JPH045768B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to a novel flat yarn in which inorganic fine pieces are mixed with polymetaphenylene isophthalamide-based wholly aromatic polyamide, and a method for producing the same. b Prior art Polymetaphenylene isophthalamide-based wholly aromatic polyamide (hereinafter sometimes abbreviated as "PMIA") has a glass transition point of about 280°C, a melting point and a thermal decomposition point of about 420°C, which are almost the same, and a limit of It has an oxygen index of approximately 30, so it has excellent heat resistance and flame retardancy.
In addition, the rigidity of the molecule is also appropriate,
It is manufactured and sold in large quantities as fiber under names such as Nomex (DuPont) and Cornex (Teijin). These commercially available fibers are, for example,
No. 870, Special Patent No. 1987-50219, U.S. Patent No. 3360598
Wet method, dry method, or Special Publication No. 42-38612 as described in the specifications of
A dry jet-wet spinning method as described in No. 815 is also known, but in any case, it is produced by a so-called melt spinning method. The main reason why PMIA has no choice but to rely on melt spinning for fiberization is that it has a high melting point and is close to its thermal decomposition point, making melt spinning extremely difficult. Problems with the melt spinning method include high costs due to solvent recovery, investment in neutralization equipment, low productivity, etc., but there are several other points that cannot be overlooked. That is, the first is
It is extremely difficult to produce thick denier fibers (bristle) of 100 de (cross-sectional area approximately 0.01 mm ² ) or more. In the desolvation process after solution spinning, the solvent in the outer skin of the fiber generally escapes preferentially, so the outer skin begins to coagulate first, and as the fiber becomes thicker, the desolvation of the core gradually becomes delayed. Not only does the solvent process have to take an abnormally long time, making production difficult as a practical matter, but the difference in physical properties caused by the desolvation between the surface and the inside creates a large difference in the microstructure, resulting in an extreme skin-core structure. This is because it becomes unusable. On the other hand, the present inventor, together with other co-researchers, conducted various studies on how to produce bristles by melt-spinning wholly aromatic polyamide polymers, and succeeded in this. No. 58-109618, Japanese Patent Publication No. 1983
-109619 and JP-A-59-144607. The key point of the production method in the above proposal is that a substantially solid wholly aromatic polyamide is instantaneously melted in a thin mesh-like spinneret heated by electricity, and the wholly aromatic polyamide has substantially fiber-forming ability. In this method, the spinneret is discharged from a number of slits in the mesh-like spinneret within a period of time without losing the spinneret, and is immediately cooled and solidified while being forcibly taken off. As described in the above-mentioned publication, the bristles obtained as described above have irregular and periodic changes in cross-sectional area size along their length and fragrance, and have an intrafiber cross-sectional variation coefficient CV (F) is in the range of 0.05 to 1.0,
The cross-section of the fibers formed is generally non-circular. The above-mentioned bristles were found to be useful as a material for heat-resistant brushes, but in order to further expand the scope of their use, they developed bristles mixed with inorganic particles such as alumina and carborundum.
This was proposed in Publication No. 136829. The proposed bristles were found to be extremely useful as heat-resistant abrasive brushes due to their heat resistance and abrasive effect. It had the disadvantage of low elongation and easy breakage. In general, as a means to prevent a decrease in strength and elongation while maintaining a constant particle mixing ratio, it is effective to mix the particles not uniformly but to concentrate them at the outer periphery of the bristles or, conversely, at the center. It is known. However, in PMIA, the solution method
As mentioned above, it is extremely difficult to form bristles with a cross-sectional area of 0.01 mm ² or more, and also because the method of JP-A-58-136829 uses a mesh-like spinneret. It was not possible to produce such bristles. Therefore, the present invention was developed as a result of reviewing the molding method of PMIA bristles and conducting further intensive research.
