阅读说明：本技术 一种低介电聚酰亚胺纤维的制备方法 (Preparation method of low-dielectric polyimide fiber ) 是由 董杰 张清华 甘锋 赵昕 郑森森 于 2020-06-24 设计创作，主要内容包括：本发明涉及一种低介电聚酰亚胺纤维的制备方法,包括：将含苯并环丁烯二胺、杂环二胺与极性非质子溶剂混合,搅拌,加入芳香族二酐,聚合反应,将得到的可溶性聚酰亚胺溶液脱泡,纺丝,然后热牵伸处理。该方法得到的低介电聚酰亚胺纤维具有低介电常数、低吸水率、尺寸稳定等特征,可用于透波复合材料、柔性电子基板及可穿戴设备等领域,赋予该类纤维一定的功能性,进一步拓展该类材料的应用范围。(The invention relates to a preparation method of a low dielectric polyimide fiber, which comprises the following steps: mixing benzocyclobutene-containing diamine, heterocyclic diamine and a polar aprotic solvent, stirring, adding aromatic dianhydride, carrying out polymerization reaction, defoaming the obtained soluble polyimide solution, spinning, and carrying out hot drawing treatment. The low dielectric polyimide fiber obtained by the method has the characteristics of low dielectric constant, low water absorption, stable size and the like, can be used in the fields of wave-transparent composite materials, flexible electronic substrates, wearable equipment and the like, endows the fiber with certain functionality, and further expands the application range of the material.)

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

(1) mixing benzocyclobutene-containing diamine, heterocyclic diamine and a polar aprotic solvent, stirring, adding aromatic dianhydride, and carrying out polymerization reaction to obtain a soluble polyimide solution, wherein the molar ratio of benzocyclobutene-containing diamine to heterocyclic diamine is 1: 9-4: 6, and the ratio of the total molar amount of benzocyclobutene-containing diamine and heterocyclic diamine to the molar amount of aromatic dianhydride is 1: 0.99-1: 1;

(2) defoaming the soluble polyimide solution obtained in the step (1), and spinning to obtain polyimide nascent fiber;

(3) and (3) carrying out hot drawing treatment on the polyimide nascent fiber in the step (2) to enable benzocyclobutene to be crosslinked, so as to obtain the polyimide fiber.

2. The method of claim 1, wherein the benzocyclobutene-containing diamine of step (1) has the formulaOne or two of them; the structural formula of the heterocyclic diamine isOne or two of them.

3. According toThe method according to claim 1, wherein the polar aprotic solvent in step (1) is N, N-dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP); the structural formula of the aromatic dianhydride is shown as

4. The method according to claim 1, wherein the total mass of the benzocyclobutene diamine, the heterocyclic diamine and the aromatic dianhydride in the step (1) is 12-15% of the total mass of the benzocyclobutene diamine, the heterocyclic diamine, the aromatic dianhydride and the polar aprotic solvent.

5. The method according to claim 1, wherein the stirring time in the step (1) is 1-2 h; the polymerization reaction is as follows: stirring and reacting for 8-12 h at 10-30 ℃, then heating to 160-190 ℃ in a gradient manner, and reacting for 6-12 h at constant temperature.

6. The method according to claim 5, wherein the gradient temperature is raised to 160-190 ℃, and the isothermal reaction is carried out for 6-12 hours: staying at 130 ℃, 145 ℃ and 155 ℃ for 1 hour respectively, and finally heating to 160-190 ℃ to react for 6-12 hours at constant temperature.

7. The method of claim 1, wherein the spinning in the step (2) is wet spinning, dry spinning or dry-jet wet spinning.

8. The method according to claim 1, wherein the temperature of the hot drawing treatment in the step (3) is 400 to 460 ℃; the residence time of the polyimide nascent fiber in the hot drawing channel is 0.5-2 min; the heat drafting multiplying power of the polyimide nascent fiber is 2-6 times.

9. A polyimide fiber prepared according to the method of claim 1.

10. Use of a polyimide fiber prepared according to the process of claim 1.

Technical Field

The invention belongs to the field of polyimide fiber preparation, and particularly relates to a preparation method of a low-dielectric polyimide fiber.

Background

The dielectric properties of the material directly affect the rapidity, accuracy and reliability of information transmission. Generally, a high dielectric constant material medium is easy to absorb electromagnetic waves and dissipate the electromagnetic waves in the form of heat, is not beneficial to information transmission and has a large potential safety hazard, so that the development of a low dielectric material has important application value in the fields of wave transmission, microelectronics, flexible display and the like.

Polyimide (PI) fibers, an important high-performance fiber, are imide ring structures containing polarity in molecular chains, have high temperature resistance, high specific strength, ultraviolet resistance and other properties, and are successfully applied to high and new fields such as high-temperature filtration, aerospace, marine equipment and the like at present. However, the imide structure has high polarity, which means that the material has high molecular polarizability, and usually the dielectric constant k of the polyimide material is greater than 3.0 (e.g. the dielectric constant k of Kapton film of dupont is approximately equal to 3.4), which is not favorable for obtaining high-performance low-dielectric composite material, so that it is of great significance to develop a low-dielectric polyimide fiber material with k < 3.0.

Polyimide has rich structure, and the molecular structure design and the hybridization of nano particles are effective strategies for reducing the dielectric constant of the material. For example, Zhang et al introduced trifluoromethyl, bulky pendant propeller groups into the polyimide molecular structure to produce an intrinsic low dielectric polyimide film with a dielectric constant of 1.52 (Chemistry of materials.2015; 27(19): 6543-. Huang et al introduced perfluoroaliphatic structures into polyimides to produce polyimide Materials having dielectric constants of about 2.43(ACS Applied Materials & interfaces.2016; 8(39): 26352-. In the early work, the hyperbranched siloxane nanoparticles are introduced into polyimide by the patent inventor group, the molecular polarizability is reduced by utilizing the intramolecular micro-crosslinking structure of the hyperbranched siloxane nanoparticles, and a high-performance polyimide fiber material with the dielectric constant of about 2.2 is prepared (Journal of Materials Chemistry C,2017,5(11): 2818-2825).

