阅读说明：本技术 一种芳纶纳米纤维/聚酰亚胺复合纸及其制备方法 (Aramid nanofiber/polyimide composite paper and preparation method thereof ) 是由 赵昕 秦秀芝 张清华 董杰 方玉婷 于 2020-06-04 设计创作，主要内容包括：本发明涉及一种芳纶纳米纤维/聚酰亚胺复合纸及其制备方法,所述复合纸上下层为芳纶纳米纤维,中间层为聚酰亚胺沉析纤维和云母的复合层。本发明制备工艺简单、可操作性高,产品具有优异的机械性能、电绝缘性能等,拓宽了使用领域。(The invention relates to aramid nano-fiber/polyimide composite paper and a preparation method thereof. The preparation method disclosed by the invention is simple in preparation process and high in operability, and the product has excellent mechanical properties, electric insulation properties and the like, so that the application field is widened.)

1. The aramid nano-fiber/polyimide composite paper is characterized in that: the upper layer and the lower layer of the composite paper are made of aramid nanofibers, and the middle layer is made of a polyimide fibrid/mica composite layer.

2. The composite paper according to claim 1, characterized in that: the mass ratio of the upper layer to the lower layer to the middle layer is 10-40: 20-80: 10-40.

3. A preparation method of aramid nano fiber/polyimide composite paper comprises the following steps:

(1) mixing the cleaned aramid fiber ANF, potassium hydroxide KOH and dimethyl sulfoxide DMSO, sealing, placing at room temperature, continuously stirring to obtain an ANF/DMSO solution, and adding deionized water to wash to obtain an ANF water dispersion;

(2) injecting the polyimide stock solution after the post-treatment into a precipitating agent to obtain polyimide fibrid suspension, and washing, filtering and vacuum drying to obtain polyimide fibrid; dispersing the polyimide/mica into water, and performing ultrasonic dispersion with mica to obtain polyimide fibrid/mica water dispersion;

(3) sequentially obtaining an ANF layer, a polyimide fibrid/mica composite layer and an ANF layer by adopting a vacuum auxiliary filtering mode to form an aramid nano fiber/polyimide composite film; and finally, carrying out vacuum drying and hot pressing to obtain the aramid nano-fiber/polyimide composite paper.

4. The production method according to claim 3, characterized in that: the dosage ratio of the ANF, the KOH and the DMSO in the step (1) is 1g to 1.5g to 500 mL.

5. The production method according to claim 3, characterized in that: the solid content of the ANF aqueous dispersion in the step (1) is 0.2-1%.

6. The production method according to claim 3, characterized in that: the preparation method of the polyimide stock solution in the step (2) comprises the following steps: adding a diamine monomer into an aprotic polar organic solvent at 0-25 ℃ under the protection of nitrogen, adding a dianhydride monomer after complete dissolution, stirring, and then adding a catalyst for heating cyclization or adding a chemical cyclization agent for chemical cyclization to obtain a polyimide stock solution.

7. The method of claim 6, wherein: the diamine monomer is one or more of p-phenylenediamine, m-phenylenediamine, hexafluoro-diamine, bisphenol A diether diamine, 4 '-diaminodiphenylmethane and 4, 4' -methylene diphenylamine; the dianhydride monomer is one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride and hydroquinone diether dianhydride; the aprotic polar organic solvent is dimethylacetamide or N-methylpyrrolidone; the catalyst is one or more of isoquinoline, acetic anhydride and triethylamine; the chemical cyclizing agent is one or more of triethylamine, acetic anhydride and pyridine.

8. The production method according to claim 3, characterized in that: the precipitation agent in the step (2) is a mixed solution consisting of deionized water and one or more of ethanol, methanol and an aprotic polar organic solvent; wherein the aprotic polar organic solvent is N-methylpyrrolidone, N-dimethylformamide or N, N-dimethylacetamide; the volume ratio of the precipitating agent to the polymerization liquid is 10-50: 1.

9. the production method according to claim 3, characterized in that: the mass ratio of the polyimide fibrid to the mica in the step (2) is 1: 9-9: 1.

10. The production method according to claim 3, characterized in that: the hot pressing process parameters in the step (3) are as follows:

the pressure is 5-25 MPa, and the time is 5-240 min; the technological parameters of vacuum drying are as follows: the temperature is 40-80 ℃ and the time is 1-10 h.

Technical Field

The invention belongs to the field of composite paper, and particularly relates to aramid nano-fiber/polyimide composite paper and a preparation method thereof.

