Polyimide water-phase synthesis method and application

Abstract

The invention relates to the field of synthetic materials, in particular to a polyimide water-phase synthetic method and application. Comprising the following steps: adding blocked diisocyanate and tetracarboxy dianhydride into water, adding a salt-forming agent, and carrying out polymerization reaction to obtain a polyimide solution. A closed diisocyanate unit is used for replacing a diamine monomer, so that water-phase synthesis of polyimide is realized, excellent mechanical properties are achieved, the mechanical properties and heat resistance of the polyimide are close to those of oily polyimide, and the structure of water-based polyimide is enriched.

Description

Technical Field

[0001] The invention relates to the field of polyimide materials, and in particular to a polyimide aqueous phase synthesis method and application. Background Art

[0002] Polyimide has excellent properties such as high temperature resistance, friction resistance, corrosion resistance, radiation resistance, oxidation resistance, high mechanical strength, and good electrical insulation performance. At the same time, with the rapid development of cutting-edge technology fields such as aerospace and microelectronics, the demand for high temperature resistant organic adhesives is becoming increasingly urgent. As one of the best organic adhesives with high temperature resistance, polyimide adhesives have attracted much attention in the industry. The traditional polyimide synthesis method is mainly a solution method with organic solvents as the reaction medium. Although the synthesis methods such as vapor deposition method and melt extrusion method have also synthesized polyimides with excellent performance, the requirements for the product form or raw materials are relatively limited. The aqueous phase method for synthesizing polyimide is a polyimide synthesis method developed in recent years. Most of them are synthesized under high temperature and high pressure conditions. There are problems such as high energy consumption and high equipment requirements. There are problems such as easy hydrolysis of polyimide, poor storage and molding stability, and poor bonding performance. In addition, in some aqueous phase synthesis methods of polyimide, although the reaction medium is water, it is inevitable to use organic solvents in the post-treatment process to finally obtain high-performance polyimide materials.

[0003] Chinese invention patent CN118909248A discloses a method for synthesizing polyimide and a polyimide film thereof, wherein a diacyl azide derivative, a dianhydride derivative and a solvent are mixed in a one-pot method, the acyl azide is converted into an isocyanate in situ at a certain temperature, and then polymerized with the dianhydride derivative to form a polyimide, and then the reaction solution is poured into an inert solvent, and a polyimide solid is obtained by filtering. This invention solves the problem of -NCO being easily hydrolyzed and difficult to preserve, and simplifies the reaction conditions so that the synthesis of polyimide can be carried out at room temperature, but the requirements for the product form or raw materials are relatively limited. Summary of the invention

[0004] The first aspect of the present invention provides a method for synthesizing polyimide in water phase, comprising the following steps: adding an aqueous solution of blocked diisocyanate and tetracarboxylic dianhydride into water, adding a salt-forming agent, and polymerizing to obtain a polyimide aqueous solution.

[0005] Preferably, the tetracarboxylic dianhydride includes at least one of phthalic anhydride, keto anhydride, biphenyl ether dianhydride, biphenyl dianhydride, and naphthalenetetracarboxylic dianhydride.

[0006] More preferably, the tetracarboxylic dianhydride includes at least one of pyrophthalic dianhydride and biphthalic dianhydride.

[0007] The polymerization reaction is carried out at a temperature of 90-100° C. and a pressure of 0.1-0.3 MPa.

[0008] The present application found that by limiting the polymerization reaction temperature to 90-100°C and the pressure to 0.1-0.3MPa, the mechanical properties of the prepared polyimide film can be improved. It may be that high temperature is conducive to the growth of polymer chains and the occurrence of cross-linking reactions, thereby increasing the total molecular weight of the polymer. However, too high a temperature may cause the molecular chain to break, which in turn reduces the performance of the polymer. At the same time, with a specific pressure, the polymer chain segments may be compressed and tend to be arranged in an orderly manner, further improving the uniformity of the polymer chain segments.

[0009] Preferably, the polymerization reaction temperature is 95-100° C. and the pressure is 0.20-0.3 MPa.

[0010] The molar ratio of the salt-forming agent to the tetracarboxylic dianhydride is (2.2-2.5):1.

[0011] Preferably, the molar ratio of the salt-forming agent to the tetracarboxylic dianhydride is (2.2-2.4):1.

[0012] The molar ratio of the blocked diisocyanate to the tetracarboxylic dianhydride is (1.05-1.2):1.

