JP6894698B2 - Reticulated structure and its manufacturing method - Google Patents

Description

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

For example, Patent Document 1 is disclosed as a three-dimensional network structure made of a thermoplastic elastic resin. This three-dimensional network structure is exemplified by using polyester-based, polyamide-based, and polyurethane-based structures, and has excellent cushioning properties and excellent heat resistance and durability at room temperature and dry heat. However, there is a problem that the hydrolysis resistance is slightly inferior.

In order to solve this problem, for example, Patent Document 2 uses a specific ethylene-based copolymer grafted with a specific ethylenically unsaturated silane compound. However, in grafting the ethylenically unsaturated silane compound to the ethylene-based polymer, it takes a long time of one week in a room where hot water is sprayed in a mist form, which is inferior in productivity. Moreover, since the cross-linking treatment was performed, the deformation recovery property and the heat resistance were excellent, but the recyclability was inferior.

Japanese Patent No. 291638 Japanese Unexamined Patent Publication No. 2013-181117

The present invention provides a network structure having excellent molding processability and durability.

As a result of diligent research to solve the above problems, the present invention has been completed. That is, the present invention comprises a three-dimensional random loop bonding structure in which strands made of a thermoplastic elastomer having a fiber diameter of 0.1 mm or more and 3.0 mm or less form a winding random loop, and the respective loops are bonded to each other. There is less 0.005 g / cm ³ or more 0.30 g / cm ^3, about the network structure in which the bonding strength of the strands are joined is characterized in that at least 25 N.

According to the present invention, it is possible to provide a net-like structure having excellent molding processability and durability. That is, the net-like structure of the present invention has excellent durability, and is used, for example, for office chairs, furniture, sofas, bedding such as beds, and vehicle seats for trains, automobiles, motorcycles, and the like. Further, it is possible to provide a network structure having excellent mold releasability even when thermoformed, and having good productivity in the next step and excellent molding processability.

Hereinafter, the present invention will be described in detail.
The present invention comprises a random loop joining structure in which strands made of a thermoplastic elastomer having a fiber diameter of 0.1 mm or more and 3.0 mm or less form a winding random loop, and each loop is joined. density of less 0.005 g / cm ³ or more 0.30 g / cm ^3, the bonding strength of the strands are joined is intended to provide a network structure, characterized in that at least 25 N.

The thermoplastic elastomer in the present invention ^{is preferably an ethylene / α-olefin polyethylene resin having a density of 940 kg / m 3} or less, and in particular, an ethylene / α-olefin co-weight composed of ethylene and an α-olefin having 3 or more carbon atoms. It is preferably made of a coalesced resin. The ethylene / α-olefin copolymer of the present invention is preferably a copolymer described in JP-A-6-293813, and is obtained by copolymerizing ethylene with an α-olefin having 3 or more carbon atoms. Is. Here, examples of the α-olefin having 3 or more carbon atoms include propylene, butene-1, penten-1, hexene-1, 4-methyl-1-pentene, heptene-1, octene-1, nonene-1, and decene. -1, undecene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonenedecene-1, eikosen-1, and the like, preferably butene. -1, penten-1, hexene-1, 4-methyl-1-pentene, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1, tetradecene-1 , Pentadecene-1, Hexadecene-1, Heptene-1, Octadecene-1, Nonadecene-1, Eikosen-1. Further, two or more of these can be used, and these α-olefins are usually copolymerized in an amount of 1% by weight or more and 40% by weight or less. This copolymer can be obtained by copolymerizing ethylene and α-olefin using a catalyst system based on a specific metallocene compound and an organometallic compound.

When the density of the thermoplastic elastomer is 940 kg / m ³ or less, it becomes softer when the reticulated structure of the present invention is used as a cushioning material. Density is more preferably 930 kg / ^{m 3} or less, more preferably 915 kg / ^{m 3} or less, still more preferably 910 kg / ^{m 3} or less. The lower limit is not particularly limited, it is preferably from the viewpoint of heat resistance holding 880 kg / ^{m 3} or more, more preferably 890 kg / ^{m 3} or more.

