CN100377760C - Electrostatically charged filter media with added active agent - Google Patents

Abstract

There is provided a protective media and a method of manufacturing the same. In one aspect, the protective media includes a porous dielectric carrier, an active agent incorporated in the porous dielectric carrier, and an electrostatic charge across at least a portion of the porous dielectric carrier. This innovative media is capable of eradicating microorganisms and/or toxins more efficiently than prior art solutions and can also self sterilize.

Description

Electrostatically charged filter media with added active agent

technical field

This application claims priority to US provisional applications 60/411,066, 60/434,526 and 60/458,800, which have their filing dates of September 16, 2002, December 19, 2002 and March 28, 2003, respectively. The contents of these are all taken as reference documents of this application.

This invention relates to electrostatically charged filter media, and more particularly, to electrostatically charged media incorporating active agents, and methods of making the same.

Background technique

Prior art filtration methods include for example mechanical filtration - particles are physically retained larger than the pores of the filter media; electrostatic filtration - particles are adhered to particles within the filter without killing/deactivating them, and Filtration was carried out in the manner taught and claimed in US Patent No. 5,980,827, issued to the present inventor on November 9, 1999, entitled "Disinfection of Air Using Iodine/Resin Disinfectant". It has been determined that filtration in fine, thin media improves the filtration of iodinated resins when the product is added to media with convoluted passages. By forcing the microbes/toxins through a detour, the microbes/toxins can eventually be killed/inactivated. One method of providing a circuitous path is to use nonwoven media.

In published US patent application 20010045398 entitled "Fixation of particles in a three-dimensional matrix structure", a nonwoven material was produced for the first time, and then, using alcohol and some solvents, added a compound such as that described in US patent 5,639,452 (' '452 patent) while using a pulsating vacuum pump to open the filter pores and allow active agents to pass through it ("ternary synthesis" resins).

US Patent No. 6,346,125 teaches adding an aqueous antimicrobial agent to a non-static non-woven material. In particular, the '125 patent describes a specific method for incorporating an aqueous antimicrobial agent into a non-statically charged nonwoven material. However, in the absence of electrostatic properties, non-woven materials must have a large thickness to allow sufficient contact between microorganisms and antimicrobial agents for decontamination.

US Patent US 5,952,092 teaches a nonwoven fiber with chemically active particles. But in this innovation, the patent does not teach the use of an electrostatic underlayer.

Nonwoven electrets and methods for their preparation are known in the prior art. For example, US Pat. No. 5,409,766 describes a nonwoven fiber in an electret state consisting of monofilaments formed with polymer components capable of collecting dust under hot and humid conditions for a long time. Also disclosed is a method for producing a nonwoven fiber, and an air filter covering material composed of the nonwoven fiber. But this prior art system does not provide antimicrobial/antiviral properties. Therefore, microbes/toxins suspended in the nonwoven fibers cannot be sterilized and inactivated. Once the electrostatic properties of the nonwoven material are lost or the material is saturated, the microorganisms/toxins can be re-released back into the atmosphere.

It is known to use electrostatically charged filter materials, for example, in masks. With respect to both, face sealing is a well known problem and attempts have been made to address limitations in the industry. The problem is that the structures or tissues of human body shapes are different from each other, and this difference produces a large range of geometric deviations, which makes it difficult to produce 100% air tightness. It is difficult for masks to create a seal between the skin and the mask over a range of facial sizes and shapes. Various techniques have been tried, such as the use of viscous seals, flat width seals and elastic seals. Attention in the industry has turned to creating an air seal, however, the pressure differential that is actually created forces the air in the gap between the seal and the skin to bypass the air filter material. The electrostatic filter material of the present invention can be made of sponge or other breathable nonwoven material to minimize pressure differentials and thus prevent air from being forced through the gaps. In addition, the cushion can be used effectively to form a seal between the user and the mask due to the fine filter material with low pressure drop (like an electrostatic filter material), which brings the benefits of active agents mixed with it.

Another known prior art teaches mechanical filtration using high pressure drop media, including HEPA filters. However, the pressure drop of the present invention is about 50% to 90% lower than that of a HEPA filter alone. Filter media also include materials that kill plant bacteria, spores and viruses in the channels. They are filtered out of the air stream and killed. Furthermore, the present invention is self-sterilizing, ie it not only filters the air passing through it, but also kills bacteria trapped in the filter material. Thus, this medium protects the user and the outside air.