In a major change of concept from the proposal in Publication No. 136829, a polymer layer (A
The inventors have invented a method for manufacturing a composite structure yarn in which layer B) and inorganic layers (layer B) made of a mixture of inorganic particles and the wholly aromatic polyamide are alternately arranged, and furthermore, this yarn is The present invention was arrived at after considering the above. c. Object of the Invention The object of the present invention is to provide a novel flattened entirely aromatic polyamide mixed with inorganic particles which has excellent mechanical properties. Another object of the present invention is to provide a wholly aromatic polyamide flat yarn that has excellent durability as well as heat resistance and abrasiveness. Still another object of the present invention is to provide a tape-shaped PMIA flat thread with added functions unique to inorganic particles (e.g., electrical conductivity, magnetism, high specific gravity, etc.) for use as various industrial materials. . Still another object of the present invention is to exhibit a structure in which a polymer layer (layer A) mainly composed of PMIA and an inorganic layer (layer B) composed of a random mixture of inorganic particles and PMIA are arranged side-by-side. The object of the present invention is to provide a PMIA flat yarn having a high mixing ratio of inorganic particles in layer B of 30% by weight or more. Still another object of the present invention is to provide a new and useful method for producing the above-mentioned bristles. d Structure of the Invention According to the research results of the present inventor, the object of the present invention is to provide a polymer layer (A layer) and an inorganic layer (layer B) consisting of a mixture of inorganic particles and the wholly aromatic polyamide, and the flatness is defined by the following formulas () to () (). (FL) has a flat cross section of at least 1.3, FL = Width of flat cross section (w) / Thickness of flat cross section (
t) () The thickness (a) of the flat cross section is in the range of 0.05 to 3 mm, and () the polymer layer (layer A) and the inorganic layer (layer B) are in the thickness direction of the flat cross section. This is achieved by alternately arranged wholly aromatic polyamide flat yarns mixed with inorganic particles, which are characterized by satisfying the following conditions. Still another object of the present invention is to provide the polymer layer (A
layer) and the inorganic layer (layer B) are achieved by the above-described wholly aromatic polyamide flat yarn having an area ratio in the range of 20:80 to 95:5 in the flat cross section. Yet another object of the invention is to provide 85 total repeating units.
Formed from a polymer layer (layer A) mainly composed of a wholly aromatic polyamide whose mole% or more is metaphenylene isophthalamide units, and an inorganic layer (layer B) composed of a mixture of inorganic particles and the aromatic polyamide. In order to obtain an inorganic fragment-mixed wholly aromatic polyamide flat yarn having a structure in which the polymer layer (layer A) and the inorganic layer (layer B) are alternately laminated in the yarn cross section from the composite molded product. is achieved by a method for producing wholly aromatic polyamide flat yarn, which is characterized by satisfying the following conditions (a) to (e). (a) The composite molded product has a void ratio (ε%) of 5% or less, and has a shape with a uniform cross section in at least one direction, and the composite molded product has a uniform cross section. The polymer layer (A
layer) and the inorganic layer (layer B) are arranged side-by-side, (b) the composite molding substantially retains its shape in a direction perpendicular to a defined uniform cross-section of the composite molding; (c) Then, the composite molded product is placed in a heating die having a narrowed passage formed by a flat nozzle having an flatness of at least 1.3 at least at the end thereof. (d) In the heating die, the composite molded product is rapidly heated in the narrowing passage until it reaches a softening temperature (Ts°C) that satisfies the following formula, and is discharged from the flat nozzle. It is taken off to form an undrawn flat thread. (Tg+40℃)≦Ts≦(Tm−20℃) (However, Tg and Tm mean the glass transition point (℃) and melting point (℃), respectively, of the fully aromatic polyamide.) (e) Furthermore, if necessary , the undrawn flat yarn is led to a drawing zone with a temperature (Td) within a range that satisfies the following formula, and is dry drawn at least 1.3 times. (Tg+20°C)≦Td≦(Tg−40°C) The polymetaphenylene isophthalamide-based wholly aromatic polyamide (PMIA) in the present invention is a homogeneous polyamide in which 85 mol% or more of the total repeating units are metaphenylene isophthalamide units. Polyamide or copolyamide. This PMIA is polycondensed using metaphenylene diamine or other aromatic diamine as the amine component, and isophthalic acid or other aromatic dibasic acid or its derivative as the acid component. be. The specific method for producing PMIA of the present invention is
The interfacial polymerization method described in Publication No. 10863 is preferred. This is because, according to this method, porous agglomerated particles are formed which are extremely suitable for molding a molded article that is a raw material for producing the bristles of the present invention. Inorganic particles used in the present invention include, for example, calcium carbide, titanium oxide, kaolin, clay, talc, diatomaceous earth, potassium titanate, feldspar, mica, glass powder, graphite, carbon black, molybdenum disulfide, metal powder ( For example, copper powder, aluminum powder, iron powder, chromium powder, nickel powder), γ
=Fe ₂ O ₃ , silicon carbide, alumina, zeolite, ceramic materials for sintering, etc. Suitable inorganic particles are selected depending on the intended use of the bristles of the present invention. For example, when used in polishing brushes, hard inorganic pieces such as silicon carbide and fused alumina are preferably used. The shape of the inorganic pieces used in the present invention may be spherical, polyhedral, acicular or irregular.
