TW202413760A - Long fiber nonwoven fabric and manufacturing method thereof, and laminate, filter, protective clothing, and face mask - Google Patents

Abstract

The subject of the present invention is to provide a nonwoven fabric having excellent particle capture efficiency and air permeability. The main purpose of the present invention is a long-fiber nonwoven fabric, which includes fibers containing a polypropylene resin, and in the long-fiber nonwoven fabric, the average fiber diameter of the fibers is greater than 0.05 μm and less than 5.00 μm, and the zero shear viscosity of the long-fiber nonwoven fabric at 190°C is greater than 5 Pa·s and less than 10 Pa·s.

Description

Long fiber nonwoven fabric and its manufacturing method, as well as laminate, filter, protective clothing, and mask

The present invention relates to a long-fiber nonwoven fabric and a manufacturing method thereof.

In recent years, fibers and nonwoven fabrics containing polypropylene resins have been used in various applications such as sanitary materials such as masks and disposable diapers, protective clothing, filters, etc. In particular, nonwoven fabrics used in masks, protective clothing, and filters are required to have extremely fine constituent fibers in order to improve particle capture efficiency and liquid barrier properties.

For example, in the technology disclosed in Patent Document 1, a polypropylene resin having a melt flow rate of a certain value or more and a molecular weight distribution (Mw/Mn) of a certain value or less is proposed as a polypropylene capable of producing a melt-blown nonwoven fabric containing ultrafine fibers with good productivity. In addition, in the technology disclosed in Patent Documents 2 to 4, a nonwoven fabric is proposed in which the number average fiber diameter or the pore diameter of the nonwoven fabric is set to a specific range. [Prior Art Document] [Patent Document]

Patent document 1: Japanese Patent Publication No. 2002-201560 Patent document 2: Japanese Patent Publication No. 2016-053241 Patent document 3: International Publication No. 2012/014501 Patent document 4: International Publication No. 2016/148174

[Problems to be solved by the invention] The technology disclosed in patent document 1 has the following problems: Since polypropylene with a high melt flow rate is used, the fibers are not easy to solidify in the spinning step. When high-speed spinning is performed to improve production efficiency, the nonwoven fabric is not cooled in time to form a dense nonwoven fabric, and the air permeability of the obtained nonwoven fabric is sometimes reduced. In addition, the technology disclosed in patent document 2 has the following problems: In order to set the maximum pore size and the average pore size below a certain value, the distance between the spinning machine and the collection part is shortened. Therefore, when the fibers are welded in the collection part, they are strongly pressed by hot air, thereby reducing the porosity and reducing the air permeability of the nonwoven fabric. Furthermore, in the technology disclosed in Patent Document 3, there is the following problem: in order to obtain fibers with a finer average fiber diameter, a voltage is applied to the fibrous molten resin, so the resin deteriorates and a nonwoven fabric with low strength is formed. Moreover, in the technology disclosed in Patent Document 4, there is the following problem: in order to obtain fibers with a finer average fiber diameter, the resin spraying amount of each spinning nozzle is extremely low, so there is a tendency for the spraying to be unstable and the uniformity of the nonwoven fabric to be reduced.

Therefore, the present invention is made in view of the above situation, and its subject is to provide a non-woven fabric with excellent particle capture efficiency and air permeability. [Means for solving the problem]

Patent document 1 states that a particularly preferred polypropylene resin is preferably one obtained by degradation of polypropylene having a melt flow rate (hereinafter, sometimes abbreviated as "MFR") of 20 g/10 minutes or less. However, the inventors and others conducted research and found that such nonwoven fabrics tend to easily cut longer molecular chains in the polypropylene during the degradation process, so that the fibers are not easily solidified during the spinning step, and the nonwoven fabrics are formed densely when they are made, and the air permeability is sometimes reduced. Therefore, further repeated efforts have led to the discovery that by setting the average fiber diameter of the acrylic resin fibers that make up the long-fiber nonwoven fabric and the zero shear viscosity of the polypropylene resin to a specific range, a nonwoven fabric with excellent particle capture efficiency and air permeability can be obtained.

The present invention is accomplished based on these findings, and the following inventions can be provided by the present invention.

[1] A long fiber nonwoven fabric comprising fibers containing a polypropylene resin, wherein the average fiber diameter of the fibers in the long fiber nonwoven fabric is greater than or equal to 0.05 μm and less than or equal to 5.00 μm, and the zero shear viscosity of the long fiber nonwoven fabric at 190°C is greater than or equal to 5 Pa·s and less than or equal to 10 Pa·s.

[2] The long fiber nonwoven fabric as described in [1], wherein the long fiber nonwoven fabric contains 100 ppm or more and 1000 ppm or less of an organic peroxide having a structure represented by the following general formula (1) or (2).

[Chemistry 1]

[Chemistry 2]

Here, R ₁ to R ₃ and R ₅ to R ₇ are alkyl, alkenyl, phenyl, benzyl or benzoyl groups having 1 to 10 carbon atoms, and R ₄ and R ₈ are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms.

[3] The long fiber nonwoven fabric according to [1] or [2], wherein the molecular weight distribution Mw/Mn of the polypropylene resin determined by gel permeation chromatography is 2.00 or more and 4.00 or less. Here, Mw and Mn are polymerization average molecular weight and number average molecular weight, respectively.

[4] The long fiber nonwoven fabric as described in [1] or [2], wherein the porosity of the long fiber nonwoven fabric is greater than or equal to 92.5% and less than or equal to 99.0%.

[5] A laminate having at least one layer comprising the long-fiber nonwoven fabric as described in any one of [1] to [4].

[6] A filter using the long fiber nonwoven fabric as described in any one of [1] to [4].

[7] A protective clothing comprising the long-fiber nonwoven fabric as described in any one of [1] to [4].

[8] A face mask comprising the long fiber nonwoven fabric as described in any one of [1] to [4].

[9] A method for producing a long-fiber nonwoven fabric comprises: melting a raw material resin composition obtained by adding an organic peroxide having a structure represented by the following general formula (1) or (2) to a polypropylene resin having a melt flow rate of 500 g/10 min or more and 2000 g/10 min or less to obtain a molten resin; and subjecting the molten resin to a melt spraying method to obtain a long-fiber nonwoven fabric.

[Chemistry 3]

[Chemistry 4]

Here, R ₁ to R ₃ and R ₅ to R ₇ are alkyl, alkenyl, phenyl, benzyl or benzoyl groups having 1 to 10 carbon atoms, and R ₄ and R ₈ are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms.

[10] The method for producing a long-fiber nonwoven fabric as described in [9], wherein the molten resin is obtained by reacting the polypropylene-based resin and the organic peroxide in an extruder for supplying raw materials to a spinning machine for performing the melt blowing method.

[11] The method for producing a long-fiber nonwoven fabric as described in [9] or [10], wherein the organic peroxide is added in the form of a masterbatch obtained by kneading a polypropylene-based resin and the organic peroxide.

[12] A method for producing a long fiber nonwoven fabric as described in any one of [9] to [11], wherein the amount of the organic peroxide added to the raw material resin composition is 0.2 mass % or more and 1.0 mass % or less. [Effect of the invention]

According to the present invention, a long-fiber nonwoven fabric can be obtained which can efficiently capture particles and has excellent air permeability and is suitable for use as a filter or a dust collecting layer or a water-resistant layer of a mask or protective clothing.

