JPH0369289B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing aromatic polyamide molded articles. More specifically, the present invention relates to a method of molding special aromatic polyamide particles into excellent molded articles by compression molding. 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 produce films, fibrids, etc., and in particular, fibers 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 molded products with a thick inner surface, and the only method known so far is to prepare a powder prepared by crushing solid particles of aromatic polyamide, as described in Japanese Patent Publication No. 131024/1983. This is a method of molding and heating the preform at a high temperature for a long period of time to sinter the preform into a molded product. According to this method, a polymer solution is added to a precipitant to form a slurry, the slurry is stirred and filtered to extract the polymer as solid particles, and the solid particles are washed, dried, and pulverized to give an apparent appearance. A powder with a bulk density of 0.2 g/cm ² or more and a surface area of 40 m ² /g or more is produced, and the powder is pressurized to 10,000 psi or more to form a preformed product, which is heated under an inert atmosphere at 260 to 320 psi.
The desired molded article is formed by heating at a temperature of 0.degree. C. for several hours to sinter the powder that makes up the preform. However, this method not only requires two steps, preforming and sintering, but also has the problem that the sintering step takes a considerable amount of time to sinter the powder into a molded product with sufficient strength. exists. Purpose of the Invention As a result of intensive research into a method for forming aromatic polyamides into molded products with good physical properties 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 compression molding aromatic polyamide particles under specific conditions, a good molded product can be obtained in one step. Therefore, the main object of the present invention is to provide a method that can make aromatic polyamide into a molded article having good physical properties all at once. Another object of the present invention is to produce molded products with good mold releasability and excellent flexibility, heat resistance, flame retardance, surface hardness, machinability, self-lubricating properties, etc. at low cost. The purpose is to provide a manufacturing method. Structure of the Invention The above-mentioned object is an aromatic polyamide particle in which a large number of microparticles with an average particle diameter of 0.1 to 10 μm, preferably 0.2 to 5 μm are aggregated to form porous granules (agglomerated particles), The aggregated particles have an average particle size of 10 to 400 μm, preferably 50 to 300 μm, and a surface area of 1 to 20 m ² /g, preferably 3 to 10 m ² /g. The particles are molded at a temperature of 200 to 400° C. in a compression molding apparatus. According to the method of the present invention, the material is heated and pressurized to a temperature of preferably 280 to 330°C and a pressure of 100 to 1000 Kg/ ^cm2 , preferably 300 to 500 Kg/ ^cm2 , and held in that state for 20 minutes to 5 hours. will be achieved. Preferred aromatic polyamides used in the process of the invention include 40 mole % of polymer repeat units;
Preferably, a homopolyamide or copolyamide in which 55 mol% or more is metaphenylene isophthalamide units is used. Such a homopolyamide or copolyamide uses isophthalic acid halide as the acid component, metaphenylenediamine as the diamine component, and if necessary, a small amount of a third component, such as terephthalic acid halide, methyl terephthalic acid halide, naphthalene-2,6. -Produced by condensing these using dicarboxylic acid halide, paraphenylene diamine, 3,4- or 4,4-diaminodiphenyl ether, meta-xylylene diamine, etc. or meta- or para-benzoic acid halide, etc. be able to. Of the aromatic polyamide copolymerized with the third component, 20 to 60 mol% of the terephthalic acid component, especially
Copolyamides containing 25 to 45 mole % give molded articles with improved impact resistance than homopolyamides. The aromatic polyamide forming the particles has an intrinsic viscosity (η in
h) is preferably 0.5 to 4.0, especially the intrinsic viscosity
A value of 0.7 to 2.5 is suitable because it has 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 nuclear terminals is 20 to 50 mol% relative to the amount. This aromatic polyamide may contain a dissipating agent, a coloring agent, a filler, etc. as necessary, but it should not contain substances that impair the heat resistance of the molded product, such as inorganic substances such as lithium chloride and calcium chloride. It is better not to include salt. The aromatic polyamide particles used in the present invention are composed of the aromatic polyamide as described above.
Unlike powder produced by the conventional precipitation-grinding method, a large number of microparticles with a specific average particle size aggregate to form porous aggregated particles with a specific average particle size that is much larger than the microparticles. ing. The average particle size of the microparticles is 0.1 to 10 μm, preferably 0.2 to 10 μm.
The average particle size of the porous aggregated particles is within the range of 5 μm, and is 10 to 400, preferably 50 to 400.
