JP5335705B2 - Superabsorbent nonwoven fabric and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonwoven fabric having high water-absorptivity and excellent flexibility. <P>SOLUTION: The nonwoven fabric containing a fiber composed of a thermoplastic water-absorbing resin containing a polyalkylene oxide unit is produced by melt-spinning the thermoplastic water-absorbing resin. The nonwoven fabric may be a melt-blown nonwoven fabric and may be constituted with an essentially continuous filament having an average fiber diameter of 1-20 &mu;m. The thermoplastic water-absorbing resin may be a polyalkylene oxide-modified material containing a poly(2-4C alkylene oxide) unit. The thermoplastic water-absorbing resin may have a melt viscosity of 100-800 Pa s at 170&deg;C under a 5 MPa load and may have a water absorptivity of 5-50 g/g. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a nonwoven fabric composed of superabsorbent fibers excellent in flexibility, a method for producing the same, and a waterstop material using the nonwoven fabric.

  As the superabsorbent polymer (SAP), a polyacrylic resin is widely used, and a superabsorbent fiber composed of the polyacrylic resin and a non-woven fabric including the superabsorbent fiber have also been proposed. For example, Japanese Patent Laid-Open No. 2006-45730 (Patent Document 1) discloses 5 to 60% adhesive fiber having a fineness of 0.5 to 2.7 dtex and 40 water absorbent fiber having a water absorption rate of 200 to 30000%. Short fiber nonwovens containing ˜95% are disclosed. However, polyacrylic acid-based SAP is highly crosslinked and does not have thermoplasticity, and it is difficult to produce fibers, particularly to produce long fibers (continuous filaments). Furthermore, since it does not have heat-fusibility, a binder component such as an adhesive or heat-fusible fiber is required to form a nonwoven fabric.

  In addition, a method of applying polyacrylic acid-based SAP to a nonwoven fabric in combination with a thermoplastic binder is also known, but a coating process is necessary and productivity is low, and the binder component is easily unevenly distributed. Flexibility is also reduced. Furthermore, since polyacrylic acid type SAP has sodium ions, its water absorption capacity is greatly affected by ions, and the water absorption capacity of seawater is lower than that of pure water (distilled water) or ion exchange water.

  On the other hand, in JP-A-5-339384 (Patent Document 2), a hydrophilic high molecular weight compound obtained by reacting a polyalkylene oxide compound with a polyvalent carboxylic acid or diisocyanate is irradiated with ionizing radiation or ultraviolet rays. A water-absorbing material obtained by crosslinking is also disclosed. However, even in the water-absorbing material obtained by this method, depending on the irradiation conditions of ionizing radiation or ultraviolet rays for cross-linking the hydrophilic high molecular weight compound, unevenness in cross-linking occurs, so that the surface of the material is likely to be slimmed during water absorption. Further, the gel strength is lowered, the melt viscosity is high, and fiberization is difficult.

Japanese Patent Laying-Open No. 2006-45730 (Claim 1, Example) JP-A-5-339384 (Claim 1)

  Accordingly, an object of the present invention is to provide a nonwoven fabric having high water absorption and excellent flexibility, a method for producing the same, and a waterstop material formed from the nonwoven fabric.

  Another object of the present invention is a non-woven fabric that has a high initial water absorption rate and excellent drainage, and also has a high water absorption capability for an aqueous solution containing an ionic component such as seawater, a method for producing the same, and a water stop formed by the non-woven fabric. To provide materials.

  Still another object of the present invention is to provide a non-woven fabric in which there is no filmed portion, it is uniformly made into fibers and excellent in appearance, and the fibers are also prevented from falling off, a method for producing the same, and a water-stop material formed from this non-woven fabric Is to provide.

  Another object of the present invention is to provide a method for producing a non-woven fabric having high water absorption by a simple method.

  As a result of intensive investigations to achieve the above-mentioned problems, the inventors of the present invention can melt and spin a thermoplastic water-absorbing resin containing a polyalkylene oxide unit, and can be made into a fiber without forming a film, maintaining a high water absorption capacity. A novel nonwoven fabric composed of such fibers has been found to have high water absorption and excellent flexibility, and the present invention has been completed.

That is, the nonwoven fabric of this invention contains the fiber comprised with the thermoplastic water absorbing resin containing a polyalkylene oxide unit. The nonwoven fabric of the present invention may be a melt blown nonwoven fabric, and may be composed of filaments having an average fiber diameter of 1 to 20 μm and substantially continuous. The thermoplastic water-absorbent resin may be a polyalkylene oxide-modified product containing poly C _2-4 alkylene oxide units. Furthermore, the thermoplastic water-absorbent resin may have a melt viscosity of 100 to 800 Pa · s at a temperature of 170 ° C. and a load of 5 MPa, and may have a water absorption capacity of 5 to 50 g / g.

  Here, the melt viscosity in the present invention specifically refers to 1.5 g of a thermoplastic water-absorbing resin containing a polyalkylene oxide unit, a flow tester (manufactured by Shimadzu Corporation, trade name “CFT-500C”). Is a value measured under the conditions of a measurement temperature of 170 ° C., a load of 5 MPa, a die hole diameter of 1 mm, and a die length of 1 mm.

  The nonwoven fabric of this invention does not contain a binder component substantially.

  The laminated body comprised by the sheet-like base material and the said nonwoven fabric laminated | stacked on this sheet-like base material is also contained in this invention. The sheet-like substrate may be composed of a thermoplastic resin, a thermoplastic elastomer, or rubber. The sheet-like substrate may be a nonwoven fabric, a woven fabric, or a knitted fabric.

The present invention also includes a method for producing the nonwoven fabric by melt spinning a thermoplastic water-absorbent resin containing polyalkylene oxide units. In the method of the present invention, the thermoplastic water-absorbing resin is melt-spun, sprayed with hot air and laminated on the sheet-like substrate, and the nonwoven fabric laminated on the sheet-like substrate is peeled off from the sheet-like substrate. Good. As this sheet-like substrate, a nonwoven fabric or a woven or knitted fabric made of hydrophobic fibers may be used. In particular, the thermoplastic water-absorbing resin is melt-spun at a spinning temperature of 150 to 260 ° C., a nozzle hole diameter of 0.1 to 1 mm at a single hole discharge rate of 0.01 to 0.5 g / min, a temperature of 160 to 270 ° C., and a nozzle length. You may spray with the hot air of 2-16 Nm < ³ > / min of air amount per meter.

