CN104695083A - Thermal stretching process of aramid III fiber precursor strand - Google Patents

Abstract

The invention discloses a thermal stretching process of aramid III fiber precursor strand. The thermal stretching process is characterized by including two steps of thermally stretching the aramid III fiber precursor strand by constant tension of 0.2-1.0 cN/tex at the low temperature of 270-300 degrees Centigrade, and further stretching the fibers treated in the last step by constant tension of 0.01-0.2 cN/tex at 340-500 degrees Centigrade, wherein both steps are performed under protection of normal-pressure inertia gas. With two-step stretching, the first step is performed by constant tension at low temperature, low glass-transition temperature of the fibers at this temperature is sufficiently utilized, and stretching orientation of macromolecular chains is benefited, and design application tension is high, so that orientation degree of finished aramid III fibers is greatly increased, and both stretching intensity and initial modulus are improved. The thermal stretching process is simple to operate, low in cost, well developed and conducive to industrial production.

Description

A kind of heat stretching process of aramid III fiber raw tow

Technical field

The invention belongs to chemical fibre spinning tow heat stretching process technical field, be specifically related to the heat stretching process of aramid III fiber raw tow of a kind of high strength, high-modulus.

Background technology

Along with the development of space technology, more and more higher requirement is proposed to enhancing fiber.Past, in the world to the research of aramid fiber be with the U.S. kevlar series for main object, but the TENSILE STRENGTH of this serial fiber can only reach about 22cN/dt, this can not meet the requirements at the higher level of aerospace field to the mechanical property of advanced composite material enhancing fiber.Aramid III fiber (Russia is called Armos fiber), as a kind of high strength and modulus organic fiber, has become the fortifying fibre of preparation Aero-Space advanced composite material at present.To this, Russ P RU2074182 and RU2130980 describes the production technology of this resin and fiber, it is specifically by p-phenylenediamine (PPD), paraphthaloyl chloride and 5 (6)-amido-2-(4-aminocarbonyl phenyl) benzimidazole, three kinds of monomers are raw material, with dimethylacetylamide/lithium chloride for solvent obtains spinning solution through low temperature copolymerization, again after filtration, deaeration, spinning, washing, the techniques such as drying and rolling obtain aramid III precursor, the general TENSILE STRENGTH of this raw tow only has 8 ~ 10cN/dt, must heat-treat raw tow and just can obtain finished fiber bundle.As the heat treatment method to this fiber precursor bundle, RU2167961 reports a kind of batch (-type) heat treatment method, the method is the silk cylinder will be wound in spinning process, put into the heat treatment still of multistation, after nitrogen replacement, under vacuum condition, be warmed up to 300-400 DEG C and keep more than 30 minutes, nitrogen is filled in cooling again, opens still taking-up silk cylinder and is finished fiber.But the finished fiber TENSILE STRENGTH that the method obtains (dry yarn, non-impregnation silk) is only 70-80% in the qualification rate of more than 26cN/dt.For RU2167961 Problems existing, CN 1473969A discloses an a kind of step heat stretching process, this technique be by aramid III fiber raw tow under constant-tension (0.2-1.0cN/tex) nitrogen protection, online hot-stretch is carried out in the heater of 340-500 DEG C, although improve the yield rate of aramid III finished fiber to a certain extent, when overcoming that in intermittent fever treatment process, silk cylinder heats in heating kettle, the inside and outside layer tow existed be heated inequality and between multistation top cylinder and cylinder tow to be heated inequality and the problem that causes product percent of pass low, but it is not ideal enough.Therefore, the mechanical property how improving aramid III fiber further remains current scientific worker's technical issues that need to address.

Summary of the invention

The object of the invention is the above-mentioned defect existed for existing aramid III fiber precursor one step heat stretching process, a kind of technique of aramid III fiber raw tow being carried out to hot-stretch is newly provided, this technique can make aramid III fiber finished silk obtain high strength and high-modulus, and process is simple, processing ease.

In order to reach object of the present invention, the present inventor has carried out deep analysis and research to existing aramid III fiber precursor one step heat stretching process, to find on benzimidazole structure contained in aramid III raw tow macromolecular chain the complexing accessory substance HCl (see Fig. 1) of material in polycondensation process, the HCl of this complexing destroys the interaction of hydrogen bond (as shown in Figure 2) in polymer macromolecule chain between benzimidazole, reduce the interaction force of macromolecular chain, thus significantly reduce the glass transition temperature of raw tow, its glass transition temperature has been reduced to 254 DEG C (see Fig. 3) by 276 before complexing DEG C.Simultaneously research in also find the complexing of aramid III fiber precursor HCl separate complexing (deviating from) temperature be 300 ~ 330 DEG C (see Fig. 3).Although an existing step heat stretching process can make the HCl of complexing in precursor separate complexing, but because it is the at high temperature online hot-stretch of a step, because of the rapid solution complexing of complexing HCl, increase the interaction of intermolecular hydrogen bonding, thus be unfavorable for the raising of the tensility of precursor, cause the increase of its strength and modulus limited.

