CN117083426B

CN117083426B - Biodegradable three-dimensional network structure

Info

Publication number: CN117083426B
Application number: CN202280025227.4A
Authority: CN
Inventors: 谷中辉之; 川野史香; 佐仓大介; 小渊信一
Original assignee: Dongyang Textile Mc Co ltd
Current assignee: Dongyang Textile Mc Co ltd
Priority date: 2021-03-30
Filing date: 2022-03-17
Publication date: 2025-10-31
Anticipated expiration: 2042-03-17
Also published as: JP2023129674A; CN117083426A; AU2022249508A1; TW202302018A; JPWO2022209976A1; TWI877471B; EP4317567A1; US20240150945A1; JP7207614B1; WO2022209976A1; KR20230161948A; JP7327694B2; JP2023026596A; EP4317567A4

Abstract

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

Description

Biodegradable three-dimensional network structure

Technical Field

The present invention relates to a biodegradable three-dimensional network structure.

Background

Various biodegradable three-dimensional network structures have been known heretofore. For example, patent document 1 discloses a biodegradable aquatic plant support for greening, which is formed of a three-dimensional network body having three-dimensional random rings formed by joining a plurality of continuous linear bodies which are bent and curved and have a biodegradable thermoplastic resin at least in part. Patent document 2 discloses a three-dimensional network fiber material aggregate which is biodegradable, the aggregate being composed of a plurality of fiber materials forming partial bonds with each other, the fiber materials having a composition containing at least a biodegradable resin and a bonding promoting resin for partial bonds. Patent document 3 discloses a biodegradable three-dimensional structure in which a string composed mainly of a thermoplastic polylactic acid resin having a fineness of 300 to 100000 denier is repeatedly bent and bonded to a large part of a contact portion.

Prior art literature

Patent literature

Patent document 1 Japanese patent laid-open No. 2001-32236

Patent document 2 Japanese patent application laid-open No. 2020-128608

Patent document 3 Japanese patent laid-open No. 2000-328422

Disclosure of Invention

Problems to be solved by the invention

Patent document 1 discloses a technique for improving plant retention of a biodegradable network structure. Further, patent document 2 discloses a technique of locally joining fiber materials of a biodegradable mesh structure. Patent document 3 discloses a technique of forming a coil spring-like or annular portion in a biodegradable three-dimensional structure, and appropriately deforming the portion against compressive stress to disperse the stress. As described above, various attempts have been made to improve the function of the biodegradable net structure, but the biodegradable net structure having excellent properties of both compression durability and compression recovery after heat compression has not been known. The present invention has been made in view of the above circumstances, and an object thereof is to provide a biodegradable three-dimensional network structure excellent in compression durability and compression recovery after heat compression.

Solution for solving the problem

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

[1] A biodegradable three-dimensional network structure characterized by having an apparent density of 0.005g/cm ³～0.30g/cm³ and a thickness of 10mm to 100mm and comprising linear fibers,

The linear fiber has a fiber diameter of 0.2-2.0 mm, a crystalline melting enthalpy of 16J/g or more, and comprises a polybutylene adipate terephthalate resin having a weight average molecular weight of 35000 or more.

With the above configuration, compression durability and compression recovery after heat compression can be improved. A preferred mode 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 ring structure.

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

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

[5] The biodegradable three-dimensional network structure according to any one of [1] to [4], wherein the polybutylene adipate terephthalate resin has a weight-average molecular weight of 150000 or less.

[6] The biodegradable three-dimensional network structure according to any one of [1] to [5], wherein the linear fiber has a melting point of 100 ℃ to 120 ℃.

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

[8] The biodegradable three-dimensional network structure according to item [7], wherein the hollow ratio of the linear fiber is 1% or more and 30% or less.

[9] The biodegradable three-dimensional network structure according to item [7], wherein the hollow ratio of the linear fibers is 2% or more and 25% or less.

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

[11] The biodegradable three-dimensional network structure according to any one of [1] to [10], wherein the crystal fusion enthalpy is 28J/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 120000 or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, with the above configuration, a biodegradable three-dimensional network structure excellent in compression durability and compression recovery after heat compression can be provided.

Drawings

Fig. 1 is an example of an endothermic heat release curve for measuring the crystal fusion enthalpy of linear fibers contained in a three-dimensional network structure.

Detailed Description

The biodegradable three-dimensional network structure according to the embodiment of the present invention has an apparent density of 0.005g/cm ³～0.30g/cm³, a thickness of 10mm to 100mm, and comprises linear fibers having a fiber diameter of 0.2mm to 2.0mm, a crystalline melting enthalpy of 16J/g or more, and a polybutylene adipate terephthalate resin having a weight average molecular weight of 35000 or more. With the above configuration, compression durability and compression recovery after heat compression can be improved. Hereinafter, each configuration will be described in detail.

