Blended nonwoven fabric and method for manufacturing the same

Abstract

To provide: a combined filament nonwoven fabric, which achieves high morphological stability during moisture absorption and suppresses fibers from adhering to a conveyer net by combining at least two specific continuous fibers; and a manufacturing method thereof.SOLUTION: A combined filament nonwoven fabric includes first continuous fibers and second continuous fibers. The first continuous fiber is a thermoplastic non-water absorbing fiber 16. The second continuous fiber is a thermoplastic water absorbing fiber 15 including polyalkylene oxide unit. The first continuous fibers and the second continuous fibers are combined. A manufacturing method of the combined filament nonwoven fabric forms the combined filament nonwoven fabric by melting and spinning thermoplastic non-water absorbing resin of the first continuous fibers and thermoplastic water absorbing resin of the second continuous fibers from separate spinning nozzles respectively.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a blended nonwoven fabric and a method for producing the same. [Background technology]

[0002] Nonwoven fabrics made from general-purpose thermoplastic resins such as polyamide, polyester, and polypropylene are used in applications related to daily life, medical and hygiene materials, agriculture and horticulture, and industry. Because these thermoplastic resins are hydrophobic, nonwoven fabrics made from these materials are also hydrophobic, resulting in very low water absorption and moisture absorption. Therefore, proposals have been made to impart water absorption or moisture absorption / release properties to hydrophobic fibers.

[0003] For example, polyacrylic acid resins are commonly used as superabsorbent polymers (SAPs), and superabsorbent fibers composed of polyacrylic acid resins, as well as nonwoven fabrics containing these superabsorbent fibers, have been proposed (Patent Document 1). Patent Document 2 proposes a water-absorbing material obtained by crosslinking a hydrophilic high molecular weight compound, which is obtained by reacting a polyalkylene oxide compound with a polycarboxylic acid or diisocyanate, by irradiating it with ionizing radiation or ultraviolet light. Patent Document 3 proposes a method using superabsorbent polymers and water-absorbing fibers. Patent Document 4 discloses a superabsorbent nonwoven fabric and a method for producing the same, which is prepared by melt-spinning a thermoplastic water-absorbing resin containing polyalkylene oxide units to produce a nonwoven fabric containing fibers composed of a thermoplastic water-absorbing resin, as a nonwoven fabric having high water absorption and excellent flexibility. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-45730 [Patent Document 2] Japanese Patent Application Publication No. 5-339384 [Patent Document 3] Japanese Patent Application Publication No. 8-120550 [Patent Document 4] Patent No. 5335705 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the nonwoven fabric composed of superabsorbent fibers described in Patent Document 1 uses polyacrylic acid-based SAP, which is highly crosslinked and lacks thermoplasticity, making it difficult to manufacture fibers, especially long fibers (continuous filaments). Furthermore, it does not have heat-fusible properties, so there was a problem in that binder components such as adhesives or heat-fusible fibers were required to form a nonwoven fabric. The superabsorbent material described in Patent Document 2 had problems with uneven crosslinking depending on the irradiation conditions of ionizing radiation or ultraviolet light used to crosslink the hydrophilic high molecular weight compound, which made the material surface prone to sliminess when absorbing water, reduced gel strength, and high melt viscosity, making it difficult to manufacture fibers. The superabsorbent nonwoven laminate described in Patent Document 3 uses a superabsorbent polymer and superabsorbent fibers, and although it has excellent water absorption, it is a nonwoven laminate with a superabsorbent polymer, so it is generally difficult to obtain one with high strength. In the superabsorbent nonwoven fabric described in Patent Document 4, the solidification rate of the melt-spun fibers is slow during the spinning process of the thermoplastic superabsorbent resin, causing the molten fibers to stick to the conveyor net and making nonwoven fabric production impossible. Therefore, the fibers are spun onto a sheet-like base material, and then the nonwoven fabric is removed from the base material. When moisture is absorbed, the surface of the absorbent fibers becomes sticky, and therefore, if a nonwoven fabric is made only from absorbent fibers, the shape of the nonwoven fabric changes when moisture is absorbed. Furthermore, there was a problem that the shape also changed when moisture was released. Although the absorbent fibers themselves have the ability to be used repeatedly, if they are layered with other materials to prevent shape change, the moisture absorption and release performance cannot be exhibited, and the layer of absorbent fibers deforms.

[0006] To solve the problems of the prior art, the present invention provides a nonwoven fabric made by blending at least two specific continuous fibers, which has high shape stability when absorbing moisture and prevents fibers from adhering to a conveyor net, as well as a method for manufacturing the same. [Means for solving the problem]

[0007] The conjugate nonwoven fabric of the present invention is a conjugate nonwoven fabric containing a first continuous fiber and a second continuous fiber, wherein the first continuous fiber is a thermoplastic non-absorbent fiber, the second continuous fiber is a thermoplastic absorbent fiber containing a polyalkylene oxide unit, the first continuous fiber and the second continuous fiber are conjugated, the single fiber fineness of the second continuous fiber is larger than that of the first continuous fiber, The first continuous fiber is intertwined with the second continuous fiber, and the conjugate nonwoven fabric has a moisture absorption rate of 30% or more and a moisture release rate of 95% That's all. which is characterized in that.

[0008] The manufacturing method of the conjugate nonwoven fabric of the present invention is the manufacturing method of the above conjugate nonwoven fabric, characterized in that a thermoplastic non-absorbent resin of the first continuous fiber and a thermoplastic absorbent resin of the second continuous fiber are melt-spun from separate spinning nozzles to form a conjugate nonwoven fabric.

