Elastic network structure with excellent quietness and hardness

Abstract

[Problem] The objective of the present invention is to provide an elastic mesh structure having exceptional cushioning and reducing noise during compression or recovery. [Solution] A mesh structure comprising a three-dimensional, random-loop, joining structure formed by winding a continuous line of thermoplastic resin to form random loops, bringing the loops into contact with one another in a molten state, and fusing the majority of the contact area, wherein (a) the apparent density of the random-loop contact structure is 0.005-0.200 g/cm.sup.3, and (b) the number of contact points per unit weight of the random-loop contact structure is 500-1200/g.

Claims

1. A network structure comprising a random loop bonded structure of a continuous linear structure of a thermoplastic resin, wherein (a) the random loop bonded structure has an apparent density of 0.02 to 0.100 g/cm.sup.3, (b) a number of bonded points per unit weight of the random loop bonded structure is 500 to 1200/gram, (c) the fineness of the continuous linear structure is 200 to 3000 decitex, (d) the network structure has a thickness of not less than 3 cm, and (e) a 25%-compression hardness of the random loop bonded structure is not less than 10 kg/φ200-mm and not more than 50 kg/φ200-mm diameter.

2. The network structure according to claim 1, wherein the number of bonded points per unit weight of the random loop bonded structure is 550 to 1150/gram.

3. The network structure according to claim 2, wherein the number of bonded points per unit weight of the random loop bonded structure is 600 to 1100/gram.

4. The network structure according to claim 1, wherein the thermoplastic resin is at least one thermoplastic resin selected from the group consisting of a soft polyolefin, a polystyrene thermoplastic elastomer, a polyester thermoplastic elastomer, a polyurethane thermoplastic elastomer and a polyamide thermoplastic elastomer.

5. The network structure according to claim 4, wherein the thermoplastic resin is at least one thermoplastic resin selected from the group consisting of a soft polyolefin and a polyester thermoplastic elastomer.

6. The network structure according to claim 5, wherein the thermoplastic resin is a polyester thermoplastic elastomer.

7. The network structure according to claim 1, wherein the continuous linear structure has a hollow cross section.

8. The network structure according to claim 7, wherein the continuous linear structure has a hollow cross section and a degree of hollowness of the hollow cross section is 10 to 50%.

9. The network structure according to claim 8, wherein the continuous linear structure has a hollow cross section and the degree of hollowness of the hollow cross section is 20 to 40%.

10. The network structure according to claim 1, wherein the continuous linear structure has a modified cross section.

11. The network structure according to claim 1, wherein the 25%-compression hardness of the random loop bonded structure is not less than 15 kg/φ200-mm and not more than 50 kg/φ200-mm diameter.

Description

EXAMPLES

(1) Hereinafter, the present invention will be described by way of Examples.

(2) It should be noted that evaluations in Examples were performed in the following manner.

(3) <Properties of Resin>

(4) (1) Melting Point (Tm)

(5) Using a TA50, DSC50 differential scanning calorimeter available from SHIMADZU CORPORATION, 10 g of a sample was subjected to measurement at a temperature rising rate of 20° C./minute from 20° C. to 250° C. to obtain an endothermic and exothermic curve. An endothermic peak (melting peak) temperature was found from the endothermic and exothermic curve.

(6) (2) Flexural Modulus

(7) With an injection molding machine, a sample piece measuring 125 mm in length×12 mm in width×6 mm in thickness was formed, and the sample piece was subjected to measurement in accordance with ASTM D790.

(8) <Properties of Network Structure>

(9) (1) Apparent Density

(10) A sample was cut into the shape of a rectangular parallelepiped measuring 15 cm in length×15 cm in width so that the rectangular parallelepiped included two surface layers of the sample but did not include the peripheral portion of the sample, the heights of four corners of the rectangular parallelepiped were measured, and thereafter the volume (cm.sup.3) was found, and the weight (g) of the sample was divided by the volume, whereby the apparent density (g/cm.sup.3) was calculated. It should be noted that the apparent density was the average of n=4.