The nonwoven fabric of the present invention is a long-fiber nonwoven fabric including fibers containing a polypropylene resin, and the average fiber diameter of the fibers is 0.05 μm or more and 5.00 μm or less, and the zero shear viscosity of the long-fiber nonwoven fabric at 190° C. is 5 Pa·s or more and 10 Pa·s or less. The structural elements thereof are described in detail below, but the present invention is not limited to the scope of the following description as long as it does not exceed the gist thereof.

[Polypropylene resin] The long-fiber nonwoven fabric of the present invention contains a polypropylene resin. The so-called "polypropylene resin" in the present invention refers to a resin in which the molar fraction of propylene units in repeating units is 80 mol% to 100 mol%. By using a polypropylene resin, a nonwoven fabric with low cost and excellent tensile strength or processability can be formed.

The polypropylene resin in the present invention may contain, for example, a propylene homopolymer, a copolymer of propylene and various α-olefins, etc. Here, the so-called α-olefin refers to a hydrocarbon with a double bond at the α position, such as ethylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, etc. In addition, the polypropylene resin in the present invention may also contain other polymers such as polyethylene terephthalate, polyethylene or polystyrene within a range where the molar fraction of the propylene unit does not deviate from the range of 80 mol% to 100 mol%.

In the present invention, the molar fraction (mol %) of the propylene unit in the repeating unit is determined as follows.

First, 1 mL of a mixed solvent of o-dichlorobenzene/benzene-d6 (volume ratio of o-dichlorobenzene to benzene-d6 = 9:1) was added to a test piece of about 50 mg taken from an arbitrary position of a long-fiber nonwoven fabric, and the mixture was dissolved by heating to 135°C. Then, the obtained solution was subjected to ¹³ C-nuclear magnetic resonance (NMR) measurement, and the area of the peak due to the propylene unit and the area of the peak due to the repeating unit other than the propylene unit were calculated from the NMR spectrum. The molar fraction (molar %) of the propylene unit in all the repeating units constituting the polypropylene resin was calculated from the peak area ratio of the propylene unit to the repeating unit other than the propylene unit, and the first decimal place was rounded off.

The polypropylene resin of the present invention may also contain various additives such as inorganic substances such as titanium oxide, silicon dioxide, barium oxide, calcium carbonate, carbon black, coloring agents such as dyes or pigments, flame retardants, fluorescent brighteners, antioxidants, charge stabilizers, antistatic agents or ultraviolet absorbers.

In the long fiber nonwoven fabric of the present invention, the melting point of the polypropylene resin is preferably 140° C. or higher and 170° C. or lower. The polyolefin resin having a melting point within the above range has excellent strength when made into fibers, and yarn breakage is less likely to occur during the manufacturing process, so the obtained long fiber nonwoven fabric can be obtained with fewer defects.

In addition, the melting point of the polypropylene resin in the present invention is determined as follows.

First, about 2 mg of the long-fiber nonwoven fabric was taken from any position and placed in a differential scanning calorimeter. After melting, the temperature was raised to 250°C at a heating rate of 10°C/min in a nitrogen environment, and then cooled to 20°C by air cooling. Next, the sample that had become solid again was subjected to differential scanning calorimetry in a nitrogen environment at a heating rate of 10°C/min and a measurement temperature range of 50°C to 250°C. The temperature of the top of the endothermic peak in the obtained measurement result (Differential Scanning Calorimetry (DSC) curve) was taken as the melting point. Furthermore, when multiple endothermic peaks were observed, the temperature of the top of the peak with the largest endothermic amount was taken as the melting point.

In the long fiber nonwoven fabric of the present invention, the crystallization fusion heat of the polypropylene resin is preferably 75 J/g or more and 150 J/g or less. The polypropylene resin having a crystallization fusion heat within the above range is preferred because it has excellent processability when made into a long fiber nonwoven fabric.

In addition, the crystal fusion heat of the polypropylene resin in the present invention refers to that obtained as follows.

First, about 2 mg was collected from an arbitrary position of the long-fiber nonwoven fabric and placed in a differential scanning calorimeter. The sample was melted by heating it up to 250°C at a rate of 10°C/min in a nitrogen atmosphere, and then cooled to 20°C by air cooling. Next, the sample that had become solid again was subjected to differential scanning calorimetry in a nitrogen atmosphere at a rate of 10°C/min in a measurement temperature range of 50°C to 250°C. The crystal melting heat was calculated from the area of the endothermic peak in the obtained measurement result (DSC curve). Furthermore, when multiple endothermic peaks were observed, the crystal melting heat was calculated from the value obtained by adding up the areas of all the endothermic peaks.

The polypropylene resin in the present invention preferably has an Mw of 20,000 or more and 120,000 or less. By setting the Mw to preferably 20,000 or more, more preferably 25,000 or more, and further preferably 30,000 or more, yarn breakage is less likely to occur in the spinning step. On the other hand, by setting the Mw to preferably 120,000 or less, more preferably 100,000 or less, and further preferably 80,000 or less, a soft nonwoven fabric that is easily processed into a laminate can be formed.

The polypropylene resin in the present invention preferably has an Mw/Mn of 2.00 or more and 4.00 or less. By making Mw/Mn preferably 2.00 or more, more preferably 2.20 or more, further preferably 2.40 or more, and particularly preferably 2.60 or more, the adhesion during embossing is improved. On the other hand, by making Mw/Mn preferably 4.00 or less, more preferably 3.90 or less, and further preferably 3.80 or less, the quality of long fiber nonwoven fabric is improved.

In the present invention, Mw and Mn refer to values calculated by the following method. (1) Randomly sample 5 test pieces of 5 mg each from the region excluding the ends of the long fiber nonwoven fabric. The ends of the long fiber nonwoven fabric refer to the region that is 10% of the length of the long fiber nonwoven fabric in the width direction. (2) Add 5 mL of 1,2,4-trichlorobenzene (for example, manufactured by Fuji Films and Kou Pure Chemical Industries, Ltd.) to the test piece obtained in (1), and heat at 165°C for 20 minutes to dissolve. Next, the solution is filtered through a polytetrafluoroethylene (PTFE) filter (pore size: 0.45 μm) to prepare a sample solution. Here, the PTFE filter can be, for example, "T010A" manufactured by Advantec Toyo Co., Ltd. (3) The sample solution obtained in (2) is measured using gel permeation chromatography (hereinafter sometimes referred to as GPC) under the following conditions, for example, using "Empower" manufactured by Wyatt Technology to analyze the elution curve in GPC, thereby determining Mw and Mn. ‧ Apparatus: e.g. "PL-220" manufactured by Polymer Laboratories, Inc. ‧ Detector: Differential refractive index detector RI ‧ Column: Shodex HT-G (guard column) + Shodex HT-806M × 2 pieces (8.0 mm × 30 cm, e.g. manufactured by Showa Denko Co., Ltd., etc.) ‧ Solvent: 1,2,4-trichlorobenzene (with 0.1% BHT added) ‧ Flow rate: 1.0 mL/min ‧ Column temperature: 145°C ‧ Injection volume: 0.20 mL ‧ Standard sample: Monodisperse polystyrene (e.g. manufactured by Tosoh Co., Ltd., etc.), bibenzyl (e.g. manufactured by Tokyo Chemical Industry Co., Ltd., etc.)

