WO2023190074A1

WO2023190074A1 - Melt-blown nonwoven fabric and hygienic material

Info

Publication number: WO2023190074A1
Application number: PCT/JP2023/011624
Authority: WO
Inventors: 翔飯濱; 秀超北山; 尚貴山岸; 稔久田; 暁雄松原
Original assignee: 三井化学株式会社
Priority date: 2022-03-29
Filing date: 2023-03-23
Publication date: 2023-10-05
Also published as: JP2023147247A

Abstract

The melt-blown nonwoven fabric according to the present disclosure comprises a thermoplastic polyurethane-based elastomer having a number average molecular weight (Mn) of 100,000 or more and a molecular distribution (Mw/Mn), which is a ratio of the weight average molecular weight (Mw) to a number average molecular weight (Mn), of 2.4 or less and has an average fiber diameter of less than 6.5 μm.

Description

Meltblown nonwovens and sanitary materials

The present disclosure relates to meltblown nonwoven fabrics and sanitary materials.

In recent years, nonwoven fabrics have been widely used for various purposes due to their excellent breathability and flexibility. Therefore, nonwoven fabrics are required to have various properties depending on their uses, and improvements in these properties are also required.

For example, Patent Document 1 discloses a polyurethane fiber nonwoven fabric (hereinafter also simply referred to as "nonwoven fabric"). The nonwoven fabric disclosed in Patent Document 1 is made of ultrafine polyurethane fibers with an average fiber diameter of 10 μm or less, and 15 to 80% of the fibers are fused into bundles. The nonwoven fabric disclosed in Patent Document 1 has an equilibrium dyeing amount of 60 mg/g or more.

Patent Document 2 discloses a filter. The filter disclosed in Patent Document 2 is made of a fibrous nonwoven fabric whose main component is a thermoplastic elastomer resin. In the filter disclosed in Patent Document 2, the fibrous nonwoven fabric satisfies the following (1) to (4). (1) indicates that the average fiber diameter of the fibers constituting the fibrous nonwoven fabric is 10 μm or less. (2) indicates that 15 to 80% of the fibers are composed of two or more fibers fused together in a bundle. (3) indicates that the material has an elongation at break of 100% or more and a 50% elongation recovery rate of 60% or more. (4) indicates that the air permeability when stretched by 50% in at least one direction is less than twice the air permeability when not stretched.

Patent Document 3 discloses fibers (hereinafter also simply referred to as "fibers") based on thermoplastic polyurethane. The fiber disclosed in Patent Document 3 contains an inorganic additive. In the fibers disclosed in US Pat. No. 5,302,303, at least 70% of the particles of the inorganic additive have a maximum particle diameter that is smaller than 75% of the fiber diameter of the thermoplastic polyurethane.

Patent Document 1: Japanese Patent Application Publication No. 2003-064567 Patent Document 2: Japanese Patent Application Publication No. 2004-057882 Patent Document 3: Japanese Patent Publication No. 2010-509512

As mentioned above, a wide range of applications are being considered for nonwoven fabrics.
For example, nonwoven fabrics can be used for disposable diapers, absorbent materials such as sanitary products, sanitary materials such as sanitary masks, medical materials such as bandages, clothing materials, packaging materials, and the like.
In the various uses mentioned above, nonwoven fabrics are often required to have excellent elongation at break and water pressure resistance.

A problem to be solved by an embodiment of the present disclosure is to provide a melt-blown nonwoven fabric with excellent elongation at break and water pressure resistance, and a sanitary material containing the melt-blown nonwoven fabric.

Means for solving the above problems include the following embodiments.
<1> Heat having a number average molecular weight (Mn) of 100,000 or more and a molecular weight distribution (Mw/Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 2.4 or less. A meltblown nonwoven fabric containing a plastic polyurethane elastomer and having an average fiber diameter of less than 6.5 μm.
<2> Heat having a number average molecular weight (Mn) of 100,000 or more and a molecular weight distribution (Mw/Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 2.4 or less. Contains a plastic polyurethane elastomer, and has a recovery stress of 0.034N・m ² /50mm in the MD direction relative to the basis weight (g/m ² ).
・Meltblown nonwoven fabric larger than g.
<3> The meltblown nonwoven fabric according to <1> or <2>, having an average fiber diameter of 5.5 μm or less.
<4> The meltblown nonwoven fabric according to any one of <1> to <3>, wherein the thermoplastic polyurethane elastomer satisfies the following formula I.
a/(a+b)≦0.8 (I)
(In Formula I, a represents the sum of the heat of fusion obtained from endothermic peaks in the range of 90°C to 140°C measured by a differential scanning calorimeter, and b represents 140°C measured by a differential scanning calorimeter. (Represents the total amount of heat of fusion obtained from endothermic peaks in the range of 220℃ or less.)
<5> The meltblown nonwoven fabric according to any one of <1> to <4>, wherein the thermoplastic polyurethane elastomer has a number average molecular weight (Mn) of 101,500 or more.
<6> The meltblown nonwoven fabric according to any one of <1> to <5>, which has an elongation at break in the MD direction of 250% or more.
<7> The melt-blown nonwoven fabric according to any one of <1> to <6>, which has a water pressure resistance to basis weight (g/m ² ) of 6.0 mmH ₂ O·m ² /g or more.
<8> The meltblown nonwoven fabric according to any one of <1> to <7>, which has a recovery stress in the MD direction with respect to basis weight (g/m ² ) of 0.035 N·m ² /50 mm·g or more.
<9> A sanitary material comprising the meltblown nonwoven fabric according to any one of <1> to <8>.
<10> A water-resistant sheet comprising the meltblown nonwoven fabric according to any one of <1> to <8>.
<11> A medical sheet comprising the meltblown nonwoven fabric according to any one of <1> to <8>.

An embodiment of the present disclosure can provide a meltblown nonwoven fabric with excellent elongation at break and water pressure resistance, and a sanitary material containing the meltblown nonwoven fabric.

FIG. 1 is a schematic diagram showing an example of the configuration of a meltblown nonwoven fabric manufacturing apparatus 10. As shown in FIG.

In the present disclosure, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits.
In the present disclosure, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, the amount of each component contained in the composition refers to the total amount of the multiple substances present in the composition. means.
In the numerical ranges described step by step in this disclosure, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of another numerical range described step by step. . In the numerical ranges described in this disclosure, the upper limit or lower limit of the numerical range may be replaced with the values shown in the Examples.
In the present disclosure, if there are multiple substances corresponding to each component in the material, the amount of each component in the material means the total amount of the multiple substances present in the material, unless otherwise specified.

≪Meltblown nonwoven fabric≫
The meltblown nonwoven fabric of the present disclosure includes the meltblown nonwoven fabric of the first aspect and the meltblown nonwoven fabric of the second aspect.
The melt-blown nonwoven fabric of the first aspect and the melt-blown nonwoven fabric of the second aspect will be described below.

[First aspect]
The melt-blown nonwoven fabric of the first aspect has a number average molecular weight (Mn) of 100,000 or more, and a molecular weight distribution (Mw/Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (hereinafter, It contains a thermoplastic polyurethane elastomer having a molecular weight distribution (Mw/Mn) of 2.4 or less, and has an average fiber diameter of less than 6.5 μm.