(11) (2) Number of Bonded Points Per Unit Weight

(12) First, a sample was cut into the shape of a rectangular parallelepiped measuring 5 cm in length×5 cm in width so that the rectangular parallelepiped included two surface layers of the sample but did not include the peripheral portion of the sample, whereby a piece was formed. Next, the heights of four corners of the piece were measured, and thereafter the volume (unit: cm.sup.3) was found, and the weight (unit: g) of the sample was divided by the volume, whereby the apparent density (unit: g/cm.sup.3) was calculated. Next, the number of bonded points in this piece was counted, the number was divided by the volume of the piece, whereby the number of bonded points per unit volume (unit: the number of bonded points/cm.sup.3) was calculated. The number of bonded points per unit volume was divided by the apparent density, whereby the number of bonded points per unit weight (unit: the number of bonded points/gram) was calculated. It should be noted that a bonded point is a welded part between two linear structures. The number of bonded points was measured by a method of pulling two linear structures and detaching the welded part. Furthermore, the number of bonded points per unit weight was the average of n=2. Furthermore, in the case of a sample having a 0.005 g/cm.sup.3 or greater band-like difference in apparent density along the length or width direction of the sample, the sample was cut so that the border between a dense portion and a sparse portion ran through the center of the piece along the length or width direction, and the number of bonded points per unit weight was measured in the same manner (n=2).

(13) (3) Fineness of Linear Structure

(14) First, a sample was cut into the shape of a rectangular parallelepiped measuring 30 cm in length×30 cm in width so that the rectangular parallelepiped included two surface layers of the sample but did not include the peripheral portion of the sample, the rectangular parallelepiped was divided into equally sized 4 cells, linear structures measuring 1 cm in length were taken at 5 places per cell, 20 places in total, and the specific gravity of each linear structure was measured at 40° C. using a density gradient tube. Next, the cross sectional area of a resin portion of each of the above-described linear structures taken at 20 places was found from a photograph enlarged with a microscope, the volume per 10000 m of the linear structure was obtained from the cross-sectional area, and thereafter the product of a specific gravity and the volume obtained represents fineness (weight in grams per 10000 m of linear structure: decitex(dtex)) (average of n=20).

(15) (4) Degree of Hollowness

(16) First, a sample was cut into the shape of a rectangular parallelepiped measuring 30 cm in length×30 cm in width so that the rectangular parallelepiped included two surface layers of the sample but did not include the peripheral portion of the sample, the rectangular parallelepiped was divided into equally sized 4 cells, linear structures measuring 1 cm in length were taken at 5 places per cell, 20 places in total, the linear structures were cooled with liquid nitrogen, and thereafter were cut into pieces. A cross section of each piece was observed under an electron microscope at a magnification of 50 times, the obtained image was analyzed using a CAD system and thereby the cross sectional area (A) of a resin portion and the cross sectional area (B) of a hollow portion were measured, and the degree of hollowness was calculated through the equation {B/(A+B)}×100 (average of n=20).

(17) (5) 25%-Compression Hardness

(18) A sample was cut into the shape of a rectangular parallelepiped measuring 30 cm in length×30 cm in width so that the rectangular parallelepiped included two surface layers of the sample but did not include the peripheral portion of the sample, and the 25%-compression hardness was indicated as a stress at 25% compression on a stress-strain curve obtained by compressing the rectangular parallelepiped to 75% with a compression board measuring 200 mm in diameter with TENSILON available from ORIENTEC Co., LTD. (average of n=3).

