KR20230161948A - Biodegradable three-dimensional network structure - Google Patents

Abstract

A biodegradable three-dimensional network structure with excellent compression durability and compression recovery after heat compression is provided. It has an apparent density of 0.005 g/cm3 to 0.30 g/cm3, a thickness of 10 mm to 100 mm, and includes linear fibers, wherein the linear fibers have a fiber diameter of 0.2 mm to 2.0 mm and a crystal fusion enthalpy of 16 J/cm. g or more and a biodegradable three-dimensional network structure comprising a polybutylene adipate terephthalate resin having a weight average molecular weight of 35,000 or more.

Description

Biodegradable three-dimensional network structure

The present invention relates to biodegradable three-dimensional network structures.

Until now, various biodegradable three-dimensional network structures are known. For example, Patent Document 1 discloses a biodegradable aquatic plant support for greening consisting of a three-dimensional network having three-dimensional random loops joined at least in part to a plurality of twisted continuous linear bodies made of a biodegradable thermoplastic resin. In Patent Document 2, it is a biodegradable three-dimensional network fiber material assembly, and is composed of a plurality of fiber materials that are locally bonded to each other, and the fiber materials have at least a composition containing a biodegradable resin and a bonding promoting resin for local bonding. An island material aggregate is disclosed. Additionally, Patent Document 3 discloses a biodegradable three-dimensional structure in which a line mainly made of thermoplastic polylactic acid resin with a fineness of 300 to 100,000 denier is repeatedly bent and bonded at most of the contact portions.

Japanese Patent Publication No. 2001-32236 Japanese Patent Publication No. 2020-128608 Japanese Patent Publication No. 2000-328422

Patent Document 1 discloses a technology for improving plant retention of a biodegradable network structure. Additionally, Patent Document 2 discloses a technique for improving local bonding of fibers of a biodegradable network structure. Additionally, Patent Document 3 discloses a technique for dispersing stress by forming a coiled spring-like or loop-shaped portion in a biodegradable three-dimensional structure, thereby deforming the portion appropriately in response to compressive stress. In this way, various attempts have been made to improve the function of the biodegradable network structure, but a biodegradable network structure with excellent compression durability and compression recovery after heat compression is not yet known. The present invention was made in consideration of the above circumstances, and its purpose is to provide a biodegradable three-dimensional network structure with excellent compression durability and compression recovery after heat compression.

The biodegradable three-dimensional network structure according to an embodiment of the present invention is as follows.

[1] The apparent density is 0.005 g/cm3 to 0.30 g/cm3,

The thickness is 10 mm to 100 mm,

Comprising linear fibers, wherein the linear fibers include a polybutylene adipate terephthalate resin having a fiber diameter of 0.2 mm to 2.0 mm, a crystal melting enthalpy of 16 J/g or more, and a weight average molecular weight of 35,000 or more. Characterized by a biodegradable three-dimensional network structure.

With the above configuration, compression durability and compression recovery after heat compression can be improved. The preferred form of the biodegradable three-dimensional network structure is as follows.

[2] The biodegradable three-dimensional network structure according to [1], wherein the linear fibers form a three-dimensional random loop structure.

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

[4] The biodegradable three-dimensional network structure according to any of [1] to [3], which is used for cushions.

[5] The biodegradable three-dimensional network structure according to any one of [1] to [4], wherein the polybutylene adipate terephthalate-based resin has a weight average molecular weight of 150,000 or less.

[6] The biodegradable three-dimensional network structure according to any of [1] to [5], wherein the linear fibers have a melting point of 100°C or higher and 120°C or lower.

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

[8] The biodegradable three-dimensional network structure according to [7], wherein the linear fibers have a porosity of 1% or more and 30% or less.

[9] The biodegradable three-dimensional network structure according to [7], wherein the linear fibers have a porosity of 2% or more and 25% or less.

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

[11] The biodegradable three-dimensional network structure according to any of [1] to [10], wherein the crystal melting enthalpy is 28 J/g or less.

[12] The biodegradable three-dimensional network structure according to any one of [1] to [11], wherein the polybutylene adipate terephthalate resin has a weight average molecular weight of 37000 or more.

[13] The biodegradable three-dimensional network structure according to any one of [1] to [12], wherein the polybutylene adipate terephthalate resin has a weight average molecular weight of 120,000 or less.

According to the present invention, with the above configuration, it is possible to provide a biodegradable three-dimensional network structure with excellent compression durability and compression recovery after heat compression.

Figure 1 is an example of an adsorption/exotherm curve for measuring the enthalpy of crystal fusion of linear fibers included in a three-dimensional network structure.

The biodegradable three-dimensional network structure according to an embodiment of the present invention has an apparent density of 0.005 g/cm3 to 0.30 g/cm3, a thickness of 10 mm to 100 mm, and includes linear fibers, wherein the linear fibers have a fiber diameter It is 0.2 mm to 2.0 mm, has a crystal melting enthalpy of 16 J/g or more, and includes a polybutylene adipate terephthalate-based resin having a weight average molecular weight of 35,000 or more. The above configuration can improve compression durability and compression recovery after heat compression. Below, each configuration will be described in detail.