Since the melt-blown nonwoven fabric of the first aspect has the above configuration, it has excellent elongation at break and water pressure resistance.
The thermoplastic polyurethane elastomer in the present disclosure has a relatively large number average molecular weight (Mn). This can increase the breaking strength of the fibers and prevent them from breaking easily. High breaking strength also contributes to improved water pressure resistance.
The thermoplastic polyurethane elastomer in the present disclosure has a molecular weight distribution (Mw/Mn) of 2.4 or less. This makes the molecular weight in the fiber uniform. This reduces the number of weak portions of molecular chain entanglement that serve as starting points for rupture. As a result, the breaking strength of the fibers and the water pressure resistance of the meltblown nonwoven fabric are improved.
When the average fiber diameter of the melt-blown nonwoven fabric is less than 6.5 μm, the fiber amount of the melt-blown fibers and, as a result, the self-fusion point increases, and the entanglement becomes strong. The combination of the strong intertwining of the fibers and the high breaking strength of the fibers described above produces a synergistic effect in that the entangled fibers can be stretched well without breaking.

The number average molecular weight (Mn) and weight average molecular weight (Mw) of the thermoplastic polyurethane elastomer refer to the number average molecular weight (Mn) and weight average molecular weight (Mw) in a state included in the meltblown nonwoven fabric.
The number average molecular weight (Mn) and weight average molecular weight (Mw) of the thermoplastic polyurethane elastomer in a state included in the melt blown nonwoven fabric can vary depending on the conditions when forming the melt blown nonwoven fabric.
For example, in Patent Document 1 mentioned above, the molecular weight of the elastomer is considered to be low because the molding temperature is high and the air permeability and elongation at break are extremely low. There is a possibility that high fusion has occurred due to high temperature molding.

The meltblown nonwoven fabric of the first aspect has an average fiber diameter of less than 6.5 μm.
As a result, the fiber content of the meltblown fibers and, as a result, the self-fusion point increases, and the entanglement becomes stronger.
The melt-blown nonwoven fabric of the first aspect preferably has an average fiber diameter of 6.4 μm or less, more preferably 5.5 μm or less. When the average fiber diameter is 5.5 μm or less, the fiber amount and self-fusion point of the above-mentioned meltblown fibers further increase, and the entanglement becomes stronger. In addition, thin uneven parts of the nonwoven fabric, which can be the starting point for breakage and water leakage, are reduced. This further improves the elongation at break and the water pressure resistance.
The melt-blown nonwoven fabric of the first aspect preferably has an average fiber diameter of 2.5 μm or more, more preferably 3.0 μm or more.
The melt-blown nonwoven fabric of the first aspect may have an average fiber diameter of 2.5 μm or more and less than 6.5 μm.

The average fiber diameter is measured by the following method.
A photograph of the melt-blown nonwoven fabric is taken at a magnification of 1000 times using an electron microscope (eg, Hitachi S-3500N). Measure the diameter of the fiber from the photograph obtained. The imaging and measurement are repeated until the total number of fibers exceeds 100, and the arithmetic mean value of the obtained fiber diameters is defined as the average fiber diameter (μm).

<Thermoplastic polyurethane elastomer>
The melt-blown nonwoven fabric of the first embodiment includes a thermoplastic polyurethane elastomer.

(Number average molecular weight (Mn))
The thermoplastic polyurethane elastomer has a number average molecular weight (Mn) of 100,000 or more.
This can increase the breaking strength of the fibers and prevent them from breaking easily. High breaking strength also contributes to improved water pressure resistance.
The thermoplastic polyurethane elastomer preferably has a number average molecular weight (Mn) of 101,500 or more, more preferably 102,500 or more, and even more preferably 103,500 or more. When the number average molecular weight (Mn) is 101,500 or more, the entanglement of molecular chains further increases, and the breaking strength of the fibers and, by extension, the breaking elongation and water pressure resistance of the nonwoven fabric are further improved.

(Weight average molecular weight (Mw))
From the viewpoint of spinnability, the weight average molecular weight (Mw) of the thermoplastic polyurethane elastomer is preferably 180,000 or more, and preferably 190,000 or more.

(molecular weight distribution)
The molecular weight distribution (Mw/Mn) of the thermoplastic polyurethane elastomer is 2.4 or less, preferably 2.3 or less, and more preferably 2.2 or less. The upper limit of the molecular weight distribution (Mw/Mn) is not particularly limited, but may be, for example, 1.0 or more.
In other words, the molecular weight distribution (Mw/Mn) is preferably 1.0 to 2.4, more preferably 1.0 to 2.3, and even more preferably 1.0 to 2.2. preferable.

The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw/Mn) are measured by the following methods.
The produced melt-blown nonwoven fabric is heated and melted at 80° C. in the following eluent to produce a measurement sample. Using gel permeation chromatography (GPC), the number average molecular weight (Mn) and weight average molecular weight (Mw) are obtained based on monodisperse polystyrene under the following conditions. The ratio of the obtained weight average molecular weight (Mw) to the obtained number average molecular weight (Mn) was defined as the molecular weight distribution (Mw/Mn).
GPC measurement conditions;
Column: Shodex GPC KD-806M (8.0mm ID x 300mmL) x 2
Column temperature: 40℃
Eluent: 0.01 mol/L-LiBr in dimethylformamide Flow rate: 0.7 mL/min Detection wavelength: UV 264 nm
Injection volume: 100μL
Measuring equipment: 515 pump, 717plus automatic injection device, 2487UV detector (manufactured by Nippon Waters Co., Ltd.)

(solidification start temperature)
The thermoplastic polyurethane elastomer preferably has a solidification start temperature of 65°C or higher, more preferably 75°C or higher, and even more preferably 85°C or higher.
When the solidification start temperature is 65°C or higher, molding defects such as fusion of fibers, thread breakage, and resin lumps can be suppressed when obtaining a meltblown nonwoven fabric, and meltblown molded during hot embossing can be suppressed. It is possible to prevent the nonwoven fabric from wrapping around the embossing roller.
In addition, when the thermoplastic solidification start temperature is 65° C. or higher, stickiness of the resulting melt-blown nonwoven fabric can be suppressed. Therefore, melt-blown nonwoven fabrics can be suitably used as materials that come into contact with the skin, such as clothing, sanitary materials, and sports materials.

The thermoplastic polyurethane elastomer preferably has a solidification start temperature of 195°C or lower.
By setting the solidification start temperature to 195° C. or lower, moldability can be improved.

The solidification onset temperature is measured using a differential scanning calorimeter (DSC).
Specifically, the temperature of the thermoplastic polyurethane elastomer is raised to 230°C at a rate of 10°C/min, held at 230°C for 5 minutes, and then lowered at a rate of 10°C/min. The starting temperature of the exothermic peak resulting from the solidification of the thermoplastic polyurethane elastomer that occurs at this time is the solidification start temperature.

