JP2014034738A - Heat-resistant organic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant organic fiber that excels in both radioactive shielding properties and durability, particularly cut resistance.SOLUTION: In a heat-resistant organic fiber, the fiber contains at least one kind of inorganic particles comprising an elementary substance or a compound composed of a chemical element whose atomic number is equal to or greater than 40, and some of the inorganic particles are exposed on the surface of the fiber, with an area ratio of exposed inorganic particles on the surface of the fiber being 25-60%.

Description

  The present invention relates to a heat-resistant organic fiber having radiation shielding ability in which inorganic particles are dispersed in a heat-resistant organic fiber.

  The industrial use and importance of radiation is expanding, and with it, the work that can be exposed to radiation is increasing. For example, the radioactivity of the work environment and the materials handled varies widely, such as experiments dealing with radioisotopes, operation of X-ray generators, and processing of radioactive waste. In these operations, radiation protection products such as protective clothing or sheets are used to protect the body from radiation or to prevent leakage of radiation.

  Due to the diversification of radiation handling operations as described above, further enhancement of functionality is required for radiation protection products. For example, in order to reduce the burden on patients and workers handling radioactive materials, there is a need for radiation protection products that are lightweight and comfortable. In the event of incineration of radioactive waste and accidents / troubles at nuclear facilities, radiation protection products with excellent safety such as flame resistance and cut resistance are required to ensure the safety of workers. Generally, the higher the atomic number of an element, the better the radiation shielding ability. However, since such heavy metals are expensive and valuable, radiation protection products are required to have excellent durability from the economical viewpoint. In addition, from the viewpoint of global environmental pollution, there is a need for radiation protection products that are easy to dispose and reusable.

  Conventional radiation protection products have often used lead plates and rubber materials containing lead. However, radiation shielding protection products using these have a problem that they are inferior in workability and comfort due to limitations in thickness, shape and flexibility. In addition, lead and rubber materials have problems such as generation of lead damage and harmful gases at the time of incineration and disposal, which has been one of the causes for restricting the use of these products.

  Here, the fiber material can be easily processed into various shapes such as protective clothing such as clothes, gloves, hats, and masks, interiors such as curtains, sheets, and cloth, and industrial materials. That is, it is expected that selecting a fiber material instead of a lead plate or a rubber composition as a material for the radiation shielding / protection product will greatly expand the applicable range as compared with the lead plate or the rubber material.

  Examples of the fiber material having radiation shielding performance include a fiber material made from a radiation shielding metal. However, in order to process a radiation shielding metal into a fiber shape, advanced processing techniques are required, and the characteristics of such a fiber material are considered to depend greatly on the characteristics of the metal. Examples of fiber materials having other radiation shielding performance include fiber materials obtained by combining a synthetic fiber with a radiation shielding agent, and such fiber materials are expected to have characteristics of synthetic fiber and radiation shielding agent. . As a method for producing such a fiber material, a method of applying particles or agents having radiation shielding properties to the fiber surface, or a method of kneading the agent in the fibers can be considered. Here, the fiber such as the former has a possibility of lowering the radiation shielding ability due to the peeling of the radiation shielding metal on the surface. Therefore, in order to improve the durability of the radiation shielding ability, the fiber in which shielding particles are kneaded inside the fiber The material is considered effective. In addition, kneading a shielding agent in the fiber is expected to allow a larger amount of the agent to be supported on the fiber than to apply to the surface and to obtain a fiber material with higher shielding ability. On the other hand, the exposure of the shielding agent (generally metal compounds are often used) on the fiber surface is considered to have an effect of protecting the fiber from physical damage such as cutting and friction. It is considered effective in terms of enabling long-term use. That is, a fiber material having a radiation shielding agent in the fiber and further exposing the radiation shielding agent on the fiber surface is expected to be excellent in terms of radiation shielding ability and durability.

  As a radiation shielding property proposed so far, Patent Document 1 proposes a technique of coating a radiation shielding metal on the surface of an acrylic fiber. As a fiber material in which shielding particles are kneaded inside the fiber, Patent Document 2 proposes a core-sheath structure fiber in which a thermoplastic resin of polyester or polyamide is used as a base material and radiation shielding inorganic particles are contained in the fiber core part. ing. However, a radiation shielding fiber material having a radiation shielding agent in the fiber and further exposing the radiation shielding agent on the fiber surface has not been achieved so far.

