Hydrophobic separation membrane with negative charges on surface as well as preparation method and application of hydrophobic separation membrane

Abstract

The invention provides a hydrophobic separation membrane with negative charges on the surface as well as a preparation method and application of the hydrophobic separation membrane. The hydrophobic separation membrane comprises a base membrane and a separation layer which is deposited on the surface of the base membrane and is provided with negative charges, the separation layer is prepared by cross-linking polymerization of a first reaction monomer and a second reaction monomer; the molar ratio of the first reaction monomer to the second reaction monomer is 1: 1; both the first reaction monomer and the second reaction monomer contain hydrophobic groups, and the number of carboxyl groups in the second reaction monomer is 1 more than that of amino groups in the first reaction monomer. The hydrophobic separation membrane has a good interception effect on water and sulfonate ions, and can reduce entrainment loss of water and sulfonate ions when being used for rectification of an organic solvent in the preparation process of a waterborne polyurethane dispersion, so that the water content and pH in the recovered organic solvent meet the requirements of direct use, further rectification and refining are not needed, and the production cost is reduced. And water is basically free of loss, so that the system is more stable in the production process, and no solid is separated out.

Description

Technical Field

[0001] The invention belongs to the field of composite membrane materials and separation technology, and relates to a hydrophobic separation membrane with negative charges on the surface and a preparation method and application thereof. Background Art

[0002] Waterborne polyurethane adhesives are environmentally friendly during use, in line with current international development trends and national policy orientations, and are gaining more and more attention in the manufacturing industry. Based on the different hydrophilic groups, waterborne polyurethane dispersions are divided into cationic, anionic and nonionic types, among which anionic waterborne polyurethane is the most important and widely used.

[0003] According to the type of anionic groups introduced into the polyurethane macromolecular chain, anionic waterborne polyurethanes are mainly divided into carboxylic acid type and sulfonic acid type. Sulfonic acid type waterborne polyurethane dispersions can meet the occasions of harsh conditions and high performance requirements due to their good hydrolysis resistance and stability. The existing preparation method of sulfonate type waterborne polyurethane is usually an acetone method, which generates a prepolymer terminated with an NCO group by reacting polyester polyol with an excess of polyisocyanate, and then adding acetone to reduce the viscosity of the system, followed by adding a sulfonate chain extender for chain extension reaction, adding water after chain extension to complete phase inversion, and finally distilling out acetone to obtain a waterborne polyurethane product.

[0004] However, since water reacts with isocyanate and affects product performance, strict requirements are imposed on the water content of the solvent used in the preparation process of waterborne polyurethane. In addition, pH also affects the performance of waterborne polyurethane. When waterborne polyurethane is produced by the acetone method, the reuse of acetone is an indispensable part of reducing costs. In the process of distilling acetone, a large amount of water is often entrained in the recovered acetone. At the same time, since the boiling point of the sulfonate chain extender solution is close to that of water (such as the boiling point of the aqueous solution of sodium ethylenediaminoethanesulfonate is 106°C), a small amount of sulfonate ions will be mixed in the recovered acetone, resulting in the need for further distillation and purification of the recovered acetone and the addition of acid to adjust the pH, which undoubtedly increases the production cost of sulfonic acid-type waterborne polyurethane. In addition, since part of the water is entrained and lost by acetone, the solid content of the waterborne polyurethane system increases during the production process, the stability of the system decreases, and some solids in the system precipitate, resulting in product loss. Secondly, the increase in solid content will also increase the viscosity of the system, foaming and swelling of the kettle, causing the product to mix into the acetone recovery kettle.

[0005] CN115445228A discloses a device and process for continuously removing acetone solvent from an aqueous polyurethane dispersion, the device comprising a microwave heater and a desolventizing kettle connected in sequence, the desolventizing kettle being provided with a scraper mechanism, and by spraying a dibutyl mercaptan tin-vanadium-polytetrafluoroethylene coating on the inner wall of the desolventizing kettle and the surface of the scraper mechanism, efficient and continuous removal of acetone is achieved. CN116410438A discloses an aqueous polyurethane dispersion and its preparation method and application, which adopts a step-by-step chain extension method to solve the problem of NCO group and water side reaction in the prepolymer chain extension / dispersion process, thereby obtaining an aqueous polyurethane dispersion with excellent viscosity, chemical resistance and storage stability. At present, the production technology of aqueous polyurethane often only involves the optimization of the preparation process or the solvent removal process, and does not involve the repeated reuse of the solvent.

