CN110732186A - A kind of porous air filter membrane and its preparation method and use - Google Patents

Abstract

The present invention provides a porous air filter membrane and its preparation method and use. The porous air filtration membrane includes a porous base material and a polymer layer with pyroelectric function overlying fibers of the porous base material. The porous air filtration membrane of the present invention can retain fine particles much smaller than its own pores, has high dust holding capacity, high filtration efficiency, low air filtration resistance, and can be regenerated for repeated use. The invention uses a spraying method to coat the polymer layer with pyroelectric function on the fibers of the porous base material, thereby preparing the porous air filtration membrane. The preparation method is simple, the preparation conditions are mild, the energy consumption is low, and the industrial production is easy.

Description

A kind of porous air filter membrane and its preparation method and use

technical field

The invention belongs to the field of composite materials, and in particular relates to a porous air filter membrane and a preparation method and application thereof.

Background technique

In the context of the continuous advancement of industrialization and urbanization, the consumption of energy and resources is also increasing, and the environmental pollution problems caused by this are becoming more and more important. At the same time, people's living standards are gradually improving, especially the air quality requirements for indoor and car airtight environments such as living, office, travel vehicles, leisure and entertainment places are also getting higher and higher, and the demand for various air purification products is increasing. more prosperous.

The core of the various air purification products currently on the market is the filtering medium. On the basis of the network, it is charged with a certain amount of electricity by applying high-voltage static electricity or corona, so that the filter material can improve the filtration efficiency as much as possible on the premise of ensuring low filtration air resistance. However, the main disadvantage of this type of material is that its electric charge is seriously affected by the use environment (such as high temperature, high humidity, etc.), so its service life is short and cannot be reused, and the waste after use will also produce dangerous Waste and other secondary pollution.

CN106237717A discloses a high-efficiency and low-resistance electrospinning nanofiber air filter material and a batch preparation method. The filter material is a sandwich structure in which spunbond non-woven fabric and nanofibers are arranged alternately; The nanofiber/microsphere composite membrane is prepared by the synchronous combination of electrospinning and electrostatic spraying. Although this invention can realize the mass production of nanofiber filter materials, it has low filtering ability for fine dust in the air, and The utilization rate of filter material regeneration and reuse is low.

CN107583377A discloses a functionalized graphene-modified air filter membrane and a preparation method thereof. The composite filter membrane includes two parts: a non-woven base support layer and an electrospinning composite fiber dense layer. Filter smoke, pollen, PM2.5 and other fine particles in the air, but when used for a long time, functionalized graphene is easy to agglomerate into large graphite particles, resulting in a decrease in adsorption capacity, and the air filter membrane is also difficult to regenerate for repeated use.

CN110028741A discloses a pyroelectric composite material and its preparation method and application. The composite material includes a pyroelectric polymer matrix material and an inorganic nanoparticle filler. The fiber network structure formed by the composite material has a large porosity and a weak adsorption capacity for fine particles such as PM2.5, and the composite material is prepared by a fusion hot pressing method, which has high material cost and high energy consumption.

Therefore, it is one of the current research priorities in this field to develop a filter material that has good filtering effect and can be regenerated for repeated use.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the purpose of the present invention is to provide a porous air filter membrane, its preparation method and use, which can absorb fine particles in the air and can be regenerated for repeated use.

In order to achieve this object of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a porous air filtration membrane, the porous air filtration membrane comprising a porous base material and a polymer layer with pyroelectric function covering fibers of the porous base material.

In the present invention, the electrostatic adsorption effect of the polymer layer with pyroelectric function is utilized to adsorb fine particles in the air. The pores of the filter material of the present invention are equivalent to countless passive dust collecting electrodes. When the polar fine particles in the air flow, especially the submicron particles pass through the pores of the material, they are captured under the action of electrostatic force. Neutral fine particles in the airflow become dipoles due to induction or polarization, which can also be effectively trapped.

In the present invention, the porous base material is combined with the polymer layer with pyroelectric function covering the fibers of the porous base material, so that the porous air filtration membrane maintains a relatively large porosity, high pore density, Under the premise that the pore size is also larger, the adsorption capacity for finer particles in the air is stronger.

Preferably, the porous base material is a needle-punched non-woven fabric.

The needle-punched non-woven fabric has a dense three-dimensional structure, and its pores are curved and circuitous channels. The pores between the fibers are larger, the filtration resistance is lower, and the filtration efficiency is also lower, which can retain dust particles equivalent to their own pores, and has a high dust holding capacity, which can still maintain a certain filtration effect under a larger filtration air volume. characteristics. In addition, needle punched non-woven fabrics also have the characteristics of moisture permeability, uniform structure and high strength.

