Raw material for three-dimensional net-like structure, three-dimensional net-like structure, and method for manufacturing three-dimensional net-like structure

Abstract

Provided is a raw material for manufacturing a recycled three-dimensional net-like structure which is easy to carry in piping and is resistant to durability deterioration. The raw material is a direct raw material for manufacturing a three-dimensional net-like structure having a three-dimensional random loop joining structure. The direct raw material includes a fiber piece group including joined fibers in which single fibers are joined to each other, and non-joined fibers which are single fibers not joined to other single fibers, wherein the number of joined fibers per 1.0 g of the fiber piece group is 1 to 700 inclusive.

Description

Raw material for three-dimensional network structure, three-dimensional network structure, and method for manufacturing three-dimensional network structure

[0001] The present invention relates to a raw material for a three-dimensional network structure, a three-dimensional network structure, and a method for producing a three-dimensional network structure.

[0002] Three-dimensional mesh structures have been widely used as cushioning materials for furniture, bedding such as beds, and vehicle seats for trains, automobiles, motorcycles, etc. Regarding such three-dimensional mesh structures, for example, Patent Document 1 discloses a cushion body including a three-dimensional mesh material formed by bending thermoplastic resin filaments to form random loops and bonding the contacting portions of the filaments, and a cushion material formed of polyester solid cotton that entirely surrounds the three-dimensional mesh material and can abut against the three-dimensional mesh material, the three-dimensional mesh material being disposed inside the cushion material without being adhered to the cushion material. Patent Document 2 discloses a vehicle seat having a cushion layer having a laminated structure of a three-dimensional mesh structure (T) in which filaments made of thermoplastic elastic resin form loops and are bonded at most of their contacting portions, and a nonwoven fabric (N) to which fibers made of thermoplastic resin are bonded.

[0003] Utility Model Registration No. 3211474 JP 2001-061605 A

[0004] Patent Documents 1 and 2 describe recycling of three-dimensional network structures. As a result of the inventor's investigations into recycling used three-dimensional network structures, it was found that when a new three-dimensional network structure is produced by cutting a used three-dimensional network structure, melting and pelletizing the cut pieces, and then melting and spinning the resulting pellets, the repeated heating can cause some of the resin to deteriorate, resulting in a decrease in the durability of the recycled three-dimensional network structure. It was also found that when a large number of small pieces obtained by cutting a used three-dimensional network structure are transported through a pipeline, the small pieces can become trapped within the pipeline. The present invention was made in light of the above circumstances, and its object is to provide a raw material for producing a recycled three-dimensional network structure that is easy to transport through a pipeline and is resistant to deterioration in durability. Another object is to provide a recycled three-dimensional network structure that is resistant to deterioration in durability. Yet another object is to provide a method for efficiently producing a recycled three-dimensional network structure that is resistant to deterioration in durability.

[0005] A raw material according to an embodiment of the present invention is as follows [1]: [1] A direct raw material for producing a three-dimensional network structure having a three-dimensional random loop bonded structure, the direct raw material having a group of fiber pieces, the group of fiber pieces including bonded fibers in which single fibers are bonded to each other and unbonded fibers which are single fibers that are not bonded to other single fibers, and the number of bonded fibers per 1.0 g of the group of fiber pieces is 1 or more and 700 or less.

[0006] As described above, the number of bonded fibers is 1 to 700 per 1.0 g, which facilitates transport inside a supply pipe for the raw material to an extruder. Furthermore, as described above, the raw material is used directly, i.e., the raw material is used for producing the three-dimensional network structure without being pelletized, which reduces deterioration due to heating, and as a result, the durability of the resulting recycled three-dimensional network structure is less likely to decrease.

[0007] The raw material according to the embodiment is preferably any one of the following [2] to [7], the three-dimensional network structure according to the embodiment is preferably any one of the following [8] to

[14] , and the manufacturing method according to the embodiment is preferably any one of the following [9] to

[14] . [2] The direct raw material according to [1], wherein the fiber fragments are obtained from a recovered three-dimensional network structure having a three-dimensional random loop bonded structure. [3] The direct raw material according to [1] or [2], wherein the average number of bonded points per bonded fiber is 1.00 to 3.0. [4] The direct raw material according to any one of [1] to [3], wherein the diameter of a single fiber of the bonded fiber is 0.1 mm to 3.0 mm. [5] The direct raw material according to any one of [1] to [4], wherein the diameter of the unbonded fiber is 0.1 mm to 3.0 mm. [6] The direct raw material according to any one of [1] to [5], wherein the angle of repose of the fiber fragments is 25 degrees to 65 degrees. [7] The direct raw material according to any one of [1] to [6], wherein resin pellets are included. [8] A three-dimensional network structure having a three-dimensional random loop bonded structure obtained from the direct raw material described in any one of [1] to [7]. [9] A method for producing a three-dimensional network structure, comprising the steps of: pulverizing at least a portion of the three-dimensional network structure having a three-dimensional random loop bonded structure to obtain a group of fiber pieces including bonded fibers in which single fibers are bonded to each other and unbonded fibers, which are single fibers not bonded to other single fibers; and melting the group of fiber pieces without granulation to form a three-dimensional network structure having a three-dimensional random loop bonded structure, wherein the number of bonded fibers per 1.0 g of the group of fiber pieces is 1 to 700.

[10] The method for producing a three-dimensional network structure described in [9], wherein the average number of bonded points per bonded fiber is 1.00 to 3.0.

[11] The method for producing a three-dimensional network structure described in [9] or

[10] , wherein the diameter of the single fiber of the bonded fiber is 0.1 mm to 3.0 mm.

[12] The method for producing a three-dimensional network structure according to any one of [9] to

[11] , wherein the diameter of the non-bonded fibers is 0.1 mm or more and 3.0 mm or less.

[13] The method for producing a three-dimensional network structure according to any one of [9] to

[12] , wherein the angle of repose of the group of fiber pieces is 25 degrees or more and 65 degrees or less.

[14] The method for producing a three-dimensional network structure according to any one of [9] to

[13] , wherein in the step of forming the three-dimensional network structure, the fiber pieces and resin pellets are melted without granulation to form the three-dimensional network structure.

[0008] The above configuration makes it possible to provide a raw material for manufacturing a recycled three-dimensional mesh structure that is easy to transport through a pipe and is resistant to deterioration in durability.The above configuration also makes it possible to provide a recycled three-dimensional mesh structure that is resistant to deterioration in durability.The above configuration also makes it possible to provide a method for efficiently manufacturing a recycled three-dimensional mesh structure that is resistant to deterioration in durability.

[0009] Fig. 1 is a schematic diagram showing a portion of an example of a group of fiber pieces in a direct feedstock according to an embodiment. Fig. 2 is a schematic diagram of an extruder and its peripheral members used in Example 1. Fig. 3 is a schematic diagram of an extruder and its peripheral members used in Examples 2 and 3. Fig. 4 is a schematic diagram of an extruder and its peripheral members used in Example 4.

[0010] The raw material according to the embodiment is a direct raw material for producing a three-dimensional network structure having a three-dimensional random loop bonded structure, and includes a group of fiber pieces. The group of fiber pieces includes bonded fibers, in which single fibers are bonded to each other, and unbonded fibers, which are single fibers not bonded to other single fibers. The number of bonded fibers per 1.0 g of the group of fiber pieces is 1 to 700. Having a bonded fiber count of 1 to 700 per 1.0 g facilitates transport, for example, within the supply pipe for the raw material to an extruder. Furthermore, because the raw material is a direct raw material, i.e., the raw material is used to produce the three-dimensional network structure without being pelletized, deterioration due to heating is reduced, resulting in less deterioration in the durability of the resulting recycled three-dimensional network structure. The direct raw material for the three-dimensional network structure according to the embodiment is described in detail below.

[0011] The three-dimensional network structure having a three-dimensional random loop bonded structure manufactured using the raw materials according to the embodiment preferably includes at least one continuous filament, the at least one continuous filament having a plurality of three-dimensional random loops, and the random loops are bonded to each other. The three-dimensional network structure will be described in detail in the description of the three-dimensional network structure according to the embodiment below.

