High-temperature-resistant polyimide composite fabric and production process thereof

Abstract

The invention discloses a high-temperature-resistant polyimide composite fabric and a production process thereof, and belongs to the technical field of textile materials.The production process comprises the following steps that S1, water-soluble polyamide acid is used for preparing a polyamide acid spinning solution, then freeze spinning is conducted, and polyamide acid aerogel fibers are obtained; s2, carrying out surface modification treatment on the polyamide acid aerogel fibers in a steam treatment tank, drying, and rolling to obtain polyamide acid aerogel composite fibers; s3, carrying out thermal imidization reaction on the polyamide acid aerogel composite fiber under a vacuum condition, and cooling to obtain a polyimide aerogel composite fiber; s4, the polyimide aerogel composite fibers are used as yarn for spinning, and the high-temperature-resistant polyimide composite fabric is obtained. The production process is simple and easy to implement, and the prepared polyimide composite fabric is good in flexibility, better in wear resistance, heat resistance, flame retardance and mechanical property and wide in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of textile materials, and in particular relates to a high-temperature resistant polyimide composite fabric and a production process thereof. Background Art

[0002] In the field of special protection such as military police and fire fighting, flame retardant and heat-insulating textile fabrics play an important role and are the last line of defense to protect human safety. Polyimide fiber has excellent thermal, electrical, chemical corrosion resistance and mechanical properties due to its stable aromatic heterocyclic structure. Its limiting oxygen index is as high as 37%, the initial thermal decomposition temperature is as high as 537°C, and the thermal conductivity of the material itself is low, which has excellent flame retardant and heat-insulating effects. However, textile fabrics made of pure polyimide fiber have certain limitations, such as insufficient flexibility. Although the polyimide composite fabric obtained by blending with other flexible chemical fibers can improve the flexibility of the fabric, it is difficult to take into account the high temperature resistance and flame retardant properties. The more advanced polyimide aerogel fiber has excellent thermal insulation properties due to its rich pore structure, but its mechanical properties are poor and it is difficult to be used in existing fully automatic textile machines to weave into complete fabrics. Therefore, it is of great significance to develop a polyimide composite fabric with both high temperature resistance and good flexibility. Summary of the invention

[0003] The object of the present invention is to provide a high temperature resistant polyimide composite fabric and a production process thereof, so as to solve the problems in the background technology.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A production process of a high temperature resistant polyimide composite fabric comprises the following steps:

[0006] Step S1, adding water-soluble polyamic acid and triethylamine into deionized water, stirring until the water-soluble polyamic acid is completely dissolved to obtain a polyamic acid spinning solution, and then freeze-spinning the polyamic acid spinning solution to obtain a polyamic acid aerogel fiber;

[0007] Step S2, adding the polyamic acid aerogel fiber to a steam treatment tank, then simultaneously introducing saturated water vapor and nano-silicon dioxide mist into the steam treatment tank, and performing surface modification treatment on the polyamic acid aerogel fiber after being fully mixed, the surface layer of the water-soluble polyamic acid aerogel fiber swells after adsorbing water vapor and nano-silicon dioxide, and after being taken out and dried until there is no obvious stickiness on the fiber surface, winding it up to obtain a polyamic acid aerogel composite fiber with nano-silicon dioxide uniformly dispersed in the shell layer;

[0008] Step S3, placing the polyamic acid aerogel composite fiber in a vacuum tube furnace, performing a thermal imidization reaction under vacuum conditions, and naturally cooling to room temperature to obtain a polyimide aerogel composite fiber;

[0009] Step S4: Use the polyimide aerogel composite fiber as yarn and weave it on a fully automatic weaving machine to obtain a high temperature resistant polyimide composite fabric.

