JP2996867B2 - Method for producing wholly aromatic polyamide molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing molded articles such as fibers, tapes and films which are excellent in gloss without devitrification from a wholly aromatic polyamide having excellent heat resistance by a wet molding method. is there. More specifically, a polymer solution obtained by dissolving a wholly aromatic polyamide in an aprotic polar amide-based solvent is wet-formed using an aqueous coagulation bath containing a specific inorganic salt, and has good gloss without devitrification. Also, the present invention relates to a method for producing molded products such as fibers, tapes and films having excellent heat resistance with good productivity.

[0002]

2. Description of the Related Art A wholly aromatic polyamide obtained from an aromatic diamine and an aromatic dicarboxylic acid or a halide thereof, in particular, poly (meta-phenylene isophthalamide) or a copolymer polyamide containing the same as a main component is resistant to heat and flame. It is well known in the art that this is superior. In addition, these wholly aromatic polyamides are soluble in aprotic polar amide solvents, and wet-molded into an inorganic salt-containing aqueous coagulation bath using this polymer solution to obtain fibers, tapes, films, etc. It is conventionally known to obtain a molded product of

For example, Japanese Patent Publication No. 47-41743 discloses a method in which a solution obtained by dissolving a wholly aromatic polyamide in an aprotic polar amide solvent is wet-spun using a high-temperature aqueous coagulation bath comprising a concentrated aqueous solution of calcium chloride. Is described. According to the method using a coagulation bath of a concentrated aqueous solution of calcium chloride, a relatively good molded product having a uniform and less devitrification can be obtained. In this method, however, the concentration of calcium chloride in the coagulation bath is at least 30% by weight. This is equivalent to 43 parts by weight or more of calcium chloride with respect to 100 parts by weight of water. Since the concentration is very high, there is a problem such as corrosion of the apparatus, and it is not necessarily an industrially preferable method. hard.

As a solution to this problem, a method has been proposed in which an aqueous solution of various inorganic salts other than calcium chloride is used as a coagulation bath (see Japanese Patent Publication No. 47-50219). In this method, lithium chloride, sodium chloride,
It contains at least one inorganic salt selected from the group consisting of magnesium chloride, zinc chloride, strontium chloride, aluminum chloride, stannic chloride, nickel chloride, calcium bromide, zinc nitrate and aluminum nitrate. An aqueous coagulation bath having a total content of the above salts of at least 2 mol (concentration in terms of anhydrous salt) is used. Among the chlorides, nitrates and the like used in this method, sodium chloride is advantageous because it has few problems in terms of cost and pollution such as environmental pollution, but it can be said that other compounds are not necessarily suitable as salts used in the coagulation bath. Absent.

For example, lithium chloride and nickel chloride are
Compounds of heavy metals such as zinc, strontium, tin, and nickel are highly toxic and require special treatment after use as an aqueous solution, which makes the treatment complicated and costly. Since an aqueous solution of tin is strongly acidic and corrodes a device containing iron, neither is preferable.

On the other hand, sodium chloride among the inorganic salts described in JP-B-47-50219 is an inorganic salt which is advantageous in terms of price, environment and equipment, but it is described in Examples 1 to 3 of the above-mentioned publication. As described, poor spinnability,
Since there are many yarn breaks during spinning and drawing, it is difficult to industrially produce wholly aromatic polyamide fibers using a coagulation bath of an aqueous sodium chloride solution.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the conventional method, and provides a wholly aromatic polyamide molded article having low devitrification and excellent in mechanical properties with good productivity. It is an object of the present invention to provide a novel method which can be produced industrially advantageously.

Accordingly, an object of the present invention is to provide a molded article such as a fiber, a tape or a film from a polymer solution of a wholly aromatic polyad by a wet molding method.
Provided is a novel method capable of industrially producing a molded product having good gloss and mechanical properties with good productivity by using an inexpensive inorganic salt that is less susceptible to environmental pollution and equipment and machinery. It is in.