  Furthermore, as mentioned above, while radiation shielding fibers with improved safety are strongly desired, the fibers proposed in Patent Document 1 or 2 do not sufficiently satisfy the requirements. In other words, since the fiber described in Patent Document 2 uses a thermoplastic resin as a base material, there is a limit to flame resistance and flame retardancy, and it is within the range of use in a fire site or work that handles high-temperature objects. There was a limit. In addition, when considering using radiation shielding fibers for protective clothing and industrial materials, there has not yet been proposed a product that can satisfy the creativity.

JP 63-198898 A JP 11-337682 A

  The present invention has been made against the background of such prior art, and an object of the present invention is to provide a heat-resistant organic fiber that has excellent radiation shielding properties and durability, in particular, cut resistance.

  As a result of intensive research to solve the above problems, the present inventors have formulated inorganic particles such as tungsten into fibers in an appropriately aggregated state, and the heat resistance in which the inorganic particles are exposed on the fiber surface. It has been found that organic fibers have a radiation shielding property and are excellent in cut resistance when used as a fabric, and the present invention has been completed.

  Thus, according to the present invention, in the heat-resistant organic fiber, the fiber contains at least one kind of inorganic particles composed of a simple substance or a compound having an atomic number of 40 or more, and a part of the inorganic particles is exposed on the fiber surface. Thus, a heat-resistant organic fiber is provided in which the area ratio of the exposed inorganic particles in the fiber surface is 25 to 60%.

  The heat-resistant organic fiber of the present invention is a fiber having excellent durability, particularly cut resistance, and having radiation shielding properties. For this reason, according to the fiber of this invention, the radiation shielding product in which durability is requested | required can be provided.

  Hereinafter, embodiments of the present invention will be described in detail. The heat-resistant organic fiber of the present invention (hereinafter sometimes simply referred to as “fiber”) is a fiber containing at least one kind of inorganic particles composed of a single element or a compound composed of an element having an atomic number of 40 or more.

  The heat-resistant organic fiber in the present invention is a fiber having a limiting oxygen index of 25 or more, and is a wholly aromatic polyamide fiber, aromatic polyetheramide fiber, polyparaphenylene benzobisoxazole fiber, polybenzimidazole fiber, polyimide fiber, poly Examples include ether ether ketone fibers, polyetherimide fibers, and flame retardant-containing aromatic polyester fibers. Among these, wholly aromatic polyamide fibers are preferable for making radiation shielding products from the balance of mechanical properties, flame retardancy, light resistance and the like. Here, the wholly aromatic polyamide fiber is composed of a polymer such as a wholly aromatic polyamide composed of an aromatic dicarboxylic acid component and an aromatic diamine component, or an aromatic aminocarboxylic acid component, or a wholly aromatic copolymerized polyamide. Examples of the polymer include polyparaphenylene terephthalamide, copolyparaphenylene 3,4'-oxydiphenylene terephthalamide, and polymetaphenylene isophthalamide. In particular, fibers made of copolyparaphenylene, 3,4'-oxydiphenylene terephthalamide and polymetaphenylene isophthalamide are mechanical properties such as strength and elastic modulus, cut resistance, and ease of manufacture by the manufacturing method described later. To preferred.

  Next, examples of inorganic particles made of a single element or compound composed of an element having an atomic number of 40 or more used in the present invention include barium, zirconium, niobium, silver, indium, tin, lanthanum, cerium, neodymium, tantalum, and tungsten. And elemental elements such as oxides, hydroxides, chlorides and halides thereof. In particular, barium and tungsten are preferable from the viewpoint of safety.

  In the present invention, the heat-resistant organic fiber contains at least one kind of such inorganic particles, a part of the inorganic particles are exposed on the fiber surface, and the area of the exposed inorganic particles occupied on the fiber surface It is essential that the proportion is 25-60%, preferably 25-50%, more preferably 25-40%. Thereby, the heat-resistant organic fiber can exhibit not only high radiation shielding performance as a radiation shielding protective product such as protective clothing, interior / interior, industrial materials, but also excellent durability, in particular, cut resistance.

