JP2922432B2 - Method for producing meta-type aramid fiber - 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 a meta-aramid fiber having good mechanical properties and heat resistance from a solution of a meta-aramid polymer obtained by a solution polymerization method by a wet spinning method. is there. More specifically, after reacting meta-type aromatic diamine and isophthalic chloride in an amide solvent, a polymer solution containing calcium chloride and water formed by neutralizing hydrochloric acid by-produced is used. ,
The present invention relates to a method for producing a meta-aramid fiber having excellent mechanical properties, excellent heat resistance and good flame retardancy with good productivity by a special wet spinning method using a two-stage coagulation bath. .

[0002]

2. Description of the Related Art It is well known that a wholly aromatic polyamide (referred to as "aramid" in the present invention) produced from an aromatic diamine and an aromatic dicarboxylic acid chloride has excellent heat resistance and flame retardancy. It is also well known that these aramids are soluble in a series of amide solvents and can be made into fibers by dry spinning, wet spinning, semi-dry semi-wet spinning, and the like.

Among such aramids, meta-type aramid fibers represented by polymetaphenyleniisophthalamide are particularly useful as heat-resistant and flame-retardant fibers.
At present, industrial production is mainly performed by the following two methods (a) and (b). In addition, the following methods (c) and (d) have been proposed as methods for producing meta-aramid fibers. (a) A low-temperature solution polymerization of metaphenylenediamine and isophthalic acid chloride in N, N-dimethylacetamide to prepare a polymetaphenylene isophthalamide solution, and then the hydrochloric acid by-produced in the solution is hydroxylated. A method for producing fibers by dry spinning a polymer solution containing calcium chloride obtained by neutralization with calcium (Japanese Patent Publication No. 35-14399)
And US Pat. No. 3,360,595). (b) contacting an organic solvent system (eg, tetrahydrofuran) which is not a good solvent for the resulting polyamide containing a metaphenylenediamine salt and isophthalic acid chloride with an aqueous solution system containing an inorganic acid acceptor and a soluble neutral salt; A method of isolating a powder of a metaphenylene isophthalamide polymer (see Japanese Patent Publication No. 47-10863), re-dissolving the polymer powder in an amide-based solvent, and wet-spinning in an aqueous coagulation bath containing an inorganic salt ( See Japanese Patent Publication No. 48-17551). (c) A meta-aramid synthesized by a solution polymerization method is dissolved in an amide-based solvent and contains no inorganic salt or a small amount (2).
(3%) of a meta-aramid solution containing lithium chloride by a wet molding method to produce molded articles such as fibers (see Japanese Patent Application Laid-Open No. 50-52167). (d) solution polymerization in an amide solvent, calcium hydroxide,
A meta-type aramid polymer solution containing calcium chloride and water neutralized with calcium oxide or the like is extruded from an orifice into a gas, allowed to pass through the gas, and then introduced into an aqueous coagulation bath. (See JP-A-56-31009).

The method (a) has the advantage that a spinning solution can be prepared without isolating the polymer, but the dry spinning using an amide-based solvent having a high boiling point requires a high energy cost in production, and furthermore, Increasing the number of holes per spinneret rapidly reduces spinning stability. In addition, even when the polymer solution is wet-spun in an aqueous coagulation bath, only weak fibers having a large amount of devitrification are often obtained, so that the meta-type aramid polymer solution obtained by solution polymerization is still prepared using the aqueous coagulation bath. The method of wet spinning has not been practiced industrially.

On the other hand, the above-mentioned methods (b) and (c) avoid the above-mentioned problem of dry spinning, but use different solvents in the polymerization system and the spinning system, and recycle the isolated polymer. There are problems such as the necessity of a step for dissolution, and the need for special consideration and meticulous process control in order to obtain a stable solution by re-dissolution (see Japanese Patent Publication No. 48-4661).

In the method (d), when the yarn is spun from the spinneret into the air, the spinning stability is remarkably reduced when the number of holes per spinneret is increased, so that the productivity is low and the method is not efficient.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the conventional method for producing meta-aramid fibers, and provides a polymer solution obtained by solution polymerization by wet spinning having excellent productivity. The aim is to provide a novel method for industrially producing meta-aramid fibers with low devitrification, excellent homogeneity and excellent transparency, good mechanical properties and good thermal properties at good productivity. It is.

Accordingly, an object of the present invention is to react a meta-type aromatic diamine with an aromatic dicarboxylic acid containing isophthalic chloride as a main component in an amide solvent,
By directly spinning a polymer solution containing calcium chloride and water generated by neutralizing hydrochloric acid produced as a by-product, meta-aramid fibers with good gloss and mechanical properties can be industrially manufactured with good productivity. To provide a new method that can be manufactured.

