JP2007231482A - Polyvinyl alcohol-based fiber having both of electroconductivity and flame retardancy and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive, flame retardant polyvinyl alcohol (PVA)-based fiber having all of practically sufficient mechanical properties, excellent flame retardancy 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 same. <P>SOLUTION: The PVA (polyvinyl alcohol)-based fiber comprises a PVA (polyviny alcohol)-based polymer, a halogen-containing vinyl polymer, a tin compound, an antimony compound, and copper sulfide having an average particle diameter of ≤500 nm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having both mechanical properties sufficient for practical use and excellent conductivity and flame retardancy, a method for producing the same, and a fabric using the fiber. .

  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, 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 (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 and flame retardancy are required. Because of its lack of properties, it cannot exhibit the ability to shield electromagnetic waves, but also has no flame retardancy. In general, a metal film is formed on the surface of a fabric made of lightweight and flexible synthetic fiber by a vacuum deposition method, a sputtering method, an electroless plating method, etc., and further coated with a flame retardant, thereby providing conductivity. Fabrics having flame retardancy are known. 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 and flame retardancy imparted by these methods are very costly and limit actual use.

  As a method of imparting higher conductive performance, cupric chloride, etc. as known in polyacrylonitrile fiber, apart from the method of charging the conductive filler as shown above from the stock solution or raw material stage, etc. A technology has been widely proposed in which a copper sulfide thin layer showing conductivity is formed on the surface of the fiber itself by adsorbing the copper compound on the fiber surface and then reducing it with sulfide (for example, patents). 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 a conductive performance only with a copper sulfide plating layer having an extremely thin surface of about 100 nm, and therefore, the durability is insufficient, and a desired amount of sulfide is applied to the fiber surface. In order to deposit copper, it is necessary to treat at high temperature for a long time. Furthermore, the cyano group and mercapton group described above are excellent in monovalent copper ion scavenging ability. In other words, it was necessary to reduce the copper salt to monovalent copper ions. Naturally, it does not have flame retardancy, and in order to impart this performance, it is necessary to copolymerize a flame retardant monomer or to incorporate a flame retardant, and there are problems such as higher costs. It was. Acrylic fibers also have fundamental problems such as the generation of cyan gas when burned, and are restricted under actual use.

  So far, the present inventors have been able to obtain conductive PVA fibers having both excellent conductivity and durability by finely dispersing copper sulfide fine particles having a specific average particle diameter inside the fibers. (See, for example, Patent Document 9). However, this conductive PVA-based fiber does not have flame retardancy and is restricted in applications that require flame retardancy.

  On the other hand, flame retardant PVA fiber has no melt drip, and has high strength and excellent washing durability. Therefore, it has been attracting attention as a flame retardant fiber. It is known that a flame retardant PVA fiber composited with (abbreviated as PVX) exhibits a high degree of flame retardancy (for example, see Patent Documents 10 and 11). However, these flame retardant PVA fibers do not have electrical conductivity, and therefore, it is assumed that fibers that are extremely effective for various applications can be provided by imparting electrical conductivity thereto.

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 2005-264419 A Japanese Patent Laid-Open No. 3-126749 Japanese Patent Laid-Open No. 5-78909

  An object of the present invention is to provide a PVA fiber having excellent conductivity and flame retardancy without impairing mechanical properties such as strength and elastic modulus of a conventional PVA fiber, a method for producing the same, and the method It is providing the fabric which uses a fiber.

  As a result of intensive studies to solve the above problems, the present inventors have reduced mechanical properties by combining PVX polymer, tin compound, antimony compound, and copper sulfide fine particles with PVA polymer under specific conditions. The present inventors have found that PVA fibers having excellent conductivity and flame retardancy can be produced without any problems.

That is, the present invention is a PVA-based fiber having both conductivity and flame retardancy, characterized by comprising a PVA-based polymer, PVX, a tin compound, an antimony compound, and copper sulfide having an average particle diameter of 500 nm or less, Preferably, the above PVA system is characterized in that a halogen-containing vinyl polymer, a tin compound, an antimony compound, and copper sulfide having an average particle diameter of 500 nm or less are contained so as to satisfy the following conditions 1) to 4): Fiber.
1) The halogen-containing vinyl polymer is contained in an amount of 15 to 65% by mass with respect to the polyvinyl alcohol polymer.
2) The tin compound is contained in an amount of 2 to 10% by mass based on the whole polymer.
3) The antimony compound is contained so that the ratio of the antimony compound to the tin compound is 1/5 to 5/1.
4) Containing 1 to 50% by mass of copper sulfide with respect to the polyvinyl alcohol-based polymer.
More preferably, the volume specific resistance value is 1.0 × 10 ^{−3 to} 1.0 × 10 ⁸ Ω · cm, and the PVA fiber having both conductivity and flame retardancy, and The present invention relates to a fabric using fibers.

