CN1256474C - Manufacturing method of poly p phenylene diamine terephthalamide fiber - Google Patents

Abstract

The invention relates to a method for manufacturing poly-p-phenylene terephthalamide fiber (PPTA). The method is to fully mix PPTA resin with sulfuric acid with a concentration greater than 99%, enter into a twin-screw extruder for dissolution and defoaming, and then prepare PPTA fibers through a dry spray-wet spinning method. The present invention solves the technical difficulty of dissolving and defoaming the high-viscosity PPTA/ _H2SO4 liquid crystal solution through the transformation of the twin-screw structure in the twin-screw extruder, greatly shortens the dissolving and _defoaming time, and alleviates the PPTA in the The degradation problem under high temperature dissolution conditions in sulfuric acid is beneficial to the industrial implementation of obtaining high-strength PPTA fibers and spinning processes.

Description

Method for producing poly(p-phenylene terephthalamide) fiber

technical field

The invention relates to the technical field of textiles, in particular to a method for manufacturing poly-p-phenylene terephthalamide (PPTA) fibers.

Background technique

As we all know, poly-p-phenylene terephthalamide fiber is a typical aromatic polyamide fiber, also known as aramid 1414 or PPTA fiber, which has excellent properties such as high strength, high modulus, and high temperature resistance. The fastest growing type of high-tech fiber in fiber materials is mainly used in industrial textiles, especially when many products require lightweight and high performance, only this kind of fiber can be used.

In the early 1970s, DuPont of the United States first invented the liquid crystal spinning method of dry-jet wet spinning, and produced this high-strength and high-modulus PPTA fiber, but there are still PPTA/H ₂ SO ₄ spinning solutions. The technical problem of difficult stirring and defoaming of high-viscosity liquid crystals during the preparation process. Usually, PPTA resin is dissolved in 99-100% sulfuric acid at 80-90°C, and it takes at least 3 hours, while PPTA/H ₂ SO ₄ The degassing of the spinning solution often takes longer time, up to tens of hours to tens of hours, which is not conducive to continuous industrial production, and PPTA is prone to degradation during the long-term dissolution and degassing process, thus affecting Strength of PPTA fibers.

The inventor discloses a kind of ultra-high-strength polyethylene fiber spinning device that carries out rapid degassing for high-viscosity jelly spinning solution in Chinese patent 95111657.6, that is, adopts twin-screw extruder for degassing, so that the degassing time is long for shortening. However, the dissolution process of ultra-high molecular weight polyethylene is still carried out in a pressure dissolution kettle, which takes 3 to 4 hours, and the macromolecular chains are easily degraded under high temperature dissolution conditions, which is not conducive to obtaining high-strength fibers.

Contents of the invention

The purpose of the present invention is to overcome the shortcoming of above-mentioned existing PPTA spinning process, by improving the screw structure in the twin-screw extruder, provide a kind of fast dissolving and defoaming, spin the new technique of high-strength PPTA fiber.

The technical scheme of spinning PPTA provided by the invention comprises the following steps:

(1) Add PPTA resin with an intrinsic viscosity of 4.0 to 8.5dl/g and sulfuric acid with a concentration greater than 99% into the mixing cylinder so that the weight percentage of PPTA is 14 to 24%, and mix for 3 to 50 minutes at 50 to 100°C;

(2) The mixed material is continuously extruded into a twin-screw extruder, and the dissolution of the PPTA resin in _H2SO4 and the deaeration of the spinning solution are completed in the twin-screw _;

(3) The twin-screw extruder extrudes a spinning solution that is fully mixed, temperature-regulated, and air bubbles are removed. After passing through a metering pump and filtering, perform dry spraying-wet spinning to obtain PPTA fibers.

In order to realize the technical scheme of the present invention, the screw diameter of the twin-screw extruder should be 25-145mm, the length-to-diameter ratio is greater than or equal to 30, the screw speed is 10-200rpm, and the residence time of the mixed material in the twin-screw is 10-200mm. After 60 minutes, ensure that the PPTA resin is completely dissolved and the air bubbles are completely removed. When the screw diameter is less than 45mm, that is, when the screw diameter is 25-45mm, the material can be circulated to ensure the residence time of the material in the twin-screw.

