JPH0373655B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to a novel bristles in which inorganic particles 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 biggest reason why PMIA cannot be made into fibers by relying on melt spinning is that it has a high melting point and is close to the 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 physically, the difference in 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 to produce bristles by melt-spinning wholly aromatic polyamide polymers, and succeeded in this, and published Japanese Patent Application Laid-Open No. 57-192436, 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 along their length, 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 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 carbon random.
Proposed in 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.
The present invention was achieved by a major change in concept from the proposal in No. 136829. c. Object of the invention The object of the invention is to provide a novel bristles made of fully aromatic polyamide mixed with inorganic particles and having excellent mechanical properties. Another object of the present invention is to provide wholly aromatic polyamide bristles that have excellent heat resistance, abrasiveness, and durability. Yet another object of the present invention is to provide PMIA bristles with added features inherent to the inorganic particles (eg, electrical conductivity, magnetic properties, high specific gravity, etc.). 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 PMIA bristles 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) made of a random mixture of inorganic particles and the wholly aromatic polyamide, wherein the polymer layer ( A layer) and the inorganic layer (B layer)
This is achieved by fully aromatic polyamide bristles mixed with inorganic particles, which are arranged side-by-side and are characterized by a cross-sectional area in the cross-section of the bristles ranging from 0.01 mm ² to 10 mm ² . Yet another object of the invention is to provide 85 total repeating units.
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 random mixture of inorganic particles and the aromatic polyamide.
The polymer layer (layer A) and the inorganic layer (layer B) are arranged side-by-side in a cross section perpendicular to the length direction, and the cross-sectional area in the cross-section is 0.01 mm ² from the composite molded article formed by the above. In order to obtain fully aromatic polyamide bristles mixed with inorganic particles in the range of ~10 mm ² , a method for producing fully aromatic polyamide bristles characterized by satisfying the following conditions (a) to (d) is used. achieved. (a) The composite molded product has a porosity (ε%) of 5% or less and 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) Next, the composite molded product is press-fitted into a heating mouthpiece having a narrowed passageway whose end portion is constituted by an orifice; (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 orifice and taken off. (Tg+40℃)≦Ts≦(Tm−20℃) (However, Tg and Tm mean the glass transition point (℃) and melting point (℃) of the fully aromatic polyamide, respectively.) Polymetaphenylene isophthalic in the present invention Amide-based wholly aromatic polyamide (PMIA) is a homophoryamide or copolyamide in which 85 mol% or more of the total repeating units are metaphenylene isophthalamide units. 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, and the like. 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 particles 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. If the inorganic particles have a needle-like or elongated shape (aspaku ratio is about 5 or more), the minimum cross-sectional area is 1 mm ² to 2.5 × 10 ^-7 mm ² , preferably 2.5 × 10 ^-3
It may be in the range of mm ² to 2.5×10 ^-7 mm ² , and its longest strip length is 5 mm to 0.0005 mm, preferably 0.25 mm.
Any material in the range of mm to 0.0005 mm is sufficient. The thickness of the bristles of the present invention (area of cross section perpendicular to the length direction of the bristles) is in the range of 0.01 mm ² to 10 mm ² . If the thickness is less than 0.01 mm ² , it is not impossible to obtain side-by-side composite fibers similar to those of the present invention by conventional solution methods, which does not meet the purpose of the present invention. Moreover, bristles thicker than 10 mm ² are not only so thick as to have little utility value, but also cannot be molded by other means such as compression molding, so the characteristics of the present invention are lost. The range in which the thickness of the bristles of the present invention is particularly useful is from 0.1 mm ² to 5.0 mm ² . The bristles of the present invention have a polymer layer mainly composed of PMIA (A
layer) and an inorganic layer (layer B) consisting of a random mixture of inorganic particles and the PMIA are arranged side-by-side to exhibit a composite structure. FIG. 1 is a cross-sectional view of a bristle schematically showing a typical example of this composite structure. Which of the structures shown in Figs. 1 to 3 is adopted depends on the purpose, but the features of the present invention are more noticeable when using the Sanderch structure as shown in Fig. 2 or the multilayer structure as shown in Fig. 3. It is often demonstrated. For example, in the case of heat-resistant and durable abrasive bristles, which is one of the objects of the present invention, as shown in FIG. The layer (B layer) is a polymer layer (A