[0012] The direct raw material is a raw material for producing a three-dimensional network structure having a three-dimensional random loop bonded structure. Hereinafter, a three-dimensional network structure having a three-dimensional random loop bonded structure may be simply referred to as a three-dimensional network structure. The direct raw material is used to form the three-dimensional network structure without being heated and melted to form pellets. When granulating by heating and melting, the material must be heated and melted again after granulation. However, the direct raw material is used without the heating required for granulation, thereby reducing thermal degradation of the components. As a result, deterioration in the mechanical properties of the resulting recycled three-dimensional network structure, such as yellowing, can be suppressed.

[0013] The fiber fragments are an aggregate of fiber fragments. The fiber fragments are preferably obtained by, for example, pulverizing at least a portion of a three-dimensional network structure having a three-dimensional random loop bonded structure. The fiber fragments preferably contain single fibers having a length direction. In this case, the time and cost of pulverization can be reduced compared to when the three-dimensional network structure is pulverized to the extent that the length direction of the single fibers is completely eliminated during the production of the fiber fragments. The fiber fragments may contain powder, granules, scale-like materials, etc. in addition to single fibers having a length direction.

[0014] The number of bonded fibers per 1.0 g of fiber fragments is 1 or more and 700 or less. When the number of bonded fibers is 700 / g or less, the bonded fibers are less likely to entangle with each other during transport, and as a result, the fiber fragments are less likely to aggregate in the pipe, making them easier to transport through the pipe. The number of bonded fibers is preferably 600 / g or less, more preferably 500 / g or less, and even more preferably 400 / g or less. On the other hand, when the number of bonded fibers is 1 / g or more, voids are more likely to form within the fiber fragments, making them easier to transport through the pipe. The number of bonded fibers is preferably 10 / g or more, more preferably 50 / g or more, and even more preferably 100 / g or more.

[0015] The average number of bonded points per bonded fiber is preferably 1.00 or more and 3.0 or less. A bonded point is a point where adjacent single fibers are bonded. FIG. 1 shows a bonded fiber 11a with one bonded point, a bonded fiber 11b with two bonded points, and a bonded fiber 11c with three bonded points. By keeping the average number of bonded points at 3.0 or less, the weight per bonded fiber can be reduced, making it easier to transport the fiber fragments through a pipe. Furthermore, when the direct raw material contains resin pellets, as described below, this reduces the occurrence of blocking between the bonded fibers and the resin pellets. Therefore, the average number of bonded points is more preferably 2.7 or less, and even more preferably 2.5 or less. On the other hand, the average number of bonded points is preferably 1.00 or more, more preferably 1.01 or more, and even more preferably 1.02 or more. This facilitates the formation of voids within the fiber fragments, making them easier to transport through air.

[0016] The diameter of the unbonded fibers is preferably 0.1 mm or more and 3.0 mm or less. If the diameter is 3.0 mm or less, the weight per bonded fiber can be reduced, making it easier to transport the fiber pieces through the pipe. The diameter is more preferably 2.0 mm or less, even more preferably 1.6 mm or less, even more preferably 1.2 mm or less, and particularly preferably 1.0 mm or less. On the other hand, if the diameter is 0.1 mm or more, the generation of fines (powdery matter) and floss (tape-like matter) during pneumatic transport can be suppressed. The diameter is more preferably 0.2 mm or more, even more preferably 0.3 mm or more, and even more preferably 0.4 mm or more.

[0017] The diameter of the single fiber of the bonded fiber is preferably 0.1 mm or more and 3.0 mm or less. If the diameter is 3.0 mm or less, the weight per bonded fiber can be reduced, making it easier to transport the fiber pieces through the pipe. The diameter is more preferably 2.0 mm or less, even more preferably 1.6 mm or less, even more preferably 1.2 mm or less, and particularly preferably 1.0 mm or less. On the other hand, if the diameter is 0.1 mm or more, the generation of fines (powder-like materials) and floss (tape-like materials) during pneumatic transport can be suppressed. The diameter is more preferably 0.2 mm or more, even more preferably 0.3 mm or more, and even more preferably 0.4 mm or more.

[0018] The diameter of the single fiber contained in the fiber fragments is preferably 0.1 mm or more and 3.0 mm or less. If the diameter is 3.0 mm or less, the weight per fiber can be reduced, making it easier to transport the fiber fragments through a pipe. The diameter is more preferably 2.0 mm or less, even more preferably 1.6 mm or less, even more preferably 1.2 mm or less, and particularly preferably 1.0 mm or less. On the other hand, if the diameter is 0.1 mm or more, the generation of fines (powdery matter) and floss (tape-like matter) during pneumatic transport can be suppressed. The diameter is more preferably 0.2 mm or more, even more preferably 0.3 mm or more, and even more preferably 0.4 mm or more.

[0019] The diameter of a single fiber of an unbonded fiber or a bonded fiber can be measured by the method described in the Examples below. When determining the diameter of a single fiber of a bonded fiber, if the bonded fiber has a bonded point near the center in the longitudinal direction, the fiber diameter of a branched portion adjacent to the bonded point can be measured.

[0020] The average length of the single fibers contained in the bonded fibers and non-bonded fibers is preferably 0.2 mm or more and 10 mm or less, more preferably 0.5 mm or more and 8 mm or less, and even more preferably 1.0 mm or more and 7 mm or less. The average length of the single fibers contained in the fiber pieces is preferably 0.2 mm or more and 10 mm or less, more preferably 0.5 mm or more and 8 mm or less, and even more preferably 1.0 mm or more and 7 mm or less. The average length of the single fibers can be determined by dividing the total length of the single fibers by the number of single fibers. The length of each single fiber corresponds to the diameter of the circumscribing circle of each single fiber in a planar view.

[0021] The repose angle of the fiber fragments is preferably 25 degrees or more and 65 degrees or less. The repose angle of the fiber fragments is expressed as a combined effect of variations in the length and diameter of the single fibers, the shape of the single fibers, friction between the single fibers, the cohesive force of the resin constituting the single fibers, the specific gravity of the resin, and the surface adhesiveness of the resin, and is an indicator of the flowability of the single fiber material. In particular, the repose angle of the fiber fragments tends to be large when the fiber fragments contain a large number of curved fibers. Such an angle of repose of 65 degrees or less can reduce entanglement between fibers, making it possible to supply the fiber fragments from the raw material storage tank to the extruder without installing any auxiliary equipment for deflocculating the fibers in the raw material storage tank, as described below. Furthermore, the reduction in entanglement between fibers makes it even easier to transport the fiber fragments through the piping. The angle of repose is more preferably 60 degrees or less, even more preferably 55 degrees or less, and even more preferably 50 degrees or less. On the other hand, if the angle of repose is 25 degrees or more, the fiber pieces will not be unevenly distributed in the raw material storage tank when they are supplied from the raw material storage tank to the extruder. The angle of repose is more preferably 28 degrees or more, even more preferably 30 degrees or more, and even more preferably 33 degrees or more.

[0022] Bonded fibers are formed by bonding multiple single fibers together. For example, like bonded fibers 11a and 11b in the fiber piece group 13 of the direct raw material 20 in Figure 1, multiple single fibers 14 may be bonded in parallel to form a bundle, or multiple single fibers 14 may be bonded in a branched shape, or like bonded fiber 11c, multiple single fibers 14 may be bonded so that there are voids surrounded by the multiple single fibers 14. Note that non-bonded fibers 12 are single fibers that are not bonded to other single fibers. The number of bonded single fibers per bonded fiber may be 2 to 10, 2 to 5, 2 to 4, or 2 to 3.

[0023] The bonded and / or non-bonded single fibers may have different or the same radial cross-sectional shapes, and may have different or the same radial cross-sectional diameters. The radial cross-sections of the single fibers may be round, irregular, solid, or hollow. The bonded and / or non-bonded fibers may contain two or more types of single fibers that differ in properties such as fiber diameter and fiber cross-sectional shape.

[0024] The bonded fibers and the non-bonded fibers each preferably contain a thermoplastic resin. The thermoplastic resin preferably contains a polyester-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, polyethylene, polypropylene, an ethylene / α-olefin copolymer obtained by copolymerizing at least ethylene and an α-olefin, an ethylene-vinyl acetate copolymer, polylactic acid, polybutylene adipate, polybutylene adipate terephthalate, or a mixture thereof, more preferably a polyester-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, or a mixture thereof, and even more preferably a polyester-based thermoplastic elastomer. Polyester-based thermoplastic elastomers are particularly excellent in compression durability and heat resistance.