(19) (6) Feeling of Floor Contact

(20) On a rectangular parallelepiped sample prepared by cutting a sample into the shape of a rectangular parallelepiped measuring 50 cm in length×50 cm in width so that the rectangular parallelepiped sample included two surface layers of the sample, 30 panelists weighing 40 kg to 100 kg (the number of 20- to 39-year-old men; 5, the number of 20- to 39-year-old women: 5, the number of 40- to 59-year-old men: 5, the number of 40- to 59-year-old women: 5, the number of 60- to 80-year-old men: 5, the number of 60- to 80-year-old women: 5) sat down, and the panelists qualitatively evaluated the degree of feeling of “bumping” on the floor sensuously when they sat down. No feeling: Excellent, weak feeling: Good, moderate feeling; Moderate, strong feeling; Poor

(21) (7) Sound Deadening Property

(22) On a rectangular parallelepiped sample prepared by cutting a sample into the shape of a rectangular parallelepiped measuring 50 cm in length×50 cm in width so that the rectangular parallelepiped sample included two surface layers of the sample, 30 panelists weighing 40 kg to 100 kg (the number of 20- to 39-year-old men; 5, the number of 20- to 39-year-old women: 5, the number of 40- to 59-year-old men: 5, the number of 40- to 59-year-old women: 5, the number of 60- to 80-year-old men: 5, the number of 60- to 80-year-old women: 5) sat down, and the panelists qualitatively evaluated the sound coming from the network structure sensuously. No sound; Excellent, small sound; Good, moderate sound; Moderate, large sound; Poor

Synthesis Example 1

(23) Dimethyl terephthalate (DMT), 1,4-butanediol (1,4-BD) and polytetramethylene glycol (PTMG: average molecular weight 1000) were charged together with a small amount of a catalyst, transesterification was performed by a conventional method, and thereafter the resultant was subjected to polycondensation with increasing temperature under reduced pressure, whereby a polyester-ether block copolymer elastomer of DMT/1,4-BD/PTMG=100/88/12 mol % was prepared. Next, 1% antioxidant was added thereto, and the resultant was mixed and kneaded, and thereafter the mixture was made into pellets. The pellets were dried in a vacuum at 50° C. for 48 hours, whereby a polyester thermoplastic elastomer raw material (A-1) was obtained. The properties of the polyester thermoplastic elastomer raw material are shown in Table 1.

Synthesis Example 2

(24) Dimethyl terephthalate (DMT), 1,4-butanediol (1,4-BD) and polytetramethylene glycol (PTMG: average molecular weight 1000) were charged together with a small amount of a catalyst, transesterification was performed by a conventional method, and thereafter the resultant was subjected to polycondensation with increasing temperature under reduced pressure, whereby a polyester-ether block copolymer elastomer of DMT/1,4-BD/PTMG=100/84/16 mol % was prepared. Next, 1% antioxidant was added thereto, and the resultant was mixed and kneaded, and thereafter the mixture was made into pellets. The pellets were dried in a vacuum at 50° C. for 48 hours, whereby a polyester thermoplastic elastomer raw material (A-2) was obtained. The properties of the polyester thermoplastic elastomer raw material are shown in Table 1.

Synthesis Example 3

(25) Dimethyl terephthalate (DMT), 1,4-butanediol (1,4-BD) and polytetramethylene glycol (PTMG: average molecular weight 1000) were charged together with a small amount of a catalyst, transesterification was performed by a conventional method, and thereafter the resultant was subjected to polycondensation with increasing temperature under reduced pressure, whereby a polyester-ether block copolymer elastomer of DMT/1,4-BD/PTMG=100/72/28 mol % was prepared. Next, 1% antioxidant was added thereto, and the resultant was mixed and kneaded, and thereafter the mixture was made into pellets. The pellets were dried in a vacuum at 50° C. for 48 hours, whereby a polyester thermoplastic elastomer raw material (A-3) was obtained. The properties of the polyester thermoplastic elastomer raw material are shown in Table 1.

(26) TABLE-US-00001 TABLE 1 Properties of resin Number Flexural of resin Resin composition Melting point modulus Synthesis A-1 DMT/1,4-BD/ 203° C. 0.16 Gpa Example 1 PTMG = 100/88/12 Synthesis A-2 DMT/1,4-BD/ 200° C. 0.11 Gpa Example 2 PTMG = 100/84/16 Synthesis A-3 DMT/1,4-BD/ 170° C. 0.05 Gpa Example 3 PTMG = 100/72/28