[0006] In summary, providing a method for producing waterborne polyurethane that reduces the loss of water and chain extender entrainment is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention aims to provide a hydrophobic separation membrane with a negatively charged surface and a preparation method and application thereof. The hydrophobic separation membrane has a good interception effect on water and sulfonate ions. When the hydrophobic separation membrane is used for the distillation of organic solvents in the preparation process of aqueous polyurethane dispersions, it can reduce the entrainment loss of water and sulfonate ions, so that the water content and pH value of the recovered organic solvent meet the requirements for direct use, and no further distillation and refining are required, thereby reducing production costs. At the same time, since there is basically no loss of water, the system is more stable during the production process, no solid precipitation is produced, and product losses are reduced.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a hydrophobic separation membrane with a negatively charged surface, the hydrophobic separation membrane comprising a base membrane and a negatively charged separation layer deposited on the surface of the base membrane;

[0010] The separation layer is prepared by cross-linking polymerization of the first reaction monomer and the second reaction monomer;

[0011] The molar ratio of the first reactive monomer to the second reactive monomer is 1:1;

[0012] The first reactive monomer and the second reactive monomer both contain hydrophobic groups, and the number of carboxyl groups in the second reactive monomer is one more than the number of amino groups in the first reactive monomer.

[0013] The hydrophobic separation membrane provided by the present invention has a large number of hydrophobic groups in the selected first reaction monomer and the second reaction monomer, so the membrane obtained by the cross-linking polymerization reaction is a hydrophobic membrane; in addition, by controlling the molar ratio of the first reaction monomer to the second reaction monomer to be 1:1, and the number of carboxyl groups in the reaction monomer is 1 more than the number of amino groups in the molar amount, the unreacted carboxyl groups are hydrolyzed after the cross-linking polymerization to form a membrane so that the membrane surface has a negative charge, which can better retain sulfonate ions.

[0014] Therefore, the hydrophobic separation membrane with a negative charge on the surface can be used in the organic solvent distillation process in the preparation process of the aqueous polyurethane dispersion, reducing the entrainment loss of water and sulfonate ions in the acetone distillation process, so that the water content and pH of the recovered acetone meet the requirements for direct use, and no further distillation and purification are required, thereby reducing the production cost. At the same time, since there is basically no loss of water, the system in the production process is more stable, no solid precipitation occurs, and the product loss is reduced.

[0015] It is worth noting that by controlling the molar ratio of the first reaction monomer to the second reaction monomer to be 1:1, and the number of carboxyl groups is one more than the number of amino groups, not only the surface of the hydrophobic separation membrane is negatively charged after film formation, but also the surface of the hydrophobic separation membrane has only one hydrophilic group and is far less than the number of hydrophobic groups, which can enhance the hydrophobicity of the membrane surface. + The concentration in the membrane is greater than that in the condensate, and SO3 2- The concentration in the membrane is lower than that in the condensate, thus forming a Donnan potential difference to prevent SO3 2- Diffusion from the condensate into the membrane, in order to maintain electrical neutrality, Na + will also be retained by the membrane; therefore, hydrophobic separation membranes are able to retain sulfonate ions.

[0016] As a preferred technical solution of the present invention, the base membrane includes any one of a polyacrylonitrile base membrane, a polysulfone base membrane or a polyvinylidene fluoride based membrane, or a combination of at least two of them; wherein the combinations are typical but not limiting: a combination of a polyacrylonitrile base membrane and a polysulfone base membrane, a combination of a polysulfone base membrane and a polyvinylidene fluoride based membrane, or a polyacrylonitrile base membrane, a polysulfone base membrane and a polyvinylidene fluoride based membrane, etc.

[0017] In the present invention, the polysulfone-based membrane includes a polyethersulfone-based membrane. The present invention does not specifically limit the structure and parameters of the base membrane, as long as it can play a role in structural support and interface bonding, it can be used in the present invention, and those skilled in the art can select it according to actual needs.

[0018] Preferably, the base film has a thickness of 175-275 nm, for example, 175 nm, 185 nm, 195 nm, 200 nm, 205 nm, 215 nm, 225 nm, 235 nm, 245 nm, 255 nm, 265 nm or 275 nm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 200-250 nm.

[0019] As a preferred technical solution of the present invention, the number of separation layers is ≥ 2, for example, it can be 2 layers, 3 layers, 4 layers or 5 layers, etc., preferably 3 layers.

[0020] In the present invention, in order to enhance the stability of the hydrophobic separation membrane, at least two separation layers are deposited on the surface of the base membrane by electrospraying to form a multilayer hydrophobic separation membrane with a network cross-linked structure.

[0021] As a preferred technical solution of the present invention, the first reactive monomer includes a first compound containing an amino group and a benzene ring.

[0022] Preferably, the number of benzene rings in the first compound is ≥2, for example, it can be 2, 3, 4 or 5, etc., preferably 2-4.

