PI transfer film for graphite calendering and preparation method thereof

Abstract

The invention discloses a PI transfer membrane for graphite calendaring and a preparation method thereof, 4, 4 '-diaminodiphenyl ether, a modified monomer and 3, 3', 4, 4 '-biphenyltetracarboxylic dianhydride are used as raw materials to react to prepare a polyamide acid solution, the polyamide acid solution, modified lignin and dimethyldiethoxysilane are hydrolyzed and grafted to prepare a membrane casting solution, the membrane casting solution is scraped to prepare the PI transfer membrane for graphite calendaring, and the PI transfer membrane for graphite calendaring is obtained. The preparation method comprises the following steps: heating to condense siloxane subjected to hydrolysis grafting, continuously heating to convert polyamide acid molecules into a polyimide structure to prepare a PI transfer membrane, and forming an organic silicon structure among a polyamide acid solution, modified lignin and dimethyldiethoxysilane in the hydrolysis grafting and condensation process of the polyamide acid solution, the modified lignin and the dimethyldiethoxysilane, so that the crosslinking degree of the material can be properly improved, and the tensile strength of the material is improved. Meanwhile, a hydrophobic protection film is formed on the surface of the transfer film, so that the water resistance of the transfer film is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of graphite calendering preparation, and in particular to a PI transfer film for graphite calendering and a preparation method thereof. Background Art

[0002] Polyimide film is the best performing thin-film insulating material in the world. It is made of pyromellitic dianhydride and diaminodiphenyl ether in a strong polar solvent through condensation and cast film formation and then imidization. During the graphite calendering process, the PI film is double-layered, in which the fired graphite sheet is directly placed on a heavy release film, and then a layer of lighter transfer film is compounded on the graphite sheet, and then it is pressed by precision chrome-plated steel rollers. After pressing, the light release film is peeled off and finally collected. The existing polyimide transfer film, due to the high brittleness and easy moisture of polyimide itself, is used in an environment with high air humidity. The transfer film absorbs water, resulting in a decrease in performance, which in turn affects the graphite calendering. Summary of the invention

[0003] The purpose of the present invention is to provide a PI transfer film for graphite calendering and a preparation method thereof, which solves the problem that the current PI transfer film is brittle and easily affected by moisture, resulting in a decrease in its own mechanical properties.

[0004] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a PI transfer film for graphite calendering comprises the following steps: Step A1: 4,4'-diaminodiphenyl ether, a modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide are mixed, nitrogen is introduced for protection, and the reaction is carried out for 3-5 hours at a speed of 200-300 r / min and a temperature of 25-30° C. to obtain a polyamic acid solution, lignin is dissolved in DMF, and dibutyltin dilaurate and isocyanatepropyltrimethoxysilane are added under stirring at a speed of 120-150 r / min and a temperature of 30-40° C., and the reaction is carried out for 2-3 hours to obtain modified lignin; Step A2: The polyamic acid solution, modified lignin, dimethyldiethoxysilane and DMF are mixed evenly, stirred at a speed of 200-300r / min and a temperature of 65-70°C, and deionized water and hydrochloric acid solution are added to react for 3-5h to obtain a casting liquid, and the film is scraped at a temperature of 120-130°C for 3-5h, heated to 250-260°C, heated for 15-20min, heated to 340-350°C, and heated for 10-15min to obtain a PI transfer film.

[0005] Furthermore, the amount ratio of 4,4'-diaminodiphenyl ether, modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide described in step A1 is 200mmol:50mol:150mL:400mL, the amount ratio of lignin and isocyanatepropyltrimethoxysilane is 1g:1mL, and the amount of dibutyltin dilaurate is 1% by mass of isocyanatepropyltrimethoxysilane.

[0006] Furthermore, the dosage ratio of the polyamic acid solution, modified lignin, dimethyldiethoxysilane, DMF, deionized water and hydrochloric acid solution described in step A2 is 500mL:3g:10mL:20mL:40mL:5mL, and the mass fraction of the hydrochloric acid solution is 10%.