The apparent density of the three-dimensional network structure was 0.005g/cm ³～0.30g/cm³. The apparent density is set to 0.005g/cm ³ or more, whereby the hardness of the three-dimensional network structure is improved. As a result, the use of the three-dimensional network structure for cushioning and the like can reduce the feeling of bottoming. For this reason, the apparent density is preferably 0.01g/cm ³ or more, more preferably 0.02g/cm ³ or more, still more preferably 0.03g/cm ³ or more, still more preferably 0.05g/cm ³ or more. On the other hand, when the apparent density is not more than 0.30g/cm ³, the flexibility is improved, and the composition can be suitably used for cushioning materials and the like. For this reason, the apparent density is preferably 0.20g/cm ³ or less, more preferably 0.15g/cm ³ or less. The apparent density of the three-dimensional network structure can be measured by the method described in examples below.

Three-dimensional net-like structure the thickness is 10 mm-100 mm. By making the thickness 10mm or more, the three-dimensional net-like structure can be easily used as a cushioning material or the like. The thickness is preferably 15mm or more, more preferably 20mm or more, and still more preferably 22mm or more. On the other hand, the thickness is 100mm or less, preferably 90mm or less, more preferably 80mm or less, and still more preferably 50mm or less, considering the size of the manufacturing apparatus. The thickness of the three-dimensional network structure can be measured by the method described in examples below.

The three-dimensional network structure comprises linear fibers. The linear fibers preferably form a three-dimensional random loop structure. The linear fiber is preferably a continuous linear body. The continuous filament means a filament having a continuous portion of at least 5mm or more. The three-dimensional net-like structure is easily formed by bonding the intersecting portions of the continuous linear bodies. Therefore, the three-dimensional net-like structure preferably has an adhesion portion where the intersecting portions of the linear fibers adhere to each other.

The linear fibers may be composite linear bodies such as core-sheath type, side-by-side type, core-spun type, and the like. The composite yarn may be a composite yarn obtained by combining a polybutylene adipate terephthalate resin with another thermoplastic resin. The linear fiber may have a hollow cross section or a solid cross section, and is preferably a hollow cross section because it can be reduced in weight. In addition, by setting the cross-sectional shape of the linear fiber to be a hollow cross-section, the compression recovery after the heat compression is improved. The linear fiber preferably has an irregular cross section in cross section. This makes it possible to easily impart appropriate hardness and cushioning properties to the three-dimensional network structure. The hollow ratio of the linear fibers is preferably 1% or more, more preferably 2% or more, still more preferably 5% or more, and is preferably 30% or less, more preferably 25% or less, still more preferably 20% or less. The hollow ratio of the linear fiber can be measured by the method described in examples described below.

The fiber diameter of the linear fiber is 0.2 mm-2.0 mm. The hardness is improved by setting the fiber diameter to 0.2mm or more. For this reason, the fiber diameter is preferably 0.3mm or more, more preferably 0.4mm or more. On the other hand, by setting the fiber diameter to 2.0mm or less, the compactness of the net structure can be improved, cushioning properties and the like can be improved, and the touch of the net structure can be easily softened. For this reason, the fiber diameter is preferably 1.7mm or less, more preferably 1.5mm or less, and still more preferably 1.2mm or less. The fiber diameter of the linear fiber can be measured by the method described in examples described later. The shape of the cross-sectional profile of the linear fibers may be circular, elliptical, polygonal, or rounded-corner polygonal. The fiber diameter of a fiber whose contour is a shape other than a circle corresponds to the maximum distance between any two points on the fiber contour.

The Melt Flow Rate (MFR) of the linear fibers is preferably 3g/10 min to 60g/10 min. When the MFR is 3g/10 min or more, the melt viscosity is easily increased, and the fiber diameter of the linear fiber can be increased. The MFR is more preferably 4g/10 min or more, still more preferably 6g/10 min or more, still more preferably 8g/10 min or more, particularly preferably 10g/10 min or more. On the other hand, when the MFR is 60g/10 min or less, the compression recovery after heat compression is easily improved. The MFR is more preferably 50g/10 min or less, still more preferably 40g/10 min or less, still more preferably 30g/10 min or less, particularly preferably 25g/10 min or less. The MFR of the linear fiber can be measured by the method described in examples described below.

When a commercially available resin is used as the polybutylene adipate terephthalate-based resin constituting the linear fibers and the Melt Flow Rate (MFR) of the resin is low, the MFR of the resin can be increased by adding moisture to the resin and hydrolyzing the resin at the time of melt extrusion. This can increase the MFR of the linear fiber. 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 performing melt extrusion. This can reduce the MFR of the linear fiber.

The enthalpy of crystal fusion of the linear fiber is more than 16J/g. By setting the crystal fusion enthalpy to 16J/g or more, the compression durability and the compression recovery after heat compression of the three-dimensional network structure can be improved. The enthalpy of crystallization and melting is preferably 17J/g or more, more preferably 18J/g or more, still more preferably 19J/g or more, still more preferably 20J/g or more, particularly preferably 21J/g or more. On the other hand, the enthalpy of crystallization and melting is preferably 30J/g or less. Thus, the flexibility of the three-dimensional net structure is improved, and noise generation during compression and recovery can be reduced. The enthalpy of crystal fusion is more preferably 28J/g or less, still more preferably 26J/g or less.