[Fiber] The long-fiber nonwoven fabric of the present invention includes fibers containing the polypropylene resin. Moreover, the average fiber diameter of the fibers is greater than 0.05 μm and less than 5.00 μm. By setting the lower limit of the range of the average fiber diameter to greater than 0.05 μm, preferably greater than 0.08 μm, and more preferably greater than 0.20 μm, a long-fiber nonwoven fabric having higher tensile strength and excellent stability during winding or unwinding is formed. On the other hand, by setting the upper limit of the average fiber diameter range to 5.00 μm or less, preferably 2.00 μm or less, more preferably 1.00 μm or less, and further preferably 0.50 μm or less, the specific surface area of the long fiber nonwoven fabric is increased, thereby forming a long fiber nonwoven fabric with excellent particle collection efficiency.

Furthermore, the average fiber diameter (μm) of the fiber in the present invention refers to the following value, that is, from 3 points in the width direction of the long fiber non-woven fabric (2 points at the side ends and 1 point in the center) each point in the length direction at intervals of 5 cm, a total of 15 points are cut out to obtain a measurement sample of 10 mm×5 mm, and a scanning electron microscope (SEM, such as "S-5500" manufactured by Hitachi High-technologies Co., Ltd.) is used. Photographs of the surface of the long fiber non-woven fabric are taken one by one from the cut measurement sample at a magnification of 5000 times, and a total of 15 photos are obtained. For all fibers in the photograph whose fiber side widths can be clearly confirmed, the widths (μm) are measured, and the arithmetic average of the values is rounded off to the third decimal place. Even if the cross-sectional shape of the fiber is a flat cross-section or an irregular cross-section, the width of the fiber side is regarded as the fiber diameter for measurement as described above.

The fibers constituting the long-fiber nonwoven fabric of the present invention may have a flat cross section or an irregular cross section, preferably a round cross section. By setting the cross section to a round cross section, the spinnability is improved and yarn breakage is less likely to occur.

[Long-fiber nonwoven fabric] The long-fiber nonwoven fabric of the present invention includes the above-mentioned fibers. Moreover, the "long-fiber nonwoven fabric" described in the present invention refers to a nonwoven fabric such as a meltblown nonwoven fabric or a spunbonded nonwoven fabric produced by the production method described below, and excludes a nonwoven fabric (short-fiber nonwoven fabric) containing only fibers cut into a certain length (e.g., 100 mm).

The zero shear viscosity of the long fiber nonwoven fabric of the present invention at 190°C is 5 Pa·s or more and 10 Pa·s or less. By setting the lower limit of the zero shear viscosity range to 5 Pa·s or more, preferably 6.0 Pa·s or more, a fiber having high tensile strength is formed, and even if a long fiber nonwoven fabric is made, the tensile strength is high. On the other hand, by setting the upper limit of the zero shear viscosity range to 10 Pa·s or less, preferably 9.0 Pa·s or less, a long fiber nonwoven fabric having high air permeability is formed.

Furthermore, in the present invention, the zero shear viscosity of the long-fiber nonwoven fabric refers to the value calculated by measuring as follows. (1) Take two test pieces from any position of the long-fiber nonwoven fabric. At this time, the amount taken is set to be sufficient to fill the space between the parallel plates of the rheometer described later, that is, the amount sufficient to fill a cylinder with a bottom radius of 10 mm and a height of 0.5 mm. The amount is at least 0.15 g and is adjusted in combination with the specifications of the measuring device. (2) Using a rheometer set at 190°C (e.g., "Reosol G3000" manufactured by UBM Co., Ltd.), a parallel plate with one of the test pieces is set, and the melt viscosity is measured when strain is applied at angular frequencies of 1.26 rad/sec, 3.14 rad/sec, 6.28 rad/sec, 12.57 rad/sec, 31.42 rad/sec, and 62.83 rad/sec. The other test piece is measured in the same manner. (3) The relationship between the value obtained by averaging the results obtained from the two test pieces at each angular frequency and the angular frequency is linearly approximated. (4) The value of the melt viscosity calculated by extrapolating the approximate formula obtained by the linear approximation to 0 rad/sec is taken as the zero shear viscosity.

In addition, the zero shear viscosity of the long fiber nonwoven fabric of the present invention at 190°C can be controlled by the melt flow rate or molecular weight distribution of the polypropylene resin, the addition form of the organic peroxide described later (whether a masterbatch is used, etc.), the temperature of the extruder for reacting the polypropylene resin with the organic peroxide, or the type of the organic peroxide.

The long-fiber nonwoven fabric of the present invention preferably contains an organic peroxide having a structure represented by the following general formula (1) or (2) in a ratio of 100 ppm to 1000 ppm.

[Chemistry 5]

[Chemistry 6]

Here, R ₁ to R ₃ and R ₅ to R ₇ are alkyl, alkenyl, phenyl, benzyl or benzoyl groups having 1 to 10 carbon atoms, and R ₄ and R ₈ are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms.

The lower limit of the content of the organic peroxide is preferably 100 ppm or more, more preferably 120 ppm or more, and further preferably 150 ppm or more, thereby forming a long-fiber nonwoven fabric with a larger volume and excellent air permeability. On the other hand, the upper limit of the content is preferably 1000 ppm or less, more preferably 750 ppm or less, and further preferably 500 ppm or less, thereby forming a long-fiber nonwoven fabric with excellent particle capture performance.

Examples of the organic peroxide include dialkyl peroxides such as "di-tert-butyl peroxide, diisopropylbenzene peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexyne-3, α,α'-bis(tert-butylperoxide)diisopropylbenzene", and peroxyketal such as "1,1-bis(tert-butylperoxide)-3,3,5-trimethylcyclohexane, 2,2-bis(tert-butylperoxide)butane".

Furthermore, in the present invention, the content of the organic peroxide refers to a value calculated by the following method. (1) Randomly take 5 test pieces of 25 mg each from the area excluding the end of the long fiber nonwoven fabric. Furthermore, the end of the nonwoven fabric refers to an area that is 10% of the length of the two ends relative to the length in the width direction of the nonwoven fabric. (2) The test piece obtained in (1) is immersed in a chloroform/methanol solvent with a volume ratio of 1:1, and ultrasonically treated and dissolved under the conditions of 45 kHz for 15 minutes. For the ultrasonic treatment, for example, the ultrasonic cleaner "VS-100 III" manufactured by ASONE Co., Ltd. can be used. In addition, the amount of the solvent relative to the mass of the test piece is set to 0.8 mL of the solvent relative to 1 mg of the test piece. (3) The solution obtained after the ultrasonic treatment in (2) is filtered using a filter made of polytetrafluoroethylene (PTFE) (hereinafter, sometimes referred to as "PTFE filter"; pore size: 0.45 μm) to prepare a sample solution. Here, the PTFE filter can be, for example, "T010A" manufactured by Advantec Toyo Co., Ltd. (4) 0.1 g of an organic peroxide is dissolved in 10 mL of a chloroform/methanol solution with a volume ratio of 1:1 to prepare a standard stock solution (10 μg/mL). Then, the standard stock solution is diluted with the chloroform/methanol solution to prepare standard solutions of various concentrations (0.1 μg/mL, 0.2 μg/mL, 0.5 μg/mL, 1.0 μg/mL). At this time, the following can be listed as the organic peroxides, and standard solutions of various concentrations are prepared for each. In addition, when an organic peroxide having a structure represented by the general formula (1) or (2) other than the organic peroxide described below is clearly contained by other methods (e.g., iodine titration, polarography, etc.) or is estimated to be contained, a standard solution of the organic peroxide is also prepared. ‧Di-tert-butyl peroxide ‧Diisopropylbenzene peroxide ‧2,5-Dimethyl-2,5-bis(tert-butyl peroxide)hexane ‧2,5-Dimethyl-2,5-bis(tert-butyl peroxide)hexyne-3 ‧α,α'-bis(tert-butyl peroxide)diisopropylbenzene ‧1,1-bis(tert-butyl peroxide)-3,3,5-trimethylcyclohexane ‧2,2-bis(tert-butyl peroxide)butane (5) The sample solution was subjected to liquid chromatography-tandem mass spectrometry (LC/MS/MS) under the following conditions. ‧High performance liquid chromatograph (HPLC): such as "LC-20A" manufactured by Shimadzu Corporation ‧Mass spectrometer (MS): such as "API4000" manufactured by Sciex ‧Column: ODS series column (such as "SUMIPAX ODS A series" manufactured by Sumika Analytical Center Co., Ltd.) ‧Mobile phase: 0.1% formic acid aqueous solution + methanol (gradient extraction conditions) ‧Injection volume: 5 μL ‧Ionization: electrospray ionization (ESI) (6) Organic peroxides were identified based on the mass spectrum (MS) of each sample solution, and the amount of organic peroxides (ppm) was quantified based on the peak area using a calibration curve obtained based on a standard solution of the organic peroxide. (7) The arithmetic mean (ppm) of the values measured for each test piece was rounded off to the first decimal point to calculate the amount of organic peroxides (ppm).

