CN109082119B - Cellulose modified polyimide corona-resistant film and preparation method thereof - Google Patents
Cellulose modified polyimide corona-resistant film and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a cellulose modified polyimide corona-resistant film and a preparation method thereof, wherein the preparation method comprises the following steps: adding aluminum isopropoxide, KH550 silane coupling agent and emulsifier into the pretreated cellulose, and dispersing at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 4, 4' -diaminodiphenyl ether and dimethylacetamide to form an amine-containing solution, stirring and mixing the emulsion and the amine-containing solution, and then adding pyromellitic dianhydride to the mixed solution in steps to prepare polyamic acid resin; the obtained polyamic acid resin forms a film through a tape casting process, and the film is heated to obtain the cellulose modified polyimide film. In the film of the invention, alumina particles are uniformly distributed in the polyimide film; the cellulose forms a net structure in the film, so that the strength of the film is improved; the introduction of the cellulose can also improve the dielectric property and corona resistance of the film.
Description
Technical Field
The invention relates to the field of chemical and chemical material preparation, in particular to a polyimide film, and more particularly relates to a cellulose modified polyimide corona-resistant film and a preparation method thereof.
Background
The Polyimide (PI) film has good heat resistance, mechanical property, electrical property and radiation resistance, and plays an important role in the fields of electronic industry, aerospace and the like. However, the common PI film has poor corona resistance, and cannot meet the requirements of special electrical equipment such as a high-voltage generator, a high-voltage engine, a variable frequency motor and the like.
In order to solve the deficiency of the corona resistance of the PI film, the U.S. Dupont company successively proposed the series of the corona resistant PI film filled with nano alumina Kapton CR and Kapton FCR in about 1994. The service life of the Kapton CR can exceed one hundred thousand hours under the alternating current of 50Hz and the electric field intensity of 20MV/m, while the service life of the traditional Kapton 100HN film is only about 200 hours. But are expensive and are due to strategic considerations of high-end equipment. It is necessary to master the mature corona-resistant PI film preparation technology in China.
In recent decades, China has made detailed research on corona-resistant PI films and has achieved certain achievements and conclusions, wherein the research is considered to be specific to polyimide corona-resistant nano composite materialsThe material has many factors which influence the performance of the material. The preparation process, the type, the content and the surface chemical modification of the nano filler are key factors influencing the performance of the composite material. The preparation process of the polyimide corona-resistant film mainly comprises an in-situ compounding method and a sol-gel method, and the two processes have advantages and disadvantages respectively. In-situ compounding often requires surface chemical modification of the nanofiller, but the surface chemical modification effect of the inorganic nanofiller is poor, and the dispersibility of the nanofiller in a polyimide matrix is difficult to improve. However, the method has simple flow and mature process and is very suitable for industrial production. The sol-gel method allows the nanoparticles to be uniformly dispersed in the matrix, but has many disadvantages. If a certain amount of water and catalyst are added, the performance of the polymer is obviously influenced; secondly, in the process of drying the gel, the volatilization of solvents, small molecules and water can cause the internal shrinkage stress of the material, and the mechanical property of the material are influenced; in addition, the method cannot realize the control of the crystal form of the inorganic particles. The sol-gel process has many problems in industrial production. Regarding the kind of nano-filler, except for nano-Al adopted by DuPont2O3Other than, nano SiO2Nano TiO 22The corona resistance of the polyimide film can be improved to different degrees by nano ZnO, nano AlN and montmorillonite (MMT). The corona resistance of the film can be further improved by the synergistic addition of different nano-fillers (Applied Surface Science 2012, 263: 30).
Chinese patent CN101812183A discloses a method for preparing a polyimide multilayer composite film containing inorganic nano-powder, which comprises the following steps: (1) pretreating inorganic nano powder; (2) dissolving 4, 4' -diaminodiphenyl ether and pyromellitic dianhydride serving as raw material monomers in a solvent, and polymerizing to generate a polyamic acid solution; (3) dispersing the pretreated inorganic nano powder in a solvent by ultrasonic waves, and adding the solvent into a polyamic acid solution to prepare the polyamic acid solution containing the inorganic nano powder; (4) respectively sequentially paving films on a polyamic acid solution containing inorganic nano powder and a pure polyamic acid solution; (5) and putting the film into an oven for thermal imidization treatment at 50-400 ℃ to obtain the polyimide hybrid multilayer composite film containing the inorganic nano powder. The obtained polyimide composite material containing inorganic nano powder often reduces the mechanical property of the film, and particularly, when the nano powder is not uniformly dispersed, the reduction of the film property is more obvious.
