Meltblown nonwoven fabric made from ultrafine fibers

Abstract

To provide a melt-blown nonwoven fabric for which average fiber diameter is small and the number of shots is reduced and raw material thereof is thermoplastic resin with melting point of 200°C or higher.SOLUTION: A melt-blown nonwoven fabric includes fibers made of thermoplastic resin with melting point of 200°C or higher and an additive of 0.1 wt.% or more and 20 wt.% or less with respect to total weight of the melt-blown nonwoven fabric. The melt-blown nonwoven fabric has 0.1 μm or more and 1.5 μm or less of average fiber diameter and 0.45 or more and 1.3 or less of ratio of fiber diameter variation, which is ratio of standard deviation of fiber diameter to the average fiber diameter.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a meltblown nonwoven fabric made of ultrafine fibers. [Background technology]

[0002] Development of ultrafine fiber meltblown nonwoven fabrics has progressed, and when polypropylene (PP) resin is used as the constituent polymer of meltblown nonwoven fabrics, it has become possible to stably meltblown ultrafine fibers of 1 μm or less. Polypropylene is available in low-viscosity grades specifically for meltblown fabrics, and viscosity can be relatively easily adjusted by heating, making it easy to produce fine fibers. For example, Patent Document 1 discloses a method for producing meltblown nonwoven fabrics made of ultrafine fibers with a number-average fiber diameter of 1 μm or less, a fiber diameter distribution (weight-average fiber diameter / number-average fiber diameter) of 1.3 or less, and a fiber diameter variation rate of 55% or less.

[0003] However, with thermoplastic resins with high melting points and high polarity, such as polybutylene terephthalate (PBT) and polyamide, very few ultrafine fiber technologies have been established, except for the technologies described in Patent Documents 2 and 3. Polybutylene terephthalate and polyamide resins do not have grades specifically for melt-blowing, and viscosity adjustment is not easy, so they cannot be effectively thinned, resulting in an increase in shot, which is a granular product of the resin that can be observed on the surface of the nonwoven fabric.

[0004] Patent Document 2 discloses a nanofiber nonwoven fabric product containing polyamide nanofibers, where the polyamide of the nanofibers includes at least one of N6, N66, N6T / 66, N612, N6 / 66, N6I / 66, N66 / 6I / 6T, N11, N12, or a combination thereof, where "N" represents nylon. The polyamide of the nanofibers has a relative viscosity of 4 to 330, the nanofibers have an average diameter of 100 to 950 nanometers, and 1 to 20% of the nanofibers have a fiber diameter greater than 700 nanometers. Patent Document 2 discloses a nanofiber nonwoven fabric product with the above characteristics, using a specific polyamide.

[0005] Patent Document 3 discloses a fabric made of polyamide resin fibers having an average fiber diameter of 0.1 μm or more and less than 0.5 μm, and a CV value of the fiber diameter of 20% or more and less than 65%, and a basis weight of 10 g / m 2 Patent Document 3 discloses a nonwoven fabric characterized by the above. In Patent Document 3, ultra-thin fibers are achieved by rectifying the spinning gas pressure and the air flow in the distance from the spinning nozzle to the collection support to suppress entanglement of the fibers. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5905400 [Patent Document 2] Patent No. 6901594 [Patent Document 3] Patent Publication No. 2020-190057 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a melt-blown nonwoven fabric made from a high-melting thermoplastic resin having a melting point of 200°C or higher, which has a small average fiber diameter and reduced shot. [Means for solving the problem]

[0008] Until now, the inventors have mainly searched for low-viscosity resins and conducted prototypes of thin fibers, but although resin selection strategies could reduce the average fiber diameter in nonwoven fabrics to around 1 μm, making the average fiber diameter smaller than that resulted in fibers breaking and making it impossible to stably produce nonwoven fabrics, making it difficult to achieve significant ultra-thin fibers. Therefore, as a result of extensive research to solve the above-mentioned problems, the inventors discovered that a specific additive can reduce the extrusion pressure of molten polymers containing thermoplastic resins with a melting point of 200°C or higher, thereby enabling thin fibers while suppressing the occurrence of shot, and thus completed the present invention.

[0009] The present invention encompasses the embodiments described below.

[0010] Item 1. A melt-blown nonwoven fabric containing fibers made of a thermoplastic resin having a melting point of 200°C or higher and an additive in an amount of 0.1% by weight to 20% by weight based on the total weight of the melt-blown nonwoven fabric, wherein the average fiber diameter is 0.1 μm or more and 1.5 μm or less, and the fiber diameter variation rate, which is the ratio of the standard deviation of the fiber diameter to the average fiber diameter, is 0.45 or more and 1.3 or less.

[0011] Item 2. The melt-blown nonwoven fabric according to Item 1, wherein the additive is an additive for reducing intermolecular forces between polymer chains of the thermoplastic resin in a molten state.

[0012] Item 3. The melt-blown nonwoven fabric according to Item 1, wherein the value of the following formula (1) is 0.1 or more: Meltblown nonwoven fabric MD strength [N] / basis weight [g / m 2 ] ≧ 0.1 (1) In the formula, the MD strength is the maximum strength when a nonwoven fabric is cut into a length of 200 mm in the machine direction and 50 mm in the direction perpendicular to the machine direction, both ends of which are clamped with chucks spaced 100 mm apart, and pulled at a speed of 300 mm / min.

