阅读说明：本技术 聚酰亚胺纤维以及制备聚酰亚胺纤维的方法 (Polyimide fiber and method for producing polyimide fiber ) 是由 武德珍 韩恩林 牛鸿庆 张梦颖 于 2021-10-21 设计创作，主要内容包括：本发明涉及一种聚酰亚胺纤维及其制备方法,包括：将二酐单体、二胺单体与反应溶剂进行混合、缩合聚合反应得到聚酰胺酸纺丝溶液；将脱水剂、催化剂与聚酰胺酸溶液进行混合、进行第一亚胺化反应,得到预亚胺化的聚酰胺酸纺丝溶液；按照湿法或干湿法纺丝工艺,将上述纺丝溶液经过滤、脱泡后,通过计量泵从喷丝板喷出；原丝浸入亚胺化试剂进行第二亚胺化反应,经导丝辊牵引后进行高倍牵伸；然后,经凝固、洗涤、干燥及热处理即得到聚酰亚胺纤维。该方法将聚酰亚胺纤维制备过程中的高倍牵伸阶段前移至热处理前,可以降低后期热处理温度和能耗,同时提高了纤维的牵伸比,制备的聚酰亚胺纤维具有优异的力学性能。(The invention relates to a polyimide fiber and a preparation method thereof, wherein the preparation method comprises the following steps: mixing dianhydride monomer, diamine monomer and reaction solvent, and carrying out condensation polymerization reaction to obtain polyamic acid spinning solution; mixing a dehydrating agent, a catalyst and a polyamic acid solution, and carrying out a first imidization reaction to obtain a pre-imidized polyamic acid spinning solution; according to a wet method or dry-wet method spinning process, filtering and defoaming the spinning solution, and then spraying the spinning solution from a spinneret plate through a metering pump; immersing the precursor into an imidizing agent for a second imidization reaction, and drawing by a godet roller to perform high-power drawing; then, the polyimide fiber is obtained after solidification, washing, drying and heat treatment. The method moves the high-power drafting stage in the polyimide fiber preparation process to the position before heat treatment, so that the later heat treatment temperature and energy consumption can be reduced, the drafting ratio of the fiber is improved, and the prepared polyimide fiber has excellent mechanical properties.)

1. A method of making a polyimide fiber, comprising the steps of:

(1) stirring and mixing a dianhydride monomer, a diamine monomer and a reaction solvent, and then carrying out a condensation polymerization reaction to obtain a polyamic acid solution;

(2) mixing a dehydrating agent, a catalyst and the polyamic acid solution, and then carrying out a first imidization reaction to obtain a pre-imidized polyamic acid solution;

(3) according to a wet method or dry-wet method spinning process, filtering and defoaming the spinning solution, and then spraying the spinning solution from a spinneret plate through a metering pump;

(4) the filament is directly immersed into the imidization reagent after being sprayed out from the spinneret plate or is immersed into the imidization reagent after passing through a section of air layer, the second imidization reaction is carried out, and the filament is drawn by a godet roller and then is subjected to high-power drawing;

(5) and (3) carrying out coagulating bath, water washing, drying and thermal cyclization treatment on the high-power drafted fiber to obtain the polyimide fiber.

2. The process according to claim 1, wherein the polyamic acid solution in step (1) has a solid content of 10% to 30%. The molar ratio of dianhydride monomer to diamine monomer is 0.98:1-1.02:1.

