KR970000403B1 - Method for manufacturing aromatic polyamide - Google Patents

Abstract

In the process for preparing aromatic polyamide by polymerizing aromatic diamine and aromatic dicarbonic acid chloride, a method for neutralizing an obtained reaction solution with alkali is described. Thus, 90-99.9 equiv.% of inorganic alkali is added in polyamide solution and 0.1-10 equiv.% of basic inorganic salt(M(OAc)n(H2O)m) is added continuously in neutralized amide solution. In formular, M is an alkali or alkali earth metal, n is an integer of 1 or 2, m is an integer of 0.1 or 2, OAC is an acetic acid group.

Description

Process for producing aromatic polyamide

The present invention relates to a method for producing an aromatic polyamide, and more particularly, to the generation of insoluble foreign matter in a polyamide solution by using a basic organic salt as a neutralizing agent during the neutralization reaction carried out after the polymerization of aromatic diamine and aromatic dicarboxylic acid chloride. The present invention relates to a method for producing an aromatic polyamide that can reduce manufacturing costs by improving the process management by reducing the filter and extending the use time of the filter.

Aromatic polyamide is an industrially important material because it is excellent in heat resistance, flame resistance, chemical resistance, high temperature form stability, thermal decomposition resistance, electrical properties and mechanical properties, and can be molded into various forms such as films, sheets, and fibers.

Aromatic polyamides are generally industrially advantageously prepared by low temperature solution polymerization in which an aromatic diamine and an aromatic dicarboxylic acid chloride are reacted in a polar amide solvent. The reason for this is that in the case of low temperature solution polymerization, as in the case of the interfacial polymerization, the cumbersome process of separating the produced polymer and re-dissolving it in a solvent is not necessary to prepare a molded article. Because it is possible.

In the low temperature solution polymerization method, first, an aromatic diamine is dissolved in a polar amide solvent and an aromatic dicarboxylic acid chloride is added to the obtained solution to produce an aromatic polyamide. In the polyamide solution obtained by this polymerization reaction, hydrochloric acid produced during the polymerization reaction is present, and an alkali equivalent of calcium hydroxide, lithium hydroxide and the like equivalent to hydrochloric acid produced during the polymerization reaction is added to neutralize the hydrochloric acid generated during the polymerization reaction. The polyamide solution in which the neutralization reaction is completed can be formed into a fiber or a film by the dry method in the state, or can be formed into a fiber, a film, a pulp-like particle by the wet method.

However, when the polyamide is prepared by the low temperature solution polymerization method, the inorganic alkali used during the neutralization reaction reacts with hydrochloric acid of the polyamide solution to form salts, and increases the solubility of the polyamide to increase the polyamide. Although it has the advantage of lowering the viscosity of the solution, in the strong acid state in which the hydrochloric acid of the polyamide solution is high before neutralization, the inorganic alkali reacts rapidly and the neutralization rate is high, but in the late stage of the neutralization, that is, the pH is neutralized. When pH 7 is reached, the reaction rate of inorganic alkali with hydrochloric acid decreases rapidly, and particles of inorganic alkali remain in neutralized solution in an unreacted state, and after the neutralization is completed, insoluble inorganic alkalis must be filtered through a filter. It has been a cause of process delay such as shortening of the filter replacement cycle during the process.

The present invention has been made to solve the above problems, it is an object of the present invention to provide a method for producing a polyamide that can prevent the production of insoluble residues in the polyamide solution to prevent the process delay due to the replacement of the filter.

In order to achieve the above object, the present invention provides an aromatic polyamide comprising a step of dissolving aromatic diamine in a polar amide solvent, adding aromatic dicarboxylic acid chloride to carry out a polymerization reaction and neutralizing hydrochloric acid generated during the polymerization reaction. In the manufacturing method of the above, the said neutralization process is carried out by 1) putting 90-99.9 equivalent% of neutralizing agents required for neutralization as an inorganic alkali to the polyamide solution to which polyamide was polymerized first; 2) After the inorganic alkali is added, 0.1 to 10 equivalent% of the neutralizing agent required for the second neutralization is represented by the general formula M (OAc) _n (H ₂ O) _m (M is a monovalent or divalent alkali or alkaline earth metal, n is 1 or Provided is a method for producing a polyamide comprising a basic organic salt represented by an integer of 2, m is an integer of 0, 1 or 2, OAc is an acetic acid group, and is added to a polyamide solution primarily neutralized with an inorganic alkali. .

