JPS584740B2 - Polyamide Seikeibutsuno Seizou Hohou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing molded articles from an aromatic polyamide solution.

More specifically, a solution consisting of an aromatic polyamide, an inorganic salt such as calcium chloride, and an amide solvent is coagulated with a polyethylene glycol coagulating liquid that is recycled while recovering the amide solvent to form fibers, tapes, films, etc. It relates to methods of manufacturing things.

Fibers and films made of aromatic polyamides are characterized by excellent Young's modulus and strength due to high orientation and crystallinity, as well as thermal rigidity as expected from the rigidity of their molecular structure and intermolecular forces.

In order to increase the solubility of the polymer and the stability of the dope, a dope obtained by dissolving the polymer in an amide solvent containing an inorganic salt such as calcium chloride is used to form a molded article of aromatic polyamide. A method has been proposed in which the liquid is discharged into an aqueous coagulating liquid containing an inorganic salt such as.

However, in order to obtain fibers and films with good transparency and high quality using this method, the temperature of the aqueous coagulation bath and the concentration of inorganic salts such as calcium chloride must be strictly controlled to maintain them within the optimum range. There is a need to.

Furthermore, in order to obtain fibers and films with excellent performance, the concentration of the amide solvent in the aqueous coagulation liquid must also be 10% by weight or less.

Therefore, in order to recover the amide solvent from such a coagulated liquid, it is necessary to evaporate a large amount of water, or to extract the amide solvent with a large amount of extractant and then distill it, making the operation complicated. , and there is no escape from economic disadvantage.

Furthermore, it is known that amide solvents sometimes form complexes with inorganic salts such as calcium chloride, which makes it extremely difficult to efficiently recover amide solvents.

Therefore, methods for preparing dope without adding inorganic salts such as calcium chloride to amide solvents have been proposed;
The operation becomes complicated, and if an aqueous coagulating liquid containing salts such as calcium chloride is used, the above-mentioned drawbacks cannot be solved.

As a result of intensive research to improve the above-mentioned drawbacks in the method of manufacturing molded articles from aromatic polyamide solutions, the present inventors have discovered aromatic polyamide fibers and fibers with excellent performance when polyethylene glycol is used as a coagulating liquid. We found that a film could be obtained and proposed it separately, but as a result of further investigation, we found that a polyethylene glycol solution containing an amide solvent and an i-ide or bromide of calcium, lithium, magnesium, strontium, etc. Alternatively, by adding sodium salt or ammonium salt of oxalic acid, inorganic salts such as calcium chloride become sodium chloride or ammonium chloride, etc. and calcium salts of sulfuric acid, carbonic acid, or oxalic acid, and these salts can be mixed with amide solvents. The present invention was achieved by discovering that it does not form a complex and does not dissolve in polyethylene glycol.

That is, in the present invention, when producing molded articles such as fibers, tapes, and films by discharging and coagulating a solution consisting of an aromatic polyamide, an inorganic salt such as calcium chloride, and an amide solvent into a polyethylene glycol coagulating liquid, Parts by weight of polyethylene glycol (coagulation liquid I) Z containing amide solvent a and inorganic salts such as calcium chloride and b weight % are supplied to a coagulation bath to form a molded article, and then amide solvent a' is added from the coagulation bath. Weight %, inorganic salt b' weight % such as calcium chloride
The following (1) is used as a polyethylene glycol coagulating solution containing
) and formula (2), and divide it into X parts by weight (solidifying liquid ■) and Y parts by weight (solidifying liquid ■),
The thus obtained coagulation liquid is added with the theoretical amount of sodium sulfate, ammonium sulfate, sodium carbonate, ammonium carbonate,
At least one salt selected from the group consisting of sodium oxalate and ammonium oxalate is added, then the amide solvent is removed by evaporation from the coagulated liquid, and the salt precipitated by the addition of the salt is separated. This method for producing an aromatic polyamide molded article is characterized in that the remaining liquid is recycled and used as a coagulating liquid I by combining it with the coagulating liquid (1).

X+Y=Z+Ya'/100+Yb'/100 (2) The aromatic polyamide as referred to in the present invention means that 80 mol% or more, preferably 85 mol% or more of the repeating units of the synthetic linear polymer are represented by the following formula (3) and/or those constituted by formula (4) are collectively referred to.