  Therefore, when the area ratio of the exposed inorganic particles in the fiber surface is less than 25%, when the radiation shielding product is obtained, the excellent radiation shielding property and cut resistance targeted by the present invention cannot be obtained. On the other hand, even if it exceeds 60%, the above performance does not improve so much and the inorganic particles easily fall off, which is not preferable.

  Further, in the present invention, when the inorganic particles as described above are heat-resistant organic fibers having a specific amount exposed on the fiber surface, for example, in the inorganic particles, the primary particle diameter, the average equivalent particle diameter of dispersed particles, the content, etc. This can be easily realized as follows.

  The content of the inorganic particles is preferably 50 to 80% by weight, more preferably 60 to 75% by weight, based on the total weight of the fiber. The higher the inorganic particle content, the higher the radiation shielding performance, and the exposed area of the inorganic particles on the fiber surface also increases. On the other hand, if the inorganic particle content is excessively increased, the mechanical properties are lowered. . For this reason, by setting it as the said content, the ratio which occupies for the fiber surface can be made into the said range, and the mechanical physical property of a fiber can be maintained.

  In the present invention, the inorganic particles are contained in the fiber, that is, the inorganic particles are dispersed in the wholly aromatic polyamide polymer constituting the fiber. At this time, as described later, it is preferable to improve the cut resistance by appropriately agglomerating the inorganic particles, and it is preferable not to subject the inorganic particles to surface treatment. Surface treatment can be optionally performed for the purpose of controlling the dispersion state of the inorganic particles in the polymer at the stage of obtaining the fibers. For example, the inorganic particles can be treated with a surface treatment agent such as a coupling agent or a surfactant. Thus, by controlling the affinity between the inorganic particles and the coagulation liquid as described below, exposure of the inorganic particles to the fiber surface can be promoted, and the ratio of the inorganic particles to the fiber surface can be easily within the above range.

  The primary particle size of the inorganic particles is preferably 0.1 to 3 μm, more preferably 0.5 to 2 μm. Specific examples of the inorganic particles used in the present invention include W-1 kD and W-3 kD (primary particle diameters: 0.6 to 0.9 μm, 1.5 to 2.0 μm) manufactured by Nippon Shin Metals Co., Ltd. is there.

  In the present invention, in order to increase the cut resistance when the area ratio of the inorganic particles occupying the fiber surface is in the above range and the radiation shielding product is obtained, it is desirable that the inorganic particles contained in the fibers are partially aggregated. . In general, it is desirable to uniformly divide the inorganic particles, but in the present invention, it is possible to achieve both radiation resistance and cut resistance simultaneously by appropriately agglomerating the inorganic particles and exposing them to the fiber surface. It is what I found.

  Specifically, the inorganic particles having the primary particle diameter are kneaded in the fiber by the method described later, so that the average equivalent diameter of the dispersed particles of the inorganic particles is 1.0 to 1.0 by van der Waals force between the particles. Aggregation to 3.0 μm is preferred. When only dispersed particles have an average equivalent particle diameter of less than 1.0 μm, the cut resistance is undesirably lowered. When only dispersed particles have an average equivalent particle diameter of more than 3.0 μm, the mechanical properties of the fiber are low. Decreasing and not preferable.

In order to produce the fiber of the present invention, a wholly aromatic polyamide solution (which may be a polymer dope produced at the time of producing a wholly aromatic polyamide) and an inorganic particle dispersion are mixed and wet-spun, and then the solvent is added. By removing, the fiber is obtained. The average dispersed particle equivalent diameter of the inorganic particles referred to here is a 625 μm ² observation cut when the fiber is cut in a direction perpendicular to the fiber length and the fiber cross section is observed with an electron microscope at a magnification of 5000 times. When the average particle dispersion area per area is s (μm ² ), the value is obtained by the following formula (Y).