Preferably, the needle-punched non-woven fabric includes polypropylene (PP) needle-punched non-woven fabric, polyethylene terephthalate (PET) needle-punched non-woven fabric, and polyamide (PA) needle-punched non-woven fabric Or any one or a combination of at least two of the polyimide (PI) needle punched non-woven fabrics.

Preferably, the density of the needle-punched non-woven fabric is above 50g/m ² , such as 50g/m ² , 60g/m ² , 70g/m ² , 80g/m ² , 90g/m ² , 100g/m ² , 110g/m ² , 120g/m ² , 130g/m ² , 140g/m ² , 150g/m ² , 160g/m ² , 170g/m ² , 180g/m ² , 190g/m ² , 200g/m ² , 210g/m ² , 220g/m ² , 230g/m ² , 240g/m ² , 250g/m ² , 300g/m ² , 350g/m ² , 400g/m ² , 450g/m ² , 500g/m ² .

Preferably, the density of the needle-punched non-woven fabric is 100-250 g/m ² , preferably 100-200 g/m ² .

Preferably, the thickness of the polymer layer with pyroelectric function is 0.1-10 μm, such as 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm , 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, preferably 0.2-2 μm.

As a preferred solution of the present invention, the thickness of the polymer layer with pyroelectric function is 0.2-2 μm. Within this range, it can not only ensure high filtration efficiency, but also ensure that the gas resistance will not be too large. The reason is that Because when the thickness of the polymer layer with pyroelectric function reaches 0.2μm, it can generate a sufficient amount of electrostatic charge, maintain a sufficient electrostatic field strength, and meet the requirements of adsorbing particles; but when the thickness exceeds 2μm, it will be due to a large amount of electrostatic charge. The reduction of porosity leads to excessive air resistance of the entire porous filter membrane.

Preferably, the polymer layer with pyroelectric function includes pyroelectric polymer and pyroelectric particles.

In the present invention, the pyroelectric polymer is used as an organic electret, and pyroelectric particles are added therein to increase the charge storage capacity, slow down the charge decay rate of the polymer layer, and improve fiber-forming properties. Therefore, when the fine particles in the atmosphere pass through, whether they are polar or can be polarized, they can be captured by the polymer layer with pyroelectric function, and in addition, the polymer layer with pyroelectric function can be extended the decay period of the layer, thereby extending its service life.

Preferably, the pyroelectric particles account for 0.1-20% of the total weight of the polymer layer with pyroelectric function, such as 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 10% , 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 17%, 18%, 19%, 20%.

Preferably, the pyroelectric polymer comprises polyvinylidene fluoride (PVDF) and/or polyamide-11 (PA-11).

In the present invention, the polyvinylidene fluoride (PVDF) is a stable and flexible organic material, which has strong piezoelectricity and pyroelectricity after being polarized. All the F atoms and H atoms of , are located on both sides of the molecular chain, respectively, in an all-trans conformation. Pyroelectric particles are added therein to increase the charge storage capacity and slow down the charge decay rate of the polymer layer.

In the present invention, the polyamide-11 has a long methylene chain in the molecular chain and a low density of amide groups, and pyroelectric particles are added to it to increase the charge storage capacity and slow down the charge decay of the polymer layer. speed and improve fiber forming performance.

Preferably, the polyvinylidene fluoride has a weight average molecular weight of 5,000-600,000, such as 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 20,000, 50,000, 80,000, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000.

Preferably, the weight average molecular weight of the polyamide-11 is 5000-200000, such as 5000, 6000, 8000, 10000, 12000, 14000, 16000, 18000, 20000, 30000, 50000, 80000, 100000, 150000, 200000 .

Preferably, the pyroelectric particles are pyroelectric electret inorganic micro-nano particles.

Preferably, the pyroelectric particles include lithium niobate and/or tourmaline.

Lithium niobate has a ferroelectric phase structure and belongs to the 3m point group. It is currently known as a ferroelectric with the highest Curie point and the largest spontaneous polarization trend. Therefore, a large amount of surface charges can be generated on the surface of the lithium niobate by simply adjusting the temperature, which has the advantages of simple electrification process and convenient operation. Since the fine particles in the atmosphere have a certain polarity or can be polarized, the polar particles in the air can be directly captured or neutral particles can be captured after being polarized by using the charge generated by lithium niobate pyroelectricity. Moreover, since the lithium niobate crystal does not suffer from dielectric loss, it can be repeatedly charged and the service life can be extended. Therefore, combining the pyroelectric properties of lithium niobate itself and the good power storage properties of polymer electret materials, the prepared polymer layer with pyroelectric function has both the pyroelectric effect of lithium niobate itself, It is also easy to fabricate an air filtration membrane with a porous structure.