[0007] Further, the modified monomer is prepared by the following steps: Step B1: Hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water are mixed uniformly, and reacted for 10-15 hours at a speed of 120-150 r / min and a temperature of 85-90° C. to obtain sodium hexadecylcyclotetrasiloxane tetrasiloxide. Hexadecylcyclotetrasiloxane tetrasiloxide sodium, triethylamine and tetrahydrofuran are mixed uniformly, nitrogen is introduced for protection, and methyldichlorosilane is added under stirring at a speed of 150-200 r / min and a temperature of 0° C. to react for 3-5 hours, and the temperature is raised to 20-25° C. and reacted for 20-25 hours to obtain dihydrogen cage-type silsesquioxane; Step B2: Mix dihydrogen cage silsesquioxane, caffeic acid, Custer catalyst and DMF uniformly, introduce nitrogen protection, react for 20-25 hours at a speed of 60-80 r / min and a temperature of 80-85° C. to obtain intermediate 1; mix intermediate 1, p-nitrophenylboric acid, 5A molecular sieve and DMF uniformly, introduce nitrogen protection, react for 10-15 hours at a speed of 120-150 r / min and a temperature of 60-65° C. to obtain intermediate 2; Step B3: Intermediate 2, KH550, dicyclohexylcarbodiimide, toluene and DMF are mixed evenly, and reacted at a speed of 200-300 r / min and a temperature of 30-40° C. for 3-5 hours to obtain intermediate 3; 4-hydroxyphthalonitrile, potassium carbonate and DMF are mixed evenly, and nitrogen is introduced for protection, and reacted at a speed of 150-200 r / min and a temperature of 20-25° C. for 1-1.5 hours, and intermediate 3 is added, and the reaction is continued for 20-25 hours to obtain intermediate 4; Step B4: Mix intermediate 4, sodium hydroxide and DMF evenly, introduce nitrogen protection, react at a temperature of 90-95°C for 10-15h, heat to 100-110°C, continue to react at 25-30°C to obtain intermediate 5, mix intermediate 5, acetic anhydride and glacial acetic acid evenly, introduce nitrogen protection, react at a speed of 60-80r / min and a temperature of 100-105°C for 10-15h to obtain a modified monomer.

[0008] Furthermore, the amount ratio of hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water in step B1 is 150mmol:80mmol:120mL:5mL, and the amount ratio of hexadecylcyclotetrasiloxane sodium tetrasiloxide, triethylamine, tetrahydrofuran and methyldichlorosilane is 20g:5g:30mL:4g.

[0009] Furthermore, the molar ratio of the dihydrogen cage silsesquioxane and caffeic acid in step B2 is 1:2, the amount of the Custer catalyst is 2‰ of the mass of caffeic acid, and the amount ratio of the intermediate 1, p-nitrophenylboric acid and 5A molecular sieve is 16mmol:8mmol:2g.

[0010] Furthermore, the molar ratio of the intermediate 2, KH550 and dicyclohexylcarbodiimide described in step B3 is 1:2:2.1, and the molar ratio of 4-hydroxyphthalonitrile, potassium carbonate and intermediate 3 is 2:1:1.

[0011] Furthermore, the usage ratio of the intermediate 4, sodium hydroxide and DMF in step B4 is 1 mmol:5 mmol:2 mL, and the usage ratio of the intermediate 5, acetic anhydride and glacial acetic acid is 10 mmol:1 mL:2 mL.

[0012] The beneficial effects of the present invention are as follows: a PI transfer film for graphite calendering prepared by the present invention is prepared by reacting 4,4'-diaminodiphenyl ether, a modified monomer and 3,3',4,4'-biphenyltetracarboxylic dianhydride as raw materials to obtain a polyamic acid solution, treating lignin with isocyanate propyltrimethoxysilane so that a hydroxyl group on the lignin reacts with an isocyanate group on the isocyanate propyltrimethoxysilane to obtain a modified lignin, hydrolyzing and grafting the polyamic acid solution, the modified lignin and dimethyldiethoxysilane to obtain a casting liquid, scraping the casting liquid, heating up to condense the hydrolyzed and grafted siloxane, and continuing to heat up to convert the polyamic acid molecules into a polyimide structure to obtain a PI transfer film.

