An isocyanate monomer containing acyl chloride, a preparation method thereof and application thereof in acid-resistant nanofiltration membranes

Abstract

The application relates to an acid-resistant nanofiltration membrane containing an isocyanate monomer with an acid chloride, a preparation method of the monomer and application of the monomer in the acid-resistant nanofiltration membrane. The application belongs to the field of acid-resistant nanofiltration membranes. The application provides a variety of aromatic polyisocyanate monomers containing an acid chloride, and a series of acid-resistant nanofiltration membranes are prepared by taking the monomers as organic phase monomers. The nanofiltration membrane prepared from the monomers introduces amide bonds and carboxyl groups on the basis of a polyurea membrane. Hydrophilic groups are further introduced on the basis of retaining original hydrogen bond density. Meanwhile, roughness of an active layer of the nanofiltration membrane can be appropriately changed, which is beneficial to improving the flux of the nanofiltration membrane.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of acid-resistant nanofiltration membranes, and particularly relates to an acid-resistant nanofiltration membrane containing an isocyanate monomer containing acyl chloride and a preparation method and application thereof. BACKGROUND

[0002] Membrane separation as a new type of efficient separation technology is widely used in improving industrial production efficiency, reducing cost, saving energy and protecting environment. At present, membrane separation technology has been widely used in seawater desalination, industrial separation and other processes. In the process of industrial production or separation, the separation membrane will inevitably encounter an acidic environment, such as the recovery of lithium iron phosphate batteries, the titanium dioxide industry, the mining of various ores, etc.

[0003] The most widely used commercial water treatment separation membrane at present is a polyamide membrane. However, the carbonyl carbon in the main chain is easy to be attacked by hydrogen ions, and it is not suitable for an acidic environment. At present, the nanofiltration membrane that performs well in the process of acid wastewater treatment comes from abroad and is expensive. The domestic market of acid-resistant nanofiltration membrane is still controlled by foreign products. Therefore, some scholars have developed nanofiltration membranes based on new structures such as triazine rings, or adopted strategies such as grafting a protective layer on the surface of a polyamide membrane. However, the acid resistance of the nanofiltration membrane is still not ideal.

[0004] Polyurea membranes have advantages such as small group polarity and excellent acid resistance. In 2020, China University of Petroleum proposed using a difunctional isocyanate monomer and a polyamine monomer to perform interfacial polymerization to prepare an acid-resistant nanofiltration membrane containing polyurea. The nanofiltration membrane still has the characteristics of low flux, and the rejection rate continuously and slowly decays when running in an acidic environment, which has a certain acid resistance, but in terms of industrialization, there is still a lot of room for improvement.

[0005] The acid resistance of the acid-resistant nanofiltration membrane on the market is poor, the service life is short, and the price is expensive, which undoubtedly increases the cost of industrial production, greatly limits the application field of the separation membrane, and greatly limits the development of the industry of China. The polyurea nanofiltration membrane with good acid resistance is still in the research stage. At present, the acid-resistant nanofiltration membrane containing polyurea mostly uses aliphatic amine as an amine monomer, and the conjugation between the molecular chains is poor, and the acid resistance and flux still need to be improved. SUMMARY

[0006] In order to overcome the deficiencies of the prior art, the application provides an acid-resistant nanofiltration membrane containing an isocyanate monomer containing acyl chloride and a preparation method and application thereof.

[0007] The purpose of the application is achieved by the following technical solutions:

[0008] One of the purposes of the present application is to provide an acyl chloride-containing isocyanate monomer, which is an aromatic polyisocyanate monomer containing one or more acyl chloride groups, wherein the number of benzene rings is ≥1, the number of isocyanate groups is ≥1, and the number of isocyanate groups is ≥ the number of acyl chloride groups, and the number of benzene rings is ≥ the number of acyl chloride groups.

[0009] Preferably, the number of benzene rings is 1-2, the number of acyl chloride groups is 1-2, and the number of isocyanate groups is 1-3.

[0010] Further preferably, the acyl chloride-containing isocyanate monomer is selected from one or more of the structures of formulae (1-1) to (1-8):

[0011]

[0012] The second purpose of the present application is to provide a method for preparing an acyl chloride-containing isocyanate monomer, which is performed according to the following steps:

[0013] Preferably, the number of benzene rings is 1-2, the number of acyl chloride groups is 1-2, and the number of isocyanate groups is 1-3.

