Long-fiber non-woven fabric, method for producing same, laminate, filter, protective clothing, and mask

Abstract

The present invention provides a non-woven fabric having both excellent particle collection efficiency and air permeability, and the main object of the present invention is a long-fiber non-woven fabric comprising fibers containing a polypropylene-based resin, the fibers having an average fiber diameter of 0.05-5.00 [mu] m inclusive, and the average fiber diameter of the fibers being less than 0.05 [mu] m and less than 5.00 [mu] m, and the average fiber diameter of the fibers being less than 0.05 [mu] m and less than 5.00 [mu] m. The long fiber non-woven fabric has a zero shear viscosity at 190 DEG C of from 5 Pa * s to 10 Pa * s (inclusive).

Description

Technical Field

[0001] The invention relates to a long-fiber nonwoven fabric and a method for making the same. Background Art

[0002] In recent years, fibers or 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 be extremely fine in order to improve particle capture efficiency and liquid barrier properties.

[0003] For example, the technology disclosed in Patent Document 1 proposes 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 as a polypropylene capable of producing a melt-blown nonwoven fabric containing ultrafine fibers with good productivity. In addition, the technologies disclosed in Patent Documents 2 to 4 propose a nonwoven fabric having a number average fiber diameter or a pore diameter of the nonwoven fabric set within a specific range.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2002-201560

[0007] Patent Document 2: Japanese Patent Application Publication No. 2016-053241

[0008] Patent Document 3: International Publication No. 2012 / 014501

[0009] Patent Document 4: International Publication No. 2016 / 148174 Summary of the invention

[0010] Problems to be solved by the invention

[0011] The technology disclosed in Patent Document 1 has the following problems: Since polypropylene with a relatively high melt flow rate is used, the fibers are not easily solidified in the spinning process. When high-speed spinning is performed to improve production efficiency, the nonwoven fabric is not cooled in time when it is made into 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 to be less than a certain value, the distance between the spinning machine and the collection part is shortened. Therefore, when the fibers in the collection part are welded, 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. Furthermore, the technique disclosed in Patent Document 4 has a problem that the ejection amount of resin per spinning nozzle is extremely reduced in order to obtain fibers with a finer average fiber diameter, so ejection tends to be unstable and the uniformity of the nonwoven fabric tends to decrease.

[0012] Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a nonwoven fabric having both excellent particle collection efficiency and air permeability.

[0013] Technical means of solving problems

[0014] Patent document 1 states that as a particularly preferred polypropylene resin, a polypropylene resin obtained by degradation of polypropylene having a melt flow rate (hereinafter, sometimes abbreviated as "MFR") of 20 g / 10 minutes or less is preferred. However, the inventors and others conducted research and found that such nonwoven fabrics tend to easily cut off polypropylene with longer molecular chains in the polypropylene during the degradation process, so the fibers are not easy to solidify during the spinning process, and the nonwoven fabrics are formed densely when made, and the air permeability is sometimes reduced. Therefore, further efforts were repeated and it was found that by setting the average fiber diameter of the propylene resin fibers constituting 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.

[0015] The present invention has been accomplished based on these findings, and the present invention can provide the following inventions.

[0016] [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.

[0017] [2] The long-fiber nonwoven fabric according to [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).

[0018] [Chemistry 1]

[0019]

[0020] [Chemistry 2]

[0021]

[0022] Here, R1 to R3 and R5 to R7 are alkyl groups, alkenyl groups, phenyl groups, benzyl groups or benzoyl groups having 1 to 10 carbon atoms, and R4 and R8 are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms.

[0023] [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.

[0024] [4] The long-fiber nonwoven fabric according to [1] or [2], wherein the porosity of the long-fiber nonwoven fabric is 92.5% or more and 99.0% or less.

[0025] [5] A laminate having at least one layer comprising the long-fiber nonwoven fabric according to any one of [1] to [4] above.

[0026] [6] A filter using the long-fiber nonwoven fabric according to any one of [1] to [4].

[0027] [7] A protective clothing comprising the long-fiber nonwoven fabric according to any one of [1] to [4].

[0028] [8] A mask using the long-fiber nonwoven fabric according to any one of [1] to [4].

[0029] [9] A method for producing a long-fiber nonwoven fabric, comprising: 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 blown method to obtain a long-fiber nonwoven fabric.

[0030] [Chemistry 3]

[0031]

[0032] [Chemistry 4]

[0033]

[0034] Here, R1 to R3 and R5 to R7 are alkyl groups, alkenyl groups, phenyl groups, benzyl groups or benzoyl groups having 1 to 10 carbon atoms, and R4 and R8 are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms.

[0035]

[10] The method for producing a long-fiber nonwoven fabric according to [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.

[0036]

[11] The method for producing a long-fiber nonwoven fabric according to [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.

[0037]

[12] The method for producing a long fiber nonwoven fabric according to any one of [9] to

[11] , wherein the amount of the organic peroxide added to the raw resin composition is 0.2% by mass or more and 1.0% by mass or less.

