Three-dimensional network structure

Abstract

To provide a three-dimensional net-like structure that is excellent in hydrolysis resistance and does not easily deteriorate due to moisture in air when used in a long term.SOLUTION: A three-dimensional net-like structure is made of a resin composition of polyester-based thermoplastic elastomer and has a three-dimensional random loop joint structure consisting of continuous wires. The resin composition contains borosilicate glass.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a three-dimensional network structure suitable for cushioning materials used in office chairs, furniture, sofas, bedding such as beds, vehicle seats such as railway, automobile, motorcycle, child seat, baby stroller, impact-absorbing mats such as floor mats and collision or pinching prevention members, etc.

Background Art

[0002] Currently, as cushioning materials used in furniture, bedding such as beds, and vehicle seats such as trains, automobiles, and motorcycles, "foamed-crosslinked urethane" is widely used from the viewpoints of good durability and processability. However, "foamed-crosslinked urethane" has problems such as poor moisture permeability and air permeability, and is prone to stuffiness due to heat storage. Furthermore, since "foamed-crosslinked urethane" is not thermoplastic, recycling is difficult. Also, when "foamed-crosslinked urethane" is incinerated, problems such as significant damage to the incinerator and high costs for removing toxic gases generated during incineration have been pointed out. Therefore, unnecessary "foamed-crosslinked urethane" is often landfilled. However, since it is difficult to stabilize the ground, there are problems such as limited landfill sites and high landfill costs. In addition, various problems such as pollution problems of chemicals used during manufacturing, residual chemicals after foaming, and associated odors have been pointed out.

[0003] Patent Document 1 discloses a three-dimensional network structure composed of continuous linear strips of a thermoplastic resin composition and having a three-dimensional random loop joining structure. This can solve various problems derived from the above-mentioned "foamed-crosslinked urethane" and is also excellent in cushioning performance. However, when this three-dimensional network structure is used as a product such as bedding or vehicle seats, there is room for improvement in that the resin composition constituting the three-dimensional network structure is hydrolyzed and deteriorated by being exposed to moisture in the air for a long time.

[0004] In addition, Patent Document 2 discloses a three-dimensional network structure that is excellent in hydrolysis resistance during high-temperature heating or remelting. This document describes that by keeping the acid value of the thermoplastic elastomer low, there is an effect of suppressing hydrolysis that occurs in a hot processing step of heating to a high temperature near the melting temperature or in a remelting step during recycling. However, when used as a product, the effect of suppressing the hydrolysis of the resin due to long-term exposure to moisture in the air was not sufficient. Therefore, there was room for improvement in terms of suppressing the deterioration of the resin composition constituting the three-dimensional network structure.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is made in view of the above problems of the prior art, and is to provide a three-dimensional network structure excellent in hydrolysis resistance.

Means for Solving the Problems

[0007] The present invention that has been able to solve the above problems is as follows. [1] A three-dimensional network structure made of a resin composition of a polyester-based thermoplastic elastomer and having a three-dimensional random loop joint structure composed of continuous linear strips, The resin composition is a three-dimensional network structure containing borosilicate glass. [2] The three-dimensional network structure according to [1], wherein the borosilicate glass contains B2O3, SiO 2、 and an alkali metal oxide.

Effects of the Invention

[0008] The three-dimensional network structure of the present invention is excellent in hydrolysis resistance of the thermoplastic elastomer resin composition constituting the three-dimensional network structure, and has the property that deterioration due to moisture in the air is less likely to occur during long-term use.

Mode for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in detail. The three-dimensional network structure of the present invention is composed of a resin composition containing a polyester-based thermoplastic elastomer and borosilicate glass. When the three-dimensional network structure of the present invention comes into contact with moisture in the air, boron, which is a component of borosilicate glass contained in the resin composition, dissolves in the moisture to consume the moisture, and hydrolysis of the thermoplastic elastomer resin composition can be suppressed.

[0010] Next, borosilicate glass will be described. Borosilicate glass refers to a composite glass containing at least boron trioxide (B2O3) and silicon dioxide (SiO2) as network-forming oxides. Specifically, composite glasses containing B2O3, SiO2, and alkali metal oxides can be mentioned. Examples of the alkali metal oxides include K2O, Na2O, and Li2O. In addition, the borosilicate glass may contain alkaline earth metal oxides such as MgO and CaO, and ZnO, Al2O3, and P2O5 in order to adjust the solubility in water. In addition, within a range where the properties are not impaired, Ag2O, GeO2, BeF2, As2S3, CuO, TiO2, LaO3, ZrO2, MoO3, GeS2, etc. may also be contained.

[0011] The borosilicate glass contains a relatively large amount of B2O3. In order to more efficiently exhibit the effect of suppressing the hydrolysis of the above-mentioned polyester-based thermoplastic elastomer, the borosilicate glass preferably has a molar ratio (B / Si) of boron atomic weight B (mol) to silicon atomic weight Si (mol) in the range of 0.3 to 20. It is preferable to adjust the B / Si molar ratio in the range of 0.3 to 20 according to the B concentration. When the B concentration is high, even if the B / Si molar ratio is small within the above range, the reduction viscosity retention rate after heat treatment can be made 65% or more. When the molar ratio (B / Si) is too small, the rate of boron elution tends to be slow with respect to moisture. Therefore, the efficiency of suppressing hydrolysis tends to decrease. Furthermore, unless the content of borosilicate glass in the three-dimensional network structure is increased, it is difficult to obtain the effect of suppressing hydrolysis. On the other hand, from the viewpoints of heat resistance and chemical durability of the borosilicate glass, the molar ratio (B / Si) is preferably 20 or less. The molar ratio (B / Si) is more preferably 0.6 to 20, still more preferably 1.0 to 10, and particularly preferably 1.5 to 5.0.