When the thermoplastic elastomer is an ethylene / α-olefin copolymer, the higher the molecular weight (Mw), the more Thai molecules (molecules existing between one crystalline lamella and another crystalline lamella in the amorphous part). ) Is easy to form. The higher the tie molecule existence probability (P), the more effective it is in improving the durability. However, from the viewpoint of molding processability, Mw is preferably 40,000 or more and 150,000 or less, and the Thai molecule presence probability (P) is 0.15 or more, and Mw is 50,000 or more and 110,000 or less, and the Thai molecule presence probability (P) is 0.16 or more. More preferred.

The above-mentioned tie molecule existence probability (P) is equal to or higher than the critical molecular weight (Mc) at which the tie molecule can be formed in the relationship of molecular weight-elution amount obtained by gel permeation chromatography (GPC) measurement of the thermoplastic elastomer of the present invention. It can be calculated from the ratio of the elution area to the total elution area.
Here, the critical molecular weight (Mc) at which Thai molecules can be formed is determined by J.I. Polym. Sci. , Polym. Phys. Ed. , 29, 129 (1991), can be calculated by the following method with reference to the concept of Thai molecule formation. The details will be described below. Tie molecules are formed when the spread of the molecular chain in the molten state (average distance between molecular ends: r) is larger than the critical thickness (2 Lc + La) consisting of crystals and amorphous in the solid state. The critical condition in which is formed can be expressed by the following equation (I).
r = (2Lc + La) (I)
(In the formula, Lc is the crystal thickness and La is the amorphous thickness.)
In the case of an ethylene / α-olefin copolymer, r has a relationship of the following formula (II) with the molecular weight (M).
r = C _∞・ M / M ₀・ lv ² (II)
Here, C ∞ is a characteristic ratio of 6.8, M ₀ is a skeletal molecular weight 14, lv skeletal bond length is 1.53, and M is a molecular weight.
Substituting the formula (II) into the formula (I), Mc is the same as M, so that the formula (III) is obtained, and the Thai molecule can be formed from the formula (III) by obtaining the values of Lc and La. The critical molecular weight (Mc) can be calculated.
Mc = 0.88 (2Lc + La) ² (III)
Further, Lc can be calculated by the following formula (IV) from the melting point (Tm) of the ethylene / α-olefin copolymer obtained by measurement using a differential scanning calorimeter (DSC).
Lc = (6.26 × 414) / (414-Tm) (IV)
(Here, the unit of Tm is [K].)
La can be calculated from Lc and the crystallinity (Xc) by the following equation (V).
La = (Lc (1-Xc)) / Xc (V)
Xc can be calculated by the following equation (VI) from the density (d) measured by the density gradient tube.
Xc = (d-0.86) /0.14d (VI)

