JPH0146606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new type of heat-resistant aromatic polyamide fiber and a novel and economically advantageous method for producing the same. The present invention relates to fibers produced by melt molding, particularly ultra-thick aromatic polyamide fibers and methods for producing the same.

Aromatic polyamides have been widely proposed for their heat resistance and
Flame-retardant polymers, particularly polymetaphenylene isophthalamide, are commercially available in large quantities as fibers under the names of Nomex (manufactured by DuPont) and Conex (manufactured by Teijin Ltd.). This fiber has a flexibility comparable to that of conventional Yuki fibers, and has a limiting oxygen index (LOI) of 27 and a melting point of 400-410.
It has flame retardancy and heat resistance, with a decomposition starting point of approximately 400°C, making it useful as fireproof clothing, bag filters, and insulation materials. Polyparaphenylene terephthalamide is Kevlar [manufactured by DuPont]
This fiber is commercially available as a fiber under the name of polymethaphenylene isophthalamide fiber, which has flame retardancy and heat resistance comparable to the above-mentioned polymetaphenylene isophthalamide fiber, and also exhibits high strength and high Young's modulus, making it useful for composite materials, ropes, etc. It is.
Various modifications (copolymerization, blending, etc.) have been performed mainly on these two types of aromatic polyamides, and compositions suitable for each purpose have been studied.

Generally, aromatic polyamides have a high melting point, which is close to the decomposition onset temperature, so it is impossible to melt extrude them using conventional melt spinning equipment. Therefore, it is customary to dissolve the polymer in a solvent and perform wet or dry spinning.The solvent may be aprotic polar solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc. alone or in combination with lithium chloride, chloride, etc. It is known to use a mixed solution of a halide salt of a metal of a periodic table group or group such as calcium, sulfuric acid, chlorosulfuric acid, hydrofluoric acid, acetic acid difluoride, and the like. For industrial use, equipment is required to recover or neutralize these solvents, and the amount of solvent used per unit weight of the polymer is usually 3 to 20 times the weight of the polymer, so spinning Requires collection or processing equipment that is extremely large compared to the equipment itself. Moreover, the cost of solvents that cannot be recovered is directly added to the cost of fibers.

For these reasons, it is self-evident that if the polymer can be made melt-spun, it is more advantageous to employ the melt-spinning method (wet, dry, or semi-dry/semi-wet). . this is,
This also applies if the polymerization of the polymer is carried out in solution. This is because first separating (precipitating) the polymer from a solution and performing melt spinning is a much simpler process than solution spinning.

In addition, in the case of solution spinning, when the target fiber becomes thick, it becomes very difficult to extract and remove the solvent sufficiently. For example, when dry spinning a solution of polymetaphenylene isophthalamide dissolved in a dimethylacetamide/calcium chloride solvent, the solvent in the outer skin of the fiber preferentially escapes, so the outer skin coagulates into a dense structure and the core Significantly inhibits solvent diffusion. Therefore, it becomes more difficult to extract and remove the solvent from the core as the fiber becomes thicker.
It is necessary to make the spinning tube extremely long. The same is true when wet spinning a solution of polymetaphenylene isophthalamide dissolved in N-methylpyrrolidone solvent, which requires extremely long coagulation baths and water washing baths.

What is more undesirable is that the structure of the outer shell and core is extremely different, resulting in a fiber with an advanced so-called skin-core structure, which deteriorates the various physical properties of the fiber, making it difficult to obtain a normal extremely thick aromatic polyamide fiber. I couldn't do it.

Furthermore, in the conventional method using solution spinning, the cross-sectional shape of the resulting fibers is almost a perfect circle, and the cross-sectional area is almost constant in the axial direction, so it is difficult to create a texture similar to that of natural fibers. .

The present invention aims to solve these problems. That is, an object of the present invention is to provide an extremely thick aromatic polyamide fiber that has not been obtained hitherto. Another object of the present invention is to provide a method for producing extremely thick aromatic polyamide fibers by a highly productive melt spinning method that does not require complicated steps such as solvent treatment. Furthermore, another object of the present invention is to provide an extremely thick aromatic polyamide fiber having characteristics similar to natural fibers whose cross-sectional shape and cross-sectional area are not constant.

The inventors of the present invention have conducted intensive research for the above purpose, and have discovered that extremely thick aromatic polyamide fibers having a shape similar to natural fibers can be obtained by a novel melt-spinning method with high productivity. reached.

That is, the present invention provides fibers made of at least one type of aromatic polyamide, the average single filament fineness (e) of which is from 100 to
This relates to an extremely thick aromatic polyamide fiber characterized by a denier of 100,000 denier, and in producing a fiber aggregate from at least one kind of aromatic polyamide polymer, the following formula () α=Va−Vf/Va× 100...() [In the formula, α is the void ratio [%] occupied by a large number of fine particles in the spinneret, Va is the apparent total volume occupied by the mesh-like part of the spinneret under a unit area, Vf is the total area occupied by the mesh-like member surrounding the narrow part under the unit area of the mesh-like part of the spinneret. ] Using a mesh-like spinneret having a large number of closely spaced threads with a void ratio of 25 to 95%,
The aromatic polyamide polymer powder is supplied to the surface opposite to the discharge surface of the spinneret, and the solid powder is supplied while supplying heat from the heat-generating partition member of the mesh spinneret. The melt is extruded through a large number of narrow holes surrounded by the partition member, and at this time cooling granules are supplied to the melt discharge surface of the spinneret and its vicinity to cool it. The details
taking the melt extruded through the molten polymer, converting the melt into a large number of separated fibrous rivulets and solidifying the melt within a time during which the molten polymer does not substantially lose its ability to form moldings; The cross-sectional area changes irregularly and periodically along the length of the fiber, and the intra-fiber cross-sectional area coefficient of variation [CV(F)] is 0.05 to 1.0.
The present invention relates to a method for producing ultra-thick aromatic polyamide fibers having the following range.

