Biodegradable three-dimensional network structure

Abstract

A biodegradable three-dimensional network structure is provided, exhibiting excellent compression durability and compression recovery after heat compression. A biodegradable three-dimensional network structure is characterized by an apparent density of 0.005 g / cm³. 3 ~0.30g / cm 3 The thickness is 10mm to 100mm, and it contains linear fibers with a fiber diameter of 0.2mm to 2.0mm and a crystallization melting enthalpy of 16J / g or more, and it contains polybutylene adipate terephthalate resin with a weight average molecular weight of 35,000 or more.

Description

Technical Field

[0001] This invention relates to biodegradable three-dimensional network structures. Background Technology

[0002] Various biodegradable three-dimensional mesh structures are known to date. For example, Patent Document 1 discloses a biodegradable aquatic plant support for landscaping, which is formed of a three-dimensional mesh with three-dimensional random rings. These three-dimensional random rings are obtained by joining multiple continuous linear bodies with a biodegradable thermoplastic resin in at least a portion. Patent Document 2 discloses a three-dimensional mesh fiber material assembly, which is a biodegradable three-dimensional mesh fiber material assembly. This assembly is composed of multiple fiber materials that are partially joined together. The fiber materials have at least a composition including a biodegradable resin and a bonding-promoting resin for partial joining. In addition, Patent Document 3 discloses a biodegradable three-dimensional structure in which lines with a fineness of 300 to 100,000 denier and mainly composed of thermoplastic polylactic acid resin are repeatedly bent and joined in most of the contact area.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-32236

[0006] Patent Document 2: Japanese Patent Application Publication No. 2020-128608

[0007] Patent Document 3: Japanese Patent Application Publication No. 2000-328422 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Patent Document 1 discloses a technique for improving the plant retention properties of a biodegradable mesh structure. Patent Document 2 discloses a technique for locally bonding fibrous materials in a biodegradable mesh structure. Patent Document 3 discloses a technique for dispersing stress by forming helical spring-like or ring-shaped portions within a biodegradable three-dimensional structure, allowing these portions to deform appropriately under compressive stress. Thus, various attempts have been made to improve the functionality of biodegradable mesh structures until now, but biodegradable mesh structures with excellent compression durability and compression recovery after thermal compression are still unknown. The present invention was made in view of the above, and its object is to provide a biodegradable three-dimensional mesh structure with excellent compression durability and compression recovery after thermal compression.

[0010] Solution for solving the problem

[0011] The biodegradable three-dimensional network structure described in the embodiments of the present invention is shown below.

[0012] [1] A biodegradable three-dimensional network structure, characterized in that its apparent density is 0.005 g / cm³. 3 ~0.30g / cm 3 It has a thickness of 10mm to 100mm and contains linear fibers.

[0013] The aforementioned linear fibers have a fiber diameter of 0.2 mm to 2.0 mm, a crystallization melting enthalpy of 16 J / g or higher, and contain polybutylene adipate terephthalate resin with a weight-average molecular weight of 35,000 or higher.

[0014] The above configuration improves compression durability and compression recovery after heated compression. A preferred embodiment of the biodegradable three-dimensional network structure is shown below.

[0015] [2] According to the biodegradable three-dimensional network structure described in [1], wherein the aforementioned linear fibers form a three-dimensional random ring structure.

[0016] [3] The biodegradable three-dimensional network structure according to [1] or [2], wherein the aforementioned enthalpy of crystallization melting is less than 30 J / g.

[0017] [4] A biodegradable three-dimensional mesh structure according to any one of [1] to [3], used as a buffer.

[0018] [5] A biodegradable three-dimensional network structure according to any one of [1] to [4], wherein the weight-average molecular weight of the aforementioned polybutylene adipate terephthalate resin is 150,000 or less.

[0019] [6] A biodegradable three-dimensional network structure according to any one of [1] to [5], wherein the melting point of the aforementioned linear fibers is above 100°C and below 120°C.

[0020] [7] A biodegradable three-dimensional network structure according to any one of [1] to [6], wherein the aforementioned linear fibers have a hollow cross-sectional shape.

[0021] [8] The biodegradable three-dimensional network structure according to [7], wherein the hollowness of the aforementioned linear fibers is more than 1% and less than 30%.

[0022] [9] The biodegradable three-dimensional network structure according to [7], wherein the hollowness of the aforementioned linear fibers is more than 2% and less than 25%.

[0023]

[10] A biodegradable three-dimensional network structure according to any one of [1] to [9], wherein the aforementioned enthalpy of melting of crystals is 17 J / g or more.

[0024]

[11] A biodegradable three-dimensional network structure according to any one of [1] to

[10] , wherein the aforementioned enthalpy of crystallization melting is 28 J / g or less.

[0025]

[12] A biodegradable three-dimensional network structure according to any one of [1] to

[11] , wherein the weight-average molecular weight of the aforementioned polybutylene adipate terephthalate resin is 37,000 or more.

[0026]

[13] A biodegradable three-dimensional network structure according to any one of [1] to

[12] , wherein the weight-average molecular weight of the aforementioned polybutylene adipate terephthalate resin is 120,000 or less.

