초록 ▼

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. A sound absorbing material which is able to attain a high sound absorption coefficient in a wide acoustic frequen

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. A sound absorbing material which is able to attain a high sound absorption coefficient in a wide acoustic frequency range is provided by a molded article produced by using resin particles, having 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.

대표청구항 ▼

1. A method for forming a molded article comprising the steps of:providing small resin pieces comprising thermoplastic resin and having a porosity of 45 to 80% in a most densely packed state;filling a mold with the small resin pieces; andheating the small resin pieces in said mold to thereby fuse th

1. A method for forming a molded article comprising the steps of:providing small resin pieces comprising thermoplastic resin and having a porosity of 45 to 80% in a most densely packed state;filling a mold with the small resin pieces; andheating the small resin pieces in said mold to thereby fuse the small resin pieces to each other and form said molded article, said molded article comprising open voids, a void content of 10 to 60%, and a bulk density of 0.01 to 0.6 g/cm 3 , and said molded article having 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 as set forth in JIS A 1409. 2. The method according to claim 1, wherein the small resin pieces are foamed thermoplastic resin particles, whereby the step of heating causes expansion molding of the small foamed thermoplastic resin particles. 3. The method according to claim 1, further comprising providing a skin material which is fusible with the small resin pieces fitting the skin material into the mold; whereby the step of heating the small resin pieces in the mold, results in the pieces being fused to each other and to the skin material. 4. The method according to claim 1, wherein each small resin piece has through hole(s), and has a length L to diameter D ratio (L/D) in the range of from 0.7 to 1.2. 5. The method according to claim 1, wherein the small resin pieces are in the form of at least one of particles, chips or a crushed product. 6. The method according to claim 2, wherein the small resin pieces are foamed particles of polyolefin resin. 7. The method according to claim 6, wherein each foamed particle of polyolefin resin has through hole(s). 8. The method according to claim 6, wherein each foamed particle of polyolefin resin has a cylindrical structure satisfying the relation L/D≧2, or a polygonal prism structure satisfying the relation L/D≧2.5, wherein L denotes length and D denotes diameter. 9. The method according to claim 6, wherein each foamed particle of polyolefin resin has branch-like projections on the surface. 10. The method according to claim 3, wherein the skin material has a multi-layered structure, and at least an inner side of this multi-layered skin material comprises a material that fuses with the small resin pieces. 11. The method according to claim 6, wherein each foamed particle has a length L to diameter D ratio (L/D) in the range of from 0.7 to 1.2. 12. A method for manufacturing an expansion-molded article having a skin, wherein the skin material is integrally bonded to surface of the expansion-molded article, comprising the steps of:fitting the skin material into a mold;filling small resin pieces of foamed thermoplastic resin into the mold; andheating the small resin pieces with steam to fuse the small resin pieces to one another and to fuse the small resin pieces to the skin material;wherein the skin material comprises a multi-layered structure having a foamed layer; andwherein each small resin piece has through-hole(s) and the small resin pieces have a porosity of 45 to 80% in their most densely packed state; andwherein said molded article comprises open void content 10 to 60%, and a bulk density of 0.01 to 0.6 g/cm 3 . 13. The method according to claim 12, wherein the expansion-molded article has a side of the molded article on which no skin is laminated. 14. The method according to claim 12, wherein each small resin piece is a foamed particle of polyolefin resin having through hole(s) and having a length L to diameter D ratio (L/D) in the range of from 0.7 to 1.2.