A polytetrafluoroethylene membrane for air purification and its preparation process

Abstract

The present invention relates to the technical field of polytetrafluoroethylene membrane materials, specifically a polytetrafluoroethylene membrane for air purification and a preparation process thereof. The present invention first selects a mixed solution of carboxymethyl cellulose and polyethyleneimine as a cross-linking agent to modify the polytetrafluoroethylene membrane fiber; in order to improve the antibacterial performance of the polytetrafluoroethylene membrane, the present invention reacts and grafts trimethoxysilane and 4-vinyl pyridine through a hydrosilylation reaction, and then reacts with epichlorohydrin to obtain an epoxy-based organosilicon quaternary ammonium salt; the modified polytetrafluoroethylene is immersed in an epoxy-based organosilicon quaternary ammonium salt dispersion to react and obtain an air purification polytetrafluoroethylene membrane. The air purification polytetrafluoroethylene membrane prepared by the present invention not only has long-lasting antibacterial performance, but also has good water-washing resistance and can still maintain a high antibacterial effect after washing.

Description

Technical Field

[0001] The invention relates to the technical field of polytetrafluoroethylene membrane materials, in particular to a polytetrafluoroethylene membrane for air purification and a preparation process thereof. Background Art

[0002] Air quality is closely linked to human health. PM2.5 is a common and harmful pollutant in the air, primarily derived from the combustion of fossil fuels. PM2.5 harms the respiratory and cardiovascular systems, and the elderly, children, and those with cardiopulmonary diseases are all susceptible to PM2.5 pollution. Polytetrafluoroethylene membranes, with their excellent filtration capabilities, can be used to purify PM2.5 from the air, reducing its harmful effects on the human body.

[0003] However, PTFE membranes are not very effective at purifying microorganisms such as bacteria and fungi. Under certain conditions, microorganisms exist in the air as aerosols. Once inhaled by the human body, they can cause infection, endangering human health and causing various diseases. Therefore, it is very necessary to improve the antibacterial properties of PTFE membranes and develop PTFE membranes for air purification. Summary of the Invention

[0004] The object of the present invention is to provide a polytetrafluoroethylene membrane for air purification and a preparation process thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a polytetrafluoroethylene membrane for air purification and a preparation process thereof, comprising the following steps:

[0006] Step 1:

[0007] S11: mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at a temperature of 80° C. to 90° C. for 5 to 8 hours to obtain a polytetrafluoroethylene material;

[0008] S12: pressing a polytetrafluoroethylene material at 60-70° C.; extruding and calendering the polytetrafluoroethylene tape at 70-90° C.; degreasing the polytetrafluoroethylene tape, and then longitudinally stretching and transversely stretching the tape at 200-250° C., sintering and finalizing the tape, and then water-cooling and solidifying the tape to obtain a polytetrafluoroethylene film;

[0009] Step 2:

[0010] S21: dissolving carboxymethyl cellulose in deionized water to prepare a 3-5% by mass carboxymethyl cellulose solution, dissolving polyethyleneimine in deionized water to obtain a 25-30% by mass polyethyleneimine solution; and adding the polyethyleneimine solution to the carboxymethyl cellulose solution to obtain a crosslinker solution.

[0011] S22: soaking the polytetrafluoroethylene membrane in a crosslinker solution for 15 to 30 minutes, adding a 2 to 3% by mass glutaraldehyde solution and reacting for 1 to 2 hours, and then removing and drying to obtain a modified polytetrafluoroethylene membrane;

[0012] Step 3:

[0013] S31: Disperse trimethoxysilane and Custer's catalyst in toluene, raise the temperature to 80-90°C under nitrogen protection, add a toluene solution of 4-vinylpyridine while maintaining the temperature, and react for 2-3 hours. After the reaction is completed, stop the nitrogen flow, remove the toluene by vacuum distillation, and dissolve the product in ethanol-ether solvent. Precipitate the precipitate with tetrahydrofuran precipitant, and dry to obtain vinylpyridine-grafted trimethoxysilane;

[0014] S32: Vinylpyridine-grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then epichlorohydrin is added. The temperature is raised and refluxed for 24 to 30 hours, and then the reaction is stopped. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, and the solvent is removed by filtration. The precipitate is washed with tetrahydrofuran and dried in vacuo to obtain an epoxy organosilicon quaternary ammonium salt;

[0015] S33: dispersing epoxy organosilicon quaternary ammonium salt in deionized water to obtain epoxy organosilicon quaternary ammonium salt dispersion; immersing the modified polytetrafluoroethylene membrane in the epoxy organosilicon quaternary ammonium salt dispersion, reacting at 60-70° C. for 6-8 hours, taking out, washing with deionized water, and drying to obtain a polytetrafluoroethylene membrane for air purification.