+NR1-Ar1-NR2CO-Ar2-co+-(3
)-fNRs-Ars-CO-+ (4) However, Ar1, Ar2, and Ar3 are divalent aromatic residues and may be the same or different, and R1, R2, and R3 represent hydrogen or a methyl group. be.

Suitable examples thereof include polymethaphenylene isophthalamide and polymetabenzamide.

These aromatic polyamides are easily synthesized by any known method, such as low-temperature solution polymerization using the corresponding diamine and hydrochloride of dicarboxylic acid chloride and/or aminocarboxylic acid chloride;
Interfacial polymerization methods etc. can be applied.

The polymer used in the present invention has an ηinh of 0.5 or more, preferably 0.8 or more, as determined from a value measured at a concentration of 0.5g/100Ll in 96% sulfuric acid at 25°C. .

To prepare the dope used in the present invention, a polymer is obtained by the above-mentioned polymerization method, etc., and after the polymer is isolated, the dried polymer is added to an amide solvent to increase the solubility of the polymer and the stability of the dope. A method of dissolving in a solution to which at least one inorganic salt such as chloride or bromide of calcium, lithium, magnesium, strontium, etc., particularly preferably calcium chloride, is appropriately added, or diamine and dicarboxylic acid chloride and/or aminocarboxylic acid. After polymerizing acid chloride hydrochloride in an amine solvent, at least one base such as a hydroxide or oxide of calcium, lithium, magnesium, strontium, etc., without isolating the resulting polymer, Particularly preferably, a method of neutralizing with calcium hydroxide can be applied.

In the case of the latter method, the dope will contain water as a by-product due to the neutralization reaction, but this is not a problem.

Examples of amide solvents applicable to the present invention include dimethylacetamide, N-methylpyrrolidone, hexamethylphosphoramide, and tetramethylurea.

These may be used alone or in combination of two or more.

Dimethylacetamide is particularly preferred because it has a low boiling point and a low heat of vaporization and is advantageous for recovery.

The concentration of the polymer in the dope used in the present invention varies depending on the degree of polymerization, composition, and type of solvent, but usually,
It is used in an amount of 10 to 40% by weight, preferably 15 to 25% by weight.

If the polymer concentration is outside this range, moldability may be poor, the physical properties of the resulting molded product may be poor, or the dope viscosity may become too high, making it difficult to mold, which is not preferred.

The polyethylene glycol used as a coagulating liquid in the present invention has an average molecular weight of 100 to 6000, particularly 200.
~4000 is preferred.

If the average molecular weight is less than 100, the transparency of the resulting molded product will be poor, and if it exceeds 6,000, the viscosity of the coagulating liquid will become too high, which is not preferable because it will cause operational difficulties.

The polyethylene glycol concentration in the coagulation liquid is preferably 70% by weight or more, particularly 80% by weight or more.

Therefore, the coagulation liquid may contain an amide solvent, an inorganic salt such as calcium chloride, or water in addition to polyethylene glycol, but the total amount of these substances is preferably less than 30% by weight.

Even if the polyethylene glycol concentration in the coagulation liquid is less than 70% by weight, there is no problem in recovering the amide solvent, but this is not preferable because the performance of the resulting molded product will be inferior.

The temperature of the coagulating liquid may be above the melting point and below the boiling point of the coagulating liquid used, but a temperature of 65 to 150° C. is particularly preferable from the viewpoint of the performance of the molded product that can be obtained.

As a molding method for carrying out the method of the present invention, a conventionally known normal wet molding method is used.

For example, a horizontal type system in which the coagulating liquid is supplied in parallel or countercurrent to the discharged dope, and a vertical type system in which the coagulating liquid is supplied from the bottom to the top or from the top to the bottom can also be applied.

The molded product solidified with the coagulation liquid can be made tough by washing with water and then subjecting it to a wet heat stretching treatment, or by washing with water, moist heat stretching, and drying followed by heat treatment or stretching heat treatment. can.

The coagulating liquid in the present invention is used cyclically, for example, as shown below.

