Chloroethylene-vinyl acetate copolymer gas filter membrane, method for preparing the same, and use thereof

Abstract

The application provides a vinyl chloride-vinyl acetate copolymer gas filter membrane and a preparation method and application thereof, and relates to the technical field of gas filter membranes.The gas filter membrane provided by the application comprises a non-woven fabric support layer and a polymer coating layer; the polymer coating layer is arranged on the front and back surfaces of the non-woven fabric support layer; the casting solution comprises, in terms of mass fraction, 4-10 parts of vinyl chloride-vinyl acetate copolymer, 40-90 parts of a solvent and 10-60 parts of a pore former; in the vinyl chloride-vinyl acetate copolymer, the mass percentage of vinyl acetate is 1%-5%. The non-woven fabric support layer gives the membrane greater mechanical strength; the polymer coating layer is combined with the support layer closely, and can effectively filter solid particles in gas. The gas filter membrane has high flux, good water-blocking performance and good processing performance, and can be used as a gas filter membrane for laboratory or medical equipment.

Description

Technical Field

[0001] This invention relates to the field of gas filtration membrane technology, and in particular to a vinyl chloride-vinyl acetate copolymer gas filtration membrane, its preparation method, and its application. Background Technology

[0002] Microporous filtration membranes have a wide range of applications. For gas filtration membranes used in laboratory or medical equipment, the membranes are required to have high flux, high water resistance, and certain processing and service strength. PP, PTFE composite membranes and glass fiber are currently the main materials used.

[0003] Polyvinyl chloride (PVC) is an amorphous polymer with advantages such as good chemical stability, good physical stability, and resistance to microbial corrosion. Its low cost makes it a widely studied membrane material. PVC homopolymers or copolymers are prepared into hydrophilic flat sheet membranes or hollow fiber membranes, and their applications in wastewater treatment and other fields are extensively studied. Chinese patent publication CN110038453B discloses a reinforced PVC hollow fiber ultrafiltration membrane and its preparation method. The casting solution contains PVC, a pore-forming agent, a hydrophilic additive, a crosslinking agent, and a solvent. The resulting ultrafiltration membrane has a three-dimensional network structure, thus exhibiting high mechanical strength, good hydrophilicity, and hydrophilic stability, making it suitable for water treatment, especially water purification and wastewater treatment. However, this hollow fiber ultrafiltration membrane is only suitable for wastewater filtration and not for applications requiring water-blocking and aeration functions, such as the air inlet membrane of medical infusion sets or the vent membrane of urine bags, which can both prevent liquid leakage and filter solid suspended particles in the gas. Research on PVC in this area is limited. In his master's thesis, "Preparation and Performance Study of Superhydrophobic Medical Infusion and Exhaust Membrane," Wang Jincheng mentioned a method for preparing an enhanced PVC / PAN blend membrane, which has good water resistance and air flux performance. However, this preparation method still has problems such as the instability of the casting solution.

[0004] In summary, it is necessary to develop a hydrophobic PVC gas filtration membrane that is stable in casting solution, has high flux, high water resistance, and high strength.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The first objective of this invention is to provide a gas filtration membrane to solve at least one of the above-mentioned problems.

[0007] A second objective of the present invention is to provide a method for preparing the above-mentioned gas filter membrane.

[0008] A third objective of the present invention is to provide the application of the above-mentioned gas filter membrane in gas filtration.

[0009] In a first aspect, the present invention provides a gas filter membrane, comprising a nonwoven fabric support layer and a polymer coating;

[0010] The polymer coating is applied to both sides of the nonwoven fabric support layer;

[0011] The polymer coating is mainly prepared by a solvent-free phase inversion method from the casting solution.

[0012] The casting solution comprises, by weight parts: 4-10 parts of vinyl chloride-vinyl acetate copolymer, 40-90 parts of solvent and 10-60 parts of pore-forming agent;

[0013] In the vinyl chloride-vinyl acetate copolymer, the mass percentage of vinyl acetate is 1%-5%.

[0014] As a further technical solution, the casting solution comprises, by weight, 8 parts of vinyl chloride-vinyl acetate copolymer, 70 parts of solvent, and 22 parts of pore-forming agent.

[0015] As a further technical solution, the solvent includes at least one of dimethylformamide, dimethylacetamide, or methylpyrrolidone;

[0016] And / or, the pore-forming agent includes at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, polyethylene glycol 200, polyethylene glycol 400, and glycerol.