[0012] Examples of the composition of such borosilicate glass include those containing 50 to 80 mol% of B2O3 and 5 to 30 mol% of SiO2, and those containing 20 to 50 mol% of B2O3 and 5 to 15 mol% of SiO2. Examples of the form of the borosilicate glass include polyhedral objects and spherical objects such as fine powder, frit, particles, and beads. The size of the polyhedral object or spherical object preferably has an average particle diameter of 0.1 to 100 μm, more preferably 0.5 to 50 μm, and particularly preferably 1 to 30 μm. If the average particle diameter is less than 0.1 μm, secondary aggregation occurs during spinning and the grinding cost increases, which is not preferable. If the average particle diameter exceeds 100 μm, it induces an increase in back pressure during spinning, which is not preferable.

[0013] The manufacturing method of borosilicate glass generally includes a melting and pulverizing method in which raw materials such as B2O3, SiO2, and alkali metal oxides are mixed in a preset composition ratio, melted at a high temperature, then the melt is rapidly cooled to form glass pieces, and the glass pieces are pulverized by a ball mill or the like. Such borosilicate glass is available, for example, from Nippon Electric Glass, Nippon Flit, Ishizuka Glass, Koa Glass, Toagosei, Potter's Barotti, etc., but is not limited thereto.

[0014] In the three-dimensional network structure of the present invention, the boron content in the three-dimensional network structure is preferably 5 ppm or more on a mass basis. When the three-dimensional network structure contains boron at 5 ppm or more on a mass basis, it becomes easier to uniformly blend the borosilicate glass into the three-dimensional network structure. From the viewpoint of suppressing the hydrolysis of the resin composition by moisture in the air, the boron content in the three-dimensional network structure is preferably 10 ppm or more on a mass basis, more preferably 15 ppm or more, particularly preferably 150 ppm or more, and most preferably 400 ppm or more. Further, by containing boron in the three-dimensional network body at 10 ppm or more on a mass basis, an effect of suppressing the growth of mites on the fibers of the three-dimensional network structure can also be expected. On the other hand, if the boron content in the three-dimensional network structure is too high, the borosilicate glass is likely to precipitate on the fiber surface, and a sticky feeling is likely to occur when the three-dimensional network structure is touched by hand. Therefore, the boron content in the three-dimensional network structure is preferably 36000 ppm or less on a mass basis. Further, from the viewpoint of reducing the influence on the mechanical properties of the three-dimensional network structure, the boron content is preferably 18000 ppm or less, more preferably 10000 ppm or less, particularly preferably 5000 ppm or less, and most preferably 2000 ppm or less.

[0015] Next, the polyester-based thermoplastic elastomer used in the present invention will be described. Examples of polyester-based thermoplastic elastomers include polyester ether block copolymers having a thermoplastic polyester as a hard segment and a polyalkylene diol as a soft segment, or polyester block copolymers having an aliphatic polyester as a soft segment.

[0016] Examples of polyester ether block copolymers include at least one dicarboxylic acid selected from aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, or ester-forming derivatives thereof, at least one diol component selected from aliphatic diols such as 1,4-butanediol, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, alicyclic diols such as 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, or ester-forming derivatives thereof, and at least one selected from polyalkylene diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene oxide-propylene oxide copolymer having a number average molecular weight of about 300 or more and 5000 or less, and is a triblock copolymer composed of these.

[0017] Examples of the polyester ester block copolymer include a ternary block copolymer composed of at least one of the above dicarboxylic acids, diols, and polyester diols such as polylactone having a number average molecular weight of about 300 or more and 5000 or less. Considering thermal adhesiveness, hydrolysis resistance, stretchability, heat resistance, etc., as the dicarboxylic acid, terephthalic acid and / or naphthalene 2,6-dicarboxylic acid, as the diol component, 1,4-butanediol, and as the polyalkylene diol, a ternary block copolymer of polytetramethylene glycol or a ternary block copolymer of polylactone as the polyester diol is particularly preferred. In a special example, those into which a polysiloxane-based soft segment is introduced can also be used.

[0018] In addition, those obtained by blending a non-elastomer component with the above polyester-based thermoplastic elastomer, copolymerizing it, using a polyolefin-based component as a soft segment, etc. are also included in the polyester-based thermoplastic elastomer. Furthermore, those obtained by adding various additives, etc. to the polyester-based thermoplastic elastomer as needed are also included.

[0019] The polyester-based thermoplastic elastomer containing borosilicate glass can be obtained, for example, as follows. The above polyester-based thermoplastic elastomer is polymerized by a conventional method and pelletized once. The obtained pellets of the polyester-based thermoplastic elastomer and the fine powder of the above borosilicate glass are mixed at a predetermined blending ratio, melt-extruded with a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of the polyester-based thermoplastic elastomer containing the above borosilicate glass. Alternatively, while melting and extruding the pellets of the above polyester-based thermoplastic elastomer with a twin-screw extruder, the fine powder of the above borosilicate glass is supplied from a side feeder installed in the extruder at a predetermined blending ratio, and melt-extruded while kneading and mixing the polyester-based thermoplastic elastomer and the borosilicate glass in the extruder, cooled, pelletized, and dried to obtain a resin composition of the polyester-based thermoplastic elastomer containing the above borosilicate glass.