A structure in which the material is sandwiched between two layers is desirable. In other words, one of the advantages of abrasive bristles exhibiting such a structure is that the degree of exposure of the inorganic layer on the bristle surface is small, so that the abrasive agent (inorganic particles) from the bristle surface that has no direct effect on the abrasive action is removed. This means that there is very little drop-off. This effect can be cited as a great advantage not only when the bristles are used as an abrasive brush, but also in the packaging and transportation process of bristle products. Other advantages of the bristles of the present invention, including the structure of FIG. 1, include greater tensile strength as well as greater bending durability compared to simple random structures of inorganic strips and PMIA. In other words, since wholly aromatic polyamides have a molecular structure with a hard skeleton, the fibers themselves are generally hard and tend to be brittle. If inorganic particles are randomly mixed into such PMIA, this tendency will further increase, and even a small external strain will easily cause the PMIA to break. In the case of bristles with a thickness of 0.01 mm ² to 10 mm ² , which is the object of the present invention, the strain on the bristle surface portion due to bending is quite large, so a simple random structure is very likely to break. This phenomenon becomes more noticeable as the mixing ratio of inorganic particles increases. However, in the sandwich-shaped bristles as shown in Fig. 2 of the present invention, bending due to natural buckling occurs in a direction perpendicular to the boundary line between layers A and B (i.e., the direction in which the bending stiffness EI is smallest). The strain occurring in layer B, which exists in the center and is thin, is extremely small, and therefore is difficult to break. The polymer layer (A layer) and the inorganic layer (B layer) in the present invention
In terms of bending durability, the total number of
The three layers shown in the figure are desirable, 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 bristles, two layers as shown in FIG. 1 are preferable. Furthermore, when it is desired to impart electrical or magnetic functions to the bristles, it has been found that there are cases in which about seven layers as shown in FIG. 3 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 bristles can be changed arbitrarily, but the characteristics of the bristles of the present invention are more fully exhibited at a high mixing ratio of 30 to 95% (by weight). . 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 length direction of the bristles can be changed to an arbitrary ratio, but the feature of the present invention is 20:80 to 95:5. It is even more effective in the range of As shown in FIGS. 4 and 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 drawings),
And the porosity (ε%) is 5% or less. The porosity (ε%) here is defined by the following formula, where Va is the apparent volume of the molded product, and Vr is the true volume of the PMIA component and inorganic fines component that constitute the molded product. ε=Va−Vr/Va×100 (%) In order to produce the bristles of the present invention, a molded product with ε of 5% or less, preferably 1% or less should be used as a raw material. If a molded product with ε exceeding 5% or more is used, a large amount of gas will be mixed into the bristles during the manufacturing process, and the mechanical properties of the resulting bristles will deteriorate, making it impossible to achieve the object of the present invention. Although the manufacturing method for the above-mentioned 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 product is not only rectangular as shown in Figure 4 and circular as shown in Figure 5, but also triangular, hexagonal,
Alternatively, it may be of any shape, such as an ellipse, but it must be substantially uniform in the length direction. 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. 4 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 upper part, and then the B component is further fed into the second A component (A-
2). Next, the heating plate 2 is slid toward the drawing surface and the lid is closed, and the piston 7 of the hydraulic cylinder 8 is operated upward to gradually increase the pressure.
Heaters are built into 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, and the temperature is controlled at 300 to 350°C. The pressure continues to increase gradually, and the pressure eventually reaches 1 to 20.
When the pressure reaches Kg/cm ² , preferably 3 to 10 Kg/cm ² , the operation of the piston is temporarily stopped. The compression pressure starts 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 the figure, slide the upper heating plate 2 toward the back of the drawing to release the upper part, and then move the piston 7 upward to remove the PMIA.
This is done by extruding the 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 the product, such as treating the inner wall of the molding machine with fluororesin. The molded product thus obtained has a shape that has 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 bristles 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.
It is then forcibly pushed into the preheating zone (Zp) while being held between rollers. At this time, the preheating zone needs to have a passage that can move in the vertical direction (Z direction) of the 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 molding. A heater 50' is embedded in the wall of this preheating box to precisely 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 constant 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
