A system and process for applying an anti-fouling coating to a reverse osmosis membrane during production

Abstract

The application provides an anti-pollution coating system and process in a reverse osmosis membrane production process, comprising a first power roller, a first guide roller, a pressure roller, a second guide roller, a third guide roller, a second power roller, and a spraying device arranged on the side between the first guide roller and the pressure roller, wherein the pressure roller is arranged in a sunken structure relative to the first guide roller and the second guide roller, and the two side roller surfaces of the pressure roller form an acute angle with the common tangent of the roller surfaces of the first guide roller and the second guide roller; the second guide roller and the third guide roller are arranged in an S shape between the pressure roller and the second power roller, and the turning angles are acute angles, and then the second power roller is used for transmission to the downstream. The application utilizes twice rolling and once direction expansion treatment, so that the anti-pollution coating can be kept flat during transmission, and is well combined with the reverse osmosis membrane substrate, and the thickness deviation of the coating is controlled within ±1 μm.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis membrane production technology, and in particular to an antifouling coating system and process for reverse osmosis membrane production. Background Technology

[0002] Reverse osmosis membranes, as the core component of high-efficiency liquid membrane separation technology, are widely used in seawater desalination, wastewater treatment, drinking water purification, and the preparation of electronic-grade ultrapure water. Their performance directly determines separation efficiency, operational stability, and service life. The post-treatment process after applying the antifouling coating is a crucial step in determining the antifouling performance of the reverse osmosis membrane. Antifouling coatings, as water-soluble polymer materials with good hydrophilicity, can form a uniform and dense antifouling layer after being coated onto the surface of the dense polyamide layer of the reverse osmosis membrane and undergoing cross-linking treatment. This effectively blocks the adsorption of pollutants while maximizing the retention of the membrane's water permeability and salt rejection rate. Therefore, they are widely used in the post-treatment process of reverse osmosis membranes.

[0003] Currently, in existing reverse osmosis membrane antifouling coating spraying processes, the sprayed reverse osmosis membrane needs to be rolled by pressure rollers to achieve initial smoothness of the antifouling coating before being transferred to an oven for drying and cross-linking. However, existing process equipment faces many problems: (1) After the antifouling coating is sprayed, the reverse osmosis membrane substrate needs to go through a long distance and high drop path before entering the oven. During the transmission process, the antifouling coating on the membrane surface that is not dry is easily affected by factors such as gravity, ambient airflow, and friction of the transmission roller, resulting in defects such as flow, accumulation, and scratches, which further increases the coating thickness deviation, ultimately leading to a decrease in the antifouling performance of the reverse osmosis membrane, a shortened service life, or even scrapping of the membrane product, increasing production costs. (2) After the antifouling coating is sprayed, the reverse osmosis membrane substrate needs to be rolled by the pressure roller. The reverse osmosis membrane substrate also bears the traction force during the conveying process. Due to the traction force and the bearing angle, the reverse osmosis membrane substrate forms rolling tension when passing through the pressure roller. The pressure roller in the prior art is designed so that the reverse osmosis membrane substrate forms a right angle or obtuse angle when passing through the pressure roller, resulting in a short contact distance between the pressure roller and the reverse osmosis membrane substrate. At the same time, the rolling tension becomes smaller, which easily causes uneven force on the membrane surface, resulting in problems such as local accumulation of antifouling coating, local missed coating, or excessive coating thickness deviation (uneven performance, horizontal lines). (3) After being crushed by the pressure roller, the reverse osmosis membrane only needs to pass through a guide roller. The pressure of the guide roller on the reverse osmosis membrane substrate is still to form a secondary crushing on the surface of the antifouling coating. During this period, the force of the reverse osmosis membrane substrate on the antifouling coating is a squeezing action, which inhibits the solution of the antifouling coating from penetrating into the deep layer of the reverse osmosis membrane substrate.

[0004] A search revealed that existing improvements to antifouling coatings primarily focus on the formulation of the antifouling coating solution (such as adjusting the degree of polymerization and degree of hydrolysis), the selection of crosslinking agents and catalysts, and the optimization of crosslinking process parameters (temperature and time). The core objective is to enhance the adhesion between the antifouling coating and the dense polyamide layer, reducing coating peeling. However, none of these improvements address the synergistic effects of the roller structure layout (diameter and wrap angle) and the post-spraying transport path on the uniformity of antifouling coating application. Consequently, they fail to resolve the membrane performance defects caused by uneven coating, making it difficult to meet the production requirements of high-performance reverse osmosis membranes (with uniform performance and reduced horizontal streaks) and adapting to the efficiency requirements of large-scale industrial production. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide an antifouling coating system and process in the production of reverse osmosis membranes, so as to solve the problem of performance defects of antifouling coatings in reverse osmosis membranes.

