JPH0520459B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to novel aromatic polyamide particles that can be made into excellent molded products by compression molding. More specifically, it has a special form that can be made into a molded product with excellent heat resistance, hardness, flexibility, surface smoothness, machinability, etc. simply by compression molding,
The present invention relates to aromatic polyamide particles having a structure. Prior Art A polymer whose main repeating unit is metaphenylene isophthalamide has excellent heat resistance and flame retardancy, and also has good solubility in solvents. It is well known to manufacture , films, fibrids, etc., and the fibers in particular are commercially available and widely used under names such as "Konex" (registered trademark) and "NOMEX" (registered trademark). However, since the polymer cannot be melt-molded,
It has the disadvantage that it is difficult to make thick molded products, and the only method known so far is to prepare a powder prepared by crushing solid particles of aromatic polyamide, as recorded in Japanese Patent Publication No. 56-20291. This is a method in which the preform is molded and heated at high temperature for a long period of time to sinter the preform into a molded product. According to this method, a polymer solution of aromatic polyamide obtained by solution polymerization etc. is added to a precipitant to generate a slurry, the slurry is stirred and filtered to extract the polymer as solid particles, and the solid After washing and drying the particles, they are crushed to reduce the apparent bulk density.
Produce a powder with a surface area of 0.2 g/cm ² or more and a surface area of 40 m ² /g or more, pressurize the powder to 10,000 psi or more to make a preform, and heat it under an inert atmosphere at 260 to 320°C.
The powder constituting the preform is sintered to form the desired molded article. However, this method not only requires two steps: preforming and sintering, but also requires a considerable amount of time in the sintering process to sinter the powder into a molded product with sufficient strength. There is a problem. Purpose of the Invention As a result of intensive research into a method for manufacturing molded products with good physical properties by compression molding without requiring the two steps of preforming and sintering as described above, the present inventors have developed a special method. It has been found that by using aromatic polyamide particles, compression molding of aromatic polyamide, which was previously considered impossible, becomes possible. Therefore, the main object of the present invention is to provide novel aromatic polyamide particles that can be formed into molded articles having good physical properties by compression molding. Another object of the present invention is to provide aromatic polyamide particles for compression molding, which are easier to produce and cheaper to produce than conventional precipitation-grinding methods. Composition of the Invention The aromatic polyamide particles for compression molding according to the present invention that can achieve the above-mentioned objects are particles made of an aromatic polyamide in which 40 mol% or more of the polymer repeating units are metaphenylene isophthalamide units, and Average particle size 0.1-10μm (preferably 0.2-5μm)
A large number of microparticles aggregate to form porous granules (agglomerated particles), and the average particle size of the aggregated particles is 10 to 400 μm (preferably 50 to 300 μm) and the surface area is 1 to 20 m ² /g (preferably 3-10m ² /
g). Examples of the aromatic polyamide forming the particles of the present invention include homopolyamides or copolyamides in which 40 mol% or more, preferably 55 mol% or more of polymer repeating units are metaphenylene isophthalamide units. Such a homopolyamide or copolyamide uses isophthalic acid halide as an acid component, metaphenylene diamine as a diamine component, and, if necessary, a small amount of a third component such as terephthalic acid halide, methyl terephthalic acid halide, naphthalene-2. , 6-dicarboxylic acid halide, paraphenylene diamine, 3,4'- or 4,4'-diaminodiphenyl ether, meta-xylylene diamine, etc. or meta- or para-benzoic acid halide, etc. to condense these. It can be manufactured by. 85 mol% poly(metaphenylene isophthalamide) or metaphenylene isophthalamide units
The copolyamides containing the above materials are excellent in heat resistance, hardness, flexibility, etc. of molded products, but are somewhat inferior in impact resistance. Therefore, in fields where impact resistance is required, 20% of polymer repeating units are used.
