meltblown nonwoven fabric

Abstract

The present invention provides a meltblown nonwoven fabric composed of fibers containing a cyclic olefin resin and a method for producing the meltblown nonwoven fabric. The meltblown nonwoven fabric is composed of fibers containing a cyclic olefin resin, wherein the average value of fiber diameters greater than the third quartile of 100 randomly selected fiber diameter data points in a 1000x magnified SEM image, arranged from smallest to largest, is 30 μm or less.

Description

[0001] This application is a divisional application of the application with the application date of August 27, 2018, application number 201880057886.X, and invention name “Meltblown non-woven fabric and its manufacturing method”.

[0002] Related applications

[0003] This application claims the benefit of Japanese Patent Application No. 2017-173124, filed on September 8, 2017, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The present invention relates to a meltblown (MB) nonwoven fabric composed of fibers containing a cyclic olefin resin and having reduced inclusion of thick-diameter fibers, and a method for producing the meltblown (MB) nonwoven fabric. Existing technology

[0005] Cyclic olefin resins have the characteristics of high transparency, high heat resistance, chemical resistance, low solubility of impurities, and low adsorption. Therefore, they can be molded using various methods and used in medical applications such as pharmaceutical packaging materials and test containers, optical applications such as lenses and optical films, and electronic devices.

[0006] For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-210549) describes an electret comprising a resin composition containing a cyclic hydrocarbon polymer. It is disclosed that the electret can be formed into a film, sheet, fiber, nonwoven fabric, or the like, and that a meltblowing method is preferably used to form the nonwoven fabric into the electret.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-210549 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] However, Patent Document 1 describes only the conditions of a general melt-blowing method regarding the method for producing a melt-blown nonwoven fabric, and only films are produced in the examples.

[0012] Therefore, an object of the present invention is to provide a meltblown nonwoven fabric composed of fibers containing a cyclic olefin resin and having suppressed incorporation of coarse fibers, a filter using the meltblown nonwoven fabric, a support for a transdermal drug administration tablet, and a transdermal drug administration tablet (particularly a transdermal absorption agent or patch).

[0013] Another object of the present invention is to provide a method for producing a melt-blown nonwoven fabric composed of fibers containing a cyclic olefin resin, in which the incorporation of crude fibers is suppressed.

[0014] Solutions to Problems

[0015] The inventors of the present invention conducted intensive research to achieve the above-mentioned objectives and found that (i) when a cyclic olefin resin is melt-blown, the mechanical energy applied during resin kneading causes the main chain to decompose, and the decomposed double bonds form new bonds, inducing a phenomenon known as a "mechanochemical reaction" that causes gelation. As a result, MB nonwoven fabrics obtained using cyclic olefin resins produce bead-like agglomerates known as shot. Furthermore, even when shot is not mixed in, fibers thicker than the allowable diameter due to the mechanochemical reaction may still be mixed in, causing defects. Furthermore, (ii) in the melt-blown method, mechanical energy (particularly compressive stress) applied to the resin during kneading in an extruder or feeding to a die easily causes mechanochemical reactions in the resin. Furthermore, further research revealed that (iii) by using a method that minimizes the compression of the resin by reducing the viscosity of the resin melt before introduction into the kneading section, or by reducing the ratio (Q / N) of the ejection amount (Q) of the resin kneaded material to the screw rotation speed (N), an MB nonwoven fabric in which the generation of coarse fibers is suppressed can be obtained, thereby completing the present invention.

[0016] That is, the present invention can be constructed as follows.

[0017] [Method 1]

[0018] A meltblown nonwoven fabric comprising fibers containing a cyclic olefin resin, wherein, in fiber diameter data of 100 points randomly selected from an SEM image magnified 1000 times, the average value of the data having a fiber diameter greater than the third quartile, the data being arranged from the smallest fiber diameter to the largest fiber diameter and divided into four equal parts, is 30 μm or less.

[0019] [Method 2]

[0020] The melt-blown nonwoven fabric according to aspect 1, wherein the cyclic olefin-based resin is a copolymer containing at least norbornene units.

[0021] [Method 3]

[0022] The meltblown nonwoven fabric according to embodiment 1 or 2, wherein the air permeability measured according to JIS L 1906 is 10 to 550 cm 3 / cm 2 ·s.

[0023] [Method 4]

[0024] The meltblown nonwoven fabric according to any one of embodiments 1 to 3 has a weight per unit area of ​​10 to 50 g / m 2 .

[0025] [Method 5]

[0026] The meltblown nonwoven fabric according to any one of aspects 1 to 4, which satisfies the following formula (1):

[0027] 80≤B / A≤800 (1)

[0028] Where A represents thickness (mm), B represents air permeability (cm 3 / cm 2 ·s).

[0029] [Method 6]

[0030] The melt-blown nonwoven fabric according to any one of aspects 1 to 5, wherein the melt-blown nonwoven fabric is composed of fibers having an average fiber diameter of 1 to 15 μm.

[0031] [Method 7]

[0032] A filter using the meltblown nonwoven fabric according to any one of aspects 1 to 6.

[0033] [Method 8]

[0034] A support for a transdermal drug delivery tablet that releases an active ingredient, the support comprising the meltblown nonwoven fabric according to any one of embodiments 1 to 6.

[0035] [Method 9]

[0036] A transdermal drug delivery tablet comprising at least an active ingredient and the support according to embodiment 8.