First, an amide solvent a weight %, an inorganic salt such as calcium chloride b weight % (or an amide solvent a weight %, an inorganic salt such as calcium chloride b weight % and water C weight % or less) Aromatic polyamide is obtained from diamine and hydrochloride of dicarboxylic acid chloride and/or aminocarboxylic acid chloride in a solvent, and molded products are produced from the dope which is neutralized with a base such as calcium hydroxide without isolating the polymer. Cases in which water is contained in the dope, such as in the method of doping, are shown in parentheses.

) is supplied to the coagulation bath to coagulate the dope discharged from the nozzle.

At the same time as the aromatic polyamide molded article is formed by the coagulation reaction, amide solvents and inorganic salts such as calcium chloride (or amide solvents, inorganic salts such as calcium chloride, and water) are brought into the coagulation liquid from the dope. The concentrations of the amide solvent and inorganic salts such as calcium chloride in the coagulation solution I in the coagulation bath are a'% by weight and b'% by weight, respectively (or the concentrations of the amide solvent, inorganic salts such as calcium chloride, and water are respectively a' weight %, b' weight addition %, c' weight %).

In this case, if necessary, a/a'=b/b' (or a/a'=b/
b'=c/c') can be made to hold.

Next, the amide solvent a' weight %, inorganic salt such as calcium chloride b' weight (or amide solvent a' weight %, inorganic salt such as calcium chloride b' weight %, water C' weight %) whose concentration has increased A polyethylene glycol coagulation solution containing
A proportion satisfying the following formulas (1) and (2) is taken out from the coagulation bath and divided into X parts by weight (coagulation liquid (■)) and Y parts by weight (coagulation liquid (■)).

X+Y-Z+Ya'/100+Yb'/100(2)(
(or X+Y=Z+Ya'/I00 +Yb'/100+Yc'/100) The thus obtained coagulated solution (2) is led to a reaction tank, for example, and an inorganic salt such as calcium chloride Yb'/1 is contained in the Y weight part.
The theoretical amount of sodium sulfate required for reaction with 00 parts by weight,
An aqueous solution of ammonium sulfate, sodium carbonate, ammonium carbonate, sodium oxalate or ammonium oxalate, or a salt thereof is added to the reaction vessel.

These salts added to the coagulation solution (2) can be used alone or in combination, but from an operational standpoint, it is preferable to use them alone.

In particular, sodium sulfate is preferred because it is inexpensive, neutral, easily reacts with inorganic salts such as calcium chloride, and causes few troubles when added in excess.

If the water content of the coagulating liquid ■ is 2% by weight or less,
In order to facilitate the reaction with an inorganic salt such as calcium chloride, it is preferable to add the above salt as an aqueous solution.

In particular, a saturated aqueous solution is desirable in order to reduce the amount of water that needs to be removed by evaporation.

By adding the above-mentioned salts to the coagulation liquid ■, the inorganic salts such as calcium chloride contained in the coagulation liquid The amide solvent Ya that becomes calcium salt of acid and is contained in the coagulating liquid ■
'/100 parts by weight can be efficiently recovered.

In addition, sodium chloride or ammonium chloride, etc., and calcium salts of sulfuric acid, carbonic acid, or oxalic acid, etc., are insoluble in polyethylene glycol, so they can be easily separated from the coagulating liquid ■ using a solid-liquid separator such as a centrifuge. .

Next, the amide solvent was removed by evaporation from the coagulation solution (1), and the salt insoluble in the polyethylene glycol precipitated by the addition of the above salt was separated, resulting in a residual liquid (y-Ya'/100-Yb'/
100) parts by weight can be recycled and reused as a coagulating liquid that can be directly supplied to the coagulating bath without adjusting the concentration by combining it with the coagulating liquid (1) X parts by weight.

In other words, the amount A by weight of the amide solvent brought into the coagulation bath from the dope is determined by (Y
a'/100 parts by weight, and similarly, the amount of inorganic salts such as calcium chloride brought from the dope to the coagulation bath, parts by weight B, is Yb'7100 parts by weight (also, the amount of water brought from the dope to the coagulation bath). C is Yc' (100 parts by weight), but first, an inorganic salt such as calcium chloride Yb'/
100 parts by weight was converted into a salt insoluble in polyethylene glycol, and then the amide solvent Ya was added from the coagulation solution
'/100 parts by weight (and Yc'/100 parts by weight of water) are removed, and the insoluble salts are removed. This is because parts by weight of inorganic salt B (or parts by weight of amide solvent A, parts by weight of inorganic salt B such as calcium chloride, and parts by weight of water C) are all removed from the coagulation bath.