[0009]

An object of the present invention is to neutralize hydrochloric acid (HCl) by-produced after reacting an aromatic diamine and an aromatic dicarboxylic acid chloride in the presence of an amide solvent. The method for producing a meta-aramid fiber by wet-spinning a meta-aramid polymer solution containing calcium chloride (CaCl ₂ ) and water obtained by the above method comprises: (1) N-methyl-2 as an amide solvent After reacting an aromatic diamine mainly composed of meta-phenylenediamine with an aromatic dicarboxylic acid chloride mainly composed of isophthalic chloride using pyrrolidone (NMP), hydrochloric acid (HCl) by-produced is converted to calcium hydroxide. Neutralized with at least one neutralizing agent selected from the group consisting of calcium oxide and calcium carbonate; And the concentration of the polymer in the polymer solution (the weight of the polymer with respect to 100 parts by weight of N-methyl-2-pyrrolidone) is 18 to 35 (parts by weight). ), The concentration of calcium chloride (weight per 100 parts by weight of the polymer) is 40 to 4
7 (parts by weight), the concentration of water (weight relative to 100 parts by weight of the polymer) is 13 to 60 (parts by weight). (2) The polymer solution is converted into a chloride containing N-methyl-2-pyrrolidone. The yarn is formed by spinning into a first coagulation bath composed of a calcium aqueous solution, and at this time,
The bath temperature of the first coagulation bath is maintained at 70 to 110 ° C., and calcium chloride (CaCl ₂ ), N
-Methyl-2-pyrrolidone (NMP) and water (H
The content of ₂ O) is the following conditions (a) to (e): (a) CaCl ₂ + NMP + H ₂ O = 100 to 150 (b) CaCl ₂ + NMP = 40 to 90 (c) CaCl ₂ 5 to 50 ( d) NMP = 50 to 5 (e) adjusting the range that satisfies all the H ₂ O = 40 to 70, containing (3) Next, calcium chloride yarn was pulled out from the first coagulation bath N -Methyl-2-pyrrolidone (NM
P) into a second coagulation bath composed of an aqueous solution, and at this time, NNP / (CaCl2) in the second coagulation bath aqueous solution
The ₂ + H ₂ O) weight ratio of 5 / 95~25 / 75, CaC
The composition has a weight ratio of l ₂ / H ₂ O of 40/60 to 60/40 and the second coagulation bath temperature is 80 to 130 ° C.
It is preferably 85-130 ° C. and a temperature higher than the first coagulation bath, preferably at least 5 ° C. higher. (4) After that, the yarn is taken out from the second coagulation bath, washed and dried. And stretching, which is achieved by the method for producing a meta-aramid fiber of the present invention, which is characterized in that the fiber is drawn.

Hereinafter, a method for efficiently producing a good meta-type aramid fiber at low cost by the method of the present invention will be described in detail.

As described above, the method of the present invention is a method for neutralizing hydrochloric acid by-produced by solution polymerization-polymerization in which a meta-type aromatic diamine and a meta-type aromatic dicarboxylic acid chloride are reacted in an amide solvent. Summing reaction-a method for producing a meta-aramid fiber having excellent performance by each step of wet spinning of the obtained polymer solution.

Next, the raw materials and solvents used in the method of the present invention, solution polymerization, neutralization reaction, wet spinning, and washing / drying / stretching will be described in detail in order. (A) Raw material and solvent As the meta-type aromatic diamine which is one of the raw materials used in the method of the present invention, a diamine represented by the following formula is mainly used.

[0013]

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(Wherein R is halogen or a group having 1 to 3 carbon atoms)
Specific examples of such meta-type aromatic diamines include metaphenylenediamine, 2,4-toluenediamine, 2,6-toluenediamine, 2,4-diaminochlorobenzene, 2, and 6-diaminochlorobenzene and the like. Other meta-type aromatic diamines include 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfone, and the like.

In the method of the present invention, metaphenylenediamine or a mixed diamine containing the same as the main component is preferred. Other aromatic diamines that can be used in combination with metaphenylenediamine include, in addition to the above meta-type aromatic diamines, paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene, aminoanisidine and the like. Such benzene derivatives, 1,5-paranaphthylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylketone, bis (aminophenyl) phenylamine, bis (paraaminophenyl) methane and the like.

When a polymer having good solubility is desired,
The amount of such other aromatic diamines can be used up to about 20 mol% of the whole, but if a polymer having high crystallinity is desired, metaphenylenediamine can be used in an amount of 90 mol%.
Preferably, it is contained in an amount of at least 95 mol%.

On the other hand, the aromatic dicarboxylic acid chloride used in the method of the present invention is isophthalic acid chloride or an aromatic dicarboxylic acid chloride mainly containing the same.
Other aromatic dicarboxylic acid chlorides that can be used in combination with isophthalic acid chloride include terephthalic acid chloride,
1,4-naphthalenedicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, 4,4′-biphenyldicarboxylic acid chloride, 3-chloroisophthalic acid chloride,
3-methoxyisophthalic acid chloride, bis (chlorocarbonylphenyl) ether and the like can be mentioned.

In the practice of the method of the present invention, if a polymer having good solubility is desired, a mixture of these other dicarboxylic acids at a high ratio (up to about 20 mol%) is possible. When coalescence is desired, it is preferable that isophthalic acid chloride be contained in an amount of 90 mol% or more, particularly 95 mol% or more.

The amide solvents used for solution polymerization of meta-type aramid include N, N-dimethylformamide, N, N
N-dimethylacetamide, N-methyl-2-pyrrolidone and the like are known. However, in the method of the present invention, N-dimethylacetamide is used because of the stability of the polymer solution from solution polymerization to the wet spinning step.
-Methyl-2-pyrrolidone (sometimes abbreviated as "NMP" in the present invention) is used.

(A) Solution Polymerization In the method of the present invention, solution polymerization is carried out using the above-mentioned raw materials and solvents. Next, the operation of the solution polymerization will be described in detail.