The thermoplastic elastomer constituting the network structure of the present invention preferably has an endothermic peak below the melting point in the melting curve measured by using a differential scanning calorimeter. Those having an endothermic peak below the melting point have significantly improved heat resistance and settling resistance as compared with those having no endothermic peak.
For example, when the density of the thermoplastic elastomer is 905 kg / m ³ or less, the heat absorption peak is 80 ° C. or more and 130 ° C. or less in the melting curve measured by a differential scanning calorimeter. It is preferably one in the range and two or more in the range of less than 80 ° C., which is a temperature lower than the melting point (99 ° C.), from the viewpoint of heat resistance and sag resistance. At this time, the melting point of the ethylene / α-olefin copolymer is 99 ° C.
For example, in the case of an ethylene / α-olefin copolymer obtained by polymerizing hexane, hexene, and ethylene by a known method using a metallocene compound as a preferable thermoplastic elastomer of the present invention, the number of branches of the main chain can be determined. If the amount is reduced, the crystal restrains the molecular chain and the heat resistance and settling resistance are improved, but if the annealing treatment is further performed at a temperature at least 20 ° C. to 50 ° C. lower than the melting point after molding, the settling resistance is further improved. The annealing treatment may be performed as long as the sample can be heat-treated at a temperature at least 20 ° C. lower than the melting point. Annealing at a temperature close to the melting point is not preferable because the shape cannot be maintained and the shape is deformed. In the melting curve of the reticulated structure treated in this way measured with a differential scanning calorimeter, one endothermic peak appears in the range of 80 ° C. or higher and 110 ° C. or lower, and the endothermic peak appears at a temperature of room temperature or higher and melting point or lower. Is expressed in two or more. If annealing is not performed, one endothermic peak appears in the range of 30 ° C. to 40 ° C. on the melting curve. From this, it is considered that crystals are formed at a temperature 5 to 10 ° C. higher than the annealing temperature, and the settling resistance is improved. As a method of utilizing the sagging resistance improving effect in the present invention, it is useful for improving durability in a usage application such as a cushion or a mat, which is relatively repeatedly compressed.

If necessary, the thermoplastic elastomer according to the present invention can be blended with two or more types of polymers polymerized by the above method, or polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene. Further, a modifier may be blended with the thermoplastic elastomer, and an antioxidant, a lubricant, a weather resistant agent, a flame retardant and the like can be added as needed.

Examples of the antioxidant include known phenol-based antioxidants, phosphite-based antioxidants, thioether-based antioxidants, benzotriazole-based UV absorbers, triazine-based UV absorbers, benzophenone-based UV absorbers, and NH-type. It is desirable to add at least one of a hindered amine-based light stabilizer and an N-CH3 type hindered amine-based light stabilizer.

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

Phosphite-based antioxidants include 3,9-bis (octadecyloxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane and 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-dimethyl) Ethyl) -6-[(2-ethylhexyl) oxy] -12H-dibenzo [d, g] [1,3,2] dioxaphosphosin, tris phosphite (2,4-di-tert-butylphenyl) , Tris (4-nonylphenyl) phosphite, 4,4'-Isopropylidenediphenyl C12-15 alchohol phosphite, diphenyl phosphite (2-ethylhexyl), diphenylisodecylphosphite, triisodecylphosphite, triphenyl phosphite, etc. Can be mentioned.

As thioether-based antioxidants, bis [3- (dodecylthio) propionic acid] 2,2-bis [[3- (dodecylthio) 1-1oxopropyloxy] methyl] 1,3-propanediyl, 3,3' -Ditridecyl thiobispropionate and the like.

In order to prevent thermal deterioration, it is desirable to use a mixture of a phenolic antioxidant and a phosphite-based antioxidant. The amount of the antioxidant added is preferably 0.1% by weight or more and 0.6% by weight or less.

As the lubricant, a hydrocarbon-based wax, a higher alcohol-based wax, an amide-based wax, an ester-based wax, a metal soap-based wax, or the like is selected. The lubricant does not have to be added, and when it is added, it is preferably 0.1% by weight or less.

The strands constituting the network structure of the present invention may be formed into a composite linear shape in combination with another thermoplastic resin as long as the object of the present invention is not impaired. Examples of the composite form include a composite linear body such as a sheath-core type, a side-by-side type, and an eccentric sheath-core type when the linear body itself is composited.

The network structure of the present invention may have a multi-layer structure as long as the object of the present invention is not impaired. Examples of the multi-layer structure include a structure in which the surface layer and the back layer are composed of linear bodies having different fineness, and a structure in which the surface layer and the back layer are composed of structures having different apparent densities. As a multi-layer method, a method of changing the hole diameter of the nozzle orifice, a method of stacking network structures and fixing them on a side surface, a method of melting and fixing by heating, a method of adhering with an adhesive, a method of binding with an adhesive, a method of restraining with sewing or a band, etc. The method of doing this can be mentioned.

