KR900003327B1 - Aromatic polyamide pulp type single fuber and that's process of manufacture - Google Patents

Abstract

Aromatic polyamide pulp-type single fiber is prepd. by: preparing an optical anisotropic liquid crystalline propolymer having repeat unit of formula (I), of 1.0-4.0 inherent viscosity, which is prepd. by reacting p-phenylene diamine and terephthaloyl chloride of same equivalent ratio in inorg. salts-insolved amide or urea based solvent; compress-spray out the prepolymer together with tertiary- amine polymm. accelerating precipitator at below 50 C and at more than 20 sec-1 of shearing velocity; curing that in state of containing a small amt of polymn. accelerating precipitator before drying.

Description

Novel aromatic polyamide pulp-like short fibers and preparation method thereof

The present invention relates to a method for producing an aromatic polyamide pulp-like short fiber, and more particularly, after preparing a liquid crystal prepolymer of an aromatic polyamide, it is subjected to extrusion spraying and heat treatment together with a polymerization accelerator precipitate under mechanical shearing force. Therefore, the present invention relates to an aromatic polyamide pulp-like short fiber having remarkably improved overall physical properties and a method of producing the same.

Recently, various polymeric compound fiber materials have been used as fiber composite materials. Among them, aromatic polyamide fibers have excellent physical properties such as chemical resistance and heat resistance, as well as excellent mechanical properties such as strength and elasticity, as well as other fiber composite materials. Because of its light and solid advantages, it is widely used in various industries. In addition, when the aromatic polyamide fibers are manufactured in the structure of pulp-like short fibers, they have the great characteristics as described above and a very good wear resistance.

As described above, aromatic polyamide fibers have excellent physical properties or mechanical properties, and as their practical value increases, various methods for manufacturing them have been developed. For example, many prior arts including Kwolek's German Patent No. 181426 have been developed. Known.

For example, U.S. Patent Nos. 3,869,429 and 3,869,430 propose methods for producing pulp-like short fibers by a series of physical processing methods in which fibers obtained by producing, spinning and stretching polyamide sulfate dope are prepared. The production of aromatic polyamide fibers according to this method complicates the entire process because it requires additional processes such as manufacturing, spinning, stretching, washing, and crushing sulfuric acid dope. There are drawbacks such as that the physical properties are affected.

Further, Japanese Unexamined Patent Publication No. 59-47694 proposes a method for producing pulp-like short fibers by precipitating and stirring a polymer solution obtained by dissolving an aromatic polyamide polymer in an amide organic solvent in water or methyl alcohol. In this case, however, the polymer to be used must be a low molecular weight polymer to be dissolved in an organic solvent, and the polymer solution can be precipitated and stirred in water or methyl alcohol, thereby improving the intrinsic viscosity (I.V).

On the other hand, a simple manufacturing process for producing aromatic polyamide fibers by extruding the dope into a precipitation solvent using a polymerization medium solution before the completion of the polymerization as a doping is US Patent Nos. 3,673,143 and 3,817,914 In the case of using the above method, the whole process is simplified, whereas water is used as the precipitation solvent, so that a low molecular weight polymer is produced and the intrinsic viscosity is also lowered.

Therefore, the object of the present invention is to completely solve the problems of the prior art as described above, it is easy to process management during manufacturing and excellent physical properties, in particular has an intrinsic viscosity of at least 4.0 or more, and promote polymerization after extrusion, injection The present invention provides a high-strength aromatic polyamide pulp-like short fiber having excellent fibril growth, focusing, high crystallinity and orientation by heat treatment with a precipitant, and a method of manufacturing the same.

Hereinafter, the present invention will be described in detail.

The present invention reacts p-phenylenediamine and terephthaloyl chloride in the same equivalence ratio in an amide-based or urea-based polymerization solvent in which an inorganic salt is dissolved, and has an intrinsic viscosity of 1.0 to 4.0 and a repeating unit represented by the following structural formula (I): After preparing an optically anisotropic liquid crystalline prepolymer having a, and extruding the same, but simultaneously extruded to a shear rate of at least 20 sec ^-l with a tertiary amine polymerization accelerator at a low temperature of 50 ℃ or less, and before washing it A method for producing an aromatic polyamide pulp-like short fiber characterized by heat treatment in the state of containing a small amount of polymerization accelerator precipitation agent.

