Method for producing fine metallic particles-containing fibers

Abstract: Fine metallic particles-containing fibers, characterized by having ion-exchangeable or ion-coordinable polar groups, having crosslinked structure, and containing fine particles of metals and/or hardly-soluble metallic salts.

Description: The present invention relates to producing fine particles-containing fibers. The incorporation of fine particles of metals and/or hardly-soluble metal compounds into fibers can give the fibers various functions intrinsic to such fine particles, such as antibacterial property, antifungal property, odor-repelling property, deodorizing property, flame-retarding property, ultraviolet-preventing property, heat-retaining property, surface-improving property, designed property, refreshing property, electroconductive property, rust-preventing property, lubricative property, magnetic property, light-reflecting property, selectively light-absorbing property, heat-absorbing property, heat-conductive property, and heat-reflecting property. Therefore, the fine particles-containing fibers with such functions can be used in various fields. [Prior Art] Fibers with various functions have heretofore been proposed which contain fine metallic particles having particle sizes of not larger than micron orders or so in fiber matrices. The most popular are fine metallic particles-containing fibers to be obtained by adding and dispersing fine metallic particles themselves in a polymer followed by making the resulting polymer fibrous, such as those disclosed in Japanese Patent Application Laid-Open Nos. 1-96244, 2-16940 and 6-293611. Also known are fine metallic particles-containing fibers to be obtained by making fine inorganic particles carry fine metallic particles thereon, adding the resulting fine inorganic particles to a resin, and shaping the resulting resin, such as those disclosed in Japanese Patent Application Laid-Open Nos. 7-165519 and 7-173392. However, in such conventional, fine metallic particles-containing fibers to be obtained according to the known methods, it is difficult to uniformly disperse the fine metallic particles or the inorganic particles in the polymer since the specific gravity of the metallic particles or the inorganic particles differs from that of the polymer, since the affinity of the particles for the polymer is poor. In addition, the methods are still problematic in that, of the fine metallic particles to be added in them, finer metallic particles of not larger than sub-micron orders are difficult to prepare, that the cost of such finer particles is high, and that it is difficult to safely handle such finer particles. For these reasons, therefore, the particle sizes of fine metallic particles capable of being actually used in industrial plants are limited. Moreover, there is still another problem with the known methods in that the fibers shall frequently experience a heat history in the shaping and processing steps, in which the metals themselves in the fibers are often deteriorated. In Japanese Patent Application Laid-Open Nos. 6-287355 and 6-293611, disclosed are shaped articles such as fibers to be produced by incorporating a metallic salt or the like into a polymer matrix, then reducing the metallic salt through heat-treatment of the polymer to thereby give a resin containing ultra-fine particles as uniformly dispersed therein, and finally shaping the resin. However, this method is problematic in that (1) there is a probability that the metallic complex or metallic salt is not uniformly dispersed in the polymer matrix during the step of mixing them, (2) the cost of the metallic complex or metallic salt to be used is high, (3) the ligand of the metallic complex used or the compound having a counter ion to the metal ion of the metallic salt used becomes unnecessary after the conversion of the metallic complex or the metallic salt into fine metallic particles, and such unnecessary substances, as often dissolving out of the final product, have some negative influences on the basic physical properties and other properties of the final product, (4) since the final product shall contain a large amount of the ligand of the metallic complex used or the compound having a counter ion to the metal ion of the metallic salt used, which becomes unnecessary after the precipitation of fine metallic particles, it is impossible to increase the content of the fine metallic particles in the final product, and (5) since the matrix to be used in the conventional techniques as referred to hereinabove is a thermoplastic resin capable of being shaped and processed under heat, the final product to be obtained could not have high heat resistance. Japanese Patent Application Laid-Open No. 56-148965 discloses fine silver particles-containing fibers in which metal silver is in the surface layer of each fiber. However, this prior art technique is also problematic in that (1) since a carboxylic acid is localized in the smallest possible area in the surface layer of each fiber in order to prevent the physical properties of the fibers from being impaired the amount of the polar group capable of carrying the metal is reduced with the result that the amount of the fine metallic particles to be in the fibers is limited; and (2) since fibers that are generally obtainable in ordinary industrial plants have a thickness of about 10 µm or more and therefore have a small surface area relative to the unit weight their efficiency of expressing the functions of the fine metallic particles contained therein is low, and in addition the fine metallic particles existing in the inside of the fibers but not on their surfaces could not be utilized effectively. For these problematic reasons (1) and (2), if the functions of metals are desired to be effectively utilized or, for example, if a large amount of a metal is desired to be incorporated into fibers in order to make the fibers anti-fungal, the amount of the fine metallic particles-containing fibers themselves to be mixed with other fibers must be increased, resulting in the increase in the cost of the mixed fibers. Moreover, since the amount itself of the metal existing in the fibers is not satisfactorily large, the fibers could not often express the intended functions. In addition to these (1) and (2), the prior art technique disclosed is still further problematic in that (3) since the fine metallic particles are localized only in the surface area of each fiber, the fine metallic fibers are dropped off, when the fibers are mechanically abraded, for example, in the post-processing