JP2007321309A - Highly functional nonwoven fabric, method for producing the same and use thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a highly functional nonwoven fabric having durable water absorption properties, excellent softness and excellent functionality and to provide a method for producing the same and a use thereof. <P>SOLUTION: The nonwoven fabric comprises 0.001-10 mass% based on the mass of the nonwoven fabric of a water-soluble thermoplastic polyvinyl alcohol existing in a nonwoven fabric structure and a metal compound having an average particle diameter of ≤50 nm finely dispersed in the polyvinyl alcohol and has the content of the metal compound of ≥0.5 mass% based on the polyvinyl alcohol. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a highly functional nonwoven fabric, a method for producing the same, and an application. More specifically, the non-woven fabric in which the water-soluble and thermoplastic polyvinyl alcohol constituting the composite fiber partially remains inside the non-woven fabric, and the functional metal compound is finely dispersed in the polyvinyl alcohol, and its production The present invention relates to a method and uses such as a wiper and a filter using the method.

  Conventionally, various techniques have been developed as methods for imparting various performances to fibers and non-woven fabrics to enhance functionality. For example, a method for producing a non-woven fabric by fiberizing a high-functional polymer, a method for blending various functionalizing agents in advance with the polymer to form a fiber / non-woven fabric, or a method for imparting various functionalizing agents to the non-woven fabric in a later step Etc. In particular, since various functionalizing agents have been developed recently, it can be used in various fields such as hydrophilicity, conductivity, antibacterial / deodorant, etc. by using functional agents. Has been.

However, various problems remain in order to efficiently impart performance with the functionalizing agent. For example, when compounded in advance in the polymer, the functional agent is present uniformly in the fiber after spinning, and it is extremely difficult to make it exist only on the fiber surface. There is. In addition, when a functionalizing agent is applied by coating or the like in post-processing, it is difficult to uniformly disperse the nonwoven fabric structure, which may cause a problem in quality stability.
Furthermore, when adhesives such as binder resins are required, they may adversely affect the quality, and furthermore, the functional expression surface may be covered with the binder resin or the like, thereby preventing the expression of functions. There is.
Therefore, if a method for uniformly applying various functionalizing agents to the fiber surface in the nonwoven fabric structure can be established, it can be expected to be a useful technique in all fields.

  On the other hand, the present inventors have proposed water-soluble thermoplastic polyvinyl alcohol as a water-soluble and melt-moldable polymer. Polyvinyl alcohol (hereinafter also abbreviated as PVA) is a water-soluble polymer, and it is known that the degree of water-solubility can be changed by its basic skeleton, molecular structure, form, and various modifications. In addition, PVA has been confirmed to be biodegradable, and how to harmonize the synthetic material with the natural world is a major issue in the global environment. Currently, there are many PVA having such basic performance. Attention has been paid.

  As a method of applying the PVA as described above to the nonwoven fabric, a method of applying a PVA aqueous solution to the nonwoven fabric and drying it can be considered. In this method, the applied PVA is easily dropped by water or hot water, and the present invention. However, the intended durable water absorption and functionality cannot be obtained. Further, in this method, as a method for preventing PVA from easily falling off with water, by adopting a high temperature at which PVA crystallizes as the drying condition of the applied PVA aqueous solution, the durability of the applied PVA A method of increasing water absorption is also conceivable, but in this method, there is a problem that the water absorption of the PVA after crystallization is lowered, and sufficient water absorption is not obtained.

  The present inventors extract other PVA from a nonwoven fabric composed of a composite fiber by melt spinning composed of a water-soluble thermoplastic PVA and another thermoplastic polymer under a specific condition and remove the other PVA. It has been found that a non-woven fabric having durability and water absorption can be obtained when a very small amount of PVA remains uniformly in the non-woven fabric structure while containing ultrafine fibers made of a plastic polymer as a main component ( For example, see Patent Document 1.)

  PVA has a large number of hydroxyl groups in its molecular structure, and by utilizing these functional groups, various compounds such as metal compounds and inorganic compounds can be coordinated. It is possible to impart new performances to these materials, but the technology for imparting new performances other than such hydrophilic properties has not yet been established.

JP 2006-089851 A

  The object of the present invention is to provide a high functionality that has durable water absorption, excellent flexibility, and excellent functionality by finely dispersing PVA and various functionalizing agents in the nonwoven fabric structure. It is providing the nonwoven fabric, its manufacturing method, and its use.

  As a result of intensive investigations to achieve the above object, the present inventors have determined the water-soluble thermoplastic PVA from a nonwoven fabric made of a composite spun fiber composed of a water-soluble thermoplastic PVA and another thermoplastic polymer under specific conditions. It was found that a non-woven fabric having excellent durability and water absorption and excellent functionality can be obtained by extracting and removing underneath, and further finely dispersing the functionalizing agent in PVA remaining in a trace amount. .

  That is, in the present invention, 0.001 to 10% by mass of water-soluble thermoplastic PVA is present in the nonwoven fabric structure with respect to the mass of the nonwoven fabric, and a metal compound having an average particle size of 50 nm or less is dispersed in PVA. The non-woven fabric is characterized in that its content is 0.5% by mass or more with respect to PVA, and preferably the non-woven fabric structure is composed of ultrafine fibers having an average fineness of 0.5 dtex or less. The non-woven fabric described above, more preferably the non-woven fabric described above in which 30% or more of the surface of the non-woven fabric structure is coated with water-soluble thermoplastic PVA.

  Further, the present invention is the above-mentioned nonwoven fabric in which the water-soluble thermoplastic PVA is preferably a modified PVA containing 0.1 to 20 mol% of α-olefin units having 4 or less carbon atoms, more preferably water-soluble thermoplastic PVA. Is a modified PVA containing 3 to 20 mol% of ethylene units, more preferably at least one selected from the group consisting of copper sulfide, zinc sulfide, iron oxide (ferrite) and silver oxide in the nonwoven fabric. The above-mentioned nonwoven fabric is characterized in that the metal compound is dispersed.

  In the present invention, the nonwoven fabric is preferably the above-described nonwoven fabric in which the shape is maintained by partial thermocompression bonding by the hot embossing and calendering method, more preferably the nonwoven fabric is fiber entangled by the water jet method or needle punch method. Thus, the nonwoven fabric maintains its form.

  Furthermore, in the present invention, the nonwoven fabric is preferably the above-described nonwoven fabric made of at least one thermoplastic polymer selected from the group consisting of polyester, polyamide, and polyolefin, and more preferably the above-mentioned nonwoven fabric and another nonwoven fabric are laminated. It is a nonwoven fabric laminate.

In the method for producing a composite fiber nonwoven fabric made of water-soluble thermoplastic PVA and other thermoplastic polymer, the present invention is to form a metal compound in the nonwoven fabric structure by the following steps (a) and (b). It is the manufacturing method of the functional nonwoven fabric characterized.
(A) A step of dissolving and removing most of the PVA from the composite fiber with water and leaving a part of the PVA in the nonwoven fabric structure.
(B) The non-woven fabric obtained in the above step is uniformly permeated into the PVA through a bath in which the compound (A) containing metal ions is dissolved at a concentration of 10 to 200 g / L, and then the metal ions are reduced. A step of generating a metal compound having an average particle diameter of 50 nm or less by reacting with the metal compound through a bath in which the reactant (B) to be dissolved is dissolved in a concentration of 1 to 100 g / L.
Furthermore, this invention relates to the wiper, filter, etc. which consist of the said nonwoven fabric.

  In the present invention, fibers made of a thermoplastic polymer can be formed as ultrafine fibers. As a result, the fiber surface area is increased, and various functionalizing agents can be finely dispersed in the fiber, so that it is possible to obtain a nonwoven fabric having excellent durability and water absorption and excellent functionality.

Hereinafter, the present invention will be described in detail.
The water-soluble thermoplastic PVA used in the present invention includes not only PVA homopolymers but also modified PVA having functional groups introduced by copolymerization, terminal modification, and post-modification. Of course, it must be melt-spinnable. Ordinary general commercial PVA has a melting temperature and a thermal decomposition temperature close to each other, so that it is difficult to perform melt spinning (that is, not thermoplastic), and various devices are required.

  The viscosity average polymerization degree of PVA (hereinafter simply referred to as the polymerization degree) is preferably from 200 to 800, more preferably from 230 to 600, particularly preferably from 250 to 500. PVA used for ordinary fibers has a higher degree of polymerization, and higher strength fibers are obtained. Therefore, those having a degree of polymerization of 1500 or more are common, for example, those having a degree of polymerization of about 1700 or about 2100. It is common. In view of that, it can be said that the polymerization degree of PVA used in the present invention is extremely low. When the degree of polymerization is less than 200, sufficient spinnability cannot be obtained during spinning, and as a result, a satisfactory composite fiber nonwoven fabric may not be obtained. On the other hand, if the degree of polymerization exceeds 800, the melt viscosity is too high and the polymer cannot be discharged from the spinning nozzle, and a satisfactory composite fiber nonwoven fabric may not be obtained.