It is within the range of 300μm. Although the agglomerated particles are porous, their surface area is much smaller than that of the conventional sedimentation-pulverization method, 1 to 20 m ² /
g, preferably in the range of 3 to 10 m ² /g. That is, the aromatic polyamide for compression molding used in the present invention has a nearly spherical or cylindrical shape as a whole, but is porous like pumice. 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 bulk density of the particles is usually 0.2 to 0.4 g/cm ³
It is within the range of , which is considerably smaller than the density of the polymer. Although the particles have a porous structure, they have a surface area of 1 to 20 m ² /g compared to conventional aromatic polyamide particles (surface area of 50 to 80 m ² /g).
This relatively small value is presumed to mean that most of the cavities and voids within the particles exist independently and do not communicate to the surface. The methods for measuring the average particle diameter, surface area, apparent density, etc. mentioned here are as follows. (a) Average particle size Take a micrograph (100x magnification) of the aggregated particles,
The particle size of 100 randomly selected particles is determined from a micrograph, and the average value is taken as the average particle size of the aggregated particles. Also, a magnified micrograph of 10 of the aggregated particles (5000x magnification)
In each photograph, randomly select 10 microparticles that can be seen on the surface of the aggregated particles, determine the particle size of each from the micrograph, and use the average value 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 automobile surface area measuring device Model 2200 manufactured by Micrometrics Instruments, Inc., USA. (c) Apparent bulk density The volume of a sample in which dried particles are poured into a graduated cylinder (volume 5 ml) with a bowl-shaped inlet so as to flow down along the inner wall of the cylinder, and the cylinder is loosely filled without tapping the cylinder. and weight. Such porous aggregated particles of aromatic polyamide can basically be produced according to the interfacial polymerization method described in Japanese Patent Publication No. 47-10863. According to this interfacial polymerization method, the resulting polymer Since no inorganic salt is contained therein, polymer particles with good heat resistance can be obtained. In order to obtain the particles specified in the present invention, 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 the interfacial polymerization, it is preferable to adjust the conditions of the secondary reaction as follows in order to produce the above-mentioned special aromatic polyamide particles. (1) The volume ratio v of the dispersion of the initial condensate and the aqueous solution such as sodium carbonate should be 0.4 to 0.6. However, v = dispersion of the initial condensate (vo1) / dispersion of the initial condensate (vo1) + aqueous solution of soda carbonate, etc. (vo1) (2) The tip speed of the stirring blade in the secondary reaction tank is set to 10 m/
Must be sec or more. In addition, in the first reaction, by adding an appropriate amount of 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 above-mentioned interfacial polymerization method can be used as they are, or further washed with water, dried, and if necessary, further sieved to obtain particles for compression molding used in the method of the present invention. In the present invention, compression molding is performed using such special aromatic polyamide particles, but the molding equipment used is, for example, a molding equipment similar to that used for conventional compression molding of thermosetting resins or thermoplastic resins. using a temperature of 200~400℃, preferably 280~
330℃, pressure 100~1000Kg/ ^cm2 , preferably 300~
By heating and pressurizing to 500 kg/cm ² and maintaining that state for 20 minutes to 5 hours, a molded article having desired physical properties can be obtained. When carrying out compression molding according to the present invention, the molding particles may be preheated and then supplied to the molding device. In addition, when molding at high temperatures, the aromatic polyamide is prevented from coming into contact with air by degassing and creating a vacuum in the molding area, sealing the molding area with an inert gas such as N ₂ or He, or creating a vacuum. It is preferable not to do so. Although a molded article compression-molded using only the aromatic polyamide particles according to the method of the present invention has various properties described below, its impact resistance is somewhat insufficient. Therefore, when manufacturing molded products that require impact resistance, reinforcing fibrous materials are added to the aromatic polyamide particles in an amount of 3 to 30% by weight based on the particles.