The present invention will be explained in more detail below.

As mentioned above, the novel extra-thick aromatic polyamide fiber of the present invention is greatly different from conventional aromatic polyamide fibers in terms of morphology.

That is, the novel aromatic polyamide fiber of the present invention is characterized in that it is extremely thick, which has not been previously available. The ultra-thick aromatic polyamide fiber in the present invention refers to its average fineness (e)
is in the range of 100 to 40,000 denier, preferably 100 to 40,000 denier
It is in the 10,000 denier range. If the average fineness (e) exceeds 40,000 deniers, it becomes difficult to continue stable spinning, which is not very preferable.

Furthermore, the novel ultra-thick aromatic polyamide fiber of the present invention has irregular and periodic changes in cross-sectional area along its length, and has an intrafiber cross-sectional area variation coefficient [CV (F)
It is characterized by a range of 0.05 to 1.0.
Conventional fibers have a CV(F) of less than 0.05. This CV(F)
means that when the fiber is cut at intervals of, for example, 1 mm along its length, the size of each cross-sectional area varies randomly, and the variation in the size of the cross-sectional area has an irregular period. It means that there is, and the width of the fluctuation is within a statistically constant range.

More specifically, this novel ultra-thick aromatic polyamide fiber has a non-circular cross section, and has irregular and periodic changes in cross-sectional area along the length of the fiber, Moreover, it is characterized in that the cross-sectional shape also changes accordingly.

The coefficient of variation of the fiber cross-sectional area [CV(F)] here refers to the variation in fineness in the length direction (axial direction) of the fiber, and it indicates the variation in the fineness in the longitudinal direction (axial direction) of the fiber, and it refers to the variation in the fineness of the fiber in the longitudinal direction (axial direction). Select 3 cm of , measure the size of the cross-sectional area at 1 mm intervals by microscopic observation, and calculate the average value () of the 30 cross-sectional areas and the standard deviation (σ _A ) of the 30 cross-sectional areas. It can be calculated using the following formula.

CV (F) = σ _A / The very thick aromatic polyamide fiber of the present invention has the above CV
(F) is in the range of 0.05 to 1.0, especially 0.08 to
0.7, particularly in the range of 0.1 to 0.5.

Another feature of the novel ultra-thick aromatic polyamide fiber of the present invention is that the cross section is non-circular, and the cross-sectional area changes irregularly and periodically along the length of the fiber. and a corresponding change in cross-sectional shape.

The degree of non-circularity of the fiber cross-section is determined by the circumference 2
It can be expressed by the irregularity coefficient expressed as the ratio (D/d) of the maximum distance between parallel lines (D) and the minimum distance (d) between two circumscribed parallel lines. The ultra-thick aromatic polyamide fiber of the present invention has a deformation coefficient (D/d) of at least 1.1, and most have a deformation coefficient (D/d) of at least 1.2.

Furthermore, the ultra-thick aromatic polyamide fiber of the present invention is characterized in that the above-mentioned deformation coefficient (D/d) changes along the length direction of the fiber. In other words, the fiber has a maximum difference in shape coefficient [(D/d)max] and a minimum shape coefficient [(D/d)min] in any 30 mm range along its length. (D/d)max−(D/d)min] is at least 0.05, preferably at least 0.1.

The aromatic polyamide polymers targeted in the method of the present invention are of the following formulas (), (), () [In formulas (), () and (), () and (), if present, are present in substantially equimolar amounts, and the groups R ¹ , R ² and R ³ are the same or different. Indicates a divalent group, R ¹ , R ² and R ³
At least 50% by weight of the total of is aromatic groups. ] It is a polymer substantially consisting of at least one type of repeating unit selected from the group consisting of the following, and is generally referred to as an aromatic polyamide or a wholly aromatic polyamide.

R ¹ in the above formulas (), () and (),
R ² and R ³ are the same or different divalent groups, and at least 50% by weight of their total, preferably at least 70% by weight, is an aromatic group. The aromatic group referred to herein means a group having a normal benzene nucleus or a benzene nucleus in a condensed ring, such as benzene, naphthalene, anthracene, etc.

That is, examples of such groups include paraphenylene group, metaphenylene group, 1,5-naphthylene group, 2,6-naphthylene group, 3,3'-,
4,4'- or 3,4'-diphenylene group, 3,
3'-, 4,4'-, 3,4'-diphenyl ether group,
Examples include para-xylylene group, meta-xylylene group, and para-(meth)methylphenylene group.

Preferred aromatic polyamides in the present invention include polyparaphenylene isophthalamide, polymetaphenylene isophthalamide, polymetaphenylene terephthalamide, poly-1,5-naphthylene isophthalamide, and poly-3,4'-diphthalamide. Examples include enylene terephthalamide, polymethaxylylene isophthalamide, and copolymers thereof. Particularly preferred aromatic polyamides include polymetaphenylene isophthalamide, polymetaxylylene isophthalamide, (metaphenylene diamine, isophthalic acid chloride, and meta-aminobenzoic acid chloride) copolymers, and the like.

