CN110791833A

CN110791833A - Polyimide fiber and preparation method thereof

Info

Publication number: CN110791833A
Application number: CN201911173839.4A
Authority: CN
Inventors: 董志鑫; 姚海波; 代学民; 刘芳芳; 李国民; 蔡艳春; 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: 2020-02-14
Anticipated expiration: 2039-11-26
Also published as: CN110791833B

Abstract

The invention provides a polyimide fiber and a preparation method thereof. The preparation method of the polyimide fiber provided by the invention 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; wherein, the monomer A is selected from one or more of structures shown in formulas a-1 to a-3; the monomer B is selected from one or more of structures shown in the following formulas B-1 to B-7. According to the invention, the specific monomer A with the side chain containing the o-hydroxy benzophenone structural unit and the monomer B are matched to be used as diamine monomers, and are polymerized with the dianhydride monomers together and spun to obtain the polyimide fiber, 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 irradiation.

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.

The method is to dope components with the ultraviolet resistance function, such as nano particles and organic micromolecules, as objects into the polyimide host material to prepare the ultraviolet radiation resistant polyimide material. 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-3:

wherein R is₁Selected from: alkyl, substituted or unsubstituted phenyl;

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:

preferably, the molar ratio of the aromatic dianhydride monomer to the diamine monomer is 1 to (0.85-1.20);

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 280-450 ℃, 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-3 shown above. According to the invention, the specific monomer A with the side chain containing the o-hydroxy benzophenone structural unit and the monomer B are matched as diamine monomers and are polymerized with dianhydride monomers together, and the polyimide fiber is obtained through spinning, 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 irradiation.

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 R is₁Selected from: alkyl, substituted or unsubstituted phenyl;

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 invention, firstly, an aromatic dianhydride monomer and a diamine monomer are polymerized in a solvent to obtain a polyamide 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 formulas a-1 to a-3:

wherein R is₁Selected from alkyl, substituted or unsubstituted phenyl. The alkyl group is preferably a C1-C12 alkyl group. In the substituted phenyl, the substituent is selected from methyl, hexyl and fluorine atoms.

In the present invention, the monomer a can be prepared by the following method:

a) carrying out etherification reaction on methoxyphenol and a compound with a structure shown in a formula (I) in the presence of a basic catalyst to obtain a compound with a structure shown in a formula (II); the methoxyphenol is 3-methoxyphenol, 4-methoxyphenol or 3, 5-dimethoxyphenol;

X-R₁formula (I);

in the formula (I), X is fluorine, chlorine, bromine, iodine, methylsulfonyloxy, trifluoromethanesulfonyloxy or p-toluenesulfonyloxy;

in the formula (II), R₅And R₆Independently selected from hydrogen orAnd R is₅And R₆Different; r₄Selected from hydrogen or

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

in the formula (III), R₇And R₈Independently selected from

And R is₇And R₈Different;

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 (IV);

in the formula (IV), R₉And R₁₀Independently selected from

And R is₉And R₁₀Different;

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 a-1-a-3;

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), R₁₁And R₁₂Independently selected from hydroxy or

And R is₁₁And R₁₂Different;

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-3.

In the preparation method, the methoxyphenol is 3-methoxyphenol, 4-methoxyphenol or 3, 5-dimethoxyphenol. The source of the methoxyphenol in the present invention is not particularly limited, and commercially available products of the above-mentioned 3-methoxyphenol, 4-methoxyphenol and 3, 5-dimethoxyphenol known to those skilled in the art can be used.

In the above preparation method, the structure shown in formula (I) is:

X-R₁formula (I);

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, and are beneficial to carrying out etherification reaction to obtain corresponding reaction products; r₁Selected from alkyl, phenyl or substituted phenyl.

Wherein when R is₁In the case of alkyl, the basic catalyst is preferably an alkali metal or alkaline earth metal carbonate, more preferably sodium carbonate and/or potassium carbonate, most preferably potassium carbonate; wherein, when X is chlorine or bromine, potassium iodide is preferably selected for co-catalysis; wherein the dosage of the potassium iodide is 0.01 to 0.05 times of the molar weight of the methoxyphenol. In the present invention, when R is₁When the catalyst is phenyl or substituted phenyl, the alkaline catalyst is preferably co-catalyzed by carbonate and copper salt of alkali metal or alkaline earth metal; wherein the carbonate is 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 methoxyphenol. 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 above preparation method, the molar ratio of the compound having a structure represented by the formula (I), the basic catalyst and the methoxyphenol is preferably (0.8 to 1.25): (1-1.5): 1, more preferably (0.9 to 1.1): (1.1-1.3): 1.

in the above preparation method, the X is preferably chlorine or bromine, and on this basis, the etherification reaction process preferably employs a first reaction solvent; the first reaction solvent is preferably one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, acetonitrile, acetone, and 1, 4-dioxane, and more preferably acetonitrile (R)₁Is alkyl) or N, N-dimethylformamide (R)₁Phenyl, substituted phenyl). The source of the first reaction solvent is not particularly limited in the present invention, and commercially available products of the above 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 5 times, and more preferably 2 to 3 times the sum of the mass of the compound and the mass of the methoxyphenol.

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 room temperature, adding the reaction product into water with the volume 3-8 times that of a first reaction solvent, extracting a product with dichloromethane, drying anhydrous magnesium sulfate, concentrating the solvent, and purifying to obtain a refined product of the structural compound shown in the formula (II);

more preferably:

cooling a reaction product obtained after etherification reaction to room temperature, adding the reaction product into water with the volume 6 times that of the first reaction solvent, extracting a product with dichloromethane, drying the product with anhydrous magnesium sulfate, concentrating the solvent, and purifying to obtain a refined product of the structural compound shown in the formula (II).

In the present invention, the structure represented by the formula (II) preferably 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 dinitrobenzoyl 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 dinitrobenzoyl halide is 3, 5-dinitrobenzoyl 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 dinitrobenzoyl 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 trichloromethane 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 10 times, more preferably 4 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-20-30 ℃, and more preferably-10-20 ℃; the time of the Friedel-crafts acylation reaction is preferably 8 to 24 hours, and more preferably 12 to 18 hours; 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 the formula (III) preferably 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-3.