[0013] Preferably, the molar ratio of the blocked diisocyanate to tetracarboxylic dianhydride is (1.08-1.15):1.

[0014] Preferably, the solid content of the polyimide aqueous solution is 5-10 wt %.

[0015] The blocked diisocyanate includes sodium bisulfite blocked diisocyanate.

[0016] The method for preparing sodium bisulfite-blocked diisocyanate comprises the following steps: dissolving sodium bisulfite in water, then slowly adding diisocyanate into an aqueous solution of sodium bisulfite, sampling and infrared detection for no -NCO (isocyanate group) characteristic peak, and obtaining the sodium bisulfite-blocked diisocyanate.

[0017] The diisocyanate includes at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate and naphthalene diisocyanate.

[0018] Preferably, the diisocyanate includes at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

[0019] The molar concentration of the aqueous solution of the blocked diisocyanate is 1.0-1.5 mol / L.

[0020] Preferably, the molar concentration of the aqueous solution of the blocked diisocyanate is 1.0-1.2 mol / L.

[0021] The molar ratio of the sodium bisulfite to the diisocyanate is (1.05-1.20):1.

[0022] Preferably, the molar ratio of the sodium bisulfite to the diisocyanate is (1.1-1.15):1.

[0023] Preferably, the molar ratio of the sodium bisulfite to the diisocyanate is 1.1:1.

[0024] The salt-forming agent includes at least one of triethylamine, diethylamine, N,N-dimethylethanolamine, N-methyl-4-hydroxypiperidine, methylimidazole, dimethylimidazole, 4-ethyl-methylimidazole and pyridine.

[0025] The second aspect of the present invention provides an application of a polyimide aqueous phase synthesis method for preparing a polyimide film.

[0026] Preferably, the polyimide film is prepared by a casting method.

[0027] Beneficial Effects

[0028] 1. The present application uses blocked diisocyanate to replace diamine, thereby achieving aqueous phase synthesis of polyimide and enriching the structure of water-based polyimide.

[0029] 2. By limiting the polymerization reaction temperature to 90-100°C and the pressure to 0.1-0.3MPa, the mechanical properties of the prepared polyimide film can be improved.

[0030] 3. By limiting the polymerization reaction temperature to 95-100°C and the pressure to 0.20-0.3MPa, the prepared polyimide film has a tensile strength of more than 120MPa and an elongation at break greater than 20%.

[0031] 4. The molar ratio of the salt-forming agent to the tetracarboxylic dianhydride is (2.2-2.5):1, which can control the viscosity of the polyimide solution to 3000-5000 cP and avoid gelation.

[0032] 5. The polyimide synthesized in the water phase of the present application has mechanical properties and heat resistance similar to those of oily polyimide. DETAILED DESCRIPTION

[0033] Example 1

[0034] A polyimide aqueous phase synthesis method comprises the following steps:

[0035] Take 114.47g (1.1mol) of sodium bisulfite and dissolve it in 1000mL of deionized water. Keep the temperature at 30°C. Slowly add 222.32g (1mol) of isophorone diisocyanate (IPDI) into the above solution through a constant pressure titration funnel and stir for 2h. When there is no -NCO characteristic absorption peak in infrared detection, the reaction is completed to obtain a 1.0mol / L sodium bisulfite blocked diisocyanate aqueous solution.

[0036] In a closed reactor, add the above 1L of closed IPDI aqueous solution, add 267.47g (0.91mol) of biphenyl dianhydride, 211.6g (2.1mol) of triethylamine and 3.41kg of deionized water, stir at room temperature for 1h, after the biphenyl dianhydride is completely dissolved, the reaction solution is heated to 95°C, at which time the reactor is slowly pressurized to 0.25MPa, and the reaction is continued for 7h. After the reaction is completed, the temperature is lowered, the pressure is released, and the material is discharged. The reaction solution is a viscous liquid with a polyimide solid content of 10wt%.

[0037] Example 2

[0038] Take 114.47g (1.1mol) of sodium bisulfite and dissolve it in 1000mL of deionized water. Keep the temperature at 30°C. Slowly add 174.16g (1mol) of toluene diisocyanate (TDI) into the above solution through a constant pressure titration funnel and stir for 2h. When there is no -NCO characteristic absorption peak in infrared detection, the reaction is completed to obtain a 1.0mol / L sodium bisulfite blocked diisocyanate aqueous solution.