[0013] The modified monomer is hydrolyzed and grafted with hexadecyl trimethoxysilane to form sodium hexadecyl cyclotetrasiloxane tetrasiloxide, and the sodium hexadecyl cyclotetrasiloxane tetrasiloxide is reacted with methyl dichlorosilane so that the sodium tetrasiloxide reacts with the chlorine atom site to obtain dihydrogen cage silsesquioxane, and the dihydrogen cage silsesquioxane and caffeic acid are reacted with the action of Custer catalyst so that the Si-H bond on the dihydrogen cage silsesquioxane and the double bond on the caffeic acid are grafted to obtain intermediate 1, and the intermediate 1 is reacted with p-nitrophenyl boric acid so that the catechol on the intermediate 1 reacts with p-nitrophenyl boric acid. The boronic acid group on the boronic acid is reacted to obtain intermediate 2, intermediate 2 is reacted with KH550, so that the carboxyl group on intermediate 2 and the amino group on KH550 undergo a dehydration reaction to obtain intermediate 3, intermediate 3 is reacted with 4-hydroxyphthalonitrile, so that the nitro group on intermediate 3 reacts with 4-hydroxyphthalonitrile to obtain intermediate 4, intermediate 4 is treated with sodium hydroxide to convert the nitrile group into a carboxyl group to obtain intermediate 5, and intermediate 5 is treated with acetic anhydride and glacial acetic acid to convert the phthalic acid group on intermediate 5 into phthalic anhydride to obtain a modified monomer.

[0014] The modified monomer contains cage-type silsesquioxane and long-chain alkyl groups, which can increase the mechanical properties of the transfer film. In the process of hydrolysis, grafting and condensation of the polyamic acid solution, modified lignin and dimethyldiethoxysilane, an organic silicon structure is formed between the three, which can appropriately improve the cross-linking degree of the material, thereby greatly improving the impact resistance and toughness of the transfer film. The addition of lignin structure to the molecular chain segment can further improve the mechanical properties. At the same time, a hydrophobic protective film is formed on the surface of the transfer film, and the long-chain alkyl group has a hydrophobic effect, which further improves the water resistance of the transfer film. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0016] A method for preparing a PI transfer film for graphite calendering comprises the following steps: Step A1: 4,4'-diaminodiphenyl ether, a modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide are mixed, nitrogen is introduced for protection, and the mixture is reacted for 3 hours at a speed of 200 r / min and a temperature of 25° C. to obtain a polyamic acid solution; lignin is dissolved in DMF, and dibutyltin dilaurate and isocyanatepropyltrimethoxysilane are added under stirring at a speed of 120 r / min and a temperature of 30° C. to obtain a modified lignin; Step A2: Mix the polyamic acid solution, modified lignin, dimethyldiethoxysilane and DMF evenly, stir and add deionized water and hydrochloric acid solution at a speed of 200 r / min and a temperature of 65°C, and react for 3 hours to obtain a casting liquid, and perform a film scraping treatment at a temperature of 120°C for 3 hours, heat to 250°C, heat for 15 minutes, heat to 340°C, and heat for 10 minutes to obtain a PI transfer film.

[0017] The amount ratio of 4,4'-diaminodiphenyl ether, modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide described in step A1 is 200mmol:50mol:150mL:400mL, the amount ratio of lignin and isocyanatepropyltrimethoxysilane is 1g:1mL, and the amount of dibutyltin dilaurate is 1% by mass of isocyanatepropyltrimethoxysilane.

[0018] The dosage ratio of the polyamic acid solution, modified lignin, dimethyldiethoxysilane, DMF, deionized water and hydrochloric acid solution described in step A2 is 500mL:3g:10mL:20mL:40mL:5mL, and the mass fraction of the hydrochloric acid solution is 10%.

[0019] The modified monomer is prepared by the following steps: Step B1: Hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water are mixed evenly, and reacted at a speed of 120 r / min and a temperature of 85° C. for 10 hours to obtain sodium hexadecylcyclotetrasiloxane tetrasiloxide. Hexadecylcyclotetrasiloxane tetrasiloxide sodium, triethylamine and tetrahydrofuran are mixed evenly, nitrogen is introduced for protection, and methyldichlorosilane is added under stirring at a speed of 150 r / min and a temperature of 0° C. to react for 3 hours, and the temperature is raised to 20° C. and reacted for 20 hours to obtain dihydrogen cage-type silsesquioxane; Step B2: Dihydrogen cage silsesquioxane, caffeic acid, Custer catalyst and DMF were mixed evenly, nitrogen was introduced for protection, and the reaction was carried out at a speed of 60 r / min and a temperature of 80° C. for 20 h to obtain intermediate 1; intermediate 1, p-nitrophenylboric acid, 5A molecular sieve and DMF were mixed evenly, nitrogen was introduced for protection, and the reaction was carried out at a speed of 120 r / min and a temperature of 60° C. for 10 h to obtain intermediate 2; Step B3: Intermediate 2, KH550, dicyclohexylcarbodiimide, toluene and DMF were mixed evenly, and reacted at a speed of 200 r / min and a temperature of 30°C for 3 hours to obtain intermediate 3; 4-hydroxyphthalonitrile, potassium carbonate and DMF were mixed evenly, and nitrogen was introduced for protection, and reacted at a speed of 150 r / min and a temperature of 20°C for 1 hour, and intermediate 3 was added, and the reaction was continued for 20 hours to obtain intermediate 4; Step B4: Mix intermediate 4, sodium hydroxide and DMF evenly, introduce nitrogen protection, react at 90°C for 10 hours, raise the temperature to 100°C, and continue the reaction at 25°C to obtain intermediate 5. Mix intermediate 5, acetic anhydride and glacial acetic acid evenly, introduce nitrogen protection, and react at a speed of 60r / min and a temperature of 100°C for 10 hours to obtain a modified monomer.