The apparent density of the three-dimensional network structure is 0.005 g/cm3 to 0.30 g/cm3. The hardness of the three-dimensional network structure is improved when the apparent density is 0.005 g/cm3 or more. As a result, when the three-dimensional network structure is used for cushions, etc., the feeling of floor impact can be reduced. Therefore, the apparent density is preferably 0.01 g/cm 3 or more, more preferably 0.02 g/cm 3 or more, even more preferably 0.03 g/cm 3 or more, and even more preferably 0.05 g/cm 3 or more. On the other hand, when the apparent density is 0.30 g/cm3 or less, flexibility is improved and it can be suitably used for cushioning materials and the like. Therefore, the apparent density is preferably 0.20 g/cm 3 or less, more preferably 0.15 g/cm 3 or less. The apparent density of the three-dimensional network structure can be measured by the method described in the Examples described later.

The thickness of the three-dimensional network structure is 10 mm to 100 mm. When the thickness is 10 mm or more, it becomes easier to use the three-dimensional network structure as a cushion material or the like. The thickness is preferably 15 mm or more, more preferably 20 mm or more, and still more preferably 22 mm or more. Meanwhile, considering the size of the manufacturing device, 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 network structure can be measured by the method described in the Examples described later.

The three-dimensional network structure contains linear fibers. It is preferable that the linear fibers form a three-dimensional random loop structure. Additionally, it is preferable that the linear fibers are continuous linear fibers. A continuous linear body is a linear filament having continuous portions of at least 5 mm or more. By having locations where the intersections of continuous linear structures are bonded, it becomes easy to form a three-dimensional network structure. Therefore, it is preferable that the three-dimensional network structure has an adhesive portion where the intersection portions of linear fibers are bonded to each other.

The linear fiber may be a composite linear body such as sheath-core type, side-by-side type, or eccentric sheath-core type. The composite linear body may be a composite linear body combining polybutylene adipate terephthalate-based resin and another thermoplastic resin. The cross-sectional shape of the linear fiber may be either a hollow cross-section or a solid cross-section, but a hollow cross-section is preferable because it can reduce weight. Additionally, since the cross-sectional shape of the linear fiber is a hollow cross-section, compression recovery after heat compression is improved. Additionally, it is preferable that the cross-sectional shape of the linear fiber is a heterogeneous cross-section. Thereby, it is possible to easily provide appropriate hardness and cushioning properties to the three-dimensional network structure. The hollowness of the linear fiber is preferably 1% or more, more preferably 2% or more, even more preferably 5% or more, preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less. % or less. The porosity of linear fibers can be measured by the method described in the Examples described later.

Linear fibers have a fiber diameter of 0.2 mm to 2.0 mm. Hardness improves when the fiber diameter is 0.2 mm or more. Therefore, the fiber diameter is preferably 0.3 mm or more, more preferably 0.4 mm or more. On the other hand, when the fiber diameter is 2.0 mm or less, the density of the network structure can be improved, cushioning properties, etc. can be improved, and the texture of the network structure can be easily made soft. Therefore, the fiber diameter is preferably 1.7 mm or less, more preferably 1.5 mm or less, and still more preferably 1.2 mm or less. The fiber diameter of linear fibers can be measured by the method described in the Examples described later. The cross-sectional outline shape of the linear fiber may be circular, oval, polygonal, or polygonal with rounded corners. The fiber diameter of a fiber whose outline is other than a circle corresponds to the longest distance between any two points on the outline of the fiber.

The melt flow rate (MFR) of linear fibers is preferably 3 g/10 min to 60 g/10 min. If the MFR is 3 g/10 minutes or more, the melt viscosity can be easily improved and the fiber diameter of the linear fiber can be increased. The MFR is more preferably 4 g/10 min or more, further preferably 6 g/10 min or more, even more preferably 8 g/10 min or more, and particularly preferably 10 g/10 min or more. On the other hand, if the MFR is 60 g/10 minutes or less, it is easy to improve compression recovery after heat compression. The MFR is more preferably 50 g/10 min or less, further preferably 40 g/10 min or less, even more preferably 30 g/10 min or less, and particularly preferably 25 g/10 min or less. The MFR of linear fibers can be measured by the method described in the Examples described later.

This is the case when using a commercially available polybutylene adipate terephthalate resin that makes up linear fibers. If the melt flow rate (MFR) of the resin is low, moisture is added to the resin and the resin is hydrated during melt extrusion. By decomposing, the MFR of the resin can be improved. Thereby, the MFR of linear fibers can be improved. On the other hand, when the MFR of the resin is high, the MFR of the resin can be reduced by drying the resin and then melt-extruding it. Thereby, the MFR of linear fibers can be reduced.

Linear fibers have a crystal fusion enthalpy of 16 J/g or more. When the crystal melting enthalpy is 16 J/g or more, the compression durability of the three-dimensional network structure and the compression recovery after heat compression can be improved. The enthalpy of crystal fusion is preferably 17 J/g or more, more preferably 18 J/g or more, even more preferably 19 J/g or more, even more preferably 20 J/g or more, particularly preferably 21 J/g. g or more. Meanwhile, the enthalpy of crystal fusion is preferably 30 J/g or less. As a result, the flexibility of the three-dimensional network structure is improved, and the generation of noise during compression and recovery can be reduced. The enthalpy of crystal fusion is more preferably 28 J/g or less, and even more preferably 26 J/g or less.