[0027] The effects of the invention

[0028] According to the present invention, the above-described configuration provides a biodegradable three-dimensional mesh structure with excellent compression durability and compression recovery after heat compression. Attached Figure Description

[0029] Figure 1 This is an example of an endothermic / exothermic curve used to determine the enthalpy of melting of linear fibers contained in a three-dimensional network structure. Detailed Implementation

[0030] The apparent density of the biodegradable three-dimensional network structure described in the embodiments of the present invention is 0.005 g / cm³. 3 ~0.30g / cm 3 The resin has a thickness of 10 mm to 100 mm and contains linear fibers with a diameter of 0.2 mm to 2.0 mm, a crystalline melting enthalpy of 16 J / g or higher, and contains a polybutylene adipate terephthalate resin with a weight-average molecular weight of 35,000 or higher. This composition improves compression durability and compression recovery after heat compression. The following provides a detailed description of each component.

[0031] The apparent density of the three-dimensional network structure is 0.005 g / cm³. 3 ~0.30g / cm 3 By making the apparent density 0.005 g / cm³ 3 The above results in increased rigidity of the three-dimensional mesh structure. Consequently, when the three-dimensional mesh structure is used in cushioning materials, the tactile feedback can be reduced. Therefore, the apparent density is preferably 0.01 g / cm³. 3 The above, and more preferably, is 0.02 g / cm³.3 The above, and more preferably, is 0.03 g / cm³. 3 The above, and more preferably, is 0.05 g / cm³. 3 That's all. On the other hand, if the apparent density is 0.30 g / cm³... 3 The following properties improve softness, making it suitable for use in cushioning materials, etc. Therefore, an apparent density of 0.20 g / cm³ is preferred. 3 The following, or more preferably, is 0.15 g / cm³. 3 The apparent density of the three-dimensional network structure can be determined using the methods described in the examples below.

[0032] The thickness of the three-dimensional mesh structure is 10 mm to 100 mm. By making the thickness 10 mm or more, the three-dimensional mesh structure can be easily used as a cushioning material, etc. The thickness is preferably 15 mm or more, more preferably 20 mm or more, and even more preferably 22 mm or more. On the other hand, considering the size of the manufacturing apparatus, the thickness is 100 mm or less, preferably 90 mm or less, more preferably 80 mm or less, and even more preferably 50 mm or less. The thickness of the three-dimensional mesh structure can be measured using the method described in the embodiments described later.

[0033] The three-dimensional mesh structure comprises linear fibers. Preferably, the linear fibers form a three-dimensional random ring structure. Furthermore, the linear fibers are preferably continuous linear bodies. A continuous linear body refers to a linear filament having a continuous portion of at least 5 mm. A three-dimensional mesh structure is easily formed by bonding the intersections of these continuous linear bodies. Therefore, the three-dimensional mesh structure preferably has adhesive portions where the intersections of the linear fibers are bonded together.

[0034] The linear fibers can be composite linear bodies of core-sheath type, parallel type, off-core core-sheath type, etc. The composite linear body can be a composite linear body obtained by combining polybutylene adipate terephthalate resin with other thermoplastic resins. The cross-sectional shape of the linear fibers can be either hollow or solid, with a hollow cross-section being preferred due to its lightweight properties. Furthermore, by making the cross-sectional shape of the linear fibers hollow, the compression recovery after heating and compression is improved. Additionally, the cross-sectional shape of the linear fibers is preferably irregular. This allows for the easy imparting of suitable stiffness and cushioning properties to the three-dimensional mesh structure. The hollowness of the linear fibers is preferably 1% or more, more preferably 2% or more, further preferably 5% or more, and preferably 30% or less, more preferably 25% or less, and further preferably 20% or less. The hollowness of the linear fibers can be measured using the method described in the examples described later.

[0035] The diameter of the linear fibers is 0.2 mm to 2.0 mm. By making the fiber diameter 0.2 mm or more, the stiffness is increased. Therefore, the fiber diameter is preferably 0.3 mm or more, more preferably 0.4 mm or more. On the other hand, by making the fiber diameter 2.0 mm or less, the density of the mesh structure can be improved, the cushioning properties can be improved, and the mesh structure is more easily made soft to the touch. Therefore, the fiber diameter is preferably 1.7 mm or less, more preferably 1.5 mm or less, and even more preferably 1.2 mm or less. The fiber diameter of the linear fibers can be measured using the method described in the embodiments described later. The shape of the cross-sectional profile of the linear fibers can be circular, elliptical, polygonal, or rounded polygonal. The fiber diameter of fibers with a profile other than circular is equivalent to the maximum distance between any two points on the fiber profile.

[0036] The melt flow rate (MFR) of the filamentous fibers is preferably 3 g / 10 min to 60 g / 10 min. If the MFR is 3 g / 10 min or higher, the melt viscosity is easily increased, which allows for an increase in the fiber diameter of the filamentous fibers. More preferably, the MFR is 4 g / 10 min or higher, further preferably 6 g / 10 min or higher, even more preferably 8 g / 10 min or higher, and particularly preferably 10 g / 10 min or higher. On the other hand, if the MFR is 60 g / 10 min or lower, the compression recovery after heat compression is easily improved. More preferably, the MFR is 50 g / 10 min or lower, further preferably 40 g / 10 min or lower, even more preferably 30 g / 10 min or lower, and particularly preferably 25 g / 10 min or lower. The MFR of the filamentous fibers can be measured using the method described in the examples described later.

[0037] When using commercially available polybutylene terephthalate (PET) resins to form filamentous fibers, and the resin has a low melt flow rate (MFR), the MFR of the resin can be increased by adding water to the resin and hydrolyzing it during melt extrusion. This increases the MFR of the filamentous fibers. Conversely, when the resin has a high MFR, the MFR can be decreased by drying the resin before melt extrusion. This also decreases the MFR of the filamentous fibers.