[0038] Effects of the Invention

[0039] According to the present invention, a long-fiber nonwoven fabric which can efficiently capture particles and has excellent air permeability and is suitable for use as a filter, a dust collecting layer or a water-resistant layer of a mask or protective clothing can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] [ Figure 1 ] Figure 1 This is a cross-sectional conceptual diagram for illustrating and explaining a collection efficiency measuring device for measuring the particle collection efficiency of the long-fiber nonwoven fabric of the present invention. DETAILED DESCRIPTION

[0041] The nonwoven fabric of the present invention is a long-fiber nonwoven fabric comprising fibers containing a polypropylene resin, wherein 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 are described in detail below, but the present invention is not limited to the scope described below as long as it does not exceed the gist of the present invention.

[0042] [Polypropylene resin]

[0043] 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 the 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 is formed.

[0044] 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 hydrocarbons having double bonds at the α position such as ethylene, 1-butene, 1-hexene, 1-octene, 1-decene, and 1-dodecene. In addition, the polypropylene resin in the present invention may also contain other polymers such as polyethylene terephthalate, polyethylene, or polystyrene within the range of the molar fraction of the propylene unit not departing from the range of 80 mol % to 100 mol %.

[0045] In the present invention, the mole fraction (mol %) of the propylene unit in the repeating unit means the mole fraction determined as follows.

[0046] 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 the long-fiber nonwoven fabric, and the mixture was heated to 135°C to dissolve. 13 C-nuclear magnetic resonance (NMR) measurement, the peak area due to propylene unit and the peak area due to repeating units other than propylene unit are calculated from the NMR spectrum. The molar fraction (mol %) of propylene unit in all repeating units constituting the polypropylene resin is calculated from the peak area ratio of propylene unit to repeating units other than propylene unit, and the first decimal place is rounded off.

[0047] The polypropylene resin in the present invention may also contain various additives such as inorganic substances such as titanium oxide, silicon dioxide, barium oxide, calcium carbonate, carbon black, colorants such as dyes or pigments, flame retardants, fluorescent whitening agents, antioxidants, charge stabilizers, antistatic agents or ultraviolet absorbers.

[0048] In the long fiber nonwoven fabric of the present invention, the melting point of the polypropylene resin is preferably 140° C. to 170° C. The polyolefin resin having a melting point within the above range has excellent strength when made into fibers and is less likely to break during the manufacturing process, so the obtained long fiber nonwoven fabric can be obtained with fewer defects.

[0049] In addition, the melting point of the polypropylene resin in the present invention means a melting point determined as follows.

[0050] First, about 2 mg is taken from any position of the long-fiber nonwoven fabric and placed in a differential scanning calorimeter. In a nitrogen environment, the temperature is raised to 250°C at a heating rate of 10°C / min to melt, and then the temperature is lowered to 20°C by air cooling. Secondly, for the sample that has become solid again, a differential scanning calorimetry is performed 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) is taken as the melting point. In addition, when multiple endothermic peaks are seen, the temperature of the top of the peak with the largest endothermic amount is taken as the melting point.

[0051] In the long fiber nonwoven fabric of the present invention, the crystalline fusion heat of the polypropylene resin is preferably 75 J / g or more and 150 J / g or less. A polypropylene resin having a crystalline fusion heat within the above range is preferred because it has excellent processability when made into a long fiber nonwoven fabric.

[0052] In addition, the crystalline fusion heat of the polypropylene resin in the present invention means the crystalline fusion heat determined as follows.

[0053] First, about 2 mg was taken from any position of the long-fiber nonwoven fabric 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. Secondly, for the sample that has become solid again, a differential scanning calorimeter was measured in a nitrogen environment at a heating rate of 10°C / min and a measurement temperature range of 50°C to 250°C, and the crystal melting heat was calculated based on the area of ​​the endothermic peak in the obtained measurement result (DSC curve). In addition, when multiple endothermic peaks are seen, the crystal melting heat is calculated based on the value obtained by adding up the areas of all endothermic peaks.

[0054] 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 during the spinning process. 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 is formed.

[0055] 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 adhesiveness 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 when made into a long fiber nonwoven fabric is improved.

[0056] In addition, in the present invention, Mw and Mn are values ​​measured and calculated by the following method.

[0057] (1) Randomly sample 5 test pieces of 5 mg each from the area excluding the end portions of the long fiber nonwoven fabric. The end portions of the long fiber nonwoven fabric refer to the area that is 10% of the length of both ends in the width direction of the long fiber nonwoven fabric.

[0058] (2) 5 mL of 1,2,4-trichlorobenzene (e.g., manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is added to the test piece obtained in (1), and the solution is dissolved by heating at 165°C for 20 minutes. The solution is then 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.

[0059] (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, Mw and Mn are determined by analyzing the elution curve in GPC using "Empower" manufactured by Wyatt Technology.

[0060] ‧Device: For example, the "PL-220" manufactured by Polymer Laboratories

[0061] ‧Detector: Differential refractive index detector RI

[0062] ‧Column: Shodex HT-G (guard column) + Shodex HT-806M × 2 pieces (8.0 mm × 30 cm, such as Showa Denko Co., Ltd.)