The reticulated structure of the present invention is deodorized and antibacterial, deodorant, antifungal, colored, fragrant, and difficult at any stage of processing into a molded product from the resin manufacturing process and commercializing the structure without impairing the object of the present invention. Functions such as combustion and moisture absorption / desorption may be imparted by a treatment process such as addition of a chemical agent.

The molded reticulated structure of the present invention can be used for automobile and railroad seats, chairs, beds, sofas, mattresses, pillows and the like.

If the fiber diameter of the strands constituting the network structure of the present invention is small, the hardness required for use as a cushioning material cannot be maintained, and conversely, if the fiber diameter is too large, the fiber diameter becomes too hard. It is necessary to set it in an appropriate range. The fiber diameter is 0.1 mm or more, preferably 0.5 mm or more. If the fiber diameter is less than 0.1 mm, it will be too thin, and the fineness and soft touch will be good, but it will be difficult to secure the hardness required for the network structure. The fiber diameter is 3.0 mm or less, preferably 2.0 mm or less. When the fiber diameter exceeds 3.0 mm, the hardness of the reticulated structure can be sufficiently secured, but the reticulated structure becomes rough and the cushioning performance may be inferior.

The strands form a winding random loop. Each loop is joined to form a three-dimensional random loop joining structure. In the random loop bonding structure, for example, the molten thermoplastic elastomer is extruded downward in a strand shape from a die having a plurality of holes to bend the strand to form a random loop, and each loop is in a molten state with each other. It can be formed by contact. The resulting random loop junction structure has a network structure in which a plurality of strands are spirally entwined in a disorderly manner and partially heat-bonded.

Apparent density of the network structure of the present invention is less 0.005 g / cm ³ or more ^{0.30g / cm 3, 0.01g / cm} 3 or more 0.18 g / cm ³ or less are preferred, 0.02 g / cm ³ to 0.15 g / cm ³ or less is more preferable. Apparent density is not maintained when the hardness required when used as 0.005 g / cm ³ less than the cushion member, becomes too hard exceeds 0.30 g / cm ³ Conversely, unsuitable cushioning material May be.

The bonding strength of the strands to be bonded is 25 N or more, preferably 30 N or more. If the joint strength is less than 25 N, the settling resistance of the cushion material is lowered, which is not preferable.

In the network structure of the present invention having excellent durability and moldability, for example, a thermoplastic elastomer is melted at a temperature at which the zero shear viscosity is 200 Pa · s or more and 1000 Pa · s or less, and the fiber diameter is 0.1 mm or more. It can be obtained by forming strands of 3.0 mm or less, winding the strands to form random loops, and bringing the loops into contact with each other in a molten state.
Specifically, the network structure of the present invention can be obtained according to a known method described in International Publication No. 2012/035736 and the like. For example, a thermoplastic elastomer is distributed to the nozzle orifice from a multi-row nozzle having a plurality of orifices, and is discharged downward from the nozzle at a temperature in which the zero shear viscosity is in the range of 200 Pa · s to 1000 Pa · s, and is in a molten state. While forming a three-dimensional structure by bringing the strands into contact with each other and fusing them together, they are sandwiched between take-back conveyor nets, cooled with the cooling water in the cooling tank, and then drawn out, drained or dried to form both sides or one side. Obtain a smoothed reticulated structure. When smoothing only one surface, it is preferable to discharge it onto a take-up net having an inclination, bring it into contact with each other in a molten state and fuse it to form a three-dimensional structure, and cool only the take-up net surface while relaxing the form. The obtained network structure can also be annealed. The drying treatment of the reticulated structure may be an annealing treatment.

The molding temperature of the network structure of the present invention preferably has a melt viscosity of the thermoplastic elastomer of 200 Pa · s or more and 1000 Pa · s or less, and more preferably 300 Pa · s or more and 800 Pa · s or less. If the melt viscosity is lower than 200 Pa · s, the strands cannot form a network structure and become lumps, which may be unsuitable for cushioning material. Further, if the viscosity is higher than 1000 Pa · s, the strength of the fused strand becomes low and the durability may deteriorate.