[0023] Preferably, the first reaction monomer includes any one of 2-phenyl-5-aminoindole, 2,6-diaminonaphthalene, 1,8-diaminopyrene, 1,6-diaminopyrene, 9,10-diaminophenanthrene or 1,2-diaminoanthraquinone, or a combination of at least two thereof; wherein the combinations are typical but not limiting: a combination of 2-phenyl-5-aminoindole and 2,6-diaminonaphthalene, a combination of 1,8-diaminopyrene and 1,6-diaminopyrene, or a combination of 9,10-diaminophenanthrene and 1,2-diaminoanthraquinone, etc.

[0024] As a preferred technical solution of the present invention, the second reactive monomer includes a second compound containing a carboxyl group, a nitro group and a benzene ring.

[0025] Preferably, the number of carboxyl groups in the second compound is ≥ 2, for example, 2, 3, 4, 5, 6 or 7, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the number of nitro groups in the second compound is 1-5, for example, 1, 2, 3, 4 or 5.

[0027] Preferably, the number of benzene rings in the second compound is ≥2, for example, it can be 2, 3, 4 or 5, etc., preferably 2-4.

[0028] It is worth noting that the hydrophobic groups include nitro groups and benzene rings, which repel water molecules and are not easily wetted by water, but are easily wetted by organic solvents. In addition, the number of benzene rings and nitro groups in the first reaction monomer and the second reaction monomer needs to be controlled. If the number of benzene rings and nitro groups is too large, the molecular structure and molecular weight of the reaction monomer will increase, and the membrane pores will increase after film formation, reducing the retention rate of sulfonate ions. If the number of benzene rings is too small, the hydrophobic performance will decrease.

[0029] Preferably, the second reactive monomer comprises any one or a combination of at least two of 5'-(4-carboxyphenyl)-2'-nitro-[1,1':3',1"-terphenyl]-4,4"-dicarboxylic acid, 2-(3,5-dicarboxyphenyl)-4-p-nitrobenzoic acid, 5'-nitro-3,3',5-biphenyltricarboxylic acid, 2'-nitro-[1,1'-biphenyl]-3,4',5-tricarboxylic acid or 4-(3,5-diphenylmethanecarboxy)-3-nitrobenzoic acid; wherein the combination is typical but not limited to Restrictions include: the combination of 5'-(4-carboxyphenyl)-2'-nitro-[1,1':3',1"-terphenyl]-4,4"-dicarboxylic acid and 2-(3,5-dicarboxyphenyl)-4-nitrobenzoic acid, the combination of 5'-nitro-3,3',5-biphenyltricarboxylic acid and 2'-nitro-[1,1'-biphenyl]-3,4',5-tricarboxylic acid or 2'-nitro-[1,1'-biphenyl]-3,4',5-tricarboxylic acid and 4-(3,5-diphenylmethanecarboxy)-3-nitrobenzoic acid, etc.

[0030] As a preferred technical solution of the present invention, the pore size of the hydrophobic separation membrane is 1-20nm, for example, it can be 1nm, 2nm, 4nm, 5nm, 6nm, 8nm, 10nm, 12nm, 14nm, 15nm, 16nm, 18nm or 20nm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 5-10nm.

[0031] Preferably, the membrane thickness of the hydrophobic separation membrane is 200-400nm, for example, it can be 200nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 320nm, 330nm, 340nm, 360nm, 380nm or 400nm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 275-325nm.

[0032] Preferably, the membrane surface Zeta potential of the hydrophobic separation membrane is -75 to 0 mV, for example, it can be -75 mV, -70 mV, -60 mV, -50 mV, -40 mV, -35 mV, -30 mV, -25 mV, -20 mV, -15 mV, -10 mV or 0 mV, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably -40 to -10 mV.

[0033] Preferably, the membrane surface contact angle of the hydrophobic separation membrane is 90°-170°, for example, it can be 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160° or 170°, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 120°-150°.

[0034] In the present invention, according to the wettability theory, when the mixture of oil and water contacts the surface of the hydrophobic and oleophilic membrane, the oil droplets quickly diffuse and penetrate into the membrane surface, and when the contact angle between water and the surface of the hydrophobic separation membrane is greater than 90°, the water molecules cannot wet the surface, but form water droplets or water beads, and are thus intercepted by the hydrophobic separation membrane. In addition, water is a polar substance and can form hydrogen bonds inside, but the surface of the hydrophobic separation membrane is not electronically polarized and cannot form hydrogen bonds, so water will repel the hydrophobic separation membrane.

[0035] In the present invention, the permeate side pressure of the hydrophobic separation membrane is 1-100 kPa, for example, it can be 1 kPa, 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa or 100 kPa, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 10-100 kPa.

[0036] In the present invention, the osmotic pressure of the hydrophobic separation membrane is 10-90 kPa, for example, it can be 10 kPa, 15 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa or 90 kPa, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 10-20 kPa.