Effects of the Invention

[0009] In the present invention, the first continuous fiber is a thermoplastic non-absorbent fiber, the second continuous fiber is a thermoplastic absorbent fiber containing a polyalkylene oxide unit, and the first continuous fiber and the second continuous fiber are conjugated, so that the first continuous fiber serves as an aggregate, and the conjugate nonwoven fabric has high shape stability during moisture absorption, high initial water absorption rate, and high moisture release property. Further, since the thermoplastic non-absorbent resin having a faster solidification rate than the thermoplastic absorbent resin and the thermoplastic absorbent resin are melt-spun from individual nozzles, the contact points between the absorbent second continuous fiber and the conveyor net are reduced, and it is possible to prevent the fibers from adhering to the conveyor net. Furthermore, since the non-absorbent first continuous fiber is spun so as to entangle with the absorbent second continuous fiber, the contact points between the absorbent first continuous fiber and the conveyor net are further reduced, and it is possible to prevent the fibers from adhering to the conveyor net.

Brief Description of the Drawings

[0010] [Figure 1]FIG. 1 is a schematic explanatory diagram showing an apparatus for manufacturing a melt blown nonwoven fabric according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic explanatory diagram showing an apparatus for manufacturing a melt blown nonwoven fabric according to another embodiment of the present invention. [Figure 3] FIGS. 3A-D are schematic plan views of a melt spinning nozzle according to an embodiment of the present invention. [Figure 4] FIG. 4 is a planar photograph of a conjugate nonwoven fabric according to an example of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0011] The conjugate nonwoven fabric of the present invention contains a first continuous fiber and a second continuous fiber. The first continuous fiber is a thermoplastic non-water-absorbent fiber, and the second continuous fiber is a thermoplastic water-absorbent fiber containing a polyalkylene oxide unit. The first continuous fiber and the second continuous fiber are conjugate. Thereby, the first continuous fiber serves as an aggregate, and a conjugate nonwoven fabric having high shape stability during moisture absorption, a high initial water absorption rate, and a high moisture release rate can be obtained.

[0012] When the conjugate nonwoven fabric is used as a base number, it preferably contains 1 to 99% by mass of the water-absorbent second continuous fiber, more preferably 10 to 90% by mass, and still more preferably 20 to 80% by mass. Also, the non-water-absorbent first continuous fiber preferably contains 1 to 99% by mass, more preferably 10 to 90% by mass, and still more preferably 20 to 80% by mass.

[0013] The water-absorbent second continuous fiber is preferably a modified product containing a polyalkylene oxide unit. Specifically, examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, polybutylene oxide, copolymers or mixtures thereof, etc., but units containing at least polyethylene oxide, for example, polyethylene oxide units, poly C 2-4 alkylene oxide units. 2-4Alkylene oxide copolymer units are preferred. The proportion of polyethylene oxide units in the polyalkylene oxide units is 50 to 100 mol%, preferably 70 to 100 mol%, and more preferably 90 to 100 mol%. For example, if polypropylene oxide units are included, the proportion is 80 to 95 mol%, and the polymerization form of the copolymer may be either random copolymerization or block copolymerization, but block copolymerization is usually used.

[0014] The number-average molecular weight of the polyalkylene oxide units is preferably 3,000 to 50,000, more preferably 5,000 to 30,000, and even more preferably 15,000 to 22,000. If the molecular weight is too low, the melt viscosity of the thermoplastic water-absorbent resin becomes high, requiring a high molding temperature during the production of the blended nonwoven fabric, which makes the resin prone to decomposition and discoloration. On the other hand, if the molecular weight is too high, the melt viscosity becomes low, reducing the flexibility of the blended nonwoven fabric, and making the gel prone to becoming slimy when water is absorbed.

[0015] Examples of thermoplastic water-absorbent resins containing polyalkylene oxide units in the main chain include polyester resins and polyester elastomers containing polyalkylene oxide units as diol units. However, thermoplastic water-absorbent resins obtained by reacting a polyol component containing polyalkylene oxide with a polyisocyanate component are preferred because they offer a balance between flexibility and water absorption.

[0016] In polyalkylene oxide modified products, it is preferable to use other polyol components (low molecular weight polyol components) in addition to the polyalkylene oxide, for example, to enhance the ability to form fibers. Other polyol components include aliphatic diols (ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-, 1,3- or 1,2-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 2,2,4-trimethylpentane-1,3-diol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-undecanediol, etc.). 2-12 Alkanediols), aliphatic polyols or their esters (such as glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, etc.) 3-12 Aliphatic polyols, glyceryl monoacetate, glyceryl monobutyrate and other glycerol monoacyl esters, alicyclic diols (cycloalkanediols such as cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and hydrogenated xylylenediol, and C of these cycloalkanediols) 2-4 (such as alkylene oxide adducts), aromatic diols (such as xylylenediol, bisphenol A, bisphenol S, catechol, resorcinol, hydroquinone, and other aromatic diols, and C of these aromatic diols) 2-4 Examples include alkylene oxide adducts. These other polyol components can be used individually or in combination of two or more.