In the polymerization step, NMP is used as a polymerization solvent as described above. The NMP is dehydrated and dried as much as possible to reduce the water content of the solvent to at least 50 ppm or less and to dissolve the meta-aromatic diamine therein. Then, an aromatic dicarboxylic acid chloride containing isophthalic acid chloride as a main component is added thereto in a powdered or molten state with sufficient stirring to cause a reaction. The reaction temperature is preferably from -10C to 100C, more preferably from 0C to 100C.

The degree of polymerization of the polymer is determined by the reaction temperature, reaction time,
Although it is affected by the stirring effect and the like, it is also greatly affected by the purity of the aromatic diamine and the aromatic dicarboxylic acid chloride used in the polymerization reaction and the usage ratio of both. Generally, the highest degree of polymerization is obtained when the molar ratio of aromatic diamine / aromatic dicarboxylic acid chloride is 1.00, but in practice, even if a sufficiently purified raw material is used, There is a small amount of decomposition of the aromatic dicarboxylic acid chloride, and the molar ratio at which the polymer exhibits the highest degree of polymerization is at the slight increase of the aromatic dicarboxylic acid chloride. That is, the highest degree of polymerization is often exhibited in the range of the molar ratio of aromatic dicarboxylic acid chloride / aromatic diamine = 1.000 / 1 to 1.002 / 1. However, the value of the molar ratio may change depending on the difference in the degree of purification between the two components. Therefore, it is desirable to verify the relationship between the two components in advance by experiments.

The required level of the degree of polymerization of the polymer is set according to the purpose of use of the polymer or its solution, the use of fibers, and the like. If necessary, the degree of polymerization is controlled by a conventionally known method. be able to. As one of the typical methods, the degree of polymerization can be adjusted by using a terminal terminator (such as alkylaniline such as aniline and toluidine, and benzoic acid chloride).

In the method of the present invention, it is important to control the degree of polymerization in order to produce a heat-resistant fiber having good mechanical properties and transparency from meta-type aramid. In particular, in order to obtain a fiber having good performance from a polymetaphenylene isophthalamide-based polymer, a polymer concentration of 0.5 g / 10% in concentrated sulfuric acid at 30 ° C.
The intrinsic viscosity (IV) determined from the value measured at 0 ml is 0.8 to 4.0, especially 1.0 to 3.0, especially 1.3.
Polymers of ~ 2.2 are preferred.

The method of the present invention is a method for producing meta-aramid fibers having excellent performance in a series of processes including a solution polymerization step, a neutralization reaction step, and a wet spinning step. It is important to adjust the polymer concentration in the spinning solution. Although the polymer concentration of the spinning dope can be adjusted in the next neutralization reaction step, it is possible to perform the polymerization reaction by setting the polymer concentration, including the range that can be adjusted in the neutralization reaction step in the solution polymerization step. is important.

In the present invention, the concentration of the polymer in the polymerization solution is part by weight based on 100 parts by weight of the solvent (NMP) [In the present invention, it is referred to as "P concentration". In the following description, the unit (parts by weight) of the P concentration will be omitted], which is 18 to 35, preferably 19 to 34, and more preferably 20 to 3
0. If the P concentration is less than 18, the concentration is too low, and the spinnability of the solution is deteriorated. As a result, not only the fiber performance is reduced, but also the circulation ratio of the solvent (NMP) is increased due to the low concentration. It is not economically favorable. Also,
The higher the P concentration, the higher the transparency of the molded article tends to be. However, if the P concentration exceeds 35, the viscosity becomes too high,
A problem arises in that the polymerization reaction and especially the neutralization reaction cannot be performed smoothly. Therefore, when a high concentration (for example, P concentration> 35 or more) polymerization is carried out in the polymerization reaction, calcium hydroxide as a neutralizing agent is replaced with an appropriate amount of NMP (for example, when the P concentration finally becomes 25) in the neutralization reaction step. ), The neutralization reaction becomes easy and the P concentration can be adjusted.

(C) Neutralization reaction As described above, the solution subjected to the solution polymerization reaction contains an amount of H corresponding to the dicarboxylic acid chloride used in the polymerization reaction.
Since Cl is by-produced, substantially all of this HCl is converted to Ca
Neutralized with a neutralizing agent to form a soluble salt, such as Cl _2.

As the neutralizing agent, generally, oxides, hydroxides, hydrides, carbonates and the like of metals of Group I and / or II of the periodic table can be used. Is, from the viewpoint of the stability of the polymer solution after neutralization and the solubility and economical viewpoint of the metal chloride generated by the neutralization,
As the neutralizing agent, calcium oxide, calcium hydroxide, calcium carbonate, or a mixture of two or more thereof is used.

Although the preferred temperature range of the neutralization reaction varies depending on the chemical composition of the polymer, the type of the solvent, the mixing ratio of the polymer and the solvent, the content of HCl to be neutralized, etc., it is difficult to say unconditionally. It can be selected from a range of 0 to 150 ° C. by a series of experimental studies. It is preferable to select a suitable temperature range according to each stage of the progress of the neutralization reaction, that is, each step of the initial stage, the middle stage and the final stage of the neutralization reaction.

It is preferable that the polymerization solution at the time of the neutralization reaction is sufficiently kneaded and kneaded and is homogenized. Therefore, it is appropriate to carry out the polymerization with stirring. The neutralization rate of HCl in this neutralization reaction step is preferably substantially 100%. In this case, calcium oxide, calcium hydroxide,
When a water-insoluble solid such as calcium carbonate is used, fine particles of these neutralizing agents may remain slightly in a highly viscous solution (or a highly concentrated solution). At this time, 95% of HCl is added using calcium oxide or calcium hydroxide.
After neutralizing ９８98%, the remaining 5-2% is neutralized by using a mixed solution of a water-soluble alkali solution such as sodium hydroxide and a predetermined amount of NMP so as to prevent generation of NaCl precipitate. be able to.