Simultaneously, the first half of the two intermeshed twin-screws in the twin-screw extruder of the present invention, from the entrance to the part between 30% and 80% of the total length of the screw, is made of various positive thread sleeves and kneading kneaders of different directions of rotation. block, and a small amount of reverse screw sleeve, wherein the total length of the kneading block accounts for more than 30% of the length of this part, so that PPTA/H ₂ SO ₄ is strongly subjected to continuous compression, expansion, and axial reverse mixing. The shearing and mixing action is beneficial to the dissolution of PPTA resin.

The second half of the twin-screw in the twin-screw extruder is composed of threaded sleeves whose pitch gradually decreases along the direction of the outlet, so that the pressure of the PPTA/H ₂ SO ₄ spinning solution increases gradually during the process of pushing it to the outlet, so that the solution The air bubbles escape to the direction of low pressure to achieve the purpose of degassing.

Attached drawing 1 is a schematic diagram of the screw in the twin-screw extruder, wherein AB is the first half, D is the forward thread sleeve, E is the kneading block, F is the reverse thread sleeve; BC is the second half, and the pitch gradually decreases along the direction of the exit. Small.

Compared with the prior art, the present invention has the following advantages:

(1) The dissolution of the PPTA resin and the defoaming of the spinning solution are all completed in a twin-screw extruder, and it only takes 30 minutes to 60 minutes to obtain PPTA that is fully mixed, the temperature is well adjusted, and the bubbles are completely removed The spinning solution is then passed through a metering pump, filtered, and dry-jet-wet-spun to obtain PPTA fibers, thereby avoiding the need for at least 3 hours to dissolve PPTA resin in sulfuric acid with a concentration greater than 99% in the traditional process at 80-90°C. PPTA/H The defoaming of ₂ SO ₄ spinning solution often takes longer time, up to tens of hours to tens of hours, which is beneficial to the continuous spinning of PPTA.

(2) The two intermeshing screws of the twin-screw extruder, the front half of which is composed of various forward thread sleeves, kneading blocks of different rotation directions, and a small amount of reverse thread sleeves, wherein the total length of the kneading block Accounting for more than 30% of the length of this part, the screw has a good self-cleaning effect and a high shear rate, so that the material can be micro-mixed in a short time, which can greatly accelerate the dissolution rate of PPTA resin in sulfuric acid .

(3) The second half of the two intermeshing screws of the twin-screw extruder is composed of a threaded sleeve whose pitch gradually decreases along the outlet direction, so that the PPTA/H ₂ SO ₄ spinning solution is pushed to the outlet. , the pressure gradually increases, so that the bubbles in the solution escape to the direction of low pressure, so as to achieve the purpose of degassing in a short time.

(4) The temperature of the twin-screws can be adjusted and controlled as needed, and the extremely thin solution between the twin-screws and the outer sleeve is constantly divided and recombined during the process of being pushed by the twin-screws, so that in a very short time , continuously mix and adjust the temperature, you can get a spinning solution that is evenly mixed and stable at a certain set temperature, which plays a role in stabilizing spinning and improving fiber strength.

(5) Due to the dissolution of PPTA resin and the defoaming of PPTA/H ₂ SO ₄ spinning solution in the twin-screw extruder, the time of these two sections is greatly shortened, only 10 minutes to 60 minutes, so both It is conducive to the realization of industrialized continuous spinning, and at the same time, it can avoid the violent cracking of macromolecules during the long-term dissolution and defoaming process, and is beneficial to obtain high-strength poly-p-phenylene terephthalamide fibers.