Y (μm) = 2 × √ (s / π)
In the present invention, the fiber can contain a filler other than the inorganic particles as long as the physical properties are not impaired. Examples of the filler include fibrous or plate-like, scaly, granular, indeterminate, and non-fibrous fillers such as crushed products. Specific examples include glass fibers, PAN-based and pitch-based carbon fibers. , Stainless steel fiber, metal fiber such as aluminum fiber and brass fiber, organic fiber other than heat resistant organic fiber, gypsum fiber, ceramic fiber, zirconia fiber, alumina fiber, silica fiber, titanium dioxide fiber, silicon carbide fiber, rock wool, titanium Potassium oxide whisker, barium titanate whisker, aluminum borate whisker, silicon nitride whisker, mica, layered clay mineral, talc, kaolin, silica, calcium carbonate, glass beads, glass flakes, glass microballoon, clay, molybdenum disulfide, wollastonite , Titanium dioxide, zinc oxide, poly Calcium acid, graphite, metal powder, metallic flakes, metal ribbons, metal oxides, other than the inorganic particles of the present invention, carbon powder, graphite, carbon flake, such flake carbon. Moreover, said filler can also be used in combination of 2 or more types.

  In addition, the fiber of the present invention includes various additives such as antioxidants, ultraviolet absorbers, anti-degradation agents such as light-resistant stabilizers, lubricants, antistatic agents, mold release agents, plasticizers, pigments, etc. These colorants may be used in combination. The amount of the additive used can be appropriately selected according to the type of additive as long as the original physical properties of the resulting fiber are not impaired.

  As the production method of the heat-resistant organic fiber of the present invention described above, a wholly aromatic polyamide fiber is exemplified, but the following method is preferably adopted.

  First, a mixed solution (dope) of wholly aromatic polyamide and inorganic particles is prepared. The method for adjusting the dope is not particularly limited, for example, a method of adding inorganic fine particles to a solution of wholly aromatic polyamide, a method of mixing a solution of wholly aromatic polyamide and a dispersion of inorganic particles, Examples thereof include a method in which a wholly aromatic polyamide is added to the dispersion and dissolved, and a method in which the wholly aromatic polyamide to which inorganic particles are added during polymerization is dissolved in a solvent. As the solvent used in the dispersion of the wholly aromatic polyamide solution and the inorganic particles, the above-mentioned solvents of the wholly aromatic polyamide can be used, and these solvents can be used alone or in combination of two or more. May be.

  For spinning, the wholly aromatic polyamide solution and the solvent used for dispersing the inorganic particles are preferably the same.

  In the present invention, some of the aggregated inorganic particles are exposed on the fiber surface, but by reducing the polymer concentration in the dope and reducing the viscosity, some of the aggregated inorganic particles are likely to bleed out to the outside. It becomes possible to expose the inorganic particles on the fiber surface. Therefore, it is preferable that the polymer concentration of the dope used in the production of wholly aromatic polyamide fiber is as low as possible in a spinnable range. For example, in the case of copolyparaphenylene 3,4'-oxydiphenylene terephthalamide, it is preferably 0.5 to 30% by weight, more preferably 1 to 10% by weight, and in the case of polymetaphenylene isophthalamide. Is preferably 10 to 30% by weight, more preferably 10 to 25% by weight. In each polymer, when the polymer concentration is lower than the above range, there is little entanglement of the polymer and it is difficult to obtain the viscosity necessary for spinning. On the other hand, if the polymer concentration is larger than the above range, the flow tends to become unstable when ejected from the nozzle, and it tends to be difficult to perform stable spinning. The dope may contain a small amount (for example, 10% by mass or less) of an inorganic salt such as calcium chloride or lithium chloride.

  Next, the dope obtained as described above is wet-spun. In this case, the dope may be discharged directly into the coagulation bath, or an air gap may be provided. As the coagulation liquid, a poor solvent for wholly aromatic polyamide is used. Usually, a good solvent is added to increase the coagulation rate so that the solvent for the wholly aromatic polyamide dope quickly escapes and the heat-resistant organic fiber is not defective. Adjust. In general, it is preferable to use water as the poor solvent and a solvent for the wholly aromatic polyamide dope as the good solvent. The weight ratio of good solvent / poor solvent is generally preferably 15/85 to 40/60, although it depends on the solubility and coagulability of the wholly aromatic polyamide.