[0020] The amount ratio of hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water in step B1 is 150mmol:80mmol:120mL:5mL, and the amount ratio of hexadecylcyclotetrasiloxane sodium tetrasiloxide, triethylamine, tetrahydrofuran and methyldichlorosilane is 20g:5g:30mL:4g.

[0021] The molar ratio of the dihydrogen cage silsesquioxane and caffeic acid described in step B2 is 1:2, the amount of the Custer catalyst used is 2‰ of the mass of caffeic acid, and the amount ratio of the intermediate 1, p-nitrophenylboric acid and 5A molecular sieve is 16mmol:8mmol:2g.

[0022] The molar ratio of intermediate 2, KH550 and dicyclohexylcarbodiimide in step B3 is 1:2:2.1, and the molar ratio of 4-hydroxyphthalonitrile, potassium carbonate and intermediate 3 is 2:1:1.

[0023] The usage ratio of intermediate 4, sodium hydroxide and DMF in step B4 is 1 mmol:5 mmol:2 mL, and the usage ratio of intermediate 5, acetic anhydride and glacial acetic acid is 10 mmol:1 mL:2 mL. Example

[0024] A method for preparing a PI transfer film for graphite calendering comprises the following steps: Step A1: 4,4'-diaminodiphenyl ether, modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide are mixed, nitrogen is introduced for protection, and the mixture is reacted for 4 hours at a speed of 200 r / min and a temperature of 30° C. to obtain a polyamic acid solution; lignin is dissolved in DMF, and dibutyltin dilaurate and isocyanatepropyltrimethoxysilane are added under stirring at a speed of 120 r / min and a temperature of 35° C. to obtain a modified lignin; Step A2: Mix the polyamic acid solution, modified lignin, dimethyldiethoxysilane and DMF evenly, stir and add deionized water and hydrochloric acid solution at a speed of 200 r / min and a temperature of 70°C, and react for 4 hours to obtain a casting liquid, and perform a film scraping treatment at a temperature of 125°C for 4 hours, heat it to 255°C, heat it for 20 minutes, heat it to 345°C, and heat it for 15 minutes to obtain a PI transfer film.

[0025] The amount ratio of 4,4'-diaminodiphenyl ether, modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide described in step A1 is 200mmol:50mol:150mL:400mL, the amount ratio of lignin and isocyanatepropyltrimethoxysilane is 1g:1mL, and the amount of dibutyltin dilaurate is 1% by mass of isocyanatepropyltrimethoxysilane.

[0026] The dosage ratio of the polyamic acid solution, modified lignin, dimethyldiethoxysilane, DMF, deionized water and hydrochloric acid solution described in step A2 is 500mL:3g:10mL:20mL:40mL:5mL, and the mass fraction of the hydrochloric acid solution is 10%.