[0037] In a second aspect, the present invention provides a method for preparing the hydrophobic separation membrane as described in the first aspect, the preparation method comprising the following steps:

[0038] (1) providing a basement membrane;

[0039] (2) depositing the first reaction monomer solution and the second reaction monomer solution on the surface of the base film in sequence by electrospraying, and then polymerizing;

[0040] (3) Repeat step (2) at least twice to obtain the hydrophobic separation membrane.

[0041] The preparation method provided by the present invention adopts the electrospray-self-assembly method to prepare a hydrophobic separation membrane with a negatively charged surface. The obtained hydrophobic separation membrane has excellent performance and a simple process, which is conducive to realizing industrial large-scale production.

[0042] It should be noted that the present invention does not specifically limit the electrospraying method and the equipment used. Those skilled in the art can use conventional electrospraying equipment. The electrospraying method can also be carried out with reference to the method provided by the prior art, or with reference to the following method: placing the first reaction monomer solution and the second reaction monomer solution in two pressure barrels respectively, and spraying the reaction monomer solution to the nozzle outlet under high pressure. The shear force generated by its faster flow rate will shear the reaction monomer solution into small droplets, and gradually form a liquid mist that is evenly deposited on the surface of the base film.

[0043] As a preferred technical solution of the present invention, the pressure of the electrospray in step (2) is 1-20 bar, for example, it can be 1 bar, 3 bar, 5 bar, 6 bar, 8 bar, 10 bar, 12 bar, 15 bar, 16 bar, 18 bar or 20 bar, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 3-10 bar.

[0044] Preferably, the flow rate of the electrospray in step (2) is 0.1-1.2 L / min, for example, it can be 0.1 L / min, 0.2 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.8 L / min, 1 L / min or 1.2 L / min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.4-0.6 L / min.

[0045] Preferably, the distance of the electrospray in step (2) is 5-20 cm, for example, 5 cm, 7 cm, 10 cm, 12 cm, 15 cm, 17 cm, 19 cm or 20 cm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable, preferably 10-15 cm.

[0046] In the present invention, by controlling the distance of electrospraying within the range of 5-20 cm, the monomer solution can be sprayed uniformly on the base film, thereby avoiding uneven film thickness caused by secondary spraying, which further affects the flux.

[0047] Preferably, the solvent in the first reaction monomer solution in step (2) comprises any one of benzene, toluene, ethyl acetate, n-hexane, cyclohexane or acetone, or a combination of at least two thereof.

[0048] Preferably, the solvent in the second reaction monomer solution in step (2) comprises any one of benzene, toluene, ethyl acetate, n-hexane, cyclohexane or acetone, or a combination of at least two thereof.

[0049] Preferably, the polymerization time in step (2) is 0.5-2 h, for example, 0.7 h, 0.9 h, 1 h, 1.2 h, 1.5 h, 1.6 h, 1.8 h or 2 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] Preferably, step (3) is repeated twice.

[0051] In a third aspect, the present invention provides an application of the hydrophobic separation membrane as described in the first aspect, wherein the hydrophobic separation membrane is used for distillation of organic solvents in the preparation of anionic aqueous polyurethane dispersions, preferably in the preparation of sulfonate aqueous polyurethane dispersions.

[0052] It should be noted that the present invention does not specifically limit the preparation method of the sulfonate type aqueous polyurethane dispersion. Those skilled in the art may refer to the method provided by the prior art, or refer to the following preparation method: a polyester polyol and an excess of isocyanate monomer are added to a reaction device for prepolymerization, and when the prepolymer target value is reached, an organic solvent is added to reduce the viscosity and temperature of the system, and then a chain extender is added for chain extension reaction. After the chain extension reaction is completed, deionized water is added for water dispersion, and then the organic solvent is distilled by vacuuming. The distilled organic solvent passes through a condensing device and enters a separation device loaded with a hydrophobic separation membrane. The organic solvent enters an organic solvent collecting tank through the hydrophobic separation membrane. The distillation is terminated after the organic solvent content of the aqueous polyurethane solution in the reaction device is qualified to obtain a sulfonate type aqueous polyurethane dispersion with stable dispersion.

[0053] In the present invention, the isocyanate monomer includes 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, toluene diisocyanate, isomers of xylylene diisocyanate, p-phenylene diisocyanate or its isomers, tetramethylxylene diisocyanate, 1,3-dimethylcyclohexane isocyanate, 2,6-xylene isocyanate, 1,5-naphthalene diisocyanate, 1,4-butane diisocyanate, 1,5-pentane diisocyanate, 1,10-decane diisocyanate, 2,2-dimethylpentane-1,5-diisocyanate, 2-methyl-1,5-pentane diisocyanate, 2,4,4 (or 2,2,4)-trimethyl-1,6- Hexane diisocyanate, 1,3- and 1,4-cyclohexane diisocyanate, isophorone diisocyanate, 2,4- or 2,6-diisocyanato-1-methylcyclohexane, 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 1,3 (and / or 1,4)-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane, triisocyanatocyclohexane, tris(isocyanatomethyl)cyclohexane Any one or a combination of at least two of 1,3,5-tris(isocyanatomethyl)cyclohexane, 1,8-diisocyanato-4-(isocyanatomethyl)octane, 1,6,11-undecane triisocyanate, 1,7-diisocyanato-4-(3-isocyanatopropyl)heptane, 1,6-diisocyanato-3-(isocyanatomethyl)hexane or 1,3,5-tris(isocyanatomethyl)cyclohexane.