  Further, the present invention provides a yarn obtained by spinning and drawing a stock solution in which PVX, a tin compound, and an antimony compound are uniformly dispersed in a PVA polymer solution, and a copper-containing compound containing 10 to 400 g / L of copper. Each fiber is contained in the fiber through a bath dissolved at an ion concentration and a compound containing sulfide ions at a sulfur ion concentration of 1 to 100 g / L. Further, the present invention relates to a method for producing a PVA-based fiber having both flame retardancy and conductivity, wherein copper sulfide having an average particle size of 500 nm or less is finely produced.

  According to the present invention, it is possible to provide a PVA fiber having both high conductivity and flame retardancy in addition to mechanical properties such as strength and elastic modulus. 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 extremely useful for many applications that require particularly high conductivity and flame retardancy, 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 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.

  The fiber of the present invention needs to contain PVX as the first constituent component other than the PVA polymer. PVX as used in the present invention is a vinyl polymer having 50% or more of units containing halogen elements, that is, fluorine, chlorine, bromine and iodine. Examples of PVX include vinyl chloride polymer (PVC), vinylidene chloride polymer, vinyl bromide polymer, vinylidene bromide polymer, chlorinated polyolefin, brominated polyolefin, and the like. PVC is preferable in terms of flame retardancy, heat decomposability and cost.

  Since PVX contributes to the improvement of flame retardancy, the flame retardancy improves as the content increases. In order to impart desired flame retardancy, the content is preferably 15% by mass or more, and more preferably 30% by mass or more based on the PVA polymer. When the content of PVX exceeds 65% by mass, the mechanical properties of the fibers become insufficient. Therefore, the content of PVX is more preferably 50% by mass or less. For the purpose of improving flame retardancy, additives other than PVX, that is, known flame retardant aids such as magnesium hydroxide, aluminum hydroxide, phosphoric acid compounds and iron oxides can be added.

  Moreover, the fiber of this invention needs to contain a tin compound as 2nd structural components other than said PVA-type polymer. The tin compound to be used is not particularly limited as long as it contains tin, and specific examples thereof include tin oxide, metastannic acid, stannous chloride, and zinc stannate. Furthermore, in the present invention, these tin compounds can be used alone or in combination of two or more. Among these, tin oxide and metastannic acid are low cost, and are particularly preferable from the viewpoint of fiber forming processability, fiber flame retardancy, and combustion shrinkage suppression.

  As the content of the tin compound is increased, the flame retardancy is improved, and further, shrinkage during combustion can be suppressed. In order to obtain desired flame retardancy and combustion shrinkage suppression effects, the content of the tin compound is preferably 2 to 10% by mass with respect to the total polymer. When the content of the tin compound is less than 2% by mass, the intended effects of flame retardancy and combustion shrinkage suppression cannot be obtained. On the other hand, when the content of the tin compound exceeds 10% by mass, the mechanical properties of the fiber are impaired. Therefore, the content is more preferably in the range of 4 to 8% by mass.

  Furthermore, the fiber of the present invention needs to contain an antimony compound as a third constituent component other than the PVA polymer. The antimony compound to be used is not particularly limited as long as it contains an antimony atom. Specifically, antimony pentoxide, antimony trioxide, antimony trichloride, antimony potassium tartrate, potassium acid pyroantimonate, lead antimonate, etc. Can be mentioned. Furthermore, in the present invention, these antimony compounds can be used alone or in combination of two or more. Among these, antimony pentoxide and antimony trioxide are low in cost, and are particularly preferable from the viewpoint of fiber forming processability, fiber flame retardancy, and combustion shrinkage suppression.

  The content of the antimony compound, like the tin compound, increases the flame retardancy, and can also suppress shrinkage during combustion. In order to obtain the desired flame retardancy and combustion shrinkage suppression effect, the antimony compound is preferably contained so that the ratio of the antimony compound to the tin compound is 1/5 to 5/1. If the ratio of the tin compound increases beyond this ratio, or the ratio of the antimony compound increases, the synergistic effect on the flame retardancy of both additive drugs becomes insufficient, and the flame retardancy decreases. Problems arise. More preferably, it is in the range of 1/3 to 3/1.