The degree of polymerization (P) of PVA is measured according to JIS-K6726. That is, after the PVA is completely re-saponified and purified, the intrinsic viscosity [η] (dl / g) measured in water at 30 ° C. is obtained by the following formula.
P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

  The saponification degree of the PVA used in the present invention is preferably in the range of 90 to 99.99 mol%, more preferably 92 to 99.9 mol%, and particularly preferably 94 to 99.8 mol%. If the degree of saponification is less than 90 mol%, the thermal stability of PVA is poor and stable composite melt spinning may not be performed due to thermal decomposition or gelation. On the other hand, PVA having a saponification degree larger than 99.99 mol% is difficult to produce stably.

  PVA is obtained by saponifying the vinyl ester unit of the vinyl ester polymer. Vinyl compound monomers for forming vinyl ester units include vinyl formate, vinyl acetate, vinyl propionate, vinyl valenate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and Examples thereof include vinyl versatate. Among these, vinyl acetate is preferable from the viewpoint of obtaining PVA with high productivity.

  The PVA constituting the nonwoven fabric of the present invention may be a homopolymer or a modified PVA having a copolymer unit introduced, but from the viewpoint of composite melt spinnability, water absorption, fiber properties, and nonwoven fabric properties, It is preferable to use modified PVA into which polymerized units are introduced. Examples of the comonomer include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene, acrylic acid and salts thereof, methyl acrylate, ethyl acrylate, and acrylic acid n- Acrylic acid esters such as propyl and i-propyl acrylate, methacrylic acid and salts thereof, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, methacrylic acid esters such as i-propyl methacrylate, acrylamide, N- Acrylamide derivatives such as methyl acrylamide and N-ethyl acrylamide, methacrylamide derivatives such as methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propiyl Vinyl ethers such as vinyl ether, n-butyl vinyl ether, ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, hydroxy group-containing vinyl ethers such as 1,4-butanediol vinyl ether, allyl acetate, propyl allyl ether, butyl allyl ether, Allyl ethers such as hexyl allyl ether, monomers having an oxyalkylene group such as polyoxyethylene group, polyoxypropylene group and polyoxybutylene group, vinylsilanes such as vinyltrimethoxysilane, isopropenyl acetate, 3-butene -1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decene-1-ol, 3-methyl-3-buten-1-ol, etc. Hydroxy group included Α-olefins or esterified products thereof, N-vinylamides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, anhydrous Monomers having a carboxyl group derived from trimellitic acid or itaconic anhydride; sulfonic acid groups derived from ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc. Monomer having: vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylic Bromide trimethylammonium chloride, N- acrylamide dimethylamine, allyl trimethyl ammonium chloride, methallyl trimethylammonium chloride, dimethyl allyl amine include monomers having a cationic group derived from the allyl ethyl amine. The content of these monomers is usually 20 mol% or less when the number of moles of all units constituting the copolymerized PVA is 100%. Moreover, in order to exhibit the merit of being copolymerized, it is preferable that 0.01 mol% or more is the said copolymerization unit.

  Among these monomers, α-olefins such as ethylene, propylene, 1-butene, isobutene, 1-hexene, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl are available because of their availability. Vinyl ethers such as vinyl ether and n-butyl vinyl ether, hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether and 1,4-butanediol vinyl ether, allyl esters represented by allyl acetate, propyl Allyl ethers such as allyl ether, butyl allyl ether, hexyl allyl ether, N-vinyl amides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, oxyalkylene A monomer having an amine group, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decene-1-ol, 3- Monomers derived from hydroxy group-containing α-olefins such as methyl-3-buten-1-ol are preferred.

Particularly, from the viewpoints of copolymerizability, melt spinnability, fiber properties, etc., ethylene, propylene, 1-butene, isobutene having 4 or less α-olefins, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl Vinyl ethers such as vinyl ether and n-butyl vinyl ether are more preferable. The unit derived from α-olefins having 4 or less carbon atoms and vinyl ethers is preferably present in the PVA in an amount of 0.1 to 20 mol%, more preferably 0.5 to 18 mol%.
Further, when the α-olefin is ethylene, it is most preferable because the fiber physical properties are particularly high, and it is particularly preferable that the ethylene unit is present in an amount of 3 to 20 mol%, more preferably 5 to 18 mol% ethylene. This is a case where modified PVA into which units are introduced is used.

  Examples of the PVA used in the present invention include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without solvent or in a solvent such as alcohol is usually employed. Examples of alcohol used as a solvent during solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. As initiators used for copolymerization, α, α′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), benzoyl peroxide, n-propyl peroxycarbonate And known initiators such as azo initiators or peroxide initiators. Although there is no restriction | limiting in particular about superposition | polymerization temperature, The range of 0 to 200 degreeC is suitable.

  The PVA used in the present invention contains alkali metal ions, and the proportion is preferably 0.00001 to 0.05 parts by mass, more preferably 0.0001 to 0.03 parts by mass in terms of sodium ions with respect to 100 parts by mass of PVA. Preferably, 0.0005 to 0.01 part by mass is particularly preferable. Those having an alkali metal ion content of less than 0.00001 parts by mass are industrially difficult to produce. On the other hand, when the content of alkali metal ions is more than 0.05 parts by mass, polymer decomposition, gelation and yarn breakage at the time of composite melt spinning are remarkable, and it may not be possible to fiberize stably. Examples of the alkali metal ion include potassium ion and sodium ion.

  Usually, when alkali metal ions are used to produce PVA by saponifying a vinyl ester resin, an alkaline substance containing alkali metal ions is used as a saponification catalyst, and the saponified PVA resin is washed with a washing solution. The content in the PVA resin is controlled. However, for the purpose of containing a specific amount of alkali metal ions in PVA, a compound containing alkali metal ions may be added after polymerizing PVA. The content of alkali metal ions can be determined by atomic absorption method.

  Examples of the alkaline substance used as the saponification catalyst include potassium hydroxide and sodium hydroxide. The molar ratio of the alkaline substance used for the saponification catalyst is preferably from 0.004 to 0.5, particularly preferably from 0.005 to 0.05, based on the vinyl acetate unit. The saponification catalyst may be added all at the beginning of the saponification reaction, or may be added additionally during the saponification reaction.

Examples of the saponification solvent include methanol, methyl acetate, dimethyl sulfoxide, dimethylformamide and the like. Among these solvents, methanol is preferable, methanol whose water content is controlled to 0.001 to 1% by mass is more preferable, methanol whose water content is controlled to 0.003 to 0.9% by mass is more preferable, and water content is Methanol controlled to 0.005 to 0.8% by mass is particularly preferable. Examples of the cleaning liquid include methanol, acetone, methyl acetate, ethyl acetate, hexane, water, and the like. Among these, methanol, methyl acetate, water alone or a mixed liquid is more preferable.
Although it sets so that the content rate of an alkali metal ion may be satisfied as a quantity of a washing | cleaning liquid, 300-10000 mass parts is preferable with respect to 100 mass parts of PVA normally, and 500-5000 mass parts is more preferable. As washing | cleaning temperature, 5-80 degreeC is preferable and 20-70 degreeC is more preferable. The washing time is preferably 20 minutes to 100 hours, more preferably 1 hour to 50 hours.

  Further, a plasticizer can be added to PVA for the purpose of adjusting the melting point and the melt viscosity within a range that does not impair the purpose and effect of the present invention. As the plasticizer, all conventionally known plasticizers can be used, but diglycerin, polyglycerin alkyl monocarboxylic acid esters, and glycols added with ethylene oxide and propylene oxide are preferably used. Among these, the compound which added 1-30 mol% of ethylene oxide with respect to 1 mol of sorbitol is preferable.

  The ratio of the water-soluble thermoplastic PVA present in the nonwoven fabric structure of the present invention is required to be 0.001 to 10% by mass, and 0.01 to 4% by mass with respect to the mass of the nonwoven fabric. Preferably, it is 0.03-3.5 mass%, More preferably, it is 0.05-3 mass%. When the proportion of the water-soluble thermoplastic PVA is more than 10% by mass, the elution of the water-soluble thermoplastic PVA becomes high during use, and the flexibility of the nonwoven fabric decreases. On the other hand, when the proportion of the water-soluble thermoplastic PVA is less than 0.001% by mass, the blending amount of the functionalizing agent is also reduced, the functionalization of the nonwoven fabric is not sufficient, and the performance satisfied when used in various applications. Can't get. The proportion of water-soluble thermoplastic PVA in the nonwoven fabric structure is adjusted by controlling extraction conditions such as temperature, time, and bath ratio when the water-soluble thermoplastic PVA is extracted and removed from the composite fiber nonwoven fabric with water. Is possible. That is, the residual amount of PVA can be reduced by increasing the extraction removal temperature, extending the extraction time, or increasing the bath ratio during extraction.

