JPS59112018A - Magnetizable fiber, their bundle, production, magnetic fiber and magnetic fiber structure - Google Patents

Abstract

PURPOSE:The titled fiber that contains a large amount of a magnetizable fine powder, having certain ranges of the modification factor of the fiber cross section and the fluctuation factor of the cross section area where both of them irregularly changes along the fiber axis and showing practically usable strength and flexibility with a relatively thin fineness. CONSTITUTION:The objective fiber contains 30-95wt% of a magnetizable fine powder, has a not round cross section vertical to the fiber axis where the modification factor D/d (D is the maximum distance between parallel lines tangential at the cross section; D is the minimum distance) is 1.1 or more and irregularly changes along the fiber axis. The cross section area vertical to the fiber axis irregularly changes along the fiber axis and the cross section variation factor [CVF] is in the range from 0.05 to 1.5. As the spinneret, is preferably used a net which is formed by a substance generating heat by application of electricity or a mesh-like porous plate formed by photoetching.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fiber made of a mixture of a thermoplastic polymer and a magnetic fine powder substance, a bundle thereof, a method for producing the same, and a magnetic fiber structure using the bundle.

More specifically, a magnetizable fine powder characterized in that the shape of the cross section perpendicular to the fiber axis is non-circular, and the cross-sectional area varies irregularly in the axial direction. This field relates to fibers containing substances, bundles thereof, and methods for producing the same.

Conventional technologies related to fibrous materials containing magnetic fine powder include fibers that are simply mixed with magnetic fine powder or covered with thread (Japanese Patent Application Laid-open No. 53-2654), Threads are buried or coated with an adhesive layer mixed with magnetic powder (Japanese Patent Laid-Open No. 53-111)
118), a mixture of 25% of a substance that magnetizes rubber strings (
JP-A-54-112953), magnetized after spinning and braiding yarns made of rubber or synthetic resin containing a hard magnetic compound (JP-A-55-30453), fibrous material partially or entirely magnetic. Knitted and woven fabric formed by
983), a composite magnetic fiber comprising a magnetic layer containing at least 0.2 wt% of magnetic particles and a protective layer (Japanese Patent Application Laid-open No. 167416/1983), etc. have been proposed. However, none of these fibers contain a large amount of magnetic fine powder material and still have excellent flexibility.

Furthermore, thin fibers containing many needles of magnetic fine powder have traditionally been difficult to spin, and even if they can be spun, the fibers are quite large in thickness and lack flexibility. Ta.

The present inventors have conducted intensive research to improve these points, and as a result, have arrived at the present invention. That is, the present invention provides a fiber made of a mixture of a thermoplastic polymer and a magnetizable fine powder substance, comprising: (2) the fiber has a deformation coefficient (D/d) of at least 1.1, and the deformation coefficient varies irregularly along the fiber axis; The area of the cross section has irregular changes along the axial direction, and the coefficient of variation of the cross-sectional area within the fiber [CV (F
)] is in the range of 0.05 to 15, and (3) the magnetizable fine powder substance is contained in the range of 30 to 95% by weight; A fiber bundle made of a mixture of a thermoplastic polymer and a magnetizable fine powder substance; The shape is non-circular, and its irregularity coefficient (D/d
) is at least 1.1, and the deformation coefficient varies irregularly along the fiber axis direction, and (2) the fiber has a cross-sectional area perpendicular to the fiber axis that is (3) The fiber axis changes at any position of the bundle, and the coefficient of variation of cross-sectional area within the fiber (CV(F)) is in the range of 0.05 to 1.5. The variation in the cross-sectional area of each fiber when the bundle is cut perpendicular to is expressed as the intra-bundle fiber cross-sectional area variation coefficient CCV (A): ]0.
05 to 2.0, and (4) the magnetic fine powder substance is contained in a range of 30 to 95% by weight; A molten liquid having a large number of slits partitioned by a partition 9 member having unevenness, and in which the molten liquid extruded from the slit formed by the slits is extruded from other slits adjacent thereto, and the partition member. Extruding a suspension of a melted thermoplastic monomer and a magnetic fine powder substance by directing the concavo-convex surface of a mesh-like spinneret, which is configured so that they can come and go each other through the concave portions, toward the melt discharge side; At this time, cooling fluid is supplied to the suspension discharge surface of the spinneret and its vicinity to cool it, and the suspension extruded through the slits is taken over and separated into multiple separations. A method for producing the magnetizable fiber bundle, which is characterized by converting the magnetic fiber bundle into a fibrous rivulet and solidifying it; and a magnetic fiber structure, which is characterized by being magnetized by magnetization using the magnetizable fiber bundle. It is the body.