[0014] Preferably, the number of benzene rings is 1-2, the number of acyl chloride groups is 1-2, and the number of isocyanate groups is 1-3.

[0015] Further preferably, the acyl chloride-containing isocyanate monomer is selected from one or more of the structures of formulae (1-1) to (1-8):

[0016]

[0017] Preferably, the molar ratio of the carboxylic acid-containing aromatic amine monomer to oxalyl chloride is 1:(5-30).

[0018] Preferably, the catalyst is one or more of triethylamine, tripropylamine, pyridine, imidazole, N-methyl imidazole, and DMF.

[0019] Preferably, the molar ratio of the catalyst to the carboxylic acid-containing aromatic amine monomer is (0.05-1):1.

[0020] The third purpose of the present application is to provide a carboxylic acid-containing polyurea-amide compound, which is prepared by interfacial polymerization of the above-mentioned acyl chloride-containing isocyanate monomer and a multifunctional amine monomer.

[0021] The fourth purpose of the present application is to provide a method for preparing a carboxylic acid-containing polyurea-amide compound, which is performed according to the following steps:

[0022] S1: dissolving the multifunctional amine monomer and the additive in water to obtain an aqueous phase solution;

[0023] S2: dissolving the acyl chloride-containing isocyanate monomer in an organic solvent to obtain an organic phase solution;

[0024] S3: reacting the aqueous phase solution and the organic phase solution through an interfacial polymerization reaction for a certain time to obtain a carboxylic acid-containing polyurea-amide compound.

[0025] The fifth object of the present application is to provide an application of the carboxylic acid-containing polyurea-amide compound as an active layer in an acid-resistant nanofiltration membrane.

[0026] The sixth object of the present application is to provide a high-flux acid-resistant nanofiltration membrane, which comprises a base film and an active layer, and the active layer is the carboxylic acid-containing polyurea-amide compound described above.

[0027] Compared with the prior art, the present application has the following remarkable effects:

[0028] The present application provides a plurality of acyl chloride-containing aromatic polyisocyanates, and a series of acid-resistant nanofiltration membranes are prepared by using such monomers as organic phase monomers. The nanofiltration membrane prepared from the monomers introduces amide bonds and carboxyl groups on the basis of the polyurea membrane. On the basis of retaining the original hydrogen bond density, hydrophilic groups are further introduced. At the same time, the roughness of the active layer of the nanofiltration membrane can be appropriately changed, which is all conducive to improving the flux of the nanofiltration membrane. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 NMR spectrum of the acyl chloride-containing isocyanate monomer obtained in Example 1 1 H spectrum;

[0030] Figure 2 NMR spectrum of the acyl chloride-containing isocyanate monomer obtained in Example 1 13 C spectrum;

[0031] Figure 3 Acid resistance test results of the high-flux acid-resistant nanofiltration membrane obtained in Example 2 in a 20wt% sulfuric acid solution;

[0032] Figure 4 Acid resistance test results of the high-flux acid-resistant nanofiltration membrane obtained in Example 2 in a 20wt% sulfuric acid solution. DETAILED DESCRIPTION

[0033] Specific embodiment one: provide an acyl chloride-containing isocyanate monomer, the acyl chloride-containing isocyanate monomer is aromatic polyisocyanate monomer containing more than one acyl chloride group, wherein the number of benzene rings is greater than or equal to 1, the number of isocyanate groups is greater than or equal to 1, and the number of isocyanate groups is greater than or equal to the number of acyl chloride groups, and the number of benzene rings is greater than or equal to the number of acyl chloride groups. Preferably, the number of benzene rings is 1-2, the number of acyl chloride groups is 1-2, and the number of isocyanate groups is 1-3. Further preferably, the acyl chloride-containing isocyanate monomer is selected from one or more of the structures of formula (1-1) to (1-8):

[0034]

[0035] Specific embodiment two: a preparation method of an acyl chloride-containing isocyanate monomer, the method is carried out according to the following steps:

[0036] Prepared by reacting a carboxylic acid-containing aromatic amine monomer and oxalyl chloride under the action of a catalyst and then recrystallizing, the carboxylic acid-containing aromatic amine monomer has a number of benzene rings greater than or equal to 1, a number of carboxylic acids greater than or equal to 1, and a number of amino groups greater than or equal to 1, and the number of amino groups is greater than or equal to the number of carboxylic acids, and the number of benzene rings is greater than or equal to the number of carboxylic acids. Preferably, the number of benzene rings in the carboxylic acid-containing aromatic amine monomer is 1-2, the number of carboxylic acids is 1-2, and the number of amino groups is 1-3. Further preferably, the carboxylic acid-containing aromatic amine monomer is selected from one or more of the structures of formula (2-1) to (2-8):

[0037]

[0038] Preferably, the molar ratio of the carboxylic acid-containing aromatic amine monomer to oxalyl chloride is 1:(5-30). Further preferably, the molar ratio of the carboxylic acid-containing aromatic amine monomer to oxalyl chloride is 1:(10-15).

[0039] Preferably, the catalyst is one or more of triethylamine, tripropylamine, pyridine, imidazole, N-methyl imidazole, and DMF. The molar ratio of the catalyst to the carboxylic acid-containing aromatic amine monomer is (0.05-1):1. Further preferably, the molar ratio of the catalyst to the carboxylic acid-containing aromatic amine monomer is (0.1-0.3):1.

[0040] Preferably, the recrystallization reagent is one or more of dichloroethane, toluene, xylene, and carbon tetrachloride. The mass ratio of the recrystallization reagent to the solid product after reaction is (50-200):1. Further preferably, the mass ratio of the recrystallization reagent to the solid product after reaction is (80-150):1.

[0041] In some embodiments, the preparation method of the acyl chloride-containing isocyanate monomer comprises the following steps:

[0042] First, under ice bath, a carboxylic acid-containing aromatic amine monomer selected from one or more of the structures of formula (2-1) to (2-8) is added to oxalyl chloride, and a suspension is formed by stirring;

[0043] Then, under ice water bath, a catalyst is added dropwise to the suspension, and after stirring for 1-3 h, the temperature is raised to 50-70 °C, and heating and stirring are performed for 3-5 h, and then the temperature is raised to 90-110 °C, and heating and stirring are performed for 5-7 h;

[0044] Finally, the reaction solution is filtered, and excess solvent and oxalyl chloride are removed by rotary evaporation, and then recrystallization is performed using a recrystallization solvent.

[0045] Specific embodiment three: a carboxylic acid-containing polyurea-amide compound, which is prepared by interfacial polymerization of the isocyanate monomer containing acyl chloride and the multifunctional amine monomer described in specific embodiment one.

[0046] Preferably, the multifunctional amine monomer is selected from one or more of the structures of formula (3-1) to (3-7):

[0047]

[0048] In the formula, R is selected from -H, -COOH, -SO3H, or -PO(OH)2.

[0049] Specific embodiment four: a method for preparing a carboxylic acid-containing polyurea-amide compound, which is performed according to the following steps:

[0050] (1) Dissolve the multifunctional amine monomer and the additive in water to obtain an aqueous phase solution, and the concentration of the multifunctional amine monomer in the aqueous phase solution is 0.05-10% (w / v), further preferably 1-3% (w / v), and most preferably 1.5-2.5% (w / v); the additive includes but is not limited to one or more of camphorsulfonic acid, triethylamine, tripropylamine, tributylamine, triamylamine, sodium dodecylsulfate, methanol, ethanol, lactic acid, citric acid, and maleic acid. The concentration of the additive in the aqueous phase solution is 0.05-8% (w / v), further preferably 0.2-3% (w / v).

[0051] (2) Dissolve the isocyanate monomer containing acyl chloride in an organic solvent to obtain an organic phase solution; the organic solvent includes one or more of isoparG, toluene, cyclohexane, n-hexane, ethyl acetate, xylene, and chlorobenzene. The concentration of the isocyanate monomer containing acyl chloride in the organic phase solution is 0.05-2% (w / v), further preferably 0.05-0.5% (w / v), and most preferably 0.1-0.3% (w / v).

[0052] (3) The aqueous phase solution and the organic phase solution are subjected to interfacial polymerization for 5-40 s to obtain a carboxylic acid-containing polyurea-amide compound.

[0053] Embodiment five: Use of a carboxylic acid-containing polyurea-amide compound as an active layer in an acid-resistant nanofiltration membrane.

[0054] Embodiment six: A high-flux acid-resistant nanofiltration membrane comprising a base membrane and an active layer, the active layer being a carboxylic acid-containing polyurea-amide compound as described in embodiment three. The base membrane is selected from one of polyacrylonitrile, polyether ether ketone, polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene. The base membrane has a thickness of 60-200 pm, further preferably 100-150 pm.