Due to the deficiencies of the prior art, it would be better to use an electret with characteristics superior to existing solutions. The improvement of the present invention includes a substratum, ie, dielectric, that facilitates the active agent.

Contents of the invention

The present invention overcomes the above-mentioned problems of the prior art. In particular, according to one aspect of the present invention, there is provided an electrostatically chargeable nonwoven medium having an active agent incorporated therein. This improved media eradicates microorganisms and/or toxins more effectively than prior art solutions and is also self-sterilizing.

The present invention also provides a method of making an electrostatically chargeable filter medium having an active agent incorporated therein. The bottom layer can be prepared in various ways; the active agent can be added in different ways; and it can be electrostatically charged in different ways, all of which are described in these or are known in the art.

Because very little active agent is used per filter media, costs can be reduced while maintaining effectiveness. In addition, the enhanced electrostatic filtration of the present invention provides additional active agent performance and electrostatic properties.

In addition to the above-mentioned aspects of the present invention, other aspects, features and advantages will be better understood after reading the following description with reference to the accompanying drawings.

Description of drawings

Fig. 1 is the appearance figure that represents a typical embodiment according to the technical teaching of the present invention;

Figures 2 and 3 represent exemplary embodiments of electrostatically chargeable bottom layers;

Figure 4 is a diagram illustrating an exemplary embodiment for providing an active agent-incorporated nonwoven medium.

Detailed ways

Some typical embodiments of the present invention are described below. The described embodiments of the present invention are obvious to those skilled in the art for the purpose of illustrating by way of example rather than limitation. All features disclosed in this specification, unless stated otherwise, may be replaced by other features serving the same or a similar purpose. Accordingly, many other embodiments which are modifications of the invention will fall within the scope of the invention as defined herein and equivalents thereof.

SUMMARY OF THE INVENTION The present invention provides an electrostatically charged filter medium comprising a bottom layer having an active agent incorporated therein.

filter media

The filter media of the present invention comprise (1) a bottom layer, (2) an added active agent and (3) an electrostatic charge.

bottom layer

The bottom layer includes any material having dielectric properties that can be enhanced to have dielectric properties, and the active agent is incorporated into these materials.

In a particular embodiment, the substrate may be a fiber-based material with a fibrous matrix structure; it may be a sponge-like material with an open cell matrix structure; it may be elastic or inelastic; and the like.

As noted above, in one embodiment, the substrate is nonwoven fibers. Nonwovens are fibers bonded together rather than spun and woven. It may be an oriented or randomly oriented sheet, mat, web or batt of fibers combined by friction or bonding methods; it may take the form of fibers. Figure 1 provides a typical example of a nonwoven fiber.

In another embodiment, the substrate may be a variable loft nonwoven fabric comprising polymeric fibers. The polymer can be, for example, nylon, polyethylene, polypropylene, polyester, etc., or any other polymer suitable for use as a backing layer. Alternatively, the bottom layer may be made of non-polymeric fibrous materials.

The nonwoven material may be a material suitable for use in a high efficiency particulate air filter (ie, a HEPA filter). A suitable nonwoven material is available from Technol Aix en Provence Cedex 03 France (see Canadian Patent 1,243,801); another suitable material is available from Minnesota Mining & Manufacturing Co. (3M). The nonwoven material can have a three-dimensional structure that provides a matrix capable of trapping (ie, physically) the desired active agent. For example, if the nonwoven material is a fiber-based material, the structural fibers of the nonwoven material are present and distributed in such a way as to provide a fibrous matrix structure capable of trapping the desired active agent. Nonwoven materials can have a microstructure. In a particular embodiment, the active agent has a particle size suitable for entrapment by the three-dimensional (eg, network) matrix structure of the desired nonwoven material.