[0027] The modified monomer is prepared by the following steps: Step B1: Hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water are mixed evenly, and reacted at a speed of 120 r / min and a temperature of 90° C. for 10 hours to obtain sodium hexadecylcyclotetrasiloxane tetrasiloxide. Hexadecylcyclotetrasiloxane tetrasiloxide sodium, triethylamine and tetrahydrofuran are mixed evenly, nitrogen is introduced for protection, and methyldichlorosilane is added under stirring at a speed of 200 r / min and a temperature of 0° C. to react for 4 hours, and the temperature is raised to 25° C. and reacted for 20 hours to obtain dihydrogen cage-type silsesquioxane; Step B2: Dihydrogen cage silsesquioxane, caffeic acid, Custer catalyst and DMF were mixed evenly, nitrogen was introduced for protection, and the reaction was carried out at a speed of 60 r / min and a temperature of 85° C. for 20 hours to obtain intermediate 1; intermediate 1, p-nitrophenylboric acid, 5A molecular sieve and DMF were mixed evenly, nitrogen was introduced for protection, and the reaction was carried out at a speed of 150 r / min and a temperature of 60° C. for 15 hours to obtain intermediate 2; Step B3: Intermediate 2, KH550, dicyclohexylcarbodiimide, toluene and DMF were mixed evenly, and the mixture was reacted at a speed of 200 r / min and a temperature of 35°C for 4 hours to obtain intermediate 3; 4-hydroxyphthalonitrile, potassium carbonate and DMF were mixed evenly, and nitrogen was introduced for protection, and the mixture was reacted at a speed of 150 r / min and a temperature of 25°C for 1.5 hours, and intermediate 3 was added, and the reaction was continued for 20 hours to obtain intermediate 4; Step B4: Mix intermediate 4, sodium hydroxide and DMF evenly, introduce nitrogen protection, react at 90°C for 15 hours, raise the temperature to 105°C, and continue to react at 30°C to obtain intermediate 5. Mix intermediate 5, acetic anhydride and glacial acetic acid evenly, introduce nitrogen protection, and react at a speed of 60r / min and a temperature of 100°C for 15 hours to obtain a modified monomer.

[0028] The amount ratio of hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water in step B1 is 150mmol:80mmol:120mL:5mL, and the amount ratio of hexadecylcyclotetrasiloxane sodium tetrasiloxide, triethylamine, tetrahydrofuran and methyldichlorosilane is 20g:5g:30mL:4g.

[0029] The molar ratio of the dihydrogen cage silsesquioxane and caffeic acid described in step B2 is 1:2, the amount of the Custer catalyst used is 2‰ of the mass of caffeic acid, and the amount ratio of the intermediate 1, p-nitrophenylboric acid and 5A molecular sieve is 16mmol:8mmol:2g.

[0030] The molar ratio of intermediate 2, KH550 and dicyclohexylcarbodiimide in step B3 is 1:2:2.1, and the molar ratio of 4-hydroxyphthalonitrile, potassium carbonate and intermediate 3 is 2:1:1.

[0031] The usage ratio of intermediate 4, sodium hydroxide and DMF in step B4 is 1 mmol:5 mmol:2 mL, and the usage ratio of intermediate 5, acetic anhydride and glacial acetic acid is 10 mmol:1 mL:2 mL. Example

[0032] A method for preparing a PI transfer film for graphite calendering comprises the following steps: Step A1: 4,4'-diaminodiphenyl ether, modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide are mixed, nitrogen is introduced for protection, and the mixture is reacted for 5 hours at a speed of 300 r / min and a temperature of 30° C. to obtain a polyamic acid solution; lignin is dissolved in DMF, and dibutyltin dilaurate and isocyanatepropyltrimethoxysilane are added under stirring at a speed of 150 r / min and a temperature of 40° C. to obtain a modified lignin; Step A2: Mix the polyamic acid solution, modified lignin, dimethyldiethoxysilane and DMF evenly, stir and add deionized water and hydrochloric acid solution at a speed of 300 r / min and a temperature of 70°C, and react for 5 hours to obtain a casting liquid, and perform a film scraping treatment at a temperature of 130°C for 5 hours, heat it to 260°C, heat it for 20 minutes, heat it to 350°C, and heat it for 15 minutes to obtain a PI transfer film.

[0033] The amount ratio of 4,4'-diaminodiphenyl ether, modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide described in step A1 is 200mmol:50mol:150mL:400mL, the amount ratio of lignin and isocyanatepropyltrimethoxysilane is 1g:1mL, and the amount of dibutyltin dilaurate is 1% by mass of isocyanatepropyltrimethoxysilane.

[0034] The dosage ratio of the polyamic acid solution, modified lignin, dimethyldiethoxysilane, DMF, deionized water and hydrochloric acid solution described in step A2 is 500mL:3g:10mL:20mL:40mL:5mL, and the mass fraction of the hydrochloric acid solution is 10%.

