JP2007239144A - Electroconductive polyvinyl alcohol-based fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based fiber having all of practically sufficient mechanical characteristics, heat resistance and electroconductive performance, applicable to fabrics such as paper, a nonwoven fabric, a woven fabric and a knit fabric and much useful for several uses such as a charging material, a discharging material, a brush, a sensor, an electromagnetic wave shielding material and an electronic material, and to provide a method for producing the fiber. <P>SOLUTION: The polyvinyl alcohol-based fiber comprises a polyvinyl alcohol-based polymer, and copper sulfide nanoparticulates finely dispersed in the polymer and having ≤100 nm average particle diameter, wherein the polyvinyl alcohol-based fiber has continuous convex parts continuing in the fiber axis direction and continuous recessed parts continuing in the fiber axis direction, on the fiber surface by turns. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having mechanical properties such as strength and elastic modulus, heat resistance, and conductive performance, a method for producing the same, and a fabric using the fiber. is there.

  Conventionally, conductive fibers kneaded with conductive fillers such as carbon black, which have been proposed as a method for imparting conductivity to synthetic fibers, are relatively inexpensive and suitable for mass production. Widely used in industrial fields. For example, such conductive fibers are widely used as charging and static elimination brushes used in electrostatic copying machines. However, in copying machines, etc., the temperature inside the machine becomes high due to heating during fixing. Conductive fibers used for applications are required not to be deformed even when subjected to heat for a long time.

  Most general-purpose synthetic fibers such as polyester fibers, polyamide fibers, acrylic fibers, and polyolefin fibers obtained by melt spinning have insufficient heat resistance and high form stability at high temperatures. In Japan, conductive regenerated cellulosic fibers are widely used (see, for example, Patent Documents 1 to 4). However, because conductive cellulose fibers have low mechanical properties, they are sufficient to meet the demands for higher performance such as handling at the stage of manufacturing charging brushes and static elimination brushes and durability for long-term use. It is no longer available.

  On the other hand, it has also been proposed to use a PVA fiber excellent in heat resistance and mechanical performance as a conductive fiber for these applications (for example, see Patent Document 5). However, in this conductive PVA fiber, a large amount of conductive filler of about 50 μm is added to the spinning stock solution in advance, which causes aggregation and sedimentation of the filler in the stock solution, which not only decreases the stability of the manufacturing process. As a result, the stretchability of the obtained yarn is remarkably inferior to that of the conductive filler-free system, and as a result, even if conductivity can be imparted, mechanical properties such as fiber strength and elastic modulus are reduced. There were problems such as. On the other hand, in order to obtain conductive PVA fibers with improved processability and quality problems, the average particle size of conductive fillers such as carbon black charged in the stock solution is reduced, and polyoxyalkylene-based fibers, etc. It has been proposed to prevent aggregation and sedimentation in the stock solution by using a nonionic dispersant together (for example, see Patent Document 6). In this case, the particle size of the conductive filler can be reduced to about 1 μm, which is desirable from the viewpoint of imparting conductivity by increasing the specific surface area of the particles, but in order to obtain the desired conductivity, Addition of several tens of percent or more was necessary, and there were problems such as aggregation in the undiluted solution and reduced stretchability.

  In recent years, with the rapid spread of mobile phones and electronic devices, problems such as the influence of electromagnetic waves leaking from them on the human body or malfunctions of other electronic devices have been investigated. A conductive fabric is often used as an electromagnetic wave shielding material for shielding it. However, in this application, higher conductive performance is necessary, and the above-described conductive filler kneaded fiber cannot exhibit the shielding performance. . In general, it is widely known that a metal film is formed on the surface of a fabric made of a lightweight and flexible synthetic fiber, which can be achieved by a vacuum deposition method, a sputtering method, an electroless plating method, or the like. However, the metal film produced by such a method has problems such as wear resistance, weather resistance, and deterioration of physical properties due to chemical changes due to long-term use, and further improvement is required. Furthermore, the conductive treatment by these methods is very expensive and restricts practical use.

  As a method for imparting such a high conductive performance, as known in the polyacrylonitrile fiber, apart from the method in which the conductive filler as shown above is charged from the stock solution or raw material stage, a second chloride chloride is used. A technique for forming a copper sulfide thin layer exhibiting conductivity on the surface of the fiber itself by adsorbing a copper compound such as copper on the fiber surface and then reducing it with sulfide has been widely proposed (for example, And Patent Documents 7 and 8). The conductive fiber obtained by these methods is one in which about 5 to 15 parts by mass of copper sulfide is bonded to the fiber via a copper ion capturing group of a cyano group or mercapton group present on the surface of the fiber. It has a thin surface layer on the fiber surface and exhibits high electrical conductivity. However, these fibers exhibit electrical conductivity only with a copper sulfide layer having a very thin surface of about 100 nm, and therefore have insufficient durability, and a desired amount of copper sulfide on the fiber surface. In order to adhere, it is necessary to process at a high temperature for a long time. Furthermore, the cyano group and mercapton group described above are excellent in monovalent copper ion scavenging ability. There was a problem that the cost was high, for example, it was necessary to reduce the copper salt to monovalent copper ions.

  For the purpose of improving conductivity and durability, which are the above-mentioned problems, as a method of infiltrating the copper sulfide particles into the inside of the fiber, using a sulfur dye-containing polymer material, copper sulfide is passed through the sulfide dye in the polymer. Has been proposed (for example, see Patent Document 9). Moreover, in the Example, the electroconductive PVA fiber is specifically proposed. This method is achieved for the first time by a step of obtaining a polymer material containing a sulfur dye and a step of obtaining a conductive polymer material by bonding copper sulfide to the sulfur dye polymer material. In addition to the complexity of the process that needs to be set several times, the PVA fiber swells during this treatment, so even if conductivity can be imparted, the mechanical properties are reduced, There was a problem that the fabric could not be manufactured. Further, in order to infiltrate the copper sulfide particles into the inside of the fiber, a sulfur dye must be used, which causes problems such as high cost.