Description of drawings

Figure 1 Schematic diagram of the screw in the twin-screw extruder

Detailed ways

Example 1

Add 1.43 kg of dry PPTA resin with an intrinsic viscosity of 6.5 dl/g and 3.5 liters of 100% sulfuric acid into a 10 liter mixing cylinder. After mixing for 20 minutes at 85° C., the mixed material is continuously extruded into a diameter of 55 mm. In a twin-screw extruder with an aspect ratio of 60 and a rotational speed of 30rpm, the temperature of the twin-screw is controlled at 85°C. The length of the first half of the screw is 1400mm, and the length of the second half is 1900mm. The PPTA resin is completed in the twin-screw in H ₂ Dissolving in SO ₄ and defoaming of the spinning solution, after 50 minutes, extrude the spinning solution that is fully mixed, the temperature is adjusted, and the air bubbles are completely removed. After being filtered by a metering pump, it is sent to the spinneret. The hole is 0.06×300, through the air gap layer of 5cm, enters the spinning tube in the coagulation bath, the temperature of the coagulation bath is 5°C, the spinning speed is 120 m/min, the nozzle is stretched 6 times, and the spun tow is washed in water And after that, send it to the heat treatment device, treat it at 525°C for 10 seconds, and then oil it and wind it into a tube. The obtained PPTA fiber has a strength of 2.60GP, an initial modulus of 18OGP, and an elongation at break of 1.43%.

Example 2

Add 1.43 kg of dry PPTA resin with an intrinsic viscosity of 5.3 dl/g and 3.5 liters of 100% sulfuric acid into a 10 liter mixing cylinder. After mixing for 5 minutes at 85 ° C, the mixed material is continuously extruded into a 55 mm diameter. In a twin-screw extruder with an aspect ratio of 60 and a rotational speed of 50rpm, the length of the first half of the screw is 1550mm, and the length of the second half is 1750mm. The temperature of the twin-screw is controlled at 85°C, and the PPTA resin is completed in the twin-screw in H ₂ Dissolving in SO ₄ and defoaming of the spinning solution. After 35 minutes, extrude the spinning solution that is fully mixed, temperature-adjusted, and air bubbles have been completely removed. After being filtered by a metering pump, it is sent to the spinneret. The specifications of the spinneret The hole is 0.06×300, through the air gap layer of 5cm, enters the spinning tube in the coagulation bath, the temperature of the coagulation bath is 5°C, the spinning speed is 120 m/min, the nozzle is stretched 6 times, and the spun tow is washed in water After blending, it is sent to a heat treatment device, treated at 525°C for 10 seconds, and then oiled and wound into a tube. The obtained PPTA fiber has a strength of 2.35GP, an initial modulus of 175GP, and an elongation at break of 1.51%.

The comparison of embodiment 3 common spinning method and the method of the present invention

Table 1 Comparison between common spinning method and this method sample Strength (GPa) Intensity cv(%) Dissolving spinning time Solution spinning method sample 2.62 0.7 12 hours Example 1 sample 2.6 0.66 4 hours Example 2 sample 2.35 0.5 3.5 hours

Claims (4)

1, a kind of manufacture method of poly-p-phenylene terephthalamide fiber, it is characterized in that the method comprises the following steps: (1) Add poly-p-phenylene terephthalamide resin with an intrinsic viscosity of 4.0 to 8.5dl/g and sulfuric acid with a concentration greater than 99% into the mixing cylinder so that the weight percentage of poly-p-phenylene terephthalamide 14-24%, mixed for 3-50 minutes at 50-100°C; (2) Continuously extrude the mixed material into a twin-screw extruder, and complete the dissolution of the poly-p-phenylene terephthalamide resin in _H2SO4 and the defoaming of the spinning solution in _the twin-screw; (3) The twin-screw extruder extrudes the spinning solution that is fully mixed, the temperature is well adjusted, and the air bubbles are completely removed. After being filtered by a metering pump, dry spray-wet spinning is performed to obtain poly-p-phenylene terephthalamide fibers ; The twin-screw diameter of the twin-screw extruder is 25-145 mm, the aspect ratio is greater than or equal to 30, the screw speed is 10-200 rpm, and the residence time of the mixed material in the twin-screw is 10-60 minutes. 2. The manufacturing method according to claim 1, characterized in that when the screw diameter of the twin-screw extruder is 25-45mm, the material is circulated so that the residence time of the mixed material in the twin-screw is 10 -60 minutes. 3. The manufacturing method according to claim 1, characterized in that the first half of the two intermeshed twin-screws in the twin-screw extruder is 30-80% from the entrance to the full length of the screw. The part is composed of various forward threaded sleeves, kneading blocks of different rotation directions, and a small amount of reverse threaded sleeves, wherein the total length of the kneading blocks accounts for more than 30% of the length of the part. 4. The manufacturing method according to claim 1, wherein the second half of the twin-screw in the twin-screw extruder is composed of threaded sleeves whose pitch gradually decreases along the exit direction.