[0009]

That is, the present invention relates to a method of producing fibers, tapes, films and the like from a wholly aromatic polyamide by a wet molding method using an aqueous coagulation bath containing an inorganic salt. By extruding a polymer solution obtained by dissolving an aromatic polyamide in an aprotic polar amide solvent into an aqueous coagulation bath comprising an aqueous solution containing sodium chloride and sodium hydroxide, there is no devitrification and transparency,
This is a method characterized by producing a wholly aromatic polyamide molded article having excellent mechanical properties with good economy and productivity.

Hereinafter, a method of efficiently producing a good wholly aromatic polyamide molded article at low cost and efficiently by the method of the present invention will be described in detail.

As the wholly aromatic polyamide used in the method of the present invention, 85 mol% of the repeating unit of the synthetic linear polymer is used.
Above, preferably 90 mol% or more is composed of units of the following formula (1) and / or formula (2).

[0012]

Embedded image

[In equations (1) and (2), A
r ₁ , Ar ₂ and Ar ₃ are the same or different bifunctional aromatic rings, and even if some or all of the hydrogen atoms on the aromatic ring are substituted with halogen or lower alkyl, etc. Good. As Ar ₁ , Ar ₂ and Ar ₃ , for example, 1,
3- or 1,4-phenylene, 3,3'- or 4,4'-biphenylene, 1,4-, 1,5- or 1,6-naphthylene, 4,4'-oxadiphenyl, 4,4 ' -Methylenediphenyl, 3,3'- or 4,4
'-Sulfonediphenyl and the like, and particularly preferred are 1,3-phenylene, 4,4'-oxadiphenyl, 4,4'-methylenediphenyl, 3,3'- and 4,4'
-Sulfone diphenyl and the like.

Examples of the wholly aromatic polyamide polymer suitable for producing a molded article having good heat and flame resistance include poly (metaphenylene isophthalamide), a copolymer containing the same as a main component, and poly (metaphenylene-5. -Sulfonic acid-1,3-phenyleneisofluamide) copolymer, poly (5-methyl-
1,3-phenyleneisophthalamide) and the like,
In particular, a poly (metaphenylene isophthalamide) polymer is preferred.

In order to produce a heat-resistant and flame-resistant fiber having good mechanical properties from such a wholly aromatic polyamide polymer, 30 fibers are required.
The intrinsic viscosity obtained from the value measured at a concentration of 0.5 g / 100 ml in concentrated sulfuric acid at 0.8 ° C. is 0.8 to 4.0, particularly 1.0 to 3.0.
It is preferred to use zero.

The wholly aromatic polyamide polymer may contain additives such as a stabilizer, a flame retardant, a matting agent, a lubricant, and a coloring agent, if necessary.

In the method of the present invention, a stock solution for molding is prepared by dissolving the wholly aromatic polyamide in an aprotic polar amide solvent. In this case, not only a solution prepared by dissolving a wholly aromatic polyamide polymer previously produced by a known method such as an interfacial polymerization method or a solution polymerization method in an aprotic polar amide solvent, but also an aprotic polar amide as a polymerization solvent in solution polymerization. A wholly aromatic polyamide polymer solution obtained by using a solvent may be used.

The term "aprotic polar amide solvent" used herein refers to a group consisting of N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam and tetramethylurea. Refers to at least one solvent selected from

These aprotic polar amide solvents are:
They may be used alone or as a mixture of two or more. Further, if necessary, it can be used as a mixture with another solvent.

When the aprotic polar amide solvents are mixed with each other, the mixing ratio can be arbitrarily selected, but when mixed with another solvent, the mixing ratio is set to a range that does not decrease the solubility to the polymer. There is a need.

In the method of the present invention, a solvent containing N-methyl-2-pyrrolidone or N, N-dimethylacetamide as a main component is particularly preferable, and N-methyl-2-pyrrolidone is particularly preferable.

Further, a small amount of an inorganic salt, for example, potassium chloride, lithium chloride or the like may be contained in the above-mentioned solvent in order to increase the dissolving power of the polymer.