The present invention will be explained in more detail below.

The magnetizable fiber of the present invention is formed from a mixture of a thermoplastic polymer and a fine powder substance, and the fiber shape has a non-uniform cross-sectional shape when cut perpendicularly to the fiber axis direction. It is characterized in that it is circular and its cross-sectional area changes along the axial direction.

Here, the degree of non-circularity of the cross-sectional shape is the circumference 2 of the cross-section.
It can be expressed by an irregularity coefficient expressed as the ratio (D/d) of the maximum interval (D) between 1,000-line lines and the minimum interval (d) between 2,000-line lines circumscribing the line. The filaments of the present invention have a deformation factor (D/d) of at least 1.1, and most have a deformation factor (D/d) of at least 1.2.

Furthermore, the fiber of the present invention has the above-mentioned deformation coefficient (D/d) that varies irregularly along the length of the fiber.

The fibers of the present invention have a variation in cross-sectional area along their length. This change in the cross-sectional area in the length direction can be seen by selecting 3 crn at any one location on the fiber and measuring the size of the cross-sectional area at every 1u interval by microscopic observation. say something that is acceptable.

In this case, it is convenient to take a micrograph at a magnification of about 200 to about 400 times and observe changes in cross-sectional area. In particular, measure 30 cross-sectional areas as described above, calculate the average value,
After determining the standard deviation (δA) of 30 cross-sectional areas, the cross-sectional area variation coefficient (CV(F)) calculated from the following formula is 0.
Preferably, the variation is in the range 0.05 to 1.5, especially in the range 0.08 to 1.0.

δA CV (Ladle=~=- The thermoplastic polymer in the present invention means all polymers that can form fibers, such as polyester, polyamide, polyolefin, polyacetal, polyvinyl, polyether, polycarbonate, polyurea, Examples include synthetic resins such as polyurethane and fluorine-containing polymers, and rubber.

More specifically, polyolefins or polyvinyls include, for example, polyethylene, polypropylene, polybutylene, polystyrene, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, polyacrylic esters, or mutual copolymers thereof; polyamides include, For example, polyε-caprolactam,
Aliphatic polyamides such as polyhexamethylene adipamide, polyhexamethylene sebacamide, and polyparaphenylene isophthalamide, polymetaphenylene isophthalamide, polymetaphenylene terephthalamide, poly-1
, 5-naphthylene isophthalamide, poly-3,4'-
Aromatic polyamides such as dienylene terephthalamide, polymethaxylylene inphthalamide, or copolymers thereof; Examples of polyesters include aromatic polyesters such as phthalic acid, isophthalic acid, terephthalic acid, diphenyl dicarboxylic acid, and naphthalene dicarboxylic acid. Dicarboxylic acid; aliphatic dicarboxylic acid such as adipic acid, sepatic acid, decanedicarboxylic acid; or alicyclic dicarboxylic acid such as hexahydroterephthalic acid as dibasic acid component, ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene Glycol, decamethylene glycol, diethylene glycol.

2. Aliphatic glycols such as 2-dimethylpropanediol, aliphatic glycols such as cyclohexane dimetatool, aromatic aliphatic glycols such as xylylene glycol, resorcinol.

