阅读说明：本技术 网状结构体的制造方法 (Method for producing net-like structure ) 是由 小渊信一 谷中辉之 涌井洋行 仓本隆宏 福西范树 井上拓勇 安井章文 于 2016-04-28 设计创作，主要内容包括：网状结构体的制造方法,其中,如下得到网状结构体：从具有多个孔口、且具有多个不同孔口孔径的多列喷嘴,将聚酯系热塑性弹性体分配于喷嘴孔口,在比所述聚酯系热塑性弹性体的熔点高20℃以上且低于120℃的纺丝温度下,从所述喷嘴向下方排出,以熔融状态使连续线状体彼此接触并熔接,形成三维结构,由此得到网状结构体,所述孔口包含多个实心截面纤维用孔口和多个中空截面纤维用孔口,所述实心截面纤维用孔口的宽度方向孔间间距与所述中空截面纤维用孔口的宽度方向孔间间距之差为2mm以下。(A method for producing a net-like structure, wherein the net-like structure is obtained by: a polyester-based thermoplastic elastomer is distributed to nozzle orifices from a plurality of rows of nozzles having a plurality of orifices and a plurality of different orifice diameters, discharged downward from the nozzles at a spinning temperature which is higher than the melting point of the polyester-based thermoplastic elastomer by 20 ℃ or higher and lower than 120 ℃, and continuous linear bodies are brought into contact with each other in a molten state and welded to form a three-dimensional structure, thereby obtaining a net-like structure, wherein the orifices include a plurality of solid-section fiber orifices and a plurality of hollow-section fiber orifices, and the difference between the width-direction inter-hole distances of the solid-section fiber orifices and the width-direction inter-hole distances of the hollow-section fiber orifices is 2mm or less.)

1. A method for producing a net-like structure, wherein the net-like structure is obtained by: distributing a polyester-based thermoplastic elastomer to nozzle orifices from a plurality of rows of nozzles having a plurality of orifices and a plurality of different orifice diameters, discharging the polyester-based thermoplastic elastomer downward from the nozzles at a spinning temperature which is higher than the melting point of the polyester-based thermoplastic elastomer by 20 ℃ or higher and lower than 120 ℃, bringing continuous linear bodies into contact with each other in a molten state and welding the linear bodies to form a three-dimensional structure,

the orifices comprise a plurality of orifices for solid section fibers and a plurality of orifices for hollow section fibers,

the orifice holes in the nozzle are made up of 3 groups:

a group: the solid cross-section fiber is arranged in a plurality of rows along the thickness direction to form an orifice group;

ab group: a hole group in which the solid-section fiber holes and the hollow-section fiber holes are mixed and arranged in a plurality of rows in the thickness direction;

b group: the hollow-section fiber has a plurality of holes arranged in a thickness direction,

alternatively, the orifice holes in the nozzle are comprised of 2 groups:

group α: the solid cross-section fiber is arranged in a plurality of rows along the thickness direction to form an orifice group;

group β: the hollow-section fiber has a plurality of holes arranged in a thickness direction,

the difference between the width-direction inter-hole pitch of the solid-section fiber orifice and the width-direction inter-hole pitch of the hollow-section fiber orifice is 2mm or less.

2. The method of manufacturing a net-shaped structure according to claim 1, wherein a difference between a width-direction inter-hole pitch of the solid-section fiber apertures and a width-direction inter-hole pitch of the hollow-section fiber apertures is 1mm or less.

3. The method of manufacturing a net-shaped structure according to claim 1, wherein a difference between a width-direction inter-hole pitch of the solid-section fiber apertures and a width-direction inter-hole pitch of the hollow-section fiber apertures is 0 mm.

4. The method of manufacturing a net-shaped structure according to claim 1, wherein the width-direction inter-hole pitch of the solid-section fiber apertures and the width-direction inter-hole pitch of the hollow-section fiber apertures are both 4mm or more and 12mm or less.

5. The method of manufacturing a net-like structure according to claim 1, wherein the orifice diameter of the solid-section fiber orifice is 1.5mm or less, and the orifice diameter of the hollow-section fiber orifice is 2mm or more.

Technical Field

The present invention relates to: a method for producing a net-like structure of a net-like cushioning material suitable for use in bedding such as office chairs, furniture, sofas, and beds, vehicle seats such as railways, cars, motorcycles, strollers, child seats, and car seats, floor mats, impact absorbing mats such as impact absorbing members for preventing collisions and sandwiching.

Background

Mesh structures have been widely used as cushioning materials for bedding such as furniture and beds, and vehicle seats such as electric cars, automobiles, and motorcycles. Japanese patent laid-open Nos. 7-68061 (patent document 1) and 2004-244740 (patent document 2) disclose methods for producing a mesh-like structure. The network structure has the following advantages compared with foaming-crosslinking carbamate: has the same degree of durability, excellent moisture and water permeability and air permeability, and less heat storage property, so that the coating is not easy to evaporate. Further, the following advantages can be mentioned: is made of thermoplastic resin, is easy to recycle, has no worry about residual medicine, and is environment-friendly. However, these mesh structures use any surface without any concept such as a surface and a back with some exceptions, and the cushioning feeling is also the same.

The net structure has unique cushioning properties, but it alone has difficulty in changing the cushioning properties. In order to solve this problem, japanese patent application laid-open No. 7-189105 (patent document 3) discloses a mesh structure having different fineness and a method for producing the same. A base layer which takes on vibration absorption and body shape retention; and a surface layer which is soft and has a property of uniformly dispersing pressure. As described above, the effects of the respective layers play different roles, and in order to improve the feeling when seated from the surface layer side, regardless of the use of seating from both the surface layer side and the base layer side, the compression durability is lower in the case of seating from the surface layer side than in the case of seating from the base layer side, and the compression durability is different in the case of seating from the surface layer side and the base layer side.

Further, mesh-shaped structures of different designs may be bonded together by adhesion or bundled with a band to be integrated with side cloth (side ground), but there are problems as follows: the production cost is high, and there is a concern that the cushioning feeling may be changed by using an adhesive to feel a foreign substance feeling, and there is a problem that the compression durability is largely different between both sides.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a method for manufacturing a mesh structure, which has the following effects: can provide different cushioning properties to both sides, and has a small difference in compression durability from either side.

Means for solving the problems

The present inventors have conducted extensive studies to solve the above problems, and as a result, the present invention has been completed. Namely, the present invention is as follows.