The crystal melting enthalpy (J/g) of the linear fiber is the endothermic peak (melting) of the endothermic curve measured under a nitrogen atmosphere at a temperature increase rate of 20°C/min using a differential scanning calorimeter with a sample mass of 2.0 mg ± 0.1 mg. It can be obtained from the integral value of the peak). The integral value takes as the starting point the point where the curve related to the endothermic peak (melting peak) begins to separate from the base line on the low temperature side, and takes the point where it begins to touch the base line on the high temperature side as the ending point, and sets the starting point as the starting point. It can be obtained by drawing a straight line connecting the and end points and integrating the portion surrounded by the straight line and the curve. An example of an exothermic absorption curve is shown in Figure 1. The broken line in FIG. 1 is a straight line connecting the start and end points of the endothermic peak (melting peak), and the portion surrounded by the broken line and curve is an integration area where integration is performed.

In the case where a commercially available resin is used as the polybutylene adipate terephthalate resin constituting the linear fiber, and the crystal melting enthalpy is lower than the desired range, annealing is performed as described later to bring the crystal melting enthalpy into the desired range. It can be controlled with .

Polybutylene adipate terephthalate resin is a biodegradable resin and is a copolymer of adipic acid, terephthalic acid, and butanediol. Since polybutylene adipate terephthalate resin is a biodegradable resin, it is expected to be a solution to the problem of waste disposal and microplastics. Adipic acid, terephthalic acid, and butanediol do not need to be copolymerized simultaneously, and may be copolymerized in multiple stages. In addition, it is preferable that the polybutylene adipate terephthalate resin is a thermoplastic resin.

When synthesizing polybutylene adipate terephthalate resin, trace amounts of other copolymerization components may be added in addition to adipic acid, terephthalic acid, and butanediol. Other copolymerization components include dicarboxylic acids other than terephthalic acid and adipic acid, and modifiers for the purpose of chain extension or end blocking. These may be used individually or in combination of two or more types.

Other dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, and suberic acid. These may be used individually or in combination of two or more types.

Modifiers include polyisocyanate compounds and glycol compounds. As a polyisocyanate compound, a diisocyanate compound can be mentioned. As diisocyanate compounds, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, and 1,5-naphthylene diisocyanate. , p-phenylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, carbodiimide modified MDI, polymethylene phenyl polyisocyanate, etc. These may be used individually or in combination of two or more types. Examples of glycol compounds include diols other than butanediol and polyalkylene glycol. Examples of other diols include methanediol, ethanediol, propanediol, pentanediol, and hexanediol. Examples of polyalkylene glycol include polymethylene glycol, polyethylene glycol, polypropylene glycol, and polybutylene glycol (polytetramethylene glycol). These may be used individually or in combination of two or more types.

Examples of polybutylene adipate terephthalate-based resins include biodegradable synthetic polymer compounds listed in the positive list of classification number A-1 for green plastics (biodegradable plastics) of the Japan Bioplastics Association. Specifically, Ecoplex (registered trademark) manufactured by BASF Japan Co., Ltd., Eastar Bio, GP, Eastar Bio, Ultra manufactured by BASF Japan Co., Ltd., GSI Creos (Novamont Co., Ltd.), and A400 (ECOPOND KD) manufactured by KINGFA Co., Ltd. 1024), and TUNHE PBAT TH-801T manufactured by XINJIANG BLUE RIDGE TUNHE CHEMICAL INDUSTRY JOINT STOCK. These may be used individually or in combination of two or more types.

The weight average molecular weight (g/mol) of the polybutylene adipate terephthalate-based resin is 35,000 or more. Thereby, compression recovery after heat compression can be improved. The weight average molecular weight is preferably 37000 or more, more preferably 40000 or more. On the other hand, flexibility can be improved by having a weight average molecular weight of 150,000 or less. The weight average molecular weight is preferably 150000 or less. Additionally, when the weight average molecular weight is 120000 or less, the polymer melt viscosity can be reduced. The weight average molecular weight is more preferably 120000 or less. Additionally, it is preferable that the weight average molecular weight (g/mol) of the resin constituting the linear fibers is also within the range. The weight average molecular weight can be obtained by gel permeation chromatography (GPC) or the like.

The linear fiber may contain a biodegradable resin other than polybutylene adipate terephthalate resin. 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, cellulose acetate, etc. are preferred. These may be used individually or in combination of two or more types. For details on these, please refer to the Japan Bioplastics Association's positive list of green plastics (biodegradable plastics), classification number A-1. The linear fibers may contain resins other than biodegradable resins. Examples of the resin include thermoplastic resins such as polyurethane and polyester.