  It is preferable that the LOI value which shows the flame retardance performance of the PVA-type fiber of this invention comprised with an above-described component is 28 or more. When the LOI value is less than 28, application to applications requiring flame retardancy is limited. Preferably it is 29 or more, More preferably, it is 30 or more. The LOI value is a value measured by a method described later.

  Furthermore, it is essential that the fiber of the present invention contains copper sulfide fine particles as a fourth constituent component other than the PVA polymer. Specifically, the copper sulfide fine particles having an average particle diameter of 500 nm or less are finely dispersed inside the fiber, and the content thereof needs to be 1% by mass or more. The fiber in which copper sulfide particles are attached only on the fiber surface, or the fiber in which many large particles of 1 μm or more that can be confirmed visually or by a stereoscopic microscope exist within the fiber are within the scope of the PVA fiber of the present invention. It is outside, and the intended conductive performance is not exhibited.

  In this invention, it is preferable to contain 1-50 mass% of copper sulfide fine particles with respect to a PVA type polymer, More preferably, it contains 2-40 mass%. 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%.

  The average particle diameter of such copper sulfide fine particles needs to be fine particles of 500 nm or less, preferably fine particles such as 300 nm or less, and more preferably fine particles such as 100 nm or less. Such fine particles can significantly reduce the interparticle distance in the fiber. For example, it is known that when the particle diameter becomes 1/100 in the same mass part content, the inter-particle distance decreases 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 500 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 uniformly disperse the copper sulfide fine particles inside the fiber, and the present invention was finally completed. In the present invention, this copper ion is contained inside the fiber and coordinated with the hydroxyl group of the PVA polymer to form a coordinate bond between PVA and copper. Although details will be described later, this can be achieved by allowing the PVA fibers to pass through a bath in which a compound containing copper ions is dissolved, so that the fibers are uniformly infiltrated and coordinated.

  Subsequently, copper sulfide fine particles can be formed by sulfiding copper ions coordinated with the hydroxyl groups of the PVA polymer up to the inside of the PVA fiber. That is, following the copper ion impregnation treatment described above, by passing through a bath in which a compound containing sulfide ions having a sulfurizing ability is dissolved, the coordination between the PVA polymer and the copper ions is removed, thereby removing the copper sulfide fine particles from the fiber. It can be formed inside. Also at this time, in order for the sulfidation process to proceed to the copper ions inside the fiber, it is important that the swell is still in the bath solvent, and it is desirable to perform the process continuously. 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 a copper ion 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 point of view, copper nitrate is suitably 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 fine particles are dispersed inside the fibers, and the distance between the particles is remarkably reduced, so that the amount of current when energized can be increased. A fiber having excellent properties 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 stretching ratio and mechanical properties equivalent to those of the PVA fiber not containing copper sulfide.

The volume specific resistance value of the PVA fiber of the present invention is more 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 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 1-1000 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 fiber obtained by this invention is demonstrated. The PVA fiber having both flame retardancy and conductivity according to the present invention is produced by a method described later using a spinning dope containing a PVA polymer, PVX, a tin compound, and an antimony compound. Solvents used in the spinning dope include solvents conventionally used in the production of PVA fibers, such as water, dimethyl sulfoxide (DMSO), dimethylformamide, dimethylacetamide, or glycerin, ethylene glycol, triethylene glycol, and the like. One kind or a combination of two or more kinds of monohydric alcohols, diethylenetriamine, rhodan salts and the like can be used. Among these, water and DMSO are particularly preferable from the viewpoint of supplyability and influence on environmental load. The method for preparing the stock solution is not particularly limited. A method in which PVA polymer, PVX, tin compound, and antimony compound are each dissolved or dispersed in the stock solution solvent and mixed in an appropriate ratio, in the stock solution solvent. Any of the methods of dissolving and dispersing after charging all at once can be employed. The order of addition is not particularly limited. The solid content concentration (total amount of PVA polymer, PVX, tin compound, and antimony compound) in the spinning dope varies depending on the composition, polymerization degree, and solvent of the PVA polymer, but is generally in the range of 6 to 60% by mass. It is. 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 150 ° C. is preferable. Wet spinning is a method of discharging a spinning solution directly from a spinning nozzle to a solidification bath. On the other hand, dry-wet spinning is spinning in an air or an inert gas at an arbitrary distance from a spinning nozzle. This is a method of discharging the stock solution and then introducing it into the solidification bath.Dry spinning is a method in which the spinning stock solution is discharged from the spinning nozzle into air or inert gas and dried without going through the solidification bath. It is a method of obtaining fibers.

