Preparation method of fluoride-free colorless transparent polyimide resin and fluoride-free colorless transparent polyimide film

Abstract

The invention provides a preparation method of fluorine-free colorless transparent polyimide resin and a fluorine-free colorless transparent polyimide film, and the specific technical route is as follows: pre-polymerizing a diamine monomer and a diacyl chloride monomer in a reaction solvent, then adding a dianhydride monomer, a catalyst and a water-carrying agent for stepwise polymerization, and finally adding an end-capping reagent to obtain the fluorine-free colorless transparent polyimide resin. Precipitating, powdering, washing and drying the obtained polymerization liquid in a non-good solvent, dissolving the obtained polyimide resin, coating and drying to obtain the fluoride-free colorless transparent polyimide film. The invention discloses adjustment of the adding proportion of different reaction monomers, realizes regulation and control of the optical transmittance, the glass transition temperature and the linear expansion coefficient of polyimide, and finally meets the requirements of the display industry.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically, it demonstrates a method for preparing a fluorine-free, colorless, and transparent polyimide resin and a fluorine-free, colorless, and transparent polyimide film. Background Technology

[0002] Polyimide films have been widely used in the flexible display industry, including organic light-emitting diodes (OLEDs), electronic paper, and liquid crystal displays (LCDs), due to their outstanding thermal stability, dimensional stability, and mechanical properties. Because of the strong inter-electron / internal charge interactions caused by the different molecular structures of polyimide, polyimide films often exhibit a golden-yellow (YPI) color. These products have been used in TFT backplanes. However, with the iterative upgrades in display technology, the requirements for the full visible light transmittance of TFT backplanes have increased. There is a desire to develop a type of film with high full visible light transmittance (>88%), while also possessing excellent dimensional stability and thermal resistance. Therefore, colorless transparent polyimide (CPI) films have been researched and developed.

[0003] Common CPI development paths mainly include introducing fluorinated monomers into the polyimide structure, such as a semi-aromatic CPI film and its preparation method disclosed in Chinese patent CN120484503A, a colorless transparent polyimide film and its preparation method and application disclosed in Chinese patent CN121021831A, and a fluorinated diamine monomer, slurry and polyimide film disclosed in Chinese patent CN119954850A, etc., all of which are aimed at improving the full visible light transmittance of polyimide films.

[0004] However, given the EU's increasingly stringent controls on perfluorinated and polyfluoroalkyl substances (PFAS), fluorinated CPI and its downstream products also face export risks in the future. Therefore, it is necessary to develop a class of fluorine-free, colorless, and transparent polyimide resins and films. Summary of the Invention

[0005] In view of the above-mentioned defects in the prior art, the purpose of this invention is to provide a method for preparing fluorine-free, colorless, and transparent polyimide resin and fluorine-free, colorless, and transparent polyimide film.

[0006] The technical solution is as follows: In a first aspect, a method for preparing a fluorine-free, colorless, and transparent polyimide resin is provided, characterized by comprising the following steps: S1, Prepolymerization: Diamine monomer and diacyl chloride monomer are reacted in a reaction solvent at -2 to 15°C. ℃ The prepolymer was subjected to a prepolymerization reaction for 1-2 hours, wherein the molar ratio of diamine monomer to diacyl chloride monomer was 1.2-2.0, to obtain the prepolymer. S2, Step-growth polymerization: Add dianhydride monomer, catalyst, and dehydrating agent to the prepolymer from step S1, and polymerize at 180–200 °C. ℃ The stepwise polymerization reaction is carried out for 12 to 24 hours, wherein the ratio of the total molar number of dianhydride monomer and diacyl chloride monomer to the molar number of diamine monomer is 0.98 to 1.00. S3. Capping: Add a capping agent to the product obtained in step S2 to carry out the capping reaction. The molar amount of the capping agent is 0.005 to 0.02 of the molar amount of the diamine monomer. S4. Post-treatment: The polymer solution after the end-capping reaction in step S3 is precipitated in a non-good solvent. The resulting solid is then powdered, washed, and dried to obtain fluorine-free polyimide resin.