Chinese patent CN101805517A discloses a method for preparing polyimide film filled with inorganic particles, which comprises adding grinding balls with diameter not more than 6mm into a grinding barrel of a medium motion grinder, adding part of organic solvent, inorganic particles and surface modifier for ball milling, and uniformly dispersing the inorganic particles into the organic solvent to obtain inorganic particle/organic solvent suspension. And adding the inorganic particle/organic solvent suspension, the residual organic solvent, the diamine and the dianhydride in equal molar ratio into a reaction kettle, preparing an inorganic particle/polyamic acid solution suspension according to a conventional method, and obtaining the polyimide film filled with the inorganic particles according to a conventional tape casting production process. The film has good transparency and excellent mechanical property.
However, the polyimide film obtained by compounding the inorganic particles has a limited degree of improvement in corona resistance, and has disadvantages such as uneven dispersion of the inorganic particles. Therefore, it is urgently needed to develop a polyimide film which can significantly improve the corona resistance of the polyimide film, can better control the uniform distribution of inorganic particles in the film, and can meet the requirement of industrialization.
Disclosure of Invention
The present inventors have developed a cellulose-modified polyimide film to solve one or more of the above-mentioned problems, in view of the disadvantages of non-uniform dispersion of inorganic particles, insufficient bonding strength, limited improvement of corona resistance, and the like in the conventional inorganic particle-compounded polyimide film.
According to a first aspect of the present invention, there is provided a polyimide film, which comprises the following specific scheme:
a composition of a cellulose modified polyimide film comprises the following components in parts by weight:
about 150-200 parts of polyimide, about 1-5 parts of nano alumina particles, about 0.01-1 part of cellulose and about 1-5 parts of silane coupling agent, and is characterized in that the cellulose is loaded on the nano alumina particles and uniformly distributed in the film.
Preferably, the nano alumina particles have a particle size of about 2 to 50 nm.
Preferably, the weight fraction of the cellulose relative to the nano-alumina is 15-20%.
The invention also provides a preparation method of the cellulose modified polyimide film, which comprises the following steps:
(1) cellulose pretreatment: properly crushing cellulose, performing alkaline leaching treatment, washing with water, and drying in the air; then carrying out steam explosion treatment;
(2) preparing an emulsion: adding the pretreated cellulose obtained in the step (1) into deionized water, magnetically stirring, adding aluminum isopropoxide, a KH550 silane coupling agent and an emulsifier, and dispersing at a high speed in a high-pressure emulsifying machine to form uniform emulsion;
(3) preparation of a polyamic acid resin: mixing and dissolving 4, 4 '-diaminodiphenyl ether and dimethylacetamide to form an amine-containing solution, simultaneously adding the emulsion obtained in the step (2) and the amine-containing solution obtained in the step (3) into a reaction kettle according to the mass ratio of 1: 1.1-20, stirring and mixing, and then adding pyromellitic dianhydride to the mixed solution in steps according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride to 4, 4' -diaminodiphenyl ether to obtain polyamide acid resin;
(4) casting and film forming: forming a film from the polyamic acid resin obtained in the step (3) through a tape casting process;
(5) film imidization: and (4) heating the film obtained in the step (4) to obtain the corona-resistant porous alumina/polyimide film.
Preferably, in the step (1), the cellulose is lignocellulose.
Preferably, in the step (1), the pressure of the steam explosion process is about 1.0-3.0Mpa, and the time is about 300-.
Preferably, in the step (2), the mass ratio of the cellulose to the aluminum isopropoxide to the KH550 to the emulsifier is 0.1-1: 0.001-0.02: 0.005-0.01; more preferably, the mass ratio of the cellulose, the aluminum isopropoxide, the KH550 and the emulsifier is 0.8-1: 0.001-0.005: 0.008-0.01, and most preferably 1: 0.002: 0.01.
Preferably, the emulsifier is alkylphenol ethoxylates.
Preferably, in the step (3), the amine-containing solution is prepared by mixing 20-25% of 4, 4' -diaminodiphenyl ether and 75-80% of dimethylacetamide in a mass ratio.