[1] A method for producing a net-like structure, wherein the net-like structure is obtained by: distributing a polyester-based thermoplastic elastomer to nozzle orifices from a plurality of rows of nozzles having a plurality of orifices and a plurality of different orifice diameters, discharging the polyester-based thermoplastic elastomer downward from the nozzles at a spinning temperature which is higher than the melting point of the polyester-based thermoplastic elastomer by 20 ℃ or higher and lower than 120 ℃, bringing continuous linear bodies into contact with each other in a molten state and welding the linear bodies to form a three-dimensional structure,

the orifices comprise a plurality of orifices for solid section fibers and a plurality of orifices for hollow section fibers,

the orifice holes in the nozzle are made up of 3 groups:

a group: the solid cross-section fiber is arranged in a plurality of rows along the thickness direction to form an orifice group;

ab group: a hole group in which the solid-section fiber holes and the hollow-section fiber holes are mixed and arranged in a plurality of rows in the thickness direction;

b group: the hollow-section fiber has a plurality of holes arranged in a thickness direction,

alternatively, the orifice holes in the nozzle are comprised of 2 groups:

group α: the solid cross-section fiber is arranged in a plurality of rows along the thickness direction to form an orifice group;

group β: the hollow-section fiber has a plurality of holes arranged in a thickness direction,

the difference between the width-direction inter-hole distance of the solid-section fiber orifice and the width-direction inter-hole distance of the hollow-section fiber orifice is 2mm or less

[2] The method of producing a net-like structure according to the above [1], wherein a difference between a width-direction inter-hole pitch of the solid-section fiber openings and a width-direction inter-hole pitch of the hollow-section fiber openings is 1mm or less.

[3] The method of producing a net-like structure according to the above [1], wherein a difference between a width-direction inter-hole pitch of the solid-section fiber openings and a width-direction inter-hole pitch of the hollow-section fiber openings is 0 mm.

[4] The method of producing a net-like structure according to any one of the above [1] to [3], wherein both the width-direction inter-hole pitch of the solid-section fiber orifices and the width-direction inter-hole pitch of the hollow-section fiber orifices are 4mm to 12 mm.

[5] The method of producing a net-like structure according to any one of the above [1] to [4], wherein the orifice diameter of the solid-section fiber orifice is 1.5mm or less, and the orifice diameter of the hollow-section fiber orifice is 2mm or more.

ADVANTAGEOUS EFFECTS OF INVENTION

The net-like structure of the present invention is a net-like structure having different cushioning properties on both the front and back surfaces of the net-like structure, and has an effect that the difference in durability between compression and compression is small from either of the two surfaces. Therefore, the mesh structure can be used in both front and back directions, and the following can be provided: the mesh structure is suitable for bedding such as office chairs, furniture, sofas, and beds, and vehicle seats such as railways, automobiles, and motorcycles. As an example of the effects that can be used in both front and rear directions, the following effects can be given: a cushioning material having a hard cushioning feeling and a characteristic of feeling cool due to a reduction in contact area by using a fiber side having a hollow cross section with a large fiber diameter on the surface in summer; in winter, a cushioning material having a soft cushioning feeling and a characteristic of feeling warm by increasing a contact area is formed by using a fiber side having a solid cross section with a small fiber diameter on the surface.

In addition, when the fiber side having a solid cross section with a small fiber diameter is used as the surface of the mesh structure of the present invention, the mesh structure composed of 100% of the fibers having a solid cross section with a small fiber diameter is excellent in compression durability. Therefore, when the fiber side having a solid cross section with a small fiber diameter is used as the surface, the fiber side is excellent in compression durability as compared with the conventional product, and therefore, it can be preferably used.

Drawings

Fig. 1A is a schematic view showing a 2 nd order stress-strain curve in the hysteresis loss measurement of a mesh-shaped structure.

Fig. 1B is a schematic diagram showing a stress-strain curve at the 2 nd compression in the hysteresis loss measurement of the mesh-shaped structure.

Fig. 1C is a schematic view showing a stress-strain curve at the time of the 2 nd decompression in the hysteresis loss measurement of the mesh-shaped structure.

Detailed Description

The present invention will be described in detail below. The present invention is a net-like structure having a three-dimensional random loop-bonded structure, which is composed of a thermoplastic elastomer continuous filament body that is any of a polyester-based thermoplastic elastomer continuous filament body and a polyolefin-based thermoplastic elastomer continuous filament body having a fiber diameter of 0.1mm to 3.0mm, wherein the following regions are present in the thickness direction of the net-like structure: a solid-section fiber main region mainly composed of a fiber having a solid section (hereinafter, referred to as "solid-section fiber"); a hollow-section fiber main region mainly composed of a fiber having a hollow section (hereinafter, referred to as "hollow-section fiber"); and a mixed region in which the solid-section fiber and the hollow-section fiber are mixed and located between the solid-section fiber main region and the hollow-section fiber main region, wherein both the solid-section fiber main region-side residual strain after repeated compression at a constant load of 750N when pressurized from the solid-section fiber main region side and the hollow-section fiber main region-side residual strain after repeated compression at a constant load of 750N when pressurized from the hollow-section fiber main region side of the mesh-shaped structure are 20% or less, and the difference between the solid-section fiber main region-side residual strain and the hollow-section fiber main region-side residual strain is 10 points or less.

The network structure of the present invention is a structure having a three-dimensional random ring junction structure: a continuous filament body comprising a continuous filament body of a polyester-based thermoplastic elastomer and a polyolefin-based thermoplastic elastomer having a fiber diameter of 0.1 to 3.0mm is bent to form random loops, and the loops are brought into contact with each other in a molten state and joined. The thermoplastic elastomer continuous linear body in the present invention is any of a polyester-based thermoplastic elastomer and a polyolefin-based thermoplastic elastomer continuous linear body having a fiber diameter of 0.1mm to 3.0 mm.

Examples of the polyester-based thermoplastic elastomer include polyester ether block copolymers having a thermoplastic polyester as a hard segment and a polyalkylene glycol as a soft segment; or a polyester block copolymer having an aliphatic polyester as a soft segment.