[0006] To address the aforementioned technical problems, this invention provides an antifouling coating system for reverse osmosis membrane production. The system comprises, sequentially along the conveying direction of the reverse osmosis membrane, a first power roller, a first guide roller, a pressure roller, a second guide roller, a third guide roller, and a second power roller. A spraying device is also provided on the side between the first guide roller and the pressure roller. The pressure roller has a recessed structure relative to the first and second guide rollers, and the two sides of the pressure roller form an acute angle with the common tangent of the roller surfaces of the first and second guide rollers. The second and third guide rollers are arranged in an S-shape between the pressure roller and the second power roller, with both turning angles being acute. The membrane is then conveyed downstream via the second power roller. The wrap angle α of the reverse osmosis membrane on the pressure roller is ≥110°, and the length of the reverse osmosis membrane in contact with and pressed by the pressure roller exceeds one-quarter of the conveying path length between the pressure roller and the second power roller.

[0007] The spraying device sprays an anti-pollution coating solution with a polymerization degree of 400~2600 and a mass concentration of 0.05%~10%, with a spraying pressure of 0.2~0.5Mpa and a thickness of 10~50μm for the sprayed anti-pollution solution.

[0008] A crosslinking agent precursor is added to the anti-fouling coating solution, wherein the crosslinking agent precursor is glutaraldehyde or boric acid.

[0009] Upstream of the first power roller, there is also a water washing and drying device to ensure that the surface moisture content of the reverse osmosis membrane substrate does not exceed 3%.

[0010] The drying equipment includes a clean air knife purging device and a vacuum adsorption device, which are respectively installed on both sides of the reverse osmosis membrane substrate.

[0011] An oven is located downstream of the second power roller; and the oven is heated in multiple gradients to raise the temperature from room temperature to 100-120°C.

[0012] The temperatures of the four cross-linking gradients in the oven are 50~60℃, 65~75℃, 80~90℃, and 100~120℃ respectively, the total drying and cross-linking time is 1~5min, and the air velocity in the oven is 0.5~2m / s and uniformly distributed.

[0013] As the reverse osmosis membrane passes over the upper surface of the first guide roller and the lower surface of the pressure roller, the overall tilt angle of the reverse osmosis membrane is between 30 and 60 degrees downward from the horizontal surface, which forms a rolling action on the surface of the reverse osmosis membrane coated with antifouling coating.

[0014] The second guide roller is located above the pressure roller, causing the reverse osmosis membrane, after passing the lower surface of the pressure roller, to be transported at an angle upwards towards the pressure roller, causing the surface of the reverse osmosis membrane coated with the antifouling coating to tilt downwards; the surface of the reverse osmosis membrane coated with the antifouling coating passes through the second guide roller at an angle, and is supported by the second guide roller, which creates greater tension on the surface of the reverse osmosis membrane coated with the antifouling coating, thereby causing the surface of the reverse osmosis membrane coated with the antifouling coating to expand in the opposite direction, so that the antifouling solution can penetrate into the deeper layers of the reverse osmosis membrane.

[0015] After passing through the second guide roller, the reverse osmosis membrane is conveyed to the third guide roller in a horizontal or near-horizontal manner, so that the surface of the antifouling coating sprayed on the reverse osmosis membrane is on top of the reverse osmosis membrane. After the reverse expansion action of the second guide roller, the antifouling solution can continue to penetrate deep into the reverse osmosis membrane substrate. After passing through the third guide roller, the reverse osmosis membrane is output again at an acute angle, so that after deep penetration, it is rolled again to lock the antifouling solution and the reverse osmosis membrane substrate at a deep depth.

[0016] A crosslinking agent precursor is added to the anti-fouling coating solution, wherein the crosslinking agent precursor is glutaraldehyde or boric acid.

