JP2007231483A - Electroconductive fiber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive fiber having practically sufficient mechanical characteristics, heat resistance and electroconductive performances in combination, formable into a fabric such as paper, a nonwoven fabric, a woven fabric or a knitted fabric and excellently usable for various applications including an electrostatic charging material, a destaticizing material, a brush, a sensor, an electromagnetic wave-shielding material and an electronic material and to provide a method for producing the electroconductive fiber. <P>SOLUTION: The fiber is composed of a polyvinyl alcohol-based polymer having ≥88 mol% degree of saponification and 1,200-15,000 degree of average polymerization and has 1-50 mass% degree of swelling of the polyvinyl alcohol-based fiber. Copper sulfide is applied to the surface and contained in the interior of the polyvinyl alcohol-based fiber. The pickup and content thereof is ≥0.5 mass% based on the polyvinyl alcohol-based component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to conductive fibers having practically sufficient mechanical properties such as strength and elastic modulus, conductivity, and durability, and a method for producing the same.

  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 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 polyvinyl alcohol (hereinafter referred to as PVA) fiber excellent in heat resistance and mechanical performance as a conductive fiber for these applications (see Patent Document 5). However, in this conductive PVA fiber, since a large amount of conductive filler of about 50 μm is added to the spinning stock solution in advance, the filler is agglomerated or settled in the stock solution, and the stability of the production process is reduced. 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, the mechanical properties such as fiber strength and elastic modulus are reduced. There were problems such as inviting. On the other hand, as conductive PVA fibers with improved processability and quality problems, reducing the average particle size of conductive fillers such as carbon black charged in the stock solution, and nonionic dispersions such as polyoxyalkylenes It has been proposed to use an agent together to prevent aggregation and sedimentation in the stock solution (see Patent Document 6). In this case, the particle diameter of the conductive filler can be reduced to about 1 μm, which is desirable from the viewpoint of imparting conductivity by increasing the surface area of the particle. Addition of 10% or more was necessary, and had problems such as aggregation in the stock solution and deterioration of 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 formed 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 technology has been widely proposed in which a copper compound such as copper is adsorbed on the fiber surface and then reduced with sulfide to form a copper sulfide thin layer showing conductivity on the surface of the fiber itself (patent) References 7 and 8). The conductive fiber obtained by these methods is one in which copper sulfide is bonded to the fiber by about 5 to 15% by mass 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 (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, the PVA fiber swells during this treatment, and even if conductivity can be imparted, the mechanical properties deteriorate, We had problems such as being unable to manufacture. 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 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. From these facts, in addition to the mechanical properties such as the original strength and elastic modulus of the PVA fiber, the development of a PVA fiber in which the fiber itself has high conductive performance and a method for producing it at low cost have been proposed. It is desired.

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

  An object of the present invention is to provide a conductive fiber having excellent conductivity and durability without impairing performance such as mechanical properties such as strength and elastic modulus, and a method for producing the same.

  As a result of intensive studies to obtain the above-described conductive fibers, the present inventors use a specific PVA-based polymer, so that no specially expensive equipment is required, and in the normal fiber manufacturing process, copper is used. Each compound is adhered and contained on the surface and inside of the fiber through a bath in which a compound containing ions is dissolved and a bath in which a compound containing sulfide ions is dissolved, and copper is sulfided to form copper sulfide. Thus, it has been found that conductive fibers having both mechanical properties and excellent conductivity can be produced at low cost.

That is, the present invention is a fiber composed of a PVA polymer having a saponification degree of 88 mol% or more and an average polymerization degree of 1200 to 15000, and the swelling degree of the PVA fiber is 1 to 50% by mass, and It is a conductive fiber characterized in that 0.5 to 50% by mass of copper sulfide is attached to, or attached to and contained in, the surface of the PVA fiber, or the surface and the inside thereof, preferably Relates to the above-mentioned conductive fiber, characterized in that the volume resistivity value is 1.0 × 10 ^{−3 to} 1.0 × 10 ⁸ Ω · cm.

  In the present invention, the PVA fiber is passed through a 20 to 80 ° C. bath in which the compound (A) containing copper ions is dissolved at a concentration of 10 to 400 g / L for 30 seconds to 10 minutes, and then the sulfide ions are added. Passing through a bath at 20 to 80 ° C. in which the compound (B) contained is dissolved at a concentration of 1 to 100 g / L for 10 seconds to 5 minutes, copper sulfide is generated on the surface of the fiber or on the surface and inside thereof. The above relates to a method for producing the conductive fiber.

