KR920009001B1 - Process for the production of aromatic polyamide fiber - Google Patents

Abstract

The method for producing an aromatic polyamide fiber comprises (a) polymerizing the mixture soln. of amide solvent, inorganic salt, aromatic diamine and aromatic diacid chloride at a low temp. of 40 deg.C or less to obtain a prepolymer, (b) adding a tertiary amine to the prepolymer to obtain a spinning soln., and (c) spinning, washing, drying and winding it. The tertiary amine for mfg. the spinning soln. is pref. pyridine, quinoline, triethylamine, t-butylamine, pirimidine, pyrazine, picoline or quinoxaline. The fiber has a high tenacity and elasticity.

Description

Method for producing aromatic polyamide fibers

1 is a schematic diagram of a process for producing a fiber according to the present invention.

* Explanation of symbols for the main parts of the drawings

1: liquid crystal prepolymer supply tank 2: tertiary amine storage tank

3: liquid crystal prepolymer supply pump 4: tertiary amine supply pump

5: static mixer 6: spinneret

7: coagulation bath 8: winding roller

The present invention relates to a method for producing an aromatic polyamide fiber, and more particularly, by preparing a liquid crystal prepolymer of an aromatic polyamide in advance and using a tertiary amine containing a tertiary amine or an amide solvent therein. The present invention relates to a method for producing a high-strength and high modulus aromatic polyamide fiber having a single structure without increasing the molecular weight and spinning and stretching the solidification liquid through an orifice or a mold for manufacturing a fiber.

Recently, the development of new materials that can be used very lightly, strong, and robust in the aircraft and aerospace industries, etc., has been requested to develop high strength, high elastic inorganic fibers using ceramics, graphite, or boron. It is quite expensive and difficult to handle, so it is not widely applied. As a new material, aromatic polyamide fibers not only have high abrasion resistance, high strength and high elasticity, but also have insoluble and insoluble properties, and thus are widely used as raw materials for plastics reinforced in automobiles and aviation industries. Due to this usefulness, various methods for producing aromatic polyamide fibers have been researched and developed, and the related arts are as follows.

That is, conventional techniques for polymerization and spinning of polyamide fibers have been introduced in U.S. Patent Nos. 3,869,429 and 3,869,430. The technique dissolves an inorganic salt and an aromatic diamine in an amide solvent and then aromatic dieside chloride. The crumb obtained by polymerization at low temperature, for example, acid crumb polymer was washed with water to separate the polymerization solvent and the inorganic salt and dried, and then dried in a sulfuric acid solvent such as sulfuric acid, chlorosulfuric acid or fluorosulfuric acid at least 98%. It is a technology for producing aromatic polyamide fibers by melting about 20% by weight to form a liquid crystal dope (Dope), and the dope is spun, neutralized, washed, dried and mechanically treated in water. However, when using such a method, for example, a polymerization method, a washing process, a preparation of a dope using sulfuric acid, a spinning and a mechanical treatment process must be performed, and thus, the manufacturing process is complicated and the manufacturing cost increases accordingly. Due to the use of sulfuric acid, there is a risk that the manufacturing apparatus may be corroded and the risks are not followed. In addition, it is difficult to treat calcium sulfate (CaSO ₄ ), which is produced as a byproduct, due to degradation of the polymer in the dope. Due to the residual sulfuric acid in the fiber, the color of the fiber was not good to change over time.

In addition, the fibers provided by this method have a weak compressive strength due to their own kink band phenomena, which results in a strength much lower than the original theoretical strength of the aromatic polyamide fibers, and has a crystal defect layer on the fiber itself. There was a drawback that the chemical resistance is also significantly inferior. Therefore, the present inventors prepared a liquid crystal prepolymer in advance in order to solve such a conventional problem, and then contains an equivalent amount of a tertiary amine or an amide solvent (which reacts all HCl generated during the preparation of the liquid crystal prepolymer). Method of producing a high strength and high modulus aromatic polyamide fiber having a single structure without increasing the molecular weight by using a tertiary amine and spinning or stretching the coagulation solution through an orifice or a fiber manufacturing mold, without a crystal binding layer To provide.