On the above basis analysed in depth and study, the invention provides following so a kind of technical solution to reach goal of the invention:

The raw tow of aramid III fiber is carried out two step hot-stretchs; The first step is that the raw tow of aramid III fiber is carried out identical tension hot-stretch under the low temperature of 270 ~ 300 DEG C; second step is stretched under identical tension in 340-500 DEG C of continuation by the fiber of first step process, and two sections of hot-stretchs are all carried out under normal pressure inert gas shielding.

The temperature of the first step identical tension hot-stretch described in above technique preferably 280 ~ 290 DEG C; The temperature of second step identical tension hot-stretch preferably 380 ~ 420 DEG C.

The tension force of the first step identical tension hot-stretch described in above technique is 0.2-1.0cN/tex, preferred 0.5-0.8cN/tex, and the processing time is 1-5 minute, preferred 2-3 minute.

The tension force of the second step identical tension hot-stretch described in above technique is 0.01 ~ 0.2cN/tex, preferred 0.05-0.1cN/tex, and the processing time is 0.5-5 minute, preferred 1-2 minute.

Inert gas described in above technique is any one in nitrogen, argon gas, helium or carbon dioxide.

Be 0.89-0.92, TENSILE STRENGTH 29-33cN/dt by the degree of orientation of the aramid III finished fiber of gained after above PROCESS FOR TREATMENT, initial modulus is 980-1050cN/dt.

The present invention compared with prior art, has following good effect:

1, due to the present invention's employing is two step heat stretching process, and the first step wherein carries out identical tension hot-stretch at low temperatures, the HCl not only taking full advantage of benzimidazole unit complexing in macromolecular chain at this temperature not yet removes, the HCl of complexing destroys the interaction of hydrogen bond in macromolecular chain between benzimidazole unit, the glass transition temperature of fiber is lower, more be conducive to the feature of the stretch orientation of macromolecular chain, in addition the tension force designing applying is larger, thus the degree of orientation of aramid III finished fiber is substantially increased, its TENSILE STRENGTH and initial modulus are all improved, overcome in the published one-step method hot-stretching step of CN 1473969A, aramid III fiber raw tow is being placed under 340-500 DEG C of hot environment instantaneously, the HCl of complexing separates complexing rapidly and increases the problem that the tensility being unfavorable for precursor that intermolecular interaction produces improves.

2, due to the present invention's employing is two step heat stretching process, and the first step wherein carries out identical tension hot-stretch at low temperatures, thus the stretch orientation of macromolecular chain is not only conducive to, and to also help in raw tow residual solvent and can slowly overflow from fibrous inside, fibrous inside hole is reduced, can reduce or avoid in one-step method hot-stretching step disclosed in CN 1473969A, solvent residual a small amount of in aramid III fiber raw tow, in high temperature 340 DEG C and above abrupt release thereof, can cause aramid III fiber inside to occur the problem of hole.

3, because heat stretching process provided by the invention can not change existing equipment device etc., thus simple to operate, cost is lower, technical maturity, is conducive to suitability for industrialized production.

Accompanying drawing illustrates:

Fig. 1 is the infrared spectrum of non-complexing HCl aramid III (curve a, dotted line) and complexing HCl aramid III (curve b, solid line).Wherein curve b is presented at 2500 ~ 2900cm ^-1have and obviously belong to N ⁺-H vibration peak, illustrates that HCl complexing is on the macromolecular chain of aramid III; 3400 ~ 3500cm simultaneously ^-1belong to the N-H vibration not forming hydrogen bond, from figure, clearly can find out that complexing HCl aramid III (curve b) goes out peak more obviously at this, illustrate that inchoate hydrogen bond is more, interaction of hydrogen bond is weak.

Fig. 2 is the structure of benzimidazole unit in complexing HCl aramid III macromolecular chain and the structural representation separated after complexing HCl.

Fig. 3 is loss tangent (Tan the Delta)/hygrogram that aramid III fiber dynamic mechanical analysis (DMA) tests gained, and the temperature that wherein peak of curve is corresponding is glass transition temperature.The glass transition temperature separating complexing HCl aramid III fiber is as seen from the figure 276 DEG C (a curves), and the glass transition temperature of the aramid III fiber of complexing HCl is 254 DEG C (b curves).