In the aromatic polyamide polymer of the present invention, the moldability can be improved by introducing flexible chain groups such as aliphatic chains into the R ¹ , R ² and R ³ portions in the formulas (), (), and (). However, if the proportion of the group exceeds 50% by weight of the total of R ¹ , R ² and R ³ ,
This is not preferable because properties such as heat resistance, which are important characteristics of aromatic polyamides, deteriorate.

Further, in the novel extra-thick aromatic polyamide fiber of the present invention, partial crosslinking of the polymer may be included. In this case, additional advantages include improved heat resistance of the fibers.

The novel ultra-thick aromatic polyamide fiber of the present invention has been described above, and now the manufacturing method thereof will be explained in detail.

The method for producing the novel ultra-thick aromatic polyamide fiber of the present invention is as follows: (1) The void ratio (α) expressed by the above formula () is 25
(2) supplying the aromatic polyamide polymer powder to the surface opposite to the discharge surface of the spinneret; 3) melting the solid powder while supplying heat from a heat-generating partition member of the mesh-like spinneret, and extruding the molten liquid through a number of narrow holes surrounded by the partition member; (4) At this time, cooling granules are supplied to the melt discharge surface of the spinneret and its vicinity, and while cooling the melt extruded through the slitter, (5) the molten polymer is It is characterized in that the melt is converted into a large number of separated fibrous rivulets and solidified within a period of time without substantially losing the ability to form a molded article.

As explained above, in the method of the present invention, the discharge surface of the conventionally known melt of a normal thermoplastic polymer is a smooth surface, and the discharge holes (orifices) for the melt are arranged independently and in a regular arrangement. This method is fundamentally different from the method of manufacturing fibers in which the melt is extruded through a spinneret that is drilled through a spinneret.

The spinneret used in the present invention has the above formula ()
It has a large number of closely spaced strips defined by the value of the void ratio (α), as shown in FIG. The mesh-shaped portion of the spinneret in the above formula () that defines the void ratio is literally a mesh-shaped portion of the mesh-shaped spinneret.

As long as the spinneret used in the present invention has a large number of closely spaced strips defined by the value of the void ratio, the shape of the strips or the shape of the partition member that defines the strips may be of any shape. .

The mesh-like spinneret used in the present invention may therefore have, for example, a circular, elliptical, triangular, quadrangular or other polygonal shape, or the partition member defining the width may have unevenness. You don't have to.

FIG. 1-a of the accompanying drawings illustrates a typical example of a mesh-like spinneret used in the present invention. The mesh spinneret illustrated is a plain weave wire mesh. FIG. 1-b illustrates a cross-sectional view of the wire mesh of FIG. 1-a.

The plain weave wire mesh shown in the figure has rectangular strips, and the partition member between the adjacent strips has a concave portion so that the melt extruded from adjacent strips can pass through each other.

FIG. 2-a of the accompanying drawings illustrates another example of the mesh-like spinneret used in the present invention. The illustrated mesh-like spinneret is an etched perforated plate in which a large number of holes are formed on a thin metal plate using a precise etching technique. This etched perforated plate has a roughly triangular shape, as shown in Figure 2-b.
As is clear from the cross-sectional view illustrated in , the partition members existing between adjacent slots do not have recesses.

The mesh-like spinneret used in the present invention may be a twill wire mesh, or may be a thin sintered body in which a large number of microscopic metal spheres are sintered to form a large number of fine threads. . In addition, the adjacent narrow
The partition member present therebetween may be an etched perforated plate having recesses.

In the present invention, these mesh-like spinnerets can be used not only alone, but also in combination and laminated.

FIG. 3 of the accompanying drawings shows a cross-sectional view of a mesh-like spinneret used in the present invention, which is formed by laminating two plain-woven wire meshes.

Among these spinnerets, according to the present invention, preferably, the discharge surface of the spinneret has a large number of narrow partition members partitioned by narrow partition members having uneven portions, and A mesh-like spinneret is used, which is structured so that the melt extruded from one narrow thread can communicate with the melt extruded from another adjacent thin thread through the partition member.

In the above formula expressing the void ratio that defines the mesh-like spinneret used in the present invention, Va is the apparent total volume occupied under a unit area of the mesh-like part of the spinneret, and Vf is the mesh-like part of the spinneret. This is the total area occupied by the partition member surrounding the thin wall, based on the unit area of the area.

As can be seen from the illustrations in FIGS. 1-a and 1-b of the single drawing, assuming a virtual surface that contacts the front and back surfaces of the spinneret, the unit of these two virtual surfaces is The volume of the part surrounded by the area (1 cm ² ) is defined as the apparent total volume (Va) of the above formula ().

It will be easily understood that in the case of a laminated mesh-like spinneret as shown in FIG. 3, the apparent total volume (Va) is determined assuming a virtual plane in the same manner as described above.

In order to find Va for an actual mesh-like spinneret, Va can be easily obtained by measuring the thickness of the mesh-like spinneret with a dial gauge having a contact surface of 1 cm ² .

Further, in order to determine Vf for a certain mesh-like spinneret, it is sufficient to cut the mesh-like spinneret into a predetermined area, immerse it in a liquid, and measure the increased volume at this time. The value calculated by converting this increased volume per 1 cm ² of the mesh-like spinneret is
It becomes Vf.

The mesh spinneret used in the present invention has a void ratio (α) of about 10
% or more, preferably about 25% to about 90%.

Further, according to the present invention, the mesh-like spinneret used in the present invention ^preferably has about 5
or more, preferably about 10 to about 1000.