[0037] [Method 10]

[0038] A method for producing a meltblown nonwoven fabric comprising a cyclic olefin resin, the method comprising at least the following steps:

[0039] a melting step of heating and melting a resin composition containing at least a cyclic olefin resin in a supply section to obtain a resin melt;

[0040] a kneading step of introducing the resin melt into a kneading section and kneading the mixture by rotating a screw under heating to obtain a resin mixture;

[0041] a spraying step of spraying the resin mixture together with air from a nozzle; and

[0042] a collecting step of collecting the filaments ejected from the nozzles on a collecting surface to obtain a net;

[0043] in,

[0044] The viscosity η of the resin melt introduced into the kneading section is 80 to 200 poise.

[0045] [Method 11]

[0046] The method for producing a meltblown nonwoven fabric according to embodiment 10 satisfies the following formula (2):

[0047] 20≤(Q×η) / N≤100 (2)

[0048] Wherein, Q represents the discharge rate of the resin kneaded material discharged from the nozzle (kg / hr), η represents the viscosity (poise) of the resin melt introduced into the kneading section, and N represents the screw speed (rpm).

[0049] It should be noted that any combination of at least two components disclosed in the claims and / or the specification and / or the drawings is also included in the present invention. In particular, any combination of two or more claims is also included in the present invention.

[0050] Effects of the Invention

[0051] The MB nonwoven fabric of the present invention, although composed of fibers containing a cyclic olefin resin that produces unique side reactions, can provide an MB nonwoven fabric in which the incorporation of coarse fibers is suppressed, and can provide filters and transdermal drug delivery sheets (particularly transdermal absorbable preparations and patches) using the MB nonwoven fabric.

[0052] In addition, in the present invention, when non-woven fabrics are manufactured using the meltblowing method, the viscosity of the resin melt before being introduced into the mixing section is set to a specific range, thereby suppressing the unique "mechanical chemical reaction" of the cyclic olefin resin. As a result, a method for manufacturing meltblown non-woven fabrics in which the mixing of coarse fibers is suppressed can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The present invention can be more clearly understood by referring to the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and the accompanying drawings are for illustration and explanation only and are not intended to limit the scope of the present invention. The scope of the present invention is determined by the appended claims.

[0054] Figure 1 This is a schematic cross-sectional view showing an apparatus used for producing MB nonwoven fabric according to one embodiment of the present invention.

[0055] Figure 2 This is a SEM image of the MB nonwoven fabric obtained in Example 1 (magnification: 300 times).

[0056] Figure 3 This is a SEM image of the MB nonwoven fabric obtained in Example 2 (magnification: 300 times).

[0057] Figure 4 This is a SEM image of the MB nonwoven fabric obtained in Example 3 (magnification: 300 times).

[0058] Figure 5 This is a SEM image of the MB nonwoven fabric obtained in Example 4 (magnification: 300 times).

[0059] Figure 6 This is a SEM image of the MB nonwoven fabric obtained in Comparative Example 1 (magnification: 300 times).

[0060] Explanation of symbols

[0061] 10···Extruder

[0062] 12···Hopper

[0063] 20···Screw

[0064] 22···Supply Department

[0065] 24···Mixing Department

[0066] 26···Compression section

[0067] 28···Metrology Department

[0068] 30···Barrel

[0069] 40···die head

[0070] 42···Nozzle

[0071] 50···Spraying out filaments

[0072] 60···Capturing component

[0073] 62···Collecting surface DETAILED DESCRIPTION

[0074] (Meltblown nonwoven fabric)

[0075] The MB nonwoven fabric of the present invention is composed of fibers containing a cyclic olefin resin, wherein, in fiber diameter data of 100 points randomly selected from a scanning electron microscope (SEM) image magnified at 1000 times, the data are arranged from the smallest fiber diameter to the largest fiber diameter and the data are divided into four equal parts, and the average value of the data having a fiber diameter greater than the third quartile is 30 μm or less.

[0076] "Quartile" refers to the value located at the four equal divisions when the data values ​​are arranged in ascending order. From small to large, the value of 1 / 4 of the data is called the first quartile, the value of 2 / 4 of the data is called the second quartile (center value), and the value of 3 / 4 of the data is called the third quartile.

[0077] The MB nonwoven fabric of the present invention has low coarse fibers derived from mechanochemical reactions and an average fiber diameter (Db) of 30 μm or less, preferably 20 μm or less, and more preferably 16 μm or less. The average fiber diameter is the average of data (data from the 76th to the 100th) with fiber diameters greater than the third quartile of fiber diameter data from 100 randomly selected points in a scanning electron microscope image of the nonwoven fabric magnified 1000x. By reducing the average of data with fiber diameters greater than the third quartile of fiber diameter data, the density of the nonwoven fabric can be improved, resulting in a nonwoven fabric with good texture and a pleasant feel. The lower limit of the average fiber diameter Db is not particularly limited and can be, for example, the average fiber diameter of the fibers constituting the nonwoven fabric.

[0078] Furthermore, in the MB nonwoven fabric of the present invention, the average fiber diameter of the fibers constituting the nonwoven fabric may be, for example, 1 to 15 μm, preferably 1 to 12 μm, more preferably 1 to 10 μm, and even more preferably 1 to 8 μm, from the perspective of improving the density of the nonwoven fabric. The average fiber diameter refers to the average value of all measured fiber diameter data and is a value measured according to the method described in the Examples below.