[0017] The pressure roller is made of stainless steel or polytetrafluoroethylene. The pressure roller wrap angle is the central angle corresponding to the arc length of the contact between the film substrate and the surface of the pressure roller. It is adjusted by adjusting the installation angle of the pressure roller. The diameter of the pressure roller is 25-30cm, which is more than twice the diameter of each guide roller.

[0018] This invention also provides an antifouling coating application process in the production of reverse osmosis membranes, using the aforementioned antifouling coating application system for reverse osmosis membrane production, comprising: S1. Provide a pretreated reverse osmosis membrane, and the surface water content of the reverse osmosis membrane shall not exceed 3%; S2. Spray an antifouling solution onto the first surface of the reverse osmosis membrane, with a spray thickness between 10 and 50 μm. S3. The reverse osmosis membrane is conveyed through the pressure roller, and the pressure roller performs the first rolling on the first surface of the reverse osmosis membrane and the anti-fouling coating thereon. S4. The reverse osmosis membrane is conveyed through the second guide roller, and the second guide roller performs reverse expansion treatment on the first surface of the reverse osmosis membrane, so that the antifouling solution penetrates into the deep layer of the reverse osmosis membrane. S5. The reverse osmosis membrane is conveyed through the third guide roller, and the first surface of the reverse osmosis membrane is rolled a second time by the third guide roller. S6. The reverse osmosis membrane is transported to an oven for drying.

[0019] This invention provides an antifouling coating system and process for reverse osmosis membrane production. Utilizing two rolling processes and one directional expansion treatment, the antifouling coating remains flat during transport and bonds well with the reverse osmosis membrane substrate, controlling the coating thickness deviation within ±1μm. Compared to conventional long-distance transport using only obtuse-angled pressure rollers, this system improves the uniformity of the antifouling coating sprayed onto the reverse osmosis membrane substrate surface by over 60%, reduces energy consumption by over 30%, increases the yield by 12%, enhances the antifouling performance of the reverse osmosis membrane, and significantly extends its service life. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structural layout of an antifouling coating system in the reverse osmosis membrane production process according to an embodiment of the present invention. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] like Figure 1 As shown, this invention provides an antifouling coating system for reverse osmosis membrane production. Along the conveying direction of the reverse osmosis membrane, it sequentially includes a first power roller, a first guide roller, a pressure roller, a second guide roller, a third guide roller, and a second power roller. A spraying device is also provided on the side between the first guide roller and the pressure roller. The pressure roller has a sunken structure relative to the first and second guide rollers, and the two sides of the pressure roller form an acute angle with the common tangent of the roller surfaces of the first and second guide rollers. The second and third guide rollers form an S-shaped arrangement between the pressure roller and the second power roller, with both turning angles being acute angles. The membrane is then conveyed downstream via the second power roller. The wrap angle α of the reverse osmosis membrane on the pressure roller is ≥110°, and the length of the reverse osmosis membrane in contact with and pressed by the pressure roller exceeds one-quarter of the conveying path length between the pressure roller and the second power roller.

[0025] The spraying device sprays an anti-pollution coating solution with a polymerization degree of 400~2600 and a mass concentration of 0.05%~10%, with a spraying pressure of 0.2~0.5Mpa and a thickness of 10~50μm for the sprayed anti-pollution solution.

[0026] A crosslinking agent precursor is added to the anti-fouling coating solution, wherein the crosslinking agent precursor is glutaraldehyde or boric acid.

[0027] Upstream of the first power roller, there is also a water washing and drying device to ensure that the surface moisture content of the reverse osmosis membrane substrate does not exceed 3%.

[0028] The drying equipment includes a clean air knife purging device and a vacuum adsorption device, which are respectively installed on both sides of the reverse osmosis membrane substrate.

[0029] An oven is located downstream of the second power roller; and the oven is heated in multiple gradients to raise the temperature from room temperature to 100-120°C.

[0030] The temperatures of the four cross-linking gradients in the oven are 50~60℃, 65~75℃, 80~90℃, and 100~120℃ respectively, the total drying and cross-linking time is 1~5min, and the air velocity in the oven is 0.5~2m / s and uniformly distributed.

[0031] As the reverse osmosis membrane passes over the upper surface of the first guide roller and the lower surface of the pressure roller, the overall tilt angle of the reverse osmosis membrane is between 30 and 60 degrees downward from the horizontal surface, which forms a rolling action on the surface of the reverse osmosis membrane coated with antifouling coating.

