Method for manufacture of fibrous electret web with the use of non-aqueous polar liquid

FIELD: methods for imparting charge to fibrous webs by means of non-aqueous liquid for usage of said webs as filters in filtering face masks for protection of user's mouth and nose.

SUBSTANCE: method involves wetting web formed from non-conductive fibers with non-aqueous polar liquid; substantially drying web for producing fibrous electronic web. Method differs from known methods of imparting charge to web in that it requires less energy for drying of web than methods using aqueous liquids. Also, many kinds of filaments poorly wetted with aqueous liquids are immediately wetted with non-aqueous liquids.

EFFECT: increased efficiency and simplified method.

12 cl, 2 dwg, 6 tbl, 26 ex

 

The present invention relates to a method of imparting charge fibrous paintings by nonaqueous polar liquid.

Electrically charged nonwoven fabrics are widely used as filters in respirators that protect the user from inhaling present in the air of pollutants. In U.S. patents№4,536, 440, №4,807,619, №5,307,796 and no 5,804,295 examples of respirators that use such filters. Electric charges improve the ability of non-woven cloth to hold suspended in the stream of particles. When the flow passes through the non-woven fabric, these particles are trapped in the fabric. Nonwoven fabrics are typically composed of a dielectric - i.e., not conducting current of the polymers. In recent years, developed many methods of making electrically charged dielectric materials, often called "electrets".

The first works related to electrically charged polymeric films, P.V.Chudleigh described in the articles "the Mechanism of charge transfer at the polymer surface by contact with a conducting fluid" (Mechanism of Charge Transfer to a Polymer Surface by a Conducting Liquid Contact), 21 Appl. Phys. Lett., 547-48 (Dec. 1, 1972), and "Charging of polymer films using a liquid contact Charging of Polymer Foils Using Liquid Contacts), 47 J. Appl. Phys., 4475-83 (October 1976). The method, which was used Chudleigh, included charging polymer poliferation square the NCI by the application thereto of a voltage. Voltage to the film was applied through the conductive fluid in contact with the surface of the film.

The first of the known technology of manufacturing fibrous polymer electrets are described in U.S. patent No. 4,215,682 (Kubic and Davis). According to this method, the fiber was bombardopolis flow of electrically charged particles directly at the exit of the nozzle of the extruder. Themselves fibers were obtained by the method of "pulling from the melt", in which the gas stream, passing at high speed in front of the nozzle of the extruder, drains and cools extrudable polymeric material, turning it into a hardened fiber. Bombed fibers randomly accumulate on the collector, forming a fibrous electret web. The patent says that if extruded from the melt fiber is electrically charged in the described manner, the filtration efficiency can be increased two or more times.

Fibrous electret paintings were made by charging them using corona discharge. For example, in U.S. patent No. 4,588,537 (Klaase and others) shows how the fibrous fabric is continuously fed into the device, creating a corona discharge, where is located near one of the main surfaces firmly fixed dielectric film. Crown creates a high voltage source connected to protivopul is tenderly charged thin tungsten wires. Another high-voltage design to create electrostatic charges in the non-woven fabric described in U.S. patent No. 4,592,815 (Nakao). In this design the canvas is held in tight contact with a smooth grounded electrode.

Fibrous electret paintings can also be made of a polymer tape or film as described in U.S. patents Re. 30,782, Re. 31,285 and Re 32,171 (van Turnhout). Polymer tape or film is electrostatically charged before cutting into fibres, which are then collected and processed into a fibrous nonwoven filter.

For giving electric charge to the polymer fibers were used and mechanical approaches. In U.S. patent No. 4,798, 850 (Brown) described filter fabric, consisting of a mixture of two different composition woven polymer fibers, which initially standing, forming a loose layer, and then sewn together in the likeness of felt. In the patent indicated that the fibers are thoroughly mixed so that they are electrically charged when brushing. Described Brown process is based on the well-known phenomenon of electrification by friction.

Electrification by friction can also occur at high speed jet of inert gas or liquid along the surface of the polymer film. In U.S. patent No. 5,280,406 (Coufal and others) have shown that when the stream of uncharged liquid hits the surface rnost dielectric film, this surface acquires an electric charge.

