Solid net-like structure body

Abstract

The purpose of the present invention is to provide a solid net-like structure body having excellent cushioning properties and quietness. This solid net-like structure body has a three-dimensional random loop-joined structure. The three-dimensional random loop-joined structure includes continuous linear bodies containing a thermoplastic resin composition. The thermoplastic resin composition contains 70-100 mass% of a polybutylene adipate terephthalate resin. The polybutylene adipate terephthalate resin includes an adipate unit and a terephthalate unit. The mol ratio of the terephthalate unit with respect to the adipate unit is 0.5-2.0. The number of joining points per unit mass of the three-dimensional random loop-joined structure is 150-500 points / g.

Description

Three-dimensional mesh structure

[0001] The present invention relates to a three-dimensional network structure.

[0002] Three-dimensional network structures have been widely used as cushioning materials for furniture, bedding such as beds, and seats for vehicles such as trains, automobiles, and motorcycles due to their excellent breathability and recyclability. For example, Patent Document 1 discloses a technology for improving the plant retention of a biodegradable network structure. Patent Document 2 discloses a technology for improving the local bonding of fiber materials in a biodegradable network structure. Patent Document 3 discloses a technology for forming coil spring-shaped or loop-shaped portions in a biodegradable three-dimensional structure, thereby allowing the portions to deform favorably in response to compressive stress and disperse the stress. Patent Document 4 discloses a biodegradable three-dimensional network structure containing linear fibers that contain a polybutylene adipate terephthalate resin and form a three-dimensional random loop structure.

[0003] JP 2001-032236 A JP 2020-128608 A JP 2000-328422 A International Publication No. 2022 / 209976

[0004] Various attempts have been made to improve the functionality of three-dimensional mesh structures, as described in Patent Documents 1 to 4, but these have sometimes produced sounds like random loops rubbing against each other or popping when compressed and restored. Particularly when three-dimensional mesh structures are used as cushioning materials, reduction of such sounds is required. The present invention has been made in view of the above circumstances, and its object is to provide a three-dimensional mesh structure that has excellent cushioning properties and quietness.

[0005] A three-dimensional network structure according to an embodiment of the present invention is as follows: [1] A three-dimensional network structure having a three-dimensional random loop bonded structure, wherein the three-dimensional random loop bonded structure comprises continuous linear bodies containing a thermoplastic resin composition, the thermoplastic resin composition contains 70 to 100 mass% of a polybutylene adipate terephthalate resin, the polybutylene adipate terephthalate resin contains adipic acid units and terephthalic acid units, the molar ratio of the terephthalic acid units to the adipic acid units is 0.5 to 2.0, and the number of bonds per unit mass of the three-dimensional random loop bonded structure is 150 to 500 / g.

[0006] With the above configuration, the three-dimensional network structure has excellent cushioning and quietness. Further examples of three-dimensional network structures according to the present invention include the following [2] to

[10] . [2] The three-dimensional network structure according to [1], wherein the continuous filaments have a fiber diameter of 0.20 to 0.80 mm. [3] The three-dimensional network structure according to [1] or [2], wherein a differential scanning calorimeter curve of the continuous filaments measured using a differential scanning calorimeter has an endothermic peak with a minimum enthalpy in the range of 30 to 70°C of 0.1 to 2.5 J / g. [4] The three-dimensional network structure according to any one of [1] to [3], wherein the continuous filaments have a hollow cross section, and the hollow cross section has a void ratio of 5 to 40%. [5] The three-dimensional network structure according to any one of [1] to [4], wherein the polybutylene adipate terephthalate resin has a melting point of 100 to 170°C. [6] The three-dimensional network structure according to any one of [1] to [4], wherein the apparent density is 0.005 to 0.30 g / cm. ３[7] The three-dimensional network structure according to any one of [1] to [6], wherein the three-dimensional network structure has a 40°C compression set of 1 to 25%. [8] The three-dimensional network structure according to any one of [1] to [6], wherein the three-dimensional network structure has a 40°C compression set of 1 to 15% and a 70°C compression set of 1 to 30%. [9] The three-dimensional network structure according to any one of [1] to [8], wherein the crystalline melting enthalpy is 16 to 30 J / g.

[10] The three-dimensional network structure according to any one of [1] to [9], wherein the molar ratio of the terephthalic acid units to the adipic acid units is 0.7 to 1.6.

[0007] According to the present invention, with the above-mentioned configuration, it is possible to provide a three-dimensional netted structure having excellent cushioning properties and quietness.

[0008] FIG. 1 is a differential scanning calorimetry curve of a continuous linear body constituting a three-dimensional network structure, and is an example of a differential scanning calorimetry curve for measuring the enthalpy of an endothermic peak having a minimum value in the range of 30° C. to 70° C. and the crystalline melting enthalpy.

[0009] The three-dimensional network structure according to the embodiment has a three-dimensional random loop bonded structure, and the three-dimensional random loop bonded structure includes continuous linear bodies containing a thermoplastic resin composition. The thermoplastic resin composition contains 70 to 100% by mass of a polybutylene adipate terephthalate resin, and the polybutylene adipate terephthalate resin contains adipic acid units and terephthalic acid units, with a molar ratio of the terephthalic acid units to the adipic acid units being 0.5 to 2.0. The number of bonded points per unit mass of the three-dimensional random loop bonded structure is 150 to 500 / g. This configuration improves the cushioning and quietness of the three-dimensional network structure. The cushioning properties mean that the three-dimensional network structure has at least adequate compression recovery and compression hardness as a cushioning material. Each component of the three-dimensional network structure according to the embodiment is described in detail below.

[0010] The continuous filaments need only contain a thermoplastic resin composition, and may consist of a thermoplastic resin composition. The thermoplastic resin composition contained in the continuous filaments contains 70 to 100% by mass of polybutylene adipate terephthalate resin. This content is preferably 75 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, and particularly preferably 95 to 100% by mass. Cushioning properties can be improved by using a thermoplastic resin composition containing 70% or more by mass of polybutylene adipate terephthalate resin. Therefore, this content is 70% or more by mass, preferably 75% or more by mass, more preferably 80% or more by mass, even more preferably 90% or more by mass, and particularly preferably 95% or more by mass. On the other hand, this content may be 100% or less by mass, or even 99% or less by mass.

[0011] The polybutylene adipate terephthalate resin is preferably a copolymer of adipic acid, terephthalic acid, and butanediol. Therefore, the polybutylene adipate terephthalate resin preferably contains adipic acid units, terephthalic acid units, and butanediol units. Furthermore, the polybutylene adipate terephthalate resin is preferably a biodegradable resin. This is expected to provide a solution to waste disposal and microplastic problems. The adipic acid, terephthalic acid, and butanediol do not need to be copolymerized simultaneously; they may be copolymerized in multiple stages. Furthermore, an alkyl group, such as dimethyl terephthalate, may be bonded to the carboxyl group of the monomer before copolymerization. Furthermore, the polybutylene adipate terephthalate resin is preferably a thermoplastic resin.

[0012] The polybutylene adipate terephthalate resin contains adipic acid units and terephthalic acid units, and the molar ratio of terephthalic acid units to adipic acid units is 0.5 to 2.0. This molar ratio is preferably 0.6 to 1.8, more preferably 0.7 to 1.6, even more preferably 0.8 to 1.5, and particularly preferably 0.8 to 1.2. A molar ratio of 0.5 or greater facilitates improved compression recovery of the three-dimensional network structure. Therefore, this molar ratio is 0.5 or greater, preferably 0.6 or greater, more preferably 0.7 or greater, and even more preferably 0.8 or greater. On the other hand, a molar ratio of 2.0 or less improves quietness. Therefore, this molar ratio is 2.0 or less, preferably 1.8 or less, more preferably 1.6 or less, even more preferably 1.5 or less, and particularly preferably 1.2 or less.