step, thereby resulting in significant reduction in the functions of the fibers, though such is not so much problematic if the post-processing step is conducted under relatively mild conditions, and (4) since the ion-exchanged silver ion is once precipitated in the form of a silver compound and thereafter the compound is reduced, the silver compound precipitated is often removed out of the system, resulting in the reduction in the utilization of the silver ions, and in addition, the two-step reaction is troublesome and expensive. On the other hand, with the recent diversification in the life style and with the recent increase in the density of the living environment and also the recent increase in the airtight condition in the living environment, odors have become considered problematic in the living environment and the demand for removing odors from the living environment is increasing. Some conventional deodorizing fibers are known, for example, activated charcoal-containing fibers, and also fibers with a deodorizing substance as adhered to and fixed on their surfaces or kneaded into the fibers by post-treatment, which, however, are all problematic. Precisely, since activated charcoal-containing fibers are black and, in addition, basically have low physical properties, their use is limited. The fibers with a deodorizing substance as adhered to and fixed on their surfaces by post-treatment could not basically have large deodorizing capacity. The fibers with a deodorizing substance as kneaded thereinto by post-treatment are problematic in that, if the particles of the deodorizing substance as kneaded into the fibers have large particle sizes, they greatly worsen the physical properties of the fibers. Therefore, in the deodorizing substance-kneaded fibers, the particles of the deodorizing substance are desired to have small particle sizes. In these, in addition, it is desired that the particles of the deodorizing substance have the smallest possible particle sizes also in view of the deodorizing capacity of the fibers. However, since the particles of the deodorizing substance to be kneaded into fibers are limited in reducing their particle sizes, the deodorizing substance-kneaded fibers are still problematic in that they could not sufficiently express the deodorizing effect of the substance. [Problems to be Solved by the Invention] One object of the present invention is to produce with ease at low costs fine particles-containing fibers which are free from the problems in the prior art, such as those mentioned hereinabove. Another object of the present invention is to produce deodorizing fibers which exhibit excellent deodorizing capacity for nitrogen-containing compounds such as ammonia, and also for sulfur-containing compounds such as hydrogen sulfide, and which are free from the problems in the prior art, such as those mentioned hereinabove. The present invention provides a method of producing fibres containing precipitated particles of 10 µm or less particle size which comprises : (1) forming fibres of acrylonitrile polymer; (2) crosslinking the acrylonitrile polymer fibres with hydrazine to cause an increase in the nitrogen content of the polymer of from 1.0 to 15.0% by weight; (3) introducing carboxylic groups into the crosslinked acrylonitrile polymer fibres to obtain crosslinked acrylonitrile polymer fibres having from 1 to 16 mmol/g of carboxylic groups; (4) applying metal ions to said crosslinked acrylonitrile polymer fibres having the carboxylic groups to ion-exchange or ion-coordinate said metal ions with said carboxylic groups, and then (5) either [a] reducing said exchanged or coordinated metal ions directly to precipitated metal particles in the crosslinked acrylonitrile polymer fibres or [b] adding to the crosslinked acrylonitrile polymer fibres a compound which reacts with said exchanged or coordinated metal ions to precipitate hardly soluble metal compound particles in the crosslinked acrylonitrile polymer fibres. The counter ions or ligand ions for the carboxyl groups of the polymer matrix in the present invention are not specifically defined and can be suitably selected in accordance with the use of the fibers. It is also possible to make the counter ions or ligand ions have some favorable functions. For example, if a compound having a quaternary cation group as the counter ion is employed in the present invention, it is possible to enhance the advantages of the product, for example by making the fibers additionally have an antibacterial property or by enhancing the antibacterial property of the fibers. The amount of the carboxylic groups which the crosslinked fibers shall have can be suitably determined, depending on the amount of the fine particles of metal and/or hardly-soluble metal compound to be incorporated. For the crosslinked polymer to have fibrous properties, the amount of the carboxylic groups therein is 16 mmol/g or smaller, and for the fibres to sufficiently express the effects of the fine particles of metal and/or hardly-soluble metal compound they mush contain at least 1 mmol/g of carboxylic groups. The means of introducing the carboxylic groups into the polymer is not specifically defined. Fibers of polyacrylonitrile polymers crosslinked with hydrazine are chemically and physically stable and have good fibrous properties. In addition, the fibers can have a high content of fine particles of metals and/or hardly-soluble metal compounds, and have high heat resistance, while their costs are low. The invention uses such hydrazine-crosslihked polyacrylonitrite fibers in which the increase in the nitrogen content therein caused by the hydrazine crosslinking is from 1.0 to 15.0 % by weight. The increase in the nitrogen content as referred to herein indicates the difference in the nitrogen content between the original, non-crosslinked fibers and the hydrazine-crosslinked fibers. The degree of crosslinking of the polymer matrix skeleton, which indicates the proportion of crosslinked structure in the skeleton, is not specifically defined, provided that the polymer matrix skeleton can still maintain its original shape even after the chemical reaction that induces the formation of the particles of metals and/or hardly-soluble metal compounds therein. The precipitated particles of metals and hardly-soluble metal compounds referred to herein are not specifically defined, except that the hardly-soluble metal compounds have a solubility product of 10 -5 or less. Preferred examples of such metals and hardly-soluble metal compounds are one or more metals selected from