Another object of the present invention is to prepare a method for producing an aromatic polyamide fiber which can be directly obtained simultaneously with polymerization of an aromatic polyamide fiber which is easy to process and has low manufacturing cost and is capable of continuous production.

Still another object of the present invention is to prepare aromatic polyamide fibers having an intrinsic viscosity of 4.0 or more, uniform molecular chain end distribution, no crystal bonding layer and kinkband, and no change in color.

Hereinafter, the present invention will be described in detail.

The present invention provides a liquid crystal prepolymer by polymerizing a mixed solution obtained by isotropically adding an molar amount of an aromatic diamine and an aromatic dieside chloride to a solvent in which an inorganic salt is dissolved in an amide solvent or an amide solvent containing a small amount of tertiary amine. After spinning in a coagulation bath, washing with water, drying, and winding to prepare aromatic polyamide fibers, after preparing a liquid crystal prepolymer, a tertiary amine was added thereto to prepare a spinning solution having a high molecular weight and a viscosity. 4 to 4, which is a method for producing an aromatic polyamide fiber, which is spun into a coagulation bath made of water and washed with water, dried and wound by a conventional method.

Hereinafter, the present invention will be described in more detail.

The present invention adds and dissolves an inorganic salt in an amide solvent alone or an amide solvent containing a small amount of tertiary amine, and polymerizes an equimolar amount of aromatic diamine and dieside chloride at a low temperature of 40 ° C. or lower to intrinsic viscosity of 0.8 to An optically anisotropic liquid crystalline prepolymer (hereinafter referred to as a prepolymer) having a repeating unit of formula (I) or (II), which is 2.5, and is a copolymer or homopolymer is prepared.

After preparing a spinning solution (hereinafter referred to as spinning solution) having a molecular weight increased after mixing with a tertiary amine mixed with a tertiary amine or an amide solvent, which serves to increase the degree of polymerization, It is a method of spinning at an elongation of 1 to 4, washing and drying to produce an aromatic polyamide fiber.

,

,

,

,

,

,

,

,

,

,

,

,

,

,

(X is H, Cl, Br, I.)

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

R ₁ and R ₂ may be the same or may be different, and R ₁ and R ₂ are generally present in equimolar amounts.

An optically anisotropic liquid crystalline prepolymer characterized by the present invention is a polymerization reaction by adding an aromatic diamine and an aromatic dieside chloride to a solution in which an inorganic salt is dissolved in an amide solvent or an amide solvent containing a small amount of tertiary amine. It refers to a polymer solution formed at the point before the gelation after the stear opalesence (stir opalesence) during the process, the polymer has the characteristics of a copolymer (copolymer) or homopolymer (homopolymer). In addition, the spinning solution refers to a solution containing a tertiary amine or an amide solvent in the liquid crystal prepolymer as described above and tertiary amine mixed to increase molecular weight and viscosity. Unlike here, as in Korean Patent Publication No. 84-726 (Method for Preparing Aromatic Polyamide Short Fiber), at least 3% by weight of the tertiary amine in the amide-based solvent at the initial stage (before preparing the liquid crystal prepolymer) In the case of the polymerization, the aromatic dieside chloride, which is the final charged monomer, is gelled within a few seconds (2 to 7 seconds) immediately after the injection, and thus it is difficult to manufacture the liquid crystal prepolymer and the spinning solution.

For example, the polymerization method of the liquid crystal prepolymer solution of the present invention includes an amide solvent in which an inorganic salt (halogenated metal salt) is dissolved or an amide containing a small amount (0 to 2% by weight of tertiary amine) based on the amide solvent. It is obtained by dissolving aromatic diamine in a solvent and then cooling it to a low temperature under a nitrogen stream and then polymerizing it by a solution polymerization method in which aromatic dieside chloride is reacted at a low temperature of 40 ° C. or lower. Must be contained and allowed to proceed quantitatively. In addition, as a method for preparing a spinning solution, when a tertiary amine containing a tertiary amine or an amide solvent is mixed with the liquid crystal prepolymer prepared as described above, a high molecular weight spinning solution is obtained.