[0013] The polybutylene adipate terephthalate resin preferably has a melting point of 100 to 170°C. The melting point is more preferably 110 to 160°C, even more preferably 115 to 150°C, and particularly preferably 120 to 145°C. A melting point of 100°C or higher facilitates improved compression recovery of the three-dimensional network structure. Therefore, the melting point is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 115°C or higher, and particularly preferably 120°C or higher. On the other hand, a melting point of 170°C or lower improves flexibility, making the three-dimensional network structure suitable for use as a cushioning material, etc. Therefore, the melting point is preferably 170°C or lower, more preferably 160°C or lower, even more preferably 150°C or lower, and particularly preferably 145°C or lower. Furthermore, the melting point of the thermoplastic resin composition constituting the continuous filaments is also preferably within this range.

[0014] The polybutylene adipate terephthalate resin preferably has a melt flow rate (MFR) of 3 to 60 g / 10 min, more preferably 4 to 50 g / 10 min, even more preferably 6 to 40 g / 10 min, and particularly preferably 10 to 30 g / 10 min. An MFR of 3 g / 10 min or higher can increase the melt viscosity and the fiber diameter of the continuous linear body. Therefore, the MFR is preferably 3 g / 10 min or higher, more preferably 4 g / 10 min or higher, even more preferably 6 g / 10 min or higher, and particularly preferably 10 g / 10 min or higher. On the other hand, an MFR of 60 g / 10 min or lower facilitates improved compression recovery. Therefore, the MFR is preferably 60 g / 10 min or lower, more preferably 50 g / 10 min or lower, even more preferably 40 g / 10 min or lower, and particularly preferably 30 g / 10 min or lower. It is also preferable that the MFR of the thermoplastic resin composition constituting the continuous linear body is within the above range. The MFR of the resin can be measured by the method described in the examples below.

[0015] When a commercially available resin is used as the polybutylene adipate terephthalate resin, if the resin has a low melt flow rate (MFR), the MFR of the resin can be increased by adding water to the resin to hydrolyze the resin during melt extrusion. On the other hand, if the resin has a high MFR, the MFR of the resin can be decreased by drying the resin before melt extrusion.

[0016] The weight-average molecular weight (g / mol) of the polybutylene adipate terephthalate resin is preferably 35,000 to 150,000, more preferably 37,000 to 140,000, and even more preferably 40,000 to 120,000. A weight-average molecular weight of 35,000 or more can improve compression recovery. Therefore, the weight-average molecular weight is preferably 35,000 or more, more preferably 37,000 or more, and even more preferably 40,000 or more. On the other hand, a weight-average molecular weight of 150,000 or less can improve flexibility. Therefore, the weight-average molecular weight is preferably 150,000 or less, more preferably 140,000 or less, and even more preferably 120,000 or less. It is also preferable that the weight-average molecular weight (g / mol) of the thermoplastic resin constituting the continuous linear body is within the above range. The weight-average molecular weight can be determined by gel permeation chromatography (GPC) or the like.

[0017] The total content of adipic acid units, terephthalic acid units, and butanediol units is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, even more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, and particularly preferably 99 to 100 mol%, relative to 100 mol% of all structural units in the polybutylene adipate terephthalate resin. That is, the total content is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, still more preferably 95 mol% or more, and particularly preferably 99 mol% or more, and preferably 100 mol% or less.

[0018] The thermoplastic resin composition of the continuous linear body may contain a biodegradable resin other than polybutylene adipate terephthalate resin. Preferred examples of such other biodegradable resins include polylactic acid, polylactic acid / polycaprolactone copolymer, polylactic acid / polyether copolymer, polyethylene terephthalate succinate, polybutylene succinate, polybutylene succinate adipate, polyglycolic acid, polycaprolactone, polyvinyl alcohol, and cellulose acetate. These may be used alone or in combination of two or more. For details, please refer to the positive list of GreenPla (biodegradable plastics) classification number A-1 of the Japan BioPlastics Association. The thermoplastic resin composition may also contain a resin other than biodegradable resin. Examples of such resins include thermoplastic resins such as polyolefin, polyurethane, and polyester. These may be used alone or in combination of two or more.

[0019] Petroleum-derived monomers may be used as monomers for synthesizing the thermoplastic resin composition. However, it is preferable to use biomass-derived monomers from the viewpoint of reducing the environmental load. As the biomass-derived monomers, for example, monomers listed in the positive list of classification number A (biomass plastics) of the Japan Bioplastics Association can be used.

[0020] The thermoplastic resin composition may contain a deodorizer, an antibacterial agent, an antifungal agent, an antimite agent, a deodorizer, an aromatic agent, a flame retardant, a moisture absorbing and releasing agent, an antioxidant, a lubricant, etc. These may be used alone or in combination of two or more kinds.

[0021] The thermoplastic resin composition may contain, in addition to the polybutylene adipate terephthalate resin, a resin containing a copolymerization component other than adipic acid, terephthalic acid, and butanediol as a constituent unit. Examples of the copolymerization component include a dicarboxylic acid other than terephthalic acid and adipic acid, a diol other than butanediol, a polyalkylene glycol, a modifier for the purpose of chain extension or terminal blocking, etc. These may be used alone or in combination of two or more types.

[0022] Other dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, etc. These may be used alone or in combination of two or more.

[0023] Examples of other diols include methanediol, ethanediol, propanediol, pentanediol, and hexanediol. Examples of polyalkylene glycols include polymethylene glycol, polyethylene glycol, polypropylene glycol, and polybutylene glycol (polytetramethylene glycol). These may be used alone or in combination of two or more.

[0024] Examples of the modifier include polyisocyanate compounds and glycol compounds. Examples of the polyisocyanate compound include diisocyanate compounds. Examples of the diisocyanate compound include hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, carbodiimide-modified MDI, and polymethylene phenyl polyisocyanate. These may be used alone or in combination of two or more.

[0025] The three-dimensional network structure according to the embodiment has a three-dimensional random loop bonded structure. The three-dimensional random loop bonded structure includes continuous filaments containing a thermoplastic resin composition. More specifically, the three-dimensional random loop bonded structure includes continuous filaments having a three-dimensional random loop shape, and preferably has portions where the continuous filaments intersect and bond. The three-dimensional random loop bonded structure is more likely to maintain its shape due to the continuous filaments having portions where they intersect and bond. Examples of bonding methods include adhesion, welding, fusion, or a combination thereof. The continuous filaments are preferably linear filaments having a continuous portion of 5 mm or more.

[0026] The number of bonded points per unit mass of the three-dimensional random loop bonded structure is 150 to 500 / g. The number of bonded points is preferably 160 to 400 / g, more preferably 170 to 350 / g, and particularly preferably 180 to 300 / g. By setting the number of bonded points to 150 / g or more, the continuous filaments are fixed at multiple points, thereby reducing the frequency of collisions between the continuous filaments and improving quietness. Therefore, the number of bonded points is 150 / g or more, preferably 160 / g, more preferably 170 / g or more, and particularly preferably 180 / g or more. On the other hand, by setting the number of bonded points to 500 / g or less, flexibility is more easily exhibited. Therefore, the number of bonded points is 500 / g or less, preferably 400 / g or less, more preferably 350 / g or less, and particularly preferably 300 / g or less.

