Synthesis process of nano environment-friendly functional membrane material

Abstract

The invention belongs to the technical field of functional membrane materials, and particularly relates to a synthesis process of a nano environment-friendly functional membrane material. By adopting a composite emulsifier system with a specific ratio, the particle size and distribution in the emulsion polymerization process are effectively controlled by the generated synergistic stabilization effect, the polymer emulsion with uniform particle size and high stability is obtained, and nano silicon dioxide is uniformly dispersed in a polymer matrix after being subjected to dual modification by dopamine and a silane coupling agent, so that the nano silicon dioxide can be dispersed in the polymer matrix. The mechanical property and the thermal stability of the material are effectively enhanced. Through low-temperature initiation and staged heating crosslinking, a polymer network is formed more uniformly and compactly, so that the water resistance and barrier property of the material are remarkably improved. According to the invention, recovery of organic matters in wastewater and cyclic utilization of water are realized through a ceramic membrane separation and reverse osmosis combined process. According to the overall scheme, the comprehensive performance of the membrane material is improved, meanwhile, process feasibility and environment friendliness are considered, and the method is suitable for large-scale production of the high-performance environment-friendly membrane material.

Description

Technical Field

[0001] This invention belongs to the field of functional membrane materials technology, specifically relating to a synthesis process for a nano-environmentally friendly functional membrane material. Background Technology

[0002] Nanoscale environmentally friendly functional membrane materials are a class of polymer composite materials that combine nanoscale effects with environmental protection characteristics. With their excellent mechanical properties, barrier properties, flame retardancy and low VOC emissions, they have been widely used in key fields such as waterproof and breathable coatings, flame-retardant engineering plastics, and lithium battery separator substrates, becoming core supporting materials for the upgrading and development of industries such as new energy, high-end manufacturing and environmentally friendly building materials.

[0003] At present, the mainstream synthesis process of nano-environmentally friendly functional membrane materials is emulsion polymerization. However, there are still many technical bottlenecks in the existing technology that need to be solved, which restrict the upgrading of product performance and large-scale application: (1) Insufficient compatibility of emulsifier system: The existing process mostly uses a single anionic emulsifier or a simple compound system, which can only achieve monomer dispersion through single electrostatic repulsion and lacks the ability to synergistically stabilize nanoparticles and monomer droplets. This leads to the easy occurrence of particle agglomeration during polymerization, wide particle size distribution of membrane material, insufficient film density, and ultimately low tensile strength and high water absorption, which makes it difficult to meet the requirements of high-end application scenarios for material stability. (2) Problems of nanofiller dispersion and interface bonding: Due to their high surface energy and strong hydrophilicity, inorganic fillers such as nano silica are prone to agglomeration in polymer matrix. The existing technology mostly uses a single silane coupling agent for modification, which can only improve surface compatibility and cannot solve the problem of synergistic dispersion stability and interface bonding. Unmodified or single-modified nanofillers are difficult to form an effective reinforcing network, resulting in limited improvement in the elongation at break and thermal stability of membrane materials, which limits the application of materials in high-requirement scenarios. (3) Insufficient precision in polymerization process control: Traditional emulsion polymerization often adopts a single temperature reaction mode, and the temperature requirements of the initiation stage and the polymerization stage cannot be taken into account at the same time, which easily leads to an imbalance in the free radical generation rate: low temperature initiation leads to insufficient monomer conversion rate, and high temperature polymerization leads to local overheating, both of which will cause the polymer molecular weight distribution to be too wide and the crosslinking to be uneven. This directly leads to high moisture permeability and poor pollution resistance of membrane materials. (4) Shortcomings in environmental protection and sustainability: The existing process has low efficiency in recovering unreacted monomers and lacks targeted means to eliminate residual monomers, resulting in excessive VOC emissions; at the same time, polymerization wastewater is mostly treated and discharged directly, without realizing the recovery of organic matter and the recycling of water resources, which not only increases the cost of environmental treatment, but also causes resource waste, which is contrary to the development concept of green chemical industry.

[0004] Based on this, we propose a synthesis process for nano-environmentally friendly functional membrane materials, hoping to address the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to address existing problems by providing a synthesis process for nano-environmentally friendly functional membrane materials.

[0006] This invention is achieved through the following technical solution:

[0007] A synthesis process for a nano-environmentally friendly functional membrane material includes the following steps:

[0008] S1. Raw material preparation:

[0009] Weigh the following raw materials according to the following weight proportions: 65-75 parts of acrylate monomers, 10-18 parts of carboxyl-containing monomers, 2-5 parts of acrylamide, 5-15 parts of vinyl chloride monomers, 1.5-3.5 parts of composite emulsifier, 40-100 parts of modified nano-silica dispersion, 120-180 parts of deionized water, 0.03-0.08 parts of chain transfer agent, 0.1-0.3 parts of potassium persulfate or ammonium persulfate, 0.05-0.1 parts of sodium bisulfite, and 0.2-0.6 parts of crosslinking agent;

[0010] S2. Preparation of pre-emulsion:

[0011] Take all the acrylate monomers, carboxyl-containing monomers, acrylamide, modified nano-silica dispersion, 1-2.5 parts of composite emulsifier, and 60-100 parts of deionized water, potassium persulfate or ammonium persulfate, weigh them out and mix them at high speed to obtain a stable pre-emulsion.

