CN110863258B

CN110863258B - Polyimide fiber and preparation method thereof

Info

Publication number: CN110863258B
Application number: CN201911173054.7A
Authority: CN
Inventors: 姚海波; 董志鑫; 刘芳芳; 代学民; 李国民; 王汉夫; 邱雪鹏
Original assignee: Changchun Institute of Applied Chemistry of CAS
Current assignee: Changchun Institute of Applied Chemistry of CAS
Priority date: 2019-11-26
Filing date: 2019-11-26
Publication date: 2021-04-27
Anticipated expiration: 2039-11-26
Also published as: CN110863258A

Abstract

The invention provides a polyimide fiber and a preparation method thereof. The polyimide fiber and the preparation method thereof provided by the invention comprise the following steps: a) polymerizing an aromatic dianhydride monomer and a diamine monomer in a solvent to obtain polyamic acid spinning solution; b) spinning the polyamic acid spinning solution to obtain polyamic acid fiber; c) carrying out imidization treatment on the polyamic acid fiber to obtain a polyimide fiber; the diamine monomer comprises a monomer A and a monomer B; the monomer A is selected from one or more of structures shown in formulas a-1 to a-8; the monomer B is selected from one or more of structures shown in formulas B-1 to B-7. According to the invention, a specific monomer A with a main chain containing an o-hydroxy benzophenone structural unit and a monomer B are matched as diamine monomers, and the diamine monomers are polymerized and spun with a dianhydride monomer to obtain the polyimide fiber, and the introduction of the specific monomer can improve the ultraviolet aging resistance of the polyimide.

Description

Polyimide fiber and preparation method thereof

Technical Field

The invention relates to the technical field of fibers, in particular to a polyimide fiber and a preparation method thereof.

Background

The polyimide fiber material is a novel special fiber with excellent comprehensive performance, contains imide rings in molecular chains, has a plurality of excellent performances such as high strength, high modulus, high temperature resistance, flame retardance, chemical corrosion resistance, low temperature resistance and the like, and is widely applied to the high and new technical fields such as aerospace, weaponry, transportation and the like.

In the using process of the polyimide fiber material, the performance of the polyimide fiber material can be influenced by the environment, and particularly, after ultraviolet irradiation, the fiber surface can generate chemical reaction, so that the performance of the fiber is reduced. Particularly, the polyimide fiber material used on the aerospace vehicle has no obstruction of high-altitude atmospheric layers (particularly ozone layers), is in an ultraviolet radiation environment with intensity much higher than that of a ground environment, can accelerate degradation and aging, and seriously influences the service life of the polyimide fiber material. Therefore, in order to ensure that the comprehensive performance of the polyimide fiber material and the product can be maintained for a long time in the ultraviolet irradiation environment, the development of ultraviolet irradiation resistant polyimide fibers is urgently needed, and the application of the ultraviolet irradiation resistant polyimide fibers in the fields of ground and aerospace is met.

Currently, for the ultraviolet radiation resistant polyimide materials, mainly focusing on polyimide films and resins, for example, patent application CN105348750A discloses a method for preparing a heat-insulating ultraviolet-resistant automobile film by adding nanoparticles. Patent application CN103255501B discloses a preparation method of ultraviolet radiation resistant polyimide fiber: adding a light stabilizer into polyamide acid which is a precursor of polyimide, and then spinning, imidizing and drafting to obtain the polyimide fiber with ultraviolet irradiation resistance.

In the method, components with the ultraviolet resistance function, such as nano particles and organic micromolecules, are doped into the polyimide host material as an object, so that the ultraviolet radiation resistant polyimide material is prepared. The method for adding the anti-ultraviolet nano particles has the main problems that the specific surface area of the nano particles is large and the nano particles are easy to agglomerate, so that the dispersibility of the nano particles in a matrix is difficult to control, the processing repeatability is poor, and the ultraviolet irradiation resistance of a product is influenced; the method for adding the organic micromolecules mainly solves the problems that the organic micromolecules have poor heat-resistant aging resistance, can be decomposed and lost under the high-temperature condition, cause the mechanical property of the material to be poor, and cause the ultraviolet radiation resistance of the material to be reduced and even lost.

Disclosure of Invention

In view of the above, the present invention is directed to a polyimide fiber and a method for preparing the same. The polyimide fiber prepared by the preparation method has excellent ultraviolet irradiation aging resistance.

The invention provides a preparation method of polyimide fibers, which comprises the following steps:

a) polymerizing an aromatic dianhydride monomer and a diamine monomer in a solvent to obtain polyamic acid spinning solution;

b) spinning the polyamic acid spinning solution to obtain polyamic acid fiber;

c) carrying out imidization treatment on the polyamic acid fiber to obtain a polyimide fiber;

the diamine monomer comprises a monomer A and a monomer B;

the monomer A is selected from one or more of structures shown in formulas a-1 to a-8:

the monomer B is selected from one or more of structures shown in formulas B-1 to B-7:

wherein the content of the first and second substances,

m is selected from-O-, -S-, or-NH-;

x is selected from-O-, -S-, or-NH-;

d is selected from-O-, -S-, or-NH-;

e is selected from-O-, -S-, -SO₂-、-CH₂-、-C(CF₃)₂-、-CO-、

Preferably, the aromatic dianhydride monomer is selected from one or more of structures shown in formulas I-1 to I-3:

wherein A is selected from:

-S-、-O-、

preferably, the molar ratio of the aromatic dianhydride monomer to the diamine monomer is 1 to (0.95-1.20);

in the diamine monomer, the monomer A accounts for 0.1 to 99 percent of the total mole ratio of the diamine monomer.

Preferably, in the step a), the polymerization temperature is-20 ℃ to 50 ℃ and the time is 4 to 60 hours.

Preferably, in step a), the solvent is a polar aprotic solvent;

the polar aprotic solvent is selected from one or more of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone;

the concentration of the polyamic acid spinning solution is 5-35 wt%.

Preferably, in the step c), the imidization treatment is a thermal imidization treatment;

the thermal imidization treatment is gradient heating treatment or constant temperature treatment;

the conditions of the gradient temperature-rising heat treatment are as follows:

the initial temperature is 30-50 ℃, the end point temperature is 280-450 ℃, the heating rate is 1-30 ℃/min, and the temperature is kept for 5-60 min after the temperature is raised to the end point temperature;

the conditions of the constant temperature heat treatment are as follows:

the heat treatment temperature is 280-500 ℃, and the constant temperature is kept for 5-60 min.

Preferably, in the step b), the spinning is dry-jet wet spinning, wet spinning or dry spinning;

the dry-jet wet spinning method comprises the following steps: extruding the polyamic acid spinning solution from a spinneret orifice, allowing the polyamic acid spinning solution to enter a coagulating bath for forming after passing through an air layer, and washing and drying to obtain polyamic acid fibers;

in the dry-jet wet spinning, the height of the air layer is 10-100 mm, the aperture of each spinneret orifice is 0.05-0.2 mm, the jet-draw ratio of the spinneret is 1.5-7.0 times, and the spinning speed is 10-100 m/min;

the wet spinning comprises the following steps: extruding the polyamic acid spinning solution from a spinneret orifice, directly entering a coagulating bath for forming, and then washing and drying to obtain polyamic acid fiber;

in the wet spinning, the aperture of the spinneret orifice is 0.02-0.14 mm, the spray-draw ratio of the spinneret is 1.1-4.5 times, and the spinning speed is 4-80 m/min;

the dry spinning method comprises the following steps: extruding the polyamic acid spinning solution from a spinneret orifice, and drying to obtain polyamic acid fiber;

in the dry spinning, the drying temperature is 150-350 ℃.

Preferably, the imidization treatment is followed by a heat-drawing treatment;

the temperature of the hot drawing is 350-600 ℃, and the multiplying power is 1.0-6.0 times;

the thermal drawing is carried out under an inert gas atmosphere.

Preferably, the coagulating bath is a mixture of organic matter and water;

the volume ratio of the organic matter to the water is 1: (3-10);

the organic matter is selected from one or more of ethanol, glycol, butanol, acetone, butanone, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone.

The invention also provides the polyimide fiber prepared by the preparation method in the technical scheme.

The invention provides a preparation method of polyimide fibers, which comprises the following steps: a) polymerizing an aromatic dianhydride monomer and a diamine monomer in a solvent to obtain polyamic acid spinning solution; b) spinning the polyamic acid spinning solution to obtain polyamic acid fiber; c) carrying out imidization treatment on the polyamic acid fiber to obtain a polyimide fiber; the diamine monomer comprises a monomer A and a monomer B; the monomer A is selected from one or more of the structures of the formulas a-1 to a-8 shown above. According to the invention, a specific monomer A with a main chain containing an o-hydroxybenzophenone structural unit and a monomer B are matched to be used as diamine monomers, and are polymerized with a dianhydride monomer together to form polyamic acid, and the o-hydroxybenzophenone structural unit is introduced into a polyimide high-molecular main chain through a copolymerization reaction to prepare the intrinsic anti-ultraviolet radiation polyimide fiber material, so that the ultraviolet aging resistance of the polyimide fiber can be improved, and the good breaking strength can be maintained after long-time ultraviolet radiation.