[0054] In the present invention, the polyester polyol includes any one of polyethylene adipate diol, polybutylene adipate diol, polyneopentyl adipate diol, polyhexylene adipate diol or polyhexylene adipate neopentyl glycol ester diol or a combination of at least two thereof; the number average molecular weight of the polyester polyol is 500-3000.

[0055] In the present invention, the chain extender includes any one of ethylene glycol, propylene glycol, butanediol, ethylenediamine, propylenediamine, butanediamine, hexamethylenediamine, isophoronediamine, hydroxyethylethylenediamine, sodium ethylenediaminoethanesulfonate, sodium diaminobenzenesulfonate or diethylene glycolamine, or a combination of at least two thereof.

[0056] In the present invention, the temperature of the chain extension reaction is 30-60°C, preferably 40-50°C; the time of the chain extension reaction is 3-20min, preferably 5-10min; the time of the water dispersion is 5-12h, preferably 7-9h.

[0057] As a preferred technical solution of the present invention, the hydrophobic separation membrane is used to remove water and sulfonate ions from the organic solvent.

[0058] Preferably, the organic solvent comprises acetone.

[0059] It is worth noting that in the preparation process of sulfonate-type waterborne polyurethane, a device containing a hydrophobic separation membrane is provided at the extraction point of the organic solvent (acetone). The hydrophobic separation membrane carried by the device has a repelling effect on water molecules and is not easily wetted by water, but is easily wetted by the organic solvent, thereby achieving water interception and reflux, thereby reducing water entrainment. At the same time, the hydrophobic separation membrane is also loaded with negative charges. Since the same charges repel each other, the hydrophobic separation membrane also has a good intercepting effect on sulfonate ions, and finally the recovery of acetone meets the solvent requirements used in waterborne polyurethane, and can be used directly without refining, and the waterborne polyurethane solution is stable without solid precipitation during the preparation process.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The hydrophobic separation membrane provided by the present invention has a first reaction monomer and a second reaction monomer both having a large number of hydrophobic groups, and the molar ratio of the first reaction monomer to the second reaction monomer is further controlled to be 1:1 and the number of carboxyl groups in the second reaction monomer is one more than the number of amino groups in the first reaction monomer, so as to ensure that the obtained membrane is a hydrophobic membrane and its surface is negatively charged, so that it has a good interception effect on water and sulfonate ions; wherein the obtained hydrophobic separation membrane has a pore size of 1-20nm, a membrane thickness of 200-400nm, a membrane surface Zeta potential of -75 to 0mV, and a membrane surface contact angle of 90° to 170°;

[0062] (2) The hydrophobic separation membrane provided by the present invention can reduce the entrainment loss of water and sulfonate ions when used for the distillation of organic solvents in the preparation process of aqueous polyurethane dispersions, so that the water content and pH of the recovered organic solvent meet the requirements for direct use, and no further distillation and purification are required, thereby reducing production costs. At the same time, since there is no loss of deionized water, the system in the production process of aqueous polyurethane dispersions is more stable, no solid precipitation occurs, and product losses are reduced;

[0063] (3) The preparation method provided by the present invention adopts the electrospray-self-assembly method to prepare a hydrophobic separation membrane with a negatively charged surface. The obtained hydrophobic separation membrane has excellent performance and a simple process, which is conducive to industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a schematic diagram of a device system for preparing a sulfonate-type aqueous polyurethane dispersion provided by the present invention;

[0065] Among them, 1-reaction device, 2-condensation device, 3-separation device, 4-acetone collection tank, 5-vacuum device, 6-first valve, 7-second valve, 8-third valve, 9-fourth valve, 10-hydrophobic separation membrane. DETAILED DESCRIPTION

[0066] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0067] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0068] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0069] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0070] The specific embodiment of the present invention provides a device system for preparing a sulfonate type aqueous polyurethane dispersion, such as Figure 1 As shown, the device system comprises a reaction device 1, a condensation device 2, a separation device 3, an acetone collection tank 4 and a vacuum device 5 which are connected in sequence;

[0071] The separation device 3 is provided with a hydrophobic separation membrane 10 with a negatively charged surface;

[0072] The separation device 3 is connected to the reaction device 1, and a second valve 7 is provided on the connecting pipeline;

[0073] A first valve 6 is provided on the pipeline connecting the reaction device 1 and the condensation device 2;

[0074] A third valve 8 is provided on the pipeline connecting the separation device 3 and the acetone collection tank 4;

[0075] A fourth valve 9 is provided on the pipeline connecting the acetone collecting tank 4 and the vacuum device 5 .