  The present invention also includes a method in which a thermoplastic water-absorbing resin containing a polyalkylene oxide unit is melt-spun and sprayed with hot air to be laminated on a sheet-like substrate to produce the laminate.

  The present invention also includes a waterstop material formed of the nonwoven fabric or the laminate.

  In the present invention, a novel nonwoven fabric obtained by melt spinning a thermoplastic water-absorbing resin containing a polyalkylene oxide unit has high water absorption and excellent flexibility. This nonwoven fabric has a high initial water absorption rate and excellent drainage, and also has a high water absorption capability for aqueous solutions containing ionic components such as seawater. Furthermore, since there is no film-formed part, it is made into a uniform fiber and excellent in appearance, and it is composed of continuous filaments, so that the fibers are prevented from falling off. In this invention, the nonwoven fabric which has such a high water absorption can be manufactured by a simple method.

FIG. 1 is a schematic view showing an example of a process for producing a nonwoven fabric of the present invention.

[Nonwoven fabric]
The nonwoven fabric of this invention contains the fiber comprised with the thermoplastic water absorbing resin containing a polyalkylene oxide unit.

The thermoplastic water-absorbing resin contains polyalkylene oxide units having high hydrophilicity, and preferably has poly C _2-4 alkylene oxide (particularly polyethylene oxide) from the viewpoint of having high water absorption. Specifically, examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, polybutylene oxide, a copolymer or a mixture thereof, and the like. C _2-4 alkylene oxide copolymer (for example, ethylene oxide-propylene oxide copolymer) units are preferred. The ratio of the polyethylene oxide unit in the polyalkylene oxide unit is, for example, 50 mol% or more (for example, 50 to 100 mol%), preferably 70 mol% or more (for example, 70 to 100 mol%), more preferably 90 mol. % Or more (for example, 90 to 100 mol%), for example, when it contains a polypropylene oxide unit, it may be about 80 to 95 mol%. Furthermore, the polymerization form of the copolymer may be either random copolymerization or block copolymerization, and is usually block copolymerization.

  The number average molecular weight (by the hydroxyl value method) of the polyalkylene oxide (particularly polyethylene oxide) unit is, for example, about 3,000 to 50,000, preferably about 5,000 to 30,000, and more preferably about 10,000 to 25,000 (particularly 15,000 to 22,000). If the molecular weight is too small, the melt viscosity of the thermoplastic water-absorbent resin becomes high, and it is necessary to increase the molding temperature during the production of the nonwoven fabric, and the resin is likely to be decomposed or colored. On the other hand, when the molecular weight is too large, the melt viscosity is lowered, the flexibility of the nonwoven fabric is lowered, and the gel during water absorption tends to be slimmed.

  The thermoplastic resin only needs to have a polyalkylene oxide (especially polyethylene oxide) unit. For example, polyolefin resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyester resin, polyamide resin, polyurethane resin. Examples thereof include resins and thermoplastic elastomers. The polyalkylene oxide unit may be contained in the main chain and / or side chain of these resins, but is preferably contained in the main chain from the viewpoint of mechanical properties as a fiber.

  The thermoplastic water-absorbing resin containing a polyalkylene oxide unit in the main chain may be a polyester-based resin or a polyester-based elastomer containing a polyalkylene oxide unit as a diol unit. However, both flexibility and water absorption can be achieved. In view of the above, a thermoplastic water absorbent resin (polyalkylene oxide-modified product) obtained by reacting a polyol component containing polyalkylene oxide and a polyisocyanate component is preferable.

In the modified polyalkylene oxide, it is preferable to use other polyol components (low molecular polyol components) in addition to the polyalkylene oxide as the polyol component in view of enhancing the fiber forming ability. Examples of 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 C _2- such as -1,3-diol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-undecanediol, etc. ₁₂ alkanediols), aliphatic polyols or esters thereof (glycerin, trimethylolpropane, trimethylolethane, C _3-12 aliphatic polyols such as intererythritol, glycerin monoacyl esters such as glyceryl monoacetate and glyceryl monobutyrate), alicyclic diols (cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated xylylene diene Cycloalkane diols such as all, C _2-4 alkylene oxide adducts of these cycloalkane diols), aromatic diols (aromatic diols such as xylylene diol, bisphenol A, bisphenol S, catechol, resorcin, hydroquinone, etc. C _2-4 alkylene oxide adducts of aromatic diols, etc.). These other polyol components can be used alone or in combination of two or more.

Among these other polyol components, aliphatic diols (for example, C _2-6 alkylene glycols such as propylene glycol, butanediol, neopentyl glycol, hexanediol) from the viewpoint of compatibility with polyalkylene oxide and water absorption. In particular, C _3-5 alkylene glycol such as 1,4-butanediol is preferred.

  The ratio of the other polyol component (low molecular polyol component) is, for example, about 0.5 to 6 mol, preferably 1 to 5 mol, more preferably about 1.5 to 3 mol, relative to 1 mol of the polyalkylene oxide. is there. If the proportion of the other polyol component is too small, the water absorbing ability of the resin is increased, but the gel strength is lowered, so that the surface of the nonwoven fabric tends to become slimy (i.e., a slimy feeling is generated) during liquid absorption. On the other hand, if the proportion of the other polyol component is too large, the melt viscosity of the resin becomes high, and there is a risk of decomposition or coloring of the resin. The number of moles of polyalkylene oxide can be determined by dividing its mass by the number average molecular weight.