[0063] ‧Solvent: 1,2,4-trichlorobenzene (add 0.1% BHT)

[0064] ‧Flow rate: 1.0 mL / min

[0065] ‧Column temperature: 145℃

[0066] ‧Injection volume: 0.20 mL

[0067] ‧Standard samples: monodisperse polystyrene (for example, manufactured by Tosoh Co., Ltd., etc.), bibenzyl (for example, manufactured by Tokyo Chemical Industry Co., Ltd., etc.).

[0068] [fiber]

[0069] 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. The lower limit of the range of the average fiber diameter is greater than 0.05 μm, preferably greater than 0.08 μm, and more preferably greater than 0.20 μm, thereby forming a long fiber nonwoven fabric with higher tensile strength and excellent process stability during winding or unwinding. On the other hand, the upper limit of the range of the average fiber diameter is less than 5.00 μm, preferably less than 2.00 μm, more preferably less than 1.00 μm, and further preferably less than 0.50 μm, so that the specific surface area of ​​the long fiber nonwoven fabric is increased, thereby forming a long fiber nonwoven fabric with excellent particle capture efficiency.

[0070] In addition, 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 of 10 mm × 5 mm measurement samples, and a scanning electron microscope (SEM, such as "S-5500" manufactured by Hitachi High-technologies Co., Ltd.) is used. From the cut measurement sample, one surface photo of the long fiber non-woven fabric is taken at a magnification of 5000 times to obtain a total of 15 photos. For all fibers in the photo where the width of the fiber side can be clearly confirmed, the width (μm) is measured, and the value obtained by rounding off the third decimal place of the value obtained by arithmetic average. In addition, even if the cross-sectional shape of the fiber is a flat cross-section or a non-shaped cross-section, the width of the fiber side is regarded as the fiber diameter for measurement as described above.

[0071] The fibers constituting the long fiber nonwoven fabric of the present invention may have a flat cross section or a deformed cross section, preferably a circular cross section. The circular cross section improves the spinning properties and makes yarn breakage less likely to occur.

[0072] [Long fiber nonwoven fabric]

[0073] The long-fiber nonwoven fabric of the present invention contains 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 is a long-fiber nonwoven fabric excluding a nonwoven fabric (short-fiber nonwoven fabric) containing only fibers cut into a certain length (e.g., 100 mm).

[0074] The long fiber nonwoven fabric of the present invention has a zero shear viscosity of 5 Pa·s or more and 10 Pa·s or less at 190°C. 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 it is made into a long fiber nonwoven fabric, 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.

[0075] In the present invention, the zero shear viscosity of the long-fiber nonwoven fabric refers to a value measured and calculated as follows.

[0076] (1) Take two test pieces from any position of the long-fiber nonwoven fabric. At this time, the amount taken is set to be enough to fill the space between the parallel plates of the rheometer described later, that is, enough 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 according to the specifications of the measuring device.

[0077] (2) Using a rheometer set at 190°C (e.g., "Reosol G3000" manufactured by UBM Co., Ltd.), parallel plates are provided with one of the test pieces, 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.

[0078] (3) A linear approximation is performed on the relationship between the value obtained by averaging the results obtained from the two test pieces at each angular frequency and the angular frequency.

[0079] (4) The value of the melt viscosity calculated by extrapolating the approximate formula obtained by linear approximation to 0 rad / sec was defined as the zero shear viscosity.

[0080] 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.

[0081] 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) at a ratio of 100 ppm to 1000 ppm.

[0082] [Chemistry 5]

[0083]

[0084] [Chemistry 6]

[0085]

[0086] Here, R1 to R3 and R5 to R7 are alkyl groups, alkenyl groups, phenyl groups, benzyl groups or benzoyl groups having 1 to 10 carbon atoms, and R4 and R8 are structures having 1 to 20 carbon atoms and containing only hydrogen atoms other than carbon atoms.

[0087] 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 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.

[0088] Examples of the organic peroxide include dialkyl peroxides such as "di-tert-butyl peroxide, diisopropylbenzene peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne-3, and α,α'-bis(tert-butylperoxy)diisopropylbenzene" and peroxyketals such as "1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane and 2,2-bis(tert-butylperoxy)butane".

[0089] In the present invention, the content of the organic peroxide refers to a value measured and calculated by the following method.

[0090] (1) Randomly sample 5 test pieces of 25 mg each from the area excluding the end portions of the long-fiber nonwoven fabric. The end portions of the nonwoven fabric refer to the area that is 10% of the length of both ends in the width direction of the nonwoven fabric.

[0091] (2) The test piece obtained in (1) is immersed in a chloroform / methanol solvent having a volume ratio of 1:1, and is subjected to ultrasonic treatment for 15 minutes at 45 kHz to dissolve the test piece. For example, an ultrasonic cleaner "VS-100 III" manufactured by ASONE Co., Ltd. can be used for the ultrasonic treatment. 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.

[0092] (3) The solution after ultrasonic treatment obtained in (2) is filtered using a polytetrafluoroethylene (PTFE) filter (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.).