[0012] S3, Segmented Temperature-Controlled Polymerization and Crosslinking:

[0013] S301. Add the remaining deionized water to the polymerization reactor, pass N2 to deoxygenate for 20-30 minutes, then add the remaining composite emulsifier, chain transfer agent, sodium bisulfite and 0.25-2.25 parts of vinyl chloride monomer, and heat to 42-48℃ to initiate the polymerization.

[0014] S302. Add all the pre-emulsion obtained in step S2 and the remaining vinyl chloride monomer to the reaction system, and carry out the copolymerization reaction at 42~48℃.

[0015] S303, heat to 55~60℃, and continue polymerization for 3~5 hours under a pressure of 0.7~0.75MPa;

[0016] S304, cool to 40~45℃, add all the crosslinking agent and carry out in-situ crosslinking reaction for 1~2 hours, and terminate the reaction when the pressure in the reactor drops to 0.3~0.5MPa;

[0017] S4. Post-processing:

[0018] Unreacted monomers are recovered, modified, and the pH is adjusted to 6-9. Industrial wastewater is then purified by membrane separation and reused.

[0019] Further, the acrylate monomer is preferably one or a mixture of n-butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate, more preferably a mixture of n-butyl acrylate and methyl methacrylate, with a mass ratio of (7:3) to (8:2).

[0020] Furthermore, the carboxyl-containing monomer is a mixture of acrylic acid and methacrylic acid, with a mass ratio of (2~3):1;

[0021] The acrylamide monomer is acrylamide or N-(hydroxymethyl)acrylamide.

[0022] Further, the preparation method of the composite emulsifier is as follows: sodium allyl hydroxypropyl sulfonate, sodium dodecylbenzene sulfonate and potassium laurate are mixed in a mass ratio of (1~3):(2~4):(4~6), and then 2~3 times the total mass of the solids is added to deionized water. The mixture is stirred at 38~42℃ for 4~5 hours to obtain the composite emulsifier.

[0023] Furthermore, the preparation of the modified nano-silica dispersion includes the following steps:

[0024] (1) Take nano-silica powder with an original particle size of 30~50nm, add 5~8 times its mass of deionized water, stir and disperse to form a suspension;

[0025] (2) Add 3-5% by weight of nano-silica powder dopamine hydrochloride to the suspension, adjust the pH of the system to 8.0-8.5, and stir the reaction at 25-30℃ for 4-6 hours;

[0026] (3) Add 3-8% by weight of nano silica powder and silane coupling agent KH-570 to the system, heat to 50-70℃ and react for 3-6 hours to obtain modified nano silica slurry;

[0027] (4) Add 4-6% of the initial mass of nano silica powder and polyvinyl alcohol 0588 as a dispersant to the slurry, and ultrasonically disperse it for 30-60 min at a power of 300-500W to obtain a modified nano silica dispersion.

[0028] Furthermore, the chain transfer agent is mercaptoethanol, tert-dodecyl mercaptan, or n-dodecyl mercaptan;

[0029] The crosslinking agent is vinyltrimethoxysilane (A-171).

[0030] Furthermore, in step S2, the mixing temperature is controlled at 35~45℃, the stirring speed is 500~800rpm, and the stirring time is 60~90min.

[0031] Furthermore, in step S302, the pre-emulsion and the remaining vinyl chloride monomer are added sequentially, with the pre-emulsion added first for 1-2 hours, and then the remaining vinyl chloride monomer added within 0.5-1 hour.

[0032] After the pre-emulsion is added, keep the reaction at a constant temperature for 0.5 to 1 hour, and then proceed with the heating operation in step S303.

[0033] Further, the modification in step S4 is as follows: add 0.5-2 parts by weight of surface-modifying monomer, and then, under stirring, first add 0.03-0.08 parts by weight of aqueous solution of tert-butyl hydrogen peroxide, and after an interval of 5-15 minutes, add an aqueous solution of vitamin C with an equimolar amount of the tert-butyl hydrogen peroxide, stir for 30-40 minutes, then add 0.02-0.05 parts by weight of soybean oil-based mineral oil defoamer, and then adjust the pH.

[0034] The surface-modifying monomer is a mixture of styrene and dodecafluoroheptyl methacrylate in a mass ratio of 1:(0.5~2);

[0035] The method for preparing the aqueous solutions of tert-butyl hydrogen peroxide and vitamin C is as follows: prepare aqueous solutions of tert-butyl hydrogen peroxide with a concentration of 5-10 wt% and aqueous solutions of vitamin C with a concentration of 3-5 wt%, respectively.