Preferably, the particle size is such that it passes through a sieve of at least 20 mesh, more preferably a particle size that passes through a sieve of 500 mesh. However, even if the particles are apparently large, they may be pulverized to the above-mentioned mesh size during the mixing process with the aromatic polyamide powder. The maximum particle size is usually around 50,000 mesh. The minimum cross-sectional area of inorganic particles having a needle-like or elongated shape (aspaku ratio of about 5 or more) is 1 mm ² to 2.5 × 10 ^-7 mm ² , preferably 2.5 × 10 ^-3 mm ²
~ 2.5 x 10 ^-7 mm ² and the longest strip length is 5 mm ~ 0.0005 mm, preferably 0.25 mm
It is sufficient if it is in the range of ~0.0005mm. The PMIA flat thread of the present invention has a flat cross section with a flatness (FL) defined by the following formula of at least 1.3. FL = Width of flat section (w) / Thickness of flat section (
t) Here, the thickness (t) of the flat cross section is defined as two parallel straight lines Lt circumscribing the cross section perpendicular to the length direction of the PMIA flat thread (this is simply referred to as the flat cross section) as illustrated in Fig. 1. , L't, the one with the shortest interval is adopted and defined by the interval t. In addition, the width (w) of the flat cross section is defined as two parallel straight lines (Lw,
L′w) is defined as the interval w. PMIA flat yarn with a flatness of less than 1.3 has little flattening effect on bending fatigue resistance, does not exhibit any noteworthy characteristics as a brush material, and cannot be expected to be used as a tape-shaped flat yarn. The flatness (FL) suitable for brush material is 2~
It is 5. In addition, when used as a tape for various industrial materials, the flatness (FL) is preferably about 20 to 500. In this case, the flat surface (Lt, L't side surface) is substantially parallel and smooth. This is very important.
Such a tape-shaped flat thread was first formed by the method of the present invention as described below. The thickness (t) of the flat cross-section yarn of the present invention is 0.05 to 3 mm
within the range of A flat thread with a thickness of less than 0.05 mm is too soft and unsuitable as a brush material, and if it is simply thick, it is not impossible to manufacture it by a solution method. Flat threads with a thickness (t) exceeding 3 mm are unsuitable as brush materials because they are too thick and break easily, but if the thread is simply thick, it is not impossible to manufacture it by compression molding. . The thickness (t) of flat thread suitable as a brush material is
In the range of 0.1 to 1 mm, more preferably 0.2 to 0.5
It is in the range of mm. When used as a tape-like flat thread, the thickness is preferably in the range of 0.05 to 0.5 mm. Further, when used as a plastic molding material, a thickness in the range of 0.5 mm to 2 mm is suitable. The bristles of the present invention have a polymer layer mainly composed of PMIA (A
It exhibits a composite structure in which layer B) and an inorganic layer (layer B) made of a random mixture of inorganic particles and the PMIA are alternately arranged in the thickness direction of the flat cross section. FIGS. 2 to 4 are cross-sectional views of flat threads schematically showing typical examples of this composite structure. Figure 2~
Which of the structures shown in Fig. 4 is adopted differs depending on the purpose, but the features of the present invention can be clearly demonstrated by the sandwich structure shown in Fig. 3 or the multilayer structure shown in Fig. 4. There are many. For example, in the case of heat-resistant and durable abrasive flat threads, which is one of the objects of the present invention, a random mixture of abrasive inorganic particles such as alumina or carbon random and PMIA is shown in Fig. 3 or 4. A structure in which an inorganic layer (layer B) consisting of PMIA is sandwiched between a polymer layer (layer A) consisting of PMIA is desirable. In other words, one of the advantages of flat abrasive threads with such a structure is that the surface exposure of the inorganic layer is small, so that the abrasive agent (inorganic particles) does not fall off from the sides, which has no direct effect on the abrasive action. This is extremely rare. This effect can be cited as a great advantage not only when the flat thread is used as an abrasive brush, but also during the packaging process and transportation process of the product. Another advantage of the flat threads of the present invention is that they
Compared to the simple random structure of PMIA, it has greater tensile strength and bending durability. In other words, since wholly aromatic polyamides have a molecular structure with a hard skeleton, the transition itself is generally hard and tends to be brittle.
If inorganic particles are randomly mixed into such PMIA, this tendency will further increase, and even external strain that is not very large will easily destroy it. In particular, as a brush material, it requires considerable bending stiffness, so it needs to be quite thick, and the distortion of the surface part during bending deformation is quite large, so if it is a simple random structure, it will break easily. It is. This phenomenon becomes more significant as the mixing ratio of inorganic particles increases. However, in the case of the flat yarn in the shape of a sand German trench as shown in FIG. , the strain generated in layer B, which exists in the center and is thin, is extremely small, and therefore becomes difficult to break. The polymer layer (A layer) and the inorganic layer (B layer) in the present invention
Regarding the total number of layers, three layers as shown in FIG. 3 is desirable from the viewpoint of bending durability, but if other functions are important, two or four layers may be more useful. For example, when it is desired to expose an inorganic layer on the surface of the flat thread, two layers as shown in FIG. 2 are preferable. Furthermore, when it is desired to impart electrical or magnetic functions to the flat yarn, it has been found that there are cases in which about seven layers as shown in FIG. 4 are more useful. However, if the number of layers is increased unnecessarily, not only will molding of the molded product be complicated, but if the number of layers becomes 10 or more, there will be a limit to the effect of multilayering. According to the present invention, the content ratio of inorganic particles in the B layer of the flat yarn can be changed arbitrarily, but the characteristics of the flat yarn of the present invention are more fully exhibited at a high mixing ratio of 30 to 95% (by weight). be done. It has been demonstrated that such a high mixing ratio is possible for the first time by the novel method of the present invention. Furthermore, according to the method of the present invention, the area ratio of layer A and layer B in a cross section perpendicular to the longitudinal direction of the flat yarn can be changed to an arbitrary ratio;
It is even more effective in the 95:5 ratio. As shown in FIG. 5, the composite molded product used in the method of the present invention has a shape with a uniform cross section in at least one direction (the Y direction in the drawing) and a porosity (ε ratio) of 5. % or less. The porosity (ε ratio) here refers to the apparent volume of the molded product.