[0007] According to one embodiment of the present invention, the diamine monomer is selected from one or more of m-toluenediamine, o-toluenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzoylaniline, and 1,4-cyclohexanediamine. These monomers share the common characteristics of having fewer aromatic ring structures, asymmetrical structures, or containing flexible units such as ether bonds or alicyclic rings. This can effectively reduce charge transfer complexation between polyimide molecular chains, thereby achieving a colorless and transparent finish.

[0008] According to one embodiment of the present invention, the diacyl chloride monomer is terephthaloyl chloride. Terephthaloyl chloride has a rigid linear structure, and its reaction with diamine produces amide bonds instead of traditional imide bonds. The amide bonds have a rigid rod-like structure, which ensures good mechanical properties while reducing the CTE of the polymer film.

[0009] According to one embodiment of the present invention, the reaction solvent is selected from one or more of N-methylpyrrolidone, m-cresol, butyrolactone, and N,N-dimethylacetamide. This ensures that the reactants have good solubility.

[0010] According to one embodiment of the present invention, the dianhydride monomer is selected from one or more of hydrogenated pyromellitic dianhydride, biphenyl dianhydride, and cyclobutanetetracarboxylic dianhydride. Containing an alicyclic structure avoids the strong conjugated system formed by traditional aromatic dianhydrides such as pyromellitic dianhydride (PMDA), thus facilitating the achievement of fluorine-free and high transparency.

[0011] According to one embodiment of the present invention, the catalyst is selected from one or more of triethylamine, pyridine, and isoquinoline. This ensures that the reaction proceeds efficiently and completely.

[0012] According to one embodiment of the present invention, the dehydrating agent comprises one or more of benzene, toluene, and xylene. A co-catalyst promotes imidization.

[0013] According to one embodiment of the present invention, the capping agent includes one or more of phthalic anhydride, trimellitic anhydride, and biphenyl tetracarboxylic acid.

[0014] According to one embodiment of the present invention, the non-good solvent includes one or more of methanol, ethanol, and isopropanol, which assist in the precipitation of the product.

[0015] Secondly, a method for preparing a fluorine-free, colorless, and transparent polyimide film is provided, wherein the fluorine-free polyimide resin obtained in the first aspect is dissolved in a solvent to prepare a film with a solid content of 10-20%. % Rotational viscosity is 3000–20000. cP The slurry is applied to the substrate and then baked and dried at a maximum temperature of 250–300 °C. ℃ A fluorine-free, colorless, and transparent polyimide film was prepared.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention does not use any fluorinated monomers, so that the polyimide resin and film produced are not subject to increasingly strict restrictions on PFAS substances in markets such as the EU, and have huge market prospects and commercial viability; the colorless mechanism is mainly achieved by introducing aliphatic monomers to reduce intermolecular charge interaction, and then by introducing amide bonds to reduce CTE, thus achieving a balance between high transmittance and low CTE.

[0017] 2. The raw materials for this invention are simple and readily available, and have been commercialized. The polyimide film prepared has excellent full visible light transmittance, good heat resistance and mechanical properties, and has certain application prospects. Detailed Implementation

[0018] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] First, the solution provided in this application will be explained in a more accessible and understandable way, as follows: This invention provides a method for preparing fluorine-free, colorless, and transparent polyimide resin and film. The specific technical route is as follows: diamine monomer and diacyl chloride monomer are prepolymerized in a reaction solvent, then dianhydride monomer, catalyst, and dehydrating agent are added for stepwise polymerization, and finally a capping agent is added. The resulting polymer solution is precipitated in a non-good solvent, powdered, washed, and dried. The obtained polyimide resin is dissolved, coated, and dried to obtain a fluorine-free, colorless, and transparent polyimide film.