A=(X+Y)a'/100-Za/100=Ya'/
100(5) (because X/Z=a/a') According to the method of the present invention, a specific salt is added to the coagulation liquid, and an inorganic salt such as calcium chloride is converted into a salt insoluble in polyethylene glycol. Since the amide solvent is separated, the amide solvent can be efficiently recovered.

Furthermore, by dividing the liquid discharged from the coagulation bath into coagulation liquid (1) and coagulation liquid (I), the amount of liquid sent to the amide solvent recovery process can be reduced to Y/X10Y.

Furthermore, there is no need for complicated operations to control the amount of amide solvents or inorganic salts such as calcium chloride (or amide solvents, inorganic salts such as calcium chloride, and water) removed from the coagulation solution, and amide As long as the remaining liquid after recovering the solvent and separating the precipitated salt is combined with the coagulating liquid (2), it can be recycled as a coagulating liquid without adjusting the concentration.

When treating the liquid discharged from the coagulation bath without dividing it,
To recycle the residual liquid after recovering the amide solvent and separating the precipitated salt as a coagulating liquid, add an inorganic salt such as calcium chloride to the residual liquid, or reduce the amount of evaporation during recovery of the amide solvent. It is necessary to adjust the concentration by controlling or adding an amide solvent to the residual liquid.

As described above, according to the method of the present invention, molded products such as aromatic polyamide fibers, tapes, and films with good properties can be produced, and the solvent can be recovered economically and efficiently.

Examples are shown below, but these examples are intended to illustrate the present invention and are not intended to limit the present invention.

All parts and percentages in the examples are based on weight.

Example 1 Interfacial polymerization was carried out using 108 parts of metaphenylene diamine and 203 parts of isophthalic acid chloride in a tetrahydrofuran-water system to obtain polymetaphenylene isophthalamide having an ηinh of 1.26.

Using the thus obtained polymer, calcium chloride 3
%, N-methylpyrrolidone 75%, polymer 22% dope was prepared.

This dope was discharged into a coagulation bath through a spinneret having a hole diameter of 0.08 mm and a number of holes of 2000 to obtain a yarn, which was then sent to the subsequent washing and drawing steps.

A polyethylene glycol (average molecular weight 1000) solution containing 14.1% N-methylpyrrolidone and 0.47% calcium chloride was added to the coagulation bath from the back of the spinneret at 120°C.
N-methylpyrrolidone and calcium chloride are taken out from the previous dope in the coagulation bath at a rate of 3000 kg/min, and N-methylpyrrolidone 16 is fed from the other end of the coagulation bath.
．． It was discharged as a polyethylene glycol solution containing 0% calcium chloride and 0.50% calcium chloride.

The effluent was divided into a ratio of 2,820 parts to 213 parts, and then a saturated aqueous sodium sulfate solution containing an equimolar amount of sodium sulfate to the calcium chloride contained in the 213 parts was added to the 213 parts.
After adding the mixture to 3 parts, water was removed by evaporation using an evaporative distillation machine, and then N-methylpyrrolidone was recovered.

The recovery rate of N-methylpyrrolidone was 98%.

Next, the precipitated sodium chloride and calcium sulfate were separated using a centrifugal separator, and the resulting residual liquid was transferred to the previously discharged liquid 282.
When it was combined with 0 parts, it could be used for circulation as a coagulating liquid as it was.

On the other hand, after taking the yarn that has come out of the coagulation solution and thoroughly removing the solvent in a washing process, it is then stretched 2.5 times in hot water at 97°C, and then 1.5 times in a nitrogen atmosphere at 335°C. Hot stretching was performed.

The obtained fiber had a strength of 4.1 g/d and an elongation of 20%.