Va is defined by the following formula, where Vr is the true volume of the PMIA component and inorganic chip component that make up the molded product. ε=Va−Vr/Va×100(%) In order to produce the flat yarn of the present invention, ε must be 5%.
Hereinafter, preferably 1% or less of the molded product should be used as a raw material. If a molded product with ε exceeding 5% is used, a large number of gases will be mixed into the flat yarn during the manufacturing process, and the mechanical properties of the obtained flat yarn will deteriorate, making it impossible to achieve the object of the present invention. Although the method for producing the composite molded article is not specified, it is preferable to compression mold the PMIA using porous aggregated particulate powder by interfacial polymerization. Compression molding conditions vary depending on the shape of the molded product, but the glass transition point (Tg℃) of PMIA
It should be carried out at a temperature above the melting point and below a pressure of 20 to 1000 kg/cm ² . The uniform cross section of the composite molded article is preferably rectangular as shown in FIG. Moreover, since the molded products have a finite length except in special cases, the uniform cross-sectional shape and area of the plurality of molded products as raw materials must be substantially the same. A plate-shaped composite molded product as shown in FIG. 5 can be manufactured using a compression molding machine as shown in FIG. 6 in the following manner. First, PMIA powder (A) and inorganic particles are used as raw materials.
Prepare PMIA mixed powder ( ) (B), preferably preheat the powder to about 200°C, and then add the first A component ( A-1) is fed into a compression molding machine in which the upper heating plate 2 slides toward the back of the drawing to open the top, and then the B component and then the second A component (A
-2). Next, the heating plate 2 is slid toward the front of the drawing, the lid is closed, and the piston 7 of the hydraulic cylinder 8 is operated upward to gradually increase the pressure. The outer walls of this compression molding machine, that is, the upper heating plate 2, the heating frame 3, and the lower heating plate 4, all have heaters built in, and are controlled at 300 to 350°C. Gradually the pressure continues to rise until the pressure reaches 1
When reaching ~20 Kg/cm ² , preferably 3-10 Kg/cm ² , the operation of the piston is temporarily stopped. The compression pressure begins to decrease at the same time as the piston stops, but when the pressure decreases to 1/10 or less, preferably to substantially 0, the piston is operated again to start increasing the pressure. This 1 at the stage when the compression pressure reaches 1 to 20Kg/cm ²
The time-stopping process is extremely important in performing the roles of heat transfer to the interior of the PMIA powder aggregate, uniform moisture containment within the PMIA polymer, and removal of air and excess moisture. This temporary stopping process is required at least once, preferably twice, and more preferably from 3 to 7 times. In other words, when the pressure becomes substantially 0 in the first 1-pause process, the pressure increase is started again, and when the pressure reaches 1 to 20 kg/cm ² , a second 1-pause process is performed, and the pressure becomes substantially 0. When it reaches 0, start increasing the pressure again. After completing the above pressure raising/lowering operation, the final pressure is increased to at least 30 kg/cm ² , and if necessary, this state is maintained for a certain period of time to ensure uniform density, and compression molding is completed. To take out the molded product, in the case of the molding machine shown in Figure 5,
Slide the upper heating plate 2 toward the back of the drawing to release the upper part, and then operate the piston 7 upward.
This is done by extruding the PMIA molded product to the outside. If the PMIA molded product sticks to the inner wall of the molding machine, it may be difficult to remove it, so it is desirable to take measures to release it from the mold, such as treating the inner wall of the molding machine with fluorine resin. The molded product thus obtained has a shape with a uniform cross section in at least one direction (Z direction) as shown in FIG. The structure is arranged side by side. FIG. 7 is a schematic diagram of an apparatus for producing flat yarn of the present invention using the plate-shaped molded product of FIG. 4 as an intermediate raw material. In FIG. 7, a plate-shaped molded product 10 as shown in FIG.
is the vertical direction (Z direction) of a defined uniform cross section
A large number of slides are arranged facing upward on the slide 20 as shown in the figure. The molded products 10 arranged in this way are
A push roller group 40 (three pairs of rollers in the drawing) is sequentially supplied downward along the guide wall 30.