In later developments for the introduction of electric charges in the fibrous non-woven cloth used water (see U.S. patent No. 5,496,507 name Angadjivand, and others). To make the canvas properties electret jet of water under pressure or flow of water droplets were directed to the non-woven fabric consisting of a non-conductive microfibers. The resulting charges improved filtering properties of the canvas. Pre "hydraulic" by charging the processing of fabric in order to remove charges under the action of a corona discharge in air gave an additional improvement of the parameters of electret.

The introduction of the fibrous polymeric fabric of certain additives improves the filtration properties of electrets. For example, resistant to oil mist electret filter cloth was obtained with the introduction of fluoride additives in polypropylene microfiber, pulling from the melt (see U.S. patent No. 5,411,576 and 5,472,481 (Jones and others)). The melting temperature of fluoride supplements was not less than 25°With a molecular weight from about 500 to 2000.

U.S. patent No. 5,908,598 (Rousseau and others) describes a technique in which the additive is mixed with thermoplastic resin intended for the manufacture of a fibrous web. A jet of water under pressure or flow of water droplets voltage is alauda on canvas under pressure, sufficient to create a canvas of electric charges, which improves its filtering properties. Then the fabric is dried. As additives can be used: 1) thermostable organic compound or oligomer, and such compound or oligomer contains at least one perforated component; 2) thermally stable organic triazine compound or oligomer containing, in addition to the nitrogen atoms included in the triazine group, at least one additional nitrogen atom; or 3) a combination of compounds 1) and 2).

In U.S. patent No. 5,057,710 (Nishura) described another species containing additives of electrets. In the composition described Nishura polypropylene electrets includes at least one stabilizer selected from the spatial difficult amines, spatial difficult phenols, nitrogen-containing, or spatial difficult phenols containing the metal atom. The patent States that the electrets containing such additives are able to demonstrate high thermal stability. Electrostatic processing is performed by placing sheets of nonwoven fabric between the needle and the grounded electrodes. In U.S. patent No. 4,652,282 and No. 4,789,504 (Ohmory and others) described the inclusion of an insulating polymer metal salts of fatty acids to ensure the long term preservation of high nature the istics of dust filtration. In Japanese patent Kokoku JP60-947 describes the electrets consisting of poly-4-methyl-1-pentene and at least one compound selected from among (a) compounds containing hydroxyproline group; b) higher aliphatic carboxylate and their metal salts; compounds containing dicarboxylate; g) compounds containing phosphorus; and d) compounds containing ester. The patent States that such electrets have a high stability during long-term storage.

The recently published U.S. patent indicates that the filter cloth can be manufactured without the use of special operations additional charge or charges fibers or ready fiber fabric (see U.S. patent No. 5,780,153 on the name of the LUT and others). These fibers are manufactured from a copolymer, which consists of a copolymer of ethylene, from 5 to 25% (by weight) of (meth)acrylic acid and possibly, but less preferably, to 40% (by weight) of alkyl(meth) acrylate, alkyl groups which have from 1 to 8 carbon atoms. From 5 to 70% of the acid groups neutralized by metal ions, particularly zinc, sodium, lithium, magnesium or mixtures thereof. The copolymer has an index of fusion of from 5 to 1000 grams per 10 minutes. The rest can be a polyolefin, such as polypropylene or polyethylene. These fibers can be produced by means of extrusion from the melt, and DL is prevent excessive clumping can quickly be cooled with water. In the patent it is said that these fibers are very good at keeping electrostatic charges - both existing and intentionally created.

SUMMARY of the INVENTION

The present invention offers a new method of making fibrous electrets. This method can appropriately to comprise or essentially consist of soaking consisting of non-conductive fibers of the fabric by contact of the fibers with a non-aqueous polar liquid. After soaking the cloth thoroughly dried, becoming fibrous electret web. The present invention also includes a filtering face mask that uses a fibrous electret fabric according to the present invention.

The proposed method differs from the known ways of generating electrostatic charges that according to the present invention, the electrostatic charges are generated in the fibrous fabric by nonaqueous polar liquid. Until the present invention the electrostatic charges, as a rule, attached to fibrous cloths or using a device that generates corona discharge or by way of hydraulic charging (see, for example, U.S. patent No. 4,588,537 (Klaase and others), No. 4,592,815 (Nakao), No. 5,496,507 (Angadjivand, and others)). Instead of applying the high voltage or high water JV the property according to the present invention uses a non-aqueous polar liquid. The use of such liquid to create electrostatic charges preferred application of corona discharge, as it allows to do without high-voltage equipment and associated energy costs. And since the non-aqueous liquid is usually more volatile than water, the method according to the present invention preferably hydraulic charging, because it reduces the power consumption associated with the drying cloth. In addition, there are filter materials, which are easily wetted non-aqueous liquids, but poorly wetted by water. Therefore, the use of nonaqueous polar liquids may be desirable in situations when to use water to generate electrostatic charges in the canvas uncomfortable.