As a monomer for synthesizing the resin constituting the linear fiber, a monomer derived from petroleum may be used, but it is preferable to use a monomer derived from biomass because it can reduce the environmental load. For monomers derived from biomass, for example, please refer to the monomers listed in the positive list of classification number A (biomass plastics) of the Japan Bioplastics Association.

Among 100 mol% of all components constituting the polybutylene adipate terephthalate resin, the total content of the adipic acid component, terephthalic acid component, and butanediol component is preferably 70 mol% or more, and more preferably 80 mol% or more. , it is more preferable that it is 90 mol% or more, it is still more preferable that it is 95 mol% or more, and it is especially preferable that it is 99 mol% or more.

The linear fiber may contain a deodorant, an antibacterial agent, an anti-mold agent, an anti-mite agent, a deodorant, an anti-fungal agent, a fragrance, a flame retardant, a moisture absorptive and desorptive agent, an antioxidant, a lubricant, etc. These may be used individually or in combination of two or more types.

Among 100% by mass of linear fibers, the content of polybutylene adipate terephthalate resin is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 80% by mass or more, and 90% by mass or more. It is even more preferable, it is especially preferable that it is 95 mass % or more, and it is most preferable that it is 98 mass % or more. Additionally, the linear fiber may be made of polybutylene adipate terephthalate-based resin.

The linear fiber preferably has a melting point of 100°C or higher and 120°C or lower. As a result, it is possible to easily improve the compression recovery of the three-dimensional network structure after heat compression. The melting point is more preferably 115°C or lower. By performing the annealing treatment described later, the melting point of the polybutylene adipate terephthalate-based resin is reduced, and as a result, the melting point of the linear fiber can be easily reduced to 120°C or lower.

The three-dimensional network structure may have a multilayer structure. Examples of the multilayer structure include those in which the surface layer and the second layer are composed of linear fibers of different fineness, those in which the surface layer and the second layer are composed of structures with different apparent densities, and those in which long fiber nonwoven fabrics or short fiber nonwoven fabrics are laminated to create a multilayer structure. . Examples of the multilayering method include a method of melting and sticking by heating, a method of bonding with an adhesive, and a method of restraining with sewing or a band.

The shape of the three-dimensional network structure is not particularly limited, and examples include polygons such as plate shapes, triangular pillars, and square pillars, cylinders, spheres, and combinations thereof. In molding the three-dimensional network structure, a regulating plate may be used during melt extrusion of the resin, or it may be molded by cutting, heat pressing, etc.

The three-dimensional network structure preferably has a compression residual strain of 30% or less at 70°C. Thereby, compression recovery after heat compression can be improved. More preferably, it is 25% or less, and even more preferably, it is 23% or less. Additionally, the compression residual strain at 70°C may be 1% or more, and may be 5% or more. 70°C compression residual strain can be measured by the method described in the Examples described later.

The hardness of the three-dimensional network structure when compressed by 25% is preferably 5.0 N/ϕ50 mm or more and 100 N/ϕ50 mm or less. Since it is 5.0 N/ϕ50 mm or more, it is possible to reduce the impact feeling on the floor when the three-dimensional network structure is used for a cushion material or the like. Therefore, it is more preferably 5.4 N/ϕ50 mm or more, further preferably 6.0 N/ϕ50 mm or more, and even more preferably 7.0 N/ϕ50 mm or more. On the other hand, by setting it to 100N/ϕ50mm or less, cushioning properties can be improved. Therefore, it is more preferably 80 N/ϕ50 mm or less, further preferably 60 N/ϕ50 mm or less, and even more preferably 30 N/ϕ50 mm or less. Hardness at 25% compression can be measured by the method described in the Examples described later.

It is preferable that the three-dimensional network structure does not contain a bonding promoter. As a result, it is possible to easily prevent excessive hardening due to excessive bonding within the three-dimensional network structure caused by the bonding accelerator. In addition, it is possible to easily prevent a decrease in the density of the three-dimensional network structure caused by an excessive increase in the bonding range per contact point. Examples of bonding promoting resins include polycaprolactone, polybutylene succinate, polybutylene sebacate terephthalate, and polybutylene azelate terephthalate.

The three-dimensional network structure may be colored. Coloring agents such as pigments and dyes can be used for coloring. The colorant may be contained in the resin before melt spinning, or the linear fiber may be coated with the colorant by dipping or application after forming the three-dimensional network structure.

The three-dimensional network structure is preferably used for cushions. The cushion can be an elastic object that supports the object or one that reduces impact. Cushions include bedding for office chairs, furniture, sofas, and beds, cushions used for vehicle seats such as trains, automobiles, two-wheeled vehicles, car seats, and strollers, and shock absorbing mats such as floor mats and collision and pinch prevention members. You can lift a cushion.