The thickness of the network structure of the present invention is preferably 10 mm or more, more preferably 20 mm or more. If the thickness is less than 10 mm, it may be too thin when used as a cushioning material, giving a feeling of bottoming. The upper limit of the thickness is preferably 300 mm or less, more preferably 100 mm or less, and further preferably 80 mm or less from the viewpoint of the manufacturing apparatus.

Next, the present invention will be described with specific examples, but the present invention is not limited thereto. The evaluation of the characteristic values in the examples is as follows.

(1) Density of Thermoplastic Elastomer Using a MI meter with a hood, a sample extruded at 190 ° C. with a load of 5 kg was slowly cooled in the hood for 5 minutes, and then measured with a density gradient tube at 23 ° C.

(2) GPC
GPC was measured under the following conditions.
[Device] HLC-8121GPC / HT manufactured by Tosoh Corporation
[Measurement conditions] Column: TSKgel GMHHR-H (20) HT x 3, eluent: trichlorobenzene + antioxidant (BHT 0.05%), flow velocity: 1.0 ml / min, sample concentration: 1.0 mg / ml , Injection volume: 0.3 ml, Column temperature: 140 ° C., Detector: HLC-8121 GPC / HT

(3) Melt flow rate (MFR)
According to JIS K7210, the measurement was performed at a temperature of 190 ° C. and a load of 21.18 N.

(4) Zero shear viscosity (melt viscosity at processing temperature)
Zero shear viscosity was measured under the following conditions.
[Device] Reometrics Scientific Stress Rheometer SR2000
[Measurement conditions] The dynamic melt viscosity η * (ω) was measured with a frequency (ω) in the range of 0.01 to 100 rad / s and a strain of 10 to 15%. As a jig for applying shear to the resin, a parallel plate having a diameter of 25 mm was used, and the plate spacing was set to 1.5 mm.

(5) Bond strength Measured with JIS L 1096 (general textile test method) method A (strip method), test speed: 200 mm / min, initial test length (distance between chucks of tensile tester): 200 mm, number of tests: 5. did.

(6) Hardness retention rate The sample was cut into a size of 30 cm × 30 cm and heat-treated at 60 ° C. for 10 minutes in a heating oven. After measuring the thickness using a caliper, compression was performed at a speed of 10 mm / min, and the hardness at 25% compression was defined as the pretreatment load (c). After that, with a Shimadzu servo pulsar, compression recovery was repeated in a 1 Hz cycle to a thickness of 50% of the pre-treatment thickness in an environment of 20 ° C ± 2 ° C, and the sample after 80,000 times was allowed to stand for 30 minutes, and then the speed was 10 mm / It was compressed at a rate of minutes and the hardness at 25% compression was defined as the post-treatment load (d). From the formula (d) / (c) × 100, the hardness retention rate at the time of 25% compression after 50% constant displacement repeated compression was calculated: unit% (average value of n = 3).

(7) Apparent density A sample is cut into a size of 30 cm x 30 cm, left unloaded for 24 hours, and then the heights of four locations are measured with an FD-80N type thickener manufactured by FD-80N, and the average value is used as the sample. The thickness. The sample weight is measured by placing the sample on an electronic balance. The apparent density is indicated by the volume obtained from the sample thickness and the weight of the sample divided by the volume (the average value of n = 3 for each).

(8) Formability The state of the strands extruded from the die at a predetermined temperature was determined according to the following criteria.
"○": It becomes a loop and the strand does not hang down.
"X": The strands do not hang down and form a loop.

(9) Measurement using a differential scanning calorimeter Using a DSC6220 ASD differential thermal analyzer manufactured by SII Nanotechnology, 10 mg of the reticulated structure after annealing was sampled at 60 ° C, and the temperature rise rate was 10 ° C / min. The endothermic peak (melting peak) temperature was determined from the measured endothermic heat absorption curve.