  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. 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 crystallinity and orientation of the fiber are increased and the mechanical properties of the fiber are remarkably improved. When the temperature is less than 100 ° C., whitening of the fiber occurs, resulting in 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 flame-retardant PVA fiber of the present invention, the swollen state of the yarn after wet drawing, or the yarn after drying or drawing was dissolved in a compound containing copper ions. The compound is impregnated into the fibers by passing through a bath. In this case, it is essential that the fiber is swollen by a bath solvent in order to uniformly infiltrate the compound containing copper ions into the fiber and form a coordinate bond with the hydroxyl group of the PVA polymer. For this purpose, 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% 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 ratio is less than 20% by mass, copper ions cannot form a sufficient coordination bond with the hydroxyl group of the PVA polymer, and therefore copper sulfide nanoparticles cannot be formed inside the fiber. 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 ratio in the bath in which the compound containing copper ions is dissolved is more preferably 30% by mass or more and 300% by mass or less, and further preferably 50% by mass or more and 250% by mass or less.

  As described above, the volume specific resistance value of the PVA fiber of the present invention can be appropriately controlled by the fiber structure such as the amount of copper sulfide introduced and the degree of orientation. The amount of the compound containing copper ions dissolved in the bath may be set as appropriate according to the required electrical conductivity, but it is a bath in which the compound containing copper ions is dissolved at a copper ion concentration in the range of 10 to 400 g / L. Preferably there is. If this bath has a copper ion concentration of less than 10 g / L, the desired physical properties cannot be obtained, and if it exceeds 400 g / L, poor processability such as adhesion to a roller is caused. More preferably, it is 20-150 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, preferably 30 seconds or more for the purpose of uniformly impregnating copper ions into the fiber and ensuring sufficient coordination with the PVA polymer. It is desirable to be.

Next, for the purpose of sulfiding copper ions coordinated within the PVA fiber, it is necessary to pass through a bath in which a compound containing sulfide ions is dissolved. 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 having a high sulfidation-reducing ability is used. For the purpose of performing a reduction treatment, the residence time is desirably 0.1 seconds or longer.

  In order to increase the conductive performance of the PVA-based fiber, it is effective to increase the copper sulfide content in the fiber by repeating the above-described step of impregnating the copper ions into the fiber and the step of sulfiding the copper ions. is there. 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. Furthermore, the higher the degree of orientation of the fibers, that is, the higher the total draw ratio of the fibers, 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 the copper sulfide particles are previously prepared from the stock solution, the fine particles cannot be dispersed in the fiber, and a large amount of copper sulfide particles must be added to develop 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 subjecting the raw yarn or drawn yarn, in which the copper sulfide fine particles are introduced into the fiber, to heat treatment to improve the fiber properties. . 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 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. I can do it. 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 flame retardancy, it can be advantageously used as a fabric. For example, the PVA fiber according to the present invention is 50% by weight or more, preferably 80%. By using a fabric containing at least 90% by weight, particularly 90% by weight, a PVA fiber product exhibiting high conductivity and flame retardancy 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 fiber of the present invention is excellent in electrical conductivity and flame resistance in addition to mechanical properties and heat resistance, and therefore can be made into filaments, spun yarns, and further fabrics such as paper, nonwoven fabric, woven fabric and knitted fabric. Yes, it can be suitably used for all uses such as industrial materials, clothing, and medical use. For example, it is extremely useful for many uses including a charging material, a charge eliminating material, a brush, a sensor, an electromagnetic shielding material, and an electronic material.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the examples. In the examples, the average particle diameter, content, volume specific resistance value, critical oxygen index value (LOI value), electromagnetic wave shielding characteristics, etc. of the copper sulfide in the fiber can be obtained by the following measurement methods. .

[Average particle diameter of copper sulfide fine particles in fiber 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. 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.

[Limited oxygen index value (LOI value)]
In accordance with JIS K7201, when a sample with a test length of 18 cm made of braided fibers is made and the upper end of the sample is ignited, the burning time of the sample continues for 3 minutes or more, or combustion after ignition The minimum oxygen concentration required to continue burning over 5 cm in length was measured, and an average value of n = 3 was adopted.

[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.

[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 strength of 50% / min, and an average value of n = 5 was adopted. The fiber fineness (dtex) was determined by a mass method.