[0027] The junctions refer to the intersections of the continuous linear bodies that are joined together. The number of junctions per unit mass (units / g) can be measured by the following method. First, the three-dimensional random loop junction structure is cut into rectangular parallelepiped pieces, and the number of junctions per unit volume in the resulting rectangular parallelepiped pieces (units / cm ３ ) and the apparent density of the individual pieces (g / cm ３ ) and divide the number of bonding points by the apparent density to determine the number of bonding points per unit mass (pieces / g). The number of bonding points can be determined by pulling two continuous filaments bonded at a bonding point to separate them, and counting the number of times they are peeled. In the case of a portion where three or more continuous filaments are bonded, that portion is counted as one bonding point. Note that, in the longitudinal direction or width direction of the three-dimensional random loop bonded structure, the apparent density is 0.005 g / cm ３ When there is a band-like difference in density as described above, it is preferable to cut the piece into a rectangular parallelepiped shape so that the boundary line between the dense and sparse areas is the midline in the longitudinal or width direction of the piece, and then determine the number of bonding points per unit mass (pieces / g).

[0028] The continuous filamentary body preferably has a fiber diameter of 0.20 to 0.80 mm. The fiber diameter is more preferably 0.25 to 0.77 mm, even more preferably 0.30 to 0.75 mm, and particularly preferably 0.40 to 0.73 mm. A fiber diameter of 0.20 mm or more exhibits compressive resistance and facilitates the function of the cushioning material. Therefore, the fiber diameter is preferably 0.20 mm or more, more preferably 0.25 mm or more, even more preferably 0.30 mm or more, and particularly preferably 0.40 mm or more. On the other hand, a fiber diameter of 0.80 mm or less improves flexibility and reduces the impact noise of the continuous filamentary body. Therefore, the fiber diameter is preferably 0.80 mm or less, more preferably 0.77 mm or less, even more preferably 0.75 mm or less, and particularly preferably 0.73 mm or less.

[0029] The fiber diameter can be measured by the following method. First, continuous filaments are collected in lengths of approximately 5 mm from 10 locations in a region within 30% of the thickness direction from the center point of the thickness of the three-dimensional network structure. In other words, continuous filaments are collected in lengths of approximately 5 mm from 10 locations in a region whose thickness direction length is 30% of the thickness of the three-dimensional network structure and which includes the thickness center point of the three-dimensional network structure at the center position in the thickness direction. The average fiber diameter of the collected samples is calculated, and this is used as the fiber diameter of the continuous filaments. The fiber diameter can be determined by imaging the side surface of the continuous filaments with an optical microscope, focusing at an appropriate magnification, and measuring the length of the continuous filaments in the direction perpendicular to the longitudinal direction in the obtained image. When imaging, the side surface of the continuous filaments is imaged in the direction in which the length perpendicular to the longitudinal direction of the continuous filaments is longest.

[0030] The continuous filament may be a composite filament of a sheath-core type, a side-by-side type, an eccentric sheath-core type, or the like. The composite filament may be a composite filament made by combining polybutylene adipate terephthalate resin with another thermoplastic resin. The cross-sectional shape of the continuous filament may be either a hollow cross-section or a solid cross-section, with a hollow cross-section being preferred from the viewpoint of weight reduction. The cross-sectional shape of the continuous filament may also be a round cross-section or an irregular cross-section.

[0031] The continuous filamentary body has a hollow cross section, and the hollow ratio of the hollow cross section is preferably 5 to 40%. The hollow ratio is more preferably 8 to 35%, even more preferably 10 to 30%, and particularly preferably 12 to 20%. A hollow ratio of 5% or more allows for weight reduction, which, for example, results in energy savings when used in automobile seats, and improves handling when used in futons and the like. Therefore, the hollow ratio is preferably 5% or more, more preferably 8% or more, even more preferably 10% or more, and particularly preferably 12% or more. On the other hand, a hollow ratio of 40% or less allows for reduced rigidity of the continuous filamentary body, thereby reducing high-pitched sounds generated by collisions between continuous filaments. Therefore, the hollow ratio is preferably 40% or less, more preferably 35% or less, even more preferably 30% or less, and particularly preferably 20% or less. The hollow ratio of the continuous filamentary body can be measured by the method described in the Examples below.

[0032] The hollow ratio can be measured, for example, by the following method. Ten continuous filaments are randomly taken out from the three-dimensional network structure. The continuous filaments are then cut into slices and placed on a slide glass in a state where they are standing in the fiber axial direction, and the fiber cross section is observed under an optical microscope. In this case, only continuous filaments having hollow fiber cross sections are selected, and the area (a) within the outer circumferential line of the fiber and the area (b) of the hollow portion are calculated, and the hollow ratio is calculated based on the following formula, and the average hollow ratio (n=10) of the selected continuous filaments having hollow cross sections is determined. Hollow ratio (%)=(b) / (a)×100

[0033] The continuous filaments preferably have a crystalline melting enthalpy of 16 to 30 J / g, more preferably 17 to 28 J / g, and even more preferably 18 to 26 J / g. Having a crystalline melting enthalpy of 16 J / g or more can improve the compression recovery and hardness of the three-dimensional network structure during compression. Therefore, the crystalline melting enthalpy is preferably 16 J / g or more, more preferably 17 J / g or more, and even more preferably 18 J / g or more. On the other hand, having a crystalline melting enthalpy of 30 J / g or less can improve the flexibility of the three-dimensional network structure and reduce the impact noise of the continuous filaments during compression and recovery. Therefore, the crystalline melting enthalpy is preferably 30 J / g or less, more preferably 28 J / g or less, and even more preferably 26 J / g or less.

[0034] The crystalline melting enthalpy (J / g) of the continuous linear body can be determined from the integrated value of the endothermic peak (melting peak) of a differential scanning calorimetry curve (DSC curve) measured using a differential scanning calorimeter with a sample mass of 2.0 mg±0.1 mg under a nitrogen atmosphere at a heating rate of 20°C / min. The integrated value can be determined by drawing a line connecting the start point and end point of the curve relating to the endothermic peak (melting peak), setting the point where the curve begins to deviate from the baseline on the low temperature side as the starting point and the point where the curve begins to contact the baseline on the high temperature side as the end point, and integrating the area enclosed by the line and the curve. An example of a differential scanning calorimetry curve (endothermic / exothermic curve) is shown in Figure 1. The dashed line on the high temperature side (right side) in Figure 1 is the line connecting the start point and end point of the endothermic peak (melting peak), and the area enclosed by the dashed line and the curve is the integration region where integration is performed.

[0035] The differential scanning calorimeter curve of the continuous linear body measured using a differential scanning calorimeter preferably has an endothermic peak with a minimum enthalpy in the range of 30°C to 70°C of 0.1 to 2.5 J / g. The enthalpy is more preferably 0.1 to 2.0 J / g, even more preferably 0.1 to 1.5 J / g, and particularly preferably 0.1 to 1.0 J / g. An enthalpy of 2.5 J / g or less improves hardness during compression, thereby reducing the feeling of bottoming out when used as a cushioning material or the like. Therefore, the enthalpy is preferably 2.5 J / g or less, more preferably 2.0 J / g or less, even more preferably 1.5 J / g or less, and particularly preferably 1.0 J / g or less. On the other hand, the lower limit of the enthalpy is not particularly limited and may be, for example, 0.1 J / g or more, or 0.2 J / g or more. The above "enthalpy of the endothermic peak having a minimum value in the range of 30°C to 70°C" may be referred to as "low-temperature phase enthalpy" in this specification.