The enthalpy of crystal fusion (J/g) of the linear fiber can be determined by measuring the sample mass at 2.0 mg.+ -. 0.1mg using a differential scanning calorimeter at a temperature rise rate of 20 ℃ per minute under a nitrogen atmosphere and determining the integral value of the endothermic peak (melting peak) of the endothermic/exothermic curve obtained thereby. The integrated value can be obtained by integrating a portion surrounded by a straight line connecting a start point and an end point of a curve relating to the endothermic peak (melting peak) with the start point of the curve starting to be separated from the low-temperature side base line as the start point and the point of the curve starting to be contacted with the high-temperature side base line as the end point. An example of the endothermic/exothermic curve is shown in fig. 1. The broken line in fig. 1 is a straight line connecting the above-described start point and end point of the endothermic peak (melting peak), and the portion surrounded by the broken line and the curve is an integration region where integration is performed.

When a commercially available resin is used as the polybutylene adipate terephthalate resin constituting the linear fibers and the crystal fusion enthalpy is lower than the desired range, the crystal fusion enthalpy can be controlled to the desired range by annealing as described later.

The polybutylene adipate terephthalate-based resin is a biodegradable resin, which is a copolymer of adipic acid, terephthalic acid and butanediol. Since polybutylene adipate terephthalate-based resin is a biodegradable resin, it is expected to be a strategy for solving the problem of disposal of garbage and the problem of microplastic. The adipic acid, terephthalic acid and butanediol do not need to be copolymerized simultaneously, and the copolymerization can also be carried out in multiple stages. The polybutylene adipate-based resin is preferably a thermoplastic resin.

In the synthesis of the polybutylene adipate-terephthalate resin, a small amount of other copolymerization components may be added in addition to adipic acid, terephthalic acid, and butanediol. Examples of the other copolymerization component include dicarboxylic acids other than terephthalic acid and adipic acid, and modifiers for chain extension, end capping, and the like. These may be used singly or in combination of two or more.

Examples of the other dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, and suberic acid. These may be used singly or in combination of two or more.

The modifier may be a polyisocyanate compound, a diol compound, or the like. The polyisocyanate compound may be a diisocyanate compound. Examples of the diisocyanate compound include hexamethylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, xylylene diisocyanate, 1, 5-naphthalene diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, carbodiimide-modified MDI, and polymethylene phenyl polyisocyanate. These may be used singly or in combination of two or more. The diol compound includes diols other than butanediol and polyalkylene glycols. Examples of the other diols include methyl glycol, ethylene glycol, propylene glycol, pentanediol, and hexanediol. Examples of the polyalkylene glycol include polymethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol (polytetramethylene glycol), and the like. These may be used singly or in combination of two or more.

The polybutylene adipate terephthalate resin may be a biodegradable synthetic polymer compound described in the accepted order (positive list) of green plastics (biodegradable plastics) of the japanese bioplastic society, classification No. a-1. Specifically, ECOFLEX (registered trademark) manufactured by BASF JAPAN, eastar Bio, GP, eastar Bio, ultra manufactured by GSI Creos (Novamont Co.), A400 (ECOPOND KD) manufactured by KINGFA, and TUNHE PBAT TH-801T manufactured by XINJIANG BLUE RIDGE TUNHE CHEMICAL INDUSTRY JOINT STOCK are exemplified. These may be used singly or in combination of two or more.

The weight average molecular weight (g/mol) of the polybutylene adipate-terephthalate resin is 35000 or more. This can improve the compression recovery after the heat compression. The weight average molecular weight is preferably 37000 or more, more preferably 40000 or more. On the other hand, the flexibility can be improved by making the weight average molecular weight 150000 or less. The weight average molecular weight is preferably 150000 or less. Further, by setting the weight average molecular weight to 120000 or less, the melt viscosity of the polymer can be reduced. The weight average molecular weight is more preferably 120000 or less. The weight average molecular weight (g/mol) of the resin constituting the linear fibers is also preferably within this range. The weight average molecular weight can be determined by Gel Permeation Chromatography (GPC) or the like.

The linear fibers may contain a biodegradable resin other than the polybutylene adipate terephthalate-based resin. The other biodegradable resin is preferably polylactic acid, polylactic acid/polycaprolactone copolymer, polylactic acid/polyether copolymer, polyethylene terephthalate polysuccinate, polybutylene succinate, polybutylene adipate succinate, polyglycolic acid, polycaprolactone, polyvinyl alcohol, cellulose acetate, or the like. These may be used singly or in combination of two or more. Their details are referred to the imported goods list of class number a-1 of green plastics (biodegradable plastics) of japan bio-plastics society. The linear fibers may contain resins other than the biodegradable resin. Examples of the resin include thermoplastic resins such as polyurethane and polyester.

As the monomer for synthesizing the resin constituting the linear fiber, a monomer derived from petroleum may be used, but when a monomer derived from biomass is used, the environmental load can be reduced, so that it is preferable. For the biomass-derived monomer, for example, a monomer described in the accepted bill of classification No. a (biomass plastics) of japan bio-plastics society may be referred to.