Test results show that the polyimide fiber prepared by the invention has the breaking strength retention rate of over 99 percent after being irradiated by ultraviolet light for 2000 hours, and shows excellent ultraviolet aging resistance.

Detailed Description

b) spinning the polyamic acid spinning solution to obtain polyamic acid fiber;

the diamine monomer comprises a monomer A and a monomer B;

wherein the content of the first and second substances,

m is selected from-O-, -S-, or-NH-;

x is selected from-O-, -S-, or-NH-;

d is selected from-O-, -S-, or-NH-;

e is selected from-O-, -S-, -SO₂-、-CH₂-、-C(CF₃)₂-、-CO-、

According to the present invention, an aromatic dianhydride monomer and a diamine monomer are first polymerized in a solvent to obtain a polyamic acid spinning solution.

In the invention, the aromatic dianhydride monomer is preferably one or more of structures shown in formulas I-1 to I-3:

wherein A is selected from:

-S-、-O-、

the aromatic dianhydride monomer of the present invention is not particularly limited in its source, and may be available as a general commercial product or prepared according to a preparation method well known to those skilled in the art.

In the invention, the diamine monomer comprises a monomer A and a monomer B;

according to the invention, the monomer A is selected from one or more of structures shown in a formula a-1 to a formula a-8:

in the present invention, the monomer a can be obtained by the following preparation method:

a) carrying out etherification reaction on methoxyphenol and substituted nitrobenzene with the structure shown in the formula (I) in the presence of an alkaline catalyst to obtain a compound with the structure shown in the formula (II); the methoxyphenol is 3-methoxyphenol or 4-methoxyphenol;

in the formula (I), X is fluorine, chlorine,Bromine, iodine, mesyloxy, trifluoromethanesulfonyloxy or p-toluenesulfonyloxy, R₇And R₈Independently selected from hydrogen or nitro, and R₇And R₈Different;

in the formula (II), R₉And R₁₀Independently selected from hydrogen or methoxy, and R₉And R₁₀Different.

b) Carrying out Friedel-crafts acylation reaction on a compound with a structure shown in a formula (II) and nitrobenzoyl halide in the presence of a catalyst to obtain a compound with a structure shown in a formula (III); the nitrobenzoyl halide is 3-nitrobenzoyl halide or 4-nitrobenzoyl halide;

in the formula (III), R₁₁And R₁₂Independently selected from methoxy or

And R is₁₁And R₁₂In a different sense, R₁₃And R₁₄Independently selected from hydrogen or nitro, and R₁₃And R₁₄Different;

c) carrying out reduction reaction on the compound with the structure shown in the formula (III) to obtain a compound with the structure shown in the formula a-1-a-8;

in the formula (IV), R₁₅And R₁₆Independently selected from methoxy or

And R is₁₅And R₁₆Different;

then carrying out demethylation reaction on the compound with the structure shown in the formula (IV) to obtain an aromatic diamine monomer with the structure shown in the formula (V);

or the like, or, alternatively,

carrying out demethylation reaction on the compound with the structure shown in the formula (III) to obtain a compound with the structure shown in the formula (VI);

in the formula (VI), R₁₇And R₁₈Independently selected from hydroxy or

And R is₁₇And R₁₈Different;

then carrying out reduction reaction on the compound with the structure shown in the formula (VI) to obtain the aromatic diamine monomer with the structure shown in the formula a-1-a-8.

In the preparation method, firstly, methoxyphenol and substituted nitrobenzene with the structure shown in the formula (I) are subjected to etherification reaction in the presence of an alkaline catalyst to obtain a compound with the structure shown in the formula (II). In the present invention, the methoxyphenol is 3-methoxyphenol or 4-methoxyphenol. The source of the methoxyphenol in the present invention is not particularly limited, and commercially available products of the above-mentioned 3-methoxyphenol and 4-methoxyphenol, which are well known to those skilled in the art, may be used.

In the present invention, the structure represented by formula (I) specifically includes:

in the formula (I), X is fluorine, chlorine, bromine, iodine, methylsulfonyloxy, trifluoromethanesulfonyloxy or p-toluenesulfonyloxy, preferably chlorine, bromine or p-toluenesulfonyloxy; the above groups are easy to leave, which is beneficial to carrying out etherification reaction to obtain corresponding reaction products.

In the present invention, when the substituted nitrobenzene has the structure represented by the formula (I-1), the basic catalyst is preferably an alkali metal carbonate and/or an alkaline earth metal carbonate, more preferably sodium carbonate and/or potassium carbonate, and still more preferably potassium carbonate. When the substituted nitrobenzene has the structure shown in the formula (I-2), the basic catalyst is preferably co-catalyzed by carbonate and copper salt of alkali metal carbonate and/or alkaline earth metal; more preferably sodium carbonate and/or potassium carbonate, more preferably potassium carbonate; the cupric salt is preferably cuprous chloride, cuprous bromide or cuprous iodide, and more preferably cuprous iodide; wherein the dosage of the copper salt is 0.01 to 0.05 times of the molar weight of the substituted nitrobenzene. The source of the basic catalyst in the present invention is not particularly limited, and commercially available products known to those skilled in the art may be used.

In the invention, the molar ratio of the substituted nitrobenzene, the basic catalyst and the methoxyphenol is preferably (0.8-1.25): (1-1.5): 1, more preferably (0.9 to 1.1): (1.1-1.3): 1.

in a preferred embodiment of the present invention, X is chlorine or bromine, and on this basis, the etherification reaction is preferably carried out using a first reaction solvent; the first reaction solvent is preferably one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide. When the substituted nitrobenzene has the structure shown in the formula (I-1), dimethyl sulfoxide and/or N-methylpyrrolidone are more preferable; when the substituted nitrobenzene has the structure represented by the formula (I-2), N-dimethylformamide is more preferable. The source of the first reaction solvent is not particularly limited in the present invention, and commercially available ones of the above-mentioned high-boiling polar aprotic solvents known to those skilled in the art may be used. In the present invention, the mass of the first reaction solvent is preferably 1 to 3 times, more preferably 1.2 to 1.8 times the sum of the masses of the substituted nitrobenzene and the methoxyphenol.

In the present invention, the temperature of the etherification reaction is preferably 140 to 170 ℃, more preferably 150 to 165 ℃.

After the etherification reaction is completed, the present invention preferably further comprises:

and (3) carrying out primary post-treatment on a reaction product obtained after the etherification reaction to obtain a compound with a structure shown in a formula (II). In the present invention, the first post-treatment process preferably includes:

cooling a reaction product obtained after etherification reaction to 50-70 ℃, adding the reaction product into water with the volume 5-15 times of that of a first reaction solvent, separating out a crude product, filtering, washing with water, dissolving in dichloromethane, drying with anhydrous magnesium sulfate, concentrating the solvent to obtain the crude product again, and recrystallizing to obtain a refined product of the compound with the structure shown in the formula (II);

more preferably:

cooling a reaction product obtained after etherification reaction to 60 ℃, adding the reaction product into water with the volume 10 times that of the first reaction solvent, separating out a crude product, filtering, washing with water, dissolving in dichloromethane, drying with anhydrous magnesium sulfate, concentrating the solvent to obtain the crude product again, and recrystallizing to obtain a refined product of the compound with the structure shown in the formula (II).

In the present invention, the structure represented by formula (II) specifically includes:

after the compound with the structure shown in the formula (II) is obtained, the compound with the structure shown in the formula (II) and nitrobenzoyl halide are subjected to Friedel-crafts acylation reaction in the presence of a catalyst to obtain the compound with the structure shown in the formula (III). In the present invention, the nitrobenzoyl halide is 3-nitrobenzoyl halide or 4-nitrobenzoyl halide; among them, the acid halide is preferably an acid fluoride, an acid chloride, an acid bromide or an acid iodide, and more preferably an acid chloride or an acid bromide. The source of the nitrobenzoyl halide is not particularly limited in the present invention and commercially available products well known to those skilled in the art may be used.

In the present invention, the catalyst is preferably a lewis acid, more preferably aluminum trichloride. The source of the catalyst is not particularly limited in the present invention, and a commercially available Lewis acid known to those skilled in the art may be used.