[0036] The low-temperature phase enthalpy can be determined, for example, from the integrated value of the endothermic peak having a minimum value in the range of 30°C to 70°C in the differential scanning calorimetry curve (DSC curve). The integrated value can be determined by taking the point where the curve relating to the endothermic peak having the minimum value starts to deviate from the baseline on the low-temperature side as the starting point and the point where it starts to contact the baseline on the high-temperature side as the end point, drawing a straight line connecting the starting point and the end point, and integrating the portion enclosed by the straight line and the curve over the range of 30°C to 70°C. An example of a differential scanning calorimetry curve (endothermic curve) is shown in Figure 1. The dashed line on the low-temperature side (left side) in Figure 1 is the straight line connecting the starting point and the end point of the endothermic peak having the minimum value, and the portion enclosed by the dashed line and the curve is the integration region over which integration is performed.

[0037] 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 ３By satisfying the above, 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. Therefore, the apparent density is preferably 0.005 g / cm ３ More preferably, 0.01 g / cm ３ More preferably, 0.02 g / cm ３ More preferably, 0.03 g / cm ３ On the other hand, the apparent density is 0.30 g / cm ３ When the apparent density is 0.30 g / cm or less, the flexibility is improved and the material can be suitably used as a cushioning material, etc. Therefore, the apparent density is preferably 0.30 g / cm or less. ３ or less, more preferably 0.20 g / cm ３ More preferably, 0.15 g / cm or less ３ Particularly preferably 0.10 g / cm ３ The apparent density of the three-dimensional network structure can be measured by the method described in the examples below.

[0038] 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 22 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. Therefore, the thickness is preferably 10 mm or more, more preferably 15 mm or more, even more preferably 20 mm or more, and particularly preferably 22 mm or more. On the other hand, a thickness of 120 mm or less improves handleability. Therefore, the thickness is preferably 120 mm or less, more preferably 100 mm or less, even more preferably 80 mm or less, and particularly preferably 50 mm or less. The thickness of the three-dimensional network structure can be measured by the method described in the examples below.

[0039] The three-dimensional network structure preferably has a 40°C compression set of 1 to 25%. The 40°C compression set is more preferably 1 to 20%, even more preferably 1 to 18%, and particularly preferably 1 to 15%. Having a 40°C compression set of 25% or less can improve compression recovery. Therefore, the 40°C compression set is preferably 25% or less, more preferably 20% or less, even more preferably 18% or less, and particularly preferably 15% or less. On the other hand, the lower limit of the 40°C compression set may be 1% or more, or may be 5% or more. The 40°C compression set refers to the residual strain after applying a compressive load in an environment of 40°C, which is an example of an operating temperature environment. The 40°C compression set can be specifically measured by the method described in the Examples section below.

[0040] The three-dimensional network structure preferably has a 70°C compression set of 1 to 30%. The 70°C compression set is more preferably 1 to 27%, even more preferably 1 to 25%, and particularly preferably 1 to 23%. A 70°C compression set of 30% or less can improve compression recovery. Therefore, the 70°C compression set is preferably 30% or less, more preferably 27% or less, even more preferably 25% or less, and particularly preferably 23% or less. On the other hand, the lower limit of the 70°C compression set may be 1% or more, or even 5% or more. The 70°C compression set refers to the residual strain after applying a compressive load in an environment of 70°C. This serves as an indicator of compression recovery when used in a high-temperature environment. For example, when a three-dimensional network structure is placed in a car, or when bedding including the three-dimensional network structure is used in combination with a heating element such as a hot water bottle or an electric blanket, the three-dimensional network structure will become hot. The 70°C compression set can be measured specifically by the method described in the Examples below.

[0041] The three-dimensional network structure preferably has a 40°C compression set of 1 to 15% and a 70°C compression set of 1 to 30%, thereby improving compression recovery at the ambient temperature and in a high-temperature environment.

[0042] The hardness when the three-dimensional network structure is compressed 25% in the thickness direction (hereinafter referred to as "hardness at 25% compression") is preferably 5.0 to 100 N / φ50 mm, more preferably 6.0 to 80 N / φ50 mm, even more preferably 7.0 to 60 N / φ50 mm, and particularly preferably 7.0 to 30 N / φ50 mm. When the three-dimensional network structure has a hardness at 25% compression of 5.0 N / φ50 mm or more, the feeling of bottoming out can be reduced when the three-dimensional network structure is used as a cushioning material, etc. Therefore, the hardness at 25% compression is preferably 5.0 N / φ50 mm or more, more preferably 6.0 N / φ50 mm or more, even more preferably 7.0 N / φ50 mm or more, and particularly preferably 7.0 N / φ50 mm or more. On the other hand, when the hardness at 25% compression is 100 N / φ50 mm or less, flexibility can be improved. Therefore, the hardness at 25% compression is preferably 100 N / φ50 mm or less, more preferably 80 N / φ50 mm or less, even more preferably 60 N / φ50 mm or less, and particularly preferably 30 N / φ50 mm or less. The hardness at 25% compression can be measured by the method described in the examples below.

[0043] The three-dimensional network structure preferably does not contain a bonding promoter. Specifically, the continuous linear body preferably does not contain a bonding promoter. This makes it easier to prevent excessive hardening due to excessive bonding within the three-dimensional network structure caused by the bonding promoter. It also makes it easier to prevent a decrease in the density of the three-dimensional network structure due to an excessive increase in the bonding area per contact point. Examples of bonding promoter resins include polycaprolactone, polybutylene succinate, polybutylene sebacate terephthalate, and polybutylene azelate terephthalate.

[0044] The three-dimensional network structure may contain a colorant. Specifically, the continuous filament may contain a colorant. The colorant may contain a pigment, a dye, or both. The colorant may be incorporated into the resin before melt spinning, or the colorant may be coated on the continuous filament by immersion or application after the three-dimensional network structure is formed.

[0045] The three-dimensional netted structure is preferably used for cushions. The cushion may be any cushion that has elasticity to support an object or that reduces impact. Examples of cushions include cushions used in bedding such as office chairs, furniture, sofas, and beds, vehicle seats such as trains, automobiles, motorcycles, child seats, and strollers, and cushions used for impact-absorbing mats such as floor mats and collision and pinch prevention members.

[0046] The three-dimensional network structure may have a multilayer structure. Examples of the multilayer structure include a structure in which the surface layer and the back layer are made of continuous filaments with different finenesses, a structure in which the surface layer and the back layer are made of structures with different apparent densities, or a structure in which long-fiber nonwoven fabrics, short-fiber nonwoven fabrics, etc. are laminated together to form a multilayer structure. Examples of the multilayer structure include a method in which multiple layers are laminated and melt-bonded by heating, a method in which multiple layers are bonded together with an adhesive, and a method in which multiple layers are restrained by sewing or a band, etc.

[0047] The shape of the three-dimensional network structure is not particularly limited. Examples include 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.

[0048] The method for producing a three-dimensional network structure preferably includes an extrusion step of extruding a molten thermoplastic resin composition from a nozzle, a molding step of molding a continuous filament composed of the thermoplastic resin composition extruded from the nozzle into a three-dimensional network structure, and a heat treatment step of heat treating the three-dimensional network structure.