[0016] Furthermore, in S11, the weight of the composite lubricant is 20-30% of the weight of the polytetrafluoroethylene powder; and the amount of each component in the composite lubricant, by weight, is 10-30 parts of kerosene and 5-10 parts of silicone oil.

[0017] Furthermore, in S12, the longitudinal stretching ratio is 3 to 5 times, and the transverse stretching ratio is 2 to 3 times.

[0018] Furthermore, in S12, the sintering temperature is 285-320°C, and the sintering time is 90-120s.

[0019] Furthermore, in S21, 5 to 8 parts by weight of polyethyleneimine solution are added to 100 parts by weight of the carboxymethyl cellulose solution to obtain a crosslinking agent solution.

[0020] Furthermore, in S22, the polytetrafluoroethylene membrane is immersed in a cross-linking agent solution at a bath ratio of 1:(15-20).

[0021] Furthermore, in S31, trimethoxysilane and 4-vinylpyridine are reacted in a molar ratio of 1:1.

[0022] Furthermore, in S32, vinylpyridine grafted trimethoxysilane and epichlorohydrin are reacted in a molar ratio of 1:1.

[0023] Furthermore, in S33, the modified polytetrafluoroethylene membrane is immersed in an epoxy-based organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:(10-15); the mass fraction of the epoxy-based organosilicon quaternary ammonium salt dispersion is 8-10%.

[0024] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention provides a preparation process of a polytetrafluoroethylene membrane for air purification. When preparing the polytetrafluoroethylene membrane, the present invention mixes polytetrafluoroethylene powder and a composite lubricant, extrudes and calenders to form a polytetrafluoroethylene-based tape, degreases, longitudinally stretches, and transversely stretches the tape, and then sinters and shapes the tape, and water cools and solidifies the tape to obtain the polytetrafluoroethylene membrane.

[0025] The present invention uses carboxymethyl cellulose and polyethyleneimine as cross-linking agents. The hydroxyl groups on the carboxymethyl cellulose molecules and the amino groups on the polyethyleneimine molecules can react with the two carbonyl groups on glutaraldehyde to form crosslinks and coat the polytetrafluoroethylene (PTFE) membrane fibers, thereby achieving modification. To further improve the antibacterial properties of the PTFE membrane, the present invention first performs a hydrosilylation reaction to graft trimethoxysilane and 4-vinylpyridine to obtain vinylpyridine-grafted trimethoxysilane. Epichlorohydrin is then reacted with the vinylpyridine-grafted trimethoxysilane to obtain an epoxy-organic silicon quaternary ammonium salt. The modified PTFE is immersed in an epoxy-organic silicon quaternary ammonium salt dispersion. The carboxyl groups on the carboxymethyl cellulose and the amino groups on the polyethyleneimine on the surface of the modified PTFE react with the epoxy groups to form chemical bonds, firmly fixing the epoxy-organic silicon quaternary ammonium salt on the surface of the PTFE membrane. The presence of silicone in the epoxy silicone quaternary ammonium salt itself also has good water resistance. Therefore, the polytetrafluoroethylene membrane for air purification prepared by the present invention not only has long-lasting antibacterial performance, but also has certain water washability, and can still maintain a high antibacterial effect after washing.