Preferred are copolyamides in which ~60 mol% (preferably 30-45 mol%) are metaphenylene terephthalamide units and 80-40 mol% (preferably 70-55 mol%) are metaphenylene isophthalamide units. . Such a copolyamide uses isophthalic acid halide or terephthalic acid halide as an acid component, metaphenylene diamine as a diamine component, and optionally a small amount (for example, 10 mol or less of the total) of a fourth component, such as methyl terephthalic acid. halide, naphthalene-2,6-dicarboxylic acid halide, paraphenylenediamine, 3,4'- or 4,
It can be produced by polycondensation using 4'-diaminodiphenyl ether, metaxylylene diamine, etc., or meta- or para-benzoic acid halide. In such copolyamides the content of terephthalamide units is 20
If the amount is less than mol %, the molded product will have improved impact resistance. However, if the terephthalamide unit exceeds 60 mol%, moldability deteriorates. Conventionally, it has been generally believed that when a third component is introduced into a homopolymer to form a copolymer, the physical properties of the molded product deteriorate, but in the case of the aromatic polyamide particles of the present invention, contrary to the conventional wisdom, However, a unique phenomenon has been observed in which the physical properties of compression molded products are improved by using a copolymer. The homopolyamide or copolyamide forming such aromatic polyamide particles was prepared by dissolving 0.5 g of the polymer in 100 ml of N-methyl-2-pyrrolidone.
Intrinsic viscosity (2inh) measured in solution at °C is 0.5~4.0
Those having an intrinsic viscosity of 0.7 to 2.5 are particularly preferred because they have excellent moldability and the physical properties of the molded product are good. In addition, in order to improve the heat resistance of molded products, it is preferable to use an aromatic polyamide whose polymer chain ends are blocked with a monofunctional aromatic compound such as aniline or benzoyl chloride. It is preferable that the amount of aromatic terminals is 20 to 50 mol% relative to the amount of groups. This aromatic polyamide can contain a matting agent, a coloring agent, a filler, etc. as necessary, but
It is better not to contain substances that impair the heat resistance of the molded product, such as inorganic salts such as lithium chloride and calcium chloride. The particles for compression molding of the present invention are composed of the aromatic polyamide as described above, but the particles are made of the aromatic polyamide as described above.
Unlike powder produced by a pulverization method, a large number of microparticles having a specific average particle size are aggregated to form porous aggregated particles having a specific average particle size that is much larger than the above-mentioned microparticles. The average particle size of the microparticles is in the range of 0.1 to 10 μm, preferably 0.2 to 5 μm, and the average particle size of the porous aggregated particles is 10 to 400 μm, preferably 50 to 300 μm.
is within the range of Although the agglomerated particles are porous, the surface area is 1 to 20 m 2 /g, preferably 3 to 20 m ² /g, which is much smaller than the 50 to 80 m ² /g obtained by the conventional precipitation-pulverization method. It is in the range of 10m ² /g. According to the research conducted by the present inventors, only aromatic polyamide particles that meet the above-mentioned conditions can be made into good molded products by simply compression molding them. For example, by separating the fine particles, It was confirmed that even when subjected to compression molding, a good molded product could not be obtained. Figures 1 and 2 are microscopic photographs showing an example of particles for compression molding according to the present invention, and Figure 1 is a microscopic photograph (100x magnification) showing the appearance of each aggregated particle.