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

  Hereinafter, the present invention will be specifically described. First, the PVA polymer constituting the conductive fiber of the present invention will be described. The saponification degree of the PVA polymer used in the present invention needs to be 88 mol% or more from the viewpoint of the mechanical properties of the resulting fiber. When the degree of saponification of the PVA-based 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, and is more preferably 96 mol% or more.

  The degree of polymerization of the PVA polymer used in the present invention should be one having an average degree of polymerization of 1200 to 15000 determined from the viscosity of a 30 ° C. aqueous solution in consideration of the mechanical properties and dimensional stability of the resulting fiber. The use of a polymer having a high degree of polymerization is preferred because it is excellent in terms of strength, heat and moist heat resistance, etc., but from the viewpoint of polymer production cost and fiberization cost, the average degree of polymerization is more preferably 1500 to 5000. When the average degree of polymerization is less than 1200, the strength and heat-and-moisture resistance of the obtained fiber are extremely low, which is not practical.

  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 methacrylic acid such as methyl methacrylate. Esters, acrylamide derivatives such as acrylamide and N-methylacrylamide, methacrylamide derivatives such as methacrylamide and N-methylolmethacrylamide, N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide and N-vinylacetamide, poly Allyl ethers having an alkylene oxide in the side chain, vinyl ethers such as methyl vinyl ether, nitriles such as acrylonitrile, vinyl halides such as vinyl chloride, maleic acid, salts thereof, anhydrides thereof, and esters thereof And the like unsaturated dicarboxylic acids and the like. 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, and special functional agents are included in the polymer depending on the purpose. It may be.

The fiber of the present invention is a fiber obtained from the PVA polymer, and the degree of swelling needs to be 1 to 50% by mass. This is because in the process of producing copper sulfide later, fibers with a degree of swelling of less than 1% by mass require high concentration, high temperature, and long-time treatment in order to obtain the target conductive performance, resulting in decreased productivity. And cost increases. On the other hand, in the case of fibers having a degree of swelling exceeding 50% by mass, copper sulfide can be easily produced, but it is not satisfactory in terms of the strength and heat and heat resistance of the obtained conductive fibers. Therefore, the degree of swelling is more preferably 2 to 40% by mass, and further preferably 3 to 30% by mass. In addition, the swelling degree said by this invention is measured by the method mentioned later.
Further, the average particle diameter of the produced copper sulfide is preferably 500 nm or less, and more preferably 50 nm or less. In particular, it is desirable that copper sulfide is finely dispersed inside the fiber. The adhesion amount / content of copper sulfide is required to be 0.5 to 50% by mass, and preferably 1 to 40% by mass. If the adhesion amount / content of copper sulfide is less than 0.5% by mass, the target conductive performance cannot be obtained, and problems such as large variations occur. Also, if the amount of copper sulfide deposited and contained exceeds 50% by mass, methods such as increasing the number of times of conducting treatment or increasing the residence time in the bath are required, resulting in decreased productivity and more than necessary. Including this copper sulfide causes a problem that the cost increases. In addition, the adhesion amount as used in this invention refers to the amount of copper sulfide which exists in the fiber surface, and content refers to the amount of copper sulfide which exists in a fiber inside.

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. As will be described later, the volume specific resistance value of the PVA fiber of the present invention can be appropriately controlled by the amount of copper sulfide introduced.

  In general, it is known that a PVA polymer is strongly coordinated with a metal ion such as copper via its hydroxyl group [see, for example, Polymer, Vol. 14, 3097, (1996)]. In the present invention, paying attention to the unique behavior of this PVA polymer, we tried to attach and contain copper sulfide on the fiber surface and inside, and as a result of various studies, the complex block formed of PVA molecular chains and copper ions is Therefore, it was discovered that it can be a unit composed of copper sulfide nanoparticles because its size is several angstroms. Further investigations and finding that using a specific PVA-based polymer and having a fiber with a predetermined swelling degree is superior in the mechanical properties of the fiber, and that conductive fibers having excellent electrical conductivity can be obtained. Finally, the present invention has been completed.

  Next, the compound containing copper ions used in the present invention is not particularly limited as long as it is soluble, and includes copper acetate, copper formate, copper nitrate, copper citrate, cuprous chloride, and second chloride. Copper, 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. From this viewpoint, copper acetate, copper formate, copper nitrate, 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.