Methods for adjusting the solidification initiation temperature of thermoplastic polyurethane elastomers to 65°C or higher include methods of appropriately selecting the chemical structures of polyol compounds, isocyanate compounds, chain extenders, etc. used as raw materials for thermoplastic polyurethane elastomers; Examples include a method of adjusting the amount of hard segments in the plastic polyurethane elastomer.

"Hard segment amount" is the total content of isocyanate compounds and chain extenders used in the production of thermoplastic polyurethane elastomers, divided by the total amount of polyol compounds, isocyanate compounds, and chain extenders, and multiplied by 100. Mass percentage (mass %) value is meant.
The amount of hard segments is preferably 20% by mass to 60% by mass, more preferably 22% by mass to 50% by mass, and even more preferably 25% by mass to 48% by mass.

(Number of particles insoluble in polar solvent)
The thermoplastic polyurethane elastomer preferably has a polar solvent insoluble particle number of preferably 3 million particles (3 million particles/g) or less, more preferably 2.5 million particles per 1 g of the thermoplastic polyurethane elastomer. /g or less, more preferably 2 million pieces/g or less.
The "polar solvent insoluble matter in the thermoplastic polyurethane elastomer" mainly refers to lumps such as fish eyes and gel that are generated during the production of the thermoplastic polyurethane elastomer.
Components that cause the generation of polar solvent insoluble matter include components derived from hard segment aggregates of thermoplastic polyurethane elastomers, components in which hard segments and/or soft segments are crosslinked by allophanate bonds, burette bonds, etc. Examples include raw materials constituting the plastic polyurethane elastomer, components generated by chemical reactions between raw materials, and the like.

The number of particles insoluble in a polar solvent was measured by measuring the insoluble content when a thermoplastic polyurethane elastomer was dissolved in a dimethylacetamide solvent using a particle size distribution measuring device using a pore electrical resistance method equipped with a 100 μm aperture. It is a value.
By installing a 100 μm aperture, it is possible to measure the number of particles of 2 μm to 60 μm in terms of uncrosslinked polystyrene.

By reducing the number of particles insoluble in polar solvents to 3 million particles/g or less, problems such as increased fiber diameter distribution and yarn breakage during spinning can be prevented within the solidification start temperature range of thermoplastic polyurethane elastomers. It can be suppressed further. A thermoplastic polyurethane elastomer with a small content insoluble in polar solvents can be obtained by carrying out a polymerization reaction of a polyol compound, an isocyanate compound, and a chain extender, followed by filtration.

From the viewpoint of suppressing the inclusion of air bubbles in the strand and the occurrence of yarn breakage during the molding of melt blown nonwoven fabric with a large melt blown molding machine, the moisture value of the thermoplastic polyurethane elastomer is preferably 350 ppm or less, and 300 ppm or less. It is more preferable that it be present, and even more preferably that it is 150 ppm or less.

From the viewpoint of improving the elasticity of the melt-blown nonwoven fabric, the thermoplastic polyurethane elastomer preferably satisfies the following formula I, more preferably satisfies the following formula II, and even more preferably satisfies the following formula III.

a/(a+b)≦0.8(I)
a/(a+b)≦0.7(II)
a/(a+b)≦0.6(III)

(In Formula I, Formula II, and Formula III, a represents the sum of the heat of fusion obtained from endothermic peaks in the range of 90°C to 140°C measured by differential scanning calorimeter. (Represents the total amount of heat of fusion obtained from endothermic peaks in the range of more than 140 degrees Celsius and less than 220 degrees Celsius measured by

(heat of fusion ratio)
The above "a/(a+b)" means the heat of fusion ratio (unit: %) of the hard domain of the thermoplastic polyurethane elastomer.
When the heat of fusion ratio of the hard domain of the thermoplastic polyurethane elastomer is 80% or less, the strength and stretchability of the fiber and meltblown nonwoven fabric are improved. In the melt-blown nonwoven fabric of the first aspect, the lower limit of the heat of fusion ratio of the hard domain of the thermoplastic polyurethane elastomer is preferably about 0.1%.

The thermoplastic polyurethane elastomer preferably has a melt viscosity (hereinafter also simply referred to as "melt viscosity") of 100 Pa.s to 3000 Pa.s, and preferably 200 Pa.s to 3000 Pa.s at a temperature of 200° C. and a shear rate of 100 sec ^-1 It is more preferably 2000 Pa·s, and even more preferably 900 Pa·s to 1600 Pa·s.
The melt viscosity is measured with a capillograph (manufactured by Toyo Seiki Co., Ltd., with a nozzle length of 30 mm and a diameter of 1 mm).
A thermoplastic polyurethane elastomer having such characteristics can be obtained, for example, by the manufacturing method described in JP-A No. 2004-244791.
Note that the thermoplastic polyurethane elastomer may contain a biomass raw material. Details of the thermoplastic polyurethane elastomer containing biomass-derived raw materials (biomass-derived thermoplastic polyurethane elastomer) will be described later.

The melt-blown nonwoven fabric preferably contains 50% by mass or more of a thermoplastic polyurethane elastomer, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 99% by mass or more.

The basis weight of the melt-blown nonwoven fabric may be determined as appropriate depending on the application. For example, the basis weight of the meltblown nonwoven fabric is preferably 1 g/m ² to 100 g/m ² , more preferably 4 g/m ² to 65 g/m ² .

The basis weight of meltblown nonwoven fabric is measured by the following method.
Six test pieces of 200 mm (machine direction: MD direction) x 50 mm (lateral direction: CD direction) are taken from the melt-blown nonwoven fabric. The sampling locations are any three locations in both the MD and CD directions (six locations in total). Next, the mass (g) of each sampled test piece is measured using an electronic balance (for example, an electronic balance manufactured by Kensei Kogyo Co., Ltd.). Find the average mass of each test piece. The obtained average value is converted into mass (g) per 1 m ² , and the value rounded to the second decimal place is defined as the basis weight [g/m ² ] of each sample.

The thickness of the melt-blown nonwoven fabric may be determined as appropriate depending on the application.
For example, the thickness of the meltblown nonwoven fabric may be 0.01 mm to 1.00 mm.

"MD (Machine Direction) direction" means the flow direction of the fibers. The MD (Machine Direction) direction is also the conveyance direction when manufacturing the meltblown nonwoven fabric.
"CD (Cross Direction) direction" means a direction perpendicular to the MD direction (that is, the flow direction of the fibers).

(Elongation at break)
The melt-blown nonwoven fabric of the first aspect preferably has an elongation at break in the MD direction of 250% or more, more preferably 270% or more, even more preferably 300% or more, and even more preferably 340% or more. It is particularly preferable.
The elongation at break in the MD direction of the melt-blown nonwoven fabric of the first aspect is preferably 700% or less, more preferably 650% or less, and even more preferably 600% or less.
It is also preferable that the melt-blown nonwoven fabric of the first aspect has a breaking elongation in the MD direction of 250% or more and 600% or less.
If the elongation at break in the MD direction is 250% or more, the melt-blown non-woven fabric will resist deformation in the stretching direction in applications where it is necessary to follow the deformation of the human body (for example, disposable diapers, bandages, etc.). It can be tracked well without breaking.