In order to prepare a stock solution by dissolving the wholly aromatic polyamide polymer in the aprotic polar amide solvent described above, for example, a method in which the polymer is charged into a solvent at room temperature and stirred and dissolved, It is possible to adopt a method in which the polymer is cooled to room temperature or lower in advance, and the polymer is charged into the slurry, stirred, heated to a slurry state, and heated immediately before molding. The molding solution needs to be defoamed, but in the case of the slurry method, it is preferable to degas under reduced pressure in the form of a slurry, and in the case of the room temperature dissolution method, heat defoaming is performed by utilizing the high boiling point of the solvent. It is preferred to do so.

Although the concentration of the stock solution for molding differs depending on the concentration of the polymer, it is generally 10 to 40% by weight, preferably 1 to 40% by weight.
A concentration of 5 to 30% by weight is suitable.

In the method of the present invention, a stock solution prepared by dissolving a wholly aromatic polyamide polymer in an aprotic polar amide solvent is extruded from a spinneret, die or the like into an aqueous coagulation bath containing sodium chloride and sodium hydroxide. Thereby, a desired molded product is obtained.

In this case, it is preferable to adopt a usual wet molding method in which the stock solution is directly extruded into the aqueous coagulation bath. However, when the stock solution and the coagulation bath temperature are significantly different,
A so-called dry-jet wet molding method in which a stock solution for molding is once extruded into the air and immediately introduced into a coagulation bath may be employed.

Here, the sodium chloride to be contained in the aqueous coagulation bath may be of any kind, for example, industrial sodium chloride called so-called rock salt, or may be produced by evaporation of seawater. Its purity is 9
It may be 0% or more, and a small amount of calcium chloride, magnesium chloride, aluminum chloride, potassium chloride, or the like may be contained.

The concentration of sodium chloride in the aqueous solution constituting the coagulation is from 10 parts by weight to its saturated concentration, preferably from 10% by weight to less than 40 parts by weight, based on 100 parts by weight of water. If the sodium chloride concentration is lower than this, coagulation tends to be slow and incomplete.

As described above, it is conventionally known to use an aqueous solution of sodium chloride for coagulation in wet molding of a wholly aromatic polyamide polymer. However, a coagulation bath made of an aqueous solution of sodium chloride has poor spinnability. , Not practical.

In the method of the present invention, sodium hydroxide as the second component is used together with sodium chloride as the first component (main component) as the inorganic salt constituting the coagulation bath. The sodium hydroxide may have a purity of 80% or more, and may contain a small amount of potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, or aluminum hydroxide.

The concentration of sodium hydroxide in the aqueous solution constituting the solidification line is 0.1 to 20 parts by weight per 100 parts by weight of water.
Parts by weight, preferably 0.2 to 10 parts by weight.

The concentration of sodium hydroxide in the coagulation bath is 10
If the amount is less than 0.1 part by weight with respect to 0 part by weight, the molded article is devitrified by wet molding of the wholly aromatic polyamide, and at the same time, the spinnability deteriorates remarkably and yarn breakage during spinning and drawing frequently occurs. On the other hand, if the concentration of sodium hydroxide exceeds 20 parts by weight with respect to 100 parts by weight of water, not only is the surface of the molded product uneven, but also the amount of hydrochloric acid used for neutralization in wastewater treatment becomes larger. Is not preferred. Therefore, the concentration of sodium hydroxide is 0.1 to 20 parts by weight with respect to 100 parts by weight of water.
It is necessary to be parts by weight, preferably 0.2 to 10 parts by weight, particularly preferably 0.5 to 5 parts by weight.

This aqueous coagulation bath may contain the same solvent as the solvent contained in the stock solution for molding, in addition to the above sodium compounds. In this case, the content of the solvent is 30% by weight or less, preferably 20% by weight or less based on the whole coagulation bath. If the amount of the solvent is too large, coagulation tends to be slow and insufficient.