[0079] Furthermore, for the MB nonwoven fabric of the present invention, the CV value of the average fiber diameter of the fibers constituting the nonwoven fabric can be, for example, 110% or less, preferably 105% or less, from the perspective of improving the density and texture uniformity of the nonwoven fabric. The lower limit of the CV value is not particularly limited and can be 50% or greater. It should be noted that the CV value of the average fiber diameter refers to the ratio of the standard deviation of measured fiber diameter data to the average fiber diameter, and is an indicator of the dispersion of the fiber diameter distribution. It is measured according to the method described in the Examples below.

[0080] In addition, for the MB nonwoven fabric of the present invention, from the viewpoint of improving the density and uniformity of the texture of the nonwoven fabric, the average fiber diameter (Db) relative to the average fiber diameter (Dc), for example, expressed as Db / Dc, can be 4.0 or less, preferably 3.5 or less. Moreover, from the viewpoint of uniformity, Db / Dc is preferably 1 or more. The average fiber diameter (Db) is the average value of data (76th to 100th data) having a fiber diameter larger than the 3rd quartile of fiber diameter data of 100 points randomly selected from a scanning electron microscope image of the nonwoven fabric magnified 1000 times, and the average fiber diameter (Dc) is the average value of data (26th to 75th data) having a fiber diameter larger than the 1st quartile and smaller than the 3rd quartile.

[0081] The fibers constituting the MB nonwoven fabric of the present invention are fibers containing a cyclic olefin resin. For example, the resin composition constituting the fibers may contain 50% by mass or more of the cyclic olefin resin, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 98% by mass or more.

[0082] The MB nonwoven fabric of the present invention is not particularly limited as long as it can achieve the effects of the present invention. In addition to the cyclic olefin resin described below, it may also contain a thermoplastic resin. Examples of thermoplastic resins include linear polyolefin resins (e.g., polyethylene resins, polypropylene resins) and polyester resins (e.g., polyethylene terephthalate resins, polybutylene terephthalate resins).

[0083] Furthermore, from the viewpoint of low solubility, at least a portion of the fiber surface of the fibers constituting the MB nonwoven fabric of the present invention may be formed of a cyclic olefin resin described below.

[0084] The fibers constituting the MB nonwoven fabric of the present invention are not particularly limited as long as they can achieve the effects of the present invention. They may be composite fibers, for example, core-sheath fibers, side-by-side fibers, or islands-in-the-sea fibers.

[0085] The MB nonwoven fabric of the present invention can be appropriately weighted according to the application. The weight per unit area is not particularly limited. For example, from the perspective of lightness and density, the weight per unit area can be 10 to 50 g / m 2 About 10 to 45 g / m 2 More preferably, it can be 10 to 40 g / m 2 It should be noted that the basis weight is a value measured by the method described in the Examples described below.

[0086] The thickness of the MB nonwoven fabric of the present invention can be appropriately determined depending on the intended use and is not particularly limited. For example, from the perspective of weight reduction and hand feel, the thickness can be approximately 0.10 to 1.00 mm, preferably approximately 0.10 to 0.85 mm, and more preferably approximately 0.10 to 0.70 mm. Note that the thickness is measured using the method described in the Examples below.

[0087] The MB nonwoven fabric of the present invention can appropriately determine the air permeability according to the application, and the air permeability is not particularly limited. For example, from the viewpoint of density, the air permeability can be, for example, 10 to 550 cm 3 / cm 2 ·s, preferably 10 to 500 cm 3 / cm 2·s, more preferably 10 to 400 cm 3 / cm 2 It should be noted that the air permeability is a value measured by the method described in the examples below.

[0088] Furthermore, the MB nonwoven fabric of the present invention is preferably a nonwoven fabric having excellent density despite being thin. For example, the air permeability B (cm 3 / cm 2 The ratio (B / A) of s) to thickness A (mm) may be 80≤B / A≤800, preferably 90≤B / A≤500, and more preferably 100≤B / A≤400.

[0089] The MB nonwoven fabric of the present invention can be used in a variety of applications, including medical, cosmetic, and sanitary materials, industrial materials, daily necessities, and clothing. Among them, it is suitable for use in filters such as filters for filtering liquids such as water, air filters (e.g., clean room air filters), and transdermal drug delivery tablets (e.g., transdermal absorbents and patches). Due to its excellent low solubility of impurities, it is particularly suitable for use in liquid filtration filters and transdermal drug delivery tablets (e.g., transdermal absorbents and patches).

[0090] When the MB nonwoven fabric of the present invention is used in various filters, the collection efficiency of the filter, as measured according to JIS T 8151, is preferably 85% or higher, more preferably 88% or higher, and even more preferably 90% or higher. Furthermore, the pressure loss of the filter, as measured according to JIS T 8151, is preferably 15 Pa or lower, more preferably 13 Pa or lower, and even more preferably 10 Pa or lower. The collection efficiency and pressure loss are values ​​measured according to the methods described in the Examples below.

[0091] The MB nonwoven fabric of the present invention is highly effective as an air filter with low pressure loss and high collection efficiency. Furthermore, since the cyclic olefin resin has low solubility and is an FDA-approved polymer, it is also expected to be used in filters for filtration of liquids such as water purification. When used in filters for filtration of liquids such as water purification, the fiber diameter of the MB nonwoven fabric can be reduced. For example, the average fiber diameter of the MB nonwoven fabric can be 1 to 8 μm, preferably 1 to 7 μm.