In the present invention, it is preferable that 30% or more of the surface of the nonwoven fabric structure is coated with water-soluble thermoplastic PVA, and more preferably 50% or more. When the coverage with water-soluble thermoplastic PVA is less than 30%, the performance of the nonwoven fabric may not be sufficient.
The water-soluble thermoplastic PVA coverage on the surface of the nonwoven structure can be analyzed by X-ray photoelectron spectroscopy.

In the present invention, it is essential to contain metal compound nanoparticles as a functionalizing agent.
The average particle size of the metal compound is required to be nanoparticles of 50 nm or less, and preferably 20 nm or less. By existing as such nano fine particles, the distance between particles can be remarkably reduced, and an excellent function as a nonwoven fabric can be exhibited. On the other hand, when the average particle diameter is larger than 50 nm, a sufficient nanosize effect cannot be obtained, and a sufficient function as a nonwoven fabric cannot be exhibited.
The particle diameter of the metal compound can be controlled by the treatment conditions when the metal ions are infiltrated. For example, increasing the concentration of the treatment liquid and decreasing the number of treatments increase the particle diameter, while decreasing the concentration of the treatment liquid and increasing the number of treatments tend to make the particle diameter finer.

  Moreover, in this invention, it is required to contain 0.5 mass% or more of metal compound nanoparticle with respect to water-soluble thermoplastic PVA, and it is preferable to contain 1.0 mass% or more. When the content of the metal compound nanoparticles is less than 0.5% by mass, it is difficult to develop a sufficient function. On the other hand, if the content of the metal compound nanoparticles is too large, other properties such as mechanical properties may be deteriorated. Therefore, the content is preferably 50% by mass or less based on the water-soluble thermoplastic PVA. It is more preferable that the amount is not more than mass%.

  The present invention is characterized in that the metal compound fine particles are uniformly dispersed in the water-soluble thermoplastic PVA by taking advantage of the feature that PVA forms a strong coordinate bond with a metal ion via a hydroxyl group. That is, in the present invention, it is important that metal ions are first permeated into water-soluble thermoplastic PVA present in the nonwoven fabric structure and coordinated with the hydroxyl group of PVA. Next, the metal ion that has been coordinated and bonded is treated by a reduction reaction or the like, whereby the desired functional metal compound nanoparticle can be formed.

The compound (A) containing a metal ion used in the present invention is not particularly limited as long as it is soluble. Examples of the metal ion include manganese ion, iron ion, cobalt ion, nickel ion, and copper ion. Various metal ions such as zinc ion and silver ion are applicable, and as the compound containing these metal ions, various compounds such as acetate, formate, nitrate, chloride, bromide and the like are used. be able to.
On the other hand, the reactant (B) for reducing the metal ion is not particularly limited as long as it can achieve the purpose of forming the nanoparticle by cutting the coordination bond between the hydroxyl group of PVA and the metal ion. Further, an oxidizing agent, a sulfiding agent, an iodinating agent and the like are applicable. Among them, the reduction reaction with sulfide ions is most often used, and examples of the compound include sodium sulfide, sodium thiosulfate, sodium hydrogensulfite, hydrogen sulfide and the like.

  Various kinds of fine particles can be formed and functionalized by combining the various metal ions and the reactants. For example, conductivity by copper sulfide, thermal conductivity, ultraviolet / near infrared absorption, zinc sulfide, magnetism by ferrite (iron oxide), superionic conductivity by silver iodide, silver oxide Examples include deodorant and antibacterial properties.

Specific examples of thermoplastic polymers other than the water-soluble thermoplastic PVA used in the present invention include polyesters such as aromatic polyesters such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, and polylactic acid. , Polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutyrate-polyhydroxyvalylate copolymer, aliphatic polyester such as polycaprolactone and copolymers thereof, and nylon 6, Nylon 66, nylon 610, nylon 10, nylon 12, nylon 6-12 and other aliphatic polyamides and copolymers thereof, polypropylene, polyethylene, polybutene, polymethylpente Polyolefins such as ethylene and copolymers thereof, water-insoluble ethylene-vinyl alcohol copolymers containing 25 mol% to 70 mol% of ethylene units, polystyrene, polydiene, chlorine, polyolefin, polyester, polyurethane At least one kind selected from polyamide-based and fluorine-based elastomers can be used.
Polyethylene terephthalate and a copolymer thereof, polylactic acid, nylon 6, polypropylene and polyethylene are preferable from the viewpoint of easy composite spinning with PVA suitably used in the present invention.

  In the present invention, the fiber made of a thermoplastic polymer other than the water-soluble thermoplastic PVA is preferably a long fiber having an average fineness of 0.5 dtex or less, more preferably 0.4 dtex or less. It is particularly preferable to have a fineness of 0.3 dtex or less. When the fineness is larger than 0.5 dtex, the fiber surface area becomes insufficient, and the flexibility may be further lowered. Moreover, although there is no limitation in particular regarding a lower limit, 0.001 dtex or more is preferable at the point of the ease of production.

  Next, the manufacturing method of the nonwoven fabric of this invention is demonstrated. The nonwoven fabric of the present invention is obtained by dissolving (extracting) water-soluble thermoplastic PVA with water from a nonwoven fabric composed of a composite fiber composed of water-soluble thermoplastic PVA and another thermoplastic polymer, and further in the water-soluble thermoplastic PVA. It can be produced by finely dispersing a metal compound that imparts the above-described functionality.

  A composite fiber nonwoven fabric made of water-soluble thermoplastic PVA and another thermoplastic polymer can be efficiently produced by a so-called spunbond nonwoven fabric production method in which melt spinning and nonwoven fabric formation are directly connected.

  For example, water-soluble thermoplastic PVA and other thermoplastic polymers are melted and kneaded in separate extruders, and then these melted polymer flows are respectively guided to the spinning head, merged, and the flow rate is measured. After discharging and cooling the discharged yarn with a cooling device, using a suction device such as an air jet nozzle, the yarn is taken up at a speed of 1000 to 6000 m / min so as to achieve the desired fineness. After pulling and thinning with high-speed airflow at the appropriate speed, it is deposited on a movable collection surface while opening the fiber to form a nonwoven web, and then this web is partially thermocompression bonded and wound up A fiber nonwoven fabric can be obtained.

  As a composite cross-section separable in the length direction of the composite fiber constituting the composite fiber nonwoven fabric, a sea island composed of a sea component and an island component as shown in FIG. Those having the shape of a mold, those having a cross-sectional shape of a mandarin orange as shown in FIG. 2 or those having a fan shape, and those having a laminated shape arranged in a strip shape are preferable. When the cross-sectional shape of the composite fiber is a sea-island type, the number of island components that are ultrafine fiber forming components is preferably in the range of 5 to 1000 in terms of homogeneity, and more preferably in the range of 10 to 600. . In addition, when the composite cross section has a mandarin orange cross-sectional shape, fan shape, or bonded shape, the ultrafine fiber forming component constituting the composite fiber is divided into 2 to 20 by water-soluble thermoplastic PVA. It is preferable in terms of productivity.

  When used in filters, the fineness of the fibers is important, so a sea-island shape is preferred, where thin fibers can be easily obtained. On the other hand, when used in wipers, a fiber with a square fiber cross section can be wiped off. Therefore, those having a mandarin orange cross-sectional shape or a fan-like shape, and those having a laminated shape arranged in a strip shape are preferable.

  The mass ratio of the water-soluble thermoplastic PVA and the thermoplastic polymer in the composite long-fiber nonwoven fabric composed of the water-soluble thermoplastic PVA and the thermoplastic polymer used in the present invention is appropriately set according to the purpose and is not particularly limited. / 95 to 95/5 is preferable, and 10/90 to 90/10 is more preferable. If it is outside the preferred range, the combined effect may not appear.

  Further, as long as the purpose and effect of the present invention are not impaired, the thermoplastic polymer and the water-soluble thermoplastic PVA include a plasticizer, a stabilizer, a lubricant, a colorant, an ultraviolet absorber, a light stabilizer, and an antioxidant as necessary. An agent, an antistatic agent, a flame retardant, a lubricant, and a crystallization rate retarder can be added during the polymerization reaction or in a subsequent step.