[0013] Item 4. The melt-blown nonwoven fabric according to Item 1, wherein the value of the following formula (2) is 0.2 or more: MD elongation [%] / basis weight [g / m 2 ] / average fiber diameter [μm] ≧ 0.2 (2) In the formula, the MD elongation is the maximum elongation when a nonwoven fabric is cut to a length of 200 mm in the machine direction and 50 mm in the direction perpendicular to the machine direction, both ends of which are clamped with chucks spaced 100 mm apart and pulled at a speed of 300 mm / min.

[0014] Item 5. The melt-blown nonwoven fabric according to any one of Items 1 to 4, wherein the additive is an organic compound containing carbon atoms and hydrogen atoms in its basic skeleton, and is a compound containing a hydroxy group, an amino group, an amide group, a carbonyl group, a carboxy group, a formyl group, an ester group, an alkoxy group, a cyano group, a derivative of any of these, or a combination of two or more of these.

[0015] Item 6. The melt-blown nonwoven fabric according to any one of Items 1 to 5, wherein the additive is a polymer compound having a plurality of nitrogen-containing rings in one molecule.

[0016] Item 7. The melt-blown nonwoven fabric according to Item 6, wherein the additive includes a hindered amine light stabilizer having a 2,2,6,6-tetramethylpiperidinyl skeleton in the molecule.

[0017] Item 8. The melt-blown nonwoven fabric according to any one of Items 1 to 5, wherein the additive is a compound having a fluorene skeleton.

[0018] Item 9. A filter comprising the melt-blown nonwoven fabric according to any one of items 1 to 8. [Effects of the Invention]

[0019] According to the present invention, there is provided a melt-blown nonwoven fabric having a small average fiber diameter, reduced shot, and made from a thermoplastic resin having a melting point of 200°C or higher. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram of a process for producing a meltblown nonwoven fabric according to an embodiment of the present invention. [Figure 2] (A) Micrograph of fibers in the nonwoven fabric of Example 5 at 2000x magnification, (B) Micrograph of fibers in the nonwoven fabric of Comparative Example 1 at 2000x magnification. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described below.

[0022] A melt-blown nonwoven fabric according to an embodiment of the present invention comprises fibers made of a thermoplastic resin having a melting point of 200°C or higher and an additive in an amount of 0.1% by weight to 20% by weight based on the total weight of the melt-blown nonwoven fabric, and has an average fiber diameter of 0.1 μm or more and 1.5 μm or less (1.0 μm or less), and a fiber diameter variation rate, which is the ratio of the standard deviation of fiber diameter to the average fiber diameter (standard deviation of fiber diameter / average fiber diameter), is 0.45 or more (0.65 or more) and 1.3 or less.

[0023] The meltblown nonwoven fabric of the present invention uses a thermoplastic resin with a melting point of 200°C or higher. Therefore, the meltblown nonwoven fabric of the present invention has excellent heat resistance. Examples of the thermoplastic resin with a melting point of 200°C or higher include polyamide, polyester, polyphenylene sulfide (PPS), and polyolefins other than polyethylene and polypropylene.

[0024] Examples of polyamides include polyamide 3 (nylon 3, registered trademark), polyamide 4 (nylon 4, registered trademark), polyamide 6 (nylon 6, registered trademark), and polyamide 6-6 (nylon 6-6, registered trademark).

[0025] Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate. Of these, polyethylene terephthalate or polybutylene terephthalate is preferred. When a mixture of multiple polyesters is used, one of the above polyesters preferably accounts for 50% by weight or more of the thermoplastic resin, more preferably 70% by weight or more, and most preferably 90% by weight or more. Meltblown nonwoven fabrics made of polyethylene terephthalate, polybutylene terephthalate, or polytrimethylene terephthalate have excellent heat resistance due to their relatively high melting points.

[0026] Examples of polyolefins include homopolymers of cyclic olefins, random or block copolymers of two or more types of cyclic olefins, homopolymers of α-olefins such as 4-methyl-1-pentene, and random or block copolymers of two or more types of α-olefins.

[0027] The thermoplastic resin fibers account for 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more of the total weight of the meltblown nonwoven fabric, and 99.9% by weight or less, preferably 98% by weight or less of the total weight of the meltblown nonwoven fabric.

[0028] The additives are added to enable the production of melt-blown nonwoven fabrics with small average fiber diameters and reduced shot counts, even when high-melting-point fibers made of thermoplastic resins with melting points of 200°C or higher are used.

[0029] In one embodiment, the additive is an additive for reducing the intermolecular forces between polymer chains of the thermoplastic resin in a molten state. In other words, when producing a meltblown nonwoven fabric, the thermoplastic resin is melted and the molten polymer is extruded into ultrafine fibers. In this embodiment, by adding an additive to the molten thermoplastic resin, the polar atoms or functional groups of the additive intervene in the areas where attractive forces act due to chemical interactions between the polymer chains of the thermoplastic resin in a molten state, thereby reducing the intermolecular forces between the polymer chains. The intermolecular forces between polymer chains typically include hydrogen bonds, but are not limited to other interactions that act in an affinity between the polymer chains of the thermoplastic resin, such as dipole interactions, van der Waals forces, and London dispersion forces.

