CN110812947A - Electret non-woven filter material with cavity structure and preparation method thereof - Google Patents
Electret non-woven filter material with cavity structure and preparation method thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/14—Other self-supporting filtering material ; Other filtering material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/14—Other self-supporting filtering material ; Other filtering material
- B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
- B01D39/1607—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous
- B01D39/1623—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous of synthetic origin
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
- D01D5/30—Conjugate filaments; Spinnerette packs therefor
- D01D5/34—Core-skin structure; Spinnerette packs therefor
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- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
- D04H1/4382—Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/02—Types of fibres, filaments or particles, self-supporting or supported materials
- B01D2239/0216—Bicomponent or multicomponent fibres
- B01D2239/0233—Island-in-sea
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/04—Additives and treatments of the filtering material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/04—Additives and treatments of the filtering material
- B01D2239/0407—Additives and treatments of the filtering material comprising particulate additives, e.g. adsorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
- B01D2239/0604—Arrangement of the fibres in the filtering material
- B01D2239/0618—Non-woven
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
- B01D2239/0604—Arrangement of the fibres in the filtering material
- B01D2239/0622—Melt-blown
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/10—Filtering material manufacturing
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Abstract
The invention provides an electret non-woven filter material with a cavity structure and a preparation method thereof. The filter material comprises an outer layer fiber tube and nano-fiber filaments nested in the outer layer fiber tube. The outer layer fiber pipe is composed of polyolefin fibers and electret material micro-nano particles loaded on the surfaces of the polyolefin fibers. The electret material micro-nano particles are loaded on the surface of the polyolefin fiber through the jet of melt-blown air flow, and under the action of the jet of the air flow, the electret material micro-nano particles and the polyolefin fiber generate electret charges through the friction action. The nanometer fiber is thermoplastic polyester fiber with the diameter less than or equal to 200 nm. According to the invention, through the friction action of the polyolefin fiber tube loaded with the electret material micro-nano particles with the lower dielectric constant at the outer layer and the polyester nanofiber silk with the relatively higher dielectric constant at the inner layer, electret charge is continuously formed, so that the electrostatic adsorption durability is improved.
Description
Technical Field
The invention belongs to the technical field of filter materials, and particularly relates to an electret non-woven filter material with a cavity structure and a preparation method thereof.
Background
With the increasing living standard, people pay more attention to the index of PM2.5 (fine particulate matter with the particle size of below 2.5 microns) in the air. Suspended particles can be inhaled in the air, and can directly cause serious harm to the respiratory tract, the cardiovascular system and the central nervous system of human beings after entering the human bodies, even possibly cause lung and systemic inflammation, increase the risk of arteriosclerosis and hyperlipidemia, and cause symptoms of arrhythmia, blood pressure rise and the like. Therefore, how to remove these dust-containing gases has become an urgent problem to be solved.
In recent years, electret filter materials become important ways for effectively preventing and treating PM2.5 pollution, and the filtration efficiency is improved by utilizing the synergistic effect of a mechanical filtration mechanism and an electrostatic adsorption mechanism. The electret fiber material can be effectively charged with static electricity by the electret technology, and the modes of thermal polarization, corona discharge, electrostatic spinning, friction electrification and the like are common electret methods which are researched and applied to non-woven filter materials at present. For example, the invention patent with the application number of CN201610233859.6 discloses an electret non-woven filter material for air filtration, which is prepared by mixing and carding PET/PET island-shaped sea-island short fibers and PE/PET skin-core composite short fibers according to a certain mass ratio, and then carrying out needle-punching to form a net, alkali liquor ablation, rolling and washing, PTFE emulsion impregnation, tentering and heat setting, and cooling and curing. When the fabric is subjected to needling processing, mutual friction among fibers generates electron transfer to charge, and the PTFE has high electron work function and low dielectric constant, so that the electrostatic adsorption effect on PM2.5 dust is good; in addition, the attenuation of static electricity is also weak in humid air due to the super-hydrophobic property.
