KR910003959B1 - Aromatic polyamide film and process for fiber - Google Patents

Abstract

Inorganic salt is solubilized in amide solvent. Aromatic diamine and aromatic diacidchloride are added to the above solution. The mixed compds. are polymerized at below 30 deg.C, thus making optically anisotropic liquid crystal pre-polymer. The pre-polymer is added shearing speed at least above 50 sec by the high speed rotating force of cylinder, after it is put into between cylinder and round vessel. The distance between round vessel and cylinder is 0.05-5 mm and the ratio of shearing force height and cross-section diameter of cylinder is set above 4. Then the polymerization accelerating precipitart is added to the prepolymer in that the volume ratio is 0.5-20, thus making aromatic polymide film, fiber.

Description

Method for producing aromatic polyamide film and short fibers

1 is a longitudinal sectional view of an aromatic polyamide film and a short fiber manufacturing apparatus according to the present invention.

2 shows a cross-sectional view along the line A-A of FIG.

* Explanation of symbols for main parts of the drawings

1 liquid crystal prepolymer inlet 2 polymer accelerator precipitator inlet

3: cylinder 4: cylinder

5: Rotation axis of the cylinder 6: Shear force giving height (h)

7: Distance between cylinder and cylinder (t) 8: Diameter of cross section of cylinder (ø)

9: angle (θ) between the inlet of the liquid crystal prepolymer or the inlet of the polymerization accelerator

The present invention relates to an aromatic polyamide film having excellent molecular orientation and a method for producing aromatic polyamide short fibers. Aromatic polyamide films and short fibers according to the present invention can be generally used in reinforcement materials, heat-resistant materials and electrically insulating materials of composite materials, industrial production is advantageous and good molecular orientation.

Conventionally, the method for producing aromatic polyamide is described in US Pat. No. 3,869,430, in which an inorganic salt, an aromatic diamine, and an aromatic dieside chloride are dissolved in an amide solvent to polymerize the polymer, and the polymer is washed with water, dried and sulfuric acid of 98% or more. The dope is prepared by dissolving in a solvent, and then spinning into water through a mold to obtain a fiber, and then, using the method of cutting or pulverizing the fiber, an aromatic polyamide short fiber is used. According to the manufacturing method, since the polymer is separated, washed with water, dried, dissolved in a sulfuric acid solvent and spun again, the cost increases not only because of the several steps, but also because of the use of sulfuric acid solvents. There are process problems such as this to follow.

In addition, the method described in Japanese Unexamined Patent Publication No. 59-47694 is to prepare a short fiber particle by adding a polymer solution polymerized in an amide solvent to a precipitant of an amide solvent, followed by stirring. The amount of precipitant to be used must be considerably excessive compared to the final amount, and the resulting short fibers have poor orientation, and the concentration of the amide solvent in the precipitant is not more than 50% by weight, and the remainder is an aqueous solvent. In this case, there is a disadvantage in that the degree of polymerization cannot be improved.

Accordingly, the present inventors have diligently studied to solve the above-mentioned conventional problems, and as a result, aromatic polyamide films and short fibers having excellent physical properties such as molecular orientation can be prepared from a prepolymer solution of aromatic polyamides polymerized in an amide solvent. We have developed a useful way to do this.

Accordingly, an object of the present invention is to prepare a film having excellent molecular orientation by introducing an optically anisotropic liquid crystalline prepolymer and a small amount of an amide type polymerization promoter precipitator between the cylinder and the cylinder at high speed during the polymerization of the aromatic polyamide. To provide a method for producing short fibers.

Hereinafter, the present invention will be described in detail.

In the production of aromatic polyamide films and short fibers, an inorganic salt is added to and dissolved in an amide solvent, and an equimolar amount of aromatic diamine and an aromatic dieside chloride are added thereto, followed by polymerization at a low temperature of 30 ° C. or lower. An optically anisotropic liquid crystalline prepolymer having an intrinsic viscosity of 1.0 to 4.0 and having a repeating unit represented by the following general structural formulas (I) and (II) was prepared, and then introduced into the space between the cylinder and the cylinder so that the cylinder was rotated at high speed. After imparting a shear rate of at least 50 sec ⁻¹ or more, the polymerization accelerator is introduced therein to produce an aromatic polyamide film, and its short fibers are manufactured using a known grinder.