In addition, the present invention provides an aromatic polyamide pulp phase stage having a repeating unit represented by Structural Formula (I) having a fully extended molecular chain structure and having an intrinsic viscosity of at least 4.0 or more, prepared by the production method as described above. It is a fiber.

Referring to the present invention in more detail as follows.

The optically anisotropic liquid crystalline prepolymer according to the present invention polymerizes aromatic diamines and aromatic dieside chlorides such as p-phenylenediamine and terephthaloyl chloride in amide or urea polymerization solvents containing inorganic salts such as metal halide salts. By dissolving an inorganic salt in an amide-based or urea-based polymerization solvent, then dissolving the aromatic diamine therein and cooling it to a low temperature of 40 DEG C or lower under a nitrogen stream, followed by aromatic dieside chloride. The liquid crystal prepolymer was prepared by adding low temperature polymerization.

In this case, as the polymerization solvent used in the present invention, an amide solvent or a urea solvent may be used alone, or a mixed solvent thereof may be used. For example, N-methyl-2-pyrrolidone (NMP), N, N-dimethyl ac Cetamide (DMAc), hexamethylphosphoramide and the like are mainly used, and in addition, N-methylpiperidone, N-methyl caprolactam or dimethylpropylurea may be used.

Lithium chloride, calcium chloride, potassium chloride or potassium bromide is mainly used as the inorganic salt dissolved in the polymerization solvent, and the amount of the inorganic salt is preferably added in an amount of 0.5 to 15% by weight based on the polymerization solvent.

Meanwhile, the optically anisotropic liquid crystal prepolymer solution prepared as described above is extrusion sprayed using a conventional pulp-like short fiber manufacturing apparatus, that is, a nozzle jet or a coaxial unit, wherein the optically anisotropic The liquid crystal prepolymer solution is extruded to receive a shear rate of at least 20 sec ⁻¹ together with the polymerization promoter flowing into the apparatus, so that the liquid crystal prepolymer and the polymerization accelerator precipitant are brought into contact with each other. As the rate increases rapidly, the polymerization is complete. As the polymerization proceeds in this way, the intrinsic viscosity is remarkably increased, and the molecular orientation of the polymer is highly grown by applying a shearing force by the polymerization promoting precipitant to form fibrils.

At this time, the liquid crystal prepolymer solution to be sprayed by extrusion should contain a polymer in the range of 4 to 20% by weight, considering the ease of extrusion as a dope, growth of molecular chain orientation and final polymerization, the intrinsic viscosity is 1.0 to 4.0, preferably 1.0 to 3.0, more preferably about 1.5 to 2.7.

In addition, tertiary amines are used as the polymerization precipitating agent according to the present invention. For example, pyridine, triethylamine, t-butylamine, and pyrimidine may be selected and used, but pyridine is particularly effective. Generally, the polymerization promoting precipitate is preferably used at a low temperature of 50 ° C. or lower, and may be partially mixed in an eyed polymerization solvent.

The aromatic polyamide pulp-like short fibers polymerized and oriented by the above-described process to form fibrils are separated from the polymerization accelerator in the filtration tank and then transferred to the heat treatment apparatus without being washed.

The pulp-like short fibers transferred to the heat treatment apparatus are heat treated at a temperature of 150 ° C. to 350 ° C. under a nitrogen atmosphere, thereby finishing the final polymerization such as growth of molecular orientation, concentration of fibrils, and increase of crystallinity. At this time, the pulp-like monolayer oil is not washed, so the polymer molecular chain is oriented considerably, but because of the gap there is a small amount of a polymerization solvent and a polymerization accelerator precipitant therebetween. They can be easily removed by the heat treatment process.

That is, in general, the method of washing the fibers with water is mainly used to remove the organic solvent, whereas in the present invention, the aromatic polyamide pulp-like short fibers are heat-treated before washing with water, thereby remaining solvent by heat treatment In addition, the gap between polymer chains is narrowed, thereby increasing the regularity of molecular arrangements and developing fibrils, which significantly improves the concentration, and the residual solvent contained in the fibers. The qualitative area is relatively reduced, thereby improving the crystallinity of the fiber.

In addition, since the polymerization accelerator contained in the fiber is heated, the degree of polymerization is further increased because the final polymerization may be completed by a slight residual reaction between the unreacted monomer or the oligomer and the oligomer, the polymer and the oligomer even in the solidified state. There is an advantage to this.