For the purposes of this invention the terms in this document are used in meanings:

"sufficient" means that the nonaqueous polar liquid used in a quantity sufficient to ensure that after contact with the polar liquid and drying the fibers acquired properties of electrets;

"electret a substance that retains an electrostatic charge, at least, almost constantly;

"electrostatic charge" means that the substance has occurred, the charge separation;

"fibrous" means "consisting of fibers and possibly other components of the Sabbath.";

"fibrous electret canvas - woven or non-woven fabric containing fibers, retaining an electrostatic charge;

"liquid" is a state of matter intermediate between solid and gaseous;

"non-aqueous liquid - liquid, containing not more than 10% water (by volume);

"non-conductive" - possessing at room temperature (22°C) resistivity of more than 1014Ohm×sm;

"nonwoven" is a structure or part of a structure in which the fibers are connected other than weaving, by the way;

"the polar liquid" is a liquid substance, in which the dipole moment is at least about 0.5 Debye, and dielectric constant of at least about 10;

"polymer" is an organic substance consisting of repeating molecular units or groups, regularly or irregularly interconnected;

"polymer" is composed of polymer and possibly other ingredients;

"polymeric fibre-forming substance is a substance from which it is possible to make solid fiber consisting of a polymer or capable of conversion into a polymer of the monomer and possibly other ingredients;

"almost continuously" means that under standard conditions (temperature 22°C, atmospheric pressure 101,300 PA, humidity 50%) of the electrostatic charge stored in the material as to what th it can be measured;

"saturation" means that the fabric has absorbed the maximum (or close enough to it) the quantity of liquid;

"staple fiber" is cut into sections of standard length (typically from 2 to 25 cm) fiber with an effective diameter of not less than 15 micrometers;

"thermoplastic" is a polymeric material, razmyagchayuschiesya when heated;

"canvas" is air-permeable structure having two dimensions substantially larger than in the third dimension;

"soaking" - contact (liquid) or floor (it) almost all of the surface area subject to moisture cloth.

BRIEF DESCRIPTION of DRAWINGS

Figure 1 - schematic (with partial cuts) the side view of the device 10 for soaking and drying fiber fabric 20 according to the present invention.

Figure 2 - example of the construction of the filtering face masks 40, in which you can use electret filter material made in accordance with the present invention.

DETAILED DESCRIPTION of PREFERRED embodiments of the INVENTION

According to the present invention, an electrostatic charge is created in the fibrous cloth by soaking the last nonaqueous polar liquid and subsequent drying. Specified fibrous fabric includes a non-conductive fiber is a, and after soaking nonaqueous polar liquid and its subsequent removal by drying becomes fibrous electret fabric suitable for use as a filter.

Fibrous nonwoven webs made in accordance with the present invention, demonstrate the presence of "almost constant electrical charge. Preferably, the fibrous non-woven fabric had a permanent electric charge, so that this electric charge remained in the fibers and, thus, non-woven cloth, at least within the common life of the product, which used this electret.

Evaluation of the filtering characteristics of the fiber cloths by using the following procedure, called "Test DOP-permeability and pressure drop". The test is bursting through the fabric of particles dioctylphthalate (DOP) and measuring the amount of particles that passed through a cloth, and the differential pressure before and after paintings. For measured values DOP-permeability and pressure drop can be calculated quality factor (QF). The filtration efficiency of electret usually estimated in comparison with the initial quality factor (QFH). The initial quality factor (OFHthis quality factor (QF), measured before the load Volosnikov the electret nonwoven cloth - i.e. before on this canvas will act to filter the aerosol.

Preferred fibrous electret nonwoven fabric, made according to the present invention, may have an electric charge, allowing the product when conducting the test described below DOP-permeability and pressure drop show values QFHgreater than 0,10 mm H2O)-1more preferably greater than 0,20 mm H2O)-1even more preferably greater than 0.40 (mm H2O)-1and , most preferred more than 0,60 mm H2O)-1. The quality factor of the fibrous non-woven electret paintings made according to the present invention, preferably not less than twice QF raw canvas is practically of the same construction and, more preferably, not less than five times.