  Thus, unlike conventional conductive fibers, copper sulfide particles are dispersed on the fiber surface and inside, and the distance between particles is remarkably reduced, so that the amount of current when energized can be increased, A fiber excellent in conductivity can be obtained. In addition, since the particle diameter is small, there is no problem when stretching this, and since the copper sulfide particles are uniformly dispersed only in the fiber surface layer part, it becomes possible to maintain mechanical properties in the fiber inner layer part. Moreover, the draw ratio and mechanical physical property equivalent to the PVA type fiber which does not contain copper sulfide can be expressed.

  The fineness of the conductive fiber obtained by the present invention is not particularly limited. For example, fibers having a fineness of 0.1 to 10000 dtex, preferably 1 to 1000 dtex can be widely used. 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 conductive fiber of this invention is demonstrated. In the present invention, copper sulfide particles having an average particle diameter of 500 nm or less are dispersed on the fiber surface and inside by producing fibers by a method described later using a spinning solution in which a PVA polymer is dissolved in water or an organic solvent. Thus, it is possible to efficiently and inexpensively manufacture fibers excellent in mechanical properties and conductive performance. 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, polymerization degree, and solvent, but is preferably in the range of 8 to 60% 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. Among these spinning methods, PVA fibers obtained by wet spinning are suitable for the conductive fibers of the present invention, and the obtained fibers have a skin / core structure. It is more preferable to use a fiber in which oriented crystallization is promoted. If such a fiber is used, copper ions are more coordinated to the amorphous part of the core part, copper sulfide is generated, and the incorporated copper sulfide is covered so as not to flow out to the outside at the skin part. Because.

  In the present invention, the solidification bath used in wet spinning or dry wet spinning differs depending on whether the stock solution solvent 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 mechanical properties. In that case, the wet draw ratio is preferably 2 to 10 times in terms 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.

  After wet stretching, the film is dried, and in some cases, dry heat stretching and heat treatment are performed. The stretching conditions for this are generally 100 ° C or higher, preferably 150 ° C to 260 ° C, and the total stretching ratio is 3 times or more, preferably 5 to 25 times. Is preferred because the fiber crystallinity and orientation become high and the mechanical properties of the fiber are remarkably improved. When the temperature is less than 100 ° C., whitening of the fiber occurs, which leads to a decrease in mechanical properties. On the other hand, if the temperature exceeds 260 ° C., partial melting of the fiber occurs, and in this case, mechanical properties are deteriorated, which is not preferable. In addition, the draw ratio here is the product of the wet draw in the solidification bath before drying described above and the draw ratio after drying. For example, when the wet stretching is 3 times and the subsequent dry heat stretching is 2 times, the total stretching ratio is 6 times.

  In order to obtain the conductive fiber which is the object of the present invention, the above-mentioned swollen fiber after wet drawing or the fiber after drying or drawing is passed through a bath in which a compound containing copper ions is dissolved. To the inside of the fiber. In particular, in this case, in order to uniformly infiltrate the compound containing copper ions into the inside of the fiber and form a coordinate bond with the hydroxyl group of the PVA polymer, the fiber is desirably swollen by a bath solvent, For this purpose, the solvent used in the bath is preferably alcohols such as methanol, water, salts or a mixture thereof. The swelling degree of the fiber by the bath solvent at that time is preferably 1% by mass or more. In order to adjust the degree of swelling, it may be desirable to first immerse the fibers in a predetermined bath and then immerse them in a bath in which a compound that releases copper ions is dissolved. When the degree of swelling is less than 1% by mass, it is difficult to produce copper sulfide inside the fiber. On the other hand, when the degree of swelling 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 degree of swelling in a bath in which a compound containing copper ions is dissolved is more preferably 2 to 40% by mass, and further preferably 3 to 30% by mass.

  As described above, the volume resistivity of the conductive 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 20-100 g / L. As described above, when the fibers are passed through the bath in which the copper ions are dissolved in the predetermined swelling state, impregnation of the compound containing copper ions into the fibers occurs. Although not particularly limited, it is desirable that the residence time in the bath is 30 seconds or more, preferably 60 seconds or more in order to contain copper ions even inside the fiber and make the coordination bond with the PVA polymer sufficiently. .