[0076] In a specific embodiment of the present invention, the base membrane, the first reaction monomer and the first reaction monomer of the synthetic hydrophobic separation membrane are all commercially available products; the electrospray equipment is also a commercially available product; the pore size, membrane thickness, membrane surface Zeta potential and membrane surface contact angle parameters of the prepared hydrophobic separation membrane are measured using conventional testing methods in the prior art, and the performance parameters of the prepared aqueous polyurethane dispersion and recovered acetone are also measured using conventional testing methods in the prior art, which are not specifically limited herein.

[0077] Example 1

[0078] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof, wherein the hydrophobic separation membrane comprises a base membrane and three separation layers deposited on the surface of the base membrane to form a negatively charged separation layer;

[0079] The separation layer is prepared by cross-linking polymerization of the first reaction monomer and the second reaction monomer;

[0080] The molar ratio of the first reactive monomer to the second reactive monomer is 1:1;

[0081] The first reactive monomer and the second reactive monomer both contain hydrophobic groups, and the number of carboxyl groups in the second reactive monomer is one more than the number of amino groups in the first reactive monomer;

[0082] The base film is a polyacrylonitrile base film with a thickness of 225 nm;

[0083] The first reaction monomer is 2,6-diaminonaphthalene; the second reaction monomer is 2-(3,5-dicarboxyphenyl)-4-p-nitrobenzoic acid;

[0084] The preparation method comprises the following steps:

[0085] (1) providing a polyacrylonitrile-based film;

[0086] (2) depositing 1 L of a 1 mol / L first reaction monomer solution and 1 L of a 1 mol / L second reaction monomer solution on the surface of the base film in sequence by electrospraying, and then polymerizing for 1 h;

[0087] Wherein, the solvents in the first reaction monomer solution and the second reaction monomer solution are both n-hexane;

[0088] The electrospray pressure was 10 bar, the flow rate was 0.5 L / min, and the distance was 12 cm;

[0089] (3) Repeat step (2) twice to obtain the hydrophobic separation membrane with negatively charged surface.

[0090] Example 2

[0091] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof, except that the base membrane is a polyvinylidene fluoride based membrane with a thickness of 225 nm; the first reaction monomer is 1,6-diaminopyrene; and the second reaction monomer is 5'-nitro-3,3',5-biphenyltricarboxylic acid, other conditions are the same as those in Example 1.

[0092] Example 3

[0093] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the pressure of the electrospray in step (2) is 3 bar, the flow rate is 0.6 L / min, and the distance is 5 cm, other conditions are the same as those in Example 1.

[0094] Example 4

[0095] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the pressure of the electrospray in step (2) is 10 bar, the flow rate is 0.4 L min, and the distance is 20 cm, other conditions are the same as those in Example 1.

[0096] Example 5

[0097] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the first reaction monomer is o-phenylenediamine, other conditions are the same as those in Example 1.

[0098] Example 6

[0099] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the second reaction monomer is 2-nitrotricromellitic acid, other conditions are the same as those in Example 1.

[0100] Example 7

[0101] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the second reaction monomer is 3,4',5-biphenyltricarboxylic acid, other conditions are the same as those in Example 1.

[0102] Example 8

[0103] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the number of separation layers is 1, other conditions are the same as those in Embodiment 1.

[0104] Example 9

[0105] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the pressure of the electrospray in step (2) is 0.5 bar, other conditions are the same as those in Example 1.

[0106] Example 10

[0107] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the pressure of the electrospray in step (2) is 22 bar, other conditions are the same as those in Example 1.

[0108] Embodiment 11

[0109] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the flow rate of the electrospray in step (2) is 0.05 L / min, other conditions are the same as those in Example 1.

[0110] Example 12

[0111] This embodiment provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the flow rate of the electrospray in step (2) is 1.5 L / min, other conditions are the same as those in Example 1.

[0112] Comparative Example 1

[0113] This comparative example provides a hydrophobic separation membrane with a negatively charged surface and a preparation method thereof. Except that the molar ratio of the first reaction monomer to the second reaction monomer is 2:1, other conditions are the same as those in Example 1.

[0114] Comparative Example 2

[0115] This embodiment provides a hydrophobic separation membrane with a negatively charged surface. Except that the second reaction monomer is 2-(3-carboxyphenyl)-4-p-nitrobenzoic acid, other conditions are the same as those in Embodiment 1.