3. The method according to claim 1 or 2, wherein the dianhydride monomer in step (1) is one or more of 3,3 ', 4,4 ' -benzophenone tetracarboxylic dianhydride, 3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 2,3 ', 3,4 ' -biphenyl tetracarboxylic dianhydride, bisphenol a type dianhydride, 4,4 ' -oxydiphthalic anhydride, hexafluoroisopropylene phthalic acid, diphenyl sulfide tetracarboxylic dianhydride, and 3,3 ', 4,4 ' -diphenyl sulfone tetracarboxylic dianhydride mixed in an arbitrary ratio; the diamine monomer is one or more of p-phenylenediamine, m-phenylenediamine, 4 '-diaminodiphenyl ether, 2- (4-aminophenyl) -5-aminobenzimidazole, 4' -diaminodiphenyl sulfone and 4,4 '-diamino-2, 2' -bistrifluoromethyl biphenyl which are mixed in any proportion; the reaction solvent is one of N, N-dimethylformamide, N-dimethylacetamide, N-vinyl pyrrolidone and dimethyl sulfoxide.

4. The process according to claim 1, wherein the volume ratio of dehydrating agent to catalyst in steps (2) and (4) is from 5:1 to 1:10.

5. The process according to claim 1, wherein the dehydrating agent in steps (2) and (4)) is a mixture of one or more of acetic anhydride, propionic anhydride, butyric anhydride; the catalyst is one or a mixture of pyridine, triethylamine, imidazole, isoquinoline, 2-methylpyridine and 3-methylpyridine.

6. A polyimide fiber prepared according to the method of any one of claims 1 to 5.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a method for preparing polyimide fibers and polyimide fibers prepared by the method.

Technical Field

The polyimide fiber is widely applied to the high-temperature resistant fields of aerospace, atomic energy industry, high-temperature dust removal bags, firefighter uniforms and the like due to good mechanical property and thermal stability and excellent radiation resistance, acid and alkali corrosion resistance and flame retardant property. At present, the preparation of polyimide fiber mostly adopts a two-step method, firstly polyamide acid solution is used as spinning dope to prepare polyamide acid fiber, and then the polyimide fiber is obtained through chemical imidization or thermal imidization and back drawing. The mechanical properties of polyimide fibers are closely related not only to the chemical structure but also to the degree of orientation. Therefore, in order to obtain the high-strength and high-modulus polyimide fiber, the key point is to improve the draft multiple of the fiber in the preparation process.

The conventional method for preparing polyimide fibers in the prior art is to realize the drafting of the fibers by adjusting the roller speed under the conditions of air or nitrogen at the temperature of 300-600 ℃. For example, in patent CN 102943331 a, a hot steam humidifying device is added on the basis of the original high-temperature hot drawing device, and the drawing multiple of the fiber is improved by 30% and the mechanical property is improved by 40% by humidifying treatment before high-temperature drawing. In patent CN 109402760A, the problems of broken filaments, broken filaments and the like in the production process of polyimide fibers are solved by a method of carrying out negative drafting with a draft ratio of-5% to-50% in a first coagulating bath and then carrying out positive drafting in the coagulating bath and water washing stages. In patent CN 101487143 a, the draw ratio of the fiber is increased by multi-step drawing methods such as coagulation bath, drawing bath, water washing bath, and later thermal cyclization stage, and the prepared polyimide fiber has excellent mechanical properties. In patent CN 103014902B, the polyamic acid fiber is passed through a heat furnace with temperature gradient range of 100-500 deg.C, each temperature gradient is heat-drawn, the total drawing multiple is 1.5-3.0 times, and the tensile strength and modulus of the prepared polyimide fiber respectively reach 3.7GPa and 120 GPa.

Although the prior art refers to the preparation of polyimide fibers, the above methods have some disadvantages and problems, such as that the above techniques involve drawing at high temperature or in multiple stages, the drawing process is complicated, the energy consumption is large, the drawing ratio is low, and more fuzz is easily generated. In order to solve the problems, researchers propose some improved technical schemes. For example, patent CN 107130445B discloses a method for improving mechanical properties of dyed polyimide fibers, which comprises soaking polyamic acid fibers in an imidizing agent for 4-24h, drying, and performing thermal cyclization to obtain polyimide fibers. Then, alkali etching and dyeing are performed. The fiber after chemical imidization dyeing has better mechanical property. Patent CN 107034542B discloses a method for preparing polyimide fiber by three-step hybrid imidization, in which a partially imidized fiber is soaked in an imidizing agent for 4-24h, and then subjected to further thermal cyclization, so that the obtained polyimide fiber has excellent mechanical properties. However, the above two methods have long soaking time in the imidizing agent, which is not favorable for industrial continuous production. In addition, researchers (j.mater.sci.2019,54, 3619-. Because the solubility of aromatic polyimide in most organic solvents is poor, the pre-imidization degree of the spinning solution is low, and the improvement of the mechanical property of the fiber is limited.

