JPS5839051B2 - Method for manufacturing aromatic polyamide molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for manufacturing aromatic polyamide molded articles, and more specifically, a wet molding method or a dry molding method from a solution containing an aromatic boric acid. The present invention relates to an improved method for producing molded products that do not contain air bubbles when producing molded products such as fibers, tapes, and films.

In general, aromatic polyamides have a significantly higher melting point or glass transition point than aliphatic boric acids such as nylon 6 and nylon 66 due to the rigidity of molecules based on polar bonds called amide bonds and aromatic groups. It has excellent shape stability at high temperatures, flame resistance, thermal decomposition resistance, chemical resistance, and retention of electrical and mechanical properties, making it extremely valuable industrially as a heat-resistant fiber, film, or molding material. It's expensive.

Aromatic polyamide is industrially dimethylacetamide,
N-methylpyrrolidone, hexamethylphosphoramide,
Polymerization is carried out by reacting an aromatic diamine with an aromatic dicarboxylic acid chloride in a so-called amide solvent such as tetramethylurea, and molded products are manufactured by directly using the polymerized solution or by using the generated hydrochloric acid. After neutralizing the polymer, or after redissolving the isolated polymer in a solvent, it is carried out by a wet method or a dry method.

The viscosity of the aromatic polyamide solution during molding is usually 50 to 1000 poise, and the solution contains many bubbles due to mechanical stirring, so it is necessary to defoam before molding. must be done.

Conventional methods for removing air bubbles contained in a polymer solution include leaving it in a storage tank for a long time or reducing the pressure, forming the solution into a thin film and depressurizing it to degas it, and stirring the solution while stirring in the tank. Methods of degassing by reducing the pressure are known, but even if these methods are used to completely defoam, it takes too long, and reducing the pressure causes the solvent to evaporate and the polymer concentration to fluctuate. This is not necessarily a satisfactory method.

In particular, when the polymer concentration in the solution is increased in order to increase productivity, the solution viscosity is about 500 to 100 poise, and the bubbles contained in such a solution cannot be completely removed by the above method. is almost impossible.

When manufacturing fibers from a solution that has not been completely defoamed, thread breakage during spinning is frequent, the wound system has a lot of fuzz, and the mechanical performance of the thread is poor due to the bubbles contained in the thread. It becomes.

In addition, in film manufacturing, air bubbles remain in the product film, which not only reduces mechanical performance, but also reduces electrical performance, especially dielectric breakdown voltage, making it impossible to apply it to the field of electrical insulation materials. It is something.

As described above, sufficiently removing air bubbles contained in the polymer solution not only improves the operability but also significantly improves the quality of the product, which is an extremely important issue.

The present inventors have arrived at the present invention as a result of intensive research into a method for sufficiently removing bubbles contained in a solution of aromatic boria □ in a short time and without evaporating the solvent.

That is, the present invention provides an aromatic polyamide molding characterized in that a solution of an aromatic polyamide is supplied to a screw extruder, extruded under a back pressure of at least 3 to 9/CyA, and then subjected to wet molding or dry molding. It is a method of manufacturing products.

According to the method of the present invention, there is no operational problem due to air bubbles during molding, and it is possible to produce molded products of excellent quality that do not contain air bubbles.

Conventionally, aromatic polyamide molded articles have never been molded using such a method.

In the present invention, the aromatic boria □ solution means a multi-liquid solution containing 5 to 30 parts by weight of an aromatic polyamide represented by the following general formulas 0) and/or (2).

NH-Ar1-NHCO-Ar2-CO-(1)-■-
Ar3-CO-(2) (However, Ar1.Ar2.Ar3 are divalent aromatic groups and may be the same or different.) Examples of aromatic polyamides include m-phenylene terephthalamide ; m-phenylene isophthalamide; P
-phenylene terephthalate, P-phenylene isophthalate, 4. 4'-oxydiphenylene terephthalamide, 4. Examples include 4'-oxydiphenylene isophthalamide, P-benzado 1m-benzamide, etc., and copolymers of these may also be used, as well as small amounts of components other than aromatic groups, such as piperazine and cyclohexanedicarboxylic acid. It may also include.

Typical solvents for aromatic polyamides include dimethylformamide, dimethylacetamide, N-methylpyrrolidone, tetramethylurea, hexamethylphosphoramide, and dimethylsulfoxide, but mixtures of these or those that increase solubility Therefore, a solvent containing a soluble metal chloride such as lithium chloride or calcium chloride, or a strong acid such as sulfuric acid, chromium sulfuric acid, or fluorosulfuric acid may be used.

The screw extruder used in the present invention can be any conventional screw extruder for molding powder or granular plastic, and there are no particular limitations on the shape, but the distance between the compressed parts It is preferable that it not be too short.

The back pressure when extruding a solution of aromatic polyamide is at least 3';! /cl, preferably 5 kg/c4 or more pressure is required, and if the back pressure is less than 3 kti/c4, defoaming is incomplete.