Fig. 4 is thermal analyses (TGA) resolution chart of aramid III fiber raw tow under heating rate 10 DEG C/min.Deviate from temperature for HCl is initial for T1=300 DEG C in figure, deviate from temperature completely for HCl for T2=330 DEG C.

Fig. 5 is Two dimensional X ray diffraction (XRD) resolution chart of aramid III fiber finished silk after two step hot-stretchs in the embodiment of the present invention 1.

Fig. 6 is Two dimensional X ray diffraction (XRD) resolution chart of aramid III fiber finished silk after a step hot-stretch in comparative example 1.

Comparison diagram 5,6, clearly can see that in Fig. 5, diffraction speck is brighter, distribution is narrower, illustrates that its degree of orientation is higher.

Detailed description of the invention

Provide embodiment below so that the invention will be further described.What be necessary to herein means out is that following examples can not be interpreted as limiting the scope of the invention; if the person skilled in the art in this field makes some nonessential improvement and adjustment according to the invention described above content to the present invention, still belong to scope.

In addition, what deserves to be explained is, 1) degree of orientation of the aramid III finished fiber of following examples and comparative example gained adopts Two dimensional X ray diffraction instrument---De Luke (Bruker D8) diffractometer is tested, and calculate according to following fiber-wall-element model degree computing formula:

$f_2=\frac{3\stackrel{\‾}{{\cos }^2\mathrm{\φ}}-1}{2}---\left(1\right)$

$\stackrel{\‾}{{\cos }^2\mathrm{\φ}}=\frac{{\∫}_0^{\mathrm{\π}/2}I\left(\mathrm{\φ}\right){\cos }^2\mathrm{\φ}\sin \mathrm{\φd\φ}}{{\∫}_0^{\mathrm{\π}/2}I\left(\mathrm{\φ}\right)\sin \mathrm{\φd\φ}}---\left(2\right)$

Wherein φ is azimuth, the scanning intensity that I (φ) is azimuth φ, f ₂be called as Herman orientation factor, be used for representing fiber-wall-element model degree, the degree of orientation is larger, illustrates that fiber is better along draw direction degree of orientation.2) TENSILE STRENGTH of the aramid III finished fiber of following examples and comparative example gained and initial modulus adopt Britain Instron4302 type tensometer, according to the method for ASTM D885-2007, according to spacing jig 215mm, fixture translational speed 25mm/min, simple tension test.

Embodiment 1

Be 10cN/dt by intensity, modulus be 600cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.6cN/tex; under being placed on nitrogen protection under normal pressure; furnace temperature is process 3min in the first paragraph heating furnace of 285 DEG C; then be adjusted to by tensile stress under 0.08cN/tex enters nitrogen protection under normal pressure, furnace temperature is process 2min in the hot stove of second segment of 400 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.92, and TENSILE STRENGTH is 33cN/dt, and initial modulus is 1010cN/dt.

Embodiment 2

Be 8cN/dt by intensity, modulus be 500cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.5cN/tex; under being placed on normal pressure argon shield; furnace temperature is process 5min in the first paragraph heating furnace of 270 DEG C; then be adjusted to by tensile stress under 0.01cN/tex enters normal pressure argon shield, furnace temperature is process 0.5min in the hot stove of second segment of 500 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.90, and TENSILE STRENGTH is 30cN/dt, and initial modulus is 980cN/dt.

Embodiment 3

Be 10cN/dt by intensity, modulus be 600cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 1cN/tex; under being placed on the protection of normal pressure helium; furnace temperature is process 1min in the first paragraph heating furnace of 290 DEG C; then tensile stress is adjusted to 0.2cN/tex enter normal pressure helium protection under, furnace temperature is process 5min in the hot stove of second segment of 450 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.91, and TENSILE STRENGTH is 30cN/dt, and initial modulus is 1050cN/dt.

Embodiment 4

Be 9cN/dt by intensity, modulus be 550cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.8cN/tex; be placed on normal pressure CO 2 gas-shielded under; furnace temperature is process 4min in the first paragraph heating furnace of 280 DEG C; then tensile stress is adjusted to 0.1cN/tex enter normal pressure CO 2 gas-shielded under; furnace temperature is process 1min in the hot stove of second segment of 340 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.88, and TENSILE STRENGTH is 29cN/dt, and initial modulus is 980cN/dt.