[0010] Furthermore, the water-soluble polyamic acid is prepared by the following method:

[0011] Step A1, adding 4,4'-diaminodiphenyl ether to N,N-dimethylacetamide in an ice-water bath and stirring until completely dissolved, then slowly adding pyromellitic anhydride and stirring for 4-6 hours to obtain a polyamic acid solution;

[0012] Step A2, slowly adding triethylamine to the polyamic acid solution, stirring and mixing in an ice-water bath for 4-6 hours to obtain a polyamic acid salt solution;

[0013] Step A3, add the polyamic acid salt solution into a syringe, centrifuge to remove internal bubbles, squeeze the polyamic acid salt solution into deionized water with a syringe pump, then wash with water 3-5 times, replace and remove the solvent N,N-dimethylacetamide, and vacuum freeze-dry to obtain water-soluble polyamic acid.

[0014] Furthermore, the usage ratio of the 4,4'-diaminodiphenyl, N,N-dimethylacetamide and pyromellitic anhydride is 21.5-22 g: 270-280 mL: 24-25 g.

[0015] Furthermore, the volume ratio of the polyamic acid solution to triethylamine is 20:0.96-1; in the process of preparing water-soluble polyamic acid, by adding triethylamine to form a salt with the polyamic acid and controlling the amount of triethylamine, the polyamic acid can form a hydrogel in the process of replacing the organic solvent, which can slow down the hydrolysis of the polyamic acid, so that the polyamic acid can maintain a high molecular weight and is easier to separate from deionized water. Further increasing the amount of triethylamine will increase the water solubility of the polyamic acid, causing it to partially dissolve during the water washing process, and reduce the yield of the water-soluble polyamic acid.

[0016] Furthermore, the mass ratio of the water-soluble polyamic acid, triethylamine and deionized water is 1:1:8. A sufficient amount of triethylamine is added to react with the water-soluble polyamic acid to completely dissolve the polyamic acid.

[0017] Furthermore, the freeze spinning described in step S1 is a prior art, in which the polyamic acid spinning solution is added into a syringe and centrifuged to remove bubbles, and then extruded through a syringe pump. The extruded spinning solution vertically passes through a low-temperature copper ring at -30 to -90°C. The low-temperature environment formed by the low-temperature copper ring causes the polyamic acid spinning solution passing through the inside to gradually solidify, and the fibrous material is freeze-formed and rolled up, and then vacuum freeze-dried for use.

[0018] Furthermore, the saturated water vapor in step S2 is generated by boiling deionized water, and the flow rate of the saturated water vapor is 300-400 mL / min.

[0019] Furthermore, in step S2, the nano-silicon dioxide mist is sprayed out by atomizing a gas-phase nano-silicon dioxide aqueous dispersion having a concentration of 8-10 wt % through a spray dryer or an ultrasonic nozzle, and the flow rate of the nano-silicon dioxide mist is 50-60 mL / min.

[0020] Furthermore, the surface modification treatment time in step S2 is 40-60s. By controlling the duration of the surface modification treatment, the thickness of the polyimide hydrogel composite fiber shell and the content of nano-silica in the shell can be regulated, thereby improving the mechanical properties and heat resistance of the polyimide composite fiber.

[0021] Furthermore, the conditions of the thermal imidization reaction in step S3 are: heating to 110° C., 210° C. and 260° C. at a heating rate of 2° C. / min and keeping the temperature for 1 h each.

[0022] A high temperature resistant polyimide composite fabric is prepared by the above production process.

[0023] Beneficial effects of the present invention:

[0024] In the process of preparing the water-soluble polyamic acid, an appropriate amount of triethylamine is added as an organic base to carry out an acid-base neutralization reaction with part of the carboxyl groups of the polyamic acid, so that the polyamic acid salt can bind part of the carboxyl protons, slowing down the hydrolysis of the polyamic acid when replacing the organic solvent. At the same time, the partially blocked polyamic acid salt can form a hydrogel in deionized water, making it easier to separate the polyamic acid from the deionized water, thereby providing convenience for subsequent processes.