However, the above prior art also has the following drawbacks: (1) in the needling process, a large amount of charges are generated by friction between the fibers and the metal card clothing, and the charges are easy to dissipate in the needling process; (2) a PTFE coating layer is formed by adopting an emulsion impregnation method, and the coating fastness is difficult to ensure; (3) it is difficult to extend the electrostatic charge decay period of the filter material to a greater extent only by virtue of the superhydrophobic property.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an electret non-woven filter material with a cavity structure and a preparation method thereof. The electret material micro-nano particles are sprayed and loaded on the surface of the polyolefin fiber through melt-blown airflow; the nanometer fiber is thermoplastic polyester fiber with the diameter less than or equal to 200 nm. Therefore, through the friction action of the polyolefin fiber tube loaded with the electret material micro-nano particles with the lower dielectric constant at the outer layer and the polyester nanofiber silk with the relatively higher dielectric constant at the inner layer, electret charge is continuously formed, and therefore the electrostatic adsorption durability is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
an electret nonwoven filter material having a cavity structure, comprising: the device comprises an outer-layer fiber tube and nano-fiber filaments nested in the outer-layer fiber tube; the outer layer fiber pipe consists of polyolefin fibers and electret material micro-nano particles loaded on the surfaces of the polyolefin fibers; the nano-fiber yarn is thermoplastic polyester fiber yarn and is obtained by melt spinning and phase separation of thermoplastic polyester and matrix which are thermodynamically incompatible.
Furthermore, the electret material micro-nano particles are loaded on the surface of the polyolefin fiber through jet blowing of melt-blown air flow, and under the action of jet blowing of the air flow, the electret material micro-nano particles and the polyolefin fiber generate electret charges through a friction action.
Further, the diameter of the nanofiber filaments is less than or equal to 200 nm; the average particle size of the electret material micro-nano particles is less than or equal to 1 mu m, and the loading capacity of the electret material micro-nano particles is 3-12 wt% of the mass of the polyolefin fiber.
Furthermore, the thickness of the electret non-woven filter material with the cavity structure is 0.2-5 mm, the interception efficiency of the electret non-woven filter material on micro dust with the diameter of more than or equal to 0.3 mu m in air is more than or equal to 99.5%, the filter resistance is less than or equal to 30Pa, the surface electrostatic voltage is more than or equal to 3.2kV, and the electrostatic voltage after being placed for 4 months is more than or equal to 3 kV.
Further, the polyolefin fiber is any one of polypropylene fiber, polyethylene fiber or polyvinyl chloride; the electret material micro-nano particles are polytetrafluoroethylene micro-nano particles; the matrix is any one of cellulose acetate, ethyl cellulose or cellulose acetate butyrate.
The preparation method of the electret non-woven filter material with the cavity structure comprises the following steps:
s1, melting polyolefin to obtain a melt spinning raw material a, and melting and blending thermoplastic polyester which is thermodynamically incompatible with matrix according to a preset mass ratio to obtain a melt spinning raw material b;
s2, spraying the melt spinning raw material a and the melt spinning raw material b in the step S1 from a double-channel coaxial spinneret hole for melt spinning;
wherein, the melt spinning raw material a is sprayed out from an outer layer spinneret orifice, and the melt spinning raw material b is sprayed out from an inner layer spinneret orifice;
s3, blowing the polymer melt fiber sprayed from the spinneret orifice by using the melt-blown airflow dispersed with the electret material micro-nano particles to obtain a skin-core structure fiber with the surface loaded with the electret material micro-nano particles;
s4, laying the skin-core structure fibers in the step S3 into a net through a receiving device to obtain a skin-core structure fiber net;
s5, the fiber net with the skin-core structure in the step S4 is subjected to solvent extraction, the matrix in the step S1 is removed, and then electret treatment is carried out, so that the electret non-woven filter material with the cavity structure is obtained.
Further, in step S1, the preset mass ratio is 1:9 to 3: 7.
Further, in step S2, the receiving distance of the melt spinning is 8 to 30cm, the diameter of the inner layer spinneret orifice of the dual-channel coaxial spinneret orifice is 0.1 to 1mm, and the diameter of the outer layer spinneret orifice is 0.1 to 2 mm.
Further, in step S3, the temperature of the melt-blown airflow is 280-320 ℃, the flow rate of the melt-blown airflow is 300-500 m/S, and the ejection volume of the electret material micro-nano particles is 30-80 mg/S.
Further, in step S5, the solvent is acetone; the electret treatment is corona discharge electret treatment.