  Since the fiber obtained by wet spinning is not sufficiently oriented at this stage, it is preferably oriented and crystallized. Accordingly, when either or both of the crystal orientation degree and the crystallinity degree are low, the mechanical properties of the resulting fiber are likely to be insufficient even when heat (stretching) treatment is performed. The temperature of hot stretching depends on the polymer backbone of the wholly aromatic polyamide, but is preferably 300 to 600 ° C., more preferably 350 to 550 ° C., and the draw ratio is preferably 0.7 times or more, more preferably 2 ~ 15 times.

  In the present invention, the single fiber fineness of the fiber is preferably 0.5 to 50 dtex, more preferably 1.0 to 10 dtex. If it is less than 0.5 dtex, the added inorganic particles may act as a yarn defect, and the spinning property may become unstable. Moreover, since the specific surface area of the fiber is increased, it is susceptible to light resistance degradation. On the other hand, when it exceeds 50 dtex, the specific surface area of the fiber becomes small and is not easily subjected to light resistance deterioration. On the other hand, since the specific surface area is small in the spinning process, coagulation tends to be incomplete, and as a result, the process condition tends to be disturbed in the spinning and drawing processes, and the physical properties are also likely to be lowered.

  In the present invention, the higher the strength of the fiber, the better, preferably 2.5 cN / dtex or more, more preferably 5 to 30 cN / dtex. The strength tends to decrease as the content of inorganic particles in the fiber is increased, and if it is less than 2.5 cN / dtex, the mechanical properties of the fiber as a radiation shielding product tend to decrease, which is not preferable. The elongation of the fiber is preferably 2.5% or more, more preferably 3.0 to 60%. When it is less than 2.5%, yarn breakage increases during weaving or knitting, which is not preferable.

  The heat-resistant organic fiber of the present invention thus obtained constitutes a planar body such as a textile structure such as a braid, a rope, a twisted cord, a yarn, and cotton, and a sheet in addition to a fabric such as a woven fabric, a knitted fabric, and a nonwoven fabric.

In order to prevent the transmission of radiation, it is desirable that there are few voids between fibers present in the product, or that the voids are filled with another material having radiation shielding properties. For example, in the case of a fabric, the basis weight (mass per unit area) is preferably 100 g / m ² or more, and is preferably a high-density fabric.

  The fiber of the present invention has excellent radiation shielding properties and cut resistance at the same time, protective clothing such as clothes, gloves, hats and masks, interiors such as curtains, sheets and cloth, and various radiation protection products such as industrial materials. Especially when it is used as protective clothing.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, these Examples and Comparative Examples are for helping understanding of the present invention, and the scope of the present invention is not limited by these descriptions.

In Examples and Comparative Examples, the following items were measured and evaluated by the following methods.
(1) Ratio of exposed area of inorganic particles The area ratio of exposed inorganic particles on the fiber surface (exposed area ratio of inorganic particles) was measured by the following method. When the inorganic particle area per observation area of 25 μm ² (5 μm × 5 μm) arbitrarily selected when observing the fiber side surface with an electron microscope at a magnification of 100,000 times is S (μm ² ), the following formula is calculated. (Z) was defined as the exposed area ratio (%) of the inorganic particles.
Z (%) = S / 25 × 100
(2) Fineness It measured according to JIS-L-1015.
(3) Strength and elongation of fiber Using tensile tester (Orientec Co., Ltd., trade name: Tensilon Universal Tester, model: RTC-1210A), based on the procedure of ASTM D885, measurement sample length 500 mm, chuck tension Measurement was performed under the conditions of a speed of 250 mm / min and an initial load of 0.2 cN / dtex.
(4) Lead equivalent (radiation resistance) of the fabric
It measured according to JIS-Z-4501.
(5) Fabric thickness, basis weight (mass per unit area), apparent specific gravity Measured according to JIS-L-1096. The apparent specific gravity was expressed by converting the unit to g / cm ³ . The basis weight was measured based on the mass per unit area of JIS-L-1096.
(6) Cut resistance of fabric Measured according to ISO-13997.