The total content of the adipic acid component, the terephthalic acid component, and the butanediol component in 100 mol% of the total components constituting the polybutylene adipate-terephthalate resin is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, still more preferably 95 mol% or more, and particularly preferably 99 mol% or more.

The linear fibers may contain deodorant, antibacterial, antifungal, anti-mite, deodorant, antifungal, aromatic, flame retardant, hygroscopic and hygroscopic agent, antioxidant, lubricant, etc. These may be used singly or in combination of two or more.

The content of the polybutylene adipate terephthalate resin in 100 mass% of the linear fiber is preferably 50 mass% or more, more preferably 60 mass% or more, still more preferably 80 mass% or more, still more preferably 90 mass% or more, particularly preferably 95 mass% or more, and most preferably 98 mass% or more. The linear fibers may be composed of polybutylene adipate terephthalate resin.

The melting point of the linear fiber is preferably 100 ℃ or more and 120 ℃ or less. This makes it easy to improve the compression recovery of the three-dimensional network after heat compression. The melting point is more preferably 115 ℃ or less. By performing the annealing treatment described later, the melting point of the polybutylene adipate terephthalate resin is reduced, and as a result, the melting point of the linear fiber is easily reduced to 120 ℃.

The three-dimensional network structure may have a multi-layer structure. Examples of the multilayer structure include a structure in which the top layer and the back layer are made of linear fibers having different deniers, a structure in which the top layer and the back layer are made of structures having different apparent densities, and a structure in which a long fiber nonwoven fabric, a short fiber nonwoven fabric, or the like is laminated and multilayered. Examples of the multilayered method include a method of fusion-fixing by heating, a method of bonding by an adhesive, and a method of binding by sewing or a binding tape.

The shape of the three-dimensional network structure is not particularly limited, and examples thereof include polygonal bodies such as a plate, a triangular prism, and a quadrangular prism, and cylindrical, spherical, and a combination thereof. In forming the three-dimensional net-like structure, the resin may be formed by using a limiting plate at the time of melt extrusion, or may be formed by cutting, hot pressing, or the like.

The compression set at 70 ℃ of the three-dimensional network structure is preferably 30% or less. This can improve the compression recovery after the heat compression. More preferably 25% or less, and still more preferably 23% or less. The compression set at 70 ℃ may be 1% or more, or may be 5% or more. Compression set at 70℃can be measured by the method described in examples below.

The three-dimensional network structure preferably has a 25% compression hardness of 5.0N/phi 50mm or more and 100N/phi 50mm or less. When the thickness is 5.0N/50 mm or more, the bottoming sensation can be reduced when the three-dimensional network structure is used as a cushioning material or the like. Therefore, it is more preferably 5.4N/phi 50mm or more, still more preferably 6.0N/phi 50mm or more, still more preferably 7.0N/phi 50mm or more. On the other hand, the cushioning property can be improved by setting the ratio to 100N/. Phi.50 mm or less. Therefore, it is more preferably 80N/50 mm or less, still more preferably 60N/50 mm or less, still more preferably 30N/50 mm or less. The 25% compression hardness can be measured by the method described in examples below.

The three-dimensional network preferably contains no bonding promoter. This can easily prevent excessive curing caused by excessive bonding in the three-dimensional network structure by the bonding accelerator. In addition, it is possible to easily prevent the decrease in compactness of the three-dimensional network structure accompanied by an excessive increase in the joining range per 1 contact point on average. Examples of the bonding-promoting resin include polycaprolactone, polybutylene succinate, polybutylene sebacate and polybutylene azelate.

The three-dimensional network may be colored. As the coloring agent, a coloring agent such as pigment and dye can be used. The colorant may be contained in the resin before melt spinning, or may be coated on the linear fibers by dipping or coating after forming the three-dimensional network structure.

The three-dimensional network is preferably used for a buffer. The buffer may be any one having an elastic force for supporting the object or an impact-reducing object. Examples of the cushion include cushions used for bedding such as office chairs, furniture, sofas, and beds, seats for vehicles such as electric cars, automobiles, two-wheelers, child seats, and strollers, and cushions used for impact absorbing mats such as floor mats, impact-resistant members, and anti-pinch members.

The three-dimensional network structure can be formed by, for example, the following method. First, a polybutylene adipate terephthalate resin is dispensed from a plurality of rows of nozzles having a plurality of orifices to the nozzle orifices, and the polybutylene adipate terephthalate resin is discharged downward from the nozzles at a spinning temperature ((melting point +20 ℃) or more and less (melting point +180 ℃) of the resin). Then, the continuous linear bodies are brought into contact with each other in a molten state to be welded, and the three-dimensional net structure is formed, and the three-dimensional net structure is sandwiched by the traction conveyor and cooled by cooling water in the cooling tank. The distance between the nozzle surface and the water surface of the cooling water is preferably 15cm or more, more preferably 20cm or more. This can improve the hollow rate of the fiber and the compactness of the network structure. On the other hand, the distance is preferably 40cm or less, more preferably 35cm or less. Thus, a three-dimensional network structure having an appropriate apparent density and fiber diameter can be easily obtained. After cooling, the solidified three-dimensional network structure is drawn out, and after water control or drying, a three-dimensional network structure with both sides or one side smoothed is obtained. For these spinning and cooling steps, refer to the description of Japanese patent application laid-open No. 7-68061. When smoothing only one surface, the continuous linear body is ejected onto a traction net having a slope, and the continuous linear body is brought into contact with each other in a molten state to be welded. At this time, the three-dimensional net structure is formed and only the traction net surface is cooled while in a relaxed state. And annealing the obtained three-dimensional network structure. The drying treatment of the three-dimensional network structure may be an annealing treatment.