The polyester ether block copolymer is a ternary block copolymer comprising a dicarboxylic acid selected from at least 1 of dicarboxylic acids selected from the group consisting of terephthalic acid, isophthalic acid, aromatic dicarboxylic acids such as naphthalene-2, 6-dicarboxylic acid, naphthalene-2, 7-dicarboxylic acid, diphenyl-4, 4' -dicarboxylic acid and the like, alicyclic dicarboxylic acids such as 1, 4-cyclohexanedicarboxylic acid and the like, aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid dimer acid and the like, and ester-forming derivatives thereof, a diol component, and a polyalkylene glycol; at least 1 diol component selected from the group consisting of aliphatic diols such as 1, 4-butanediol, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, and hexamethylene glycol, alicyclic diols such as 1, 1-cyclohexanedimethanol and 1, 4-cyclohexanedimethanol, and ester-forming derivatives thereof; the polyalkylene glycol is at least 1 of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycol containing ethylene oxide-propylene oxide copolymer, and the like with the number average molecular weight of about 300-5000.

The polyester block copolymer is a triblock copolymer comprising at least 1 of the above dicarboxylic acid and diol and a polyester diol such as a polylactone having a number average molecular weight of about 300 to 5000. In view of hot adhesiveness, hydrolysis resistance, stretchability, heat resistance and the like, a 3-membered block copolymer of terephthalic acid and/or naphthalene 2, 6-dicarboxylic acid as a dicarboxylic acid, 1, 4-butanediol as a diol component, and polytetramethylene glycol as a polyalkylene glycol is particularly preferable; or polylactones as 3-membered block copolymers of polyester diols. In a specific example, a polysiloxane-based soft segment may be introduced.

In addition, the polyester-based thermoplastic elastomer of the present invention includes a material obtained by blending a non-elastomer component with the above-mentioned polyester-based thermoplastic elastomer, a material obtained by copolymerization, a material having a polyolefin component as a soft segment, and the like. Further, the thermoplastic elastomer composition may further include one obtained by adding various additives to the polyester-based thermoplastic elastomer, if necessary.

In order to realize a net-like structure having the effects of imparting different cushioning properties to both sides and reducing the difference in compression durability from either side, which is an object of the present invention, the soft segment content of the polyester-based thermoplastic elastomer is preferably 15% by weight or more, more preferably 25% by weight or more, further preferably 30% by weight or more, and particularly preferably 40% by weight or more, and from the viewpoint of ensuring hardness and heat-resistant sagging resistance, is preferably 80% by weight or less, and more preferably 70% by weight or less.

The component containing the polyester-based thermoplastic elastomer constituting the network structure of the present invention preferably has an endothermic peak at a melting point or lower in a melting curve measured by a differential scanning calorimeter. When the melting point or less has an endothermic peak, the heat resistance and sagging resistance are significantly improved as compared with the case where no endothermic peak is present. For example, in the case where the polyester-based thermoplastic elastomer of the present invention contains 90 mol% or more of a rigid terephthalic acid, naphthalene-2, 6-dicarboxylic acid or the like in the acid component of the hard segment, more preferably, the content of the terephthalic acid or naphthalene-2, 6-dicarboxylic acid is 95 mol% or more, particularly preferably 100 mol% and the diol component are transesterified, and then polymerized to a desired degree of polymerization, and then polytetramethylene glycol having an average molecular weight of preferably 500 to 5000, more preferably 700 to 3000, still more preferably 800 to 1800 or less as polyalkylene glycol is copolymerized in an amount of preferably 15 to 80 wt%, more preferably 25 to 70 wt%, further preferably 30 to 70 wt%, particularly preferably 40 to 70 wt%, when the content of terephthalic acid or naphthalene-2, 6-dicarboxylic acid having rigidity in the acid component of the hard segment is large, the crystallinity of the hard segment is improved, plastic deformation is less likely to occur, and the heat resistance and sag resistance are improved, but the heat resistance and sag resistance are improved by further annealing at a temperature at least 10 ℃ lower than the melting point after melt thermal bonding. The annealing treatment may be carried out by heat-treating the sample at a temperature at least 10 ℃ lower than the melting point, and the heat resistance and sagging resistance are further improved by applying a compressive strain. When the thus treated network structure is measured by a differential scanning calorimeter, an endothermic peak is more clearly expressed in a melting curve at a temperature of room temperature (for example, 20 ℃) or higher and a melting point or lower. When annealing is not performed, an endothermic peak is not clearly shown at room temperature (20 ℃) or higher and at a melting point or lower in the melting curve. By analogy, it is considered that a metastable mesophase in which hard segments are rearranged may be formed by annealing, and the heat resistance and sagging resistance are improved. As a method of utilizing the effect of improving heat resistance in the present invention, it is useful because the flow resistance is good in applications where a cushion for a vehicle or a floor mat for a floor heater using an electric heater may be brought to a relatively high temperature.

The polyolefin-based thermoplastic elastomer in the present invention is preferably an ethylene/α -olefin copolymer obtained by copolymerizing ethylene and an α -olefin, and more preferably an olefin block copolymer, i.e., a multi-block copolymer of ethylene/α -olefin. The reason why the multi-block copolymer composed of ethylene- α -olefin is more preferable is that in a general random copolymer, the chain length of the main chain becomes short, the crystal structure is not easily formed, and the durability is lowered. The α -olefin copolymerized with ethylene is preferably an α -olefin having 3 or more carbon atoms.

Examples of the α -olefin having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, and 1-eicosene, and 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-eicosene are preferable, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene. In addition, they can also use more than 2.

The random copolymer of the ethylene/α -olefin copolymer of the present invention can be obtained by copolymerizing ethylene and α -olefin using a catalyst system basically composed of a specific metallocene compound and an organometallic compound, and the multiblock copolymer can be obtained by copolymerizing ethylene and α -olefin using a chain shuttling (chain shuttling) reaction catalyst. If necessary, two or more kinds of polymers obtained by polymerization by the above-mentioned method, polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, and the like may be blended.

In the ethylene/α -olefin copolymer of the present invention, the ratio of ethylene to α -olefin having 3 or more carbon atoms is preferably 70 mol% or more and 95 mol% or less of ethylene, and 5 mol% or more and 30 mol% or less of α -olefin having 3 or more carbon atoms. It is generally known that when the polymer compound has elasticity, a hard segment and a soft segment are present in the polymer chain. In the polyolefin thermoplastic elastomer of the present invention, it is considered that ethylene plays a role as a hard segment and α -olefin having 3 or more carbon atoms plays a role as a soft segment. Therefore, when the ethylene content is less than 70 mol%, the hard segment is small, and the recovery performance of rubber elasticity is lowered. The ethylene ratio is more preferably 75 mol% or more, and still more preferably 80 mol% or more. On the other hand, when the ethylene content exceeds 95 mol%, the soft segment is small, and therefore, the elastomer is hardly exhibited, and the cushion performance is poor. The ethylene ratio is more preferably 93 mol% or less, and still more preferably 90 mol% or less.