The melt-blown nonwoven fabric of the first aspect preferably has a breaking elongation in the CD direction of 250% or more, more preferably 350% or more, even more preferably 400% or more, and even more preferably 430% or more. This is particularly preferred.
The elongation at break in the CD direction of the melt-blown nonwoven fabric of the first aspect is preferably 700% or less, more preferably 650% or less, and even more preferably 600% or less.
It is also preferable that the melt-blown nonwoven fabric of the first aspect has a breaking elongation in the CD direction of 250% or more and 600% or less.

The elongation at break is measured by the following method.
Five test pieces of 200 mm (measurement direction) x 50 mm (measurement direction) are taken from the melt-blown nonwoven fabric. The sampling locations are five arbitrary locations. Next, each sampled test piece was stretched in the MD direction of the test piece using a universal tensile tester (for example, model IM-201 manufactured by Intesco) under conditions of a chuck distance of 100 mm and a tensile speed of 100 mm/min. The stretching ratio at which the piece breaks is defined as the elongation at break [%] in the MD direction. The stretching ratio is measured in the same manner as the method for measuring the elongation at break [%] in the MD direction, except that the tensile direction of the test piece is changed from the MD direction of the test piece to the CD direction of the test piece. The measured value of the stretching ratio is defined as the elongation at break in the CD direction [%].

(water pressure resistance)
The melt-blown nonwoven fabric of the first aspect preferably has a water pressure resistance (hereinafter also simply referred to as "water pressure resistance") with respect to basis weight (g/m ² ) of 6.0 mmH ₂ O·m ² /g or more, and 9.0 mmH It is more preferably ₂ O·m ² /g or more, and even more preferably 12.0 mmH ₂ O·m ² /g or more.
The melt-blown nonwoven fabric of the first aspect preferably has a water pressure resistance of 30.0 mmH ₂ O·m ² /g or less, more preferably 20.0 mmH ₂ O·m ² /g or less, and 15.0 mmH ₂ More preferably, it is not more than O·m ² /g.
It is also preferable that the melt-blown nonwoven fabric of the first aspect has a water pressure resistance of 6.0 mmH ₂ O·m ² /g or more and 30.0 mmH ₂ O·m ² /g or less.
When the water pressure resistance is 6.0 mmH ₂ O・m ² /g or more, melt-blown nonwoven fabrics are suitable for applications that require liquid leakage resistance (e.g., disposable diapers, sanitary products, etc.). ) can be prevented from leaking.

The water pressure resistance is a value obtained by dividing the water pressure resistance of the melt-blown nonwoven fabric measured according to method A (low water pressure method) specified in JISL1096 by the basis weight. The unit of water pressure resistance of the melt-blown nonwoven fabric is (mmH ₂ O)/(g/m ² ), that is, mmH ₂ O·m ² /g.

(Recovery stress)
The melt-blown nonwoven fabric of the first aspect has a recovery stress in the MD direction (hereinafter also simply referred to as "recovery stress in the MD direction") with respect to basis weight (g/m ² ) of 0.035 N·m ² /50 mm·g or more. is preferable, and more preferably 0.036 N·m ² /50 mm·g or more.
The melt-blown nonwoven fabric of the first aspect preferably has a recovery stress in the MD direction of 0.060 N·m ² /50 mm·g or less, more preferably 0.050 N·m ² /50 mm·g or less, and 0.050 N·m 2 /50 mm·g or less. More preferably, it is .040 N·m ² /50 mm·g or less.
It is also preferable that the melt blown nonwoven fabric of the first aspect has a recovery stress in the MD direction of 0.035 N·m ² /50 mm·g or more and 0.060 N·m ² /50 mm·g or less.
If the recovery stress in the MD direction is 0.035 N m ² /50 mm g or more, the melt blown nonwoven fabric will shrink in applications that need to follow the deformation of the human body (for example, disposable diapers, bandages, etc.). It can follow the deformation in the direction well without remaining stretched.

The recovery stress in the MD direction is measured by the following method.
Five test pieces of 200 mm (MD) x 50 mm (CD) are taken from the melt-blown nonwoven fabric. The sampling locations are five arbitrary locations. Next, each sampled test piece was stretched in the MD direction using a universal tensile tester (for example, IM-201 model manufactured by Intesco) under conditions of a chuck distance of 100 mm, a tensile speed of 100 mm/min, and a stretching ratio of 100%. Afterwards, it is restored to its original length at the same speed. This operation is carried out for two cycles, and the value obtained by dividing the stress when the stretching ratio in the MD direction becomes 50% at the time of recovery in the second cycle by the basis weight is calculated as the MD for the basis weight (g/m ² ). Let it be the recovery stress in the direction.
The unit of the recovery stress in the MD direction with respect to the basis weight (g/m ² ) is (N/50mm)/(g/m ² ), that is, N·m ² /50mm·g.

(More preferred configuration)
In the first aspect, the average fiber diameter of the meltblown nonwoven fabric is preferably 3.0 μm to 3.7 μm. In the first embodiment, the thermoplastic polyurethane elastomer preferably has a number average molecular weight (Mn) of 101,500 to 104,000. In the first embodiment, it is preferable that the thermoplastic polyurethane elastomer has a number average molecular weight (Mn) of 101,500 to 104,000, and the meltblown nonwoven fabric has an average fiber diameter of 3.0 μm to 3.7 μm. As a result, the melt-blown nonwoven fabric has excellent overall performance in terms of elongation at break and water pressure resistance.

In the first aspect, it is preferable that the average fiber diameter of the meltblown nonwoven fabric is 3.0 μm to 3.7 μm, and the basis weight of the meltblown nonwoven fabric is 4 g/m ² to 30 g/m ² . In the first aspect, it is preferable that the thermoplastic polyurethane elastomer has a number average molecular weight (Mn) of 101,500 to 104,000, and the melt blown nonwoven fabric has a basis weight of 4 g/m ² to 30 g/m ² . In the first aspect, the number average molecular weight (Mn) of the thermoplastic polyurethane elastomer is 101,500 to 104,000, the average fiber diameter of the meltblown nonwoven fabric is 3.0 μm to 3.7 μm, and the basis weight of the meltblown nonwoven fabric is It is preferably 4 g/m ² to 30 g/m ² . As a result, the overall performance of the melt-blown nonwoven fabric in elongation at break and water pressure resistance is more excellent.

Applications of the melt-blown nonwoven fabric of the first aspect include, for example, disposable diapers, absorbent articles such as sanitary products, sanitary articles such as sanitary masks, medical articles such as bandages, clothing materials, packaging materials, waterproof sheets, medical sheets, etc. can be mentioned.

≪Hygiene materials≫
Preferably, the sanitary material of the present disclosure includes the meltblown nonwoven fabric of the present disclosure.
The melt-blown nonwoven fabric of the first aspect can be suitably used for top sheets, back sheets, waistbands (e.g. extension tapes, side flaps, etc.), fastening tapes, three-dimensional gathers, and leg cuffs in expandable disposable diapers or pants-type disposable diapers. I can do it. The melt-blown nonwoven fabric of the first aspect can be suitably used for parts such as side panels of pants-type disposable diapers.
By using the melt-blown nonwoven fabric of the first aspect in these parts, it becomes possible to follow the movements of the wearer and fit the wearer's body, and a comfortable state is maintained even while being worn.