, and is forcibly pushed into the preheating zone (Zp) while being held between rollers. At this time, it is necessary that the preheating zone has a passage that allows it to move in the vertical direction (Z direction) of the predetermined uniform cross section of the molded product 1 while substantially maintaining its shape, as shown in FIG. The passage of the apparatus is formed by a preheating box 50 having a similar cross-sectional space slightly larger than the defined uniform cross section (a x b) of the molded product. A heater 50' is embedded in the wall of this preheating box to accurately control the temperature of the passage. This passage does not necessarily have to be box-shaped as shown in FIG. 7, but may be regulated so that the molded product within the preheating zone always moves accurately along a fixed path. For example, even if the boxes have a similar box shape, the inner wall may have a corrugated shape. In the preheating zone formed by such a preheating box 50, the PMIA molded product is preheated while being gradually preheated to a preheating temperature (Tp°C) not exceeding 20°C higher than the glass transition point (Tg°C) of PMIA. It is moved to the end of the zone (Zp). This preheating temperature (Tp°C) should be controlled by measuring the internal temperature of the PMIA molded product. It can be controlled indirectly by controlling Tp. The preferred preheating temperature (Tp) should be the maximum temperature at which the molding in the preheating zone remains substantially unchanged in cross section even with high indentation pressures. If Tp is too high, the molded product in the preheating zone will soften due to the heat, greatly changing its cross-sectional form, and may stick to the inner wall of the preheating box or buckle, causing it to become clogged in the passage. If Tp is too low, the temperature must be raised too quickly in the next softening zone, resulting in uneven heating. Appropriate ranges for the preheating temperature Tp and the softening temperature Ts in the next step were found by examining in detail the various behaviors of the PMIA molded product due to thermal changes. For example, according to differential thermal analysis (DTA) and differential scanning calorimetry (DSC), the glass transition temperature (Tg)
You can know the temperature and melting point (Tm). DTA and
Since the Tg and Tm obtained by DSC may differ slightly depending on the measurement conditions, in the present invention, the Tg and Tm obtained by DSC are
^Tg
Read Tg ^-, define the midpoint as Tg, and define the endothermic peak in the melting temperature region (around 420℃).
Established Tm. In addition, the thermal decomposition point was determined from thermogravimetric analysis (TGA), and it was found that for PMIA, it is almost the same as Tm. A detailed examination of the TGA curve in air at a heating rate of 10°C/mm shows that at such a slow heating rate, there is a gradual weight loss trend from around 380°C. Therefore, it can be seen that it is not preferable to maintain this temperature state for a long time. In addition, dynamic elasticity measurement equipment (mentioned above) and thermomechanical analysis equipment (for example, Rigaku Denki's Thermoflex
According to the TMA device, it is possible to obtain the elongation (contraction) curve under a constant load for a sample piece of a PMIA molded product.The response of the mechanical properties of PMIA due to thermal changes can be determined by measuring the elongation (contraction) curve under a constant load. According to these measurement results, the elastic modulus begins to decrease significantly from about (Tg - 10°C), but up to about (Tg + 20°C), the viscous resistance is strong and it does not change much against external force. However, from about (Tg + 40°C) it begins to soften extremely rapidly and becomes fluid. The inventor calls this temperature the softening point of PMIA. Based on the above basic study results, PMIA
According to the results of indentation experiments with various preheating temperatures Tp for molded products, when the preheating temperature exceeds Tg + 20°C, the minimum pressure required to extrude PMIA (approx.
kg/cm ² ), the molded product is compressively deformed in the preheating zone, and the cross section of the molded product expands or buckles.
It sticks to the inner wall of the passage in the preheating zone, making it difficult to move smoothly in the passage. When setting the preheating temperature specifically, it is necessary to consider the pressure required to extrude softened PMIA from the flat cross-section nozzle. This pressure varies depending on various factors such as the structure of the softening zone and the softening temperature, but according to the inventor's experimental results, it is between 20Kg/cm ² and 1000.
Kg/cm ² , and the required pressure can be obtained by increasing the number of push roller groups 40. The basic role of the molded product in the preheating zone is to act as a flange for extruding the softened PMIA through a flat cross-section nozzle, so it is important that it substantially maintain its shape. Therefore, during high pressure extrusion,
The temperature at which the elastic modulus begins to decrease significantly (Tg−
(10℃) or below. However, if the preheating temperature is set too low, it becomes difficult to raise the temperature in the softening zone, making it difficult to increase the extrusion speed. The preferred range of preheating temperature is (Tg-30℃) to (Tg-
10℃). The length Zp of the preheating zone in the present invention is long enough to raise the temperature inside the molded product to the above preheating temperature. Therefore, if the temperature of the preheating box is set to Tp, the temperature of the molded product moving at a constant speed in the preheating zone will reach Tp in the middle of the preheating zone, and while maintaining this temperature, it will reach Tp at the end of the preheating zone. Move up to. The terminus of the preheating zone here refers to a location within about 10 mm from the entrance of the heating die 70 (softening zone) in the next step.