For comparison, 2820 parts of the liquid discharged from the coagulation bath versus 213 parts
When N-methylpyrrolidone was divided into 213 parts and then directly collected in an evaporative distillation machine without adding sodium sulfate to the 213 parts, the recovery rate of N-methylpyrrolidone was 60%.

Furthermore, N-methylpyrrolidone and calcium chloride in the residual liquid formed a complex, which resulted in loss of fluidity, making it impossible to recycle it as a coagulating liquid.

In addition, when attempting to recover N-methylpyrrolidone without dividing the liquid discharged from the coagulation bath, recovery can only be achieved by adding an equimolar amount of sodium sulfate to the calcium chloride contained in the discharged liquid. Although the process was efficient, in order to recycle the residual liquid after recovering N-methylpyrrolidone and separating the precipitated salt as a coagulating liquid, calcium chloride was added to the residual liquid after recovery to adjust the calcium chloride concentration. In addition, it was necessary to adjust the concentration of N-methylpyrrolidone by controlling the amount of evaporation during recovery of N-methylpyrrolidone, or by newly adding N-methylpyrrolidone to the residual liquid.

Example 2 108 parts of metaphenylenediamine was dissolved in 900 parts of dimethylacetamide, the temperature was adjusted to 10°C, and 203 parts of isophthalic acid chloride was added, and the viscosity of the solution gradually increased.

While vigorously stirring this solution, 74 parts of calcium hydroxide was added after 2 hours to prepare a dope containing 18.6% polymetaphenylene isophthalamide, 8.6% calcium chloride, and 2.8% water.

In addition, ηinh of the polymer was 1.93.

The dope obtained as described above was discharged into the coagulation bath from a spinneret with a hole diameter of 0.15 mm and a number of holes of 2000 placed upward in the coagulation bath to obtain a yarn, which was subjected to drawing heat treatment in the same manner as in Example 1. As a result, fibers having a strength of 4.99/d and an elongation of 28% were obtained.

From the bottom to the top of the spinneret, dimethylacetamide 17.2%, calcium chloride 1.72%,
A polyethylene glycol (average molecular weight 600) solution containing 0.688% water was supplied at a rate of 7200 kg/min at 100°C, and dimethylacetamide 1
8.0%, calcium chloride 1.80%, water 0.720%
It was discharged as a polyethylene glycol solution containing

The effluent was divided into a ratio of 6,880 parts to 403 parts, and then a saturated aqueous sodium sulfate solution containing an equimolar amount of sodium sulfate to the calcium chloride contained in the 403 parts was added to the 40 parts.
After adding it to 3 parts, water was removed by evaporation using an evaporative distillation machine.
Then, dimethylacetamide was recovered.

The recovery rate of dimethylacetamide was 97%.

Next, the precipitated sodium chloride and calcium sulfate were separated using a centrifuge, and the residual liquid obtained was mixed with the previously discharged liquid 6880.
The coagulated liquid was combined with the other parts and used as a coagulating liquid for circulation.

Claims (1)

[Claims] 1. When producing molded articles such as fiber tapes and films by discharging a solution consisting of an aromatic polyamide, an inorganic salt such as calcium chloride, and an amide solvent into a polyethylene glycol coagulation solution and coagulating it, the amide solvent a. weight%,
Polyethylene glycol (coagulation liquid I) Z weight part containing inorganic salt b weight % such as calcium chloride is supplied to a coagulation bath to form a molded article, and then an amide solvent a' weight % is added from the coagulation bath.
A polyethylene glycol coagulating liquid containing b weight % of an inorganic salt such as calcium chloride is taken out in a proportion that satisfies the following formulas (1) and (2), and X parts by weight (coagulating liquid ■)
and Y parts by weight (coagulation liquid ■), and to the thus obtained coagulation liquid l, the theoretical amounts of sodium sulfate, ammonium sulfate, and
At least one salt selected from the group consisting of sodium carbonate, ammonium carbonate, sodium oxalate, and ammonium oxalate was added, and then the amide solvent was removed by evaporation from the coagulated liquid, and the above-mentioned salt was added to precipitate. A method for producing an aromatic polyamide molded article, characterized in that the residual liquid obtained by separating the salt is combined with the coagulating liquid (1) and recycled as the coagulating liquid (2).