  A method of imparting conductivity to a polymer material having an amide group or a hydroxyl group has also been proposed (see, for example, Patent Document 10). In this method, by immersing the molded body in a mixed aqueous solution of a copper salt and a reducing agent having a mild sulfidizing ability for a long time at a high temperature, a conductive copper sulfide layer is formed even inside the molded body. However, substantially, the copper sulfide layer is present only in the vicinity of the very surface of the molded body, and therefore, the obtained conductive performance is low. In other words, since the copper salt and the sulfide reducing agent in the aqueous solution are directly reacted at a high temperature for a long time, the produced copper sulfide particles grow large, and the dispersed particle size inside the molded body must be large. Rather than internal conductivity, the surface conductive layer was the main component. For this reason, the conductive performance is not only low but also inferior in durability, and further has a problem of high cost.

  So far, the present inventors have proposed a PVA fiber excellent in conductivity in which copper sulfide nanoparticles are finely dispersed in the fiber (see, for example, Patent Document 11), in order to impart high conductivity. Therefore, it is necessary to increase the amount of copper sulfide in the fiber. For example, a sulfurizing agent is dissolved for the purpose of impregnating copper in the fiber through a bath in which a copper compound is dissolved, and subsequently sulfurizing copper in the fiber. The process of passing through the bath had to be repeated several times, which caused problems such as high costs. Further, repeating this conductive step has been a problem in that the quality deteriorates, for example, the mechanical properties of the fiber are lowered or unnecessary copper sulfide particles are deposited on the fiber surface.

JP-A-63-249185 Japanese Patent Laid-Open No. 4-289766 Japanese Patent Laid-Open No. 4-289877 Japanese Patent Publication No. 1-229887 JP-A-52-144422 Japanese Patent Laid-Open No. 2002-212829 JP 57-21570 A JP 59-108043 A JP-A-7-179769 JP 59-132507 A JP 2005-264419 A

  An object of the present invention is to provide a PVA fiber imparted with excellent conductivity without impairing the performance of conventional PVA fibers such as mechanical properties such as strength and elastic modulus, heat resistance, etc. It is providing the fabric which uses a fiber.

  As a result of intensive studies to obtain the above-described PVA fibers, the present inventors do not require specially expensive equipment for PVA polymers, and in the normal fiber manufacturing process, a compound containing copper ions is used. By impregnating the fiber and sulfiding copper in the subsequent process, finely dispersed copper sulfide nanoparticles are formed inside the fiber, and by controlling the surface structure of the fiber according to the stretching conditions, mechanical properties are obtained. It has been found that PVA fibers having excellent electrical conductivity can be manufactured at low cost.

That is, the present invention is a fiber composed of a PVA polymer and copper sulfide nanoparticles having an average particle diameter of 100 nm or less finely dispersed in the polymer, and the fiber surface has convex portions continuous in the fiber axis direction. In addition, the present invention relates to a conductive PVA-based fiber characterized in that recesses continuous in the fiber axis direction are alternately present, and preferably a protrusion continuous in the fiber axis direction and a recess continuous in the fiber axis direction. The conductive PVA fiber is characterized in that the interval of the above is 1 μm or less, and more preferably the volume resistivity value is 1.0 × 10 ^{−3 to} 1.0 × 10 ⁸ Ω · cm. The conductive PVA fiber described above. More preferably, the present invention relates to the above conductive PVA fiber, wherein 1 to 50% by mass of copper sulfide fine particles are contained with respect to 100% by mass of the PVA polymer.

  Further, the present invention is a fiber stretched at a stretching temperature of 100 to 250 ° C. at a stretching speed of 30 m / min or more and a stretching ratio of 1.5 times or more, and on the fiber surface, a convex portion continuous in the fiber axis direction. And a bath in which a compound containing copper ions is dissolved at a concentration of 10 to 400 g / L, a PVA-based fiber in which concave portions continuous in the fiber axis direction are alternately present and the interval is 1 μm or less; In addition, each compound is contained in the fiber through a bath in which a compound containing sulfide ions is dissolved at a concentration of 1 to 100 g / L, and copper is further sulfided, so that the average particle diameter is 100 nm or less inside the fiber. This is a method for producing the above-mentioned conductive PVA-based fiber, characterized in that the copper sulfide nanoparticles are finely produced. Furthermore, this invention relates to the fabric which uses said electroconductive PVA type fiber.

  According to the present invention, it is possible to provide a PVA fiber having excellent electrical conductivity as well as mechanical properties such as strength and elastic modulus, and heat resistance. Moreover, the PVA fiber of the present invention does not require a special process, can be achieved by a normal fiber manufacturing process, can be manufactured at low cost, and can be made into a fabric such as paper, nonwoven fabric, woven fabric, and knitted fabric. It is possible and is extremely useful for many applications including a charging material, a static eliminating material, a brush, a sensor, an electromagnetic shielding material, and an electronic material.

  Hereinafter, the present invention will be specifically described. First, the PVA polymer constituting the PVA fiber of the present invention will be described. The degree of polymerization of the PVA polymer used in the present invention is not particularly limited, but the average degree of polymerization obtained from the viscosity of the 30 ° C. aqueous solution is 1200 to 20000 in consideration of the mechanical properties and dimensional stability of the obtained fiber. Is desirable. The use of a polymer having a high degree of polymerization is preferable because it is excellent in terms of strength, heat and humidity resistance, and the like, but the average degree of polymerization is more preferably 1500 to 5000 from the viewpoint of polymer production cost and fiberization cost.

  The saponification degree of the PVA polymer used in the present invention is not particularly limited, but is preferably 88 mol% or more from the viewpoint of the mechanical properties of the obtained fiber. When the saponification degree of the PVA polymer is lower than 88 mol%, it is not preferable in terms of mechanical properties, process passability, production cost and the like of the obtained fiber.