[0017] Among these other polyol components, aliphatic diols, particularly 1,4-butanediol, are preferred due to their compatibility with polyalkylene oxides and water absorption properties. 3-5 Alkylene glycol is preferred. The proportion of other polyol components is, for example, 0.5 to 6 moles, preferably 1 to 5 moles, and more preferably 1.5 to 3 moles, per mole of polyalkylene oxide. If the proportion of other polyol components is too low, the water absorption capacity of the resin will increase, but the gel strength will decrease, so the surface of the blended nonwoven fabric tends to become slimy (a slimy feeling will occur) when absorbing liquid. On the other hand, if the proportion of other polyol components is too high, the melt viscosity of the resin will increase, which may lead to decomposition or discoloration of the resin. The number of moles of polyalkylene oxide can be determined by dividing its mass by its number-average molecular weight.

[0018] Examples of the polyisocyanate component include aliphatic polyisocyanates and aromatic polyisocyanates. These polyisocyanate components may also be derivatives such as polymers (dimers, trimers, tetramers, etc.), adducts, and modified forms (bulet modified forms, alohanate modified forms, urea modified forms, etc.), or urethane oligomers having multiple isocyanate groups.

[0019] Of these polyisocyanate components, non-aromatic polyisocyanates, such as symmetric aliphatic or alicyclic polyisocyanates, aliphatic diisocyanates such as HDI, and alicyclic diisocyanates such as HMDI, are preferred from the viewpoint of weather resistance and other factors. The proportion (usage ratio) of the polyisocyanate component is 0.5 to 3 moles, preferably 0.7 to 2 moles, and more preferably 0.8 to 1.2 moles, per 1 mole of the total of the polyalkylene oxide and other polyol components. If the amount of polyisocyanate component used is too small, the water absorption capacity of the resin will increase, but a slimy feeling is likely to occur. On the other hand, if the amount of polyisocyanate component used is too large, there is a risk of decomposition and discoloration of the resin. Polyalkylene oxide modified products are usually obtained in the form of pellets, sheets, or films. Polyalkylene oxide modified products may be used as they are, but they may also be crushed using a pulverizer or the like.

[0020] The thermoplastic water-absorbent resin (particularly the polyalkylene oxide modified product) preferably has an appropriate melt viscosity for fiber formation. Specifically, the melt viscosity is 100 to 800 Pa·s, more preferably 200 to 600 Pa·s, under the conditions of a die hole diameter of 1 mm and die length of 1 mm at a temperature of 150 to 200°C and a load of 3 to 5 MPa. If the melt viscosity is too low, the processability decreases and the flexibility of the blended nonwoven fabric decreases. On the other hand, if the melt viscosity is too high, it becomes necessary to raise the molding temperature during the formation of the blended nonwoven fabric, which can lead to decomposition of the polyalkylene oxide modified product and make the resulting blended nonwoven fabric prone to discoloration.

[0021] The aforementioned thermoplastic water-absorbent resin (particularly polyalkylene oxide modified product) has high water absorption, with a water absorption capacity (water absorption relative to its own weight) of 10 to 50 g / g, preferably 15 to 45 g / g, and more preferably 20 to 40 g / g. If the water absorption capacity is too high, the morphological stability of the blended nonwoven fabric tends to decrease during water absorption. Furthermore, in the present invention, the water absorption capacity does not depend on the ion concentration in the water, and for example, even with seawater, it has the same water absorption capacity as with fresh water (pure water).

[0022] The cross-sectional shape (cross-sectional shape perpendicular to the length direction of the fiber) of such thermoplastic superabsorbent resin fibers containing polyalkylene oxide units is not limited to common solid cross-sectional shapes such as round cross-sections or irregular cross-sections (flattened, elliptical, polygonal, etc.), but may also be hollow cross-sections.

[0023] The average fiber diameter of the absorbent and non-absorbent fibers can be selected from a range of 0.1 to 100 μm depending on the application, for example, 1 to 50 μm, preferably 3 to 30 μm, and more preferably 10 to 20 μm. If the fiber diameter is too small, fuzzy material is likely to form and clumps are likely to occur. On the other hand, if the fiber diameter is too large, the fabric becomes coarse and the texture is likely to deteriorate. The single fiber fineness of the absorbent fiber (second continuous fiber) is the same as that of the non-absorbent fiber (first continuous fiber). (main) Larger is preferable. This results in non-absorbent fibers (first continuous fibers) (main)This makes it easier for the absorbent fibers (second continuous fibers) to intertwine and entangle, further reducing the contact points between the absorbent fibers and the conveyor net, thus preventing the absorbent fibers from adhering to the conveyor net. The average fiber diameter can be measured by the method described in the examples below.

[0024] The first continuous fiber is preferably a polyolefin fiber, a polyamide fiber, or a polyester fiber. These fibers have a water absorption capacity of less than 10 g / g relative to their own weight. Examples of polyolefin fibers include polyethylene fibers and polypropylene fibers. Examples of polyester fibers include polyethylene terephthalate fibers, polybutylene terephthalate fibers, and polytrimethylene terephthalate fibers. Examples of polyamide fibers include polyamide 6 fibers and polyamide 66 fibers. Examples of polyurethane fibers include polyester polyol type urethane fibers. These thermoplastic non-absorbent resins can be used alone or in combination of two or more. Examples of official moisture content are 0% for polyethylene fibers, 4.5% for polyamide fibers, and 0.4% for polyester fibers (Encyclopedia of Fibers, p. 472, March 25, 2002, Maruzen).

[0025] The average fiber diameter of the first continuous fiber and the second continuous fiber is preferably 0.1 to 50 μm. Note that continuous fibers are also called long fibers or filaments.