Preferably, water is added to the resin before ejection from the nozzle. The amount of water to be added is preferably 0.005% by mass or more based on 100% by mass of the solid content of the resin. This can promote resin decomposition in the process of producing the three-dimensional net-like structure, and can improve flexibility of the resin. On the other hand, the amount of water to be fed is preferably 2.0 mass% or less. This prevents excessive decomposition of the resin in the process of producing the three-dimensional net-like structure, and easily improves the compression recovery after heat compression. The amount of water to be added is more preferably 1.0 mass% or less, still more preferably 0.5 mass% or less, still more preferably 0.2 mass% or less. The method of adding water to the resin is not particularly limited, and for example, before the resin is ejected from the nozzle, the resin may be dried in vacuo at 100 ℃ for 12 hours or more to be dried in absolute terms, and a predetermined amount of pure water may be added to 100 mass% of the resin dried in absolute terms.

The Melt Flow Rate (MFR) of the polybutylene adipate-based resin is preferably 0.5 or more and less than 20.0 smaller than the MFR of the desired three-dimensional network at a time before melt extrusion. Since thermal degradation and shear degradation of the resin are induced during melt extrusion, a three-dimensional network structure having a desired MFR can be easily obtained by controlling the MFR before melt extrusion as described above.

Cooling water is preferably used for cooling the polybutylene adipate-based resin after melt molding. The polybutylene adipate terephthalate resin may shrink until it is cooled and solidified. Therefore, a three-dimensional network structure having a width and a thickness in consideration of molding shrinkage may be formed, and the molding shrinkage can be reduced by lowering the melt-curing temperature. Therefore, the water temperature of the cooling water is preferably 20 ℃ or less, more preferably 15 ℃ or less. The cooling time by the cooling water is preferably 30 seconds or longer. The cooling and solidification are preferably performed in a water tank.

The annealing may be performed using a commercially available hot air drying furnace or in a warm water bath. The annealing temperature is above 70 ℃. This can improve the enthalpy of crystal fusion. Preferably 75 ℃ or higher, more preferably 80 ℃ or higher. On the other hand, the annealing temperature is 105 ℃ or lower. This can also increase the enthalpy of crystal fusion.

The annealing time is preferably 1 minute or more. This can improve the enthalpy of crystal fusion. The annealing time is more preferably 5 minutes or more, still more preferably 10 minutes or more, still more preferably 15 minutes or more. On the other hand, the annealing time is preferably 60 minutes or less. This can reduce yellowing, off-flavor, and molecular weight reduction of the polybutylene adipate terephthalate resin associated with decomposition, degradation, and the like of the polymer during annealing. Further, productivity can be improved. The annealing time is more preferably 50 minutes or less.

After cooling and solidifying and before annealing, the temperature is preferably kept at 20-50 ℃ for more than 1 minute. In the annealing treatment, the thickness change may be caused by its own weight, and the thickness change caused by annealing can be reduced by holding the material at a temperature of 20 ℃ to 50 ℃ after cooling and solidification. For example, after cooling and solidification by a water tank, a continuous dryer may be used to lower the temperature of the first half of the oven and hold the temperature, and further to raise the temperature of the second half of the oven to perform annealing.

The water content of the three-dimensional network structure before annealing is preferably 15% or less. This can reduce the decomposition of the resin and the like. The water content is more preferably 12% or less, and still more preferably 10% or less. The water content was calculated by the following formula. The mass after vacuum drying in the formula was set to a mass after vacuum drying at 90 ℃ for 2 hours.

Water content (%) = { (mass of the three-dimensional network before vacuum drying) - (mass of the three-dimensional network after vacuum drying) }/(mass of the three-dimensional network before vacuum drying) ×100

The resin may be provided with functions such as deodorization, antibacterial, mildewproof, anti-mite, deodorizing, mildewproof, aromatic, flame retardant, moisture absorbing and releasing properties, and the like at any stage from the resin production process to the molding process of the three-dimensional net-like structure. In addition, in the production of the three-dimensional network structure, the polybutylene adipate terephthalate resin as a raw material may contain a function-imparting material such as an antioxidant or a lubricant. These may be used singly or in combination of two or more. It is preferable to mix various functional imparting materials with the resin at the time of melt extrusion and adjust the content of the functional imparting materials according to the color tone and quality of the melted resin.

Examples of the antioxidant include known phenol antioxidants, phosphite antioxidants, thioether antioxidants, benzotriazole ultraviolet absorbers, triazine ultraviolet absorbers, benzophenone ultraviolet absorbers, N-H type hindered amine light stabilizers, N-CH ₃ type hindered amine light stabilizers, and the like, and preferably at least one of these is contained.