Advantageous effects
Compared with the prior art, the electret non-woven filter material with the cavity structure and the preparation method thereof have the following beneficial effects:
(1) the electret non-woven filter material with the cavity structure comprises an outer-layer fiber tube and nano-fiber filaments embedded in the outer-layer fiber tube, wherein the outer-layer fiber tube consists of polyolefin fibers and electret material micro-nano particles loaded on the surfaces of the polyolefin fibers; the nanometer fiber is thermoplastic polyester fiber with the diameter less than or equal to 200 nm. Under the condition of air circulation, electret charge is continuously formed through the friction action of the outer polyolefin fiber tube with lower dielectric constant and the inner polyester nanofiber yarn with relatively higher dielectric constant, so that the durability of electrostatic adsorption is improved.
(2) The invention provides a preparation method of an electret non-woven filter material with a cavity structure, which comprises the steps of selecting polyolefin with relatively low dielectric constant as outer-layer melt spinning liquid, selecting polyester with relatively high dielectric constant to be blended with a substrate as inner-layer melt spinning liquid, carrying out melt spinning by adopting double-channel coaxial spinneret orifices to obtain fibers with a skin-core structure, laying the fibers into a net, and removing the substrate in the inner layer by adopting a solvent to obtain the electret non-woven filter material with the cavity structure. After the spinning solution is sprayed out, the polymer melt fiber sprayed out of the spinneret orifice is sprayed by adopting melt-blown airflow dispersed with electret material micro-nano particles, and under the action of airflow spraying, the electret material micro-nano particles are loaded on the surface of the polyolefin fiber and generate electret charges through the friction action with the polyolefin fiber. In the traditional method, the micro-nano particles with high dielectric constant difference are dispersed in the spinning solution to carry out solution spinning, if the addition amount is too large, the spinning performance of the spinning solution can be influenced, and further the mechanical property, the air permeability and the like of the polymer fiber are influenced, so that excellent comprehensive performance is difficult to realize. In addition, thermoplastic polyester and matrix which are not compatible with thermodynamics are selected as inner layer spinning raw materials, and the matrix is removed by solvent extraction after the spinning and the web forming, so that the defect that the structural performance of the fiber skin layer is deteriorated due to the removal of the core layer material by heat treatment is overcome.
(3) According to the invention, the electret material micro-nano particles are added into the air flow of the conventional melt-blown processing, the jet loading is carried out by utilizing the action of the blowing air flow, and the melt fiber is still in a melt state and is easy to generate tensile deformation in the blowing process, so that the load fastness of the electret material micro-nano particles is improved, and the non-woven filter material with the surface loaded with the electret material micro-nano particles is prepared. In the traditional method, solution spinning is carried out mainly by dispersing electret material micro-nano particles in a spinning solution, and if the addition amount is too much, the spinning performance of the spinning solution can be influenced, so that the mechanical property, the air permeability and the like of polymer fibers are influenced, and excellent comprehensive performance is difficult to realize; or a coating layer is formed by a dipping adsorption method, and the coating fastness is difficult to ensure.
(4) The preparation method provided by the invention is simple, the preparation principle is scientific and reasonable, and single-layer or multi-layer electret material micro-nano particles can be accurately loaded on the surface of the polyolefin fiber melt through reasonable selection of spinning raw materials and reasonable control of a spinning process, so that the electrostatic adsorption performance of the non-woven filter material can be accurately regulated and controlled.
Drawings
FIG. 1 is a schematic diagram of the principle of the present invention of blowing and blowing a melt-blown gas stream to jet loaded micro-nano particles on-line;
FIG. 2 is a schematic representation of the structure of a fiber having a hollow structure prepared according to the present invention;
in the figure, 1 is an outer layer fiber tube, 2 is a nano fiber filament, and 3 is a cavity structure between the fiber tube and the fiber filament.