In order to maximize the efficiency of the heat treatment process according to the present invention, the anti-aromatic polyamide pulp-like short fibers obtained through a recovery tank before heat treatment are polymerized 0.5 to 6 times, more preferably 0.1 to 5.0 times the weight of the fiber. It is preferable to contain an accelerating precipitant, and the heat treatment conditions are preferably 5 to 60 minutes at 150 ° C to 350 ° C, and most preferably 15 to 40 minutes at 180 ° C to 300 ° C. The higher the heat treatment temperature, the higher the temperature at 150 ° C. However, if the heat treatment is performed at a temperature higher than 350 ° C, there is a risk of degradation and disorientation as well as the color change of the fiber over time by the polymerization solvent contained in the fiber. Therefore, it is not preferable.

On the other hand, the aromatic polyamide pulp-like short fibers according to the present invention significantly improve the degree of polymerization of the liquid crystal prepolymer solution by using a polymerization promoter in the production process, and at the same time, form an amide bond and a hydrogen bond of the polymer to improve molecular orientation. In addition to having an extended molecular chain structure by the molecular orientation polymerization method that develops the fiber bundle by giving a direct mechanical shear force during extrusion spraying, it also contains a polymerization precipitant in the fiber before the washing step after extrusion spraying. By heat treatment in a state of presence, the molecular structure has a fully extended molecular chain structure and improved overall physical properties such as orientation and crystallization degree, and has a repeating unit represented by the following structural formula (I) having an intrinsic viscosity of at least 4.0 or more. It is characterized by a fiber.

Here, the degree of polymerization of the poly (p-phenylene terephthalamide) according to the present invention is represented by intrinsic viscosity (I.V) by the following equation.

IV = ln η _rel / C

Where η _rel relative viscosity and C represents the concentration of 0.5% of the polymer in 100 ml of solvent, expressed in g / l. The relative viscosity η _rel is a value obtained by dividing the flow time of the polymer solution in the capillary viscometer by the flow time of the pure solvent, and the flow time is measured at 30 ° C. using concentrated sulfuric acid (97%).

In addition, the crystallinity and orientation angle of the aromatic polyamide pulp-like short fibers according to the present invention can be measured by an X-ray diffractometer by the method described in US Pat. No. 3,869,430.

The present invention as described above exhibits the following superior effects as compared to the prior art.

First, the process is simple by producing pulp-like short fibers directly in the polymerization process, without the need for the secondary processes of preparing and spinning the sulphate dope after preparing, separating and washing the polymer; Secondly, by extruding the liquid crystal prepolymer at a shear rate of 20 sec ^-1 or more together with a polymerization accelerator precipitating agent, the reaction rate is increased so that the polymerization is promoted and the aromatics have high strength and high orientation by molecular alignment polymerization method which grows molecular alignment. Polyamide pulp-like short fibers can be obtained; Third, in the present invention, the fibrill can be sufficiently developed even at a temperature lower than the conventional heat treatment temperature by subjecting the short fibers obtained by the molecular alignment polymerization method to the heat treatment before washing in the state containing the polymerization accelerator precipitant, and the degree of orientation And it is possible to obtain a short fiber with improved crystallinity, it is possible to easily remove the polymerization accelerator precipitant and the polymerization solvent remaining in the fiber.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

In a nitrogen atmosphere, 250 ml of N-methyl-2-pyrrolidone was added to the reactor, the temperature was raised, and calcium chloride was added to dissolve it. After dissolving 10.38 g of p-phenylenediamine in the solution, 19.55 g of terephthaloyl chloride was added at a low temperature of 30 ° C. or lower and stirred vigorously.

The liquid crystal prepolymer thus obtained is transferred to the nozzle jet apparatus through a transfer pipe at a speed of 2 m / min using a gear pump, and the pyridine is extruded from the nozzle jet apparatus at a speed of 30 m / min.

The liquid crystal prepolymer solution and pyridine contacted with each other in the nozzle jet apparatus pass through the filtration apparatus, and the pulp-like short fibers are filtered and transferred to the heat treatment apparatus, and the pyridine is recycled again, wherein the pulp phase is transferred to the heat treatment apparatus under a nitrogen atmosphere. Short fibers contain 1.5 times of pyridine based on fiber weight. The final pulp-like short fibers obtained by heating at a temperature of 200 ° C. for 30 minutes in a heat treatment apparatus are washed with water to remove inorganic salts contained in the fiber bundle and dried in a vacuum dryer for 2 hours.