Examples of the 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, 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4 '-butylidenebis (6-t-butyl-m-cresol), stearyl 3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], sumilizer AG 80, 2,4, 6-tris (3', 5 '-di-t-butyl-4' -hydroxybenzyl) mesitylene, and the like.

Examples of the phosphite-based antioxidant include 3, 9-bis (octadecyloxy) -2,4,8, 10-tetraoxa-3, 9-diphosphaspiro [5.5] undecane, 3, 9-bis (2, 6-di-t-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-dioxaphosph octa (dioxaphosphocin), tris (2, 4-di-t-butylphenyl) phosphite, tris (4-nonylphenyl) phosphite, 4' -isopropylidenediphenol C12-15 alcohol phosphite, diphenyl (2-ethylhexyl) phosphite, diphenylisodecyl phosphite, triisodecyl phosphite, triphenyl phosphite and the like.

Examples of the thioether antioxidant include 2, 2-bis [ (3- (dodecylthio) -1-oxopropoxy) methyl ] -1, 3-propane diester of bis [3- (dodecylthio) propionic acid ] and ditridecyl 3,3' -thiodipropionate.

In order to prevent thermal degradation of the resin, a phenolic antioxidant and a phosphite antioxidant are preferably used in combination. The content of these two antioxidants is preferably 0.05 mass% or more and 1.0 mass% or less relative to 100 mass% of the resin composition.

Examples of the lubricant include hydrocarbon waxes, higher alcohol waxes, amide waxes, ester waxes, and metal soaps. If necessary, the lubricant is preferably contained in an amount of 0.5 mass% or less based on 100 mass% of the resin composition.

The present application claims priority based on japanese patent application No. 2021-058475 filed on 3 months of 2021. The entire contents of the specification of Japanese patent application No. 2021-058475 filed on 3/30/2021 are incorporated herein by reference.

Examples

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples, and may be implemented with modifications within the scope of the above-described and the following gist, and all of them are included in the technical scope of the present invention.

The measurement and evaluation of the characteristic values of the three-dimensional network structures of examples 1 to 7 and comparative examples 1 to 3 described below were performed according to the following methods. The size of the sample was measured using a sample of a size that can be achieved when the sample was insufficient, with the following size as a standard.

(1) Fiber diameter

The three-dimensional net-like structure was cut into a size of 10cm×10cm, and the linear fibers were collected from 10 sites at a length of about 5 mm. Next, the diameter was measured by focusing on the fiber diameter measurement site of the collected linear fiber using an optical microscope, and the average value of the fiber diameters of 10 sites was obtained (n=10).

(2) Hollow rate

10 Linear fibers were randomly taken out of the three-dimensional net-like structure. Next, the linear fibers were cut into round pieces, and the round pieces were placed on a glass slide while standing along the fiber axis direction, and the fiber cross section in the round cut direction was observed by an optical microscope. At this time, only the linear fibers having a hollow cross section are selected, the area (a) and the hollow area (b) in the outer peripheral line of the fiber are calculated, and the hollow ratio is calculated from the following equation, and the average value of the hollow ratio of the selected hollow linear fibers is obtained.

Hollow ratio (%) = (b)/(a) ×100

(3) Thickness, apparent density

The three-dimensional network structure was cut into a size of 10cm×10cm in the longitudinal and transverse directions, the obtained sample was left under no load for 24 hours, and then the 1-position height of the center was measured by an FD-80N type thickness gauge manufactured by polymer counter company, and the height of the sample was defined as the thickness of the three-dimensional network structure. Further, the sample was placed on an electronic balance, and the weight of the sample was measured. The apparent density was obtained by multiplying the height of the sample by the longitudinal and transverse area (100 cm ²) to obtain the volume of the sample and dividing the weight of the sample by the volume. This operation was performed 3 times, and the average value of the thickness and apparent density of the three-dimensional network structure was obtained (n=3).

(4) Melting point (Tm)

A sample was collected from the three-dimensional network structure by using a differential scanning calorimeter Discovery DSC25 manufactured by TA Instruments, the mass of the sample was weighed to 2.0 mg.+ -. 0.1mg, and the temperature was measured under a nitrogen atmosphere at a temperature rise rate of 20 ℃ per minute, whereby the endothermic peak (melting peak) temperature was obtained from the endothermic/exothermic curve obtained. This operation was performed 3 times, and the average value of the melting points (n=3) was obtained.

(5) Enthalpy of fusion

Samples were collected from the three-dimensional network, and the mass of the samples was weighed to 2.0 mg.+ -. 0.1mg, and the samples were measured under nitrogen atmosphere at a temperature rise rate of 20 ℃ per minute by using a differential scanning calorimeter Discovery DSC25 manufactured by TAInstruments, whereby the enthalpy of crystal fusion (J/g) was obtained from the integral value of the endothermic peak (melting peak) based on the endothermic heat release curve obtained. Specifically, the integral value of the endothermic peak (melting peak) is obtained by integrating a portion surrounded by a straight line and a curve, with the point at which the curve relating to the endothermic peak (melting peak) starts to separate from the low-temperature side base line as a start point and the point at which the curve starts to contact the high-temperature side base line as an end point, and by drawing the straight line connecting the start point and the end point. This operation was performed 3 times, and the average value of the enthalpy of crystal fusion was obtained (n=3). In addition, the above starting point was taken as the melting start temperature (°c).