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 40 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 40-80 ℃, and more preferably 50-65 ℃; 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 the formula (IV) preferably 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 is preferably 10 to 40 hours, and more preferably 20 to 30 hours; 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-3. 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 a residue 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-3.

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-3.

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-3. 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-3.

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' -biphenyl dianhydride of the structure shown in the formula I-2, 3',4,4' -benzophenone tetracarboxylic dianhydride of the structure shown in the formula I-3, diamine- (3, 5-diaminophenyl) (2-hydroxy-4-methoxyphenyl) ketone of the structure shown in the formula a-1, p-phenylenediamine of the structure shown in the formula b-1, 2, 5-bis (4-aminophenyl) pyrimidine of the structure shown in the formula b-4 and 2, 4-bis (4-aminophenyl) pyrimidine of the structure shown in the formula b-4;

or

4,4 '-biphenyl dianhydride of the structure shown in the formula I-2, 3',4,4 '-triphenyl diether tetracarboxylic dianhydride of the structure shown in the formula I-3, diamine- (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) ketone of the structure shown in the formula a-1, p-phenylenediamine of the structure shown in the formula b-1, 2, 5-bis (4-aminophenyl) pyrimidine of the structure shown in the formula b-4 and 2,2' -bis (4-aminophenyl) hexafluoropropane of the structure shown in the formula b-2;

or

4,4' -biphenyl dianhydride of the structure shown in formula I-2, diamine- (3, 5-diaminophenyl) (2-hydroxy-4-methoxyphenyl) methanone of the structure shown in formula a-1, and 2- (4-aminophenyl) -5-aminobenzimidazole of the structure shown in formula b-5;

or

Pyromellitic dianhydride of the structure shown in the formula I-1, 4' -biphenyl dianhydride of the structure shown in the formula I-2, diamine- (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxyphenyl) ketone of the structure shown in the formula a-1 and 5-amino-2- (4-aminophenyl) benzoxazole of the structure shown in the formula b-5;

or

Pyromellitic dianhydride of the structure shown in the formula I-1, 2', 3,3' -triphendiethanetetracarboxylic dianhydride of the structure shown in the formula I-3, diamine- (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone and (3, 5-diaminophenyl) (2-hydroxy-5-methoxyphenyl) methanone of the structures shown in the formulae a-1 and a-2, 3,4 '-diaminodiphenyl ether of the structure shown in the formula b-4 and 4,4' -diaminodiphenyl ether of the structure shown in the formula b-4;

or

A first dianhydride monomer shown as a formula I-3, a second dianhydride monomer shown as a formula I-3, 2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl with a structure shown as a formula b-2, a diamine monomer with structures shown as a formula b-6 and a formula b-7, and (3, 5-diaminophenyl) (2-hydroxy-5- (4-fluorophenoxy) phenyl) ketone with a structure shown as a formula a-2;

the diamine monomer b-6 used has the following structural formula:

the diamine monomer b-7 used has the following structural formula:

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

a first anhydride monomer, a second anhydride monomer,

a second dianhydride monomer;

or

Pyromellitic dianhydride of the structure shown in the formula I-1, 3',4,4' -diphenyl ether tetracarboxylic dianhydride of the structure shown in the formula I-3, 2- (4-aminophenyl) -5-aminobenzimidazole of the structure shown in the formula b-5, and (3, 5-diaminophenyl) (2-hydroxy-4, 6-dimethoxyphenyl) ketone of the structure shown in the formula a-3;

or

4,4 '-biphenyl dianhydride of the structure shown in the formula I-2, 4' -diaminodiphenyl ether of the structure shown in the formula b-4, a diamine monomer of the structure shown in the formula b-6, and (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) -6-methoxyphenyl) methanone of the structure shown in the formula a-3;

the diamine monomer b-6 used has the following structural formula:

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 with a structure shown in a formula b-7, and (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxy-6-methoxyphenyl) methanone with a structure shown in a formula a-3;

the structural formula of the diamine monomer b-7 is as follows:

in the present invention, the molar ratio of the aromatic dianhydride monomer to the diamine monomer is preferably 1: (0.85 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 5% to 50%. In some embodiments of the invention, the molar ratio of monomer A to monomer B is 0.50: 0.50, 0.10:0.90, 0.08: 0.92, 0.10:1.40, 0.70:0.80, 0.20:0.90, 0.05:0.95, 0.30:0.70, 0.10: 0.90.

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, -20 ℃, 10 ℃, 15 ℃, 20 ℃ or 30 ℃. The polymerization time is preferably 4 to 60 hours; in particular embodiments 8 hours, 12 hours, 16 hours, 20 hours, 24 hours, 30 hours, or 36 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 10mm, 15mm, 20mm, 30mm, 50mm, or 60 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 150-300 ℃. 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 300 ℃, from 50 ℃ to 350 ℃, from 50 ℃ to 380 ℃, from 50 ℃ to 400 ℃, or from 50 ℃ to 450 ℃. The heating rate is 1-30 ℃/min; in some embodiments, 5 deg.C/min, 15 deg.C/min, 20 deg.C/min, 25 deg.C/min, or 30 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 300-500 ℃, 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 ℃, 500 ℃, 520 ℃, 530 ℃, 550 ℃ or 580 ℃. The multiplying power of the hot drawing is preferably 1.0-6.0 times; in some embodiments, 1.5 times, 1.8 times, 1.9 times, 2.1 times, 2.8 times, 3.0 times, 4.0 times, or 5.0 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 with a side chain containing a specific o-hydroxybenzophenone structural unit and the monomer B are matched to serve as diamine monomers and are polymerized with a dianhydride monomer to form polyamic acid, and the o-hydroxybenzophenone structural unit is introduced into the side chain of a polyimide fiber molecule through copolymerization reaction, so that the ultraviolet aging resistance of the polyimide fiber 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.

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

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 are prepared according to methods well known to those skilled in the art, in which the monomers A are prepared according to the methods described above in the following examples of preparation of starting materials.