[0039] In a closed reactor, add the above-mentioned 1L closed TDI aqueous solution, add 267.47g (0.91mol) of biphenyl dianhydride, 171.66g (2.09mol) of methylimidazole and 2.97kg of deionized water, stir at room temperature for 1h, after the biphenyl dianhydride is completely dissolved, the reaction solution is heated to 95°C, at this time the reactor is slowly pressurized to 0.25MPa, the reaction is continued for 7h, the reaction is completed, the temperature is lowered, the pressure is released, and the material is discharged. The reaction solution is a viscous liquid with a polyimide solid content of 10wt%.

[0040] Example 3

[0041] Take 114.47g (1.1mol) of sodium bisulfite and dissolve it in 1000mL of deionized water. Keep the temperature at 30°C. Slowly add 250.25g (1mol) of diphenylmethane diisocyanate (MDI) into the above solution through a feeding funnel and stir for 2h. When there is no -NCO characteristic absorption peak in infrared detection, the reaction is completed to obtain a 1.0mol / L sodium bisulfite blocked diisocyanate aqueous solution.

[0042] In a closed reactor, add the above 1L of closed IPDI aqueous solution, add 198.29g (0.91mol) of isophthalic anhydride, 165.39g (2.09mol) of pyridine and 4.16kg of deionized water, stir at room temperature for 1h, after the biphthalic anhydride is completely dissolved, the reaction solution is heated to 95°C, at which time the reactor is slowly pressurized to 0.25MPa, and the reaction is continued for 7h. After the reaction is completed, the temperature is lowered, the pressure is released, and the material is discharged. The reaction solution is a viscous liquid with a polyimide solid content of 8wt%.

[0043] Comparative Example 1

[0044] A method for synthesizing polyimide comprises the following steps:

[0045] Take 114.47g of sodium bisulfite and dissolve it in 1000mL of deionized water. Keep the temperature at 30°C. Slowly add 222.32g of IPDI into the above solution through a constant pressure titration funnel and stir for 2h. When there is no -NCO characteristic absorption peak in infrared detection, the reaction is completed to obtain a 1.0 mol / L sodium bisulfite blocked diisocyanate aqueous solution.

[0046] In a closed reactor, add the above 1L of closed IPDI aqueous solution, add 267.47g of biphenyl dianhydride, 211.6g of triethylamine and 3.41kg of deionized water, stir at room temperature for 1h. After the biphenyl dianhydride is completely dissolved, heat the reaction solution to 95°C and continue the reaction for 7h. After the reaction is completed, cool down, discharge the material, and obtain a polyimide solution.

[0047] Comparative Example 2

[0048] A method for synthesizing polyimide comprises the following steps:

[0049] Take 114.47g of sodium bisulfite and dissolve it in 1000mL of deionized water. Keep the temperature at 30°C. Slowly add 222.32g of IPDI into the above solution through a constant pressure titration funnel and stir for 2h. When there is no -NCO characteristic absorption peak in infrared detection, the reaction is completed to obtain a 1.0 mol / L sodium bisulfite blocked diisocyanate aqueous solution.

[0050] In a closed reactor, add the above-mentioned 1L closed IPDI aqueous solution, add 267.47g of biphenyl dianhydride, 211.6g of triethylamine and 3.41kg of deionized water, and stir at room temperature for 1h. After the biphenyl dianhydride is completely dissolved, the reaction solution is heated to 60°C. At this time, the reactor is slowly pressurized to 0.25MPa and the reaction is continued for 7h. After the reaction is completed, the temperature is lowered, the pressure is released, and the material is discharged to obtain a polyimide solution.

[0051] Comparative Example 3

[0052] A method for synthesizing polyimide comprises the following steps:

[0053] Take 114.47g of sodium bisulfite and dissolve it in 1000mL of deionized water. Keep the temperature at 30°C. Slowly add 222.32g of IPDI into the above solution through a constant pressure titration funnel and stir for 2h. When there is no -NCO characteristic absorption peak in infrared detection, the reaction is completed to obtain a 1.0 mol / L blocked IPDI aqueous solution.

[0054] In a closed reactor, add the above-mentioned 1L closed IPDI aqueous solution, add 267.47g biphenyl dianhydride, 165.6g (1.64mol) triethylamine and 3.41kg deionized water, stir at room temperature for 1h. After the biphenyl dianhydride is completely dissolved, the reaction solution is heated to 95°C. At this time, the reactor is slowly pressurized to 0.25MPa, and the reaction is continued for 7h. After the reaction is completed, the temperature is lowered and the pressure is released to obtain a polyimide gel.