(6) Melt Flow Rate (MFR)

The three-dimensional network structure was finely cut and dried under vacuum at 80 ℃ for 2 hours or more as a raw material, and then Melt Flow Rate (MFR) measurement was rapidly performed so as to be as free of moisture in the air as possible. The melt flow rate was measured in accordance with ISO1133 using a melt index meter F-F01 machine manufactured by Toyo Seisakusho machine. The measured temperature was 190℃and the load was 2.16kg. This operation was performed 3 times, and the melt flow rate was averaged (n=3).

(7) Weight average molecular weight

Samples were collected from the three-dimensional network, and in order to reduce the variation of the samples, 40mg samples, which are usually 10 times, were finely cut and dissolved. The sample solution was diluted with chloroform, and the sample concentration was adjusted to 0.05%. Filtration was performed by using a membrane filter of 0.2 μm, and GPC analysis of the obtained sample solution was performed under the following conditions. The molecular weight was calculated according to standard polystyrene conversion.

Device TOSOH HLC-8320GPC

TSKgel SuperHM-H X2+TSKgel SuperH2000 (TOSOH)

Solvent of chloroform

Flow rate 0.6ml/min

Concentration is 0.05%

Injection amount of 20. Mu.L

Temperature of 40 DEG C

Detector RI, UV254nm

(8) Compression set at 70 °c

The three-dimensional network structure was cut into a size of 10cm×10cm, and the thickness (c) before treatment was measured by the method described in (2) above for the obtained sample. The measured thickness of the sample was clamped in a clamp capable of maintaining a 50% compression state, and the sample was put into a dryer set at 70 ℃ and left for 22 hours. Thereafter, the sample was taken out and cooled, and the thickness (d) after the compression set was removed and left for 30 minutes was obtained. These thicknesses were substituted into the expression { (C) - (d) }/(C) ×100, and compression set at 70 ℃. This operation was performed 3 times, and an average value of compression set at 70 ℃ (n=3) was obtained.

(9) Hardness at 25% compression

The three-dimensional network was cut to a size of 10cm×10cm, and the resulting sample was left under an environment of 23±2 ℃ for 24 hours under no load. Next, measurement was performed according to ISO2439 (2008) E using Autograph AG-X plus manufactured by shimadzu corporation under an environment of 23±2 ℃. Specifically, a pressing plate having a diameter (Φ) of 50mm was placed at the center of the sample, and the thickness at a load of 0.5N was measured as the initial thickness. The position of the pressing plate at this time was set as a zero point, precompressed 1 time at a speed of 100 mm/min to 75% of the initial thickness, and the pressing plate was returned to the zero point at the same speed, and then left to stand for 4 minutes in this state. Immediately thereafter, the steel sheet was compressed to 25% of the original thickness at a rate of 100 mm/min, and the load at this time was measured and used as a 25% compression hardness (N/. Phi.50 mm). This operation was performed 3 times, and the average value of the hardness at 25% compression was obtained (n=3).

As the polybutylene adipate-based resin, TH-801T manufactured by XINJIANG BLUE RIDGE TUNHE CHEMICAL INDUSTRY JOINT STOCK was used. The weight average molecular weight of the resin was 12.3X10 ⁴ g/mol, and the Melt Flow Rate (MFR) was 4g/10 min.

Example 1

The water tank was disposed so that the cooling water surface was located 17cm below the nozzle surface of the nozzle for ejecting the molten resin, the water temperature was set to 12 ℃, and the pair of traction belts were disposed in the water tank so that a part of the traction belts was exposed to the water surface. The traction conveyor belt has a 20cm wide stainless steel endless net, the conveyor belt is arranged parallel to the width direction of the nozzle surface, the opening width of the endless net is set to 30mm, the aluminum plate is arranged at 90 degrees relative to the net direction for forming the side surface part, and water is circulated at a speed of 1.0L/min to form the side surface part.

As the nozzle for ejecting the molten resin, a nozzle in which orifices having an outer diameter of 0.5mm and circular holes were formed in a zigzag pattern having an inter-hole pitch of 6mm on the nozzle effective surface having a width of 96mm in the width direction and a width of 31mm in the thickness direction was used. The raw material resin was dried to be absolutely dry, and after adding 0.01 mass% of water to 100 mass% of the solid content of the resin, the molten resin was discharged to the lower side of the nozzle at a spinning temperature of 260 ℃ and a single-hole discharge rate of 1.0 g/min.