Starting Material preparation example 1 monomer A- (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxyphenyl) methanone

(1) 37.24 g (0.30 mol) of 3-methoxyphenol, 54.47 g (0.33 mol) of bromon-hexane, 49.76 g (0.36 mol) of potassium carbonate, 2.49 g (0.015 mol) of potassium iodide and 275 g of acetonitrile were successively charged into a reaction flask, followed by heating the reaction system to 80 ℃ for 6 hours. After cooling to room temperature, the reaction mixture was added to 1500 ml of water, and the product was extracted with methylene chloride, dried over anhydrous magnesium sulfate, concentrated in a solvent, and purified to obtain 53.74 g of a purified product of 1-hexyloxy-3-methoxybenzene represented by the formula (II) in a yield of 86.0%.

¹H NMR(400MHz,DMSO)δ＝7.152(t,J＝8.0Hz,1H),6.445-6.510(m,3H),3.920(t,J＝6.4Hz,2H),3.718(s,3H),1.735-1.625(m,2H),1.460–1.355(m,2H),1.345–1.205(m,4H),0.875(t,J＝6.8Hz,3H)。

(2) 27.67 g (0.12 mol) of 3, 5-dinitrobenzoyl chloride, 17.33 g (0.13 mol) of aluminum trichloride, 350 g of 1, 2-dichloroethane and 20.83 g (0.10 mol) of 1-hexyloxy-3-methoxybenzene were successively charged into a reaction flask and reacted with stirring at 10 ℃ for 15 hours. Then, the resulting mixture was slowly added to ice-hydrochloric acid to be treated, followed by liquid separation, drying over anhydrous magnesium sulfate, and concentration of the solvent to obtain a crude product, which was purified to obtain 21.05 g of a purified product of (3, 5-dinitrophenyl) (4-hexyloxy-2-methoxyphenyl) methanone, a compound represented by the formula (III), in a yield of 52.3%.

¹H NMR(400MHz，DMSO)δ＝8.987(s,1H),8.631(s,2H),7.610-7.520(m,1H),6.765-6.685(m,2H),4.106(t,J＝6.2Hz,2H),3.633(s,3H),1.805–1.685(m,2H),1.495-1.390(m,2H),1.380-1.260(m,4H),0.891(t,J＝6.4Hz,3H)。

(3) 40.24 g (0.1 mol) of (3, 5-dinitrophenyl) (4-hexyloxy-2-methoxyphenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction vessel, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid are concentrated and recovered, the residue is dissolved by dichloromethane, a saturated sodium carbonate solution is neutralized to be alkaline, liquid separation is carried out, anhydrous magnesium sulfate is dried, and the solvent is concentrated to obtain a crude product, 25.83 g of a refined product of a compound (3, 5-dinitrophenyl) (2-hydroxy-4-hexyloxyphenyl) ketone represented by the structure shown in the formula (VI) is obtained through recrystallization, and the yield is 66.5%.

¹H NMR(400MHz，DMSO)δ＝11.270(s,1H),8.992(s,1H),8.736(s,2H),7.507(d,J＝8.4Hz,1H),6.605-6.525(m,2H),4.066(t,J＝6.2Hz,2H),1.785-1.665(m,2H),1.475-1.367(m,2H),1.313(d,J＝2.8Hz,4H),0.883(t,J＝6.4Hz,3H)。

(4) 38.84 g (0.10 mol) of (3, 5-dinitrophenyl) (2-hydroxy-4-hexyloxyphenyl) methanone, 203.09 g (0.90 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask, and the reaction was stirred at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to alkalinity by adding a saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and concentrated in a solvent to obtain a crude product, which was recrystallized to obtain 23.52 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxyphenyl) methanone, a compound represented by the structure of formula a-1, in a yield of 71.6%.

¹H NMR(400MHz，DMSO)δ＝12.397(s,1H),7.595-7.530(m,1H),6.540-6.470(m,2H),6.026(s,3H),5.026(s,4H),4.038(t,J＝6.4Hz,2H),1.765–1.645(m,2H),1.450-1.350(m,2H),1.340-1.245(m,4H),0.874(t,J＝6.6Hz,3H)。

Starting Material preparation example 2 monomer A- (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone

(1) 62.07 g (0.50 mol) of 3-methoxyphenol, 78.75 g (0.45 mol) of p-bromofluorobenzene, 4.76 g (0.025 mol) of cuprous iodide, 82.93 g (0.60 mol) of potassium carbonate and 420 g of N, N-dimethylformamide were sequentially added to a reaction flask, and the reaction system was heated to 150 ℃ under nitrogen protection for 8 hours. After cooling to room temperature, the reaction product was added to 2500 ml of water, and the product was extracted with methylene chloride, washed with dilute hydrochloric acid, dried over anhydrous magnesium sulfate, and the solvent was concentrated and purified to obtain 77.58 g of a purified product of 1- (4-fluorophenoxy) -3-methoxybenzene, which is a compound represented by the formula (II), in a yield of 79.0%.

¹H NMR(400MHz，DMSO)δ＝7.295–7.175(m,3H),7.105–7.025(m,2H),6.703(dd,J＝8.4Hz,2.2Hz,1H),6.557(t,J＝2.2Hz,1H),6.504(dd,J＝8.2Hz,2.2Hz,1H),3.728(s,3H)。

(2) 27.67 g (0.12 mol) of 3, 5-dinitrobenzoyl chloride, 17.33 g (0.13 mol) of aluminum trichloride, 360 g of 1, 2-dichloroethane and 21.82 g (0.10 mol) of 1- (4-fluorophenoxy) -3-methoxybenzene were successively charged into a reaction flask and reacted with stirring at 15 ℃ for 15 hours. Then, the resulting mixture was slowly added to ice-hydrochloric acid to be treated, followed by liquid separation, drying over anhydrous magnesium sulfate, and concentration of the solvent to obtain a crude product, which was recrystallized to obtain 25.17 g of a purified product of (3, 5-dinitrophenyl) (4- (4-fluorophenoxy) -2-methoxyphenyl) methanone, a compound represented by the formula (III), in a yield of 61.0%.

¹H NMR(400MHz，DMSO)δ＝8.947(s,1H),8.686(s,2H),7.768(d,J＝8.8Hz,1H),7.125(t,J＝8.6Hz,2H),6.985(d,J＝8.6Hz,1H),6.910-6.810(m,2H),6.495(s,1H),3.821(s,3H)。

(3) 41.23 g (0.1 mol) of (3, 5-dinitrophenyl) (4- (4-fluorophenoxy) -2-methoxyphenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction flask, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid were recovered by concentration, the residue was dissolved in methylene chloride, neutralized with a saturated sodium carbonate solution to be alkaline, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 28.75 g of a purified product of (3, 5-dinitrophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone, a compound represented by the formula (vi), in a yield of 72.2%.