In formulas (I) and (II), R ₁ , R ₂ , and R ₃ are each

또는 -O-이고, 이때, R₁과 R₂는 같거나 다를 수 있으며 대체로 등몰량으로 존재하고, X는 H,Cl 또는 Br이다.

Or -O-, wherein R ₁ and R ₂ may be the same or different and are generally present in equimolar amounts and X is H, Cl or Br.

The aromatic polyamide film prepared according to the method of the present invention is characterized by having an intrinsic viscosity of 6.0 or more and an orientation of 85% or more.

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

The optically anisotropic liquid crystalline prepolymer solution of the present invention is prepared by adding and dissolving an inorganic salt in an amide solvent, and then adding an aromatic diamine and an aromatic diesid chlorine, wherein the inorganic salt is 0.5 to the total solvent. To 15% by weight, and the method of polymerizing the liquid crystal prepolymer solution is to dissolve an aromatic diamine in an amide solvent in which an inorganic salt such as a halogenated metal salt is dissolved, and then cooled to low temperature under a nitrogen stream, followed by aromatic dieside. The chloride is reacted at a low temperature of 40 ° C. or lower. In this case, the solvent and the monomer should be quantitatively reacted with a minimum amount of impurities.

For example, N-methyl-2-pyrrolidone (MNP) and N, N-dimethylacetamide (DMAc) may be used alone or as a mixture thereof. Hexamethylphosphoramide (HMPA), and the like, and inorganic salts in the polymerization solvent include metal halides, and examples thereof include lithium chloride, calcium chloride, potassium chloride or potassium bromide.

In addition, when the reaction proceeds to some extent by adding and stirring the aromatic diamine such as p-phenylenediamine and the aromatic dieside chloride such as terephthaloyl chloride in the amide solvent in which the inorganic salt is dissolved at low temperature, the reaction is carried out. An optically anisotropic liquid crystalline prepolymer which is in a state before completion is obtained as poly (P-phenylene terephthalamide) having a repeating unit represented by the following structural formula (III).

In this case, the polymer content of the liquid crystal prepolymer solution may be 4 to 20% by weight, more preferably 5 to 15% by weight, and its intrinsic viscosity may be 1.0 to 4.0, but 1.5 to 3.0 is more preferable in terms of process control.

If the polymer content rate and the intrinsic viscosity of the prepolymer solution is outside the above range, it is difficult to use as a dope, and there is a problem in that it is difficult to obtain the effect of the present invention when it is introduced between the cylinder and the cylinder of the apparatus according to the present invention. It is preferable that it exists in the range.

And the process for producing a film from the liquid crystal prepolymer prepared as described above in detail based on the illustrated drawings as follows.

The liquid crystal prepolymer is introduced through the liquid crystal prepolymer inlet 1 of FIG. 1, and polymerization is promoted from the liquid crystal prepolymer inlet 1 while maintaining a proper distance t (7) between the cylinder 3 and the cylinder 4. By rotating in the direction of the precipitant inlet (2) to impart a shear force to the liquid crystal prepolymer supplied from the inlet (1) and to form a film form at this time the liquid crystal pre-group polymer is introduced by adjusting the number of revolutions of the cylinder (3) appropriately Give a shear rate of at least 50 sec ^-1 or greater. In addition, the angle θ (9) between the polymerization accelerator precipitator inlet 2 and the liquid crystal prepolymer inlet 1 may be 45 to 90 °, and the shear rate may be closer to 45 °.

It is advantageous to process the polymerization precipitant inlet (2) slightly higher than the prepolymer inlet (1) and the distance t (7) between the cylinder and the cylinder is 0.05 to 5 mm, preferably 0.1 to 0.3 mm. If it is less than 0.1mm, there is less chance of contact between the polymerization accelerator and the liquid crystal prepolymer, so that it is impossible to obtain a product with good physical properties. If the thickness is more than 2mm, the appearance of the film to be manufactured becomes very uneven due to shrinkage. Short fiber production also becomes impossible.

On the other hand, the ratio (ø / h) of the cross-sectional diameter ø (8) of the rotating cylinder to the height of the shearing force h (6) is possible if it is 4 or more. To 14 are most suitable.

And the shape and size of the polymerization promoter precipitator inlet (2) is not a problem in the process, but the size is preferably limited to about 0.5 to 2 times the size of the liquid crystal prepolymer inlet (1) as possible, the size of the prepolymer inlet (1) Depending on the flow rate, it is usually 1mm ² or more.