[0020] Preferably, the diamine monomer includes one or more of the following diamine monomers: The diacyl chloride monomer is terephthaloyl chloride, and its molecular structure is as follows: Preferably, the reaction solvent includes one or more of N-methylpyrrolidone (NMP), m-cresol, butyrolactone, and N,N-dimethylacetamide (DMAc), more preferably m-cresol and butyrolactone.

[0021] Preferably, the diamine monomer and the diacyl chloride monomer are prepolymerized in a reaction solvent, the molar ratio of the diamine monomer to the diacyl chloride monomer is 1.2 to 2.0, more preferably 1.5 to 2.0, the reaction temperature is -2 to 15°C, and the reaction time is 1 to 2 hours.

[0022] Preferably, the dianhydride monomer includes one or more of the following dianhydride monomers: Preferably, the catalyst includes one or more of triethylamine, pyridine, and isoquinoline, more preferably triethylamine and isoquinoline.

[0023] Preferably, the water-removing agent includes one or more of benzene, toluene, and xylene, more preferably toluene or xylene.

[0024] Preferably, the capping agent includes one or more of phthalic anhydride, trimellitic anhydride, and biphenyl tetracarboxylic acid, more preferably phthalic anhydride or trimellitic anhydride.

[0025] Preferably, the molar ratio of the total molar of dianhydride monomer and diacyl chloride monomer to diamine monomer is 0.98 to 1.00, more preferably 0.99 to 1.00.

[0026] Preferably, the molar amount of the capping agent is 0.005 to 0.02% of the diamine monomer, more preferably 0.01 to 0.02%.

[0027] Preferably, the polymerization is carried out stepwise with the addition of dianhydride monomer and reaction aid, the reaction temperature is 180-200°C, and the reaction time is 12-24 h, more preferably 12-20 h.

[0028] Preferably, the non-good solvent includes one or more of methanol, ethanol, and isopropanol, more preferably methanol or ethanol.

[0029] Preferably, the fluorine-free polyimide resin is dissolved in a solvent, which includes one or more of N-methylpyrrolidone (NMP), butyrolactone, and N,N-dimethylacetamide (DMAc), more preferably N,N-dimethylacetamide (DMAc), with a dissolved solid content of 10-20% and a rotational viscosity of 3000-20000 cP (25°C).

[0030] Preferably, the maximum temperature for drying the slurry coating is 250–300°C, and more preferably 250–270°C.

[0031] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0032] Example 1: Preparation of fluorine-free, colorless, transparent polyimide resin A Step S1: Prepolymerization In a reaction vessel under nitrogen protection, add 40.00 g of 188.4 g of [a specific chemical compound]. mmol m-Toluenediamine (MTD) and 42.82g, 188.4g. mmol 4,4'-Diaminobenzoylaniline (DABA) was added, followed by 484 g of m-cresol solvent. The reaction system was heated to 60 °C and mechanically stirred until the diamine monomer was completely dissolved. The temperature was then lowered to 0–5 °C, and 38.25 g and 188.4 g of m-cresol were slowly added in five separate portions. mmol Terephthaloyl chloride (TPC) was used, and the reaction solution temperature was controlled between 0 and 15 °C. The prepolymerization reaction lasted for 1.5 hours to obtain the prepolymer.

[0033] Step S2: Stepwise aggregation Slowly add 41.81 g and 186.5 g of [a specific ingredient] to the above prepolymer. mmo Hydrogenated pyromellitic dianhydride (HPMDA) and 1.20 g, 9.3 g... mmol The catalyst is isoquinoline, and the mixture is heated to 80 °C and stirred for 1 hour to ensure that the reactants are completely dissolved. Then, 67 g of toluene, a dehydrating agent, is added, and the reaction system is heated to 180 °C for stepwise polymerization for 12 hours. During the reaction, the generated water is removed by a dehydration device to promote imidization. After the reaction is completed, toluene is removed by vacuum distillation.

