Nonwoven Sound Absorbing Material
A nonwoven sound absorbing material according to the present invention includes a nonwoven laminate formed of a stack of a plurality of sheets of a filament nonwoven fabric having a plurality of drawn filaments arranged and oriented in one direction, and the mode value of the diameter distribution of the plurality of drawn filaments is 1 to 4 μm. The nonwoven sound absorbing material according to the present invention has improved sound absorption performance in a relatively low frequency band as compared to a conventional one.
1 . A nonwoven sound absorbing material comprising a nonwoven laminate formed of a stack of a plurality of sheets of a filament nonwoven fabric having a plurality of drawn filaments arranged and oriented in one direction,
wherein a mode value of a diameter distribution of the plurality of drawn filaments is 1 to 4 μm.
2 . The nonwoven sound absorbing material according to claim 1 ,
wherein a drawing ratio of each of the plurality of drawn filaments is in a range of 3 to 6,
wherein an average diameter of the plurality of drawn filaments is in a range of 1 to 4 μm, and
wherein a variation coefficient of the diameter distribution of the plurality of drawn filaments is in a range of 0.1 to 0.3.
3 . The nonwoven sound absorbing material according to claim 1 , wherein a grammage of the filament nonwoven fabric is in a range of 5 to 60 g/m 2 .
4 . The nonwoven sound absorbing material according to claim 3 , wherein a specific volume obtained by dividing a thickness of the filament nonwoven fabric by the grammage of the filament nonwoven fabric is in a range of 2.0 to 3.5 cm 3 /g.
5 . The nonwoven sound absorbing material according to claim 1 , wherein a tensile strength of the filament nonwoven fabric in a drawing direction of the plurality of drawn filaments is 20 N/50 mm or more.
6 . The nonwoven sound absorbing material according to claim 1 , wherein an air permeability of the filament nonwoven fabric is in a range of 5 to 250 cm 3 /cm 2 ⋅s.
7 . The nonwoven sound absorbing material according to claim 1 , wherein the nonwoven laminate is formed of a stack of 50 to 200 sheets of the filament nonwoven fabric.
8 . The nonwoven sound absorbing material according to claim 1 ,
wherein a normal incident sound absorption coefficient of the nonwoven sound absorbing material has a peak at a frequency of 2000 Hz or less, and
wherein the normal incident sound absorption coefficient reaches 50% or more at the peak.
9 . The nonwoven sound absorbing material according to claim 1 , wherein each of the plurality of drawn filaments mainly contains a polyester or a polypropylene.
10 . The nonwoven sound absorbing material according to claim 9 , wherein the polyester is a polyethylene terephthalate having an intrinsic viscosity (IV) of 0.43 to 0.63.
11 . The nonwoven sound absorbing material according to claim 1 , wherein the filament nonwoven fabric further has a plurality of second drawn filaments arranged and oriented in a direction orthogonal to the one direction.