[0036] The pH adjuster is a 5 wt% ammonia solution or a 10 wt% sodium hydroxide aqueous solution;

[0037] The membrane separation and purification process specifically involves treating process wastewater using a ceramic membrane separation device with a molecular weight cutoff of 5000~10000 Da, reusing the separated organic matter in the polymerization reaction, and reusing the permeate after reverse osmosis purification.

[0038] The present invention has the following advantages over the prior art:

[0039] 1. This invention significantly improves the mechanical properties and structural stability of membrane materials by optimizing the composite emulsifier system and the nanoparticle surface modification process. By employing a composite emulsifier system with a specific ratio, the synergistic stabilizing effect effectively controls the particle size and distribution during emulsion polymerization, resulting in a polymer emulsion with uniform particle size and high stability. This lays the foundation for forming a dense, defect-free continuous membrane, thereby improving the tensile strength of the membrane material. Furthermore, the nano-silica, after dual modification with dopamine and silane coupling agents, is uniformly dispersed in the polymer matrix, effectively enhancing the material's elongation at break and thermal stability.

[0040] 2. The segmented temperature-controlled polymerization process of this invention achieves precise control of the reaction process, avoiding the problem of excessively wide molecular weight distribution caused by polymerization at a single temperature. Through low-temperature initiation and staged temperature-increasing crosslinking, the polymer network is formed more uniformly and densely, thereby significantly improving the water resistance and barrier properties of the material, with the water absorption rate controlled below 3%.

[0041] 3. This invention achieves the recovery of organic matter and water recycling in wastewater through a combination of ceramic membrane separation and reverse osmosis, significantly reducing VOC emissions and fresh water consumption. The overall solution improves the comprehensive performance of membrane materials while considering process feasibility and environmental friendliness, making it suitable for the large-scale production of high-performance, environmentally friendly membrane materials. Attached Figure Description

[0042] Figure 1 These are TEM (transmission electron microscopy) images;

[0043] Figure 2 Photos of the wet film and photos of the film formed in a 50°C oven for 30 minutes. Detailed Implementation

[0044] To further explain the present invention, the following specific embodiments are described.

[0045] Example 1

[0046] A synthesis process for a nano-environmentally friendly functional membrane material includes the following steps:

[0047] S1. Raw material preparation:

[0048] Weigh the following raw materials according to the following weight proportions: 65 parts n-butyl acrylate, 10 parts carboxyl-containing monomer, 2 parts acrylamide, 5 parts vinyl chloride monomer, 1.5 parts composite emulsifier, 40 parts modified nano silica dispersion, 120 parts deionized water, 0.03 parts chain transfer agent tert-dodecyl mercaptan, 0.1 parts potassium persulfate, 0.05 parts sodium bisulfite, and 0.2 parts crosslinking agent vinyltrimethoxysilane (A-171).

[0049] The carboxyl-containing monomer is a mixture of acrylic acid and methacrylic acid in a mass ratio of 2:1.

[0050] The preparation method of the composite emulsifier is as follows: sodium allyl hydroxypropyl sulfonate, sodium dodecylbenzene sulfonate and potassium laurate are mixed in a mass ratio of 1:2:4, and then deionized water with a mass of 2 times the total mass of the solid is added. The mixture is stirred at 38°C for 4 hours to obtain the composite emulsifier.

[0051] The preparation of the modified nano-silica dispersion includes the following steps:

[0052] (1) Take nano-silica powder with an original particle size of 30~50nm, add 5 times its mass of deionized water, stir and disperse to form a suspension;

[0053] (2) Add 3% by weight of nano-silica powder dopamine hydrochloride to the suspension, adjust the pH of the system to 8.0, and stir the reaction at 25°C for 4 hours;

[0054] (3) Add 3% by weight of nano silica powder and silane coupling agent KH-570 to the system, heat to 50℃ and react for 3h to obtain modified nano silica slurry;

[0055] (4) Add 4% of the initial mass of nano silica powder and polyvinyl alcohol 0588 as a dispersant to the slurry, and ultrasonically disperse at 300W power for 30min to obtain modified nano silica dispersion.

[0056] S2. Preparation of pre-emulsion:

[0057] Take all the above-weighed n-butyl acrylate, carboxyl-containing monomer, acrylamide, modified nano silica dispersion, 1 part composite emulsifier, 60 parts deionized water, and potassium persulfate, and mix them at high speed to obtain a stable pre-emulsion.

[0058] During mixing, the temperature was controlled at 35℃, the stirring speed at 500 rpm, and the stirring time at 60 min.