[0092] Furthermore, for medical and cosmetic applications, the MB nonwoven fabric of the present invention exhibits excellent low solubility of impurities and can reduce the transfer of active ingredients such as drugs to the nonwoven fabric. Therefore, it is suitable for use in transdermal drug delivery tablets (preferably transdermal absorbable preparations and patches) that release active ingredients (e.g., pharmaceutical or cosmetic active ingredients, preferably pharmaceutical active ingredients). Such transdermal drug delivery tablets may comprise at least the active ingredient and the MB nonwoven fabric of the present invention as a support. Specifically, in such transdermal drug delivery tablets, the MB nonwoven fabric of the present invention can be used as a support for retaining a liquid containing the active ingredient, or as a support (backing) for supporting a semi-solid or solid substance containing the active ingredient.

[0093] (Cyclic olefin resin)

[0094] Cyclic olefin resin refers to a polymer or copolymer whose main chain contains a structural unit derived from a cyclic olefin. The cyclic olefin is an unsaturated hydrocarbon compound having at least one olefinic double bond in the cyclic hydrocarbon structure, such as norbornene, dicyclopentadiene, and tetracyclododecene, and can be introduced by using it as a monomer. Cyclic olefin resins can be listed based on their production methods: addition polymers of cyclic olefins or their hydrogenates; addition copolymers of cyclic olefins and α-olefins or their hydrogenates; and ring-opening (co)polymers of cyclic olefins or their hydrogenates. For example, from the perspective of both characteristics and cost, the cyclic olefin resin in the present invention can be an addition copolymer of cyclic olefins and α-olefins.

[0095] Examples of the cyclic olefins include monocyclic cyclic olefins such as cyclopentene, cyclohexene, cyclooctene, cyclopentadiene, and 1,3-cyclohexadiene; bicyclo[2.2.1]hept-2-ene (norbornene), 5-methylbicyclo[2.2.1]hept-2-ene, 5,5-dimethylbicyclo[2.2.1]hept-2-ene, 5-ethylbicyclo[2.2.1]hept-2-ene, 5-butylbicyclo[2.2.1]hept-2-ene, 5-ethylidene Bicyclic cyclic olefins such as bicyclo[2.2.1]hept-2-ene, 5-hexylbicyclo[2.2.1]hept-2-ene, 5-octylbicyclo[2.2.1]hept-2-ene, 5-octadecylbicyclo[2.2.1]hept-2-ene, 5-methylidenebicyclo[2.2.1]hept-2-ene, 5-vinylbicyclo[2.2.1]hept-2-ene, and 5-propenylbicyclo[2.2.1]hept-2-ene; tricyclo[4.3.0.1 2,5 ]Deca-3,7-diene (dicyclopentadiene), tricyclo[4.3.0.1 2,5 ]Deca-3-ene, tricyclo[4.4.0.1 2,5 ] undec-3,7-diene or tricyclo[4.4.0.1 2 ,5] undec-3,8-diene or tricyclic [4.4.0.1] as a partially hydrogenated product thereof (or an adduct of cyclopentadiene and cyclohexene) 2,5 ] undec-3-ene, 5-cyclopentylbicyclo[2.2.1]hept-2-ene, 5-cyclohexylbicyclo[2.2.1]hept-2-ene, 5-cyclohexenylbicyclo[2.2.1]hept-2-ene, 5-phenylbicyclo[2.2.1]hept-2-ene; tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene (tetracyclododecene), 8-methyltetracyclo[4.4.0.1 2,5 .1 7,10 ]Dodec-3-ene, 8-ethyltetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, 8-methylene tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, 8-ethylidene tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, 8-vinyltetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, 8-propenyltetracyclo[4.4.0.1 2,5 .1 7,10 ] tetracyclic cyclic olefins such as dodec-3-ene; 8-cyclopentyltetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, 8-cyclohexyl tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, 8-cyclohexenyltetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, 8-phenylcyclopentyltetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene, tetracyclo[7.4.1 3,6 .0 1,9 .0 2,7 ]Tetradecane-4,9,11,13-tetraene (1,4-methylene-1,4,4a,9a-tetrahydrofluorene), tetracyclo[8.4.1 4,7 .0 1,10 .0 3,8 ]pentadeca-5,10,12,14-tetraene (1,4-methylene-1,4,4a,5,10,10a-hexahydroanthracene), pentacyclic [6.6.1.1 3,6 .0 2,7 .0 9,14]-4-hexadecene, pentacyclic [6.5.1.1 3,6 .0 2,7 .0 9,13 ]-4-pentadecenes, pentacyclic [7.4.0.0 2,7 .1 3,6 .1 10,13 ]-4-pentadecenes, heptacyclo[8.7.0.1 2,9 .1 4,7 .1 11,17 .0 3,8 .0 12,16 ]-5-eicosene, heptacyclic [8.7.0.1 2,9 .0 3,8 .1 4,7 .0 12,17 .1 13,16 ]-14-eicosene, cyclopentadiene tetramer and other polycyclic cyclic olefins. These cyclic olefins can be used alone or in combination of two or more.

[0096] Specific examples of α-olefins copolymerizable with cyclic olefins include α-olefins having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. These α-olefins can be used alone or in combination of two or more.

[0097] The polymerization method and hydrogenation method of the cyclic olefin or the cyclic olefin and α-olefin are not particularly limited and can be carried out according to a known method.

[0098] The cyclic olefin resin of the present invention is preferably a copolymer containing at least norbornene units using at least norbornene as the cyclic olefin, and is particularly preferably a copolymer of ethylene and norbornene.