¹H NMR(400MHz，DMSO)δ＝10.903(s,1H),8.996(s,1H),8.731(s,2H),7.590(d,J＝8.8Hz,1H),7.370-7.240(m,4H),6.596(d,J＝8.8Hz,1H),6.455(s,1H)。

(4) 39.83 g (0.10 mol) of (3, 5-dinitrophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone, 203.09 g (0.90 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask, and the reaction was stirred at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to basicity by adding a saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and concentrated in a solvent to give a crude product, which was recrystallized to give 28.37 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone, a compound represented by the formula a-1, in a yield of 83.8%.

¹H NMR(400MHz，DMSO)δ＝11.727(s,1H),7.545(d,J＝8.8Hz,1H),7.303(t,J＝7.6Hz,2H),7.227(d,J＝3.2Hz,2H),6.493(d,J＝8.0Hz,1H),6.416(s,1H),6.087(s,2H),6.047(s,1H),5.022(s,4H)。

Starting Material preparation example 3 monomer A- (3, 5-diaminophenyl) (2-hydroxy-4-methoxyphenyl) methanone

(1) 25.36 g (0.11 mol) of 3, 5-dinitrobenzoyl chloride, 16.00 g (0.12 mol) of aluminum trichloride, 300 g of 1, 2-dichloroethane and 13.82 g (0.10 mol) of 1, 3-dimethoxybenzene were charged in this order into a reaction flask and reacted with stirring at 0 ℃ for 18 hours. Then, the resulting mixture was gradually added to ice-hydrochloric acid to be treated, followed by liquid separation, drying over anhydrous magnesium sulfate and concentration of the solvent to obtain a crude product, which was recrystallized to obtain 19.24 g of a purified product of (3, 5-dinitrophenyl) (2, 4-dimethoxyphenyl) methanone, a compound represented by the formula (III), in a yield of 57.9%.

¹H NMR(400MHz，DMSO)δ＝8.992(t,J＝2.0Hz,1H),8.638(d,J＝2.0Hz,2H),7.620-7.540(m,1H),6.790-6.685(m,2H),3.902(s,3H),3.647(s,3H)。

(2) 33.23 g (0.1 mol) of (3, 5-dinitrophenyl) (2, 4-dimethoxyphenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction flask, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid are concentrated and recovered, the residue is dissolved by dichloromethane, a saturated sodium carbonate solution is neutralized to be alkaline, liquid separation is carried out, anhydrous magnesium sulfate is dried, the solvent is concentrated to obtain a crude product, and 24.47 g of a refined product of a compound (3, 5-dinitrophenyl) (2-hydroxy-4-methoxyphenyl) ketone represented by the formula (VI) is obtained through recrystallization, wherein the yield is 76.9%.

¹H NMR(400MHz，DMSO)δ＝11.262(s,1H),8.991(t,J＝2.0Hz,1H),8.735(d,J＝2.0Hz,2H),7.521(d,J＝9.2Hz,1H),6.620–6.530(m,2H),3.850(s,3H)。

(3) 38.18 g (0.12 mol) of (3, 5-dinitrophenyl) (2-hydroxy-4-methoxyphenyl) methanone, 243.70 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask and reacted with stirring at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to alkalinity by adding a saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and concentrated in a solvent to obtain a crude product, which was recrystallized to obtain 26.20 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-4-methoxyphenyl) methanone, a compound represented by the structure of formula a-1, in a yield of 84.5%.

¹H NMR(400MHz，DMSO)δ＝12.369(s,1H),7.566(d,J＝9.4Hz,1H),6.555–6.485(m,2H),6.027(s,3H),5.026(s,4H),3.827(s,3H)。

Starting Material preparation example 4 monomer A- (3, 5-diaminophenyl) (2-hydroxy-4, 6-dimethoxyphenyl) methanone

(1) 25.36 g (0.11 mol) of 3, 5-dinitrobenzoyl chloride, 16.00 g (0.12 mol) of aluminum trichloride, 300 g of 1, 2-dichloroethane and 16.82 g (0.10 mol) of 1,3, 5-trimethoxybenzene were successively charged into a reaction flask and reacted at-5 ℃ for 12 hours with stirring. Then, the mixture was slowly added to ice-hydrochloric acid to be treated, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain 22.10 g of a crude product of (3, 5-dinitrophenyl) (2, 4, 6-trimethoxyphenyl) methanone, a structure representative compound of the formula (III), in a yield of 61.0%.

(2) 34.83 g (0.1 mol) of a crude product of (3, 5-dinitrophenyl) (2, 4, 6-trimethoxyphenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction vessel, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid were recovered by concentration, the residue was dissolved in methylene chloride, neutralized with a saturated sodium carbonate solution to be alkaline, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 25.18 g of a purified product of (3, 5-dinitrophenyl) (2-hydroxy-4, 6-dimethoxyphenyl) methanone, a compound represented by the formula (vi), in a yield of 72.3%.

¹H NMR(400MHz，DMSO)δ＝10.517(s,1H),8.990(t,J＝1.6Hz,1H),8.663(d,J＝2.0Hz,2H),6.234(s,1H),6.191(d,J＝1.6Hz,1H),3.821(s,3H),3.621(s,3H)。

(3) 41.79 g (0.12 mol) of (3, 5-dinitrophenyl) (2-hydroxy-4, 6-dimethoxyphenyl) methanone, 243.70 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask, and the reaction was stirred at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to basicity with saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 30.03 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-4, 6-dimethoxyphenyl) methanone, a compound represented by the structure of formula a-3, in a yield of 86.8%.