Preferably, the particle size of the pyroelectric particles is 10-900 nm, such as 10 nm, 20 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm , 170nm, 180nm, 190nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, preferably 50-200nm.

As a preferred solution of the present invention, the particle size of the pyroelectric particles is 50-200 nm. If the particle size of the pyroelectric particles is too small, the pyroelectric properties cannot be guaranteed, and their ability to capture polarized neutral particles Relatively small, if the particle size of the pyroelectric particles is too large, the pyroelectric particles will seriously reduce the mechanical properties of the polymer matrix, and at the same time, the uniformity of the material will deteriorate, and the adsorption capacity of the filter membrane will decrease.

In a second aspect, the present invention provides a preparation method of the porous air filtration membrane according to the first aspect, the preparation method is: using a spraying method to coat a polymer layer with a pyroelectric function on the fibers of the porous base material to obtain the porous air filtration membrane.

Preferably, the preparation method specifically comprises the following steps:

(1) adding a solvent to the pyroelectric particles for dispersion, and then adding a pyroelectric polymer for mixing to obtain a polymer dispersion liquid containing the pyroelectric particles;

(2) After spraying the polymer dispersion liquid containing pyroelectric particles obtained in step (1) into the needle-punched non-woven fabric, drying and thermal polarization treatment are performed to obtain the porous air filter membrane.

Preferably, the solvent described in step (1) is N,N-dimethylformamide (DMF) and/or formic acid (FA).

Preferably, the dispersion in step (1) is ultrasonic dispersion.

Preferably, the ultrasonic dispersion time is 0.5-1 h, for example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h.

Preferably, the mixing temperature in step (1) is 60-70°C, such as 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C , 70℃.

Preferably, the mixing time in step (1) is 2-3h, for example, it can be 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3h .

Preferably, the concentration of the pyroelectric polymer in the polymer dispersion liquid containing pyroelectric particles in step (1) is 0.1-10 wt %, for example, it can be 0.1 wt %, 0.2 wt %, 0.4 wt %, 0.6 wt % wt%, 0.8wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%.

Preferably, after adding the pyroelectric polymer and mixing, the step (1) further includes the steps of secondary dispersion and defoaming.

Preferably, the time of the secondary dispersion is 1-2h, for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h.

Preferably, the defoaming is vacuum defoaming.

Preferably, the vacuum defoaming time is 10-30min, for example, 10min, 12min, 14min, 16min, 18min, 20min, 22min, 24min, 26min, 28min, 30min.

Preferably, the spraying in step (2) is spraying with a high-pressure spray gun.

Preferably, the spraying speed of the high-pressure spray gun is 0.5-30mL/min, such as 0.5mL/min, 1mL/min, 2mL/min, 4mL/min, 6mL/min, 8mL/min, 10mL/min, 12mL /min, 14mL/min, 16mL/min, 18mL/min, 20mL/min, 22mL/min, 24mL/min, 26mL/min, 28mL/min, 30mL/min.

Preferably, the drying in step (2) is drying in a blast drying oven.

Preferably, the temperature of the thermal polarization in step (2) is 90-150°C, such as 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc., preferably 90-120°C °C.

Preferably, the electric field strength of the thermal polarization in step (2) is 20-250MV/m, such as 20MV/m, 50MV/m, 100MV/m, 150MV/m, 200MV/m or 250MV/m, etc. , preferably 50-200MV/m.

Preferably, the time for the thermal polarization in step (2) is 5-60 min, for example, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, preferably 10-30 min.

Preferably, the preparation method specifically comprises the following steps:

(1) Add a solvent to the pyroelectric particles, ultrasonically disperse for 0.5-1h, then add the pyroelectric polymer, stir and mix at 60-70°C for 2-3h, and then perform secondary ultrasonic dispersion for 1-2h, vacuum Degassing for 10-30min to obtain a polymer dispersion containing pyroelectric particles;

(2) After spraying the polymer dispersion liquid containing pyroelectric particles obtained in step (1) into the needle-punched non-woven fabric with a high-pressure spray gun, put it into a blast drying oven to dry, and then heat it at 90-150 ° C. The polarization treatment is carried out for 5-60 min, and the electric field strength of the thermal polarization is 20-250 MV/m to obtain the porous air filtration membrane.

In a third aspect, the present invention provides the use of the porous air filtration membrane according to the first aspect, the porous air filtration membrane being used for adsorbing particulate matter in the atmosphere.