It is appropriate to mix and mold. As the reinforcing fibrous material, short cut fibers of aromatic polyamide fibers and/or pulp-like particles of aromatic polyamide are suitable. Aromatic polyamide fibers include poly(metaphenylene isophthalamide) fibers, poly(metaphenylene isophthalamide/terephthalamide) fibers, poly(paraphenylene terephthalamide) fibers, or those described in Japanese Patent Publication No. 54-43612. A para-aromatic copolyamide fiber using 3,4-diaminodiphenyl ether as a copolymerization component is suitable. All of these fibers are used as short cut fibers having a fiber length (cut length) of 3 mm or less. When the fiber length of the aromatic polyamide fiber exceeds 3 mm, the dispersibility of the fiber in the mixture deteriorates rapidly, resulting in poor moldability. On the other hand, as pulp-like particles of aromatic polyamide, pulp-like particles made of the same polymer as the fibers are suitable, and a method of introducing a polymer solution into a coagulation bath to which shear force is applied and precipitating it ( For example, Japanese Patent Publication No. 35-11851), a method in which the polymer is precipitated into pulp in the polymerization process of aromatic polyamide (for example, Japanese Patent Publication No. 59-14569, Japanese Patent Publication No. 60-56801), and pulp-like particles by beating the fibers. Any of the following methods (for example, Japanese Patent Publication No. 59-603) may be used. The mixing ratio of the reinforcing fibrous material (for example, short cut fibers, pulp particles, etc.) to the aromatic polyamide particles is suitably within the range of 3 to 30% by weight based on the weight of the particles. 5 to 25% by weight is preferred. If the amount of reinforcing fibrous material is less than 3% by weight, the effect of mixing the fibrous material will be poor, while if it exceeds 30% by weight, it will be difficult to uniformly disperse the fibrous material in the polymer during molding, resulting in poor moldability. In addition, the molded product tends to become brittle. In addition, in the method of the present invention, in addition to the above-mentioned short cut fibers of aromatic polyamide fibers and pulp-like particles of aromatic polyamide, inorganic fibers such as carbon fibers, metal fibers, and ceramic fibers can be used as reinforcing fibrous materials. Short cut fibers of heat-resistant organic fibers such as arylate fibers, polyimide fibers, and polyetheretherketone fibers may also be used. Effects of the Invention Unlike conventional aromatic polyamide powder, the aromatic polyamide particles or the mixture thereof with a reinforcing fibrous material as described above can be formed into a desired molded product at once by compression molding. Molded products with excellent mechanical properties such as tensile strength, bending strength, and compressive strength, hardness, and abrasion resistance can be obtained. Furthermore, when a reinforcing fibrous material is mixed, a molded article having excellent impact resistance, especially Izot impact value, can be obtained. Further, according to the method of the present invention, the moldability in compression molding is extremely good, the molded product has excellent mold release properties, and there is no need to use a mold release agent or the like during molding. Moreover,
The obtained molded product has excellent self-lubricating properties and also has good machinability, so it can be finished into a molded product with a precise shape by cutting after compression molding. Furthermore, since this molded product is made of aromatic polyamide, it has excellent heat resistance and can sufficiently withstand continuous use at 260°C. Therefore, molded articles produced by the method of the present invention are not only useful as mechanical parts such as bearings, gears, rollers, etc., but also extremely useful as electrical parts such as printed circuit boards. Examples Next, examples of the present invention will be described in detail, but the present invention is not limited thereto. Example 1 (a) Production of polymer particles A poly(metaphenylene isophthalamide) polymer was 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 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 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 sodium carbonate dissolved in 2 parts of water with 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 as described above. 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 molded area was replaced with N ₂ in advance to prevent the polymer from coming into contact with air during molding. In Experiment Nos. 1 to 3, the molded products had extremely good mold releasability and had a hard surface (Rockwell hardness 215°).
A molded product that was smooth and had ribs was obtained. The strength and elongation, modulus, etc. of these were measured and were as shown in Table 2 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 2 (a) Production of polymer particles The temperature of the metaphenylenediamine solution and isophthalic acid chloride solution in the first reaction was set to -15°C, and during the first reaction, the reaction system was
Example 1 except that 590 mg of aniline was added.
Interfacial polymerization is carried out in the same manner as above, and the intrinsic viscosity is
1.4 white polymer particles were obtained. 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 fine particles are aggregated, and the average particle size of the fine particles is 1 μm, and the average particle size of the aggregated particles is
200 μm, the surface area was 4.8 m ² /g, and the apparent density was 0.35 g/cm ³ . (b) Compression molding Dumbbell-shaped test pieces were 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 maintained in a substantially vacuum state from before the start of molding to the end of molding. The physical properties of the obtained test piece were as follows. Tensile strength 12.4/mm ² Elongation at break 5.0% Modulus 331 Kg/mm ² Example 3 The various poly(metaphenylene isophthalamide) particles obtained in Example 1(a) had a fineness of 2de.