Detailed Description
The technical solutions of the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
According to the invention, polyester and a matrix which are thermodynamically incompatible are used as inner layer spinning raw materials of a double-channel coaxial nozzle, and after melt spinning, the matrix is removed through solvent extraction, so that nano-fiber filaments embedded in a fiber tube are obtained, and an inner cavity structure is formed. Wherein, the principle of nanofiber silk formation is as follows: since the thermoplastic polyester and the matrix are two components that are thermodynamically incompatible, two dispersed phases are formed in the melt blend. According to the invention, the mass ratio of the thermoplastic polyester to the matrix is limited to 1: 9-3: 7, namely the content of the matrix is far greater than that of the thermoplastic polymer, so that the thermoplastic polyester is uniformly dispersed in the matrix to form a melt blend similar to a sea-island structure; in the melt-blown filamentation process, polyester forms nanofiber filaments in the inner layer, and the matrix forms a longitudinal continuous phase in the outer layer; after the matrix is removed by solvent extraction, the inner layer polyester nano-fiber filaments, namely the nano-fiber filaments nested in the outer layer fiber tube, are left.
The principle of the blowing load of the invention is shown in figure 1, after the polyolefin raw material is melted and extruded, the fiber is gradually changed from a melt state to a solid state from a spinneret to a fiber collecting end, and simultaneously, the fiber is simultaneously subjected to high speed and high power drawing. When the fiber is in a melt state, the surface temperature of the fiber can reach 300 ℃, the physical property of the fiber melt is represented by liquid property, the whole stress of a surface molecular layer is unstable, and the fiber melt presents stronger surface tension, and meanwhile, spinning melt macromolecules can freely move and slide, so that possibility is provided for surface deformation of the fiber melt. The high surface tension and the easy deformation characteristic of the fiber melt provide a natural place for the composite functional particles, the electret material particles are dispersed in an airflow field of melt-blown spinning, so that the electret material particles are sprayed on the surface of the fiber melt with certain kinetic energy while the airflow performs original blowing and stretching action on melt fibers, and then the electret material particles are drawn, laid and formed along with the fiber melt, so that the purpose of loading the electret material particles on line by the fiber melt is realized, and the electret non-woven filter material is prepared.
The fiber structure of the electret non-woven filter material with the cavity structure is shown in figure 2 and comprises an outer layer fiber tube 1, nano-fiber yarns 2 and a cavity structure 3 between the fiber tube and the fiber yarns, and electret charges are generated through the friction effect of the inner layer and the outer layer with high dielectric difference, so that the electrostatic adsorption effect is improved.
Example 1
An electret non-woven filter material with a cavity structure comprises a polypropylene fiber tube loaded with polytetrafluoroethylene on the outer layer and polyethylene glycol terephthalate nano-fiber filaments embedded in the fiber tube, wherein the average particle size of the polytetrafluoroethylene is 300nm, and the preparation method comprises the following steps:
s1, melting polypropylene to obtain a melt spinning raw material a, and melting and blending polyethylene glycol terephthalate and cellulose acetate butyrate which are thermodynamically incompatible according to a mass ratio of 1:9 to obtain a melt spinning raw material b;
s2, spraying the melt spinning raw material a and the melt spinning raw material b in the step S1 from a double-channel coaxial spinneret hole for melt spinning;
wherein, the melt spinning raw material a is sprayed out from an outer layer spinneret orifice, and the melt spinning raw material b is sprayed out from an inner layer spinneret orifice; the diameter of an inner-layer spinneret orifice of the double-channel coaxial spinneret orifice is 0.16mm, and the diameter of an outer-layer spinneret orifice of the double-channel coaxial spinneret orifice is 0.64 mm;
s3, conveying the polytetrafluoroethylene micro-nano particles into an airflow generator by adopting a particle feeding device and a conveying pipeline, and performing injection stretching on melt fibers by adopting melt-blown airflow to ensure that the polytetrafluoroethylene micro-nano particles are injected and loaded to the surface of a polypropylene fiber melt along with the airflow to obtain a skin-core structure fiber with the polytetrafluoroethylene micro-nano particles loaded on the surface;
wherein the receiving distance is 15cm, the temperature of the melt-blown airflow is 300 ℃, the gas flow rate is 400m/s, and the injection quantity of the polytetrafluoroethylene micro-nano particles is 50 mg/s;
s4, laying the skin-core structure fibers in the step S3 into a net through a receiving device to obtain a skin-core structure fiber net;
s5, extracting the skin-core structure fiber web in the step S4 by acetone, removing the cellulose acetate in the step S1, and then performing electret treatment by corona discharge equipment to obtain the electret non-woven filter material with the cavity structure;
the electret voltage of the electret treatment is 15kV, the electret distance is 2cm, and the electret treatment time is 4 s.