Other substrates include fiberglass and fibers such as cellulose, which ultimately form the paper-based fibrous media. Any sublayer that acts as an active agent carrier and has dielectric properties or can be made to impart dielectric properties is suitable as the sublayer of the present invention. Improved dielectric properties of the substrate can also be provided when using substrates without strong dielectric properties, such as fiberglass. The invention is not limited to the use of nonwoven materials. Other suitable substrates may include sponge or foam materials.

active agent

Active agents of the invention may be, for example, antibacterial agents, antitoxins or similar substances. The antimicrobial agent can be a biostatic agent or a biocide. A biostatic agent is a material that inhibits the growth of all or some bacterial spores, viruses, fungi, etc. (particles with biological activity), while a biocide is a material that kills all or some bacterial spores, viruses, fungi, etc. The biostatic agent is preferably as described in the aforementioned '452 patent, comprising iodinated resin particles. Other suitable active agents include silver, copper, zeolites with antimicrobial agents attached thereto, halogenated resins and agents known in the art to inactivate/deactivate microorganisms/toxins including for example activated carbon, other metals and other compounds . For example, a non-exhaustive list of suitable metals and/or compounds follows.

typical metal

Aluminum, barium, boron, calcium, chromium, copper, iron, magnesium, manganese, molybdenum, nickel, lead, potassium, silicon, sodium, strontium, zinc

typical compound

N-Methylpiperazine

Potassium hydroxide

Zinc chloride

calcium chloride

Mixture of Sodium Carbonate and Sodium Bicarbonate

The antibacterial agents listed in this specification are for the convenience of reading, rather than limiting the present invention.

static charge

Filter media with active agents are also electrostatically charged. Thus, an electric field is generated by the potential energy of the surface of the medium, which can attract and/or repel charged particles introduced into the medium, so that in some cases the path of motion of the charged particles can be altered.

Figure 2-3 provides a typical representation of electrostatically charged media. The electrostatically charged filter media according to the invention can be, for example, single-layer or multi-layer. Each layer can be charged separately. A single layer dielectric can have a positive charge on one side and a negative charge on the other. An example of a multi-layer media is a dual-layer media. Preferably, a bilayer dielectric is used, where the bilayer dielectric comprises two layers, one side of each layer is positively charged and the other side is negatively charged, wherein the two layers are separated by an air space, and the two layers are oriented in such a way : The negative side of one of the two layers is close to the positive side of the other. In the two-layer embodiment, this air space increases the net dielectric constant of the electrostatically charged filter media.

It is preferable to provide a high dielectric constant in order to prolong the charge retention time: for example when using the above-mentioned air space, provide air with a good dielectric constant. Thus, the present invention is very effective even in humid environments.

The final medium is an insulating carrier with the active agent attached thereto or impregnated with the active agent and electrostatically charged. The media of the present invention can be formed in varying thicknesses, densities and pressure drops. The media described herein can be used, for example, in garments, wound dressings, air filters, coverings, liners, and any filter material commonly used.

Preparation

The present invention also provides a method of making an electrostatically charged filter medium to which an active agent has been added. The bottom layer itself can be prepared according to various known methods, such as melt blown, spun blown, air laid, carted and the like.

The method of adding the active agent

Existing methods of incorporation using polypropylene require the use of polypropylene to maintain the thickness of the fibers so that the solid particles are retained for extended periods of time to prevent particulates from leaving the fibers. In the present invention, active agents, such as the iodinated resins disclosed in '452, can be physically entrapped in the fibers. Thus, the active agent does not have to adhere to the fibers to be added to the medium.

In the present invention, the active agent can be added to the base layer in different ways. For example, when melting during high temperature and high pressure mixing and melting, by emulsifying the active agent, or by extruding the non-woven fiber in the process, and then spraying the active agent and other adding methods.

In the preferred embodiment shown in Figure 4, polymer pellets, such as polypropylene pellets, are extruded through an extruder; the extruded fibers are of varying thickness and length. As the fibers are extruded, they fall towards the collecting web. The desired active agent is disposed in a cloud near the point of extrusion of the final fiber which surrounds the cooled fiber while the fiber is still semi-liquid and semi-solid. In one embodiment, the active agent particles may be in the range of 0.2 microns to 0.5 mm. However, one of ordinary skill in the art will employ both smaller and larger particle sizes of the active agent. By placing and collecting the active agent particles so that they are bound to or trapped on the fibers of the collection net. After the fibers on which the active agent has been added fall onto the collecting wire, the final media is formed into a web using known methods. In addition, agglomerates can be in different physical states, including vapour, fine dry dust, or aerosolized or aerosolized particles. Advantageously, the conjugation of the clumps can take place at room temperature, when the particles are also at room temperature. Additionally, thickness, length and pressure define the mechanical properties of the final media.

A suitable melt blowing system for use in the above embodiments is Accuweb supplied by Accurate Products Co. of Hillside, NJ.