The content of organic peroxide in the polypropylene resin constituting the long-fiber nonwoven fabric of the present invention can be controlled by the addition form and addition temperature of the organic peroxide.

The long fiber nonwoven fabric of the present invention preferably has a unit area weight of 5 g/ ^m2 or more and 100 g/ ^m2 or less. By having a unit area weight of the long fiber nonwoven fabric preferably of 5 g/ ^m2 or more, more preferably of 7 g/ ^m2 or more, and further preferably of 10 g/ ^m2 or more, a long fiber nonwoven fabric with higher tensile strength is formed. In addition, by having a unit area weight of the long fiber nonwoven fabric preferably of 100 g/ ^m2 or less, more preferably of 70 g/ ^m2 or less, and further preferably of 50 g/ ^m2 or less, a long fiber nonwoven fabric that is easy to perform lamination processing or sewing processing is formed.

The weight per unit area (g/m ² ) of the nonwoven fabric in the present invention is determined based on "6.2 Mass per unit area" of "General nonwoven fabric test methods" of Japanese Industrial Standards (JIS) L1913:2010.

Cut a 20 cm x 25 cm test piece from the nonwoven fabric. Take three pieces per 1 m of the nonwoven fabric width and weigh the mass (g) of each piece in the standard state. Calculate the mass per 1 ^m2 (g/ ^m2 ) from the arithmetic mean of the measured values, rounding off to the first decimal place.

The long fiber nonwoven fabric of the present invention preferably has a porosity of 92.5% or more and 99.0% or less. By setting the porosity to 92.5% or more, the air permeability of the long fiber nonwoven fabric is improved. On the other hand, if the porosity exceeds 99.0%, the strength decreases and is not preferred.

Here, the void ratio (%) of the nonwoven fabric in the present invention is determined as follows.

First, the thickness (μm) of the nonwoven fabric is calculated as follows. Use a 3D microscope (e.g., "VR-3050" manufactured by KEYENCE Co., Ltd.) to take a height image of the nonwoven fabric surface at a magnification of 12 times so that the nonwoven fabric is captured in the entire image, and calculate the height T (x, y) (μm) of each pixel (x, y) of the image from the sample stand. The average of T (x, y) of all pixels is taken as the thickness of the nonwoven fabric. Next, the following value, which is the value calculated according to the following formula using the unit area weight and thickness calculated using the above method and the density of the raw material used in the nonwoven fabric, is rounded to the second decimal place. Porosity (%) = [1-(unit area weight/thickness/density)] × 100

The long fiber nonwoven fabric of the present invention can be subjected to a stationary electrode treatment. By conducting the stationary electrode treatment by the method described below, the particle collection efficiency can be improved without compromising the air permeability.

[Manufacturing method of long-fiber nonwoven fabric] Next, the preferred method for manufacturing the long-fiber nonwoven fabric of the present invention will be specifically described, but the present invention is not limited thereto.

The method for producing the long-fiber nonwoven fabric of the present invention preferably comprises: a step of melting a raw material resin composition obtained by adding an organic peroxide having a structure represented by the general formula (1) or (2) to a polypropylene resin having a melt flow rate of 500 g/10 minutes or more and 2000 g/10 minutes or less (hereinafter referred to as the raw material resin) to obtain a molten resin; and a step of subjecting the molten resin to a melt spraying method to obtain a long-fiber nonwoven fabric.

(a) A step of melting a raw resin composition obtained by adding an organic peroxide to a raw resin to obtain a molten resin In the method for producing a long-fiber nonwoven fabric of the present invention, first, an organic peroxide is added to a raw resin to decompose the raw resin to obtain a molten resin. The raw resin used at this time preferably has a melt flow rate (hereinafter, sometimes referred to as MFR) of 500 g/10 minutes or more and 2000 g/10 minutes or less. For a polypropylene resin having an MFR of less than 500 g/10 minutes, the amount of organic peroxide added to decompose the polypropylene resin increases, and thus the amount of organic peroxide remaining without reaction becomes excessive, so that yarn breakage occurs frequently during spinning, and the quality of the long-fiber nonwoven fabric is reduced. In addition, polypropylene resins with an MFR exceeding 2000 g/10 minutes are usually provided in the form of powder or wax, which makes them difficult to handle in an extruder. Compared with those in the form of chips or pellets, the supply becomes unstable and the spinnability may be reduced.

In the present invention, the melt flow rate (g/10 minutes) of the polypropylene resin refers to the following value, which is measured under the conditions of a temperature of 230°C, a load of 2.16 kg, and a measurement time of 10 minutes based on "8 A method: Mass measurement method" of JIS K7210-1:2014 "Plastics-Method for determining melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics-Part 1: Standard test methods".

In addition, various additives such as titanium oxide, silicon dioxide, barium oxide, calcium carbonate and other inorganic substances, carbon black, dyes or pigments and other coloring agents, flame retardants, fluorescent whitening agents, antioxidants, charge stabilizers, antistatic agents or ultraviolet absorbers may be added to the raw material resin used in the method for producing the long-fiber nonwoven fabric of the present invention within the range that does not impair the effects of the present invention.

Examples of the organic peroxide used in the method for producing the long-fiber nonwoven fabric of the present invention include organic peroxides described in [Long-fiber nonwoven fabric].

The molten resin obtained by adding the organic peroxide to the raw material resin and decomposing the raw material resin can be provided to the "step of obtaining a long-fiber nonwoven fabric by melt-blowing" described later without being particularly dried.