[0038] The enthalpy of crystalline melting of the linear fibers is 16 J / g or higher. By setting the enthalpy of crystalline melting to 16 J / g or higher, the compression durability and compression recovery after heated compression of the three-dimensional network structure can be improved. The enthalpy of crystalline melting is preferably 17 J / g or higher, more preferably 18 J / g or higher, even more preferably 19 J / g or higher, even more preferably 20 J / g or higher, and particularly preferably 21 J / g or higher. On the other hand, the enthalpy of crystalline melting is preferably 30 J / g or lower. This improves the flexibility of the three-dimensional network structure and reduces noise generation during compression and recovery. The enthalpy of crystalline melting is more preferably 28 J / g or lower, and even more preferably 26 J / g or lower.

[0039] The enthalpy of fusion (J / g) of the linear fibers can be calculated as follows: With a sample mass of 2.0 mg ± 0.1 mg, a differential scanning calorimeter is used to measure the enthalpy at a heating rate of 20 °C / min under a nitrogen atmosphere. The enthalpy is then calculated based on the integral value of the endothermic peak (melting peak) of the resulting endothermic / exothermic curve. The integral value can be calculated as follows: Taking the point where the curve involving the endothermic peak (melting peak) begins to deviate from the low-temperature baseline as the starting point, and the point where it begins to contact the high-temperature baseline as the ending point, a straight line connecting the starting and ending points is drawn. The integral is then performed on the portion enclosed by this straight line and the curve. An example of an endothermic / exothermic curve is shown below. Figure 1 . Figure 1 The dashed line in the figure is a straight line connecting the starting point and the ending point of the endothermic peak (melting peak). The part enclosed by the dashed line and the curve is the integration region.

[0040] When using commercially available resins as polybutylene terephthalate (PET) resins that form filamentous fibers and the crystallization melting enthalpy is below the desired range, annealing as described below can control the crystallization melting enthalpy to the desired range.

[0041] Polybutylene adipate terephthalate (PBDT) resin is a biodegradable resin, a copolymer of adipic acid, terephthalic acid, and butanediol. By making PBDT resin biodegradable, it is expected to be a strategy for solving waste disposal and microplastic problems. Adipic acid, terephthalic acid, and butanediol do not need to be copolymerized simultaneously; they can be copolymerized in multiple stages. Furthermore, PBDT resin is preferably a thermoplastic resin.

[0042] In the synthesis of polybutylene adipate terephthalate resins, in addition to adipic acid, terephthalic acid, and butanediol, trace amounts of other copolymerizing components can also be added. Examples of other copolymerizing components include dicarboxylic acids other than terephthalic acid and adipic acid, and modifiers used for chain extension, end-capping, etc. These can be used alone or in combination of two or more.

[0043] Other dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, and octanoic acid. They can be used alone or in combination of two or more.

[0044] Examples of modifiers include polyisocyanate compounds and glycol compounds. Among polyisocyanate compounds are diisocyanate compounds. Examples of diisocyanate compounds include hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, phenylenediamine diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, carbodiimide-modified MDI, and polymethylene phenyl polyisocyanate. These can be used alone or in combination of two or more. Examples of glycol compounds include glycols other than butanediol and polyalkylene glycols. Examples of other glycols include methanediol, ethylene glycol, propylene glycol, pentanediol, and hexanediol. Examples of polyalkylene glycols include polymethylene glycol, polyethylene glycol, polypropylene glycol, and polybutanediol (polytetramethylene glycol). They can be used alone or in combination of two or more.

[0045] As polybutylene adipate terephthalate (PEG) resins, biodegradable synthetic polymers listed in the Japan Bioplastics Association's positive list of permitted imports under classification A-1 for green plastics (biodegradable plastics) can be cited. Specifically, examples include ECOFLEX (registered trademark) manufactured by BASF JAPAN; Eastar Bio, GP and Eastar Bio, Ultra manufactured by GSICREOS (Novamont); A400 (ECOPOND KD 1024) manufactured by KINGFA; and TUNHE PBAT TH-801T manufactured by XINJIANG BLUE RIDGE TUNHE CHEMICAL INDUSTRY JOINT STOCK. These can be used alone or in combination of two or more.

[0046] The weight-average molecular weight (g / mol) of the polybutylene adipate terephthalate (PAT) resin is 35,000 or more. This improves the compression recovery after heat compression. The weight-average molecular weight is preferably 37,000 or more, more preferably 40,000 or more. On the other hand, by keeping the weight-average molecular weight below 150,000, the flexibility can be improved. The weight-average molecular weight is preferably below 150,000. Furthermore, by keeping the weight-average molecular weight below 120,000, the melt viscosity of the polymer can be reduced. The weight-average molecular weight is more preferably below 120,000. Additionally, the weight-average molecular weight (g / mol) of the resin constituting the filamentous fibers is also preferably within this range. The weight-average molecular weight can be determined using gel permeation chromatography (GPC) or the like.