The three-dimensional network structure can be formed, for example, by the following method. First, from a multi-row nozzle having a plurality of orifices, polybutylene adipate terephthalate resin is distributed to the nozzle orifices, and at a spinning temperature of ((melting point +20°C) or more to (melting point +180°C) or less) of the resin. It is discharged downward from the nozzle. Next, the continuous linear bodies are brought into contact with each other in a molten state and fused together to form a three-dimensional network structure, and then sandwiched between take-off conveyor nets and cooled with cooling water in the cooling tank. The distance between the nozzle surface and the surface of the coolant is preferably 15 cm or more, more preferably 20 cm or more. As a result, the porosity of the fiber and the density of the network structure can be improved. Meanwhile, the distance is preferably 40 cm or less, more preferably 35 cm or less. This makes it easy to obtain a three-dimensional network structure with an appropriate apparent density and fiber diameter. After cooling, the solidified three-dimensional network structure is taken out, and the water is removed or dried to obtain a three-dimensional network structure with both sides or one side smoothed. For these spinning and cooling processes, the description in Japanese Patent Application Laid-Open No. 7-68061 can be referred to. In the case of smoothing only one side, continuous linear bodies may be discharged onto a slanted take-off net, brought into contact with each other in a molten state, and fused together. At that time, only the surface of the take-up net needs to be cooled while relaxing its shape while forming a three-dimensional network structure. The obtained three-dimensional network structure is subjected to annealing treatment. Additionally, the drying treatment of the three-dimensional network structure may be an annealing treatment.

It is preferable to add water to the resin before discharging from the nozzle. It is preferable that the amount of water added to 100% by mass of the solid content of the resin is 0.005% by mass or more. As a result, decomposition of the resin in the manufacturing process of the three-dimensional network structure can be promoted and the flexibility of the resin can be improved. Meanwhile, it is preferable that the amount of water added is 2.0% by mass or less. As a result, excessive decomposition of the resin during the manufacturing process of the three-dimensional network structure can be prevented, and compression recovery after heat compression can be easily improved. The amount of water added is more preferably 1.0 mass% or less, further preferably 0.5 mass% or less, and even more preferably 0.2 mass% or less. In addition, the method of adding water to the resin is not particularly limited, but for example, before discharging the resin from a nozzle, the resin is vacuum dried at 100°C for 12 hours or more to dry, and for 100% by mass of the dry resin, Just add a certain amount of pure water.

The melt flow rate (MFR) of the polybutylene adipate terephthalate resin is preferably 0.5 or more and less than 20.0 less than the MFR of the desired three-dimensional network structure before melt extrusion. Since thermal or shear degradation of the resin is induced during melt extrusion, by controlling the MFR before melt extrusion as described above, it is easy to obtain a three-dimensional network structure having the desired MFR.

It is preferable to use cooling water for cooling the polybutylene adipate terephthalate resin after melt molding. Polybutylene adipate terephthalate resin may undergo molding shrinkage until it cools and solidifies. Therefore, it is sufficient to form a three-dimensional network structure with a width and thickness that takes molding shrinkage into consideration, but molding shrinkage can be reduced by lowering the melting and solidification temperature. Therefore, the temperature of the cooling water is preferably 20°C or lower, and more preferably 15°C or lower. Additionally, the cooling time using coolant is preferably 30 seconds or more. The cooling and solidification is preferably performed in a water tank.

Annealing may be performed using a commercially available hot air drying furnace or may be performed in a hot water bath. The annealing temperature is 70°C or higher. Thereby, the enthalpy of crystal fusion can be improved. Preferably it is 75°C or higher, more preferably 80°C or higher. Meanwhile, the annealing temperature is 105°C or lower. This can also improve the enthalpy of crystal fusion.

The annealing time is preferably 1 minute or more. Thereby, the enthalpy of crystal fusion can be improved. The annealing time is more preferably 5 minutes or longer, more preferably 10 minutes or longer, and even more preferably 15 minutes or longer. Meanwhile, the annealing time is preferably 60 minutes or less. As a result, yellowing, bad odor, molecular weight reduction, etc. of the polybutylene adipate terephthalate resin accompanying decomposition or deterioration of the polymer during annealing can be reduced. It can also improve productivity. The annealing time is more preferably 50 minutes or less.

After cooling and solidifying, it is preferable to maintain the temperature at 20°C to 50°C for 1 minute or more before annealing. In annealing treatment, the thickness may change due to its own weight, but by maintaining the temperature at 20°C to 50°C after cooling and solidification, the change in thickness due to annealing can be reduced. For example, after cooling and solidifying in a water bath, annealing may be performed using a continuous dryer, keeping the temperature in the first half of the oven low, and raising the temperature in the second half of the oven.

It is preferable that the moisture content of the three-dimensional network structure before annealing is 15% or less. Thereby, decomposition of the resin, etc. can be reduced. The moisture content is more preferably 12% or less, and even more preferably 10% or less. The moisture content is calculated by the following formula. The mass after vacuum drying in the formula is the mass after vacuum drying at 90°C for 2 hours.

Water 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

At any stage from the resin production process of the three-dimensional network structure to the molding process, functions such as deodorizing and antibacterial properties, anti-mold properties, mite-proof properties, deodorizing properties, anti-fungal properties, aromatic properties, flame retardancy, moisture absorptive and desorptive properties, etc. may be imparted to the resin. In addition, when manufacturing a three-dimensional network structure, the raw material polybutylene adipate terephthalate resin may contain functional imparting agents such as antioxidants and lubricants. These may be used individually or in combination of two or more types. Depending on the color tone and quality of the resin after melting, it is preferable to adjust the content of the function-imparting material by kneading various functional-imparting materials into the resin during melt extrusion.