Preferably, the casting process in step (4) is to heat the polyamic acid resin on a casting machine to cast to form a film, and stretch the cast film on a longitudinal stretcher according to the required size.
Preferably, the heating temperature in the step (5) is 350-450 ℃.
Here, it should be noted that the description of the above technical solutions is exemplary, the present specification may be embodied in different forms, and should not be construed as being limited to the technical solutions set forth herein. Rather, these descriptions are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solution of the present invention is limited only by the scope of the claims.
The shapes, sizes, ratios, angles, and numbers disclosed to describe aspects of the specification and claims are examples only, and thus, the specification and claims are not limited to the details shown. In the following description, when a detailed description of related known functions or configurations is determined to unnecessarily obscure the focus of the present specification and claims, the detailed description will be omitted.
In the case of using "including", "having", and "including" described in this specification, there may be another portion or other portions unless the term "only" is used, and the terms used may generally be singular but may also mean plural.
It should be noted that although the terms "first," "second," etc. may be used and described herein to describe various elements and components, these elements and components should not be limited by these terms. These terms are only used to distinguish one element or section from another element or section. For example, a first component may be termed a second component, and, similarly, a second component may be termed a first component, without departing from the scope of the present description.
According to the technical scheme of the invention, the cellulose is uniformly loaded in the alumina precursor through the pretreatment and emulsification operations in the early stage, and the alumina can be dispersedly distributed in the polyimide film by utilizing the dispersion and winding action of the cellulose in the emulsion; without wishing to be bound by any theory, the applicant may form a network structure in the film, which also positively affects the tensile strength and the elastic modulus of the film. Meanwhile, the introduction of the cellulose and the structure also improve the dielectric property and corona resistance of the film and prolong the service life of the film in a strong electromagnetic field.
Drawings
FIG. 1a is an SEM image of the surface layer of a cellulose-modified polyimide film of example 1;
FIG. 1b is an SEM image of a cross-section of a cellulose-modified polyimide film of example 1;
Detailed Description
The following describes a specific embodiment of the present invention with reference to examples.
Example one
A preparation method of a cellulose modified polyimide film comprises the following steps:
crushing 10g of lignocellulose, carrying out alkaline leaching for 30min, washing with water, drying, carrying out steam explosion for 300s at the pressure of 1.6MPa, adding the obtained pretreated cellulose into deionized water, carrying out magnetic stirring, adding 10g of aluminum isopropoxide, 0.02gKH550 silane coupling agent and 0.1g of emulsifier, and dispersing at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 25 percent of 4, 4' -diaminodiphenyl ether and 75 percent of dimethylacetamide (mass percentage) into an amine-containing solution, and adding the emulsion and the amine-containing solution into a reaction kettle while stirring and mixing according to the mass ratio of 1: 4; then, according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride to 4, 4' -diaminodiphenyl ether, adding pyromellitic dianhydride to the mixed solution step by step to prepare polyamic acid resin; the obtained polyamic acid resin forms a film through a tape casting process; the film was heated at 400 ℃ to obtain a cellulose-modified polyimide film.
The SEM image of the surface layer of the cellulose-modified polyimide film obtained in example 1 is shown in fig. 1a, and the SEM image of the cross section is shown in fig. 1 b. From SEM, it can also be seen that cellulose and inorganic particles are uniformly distributed on the surface and inside of the film, the cellulose tends to form an interwoven structure, and the similar net structure can improve the internal tension of the film, thereby improving the elasticity and tensile mechanical property of the film.
Example two
A preparation method of a cellulose modified polyimide film comprises the following steps:
crushing 2.5g of lignocellulose, carrying out alkaline leaching for 30min, washing with water, drying, carrying out steam explosion for 400s at the pressure of 1.5MPa, adding the obtained pretreated cellulose into deionized water, carrying out magnetic stirring, adding 10g of aluminum isopropoxide, 0.01gKH550 silane coupling agent and 0.1g of emulsifier, and dispersing at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 20% of 4, 4 '-diaminodiphenyl ether and 80% of dimethylacetamide to form an amine-containing solution, adding the emulsion and the amine-containing solution into a reaction kettle at the same time according to the mass ratio of 1: 4, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution in steps according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride to 4, 4' -diaminodiphenyl ether to prepare polyamide acid resin; the obtained polyamic acid resin forms a film through a tape casting process; the film was heated at 400 ℃ to obtain a cellulose-modified polyimide film.