  Examples of the polyisocyanate component include aliphatic polyisocyanates [aliphatic diisocyanates such as propylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMDI), and lysine diisocyanate (LDI). And aliphatic triisocyanates such as 1,6,11-undecane triisocyanate methyloctane and 1,3,6-hexamethylene triisocyanate], alicyclic polyisocyanates [cyclohexane 1,4-diisocyanate, isophorone diisocyanate (IPDI) Hydrogenated xylylene diisocyanate, hydrogenated bis (isocyanatophenyl) methane (or dicyclohexylmethane-4, Alicyclic diisocyanates such as' -diisocyanate) (HMDI), alicyclic triisocyanates such as bicycloheptane triisocyanate], aromatic polyisocyanates [phenylene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate (XDI) , Aromatic diisocyanates such as tetramethylxylylene diisocyanate (TMXDI), naphthalene diisocyanate (NDI), bis (isocyanatophenyl) methane (MDI), toluidine diisocyanate (TODI), 1,3-bis (isocyanatophenyl) propane, etc. ] Etc. are mentioned.

  These polyisocyanate components include derivatives such as multimers (dimers, trimers, tetramers, etc.), adducts, modified products (burette modified products, allophanate modified products, urea modified products, etc.) It may be a urethane oligomer having an isocyanate group.

  Of these polyisocyanate components, non-aromatic polyisocyanates (symmetrical or asymmetrical aliphatic or alicyclic polyisocyanates), such as symmetric aliphatic or alicyclic polyisocyanates, such as weather resistance, for example, Aliphatic diisocyanates such as HDI and alicyclic diisocyanates such as HMDI are preferred.

  The ratio (use ratio) of the polyisocyanate component is, for example, 0.5 to 3 mol, preferably 0.7 to 2 mol, and more preferably 0 with respect to 1 mol in total of the polyalkylene oxide and other polyol components. About 0.8 to 1.2 mol (particularly 0.9 to 1.1 mol). If the amount of the polyisocyanate component used is too small, the water-absorbing ability of the resin increases, but a slimy feeling tends to occur. On the other hand, if the amount of the polyisocyanate component used is too large, the resin may be decomposed or colored.

  The production method of the polyalkylene oxide modified product is not particularly limited, but a method of reacting in a solution state using a solvent (for example, toluene, xylene, dimethylformamide, etc.), a method of reacting in a state where each component is dispersed, powder For example, a method may be used in which each component is uniformly mixed in a solid state such as a shape or a pellet, and then reacted by heating to a predetermined temperature. Among these methods, from an industrial point of view, a method in which each component is continuously supplied in a molten state and mixed and reacted in a multi-screw extruder is preferable. The reaction temperature is, for example, about 70 to 210 ° C, preferably about 100 to 200 ° C, and more preferably about 150 to 190 ° C. Furthermore, conventional catalysts and chain extenders such as amine compounds (eg triethylamine, triethanolamine, triethylenediamine etc.), tin catalysts (eg dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, stannous octoate) Etc.) may be used.

  The polyalkylene oxide-modified product obtained by such a method is usually obtained in the form of pellets, sheets or films. The modified polyalkylene oxide may be used as it is, but may be pulverized using a pulverizer or the like.

  The thermoplastic water-absorbing resin (particularly, a polyalkylene oxide-modified product) preferably has an appropriate melt viscosity for fiberization. Specifically, the melt viscosity is preferably about 100 to 800 Pa · s, more preferably about 200 to 600 Pa · s under conditions of a die hole diameter of 1 mm and a die length of 1 mm at a temperature of 170 ° C. and a load of 5 MPa. If the melt viscosity is too low, the processability is lowered and the flexibility of the nonwoven fabric is lowered. On the other hand, if the melt viscosity is too high, the molding temperature at the time of forming the nonwoven fabric needs to be increased, Decomposition and the resulting nonwoven fabric are easy to color.

  The thermoplastic water-absorbing resin (especially polyalkylene oxide-modified product) has high water absorption, and the water absorption (water absorption relative to its own weight) is, for example, 10 to 50 g / g, preferably 15 to 45 g / g. More preferably, it is about 20-40 g / g. When the amount of water absorption is too high, the shape stability of the nonwoven fabric tends to decrease during water absorption. Furthermore, in the present invention, the amount of water absorption does not depend on the ion concentration in water, and for example, even seawater has the same amount of water absorption as fresh water (pure water). In addition, water absorption can be measured by the method as described in the Example mentioned later.

  The cross-sectional shape (cross-sectional shape perpendicular to the length direction of the fiber) of the fiber composed of the thermoplastic water-absorbing resin containing such a polyalkylene oxide unit is a round cross-section that is a general solid cross-sectional shape. It is not limited to an irregular cross-section [flat shape, elliptical shape, polygonal shape, etc.], and may be a hollow cross-sectional shape.

  The average fiber diameter of the fibers composed of the thermoplastic water-absorbing resin can be selected from the range of, for example, about 0.1 to 100 μm, for example, 1 to 30 μm, preferably 3 to 25 μm, more preferably, depending on the application. Is about 5 to 20 μm (particularly 10 to 18 μm). If the fiber diameter is too small, fluff is likely to be generated and a lump is likely to be formed. On the other hand, if the fiber diameter is too large, the texture becomes rough and the texture tends to decrease. In addition, an average fiber diameter can be measured by the method as described in the Example mentioned later.

  The average fiber length of the fibers may be short fibers of about 10 to 100 mm, for example, but may be long fibers (substantially continuous filaments) exceeding 100 mm. In the present invention, filaments can be produced by the production method described later, even though they are superabsorbent fibers.