  The PVA polymer forming the fiber of the present invention is not particularly limited as long as it has a vinyl alcohol unit as a main component, and may have other structural units as desired as long as the effects of the present invention are not impaired. It doesn't matter. Examples of such a structural unit include olefins such as ethylene, propylene, and butylene, acrylic acid and salts thereof and acrylic esters such as methyl acrylate, methacrylic acid and salts thereof, and methacrylate esters such as methyl methacrylate. Acrylamide derivatives such as acrylamide, N-methylacrylamide, methacrylamide derivatives such as methacrylamide, N-methylol methacrylamide, N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, polyalkylene oxide Allyl ethers having a side chain, vinyl ethers such as methyl vinyl ether, nitriles such as acrylonitrile, vinyl halides such as vinyl chloride, maleic acid and salts thereof, anhydrides or esters thereof There like of unsaturated dicarboxylic acids. Such a modified unit may be introduced by copolymerization or post-reaction. However, in order to obtain the target fiber of the present invention, a polymer having a vinyl alcohol unit of 88 mol% or more is more preferably used. Of course, as long as the effects of the present invention are not impaired, additives such as antioxidants, antifreeze agents, pH adjusters, masking agents, colorants, oil agents, flame retardants and special functional agents may be included in the polymer depending on the purpose. May be included.

  In the fiber of the present invention, copper sulfide nanoparticles having an average particle diameter of 100 nm or less must be finely dispersed inside the fiber as a constituent component other than the PVA polymer. As described above, there are many large particles of 1 μm or more that can be confirmed visually or at the level of a stereoscopic microscope, even if the fibers have copper sulfide particles attached to the fiber surface or fibers in which copper sulfide particles are dispersed inside the fibers. The existing fiber is outside the range of the PVA fiber of the present invention, and the intended conductive performance is not exhibited. In addition, in this invention, the dispersion | distribution state of the copper sulfide nanoparticle in a fiber can confirm the presence form for the first time with a transmission electron microscope (TEM), as shown in FIG.

  Furthermore, in the PVA fiber of the present invention, copper sulfide fine particles of 100 nm or less are finely dispersed inside the fiber as described above, and the fiber surface has convex portions continuous in the fiber axis direction, and the fiber axis direction. It is a key point of the present invention that the continuous recesses are alternately present. Although details will be described later, by having such a concavo-convex structure on the fiber surface, excellent conductive performance is exhibited as compared with a fiber having a smooth fiber surface. In the present invention, the uneven structure on the fiber surface can be confirmed with a scanning electron microscope (SEM) as shown in FIG.

The volume specific resistance value of the PVA fiber of the present invention is preferably 1 × 10 ⁻³ to 1 × 10 ⁸ Ω · cm. When the volume resistivity value is higher than 1 × 10 ⁸ Ω · cm, it is no longer a conductive fiber and cannot be used as a semiconductor material. More preferably, it is in the range of 1 × 10 ⁻³ Ω · cm to 1 × 10 ⁷ Ω · cm. Although the specific resistance value of the PVA fiber of the present invention will be described later, it can be appropriately controlled by the fiber structure such as the amount of copper sulfide introduced and the degree of orientation.

  The conductive PVA fiber of the present invention preferably contains 1 to 50% by mass of copper sulfide fine particles, more preferably 2 to 40% by mass with respect to 100% by mass of the PVA polymer. When the content of the copper sulfide fine particles is less than 1% by mass, it is difficult to obtain desired conductive performance. On the other hand, if the content of the copper sulfide particles is too large, the mechanical properties and abrasion resistance of the fibers become insufficient. Therefore, the content of the copper sulfide fine particles is preferably 50% by mass or less. It is more preferable that the amount is not more than mass%. Further, in order to contain a large amount of copper sulfide nanoparticles, a method such as increasing the number of times of conducting treatment or increasing the residence time in the bath is required, resulting in a decrease in productivity and excessive sulfurization. It is not preferable because copper is added to increase the cost.

  The average particle diameter of such copper sulfide fine particles needs to be fine particles of 100 nm or less, preferably fine particles such as 80 nm or less, and more preferably fine particles such as 50 nm or less. By using such nano-particles, the interparticle distance in the fiber can be significantly reduced. For example, it is known that when the particle diameter becomes 1/100 in the same mass% content, the inter-particle distance is reduced to 1 / 10,000. In such a case, the interaction between the particles is very strong, and the polymer molecules sandwiched between them are known to function as if they were particles [for example, the world of nanocomposites, See page 22 (Industry Research Committee). Therefore, it is the key point of the present invention that the current can be more easily flowed by the size effect that can be achieved for the first time in the present invention, and that excellent conductive performance can be imparted even with a small amount. On the other hand, when the average particle diameter is larger than 100 nm, the conductivity improving effect becomes small for the above-mentioned reason, so that the conductive performance intended by the present invention cannot be obtained.

  In general, it is known that a PVA polymer is strongly coordinated with a metal ion such as copper via its hydroxyl group [for example, Polymer, Vol37, No. 14, 3097, (1996)]. In the present invention, paying attention to the unique behavior of this PVA polymer, an attempt was made to contain copper sulfide fine particles in the fiber. As a result of various studies, the complex block formed of PVA molecular chains and copper ions in the fiber was Since the size is several angstroms, it has been found that it can be a copper sulfide nanoparticle constituent unit. Further investigations will be carried out to increase the specific surface area of the fiber by using PVA fibers in which convex portions continuous in the fiber axis direction and concave portions continuous in the fiber axis direction are alternately present on the fiber surface. The present inventors have finally found that the same copper sulfide fine particle content is superior in electrical conductivity and superior in the mechanical properties of the fiber as compared with the case where it is dispersed throughout the fiber. In the present invention, this copper ion is contained in a PVA fiber in which convex portions continuous in the fiber axis direction and concave portions continuous in the fiber axis direction are alternately present on the fiber surface, and the hydroxyl group of the PVA polymer is included. To form a coordinate bond between PVA and copper. Although details will be described later, in order to achieve this, the PVA fiber is passed through a bath in which a compound containing copper ions is dissolved, so that the copper ions are uniformly infiltrated and coordinated inside the fiber. Can do.