[0116] Comparative Example 3

[0117] This embodiment provides a hydrophobic separation membrane with a negatively charged surface. Except that the second reaction monomer is 2-(3,4,5-tricarboxyphenyl)-4-p-nitrobenzoic acid, other conditions are the same as those in Embodiment 1.

[0118] The performance of the hydrophobic separation membranes prepared in the above examples and comparative examples was characterized, and the results are shown in Table 1.

[0119] Table 1

[0120]

[0121] The hydrophobic separation membrane obtained in the above examples and comparative examples was used to prepare a sulfonate-type aqueous polyurethane dispersion, and Figure 1 The device system provided is carried out, and the preparation method comprises: pumping 304.6 kg of polybutylene adipate diol from which water has been removed and the molecular weight of which is 2250 into a reaction device, and setting the temperature of the reaction device to 80° C., adding 15.38 kg of isophorone diisocyanate and 22.31 g of hexamethylene diisocyanate into a prepolymerization reaction device, mixing with the polybutylene adipate diol and increasing the stirring speed, then setting the temperature of the reaction device to 95° C., performing a prepolymerization reaction for 3 hours, sampling multiple times, and detecting the content of the prepolymer, when the prepolymer reaches a target value, adding 508 kg of acetone to the reaction device in batches to reduce the viscosity, setting the temperature of the reaction device to 50° C. and adding 8.77 kg of sodium ethylenediaminoethanesulfonate solution, performing a chain extension reaction, and after the chain extension reaction is completed, dripping water for dispersion, vacuuming to remove the acetone, and separating water and sulfonate ions through a hydrophobic separation membrane to obtain an aqueous polyurethane dispersion, and recovering the acetone at the same time.

[0122] Among them, when Figure 1 When no separation device is provided, the solid content of the aqueous polyurethane dispersion prepared by the above method is 40.5%, the pH is 7.6, the viscosity is 370 mPa·s, and the particle size is 164 nm; the water content of the recovered acetone is 10%, and the pH is 8.5. Therefore, when the hydrophobic separation membrane provided by the present invention is not used for acetone distillation recovery, the water content of the recovered acetone is high, and its pH is alkaline, and it cannot be directly reused in the reaction device.

[0123] When the hydrophobic separation membranes obtained in the above examples and comparative examples are used to prepare sulfonate-type aqueous polyurethane dispersions, the properties of the obtained products and the recovered acetone are shown in Table 2.

[0124] Table 2

[0125]

[0126]

[0127] From Table 1 and Table 2, we can see that:

[0128] (1) The hydrophobic separation membrane provided in Examples 1 to 4 of the present invention has hydrophobic properties and a negatively charged surface. It has a good interception effect on water and sulfonate ions. When it is used for the distillation of organic solvents in the preparation process of aqueous polyurethane dispersions, it can reduce the entrainment loss of water and sulfonate ions, so that the water content and pH of the recovered acetone meet the requirements for direct use, and no further distillation and purification are required, thereby reducing the production cost; wherein the acetone content in the aqueous polyurethane dispersion is less than 1%, the water content in the recovered acetone is ≤ 0.02%, and the SO3 2- Retention rate ≥99%, pH is neutral;

[0129] (2) By comparing Example 1 with Examples 5-7, it can be seen that when the first reaction monomer or the second reaction monomer contains only one benzene ring group or the second reaction monomer does not contain a nitro group, the number of hydrophobic groups on the membrane surface is reduced, and the hydrophobicity of the resulting hydrophobic separation membrane is weakened, which leads to a higher water content in the recovered acetone and a higher acetone content in the aqueous polyurethane dispersion;

[0130] (3) From the comparison between Example 1 and Example 8, it can be seen that when the separation layer is only one layer, the obtained hydrophobic separation membrane becomes thinner, and its stability and strength decrease, which leads to an increase in water permeation;

[0131] (4) Comprehensive comparison of Example 1 and Examples 9-12 shows that when the pressure of electrospray is not in the preferred range, when the pressure is low, the thickness of the obtained hydrophobic separation membrane increases, the permeation resistance of acetone increases, and the acetone content in the dispersion is high; when the pressure is high, the result is the opposite; when the flow rate of electrospray is not in the preferred range, when the flow rate is fast, the degree of monomer ionization decreases, the thickness of the obtained hydrophobic separation membrane decreases, the permeation flux of water increases while the acetone permeation increases, and the water content in the recovered acetone is high; when the flow rate is slow, the result is the opposite;

[0132] (5) From the comparison between Example 1 and Comparative Examples 1-3, it can be seen that when the number of carboxyl groups in the second reaction monomer is greater than the number of amino groups in the first reaction monomer by more than 1, the number of carboxyl groups on the membrane surface increases, which reduces the hydrophobicity of the membrane, increases the water content in the recovered acetone, and increases the acetone content in the dispersion; when the number of carboxyl groups in the second reaction monomer is less than the number of amino groups in the first reaction monomer, the surface charge of the resulting hydrophobic separation membrane is positive or uncharged, which is not conducive to the retention of sulfonate ions, thereby increasing the amount of recovered acetone sulfonate ions.