The liquid crystal prepolymer is prepared and then introduced into a device according to the present invention through a jet port, and the internal cross-sectional area of the transfer line and the present invention in order to give the liquid prepolymer a minimum shear force in the process until reaching the device. In the apparatus of the liquid crystal prepolymer inlet (1) to be the same size and the shape of the inlet (1) is advantageous in the process circle.

Tertiary amines are generally used as the polymerization promoter precipitates used in the above process. For example, pyridine, triethylamine, t-butylamine, picoline, quinoline, pyrimidine and quinoxaline can be used. However, pyridine is the most effective polymerization accelerator for high intrinsic viscosity, orientation and sufficient neutralization efficiency.

In addition, such a polymerization accelerator may be used by tertiary amines alone, but in order to increase the diffusion rate of the polymerization accelerator, it may be partially mixed with an amide solvent such as NMP, DMAc or HMPA. The water content of the polymerization promoter precipitate is preferably about 5000 ppm or less, and the temperature of the polymerization accelerator precipitate is preferably 50 ° C. or lower.

On the other hand, the inflow rate of the polymerization precipitant into the apparatus according to the present invention is preferably in the range of 0.5 to 20 times the inflow rate of the liquid crystal prepolymer, and conventionally, in order to improve the diffusion of the polymerization solvent and improve the physical properties of the product. For the prepolymer, the amount of the polymerization promoter precipitant had to be used 10 times or more. However, when the device of the present invention is used, the contact area between the liquid crystal prepolymer and the polymerization promoter precipitant is increased and the contact time is increased. Even if the amount of the polymerization accelerator is 2 to 4 times (v / v), a product having the same physical properties as in the case of using 10 times (v / v) or more conventionally can be obtained.

When the aromatic polyamide film produced by the above method is used a known grinder, pulp-like short fibers having high orientation properties can be obtained.

On the other hand, the physical property evaluation of the film and the short fiber produced according to the embodiment of the present invention can be easily seen from the intrinsic viscosity relationship shown in general.

IV = ln (η _rel ) / C

Where IV is the intrinsic viscosity, C is the concentration of the polymer solution, η _rel is the relative viscosity and is the flow time ratio between the solution and the solvent measured with a capillary viscometer at a temperature of 30 ° C., where the solvent is not particularly limited. Usually concentrated sulfuric acid (95 to 98% H ₂ SO ₄ ) is used.

In addition, the degree of orientation is measured using an X-ray diffractometer, and is obtained from the diffraction intensity distribution of the 200 plane by using the following equation.

Where π represents the degree of orientation and H is the half width of the 200 plane intensity distribution curve.

The manufacturing method of the present invention has the following excellent effects compared to the prior art.

First, an aromatic polyamide polymer is prepared and then obtained by using the apparatus of the present invention during the polymerization process, without undergoing a complicated process of separating, washing, drying, forming a spinning dope, spinning, and then grinding again. Pulp-like short fibers can be easily produced from a film.

Second, although the volume ratio of the polymerization accelerator to the liquid crystal prepolymer had to be made 10 times or more in the past, the physical properties of 10 times or more can be obtained even in an amount of 2 to 4 times in the apparatus of the present invention.

Third, by providing a shear rate of 50 sec ⁻¹ or more to the liquid crystal preliminary body introduced due to the high speed rotation of the cylinder installed in the cylinder, the bonsai orientation can be enhanced.

Fourth, the ratio of shear force giving height h (6) to the cross section diameter ø (8) of the rotating cylinder is adjusted to 4 to 14 to increase the shear force applying time due to the rotation of the cylinder, resulting in high intrinsic viscosity and excellent orientation. Polyamide films and short fibers can be produced.