In the invention, the molar ratio of the nitrobenzoyl halide, the catalyst and the compound with the structure shown in the formula (II) is preferably (1-2): (1.1-1.8): 1, more preferably (1.1 to 1.5): (1.2-1.5): 1.

in the present invention, the friedel-crafts acylation reaction is preferably carried out using a second reaction solvent; the second reaction solvent is preferably one or more of dichloromethane, trichloromethane, 1, 2-dichloroethane, carbon disulfide, carbon tetrachloride, chlorobenzene and nitrobenzene, and more preferably dichloromethane and/or 1, 2-dichloroethane. The source of the second reaction solvent in the present invention is not particularly limited, and commercially available products of the above-mentioned dichloromethane, chloroform, 1, 2-dichloroethane, carbon disulfide, carbon tetrachloride, chlorobenzene and nitrobenzene, which are well known to those skilled in the art, may be used. In the present invention, the mass of the second reaction solvent is preferably 3 to 8 times, more preferably 4.5 to 6 times the sum of the masses of the nitrobenzoyl halide, the catalyst and the compound having the structure represented by formula (II).

In the invention, the temperature of the Friedel-crafts acylation reaction is preferably 0-40 ℃, and more preferably 10-30 ℃; the time of the Friedel-crafts acylation reaction depends on specific reaction substrates and reaction conditions, the specific reaction time can be determined by tracking the reaction process through thin-layer chromatography in a laboratory, and the industrial preparation can be determined by tracking the reaction process through high performance liquid chromatography; meanwhile, the mixed solution obtained after the reaction for a certain time is slowly added into ice-hydrochloric acid for treatment, and the reaction termination can be realized.

In the present invention, after the friedel-crafts acylation reaction is completed, the present invention preferably further comprises:

and carrying out secondary post-treatment on a reaction product obtained after the Friedel-crafts acylation reaction to obtain a compound with a structure shown in a formula (III). In the present invention, the second post-treatment process preferably includes:

separating the reaction product obtained after the Friedel-crafts acylation reaction, drying the reaction product with anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing the crude product to obtain a refined product of the compound with the structure shown in the formula (III).

In the present invention, the structure represented by formula (III) specifically includes:

after the compound with the structure shown in the formula (III) is obtained, the compound with the structure shown in the formula (III) is subjected to reduction reaction to obtain a compound with the structure shown in the formula (IV); and then carrying out demethylation reaction on the compound with the structure shown in the formula (IV) to obtain the aromatic diamine monomer with the structure shown in the formulas a-1-a-8.

In the invention, stannous chloride is preferably adopted as a reducing agent in the reduction reaction; the present invention is not particularly limited in its origin. The invention adopts the reducing agent to carry out reduction reaction, has high reaction speed and simple operation process.

In the present invention, the molar ratio of the reducing agent to the compound having the structure represented by formula (III) is preferably (7 to 12): 1, more preferably (8-10): 1.

in the present invention, the reduction reaction preferably employs a solvent having a boiling point in the range of 50 ℃ to 100 ℃, more preferably methanol, ethanol, tetrahydrofuran, ethyl acetate, ethylene glycol dimethyl ether or 1, 4-dioxane, more preferably ethyl acetate or ethanol; the solvent adopted by the invention has low price and low toxicity. In the present invention, the mass ratio of the solvent having a boiling point in the range of 50 to 100 ℃ to the compound having the structure represented by the formula (III) is preferably (10 to 20): 1, more preferably (12-16): 1.

in the invention, the temperature of the reduction reaction is preferably 50-80 ℃, and more preferably 60-75 ℃; the time of the reduction reaction depends on specific reaction substrates and reaction conditions, the specific reaction time can be determined by tracking the reaction process through thin-layer chromatography in a laboratory, and the industrial preparation can be determined by tracking the reaction process through high performance liquid chromatography; meanwhile, the mixed solution obtained after the reaction is carried out for a certain time is cooled to room temperature, and the mixed solution is added into a saturated sodium carbonate solution to be neutralized to be alkaline, so that the reaction termination can be realized.

In the present invention, after the reduction reaction is completed, the present invention preferably further comprises:

and (3) carrying out third post-treatment on the reaction product obtained after the reduction reaction to obtain the compound with the structure shown in the formula (IV). In the present invention, the third post-treatment process preferably includes:

separating the reaction product obtained after the reduction reaction, drying the reaction product by using anhydrous sodium carbonate, concentrating the solvent to obtain a crude product, and recrystallizing the crude product to obtain a refined product of the compound with the structure shown in the formula (IV).

In the present invention, the structure represented by formula (IV) specifically includes:

in the present invention, the demethylation reaction preferably employs a hydrobromic acid-acetic acid system; the system has low cost, can selectively remove methyl in methoxyl adjacent to carbonyl, has simple and convenient operation, and can conveniently recycle hydrobromic acid and acetic acid. In the invention, the mass ratio of acetic acid to hydrobromic acid in the hydrobromic acid-acetic acid system is preferably (2-5): 1, more preferably (3-4): 1.

in the present invention, the molar ratio of hydrobromic acid to the compound having the structure represented by formula (IV) in the hydrobromic acid-acetic acid system is preferably (3-8): 1, more preferably (4-6): 1.

in the invention, the compound with the structure shown in the formula (IV) is preferably converted into a common strong acid salt before the demethylation reaction, and more preferably reacts with hydrochloric acid to generate hydrochloride.

In the invention, the temperature of the demethylation reaction is preferably 80-110 ℃, and more preferably 90-100 ℃; the time of the demethylation reaction depends on the specific reaction substrate and reaction conditions, and the present invention is not particularly limited thereto; meanwhile, the reaction termination can be realized by cooling the mixed solution obtained after the reaction for a certain time to room temperature.

In the present invention, after the demethylation reaction is completed, the present invention preferably further comprises:

and carrying out fourth post-treatment on the reaction product obtained after the demethylation reaction to obtain the aromatic diamine monomer with the structure shown in the formula a-1-a-8. In the present invention, the fourth post-treatment process is preferably specifically:

concentrating a reaction product obtained after the demethylation reaction to recover hydrobromic acid and acetic acid, neutralizing residues with a saturated sodium carbonate solution to be alkaline, extracting with dichloromethane, separating liquid, drying with anhydrous sodium carbonate, concentrating a solvent to obtain a crude product, and recrystallizing to obtain a refined product of the compound with the structure shown in the formula a-1-a-8.

Or the like, or, alternatively,

carrying out demethylation reaction on the compound with the structure shown in the formula (III) to obtain a compound with the structure shown in the formula (VI); then carrying out reduction reaction on the compound with the structure shown in the formula (VI) to obtain the aromatic diamine monomer with the structure shown in the formula a-1-a-8.

in the present invention, the molar ratio of hydrobromic acid to the compound having the structure represented by formula (III) in the hydrobromic acid-acetic acid system is preferably (3-8): 1, more preferably (4-6): 1.

and (3) carrying out fifth post-treatment on the reaction product obtained after the demethylation reaction to obtain the compound with the structure shown in the formula (VI). In the present invention, the fifth post-treatment process is preferably specifically:

concentrating a reaction product obtained after the demethylation reaction to recover hydrobromic acid and acetic acid, dissolving residues with dichloromethane, neutralizing a saturated sodium carbonate solution to be alkaline, separating liquid, drying with anhydrous magnesium sulfate, concentrating a solvent to obtain a crude product, and recrystallizing to obtain a refined product of the compound with the structure shown in the formula (VI).

In the present invention, the structure represented by formula (VI) specifically includes:

In the present invention, the molar ratio of the reducing agent to the compound having the structure represented by formula (VI) is preferably (7 to 12): 1, more preferably (8-10): 1.

in the present invention, the reduction reaction preferably employs a solvent having a boiling point in the range of 50 ℃ to 100 ℃, more preferably methanol, ethanol, tetrahydrofuran, ethyl acetate, ethylene glycol dimethyl ether or 1, 4-dioxane, more preferably ethyl acetate or ethanol; the solvent adopted by the invention has low price and low toxicity. In the present invention, the mass ratio of the solvent having a boiling point in the range of 50 to 100 ℃ to the compound having a structure represented by the formula (VI) is preferably (10 to 20): 1, more preferably (12-16): 1.

and carrying out sixth post-treatment on the reaction product obtained after the reduction reaction to obtain the aromatic diamine monomer with the structure shown in the formulas a-1-a-8. In the present invention, the sixth post-treatment process preferably includes: separating the reaction product obtained after the reduction reaction, drying the reaction product by using anhydrous sodium carbonate, concentrating the solvent to obtain a crude product, and recrystallizing the crude product to obtain a refined product of the structural compound shown in the formula a-1-a-8. In the present invention, when the compound having the structure represented by formula (III) is not dissolved in the reaction solvent for the demethylation reaction, a preparation process of performing the reduction reaction first and then performing the demethylation reaction is employed.

According to the invention, the monomer B is selected from one or more of structures shown in formulas B-1 to B-7:

wherein the content of the first and second substances,

m is selected from-O-, -S-, or-NH-;

x is selected from-O-, -S-, or-NH-;

d is selected from-O-, -S-, or-NH-;

e is selected from-O-, -S-, -SO₂-、-CH₂-、-C(CF₃)₂-、-CO-、

The source of the monomer B is not particularly limited in the present invention, and it may be a general commercial product or prepared according to a preparation method well known to those skilled in the art.