[0099] For example, in a copolymer of ethylene and norbornene, the mass ratio of norbornene units to the total of ethylene units and norbornene units may be 60 to 99 mass %, preferably 63 to 90 mass %, from the viewpoint of processability and solubility.

[0100] (Method for producing meltblown nonwoven fabric)

[0101] The method for producing the MB nonwoven fabric of the present invention comprises at least the following steps:

[0102] a melting step of heating and melting a resin composition containing a cyclic olefin resin in a supply section to obtain a resin melt;

[0103] A kneading step of introducing the above-mentioned resin melt into a kneading section and kneading it by rotating a screw under heating to obtain a resin mixture;

[0104] a spraying step of spraying the resin mixture together with air from a nozzle; and

[0105] In the collecting step, the filamentous material ejected from the nozzle is collected on a collecting surface to obtain a web.

[0106] Figure 1 1 is a schematic cross-sectional view showing an apparatus 100 used for producing MB nonwoven fabric according to one embodiment of the present invention. Figure 1 As shown, the apparatus 100 comprises at least an extruder 10, a die head 40, and a collecting member 60. The extruder 10 comprises at least a barrel 30 and a screw 20 rotating in the barrel 30. The screw 20 comprises a supply section 22 for supplying resin solids and a kneading section 24 for kneading the resin supplied from the supply section 22. Figure 1 In the process, the resin composition containing the cyclic olefin resin is heated and melted in the supply section 22 of the screw 20 of the extruder 10 and introduced into the kneading section 24 .

[0107] In addition, Figure 1 In the embodiment, the kneading section 24 is composed of a compression section 26 and a metering section 28. For example, the solid resin composition (resin solid) fed from the hopper 12 is conveyed from the supply section 22 toward the die head 40 to the kneading section 24 in the barrel 30 by the rotation of the screw 20.

[0108] Typically, in the screw 20 , the supply portion 22 has grooves of uniform depth (Hp), and the compression portion 26 has grooves that gradually become shallower toward the travel direction X. The depth of the grooves of the screw 20 is shallowest at the metering portion 28 , which has grooves of uniform depth (Hm) (here, Hp>Hm).

[0109] In the screw 20, the grooves of the screw 20 gradually become shallower in the travel direction X in the kneading section 24. Therefore, the mechanical energy applied to the molten resin between the screw 20 and the inner wall of the barrel 30 increases as the screw 20 travels in the travel direction X. The kneaded resin material passing through the kneading section 24 is then fed into the die head 40. The kneaded resin material is then ejected from the nozzle 42, and the ejected filaments 50 are captured on the capture surface 62, thereby producing a nonwoven fabric.

[0110] (Melting process)

[0111] like Figure 1As shown, in the melting step, a resin composition containing at least a cyclic olefin resin is conveyed in the supply section 22 of the screw 20 disposed within the barrel 30 by the rotation of the screw 20 and is heated and melted by a known heating means such as a heater disposed in the barrel 30. In the supply section 22, the resin solid material supplied from the hopper 12 forms a solid bed between the screw 20 and the barrel 30 and moves in the travel direction X.

[0112] In conventional methods, the solid bed is not destroyed in the supply section but is destroyed in the kneading section 24 to form a resin melt. However, in the present invention, by increasing the heating temperature in the supply section 22 to a level that can destroy the solid bed, a resin melt having a specific viscosity can be formed in the supply section 22. It should be noted that the above description uses a single-screw extruder as an example. As the extruder 10, a single-screw extruder, a multi-screw extruder (twin-screw or higher) or other well-known extruders can be used.

[0113] Conventionally, resin compositions are introduced into the kneading section in a solid state or in a state containing solids. However, in the MB nonwoven fabric manufacturing method of the present invention, a resin melt having a specific low viscosity is pre-formed in the kneading section before heat kneading. This reduces the mechanical energy acting on the resin melt, such as shear stress generated by the screw rotation during the kneading process and compressive stress applied during supply to the die and discharge from the nozzle. This suppresses the "mechanochemical reaction" characteristic of cyclic olefin resins, resulting in the suppression of the formation of coarse fibers.

[0114] The heating temperature of the supply section can be appropriately determined based on the viscosity characteristics and thermal decomposition temperature of the cyclic olefin resin and other thermoplastic resins included in the resin composition, and can be, for example, 200 to 400° C., preferably 250 to 390° C., and more preferably 300 to 380° C. By increasing the heating temperature of the supply section, the viscosity η of the resin melt can be reduced.

[0115] The viscosity η of the resin melt at the heating temperature of the supply section is 80 to 200 poise, preferably 85 to 195 poise, and more preferably 90 to 190 poise. It should be noted that the viscosity is measured according to the method described in the Examples below. The resin melt, adjusted to a predetermined viscosity in the supply section, is introduced into the kneading section.

[0116] (Mixing process)

[0117] The resin melt, preliminarily melted in the supply section 22, is then introduced into the kneading section 24, where it is kneaded by the rotation of the screw 20 under heating to obtain a resin kneaded product. By preliminarily reducing the viscosity of the resin melt during the supply process, the compressive stress applied to the resin kneaded product during introduction into the die can be suppressed during the kneading process.

[0118] Regarding the screw, the product (Q×η) / N of the ratio Q / N of the ejection rate Q (kg / hr) of the resin kneaded material in the ejection step described later and the viscosity η (poise) of the resin melt can be, for example, 20 to 100, preferably 30 to 90, and more preferably 40 to 80. (Q×η) / N is a parameter that reflects the mechanical energy applied to the resin by screw rotation as the viscosity of the resin during kneading. By setting it within the above range, the mechanical energy applied to the resin, particularly the compressive stress, can be reduced, thereby suppressing the "mechanochemical reaction" of the cyclic olefin resin.