[0017] As a further technical solution, the gas filter membrane has a pore size of 0.1-10 μm and a thickness of 90-230 μm.

[0018] As a further technical solution, the polymer coating is hydrophobically modified.

[0019] Secondly, the present invention provides a method for preparing the above-mentioned gas filter membrane, comprising the following steps:

[0020] The casting solution is coated on both sides of the nonwoven fabric, and then left to stand to form a nascent film. The nascent film is then immersed in a coagulation bath for curing to prepare a gas filter membrane.

[0021] As a further technical solution, the conditions for the static setting include: a temperature of 20-25°C, a humidity of no more than 50%, and a time of 1-10 minutes.

[0022] As a further technical solution, the coagulation bath includes water or a mixture of water and ethanol.

[0023] As a further technical solution, the polymer coating is also modified to be hydrophobic after curing.

[0024] Thirdly, the present invention provides the application of the above-mentioned gas filter membrane in gas filtration.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The gas filter membrane provided by this invention comprises a nonwoven fabric support layer and a polymer coating disposed on both sides of the nonwoven fabric support layer. The nonwoven fabric support layer imparts high mechanical strength to the membrane; the polymer coating is mainly prepared by a solvent-free phase inversion method using a specific casting solution, and it bonds tightly with the support layer, effectively filtering solid particles in the gas. The gas filter membrane of this invention has high flux, good water resistance, and good processability, making it suitable for use as a gas filter membrane in laboratory or medical equipment. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a 10,000x scanning electron microscope image of the air surface of the gas filter membrane in Embodiment 1 of the present invention;

[0029] Figure 2 This is a 500x scanning electron microscope image of the air surface of the gas filter membrane in Embodiment 1 of the present invention;

[0030] Figure 3 This is a 500x scanning electron microscope image of the cross-section of the gas filter membrane in Embodiment 1 of the present invention. Detailed Implementation

[0031] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0032] In a first aspect, the present invention provides a gas filter membrane, comprising a nonwoven fabric support layer and a polymer coating;

[0033] The polymer coating is applied to both sides of the nonwoven fabric support layer;

[0034] The polymer coating is mainly prepared by a solvent-free phase inversion method from the casting solution.

[0035] The casting solution mainly consists of vinyl chloride-vinyl acetate copolymer, solvent, and pore-forming agent. By mass fraction, the mass fraction of vinyl chloride-vinyl acetate copolymer in the casting solution can be, for example, but not limited to, 4 parts, 6 parts, 8 parts, or 10 parts; the mass fraction of solvent can be, for example, but not limited to, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, or 90 parts; and the mass fraction of pore-forming agent can be, for example, but not limited to, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, or 60 parts.

[0036] In the vinyl chloride-vinyl acetate copolymer, the mass percentage of vinyl acetate can be, for example, but not limited to, 1%, 2%, 3%, 4%, or 5%. Compared with PVC homopolymer, the vinyl chloride-vinyl acetate copolymer has better ductility and adhesion, the polymer coating formed is not easily broken, and it adheres more firmly to porous nonwoven fabrics, making it more conducive to the preparation of reinforced films.

[0037] It should be noted that the mass percentage of vinyl acetate in the vinyl chloride-vinyl acetate copolymer of the present invention refers to the mass proportion of vinyl acetate in the raw materials for preparing the vinyl chloride-vinyl acetate copolymer.

[0038] Polyvinyl chloride has good hydrophobicity; therefore, this invention uses vinyl chloride-vinyl acetate copolymer as raw material to prepare a gas filter membrane.

[0039] The gas filter membrane provided by this invention comprises a nonwoven fabric support layer and a polymer coating disposed on both sides of the nonwoven fabric support layer. The nonwoven fabric support layer imparts high mechanical strength to the membrane; the polymer coating is mainly prepared by a solvent-free phase inversion method using a specific casting solution, and it bonds tightly with the support layer, effectively filtering solid particles in the gas. The gas filter membrane of this invention has high flux, good water resistance, and good processability, making it suitable for use as a gas filter membrane in laboratory or medical equipment.

[0040] In some alternative embodiments, the casting solution comprises, by weight, 8 parts of vinyl chloride-vinyl acetate copolymer, 70 parts of solvent, and 22 parts of pore-forming agent.