The electret nonwoven filter material with a cavity structure prepared in the embodiment has the thickness of 0.8mm, the diameter of polyester nanofiber filaments is 105nm, the loading amount of polytetrafluoroethylene is 8%, the interception efficiency of micro dust with the diameter of more than or equal to 0.3 mu m in air is 99.92, the filtration resistance is 25Pa, the initial static voltage is 3.90kV, and the static voltage after being placed for 4 months is 3.74kV, because the polypropylene fiber tube loaded with polytetrafluoroethylene on the outer layer and the polyethylene terephthalate nanofiber filaments embedded in the fiber tube continuously form a friction effect to form static charges, so that the durability of the static charges is obviously improved.
Examples 2 to 7
The electret nonwoven filter materials with cavity structures provided in examples 2 to 7 are different from those in example 1 in that the type of the spinning raw material a is shown in table 1, and the others are substantially the same as those in example 1, and are not described again. The thickness, loading and filtration performance related parameters of the electret nonwoven filter materials prepared in examples 2-7 are also given in table 1.
From the performance test results of the electret nonwoven filter materials prepared in the embodiments 1 and 2 to 7, it can be seen that when the preparation process parameters are basically unchanged, the loading amount of the polytetrafluoroethylene is not changed greatly. When the thickness is not changed and only the polyolefin type is changed, the electrostatic voltage and the electrostatic voltage durability of the filter material are not greatly changed, so that the difference between the interception efficiency and the filter resistance is not large. As can be seen from examples 1 and 5 to 7, the electrostatic voltage and the electrostatic voltage durability of the filter material do not change much with the increase of the nonwoven filter material, but the air permeability decreases with the increase of the filter resistance; as the thickness increases, the interception efficiency also increases; when the thickness is 0.8mm, there is a relatively high interception efficiency and a low filtration resistance, and therefore, in consideration of the above, a filter material having a thickness of 0.8mm is preferable.
TABLE 1 polyolefin types and Properties of electret nonwoven filter materials prepared in examples 2-7
Examples 8 to 12
The electret nonwoven filter materials with cavity structures provided in examples 8 to 12 are different from those in example 1 in that the composition of the spinning raw material b is shown in table 2, and the rest are substantially the same as those in example 1, and are not described again. The electret nonwoven filter materials prepared in examples 8 to 12 all had a thickness of 0.8 mm.
From the performance test results of the electret nonwoven filter materials prepared in the examples 1 and 8 to 12, it can be seen that as the mass ratio of the polyester to the substrate increases, the diameter of the polyester fiber yarn in the inner layer gradually increases, the static voltage and the durability of the static voltage gradually decrease, so that the interception efficiency of the filter material also gradually decreases, and the filter resistance gradually increases. This is because the space occupied by the matrix is reduced when the content of the matrix is reduced, and the cavities between the fiber tubes and the fiber filaments are gradually reduced after the matrix is removed by solvent extraction, so that the friction frequency between the fiber tubes and the fiber filaments is reduced, resulting in a reduction in the static voltage and the durability of the static voltage. In addition, when the diameter of the fiber yarn is increased, the mass is also increased, and the friction probability with the fiber tube is reduced under the action of flowing air, so that the amount of generated electret charge is reduced, and the electrostatic adsorption effect is weakened. When the substrate is ethyl cellulose or cellulose acetate, the electrostatic voltage, the durability of the electrostatic voltage, and the interception efficiency and filtration resistance of the filter material do not vary much.
TABLE 2 polyolefin types and Properties of electret nonwoven Filter materials prepared in examples 8-12
Examples 13 to 15
Examples 13 to 15 provide electret nonwoven filter materials with a cavity structure, which are different from example 1 in that the particle size of polytetrafluoroethylene is shown in table 3, and the others are substantially the same as example 1, and are not described again. The electret nonwoven filter materials prepared in examples 13 to 15 all had a thickness of 0.8 mm.
From the performance test results of the electret nonwoven filter materials prepared in examples 1 and 13 to 15, it can be seen that as the particle size of polytetrafluoroethylene increases, the loading amount gradually decreases, the electrostatic voltage and the electrostatic voltage durability gradually decrease, and the filter resistance gradually increases. This is because polytetrafluoroethylene has a low dielectric constant, has a good ability to store static charge, is reduced in its content, has less static charge, and thus has a reduced electrostatic adsorption effect. When the particle size of polytetrafluoroethylene increases, the probability of blowing load on the fiber surface decreases, and therefore the load amount decreases. The particle size increases, and the coating surface to the fibre surface increases, probably leads to the air permeability to reduce, and then makes interception efficiency reduce, and the filtration resistance increases.