During the neutralization process, if only inorganic alkali is used, the excess inorganic alkali precipitates in the polyamide solution as described above, forming insoluble foreign matter in the polyamide solution, which must be removed by filtration through a filter for subsequent processing. Will be. In addition, the inorganic alkali compound is a strong base, the pH of the polyamide solution is greatly changed even if a small change in the input amount during the neutralization reaction, the physical properties of the polyamide is likely to be lowered.

As in the present invention, 90 to 99.9 equivalents of the total equivalent of alkali added to the primary is neutralized with 90 to 99.9 equivalents of hydrochloric acid present in the polyamide solution using an inorganic alkali, and the remaining 0.01 to 10 equivalents is By neutralizing using a basic organic salt having a weak basicity, it is possible to prevent a sudden change in pH of the polyamide solution due to the addition of a neutralizing agent in the vicinity of the equivalence point to stabilize the physical properties of the polyamide polymer.

Further, the basic organic salt added to the above is solubility in the polyamide solution that even if excessively added, there is a long nap that does not form an insoluble component in the polyamide solution.

In the present invention, the polymerization reaction in the case of producing an aromatic polyamide is carried out according to a conventional low temperature solution polymerization method. For example, when following the method described in Unexamined-Japanese-Patent No. 35-14399 etc., it is normally performed in the range of monomer concentration of 0.6-1.5 mol / L. That is, the polymerization reaction is dissolved by adding an aromatic diamine and an amide solvent in the reaction vessel, or a large amount of its dissolution in a separate container in advance (when possible to cool to a predetermined temperature at the start of the reaction if possible) The required amount of solution is added, preferably the temperature at the time of the start of the reaction is -20 ° C to + 10 ° C, and the aromatic dicarboxylic acid chloride in solid or molten phase is preferably stirred while the reaction temperature does not exceed about 70 ° C. Add it over time while avoiding. It is also preferable to make the degree of polymerization of each batch at the same level by detecting the viscosity of the reaction system with a torque-meta attached to the stirrer in the middle of the polymerization reaction and terminating the polymerization when the desired value is reached. . Moreover, the operation | movement which always reaches | attains a degree of reached polymerization degree, for example, added a small amount of a polymerization terminator (monofunctional aliphatic or aromatic anhydride, carboxylic acid halide, isocyanate, amines, etc.) in the polymerization system, or reached the desired degree of polymerization. At the same time, an operation such as adding a polymerization terminator or an excessive amount of aromatic dicarboxylic acid chloride as a monomer, and adding an inorganic alkali for neutralization is also an effective method.

In the present invention, the polymerization reaction is performed by first neutralizing by adding 90 to 99.9% equivalents of hydrochloric acid present in the reaction system in the form of an inorganic alkali in powder or dispersion state with a solvent, and the remaining amount of hydrochloric acid is the same or slightly excess of basic organic. Salt is added to complete neutralization. Although the amount of inorganic alkali used in the first neutralization may be less than 90% of hydrochloric acid, in this case, it is economically disadvantageous, and if it exceeds 99.9%, the portion of the inorganic alkali is not reacted with hydrochloric acid because it is almost the point of neutralization point. It is difficult to obtain a uniform spinning solution because it remains undissolved.

There is no particular limitation on the reaction vessel used in the present reaction, but effective stirring is required at the beginning of the neutralization reaction, and in the late stage of the polymerization reaction, it becomes a high viscosity reaching up to several thousand poise in the late stage of the polymerization reaction, and in such a high viscosity state. It is preferable to select the shape in consideration of the polymerization reaction and the like. Preferred reactors may be, for example, agitators such as anchors or rasters, and reactors such as those which are conical to allow a solution with low viscosity to flow, or a vertical or biaxial stirrer. Horizontal reactors are possible.

In this reaction, the reaction solution after the neutralization reaction and the neutralization reaction are discharged from the reaction vessel for the next step by a pressurized pump or the like which can be pressurized with an inert gas or separated at the bottom of the reaction vessel.

Aromatic diamines used in the present invention include metaphenylenediamine, paraphenylenediamine, 4,4'-diaminodiphenylether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl Ketones, 3,3'-diaminodiphenylsulfone, and the like, and aromatic dicarboxylic acid chlorides include isophthalic acid chloride, terephthalic acid chloride, 2,6-naphthalene dicarboxylic acid chloride, diphenyl dicarboxylic acid chloride, and the like. Typical ones are used alone or in combination.

Examples of the amide solvents include dimethylacetamide, N-methylpyrrolidone, tetramethylurea, hexamethylphosphoramide, and the like.