¹H NMR(400MHz，DMSO)δ＝9.657(s,1H),6.198(d,J＝2.0Hz,2H),6.093(d,J＝1.6Hz,1H),6.057(d,J＝1.6Hz,1H),6.000(s,1H),4.884(s,4H),3.730(s,3H),3.599(s,3H)。

Starting Material preparation example 5 monomer A- (3, 5-diaminophenyl) (2-hydroxy-5-methoxyphenyl) methanone

(1) 25.36 g (0.11 mol) of 3, 5-dinitrobenzoyl chloride, 16.00 g (0.12 mol) of aluminum trichloride, 300 g of 1, 2-dichloroethane and 13.82 g (0.10 mol) of 1, 4-dimethoxybenzene were charged in this order into a reaction flask and reacted with stirring at 10 ℃ for 18 hours. Then, the resulting mixture was slowly added to ice-hydrochloric acid to be treated, followed by liquid separation, drying over anhydrous magnesium sulfate, and concentration of the solvent to obtain a crude product, which was recrystallized to obtain 22.87 g of a purified product of (3, 5-dinitrophenyl) (2, 5-dimethoxyphenyl) methanone, a structure-represented compound represented by the formula (III), in a yield of 68.8%.

(2) 33.23 g (0.1 mol) of (3, 5-dinitrophenyl) (2, 5-dimethoxyphenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction flask, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid are concentrated and recovered, the residue is dissolved by dichloromethane, a saturated sodium carbonate solution is neutralized to be alkaline, liquid separation is carried out, anhydrous magnesium sulfate is dried, and the solvent is concentrated to obtain a crude product, and 26.32 g of a refined product of a compound (3, 5-dinitrophenyl) (2-hydroxy-5-methoxyphenyl) ketone represented by the formula (VI) is obtained through recrystallization, wherein the yield is 82.7%.

(3) 38.18 g (0.12 mol) of (3, 5-dinitrophenyl) (2-hydroxy-5-methoxyphenyl) methanone, 243.70 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask and reacted with stirring at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to alkalinity by adding a saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and concentrated in a solvent to obtain a crude product, which was recrystallized to obtain 25.03 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-5-methoxyphenyl) methanone, a compound represented by the structure of formula a-2, in a yield of 80.7%.

Preparation of starting Material example 6 monomer A- (3, 5-diaminophenyl) (2-hydroxy-5- (4-fluorophenoxy) phenyl) methanone

(1) 62.07 g (0.50 mol) of 4-methoxyphenol, 78.75 g (0.45 mol) of p-bromofluorobenzene, 4.76 g (0.025 mol) of cuprous iodide, 82.93 g (0.60 mol) of potassium carbonate and 420 g of N, N-dimethylformamide were sequentially added to a reaction flask, and the reaction system was heated to 150 ℃ under nitrogen protection for 12 hours. After cooling to room temperature, the reaction product was added to 2500 ml of water, and the product was extracted with methylene chloride, washed with dilute hydrochloric acid, dried over anhydrous magnesium sulfate, and the solvent was concentrated and purified to obtain 75.44 g of a purified product of 1- (4-fluorophenoxy) -4-methoxybenzene, which is a compound represented by the formula (II), in a yield of 76.8%.

(2) 27.67 g (0.12 mol) of 3, 5-dinitrobenzoyl chloride, 17.33 g (0.13 mol) of aluminum trichloride, 360 g of 1, 2-dichloroethane and 21.82 g (0.10 mol) of 1- (4-fluorophenoxy) -4-methoxybenzene were successively charged into a reaction flask and reacted with stirring at 15 ℃ for 24 hours. Then, the resulting mixture was slowly added to ice-hydrochloric acid to be treated, followed by liquid separation, drying over anhydrous magnesium sulfate, and concentration of the solvent to obtain a crude product, which was recrystallized to obtain 23.89 g of a purified product of (3, 5-dinitrophenyl) (5- (4-fluorophenoxy) -2-methoxyphenyl) methanone, a compound represented by the formula (III), in a yield of 57.9%.

(3) 41.23 g (0.1 mol) of (3, 5-dinitrophenyl) (5- (4-fluorophenoxy) -2-methoxyphenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction flask, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid were recovered by concentration, the residue was dissolved in methylene chloride, neutralized with a saturated sodium carbonate solution to alkaline, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 30.64 g of a purified product of (3, 5-dinitrophenyl) (2-hydroxy-5- (4-fluorophenoxy) phenyl) methanone, a compound represented by the formula (vi), in a yield of 76.9%.

(4) 39.83 g (0.10 mol) of (3, 5-dinitrophenyl) (2-hydroxy-5- (4-fluorophenoxy) phenyl) methanone, 203.09 g (0.90 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask, and the reaction was stirred at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to basicity by adding a saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and concentrated in the solvent to obtain a crude product, which was recrystallized to obtain 27.26 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-5- (4-fluorophenoxy) phenyl) methanone, a compound represented by the structure of formula a-2, in a yield of 80.5%.

Starting Material preparation example 7 monomer A- (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) -6-methoxyphenyl) methanone

(1) 77.09 g (0.50 mol) of 3, 5-dimethoxyphenol, 87.50 g (0.50 mol) of p-bromofluorobenzene, 4.76 g (0.025 mol) of cuprous iodide, 82.93 g (0.60 mol) of potassium carbonate and 420 g of N, N-dimethylformamide were sequentially added to a reaction flask, and the reaction system was heated to 150 ℃ under nitrogen protection for 15 hours. After cooling to room temperature, the reaction mixture was added to 2500 ml of water, and the product was extracted with methylene chloride, washed with dilute hydrochloric acid, dried over anhydrous magnesium sulfate, and the solvent was concentrated and purified to obtain 96.83 g of a purified product of 1- (4-fluorophenoxy) -3, 5-dimethoxybenzene, which is a compound represented by the formula (II), in a yield of 78.0%.

(2) 25.36 g (0.11 mol) of 3, 5-dinitrobenzoyl chloride, 16.00 g (0.12 mol) of aluminum trichloride, 300 g of 1, 2-dichloroethane and 24.83 g (0.10 mol) of 1- (4-fluorophenoxy) -3, 5-dimethoxybenzene were successively charged into a reaction flask and reacted with stirring at 5 ℃ for 12 hours. Then, the mixture was gradually added to ice-hydrochloric acid to conduct treatment, followed by liquid separation, drying over anhydrous magnesium sulfate and concentration of the solvent, whereby 23.97 g of a purified product of (3, 5-dinitrophenyl) (2, 6-dimethoxy-4- (4-fluorophenoxy) phenyl) methanone, a structure represented by the formula (III), was obtained in a yield of 54.2%.