Preferably, the particulate matter includes oily particulate matter and/or non-oily particulate matter.

Preferably, after the composite material adsorbs fine particles in the atmosphere, a method of cleaning combined with heat treatment is used to regenerate and reuse the porous air filter membrane.

As a preferred technical solution of the present invention, after the composite material adsorbs the particulate matter in the atmosphere and reaches saturation, cleaning and water washing are used for desorption, and then heat treatment is used for regeneration.

In the present invention, the method of cleaning, water desorption and heating regeneration is specifically as follows: when the pyroelectric composite material adsorbs fine particles and reaches saturation, clean it with a brush, and then put it into an ultrasonic cleaning tank for ultrasonic treatment , desorb the fine particles adsorbed on the surface; reheat the pyroelectric material based on the pyroelectric polymer/inorganic particle composite system at a certain temperature, so that the surface of the pyroelectric composite material re-exhibits charge, thereby pyroelectric Electrocomposites can re-adsorb fine particulate matter, enabling regeneration for reuse.

Preferably, the cleaning is ultrasonic cleaning.

Preferably, the temperature of the heat treatment is 40-120°C, such as 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C, etc., preferably 40-70°C °C.

Preferably, the time of the heat treatment is 0.1-2min, for example, it can be 0.1min, 0.2min, 0.5min, 0.6min, 0.8min, 1min, 1.2min, 1.5min, 1.8min or 2min, preferably 0.5-2min .

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

The porous air filtration membrane of the present invention includes a porous base material and a polymer layer with pyroelectric function covering the fibers of the porous base material, and has relatively high porosity, high pore density and large pore size. It can retain fine particles much smaller than its own pores, and has the advantages of high dust holding capacity, high filtration efficiency, low air filtration resistance, and the ability to be regenerated and reused for many times.

Description of drawings

FIG. 1 is a scanning electron microscope (SEM) image of the polypropylene needle-punched nonwoven fabric.

FIG. 2 is a scanning electron microscope (SEM) image of lithium niobate micro-nanoparticles.

FIG. 3 is a scanning electron microscope (SEM) image of tourmaline micro-nano particles.

FIG. 4 is a scanning electron microscope (SEM) image of the porous air filtration membrane prepared in Example 1. FIG.

FIG. 5 is a scanning electron microscope (SEM) image of the porous air filtration membrane prepared in Example 8. FIG.

Detailed ways

The technical solutions of the present invention are further described below through specific embodiments. It should be understood by those skilled in the art that the embodiments are only for helping the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

Example 1

This embodiment provides a porous air filter membrane, the porous air filter membrane includes a polypropylene (PP) needle-punched non-woven fabric and a polymer with pyroelectric function covered on the fibers of the polypropylene needle-punched non-woven fabric layer comprising polyvinylidene fluoride (PVDF) and lithium niobate (LN) nanoparticles.

The preparation method of this embodiment specifically comprises the following steps:

(1) Preparation of PVDF solution doped with LN nanoparticles

Add 0.04g LN nanoparticles (average particle size is about 200nm) into a stoppered conical flask containing 98g DMF solvent, ultrasonically disperse for 0.5h, then add 2g PVDF powder (weight average molecular weight is 200000), stir at 65°C Dissolved uniformly for 3 hours to obtain a uniform solution, ultrasonically dispersed again for 1 hour, and then vacuum defoamed for 10 minutes, wherein the concentration of PVDF was 2wt%, and the mass concentration of LN nanoparticles was 2% of the amount of PVDF.

(2) Preparation of porous air filter membrane by spraying method

The PVDF solution prepared in step (1) was added to the pot of the pneumatic spray gun, and the PVDF solution was sprayed into the PP needle-punched non-woven fabric substrate (the non-woven fabric density was 150 g/m ² ) at a spray rate of 3 mL/min using high-pressure gas. , a coating layer about 0.2 μm thick is formed on its fibers. Then put it into a blast drying oven for drying treatment, and then perform thermal polarization treatment at 120° C. for 10 minutes, and the electric field strength of the thermal polarization is 100 MV/m to obtain the porous air filtration membrane.

The scanning electron microscope image of the polypropylene needle-punched nonwoven fabric is shown in Figure 1, and its fiber diameter is about 5-15 μm. The scanning electron microscope image of lithium niobate micro-nanoparticles is shown in Fig. 2, and its diameter is about 100-600 nm. The scanning electron microscope image of the porous air filtration membrane prepared in Example 1 is shown in Figure 4. It can be seen from Figure 4 that the polymer layer with pyroelectric function is covered on the fibers of the porous base material, and its thickness is about is 0.2 μm. Porous air filtration membranes have relatively large porosity, large pore density and large pore size, but due to the electrostatic effect of the pyroelectric polymer layer, dust particles that are much smaller than their own pores can be retained. (The microscope model is JSM-7500F from JEOL, Japan)

Example 2

The same as in Example 1, the only difference is that the thickness of the polymer layer with pyroelectric function covering the fibers of the polypropylene needle-punched non-woven fabric is 0.5 μm.