Polyester or fully aromatic polyester containing an aromatic dihydroxy compound such as hydroquinone as a glycol component; Examples of fluorine-containing polymers include polytetrafluoroethylene,
Polytrifluorochlorinated ethylene, polyvinylizo difluoride/, BoI
JM Fluorinated ethylene-hexafluorinated globylene copolymer, polytetrafluorinated ethylene-perfluoroalkyl vinyl ether copolymer, polyfluorinated ethylene-ethylene copolymer, polytetrafluorinated ethylene-propylene copolymer, polytetrafluorinated ethylene-propylene copolymer, Fluorine-containing polymers such as vinyl fluoride or polytrifluorochloroethylene-ethylene copolymers; Polycarbonates include, for example, leather
φ piece - 4ta) 44-size storage = Kudosei 7≠ = polymer using various bisphenols; examples of rubber include chloroglene rubber, butadiene rubber, imprene rubber, and butyl rubber.

Examples include ethylene propylene rubber, SBR, ABS, natural rubber, etc.

The above-mentioned thermoplastic polymers may be used alone or in an intimate microblend mixture of two or more types, or as previously proposed by the present inventors, two or more types of polymers may be combined. It can also be used as a macroblend mixture in which the mixture forms a relatively large molten phase (see JP-A-57-29610). Furthermore, the polymer may contain a plasticizer, a viscosity increaser, etc. to increase plasticity and melt viscosity. In addition, the polymer contains light stabilizers, pigments, heat stabilizers, which are usually used as additives for fibers,
(a) A refueling agent, a lubricant, etc. may be contained.

The magnetizable fine powder material in the present invention may be of any material as long as it becomes magnetic when magnetized. The material is preferably a ferromagnetic material, a ferrimagnetic material, etc., such as iron.

Metals such as cobalt and nickel; one or more of these metals and aluminum, titanium, copper, and platinum.

Examples include alloys consisting of one or more types of carbon, etc.; metal oxides containing iron oxide, ferrite, etc. as main components; compounds of rare earth elements with iron, cobalt, nickel, etc.; Among these, iron oxide, hard ferrite (ferrite with a magnetobrambite crystal structure), cobalt in combination with rare earth elements, nickel, aluminum, and cobalt.

Particularly preferred are iron or iron alloys (for example, alnico magnets) containing one or more of titanium, copper, platinum, carbon, and the like.

In the present invention, the fine powder may be surface-treated with a coupling agent or the like to increase adhesion to the thermoplastic polymer.

More than 90% of the magnetic fine powder material has a particle size of 3 μm or less, preferably 2 μm or less. If the particle size is coarser than this, the magnetic properties of the magnetizable fine wood-like material will deteriorate, which is not preferable. Further, it is preferable that the particle size distribution is narrower.

The fine powder substance accounts for 30 to 95% by weight, preferably 50 to 90% by weight, more preferably 60% by weight in the fiber of the present invention.
It is contained in a range of 85% by weight.

The fibers in the present invention have an average cross-sectional area of I x 10
=~2×10. J, preferably 2 x 1
0-4 to 1x10-.

The magnetizable fiber bundle in the present invention is a bundle consisting of a large number of the above-mentioned magnetizable fibers, and the variation in the cross-sectional area of each fiber when cut perpendicularly to the fiber axis at an arbitrary position is
The coefficient of variation of the cross-sectional area of fibers within the bundle [0V(A)] T expressed as T is in the range of 0.05 to 2.0.

This 0V (4) is calculated by randomly extracting 100 partial bundles from the aggregate, measuring the size of each cross section by observing the cross section at an arbitrary position under a microscope, and calculating the average value of the difference. , the standard deviation (δA) of the 100 cross-sectional areas can be found and calculated from the following formula. Cv(4) in the present invention is preferably in the range of 0.1 to 1.5, particularly preferably in the range of 0.2 to 1.0.