[0049] Examples of the extrusion and molding processes include the following methods. First, a thermoplastic resin composition containing a polybutylene adipate terephthalate resin is dispensed into the nozzle orifices through a multi-row nozzle having multiple orifices, and extruded downward from the nozzle at a spinning temperature of at least 20°C above the melting point of the resin and less than 180°C above the melting point of the resin. Next, the continuous filaments are brought into contact with each other in a molten state and fused to form a three-dimensional network structure, which is then sandwiched between a take-up conveyor net and cooled with cooling water in a water tank. The solidified three-dimensional network structure is then drawn out and drained or dried to obtain a three-dimensional network structure with smoothed surfaces on both or one side. For details of these spinning and cooling processes, see, for example, Japanese Patent Laid-Open No. 7-68061. To smooth only one side, the continuous filaments are extruded onto an inclined take-up net, and the continuous filaments are brought into contact with each other in a molten state and fused to each other. In this case, while the three-dimensional network structure is being formed, only the take-up net surface is cooled while relaxing its shape. The obtained three-dimensional network structure is then subjected to a heat treatment. The drying treatment of the three-dimensional network structure may also be used as the heat treatment.

[0050] Water may be added to the thermoplastic resin composition before it is discharged from the nozzle. Adding water to the thermoplastic resin composition can promote hydrolysis of the thermoplastic resin during the process of producing a three-dimensional network structure, thereby improving the flexibility of the resin. The amount of water added is preferably 2.0% by mass or less based on the thermoplastic resin composition. This can prevent excessive decomposition of the thermoplastic resin during the process of producing a three-dimensional network structure. As a result, compression recovery after heat compression is more likely to be improved. The method for adding water to the thermoplastic resin composition is not particularly limited. For example, the thermoplastic resin composition may be vacuum-dried at 100°C for 12 hours or more to bone dryness before the resin is discharged from the nozzle, and then a predetermined amount of pure water may be added to 100% by mass of the bone-dried thermoplastic resin composition.

[0051] The single-hole discharge rate of the thermoplastic resin composition from the nozzle is preferably 1.0 to 6.0 g / min, more preferably 2.0 to 5.0 g / min. By setting the single-hole discharge rate to 1.0 g / min or more, the crystal melting enthalpy can be improved. On the other hand, by setting the single-hole discharge rate to 6.0 g / min or less, the low-temperature phase enthalpy can be reduced.

[0052] The take-up speed of the take-up conveyor is preferably 0.5 to 2.5 m / min, more preferably 0.9 to 2.3 m / min. By setting the take-up speed to 0.5 m / min or more, the crystalline melting enthalpy can be improved. On the other hand, by setting the take-up speed to 2.5 m / min or less, the low-temperature phase enthalpy can be reduced.

[0053] The distance from the nozzle surface to the surface of the cooling water in the water tank is preferably 25 to 40 cm, more preferably 25 to 35 cm. A distance of 25 cm or more can improve the crystal melting enthalpy. On the other hand, a distance of 40 cm or less can reduce the low-temperature phase enthalpy. Furthermore, a distance of 25 to 40 cm can easily control the number of junctions in the continuous filamentous body within a desired range. This also makes it easier to control the hollow ratio within a preferred range.

[0054] Cooling after melt molding is preferably performed using cooling water. Polybutylene adipate terephthalate resin may undergo molding shrinkage before being cooled and solidified. Therefore, a three-dimensional network structure with a width and thickness that takes molding shrinkage into consideration may be formed. For example, molding shrinkage can be reduced by lowering the melt solidification temperature. Therefore, the temperature of the cooling water in the water tank is preferably 20°C or less, more preferably 15°C or less, and particularly preferably 10°C or less. The temperature may be 1°C or more, or may be 5°C or more. Furthermore, the cooling time using cooling water is preferably 30 seconds or more. On the other hand, the cooling time may be 120 seconds or less. Cooling and solidification is preferably performed in a water tank.

[0055] The heat treatment may be carried out using a commercially available hot air drying oven or in a warm water bath. The heat treatment temperature is preferably 50°C or higher. This can increase the crystalline fusion enthalpy. The heat treatment temperature is more preferably 60°C or higher, and even more preferably 70°C or higher. On the other hand, the heat treatment temperature is preferably 150°C or lower. This can reduce resin decomposition. The heat treatment temperature is more preferably 130°C or lower, and even more preferably 120°C or lower. The heat treatment may be carried out in multiple steps at different temperatures.

[0056] The heat treatment may be a one-stage heat treatment or a two-stage heat treatment. In a two-stage heat treatment, for example, the first stage heat treatment may be performed at a temperature below the melting point of the thermoplastic resin composition constituting the continuous linear body, followed by the second stage heat treatment at a temperature lower than the heat treatment temperature of the first stage heat treatment. The heat treatment temperature in the first stage heat treatment step is preferably 20°C or more lower than the melting point of the thermoplastic resin composition, more preferably 25°C or more lower, and even more preferably 30°C or more lower. The heat treatment temperature in the second stage heat treatment step is preferably 15°C or more lower, more preferably 20°C or more lower than the heat treatment temperature of the first stage heat treatment step. This can improve compression recovery at ambient temperatures and high-temperature environments.

[0057] When carrying out the heat treatment, the melting point of the thermoplastic resin composition constituting the continuous filaments is preferably 100 to 170°C. The melting point is more preferably 110 to 160°C, even more preferably 115 to 150°C, and particularly preferably 120 to 145°C. When the melting point is 100°C or higher, the heat treatment can be carried out within a suitable temperature range. On the other hand, when the melting point is 170°C or lower, flexibility is improved, and the three-dimensional network structure can be suitably used as a cushioning material, etc.

[0058] The heat treatment time in each heat treatment step is preferably 1 minute or more. This allows the crystalline melting enthalpy to be increased. The heat treatment time is more preferably 5 minutes or more, even more preferably 10 minutes or more, and particularly preferably 15 minutes or more. On the other hand, the upper limit of the heat treatment time in each heat treatment step is preferably 60 minutes or less, more preferably 50 minutes or less. This allows the reduction of yellowing, odor, molecular weight reduction, etc. of the polybutylene adipate terephthalate resin due to decomposition or deterioration of the polymer during heat treatment. Furthermore, productivity can also be improved. Note that the heat treatment time means the heat treatment time in each stage in a two-stage heat treatment step.

[0059] The two-stage heat treatment process may be carried out continuously in separate hot air ovens, or may be carried out batchwise with an interval of several hours or several days. For example, the heat treatment may be carried out using a continuous dryer, or the three-dimensional network structure may be returned to room temperature after the first-stage heat treatment process using a batch-type drying oven, and then the second-stage heat treatment process may be carried out.

[0060] The three-dimensional network structure cooled and solidified in a water bath is preferably held at a temperature of 20 to 50°C for 1 minute or more before heat treatment. The holding time is more preferably 10 minutes or more, and even more preferably 30 minutes or more. Alternatively, the holding time may be 60 minutes or less. During heat treatment, the thickness of the three-dimensional network structure may change due to its own weight. However, by holding the structure at a temperature of 20 to 50°C after cooling and solidifying, it is possible to reduce changes in the thickness of the three-dimensional network structure due to heat treatment. For example, after cooling and solidifying in a water bath, a continuous dryer may be used to perform heat treatment by holding the structure at a low temperature in the first half of a hot air oven and then raising the temperature in the second half of the hot air oven.

[0061] The moisture content of the three-dimensional network structure before heat treatment is preferably 15% or less, more preferably 12% or less, and particularly preferably 10% or less. The moisture content may be 1% or more, or may be 2% or more. By controlling the moisture content within this range, hydrolysis of the resin can be reduced. The moisture content is calculated using the following formula. In the formula, the mass of the three-dimensional network structure after vacuum drying is the mass after two hours of vacuum drying at 90°C. Moisture content (%) of three-dimensional network structure = ((A - B) / A) x 100 A: Mass of three-dimensional network structure before vacuum drying B: Mass of three-dimensional network structure after vacuum drying

[0062] At any stage from the production process to the molding process of the thermoplastic resin composition used as the raw material for the three-dimensional network structure, additives capable of imparting functions such as deodorizing, antibacterial, antifungal, antimite, deodorizing, aromatic, flame retardant, and moisture absorbing and releasing properties may be added to the thermoplastic resin composition. Furthermore, when producing the three-dimensional network structure, the raw material polybutylene adipate terephthalate resin may contain function-imparting agents such as antioxidants and lubricants. These may be used alone or in combination of two or more. It is preferable to adjust the content of various function-imparting agents by kneading them into the resin during melt extrusion depending on the color tone and quality of the resin after melting.