[0020] When the addition amount of the borosilicate glass is based on 100% by mass of the resin composition, the range of 0.001 to 50% by mass is preferable. When the addition amount of the borosilicate glass is less than 0.001% by mass, the variation in the content of the borosilicate glass in the resin composition becomes large. When the addition amount of the borosilicate glass exceeds 50% by mass, the production of the resin composition becomes difficult due to the large content of the borosilicate glass. From the viewpoint of the variation in the content and the ease of producing the resin composition, the addition amount of the borosilicate glass is preferably 0.01 to 20% by mass.

[0021] When producing the resin composition, it is preferable to blend an antioxidant for the purpose of suppressing the thermal deterioration of the resin composition during spinning and melting, the thermal deterioration during the thermoforming of the three-dimensional network structure, and the deterioration by light. When the resin composition is 100% by mass, the addition amount of the antioxidant is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, particularly preferably 0.20% by mass or more, and most preferably 0.50% by mass or more. Examples of the antioxidant include known phenolic antioxidants, phosphorus-based antioxidants, and thioether-based antioxidants. Further, a benzotriazole-based ultraviolet absorber, a triazine-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, an N-H type hindered amine-based light stabilizer, and an N-CH3 type hindered amine-based light stabilizer may be used in combination. It is desirable to blend at least one of these additives.

[0022] Examples of phenolic antioxidants include 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-butylidenebis(6-tert-butyl-m-cresol), stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], Sumilizer G 80, 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene, and the like.

[0023] Examples of phosphorus antioxidants include 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 2,4,8,10-tetrakis(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]-12H-dibenz[d,g][1,3,2]dioxaphosphocin, tris(2,4-di-tert-butylphenyl) phosphite, tris(4-nonylphenyl) phosphite, 4,4'-Isopropylidenediphenol C12-15 alcohol phosphite, diphenyl(2-ethylhexyl) phosphite, diphenylisodecyl phosphite, triisodecyl phosphite, triphenyl phosphite, and the like.

[0024] Examples of thioether antioxidants include bis[3-(dodecylthio)propionic acid] 2,2-bis[[3-(dodecylthio)-1-oxopropyl)oxy]methyl]-1,3-propanediyl, ditridecyl 3,3'-thiobispropionate, and the like.

[0025] In addition to antioxidants, UV absorbers, and light stabilizers, various additives can be incorporated into the above resin composition according to the purpose. Examples of additives include plasticizers such as phthalate esters, trimellitate esters, fatty acids, epoxies, adipate esters, and polyesters; antistatic agents; molecular weight regulators such as peroxides; epoxy compounds, isocyanate compounds, carbodiimide compounds, and other compounds having reactive groups; metal deactivators; organic and inorganic nucleating agents; neutralizing agents; antacids; antibacterial agents; fluorescent brighteners; fillers; flame retardants; flame retardant aids; organic and inorganic pigments, etc.

[0026] The three-dimensional network structure of the present invention is a network structure formed by three-dimensional joining of random loops composed of continuous filaments of a resin composition of a polyester-based thermoplastic elastomer containing borosilicate glass, thereby forming a three-dimensional structure.

[0027] The continuous filaments constituting the three-dimensional network structure of the present invention may be composite filaments combined with other thermoplastic resins within a range not impairing the object of the present invention. Examples of the composite form include composite filaments such as sheath-core type, side-by-side type, and eccentric sheath-core type when the filament body itself is made composite. In the case of a sheath-core type composite filament, borosilicate glass may be contained in either the sheath component or the core component, or only in the sheath component.

[0028] The three-dimensional network structure of the present invention can be obtained based on known methods described in, for example, Japanese Patent Laid-Open No. 7-68061. For example, a resin composition of a thermoplastic elastomer containing borosilicate glass is distributed to nozzle orifices from a multi-row nozzle having a plurality of orifices, and continuous filaments are discharged downward from the nozzle at a spinning temperature 20°C or more and less than 120°C higher than the melting point of the resin composition. Next, while the continuous filaments are brought into contact with each other in a molten state and fused to form a three-dimensional structure, they are sandwiched between take-up conveyor nets and cooled with cooling water in a cooling tank. Then, they are drawn out, drained or dried to obtain a three-dimensional network structure with smoothed surfaces on both sides or one side. When smoothing only one side, it is preferable to discharge it onto a take-up net with an inclination, bring it into contact with each other in a molten state and fuse it to form a three-dimensional structure, and cool it while relaxing only the form of the take-up net surface. The obtained three-dimensional network structure can also be subjected to an annealing treatment. Note that the drying treatment of the three-dimensional network structure may be used as the annealing treatment.

[0029] The cross-sectional shape of the continuous filaments constituting the three-dimensional network structure of the present invention is not particularly limited, but a hollow cross-section or a deformed cross-section can impart preferable compressibility resistance and touch. Further, in the thickness direction, a fine fiber diameter fiber main region mainly composed of fibers having a relatively fine fiber diameter, a thick fiber diameter fiber main region mainly composed of fibers having a relatively thick fiber diameter, and a mixed region in which fine fiber diameter fibers and thick fiber diameter fibers are mixed and located between the fine fiber diameter fiber main region and the thick fiber diameter fiber main region may be present as the three-dimensional network structure.

[0030] The three-dimensional network structure of the present invention can be processed from the resin production process into a molded article within a range that does not deteriorate the performance, and functions such as deodorant antibacterial, deodorization, antifungal, coloring, fragrance, flame retardancy, moisture absorption and desorption can be imparted at any stage of commercialization by using a treatment process of attaching a chemical agent by dipping or the like.