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 adhering to the surface of the PVA fibers or adhering to / containing the surface and inside. 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. When the addition amount is less than 1 g / L, the reduction treatment may not proceed to the copper ions inside the fiber, which is not preferable. Moreover, when it exceeds 100 g / L, although it is a quantity sufficient for carrying out the sulfidation process of the copper ion contained inside a PVA-type fiber, it is not much preferable in terms of process property, such as a recovery system and an odor problem.
The reaction to sulfidize copper ions contained in the fiber occurs instantaneously when a compound having a high sulfiding ability is used.Therefore, the residence time in this case is not particularly limited. In order to sufficiently sulfidize, the residence time is desirably 10 seconds or longer.
As for the order of passing through the bath in which the copper ions are dissolved and the bath in which the compound containing sulfide ions is dissolved, the conductive performance of the obtained conductive fiber or fabric is almost the same.

  In order to enhance the conductive performance of the conductive fiber of the present invention, the copper surface is repeatedly adhered to the fiber surface, or the step of attaching and containing the copper ion on the surface and the inside, and the step of sulfidizing the copper ion, and the fiber surface It is effective to increase the adhesion amount / content of copper sulfide adhering to or on the surface and inside of the fiber. Specifically, by repeating the above treatment at least twice or more, copper sulfide can be effectively generated on the fiber surface and inside, and the conductive performance can be enhanced. However, it is not preferable to stretch the fiber surface and the inside of which copper sulfide is generated because the distance between the copper sulfide particles increases or the conductivity tends to decrease.

  On the other hand, when copper sulfide particles are charged from the stock solution in advance, poor dispersion, aggregation, sedimentation, etc. of the copper sulfide particles in the stock solution occur, and the fiberizing process and subsequent stretchability are reduced, resulting in crystals. Even if the degree of conversion is low and a certain degree of conductivity can be imparted, only fibers with low mechanical 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 fiber of the present invention is manufactured by heat-treating the fiber surface obtained in this way, or the original yarn or copper yarn containing copper sulfide particles introduced into the fiber surface and the inside to improve the physical properties of the fiber. can do. The heat treatment conditions for this are generally 100 ° C or higher, preferably 150 ° C to 260 ° 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 260 ° C., partial melting of the fiber occurs, and in this case, mechanical properties are deteriorated, which is not preferable.

  The conductive fiber of the present invention exhibits excellent conductive performance in all fiber forms such as staple fiber, shortcut fiber, filament yarn, spun yarn, string, rope, fabric, etc. Can be used. The cross-sectional shape of the fiber at that time is not particularly limited, and may be circular, hollow, or a different cross-section such as a star shape. Especially, since the electroconductive fiber by this invention is excellent in electroconductivity and a softness | flexibility, it can be advantageously used as an electroconductive cloth. For example, a conductive fiber product exhibiting highly conductive performance can be obtained by using a fabric containing 50% by mass or more, preferably 80% by mass or more, particularly 90% by mass or more of the conductive fiber according to the present invention. . At this time, although there is no limitation in particular as a fiber which can be used together, PVA type fiber which does not contain copper sulfide particles, polyester type fiber, polyamide type fiber, cellulose type fiber, etc. can be mentioned. In addition, the PVA fiber can be made into various fiber forms such as staple fiber, shortcut fiber, filament yarn, spun yarn, string-like material, rope, fabric, etc., and then conductive treatment can be performed to achieve a high degree of conductivity. The conductive fiber product which shows can be obtained.

  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 amount, presence form and particle diameter, swelling degree, volume resistivity, electromagnetic wave shielding property, and tensile strength of the copper sulfide particles inside and on the fiber surface are those measured by the following methods. .

[Quantitative measurement by mass of copper sulfide particles on the fiber surface and inside]
The quantitative measurement of the copper sulfide particles in the fiber was performed using an ICP emission analyzer IRIS-AP manufactured by Jarrel Ash.

[Fiber surface and internal copper sulfide particles, and average particle diameter nm]
The presence form of the copper sulfide particles in the fiber was performed using an H-800NA transmission electron microscope (TEM) manufactured by Hitachi, Ltd. 100 copper sulfide particles were arbitrarily selected from the photograph of the fiber cross section, their sizes were measured, and the average value was taken as the average particle diameter.