When a wholly aromatic polyamide fiber is produced by the method of the present invention, the above-mentioned aqueous coagulation bath containing sodium chloride and sodium hydroxide is used as the first bath, and the second bath is 0 to 100 ° C. , Preferably 10 to 80
The fiber coagulated in the first bath is introduced into the second bath by using a water bath at a temperature of 0 ° C., and the coagulation is further completed while removing the solvent in the second bath. It is preferable to wash and remove salts such as sodium oxide. In order to completely remove sodium hydroxide accompanying fibers, it is effective to use a slightly acidic water bath adjusted to pH 1 to 4 by adding hydrochloric acid to the second bath. The removal effect can be enhanced.

As described above, according to the method of the present invention, devitrification during molding is not observed at all, and uniform coagulation can be carried out. Etc. can be manufactured. These molded products can be stretched and heat-treated as necessary to improve their mechanical properties, and the handling properties and process condition in the wet molding process and post-processing process are extremely good, and the productivity is excellent. ing.

[0036]

As described above, according to the method of the present invention, an aqueous coagulation bath containing sodium chloride and a small amount of sodium hydroxide, which is inexpensive and abundant and has little environmental pollution and equipment corrosion, is used. Thus, a wholly aromatic polyamide molded article having extremely high properties can be obtained. The molded article is excellent in mechanical properties, acid resistance and flame resistance, and can be widely applied to various fields utilizing the properties.

[0037]

EXAMPLES The method of the present invention will be specifically described below with reference to examples and comparative examples. However, these examples and comparative examples are for helping the understanding of the present invention, and the description is not intended to limit the scope of the present invention.

The "parts" and "%" in the examples are all based on weight unless otherwise specified, and the concentrations of sodium chloride (NaCl) and sodium hydroxide (NaOH) in the coagulation bath are as follows: , Are parts by weight of salt converted to anhydrous salts with respect to 100 parts by weight of water. NMP in the text represents N-methyl-2-pyrrolidone and DMA
c represents N, N-dimethylacetamide.

Example 1 Metaphenylenediamine and isophthalic acid chloride / terephthalic acid chloride 97 /
3 mixtures prepared from NMP8 with 20 parts of a wholly aromatic polyamide (intrinsic viscosity measured in concentrated sulfuric acid at 30 ° C. of 1.73).
The spinning solution obtained by dissolving in 0 parts was dissolved from a spinneret having a pore diameter of 0.1 mm and 20 holes at a ratio of 33.3 parts of sodium chloride and 0.7 parts of sodium hydroxide per 100 parts of water. Extruded into a coagulation bath at a temperature of ° C. to obtain a yarn.

The yarn was immersed in a coagulation bath for 100 cm, and then taken out at 8 m / min. continue,
After washing through a bath of a dilute hydrochloric acid aqueous solution (25 ° C.) of pH = 4, the plate was washed with a warm water bath (70 ° C.). Then, the film was stretched 2.4 times in boiling water, dried on a drying roller at 120 ° C, and further stretched 1.6 times on a plate at 320 to 330 ° C.

Thus, fineness of 40 de and strength of 4.5 g / d
e, A uniform and transparent wholly aromatic polyamide multifilament having an elongation of 18% was obtained. When this multifilament was heat-treated at 250 ° C. for 100 hours, the strength retention was 98%, and almost no deterioration in strength was observed.

Examples 2-5, Comparative Examples 1-5 Wholly aromatic polyamides prepared from metaphenylenediamine and a 95/5 mixture of isophthalic chloride / terephthalic chloride (intrinsic viscosity measured at 30 ° C. in concentrated sulfuric acid) 1.6
5) Extrusion speed of a stock solution obtained by dissolving 20 parts in 80 parts of NMP from a single-hole spinneret having a hole diameter of 0.2 mm.
At 8 m / min, various coagulation baths shown in Table 1 (immersion length 120c
m) to obtain fibers.

Table 1 shows the spinnability, the state of devitrification, the state of pores in the cross section of the fiber, and the surface state.