[0119] From the perspective of reducing the mechanical energy applied to the resin, particularly compressive stress, the ratio Q / N of the ejection rate Q (kg / hr) of the resin kneaded material to the screw speed N (rpm) in the ejection step described below can be 0.1 to 2.0, preferably 0.2 to 1.5, and more preferably 0.3 to 1.0. Q / N refers to the resin throughput per unit screw speed. By setting this value within the above range, the mechanical energy applied to the resin in the kneading section can be minimized.

[0120] Furthermore, from the viewpoint of reducing the viscosity of the resin kneaded product and reducing the compressive stress applied to the resin kneaded product when supplied to the die, the ratio (L / D) of the axial length (L) of the screw to the diameter (D) of the screw may be 15 to 40, preferably 18 to 40, and more preferably 20 to 40.

[0121] The heating temperature of the kneading section can be appropriately determined depending on the viscosity characteristics, thermal decomposition temperature, etc. of the cyclic olefin resin and other thermoplastic resins contained in the resin composition. From the viewpoint of reducing the viscosity of the resin kneaded product, it can be, for example, 230 to 400°C, preferably 250 to 390°C, and more preferably 300 to 380°C.

[0122] (Spraying process)

[0123] The obtained resin kneaded material is introduced into a die head 40 having a nozzle 42 for ejecting the resin kneaded material and air ejection slots (not shown) provided on both sides of the nozzle 42 , and ejected from the nozzle 42 along with air ejected from the air ejection slots.

[0124] The nozzle aperture is not particularly limited as long as fibers with a given fiber diameter can be obtained, and may be, for example, 0.01 to 1.0 mm, preferably 0.05 to 0.8 mm, and more preferably 0.1 to 0.5 mm.

[0125] The heating temperature of the die, i.e., the spinning temperature, can be appropriately determined depending on the viscosity characteristics, thermal decomposition temperature, etc. of the cyclic olefin resin and other thermoplastic resins contained in the resin composition. From the viewpoint of adjusting the ejection amount of the resin kneaded product, it can be, for example, 300 to 400°C, preferably 320 to 395°C, and more preferably 350 to 390°C.

[0126] (Collection process)

[0127] Then, the filaments 50 ejected from the nozzles 42 are captured on the capturing surface 62 of the capturing member 60 to obtain a web. The capturing member 60 is not particularly limited as long as it is a member commonly used as a capturing member in the production of MB nonwoven fabrics. It may be a rotating roller or a conveyor belt. For example, the capturing member 60 may be as follows: Figure 1 The figure shows a conveyor belt that rotates in one direction, and collects the ejected filaments 50 on the collecting surface 62, and continuously forms the MB nonwoven fabric as the conveyor belt rotates.

[0128] (Electrification process)

[0129] When the MB nonwoven fabric of the present invention is used in various filters, it may be subjected to a charging treatment (a treatment to impart charging properties) in order to further improve the collection performance of the MB nonwoven fabric. "Charging" means that the MB nonwoven fabric is charged, and preferably has a surface charge density (a value obtained by dividing the charge measured using a Faraday cage [electrostatic charge meter] by the measured area) of 1.0 × 10 -10 Coulomb / cm 2 More than 1.5×10 -10 Coulomb / cm 2 More than 2.0×10 -10 Coulomb / cm 2 above.

[0130] Examples of methods for imparting chargeability to MB nonwoven fabrics include methods of imparting charge by friction or contact, methods of irradiating active energy rays (e.g., electron beams, ultraviolet rays, X-rays, etc.), methods utilizing corona discharge, gas discharge such as plasma, methods utilizing high electric fields, and liquid charging (hydrocharging) using polar solvents such as water, among others, such as appropriate electret treatments. Of these, corona discharge and hydrocharging are preferred because they can achieve high chargeability with relatively low electrical power.

[0131] The used apparatus and conditions of the corona discharge method are not particularly limited. For example, a DC high-voltage stabilized power supply can be used. For example, the linear distance between the electrodes for applying the voltage is 5 to 70 mm (preferably 10 to 50 mm), the applied voltage is -50 to -10 kV and / or 10 to 50 kV (preferably -40 to -20 kV and / or 20 to 40 kV), the temperature is room temperature (20° C.) to 100° C. (preferably 30 to 80° C.), and the treatment time is 0.1 to 20 seconds (preferably 0.5 to 10 seconds).

[0132] In the liquid charging method, a polar solvent such as water or an organic solvent (preferably water from the perspective of productivity such as drainage treatment) is sprayed onto the MB non-woven fabric, or the polar solvent is sprayed while vibrating to charge it. The pressure of the polar solvent that collides with the MB non-woven fabric is preferably 0.1 to 5 MPa, more preferably 0.5 to 3 MPa, and the suction pressure from the bottom is preferably 500 to 5000 mmH2O, more preferably 1000 to 3000 mmH2O. The treatment time for liquid charging is preferably 0.01 to 5 seconds, more preferably 0.02 to 1 second. The charged MB non-woven fabric after the liquid charging method is preferably dried at a temperature of, for example, 40 to 100°C, preferably 50 to 80°C.

[0133] Example

[0134] The present invention will be described in more detail below with reference to the following examples, but the present invention is not limited to these examples. In the following examples and comparative examples, various physical properties were measured by the following methods.