Figure 1 shows a method of making a fibrous electret cloth according to the present invention. Fibrous cloth 20 is sent to the device 10, with the vessel 12 with a nonaqueous polar liquid 14. Capture, consisting of rolls 16 and 18, compresses and then releases the cloth as it is immersed in the liquid 14. When fibrous cloth 20 expands after compression, non-aqueous polar liquid penetrates into the interstices between the fibers, zmajeva the cloth 20. This design capture most suitable for soaking, as it helps to remove gas from a cloth. After exiting the vessel 12, the cloth goes into the drying device 22, which may include press for push-UPS 24 and mating pair of rolls 26 and 28. The rolls 26 and 28 out of cloth 20 excess nonaqueous polar liquid before the cloth is held between the heating elements 34 and 36 located on both sides of the fabric 20.

The drying device may be an external device that uses an input energy in order to cause the moisture to leave the canvas. The drying device may include a heat source, for example, straight-through furnace, a vacuum source or air source, such as convective air heater, i.e., any source of drying gas. Removal of the polar fluid from the fiber fabric such drying devices can be used by themselves or in combination with such mechanical devices, such as centrifuges or presses for push-UPS. Alternatively, for drying the fibrous web can be used a mechanism of passive drying, for example drying ambient air - though usually air drying does not meet the requirement for high performance manufacturing process. The present invention essentially p is epologue the use of any methods or devices, is able, without causing significant structural damage in the final product, to cause the moisture to leave the canvas. Received electret fabric can then be cut into sheets, rolled into a roll for storage or placed in various products, such as respirators or filters.

After drying the non-woven fabric has sufficient electric charge to be considered electracom. The resulting electret may be subjected to additional charging, which is to improve the filtering characteristics of the canvas, can increase the accumulated blade charge or change it otherwise. For example, fibrous electret nonwoven fabric may be treated by corona discharge after (or possibly before) making electret using the process described above. For example, the cloth may be charged in the manner described in U.S. patent No. 4,588,537 (Klaase and others) or the method according to U.S. patent No. 4,592,815 (Nakao). Alternatively, or in combination with these methods, the cloth may be subjected to a hydraulic charging, as described in U.S. patent No. 5,496,507 (Angadjivand, and others). Charging fibrous electret paintings can also be supplemented by technologies described in the open for the public patent applications to the US under the title "Method and apparatus for manufacturing fibrous E. cretnik paintings of the free fibers with the use of polar liquids" ("Method and Apparatus for Making a Nonwoven Fibrous Electret Web from Free-Fiber and Polar Liquid" US Serial No. 09/415,566) and "Method and apparatus for making a fibrous electret paintings with applying a wetting liquid and a non-aqueous polar liquid" ("Method and Apparatus for Making a Fibrous Electret Web Using a Wetting Liquid and an Aqueous Polar Liquid " US Serial No. 09/415,291), which were submitted on the same day as the present document.

The canvas in the device can be moved essentially any mechanism able to move the canvas from the moistening device to device for drying. Driven rolls are only an example suitable for this purpose mechanism, which likewise can be used conveyor belt or seizure.

It appears that the coefficient of surface tension nonaqueous polar liquid used at the stage of soaking, plays an important role in the process of formation of electrostatic charges in the fibrous web. For example, if the coefficient of surface tension nonaqueous polar liquid is substantially less than the surface energy of the fabric, the charge can be very small or absent. Therefore, for the purposes of the present invention it is preferable that the nonaqueous polar liquid had a coefficient of surface tension greater than the surface energy of the fiber fabric, at least 5 Dyne/cm, or, more preferably, 10 Dyne/see