[0026] The aforementioned blended nonwoven fabric preferably has a water absorption capacity of 5 to 100 g / g. This results in a nonwoven fabric with high water absorption and moisture absorption properties.

[0027] The aforementioned blended nonwoven fabric preferably has a hygroscopicity of 5 to 90% by mass and a moisture release rate of 95% by mass or more, as measured by the method described later. This makes it possible to produce a blended nonwoven fabric with a high initial water absorption rate and high moisture release properties.

[0028] Since the mixed fiber non-woven fabric of the present invention has appropriate heat fusibility, it can maintain the form of the non-woven fabric even without a binder component, so it may not substantially contain a binder component. When a binder is included, the proportion of the component may be 0 to 10% by mass, preferably 5% by mass or less, more preferably 1% by mass or less, based on the entire mixed fiber non-woven fabric. Usually, however, it does not contain a binder component.

[0029] The mass (basis weight) per unit area of the mixed fiber non-woven fabric of the present invention can be selected from the range of about 5 to 2000 g / m 2 For example, 10 to 1500 g / m 2 , preferably 15 to 1000 g / m 2 , more preferably 20 to 500 g / m 2 It may be. Also, the apparent density of the mixed fiber non-woven fabric of the present invention can also be selected from the range of, for example, 0.01 to 10 g / cm 3 For example, 0.03 to 5 g / cm 3 , preferably 0.05 to 3 g / cm 3、 More preferably 0.1 to 1 g / cm 3 It may be. The thickness of the mixed fiber non-woven fabric of the present invention can also be selected from the range of 0.01 to 100 mm according to the application. For example, 0.02 to 10 mm, preferably 0.03 to 5 mm, more preferably 0.1 to 1 mm. Further, according to the application, a plurality of non-woven fabrics having such a thickness in this range may be laminated and used.

[0030] The mixed fiber non-woven fabric of the present invention is also excellent in air permeability and has an air permeability of 1 cm 3 / (cm 2 ·sec) or more. For example, 1 to 1000 cm 3 / (cm 2 ·sec), preferably 10 to 800 cm 3 / (cm 2 ·sec), more preferably 20 to 300 cm 3 / (cm 2 ·sec)). In the present invention, since it substantially does not contain a binder and film formation is also suppressed, the air permeability is high.

[0031] The blended nonwoven fabric of the present invention has a breaking strength of 1 to 200 N / 5 cm, preferably 3 to 150 N / 5 cm, and more preferably 5 to 100 N / 5 cm, at a thickness of 0.2 mm.

[0032] The blended nonwoven fabric of the present invention may be laminated onto a sheet-like substrate to form a laminate. The laminate may consist of three or more layers, for example, a laminate in which the blended nonwoven fabric is laminated on both sides of a sheet-like substrate, or a laminate in which the sheet-like substrate is laminated on both sides of the blended nonwoven fabric. The sheet-like substrate can be made of any organic polymer such as a thermoplastic resin, thermoplastic elastomer, or rubber, from the viewpoint of adhesion to the blended nonwoven fabric, and can be selected according to the application. However, from the viewpoint of flexibility and adhesion, films or sheets made of soft polymers (films or sheets made of olefin resins such as polyethylene or polypropylene, thermoplastic elastomers, rubber, etc.), nonwoven fabrics or woven or knitted fabrics made of organic polymers (woven or knitted fabrics) can be preferably used. Among these sheet-like substrates, nonwoven fabrics or woven or knitted fabrics (especially nonwoven fabrics) made of the aforementioned other fibers are particularly preferred because they have excellent adhesion and flexibility without impairing the properties of nonwoven fabrics such as breathability.

[0033] Furthermore, nonwoven or knitted fabrics composed of other fibers may have strong adhesion, and when producing a robust laminate, a sheet-like substrate composed of a hydrophilic resin (a highly polar resin) may be used, particularly a nonwoven or knitted fabric composed of hydrophilic fibers. Examples of hydrophilic fibers include vinyl alcohol-based fibers such as ethylene-vinyl alcohol copolymers, polylactic acid-based fibers such as polylactic acid, (meth)acrylic copolymer fibers containing (meth)acrylamide units, and cellulose-based fibers such as rayon fibers and acetate fibers. Of these, nonwoven fabrics composed of cellulose-based fibers such as rayon fibers or vinyl alcohol-based fibers such as ethylene-vinyl alcohol copolymer fibers are preferred.

[0034] On the other hand, nonwoven or knitted fabrics composed of the aforementioned other fibers may be used when strong adhesion between layers is not required, or when the nonwoven fabric of the present invention is to be obtained as a single layer by peeling it from a laminate. In such cases, a sheet-like substrate composed of a nonhydrophilic resin (a resin that is not very polar and is relatively hydrophobic) may be used, particularly a nonwoven or knitted fabric composed of nonhydrophilic fibers. Examples of nonhydrophilic fibers include polyolefin fibers (e.g., polyethylene fibers, polypropylene fibers, etc.), polyester fibers (e.g., polyethylene terephthalate fibers, polybutylene terephthalate fibers, etc.), polyamide fibers (e.g., polyamide 6 fibers, polyamide 66 fibers, etc.), and polyurethane fibers (e.g., polyester polyol type urethane fibers, etc.). Of these, nonwoven fabrics composed of polyolefin fibers such as polypropylene and polyester fibers such as polyethylene terephthalate are preferred, and non-absorbent fibers such as polypropylene fibers are particularly preferred.