[0093] (4) 0.1 g of an organic peroxide is dissolved in 10 mL of a chloroform / methanol solution having a volume ratio of 1:1 to prepare a standard stock solution (10 μg / mL). Then, standard solutions of various concentrations (0.1 μg / mL, 0.2 μg / mL, 0.5 μg / mL, 1.0 μg / mL) are prepared by diluting the standard stock solution with the chloroform / methanol solution. In this case, the following organic peroxides can be listed as the organic peroxides, and a standard solution of each concentration is prepared for each organic peroxide. In addition, in the case where it is clearly found by other methods (for example, iodine titration, polarography, etc.) that an organic peroxide having a structure represented by the general formula (1) or the general formula (2) other than the organic peroxides described below is contained or it is presumed that the organic peroxide is at least contained, a standard solution of the organic peroxide is also prepared.

[0094] ‧Di-tert-butyl peroxide

[0095] ‧Diisopropylbenzene peroxide

[0096] ‧2,5-Dimethyl-2,5-bis(tert-butylperoxy)hexane

[0097] ‧2,5-Dimethyl-2,5-bis(tert-butylperoxy)hexyne-3

[0098] ‧α,α'-Bis(tert-butylperoxy)diisopropylbenzene

[0099] ‧1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane

[0100] ‧2,2-Bis(tert-butylperoxy)butane

[0101] (5) The sample solution was subjected to liquid chromatography-tandem mass spectrometry (LC / MS / MS) under the following conditions.

[0102] ‧High performance liquid chromatograph (HPLC): such as the "LC-20A" manufactured by Shimadzu Corporation

[0103] ‧Mass spectrometer (MS): such as the "API4000" manufactured by Sciex

[0104] ‧Column: ODS series column (e.g. "SUMIPAX ODS A series" manufactured by Sumika Analytical Center Co., Ltd.)

[0105] ‧Mobile phase: 0.1% formic acid aqueous solution + methanol (gradient extraction conditions)

[0106] ‧Injection volume: 5 μL

[0107] ‧Ionization: electrospray ionization (ESI)

[0108] (6) The organic peroxide was identified by mass spectrometry (MS) of each sample solution, and the amount of the organic peroxide (ppm) was quantified based on the peak area using a calibration curve obtained from a standard solution of the organic peroxide.

[0109] (7) The arithmetic mean (ppm) of the values ​​measured for each test piece was rounded off to the nearest whole number to determine the amount of organic peroxide (ppm).

[0110] The content of the 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.

[0111] The long fiber nonwoven fabric of the present invention preferably has a unit area weight of 5 g / m 2 Above and 100 g / m 2 The weight per unit area of ​​the long fiber nonwoven fabric is preferably 5 g / m 2 More preferably 7 g / m 2 More preferably, 10 g / m 2 In addition, the weight per unit area of ​​the long fiber nonwoven fabric is preferably 100 g / m 2Below, more preferably 70 g / m 2 Below, more preferably 50 g / m 2 Next, a long-fiber nonwoven fabric is formed which is easy to perform lamination processing or sewing processing.

[0112] In addition, the weight per unit area (g / m 2 ) is calculated based on "6.2 Mass per unit area" of Japanese Industrial Standards (JIS) L1913:2010 "Test methods for general nonwoven fabrics".

[0113] A 20 cm × 25 cm test piece was cut out from the nonwoven fabric. Three pieces were taken for every 1 m of the nonwoven fabric width and their respective masses (g) were weighed under the standard state. The mass per 1 m was calculated from the arithmetic mean of the measured values. 2 Mass (g / m 2 ), rounding off the first decimal place.

[0114] 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 good.

[0115] Here, the porosity (%) of the nonwoven fabric in the present invention means a porosity determined as follows.

[0116] 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 surface at a magnification of 12 times so that the nonwoven fabric is included 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 height obtained by averaging the 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 method, and the density of the raw material used in the nonwoven fabric, is rounded to the second decimal place.

[0117] Void ratio (%) = [1-(unit area weight / thickness / density)] × 100

[0118] The long-fiber nonwoven fabric of the present invention may be subjected to electret processing. The electret processing is performed by the method described below, thereby improving the particle collection efficiency without impairing the air permeability.

[0119] [Manufacturing method of long fiber nonwoven fabric]

[0120] Next, a preferred embodiment of producing the long-fiber nonwoven fabric of the present invention will be specifically described, but the present invention is not limited thereto.

[0121] The method for producing a long-fiber nonwoven fabric of the present invention preferably comprises: a step of melting a raw 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 a raw resin) to obtain a molten resin; and a step of subjecting the molten resin to a melt-blowing method to obtain a long-fiber nonwoven fabric.

[0122] (a) A step of melting a raw material resin composition obtained by adding an organic peroxide to a raw material resin to obtain a molten resin

[0123] In the method for manufacturing a long-fiber nonwoven fabric of the present invention, first, an organic peroxide is added to a raw material resin, and the raw material resin is decomposed to obtain a molten resin. The raw material 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. Since the amount of organic peroxide added to decompose the polypropylene resin becomes large, the amount of organic peroxide remaining unreacted becomes excessive, so the yarn breaks 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, so they are difficult to operate in an extruder, and the supply becomes unstable compared to those in the form of fragments or particles, and the spinning performance is sometimes reduced.

[0124] In the present invention, the melt flow rate (g / 10 minutes) of the polypropylene resin refers to a value 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 “8A 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 thermoplastics - Part 1: Standard test methods”.