[0031] The three-dimensional network structure of the present invention may be laminated as long as the object of the present invention is not impaired. Examples of the laminated structure include a form in which the surface layer and the back layer are composed of linear filaments having different finenesses, or a three-dimensional network structure having different apparent densities in the surface layer and the back layer. Examples of the multilayer forming method include a method of stacking three-dimensional network structures and fixing them with a backing or the like, a method of melting and fixing by heating, a method of adhering with an adhesive, and a method of restraining with sewing or a band.

[0032] The three-dimensional network structure of the present invention has an excellent reduced viscosity retention rate after heat treatment. Here, when the viscosity of the polymer solution is η, the viscosity of the solvent is η0, and the concentration of the solute polymer in the polymer solution is c, the reduced viscosity ηsp / c is given by the formula {(η - η0) / η0} / c. The reduced viscosity retention rate is a measure for relatively comparing the molecular weights of polymers.

[0033] For example, when the molecular weight of a resin composition of a polyester-based thermoplastic elastomer decreases due to hydrolysis, the reduced viscosity of the polyester-based thermoplastic elastomer resin composition after hydrolysis is smaller than the reduced viscosity of the polyester-based thermoplastic elastomer resin composition before hydrolysis. Therefore, the resistance to hydrolysis caused by being exposed to moisture in the air for a long time can be evaluated by the change in the reduced viscosity after the accelerated test. That is, the three-dimensional network structure is heat-treated in a high-temperature and high-humidity atmosphere, and the hydrolysis resistance can be evaluated by comparing the reduced viscosity of the resin composition constituting the three-dimensional network structure before and after the treatment.

[0034] When the reduced viscosity of the resin composition constituting the three-dimensional network structure is A, and the reduced viscosity of the resin composition constituting the three-dimensional network structure after heat treatment for 240 hours in an atmosphere at a temperature of 80°C and a relative humidity of 90 RH% is B, the reduced viscosity retention rate after heat treatment is represented by the following formula (1). Reduced viscosity retention rate after heat treatment = (B / A) × 100 ··· (1)

[0035] The higher the reduced viscosity retention rate after heat treatment, the smaller the decrease in molecular weight after heat treatment, which means that the hydrolysis resistance is excellent. That is, in the present invention, the reduced viscosity retention rate after heat treatment serves as an index for evaluating the hydrolysis resistance of the three-dimensional network structure. The three-dimensional network structure of the present invention preferably has a reduced viscosity retention rate of 65% or more after heat treatment. If the reduced viscosity retention rate after heat treatment is 65% or more, hydrolysis is less likely to occur even when exposed to moisture in the air for a long time, that is, the hydrolysis resistance is excellent. From the perspective of hydrolysis resistance, the reduced viscosity retention rate after heat treatment is more preferably 70% or more, further preferably 75% or more, particularly preferably 80% or more, and most preferably 85% or more.

[0036] The thickness of the three-dimensional network structure of the present invention is preferably 10 mm or more, and more preferably 20 mm or more. If the thickness is less than 10 mm, a feeling of having a bottom may occur when used as a cushioning material. Due to the relationship of the manufacturing apparatus, the upper limit of the thickness is preferably 300 mm or less, more preferably 200 mm or less, and further preferably 120 mm or less.

[0037] The apparent density of the three-dimensional network structure of the present invention is 0.005 g / cm 3 or more and 0.20 g / cm 3 or less is preferable, 0.01 g / cm 3 or more and 0.18 g / cm 3 or less is more preferable, and 0.02 g / cm 3 or more and 0.15 g / cm 3 or less is further preferable. If the apparent density is less than 0.005 g / cm 3 , the required hardness may not be maintained when used as a cushioning material. On the other hand, if the apparent density exceeds 0.20 g / cm 3 , it may become too hard and not be suitable as a cushioning material.

[0038] Regarding the fiber diameter of the continuous linear filaments that make up the three-dimensional network structure of the present invention, if the fiber diameter is small, it may be impossible to ensure the hardness required when used as a cushioning material. On the other hand, if the fiber diameter is too large, it may become too hard depending on the use of the cushion. Therefore, it is preferably set appropriately according to the use of the cushion. The fiber diameter is preferably 0.1 mm or more, more preferably 0.2 mm or more. When the fiber diameter is less than 0.1 mm, the density and soft touch are good, but it becomes difficult to ensure the hardness required for the network structure. On the other hand, the fiber diameter is preferably 3.0 mm or less, more preferably 2.5 mm or less. When the fiber diameter exceeds 3.0 mm, the hardness of the three-dimensional network structure can be sufficiently ensured, but the network structure may become rough and other cushioning performances may be inferior.

[0039] (Effect) The three-dimensional network structure of the present invention is excellent in hydrolysis resistance, and resin deterioration due to moisture in the air hardly occurs during long-term use, and it is excellent in durability during long-term use.

Example

[0040] Examples are exemplified below to specifically explain the present invention, but the present invention is not limited thereto. The measurement and evaluation of the characteristic values in the examples were carried out as follows.