EXAMPLE III
A preparation method of a cellulose modified polyimide film comprises the following steps:
crushing 10g of lignocellulose, carrying out alkaline leaching for 30min, washing with water, drying, carrying out steam explosion for 300s at the pressure of 1.6MPa, adding the obtained pretreated cellulose into deionized water, carrying out magnetic stirring, adding 10 parts of aluminum isopropoxide, 0.02gKH550 silane coupling agent and 0.1g of emulsifier, and dispersing at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 25% of 4, 4 '-diaminodiphenyl ether and 75% of dimethylacetamide to form an amine-containing solution, adding the emulsion and the amine-containing solution into a reaction kettle at the same time according to the mass ratio of 1: 4, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution step by step according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride and 4, 4' -diaminodiphenyl ether to prepare polyamide acid resin; the obtained polyamic acid resin forms a film through a tape casting process; the film was heated at 370 ℃ to obtain a cellulose-modified polyimide film.
Example four
A preparation method of a cellulose modified polyimide film comprises the following steps:
crushing 5g of lignocellulose, carrying out alkaline leaching for 30min, washing with water, drying, carrying out steam explosion for 300s at the pressure of 2.0MPa, adding the obtained pretreated cellulose into deionized water, carrying out magnetic stirring, adding 10g of aluminum isopropoxide, 0.1gKH550 silane coupling agent and 0.1g of emulsifier, and dispersing at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 25% of 4, 4 '-diaminodiphenyl ether and 75% of dimethylacetamide to form an amine-containing solution, adding the emulsion and the amine-containing solution into a reaction kettle at the same time according to the mass ratio of 1: 10, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution step by step according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride and 4, 4' -diaminodiphenyl ether to prepare polyamide acid resin; the obtained polyamic acid resin forms a film through a tape casting process; the film was heated at 430 ℃ to obtain a cellulose-modified polyimide film.
EXAMPLE five
A preparation method of a cellulose modified polyimide film comprises the following steps:
crushing 5g of lignocellulose, carrying out alkaline leaching for 30min, washing with water, drying, carrying out steam explosion for 600s at the pressure of 2.0MPa, adding the obtained pretreated cellulose into deionized water, carrying out magnetic stirring, adding 10g of aluminum isopropoxide, 0.2gKH550 silane coupling agent and 0.1g of emulsifier, and dispersing at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 25% of 4, 4 '-diaminodiphenyl ether and 75% of dimethylacetamide to form an amine-containing solution, adding the emulsion and the amine-containing solution into a reaction kettle at the same time according to the mass ratio of 1: 10, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution step by step according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride and 4, 4' -diaminodiphenyl ether to prepare polyamide acid resin; the obtained polyamic acid resin forms a film through a tape casting process; the film is heated at 360 ℃ to obtain the cellulose modified polyimide film.
EXAMPLE six
A preparation method of a cellulose modified polyimide film comprises the following steps:
1g of lignocellulose is crushed, alkali is soaked for 30min, water washing and drying are carried out, steam explosion is carried out for 300s under the pressure of 1.6MPa, the obtained pretreated cellulose is added into deionized water, magnetic stirring is carried out, 10g of aluminum isopropoxide, 0.05gKH550 silane coupling agent and 0.1g of emulsifying agent are added, and the mixture is dispersed at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 25% of 4, 4 '-diaminodiphenyl ether and 75% of dimethylacetamide to form an amine-containing solution, adding the emulsion and the amine-containing solution into a reaction kettle at the same time according to the mass ratio of 1: 8, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution step by step according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride and 4, 4' -diaminodiphenyl ether to prepare polyamide acid resin; the obtained polyamic acid resin forms a film through a tape casting process; the film was heated at 400 ℃ to obtain a cellulose-modified polyimide film.
The following property tests were carried out on the cellulose-modified polyimide films obtained in examples 1 to 6.
(I) Corona resistance test
The polyimide film is prepared by adopting the process according to the embodiment of the invention, and the polyimide composite film with the thickness of about 10 mu m is prepared. The composite film is cut into a plurality of samples of 50mm multiplied by 50mm, and corona resistance test is carried out. The corona resistance test adopts IEC-60343 standard, namely the diameter of a corona rod electrode is 6mm (the diameter of an electrode end face is 4mm, and the radius of a fillet is R1mm), the diameter of a plate electrode is 50mm, and the test conditions are room temperature, the environmental humidity is below 40%, the frequency is 50Hz, and the field intensity is 20 kV/mm.