[0055] Embodiment seven: A method for preparing a high-flux acid-resistant nanofiltration membrane, comprising the following steps:

[0056] First, pour the aqueous phase solution obtained in step (1) of embodiment four onto the surface of the base membrane and keep for 1-10 min, preferably 1-4 min, then pour off the excess aqueous solution. Then dry the membrane in air until there is no obvious water droplets on the surface;

[0057] Then pour the organic phase solution obtained in step (2) of embodiment four onto the surface of the membrane, and carry out interfacial reaction for 5-40 s. After the reaction is completed, pour off the excess organic phase solution and place the membrane in an oven at 50-90 °C, preferably 60-80 °C, for 0.5-20 min, preferably 1-4 min. Finally, take the membrane out of the oven and store it in deionized water.

[0058] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0059] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used, unless otherwise specified, are conventional materials, reagents, methods and instruments in the art, which can be obtained by commercial channels by those skilled in the art.

[0060] Preparation of isocyanate monomer containing acyl chloride

[0061] The preparation method of the isocyanate monomer containing acyl chloride in example 1 is carried out according to the following steps:

[0062] Take 100 mL oxalyl chloride into a 500 mL flask, protect it with nitrogen and connect a dry tube and acid gas absorber, and put the flask into an ice water bath. Weigh 10 g 3,5-diaminobenzoic acid, and add it into the flask in batches within 0.5 h, and stir to form a suspension. Take 5 g N-methylimidazole, and add it into the flask drop by drop within 0.5 h. Then, carry out stage heating, react at 0 °C for 2 h, raise the temperature to 50 °C and react for 4 h, and raise the temperature to 100 °C and react for 6 h. Filter out the by-product while hot, and remove the excess solvent and oxalyl chloride from the filtrate by rotary evaporation to obtain a crude product, which is recrystallized with carbon tetrachloride to obtain 3,5-diisocyanatobenzoic chloride, 1 H spectrum and 13 C spectrum as Figures 1-2 shown.

[0063] Preparation of high-flux acid-resistant nanofiltration membrane

[0064] The preparation method of the high-flux acid-resistant nanofiltration membrane in Example 2 is carried out according to the following steps:

[0065] (1) Dissolve 3,5-diaminobenzoic acid, triethylamine and camphorsulfonic acid in water to obtain an aqueous phase solution, wherein the concentration of camphorsulfonic acid is 2.1% (w / v) + the concentration of triethylamine is 2% (w / v), and the concentration of 3,5-diaminobenzoic acid is 2% (w / v).

[0066] (2) Dissolve 3,5-diisocyanatobenzoic chloride prepared in Example 1 in cyclohexane to obtain an organic phase solution; wherein the concentration of 3,5-diisocyanatobenzoic chloride is 0.1% (w / v).

[0067] (3) First, pour the aqueous phase solution onto the surface of a polysulfone-based membrane (membrane thickness = 50 μm, pore size 21 nm), and keep it for 2 min, then pour out the excess solution. Then, dry the membrane in air until there is no obvious water droplet on the surface. Then, pour the organic phase solution onto the surface of the membrane, and carry out interfacial reaction for 30 s. After the reaction is completed, pour out the excess organic phase solution, and put the membrane into an oven at 80 °C for 2 min. Take the membrane out of the oven, and put it into deionized water for storage.

[0068] The preparation method of the high-flux acid-resistant nanofiltration membrane in Example 3 is carried out according to the following steps:

[0069] (1) Dissolve piperazine, triethylamine and camphorsulfonic acid in water to obtain an aqueous phase solution, wherein the concentration of camphorsulfonic acid is 2.1% (w / v) + the concentration of triethylamine is 1% (w / v), and the concentration of piperazine is 1% (w / v).

[0070] (2) Dissolve 3,5-diisocyanatobenzoic chloride prepared in Example 1 in isoparG to obtain an organic phase solution; wherein the concentration of 3,5-diisocyanatobenzoic chloride is 0.05% (w / v).