That is, the magnetizable fiber bundle of the present invention is characterized in that the size and shape of the cross section of each fiber when cut perpendicularly to the axial direction at any position thereof is irregular and substantially different. .

The above-mentioned magnetizable fiber bundle can be produced by a method of manufacturing fibers from a thermoplastic polymer melt, which was previously proposed by the present inventors.
For example, JP-A-56-140110 and JP-A-57
It can be produced by using a mixture of the magnetic fine powder material and the thermoplastic polymer as the melt in the method disclosed in Japanese Patent No. 39208.

This method makes it possible to industrially advantageously produce fibers containing a large amount of magnetic fine powder material, which cannot be obtained or is extremely difficult to obtain by conventional fiber means using Oriswiss. .

According to the present invention, the fiber containing the fine powder substance is
A mixed suspension of a molten thermoplastic polymer and a solid magnetic fine powder substance is passed through a spinneret having a large number of slits partitioned by partition members, and is placed between adjacent slits on the discharge side. Continuous protrusions are provided, such that the suspension extruded from the slits formed through the concave areas between the ridges can interact with the suspension extruded from other adjacent slits. The suspension is extruded from a spinneret that can be extruded through a spinneret, and while cooling the suspension by supplying a cooling fluid to the suspension discharge surface of the spinneret and its vicinity, the suspension extruded through the slits is taken up and the suspension is extruded. It is produced by converting a suspension into a number of separated fibrous rivulets and solidifying them.

The spinneret used in the method for producing a bundle of the present invention is a mesh-shaped spinneret having a large number of closely spaced pores, and has a porosity expressed by α + = X 100a of about 10% or more, preferably about 25%.
It is characterized by being ~90%.

First, the spinneret used in the present invention has a structure in which it has a large number of closely spaced slits, and the suspension extruded from the adjacent slits can pass through each other, making it more stable. It is characterized by a structure that allows for flexible spinning.

During the spinning, at least the discharge surface of the spinneret is preferably heated. In order to heat the discharge side surface of this die, it is necessary to supply energy to the die surface. There are various methods for this, including cases where the surface of the die is made to generate heat by itself, cases where it is heated by heat transfer, and cases where both are used in combination.

As a means for self-heating the surface of the cap, the surface of the cap is made of a conductor, and the surface of the cap is connected to a DC or AC power supply to supply electricity, thereby utilizing the Joule heat generated on the surface of the cap (hereinafter referred to as the energization heating method). A method that utilizes so-called induction heating, in which the surface of the cap is made of a conductor and an induced magnetic field of a suitable frequency is applied to it to generate eddy current and generate heat; There is a method using so-called dielectric heating, in which an electric field of a suitable frequency is applied thereto to cause dielectric loss and heat generation. There is a method of applying an electric field at a suitable frequency to generate dielectric loss and generating heat, which utilizes so-called dielectric heating.

Materials that can be used in the electrical heating method and dielectric heating method include platinum, gold, silver, copper, titanium, vanadium, tungsten,
Iridium, molybdenum.

Single metals such as halasium, iron, nickel, chromium, cobalt + lead, sulfur, bismuth, tin, aluminum, stainless steel, nichrome.

Alloys such as tantalum, brass, phosphor bronze, and duralumin, graphite, silicone, and germanium.

SeV7. Tin oxide, indium oxide, iron oxide.

It is advantageous to form a material having a resistivity of about 104 to 1090 in the spinneret of the above spinning mode, such as an inorganic compound exhibiting mainly semiconductor properties such as nickel oxide, or an organic compound exhibiting semiconductor properties such as polyacetylene or polyphenylene. used for.

In the method of the present invention, it is preferable to use, as the spinneret, a mesh made of a material that generates heat when energized (wire mesh) or a mesh-like perforated plate formed by photoetching. The opening of the net is determined by the thickness of the fibers.