[0041] Further optimization and adjustment of the distribution ratio of each component in the casting solution resulted in better performance of the prepared gas filter membrane.

[0042] In some alternative embodiments, the solvent includes, but is not limited to, at least one of dimethylformamide, dimethylacetamide, or methylpyrrolidone. This solvent exhibits good solubility for vinyl chloride-vinyl acetate copolymers.

[0043] In some optional embodiments, the porogen includes, but is not limited to, at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, polyethylene glycol 200, polyethylene glycol 400, and glycerol. This porogen has low toxicity, is easy to clean later, provides good dispersibility of the polymer in the solvent, and forms a uniform network of pores.

[0044] In some alternative implementations, the process after curing includes cleaning and drying the gas filter membrane to remove organic reagents and water from the membrane.

[0045] In some optional embodiments, the pore size of the gas filter membrane may be, for example, but not limited to, 0.1um, 0.5um, 1um, 5um or 10um; and the thickness may be, for example, but not limited to, 90um, 100um, 150um, 200um or 230um.

[0046] In some optional embodiments, the thickness of the nonwoven fabric is 100-200um, for example, but not limited to 100um, 120um, 140um, 160um, 180um or 200um.

[0047] The thickness of the polymer coating on both sides of the nonwoven fabric is 1-10um, for example, but not limited to 1um, 2um, 4um, 6um, 8um or 10um.

[0048] In some alternative embodiments, the polymer coating is hydrophobically modified.

[0049] The polymer coating of the gas filter membrane of the present invention has good hydrophobicity. Through hydrophobic modification, the water-blocking performance of the gas filter membrane can be further enhanced.

[0050] Secondly, the present invention provides a method for preparing the above-mentioned gas filter membrane, comprising the following steps:

[0051] The casting solution is coated on both sides of the nonwoven fabric, and then left to stand to form a nascent film. The nascent film is then immersed in a coagulation bath for curing to prepare a gas filter membrane.

[0052] The preparation method provided by this invention is simple and easy to industrialize. The gas filter membrane prepared has high flux, good water resistance, and good processability, and can be used as a gas filter membrane for laboratory or medical equipment.

[0053] In some alternative implementations, the conditions for settling include: temperature, for example, but not limited to, 20°C, 21°C, 22°C, 23°C, 24°C, or 25°C; humidity not greater than 50%, for example, 10%, 20%, 30%, 40%, or 50%; and time, for example, but not limited to, 1 min, 2 min, 4 min, 6 min, 8 min, or 10 min.

[0054] In some alternative embodiments, the coagulation bath comprises water or a mixture of water and ethanol.

[0055] In some alternative embodiments, the polymer coating is further subjected to hydrophobic modification treatment after curing.

[0056] In some optional embodiments, the hydrophobic modification treatment method may, for example, involve immersing the prepared gas filter membrane in a hydrophobic treatment solution for 1-10 seconds, and then drying it in an oven at 70-100°C to obtain a hydrophobically modified gas filter membrane. The hydrophobic treatment agent consists of 0.5-5 parts by weight of a hydrophobic treatment agent stock solution, 20-60 parts by weight of ethanol, and 50-80 parts by weight of water. The hydrophobic treatment agent stock solution can be any one or more commercially available hydrophobic treatment agents.

[0057] In some alternative implementations, the coating method includes double-sided casting via dip-extraction.

[0058] Thirdly, the present invention provides the application of the above-mentioned gas filter membrane in gas filtration.

[0059] The gas filter membrane provided by this invention has high flux, good water resistance, and good processability, and can be used as a gas filter membrane for laboratory or medical equipment.

[0060] The present invention will be further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0061] It should be noted that the following hydrophobic treatment agent stock solution is Daikin TG-4574 from Japan.