It is gradually preheated to a preheating temperature (Tp°C) not exceeding 20°C higher than the glass transition point (Tg°C) of the glass and is moved to the end of the preheating 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 heat and change its cross-sectional shape greatly, and it will stick to the inner wall of the preheating box or buckle, causing it to get stuck in the passage, or vice versa. 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 this invention we use
^Tg
Read Tg ^-, define the midpoint as Tg, and define the endothermic peak in the melting temperature region (around 420℃).
It was defined as 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. Furthermore, according to the dynamic viscoelasticity measurement device (described above) and thermomechanical analysis device (for example, Rigakudenki's Thermoflex TMA device), the elongation (contraction) curve under a constant load is (obtained), it is possible to know the response of the mechanical properties of PMIA due to thermal changes. 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 deform very much in response to external forces. 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 of the formed material, when the preheating temperature exceeds Tg + 20℃, the minimum pressure required to extrude PMIA (approximately 20Kg/
cm ² ), the molded product is compressively deformed in the preheating zone, the cross section of the molded product expands or buckles, and it sticks to the inner wall of the passageway in the preheating zone, making it difficult to move smoothly in the passageway. When setting the preheating temperature specifically, it is necessary to consider the pressure required to extrude the softened PMIA from the orifice. 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 1000Kg/cm ²
The required pressure is within the range of the pushing roller group 40.
obtained by increasing the number of . The basic role of the molded product in the preheating zone is to act as a flange for extruding the softened PMIA from the orifice, so it is important that it substantially maintain its shape. Therefore, during high-pressure extrusion, the temperature should be lower than the temperature at which the elastic modulus begins to decrease significantly (Tg - 10°C). 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°C) to (Tg - 10°C). The length Zp of the preheating zone in the present invention has a length sufficient 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 as used herein 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 that does not exceed Tg + 20°C until the complete end of the preheating zone, but if it is within about 10 mm to the entrance of the softening zone, it may be slightly exceeded due to heat conduction. I don't mind. However, the preheating temperature Tp should be designed so that it does not exceed Tg + 20°C until just before the softening zone.According to the study results of the present inventors, first, the preheating temperature should be set within the above-mentioned preferable range.
The second step is to insulate the boundary between the preheating zone and the softening zone with a heat insulating material as shown in Figure 7-60, and the third step is to minimize the heat conduction from the heating nozzle. Three points are effective. Now, the molded product preheated to the preheating temperature Tp as described above is press-fitted into the softening zone of the heating die shown in FIG. This softening zone is a softening extrusion of at least 3 mm in length with at least one attenuation passage formed by an orifice at the end. 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 an orifice. 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 cap 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, and the A and B layers are softened. While retaining the side-by-side structure, it moves while becoming thinner, and finally reaches Tg+40℃Ts (Tm
-20°C), and is subdivided and extruded by a large number of orifices N arranged close to each other in the direction perpendicular to the drawing. 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. Mixture of inorganic particles discharged from orifice N
A large number of small streams of PMIA are discharged into a heat-retaining zone of length Zk consisting of a heat-retaining box 80, and are forcibly taken away by a take-off roller 90. On this occasion,
In the heat retention zone, the temperature near the discharge port of the orifice (Tk℃) is changed to TgTk (Tm - 20℃).
should be maintained within the range of . Here, the temperature near the orifice outlet means 3.
mm to 10 mm refers to the space temperature at a distance. Tk
If it is below the glass transition point Tg of PMIA, uneven discharge may occur due to cooling of the orifice plate surface, or draft may not rise due to rapid cooling, and unevenness is likely to occur. The preferred range of Tk is Tg + 50°C, TkTm - 50°C, and it is preferably set 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 may be stretched at a temperature near Tg to increase the strength. can. 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 60% white alumina (Fujimi Abrasives Industry KK) with an average particle size of 34μ to this powder.
% mixed inorganic fine particles (component B) were prepared, and using the compression molding machine shown in Fig. 6, A-1 and A-2 were prepared.
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, and the results when used as an abrasive brush were extremely satisfactory.