[0030] Thermoplastic resins such as polyamide and polyester are highly polar thermoplastic resins and have not previously been able to be spun into strings under the same manufacturing conditions as polypropylene. While it is possible to achieve some degree of fiber thinning by reducing the nozzle hole diameter, increasing the melt-kneading temperature, or increasing the amount of high-temperature, high-velocity air blown to stretch the fibers, more severe manufacturing conditions result in thread breakage and increased shot counts, making it impossible to stably spin fibers with an average fiber diameter of 1.5 μm or less, especially 1 μm or less. The inventors believe that the difficulty in thinning highly polar polymers is due to the strong intermolecular forces between polymer chains in the thermoplastic resin (e.g., hydrogen bonding in polyamides and π-stacking of aromatic rings in PBT). Thin fibers can only be produced with reduced shot counts if the viscosity is reduced, primarily due to relaxation of the intermolecular forces between polymer chains. However, previous results suggest that the interactions between these polymer chains cannot be effectively reduced by heating or adjusting the nozzle hole diameter.

[0031] Therefore, when the additive of this embodiment was added to a thermoplastic resin, it became possible to form thin fibers while suppressing the number of shots. Although the applicant does not wish to restrict the present invention to a specific hypothesis or theory, it is speculated that the addition of the additive of this embodiment alleviates the interaction between polymer chains of the highly polar thermoplastic resin, thereby smoothly forming thin fibers from the extruded molten polymer.

[0032] The additive may be one or more additives selected from the group consisting of a quality stabilizer for thermoplastic resins, an antioxidant, an ultraviolet light resistance agent, a dispersant, a flow improver (superplasticizer), a plasticizer, a crystal nucleating agent, and a mold release agent.

[0033] In one embodiment, the additive is an organic compound containing carbon and hydrogen atoms in its basic skeleton, and also containing oxygen and / or nitrogen atoms, and one or more molecular structures capable of contributing to dipole-dipole interactions and / or hydrogen bonds. For example, the one or more additives are preferably organic compounds containing carbon and hydrogen atoms in its basic skeleton, and also containing hydroxyl groups, amino groups, amide groups, carbonyl groups, carboxyl groups, formyl groups, ester groups, alkoxy groups, cyano groups, derivatives of any of these, or combinations of two or more of these and their derivatives. Preferred examples of such additives include fatty acid amides or alkylene fatty acid amides. Examples of fatty acid amides include stearic acid amide, oleic acid amide, and erucic acid amide. Examples of alkylene fatty acid amides include methylene bis-stearic acid amide and ethylene bis-stearic acid amide.

[0034] In one embodiment, the additive is a polymer compound having multiple nitrogen-containing rings in one molecule. The nitrogen-containing rings may be saturated or unsaturated. The polymer compound may further contain a hydroxy group, an amino group, an amido group, a carbonyl group, a carboxy group, a formyl group, an ester group, an alkoxy group, a cyano group, a derivative of any of these, or a combination of two or more of these and their derivatives. Among these, a hindered amine light stabilizer having a 2,2,6,6-tetramethylpiperidinyl skeleton in the molecule is preferably used as the additive.

[0035] In another embodiment, the additive is a compound having a fluorene skeleton. An example of such a compound is a compound having a 9,9-bisarylfluorene skeleton represented by the following formula (1):

[0036] [ka]

[0037] [In the formula, ring Z is an aromatic hydrocarbon ring, R1 and R2 are substituents, X is a group -[(OR3)nY] (in the formula, Y is a hydroxyl group, a mercapto group, a glycidyloxy group, or a (meth)acryloyloxy group, R3 is an alkylene group, n is 0 or an integer of 1 or more) or an amino group, k is an integer of 0 to 4, m is an integer of 0 or more, and p is an integer of 1 or more.] The compound represented by formula (1) is particularly the following compound represented by formula (2):

[0038] [ka]

[0039] (In the formula, Z, R1, R2, k, m, R3, n, and p are the same as in formula (1).) Ring Z is preferably a benzene ring or a naphthalene ring, R1 is an alkyl group, k is 0 to 1, R2 is an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group or an alkoxy group, m is 0 to 2, R3 is a C2-4 alkylene group, n is 0 to 20 and p is 1 to 3.

[0040] Particularly preferred compounds having a 9,9-bisarylfluorene skeleton are at least one selected from 9,9-bis(hydroxyphenyl)fluorene, 9,9-bis(alkyl-hydroxyphenyl)fluorene, 9,9-bis(aryl-hydroxyphenyl)fluorene, 9,9-bis(di- or trihydroxyphenyl)fluorene, 9,9-bis(hydroxynaphthyl)fluorene, 9,9-bis(hydroxyalkoxyphenyl)fluorene, 9,9-bis(alkyl-hydroxyalkoxyphenyl)fluorene, 9,9-bis(aryl-hydroxyalkoxyphenyl)fluorene, 9,9-bis(hydroxyalkoxynaphthyl)fluorene, and alkylene oxide adducts of these compounds.

[0041] When the high-melting thermoplastic resin having a melting point of 200°C or higher is a polyamide, the additive is preferably a compound having a fluorene skeleton or a polymer compound having multiple nitrogen-containing rings in one molecule, more preferably a compound having a fluorene skeleton, and even more preferably a compound having a 9,9-bisarylfluorene skeleton represented by formula (1). Among them, MF-11 and MF-41 manufactured by Osaka Gas Chemicals Co., Ltd. can be suitably used as the additive.