[0035] The nonwoven fabric used as a sheet-like base material may be, for example, a long-fiber nonwoven fabric (such as spunbond nonwoven fabric, meltblown nonwoven fabric, or flash-spun nonwoven fabric), or a short-fiber nonwoven fabric (such as spunlace nonwoven fabric, airlace nonwoven fabric, thermal-bonded nonwoven fabric, needle-punched nonwoven fabric, chemical-bonded nonwoven fabric, or paper).

[0036] The thickness ratio of the nonwoven fabric to the sheet-like substrate can be selected depending on the application and the type of sheet-like substrate, but for example, nonwoven fabric / sheet-like substrate = 10 / 1 to 1 / 10, preferably 5 / 1 to 1 / 5, and more preferably 1 / 3 to 3 / 1.

[0037] The thickness of the laminate of the present invention can be selected from a range of, for example, 0.01 mm or more (for example, about 0.01 to 100 mm) depending on the application, and may be, for example, 0.05 to 10 mm, preferably 0.1 to 5 mm, and more preferably 0.2 to 3 mm (particularly about 0.3 to 1 mm). The basis weight, apparent density, air permeability, breaking strength, and elongation at break of the laminate can be selected from the same range as the nonwoven fabric described above.

[0038] Next, the method for producing the blended nonwoven fabric of the present invention will be described. In this method, a thermoplastic non-absorbent resin of a first continuous fiber and a thermoplastic superabsorbent resin of a second continuous fiber are melt-spun from separate spinning nozzles to produce a blended nonwoven fabric. A direct method in which the spinning process and the webing process are directly linked is preferred. As a direct method, conventional methods such as the spunbond method, meltblown method, and flash spinning method can be used. Of these methods, the meltblown method is preferred because it is a simple method that does not require a binder and can produce filaments with a small fiber diameter. A nonwoven fabric obtained by the meltblown method is also called a meltblown nonwoven fabric.

[0039] In the meltblown method, a fiber web is obtained by melt-spinning the thermoplastic superabsorbent resin, blowing off the resulting fibers with a high-temperature gas, mixing them, and collecting them. In the present invention, by spinning under the following manufacturing conditions, a novel blended nonwoven fabric can be produced using the thermoplastic superabsorbent resin, with suppressed film formation and uniform fiber formation. In particular, despite the slow solidification rate and high hydrophilicity of polyalkylene oxide modified materials, a uniform blended nonwoven fabric can be obtained without film formation by melt-spinning the polyalkylene oxide material using the method of the present invention.

[0040] Specifically, a thermoplastic superabsorbent resin containing polyalkylene oxide units (and other additives as needed) is melt-kneaded using a conventional mixer (e.g., a melt-kneading extruder). The melting temperature can be selected according to the type of thermoplastic superabsorbent resin, but in the case of a polyalkylene oxide modified product, for example, the temperature is 150 to 260°C, preferably 160 to 250°C, and more preferably 180 to 240°C.

[0041] The thermoplastic superabsorbent resin, melted and kneaded by the mixer, is supplied to two nozzles individually mounted on the spinning head. The distance between each nozzle is, for example, 0.3 mm, preferably 0.2 mm, and more preferably 0.1 mm.

[0042] The discharge volume of each nozzle can be selected from a range of approximately 0.01 to 0.5 g / (nozzle / min), for example, 0.03 to 0.4 g / (nozzle / min), preferably 0.05 to 0.3 g / (nozzle / min), and more preferably 0.15 to 0.2 g / (nozzle / min).

[0043] The spinning temperature can be selected from a range of approximately 120 to 300°C depending on the type of thermoplastic superabsorbent resin, but in the case of polyalkylene oxide modified products, for example, it is 150 to 260°C, preferably 180 to 255°C, and more preferably 220 to 245°C. If the spinning temperature is too high, the resin may deteriorate. On the other hand, if the spinning temperature is too low, it tends to become difficult to form filaments.

[0044] In the meltblown process, a method is typically used in which hot air is blown from a slit formed near the nozzle to blow the spun fibers onto a net. The air temperature can be selected from a range of approximately ±50°C (especially ±30°C) of the spinning temperature, and is usually the same temperature as the spinning temperature.

[0045] The airflow rate of the blown air is, for example, 1000 to 10000 L / min, preferably 1500 to 8000 L / min, and more preferably 2000 to 6500 L / min. The air pressure of the blown air is, for example, 0.001 to 1 MPa, preferably 0.005 to 0.5 MPa, and more preferably 0.01 to 0.3 MPa.

[0046] The distance between the nozzle opening and the collection net (collection distance) is, for example, 10 to 100 cm, preferably 20 to 90 cm, and more preferably 30 to 80 cm. If the collection distance is too small, the amount of blown cotton scattering increases, making it difficult to form a web. On the other hand, if the collection distance is too large, the web tends to become coarse. Furthermore, in this invention, suction may be applied from the bottom of the conveyor net using a suction collector (suction device). The suction pressure is, for example, 0.1 to 2.0 kPa, preferably 0.5 to 1.5 kPa.

[0047] Furthermore, in this invention, to suppress adhesion between the conveyor net and the blended nonwoven fabric, a thermoplastic water-absorbent resin containing polyalkylene oxide units may be melt-spun onto a sheet substrate. When the thermoplastic water-absorbent resin is melt-spun onto a sheet substrate, particularly a nonwoven fabric composed of non-absorbent fibers, the resulting blended nonwoven fabric can be easily peeled off the sheet substrate, allowing for the simple production of a blended nonwoven fabric.