[0063] Examples of antioxidants include phenol-based antioxidants, phosphite-based antioxidants, thioether-based antioxidants, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, N-H hindered amine-based light stabilizers, and N-CH ３ Examples of the antioxidant include a hindered amine-based light stabilizer. These may be used alone or in combination of two or more. It is preferred that at least one of the antioxidants is contained in the thermoplastic resin composition.

[0064] Examples of phenolic antioxidants include 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-butylidenebis(6-tert-butyl-m-cresol), 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], Sumilizer (registered trademark) AG 80, and 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene. These may be used alone or in combination of two or more.

[0065] Examples of phosphite antioxidants include 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 2,4,8,10-tetrakis(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]-12H-dibenzo[d,g]"1,3,2"dioxaphosphocin, tris(2,4-di-tert-butylphenyl) phosphite, tris(4-nonylphenyl) phosphite, and 4,4'-isopropylidenediphenol C12-15 alcohol. phosphite, diphenyl (2-ethylhexyl) phosphite, diphenyl isodecyl phosphite, triisodecyl phosphite, triphenyl phosphite, etc. These may be used alone or in combination of two or more.

[0066] Examples of thioether antioxidants include 2,2-bis[3-(dodecylthio)propionic acid]2,2-bis[3-(dodecylthio)-1-oxopropyloxymethyl]-1,3-propanediyl, ditridecyl 3,3'-thiobispropionate, etc. These may be used alone or in combination of two or more.

[0067] In order to prevent thermal degradation of the thermoplastic resin, a mixture of a phenolic antioxidant and a phosphite antioxidant may be used. When these two types of antioxidants are used, the total content of the two types of antioxidants is preferably 0.05% by mass or more and 1.0% by mass or less, based on 100% by mass of the thermoplastic resin composition.

[0068] Examples of lubricants include hydrocarbon waxes, higher alcohol waxes, amide waxes, ester waxes, and metal soap waxes. These may be used alone or in combination of two or more. If necessary, it is preferable to contain a lubricant in an amount of 0.5% by mass or less relative to 100% by mass of the thermoplastic resin composition. The lubricant content is preferably 0.1% by mass or more.

[0069] This application claims the benefit of priority based on Japanese Patent Application No. 2023-166465, filed on September 27, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-166465, filed on September 27, 2023, are incorporated herein by reference.

[0070] The present invention will be described 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 within the technical scope of the present invention.

[0071] The characteristic values ​​of the three-dimensional network structures of Examples 1 to 6 and Comparative Examples 1 to 4 were measured according to the following methods. The sample sizes were standardized as described below, but when there were insufficient samples, measurements were performed using samples of the largest possible size.

[0072] (1) Fiber Diameter The three-dimensional network structure was cut into pieces of 10 cm × 10 cm length and width, and continuous filaments of approximately 5 mm length were collected from 10 locations on each piece. Next, the diameters of the collected continuous filaments were measured using an optical microscope, with the focus adjusted to the locations where the fiber diameters were to be measured, and the average value of the fiber diameters at the 10 locations (n ​​= 10) was calculated.

[0073] (2) Hollowness Ten continuous filaments were randomly taken out from the three-dimensional network structure. The continuous filaments were then cut into slices and placed on a slide glass in a state where they were standing in the fiber axial direction, and the fiber cross sections were observed under an optical microscope. In this case, only continuous filaments with hollow fiber cross sections were selected, and the area (a) within the outer periphery of the fiber and the area (b) of the hollow portion were calculated, respectively. The hollowness was calculated based on the following formula, and the average hollowness (n = 10) of the selected continuous filaments with hollow cross sections was determined. Note that all of the continuous filaments taken out from the three-dimensional network structures of the Examples and Comparative Examples had hollow portions. Hollowness (%) = (b) / (a) × 100

[0074] (3) Thickness and apparent density The three-dimensional network structure was cut into a size of 10 cm x 10 cm in the length and width directions, and the obtained sample was left to stand for 24 hours in an environment of 23°C ± 2°C without load. Thereafter, the height of one point at the center was measured using a test piece thickness measuring instrument (FD-80N type, manufactured by Kobunshi Keiki Co., Ltd.), and this height of the sample was taken as the thickness of the three-dimensional network structure. Furthermore, the sample was placed on an electronic balance and the weight of the sample was measured. The height of the sample and the area (100 cm) were used to measure the thickness of the three-dimensional network structure. ２ The apparent density was calculated by dividing the weight of the sample by the volume. This operation was repeated three times to calculate the average values ​​(n=3) of the thickness and apparent density of the three-dimensional network structure.

[0075] (4) Molar ratio of terephthalic acid units to adipic acid units of polybutylene adipate terephthalate resin The molar ratio of terephthalic acid units to adipic acid units of polybutylene adipate terephthalate resin is １Measurement was performed by H-NMR. The measurement device used was a BRUKER AVANCE-NEO600 NMR device, and the measurement was performed as follows. First, 10 to 15 mg of sample was dissolved in deuterated chloroform / trifluoroacetic acid = 85 / 15 (volume ratio), and the solution was then filled into an NMR tube and measured. Deuterated chloroform was used as the lock solvent, with a waiting time of 1 second, a data acquisition time of 4 seconds, and an accumulation count of 64. When the chloroform peak was set to 7.28 ppm, the adipic acid peak was detected at 2.45 ppm, and the terephthalic acid peak was detected at 8.15 ppm. The peak integral value of adipic acid was designated A, and the peak integral value of terephthalic acid was designated B. These were then applied to the following formula to determine the molar ratio of terephthalic acid units to adipic acid units in the polybutylene adipate terephthalate resin. Molar ratio = ((B / 4) ÷ (A / 4)) × 100

[0076] (5) Melting point (Tm) A sample was taken from the three-dimensional network structure and weighed to a mass of 2.0 mg ± 0.1 mg. Next, using a differential scanning calorimeter (TA Instruments, Discovery DSC25) under a nitrogen atmosphere, the endothermic peak (melting peak) temperature was determined from the endothermic / heat-exothermic curve measured at a heating rate of 20 ° C. / min. This operation was performed three times, and the average melting point (n = 3) was calculated.

[0077] (6) Crystalline Melting Enthalpy A sample was taken from the three-dimensional network structure and weighed to a mass of 2.0 mg ± 0.1 mg. Next, using a differential scanning calorimeter (TA Instruments, Discovery DSC25) under a nitrogen atmosphere, the endothermic curve was measured at a heating rate of 20 ° C. / min. The crystalline melting enthalpy (J / g) was calculated from the integrated value of the endothermic peak (melting peak). The integrated value of the endothermic peak (melting peak) was determined by taking the point where the curve relating to the endothermic peak (melting peak) begins to depart from the low-temperature baseline as the starting point and the point where it begins to contact the high-temperature baseline as the end point, drawing a straight line connecting the starting point and the end point, and integrating the area enclosed by the straight line and the curve. This operation was performed three times to determine the average value (n = 3) of the crystalline melting enthalpy. The starting point was also designated as the melting onset temperature (° C.).