In this neutralization reaction step, the polymer concentration of the solution can be adjusted by adding NMP to the system.

As described above, the method of the present invention uses at least one of calcium oxide, calcium hydroxide and calcium carbonate as a neutralizing agent. Therefore, calcium chloride (CaCl ₂ ) is generated by neutralizing HCl by-produced in the polymerization reaction. The amount of HCl by-produced in the polymerization reaction varies depending on the chemical structure of the polymer and the average molecular weight of the minimum unit. For example, HCl by-produced in the polymerization reaction of polymetaphenylene isophthalamide is 100% neutralized with the above compound. In this case, 46.64 (parts by weight) of CaCl ₂ is produced for 100 parts (parts by weight) of the polymer. CaCl ₂ generated by this neutralization reaction is dissolved in the polymer solution,
It works to increase the stability of the polymer solution.
Conversely, this large amount of dissolved CaCl ₂
Therefore, conventionally, wet spinning from this polymer solution has been difficult.

On the other hand, the amount of water generated by the neutralization reaction varies depending on the type of the neutralizing agent.
5.13 parts (by weight) of water are produced. On the other hand, when neutralized with calcium oxide and calcium carbonate, polymer 100
7.56 parts of water are produced per part.

Although the water produced here is also dissolved in the polymer solution, the amount of the above amount hardly impairs the stability of the solution and the properties of the composition after neutralization. Rather, the presence of water may impart desirable properties such as lowering the viscosity, but if too much, the stability of the solution will be significantly reduced (gelling).

Suitable amount (weight) of water to be added in the neutralization reaction step
Depends on the polymer concentration. The polymer concentration in the method of the present invention is, as described above, a P concentration of 18 to 35,
Preferably it is 19-34, More preferably, it is 20-30. Therefore, for example, in the case of a polymetaphenylenisophthalamide polymer solution, the dissolved amount of water at a P concentration of 18 is determined by converting HCl by-produced in the polymerization step to 1 with Ca (OH) ₂ .
About 2.72 (15 parts with respect to 100 parts of the polymer) when neutralized at 00%, which is about 6 times the amount of water, that is, the polymer 100
It is soluble up to about 90 parts per part, but the stable region of the solution is water from 2.72 to 10.9 parts per 100 parts of polymer.
Parts (water / polymer = 15 to 60). P concentration =
At 20 the P concentration is almost the same as at 18; about 15 to 60 parts per 100 parts of polymer; the stable region at P concentration = 25 is 15 to 45 parts;
5 to 30 parts.

The above ranges are approximate values when the polymer solution is allowed to stand at 60 to 70 ° C., and vary somewhat depending on conditions such as the degree of polymerization of the polymer and the storage temperature. In any case, the permissible concentration of water in the polymer solution is limited as the concentration of the polymer increases. However, in carrying out the method of the present invention, the concentration of water in the total polymer solution composition must be 10% or less in advance. By conducting an experimental study as a guide, it is possible to know the allowable concentration range of dissolution at which gelation of the solution can be prevented.

(D) Wet spinning of the polymer solution As described above, the polymer solution subjected to solution polymerization (HCl is a by-product) -neutralization (CaCl ₂ generation) with a basic calcium compound isolates the polymer. The fiber is fed to the wet spinning step as it is, or after the concentration is adjusted as required, and is fiberized. However, in the method of the present invention, a special two-stage coagulation bath is used to obtain excellent mechanical properties and transparency. Aramid fibers having heat resistance and heat resistance can be efficiently produced with good productivity.

Conventionally, it has been difficult to convert an equimolar CaCl ₂ meta-type aramid polymer solution into a fiber by wet spinning. Conventionally, dry spinning or semi-dry semi-wet spinning has been employed as a spinning method. . Further, in order to perform wet spinning, chlorides (CaCl ₂ ,
NaCl, NH ₄ Cl, etc.) must be reduced by some means to at least 70% or less, preferably to 20% or less. However, removal of chlorides by these means is often industrially difficult.For example, in the case of interfacial polymerization, since the polymerization solvent and the spinning solvent are different, separate recovery devices are required for their recovery. Also, when performing polymerization and spinning with the same solvent by solution polymerization, inorganic chloride by-produced by neutralization is removed by pressure filtration (industrial extremely difficult due to high viscosity), or water is added to the polymer solution. After adding and washing the inorganic chloride to remove water, a difficult process such as drying and re-dissolving the polymer is required.Therefore, there are many difficulties in terms of energy cost and environmental pollution, and both are preferable. Hard to say.

The method of the present invention has heretofore been difficult to carry out.
This equimolar CaCl ₂ polymer solution was treated with 300 spinning holes.
Through a multi-hole spinneret with ~ 30000 pieces
By a wet spinning method of directly spinning in a coagulation bath, it is possible to produce a meta-aramid fiber excellent in gloss, heat resistance and mechanical properties with high productivity.