[0062] Example 1

[0063] A vinyl chloride-vinyl acetate copolymer gas filtration membrane is prepared by the following method:

[0064] 8 wt% vinyl chloride-vinyl acetate copolymer (3% vinyl acetate by mass), 70 wt% dimethylacetamide, and 22 wt% butyl acetate were thoroughly stirred at room temperature to form a homogeneous and stable casting solution. After standing to remove bubbles, the solution was set aside. The film-forming environment was controlled at room temperature and humidity not exceeding 50%. The casting solution was cast on both sides of a nylon porous nonwoven fabric using an extraction method, and then passed through a doctor blade with a gap of 250 μm. After standing in air for 8 minutes, the nascent membrane was placed in a coagulation bath for final curing. The coagulation bath consisted of 20 wt% ethanol and 80 wt% pure water, and the coagulation bath temperature was room temperature. The membrane was then thoroughly rinsed with pure water and dried. The dried membrane was immersed in a hydrophobic treatment solution consisting of 2% hydrophobic treatment agent stock solution, 40% ethanol, and 58% pure water for 5 seconds, and then dried in a 90°C oven to obtain the final vinyl chloride-vinyl acetate copolymer gas filter membrane. Its electron micrograph is shown below. Figures 1-3 As shown.

[0065] Example 2

[0066] A vinyl chloride-vinyl acetate copolymer gas filter membrane differs from Example 1 in that the casting solution composition is: 4 parts vinyl chloride-vinyl acetate copolymer, 86 parts dimethylformamide, and 10 parts polyethylene glycol 200. The mass ratio of vinyl acetate in the vinyl chloride-vinyl acetate copolymer is 5%.

[0067] Example 3

[0068] A vinyl chloride-vinyl acetate copolymer gas filter membrane differs from Example 1 in that the casting solution comprises: 10 parts vinyl chloride-vinyl acetate copolymer, 40 parts methylpyrrolidone, and 50 parts methyl acetate. The mass ratio of vinyl acetate in the vinyl chloride-vinyl acetate copolymer is 1%.

[0069] Comparative Example 1

[0070] A gas filter membrane, differing from Example 1 in that the vinyl chloride-vinyl acetate copolymer is replaced with polyvinyl chloride.

[0071] Comparative Example 2

[0072] A gas filter membrane, which differs from Example 1 in that the vinyl chloride-vinyl acetate copolymer has a mass percentage of 20%.

[0073] Comparative Example 3

[0074] A PP film (commercial film 1) with the same thickness as in Example 1.

[0075] Comparative Example 4

[0076] An acrylic copolymer film (commercial film 2) has the same thickness as in Example 1.

[0077] Experimental Example 1

[0078] The membranes provided in Examples 1-3 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.

[0079] Table 1

[0080]

[0081] As can be seen from the table, the gas filter membrane provided by the present invention has comparable performance to the acrylic copolymer membrane provided in Comparative Example 4.

[0082] Experimental Example 2

[0083] The casting solution from Example 1 was stored at room temperature. The changes in the state of the casting solution were observed, and its viscosity was tested. The results are shown in the table below. It can be seen that the casting solution can remain stable for a long time.

[0084] 1 Clarity and transparency 118 3 Clarity and transparency 120 7 Clarity and transparency 115 14 Clarity and transparency 116 21 Clarity and transparency 123 30 Clarity and transparency 121

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gas filtration membrane, characterized in that, Includes a nonwoven support layer and a polymer coating; The polymer coating is applied to both sides of the nonwoven fabric support layer; The polymer coating is mainly prepared by a solvent-free phase inversion method from the casting solution. The casting solution comprises, by weight parts: 8 parts vinyl chloride-vinyl acetate copolymer, 70 parts solvent and 22 parts pore-forming agent; In the vinyl chloride-vinyl acetate copolymer, the mass percentage of vinyl acetate is 3%; The solvent includes at least one of dimethylformamide, dimethylacetamide, or methylpyrrolidone; The pore-forming agent includes at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, polyethylene glycol 200, polyethylene glycol 400, and glycerin. The polymer coating is hydrophobically modified.

2. The gas filter membrane according to claim 1, characterized in that, The gas filter membrane has a pore size of 0.1-10 μm and a thickness of 90-230 μm.

3. The method for preparing the gas filter membrane according to claim 1 or 2, characterized in that, Includes the following steps: The casting solution is coated on both sides of the nonwoven fabric, and then left to stand to form a nascent film. The nascent film is then immersed in a coagulation bath for curing to prepare a gas filter membrane. After curing, the process also includes hydrophobic modification of the polymer coating.

4. The preparation method according to claim 3, characterized in that, The conditions for static placement include: temperature of 20-25℃, humidity of no more than 50%, and time of 1-10 minutes.

5. The preparation method according to claim 3, characterized in that, The coagulation bath comprises water or a mixture of water and ethanol.

6. The application of the gas filter membrane according to claim 1 or 2 in gas filtration.

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