(II) measurement of relative dielectric constant
The series experiment adopts a tricigen dielectric temperature spectrometer, a test fixture is designed according to an international standard ASTMD150 method, and a parallel plate electrode principle is adopted, wherein a test electrode consists of an upper electrode, a lower electrode and a protective electrode. To ensure the accuracy of the measurement results, the samples were prepared in the following dimensions: 1. sample size: the diameter is 5-40mm, and the thickness is less than 1 mm; 2. preparing a sample into a circular film sample, and plating electrodes on two sides of the sample; 3. the surface of the sample is flat and smooth, and good contact with the parallel electrodes is ensured.
(III) volume resistivity test
The composite film was cut into a number of 50mm x 50mm samples and subjected to resistivity testing. The method of the national standard GBT 1410-2006 is adopted to test the volume resistivity of the thin film. The instrument is a ZST-121 volume resistance tester in the middle aviation age.
(IV) tensile Strength and elongation at Break test
The stretching device is an electronic stretching machine (thin film electronic stretching machine) of a TSL advanced servo system. Sample preparation: the polyimide film had a thickness of 10 μm and a width of 30 mm. Test speed: 100 plus or minus 30 mm/min. The test load range is adjustable between 50N and 1000N. Sample clamping: the sample is placed in two clamps of the testing machine, so that the longitudinal axis of the sample is superposed with the central connecting line of the upper clamp and the lower clamp, and the tightness of the clamps is proper. Calculation formula of tensile strength:
tensile strength calculation formula:
σ＝F/b
σ: tensile Strength (kN/m)
F: force value (N)
b: width (mm).
The elongation at break calculation formula:
elongation at break ═ Δ L/L ═ 100%
The original length L, the length at break after deformation is L ', and the elongation at break Δ L ═ L' -L.
(V) elastic modulus test
The elastic modulus of the film is tested by a testing method recorded in 'nano indenter and laser ultrasonic technology for testing the elastic modulus of the film' (Chinese testing technology, No. 33, No. 1 of 2007), and the thickness of the film is 100 μm. The indentation tester used is a microhardness tester Fischer scopo H100. The indenter used in the test was a triangular pyramid indenter and the indentation test was performed according to ISO standard 14577-1. Three maximum loads of 5, 10 and 15mN are set in the test. The loading process was completed in 60 times in 30s, and the creep time at maximum load was set to 30 s. The unloading process is the same as loading. After the maximum load and the loading speed are set and the position of the sample to be positioned is selected, the test system automatically and continuously records the load-displacement relation in the loading and unloading processes. Two different curves were obtained because the specimen undergoes elastic-plastic deformation of the material upon loading of the force and elastic recovery upon unloading of the force. The elastic modulus is then calculated by the formula.
The samples of the examples were subjected to electrical and mechanical property tests, and the results are shown in table 1.
TABLE 1
As can be seen from the table, compared with the prior art, the cellulose modified polyimide film of the invention has the advantages that various electrical properties including corona resistance are improved, and the service life under a high-voltage electric field is obviously prolonged. Meanwhile, since the cellulose is uniformly introduced even in a net structure, the mechanical properties of the film in terms of tensile strength and elastic modulus are also improved.
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
The invention provides at least the following solutions:
scheme 1. a cellulose modified polyimide film comprises the following components in parts by weight:
about 150-200 parts of polyimide, about 1-5 parts of nano alumina particles, about 0.01-1 part of cellulose and about 1-5 parts of silane coupling agent, and is characterized in that the cellulose can be loaded on the nano alumina particles and uniformly distributed in the film.
Scheme 2. a cellulose modified polyimide film according to scheme 1 or 2, wherein the nano alumina particles have an average particle size of about 2 to 50 nm.
Scheme 3. a cellulose modified polyimide film according to any of schemes 1 to 3, wherein the weight fraction of the cellulose relative to the nano alumina particles is 15 to 20%.