[0026] In addition, it should be noted that when using a crosslinking agent to modify polytetrafluoroethylene, if the crosslinking agent dosage is too low, the amount of epoxy organosilicon quaternary ammonium salt grafted subsequently will be reduced. However, if the dosage is too high, on the one hand, due to the existence of marginal effects, the antibacterial performance is not significantly improved. On the other hand, the crosslinked product of carboxymethyl cellulose and polyethyleneimine will block the membrane pores, resulting in reduced air permeability. In order to balance air permeability and antibacterial efficiency, the present invention immerses the polytetrafluoroethylene membrane in a crosslinking agent solution at a bath ratio of 1: (15-20) for modification. The resulting polytetrafluoroethylene membrane for air purification has good air permeability and efficient, long-lasting antibacterial properties. DETAILED DESCRIPTION

[0027] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0028] Materials used in the present invention and their sources: polytetrafluoroethylene powder (brand name Teflon 605XT) is from DuPont, USA; kerosene is 3# aviation kerosene from Qilu Petrochemical; silicone oil (brand name IOTA 702) is from Anhui Aiyota Silicone Oil Co., Ltd.; carboxymethyl cellulose (brand name gs126122) is from Renqiu Guangshun Environmental Protection Technology Co., Ltd.; polyethyleneimine is from Sinopharm Group, with a relative molecular mass of 3000.

[0029] Example 1: A polytetrafluoroethylene membrane for air purification and a preparation process thereof, comprising the following steps:

[0030] Step 1:

[0031] S11: Mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at 80° C. for 5 hours to obtain a polytetrafluoroethylene material; wherein the weight of the composite lubricant is 20% of the weight of the polytetrafluoroethylene powder; and the composite lubricant is obtained by mixing 30 g of kerosene and 10 g of silicone oil;

[0032] S12: pressing a polytetrafluoroethylene material at 60° C.; extruding and calendering the polytetrafluoroethylene tape at 70° C.; degreasing the polytetrafluoroethylene tape, stretching it longitudinally by 3 times and transversely by 2 times at 200° C., sintering it at 285° C. for 90 seconds, and water cooling and solidifying it to obtain a polytetrafluoroethylene film;

[0033] Step 2:

[0034] S21: dissolving carboxymethyl cellulose in deionized water to prepare a 5% by mass carboxymethyl cellulose solution, dissolving polyethyleneimine in deionized water to obtain a 30% by mass polyethyleneimine solution; and adding 5 g of the polyethyleneimine solution to 100 g of the carboxymethyl cellulose solution to obtain a crosslinker solution;

[0035] S22: After soaking the polytetrafluoroethylene membrane in a crosslinker solution at a bath ratio of 1:15 for 15 minutes, a 2.5% by mass glutaraldehyde solution was added and reacted for 1 hour, and then the membrane was removed and dried to obtain a modified polytetrafluoroethylene membrane;

[0036] Step 3:

[0037] S31: dispersing trimethoxysilane and Custer's catalyst in toluene, raising the temperature to 80°C under nitrogen protection, adding a toluene solution of 4-vinylpyridine while maintaining the temperature, and reacting for 2 hours. After the reaction is completed, the nitrogen is stopped, and the toluene is removed by vacuum distillation. The product is added to an ethanol-ether solvent and dissolved. The precipitate is precipitated with tetrahydrofuran as a precipitant, and dried to obtain vinylpyridine-grafted trimethoxysilane; wherein the trimethoxysilane and 4-vinylpyridine are reacted in a molar ratio of 1:1;

[0038] S32: Vinylpyridine grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then epichlorohydrin is added. The temperature is raised to reflux and the reaction is stopped after 24 hours. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, the solvent is removed by suction filtration, and the precipitate is washed with tetrahydrofuran and vacuum dried to obtain an epoxy organosilicon quaternary ammonium salt; wherein the vinylpyridine grafted trimethoxysilane and epichlorohydrin are reacted in a molar ratio of 1:1;

[0039] S33: Dispersing epoxy organosilicon quaternary ammonium salt in deionized water to obtain a 10% by mass epoxy organosilicon quaternary ammonium salt dispersion; immersing a modified polytetrafluoroethylene membrane in the epoxy organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:10, reacting at 60° C. for 6 hours, taking out, washing with deionized water, and drying to obtain a polytetrafluoroethylene membrane for air purification.