[0041] (1) Reduced viscosity [Adjustment of test solution] Place the pellets or three-dimensional network structure to be tested in a hot air dryer set at an internal temperature of 70°C and leave it for 25 minutes to dry. Cut the dried pellets or three-dimensional network structure finely so that the length of the pellets or fibers is within 2 mm, and weigh 0.08 ± 0.003 g of the sample. To the obtained sample, add a phenol / 1,1,2,2-tetrachloroethane mixed solvent (=60 / 40; mass ratio) with an accuracy of ±0.01 ml to obtain a solution with a concentration of 0.2 g / dl. Heat the obtained solution to 70°C and stir for 30 minutes to dissolve the sample. After cooling the solution in a water bath at 15 ± 1°C, leave it at room temperature to obtain a test solution. [Measurement of the outflow time t0 of the solvent (blank test)] Use a capillary (Ubbelohde viscometer) type automatic viscometer AVL-2C manufactured by Asahi Kasei Techno Systems. As the viscometer, use a Ubbelohde type viscometer with a capillary diameter of 0.77 mm (±2%). Set the temperature of the constant temperature bath of the automatic viscometer and the test temperature to 30 ± 0.1 °C. Put a phenol / 1,1,2,2-tetrachloroethane mixed solvent (= 60 / 40; mass to weight ratio) into the viscometer. Attach the viscometer to the constant temperature bath and adjust it at a temperature of 30 ± 0.1 °C for 10 minutes. Then, start the test and continuously measure the outflow time (seconds) of the mixed solvent twice. Take the average of the two measured values as the outflow time t0 (seconds) of the solvent.

[0042] [Measurement of the outflow time t1 of the test solution] Use the same automatic viscometer as that used for the measurement of t0. Also use the same viscometer as that used for the measurement of t0 (the viscometer must not be changed). Set the temperature of the constant temperature bath of the automatic viscometer and the test temperature to 30 ± 0.1 °C. Wash the viscometer with the test solution. Put the test solution into the viscometer. Attach the viscometer to the constant temperature bath and adjust it at a temperature of 30 ± 0.1 °C for 10 minutes. Then, start the test and continuously measure the outflow time (seconds) of the mixed solvent twice. Take the average of the two measured values as the outflow time t1 (seconds) of the solvent.

[0043] [Calculation of reduced viscosity] Calculate the reduced viscosity (dl / g) from the following formula. Reduced viscosity ηsp / c = (t1 / t0 - 1) / c t1: Outflow time (seconds) of the test solution, t0: Outflow time (seconds) of the solvent, c: Concentration of the test solution (0.2 g / dl)

[0044] (2) Retention rate of reduced viscosity after heat treatment Cut out a test piece with a size of "5 cm × 5 cm × thickness of the three-dimensional network structure" from the three-dimensional network structure before heat treatment, put it into a bag with moisture-proof and light-shielding properties and seal it, and store it at room temperature as test piece A before heat treatment. Cut out a test piece with dimensions of "10 cm × 10 cm × the thickness of the three-dimensional network structure" from the three-dimensional network structure, place it in a thermo-hygrostat with the internal environment set to a temperature of 80 °C and a relative humidity of 90 RH%, and perform heat treatment for 240 hours. Then, take out the test piece from the thermo-hygrostat and cool it at room temperature for 1 hour to obtain the test piece B after heat treatment. Measure the "reduced viscosity of the resin composition of the three-dimensional network structure before heat treatment (reduced viscosity A)" from the test piece A by the method for measuring the reduced viscosity in (1) above. Similarly, measure the "reduced viscosity of the resin composition of the three-dimensional network structure after heat treatment (reduced viscosity B)" from the test piece B by the method for measuring the reduced viscosity in (1) above. At this time, the reduced viscosity A and the reduced viscosity B are measured on the same day using the same automatic viscosity measuring device and the same viscosity tube. Next, the reduced viscosity retention rate after heat treatment was calculated using the following formula. Reduced viscosity retention rate after heat treatment (%) = (B / A) × 100

[0045] (3) Boron content in the three-dimensional network structure Collect 0.2 g of sample from the three-dimensional network structure, add 10 ml of concentrated nitric acid, and perform wet acid decomposition using a microwave digestion apparatus (manufactured by Anton Paar; Multiwave PRO). Specifically, heat up to 700 W in 10 minutes, hold at 700 W for 50 minutes to dissolve the sample. Then, cool it to 40 °C to obtain a sample solution. After preparing a pretreatment solution by diluting this sample solution to 50 ml with ultrapure water, measure it using a high-frequency inductively coupled plasma optical emission spectrometer (manufactured by Hitachi High-Technologies Corporation, SPECTROBLUE). Calculate the boron concentration (mg / l) of the pretreatment solution from the calibration curve prepared previously and denote it as C (mg / l). Next, prepare a blank test solution by diluting 10 ml of concentrated nitric acid to 50 ml with ultrapure water and measure it using the same apparatus. Calculate the boron concentration (mg / l) of the blank test solution from the calibration curve prepared previously and denote it as D (mg / l). Next, the boron content (ppm; mass basis) in the three-dimensional network structure was calculated using the following formula. Boron content in the three-dimensional network structure (ppm; mass basis) = (C - D) × 50 / 0.2

[0046] (4) Silicon content in the three-dimensional network structure Collect 0.2 g of sample from the three-dimensional network structure and weigh the sample in a platinum crucible. Next, pre-carbonize the sample up to 400 °C on a hot plate. Then, perform ashing treatment at 550 °C for 8 hours using an electric furnace (manufactured by Yamato Scientific Co., Ltd., model FO610). After ashing, add 5 ml of 5% sodium carbonate aqueous solution and heat on a hot plate until the water completely evaporates. Then, perform alkali fusion treatment using a burner and add ultrapure water to the obtained white residue. Next, perform heat treatment on a hot plate and confirm that the salt is completely dissolved. Then, add 5 ml of 6N hydrochloric acid and prepare a pretreatment solution diluted to 25 ml using ultrapure water. Calculate the silicon concentration (mg / l) of the pretreatment solution using a high-frequency inductively coupled plasma optical emission spectrometer (manufactured by Hitachi High-Tech Sciences Corporation, SPECTROBLUE) and denote it as E (mg / l). Next, prepare a blank test solution by adding 5 ml of 6N hydrochloric acid to 5 ml of 5% sodium carbonate aqueous solution and diluting to 25 ml with ultrapure water. Calculate the silicon concentration (mg / l) of the blank test solution from the calibration curve prepared previously using the above high-frequency inductively coupled plasma optical emission spectrometer and denote it as F (mg / l). Next, calculate the silicon content (ppm; mass basis) in the three-dimensional network structure using the following formula. Silicon content (ppm; mass basis) in the three-dimensional network structure = (E - F) × 25 / 0.2