[Example 1]
An ethylene / α-olefin copolymer polymerized by a known method described in JP-A No. 7-133323 with a density of 905 kg / m ³ and an MFR of 4.0 g / 10 minutes using a twin-screw extruder (manufactured by Toyo Seiki Co., Ltd.). After adding 1000 ppm of a phenolic antioxidant (trade name: Irganox 1010, manufactured by BASF Japan) and 1000 ppm of a phosphorus-based antioxidant (manufactured by Irgafos 168 BASF Japan), the screw rotation speed is 20 rpm and the barrel set temperature is 220 ° C. It was mixed and kneaded and pelletized to obtain a thermoplastic elastomer.
The obtained thermoplastic elastomer is extruded from a die having a fiber diameter of 0.9 mm at a resin temperature of 260 ° C. (zero shear viscosity: 450 Pa · s) according to a known method described in International Publication No. 2012/035736 and the like. , A reticulated structure was formed.
The hardness retention rate of the obtained network structure was 80%, the bonding strength was 35 N, and the apparent density was 0.06 g / cm ³ , which were excellent in molding processability.

[Example 2]
An ethylene / α-olefin copolymer polymerized by a known method described in JP-A No. 7-133323 with a density of 890 kg / m ³ and an MFR of 1.0 g / 10 minutes using a twin-screw extruder (manufactured by Toyo Seiki Co., Ltd.). After adding 1000 ppm of a phenolic antioxidant (trade name: Irganox 1010 BASF Japan) and 1000 ppm of a phosphorus-based antioxidant (trade name: Irgafos 168 BASF Japan), the screw rotation speed is 20 rpm and the barrel set temperature is 220 ° C. Melt-kneading was carried out under the conditions to obtain a thermoplastic elastomer.
The obtained thermoplastic elastomer was molded into a network structure at a resin temperature of 300 ° C. (zero shear viscosity: 530 Pa · s) according to a known method described in International Publication No. 2012/037576 (fiber diameter: 1). .05 mm).
The hardness retention rate of the obtained network structure was 83%, the bonding strength was 38 N, and the apparent density was 0.070 g / cm ³ , which were excellent in molding processability.

[Example 3]
An ethylene / α-olefin copolymer polymerized by a known method described in JP-A No. 7-133323 with a density of 910 kg / m ³ and an MFR of 6.0 g / 10 minutes using a twin-screw extruder (manufactured by Toyo Seiki Co., Ltd.). After adding 1000 ppm of a phenolic antioxidant (trade name: Irganox 1010 BASF Japan) and 1000 ppm of a phosphorus-based antioxidant (trade name: Irgafos 168 BASF Japan), the screw rotation speed is 20 rpm and the barrel set temperature is 220 ° C. Melt-kneading was carried out under the conditions to obtain a thermoplastic elastomer.
The obtained thermoplastic elastomer was molded into a network structure at a resin temperature of 240 ° C. (zero shear viscosity: 680 Pa · s) according to a known method described in International Publication No. 2012/037576 (fiber diameter: 1). .10 mm).
The hardness retention rate of the obtained network structure was 78%, the bonding strength was 33 N, and the apparent density was 0.075 g / cm ³ , which were excellent in molding processability.

[Comparative Example 1]
Ethylene / α-olefin copolymer polymerized by a known method described in JP-A No. 7-133323 with a density of 905 kg / m ³ and MFR of 20 g / 10 minutes using a twin-screw extruder (manufactured by Toyo Seiki Co., Ltd.). After adding 1000 ppm of phenolic antioxidant (trade name: Irganox 1010 BASF Japan) and 1000 ppm of phosphorus-based antioxidant (trade name: Irgafos 168 BASF Japan), the screw rotation speed is 20 rpm and the barrel set temperature is 220 ° C. Melt-kneading was performed to obtain a thermoplastic elastomer. The obtained thermoplastic elastomer was molded into a network structure at a resin temperature of 200 ° C. (zero shear viscosity: 120 Pa · s) according to a known method described in International Publication No. 2012/035736 and the like.
Since the melt viscosity was lower than the optimum range, the strands did not form a loop and a network structure could not be obtained.