[0040] Example 2: A polytetrafluoroethylene membrane for air purification and a preparation process thereof, comprising the following steps:

[0041] Step 1:

[0042] S11: Mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at 85° C. for 7 hours to obtain a polytetrafluoroethylene material; wherein the weight of the composite lubricant is 20% of the weight of the polytetrafluoroethylene powder; and the composite lubricant is obtained by mixing 30 g of kerosene and 10 g of silicone oil;

[0043] S12: pressing a polytetrafluoroethylene material at 65° C.; extruding and calendering the polytetrafluoroethylene tape at 80° C.; degreasing the polytetrafluoroethylene tape, stretching it longitudinally by 3 times and transversely by 2 times at 230° C., sintering it at 300° C. for 100 seconds, and water cooling and solidifying it to obtain a polytetrafluoroethylene film;

[0044] Step 2:

[0045] S21: dissolving carboxymethyl cellulose in deionized water to prepare a 5% by mass carboxymethyl cellulose solution, dissolving polyethyleneimine in deionized water to obtain a 30% by mass polyethyleneimine solution; and adding 5 g of the polyethyleneimine solution to 100 g of the carboxymethyl cellulose solution to obtain a crosslinker solution;

[0046] S22: After soaking the polytetrafluoroethylene membrane in a crosslinker solution at a bath ratio of 1:18 for 25 minutes, a 2.5% by mass glutaraldehyde solution was added and reacted for 1.5 hours, and then the membrane was removed and dried to obtain a modified polytetrafluoroethylene membrane;

[0047] Step 3:

[0048] S31: dispersing trimethoxysilane and Custer's catalyst in toluene, heating the mixture to 85°C under nitrogen protection, adding a toluene solution of 4-vinylpyridine while maintaining the temperature, and reacting for 2.5 hours. After the reaction is completed, the nitrogen is stopped, and the toluene is removed by vacuum distillation. The product is dissolved in an ethanol-ether solvent, precipitated with tetrahydrofuran as a precipitant, and dried to obtain vinylpyridine-grafted trimethoxysilane; wherein the trimethoxysilane and 4-vinylpyridine are reacted in a molar ratio of 1:1;

[0049] S32: Vinylpyridine grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then epichlorohydrin is added. The temperature is raised and refluxed for 27 hours, and then the reaction is stopped. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, the solvent is removed by suction filtration, and the precipitate is washed with tetrahydrofuran and vacuum dried to obtain an epoxy organosilicon quaternary ammonium salt; wherein the vinylpyridine grafted trimethoxysilane and epichlorohydrin are reacted in a molar ratio of 1:1;

[0050] S33: Dispersing epoxy organosilicon quaternary ammonium salt in deionized water to obtain a 10% by mass epoxy organosilicon quaternary ammonium salt dispersion; immersing a modified polytetrafluoroethylene membrane in the epoxy organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:10, reacting at 65°C for 7h, taking out, washing with deionized water, and drying to obtain a polytetrafluoroethylene membrane for air purification.

[0051] Example 3: A polytetrafluoroethylene membrane for air purification and a preparation process thereof, comprising the following steps:

[0052] Step 1:

[0053] S11: Mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at 90° C. for 8 hours to obtain a polytetrafluoroethylene material; wherein the weight of the composite lubricant is 20% of the weight of the polytetrafluoroethylene powder; and the composite lubricant is obtained by mixing 30 g of kerosene and 10 g of silicone oil;

[0054] S12: pressing a polytetrafluoroethylene material at 70° C.; extruding and calendering the polytetrafluoroethylene tape at 90° C.; degreasing the polytetrafluoroethylene tape, stretching it longitudinally by 3 times and transversely by 2 times at 250° C., sintering it at 320° C. for 120 seconds, and water-cooling and solidifying it to obtain a polytetrafluoroethylene film;

[0055] Step 2:

[0056] S21: dissolving carboxymethyl cellulose in deionized water to prepare a 5% by mass carboxymethyl cellulose solution, dissolving polyethyleneimine in deionized water to obtain a 30% by mass polyethyleneimine solution; and adding 5 g of the polyethyleneimine solution to 100 g of the carboxymethyl cellulose solution to obtain a crosslinker solution;

[0057] S22: After soaking the polytetrafluoroethylene membrane in a crosslinker solution at a bath ratio of 1:20 for 30 minutes, a 2.5% by mass glutaraldehyde solution was added and reacted for 2 hours, and then the membrane was removed and dried to obtain a modified polytetrafluoroethylene membrane;

[0058] Step 3:

[0059] S31: dispersing trimethoxysilane and Custer's catalyst in toluene, heating to 90°C under nitrogen protection, adding a toluene solution of 4-vinylpyridine while maintaining the temperature, and reacting for 3 hours. After the reaction is completed, the nitrogen is stopped, and the toluene is removed by vacuum distillation. The product is dissolved in an ethanol-ether solvent, precipitated with tetrahydrofuran as a precipitant, and dried to obtain vinylpyridine-grafted trimethoxysilane; wherein the trimethoxysilane and 4-vinylpyridine are reacted in a molar ratio of 1:1;

[0060] S32: Vinylpyridine grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then epichlorohydrin is added. The temperature is raised to reflux and the reaction is stopped after 30 hours. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, the solvent is removed by suction filtration, and the precipitate is washed with tetrahydrofuran and vacuum dried to obtain an epoxy organosilicon quaternary ammonium salt; wherein the vinylpyridine grafted trimethoxysilane and epichlorohydrin are reacted in a molar ratio of 1:1;

[0061] S33: Dispersing epoxy organosilicon quaternary ammonium salt in deionized water to obtain a 10% by mass epoxy organosilicon quaternary ammonium salt dispersion; immersing a modified polytetrafluoroethylene membrane in the epoxy organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:10, reacting at 70°C for 8 hours, taking out, washing with deionized water, and drying to obtain a polytetrafluoroethylene membrane for air purification.

[0062] Comparative Example 1: The polytetrafluoroethylene membrane was not modified, and the other parameters were the same as those in Example 1.

[0063] Step 1:

[0064] S11: Mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at 80° C. for 5 hours to obtain a polytetrafluoroethylene material; wherein the weight of the composite lubricant is 20% of the weight of the polytetrafluoroethylene powder; and the composite lubricant is obtained by mixing 30 g of kerosene and 10 g of silicone oil;

[0065] S12: pressing a polytetrafluoroethylene material at 60° C.; extruding and calendering the polytetrafluoroethylene tape at 70° C.; degreasing the polytetrafluoroethylene tape, stretching it longitudinally by 3 times and transversely by 2 times at 200° C., sintering it at 285° C. for 90 seconds, and water cooling and solidifying it to obtain a polytetrafluoroethylene film;

[0066] Step 2:

[0067] S21: dispersing trimethoxysilane and Custer's catalyst in toluene, raising the temperature to 80°C under nitrogen protection, adding a toluene solution of 4-vinylpyridine while maintaining the temperature, and reacting for 2 hours. After the reaction is completed, stopping the nitrogen flow, removing the toluene by vacuum distillation, and adding the product to an ethanol-ether solvent to dissolve it. Precipitating the precipitate with tetrahydrofuran as a precipitant, and drying it to obtain vinylpyridine-grafted trimethoxysilane; wherein the trimethoxysilane and 4-vinylpyridine react in a molar ratio of 1:1;

[0068] S22: Vinylpyridine grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then epichlorohydrin is added. The temperature is raised to reflux and the reaction is stopped after 24 hours. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, the solvent is removed by suction filtration, and the precipitate is washed with tetrahydrofuran and vacuum dried to obtain an epoxy organosilicon quaternary ammonium salt; wherein the vinylpyridine grafted trimethoxysilane and epichlorohydrin are reacted in a molar ratio of 1:1;

[0069] S23: Dispersing epoxy organosilicon quaternary ammonium salt in deionized water to obtain a 10% by mass epoxy organosilicon quaternary ammonium salt dispersion; immersing a polytetrafluoroethylene membrane in the epoxy organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:10, reacting at 60° C. for 6 hours, taking out, washing with deionized water, and drying to obtain a polytetrafluoroethylene membrane for air purification.

[0070] Comparative Example 2: propylene glycol was used instead of epichlorohydrin, and the other parameters were the same as those in Example 2.