[0047] (5) Melting point (Tm) Slice the pellets of the thermoplastic elastomer thinly and enclose them in a test pan. Next, use a differential scanning calorimeter (manufactured by TA Instruments, model Q200) to determine the endothermic peak (melting peak) temperature at the time of crystal melting from the endothermic and exothermic curves measured at a heating rate of 20 °C / min, and take it as the melting point of the thermoplastic elastomer.

[0048] (6) Acid value Using a proton nuclear magnetic resonance spectrometer (manufactured by BRUKER, NMR spectrometer AVANCE-500), 1H-NMR measurement was performed at a resonance frequency of 500 MHz to quantify the acid value of the polyester-based thermoplastic elastomer. The measurement solution was prepared as follows. <Measurement i> Dissolve 10 - 20 mg of the sample in 0.12 ml of deuterated chloroform / hexafluoroisopropanol = 1 / 1 (volume ratio). Next, add 0.48 ml of deuterated chloroform and stir well. Then, fill the solution into an NMR tube and perform 1H-NMR measurement. <Measurement ii> After the measurement of Measurement i, add 25 μL of a deuterated chloroform solution prepared so that the concentration of triethylamine is 0.2 mol / L, and perform 1H-NMR measurement again. Deuterated chloroform was used as the lock solvent in all cases, and the number of integrations was 128 times. <Measurement of acid value> The acid value was quantified as follows. When the peak of chloroform was set at 7.27 ppm, the peak at 8 ppm in Measurements i and ii was the peak of terephthalic acid (a), the peak at 2 ppm was the peak of 1,4-butanediol (b), the peak at 3.5 ppm was the peak of polytetramethylene glycol (c), the peak at 7.87 - 7.96 ppm in Measurement i was the satellite peak of terephthalic acid (d), and the peak at 7.87 - 7.96 ppm in Measurement ii was calculated as the peak of the terephthalic acid terminal and the satellite peak of terephthalic acid (e). Let a - e in the parentheses be the integral values of each peak, and the acid value was obtained from the following formula. (f)=(a / 4×132)+(b / 4×88)+(c / 4×72) Acid value (eq / ton)=((e - d) / 2×1000000) / (f) : Unit meq / kg (average value of n = 2)

[0049] (7) Thickness and apparent density of the three-dimensional network structure Four test pieces with dimensions of "10 cm × 10 cm × the thickness of the three-dimensional network structure" are taken from the three-dimensional network structure. The test pieces are left at room temperature for 24 hours under no load. Then, for each test piece, the height (mm) in the thickness direction is measured using a thickness gauge (FD-80N type, manufactured by Polymer Instruments). The average value of the heights of the four test pieces is taken as the thickness (mm) of the three-dimensional network structure. Also, the weight W (g) of each test piece is measured using an electronic balance, and the apparent density (g / cm 3 ) of each test piece is calculated using the following formula. The average value of the apparent densities of the four test pieces is taken as the apparent density (g / cm 3 ) of the three-dimensional network structure. Apparent density (g / cm 3 ) = W / (10 × 10 × test piece height / 10)

[0050] (8) Fiber diameter of the three-dimensional network structure One test piece with dimensions of "10 cm × 10 cm × the thickness of the three-dimensional network structure" is taken from the three-dimensional network structure. From the obtained test piece, 10 linear strips are collected, each about 5 mm in length. For the collected linear strips, the optical microscope is adjusted to an appropriate magnification, focused on the measurement location, and the fiber diameter is measured. The average value of the 10 measurements is taken as the fiber diameter (mm) of the three-dimensional network structure.

[0051] [Example 1] (1) Production of polyester-based thermoplastic elastomer As the polyester-based thermoplastic elastomer, dimethyl terephthalate (DMT), 1,4-butanediol (1,4-BD), and polytetramethylene glycol (PTMG: average molecular weight 1000) were charged together with a small amount of catalyst, and transesterification was carried out by a conventional method. Subsequently, polycondensation was carried out while raising the temperature under reduced pressure, and pelletization was performed to produce a polyether-ester block copolymer elastomer. At this time, it was produced by a conventional method that does not use a method to reduce the thermal history from after polymerization by the polycondensation reaction until pelletization. The monomer composition, melting point, acid value, and reduced viscosity of the obtained polyester-based thermoplastic elastomer (A-1) are shown in Table 1.

