Three-dimensional net-like structure
By taking into account the difficulty in smoothly bending along the shape of, for example, a care bed, there is provided a three-dimensional net-like structure made from polyester having a swelling ratio dependent on a shear rate such as to be 1.10 to 1.38 at a shear rate of 60.8 sec −1 and 1.17 to 1.43 at a shear rate of 608 sec −1 and having an MFR of 3 to 35 g/10 min and a density of 1.01 to 1.60 g/cm 3 and configured to have a spring structure of filaments randomly brought into contact with and tangled with one another, have a three-dimensional striped sparse-dense configuration in a lateral direction relative to an extrusion direction. The swelling ratio is shown as D 2 /D 1 against shear rate when a molten thermoplastic resin is extruded to filaments from a capillary having a tube inner diameter D 1 of 1.0 mm and a length of 10 mm and D 2 denotes a diameter of cross section of the filaments extruded and cooled down.
1. A three-dimensional netted structure bendable in the direction of the extrusion direction made from polyester having a swelling ratio dependent on a shear rate and configured to have a curled spring structure of filaments randomly brought into contact with and tangled with each other, having a three-dimensional striped sparse-dense configuration in a lateral direction relative to an extrusion direction, and having a filament diameter of 0.2 to 1.3 mm and a bulk density of 0.01 to 0.2 g/cm 3 ,
wherein
the swelling ratio is shown as D 2 /D 1 against shear rate when the polyester in molten state is extruded to the filaments from a capillary having a tube inner diameter D 1 of 1.0 mm and a length of 10 mm at a temperature of 210° C. and D 2 denotes a diameter of a cross section of the polyester filaments extruded and cooled down;
the swelling ratio of the polyester is 1.00 to 1.60 at a shear rate range of 25 to 1000/sec −1 ;
the polyester is a polyester block copolymer (A) having a high melting-point crystalline polymer segment (a) mainly comprising a crystalline aromatic polyester unit and a low melting-point polymer segment (b) mainly comprising an aliphatic polyether unit and/or an aliphatic polyester unit as main components; and
the three-dimensional netted structure has a surface layer in the extrusion direction which has a higher bulk density than the other area.
2. The three-dimensional netted structure of claim 1 , wherein the swelling ratio is 1.10 to 1.50 in a shear rate range of 25 to 1000/sec −1 .
3. The three-dimensional netted structure of claim 2 , wherein the swelling ratio of the polyester is 1.10 to 1.38 at a shear rate of 60.8 sec −1 , is 1.12 to 1.39 at a shear rate of 122 sec −1 , is 1.15 to 1.42 at a shear rate of 243 sec −1 , is 1.17 to 1.43 at a shear rate of 608 sec −1 , and is 1.19 to 1.47 at a shear rate of 1220 sec −1 .
4. A three-dimensional structure, the three-dimensional structure comprising polyester filaments, the polyester filaments comprising a polyester block copolymer, the polyester block copolymer comprising a high melting-point crystalline polymer segment and a low melting-point polymer segment; the high melting-point crystalline polymer segment comprising a crystalline aromatic polyester unit, the low melting-point polymer segment comprising an aliphatic polyether unit and/or an aliphatic polyester unit; each of the polyester filaments being produced by extruding polyester in molten state through a capillary to form an intermediate polyester filament and then cooling down the intermediate polyester filament, the polyester in the molten state having a shear rate;
wherein:
the polyester filaments have a curled spring shape and are randomly contacted and tangled with each other;
the three-dimensional structure comprises a plurality of sparse portions, a plurality of dense portions, and a surface layer;
the surface layer is in a sheet shape and has a sheet surface;
each of the plurality of sparse portions has a first density;
each of the plurality of dense portions has a second density;
the surface layer has a third density;
the first density is lower than the second density;
the second density is lower than the third density;
each of the plurality of sparse portions and each of the plurality of dense portions are disposed alternately along the sheet surface to form a sparse-dense configuration;
the polyester filaments have a filament diameter of 0.2 to 1.3 mm and a bulk density of 0.01 to 0.2 g/cm 3 ;
the polyester filaments have a swelling ratio;
the swelling ratio is defined as D 2 /D 1 , wherein D 1 denotes an inner diameter of the capillary and is 1.0 mm, and the capillary has a length of 10 mm, and D 2 denotes a diameter of a cross section of the polyester filaments; and
the swelling ratio is 1.00 to 1.60 when the shear rate is 25 to 1000 sec −1 .
5. The three-dimensional structure of claim 4 , wherein the polyester filaments comprise an antimicrobial agent.
6. The three-dimensional structure of claim 5 , wherein the swelling ratio is 1.10 to 1.50 when the shear rate range is 25 to 1000/sec −1 .
7. The three-dimensional structure of claim 6 , wherein the swelling ratio of the polyester is 1.10 to 1.38 when the shear rate is 60.8 sec −1 , the swelling ratio of the polyester is 1.12 to 1.39 when the shear rate is 122 sec −1 , the swelling ratio of the polyester is 1.15 to 1.42 when the shear rate is 243 sec −1 , the swelling ratio of the polyester is 1.17 to 1.43 when the shear rate is 608 sec −1 , or the swelling ratio of the polyester is 1.19 to 1.47 when the shear rate is 1220 sec −1 .