In the case of the above-mentioned salt-free polymer solution containing no metal salt such as CaCl ₂ or a reduced salt polymer solution in which a part of the metal salt is removed, for example, as described in JP-B-48-17551, CaCl 2 is used. _A transparent thread is formed in a one-stage coagulation bath composed of _two aqueous solutions, and a fiber having excellent performance can be produced in the subsequent washing step and drawing step. However, in the case of wet spinning of a polymer solution containing equimolar CaCl ₂ , coagulation is rapid and devitrification is remarkable in a conventional single-stage coagulation bath.
A transparent yarn cannot be obtained, and therefore, even after a subsequent treatment step such as washing with water or drawing, only a devitrified fiber having poor mechanical properties can be obtained. Further, there are many cases in which a large number of breaks occur at the time of spinning and spinning cannot be performed at all.

In the method of the present invention, in order to solve this problem, a first coagulation bath and a second coagulation bath under different conditions are provided. By forming the structure, and in the second coagulation bath, the thread devitrified in the first coagulation bath is made transparent and the internal structure is adjusted, so that a meta-material having excellent gloss, heat resistance and mechanical properties is obtained. Thus, it is possible to produce a type of aramid fiber at low cost.

That is, in the method of the present invention, the polymer solution obtained by the solution polymerization-neutralization reaction described above is preferably adjusted to a temperature of 70 to 110 ° C. in consideration of the coagulation bath temperature.
After spinning (filing) from the spinneret into a first coagulation bath having the composition and temperature described below to form a yarn, the yarn is drawn out of the first coagulation bath, and subsequently, the composition described below. ,
It is introduced into a second coagulation bath at a temperature to fibrillate.

(I) First Coagulation Bath In the method of the present invention, there is a close relationship between the composition of the equimolar CaCl ₂ polymer solution and the composition of the first coagulation bath, which greatly affect the fiber performance. . Therefore, setting of the composition and temperature conditions of the first coagulation bath is important. The first coagulation bath in the present invention comprises calcium chloride (CaCl ₂ ) and N-
Consisting of an aqueous solution consisting of 3 components of methyl-2-pyrrolidone (NMP) and water (H ₂ O).

In the first coagulation bath, the above three components must always be within a range satisfying all of the following conditions. The following numerical values indicate parts by weight.

CaCl ₂ + NMP + H ₂ O = 100-1
50 (preferably 100 to 130) CaCl ₂ + NMP = 40 to 90 (preferably 45 to 8)
0) CaCl ₂ = 5 to 50 (preferably 10 to 45) NMP = 50 to 5 (preferably 45 to 10) H ₂ O = 40 to 70 (preferably 45 to 65) The composition of the first coagulation bath is in this range. Outside, even if the thread is formed, it breaks and cannot be spun, or even if it can be spun, the subsequent hot water drawing may cause a break or a dry heat drawing may cause a broken fuzz. There is a problem.

The first coagulation bath temperature is 70 to 110 ° C., preferably 80 to 95 ° C. When the temperature of the first coagulation bath is out of this range, the thread is remarkably devitrified, and it cannot be made transparent even when introduced into the following second coagulation bath.

The immersion time of the yarn in the first coagulation bath is 0.5.
1 to 20 seconds is preferred. If the immersion time is too short, the formation of the thread is insufficient, and the yarn breaks. If the immersion time is too long, the devitrification is remarkable and it does not become transparent even when introduced into the following second coagulation bath.
Therefore, the immersion time should be appropriately selected within the above range.

(Ii) Second coagulation bath The yarn formed in the first coagulation bath is devitrified and unstable in fiber structure. In the method of the present invention, the devitrified yarn drawn out of the first coagulation bath is introduced into a second coagulation bath made of a concentrated aqueous solution of CaCl ₂ containing NMP to clarify, and the inside of the fiber is adjusted to a dense structure. By doing so, a meta-type aramid fiber having excellent performance can be produced.

The CaCl ₂ concentration of the second coagulation bath is higher than that of the first coagulation bath, and the temperature is higher than that of the first coagulation bath. Therefore, CaCl _{2 in} the second coagulation bath
Concentration in a weight ratio of _{CaCl 2 / H 2 O 40 /} 60~60
/ 40 (preferably 45/55 to 55/45), NM
The concentration of P is 5/95 to 25/75 (preferably 10/90 to ₂₀ ) in a weight ratio of NMP / (CaCl ₂ + H ₂ O).
/ 80), and the temperature of the second coagulation bath is 80 to 130.
° C, preferably 90 to 125 ° C, and a temperature higher than the first coagulation bath temperature, preferably at least 5 ° C higher.

If the composition and temperature conditions of the second coagulation bath are out of these ranges, even if the conditions of the first coagulation bath are adjusted to the above-mentioned ranges, fibers having good transparency and excellent stretchability cannot be obtained. .
The dipping time of the yarn in the second coagulation bath is preferably 0.5 to 60 seconds.

Thus, the devitrified and unstable fiber structure formed in the first coagulation bath becomes transparent and converted into a dense structure in the second coagulation bath.

(E) Washing / Drying / Stretching The yarn after the second coagulation bath is washed with cold water of 30 ° C. or less, further washed with warm water of 50 to 90 ° C., and subsequently with 90 to 100 ° C. 2. Warm water at a stretching ratio of 1.5 to 3.
After washing with hot water while stretching at 0, drying is performed at a temperature of 100 ° C. or higher, and then dry-heat stretching is performed at 270 to 350 ° C. using a hot plate, a hot roller, or the like. The latter is stretched so that the total stretching ratio including the hot water stretching is 3.0 to 7.0, preferably 4.0 to 6.0.