Example 1

(27) One hundred kg of the polyester thermoplastic elastomer (A-1) obtained in Synthesis Example 1, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 240° C., and discharged in an amount of 2.4 g/minute per single hole through hollow rounded orifices, each having a hole size of 3.0 mm, disposed in an interval of 6 mm in a nozzle surface area measuring 66 cm in width and 5 cm in length. Cooling water was arranged at a position 35 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 2.2 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Example 2

(28) One hundred kg of the polyester thermoplastic elastomer (A-2) obtained in Synthesis Example 2, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 245° C., and discharged in an amount of 2.2 g/minute per single hole through solid rounded orifices, each having a hole size of 1.0 mm, disposed in an interval of 4 mm in a nozzle surface area measuring 64 cm in width and 3.5 cm in length. Cooling water was arranged at a position 50 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 3 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 2.6 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Example 3

(29) One hundred kg of the polyester thermoplastic elastomer (A-2) obtained in Synthesis Example 1, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 230° C., and discharged in an amount of 2.4 g/minute per single hole through hollow rounded orifices, each having a hole size of 3.0 mm, disposed in an interval of 6 mm in a nozzle surface area measuring 66 cm in width and 5 cm in length. Cooling water was arranged at a position 37 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 1.9 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Example 4

(30) One hundred kg of the polyester thermoplastic elastomer (A-2) obtained in Synthesis Example 2, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 230° C., and discharged in an amount of 2.4 g/minute per single hole through hollow rounded orifices, each having a hole size of 3.0 mm, disposed in an interval of 6 mm in a nozzle surface area measuring 66 cm in width and 5 cm in length. Cooling water was arranged at a position 32 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 1.8 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Example 5

(31) One hundred kg of the polyester thermoplastic elastomer (A-3) obtained in Synthesis Example 3, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 200° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 220° C., and discharged in an amount of 2.4 g/minute per single hole through hollow rounded orifices, each having a hole size of 3.0 mm, disposed in an interval of 6 mm in a nozzle surface area measuring 66 cm in width and 5 cm in length. Cooling water was arranged at a position 37 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4.5 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 1.8 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Example 6

(32) One hundred kg of low density polyethylene (“Nipolon Z 1P55A” available from TOSOH CORPORATION) was melted at a temperature of 200° C., and discharged in an amount of 2.0 g/minute per single hole through hollow rounded orifices, each having a hole size of 3.0 mm, disposed in an interval of 6 mm in a nozzle surface area measuring 66 cm in width and 5 cm in length. Cooling water was arranged at a position 37 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4.5 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 1.7 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Comparative Example 1

(33) One hundred kg of the polyester thermoplastic elastomer (A-1) obtained in Synthesis Example 1, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 245° C., and discharged in an amount of 3.6 g/minute per single hole through hollow rounded orifices, each having a hole size of 5.0 mm, disposed in an interval of 8 mm in a nozzle surface area measuring 64 cm in width and 4.8 cm in length. Cooling water was arranged at a position 35 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 2.2 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Comparative Example 2

(34) One hundred kg of the polyester thermoplastic elastomer (A-2) obtained in Synthesis Example 2, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 235° C., and discharged in an amount of 1.6 g/minute per single hole through solid rounded orifices, each having a hole size of 1.0 mm, disposed in an interval of 6 mm in a nozzle surface area measuring 66 cm in width and 3.5 cm in length. Cooling water was arranged at a position 30 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 3 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 1.0 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Comparative Example 3

(35) One hundred kg of the polyester thermoplastic elastomer (A-2) obtained in Synthesis Example 2, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 240° C., and discharged in an amount of 3.6 g/minute per single hole through hollow rounded orifices, each having a hole size of 5.0 mm, disposed in an interval of 8 mm in a nozzle surface area measuring 64 cm in width and 4.8 cm in length. Cooling water was arranged at a position 38 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 2.0 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Comparative Example 4

(36) One hundred kg of the polyester thermoplastic elastomer (A-2) obtained in Synthesis Example 2, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 220° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 240° C., and discharged in an amount of 1.6 g/minute per single hole through hollow rounded orifices, each having a hole size of 3.0 mm, disposed in an interval of 6 mm in a nozzle surface area measuring 64 cm in width and 4.8 cm in length. Cooling water was arranged at a position 25 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 1.4 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Comparative Example 5