Furthermore, the mesh-like spinneret used in the present invention is about 10 mm or less, more preferably about 0.1 to about 5 mm,
Particularly preferred is a thickness of about 0.2 to about 2 mm.

The spinneret having the above-described structure of the present invention has an average distance ( ) of 0.03 to 4 mm between the slits from which the polymer melt is discharged on the surface of the forming region.
It is preferable to have a range of .

In particular, according to the definition explained below, the molding area has (1) an average distance between discharge ports () in the range of 0.03 to 4 mm, (2) an average peak height () in the range of 0.01 to 3.0 mm, (3) ) Fine irregularities in which the average peak width () is in the range of 0.02 to 1.5 mm, and (4) the average peak height () and the average peak width () satisfy the range of 0.3 to 5.0, expressed as ()/(). It is advantageous to use a spinneret with a discharge surface having a large number of slots.

The above-mentioned molding area, average distance between discharge ports ( ), average peak height ( ), average peak width ( ), and width are each defined by the following explanation.

The average narrow distance (), average peak height (), average peak width (), etc. defined in the present invention are all values determined based on the concept of geometric probability theory, and the shape of the surface of the forming area For things that are geometrically obvious, they are calculated mathematically using the definitions and methods of integral geometry.

For example, theoretically, for the molding area of a die in which sintered bodies of spherical objects with radius r are packed close-packed, =√
3r, = (x/4)r, = (x/2)r.

In this way, it can be determined theoretically for a cap whose surface is composed of a collection of microscopically uniform geometric shapes, but for a cap with a microscopically non-uniform surface shape, it is possible to determine how many caps there are. can be determined by cutting at a right angle cross section, or by making a mold of the surface of the cap using a material that is easy to cut, cutting it, and actually measuring it. For actual measurements, as long as the surface of the molding area is macroscopically uniform, the vertex can be set at the center of the molding area and six cross-sections taken every 30 degrees around the vertex can be approximately measured. This is sufficient for practical purposes.

The forming area refers to the area in the spinneret for discharging the molten polymer and spinning and forming the extremely thick fiber aggregate.
A region where a fiber bundle having a substantially uniform density is formed.

The thinness of the present invention is defined as the shape when the molding area of the die is cut at right angles to its average plane (a smooth virtual surface viewed macroscopically by averaging minute irregularities). ) refers to the first minimum visible flow width when viewed from the surface side of the molding area at right angles to the average plane of the flow path through which the polymer can be discharged and flowed.

FIG. 4 shows a schematic enlarged view of an arbitrary cross section in the generalized molding region of the present invention. In this FIG. 4, the Ai and Ai+1 portions are thin.

In addition, the distance between the centers of each of the adjacent arbitrary strips Ai and Ai+1 is called the spacing distance Pi, and the average of Pi in all cross sections is defined as the average spacing distance.

The partition member of the spinneret used in the present invention is in a state in which heat is generated to melt the supplied powdered polymer as described above.

In order to generate heat from the partition member itself,
A method in which the partition member is heated by passing an electric current through it (current heating method), a method in which a high-frequency electric field is applied and heated by induction heating method, a method in which the partition member is made up of thin tubes and heating is performed by flowing a heating medium through the thin tubes (thermal fluid heating method) heating method) etc. are advantageously employed.

Materials that can be used in the current heating method and induction heating method include platinum, gold, silver, copper, titanium, vanadium,
Tungsten, iridium, molybdenum, palladium, iron, nickel, chrome, cobalt, lead,
Metals such as zinc, bismuth, tin, aluminum, stainless steel, nichrome, tantalum,
Alloys such as silver, phosphor bronze, and duralumin,
Inorganic compounds that mainly exhibit semiconductor properties such as graphite, silicone, germanium, selenium, tin oxide, indium oxide, iron oxide, nickel oxide, etc.; organic compounds that exhibit semiconductor properties such as polyacetylene and polyphelene, etc., 10 ^-7 to 10 ⁹ Advantageously, the spinneret is formed of a material having a resistivity on the order of Ωcm.

The spinnerets described in the accompanying drawings, FIGS. 1, 2 and 3 are all electrically conductive and suitable for the purpose of the present invention. Other examples include coating the surface of glass beads with silver to make them conductive by pressurizing contact, and evaporating metals such as aluminum onto ceramic fibers such as alumina and zirconia.
Examples include a pressure-molded conductive spinneret structure, a conductive mesh spinneret structure in which a porous ceramic plate is immersed and deposited in a graphite particle dispersion, and various other possible structures may be improved and implemented. Can be done.

The electrically conductive mesh-like spinneret obtained in this way usually has a voltage of 0.1 to several hundreds of V/cm in the case of the current heating method.
An electric field of 0.1 to several hundred A is applied, and a watt density of 0.1 to several thousand W/cm ³ is applied, but these values may vary depending on the purpose of use.

The conductive mesh spinneret for the current heating method is attached to the extruder, and should be installed in such a way that a desired current flows through the conductive mesh spinneret. The conductive mesh spinneret and the extruder may be insulated, or the extruder and the conductive mesh spinneret may be electrically connected so that the current flowing to the extruder and the current flowing to the conductive mesh spinneret are controlled. It is also possible to obtain the desired performance by allocating it to

As an insulating material for insulating the conductive mesh spinneret and the extruder, a combination of a general ceramic plate and an inorganic adhesive such as silica, alumina, or zirconia can be used.

