Method for preparing tubular ultrafiltration membrane by integrated roll coating process

Abstract

The invention discloses a method for preparing a tubular ultrafiltration membrane by an integrated roll coating process, which specifically comprises the following steps: S1, base material selection: selecting a non-woven fabric material with high porosity and good mechanical property as a base material, carrying out surface cleaning and activating treatment, and cutting into a non-woven fabric belt for later use; s2, preparing a membrane casting solution, namely uniformly mixing a high polymer material, an additive and a solvent, dissolving, filtering and defoaming to obtain the membrane casting solution; s3, non-woven fabric rolling is conducted, specifically, on an automatic pipe rolling machine device, the two non-woven fabric belts are wound and rotated forwards around the metal center pipe according to a certain angle, and a non-woven fabric supporting pipe is formed; s4, synchronous coating: pressing the membrane casting liquid into the metal central tube while rolling the non-woven fabric supporting tube, so that the membrane casting liquid is uniformly coated on the inner wall of the non-woven fabric supporting tube to prepare a tubular ultrafiltration membrane liquid membrane; and S5, post-treatment: solidifying the tubular ultrafiltration membrane liquid membrane in deionized water to obtain the tubular ultrafiltration membrane liquid membrane. According to the invention, an automatic tube coiling machine device and a synchronous coating technology are adopted, the membrane casting liquid is uniformly coated on the inner wall of the non-woven fabric supporting tube while the non-woven fabric supporting tube is coiled, and continuous preparation of the tubular ultrafiltration membrane is realized. And the stability of the non-woven fabric supporting pipe is enhanced by adopting dual bonding reinforcement of the hot melt adhesive and the ultrasonic generator.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment separation membranes, and in particular to a method for preparing a tubular ultrafiltration membrane by an integrated coil coating process. Background Art

[0002] Tubular ultrafiltration membrane, as an innovative membrane separation technology, achieves efficient separation of gas or liquid mixtures through membrane tube filtration. It has been widely used in many water treatment fields due to its high flux, ease of operation, cost-effectiveness and excellent environmental protection characteristics.

[0003] The production of tubular ultrafiltration membranes usually involves two core steps: winding and coating. The winding step involves winding the membrane material on a specific support tube to form a preliminary membrane structure. The subsequent coating step is to apply one or more layers of specific materials on the rolled membrane to improve the performance of the membrane, such as enhancing selectivity, flux or durability.

[0004] However, this traditional roll-to-coat process has limitations, such as the bonding between film layers may not be strong enough, which may lead to unstable film performance or shortened service life. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a tubular ultrafiltration membrane by an integrated coil coating process, so as to solve the problems of uneven coating and easy separation in the traditional tubular ultrafiltration preparation process.

[0006] A method for preparing a tubular ultrafiltration membrane by an integrated coil coating process of the present invention comprises the following steps: S1 Substrate selection: Select non-woven fabrics with high porosity and good mechanical properties as the substrate, clean and activate the surface, and cut them into non-woven fabric tapes for use; S2 Preparation of casting solution: Mix the polymer material, additives and solvent evenly, dissolve and filter , degassing to obtain the casting solution; S3 non-woven fabric rolling: On an automatic tube rolling machine, the two non-woven fabric strips are wound around the metal center tube at a certain angle and rotated forward to form a non-woven fabric support tube; S4 synchronous coating: while the non-woven fabric support tube is being rolled, the casting liquid is pressed into the metal central tube so as to be evenly coated on the inner wall of the non-woven fabric support tube to obtain a tubular ultrafiltration membrane liquid membrane; S5 post-treatment: the tubular ultrafiltration membrane liquid membrane is coagulated in deionized water to obtain a membrane.

[0007] According to the present invention, the non-woven fabric material in step S1 is polyester, polyethylene, polypropylene or polyamide.

[0008] According to the present invention, the surface cleaning method in step S1 is one or a combination of solvent cleaning, ultrasonic cleaning and plasma cleaning.