[0125] In addition, various additives such as inorganic substances such as titanium oxide, silicon dioxide, barium oxide, calcium carbonate, carbon black, colorants such as dyes or pigments, flame retardants, fluorescent whitening agents, antioxidants, charge stabilizers, antistatic agents or ultraviolet absorbers can be added to the raw resin used in the method for manufacturing the long fiber nonwoven fabric of the present invention within the range that does not impair the effects of the present invention.

[0126] Examples of the organic peroxide used in the method for producing the long-fiber nonwoven fabric of the present invention include the organic peroxides described in [Long-fiber nonwoven fabric].

[0127] 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 or the like.

[0128] Moreover, as a method for obtaining a molten resin by adding the organic peroxide to the raw material resin, it is preferred to react in an extruder for supplying raw materials to a spinning machine. Here, the so-called spinning machine refers to the spinning machine used in the "process of implementing a melt-blowing method to obtain a long-fiber nonwoven fabric" described later. For example, the raw material resin and the organic peroxide are simultaneously put into the extruder by dry blending or separate measurement, and kneaded by using an extruder for supplying raw materials to the spinning machine, thereby continuously obtaining a molten resin obtained by adding the organic peroxide to the raw material resin, and continuously supplying the raw material to the spinning machine, thereby simplifying the process. As other methods for obtaining a molten resin by adding the raw material resin and the organic peroxide, there are the following methods: before being put into the extruder for supplying raw materials to the spinning machine, the organic peroxide is kneaded in the raw material resin in advance by an extruder independent of the spinning machine and granulated, and the granules are put into the extruder for supplying raw materials to the spinning machine for melting.

[0129] When the raw material resin and the organic peroxide are simultaneously introduced into an extruder for kneading, the temperature of the extruder is preferably above (melting point of the raw material resin + 20° C.) and below (melting point of the raw material resin + 60° C.). That is, it can be said that approximately 180° C. to 220° C. is a preferred 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.

[0130] In addition, the organic peroxide is preferably kneaded with a polypropylene resin in advance to produce a masterbatch, and the masterbatch is added to the raw resin to obtain a molten resin. As the polypropylene resin used to produce 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 to localize the organic peroxide, and even if it is kneaded for a short time, the viscosity of the polypropylene resin can be uniformly reduced.

[0131] The amount of organic peroxide added to the raw material resin is preferably 0.20% by mass or more and 1.0% by mass or less of the whole raw material. By setting the added amount to preferably 0.20% by 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 preferably 1.0% by mass or less, more preferably 0.90% by mass or less, and further preferably 0.80% by mass or less, the spinning property is improved, and a high-quality long-fiber nonwoven fabric can be obtained.

[0132] 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 to be above 190°C, the viscosity of the spun molten resin is reduced, which can promote the ultrafineness of the fiber. In addition, by setting the spinning temperature preferably to be 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 the tensile strength when made into a long-fiber nonwoven fabric can be improved.

[0133] (b) Process of melt-blowing the molten resin to obtain a long-fiber nonwoven fabric

[0134] The meltblowing method is a method of forming fibers by blowing raw materials from a meltblowing die with a predetermined aperture, spraying hot air at a certain angle to the blowing portion to extremely fine the fibers, and causing the extremely fine fibers to accumulate in a collecting portion to form a long-fiber nonwoven fabric.

[0135] The die mouth in 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 process stability in the spinning process, so it is preferred. In the case of a circular ejection hole, its diameter is preferably 0.08 mm to 1.0 mm. By making the diameter of the ejection hole preferably greater than 0.08 mm, more preferably greater than 0.10 mm, it is not easy to cause hole clogging, and productivity is improved. In addition, by making the diameter of the ejection hole preferably less than 1.0 mm, more preferably less than 0.70 mm, and further preferably less than 0.50 mm, the distribution of the resin inside the die mouth is improved, and a uniform nonwoven fabric can be manufactured.

[0136] 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 making the single hole ejection amount of the molten resin 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 making the single hole ejection amount of the molten resin 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 fine, and the collection efficiency when made into an air filter is improved.

[0137] In the present invention, the distance from the die opening to the collection part is preferably 3 cm to 100 cm. By setting the distance from the die opening to the collection 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 texture and uniformity can be obtained.

[0138] In addition, the method of manufacturing a long fiber nonwoven fabric by meltblowing has been described so far, but of course, a long fiber nonwoven fabric can also be formed by spunbonding. The spunbonding method is a method of manufacturing a long fiber nonwoven fabric by spinning a molten resin through a die, cooling and solidifying it, stretching the obtained yarn, capturing it on a moving net to form a fiber net, and then performing a heat bonding process.

[0139] When the long fiber nonwoven fabric of the present invention is manufactured by the spunbond method, it is preferred that the diameter of the ejection hole of the die used is set to be greater than 0.10 mm and less than 0.20 mm, and spinning is performed 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.