[0133] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A hydrophobic separation membrane with a negatively charged surface, characterized in that: The hydrophobic separation membrane comprises a base membrane and a negatively charged separation layer deposited on the surface of the base membrane; The separation layer is prepared by cross-linking polymerization of the first reaction monomer and the second reaction monomer; The molar ratio of the first reactive monomer to the second reactive monomer is 1:1; The first reactive monomer and the second reactive monomer both contain hydrophobic groups, and the number of carboxyl groups in the second reactive monomer is one more than the number of amino groups in the first reactive monomer.

2. The hydrophobic separation membrane according to claim 1, characterized in that The base film includes any one of a polyacrylonitrile base film, a polysulfone base film or a polyvinylidene fluoride base film or a combination of at least two thereof; Preferably, the base film has a thickness of 175-275 nm, preferably 200-250 nm.

3. The hydrophobic separation membrane according to claim 1 or 2, characterized in that The number of the separation layers is ≥2.

4. The hydrophobic separation membrane according to any one of claims 1 to 3, characterized in that: The first reactive monomer includes a first compound containing an amino group and a benzene ring; Preferably, the number of benzene rings in the first compound is ≥2, preferably 2-4; Preferably, the first reaction monomer includes any one or a combination of at least two of 2-phenyl-5-aminoindole, 2,6-diaminonaphthalene, 1,8-diaminopyrene, 1,6-diaminopyrene, 9,10-diaminophenanthrene or 1,2-diaminoanthraquinone.

5. The hydrophobic separation membrane according to any one of claims 1 to 4, characterized in that: The second reactive monomer includes a second compound containing a carboxyl group, a nitro group and a benzene ring; Preferably, the number of carboxyl groups in the second compound is ≥2; Preferably, the number of nitro groups in the second compound is 1-5; Preferably, the number of benzene rings in the second compound is ≥2, preferably 2-4; Preferably, the second reactive monomer comprises any one or a combination of at least two of 5'-(4-carboxyphenyl)-2'-nitro-[1,1':3',1"-terphenyl]-4,4"-dicarboxylic acid, 2-(3,5-dicarboxyphenyl)-4-p-nitrobenzoic acid, 5'-nitro-3,3',5-biphenyltricarboxylic acid, 2'-nitro-[1,1'-biphenyl]-3,4',5-tricarboxylic acid or 4-(3,5-diphenylmethanecarboxy)-3-nitrobenzoic acid.

6. The hydrophobic separation membrane according to any one of claims 1 to 5, characterized in that: The pore size of the hydrophobic separation membrane is 1-20 nm, preferably 5-10 nm; Preferably, the membrane thickness of the hydrophobic separation membrane is 200-400 nm, preferably 275-325 nm; Preferably, the membrane surface Zeta potential of the hydrophobic separation membrane is -75 to 0 mV, preferably -40 to -10 mV; Preferably, the membrane surface contact angle of the hydrophobic separation membrane is 90°-170°, preferably 120°-150°.

7. A method for preparing a hydrophobic separation membrane according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: (1) providing a basement membrane; (2) depositing the first reaction monomer solution and the second reaction monomer solution on the surface of the base film in sequence by electrospraying, and then polymerizing; (3) Repeat step (2) at least twice to obtain the hydrophobic separation membrane.

8. The preparation method according to claim 7, characterized in that: The pressure of the electrospray in step (2) is 1-20 bar, preferably 3-10 bar; Preferably, the flow rate of the electrospray in step (2) is 0.1-1.2 L / min, preferably 0.4-0.6 L / min; Preferably, the distance of the electrospray in step (2) is 5-20 cm, preferably 10-15 cm; Preferably, the solvent in the first reaction monomer solution in step (2) comprises any one of benzene, toluene, ethyl acetate, n-hexane, cyclohexane or acetone, or a combination of at least two thereof; Preferably, the solvent in the second reaction monomer solution in step (2) comprises any one of benzene, toluene, ethyl acetate, n-hexane, cyclohexane or acetone, or a combination of at least two thereof; Preferably, the polymerization time in step (2) is 0.5-2h; Preferably, step (3) is repeated twice.

9. Use of the hydrophobic separation membrane according to any one of claims 1 to 6, characterized in that: The hydrophobic separation membrane is used for the distillation of organic solvents in the preparation of anionic aqueous polyurethane dispersions, preferably in the preparation of sulfonate aqueous polyurethane dispersions.

10. The use according to claim 9, characterized in that: The hydrophobic separation membrane is used to remove water and sulfonate ions from the organic solvent; Preferably, the organic solvent comprises acetone.

Images