(3) 44.24 g (0.1 mol) of (3, 5-dinitrophenyl) (2, 6-dimethoxy-4- (4-fluorophenoxy) phenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction flask, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid were recovered by concentration, the residue was dissolved in methylene chloride, neutralized with a saturated sodium carbonate solution to alkaline, separated, dried over anhydrous magnesium sulfate, and the solvent was concentrated to obtain a crude product, which was recrystallized to obtain 35.62 g of a purified product of (3, 5-dinitrophenyl) (2-hydroxy-4- (4-fluorophenoxy) -6-methoxyphenyl) methanone, a compound represented by the formula (vi), in a yield of 83.2%.

(4) 51.40 g (0.12 mol) of (3, 5-dinitrophenyl) (2-hydroxy-4- (4-fluorophenoxy) -6-methoxyphenyl) methanone, 243.70 g (1.08 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask and reacted with stirring at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to basicity by adding a saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and concentrated in the solvent to obtain a crude product, which was recrystallized to obtain 38.74 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) -6-methoxyphenyl) methanone, a compound represented by the formula a-3, in a yield of 87.6%.

Starting Material preparation example 8 monomer A- (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxy-6-methoxyphenyl) methanone

(1) 46.25 g (0.30 mol) of 3, 5-dimethoxyphenol, 54.47 g (0.33 mol) of bromon-hexane, 49.76 g (0.36 mol) of potassium carbonate, 2.49 g (0.015 mol) of potassium iodide and 275 g of acetonitrile were successively charged into a reaction flask, followed by heating the reaction system to 80 ℃ for 6 hours. After cooling to room temperature, the reaction mixture was added to 1500 ml of water, and the product was extracted with methylene chloride, dried over anhydrous magnesium sulfate, concentrated in a solvent, and purified to obtain 59.83 g of a purified product of 1-hexyloxy-3, 5-dimethoxybenzene having a structure represented by the formula (II) in a yield of 83.7%.

(2) 27.67 g (0.12 mol) of 3, 5-dinitrobenzoyl chloride, 17.33 g (0.13 mol) of aluminum trichloride, 350 g of 1, 2-dichloroethane and 23.83 g (0.10 mol) of 1-hexyloxy-3, 5-dimethoxybenzene were successively charged into a reaction flask and reacted with stirring at 0 ℃ for 15 hours. Then, the resulting mixture was slowly added to ice-hydrochloric acid to be treated, followed by liquid separation, drying over anhydrous magnesium sulfate, and concentration of the solvent to obtain a crude product, which was purified to obtain 17.42 g of a purified product of (3, 5-dinitrophenyl) (4-hexyloxy-2, 6-dimethoxyphenyl) methanone, a compound represented by the formula (III), in a yield of 40.3%.

(3) 43.24 g (0.1 mol) of (3, 5-dinitrophenyl) (4-hexyloxy-2, 6-dimethoxyphenyl) methanone, 84.29 g (48%, 0.5 mol) of hydrobromic acid and 250 g of acetic acid were successively charged into a reaction flask, and the reaction was stirred at 100 ℃ for 30 hours. After hydrobromic acid and acetic acid are concentrated and recovered, the residue is dissolved by dichloromethane, a saturated sodium carbonate solution is neutralized to be alkaline, liquid separation is carried out, anhydrous magnesium sulfate is dried, and the solvent is concentrated to obtain a crude product, and then 31.25 g of a refined product of a compound (3, 5-dinitrophenyl) (2-hydroxy-4-hexyloxy-6-methoxyphenyl) ketone represented by the formula (VI) is obtained through recrystallization, wherein the yield is 74.7%.

(4) 41.84 g (0.10 mol) of (3, 5-dinitrophenyl) (2-hydroxy-4-hexyloxy-6-methoxyphenyl) methanone, 203.09 g (0.90 mol) of stannous chloride dihydrate and 700 ml of ethanol were added in this order to a reaction flask and reacted with stirring at 50 ℃ for 1 hour. After cooling to room temperature, the reaction mixture was neutralized to alkalinity by adding a saturated sodium carbonate solution, extracted with ethyl acetate, separated, dried with anhydrous sodium carbonate, and concentrated in a solvent to obtain a crude product, which was recrystallized to obtain 31.74 g of a purified product of (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxy-6-methoxyphenyl) methanone, a compound represented by the formula a-3, in a yield of 88.6%.

Example 1

S1, 21.63g (0.200 mol) of p-phenylenediamine, 52.46 g (0.200 mol) of 2, 5-bis (4-aminophenyl) pyrimidine, 26.23 g (0.100 mol) of 2, 4-bis (4-aminophenyl) pyrimidine and 129.15 g (0.500 mol) of (3, 5-diaminophenyl) (2-hydroxy-4-methoxyphenyl) methanone (prepared from preparation example 3 of the raw material) were dissolved in 4000 ml of N, N '-dimethylacetamide, and 147.11 g (0.500 mol) of 3,4' -biphenyldianhydride and 161.11 g (0.500 mol) of 3,3',4,4' -benzophenonetetracarboxylic dianhydride were added under stirring at 20 ℃ to polymerize at 20 ℃ for 8 hours to obtain a viscous polyamic acid solution, which was filtered and vacuum defoamed to obtain a spinning dope.

The diamine monomer A- - (3, 5-diaminophenyl) (2-hydroxy-4-methoxyphenyl) methanone used was the monomer obtained in preparation example 3, and the structural formula was as follows:

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 1:5 in a coagulating bath of N, N' -dimethylacetamide and water, washing with water, and drying by a hot argon channel to obtain the polyamic acid fiber. Wherein the spinneret plate has 400 holes, the aperture is phi 0.12mm, the spray-draw ratio is 3.5 times, the spinning speed is 70m/min, and the height of the air layer is 20 mm.

And S3, treating the polyamic acid fiber in a gradient heating thermal imidization furnace under a vacuum environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-450 ℃, and the heating rate is 15 ℃/min.

S4, drafting the obtained polyimide fiber by 3.0 times at 530 ℃ in a nitrogen environment to obtain the polyimide finished product fiber.