  The nonwoven fabric of the present invention includes other fibers such as polyolefin fibers (for example, polyethylene fibers and polypropylene fibers), vinyl, in addition to fibers composed of such a thermoplastic water-absorbing resin containing polyalkylene oxide units. Alcohol fibers (for example, ethylene-vinyl alcohol copolymer fibers), acrylic fibers (for example, acrylonitrile fibers), polyester fibers (for example, polyethylene terephthalate fibers, polybutylene terephthalate fibers, etc.), polyamide fibers (for example, , Polyamide 6 fiber, polyamide 66 fiber etc.), polyurethane fiber (eg polyester polyol type urethane fiber etc.), cellulosic fiber [eg natural fiber (cotton, wool, silk, hemp etc.), semi-synthetic fiber (triacetate fiber etc.) Ase Over door fiber, etc.), regenerated fibers (rayon, polynosic, cupra, lyocell (for example, registered trade name: such as "Tencel"), etc.), etc.] may be contained, and the like. These other fibers can be used alone or in combination of two or more. The ratio of these other fibers is, for example, 50% by mass or less (for example, 0 to 50% by mass), preferably 30% by mass or less (for example, 0.1 to 30% by mass) with respect to the entire nonwoven fabric. Preferably, it may be 10% by mass or less (for example, 1 to 10% by mass).

  The nonwoven fabric of the present invention has a conventional additive such as a stabilizer (a heat stabilizer such as a copper compound, an ultraviolet absorber, a light stabilizer, an antioxidant, etc.), a dispersant, a thickener on the surface or inside of the fiber. Agents, fine particles, colorants, antistatic agents, flame retardants, plasticizers, lubricants, crystallization rate retarders, lubricants, antibacterial agents, insect and acaricides, fungicides, matting agents, heat storage agents, fragrances, fluorescence It may contain a brightening agent, a wetting agent, a plasticizer, and the like. These additives can be used alone or in combination of two or more. These additives may be carried on the surface of the fiber or may be contained in the fiber. The ratio of these additives is, for example, 30% by mass or less (for example, 0 to 30% by mass), preferably 0.01 to 20% by mass, and more preferably 0.1 to 10% by mass with respect to the entire nonwoven fabric. It may be a degree.

  However, since the nonwoven fabric of the present invention has moderate heat-fusibility, it can maintain the form of the nonwoven fabric even without the binder component, and therefore does not need to contain a binder component substantially. The ratio of the binder component may be, for example, 10% by mass or less (for example, 0 to 10% by mass), preferably 5% by mass or less, more preferably 1% by mass or less, based on the whole nonwoven fabric. Contains no binder component.

The basis weight of the nonwoven fabric of the present invention can be selected from the range of, for example, about 10 to 10000 g / m ² depending on the application, for example, 15 to 5000 g / m ² , preferably 20 to 3000 g / m ² , and more preferably 50. It may be about ˜1000 g / m ² .

The apparent density of the nonwoven fabric of the present invention can also be selected from the range of about 0.01 to 10 g / cm ³ , for example, depending on the application, for example, 0.03 to 5 g / cm ³ , preferably 0.05 to ³ g / cm. It may be about cm ^3, more preferably about 0.1 to 2 g / cm ³ (particularly 0.1 to 1 g / cm ³ ).

  The thickness of the nonwoven fabric of the present invention can also be selected, for example, from the range of 0.01 mm or more (for example, about 0.01 to 100 mm), for example, 0.02 to 10 mm, preferably 0.03 to 5 mm, depending on the application. More preferably, it may be about 0.05 to 3 mm (particularly 0.1 to 1 mm). Furthermore, a plurality of nonwoven fabrics having a thickness in such a range may be laminated and used depending on the application.

The nonwoven fabric of the present invention is excellent in air permeability and has an air permeability of 1 cm ³ / (cm ² · sec) or more by the Frazier method, for example, 1 to 1000 cm ³ / (cm ² · sec), preferably 1. It may be about ^{2 to} 800 cm ³ / (cm ² · sec), more preferably about 1.5 to 500 cm ³ / (cm ² · sec) (particularly ^{2 to} 300 cm ³ / (cm ² · sec)). In this invention, since a binder is not included substantially and film formation is also suppressed, air permeability is high.

  The nonwoven fabric of the present invention has a breaking strength of 1 N / 5 cm or more (for example, 1 to 200 N / 5 cm), preferably 3 to 150 N / 5 cm, more preferably 5 to 120 N / 5 cm (particularly 10 to 100 N) at a thickness of 0.2 mm. The elongation at break is 1% or more (for example, 1 to 30%), preferably 2 to 50%, and more preferably about 3 to 30%.

  The nonwoven fabric of the present invention may be laminated on a sheet-like substrate to form a laminate. The laminate may be a laminate of three or more layers, for example, a laminate in which a nonwoven fabric is laminated on both sides of a sheet-like substrate, a laminate in which sheet-like substrates are laminated on both sides of a nonwoven fabric, or the like. Good.

  The sheet-like substrate may be selected from organic polymers such as a thermoplastic resin, a thermoplastic elastomer, or rubber from the viewpoint of adhesiveness to the nonwoven fabric, and can be selected depending on the application. From the above point, a film or sheet composed of a soft polymer (an olefin resin such as polyethylene or polypropylene, a film or sheet composed of a thermoplastic elastomer, rubber, etc.), a non-woven fabric composed of an organic polymer, or Woven knitted fabric (woven fabric or knitted fabric) can be preferably used. Among these sheet-like substrates, a nonwoven fabric or a woven or knitted fabric (particularly a nonwoven fabric) composed of the above-mentioned other fibers from the viewpoint of excellent adhesion and flexibility without impairing the properties of the nonwoven fabric such as air permeability. Is particularly preferred.

  Furthermore, a non-woven fabric or woven or knitted fabric composed of other fibers has a strong adhesion, and in the case of producing a strong laminate, a sheet-like base material composed of a hydrophilic resin (a highly polar resin), In particular, it may be a nonwoven fabric or a woven / knitted fabric made of hydrophilic fibers. Examples of hydrophilic fibers include vinyl alcohol fibers such as ethylene-vinyl alcohol copolymers, polylactic acid fibers such as polylactic acid, (meth) acrylic copolymer fibers containing (meth) acrylamide units, and rayon fibers. And cellulose fibers such as acetate fiber. Of these, non-woven fabrics composed of cellulose fibers such as rayon fibers and vinyl alcohol fibers such as ethylene-vinyl alcohol copolymer fibers are preferred.