[0009] Furthermore, the solvent cleaning is to use acetone, ethanol or deionized water for multiple cleanings to ensure the cleanliness of the surface of the non-woven fabric.

[0010] Furthermore, the ultrasonic cleaning uses an ultrasonic generator with a specific frequency to improve cleaning efficiency and depth.

[0011] Furthermore, the frequency is 20-40 kHz.

[0012] Furthermore, the plasma cleaning achieves the purpose of cleaning and activation by generating a plasma environment and using its high-energy particles to bombard the surface of the non-woven fabric.

[0013] Furthermore, the plasma cleaning conditions are: power 100-300W, treatment time 1-5min, to ensure the activation effect of the non-woven fabric surface.

[0014] According to the present invention, the activation treatment method in step S1 is a method such as chemical activation, plasma activation or physical activation, so as to increase the active functional groups on the surface of the non-woven fabric material and improve its bonding strength with subsequent coatings or adhesives.

[0015] Furthermore, the chemical activation is to treat the non-woven material with a specific chemical reagent, such as sulfuric acid, nitric acid or alkaline solution, to introduce new functional groups or change the chemical properties of the non-woven material. Chemical activation can increase the hydrophilicity or lipophilicity of the non-woven material and change the surface roughness to increase the specific surface area of ​​the material, further enhancing the adhesion of the coating or adhesive.

[0016] Furthermore, the plasma activation is to use specific gases such as oxygen, nitrogen or argon to generate plasma under low pressure conditions, and the active substances in the plasma react with the non-woven fabric material to form new functional groups on the material surface or change the surface chemical structure. Plasma activation can significantly improve the surface activity of the non-woven fabric, enhance its bonding with the coating material, and improve the hydrophilicity or lipophilicity of the non-woven fabric, providing a better foundation for subsequent coating processes.

[0017] Furthermore, the pressure is 10-100 Pa, and the time is 1-10 min.

[0018] Furthermore, the physical activation is to change the morphology and structure of the non-woven fabric material by physical force using methods such as mechanical grinding, high-pressure spraying or laser treatment, thereby increasing the surface roughness and specific surface area. The physical activation method can effectively improve the surface activity of the non-woven fabric and provide a better adhesion basis for the subsequent coating process.

[0019] According to the present invention, the width of the non-woven fabric tape in step S1 is 10 to 40 mm.

[0020] According to the present invention, the polymer material in step S2 can be a polymer material suitable for preparing ultrafiltration membranes, such as polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, polysulfone or cellulose acetate. These materials are selected based on their chemical stability, heat resistance and mechanical strength to ensure the reliability and durability of the final membrane product in various application environments.

[0021] According to the present invention, the additive in step S2 is a porogen, a surfactant or an inorganic particle. The porogen is polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, methanol or ethanol. The surfactant is one of Tween 80, Tween 20, Tween 40, Tween 60, Tween 85, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene, polyoxyethylene fatty alcohol ether ammonium sulfate and polyoxyethylene fatty alcohol ether carboxylate. The inorganic particle is silicon dioxide, aluminum oxide, zirconium oxide or titanium dioxide. The porogen is used to adjust the pore structure of the membrane, the surfactant can optimize the surface properties of the membrane, and the inorganic particles can increase the mechanical strength of the membrane or change the air permeability of the membrane.

[0022] According to the present invention, the solvent in step S2 is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0023] According to the present invention, the mass ratio of the polymer material, the additive and the solvent in step S2 is (10-30): (1-10): (60-90).

[0024] According to the present invention, the two non-woven fabric strips in step S3 are placed as inner and outer layers.

[0025] Furthermore, the outer layer of non-woven fabric is coated with hot melt adhesive slurry dots, and the two layers of non-woven fabric are bonded together by heating, and an ultrasonic generator is used to bond and reinforce the cross-over and overlapped parts.

[0026] Furthermore, the amount of the hot melt slurry is 10 to 50 g / m 2 To ensure that sufficient adhesion can be formed during the heating process, while avoiding excessive glue points affecting the air permeability and filtration performance of the membrane.