[0052]

Table 1

[0053] (2) Production of the resin composition constituting the three-dimensional network fiber structure 99.49% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.01% by mass of fine powder of borosilicate glass (manufactured by Ishizuka Glass, E74527), and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. Next, the mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition as a raw material for the three-dimensional network fiber structure. The main composition of the borosilicate glass used in the experiment is as follows. B2O3; 61 mol%, SiO2; 23 mol%, alkali metal oxide: 16 mol%

[0054] (3) Production of the three-dimensional network structure A nozzle with an effective nozzle surface of 1120 mm in the width direction and 34.5 mm in the width in the thickness direction was prepared, in which orifices with a triple-bridge hollow-forming cross-section and an outer diameter of 5.0 mm were arranged in a staggered pattern with a pitch of 8 mm between holes. A resin composition in which 0.01% by mass of the borosilicate glass was added to a polyester-based thermoplastic elastomer (A-1) as a base resin was discharged downward from the nozzle at a spinning temperature of 240 °C at a rate of 1.5 g / min of single-hole discharge amount using the nozzle. Next, through a cooling space with an ambient temperature of 25 to 35 °C, without blowing cooling air, cooling water was arranged 23 cm below the nozzle surface, and a pair of take-up conveyors composed of a stainless-steel endless net with a width of 150 cm were arranged in parallel at an interval of 25 mm in the opening width so as to partially protrude above the water surface, and the molten discharge filaments were bent to form loops and the contact portions were fused to form a three-dimensional network structure. While sandwiching both sides of the molten three-dimensional network structure with the take-up conveyor, it was drawn into the cooling water at a speed of 0.9 m per minute for solidification, and both sides were flattened. Then, it was cut to a predetermined size and dried and heat-treated with hot air at 105 °C for 30 minutes to obtain a three-dimensional network structure. The properties of the obtained three-dimensional network structure are shown in Table 3. The obtained three-dimensional network structure had a reduced viscosity retention rate of 70% after heat treatment and was excellent in hydrolysis resistance.

[0055] In addition, the following two methods for reducing the thermal history were not used during melt extrusion. (a) The shear amount per discharge (Q / N, unit: cm 3 / rev) is 3 or more and 200 or less Q: Discharge amount per minute (cm 3 / min) of the resin discharged from the nozzle N: Screw rotation speed (rev / min) for discharging Q (b) The passing time in the pipe (V / Q, unit: min) is 1 or more and 30 or less V: Total volume (cm 3 ) from when the resin melted and extruded by the extruder exits the extruder until it is discharged from the nozzle via the pipe Q: Discharge amount per minute (cm 3 / min) of the resin discharged from the nozzle

[0056] [Example 2] 99.40% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.10% by mass of fine powder of the same borosilicate glass as in Example 1, and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. Then, the mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 3. The obtained three-dimensional network structure had a reduced viscosity retention rate of 79% after heat treatment and was excellent in hydrolysis resistance.

[0057] [Example 3] To 99.25% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.25% by mass of fine powder of the same borosilicate glass as in Example 1, and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. Then, the mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 3. The obtained three-dimensional network structure had a reduced viscosity retention rate of 87% after heat treatment and was excellent in hydrolysis resistance.

[0058] [Example 4] To 99.00% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.50% by mass of fine powder of the same borosilicate glass as in Example 1, and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. Then, the mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 3. The obtained three-dimensional network structure had a reduced viscosity retention rate of 89% after heat treatment and was excellent in hydrolysis resistance.

[0059] [Example 5] To 98.50% by mass of the above polyester-based thermoplastic elastomer (A-1), 1.00% by mass of the same fine powder of borosilicate glass as in Example 1, 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition for a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 3. The obtained three-dimensional network structure had a reduced viscosity retention rate of 90% after heat treatment and was excellent in hydrolysis resistance.

[0060] [Comparative Example 1] To 99.50% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. Then, the mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition for a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 3. Since the obtained three-dimensional network structure did not contain borosilicate glass, the reduced viscosity retention rate after heat treatment was 62% and it was inferior in hydrolysis resistance.

[0061] [Comparative Example 2] (1) Production of Thermoplastic Elastomer As a polyester-based thermoplastic elastomer, dimethyl terephthalate (DMT) and 1,4-butanediol (1,4-BD) were charged with a small amount of catalyst, and after transesterification by a conventional method, polytetramethylene glycol (PTMG) was added and polycondensation was carried out while raising the temperature and reducing the pressure to produce a polyether ester block copolymer elastomer. Next, a method for lowering the thermal history after polymerization was used, 1% of an antioxidant was added, and mixing and kneading were performed. Then, it was pelletized and vacuum dried at 50 °C for 48 hours to obtain a thermoplastic elastomer (A-2). The monomer composition, melting point, acid value, and reduced viscosity of the polyester-based thermoplastic elastomer (A-2) are shown in Table 2. The polyester-based thermoplastic elastomer (A-2) had a lower acid value than the polyester-based thermoplastic elastomer (A-1).

[0062] [Table 2]

[0063] (2) Production of three-dimensional network structure A nozzle with an effective orifice area of 1120 mm in the width direction and 64 mm in the thickness direction was prepared, and an orifice having a triple-bridge hollow-forming cross-sectional shape with an outer diameter of 5.0 mm was arranged in a staggered pattern with a hole pitch of 8 mm. Also, in Comparative Example 2, the method for reducing the thermal history during melt extrusion during spinning described in Example 1 was used. The resin composition of the above polyester-based thermoplastic elastomer was discharged downward from the nozzle under the following conditions using the nozzle at a melting temperature of 240 °C at a rate of a single-hole discharge amount (Q) of 3.2 g / min. The screw rotation speed (N) was 70 rpm, the shear amount per discharge (Q / N) was 48.7 cm 3 / rev, and the passing time in the pipe was 1 min. Also, cooling water was arranged 33 cm below the nozzle surface. An endless net made of stainless steel with a width of 150 cm was arranged in parallel with a pair of take-up conveyors at intervals of 50 mm in the opening width so that a part was above the water surface. On the conveyor net above the water surface, the molten discharge line was bent to form loops to form a three-dimensional network structure while fusing the contact parts. Both sides of the molten network body were sandwiched by take-up conveyors and drawn into cooling water at a speed of 2.0 m / min and solidified. After flattening both sides in the thickness direction, it was cut into a predetermined size and dried and heat-treated with hot air at 110 °C for 15 minutes to obtain a three-dimensional network structure body. The properties of the obtained three-dimensional network structure body made of a polyester-based thermoplastic elastomer resin are shown in Table 3. The obtained three-dimensional network structure body had a reduced viscosity retention rate of 62% after heat treatment and was inferior in hydrolysis resistance.