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

Example 1

After fully purifying the reactor with N ₂ gas to remove water, 500 ml of N-methyl-2-pyrrolidone was added thereto, and the temperature was raised, followed by dissolving by adding calcium chloride (CaCl ₂ ) as an inorganic salt. After dissolving 20.76 g of p-phenylenediamine in an amide-based polymerization solvent in which an inorganic salt was dissolved, 39.10 g of terephthaloyl chloride (TPC) was added at a low temperature of 30 ° C. or lower and stirred vigorously. The liquid crystal prepolymer obtained at this time was introduced into the inlet of the apparatus of the present invention through a 1 / 4-inch feed tube at a speed of 200 cc / min using a gear pump in a reactor. At this time, the interval between the cylinder and the cylinder was 0.2 mm, the cross section diameter ø of the cylinder was 100 mm, and the shearing force applying height h was 800 mm. The shear rate by rotation of the cylinder was 100 sec ^-1 and the inflow rate of pyridine, a polymerization accelerator, was 400 cc / min. The film and pyridine thus obtained were filtered by a filtration device, and the filtered film was washed with water and dried in a vacuum drying apparatus at 110 ° C. for 5 hours. The dried film was ground to prepare short fibers on the pump. The intrinsic viscosity IV of the film and single fiber at this time was 6.31, and orientation degree (pi) was 89.2%.

Example 2

Preparation and device conditions of the liquid crystal prepolymer solution were the same as in Example 1, except that only the polymerization accelerator and the precipitation solution to prepare a film and short fibers, the physical properties of the film and the short fiber prepared in Table 1 Indicated.

TABLE 1

Example 3

The preparation conditions and the flow rate of the liquid crystal prepolymer solution are the same as in Example 1, except that the conditions of the rotating cylinder to produce a film and short fibers, the physical properties of the film and the short fibers are shown in Table 2 below It was.

TABLE 2

Example 4

The preparation conditions and the inflow amount of the liquid crystal epolymer solution are the same as those of Example 1, except that the inflow ratio of the liquid crystal prepolymer and pyridine, a polymerization accelerator precipitant, to prepare a film and short fibers, the film and the short fibers Physical properties of are shown in Table 3 below.

TABLE 3

Example 5

The preparation conditions of the liquid crystal prepolymer solution are the same as those of Example 1, except that the shear force is imparted to the liquid crystal prepolymer by the interval t of the cylinder and the cylinder and the rotation of the cylinder to produce a film and short fibers, and the prepared film And the physical properties of the short fibers are shown in Table 4 below.

TABLE 4

Claims (9)

In preparing an aromatic polyamide film, an inorganic salt is dissolved in an amide solvent, an equimolar amount of aromatic diamine and an aromatic dieside chloride are added thereto, followed by polymerization at a low temperature of 30 ° C. or lower to prepare an optically anisotropic liquid crystal prepolymer. Then, it is introduced between the cylinder and the cylinder to give a shear rate of at least 50 sec ^-1 or more by high-speed rotation of the cylinder, and then the liquid crystal prepolymer is introduced into the manufacturing method of an aromatic polyamide film. The method of claim 1, wherein the inflow ratio of the polymerization accelerator and the liquid crystal prepolymer is 0.5 to 20 in volume ratio. A method according to claim 1, characterized in that the ratio of the shear force giving height h and the cylinder cross section diameter ø is equal to or greater than 4. The method of claim 1 wherein the distance between the cylinder and the cylinder is between 0.05 and 5 mm. In preparing aromatic polyamide short fibers, an inorganic salt is dissolved in an amide solvent, an equimolar amount of aromatic diamine and an aromatic dieside chloride are added thereto, followed by polymerization at a low temperature of 30 ° C. or lower, to form an optically anisotropic liquid crystal prepolymer. After preparing, and then flowing it between the cylinder and the cylinder to give a shear rate of at least 50sec ^-1 or more by the high-speed rotation of the cylinder, and to introduce the polymerization precipitant therein to prepare an aromatic polyamide film, which is a known grinder A method for producing an aromatic polyamide short fiber, characterized in that the production of short fibers using. The method according to claim 5, wherein the ratio of the inflow rate of the polymerization accelerator and the liquid crystal prepolymer is such that the volume ratio is 0.5 to 20. 6. A method according to claim 5, wherein the cylinder is such that the ratio of its shearing force giving height (h) to the cylinder cross section diameter (ø) is at least four. 6. A method according to claim 5, wherein the distance between the cylinder and the cylinder is between 0.05 and 5 mm. In the aromatic polyamide film, the intrinsic viscosity produced by the molecular orientation polymerization method from the optical and anisotropic liquid crystalline preliminary body obtained by adding an inorganic salt, an aromatic diamine and an aromatic dieside chloride to an amide solvent is 6.0 or more. An orientation degree is 85% or more, The aromatic polyamide film characterized by the above-mentioned.

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