[0047] The filamentous fibers may contain other biodegradable resins besides polybutylene adipate-terephthalate (PAT) resins. Preferred other biodegradable resins include polylactic acid, polylactic acid / polycaprolactone copolymer, polylactic acid / polyether copolymer, polyethylene terephthalate (PET), polybutylene succinate, polybutylene adipate-succinate, polyglycolic acid, polycaprolactone, polyvinyl alcohol, and cellulose acetate. These can be used alone or in combination of two or more. For details, refer to the import permit for green plastics (biodegradable plastics) under classification number A-1 of the Japan Bioplastics Association. The filamentous fibers may contain resins other than biodegradable resins. Examples of such resins include thermoplastic resins such as polyurethane and polyester.

[0048] While petroleum-derived monomers can be used as monomers for synthesizing resins that form filamentous fibers, biomass-derived monomers are preferred as they reduce environmental impact. For biomass-derived monomers, refer to, for example, the monomers listed in the import declarations permitted under classification number A (biomass plastics) of the Japan Bioplastics Association.

[0049] Of the total 100 mol% of the components constituting the polybutylene adipate terephthalate resin, the total content of adipic acid, terephthalic acid and butylene glycol is preferably 70 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 99 mol% or more.

[0050] Linear fibers can contain deodorizing agents, antibacterial agents, antifungal agents, anti-mite agents, odor-reducing agents, mildew inhibitors, fragrances, flame retardants, moisture-wicking agents, antioxidants, lubricants, etc. They can be used alone or in combination of two or more.

[0051] In 100% by weight of the linear fibers, the content of polybutylene adipate terephthalate resin is preferably 50% by weight or more, more preferably 60% by weight or more, further preferably 80% by weight or more, even more preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 98% by weight or more. Furthermore, the linear fibers may be composed of polybutylene adipate terephthalate resin.

[0052] The melting point of the linear fibers is preferably above 100°C and below 120°C. This facilitates improved compression recovery of the three-dimensional network structure after heat compression. A melting point below 115°C is more preferable. By performing the annealing treatment described later, the melting point of the polybutylene adipate terephthalate resin is lowered, thereby easily reducing the melting point of the linear fibers to below 120°C.

[0053] Three-dimensional mesh structures can have multi-layered structures. Examples of multi-layered structures include: structures where the outer and inner layers are composed of linear fibers with different fineness; structures where the outer and inner layers are composed of structures with different apparent densities; and structures obtained by layering long-fiber or short-fiber nonwoven fabrics. Examples of multi-layering methods include: methods of melting and fixing by heating; methods of bonding using adhesives; and methods of binding by sewing or strapping.

[0054] The shape of the three-dimensional mesh structure is not particularly limited, and examples include plate-shaped, triangular prism, square prism and other polyhedrons; cylinder, sphere, and combinations thereof. When forming a three-dimensional mesh structure, it can be formed by using a limiting plate during the melt extrusion of resin, or by cutting, hot pressing, etc.

[0055] The compression set at 70°C for the three-dimensional mesh structure is preferably 30% or less. This improves the compression recovery after heat compression. More preferably, it is 25% or less, and even more preferably, it is 23% or less. Furthermore, the compression set at 70°C can be 1% or more, or 5% or more. The compression set at 70°C can be measured using the method described in the examples below.

[0056] The hardness of the three-dimensional mesh structure at 25% compression is preferably 5.0 N / φ50 mm or more and 100 N / φ50 mm or less. By having a hardness of 5.0 N / φ50 mm or more, the bottoming sensation when using the three-dimensional mesh structure in cushioning materials can be reduced. Therefore, 5.4 N / φ50 mm or more is more preferred, 6.0 N / φ50 mm or more is even more preferred, and 7.0 N / φ50 mm or more is still more preferred. On the other hand, by having a hardness of 100 N / φ50 mm or less, the cushioning performance can be improved. Therefore, 80 N / φ50 mm or less is more preferred, 60 N / φ50 mm or less is even more preferred, and 30 N / φ50 mm or less is still more preferred. The hardness at 25% compression can be measured using the method described in the examples below.

[0057] The three-dimensional network structure preferably does not contain bonding accelerators. This easily prevents over-curing caused by excessive bonding within the three-dimensional network structure based on bonding accelerators. Furthermore, it easily prevents the decrease in density of the three-dimensional network structure that accompanies an excessive increase in the bonding area per average contact point. Examples of bonding accelerator resins include polycaprolactone, polybutylene succinate, polybutylene sebacic acid terephthalate, and polybutylene azelaic acid terephthalate.

[0058] The three-dimensional network structure can be colored. Coloring can be achieved using pigments, dyes, and other coloring agents. The coloring agent can be contained in the resin before melt spinning, or it can be applied to the linear fibers after the three-dimensional network structure is formed through impregnation or coating.

[0059] Three-dimensional mesh structures are preferred for cushioning materials. Cushioning materials can be any objects that have the elasticity to support the object or reduce impact. Examples of cushioning materials include those used in office chairs, furniture, sofas, beds and other bedding, trams, automobiles, bicycles, child seats, strollers and other vehicle seats; and cushioning materials used in floor mats, impact-resistant components, anti-pinch components and other impact-absorbing pads.