Embodiment 5

Be 9cN/dt by intensity, modulus be 550cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.2cN/tex; under being placed on nitrogen protection under normal pressure; furnace temperature is process 2.5min in the first paragraph heating furnace of 300 DEG C; then be adjusted to by tensile stress under 0.05cN/tex enters nitrogen protection under normal pressure, furnace temperature is process 1.5min in the hot stove of second segment of 420 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.91, and TENSILE STRENGTH is 31cN/dt, and initial modulus is 1010cN/dt.

Embodiment 6

Be 10cN/dt by intensity, modulus be 580cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.4cN/tex; under being placed on nitrogen protection under normal pressure; furnace temperature is process 2min in the first paragraph heating furnace of 275 DEG C; then be adjusted to by tensile stress under 0.04cN/tex enters nitrogen protection under normal pressure, furnace temperature is process 4min in the hot stove of second segment of 380 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.91, and TENSILE STRENGTH is 30cN/dt, and initial modulus is 1020cN/dt.

Embodiment 7

Be 10cN/dt by intensity, modulus be 560cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.9cN/tex; under being placed on nitrogen protection under normal pressure; furnace temperature is process 1.8min in the first paragraph heating furnace of 295 DEG C; then be adjusted to by tensile stress under 0.14cN/tex enters nitrogen protection under normal pressure, furnace temperature is process 0.8min in the hot stove of second segment of 360 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.91, and TENSILE STRENGTH is 31cN/dt, and initial modulus is 1010cN/dt.

Embodiment 8

Be 10cN/dt by intensity, modulus be 600cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.7cN/tex; under being placed on nitrogen protection under normal pressure; furnace temperature is process 3.5min in the first paragraph heating furnace of 285 DEG C; then be adjusted to by tensile stress under 0.05cN/tex enters nitrogen protection under normal pressure, furnace temperature is process 1min in the hot stove of second segment of 420 DEG C, and last rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.92, and TENSILE STRENGTH is 32cN/dt, and initial modulus is 1050cN/dt.

Comparative example 1

Be 10cN/dt by intensity, modulus be 600cN/dt, raw tow that fiber number is the aramid III fiber of 95tex; be placed on rotatable transfer roller; after through tensioner, to be stretched to tension force be 0.6cN/tex; under being placed on nitrogen protection under normal pressure; furnace temperature is process 5min in the heating furnace of 400 DEG C, and then rolling becomes aramid III finished fiber.

The degree of orientation of this fiber is 0.86, and TENSILE STRENGTH is 28cN/dt, and initial modulus is 900cN/dt.

Claims (7)

1. a heat stretching process for aramid III fiber raw tow, is characterized in that this heat stretching process is divided into two steps to carry out:

The first step is that the raw tow of aramid III fiber is carried out identical tension hot-stretch under the low temperature of 270 ~ 300 DEG C; second step be by first step process after fiber stretch under identical tension in 340-500 DEG C of continuation, two sections of hot-stretchs are all carried out under normal pressure inert gas shielding.

2. the heat stretching process of aramid III fiber raw tow according to claim 1, is characterized in that the temperature of the first step identical tension hot-stretch described in this technique is 280 ~ 290 DEG C.

3. the heat stretching process of aramid III fiber raw tow according to claim 1 and 2, is characterized in that the temperature of the second step identical tension hot-stretch described in this technique is 380 ~ 420 DEG C.

4. the heat stretching process of aramid III fiber raw tow according to claim 1 and 2, it is characterized in that the tension force of the first step identical tension hot-stretch described in this technique is 0.2-1.0cN/tex, the processing time is 1-5 minute; The tension force of second step identical tension hot-stretch is 0.01 ~ 0.2cN/tex, and the processing time is 0.5-5 minute.

5. the heat stretching process of aramid III fiber raw tow according to claim 3, it is characterized in that the tension force of the first step identical tension hot-stretch described in this technique is 0.2-1.0cN/tex, the processing time is 1-5 minute; The tension force of second step identical tension hot-stretch is 0.01 ~ 0.2cN/tex, and the processing time is 0.5-5 minute.

6. the heat stretching process of aramid III fiber raw tow according to claim 1 and 2, it is characterized in that the tension force of the first step identical tension hot-stretch described in this technique is 0.5-0.8cN/tex, the processing time is 2-3 minute; The tension force of second step identical tension hot-stretch is 0.05-0.1cN/tex, and the processing time is 1-2 minute.

7. the heat stretching process of aramid III fiber raw tow according to claim 3, it is characterized in that the tension force of the first step identical tension hot-stretch described in this technique is 0.5-0.8cN/tex, the processing time is 2-3 minute; The tension force of second step identical tension hot-stretch is 0.05-0.1cN/tex, and the processing time is 1-2 minute.