[0027] Furthermore, the hot melt adhesive points are distributed in a staggered manner to improve the uniformity of the bonding area and the stability of the overall structure.

[0028] Furthermore, the heating temperature is 120-180° C. to ensure that the hot melt slurry points can be fully melted and form a stable bond.

[0029] Furthermore, the ultrasonic generator generates high-frequency vibrations, causing the non-woven fabric tape to generate minute vibrations during the winding process, thereby enhancing the bonding effect between the non-woven fabric tapes.

[0030] Furthermore, the frequency range of the ultrasonic generator is 20-40KHz, and the power is 50-200W.

[0031] According to the present invention, the angle in step S3 is 30-60°.

[0032] According to the present invention, the forward winding speed of the non-woven fabric tape in step S3 is 3 to 8 m / min.

[0033] According to the present invention, the injection speed of the casting solution in step S4 is 5 to 20 ml / min.

[0034] According to the present invention, the injection pressure of the casting solution in step S4 is 0.1-0.5 MPa.

[0035] According to the present invention, the solidification conditions in step S5 are a temperature of 10 to 30° C. and a time of 1 to 10 min.

[0036] Compared with the prior art, the present invention has the following advantages: 1) The present invention selects a non-woven fabric material with high porosity and good mechanical properties as the substrate, and performs surface cleaning and activation treatment, which effectively improves the cleanliness and activity of the non-woven fabric surface, provides a better foundation for the subsequent coating process, and thus solves the problem of uneven coating in the traditional process.

[0037] 2) The present invention combines the tube winding and film coating processes to form an integrated coil coating process, which simplifies the production process and improves production efficiency; by synchronously and precisely controlling the winding and coating speeds, the uniformity and density of the film layer are enhanced, thereby improving the performance of the film.

[0038] 3) The present invention adopts an automatic tube winding device and synchronous coating technology to evenly coat the casting liquid on the inner wall of the non-woven support tube while rolling the non-woven support tube, thereby realizing the continuous preparation of tubular ultrafiltration membranes; this process not only improves production efficiency, but also ensures the uniformity and consistency of the membrane layer, avoiding the coating separation problem that is prone to occur in traditional processes.

[0039] 4) The double bonding reinforcement of hot melt adhesive and ultrasonic generator is used to enhance the stability of the non-woven support tube. The hot melt adhesive plays the role of the first layer of bonding and serves as the first layer of support, while the ultrasonic generator plays the role of the second layer of reinforcement, making the bonding between the non-woven fabrics tighter and having stronger support. DETAILED DESCRIPTION Example 1

[0040] 1) Substrate selection: Select polyester non-woven fabric as the substrate, use a combination of deionized water cleaning and 20kHz ultrasonic cleaning to clean the surface, then perform physical activation treatment by mechanical grinding, and cut it into non-woven fabric tapes with a width of 10 mm for standby use; 2) Preparation of casting solution: 30g PES, 10g methanol and 60g N,N-dimethylformamide were mixed, dissolved, filtered and degassed to obtain casting solution; 3) Non-woven fabric rolling: On the automatic tube rolling machine, place the two non-woven fabric tapes as inner and outer layers, and coat the outer non-woven fabric tape with 10g / m2 in a staggered manner. 2 The hot melt adhesive point is wound around the metal center tube at an angle of 30° and a forward speed of 3m / min to form a non-woven fabric support tube. While winding and rotating, the two layers of non-woven fabric tapes are heated to 120°C to bond them together. At the same time, an ultrasonic generator with a frequency of 20KHz and a power of 50W is used to bond and reinforce the cross-heavy stacking parts. 4) Synchronous coating: while the tube is being rolled, the casting liquid is pressed into the metal central tube at a speed of 5 ml / min and a pressure of 0.1 MPa, so that the casting liquid is evenly coated on the inner wall of the non-woven fabric support tube to obtain a tubular ultrafiltration membrane liquid membrane; 5) Post-treatment: solidifying the tubular ultrafiltration membrane liquid film in water at a temperature of 10° C. for 10 minutes to form a tubular ultrafiltration membrane. Example 2