[0060] A three-dimensional network structure can be formed, for example, by the following method. First, polybutylene adipate terephthalate resin is dispensed from a multi-row nozzle with multiple orifices to the nozzle orifices, and sprayed downwards from the nozzle at a spinning temperature of (melting point + 20°C) or higher and (melting point + 180°C) of the resin. Next, continuous linear bodies are brought into contact with each other in a molten state to fuse them together, forming a three-dimensional network structure. Simultaneously, the fibers are clamped by a traction conveyor and cooled using cooling water in a cooling tank. The distance between the nozzle surface and the surface of the cooling water is preferably 15 cm or more, more preferably 20 cm or more. This improves the hollowness of the fibers and the density of the network structure. On the other hand, this distance is preferably 40 cm or less, more preferably 35 cm or less. This readily yields a three-dimensional network structure with appropriate apparent density and fiber diameter. After cooling, the cured three-dimensional network structure is drawn out, and after water control or drying, a three-dimensional network structure with smoothed surfaces on one or both sides is obtained. For details regarding these spinning and cooling processes, please refer to Japanese Patent Application Publication No. 7-68061. In the case of smoothing only one side, continuous linear materials are sprayed onto a traction net with an angle, and then brought into contact with each other in a molten state to fuse them. At this time, the three-dimensional mesh structure is formed while the traction net surface is relaxed and cooled. The resulting three-dimensional mesh structure is then annealed. It should be noted that the drying process of the three-dimensional mesh structure can be considered as annealing.

[0061] It is preferable to add water to the resin before it is ejected from the nozzle. The amount of water added is preferably 0.005% by mass or more relative to 100% by mass of the solid content of the resin. This promotes resin decomposition during the manufacturing process of the three-dimensional network structure and improves the resin's softness. On the other hand, the amount of water added is preferably 2.0% by mass or less. This prevents excessive decomposition of the resin during the manufacturing process of the three-dimensional network structure and easily improves the compression recovery after heat compression. The amount of water added is more preferably 1.0% by mass or less, further preferably 0.5% by mass or less, and even more preferably 0.2% by mass or less. In addition, there is no particular limitation on the method of adding water to the resin. For example, before ejecting the resin from the nozzle, the resin can be vacuum dried at 100°C for more than 12 hours to make it absolutely dry, and then a predetermined amount of pure water can be added to 100% by mass of the absolutely dried resin.

[0062] The melt flow rate (MFR) of the polybutylene adipate terephthalate resin is preferably 0.5 or more but less than 20.0 less than the MFR of the desired three-dimensional network structure at the moment before melt extrusion. Since thermal and shear degradation of the resin are induced during melt extrusion, a three-dimensional network structure with the desired MFR can be easily obtained by controlling the MFR before melt extrusion as described above.

[0063] Cooling of polybutylene adipate terephthalate (PBT) resin after melt molding is preferably performed using cooling water. PBT resin sometimes experiences molding shrinkage until it solidifies. Therefore, it is feasible to form a three-dimensional mesh structure with width and thickness taking into account molding shrinkage, thereby reducing molding shrinkage by lowering the melt-curing temperature. Therefore, the temperature of the cooling water is preferably below 20°C, more preferably below 15°C. Furthermore, the cooling time using the cooling water is preferably 30 seconds or more. This cooling and curing is preferably performed in a water bath.

[0064] Annealing can be performed using a commercially available hot air drying oven or in a warm water bath. The annealing temperature is 70°C or higher. This increases the enthalpy of melting for crystallization. Preferably, it is 75°C or higher, more preferably 80°C or higher. On the other hand, the annealing temperature is 105°C or lower. This also increases the enthalpy of melting for crystallization.

[0065] The annealing time is preferably 1 minute or more. This increases the melting enthalpy for crystallization. More preferably, the annealing time is 5 minutes or more, further preferably 10 minutes or more, and even more preferably 15 minutes or more. On the other hand, the annealing time is preferably 60 minutes or less. This reduces yellowing, off-odors, and molecular weight reduction of polybutylene adipate terephthalate resins associated with polymer decomposition and degradation during annealing. Furthermore, it also improves productivity. The annealing time is more preferably 50 minutes or less.

[0066] After cooling and curing but before annealing, it is preferable to maintain the temperature at 20°C to 50°C for at least 1 minute. During annealing, thickness changes can sometimes occur due to the weight of the material. By maintaining the temperature at 20°C to 50°C after cooling and curing, the thickness changes caused by annealing can be reduced. For example, after cooling and curing in a water bath, a continuous dryer can be used to lower and maintain the temperature in the first half of the oven, and then raise the temperature in the second half of the oven for annealing.

[0067] The moisture content of the three-dimensional network structure before annealing is preferably 15% or less. This reduces resin decomposition and other issues. More preferably, the moisture content is 12% or less, and even more preferably 10% or less. This moisture content is calculated using the following formula. The mass after vacuum drying is defined as the mass after vacuum drying at 90°C for 2 hours.

[0068] Moisture content (%) of the three-dimensional network structure = {(mass of the three-dimensional network structure before vacuum drying) - (mass of the three-dimensional network structure after vacuum drying)} / (mass of the three-dimensional network structure before vacuum drying) × 100

[0069] At any stage from the resin manufacturing process of the three-dimensional network structure to the molding process, the resin can be endowed with functions such as deodorizing and antibacterial properties, mildew prevention, mite prevention, odor elimination, mildew prevention, fragrance, flame retardancy, and moisture absorption and release. Furthermore, when manufacturing the three-dimensional network structure, the polybutylene adipate terephthalate resin used as a raw material can contain functional imparting materials such as antioxidants and lubricants. These can be used alone or in combination of two or more. Preferably, various functional imparting materials are blended into the resin during melt extrusion according to the color and quality of the melted resin, and the content of the functional imparting materials is adjusted.