TABLE 3 polyolefin types and Properties of electret nonwoven filter materials prepared in examples 13-15
Examples 16 to 30
The electret nonwoven filter materials with cavity structures provided in examples 16 to 30 are different from those in example 1 in that the preparation conditions are shown in table 4, and the others are substantially the same as those in example 1, and are not described again. The electret nonwoven filter materials prepared in examples 16 to 30 all had a thickness of 0.8 mm.
Table 5 shows the performance test results of the electret nonwoven filter materials prepared in examples 16 to 30, and it can be seen from examples 16 to 18 that the fiber diameter, the loading amount, and the electrostatic voltage do not change much with the increase of the outer layer spinning pore size, but the interception efficiency decreases gradually and the filtration resistance increases gradually, which is probably because the fiber diameter increases gradually and the specific surface area decreases with the increase of the outer layer spinning pore size when the inner layer spinning pore size does not change, resulting in the decrease of the air permeability. It can be seen from examples 19 to 21 that, as the inner and outer layer spinneret orifices are increased synchronously, the diameter of the filament is gradually increased, the electrostatic voltage and the durability of the electrostatic voltage are gradually reduced, so the interception efficiency is also gradually reduced, and the filtration resistance is gradually increased, because when the inner layer spinneret orifice is increased, the diameter of the fiber tube is increased, the quality of the filament is increased, the friction resistance with the fiber tube is increased, the friction probability is reduced, and the filtration performance is reduced. As can be seen from examples 22 to 24, as the receiving distance increases, the polytetrafluoroethylene loading amount gradually increases, the electrostatic voltage and the electrostatic voltage durability gradually increase, but the interception efficiency does not change much, and the filtration resistance increases. This is because the receiving distance is increased, the blowing load time is prolonged, so the load is increased, the micropore content of the fiber is reduced, the air permeability is reduced, and the filtration resistance is increased; but the load capacity is increased, and the generated electret charge is increased, so that the interception efficiency is not greatly changed under the comprehensive action. Examples 25 and 26 show that the temperature of the gas stream has little effect on the filtration performance of the filter material over a defined temperature range. However, too low a temperature may result in low load fastness, and too high a temperature may result in thermal degradation of the fibers. It can be seen from examples 27 and 28 that as the airflow velocity increases, the amount of load gradually increases, the electrostatic voltage and the electrostatic voltage durability tend to increase slightly, the interception efficiency also increases slightly, but the filtration resistance also increases. This is because the amount of charge is increased, the amount of charge of the electret is increased, and the electrostatic adsorption is increased, but the increase in the amount of charge causes a decrease in air permeability, and further increases filtration resistance. It can be seen from examples 29 and 30 that as the ejection amount increases, the load amount gradually increases, the electrostatic voltage and the electrostatic voltage durability gradually increase, the interception efficiency also gradually increases, and the filtration resistance slightly increases, because when the load amount increases, the electret charge and the electrostatic voltage of the material can be increased due to the low dielectric property and the electret property of the polytetrafluoroethylene, thereby improving the electrostatic adsorption property. However, since an increase in the amount of the supported substance leads to a decrease in the surface micropores of the fiber and a decrease in the air permeability, the supported amount is preferably 8%.
TABLE 4 preparation conditions of examples 16 to 30
TABLE 5 Performance of electret nonwoven filter materials prepared in examples 16-30
Comparative example 1
Comparative example 1 is different from example 1 in that in step S5, the electret treatment is directly performed without acetone extraction, and an electret nonwoven filter material without a cavity structure is obtained, which is otherwise substantially the same as example 1 and will not be described herein again.