  On the other hand, the non-woven fabric or woven or knitted fabric composed of the other fibers described above is not used when a strong adhesive force is not required between the layers, when the non-woven fabric of the present invention is obtained as a single layer by peeling from the laminate. It may be a sheet-like substrate composed of a hydrophilic resin (a resin having a very low polarity and a relatively strong hydrophobic property), in particular, a nonwoven fabric or a woven / knitted fabric composed of non-hydrophilic fibers. Examples of non-hydrophilic fibers include polyolefin fibers (for example, polyethylene fibers and polypropylene fibers), polyester fibers (for example, polyethylene terephthalate fibers and polybutylene terephthalate fibers), polyamide fibers (for example, polyamide 6 fibers, Polyamide 66 fibers), polyurethane fibers (for example, polyester polyol type urethane fibers) and the like. Among these, non-woven fabrics composed of polyolefin fibers such as polypropylene and polyester fibers such as polyethylene terephthalate are preferable, and hydrophobic fibers such as polypropylene fibers are particularly preferable.

  The nonwoven fabric as the sheet-like substrate may be, for example, a long fiber nonwoven fabric (spunbond nonwoven fabric, meltblown nonwoven fabric, flash spun nonwoven fabric, etc.), and short fiber nonwoven fabric (spunlace nonwoven fabric, air race nonwoven fabric, thermal bond nonwoven fabric, needle). Punch nonwoven fabric, chemical bond nonwoven fabric, paper, etc.) may be used.

  Although the thickness ratio of a nonwoven fabric and a sheet-like base material can be selected according to a use or the kind of sheet-like base material, for example, a nonwoven fabric / sheet-like base material = 10/1-1/10, Preferably 5/1- It is about 1/5, more preferably about 1/3 to 3/1.

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

[Method for producing nonwoven fabric (or laminate)]
The nonwoven fabric of the present invention is obtained by melt spinning the thermoplastic water-absorbent resin, and a direct method in which a spinning process and a web forming process are directly connected is particularly preferable. As the direct method, a conventional method such as a spunbond method, a melt blown method, or a flash spinning method can be used. Among these methods, the melt blown method is preferred because a simple method can be used to obtain a filament that does not require a binder and has a small fiber diameter.

  In the melt blown method, a fiber web is obtained by blowing and collecting the obtained fibers with a high-temperature gas while melt spinning the thermoplastic water-absorbent resin. In the present invention, by spinning under the following production conditions, the thermoplastic water-absorbent resin was used to succeed in producing a novel nonwoven fabric in which film formation was suppressed and fiber was uniformly formed. In particular, although the polyalkylene oxide-modified product has a low solidification rate and high hydrophilicity, a uniform nonwoven fabric can be obtained without forming a film by melt spinning the polyalkylene oxide product by the method of the present invention. .

  Specifically, a thermoplastic water-absorbing resin containing polyalkylene oxide units (including other additives as necessary) is melt-kneaded using a conventional mixer (for example, a melt-kneading extruder). The The melting temperature can be selected according to the kind of the thermoplastic water-absorbent resin. In the case of a polyalkylene oxide-modified product, for example, the temperature is 150 to 260 ° C., preferably 160 to 250 ° C., more preferably about 180 to 240 ° C. It is.

  The thermoplastic water-absorbent resin melt-kneaded by a mixer is supplied to a spinning port. Spinning holes are usually formed in a row at the spinneret, and the interval between the spinning holes is, for example, 100 to 5000 holes / m, preferably 500 to 3000 holes / m, and more preferably 1000 to 2000 holes / m. m.

  The single-hole discharge rate can be selected from a range of about 0.01 to 0.5 g / (hole / minute), for example, 0.03 to 0.4 g / (hole / minute), preferably 0.05 to 0.00. It is about 3 g / (holes / minute), more preferably about 0.1-0.25 g / (holes / minute) (especially 0.15-0.2 g / (holes / minute)).

  The spinning temperature can be selected from the range of about 120 to 300 ° C. depending on the type of the thermoplastic water-absorbent resin, but in the case of a modified polyalkylene oxide, for example, 150 to 260 ° C., preferably 180 to 255 ° C., More preferably, it is about 200-250 degreeC (especially 220-245 degreeC). If the spinning temperature is too high, the resin may be deteriorated. On the other hand, if the spinning temperature is too low, filamentation tends to be difficult.

  In the melt blown method, usually, a method of blowing high-temperature air from a slit formed in the vicinity of the spinneret is used in order to blow the spun fiber toward the net. The temperature of the air can be selected from a range of spinning temperature ± 50 ° C. (particularly ± 30 ° C.), and is usually the same temperature as the spinning temperature.

The flow rate of air to be blown (air flow rate) is, for example, 2 to 16 N · m ³ / m, preferably ^{3 to} 15 N · m ³ / m, more preferably 4 to 12 N · m ³ / m (particularly 5 to 10 N · m). ³ / m). The pressure of the air to be blown (air pressure) is, for example, about 0.001 to 1 MPa, preferably about 0.005 to 0.5 MPa, and more preferably about 0.01 to 0.3 MPa.

  The distance (collection distance) between the nozzle opening and the collection net is, for example, about 10 to 50 cm, preferably about 15 to 40 cm, and more preferably about 15 to 30 cm (particularly 15 to 25 cm). If the collection distance is too small, the amount of fluff scattering tends to increase and web formation tends to be difficult. On the other hand, if the collection distance is too large, the web formation tends to be rough. Furthermore, in this invention, you may attract | suck with a suction collector (suction apparatus) from the lower part of a collection net | network. The suction pressure is, for example, about 0.1 to 2.0 kPa, preferably about 0.5 to 1.5 kPa.

  Furthermore, in the present invention, from the point of suppressing the adhesion between the collection net and the nonwoven fabric, the collection net may be subjected to a release treatment or the like, but the additive such as a release agent can suppress the mixing into the nonwoven fabric. From the above, a method in which a thermoplastic water-absorbing resin containing a polyalkylene oxide unit is melt-spun on a sheet-like substrate supplied to a collection net is preferable. When the thermoplastic water-absorbing resin is melt-spun onto a sheet-like substrate, particularly a nonwoven fabric composed of hydrophobic fibers, the resulting nonwoven fabric can be easily peeled from the sheet-like substrate, and the nonwoven fabric can be easily produced. . In addition, you may utilize as a laminated body, without peeling a nonwoven fabric from a sheet-like base material, and the laminated body adhere | attached more firmly by using the nonwoven fabric comprised by the hydrophilic fiber as a sheet-like base material May be formed.