The melt-blown nonwoven fabric of the first aspect is also suitably used for a disposable mask, etc., which is composed of a mouth-periphery covering part and ear hook parts extending from both sides of the covering part.
The melt-blown nonwoven fabric of the first aspect is suitably used as a base material for movable joints such as arms, elbows, and shoulders in disposable surgical gowns, rescue gowns, and the like.

≪Waterproof sheet≫
The water-resistant sheet of the present disclosure preferably includes the melt-blown nonwoven fabric of the present disclosure. The water-resistant sheet of the present disclosure may have any known configuration except that it includes the melt-blown nonwoven fabric of the present disclosure. For example, the water-resistant sheet of the present disclosure may be made of the melt-blown non-woven fabric of the present disclosure, or may include a layer made of the melt-blown non-woven fabric of the present disclosure (hereinafter also referred to as "melt-blown non-woven fabric layer") and known fibers (for example, cellulose fibers). etc.) (hereinafter also referred to as a "fibrous layer"). The fibrous layer is laminated on one main surface of the meltblown nonwoven fabric layer. The water-resistant sheet of the present disclosure can be used for absorbent materials such as disposable diapers and sanitary products, sanitary materials such as sanitary masks and cosmetic materials, medical materials such as bandages, household materials such as clothing materials and packaging materials, and industrial materials such as filters. It can be used for purposes such as In particular, it has excellent flexibility, breathability, stretchability, and barrier properties, so it is suitably used for sanitary materials such as paper diapers, sanitary napkins, base fabrics for poultice materials, and bed covers. Examples of medical materials and clothing materials include gowns, caps, drapes, masks, gauze, bandages, and various protective clothing. In addition, it has good post-processing properties such as heat sealing, so it can be used to wrap oxygen absorbers, body warmers, hot air bags, masks, various powders, semi-solids, gels, and liquid substances, CD (compact disc) bags, and food products. It can be applied to all kinds of household materials such as packaging materials, clothing covers, and agricultural sheets. For the same reason, it can also be suitably used as an industrial material such as automobile interior materials, various backing materials, and building materials. Furthermore, since it is composed of fine fibers, it can be widely applied as a material for liquid filters and air filters.

≪Medical sheet≫
Preferably, the medical sheet of the present disclosure includes the melt-blown nonwoven fabric of the present disclosure. The medical sheet of the present disclosure may have any known configuration except that it includes the melt-blown nonwoven fabric of the present disclosure. For example, the medical sheet of the present disclosure may be made of a meltblown nonwoven fabric, or may include a meltblown nonwoven fabric layer and a fiber layer. The fibrous layer is laminated on one main surface of the meltblown nonwoven fabric layer. The medical sheet of the present disclosure is suitably used for materials such as gowns, caps, drapes, masks, gauze, bandages, and various protective clothing, plaster base fabrics, poultice materials, wound dressings, wound tapes, and the like. Furthermore, by using raw materials that are stable against electron beams and gamma rays that are irradiated during sterilization and sterilization, they can be suitably used for sterilized medical sheets.

(Thermoplastic polyurethane elastomer derived from biomass)
Biomass-derived thermoplastic polyurethane elastomers can also be obtained by polymerizing propylene obtained by dehydrating isopropanol produced by fermentation from biomass raw materials mainly made of inedible plants such as sorghum.

In the present disclosure, "biomass degree" indicates the content rate of carbon derived from biomass, and is calculated by measuring radioactive carbon (C14). Since carbon dioxide in the atmosphere contains C14 at a certain rate (approximately 105.5 pMC), the C14 content in plants (e.g. corn) that grow by taking in atmospheric carbon dioxide is also approximately 105.5 pMC. It is known that the degree of It is also known that fossil fuels contain almost no C14. Therefore, by measuring the proportion of C14 contained in all carbon atoms in the raw material, the content rate of biomass-derived carbon in the raw material can be calculated.

For example, when the content of C14 in the raw material is PC14, the content rate Pbio (%) of biomass-derived carbon in the raw material can be calculated using the following formula (1).
Pbio (%) = PC14/105.5×100...Formula (1)

That is, if all the raw materials for polyurethane are derived from biomass, the content of biomass-derived carbon is theoretically 100%, so the biomass degree of the biomass-derived thermoplastic polyurethane elastomer is 100%. In addition, since fossil fuel-derived raw materials hardly contain C14, the content of biomass-derived carbon in polyurethane produced only from fossil fuel-derived raw materials is 0%, and the biomass content of fossil fuel-derived polyurethane is 0%. becomes 0%.

The biomass content of the biomass-derived polyurethane thermoplastic elastomer used as a raw material for the spunbond nonwoven fabric of the present disclosure is preferably 1% or more.

In general, thermoplastic polyurethane elastomers are manufactured using polymer glycols such as polyether polyols, polyester polyols, and polycarbonate polyols; short chain glycols (chain extenders) such as aliphatic glycols, aromatic glycols, and alicyclic glycols as raw materials. and isocyanate compounds such as aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. In the present disclosure, the isocyanates preferably used include aliphatic isocyanates such as 1,5-pentamethylene diisocyanate-based polyisocyanate (trade name: Stabio (registered trademark)) manufactured by Mitsui Chemicals, Inc., aromatic isocyanates, etc. Can be mentioned.

When the raw material for the spunbond nonwoven fabric of the present disclosure includes a recycled polymer, the thermoplastic polyurethane elastomer used as the raw material for the spunbond nonwoven fabric of the present disclosure may contain a so-called recycled polymer obtained by recycling.

"Recycled polymer" includes a polymer obtained by recycling waste polymer products, and can be produced, for example, by the method described in DE102019127827 (A1). The recycled polymer may include a marker that allows it to be identified as having been obtained through recycling.

[Second aspect]
The melt-blown nonwoven fabric of the second aspect has a number average molecular weight (Mn) of 100,000 or more, and a molecular weight distribution (Mw/Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (hereinafter, It contains a thermoplastic polyurethane elastomer with a recovery stress in the MD direction (hereinafter simply referred to as "recovery in the MD direction") with respect to basis weight (g/m ² ) of 2.4 or less (also simply referred to as "molecular weight distribution (Mw/Mn)"). (also referred to as "stress") is greater than 0.034N·m ² /50mm·g.