The electret nonwoven filter material without a cavity structure prepared in comparative example 1 had a thickness of 0.8mm, a diameter of polyester nanofiber filaments of 105nm, a loading amount of polytetrafluoroethylene of 8%, an interception efficiency against fine dust having a diameter of 0.3 μm or more in the air of 99.78, a filtration resistance of 25Pa, an initial electrostatic voltage of 3.55kV, and an electrostatic voltage after standing for 4 months of 2.8 kV. Therefore, when the filter material does not have a cavity structure, the initial static voltage and the durability of the static voltage are obviously reduced, so that the friction effect of the outer-layer fiber tube and the inner-layer nanofiber filaments has an obvious effect on improving the durability of the static voltage.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (10)
1. An electret nonwoven filter material having a cavity structure, comprising: the device comprises an outer-layer fiber tube and nano-fiber filaments nested in the outer-layer fiber tube; the outer layer fiber pipe consists of polyolefin fibers and electret material micro-nano particles loaded on the surfaces of the polyolefin fibers; the nano-fiber yarn is thermoplastic polyester fiber yarn and is obtained by melt spinning and phase separation of thermoplastic polyester and matrix which are thermodynamically incompatible.
2. The electret nonwoven filter material with a cavity structure of claim 1, wherein the electret micro-nano particles are loaded on the surface of the polyolefin fiber by melt-blown airflow injection, and under the action of the airflow injection, the electret micro-nano particles and the polyolefin fiber generate electret charges by friction.
3. The electret nonwoven filter material with a cavity structure of claim 1 wherein the diameter of the nanofiber filaments is 200nm or less; the average particle size of the electret material micro-nano particles is less than or equal to 1 mu m, and the loading capacity of the electret material micro-nano particles is 3-12 wt% of the mass of the polyolefin fiber.
4. The electret nonwoven filter material with a cavity structure as claimed in claim 1, wherein the thickness of the electret nonwoven filter material with a cavity structure is 0.2-5 mm, the interception efficiency of the electret nonwoven filter material with a diameter of 0.3 μm or more in the air is 99.5% or more, the filtration resistance is 30Pa or less, the surface electrostatic voltage is 3.2kV or more, and the electrostatic voltage after being placed for 4 months is 3kV or more.
5. The electret nonwoven filter material with a cavity structure of claim 1 wherein the polyolefin fibers are any of polypropylene fibers, polyethylene fibers or polyvinyl chloride; the electret material micro-nano particles are polytetrafluoroethylene micro-nano particles; the matrix is any one of cellulose acetate, ethyl cellulose or cellulose acetate butyrate.
6. A method for preparing the electret nonwoven filter material with a cavity structure of any one of claims 1 to 5, comprising the steps of:
s1, melting polyolefin to obtain a melt spinning raw material a, and melting and blending thermoplastic polyester which is thermodynamically incompatible with matrix according to a preset mass ratio to obtain a melt spinning raw material b;
s2, spraying the melt spinning raw material a and the melt spinning raw material b in the step S1 from a double-channel coaxial spinneret hole for melt spinning;
wherein, the melt spinning raw material a is sprayed out from an outer layer spinneret orifice, and the melt spinning raw material b is sprayed out from an inner layer spinneret orifice;
s3, blowing the polymer melt fiber sprayed from the spinneret orifice by using the melt-blown airflow dispersed with the electret material micro-nano particles to obtain a skin-core structure fiber with the surface loaded with the electret material micro-nano particles;
s4, laying the skin-core structure fibers in the step S3 into a net through a receiving device to obtain a skin-core structure fiber net;
s5, the fiber net with the skin-core structure in the step S4 is subjected to solvent extraction, the matrix in the step S1 is removed, and then electret treatment is carried out, so that the electret non-woven filter material with the cavity structure is obtained.
7. The method for preparing the electret nonwoven filter material with a cavity structure of claim 6, wherein in step S1, the predetermined mass ratio is 1: 9-3: 7.
8. The method of claim 6, wherein in step S2, the melt spinning has a receiving distance of 8-30 cm, the diameter of the inner layer spinneret orifice of the two-channel coaxial spinneret orifices is 0.1-1 mm, and the diameter of the outer layer spinneret orifice is 0.1-2 mm.
9. The method for preparing the electret nonwoven filter material with the cavity structure as claimed in claim 6, wherein in step S3, the temperature of the melt-blown air flow is 280-320 ℃, the flow rate of the melt-blown air flow is 300-500 m/S, and the ejection amount of the electret micro-nano particles is 30-80 mg/S.
10. The method of claim 6, wherein in step S5, the solvent is acetone; the electret treatment is corona discharge electret treatment.
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