[0059] S3, Segmented Temperature-Controlled Polymerization and Crosslinking:

[0060] S301. Add the remaining deionized water to the polymerization reactor, pass N2 through for 20 minutes to deoxygenate, then add the remaining composite emulsifier, chain transfer agent, sodium bisulfite and 0.25 parts of vinyl chloride monomer, and heat to 42°C to initiate the polymerization.

[0061] S302. Add all the pre-emulsion obtained in step S2 and the remaining vinyl chloride monomer to the reaction system dropwise, and carry out the copolymerization reaction at 42°C;

[0062] The pre-emulsion and the remaining vinyl chloride monomer are added sequentially, with the pre-emulsion added first for 1 hour and the remaining vinyl chloride monomer added within 0.5 hours.

[0063] After the pre-emulsion is added, keep the reaction at a constant temperature for 0.5 hours, and then proceed with the heating operation in step S303.

[0064] S303, heat to 55℃, and continue polymerization for 3 hours under a pressure of 0.7MPa;

[0065] S304, cool to 40℃, add all the crosslinking agent and carry out in-situ crosslinking reaction for 1 hour, and terminate the reaction when the pressure in the reactor drops to 0.3MPa;

[0066] S4. Post-processing:

[0067] Unreacted monomers are recovered, modified, and the pH is adjusted to 6. Industrial wastewater is then purified by membrane separation and reused.

[0068] The modification is as follows: 0.5 parts by weight of surface-modifying monomer is added, and then, under stirring, 0.03 parts by weight of aqueous solution of tert-butyl hydroperoxide is added dropwise. After an interval of 5 minutes, an aqueous solution of vitamin C with an equimolar amount of the tert-butyl hydroperoxide is added dropwise. After stirring for 30 minutes, 0.02 parts by weight of soybean oil-based mineral oil defoamer is added, and then the pH is adjusted.

[0069] The surface-modifying monomer is a mixture of styrene and dodecafluoroheptyl methacrylate in a mass ratio of 1:0.5;

[0070] The method for preparing the aqueous solutions of tert-butyl hydrogen peroxide and vitamin C is as follows: prepare an aqueous solution of tert-butyl hydrogen peroxide with a concentration of 5 wt% and an aqueous solution of vitamin C with a concentration of 3 wt%, respectively.

[0071] The pH adjuster is a 5 wt% ammonia solution or a 10 wt% sodium hydroxide aqueous solution;

[0072] The membrane separation and purification process specifically involves: treating process wastewater with a ceramic membrane separation device that has a molecular weight cutoff of 5000 Da, and reusing the separated organic matter in the polymerization reaction; and reusing the permeate after reverse osmosis purification.

[0073] Example 2

[0074] A synthesis process for a nano-environmentally friendly functional membrane material includes the following steps:

[0075] S1. Raw material preparation:

[0076] Weigh the following raw materials according to the following weight proportions: 70 parts n-butyl acrylate, 14 parts carboxyl-containing monomer, 3.5 parts acrylamide, 10 parts vinyl chloride monomer, 2.5 parts composite emulsifier, 70 parts modified nano silica dispersion, 150 parts deionized water, 0.05 parts chain transfer agent tert-dodecyl mercaptan, 0.2 parts potassium persulfate, 0.07 parts sodium bisulfite, and 0.4 parts crosslinking agent vinyltrimethoxysilane (A-171).

[0077] The carboxyl-containing monomer is a mixture of acrylic acid and methacrylic acid in a mass ratio of 2.5:1;

[0078] The composite emulsifier is prepared by mixing sodium allyl hydroxypropyl sulfonate, sodium dodecylbenzene sulfonate, and potassium laurate in a mass ratio of 2:3:5, then adding 2.5 times the total mass of the solids in deionized water, and stirring at 40°C for 4.5 hours to obtain the composite emulsifier.

[0079] The preparation of the modified nano-silica dispersion includes the following steps:

[0080] (1) Take nano-silica powder with an original particle size of 30~50nm, add 6.5 times its mass of deionized water, stir and disperse to form a suspension;

[0081] (2) Add 4% by weight of nano-silica powder dopamine hydrochloride to the suspension, adjust the pH of the system to 8.3, and stir the reaction at 27°C for 5 hours;

[0082] (3) Add 5% by weight of nano silica powder and silane coupling agent KH-570 to the system, heat to 60℃ and react for 5h to obtain modified nano silica slurry;

[0083] (4) Add 5% of the initial mass of nano silica powder and polyvinyl alcohol 0588 as a dispersant to the slurry, and ultrasonically disperse at 400W power for 45min to obtain modified nano silica dispersion.

[0084] S2. Preparation of pre-emulsion:

[0085] Take all the above-weighed n-butyl acrylate, carboxyl-containing monomer, acrylamide, modified nano silica dispersion, 1.5 parts of composite emulsifier, 80 parts of deionized water, and potassium persulfate, and mix them at high speed to obtain a stable pre-emulsion.