On the other hand, when heating a conductive mesh-like spinneret as described above by a dielectric heating method, a coil is generally arranged approximately parallel to the spinneret, and a magnetic field approximately perpendicular to the spinneret is applied, and a magnetic field is applied on the spinneret surface. Eddy currents are generated and Joule heat is generated. If the heating frequency is selected to be high, the penetration of eddy current becomes shallow due to the skin effect, and local heating of only the surface can be performed.
Depending on the thermal properties of the aromatic polyamide polymer to be molded and the material and shape of the device, the optimum state can be obtained by appropriately combining the arrangement of the coils, the strength and frequency of the magnetic field.

The material of the spinneret that can be used in the dielectric heating method is generally a substance that causes dielectric loss, and it depends on the frequency of the applied electric field and the nature of the polymer to be formed.
Examples include ceramics with polar groups.

When heating such a dielectric mesh spinneret using a dielectric heating method, an electrode is usually arranged parallel or perpendicular to the surface of the spinneret, and an alternating electric field parallel or perpendicular to the surface of the spinneret is applied. Loss occurs and heat is generated.

The thin tubes used in the thermal fluid heating method are preferably of high thermal conductivity, such as aluminum, stainless steel, iron, copper, brass, silica, nickel, Inconel, tungsten, tantalum, molybdenum,
Materials such as rhenium, titanium, and niobium are used. The heat medium is selected to be compatible with the operating temperature and the thin tube, such as water, ammonia, methanol,
Acetone, Freon 11, Freon 21, Freon
113, _C6F4 , n-butane, n-pentane, n-heptane, benzene, toluene, Dowsome A, _Dowsome B, DC200, DC209, parachloroethylene,
Dimethyl sulfide, Monsanto CP-9, pyridine,
Monsanto CP-34, lithium, sodium, potassium, cesium, mercury, lead, indium, tin, etc. are used in fluid or gas form.

The width of the narrow thread of the mesh-like spinneret depends on its material and the heat transfer efficiency between the polymers, but is preferably in the range of 50 μm to 3 mm, preferably 100 μm to 1 mm. If the narrow strip is too narrow, it will be difficult for a high viscosity polymer to pass through, and if the narrow strip is too wide, the polymer will not be heated properly or unevenly, which is undesirable.

It is necessary for the polymer to pass through the narrow group of mesh-like spinnerets within a time period that does not cause the polymer to lose its ability to form a molded article. If the time for passing through the narrow group is too long, the ability to form a molded article will be lost, and if it is too short, the polymer cannot be heated to an appropriate temperature, so there is an optimum range of passing time. This range depends on the type of the polymer, the temperature and thickness of the mesh spinneret, the size of the slivers, the discharge rate, etc.

Next, a method of supplying the aromatic polyamide powder to the mesh spinneret and melt-spinning it in the present invention will be explained.

Aromatic polyamides are usually prepared using tetrahydrofuran/
It is prepared by an interfacial polymerization method in a system such as water or methyl ethyl ketone/water, or a melt polymerization method in a system using an aprotic polar solvent such as dimethylformamide, dimethylacetamide, or N-methylpyrrolidone.
The polymer is generally dissolved or present in fine powder form in these polymerization solvents. As a method for separating the polymer from the polymerization solvent, it is usually preferable to extract and remove the solvent by washing, and the solvent contained in the washing liquid is recovered by distillation, freeze separation, or a combination of these and extraction. The size and shape of the polymer powder are influenced by the temperature, shear rate, coagulation rate of the polymer, etc. when prepared by interfacial polymerization, and when prepared by solution polymerization, the size and shape of the polymer powder are It is influenced by the temperature, shear rate, coagulation rate of the polymer, etc. when adding the extraction washing liquid to the polymer solution prepared by the polymerization method. The average diameter of easily handled polymer powder is 1μ to 1000μ.

In the present invention, the powder of the polymer may be used as it is, or it may be compressed into an appropriate shape such as a rod.

As a device for feeding the solid polymer to the mesh spinneret, a screw or a plunger can be used in the case of a powder, and a plunger can be used in the case of a rod. It is preferable that the solid polymer is supplied by being pressed against the die with a certain pressure (~50 Kg/cm ² ). This not only makes heat transfer more efficient, but also causes melting to occur under pressure, resulting in the so-called pressurized defoaming effect. Defoaming is required in order to continuously discharge the melt from the discharge port. However, the length of the zone required for this defoaming may be very short. When producing fibers as shown in Example 1 below, the pressure was 50 Kg/cm ² and the length of the zone required for defoaming was 5 mm. It is more preferable that the atmosphere in the apparatus for supplying the solid polymer to the planar body be replaced with an inert gas such as nitrogen gas.

The aromatic polyamide polymer used in the present invention melts, albeit temporarily. The melting point can be measured by thermally analyzing the polymer using a means such as differential thermal analysis (DTA), differential calorimetry (DSC), or a Protester. The melting point and decomposition start point of this polymer are close to each other, and the two are usually observed to overlap in DTA and DSC in air, so in order to clearly determine the melting point, it is necessary to It is preferable to measure inside the room and then move the decomposition initiation point to a higher temperature.

For example, polymetaphenylene isophthalamide
When thermally analyzed by DTA in nitrogen at a heating rate of 10°C/min, a melting start point is observed at approximately 400°C. On the other hand, when the same polymer is examined by TG (thermogravimetric analysis) under the same conditions, a weight loss initiation point (almost the same as the decomposition initiation point) is observed at approximately 430°C. Since such polymers either melt temporarily or their melting point and decomposition start point are close to each other, they must be melt-molded quickly, which has not been possible using conventional methods.