[0135] [Viscosity of resin melt (poise)]

[0136] The cyclic olefin resins used in the examples and comparative examples were prepared using a Toyo Seiki CAPILOGRAPH 1B, with the feed section temperature set to that of the examples and comparative examples, and at a shear rate of r = 1200 sec. -1 The viscosity was measured under the conditions of . The viscosity measured under these conditions was defined as the viscosity (η) of the resin melt introduced into the kneading section.

[0137] [Average fiber diameter, average fiber diameter greater than the 3rd quartile]

[0138] The MB nonwoven fiber structure was observed using a scanning electron microscope. The fiber diameters of 100 randomly selected fibers from electron micrographs magnified 1000x were measured. Based on this fiber diameter distribution, the average fiber diameter, CV value, average fiber diameter Dc of fibers with a fiber diameter greater than the first quartile and less than the third quartile, and average fiber diameter Db of fibers with a fiber diameter greater than the third quartile were determined.

[0139] [Weight per unit area]

[0140] The weight per unit area (g / m2) of MB nonwoven fabric was measured according to 6.2 of JIS L 1913 “Test methods for general nonwoven fabrics”. 2 ).

[0141] [thickness]

[0142] The thickness of the MB nonwoven fabric was measured in accordance with 6.1 of JIS L 1913 "Test methods for general nonwoven fabrics".

[0143] [Breathability]

[0144] The air permeability (cm2) was measured by the Frazier method according to 8.26 of JIS L 1096 “Test methods for woven and knitted fabrics”. 3 / cm 2 ·s).

[0145] [Capture performance]

[0146] Collection efficiency (%) and pressure loss (Pa)

[0147] According to JIS T 8151, a piece of 11 cm φ was cut from the charged nonwoven fabric and placed on a sample stand of 8.6 cm φ in the filter section (filtration area: 58.1 cm 2 ), the collection efficiency (%) and pressure loss (Pa) when filtering NaCl particles (average particle size: 0.1 μm) at an air volume of 20 L / min and a surface velocity of 5.7 cm / s were measured.

[0148] (Example 1)

[0149] In the supply section, an ethylene-norbornene copolymer (manufactured by Polyplastics, trade name "TOPAS" 5013) having a norbornene content of 75% by mass as a cyclic olefin resin is heated and melted at 360°C, and the resin melt is introduced into the kneading section. The viscosity (η) of the resin melt introduced into the kneading section is 100 poise. In the kneading section, the resin melt is kneaded at a screw speed (N) of 5.0 rpm under heating at 380°C. The obtained resin mixture is supplied to a die head having a nozzle with a nozzle single hole diameter (diameter) of 0.15 mm, a nozzle single hole length / nozzle single hole diameter = 10, and a nozzle hole spacing of 0.75 mm, while an air amount of 15 Nm per 1 m nozzle width is supplied. 3 / min blowing hot air at a temperature of 340 ° C, while the resin kneaded material was ejected from the nozzle at a spinning temperature of 380 ° C and an ejection rate (Q) of 2.2 kg / hr. The ejected filaments ejected from the nozzle were collected on a collection net to obtain a unit area weight of 34.2 g / m 2, a cyclic olefin meltblown nonwoven fabric having a thickness of 0.430 mm. An electron microscope magnified photograph of the obtained meltblown nonwoven fabric is shown in Figure 2 .

[0150] (Example 2)

[0151] The same procedure as in Example 1 was carried out except that the nozzle single hole diameter (diameter) was changed to 0.3 mm. The obtained melt-blown nonwoven fabric had a basis weight of 31.8 g / m 2 , thickness is 0.608mm, and the electron microscope magnified photo is shown in Figure 3 .

[0152] (Example 3)

[0153] The same procedures as in Example 2 were followed except that the heating temperature of the supply section was set to 350°C, the kneading conditions in the kneading section were set to 360°C with a screw speed (N) of 10.5 rpm, and the spinning conditions were set to a spinning temperature of 360°C and a discharge rate (Q) of 4.3 kg / hr. The viscosity (η) of the resin melt introduced into the kneading section was 150 poise. The weight per unit area of ​​the obtained meltblown nonwoven fabric was 31.2 g / m 2 , thickness is 0.612mm, and the electron microscope magnified photo is shown in Figure 4 .

[0154] (Example 4)

[0155] The same procedure as in Example 2 was followed except that the resin used was an ethylene-norbornene copolymer having a norbornene content of 75% by mass (manufactured by Polyplastics, trade name "TOPAS" 6013). The viscosity (η) of the resin melt introduced into the kneading section was 180 poise. The resulting meltblown nonwoven fabric had a basis weight of 20.7 g / m². 2 , thickness is 0.286mm, and the electron microscope magnified photo is shown in Figure 5 .

[0156] (Comparative Example 1)

[0157] The same procedure as in Example 2 was followed except that the heating temperature of the supply section was set to 300°C, the kneading conditions of the kneading section were set to 320°C with a screw speed (N) of 10.8 rpm, and the spinning conditions were set to a spinning temperature of 320°C and a discharge rate (Q) of 4.8 kg / hr. The viscosity (η) of the resin melt introduced into the kneading section was 270 poise. The weight per unit area of ​​the obtained meltblown nonwoven fabric was 70.3 g / m 2 , thickness is 1.154mm, and the electron microscope magnified photo is shown in Figure 6 .