A short cut fiber with a cut length of 3 mm made of poly(metaphenylene isophthalamide) fiber was mixed with 10% by weight of the polymer particles and compression molded under the following conditions to form a flat plate with a thickness of 3 mm. It was a classy item. Heating temperature: 320℃ Pressure: 330Kg/cm Pressure time: 40 minutes During molding, replace the molded area with _N2 in advance.
Care was taken to prevent the mixture of polymer and short cut fiber 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 hard, smooth surfaces and ribbed edges were obtained. The strength and elongation, modulus and Izo impact value (notched) of these were measured and were as shown in the following table.

[Table] Example 4 (a) Production of polymer particles The temperature of the metaphenylenediamine solution and isophthalic acid chloride solution in the first reaction was set to -15°C, and during the first reaction, the reaction system was
Example 1 except that 590 mg of aniline was added.
Interfacial polymerization is carried out in the same manner as above, and the intrinsic viscosity is
1.4 white polymer particles were obtained. 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 approximately 1 μm, and the average particle size of the aggregated particles is approximately 1 μm.
0.2mm, surface area is 4.8m ² /g, and apparent density
It was 0.35g/ ^m3 . (b) Compression molding The polymer particles were compressed using a mixture of 10% by weight of short cut fibers with a cut length of 1 mm made of poly(paraphenylene terephthalamide) fibers with a fineness of 1.5 DE. Dampel-shaped test pieces were made by molding. The molding conditions at this time were as follows. Heating temperature: 300° C. Pressure: 310 Kg/cm Pressure time: 35 minutes In this molding, the molding section was kept in a vacuum from before the start of molding until the end of the formed paper. The physical properties of the obtained test piece were as follows. Tensile strength 12.9Kg/mm ² Elongation at break 5.2% Modulus 350Kg/mm ² Izot impact strength (with notch)
8.5Kg・cm/cm Example 5 27g of the poly(metaphenylentisophthalamide) particles of Example 2 were mixed with water in a home blender.
Pour 100ml and add under stirring to create a water dispersion system.
3 g of commercially available poly(paraphenylene terephthalamide) pulp particles or para(meth)aramid pulp particles described in Japanese Patent Publication No. 59-16002 were added to it,
Stirring was continued for about 5 minutes to create a mixed dispersion system of polymer powder and pulp particles. Immediately after stopping stirring,
After separating the mixture of polymer particles and pulp particles using a nuttie, it was crushed and spread on a shear tray and dried in an oven at 120°C. The dried mixture was compression molded using a compression molding machine under the following conditions.
A flat plate with a length of 100 mm and a thickness of 4 mm was obtained. Compression molding conditions Temperature: 320℃ Pressure: 490Kg/ ^cm2 Molding time: 30 minutes _N2 substitution during compression molding The above flat plate was processed to the size of a sample for measuring physical properties according to JIS standards, and the tensile strength, bending strength,
The Izot impact value was measured. The results were compared to those not containing pulp particles (experiment no.
1) and shown in Table 4.

[Table] Example 6 10% by weight of carbon fiber (fiber diameter
Compression molding was carried out under the same conditions as in Example 2 with the addition of short cut fibers (3.7 μm, fiber length 1 mm). The physical properties of the obtained molded article were as follows. Tensile strength 13.5Kg/mm ^2Elongation at break 5.0% Modulus 400Kg/mm ^2Izot impact value 10.5・cm/cm

Claims (1)

[Claims] 1. A large number of microparticles with an average particle size of 0.1 to 10 μm are aggregated to form porous aggregated particles, and the average particle size of the aggregated particles is 10 to 400 μm, and the surface area is 1
~20 m ² /g of aromatic polyamide particles are supplied to a compression molding device alone or together with a reinforcing fibrous material, and heated at a temperature of 200 to 400°C and a pressure of 100 to 1000.
A method for producing an aromatic polyamide molded article, which comprises heating and pressurizing to a condition of Kg/cm ² and maintaining that state for 20 minutes to 5 hours. 2. A method for producing an aromatic polyamide molded article according to claim 1, wherein the molded article is kept in a non-contact state with air during heating and pressurization. 3. The manufacturing method according to claim 1 or 2, wherein the amount of the reinforcing fibrous material is 3 to 30% by weight based on the aromatic polyamide particles. 4. The manufacturing method according to claim 3, wherein the reinforcing fibrous material is a short cut fiber made of aromatic polyamide and having a fiber length of 3 mm or less. 5. The manufacturing method according to claim 3, wherein the reinforcing fibrous material is pulp-like particles made of aromatic polyamide.