As antioxidants, known phenolic antioxidants, phosphite antioxidants, thioether antioxidants, benzotriazole UV absorbers, triazine UV absorbers, benzophenone UV absorbers, NH-type hindered amine light stabilizers, N -CH ₃ type hindered amine light stabilizers, etc. are included, and it is preferable to contain at least one type of these.

As a phenolic antioxidant, 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 AG 80, 2, 4,6-tris (3', 5'-di-tert-butyl-4'-hydroxybenzyl) mesitylene, etc. You can.

As phosphite-based antioxidants, 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」dioxaphosphosine, tris(2,4-diphosphite) -tert-butylphenyl), tris(4-nonylphenyl) phosphite, 4,4'-isopropylidenediphenol C12-15 alcohol phosphite, diphenyl phosphite (2-ethylhexyl), diphenyl isodecyl phosphite, Triisodecyl phosphite, triphenyl phosphite, etc. can be mentioned.

As a thioether antioxidant, bis[3-(dodecylthio)propionic acid]2,2-bis["3-(dodecylthio)-1-oxopropyloxy"methyl]-1,3-propanediyl, 3 , 3'-thiobispropionate ditridecyl, etc.

In order to prevent thermal deterioration of the resin, it is preferable to use a mixture of phenol-based antioxidant and phosphite-based antioxidant. The content of these two types of antioxidants is preferably 0.05% by mass or more and 1.0% by mass or less with respect to 100% by mass of the resin composition.

Lubricants include hydrocarbon-based wax, higher alcohol-based wax, amide-based wax, ester-based wax, and metal soap-based wax. If necessary, it is preferable to contain 0.5% by mass or less of the lubricant based on mass with respect to 100% by mass of the resin composition.

This application claims the benefit of priority based on Japanese Patent Application No. 2021-058475 filed on March 30, 2021. The entire content of the specification of Japanese Patent Application No. 2021-058475 filed on March 30, 2021 is incorporated herein by reference.

Example

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and can be implemented with changes within the scope suitable for the spirit described above and below, and they are all part of the present invention. Included in technical scope.

The characteristic values of the three-dimensional network structures of Examples 1 to 7 and Comparative Examples 1 to 3 described later were measured and evaluated based on the following methods. In addition, the size of the sample was set as the standard size described below, but when there was a shortage of sample, measurement was performed using a sample of the available size.

(1) Fiber diameter

The three-dimensional network structure was cut into pieces of 10 cm x 10 cm, and linear fibers with a length of about 5 mm were collected from 10 locations each. Next, the diameter was measured by focusing on the fiber diameter measurement point of the linear fiber collected using an optical microscope, and the average value of the fiber diameter at 10 locations (n=10) was obtained.

(2) Hollow ratio

Ten linear fibers were randomly taken out from the three-dimensional network structure. Next, the linear fiber was cut into a circle, placed on a glass slide while standing in the direction of the fiber axis, and the cross-section of the fiber in the circle-cut direction was observed under an optical microscope. At this time, only linear fibers with a hollow cross-section are selected, the area (a) and hollow area (b) within the outer circumference of the fiber are respectively calculated, the hollowness is calculated based on the formula below, and the hollow linear fibers selected are The average value of porosity was obtained.

Porosity (%)=(b)/(a)×100

(3) Thickness, apparent density

The three-dimensional network structure was cut into a size of 10 cm was measured, and the height of the sample was taken as the thickness of the three-dimensional network structure. Additionally, the weight of the sample was measured by placing it on an electronic balance. The volume of the sample was obtained by multiplying the height of the sample by the vertical and horizontal area (100㎠), and the weight of the sample was divided by the volume to obtain the apparent density. This operation was performed three times, and the average values (n=3) of the thickness and apparent density of the three-dimensional network structure were obtained.

(4) Melting point (Tm)

Using a differential scanning calorimeter Discovery DSC25 manufactured by TA Instruments, a sample was taken from the three-dimensional network structure, the sample mass was weighed to 2.0 mg ± 0.1 mg, and the endothermic heat was measured under the conditions of a temperature increase rate of 20°C/min and a nitrogen atmosphere. From the curve, the endothermic peak (melting peak) temperature was determined. This operation was performed three times, and the average value of melting point (n=3) was determined.

(5) Enthalpy of fusion

A sample was taken from the three-dimensional network structure, the sample mass was weighed to 2.0 mg ± 0.1 mg, and the endothermic heat was measured using a differential scanning calorimeter Discovery DSC25 manufactured by TA Instruments at a temperature increase rate of 20°C/min and a nitrogen atmosphere. The crystal melting enthalpy (J/g) was obtained from the integrated value of the endothermic peak (melting peak) from the curve. In detail, the integrated value of the endothermic peak (melting peak) takes as the starting point the point where the curve related to the endothermic peak (melting peak) begins to separate from the base line on the low temperature side, and touches the base line on the high temperature side. The starting point was used as the end point, a straight line was drawn connecting the start point and the end point, and the result was obtained by integrating over the portion surrounded by the straight line and the curve. This operation was performed three times, and the average value of the enthalpy of crystal fusion (n=3) was determined. Additionally, the starting point was set as the melting onset temperature (°C).