  If necessary, fine particles having an average particle size of 0.01 μm or more and 5 μm or less are added to the thermoplastic polymer and the water-soluble thermoplastic PVA at the polymerization reaction or in the subsequent steps at 0.05 to 10% by mass. can do. The type of fine particles is not particularly limited, and for example, inert fine particles such as silica, titanium oxide, calcium carbonate, and barium sulfate can be added, and these may be used alone or in combination of two or more. In particular, inorganic fine particles having an average particle diameter of 0.02 μm or more and 1 μm or less, such as silica, are preferably added. In this case, spinnability and stretchability are improved.

In the present invention, the fiberizing conditions constituting the composite fiber nonwoven fabric need to be appropriately set according to the combination of the polymers and the composite cross section, but mainly determine the fiberizing conditions while paying attention to the following points. Is desirable.
The spinneret temperature is preferably in the range of Mp + 10 ° C. to Mp + 80 ° C. when the melting point of the polymer having a high melting point among the polymers constituting the composite fiber is Mp, the shear rate (γ) is 500 to 25000 sec ⁻¹ , and the draft (V ) Is preferably spun in the range of 50-2000. Further, when viewed from the combination of polymers to be composite-spun, a polymer having a close melt viscosity as measured by the die temperature at the time of spinning and the shear rate at the time of passing through the nozzle, for example, at a melt spinning die temperature at a shear rate of 1000 sec ⁻¹ . From the viewpoint of spinning stability, it is preferable to perform composite spinning with a combination having a difference in melt viscosity within 2000 poise.

The melting point Tm of the polymer in the present invention is a peak temperature of a main endothermic peak observed with a differential scanning calorimeter (DSC: for example, “TA3000” manufactured by Mettler). The shear rate (γ) is calculated as γ = 4Q / πr ³ where r (cm) is the nozzle radius and Q (cm ³ / sec) is the polymer discharge rate per single hole. The draft V is calculated as V = 1000 A · πr ² / Q, where the take-up speed is A (m / min).

In producing the conjugate fiber of the present invention, when the spinneret temperature is lower than the melting point Mp + 10 ° C. of the polymer having a high melting point among the polymers constituting the conjugate fiber, the melt viscosity of the polymer is too high and It is inferior in yarn / thinning property, and when it exceeds Mp + 80 ° C., PVA tends to be thermally decomposed, so that stable spinning cannot be performed. Further, the shear rate is easily Dan'ito lower than 500 sec ^-1, spinnability becomes high back pressure of the nozzle and higher than 25000Sec ^-1 deteriorates. When the draft is lower than 50, unevenness in fineness becomes large and stable spinning is difficult, and when the draft is higher than 2000, the yarn is easily broken.

  In the present invention, when the discharged yarn is pulled and thinned using a suction device such as an air jet nozzle, it is pulled and thinned by a high-speed air stream at a speed corresponding to a yarn take-up speed of 1000 to 6000 m / min. Is preferred. The conditions for taking up the yarn by the suction device are appropriately selected depending on the melt viscosity of the molten polymer discharged from the spinning nozzle hole, the discharge speed, the spinning nozzle temperature, the cooling conditions, etc., but if it is less than 1000 m / min, the discharged yarn is cooled and solidified Adhesion between adjacent yarns may occur due to delay, and the orientation and crystallization of the yarn does not progress, and the resulting composite nonwoven fabric is coarse and low in mechanical strength. On the other hand, if it exceeds 6000 m / min, the warp / thinning property of the discharged yarn cannot follow, and the yarn may be cut, and a stable composite long-fiber nonwoven fabric may not be manufactured.

  Further, when the composite long fiber nonwoven fabric of the present invention is stably produced, the distance between the spinning nozzle hole and the suction device such as an air jet nozzle is preferably 30 to 200 cm. The spacing depends on the polymer used, the composition, and the spinning conditions described above, but if the spacing is less than 30 cm, fusion between adjacent yarns may occur due to a delay in cooling and solidification of the discharged yarn. In addition, since the orientation and crystallization of the yarn does not proceed, the resulting composite nonwoven fabric is undesirably rough and low in mechanical strength. On the other hand, when the length exceeds 200 cm, cooling and solidification of the discharged yarn has progressed too much, so that the discharged yarn cannot follow the stringing / thinning property, and the yarn is cut to produce a stable composite long fiber nonwoven fabric. May not be possible.

The composite long fibers refined by a suction device such as an air jet nozzle are dispersed and collected so as to have a substantially uniform thickness on the surface of the collecting sheet to form a web. The distance between the suction device and the collection surface is preferably 30 to 200 cm from the viewpoint of productivity and fiber physical properties of the resulting nonwoven fabric. Moreover, as a basis weight of a web, the range of 5-500 g / m < ² > is preferable at the point of productivity and post-processability of a nonwoven fabric. Further, the thickness of the suction-thinned web-forming composite fiber is preferably in the range of 0.2 to 8 dtex from the viewpoint of productivity.

Moreover, in this invention, the range of 5-500 g / m < ² > as a fabric weight of a nonwoven fabric is preferable at the point of productivity and post-processability.

  In the present invention, the water-soluble thermoplastic PVA is extracted and removed from the composite fiber nonwoven fabric with water, so that the thermoplastic polymer can be made extremely fine. There are no particular restrictions on the method used to extract water-soluble thermoplastic PVA from composite fiber nonwoven fabrics with water. Use dyeing machines such as circular, beam, zicker, and Wiens, and hot water treatment equipment such as vibro washers, relaxers, and timing washers. Any method can be selected as appropriate, such as a method for performing high pressure water flow or a method for jetting steam. The method of injecting high-pressure water flow or steam is a very effective method in that the split ultra-thin fibers are strongly entangled with each other and the water absorption is further improved by capillary action. In many cases, the reduction amount of the water-soluble thermoplastic PVA is insufficient. Therefore, it is preferable to use a method in which the non-woven fabric is stirred in a water bath after the treatment with a high-pressure water stream or steam and the amount of water-soluble thermoplastic PVA is within the intended range. The extraction water may be neutral, and may be an alkaline aqueous solution, an acidic aqueous solution, or an aqueous solution to which a surfactant or the like is added.

  Particularly important in the present invention is that when water-soluble thermoplastic PVA is extracted and removed with water, a removal treatment must be performed so that a part of the water-soluble thermoplastic PVA remains in the nonwoven fabric. . In order to do so, the amount of water used for the removal treatment, treatment method, treatment time, treatment temperature, etc. are variously changed, and these conditions are determined so that the remaining amount of water-soluble thermoplastic PVA falls within an appropriate range. It is preferable to keep it.

  Specifically, in the present invention, the method of extracting and removing water-soluble thermoplastic PVA with water is preferably a method of treating the composite fiber nonwoven fabric in a water bath to dissolve and remove the contained water-soluble thermoplastic PVA. The water bath ratio is preferably 100 to 2000 times, more preferably 200 to 1000 times the mass of the composite fiber nonwoven fabric. When the water bath ratio is less than 100 times, the water-soluble thermoplastic PVA is not sufficiently dissolved and removed, and the intended ultrafine fiber nonwoven fabric may not be obtained. Further, when the water bath ratio exceeds 2000 times, the splitting property from the composite fiber to the ultrafine fiber may be lowered. Of course, when extraction and removal are insufficient, a method of extracting and removing water-soluble thermoplastic PVA in a water bath again using fresh water not containing water-soluble thermoplastic PVA is used.

The extraction treatment temperature may be appropriately adjusted according to the purpose, but when extracting with hot water, it is preferably treated at 40 to 120 ° C, more preferably at 60 to 110 ° C, and 80 It is particularly preferable to perform the extraction treatment at -100 ° C. When processing temperature is lower than 40 degreeC, the extractability of water-soluble thermoplastic PVA is not enough, and productivity falls. Moreover, when processing temperature is higher than 120 degreeC, the melt | dissolution time of water-soluble thermoplastic PVA becomes extremely short, and the stable production in the ratio of the target water-soluble thermoplastic PVA may be difficult. Once the water-soluble thermoplastic PVA is completely extracted and removed from the nonwoven fabric, the water-soluble thermoplastic PVA may be added to the nonwoven fabric using a method such as applying a water-soluble thermoplastic PVA aqueous solution. Durable water absorption as specified in the present invention is difficult to obtain.
The reason why the nonwoven fabric of the present invention has excellent water absorption is that the water-soluble thermoplastic PVA is one component constituting the fiber at the stage of the composite fiber, so The presence of some bond with the thermoplastic polymer of PVA, and after removal of the water-soluble thermoplastic PVA, the PVA is mainly present in the fiber or in the back of the gap between the fibers. In the process of extracting and removing the thermoplastic polymer with water, it is difficult for the thermoplastic polymer to come off from the fiber surface, which is expected to provide durable water absorption.