Therefore, although the preparation research of the polyimide fiber exists to a certain extent in the prior art, basically, the prior art has the defects of difficult traction, large energy consumption and incapability of realizing high draft ratio. Therefore, there is a need to develop fiber draft ratios and methods that reduce energy consumption.

Disclosure of Invention

The invention aims to overcome the technical problems that the existing polyimide fiber drafting process is complex, the energy consumption is high and the high drafting ratio cannot be realized, and provides a method for preparing high-performance polyimide fiber through chemical imidization.

In order to achieve the above object, the present invention discloses a method for preparing polyimide fibers, comprising the steps of:

(1) stirring and mixing a dianhydride monomer, a diamine monomer and a reaction solvent, and then carrying out a condensation polymerization reaction to obtain a polyamic acid solution;

(2) mixing a dehydrating agent, a catalyst and the polyamic acid solution, and then carrying out a first imidization reaction to obtain a pre-imidized polyamic acid solution;

(3) according to a wet method or dry-wet method spinning process, filtering and defoaming the spinning solution, and then spraying the spinning solution from a spinneret plate through a metering pump;

(4) the filament is directly immersed into the imidization reagent after being sprayed out from the spinneret plate or is immersed into the imidization reagent after passing through a section of air layer, the second imidization reaction is carried out, and the filament is drawn by a godet roller and then is subjected to high-power drawing;

(5) and (3) obtaining the polyimide fiber through coagulating bath, water washing, drying and thermal cyclization treatment.

Preferably, the solid content of the polyamic acid solution in step (1) is 10% to 30%. The molar ratio of dianhydride monomer to diamine monomer is 0.98:1-1.02:1.

Preferably, the dianhydride monomer in step (1) is one or more of 3,3 ', 4,4 ' -Benzophenone Tetracarboxylic Dianhydride (BTDA), 3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), 2,3 ', 3,4 ' -biphenyl tetracarboxylic dianhydride (α -BPDA), bisphenol a type dianhydride (BPADA), 4,4 ' -oxydiphthalic anhydride (ODPA), hexafluoroisopropylene phthalic acid (6FDA), diphenyl sulfide Tetracarboxylic Dianhydride (TDPA), and 3,3 ', 4,4 ' -diphenyl sulfone tetracarboxylic dianhydride mixed in any proportion; the diamine monomer is one or more of p-Phenylenediamine (PDA), m-phenylenediamine, 4 '-diaminodiphenyl ether (ODA), 2- (4-aminophenyl) -5-aminobenzimidazole (BIA), 4' -diaminodiphenyl sulfone and 4,4 '-diamino-2, 2' -bistrifluoromethyl biphenyl mixed in any proportion; the reaction solvent is one of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-vinyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO).

Preferably, the volume ratio of the dehydrating agent to the catalyst in steps (2) and (4) is from 5:1 to 1:10.

Preferably, the dehydrating agent in steps (2) and (3) is a mixture of one or more of acetic anhydride, propionic anhydride and butyric anhydride; the catalyst is one or a mixture of pyridine, triethylamine, imidazole, isoquinoline, 2-methylpyridine and 3-methylpyridine.

Another object of the present invention is to provide a polyimide fiber having excellent mechanical properties, which is prepared by the above method.