[0071] Step 1:

[0072] S11: Mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at 85° C. for 7 hours to obtain a polytetrafluoroethylene material; wherein the weight of the composite lubricant is 20% of the weight of the polytetrafluoroethylene powder; and the composite lubricant is obtained by mixing 30 g of kerosene and 10 g of silicone oil;

[0073] S12: pressing a polytetrafluoroethylene material at 65° C.; extruding and calendering the polytetrafluoroethylene tape at 80° C.; degreasing the polytetrafluoroethylene tape, stretching it longitudinally by 3 times and transversely by 2 times at 230° C., sintering it at 300° C. for 100 seconds, and water cooling and solidifying it to obtain a polytetrafluoroethylene film;

[0074] Step 2:

[0075] S21: dissolving carboxymethyl cellulose in deionized water to prepare a 5% by mass carboxymethyl cellulose solution, dissolving polyethyleneimine in deionized water to obtain a 30% by mass polyethyleneimine solution; and adding 5 g of the polyethyleneimine solution to 100 g of the carboxymethyl cellulose solution to obtain a crosslinker solution;

[0076] S22: After soaking the polytetrafluoroethylene membrane in a crosslinker solution at a bath ratio of 1:18 for 25 minutes, a 2.5% by mass glutaraldehyde solution was added and reacted for 1.5 hours, and then the membrane was removed and dried to obtain a modified polytetrafluoroethylene membrane;

[0077] Step 3:

[0078] S31: dispersing trimethoxysilane and Custer's catalyst in toluene, heating the mixture to 85°C under nitrogen protection, adding a toluene solution of 4-vinylpyridine while maintaining the temperature, and reacting for 2.5 hours. After the reaction is completed, the nitrogen is stopped, and the toluene is removed by vacuum distillation. The product is dissolved in an ethanol-ether solvent, precipitated with tetrahydrofuran as a precipitant, and dried to obtain vinylpyridine-grafted trimethoxysilane; wherein the trimethoxysilane and 4-vinylpyridine are reacted in a molar ratio of 1:1;

[0079] S32: Vinylpyridine grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then chloropropane is added. The temperature is raised to reflux and the reaction is stopped after 27 hours. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, the solvent is removed by suction filtration, and the precipitate is washed with tetrahydrofuran and vacuum dried to obtain an organosilicon quaternary ammonium salt; wherein the vinylpyridine grafted trimethoxysilane and chloropropane are reacted in a molar ratio of 1:1;

[0080] S33: Dispersing an organosilicon quaternary ammonium salt in deionized water to obtain an organosilicon quaternary ammonium salt dispersion having a mass fraction of 10%; immersing a modified polytetrafluoroethylene membrane in the organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:10, reacting the membrane at 65° C. for 7 h, removing the membrane, washing the membrane with deionized water, and drying the membrane to obtain a polytetrafluoroethylene membrane for air purification.

[0081] Comparative Example 3: The amount of the cross-linking agent solution was increased, and the other parameters were the same as those in Example 3.

[0082] Step 1:

[0083] S11: Mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at 90° C. for 8 hours to obtain a polytetrafluoroethylene material; wherein the weight of the composite lubricant is 20% of the weight of the polytetrafluoroethylene powder; and the composite lubricant is obtained by mixing 30 g of kerosene and 10 g of silicone oil;

[0084] S12: pressing a polytetrafluoroethylene material at 70° C.; extruding and calendering the polytetrafluoroethylene tape at 90° C.; degreasing the polytetrafluoroethylene tape, stretching it longitudinally by 3 times and transversely by 2 times at 250° C., sintering it at 320° C. for 120 seconds, and water-cooling and solidifying it to obtain a polytetrafluoroethylene film;

[0085] Step 2:

[0086] S21: dissolving carboxymethyl cellulose in deionized water to prepare a 5% by mass carboxymethyl cellulose solution, dissolving polyethyleneimine in deionized water to obtain a 30% by mass polyethyleneimine solution; and adding 5 g of the polyethyleneimine solution to 100 g of the carboxymethyl cellulose solution to obtain a crosslinker solution;

[0087] S22: After soaking the polytetrafluoroethylene membrane in a crosslinker solution at a bath ratio of 1:30 for 30 minutes, a 2.5% by mass glutaraldehyde solution was added and reacted for 2 hours, and then the membrane was removed and dried to obtain a modified polytetrafluoroethylene membrane;

[0088] Step 3:

[0089] S31: dispersing trimethoxysilane and Custer's catalyst in toluene, heating to 90°C under nitrogen protection, adding a toluene solution of 4-vinylpyridine while maintaining the temperature, and reacting for 3 hours. After the reaction is completed, the nitrogen is stopped, and the toluene is removed by vacuum distillation. The product is dissolved in an ethanol-ether solvent, precipitated with tetrahydrofuran as a precipitant, and dried to obtain vinylpyridine-grafted trimethoxysilane; wherein the trimethoxysilane and 4-vinylpyridine are reacted in a molar ratio of 1:1;

[0090] S32: Vinylpyridine grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then epichlorohydrin is added. The temperature is raised to reflux and the reaction is stopped after 30 hours. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, the solvent is removed by suction filtration, and the precipitate is washed with tetrahydrofuran and vacuum dried to obtain an epoxy organosilicon quaternary ammonium salt; wherein the vinylpyridine grafted trimethoxysilane and epichlorohydrin are reacted in a molar ratio of 1:1;

[0091] S33: Dispersing epoxy organosilicon quaternary ammonium salt in deionized water to obtain a 10% by mass epoxy organosilicon quaternary ammonium salt dispersion; immersing a modified polytetrafluoroethylene membrane in the epoxy organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:30, reacting at 70° C. for 8 hours, taking out, washing with deionized water, and drying to obtain a polytetrafluoroethylene membrane for air purification.

[0092] Experiment: The performance of the polytetrafluoroethylene membranes for air purification prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was tested.

[0093] Air permeability test: Use an air permeability meter to test the air permeability of the sample.

[0094] Antibacterial performance testing: The antibacterial effect was quantitatively determined using the shake flask method. Samples were cut into 10 mm x 30 mm pieces and placed in a 150 mL Erlenmeyer flask. 70 mL of PBS buffer and 500 μL of E. coli suspension were added, respectively. The flask was fixed on a shaker and shaken at 120 rpm for 24 hours. 500 μL of the shaken sample was diluted with PBS buffer and then cultured and counted for viable bacteria. A control sample group was also included. No sample was added to the control group, and all other procedures were the same. The initial antibacterial rate was calculated. After the test, the sample was removed and ultrasonically placed in 50°C water for 30 minutes. After drying, the antibacterial rate was tested again following the above steps after washing.

[0095] The antibacterial rate is calculated as follows:

[0096] A=(C0-C0) / C0×100%;

[0097] Wherein, A is the antibacterial rate, %; C0 is the number of surviving bacteria in the control group, pieces; and C is the number of bacteria in the test group (pieces).

[0098] The experimental results are shown in Table 1.

[0099] Table 1. Test results of various properties of polytetrafluoroethylene membrane for air purification

[0100] project Air permeability (mm / s) Initial antibacterial rate Antibacterial rate after washing Example 1 58.73 99.3％ 99.1％ Example 2 55.36 99.5％ 99.4％ Example 3 51.91 99.6％ 99.4％ Comparative Example 1 62.69 59.7％ 59.7％ Comparative Example 2 55.24 88.4％ 60.2％ Comparative Example 3 46.72 99.6％ 99.5％

[0101] Conclusion: The data of Examples 1 to 3 show that the polytetrafluoroethylene membrane prepared by the present invention has good performance. The data of Example 1 and Comparative Example 1 show that the modified polytetrafluoroethylene membrane has better antibacterial properties. The data of Example 2 and Comparative Example 2 show that the epoxy organic silicon quaternary ammonium salt obtained by the reaction of epichlorohydrin and vinylpyridine grafted trimethoxysilane can react with the groups on the modified polytetrafluoroethylene membrane to form chemical bonds, and still has good antibacterial properties after washing. The data of Example 3 and Comparative Example 3 show that when a cross-linking agent is used to modify the polytetrafluoroethylene membrane, too high a dosage of the cross-linking agent will cause the pores on the membrane surface to be blocked, affecting the air permeability.