  FIG. 1 is a schematic view showing an example of a process for producing a nonwoven fabric using a sheet-like substrate. The sheet-like substrate 2 is spread (supplied) on the metal net (collector net) 6 of the molding machine 5 from the sheet-like substrate supply roll 1, and the above-described metal net 6 is laid by the melt blown method. Under such conditions, the spun fibers 4 were sprayed with a high-temperature and high-speed fluid while melt spinning the thermoplastic water-absorbing resin containing polyalkylene oxide units from the nozzle 3. The sprayed fibers 4 are sucked and collected on the sheet-like base material 2 using a suction device (suction collector) 7 from the lower part of the metal net 6, and are composed of the fibers 4. And a sheet-like base material are heat-bonded to a laminated body 8 and collected by a take-up roll 9.

  As the sheet-like substrate, the above-mentioned sheet-like substrate can be used, but in order to enable suction from the suction device, a breathable nonwoven fabric, woven fabric, knitted fabric or the like is preferable. In particular, the above-mentioned long-fiber nonwoven fabric may be used to peel the nonwoven fabric from the sheet-like substrate to form a single-layer nonwoven fabric or a laminate. Since the polyalkylene oxide modified product has a low solidification rate and high hydrophilicity, it is extremely difficult to produce a uniform non-woven fabric (particularly, a single-layer non-woven fabric). By using the above-mentioned long-fiber nonwoven fabric (particularly, a nonwoven fabric or woven / knitted fabric composed of hydrophobic fibers such as polypropylene fibers such as polypropylene), a uniform nonwoven fabric can be obtained without forming a film. . Further, an aggregate of the opened short fibers is supplied by a card, and a thermoplastic water-absorbing resin containing a polyalkylene oxide unit that also serves as a binder component for the short fibers is melt-spun on the card and laminated (or (Integrated product) may be formed.

  When the nonwoven fabric is peeled from the laminate, the laminate may be cooled with a cooling device in order to improve peelability. For example, you may adjust the temperature of a winding roll to about 0-35 degreeC, for example.

  The obtained non-woven fabric or laminate is usually obtained as a plate-shaped or sheet-shaped molded body, and is used after being processed into a desired shape by cutting or the like, but if necessary, secondary molding by conventional thermoforming May be. Further, the nonwoven fabric or laminate may be further laminated with a sheet-like or film-like material by a conventional lamination method, a method using a rubber / steel roll, an emboss / steel roll or the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Each physical property value in the examples was measured by the following method. In the examples, “parts” and “%” are based on mass unless otherwise specified.

(1) Melt viscosity of polyalkylene oxide modified product 1.5 g of polyalkylene oxide modified product was measured using a flow tester (manufactured by Shimadzu Corporation, trade name “CFT-500C”) at a measurement temperature of 170 ° C., a load of 5 MPa, Measurement was performed under the conditions of a die hole diameter of 1 mm and a die length of 1 mm.

(2) Water absorption (modified polyalkylene oxide)
1 g of polyalkylene oxide-modified product is added to 100 ml of ion-exchanged water or artificial seawater (trade name “Aquamarine” manufactured by Yashima Pharmaceutical Co., Ltd.), and gently swirled for 24 hours to be sufficiently swollen. Next, the swollen gel is filtered with a JIS standard metal sieve having an opening of 75 μm and measuring the weight (Wa) g. The metal sieve containing the swollen gel is allowed to stand for 30 minutes in a moderately tilted state to remove excess water. The weight (Wb) g of the metal sieve containing the swollen gel was measured, and the water absorption amount of ion-exchanged water or artificial seawater was calculated from the following formula.

  Water absorption (g / g) = [Wb−Wa] (g) / weight of polyalkylene oxide modified product (g).

(Polyacrylic SAP)
To 1000 ml of ion-exchanged water or artificial seawater (trade name “Aquamarine” manufactured by Yasu Pharmaceutical Co., Ltd.), 1 g of polyacrylic acid-based SAP is added, and the mixture is gently swirled for 3 hours to sufficiently swell. Next, the swollen gel is filtered with a JIS standard metal sieve having an opening of 75 μm and measuring the weight (Wa) g. The metal sieve containing the swollen gel is allowed to stand for 30 minutes in a moderately tilted state to remove excess water. The weight (Wb) g of the metal sieve containing the swollen gel was measured, and the water absorption amount of ion-exchanged water or artificial seawater was calculated from the following formula.

  Water absorption (g / g) = [Wb−Wa] (g) / weight of polyacrylic acid SAP (g).

(3) Water Absorption Rate of Nonwoven Fabric After immersing the obtained meltblown nonwoven fabric in ion-exchanged water or artificial seawater (trade name “Aquamarine” manufactured by Yasu Pharmaceutical Co., Ltd.) for 30 seconds, the weight of the nonwoven fabric before and after water absorption was measured. The water absorption rate of ion-exchanged water or artificial seawater was calculated from the following formula.

    Water absorption rate (%) = (weight after water absorption−weight before water absorption) / weight before water absorption × 100.

(4) Fabric weight of nonwoven fabric (g / m ² )
Measured according to JIS L1913 “Testing method for general short fiber nonwoven fabric”.

(5) Non-woven fabric thickness (mm), apparent density (g / cm ³ )
The thickness was measured according to JIS L1913 “General Short Fiber Nonwoven Fabric Testing Method”, and the apparent density was calculated from this value and the basis weight value.

(6) Average fiber diameter of nonwoven fabric The nonwoven fabric was magnified and photographed with a scanning microscope, the diameter of 100 arbitrary fibers was measured, and the average value was calculated.

(7) Air permeability of non-woven fabric It was measured by a fragile method according to JIS L1096.