In the net-like structure of the present invention, in addition to the polyester-based thermoplastic elastomer or the polyolefin-based thermoplastic elastomer, if necessary, a polymer modifier such as a styrene-isoprene copolymer, a styrene-butadiene copolymer, or a hydrogenated copolymer thereof, which is a polybutadiene-based, polyisoprene-based, or styrene-based thermoplastic elastomer as a sub-material, may be blended. Further, there may be added: phthalate-based, trimellitate-based, fatty acid-based, epoxy-based, adipate-based, or polyester-based plasticizers, known hindered phenol-based, sulfur-based, phosphorus-based, or amine-based antioxidants, hindered amine-based, triazole-based, benzophenone-based, benzoate-based, nickel-based, or salicylic acid-based light stabilizers, antistatic agents, molecular weight regulators such as peroxides, epoxy-based compounds, cyanate-based compounds, or carbodiimide-based compounds having a reactive group, metal deactivators, organic and inorganic nucleating agents, neutralizers, acid inhibitors, antibacterial agents, fluorescent brighteners, fillers, flame retardants, flame retardant aids, and organic and inorganic pigments. In addition, it is also effective to increase the molecular weight of the polyolefin thermoplastic elastomer in order to improve heat resistance and durability and sag resistance.

One feature of the present invention is that different cushioning properties can be imparted to both sides. In order to change the cushioning properties when the two surfaces are compressed, respectively, a method of obtaining a net-like structure having cushioning properties different between the two surfaces is such that at least the following regions are present in the thickness direction of the net-like structure: the main solid section fiber area is mainly composed of solid section fibers and formed into a thickness; a hollow-section fiber main region mainly composed of hollow-section fibers and having a thickness formed by the hollow-section fibers; and a region other than the region between the solid-section fiber main region and the hollow-section fiber main region, that is, a mixed-existing region.

The term "mainly" in the solid cross-section fiber main region and the hollow cross-section fiber main region means that the ratio of the number of fibers having the cross section to the total number of fibers contained in the region is 90% or more. In the mixed region in which the solid-section fibers and the hollow-section fibers are mixed and present between the solid-section fiber main region and the hollow-section fiber main region, the ratio of the number of solid-section fibers to the total number of fibers contained in the region is lower than that of the solid-section fiber main region, and the ratio of the number of hollow-section fibers to the total number of fibers contained in the region is lower than that of the hollow-section fiber main region. That is, the mixed region is a region in which the number of fibers of the solid cross-section fibers and the number of fibers of the hollow cross-section fibers are less than 90% of the total number of fibers contained in the region.

Here, the ratio of the number of fibers in each fiber in the predetermined region is measured by the following method. First, a sample was cut into 10 pieces in a width direction of 3cm × a length direction of 3cm × a sample thickness, and the weight of each piece was measured by an electronic balance. Next, fibers constituting the sample were drawn out one by one from the same surface side of each sample so that the thickness of the sample was reduced as uniformly as possible. The operation of drawing the fibers one by one is continued until the weight of the sample becomes 90% or less of the weight of the sample prepared first. The fiber cross section of the drawn fiber was confirmed visually or by an optical microscope, and the fiber was divided into a solid cross section fiber and a hollow cross section fiber, and the number of the solid cross section fiber and the hollow cross section fiber was counted. The total number of fibers contained in the region was determined by adding the numbers of fibers of the solid-section fibers and the hollow-section fibers of 10 samples. The ratio of the number of fibers of the solid cross-section fiber to the number of fibers of the hollow cross-section fiber to the total number of fibers contained in the region is calculated from the number of fibers of the solid cross-section fiber and the number of fibers of the hollow cross-section fiber, respectively, and it is determined whether the region is a solid cross-section fiber main region, a hollow cross-section fiber main region, or a mixed region.

Next, the operation of drawing the fibers from each sample is resumed, and the operation of drawing the fibers one by one is continued until the weight of the sample becomes 80% or less of the weight of the sample prepared first, and as described above, the ratios of the number of fibers of the solid-section fibers and the number of fibers of the hollow-section fibers to the total number of fibers contained in the region are calculated from the number of fibers of the solid-section fibers and the number of fibers of the hollow-section fibers, respectively, and it is determined whether or not the region is the solid-section fiber main region, the hollow-section fiber main region, or the mixed existing region.

Then, the above operation is repeated for about every 10% of the sample weight until the sample weight initially becomes 70% or less of the weight of the initially prepared sample, until the sample weight initially becomes 60% or less of the weight of the initially prepared sample, until the sample weight initially becomes 50% or less of the weight of the initially prepared sample, until the sample weight initially becomes 40% or less of the weight of the initially prepared sample, until the sample weight initially becomes 30% or less of the weight of the initially prepared sample, until the sample weight initially becomes 20% or less of the weight of the initially prepared sample, until the sample weight initially becomes 10% or less of the weight of the initially prepared sample, and further until the sample weight becomes 0% of the weight, as described above, the ratio of the number of fibers of the solid cross-section fiber to the number of fibers of the hollow cross-section fiber to the total number of fibers contained in each of the 10 regions divided in the thickness direction from the surface side is calculated, and whether each of the regions is the solid cross-section fiber main region, the hollow cross-section fiber main region, or the mixed region is determined.

Another feature of the present invention is that the difference in compression durability between the solid cross-section fiber main region side and the hollow cross-section fiber main region side of the mesh-like structure is small. Specifically, the difference between the residual strain on the solid-section fiber main region side after repeated compression at a constant load of 750N when pressurized from the solid-section fiber main region side and the residual strain on the hollow-section fiber main region side after repeated compression at a constant load of 750N when pressurized from the hollow-section fiber main region side is 10 dots or less, preferably 9 dots or less, more preferably 8 dots or less, and still more preferably 6 dots or less. When the difference between the residual strain on the solid-section fiber main region side and the residual strain on the hollow-section fiber main region side after repeated compression with a constant load of 750N exceeds 10 points, the difference in compression durability between the solid-section fiber main region side and the hollow-section fiber main region side becomes excessively large, and when the mesh structure of the present invention is used in both front and rear applications, the permanent residual strain of the mesh structure differs depending on the direction of use, which is not preferable. The lower limit of the difference between the residual strain on the solid-section fiber main region side and the residual strain on the hollow-section fiber main region side after repeated compression at a constant load of 750N is 0 point when there is no difference in compression durability at all between the solid-section fiber main region side and the hollow-section fiber main region side. Here, the "difference" in the present application means a value obtained by subtracting a smaller value from a larger value among 2 values. The term "dot" means a unit representing a difference between 2 values in "%", for example, a difference between the residual strain in the solid-section fiber main region and the residual strain in the hollow-section fiber main region.