[0034] Step S3: End sealing Add 1.12 g and 7.5 g of [unspecified ingredient] to the reaction solution. mmol The phthalic anhydride end-capping agent was reacted at 180°C for 2 hours to achieve molecular chain end-capping.

[0035] Step S4: Post-processing The reaction solution was cooled to 120°C, and 172 g of m-cresol was added to reduce the viscosity. The cooled polymer solution was slowly poured into methanol to precipitate. After the polymer resin precipitated, it was pulverized with a pulverizer and washed with methanol 2-3 times to remove impurities. Finally, it was dried in a vacuum oven to obtain fluorine-free, colorless, and transparent polyimide resin A.

[0036] Preparation of fluorine-free, colorless, transparent polyimide film A The obtained polyimide resin A was dissolved in N,N-dimethylacetamide (DMAc) solvent to prepare a solution with a solid content of 15%. wt% The slurry has a rotational viscosity of 4321. cP (25℃) After filtration and degassing, the slurry was coated onto a quartz substrate using a slot coater and baked in a stepped manner in a high-temperature oven under nitrogen protection, with a maximum temperature of 260℃, ultimately yielding a thickness of 10±0.5 mm. μm A fluorine-free, colorless, transparent polyimide film.

[0037] Example 2: Preparation of fluorine-free, colorless, and transparent polyimide resin B Step S1: Prepolymerization In a reaction vessel under nitrogen protection, add 30.00 g of 141.3 g of [a specific compound / material]. mmol m-Toluenediamine (MTD) and 32.27g, 282.6g. mmol The 1,4-cyclohexanediamine (CHDA) was added, followed by 421 g of m-cresol solvent. The reaction system was heated to 60 °C and mechanically stirred until the diamine monomer was completely dissolved. The temperature was then lowered to 0–5 °C, and 43.03 g of methyl methacrylate (MCMA) and 212.0 g of methyl methacrylate (MCMA) were slowly added in five separate portions. mmol Terephthaloyl chloride (TPC) was used, and the reaction solution temperature was controlled between 0 and 15 °C. The prepolymerization reaction lasted for 1.5 hours to obtain the prepolymer.

[0038] Step S2: Stepwise aggregation Slowly add 61.12 g and 207.7 g of [a specific ingredient] to the above prepolymer. mmo Biphenyltetracarboxylic dianhydride (BPDA) and 1.34 g, 10.4 g mmol The catalyst is isoquinoline, and the mixture is heated to 80 °C and stirred for 1 hour to ensure that the reactants are completely dissolved. Then, 75 g of toluene, a dehydrating agent, is added, and the reaction system is heated to 180 °C for stepwise polymerization for 14 hours. During the reaction, the generated water is removed by a dehydration device to promote imidization. After the reaction is completed, toluene is removed by vacuum distillation.

[0039] Step S3: End sealing Add 1.26 g and 8.5 g of [agent / material] to the reaction solution. mmol The phthalic anhydride end-capping agent was reacted at 180°C for 2 hours to achieve molecular chain end-capping.

[0040] Step S4: Post-processing The reaction solution was cooled to 120°C, and 280 g of m-cresol was added to reduce the viscosity. The cooled polymer solution was slowly poured into methanol to precipitate. After the polymer resin precipitated, it was pulverized with a pulverizer and washed with methanol 2-3 times to remove impurities. Finally, it was dried in a vacuum oven to obtain fluorine-free, colorless, and transparent polyimide resin B.

[0041] Preparation of fluorine-free, colorless, transparent polyimide film B The obtained polyimide resin B was dissolved in N,N-dimethylacetamide (DMAc) solvent to prepare a solution with a solid content of 15%. wt% The slurry has a rotational viscosity of 5388. cP (25℃) After filtration and degassing, the slurry was coated onto a quartz substrate using a slot coater and baked in a stepped manner in a high-temperature oven under nitrogen protection, with a maximum temperature of 260℃, ultimately yielding a thickness of 10±0.5 mm. μm B is a fluorine-free, colorless, and transparent polyimide film.