[Example 1]
As inorganic particles, tungsten particles (W-1 kD made by Nippon Shin Metal Co., Ltd.) having a primary particle diameter of 0.6 to 0.9 μm were used. The tungsten particles were dispersed in N-methyl-2-pyrrolidone (NMP) so as to be 28.3% by weight without performing surface treatment. This dispersion was treated with copolyparaphenylene 3,4'-oxydiphenylene terephthalamide (inherent viscosity (IV) measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid at 3 ° C.). .4) was added to an NMP solution having a concentration of 6% by weight and stirred at 60 ° C. to obtain a dope. At this time, the compounding amount of the tungsten particles with respect to the copolyparaphenylene · 3,4′-oxydiphenylene terephthalamide was set to 61% by weight. At this time, the polymer concentration in the dope was 5.3%. Further, NMP was added to lower the polymer concentration, so that the polymer concentration in the dope was 5.0%. Using the obtained dope, discharging from a spinneret with 100 holes and spinning and coagulating in an aqueous solution having an NMP concentration of 30% by weight through a void called an air gap (semi-dry semi-wet spinning method) Then, after washing and drying, the film was stretched 10 times at a temperature of 500 ° C., and then wound up to obtain heat-resistant organic fibers added with tungsten particles dispersed therein. When the fiber cross section and the side surface of the obtained heat-resistant organic fiber were observed, some of the tungsten particles inside the fiber were aggregated, and a part of the tungsten particle was exposed on the fiber surface. Next, this heat-resistant organic fiber was used for warp and weft without twisting, and a plain woven fabric having a fabric with a density of 11.4 / cm was prepared. The results are shown in Table 1.

[Example 2]
A heat-resistant organic fiber containing tungsten particles and the same method as in Example 1 except that the blending amount of tungsten particles with respect to copolyparaphenylene-3,4'-oxydiphenylene terephthalamide was 72.6% by weight, and A plain fabric was obtained. The results are shown in Table 1.

[Example 3]
Tungsten particles with a primary particle diameter of 1.5 to 2.0 μm (W-3kD, manufactured by Nippon Shin Metals Co., Ltd.) as the inorganic particles, with respect to copolyparaphenylene 3,4'-oxydiphenylene terephthalamide A heat-resistant organic fiber and a plain woven fabric containing tungsten particles were obtained in the same manner as in Example 1 except that the blending amount of the particles was 72.6% by weight. The results are shown in Table 1.

[Example 4]
Molybdenum particles having a primary particle diameter of 1.0 to 2.0 μm (trade name; Mo-3kD, manufactured by Nippon Shin Metal Co., Ltd.) are used as inorganic particles, and copolyparaphenylene 3,4′-oxydiphenylene terephthalate. A heat-resistant organic fiber and plain fabric containing molybdenum particles were obtained in the same manner as in Example 1 except that the amount of molybdenum particles to amide was 72.6% by weight. The results are shown in Table 1.

[Example 5]
A 3% aqueous solution prepared by adjusting pH of bis (triethoxysilylpropyl) tetrasulfide (trade name: KBE846, manufactured by Shin-Etsu Chemical Co., Ltd.) with acetic acid was prepared, and tungsten particles (trade name: W-1 kD, manufactured by Nippon Shin Metal Co., Ltd.) Was immersed and stirred for 1 hour, and then filtered and dried. The adhesion amount was 0.45% by weight with respect to the particle weight. A heat-resistant organic fiber having tungsten particles dispersed therein was obtained in the same manner as in Example 1 except that the tungsten particles were used. The tungsten particles are surface-treated with a sulfide having a hydrophilic functional group, so that the affinity with the polymer constituting the fiber is reduced (however, the dispersion state in the dope is within a range where sufficient spinnability can be obtained). Furthermore, the affinity with the coagulation liquid was improved, and the exposure ratio of tungsten particles to the fiber surface was improved. Further, a plain woven fabric was obtained in the same manner as in Example 1. The results are shown in Table 1.