[0035] The modified monomer is prepared by the following steps: Step B1: Hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water are mixed evenly, and reacted for 15 hours at a speed of 150 r / min and a temperature of 90° C. to obtain sodium hexadecylcyclotetrasiloxane tetrasiloxide. Hexadecylcyclotetrasiloxane tetrasiloxide sodium, triethylamine and tetrahydrofuran are mixed evenly, nitrogen is introduced for protection, methyldichlorosilane is added under stirring at a speed of 200 r / min and a temperature of 0° C., and the mixture is reacted for 5 hours, the temperature is raised to 25° C., and the mixture is reacted for 25 hours to obtain dihydrogen cage-type silsesquioxane; Step B2: Dihydrogen cage silsesquioxane, caffeic acid, Custer catalyst and DMF were mixed evenly, nitrogen was introduced for protection, and the reaction was carried out at a speed of 80 r / min and a temperature of 85° C. for 25 hours to obtain intermediate 1; intermediate 1, p-nitrophenylboric acid, 5A molecular sieve and DMF were mixed evenly, nitrogen was introduced for protection, and the reaction was carried out at a speed of 150 r / min and a temperature of 65° C. for 15 hours to obtain intermediate 2; Step B3: Intermediate 2, KH550, dicyclohexylcarbodiimide, toluene and DMF were mixed evenly, and reacted at a speed of 300 r / min and a temperature of 40°C for 5 hours to obtain intermediate 3; 4-hydroxyphthalonitrile, potassium carbonate and DMF were mixed evenly, and nitrogen was introduced for protection, and reacted at a speed of 200 r / min and a temperature of 25°C for 1.5 hours, and intermediate 3 was added, and the reaction was continued for 25 hours to obtain intermediate 4; Step B4: Mix intermediate 4, sodium hydroxide and DMF evenly, introduce nitrogen protection, react at 95°C for 15 hours, heat to 110°C, and continue to react at 30°C to obtain intermediate 5. Mix intermediate 5, acetic anhydride and glacial acetic acid evenly, introduce nitrogen protection, and react at a speed of 80r / min and a temperature of 105°C for 15 hours to obtain a modified monomer.

[0036] The amount ratio of hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water in step B1 is 150mmol:80mmol:120mL:5mL, and the amount ratio of hexadecylcyclotetrasiloxane sodium tetrasiloxide, triethylamine, tetrahydrofuran and methyldichlorosilane is 20g:5g:30mL:4g.

[0037] The molar ratio of the dihydrogen cage silsesquioxane and caffeic acid described in step B2 is 1:2, the amount of the Custer catalyst used is 2‰ of the mass of caffeic acid, and the amount ratio of the intermediate 1, p-nitrophenylboric acid and 5A molecular sieve is 16mmol:8mmol:2g.

[0038] The molar ratio of intermediate 2, KH550 and dicyclohexylcarbodiimide in step B3 is 1:2:2.1, and the molar ratio of 4-hydroxyphthalonitrile, potassium carbonate and intermediate 3 is 2:1:1.

[0039] The usage ratio of intermediate 4, sodium hydroxide and DMF in step B4 is 1 mmol:5 mmol:2 mL, and the usage ratio of intermediate 5, acetic anhydride and glacial acetic acid is 10 mmol:1 mL:2 mL.

[0040] Comparative Example 1 Compared with Example 1, this comparative example does not add the modified monomer, and the remaining steps are the same.

[0041] Comparative Example 2 Compared with Example 1, this comparative example uses lignin instead of modified lignin, and the other steps are the same.

[0042] Comparative Example 3 Compared with Example 1, this comparative example uses p-nitrostyrene instead of caffeic acid to obtain a product instead of intermediate 3, and the remaining steps are the same.

[0043] Comparative Example 4 Compared with Example 1, this comparative example uses 1,1'-biphenyl]-3,3',4,4'-tetrol to replace intermediate 1, and the remaining steps are the same.

[0044] The transfer films prepared in Examples 1-3 and Comparative Examples 1-4 were made into samples with a length of 12 cm, a width of 2 cm, and a thickness of 0.5 mm. The tensile strength of the films was measured using a universal tensile testing machine XLM. The samples were immersed in water at a temperature of 25°C for 24 h and 72 h, and the tensile strength was tested. The test results are shown in the following table.

[0045]

[0046] It can be seen from the above table that the present application has very good mechanical properties and good water resistance.