As the polymerization solvent used in the present invention, an amide urea-based organic solvent may be used alone and a mixture thereof, or an amide- and urea-based organic solvent containing a small amount of tertiary amine may be used. Methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAC), hexamethylphosphoramide (HMPA), N, N-dimethylformamide (DMF), N, N-dimethylsulfoxide ( DMSO), N, N, N ', N'-tetramethylurea (TMU), etc. are mainly used, and other than that, N-methylpiperidone, N-methylcaprolactam, N-acetylpyrrolidone, dimethylpropionamide, dimethyl Isobutylamide, dimethylpropylurea and the like can also be used as the polymerization solvent.

In the preparation of the liquid crystal prepolymer, the tertiary amine is preferably used in an amount of 0 to 2% by weight based on the amide solvent. As the tertiary amines, pyridine, quinoline, triethylamine, t-butylamine, picoline, and pyriline are generally used. It can be selected from midines, pyrazine and quinoxaline. If the addition amount of the tertiary amine in the polymerization solvent is 2% by weight or more, it is difficult to control the reaction rate, so that it is not easy to manage the process, and it is preferable to add it in 2% by weight or less.

On the other hand, the inorganic salt used to increase the solubility of the polymer is a metal halide salt, for example, lithium chloride (LiCl), calcium chloride (CaCl ₂ ), potassium chloride (KCl), potassium bromide (KBr), lithium bromide ( LiBr) and the like are mainly used and the amount used is preferably used by adding 1.0 to 10.0% by weight (weight of salt / amide solvent volume).

A halogenated metal salt is added to an amide solvent containing such an amide alone or a small amount of tertiary amine, and then at low temperature, an aromatic diamine such as p-phenylenediamine and an aromatic dieside chloride such as terephthalate. When some reaction is carried out by adding and stirring monochloride, the polymer in the optically anisotropic liquid crystalline prepolymer solution which is in the state before the reaction is completed is obtained as poly (p-phenylene terephthalamide) having the following structural formula (III).

At this time, the dope is separated from the dope (isolated polymer dope) to separate the polymer after the polymerization is completed and dissolved in a solvent.

Wherein the liquid crystal prepolymer solution is good if the content of the polymer is 4 to 20% by weight, but if more than 20% by weight is not suitable for use as a dope, that is, the reaction rate is rapidly increased, difficult to process management On the contrary, if the content is less than 4% by weight, the intrinsic viscosity of the final polymer is sharply lowered, and it is preferable to adjust the content ratio within the above range because loss is caused in cost. More preferably, it is 5 to 13 weight% further.

The intrinsic viscosity of the liquid crystal prepolymer may be 0.8 to 2.5, but more preferably 1.0 to 1.8 in terms of process control.

On the other hand, the amount of tertiary amine used in the production of spinning solution varies depending on the content of the polymer, but in general, the use of tertiary amine in an amount equal to the range of the following formula (IV) can sufficiently control the reaction rate. Management is possible.

Where P is the amount of liquid crystal prepolymer, M is the amount of tertiary amine, and S is the content percentage of the polymer.

Referring to the process for producing an aromatic polyamide fiber according to the present invention as illustrated in the drawings as follows.

That is, FIG. 1 is a process diagram showing a supply tank 1 having a size capable of storing a predetermined level of the liquid crystal prepolymer as described above, and a storage tank 2 of a tertiary amine containing a tertiary amine or an amide solvent. ) Is a static mixer (5; static), which is a spinning solution maker, with the liquid crystal prepolymer and tertiary amine contained in the supply tank 1 and the storage tank 2 through the supply pumps 3 and 4, respectively. to a mixer).

The spinning solution prepared in this way is to produce the fibers required by the present invention when the spinneret (6) after the coagulation, washing, drying and winding up.