Example 3

The same as in Example 1, the only difference is that the thickness of the polymer layer with pyroelectric function covering the fibers of the polypropylene needle-punched non-woven fabric is 1 μm.

Example 4

Same as Example 1, the only difference is that the thickness of the polymer layer with pyroelectric function covering the fibers of the polypropylene needle-punched non-woven fabric is 2 μm.

Example 5

The same as in Example 1, the only difference is that the thickness of the polymer layer with pyroelectric function covering the fibers of the polypropylene needle-punched non-woven fabric is 5 μm.

Example 6

Same as Example 1, the only difference is that the thickness of the polymer layer with pyroelectric function covering the fibers of the polypropylene needle-punched non-woven fabric is 8 μm.

Example 7

This embodiment provides a porous air filter membrane, the porous air filter membrane includes a polypropylene (PP) needle-punched non-woven fabric and a polymer with pyroelectric function covered on the fibers of the polypropylene needle-punched non-woven fabric layer comprising polyamide-11 (PA-11) and lithium niobate (LN) nanoparticles.

(1) Preparation of PA-11 solution doped with LN nanoparticles

Add 0.02g of LN nanoparticles (average particle size is about 200nm) into a stoppered conical flask containing 99g of FA solvent, ultrasonically disperse for 1h, then add 1g of PA-11 particles (weight average molecular weight is 30000), room temperature Stir under stirring for 3h to dissolve uniformly to obtain a homogeneous solution, ultrasonically dispersed again for 2h, and then vacuum defoamed for 20min, wherein the concentration of PA-11 is 1wt%, and the mass concentration of LN nanoparticles is 2% of the amount of PA-11.

(2) Preparation of porous air filter membrane by spraying method

The PA-11 solution prepared in step (1) was added to the pot of the pneumatic spray gun, and the PA-11 solution was sprayed into the PP needle-punched non-woven substrate (the non-woven fabric density was 150 g at a spray rate of 2 mL/min) using high pressure gas. /m ² ), a coating layer of about 0.3 μm thick is formed on the fibers thereof. Then put it into a blast drying oven for drying treatment, and then perform thermal polarization treatment at 100° C. for 40 min. The electric field strength of the thermal polarization is 120 MV/m to obtain the porous air filter membrane.

Example 8

This embodiment provides a porous air filter membrane, the porous air filter membrane includes a polypropylene (PP) needle-punched non-woven fabric and a polymer with pyroelectric function covered on the fibers of the polypropylene needle-punched non-woven fabric layer comprising polyamide-11 (PA-11) and tourmaline nanoparticles.

(1) Preparation of PA 11 solution doped with tourmaline nanoparticles

Add 0.04g of tourmaline nanoparticles (average particle size is about 200nm) into a stoppered conical flask containing 98g of DMF, ultrasonically disperse for 1h, then add 2g of PVDF powder (weight average molecular weight is 200000), stir at 65°C for 3h Dissolve uniformly to obtain a uniform solution, ultrasonically dispersed again for 1.5h, and then vacuum defoamed for 20min, wherein the concentration of PVDF is 2wt%, and the mass concentration of tourmaline nanoparticles is 2% of the amount of PVDF.

(2) Preparation of reusable porous air filter membrane with pyroelectric function by spraying method

The PVDF solution prepared in step (1) was added to the pot of the pneumatic spray gun, and the PVDF solution was sprayed into the PP needle-punched non-woven fabric substrate (the non-woven fabric density was 150 g/m ² ) at a spray rate of 3 mL/min using high-pressure gas. , a coating layer about 0.2 μm thick is formed on its fibers. Then put it into a blast drying oven for drying treatment, and then perform thermal polarization treatment at 90° C. for 30 min. The electric field strength of the thermal polarization is 200 MV/m to obtain the porous air filtration membrane.

The scanning electron microscope (SEM) image of tourmaline micro-nano particles is shown in Figure 3. It can be seen from Figure 3 that its diameter is about 100-700 nm. The scanning electron microscope image of the porous air filtration membrane prepared in Example 8 is shown in Figure 5 As shown in FIG. 5 , it can be seen from FIG. 5 that the polymer layer with pyroelectric function covers the fibers of the porous base material, and its thickness is about 0.2 μm. Porous air filtration membranes have relatively large porosity, large pore density and large pore size, but due to the electrostatic charge of pyroelectric materials, they can retain dust particles that are much smaller than their own pores.