In the mesh structure of the present invention, both the residual strain on the solid cross-section fiber main region side and the residual strain on the hollow cross-section fiber main region side are 20% or less, preferably 15% or less, more preferably 13% or less, and still more preferably 11% or less. When at least either of the solid-section fiber main region-side residual strain and the hollow-section fiber main region-side residual strain becomes a high value, it indicates that the compression durability is poor.

In order to reduce the difference between the residual strain on the solid-section fiber main region side and the residual strain on the hollow-section fiber main region side in the residual strain after repeated compression at a constant load of 750N, it is important that a mixed region in which the solid-section fiber and the hollow-section fiber are mixed exists at a position between the solid-section fiber main region and the hollow-section fiber main region, and these regions are integrated without being separated, so that the entire thickness of the mesh structure can be formed.

The present invention is based on the finding that, even if a laminated network structure of 2 sheets of stacked network structures, which are easily separable and are not integrated, can be provided with cushioning properties different between both surfaces, by merely overlapping a network structure mainly composed of solid-section fibers and a network structure mainly composed of hollow-section fibers without a mixed region where solid-section fibers and hollow-section fibers are mixed. However, in the case of the laminated mesh structure, if the compression is performed from the surface of the mesh structure having low compression hardness, first, only the mesh structure having low compression hardness is compressively deformed, and only the mesh structure having low compression hardness is independently bent from the mesh structure having high compression hardness. In addition, only in the mesh structure having low compressive hardness, the compressive stress is barely transmitted to the mesh structure having high compressive hardness at a stage where the compressive load cannot be endured, and the deformation and deflection of the mesh structure having high compressive hardness are started. Therefore, when the compression is repeated, the net-like structure having low compression hardness first accumulates fatigue, and the thickness is reduced and the compression hardness is reduced more than the net-like structure having high compression hardness. That is, the cushioning properties can be provided differently on both sides, but the difference in compression durability when the pressure is applied from both sides is largely different.

Further, even if the net-like structure mainly composed of the solid-section fibers and the net-like structure mainly composed of the hollow-section fibers are bonded and integrated by adhesion to each other without the mixed region where the solid-section fibers and the hollow-section fibers are mixed, the two surfaces of the net-like structure can be provided with different cushioning properties. However, in the above laminated and laminated net-like structure, in the initial stage of repeated compression, the net-like structures of both are deformed and bent as a whole against a compressive load, but stress concentrates on the adhesive surface with repeated compression, and a decrease in adhesive strength and peeling occur, and therefore, the 2 laminated net-like structure also becomes a net-like structure in which a difference in compression durability when the net-like structures are separately pressed from both surfaces is greatly different.

Further, even in a mesh structure in which a mixed region in which solid-section fibers and hollow-section fibers are mixed does not exist and a main solid-section fiber region mainly composed of solid-section fibers and a main hollow-section fiber region mainly composed of hollow-section fibers are fusion-integrated, it is possible to impart cushioning properties different between both sides. Such a net-like structure can be obtained by a method in which solid cross-section fibers are discharged onto a net-like structure mainly composed of hollow cross-section fibers, and the net-like structure mainly composed of solid cross-section fibers is fusion-laminated. However, in the above-mentioned net-like structure obtained by this method, since the hollow-section fibers are once cured and then the solid-section fibers are welded, the welding force at the boundary surface between the hollow-section fiber layer and the solid-section fiber layer is low, and when a repeated compression load is applied, stress concentrates on the boundary surface to cause interfacial separation, and as a result, durability is deteriorated.

In the case where the net-like structure of the present invention is formed to have a thickness of the entire net-like structure by integrating the mixed regions in which the solid-section fibers and the hollow-section fibers are mixed and located between the solid-section fiber main region and the hollow-section fiber main region without separating the regions, even if the pressure compression is performed from the side having low compression hardness, the stress is transmitted from the initial stage of the compression to the side having high compression hardness through the mixed regions, the stress is efficiently dispersed in the thickness direction, and the entire net-like structure is deformed and bent by the pressure compression load. This makes it possible to reduce the difference between the repeated compression durability when the pressure is applied from the side having low compression hardness and the repeated compression durability when the pressure is applied from the side having high compression hardness.

The mesh structure of the present invention can be obtained by adding a new technique to the known method described in japanese patent application laid-open publication No. 2014-194099 and the like. For example, any of a polyester-based thermoplastic elastomer and a polyolefin-based thermoplastic elastomer is distributed to nozzle orifices from a plurality of rows of nozzles having a plurality of orifices and a plurality of different orifice diameters, which will be described later, discharged downward from the nozzles at a spinning temperature (melting temperature) higher by 20 ℃ or more and lower than 120 ℃ than the melting point of the thermoplastic elastomer, and continuous linear bodies are brought into contact with each other in a molten state and welded to form a three-dimensional structure, and held by a pull-in conveying web, cooled by cooling water in a cooling tank, pulled out, dewatered or dried to obtain a mesh structure with both or one side smoothed. When only one side is smoothed, the sheet is discharged onto a drawing web having an inclination, and the sheet is brought into contact with each other in a molten state and welded to form a three-dimensional structure, and only the drawing web surface can be cooled while in a relaxed state. The obtained net-like structure may be subjected to annealing treatment. The drying treatment of the mesh-like structure may be an annealing treatment.

The resultant network structure may be subjected to a heat treatment (annealing treatment). The heat treatment is preferably performed at a temperature not higher than the melting point of the thermoplastic elastomer, preferably at a temperature not lower than 5 ℃ lower than the melting point, and more preferably at a temperature not lower than 10 ℃ lower than the melting point. The heat treatment temperature is preferably 90 ℃ or higher, more preferably 95 ℃ or higher, and still more preferably 100 ℃ or higher, among the polyester-based thermoplastic elastomers. The polyolefin-based thermoplastic elastomer is preferably 70 ℃ or higher, more preferably 80 ℃ or higher, and still more preferably 90 ℃ or higher. The heat treatment time is preferably 1 minute or more, more preferably 10 minutes or more, further preferably 20 minutes or more, and particularly preferably 30 minutes or more. The heat treatment time is preferably long, but even if it is a certain time or longer, the effect of the heat treatment does not increase, and on the contrary, deterioration of the resin is caused, and therefore, the heat treatment time is preferably within 1 hour.