Various other methods of incorporation of the active agent onto the fibrous media are also suitable for use in the present invention. First, for example using the method disclosed in US patent application 20010045398A1. Second, a bail of extruded hair fibers is submerged in the active agent (alcohol is used to achieve wetting) and then felt using pressure and temperature. Third, mixing is made using solid polymer particles prepared from the active agent added to an extrusion funnel, then extruded into a fine hair-like bail. It is made into felt through a certain temperature and pressure process. Fourth, an extruded base layer, such as a polymer base layer in a hair replacement, and injecting the active agent into a solid state after extrusion. The active agent can evaporate like smoke. Fifth, the active agent can be sprayed or sprayed into the nonwoven fibers while the fibers are compressed. Sixth, a bail of filaments is extruded and the final medium is mixed with the active agent to form a tablet into which the active agent is incorporated. Seventh, the active agent is deposited on the nonwoven medium, and the medium is punched by needling to impregnate and pass the active agent through the medium. Other methods can also be used.

In another embodiment of the invention, the polymer particles are placed in the funnel of the extruder of the powdered active agent formed prior to extrusion. Therefore, the active agents are mixed in the funnel before being melted. The two ingredients are mixed, heated, and extruded to form the fine "hair"-like fibers used to make felt. The final fine hair added to the active agent in the above examples was a bail-like flock. Depending on the polymer requirements, the bottom layer can be transparent. Thus, the polymer fibers to which the active agent has been added can be treated with pressurized water and then heated to form a mat. In other embodiments, the final polymeric fibers onto which the active agent is added may be air laid, vacuum laid, water laid, etc.

Although not specifically described herein, other conventional or known methods of combining the active agent with the substrate are also suitable for use in the present invention. Thus, at this point, the bottom layer has the active agent incorporated therein.

Electrostatic charging method

The bottom layer to which the active agent is added is electrostatically charged. The charge can be generated by corona, acupuncture, chemical amplification, any other known inductive system or method, or using a combination of the above methods to generate the charge. Needle punching creates a high level of friction and therefore increases the charge.

In one particular embodiment, to spin the forming medium, eg statically charged non-woven fibers of felt, into a corona system of about 25Kv, it is passed slowly until fully charged. The final material retains its charge for about 6 months to 2 years.

Working process of electrostatic filter media

In operation, a contaminated air or liquid stream is directed to the filter of the present invention using an electrostatically charged filter media, and a pressure gradient is used to force or draw the air/fluid stream through the filter media. The stream may contain contaminating particles of various sizes to be removed or treated by the filter element. As the stream approaches the filter media, it is directed through the filter media, contacting the contaminating particles with the filter media, and removing or treating the contaminating particles from the stream using active agents as described elsewhere in this application. This is accomplished by utilizing the filter properties of the filter media to take particles through a convoluted path, thereby prolonging the contact time of the contaminants with the active agent. The extended contact time increases the effectiveness of the active agent when processing the particles in this stream.

The convoluted path of the particles allows them to increase the electrostatic and nonwoven properties of the underlying filter element. With respect to the electrostatic properties of filter elements, the convoluted path of contamination particles can be attributed to the polarity of the particles. Polar molecules are neutral and have a larger size. Due to their large size, pollutants have a magnetic moment when they are deflected from their path by an electric field.

Furthermore, the coiled path of the pollution particles is attributed to the non-woven nature of the filter substrate. This is achieved by the fact that the nonwoven base layer does not have a direct and continuous path for fluid flow to pass through. Instead, due to the nonwoven nature, the bottom layer is composed of a porous material, wherein no continuous path through the bottom layer is formed by a single porous material. Thus, the fluid flow and the particles carried by the fluid flow are continuously diverted through the bottom layer. This prolongs the time through the filter and the exposure to the active agent is enhanced.

Additional use

The present invention can also be used in a manner compatible with existing nonwoven fibers. Use a variety of items, both durable and disposable. For example, nonwoven materials can be used in products such as diapers, sanitary napkins, adult incontinence napkins, wipes, bed liners, automotive products, masks, air filtration, water filtration, biological fluid filtration, home furnishings, and floor coverings. The media described herein can be used, for example, in cloths, wound dressings, air filters, coverings, liners. Other uses include electrostatic filters and antimicrobial or antitoxin filters known in the art.