The meta-type aramid fiber according to the method of the present invention comprises:
It has good stretchability, and can be smoothly stretched to a high magnification without causing breakage or fluff.

In the method of the present invention, the above-mentioned solution polymerization-neutralization reaction-wet spinning-washing / drying / drawing can all be performed in a continuous and continuous process, which is one of the advantages of the method of the present invention. In some cases, the process may be divided into several steps.

Thus, meta-type aramid fibers having excellent heat resistance and mechanical properties can be produced with high productivity. For example, in the method of the present invention, it is possible to easily produce a meta-aramid fiber having a tensile strength exceeding 5.0 g / de, which cannot be realized by spinning from a meta-aramid solution by conventional solution polymerization.

The fiber thus produced is subjected to crimping as required, cut into an appropriate fiber length, and provided to the next step.

The meta-type aramid fiber according to the method of the present invention comprises:
It can be applied to various uses that make use of its heat resistance, flame resistance, and mechanical properties.For example, heat-resistant flame-resistant clothing such as fire-fighting clothing, protective clothing, etc., alone or in combination with other fibers, fire-resistant bedding It is useful as an interior material, and can be effectively used as a nonwoven fabric as a raw material for various industrial materials such as filters, synthetic paper, and composite materials.

[0058]

The method of the present invention will be described in more detail with reference to the following 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.

In the examples and comparative examples, the intrinsic viscosity (IV) was determined by isolating the polymetaphenylene isophthalamide polymer from the polymer solution and drying the solution.
It is a value measured at 30 ° C. at a polymer concentration of 0.5 g / 100 ml. Further, “parts” and “%” are all based on weight unless otherwise specified, and the ratio by weight indicates the weight ratio. Furthermore, the polymer concentration (P concentration) in the polymer solution is the weight part of the polymer with respect to 100 parts by weight of the solvent (= polymer / solvent × 100), and the concentrations of calcium chloride and water are each with respect to 100 parts by weight of the polymer. Parts by weight.

[Example 1] (a) Preparation of solution polymerization spinning stock solution A reaction vessel equipped with a thermometer, a stirrer, and a raw material inlet was charged with 815 parts of MMP dehydrated with molecular sieves, and metaphenylenediamine was added to the NMP. (Less than,
After dissolving 108 parts, the mixture was cooled to 0 ° C. Isophthalic acid chloride (hereinafter referred to as IPC) pulverized by distillation and pulverized in a nitrogen atmosphere is added to the cooled diamine solution.
203 parts) was added thereto with stirring to cause a reaction. The reaction temperature rose to about 50 ° C., and stirring was continued at this temperature for 60 minutes, and the mixture was further heated to 60 ° C. and reacted for 60 minutes.
After the completion of the reaction, 70 parts of calcium hydroxide was added in the form of a fine powder and neutralized and dissolved for 60 minutes (primary neutralization). A slurry was prepared by dispersing the remaining 4 parts of calcium hydroxide in a mixed solvent of 85 parts of NMP and 36 parts of water, and the calcium hydroxide-containing slurry was added to the polymerization solution with stirring to neutralize (secondary neutralization). This secondary neutralization was carried out with stirring at 40 to 60 ° C. for about 60 minutes to prepare a spinning solution in which calcium hydroxide was completely dissolved.

The polymer concentration (P concentration) of this solution (stock solution for spinning) was 26.6, and the I.V. V. Was 1.75. The composition of the polymer solution is as follows: polymer / NMP / CaCl ₂ / H ₂ O = 26.6 / 100 /
12.4 / 8.0.

(B) Wet spinning / washing / drawing The spinning solution of 82-84 ° C. prepared in the above (a) was put into a first coagulation bath having a bath temperature of 82-84 ° C. from a die having a pore size of 0.08 mm and 50 holes. And spun. This first coagulation bath is composed of a calcium chloride-containing NMP aqueous solution, and the ratio of NMP and water in this aqueous solution is NMP / water = 40/60, and the calcium chloride concentration is 100 parts of NMP and water in total. The composition was 15 parts. After passing through the first coagulation bath at a yarn speed of 5 m / min at an immersion length of 30 cm, it was once drawn into the air, and then introduced into a second coagulation bath at a bath temperature of 95 ° C. The second coagulation bath had a composition in which 6 parts of NMP was added to 100 parts of an aqueous calcium chloride solution of calcium chloride / water = 45/55. The yarn was passed through the second coagulation bath at an immersion length of 2.5 m, subsequently washed with cold water (room temperature), and then washed with 70 ° C warm water.

Next, the film was stretched 2.4 times in hot water at 95 ° C. The hot water drawn yarn was dried with a drying roller having a surface temperature of 120 ° C. Thereafter, the film was stretched 1.8 times on a hot plate at 320 to 340 ° C. and wound at a final winding speed of 21.6 m / min.

The physical properties of the obtained drawn fiber are as follows: fineness: 2.1 d
e, tensile strength 5.5 g / de, elongation 35%, Young's modulus 1
It was 05 g / de.

[Example 2] (a) Preparation of solution polymerization spinning stock solution A polymerization reaction was carried out using the same reaction vessel, raw materials and solvent as used in Example 1. First, 108 parts of mPDA was dissolved in 980 parts of NMP, and then cooled to 3 ° C. IPC purified as in Example 1 was added to the cooled amine solution.
203 parts were added and reacted under stirring. The reaction temperature rose to 50 ° C., and stirring was continued at this temperature for 1 hour, and the mixture was further heated to 60 ° C. and reacted for 1 hour.

