阅读说明：本技术 一种高强高模聚酰亚胺纤维的制备方法 (Preparation method of high-strength high-modulus polyimide fiber ) 是由 董杰 张清华 赵昕 郑森森 甘锋 于 2020-06-24 设计创作，主要内容包括：本发明涉及一种高强高模聚酰亚胺纤维的制备方法,包括：将氟化二胺与联苯四胺或均苯四胺与溶剂混合,搅拌,加入二酐化合物,聚合反应,向得到的聚酰胺酸溶液中加入催化剂,继续反应,将得到的聚酰亚胺溶液与复配剂混合,干法纺丝,然后热牵伸。该方法可在纤维纺丝中同步发生化学反应,实现纤维形态结构与化学结构的同步调控,避免了传统“两步法”复杂的工序。(The invention relates to a preparation method of a high-strength high-modulus polyimide fiber, which comprises the following steps: mixing fluorinated diamine and biphenyl tetramine or pyromellitic dianhydride with a solvent, stirring, adding a dianhydride compound, carrying out polymerization reaction, adding a catalyst into the obtained polyamide acid solution, continuing the reaction, mixing the obtained polyimide solution with a compound agent, carrying out dry spinning, and then carrying out hot drawing. The method can synchronously generate chemical reaction in fiber spinning, realizes synchronous regulation and control of the fiber morphological structure and the chemical structure, and avoids the complicated process of the traditional two-step method.)

1. A polyimide fiber is characterized in that a dianhydride compound, fluorinated diamine and biphenyltetramine or pyromellitic tetramine are subjected to polymerization reaction, an obtained soluble copolymerized polyimide precursor containing an o-amino unit and 3-methyl-4 chloro-1-butene are mixed to prepare a spinning solution, and the spinning solution is formed by dry spinning and then subjected to heat treatment to obtain the polyimide fiber containing a benzimidazole unit.

2. The fiber of claim 1, wherein the dianhydride compound is 3,3',4,4' -benzophenonetetracarboxylic dianhydride; the fluorinated diamine has the structural formula

3. The fiber of claim 1, wherein the biphenyltetramine structure is a structure of biphenyltetramineStructure is asThe structural formula of the pyromellitic dianhydride is

4. A method for preparing a polyimide fiber, comprising:

(1) mixing fluorinated diamine and biphenyl tetramine or pyromellitic dianhydride with a solvent according to a molar ratio of 9: 1-5: 5, stirring, adding a dianhydride compound, carrying out polymerization reaction, adding a catalyst into the obtained polyamic acid solution, and continuing to react to obtain a polyimide solution, wherein the molar ratio of the total molar amount of the fluorinated diamine and the biphenyl tetramine or pyromellitic dianhydride compound to the molar amount of the dianhydride compound is 1: 0.98-1: 1.02;

(2) mixing a polyimide solution with a compound agent of 3-methyl-4 chloro-1-butene to form a polyimide intermediate containing an allylamine side group structure, and sequentially performing curing, filtering and defoaming treatment to obtain a spinning solution, wherein the molar ratio of the compound agent to the biphenyltetramine or the pyromellitic tetramine in the step (1) is 2-3: 1;

(3) and (3) metering the spinning stock solution in the step (2), extruding the spinning stock solution into a dry spinning channel through a spinneret plate, solidifying and forming the fiber, converting the allylamine side group into a benzimidazole unit, and carrying out hot drafting on the obtained nascent fiber to obtain the copolymerized polyimide fiber containing the benzimidazole unit.

5. The method according to claim 4, wherein the polymerization temperature in the step (1) is 0-5 ℃, and the polymerization time is 10-12 h; the continuous reaction is as follows: heating to 100 ℃ and 120 ℃ for reaction for 1-2 h, heating to 150 ℃ for reaction for 1-2 h, and heating to 200 ℃ for constant temperature reaction for 12-28 h.

6. The method according to claim 4, wherein the total mass of the fluorinated diamine, the biphenyl tetramine or the pyromellitic tetramine and the dianhydride compound in the step (1) accounts for 10-13 wt% of the total mass of the fluorinated diamine, the biphenyl tetramine or the pyromellitic tetramine, the dianhydride compound and the solvent; the solvent is N-methyl-pyrrolidone, NMP; the catalyst is pyridine, and the molar ratio of the pyridine to the fluorinated diamine is 1 (15-30).

7. The process of claim 4, wherein in step (3), the diameter of the spinneret plate is 50-100mm, the spinneret plate has 20-100 holes, and the extrusion speed is 5-18cm³Min, the temperature of the spinning shaft is 300-400 ℃.