[0055] Comparative Example 4

[0056] A method for synthesizing polyimide comprises the following steps:

[0057] Phthalic anhydride (5.000 g), 4,4-diaminodiphenylmethane (4.546 g), and N,N-dimethylacetamide (54.09 g) were added to a three-necked glass bottle and stirred at room temperature for 5.5 h to obtain a polyimide solution.

[0058] Performance testing methods and data

[0059] The viscosity of the polyimide solutions of the test examples and comparative examples: rotational viscosity (Brookfield-DV2T, #21 rotor, 25°C). The viscosity of comparative examples 1-3 was too low and the viscosity values ​​were not measured. Comparative example 4 was not tested and is indicated by "-". The test data are listed in Table 1.

[0060] The polyimide solutions of Examples 1-3 and Comparative Example 4 were used to prepare polyimide films (by casting on a glass plate, keeping at 60°C in a forced air oven for 3 hours, and then heating to 300°C at 5°C / min to obtain a polyimide film) and the following performance tests were performed. The test data are listed in Table 1.

[0061] Tensile test: electronic universal testing machine (Shimadzu AGS-X-10KN), sample size 5×100 mm, tensile rate 50 mm / min.

[0062] Thermal gravimetric analysis: thermogravimetric analyzer (TA, TGA55), nitrogen atmosphere, heating rate 10℃ / min.

[0063] Table 1

[0064]

[0065] Analysis of Example 1 and Comparative Examples 1-2 revealed that the aqueous phase synthesis method of polyimide proposed in the present invention requires the counter monomer to be prepared under certain temperature and pressure conditions. Analysis of Example 3 revealed that the amount of salt-forming agent added must be within the addition equivalent range specified in the present invention. If too little salt-forming agent is added, the solubility of the polymer in water will decrease, and polymer gel will occur.

[0066] From the test results in Table 1, the polyimide prepared by the aqueous phase synthesis method has good mechanical properties and heat resistance. At the same time, compared with the oily polyimide with the same molecular structure (Example 3 and Comparative Example 4), the mechanical properties and heat resistance are similar.

Claims

1. A method for synthesizing polyimide in aqueous phase, characterized in that: The following steps are involved: The aqueous solution of blocked diisocyanate and tetracarboxylic dianhydride are put into water, and a salt-forming agent is added to carry out polymerization reaction to obtain a polyimide aqueous solution.

2. The method for synthesizing polyimide in aqueous phase according to claim 1, characterized in that: The polymerization reaction is carried out at a temperature of 90-100° C. and a pressure of 0.1-0.3 MPa.

3. The method for synthesizing polyimide in aqueous phase according to claim 2, characterized in that: The molar ratio of the salt-forming agent to the tetracarboxylic dianhydride is (2.2-2.5):

1.

4. The method for synthesizing polyimide in aqueous phase according to claim 1 or 3, characterized in that: The tetracarboxylic dianhydride includes at least one of phthalic anhydride, keto anhydride, biphenyl ether dianhydride, biphenyl dianhydride, and naphthalenetetracarboxylic dianhydride.

5. The method for synthesizing polyimide in aqueous phase according to claim 4, characterized in that: The salt-forming agent includes at least one of triethylamine, diethylamine, N,N-dimethylethanolamine, N-methyl-4-hydroxypiperidine, methylimidazole, dimethylimidazole, 4-ethyl-methylimidazole and pyridine.

6. The method for synthesizing polyimide in aqueous phase according to claim 1 or 5, characterized in that: The blocked diisocyanate includes sodium bisulfite blocked diisocyanate.

7. The method for synthesizing polyimide in aqueous phase according to claim 6, characterized in that: The method for preparing the aqueous solution of the blocked diisocyanate comprises the following steps: dissolving sodium bisulfite in water, then adding diisocyanate into the aqueous solution of sodium bisulfite, sampling and infrared detection for no -NCO characteristic peak, and obtaining the aqueous solution of the blocked diisocyanate.

8. The method for synthesizing polyimide in aqueous phase according to claim 7, characterized in that: The molar ratio of the sodium bisulfite to the diisocyanate is (1.05-1.20):

1.

9. An application of the polyimide aqueous phase synthesis method according to any one of claims 1 to 8, characterized in that: Used in the preparation of polyimide films.

10. The use of the polyimide aqueous phase synthesis method according to claim 9, characterized in that: The polyimide film was prepared by a tape casting method.

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