[0048] Figure 1 is a schematic diagram showing a meltblown nonwoven fabric manufacturing apparatus 10 according to one embodiment of the present invention. On the metal net 6 (conveyor net) of the molding machine 5, thermoplastic non-absorbent fibers and thermoplastic absorbent fibers containing polyalkylene oxide units are melt-spun from a nozzle 3 by the meltblown method, and the spun fibers 4 are compositely formed with a high-temperature, high-speed fluid and sprayed. The sprayed fibers 4 are collected and deposited on the metal net 6 from below using a suction device 7 (suction collector) to form a blended nonwoven fabric 8 composed of the fibers 4, which is then wound up on a winding roll 9.

[0049] Figure 2 is a schematic diagram showing a meltblown nonwoven fabric manufacturing apparatus 11 of another embodiment of the present invention, which is an example of melt spinning on a sheet substrate 2. The sheet substrate 2 is laid out (supplied) from the sheet substrate supply roll 1 onto the metal net 6 (conveyor net) of the molding machine 5. Using the meltblown method, thermoplastic non-absorbent fibers and thermoplastic absorbent fibers containing polyalkylene oxide units are melt-spun from the nozzle 3, and the spun fibers 4 are compositely formed with a high-temperature, high-speed fluid and sprayed. The sprayed fibers 4 are collected and deposited on the sheet substrate 2 from the bottom of the metal net 6 using a suction device 7 (suction collector), forming a blended nonwoven fabric 8 composed of the fibers 4, which is then wound up on a winding roll 9. As the sheet-like substrate 2, the aforementioned sheet-like substrate can be used, but in order to enable suction from a suction device, a nonwoven fabric, woven fabric, or knitted fabric with good breathability is preferred. In particular, the aforementioned long-fiber nonwoven fabric may be used to peel off the blended nonwoven fabric from the sheet-like substrate to obtain a single layer of blended nonwoven fabric, or it may be used as is as a laminate. Polyalkylene oxide modified materials have a slow solidification rate and high hydrophilicity, making it extremely difficult to produce a uniform nonwoven fabric (especially a single layer of nonwoven fabric). However, in the method of the present invention, by using the aforementioned long-fiber nonwoven fabric (especially a nonwoven fabric or woven / knitted fabric composed of non-absorbent fibers such as polyolefin fibers such as polypropylene) as the sheet-like substrate, a uniform blended nonwoven fabric can be obtained without forming a film.

[0050] Alternatively, an aggregate of opened short fibers may be supplied by card, and a thermoplastic superabsorbent resin containing polyalkylene oxide units, which also serves as a binder component for the short fibers, may be melt-spun onto the card to form a laminate (or integrated product). When obtaining a nonwoven fabric by peeling it from a laminate, the laminate may be cooled with a cooling device to improve peelability. For example, the temperature of the winding roll may be adjusted to, for example, 0 to 35°C.

[0051] The resulting blended nonwoven fabric or laminate is usually obtained as a plate-like or sheet-like molded body and is used after being processed into the desired shape by cutting or other methods, but may be secondarily molded by conventional thermoforming if necessary. Furthermore, the blended nonwoven fabric or laminate may be further laminated with sheet-like or film-like material by conventional lamination methods, rubber / steel rolls, embossing / steel rolls, etc.

[0052] Figures 3A-D are schematic plan views of a melt spinning nozzle according to one embodiment of the present invention. The melt spinning nozzle 12a in Figure 3A is an example in which a large-diameter nozzle 13 and a small-diameter nozzle 14 are arranged in a single row in this order. A thermoplastic water-absorbent resin is discharged from the large-diameter nozzle 13, and a thermoplastic water-insoluble resin is discharged from the small-diameter nozzle 14. CD is the width direction of the blended nonwoven fabric 8. The melt spinning nozzle 12b in Figure 3B is an example in which a large-diameter nozzle 13 and small-diameter nozzles 14a and 14b are arranged in a single row in this order. The melt spinning nozzle 12c in Figure 3C is an example in which a large-diameter nozzle 13 and a small-diameter nozzle 14 are arranged in two rows. The melt spinning nozzle 12d in Figure 3D is an example in which small-diameter nozzles 14a and 14b are arranged on both sides of the large-diameter nozzle 13, for a total of three rows.

[0053] Figure 4 is a plan view of a blended nonwoven fabric according to one embodiment of the present invention. The fibers with a larger diameter are absorbent fibers 15, and the fibers with a smaller diameter are non-absorbent fibers 16. The fiber thickness relationship can be controlled by the nozzle diameter and the air velocity of the sprayed fluid. [Examples]

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to these examples. The physical properties in the examples were measured by the methods shown below. Note that "parts" and "%" in the examples are based on mass.