[0158] [Table 1]

[0159]

[0160] As shown in Table 1, in Comparative Example 1, since the viscosity of the resin melt introduced into the kneading section is high and (Q×η) / N is also high, mechanical energy acts on the cyclic olefin resin, and a large amount of crude fibers ( Figure 6 Due to the incorporation of these coarse fibers, the average fiber diameter and the average fiber diameter Db of fibers larger than the third quartile of the MB nonwoven fabric of Comparative Example 1 were larger than those of the MB nonwoven fabrics of Examples 1 to 4. Furthermore, due to the incorporation of these coarse fibers, the air permeability was greater than that of Examples 1 to 4, resulting in insufficient density.

[0161] On the other hand, in Examples 1 to 4, since the viscosity of the resin melt introduced into the kneading section was controlled to be low, the generation of coarse fibers due to the mechanochemical reaction could be suppressed ( Figures 2 to 5 Therefore, the MB nonwoven fabrics of Examples 1 to 4 can make both the average fiber diameter and the average fiber diameter Db of fibers larger than the third quartile smaller than that of Comparative Example 1.

[0162] The resulting MB nonwoven fabric also had lower air permeability than Comparative Example 1, indicating improved density. Furthermore, the MB nonwoven fabrics of Examples 1, 2, and 4 exhibited low air permeabilities per unit thickness (B / A), demonstrating particularly excellent density. The MB nonwoven fabrics of Examples 2 and 4, in particular, exhibited a favorable feel, likely due to the ability to suppress the CV value of the average fiber diameter of the constituent fibers to 90% or less.

[0163] (Example 5)

[0164] The meltblown nonwoven fabric obtained in Example 2 was charged using a corona discharge method. The specific conditions for the corona discharge method are as follows. The collection efficiency (%) and pressure loss (Pa) of the resulting charged nonwoven fabric were measured using the above methods. The results are shown in Table 2.

[0165] Power supply: DC high voltage stable power supply

[0166] Linear distance between electrodes applying voltage: 35mm

[0167] Applied voltage: -28kV

[0168] Applied current: 8.0mA

[0169] Temperature: 25°C

[0170] Processing time: 1 second

[0171] (Example 6)

[0172] A charged nonwoven fabric was obtained in the same manner as in Example 5, except that the meltblown nonwoven fabric obtained in Example 4 was used instead of the meltblown nonwoven fabric obtained in Example 2. The collection efficiency (%) and pressure loss (Pa) of the obtained charged nonwoven fabric were measured according to the above methods. The results are shown in Table 2.

[0173] [Table 2]

[0174] Example 5 Example 6 Collection efficiency [%] 96.4 89.0 Pressure loss [Pa] 9 7

[0175] The charged nonwoven fabrics obtained in Examples 5 and 6 had a collection efficiency of 85% or more and a pressure loss of 10 Pa or less, and thus were suitable for various filter applications.

[0176] Industrial Applicability

[0177] As described above, the MB nonwoven fabric of the present invention can be used in a variety of applications, including medical, cosmetic, and sanitary materials, industrial materials, daily necessities, and clothing. In particular, due to its excellent density and low solubility of impurities, it is preferably used in liquid filtration filters, air filters (e.g., clean room air filters), and transdermal drug delivery tablets (e.g., transdermal absorbable preparations and patches).

[0178] As described above, preferred embodiments of the present invention have been described with reference to the drawings. However, various additions, changes, and deletions may be made without departing from the spirit of the present invention, and such embodiments are also included in the scope of the present invention.

Claims

1. A meltblown nonwoven fabric comprising fibers containing a cyclic olefin resin, wherein: In the fiber diameter data of 100 points randomly selected from the SEM image magnified 1000 times, the data are arranged from the smaller fiber diameter to the larger fiber diameter and divided into four equal parts. The average value of the data with a fiber diameter greater than the obtained third quartile is less than 30 μm, and the CV value of the average fiber diameter of the fiber is less than 110%.

2. The meltblown nonwoven fabric according to claim 1, wherein The ratio Db / Dc of the average fiber diameter Db to the average fiber diameter Dc is 4.0 or less, wherein the average fiber diameter Db is the average value of the data having a fiber diameter larger than the 3rd quartile, and the average fiber diameter Dc is the average value of the data having a fiber diameter larger than the 1st quartile and smaller than the 3rd quartile.

3. The meltblown nonwoven fabric according to claim 1 or 2, wherein The cyclic olefin-based resin is a copolymer containing at least norbornene units.

4. The meltblown nonwoven fabric according to claim 1 or 2, wherein the air permeability thereof is 10 to 550 cm3 as measured in accordance with JIS L 1906. 3 / cm 2 ·s.

5. The meltblown nonwoven fabric according to claim 1 or 2, wherein the weight per unit area is 10 to 50 g / m 2 .

6. The meltblown nonwoven fabric according to claim 1 or 2, which satisfies the following formula (1): 80≤B / A≤800 (1) In the formula, A represents thickness, the unit of thickness is mm, B represents air permeability, the unit of air permeability is cm 3 / cm 2 ·s. 7 . The melt-blown nonwoven fabric according to claim 1 , which is composed of fibers having an average fiber diameter of 1 to 15 μm. 8 . A filter comprising the melt-blown nonwoven fabric according to claim 1 . 9 . A support for a transdermal drug delivery tablet that releases an active ingredient, the support comprising the meltblown nonwoven fabric according to claim 1 .

10. A transdermal drug administration sheet comprising at least an active ingredient and the support according to claim 9.

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