8. The method according to claim 4, wherein the hot drawing in step (3) comprises the following process parameters: the processing environment is nitrogen atmosphere, the drawing temperature is 300-500 ℃, the drawing multiplying power is 3-5 times, and the drawing tension is 100-300 cN.

9. A polyimide fiber prepared according to the method of claim 4.

10. Use of a fiber according to claim 1.

Technical Field

The invention belongs to the field of polyimide fiber preparation, and particularly relates to a preparation method of a high-strength high-modulus polyimide fiber.

Background

Polyimide fibers are typical representatives of novel high-performance fibers, and the structure of highly conjugated aromatic rings and imide rings in molecular chains endows the novel high-performance fibers with excellent heat resistance, outstanding solvent corrosion resistance and radiation irradiation resistance stability and excellent mechanical properties. Compared with carbon fiber (rho is approximately equal to 1.5-2.0 g/cm)³) Glass fiber (rho is approximately equal to 2.2-2.4 g/cm)³) The polyimide fiber has lower density, higher specific strength and specific modulus; in addition, the polyimide fiber has more excellent ultraviolet radiation stability than the traditional aramid fiber, PBO and polyarylate fiber, so the fiber has wider application prospect in the fields of aerospace, advanced weapons, electronic communication, special protection, advanced composite materials and the like. However, the mechanical properties of the polyimide fiber are far lower than the theoretical level at present, and the scale development of the high-strength and high-modulus polyimide fiber is slow, and the reasons include: (1) the conventional polyimide molecular interchain/intrachain interaction is weaker, and the interchain/intrachain hydrogen bond equivalent valence bond action is lacked; (2) polyimide fibers are mostly prepared by a two-step process, namely the forming and imidization treatment of precursor polyamic acid fibers are two independent processes, the flow is long, and the synchronous regulation and control of the fiber solidification process and the cyclization reaction are difficult to realize; (3) heterocyclic diamine monomers such as benzimidazole, benzoxazole, pyrimidine and the like adopted for improving the interaction between/in the molecular chains of the polyimide are expensive and difficult to adapt to the requirement of large-scale development.

As early as 1912, Claisen et al found that during heating, the o-diketene unit first formed an o-diphenol intermediate that was eventually converted to a benzoxazole unit by thermal rearrangement, known as "Claisen thermal rearrangement". Through this thermal rearrangement reaction, the rigid benzoxazole units formed in the molecular chain impart outstanding mechanical properties, heat-resistant stability, and excellent dimensional stability to the material (Science Advance,2016,2, e 1501859). The Claisen thermal rearrangement can be realized at the temperature of 150-300 ℃, does not need harsh reaction conditions, is simple and easy to implement, and provides a new idea for introducing heterocyclic units such as benzoxazole, benzimidazole and the like into a molecular chain.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method of a high-strength high-modulus polyimide fiber, so as to overcome the defects of poor mechanical property, difficulty in cooperative regulation and control of fiber forming and chemical structure, high price of specific raw materials and the like of the polyimide fiber in the prior art.

The invention provides a polyimide fiber, which is prepared by carrying out polymerization reaction on dianhydride compound, fluorinated diamine and biphenyltetramine or pyromellitic tetramine, mixing the obtained soluble copolymerized polyimide precursor containing an ortho-amino unit with 3-methyl-4 chloro-1-butene to prepare spinning solution, carrying out dry spinning forming, and then carrying out heat treatment.

The dianhydride compound is 3,3',4,4' -benzophenonetetracarboxylic dianhydride BTDA, and the structural formula is

The fluorinated diamine has the structural formula:

the structural formula of the biphenyl tetramine is shown as

The structural formula of the pyromellitic dianhydride is shown in the specification

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

(1) mixing fluorinated diamine and biphenyl tetramine or pyromellitic dianhydride with a solvent according to a molar ratio of 9: 1-5: 5, stirring, adding a dianhydride compound, carrying out polymerization reaction, adding a catalyst into the obtained polyamic acid solution, and continuing to react to obtain a polyimide solution, wherein the molar ratio of the total molar amount of the fluorinated diamine and the biphenyl tetramine or pyromellitic dianhydride compound to the molar amount of the dianhydride compound is 1: 0.98-1: 1.02;

(2) mixing a polyimide solution with a compound agent of 3-methyl-4 chloro-1-butene to form a polyimide intermediate containing an allylamine side group structure, and sequentially performing curing, filtering and defoaming treatment to obtain a spinning solution, wherein the molar ratio of the compound agent to the biphenyltetramine or the pyromellitic tetramine in the step (1) is 2-3: 1;

(3) and (3) metering the spinning stock solution in the step (2), extruding the spinning stock solution into a dry spinning channel through a spinneret plate, solidifying and forming the fiber, converting the allylamine side group into a benzimidazole unit, and performing hot drafting, upstream and winding treatment on the obtained nascent fiber to obtain the copolymerized polyimide fiber containing the benzimidazole unit.