[0041] 1) Substrate selection: Select polyamide non-woven fabric as the substrate, use plasma cleaning with a power of 100W and a treatment time of 5 minutes to clean the surface, then perform plasma activation treatment with a pressure of 10Pa and a time of 10 minutes, and cut it into non-woven fabric tapes with a width of 40mm for standby use; 2) Preparation of casting solution: 10g polyvinyl chloride, 1g polyethylene oxide and 89g N,N-dimethylacetamide were mixed, dissolved, filtered and degassed to obtain casting solution; 3) Non-woven fabric rolling: On the automatic tube rolling machine, place the two non-woven fabric tapes as inner and outer layers, and coat the outer non-woven fabric tape with 50g / m2 in a staggered manner. 2The hot melt adhesive point is wound around the metal center tube at an angle of 60° and a forward speed of 8m / min to form a non-woven fabric support tube. While winding and rotating, the two layers of non-woven fabric tapes are heated to 180°C to bond them together. At the same time, an ultrasonic generator with a frequency of 40KHz and a power of 200W is used to bond and reinforce the cross-heavy stacking parts. 4) Synchronous coating: while the tube is being rolled, the casting liquid is pressed into the metal central tube at a speed of 20 ml / min and a pressure of 0.5 MPa, so that the casting liquid is evenly coated on the inner wall of the non-woven fabric support tube to obtain a tubular ultrafiltration membrane liquid membrane; 5) Post-treatment: solidifying the tubular ultrafiltration membrane liquid film in water at a temperature of 30° C. for 1 minute to form a tubular ultrafiltration membrane. Example 3

[0042] 1) Substrate selection: Select polypropylene non-woven fabric as the substrate, use an ultrasonic generator with a frequency of 40kHz to clean the surface, then use sulfuric acid solution for chemical activation, and cut it into non-woven fabric tapes with a width of 40mm for standby use; 2) Preparation of casting solution: 20g polyvinylidene fluoride, 5g polyvinyl pyrrolidone and 75g N-methyl pyrrolidone were mixed, dissolved, filtered and degassed to obtain casting solution; 3) Non-woven fabric rolling: On the automatic tube rolling machine, place the two non-woven fabric tapes as inner and outer layers, and coat the outer non-woven fabric tape with 30g / m2 in a staggered manner. 2 The hot melt adhesive point is wound around the metal center tube at a forward speed of 6m / min at an angle of 45° to form a non-woven fabric support tube. While winding and rotating, the two layers of non-woven fabric tapes are heated at 150°C to bond them together. At the same time, an ultrasonic generator with a frequency of 30KHz and a power of 125W is used to bond and reinforce the cross-heavy stacking parts. 4) Synchronous coating: while the tube is being rolled, the casting liquid is pressed into the metal central tube at a speed of 12 ml / min and a pressure of 0.3 MPa, so that the casting liquid is evenly coated on the inner wall of the non-woven fabric support tube to obtain a tubular ultrafiltration membrane liquid membrane; 5) Post-treatment: solidifying the tubular ultrafiltration membrane liquid film in water at a temperature of 20° C. for 5 minutes to form a tubular ultrafiltration membrane.

Claims

1. A method for preparing a tubular ultrafiltration membrane by an integrated coil coating process, characterized in that: The following steps are involved: S1 Substrate selection: Select non-woven fabrics with high porosity and good mechanical properties as the substrate, clean and activate the surface, and cut them into non-woven fabric tapes for use; S2 Preparation of casting solution: mixing polymer materials, additives and solvents uniformly, dissolving, filtering and degassing to obtain casting solution; S3 non-woven fabric rolling: On an automatic tube rolling machine, the two non-woven fabric strips are wound around the metal center tube at a certain angle and rotated forward to form a non-woven fabric support tube; S4 synchronous coating: while the non-woven fabric support tube is being rolled, the casting liquid is pressed into the metal central tube so as to be evenly coated on the inner wall of the non-woven fabric support tube to obtain a tubular ultrafiltration membrane liquid membrane; S5 post-treatment: the tubular ultrafiltration membrane liquid membrane is coagulated in deionized water to obtain a membrane.