The melt-blown nonwoven fabric of the second aspect has excellent elongation at break and water pressure resistance.
The thermoplastic polyurethane elastomer in the present disclosure has a relatively large number average molecular weight (Mn). This can increase the breaking strength of the fibers and prevent them from breaking easily. High breaking strength also contributes to improved water pressure resistance.
The thermoplastic polyurethane elastomer in the present disclosure has a molecular weight distribution (Mw/Mn) of 2.4 or less. This makes the molecular weight in the fiber uniform. This reduces the number of weak portions of molecular chain entanglement that serve as starting points for rupture. As a result, the breaking strength of the fibers and the water pressure resistance of the nonwoven fabric are improved.
The fact that the recovery stress in the MD direction is greater than 0.034 N·m ² /50 mm·g indicates that the structure of the hard segment and soft segment of the thermoplastic polyurethane elastomer is sufficiently formed. This can suppress plastic deformation of the fibers. As a result, even when high water pressure is applied, the fibers can maintain their shape, the opening of the fibers is suppressed, and the water pressure resistance is improved.
When the hard segments of the thermoplastic polyurethane elastomer are sufficiently formed, the entanglement of the polyurethane molecules in the fibers is easily maintained, and the fibers can be elastically deformed to a high elongation without breaking. The combination of the high elongation of the fibers and the high breaking strength of the fibers described above provides a synergistic effect in that the entangled fibers can be stretched well without breaking.

The explanation of each item described in the section of the first aspect can also be applied to the second aspect.
For example, the details of the preferred range, definition, measuring method, etc. of the average fiber diameter in the second aspect are the same as the details of the preferred range, definition, measuring method, etc. of the average fiber diameter in the first aspect.
Number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw/Mn), coagulation start temperature, hard segment amount, number of particles insoluble in polar solvent, moisture value of the thermoplastic polyurethane elastomer in the second embodiment , Formula I, Formula II, Formula III, heat of fusion ratio, melt viscosity, preferred ranges such as content, definitions, measurement methods, etc. Details of the number average molecular weight (Mn) of the thermoplastic polyurethane elastomer in the first embodiment, Weight average molecular weight (Mw), molecular weight distribution (Mw/Mn), solidification start temperature, hard segment amount, number of particles insoluble in polar solvent, moisture value, formula I, formula II, formula III, heat of fusion ratio, melt viscosity, The details are the same as the preferred range of content, definition, measurement method, etc.
The details of the preferred ranges, preferred embodiments, definitions, measurement methods, etc. of the melt-blown nonwoven fabric in the second aspect include the basis weight, thickness, elongation at break, water pressure resistance, recovery stress, application, etc. Details such as elongation at break, water pressure resistance, recovery stress, preferred ranges of uses, preferred embodiments, definitions, measuring methods, etc. are the same.

≪Production method of melt-blown nonwoven fabric≫
The method for producing a melt-blown nonwoven fabric of the present disclosure includes a step (hereinafter, " (also referred to as "fiberization process"). In the fiberization step, a melt of the resin composition is discharged from a spinneret together with a heated gas, and the discharged melt of the resin composition (hereinafter also referred to as "discharged product") is stretched by the heated gas.

The method for producing a meltblown nonwoven fabric of the present disclosure is a method for producing a meltblown nonwoven fabric by a meltblown method using a resin composition. A method for producing a melt-blown nonwoven fabric using a thermoplastic polyurethane elastomer by a melt-blown method is described in, for example, JP-A-2003-64567 (Patent Document 1), JP-A-2004-57882, and the like.

The "melt blown method" is a process in which a molten resin composition is discharged from a spinneret in the form of fibers, and heated gas is applied to the discharged material from both sides of the fiber-shaped discharged material, and heated gas is applied to the moving discharged material. This is a method of reducing the diameter of the ejected material by making it accompany the ejected material.
Specifically, for example, a resin composition as a raw material is melted using an extruder or the like. The molten resin composition is introduced into a spinneret connected to the tip of the extruder, and is discharged in the form of fibers from the spinning nozzle of the spinneret. A heated gas ejected from a gas nozzle of a spinneret is applied to the fibrous material, and the heated gas stretches the fibrous material, thereby making the fibrous material thinner.

The resin composition only needs to contain the thermoplastic polyurethane elastomer according to the present disclosure, and may be the thermoplastic polyurethane elastomer itself according to the present disclosure, or the thermoplastic polyurethane elastomer according to the present disclosure and other resins. and at least one of an additive.
The temperature (Ta) of the heating gas may be appropriately selected depending on the type of thermoplastic polyurethane elastomer. The temperature (Ta) of the heating gas may be, for example, 210°C to 240°C.
The temperature (Tp) of the melt of the resin composition may be appropriately selected depending on the type of thermoplastic polyurethane elastomer. The temperature (Tp) of the melt of the resin composition may be, for example, 200°C to 230°C.

The temperature (Tp) of the melt of the resin composition can be measured as the set temperature of the spinneret (die).

The temperature (Ta) of the heated gas can be measured as the temperature of the heated gas immediately after being discharged from the spinneret (die). Specifically, the temperature of the heated gas (Ta) can be measured as the temperature of the heated gas at the opening of the gas nozzle of the spinneret (die).
The temperature (Ta) of the heated gas can be adjusted, for example, while measuring the temperature (Ta) of the heated gas at the opening of the gas nozzle of the spinneret (die), until the temperature (Ta) of the heated gas at the opening of the gas nozzle is set to a predetermined value. The temperature of the heated gas at the opening of the gas nozzle (Ta) may be adjusted under predetermined conditions (e.g., die temperature, heated gas flow rate). Data (calibration curve) showing the relationship between the temperature and the supply temperature of the heated gas is prepared in advance, and based on that data, the temperature of the heated gas (Ta) at the opening of the gas nozzle is set to a predetermined temperature. This may also be done by adjusting the supply temperature of the heating gas.

The discharge amount of the melt of the resin composition per spinning nozzle of the spinneret may be, for example, 0.05 g/min to 0.20 g/min.
The flow rate of the heating gas may be between 300 Nm ³ /hr/m and 500 Nm ³ /hr/m.
The type of heating gas is not particularly limited, and examples include gases that are inert to the melted resin composition (eg, air, carbon dioxide gas, nitrogen gas, etc.). Among these, air is preferred from the viewpoint of economy.

The method for producing a meltblown nonwoven fabric of the present disclosure may further include a step of collecting the fibrous extrudate in the form of a web after performing the above-described fiberizing step. In this collection step, the obtained discharged material is collected in the form of a web on a collector, for example. When collecting the ejected material on the collector, the ejected material is collected by suctioning air from the side of the collector opposite to the surface that collects the ejected material (hereinafter also referred to as the "back side"). May be promoted.

Specific examples of collectors include perforated belts, perforated drums, and the like. Note that collection of fibrous materials may be promoted by sucking air from the back side of the collector.
The ejected material may be collected on a desired base material provided in advance on the collector. Examples of pre-provided substrates include other nonwoven fabrics (eg, meltblown nonwoven fabrics, spunbond nonwoven fabrics, needle punched and spunlaced nonwoven fabrics, etc.), woven fabrics, knitted fabrics, paper, and the like.

A meltblown nonwoven fabric manufacturing apparatus used in the meltblown nonwoven fabric manufacturing method of the present disclosure will be described with reference to FIG. 1.

FIG. 1 is a schematic diagram showing an example of the configuration of a meltblown nonwoven fabric manufacturing apparatus 10. As shown in FIG.
As shown in FIG. 1, a meltblown nonwoven fabric manufacturing apparatus 10 includes an extruder 20, a die (spinneret) 30, and a collection mechanism 40.