The polymerization reaction temperature in the step (1) is 0-5 ℃, and the polymerization reaction time is 10-12 h.

The continuous reaction in the step (1) comprises the following steps: the reaction temperature was gradually raised to 200 ℃ for reaction.

The reaction temperature is gradually increased to 200 ℃ to react: heating to 100 ℃ and 120 ℃ for reaction for 1-2 h, heating to 150 ℃ for reaction for 1-2 h, heating to 200 ℃ for constant temperature reaction for 12-28 h, and carrying out the reaction under the protection of nitrogen.

In the step (1), the total mass of the fluorinated diamine, the biphenyl tetramine or the pyromellitic tetramine and the dianhydride compound accounts for 10-13 wt% of the total mass of the fluorinated diamine, the biphenyl tetramine or the pyromellitic tetramine, the dianhydride compound and the solvent.

The solvent in the step (1) is N-methyl-pyrrolidone NMP.

In the step (1), the catalyst is pyridine, and the molar ratio of the pyridine to the fluorinated diamine is 1 (15-30).

The step (1) is carried out under the protection of nitrogen.

In the step (3), the diameter of the spinneret plate is 50-100mm, the spinneret plate is provided with 20-100 holes, and the extrusion speed is 5-18cm³Min, the temperature of the spinning shaft is 300-400 ℃.

The hot drawing in the step (3) comprises the following technological parameters: the processing environment is nitrogen atmosphere, the drawing temperature is 300-500 ℃, the drawing multiplying power is 3-5 times, and the drawing tension is 100-300 cN.

The invention also provides the polyimide fiber prepared by the method.

The invention also provides an application of the polyimide fiber.

In the previous experiment, the inventor finds that an amino group on an ortho side chain of imide can be subjected to condensation reaction with 3-methyl-4 chloro-1-butene to form an allylamine side group structure, and the allylamine side group structure can be converted into a benzimidazole unit when heated to 300 ℃, so that an intra-chain/inter-chain hydrogen bond effect is formed, and the mechanical property and the flame retardance of the material are greatly improved. Based on the method, the invention provides a novel preparation method of the high-strength high-modulus polyimide fiber, namely, soluble polyimide containing an o-amino side group structure is synthesized by a tetramine monomer, the soluble polyimide and a compound agent 3-methyl-4-chloro-1-butylene are compounded to form an allylamine intermediate, a benzimidazole unit is formed in high-temperature dry spinning, and the high-strength high-modulus polyimide fiber containing the benzimidazole unit is further prepared through treatments such as thermal drafting and the like.

According to the invention, the 3-methyl-4-chloro-1-butene compound is added to form an o-allylamine intermediate with an amino side group in a polyimide main chain, and the intermediate can be thermally rearranged in fiber dry spinning to be converted into a benzimidazole unit, so that the molecular chain rigidity is improved, and an equivalent valence bond effect of an inter-molecular chain/inner hydrogen bond is formed, thus the mechanical property of the fiber is greatly improved, and the high-strength high-modulus polyimide fiber is prepared.

Advantageous effects

(1) The invention can synchronously generate chemical reaction in fiber spinning, realizes the synchronous regulation and control of the fiber morphological structure and the chemical structure, and avoids the complicated working procedure of the traditional two-step method.

(2) The method can be used for continuous preparation, is simple to operate, has an environment-friendly process, is beneficial to large-scale preparation of the high-strength high-modulus polyimide fiber, and has a good industrial prospect.

(3) The polyimide fiber prepared by the invention has excellent tensile strength and modulus.

Drawings

FIG. 1(A) is a sectional SEM photograph of a polyimide fiber in example 2 of the present invention; (B) is a comparison graph of the mechanical properties of the polyimide fiber prepared in example 2 of the present invention and the polyimide fiber prepared without the compound agent.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The main reagents and sources in the examples of the present invention are: 3,3',4,4' -benzophenonetetracarboxylic dianhydride BTDA, 2-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane, 2 '-bistrifluoromethyl-4, 4' -diaminobiphenyl, and 3,3 '-bistrifluoromethyl-4, 4' -diaminobiphenyl were all commercial raw materials, purchased from vingzhou sunshine pharmaceutical co; chemical reagents N-methyl-pyrrolidone (NMP) and pyridine were purchased from the national pharmaceutical group; pyromellitic dianhydride and biphenyltetramine are commercial raw materials and purchased from Zhengzhou alpha chemical industry Co.

The mechanical property of the fiber is tested according to GB/T35441-2017.