[Swelling percentage by mass]
The fiber was cut to about 1 cm and immersed in water at 30 ° C. for 30 minutes. Thereafter, the fibers were collected by filtration, subjected to centrifugal dehydration for 10 minutes with a centrifuge at a rotation speed of 3000 rpm, and the weight (A) was measured. The dehydrated fiber was left in a dryer at 90 ° C. for 4 hours, completely dried, and the weight (B) was measured. The degree of swelling was calculated by the following formula.
Swelling degree (mass%) = {weight (A) −weight (B)} / weight (B) × 100

[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 determined 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.

[Fiber strength cN / dtex]
In accordance with JIS L1013, a yarn conditioned in advance was measured under the conditions of a test length of 20 cm, an initial load of 0.25 cN / dtex and a tensile speed of 50% / min, and an average value of n = 20 was adopted. The fiber fineness (dtex) was determined by a mass method.

[Example 1]
(1) PVA having a viscosity average polymerization degree of 1700 and a saponification degree of 99.9 mol% was added to water so as to have a PVA concentration of 15.8% by mass, and heated and dissolved in a nitrogen atmosphere at 90 ° C. The obtained spinning dope was wet-spun into a coagulation bath made of a saturated sodium sulfate aqueous solution through a nozzle having a hole diameter of 0.10 mm and a hole number of 4000.
(2) Further, the obtained fiber was wet-stretched 4 times in water and then subjected to dry heat stretching 2 times at 235 ° C. (8 times as the total stretching ratio). Thereafter, formalin 28 g / L, sulfuric acid It was formalized by being immersed in a bath of 240 g / L, sodium sulfate 130 g / L, and 75 ° C. for 30 minutes to obtain a PVA fiber. This PVA fiber was introduced into a 75 ° C. aqueous solution in which 230 g / L of copper nitrate manufactured by Wako Pure Chemical Industries, Ltd. was dissolved so that the residence time was 5 minutes, and subsequently manufactured by Wako Pure Chemical Industries, Ltd. Was introduced into a 25 ° C. water bath in which 50 g / L of sodium sulfide was dissolved so that the residence time was 2 minutes. Table 1 shows the performance evaluation results of the fibers obtained by repeating this treatment four times and then drying with hot air at 100 ° C.
(3) In the obtained fiber, the adhesion amount / content of copper sulfide particles on the surface and inside of the fiber was 7.8% by mass. As a reference, a TEM photograph is shown in FIG. The fiber physical properties were a single yarn fineness of 1.9 dtex, the strength of the fiber was 5.1 cN / dtex, and the volume resistivity was 1.4 × 10 ⁰ Ω · cm. Furthermore, the appearance of the fiber was good, there were no yarn spots and the like, and it had sufficient mechanical properties and conductivity.

[Example 2]
(1) After crimping the PVA fiber obtained in Example 1, it was cut into 44 mm and spun to obtain a C40 / 1 spun yarn. This spun yarn was subjected to conductive treatment six times by the same method as in Example 1.
(2) In the obtained spun yarn, the adhesion amount / content of copper sulfide particles on the fiber surface and inside was 9.5% by mass, the strength was 2.2 cN / dtex, and the volume resistivity was 3.1. × 10 ⁰ Ω · cm. Furthermore, the appearance of the fiber was good, there were no yarn spots and the like, and it had sufficient mechanical properties and conductivity.

[Example 3]
(1) The C40 / 1 PVA spun yarn obtained in Example 2 was used to make a plain weave fabric with a warp of 20 / cm and a weft of 15 / cm.
(2) The plain weave fabric using this PVA fiber was subjected to conductive treatment six times by the same method as in Example 1. The performance evaluation results of the obtained fabric are shown in Table 1. In the obtained fabric, the amount and the content of copper sulfide particles on the fiber surface and inside the copper sulfide particles were 9.9% by mass, and the volume resistivity value was 8.9 × 10. The electromagnetic wave shielding performance at ⁻¹ Ω · cm and 100 MHz was 31 dB.

[Comparative Example 1]
Fibers were obtained in the same manner as in Example 1 except that the bath was not passed 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 1. The fiber physical properties were a single yarn fineness of 1.7 dtex, the strength of the fiber was 5.5 cN / dtex, and the volume resistivity was 5.9 × 10 ¹² Ω · cm, which was inferior in the conductive performance.