In other words, when the temperature rises above the decomposition initiation point, the main chain of the polymer progresses, and at the same time, a complex reaction that usually involves crosslinking between the main chains occurs.
All of these reactions tend to cause the molding ability to be lost, and the smaller the amount that proceeds during molding, the better.

The ability to form a molded article as used in the present invention refers to performance when all of the following requirements (1) to (3) are satisfied.

(1) It must be possible to discharge from the discharge port referred to in the present invention.

(The viscosity of the polymer can be reduced to the viscosity necessary for passing through the discharge port.) For this purpose, there is an appropriate degree of polymerization range, for example, in the case of polymetaphenylene isophthalamide, as defined later.
It is preferable that the IV in NMP is 0.3 to 3.0.

(2) The polymer can be continuously discharged from the discharge port along the discharge direction.

(3) The mechanical strength of the discharged polymer continuum after cooling is within a practical range.

The range of specific physical property values for the requirements (1) to (3) above is that the viscosity in (1) is 100,000 poise or less, and the mechanical strength in (3) is a tensile strength of 0.5 g/de or more. It's amazing.

Generally, it is considered that the following qualitative equation holds true between the time for which the polymer is kept in a molten state and the amount of modification at which the ability to form a molded article is lost.

q/λ. | dT/dx | <t<m/K ₀ exp (-Ed/RT) t: Time to maintain the polymer in a molten state q: Amount of heat required for melting λ: Thermal conductivity T: Heating temperature | dT/dx｜: Heating temperature gradient Ed: Activation energy at which the ability to form a molded product is lost m: Amount of transformation at which the ability to form a molded product is lost R: Gas constant In other words, it is necessary to pass through the mesh-like spinneret within this time t. Conceivable.

For example, the polymer is polymetaphenylene isophthalamide, the mesh spinneret is a plain weave of 30 meshes, and the molten state retention time (t) is 0.5 to 200.
seconds, preferably in the range of 1 to 50 seconds.

In the present invention, the aromatic polyamide polymer extruded from the mesh spinneret is cooled and solidified by cooling gas or cooling liquid immediately after spinning, and is taken off at the same time as solidification.

The extremely thick aromatic polyamide fiber melt-spun as described above is subjected to stretching, heat treatment, etc.
The oriented crystallization of the fibers is increased. For the stretching and heat treatment, known methods for the aromatic polyamide fibers are applied. For example, the fibers are stretched in a high-temperature wet state such as hot water, boiling water, or high-temperature steam to advance the orientation of the fibers, and then stretched at a temperature above the glass transition point of the fibers (around 250 to 280°C, depending on the type of polymer). A method of dry heat stretching and heat treatment to advance the orientation and crystallization of the fibers; or a method of dry heat stretching and heat treatment without stretching in a wet state is applied. When drawing and heat treating the fibers using dry heat, it is preferable to carry out the stretching and heat treatment after removing most of the water contained in the fibers by preliminary drying.

One of the effects of the present invention is that it has been able to provide a novel, extremely thick aromatic polyamide fiber that has not been available until now.

In other words, the novel ultra-thick aromatic polyamide fiber of the present invention has a cross-sectional shape, size, distribution, and cross-sectional variation along the fiber axis within a certain range, and such fibers are different from those of conventionally known fibers. It is something that could not be obtained from any manufacturing means, and its structural properties also exhibit various interesting properties that could not be obtained from conventionally known products.

The cross-sectional shape, size, distribution thereof, and range of variation of the fiber cross-section along the machine axis direction are partially similar to natural bristles, so the ultra-thick aromatic polyamide fiber of the present invention It can be said that it is possible to provide heat-resistant, extremely thick fibers with properties similar to those of natural products.

Thus, the novel ultra-thick aromatic polyamide fiber of the present invention can be used in brush materials, brush materials, lightweight concrete reinforcement materials, heat-resistant net belts, etc.
In addition, it can be used as a material for extremely thick fiber products where conventional aromatic polyamide fibers cannot be used, particularly in fields where heat resistance is required.

The fibers of the present invention often develop a high degree of crimp upon heat treatment due to moderate irregularities in the fiber cross section and length direction and an anisotropic cooling effect provided during fiber formation, and this property can be applied to increase the intertwining of fibers.

The fibers of the present invention can also be easily applied to the above-mentioned parallel array sheets, orthogonal nonwoven fabrics made by orthogonally bonding them, random structure nonwoven fabrics randomized by applying electricity or air, artificial leather, etc. can.

Another major effect of the present invention is that it has provided a method for producing ultra-thick aromatic polyamide fibers having the various useful features described above by melt spinning. That is, according to the present invention, it has become possible to produce extremely thick aromatic polyamide fibers by a highly productive melt spinning method that does not require complicated steps such as solvent treatment.

In addition, conventional dry methods, which require solvent extraction,
In wet and semi-dry semi-wet spinning methods, solvent extraction is insufficient especially in the case of extremely thick fibers, making it impossible to obtain products with satisfactory mechanical properties and heat resistance. The present invention provides an extremely thick aromatic polyamide fiber having properties such as mechanical properties and heat resistance.

EXAMPLES Hereinafter, the present invention will be explained using specific examples, but these are not intended to limit the present invention in any way.

In addition, the intrinsic viscosity (IV) in the examples is based on the following formula.