  Subsequently, in the fiber surface of the PVA fiber in which convex portions continuous in the fiber axis direction and concave portions continuous in the fiber axis direction are alternately present on the fiber surface, it is coordinated with the hydroxyl group of the PVA polymer. By subjecting the copper ions to sulfuration treatment, copper sulfide nanoparticles having an average particle diameter of 100 nm or less can be formed. That is, following the copper ion impregnation treatment described above, by passing through a bath in which a compound containing sulfide ions having sulfiding ability is dissolved, the coordination between the PVA polymer and the copper ions is removed, and thereby the copper sulfide nanoparticles are removed. It can be formed inside the fiber. In addition, the process here does not need to provide an especially expensive process, but can process in a normal fiber manufacturing process.

  The compound containing copper ions used in the present invention is not particularly limited as long as it is soluble, copper acetate, copper formate, copper nitrate, copper citrate, cuprous chloride, cupric chloride, Cuprous bromide, cupric bromide, cuprous iodide, cupric iodide and the like are used. Such copper ions may be monovalent or divalent and are not particularly limited. When a compound containing monovalent copper ions is used, hydrochloric acid, potassium iodide, ammonia or the like may be used in combination for the purpose of improving the solubility. Among these, those that are easily coordinated with a PVA polymer in a solution state are more desirable, and from this viewpoint, copper nitrate, copper acetate, copper formate, and the like are preferably used as the compound containing copper ions.

  As the sulfiding agent for sulfiding copper ions coordinated in the PVA fiber, compounds capable of releasing sulfide ions are used. For example, sodium sulfide, sodium dithionate, sodium thiosulfate, sodium hydrogen sulfite, pyrosulfuric acid Sodium, hydrogen sulfide, thiourea, thioacetamide and the like can be mentioned. Among these, sodium sulfide is preferable as the compound containing sulfide ions from the viewpoint of cost, availability, and low corrosivity.

  Furthermore, in the PVA-based fiber of the present invention, in order to impart high conductivity, convex portions that are continuous in the fiber axis direction and concave portions that are continuous in the fiber axis direction are alternately present on the fiber surface, and The interval is preferably 1 μm or less. When the distance between the concave portion and the convex portion is larger than 1 μm, the effect of increasing the specific surface area of the fiber is small, and the conductive performance is hardly exhibited. Further, the fiber strength tends to be low, the wearability in the direction perpendicular to the fiber axis direction is deteriorated, and further, the variation in the conductive performance in one fiber tends to increase. Preferably, it is 1 μm or less, more preferably 0.8 μm or less, and more preferably 0.7 μm or less.

  Thus, unlike conventional conductive fibers, copper sulfide nanoparticles are dispersed inside the fiber, and the fiber surface has convex portions that are continuous in the fiber axis direction and concave portions that are continuous in the fiber axis direction. By using the PVA fiber existing in the fiber, the amount of current when energized can be increased, and a fiber excellent in conductivity, mechanical properties, and durability can be obtained. In addition, since the particle diameter is small, there is no problem even when this is stretched, and it is possible to express the draw ratio and mechanical properties equivalent to those of the PVA fiber not containing copper sulfide.

  The fineness of the fiber obtained by this invention is not specifically limited, For example, the fiber of the fineness of 0.1-10000 dtex, Preferably 1-5000 dtex can be used widely. What is necessary is just to adjust the fineness of a fiber suitably with a nozzle diameter or a draw ratio.

  Next, the manufacturing method of the PVA type fiber of this invention is demonstrated. In the present invention, by producing a fiber by a method described later using a spinning solution in which a PVA polymer is dissolved in water or an organic solvent, copper sulfide nanoparticles are finely dispersed inside the fiber, and the fiber It is possible to efficiently and inexpensively produce a fiber excellent in mechanical properties and conductivity in which convex portions continuous in the fiber axis direction and concave portions continuous in the fiber axis direction are alternately present on the surface. Examples of the solvent constituting the spinning dope include polar solvents such as water, dimethyl sulfoxide (hereinafter abbreviated as DMSO), dimethylacetamide, dimethylformamide, N-methylpyrrolidone, polyhydric alcohols such as glycerin and ethylene glycol, and the like. And a mixture of swellable metal salts such as rhodan salts, lithium chloride, calcium chloride, zinc chloride and the like, or a mixture of these solvents, or a mixture of these solvents and water. Among these, water and DMSO are particularly preferable. Most suitable in terms of process passability such as cost and recoverability.

  The polymer concentration in the spinning dope varies depending on the composition, degree of polymerization, and solvent, but is preferably in the range of 8 to 60 parts by mass. The liquid temperature at the time of discharging the spinning dope is preferably in a range in which the spinning dope is not decomposed or colored, and specifically 50 to 200 ° C. is preferable. Moreover, as long as the effect of the present invention is not impaired, the spinning dope includes a flame retardant, an antioxidant, an antifreezing agent, a pH adjuster, a concealing agent, and a colorant in addition to the PVA polymer. In addition, additives such as oil agents and special functional agents may be included. Furthermore, these may be used alone or in combination of two or more.

  Such a spinning stock solution may be discharged from a nozzle to perform wet spinning, dry wet spinning, or dry spinning, and may be discharged into a solidified liquid or a gas having a solidifying ability for a PVA polymer. Wet spinning is a method in which a spinning stock solution is discharged directly from a spinning nozzle to a solidification bath, and dry-wet spinning is a method in which spinning stock solution is once discharged into air or inert gas at an arbitrary distance from the spinning nozzle. It is a method of discharging and then introducing into the solidification bath. Dry spinning is a method of discharging a spinning solution into air or an inert gas.