The molten resin is ejected in a linear shape onto the openings of the mesh of the conveyor belt, and the aluminum plate on the side surface portion, and the continuous linear body is dropped to form a curved loop, so that the contact portions are fused together to form a three-dimensional network structure. While holding the two surfaces of the three-dimensional network structure in the molten state by a traction conveyor, the three-dimensional network structure was introduced into cooling water at a speed of 0.86 m/min and solidified, whereby the two surfaces in the thickness direction and the side direction were flattened and cut into a predetermined size. Then, the mixture was allowed to stand in a space at 25℃for 1 hour. The three-dimensional network structure obtained had a water content of 9%, and was dried by hot air heating at 80℃for 20 minutes, whereby annealing was performed to obtain a three-dimensional network structure having a width of 100 mm. The three-dimensional net-like structure has a circular cross-sectional shape of the linear fibers.

Example 2

A three-dimensional net-like structure was obtained in the same manner as in example 1, except that water was added in an amount of 0.30 mass% to 100 mass% of the solid content of the resin, and a nozzle having orifices having a hollow cross section, which had an outer diameter of 5.0mm, an inner diameter of 4.4mm and a three-bridge (triple bridge), were arranged in a zigzag manner with a pitch of 8mm, the spinning temperature was 231 ℃, the single-orifice discharge amount was 1.5 g/min, the drawing speed was 0.92 m/min, and the drying temperature was 105 ℃. The three-dimensional net-like structure has a hollow cross-sectional shape of the linear fibers.

Example 3

A three-dimensional network structure was obtained in the same manner as in example 2, except that water was added in an amount of 0.40 mass% relative to 100 mass% of the solid content of the resin, the spinning temperature was 230 ℃ and the drying temperature was 90 ℃.

Example 4

A three-dimensional net-like structure was obtained in the same manner as in example 3, except that water was added in an amount of 0.01 mass% relative to 100 mass% of the solid content of the resin, the spinning temperature was 240 ℃ and the nozzle face-cooling water distance was 25 cm.

Example 5

A three-dimensional net-like structure was obtained in the same manner as in example 1, except that the resin as a raw material was dried, water was not added, the single-hole ejection amount was set to 0.5 g/min, and the drawing speed was set to 0.64 m/min.

Example 6

A three-dimensional net-like structure was obtained in the same manner as in example 3, except that water was added in an amount of 0.20 mass% relative to 100 mass% of the solid content of the resin, the spinning temperature was 190 ℃, and the nozzle face-cooling water distance was 30 cm.

Example 7

A web was obtained in the same manner as in example 5, except that the spinning temperature was 210 ℃, the single-hole discharge amount was 1.0 g/min, and the drawing speed was 1.28 m/min.

Comparative example 1

A three-dimensional network structure was obtained in the same manner as in example 1, except that 2.5 mass% of water was added to 100 mass% of the solid content of the resin, the single-hole ejection amount was set to 0.9 g/min, the nozzle face-cooling water distance was set to 18cm, and the drawing speed was set to 0.52 m/min.

Comparative example 2

A three-dimensional network structure was obtained in the same manner as in example 4, except that water was added in an amount of 0.02 mass% relative to 100 mass% of the solid content of the resin, and the resin was dried at 20 to 25 ℃ for 2 days without annealing.

Comparative example 3

A web was obtained in the same manner as in example 2, except that the spinning temperature was 230 ℃, the drawing speed was 1.54 m/min, and the drying temperature was 107 ℃.

The production conditions and the properties of the obtained three-dimensional network structure in examples 1 to 7 and comparative examples 1 to 3 are shown in table 1. In table 1, the characteristic values that were evaluated a plurality of times are average values.

TABLE 1

The three-dimensional network structures obtained in examples 1 to 7 were excellent in compression durability and compression recovery after heat compression. Further, examples 1 to 6 can reduce the melt viscosity of the polymer at the time of ejection, and therefore can produce a precise ring, and are excellent in surface and appearance quality.

The mesh-like structure obtained in comparative example 1 has a low weight average molecular weight and is inferior in compression recovery after compression under heating. In addition, the network structure obtained in comparative example 1 was slightly yellow. This is considered to be due to the influence of the high water content of the three-dimensional network structure before annealing.

The net-like structures obtained in comparative examples 2 and 3 have low enthalpy of crystal fusion, and have poor compression durability and compression recovery after heat compression.

Claims

1. A biodegradable three-dimensional network structure characterized by comprising,

The apparent density is 0.005g/cm ³~0.30g/cm³, the thickness is 10 mm-100 mm, and the fiber comprises linear fibers,

The linear fiber has a fiber diameter of 0.2-2.0 mm, a crystallization melting enthalpy of 16J/g or more, and comprises a polybutylene adipate terephthalate resin having a weight average molecular weight of 35000 or more,

The biodegradable three-dimensional network structure has a compression set at 70 ℃ of 1% to 30%, and a hardness at 25% compression of 5.0N/phi 50mm to 100N/phi 50 mm.

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 crystalline melting enthalpy is 30J/g or less.

4. The biodegradable three-dimensional network according to any one of claims 1 to 3, which is used for a buffer.

5. The biodegradable three-dimensional network structure according to any one of claims 1 to 3, wherein said polybutylene adipate terephthalate resin has a weight average molecular weight of 150000 or less.

6. The biodegradable three-dimensional network structure according to any one of claims 1 to 3, wherein the linear fibers have a melting point of 100 ℃ to 120 ℃.

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

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