[0086] During mixing, the temperature is controlled at 40℃, the stirring speed is 700 rpm, and the stirring time is 75 min;

[0087] S3, Segmented Temperature-Controlled Polymerization and Crosslinking:

[0088] S301. Add the remaining deionized water to the polymerization reactor, pass N2 through for 25 minutes to deoxygenate, then add the remaining composite emulsifier, chain transfer agent, sodium bisulfite and 1.5 parts of vinyl chloride monomer, and heat to 45°C to initiate the polymerization.

[0089] S302. Add all the pre-emulsion obtained in step S2 and the remaining vinyl chloride monomer to the reaction system dropwise, and carry out the copolymerization reaction at 45°C.

[0090] The pre-emulsion and the remaining vinyl chloride monomer are added sequentially, with the pre-emulsion added first for 1.5 hours and the remaining vinyl chloride monomer added within 0.7 hours.

[0091] After the pre-emulsion is added, the reaction is kept at a constant temperature for 0.7 hours, followed by the heating operation in step S303.

[0092] S303, heat to 58℃, and continue polymerization for 4 hours under a pressure of 0.73MPa;

[0093] S304, cool to 43℃, add all the crosslinking agent and carry out in-situ crosslinking reaction for 1.5h, and terminate the reaction when the pressure in the reactor drops to 0.4MPa;

[0094] S4. Post-processing:

[0095] Unreacted monomers are recovered, modified, and the pH is adjusted to 7.5. Industrial wastewater is then purified by membrane separation and reused.

[0096] The modification is as follows: 1 part by weight of surface-modifying monomer is added, and then, under stirring, 0.05 parts by weight of aqueous solution of tert-butyl hydroperoxide is added dropwise. After an interval of 10 minutes, an aqueous solution of vitamin C with an equimolar amount of the tert-butyl hydroperoxide is added dropwise. After stirring for 35 minutes, 0.035 parts by weight of soybean oil-based mineral oil defoamer is added, and then the pH is adjusted.

[0097] The surface-modifying monomer is a mixture of styrene and dodecafluoroheptyl methacrylate in a mass ratio of 1:1;

[0098] The method for preparing the aqueous solutions of tert-butyl hydrogen peroxide and vitamin C is as follows: prepare an aqueous solution of tert-butyl hydrogen peroxide with a concentration of 8 wt% and an aqueous solution of vitamin C with a concentration of 4 wt%, respectively.

[0099] The pH adjuster is a 5 wt% ammonia solution or a 10 wt% sodium hydroxide aqueous solution;

[0100] The membrane separation and purification process specifically involves: treating process wastewater with a ceramic membrane separation device that has a molecular weight cutoff of 7000 Da, and reusing the separated organic matter in the polymerization reaction; and reusing the permeate after reverse osmosis purification.

[0101] Example 3

[0102] A synthesis process for a nano-environmentally friendly functional membrane material includes the following steps:

[0103] S1. Raw material preparation:

[0104] Weigh the following raw materials according to the following weight proportions: 75 parts n-butyl acrylate, 18 parts carboxyl-containing monomer, 5 parts acrylamide, 15 parts vinyl chloride monomer, 3.5 parts composite emulsifier, 100 parts modified nano silica dispersion, 180 parts deionized water, 0.08 parts chain transfer agent tert-dodecyl mercaptan, 0.3 parts potassium persulfate, 0.1 parts sodium bisulfite, and 0.6 parts crosslinking agent vinyltrimethoxysilane (A-171).

[0105] The carboxyl-containing monomer is a mixture of acrylic acid and methacrylic acid in a mass ratio of 3:1.

[0106] The preparation method of the composite emulsifier is as follows: sodium allyl hydroxypropyl sulfonate, sodium dodecylbenzene sulfonate and potassium laurate are mixed in a mass ratio of 3:4:6, and then 23 times the total mass of the solids are added to deionized water. The mixture is stirred at 42°C for 5 hours to obtain the composite emulsifier.

[0107] The preparation of the modified nano-silica dispersion includes the following steps:

[0108] (1) Take nano-silica powder with an original particle size of 50 nm, add 8 times its mass of deionized water, stir and disperse to form a suspension;

[0109] (2) Add 5% by weight of nano-silica powder dopamine hydrochloride to the suspension, adjust the pH of the system to 8.5, and stir the reaction at 30°C for 6 hours;

[0110] (3) Add 8% by weight of nano silica powder and silane coupling agent KH-570 to the system, heat to 70℃ and react for 6h to obtain modified nano silica slurry;

[0111] (4) Add 6% of the initial mass of nano silica powder and polyvinyl alcohol 0588 as a dispersant to the slurry, and ultrasonically disperse at 500W power for 60min to obtain modified nano silica dispersion.