[0025] The present invention firstly utilizes water-soluble polyamic acid to react with triethylamine and dissolve in deionized water to obtain polyamic acid spinning solution, and then freeze-spins the spinning solution to obtain uniform and porous polyamic acid aerogel fibers, and then fully contacts and mixes nano-silicon dioxide mist with saturated water vapor in a steam treatment tank, so that the nano-silicon dioxide is uniformly dispersed in the saturated water vapor. Due to the open-pore structure of the polyamic acid aerogel fibers, during the surface modification process, the saturated water vapor dispersed with nano-silicon dioxide moves violently and diffuses to the surface layer of the polyamic acid aerogel fibers, and the polyamic acid on the fiber surface rapidly swells and dissolves to form a continuous and dense shell, and the dense shell prevents the water vapor from further diffusing into the fiber. After drying, a polyamic acid aerogel composite fiber with a porous inner core and a dense outer shell containing a special structure of nano-silicon dioxide is obtained, and then after a thermal imidization reaction and weaving into a fabric, a high-temperature resistant polyimide composite fabric of the present invention is obtained; on the one hand, the porous inner core structure can provide excellent thermal insulation performance for the composite fabric, so that the composite fabric can be applied to the field of special protection; on the other hand, the dense shell layer can improve the strength and toughness of the polyimide aerogel composite fiber, and the nano-silicon dioxide therein can not only improve the wear resistance of the polyimide aerogel composite fiber, but also improve the thermal stability and flame retardant performance of the polyimide aerogel composite fiber, and the composite fabric prepared using the same has more excellent heat resistance;

[0026] The production process of the invention is simple and easy. Compared with directly mixing nano-silica with polyamic acid salt, nano-silica only exists in the fiber shell layer and will not fill or block the pores in the fiber core. The prepared polyimide composite fabric not only has good flexibility, but also has better wear resistance, heat resistance and flame retardancy, and has broad application prospects. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a water-soluble polyamic acid, which is prepared by the following method:

[0030] Step A1, adding 21.5 g of 4,4'-diaminodiphenyl ether to 270 mL of N,N-dimethylacetamide in an ice-water bath and stirring until completely dissolved, then slowly adding 24 g of pyromellitic anhydride and stirring for 4 hours to obtain a polyamic acid solution;

[0031] Step A2, slowly adding 13 mL of triethylamine to the polyamic acid solution, stirring and mixing in an ice-water bath for 4 h to obtain a polyamic acid salt solution;

[0032] Step A3, add the polyamic acid salt solution into a syringe, centrifuge to remove internal bubbles, squeeze the polyamic acid salt solution into deionized water with a syringe pump, then wash with water three times, replace and remove the solvent N,N-dimethylacetamide, and vacuum freeze-dry to obtain water-soluble polyamic acid.

[0033] Example 2

[0034] This embodiment provides a water-soluble polyamic acid, which is prepared by the following method:

[0035] Step A1, adding 21.8 g of 4,4'-diaminodiphenyl ether to 275 mL of N,N-dimethylacetamide in an ice-water bath and stirring until completely dissolved, then slowly adding 24.5 g of pyromellitic anhydride and stirring for 5 hours to obtain a polyamic acid solution;

[0036] Step A2, slowly adding 13.5 mL of triethylamine to the polyamic acid solution, stirring and mixing for 5 h in an ice-water bath to obtain a polyamic acid salt solution;

[0037] Step A3, add the polyamic acid salt solution into a syringe, centrifuge to remove internal bubbles, squeeze the polyamic acid salt solution into deionized water with a syringe pump, then wash with water 4 times, replace and remove the solvent N,N-dimethylacetamide, and vacuum freeze-dry to obtain water-soluble polyamic acid.