  The extraction processing time can also be adjusted as appropriate according to the purpose, equipment to be used, and processing temperature. However, in consideration of production efficiency, stability, quality and performance of the resulting ultrafine fiber nonwoven fabric, batch processing is performed. Is preferably 10 to 200 minutes, and in the case of continuous treatment, it is preferably 1 to 20 minutes.

  The PVA used in the present invention has biodegradability, and is decomposed into water and carbon dioxide when treated with activated sludge or buried in soil. Although there is no restriction | limiting in particular in the process of the waste liquid after melt | dissolving PVA, the activated sludge method is preferable. When the PVA aqueous solution is continuously treated with activated sludge, it is decomposed in 2 days to 1 month. Moreover, since PVA used for this invention has low combustion heat and the load with respect to an incinerator is small, you may incinerate PVA by drying the waste_water | drain which melt | dissolved PVA.

Next, a method for forming metal compound nanoparticles that impart the functionality of the present invention will be described.
First, the nonwoven fabric in which the water-soluble thermoplastic PVA exists is passed through a bath in which the compound (A) containing metal ions is dissolved, and the compound is impregnated in the water-soluble thermoplastic PVA. At that time, the solvent used in the bath is preferably an alcohol such as methanol or water. Moreover, what is necessary is just to set the melt | dissolution amount to the bath of the compound (A) containing a metal ion suitably according to the objective, However, It is preferable that it is the range of 10-200 g / L. When the addition amount is less than 10 g / L, the intended physical properties may not be obtained, and when it exceeds 200 g / L, the process properties may not be stable. Further, the residence time of the bath is not particularly limited, but the residence time in the bath is 3 seconds or more, preferably 30 in order to uniformly impregnate the metal ions and form a sufficient coordination bond with the hydroxyl group of PVA. It is desirable to be at least 2 seconds.

  Next, it is necessary to pass through the bath which melt | dissolved the target reactive agent (B) which carries out the oxidation reduction process etc. of the metal ion coordinated by the above. In this case, the amount of the reactant (B) added to the bath may be appropriately set depending on the amount of metal ions introduced, but is preferably in the range of 1 to 100 g / L. When the addition amount is less than 1 g / L, the formation of the intended functional agent may not be sufficient, and when it exceeds 100 g / L, the processability may not be stable. In this case as well, the residence time is not particularly limited, but the residence time is preferably 0.1 seconds or longer in order to perform sufficient treatment.

  Further, when it is desired to enhance the functionalization of the nonwoven fabric, it is effective to repeatedly pass the step of impregnating the metal ions and the step of performing oxidation-reduction treatment.

  There is no restriction | limiting in particular regarding the method of drying the functional nonwoven fabric of this invention, The objective, an apparatus, temperature, etc. can be selected suitably. However, the drying temperature is preferably 120 ° C. or lower, more preferably 100 ° C. or lower, and particularly preferably 90 ° C. or lower in order to develop good water absorption performance in wiper applications and the like. When the drying temperature exceeds 120 ° C., crystallization of the remaining water-soluble thermoplastic PVA proceeds, so that the moisture content of the nonwoven fabric structure decreases and the water absorption performance decreases. Of course, you may dry at room temperature. Further, the drying time is preferably within 24 hours in the case of batch processing, and is preferably within 1 hour in the case of continuous processing.

  Further, in the present invention, the functional nonwoven fabric obtained as described above is subjected to hot embossing / calendar method, water jet method, needle punch method, ultrasonic sealing method, through-air method, stitch bond method, emulsion bonding method, powder dot bonding. A method of maintaining the form by an adhesion / entanglement method such as a method is employed. Among these, the hot embossing method, the water jet method, and the needle punch method are particularly preferable from the viewpoints of appearance, quality, and the like as the long fiber nonwoven fabric. There is no restriction | limiting in particular about in which stage joining is performed, It is possible to implement suitably as needed. For example, it may be before the PVA is extracted with water, or after the PVA is extracted with water and before the functional agent is dispersed.

  As a method of performing partial hot-pressure fusion by hot embossing, the fibers are bonded by partial thermocompression bonding through the web between a heated metal roll (embossing roll) having a concavo-convex pattern and a heated smooth roll. Bonded to stabilize the form as a nonwoven fabric. The temperature of the heating roll, the pressure for hot pressing, the processing speed, the pattern of the embossing roll, etc. in the thermocompression bonding process can be appropriately selected according to the purpose. Moreover, it is preferable that the part thermocompression-bonded by the embossed pattern is 5 to 30% of the surface area of a nonwoven fabric from a viewpoint of form stability, a softness | flexibility, and water absorption.

Further, as the water jet method, for example, the nozzle diameter is 0.02 to 0.4 mm, preferably 0.05 to 0.2 mm, the pitch is 0.1 to 5 mm, preferably 0.5 to 2 mm, and 1 row to 3 mm. A method may be considered in which fibers are dispersed and entangled by using a nozzle plate or the like arranged in a row and treating with a water flow having a water pressure of 1 to 300 kg / cm ² once or a plurality of times.

Further, the needle punch method can be appropriately selected from known conditions such as an oil agent, a needle shape, a needle depth, and the number of punches. For example, the needle shape is more efficient when the number of barbs is large, but 1 to 9 barbs are preferable as long as needle breakage does not occur, and the depth is such that the needle needle barbs penetrate to the nonwoven fabric surface and the needle mark is A range that does not come out strongly is preferred. Although the required number of punches depends on the type of needle, the oil agent, etc., a method of treating at 50 to 5000 punches / cm ² is preferable because of the homogeneity or flexibility of the nonwoven fabric.

  Further, the ultra-fine long-fiber non-woven fabric obtained in the present invention is not only used alone, but can also be used by laminating with other long-fiber non-woven fabrics, short-fiber non-woven fabrics, woven fabrics, knitted fabrics, etc. When used, practical functions can be further imparted. For example, when a melt-blown nonwoven fabric is laminated on one side of the ultra-thin fiber nonwoven fabric of the present invention, a laminated nonwoven fabric made of ultra-fine fibers suitable for filter applications can be obtained.

  The non-woven fabric functionalized as described above is excellent in water absorption and water retention by leaving a part of the water-soluble thermoplastic PVA in the non-woven fabric structure, and also has good flexibility. Can be used as a highly functional wiper. Specifically, the wiper can be suitably used as a wiper such as a wiper for wiping off an aqueous liquid or a wet wiper used in a state where an aqueous liquid is included in the wiper.

  When the highly functional nonwoven fabric of the present invention is used as a wiper, it is preferable that the wicking property at 20 ° C. for 10 minutes after immersing in 80 ° C. water for 60 minutes is 30 mm or more, 50 mm More preferably, it is 60 mm or more. When the wicking property is less than 30 mm, a sufficient water absorbing function cannot be achieved. Such durable water absorption is achieved by leaving a specific thermoplastic PVA in a non-woven fabric made of ultrafine fibers having a specific thickness and drying it under specific conditions. However, it is difficult to manufacture a product whose wicking property exceeds 300 mm. As used herein, “60-minute immersion in 80 ° C. water” means “20 g of non-woven fabric is immersed in 80 ° C. water, 1000 times the amount of the nonwoven fabric, and allowed to stand for 60 minutes under light stirring conditions. Thereafter, the nonwoven fabric is taken out, the surface is washed away with water at 20 ° C., dried in that state at 80 ° C. for 3 minutes, and the wicking property of the resulting nonwoven fabric is measured ”.

  The wicking property of the nonwoven fabric is measured in accordance with JIS-1018-70 “Knitted Fabric Testing Method” (Water Absorption B Method (Byreck Method) KRT No. 411-2). A load is attached to the lower end of a 2.5 cm × 20 cm non-woven fabric, and the suction height is measured when the test piece is submerged in water-soluble ink (ink / water = 1/5) to the lower end of the test piece 1 cm and held for 10 minutes.

Moreover, since the functional nonwoven fabric of the present invention can be made into ultrafine fibers, has a large surface area and excellent filterability, it can also be used as a highly functional filter substrate. In this case, not only the gas filter but also a liquid filter that removes the foreign matter from the aqueous liquid in which the foreign matter is mixed can be suitably used by taking advantage of its excellent water absorption characteristics. When used as a filter substrate, the air permeability is preferably 200 cc / cm ² / sec or less, more preferably 160 cc / cm ² / sec or less, and particularly preferably 120 cc / cm ² / sec or less. preferable. When the air permeability exceeds 200 cc / cm ² / sec, a sufficient filter function may not be achieved. Although it does not specifically limit regarding a lower limit, in order to achieve the objective as a filter, 1 cc / cm < ² > / sec is a lower limit. Such air permeability is measured according to the fragile method of JIS-L1906 “General Long Fiber Nonwoven Fabric Testing Method”.