In some embodiments of the invention, the monomer feed used is specifically as follows:

3,4 '-triphenyl diether dianhydride with a structure shown in a formula I-3, 4' -biphenyl dianhydride with a structure shown in a formula I-2, p-phenylenediamine with a structure shown in a formula b-1, 2, 5-bis (4-aminophenyl) pyrimidine with a structure shown in a formula b-4 and diamine monomer with a structure shown in a formula a-1;

or

3,3',4,4' -benzophenone tetracarboxylic dianhydride with the structure shown in formula I-3, 4,4' -triphenyl diether dianhydride with the structure shown in formula I-3, m-phenylenediamine with the structure shown in formula b-1, 2, 4-di (4-aminophenyl) pyrimidine with the structure shown in formula b-4 and diamine monomers with the structures shown in formula a-2 and formula a-6;

or

Pyromellitic dianhydride with a structure shown in a formula I-1, 4' -biphenyl dianhydride with a structure shown in a formula I-2, 2- (4-aminophenyl) -5-aminobenzimidazole with a structure shown in a formula b-5 and diamine monomer with a structure shown in a formula a-3;

or

Hexafluoro dianhydride and 3,3',4,4' -diphenyl ether tetracarboxylic dianhydride with the structure shown in formula I-3, 5-amino-2- (4-aminobenzene) benzoxazole with the structure shown in formula b-5, 2 '-bis (trifluoromethyl) -4, 4' -biphenyl diamine with the structure shown in formula b-2 and diamine monomers with the structures shown in formula a-4 and formula a-8;

or

A first dianhydride monomer and a second dianhydride monomer with a structure shown in a formula I-3, 4' -diaminodiphenyl ether with a structure shown in a formula b-4 and diamine monomers with structures shown in formulas a-5 and a-7;

wherein the structures of the first dianhydride monomer and the second dianhydride monomer shown in I-3 are respectively as follows:

a first anhydride monomer, a second anhydride monomer,

a second dianhydride monomer;

or

Pyromellitic dianhydride with a structure shown in a formula I-1, 4' -biphenyl dianhydride with a structure shown in a formula I-2, a diamine monomer shown in a formula b-7, a diamine monomer shown in a formula b-6 and a diamine monomer shown in a formula a-8;

wherein the structures of the diamine monomer shown in the formula b-7 and the diamine monomer shown in the formula b-6 are specifically as follows:

in the present invention, the molar ratio of the aromatic dianhydride monomer to the diamine monomer is preferably 1: (0.95 to 1.20).

In the present invention, in the diamine monomer, the total molar ratio of the monomer a to the diamine monomer is preferably 0.1% to 99%, and more preferably 3% to 70%. In some embodiments of the invention, the molar ratio of monomer a is 10%, 8%, 6.67, 66%.

In the present invention, the solvent is preferably a polar aprotic solvent. The polar aprotic solvent is selected from one or more of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone.

In the invention, the polymerization temperature is preferably-20-50 ℃; in specific examples, -10 ℃, -15 ℃,5 ℃, 10 ℃, 20 ℃ or 30 ℃. The polymerization time is preferably 4 to 60 hours; in specific embodiments 6 hours, 12 hours, 15 hours, 24 hours, or 30 hours.

In the present invention, it is preferable to further perform filtration and vacuum defoaming after the polymerization. The present invention is not particularly limited in the manner and conditions of the filtration and vacuum defoaming, and may be carried out according to a conventional filtration and defoaming treatment well known to those skilled in the art. And obtaining the polyamic acid spinning solution after the filtration and vacuum defoaming treatment. In the present invention, the concentration of the polyamic acid spinning solution is preferably 5 wt% to 35 wt%.

According to the present invention, after a polyamic acid spinning dope is obtained, the polyamic acid spinning dope is spun to obtain a polyamic acid fiber.

In the present invention, the spinning is preferably dry-jet wet spinning, wet spinning or dry spinning.

The dry-jet wet spinning method comprises the following steps: and extruding the polyamic acid spinning solution from a spinneret orifice, allowing the polyamic acid spinning solution to enter a coagulating bath for forming after passing through an air layer, and washing and drying to obtain the polyamic acid fiber.

Wherein the height of the air layer is preferably 10-100 mm; in particular embodiments, the air layer height is 5mm, 15mm, 20mm, or 30 mm. Wherein the aperture of the spinneret orifice is preferably phi 0.05 mm-phi 0.2 mm; the number of holes of the spinneret plate for spinning is preferably 20-5000 holes. The spinning jet-draw ratio is preferably 1.5-7.0 times, and the spinning speed is preferably 10-100 m/min.

The coagulation bath is preferably a mixture of an organic substance and water. The organic matter is preferably one or more of ethanol, glycol, butanol, acetone, butanone, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone. The volume ratio of the organic matter to the water is preferably 1 to (3-10).

Wherein the drying temperature is preferably 90-200 ℃. In a specific embodiment, drying is carried out in a heat shaft or hot-roll drying. The dry atmosphere is preferably air or an inert gas. The kind of the inert gas is not particularly limited, and may be a conventional inert gas known to those skilled in the art, such as nitrogen, helium, argon, or the like.

The wet spinning comprises the following steps: and extruding the polyamic acid spinning solution from a spinneret orifice, directly entering a coagulating bath for forming, and then washing and drying to obtain the polyamic acid fiber.

Wherein the aperture of the spinneret orifice is preferably phi 0.02 mm-phi 0.14 mm; the number of holes of the spinneret plate for spinning is preferably 30-10000. The jet-draw ratio of the spinning is preferably 1.1-4.5 times, and the spinning speed is preferably 4-80 m/min.

The term "directly" as used herein means directly entering the coagulation bath after extrusion without passing through other medium such as an air layer. The coagulation bath is preferably a mixture of organic matter and water. The organic substance is preferably ethanol, ethylene glycol, butanol, acetone, butanone, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide or N-methylpyrrolidone. The volume ratio of the organic matter to the water is preferably 1 to (3-10).

The dry spinning preferably comprises: and extruding the polyamic acid spinning solution from a spinneret orifice, and drying to obtain the polyamic acid fiber.

Wherein the aperture of the spinneret orifice is preferably phi 0.05 mm-phi 0.2 mm; the number of holes of the spinneret plate for spinning is preferably 20-5000 holes. The spinning jet-draw ratio is preferably 1.5-7.0 times, and the spinning speed is preferably 80-150 m/min.

Wherein the drying temperature is preferably 150-350 ℃, and more preferably 150-300 ℃. In one embodiment, the mixture is dried in a hot gas shaft to remove the solvent and form the product. After the above spinning treatment, a polyamic acid fiber is obtained.

According to the present invention, after a polyamic acid fiber is obtained, the polyamic acid fiber is imidized to obtain a polyimide fiber.

The imidization treatment in the present invention is preferably a thermal imidization treatment. The thermal imidization treatment is preferably a gradient temperature-rising heat treatment or a constant-temperature heat treatment.

The conditions of the gradient temperature-rising heat treatment are preferably as follows: the initial temperature is 30-50 ℃, and the end point temperature is 280-450 ℃; in some embodiments, from 50 ℃ to 400 ℃, from 50 ℃ to 420 ℃, from 50 ℃ to 450 ℃, or from 50 ℃ to 350 ℃. The heating rate is 1-30 ℃/min; in some embodiments, 5 deg.C/min, 10 deg.C/min, 15 deg.C/min, 20 deg.C/min, or 25 deg.C/min. And (5) keeping the temperature for 5-60 min after the temperature is raised to the end point temperature.

The conditions of the constant-temperature heat treatment are preferably as follows: the heat treatment temperature is 280-500 ℃, and the constant temperature is kept for 5-60 min.

In the present invention, it is preferable to further perform a heat-drawing treatment after the imidization treatment. In the invention, the temperature of the hot drawing treatment is preferably 350-600 ℃; in some embodiments, 490 ℃, 510 ℃, 550 ℃, or 580 ℃. The multiplying power of the hot drawing is preferably 1.0-6.0 times; in some embodiments, 1.3 times, 1.5 times, 2.1 times, 2.8 times, 3.0 times, or 4.0 times. The thermal drawing is preferably carried out under an inert gas atmosphere. The inert gas is not particularly limited in the present invention, and may be any conventional inert gas known to those skilled in the art, such as nitrogen, helium, argon, or the like; preferably nitrogen or argon. And (3) obtaining the polyimide fiber after the hot drawing treatment.