[0038] Example 3

[0039] This embodiment provides a water-soluble polyamic acid, which is prepared by the following method:

[0040] Step A1, adding 22 g of 4,4'-diaminodiphenyl ether to 280 mL of N,N-dimethylacetamide in an ice-water bath and stirring until completely dissolved, then slowly adding 25 g of pyromellitic anhydride and stirring for 6 hours to obtain a polyamic acid solution;

[0041] Step A2, slowly adding 14 mL of triethylamine to the polyamic acid solution, stirring and mixing in an ice-water bath for 6 h to obtain a polyamic acid salt solution;

[0042] Step A3, add the polyamic acid salt solution into a syringe, centrifuge to remove internal bubbles, squeeze the polyamic acid salt solution into deionized water with a syringe pump, then wash with water 5 times, replace and remove the solvent N,N-dimethylacetamide, and vacuum freeze-dry to obtain water-soluble polyamic acid.

[0043] Example 4

[0044] This embodiment provides a high temperature resistant polyimide composite fabric, which is produced by the following production process:

[0045] Step S1, adding 10 g of the water-soluble polyamic acid prepared in Example 1 and 10 g of triethylamine into 80 mL of deionized water, stirring until the water-soluble polyamic acid is completely dissolved to obtain a polyamic acid spinning solution, and then freeze-spinning the polyamic acid spinning solution to obtain a polyamic acid aerogel fiber;

[0046] Step S2, adding the polyamic acid aerogel fiber to a steam treatment tank, and then simultaneously introducing saturated water vapor and nano-silicon dioxide mist into the steam treatment tank, the flow rate of saturated water vapor is 300 mL / min, the nano-silicon dioxide mist is atomized and sprayed by an ultrasonic nozzle from a gas-phase nano-silicon dioxide aqueous dispersion with a concentration of 8wt%, and the flow rate of the nano-silicon dioxide mist is 50 mL / min. After fully mixing, the polyamic acid aerogel fiber is surface-modified for 60 seconds, and the surface layer of the water-soluble polyamic acid aerogel fiber adsorbs water vapor and nano-silicon dioxide and swells. After being taken out and dried until there is no obvious stickiness on the fiber surface, it is rolled up to obtain a polyamic acid aerogel composite fiber with nano-silicon dioxide uniformly dispersed in the shell layer;

[0047] Step S3, placing the polyamic acid aerogel composite fiber in a vacuum tube furnace, heating to 110° C., 210° C. and 260° C. at a heating rate of 2° C. / min under vacuum conditions, and keeping the temperature for 1 h each for thermal imidization reaction, and naturally cooling to room temperature to obtain a polyimide aerogel composite fiber;

[0048] Step S4: Use the polyimide aerogel composite fiber as yarn and weave it on a fully automatic weaving machine to obtain a high temperature resistant polyimide composite fabric.

[0049] Example 5

[0050] This embodiment provides a high temperature resistant polyimide composite fabric, which is produced by the following production process:

[0051] Step S1, adding 10 g of the water-soluble polyamic acid prepared in Example 2 and 10 g of triethylamine to 80 mL of deionized water, stirring until the water-soluble polyamic acid is completely dissolved to obtain a polyamic acid spinning solution, and then freeze-spinning the polyamic acid spinning solution to obtain a polyamic acid aerogel fiber;

[0052] Step S2, adding the polyamic acid aerogel fiber to a steam treatment tank, and then simultaneously introducing saturated water vapor and nano-silicon dioxide mist into the steam treatment tank, the flow rate of the saturated water vapor is 350 mL / min, the nano-silicon dioxide mist is atomized and sprayed by an ultrasonic nozzle from a gas-phase nano-silicon dioxide aqueous dispersion with a concentration of 9wt%, and the flow rate of the nano-silicon dioxide mist is 55 mL / min. After fully mixing, the polyamic acid aerogel fiber is surface-modified for 50 seconds, and the surface layer of the water-soluble polyamic acid aerogel fiber adsorbs water vapor and nano-silicon dioxide and swells. After being taken out and dried until there is no obvious stickiness on the fiber surface, it is rolled up to obtain a polyamic acid aerogel composite fiber with nano-silicon dioxide uniformly dispersed in the shell layer;