As a result, the intrinsic viscosity (I.V) of the final pulp-like short fibers obtained was 6.9, and the orientation angle and crystallinity were 18 and 75%, respectively.

Example 2 (Comparative Example 1)

Except for the use of pyridine, t-butylamine, methyl alcohol and water as the precipitant, the preparation of the liquid crystal prepolymer solution, the extrusion conditions, the heat treatment conditions and the like were carried out in the same manner as in Example 1 to prepare pulp-like short fibers. The results of the heat treatment are shown in Table 1 below.

TABLE 1

Example 3

The liquid crystal prepolymer solution was prepared and extruded under the same conditions as in Example 1 to prepare pulp-like short fibers of poly (p-phenylene terephthalamide), and the short fibers contained 1.7 times of pyridine based on fiber weight. It is transferred to the heat treatment apparatus in the state of being. The short fibers transferred to the heat treatment apparatus were heat treated while changing the heat treatment temperature and time according to the following Table 2, and the results are shown in Table 2 below.

Here, the pulp-like short fibers before heat treatment have physical properties of intrinsic viscosity 5.9, orientation angle 18 ° and crystallinity 59%.

TABLE 2

Example 4

This Example shows the results of heat treatment on the amount of polymerization accelerator precipitant contained in the pulp-like short fibers during the heat treatment conditions. The pulp-like short fibers before heat treatment had physical properties of intrinsic viscosity 6.12, orientation angle 18 ° and crystallinity 58%. The heat treatment temperature and time were carried out for 15 minutes at 300 ℃.

The results are shown in the following Table 3, where the polymerization accelerator content (%) represents the ratio to the weight of the fiber.

TABLE 3

Comparative Example 2

The reactor was sufficiently purged with nitrogen gas to remove water, and then 250 ml of N-methyl-2-pyrrolidone was added, the temperature was raised, and calcium chloride was added to dissolve it. Subsequently, 10.38 g of p-phenylene diamine is dissolved in the solution, cooled to low temperature, and then terephthaloyl chloride is added and stirred vigorously to obtain a powdered polymer compound (PPD-T).

It was left under nitrogen atmosphere for 5 hours, washed with excess water and acetone, and dried at 105 DEG C. (polymer intrinsic viscosity at this time was 6.0).

Again, the dried PPD-T is made of 20% dope with 100% sulfuric acid and cooled with water spinning at a rate of 250 m / min through a 0.06 mm nozzle at 75 ° C. and nitrogen pressure of about 4 kg.

The overall physical properties of the fiber produced as described above, and the general physical properties of the fiber heat-treated according to the heat treatment conditions of Example 1 are shown in Table 4 below.

TABLE 4

Claims (6)

To prepare aromatic polyamide pulp-like short fibers, p-phenylene diamine and terephthaloyl chloride are reacted in the same equivalence ratio in an amide-based or urea-based polymerization solvent in which an inorganic salt is dissolved. After preparing an optically anisotropic liquid crystalline prepolymer having a repeating unit represented by Structural Formula (I), it is extruded and sprayed at the same time so as to receive a shear rate of at least 20 sec ⁻¹ or more together with a tertiary amine polymerization accelerator. A method for producing an aromatic polyamide pulp-like short fiber characterized in that it is subjected to extrusion dispersion and heat treatment in the state containing a small amount of polymerization accelerator precipitant before washing it.

The method of claim 1, wherein the polymerization promoter is selected from pyridine, triethylamine, t-butylamine and pyrimidine. The method of claim 1 wherein the inorganic salt is selected from calcium chloride, lithium chloride, potassium chloride and potassium bromide. The method of claim 1, wherein the heat treatment is performed for 5 to 60 minutes in the temperature range of 150 ℃ to 350 ℃. The method of claim 1, wherein the aromatic polyamide pulp-like short fibers before the heat treatment contain 0.5 to 6 times the polymerization accelerator precipitant based on the weight of the fiber. In an aromatic polyamide pulp-like short fiber, an optically anisotropic liquid crystalline prepolymer having a repeating unit represented by the following structural formula (I) is made by extrusion spraying with a tertiary amine polymerization precipitant simultaneously and heat-treated before washing it. An aromatic polyamide pulp-like short fiber having a make-up molecular chain structure and having an intrinsic viscosity of at least 4.0 or more.