(6) Melt flow rate (MFR)

The three-dimensional network structure was finely chopped to use as a raw material, and after vacuum-drying at 80°C for more than 2 hours, the melt flow rate (MFR) was quickly measured to ensure that it did not contain as much moisture in the air as possible. The melt flow rate was measured in accordance with ISO1133 using a melt indexer F-F01 manufactured by Toyo Seki Seisakusho. The measurement temperature was 190°C and the load was 2.16 kg. This operation was performed three times, and the average value of the melt flow rate (n=3) was determined.

(7) Weight average molecular weight

A sample was taken from the three-dimensional network structure, and in order to reduce sample variation, 40 mg of the sample, 10 times the amount of the normal sample, was finely cut and dissolved. The sample solution was diluted with chloroform to adjust the sample concentration to 0.05%. GPC analysis of the sample solution obtained by filtration through a 0.2 μm membrane filter was performed under the following conditions. The molecular weight was calculated using standard polystyrene conversion.

Device: TOSOH HLC-8320GPC

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

Solvent: Chloroform

Flow rate: 0.6ml/min

Concentration: 0.05%

Injection volume: 20μL

Temperature: 40℃

Detector: RI, UV254㎚

(8) 70℃ compression residual strain

The three-dimensional network structure was cut into a size of 10 cm x 10 cm, and the thickness (c) before treatment was measured for the obtained sample by the method described in (2) above. The sample whose thickness was measured was sandwiched between a jig capable of maintaining 50% compression, placed in a dryer set at 70°C, and left for 22 hours. After that, the sample was taken out, cooled, compressive strain was removed, and the thickness (d) after being left for 30 minutes was determined. These thicknesses were applied to the equation {(c)-(d)}/(c)×100 to obtain the 70°C compression residual strain. This operation was performed three times, and the average value of 70°C compression residual strain (n=3) was determined.

(9) Hardness at 25% compression

The three-dimensional network structure was cut into a size of 10 cm x 10 cm, and the obtained sample was left unloaded in an environment of 23°C ± 2°C for 24 hours. Next, measurement was performed in accordance with ISO2439 (2008) E method using Autograph AG-X plus manufactured by Shimadzu Seisakusho under an environment of 23°C ± 2°C. Specifically, a pressure plate with a diameter (ϕ) of 50 mm was placed at the center of the sample, the thickness when the load reached 0.5 N was measured, and this was taken as the initial thickness. At this time, the position of the pressure plate was set as the zero point, preliminary compression was performed once at a speed of 100 mm/min to 75% of the initial thickness, the pressure plate was returned to the zero point at the same speed, and then left in the same state for 4 minutes. . After that, compression was immediately performed to 25% of the initial thickness at a speed of 100 mm/min, the load at that time was measured, and the load was defined as hardness (N/ϕ50 mm) at the time of 25% compression. This operation was performed three times, and the average value of hardness at 25% compression (n=3) was obtained.

As a polybutylene adipate terephthalate resin, TH-801T manufactured by XINJIANG BLUE RIDGE TUNHE CHEMICAL INDUSTRY JOINT STOCK was used. The weight average molecular weight of the resin was 12.3×10 ⁴ g/mol, and the melt flow rate (MFR) was 4 g/10 min.

[Example 1]

The water tank was arranged so that the cooling water surface was located 17 cm below the nozzle surface of the nozzle for discharging the molten resin, the water temperature was set to 12°C, and a pair of take-up conveyors were placed in the water tank so that a part of them was above the water surface. The take-off conveyor has an endless net made of stainless steel with a width of 20 cm, the conveyor is arranged in parallel with the width direction of the nozzle surface, the opening width of the endless net is set to 30 mm, and an aluminum plate is placed in the net direction to form the side portion. It was placed in a direction of 90 degrees with respect to the side portion and water was flowed at a rate of 1.0 L/min.

As the molten resin discharge nozzle, a nozzle was used in which round hole-shaped orifices with an outer diameter of 0.5 mm were formed in a zigzag arrangement with an inter-hole pitch of 6 mm on an effective surface of the nozzle with a width of 96 mm in the width direction and a width of 31 mm in the thickness direction. . The raw material resin was dried and dried, and 0.01% by mass of water was added based on 100% by mass of the solid content of the resin. Then, the molten resin was discharged below the nozzle at a spinning temperature of 260°C and a single hole discharge rate of 1.0 g/min.

The molten resin is discharged in a linear form at the opening of the net of the conveyor, on the net of the conveyor, and on the aluminum plate on the side surface, and a continuous linear body is dropped and bent to form a loop, and the contact portion is fused. This formed a three-dimensional network structure. The two sides of the three-dimensional network structure in the molten state are inserted into the cooling water at a speed of 0.86 m/min while being sandwiched between the conveyors, and are solidified to flatten both sides in the thickness direction and the lateral direction, and then to a predetermined size. was cut into Next, it was left to stand in a space at 25°C for 1 hour. The water content of the obtained three-dimensional network structure was 9%, and it was annealed by drying with hot air at 80°C for 20 minutes to obtain a three-dimensional network structure with a width of 100 mm. The cross-sectional shape of the linear fibers of the three-dimensional network structure was circular.