[0140] (c) Electret processing and post-processing

[0141] In the method for manufacturing the long-fiber nonwoven fabric of the present invention, it is also preferred to perform electret processing. Specifically, for example, the following methods can be used: a method in which the fiber sheet accumulated on the collection part through the above process is brought into contact with the ground electrode, the ground electrode is moved together with the fiber sheet, and high voltage is applied by a non-contact type application electrode, and the electret processing is continuously performed to obtain the long-fiber nonwoven fabric; a method in which a jet of water or a stream of water droplets is sprayed on the fiber sheet at a pressure sufficient to allow the water to penetrate into the fiber sheet and electretized to uniformly mix positive and negative charges to obtain the long-fiber nonwoven fabric; or a method in which the fiber sheet is passed through a slit-shaped nozzle, water is sucked by the nozzle, and the water is penetrated into the fiber sheet, thereby obtaining the long-fiber nonwoven fabric uniformly mixed with positive and negative charges (hydraulic charging method). Among these methods, the hydraulic charging method is preferably used in terms of excellent collection performance during electretization.

[0142] In addition, in the method for producing the long-fiber nonwoven fabric of the present invention, post-processing such as antibacterial processing or pleating processing may be performed in combination with the application of the long-fiber nonwoven fabric.

[0143] [Laminated body]

[0144] Since the long fiber nonwoven fabric of the present invention has the above-mentioned characteristics, it can be made into a laminate having at least one layer of long fiber nonwoven fabric. In particular, a laminate having a structure in which spunbonded nonwoven fabrics are laminated on both sides of the long fiber nonwoven fabric of the present invention (structure of spunbonded nonwoven fabric / long fiber nonwoven fabric of the present invention / spunbonded nonwoven fabric) is suitable for use as a mask or protective clothing. The following specifically describes a preferred form of a method for laminating the long fiber nonwoven fabric of the present invention with a spunbonded nonwoven fabric.

[0145] 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 long fiber nonwoven fabric can be directly formed by meltblowing after the spunbond nonwoven fabric is formed.

[0146] In addition, as a method for thermally bonding the spunbonded nonwoven fabric and the long fiber nonwoven fabric of the present invention, there can be listed: a method of thermally bonding by various rollers such as a heat embossing roller with engravings (concavoconvex parts) on the surfaces of a pair of upper and lower rollers, a heat embossing roller comprising a combination of a roller with a flat (smooth) surface and a roller with an engraving (concavoconvex part) on the surface of the other roller, and a heat calendering roller comprising a combination of a pair of flat (smooth) rollers; or an ultrasonic bonding method such as thermal fusion bonding by ultrasonic vibration of a horn. Among them, in terms of excellent productivity, imparting strength to a portion of the thermal bonding portion, and maintaining the skin touch or breathability of the nonwoven fabric in the portion other than the partial thermal bonding portion (non-bonding portion), a preferred form is to use a heat embossing roller with engravings (concavoconvex parts) on the surfaces of a pair of upper and lower rollers, or a heat embossing roller comprising a combination of a roller with a flat (smooth) surface and a roller with an engraving (concavoconvex part) on the surface of the other roller.

[0147] The surface material of the heat embossing roll is preferably made of metal in order to obtain a sufficient effect due to thermal bonding and prevent the engraving (concavoconvex part) of one embossing roll from being transferred to the surface of the other roll.

[0148] The embossing bonding area ratio caused by this kind of 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 for practical use 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.

[0149] The embossed bonding area ratio mentioned here refers to the proportion of the heat-bonded part in the whole laminated nonwoven fabric. Specifically, when heat bonding is performed by a pair of rollers with convex and concave parts, it refers to the proportion of the part (heat-bonded 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 in the whole laminated nonwoven fabric. In addition, when heat bonding is performed by a roller with convex and concave parts and a flat roller, it refers to the proportion of the part (heat-bonded part) where the convex part of the roller with convex and concave parts abuts against the nonwoven fabric layer in the whole laminated nonwoven fabric. Furthermore, when ultrasonic bonding is performed, it refers to the proportion of the part (heat-bonded part) that is heat-fused by ultrasonic processing in the whole laminated nonwoven fabric.

[0150] As the shape of the heat-bonded portion formed by the heat embossing roller 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 deviation of the strength of the laminated nonwoven fabric can be reduced.

[0151] The surface temperature of the heat embossing roller during heat bonding is preferably set to (melting point of the used polypropylene resin - 50°C) or more and (melting point of the used polypropylene resin - 15°C) or less. By setting the lower limit of the surface temperature of the heat embossing roller to preferably -50°C or more relative to the melting point of the used polypropylene resin, and more preferably -45°C or more relative to the melting point of the used polypropylene resin, 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 less relative to the melting point of the used polypropylene resin, and more preferably -20°C or less relative to the melting point of the used polypropylene resin, excessive heat bonding can be suppressed, and a laminated nonwoven fabric with high air permeability can be obtained.

[0152] 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 with respect to the lowest temperature among the observed melting points.

[0153] The linear pressure of the heat embossing roll during heat bonding is preferably 10 N / cm or more and 500 N / cm or less. By setting the linear pressure of the roll to 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, 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 roll to 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.

[0154] 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 by the heat embossing roller, heat pressing can be performed by a heat calendering roller including a pair of upper and lower flat rollers. The pair of upper and lower flat rollers refers to a metal roller or an elastic roller having no uneven surface, and can be configured by pairing a metal roller with a metal roller, or by pairing a metal roller with an elastic roller.