Ideally, the preheating temperature Tp should be maintained at a temperature not exceeding (Tg + 20°C) until the complete end of the preheating zone, but approximately 10°C up to the entrance of the softening zone.
If it is within mm, it is okay to exceed it slightly due to heat conduction. However, the preheating temperature Tp should be designed so that it does not exceed (Tg + 20℃) as far as possible just before the softening zone.According to the study results of the present inventors, firstly, the preheating temperature should be set within the above preferable range (Tg - 30℃). ℃) to (Tg - 10℃).Secondly, the boundary between the preheating zone and softening zone should be insulated with a heat insulating material as shown in Figure 7-60.Thirdly, the heat conduction from the heating nozzle should be minimized. Three points are effective. Now, the molded product preheated to the preheating temperature Tp as described above is press-fitted into the softening zone formed by the heating die shown in FIG. This softening zone is a softening extrusion of at least 3 mm in length with a narrowing channel formed at least at the distal end by a flat-section nozzle. The role of this softening zone is primarily the preheated
The process involves rapidly heating the PMIA molded product to a softening temperature Ts to soften it.Secondly, during the thinning process while softening, the joints of the PMIA molded product are crimped and connected.
The third purpose is to convert the continuous softened product into a continuous softened product, and the third purpose is to uniformly discharge the continuous softened product from a flat cross-section nozzle. Although various measures are required to effectively fulfill the above-mentioned role, one example is shown in FIG. 8, which is an enlarged view of the vicinity of the heating nozzle 70 in FIG. 7. That is, the molded product preheated to Tp in the preheating zone is press-fitted into a heating die 70 having an inlet with a V-shaped cross section as shown in FIG. A heater 70' is installed in the heating mouthpiece 70, and the press-fitted composite molded product 10 comes into contact with the inner wall of the inlet heated by this heater and is softened from the surface, while the A layer and B layer are softened. While maintaining the side-by-side structure of
(Tm - 20°C), and is subdivided by a plurality of flat cross-section nozzles N arranged close to each other in the direction perpendicular to the drawing, and extruded as flat cross-section filaments. At this time, the set temperature of the heating die is naturally set higher than Ts, but the degree depends on the moving speed of the molded product. Incidentally, an enlarged bottom view of the vicinity of the flat cross-section nozzle portion (N) of the base 70 shown in FIG. 8 is shown in FIG. 9.
In Figure 9, nozzle pressure (T) and width (W)
may be set appropriately according to the thickness (t) and width (w) of the flat yarn to be manufactured, but T and W applied to the flat yarn of the present invention are T = 0.1 to 6 mm, W = 0.5
A range of ~100 mm is preferred, and the flatness T/W of the flat cross section should be at least 1.3. The arrangement and ratio of layer A and layer B in the cross section of the PMIA composite extruded from such a die are substantially the same as in the original composite molded product. That is, the thicknesses of layers A and B are only compressed by the proportion that the thickness a of the molded product is compressed to the thickness (t) of the flat nozzle. Mixed inorganic particles discharged from flat cross-section nozzle N
Many flat cross-section trickles of PMIA
It is discharged into a heat retention zone with a length Zk consisting of 0, and is forcibly taken up by a take-up roller 90 at a draft ratio of at least 1.2 times. At this time, in the heat retention zone, the temperature near the outlet of the orifice (Tk°C) should be maintained within the range of TgTk (Tm - 20°C). Here, the temperature near the nozzle discharge port refers to the space temperature at a location 3 mm to 10 mm away from the nozzle discharge port. If Tk is below the glass transition point Tg of PMIA, uneven discharge may occur due to cooling of the nozzle surface, or draft may not rise due to rapid cooling, and unevenness is likely to occur. The preferred range of Tk is (Tg+50℃)Tk
(Tm - 50°C), which is preferably set to be approximately equal to the softening temperature Ts in the softening zone. The wholly aromatic polyamide bristles 10' mixed with inorganic particles and exhibiting a side-by-side structure taken by the take-up roller 90 may be used as a product as is, but it is recommended to stretch it at a temperature near Tg to increase the strength. I can do it. The flat cross-section filaments of the PMIA composite discharged from the flat cross-section nozzle are at least 1.2 times thicker in order to prevent adhesion between adjacent filaments and to give a slight molecular orientation to facilitate stretching in the heat retention zone. It has a higher tensile strength than draft, and in order to further increase the strength and elongation, it is stretched at least 1.3 times in the stretching process. The flat thread of the present invention using alumina, carborundum, etc. as inorganic particles is used as a brush material for a channel brush as shown in FIG. 10, and is processed into a brush roll and utilized as an abrasive brush.