After the completion of the reaction, 72 parts of fine powder of calcium hydroxide was added to the polymerization solution with stirring as primary neutralization. In the neutralization step, the mixture is stirred at 40-60 ° C. for 1 hour 30 minutes,
The calcium hydroxide was completely dissolved. At this stage, the neutralization rate was about 97.3%, and the remaining 2.7% was neutralized with an aqueous solution of sodium hydroxide (NaOH). That is, Na
Dissolve 2.10 parts of OH in 20 parts of water and add NMP21
0 parts were added to prepare a second neutralizing agent. This secondary neutralizer was added to the polymer solution with stirring over 45 minutes to complete the neutralization, and a spinning stock solution was prepared. The HCl neutralization rate of this solution is 99.9%.

The polymer concentration (NMP 100
(Parts by weight of polymer relative to parts by weight) is 20 parts, and the I.V. V. Was 1.95. The total composition of this solution is polymer / NMP / CaCl ₂ / NaC
1 / H ₂ O = 20/100 / 9.1 / 0.26 / 4.7
Met.

(B) Wet spinning / washing / drawing The spinning stock solution of 83 to 85 ° C. prepared by the above polymerization reaction was passed through a spinneret having a hole diameter of 0.1 mm and 100 holes with a bath temperature of 83 to 85 ° C.
It was discharged into a first coagulation bath at 85 ° C. to form a thread.
The ratio of CaCl ₂ , water and NMP in the first coagulation bath is CaC
l ₂ / water / NMP = 35/60/15. The yarn was passed through an immersion length of 30 cm at a yarn speed of 7 m / min, pulled out into the air, and then led to a second coagulation bath at 95 ° C. This second coagulation bath was CaCl ₂ / water = 47/53.
Then, using a material obtained by adding 7 parts of NMP to the immersion length 2
After passing through the second coagulation bath at 50 cm, the thread drawn from the bath is washed with cold water (30 ° C. or less),
Washed with warm water at ℃.

Next, the film was stretched 2.4 times in hot water at 95 ° C. and washed with hot water at the same time. 100-120 ° C
And then stretched by dry heat at a stretching ratio of 1.9 on a hot plate at 320 to 340 ° C, and then wound at a winding speed of 31 m / min.

The performance of the obtained drawn fiber was 2.2 d fineness.
e, strength 5.3 g / de, elongation 31%, Young's modulus 101
g / de.

[Comparative Examples 1 and 2] For comparison, a coagulation bath (Comparative Example 1) in which only 60 parts of water and 40 parts of NMP were used in Example 2 except that CaCl ₂ was excluded from the composition of the first coagulation bath,
Alternatively, spinning was performed using a coagulation bath (Comparative Example 2) having a composition of 35 parts of CaCl ₂ and only 60 parts of water without adding NMP.
In any case, since the fiber is broken in a coagulation bath or broken in a warm water bath and cannot be drawn sufficiently, the fiber performance of the final wound yarn has a low strength of 2-3 g / de, and the meta-type aramid fiber Was insufficient.

Example 3 (a) Preparation of a solution polymerization spinning stock solution This example is an example using a spinning stock solution having a polymer concentration (P concentration) = 25. The same reaction vessel as in Example 1 was used, and the polymerization reaction was carried out using the same mPA and IPC as raw materials used here and the polymerization solvent NMP purified by the same operation as in Example 1.

First, after dissolving 108 parts of mPA in 852 parts of NMP, the mixture was cooled to 0 ° C.
The reaction was carried out by adding 203.2 parts of C under stirring. The reaction temperature was raised to about 50 ° C., and stirring was continued at this temperature for 60 minutes, and the reaction was further heated to 60 ° C. for 60 minutes. After the completion of the reaction, 72 parts of calcium hydroxide fine powder was gradually added and neutralized and dissolved for 60 minutes to complete the primary neutralization. Replace the remaining 2 parts of calcium hydroxide with 18 parts of water and MNP1
The resulting mixture was stirred and dispersed in a solution consisting of 00 parts to prepare a slurry dispersion liquid (secondary neutralizing agent). This calcium hydroxide slurry dispersion was added to the primary neutralized polymer solution with stirring over 30 minutes, and further dissolved at 60 ° C. to dissolve the neutralizing agent to complete secondary neutralization. A spinning dope was obtained.

The polymer concentration (P concentration) of this spinning dope was 2
In 5, the IV of the produced polymer was 2.1. This spinning
The composition of the thread stock solution (polymer solution) is polymer / NMP / Ca
Cl _Two/ H_Two0 = 25/100 / 11.9 / 5.7,
The amount of water based on 100 parts of the polymer was 23 parts.

(B) Wet spinning, washing and drawing The spinning solution prepared in the above (a) was discharged from a die having a hole diameter of 0.09 mm and 50 holes into a first coagulation bath at a bath temperature of 84 to 86 ° C. It was formed into a thread. CaCl of this first coagulation bath
The ratio of ₂ , water and NMP was CaCl ₂ / water / NMP (weight ratio) = 20/60/35. The yarn was passed through an immersion length of 30 cm at a yarn speed of 6 m / min, once drawn into the air, and subsequently introduced into a second coagulation bath at a bath temperature of 95 to 98 ° C. The composition of the second coagulation bath is CaCl ₂ / water / NMP
= 45/55/10, after passing through an immersion length of 260 cm, washed with cold water (20 ° C) and further washed with 70 ° C warm water.