[0047] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a PI transfer film for graphite calendering, characterized in that: Specifically, the method comprises the following steps: Step A1: mixing 4,4'-diaminodiphenyl ether, a modified monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and N,N-dimethylacetamide, introducing nitrogen protection, reacting to obtain a polyamic acid solution, dissolving lignin in DMF, stirring, adding dibutyltin dilaurate and isocyanate propyltrimethoxysilane, reacting to obtain a modified lignin; Step A2: Mix and stir the polyamic acid solution, modified lignin, dimethyldiethoxysilane and DMF, add deionized water and hydrochloric acid solution, react to obtain a casting solution, perform film scraping treatment, and heat preservation at high temperature to obtain a PI transfer film.

2. The method for preparing a PI transfer film for graphite calendering according to claim 1, characterized in that: The amount ratio of 4,4'-diaminodiphenyl ether, modified monomer, 3,3',4,4'-biphenyltetracarboxylic dianhydride and N,N-dimethylacetamide described in step A1 is 200mmol:50mol:150mL:400mL, and the amount ratio of lignin and isocyanatepropyltrimethoxysilane is 1g:1mL.

3. The method for preparing a PI transfer film for graphite calendering according to claim 1, characterized in that: The amount ratio of the polyamic acid solution, modified lignin, dimethyldiethoxysilane, DMF, deionized water and hydrochloric acid solution described in step A2 is 500mL:3g:10mL:20mL:40mL:5mL.

4. The method for preparing a PI transfer film for graphite calendering according to claim 1, characterized in that: The modified monomer is prepared by the following steps: Step B1: Hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water are mixed for reaction to obtain sodium hexadecylcyclotetrasiloxane tetrasilanolate, sodium hexadecylcyclotetrasiloxane tetrasilanolate, triethylamine and tetrahydrofuran are mixed evenly, nitrogen is introduced for protection, methyldichlorosilane is added for stirring and reaction is carried out to obtain dihydrogen cage-type silsesquioxane; Step B2: mixing dihydrogen cage silsesquioxane, caffeic acid, Custer catalyst and DMF uniformly, introducing nitrogen protection, and reacting to obtain intermediate 1; mixing intermediate 1, p-nitrophenylboric acid, 5A molecular sieve and DMF uniformly, introducing nitrogen protection, and reacting to obtain intermediate 2; Step B3: Intermediate 2, KH550, dicyclohexylcarbodiimide, toluene and DMF are mixed for reaction to obtain Intermediate 3, 4-hydroxyphthalonitrile, potassium carbonate and DMF are mixed evenly, nitrogen is introduced for protection, and the reaction is carried out, and Intermediate 3 is added and the reaction is continued to obtain Intermediate 4; Step B4: Intermediate 4, sodium hydroxide and DMF are mixed evenly, nitrogen is introduced to protect the reaction, and intermediate 5 is obtained. Intermediate 5, acetic anhydride and glacial acetic acid are mixed evenly, nitrogen is introduced to protect the reaction, and a modified monomer is obtained.

5. The method for preparing a PI transfer film for graphite calendering according to claim 4, characterized in that: The amount ratio of hexadecyltrimethoxysilane, sodium hydroxide, isopropanol and deionized water in step B1 is 150mmol:80mmol:120mL:5mL, and the amount ratio of hexadecylcyclotetrasiloxane sodium tetrasiloxide, triethylamine, tetrahydrofuran and methyldichlorosilane is 20g:5g:30mL:4g.

6. The method for preparing a PI transfer film for graphite calendering according to claim 4, characterized in that: The molar ratio of the dihydrogen cage silsesquioxane and caffeic acid in step B2 is 1:2, and the usage ratio of intermediate 1, p-nitrophenylboric acid and 5A molecular sieve is 16mmol:8mmol:2g.

7. The method for preparing a PI transfer film for graphite calendering according to claim 4, characterized in that: The molar ratio of intermediate 2, KH550 and dicyclohexylcarbodiimide in step B3 is 1:2:2.1, and the molar ratio of 4-hydroxyphthalonitrile, potassium carbonate and intermediate 3 is 2:1:

1.

8. The method for preparing a PI transfer film for graphite calendering according to claim 4, characterized in that: The usage ratio of intermediate 4, sodium hydroxide and DMF in step B4 is 1 mmol:5 mmol:2 mL, and the usage ratio of intermediate 5, acetic anhydride and glacial acetic acid is 10 mmol:1 mL:2 mL.

9. A PI transfer film for graphite calendering, characterized in that: Prepared according to any one of claims 1 to 8.

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