[0042] When the high-melting thermoplastic resin having a melting point of 200° C. or higher is polybutylene terephthalate, the additive is preferably a compound having a fluorene skeleton, an alkylene fatty acid amide, or a fatty acid amide.

[0043] The additive may be a single additive or a combination of two or more additives from those described above.

[0044] The molecular weight of the additive may be from 10 to 100,000, and may be either a low molecular weight compound of about several tens or a high molecular weight compound of about several tens of thousands.

[0045] The content of the additive is 0.1 to 20% by weight of the total weight of the meltblown nonwoven fabric, more preferably 0.3 to 15% by weight, and even more preferably 0.5 to 10% by weight. The content of the additive is 0.1% by weight or more to obtain an average fiber diameter of 1.5 μm or less even for high-melting-point fibers made of thermoplastic resins with a melting point of 200° C. or more, and 20% by weight or less to ensure the performance of fibers made of thermoplastic resins.

[0046] In one embodiment, the meltblown nonwoven fabric is a meltblown nonwoven fabric made of fibers formed from a resin composition containing a thermoplastic resin having a melting point of 200°C or higher and one or more additives in an amount of 0.1% by weight to 20% by weight based on the total weight of the meltblown nonwoven fabric, wherein the content of the thermoplastic resin having a melting point of 200°C or higher in the resin composition is 80% by weight to 99.9% by weight, and the content of the additives is 0.1% by weight to 20% by weight. In this case, the resin composition may or may not contain components other than the thermoplastic resin having a melting point of 200°C or higher and the additives.

[0047] The raw material thermoplastic resin having a melting point of 200°C or higher may contain components such as a crystal nucleating agent, a matting agent, a pigment, an antifungal agent, an antibacterial agent, a flame retardant, a hydrophilic agent, etc., within the range that does not impair the effects of the present invention. The resin composition containing a thermoplastic resin having a melting point of 200°C or higher and one or more additives in an amount of 0.1% by weight to 20% by weight may further contain such components.

[0048] The meltblown nonwoven fabric according to an embodiment of the present invention has an average fiber diameter of 0.1 μm or more from the viewpoint of the strength of the nonwoven fabric, and 1.5 μm or less from the viewpoint of the functionality of the final product, such as filtration efficiency when used as a filter or sound absorption performance when used as a sound absorbing material. Preferably, the average fiber diameter is 0.1 μm or more and 1.0 μm or less.

[0049] The meltblown nonwoven fabric according to an embodiment of the present invention has a fiber diameter variation rate of 0.45 or more from the viewpoint of nonwoven fabric strength, and 1.3 or less from the viewpoint of suppressing uneven distribution of nonwoven fabric fibers. Preferably, the fiber diameter variation rate is 0.65 or more and 1.3 or less. The fiber diameter variation rate reflects the manufacturing method of the nonwoven fabric.

[0050] In a specific embodiment of the present invention, the meltblown nonwoven fabric has an average fiber diameter of 0.1 μm or more and 1.0 μm or less, and a fiber diameter variation rate of 0.65 or more and 1.3 or less.

[0051] The melt-blown nonwoven fabric of the present embodiment having the above-described configuration is a melt-blown nonwoven fabric made from a high-melting point thermoplastic resin, which has a smaller average fiber diameter and reduced shot compared to a nonwoven fabric containing no additives.

[0052] In a preferred embodiment, the meltblown nonwoven fabric satisfies the following formula (1) in which the value is 0.1 or more.

[0053] Meltblown nonwoven fabric MD strength [N] / basis weight [g / m 2 ] ≧ 0.1 (1) In the formula, MD strength (MD: Machine Direction) is the strength (N) at the maximum load when a nonwoven fabric is cut into a piece 200 mm long in the machine direction and 50 mm long in the perpendicular direction, and both ends of the piece are clamped with chucks spaced 100 mm apart and pulled at a speed of 300 mm / min.

[0054] The value of formula (1) is preferably 0.15 or more, and more preferably 0.2 or more.

[0055] A melt-blown nonwoven fabric having such a structure has excellent tensile strength in the machine direction of the nonwoven fabric.

[0056] In a preferred embodiment, the meltblown nonwoven fabric satisfies the following formula (2) in which the value is 0.2 or more.

[0057] MD elongation [%] / basis weight [g / m 2 ] / average fiber diameter [μm] ≧ 0.2 (2) In the formula, MD elongation is the elongation (%) at the maximum load when a nonwoven fabric is cut to a length of 200 mm in the machine direction and 50 mm in the direction perpendicular to the machine direction, and both ends of the fabric are clamped with chucks spaced 100 mm apart and pulled at a speed of 300 mm / min.

[0058] A melt-blown nonwoven fabric having such a structure has excellent tensile elongation in the machine direction of the nonwoven fabric.

[0059] The basis weight of the melt-blown nonwoven fabric of the present embodiment is not particularly limited, but from the viewpoint of strength and filtering, the average basis weight is preferably in the range of 5 to 150 g / m 2 and more preferably 10 to 100 g / m 2 is.