In a particular embodiment, the filter media of the present invention, with or without active agent, can be used as an enclosure, or filter enclosure for filtering air in products such as masks and HVAC. In accordance with the present invention, there is provided a closure material comprising a bottom layer having electrostatic properties and an active agent-added electrostatic material which is a three-dimensional structure of highly stretchable (in one embodiment, a thickness of 1") scalable Breathable material, which is placed around the mask or air filter so that it does not form a so-called airtight connection, but instead forms a breathable seal, which actually covers all shapes with different geometric surfaces to provide a breathable Air-permeable seal. This method places the closure in a filter so that air that bypasses the gap formed by the imperfect Harmful pressure differentials are harmless in our approach, as the air passing through the least resistance will pass through the filter material of the mask. This method of closing a mask or other filter type can be achieved by replacing a breathable The non-woven filter element of the foam is realized.Therefore, the mask of the prior art tries to prevent the flow of air in the seal, while the mask of the present invention acts as a sealing gasket, which allows the air to pass through and kills spores, viruses, bacteria entering the airflow , fungus, etc., the air stream contains effective active agents such as the iodinated resins disclosed in the aforementioned '452 patent. Therefore, some straps are used to hold the mask in place to compress the gasket of the present invention so that it is substantially compatible with Fits the entire face.

Test Data

A specific embodiment of the filter media of the present invention was experimentally tested in comparison to existing electrostatic filters. Each test was performed under the same environment treating air with different pollutants. During these tests, the provided experimental data was collected. In each test, a controlled amount of a contaminant was introduced into a chamber and fed into four lines. Both lines included filters of the present invention comprising electrostatically charged filters incorporating the iodinated resin of the '452 patent. The third line includes static-charged filters known as Transweb. This filter has no antimicrobial properties or any other kind of properties with active agents added. And a fourth line is provided for the control, which has no filter, and is used to determine whether the amount of contamination entering the control chamber is equal to the amount of contamination exiting the control chamber.

Table A lists certain characteristics representative of some exemplary embodiments of the invention. Test No. AF276 describes the performance of different filter membranes for GB spore filtration for 30, 60, 120, 180, 240, 300 and 360 minutes. BG spores must have an amount of about 8,000 to 30,000 spores, which is the amount that makes the average human sick. As can be seen from Table A, for each of the 30, 60, 120, 180, 240, 300 and 360 minute tests, the filter of the present invention reduced the amount of BG spores in the air stream by 100%.

As can be seen from Table A, the electrostatic filter of the present invention achieved substantially the same or similar net effect as Transweb in these tests. However, the present invention has an important advantage in that it kills the spores rather than just keeping them in the filter. Therefore, unlike the present invention, contamination may occur if the Transweb is handled by the user or comes into contact with the skin. The invention can keep the filter hygienic.

Turning now to Table B, the results of Test No. AF270 show the performance of different filter membranes for MS2 virus filtration for 30, 60, 120, 180, 240, 300 and 360 minutes. Viral loads ranging from 1 to 1000 will make the average person sick. Therefore, even a single virus can make a person sick. As can be seen from Table B, for the 30, 60, 120, 180, 240, 300 and 360 minute tests, the filter of the present invention reduced the MS2 virus in the gas stream by 100%. But Transweb could not achieve 100% reduction of MS2 virus and found 1000 to 10000 virus units in the outgoing air stream. Using Transweb to deal with the air polluted by the MS2 virus cannot achieve the desired effect. Thus, it can be seen from Table B that, relative to Table A, the present invention is more effective over time against viruses such as MS2, in addition to the advantages of the disinfection properties described above. Since only a small number of viruses contaminate humans (1 to 1000 viruses), Transweb, unlike the present invention, cannot effectively protect users from these viruses.

in conclusion

Now that one or more exemplary embodiments of the present invention have been described, it will be apparent to those skilled in the art that the foregoing description is for illustration by way of example only, rather than limitation. All the features described in (including all claims, abstract and drawings) may be replaced by other features serving the same, equivalent or similar purpose. Accordingly, many other embodiments of additions and alterations would fall within the scope of the invention as defined by the claims and their equivalents.

Claims (28)

1. protective medium comprises:

A porous dielectric carrier;

A kind of activating agent that is added in the porous dielectric carrier, described activating agent is a halogenated resin; And

Electrostatic charge at least a portion of described porous dielectric carrier.