What is preferable as an inorganic alkali used for this invention is that the salt produced by neutralization improves the solubility of an aromatic amide, and such inorganic alkali is calcium hydroxide, calcium carbonate, lithium hydroxide, lithium carbonate, etc. As the basic organic salt having a general formula of M (OAc) _n · (H ₂ O) _m , it is preferable that the salt produced after neutralization improves the solubility of the aromatic amide as in the case of inorganic alkali, and as such basic organic salt, calcium acetate , Lithium acetate, calcium acetate monohydrate, lithium acetate monohydrate, calcium acetate dihydrate, lithium acetate dihydrate and the like.

Next, the present invention will be described in more detail with reference to preferred embodiments. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to these examples.

Intrinsic viscosity (η inh) in the Examples is a value measured at 25 ° C. with a polymer concentration of 0.5 g / 100 ml in 96% sulfuric acid. The filter used for the transfer after neutralization uses a filter with an external steam heating device and is transferred by using a filter element having a length of 250 m, a diameter of 20 mm and a particle diameter of 20 micro (micro). Transferred.

Comparative Example (Preparation of Polyamide Solution)

A 100-liter anchor-type stirrer having a conical shape of 1700 mm in diameter and having a bottom portion of 90 degree cones was cooled to −5 ° C. while adding 4540 g of m-phenylenediamine and 60 L of N-methylpyrrolidone in a reaction vessel. While stirring this solution, 8400 g of molten isophthalic acid chloride was added over about 13 minutes, and isophthalic acid chloride was then added in small portions until the torque-meta value attached to the stirrer reached a predetermined value. This additional amount was 130 g. When the torque-meta value reached the predetermined value, 4204 g of calcium carbonate was dispersed and added with the same amount of N-methylpyrrolidone and stirred for 2 hours to obtain a clear viscous solution. Ηinh, measured by taking a part of this solution, was 1.33 and was a value sufficient for producing a molded article. PH of the obtained neutralization solution was measured and it was acidic as 2.6. Subsequently, the feed amount was 15 kg until the filter tip pressure reached 100 kg / cm 2 when the pump was transferred to the defoaming pipe through the filter.

Example 1

4540 g of m-phenylenediamine and 60 L of N-methylpyrrolidone were added to the same reaction container as used in the comparative example and cooled to -8 ° C while stirring. While stirring this solution, 8400 g of molten isophthalic acid chloride was added over about 20 minutes, and then isophthalic acid chloride was added in small portions until the torque-meta value attached to the stirrer reached a predetermined value. This additional amount was 180 g. At the time when the torque-meta value reached the predetermined value, a solution of 4,000 g of powdered calcium carbonate dispersed in the same amount of N-methylpyrrolidone was added to undergo a first neutralization reaction, followed by a slight excess of 350 g of calcium acetate. The solution dissolved in -methylpyrrolidone was added and stirred to complete the neutralization reaction to obtain a clear viscous solution. The? Inh measured by taking a part of this solution was 1.70 and was a value sufficient for producing a molded article. PH of the obtained neutralization solution was measured and it was neutral at 7.1. Subsequently, the feed amount until the filter tip pressure reached 100 kg / cm 2 was transferred to the defoaming tube through the filter using a pump.

Example 2

4540 g of m-phenylenediamine and 60 L of acetamide were added to the same reaction container as used in the Comparative Example, and the mixture was cooled to -8 ° C while stirring. While stirring this solution, 8400 g of molten isophthalic acid chloride was added over about 20 minutes, and then isophthalic acid chloride was added in small portions until the torque-meta value attached to the stirrer reached a predetermined value. This additional amount was 180 g. When the torque-meta value reached the predetermined value, the solution was prepared by dispersing 2963 g of powdered calcium hydroxide with the same amount of acetamide, followed by a first neutralization reaction, and then a solution of 350 g of slightly excess calcium acetate in the same amount of acetamide. Was added and stirred to complete the polymerization reaction to obtain a clear viscous solution. Ηinh, measured by taking a part of this solution, was 1.65 and was a value sufficient for producing a molded article. PH of the obtained neutralization solution was measured and it was neutral at 7.1. Subsequently, the feed amount until the filter tip pressure reached 100 kg / cm 2 was transferred to the defoaming tube through the filter using a pump, and the feeding amount was 45 kg.