[0071] (3) First, the aqueous solution was poured onto the surface of the polysulfone base membrane (membrane thickness = 50 μm, pore size 21 nm), and after 1 min, the excess solution was poured off. Subsequently, the membrane was air-dried until no obvious water droplets were present on the surface. Then, the organic phase solution was poured onto the surface of the membrane, and the interfacial reaction was carried out for 20 s. After the reaction was completed, the excess organic phase solution was poured off and the membrane was placed in an oven at 80 °C for 4 min. The membrane was taken out of the oven and placed in deionized water.

[0072] Example 4, Method for preparing high flux acid resistant nanofiltration membrane was carried out according to the following steps:

[0073] (1) Polyethylenimine (PEI), triethylamine and camphorsulfonic acid were dissolved in water to obtain an aqueous solution, wherein the concentration of camphorsulfonic acid was 2.1% (w / v) + the concentration of triethylamine was 1% (w / v), and the concentration of PEI was 1% (w / v).

[0074] (2) 3,5-diisocyanatobenzoyl chloride prepared in Example 1 was dissolved in isopar G to obtain an organic phase solution; wherein the concentration of 3,5-diisocyanatobenzoyl chloride was 0.05% (w / v).

[0075] (3) First, the aqueous solution was poured onto the surface of the polysulfone base membrane (membrane thickness = 50 μm, pore size 21 nm), and after 2 min, the excess solution was poured off. Subsequently, the membrane was air-dried until no obvious water droplets were present on the surface. Then, the organic phase solution was poured onto the surface of the membrane, and the interfacial reaction was carried out for 20 s. After the reaction was completed, the excess organic phase solution was poured off and the membrane was placed in an oven at 80 °C for 4 min. The membrane was taken out of the oven and placed in deionized water.

[0076] The membranes obtained in Example 2 were respectively immersed in 20 wt% sulfuric acid and 20 wt% hydrochloric acid solutions to test their acid resistance, and the results are shown in Table 1. Figures 3-4 After each immersion for 70 days, the acid resistance of the nanofiltration membranes obtained in Examples 2-4 was characterized by testing the rejection rate of a 2000 ppm aqueous magnesium sulfate solution and the water flux. The pressure during the test was 4-20 bar. The results are shown in Table 1.

[0077] Table 1 Acid resistance performance

[0078]

[0079]

[0080] The above merely describes preferred specific embodiments of the present application, which are based on different implementations of the overall concept of the present application, and the protection scope of the present application is not limited thereto. Any changes or replacements that are easily conceived by those skilled in the art within the technical scope disclosed by the present application shall be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A carboxylic acid-containing polyurea-amide compound, characterized by, The isocyanate monomer containing acyl chloride is selected from one or more of the structures of formula (1-2)~(1-3), (1-6)~(1-8): ； The multifunctional amine monomer is selected from one or more of the structures of formula (3-1)~(3-7): ； In the formula, R is selected from -H, -COOH, -SO3H or -PO(OH)2.

2. The carboxylic acid-containing polyurea-amide compound according to claim 1, characterized in that, The preparation method of the isocyanate monomer containing acyl chloride is carried out according to the following steps: The isocyanate monomer containing acyl chloride is prepared by reacting the carboxylic acid-containing aromatic amine monomer with oxalyl chloride under the action of a catalyst and then recrystallizing, and the carboxylic acid-containing aromatic amine monomer is selected from one or more of the structures of formula (2-2)~(2-3), (2-6)~(2-8): ， The molar ratio of the carboxylic acid-containing aromatic amine monomer to oxalyl chloride is 1: (5-30), the catalyst is one or more of triethylamine, tripropylamine, pyridine, imidazole, N-methyl imidazole and DMF, and the molar ratio of the catalyst to the carboxylic acid-containing aromatic amine monomer is (0.05-1):

1.

3. The method for preparing the carboxylic acid-containing polyurea-amide compound according to claim 1, characterized by, The preparation method is carried out according to the following steps: S1: dissolving the multifunctional amine monomer and the additive in water to obtain an aqueous phase solution; S2: dissolving the isocyanate monomer containing acyl chloride in an organic solvent to obtain an organic phase solution; S3: carrying out interfacial polymerization for a certain time by mixing the aqueous phase solution and the organic phase solution to obtain the carboxylic acid-containing polyurea-amide compound.

4. Use of the carboxylic acid-containing polyurea-amide compound of claim 1 as an active layer in an acid-resistant nanofiltration membrane.

5. A nanofiltration membrane, characterized in that, The active layer is the carboxylic acid-containing polyurea-amide compound of claim 1.

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