In the method of the present invention, in order to use a spinneret having the above-mentioned characteristics, by orienting the discharge surface of the spinneret upward, the suspension extruded onto the discharge surface is drawn as a trickle. Gravity acts in the opposite direction to the taking direction, making it easier for the suspension to flow through the narrow gaps on the discharge surface, thereby further stabilizing the supply of the suspension to each narrow gap. .

That is, in the production of the bundle in the present invention, the discharge surface of the spinneret is directed upward, and the normal vector of the discharge surface is completely aligned with the vector in the opposite direction to gravity, or even if it deviates by only a few degrees. It is preferable to use so-called upward spinning, which is in the range of .

In the manufacturing method of the present invention in which upward spinning is performed using a spinneret having a large number of slits as described above, the pressure applied to the spinneret can be reduced, thereby improving the mechanical strength of the spinneret, e.g. It has become possible to make the thickness of the spinneret extremely thin. By using this extremely thin spinneret, the supplied suspension is made into a trickle as if it were simply cut by the partition member of the spinneret, so the pressure loss during discharge can be reduced, and therefore It has become possible to stably perform spinning using a suspension containing a high concentration of a solid fine powder substance as in the present invention. In particular, the method of the present invention has made it possible for the first time to spin relatively thin fibers or ultra-fine fibers from a solution containing a high concentration of solid fine powder substances, which was extremely difficult to achieve by conventional orifice spinning. That is, according to the present invention, it is possible to produce magnetic fibers that require a high content of magnetic fine powder substances.

Furthermore, in the method of the present invention, the cooling effect immediately after discharge can be increased, and the temperature of the trickle that has left the spinneret can be rapidly lowered in a shorter distance and in a shorter time. It becomes easy to stably produce highly oriented undrawn fibers. Containing a high concentration of magnetic fine powder material that has been tried so far by orifice spinning
However, using the method of the present invention, which facilitates orientation, it has become possible to obtain fibers containing a highly concentrated magnetic fine powder substance that has a strength that can withstand practical use. It is possible to obtain the relatively thin fibers that were not obtained, and even ultra-fine fibers.

Further, according to the method for producing a bundle of the present invention having the above-mentioned characteristics, the magnetizable fibers having the above-mentioned characteristics such as being swamped in the fiber axis direction and whose cross-sectional shape and cross-sectional area change irregularly. and a bundle thereof can be obtained. The fibers and fiber bundles have a high degree of flexibility due to their cross-sectional shape and cross-sectional shape, which cannot be obtained with conventional magnetic fibers, and contain a large number of magnetic fine powder substances.

In the method for manufacturing a bundle of the present invention, by increasing the take-up speed of the trickle compared to the discharge speed, the change in cross-sectional shape and cross-sectional area is larger, and the orientation is more advanced, that is, it is more flexible. , it is easy to obtain magnetic fibers with higher strength.

Furthermore, the magnetizable fibers and bundles thereof of the present invention have a non-circular cross-sectional shape and have irregular changes,
In some cases, various special cross-sectional shapes, e.g. triangular,
Since it can also have cross-sectional shapes such as star-shaped or T-shaped,
It has a large surface area. Therefore, its characteristics are fully exhibited in applications that utilize the fiber surface, such as magnetic filters.

The magnetizable fiber of the present invention can be used as a single fiber, and the magnetizable fiber bundle can be used in the form of a filament or a cut stable in a crimped or uncrimped state. Examples of its form include yarn, knitted fabric, woven fabric, woven fabric, nonwoven fabric, and other fibrous structures. It is also possible to mix and use ordinary fibers in these structures, if necessary.

Furthermore, any known method may be used to magnetize the magnetizable fibers of the present invention, their aggregates, or fiber structures using the same, such as keeping the fibers or bundles in a magnetic field. method, and a method in which the fiber structure is formed into a fiber structure and then held in a magnetic field. It is also possible to magnetize during spinning, and it is also possible to combine demagnetization and magnetization.