Scheme 4. a method of preparing a cellulose modified polyimide film as described in any one of schemes 1 to 3, comprising the steps of:
step (1): cellulose pretreatment: crushing cellulose, then carrying out alkaline leaching treatment, washing and airing; then carrying out steam explosion treatment;
step (2): preparing an emulsion: adding the pretreated cellulose obtained in the step (1) into deionized water, magnetically stirring, adding aluminum isopropoxide, a KH550 silane coupling agent and an emulsifier, and dispersing at a high speed in a high-pressure emulsifying machine to form uniform emulsion;
and (3): preparation of a polyamic acid resin: mixing and dissolving 4, 4 '-diaminodiphenyl ether and dimethylacetamide to form an amine-containing solution, simultaneously adding the emulsion obtained in the step (2) and the amine-containing solution into a reaction kettle according to the mass ratio of 1: 1.1-20, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution in steps according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride to 4, 4' -diaminodiphenyl ether to obtain polyamide acid resin;
and (4): casting and film forming: forming a film from the polyamic acid resin obtained in the step (3) through a tape casting process;
and (5): film imidization: and (3) heating the film obtained in the step (4) to obtain the cellulose modified polyimide film with improved corona resistance.
Scheme 5. the preparation method according to scheme 4, wherein in step (1), the cellulose is lignocellulose.
Scheme 6. the preparation method according to scheme 4, wherein in the step (1), the steam explosion process is performed at a pressure of about 1.0-3.0Mpa for about 300-600 s.
Scheme 7. the preparation method according to scheme 4, wherein in the step (2), the mass ratio of the pretreated cellulose, aluminum isopropoxide, KH550 and the emulsifier is 0.1-1: 0.001-0.02: 0.005-0.01.
Scheme 8. the preparation method according to any of the claims 4 to 7, characterized in that the emulsifier is alkylphenol ethoxylates.
Scheme 9. the preparation method according to any one of schemes 4 to 8, characterized in that in the step (3), the amine-containing solution is mixed by 20-25% of 4, 4' -diaminodiphenyl ether and 75-80% of dimethylacetamide in a mass ratio.
Scheme 10. the preparation process according to any of schemes 4 to 9, characterized in that the heating temperature in step (5) is 350-450 ℃.
The invention can also independently provide a preparation method of one or more cellulose modified polyimide films. For example:
scheme 11. a method for preparing a cellulose-modified polyimide film, the method comprising the steps of:
step (1): cellulose pretreatment: crushing cellulose, then carrying out alkaline leaching treatment, washing and airing; then carrying out steam explosion treatment;
step (2): preparing an emulsion: adding the pretreated cellulose obtained in the step (1) into deionized water, magnetically stirring, adding aluminum isopropoxide, a KH550 silane coupling agent and an emulsifier, and dispersing at a high speed in a high-pressure emulsifying machine to form uniform emulsion;
and (3): preparation of a polyamic acid resin: mixing and dissolving 4, 4 '-diaminodiphenyl ether and dimethylacetamide to form an amine-containing solution, simultaneously adding the emulsion obtained in the step (2) and the amine-containing solution into a reaction kettle according to the mass ratio of 1: 1.1-20, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution in steps according to the mass ratio of 1: 1-1.2 of pyromellitic dianhydride to 4, 4' -diaminodiphenyl ether to obtain polyamide acid resin;
and (4): casting and film forming: forming a film from the polyamic acid resin obtained in the step (3) through a tape casting process;
and (5): film imidization: and (3) heating the film obtained in the step (4) to obtain the cellulose modified polyimide film with improved corona resistance.
Scheme 12. the preparation method according to scheme 11, wherein in step (1), the cellulose is lignocellulose.
Scheme 13. the preparation method according to scheme 11, wherein in the step (1), the steam explosion process is performed at a pressure of about 1.0-3.0Mpa for about 300-600 s.
Scheme 14. the preparation method according to scheme 11, wherein in the step (2), the mass ratio of the pretreated cellulose, aluminum isopropoxide, KH550 and the emulsifier is 0.1-1: 0.005-0.02: 0.005-0.01.
Scheme 15. the preparation method according to any of the claims 11 to 14, characterized in that the emulsifier is alkylphenol ethoxylates.
Scheme 16. the preparation method according to any of schemes 11 to 15, characterized in that in step (3), the amine-containing solution is mixed by 20-25% of 4, 4' -diaminodiphenyl ether and 75-80% of dimethylacetamide in a mass ratio.