[Example 6]
As inorganic particles, tungsten particles (W-1 kD made by Nippon Shin Metal Co., Ltd.) having a primary particle diameter of 0.6 to 0.9 μm were used. The tungsten particles were dispersed in N-methyl-2-pyrrolidone (NMP) so as to be 28.3% by weight without performing surface treatment. Further, a polymetaphenylene isophthalamide powder of IV = 1.9 produced by an interfacial polymerization method according to the method described in Japanese Patent Publication No. 47-10863 is prepared by using a N-methyl-2-pyrrolidone (NMP) concentration of 21.5. The dope was obtained by adding in a NMP solution of wt% and stirring at 60 ° C. At this time, the compounding amount of the tungsten particles with respect to polymetaphenylene isophthalamide was adjusted to be 61% by weight. At this time, the polymer concentration in the dope was 14.7%. Further, NMP was added to lower the polymer concentration, so that the polymer concentration in the dope was 14%. The obtained dope was spun from a spinneret having a hole number of 1500 holes into a coagulation bath having a bath temperature of 85 ° C. for spinning. For this coagulation bath, an aqueous solution having a composition of 40% by weight of calcium chloride, 5% by weight of NMP and 55% by weight of water was used. Next, the drawn yarn was washed with water, stretched 2.4 times with warm water at 95 ° C., dried with a roll at 200 ° C., and then stretched 1.75 times on a hot plate at 300 ° C. to contain tungsten particles. A heat resistant organic fiber was obtained. Further, a plain woven fabric was obtained in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
Copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fiber and plain fabric were obtained in the same manner as in Example 1 without adding tungsten particles. The results are shown in Table 1.

[Comparative Example 2]
Tungsten particles with a primary particle diameter of 1.5 to 2.0 μm (W-3kD, manufactured by Nippon Shin Metals Co., Ltd.) as the inorganic particles, with respect to copolyparaphenylene 3,4'-oxydiphenylene terephthalamide A heat-resistant organic fiber and a plain woven fabric containing tungsten particles were obtained in the same manner as in Example 1 except that the blending amount of the particles was 40% by weight. The results are shown in Table 1.

[Comparative Example 3]
A 3% aqueous solution prepared by adjusting the pH of N-phenyl-3-aminopropyltrimethoxysilane (trade name: KBM-573, manufactured by Shin-Etsu Silicone) with acetic acid was prepared, and tungsten particles (W-1kD, manufactured by Nippon Shinkinzoku Co., Ltd.) 1 It was allowed to soak and stir for a period of time, and then filtered and dried. The adhesion amount was 0.5% by weight with respect to the particle weight. A heat-resistant organic fiber having tungsten particles dispersed therein was obtained in the same manner as in Example 1 except that the tungsten particles were used. The tungsten particles are surface-treated with a silane having an aromatic ring, so that the affinity with the polymer constituting the fiber is improved and the affinity with the coagulating liquid is reduced, and the tungsten particles are exposed to the fiber surface. The rate was reduced. Further, a plain woven fabric was obtained in the same manner as in Example 1. The results are shown in Table 1.

  The heat-resistant organic fiber of the present invention has excellent radiation shielding properties and cut resistance at the same time, and various radiations such as protective clothing such as clothes, gloves, hats and masks, interiors such as curtains, sheets and cloths, and industrial materials. It can be used as a protective product, and is particularly useful as a material for protective clothing.

Claims (6)

  In the heat-resistant organic fiber, the fiber contains at least one kind of inorganic particles composed of a single element or a compound having an atomic number of 40 or more, and a part of the inorganic particles are exposed on the fiber surface, A heat-resistant organic fiber, wherein the area ratio of the exposed inorganic particles is 25 to 60%.   The heat-resistant organic fiber according to claim 1, wherein the heat-resistant organic fiber is a wholly aromatic polyamide fiber.   The heat-resistant organic fiber according to claim 2, wherein the wholly aromatic polyamide fiber comprises copolyparaphenylene 3,4'-oxydiphenylene terephthalamide or polymetaphenylene isophthalamide.   The heat-resistant organic fiber according to any one of claims 1 to 3, wherein the average equivalent diameter of the dispersed particles of the inorganic particles is 1.0 to 3.0 µm.   The heat-resistant organic fiber according to any one of claims 1 to 4, wherein the content of the inorganic particles is 50 to 80% by weight based on the total weight of the wholly aromatic polyamide fiber.   A radiation protection product comprising the heat-resistant organic fiber according to claim 1.