[0060] The thickness of the melt-blown nonwoven fabric of this embodiment is not particularly limited, but the average thickness per sheet of melt-blown nonwoven fabric is preferably 0.01 to 10 mm, and more preferably 0.1 to 5 mm.

[0061] The air permeability of the melt-blown nonwoven fabric of the present embodiment is not particularly limited, but from the viewpoint of suppressing an increase in pressure resistance during filtration and obtaining a nonwoven fabric with a predetermined strength, the value measured on a 100 mm × 100 mm melt-blown nonwoven fabric test piece using a Frazier type testing machine in accordance with JIS L1096 is 1 to 1700 cm 3 / cm 2 / sec, preferably 1 to 800 cm 3 / cm 2 / second is more preferable.

[0062] The shot of the melt-blown nonwoven fabric of this embodiment is not particularly limited, but from the viewpoint of appearance and substance collection performance, it is preferable to use a shot of 1 m 2 For the melt-blown nonwoven fabric, preferably, transparent spots (resin lumps) with a diameter of 1 mm or more are 10 pieces / m 2 Less than or equal to 5 pieces / m 2 The following is the result.

[0063] In the nonwoven fabric according to this embodiment, the fibers constituting the fabric are preferably continuous long fibers. In the preferred production method described below, the fibers are thinned as single threads, making it possible to obtain a nonwoven fabric composed of fibers with high uniformity and a desired average fiber diameter.

[0064] The melt-blown nonwoven fabric of this embodiment has a small average fiber diameter and reduced shot, resulting in a good appearance and excellent substance collection ability. Therefore, the melt-blown nonwoven fabric of this embodiment and a laminate formed by laminating multiple melt-blown nonwoven fabrics are useful as filter materials for fluid filters. Fluids include gases and liquids.

[0065] The present invention also provides a fluid filter comprising the laminate. Even when the melt-blown nonwoven fabric of the above embodiment is used alone as the melt-blown nonwoven fabric, a fluid filter with a good appearance and high substance collection capacity can be obtained. Meanwhile, in another embodiment of the present invention, the melt-blown nonwoven fabric of the present embodiment may be combined with other layers as components constituting the filter material, depending on the purpose of filtration, and liquid filters comprising a laminate including such a combination of a melt-blown nonwoven fabric and other layers are also included in the liquid filter of the present invention.

[0066] Examples of the other layers include knitted fabric, woven fabric, nonwoven fabric, and film.

[0067] When laminating another layer on the melt-blown nonwoven fabric according to the present embodiment, various known methods can be used, including heat fusion methods such as thermal embossing and ultrasonic fusion, mechanical entanglement methods such as needle punching and water jetting, methods using adhesives such as hot melt adhesives and urethane adhesives, and extrusion lamination.

[0068] Examples of nonwoven fabrics that can be laminated as other layers include spunbond nonwoven fabrics, wet-laid nonwoven fabrics, dry-laid nonwoven fabrics, dry-laid pulp nonwoven fabrics, flash-spun nonwoven fabrics, and spread-fiber nonwoven fabrics.

[0069] Next, an example of a manufacturing method for a melt-blown nonwoven fabric according to this embodiment will be described with reference to the drawings, but the manufacturing method is not limited to the following. Figure 1 shows an example of a manufacturing apparatus for a melt-blown nonwoven fabric according to the present invention. This manufacturing apparatus includes a hopper 1a for introducing raw materials, an extruder 1b for melt-kneading the raw materials, a metering pump 2 for sending the molten polymer extruded from the extruder 1b downstream, a die 3a for horizontally discharging the fibrous polymer, a temperature-regulating heater 3b for the high-temperature, high-velocity air discharged from the die 3a together with the molten polymer, a spinning nozzle 3c attached to the tip of the die, a collector 4a for collecting fibers provided near the die 3a, a suction blower 4b for sucking the collector 4a (and the fibrous molten polymer 5a collected by the collector 4a), the fibrous molten polymer 5a discharged from the die, a melt-blown nonwoven fabric 5b formed by cooling and solidifying the fibrous molten polymer 5a on the collector 4a, and a winder 6 for winding up the melt-blown nonwoven fabric 5b.

[0070] The melt-blown nonwoven fabric of the present invention can be produced by a method including the steps of melt-kneading a polymer, discharging the molten polymer from a spinning nozzle, and spraying heated air from another nozzle to form polymer fibers. Referring to the apparatus described above, when producing a melt-blown nonwoven fabric, the fibrous molten polymer 5a discharged from the spinning nozzle 3c is stretched with heated air sprayed from an air nozzle, and additional processes can be performed as necessary to obtain the melt-blown nonwoven fabric. The resulting melt-blown nonwoven fabric may be subjected to calendering, charging, hydrophilization, etc., as necessary.

[0071] (1) Melt-kneading process The melt-kneading temperature of the polymer is preferably (melting point of the polymer + 30°C) to (melting point of the polymer + 150°C). For example, in the case of polyamide, the melt-kneading temperature is preferably 250 to 370°C, and in the case of PBT, the melt-kneading temperature is preferably 250 to 370°C.

[0072] (2) Fiber formation process The molten polymer is extruded from a number of spinning nozzles 3c, and heated air is sprayed from the nozzles to form fibers of the polymer. The temperature of the die 3a and the heated air is preferably set to (the melting point of the polymer) to (the melting point of the polymer + 200°C). The above temperature range is preferable from the viewpoints of preventing the polymer from solidifying rapidly immediately after being extruded from the spinning nozzles 3c, preventing fusion of the formed polymer fibers, and suppressing variation in fiber diameter.