[0025] The polyester-based thermoplastic elastomer preferably contains a hard segment and a soft segment, the hard segment containing a thermoplastic polyester, and the soft segment containing a polyalkylene glycol, an aliphatic polyester, or a combination thereof. More preferably, the soft segment contains a polyalkylene glycol.

[0026] The thermoplastic polyester of the hard segment is preferably a copolymer of a dicarboxylic acid and / or its ester-forming derivative and a diol component and / or its ester-forming derivative.

[0027] The dicarboxylic acid and / or its ester-forming derivative preferably includes an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid, an aliphatic dicarboxylic acid, an ester-forming derivative thereof, or a combination thereof, and more preferably includes an aromatic dicarboxylic acid, an ester-forming derivative thereof, or a combination thereof. The aromatic dicarboxylic acid preferably includes terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, or a combination thereof, and more preferably includes terephthalic acid, naphthalene-2,6-dicarboxylic acid, or a combination thereof, and even more preferably includes terephthalic acid. The alicyclic dicarboxylic acid preferably includes 1,4-cyclohexanedicarboxylic acid. The aliphatic dicarboxylic acid preferably includes succinic acid, adipic acid, sebacic acid, dimer acid, or a combination thereof. The ester-forming derivative of a dicarboxylic acid preferably includes an ester-forming derivative of an aromatic dicarboxylic acid, and more preferably includes dimethyl terephthalate.

[0028] The diol component and / or its ester-forming derivative preferably includes an aliphatic diol, an alicyclic diol, an ester-forming derivative thereof, or a combination thereof, and more preferably includes an aliphatic diol, an ester-forming derivative thereof, or a combination thereof. The aliphatic diol preferably includes 1,4-butanediol, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, or a combination thereof, and more preferably includes 1,4-butanediol. The alicyclic diol preferably includes 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, or a combination thereof, and more preferably includes 1,4-cyclohexanedimethanol. The ester-forming derivative of the aliphatic diol preferably includes dimethylpolytetramethylene glycol.

[0029] The polyalkylene glycol of the soft segment preferably includes polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycol consisting of an ethylene oxide-propylene oxide copolymer, or a combination thereof, each having a number average molecular weight of about 300 or more and 5000 or less, and more preferably includes polytetramethylene glycol.

[0030] The aliphatic polyester of the soft segment preferably contains polylactone having a number average molecular weight of about 300 to 5000. The soft segment may contain polysiloxane.

[0031] The polyester-based thermoplastic elastomer preferably contains the above-mentioned thermoplastic polyester, polyalkylene glycol, aliphatic polyester, or a combination thereof, and more preferably contains a thermoplastic polyester and a polyalkylene glycol.

[0032] The polyolefin-based thermoplastic elastomer preferably includes an ethylene-α-olefin random block copolymer. The ethylene-α-olefin random block copolymer is a random block copolymer of ethylene and at least one other alkene, such as linear low-density polyethylene. The other alkene preferably includes propylene, butene, pentene, hexene, heptene, octene, nonene, decene, or a combination thereof, and more preferably includes propylene, butene, pentene, hexene, heptene, octene, or a combination thereof.

[0033] Of the total 100% by mass of the bonded fibers and non-bonded fibers, the thermoplastic resin content is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. While this content is preferably 100% by mass or less, if the bonded fibers and non-bonded fibers contain additives, the content may be 99% by mass or less, 98% by mass or less, 95% by mass or less, 90% by mass or less, or 85% by mass or less. The additives may include antioxidants, light stabilizers, antibacterial agents, anti-mite agents, fluorescent brighteners, fillers, flame retardants, flame retardant assistants, organic pigments, inorganic pigments, or mixtures thereof.

[0034] The content of single fibers having a length of 0.2 to 10 mm in 100% by mass of fiber pieces is preferably 90 to 100% by mass, more preferably 95 to 100% by mass. The upper limit of the content may be 99% by mass or less, or 98% by mass or less.

[0035] The fiber fragments are preferably obtained from a recovered three-dimensional network structure having a three-dimensional random loop bonded structure. Examples of recovered three-dimensional network structures include those recovered from any of the following stages: the manufacturing stage, distribution stage, consumption stage (market), and disposal stage of the three-dimensional network structure. Examples of recovered three-dimensional network structures at the manufacturing stage include offcuts generated when cutting to a predetermined size during the manufacturing process of the three-dimensional network structure, non-standard products that do not meet inspection standards and are rejected, and cutting waste generated during thermoforming in post-processing. Examples of recovered three-dimensional network structures at the distribution stage include those recovered from the distribution process due to logistics accidents, products returned due to obsolescence or quality deterioration after long-term inventory, and disassembled products. Examples of recovered three-dimensional network structures at the consumption stage include those returned as defective products after sale, etc. Examples of recovered three-dimensional network structures at the disposal stage include those discarded by consumers after use, etc.

[0036] The recovered three-dimensional network structure may contain foreign matter such as metals, human sebum, hair, food scraps, other fibers, dust, and sand, and may therefore be subjected to a cleaning process, disinfection process, metal removal process, or other treatments. The cleaning process, disinfection process, and metal removal process may be performed before and / or after shredding. After shredding, the recovered three-dimensional network structure may be subjected to a drying process. If it is difficult to completely remove the foreign matter, the content of the foreign matter is preferably 2% or less of the total mass.

[0037] The recovered three-dimensional network structure may be a plurality of different three-dimensional network structures. In this case, the plurality of different three-dimensional network structures may differ from one another in properties such as apparent density, thickness, fiber diameter, fiber cross section, and whether or not they have been shaped. These may be sorted into types and then shredded separately, or may be shredded together without being sorted into types.

[0038] The direct raw material may contain resin pellets. The resin pellets preferably contain a thermoplastic resin. The thermoplastic resin preferably contains the same type of thermoplastic resin as the thermoplastic resin contained in the bonded fibers and / or unbonded fibers, but may contain a different type of thermoplastic resin. The resin pellets are preferably unused pellets, or so-called virgin pellets, but may also be recycled resin pellets obtained by melting and granulating a recovered three-dimensional network structure. When the fiber fragments contained in the direct raw material are derived from a recovered three-dimensional network structure, the inclusion of virgin pellets in the direct raw material can further suppress deterioration of mechanical properties and yellowing. When a mixture of fiber fragments and resin pellets is used as a raw material for a three-dimensional network structure without being heated and melted for granulation (pelletization) after mixing, not only the fiber fragments before mixing but also the mixture itself constitutes the direct raw material. Resin pellets are solid and do not entangle with each other like fiber fragments, making them easy to transport through a pipe. The resin pellets may be shaped, for example, cylindrical or spherical. Examples of cylindrical shapes include polygonal prisms such as triangular prisms and quadrangular prisms, elliptical prisms, and circular prisms. In the case of a columnar shape, the axial length is preferably 1 to 5 mm, more preferably 2 to 3 mm. In the case of a spherical shape, the diameter is preferably 1 to 5 mm, more preferably 2 to 3 mm.

[0039] To prevent filters in the spinning process from being clogged with foreign matter, the content of fiber pieces in 100% by mass of direct raw materials is preferably 95 to 100% by mass, more preferably 98 to 100% by mass. On the other hand, when the direct raw materials contain resin pellets, the content of fiber pieces in 100% by mass of direct raw materials is preferably 1 to 90% by mass, more preferably 2 to 70% by mass, even more preferably 3 to 60% by mass, and even more preferably 5 to 50% by mass. The higher the content of direct raw materials, the higher the recycling rate. Furthermore, the content of resin pellets in 100% by mass of direct raw materials is preferably 10 to 99% by mass, more preferably 30 to 98% by mass, even more preferably 40 to 97% by mass, and even more preferably 50 to 95% by mass. The higher the content of resin pellets, the more effectively the increase in production costs due to recycling can be suppressed.