[0042] Comparative Example 1: Preparation of traditional polyimide films (without prepolymerization step) Add 70.00 g and 349.6 g of [unspecified ingredient] to the reactor. mmol 4,4'-Diaminodiphenyl ether (ODA) and 594 g of m-cresol were added, heated to 60°C under nitrogen protection, and mechanically stirred until the diamine monomer was completely dissolved. Then, 77.58 g of 346.1 g of [unspecified ingredient] was added directly. mmol Hydrogenated pyromellitic dianhydride (HPMDA) and 2.26 g, 17.5 g. mmol The catalyst is isoquinoline. After stirring at 80°C for 1 hour, the reactants are completely dissolved. 124 g of toluene is added, and the reaction is carried out at 180°C for 20 hours. The entire reaction reaches water equilibrium. Then, the toluene is distilled off under reduced pressure. 1.04 g of 7.0 mmol of phthalic anhydride is added for end-capping for 2 hours. The cooled polymer solution is slowly poured into a methanol precipitation vessel. The polymer resin precipitates out and is then crushed with a pulverizer. It is then washed with methanol 2-3 times and finally dried in a vacuum oven.

[0043] The obtained polyimide resin was dissolved in DMAc to prepare a 15 wt% Slurry (viscosity 3450) cP The fluorine-free polyimide slurry was filtered and degassed for later use. The slurry was then coated onto a quartz plate using a slit coater and baked in a high-temperature nitrogen oven at a maximum temperature of 260°C. This resulted in a fluorine-free, colorless, and transparent polyimide film C with a thickness of 10±0.5μm.

[0044] Comparative Example 2: Preparation of polyimide films without prepolymerization and with inappropriate monomer ratios Add 40.00 g of 188.4 g of [agent name] to the reactor. mmol o-Toluenediamine (OTD), 42.82 g, 188.4 g. mmol 4,4'-Diaminobenzoylaniline (DABA) and 669 g of m-cresol were heated to 60°C under nitrogen protection and mechanically stirred until the diamine monomer was completely dissolved. Then, 84.05 g of 375.0 g of [unspecified ingredient] was directly added. mmol Hydrogenated pyromellitic dianhydride (HPMDA) and 2.42 g, 18.7 g. mmol The catalyst is isoquinoline. After stirring at 80°C for 1 hour, the reactants are completely dissolved. 135 g of toluene is added, and the reaction is carried out at 180°C for 20 hours. The entire reaction reaches water equilibrium. Then, the toluene is distilled off under reduced pressure. 0.56 g of phthalic anhydride (3.8 mmol) is added for end-capping for 2 hours. The cooled polymer solution is slowly poured into a methanol precipitation vessel. The polymer resin precipitates out and is then crushed with a pulverizer. It is then washed with methanol 2-3 times and finally dried in a vacuum oven.

[0045] The obtained polyimide resin was dissolved in DMAc to prepare a 15 wt% Slurry (viscosity 5253) cP The fluorine-free polyimide slurry was filtered and degassed for later use. It was then coated onto a quartz plate using a slit coater and baked in a high-temperature nitrogen oven at a maximum temperature of 260°C. The final product was a fluorine-free, colorless, and transparent polyimide film D with a thickness of 10±0.5μm.

[0046] Performance testing and results analysis.

[0047] The performance of the films prepared in the above embodiments and comparative examples was tested using the following methods: Optical performance: using a photometer ( EZMQC The total transmittance was measured in the wavelength range of 380–780 nm, with a sample size of 50 mm × 50 mm.

[0048] Mechanical properties: Use Instron 68SC-1 Tensile testing machine, sample size 5 mm × 100 mm, tensile speed 12.5 mm / min, to test tensile strength, elongation at break and tensile modulus.