[0073] To form polymer fibers, the discharge rate of the molten polymer per spinning nozzle 3c is preferably 0.1 to 2 g / min / hole or less, more preferably 0.5 to 1 g / min / hole or less. From the viewpoint of obtaining a discharge pressure sufficient for fiber formation and avoiding damage to the nozzle due to excessive discharge pressure, the discharge rate of the molten polymer per spinning nozzle 3c is preferably within the above range.

[0074] Heated air ejection volume per width: 5 to 50 Nm 3 / min / m is preferable, 10 to 40Nm 3 / min / m is more preferred.

[0075] The meltblown nonwoven fabric and the method for producing the same of the present invention have been described above with reference to preferred embodiments, but the present invention is not limited to the specific embodiments described above.

[0076] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Example]

[0077] 1. Meltblown nonwoven fabric manufacturing (1) Manufacturing of melt-blown nonwoven fabrics using polyamide resin as raw material Example 1 A mixture of 95% 6-nylon resin with a relative viscosity of 3.0 and 5% additive 1 was placed in the raw material hopper of the melt-blown manufacturing equipment, and the melt-blending temperature was set to 325°C. The gap between the die and the collector was 370 mm, and 10 Nm of heated compressed air at 340°C was used. 3 / min / m, and the resin was discharged into the atmosphere from a nozzle with a nozzle diameter of 0.3 mm, with a suction volume of 400 Nm 3 The fibrous resin was continuously collected on a collector at a rate of 51 g / m² / min. The rotation speed of the collector was adjusted appropriately to obtain a mass of 51 g / m². 2 , thickness 0.54mm, breathability 39cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 1.03 μm was obtained.

[0078] Example 2 The same procedure as in Example 1 was carried out, except that a material containing 97% of 6-nylon resin with a relative viscosity of 3.0 and 3% of Additive 2 was added to the raw material hopper of the melt-blown manufacturing equipment, and a basis weight of 51 g / m was obtained. 2 , thickness 0.52mm, breathability 40cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 1.39 μm was obtained.

[0079] Example 3 The same procedure as in Example 1 was carried out, except that a material containing 95% of 6-nylon resin with a relative viscosity of 3.0 and 5% of additive 3 was added to the raw material hopper of the melt-blown manufacturing equipment, and a basis weight of 50 g / m was obtained. 2 , thickness 0.52mm, breathability 38cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 0.59 μm was obtained.

[0080] Example 4 The same procedure as in Example 1 was carried out, except that a material containing 90% of 6-nylon resin with a relative viscosity of 3.0 and 10% of Additive 4 was added to the raw material hopper of the melt-blown manufacturing equipment, and a basis weight of 54 g / m was obtained. 2 , thickness 0.44mm, breathability 10cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 0.36 μm was obtained.

[0081] Example 5 A mixture of 90% 6-nylon resin with a relative viscosity of 2.0 and 10% additive 4 was placed in the raw material hopper of the melt-blown manufacturing equipment, and the melt-blending temperature was set to 325°C. The gap between the die and the collector was 450 mm, and 10 Nm of heated compressed air at 300°C was used. 3 / min / m, and the resin was discharged into the atmosphere from a nozzle with a nozzle diameter of 0.2 mm, with a suction volume of 400 Nm 3 The fibrous resin was continuously collected on a collector at a rate of 48 g / m² / min. The rotation speed of the collector was adjusted appropriately to obtain a fibrous resin with a basis weight of 48 g / m². 2 , thickness 0.37mm, breathability 9cm 3 / cm 2 A melt-blown nonwoven fabric with an average fiber diameter of 0.14 μm was obtained.

[0082] The compounds of the additive abbreviations in Table 1 are as follows: Additive 1 Chimassorb® 944FDL BASF Japan Ltd. Additive 2 Chimassorb® 2020FDL BASF Japan Ltd. Additive 3: Mixture of Additive 1 and Tinuvin® 622SF (BASF Japan Ltd.) Additive 4 OGSOL MF11 Fluorene-based resin modifier Osaka Gas Chemicals Co., Ltd. Additive 5 Light Amide WH-510K Fatty acid amide compound similar to ethylene bisstearylamide Kyoeisha Chemical Co., Ltd.

[0083] [ka]

[0084] [ka]

[0085] [ka]

[0086] Comparative Example 1 As shown in Table 1, a melt-blown nonwoven fabric having a basis weight of 50 g / m was produced under the same conditions as in Example 1, except that no additives were added. 2 , thickness 0.49mm, breathability 48cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 3.70 μm was obtained.

[0087] Comparative Example 2 Only 6-nylon resin with a relative viscosity of 2.0, the same as in Example 5, was placed in the raw material hopper of the melt-blown manufacturing equipment without using any additives, and the melt-kneading temperature was set to 330°C. The gap between the die and the collector was 130 mm, and 10 Nm of heated compressed air at 300°C was used. 3 / min / m, and the resin was discharged into the atmosphere from a nozzle with a nozzle diameter of 0.2 mm, with a suction volume of 400 Nm 3 The fibrous resin was continuously collected on a collector at a rate of 1 / min / m, and the rotation speed of the collector was adjusted appropriately to obtain a basis weight of 21 g / m. 2 , thickness 0.22mm, breathability 14cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 1.65 μm was obtained.