FIG. 2 is a micrograph (5000x magnification) showing the surface appearance of microparticles constituting aggregated particles. As is clear from FIG. 1, the particles for compression molding according to the present invention form an almost spherical or cylindrical mass as a whole, but are porous like pumice. As is clear from FIG. 2, this porous structure is formed by agglomeration of countless fine particles. Therefore, countless minute voids or cavities exist on the surface and inside of the aggregated particles. Therefore, the apparent density of the particles is usually in the range of 0.2 to 0.4 g/cm ³ , which is a much smaller value than the density of the polymer. Although the particles have a porous structure, the surface area is relatively small at 1 to 20 m ² /g, which means that most of the cavities and voids within the particles exist independently. This is presumed to mean that there is no communication to the surface. (Methods for measuring each index) The methods for measuring the average particle diameter, surface area, apparent density, etc. of the particles specified in the present invention are as follows. (a) Average particle size Take a micrograph (100x magnification) of the aggregated particles, determine the particle diameter of 100 randomly selected particles using the microscope, and use the average value as the average particle size of the aggregated particles. In addition, we took microscopic photographs of 10 of the aggregated particles at a magnification of 5000 times, randomly selected 10 microparticles visible on the surface of the aggregated particles in each photo, and determined the particle size of each from the microscopic photographs. The average value is defined as the average particle size of the microparticles. (b) Surface area The surface area of the dried particles is measured by the nitrogen adsorption method using an automatic surface area measuring device Model 2200 manufactured by Micrometrics Instruments, Inc., USA. (c) Bulk density The dry particles are poured into a graduated cylinder (volume 5 ml) with a funnel-shaped inlet so as to flow down along the inner wall of the cylinder, and the sample is loosely filled without tapping the graduated cylinder. Determined from volume and weight. (Production method of particles) The aromatic polyamide porous aggregated particles of the present invention having the structure and characteristics as described above are basically produced according to the interfacial polymerization method described in Japanese Patent Publication No. 10863/1983. However, in order to obtain the particles of the present invention suitable for compression molding, it is necessary to appropriately control the conditions of the first reaction and/or the second reaction in the interfacial polymerization method. In particular, in order to produce the particles of the present invention in the interfacial polymerization, it is preferable to adjust the conditions of the secondary reaction as follows. (1) The volume ratio (υ) of the dispersion of the initial condensate and the aqueous solution of sodium carbonate, etc. should be 0.4 to 0.6. However, υ = dispersion of initial condensate (vol.) / dispersion of initial condensate (vol.) + aqueous solution of soda carbonate, etc. (vol.) (2) Terminal speed of stirring blade in secondary reaction tank ( V) 10m/
Must be sec or more. In addition, in the first reaction, by appropriately adding a monofunctional aromatic compound such as aniline,
The ends of the polymer chains can be capped with a monofunctional aromatic compound to improve the thermal stability of the polymer. The particles obtained by the interfacial polymerization method can be used as they are, or further washed with water, dried, and if necessary, further sieved to obtain the particles for compression molding of the present invention. (Suitable compression molding conditions) The conditions for molding using such compression molding particles are not particularly limited, but, for example, molding equipment similar to that used for conventional compression molding of thermosetting resins or thermoplastic resins. Using temperature 200-400
℃, especially preferably 280-330℃, pressure 100-1000
A molded article having good physical properties can be obtained by heating and pressurizing the molded product under conditions of Kg/cm ² , particularly preferably 300 to 500 Kg/cm ² , and maintaining that state for about 20 minutes to 5 hours. In addition, when molding the compression molding particles according to the present invention, the molding particles may be preheated and then supplied to a molding device. Furthermore, during molding at high temperatures, it is preferable to seal the molded part with an inert gas such as nitrogen or helium, or to create a substantial vacuum to prevent the aromatic polyamide from coming into contact with air. The particles for compression molding of the present invention can be used in combination with reinforcing heat-resistant fibers, fillers, and other additives during molding. It may also be used in combination with other heat-resistant resins. Effects of the Invention Unlike conventional aromatic polyamide powders, the aromatic polyamide particles for compression molding of the present invention as described above can be formed into a desired molded product at once by compression molding. The moldability is extremely good, and in particular, mold release properties of particles molded from the particles according to the present invention are excellent, and there is no need to use a mold release agent during molding. Moreover,
The resulting molded product not only has the excellent heat resistance, flame retardance, and mechanical properties such as sufficient tensile strength and elongation, compressive strength, and flexural strength of aromatic polyamide, but surprisingly, The molded product has high hardness, good self-lubricating properties, and is easy to cut. Furthermore, the particles made of the copolyamide have extremely good impact resistance in molded articles. Therefore, the molded product is particularly suitable for the field of mechanical parts, such as bearings, gear rollers, printed circuit boards, etc., but is of course also useful for other fields. Furthermore, since the particles of the present invention can be efficiently produced by interfacial polymerization, there is no need for the conventional steps of precipitation and pulverization, and the production cost is significantly lower than that of conventional powders. Examples Next, examples of the present invention will be described in detail, but the present invention is not limited thereto. Examples 1 to 3 (a) Production of polymer particles Poly(metaphenylene isophthalamide)-based polymers containing no inorganic salts were produced according to the interfacial polymerization method described in Japanese Patent Publication No. 10863/1983. That is, 173 g of metaphenylenediamine was dissolved in tetrahydrofuran 1 dehydrated with metallic sodium, and this was cooled to 0°C. on the other hand,
325 g of isophthaloyl chloride was dissolved in 1 ml of tetrahydrofuran dehydrated with sodium metal and cooled to 0°C. Next, the tetrahydrofuran solution was stirred while being maintained at 0° C., and the isophthalic acid chloride solution was gradually added thereto as a trickle to obtain a dispersion of the initial condensate (first reaction). Subsequently, the dispersion of the initial condensate was quickly added to a solution of 200 g of soda carbonate dissolved in 2 parts of water under high-speed stirring to obtain white polymer particles with an intrinsic viscosity of 1.8 (secondary reaction). . At this time, the stirring conditions for the second reaction, the volume ratio of the initial condensate dispersion to the aqueous sodium carbonate solution, etc. were varied as shown in Table 1 to produce particles with various average particle sizes. After washing and drying these particles, each particle was observed under a microscope, and both were found in Figures 1 and 2.