Furthermore, as a method for obtaining a molten resin by adding the organic peroxide to a raw material resin, a method of reacting in an extruder for supplying raw materials to a spinning machine is preferred. Here, the so-called spinning machine refers to the spinning machine used in the "step of obtaining a long-fiber nonwoven fabric by melt-blowing method" described later. For example, the raw material resin and the organic peroxide are simultaneously introduced into an extruder by dry blending or separate measurement, and kneaded by an extruder for supplying raw materials to a spinning machine, thereby continuously obtaining a molten resin obtained by adding an organic peroxide to a raw material resin, and continuously supplying the raw materials to the spinning machine, thereby simplifying the steps. As another method for obtaining a molten resin by adding a raw material resin and the organic peroxide, there is a method in which an organic peroxide is kneaded and granulated in a raw material resin by an extruder independent of a spinning machine before being fed into an extruder for feeding a raw material into a spinning machine, and the granules are fed into an extruder for feeding a raw material into a spinning machine to be melted.

When the raw material resin and the organic peroxide are simultaneously introduced into an extruder for kneading, the temperature of the extruder is preferably not less than (melting point of the raw material resin + 20°C) and not more than (melting point of the raw material resin + 60°C). That is, it can be said that approximately 180°C to 220°C is a preferable range. By setting the temperature of the extruder within the above range, a large shear force is applied to the raw material in the extruder, and the raw material resin and the organic peroxide are easily and uniformly kneaded, so that the organic peroxide can function more efficiently.

In addition, the organic peroxide is preferably kneaded with a polypropylene resin in advance to prepare a masterbatch, and the masterbatch is added to the raw resin to obtain a molten resin. As the polypropylene resin used to prepare the masterbatch, the same polypropylene resin as the raw resin can be used. By adding the organic peroxide in the form of a masterbatch, it is difficult for the organic peroxide to be localized, and even if the kneading is performed for a short time, the viscosity of the polypropylene resin can be uniformly reduced.

The amount of organic peroxide added to the raw material resin is preferably 0.20 mass% or more and 1.0 mass% or less of the total raw material. By setting the added amount to 0.20 mass% or more, even when adding by dry blending, the viscosity of the polypropylene resin can be efficiently reduced. On the other hand, by setting the added amount to 1.0 mass% or less, more preferably 0.90 mass% or less, and further preferably 0.80 mass% or less, the spinnability is improved, thereby obtaining a high-quality long-fiber nonwoven fabric.

The spinning temperature in the present invention is preferably set to be above (melting temperature of raw material resin + 30°C) and below (melting point of raw material resin + 160°C). That is, it can be said that approximately 190°C to 320°C is a preferred range. By setting the spinning temperature preferably above 190°C, the viscosity of the spun molten resin is reduced, which can promote the ultra-fine fiber. In addition, by setting the spinning temperature preferably below 320°C, more preferably below 300°C, the thermal decomposition of the polypropylene resin in the spinning machine can be suppressed, and the spinnability or tensile strength when making a long-fiber non-woven fabric can be improved.

(b) Step of obtaining a long-fiber nonwoven fabric by melt-blowing the molten resin The melt-blowing method is a method of forming fibers by spraying raw materials from a melt-blowing die having a predetermined aperture, spraying hot air at a certain angle to the spraying portion to extremely refine the fibers, and accumulating the extremely refined fibers in a collecting portion to form a long-fiber nonwoven fabric.

The die mouth of the present invention preferably has a plurality of ejection holes. As the shape of the ejection hole, a circular, triangular, quadrilateral, Y-shaped, etc. can be used. Among them, a circular ejection hole is excellent in step stability in the spinning step and is therefore preferred. In the case of a circular ejection hole, the diameter is preferably 0.08 mm to 1.0 mm. By making the diameter of the ejection hole preferably 0.08 mm or more, more preferably 0.10 mm or more, hole clogging is less likely to occur, and productivity is improved. In addition, by making the diameter of the ejection hole preferably 1.0 mm or less, more preferably 0.70 mm or less, and further preferably 0.50 mm or less, the distribution of the resin inside the die mouth is improved, and a uniform nonwoven fabric can be produced.

The single-hole ejection amount of the molten resin in the present invention is preferably 0.01 g/min or more and 0.30 g/min or less. By setting the single-hole ejection amount of the molten resin to preferably 0.01 g/min or more, more preferably 0.03 g/min or more, and further preferably 0.05 g/min or more, yarn breakage is less likely to occur, and a uniform nonwoven fabric can be manufactured. In addition, by setting the single-hole ejection amount of the molten resin to preferably 0.30 g/min or less, more preferably 0.25 g/min or less, and further preferably 0.20 g/min or less, the fiber is easily extremely refined, and the collection efficiency when it is made into an air filter is improved.

In the present invention, the distance from the die opening to the collecting part is preferably 3 cm to 100 cm. By setting the distance from the die opening to the collecting part to preferably 3 cm or more, more preferably 5 cm or more, further preferably 10 cm or more, and particularly preferably 15 cm or more, a long fiber nonwoven fabric with high tensile strength is formed. In addition, by setting the distance to preferably 100 cm or less, more preferably 80 cm or less, and further preferably 50 cm or less, a long fiber nonwoven fabric with good quality and uniformity can be obtained.

Furthermore, so far, the method of manufacturing long-fiber nonwoven fabrics by meltblowing has been described, but of course, long-fiber nonwoven fabrics can also be formed by spunbonding. The spunbonding method is a method of manufacturing long-fiber nonwoven fabrics by spinning molten resin through a die, cooling and solidifying it, extending the obtained yarn, capturing it on a moving net to form a fiber net, and then performing a heat-bonding step.

When the long fiber nonwoven fabric of the present invention is manufactured by the spunbond method, it is preferred to set the diameter of the ejection hole of the die used to be greater than 0.10 mm and less than 0.20 mm, and to perform spinning under the condition of a single hole ejection amount of greater than 0.01 g/min and less than 0.20 g/min. By setting the ejection hole diameter and the single hole ejection amount to the above range, it is easy to make the fiber extremely fine. When the spunbond method is used for manufacturing, the molecular orientation of the polypropylene resin constituting the fiber is improved, thereby forming a long fiber nonwoven fabric with excellent tear strength.

(c) Electrode processing and post-processing In the method for manufacturing the long-fiber nonwoven fabric of the present invention, it is also preferred to perform electrode processing. Specifically, for example, the following method can be used: in a state where the fiber sheet accumulated on the collection portion by the above step is in contact with the ground electrode, the ground electrode is moved together with the fiber sheet, and a non-contact type application electrode is used to apply high voltage, and the electrode processing is continuously performed to obtain a long-fiber nonwoven fabric; water is sprayed on the fiber sheet at a pressure sufficient to allow water to penetrate into the fiber sheet. A method of obtaining a long fiber nonwoven fabric by using a jet or water droplet flow to polarize the fiber sheet so that positive and negative charges are evenly mixed; or a method of passing the fiber sheet through a slit-shaped nozzle and using the nozzle to suck water so that the water penetrates into the fiber sheet to obtain a long fiber nonwoven fabric in which positive and negative charges are evenly mixed (hydraulic charging (hydrocharge) method). Among these methods, the hydrocharge method is preferably used in terms of excellent capture performance during polarization.

In addition, in the manufacturing method of the long-fiber nonwoven fabric of the present invention, post-processing such as antibacterial processing or pleating processing can also be performed in combination with the use of the long-fiber nonwoven fabric.