[0112] S2. Preparation of pre-emulsion:

[0113] Take all the above-weighed n-butyl acrylate, carboxyl-containing monomer, acrylamide, modified nano silica dispersion, 2.5 parts of composite emulsifier, 100 parts of deionized water, and potassium persulfate, and mix them at high speed to obtain a stable pre-emulsion.

[0114] During mixing, the temperature was controlled at 45℃, the stirring speed at 800 rpm, and the stirring time at 90 min.

[0115] S3, Segmented Temperature-Controlled Polymerization and Crosslinking:

[0116] S301. Add the remaining deionized water to the polymerization reactor, pass N2 to deoxygenate for 30 minutes, then add the remaining composite emulsifier, chain transfer agent, sodium bisulfite and 2.25 parts of vinyl chloride monomer, and heat to 48°C to initiate the polymerization.

[0117] S302. Add all the pre-emulsion obtained in step S2 and the remaining vinyl chloride monomer to the reaction system dropwise, and carry out the copolymerization reaction at 48°C;

[0118] The pre-emulsion and the remaining vinyl chloride monomer are added sequentially, with the pre-emulsion added first for 2 hours and the remaining vinyl chloride monomer added within 1 hour.

[0119] After the pre-emulsion is added, keep the reaction at the temperature for 1 hour, and then proceed with the heating operation in step S303.

[0120] S303, heat to 60℃, and continue polymerization for 5 hours under a pressure of 0.75MPa;

[0121] S304, cool to 45℃, add all the crosslinking agent and carry out in-situ crosslinking reaction for 2 hours, and terminate the reaction when the pressure in the reactor drops to 0.5MPa;

[0122] S4. Post-processing:

[0123] Unreacted monomers are recovered, modified, and the pH is adjusted to 9. Industrial wastewater is then purified by membrane separation and reused.

[0124] The modification is as follows: 2 parts by weight of surface-modifying monomer are added, and then, under stirring, 0.08 parts by weight of aqueous solution of tert-butyl hydroperoxide is added dropwise. After an interval of 15 minutes, an aqueous solution of vitamin C with an equimolar amount of the tert-butyl hydroperoxide is added dropwise. After stirring for 40 minutes, 0.05 parts by weight of soybean oil-based mineral oil defoamer is added, and then the pH is adjusted.

[0125] The surface-modifying monomer is a mixture of styrene and dodecafluoroheptyl methacrylate in a mass ratio of 1:2;

[0126] The method for preparing the aqueous solutions of tert-butyl hydrogen peroxide and vitamin C is as follows: prepare an aqueous solution of tert-butyl hydrogen peroxide with a concentration of 10 wt% and an aqueous solution of vitamin C with a concentration of 5 wt%, respectively.

[0127] The pH adjuster is a 5 wt% ammonia solution or a 10 wt% sodium hydroxide aqueous solution;

[0128] The membrane separation and purification process specifically involves: treating process wastewater with a ceramic membrane separation device that has a molecular weight cutoff of 10,000 Da, and reusing the separated organic matter in the polymerization reaction; and reusing the permeate after reverse osmosis purification.

[0129] The nano-environmentally friendly functional membrane materials prepared by the methods in Examples 1-3 were tested for their properties, and the test results are shown in Table 1 below.

[0130] Table 1

[0131] Solid content (w / w) pH value Median particle size / D50 Example 1 42% 6.5 0.128 Example 2 45% 7.2 0.118 Example 3 47% 8.0 0.108

[0132] from Figure 1 As shown in Table 1, the majority of the emulsion particles have a diameter of 100–130 nm, while a small portion have a diameter of 130–150 nm. Figure 2 It can be seen that the present invention has prepared a nanocomposite emulsion with high solid content, fine particle size and uniform distribution.

[0133] To further compare the technical effects of the present invention, the following comparisons were made, and experimental tests were conducted.

[0134] Comparative Example 1

[0135] Compared with Example 2, Comparative Example 1 replaced the composite emulsifier with a single emulsifier (sodium dodecylbenzenesulfonate), while the other steps and technical parameters were the same as in Example 2.

[0136] Comparative Example 2

[0137] Compared with Example 2, Comparative Example 2 replaces the modified nano-silica with unmodified nano-silica, while the other steps and technical parameters are the same as in Example 2.

[0138] Comparative Example 3

[0139] Compared with Example 2, Comparative Example 3 uses single-temperature polymerization instead of segmented temperature control, and changes the segmented temperature control polymerization to be carried out at a constant temperature of 50±2℃ throughout the process. Other steps and technical parameters are the same as in Example 2.

[0140] Comparative Example 4

[0141] Compared with Example 2, Comparative Example 4 omits the defoamer in step S3, while the other steps and technical parameters are the same as in Example 2.

[0142] Performance testing

[0143] (1) Mechanical property testing

[0144] Standard basis: GB / T 1040.3-2006

[0145] Equipment: Electronic universal testing machine

[0146] Specimen dimensions: dumbbell-shaped specimen, gauge length 25 mm, width 5 mm, specimen thickness 3 ± 0.1 mm.