Background

Aramid Nanofiber (ANF) is a novel polymer nanofiber newly developed in recent years, and has the dual advantages of aramid fiber and polymer nanofiber. The exposed functional groups of the ANF obtained by the deprotonation method are easy to form hydrogen bonds with other matrixes or reinforcements, and the ANF is in a gel form in an aqueous solution and has high interface bonding performance and self-assembly performance. Based on the excellent performance, the aramid nano-fiber based composite material with excellent mechanical system energy, heat resistance, ageing resistance and the like can be developed by utilizing a solvent exchange method and a layer-by-layer self-assembly technology.

Chinese patent CN 108316056A discloses an aramid nano-fiber film composite aramid paper and a preparation method thereof, wherein forming nets with different meshes are used for respectively obtaining ANF films as a surface layer and a bottom layer, aramid chopped fibers and aramid pulp or aramid fibrid paper are used as a core layer, then three layers are laminated and compounded, the aramid nano-fiber film composite aramid paper is obtained through post-treatment, the three layers are compounded together by directly utilizing the compatibility of aramid fibers, the interface bonding of the three layers is easy to occur, the mechanical property is reduced due to slippage, and meanwhile, other insulating materials are not added, so that the electrical insulating property of the final product is slightly low. Chinese invention patent CN 110485195A discloses a preparation method of aramid nano-fiber-based insulating paper, which comprises the steps of mixing an ANF/DMSO dispersion liquid with an inorganic insulating material/DMSO dispersion liquid to obtain a sol, replacing the sol with water to obtain hydrogel, and drying to obtain the aramid nano-fiber-based insulating paper.

The Polyimide (PI) fibrids are fibrous or film-like fibrids formed by precipitating a polyimide stock solution from a poor solvent thereof under high-speed stirring. The method has simple process, and the prepared fibrid has the advantages of stable performance, large specific surface area, low crystallinity, easy processing and forming, and the like. In the paper making process, the polyimide fibrids play roles in connection, filling and stress transmission, and the mechanical property of the finished paper is further improved.

Disclosure of Invention

The invention aims to solve the technical problem of providing the aramid nano-fiber/polyimide composite paper and the preparation method thereof, wherein the composite paper has excellent mechanical properties, electric insulation properties and the like, and the application field is widened.

The invention provides aramid nano-fiber/polyimide composite paper, wherein the upper layer and the lower layer of the composite paper are aramid nano-fiber, and the middle layer is a polyimide fibrid (PI)/mica composite layer.

The mass ratio of the upper layer to the lower layer to the middle layer is 10-40: 20-80: 10-40.

The composite paper has a basis weight of 50g/m²～100g/m²。

The invention also provides a preparation method of the aramid nano-fiber/polyimide composite paper, which comprises the following steps:

(1) mixing the cleaned aramid fiber ANF, potassium hydroxide KOH and dimethyl sulfoxide DMSO, sealing, placing at room temperature, continuously stirring to obtain an ANF/DMSO solution, and adding deionized water to wash to obtain an ANF water dispersion;

(2) injecting the polyimide stock solution after the post-treatment into a precipitating agent to obtain polyimide fibrid suspension, and washing, filtering and vacuum drying to obtain polyimide fibrid; dispersing the polyimide/mica into water, and performing ultrasonic dispersion with mica to obtain polyimide fibrid/mica water dispersion;

(3) sequentially obtaining an ANF layer, a polyimide fibrid/mica composite layer and an ANF layer (on a filter membrane) by adopting a vacuum auxiliary filtration mode to form an aramid nano fiber/polyimide composite membrane; and finally, carrying out vacuum drying and hot pressing to obtain the aramid nano-fiber/polyimide composite paper.

The method for cleaning the aramid fiber ANF in the step (1) comprises the following steps: soaking in acetone for 6-12 h, and then washing with deionized water for 4-6 times.

The dosage ratio of the ANF, the KOH and the DMSO in the step (1) is 1g to 1.5g to 500 mL.

The continuous stirring speed in the step (1) is 500-1000 r/min.

And (2) the volume ratio of the deionized water to the DMSO in the step (1) is 1:1, so that ANF is precipitated and repeatedly washed for 4-6 times.

The solid content of the ANF aqueous dispersion in the step (1) is 0.2-1%.

The preparation method of the polyimide stock solution in the step (2) comprises the following steps: adding a diamine monomer into an aprotic polar organic solvent at 0-25 ℃ under the protection of nitrogen, adding a dianhydride monomer after complete dissolution, stirring, and then adding a catalyst for heating cyclization or adding a chemical cyclization agent for chemical cyclization to obtain a polyimide stock solution.