In this case, in order to improve the bending fatigue resistance of the PMIA polymer layer (layer A),
Immediately after the zero stretching, a stretching plate and a stretching roller should be installed to create a stretching zone for dry stretching. The stretching temperature Td in the stretching zone is Tg−20℃
It is necessary to carry out dry stretching at a stretching ratio of at least 1.3 times at a temperature in the range of TdTg + 40°C. When drawing, it is important that the flat yarn reaches the desired drawing temperature as quickly and uniformly as possible.
Since the plurality of flat yarns spun from the die shown in FIG. 8 are arranged in one line, they uniformly contact the drawing plate, which is advantageous. The heating method for the stretching zone may be a non-contact box type in addition to such a heating plate. In any case, since it is necessary to uniformly heat the flat yarn to a predetermined drawing temperature, it is necessary to make the length of the heating zone sufficiently long. It is undesirable to create a large temperature difference between the device and the flat surface. When the stretching temperature is below Tg-20°C, PMIA flat yarns that do not contain an aprotic polar solvent are difficult to undergo large deformations, and it is difficult to stretch them by a factor of 1.3 or more. On the other hand, if the temperature is higher than Tg + 40°C, PMIA tends to flow easily and not only tends to cause troubles such as sticking to the stretched plate or cutting under its own weight, but it is also undesirable because it does not become oriented very much and instead advances in the direction of crystallization. More preferable stretching conditions for producing flat yarn with excellent bending fatigue resistance are such that the stretching temperature Td is (Tg−
10℃) Td (Tg + 20℃), stretching ratio
It is 1.3 times or more, especially in the range of 1.5 times to 3.0 times. In the case of PMIA flat yarns that do not contain aprotic polar solvents, it is extremely important to carry out the process from spinning to drawing continuously. For example, if an undrawn yarn with PMIA bristles is left in the air, it will absorb moisture and have a moisture content of about 7%, but if it is rapidly heated to the drawing temperature while still containing this moisture, it may foam and become difficult to draw. However, in the present invention, which involves continuous spinning and drawing, there is no such concern at all. e Examples Example 1 A powder of porous aggregated particles with an average particle diameter of 50 μm of polymetaphenylene isophthalamide obtained by polymerizing metaphenylene diamine and isophthalic acid chloride at the tetrahydrofuran/water interface was used as a polymer raw material. It was adopted as This PMIA powder (intrinsic viscosity measured in n-methylpyrrolidone is 1.35, Tg and Tm measured by DSC are 277°C and 423°C, respectively)
100% (component A) and white alumina (Fujimi Abrasives Industry KK) with an average particle size of 34μ is added to this powder.
Prepare 60% mixed inorganic fine particles (component B) and use the compression molding machine shown in Figure 6 to mold A-1 and A-2.
40g of each component and 35g of component B were laminated as shown in Figure 6, and compression molded at 320℃ and 100Kg/ ^cm2 pressure to form a plate-shaped composite molded product as shown in Figure 4 (a = 8mm, b = c
= 100 mm, ε = 0.1%) were manufactured in large numbers. Next, using this composite molded product as a raw material, bristles were manufactured using the apparatus shown in FIG. 7 under the conditions shown in Table 1. The physical properties of the obtained bristles are shown in Table 2.

【table】

[Table] A channel brush as shown in FIG. 10 was prepared using the above-mentioned flat yarn as a brush material, and this was wound around the outer periphery of a roller to make an abrasive brush roll. This research brush roll is used for polishing the superheating line of steel manufacturing,
When used for cleaning, it was found that it was extremely heat resistant compared to conventionally used abrasive-mixed nylon bristle brushes, so it not only withstood long-term use, but also had the effect of alleviating the cooling of overheated lines.
It has become clear that this contributes to energy saving. It has also been revealed that the polishing effect is extremely large, with the B layer constantly protruding in the shape of a mountain at the tip of the flat thread due to the difference in wear between the A layer and the B layer. Example 2 The same PMIA powder (component A) as in Example 1 and strontium ferrite powder 70 with an average particle size of 20μ
% random mixed powder (component B) was prepared, and using the compression molding machine shown in Fig. 6, 40 g each of the A-1 component and A-2 component and 30 g of the B component were layered and compressed as shown in Fig. 6. By molding, a large number of plate-shaped composite molded products as shown in FIG. 5 were manufactured. Next, using this composite molded product as a raw material, tape-shaped flat threads were manufactured using the apparatus shown in FIG. 7 and under the conditions shown in Table 3. The cross-sectional form of the obtained bristles was as shown in FIG. 3, and the physical properties were as shown in Table 4. Next, thread this flat thread in the direction parallel to layers A and B.