[0147] Test conditions: tensile speed 50 mm / min, room temperature (23±2℃)

[0148] Test parameters: tensile strength (MPa), elongation at break (%)

[0149] (2) Water resistance test

[0150] Pour 10 grams of the sample to be tested into a polytetrafluoroethylene sample cell with a diameter of 8 cm and a depth of 3 mm, place it in a 50°C oven, and remove it after the sample in the sample cell becomes completely transparent and forms a film. Cut 4 grams of the film material, put it in deionized water for 24 hours, and then remove it. After removing it, use filter paper to absorb the surface moisture and calculate the water absorption rate.

[0151] Calculation formula: Water absorption rate (%) = [(W1-W0) / W0] × 100

[0152] (3) Thermal stability test

[0153] Standard basis: GB / T 27761-2011

[0154] Equipment: Thermogravimetric analyzer (TGA)

[0155] Test conditions: nitrogen atmosphere, heating rate 10℃ / min, temperature range 30~600℃

[0156] Indicator: Initial decomposition temperature (T5%, the temperature at which 5% weight loss occurs)

[0157] (4) Surface hydrophobicity test

[0158] Equipment: Contact angle measuring instrument

[0159] Method: The water contact angle (°) was measured using the static drop method, and the average value of 5 points was taken.

[0160] (5) Stain resistance test

[0161] Standard basis: GB / T 9789-2013

[0162] Method: Apply the sample evenly to a flat and clean glass plate using a 100μm coater, dry it in an oven at 50±2℃ for 30min, and then remove and cool to room temperature;

[0163] The standard contaminant was a carbon black suspension with a mass fraction of 5%. The carbon black suspension was uniformly coated on the sample surface and allowed to dry naturally for 24 hours.

[0164] Rinse the sample surface with running tap water for 1 minute, allow it to air dry, and then compare its color with that of the uncontaminated original sample. Rating the sample according to the standard.

[0165] The rating criteria are shown in Table 2 below.

[0166] Table 2

[0167] Level 5 No visible contamination on the surface, no color change. Level 4 The surface is slightly contaminated, and the color has changed slightly. Level 3 The surface is obviously contaminated, and the color has changed significantly. Level 2 The surface is heavily contaminated, and the color has changed significantly. Level 1 The surface is severely contaminated, and the color has almost completely changed.

[0168] The experimental results are shown in Table 3 below.

[0169] Table 3

[0170] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Tensile strength (MPa) 19.5 23.8 27.2 14.1 15.9 18.5 20.3 Elongation at break (%) 350 320 290 260 280 330 310 Water absorption rate (%) 2.8 2.1 1.5 9.5 8.0 6.8 5.5 Ts% (°C) 285 298 310 260 275 280 298 Water contact angle (°) 115 122 128 78 82 95 105 Stain resistance (grade) 4 4.5 5 3 3.5 4 4

[0171] As can be seen from Table 3 above, in Examples 1 to 3, with the systematic improvement of parameters such as the amount of composite emulsifier, the content of nano silica, and the reaction temperature and time, the overall performance of the membrane material shows a gradual optimization trend.

[0172] Comparative Example 1, using a single emulsifier, showed a comprehensive decline in performance, especially a significant increase in water absorption and a substantial decrease in tensile strength and hydrophobicity, demonstrating the irreplaceable synergistic effect of composite emulsifiers in forming stable and uniform nanoemulsions.

[0173] Comparative Example 2 used unmodified nano-SiO2, which had poor nanoparticle dispersion, resulting in limited improvement in mechanical properties, as well as poor thermal stability and water resistance. This highlights the key role of two-step surface modification with dopamine and silane coupling agent in improving the interfacial compatibility of nanofillers and achieving effective reinforcement.

[0174] Comparative Example 3 used single-temperature polymerization. Because the single-temperature reaction was not precisely controlled, the polymer had a wide molecular weight distribution, uneven cross-linking, and lower mechanical properties and thermal stability than Example 2. This confirmed the importance of segmented temperature-controlled polymerization process for optimizing polymer microstructure.

[0175] Comparative Example 4, without defoamer, showed that residual microbubbles during film formation introduced defects, leading to a decrease in tensile strength and affecting surface smoothness. This indicates that defoamer has a practical effect on obtaining a dense and defect-free film.