[Laminate] Since the long-fiber nonwoven fabric of the present invention has the above-mentioned characteristics, a laminate having at least one layer of the long-fiber nonwoven fabric can be produced. In particular, a laminate having a structure in which a spunbond nonwoven fabric is laminated on both sides of the long-fiber nonwoven fabric of the present invention (spunbond nonwoven fabric/long-fiber nonwoven fabric of the present application/spunbond nonwoven fabric structure) is suitable for use as a mask or protective clothing. The following specifically describes a preferred method of laminating the long-fiber nonwoven fabric of the present invention with a spunbond nonwoven fabric.

When laminating the spunbond nonwoven fabric and the long fiber nonwoven fabric of the present invention, the lamination can be performed offline (the spunbond nonwoven fabric and the long fiber nonwoven fabric of the present invention are manufactured separately and then laminated), or the lamination can be performed by directly forming the long fiber nonwoven fabric by melt-blowing after forming the spunbond nonwoven fabric.

In addition, as a method for thermally bonding the spunbond nonwoven fabric and the long-fiber nonwoven fabric of the present invention, there can be listed: a method of thermally bonding using various rollers, such as a heat embossing roller having engravings (concave and convex parts) on the surfaces of an upper and lower pair of rollers, a heat embossing roller comprising a combination of a roller having a flat (smooth) surface and a roller having an engraving (concave and convex part) on the surface of the other roller, and a heat embossing roller comprising a combination of an upper and lower pair of flat (smooth) rollers; or an ultrasonic bonding method of thermally melting by ultrasonic vibration of a horn. Among them, in terms of excellent productivity, imparting strength to a portion of the heat-bonded portion, and maintaining the skin-touch or breathability that is unique to non-woven fabrics in the portion other than the heat-bonded portion (non-bonded portion), a better embodiment is to use a heat embossing roller with engravings (concave and convex portions) on the surfaces of an upper and lower pair of rollers, or a heat embossing roller that is a combination of a roller with a flat (smooth) surface and a roller with an engraving (concave and convex portion) on the surface of the other roller.

As the surface material of the heat embossing roller, in order to obtain the effect brought by sufficient heat bonding and prevent the engraving (convex and concave parts) of one embossing roller from being transferred to the surface of another roller, it is preferably made of metal.

The embossing bonding area ratio by such a hot embossing roller is preferably 3% or more and 30% or less. By making the embossing bonding area ratio preferably 3% or more, more preferably 5% or more, and further preferably 8% or more, mechanical properties such as tensile strength, tear strength, and pilling resistance that can be used practically can be obtained as a laminated nonwoven fabric. On the other hand, by making the embossing bonding area ratio preferably 30% or less, more preferably 25% or less, and further preferably 20% or less, air permeability can be ensured. Even when using a bonding method such as ultrasonic bonding, the embossing bonding area ratio is preferably in the same range.

The so-called embossing bonding area ratio mentioned here refers to the ratio of the heat-bonded part to the whole laminated nonwoven fabric. Specifically, when heat bonding is performed by a pair of rollers with concave and convex shapes, it refers to the ratio of the part where the convex part of the upper roller overlaps with the convex part of the lower roller and abuts against the nonwoven fabric layer (heat-bonded part) to the whole laminated nonwoven fabric. In addition, when heat bonding is performed by a roller with concave and convex shapes and a flat roller, it refers to the ratio of the part where the convex part of the roller with concave and convex shapes abuts against the nonwoven fabric layer (heat-bonded part) to the whole laminated nonwoven fabric. Furthermore, in the case of ultrasonic bonding, it refers to the proportion of the portion that is thermally fused by ultrasonic processing (thermal bonding portion) in the entire laminated nonwoven fabric.

As the shape of the heat-bonded portion formed by heat embossing rolls or ultrasonic bonding, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, etc. can be used. In addition, the heat-bonded portion is preferably evenly present at a certain interval in the length direction (conveying direction) and the width direction of the laminated nonwoven fabric. Thereby, the variation in the strength of the laminated nonwoven fabric can be reduced.

The surface temperature of the heat embossing roller during heat bonding is preferably set to be greater than (melting point of the polypropylene resin used - 50°C) and less than (melting point of the polypropylene resin used - 15°C). By setting the lower limit of the surface temperature of the heat embossing roller to preferably be greater than -50°C relative to the melting point of the polypropylene resin used, and more preferably greater than -45°C relative to the melting point of the polypropylene resin used, a laminated nonwoven fabric having mechanical properties such as tensile strength, tear strength, and pilling resistance that can be used in practical applications can be obtained. In addition, by setting the upper limit of the surface temperature of the heat embossing roller to preferably -15°C or lower relative to the melting point of the polypropylene resin used, and more preferably -20°C or lower relative to the melting point of the polypropylene resin used, excessive heat bonding can be suppressed and a laminated nonwoven fabric with high air permeability can be obtained.

Furthermore, when the polypropylene resin contains two or more raw materials and two or more melting points are observed, it is preferred to adjust the temperature to the above range relative to the lowest temperature among the observed melting points.

The linear pressure of the heat embossing roller during heat bonding is preferably 10 N/cm or more and 500 N/cm or less. By setting the linear pressure of the roller preferably 10 N/cm or more, more preferably 50 N/cm or more, further preferably 100 N/cm or more, and particularly preferably 150 N/cm or more, a laminated nonwoven fabric having mechanical properties such as tensile strength, tear strength, and pilling resistance that can be used in practical applications can be obtained. On the other hand, by setting the linear pressure of the heat embossing roller preferably 500 N/cm or less, more preferably 400 N/cm or less, and further preferably 300 N/cm or less, a laminated nonwoven fabric having excellent air permeability or softness can be obtained.

In addition, in the present invention, for the purpose of adjusting the thickness of the laminated nonwoven fabric, before and/or after the heat bonding using the heat embossing pattern roller, heat embossing can be performed by heat embossing rollers including a pair of upper and lower flat rollers. The so-called upper and lower pair of flat rollers refers to a metal roller or elastic roller with no unevenness on the roller surface, and can be configured by pairing a metal roller with a metal roller, or a metal roller with an elastic roller.

Furthermore, the so-called elastic roller in the present invention refers to a roller made of a material having higher elasticity than a metal roller, for example, a paper roller made of paper, cotton, and aromatic polyamide paper, or a roller made of a resin made of urethane resin, epoxy resin, silicone resin, polyester resin, hard rubber, and a mixture thereof.

Functional agents can be added to the laminate of the present invention. Examples of functional agents include hydrophilic agents, water repellent agents, oil repellent agents, antistatic agents, antibacterial agents, antiviral agents, deodorants, fragrances, cooling agents, etc., but are not particularly limited.

The method of applying the functional agent is not particularly limited, and for example, impregnation, spraying, contact roller, etc. can be used.

[Filters, protective clothing, masks] The long-fiber nonwoven fabric of the present invention can be widely used in filters, medical and sanitary materials, living materials, industrial materials, etc. Due to its excellent particle capture efficiency and air permeability, it is particularly suitable for use in filters such as air filters, sanitary materials such as masks, and protective clothing for dust or antiviral use. [Examples]

Next, the present invention is described in detail based on the embodiments. However, the present invention is not limited to these embodiments. Furthermore, in the measurement of various physical properties, those not particularly described are measured based on the above methods.

[Measurement method] (1) Step passability If there is no yarn breakage in the spinning step or no sheet breakage in the winding step and a nonwoven fabric can be obtained stably, it is rated as "OK". If there is yarn breakage in the spinning step or sheet breakage in the winding step and a long-fiber nonwoven fabric cannot be obtained stably, it is rated as "NO".