When a continuous linear body constituting the network structure of the present invention is measured by a differential scanning calorimeter, it is preferable that the continuous linear body has an endothermic peak at a melting curve from room temperature (20 ℃) to a melting point or lower. The endothermic peak at the melting point or lower may have 2 or more, and may appear as a shoulder portion depending on the proximity to the melting point or the shape of the base line. When the endothermic peak is present, the heat resistance and the moist heat resistance are improved as compared with the case where the endothermic peak is not present. As a method of utilizing the effect of improving the heat resistance and sagging resistance in the present invention, it is useful to improve durability in applications where repeated compression is possible under a high temperature environment, such as a cushion for a vehicle and a floor mat for a floor heater using an electric heater.

As a method for obtaining the mesh-like structure of the present invention, it is preferable to optimize the nozzle shape, the specification, and the nozzle hole arrangement. The nozzle shape is preferably such that the diameter of the orifice for forming fine fibers is 1.5mm or less and the diameter of the orifice for forming coarse fibers is 2mm or more. The nozzle orifice shape for forming the thick fibers preferably has a hollow forming property, and examples thereof include a C-shaped nozzle, a 3-point bridge nozzle, and the like, and from the viewpoint of pressure resistance, a 3-point bridge nozzle is preferable. The pitch between the holes is preferably 4mm to 12mm, more preferably 5mm to 11mm, both of the orifice for forming the fine fibers and the orifice for forming the coarse fibers. The nozzle hole array may be a mesh array, a circumferential array, a zigzag array, or the like, and from the viewpoint of the quality of the mesh structure, a mesh array or a zigzag array is preferable. Here, the inter-hole pitch means a distance between centers of the nozzle holes, and includes an inter-hole pitch in a width direction of the mesh-like structure (hereinafter referred to as "inter-hole pitch in the width direction") and an inter-hole pitch in a thickness direction of the mesh-like structure (hereinafter referred to as "inter-hole pitch in the thickness direction"). The appropriate inter-hole pitch described above is described as an inter-hole pitch appropriate for both the width-direction inter-hole pitch and the thickness-direction inter-hole pitch.

Examples of the nozzle for obtaining the mesh structure of the present invention include nozzles composed of the following 3 groups (a group, ab mixed group, and b group):

a group: an orifice group formed by arranging a plurality of rows of orifices for solid cross-section fibers along the thickness direction;

ab mixedly present group: a hole group formed by mixing hole holes for solid section fibers and hole holes for hollow section fibers and arranging the hole holes in a plurality of rows along the thickness direction;

b group: the hollow-section fiber is provided with a plurality of holes arranged in a thickness direction.

Further, another example of the nozzle is a nozzle which is composed of the following 2 groups (α group and β group) and in which the difference between the width-direction inter-hole pitch of the solid-section fiber orifices and the width-direction inter-hole pitch of the hollow-section fiber orifices is small:

group α: an orifice group formed by arranging a plurality of rows of orifices for solid cross-section fibers along the thickness direction;

group β: the hollow-section fiber is provided with a plurality of holes arranged in a thickness direction.

From the viewpoint of simplifying the structure of the nozzle, the nozzle composed of the above-described α group and β group is more preferable.

Since the fibers obtained by spinning from the vicinity of the boundary surface between the α group and the β group, which are 2 orifice groups serving as nozzles, form a mixed region in which the solid-section fibers and the hollow-section fibers are mixed, a mesh structure including 3 regions in the thickness direction of the present invention can be obtained.

In order to obtain a net-like structure of the present invention having a small difference in compression durability even when pressure is applied from either one of the two surfaces, it is necessary to reduce the difference between the width-direction inter-hole pitch of the solid-section fiber openings and the width-direction inter-hole pitch of the hollow-section fiber openings. The reason why the difference in the pitch between the holes in the width direction is small, the difference in the durability is small is not clear in its entirety, but is presumed as follows.

In the mixed presence region in which the solid-section fibers and the hollow-section fibers are mixed, the small difference in the width-direction inter-hole pitch of the orifice means that the number of the solid-section fibers and the number of the hollow-section fibers in the mixed presence region are close to each other. When the number of the solid-section fibers and the number of the hollow-section fibers are close to each other, it can be said that the solid-section fibers and the hollow-section fibers form a plurality of joints of approximately 1 to 1. Therefore, stress is easily transmitted even when pressure is applied from either one of the two surfaces, and therefore, it is considered that the difference in compression durability is small even when pressure is applied from either one of the surfaces.

On the other hand, in the case where the mesh-like structure is formed by a nozzle having a large difference in the pitch between the holes in the width direction of the orifice, in the mixed region where the solid-section fibers and the hollow-section fibers are mixed, for example, when the number of the solid-section fibers is larger than the number of the hollow-section fibers, a portion of the solid-section fibers and the hollow-section fibers have substantially no contact point in the mixed region. Therefore, it is considered that when the pressure is applied from the hollow-section fiber side, there are solid-section fibers in which the stress is not substantially transmitted from the hollow-section fiber, and the stress is transmitted through the solid-section fibers in which the stress is transmitted from the hollow-section fiber. On the other hand, it is considered that there are solid-section fibers that cannot transmit stress to the hollow-section fibers when pressure is applied from the solid-section fiber side, and that these transmit stress to the hollow-section fibers via the solid-section fibers that can transmit stress to the hollow-section fibers.

That is, when a mesh-like structure is formed by a nozzle having a large difference in the pitch between holes in the width direction of the orifice, in the mixed region where the solid-section fibers and the hollow-section fibers are mixed, the transmission direction of the stress is dispersed in the thickness direction and the direction orthogonal to the thickness direction, and therefore, it is considered that the transmission efficiency of the stress is lowered, and the difference in the compression durability between the case of pressing from the solid-section fiber side and the case of pressing from the hollow-section fiber side becomes large.

The difference between the width-direction pitch of the solid-section fiber openings and the width-direction pitch of the hollow-section fiber openings is preferably 2mm or less, more preferably 1mm or less, and still more preferably 0mm, that is, the width-direction pitch is the same.