Example 9

This embodiment provides a porous air filter membrane, the porous air filter membrane includes a polyethylene terephthalate (PET) needle-punched non-woven fabric and a polyethylene terephthalate (PET) A polymer layer with a pyroelectric function on the fibers of a needle punched nonwoven fabric, the polymer layer comprising polyvinylidene fluoride (PVDF) and lithium niobate (LN) nanoparticles.

The preparation method of this embodiment specifically comprises the following steps:

(1) Preparation of PVDF solution doped with LN nanoparticles

Add 0.04g LN nanoparticles (average particle size is about 200nm) into a stoppered conical flask containing 98g DMF solvent, ultrasonically disperse for 0.5h, then add 2g PVDF powder (weight average molecular weight is 200000), stir at 65°C Dissolve uniformly for 3 hours to obtain a homogeneous solution, ultrasonically dispersed again for 1 hour, and then vacuum defoamed for 10 minutes, wherein the concentration of PVDF is 2wt%, and the mass concentration of tourmaline nanoparticles is 2% of the amount of PVDF.

(2) Preparation of porous air filter membrane by spraying method

The PVDF solution prepared in step (1) was added to the pot of the pneumatic spray gun, and the PVDF solution was sprayed into polyethylene terephthalate (PET) (the non-woven density was 150 g/m ² ), a coating layer of about 2 μm thick was formed on its fibers. Then put it into a blast drying oven for drying treatment, and then perform thermal polarization treatment at 120° C. for 10 min. The electric field strength of the thermal polarization is 100 MV/m to obtain the porous air filter membrane.

Example 10

This embodiment provides a porous air filter membrane, the porous air filter membrane includes a polypropylene (PP) needle-punched non-woven fabric and a polymer with pyroelectric function covered on the fibers of the polypropylene needle-punched non-woven fabric layer comprising polyvinylidene fluoride (PVDF) and lithium niobate (LN) nanoparticles.

The preparation method of this embodiment specifically comprises the following steps:

(1) Preparation of PVDF solution doped with LN nanoparticles

Add 0.04g LN nanoparticles (average particle size is about 200nm) into a stoppered conical flask containing 98g DMF solvent, ultrasonically disperse for 0.5h, then add 2g PVDF powder (weight average molecular weight is 200000), stir at 65°C Dissolve uniformly for 3 hours to obtain a homogeneous solution, ultrasonically dispersed again for 1 hour, and then vacuum defoamed for 10 minutes, wherein the concentration of PVDF is 2wt%, and the mass concentration of tourmaline nanoparticles is 2% of the amount of PVDF.

(2) Preparation of porous air filter membrane by spraying method

The PVDF solution prepared in step (1) was added to the pot of the pneumatic spray gun, and the PVDF solution was sprayed into the PP needle-punched non-woven substrate (the non-woven fabric density was 50 g/m ² ) at a spray rate of 3 mL/min by using high pressure gas. , a coating layer about 2 μm thick is formed on its fibers. Then put it into a blast drying oven for drying treatment, and then perform thermal polarization treatment at 120° C. for 10 minutes, and the electric field strength of the thermal polarization is 100 MV/m to obtain the porous air filtration membrane.

Example 11

This embodiment provides a porous air filter membrane, the porous air filter membrane includes a polypropylene (PP) needle-punched non-woven fabric and a polymer with pyroelectric function covered on the fibers of the polypropylene needle-punched non-woven fabric layer comprising polyvinylidene fluoride (PVDF) and barium titanate nanoparticles.

The preparation method of this embodiment specifically comprises the following steps:

(1) Preparation of PVDF solution doped with barium titanate particles

Add 0.04g of barium titanate nanoparticles (average particle size is about 200nm) into a stoppered conical flask containing 98g of DMF solvent, ultrasonically disperse for 0.5h, then add 2g of PVDF powder (weight average molecular weight is 200000), 65 Stir at °C for 3 hours to obtain a uniform solution, ultrasonically dispersed for 1 hour again, and then vacuum defoamed for 10 minutes, wherein the concentration of PVDF is 2wt%, and the mass concentration of barium titanate particles is 2% of the amount of PVDF.