Thus, the magnetic fibers and magnetic fiber structures obtained by the present invention are expected to have a wide range of applications.
For example, magnetic fasteners, magnetic filters, magnetic sheets (
Car accessories (- seats, etc.), health clothing, magnetic tape, wire memory.

Examples include toys using detection elements such as magnetic powder, cloth magnets, and the like.

The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these examples.

In addition, "1 part" in the examples refers to parts by weight.

Example 1 Polypropylene (manufactured by Ube Industries, Ltd. 8) was used as a thermoplastic polymer.
115M) 20 parts of barium in the form of fine powder with a particle size of 1μ.
Mix 80 parts of ferrite, knead with a 50φ extruder at a temperature of 230 to 270°C, and apply 30 parts of plain weave to the spinneret.
A current of 50 A was passed through the spinneret using a mesh wire mesh (manufactured by Nippon Filcon Co., Ltd.) to rapidly cool the spinneret while causing self-heating, and a filamentary fiber bundle was obtained at a take-up speed of sm/min. The fibers have a non-circular cross-sectional shape, and the cross-sectional area changes in the longitudinal direction, and the CV (g) of the bundle
is 0.6, and the [CV (F)
] was 0.5, and D/d was 1.6. The filamentary fiber bundle was very pliable.

Example 2 As a thermoplastic polymer, 2 parts of polybutene-1 (manufactured by General Science Corporation) and 80 parts of finely powdered Sr ferrite (manufactured by Nippon Bengara Kogyo ■) with a particle size of 1 μ were thoroughly mixed in a Ni-Goo. It was later made into a chip. 30 chips
It is melted into a suspension using a φ extruder at a temperature of 200 to 230°C, and a 30-mesh plain weave wire mesh (Nippon Kinami Shoko ■) is used as a spinneret, and a current of 2 V and 48 A is passed through the spinneret to generate self-heating while discharging. After cooling, the mixture was rapidly cooled and a filamentary fiber bundle was obtained at a drawing speed of s m for 7 minutes. ``The CV(5) of the bundle is 0.5, the (CV(F)) of one of the fibers is 0.35, and the D/d is 1.
It was 5. Further, the average cross-sectional area of the fibers was approximately 5 x 10'wJ.

Also, the filament bundle was very pliable.

Example 3 All operations were performed in the same manner as in Example 2, except that polyethylene terephthalate (intrinsic viscosity [η] = O, 64-manufactured by Teijin ■) was used as the thermoplastic polymer, and the extruder temperature was set at 280 to 300°C. A filamentary fiber bundle was obtained. The CV(4) of the bundle is 0.4, and the [V(F)] of one fiber is 0.25, D
/d was 1.4.

Example 4 The filamentary fiber bundle obtained in Example 2 was formed into a web, fixed in the form of a nonwoven fabric with a binder (acrylic acid ester), and then magnetized by applying a magnetic field of 6000 oersteds. The surface Gauss of the nonwoven fabric was measured and found to be 100 Gauss.

The helmet was ao ot/-. The nonwoven fabric was supple, stiff, and highly flexible.

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph (magnification: 100) illustrating a side view of the magnetizable fiber of the present invention.

Claims (1)