(8) Peel strength of the laminate The laminate was measured in accordance with JIS L 1085 “Nonwoven fabric test method 6.13 Peel strength”.

(9) Breaking strength and breaking elongation Measured according to JIS L1913 "Test method for general short fiber nonwoven fabric". The breaking strength and breaking elongation were measured in the flow (MD) direction and the width (CD) direction of the nonwoven fabric.

(10) Moisture Absorption Rate and Moisture Release Rate The nonwoven fabric whose mass [A (g)] was measured in advance was allowed to stand in a constant temperature and humidity chamber at 34 ° C. and 90% RH for 5 hours, and then mass [B (g)]. Was measured. Furthermore, it was allowed to stand for 2 hours under conditions of 25 ° C. and 65% RH, the mass [C (g)] at that time was measured, and the moisture absorption rate (%) and moisture release rate (%) were determined according to the following formulas. . In addition, if it has a moisture absorption rate of 30% or more and a moisture release rate of 90% or more, it can be judged that it is a nonwoven fabric which shows a favorable moisture absorption / release rate.

Moisture absorption rate (%) = (B−A) / A × 100
Moisture release rate (%) = (BC) / (BA) × 100.

(11) Production yield The amount of the nonwoven fabric produced relative to the amount of raw material input was evaluated according to the following criteria.

○: 80% or more Δ: 60% or more and less than 80% ×: less than 60%

(Production Example 1: Synthesis example of modified polyalkylene oxide)
In a storage tank A with a stirrer kept at 80 ° C., 100 parts by mass of fully dehydrated polyethylene oxide having a number average molecular weight of 20,000, 0.90 parts by mass of 1,4-butanediol, and dibutyltin dilaurate The mixture was added at a rate of 0.1 part by mass and stirred in a nitrogen gas atmosphere to obtain a uniform mixture. Separately from this tank, dicyclohexylmethane-4,4′-diisocyanate was put into a storage tank B kept at 30 ° C. and stored in a nitrogen gas atmosphere. Using a metering pump, the tank A mixture was set at 110-140 ° C. at a rate of 250 g / min and the dicyclohexylmethane-4,4′-diisocyanate in storage tank B at a rate of 9.2 g / min. The product was continuously fed to a twin-screw extruder, mixed in the extruder, reacted, the strand was extruded from the outlet of the extruder, 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 both ion-exchanged water and artificial seawater had a water absorption of 25 g / g.

(Production Example 2: Synthesis Example of Polyacrylic Acid SAP)
To a 1000 ml four-necked cylindrical round bottom flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas introduction tube, 550 ml of n-heptane was added, and hexaglyceryl monobehelate (HLB of 13.1) Surfactant; manufactured by NOF Corporation, trade name “Nonion GV-106”) was added and dispersed, heated to 50 ° C. to dissolve the surfactant, and then cooled to 30 ° C. .

  On the other hand, in a separately prepared 500 ml Erlenmeyer flask, 92 g of 80% by weight acrylic acid aqueous solution was added, and further 152.6 g of 20.1% by weight sodium hydroxide aqueous solution was dropped while cooling from the outside. Was neutralized to prepare a partially neutralized aqueous solution of acrylic acid. Furthermore, 0.11 g of a polymerization initiator potassium persulfate and 0.019 g of a crosslinking agent ethylene glycol diglycidyl ether were added to prepare a monomer aqueous solution for polymerization.

  This monomer aqueous solution for polymerization is added to and dispersed in the four-necked cylindrical round bottom flask under stirring, and the temperature inside the system is sufficiently replaced with nitrogen, and the bath temperature is maintained at 70 ° C. Then, the polymerization reaction was carried out for 3 hours. After the completion of the polymerization, 135 g of water was distilled by heating together with n-heptane by distillation, followed by drying to obtain 102 g of an ionic water-absorbing resin having an average particle size of 270 μm. The water absorption of ion-exchanged water of the obtained ionic water-absorbing resin was 500 g / g, and the water absorption of artificial seawater was 3 g / g.

Example 1
Using the apparatus shown in FIG. 1, a spunbonded nonwoven fabric (PPSB, manufactured by Shinwa Co., Ltd., trade name “6630-1A”, weight per unit area 30 g / m ² ) composed of polypropylene fibers is spread from the unwinding roll and laid. The polyalkylene oxide modified product obtained in Production Example 1 was melt-spun on the spunbonded nonwoven fabric. Specifically, the polyalkylene oxide-modified pellets are melt extruded at 240 ° C. into a spinning nozzle having a pore diameter of 0.3 mmφ and a number of holes of 1500 holes / m. The spinning nozzle has a spinning temperature of 240 ° C. and a single hole discharge amount of 0. At the same time as discharging at 17 g / min, hot air is discharged from a slit provided near the spinning hole at a temperature (primary air temperature) of 240 ° C., an air amount of 8 N · m ³ / m per 1 m of nozzle length, and a pressure of 0.09 MPa. The collected fibers are collected on a spunbonded nonwoven fabric located at a collection distance (distance between the nozzle cap and the spunbonded nonwoven fabric) of 20 cm, and the meltblown nonwoven fabric and the spunbonded nonwoven fabric are thermally bonded and laminated. Got the body.

(Example 2)
The spunbond nonwoven fabric was peeled from the laminate obtained in Example 1 to obtain a single layer meltblown nonwoven fabric.

(Example 3)
A laminated body in the same manner as in Example 1 except that a nonwoven fabric composed of rayon fibers (made by Venus Paper Co., Ltd., trade name “WJ-40R”, basis weight 40 g / m ² ) was used instead of the polypropylene spunbond nonwoven fabric. Got. Since the obtained laminate was firmly bonded, it was impossible to obtain a melt-blown non-woven fabric with no rayon fibers attached as a single layer.

Example 4
A laminate was obtained in the same manner as in Example 1 except that the spinning temperature was 140 ° C.

(Example 5)
The spunbond nonwoven fabric was peeled from the laminate obtained in Example 4 to obtain a single-layer meltblown nonwoven fabric. The obtained nonwoven fabric had a large fiber diameter, a rough texture, and a low uniformity.