The microstructure of the fiber according to the present invention prepared in this way has a fully extended molecular chain structure, the chain end distribution is formed evenly in the fiber axis direction, the defect zone (defect zone) and There is no crystal defect layer according to the corrugated sheet structure, and the intrinsic viscosity is an aromatic polyamide fiber characterized in that it has a single structure of 4.0 or more, strength of 15 g / d or more, and initial modulus of 450 g / d or more.

On the other hand, the physical property evaluation of the fiber produced according to the present invention can be easily seen from the relation of the intrinsic viscosity (I. V.) shown in the following.

IV = ln (η _rel ) / C

Where C is the concentration of the polymer (0.5 g of polymer or fiber in 100 ml of solvent), η _rel is the relative viscosity and is the ratio of the flow time between the solution and the solvent, measured by a capillary viscometer at a temperature of 30 ° C, Is usually concentrated sulfuric acid (95 to 98% sulfuric acid), unless defined.

Hereinafter, the present invention will be described based on Examples.

Example 1

A four-necked flask having a volume of 5 L was sufficiently replaced with nitrogen, and water was removed as much as possible. Then, 1,200 ml of NMP was added to the flask, and 27.0 g of inorganic salt (CaCl ₂ ) was added while raising the temperature to 100 ° C. After completely dissolving, 24.5 g of PPD was sufficiently dissolved in the solution, and a cooling water bath was installed to cool the mixture, and 45.95 g of TPC was added while lowering the temperature to stir well for 3 minutes to form a liquid crystal prepolymer. The liquid crystal prepolymer thus prepared is supplied to the static mixer at 100 g / min, and at the same time, pyridine is supplied in an amount of 10 g / min to make a spinning solution. The spinning solution thus obtained was spun through a spinneret having a diameter of ø0.2mm and an odd number of 70, and then wound up at a speed of 70m / min. At this time, the coagulant used water. It is then washed with water and dried to give aromatic polyamide fibers. At this time, the intrinsic viscosity of the fiber is 6.5ml / g, the measurement result of E / T / Mi is 3.5 / 23/520.

Example 2

Inorganic salts and tertiary amines as shown in Table 1 below are used, and the reaction solvent in the preparation of the liquid crystal prepolymer is changed. All other conditions are the same as in Example 1 above. Intrinsic viscosity and E / T / Mi measurement results are shown in Table 1 below.

Example 3

The solvent (tertiary amine) in the preparation of the spinning solution is changed by using a reaction solvent and an inorganic salt as shown in Table 2 below. All other conditions were the same as Example 2 above. Intrinsic viscosity and E / T / Mi measurement results are shown in Table 2 below.

TABLE 1

TABLE 2

※ The amount of tertiary amine used in preparing the spinning solution in Example 1 was changed to the standard (1.0).

Claims (3)

A liquid crystal prepolymer was prepared by polymerizing a mixed solution obtained by isotropically adding an molar amount of aromatic diamine and an aromatic dieside chloride to an amide-based solvent or a solvent in which an inorganic salt was dissolved in an amide solvent containing a small amount of tertiary amine. In preparing aromatic polyamide fibers by spinning in a bath, washing with water, drying, and winding, after preparing a liquid crystal prepolymer, a tertiary amine is added thereto to prepare a spinning solution having a high molecular weight and a viscosity, which is then used as an elongation of 1 to 4. A method for producing an aromatic polyamide fiber, which is spun into a coagulation bath made of water and washed with water, dried and wound in a conventional manner. The method according to claim 1, wherein the amount of tertiary amine used in the preparation of the spinning solution is in the following range. P × 6.3 / S × 2/100 <M <P × 6.3 / S × 30/100 Where P is the amount of liquid crystal prepolymer, M is the amount of tertiary amine, and S is the polymer content percentage. The method of claim 1, wherein the tertiary amine used in preparing the spinning solution is characterized in that at least one selected from pyridine, quinoline, triethylamine, t-butylamine, picoline, pyrimidine, pyrazine, quinoxaline Way.

Images