(2) Preparation of porous air filter membrane by spraying method

The PVDF solution prepared in step (1) was added to the pot of the pneumatic spray gun, and the PVDF solution was sprayed into the PP needle-punched non-woven fabric substrate (the non-woven fabric density was 150 g/m ² ) at a spray rate of 3 mL/min using high-pressure gas. , a coating layer about 2 μm thick is formed on its fibers. Then put it into a blast drying oven for drying treatment, and then perform thermal polarization treatment at 120° C. for 10 minutes, and the electric field strength of the thermal polarization is 100 MV/m to obtain the porous air filtration membrane.

Comparative Example 1

This comparative example provides a filter membrane, which is the same as Example 4, except that the filter membrane only contains a porous base material layer, and does not contain a polymer with pyroelectric function covering the fibers of the porous base material Floor.

Comparative Example 2

This comparative example provides a filter membrane, which is the same as Example 4, except that the filter membrane only contains a fiber membrane (fiber diameter of about 30-100 μm, gram weight of about 150 μm) prepared from a polymer layer with pyroelectric function. g/m ² ) without porous substrate material.

Test Example 1

Filtration efficiency and air resistance test

The filtration efficiency and air resistance of the porous filtration membranes prepared in the above-mentioned examples 1-11 and the filtration membranes prepared in the comparative examples 1-2 were carried out. The testing instrument was the 8130 type filter material tester of TSI company in the United States, and the test method was: use 2wt% NaCl solution , the mass median diameter of aerosol particles is about 0.26μm, and the air flow rate is 32L/min (the air flow rate is about 0.053m/s). The specific test results are shown in Table 1.

Table 1

project PM0.3 Filtration Efficiency/% Air resistance/Pa Example 1 85 39 Example 2 90 42 Example 3 92 45 Example 4 95 49 Example 5 96 78 Example 6 97 95 Example 7 86 41 Example 8 84 37 Example 9 94 47 Example 10 78 34 Example 11 91 44 Comparative Example 1 63 28 Comparative Example 2 45 25

It can be seen from the test data in Table 1 that the PM0.3 filtration efficiency of the porous filter membrane prepared by the present invention is more than 78%. As the preferred solution of this embodiment, the PM0.3 filtration efficiency of the prepared porous filter membrane is as high as 95% or more, and the filtration air resistance can be It reaches below 50Pa, which is better than the filtration membrane prepared in Comparative Examples 1-2. This shows that the porous air filtration membrane of the present invention has relatively small porosity, large pore density, small pore size, and can retain dust particles much smaller than its own pores, and has high dust holding capacity and high filtration efficiency. , Air filtration resistance is low.

Test Example 2

Porous air filter membrane regeneration test

The porous filter membrane prepared in Example 4, the porous filter membrane prepared in Example 8-11, and the filter membrane prepared in Comparative Example 1-2 were repeatedly processed, and then the filtration efficiency and air resistance were tested. Example 4. The porous air filtration membranes prepared in Examples 8-11 and the filtration membranes prepared in Comparative Examples 1-2 were subjected to multiple dust holdings in the same environment, and then placed in ultrasonic equipment for ultrasonic cleaning; then placed in an oven at 60°C medium heat treatment, so that the filter membrane can be regenerated, and the specific test results are shown in Table 2.

Table 2

It can be seen from the test data in Table 2 that after the porous air filtration membrane prepared by the present invention adsorbs fine particles for many times and reaches saturation, it is put into an ultrasonic cleaning tank for ultrasonic treatment, and the fine particles adsorbed on the surface can be desorbed; The pyroelectric material of the pyroelectric polymer/inorganic particle composite system can enable the pyroelectric composite material to re-adsorb fine particles, and realize regeneration and repeated use of the filter membrane. The porous air filter membrane of the present invention can still achieve PM0.3 filtration efficiency of more than 80% after repeated cleaning for 10 times, and the air resistance can be guaranteed to be less than 55Pa. The method realizes regeneration and can be used repeatedly, and its filtration efficiency only decreases slightly.

The applicant declares that the present invention illustrates the porous air filtration membrane of the present invention and its preparation method and use by the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented . Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the selected raw materials of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (10)