2. according to the protective medium of claim 1, wherein said porous dielectric carrier is a non-woven material.

3. according to the protective medium of claim 1, wherein said porous dielectric carrier is the fiber-based material with fibrous matrix structure.

4. according to the protective medium of claim 1, wherein said porous dielectric carrier is the sponge kind material with perforate cell basal body structure.

5. according to the protective medium of claim 2, wherein said non-woven material is a three-dimensional structure, in order to the matrix that can capture described halogenated resin with physics mode to be provided.

6. according to the protective medium of claim 5, wherein said halogenated resin is made up of the suitable particle of the particle diameter that is captured by described matrix.

7. according to the protective medium of claim 1, wherein said halogenated resin is an iodinated resin.

8. according to the protective medium of claim 7, wherein said porous dielectric carrier is a non-woven material.

9. according to the protective medium of claim 7, wherein said porous dielectric carrier is the fiber-based material with fibrous matrix structure.

10. according to the protective medium of claim 7, wherein said porous dielectric carrier is the sponge kind material with perforate cell basal body structure.

11. protective medium according to Claim 8, wherein said non-woven material is a three-dimensional structure, in order to the matrix that can capture described iodinated resin with physics mode to be provided.

12. according to the protective medium of claim 11, wherein said iodinated resin is made up of the suitable particle of the particle diameter that is captured by described matrix.

13. protective medium according to claim 1 also comprises:

Another one porous dielectric carrier;

Be added in the another one activating agent in the described another one porous dielectric carrier; And

Other electrostatic charge at least a portion of described another one porous dielectric carrier;

14. according to the protective medium of claim 13, wherein said other activating agent is a halogenated resin.

15. according to the protective medium of claim 13, wherein the air gap separates described porous dielectric carrier and described other porous dielectric carrier.

16. according to the protective medium of claim 15, wherein said other porous dielectric carrier is a non-woven material.

17. according to the protective medium of claim 15, wherein said other porous dielectric carrier is the fiber-based material with fibrous matrix structure.

18. according to the protective medium of claim 15, wherein said porous dielectric carrier and other porous dielectric carrier are the sponge kind materials with perforate cell basal body structure.

19. according to the protective medium of claim 17, wherein said non-woven material is a three-dimensional structure, in order to the matrix that can capture described activating agent and other activating agent with physics mode to be provided.

20. according to the protective medium of claim 19, wherein said other activating agent is made up of the suitable particle of the particle diameter that is captured by described matrix.

21. a method for preparing protective medium as claimed in claim 1 comprises:

A kind of extruder with outlet is provided;

A collecting net that is positioned at described outlet of extruder below is provided;

A kind of extrudable hot melt material is provided;

Utilize described extruder to extrude described extrudable material, make extruding fiber flow and falling of cooling towards described collecting net; And

The mixed group of halogenated resin is provided in the position near the described exit of described extruder, so that described mixed group surrounds cooled fibers, described fiber is still consolidated state at half liquid half simultaneously, thereby described halogenated resin is fixed and collects, and mutually combine or be captured on the collecting net that forms medium by described fiber.

22., also comprise described medium made net according to the method for preparing protective medium of claim 1.

23. according to the method for preparing protective medium of claim 1, wherein said mixed group is in physical state, it is selected from the group of being made up of following material: steam, thin dried dust, atomizing particle and aerosolised particles.

24. the method for preparing protective medium according to claim 1 also comprises the step that electric charge is applied to whole described net.

25. a method for preparing protective medium as claimed in claim 1 comprises:

A kind of extruder with outlet is provided;

A collecting net that is positioned at described outlet of extruder below is provided;

But provide the storage bin of an extruded material;

Utilize described extruder to extrude described extrudable material, make and extrude fiber flow and fall towards described collecting net; With

The mixed group of halogenated resin is provided in the position near the described exit of described extruder, so that described mixed group surrounds fiber, simultaneously described fiber falls, thereby described halogenated resin is fixed and collects, and mutually combines or be captured on the collecting net that forms medium by described fiber.

26., also comprise described medium made net according to the method for preparing protective medium of claim 1.

27. according to the method for preparing protective medium of claim 1, wherein wherein said mixed group is in physical state, it is selected from the group of being made up of following material: steam, thin dried dust, atomizing particle and aerosolised particles.

28. the method according to the protective medium of claim 1 wherein also comprises the step that electric charge is applied to whole described net.

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