[0155] In addition, the elastic roller in the present invention refers to a roller made of a material with high elasticity compared to a metal roller, for example, a paper roller made of paper, cotton, and aromatic polyamide paper; or a resin roller made of urethane resin, epoxy resin, silicone resin, polyester resin, hard rubber, and a mixture of these.

[0156] Functional agents may be added to the laminate of the present invention. Examples of the 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.

[0157] The method for imparting the functional agent is not particularly limited, and for example, impregnation, spraying, a touch roll, etc. may be used.

[0158] [Filters, protective clothing, masks]

[0159] The long-fiber nonwoven fabric of the present invention can be widely used in filters, medical and sanitary materials, daily materials, industrial materials, etc., and 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.

[0160] Example

[0161] Next, the present invention will be described in detail based on examples. However, the present invention is not limited to these examples. In addition, the measurements of various physical properties that are not particularly described are measured based on the above methods.

[0162] [Measurement method]

[0163] (1) Process passability

[0164] The case where there is no yarn breakage in the spinning process or no sheet breakage in the winding process and the nonwoven fabric can be stably obtained is marked as "OK", and the case where the yarn breakage occurs in the spinning process or the sheet breakage occurs in the winding process and the long-fiber nonwoven fabric cannot be stably obtained is marked as "No".

[0165] (2) Weight per unit area

[0166] The measurement was performed based on "6.2 Mass per unit area" of JIS L1913:2010 "General nonwoven fabric test methods".

[0167] (3) Zero shear viscosity of long fiber nonwoven fabrics

[0168] Using "Reosol G3000" manufactured by UBM Co., Ltd. as a rheometer, the measurement was performed as described above using parallel plates having a diameter of 20 mm.

[0169] (4) Average fiber diameter

[0170] The measurement was performed as described above using “S-5500” manufactured by Hitachi High-technologies Co., Ltd. as a scanning electron microscope.

[0171] (5) Content of organic peroxides in long fiber nonwoven fabrics

[0172] The ultrasonic cleaning device "VS-100III" manufactured by ASONE Co., Ltd. was used for the ultrasonic treatment, the "T010A" manufactured by Advantec Toyo Co., Ltd. was used for the PTFE filter, the "LC-20A" manufactured by Shimadzu Corporation was used for the high performance liquid chromatograph (HPLC), the "API4000" manufactured by Sciex was used for the mass spectrometer (MS), and the "SUMIPAX ODS A series" manufactured by Sumika Analytical Center Co., Ltd., which is an ODS series column, was used for the column, and the measurement was performed using the above-mentioned method.

[0173] (6) Porosity of long fiber nonwoven fabric

[0174] The measurement was performed by the above method using “VR-3050” manufactured by KEYENCE Corporation as a 3D microscope.

[0175] (7) Particle collection efficiency of long-fiber nonwoven fabrics

[0176] Samples for measurement of 15 cm × 15 cm in length × width were collected from 5 locations in the width direction of the nonwoven fabric, and for each sample, Figure 1 The capture efficiency measuring device shown in the figure measures the capture efficiency. Figure 1 In the collection efficiency measuring device, a dust collection box (2) is connected to the upstream side of a sample holder (1) in which a measuring 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 measuring sample (M) respectively via a switching cock (7).

[0177] When measuring the collection 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) was placed in the sample holder (1), and the air volume was adjusted using the flow control valve (4) so ​​that the filter passing speed was 6.5 m / min, and the dust concentration was kept at 10,000 / (2.83×10 -4 m 3 ) and more than 40,000 / (2.83×10 -4 m 3 ) below the range (2.83×10 -4 m 3 With 0.01 ft 3 The particle counter (6) (RION Co., Ltd., “KC-01D”) was used to measure the number of dust particles (D) upstream and downstream of the sample (M) three times for each sample. The collection efficiency (%) of particles of 0.3 μm to 0.5 μm was calculated using the following formula in accordance with “5.2 Collection rate test” of JIS K0901:1991 “Shape, size and performance test method for filter materials for collecting dust samples in gas”. The average value of the three samples was taken as the final collection efficiency.

[0178] Collection efficiency (%) = [1-(d / D)] × 100

[0179] (Wherein, d represents the total number of downstream dust measured three times, and D represents the total number of upstream dust measured three times)

[0180] (8) Air permeability of long fiber nonwoven fabrics

[0181] The air permeability evaluation device "FX3340" manufactured by TEXTEST Co., Ltd. was used to measure the air permeability according to "Method A (Fragile method)" described in "8.26 Air permeability" of JIS L1096:2010 "Fabric test methods for woven and knitted fabrics".

[0182] [Polypropylene resin]

[0183] In Examples 1 to 5 and Comparative Examples 1 to 5, the polypropylene resins used as the raw material resins are as follows.

[0184] ‧Polypropylene resin A (expressed as PP-A in Table 1): "HP461X" (trade name) manufactured by LyondellBasell

[0185] ‧Polypropylene resin B (expressed as PP-B in Table 1): "MF650Y" (trade name) manufactured by LyondellBasell

[0186] ‧Polypropylene resin C (expressed as PP-C in Table 1): "HP461Y" (trade name) manufactured by LyondellBasell

[0187] ‧Polypropylene resin D (represented as PP-D in Table 1): "S10CL" (trade name) manufactured by Prime Polymer Co., Ltd.