Cu, Fe, Ni, Zn, Ag, Ti, Co, Al, Cr, Pb, Sn, In, Zr, Mo, Mn, Cd, Bi, Mg, V, Ga, Ge, Se, Nb, Ru, Rh, Pd, Sb, Te, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg and Tl, and one or more hardly-soluble compounds selected from oxides, hydroxides, chlorides, bromides, iodides, carbonates, phosphates, chlorates, bromates, iodates, sulfates, sulfites, thiosulfates, thiocyanates, pyrophosphates, polyphosphates, silicates, aluminates, tungstates, vanadates, molybdates, antimonates, benzoates and dicarboxylates of such metals (e.g.of those from Cu to Mg in the above list). Use of two or more of these metals to give fine particles of alloys does not overstep the scope of the present invention. The amount of the metals and/or hardly-soluble metal compounds to be in the fibers is not specifically defined but can be determined freely. The size of the fine particles of metals and/or hardly-soluble metal compounds to be in the product fibers is 10 µm or smaller. However, where the surface characteristics of the particles are desired to be utilized, it is preferred that their size is as small as possible since finer particles can have larger surface areas; the size is then suitably of sub-micron order of 1.0 µm or smaller. Where the appearance of the particles or the volume thereof is desired to be utilized, the particles are required to have somewhat larger sizes up to 10 µm. The shape of the fine particles of metals and/or hardly-soluble metal compounds to be in the fibers is not specifically defined. The particles may have any desired shapes, selected for example from spherical, acicular, conical, rod-like, columnar, polyhedral and multiacicular shapes. The dispersion of the particles in the crosslinked polymer is not also specifically defined and can be suitably determined depending on the use of the fibers; the particles can be completely and uniformly dispersed in and carried by the entire fibers with ease, but it is also possible to make the fibers have so-called domain structure having a difference in the concentration of the particles between the surface area and the center area. The mode of such fibers does not overstep the scope of the present invention. The shape of the fibers that contain the fine particles of metals and/or hardly-soluble metal compounds is not specifically defined and can be freely determined depending on the use of the fibers. However, from the viewpoint of increasing the surface area per unit weight of the fibers to thereby enhance their ability to express their effects, while effectively utilizing the effects of the metals and/or hardly-soluble metal compounds inside the fibers, preferred are porous fibers as producing good results. Especially preferred are porous fibers having pore sizes of 1.0 µm or smaller, in which the pores are connected with one another and have openings on the surfaces of the fibers. Of such porous fibers, more preferred are those having a larger surface area and having a larger degree of porosity. In fact, use of porous fibers having a surface area of 1 m 2 /g or larger and a degree of porosity of 0.05 cm 3 /g or larger produces good results. However, porous fibers having pore sizes of larger than 1.0 µm are unfavorable, since their physical properties are poor and their surface area is reduced. The surface area, the degree of porosity and the pore size referred to herein are obtained from the cumulative pore volume (for the degree of porosity) and the cumulative surface area (for the internal surface area) measured at 138 and 1.38 MPa (20,000 and 200 psi) with a mercury porosimeter. Precisely, they are obtained by calculating the difference between the data measured at 138 MPa and those measured at 1.38 MPa. The pressure range employed herein is to measure the pore sizes falling between 0.009 µm and 0.85 µm. At a pressure falling within the range, the ratio, pore volume/pore surface area, is obtained in terms of cylindrical pores. In the method of the present invention, the step of ion-exchanging or ion-coordinating the carboxylic groups with metal ions is not specifically defined. For example, the step can be conducted by bringing a compound with a metal ion into contact with the polymer matrix having carboxylic groups. The compound with a metal ion may be any of inorganic compounds and organic compounds. In view of the ease of ion-exchange or ion-coordination, preferred are inorganic compounds as producing good results. The means of bringing the compound into contact with the polymer matrix is not also specifically defined. For example, employable is a process comprising dissolving metal ions in an organic solvent or water followed by contacting the polymer matrix with the resulting solution. The reduction in the method of the present invention is also not specifically defined, provided that it can convert metal ions into metals. For example, employable is a method, using as a reducing agent a compound capable of donating electrons to metal ions (e.g. selected from sodium borohydride, hydrazine, formalin, aldehyde group-having compounds, hydrazine sulfate, prussic acid and its salts, hyposulfurous acid and its salts, thiosulfates, hydrogen peroxide, Rochelle salt, glucose, alcohol group-having compounds, hypochlorous acid and its salts), and reducing the metal ions in a solution containing such reducing agent; reducing the metal ions through heat treatment in a reducing atmosphere comprising hydrogen, carbon monoxide, hydrogen sulfide or the like; reducing the metal ions through exposure to light; and combinations of these means. To conduct the reduction in solution, it is possible to add to the reaction system any pH regulating agent, for example basic compounds such as sodium hydroxide and ammonium hydroxide, and also inorganic acids and organic acids; buffers, for example hydroxycarboxylates such as sodium citrate and sodium lactate, boron, inorganic acids such as carbonic acid, organic acids, and alkali salts of inorganic acids; promoters such as sulfides and fluorides; stabilizers such as chlorides, sulfides and nitrides; and improvers such as surfactants; such addition does not overstep the scope of the present invention. For heat treatment in a reducing atmosphere, an inert gas such as nitrogen, argon, helium or the like may be in the atmosphere, also without overstepping the scope of the present invention. The reduction to be conducted in the method of the present invention is not specifically defined, provided that it is to reduce the metal ions that have been ion-exchanged or ion-coordinated, to thereby precipitate fine metal particles in the fibers. However, the reduction is