[Example 1]
(1) PVA having an average polymerization degree of 1700 and a saponification degree of 98.2% was dissolved in water so as to be 20%, and a PVC-water emulsion having a polymerization degree of 1000 (40% concentration) was added thereto. The total amount of the polymer is 5% by mass of metastannic acid as the tin compound, antimony pentoxide as the antimony compound, and the ratio of antimony pentoxide to metastannic acid is 1/1. In addition, 1% by mass of boric acid and acetic acid were further mixed to prepare a solution.
(2) This spinning stock solution was extruded through a die having a pore diameter of 0.08 mm and a pore number of 1000 into a coagulation bath at 40 ° C. containing 20 g / L sodium hydroxide and 350 g / L sodium sulfate to form a yarn. After that, the fiber was neutralized through a treatment bath containing 100 g / L sulfuric acid and 300 g / L sodium sulfate at a temperature of 35 ° C., and washed with water and dried to obtain a fiber subjected to 5 times wet drawing.
(3) The obtained fiber was introduced into a 50 ° C. hot 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 30 ° C. warm water bath in which 50 g / L of sodium sulfide manufactured by the company was dissolved so that the residence time was 120 seconds. After this conductive treatment process was repeated twice, a fiber was obtained by passing through a 25 ° C. water bath and washing with hot air at 120 ° C. for washing. The content of copper sulfide at this time was 5.0% by mass with respect to the PVA polymer, and the average particle size was 120 nm.
(4) Table 1 shows the performance evaluation results of the fibers obtained in (3) above. As shown in Table 1, the obtained fiber was excellent in both conductivity and flame retardancy.

[Example 2]
A fiber was obtained by spinning and conducting a conductive treatment under the same conditions as in Example 1 except that the amount of PVC added was 20% by mass with respect to PVA. The fiber performance evaluation results are shown in Table 1. The obtained fiber was excellent in both conductivity and flame retardancy.

[Example 3]
Fibers were 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 conductive treatment through a bath in which sodium sulfide was dissolved were repeated 10 times. Table 1 shows the performance evaluation results of the obtained fibers. The obtained fiber was excellent in both conductivity and flame retardancy as compared with the conventional PVA fiber.

[Example 4]
A fabric having a weaving width of 20 cm × 20 cm was manufactured using the PVA fiber obtained in Example 3 at a base fabric density of 50/10 cm and 50 weft / 10 cm. The performance evaluation results are shown in Table 1. The obtained fabric was superior in conductivity, electromagnetic shielding properties, and flame retardancy as compared with a fabric composed of conventional PVA fibers.

[Example 5]
A PVA fiber obtained by wet spinning in the same manner as in Example 1 was spun to give C80 / 1, with a base fabric density of 96/1 inch, weft 86/1 inch, and a weaving width of 20 cm × 20 cm. A fabric was produced. This fabric was subjected to a conductive treatment in the same manner as in Example 3. The performance evaluation results of the obtained fabric are shown in Table 1. The resulting fabric was superior in both conductivity, electromagnetic shielding properties and flame retardancy compared to a fabric composed of conventional PVA fibers.

[Comparative Example 1]
The fiber was spun by the same method as in Example 1, and the resulting fiber was subjected to a conductive treatment by the same method as in Example 1 except that the copper nitrate concentration was 8 g / L. The performance evaluation results are shown in Table 2. Although the obtained fiber was excellent in flame retardancy, the conductivity was inferior because the content of copper sulfide relative to the PVA polymer was as low as 0.4% by mass.

[Comparative Example 2]
Except not adding PVC, it spun on the same conditions as Example 1, and electrically conductive-treated, and obtained the fiber containing a tin compound, an antimony compound, and a copper sulfide fine particle as structural components other than a PVA-type polymer. Table 2 shows the performance evaluation results of the obtained fibers. The obtained fiber was excellent in electrical conductivity but inferior in flame retardancy.

[Comparative Example 3]
Except that the tin compound was not added, spinning and conducting treatment were performed in the same manner as in Example 1 to obtain a fiber containing a PVC polymer, an antimony compound, and copper sulfide fine particles as constituent components other than the PVA polymer. Table 2 shows the performance evaluation results of the obtained fibers. Although the obtained fiber was excellent in conductivity, it was inferior in flame retardancy.

[Comparative Example 4]
Except not adding an antimony compound, it spun by the same method as Example 1, and electrically conductive-treated, and obtained the fiber containing a PVC polymer, a tin compound, and a copper sulfide particle as structural components other than a PVA-type polymer. Table 2 shows the performance evaluation results of the obtained fibers. The obtained fiber was excellent in electrical conductivity but inferior in flame retardancy.