The aromatic polyamide solution extruded from a screw extruder may be stored in a tank and then molded, but it may be extruded using a metering pump (such as a gear pump) equipped with a spinning nozzle or a film molding die at the tip. It is most advantageous to attach the degassed solution to the top of the machine and immediately use it for molding.

The method for molding the aromatic polyamide solution used in the present invention includes already known methods, such as a wet molding method using water, dilute sulfuric acid, etc. as a coagulation bath when the solvent is a strong acid such as sulfuric acid, and a wet molding method using an organic solvent. In such cases, a dry molding method or a wet molding method using water, water containing metal salts, alcohols, glycerin, polyalkylene glycol, etc. as a coagulation bath can be employed.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, ηinh in the example is 25°C, 96 ton sulfuric acid, polymer concentration 0.5 da/100 a! This is the value measured at

Comparative Example 1 Poly(
m-phenylene isophthalamide) was synthesized.

Since hydrochloric acid was present in this polymerization solution, the hydrochloric acid was neutralized by adding an equivalent amount of calcium hydroxide.

This solution contained 18 weight φ of poly(m-phenylene isophthalamide) having an ηih of 1.52, and had a solution viscosity of 2880 poise at 20°C.

Transfer the obtained solution to a degassing tank (liquid depth of about 25a),
Defoaming was carried out for 4 hours at 60° C. and a degree of vacuum of 10 ηinh.

After defoaming, the degassing tank was pressurized to 3 kti/cyst and the above solution was poured into a 50 mm tube with a pore size of 0.08 mytt.
Discharged through a 0-hole nozzle into a polyethylene glycol bath with an average molecular weight of 600 heated to 100°C,
After being immersed for a distance of t711, it was taken out from the bath, washed with water, stretched with hot water (twice), dried, and wound up at a speed of 10.6 m/min.

During the spinning operation described above, yarn breakage was often observed on the nozzle surface, and numerous fluffs were observed in the wound yarn.

This fuzz became even more severe due to the subsequent dry heat stretching (2.4 times) at 320°C.

When the obtained yarn was observed under a microscope, it was found that it contained air bubbles.

Furthermore, the polymer concentration increased to 19.2% by weight due to evaporation of dimethylacetamide during the defoaming operation.

Example 1 A solution containing 18 weight of poly(m-phenylene isophthalamide) used in Comparative Example 1 was heated at 40°C at room temperature.
m diameter L/D=20 screw extruder, back pressure 13.5 kg/c! The film was wound up in the same manner as in Comparative Example 1 through a gear pump and a 5000-hole nozzle with a hole diameter of 0.0811M.

In this case, unlike the case of Comparative Example 1, no thread breakage was observed on the nozzle surface, and no fuzz was observed in the wound thread.

The polymer concentration of the solution exiting the nozzle was determined, and it showed exactly the same concentration value as before passing through the screw extruder.

Example 2 m-phenylenediamine in dimethylacetamide,
Mixture of inophthalic acid chloride and terephthalic acid chloride (isophthalic acid chloride: terephthalic acid chloride =
80:20) to synthesize poly(m-phenylene isophthalamide/terephthalamide) copolymer, the resulting hydrochloric acid was neutralized by adding an equivalent amount of calcium hydroxide, and the polymer content was 20% higher by weight. A solution was obtained.

This solution had a solution viscosity of 3400 poise at room temperature.

The resulting solution was heated at room temperature with a diameter of 20 mm, L/D = 1.
The mixture was supplied to a No. 8 screw extruder, passed through a gear pump under a back pressure of 25 kg/lJ, and extruded into a film from a T-shaped die with a width of 400 mm onto a stainless steel roller heated to 110°C.

The film was further dried on a roller by blowing hot air to remove the solvent, and then washed with water and dried.

After heat-treating this film at 300'C for 5 minutes, the dielectric breakdown voltage was measured at 20 points.
It entered the range of 210 Kv/1m.

Then, microscopic observation was performed, but no air bubbles were observed in the film.

Comparative Example 2 The same polymer solution used in Example 2 was prepared at a liquid depth of 2.
The mixture was transferred to a tank with a capacity of 5ffHf and defoamed at 60°C for 4 hours at a reduced pressure of 0.5ffffHf.

Next, tank 3 to 9/c! The solution was extruded through a T-shaped die with a width of 400 mm, and a film was produced in the same manner as in Example 2. The dielectric breakdown voltage of the resulting film was measured at 20 points, and it was 70 KV to 210 KV/ffff. The variation was very large.

Furthermore, microscopic air bubbles were observed in the film by microscopic observation.

Claims (1)

[Claims] 1. A method for producing an aromatic polyamide molded article, which comprises supplying a solution of aromatic polyamide to a screw extruder, extruding it under a back pressure of at least 3'l/cyA, and then performing wet or dry molding.