  In the present invention, the solidification bath used in wet spinning or dry wet spinning differs depending on whether the stock solution is an organic solvent or water. In the case of a stock solution using an organic solvent, it is preferably a mixed solution composed of a solidification bath solvent and a stock solution solvent from the viewpoint of fiber strength and the like obtained, and the solidification solvent is not particularly limited, but for example, methanol, ethanol, An organic solvent capable of solidifying PVA-based polymers such as alcohols such as propanol and butanol, and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone can be used. Among these, a combination of methanol and DMSO is preferable in terms of low corrosivity and solvent recovery. On the other hand, when the spinning dope is an aqueous solution, an aqueous solution of inorganic salts or caustic soda having a solidifying ability with respect to PVA-based polymers such as sodium sulfate, ammonium sulfate, and sodium carbonate can be used as the solidifying solvent constituting the solidifying bath. Further, an aqueous solution to which boric acid or the like is added together with the PVA polymer can be gel-spun in an alkaline solidification bath.

  Next, in order to extract and remove the solvent of the spinning dope from the solidified yarn, it is passed through an extraction bath. It is preferable for improving the mechanical properties. The wet draw ratio at that time is preferably 1.1 to 10 times from the viewpoint of processability and productivity. As the extraction solvent, a solidified solvent alone or a mixed solution of a stock solvent and a solidified solvent can be used.

  A hot drawing or a heat treatment is applied to the dried yarns after wet drawing or the wound yarns after dry spinning. In order to develop the concavo-convex structure on the fiber surface of the present invention, it is important to balance the drawing speed and the drawing temperature in this drawing process. The stretching temperature is generally 100 ° C to 250 ° C. In particular, when stretching at a high temperature of 220 ° C or higher, it is better to stretch at a high stretching speed, for example, 30 m / min or higher. The speed is preferable, and high-speed stretching at 100 m / min or more is more preferable. Moreover, it is preferable that the draw ratio at that time is 1.5 times or more. When the temperature is less than 100 ° C. or when the draw ratio is less than 1.5 times, not only low mechanical properties can be obtained, but also the process passability in the conductive treatment process described later is deteriorated, which is not preferable. . Further, when the stretching temperature exceeds 250 ° C. or when the stretching speed is low even if it is less than 250 ° C., partial melting of the fiber surface occurs, and the fiber surface becomes smooth, which is a feature of the present invention. The uneven structure on the fiber surface cannot be expressed.

  It is not certain why PVA fibers having a concavo-convex structure on the fiber surface can be obtained by the above production method, but it is presumed that the deformation mechanism of the fiber during the drawing process has a great influence. When the drawing temperature is low or when the drawing temperature is high, even if the drawing temperature is high, sufficient heat is not given to uniformly deform the entire fiber, and compositional deformation occurs only on the fiber surface. Only the surface of the fiber is oriented and stretched in a stretched form, and an uneven structure appears. That is, it is considered that the low energy imparting stretching is a factor for developing the fiber surface uneven structure necessary for the present invention.

  In order to obtain the conductive PVA fiber intended for the present invention, the dried or drawn yarn is passed through a bath in which a compound containing copper ions is dissolved to impregnate the compound in the fiber. In this case, in order to uniformly infiltrate the compound containing copper ions into the fiber and to form a coordinate bond with the hydroxyl group of the PVA polymer, the fiber is desirably swollen by a bath solvent. The solvent used in the bath is preferably alcohols such as methanol, water, salts, or a mixture thereof. At this time, the swelling ratio of the fiber by the bath solvent is preferably 20 parts by mass or more. In order to adjust the swelling rate, it may be desirable to first immerse Yinshino in a predetermined bath and then immerse in a bath in which a compound that releases copper ions is dissolved. When the swelling rate is less than 20 parts by mass, copper ions cannot form a sufficient coordination bond with the hydroxyl group of the PVA polymer, and therefore, copper sulfide fine particles cannot be generated in the core layer. On the other hand, when the swelling rate becomes too large, elution of the PVA polymer into the bath occurs, which is not preferable in terms of process passability. From the above, the swelling rate in the bath in which the compound containing copper ions is dissolved is preferably 30 parts by mass or more and 300 parts by mass or less, and more preferably 50 parts by mass or more and 250 parts by mass or less.

  As described above, the volume resistivity value of the PVA fiber of the present invention can be appropriately controlled by the amount of copper sulfide introduced. The amount of the compound containing copper ions dissolved in the bath may be appropriately set according to the required conductivity performance, but is preferably in the range of 10 to 400 g / L. When the addition amount is less than 10 g / L, desired physical properties cannot be obtained, and when it exceeds 400 g / L, it is not preferable because it causes poor processability such as adhesion to a roller. More preferably, it is 20-300 g / L. As described above, when the yarn is passed through a bath in which copper ions are dissolved, impregnation into the fiber of the compound containing copper ions occurs when the copper ions are dissolved. Although there is no particular limitation, the residence time in the bath is 3 seconds or more for the purpose of uniformly impregnating copper ions up to the core layer in the skin-core structure and sufficiently coordinating with the PVA polymer. Preferably it is 30 seconds or more.

Next, it is necessary to pass through a bath in which a compound containing sulfide ions is dissolved for the purpose of sulfiding copper ions coordinated and bonded to the inside and the surface of the PVA fiber. In that case, the amount of the compound containing sulfide ions added to the bath may be appropriately set depending on the amount of copper ions introduced, but is preferably in the range of 1 to 100 g / L. If the amount added is less than 1 g / L, the sulfiding treatment may not proceed to the copper ions inside the fiber, which is not preferable. On the other hand, when it exceeds 100 g / L, the amount is sufficient for sulfiding copper ions contained in the PVA fiber, but it is not so preferable in terms of processability such as recovery system and odor problem.
The reaction to sulfidize the copper ions impregnated in the fiber occurs instantaneously, especially when a compound with a high sulfidation ability is used, so there is no particular limitation on the residence time in this case, but sufficient sulfidation treatment is performed even inside the fiber. For the purpose of applying, it is desirable that the residence time is 0.1 seconds or more.