[Comparative Example 5]
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 3 μm. Was precipitated. This was thoroughly washed with water, dried at 80 ° C., added to the stock solution so as to be 30 parts by mass relative to PVA, and spun in the same manner as in Example 1. The performance evaluation of the obtained fiber is shown in Table 2. Although the obtained fiber was excellent in flame retardancy, since the average particle diameter of the copper sulfide particles was as large as 3 μm, the conductivity was inferior. In addition, the mechanical properties were low, and thread spots were observed in some places. Furthermore, in the production of fibers, the process passability is poor, such as the pressurization of the filter occurring in a short time.

[Comparative Example 6]
A commercially available flame-retardant polyester 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. Subsequently, Wako Pure Chemical Industries, Ltd. The yarn was introduced into a 30 ° C. water bath in which 50 g / L of sodium sulfide manufactured 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. Table 2 shows the performance evaluation results of the obtained fibers. The obtained fiber was inferior in both conductivity and flame retardancy.

[Comparative Example 7]
A fabric with a weaving width of 20 cm × 20 cm was produced from the flame-retardant polyester fiber obtained in Comparative Example 6 at a base fabric density of 50/10 cm and weft 50/10 cm. The performance evaluation results are shown in Table 2. The obtained fabric was inferior in electrical conductivity, electromagnetic shielding properties, and flame retardancy compared to the fabric composed of the fibers of the present invention.

As is clear from the results in Table 1, the PVA polymer of the present invention, which is shown in Examples 1 to 5, contains PVX, tin compound, antimony compound, and copper sulfide fine particles having an average particle diameter of 500 nm or less. It can be seen that the system fibers have excellent electrical conductivity and flame retardancy, and the fabric composed thereof has excellent flame retardancy and electromagnetic wave shielding performance.
On the other hand, as can be seen from Table 2, the average particle size of PVX, tin compound, antimony compound, or PVA fiber that does not satisfy any constituent of copper sulfide fine particles of 500 nm or less, or copper sulfide fine particles is larger than 500 nm. In such a case, it is impossible to combine conductivity and flame retardancy.

ADVANTAGE OF THE INVENTION According to this invention, the PVA type fiber which has the outstanding electroconductivity and flame retardance 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 conductive flame-retardant PVA fiber of the present invention can be made into a fabric such as paper, non-woven fabric, woven fabric, knitted fabric, and the like, including a charging material, a static eliminating material, a brush, a sensor, an electromagnetic shielding material, and an electronic material. As expected in many applications.

Claims (6)

  A polyvinyl alcohol fiber comprising a polyvinyl alcohol polymer, a halogen-containing vinyl polymer, a tin compound, an antimony compound, and copper sulfide having an average particle diameter of 500 nm or less. The polyvinyl chloride according to claim 1, wherein the halogen-containing vinyl polymer, tin compound, antimony compound, and copper sulfide having an average particle size of 500 nm or less are contained so as to satisfy the following conditions 1) to 4). Alcohol fiber.
1) The halogen-containing vinyl polymer is contained in an amount of 15 to 65% by mass with respect to the polyvinyl alcohol polymer.
2) The tin compound is contained in an amount of 2 to 10% by mass based on the whole polymer.
3) The antimony compound is contained so that the ratio of the antimony compound to the tin compound is 1/5 to 5/1.
4) Containing 1 to 50% by mass of copper sulfide with respect to the polyvinyl alcohol-based polymer. Volume specific resistance value is 1.0 * 10 < ^-3 > -1.0 * 10 < ⁸ > ohm * cm, The polyvinyl alcohol-type fiber of Claim 1 or 2 characterized by the above-mentioned.   The polyvinyl alcohol fiber according to any one of claims 1 to 3, wherein the LOI value is 28 or more.   The fabric formed using the polyvinyl alcohol-type fiber of any one of Claims 1-4. A stock solution in which a halogen-containing vinyl polymer, a tin compound, and an antimony compound are uniformly dispersed in a polyvinyl alcohol polymer solution is spun and drawn into a yarn, and a copper ion concentration of the compound containing copper ions is 10 to 400 g / L. Each compound is contained in the fiber through a bath in which the compound containing sulfide ions is dissolved at a sulfur ion concentration of 1 to 100 g / L, and copper is sulfided. The method for producing a polyvinyl alcohol fiber according to any one of claims 1 to 4, wherein copper sulfide having a particle diameter of 500 nm or less is finely produced.