The particles were porous aggregated particles with an appearance as shown in the figure. Next, the average particle diameter, apparent bulk density, surface area, etc. of the particles in each experiment were measured, and the results were as shown in Table 1 below.

[Table] (b) Compression molding Using the various particles obtained in the above experiment, compression molding was performed under the following conditions to form a flat plate-shaped molded product with a thickness of 3 mm. Heating temperature 320°C Pressure pressure 330Kg/cm ² Pressure time 40 minutes During molding, the molding area was replaced with nitrogen in advance to prevent the polymer from coming into contact with air during molding. In all of Examples 1 to 3, the molded products had extremely good mold releasability, and hard molded products with smooth and glossy surfaces and a Rockwell hardness (M scale) of about 125 degrees were obtained. The strength and elongation, modulus and Izo impact value (notched) (according to ASTM D256) of these were measured and were as shown in Table 2 below.

[Table] This plate-like material is stable even when used continuously at 260℃.
It also had excellent abrasion resistance. Furthermore, it was easy to cut, and a pattern could be engraved on the surface using a commercially available processing machine. Example 4 (a) Production of polymer particles The temperature of the metaphenylenediamine solution and the isophthalic acid chloride solution in the first reaction was set to -15°C, and 590°C was added to the reaction system during the first reaction.
Interfacial polymerization was carried out in the same manner as in Example 1 except that mg of aniline was added to obtain white polymer particles with an intrinsic viscosity of 1.4. This polymer had 30% of its terminal groups capped with aniline and had good heat resistance. Similar to Example 1, the polymer particles are porous particles in which countless microparticles are aggregated, and the average particle size of the microparticles is 0.9 μm, and the average particle size of the aggregated particles is 200 μm.
The surface area is 4.8m ² /g and the apparent density is 0.35
g/ ^cm3 . (b) Compression molding A dumbbell-shaped test piece was made by compression molding using the polymer particles. The molding conditions at this time were as follows. Heating temperature: 300° C. Pressure: 310 Kg/cm ² Pressure time: 35 minutes In this molding, the molding section was kept in a vacuum from before the start of molding to the end of molding. The physical properties of the obtained test piece were as follows. Strength 12.4 Kg/mm ² Elongation 5.0% Modulus 331 Kg/mm ² Examples 5 to 7 (a) Production of copolymer particles Poly(meth) A copolymer based on nylene isophthalterephthalamide was produced. That is, 173 g of metaphenylenediamine was dissolved in tetrahydrofuran 1 dehydrated with metallic sodium, and this was cooled to 0°C. on the other hand,
227.5 g of isophthalic acid chloride and 97.5 g of terephthalic acid chloride were dissolved in tetrahydrofuran 1 dehydrated with metallic sodium and cooled to 0°C. Next, the tetrahydrofuran solution was stirred while being maintained at 0° C., and the isophthaloyl chloride terephthaloyl chloride solution was gradually added thereto as a trickle to obtain a dispersion of the initial condensate (first reaction). Subsequently, the dispersion of the initial condensate was quickly added to a solution of 200 g of soda carbonate dissolved in 2 parts of water under high-speed stirring to obtain white polymer particles with an intrinsic viscosity of 1.8 (secondary reaction). . At this time, various average particle sizes were produced by changing the stirring conditions for the secondary reaction and the volume ratio of the initial condensate dispersion to the aqueous sodium carbonate solution. After washing and drying these particles, each particle was observed under a microscope and was found to be porous aggregated particles. Next, the average particle diameter, apparent density, surface area, etc. of the particles in each experiment were measured, and the results were as shown in Table 3 below.