  Furthermore, according to the purpose, it is possible to further improve the collection property by electrification by electret processing.

  Moreover, you may perform various hydrophilization treatments for the purpose of improving a water absorption further as needed. Examples of the hydrophilic treatment method include sulfonation treatment, discharge treatment such as corona discharge and plasma discharge, graft polymerization treatment, and fluorine gas treatment.

  In addition, the highly functional nonwoven fabric of the present invention can be used in various applications by taking advantage of excellent flexibility, water absorption, filterability and various functions. Examples include industrial materials such as electronics, oil adsorbents, leather base fabrics, cement compounding materials, rubber compounding materials, various tape base materials such as insulating materials; paper diapers, gauze, bandages, medical gowns, Medical and sanitary materials such as surgical tape; life-related materials such as printed materials, packaging and bag materials, storage materials; clothing; interior materials such as heat insulating materials and sound absorbing materials; construction materials; agricultural and horticultural materials; soil It can be used for civil engineering and materials such as stabilizers, filtering materials, sand flow prevention materials, reinforcing materials, etc .;

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the examples, each physical property value was measured as follows. In addition, unless otherwise indicated, the part and% in an Example are related with mass.

[Analysis method of PVA]
The analysis method of PVA followed JIS-K6726 unless otherwise specified.
The amount of modification was determined by measurement with a 500 MHz, ¹ H-NMR (“GX-500” manufactured by JEOL Ltd.) apparatus using a modified polyvinyl ester or modified PVA. The content of alkali metal ions was determined by atomic absorption method.

[Melting point ℃]
The melting point of PVA was DSC (“TA3000” manufactured by Mettler), heated to 250 ° C. in nitrogen at a heating rate of 10 ° C./min, cooled to room temperature, and again 250 ° C. at a heating rate of 10 ° C./min. The temperature at the top of the endothermic peak indicating the melting point of PVA when the temperature was raised to 0 ° C. was examined.

[Spinning state]
The melt spinning state was observed and evaluated according to the following criteria.
◎: Extremely good, ○: Good, △: Somewhat difficult, ×: Poor

[Nonwoven fabric state]
The obtained nonwoven fabric was visually observed and tentacles were evaluated according to the following criteria.
◎: Uniform and extremely good, ○: Almost homogeneous and good, △: Somewhat difficult, ×: Poor

[PVA remaining rate%]
A 30 cm × 30 cm nonwoven fabric sample was immersed in 2000 cc of water in an autoclave and heat-treated at 120 ° C. for 1 hour. After the treatment, remove the nonwoven fabric from the hot water and squeeze it lightly. The water-soluble thermoplastic resin in the non-woven fabric is completely extracted and removed by a total of 3 repeated treatments. From the mass change before and after the treatment, the ratio of the water-soluble thermoplastic resin in the nonwoven fabric was determined.

[PVA coverage%]
The constituent elements and bonding state of the nonwoven fabric surface were analyzed by X-ray photoelectron spectroscopy (XPS), and the proportion of PVA was calculated from the results.

[Fiber fineness dtex]
Ten fibers were randomly selected from an enlarged photograph of the nonwoven fabric sample taken at a magnification of 1000 times with a microscope, the fiber diameters were measured, and the average value was taken as the average fiber diameter.

[Non-woven fabric weight g / m ² ]
Measured according to JIS L1906 “General long fiber nonwoven fabric test method”.

[Tensile strength of nonwoven fabric N / 5cm]
Measured according to JIS L1906 “General long fiber nonwoven fabric test method”.

[Metal compound (copper sulfide) content% / PVA]
The content of the metal compound (copper sulfide) in the nonwoven fabric after the functionalization treatment was determined by an atomic absorption method.

[Metal compound (copper sulfide) particle size nm]
From the fiber surface enlarged photograph of the nonwoven fabric sample photographed with a microscope at a magnification of 10,000 times, 50 metal compound fine particles were randomly selected, their sizes were measured, and the average value was taken as the average particle diameter.

[Flexibility]
The obtained nonwoven fabric was observed with tentacles and evaluated according to the following criteria.
◎: Extremely good, ○: Almost good, △: Slightly hard, ×: Hard and difficult

[Volume resistivity (conductivity) measurement]
The nonwoven fabric was dried at a temperature of 105 ° C. for 1 hour, and then allowed to stand for 24 hours or more under conditions of a temperature of 20 ° C. and a humidity of 30% to adjust the humidity. A test piece of 5 cm × 5 cm is taken from this nonwoven fabric, and a resistance value measuring device “MULTITIMETER” manufactured by YOKOGAWA Hewlett-Packard Co. is used between both ends of the test piece to apply a voltage of 10 V to the resistance value ( Ω) was measured. From the volume resistivity (ρ) (Ω · cm) = R × (S / L), the volume resistivity of each test piece was measured, and the average value was taken as the volume resistivity of the nonwoven fabric. Here, R represents the resistance value (Ω) of the test piece, S represents the cross-sectional area (cm ² ), and L represents the length (cm).

[Example 1]
<Production of ethylene-modified PVA>
A 50 L pressure reactor equipped with a stirrer, nitrogen inlet, ethylene inlet and initiator inlet was charged with 15.0 kg of vinyl acetate and 16.0 kg of methanol, heated to 60 ° C., and then nitrogen bubbling for 30 minutes. The inside was replaced with nitrogen. Next, ethylene was introduced and charged so that the reactor pressure was 5.5 kg / cm ² (5.4 × 10 ⁵ Pa). Prepare a 2.8 g / L solution of 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (AMV) dissolved in methanol as an initiator, and perform nitrogen replacement by bubbling with nitrogen gas. did. After adjusting the temperature inside the polymerization tank to 60 ° C., 170 ml of the initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced, the reactor pressure was maintained at 5.5 kg / cm ² (5.4 × 10 ⁵ Pa), the polymerization temperature was maintained at 60 ° C., and the above initiator solution was used at 300 ml / hr. Polymerization was carried out with continuous addition of AMV. After 9.0 hours, when the polymerization rate reached 68%, the polymerization was stopped by cooling. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled to completely remove ethylene. Next, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate.

  Methanol was added to the obtained polyvinyl acetate solution to adjust the concentration to 50% to 2.0 kg of the polyvinyl acetate methanol solution (1.0 kg of polyvinyl acetate in the solution). Saponification was performed by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.11) to vinyl acetate units in vinyl acetate. About 5 minutes after the addition of alkali, the gelled system was pulverized by a pulverizer and allowed to stand at 60 ° C. for 3 hours to proceed saponification, and then 0.5% acetic acid water / methanol = 20/80. 10.0 kg of the mixed solution was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 20.0 kg of a mixed solution of water / methanol = 20/80 was added to the white solid PVA obtained by filtration, and the mixture was allowed to wash at room temperature for 3 hours. After repeating the above washing operation three times, 10.0 kg of methanol was further added, and the mixture was left to wash at room temperature for 3 hours. Then, PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-1).

  The saponification degree of the obtained ethylene-modified PVA was 99.1 mol%. In addition, after the modified PVA was incinerated, the sodium content measured by an atomic absorption photometer using a material dissolved in an acid was 0.0006 parts by mass with respect to 100 parts by mass of the modified PVA.

In addition, after removing the unreacted vinyl acetate monomer after the polymerization, a methanol solution of polyvinyl acetate obtained by precipitation in n-hexane and reprecipitation purification by dissolving with acetone was performed three times, followed by drying at 80 ° C. under reduced pressure for 3 days. To obtain purified polyvinyl acetate. When the polyvinyl acetate was dissolved in DMSO-d6 and measured at 80 ° C. using 500 MHz, ¹ H-NMR (“GX-500” manufactured by JEOL Ltd.), the ethylene content was 8.4 mol%. Met. After saponifying the above methanol solution of polyvinyl acetate at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to proceed saponification, followed by methanol soxhlet for 3 days, and then at 80 ° C. And purified under reduced pressure for 3 days to obtain purified ethylene-modified PVA. It was 350 when the average degree of polymerization of this PVA was measured according to JIS K6726 of the usual method. Further, a cast film having a thickness of 10 μm was prepared by preparing a 5% aqueous solution of the purified modified PVA. After the film was dried under reduced pressure at 80 ° C. for 1 day, the melting point of PVA was measured by the above-described method using DSC (“TA3000” manufactured by Mettler), and it was 212 ° C. (Table 1).
Pellets were produced by melt-extruding the PVA obtained above with a twin screw extruder (30 mmφ) at a set temperature of 230 ° C. and a screw rotation speed of 200 rpm.