A tape-shaped magnetic flat thread was prepared by magnetizing it so as to polarize the pole and the south pole. This flat thread not only has better thermal deformability at temperatures above Tg than the random flat thread of strontium ferrite, but also exhibited stronger magnetism than expected, probably due to the high density effect and flattening effect of strontium ferrite. This magnetic flat thread has excellent heat resistance and thermal deformability, so it has been processed into various forms as a heat-resistant magnetic plastic material and used in various industrial materials.

【table】

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a diagram showing a method for measuring the thickness (t), width (w), and flatness (FL) of a wholly aromatic polyamide flat yarn mixed with inorganic particles of the present invention. Figure 2~
FIG. 4 is a diagram schematically showing a typical example of the cross-sectional structure of the wholly aromatic polyamide flat thread mixed with inorganic particles of the present invention. FIG. 5 is an example of a plate-shaped composite molded product used as an intermediate raw material in the bristle manufacturing method of the present invention. FIG. 6 is a sectional view of a compression molding machine for producing the plate-like composite molded product shown in FIG. 5. FIG. 7 is a schematic diagram of an apparatus for producing the flat yarn of the present invention using the plate-like composite molded product of FIG. 5 as an intermediate raw material. FIG. 8 is an enlarged view of the vicinity of the heating nozzle 70 in FIG. 7. FIG. 9 is an enlarged bottom view of the vicinity of the flat cross-section nozzle portion (N) of the base 70 of FIG. 8. FIG. 10 is a sketch showing a part of a channel brush, which is an example of an abrasive brush using flat threads of the present invention.

Claims (1)

[Scope of Claims] 1. A polymer layer (layer A) mainly composed of a wholly aromatic polyamide in which 85 mol% or more of the total repeating units are metaphenylene isophthalamide units, an inorganic fragment, and the wholly aromatic polyamide. It is a flat thread formed from an inorganic layer (layer B) consisting of a mixture of
It has a flat cross section with a flatness (FL) defined by the following formula of at least 1.3, FL = Width of flat cross section (w) / Thickness of flat cross section (
t) () The thickness (a) of the flat cross section is in the range of 0.05 to 3 mm, and () the polymer layer (layer A) and the inorganic layer (layer B) are in the thickness direction of the flat cross section. 1. A wholly aromatic polyamide flat yarn mixed with inorganic fine pieces, which is arranged alternately and satisfies the following conditions. 2 The polymer layer (A layer) and the inorganic layer (B layer) have an area ratio of 20:80 to 20:80 in the flat cross section.
The wholly aromatic polyamide flat yarn according to item 1, having a ratio of 95:5. 3 The inorganic layer (layer B) is a first layer in which the content of inorganic particles in the layer is in the range of 30 to 95% by weight.
The wholly aromatic polyamide flat yarn described in 2. 4. The wholly aromatic polyamide flat thread according to item 1, wherein the polymer layer (layer A) and the inorganic layer (layer B) are formed of 2 to 5 layers in total in the flat cross section. 5. A polymer layer (layer A) mainly composed of a wholly aromatic polyamide in which 85 mol% or more of the total repeating units are metaphenylene isophthalamide units, and an inorganic layer (layer A) composed of a mixture of inorganic particles and the aromatic polyamide. From the composite molded product formed from layer B),
In order to obtain an inorganic fragment-mixed wholly aromatic polyamide flat yarn having a structure in which the polymer layer (layer A) and the inorganic layer (layer B) are alternately laminated in the yarn cross section,
A method for producing wholly aromatic polyamide flat yarn, characterized by satisfying the following conditions (a) to (e). (a) The composite molded product has a void ratio (ε%) of 5% or less, and has a shape with a uniform cross section in at least one direction, and the composite molded product has a uniform cross section. The polymer layer (A
layer) and the inorganic layer (layer B) are arranged side-by-side; (c) the composite molding is then heated so that at least the distal end thereof has a narrowed passage constituted by a flat cross-section nozzle with a flatness of at least 1.3; (d) In the heating cap, the composite molded product is rapidly heated in the narrowing passage until it reaches a softening temperature (Ts°C) that satisfies the following formula, and is discharged from the flat nozzle. (Tg+40℃)≦Ts≦(Tm−20℃) [However, Tg and Tm are the glass transition point (℃) and melting point (℃) of the fully aromatic polyamide, respectively. means. (e) Further, if necessary, the undrawn flat yarn is led to a drawing zone with a temperature (Td) within a range that satisfies the following formula, and is dry-drawn at least 1.3 times. (Tg+20℃)≦Td≦(Tg−40℃)