【table】

[Table] Example 2 Same PMIA powder as Example 1 (component A) 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 Figure 6, 20 g of component A and 15 g of component B were laminated in a total of 7 layers with component A as the outer layer, and compression molded to form a plate. A large number of composite molded products were manufactured. 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 4. The cross-sectional form of the obtained bristles was as shown in FIG. 3, and the physical properties were as shown in Table 5. Next, the bristles were magnetized so that the N and S poles were polarized in a direction parallel to the A and B layers to create magnetic bristles. These magnetic bristles not only had better mechanical properties than bristles randomly mixed with equal proportions of strontium ferrite, but also exhibited stronger magnetism, probably due to the high density effect of strontium ferrite.

【table】

【table】

【table】 [Brief explanation of drawings]

FIGS. 1 to 3 are diagrams schematically showing typical examples of the cross-sectional structure of the fully aromatic polyamide bristles mixed with inorganic particles of the present invention. FIG. 4 shows an example of a plate-shaped composite molded product used as an intermediate raw material in the bristle manufacturing method of the present invention, and FIG. 5 shows an example of a rod-shaped composite molded product. FIG. 6 is a sectional view of a compression molding machine for manufacturing the plate-like composite molded product of FIG. 4. FIG. 7 is a schematic diagram of an apparatus for producing bristles of the present invention using the plate-shaped composite molded product of FIG. 4 as an intermediate raw material. FIG. 8 is an enlarged view of the vicinity of the heating nozzle 70 in FIG. 7.

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. The polymer layer (A layer) and the inorganic layer (B layer) are formed side by side in a cross section perpendicular to the length direction of the bristles. Totally aromatic polyamide bristles mixed with inorganic particles, characterized in that the cross-sectional area of the bristles in the cross-section is in the range of 0.01 mm ² to 10 mm ² . 2 The polymer layer (A layer) and the inorganic layer (B layer) have an area ratio of 20:80 to 20:80 in the vertical cross section.
Fully aromatic polyamide bristles according to claim 1 in the range 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.
Fully aromatic polyamide bristles as described in Section. 4. The wholly aromatic polyamide bristles 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 perpendicular cross section. 5. A polymer layer (layer A) mainly composed of a fully aromatic polyamide in which 85 mol% or more of the total repeating units are metaphenylene isophthalamide units, and an inorganic layer composed of a random mixture of inorganic particles and the aromatic polyamide. (B layer) from the composite molded product formed from the polymer layer (A layer) and the inorganic layer (B layer).
In order to obtain fully aromatic polyamide bristles mixed with inorganic particles, in which the bristles are arranged side-by-side in a cross section perpendicular to the length direction, and the cross-sectional area in the cross section is in the range of 0.01 mm ² to 10 mm ² , the following steps (a) to A method for producing wholly aromatic polyamide bristles, characterized by satisfying the condition (d). (a) The composite molded product has a porosity (ε%) of 5% or less and 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) Next, the composite molded product is press-fitted into a heating mouthpiece having a narrowed passageway whose end portion is constituted by an orifice; (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 orifice and taken off. (Tg+40℃)≦Ts≦(Tm−20℃) (Tg and Tm respectively mean the glass transition point (℃) and melting point (℃) of the fully aromatic polyamide.)