[0040] The direct raw materials according to the embodiments have been described above. Below, a three-dimensional network structure according to the embodiments will be described. The three-dimensional network structure according to the embodiments is a three-dimensional network structure having a three-dimensional random loop bonded structure obtained from any of the above-described direct raw materials. The three-dimensional network structure includes continuous filaments, each having a plurality of three-dimensional random loops, which are bonded to each other. This allows the three-dimensional network structure to be suitably used as a cushioning material. Furthermore, if the direct raw materials include fiber pieces obtained from a recycled three-dimensional network structure, the three-dimensional network structure formed from such direct raw materials is a so-called recycled three-dimensional network structure, which can contribute to promoting recycling. Furthermore, as described above, since the direct raw materials are used without being pelletized, the recycled three-dimensional network structure formed from such direct raw materials is less susceptible to deterioration due to heating, and therefore is less likely to lose durability.

[0041] The continuous filaments of the three-dimensional network structure according to the embodiment may have a solid portion having a solid cross-sectional shape, a hollow portion having a hollow cross-sectional shape, or both of these portions. The three-dimensional network structure may have a region made of solid fibers having a solid cross-sectional shape, a region made of hollow fibers having a hollow cross-sectional shape, and a region in which solid fibers and hollow fibers are mixed. The continuous filaments may have a round cross-section or an irregular cross-section. The continuous filaments may be composite filaments of a sheath-core type, a side-by-side type, an eccentric sheath-core type, or the like.

[0042] The diameter of the continuous filaments is preferably 0.1 mm or more and 3.0 mm or less. A diameter of 3.0 mm or less can improve flexibility. The diameter is more preferably 2.0 mm or less, even more preferably 1.6 mm or less, even more preferably 1.2 mm or less, and particularly preferably 1.00 mm or less. On the other hand, a diameter of 0.1 mm or more can exert a compressive resistance force, making it easier to function as a cushioning material. The diameter is more preferably 0.2 mm or more, even more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. The diameter can be measured by the method for measuring the fiber diameter of a three-dimensional network structure described in the Examples below.

[0043] The apparent density of the three-dimensional network structure is preferably 0.005 to 0.30 g / cm ３ The apparent density is more preferably 0.01 to 0.20 g / cm ３ , more preferably 0.02 to 0.15 g / cm ３ , particularly preferably 0.03 to 0.10 g / cm ３ The apparent density is 0.005 g / cm ３ When the apparent density is 0.30 g / cm or more, the hardness of the three-dimensional network structure is improved. As a result, when the three-dimensional network structure is used for a cushion or the like, the feeling of hitting the bottom can be reduced. ３ When the density is below 100%, the flexibility is improved and the structure can be suitably used as a cushioning material, etc. The apparent density of the three-dimensional network structure can be measured by the method described in the examples below.

[0044] The thickness of the three-dimensional network structure is preferably 10 to 120 mm. The thickness is more preferably 15 to 100 mm, even more preferably 20 to 80 mm, and particularly preferably 25 to 50 mm. A thickness of 10 mm or more makes it easier to use the three-dimensional network structure as a cushioning material, etc. On the other hand, a thickness of 120 mm or less improves handleability. The thickness of the three-dimensional network structure can be measured by the method described in the examples below.

[0045] The repeated compression set (%) of the three-dimensional network structure is preferably 1 to 10%, more preferably 3 to 8%. A value of 10% or less can improve compression recovery. The repeated compression set (%) can be measured by the method described in the examples below.

[0046] The shape of the three-dimensional network structure may be, for example, a plate, a polygon such as a triangular prism or a quadrangular prism, a cylinder, a sphere, a combination of these, etc. When molding the three-dimensional network structure, a regulating plate may be used during melt extrusion of the resin, or the structure may be molded by cutting, heat pressing, etc.

[0047] The three-dimensional network structure can be used, for example, as fillings for bedding such as futons, comforters, mattresses, bed pads, overlays, and pillows; fillings for floor cushions; cushion parts for sofas, chairs, railway vehicle seats, motorcycle seats, automobile seats, and the like; cushion parts for child seats, strollers, and the like; cushion parts for pet beds; scrubbing brushes; elastic paving materials; and the like.

[0048] The above describes the three-dimensional network structure obtained from the direct raw material according to the embodiment, but it is preferable that the three-dimensional network structure for obtaining the direct raw material according to the embodiment also satisfies the configuration of the three-dimensional network structure described above.

[0049] Next, a method for manufacturing a three-dimensional network structure according to an embodiment will be described below. The method for manufacturing a three-dimensional network structure according to an embodiment includes the steps of: pulverizing at least a portion of a three-dimensional network structure having a three-dimensional random loop bonded structure to obtain a group of fiber pieces including bonded fibers in which single fibers are bonded to each other and unbonded fibers, which are single fibers not bonded to other single fibers; and melting the group of fiber pieces without granulation to form a three-dimensional network structure having a three-dimensional random loop bonded structure. The number of bonded fibers per 1.0 g of the group of fiber pieces is 1 to 700. By forming a three-dimensional network structure without granulating the group of fiber pieces as described above, a recycled three-dimensional network structure that is less likely to deteriorate in durability can be efficiently manufactured. Hereinafter, a three-dimensional network structure having a three-dimensional random loop bonded structure may be simply referred to as a three-dimensional network structure.

[0050] Regarding the fiber fragments obtained in the process of obtaining the fiber fragments, the average number of bonding points per bonded fiber, the diameter of a single fiber of the bonded fiber, the diameter of an unbonded fiber, the angle of repose of the fiber fragments, and other configurations of the fiber fragments, please refer to the description of the fiber fragments of the direct raw material in the above-mentioned embodiment.

[0051] In the step of obtaining a group of fiber pieces, the three-dimensional network structure to be pulverized is preferably a recovered three-dimensional network structure having a three-dimensional random loop bonded structure. For the recovered three-dimensional network structure, please refer to the description of the recovered three-dimensional network structure for directly obtaining the raw material according to the above-mentioned embodiment.

[0052] In the step of obtaining fiber pieces, the method for pulverizing at least a portion of the three-dimensional network structure is not particularly limited, and may be, for example, by applying an external force such as cutting, stretching, compression, shearing, or friction to the three-dimensional network structure to break it down, defibrate it, etc. The pulverization may be dry pulverization, wet pulverization, low-temperature pulverization, or a combination thereof.

[0053] It is preferable to use a pulverizer for pulverization. Examples of pulverizers include compression pulverizers such as roll crushers; impact pulverizers such as impact crushers and hammer mills; cutting or shearing pulverizers such as cutter mills, reciprocating pulverizers, low-speed rotary pulverizers, and biaxial shear pulverizers; impact shearing pulverizers such as shredders; and fine pulverizers such as ball mills, disk mills, pin mills, hammer mills, turbo mills, and jet mills. Among these, cutting or shearing pulverizers are preferred because they can easily directly feed the three-dimensional network structure and have excellent pulverization efficiency. It is preferable to arrange a screen mesh inside the pulverizer. The number of fibers, the number of bonding points, and the fiber length of the fiber pieces can be controlled, for example, by adjusting the hole size, hole shape, and aperture ratio of the screen mesh, the rotation speed of the rotary blade, and the amount of the three-dimensional network structure fed into the pulverizer.

[0054] In the process of melting the fiber pieces without granulating them to form a three-dimensional network structure, the fiber pieces are melted and extruded from a nozzle, and the extruded continuous filaments are molded into a three-dimensional random loop bonded structure. If necessary, the three-dimensional random loop bonded structure may be further heat-treated.

[0055] Examples of extrusion and molding methods include the following. First, a spinneret with multiple orifices extrudes the fiber pieces downward at a spinning temperature equal to or higher than the melting point of the resin in the fiber pieces. Next, the continuous filaments are brought into contact with each other in the molten state and fused to form a three-dimensional random loop bonded structure. The filaments are then sandwiched between a pair of take-up conveyors and cooled with cooling water in a water tank. The solidified three-dimensional random loop bonded structure is then pulled out and drained or dried to obtain a three-dimensional network structure with smooth surfaces on one or both sides.