[Table] (b) Compression molding Using each particle made of the copolymer obtained in the above experiment, compression molding was performed under the following conditions to obtain a flat plate-shaped molded product with a thickness of 3 mm. Heating temperature: 320°C Pressure: 330Kg/cm ² Pressure time: 40 minutes In the molding diagram, the molding area was replaced with nitrogen in advance to prevent the polymer from coming into contact with air during molding. In all of Experiment Nos. 1 to 3, the molded products had extremely good mold releasability, and molded products with smooth and glossy surfaces were obtained. The strength and elongation, modulus and Izo impact value (notched) of each of these molded products were measured and were as shown in Table 4 below.

[Table] This plate-like material was easy to cut, and a pattern could be engraved on the surface using a commercially available processing machine. Example 8 (a) Production of copolymer particles The temperature of the metaphenylenediamine solution, isophthalic acid chloride solution, and terephthalic acid chloride in the first reaction was set to -15 °C,
Next, interfacial polymerization was carried out in the same manner as in Example 1 except that 590 mg of aniline was added to the reaction system during the reaction to obtain white copolymer particles with an intrinsic viscosity of 1.4. This copolymer had 30% of the terminal groups blocked with aniline and had good heat resistance.
In addition, this copolymer particle is a porous particle in which countless microparticles aggregate as in Example 1,
The average particle size of the fine particles was 0.9μ, the average particle size of the aggregated particles was 200μ, the surface area was 4.8m ² /g, and the apparent density was 0.35g/cm ³ . (b) Compression molding Dumbbell-shaped test pieces were made by compression molding using the copolymer particles. The molding conditions at this time were as follows. Heating temperature: 300° C. Pressure: 310 Kg/cm ² Pressure time: 35 minutes In this molding, the molding section was kept in a vacuum from before the start of molding to the end of molding. The physical properties of the obtained test piece were as follows. Strength 12.6Kg/mm ² Elongation 5.0% Modulus 340Kg/mm ^2Izotsu impact value (with notch) 8.2Kg・cm/
cm

[Brief explanation of the drawing]

Figures 1 and 2 are micrographs showing the appearance of the aromatic polyamide particles for compression molding of the present invention, respectively. Figure 1 shows the overall appearance of the particles (100x magnification), The figure is a partially enlarged version (5000x magnification).

Claims (1)

[Scope of Claims] 1 Particles of aromatic polyamide in which 40 mol% or more of polymer repeating units are metaphenylene isophthalamide units, which are porous particles formed by agglomeration of many microparticles with an average particle size of 0.1 to 10 μm. Agglomerated particles are formed, and the average particle size of the aggregated particles is 10 to 400μ.
Aromatic polyamide particles for compression molding, characterized in that they have a surface area of 1 to 20 m ² /g. 2 Aromatic polyamide has polymer repeating units
The aromatic polyamide particles for compression molding according to claim 1, wherein 85 mol% or more of the aromatic polyamide consists of metaphenylene isophthalamide units. 3 Aromatic polyamide has polymer repeating units
The aromatic polyamide for compression molding according to claim 1, which is a copolymerized aromatic polyamide comprising 20 to 60 mol% of metaphenylene terephthalamide units and 80 to 40 mol% of metaphenylene isophthalamide units. particle. 4 The apparent bulk density of aggregated particles is 0.2 to 0.4 g/
cm ³ Aromatic polyamide particles for compression molding according to claim 1. 5. Aromatic polyamide particles for compression molding according to claim 1, wherein the aromatic polyamide has an intrinsic viscosity (measured with an N-methyl-2-pyrrolidone solution at 30°C) of 0.5 to 4.0. 6. Aromatic polyamide particles for compression molding according to claim 1, wherein 10 mol% or more of the end groups of the aromatic polyamide are blocked by a -functional aromatic compound.