(Example 6)
A laminate was obtained in the same manner as in Example 1 except that the air amount per 1 m of the nozzle length from the slit was 17 N · m ³ / m. However, when spinning, along with the occurrence of yarn breakage, cotton dust scattered around the base, resulting in a decrease in productivity.

(Example 7)
The spunbond nonwoven fabric was peeled from the laminate obtained in Example 6 to obtain a single layer meltblown nonwoven fabric. The obtained non-woven fabric did not become thread-like in the fiberizing step, and a lump called so-called shot was generated, so the uniformity was low. In addition, cotton dust was scattered around the base, resulting in contamination.

(Comparative Example 1)
70 parts by mass of powder obtained by pulverizing an ethylene-vinyl acetate copolymer (manufactured by Sumitomo Chemical Co., Ltd., trade name “Evertate D2011”) as a binder by 30 parts by mass of the polyacrylic acid SAP obtained in Production Example 2. The powder was mixed and melt-spun. Specifically, it is melt-extruded at 150 ° C. into a spinning nozzle having a hole diameter of 0.3 mmφ and a number of holes of 1500 holes / m, discharged from the spinning nozzle cap at a spinning temperature of 200 ° C., and a single hole discharge rate of 0.15 g / min. From the slit provided in the vicinity of the hole, the temperature is 240 ° C, the amount of air is 8 N · m ³ / m per 1 m of nozzle length, the hot air is blown out at a pressure of 0.09 MPa, and the discharged fiber is refined and positioned at a collection distance of 20 cm It was collected on a spunbonded nonwoven fabric, and a melt blown nonwoven fabric and a spunbonded nonwoven fabric were thermally bonded to obtain a laminate. The obtained non-woven fabric had a large fiber diameter and an insufficient texture, and a large amount of gel was detached when absorbed.

  Tables 1 and 2 show the evaluation results of the laminates or nonwoven fabrics obtained in the examples and comparative examples.

  From the results of Tables 1 and 2, the laminate and nonwoven fabric of the present invention are excellent in mechanical strength, air permeability, and water absorption.

  The nonwoven fabric of the present invention and the laminate comprising the nonwoven fabric are, for example, sanitary materials (for example, paper diapers, incontinence pads, sanitary products, breast milk pads, etc.), water-stop tapes for communication / power cables, food packaging materials (for example, trays). Liner, dehumidifying material, shipping container lining, cold insulation packing material, drip absorbent sheet, antibacterial sheet, freshness preservation material, etc.), disaster prevention material (eg sandbag, fire clothes, digestion material, etc.), filter material (eg oil water) Separation filters, dehumidification filters, cleaning liquid separation filters, etc.), medical materials (eg, surgical sheets, medicalware, blood absorbers, drug absorbers, wound care products, medical tapes, etc.), electrical materials (eg, motor housings) , Heat exchangers for air conditioners, liquid crystal packaging, battery separators, etc., agricultural and horticultural materials (water retention sheets, anti-condensation sheets) Rooftop greening sheets, seedling sheets, etc.), civil engineering / building materials (for example, concrete curing sheets, slope greening sheets, anti-condensation sheets, wall materials, moisture-proof or humidity-controlling housing materials, waterproof sheets, etc.), daily miscellaneous goods (For example, towels, sports goods, car wash goods, masks, sweat-absorbing sheets or anti-steam sheets for hats, hanger covers, bedding mats, insoles, pet sheets, closet / tans sheets, pressed flower sheets, aroma / deodorant / deodorant / insects)・ It can be used for anti-mold sheet, desiccant / air freshener packaging, disposable warmer exterior, cupboard sheet, refrigerator sheet, etc. Especially, since it has high water absorption, utilization to a water stop material or a water stop sheet (especially the water stop material or water stop sheet with respect to seawater) is effective.

DESCRIPTION OF SYMBOLS 1 ... Sheet-like base material supply roll 2 ... Sheet-like base material 3 ... Nozzle 4 ... Fiber 5 ... Molding machine 6 ... Metal net (conveyor)
7 ... Suction device 8 ... Laminate 9 ... Winding roll

Claims (10)

A non-woven fabric in which a thermoplastic water-absorbing resin containing a polyalkylene oxide unit is melt-spun, sprayed with hot air and laminated on a sheet-like substrate, and the nonwoven fabric laminated on the sheet-like substrate is peeled off from the sheet-like substrate. Manufacturing method . Nonwoven, the average fiber diameter of 1 is ～20Myuemu, and substantially continuous process according to claim 1 Symbol placement is composed of filaments. The method according to claim 1 or 2 , wherein the thermoplastic water-absorbent resin is a polyalkylene oxide-modified product containing poly _C2-4 alkylene oxide units. The manufacturing method according to any one of claims 1 to 3 , wherein the thermoplastic water-absorbent resin has a melt viscosity of 100 to 800 Pa · s at a temperature of 170 ° C and a load of 5 MPa. The manufacturing method according to any one of claims 1 to 4 , wherein the thermoplastic water-absorbent resin has a water absorption capacity of 5 to 50 g / g. The manufacturing method according to any one of claims 1 to 5 , wherein the nonwoven fabric does not substantially contain a binder component. The manufacturing method in any one of Claims 1-6 by which the sheet-like base material is comprised with the thermoplastic resin, the thermoplastic elastomer, or rubber | gum. The manufacturing method according to any one of claims 1 to 7 , wherein the sheet-like substrate is a nonwoven fabric, a woven fabric, or a knitted fabric. The process according to any one of claims 1 to 8 base material sheet is a nonwoven fabric or textile fabric comprised of hydrophobic fibers. A thermoplastic water-absorbent resin is melt-spun at a spinning temperature of 150 to 260 ° C., a nozzle hole diameter of 0.1 to 1 mm at a single hole discharge rate of 0.01 to 0.5 g / min, and a temperature of 160 to 270 ° C. per nozzle length of 1 m. the process according to any one of claims 1 to 9 for blowing an air amount 2~16Nm ³ / min hot air.

Images