[0088] Comparative Example 3 A mixture of 90% 6-nylon resin with a relative viscosity of 3.0 and 10% ε-caprolactam, a raw material monomer used to reduce the physical viscosity of the molten resin, was placed in the raw material hopper of the melt-blown manufacturing equipment, and the melt-kneading temperature was set to 325°C. The gap between the die and collector was 120 mm, and 10 Nm of heated compressed air at 340°C was used. 3 / min / m, and the resin was discharged into the atmosphere from a nozzle with a nozzle diameter of 0.3 mm, with a suction volume of 400 Nm 3 The fibrous resin was continuously collected on a collector at a rate of 19 g / m² / min. The rotation speed of the collector was adjusted appropriately to obtain a mass of 19 g / m². 2 , thickness 0.33mm, breathability 32cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 1.26 μm was obtained.

[0089] (2) Manufacturing of melt-blown nonwoven fabrics using PBT as raw material Example 6 A mixture of 97% MFR100 polybutylene terephthalate (PBT) resin and 3% additive 4 was placed in the raw material hopper of the melt-blown manufacturing equipment, and the melt-blending temperature was set to 280°C. The gap between the die and the collector was 130 mm, and 13 Nm of heated compressed air at 305°C was used. 3 / min / m, and the resin was discharged into the atmosphere from a nozzle with a nozzle diameter of 0.2 mm, with a suction volume of 400 Nm 3 The fibrous resin was continuously collected on a collector at a rate of 1 / min / m, and the rotation speed of the collector was adjusted appropriately to obtain a mass of 30 g / m. 2 , thickness 0.28mm, breathability 12cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 0.66 μm was obtained.

[0090] Example 7 The same procedure as in Example 6 was carried out, except that a material containing 97% of polybutylene terephthalate (PBT) resin of MFR100 and 3% of Additive 5 was added to the raw material hopper of the melt-blown manufacturing equipment, and a basis weight of 11 g / m was obtained. 2 , thickness 0.11mm, breathability 38cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 0.61 μm was obtained.

[0091] Comparative Example 4 As shown in Table 1, a melt-blown nonwoven fabric having a basis weight of 30 g / m was produced under the same conditions as in Example 6, except that no additives were added. 2 , thickness 0.32mm, breathability 24cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 1.82 μm was obtained.

[0092] Comparative Example 5 Only polybutylene terephthalate (PBT) resin of MFR300 was put into the raw material hopper of the melt-blown manufacturing equipment without using any additives, and the melt-blending temperature was set to 250°C. The gap between the die and the collector was 100 mm, and 13 Nm of heated compressed air of 305°C was used. 3 / min / m, and the resin was discharged into the atmosphere from a nozzle with a nozzle diameter of 0.2 mm, with a suction volume of 400 Nm3 The fibrous resin was continuously collected on a collector at a rate of 14 g / m² / min. The rotation speed of the collector was adjusted appropriately to obtain a fibrous resin with a basis weight of 14 g / m². 2 , thickness 0.15mm, breathability 16cm 3 / cm 2 A melt-blown nonwoven fabric having an average fiber diameter of 1.12 μm was obtained.

[0093] 2.Measuring methods for various physical properties Various physical properties of the melt-blown nonwoven fabrics of Examples 1 to 7 and Comparative Examples 1 to 5 were measured according to the following measurement methods.

[0094] (1) Metsuke The average basis weight was determined by measuring the mass (g) of 10 melt-blown nonwoven fabric test pieces of 100 mm x 100 mm in a moisture equilibrium state at a temperature of 23°C and a humidity of 50% and averaging the measured values.

[0095] (2) Thickness For a 100mm x 100mm melt-blown nonwoven fabric test piece, diameter 2.5cm, load 7g / cm 2 The thickness of the central part of the test piece, which corresponds to the center of gravity, was measured using a linear gauge equipped with a measuring probe, and the measured values ​​of 10 pieces were averaged to obtain the thickness.

[0096] (3) Breathability The air permeability was determined by measuring 10 melt-blown nonwoven fabric test pieces of 100 mm x 100 mm using a Frazier type tester in accordance with JIS L1096 and averaging the results.

[0097] (4)MD strength The MD strength was determined as the maximum strength (N) when a nonwoven fabric was cut to a length of 200 mm in the machine direction and 50 mm in the perpendicular direction, and both ends of the fabric were clamped with chucks spaced 100 mm apart and pulled at a speed of 300 mm / min.

[0098] (5)MD elongation The MD elongation was determined as the maximum elongation (%) when a nonwoven fabric was cut to a length of 200 mm in the machine direction and 50 mm in the direction perpendicular to the machine direction, and both ends of the nonwoven fabric were clamped with chucks spaced 100 mm apart and pulled at a speed of 300 mm / min.

[0099] (6) Fiber diameter The average fiber diameter was calculated by taking four electron micrographs at a magnification that allowed for approximately 25 fibers to be included in each image, measuring the fiber diameters of a total of 100 fibers to the order of 0.01 μm, and averaging these. The fiber diameter fraction is the number of fibers having a particular fiber diameter expressed as a percentage of the total number of fibers.