The continuous filament constituting the mesh-like structure of the present invention has a fiber diameter (average fiber diameter, the same applies hereinafter) of 0.1mm to 3.0mm, preferably 0.2mm to 2.5mm, and more preferably 0.3mm to 2.0 mm. If the fiber diameter is less than 0.1mm, the fiber diameter is too small, and the compactness and soft touch are good, but it is difficult to secure the hardness required for the network structure, and if the fiber diameter exceeds 3.0mm, the network structure becomes thick and the other cushioning properties are inferior, although the hardness of the network structure can be sufficiently secured. From such a viewpoint, it is necessary to set a plurality of fiber diameters within an appropriate range.

If the continuous linear bodies constituting the mesh structure of the present invention have the same fineness, the hollow-section fibers have a higher second moment of area than the solid-section fibers, and therefore, when the hollow-section fibers are used, the compression resistance is high. Therefore, in order to more clearly obtain the cushioning properties different between both sides, it is preferable that the fiber diameter of the hollow-section fiber is larger than the fiber diameter of the solid-section fiber.

The difference in fiber diameter (difference in average fiber diameter, the same applies hereinafter) between the hollow-section fibers and the solid-section fibers constituting the continuous strand body of the mesh structure of the present invention is preferably 0.07mm or more, more preferably 0.10mm or more, further preferably 0.12mm or more, particularly preferably 0.15mm or more, most preferably 0.20mm or more, and further most preferably 0.25mm or more. The upper limit of the difference in fiber diameter is preferably 2.5mm or less in the present invention. When the difference in fiber diameter is less than 0.07mm, the difference in cushioning properties between both surfaces becomes small. On the other hand, if the difference in fiber diameter is too large, the foreign body sensation is excessively generated, and therefore, it is necessary to set the range to an appropriate range.

The total weight ratio of the solid cross-section fibers constituting the mesh structure of the present invention is preferably 10% to 90% of the total fibers constituting the mesh structure. In order to impart good dual-use properties to the mesh structure of the present invention, it is more preferably 20% to 80%, and still more preferably 30% to 70%. When the amount is less than 10% or more than 90%, the difference in cushioning properties between both surfaces is small.

The continuous linear body constituting the mesh-like structure of the present invention may be formed into a composite linear body in combination with another thermoplastic resin within a range not to impair the object of the present invention. In the case where the linear body itself is combined into a composite form, examples of the composite linear body include sheath/core type, parallel type, core-offset sheath/core type, and the like.

The cross-sectional shape of the continuous filament constituting the mesh-like structure of the present invention is preferably substantially circular, but compression resistance and touch may be imparted by forming a non-uniform cross section.

The mesh-like structure of the present invention can be processed into a molded article from the resin production process within a range not to deteriorate the performance, and can be processed by a treatment such as chemical addition at any stage of the production of the mesh-like structure to impart odor-resistant and antibacterial, odor-removing, mold-resistant, coloring, aroma-improving, flame-retardant, moisture-absorbing and releasing functions.

The net-like structure of the present invention includes a material molded into any shape. For example, it also includes: plate-like, triangular prism-like, polygonal, cylindrical, spherical, and a network structure including various shapes. The molding method can be performed by a known method such as cutting, hot pressing, or nonwoven fabric processing.

The mesh structure of the present invention further comprises: the mesh structure of the present invention is provided in a part of the mesh structure.

The apparent density of the network structure of the present invention is preferably 0.005g/cm³Above and 0.20g/cm³Less, more preferably 0.01g/cm³Above and 0.18g/cm³Hereinafter, more preferably 0.02g/cm³Above and 0.15g/cm³The following. Apparent density of less than 0.005g/cm³In this case, the hardness required for use as a cushioning material cannot be maintained, but on the contrary, it exceeds 0.20g/cm³In the case of the cushion material, the hardness becomes too high, and the cushion material may be unsuitable.

The thickness of the net-like structure of the present invention is preferably 5mm or more, more preferably 10mm or more. When the thickness is less than 5mm, the thickness becomes too thin when used as a cushioning material, and a feeling of bottoming may be generated. The upper limit of the thickness is preferably 300mm or less, more preferably 200mm or less, and further preferably 120mm or less, depending on the manufacturing apparatus.

In the net-like structure of the present invention, the hardness at 25% compression when pressed from the main region side of the solid cross-section fiber and the hardness at 25% compression when pressed from the main region side of the hollow cross-section fiber of the net-like structure having a three-dimensional random loop-bonded structure composed of a polyester-based thermoplastic elastomer are preferably 10N/φ 100mm or more, and more preferably 20N/φ 100mm or more, respectively. If the hardness is less than 10N/. phi.100 mm at 25% compression, the hardness as a cushioning material may be insufficient, and a bottoming feeling may occur. The upper limit of the hardness at 25% compression is not particularly limited, but is preferably 1.5 kN/. phi.100 mm or less.

The hardness at 25% compression when pressed from the main region side of the solid cross-section fiber and the hardness at 25% compression when pressed from the main region side of the hollow cross-section fiber of a web structure having a three-dimensional random loop-joined structure composed of a polyolefin-based thermoplastic elastomer are preferably 2N/φ 100mm or more, and more preferably 5N/φ 100mm or more. If the hardness is less than 2N/. phi.100 mm at 25% compression, the hardness as a cushioning material may be insufficient, and a bottoming feeling may occur. The upper limit of the hardness at 25% compression is not particularly limited, but is preferably 1.5 kN/. phi.100 mm or less.

In both the case where the net-like structure of the present invention is composed of the polyester-based thermoplastic elastomer and the case where the net-like structure is composed of the polyolefin-based thermoplastic elastomer, the ratio of the hardness at 25% compression when the solid cross-section fiber is pressurized from the main region side to the hardness at 25% compression when the hollow cross-section fiber is pressurized from the main region side is preferably 1.03 or more, more preferably 1.05 or more, still more preferably 1.07 or more, particularly preferably 1.10 or more, and most preferably 1.20 or more. When the ratio of hardness at 25% compression is less than 1.03, the difference in cushioning properties between both sides is small. Here, in the present application, the term "ratio" means that the ratio of a large value to a small value among 2 values is equal to a value obtained by dividing the large value by the small value.

In the net-like structure of the present invention, the hardness at 40% compression when pressed from the main region side of the solid cross-section fiber and the hardness at 40% compression when pressed from the main region side of the hollow cross-section fiber of the net-like structure having a three-dimensional random loop-bonded structure composed of a polyester-based thermoplastic elastomer are preferably 20N/φ 100mm or more, more preferably 30N/φ 100mm or more, and still more preferably 40N/φ 100mm or more. If the hardness is less than 20N/. phi.100 mm at a compression of 40%, the hardness as a cushioning material may be insufficient, and a feeling of bottoming may occur. The upper limit of the hardness at 40% compression is not particularly limited, but is preferably 5 kN/. phi.100 mm or less.