preferably such that the metal ions are directly reduced just after having been fixed on the polar groups in the crosslinked fibers through the ion-exchange of the metal ions for the ions in the polar groups, as producing good results. Apart from this, generally known is a process (e.g. as in JP-A-81 148965) comprising first precipitating the ion-exchanged metal ions as corresponding metal compounds, and thereafter reducing the compounds to convert them into fine metal particles. However, this process is unfavorable economically, since the metal compounds are often precipitated not in the polymer matrix but out of it and since the metal compounds thus precipitated out of the polymer matrix are reduced to also give fine metal particles not in the polymer matrix but out of it. It is believed that the behavior of metal compounds and that of the fine metal particles in the polymer matrix will be caused by the change in the size of the precipitated compounds during the reaction, thereby resulting in the dropping of the compounds out of the pores of the polymer matrix. In view of these, it is especially preferred to conduct the reduction by heat treatment in the method of the present invention, which facilitates the complete incorporation of the ion-exchanged metal ions into the crosslinked fibers and which therefore produces good results. The number of times of operation for reducing the ion-exchanged or ion-coordinated metal ions to be conducted in the method of the present invention may be one; that is, the reduction may well be effected only once, if the intended or predetermined amount of fine metal particles can be incorporated into the fibers through one reduction. However, if an increased amount of fine metal particles is desired to be incorporated into the fibers, the operation for reduction can be repeated several times until the intended, increased amount of fine metal particles is incorporated into the fibers. Anyhow, the reduction can be effected in any way, depending on the object and the use of the fibers. In particular, repetition of the reduction is often preferred, to increase the content of the fine metal powders per unit weight of the polymer matrix and as producing good results. The ions or compounds capable of bonding to metallic ions to give hardly-soluble metal compounds precipitated in fibers, which are used in the method of the present invention, are not specifically defined, but include, for example, hydroxide ion, chlorine, bromine, iodine, carbonic acid, phosphoric acid, chloric acid, bromic acid, iodic acid, sulfuric acid, sulfurous acid, thiosulfuric acid, thiocyanic acid, pyrophosphoric acid, polyphosphoric acid, silicic acid, aluminic acid, tungstic acid, vanadic acid, molybdic acid, antimonic acid, benzoic acid, and dicarboxylic acids. Where metal ions are first introduced into the polar groups in the fibers through ion-exchange or ion-coordination, the resulting compounds give hardly-soluble metal compounds precipitated in the crosslinked fibers. In the method of the present invention for producing deodorizing fibers, if fine metal particles and fine particles of hardly-soluble metal compounds precipitated in the fibers have different deodorizing properties for different odor components, it is desirable to precipitate both in the fibers. For example, if the hardly-soluble metal compounds precipitated are better for absorbing nitrogen compounds while the metals precipitated are better for absorbing sulfur compounds, it is preferred to make the crosslinked fibers carry both of these so as to exhibit broader deodorizing capacity. In order to precipitate fine particles of hardly-soluble metal compounds and to partly reduce these to metals in the method of the present invention, the same means as those mentioned hereinabove for the precipitation of hardly-soluble metal compounds and for reduction to metals shall apply thereto. [Examples] The present invention is illustrated concretely by the following Examples, which, however, are not intended to restrict the scope of the present invention. In the Examples, all parts and percentages are by weight unless otherwise specifically indicated. Example 1: 10 parts of an AN polymer (having a limiting viscosity [η] in dimethylformamide at 30°C of 1.2) comprised of 90 % of AN and 10 % of methyl acrylate (hereinafter referred to as MA) was dissolved in 90 parts of an aqueous solution of 48 % sodium rhodanate to prepare a spinning solution, which was then spun and stretched (to a whole stretching magnification of 10 times) in an ordinary manner, and thereafter dried in an atmosphere at dry-bulb temperature/wet-bulb temperature = 120°C/60°C (to a degree of shrinkage of 14 %) to obtain a raw fiber sample Ia having a single fiber strength of 1.32 cN/dtex (1.5 gd). The raw fiber sample Ia was put into an aqueous solution of 10 % hydrazine, in which it was crosslinked with hydrazine at 120°C for 5 hours. The thus-obtained, crosslinked fiber sample was washed with water, dewatered, and then put into an aqueous solution of 10 % sodium hydroxide, in which it was hydrolyzed at 120°C for 5 hours. After having been washed with water, dewatered and dried, a processed fiber sample Ib was obtained. The increase in nitrogen in the sample Ib was 2.5 %, and the sample Ib had a carboxyl content of 4.2 mmol/g. The fiber sample Ib was put into an aqueous solution of 10 % silver nitrate, then subjected to ion-exchanging reaction therein at 80°C for 30 minutes, and thereafter washed, dewatered and dried to obtain a silver ion-exchanged fiber sample Ic. This was thereafter heat-treated at 180°C for 30 minutes. As a result of this process of the invention, a fine metal particles-containing fiber sample Id was obtained which contained 15 % of fine silver particles having a mean particle size of 0.02 µm. Example 2: In the same manner as in Example 1, except that the silver ion-exchanged fiber sample Ic was dipped in an aqueous solution of 10 % hydrazine and reduced at 50°C for 20 minutes, a fine metal particles-containing fiber sample IId was obtained. Example 3: An AN polymer prepared to have a composition of acrylonitrile/methyl acrylate/sodium methallylsulfonate = 95/4.7/0.3 was dissolved in an aqueous solution of 48 % sodium rhodanate to prepare a spinning stock. Next, this spinning stock was spun into an aqueous solution of 12 % sodium rhodanate at 5°C, then washed with water, and stretched by 10 times. The thus-obtained, non-dried fiber sample was wet-heated with steam at 130°C for 10 minutes, and then dried at 100°C for 20 minutes to obtain a porous raw fiber sample IIIa