<Manufacture of sea-island type composite long-fiber nonwoven fabric>
The PVA (PVA-1) pellets obtained above and a polymer obtained by copolymerizing 6 mol% of isophthalic acid with polyethylene terephthalate having an intrinsic viscosity of 0.7 and a melting point of 240 ° C. were prepared. A composite having a sea-island cross section at 260 ° C. so that the mass ratio of the composite long fiber constituting the nonwoven fabric to the fiber cross section perpendicular to the fiber axis is PET / PVA = 70/30 by heating with a machine and melt kneading. Guided to the spinning pack, the nozzle diameter is 0.35 mmφ × 1008 holes, the discharge rate is 1050 g / min, the shear rate is 2500 sec ⁻¹ and discharged from the spinneret, and the spinning filament group is cooled with 20 ° C. cooling air while the nozzle The filaments that have been opened are drawn and thinned at a take-up speed of 4000 m / min with high-speed air using an ejector at a distance of 80 cm. To form a collecting deposited so long fiber web on the collecting conveyor on rotating in the dress. In the spinning state, no breakage was observed, and the cross-sectional shape was extremely good.

Next, the web is passed between a concavo-convex pattern embossing roll heated to 170 ° C. and a flat roll under a pressure of a linear pressure of 50 kg / cm, and the embossed part is subjected to thermocompression bonding, whereby a single fiber fineness of 3.5 dtex is obtained. A sea-island type composite long fiber nonwoven fabric having a basis weight of 82 g / m ² was obtained. The obtained non-woven fabric was homogeneous and very good. The production conditions of the composite long fiber nonwoven fabric are shown in Table 2.

About about 50 m of the obtained composite long fiber nonwoven fabric, a PVA component was extracted using a circular dyeing machine (water bath 800 L, water bath ratio 330 times the nonwoven fabric mass, nonwoven fabric rotation speed about 50 m / min). After adding the composite long fiber nonwoven fabric, the temperature was raised from room temperature to 90 ° C. at a rate of about 5 ° C./min, and further hydrothermal treatment was performed at 90 ° C. for 30 minutes. Thereby, the PVA component in the composite long fiber nonwoven fabric was extracted and removed. Further, this web was dried with hot air at 90 ° C. for 5 minutes by continuous treatment to obtain a polyethylene fiber terephthalate ultra-thin fiber nonwoven fabric.
Table 3 shows the PVA residual ratio, coverage, fineness, and basis weight of the obtained ultra-fine long fiber nonwoven fabric.

Subsequently, the ultra-thin fiber nonwoven fabric obtained above was introduced into a 25 ° C. water bath in which copper nitrate was dissolved at 280 g / L so that the residence time was 600 seconds, and then sodium sulfide was dissolved at 17 g / L. It was introduced in a water bath at 0 ° C. so that the residence time was 300 seconds. Further, after passing through a water bath at 25 ° C., it was dried with hot air at 95 ° C. for 5 minutes. Table 4 shows the performance evaluation results of the obtained nonwoven fabric. The content of the copper sulfide nanoparticle in the nonwoven fabric was 5.1% / PVA, and the average particle size was 8.2 nm. The volume resistivity value was 2.8 × 10 ³ Ω · cm, which showed good conductivity.

[Examples 2 to 6]
The same conditions as in Example 1 were used except that a thermoplastic polymer (polypropylene or 6-nylon) other than PVA2-4 or polyethylene terephthalate described in Table 1 was used instead of PVA-1 or polyethylene terephthalate used in Example 1. A non-woven web composed of composite long fibers is produced, and the PVA component is extracted under the conditions described in Table 2 using a circular dyeing machine in the same manner as in Example 1. Further, under the same conditions as in Example 1. Conductive treatment was performed. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

[Examples 7 to 9]
Instead of the composite spinneret having the cross-sectional shape of the sea-island type (25 islands) used in Example 1, using the composite spinneret of the type shown in Table 2, adopting the spinning conditions shown in Table 2, A nonwoven web composed of composite long fibers was obtained under exactly the same conditions as in Example 1 except that the nozzle-ejector distance, the line net speed, and the embossing temperature were appropriately adjusted. The mass ratio of the composite fiber component was adjusted by changing the amount of polymer introduced into the pack. Furthermore, the PVA component was extracted under the conditions described in Table 2 using a circular dyeing machine in the same manner as in Example 1, and the conductive treatment was performed under the same conditions as in Example 1. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

[Example 10]
A nonwoven web made of composite long fibers was produced under exactly the same conditions as in Example 1 except that the embossing temperature was 70 ° C. Subsequently, the composite long fiber was split and entangled by injecting a high-pressure water stream using a water-flow entanglement machine (water pressure 150 kg / cm ² , nonwoven fabric passage speed 3 m / min). The obtained web was extracted with a circular dyeing machine under the conditions shown in Table 2, and the conductive treatment was performed under the same conditions as in Example 1. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

[Example 11]
A nonwoven web made of composite long fibers was produced under exactly the same conditions as in Example 1 except that the embossing temperature was 70 ° C. Subsequently, the composite long fibers were split and entangled by a needle punch method (needle depth: 8 mm, number of punches: 500 punch / cm ² , nonwoven fabric passing speed: 2 m / min). The obtained web was extracted with a circular dyeing machine under the conditions shown in Table 2, and the conductive treatment was performed under the same conditions as in Example 1. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

[Examples 12 to 13]
The composite long fiber nonwoven web produced in Example 1 was used, PVA extraction treatment was performed with a circular dyeing machine under the conditions shown in Table 2, and conductive treatment was conducted under the same conditions as in Example 1. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

[Examples 14 to 16]
The composite long fiber nonwoven web produced in Example 1 was used, PVA extraction treatment with a circular dyeing machine was performed under the same conditions as in Example 1, and conductive treatment was performed under the conditions described in Table 4. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

[Comparative Examples 1-2]
The composite long fiber nonwoven web produced in Example 1 was used, PVA extraction treatment was performed with a circular dyeing machine under the conditions shown in Table 2, and conductive treatment was conducted under the same conditions as in Example 1. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

For Comparative Example 1, the PVA remaining rate after the hot water treatment was high, and only an ultra-thin fiber nonwoven fabric having poor flexibility was obtained, which was difficult to use as a nonwoven fabric in various applications.
As for Comparative Example 2, the performance imparted by the conductive treatment was insufficient because PVA was almost completely removed by the hot water treatment.

[Comparative Example 3]
A polyethylene terephthalate 6-mol% copolymer of polyethylene terephthalate with an intrinsic viscosity of 0.7 and a melting point of 240 ° C. is prepared, heated in an extruder, melt-kneaded, led to a spin pack at 260 ° C., nozzle diameter 0.35 mmφ × 1008 holes, discharge rate of 859 g / min, shear rate of 3000 sec ⁻¹ discharged from the spinneret, and the spinning filament group was cooled with cooling air at 20 ° C. and high-speed air was discharged by an ejector at a distance of 80 cm from the nozzle. Then, the filament group was drawn and thinned at a take-up speed of 4000 m / min, and the opened filament group was collected and deposited on an endless rotating collection conveyor device to form a long fiber web made of polyethylene terephthalate.
Next, the web was passed between a concavo-convex pattern embossing roll heated to 170 ° C. and a flat roll under a linear pressure of 50 kg / cm, and the embossed part was subjected to thermocompression bonding, whereby a single fiber fineness of 2.13 dtex was obtained. A long fiber nonwoven fabric having a basis weight of 59 g / m ² was obtained.

  Using the obtained long fiber nonwoven fabric, a conductive treatment was performed under the same conditions as in Example 1. The performance evaluation results of the obtained long fiber nonwoven fabric are shown in Table 4. Since PVA was not present, copper sulfide nanoparticles could not be formed, and conductivity could not be imparted.

[Comparative Example 4]
Polypropylene having a melt flow rate (MFR) of 400 g / 10 min was melt kneaded at 230 ° C. using a melt extruder, the molten polymer flow was guided to a melt blow die head, and measured with a gear pump, and a hole having a diameter of 0.3 mmΦ was 0 It is discharged from melt blown nozzles arranged in a row at a pitch of 75 mm, and at the same time, hot air of 240 ° C. is sprayed onto this resin and the discharged fibers are collected on a molding conveyor to obtain a polypropylene-based ultrafine fiber nonwoven fabric having a basis weight of 57 g / m ^2. Obtained.