IV=laηrel/0.5 (However, ηrel is the value obtained by dividing the viscosity of a 0.5 g/100 ml solution of the polymer in a capillary viscometer by the viscosity of the solvent determined using the same viscometer.) In the example, "parts" means "parts by weight"
means.

Example 1 Polymetaphenylene isophthalamide obtained by polymerizing metaphenylene diamine and isophthalic acid chloride at the tetrahydrofuran/water interface (IV measured in N-methylpyrrolidone (NMP) is 1.2
A dry polymer powder with an average particle size of 50 μm is pressed through a vertically installed plunger extruder (barrel inner diameter 10 mm, length 100 mm). Diameter 8
Wire mesh (stainless steel, wire diameter 0.34 mm, 30 mesh plain weave, void ratio 77%) with the non-discharge portion sealed with alumina-based inorganic adhesive so that
A current of about 3.5 W/cm ² is passed through the wire mesh, the polymer powder is melted at about 420°C, and the polymer powder is melted and flowed between the meshes (narrows) of the wire mesh and discharged.
Cooling air was blown at a speed of 1/2 m/sec towards the discharge side surface of the wire gauze to form a fibrous stream, which was drawn at 0.5 m/min. Very thick polymetaphenylene isophthalamide fibers consisting of square fibers were obtained.

The temperature of the barrel used was 340° C., the pressure of the plunger was 50 Kg/cm ² , the melting point of the polymer was 400° C., and the polymer was not melted inside the barrel.

The average strength, elongation, and initial Young's modulus of this fiber were 1.1 g/de, 35%, and 55 g/de, respectively. Also
CV(F) was 0.21, CV(A) was 0.25, and the average value of D/d was 1.4.

Then, this fiber was stretched approximately 20 times on a hot plate at 290℃, and the strength and initial Young's modulus of the yarn obtained were
2.3g/de, 15%, 70g/de, and CV(F) is
0.20, CV(A) was 0.25, and the average value of D/d was 1.4.

Example 2 Dry polymer powder of polymetaphenylene isophthalamide with an average particle size of 70 μm and having an IV of 0.7 as measured by NMP obtained by polymerization in the same manner as in Example 1 was placed vertically at 330°C. Screw extruder heated to (barrel inner diameter 25 mm, length 200 mm,
The screw is a screw with a small pitch interval for powder supply), and the thin plate attached to the bottom of the extruder is photo-etched into a die (made of stainless steel, 0.5 mm thick, the shape of the hole is shown in Figure 2). The porosity is 50%, the hole area is 5.1×10 ^-3 cm ² , and the molding area is 18 mm in diameter), and the die is supplied with approximately 7.0 W/ A current of cm ² is applied to melt the polymer powder at about 420°C, and it is melted and flowed through the hole (narrow) of the nozzle and discharged at the same time.
Cooling air at a speed of 0.5 m/sec was blown toward the outlet surface of the nozzle to form a fibrous stream, and the flow rate was 1.0 m/sec.
A very thick polymetaphenylene isophthalamide fiber having an average fineness of 390 denier and a cross-sectional area of about 3.2×10 ^-4 cm ² was obtained by taking the fiber in minutes. The average strength, elongation, and initial Young's modulus of this fiber are 1.3 g/de and 50, respectively.
%, 45 g/de. Also, CV(F) is 0.23, CV(A)
was 0.16, and the average value of D/d was 1.3.

Example 3 Polymethaxylylene isophthalamide (NMP) obtained by polymerizing metaxylylene diamine and isophthalic acid chloride at the tetrahydrofuran/water interface.
The average particle size of (IV measured in the medium is 0.7)
A 200 μm dry polymer powder is pressed using a plunger type extruder similar to that used in Example 1, and the part that is not discharged is coated with an alumina-based inorganic adhesive so that the molding area attached to the bottom of the extruder has a diameter of 6 mm. Sealed wire mesh (stainless steel, wire diameter
0.21 mm, 60 mesh plain weave, void ratio 65%), a current of about 4 W/cm ² was passed through the wire mesh, the polymer powder was melted, and the polymer powder was discharged from between the meshes (narrow) of the wire mesh. At the same time, cooling air was blown at a speed of about 1.0 m/sec toward the discharge side surface of the wire mesh to form a fibrous stream. Very thick polymethaxylylene isophthalamide fibers having an average side of about 95 μm were obtained. The average strength, elongation, and initial Young's modulus of this fiber are
It was 0.8g/de, 70%, and 30g/de. Also CV(F),
The average values of CV(A) and D/d are 0.18 and 0.19, respectively.
It was 1.3.

The temperature of the barrel is 250℃, the pressure of the plunger is 60Kg/ ^cm2 , and the melting point of the polymer is 380℃.
℃ and the polymer is not melted inside the barrel.

Example 4 42.5 parts of metaphenylene diamine, 42.5 parts of isophthalic acid chloride, and 15 parts of meta-aminobenzoic acid chloride hydrochloride were polymerized at the tetrahydrofuran/water interface (IV measured in NMP was 0.9). A dried (meta-phenylene diamine, isophthaloyl chloride and meta-aminobenzooyl chloride) copolymer powder with an average particle size of 100 μm was transferred using a screw type extruder heated to 320°C as in Example 2. It has a pattern similar to that shown in Figure 2 attached to the bottom of the extruder, the material is cast iron, the thickness is 3 mm, the porosity is 47%, and the minimum area of one hole viewed from the discharge surface is 3.1 mm ² An alternating magnetic field of 23.5KHz and 15W/cm ² is applied to the mouthpiece to generate eddy current on the surface of the mouthpiece and generate heat, melting the polymer powder and applying it to the fine diameter of the mouthpiece. The melt is flowed and discharged, and at the same time, cooling air is blown at a speed of about 20 m/sec toward the discharge side surface of the nozzle, and taken off at 0.5 m/min to obtain the average fineness (e).
obtained 4200 denier extra-thick fiber. The average strength, elongation, and initial Young's modulus of this fiber are each 0.5
g/de, 20%, and 25 g/de. Also CV(F),
The average values of CV(A) and D/d are 0.11 and 0.13, respectively.
It was 1.2.