[0053] Step S3, placing the polyamic acid aerogel composite fiber in a vacuum tube furnace, heating to 110° C., 210° C. and 260° C. at a heating rate of 2° C. / min under vacuum conditions, and keeping the temperature for 1 h each for thermal imidization reaction, and naturally cooling to room temperature to obtain a polyimide aerogel composite fiber;

[0054] Step S4: Use the polyimide aerogel composite fiber as yarn and weave it on a fully automatic weaving machine to obtain a high temperature resistant polyimide composite fabric.

[0055] Example 6

[0056] This embodiment provides a high temperature resistant polyimide composite fabric, which is produced by the following production process:

[0057] Step S1, adding 10 g of the water-soluble polyamic acid prepared in Example 3 and 10 g of triethylamine to 80 mL of deionized water, stirring until the water-soluble polyamic acid is completely dissolved to obtain a polyamic acid spinning solution, and then freeze-spinning the polyamic acid spinning solution to obtain a polyamic acid aerogel fiber;

[0058] Step S2, adding the polyamic acid aerogel fiber to a steam treatment tank, and then simultaneously introducing saturated water vapor and nano-silicon dioxide mist into the steam treatment tank, the flow rate of saturated water vapor is 400 mL / min, the nano-silicon dioxide mist is atomized and sprayed by an ultrasonic nozzle from a 10wt% gas-phase nano-silicon dioxide aqueous dispersion, the flow rate of the nano-silicon dioxide mist is 60 mL / min, and after being fully mixed, the polyamic acid aerogel fiber is subjected to surface modification treatment for 40s, and the surface layer of the water-soluble polyamic acid aerogel fiber swells after adsorbing water vapor and nano-silicon dioxide, and after being taken out and dried until there is no obvious stickiness on the fiber surface, it is rolled up to obtain a polyamic acid aerogel composite fiber with nano-silicon dioxide uniformly dispersed in the shell layer;

[0059] Step S3, placing the polyamic acid aerogel composite fiber in a vacuum tube furnace, heating to 110° C., 210° C. and 260° C. at a heating rate of 2° C. / min under vacuum conditions, and keeping the temperature for 1 h each for thermal imidization reaction, and naturally cooling to room temperature to obtain a polyimide aerogel composite fiber;

[0060] Step S4: Use the polyimide aerogel composite fiber as yarn and weave it on a fully automatic weaving machine to obtain a high temperature resistant polyimide composite fabric.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 6 is that in step S2, the polyamic acid aerogel fiber is not subjected to surface modification treatment, and the remaining steps and parameters are the same.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 6 is that in step S2, only saturated water vapor is used to perform surface modification treatment on the polyamic acid aerogel fiber, and the remaining steps and parameters are the same.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 6 is that the surface modification treatment time in step S2 is 20 s, and the other steps and parameters are the same.

[0067] Performance tests were performed on Examples 4 to 6 and Comparative Examples 1 to 2. The composite fabric was subjected to a thermal gravimetric analysis (TGA) test, and the thermal decomposition temperature was recorded. The oxygen limit index of the composite fabric was tested according to GB / T 5454-1997. The breaking strength of the composite fabric was tested according to GB / T 3923.1-2013. The composite fabric was laid flat on the surface of a heating table, and the temperature of the heating table was set to 60°C. After standing for 1 minute, the surface temperature of the composite fabric was tested using an infrared thermal imager, and the temperature difference between the surface of the composite fabric and the heating table was recorded. The results are shown in Table 1:

[0068] Table 1

[0069] Test items Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Thermal decomposition temperature / ℃ 554 560 568 535 537 546 Oxygen limit index / % 38.7 39.3 39.8 37.5 37.5 38.2 Breaking strength / N 1225 1276 1317 382 972 1018 Temperature difference / ℃ 22.3 22.9 23.4 24.6 23.1 23.7

[0070] It can be seen from the data in Table 1 that the polyimide composite fabrics prepared in Examples 4 to 6 have more excellent heat resistance, heat insulation and flame retardancy. At the same time, the prepared composite fabrics have excellent breaking strength and have broad application prospects.