[0070] As antioxidants, well-known examples include phenolic antioxidants, phosphite antioxidants, thioether antioxidants, benzotriazole UV absorbers, triazine UV absorbers, benzophenone UV absorbers, NH-type hindered amine light stabilizers, and N-CH3-type hindered amine light stabilizers, etc., and preferably contain at least one of these.

[0071] 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'-butylidene bis(6-tert-butyl-m-cresol), stearate 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetratetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], Sumilizer AG 80, and 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)trimethylbenzene.

[0072] Examples of phosphite-based antioxidants include 3,9-bis(octadecoxy)-2,4,8,10-tetraoxa-3,9-diphosspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosspiro[5.5]undecane, and 2,4,8,10-tetra(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, 4,4'-isopropylidene diphenol C12-15 alcohol phosphite, diphenyl(2-ethylhexyl) phosphite, diphenylisodecyl phosphite, triisodecyl phosphite, triphenyl phosphite, etc.

[0073] Examples of thioether-based antioxidants include bis[3-(dodecylthio)propionic acid]2,2-bis[(3-(dodecylthio)-1-oxopropoxy)methyl]-1,3-propane diester and 3,3'-thiodipropionic acid ditridecyl ester.

[0074] To prevent thermal degradation of the resin, it is preferable to use a mixture of phenolic antioxidants and phosphite antioxidants. The content of these two antioxidants relative to 100% by mass of the resin composition is preferably 0.05% by mass or more and 1.0% by mass or less.

[0075] Examples of lubricants include hydrocarbon waxes, higher alcohol waxes, amide waxes, ester waxes, and metal soaps. Preferably, the lubricant comprises 0.5% or less by weight relative to 100% by weight of the resin composition, as required.

[0076] This application claims priority based on Japanese Patent Application No. 2021-058475, filed on March 30, 2021. The entire contents of the description of Japanese Patent Application No. 2021-058475, filed on March 30, 2021, are incorporated herein by reference.

[0077] Example

[0078] The following examples illustrate the present invention in more detail, but the present invention is not limited to the following examples. It can also be implemented by making changes within the scope of the above / below spirit, and all of them are included in the technical scope of the present invention.

[0079] The characteristic values ​​of the three-dimensional mesh structures of Examples 1-7 and Comparative Examples 1-3 described later were determined and evaluated according to the following methods. It should be noted that the size of the sample was based on the following standard; if the sample size was insufficient, a sample of an achievable size was used for the measurement.

[0080] (1) Fiber diameter

[0081] The three-dimensional mesh structure was cut into 10cm × 10cm pieces, and linear fibers of approximately 5mm length were collected from 10 locations. Then, using an optical microscope, the diameter of the collected linear fibers was measured at the designated location, and the average fiber diameter from the 10 locations was calculated (n = 10).

[0082] (2) Hollow rate

[0083] Ten linear fibers were randomly selected from a three-dimensional mesh structure. These fibers were then cut into circular slices and placed vertically along their fiber axes on a glass slide. The cross-sections of the fibers along the circular tangent direction were observed using an optical microscope. Only linear fibers with hollow cross-sections were selected. The area within the outer perimeter of the fiber (a) and the hollow area (b) were calculated. The hollowness ratio was calculated using the following formula, and the average hollowness ratio of the selected hollow linear fibers was obtained.

[0084] Hollow rate (%) = (b) / (a) × 100

[0085] (3) Thickness, apparent density

[0086] The three-dimensional mesh structure was cut into 10cm x 10cm pieces. After placing the samples under no-load conditions for 24 hours, the height at the center was measured using an FD-80N thickness gauge manufactured by Polymer Instruments Co., Ltd. This height was taken as the thickness of the three-dimensional mesh structure. The samples were then placed on an electronic balance, and their weight was measured. The height of the sample was multiplied by the area (100cm²) of the mesh structure. 2 The volume of the sample is determined by dividing its weight by its volume, and the apparent density is then calculated. This operation is performed three times to obtain the average thickness and apparent density of the three-dimensional network structure (n=3).

[0087] (4) Melting point (Tm)

[0088] Using a Discovery DSC25 differential scanning calorimeter manufactured by TA Instruments, samples were taken from a three-dimensional mesh structure, weighed to a mass of 2.0 mg ± 0.1 mg, and measured under a nitrogen atmosphere at a heating rate of 20 °C / min. The endothermic peak (melting peak) temperature was determined based on the resulting endothermic and exothermic curves. This operation was performed three times, and the average melting point was calculated (n = 3).

[0089] (5) Enthalpy of fusion

[0090] A sample was taken from the three-dimensional network structure and weighed to a mass of 2.0 mg ± 0.1 mg. Measurements were performed using a Discovery DSC25 differential scanning calorimeter (TA Instruments) at a heating rate of 20 °C / min under a nitrogen atmosphere. The enthalpy of fusion (J / g) was determined based on the integral value of the endothermic peak (melting peak) from the resulting endothermic / exothermic curve. Specifically, the integral value of the endothermic peak (melting peak) was calculated as follows: the point where the curve involving the endothermic peak (melting peak) begins to deviate from the low-temperature baseline was taken as the starting point, and the point where it begins to touch the high-temperature baseline was taken as the ending point. A straight line connecting the starting and ending points was drawn, and the integral was performed over the portion enclosed by this line and the curve. This operation was performed three times, and the average enthalpy of fusion was calculated (n = 3). The starting point was then taken as the melting initiation temperature (°C).