(2) Weight per unit area Measured based on "6.2 Mass per unit area" of JIS L1913:2010 "Test methods for normal nonwoven fabrics".

(3) Zero shear viscosity of long-fiber nonwoven fabrics Using "Reosol G3000" manufactured by UBM Co., Ltd. as a rheometer, the measurement was performed as described above using parallel plates with a diameter of 20 mm.

(4) Average fiber diameter of fibers Measured as described above using "S-5500" manufactured by Hitachi High-technologies Co., Ltd. as a scanning electron microscope.

(5) Content of organic peroxides in long-fiber nonwoven fabrics For ultrasonic treatment, an ultrasonic cleaner "VS-100 III" manufactured by ASONE Co., Ltd. was used, for PTFE filter, a "T010A" manufactured by Advantec Toyo Co., Ltd. was used, for high performance liquid chromatography (HPLC), a "LC-20A" manufactured by Shimadzu Corporation was used, for mass spectrometry (MS), a "API4000" manufactured by Sciex, and for ODS columns, a "SUMIPAX ODS A Series" manufactured by Sumika Analytical Center Co., Ltd. was used, and the above method was used for measurement.

(6) Porosity of long-fiber nonwoven fabrics The measurement was performed using the VR-3050 manufactured by KEYENCE Corporation as a 3D microscope using the above method.

(7) Particle collection efficiency of long-fiber nonwoven fabric Measurement samples with a length × width = 15 cm × 15 cm were collected at 5 locations in the width direction of the nonwoven fabric, and the collection efficiency of each sample was measured using the collection efficiency measurement device shown in Figure 1. In the collection efficiency measurement device of Figure 1, a dust collection box (2) is connected to the upstream side of a sample holder (1) in which a measurement sample (M) is set, and a flow meter (3), a flow regulating valve (4) and a blower (5) are connected to the downstream side. In addition, a particle counter (6) can be used on the sample holder (1) to measure the number of dust particles on the upstream side and the number of dust particles on the downstream side of the measurement sample (M) by switching the valve (7).

When measuring the capture efficiency, a polystyrene 0.309U 10% solution (manufactured by Nacalai Tesque Co., Ltd.) was diluted 200 times with distilled water and filled into the dust collection box (2). Next, the measurement sample (M) is placed in the sample holder (1), and the air volume is adjusted using the flow control valve (4) so that the filter passing speed becomes 6.5 m/min, so that the dust concentration is stabilized within the range of 10,000 particles/(2.83 ^{×10-4 m3} ) or more and 40,000 particles/(2.83× ^{10-4 m3} ) or less (2.83× ^{10-4 m3} is equivalent to 0.01 ^ft3 ). For each measurement sample, the number of dust particles (D) upstream and the number of dust particles (d) downstream of the measurement sample (M) are measured three times using a particle counter (6) (manufactured by RION Co., Ltd., "KC-01D"), according to JIS K0901:1991 "Test Methods for Shape, Size and Performance of Filter Materials for Collecting Dust in Gases""5.2 Collection Efficiency Test", and use the following formula to calculate the collection efficiency (%) for particles of 0.3 μm to 0.5 μm. The average value of the three measured samples is taken as the final collection efficiency. Collection efficiency (%) = [1- (d/D)] × 100 (where d represents the total number of downstream dust measured three times, and D represents the total number of upstream dust measured three times)

(8) Air permeability of long-fiber nonwoven fabrics The air permeability evaluation device "FX3340" manufactured by TEXTEST Co., Ltd. was used to perform the measurement based on the "A method (Fragile method)" described in "8.26 Air permeability" of JIS L1096:2010 "Test methods for fabrics of woven and knitted fabrics".

[Polypropylene resin] In Examples 1 to 5 and Comparative Examples 1 to 5, the polypropylene resin used as the raw material resin is as follows. ‧Polypropylene resin A (described as PP-A in Table 1): "HP461X" (trade name) manufactured by LyondellBasell ‧Polypropylene resin B (described as PP-B in Table 1): "MF650Y" (trade name) manufactured by LyondellBasell ‧Polypropylene resin C (described as PP-C in Table 1): "HP461Y" (trade name) manufactured by LyondellBasell ‧Polypropylene resin D (described as PP-D in Table 1): "S10CL" (trade name) manufactured by Prime Polymer Co., Ltd. ‧Polypropylene resin E (described as PP-E in Table 1): "VS200A" (trade name) manufactured by Sun-aroma Co., Ltd. ‧Polypropylene resin F (expressed as PP-F in Table 1): "HP5036" (trade name) manufactured by LyondellBasell ‧Organic peroxide masterbatch α (expressed as MB-α in Table 1): "VMPP10X" (trade name) manufactured by Polytechs (polypropylene resin containing 10% by mass of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane).

[Example 1] Polypropylene resin A and organic peroxide masterbatch α are dry-blended at a mass ratio of polypropylene resin A: organic peroxide masterbatch α = 97.5:2.5 to obtain blended fragments. When the mass of the entire blended fragments is set to 100 mass%, the proportion of organic peroxide in the blended fragments (raw material resin composition), that is, the amount of organic peroxide added to the raw material resin composition, is 0.25 mass%. The blended fragments are placed in an extruder for supplying raw materials to a spinning machine at 200°C, and the polypropylene resin A and the organic peroxide react to obtain a molten resin.

The obtained molten resin was directly supplied to a die with ejection holes of 0.12 mm in diameter arranged in a straight line, and spinning was performed by melt blowing under the conditions of single hole ejection amount of 0.05 g/min, die temperature of 280°C, and hot air pressure of 0.16 MPa. The fibers were collected by a conveyor arranged 20 cm below the ejection hole and rolled up by a winder to obtain a long fiber nonwoven fabric.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 1.

[Example 2] A long-fiber nonwoven fabric was obtained by the same method as Example 1 except that the mass ratio of polypropylene resin A to organic peroxide masterbatch α was set to polypropylene resin A: organic peroxide masterbatch α = 95.0:5.0.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 1.

[Example 3] A long-fiber nonwoven fabric was obtained by the same method as Example 1 except that the mass ratio of polypropylene resin A to organic peroxide masterbatch α was set to polypropylene resin A: organic peroxide masterbatch α = 92.5:7.5.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 1.

[Example 4] A long-fiber nonwoven fabric was obtained by the same method as Example 1 except that the mass ratio of polypropylene resin B and organic peroxide masterbatch α was set to polypropylene resin B: organic peroxide masterbatch α = 99.0:1.0.

[Example 5] A long-fiber nonwoven fabric was obtained by the same method as Example 1 except that the mass ratio of polypropylene resin C and organic peroxide masterbatch α was set to polypropylene resin C: organic peroxide masterbatch α = 97.5:2.5.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 1.

[Example 6] A long-fiber nonwoven fabric was obtained by the same method as Example 1 except that the mass ratio of polypropylene resin D and organic peroxide masterbatch α was set to polypropylene resin D: organic peroxide masterbatch α = 92.5:7.5.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 1.