Example 5 Polymetaphenylene isophthalamide with an IV of 1.0 as measured in NMP was made into particles with an average particle size of 100 μm, and the extrusion was carried out using a screw extruder heated to 320°C as in Example 2. A stainless steel pipe with an inner diameter of 0.5 mm and an outer diameter of 1.0 mm installed at the bottom of the machine is fed into a mesh-shaped mouthpiece with a 12-mesh plain weave with an emptyness ratio of 65%.
A tin liquid heated to 500℃ is poured into the pipe,
The nozzle is made to generate heat, the polymer powder is melted, and the polymer powder is melted and flowed into the nozzle and discharged, and at the same time 1.7
Cooling air is blown at a speed of m/sec towards the discharge side surface of the nozzle and taken off at a rate of 0.6 m/min to determine the average fineness.
We obtained extremely thick fibers of 6300 denier. The average strength, elongation, and initial Young's modulus of this fiber bundle are each 0.7 g/
de, 18%, and 32 g/de. Also CV(F), CV
(A), the average values of D/d were 0.11, 0.12, and 1.3, respectively.

Reference Example 1 20% by weight of polymetaphenylene isophthalamide with an IV of 1.0 measured in NMP
It was dissolved and extruded through a die with a pore diameter of 0.5 mm and 100 holes, solidified in a calcium chloride bath at 65°C, washed with water, and dried in a fixed length. However, the winding speed is 1.0m/min.
The draft ratio is 0.5. The average strength, elongation, and Young's modulus of the obtained fibers were 2100 de, 0.2 g/de, 15%,
It was 21g/de. Also, CV(F) and CV(A) are 0.03,
0.03, the cross section of the fiber had a pronounced skin-core structure, and as mentioned above, the strength was low and it was not a normal extremely thick fiber.

[Brief explanation of drawings]

FIGS. 1-a and 1-b show an example of a mesh-like spinneret used in the present invention, which is generally called a plain weave wire mesh. Figure 1-a is a plan view of the
FIG. 1-b is a cross-sectional view. Figure 2-a and Figure 2-b
is another example of a mesh-like spinneret used in the present invention, which is made by perforating a thin metal plate by photoetching. FIG. 2-a is a plan view thereof, and FIG. 2-b is a sectional view thereof. FIG. 3 is a cross-sectional view of a mesh-like spinneret in which two plain-woven wire meshes are laminated. FIGS. 1-b, 2-b, and 3 show the portion corresponding to the apparent total volume (Va) occupied under unit area of the mesh-like portion of the spinneret used in the present invention. FIG. 4 is a cross-sectional view of a mesh-like spinneret having a general shape used in the present invention.

Claims (1)

[Claims] 1. A fiber made of at least one type of aromatic polyamide, the average single fiber fineness (e) of which is 100 to 100.
Extra-thick aromatic polyamide fiber characterized by 40,000 denier. 2 In the aromatic polyamide fiber, (1) the fiber has irregular and periodic changes in the size of its cross-sectional area along its length, and (2) the intra-fiber cross-sectional area coefficient of variation [CV (F)] is 0.05 to 1.0
The ultra-thick aromatic polyamide fiber according to item 1, which is in the range of . 3 The aromatic polyamide has the following formula (), (),
() [In formulas (), () and (), () and (), if present, are present in substantially equimolar amounts, and the groups R ¹ , R ² and R ³ are the same or different. Indicates a divalent group, R ¹ , R ² and R ³
At least 50% by weight of the total of is aromatic groups. ] The ultra-thick aromatic polyamide fiber according to claim 1 or 2, which is a polymer consisting essentially of at least one repeating unit selected from the group consisting of: 4 In producing fibers from at least one kind of aromatic polyamide polymer, the following formula () α=Va−Vf/Va×100…() [where α is the number of fine particles in the spinneret] Va is the vacancy rate [%], Va is the apparent total volume occupied under unit area of the mesh-like part of the spinneret, and Vf is the mesh-like area surrounding the narrow area under the unit area of the mesh-like part of the spinneret. This is the total volume occupied by the member. ] Using a mesh-like spinneret having a large number of closely spaced threads with a void ratio of 25 to 90%,
The aromatic polyamide polymer powder is supplied to the surface of the spinneret opposite to the discharge surface, and the solid powder is supplied while supplying heat from the heat-generating partition member of the mesh spinneret. The melt is extruded through a number of narrow holes surrounded by the partition member, and at this time, cooling fluid is supplied to the melt discharge surface of the spinneret and its vicinity to cool the melt. Thin
The melt extruded through the molten polymer is taken up and solidified by converting the melt into a large number of separated fibrous rivulets within a time period during which the molten polymer substantially loses its ability to form a molded article. The cross-sectional area size changes irregularly and periodically along the length direction, and the intrafiber cross-sectional area coefficient of variation [CV(F)] is 0.05 to 1.0.
A method for producing ultra-thick aromatic polyamide fibers.