[0091] (6) Melt Flow Rate (MFR)

[0092] The three-dimensional mesh structure was finely shredded and used as raw material. After vacuum drying at 80°C for more than 2 hours, the melt flow rate (MFR) was rapidly measured to remove as much moisture as possible from the air. A melt flow rate meter F-F01 manufactured by Toyo Seiki Co., Ltd. was used to measure the melt flow rate according to ISO 1133. The measurement temperature was set to 190°C, and the load was set to 2.16 kg. This operation was performed three times, and the average melt flow rate was calculated (n=3).

[0093] (7) Weight-average molecular weight

[0094] Samples were taken from the three-dimensional network structure. To reduce sample bias, the usual 10 times (40 mg) sample was finely cut and dissolved. The sample solution was diluted with chloroform to adjust the sample concentration to 0.05%. The solution was filtered using a 0.2 μm membrane filter, and GPC analysis was performed under the following conditions. Molecular weight was calculated according to standard polystyrene conversion.

[0095] Device: TOSOH HLC-8320GPC

[0096] Column: TSKgel SuperHM-H×2+TSKgel SuperH2000(TOSOH)

[0097] Solvent: Chloroform

[0098] Flow rate: 0.6 ml / min

[0099] Concentration: 0.05%

[0100] Injection volume: 20μL

[0101] Temperature: 40℃

[0102] Detectors: RI, UV 254nm

[0103] (8) Compression set at 70℃

[0104] The three-dimensional mesh structure was cut into 10cm × 10cm pieces. The thickness (c) of the resulting samples before treatment was measured using the method described in (2) above. The samples with the measured thickness were clamped in a fixture capable of maintaining 50% compression and placed in a dryer set at 70°C for 22 hours. Afterward, the samples were removed and cooled, and the thickness (d) after removing the compression deformation and leaving for 30 minutes was calculated. These thicknesses were substituted into the formula {(c)-(d)} / (c)×100 to calculate the compression set at 70°C. This operation was performed three times, and the average value of the compression set at 70°C was calculated (n=3).

[0105] (9) Hardness at 25% compression

[0106] The three-dimensional mesh structure was cut into 10cm × 10cm pieces, and the resulting samples were placed under no-load conditions at 23℃ ± 2℃ for 24 hours. Then, at 23℃ ± 2℃, measurements were performed using the Shimadzu Autograph AG-X plus, according to ISO 2439 (2008) E method. Specifically, a 50mm diameter (φ) pressure plate was placed at the center of the sample, and the thickness was measured when the load was 0.5N, which was taken as the initial thickness. Using this position of the pressure plate as the zero point, a pre-compression was performed at a speed of 100mm / min until 75% of the initial thickness was reached. After the pressure plate returned to the zero point at the same speed, it was left in this state for 4 minutes. Immediately afterwards, it was compressed at a speed of 100mm / min until 25% of the initial thickness was reached, and the load at this point was measured, which was taken as the hardness at 25% compression (N / φ50mm). This operation was performed three times, and the average hardness at 25% compression was calculated (n = 3).

[0107] As the polybutylene adipate terephthalate (PEG) resin, TH-801T manufactured by XINJIANG BLUE RIDGE TUNHECHEMICAL INDUSTRY JOINT STOCK was used. The weight-average molecular weight of the resin is 12.3 × 10⁻⁶. 4 g / mol, melt flow rate (MFR) is 4 g / 10 min.

[0108] [Example 1]

[0109] A water tank is configured such that the cooling water surface is 17 cm lower than the nozzle surface of the nozzle used to spray molten resin. The water temperature is set to 12°C. A pair of traction conveyor belts are positioned in the water tank with a portion protruding above the water surface. The traction conveyor belts have a 20 cm wide stainless steel ring mesh, which is arranged parallel to the width direction of the nozzle surface. The opening width of the ring mesh is set to 30 mm. To form the side surface, an aluminum plate is positioned at a 90-degree angle relative to the mesh direction. Water flows through the tank at a rate of 1.0 L / min to form the side surface.

[0110] As the nozzle used for ejecting molten resin, a nozzle with an effective nozzle surface of 96 mm in the width direction and 31 mm in the thickness direction, and orifices of 0.5 mm outer diameter and circular shape formed by a zigzag arrangement of orifice spacing of 6 mm, is used. The resin used as raw material is dried to absolute dryness, and water of 0.01% by mass relative to 100% by mass of the solid content of the resin is added. Molten resin is ejected downwards from the nozzle at a spinning temperature of 260°C and a single-orifice ejection rate of 1.0 g / min.

[0111] The molten resin was sprayed in a linear fashion onto the opening of the conveyor belt mesh, the conveyor belt mesh, and the aluminum plate on the side surface. The continuous linear body fell to form a curved loop, fusing the contact areas and forming a three-dimensional mesh structure. While holding both sides of the molten three-dimensional mesh structure with a traction conveyor belt, it was introduced into cooling water at a speed of 0.86 m / min to solidify it. After planarizing both sides in the thickness and side directions, it was cut to a specified size. Then, it was left to stand at 25°C for 1 hour. The resulting three-dimensional mesh structure had a moisture content of 9%. It was then dried using hot air at 80°C for 20 minutes, followed by annealing, to obtain a three-dimensional mesh structure with a width of 100 mm. The linear fibers of this three-dimensional mesh structure have a circular cross-sectional shape.