[Table 1] [Table 1] Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Embodiment 6 Raw material resin Polypropylene resin[1] PP-A PP-A PP-A PP-B PP-C PP-D Organic peroxide masterbatch[2] MB-α MB-α MB-α MB-α MB-α MB-α The mixing ratio of [1] and [2] (mass ratio, [1]: [2]) 97.5:2.5 95.0:5.0 92.5:7.5 99.0:1.0 97.5:2.5 92.5:7.5 Addition amount of organic peroxide [mass %] 0.25 0.50 0.75 0.10 0.25 0.75 Step Pass Can Can Can Can Can Can Fiber Average fiber diameter [μm] 0.48 0.42 0.38 0.45 0.46 0.41 Long fiber nonwoven fabric Zero shear viscosity at 190℃ [Pa·s] 8.3 6.0 5.4 8.8 7.6 5.7 Content of organic peroxides [ppm] 166 210 253 89 180 241 M 69000 57000 53000 71000 62000 55000 Mw/Mn 3.39 3.13 2.96 2.18 3.61 2.88 Weight per unit area [g/m ² ] 20 20 20 20 20 20 Void ratio [%] 93.3 93.1 92.7 91.9 93.4 92.9 Particle collection efficiency [%] 68 62 63 70 64 66 Air permeability [cm ³ / (cm ² ·s)] 35.3 34.4 32.7 26.1 32.2 31.6

[Comparative Example 1] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of the polypropylene resin A to the organic peroxide masterbatch α was set to polypropylene resin A:organic peroxide masterbatch α=99.0:1.0.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 2.

[Comparative Example 2] The mass ratio of polypropylene resin A and organic peroxide masterbatch α was set to polypropylene resin A: organic peroxide masterbatch α = 87.5:12.5. In addition, a long-fiber nonwoven fabric was obtained by the same method as in Example 1. However, due to the low strength and the sheet breaking during the winding step, the long-fiber nonwoven fabric could not be obtained.

The zero shear viscosity and the content of organic peroxide were measured for the broken pieces of the sheet, and the results are shown in Table 2.

[Comparative Example 3] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the polypropylene resin B was fed into an extruder at 260°C and supplied to a gear pump.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 2.

[Comparative Example 4] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of polypropylene resin E to organic peroxide masterbatch α was set to polypropylene resin E: organic peroxide masterbatch α = 90.0:10.0. A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of polypropylene resin E to organic peroxide masterbatch α was set to 90.0:10.0.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 2.

[Comparative Example 5] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of polypropylene resin F to organic peroxide masterbatch α was set to polypropylene resin F: organic peroxide masterbatch α = 92.5:7.5.

The evaluation results of the obtained long fiber nonwoven fabric are shown in Table 2.

[Table 2] [Table 2] Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Raw material resin Polypropylene resin[1] PP-A PP-A PP-B PP-E PP-F Organic peroxide masterbatch[2] MB-α MB-α - MB-α MB-α The mixing ratio of [1] and [2] (mass ratio, [1]: [2]) 99.0:1.0 87.5:12.5 (100:0) 90.0:10.0 92.5:7.5 Addition amount of organic peroxide [mass %] 0.10 1.25 0 1.00 0.75 Step Pass Can No Can Can Can Fiber Average fiber diameter [μm] 0.68 - 0.62 1.42 1.38 Long fiber nonwoven fabric Zero shear viscosity at 190℃ [Pa·s] 11.7 4.2 12.0 19.1 18.6 Content of organic peroxides [ppm] 98 368 0 296 229 M 75000 40000 76000 82000 80000 Mw/Mn 3.89 2.79 2.35 2.62 2.89 Weight per unit area [g/m ² ] 20 - 20 20 20 Void ratio [%] 91.1 - 89.6 90.3 89.1 Particle collection efficiency [%] 61 - 65 61 64 Air permeability [cm ³ / (cm ² ·s)] 15.6 - 12.6 20.2 18.8

The nonwoven fabrics described in Examples 1 to 6 were excellent in both particle collection efficiency and air permeability. In contrast, among the comparative examples, the nonwoven fabrics described in Comparative Examples 1, 3, 4, and 5, which obtained nonwoven fabrics, had particle collection efficiency equivalent to that of the nonwoven fabrics described in Examples 1 to 6, but had poor air permeability. In Comparative Example 2, the sheet broke during the winding step, and the nonwoven fabric could not be obtained.

1: Sample holder 2: Dust collection box 3: Flow meter 4: Flow regulating valve 5: Blower 6: Particle counter 7: Switching cock M: Measurement sample

FIG. 1 is a cross-sectional conceptual diagram for illustrating and explaining a collection efficiency measuring device for measuring the particle collection efficiency of a long-fiber nonwoven fabric of the present invention.

1: Sample holder

2: Dust collection box

3: Flow meter

4: Flow regulating valve

5: Blower

6: Particle counter

7: Switch the cock

M:Measurement sample

Claims (12)

A long fiber nonwoven fabric includes fibers containing a polypropylene resin, wherein the average fiber diameter of the fibers in the long fiber nonwoven fabric is greater than or equal to 0.05 μm and less than or equal to 5.00 μm, and the zero shear viscosity of the long fiber nonwoven fabric at 190° C. is greater than or equal to 5 Pa·s and less than or equal to 10 Pa·s. The long-fiber nonwoven fabric according to claim 1, wherein the long-fiber nonwoven fabric contains 100 ppm or more and 1000 ppm or less of an organic peroxide having a structure represented by the following general formula (1) or general formula (2); Here, R ₁ to R ₃ and R ₅ to R ₇ are alkyl, alkenyl, phenyl, benzyl or benzoyl groups having 1 to 10 carbon atoms, and R ₄ and R ₈ are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms. The long fiber nonwoven fabric according to claim 1 or 2, wherein the molecular weight distribution Mw/Mn of the polypropylene resin determined by gel permeation chromatography is 2.00 or more and 4.00 or less. The long fiber nonwoven fabric according to claim 1 or 2, wherein the porosity of the long fiber nonwoven fabric is 92.5% or more and 99.0% or less. A laminate having at least one layer comprising the long-fiber nonwoven fabric as described in claim 1 or 2. A filter using the long-fiber nonwoven fabric as claimed in claim 1 or 2. A protective clothing using the long-fiber nonwoven fabric as described in claim 1 or 2. A face mask using the long-fiber nonwoven fabric as described in claim 1 or 2. A method for producing a long-fiber nonwoven fabric comprises: melting a raw material resin composition obtained by adding an organic peroxide having a structure represented by the following general formula (1) or (2) to a polypropylene resin having a melt flow rate of 500 g/10 minutes or more and 2000 g/10 minutes or less to obtain a molten resin; and subjecting the molten resin to a melt-blowing method to obtain a long-fiber nonwoven fabric; Here, R ₁ to R ₃ and R ₅ to R ₇ are alkyl, alkenyl, phenyl, benzyl or benzoyl groups having 1 to 10 carbon atoms, and R ₄ and R ₈ are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms. The method for producing a long-fiber nonwoven fabric as described in claim 9, wherein the molten resin is obtained by reacting the polypropylene-based resin with the organic peroxide in an extruder for supplying raw materials to a spinning machine for performing the melt-blowing method. The method for producing a long-fiber nonwoven fabric according to claim 9 or 10, wherein the organic peroxide is added in the form of a masterbatch obtained by kneading a polypropylene-based resin and the organic peroxide. The method for producing a long-fiber nonwoven fabric according to claim 9 or 10, wherein the amount of the organic peroxide added to the raw resin composition is 0.2 mass % or more and 1.0 mass % or less.

Images