According to the preparation method provided by the invention, the monomer A and the monomer B, the main chain of which contains a specific o-hydroxybenzophenone structural unit, are matched to serve as diamine monomers and are polymerized with dianhydride monomers together to form polyamic acid, and the o-hydroxybenzophenone structural unit is introduced into the main chain of the polyimide fiber molecule through copolymerization reaction, so that the ultraviolet aging resistance of polyimide can be improved, the good breaking strength can be maintained after long-time ultraviolet irradiation, and the preparation method can be applied to the fields of aerospace, weaponry, transportation and the like.

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims. The following examples, starting materials which are commercially available or prepared in a conventional manner known to those skilled in the art, in which monomer A is prepared in accordance with the preparation of the starting materials described below.

Raw materials preparation example 1 preparation of monomer A-diamine represented by the formula a-1

(1) 69.52 g (0.56 mol) of 3-methoxyphenol, 88.23 g (0.56 mol) of p-nitrochlorobenzene, 85.14 g (0.616 mol) of potassium carbonate and 200 g of dimethyl sulfoxide are sequentially added into a reactor and heated to 160 ℃ for reaction for 6 hours; cooling to 60 ℃, adding the mixture into 2000 ml of water, separating out a crude product, filtering, washing with water, dissolving in dichloromethane, drying with anhydrous magnesium sulfate, concentrating the solvent to obtain the crude product again, and recrystallizing to obtain 114.23 g of a refined product of a structural compound (II-1) shown in a formula (II); the yield thereof was found to be 83.2%.

The obtained compound (II-1) with the structure shown in the formula (II) is characterized by utilizing nuclear magnetic resonance, and the obtained hydrogen spectrum result of the nuclear magnetic resonance is as follows:¹H NMR(400MHz，DMSO)δ＝8.280–8.205(m，2H)，7.389(t，J＝8.2Hz，1H)，7.170–7.095(m，2H)，6.875(dd，J＝8.3Hz，2.2Hz，1H)，6.776(t，J＝2.2Hz，1H)，6.731(dd，J＝8.0Hz，2.0Hz，1H)，3.765(s，3H)。

(2) 89.07 g (0.48 mol) of 4-nitrobenzoyl chloride, 69.34 g (0.52 mol) of aluminum trichloride, 1000 ml of dichloromethane and 105.45 g (0.43 mol) of a structural compound (II-1) shown in the formula (II) are sequentially added into a reactor and stirred for reaction for 18 hours at the temperature of 20 ℃; then slowly adding the mixture into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 90.43 g of a refined product of a structural compound (III-1) shown in a formula (III); the yield thereof was found to be 53.3%.

The obtained compound (III-1) with the structure shown in the formula (III) is characterized by utilizing nuclear magnetic resonance, and the obtained hydrogen spectrum result of the nuclear magnetic resonance is as follows:¹H NMR(400MHz，DMSO)δ＝8.325(dd，J＝12.6Hz，9.0Hz，4H)，7.942(d，J＝8.7Hz，2H)，7.575(d，J＝8.4Hz，1H)，7.320(d，J＝9.2Hz，2H)，7.087(d，J＝1.8Hz，1H)，6.871(dd，J＝8.3Hz，1.9Hz，1H)，3.643(s，3H)。

(3) 23.66 g (0.06 mol) of the structural compound (III-1) shown in the formula (III), 121.85 g (0.54 mol) of stannous chloride dihydrate and 350 ml of ethyl acetate are sequentially added into a reactor and stirred for reaction for 3 hours at 70 ℃; cooling to room temperature, adding into saturated sodium carbonate solution to neutralize to alkalinity, separating liquid, drying with anhydrous sodium carbonate, concentrating solvent to obtain crude product, and recrystallizing to obtain 15.78 g refined product of compound (IV-1) with structure shown in formula (IV); the yield thereof was found to be 78.7%.

The obtained compound (IV-1) with the structure shown in the formula (IV) is characterized by using nuclear magnetic resonance, and the obtained hydrogen spectrum result of the nuclear magnetic resonance is as follows:¹H NMR(400MHz，DMSO)δ＝7.410(d，J＝8.4Hz，2H)，7.100(d，J＝8.3Hz，1H)，6.838(d，J＝8.4Hz，2H)，6.666(s，1H)，6.621(d，J＝8.4Hz，2H)，6.535(d，J＝8.4Hz，2H)，6.375(d，J＝8.2Hz，1H)，6.069(s，2H)，5.009(s，2H)，3.624(s，3H)。

(4) 44 g (0.108 mol) of a hydrochloride of the structural compound (IV-1) represented by the formula (IV), 109.24 g (40%, 0.54 mol) of hydrobromic acid and 330 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 84 hours; after concentrating and recovering hydrobromic acid and acetic acid, neutralizing residues with a saturated sodium carbonate solution to be alkaline, extracting with dichloromethane, separating liquid, drying with anhydrous sodium carbonate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 29.75 g of a refined product of a compound with a structure shown in a formula a-1; the yield thereof was found to be 86.0%.

The obtained compound with the structure shown in the formula a-1 is characterized by utilizing nuclear magnetic resonance, and the obtained hydrogen spectrum result of the nuclear magnetic resonance is as follows:¹H NMR(400MHz，DMSO)δ＝11.440(s，1H)，7.462(d，J＝8.2Hz，2H)，7.412(d，J＝8.7Hz，1H)，6.832(d，J＝8.3Hz，2H)，6.606(dd，J＝13.3Hz，8.5Hz，4H)，6.417(d，J＝8.7Hz，1H)，6.315(s，1H)，6.090(s，2H)，5.069(s，2H)。

raw materials preparation example 2 preparation of monomer A-diamine represented by the formula a-2

(1) Adding 62.07 g (0.50 mol) of 3-methoxyphenol, 101.0 g (0.50 mol) of m-bromonitrobenzene, 4.76 g (0.025 mol) of cuprous iodide, 76.02 g (0.55 mol) of potassium carbonate and 200 g of N, N-dimethylformamide into a reaction bottle in sequence, and heating the reaction system to 150 ℃ under the protection of nitrogen to react for 12 hours; cooling to 60 ℃, adding the mixture into 2000 ml of water, separating out a crude product, filtering, washing with water, dissolving in dichloromethane, drying with anhydrous magnesium sulfate, concentrating a solvent, and purifying to obtain 90.59 g of a refined product of a compound (II-2) with a structure shown in a formula (II); the yield thereof was found to be 73.9%.

(2) 89.07 g (0.48 mol) of 4-nitrobenzoyl chloride, 69.34 g (0.52 mol) of aluminum trichloride, 1000 ml of dichloromethane and 105.45 g (0.43 mol) of a compound (II-2) with a structure shown in a formula (II) are sequentially added into a reactor and stirred for reaction for 18 hours at the temperature of 20 ℃; then slowly adding the crude product into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 96.56 g of a refined product of a structural compound (III-2) shown in a formula (III); the yield thereof was found to be 56.9%.

(3) 23.66 g (0.06 mol) of the structural compound (III-2) shown in the formula (III), 121.85 g (0.54 mol) of stannous chloride dihydrate and 350 ml of ethyl acetate are sequentially added into a reactor and stirred for reaction for 3 hours at 70 ℃; cooling to room temperature, adding into saturated sodium carbonate solution to neutralize to alkalinity, separating liquid, drying with anhydrous sodium carbonate, concentrating solvent to obtain crude product, and recrystallizing to obtain 14.23 g refined product of compound (IV-2) with structure shown in formula (IV); the yield thereof was found to be 71.0%.

(4) 44 g (0.108 mol) of a hydrochloride of the structural compound (IV-2) represented by the formula (IV), 109.24 g (40%, 0.54 mol) of hydrobromic acid and 330 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 84 hours; after concentrating and recovering hydrobromic acid and acetic acid, neutralizing residues with a saturated sodium carbonate solution to be alkaline, extracting with dichloromethane, separating liquid, drying with anhydrous sodium carbonate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 28.37 g of a refined product of a compound with a structure shown in a formula a-2; the yield thereof was found to be 82.0%.

Raw materials preparation example 3 preparation of monomer A-diamine represented by the formula a-3

(1) Referring to step (1) of raw material preparation example 1, a purified product of the compound (II-1) having a structure represented by the formula (II) was obtained.

(2) 18.56 g (0.1 mol) of 3-nitrobenzoyl chloride, 14.67 g (0.11 mol) of aluminum trichloride, 250 g of 1, 2-dichloroethane and 22.07 g (0.09 mol) of the compound (II-1) having the structure represented by the formula (II) were sequentially added to a reactor, and the reaction was stirred at 20 ℃ for 30 hours; then slowly adding the crude product into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 21.02 g of a refined product of a structural compound (III-3) shown in a formula (III); the yield thereof was found to be 59.2%.