Compared with the prior art, the invention has the beneficial effects that:

(1) the method of the invention enables the polyimide fiber to have higher draft ratio compared with the traditional spinning process through two-step chemical imidization, improves the orientation degree of the fiber and endows the fiber with more excellent mechanical property;

(2) the polyimide fiber prepared by the method can realize high-power drafting before heat treatment, can reduce the time or temperature of later heat treatment and reduce energy consumption;

(3) compared with the prior art for preparing the polyimide fiber by chemical imidization, the polyimide fiber prepared by the method does not need to change the original spinning process flow, has simple operation and high production efficiency, and is convenient for industrial production.

Detailed Description

In the description herein, references to the description of "one embodiment," "another embodiment," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

The present invention will be further described with reference to specific examples, but the present invention is not limited to the following examples. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

(1) Adding equal molar amounts of BPDA and PDA into a DMAc solvent, stirring, performing condensation polymerization reaction to obtain a polyamic acid solution with the solid content of 12 wt%, wherein the temperature of the condensation polymerization reaction is 0 ℃, and the time is 5 hours;

(2) acetic anhydride and pyridine were added to the foregoing polyamic acid solution, and sufficiently stirred to perform a first imidization reaction, thereby obtaining a pre-imidized polyamic acid solution having an imidization degree of 20%. Wherein the molar ratio of acetic anhydride to BPDA is 0.4:1, the volume ratio of acetic anhydride to pyridine is 2:1, the reaction temperature of pre-imidization is 30 ℃, and the reaction time is 5 hours;

(3) filtering and defoaming the polyamic acid spinning solution, and then spraying the polyamic acid spinning solution out of a spinneret plate through a metering pump under the nitrogen pressure of 0.3 MPa;

(4) the polyamic acid yarn is sprayed out and then directly immersed into an imidizing agent containing acetic anhydride and pyridine (the volume ratio is 1:3) to carry out a second imidization reaction, and the polyamic acid yarn is drawn by a godet roller and then subjected to high-power drawing, wherein the conditions of the second imidization reaction comprise: the reaction temperature is 35 ℃, and the reaction time is 1 min;

(5) after coagulating bath and water washing, drying the high-power drafted fiber at constant speed by a tubular furnace at the temperature of 110 ℃ for 3 min; then respectively passing through a tubular furnace at 240 ℃, 350 ℃ and 400 ℃ for thermal cyclization for 2min to obtain the polyimide fiber A1 completely imidized. The maximum draft ratio of the polyimide fiber and the mechanical properties of the polyimide fiber are shown in table 1.

Example 2

(1) Adding equal molar amounts of BPDA and BIA into a DMAc solvent, stirring, and carrying out condensation polymerization reaction at 0 ℃ for 5 hours to obtain a polyamic acid solution with the solid content of 12 wt%;

(2) acetic anhydride and pyridine were added to the foregoing polyamic acid solution, and sufficiently stirred to perform a first imidization reaction, thereby obtaining a pre-imidized polyamic acid solution having an imidization degree of 25%. Wherein the molar ratio of acetic anhydride to BPDA is 0.5:1, the volume ratio of acetic anhydride to pyridine is 2:1, the reaction temperature of pre-imidization is 30 ℃, and the reaction time is 5 hours;

(3) filtering and defoaming the polyamic acid spinning solution, and then spraying the polyamic acid spinning solution out of a spinneret plate through a metering pump under the nitrogen pressure of 0.3 MPa;

(4) the polyamic acid yarn is sprayed out and then directly immersed into an imidizing agent containing acetic anhydride and pyridine (the volume ratio is 1:3) to carry out a second imidization reaction, and the polyamic acid yarn is drawn by a godet roller and then subjected to high-power drawing, wherein the conditions of the second imidization reaction comprise: the reaction temperature is 35 ℃, and the reaction time is 1 min;

(5) after coagulating bath and water washing, drying the high-power drafted fiber at constant speed by a tubular furnace at the temperature of 110 ℃ for 3 min; then respectively passing through a tubular furnace at 240 ℃, 350 ℃ and 400 ℃ for thermal cyclization for 2min to obtain the polyimide fiber A2 completely imidized. The maximum draft ratio of the polyimide fiber and the mechanical properties of the polyimide fiber are shown in table 1.