[0078] (7) Low-temperature phase enthalpy In the endothermic curve (6) above, the enthalpy of the endothermic peak having the minimum value in the range of 30°C to 70°C was determined and defined as the low-temperature phase enthalpy. The integrated value of the endothermic peak in the low-temperature phase region was determined by setting the point where the curve relating to the endothermic peak in the low-temperature phase region begins to deviate from the baseline on the low-temperature side as the starting point and the point where it begins to contact the baseline on the high-temperature side as the end point, drawing a line connecting the starting point and the end point, and integrating the area enclosed by the line and the curve over the range of 30°C to 70°C. This operation was performed three times to determine the average value of the low-temperature phase enthalpy (n = 3). The starting point was defined as the low-temperature phase onset temperature (°C). An example of experimental data is shown in Figure 1.

[0079] (8) Melt Flow Rate (MFR) The three-dimensional network structure was finely chopped to prepare a sample. The sample was vacuum dried at 80°C for 2 hours or more, and then the melt flow rate (MFR) was measured quickly so as to minimize the inclusion of moisture in the air. The melt flow was measured in accordance with ISO 1133 using a Melt Indexer F-F01 machine manufactured by Toyo Seiki Seisakusho. The measurement temperature was 190°C and the load was 2.16 kgf. This operation was performed three times to determine the average melt flow rate (n = 3).

[0080] (9) Weight-average molecular weight A sample was taken from the three-dimensional network structure, weighed to a sample mass of 0.2 mg, and dissolved in 0.4 ml of chloroform to prepare a sample solution. The sample was filtered through a 0.2 μm membrane filter, and the obtained sample solution was subjected to GPC analysis under the following conditions, and the weight-average molecular weight was calculated in terms of standard polystyrene. Apparatus: TOSOH HLC-8320GPC Column: TSKgel Super HM-H × 2 + TSKgel Super H2000 (TOSOH) Solvent: Chloroform Flow rate: 0.6 ml / min Concentration: 0.05% Injection volume: 20 μL Temperature: 40°C Detector: RI

[0081] (10) 40°C Compression Set The three-dimensional network structure was cut into a size of 10 cm x 10 cm in the lengthwise and widthwise directions. Next, the thickness (c) of the obtained sample before treatment was measured using the method described in (3) above. The sample whose thickness had been measured was clamped in a jig capable of maintaining a 50% compressed state, and the sample in the 50% compressed state was placed in a dryer controlled at 40°C and left for 22 hours. Thereafter, the sample was removed, cooled, and the compression load was removed. After leaving the sample for 30 minutes, the thickness (d) was calculated. These thicknesses were entered into the following formula to calculate the 40°C compression set. This operation was performed three times to calculate the average value (n = 3) of the 40°C compression set. 40°C Compression Set = ((c) - (d)) / (c) x 100

[0082] (11) 70°C Compression Set The three-dimensional network structure was cut into a size of 10 cm x 10 cm in the lengthwise and widthwise directions. Next, the thickness (c) of the obtained sample before treatment was measured using the method described in (3) above. The sample whose thickness had been measured was clamped in a jig capable of maintaining a 50% compressed state, and the sample in the 50% compressed state was placed in a dryer controlled at 70°C and left for 22 hours. Thereafter, the sample was removed, cooled, and the compression load was removed. After leaving the sample for 30 minutes, the thickness (e) was calculated. These thicknesses were entered into the following formula to calculate the 70°C compression set. This operation was performed three times to calculate the average value (n = 3) of the 70°C compression set. 70°C Compression Set = ((c) - (e)) / (c) x 100

[0083] (12) Hardness at 25% Compression The three-dimensional network structure was cut into a size of 10 cm x 10 cm in the length and width directions, and the resulting sample was left unloaded in an environment of 23 ° C ± 2 ° C for 24 hours. Then, in an environment of 23 ° C ± 2 ° C, measurements were performed in accordance with ISO 2439 (2008) E method using an autograph AG-X plus manufactured by Shimadzu Corporation. Specifically, a pressure plate with a diameter (φ) of 50 mm was placed at the center of the sample, and the thickness when the load reached 0.5 N was measured, which was defined as the initial thickness. The position of the pressure plate at this time was defined as the zero point, and pre-compression was performed once to 75% of the initial thickness at a speed of 100 mm / min. The pressure plate was then returned to the zero point at the same speed, and the sample was left as is for 4 minutes. Thereafter, the sample was immediately compressed to 25% of the initial thickness at a speed of 100 mm / min. The load at this time was measured, and the weight was defined as the hardness at 25% compression (N / φ50 mm). This operation was performed three times, and the average value of the hardness at 25% compression (n=3) was determined. (13) Sound-deadening property The three-dimensional network structure was cut into pieces measuring 10 cm x 10 cm in the length and width directions, and 30 panelists (5 men aged 20 to 39, 5 women aged 20 to 39, 5 men aged 40 to 59, 5 women aged 40 to 59, 5 men aged 60 to 80, and 5 women aged 60 to 80) pressed the obtained samples with their palms, and the sound generated from the network structure was qualitatively evaluated sensorily using the following four criteria. The most common evaluation out of the four was used to evaluate the sound-deadening property. Not audible; ◎ Weakly audible; ○ Moderately audible; △ Strongly audible; × (14) Number of bonding points per unit weight The number of bonding points per unit weight (unit: pieces / g) was determined by the following method. First, the three-dimensional network structure was cut into a rectangular parallelepiped shape with a size of 5 cm in the longitudinal direction and 5 cm in the width direction. At this time, the three-dimensional network structure was cut into a rectangular parallelepiped shape so as to include two surface layers facing each other in the thickness direction of the three-dimensional network structure, but not to include the edge portions. In the obtained rectangular parallelepiped pieces, the number of bonding points per unit volume in the pieces (bonding points / cm ３ ) and the apparent density of the individual pieces (g / cm ３ The number of bonding points per unit mass (number / g) was calculated by dividing the number of bonding points by the apparent density. The number of bonding points was calculated by pulling two continuous filaments bonded at a bonding point to separate them, and counting the number of times they were peeled.

[0084] Polybutylene adipate terephthalate resin was synthesized by the following method. <Resin A> 1.5 mol of 1,4-butanediol, 0.5 mol of adipic acid, and 0.5 mol of dimethyl terephthalate were mixed in a reaction vessel equipped with a stirrer, thermometer, and distillation condenser. Next, 300 ppm of tetrabutyl titanate (Aldrich) was added as a titanium catalyst to the resulting mixture. Subsequently, transesterification and esterification reactions were carried out at 220°C under atmospheric pressure for 2 hours to prepare a prepolymer. The resulting prepolymer was heated to 240°C and then subjected to a polycondensation reaction at 0.1 mmHg for 2 hours. The resulting Resin A was cooled and then cut with a pellet cutter to produce pellets.

[0085] <Resin B> Resin B was produced in the same manner as Resin A, except that the amounts of adipic acid and dimethyl terephthalate were changed to 0.40 mol and 0.60 mol, respectively. The resulting Resin B was cooled and then cut with a pellet cutter to produce pellets.

[0086] <Resin C> Resin C was produced in the same manner as Resin A, except that the amounts of adipic acid and dimethyl terephthalate were changed to 0.53 mol and 0.47 mol, respectively. The resulting Resin C was cooled and then cut with a pellet cutter to produce pellets.

[0087] <Resin D> Resin D was produced in the same manner as Resin A, except that the amounts of adipic acid and dimethyl terephthalate were changed to 0.3 mol and 0.7 mol, respectively. The resulting Resin D was cooled and then cut with a pellet cutter to produce pellets.