having a mean pore size of 0.04 µm. Next, this was processed as in Example 1 to be converted into a fine metal particles-containing fiber sample IIId. Example 4: 60 parts of DMF was mixed with 17.5 parts of glycerin in a container while stirring. Next, 22.5 parts of an acrylonitrile copolymer comprised of 93.6 % of acrylonitrile, 5.7 % of methyl acrylate and 0.7 % of sodium methallylsulfonate was added thereto, while stirring, and the stirring was continued at 80°C for 1 hour. Next, after having been filtered, the resulting liquid was dry-spun by passing it through a spinneret with 500 orifices at a spinning duct temperature of 180°C in an ordinary manner. The viscosity of the liquid having a solid content of 22.5 % and a glycerin content of 17.5 % was 85 dropping-ball seconds. Next, the tow thus obtained was stretched in boiling water at a ratio of 1:3.6, and then washed in boiling water for 3 minutes while light tension was applied thereto. Next, this was dried in a screen drum drier at an acceptable shrinkage of 10 % and at a temperature of 100°C to obtain a porous raw fiber sample IVa having a mean pore size of 0.17 µm. Next, this fiber sample was processed as in Example 1 to be converted into a fine metal particles-containing fiber sample. The characteristic data of the fiber samples produced in Examples 1 to 4, , and also the data thereof as obtained by testing them,are shown in Table 1. In Tables 1, 2, 5 and 6 below, the SI values for the fiber and knot strengths given in g/d are as follows : 0.6 g/d=0.53 cN/dtex 0.9 g/d=0.80 cN/dtex 1.0 g/d=0.88 cN/dtex 1.1 g/d=0.97 cN/dtex 1.2 g/d=1.06 cN/dtex 1.3 g/d=1.15 cN/dtex 1.4 g/d=1.24 cN/dtex 1.5 g/d=1.32 cN/dtex 1.6 g/d=1.41 cN/dtex 1.7 g/d=1.50 cN/dtex 1.8 g/d=1.59 cN/dtex 1.9 g/d=1.68 cN/dtex 2.0 g/d=1.77 cN/dtex 2.6 g/d=2.30 cN/dtex 2.8 g/d=2.47 cN/dtex 3.1 g/d=2.74 cN/dtex Example 1 Example 2 Example 3 Example 4 Polar Group Carboxyl Group Carboxyl Group Carboxyl Group Carboxyl Group Polar Group Content 4.2 mmol/g 5.1 mmol/g 4.5 mmol/g 4.8 mmol/g Pore Size 0.04 µm 0.17 µm Surface Area 55 m 2 /g 25 m 2 /g Porosity 0.2 cm 3 /g 0.66 cm 3 /g Type of Metal Ag Ag Ag Ag Means of Reduction Heat Hydrazine Heat Heat Metal Content 15.0 % 9.0 % 11.0 % 8.0 % Size of Fine Metal; Particles 0.02 µm 0.5 µm 0.01 µm 0.03 µm Fiber Strength 1.6 g/d 1.5 g/d 1.4 g/d 1.5 g/d Fiber Elongation 31 % 18 % 25 % 26 % Knot Strength 1.3 g/d 1.0 g/d 1.2 g/d 1.4 g/d Table 1 shows that the samples of Examples 1 to 4 of the present invention all have good fiber properties, fiber strength, elongation and knot strength to such degree that the spun fibers can be post-processed, and all contain extremely fine metal particles at high concentrations. The samples in Examples 3 and 4 are porous fibers containing fine metal particles therein. Examples 6 to 10: In the manner of Example 3, except that the fine metal particles to be in the fibers and the reducing agent employed were those in Table 2, fine metal particles-containing fiber samples were obtained in Examples 6 to 10 of the invention. The physical properties and the characteristics of the fiber samples are shown in Table 2. Example 6 Example 7 Example 8 Example 9 Example 10 Aqueous Solution of Metal Salt Copper Sulfate Nickel Sulfate Palladium Chloride Zinc Sulfate Stannous Chloride + Nickel Chloride Type of Metal Cu Ni Pd Zn Sn/Ni Reducing Agent Formalin Hypophosphorous Acid NaBH 4 Hypophosphorous Acid Hypophosphorous Acid Metal Content 7.0 % 3.5 % 6.3 % 2.9 % 6.6 % Size of Fine Metal Particles 0.3 µm 0.1 µm 0.4 µm 0.05 µm 0.05 µm Fiber Strength 1.9 g/d 1.8 g/d 1.5 g/d 1.9 g/d 1.8 g/d Fiber Elongation 27 % 31 % 20 % 28 % 31 % Knot Strength 1.6 g/d 1.5 g/d 1.1 g/d 1.8 g/d 1.6 g/d Table 2 shows that the pore fibers obtained in Examples 6 to 10 contain various fine metal particles, and that, like those in Table 1, they all have good fiber properties, fiber strength, elongation and knot strength to such degree that the spun fibers can be post-processed. [Comparative Example 1] The raw fiber sample Ia obtained in Example 1 was crosslinked and hydrolyzed by heating it in an aqueous solution comprising 3 % of sodium hydroxide and 0.01 % of hydrazine, at 100°C for 20 minutes, then washed with water, treated with an aqueous solution of 0.5 % acetic acid at 100°C for 20 minutes, then again washed with water, and dried. Thus was obtained a raw material fiber sample ib having carboxyl group on its surface. This sample ib was dipped in an aqueous solution of 0.5 % silver nitrate at 40°C for 10 minutes, then washed with water, and dried. Thus was obtained a silver ion-bonded acrylic fiber sample ic containing silver ions as bonded thereto. Next, this sample ic was dipped in an aqueous solution of 0.5 % sodium carbonate at 70°C for 30 minutes to thereby make silver carbonate precipitated in the fiber sample, which was then washed with water, dewatered, dried and thereafter hot-dried in a hot air drier at 130°C for 30 minutes. Thus was obtained a comparative fiber sample id having fine silver particles on its surface. The silver content of this sample id was 1.5 %. The size of the fine silver particles bonded to the surface of the sample id was 0.05 µm. The silver concentration in the acrylic fiber with silver ion bonded thereto through ion-exchange and the silver ion concentration in the finally-obtained, fine silver particles-containing fiber sample are shown in Table 3, in comparison with those in Examples 1 and 3. As in Table 3, the silver concentration in the final fiber sample of Comparative Example 1, obtained by first precipitating the metal compound in the fiber and thereafter reducing the compound,was lowered to less than half that in the intermediate fiber having ion-exchanged silver ions therein. Thus the method employed in Comparative Example 1 is unfavorable since the utilization of silver ions is poor. As opposed to this, all the silver ions incorporated into the fibers through ion-exchange were still in the final fibers in Examples 1 and 3 of the present invention. Thus the utilization of silver ions in the method of the present invention is good. Example 1 Example 3 Comparative Example 1 Ag content of Ag ion-exchanged Fiber 15.0 % 11.0 % 3.2 % Ag Content of Final Fiber 15 % 11.0 % 1.5 % Ag Content of Knitted Fabric 14.0 % 9.5 % 0.02 % The fiber samples of Examples 1 and 3 and Comparative Example 1 each were mixed-spun at a mixing ratio of 30 %, then post-processed and knitted to give knitted fabrics. The silver content of each fiber sample and that of each knitted fabric sample were measured, and the data obtained are shown in Table 