  Conductivity treatment was performed under the same conditions as in Example 1 using the obtained ultrafine fiber nonwoven fabric. The performance evaluation results of the obtained ultrafine fiber nonwoven fabric are shown in Table 4. Since PVA was not present, copper sulfide nanoparticles could not be formed, and conductivity could not be imparted.

[Comparative Examples 5-6]
The composite long fiber nonwoven web produced in Example 1 was used, PVA extraction treatment with a circular dyeing machine was performed under the same conditions as in Example 1, and conductive treatment was performed under the conditions described in Table 4. Tables 3 and 4 show the PVA residual amount, coverage, fineness, basis weight, and performance evaluation results of the obtained ultra-fine long-fiber nonwoven fabric.

About the comparative example 5, the copper sulfide fine particle was not formed but it was inferior to electroconductivity.
About the comparative example 6, since there is little content of a copper sulfide nanoparticle, it was inferior to electroconductivity.

[Comparative Example 7]
The long-fiber nonwoven fabric obtained in Comparative Example 3 was immersed in a solution obtained by mixing and dispersing copper sulfide in a 1% aqueous solution of PVA-1 in advance, and heat-treated at 95 ° C. for 1 hour. After the treatment, the long fiber nonwoven fabric was pulled up and dried as it was at 80 ° C. for 3 minutes to obtain a long fiber nonwoven fabric containing PVA-1 in the nonwoven fabric structure. The residual ratio of PVA in the long fiber nonwoven fabric was 1.7%.
Table 4 shows the results of various performance evaluations using the obtained long-fiber nonwoven fabric.
Although copper sulfide could be provided, the particle diameter of the copper sulfide fine particles was large and the conductivity was poor.

[Example 17]
The long fiber nonwoven fabric obtained in Comparative Example 3 was immersed in a 1% aqueous solution of PVA-1, and heat-treated at 95 ° C. for 1 hour. After the treatment, the long fiber nonwoven fabric was pulled up and dried as it was at 80 ° C. for 3 minutes to obtain a long fiber nonwoven fabric containing PVA-1 in the nonwoven fabric structure. The residual ratio of PVA in the long fiber nonwoven fabric was 1.5%.
Using the obtained long-fiber nonwoven fabric, a conductive treatment was performed under the same conditions as in Example 1, and various performance evaluations were performed. The results are shown in Table 4.

[Example 18]
The ultrafine fiber nonwoven fabric obtained in Comparative Example 4 was immersed in a 1% aqueous solution of PVA-1 and heat-treated at 95 ° C. for 1 hour. After the treatment, the ultrafine fiber nonwoven fabric was pulled up and directly dried with hot air at 80 ° C. for 3 minutes to obtain an ultrafine fiber nonwoven fabric containing PVA-1 in the nonwoven fabric structure. The residual ratio of PVA in the ultrafine fiber nonwoven fabric was 0.8%.
The obtained ultrafine fiber nonwoven fabric was subjected to a conductive treatment under the same conditions as in Example 1, and various performance evaluations were performed. The results are shown in Table 4.

[Example 19]
When the long-fiber nonwoven fabric obtained in Example 1 was used, the wicking property was measured in accordance with JIS L1018-70 “Known Fabric Test Method” (Water Absorption B Method (Byreck Method) KRT No. 411-2). Further, PVA remained uniformly in the longitudinal direction of 188 mm and the lateral direction of 178 mm, which showed good water absorption. Further, the wipeability of dust, water, oil, ink, and the like was evaluated as a wiper. As a result, the wiper showed good wiping properties when composed of ultrafine fibers, and was suitable as a wiper with less static electricity.

[Example 20]
Using the long-fiber non-woven fabric obtained in Example 8, a mask tester and an average 1 μm quartz dust were used, and the collection efficiency and pressure loss were measured at a surface speed of 8.6 cm / sec. As a result, the filter efficiency was 99.59%, the pressure loss was 89 Pa, and the filter performance was good, and it was suitable as a protective material / filter with little static electricity.

[Example 21]
In Example 8, functionalization treatment was performed under the same conditions as in Example 8 except that silver nitrate was used instead of copper nitrate and sodium hydroxide was used instead of sodium sulfide. As a result, silver oxide nanoparticles were formed in the nonwoven fabric at a content of 4.4% / PVA, and the average particle size was 8.9 nm.

  Using the above-mentioned long fiber nonwoven fabric, the collection efficiency and the pressure loss were measured at a surface speed of 8.6 cm / sec using a mask tester and an average 1 μm quartz dust. As a result, a filter material having a trapping efficiency of 99.71% and a pressure loss of 83 Pa and good filter performance and having deodorant and antibacterial properties suitable for a mask or the like could be obtained.

  The highly functional nonwoven fabric of the present invention can be used in various applications by taking advantage of excellent flexibility, water absorption, filterability and various functionalities. Examples include industrial materials such as electronics, oil adsorbents, leather base fabrics, cement compounding materials, rubber compounding materials, various tape base materials such as insulating materials; paper diapers, gauze, bandages, medical gowns, Medical and sanitary materials such as surgical tape; life-related materials such as printed materials, packaging and bag materials, storage materials; clothing; interior materials such as heat insulating materials and sound absorbing materials; construction materials; agricultural and horticultural materials; soil It can be used for civil engineering and materials such as stabilizers, filtering materials, sand flow prevention materials, reinforcing materials, etc .;

Fiber cross-sectional view showing an example of the composite form of the composite long fiber used in the present invention Fiber cross-sectional view showing an example of the composite form of the composite long fiber used in the present invention

Explanation of symbols

1 Water-soluble thermoplastic polyvinyl alcohol 2 Other thermoplastic polymers

Claims (13)

  In the nonwoven fabric structure, water-soluble thermoplastic polyvinyl alcohol is present in an amount of 0.001 to 10% by mass based on the mass of the nonwoven fabric, and further, a metal compound having an average particle size of 50 nm or less is dispersed in the polyvinyl alcohol. Content is 0.5 mass% or more with respect to polyvinyl alcohol, The nonwoven fabric characterized by the above-mentioned.   The non-woven fabric according to claim 1, wherein the non-woven fabric structure is composed of ultrafine long fibers having an average fineness of 0.5 dtex or less.   The nonwoven fabric according to claim 1 or 2, wherein 30% or more of the surface of the nonwoven fabric structure is coated with a water-soluble thermoplastic polyvinyl alcohol.   The nonwoven fabric according to any one of claims 1 to 3, wherein the water-soluble thermoplastic polyvinyl alcohol is a modified polyvinyl alcohol containing 0.1 to 20 mol% of an α-olefin unit having 4 or less carbon atoms.   The nonwoven fabric according to claim 4, wherein the water-soluble thermoplastic polyvinyl alcohol is a modified polyvinyl alcohol containing 3 to 20 mol% of ethylene units.   6. At least one metal compound selected from the group consisting of copper sulfide, zinc sulfide, iron oxide (ferrite), and silver oxide is dispersed in the nonwoven fabric. Non-woven fabric.   The nonwoven fabric according to any one of claims 1 to 6, wherein the nonwoven fabric maintains a form by partial thermocompression bonding by a hot embossing and calendering method.   The nonwoven fabric according to any one of claims 1 to 7, wherein the nonwoven fabric maintains a form by fiber entanglement treatment by a water jet method or a needle punch method.   The nonwoven fabric according to any one of claims 1 to 8, wherein the nonwoven fabric is made of at least one thermoplastic polymer selected from the group consisting of polyester, polyamide, and polyolefin.   A nonwoven fabric laminate in which the nonwoven fabric according to any one of claims 1 to 9 and another nonwoven fabric are laminated. A method for producing a composite fiber nonwoven fabric comprising a water-soluble thermoplastic polyvinyl alcohol and another thermoplastic polymer, characterized in that a metal compound is produced in the nonwoven fabric structure by the following steps (a) and (b): Manufacturing method.
(A) A step of dissolving and removing most of the polyvinyl alcohol from the composite fiber with water and leaving a part of the polyvinyl alcohol in the nonwoven fabric structure.
(B) The non-woven fabric obtained in the above step is uniformly infiltrated into the polyvinyl alcohol through a bath in which the compound (A) containing metal ions is dissolved at a concentration of 10 to 200 g / L, and then the metal ions are introduced. A step of generating a metal compound having an average particle diameter of 50 nm or less by reacting with the metal compound through a bath in which the reducing agent (B) to be reduced is dissolved at a concentration of 1 to 100 g / L.   The filter which consists of a nonwoven fabric in any one of Claims 1-10. The wiper which consists of a nonwoven fabric in any one of Claims 1-10.

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