[Comparative Example 2]
Ethylene / α-olefin copolymer polymerized by a known method described in JP-A-7-133323 with a density of 905 kg / m ³ and MFR of 12 g / 10 minutes using a twin-screw extruder (manufactured by Toyo Seiki Co., Ltd.). After adding 1000 ppm of phenolic antioxidant (trade name: Irganox 1010 BASF Japan) and 1000 ppm of phosphorus-based antioxidant (trade name: Irgafos 168 BASF Japan), the screw rotation speed is 20 rpm and the barrel setting temperature is 230 ° C. Melt-kneading was performed to obtain a thermoplastic elastomer. The obtained thermoplastic elastomer was molded into a network structure at a resin temperature of 230 ° C. (zero shear viscosity: 190 Pa · s) according to a known method described in International Publication No. 2012/037576 (fiber diameter: 0). .55 mm).
The hardness retention rate of the obtained network structure was 73%, the bonding strength was 23 N, and the apparent density was 0.0048 g / cm ³ . The molding processability of the reticulated structure was good, but the hardness retention rate was 73%, and the durability was not satisfactory.

[Comparative Example 3]
Ethylene / α-olefin copolymer polymerized by a known method described in JP-A-7-133323 with a density of 905 kg / m ³ and MFR of 4 g / 10 minutes using a twin-screw extruder (manufactured by Toyo Seiki Co., Ltd.). After adding 1000 ppm of phenolic antioxidant (trade name: Irganox 1010 BASF Japan) and 1000 ppm of phosphorus-based antioxidant (trade name: Irgafos 168 BASF Japan), the screw rotation speed is 20 rpm and the barrel set temperature is 220 ° C. Melt-kneading was performed to obtain a thermoplastic elastomer. The obtained thermoplastic elastomer was molded into a network structure at a resin temperature of 200 ° C. (zero shear viscosity: 1600 Pa · s) according to a known method described in International Publication No. 2012/035736 (fiber diameter: 1). .8 mm).
The hardness retention rate of the obtained network structure was 63%, the bonding strength was 15 N, and the apparent density was 0.0105 g / cm ³ . The hardness retention rate was 63%, and the durability was not satisfactory.

Claims (2)

Strands made of thermoplastic elastomer having a fiber diameter of 0.1 mm or more and 3.0 mm or less form a winding random loop, and each loop is provided with a three-dimensional random loop bonding structure to which the loops are bonded, and the apparent density is 0.005 g /. cm ³ or more 0.30 g / cm ³ or less state, and are joint strength than 25N strands are joined,
The thermoplastic elastomer is an ethylene / α-olefin copolymer having a density of 940 kg / m ^{3 or less.}
The weight molecular weight of the ethylene / α-olefin copolymer is 40,000 or more and 150,000 or less, and the Thai molecule existence probability (P) is 0.15 or more.
The density of the ethylene / α-olefin copolymer is 905 kg / m ³ or less, and the endothermic peak is 80 ° C. or higher and 110 ° C. in the melting curve measured using a differential scanning calorimeter of the ethylene / α-olefin copolymer. A network structure characterized by one in the following range and two or more in a range of less than 80 ° C. The thermoplastic elastomer is melted at a temperature at which the zero shear viscosity is 200 Pa · s or more and 1000 Pa · s or less to form strands having a fiber diameter of 0.1 mm or more and 3.0 mm or less.
The strands are twisted to form a random loop,
The method for manufacturing a network structure according to claim 1 , wherein the loops are brought into contact with each other in a molten state.