3. Table 3 shows that the silver content of the knitted fabric of Comparative Example 1 was greatly lowered. This is because the fine silver particles on the surface of the fiber peeled off in the post-processing step that followed the spinning step, due to the friction of the fiber against metal parts such as guides in the apparatus used. It is obvious that not only could the effects of the metal in the fiber of Comparative Example 1 not be satisfactorily utilized, but also the fiber of Comparative Example 1 is disadvantageous from the viewpoint of its cost. On the other hand, some reduction in the silver content of the knitted fabrics in Examples 1 and 3 was found but the degree of the reduction was only small. The final silver content of the knitted fabrics in Examples 1 and 3 is thus satisfactory and these knitted fabrics are practicable. The fibers of Examples 1 and 3 and Comparative Example 1 were each sheeted into mixed paper of 130 g/m 2 . The mixed paper was comprised of vinylon (1 %), each fiber (its content is shown in Table 4) and the balance pulp. Each paper sample was tested for the reduction in cells of Klebsiella pneumoniae according to the shaking-in-flask method, and for the resistance to fungi according to the wet method of JIS Z 2911. The reduction in cells indicates the percentage of the reduction in cells relative to the control. The larger the value, the higher the antibacterial property of the sample tested. For the resistance to fungi, fungi were grown on each sample for 14 days, and the sample was evaluated according to the following three ranks: 1: Fungi grew in 1/3 or more of the surface area of the sample. 2: Fungi grew in less than 1/3 of the surface area of the sample. 3: No fungi grew. Example 1. Id Example 1, Id Example 3, IIId Comparative Example 1, id Comparative Example 1, id Proportion of Fine Metal Fiber-containing Fiber (%) 2 10 2 10 50 Reduction in Cells of Klebsiella pneumoniae 85 99.9 98.0 0.1 or less 38 Resistance to Fungi 2 3 3 1 1 Table 4 shows that both the antibacterial property and the fungi resistance of the samples of Comparative Example 1 are poor. This is because, since the fine silver particles exist only on the surface of the fiber, the silver content of the samples is low. The fungi resistance especially requires a high silver content. Therefore, the sample of Comparative Example 1, even though containing 50 % of the fine silver particles-containing fiber, still had poor fungi resistance. It may be considered that both the antibacterial property and the fungi resistance will increase if the content of the fine silver particles-containing fiber is increased, but this would result in increased product cost, and the product would lose its practicability. As opposed to the samples of Comparative Example 1, the samples of Examples 1 and 3 were found to exhibit good antibacterial property and fungi resistance, even though containing only 2 % of the fine silver particles-containing fiber. This is because the samples of Examples 1 and 3 had a higher silver content than those of Comparative Example 1 and therefore easily expressed the functions of the fine silver particles. The effects of silver are especially remarkable in the porous samples of Example 3. The sample of Example 3, even containing only 2 % of the fine silver particles-containing fiber, expressed almost completely the antibacterial property and the fungi resistance. This is because, since the porous fiber had an enlarged surface area, the amount of the fine silver particles in the fiber and capable of being contacted with external substances was greatly increased, and since the porous fiber had pores even in its inside, the amount of the fine silver particles in the fiber and capable of expressing their effects was substantially increased. Examples of deodorizing fibers of the present invention that contain fine particles of metals and/or hardly-soluble metal compounds are described below. The degree of deodorization, the size of pores in porous fibers, and the porosity of fibers were obtained according to the methods mentioned below. (1) Degree of Deodorization (%): 2 g of a dry fiber sample to be tested was conditioned at 20°C and at a relative humidity of 65 %, and put into a TEDLAR® BAG, which was then sealed and degassed. One liter of air at 20°C and at a relative humidity of 65 % was introduced into the bag, and then a gas containing odor components was injected thereinto to be 30 ppm. Then, the bag was left under the above-mentioned conditions. After 2 hours, the concentration of the odor components-containing gas in the bag was measured, using a detecting tube (A ppm). From the data, the degree of deodorization was obtained from the following equation. The test for determining the degree of deodorization was entirely carried out at atmospheric pressure (101 kPa - 1 atm). Degree of Deodorization (%) = [(30-A)/30] x 100 (2) Pore Size (µm): Using a Simadzu Micromelitex Poresizer, 9310 Model, the pore size of the pores in a fiber sample was measured. (3) Porosity (cm 3 /g): A fiber sample to be tested was dried in a vacuum drier at 80°C for 5 hours, and its dry weight (B g) was obtained. Next, the sample was dipped in pure water at 20°C for 30 minutes, and then centrifugally dewatered for 2 minutes, and its wet weight (C g) was obtained. The porosity of the sample was obtained from the following equation. Porosity (cm 3 /g) = (C-B)/B Example 1': 10 parts of an acrylonitrile polymer (having a limiting viscosity [η] in dimethylformamide at 30°C of 1.2) comprised of 90 % of acrylonitrile and 10 % of methyl acrylate (hereinafter referred to as MA) was dissolved in 90 parts of an aqueous solution of 48 % sodium rhodanate to prepare a spinning stock, which was then spun and stretched (to a whole stretching magnification of 10 times) in an ordinary manner, and thereafter dried in an atmosphere at dry-bulb temperature/wet-bulb temperature = 120°C/60°C (to a degree of shrinkage of 14 %) to obtain a raw fiber sample I'a having a single fiber diameter of 38 µm. The raw fiber sample I'a was put into an aqueous solution of 10 % hydrazine, in which it was crosslinked with hydrazine at 120°C for 3 hours. The thus-obtained, crosslinked fiber sample was washed with water, dewatered, and then put into an aqueous solution of 10 % sodium hydroxide, in which it was hydrolyzed at 100°C for 1 hour. After having been washed with water, dewatered and dried, a processed fiber sample I'b was obtained. The increase in nitrogen in the sample I'b was 1.7 %, and the sample I'b had a carboxyl content of 1.3 mmol/g. The fiber