What is claimed is: 1. A porous air filtration membrane, characterized in that, the porous air filtration membrane comprises a porous base material and a polymer layer with a pyroelectric function covering the fibers of the porous base material. 2. The porous air filter membrane according to claim 1, wherein the porous base material is needle punched non-woven fabric; Preferably, the needle-punched non-woven fabric includes polypropylene needle-punched non-woven fabric, polyethylene terephthalate needle-punched non-woven fabric, polyamide needle-punched non-woven fabric or polyimide needle-punched non-woven fabric Any one or a combination of at least two of the cloths; Preferably, the density of the needle-punched non-woven fabric is more than 50g/ ^m2 ; Preferably, the density of the needle-punched non-woven fabric is 100-250 g/m ² , preferably 100-200 g/m ² . 3. The porous air filtration membrane according to claim 1 or 2, wherein the thickness of the polymer layer with pyroelectric function is 0.1-10 μm, preferably 0.2-2 μm; Preferably, the polymer layer with pyroelectric function includes pyroelectric polymer and pyroelectric particles; Preferably, the pyroelectric particles account for 0.1-20% of the total weight of the polymer layer with pyroelectric function. 4. The porous air filtration membrane according to any one of claims 1-3, wherein the pyroelectric polymer comprises polyvinylidene fluoride and/or polyamide-11; Preferably, the weight average molecular weight of the polyvinylidene fluoride is 5000-600000; Preferably, the weight average molecular weight of the polyamide-11 is 5,000-200,000. 5. The porous air filter membrane according to any one of claims 1-4, wherein the pyroelectric particles are pyroelectric electret inorganic micro-nano particles; Preferably, the pyroelectric particles include lithium niobate and/or tourmaline; Preferably, the particle size of the pyroelectric particles is 10-900 nm, preferably 50-200 nm. 6. according to the preparation method of the porous air filtration membrane described in any one of claim 1-5, it is characterized in that, described preparation method is: use spray method to cover the polymer layer with pyroelectric function on porous base material on the fibers to obtain the porous air filtration membrane. 7. preparation method according to claim 6, is characterized in that, described preparation method specifically comprises the following steps: (1) adding a solvent to the pyroelectric particles for dispersion, and then adding a pyroelectric polymer for mixing to obtain a polymer dispersion liquid containing the pyroelectric particles; (2) after spraying the polymer dispersion liquid containing pyroelectric particles obtained in step (1) into the needle punched nonwoven fabric, drying and thermal polarization treatment are carried out to obtain the porous air filter membrane; Preferably, the solvent described in step (1) is N,N-dimethylformamide and/or formic acid; Preferably, the dispersion described in step (1) is ultrasonic dispersion; Preferably, the ultrasonic dispersion time is 0.5-1h; Preferably, the mixing temperature in step (1) is 60-70°C; Preferably, the mixing time of step (1) is 2-3h; Preferably, the concentration of the pyroelectric polymer in the polymer dispersion liquid containing pyroelectric particles in step (1) is 0.1-10wt%; Preferably, after adding the pyroelectric polymer and mixing in step (1), it also includes the steps of secondary dispersion and defoaming; Preferably, the time of the secondary dispersion is 1-2h; Preferably, the defoaming is vacuum defoaming; Preferably, the vacuum defoaming time is 10-30min; Preferably, the spraying described in step (2) is spraying with a high-pressure spray gun; Preferably, the spraying speed of the high-pressure spray gun is 0.5-30 mL/min, preferably 0.5-5 mL/min; Preferably, the drying described in step (2) is drying in a blast drying oven; Preferably, the temperature of the thermal polarization in step (2) is 90-150°C, preferably 90-120°C; Preferably, the electric field strength of the thermal polarization in step (2) is 20-250MV/m, preferably 50-200MV/m; Preferably, the time of the thermal polarization in step (2) is 5-60 min, preferably 10-30 min. 8. preparation method according to claim 6 or 7, is characterized in that, described preparation method specifically comprises the following steps: (1) Add solvent to pyroelectric particles, disperse by ultrasonic for 0.5-1h, then add pyroelectric polymer, stir and mix at 60-70°C for 2-3h, then carry out secondary ultrasonic dispersion for 1-2h, vacuum Degassing for 10-30min to obtain a polymer dispersion containing pyroelectric particles; (2) After spraying the polymer dispersion liquid containing pyroelectric particles obtained in step (1) into the needle-punched non-woven fabric with a high-pressure spray gun, put it into a blast drying oven to dry, and then heat it at 90-150 ° C. The polarization treatment is carried out for 5-60 min, and the electric field strength of the thermal polarization is 20-250 MV/m to obtain the porous air filtration membrane. 9. The use of the porous air filtration membrane according to any one of claims 1-5, wherein the porous air filtration membrane is used to adsorb particulate matter in the atmosphere; Preferably, the particulate matter includes oily particulate matter and/or non-oily particulate matter. 10. The use according to claim 9, characterized in that, after the composite material adsorbs fine particles in the atmosphere, a method of cleaning combined with heat treatment is used to regenerate and reuse the porous air filter membrane; Preferably, the cleaning is ultrasonic cleaning; Preferably, the temperature of the heat treatment is 40-120°C, preferably 40-70°C; Preferably, the time of the heat treatment is 0.1-2 min, preferably 0.5-2 min.

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