Example 3

(1) Adding equimolar amounts of PMDA and ODA into a DMAc solvent, stirring, and carrying out condensation polymerization reaction at 0 ℃ for 5 hours to obtain a polyamic acid solution with the solid content of 15 wt%;

(2) acetic anhydride and pyridine were added to the foregoing polyamic acid solution, and sufficiently stirred to perform a first imidization reaction, thereby obtaining a pre-imidized polyamic acid solution having an imidization degree of 30%. Wherein the molar ratio of acetic anhydride to PMDA is 0.6:1, the volume ratio of acetic anhydride to pyridine is 2:1, the reaction temperature of pre-imidization is 30 ℃, and the reaction time is 5 hours;

(3) filtering and defoaming the polyamic acid spinning solution, and then spraying the polyamic acid spinning solution out of a spinneret plate through a metering pump under the nitrogen pressure of 0.3 MPa;

(4) the polyamic acid yarn is sprayed out and then directly immersed into an imidizing agent containing acetic anhydride and pyridine (the volume ratio is 1:3) to carry out a second imidization reaction, and the polyamic acid yarn is drawn by a godet roller and then subjected to high-power drawing, wherein the conditions of the second imidization reaction comprise: the reaction temperature is 35 ℃, and the reaction time is 1 min;

(5) after coagulating bath and water washing, drying the high-power drafted fiber at constant speed by a tubular furnace at the temperature of 110 ℃ for 3 min; then respectively passing through a tubular furnace at 240 ℃, 350 ℃ and 400 ℃ for thermal cyclization for 2min to obtain the polyimide fiber A3 completely imidized. The maximum draft ratio of the polyimide fiber and the mechanical properties of the polyimide fiber are shown in table 1.

Example 4

(1) Adding equal molar amounts of BPDA and ODA into a DMAc solvent, stirring, and carrying out condensation polymerization reaction at 0 ℃ for 5 hours to obtain a polyamic acid solution with the solid content of 15 wt%;

(2) acetic anhydride and pyridine were added to the foregoing polyamic acid solution, and sufficiently stirred to perform a first imidization reaction, thereby obtaining a pre-imidized polyamic acid solution having an imidization degree of 40%. Wherein the molar ratio of acetic anhydride to BPDA is 0.8:1, the volume ratio of acetic anhydride to pyridine is 2:1, the reaction temperature of pre-imidization is 30 ℃, and the reaction time is 5 hours;

(3) filtering and defoaming the polyamic acid spinning solution, and then spraying the polyamic acid spinning solution out of a spinneret plate through a metering pump under the nitrogen pressure of 0.3 MPa;

(4) the polyamic acid yarn is sprayed out and then directly immersed into an imidizing agent containing acetic anhydride and pyridine (the volume ratio is 1:3) to carry out a second imidization reaction, and the polyamic acid yarn is drawn by a godet roller and then subjected to high-power drawing, wherein the conditions of the second imidization reaction comprise: the reaction temperature is 35 ℃, and the reaction time is 1 min;

(5) after coagulating bath and water washing, drying the high-power drafted fiber at constant speed by a tubular furnace at the temperature of 110 ℃ for 3 min; then respectively passing through a tubular furnace at 240 ℃, 350 ℃ and 400 ℃ for thermal cyclization for 2min to obtain the polyimide fiber A4 completely imidized. The maximum draft ratio of the polyimide fiber and the mechanical properties of the polyimide fiber are shown in table 1.