The hardness at 40% compression when pressed from the main region side of the solid cross-section fiber and the hardness at 40% compression when pressed from the main region side of the hollow cross-section fiber of the web structure having a three-dimensional random loop-joined structure composed of the polyolefin-based thermoplastic elastomer are preferably 5N/φ 100mm or more, more preferably 10N/φ 100mm or more, and still more preferably 15N/φ 100mm or more. If the hardness is less than 5N/. phi.100 mm at a compression of 40%, the hardness as a cushioning material may be insufficient, and a feeling of bottoming may occur. The upper limit of the hardness at 40% compression is not particularly limited, but is preferably 5 kN/. phi.100 mm or less.

In both the case where the net-like structure of the present invention is composed of the polyester-based thermoplastic elastomer and the case where the net-like structure is composed of the polyolefin-based thermoplastic elastomer, the ratio of the hardness at 40% compression when the solid cross-section fiber is pressed from the main region side to the hardness at 40% compression when the hollow cross-section fiber is pressed from the main region side is preferably 1.05 or more, more preferably 1.07 or more, still more preferably 1.10 or more, particularly preferably 1.15 or more, and most preferably 1.20 or more. When the ratio of hardness at 40% compression is less than 1.05, the difference in cushioning properties between both sides is small.

In the mesh-like structure of the present invention, in both cases where the mesh-like structure is composed of a polyester-based thermoplastic elastomer and where the mesh-like structure is composed of a polyolefin-based thermoplastic elastomer, the compression flexural coefficient when the mesh-like structure is pressurized from the solid cross-section fiber main region side and the compression flexural coefficient when the mesh-like structure is pressurized from the hollow cross-section fiber main region side are preferably 2.5 or more and 10.0 or less, more preferably 2.6 or more and 9.0 or less, and still more preferably 2.7 or more and 8.0 or less. When the compression deflection coefficient is less than 2.5, the difference in cushioning performance with respect to the change in compression rate is small, and the sitting and lying comfort may be deteriorated. Conversely, if the compression ratio exceeds 10.0, the difference in the cushioning performance due to the change in the compression ratio becomes too large, and a feeling of bottoming or discomfort may occur.

In the net-like structure of the present invention, in both cases where the net-like structure is made of a polyester-based thermoplastic elastomer and a polyolefin-based thermoplastic elastomer, the difference between the compression flexural coefficient when pressurized from the solid cross-section fiber main region side and the compression flexural coefficient when pressurized from the hollow cross-section fiber main region side is preferably 5 or less. When the difference in the compression flexural modulus exceeds 5, the touch-down feeling and the uncomfortable feeling may be felt when the sheet is used on the side having a high compression flexural modulus. The lower limit of the difference in the compression deflection coefficient is not particularly limited, and in the present invention, it is preferable that the difference is not 0 or more at all.

In the mesh structure of the present invention, the hysteresis loss when the mesh structure having a three-dimensional random loop junction structure is pressed from the solid cross-section fiber main region side and the hollow cross-section fiber main region side of the mesh structure composed of the polyester-based thermoplastic elastomer is preferably 30% or less, more preferably 29% or less, further preferably 28% or less, and particularly preferably 26% or less. When the hysteresis loss exceeds 30%, the high-resilience sitting and lying comfort of the mesh structure of the present invention cannot be maintained. The lower limit of the hysteresis loss is not particularly limited, and in the present invention, it is preferably 1% or more.

The hysteresis loss when the solid cross-section fiber main region side and the hollow cross-section fiber main region side of the net structure having a three-dimensional random loop-joined structure composed of the polyolefin-based thermoplastic elastomer are pressed is preferably 60% or less, more preferably 55% or less, further preferably 50% or less, and particularly preferably 45% or less. When the hysteresis loss exceeds 60%, the high-resilience sitting and lying comfort of the mesh structure of the present invention cannot be maintained. The lower limit of the hysteresis loss is not particularly limited, and in the present invention, it is preferably 1% or more.

In the case where the net-like structure of the present invention is composed of the polyester-based thermoplastic elastomer and the polyolefin-based thermoplastic elastomer, when the hysteresis loss when the solid cross-section fiber is pressurized from the main region side is compared with the hysteresis loss when the hollow cross-section fiber is pressurized from the main region side, the hysteresis loss on the side having low hardness under compression tends to be higher than the hysteresis loss on the side having high hardness under compression.

In the present invention, the residual strain after repeated compression with a constant load of 750N, the hardness at compression of 25%, 40% and 65%, and the hysteresis loss at the time of pressing from the main region side of the solid-section fiber and at the time of pressing from the main region side of the hollow-section fiber can be measured using a universal tester such as an Instron Japan co.

In the mesh-like structure of the present invention, the difference between the hysteresis loss when pressed from the main region side of the solid-section fiber and the hysteresis loss when pressed from the main region side of the hollow-section fiber is preferably 5 points or less. When the difference in hysteresis loss exceeds 5 points, the net structure cannot maintain high-resilience sitting/lying comfort. The lower limit of the difference in the hysteresis loss is not particularly limited, and in the present invention, it is preferable that the difference is not less than 0 point.

The net-like structure of the present invention thus obtained is imparted with cushioning properties different on both sides. In the case of producing a conventional cushion having cushioning properties different on both sides, a net-like structure having a design different from that of the net-like structure, coarse cotton, urethane, or the like is laminated in the side cloth. Although they are excellent in cushioning properties, they have the following problems: when used from either side, the sheet is different in compression durability from when used from the other side, and therefore, the sheet is expensive due to a large manufacturing cost, and needs to be separately recovered, which makes recycling cumbersome. The difference in compression durability between both surfaces of the net-shaped structure alone is small, and the net-shaped structure of the present invention to which cushioning properties different between both surfaces are imparted can solve these problems.

The cushioning material of the present invention includes the above-described net-like structure in the cushioning material, and can be used in both front and back directions. In the present invention, the term "usable both as a front and a back" means that the net-shaped structure included in the cushion material can be used from either the solid cross-section fiber main region side or the hollow cross-section fiber main region side. Therefore, the present invention is also applicable to a mode of use in which the fiber is used only from one side of the solid cross-section fiber main region side or the hollow cross-section fiber main region side.