Subsequently, in warm water at 93 to 95 ° C., 2.5
The film was stretched twice and washed with warm water at the same time. This drawn yarn is
After drying with a drying roller at 0 to 120 ° C, 320 to 330
Stretch on a hot plate at a draw ratio of 1.7 times,
The film was wound at a winding speed of 25.5 m / min.

The performance of this fiber was as follows: fineness 2.0 de, strength 5.6 g / de, elongation 31%, Young's modulus 110 g / de.
Met.

Further, the fibers obtained in Examples 1 to 3 are all excellent in gloss and have a heat resistance of 90% of the original strength even after an exposure test in heated air at 250 ° C. for 300 hours. And showed extremely excellent heat resistance.

[0079]

The solution polymerization-neutralization-wet spinning method according to the present invention is as follows: 1. The step of removing the inorganic salt generated by the neutralization becomes unnecessary, 2. Since the polymerization solvent and the solvent for the spinning polymer solution (spinning stock solution) can be unified, the recovery step is facilitated. 3. Eliminating large spinning towers such as dry spinning and the associated loss of thermal energy; From the viewpoint of a large production volume per one spinning machine, it is possible to efficiently and efficiently produce fibers having excellent fiber performance at a low cost.

Further, as compared with the method using a one-stage coagulation bath previously proposed by the present inventors, the mechanical properties (strength and Young's modulus) of the obtained fiber are much more excellent and the coagulation bath can be operated stably. Is advantageous in operation because the range of conditions is wide.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-17310 (JP, A) JP-A-6-80775 (JP, A) JP-A-56-31009 (JP, A) JP-A-54-1979 105197 (JP, A) JP-A-53-124563 (JP, A) JP-A-49-128096 (JP, A) JP-A-49-93611 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) D01F 6/60 371 C08G 69/32

Claims (7)

(57) [Claims] 1. After reacting an aromatic diamine and an aromatic dicarboxylic acid chloride in the presence of an amide solvent,
In a method for producing a meta-aramid fiber by wet spinning a meta-aramid polymer solution containing calcium chloride and water produced by neutralizing hydrochloric acid (HCl) by-produced, (1) an amide-based solvent After using N-methyl-2-pyrrolidone to react an aromatic diamine mainly composed of meta-phenylenediamine with an aromatic dicarboxylic acid chloride mainly composed of isophthalic chloride, hydrochloric acid (HCl) by-produced is reacted with water. Calcium oxide, a meta-type aramid polymer solution containing calcium chloride and water neutralized with at least one neutralizing agent selected from calcium oxide and calcium carbonate, and
The concentration of the polymer in the solution (weight of the polymer based on 100 parts by weight of N-methyl-2-pyrrolidone) is 18 to 35.
(Parts by weight), the concentration of calcium chloride (weight based on 100 parts by weight of the polymer) is 40 to 47 (parts by weight), and the concentration of water (weight based on 100 parts by weight of the polymer) is 13 to 60 (parts by weight). (2) forming a thread by spinning the polymer solution into a first coagulation bath comprising an aqueous solution of calcium chloride containing N-methyl-2-pyrrolidone And at this time the bath temperature of the first coagulation bath is 70-110 ° C., and calcium chloride (CaCl ₂ ), N-methyl-2-pyrrolidone (NMP) and water (H ₂ O) in the range of content of _{below, CaCl 2 + NMP + H 2} O = 100~150 CaCl 2 + NMP = 40~90 CaCl 2 = 5~50 NMP = 50~5 H 2 O = 40~70 (3) then, the The thread extracted from the coagulation bath is introduced into a second coagulation bath comprising an aqueous solution of N-methyl-2-pyrrolidone containing calcium chloride, and at this time, N-methyl-2 in the aqueous solution of the second coagulation bath is used. -Pyrrolidone /
(Calcium chloride + water) weight ratio of 5/95 to 25/7
5. The weight ratio of calcium chloride / water is 40 / 60-60 /
40 and the second coagulation bath temperature is 80 to
130 ° C. and higher than the first coagulation bath;
(4) A method for producing meta-type aramid fiber, comprising drawing out the thread from the second coagulation bath and washing with water. 2. The polymer solution temperature during spinning is 70-110.
The method for producing a meta-type aramid fiber according to claim 1, wherein the temperature is ° C. 3. The number of discharge holes per spinneret is 300 to 300.
The method for producing a meta-type aramid fiber according to claim 1, wherein the number is 30,000. 4. The yarn after the second coagulation bath is washed with water having a temperature of 30 ° C. or lower, and then with warm water having a temperature of 50 to 90 ° C., and subsequently, in a warm water bath of 90 to 100 ° C. The method for producing a meta-aramid fiber according to claim 1, wherein washing is performed simultaneously with the drawing. 5. The method according to claim 5, further comprising:
The method for producing a meta-type aramid fiber according to claim 1 or 4, wherein the drawing is performed by dry heat at 350 ° C. 6. The method for producing meta-aramid fibers according to claim 5, wherein the total draw ratio of hot water drawing and dry heat drawing is 3 to 7 times. 7. The method for producing a meta-type aramid fiber according to claim 5, wherein the wet spinning, washing with water, hot water drawing and dry heat drawing are performed in a continuous series of steps.