[0056] The direct discharge rate of the raw material per hole from the spinneret is preferably 0.5 to 6.0 g / min, more preferably 0.8 to 5.0 g / min. The spinning temperature is preferably the melting point of the resin of the fiber pieces + 10°C or higher and the melting point of the resin + 100°C or lower, more preferably the melting point of the resin + 15°C or higher and the melting point of the resin + 80°C or lower. The take-up speed of the take-up conveyor is preferably 0.5 to 2.5 m / min, more preferably 0.9 to 2.0 m / min. The drying treatment may be carried out using a commercially available hot air drying oven. The drying temperature is preferably 50 to 150°C, more preferably 70 to 120°C. The drying time is preferably 10 to 50 minutes, more preferably 20 to 40 minutes.

[0057] In the process of forming the three-dimensional network structure, the fiber pieces and resin pellets may be mixed, and in this case, the three-dimensional network structure is formed by melting the mixed fiber pieces without granulating them. For details of the resin pellets, please refer to the description of the direct raw material in the embodiment described above.

[0058] The fiber pieces and resin pellets may be mixed together before being fed into the extruder. Alternatively, the fiber pieces may be fed into a first feed pipe and the resin pellets into a second feed pipe, and then the two may be mixed and fed into the extruder. In this case, if either the fiber pieces or the resin pellets, or both, are fed via a metered feeder, the mixing ratio of the fiber pieces and the resin pellets in the raw material can be directly controlled. Alternatively, the resin pellets may be fed through the main raw material feed port of the extruder, and the fiber pieces may be fed through a secondary raw material feed port, such as a side feeder, and the two may be mixed by melt-kneading within the extruder. When the fiber pieces and the resin pellets are mixed, it is preferable that the resin compositions of the fiber pieces and the resin pellets are the same from the viewpoint of spinning operability.

[0059] This application claims the benefit of priority based on Japanese Patent Application No. 2024-057578, filed on March 29, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-057578, filed on March 29, 2024, are incorporated herein by reference.

[0060] The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples. Furthermore, modifications can be made within the scope of the above and below-described aims, and all such modifications are included within the technical scope of the present invention. Measurement and evaluation of property values ​​in the examples were carried out as follows. The sample sizes described below were used as standard, but when sample was insufficient, measurements were carried out using the largest possible sample size.

[0061] (1) Number of bonded fibers per 1 g of fiber fragment group Fiber fragment groups were collected in the range of 1±0.2 g, and the mass Wf of the fiber fragment group was measured using an electronic balance. Specifically, bonded fibers in which multiple single fibers were bonded to each other were collected from the obtained fiber fragment group, and the number Nf of bonded fibers was measured. The number of bonded fibers per 1 g of fiber fragment group was calculated using the following formula (1). Each bonded fiber in which two or more single fibers were bonded was counted as one. For example, in Figure 1, the number of bonded fibers is three. This operation was repeated three times, and the average of the three values ​​obtained was used. Number of bonded fibers per 1 g of fiber fragment group (number / g) = Nf / Wf (1)

[0062] (2) Average number of bonding points per bonded fiber One of the bonded fibers collected in (1) above was taken out and visually observed to determine the number of bonding points B. ｉ This operation was performed on all of the bonded fibers collected in (1) above, and the average number of bonded points per bonded fiber was calculated using the following formula (2).

[0063]

[0064] (3) Fiber Diameter of Fiber Piece Group The side of one fiber in the fiber piece group was observed with an optical microscope. The optical microscope was adjusted to an appropriate magnification, and the fiber diameter was measured by focusing on a measurement point near the center of the fiber in the longitudinal direction. If there was a bonding point near the center of the fiber in the longitudinal direction, the fiber diameter of the branched portion adjacent to the bonding point was measured. This operation was performed on 10 fibers in any fiber piece group, and the average value of the 10 values ​​was calculated (unit: mm). Of the collected fibers, non-bonded fibers with scraped fiber side surfaces were excluded from the measurement. Furthermore, bonded fibers in which the entire fiber was bonded in the longitudinal direction were excluded from the measurement.

[0065] (4) Length of Single Fiber in Fiber Piece Group A microphotograph was taken of the side of one fiber in the fiber piece group in a stationary state without stretching, and the circumscribed circle diameter was measured by drawing a circumscribed circle circumscribing the fiber. A photograph was also taken with an objective micrometer (1 division = 0.01 mm), and the actual length of the circumscribed circle diameter was calculated from the scale. This procedure was performed on 30 random fibers, and the average value of the 30 values ​​was calculated (unit: mm).

[0066] (5) Angle of repose of fiber fragments Five samples were prepared by collecting fiber fragments in the range of 200±5 g. In an environment of 23±5°C, the sample was placed in a funnel into which the damper of a bulk density measuring device had been inserted. The damper was quickly removed, and the sample was dropped onto a horizontal plate from a height of 100 mm. The angle between the apex and base of the conical specimen deposited on the horizontal plate was measured with a protractor. This procedure was performed on the five samples, and the average value was taken as the angle of repose of the fiber fragments.

[0067] (6) Reduced Viscosity [Preparation of Test Solution] The resin pellets, fiber fragments, or three-dimensional network structure to be tested were placed in a hot air dryer set at an internal temperature of 70°C and left to dry for 25 minutes. The dried resin pellets, fiber fragments, or three-dimensional network structure were finely cut so that the resin pellets or fibers were within 2 mm in length, and 0.08±0.003 g of sample was weighed. A phenol / 1,1,2,2-tetrachloroethane mixed solvent (60 / 40 by mass) was added to the resulting sample with an accuracy of ±0.01 ml to obtain a solution with a concentration of 0.2 g / dL. The resulting solution was heated to 70°C and stirred for 30 minutes to dissolve the sample. The solution was cooled in a water bath at 15±1°C and then left at room temperature to obtain the test solution. [Measurement of Solvent Egress Time t0 (Blank Test)] An AVL-2C capillary (Ubbelohde viscometer) automatic viscosity measurement device manufactured by Asahi Kasei Technosystems was used. The viscosity tube used was an Ubbelohde-type viscosity tube with a capillary diameter of 0.77 mm (±2%). The temperature of the thermostatic bath and the test temperature of the automatic viscosity measurement device were set to 30±0.1°C. A phenol / 1,1,2,2-tetrachloroethane mixed solvent (=60 / 40; mass ratio) was placed in the viscosity tube. The viscosity tube was attached to the thermostatic bath and conditioned at 30±0.1°C for 10 minutes. The test was then started, and the outflow time (seconds) of the mixed solvent was measured twice consecutively. The average of the two measurements was taken as the solvent outflow time t0 (seconds). [Measurement of the outflow time t1 of the test solution] The same automatic viscosity measurement device was used as in the measurement of t0. The same viscosity tube was used as in the measurement of t0. The temperature of the thermostatic bath and the test temperature of the automatic viscosity measurement device were set to 30±0.1°C. The viscosity tube was washed with the test solution. The test solution was placed in the viscosity tube. The viscosity tube was attached to the thermostatic bath and conditioned at 30±0.1°C for 10 minutes. Thereafter, the test was started, and the outflow time (seconds) of the mixed solvent was measured twice consecutively. The average of the two measurements was taken as the outflow time t1 (seconds) of the solvent. [Calculation of reduced viscosity] The reduced viscosity (dl / g) was calculated using the following formula (3): Reduced viscosity ηsp / c=(t1 / t0-1) / c (3) [t1: outflow time (seconds) of the test solution, t0: outflow time (seconds) of the solvent, c: concentration of the test solution (0.2 g / dl)]

[0068] (7) Apparent density and thickness of three-dimensional network structure The three-dimensional network structure was cut into a size of 30±0.5 cm × 30±0.5 cm × thickness to obtain a sample. The obtained sample was left in an environment of 23°C ± 5°C without load for 24 hours, and then the heights at four points were measured using a Kobunshi Keiki FD-80N type thickness gauge, and the average value was calculated as the sample thickness (d ０ ) (unit: mm). The sample weight (W) was measured by placing the sample on an electronic balance (unit: g). The obtained sample thickness (d ０ The apparent density (g / cm) was calculated using the sample weight (W) and the average value of n = 3 using the following formula (4). ３ ) = (W × 10) / (30 × 30 × d ０ ) ... (4)

[0069] (8) Fiber Diameter of Three-Dimensional Network Structure The three-dimensional network structure was cut into a size of 20±0.5 cm × 20±0.5 cm × thickness, and one fiber was taken from the inner layer at a distance of 2 mm or more from the surface in the thickness direction, and the side surface was observed with an optical microscope. The optical microscope was adjusted to an appropriate magnification, and the fiber diameter was measured by focusing on a measurement point near the center of the fiber in the longitudinal direction. This operation was performed on 10 random fibers, and the average value of the 10 values ​​was calculated (unit: mm).