  In order to increase the conductive performance of the PVA fiber, it is possible to increase the copper sulfide content in the fiber by repeatedly passing the step of impregnating the above copper ions into the fiber and the step of sulfiding the copper ions. . The copper sulfide fine particles are generated by sulfiding copper ions once coordinated to the PVA chain. At that time, the hydroxyl groups coordinated with the copper ions are recovered, and the hydroxyl groups capable of coordinating the copper ions again. Will exist. Therefore, by repeating the above treatment, copper sulfide fine particles can be effectively generated on the fiber and the conductive performance can be improved. However, there are concerns that the mechanical properties may be deteriorated and unnecessary copper sulfide particles may be deposited on the fiber surface by repeating the number of treatments. Therefore, the number of repeated treatments is preferably 6 or less. Further, the higher the degree of orientation of the fiber, that is, the higher the total draw ratio of the fiber, the higher the conductive performance, which is desirable. The reason for this is not clear at this stage, but it is considered that the higher the degree of orientation of the fibers, the more the copper sulfide fine particles are generated along the fiber axis direction, and the distance between the particles is further shortened. The orientation degree of a fiber here is an orientation degree after impregnating a copper ion. If the copper sulfide fine particles are produced in the fiber, stretching is not preferable because the distance between the copper sulfide fine particles in the fiber increases or the conductivity tends to decrease.

  On the other hand, when copper sulfide particles are charged from the stock solution in advance, the copper sulfide fine particles cannot be dispersed in the fiber, and a large amount of copper sulfide particles must be added in order to express desired physical properties. . In this case, poor dispersion in the stock solution, agglomeration, sedimentation, etc. occur, and the fiberization process and subsequent stretchability are reduced. As a result, the degree of crystallinity is low and a certain degree of conductivity can be imparted. Only fibers with low properties can be obtained. In addition, when a PVA polymer in which copper ions are coordinated in advance is used as a raw material, in addition to deterioration in processability such as increase in solution viscosity due to copper coordination and deterioration in solidification properties, The mechanical properties of the resulting fibers are low.

  The conductive PVA fiber of the present invention can be produced by applying heat treatment to the thus-obtained silkworm with copper sulfide fine particles introduced therein to improve the fiber properties. The heat treatment conditions for this are generally 100 ° C. or higher, preferably 150 ° C. to 250 ° C. When the temperature is less than 100 ° C., the effect of improving the fiber properties is insufficient. On the other hand, if the temperature exceeds 250 ° C., partial melting of the fiber surface occurs, the concavo-convex structure disappears, and the conductivity is lowered.

  The fibers of the present invention exhibit excellent conductivity in all fiber forms such as staple fibers, shortcut fibers, filament yarns, spun yarns, strings, ropes, and fabrics, and are therefore used for applications such as sensors and electromagnetic shielding materials. be able to. The cross-sectional shape of the fiber at that time is also not particularly limited, and may be circular, hollow, or an atypical cross section such as a star shape. Especially, since the PVA fiber according to the present invention is excellent in conductivity and flexibility, it can be advantageously used as a conductive fabric. For example, the PVA fiber according to the present invention is 50% by weight or more, preferably By using a fabric containing 80% by weight or more, particularly 90% by weight or more, a highly conductive PVA fiber product can be obtained. At this time, the fiber that can be used in combination is not particularly limited, and examples thereof include PVA fibers that do not contain copper sulfide fine particles, polyester fibers, polyamide fibers, and cellulose fibers.

  The fibers of the present invention are excellent in flexibility and electrical conductivity in addition to mechanical properties and heat resistance, and thus can be used as fabrics such as filaments and spun yarns, and further paper, nonwoven fabrics, woven fabrics, knitted fabrics, It can be suitably used for various applications such as industrial materials, clothing, and medical use, and is extremely useful for many applications including, for example, charging materials, neutralizing materials, brushes, sensors, electromagnetic shielding materials, and electronic materials.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this Example. In the following examples, the presence / absence of a concavo-convex structure on the fiber surface, the content of copper sulfide nanoparticles in the fiber, the presence form and particle diameter, the fiber volume resistivity, and the electromagnetic wave shielding performance of the fabric were measured by the following methods. Shows what

[The presence or absence of an uneven structure on the fiber surface and the average particle diameter of copper sulfide fine particles in the fiber nm]
The concavo-convex structure on the fiber surface and the existence form of the copper sulfide particles in the fiber were performed using an S-3000N scanning electron microscope (SEM) manufactured by Hitachi, Ltd. and an H-800NA transmission electron microscope (TEM). . Arbitrary 50 copper sulfide fine particles were selected from the photograph of the fiber cross section, their sizes were measured, and the average value was taken as the average particle diameter.

[Measurement of content of copper sulfide fine particles in fiber by mass%]
The content of copper sulfide fine particles in the fiber was measured using an ICP emission analyzer IRIS-AP manufactured by Jarrel Ash.

[Measurement of fiber conductivity (volume resistivity) Ω · cm]
The PVA fiber 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. For this fiber, a single fiber test piece having a length of 2 cm was collected, and a voltage of 10 V was applied between both ends of the test piece using a resistance measuring device “MULTITIMETER” manufactured by Yokogawa Hewlett-Packard Company. The resistance value (Ω) was measured. Then, the volume specific resistance value (ρ) (Ω · cm) = R × (S / L) is used to obtain the volume specific resistance value of each test piece, and this is performed for 25 sample pieces, and the average value is obtained as the volume of the sample. The specific resistance value was used. Here, R represents the resistance value (Ω) of the test piece, S represents the cross-sectional area (cm ² ), and L represents the length (2 cm). Here, the cross-sectional area of the test piece was calculated by observing the fiber under a microscope.

[Electromagnetic shield measurement dB]
The measurement of electromagnetic shielding characteristics was performed according to the Kansai Electronics Industry Promotion Center method (KEC method). The measurement temperature was 24 ° C., the measurement frequency was 10 to 1000 MHz, the distance between the radio wave transmission part and the reception part was 5 mm, and an average value of n = 5 was adopted. The presence or absence of the effect was judged by comparing the electromagnetic wave shielding characteristics (dB) at 100 MHz. 20 dB means that 90% of the incident electromagnetic wave is shielded, 40 dB means 99% shielding, and 60 dB means 99.9% shielding material.