The obtained compound (III-3) with the structure shown in the formula (III) is characterized by utilizing nuclear magnetic resonance, and the obtained hydrogen spectrum result of the nuclear magnetic resonance is as follows:¹H NMR(400MHz，DMSO)δ＝8.490(d，J＝8.0Hz，1H)，8.425(s，1H)，8.312(d，J＝9.1Hz，2H)，8.129(d，J＝7.6Hz，1H)，7.832(t，J＝7.9Hz，1H)，7.579(d，J＝8.3Hz，1H)，7.330(d，J＝9.0Hz，2H)，7.104(s，1H)，6.881(d，J＝8.3Hz，1H)，3.660(s，3H)。

(3) 39.43 g (0.1 mol) of the structural compound (III-3) represented by the formula (III), 101.15 g (40%, 0.5 mol) of hydrobromic acid and 350 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 48 hours; after hydrobromic acid and acetic acid were recovered by concentration, the residue was dissolved in methylene chloride, neutralized to alkaline with a saturated sodium carbonate solution, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 33.65 g of a purified product of the structural compound (VI-3) represented by the formula (VI), in a yield of 88.5%.

The obtained compound (VI-3) with the structure shown in the formula (VI) is characterized by utilizing nuclear magnetic resonance, and the obtained hydrogen spectrum result of the nuclear magnetic resonance is as follows:¹H NMR(400MHz，DMSO)δ＝10.889(s，1H)，8.520–8.400(m，2H)，8.316(d，J＝9.0Hz，2H)，8.149(d，J＝7.6Hz，1H)，7.834(t，J＝7.9Hz，1H)，7.569(d，J＝8.5Hz，1H)，7.350(d，J＝9.0Hz，2H)，6.748(d，J＝8.5Hz，1H)，6.701(s，1H)。

(4) adding 45.64 g (0.12 mol) of a structural compound (VI-3) shown in a formula (VI), 243.7 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethyl acetate into a reactor in sequence, and stirring and reacting for 3 hours at 70 ℃; cooling to room temperature, adding into saturated sodium carbonate solution to neutralize to alkalinity, separating liquid, drying with anhydrous sodium carbonate, concentrating solvent to obtain crude product, and recrystallizing to obtain 32.59 g refined product of the structural compound shown in formula a-3; the yield thereof was found to be 84.8%.

The obtained compound with the structure shown in the formula a-3 is characterized by utilizing nuclear magnetic resonance, and the obtained hydrogen spectrum result of the nuclear magnetic resonance is as follows:¹H NMR(400MHz，DMSO)δ＝11.727(s，1H)，7.466(d，J＝8.8Hz，1H)，7.149(t，J＝7.8Hz，1H)，6.868-6.810(m，3H)，6.806–6.723(m，2H)，6.628(d，J＝8.7Hz，2H)，6.452(dd，J＝8.8Hz，2.3Hz，1H)，6.318(d，J＝2.3Hz，1H)，5.342(s，2H)，5.136(s，2H)。

preparation of starting Material example 4 preparation of monomer A-diamine represented by the formula a-4

(1) Referring to step (1) of raw material preparation example 2, a purified product of the compound (II-2) having a structure represented by the formula (II) was obtained.

(2) 18.56 g (0.1 mol) of 3-nitrobenzoyl chloride, 14.67 g (0.11 mol) of aluminum trichloride, 250 g of 1, 2-dichloroethane and 22.07 g (0.09 mol) of the compound (II-2) having the structure represented by the formula (II) were sequentially added to a reactor, and the reaction was stirred at 20 ℃ for 30 hours; then slowly adding the crude product into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 22.98 g of a refined product of a structural compound (III-4) shown in a formula (III); the yield thereof was found to be 64.7%.

(3) 39.43 g (0.1 mol) of the structural compound (III-4) represented by the formula (III), 101.15 g (40%, 0.5 mol) of hydrobromic acid and 350 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 48 hours; after concentrating and recovering hydrobromic acid and acetic acid, dissolving the residue with dichloromethane, neutralizing with saturated sodium carbonate solution to alkalinity, separating liquid, drying with anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 32.54 g of a refined product of a compound (VI-4) with a structure shown in a formula (VI); the yield thereof was found to be 85.6%.

(4) Adding 45.64 g (0.12 mol) of a structural compound (VI-4) shown in a formula (VI), 243.7 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethyl acetate into a reactor in sequence, and stirring and reacting for 3 hours at 70 ℃; cooling to room temperature, adding into saturated sodium carbonate solution to neutralize to alkalinity, separating liquid, drying with anhydrous sodium carbonate, concentrating solvent to obtain crude product, and recrystallizing to obtain 33.72 g of refined product of the structural compound shown in formula a-4; the yield thereof was found to be 87.7%.

Preparation of starting Material example 5 preparation of monomer A-diamine represented by the formula a-5

(1) 69.52 g (0.56 mol) of 4-methoxyphenol, 88.23 g (0.56 mol) of p-nitrochlorobenzene, 85.14 g (0.616 mol) of potassium carbonate and 200 g of dimethyl sulfoxide are sequentially added into a reactor and heated to 160 ℃ for reaction for 6 hours; cooling to 60 ℃, adding the mixture into 2000 ml of water, separating out a crude product, filtering, washing with water, dissolving in dichloromethane, drying with anhydrous magnesium sulfate, concentrating the solvent to obtain the crude product again, and recrystallizing to obtain 117.56 g of a refined product of a structural compound (II-3) shown in a formula (II); the yield thereof was found to be 85.6%.

(2) 89.07 g (0.48 mol) of 4-nitrobenzoyl chloride, 69.34 g (0.52 mol) of aluminum trichloride, 1000 ml of dichloromethane and 105.45 g (0.43 mol) of a compound (II-3) with a structure shown in a formula (II) are sequentially added into a reactor and stirred for reaction for 15 hours at the temperature of 30 ℃; then slowly adding the mixture into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 84.66 g of a refined product of a structural compound (III-5) shown in a formula (III); the yield thereof was found to be 49.9%.

(3) 23.66 g (0.06 mol) of the structural compound (III-5) shown in the formula (III), 121.85 g (0.54 mol) of stannous chloride dihydrate and 350 ml of ethyl acetate are sequentially added into a reactor and stirred for reaction for 3 hours at 70 ℃; after cooling to room temperature, the solution was neutralized to alkaline by adding a saturated sodium carbonate solution, separated, dried with anhydrous sodium carbonate, and concentrated in the solvent to obtain a crude product, which was recrystallized to obtain 17.72 g of a purified product of the structural compound (IV-5) represented by the formula (IV) in a yield of 88.4%.

(4) 44 g (0.108 mol) of a hydrochloride of the structural compound (IV-5) represented by the formula (IV), 109.24 g (40%, 0.54 mol) of hydrobromic acid and 330 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 84 hours; after concentrating and recycling hydrobromic acid and acetic acid, neutralizing residues with a saturated sodium carbonate solution to be alkaline, extracting with dichloromethane, separating liquid, drying with anhydrous sodium carbonate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 30.21 g of a refined product of a compound with a structure shown in a formula a-5; the yield thereof was found to be 87.3%.

Preparation of starting Material example 6 preparation of monomer A-diamine represented by the formula a-6

(1) Adding 62.07 g (0.50 mol) of 4-methoxyphenol, 101.0 g (0.50 mol) of m-bromonitrobenzene, 4.76 g (0.025 mol) of cuprous iodide, 76.02 g (0.55 mol) of potassium carbonate and 200 g of N, N-dimethylformamide into a reaction bottle in sequence, and heating the reaction system to 150 ℃ under the protection of nitrogen to react for 12 hours; cooling to 60 ℃, adding the mixture into 2000 ml of water, separating out a crude product, filtering, washing with water, dissolving in dichloromethane, drying with anhydrous magnesium sulfate, concentrating a solvent, and purifying to obtain 92.12 g of a refined product of a compound (II-4) with a structure shown in a formula (II); the yield thereof was found to be 75.1%.

(2) 89.07 g (0.48 mol) of 4-nitrobenzoyl chloride, 69.34 g (0.52 mol) of aluminum trichloride, 1000 ml of dichloromethane and 105.45 g (0.43 mol) of a structural compound (II-4) shown in the formula (II) are sequentially added into a reactor, and stirred and reacted for 15 hours at the temperature of 30 ℃; then slowly adding the crude product into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 87.63 g of a refined product of a structural compound (III-6) shown in a formula (III); the yield thereof was found to be 51.7%.

(3) 23.66 g (0.06 mol) of the structural compound (III-6) shown in the formula (III), 121.85 g (0.54 mol) of stannous chloride dihydrate and 350 ml of ethyl acetate are sequentially added into a reactor and stirred for reaction for 3 hours at 70 ℃; cooling to room temperature, adding into saturated sodium carbonate solution to neutralize to alkalinity, separating liquid, drying with anhydrous sodium carbonate, concentrating solvent to obtain crude product, and recrystallizing to obtain 16.36 g refined product of compound (IV-6) with structure shown in formula (IV); the yield thereof was found to be 81.6%.