[Example 2]

Water was added at an dosage of 0.30% by mass based on 100% by mass of the solid content of the resin, and a nozzle was used in which the orifices on the hollow cross-section of the triple bridge with an outer diameter of 5.0 mm and an inner diameter of 4.4 mm were formed in a zigzag arrangement with a pitch between holes of 8 mm. A three-dimensional network structure was obtained in the same manner as in Example 1, except that the spinning temperature was 231°C, the single hole discharge amount was 1.5 g/min, the pulling speed was 0.92 m/min, and the drying temperature was 105°C. The cross-sectional shape of the linear fibers of the three-dimensional network structure was hollow.

[Example 3]

A three-dimensional network structure was obtained in the same manner as in Example 2, except that water was added at an amount of 0.40% by mass based on 100% by mass of the solid content of the resin, the spinning temperature was 230°C, and the drying temperature was 90°C.

[Example 4]

A three-dimensional network structure was obtained in the same manner as in Example 3, except that water was added at an amount of 0.01 mass% based on 100 mass% of the solid content of the resin, the spinning temperature was 240 ° C., and the nozzle surface-coolant distance was 25 cm.

[Example 5]

After drying the raw material resin, a three-dimensional network structure was obtained in the same manner as in Example 1, except that water was not added, the single hole discharge amount was 0.5 g/min, and the pulling speed was 0.64 m/min.

[Example 6]

A three-dimensional network structure was obtained in the same manner as in Example 3, except that water was added at an amount of 0.20% by mass based on 100% by mass of the solid content of the resin, the spinning temperature was 190°C, and the nozzle surface-coolant distance was 30cm.

[Example 7]

A network structure was obtained in the same manner as in Example 5, except that the spinning temperature was 210°C, the single hole discharge amount was 1.0 g/min, and the pulling speed was 1.28 m/min.

[Comparative Example 1]

Example 1 and 1, except that 2.5% by mass of water was added based on 100% by mass of solid content of the resin, the single hole discharge amount was 0.9g/min, the nozzle surface-coolant distance was 18cm, and the take-up speed was 0.52m/min. In the same manner, a three-dimensional network structure was obtained.

[Comparative Example 2]

A three-dimensional network structure was obtained in the same manner as in Example 4, except that water was added at an amount of 0.02% by mass based on 100% by mass of the solid content of the resin, and drying was performed at 20 to 25°C for 2 days without annealing.

[Comparative Example 3]

A network structure was obtained in the same manner as in Example 2, except that the spinning temperature was 230°C, the pulling speed was 1.54 m/min, and the drying temperature was 107°C.

Table 1 shows the production conditions in Examples 1 to 7 and Comparative Examples 1 to 3 and the properties of the obtained three-dimensional network structures. In Table 1, the numerical values of characteristics evaluated multiple times are average values.

The three-dimensional network structures obtained in Examples 1 to 7 were excellent in compression durability and compression recovery after heat compression. In addition, Examples 1 to 6 were able to reduce the polymer melt viscosity at the time of discharge, so that precise and dense loops could be produced and the surface and appearance quality were excellent.

The network structure obtained in Comparative Example 1 had a low weight average molecular weight and poor compression recovery after heat compression. Additionally, the network structure obtained in Comparative Example 1 was slightly yellowed. This is thought to be due to the high water content of the three-dimensional network structure before annealing.

The network structures obtained in Comparative Examples 2 and 3 had low crystal melting enthalpy and were poor in compression durability and compression recovery after heat compression.

Claims (8)

The apparent density is 0.005 g/cm3 to 0.30 g/cm3,
The thickness is 10 mm to 100 mm,
It includes linear fibers, and the linear fibers have a fiber diameter of 0.2 mm to 2.0 mm, a crystal melting enthalpy of 16 J/g or more, and a weight average molecular weight of 35000 or more. Characterized by comprising a polybutylene adipate terephthalate-based resin. A biodegradable three-dimensional network structure. The biodegradable three-dimensional network structure according to claim 1, wherein the linear fibers form a three-dimensional random loop structure. The biodegradable three-dimensional network structure according to claim 1 or 2, wherein the crystal melting enthalpy is 30 J/g or less. The biodegradable three-dimensional network structure according to any one of claims 1 to 3, which is used for cushions. The biodegradable three-dimensional network structure according to any one of claims 1 to 4, wherein the polybutylene adipate terephthalate-based resin has a weight average molecular weight of 150,000 or less. The biodegradable three-dimensional network structure according to any one of claims 1 to 5, wherein the linear fibers have a melting point of 100°C or higher and 120°C or lower. The biodegradable three-dimensional network structure according to any one of claims 1 to 6, wherein the linear fibers have a hollow cross-sectional shape. The biodegradable three-dimensional network structure according to claim 7, wherein the linear fibers have a porosity of 1% or more and 30% or less.