sample I'b was put into an aqueous solution of 5 % silver nitrate, then subjected to ion-exchanging reaction therein at 80°C for 30 minutes, and thereafter washed, dewatered and dried to obtain a silver ion-exchanged fiber sample I'c. This was thereafter heat-treated at 180°C for 30 minutes to obtain by the invention a fine metal particles-containing fiber sample which contained 1.6 % of fine silver particles having a mean particle size of 0.02 µm. The mean particle size of the silver particles was calculated by observing the surface and the inside of the fiber sample with a transmission electron microscope (TEM). The silver content was measured according to the atomic absorption method, after the fiber sample was wet-decomposed in a thick solution of nitric acid, sulfuric acid or perchloric acid. Example 2': The silver ion-exchanged fiber sample I'c was put into an aqueous solution of 5 % sodium hydroxide and treated therein at 50°C for 20 minutes to obtain by the invention a fiber sample II'd which contained 1.7 % of fine, hardly-soluble silver oxide particles. Example 4' : The fine, hardly-soluble metal compound particles-containing fiber sample II'd was dipped in an aqueous solution of 1 % hydrazine, and reduced therein at 30°C for 10 minutes to obtain by the present invention a fiber sample which contained 0.6 % of fine silver particles and 1.3 % of fine, hardly-soluble silver oxide particles. To quantify the silver oxide content and the silver content of this sample, silver oxide in the sample was separated by dissolving it in an aqueous ammonia. Example 5': In the manner of Example 1', except that the silver ion-exchanged fiber sample I'c was dipped in an aqueous solution of 10 % hydrazine and reduced at 50°C for 20 minutes, a fine metal particles-containing fiber sample was obtained. Example 6': An acrylonitrile polymer prepared to have a composition of acrylonitrile/methyl acrylate/sodium methallylsulfonate = 95/4.7/0.3 was dissolved in an aqueous solution of 48 % sodium rhodanate to prepare a spinning stock. Next, this spinning stock was spun into an aqueous solution of 12 % sodium rhodanate at 5°C, then washed with water, and stretched by 10 times. The thus-obtained, non-dried fiber sample was wet-heated with steam at 130°C for 10 minutes, and then dried at 100°C for 20 minutes to obtain a porous raw fiber sample VI'a having a mean pore size of 0.04 µm. Next, this was processed as in Example 1' to be converted into a fine metal particles-containing fiber sample. Example 7': 60 parts of dimethylformamide was mixed with 17.5 parts of glycerin in a container while stirring. Next, 22.5 parts of an acrylonitrile copolymer comprised of 93.6 % of acrylonitrile, 5.7 % of methyl acrylate and 0.7 % of sodium methallylsulfonate was added thereto, while stirring, and the stirring was continued at 80°C for 1 hour. Next, after having been filtered, the resulting liquid was dry-spun by passing it through a spinneret with 496 orifices in an ordinary manner. The spinning duct temperature was 180°C. The viscosity of the liquid having a solid content of 22.5 % and a glycerin content of 17.5 % was 85 dropping-ball seconds. Next, the tow thus obtained was stretched in boiling water at a ratio of 1:3.6, and then washed in boiling water for 3 minutes while light tension was applied thereto. Next, this was dried in a screen drum drier at an acceptable shrinkage of 10 % and at a temperature of 100°C to obtain a porous raw fiber sample having a mean pore size of 0.17 µm. Next, this fiber sample was processed as in Example 1' to be converted into a fine metal particles-containing fiber sample. Example 9' : In the manner of Example 1', except that a nozzle having a smaller diameter was used in the spinning to prepare a raw fiber sample having a single fiber diameter of 17 µm, a fine metal particles-containing fiber sample was obtained. Comparative Example 1': A spinning stock, to which had been added silver particles having a mean particle size of 4.6 µm, was spun as in Example 1' to obtain a comparative sample of silver particles-containing fibers. This sample contained 1.8 % of silver particles. Comparative Example 2': Spinning of a spinning stock, to which had been added the same amount as that in Comparative Example 1' of silver particles having a mean particle size of 4.6 µm, was tried as in Example 1' to obtain raw fibers, except that the same nozzle as in Example 9' was used. However, the intended fibers could not be obtained, being cut during the spinning. The fiber samples obtained in the invention Examples 1', 2', 4' to 7' and 9' and Comparative Example 1' were tested to determine their deodorizing and other characteristics, and the data obtained are shown in Table 5. The 2g samples of the invention Examples had high deodorising ability and could not be differentiated from one another by the above-mentioned method of determining the degree of deodorization. The amount of each sample was varied to 0.5 g, and the deodorization data obtained in the same manner are also shown in Table 5. The carboxyl group content of each sample was determined through potentiometry. Table 5 shows that the samples of Examples of the present invention have good deodorizing ability, with good fiber properties, fiber strength, elongation and knot strength to such degree that the fibers can be post-processed. In particular, the porous fiber samples with fine metal particles therein of Examples 6' and 7' deodorize much better than the others, since odor components can easily reach the fine metal particles inside the fibers. As opposed to these, however, the sample of Comparative Example 1' has almost no deodorizing ability,since the deodorizing particles therein are too large while having small surface areas, and therefore could not deodorize. In Comparative Example 2', no fiber was obtained, and the tests were not carried out. Examples 10' to 15': In Examples 10' to 12', fine metal particles-containing fiber samples were obtained by the invention as in Example 6', except that the fine metal particles and the reducing agent were those in Table 6. Examples 13' to 15' used raw fibre VI'a of Example 6' and obtained fine, hardly-soluble metal compound particles-containing fibre samples of the present invention as in Example 2', except that the metal salt use for ion exchange and the compound used for precipitating the hardly-soluble metal compound were those in Table 6. The deodorizing ability and other characteristics of the fiber samples obtained are shown in Table 6. Table 6 shows that the pore fiber samples of Examples 10' to 15' of the present