Example 3

4000 g of m-phenylenediamine, 540 g of P-phenylenediamine, and 60 L of dimethylacetamide were added to the same reaction vessel as used in Example 1, and the mixture was cooled to -8 ° C while stirring. While stirring this solution, 8400 g of molten isophthalic acid chloride was added over about 20 minutes, and then isophthalic acid chloride was added in small portions until the torque-meta value attached to the stirrer reached a predetermined value. This additional amount was 180 g. When the torque-meta value reached the predetermined value, the first neutralization reaction was performed by adding a dispersion in which 4000 g of powdered calcium carbonate was dispersed in 3000 ml of dimethylacetamide, followed by a slight excess of 350 g of calcium acetate in 700 ml of dimethylacetamide. The solution dispersed in was added and stirred to complete the neutralization reaction to obtain a clear viscous solution. Ηinh, measured by taking a part of this solution, was 1.65 and was a value sufficient for producing a molded article. PH of the obtained neutralization solution was measured and it was neutral at 7.2. Subsequently, the feed amount until the filter tip pressure reached 100 kg / cm 2 was transferred to the defoaming tube through the filter using a pump, which was 48 kg.

Example 4

60 g of N-methylpyrrolidone was added to 4000 g of m-phenylenediamine and 540 g of P-phenylenediamine in the same reaction container as used in the comparative example, followed by cooling to -8 ° C. While stirring this solution, 8400 g of molten isophthalic acid chloride was added over about 20 minutes, and then isophthalic acid chloride was added in small portions until the torque-meta value attached to the stirrer reached a predetermined value. This additional amount was 180 g. At the time when the torque-meta value reached the predetermined value, a solution of 3028 g of powdered calcium oxide dispersed with the same amount of N-methylpyrrolidone was added to undergo a first neutralization reaction, followed by a slight excess of 390 g of calcium acetate monohydrate. The solution dissolved in N-methylpyrrolidone was added and stirred to complete the neutralization reaction to obtain a transparent viscous solution. The? Inh measured by taking a part of this solution was 1.67 and was a value sufficient for producing a molded article. PH of the obtained neutralization solution was measured and found to be 7.5 neutral. Subsequently, the feed amount until the filter tip pressure reached 100 kg / cm 2 was transferred to the defoaming tube through the filter using a pump, and the feeding amount was 45 kg.

Example 5

4540 g of m-phenylenediamine and 60 L of N-methylpyrrolidone were added to the same reaction vessel used in the comparative example and cooled to -8 ° C while stirring. While stirring the solution, 6400 g of isophthalic acid chloride and 2000 g of terephthalic acid chloride were added over about 20 minutes while stirring the solution. Then, isophthalic acid chloride was added in small portions until the torque-meta value attached to the stirrer reached a predetermined value. This additional amount was 180 g. When the torque-meta value reached the predetermined value, a solution of 3028 g of powdered calcium oxide dispersed with the same amount of N-methylpyrrolidone was added to undergo a first neutralization reaction, and then 294 g of a slightly excess amount of lithium acetate was added to the same amount of N. The solution dissolved in -methylpyrrolidone was added and stirred to complete the neutralization reaction to obtain a clear viscous solution. Ηinh, measured by taking a part of this solution, was 1.65 and was a value sufficient for producing a molded article. PH of the obtained neutralization solution was measured and found to be 7.5 neutral. Subsequently, the feed amount was 47 kg until the filter tip pressure reached 100 kg / cm 2 when the pump was transferred to the defoaming pipe through the filter.

Claims (3)

A method of neutralizing hydrochloric acid present in a solution by adding an inorganic alkali to a solution obtained by this polymerization after addition of an aromatic dicarboxylic acid chloride to the solution in which the aromatic diamine is dissolved in a polar amide solvent to produce an aromatic polyamide. In the reaction, the first neutralization is performed by adding an inorganic alkali corresponding to 90 to 99.9 equivalent% of hydrochloric acid generated during the reaction, followed by neutralization by adding a basic inorganic salt of the following formula (1) corresponding to 0.1 to 10% equivalent Neutralization method of the aromatic polyamide polymerization solution, characterized in that to complete. M (OAc) _n (H ₂ O) _m (1) (Wherein M is a monovalent or divalent alkali or alkaline earth metal, n is an integer of 1 or 2, m is an integer of 0,1 or 2, and OAc represents an acetic acid group) The method of claim 1 wherein the inorganic alkali is selected from calcium hydroxide, calcium carbonate, lithium hydroxide, lithium carbonate. The method of claim 1, wherein the basic inorganic salt is selected from calcium acetate, lithium acetate, calcium acetate monohydrate, lithium acetate monohydrate, calcium acetate dihydrate, and lithium acetate dihydrate.