[0176] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A synthesis process for a nano-environmentally friendly functional membrane material, characterized in that, Includes the following steps: S1. Raw material preparation: Weigh the following raw materials according to the following weight proportions: 65-75 parts of acrylate monomers, 10-18 parts of carboxyl-containing monomers, 2-5 parts of acrylamide monomers, 5-15 parts of vinyl chloride monomers, 1.5-3.5 parts of composite emulsifier, 40-100 parts of modified nano-silica dispersion, 120-180 parts of deionized water, 0.03-0.08 parts of chain transfer agent, 0.1-0.3 parts of potassium persulfate or ammonium persulfate, 0.05-0.1 parts of sodium bisulfite, and 0.2-0.6 parts of crosslinking agent; S2. Preparation of pre-emulsion: Take all the acrylate monomers, carboxyl-containing monomers, acrylamide, modified nano-silica dispersion, 1-2.5 parts of composite emulsifier, and 60-100 parts of deionized water, potassium persulfate or ammonium persulfate, weigh them out and mix them at high speed to obtain a stable pre-emulsion. S3, Segmented Temperature-Controlled Polymerization and Crosslinking: S301. Add the remaining deionized water to the polymerization reactor, pass N2 to deoxygenate, then add the remaining composite emulsifier, chain transfer agent, sodium bisulfite and 0.25~2.25 parts of vinyl chloride monomer, and heat to 42~48℃ to initiate the polymerization. S302. Add all the pre-emulsion obtained in step S2 and the remaining vinyl chloride monomer to the reaction system, and carry out the copolymerization reaction at 42~48℃. S303, heat to 55~60℃, and continue polymerization for 3~5 hours under a pressure of 0.7~0.75MPa; S304, cool to 40~45℃, add all the crosslinking agent and carry out in-situ crosslinking reaction for 1~2 hours, and terminate the reaction when the pressure in the reactor drops to 0.3~0.5MPa; S4. Post-processing: Unreacted monomers are recovered, modified, and the pH is adjusted to 6-9. Industrial wastewater is then purified by membrane separation and reused.

2. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, The acrylate monomers are preferably one or a mixture of n-butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate.

3. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, The carboxyl-containing monomer is a mixture of acrylic acid and methacrylic acid, with a mass ratio of (2~3):1; The acrylamide monomer is acrylamide or N-(hydroxymethyl)acrylamide.

4. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, The composite emulsifier is prepared by mixing sodium allyl hydroxypropyl sulfonate, sodium dodecylbenzene sulfonate, and potassium laurate in a mass ratio of (1~3):(2~4):(4~6), then adding 2~3 times the total mass of the solids in deionized water, and stirring at 38~42℃ for 4~5 hours to obtain the composite emulsifier.

5. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, The preparation of the modified nano-silica dispersion includes the following steps: (1) Take nano-silica powder with an original particle size of 30~50nm, add 5~8 times its mass of deionized water, stir and disperse to form a suspension; (2) Add 3-5% by weight of nano-silica powder dopamine hydrochloride to the suspension, adjust the pH of the system to 8.0-8.5, and stir the reaction at 25-30℃ for 4-6 hours; (3) Add 3-8% by weight of nano silica powder and silane coupling agent KH-570 to the system, heat to 50-70℃ and react for 3-6 hours to obtain modified nano silica slurry; (4) Add 4-6% of the initial mass of nano silica powder and polyvinyl alcohol 0588 as a dispersant to the slurry, and ultrasonically disperse it for 30-60 min at a power of 300-500W to obtain a modified nano silica dispersion.

6. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, The chain transfer agent is mercaptoethanol, tert-dodecyl mercaptan, or n-dodecyl mercaptan; The crosslinking agent is vinyltrimethoxysilane.

7. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, In step S2, the mixing temperature is controlled at 35~45℃, the stirring speed is 500~800rpm, and the stirring time is 60~90min.

8. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, In step S302, the pre-emulsion and the remaining vinyl chloride monomer are added sequentially, with the pre-emulsion added first for 1-2 hours and the remaining vinyl chloride monomer added within 0.5-1 hour. After the pre-emulsion is added, keep the reaction at a constant temperature for 0.5 to 1 hour, and then proceed with the heating operation in step S303.

9. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, The modification in step S4 is as follows: add 0.5-2 parts by weight of surface-modifying monomer, and then, under stirring, first add 0.03-0.08 parts by weight of aqueous solution of tert-butyl hydrogen peroxide, and after an interval of 5-15 minutes, add an aqueous solution of vitamin C with an equimolar amount of the tert-butyl hydrogen peroxide, stir for 30-40 minutes, then add 0.02-0.05 parts by weight of soybean oil-based mineral oil defoamer, and then adjust the pH. The surface-modifying monomer is a mixture of styrene and dodecafluoroheptyl methacrylate in a mass ratio of 1:(0.5~2); The pH adjuster is a 5 wt% ammonia solution or a 10 wt% sodium hydroxide aqueous solution.

10. The synthesis process of a nano-environmentally friendly functional membrane material according to claim 1, characterized in that, The membrane separation and purification described in step S4 specifically involves: treating the process wastewater with a ceramic membrane separation device that has a molecular weight cutoff of 5000~10000 Da, and reusing the separated organic matter in the polymerization reaction; and reusing the permeate after purification by reverse osmosis.

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