[0032] The second guide roller is located above the pressure roller, causing the reverse osmosis membrane, after passing the lower surface of the pressure roller, to be transported at an angle upwards towards the pressure roller, causing the surface of the reverse osmosis membrane coated with the antifouling coating to tilt downwards; the surface of the reverse osmosis membrane coated with the antifouling coating passes through the second guide roller at an angle, and is supported by the second guide roller, which creates greater tension on the surface of the reverse osmosis membrane coated with the antifouling coating, thereby causing the surface of the reverse osmosis membrane coated with the antifouling coating to expand in the opposite direction, so that the antifouling solution can penetrate into the deeper layers of the reverse osmosis membrane.

[0033] After passing through the second guide roller, the reverse osmosis membrane is conveyed to the third guide roller in a horizontal or near-horizontal manner, so that the surface of the antifouling coating sprayed on the reverse osmosis membrane is on top of the reverse osmosis membrane. After the reverse expansion action of the second guide roller, the antifouling solution can continue to penetrate deep into the reverse osmosis membrane substrate. After passing through the third guide roller, the reverse osmosis membrane is output again at an acute angle, so that after deep penetration, it is rolled again to lock the antifouling solution and the reverse osmosis membrane substrate at a deep depth.

[0034] A crosslinking agent precursor is added to the anti-fouling coating solution, wherein the crosslinking agent precursor is glutaraldehyde or boric acid.

[0035] The pressure roller is made of stainless steel or polytetrafluoroethylene. The pressure roller wrap angle is the central angle corresponding to the arc length of the contact between the film substrate and the surface of the pressure roller. It is adjusted by adjusting the installation angle of the pressure roller. The diameter of the pressure roller is 25-30cm, which is more than twice the diameter of each guide roller.

[0036] This invention also provides an antifouling coating application process in the production of reverse osmosis membranes, using the aforementioned antifouling coating application system for reverse osmosis membrane production, comprising: S1. Provide a pretreated reverse osmosis membrane, and the surface water content of the reverse osmosis membrane shall not exceed 3%; S2. Spray an antifouling solution onto the first surface of the reverse osmosis membrane, with a spray thickness between 10 and 50 μm. S3. The reverse osmosis membrane is conveyed through the pressure roller, and the pressure roller performs the first rolling on the first surface of the reverse osmosis membrane and the anti-fouling coating thereon. S4. The reverse osmosis membrane is conveyed through the second guide roller, and the second guide roller performs reverse expansion treatment on the first surface of the reverse osmosis membrane, so that the antifouling solution penetrates into the deep layer of the reverse osmosis membrane. S5. The reverse osmosis membrane is conveyed through the third guide roller, and the first surface of the reverse osmosis membrane is rolled a second time by the third guide roller. S6. The reverse osmosis membrane is transported to an oven for drying.

[0037] This invention provides an antifouling coating system and process for reverse osmosis membrane production. Utilizing two rolling processes and one directional expansion treatment, the antifouling coating remains flat during transport and bonds well with the reverse osmosis membrane substrate, controlling the coating thickness deviation within ±1μm. Compared to conventional long-distance transport using only obtuse-angled pressure rollers, this system improves the uniformity of the antifouling coating sprayed onto the reverse osmosis membrane substrate surface by over 60%, reduces energy consumption by over 30%, increases the yield by 12%, enhances the antifouling performance of the reverse osmosis membrane, and significantly extends its service life.

[0038] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0039] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A system for applying an antifouling coating during the production of reverse osmosis membranes, characterized in that, The reverse osmosis membrane conveying path sequentially includes a first power roller, a first guide roller, a pressure roller, a second guide roller, a third guide roller, and a second power roller. A spraying device is also provided on the side between the first guide roller and the pressure roller. The pressure roller is arranged in a sunken structure relative to the first and second guide rollers, and the two sides of the pressure roller form an acute angle with the common tangent of the roller surfaces of the first and second guide rollers. The second and third guide rollers are arranged in an S-shape between the pressure roller and the second power roller, and the turning angles are all acute angles. The membrane is then conveyed downstream through the second power roller. The wrap angle α of the reverse osmosis membrane on the pressure roller is ≥110°, and the length of the reverse osmosis membrane in contact with and rolling the pressure roller exceeds one-quarter of the conveying path length between the pressure roller and the second power roller.