[0064] [Table 3]

[0065] [Comparative Example 3] To 99.497% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.003% by mass of fine powder of the same borosilicate glass as in Example 1, a phenolic antioxidant and a phosphorus -based antioxidant were each mixed at 0.250% by mass. The mixture was melt-extruded with a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition for a three-dimensional network fiber structure . Using the obtained resin composition, a three-dimensional network structure body was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure body are shown in Table 4. The obtained three-dimensional network structure body had a reduced viscosity retention rate of 68% after heat treatment and was excellent in hydrolysis resistance. . The properties of the obtained three-dimensional network structure body are shown in Table 4. The obtained three-dimensional network structure body had a reduced viscosity retention rate of 68% after heat treatment and was excellent in hydrolysis resistance.

[0066] [Comparative Example 4] To 99.494% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.006% by mass of fine powder of the same borosilicate glass as in Example 1, a phenolic antioxidant and a phosphorus -based antioxidant were each mixed at 0.250% by mass. 0.250% by mass of each antioxidant was mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition for a three-dimensional network fiber structure. A three-dimensional network structure was obtained in the same manner as in Example 1 using the obtained resin composition. The properties of the obtained three-dimensional network structure are shown in Table 4. The obtained three-dimensional network structure had a reduced viscosity retention rate of 69% after heat treatment and was excellent in hydrolysis resistance.

[0067] [Example 8] To 99.40% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.10% by mass of fine powder of borosilicate glass (manufactured by Toagosei Co., Ltd., VZ100), and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition for a three-dimensional network fiber structure. A three-dimensional network structure was obtained in the same manner as in Example 1 using the obtained resin composition. The properties of the obtained three-dimensional network structure are shown in Table 4. The obtained three-dimensional network structure had a reduced viscosity retention rate of 82% after heat treatment and was excellent in hydrolysis resistance.

[0068] [Example 9] To 99.00% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.50% by mass of the same fine powder of borosilicate glass as in Example 8, and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition for a three-dimensional network fiber structure. A three-dimensional network structure was obtained in the same manner as in Example 1 using the obtained resin composition. The properties of the obtained three-dimensional network structure are shown in Table 4. The obtained three-dimensional network structure had a reduced viscosity retention rate of 86% after heat treatment and was excellent in hydrolysis resistance.

[0069] [Example 10] To 99.00% by mass of the above polyester-based thermoplastic elastomer (A-1), 0.50% by mass of fine powder of borosilicate glass (manufactured by Nippon Flit, EH0151U40), and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 4. The obtained three-dimensional network structure had a reduced viscosity retention rate of 81% after heat treatment and was excellent in hydrolysis resistance.

[0070] [Example 11] To 98.50% by mass of the above polyester-based thermoplastic elastomer (A-1), 1.00% by mass of the same fine powder of borosilicate glass as in Example 10, and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 4. The obtained three-dimensional network structure had a reduced viscosity retention rate of 83% after heat treatment and was excellent in hydrolysis resistance.

[0071] [Example 12] To 79.50% by mass of the above polyester-based thermoplastic elastomer (A-1), 20.00% by mass of the same fine powder of borosilicate glass as in Example 1, and 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 4. The obtained three-dimensional network structure had a reduced viscosity retention rate of 97% after heat treatment and was excellent in hydrolysis resistance.

[0072] [Example 13] To 77.30% by mass of the above polyester-based thermoplastic elastomer (A-1), 22.20% by mass of fine powder of the same borosilicate glass as in Example 1, 0.25% by mass each of a phenolic antioxidant and a phosphorus-based antioxidant were mixed. The mixture was melt-extruded using a twin-screw extruder, cooled, pelletized, and dried to obtain a resin composition of a three-dimensional network fiber structure. Using the obtained resin composition, a three-dimensional network structure was obtained in the same manner as in Example 1. The properties of the obtained three-dimensional network structure are shown in Table 4. The obtained three-dimensional network structure had a reduced viscosity retention rate of 97% after heat treatment and was excellent in hydrolysis resistance, but the touch feeling when touching the three-dimensional network structure was strongly sticky.

[0073]

Table 4

Industrial Applicability

[0074] The three-dimensional network structure of the present invention is excellent in hydrolysis resistance and is less likely to be deteriorated by moisture in the air during long-term use. Therefore, it is suitable for long-term use of cushion materials used in office chairs, furniture, sofas, bedding such as beds, vehicle seats for railways, automobiles, motorcycles, child seats, baby carriages, etc., floor mats, mats for impact absorption such as impact and pinch prevention members.

Claims

1. A three-dimensional network structure composed of a resin composition of a polyester-based thermoplastic elastomer and having a three-dimensional random loop joint structure composed of continuous linear strips, wherein the resin composition contains borosilicate glass, and the molar ratio (B / Si) of the boron atomic weight B (mol) to the silicon atomic weight Si (mol) of the borosilicate glass is 0.3 to 20, and the addition amount of the borosilicate glass is 0.01 to 20% by mass when the resin composition is 100% by mass. A three-dimensional network structure characterized by the above.

2. The borosilicate glass is B ２ O ３ , SiO ２、 and an alkali metal oxide, and the three-dimensional network structure according to claim 1.

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