[0088] [Example 1] Using Resin B as a raw material, the molten resin was extruded downward from a nozzle at a spinning temperature of 240° C. and a single-hole extrusion rate of 4.2 g / min. The nozzle used had an effective nozzle surface of 104 mm in width and 55 mm in thickness, and had orifices with an outer diameter of 5.0 mm, an inner diameter of 4.4 mm, and a triple-bridge hollow-forming cross section formed in a staggered arrangement with a hole pitch of 9 mm.

[0089] A water tank was placed so that the cooling water level was 34 cm below the nozzle surface of the nozzle for discharging the molten resin, the water temperature was 12°C, and a pair of take-up conveyors were placed in the water tank perpendicular to the water surface so that a portion of them was above the water surface. Each of the pair of take-up conveyors had a 20 cm wide stainless steel endless net, and the conveyors were placed parallel to the width direction of the nozzle surface. The opening width of the space between the pair of endless nets was 50 mm, and a pair of aluminum plates were placed at an angle of 90 degrees to the pair of endless nets to form the side portions, and water was flowed at a rate of 1.0 L / min to form the side portions.

[0090] The molten resin was extruded linearly into the opening between the conveyor nets, i.e., the space surrounded by the pair of conveyor nets and the pair of aluminum plates, and the continuous linear body was dropped to form a meandering loop, fusing the contact portions to form a three-dimensional network structure. Both sides of the molten three-dimensional network structure were sandwiched between take-up conveyors and drawn into cooling water at a take-up speed of 2.2 m / min to solidify. This flattened both sides in the thickness direction and the lateral direction. Next, it was pulled out of the cooling water, cut to a predetermined size, and left to stand in a space at 25 °C for 1 hour. It was then heat-treated with 80 °C hot air for 20 minutes to obtain a three-dimensional network structure with a width of 100 mm. The cross-sectional shape of the continuous linear body constituting the obtained three-dimensional network structure was hollow.

[0091] [Example 2] A three-dimensional network structure was obtained in the same manner as in Example 1, except that the spinning temperature was 220°C, the single-hole discharge rate was 3.9 g / min, the distance from the nozzle surface to the surface of the cooling water in the water tank was 31 cm, and the take-up speed was 2.03 m / min.

[0092] Example 3 A three-dimensional network structure was obtained in the same manner as in Example 1, except that after spinning, the mixture was heat-treated with hot air at 120°C for 20 minutes and then with hot air at 80°C for 20 minutes.

[0093] Example 4 A three-dimensional network structure was obtained in the same manner as in Example 1, except that resin C was used as a raw material, and the molten resin was extruded downward from a nozzle at a spinning temperature of 190°C and a single-hole output rate of 1.1 g / min. The nozzle had an effective nozzle surface measuring 104 mm in width and 31 mm in thickness, and had orifices with an outer diameter of 3.0 mm, an inner diameter of 2.6 mm, and a triple-bridge hollow-forming cross section formed in a staggered arrangement with a hole-to-hole pitch of 6 mm. The conveyor was arranged parallel to the width direction of the nozzle surface, the distance from the nozzle surface to the surface of the cooling water in the water tank was 25 cm, the opening width of the openings representing the spaces between the endless nets was 30 mm, the take-up speed was 0.97 m / min, and the spinning was followed by a heat treatment with hot air at 90°C for 20 minutes and then with hot air at 50°C for 20 minutes.

[0094] Example 5 A three-dimensional network structure was obtained in the same manner as in Example 4, except that the molten resin was discharged downward from the nozzle at a single-hole discharge rate of 1.5 g / min.

[0095] Example 6 A three-dimensional network structure was obtained in the same manner as in Example 1, except that Resin A was used as the raw material, the spinning temperature was 220°C, the molten resin was discharged downward from the nozzle at a single-hole discharge rate of 2.5 g / min, the distance from the nozzle surface to the surface of the cooling water in the water tank was 32 cm, and the take-up speed was 2.02 m / min.

[0096] Comparative Example 1 A three-dimensional network structure was obtained in the same manner as in Example 1, except that the spinning temperature was set to 220°C, the molten resin was discharged downward from the nozzle at a single-hole discharge rate of 1.5 g / min, the distance from the nozzle surface to the surface of the cooling water in the water tank was set to 20 cm, and the take-up speed was set to 1.00 m / min.

[0097] Comparative Example 2 A three-dimensional network structure was obtained in the same manner as in Example 6, except that the spinning temperature was 210°C, the molten resin was discharged downward from the nozzle at a single-hole discharge rate of 1.5 g / min, the distance from the nozzle surface to the surface of the cooling water in the water tank was 20 cm, and the take-up speed was 1.22 m / min.

[0098] Comparative Example 3 A three-dimensional network structure was obtained in the same manner as in Example 1, except that the spinning temperature was 210°C, the molten resin was discharged downward from the nozzle at a single-hole discharge rate of 2.5 g / min, the distance from the nozzle surface to the surface of the cooling water in the water tank was 23 cm, the take-up speed was 1.75 m / min, and heat treatment was performed with 90°C hot air for 20 minutes after spinning.

[0099] Comparative Example 4 A three-dimensional network structure was obtained in the same manner as in Example 5, except that Resin D was used as the raw material, the spinning temperature was 240°C, the distance from the nozzle surface to the surface of the cooling water in the water tank was 35 cm, the take-up speed was 1.22 m / min, and heat treatment was performed with 100°C hot air for 20 minutes after spinning.

[0100] The production conditions and the properties of the resulting three-dimensional network structures in Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Table 1. In Table 1, the numerical values ​​of properties evaluated multiple times are average values.

[0101]

Claims

1. A three-dimensional network structure having a three-dimensional random loop bonding structure, wherein the three-dimensional random loop bonding structure comprises a continuous linear body containing a thermoplastic resin composition, the thermoplastic resin composition comprises 70 to 100 mass% of a polybutylene adipate terephthalate resin, the polybutylene adipate terephthalate resin comprises adipic acid units and terephthalic acid units, the molar ratio of the terephthalic acid units to the adipic acid units being 0.5 to 2.0, and the number of bonding points per unit mass of the three-dimensional random loop bonding structure is 150 to 500 / g.

2. The three-dimensional mesh structure according to claim 1, wherein the continuous filaments have a fiber diameter of 0.20 to 0.80 mm.

3. The three-dimensional network structure according to claim 1 or 2, wherein the differential scanning calorimeter curve of the continuous linear body is measured, and the enthalpy of the endothermic peak having a minimum value in the range of 30°C to 70°C is 0.1 to 2.5 J / g.

4. The three-dimensional mesh structure according to claim 1 or 2, wherein the continuous filament has a hollow cross section, and the hollow cross section has a void ratio of 5 to 40%.

5. The three-dimensional mesh structure according to claim 1 or 2, wherein the polybutylene adipate terephthalate resin has a melting point of 100 to 170°C.

6. Apparent density is 0.005 to 0.30 g / cm ３ 3. The three-dimensional mesh structure according to claim 1 or 2, 7. The three-dimensional mesh structure according to claim 1 or 2, wherein the three-dimensional mesh structure has a compression set at 40° C. of 1 to 25%.

8. The three-dimensional mesh structure according to claim 1 or 2, wherein the three-dimensional mesh structure has a compression set at 40° C. of 1 to 15% and a compression set at 70° C. of 1 to 30%.

9. The three-dimensional mesh structure according to claim 1 or 2, which has a crystal melting enthalpy of 16 to 30 J / g.

10. The three-dimensional network structure according to claim 1 or 2, wherein the molar ratio of the terephthalic acid units to the adipic acid units is 0.7 to 1.6.

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