Example 2

S1, 32.44 g (0.300 mol) of p-phenylenediamine, 131.16 g (0.500 mol) of 2, 5-bis (4-aminophenyl) pyrimidine, 33.43 g (0.100 mol) of 2,2' -bis (4-aminophenyl) hexafluoropropane and 33.83 g (0.100 mol) of (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone (prepared from raw material preparation example 2) were dissolved in 5500 ml of N, N ' -dimethylformamide, and 147.11 g (0.500 mol) of 4,4' -biphenyldianhydride and 201.16 g (0.500 mol) of 3,3',4,4' -triphenyldiether tetracarboxylic dianhydride were added under stirring at 10 ℃ to polymerize at 10 ℃ for 16 hours to give a viscous polyamic acid solution, which was filtered and vacuum defoamed to give a dope.

The diamine monomer A- - (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone used was the monomer prepared in preparation example 2, and the structural formula was as follows:

s2, wet spinning forming: after the spinning slurry at normal temperature is accurately metered by a metering pump, the spinning slurry is extruded from a spinneret orifice and then directly enters a reactor with the volume ratio of 1: 7, washing with water in a coagulating bath of ethanol and water, and drying by a hot air channel to obtain the polyamic acid fiber. Wherein the spinneret plate has 1000 holes, the aperture is phi 0.04mm, the spray-draw ratio is 1.5 times, and the speed is 30 m/min.

And S3, carrying out gradient heating thermal imidization treatment on the polyamic acid fiber in an argon environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-380 ℃, and the heating rate is 20 ℃/min.

And S4, drafting the obtained polyimide fiber by 1.9 times at 520 ℃ in an argon environment to obtain the polyimide finished product fiber.

Example 3

S1, 206.32 g (0.920 mol) of 2- (4-aminophenyl) -5-aminobenzimidazole and 20.66 g (0.080 mol) of (3, 5-diaminophenyl) (2-hydroxy-4-methoxyphenyl) methanone (prepared from preparation example 3 of the starting material) were dissolved in 3500 ml of N-methylpyrrolidone, 294.22 g (1.000 mol) of 4,4' -biphenyldianhydride was added under stirring, and polymerization was carried out at 30 ℃ for 36 hours to obtain a viscous polyamic acid solution, which was filtered and vacuum defoamed to obtain a spinning dope.

S2, spinning and forming by a dry-jet wet method: the normal temperature spinning slurry is accurately metered by a metering pump, extruded out from a spinneret orifice, enters a coagulating bath of N-methyl pyrrolidone and water with the volume ratio of 1:3.5 through an air layer, and is washed by water and dried by 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 4.0 times, the spinning speed is 50m/min, and the height of the air layer is 30 mm.

And S3, carrying out 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.

S4, drafting the obtained polyimide fiber by 1.8 times at 490 ℃ in a nitrogen environment to obtain the polyimide finished product fiber.

Example 4

S1, 315.35 g (1.400 mol) of 5-amino-2- (4-aminophenyl) benzoxazole and 32.84 g (0.100 mol) of (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxyphenyl) methanone (prepared from preparation example 1 of the raw material) were dissolved in 4500 ml of N, N '-dimethylacetamide, and 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 ℃ and polymerized for 20 hours while maintaining at-10 ℃ to obtain a viscous polyamic acid solution, which was filtered, deaerated and vacuumed to be used as a spinning dope.

The diamine monomer A- - (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxyphenyl) methanone used was the monomer prepared in preparation example 1, and the structural formula was as follows:

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, N' -dimethylacetamide and water, and drying by a hot nitrogen channel to obtain the polyamide acid fiber. Wherein the spinneret plate has 200 holes, the aperture is phi 0.18mm, the spray-draw ratio is 3.6 times, the spinning speed is 60m/min, and the thickness of the air layer is 10 mm.

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

S1, 60.07 g (0.300 mol) of 3,4 '-diaminodiphenyl ether, 100.12 g (0.500 mol) of 4,4' -diaminodiphenyl ether, 101.49 g (0.300 mol) of (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) phenyl) methanone (prepared from preparation example 2) and 103.32 g (0.400 mol) of (3, 5-diaminophenyl) (2-hydroxy-5-methoxyphenyl) methanone (prepared from preparation example 5) were dissolved in 3000 ml of dimethyl sulfoxide, 327.18 g (1.50 mol) of pyromellitic dianhydride and 68.39 g (0.17 mol) of 2,2', 3,3' -triphenydimethylether tetracarboxylic dianhydride were added while stirring at-20 ℃ and polymerized for 12 hours while maintaining at-20 ℃ to obtain a viscous polyamic acid solution, which was filtered, and then subjected to filtration, And the obtained product is used as spinning slurry after vacuum defoamation.

The diamine monomer A- - (3, 5-diaminophenyl) (2-hydroxy-5-methoxyphenyl) methanone used was the monomer obtained in preparation example 5, having the following structural formula:

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 1:9 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 1.5 times, the spinning speed is 90m/min, and the height of the air layer is 15 mm.

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, 96.07 g (0.300 mol) of 2,2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl, 136.93 g (0.400 mol) of b-6, 68.47 g (0.200 mol) of b-7 and 67.66 g (0.200 mol) of (3, 5-diaminophenyl) (2-hydroxy-5- (4-fluorophenoxy) phenyl) methanone (prepared from raw material preparation example 6) were dissolved in 2000 ml of N, N ' -dimethylacetamide, and 168.15 g (0.500 mol) of the first dianhydride monomer represented by formula I-3 and 239.20 g (0.500 mol) of the second dianhydride monomer represented by formula I-3 were added under stirring at 20 ℃ to polymerize at 20 ℃ for 12 hours to give a viscous polyamic acid solution, which was filtered and vacuum defoamed to give a spinning dope.

The diamine monomer b-6 used has the following structural formula:

the diamine monomer b-7 used has the following structural formula:

the diamine monomer A- - (3, 5-diaminophenyl) (2-hydroxy-5- (4-fluorophenoxy) phenyl) methanone used was the monomer prepared in preparation example 6, having the following structural formula:

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 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 1:8, washing the obtained product in a coagulating bath of N, N' -dimethylacetamide and water, and drying the obtained product by a hot argon channel to obtain the polyamic acid fiber. Wherein the spinneret plate has 800 holes, the aperture is phi 0.16mm, the spray-draw ratio is 5.0 times, the spinning speed is 85m/min, and the height of the air layer is 30 mm.