The extruder 20 has a hopper 21 and a compression section 22. The extruder 20 melts the solid material of the resin composition introduced into the hopper 21 in the compression section 22 . The extruder 20 may be a single-screw extruder or a multi-screw extruder such as a twin-screw extruder.

A die (spinneret) 30 is connected to the tip of the extruder 20 and arranged. The die 30 has a plurality of spinning nozzles 31 and two gas nozzles 32.
The plurality of spinning nozzles 31 are usually arranged in a row. The spinning nozzle 31 discharges the melted resin composition melted by the compression section 22 in the form of fibers from the nozzle opening.
The diameter of the spinning nozzle can be, for example, between 0.08 mm and 0.60 mm. The temperature (Tp) of the melt of the resin composition can be adjusted by the set temperature of the die 30.

The distance between the small holes in the spinning nozzle of the spinneret may be 0.5 mm to 3.0 mm. The two gas nozzles (air nozzles) 32 are arranged near the nozzle opening of the spinning nozzle 31 (specifically, on both sides of the row of the plurality of spinning nozzles 31). The gas nozzle 32 injects heated gas (heated compressed gas) near the opening of the spinning nozzle 31 . As shown in FIG. 1, the gas nozzle 32 injects heated gas to the discharged material immediately after being discharged from the opening of the spinning nozzle 31.

The heating gas supplied to the gas nozzle 32 is supplied from the gas heating device 50. The temperature (Ta) of the heating gas can be adjusted by a heating temperature adjustment means (not shown) attached to the gas heating device 50.

The collection mechanism 40 includes a perforated belt (collector) 41, a roller 42 that supports and transports the belt, and an air suction unit 43 arranged on the back side of the collection surface of the perforated belt 41. The air suction section 43 is connected to a blower 44. The collection mechanism 40 collects the fibrous discharge material onto a moving porous belt 41 .
According to such a configuration, the molten resin composition melted in the extruder 20 is introduced into the spinning nozzle 31 of the die (spinneret) 30 and discharged from the opening of the spinning nozzle 31. Heated gas is injected from the gas nozzle 32 toward the vicinity of the opening of the spinning nozzle 31 . The fibrous material discharged from the spinning nozzle 31 is stretched and thinned by the heated gas.

The temperature (Ta) of the heating gas is adjusted appropriately. Thereby, the discharged material is appropriately rapidly cooled and stretched. The flow rate of the heating gas is adjusted to satisfy the above range. Thereby, even if the discharged material is rapidly cooled, it can be sufficiently stretched. Then, the discharged material is collected on the porous belt 41 to obtain a meltblown nonwoven fabric.
The above-described melt-blown nonwoven fabric of the present disclosure and the melt-blown nonwoven fabric produced by the above-described manufacturing method may be electrically charged.

The charging method is not particularly limited as long as the melt-blown non-woven fabric can be made into an electret; for example, a corona charging method, a method of applying water or an aqueous solution of a water-soluble organic solvent to the melt-blown non-woven fabric and then drying it to make it an electret ( For example, methods described in Japanese Patent Publication No. Hei 9-501604, Japanese Patent Application Laid-open No. 2002-115177, etc.) can be mentioned. In the corona charging method, the electric field strength is preferably 15 kV/cm or more, more preferably 20 kV/cm or more.

Hereinafter, embodiments according to the present disclosure will be described in detail with reference to Examples. Note that the invention of the present disclosure is not limited to the description of these Examples.
The materials, amounts used, proportions, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure.
Physical property values, etc. in Examples and Comparative Examples were measured and evaluated by the following methods.

(1) Fabric weight [g/m ² ]
Measured by the method described above.
(2) Average fiber diameter (μm)
Measured by the method described above.
(3) Number average molecular weight (Mn) [-]
Measured by the method described above.
(4) Weight average molecular weight (Mw) [-]
Measured by the method described above.
(5) Molecular weight distribution (Mw/Mn) [-]
Measured by the method described above.
(6) Breaking elongation in MD direction and CD direction [%]
Measured by the method described above. The permissible range of elongation at break in the MD direction is 300% or more. The permissible range of elongation at break in the CD direction is 300% or more.
(7) Recovery stress in MD direction for basis weight (g/m ² ) [(N/50mm)/(g/m ² )]
Measured by the method described above.
(8) Water pressure resistance against area weight (g/m ² ) [(mmH ₂ O)/(g/m ² )]
Measured by the method described above. The permissible range of water pressure resistance relative to the basis weight (g/m ² ) is 4.0 (mmH ₂ O)/(g/m ² ) or more.

<Manufacture of thermoplastic polyurethane elastomer>
Polyester polyol with a number average molecular weight (Mn) of 1932: 71.7 parts by mass, 1,4-butanediol (hereinafter also referred to as "BD"): 4.8 parts by mass, pentaerythritol tetrakis [3-(3, 5-di-t-butyl-4-hydroxyphenyl)propionate] (hereinafter also referred to as "antioxidant-1"): 0.3 parts by mass, polycarbodiimide: 0.3 parts by mass, 4. 22.9 parts by mass of 4'-diphenylmethane diisocyanate (hereinafter also referred to as "MDI") was added and mixed with sufficient high speed stirring. Thereafter, the mixture was reacted at 160° C. for 1 hour.
After pulverizing this reaction product, 0.8 parts by mass of ethylene bisstearamide and triethylene glycol-bis-[3-(3,5-di-t-butyl) were added to 100 parts by mass of the pulverized product. -4-hydroxyphenyl) propionate] (hereinafter also referred to as "antioxidant-2"): 0.5 parts by mass, ethylene bisoleic acid amide (hereinafter also referred to as "EOA"): 0.8 parts by mass were mixed. Thereafter, the mixture was melt-kneaded and granulated using an extruder (set temperature: 210°C) to obtain a thermoplastic polyurethane elastomer [TPU (1)].
The obtained TPU (1) had Shore A hardness: 82, melting point (Tm) (high melting point side): 162.2°C, heat of fusion: 11.4 mJ/mg, melt viscosity: 1100 Pa・s, solidification start temperature 155 °C, heat of fusion of hard domain: 0.58.