[Example 1]
(1) Water containing PVA having a viscosity average polymerization degree of 1700 and a saponification degree of 99.8 mol% was added so that the PVA concentration was 50% by mass, heated to 165 ° C. through an extruder, a pore diameter of 0.1 mm, and the number of holes Dry spinning in the air through 200 nozzles. The fiber wound up by a winder at a speed of 160 m / min was drawn 1.6 times at a drawing speed of 30 m / min in a hot air drawing furnace at 200 ° C. to obtain a fiber having an uneven structure on the fiber surface. . A SEM photograph of the fiber surface is shown in FIG.
(2) The obtained fiber was introduced into a 50 ° C. water bath in which 280 g / L of copper nitrate manufactured by Wako Pure Chemical Industries, Ltd. was dissolved so that the residence time was 240 seconds. The yarn was introduced into a 25 ° C. water bath in which 50 g / L of sodium sulfide was dissolved so that the residence time was 120 seconds. This treatment was repeated twice, then washed with water and dried with hot air at 120 ° C. to obtain a fiber. The performance evaluation result of the obtained fiber is shown in Table 1, and a cross-sectional TEM photograph of the fiber is shown in FIG.
(3) The obtained fiber had a concavo-convex structure on the fiber surface as shown in FIG. 1, and the interval between the concave and convex portions was 0.7 μm. Further, as shown in FIG. 2, copper sulfide nanoparticles having an average particle diameter of 10 nm were finely dispersed inside the fiber, and the content thereof was 13.1% by mass. Further, the volume resistivity value was 2.0 × 10 ⁰ Ω · cm, which was superior in conductivity compared to conventional PVA fibers.

[Example 2]
A fiber was obtained by spinning under the same conditions as in Example 1 except that the treatment through a bath in which copper nitrate was dissolved and then the treatment through a bath in which sodium sulfide was dissolved were repeated five times. Table 1 shows the performance evaluation results of the obtained fibers. The obtained fiber had a concavo-convex structure on the fiber surface, and the interval between the concave portion and the convex portion was 0.7 μm. In addition, copper sulfide nanoparticles having an average particle diameter of 15 nm were finely dispersed inside the fiber, and the content thereof was 24.4% by mass. The volume resistivity value was 2.2 × 10 ⁻¹ Ω · cm, which was superior to the conventional PVA fiber.

[Example 3]
Spinning, drawing, and conducting treatment were performed in the same manner as in Example 1 except that the drawing temperature was 230 ° C., the drawing speed was 300 m / min, and the draw ratio was 2.0 times, to obtain fibers. Table 1 shows the performance evaluation results of the obtained fibers. The obtained fiber had a concavo-convex structure on the fiber surface, and the interval between the concave portion and the convex portion was 0.5 μm. In addition, copper sulfide nanoparticles having an average particle diameter of 20 nm were finely dispersed inside the fiber, and the content thereof was 10.1% by mass. Further, the volume resistivity value was 4.1 × 10 ⁰ Ω · cm, which was superior in conductivity compared to conventional PVA fibers.

[Example 4]
A PVA fiber obtained by dry spinning in the same manner as in Example 1 was spun to give C80 / 1, and a conductive treatment was performed in the same manner as in Example 1. The obtained fiber had a concavo-convex structure on the fiber surface, and the interval between the concave portion and the convex portion was 0.7 μm. In addition, copper sulfide nanoparticles having an average particle diameter of 10 nm were finely dispersed inside the fiber, and the content thereof was 14.3% by mass. Further, the volume resistivity value was 9.8 × 10 ⁻¹ Ω · cm, which was superior in conductivity compared to conventional PVA fibers.

[Example 5]
A fabric with a weaving width of 20 cm × 20 cm was produced from the conductive PVA fibers obtained in Example 1 at a base fabric density of 50/10 cm and a weft of 50/10 cm. The obtained fabric had an electromagnetic wave shielding performance at 100 MHz of 32 dB, and was excellent in electromagnetic wave shielding performance.

[Comparative Example 1]
A fiber was obtained by spinning under the same conditions as in Example 1 except that it did not pass through a bath in which copper nitrate was dissolved and a bath in which sodium sulfide was dissolved. The performance evaluation of the obtained fiber is shown in Table 2. Although the obtained fiber has a concavo-convex structure with a concavo-convex spacing of 0.7 μm on the fiber surface, the volume specific resistance value is 3.8 × 10 ¹² Ω · cm because there is no formation of copper sulfide nanoparticles. The conductivity was inferior.

[Comparative Example 2]
(1) PVA having a viscosity average polymerization degree of 1700 and a saponification degree of 99.8 mol% was added to DMSO so as to have a PVA concentration of 23% by mass, and was dissolved by heating at 90 ° C. in a nitrogen atmosphere. The obtained spinning solution was dry-wet-spun into a solidification bath of methanol / DMSO = 70/30 (mass ratio) at a liquid temperature of 5 ° C. through a nozzle having a hole diameter of 0.08 mm and a hole number of 108. The obtained solidified yarn is immersed in a second bath having the same methanol / DMSO composition as the solidified bath, and then subjected to wet stretching 1.6 times in a methanol bath having a liquid temperature of 25 ° C., and then dried with hot air at 120 ° C. Thus, a fiber having a smooth fiber surface was obtained. As a reference, an SEM photograph of the fiber surface is shown in FIG.
(2) The obtained fiber was introduced into a 50 ° C. water bath in which 280 g / L of copper nitrate manufactured by Wako Pure Chemical Industries, Ltd. was dissolved so that the residence time was 240 seconds. The yarn was introduced into a 25 ° C. water bath in which 50 g / L of sodium sulfide was dissolved so that the residence time was 120 seconds. This treatment was repeated twice, then washed with water and dried with hot air at 120 ° C. to obtain a fiber. Table 2 shows the performance evaluation results of the obtained fibers.
(3) Although the obtained fiber had finely dispersed copper sulfide nanoparticles having an average particle diameter of 11 nm inside the fiber, the fiber surface was smooth. Further, the volume resistivity value was 7.9 × 10 ¹ Ω · cm, which was inferior in conductivity compared to the fiber of the present invention.