[0070] (9) Initial Thickness and 25% Hardness of Three-Dimensional Network Structure The three-dimensional network structure was cut into a size of 30±0.5 cm × 30±0.5 cm × thickness to obtain a sample. The obtained sample was left unloaded in an environment of 23°C ± 5°C for 24 hours, and then compressed at the center of the sample at a rate of 10 mm / min using a pressure plate with a diameter of 200 mm and a thickness of 10 mm on a Shimadzu autograph in an environment of 23°C ± 5°C. The thickness when the load reached 5±0.5 N was measured and defined as the initial thickness. The position of the pressure plate at this time was defined as the zero point, and the sample was compressed to 75±1% of the initial thickness at a rate of 100 mm / min, and then the pressure plate was returned to the zero point at a rate of 100 mm / min. The sample was then compressed to 25±1% of the initial thickness at a rate of 100 mm / min, and the load at this time was measured and defined as the 25% hardness (average value of n = 3, unit: N).

[0071] (10) Repeated Compression Residual Set and Repeated Compression 25% Hardness Reduction Rate of Three-dimensional Network Structure The three-dimensional network structure was cut into a size of 30±0.5 cm × 30±0.5 cm × thickness to obtain a sample. The initial thickness and 25% hardness of the obtained sample were measured by the method described in (9) above, and the obtained initial thickness was calculated as the thickness before treatment (d ａ ), 25% hardness is measured by the load before treatment (H ａ Then, using a foam rubber repeated compression tester manufactured by Yasuda Seiki Seisakusho, the distance d when the two parallel plates of the repeated compression tester were widest was measured. １ The set value of the initial thickness obtained by the method described in (9) above was rounded up to the nearest integer. ２ The set value was 50% of the initial thickness, rounded up to the nearest integer. Next, the sample was placed between the two parallel plates, and the distance between the parallel plates was adjusted to d in an environment of 23°C ± 5°C. １ From d ２ The distance between the parallel plates is reduced by d in successive operations. １ This cycle was repeated 80,000 times at a speed of 60±5 times per minute. Then, the sample was quickly removed from the parallel plates and allowed to stand at 23°C±5°C for 30 minutes. The initial thickness was measured by the method described in (9) above, and the obtained initial thickness was used as the thickness before treatment (d ｂ ), 25% hardness after treatment load (H ｂ The repeated compression set was calculated using the following formula (5) (average value of n = 2, unit: %). The repeated compression hardness reduction rate was calculated using the following formula (6) (average value of n = 2, unit: %). Repeated compression set (%) = (d ａ -d ｂ ) / d ａ × 100 (5) Repeated compression hardness reduction rate (%) = (H ａ -H ｂ ) / H ａ × 100 ... (6)

[0072] [Spinning conditions S-1 for producing a three-dimensional network structure] A spinneret Nz-1 was prepared, in which orifices with a hole diameter of 1.2 mm were arranged in a staggered arrangement with a hole pitch of 7 mm on an effective surface of 1001 mm in the width direction and 60.6 mm in the thickness direction. The molten resin extruded from the extruder was discharged downward using the spinneret Nz-1 at a spinning temperature of 240 ° C. and a single-hole discharge rate of 1.0 g / min. Then, after passing through a cooling space with an ambient temperature of 25 to 35 ° C., cooling water was placed 23 cm below the spinneret surface without blowing cooling air, and a pair of take-up conveyors consisting of a 150 cm wide stainless steel endless net were arranged in parallel with an opening width of 35 mm spaced apart so that some of the material was above the water surface. The molten discharged filaments were twisted to form loops, and the contact portions were fused to form a three-dimensional random loop bonded structure. Both sides of this molten three-dimensional random loop bonded structure were sandwiched between a take-up conveyor and pulled into cooling water at a speed of 1.07 m / min to solidify and flatten both sides, then cut to a predetermined length and subjected to a dry heat treatment with hot air at 105°C for 30 minutes to obtain a three-dimensional network structure.

[0073] [Spinning conditions S-2 for producing a three-dimensional network structure] A spinneret Nz-2 was prepared, in which orifices with an outer diameter of 5.0 mm and a triple-bridge hollow-forming cross section were arranged in a staggered arrangement with a hole pitch of 8 mm on an effective surface of 970 mm in the width direction and 46.8 mm in the thickness direction. The molten resin extruded from the extruder was discharged downward using the spinneret Nz-2 at a spinning temperature of 240 ° C. and a single-hole discharge rate of 3.1 g / min. The spinneret was then cooled to a temperature of 25 to 35 ° C., and cooling water was placed 20 cm below the spinneret surface without blowing cooling air. A pair of take-up conveyors consisting of a 150 cm wide stainless steel endless net were arranged in parallel with an opening width of 45 mm spaced apart so that some of the material was above the water surface. The molten discharged filaments were twisted to form loops, and the contact portions were fused to obtain a three-dimensional random loop bonded structure. Both sides of this molten three-dimensional random loop bonded structure were sandwiched between conveyors and pulled into cooling water at a speed of 1.75 m / min to solidify and flatten both sides. Thereafter, the structure was cut to a predetermined length and subjected to a dry heat treatment with hot air at 105°C for 30 minutes to obtain a three-dimensional network structure.

[0074] [Spinning conditions S-3 for producing a three-dimensional network structure] A spinneret Nz-3 was prepared, with an effective surface of 970 mm in the width direction and 76.2 mm in the thickness direction, having an outer diameter of 5.0 mm and a triple-bridge hollow-forming cross-section orifice arranged in a staggered arrangement with a hole pitch of 8 mm. The molten resin extruded from the extruder was discharged downward from the spinneret using the spinneret Nz-3 at a spinning temperature of 210 ° C. and a single-hole discharge rate of 2.3 g / min. Next, after passing through a cooling space with an ambient temperature of 25 to 35 ° C., cooling water was placed 35 cm below the spinneret surface without blowing cooling air, and a pair of take-up conveyors consisting of a 150 cm wide stainless steel endless net were arranged in parallel with an opening width of 55 mm spaced apart so that some of the material was above the water surface. The molten discharged filaments were twisted to form loops, and the contact portions were fused to obtain a three-dimensional random loop bonded structure. Both sides of this molten three-dimensional random loop bonded structure were sandwiched by a take-up conveyor and pulled into cooling water at a speed of 1.84 m / min to solidify and flatten both sides, then cut to a predetermined length and subjected to a dry heat treatment with hot air at 60°C for 30 minutes to obtain a three-dimensional network structure.

[0075] Example 1 (1) Production of Virgin Pellets of Polyester-Based Thermoplastic Elastomer Resin Dimethyl terephthalate (DMT), 1,4-butanediol (1,4-BD), and polytetramethylene glycol (PTMG: average molecular weight 1000) were charged as the polyester-based thermoplastic elastomer along with a small amount of catalyst, and transesterification was carried out by a conventional method. Polycondensation was then carried out while increasing the temperature under reduced pressure, and the mixture was pelletized to produce a polyether ester block copolymer elastomer. 1% of a phenolic antioxidant was then added, mixed, and pelletized to produce virgin pellets G-1 of polyester-based thermoplastic elastomer resin (E-1). The resulting virgin pellets had an elliptical cross-section with a major axis of 3 mm and a minor axis of 2 mm, and were rod-like in length and 2.5 mm. The resulting virgin pellets were vacuum-dried at 50°C for 48 hours and then placed in the main raw material storage tank 1 shown in Figure 2. The components, melting point and reduced viscosity of the resulting polyester thermoplastic elastomer resin are shown in Table 1.

[0076]

[0077] (2) Production of a three-dimensional network structure using only virgin pellets as raw material Virgin pellets G-1 were supplied to an extruder 6 from a main raw material storage tank 1 shown in FIG. 2, and a three-dimensional network structure was formed under spinning conditions S-1. The pellets were then cut to a predetermined length and subjected to a dry heat treatment with hot air at 105°C for 30 minutes to obtain a three-dimensional network structure A-0 using only virgin pellets as raw material. The obtained three-dimensional network structure A-0 had an apparent density of 0.045 g / cm ３ The thickness was 31 mm, the width was 980 mm, and the length was 2000 mm. The physical properties of the resulting three-dimensional network structure A-0 are shown in Table 2.