[0049] Thermal properties: using a thermal analyzer ( TMA Q400 The sample size was 4.5 mm × 16 mm. A tensile force of 0.05 N was applied. The heating program was as follows: room temperature to 150℃ (heating rate 20℃ / min), hold at that temperature for 30 min, cool to 40℃, and then heat from 40℃ to 600℃ at a heating rate of 5℃ / min. The coefficient of linear expansion (CTE) in the range of 50–250℃ was calculated, and the glass transition temperature (Tg) was taken as the temperature at the intersection of the deformation tangents.

[0050] The test results are shown in Table 1: Table 1. Comparison of properties of polyimide films As can be seen from Table 1 above, in Examples 1 and 2, by introducing terephthaloyl chloride and specific diamine monomers through prepolymerization, followed by polymerization with alicyclic dianhydrides, the total visible light transmittance was greater than 88%, and the CTE was less than 20. ppm / ℃ The glass transition temperature (CTE) is greater than 300°C, meeting the application requirements of some fluorine-free, colorless, and transparent flexible substrates. Comparative Example 1 has excellent full visible light transmittance, but its CTE is relatively high, posing an application risk. Comparative Example 2 has a low CTE, meeting application requirements, but its full visible light transmittance does not meet the requirements. This invention improves the optical transmittance of polyimide by regulating the ratio of fatty dianhydride / diamine to aromatic dianhydride / diamine, and further reduces the CTE by introducing amide bonds and rigid units.

[0051] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a fluorine-free, colorless, and transparent polyimide resin, characterized in that, Includes the following steps: S1, Prepolymerization: Diamine monomer and diacyl chloride monomer are reacted in a reaction solvent at -2 to 15°C. ℃ The prepolymer was subjected to a prepolymerization reaction for 1-2 hours, wherein the molar ratio of diamine monomer to diacyl chloride monomer was 1.2-2.0, to obtain the prepolymer. S2, Step-growth polymerization: Add dianhydride monomer, catalyst, and dehydrating agent to the prepolymer from step S1, and polymerize at 180–200 °C. ℃ The stepwise polymerization reaction is carried out for 12 to 24 hours, wherein the ratio of the total molar number of dianhydride monomer and diacyl chloride monomer to the molar number of diamine monomer is 0.98 to 1.

00. S3. Capping: Add a capping agent to the product obtained in step S2 to carry out the capping reaction. The molar amount of the capping agent is 0.005 to 0.02 of the molar amount of the diamine monomer. S4. Post-treatment: The polymer solution after the end-capping reaction in step S3 is precipitated in a non-good solvent. The resulting solid is then powdered, washed, and dried to obtain fluorine-free polyimide resin.

2. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The diamine monomer is selected from one or more of m-toluenediamine, o-toluenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzoylaniline, and 1,4-cyclohexanediamine.

3. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The diacyl chloride monomer is terephthaloyl chloride.

4. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The reaction solvent is selected from one or more of N-methylpyrrolidone, m-cresol, butyrolactone, and N,N-dimethylacetamide.

5. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The dianhydride monomer is selected from one or more of hydrogenated pyromellitic dianhydride, biphenyl dianhydride, and cyclobutane dianhydride.

6. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The catalyst is selected from one or more of triethylamine, pyridine, and isoquinoline.

7. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The water-removing agent includes one or more of benzene, toluene, and xylene.

8. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The capping agent includes one or more of phthalic anhydride, trimellitic anhydride, and biphenyl tetracarboxylic acid.

9. The method for preparing a fluorine-free, colorless, and transparent polyimide resin according to claim 1, characterized in that, The non-good solvents include one or more of methanol, ethanol, and isopropanol.

10. A method for preparing a fluorine-free, colorless, transparent polyimide film, characterized in that, The fluorine-free polyimide resin obtained according to any one of claims 1 to 9 is dissolved in a solvent to prepare a solution with a solid content of 10-20%. % Rotational viscosity is 3000–20000. cP The slurry is applied to the substrate and then baked and dried at a maximum temperature of 250–300 °C. ℃ A fluorine-free, colorless, and transparent polyimide film was prepared.

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