[0112] [Example 2]

[0113] Water was added at a rate of 0.30% by mass relative to 100% by mass of the solid content of the resin. A nozzle with orifices arranged in a Z-shape with an 8mm spacing, forming a hollow cross-section with an outer diameter of 5.0mm and an inner diameter of 4.4mm (triple bridge), was used. The spinning temperature was set to 231°C, the single-orifice ejection rate to 1.5g / min, the traction speed to 0.92m / min, and the drying temperature to 105°C. Otherwise, the process was the same as in Example 1 to obtain a three-dimensional network structure. The linear fibers of this three-dimensional network structure have a hollow cross-sectional shape.

[0114] [Example 3]

[0115] Water was added at a rate of 0.40% by mass relative to 100% by mass of the solid content of the resin. The spinning temperature was set to 230°C and the drying temperature was set to 90°C. Otherwise, the same procedure as in Example 2 was followed to obtain a three-dimensional network structure.

[0116] [Example 4]

[0117] Water was added at a rate of 0.01% by mass relative to 100% by mass of the solid content of the resin. The spinning temperature was set to 240°C and the nozzle-cooling water distance was set to 25cm. Otherwise, the same operation as in Example 3 was performed to obtain a three-dimensional mesh structure.

[0118] [Example 5]

[0119] After the resin used as raw material was dried, no water was added. The single-hole spray rate was set to 0.5 g / min and the traction speed was set to 0.64 m / min. Otherwise, the same operation as in Example 1 was performed to obtain a three-dimensional mesh structure.

[0120] [Example 6]

[0121] Water was added at a rate of 0.20% by mass relative to 100% by mass of the solid content of the resin. The spinning temperature was set to 190°C and the nozzle-cooling water distance was set to 30cm. Otherwise, the same operation as in Example 3 was performed to obtain a three-dimensional mesh structure.

[0122] [Example 7]

[0123] The spinning temperature was set to 210°C, the single-hole ejection rate was set to 1.0 g / min, and the traction speed was set to 1.28 m / min. Otherwise, the same operation as in Example 5 was performed to obtain a mesh structure.

[0124] [Comparative Example 1]

[0125] Water was added at a rate of 2.5% by mass relative to 100% of the solid content of the resin. The single-hole spray rate was set to 0.9 g / min, the nozzle surface-cooling water distance was set to 18 cm, and the traction speed was set to 0.52 m / min. Otherwise, the same operation as in Example 1 was performed to obtain a three-dimensional mesh structure.

[0126] [Comparative Example 2]

[0127] Water was added at a rate of 0.02% by mass relative to 100% by mass of the solid content of the resin. The mixture was not annealed and was dried at 20–25°C for 2 days. Otherwise, the process was the same as in Example 4 to obtain a three-dimensional network structure.

[0128] [Comparative Example 3]

[0129] The spinning temperature was set to 230°C, the traction speed to 1.54 m / min, and the drying temperature to 107°C. Otherwise, the same operation as in Example 2 was performed to obtain a mesh structure.

[0130] Table 1 shows the manufacturing conditions and characteristics of the resulting three-dimensional mesh structures from Examples 1-7 and Comparative Examples 1-3. It should be noted that the characteristic values ​​in Table 1, which were evaluated multiple times, are average values.

[0131] [Table 1]

[0132]

[0133] The three-dimensional mesh structures obtained in Examples 1-7 exhibit excellent compression durability and compression recovery after heated compression. Furthermore, Examples 1-6 can reduce the polymer melt viscosity at the time of ejection, thus enabling the fabrication of precise rings with excellent surface and appearance quality.

[0134] The network structure obtained in Comparative Example 1 has a low weight-average molecular weight and poor compressibility after heating and compression. Furthermore, the network structure obtained in Comparative Example 1 shows slight yellowing. This can be attributed to the high moisture content of the three-dimensional network structure before annealing.

[0135] The network structures obtained in Comparative Examples 2 and 3 have low enthalpy of crystallization melting, poor compressibility, and poor compressibility recovery after heating and compression.

Claims

1. A biodegradable three-dimensional network structure, characterized in that, The apparent density is 0.005 g / cm³. 3 ~0.30g / cm 3 It has a thickness of 10mm to 100mm and contains linear fibers. The linear fibers have a diameter of 0.2 mm to 2.0 mm, a fusion enthalpy of crystallization of 16 J / g or higher, and contain a polybutylene adipate terephthalate resin with a weight-average molecular weight of 35,000 or higher. The biodegradable three-dimensional mesh structure has a permanent deformation of more than 1% and less than 30% under compression at 70°C, and a hardness of more than 5.0N / φ50mm and less than 100N / φ50mm under 25% compression.

2. The biodegradable three-dimensional network structure according to claim 1, wherein, The linear fibers form a three-dimensional random ring structure.

3. The biodegradable three-dimensional network structure according to claim 1, wherein, The melting enthalpy of the crystallization is below 30 J / g.

4. The biodegradable three-dimensional mesh structure according to any one of claims 1 to 3, used as a buffer.

5. The biodegradable three-dimensional network structure according to any one of claims 1 to 3, wherein, The weight-average molecular weight of the polybutylene adipate terephthalate resin is below 150,000.

6. The biodegradable three-dimensional network structure according to any one of claims 1 to 3, wherein, The melting point of the linear fibers is above 100°C and below 120°C.

7. The biodegradable three-dimensional network structure according to any one of claims 1 to 3, wherein, The linear fibers have a hollow cross-sectional shape.

8. The biodegradable three-dimensional network structure according to claim 7, wherein, The hollowness of the linear fibers is more than 1% and less than 30%.

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