(4) 44 g (0.108 mol) of a hydrochloride of the structural compound (IV-6) represented by the formula (IV), 109.24 g (40%, 0.54 mol) of hydrobromic acid and 330 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 84 hours; after concentrating and recycling hydrobromic acid and acetic acid, neutralizing residues with a saturated sodium carbonate solution to be alkaline, extracting with dichloromethane, separating liquid, drying with anhydrous sodium carbonate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 28.62 g of a refined product of a compound with a structure shown in a formula a-6; the yield thereof was found to be 82.7%.

Preparation of starting Material example 7 preparation of monomer A-diamine represented by the formula a-7

(1) Referring to step (1) of raw material preparation example 3, a purified product of the compound (II-3) having a structure represented by the formula (II) was obtained.

(2) 18.56 g (0.1 mol) of 3-nitrobenzoyl chloride, 14.67 g (0.11 mol) of aluminum trichloride, 250 g of 1, 2-dichloroethane and 22.07 g (0.09 mol) of the compound (II-3) having the structure represented by the formula (II) were sequentially added to a reactor, and the reaction was stirred at 30 ℃ for 18 hours; then slowly adding the crude product into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 22.45 g of a refined product of a structural compound (III-7) shown in a formula (III); the yield thereof was found to be 64%.

(3) 39.43 g (0.1 mol) of the structural compound (III-7) represented by the formula (III), 101.15 g (40%, 0.5 mol) of hydrobromic acid and 350 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 48 hours; after hydrobromic acid and acetic acid were recovered by concentration, the residue was dissolved in methylene chloride, neutralized to alkaline with a saturated sodium carbonate solution, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 34.22 g of a purified product of the structural compound (VI-7) represented by the formula (VI) in a yield of 90%.

(4) Adding 45.64 g (0.12 mol) of a structural compound (VI-7) shown in a formula (VI), 243.7 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethyl acetate into a reactor in sequence, and stirring and reacting for 3 hours at 70 ℃; cooling to room temperature, adding into saturated sodium carbonate solution to neutralize to alkalinity, separating liquid, drying with anhydrous sodium carbonate, concentrating solvent to obtain crude product, and recrystallizing to obtain 33.05 g of refined product of the structural compound shown in formula a-7; the yield thereof was found to be 86%.

Preparation of starting Material example 8 preparation of monomer A-diamine represented by the formula a-8

(1) Referring to step (1) of raw material preparation example 6, a purified product of the compound (II-4) having a structure represented by the formula (II) was obtained.

(2) 18.56 g (0.1 mol) of 3-nitrobenzoyl chloride, 14.67 g (0.11 mol) of aluminum trichloride, 250 g of 1, 2-dichloroethane and 22.07 g (0.09 mol) of the structural compound (II-4) represented by the formula (II) were sequentially added to a reactor, and the reaction was stirred at 30 ℃ for 18 hours; then slowly adding the mixture into ice-hydrochloric acid for treatment, separating liquid, drying by anhydrous magnesium sulfate, concentrating the solvent to obtain a crude product, and recrystallizing to obtain 20.78 g of a refined product of a structural compound (III-8) shown in a formula (III); the yield thereof was found to be 59.2%.

(3) 39.43 g (0.1 mol) of the structural compound (III-8) represented by the formula (III), 101.15 g (40%, 0.5 mol) of hydrobromic acid and 350 g of acetic acid were successively charged into a reactor, and the reaction was stirred at 100 ℃ for 48 hours; after hydrobromic acid and acetic acid were recovered by concentration, the residue was dissolved in methylene chloride, neutralized to alkaline with a saturated sodium carbonate solution, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 32.03 g of a purified product of the structural compound (VI-8) represented by the formula (VI), with a yield of 84.2%.

(4) Adding 45.64 g (0.12 mol) of a structural compound (VI-8) shown in a formula (VI), 243.7 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethyl acetate into a reactor in sequence, and stirring and reacting for 3 hours at 70 ℃; cooling to room temperature, adding into saturated sodium carbonate solution to neutralize to alkalinity, separating liquid, drying with anhydrous sodium carbonate, concentrating solvent to obtain crude product, and recrystallizing to obtain 31.14 g refined product of the structural compound shown in formula a-8; the yield thereof was found to be 81.0%.

Example 1

S1, 64.89 g (0.600 mol) of p-phenylenediamine, 196.74 g (0.750 mol) of 2, 5-bis (4-aminophenyl) pyrimidine and 48.05 g (0.150 mol) of diamine monomer a-1 are dissolved in 6300 ml of N-methylpyrrolidone, 397.20 g (1.350 mol) of 4,4 '-biphenyl dianhydride and 60.35 g (0.150 mol) of 3,4' -triphenyl diether dianhydride are added under stirring at 10 ℃ and polymerization is carried out for 15 hours while maintaining the temperature at 10 ℃ to obtain a viscous polyamic acid solution, and the solution is filtered and defoamed in vacuum to be used as a spinning slurry.

S2, spinning and forming by a dry-jet wet method: and (2) accurately metering the spinning slurry at normal temperature by using a metering pump, extruding the spinning slurry from a spinneret orifice, and entering the spinning solution into a spinning machine with the volume ratio of 1:4, washing with water in a coagulating bath of N-methyl pyrrolidone and water, and drying by a hot nitrogen channel to obtain the polyamic acid fiber. Wherein the spinneret plate has 100 holes, the aperture is phi 0.15mm, the spray-draw ratio is 2.0 times, the spinning speed is 40m/min, and the height of the air layer is 5 mm.

And S3, performing gradient heating thermal imidization treatment on the polyamic acid fiber in a vacuum environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-400 ℃, and the heating rate is 10 ℃/min.

And S4, drafting the obtained polyimide fiber by 2.1 times at 490 ℃ in a nitrogen environment to obtain the polyimide finished fiber.

Example 2

S1, 49.74 g (0.460 mol) m-phenylenediamine, 120.66 g (0.460 mol) 2, 4-bis (4-aminophenyl) pyrimidine, 12.82 g (0.040 mol) diamine monomer a-2 and 12.82 g (0.040 mol) diamine monomer a-6 are dissolved in 3400 ml N, N ' -dimethylformamide, 290.00 g (0.900 mol) 3,3',4,4' -benzophenone tetracarboxylic dianhydride and 32.18 g (0.080 mol) 3,3',4,4' -triphenyl diether dianhydride are added under stirring at 5 ℃ and polymerized for 12 hours while maintaining at 5 ℃ to obtain a viscous polyamic acid solution which is filtered and vacuum defoamed to be used as a spinning slurry.

S2, spinning and forming by a dry-jet wet method: and (2) accurately metering the spinning slurry at normal temperature by using a metering pump, extruding the spinning slurry from a spinneret orifice, and entering the spinning solution into a spinning machine with the volume ratio of 1: 3, washing with water in a coagulating bath of ethylene glycol and water, and drying by a hot nitrogen channel to obtain the polyamic acid fiber. Wherein the spinneret plate has 300 holes, the aperture is phi 0.18mm, the spray-draw ratio is 4.0 times, the spinning speed is 80m/min, and the height of the air layer is 20 mm.

And S3, performing gradient heating thermal imidization treatment on the polyamic acid fiber in a nitrogen environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-420 ℃, and the heating rate is 20 ℃/min.

S4, drafting the obtained polyimide fiber by 1.5 times at 490 ℃ in a nitrogen environment to obtain the polyimide finished product fiber.

Example 3

S1, 313.96 g (1.400 mol) of 2- (4-aminophenyl) -5-aminobenzimidazole and 32.03 g (0.100 mol) of diamine monomer a-3 are dissolved in 4500 ml of N, N '-dimethylacetamide, 163.59 g (0.750 mol) of pyromellitic dianhydride and 220.67 g (0.750 mol) of 4,4' -biphenyl dianhydride are added under stirring at-10 ℃ to polymerize at-10 ℃ for 30 hours to obtain a viscous polyamic acid solution, and the solution is filtered and vacuum defoamed to obtain a spinning dope.

S2, wet spinning forming: and (2) accurately metering the normal-temperature spinning slurry by using a metering pump, extruding the spinning slurry from a spinneret orifice, directly feeding the spinning slurry into a coagulating bath of N, N-dimethylacetamide and water in a volume ratio of 1:5, washing with water, and drying by using a hot nitrogen channel to obtain the polyamide acid fiber. Wherein the spinneret plate has 200 holes, the aperture is phi 0.15mm, the spray-draw ratio is 3.2 times, and the spinning speed is 50 m/min.

And S3, performing gradient heating thermal imidization treatment on the polyamic acid fiber in a nitrogen environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-450 ℃, and the heating rate is 5 ℃/min.

S4, drafting the obtained polyimide fiber by 1.3 times at 510 ℃ in a nitrogen environment to obtain the polyimide finished fiber.