The diamine monomer is one or more of p-phenylenediamine, m-phenylenediamine, hexafluoro-diamine, bisphenol A diether diamine, 4 '-diaminodiphenylmethane and 4, 4' -methylene diphenylamine.

The dianhydride monomer is one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride and hydroquinone diether dianhydride.

The molar ratio of the diamine monomer to the dianhydride monomer is as follows: 1: 0.9-1: 1.1.

The aprotic polar organic solvent is dimethylacetamide or N-methylpyrrolidone.

The catalyst is one or more of isoquinoline, acetic anhydride and triethylamine.

The chemical cyclizing agent is one or more of triethylamine, acetic anhydride and pyridine.

Preferably, the aprotic polar organic solvent is N-methylpyrrolidone; the diamine is a mixture of 2, 4-diaminotoluene (TDA) and 4, 4' -diaminodiphenylmethane (MDA); the dianhydride is 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride (BTDA). The reaction parameters of the heating cyclization are as follows: polymerizing for 1-3 h at 100 ℃, heating to 120 ℃, polymerizing for 3-5 h, and heating to 180 ℃ for polymerizing for 5-15 h; the chemical cyclizing agent is one or more of triethylamine, acetic anhydride and pyridine, and the molar ratio of the chemical cyclizing agent to the diamine is 0: 1-1: 1; the reaction temperature of the chemical cyclization is 60-80 ℃.

And (3) carrying out post-treatment in the step (2) including filtering, defoaming and diluting.

The precipitation agent in the step (2) is a mixed solution consisting of deionized water and one or more of ethanol, methanol and an aprotic polar organic solvent; wherein the aprotic polar organic solvent is N-methylpyrrolidone, N-dimethylformamide or N, N-dimethylacetamide. The volume ratio of the precipitating agent to the polymerization liquid is 10-50: 1.

the injection in the step (2) is specifically as follows: the stirring speed is 2000-10000 r/min, the injection speed is 0.5-1 mL/min, and the stirring time is 1-2 min after the solution is completely injected.

The mass ratio of the polyimide fibrid to the mica in the step (2) is 1: 9-9: 1. The ultrasonic dispersion time with mica is 0.5-1 h.

The hot pressing process parameters in the step (3) are as follows: the pressure is 5-25 MPa, and the time is 5-240 min; the technological parameters of vacuum drying are as follows: the temperature is 40-80 ℃ and the time is 1-10 h.

The aramid nano-fiber/polyimide composite paper is a sandwich structure composite paper with an ANF layer, a polyimide fibrid/mica composite layer and an ANF layer sequentially formed in a vacuum-assisted filtering mode, PI fibrid and mica in the middle layer are stacked to form a brick mud structure, meanwhile, fibrid plays a role of a binder to be connected with the ANF layer, the mechanical property, the heat resistance and the like of the composite paper are further improved, and in addition, the electrical insulation property of the composite paper is also improved due to the addition of the mica.

Advantageous effects

(1) According to the invention, the ANF and PI fibrid/mica composite layers are laminated layer by a vacuum auxiliary filtration method to prepare the composite paper with a sandwich structure, and the method is simple and has high operability.

(2) The mica is added in the invention, so that the electrical insulation performance of the composite paper can be improved, and meanwhile, the mica and the fibrids can be wound and stacked, so that the mechanical strength is improved.

(3) On the other hand, the polyimide fibrid of the invention can be used as a binder to connect the upper and lower ANF layers, and the ANF on the upper layer can be absorbed into the gap of the middle layer in the vacuum filtration process, so that the comprehensive performance of the composite paper is greatly improved.

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.

First, experimental medicine

Second, testing method

1. Tensile index

According to GB/T12914-2008 constant-rate loading method, a tensile strength tester is used to stretch a specimen of a prescribed size to break under constant-rate loading, measure the tensile strength thereof, and calculate the tensile index from the obtained result and the quantitative amount of the specimen.

2. Tensile strength

The paper is cut into sample strips with the length of 100mm and the width of 5mm, the tensile test is carried out on a universal material testing machine, each sample is tested repeatedly for 5 times, and the average value is taken.

3. Thermal stability test

And (3) testing the temperature index of the sample at the thermal weight loss of 5% by using a thermogravimetric analyzer to represent the thermal stability of the composite paper.

4. Breakdown strength test

The breakdown voltage of the paper is measured according to the ASTM-149 standard, and a power frequency rapid boosting method is adopted, namely the boosting speed is controlled, so that the breakdown time of the fiber paper is 15-20 s.