2. The antifouling coating system for reverse osmosis membrane production according to claim 1, characterized in that, The spraying device sprays an anti-pollution coating solution with a polymerization degree of 400~2600 and a mass concentration of 0.05%~10%, with a spraying pressure of 0.2~0.5Mpa and a thickness of 10~50μm for the sprayed anti-pollution solution.

3. The antifouling coating application system for reverse osmosis membrane production according to claim 1, characterized in that, A crosslinking agent precursor is added to the anti-fouling coating solution, wherein the crosslinking agent precursor is glutaraldehyde or boric acid.

4. The antifouling coating application system for reverse osmosis membrane production according to claim 1, characterized in that, Upstream of the first power roller, there is also a water washing and drying device to ensure that the surface moisture content of the reverse osmosis membrane substrate does not exceed 3%.

5. The antifouling coating application system for reverse osmosis membrane production according to claim 1, characterized in that, The drying equipment includes a clean air knife purging device and a vacuum adsorption device, which are respectively installed on both sides of the reverse osmosis membrane substrate.

6. The antifouling coating application system for reverse osmosis membrane production according to claim 1, characterized in that, An oven is located downstream of the second power roller; and the oven is heated in multiple gradients to raise the temperature from room temperature to 100-120°C. The temperatures of the four cross-linking gradients in the oven are 50~60℃, 65~75℃, 80~90℃, and 100~120℃ respectively, the total drying and cross-linking time is 1~5min, and the air velocity in the oven is 0.5~2m / s and uniformly distributed.

7. The antifouling coating application system for reverse osmosis membrane production according to claim 1, characterized in that, As the reverse osmosis membrane passes over the upper surface of the first guide roller and the lower surface of the pressure roller, the overall tilt angle of the reverse osmosis membrane is between 30 and 60 degrees downward from the horizontal surface, which forms a rolling action on the surface of the reverse osmosis membrane coated with antifouling coating.

8. The antifouling coating application system for reverse osmosis membrane production according to claim 1, characterized in that, The second guide roller is located above the pressure roller, which causes the reverse osmosis membrane after passing the lower surface of the pressure roller to be tilted upwards and conveyed upwards, so that the surface of the reverse osmosis membrane coated with the antifouling coating is tilted downwards. The surface of the antifouling coating on the reverse osmosis membrane passes through the second guide roller at an opposite angle. Supported by the second guide roller, the surface of the antifouling coating on the reverse osmosis membrane forms greater tension, thereby causing the surface of the antifouling coating on the reverse osmosis membrane to expand in the opposite direction, so that the antifouling solution can penetrate into the deep layers of the reverse osmosis membrane.

9. The antifouling coating system for reverse osmosis membrane production according to claim 1, characterized in that, After passing through the second guide roller, the reverse osmosis membrane is conveyed to the third guide roller in a horizontal or near-horizontal manner, so that the surface of the antifouling coating sprayed on the reverse osmosis membrane is on top of the reverse osmosis membrane. After the reverse expansion action of the second guide roller, the antifouling solution can continue to penetrate deep into the reverse osmosis membrane substrate. After passing through the third guide roller, the reverse osmosis membrane is output again at an acute angle, so that after deep penetration, it is rolled again to lock the antifouling solution and the reverse osmosis membrane substrate at a deep depth.

10. A process for applying an antifouling coating during the production of a reverse osmosis membrane, using the antifouling coating system for the production of a reverse osmosis membrane as described in any one of claims 1-9, characterized in that, include: S1. Provide a pretreated reverse osmosis membrane, and the surface water content of the reverse osmosis membrane shall not exceed 3%; S2. Spray an antifouling solution onto the first surface of the reverse osmosis membrane, with a coating thickness between 10 and 50 μm. S3. The reverse osmosis membrane is conveyed through the pressure roller, and the pressure roller performs the first rolling on the first surface of the reverse osmosis membrane and the anti-fouling coating thereon. S4. The reverse osmosis membrane is conveyed through the second guide roller, and the second guide roller performs reverse expansion treatment on the first surface of the reverse osmosis membrane, so that the antifouling solution penetrates into the deep layer of the reverse osmosis membrane. S5. The reverse osmosis membrane is conveyed through the third guide roller, and the first surface of the reverse osmosis membrane is rolled a second time by the third guide roller. S6. The reverse osmosis membrane is transported to an oven for drying.

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