[0071] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0072] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A production process of high temperature resistant polyimide composite fabric, characterized in that: The following steps are involved: Step S1, adding water-soluble polyamic acid and triethylamine into deionized water, stirring until completely dissolved to obtain a polyamic acid spinning solution, and then freeze-spinning the polyamic acid spinning solution to obtain a polyamic acid aerogel fiber; Step S2, adding the polyamic acid aerogel fiber into a steam treatment tank, then simultaneously introducing saturated water vapor and nano-silicon dioxide mist into the steam treatment tank, performing surface modification treatment on the polyamic acid aerogel fiber after sufficient mixing, and rolling up after drying to obtain a polyamic acid aerogel composite fiber; Step S3, subjecting the polyamic acid aerogel composite fiber to a thermal imidization reaction under vacuum conditions, and naturally cooling it to room temperature to obtain a polyimide aerogel composite fiber; Step S4: Use the polyimide aerogel composite fiber as yarn and weave it on a fully automatic weaving machine to obtain a high temperature resistant polyimide composite fabric.

2. The production process of a high temperature resistant polyimide composite fabric according to claim 1, characterized in that: The water-soluble polyamic acid is prepared by the following method: Step A1, adding 4,4'-diaminodiphenyl ether to N,N-dimethylacetamide in an ice-water bath and stirring to dissolve, then adding pyromellitic anhydride and stirring to react for 4-6 hours to obtain a polyamic acid solution; Step A2, adding triethylamine to the polyamic acid solution, stirring and mixing in an ice-water bath for 4-6 hours to obtain a polyamic acid salt solution; Step A3, adding the polyamic acid salt solution into a syringe, centrifuging to remove internal bubbles, squeezing the polyamic acid salt solution into deionized water using a syringe pump, washing with water, and vacuum freeze-drying to obtain a water-soluble polyamic acid.

3. The production process of a high temperature resistant polyimide composite fabric according to claim 2, characterized in that: The usage ratio of the 4,4'-diaminodiphenyl, N,N-dimethylacetamide and pyromellitic anhydride is 21.5-22 g: 270-280 mL: 24-25 g.

4. The production process of a high temperature resistant polyimide composite fabric according to claim 2, characterized in that: The volume ratio of the polyamic acid solution to triethylamine is 20:0.96-1.

5. The production process of a high temperature resistant polyimide composite fabric according to claim 1, characterized in that: The mass ratio of the water-soluble polyamic acid, triethylamine and deionized water is 1:1:

8.

6. The production process of a high temperature resistant polyimide composite fabric according to claim 1, characterized in that: The flow rate of the saturated water vapor is 300-400 mL / min.

7. The production process of a high temperature resistant polyimide composite fabric according to claim 1, characterized in that: The nano-silicon dioxide mist is sprayed out from a gas-phase nano-silicon dioxide aqueous dispersion with a concentration of 8-10wt% by a spray dryer or an ultrasonic nozzle, and the flow rate of the nano-silicon dioxide mist is 50-60mL / min.

8. The production process of a high temperature resistant polyimide composite fabric according to claim 1, characterized in that: The surface modification treatment time is 40-60s.

9. The production process of a high temperature resistant polyimide composite fabric according to claim 1, characterized in that: The conditions of the thermal imidization reaction are: heating to 110° C., 210° C. and 260° C. at a heating rate of 2° C. / min and keeping the temperature for 1 h each.

10. A high temperature resistant polyimide composite fabric, characterized in that: The invention is prepared by the production process described in any one of claims 1 to 9.