[Comparative Example 2]
Fibers were obtained in the same manner as in Example 1 except that the bath in which copper nitrate was dissolved was passed but the bath in which sodium sulfide was dissolved was not passed. The performance evaluation of the obtained fiber is shown in Table 1. The single yarn fineness of this fiber was 1.8 dtex, the strength of the fiber was 5.2 cN / dtex, the volume resistivity was 4.8 × 10 ¹² Ω · cm, and the conductive performance was inferior.

[Comparative Example 3]
An aqueous solution prepared by dissolving 230 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 10 nm. Was precipitated. This was sufficiently washed with water and dried at 80 ° C., and then added to the stock solution so as to be 30% by mass with respect to PVA, so that fibers were obtained in the same manner as in Comparative Example 1 by so-called stock solution addition. The performance evaluation of the obtained fiber is shown in Table 1. The fiber properties were a single yarn fineness of 2.2 dtex, the fiber strength was 3.0 cN / dtex, and the content of copper sulfide particles in the obtained fiber was 29.2% by mass. It was 1.1 × 10 ¹⁰ Ω · cm, which was inferior in conductive performance. In addition, aggregation of copper sulfide particles was observed inside the fiber, the spinning processability was poor, and problems such as pressurization of the spinning filter occurred in a short time.

[Comparative Example 4]
(1) A commercially available nylon 6 fiber was introduced into a 25 ° C. water bath in which 230 g / L of copper acetate manufactured by Wako Pure Chemical Industries, Ltd. was dissolved so that the residence time was 2 minutes. Yarn was introduced into a 25 ° C. water bath in which 50 g / L of sodium sulfide manufactured by the company was dissolved so that the residence time was 2 minutes. This was repeated twice, followed by drying with hot air at 120 ° C. to obtain a fiber.
(2) The amount of copper sulfide in the obtained fiber was 0.45% by mass, and copper sulfide particles of about 1 μm were attached to the large lump only on the surface. The strength of the fiber was 3.5 cN / dtex, but the volume resistivity value was 4.0 × 10 ¹⁰ Ω · cm.

[Comparative Example 5]
The nylon 6 fiber obtained in Comparative Example 4 was made into a plain weave fabric at a warp of 20 / cm and a weft of 15 / cm. The obtained cloth had an electromagnetic wave shielding performance of 3 dB, which was inferior in the electromagnetic wave shielding performance.

  As is apparent from the results of Table 1 and FIG. 1, the conductive fiber of the present invention has copper sulfide attached and contained on the fiber surface and inside, and has excellent conductivity in addition to mechanical properties. ing. On the other hand, when the content of fine copper sulfide particles in the fiber is small, or when the copper sulfide particles are charged from the stock solution, it is impossible to combine both mechanical properties and electrical conductivity properties as in the case of the fiber of the present invention. .

  ADVANTAGE OF THE INVENTION According to this invention, the electroconductive fiber which has the mechanical characteristics which were not able to be achieved with the prior art, and the outstanding electroconductivity can be provided. Further, the conductive fiber of the present invention does not require a particularly expensive process, and can be produced at low cost by ordinary spinning and drawing processes. Furthermore, the conductive 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 static eliminating material, a brush, a sensor, an electromagnetic shielding material, and an electronic material. Be expected.

In the conductive fiber of this invention, the microscope picture which shows the state in which the copper sulfide particle has adhered and contained in the surface and the inside.

Claims (3)

  A fiber comprising a polyvinyl alcohol polymer having a saponification degree of 88 mol% or more and an average polymerization degree of 1200 to 15000, wherein the polyvinyl alcohol fiber has a swelling degree of 1 to 50% by mass, and the polyvinyl alcohol system A conductive fiber, characterized in that 0.5 to 50% by mass of copper sulfide is attached to, attached to, or contained on the surface of the fiber, or on the surface and inside thereof. 2. The conductive fiber according to claim 1, wherein the volume resistivity value is 1.0 × 10 ^{−3 to} 1.0 × 10 ⁸ Ω · cm. The polyvinyl alcohol fiber was passed through a 20 to 80 ° C. bath in which a compound (A) containing copper ions was dissolved at a concentration of 10 to 400 g / L for 30 seconds to 10 minutes, and then a compound containing sulfide ions (B ) Is passed through a bath at 20 to 80 ° C. dissolved at a concentration of 1 to 100 g / L for 10 seconds to 5 minutes to form copper sulfide on the surface of the fiber or on the surface and inside thereof. 3. A method for producing a conductive fiber according to 1 or 2.

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