[0055] <Water absorption rate of nonwoven fabrics> The obtained meltblown nonwoven fabric was immersed in deionized water or artificial seawater (manufactured by Yashima Pharmaceutical Co., Ltd., product name "Aquamarine") for 30 seconds. The mass of the nonwoven fabric was measured before and after water absorption, and the amount of deionized water or artificial seawater absorbed was calculated using the following formula. <Water absorption amount> The amount of water absorbed was calculated by measuring the mass of the meltblown nonwoven fabric before and after water absorption, and using the following formula. Water absorption (g / g) = (mass after water absorption - mass before water absorption) / mass before water absorption <Moisture absorption rate and moisture release rate> Nonwoven fabrics whose mass [A(g)] was measured in advance were left to stand in a constant temperature and humidity chamber at 34°C and 90%RH for 5 hours, and then their mass [B(g)] was measured. Furthermore, they were left to stand at 25°C and 65%RH for 2 hours, and their mass [C(g)] was measured at that time. The moisture absorption rate (%) and moisture release rate (%) were then calculated according to the following formula. Note that a blended nonwoven fabric can be judged to have good moisture absorption and release rates if it has a moisture absorption rate of 30% or more and a moisture release rate of 90% or more. Moisture absorption rate (%) = [(BA) / A] × 100 Moisture release rate (%) = [(BC) / (BA)] × 100 <Balance weight of nonwoven fabric (g / m²) 2 )> Measurements were taken in accordance with JIS L1913 "Test Methods for General Short Fiber Nonwoven Fabrics". Nonwoven fabric thickness (mm), apparent density (g / cm³) 3 )> The thickness was measured in accordance with JIS L1913 "Test Methods for General Short Fiber Nonwoven Fabrics," and the apparent density was calculated from this value and the basis weight value. <Average fiber diameter of nonwoven fabrics> Nonwoven fabrics were magnified and photographed using a scanning microscope, and the diameters of 100 randomly selected fibers (hereinafter referred to as fiber diameter) were measured and the average value was calculated. <Air permeability of nonwoven fabrics> Measurements were taken using the Frazier method in accordance with JIS L1096. <Removability from conveyor net> We evaluated the nonwoven fabric, conveyor net, and their release properties. <Shape stability> The nonwoven fabric was subjected to moisture absorption for 5 hours under conditions of 34°C and 90% RH relative humidity, followed by dehumidification for 2 hours under conditions of 25°C and 65% RH relative humidity. This process was repeated 20 times to evaluate the dimensional stability of the nonwoven fabric.

[0056] (Example of production: Example of synthesis of polyalkylene oxide modified product) In storage tank A, which was kept warm at 80°C and equipped with a stirrer, 100 parts by mass of thoroughly dehydrated polyethylene oxide with a number average molecular weight of 20,000, 0.90 parts by mass of 1,4-butanediol, and 0.1 parts by mass of dibutyltin dilaurate were added and stirred under a nitrogen gas atmosphere to obtain a homogeneous mixture. Separately from this tank, dicyclohexylmethane-4,4'-diisocyanate was added to storage tank B, which was kept warm at 30°C, and stored under a nitrogen gas atmosphere. Using a metering pump, the mixture from storage tank A was continuously supplied at a rate of 250 g / min, and the dicyclohexylmethane-4,4'-diisocyanate from storage tank B was supplied at a rate of 9.2 g / min to a twin-screw extruder set to 110-140°C. The mixture was mixed and reacted in the extruder, and the strand was extruded from the extruder outlet and pelletized by a pelletizer to obtain a polyalkylene oxide modified product. The resulting polyalkylene oxide modified product had a melt viscosity of 280 Pa·s, and its water absorption rate was 25 g / g in both deionized water and artificial seawater.

[0057] (Example 1) Using the apparatus shown in Figure 1, the polyalkylene oxide modified material obtained in Production Example 1 was melt-spun as the thermoplastic water-absorbing resin, and polypropylene resin (product name Prime PolyPro S119, manufactured by Prime Polymer Co., Ltd.) was melt-spun from separate nozzles as the thermoplastic water-absorbing resin. The blend ratio was 80% thermoplastic water-absorbing fibers and 20% thermoplastic water-absorbing resin. Specifically, the polyalkylene oxide modified material pellets were extruded from the nozzle of a spinning nozzle with a hole diameter of 0.6 mmφ at a spinning temperature of 240°C, while hot air at a temperature (primary air temperature) of 220°C and an air flow rate of 2500 L / min was ejected from a slit provided near the spinning hole to thin the extruded fibers. Polypropylene resin pellets were extruded from a spinning nozzle with a pore diameter of 0.3 mm at a spinning temperature of 240°C. Simultaneously, hot air at a temperature (primary air temperature) of 220°C and an air flow rate of 2500 L / min was blown out from a slit located near the spinning hole to thin the extruded fibers. These fibers were collected on a conveyor net located at a collection distance of 60 cm, wound up, and weighed to a basis weight of 50 g / m². 2 A blended nonwoven fabric was obtained. A plan view of the obtained blended nonwoven fabric is shown in Figure 1.

[0058] (Example 2) The ratio of thermoplastic absorbent fiber to thermoplastic non-absorbent resin in Example 1 was set to 50% thermoplastic absorbent fiber and 50% thermoplastic non-absorbent resin. Except for the ratio, the process was the same as in Example 1, with a basis weight of 50 g / m². 2 A blended nonwoven fabric was obtained.

[0059] (Example 3) Using the apparatus shown in Figure 2, a crimped short-fiber nonwoven fabric was used as the sheet base material 2. On this, a blended nonwoven fabric was laminated with the thermoplastic absorbent fiber and thermoplastic non-absorbent resin from Example 1, with a ratio of 50% thermoplastic absorbent fiber and 40% thermoplastic non-absorbent resin. The sheet base material 2 was made by carding polyethylene terephthalate fibers with a fiber length of 51 mm and forming a nonwoven fabric by the thermal bonding method. The rest of the process was the same as in Example 1, with a basis weight of 50 g / m². 2 A blended nonwoven fabric was obtained.