From the above studies, it is known that the molecular polarizability of polyimide can be effectively reduced by introducing bulky side groups and aliphatic groups to construct a cross-linked structure, thereby preparing a low dielectric material.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method of low-dielectric polyimide fiber so as to fill the blank in the prior art.

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

(1) mixing benzocyclobutene-containing diamine, heterocyclic diamine and a polar aprotic solvent, stirring, adding aromatic dianhydride, and carrying out polymerization reaction to obtain a soluble polyimide solution, wherein the molar ratio of benzocyclobutene-containing diamine to heterocyclic diamine is 1: 9-4: 6, and the ratio of the total molar amount of benzocyclobutene-containing diamine and heterocyclic diamine to the molar amount of aromatic dianhydride is 1: 0.99-1: 1;

(2) defoaming the soluble polyimide solution obtained in the step (1), and spinning to obtain polyimide nascent fiber;

(3) and (3) carrying out hot drawing treatment on the polyimide nascent fiber in the step (2) to enable benzocyclobutene to be crosslinked, so as to obtain the polyimide fiber.

The structural formula of the benzocyclobutene-containing diamine in the step (1) is as follows:

one or two of them.

The structural formula of the heterocyclic diamine in the step (1) is as follows:

one or two of them.

In the step (1), the polar aprotic solvent is N, N-dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP).

The structural formula of the aromatic dianhydride in the step (1) is as follows:

one or two of them.

In the step (1), the total mass of the benzocyclobutene diamine, the heterocyclic diamine and the aromatic dianhydride accounts for 12-15% of the total mass of the benzocyclobutene diamine, the heterocyclic diamine, the aromatic dianhydride and the polar aprotic solvent.

And (2) stirring time in the step (1) is 1-2 h.

The polymerization reaction in the step (1) is as follows: stirring and reacting for 8-12 h at 10-30 ℃, then heating to 160-190 ℃ in a gradient manner, and reacting for 6-12 h at constant temperature.

The gradient temperature is increased to 160-190 ℃, and the constant-temperature reaction is carried out for 6-12 h as follows: staying at 130 ℃, 145 ℃ and 155 ℃ for 1 hour respectively, and finally heating to 160-190 ℃ to react for 6-12 hours at constant temperature.

The steps (1) and (3) are carried out under the protection of nitrogen.

And (3) spinning in the step (2) is wet spinning, dry spinning or dry-jet wet spinning.

The temperature of the hot drawing treatment in the step (3) is 400-460 ℃.

In the step (3), the retention time of the polyimide nascent fiber in the hot drawing channel is 0.5-2 min.

And (4) in the step (3), the thermal drafting multiplying power of the polyimide nascent fiber is 2-6 times.

The invention provides a polyimide fiber prepared by the method.

The invention also provides an application of the polyimide fiber prepared by the method.

According to the invention, a benzocyclobutene and aromatic heterocyclic structure is introduced into a polyimide structure, on one hand, the steric effect of the side group and the asymmetry of the aromatic heterocyclic structure are utilized to prepare soluble polyimide, and the problems of difficult dissolution and difficult processing of the polyimide are solved; on the other hand, the introduced benzocyclobutene side group has thermal crosslinking reactivity, and a micro-crosslinking network can be formed after thermal drafting, so that the polyimide molecule polarizability is greatly reduced, and the low-dielectric polyimide fiber is obtained.

According to the invention, large-volume aliphatic benzocyclobutene is introduced into a polyimide molecular structure, and the molecules are crosslinked through high-temperature drawing, so that the low-dielectric fiber material is obtained.

Advantageous effects

The low dielectric polyimide fiber prepared by the invention has the characteristics of low dielectric constant, low water absorption, stable size and the like, can be used in the fields of wave-transparent composite materials, flexible electronic substrates, wearable equipment and the like, endows the fiber with certain functionality, and further expands the application range of the material.

Drawings

FIG. 1(A) is a cross-sectional SEM of a polyimide fiber in example 2; (B) the dielectric constants of the polyimide fibers of example 2 are compared with those of the Kapton structure polyimide fibers.

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 chemical reagents and sources in the invention are as follows:

2 (4-aminophenyl) -5-aminobenzimidazole, 2 (4-aminophenyl) -5-aminobenzoxazole, hexafluorodianhydride, and 3,3',4,4' -benzophenone tetracarboxylic dianhydride were purchased from Changzhou sunshine pharmaceutical Co., Ltd; the aprotic polar solvent N-methyl-pyrrolidone (NMP) was purchased from the national pharmaceutical group; the diamine containing benzocyclobutene is synthesized by self.

Fiber performance test conditions:

the mechanical property of the fiber is tested according to GB/T35441-2017; testing the water absorption of the fiber: taking quantity (w)₁) Placing the fiber sample in deionized water, soaking for 24h at room temperature, taking out, removing water adsorbed on the surface of the fiber by using absorbent paper, and weighing the weight of the fiber sample as w₂Water absorption rate ═ w₂-w₁)/w₁× 100%, and the thermal expansion coefficient is tested by a static thermal mechanical analysis method, the temperature range is 25-400 ℃,the heating rate is 5 ℃/min, and the load (2-4) kPa is applied; dielectric property testing was performed on a Novocontrol Concept80 apparatus at a test frequency of 3 μ Hz-3 GHz at room temperature.