[0078]

[0079] (3) Production of fiber pieces Group of fiber pieces Group of fiber pieces F-1 having an average single fiber length of 3.00 mm was obtained by collecting scraps generated in the process of cutting to a predetermined product length in the production of three-dimensional network structure A-0 and naturally drying them. The scraps were then pulverized at a cutting blade rotation speed of 600 rpm using a uniaxial shear crusher DAS-42 manufactured by Daiko Seiki Co., Ltd. equipped with a screen mesh having an opening ratio of 51% and perforated with circular holes having a diameter of 3.0 mm. The physical properties of the obtained group of fiber pieces F-1 are shown in Table 3.

[0080] (4) Transportation of Fiber Pieces The obtained fiber piece group F-1 was directly charged as a raw material into the charging tank 2 shown in Fig. 2 and then pneumatically transported through a raw material supply pipe having an inner diameter of 30 mm to the auxiliary raw material storage tank 3 located above the extruder 6. During the pneumatic transport, the fiber piece group F-1 did not remain in the pipe.

[0081] (5) Production of a recycled three-dimensional network structure using fiber pieces as a direct raw material Fiber pieces F-1 were supplied from auxiliary raw material storage tank 3 to extruder 6 through a pipe with an inner diameter of 45 mm, and a three-dimensional network structure A-1 was obtained using only fiber pieces F-1 as a direct raw material under spinning conditions S-1. The obtained three-dimensional network structure A-1 had an apparent density of 0.045 g / cm ３ The thickness was 31 mm, the width was 980 mm, and the length was 2000 mm. The physical properties of the resulting three-dimensional network structure A-1 are shown in Table 3.

[0082] As described above, the fiber pieces F-1 did not remain in the piping while being pneumatically conveyed through the piping from the input tank 2 to the auxiliary material storage tank 3, or while falling through the piping from the auxiliary material storage tank 3 to the extruder 6, and three-dimensional network structure A-1 could be produced using the fiber pieces F-1 directly as a raw material. Furthermore, by using the fiber pieces F-1 directly as a raw material, i.e., by omitting the steps of remelting and granulating, deterioration in the mechanical properties of the resulting recycled three-dimensional network structure was suppressed.

[0083] [Example 2] In the same manner as in Example 1, scraps generated in the production of the three-dimensional network structure A-0 were collected and naturally dried, and then the scraps were pulverized at a cutting blade rotation speed of 600 rpm using a uniaxial shear crusher DAS-42 manufactured by Daiko Seiki Co., Ltd., equipped with a screen mesh with an opening rate of 40% and perforated with circular holes 6.0 mm in diameter, to obtain a group of fiber pieces F-2 having an average single fiber length of 4.85 mm. The physical properties of the obtained group of fiber pieces F-2 are shown in Table 3.

[0084] The obtained group of fiber pieces F-2 was directly charged as a raw material into the charging tank 2 shown in Figure 3 and then pneumatically conveyed through a raw material supply pipe having an inner diameter of 45 mm to the auxiliary raw material storage tank 3 located above the extruder 6. During the pneumatic conveyance, the group of fiber pieces F-2 did not remain in the pipe.

[0085] Virgin pellets G-1 were supplied from the main raw material storage tank 1 shown in Figure 3 through a pipe with an inner diameter of 45 mm, and fiber piece group F-2 was supplied from the auxiliary raw material storage tank 3 via a constant-volume feeder 5 to an extruder 6 through a pipe with an inner diameter of 45 mm, to obtain a three-dimensional network structure A-2 under spinning conditions S-1. The mixing ratio of the two was 95 mass% for virgin pellets G-1 and 5 mass% for fiber piece group F-2 relative to the total mass of the two. The obtained three-dimensional network structure A-2 had an apparent density of 0.045 g / cm ３ The thickness was 31 mm, the width was 980 mm, and the length was 2000 mm. The physical properties of the resulting three-dimensional network structure A-2 are shown in Table 3.

[0086] As described above, the fiber pieces F-2 did not remain in the piping while being pneumatically conveyed through the piping from the input tank 2 to the auxiliary material storage tank 3, or while falling through the piping from the auxiliary material storage tank 3 to the extruder 6, and a three-dimensional network structure A-2 could be produced using a mixture of virgin pellets G-1 and fiber pieces F-2 directly as a raw material. Furthermore, by using fiber pieces F-2 directly as a raw material, i.e., by omitting the steps of remelting and granulating, deterioration in the mechanical properties of the resulting recycled three-dimensional network structure was suppressed.

[0087] [Example 3] A mattress discarded after use by a consumer, whose filling material was a three-dimensional net structure manufactured by Toyobo Co., Ltd., was collected, and the cover and filling material were separated to remove the filling material. The filling material was a polyether ester block copolymer elastomer resin with an apparent density of 0.035 g / cm. ３ , thickness: 50 mm, and the fibers were hollow fibers. The obtained filling material was washed in a commercial washing machine to remove deposits such as dust and human sebum. It was then dried in a commercial dryer. The washed and dried filling material was pulverized using a dry shear crusher CS-54 manufactured by Nippon Seam Co., Ltd., equipped with a screen mesh with an opening rate of 51% and perforated with circular holes 6.0 mm in diameter, at a cutting blade rotation speed of 400 rpm, to obtain fiber piece group F-3 having an average single fiber length of 6.42 mm. The physical properties of the obtained fiber piece group F-3 are shown in Table 3.

[0088] The obtained fiber fragment group F-3 was directly charged as a raw material into the charging tank 2 shown in Figure 3, and then air-transported through a raw material supply pipe with an inner diameter of 30 mm to the auxiliary raw material storage tank 3 located above the extruder 6. During air-transport, the fiber fragment group F-3 did not remain in the pipe.

[0089] Virgin pellets G-1 were supplied from the main raw material storage tank 1 shown in FIG. 3 through a pipe having an inner diameter of 45 mm, and fiber piece group F-3 was supplied from the auxiliary raw material storage tank 3 via a constant-volume feeder 5 to an extruder 6 through a pipe having an inner diameter of 45 mm, to obtain a three-dimensional network structure A-3 under spinning conditions S-2. At this time, the mixing ratio of the two was 70% by mass of virgin pellets G-1 and 30% by mass of fiber piece group F-3 relative to the total mass of both. The obtained three-dimensional network structure A-3 had an apparent density of 0.035 g / cm ３The thickness was 41 mm, the width was 950 mm, and the length was 2000 mm. The physical properties of the resulting three-dimensional network structure A-3 are shown in Table 3.

[0090] As described above, the fiber fragments F-3 did not remain in the piping while being pneumatically conveyed through the piping from the input tank 2 to the auxiliary material storage tank 3, or while falling through the piping from the auxiliary material storage tank 3 to the extruder 6, and a three-dimensional network structure A-3 could be produced using a mixture of virgin pellets G-1 and fiber fragments F-3 directly as a raw material. Furthermore, by using fiber fragments F-3 directly as a raw material, deterioration in the mechanical properties of the resulting recycled three-dimensional network structure was suppressed.

[0091] Example 4 100% by mass of Nipolon (registered trademark)-Z1P55A (manufactured by Tosoh Corporation), a random block copolymer consisting of ethylene and α-olefin, was used as the polyolefin thermoplastic elastomer resin virgin pellets G-2. Only these virgin pellets G-2 were placed in the main raw material storage tank 1 shown in FIG. 4 , and the virgin pellets G-2 were supplied from the main raw material storage tank 1 to the extruder 6, where they were formed into a three-dimensional network structure under spinning condition S-3. The virgin pellets were then cut to a predetermined length and subjected to a dry heat treatment with hot air at 105°C for 30 minutes, yielding a three-dimensional network structure B-0 made solely from virgin pellets. The resulting three-dimensional network structure B-0 had an apparent density of 0.031 g / cm ３ The thickness was 53 mm, the width was 950 mm, and the length was 2000 mm. The physical properties of the resulting three-dimensional network structure B-0 are shown in Table 2.