Example 4

S1, 157.68 g (0.700 mol) of 5-amino-2- (4-aminophenyl) benzoxazole, 224.17 g (0.700 mol) of 2,2 '-bis (trifluoromethyl) -4, 4' -biphenyldiamine (b-2), 12.81 g (0.0400 mol) of diamine monomer a-4 and 19.22 g (0.0600 mol) of diamine monomer a-8 were dissolved in 5000 ml of N-methylpyrrolidone, and 466.45 g (1.05 mol) of hexafluorodianhydride and 139.59 g (0.45 mol) of 3,3',4,4' -diphenylether tetracarboxylic dianhydride were added under stirring at 20 ℃ to polymerize at 20 ℃ for 24 hours to obtain a viscous polyamic acid solution, which was filtered and vacuum defoamed to be used as a spinning dope.

S2, spinning and forming by a dry-jet wet method: and (2) accurately metering the spinning slurry at normal temperature by using a metering pump, extruding the spinning slurry from a spinneret orifice, entering a coagulating bath of N, N-dimethylacetamide and water with a volume ratio of 1:5 through an air layer, washing with water, and drying by using a hot roller to obtain the polyamic acid fiber. Wherein the spinneret plate has 1000 holes, the aperture is phi 0.10mm, the spray-draw ratio is 3.0 times, the spinning speed is 90m/min, and the height of the air layer is 30 mm.

And S3, performing gradient heating thermal imidization treatment on the polyamic acid fiber in a nitrogen environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-350 ℃, and the heating rate is 15 ℃/min.

S4, drafting the obtained polyimide fiber by 4.0 times at 550 ℃ in a nitrogen environment to obtain the polyimide finished product fiber.

Example 5

S1, dissolving 280.34 g (1.400 mol) of 3,4 '-diaminodiphenyl ether, 280.34 g (1.400 mol) of 4,4' -diaminodiphenyl ether, 32.03 g (0.100 mol) of diamine monomer a-5 and 32.03 g (0.100 mol) of diamine monomer a-7 in 10000 ml of dimethyl sulfoxide, adding 672.6 g (2.00 mol) of first dianhydride monomer shown in formula I-3 and 435.35 g (0.91 mol) of second dianhydride monomer shown in formula I-3 under stirring at 30 ℃, keeping the temperature for polymerization for 6 hours to obtain viscous spinning solution of polyamic acid, and filtering and defoaming the solution in vacuum to be used as spinning slurry.

a first anhydride monomer, a second anhydride monomer,

a second dianhydride monomer.

S2, spinning and forming by a dry-jet wet method: and (2) accurately metering the normal-temperature spinning slurry by using a metering pump, extruding the spinning slurry from a spinneret orifice, entering a solidification bath of dimethyl sulfoxide and water with the volume ratio of 1:4 through an air layer, washing with water, and drying by using a hot nitrogen channel to obtain the polyamide acid fiber. Wherein the spinneret plate has 100 holes, the aperture is phi 0.15mm, the spray-draw ratio is 1.6 times, the spinning speed is 40m/min, and the height of the air layer is 15 mm.

And S3, performing gradient heating thermal imidization treatment on the polyamic acid fiber in a nitrogen environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-400 ℃, and the heating rate is 5 ℃/min.

And S4, drafting the obtained polyimide fiber by 2.8 times at 490 ℃ in a nitrogen environment to obtain the polyimide finished fiber.

Example 6

S1, 68.47 g (0.200 mol) of the first diamine monomer shown in the formula b-7, 102.71 g (0.3000 mol) of the second diamine monomer shown in the formula b-6 and 320.3 g (1.000 mol) of the diamine monomer a-8 are dissolved in 4500 ml of N, N '-dimethylacetamide, 163.59 g (0.750 mol) of pyromellitic dianhydride and 220.67 g (0.750 mol) of 4,4' -biphenyl dianhydride are added under stirring at-15 ℃, and polymerization is carried out for 30 hours at-15 ℃ to obtain viscous polyamic acid defoaming solution, and the viscous polyamic acid defoaming solution is filtered and used as spinning slurry after vacuum deaeration.

The structures of the first diamine monomer shown in the formula b-7 and the second diamine monomer shown in the formula b-6 are as follows:

a first diamine monomer, a second diamine monomer,

a second diamine monomer.

S2, wet spinning forming: and (2) accurately metering the normal-temperature spinning slurry by using a metering pump, extruding the spinning slurry from a spinneret orifice, directly feeding the spinning slurry into a coagulating bath of N, N-dimethylacetamide and water in a volume ratio of 1:7, washing with water, and drying by using a hot nitrogen channel to obtain the polyamide acid fiber. Wherein the spinneret plate has 500 holes, the aperture is phi 0.20mm, the spray-draw ratio is 5.0 times, and the spinning speed is 70 m/min.

And S3, performing gradient heating thermal imidization treatment on the polyamic acid fiber in a nitrogen environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-450 ℃, and the heating rate is 25 ℃/min.

S4, drafting the obtained polyimide fiber by 3.0 times at 580 ℃ in a nitrogen environment to obtain the polyimide finished fiber.

Comparative example 1

72.14 g (0.667 mol) of p-phenylenediamine and 218.51 g (0.833 mol) of 2, 5-bis (4-aminophenyl) pyrimidine were dissolved in 6300 ml of N-methylpyrrolidone, 397.20 g (1.350 mol) of 4,4 '-biphenyldianhydride and 60.35 g (0.150 mol) of 3,4' -triphenyldiether dianhydride were added under stirring at 10 ℃ to polymerize at 10 ℃ for 15 hours to obtain a viscous polyamic acid solution, which was filtered and vacuum defoamed to obtain a spinning dope.

The spinning dope was treated in sequence in steps S2, S3 and S4 of example 1 to obtain a polyimide finished fiber.

Comparative example 2

336.39 g (1.500 mol) of 2- (4-aminophenyl) -5-aminobenzimidazole was dissolved in 4500 ml of N, N '-dimethylacetamide, 163.59 g (0.750 mol) of pyromellitic dianhydride and 220.67 g (0.750 mol) of 4,4' -biphenyldianhydride were added under stirring at-10 ℃ to polymerize at-10 ℃ for 30 hours to give a viscous polyamic acid solution, which was filtered and vacuum defoamed to give a spinning dope.

The spinning dope was treated in sequence in steps S2, S3 and S4 of example 3 to obtain a polyimide finished fiber.

Example 7

The ultraviolet aging resistance of the finished fibers obtained in examples 1 to 6 and comparative examples 1 to 2 was tested, and the test results were as follows: firstly, the breaking strength of the finished product fiber before ultraviolet irradiation is detected (refer to the standard GB/T14344-²) After 2000 hours of irradiation, the breaking strength of the fiber is tested again, and the strength retention rate of the fiber after long-time ultraviolet irradiation is calculated. See table 1 for results.

TABLE 1 ultraviolet aging resistance of fibers obtained in examples 1 to 6 and comparative examples 1 to 2

The test results in table 1 show that the polyimide fiber prepared by the preparation method provided by the invention has the fracture strength of more than 99% after being irradiated by ultraviolet light for 2000 hours, and shows excellent ultraviolet irradiation resistance.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The preparation method of the polyimide fiber is characterized by comprising the following steps:

b) spinning the polyamic acid spinning solution to obtain polyamic acid fiber;

the diamine monomer comprises a monomer A and a monomer B;

wherein the content of the first and second substances,

m is selected from-O-, -S-, or-NH-;

x is selected from-O-, -S-, or-NH-;

d is selected from-O-, -S-, or-NH-;

e is selected from-O-, -S-, -SO₂-、-CH₂-、-C(CF₃)₂-、-CO-、

2. The preparation method according to claim 1, wherein the aromatic dianhydride monomer is selected from one or more of the structures shown in formulas I-1 to I-3:

wherein A is selected from:

-S-、-O-、

3. the preparation method according to claim 1, wherein the molar ratio of the aromatic dianhydride monomer to the diamine monomer is 1: (0.95-1.20);

4. The method according to claim 1, wherein the polymerization temperature in step a) is-20 ℃ to 50 ℃ for 4 to 60 hours.

5. The method according to claim 1, wherein in step a), the solvent is a polar aprotic solvent;

the concentration of the polyamic acid spinning solution is 5-35 wt%.

6. The method according to claim 1, wherein in the step c), the imidization treatment is a thermal imidization treatment;

the conditions of the constant temperature heat treatment are as follows:

7. The method for preparing the fiber according to claim 1, wherein in the step b), the spinning is dry-jet wet spinning, wet spinning or dry spinning;

in the dry spinning, the drying temperature is 150-350 ℃.

8. The production method according to claim 1, further comprising a heat-drawing treatment after the imidization treatment;

the thermal drawing is carried out under an inert gas atmosphere.

9. The method of claim 7, wherein the coagulation bath is a mixture of organic matter and water;

the volume ratio of the organic matter to the water is 1: (3-10);

10. A polyimide fiber obtained by the production method according to any one of claims 1 to 9.