[0060] (Comparative Example 1) The polyalkylene oxide modified product obtained in Production Example 1 was melt-spun. The polyalkylene oxide modified product The pellets were extruded from a spinning nozzle with a hole diameter of 0.6 mm at a spinning temperature of 240°C. Simultaneously, hot air at a temperature (primary air temperature) of 220°C and an air flow rate of 2500 L / min was blown out from a slit located near the spinning hole to thin the extruded fibers. These fibers were collected on a conveyor net located at a collection distance of 60 cm, wound up, and weighed to a basis weight of 50 g / m. 2 We obtained a water-absorbent nonwoven fabric.

[0061] (Comparative Example 2) Polypropylene resin (manufactured by Prime Polymer Co., Ltd., product name Prime PolyPro S119) was melt-spun. Polypropylene resin pellets were extruded from a spinning nozzle with a 0.3 mm diameter pore at a spinning temperature of 240°C. Simultaneously, hot air at a temperature (primary air temperature) of 220°C and an air flow rate of 2500 L / min was ejected from a slit near the spinning hole to thin the extruded fibers. These fibers were collected on a conveyor net located 60 cm away, wound up, and weighed to a basis weight of 50 g / m². 2 A hydrophobic nonwoven fabric was obtained.

[0062] (evaluation) (Evaluation of hygroscopicity) A: Moisture absorption rate of 30% or more. B: Moisture absorption rate of 10% or more, but less than 30%. C: Moisture absorption rate less than 10%. (Evaluation of moisture release properties) A: Moisture release rate of 95% or more. B: Moisture release rate of 90% or more, but less than 95%. C: Moisture release rate less than 90%. (Evaluation of peelability) A: The nonwoven fabric peels off easily from the combiner net. B: The nonwoven fabric peels off the combine net, getting caught on it. C: The nonwoven fabric tears without peeling off the combine net. (Evaluation of shape stability) A: No wrinkles formed. B: Wrinkles may occur. C: It contracts. Table 1 shows the evaluation results of the laminates or nonwoven fabrics obtained in the examples and comparative examples.

[0063] [Table 1]

[0064] The results in Table 1 show that the blended nonwoven fabric of this embodiment is excellent in terms of moisture absorption, moisture release, peelability, and shape stability. [Industrial applicability]

[0065] The present invention relates to a blended nonwoven fabric with excellent water absorption, moisture absorption and release properties, and shape stability when absorbing moisture, and a method for producing the same, which can be suitably used in applications such as daily life, medical and hygiene materials, agriculture and horticulture, and industrial use. [Explanation of Symbols]

[0066] 1. Sheet-shaped substrate supply roll 2 Sheet-shaped base material 3 nozzles 4 Fibers 5 Molding machine 6. Metal net (conveyor) 7. Suction device 8 Blended nonwoven fabric 9. Winding Roll 10,11 Meltblown nonwoven fabric manufacturing equipment 12 Melt spinning nozzle 13 Large-diameter nozzle 14 Small diameter nozzles 15 Absorbent fibers 16 Non-absorbent fibers

Claims

1. A blended nonwoven fabric containing a first continuous fiber and a second continuous fiber, The first continuous fiber is a thermoplastic, non-absorbent fiber. The second continuous fiber is a thermoplastic water-absorbing fiber containing polyalkylene oxide units. The first continuous fiber and the second continuous fiber are blended together. The single fiber fineness of the second continuous fiber is greater than the single fiber fineness of the first continuous fiber. The first continuous fiber is intertwined with the second continuous fiber, A blended nonwoven fabric characterized in that its moisture absorption rate is 30% or more and its moisture release rate is 95% or more.

2. The blended nonwoven fabric according to claim 1, wherein when the blended nonwoven fabric is used as the base, the thermoplastic water-absorbing fibers of the second continuous fiber are present in an amount of 1 to 99% by mass.

3. The thermoplastic water-absorbing fiber of the second continuous fiber is poly C 2-4 The blended nonwoven fabric according to claim 1 or 2, which is a modified product containing alkylene oxide units.

4. The blended nonwoven fabric according to any one of claims 1 to 3, wherein the thermoplastic water-absorbing fiber of the second continuous fiber has a water absorption capacity of 10 to 50 g / g relative to its own weight, and the thermoplastic non-water-absorbing fiber has a water absorption capacity of less than 10 g / g relative to its own weight.

5. The blended nonwoven fabric according to any one of claims 1 to 4, wherein the thermoplastic nonabsorbent fiber of the first continuous fiber is at least one fiber selected from the group consisting of polyolefin fibers, polyamide fibers, and polyester fibers.

6. The blended nonwoven fabric according to any one of claims 1 to 5, wherein the average fiber diameter of the first continuous fiber and the second continuous fiber is 0.1 to 50 μm.

7. The blended nonwoven fabric is the blended nonwoven fabric according to any one of claims 1 to 6, having a water absorption capacity of 5 to 100 g / g.

8. A method for producing a blended nonwoven fabric according to any one of claims 1 to 6, A method for producing a blended nonwoven fabric, characterized by melt-spinning a first continuous fiber thermoplastic nonabsorbent resin and a second continuous fiber thermoplastic superabsorbent resin from separate spinning nozzles to form a blended nonwoven fabric.

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