And S3, treating the polyamic acid fiber in a gradient heating thermal imidization furnace under a vacuum environment to obtain the polyimide fiber. Wherein the thermal imidization temperature is 50-450 ℃, and the heating rate is 25 ℃/min.

And S4, drafting the obtained polyimide fiber by 4.0 times at 550 ℃ in an argon environment to obtain the polyimide finished fiber.

Example 7

S1, 213.05 g (0.950 mol) of 2- (4-aminophenyl) -5-aminobenzimidazole and 14.42 g (0.050 mol) of (3, 5-diaminophenyl) (2-hydroxy-4, 6-dimethoxyphenyl) methanone (prepared from preparation example 4 of the starting material) were dissolved in 3500 ml of N-methylpyrrolidone, 109.06 g (0.500 mol) of pyromellitic dianhydride and 155.10 g (0.500 mol) of 3,3',4,4' -diphenylether tetracarboxylic dianhydride were added under stirring, and polymerization was carried out at 10 ℃ for 20 hours to obtain a viscous polyamic acid solution, which was filtered, vacuum-defoamed and used as a spinning dope.

The monomer prepared in preparation example 4 by using diamine A- (3, 5-diaminophenyl) (2-hydroxy-4, 6-dimethoxyphenyl) methanone as a raw material has the following structural formula:

s2, spinning and forming by a dry-jet wet method: the normal temperature spinning slurry is accurately metered by a metering pump, extruded out from a spinneret orifice, enters a coagulating bath of N-methyl pyrrolidone and water with the volume ratio of 1:5 through an air layer, and is washed and dried by a hot nitrogen channel to obtain the polyamide acid fiber. Wherein the spinneret plate has 400 holes, the aperture is phi 0.20mm, the spray-draw ratio is 4.5 times, the spinning speed is 90m/min, and the height of the air layer is 50 mm.

And S3, carrying out 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 15 ℃/min.

S4, drafting the obtained polyimide fiber by 3.0 times at 520 ℃ in a nitrogen environment to obtain the polyimide finished product fiber.

Example 8

S1, 60.07 g (0.300 mol) of 4,4 '-diaminodiphenyl ether, 136.93 g (0.400 mol) of b-6, 87.68 g (0.300 mol) of (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) -6-methoxyphenyl) methanone (prepared from preparation example 7) were dissolved in 2000 ml of dimethyl sulfoxide, 294.23 g (1.000 mol) of 4,4' -biphenyldianhydride was added under stirring at-10 ℃ and polymerization was carried out at 15 ℃ for 24 hours to obtain a viscous polyamic acid spinning solution, which was filtered and vacuum defoamed to obtain a spinning dope.

The diamine monomer b-6 used has the following structural formula:

the diamine monomer A- - (3, 5-diaminophenyl) (2-hydroxy-4- (4-fluorophenoxy) -6-methoxyphenyl) methanone used as the starting monomer prepared in preparation example 7 had the following structural formula:

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 1:10 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 600 holes, the aperture is phi 0.18mm, the spray-draw ratio is 6.0 times, the spinning speed is 100m/min, and the height of the air layer is 60 mm.

And S3, carrying out 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 5.0 times at 500 ℃ in a nitrogen environment to obtain the polyimide finished fiber.

Example 9

S1, 291.92 g (0.900 mol) of b-7 and 35.84 g (0.100 mol) of (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxy-6-methoxyphenyl) methanone (prepared from raw material preparation example 8) were dissolved in 4500 ml of N-methylpyrrolidone, 65.44 g (0.300 mol) of pyromellitic dianhydride and 205.96 g (0.700 mol) of 4,4' -biphenyl dianhydride were added under stirring, and polymerization was carried out at 20 ℃ for 30 hours to obtain a viscous polyamic acid solution, which was filtered and vacuum defoamed to be used as a spinning dope.

The structural formula of the diamine monomer b-7 is as follows:

the monomer prepared in preparation example 8 by taking diamine A- (3, 5-diaminophenyl) (2-hydroxy-4-hexyloxy-6-methoxyphenyl) ketone as a raw material has the following structural formula:

s2, spinning and forming by a dry-jet wet method: the normal temperature spinning slurry is accurately metered by a metering pump, extruded out from a spinneret orifice, enters a coagulating bath of N-methyl pyrrolidone and water with the volume ratio of 1:8 through an air layer, and is washed and dried by a hot nitrogen channel to obtain the polyamide acid fiber. Wherein the spinneret plate has 1500 holes, the aperture is phi 0.15mm, the spray-draw ratio is 3.0 times, the spinning speed is 80m/min, and the height of the air layer is 30 mm.

And S3, carrying out 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 50-380 ℃, and the heating rate is 25 ℃/min.

S4, drafting the obtained polyimide fiber by 4.0 times at 580 ℃ in a nitrogen environment to obtain the polyimide finished fiber.

Comparative example 1

43.26g (0.400 mol) of p-phenylenediamine, 104.92 g (0.400 mol) of 2, 5-bis (4-aminophenyl) pyrimidine, 52.46 g (0.200 mol) of 2, 4-bis (4-aminophenyl) pyrimidine were dissolved in 4000 ml of N, N '-dimethylacetamide, and 147.11 g (0.500 mol) of 3,4' -biphenyldianhydride and 161.11 g (0.500 mol) of 3,3',4,4' -benzophenonetetracarboxylic dianhydride were added under stirring at 20 ℃ to polymerize 8 hours while maintaining at 20 ℃ to obtain a viscous polyamic acid defoaming solution, which was filtered and used as a spinning dope after vacuum deaeration.

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

337.88 g (1.500 mol) of 5-amino-2- (4-aminophenyl) benzoxazole 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 20 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 4 to obtain a polyimide finished fiber.

Example 10

The ultraviolet aging resistance of the finished fibers obtained in examples 1-9 and comparative examples 1-2 was tested 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 9 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 R is₁Selected from: alkyl, substituted or unsubstituted phenyl;

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: 0.85-1.20;

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.