2. The method according to claim 1, characterized in that The non-woven fabric material in step S1 is polyester, polyethylene, polypropylene or polyamide; the width of the non-woven fabric tape in step S1 is 10 to 40 mm; the surface cleaning method in step S1 is one or a combination of solvent cleaning, ultrasonic cleaning and plasma cleaning; the activation treatment method in step S1 is chemical activation, plasma activation or physical activation.

3. The method according to claim 2, characterized in that The solvent cleaning is to use acetone, ethanol or deionized water for multiple cleanings to ensure the cleanliness of the non-woven fabric surface; the ultrasonic cleaning uses an ultrasonic generator with a specific frequency to improve the cleaning efficiency and depth; the plasma cleaning creates a plasma environment and uses its high-energy particles to bombard the non-woven fabric surface, thereby achieving the purpose of cleaning and activation; the chemical activation uses specific chemical reagents such as sulfuric acid, nitric acid or alkaline solution to treat the non-woven fabric material; the plasma activation uses specific gases such as oxygen, nitrogen or argon to generate plasma under low pressure conditions, and the active substances in the plasma react with the non-woven fabric material to form new functional groups on the material surface or change the surface chemical structure; the physical activation uses mechanical grinding, high-pressure spraying or laser treatment.

4. The method according to claim 3, characterized in that The frequency is 20-40 kHz; the conditions for plasma cleaning are: power 100-300 W, processing time 1-5 min; the conditions for plasma activation are: pressure 10-100 Pa, time 1-10 min.

5. The method according to claim 1, characterized in that The polymer material in step S2 is polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, polysulfone or cellulose acetate; the additive in step S2 is a porogen, a surfactant or an inorganic particle; the solvent in step S2 is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide; the mass ratio of the polymer material, the additive and the solvent in step S2 is (10-30): (1-10): (60-90); Furthermore, the porogen is polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, methanol or ethanol; the surfactant is one of Tween 80, Tween 20, Tween 40, Tween 60, Tween 85, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene, polyoxyethylene fatty alcohol ether ammonium sulfate and polyoxyethylene fatty alcohol ether carboxylate; the inorganic particles are silicon dioxide, aluminum oxide, zirconium oxide or titanium dioxide.

6. The method according to claim 1, characterized in that The two non-woven fabric strips in step S3 are placed as inner and outer layers; Furthermore, the outer layer of non-woven fabric is coated with hot melt adhesive slurry dots, and the two layers of non-woven fabric are bonded together by heating, and an ultrasonic generator is used to bond and reinforce the cross-over and overlapped parts.

7. The method according to claim 6, characterized in that The amount of the hot melt slurry point is 10 to 50 g / m 2 The distribution of the hot melt slurry points is staggered; the heating temperature is 120-180°C; the ultrasonic generator generates high-frequency vibrations, causing the non-woven tape to generate tiny vibrations during the winding process, thereby enhancing the bonding effect between the non-woven tapes.

8. The method according to claim 7, characterized in that The frequency range of the ultrasonic generator is 20-40KHz, and the power is 50-200W.

9. The method according to claim 1, characterized in that: The angle described in step S3 is 30 to 60°; the forward winding speed of the non-woven fabric tape described in step S3 is 3 to 8 m / min; the injection speed of the casting liquid described in step S4 is 5 to 20 ml / min; the injection pressure of the casting liquid described in step S4 is 0.1 to 0.5 MPa; the solidification conditions described in step S5 are temperature 10 to 30°C and time 1 to 10 min.

10. A tubular ultrafiltration membrane prepared by the method according to any one of claims 1 to 9.