resin having sound absorption characteristics

Abstract

An expansion-molded article (foamed body) produced by using foamed and expanded beads, and having open voids has sound absorbing qualities, and can be used as a sound absorbing material. However, a sound absorbing material comprising such an expansion-molded article has been unable to attain a high sound absorption coefficient in a wide acoustic frequency range. The invention relates to a molded article produced by using resin particles, and having sound absorbing qualities. The resin particles used have through hole(s) and a porosity of 45 to 80% in a most densely packed state. The void content of the molded article is 10 to 60%, and the bulk density thereof is 0.01 to 0.6 g/cm 3 . The molded article has not less than 3 continuous center frequency measuring points at which the sound absorption coefficient is at least 70%, and not less than 7 continuous center frequency measuring points at which the sound absorption coefficient is at least 50% in the sound absorption coefficients at the center frequencies of 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500 and 3150 (Hz) as determined by the measuring method of reverberant absorption coefficient prescribed in JIS A 1409.

1 - 8 . (canceled)  
     
     
         9 . A sound absorbing structure of a vehicle comprising a sound absorbing material composed of an expansion-molded article and a skin material, incorporated into an interior material of the vehicle, 
 wherein the expansion-molded article being obtained by fusing and mutually bonding small resin pieces of foamed thermoplastic resin, and having continuous void with a void content of about 25 to 60%,    wherein the skin material is bonded or laminated on the surface of the expansion-molded article.    
     
     
         10 . A sound absorbing structure of a vehicle comprising a sound absorbing material composed of an expansion-molded article and a skin material, incorporated into an interior material of the vehicle, 
 wherein the expansion-molded article being obtained by fusing and mutually bonding small resin pieces of foamed thermoplastic resin, and having continuous void with a void content of about 25 to 60%,    wherein the skin material is bonded or laminated on the surface of the expansion-molded article,    wherein the small resin piece has through hole(s), and    wherein a ratio (L)/(D) of the maximum length (L) of the small resin piece in direction along the hole to the maximum diameter (D) of the small resin piece at the section perpendicular to direction along the hole is 0.7 to 1.2.    
     
     
         11 . A sound absorbing structure of a vehicle according to  claim 9 , wherein the skin material is woven fabric or non-woven fabric.  
     
     
         12 . A sound absorbing structure of a vehicle according to  claim 9 , wherein the skin material is synthetic resin sheet.  
     
     
         13 . A sound absorbing structure of a vehicle according to  claim 9 , wherein the skin material comprises a single-layer structure.  
     
     
         14 . A sound absorbing structure of a vehicle according to  claim 9 , wherein the skin material comprises a multi-layer structure having foamed layer.  
     
     
         15 . A sound absorbing structure of a vehicle according to  claim 10 , wherein the skin material is woven fabric or non-woven fabric.  
     
     
         16 . A sound absorbing structure of a vehicle according to  claim 10 , wherein the skin material is synthetic resin sheet.  
     
     
         17 . A sound absorbing structure of a vehicle according to  claim 10 , wherein the skin material comprises a single-layer structure.  
     
     
         18 . A sound absorbing structure of a vehicle according to  claim 10 , wherein the skin material comprises a multi-layer structure having foamed layer.