[Scope of Claims] 1. A fiber made of a mixture of a thermoplastic polymer and a magnetic fine powder substance, wherein (1) the fiber has a non-circular cross-sectional shape perpendicular to the fiber axis direction; the reeds have a deformation coefficient (D/d) of at least 1.1, and the deformation coefficient varies irregularly along the fiber axis; (2) the fiber has a shape coefficient (D/d) of at least 1.1; The vertical cross-sectional area has irregular changes along the axial direction, and the intrafiber cross-sectional area variation coefficient COV (F)] is 0.05 to 1.5.
(3) A magnetic fiber characterized in that the magnetic fine powder substance is contained in a range of 30 to 95% by weight. 2. The magnetic fiber according to item 1, of which 90% or more has a particle size of 3 μm or less. λ The magnetizable fiber according to item 1, wherein the fine powder substance is at least one selected from the group of ferromagnetic materials and ferrimagnetic materials. The fibers have an average cross-sectional area of I x 10-' to 2
The magnetizable fiber according to item 1, which is in the range of xlO-. & A fiber made of a mixture of a thermoplastic polymer and a magnetic fine powder substance, (1) The fiber has a non-circular cross-sectional shape perpendicular to the fiber axis direction, and has a non-circular shape coefficient (D /d) is at least 1.1, and the irregularity coefficient is in the fiber axis direction? 6
(2) The area of the cross section perpendicular to the fiber axis changes irregularly along the axial direction, and the coefficient of variation of the cross-sectional area within the fiber [CV (F)] is in the range of 0.05 to 1.5, (3) the magnetic fine powder substance is contained in the range of 30 to 95 weight tons, and (4) it is magnetized by magnetization. A magnetic fiber characterized by: α A fiber bundle made of a mixture of a thermoplastic polymer and a magnetic fine powder substance, wherein (1) the fibers constituting the bundle have a non-circular cross-sectional shape perpendicular to the fiber axis direction; Yes, its anomaly coefficient (D
/d) is at least 1.1, and the deformation coefficient varies irregularly along the fiber axis direction, and (2) the fiber has a cross-sectional area perpendicular to the fiber axis that is It has an irregular variation along the fiber cross-sectional area coefficient [C! V(F)) is in the range of 0.05 to 1.5, and (3) the variation in the cross-sectional area of each fiber when the bundle is cut perpendicular to the fiber axis at any position of the bundle is , the fiber cross-sectional area variation coefficient within the bundle CCV (A)] is 0.0
5 to 2.0, and (4) the magnetic fine powder substance is 30 to 95% by weight.
A magnetizable fiber bundle comprising: 7. It has a large number of slits partitioned by partition members having irregularities on at least one surface, and the melt extruded from the slits formed by the slits is extruded from other adjacent slits. A thermoplastic polymer and a magnetic fine powder substance melted with the uneven surface of the mesh spinneret configured to be able to pass through the melt and the concave portion of the partition member toward the discharge side of the melt. At this time, a cooling fluid is supplied to the discharge surface of the spinneret and the vicinity thereof to cool the suspension, and the suspension extruded through the slit is drawn and the suspension is extruded. is non-circular in shape and has a shape factor (D/d) of at least 1.1; The deformation coefficient varies irregularly along the fiber axis direction, and (3) the 1M fiber has an irregular variation in area of a cross section perpendicular to the fiber axis in the axial direction. The fiber internal cross-sectional area coefficient of variation [CV(F)] is 0.05 to 1.5.
(4) The variation in the cross-sectional area of each fiber when the bundle is cut in a direction perpendicular to the fiber axis at any position in the bundle is determined by the fiber cross-sectional area variation coefficient within the bundle [V(A ):lr represents 0
．． 05 to 2.0, and (5) the magnetic fine powder substance is contained in a range of 30 to 95 I. a. A fiber structure using a fiber bundle made of a mixture of a thermoplastic polymer and a magnetic fine powder substance. The shape of the cross section perpendicular to the direction is non-circular, and its irregularity coefficient (D
/d) is at least 1.1, and the deformation coefficient overflows and changes irregularly in the fiber axis direction, (2) the fiber has an area of a cross section perpendicular to the fiber axis (3) The bundle has irregular variations in the direction, and its intrafiber cross-sectional area coefficient of variation CCV(F)' is in the range of 0.05 to 1.5. The variation in the cross-sectional area of each fiber when the bundle is cut perpendicular to the fiber axis at an arbitrary position is expressed as the coefficient of variation of the cross-sectional area of the fibers within the bundle [Cv(A)], which is te 0.0.
5 to 2.0 (7) Within the range (4) The magnetizable fine powder substance is contained in a range of 30 to 95% by weight, and is characterized by being magnetized by magnetization. magnetic fiber structure.