[0188] ‧Polypropylene resin E (denoted as PP-E in Table 1): "VS200A" (trade name) manufactured by Sun-aroma Co., Ltd.

[0189] ‧Polypropylene resin F (expressed as PP-F in Table 1): "HP5036" (trade name) manufactured by LyondellBasell

[0190] ‧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).

[0191] [Example 1]

[0192] The polypropylene resin A and the organic peroxide masterbatch α were dry-blended at a mass ratio of polypropylene resin A: organic peroxide masterbatch α = 97.5:2.5 to obtain blended chips. When the mass of the entire blended chips was set to 100 mass%, the proportion of the organic peroxide in the blended chips (raw resin composition), that is, the amount of organic peroxide added in the raw resin composition, was 0.25 mass%. The blended chips were put into an extruder for supplying raw materials to a spinning machine at 200° C., and the polypropylene resin A and the organic peroxide were reacted to obtain a molten resin.

[0193] 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 carried out by a melt-blowing method under the conditions of a single-hole ejection amount of 0.05 g / min, a die temperature of 280°C, and a hot air pressure of 0.16 MPa. The fibers were captured by a conveyor arranged 20 cm below the ejection hole and wound up in a roll by a winder, thereby obtaining a long-fiber nonwoven fabric.

[0194] Table 1 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0195] [Example 2]

[0196] 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=95.0:5.0.

[0197] Table 1 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0198] [Example 3]

[0199] 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=92.5:7.5.

[0200] Table 1 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0201] [Example 4]

[0202] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of the polypropylene resin B to the organic peroxide masterbatch α was set to polypropylene resin B:organic peroxide masterbatch=99.0:1.0.

[0203] [Example 5]

[0204] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of the polypropylene resin C to the organic peroxide masterbatch α was set to polypropylene resin C:organic peroxide masterbatch=97.5:2.5.

[0205] Table 1 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0206] [Example 6]

[0207] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of the polypropylene resin D to the organic peroxide masterbatch α was set to polypropylene resin D:organic peroxide masterbatch=92.5:7.5.

[0208] Table 1 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0209] [Table 1]

[0210] [Table 1]

[0211]

[0212] [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=99.0:1.0.

[0213] Table 2 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0214] [Comparative Example 2]

[0215] The long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of polypropylene resin A to organic peroxide masterbatch α was set to 87.5:12.5. However, the long-fiber nonwoven fabric could not be obtained due to low strength and sheet breakage during the winding process.

[0216] The zero shear viscosity and the content of the organic peroxide of each of the broken pieces of the sheet were measured. The results are shown in Table 2.

[0217] [Comparative Example 3]

[0218] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that only the polypropylene resin B was charged into the extruder at 260° C. and supplied to the gear pump.

[0219] Table 2 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0220] [Comparative Example 4]

[0221] A long fiber nonwoven fabric was obtained in the same manner as in Example 1 except that the mass ratio of the polypropylene resin E to the organic peroxide masterbatch α was set to 90.0:10.0.

[0222] Table 2 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0223] [Comparative Example 5]

[0224] A long-fiber nonwoven fabric was obtained by the same method as in Example 1 except that the mass ratio of the polypropylene resin F to the organic peroxide masterbatch α was set to polypropylene resin F:organic peroxide masterbatch=92.5:7.5.

[0225] Table 2 shows the evaluation results of the obtained long-fiber nonwoven fabric.

[0226] [Table 2]

[0227] [Table 2]

[0228]

[0229] 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 poor air permeability. In Comparative Example 2, the sheet broke during the winding process, and the nonwoven fabric could not be obtained.

[0230] Description of Figure Numbers

[0231] 1: Sample holder

[0232] 2: Dust collection box

[0233] 3: Flow meter

[0234] 4: Flow control valve

[0235] 5: Blower

[0236] 6: Particle Counter

[0237] 7: Switch cock

[0238] M: Measurement sample

Claims

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 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 (2). [Chemistry 1] [Chemistry 2] Here, R1 to R3 and R5 to R7 are alkyl groups, alkenyl groups, phenyl groups, benzyl groups or benzoyl groups having 1 to 10 carbon atoms, and R4 and R8 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 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.

4. The long fiber nonwoven fabric according to claim 1 or 2, wherein: The long-fiber nonwoven fabric has a porosity of 92.5% or more and 99.0% or less. 5 . A laminate comprising at least one layer comprising the long-fiber nonwoven fabric according to claim 1 or 2 .

6. A filter using the long-fiber nonwoven fabric according to claim 1 or 2.

7. A protective clothing using the long-fiber nonwoven fabric according to claim 1 or 2.

8. A mask using the long-fiber nonwoven fabric as claimed in claim 1 or 2.

9. A method for producing a long-fiber nonwoven fabric, comprising: melting a raw 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-blowing method to obtain a long-fiber nonwoven fabric. [Chemistry 3] [Chemistry 4] Here, R1 to R3 and R5 to R7 are alkyl groups, alkenyl groups, phenyl groups, benzyl groups or benzoyl groups having 1 to 10 carbon atoms, and R4 and R8 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 according to 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.

11. 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 an organic peroxide.

12. 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% by mass or more and 1.0% by mass or less.

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