[0102] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A process for preparing a polytetrafluoroethylene membrane for air purification, characterized in that: The following steps are involved: Step 1: S11: mixing polytetrafluoroethylene powder and a composite lubricant, and placing the mixture at a temperature of 80° C. to 90° C. for 5 to 8 hours to obtain a polytetrafluoroethylene material; S12: pressing a polytetrafluoroethylene material at 60-70° C.; extruding and calendering the polytetrafluoroethylene tape at 70-90° C.; degreasing the polytetrafluoroethylene tape, and then longitudinally stretching and transversely stretching the tape at 200-250° C., sintering and finalizing the tape, and then water-cooling and solidifying the tape to obtain a polytetrafluoroethylene film; Step 2: S21: dissolving carboxymethyl cellulose in deionized water to prepare a 3-5% by mass carboxymethyl cellulose solution, dissolving polyethyleneimine in deionized water to obtain a 25-30% by mass polyethyleneimine solution; and adding the polyethyleneimine solution to the carboxymethyl cellulose solution to obtain a crosslinker solution. S22: soaking the polytetrafluoroethylene membrane in a crosslinker solution for 15 to 30 minutes, adding a 2 to 3% by mass glutaraldehyde solution and reacting for 1 to 2 hours, and then removing and drying to obtain a modified polytetrafluoroethylene membrane; Step 3: S31: Disperse trimethoxysilane and Custer's catalyst in toluene, raise the temperature to 80-90°C under nitrogen protection, add a toluene solution of 4-vinylpyridine while maintaining the temperature, and react for 2-3 hours. After the reaction is completed, stop the nitrogen flow, remove the toluene by vacuum distillation, and dissolve the product in ethanol-ether solvent. Precipitate the precipitate with tetrahydrofuran precipitant, and dry to obtain vinylpyridine-grafted trimethoxysilane; S32: Vinylpyridine-grafted trimethoxysilane is dispersed in anhydrous ethanol, stirred and mixed uniformly, and then epichlorohydrin is added. The temperature is raised and refluxed for 24 to 30 hours, and then the reaction is stopped. After cooling to room temperature, a precipitate is precipitated with tetrahydrofuran, and the solvent is removed by filtration. The precipitate is washed with tetrahydrofuran and dried in vacuo to obtain an epoxy organosilicon quaternary ammonium salt; S33: dispersing an epoxy organosilicon quaternary ammonium salt in deionized water to obtain an epoxy organosilicon quaternary ammonium salt dispersion; immersing a modified polytetrafluoroethylene membrane in the epoxy organosilicon quaternary ammonium salt dispersion, reacting at 60-70° C. for 6-8 hours, removing the membrane, washing it with deionized water, and drying it to obtain a polytetrafluoroethylene membrane for air purification; In S21, 5 to 8 parts by weight of polyethyleneimine solution are added to 100 parts by weight of carboxymethyl cellulose solution to obtain a crosslinking agent solution; In S22, the polytetrafluoroethylene membrane is immersed in a cross-linking agent solution at a bath ratio of 1:(15-20).

2. The process for preparing a polytetrafluoroethylene membrane for air purification according to claim 1, characterized in that: In S11, the weight of the composite lubricant is 20-30% of the weight of the polytetrafluoroethylene powder; the amount of each component in the composite lubricant, by weight, is 10-30 parts of kerosene and 5-10 parts of silicone oil.

3. The process for preparing a polytetrafluoroethylene membrane for air purification according to claim 1, characterized in that: In S12, the longitudinal stretching ratio is 3 to 5 times, and the transverse stretching ratio is 2 to 3 times.

4. The process for preparing a polytetrafluoroethylene membrane for air purification according to claim 1, characterized in that: In S12, the sintering temperature is 285-320°C, and the sintering time is 90-120s.

5. The process for preparing a polytetrafluoroethylene membrane for air purification according to claim 1, characterized in that: In S31, trimethoxysilane and 4-vinylpyridine are reacted in a molar ratio of 1:

1.

6. The process for preparing a polytetrafluoroethylene membrane for air purification according to claim 1, characterized in that: In S32, vinylpyridine grafted trimethoxysilane and epichlorohydrin are reacted in a molar ratio of 1:

1.

7. The process for preparing a polytetrafluoroethylene membrane for air purification according to claim 1, characterized in that: In S33, the modified polytetrafluoroethylene membrane is immersed in an epoxy-based organosilicon quaternary ammonium salt dispersion at a bath ratio of 1:(10-15); the mass fraction of the epoxy-based organosilicon quaternary ammonium salt dispersion is 8-10%.

8. A polytetrafluoroethylene membrane for air purification prepared according to the preparation process of any one of claims 1 to 7.