Scheme 17. the preparation process according to any of schemes 11 to 16, characterized in that the heating temperature in step (5) is 350-450 ℃.
Claims (8)
1. A preparation method of a cellulose modified polyimide film comprises the following steps:
step (1): cellulose pretreatment: adopting lignocellulose, crushing the lignocellulose, then carrying out alkaline leaching treatment, washing and airing; then carrying out steam explosion treatment;
step (2): preparing an emulsion: adding the pretreated lignocellulose obtained in the step (1) into deionized water, magnetically stirring, adding aluminum isopropoxide, a KH550 silane coupling agent and an emulsifier, and dispersing at a high speed in a high-pressure emulsifying machine to form uniform emulsion, wherein in the step (2), the mass ratio of the pretreated lignocellulose to the aluminum isopropoxide to the KH550 to the emulsifier is 0.1-1: 0.001-0.02: 0.005-0.01;
and (3): preparation of a polyamic acid resin: mixing and dissolving 4, 4 '-diaminodiphenyl ether and dimethylacetamide to form an amine-containing solution, adding the emulsion obtained in the step (2) and the amine-containing solution into a reaction kettle at the same time according to the mass ratio of 1: 10, stirring and mixing, and then adding pyromellitic dianhydride to the mixed solution in steps according to the mass ratio of 1: 1 of pyromellitic dianhydride and 4, 4' -diaminodiphenyl ether to obtain polyamide acid resin;
and (4): casting and film forming: forming a film from the polyamic acid resin obtained in the step (3) through a tape casting process;
and (5): film imidization: heating the film obtained in the step (4) to obtain a cellulose modified polyimide film with improved corona resistance; and
the prepared cellulose modified polyimide film comprises the following components in parts by weight: polyimide 150-200 parts, nano alumina particles 1-5 parts, cellulose 0.01-1 part, silane coupling agent 1-5 parts, wherein,
the method uniformly loads the cellulose on an alumina precursor, and utilizes the dispersion and winding effect of the cellulose in the emulsion to dispersedly distribute the alumina into the polyimide film.
2. The method as claimed in claim 1, wherein in the step (1), the steam explosion process is performed at a pressure of 1.0-3.0Mpa for a time of 300-600 s.
3. The method according to claim 1, wherein the emulsifier is alkylphenol ethoxylates.
4. The method according to claim 1, wherein in step (3), the amine-containing solution is mixed with the dimethylacetamide in a mass ratio of 20-25% of 4, 4' -diaminodiphenyl ether and 75-80% of dimethylacetamide.
5. The method as claimed in claim 1, wherein the heating temperature in the step (5) is 350-450 ℃.
6. The method according to claim 1, wherein the cellulose-modified polyimide film is produced such that the nano alumina particles have an average particle diameter of 2 to 50 nm.
7. The method according to claim 1, wherein the cellulose-modified polyimide film is produced such that the weight fraction of the cellulose with respect to the nano alumina particles is 15 to 20%.
8. The method for preparing according to claim 1, characterized in that it comprises the steps of:
crushing 5g of lignocellulose, carrying out alkaline leaching for 30min, washing with water, drying, carrying out steam explosion for 300s at the pressure of 2.0MPa, adding the obtained pretreated cellulose into deionized water, carrying out magnetic stirring, adding 10g of aluminum isopropoxide, 0.1gKH550 silane coupling agent and 0.1g of emulsifier, and dispersing at high speed in a high-pressure emulsifying machine to form uniform emulsion; mixing and dissolving 25% of 4, 4 '-diaminodiphenyl ether and 75% of dimethylacetamide into amine-containing solution according to mass percentage, adding the emulsion and the amine-containing solution into a reaction kettle at the same time according to the mass ratio of 1: 10, stirring and mixing, and then adding pyromellitic dianhydride into the mixed solution step by step according to the mass ratio of 1: 1 of pyromellitic dianhydride and 4, 4' -diaminodiphenyl ether to prepare polyamide acid resin; the obtained polyamic acid resin forms a film through a tape casting process; and heating the film at 430 ℃ to obtain the cellulose modified polyimide film.
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| CN115109285B (en) * | 2022-06-21 | 2024-04-12 | 太湖方舟新材料科技有限公司 | Wear-resistant polyimide insulating film and preparation method thereof |
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