[0044]

[Table 1]

Evaluation symbols such as spinnability, devitrification state, state of pores in fiber cross section, and surface state shown in Table 1 represent the states shown in Table 2 below. this house,
Only the surface condition indicates the result of observing the surface condition of a tape having a thickness of 0.2 mm and a width of 20 mm, which was obtained by coagulation under the same conditions.

[0046]

[Table 2]

Example 6 Metaphenylenediamine and isophthalic chloride / terephthalic chloride 95 /
5 parts of a wholly aromatic polyamide (intrinsic viscosity 1.65 measured in concentrated sulfuric acid at 30 ° C.) prepared from NMP8
The spinning solution obtained by dissolving in 0 parts was dissolved from a spinneret having a pore diameter of 0.1 mm and 20 holes at a ratio of 30 parts of sodium chloride, 0.7 parts of sodium hydroxide and 10 parts of NMP per 100 parts of water. It was extruded into a coagulation bath at 85 ° C. made of an aqueous solution to obtain a yarn.

This yarn was immersed in a coagulation bath for 110 cm and then taken out at 8 m / min. continue,
After washing through a bath of a dilute hydrochloric acid aqueous solution (20 ° C.) having a pH of 3.5, the plate was further washed with a warm water bath (75 ° C.). Then, the film is stretched 2.5 times in boiling water, dried on a drying roller at 120 ° C, and further dried on a plate at 320 to 330 ° C.
The film was stretched 6 times.

[0049] Thus, fineness of 40de and strength of 4.8g / d
e, a uniform and transparent wholly aromatic polyamide multifilament having an elongation of 20% was obtained.

Example 7 Metaphenylenediamine and isophthalic acid chloride / terephthalic acid chloride 97 /
3 mixtures and 20 parts of a wholly aromatic polyamide (intrinsic viscosity measured in concentrated sulfuric acid at 30 ° C. of 1.73) was mixed with 20 parts of DMAc.
The spinning dope obtained by dissolving in 80 parts was prepared with a pore diameter of 0.1 mm,
From a spinneret having 20 holes, an extruded yarn was obtained in a coagulation bath at 80 ° C in which 33.3 parts of sodium chloride and 0.7 part of sodium hydroxide were dissolved per 100 parts of water.

This yarn was immersed in a coagulation bath for 100 cm in the same manner as in Example 1 and then taken out at 8 m / min. Subsequently, after washing through a bath of a dilute hydrochloric acid aqueous solution (25 ° C.) of pH = 4, the plate was washed with a warm water bath (70 ° C.).
Then, the film was stretched 2.4 times in boiling water, dried on a drying roller at 120 ° C, and further stretched 1.6 times on a plate at 320 to 330 ° C.

The wholly aromatic polyamide multifilament thus obtained is uniform and has good transparency, and its fiber properties are as follows: fineness: 40 de, strength: 4.5 g / de, elongation: 2
It was 0%.

Claims (4)

(57) [Claims] In producing a molded article such as a fiber, a tape or a film from a wholly aromatic polyamide by a wet molding method using an aqueous coagulation bath containing an inorganic salt, the wholly aromatic polyamide is converted into a protic polar amide solvent. A method for producing a wholly aromatic polyamide molded article, comprising extruding a dissolved polymer solution into an aqueous coagulation bath comprising an aqueous solution containing sodium chloride and sodium hydroxide. 2. The concentration of sodium chloride in the aqueous coagulation bath is not less than 10 parts by weight and not more than the saturation concentration with respect to 100 parts by weight of water, and the concentration of sodium hydroxide is 0.1 to 20 parts by weight with respect to 100 parts by weight of water. 2. The unit according to claim 1, wherein
A method for producing the wholly aromatic polyamide molded article according to the above. 3. The method for producing a wholly aromatic polyamide molded article according to claim 1, wherein the temperature of the coagulation bath is 40 ° C. or higher and lower than the boiling point of the coagulation bath. 4. The aprotic polar amide-based solvent is N-methyl-2-pyrrolidone or N, N-dimethylacetamide.
A method for producing the wholly aromatic polyamide molded article according to the above.