Comparative example 1

(1) Adding equal molar amounts of BPDA and PDA into a DMAc solvent, stirring, performing condensation polymerization reaction to obtain a polyamic acid solution with the solid content of 12 wt%, wherein the temperature of the condensation polymerization reaction is 0 ℃, and the time is 5 hours;

(2) filtering and defoaming the polyamic acid spinning solution, and then spraying the polyamic acid spinning solution out of a spinneret plate through a metering pump under the nitrogen pressure of 0.3 MPa;

(3) the polyamic acid yarn is sprayed out and then directly immersed into an imidizing agent containing acetic anhydride and pyridine (volume ratio is 1:3) for imidization, and the polyamic acid yarn is drawn by a godet roller and then highly drawn, wherein the imidization conditions comprise: the reaction temperature is 35 ℃, and the reaction time is 3 min;

(4) after coagulating bath and water washing, drying the high-power drafted fiber at constant speed by a tubular furnace at the temperature of 110 ℃ for 3 min; then respectively passing through a tubular furnace at 240 ℃, 350 ℃ and 400 ℃ for thermal cyclization for 2min, thus obtaining the polyimide fiber D1 which is fully imidized. The maximum draft ratio of the polyimide fiber and the mechanical properties of the polyimide fiber are shown in table 1.

Comparative example 2

(1) Adding equal molar amounts of BPDA and PDA into a DMAc solvent, stirring, performing condensation polymerization reaction to obtain a polyamic acid solution with the solid content of 12 wt%, wherein the temperature of the condensation polymerization reaction is 0 ℃, and the time is 5 hours;

(2) acetic anhydride and pyridine were added to the foregoing polyamic acid solution, and the mixture was sufficiently stirred to conduct imidization reaction, thereby obtaining a pre-imidized polyamic acid solution having an imidization degree of 20%. Wherein the molar ratio of acetic anhydride to BPDA is 0.4:1, the volume ratio of acetic anhydride to pyridine is 2:1, the reaction temperature of pre-imidization is 30 ℃, and the reaction time is 5 hours;

(3) filtering and defoaming the polyamic acid spinning solution, and then spraying the polyamic acid spinning solution out of a spinneret plate through a metering pump under the nitrogen pressure of 0.3 MPa;

(4) spraying the polyamide acid filaments, directly feeding the polyamide acid filaments into a coagulating bath, washing with water, and drying the fibers at a constant speed for 3min by passing through a tube furnace at the temperature of 110 ℃; then respectively carrying out thermal cyclization for 2min in a tubular furnace at 240 ℃, 380 ℃ and 450 ℃, and drafting the fiber by adjusting the roller speed in the heat treatment process to obtain the polyimide fiber D2 completely imidized. The maximum draft ratio of the polyimide fiber and the mechanical properties of the polyimide fiber are shown in table 1.

Comparative example 3

(1) Adding equal molar amounts of BPDA and PDA into a DMAc solvent, stirring, performing condensation polymerization reaction to obtain a polyamic acid solution with the solid content of 12 wt%, wherein the temperature of the condensation polymerization reaction is 0 ℃, and the time is 5 hours;

(2) filtering and defoaming the polyamic acid spinning solution, and then spraying the polyamic acid spinning solution out of a spinneret plate through a metering pump under the nitrogen pressure of 0.3 MPa;

(3) spraying the polyamide acid filaments, directly feeding the polyamide acid filaments into a coagulating bath, washing with water, and drying the fibers at a constant speed for 3min by passing through a tube furnace at the temperature of 110 ℃; then respectively carrying out thermal cyclization for 2min in a tubular furnace at 240 ℃, 380 ℃ and 450 ℃, and drafting the fiber by adjusting the roller speed in the heat treatment process to obtain the polyimide fiber D3 completely imidized. The maximum draft ratio of the polyimide fiber and the mechanical properties of the polyimide fiber are shown in table 1.

TABLE 1 comparison of mechanical Properties of polyimide fibers obtained by different methods

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of the technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.