[0100] (7) Standard deviation, fiber diameter variation rate The standard deviation calculated when determining the average fiber diameter was divided by the average fiber diameter to determine the fiber diameter variation rate.

[0101] (8) Shot The shot is 1m 2 The melt-blown nonwoven fabric test pieces were visually inspected to determine whether or not transparent spots having a diameter of 1.0 mm or more had formed on them, and whether or not they had formed a film was judged.

[0102] 3.Results Table 1 shows that, for polyamide nonwoven fabrics of Examples 1 to 5 and Comparative Example 1, by adjusting the production conditions while using additives 1 to 4, shot count can be reduced and the nonwoven fabric can be made into fine fibers while maintaining good appearance and physical properties. Figure 2(A) is a micrograph of the fibers in the nonwoven fabric of Example 5 at a magnification of 2000 times, and Figure 2(B) is a micrograph of the fibers in the nonwoven fabric of Comparative Example 1 at a magnification of 2000 times.

[0103] Furthermore, Comparative Example 2 shows that when no additives are used and a low-viscosity raw material resin, as in the prior art, is used, the average fiber diameter does not become 1.5 μm or less even when the manufacturing conditions are adjusted, and shots cannot be reduced.

[0104] In Comparative Example 3, an attempt was made to reduce the viscosity of the molten resin by using ε-caprolactam, a raw material monomer for polyamide. However, if the additive used cannot alleviate the intermolecular interactions between the polymer chains of the raw resin, it is clear that even if the resin can be thinned to some extent, the number of shots will increase significantly.

[0105] The same is true for polybutylene terephthalate nonwoven fabrics. Examples 6 to 7 and Comparative Example 4 show that by using additives 4 and 5 and adjusting the production conditions, shots can be reduced and the nonwoven fabric can be made into fine fibers while maintaining good appearance and physical properties.

[0106] Furthermore, Comparative Example 5 shows that when no additives are used and a low-viscosity raw material resin, as in the prior art, is used, the average fiber diameter does not become 1.0 μm or less even when the manufacturing conditions are adjusted, and shots cannot be reduced.

[0107] By appropriately selecting additives and manufacturing conditions, it was confirmed that even with high-melting-point, highly polar polymers, it is possible to produce nonwoven fabrics with an average fiber diameter of 0.1 μm or more and 1.5 μm or less, and a fiber diameter variation rate of 0.45 or more and 1.3 or less, using standard melt-blown manufacturing equipment. Furthermore, it was confirmed that, unlike webs made by electrospinning, the fabric has sufficient strength to be handled even without a substrate.

[0108] [Table 1]

Claims

1. A melt-blown nonwoven fabric comprising fibers made of a thermoplastic resin having a melting point of 200°C or higher and an additive in an amount of 0.1% by weight or more and 20% by weight or less relative to the total weight of the melt-blown nonwoven fabric, wherein the average fiber diameter is 0.1 μm or more and 1.5 μm or less, and the fiber diameter variation rate, which is the ratio of the standard deviation of the fiber diameter to the average fiber diameter, is 0.45 or more and 1.3 or less, the thermoplastic resin comprises at least one selected from the group consisting of polyamide and polyester, The additive is an additive for reducing the intermolecular forces between polymer chains of the thermoplastic resin in a molten state, and is an organic compound containing carbon atoms and hydrogen atoms in its basic skeleton, and is a compound containing a hydroxy group, an amino group, an amide group, a carbonyl group, a carboxy group, a formyl group, an ester group, an alkoxy group, a cyano group, a derivative of any of these, or a combination of two or more of these.

2. The melt-blown nonwoven fabric according to claim 1, wherein the value of the following formula (1) is 0.1 or more. Meltblown nonwoven fabric MD strength [N] / basis weight [g / m ２ ] ≧ 0.1 (1) In the formula, the MD strength is the maximum strength when a nonwoven fabric is cut into a length of 200 mm in the machine direction of the nonwoven fabric and 50 mm in the direction perpendicular to the machine direction, both ends of the nonwoven fabric are clamped with chucks spaced 100 mm apart, and pulled at a speed of 300 mm / min.

3. The melt-blown nonwoven fabric according to claim 1, wherein the value of the following formula (2) is 0.2 or more. MD elongation [%] / basis weight [g / m ２ ] / Average fiber diameter [μm] ≧ 0.2 (2) In the formula, the MD elongation is the maximum elongation when a nonwoven fabric is cut into a length of 200 mm in the machine direction of the nonwoven fabric and 50 mm in the direction perpendicular to the machine direction, both ends of the nonwoven fabric are clamped with chucks spaced 100 mm apart, and pulled at a speed of 300 mm / min.

4. The melt-blown nonwoven fabric according to any one of claims 1 to 3, wherein the additive is a polymer compound having a plurality of nitrogen-containing rings in one molecule.

5. The melt-blown nonwoven fabric according to claim 4, wherein the additive comprises a hindered amine-based light stabilizer having a 2,2,6,6-tetramethylpiperidinyl skeleton in the molecule.

6. The melt-blown nonwoven fabric according to any one of claims 1 to 3, wherein the additive is a compound having a fluorene skeleton.

7. A filter comprising the meltblown nonwoven fabric according to any one of claims 1 to 6.

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