(37) One hundred kg of the polyester thermoplastic elastomer (A-3) obtained in Synthesis Example 3, 0.25 kg of a hindered phenol antioxidant (“ADEKA STAB AO330” available from ADEKA CORPORATION) and 0.25 kg of a phosphorus antioxidant (“ADEKA STAB PEP36” available from ADEKA CORPORATION) were mixed in a tumbler for 5 minutes. After that, the mixture was melted and kneaded with a φ57-mm twin screw extruder at a cylinder temperature of 200° C. and a screw speed of 130 rpm, extruded into the form of a strand in a water bath and cooled, and thereafter pellets of a resin composition were obtained. The obtained resin composition was melted at a temperature of 230° C., and discharged in an amount of 3.6 g/minute per single hole through hollow rounded orifices, each having a hole size of 5.0 mm, disposed in an interval of 8 mm in a nozzle surface area measuring 64 cm in width and 4.8 cm in length. Cooling water was arranged at a position 38 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 2.0 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

Comparative Example 6

(38) One hundred kg of low density polyethylene (“Nipolon Z 1P55A” available from TOSOH CORPORATION) was melted at a temperature of 200° C., and discharged in an amount of 3.0 g/minute per single hole through hollow rounded orifices, each having a hole size of 5.0 mm, disposed in an interval of 8 mm in a nozzle surface area measuring 64 cm in width and 4.8 cm in length. Cooling water was arranged at a position 35 cm under the nozzle face. Endless nets made from stainless steel having a width of 70 cm were disposed parallel in an interval of 4.0 cm to form a pair of take-up conveyors, partially exposed over a water surface. The copolymer raw material extruded was taken up on this conveyor, while being welded on the contacted parts, and sandwiched from both sides. The sandwiched material was introduced into cooling water with a speed of 1.5 m/minute to be solidified, then subjected to a pseudocrystallization treatment for 15 minutes in a hot-air drier at 100° C., and then cut into a predetermined size, whereby a network structure was obtained. The properties of the obtained network structure are shown in Table 2.

(39) TABLE-US-00002 TABLE 2 Number of Cross section bonded points Resin shape of per unit weight 25%- material of continuous Degree of Apparent (the number of Compression Feeling of Sound network linear hollowness Fineness Thickness density bonded points/ hardness floor deadening structure structure (%) (dtex) (cm) (g/cm.sup.3) g) (kg/φ200 mm) contact property Example-1 A-1 Hollow round 31 1950 4.1 0.045 745 15 Excellent Excellent Example-2 A-2 Solid round 0 827 3.1 0.071 650 13 Excellent Excellent Example-3 A-2 Hollow round 29 2348 3.9 0.052 758 16 Excellent Excellent Example-4 A-2 Hollow round 27 2833 4.0 0.051 540 16 Excellent Excellent Example-5 A-3 Hollow round 30 2600 4.5 0.049 800 9 Good Excellent Example-6 LDPE Hollow round 28 1872 4.3 0.053 970 9 Good Excellent Comparative A-1 Hollow round 40 4540 4.0 0.040 152 15 Excellent Poor Example-1 Comparative A-2 Solid round 0 2296 3.0 0.065 413 14 Excellent Poor Example-2 Comparative A-2 Hollow round 39 5603 4.0 0.045 160 15 Excellent Poor Example-3 Comparative A-2 Hollow round 28 3058 3.9 0.043 339 12 Excellent Poor Example-4 Comparative A-3 Hollow round 38 5451 4.0 0.045 170 4 Poor Moderate Example-5 Comparative LDPE Hollow round 39 4405 4.1 0.050 205 4 Poor Moderate Example-6

INDUSTRIAL APPLICABILITY

(40) The present invention relates to a network structure that shows excellent quietness while keeping cushioning properties. Utilizing these properties, the network structure can be used for seats for vehicles and mattresses, etc.