[Comparative Example 3]
An aqueous solution prepared by dissolving 280 g / L of copper nitrate manufactured by Wako Pure Chemical Industries, Ltd. and an aqueous solution prepared by dissolving 50 g / L of sodium sulfide manufactured by Wako Pure Chemical Industries, Ltd. are mixed to produce copper sulfide particles having a secondary particle size of about 10 μm. Was precipitated. This was sufficiently washed with water, dried at 80 ° C., and added to the stock solution so as to be 30% by mass with respect to PVA, and spinning was performed in the same manner as in Comparative Example 1 by so-called stock solution addition. The obtained fiber had a concavo-convex structure with a concavo-convex spacing of 1.0 μm on the fiber surface, and the content of copper sulfide particles in the fiber was 28.8% by mass. The value was 2.0 × 10 ⁹ Ω · cm, and the conductivity was low. Moreover, the average particle diameter of the copper sulfide particles inside the fiber was 5 μm, and it was agglomerated in some places inside the fiber. Therefore, not only yarn spots were observed, but the fiber strength was as low as 0.2 cN / dtex. In addition, the process passability was poor, such as the pressure rising of the filter occurring in a short time.

[Comparative Example 4]
A commercially available nylon 6 fiber was introduced into a 50 ° C. water bath in which 280 g / L of copper acetate manufactured by Wako Pure Chemical Industries, Ltd. was dissolved so that the residence time was 240 seconds, and subsequently manufactured by Wako Pure Chemical Industries, Ltd. Was introduced into a 30 ° C. water bath in which 50 g / L of sodium sulfide was dissolved so that the residence time was 120 seconds. This was repeated twice, followed by drying with hot air at 120 ° C. to obtain a fiber. The performance evaluation of the obtained fiber is shown in Table 2. The obtained fiber had a copper sulfide amount of 0.45% by mass, and copper sulfide particles of about 1 μm were attached on a large lump only on the surface. Further, the volume resistivity value was 4.0 × 10 ¹⁰ Ω · cm, and the conductivity was low.

[Comparative Example 5]
A fabric having a weaving width of 20 cm × 20 cm was produced from the nylon 6 fiber obtained in Comparative Example 4 at a base fabric density of 50/10 cm and a weft of 50/10/10 cm. The obtained fabric had an electromagnetic wave shielding performance at 100 MHz of 1 dB, which was inferior to the electromagnetic wave shielding performance.

As is apparent from the results of Table 1 and FIGS. 1 and 2, the PVA fiber of the present invention has alternately convex portions continuous in the fiber axis direction and concave portions continuous in the fiber axis direction on the fiber surface. The copper sulfide fine particles having an average particle diameter of 100 nm or less are dispersed inside the fiber, and thus has excellent conductivity. Moreover, the fabric comprised from such a fiber shows the outstanding electromagnetic wave shielding performance.
On the other hand, as is apparent from the results of Table 2 and FIG. 3, when the particle size of the copper sulfide particles is large even inside the fiber, or when the particle surface is small but does not have an uneven structure on the fiber surface, Like the fiber of this invention, the fiber excellent in electroconductivity cannot be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the PVA type fiber which has the outstanding electroconductivity which was not able to be achieved by the prior art can be provided. The PVA fiber of the present invention does not require a particularly expensive process, and can be manufactured at a low cost by ordinary spinning and drawing processes. Furthermore, the PVA fiber of the present invention can be made into a fabric such as paper, non-woven fabric, woven fabric, and knitted fabric, and is used in many applications including a charging material, a charge eliminating material, a brush, a sensor, an electromagnetic wave shielding material, and an electronic material. Be expected.

The scanning electron micrograph which shows the state in which the convex part which followed the fiber axis direction and the recessed part which followed the fiber axis direction exist alternately in the PVA fiber of this invention. In the PVA fiber of the present invention, a transmission electron micrograph showing a state in which copper sulfide fine particles are dispersed inside the fiber. The scanning electron micrograph which is a PVA fiber other than this invention, and shows the state which the convex part continuous in the fiber axis direction and the recessed part continuous in the fiber axis direction do not exist.

Claims (6)

  A fiber composed of a polyvinyl alcohol-based polymer and copper sulfide nanoparticles having an average particle diameter of 100 nm or less finely dispersed in the polymer, and a convex portion continuous in the fiber axis direction on the fiber surface, and the fiber axis direction Conductive polyvinyl alcohol-based fibers characterized in that continuous recesses are alternately present.   2. The conductive polyvinyl alcohol fiber according to claim 1, wherein an interval between the convex portions and the concave portions that are alternately present in the fiber axis direction is 1 μm or less. 3. The conductive polyvinyl alcohol fiber according to claim 1, wherein the volume resistivity value is 1.0 × 10 ^{−3 to} 1.0 × 10 ⁸ Ω · cm.   4. The conductive polyvinyl alcohol fiber according to claim 1, wherein 1 to 50 mass% of copper sulfide nanoparticles are contained with respect to 100 mass% of the polyvinyl alcohol polymer.   A fiber that has been stretched at a stretching temperature of 100 to 250 ° C. at a stretching speed of 30 m / min or more and a stretching ratio of 1.5 times or more, and a convex portion that is continuous in the fiber axis direction on the fiber surface, and the fiber axis direction In the polyvinyl alcohol fiber in which concave portions continuous to each other are alternately present, a bath in which a compound containing copper ions is dissolved at a concentration of 10 to 400 g / L, and a compound containing sulfide ions is 1 to 100 g / L. Each compound is contained in the fiber through a bath dissolved at a concentration of, and copper is further sulfided to produce fine copper sulfide nanoparticles having an average particle diameter of 100 nm or less inside the fiber. The manufacturing method of the electroconductive polyvinyl alcohol-type fiber of any one of Claims 1-4. A fabric comprising the conductive polyvinyl alcohol fiber according to any one of claims 1 to 4.

Images