invention all have therein fine particles of a metal or hardly-soluble metal compound and have good deodorizing ability, with good fiber properties, short fiber strength, elongation and knot strength to such degree that the fibers can be post-processed. [Advantages of the Invention] The fibers of the present invention, containing therein fine particles of metals and/or hardly-soluble metal compounds, have various functions intrinsic to such fine particles, such as antibacterial property, antifungal property, odor-repelling property, deodorizing property, flame-retarding property, ultraviolet-preventing property, heat-retaining property, surface-improving property, designed property, refreshing property, electroconductive property, rust-preventing property, lubricative property, magnetic property, light-reflecting property, selectively light-absorbing property, heat-absorbing property, heat-conductive property, and heat-reflecting property. In addition, since the fibers can be well processed and worked, they can be processed and worked to give worked products, such as paper, non-woven fabric, knitted fabric and woven fabric. Therefore, while utilizing such effects, the fibers of the present invention can be used in various fields. In particular, where the fibers contain both metals and hardly-soluble metal compounds, they can exhibit broad deodorizing ability. For example, where odor components comprising both hydrogen sulfide and ammonia are desired to be removed, and especially where it is desired to remove the acidic hydrogen sulfide odor, the fibers may be made to contain basic, hardly-soluble metal compounds, such as silver oxide, thereby exhibiting much better deodorization of hydrogen sulfide. In addition, if the fibers are made to contain both silver oxide and silver, they can deodorize even alkaline ammonia odors. The fibers of the present invention can be produced, for example, according to the methods mentioned hereinabove, which can be suitably employed depending on the chemical properties of raw fibers used and on the use of the final products to be produced. Having good processability and workability, the fibers of the present invention can be processed and worked into various types of products, such as non-woven fabric, woven fabric, knitted fabric and paper, and can also be applied to various substrates to make them have fibrous fluffy surfaces. Therefore, the fibers of the present invention can be used in various fields where deodorization is required. For example, the fibers can be used in producing water-purifying elements such as filters in drainage; elements in air-conditioning devices, such as filters in air conditioners, filters in air purifiers, air filters in clean rooms, filters in dehumidifiers, gas-treating filters in industrial use; clothing such as underwear, socks, stockings; bedding such as quilts, pillows, sheets, blankets, cushions; interior goods such as curtains, carpets, mats, wallpapers, stuffed toys, artificial flowers, artificial trees; sanitary goods such as masks, shorts for incontinence, wet tissues; car goods such as seats, upholstery; toilet goods such as toilet covers, toilet mats, toilets for pets; kitchen goods such as linings of refrigerators and trash cans; and also pads in shoes, slippers, gloves, towels, floor clothes, mops, linings of rubber gloves, linings of boots, sticking materials, garbage processors, etc. When combined or mixed with other fibers, the fibers of the present invention can be more effectively used in various fields such as those mentioned above. For example, where the fibers of the invention are used as pads in quilts or as non-woven fabrics, they can be mixed with other fibers of, for example, polyesters to be bulky. Where the fibers are mixed with other absorbing materials, such as acidic gas-absorbing materials, it is possible to obtain absorbent goods usable in much broader fields. Thus, the fibers of the present invention can be combined with other various materials, thereby making them have additional functions while reducing the proportion of the fibers in products.

Claims: A method of producing fibres containing precipitated particles of 10 µm or less particle size which comprise : (1) forming fibres of acrylonitrile polymer; (2) crosslinking the acrylonitrile polymer fibres with hydrazine to cause an increase in the nitrogen content of the polymer of from 1.0 to 15.0% by weight; (3) introducing carboxylic groups into the crosslinked acrylonitrile polymer fibres to obtain crosslinked acrylonitrile polymer fibres having from 1 to 16 mmol/g of carboxylic groups; (4) applying metal ions to said crosslinked acrylonitrile polymer fibres having the carboxylic groups to ion-exchange or ion-coordinate said metal ions with said carboxylic groups, and then (5) either [a] reducing said exchanged or coordinated metal ions directly to precipitated metal particles in the crosslinked acrylonitrile polymer fibres, or [b] adding to the crosslinked acrylonitrile polymer fibres a compound which reacts with said exchanged or coordinated metal ions to precipitate in the crosslinked acrylonitrile polymer fibres metal compound particles which have a solubility product of 10 -5 or less. A method according to claim 1 wherein said metal ions are of one or more metals selected from Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, Ga, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Mg and Al. A method according to claim 2 which employs step 5[b] and wherein said metal compound is at least one selected from oxides, hydroxides, chlorides, bromides, iodides, carbonates, phosphates, chlorates, bromates, iodates, sulfates, sulfites, thiosulfates, thiocyanates, pyrophosphates, polyphosphates, silicates, aluminates, tungstates, vanadates, molybdates, antimonates, benzoates and dicarboxylates of said metals. A method according to claim 3 wherein said metal ions are of one or more of Cu, Fe, Ni, Zn, Ag, Ti, Co, Al, Cr, Pb, Sn, In, Zr, Mo, Mn, Cd, Bi and Mg. A method according to any preceding claim which employs step 5[b] and includes reducing all or some of said precipitated metal compound particles to metal particles. A method according to any preceding claim wherein the fibres are porous fibres having pores which (a) have pore sizes of 1.0 µm or smaller, (b) are connected with one another, and (c) have openings on the surfaces of the fibres.

Inventors: NISHIDA RYOSUKE, YAMAMOTO YOKO, NISHIDA, RYOSUKE, YAMAMOTO, YOKO
Applicants: JAPAN EXLAN CO LTD, JAPAN EXLAN COMPANY, LTD.
Application year: 1996
Main classification: D06M11
IPC codes: D01F6, D06M11, D01F1