[0092] The scraps generated in the production of the three-dimensional network structure B-0 were collected and naturally dried, and then pulverized using a dry pulverizer V-480 manufactured by Horai Co., Ltd., equipped with a screen mesh with an opening rate of 58% and 8.0 mm diameter circular holes at a cutting blade rotation speed of 600 rpm, to obtain a group of fiber pieces F-4 having an average single fiber length of 9.70 mm. The physical properties of the obtained group of fiber pieces F-4 are shown in Table 3.

[0093] The obtained fiber fragment group F-3 was directly charged as a raw material into the charging tank 2 shown in Figure 4 and transported by a screw conveyor 4 with a piping inner diameter of 45 mm to the auxiliary raw material storage tank 3 located above the extruder 6. During transportation, the fiber fragment group F-4 could be transported without becoming entangled in the screw of the screw conveyor 4.

[0094] Virgin pellets G-2 were supplied from the main raw material storage tank 1 shown in Figure 4 through a pipe with an inner diameter of 50 mm, and fiber piece group F-4 was supplied from the auxiliary raw material storage tank 3 via a constant-volume feeder 5 to an extruder 6 through a pipe with an inner diameter of 50 mm, to obtain a three-dimensional network structure B-1 under spinning conditions S-3. At this time, the mixing ratio of the two was 90 mass% for virgin pellets G-2 and 10 mass% for fiber piece group F-3 relative to the total mass of both. The obtained three-dimensional network structure B-1 had an apparent density of 0.031 g / cm ３ The thickness was 53 mm, the width was 950 mm, and the length was 2000 mm. The physical properties of the resulting three-dimensional network structure B-1 are shown in Table 3.

[0095] As described above, the fiber fragments F-4 did not remain in the piping while falling through the piping from the auxiliary material storage tank 3 to the extruder 6, and the three-dimensional network structure B-1 was produced using the mixture of virgin pellets G-2 and fiber fragments F-4 directly as the raw material. Furthermore, by using fiber fragments F-4 directly as the raw material, the deterioration of the mechanical properties of the obtained recycled three-dimensional network structure was suppressed.

[0096] [Comparative Example 1] The scraps obtained in the production of the three-dimensional network structure A-0 described in Example 1 were collected and air-dried, and then the scraps and the non-standard raw fabric were pulverized at a cutting blade rotation speed of 600 rpm using a uniaxial shear crusher DAS-42 manufactured by Daiko Seiki Co., Ltd., equipped with a screen mesh with an opening rate of 54% and perforated with circular holes having a diameter of 10.0 mm, to obtain a group of fiber pieces F-5 having an average single fiber length of 11.66 mm. The physical properties of the obtained group of fiber pieces F-5 are shown in Table 3.

[0097] The obtained group of fiber pieces F-5 was charged into charging tank 2 shown in Figure 2, and an attempt was made to air-transport them through the raw material supply piping to auxiliary material storage tank 3 located above extruder 6, but the fiber pieces F-5 remained in the piping during air-transport and air-transport was not possible. Furthermore, the obtained group of fiber pieces F-5 was manually charged into auxiliary material storage tank 3, and an attempt was made to supply the group of fiber pieces F-5 from auxiliary material storage tank 3 to extruder 6, but as the group of fiber pieces F-5 fell through the piping from auxiliary material storage tank 3 to extruder 6, they remained in the piping and could not be supplied to extruder 6.

[0098] Comparative Example 2 The fiber fragment group F-3 obtained in Example 3 was remelted in a twin-screw kneading extruder TEX34αIII manufactured by The Japan Steel Works, Ltd., extruded at a die temperature of 230°C, water-cooled in a cooling bath, and granulated with a strand cutter to produce recycled pellets G-3 derived from a used three-dimensional network structure. The resulting pellets G-3 were placed in the auxiliary raw material storage tank 3 of FIG. 3, and virgin pellets G-1 were supplied from the main raw material storage tank 1 via a pipe, and recycled pellets G-3 were supplied from the auxiliary raw material storage tank 3 via a pipe to the extruder 6, whereupon a three-dimensional network structure A-4 was obtained under spinning conditions S-2. The mixing ratio of the two was 70% by mass of virgin pellets G-1 and 30% by mass of recycled pellets G-3 relative to the total mass of both. The resulting three-dimensional network structure A-4 had an apparent density of 0.035 g / cm ３ The thickness was 40 mm, the width was 950 mm, and the length was 2000 mm. The physical properties of the resulting three-dimensional network structure A-4 are shown in Table 3.

[0099] The resin of the recycled pellet G-3 had deteriorated during the remelting and granulation steps in the production process, and therefore the reduction rate in the repeated compression hardness of the three-dimensional network structure A-4 was as large as 37.5%.

[0100]

[0101] By using the direct raw material according to the embodiment as the raw material for horizontal recycling of three-dimensional network structures, industrial production of three-dimensional network structures becomes possible without stagnation of raw material in supply pipes. Furthermore, by using the direct raw material according to the embodiment as the raw material for horizontal recycling of three-dimensional network structures, the process of remelting and granulating the recovered three-dimensional network structures can be omitted, thereby suppressing deterioration of the resin during remelting and reducing deterioration in the mechanical properties of the three-dimensional network structures obtained by material recycling. Furthermore, energy consumption during the remelting and granulation processes can be reduced, enabling efficient material recycling.

[0102] 1 Main raw material storage tank 2 Input tank 3 Sub raw material storage tank 4 Screw conveyor 5 Fixed amount feeder 6 Extruder 11a, 11b, 11c Bonded fiber 12 Non-bonded fiber 13 Fiber fragments 14 Single fiber 20 Direct raw material

Claims

1. A direct raw material for producing a three-dimensional network structure having a three-dimensional random loop bonded structure, the direct raw material having a group of fiber pieces, the group of fiber pieces including bonded fibers in which single fibers are bonded to each other and non-bonded fibers which are single fibers that are not bonded to other single fibers, and the number of bonded fibers per 1.0 g of the group of fiber pieces is 1 or more and 700 or less.

2. The direct raw material according to claim 1, wherein the fiber fragments are obtained from a recovered three-dimensional network structure having a three-dimensional random loop bonded structure.

3. The direct feedstock according to claim 1, wherein the average number of bonding points per bonded fiber is 1.00 or more and 3.0 or less.

4. The direct feedstock according to claim 1, wherein the diameter of the single fiber of said bonded fiber is 0.1 mm or more and 3.0 mm or less.

5. The direct feedstock of claim 2, wherein the diameter of said unbonded fibers is 0.1 mm or more and 3.0 mm or less.

6. The direct raw material according to claim 1, wherein the angle of repose of said fiber fragments is 25 degrees or more and 65 degrees or less.

7. The direct feedstock of claim 1 comprising resin pellets.

8. A three-dimensional network structure having a three-dimensional random loop bonded structure obtained from the direct raw material according to any one of claims 1 to 7.

9. A method for producing a three-dimensional network structure, comprising: a step of pulverizing at least a portion of a three-dimensional network structure having a three-dimensional random loop bonding structure to obtain a group of fiber pieces including bonded fibers in which single fibers are bonded to each other and unbonded fibers which are single fibers that are not bonded to other single fibers; and a step of melting the group of fiber pieces without granulating them to form a three-dimensional network structure having a three-dimensional random loop bonding structure, wherein the number of bonded fibers per 1.0 g of the group of fiber pieces is 1 or more and 700 or less.

10. The method for producing a three-dimensional netted structure according to claim 9, wherein the average number of bonding points per bonding fiber is 1.00 or more and 3.0 or less.

11. The method for producing a three-dimensional network structure according to claim 9, wherein the diameter of the single fiber of the bonding fiber is 0.1 mm or more and 3.0 mm or less.

12. The method for producing a three-dimensional network structure according to claim 9, wherein the diameter of the non-bonded fibers is 0.1 mm or more and 3.0 mm or less.

13. The method for producing a three-dimensional network structure according to claim 9, wherein the angle of repose of the group of fiber pieces is 25 degrees or more and 65 degrees or less.

14. The method for producing a three-dimensional network structure according to claim 9, wherein in the step of forming the three-dimensional network structure, the fiber pieces and resin pellets are melted without being granulated to form the three-dimensional network structure.