[Example 1]
A meltblown nonwoven fabric was produced as follows.
TPU (1) was melted using a single screw extruder. The molten TPU (1) was supplied to the die, and from the die with a set temperature of 220°C (temperature of the molten TPU (1)), the amount of discharge per spinning nozzle was 0.067 g/min. It was discharged together with heated air (temperature Ta: 230°C, flow rate: 5.4 Nm ³ /cm/hour) blown from both sides. The diameter of the spinning nozzle of the die was 0.38 mm. Then, the fibrous extrudate was collected on a collector so that the basis weight became the value shown in Table 1, to obtain a meltblown nonwoven fabric.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Example 2]
The procedure was the same as in Example 1, except that the flow rate of the heated air was changed from 5.4 Nm ³ /cm / hour to 6.8 Nm ³ /cm / hour, and the basis weight was changed to the value listed in Table 1. A meltblown nonwoven fabric was obtained.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Example 3]
The discharge amount per spinning nozzle was changed from 0.067 g/min to 0.106 g/min, the flow rate of heated air was changed from 5.4 Nm ³ /cm/hour to 6.8 Nm ³ /cm/hour, A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except that the basis weight was changed to the value shown in Table 1.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Example 4]
The discharge amount per spinning nozzle was changed from 0.067 g/min to 0.142 g/min, the flow rate of heated air was changed from 5.4 Nm ³ /cm/hour to 6.8 Nm ³ /cm/hour, A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except that the basis weight was changed to the value shown in Table 1.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Example 5]
A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except that the moving speed of the collector was changed so that the basis weight was changed to the value shown in Table 1.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Example 6]
A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except that the moving speed of the collector was changed so that the basis weight was changed to the value shown in Table 1.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Example 7]
The set temperature of the die was changed from 220°C to 215°C, the discharge amount per spinning nozzle was changed from 0.067g/min to 0.047g/min, and the flow rate of heated air was changed to 5.4Nm ³ /cm/hour. A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except that the weight was changed from 4.1 Nm ³ /cm/hour to 4.1 Nm 3 /cm/hour, and the basis weight was changed to the value shown in Table 1.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Example 8]
The set temperature of the die was changed from 220°C to 215°C, the discharge amount per spinning nozzle was changed from 0.067g/min to 0.047g/min, and the flow rate of heated air was changed to 5.4Nm ³ /cm/hour. A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except that the weight was changed from 4.1 Nm ³ /cm/hour to 4.1 Nm 3 /cm/hour, and the basis weight was changed to the value shown in Table 1.
Table 1 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

In Examples 1 to 8, the heat of fusion ratio "a/(a+b)" of the hard domain of the thermoplastic polyurethane elastomer was 0.399.

[Comparative example 1]
A meltblown nonwoven fabric was obtained in the same manner as in Example 4, except that the moving speed of the collector was changed so that the basis weight was changed to the value shown in Table 2.
Table 2 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Comparative example 2]
The set temperature of the die was changed from 220°C to 230°C, the flow rate of heated air was changed from 5.4Nm ³ /cm/hour to 6.7Nm ³ /cm/hour, and the basis weight was changed to the value listed in Table 2. A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except for the following changes.
Table 2 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

[Comparative example 3]
The set temperature of the die was changed from 220°C to 230°C, the discharge amount per spinning nozzle was changed from 0.067g/min to 0.106g/min, and the flow rate of heated air was changed to 5.4Nm ³ /cm/hour. A meltblown nonwoven fabric was obtained in the same manner as in Example 1, except that the weight was changed from 6.7 Nm ³ /cm/hour to 6.7 Nm 3 /cm/hour, and the basis weight was changed to the value shown in Table 2.
Table 2 shows the average fiber diameter of the melt-blown nonwoven fabric, the molecular weight of TPU (1) contained in the melt-blown nonwoven fabric, the elongation at break in the MD and CD directions, and the water pressure resistance.

As shown in Tables 1 and 2, the melt-blown nonwoven fabrics of Examples 1 to 8 have a number average molecular weight (Mn) of 100,000 or more and a molecular weight distribution (Mw/Mn) of 2.4 or less. A meltblown nonwoven fabric containing a plastic polyurethane elastomer and having an average fiber diameter of less than 6.5 μm was used.
The melt-blown nonwoven fabrics of Examples 1 to 8 contain a thermoplastic polyurethane elastomer having a number average molecular weight (Mn) of 100,000 or more and a molecular weight distribution (Mw/Mn) of 2.4 or less, and have a basis weight ( g/m ² ) is greater than 0.034 N·m ² /50 mm·g.
Therefore, in Examples 1 to 8, the elongation at break in the MD direction and the elongation at break in the CD direction are each 300% or more, and the water pressure resistance is 4.0 (mmH ₂ O)/(g/m ² ). In other words, the elongation at break and water pressure resistance of Examples 1 to 8 were excellent.
On the other hand, the melt-blown nonwoven fabric of Comparative Example 1 had an average fiber diameter not less than 6.5 μm and a recovery stress in the MD direction relative to the basis weight (g/m ² ) of not more than 0.034 N·m ² /50 mm·g. Therefore, the water pressure resistance of the meltblown nonwoven fabric of Comparative Example 1 was less than 4.0 (mmH ₂ O)/(g/m ² ), which was inferior to Examples 1 to 8.
The melt-blown nonwoven fabrics of Comparative Examples 2 and 3 did not use a thermoplastic polyurethane elastomer having a number average molecular weight (Mn) of 100,000 or more. Therefore, each of the MD breaking elongation and CD breaking elongation of Comparative Examples 2 and 3 was less than 300%, which was inferior to Examples 1 to 8.
In Comparative Example 2, the meltblown nonwoven fabric broke at the stage of stretching at a stretching ratio of 100%. Therefore, the recovery stress of Comparative Example 2 could not be measured.

The disclosure of Japanese Patent Application No. 2022-053743 filed on March 29, 2022 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference. Incorporated herein by reference.

Claims

A thermoplastic polyurethane system having a number average molecular weight (Mn) of 100,000 or more and a molecular weight distribution (Mw/Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 2.4 or less. A meltblown nonwoven fabric containing an elastomer and having an average fiber diameter of less than 6.5 μm.
A thermoplastic polyurethane system having a number average molecular weight (Mn) of 100,000 or more and a molecular weight distribution (Mw/Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 2.4 or less. A melt-blown nonwoven fabric containing an elastomer and having a recovery stress in the MD direction relative to the basis weight (g/m 2 ) of more than 0.034 N·m 2 /50 mm·g.
The meltblown nonwoven fabric according to claim 1 or 2, wherein the average fiber diameter is 5.5 μm or less.
The meltblown nonwoven fabric according to any one of claims 1 to 3, wherein the thermoplastic polyurethane elastomer satisfies the following formula I.
a/(a+b)≦0.8 (I)
(In Formula I, a represents the sum of the heat of fusion obtained from endothermic peaks in the range of 90°C to 140°C measured by a differential scanning calorimeter, and b represents 140°C measured by a differential scanning calorimeter. (Represents the total amount of heat of fusion obtained from endothermic peaks in the range of 220℃ or less.)
The meltblown nonwoven fabric according to any one of claims 1 to 4, wherein the thermoplastic polyurethane elastomer has a number average molecular weight (Mn) of 101,500 or more.
The meltblown nonwoven fabric according to any one of claims 1 to 5, which has an elongation at break in the MD direction of 250% or more.
The meltblown nonwoven fabric according to any one of claims 1 to 6, which has a water pressure resistance relative to basis weight (g/m 2 ) of 6.0 mmH 2 O·m 2 /g or more.
The meltblown nonwoven fabric according to any one of claims 1 to 7, which has a recovery stress in the MD direction with respect to basis weight (g/m 2 ) of 0.035 N·m 2 /50 mm·g or more.
A sanitary material comprising the meltblown nonwoven fabric according to any one of claims 1 to 8.
A water-resistant sheet comprising the melt-blown nonwoven fabric according to any one of claims 1 to 8.
A medical sheet comprising the meltblown nonwoven fabric according to any one of claims 1 to 8.