At a certain composition of the nonaqueous polar liquid and fiber fabric wetting and drying can the be noiseless process, for example, consisting of immersing the fabric in a nonaqueous polar liquid for some time, extraction of the blade from the liquid and natural air drying. To improve soaking to the nonaqueous polar liquid and/or the fabric can be further applied energy or mechanical work, for example, by using the above capture. Although figure 1 shows that the soaking is carried out by immersing the fibrous fabric in nonaqueous polar liquid for the purposes of the present invention can be applied to any other suitable method of soaking. For example, fibrous cloth can be moistened aimed at him by the flow of non-aqueous polar liquid, for example, by spraying the fabric according to the method and using the apparatus described in U.S. patent No. 5,496,507 (Angadjivand, and others). Alternate soaking may be intensified by the use of vacuum equipment, pressure vessels and/or mechanical agitation, for example by means of ultrasonic vibrations. Such technologies are described in more detail in simultaneously examined the patent application US Serial No. 09/415,291, entitled "Method and apparatus for making a fibrous electret paintings with the use of a wetting liquid and a non-aqueous polar liquid" (Method and Apparatus for Making a Fibrous Electret Web Using a Wetting Liquid and an Aqueous Polar Liquid), to ora was filed on the same day, as this document. However, the fibrous non-woven fabric, especially webs of microfibers may be damaged if to improve soaking it will be accompanied by excessive energy or mechanical load.

The wetting liquid must wet the entire exposed surface is subjected to charging of the fibers. Nonaqueous polar liquid must be in contact, preferably in close contact with the fibers or to fill the voids between the fibers. It is preferable to carry out the procedure of soaking so that the fabric was essentially saturated non-aqueous polar liquid. The canvas can be filled with liquid so that upon completion of the soaking nonaqueous polar liquid dripping from the blade. For operations soaking can be used in different technologies. In those cases, when the soaking is carried out by spraying non-aqueous polar liquid, the mechanical excitation of oscillations of a cloth or a polar liquid or other mechanical means, the speed of the nonaqueous polar liquid relative to the nonwoven fabric preferably does not exceed approximately 50 m/sec, and more preferably does not exceed approximately 25 m/sec. Nonaqueous polar liquid preferentially wets the fibers of the fibrous fabric is not less than Uchenie 0,001 sec, but usually from several seconds to several minutes.

Non-aqueous polar liquid, suitable for use by the proposed method have a dipole moment of at least about 0.5 Debye, more preferably not less than about 0.75 Debye and most preferably not less than about 1.0 Debye. The dielectric constant (ε) such a fluid is equal to not less than about 10, more preferably not less than about 20, and more preferably not less than about 40. Such non-aqueous polar liquid, preferably not leave conductive non-volatile residues, which could mask or destroy the electrical charge of the canvas. Typically, there is a correlation between the value of the dielectric constant of the liquid and the degree of improvement of the characteristics of the filter. Fluids with higher values of the dielectric constant, typically provide more improved filtering performance. Examples of non-aqueous liquids suitable for use according to the present invention include methanol, isopropanol, ethylene glycol, dimethylsulfoxide, dimethylformamide, acetonitrile, and, among others, acetone and mixtures of these liquids.

Such non-aqueous liquids contain no more than 10% (by volume) of water, usually less than about 5%, and often less than about 2%. In some of the which cases nonaqueous polar liquid does not contain water.

Fabric, suitable for use in the present invention can be manufactured using various techniques, including by way of air-laying, wet-laying or pulling from the melt, as described in Van A. Wente article "Superfine thermoplastic fibers" (Superfine Thermoplastic Fibers), Indus. Engn. Chem. 48 p. 1342-46 (1956), published may 25, 1954, report No. 4364 Naval Research Laboratories, entitled "Manufacture of superfine organic fibers" ("Manufacture of Super Fine Organic Fibers", Van A. Wente, and others). For the manufacture of fiber cloths intended for use as filters, the most suitable fibers, in particular fibers, obtained by extrusion from the melt. "Microfibers" refers to fibers having an effective diameter of about 25 microns or less. The effective diameter of the fibers can be calculated from equation (12) from the work of Davies, C.N. "the Separation of airborne dust particles" ("The Separation of Airborne Dust Particles. Inst. Mech. Eng., London, Proc. 1B, 1952). For use in filters of the preferred microfiber with an effective diameter less than 20 μm, and more preferable - with diameters of approximately 1 to 10 microns.

For more light, less dense fabric, microfiber can be mixed with staple fibers. The decrease of the density of the fabric helps to reduce pressure drop. Small prepodavanija desirable in individual respirators, because it makes the mask more comfortable to the user. The content of staple fibers preferably does not exceed 90% (by weight), and more preferably does not exceed 70%. Fabrics, containing staple fiber described in U.S. patent No. 4,118,531 (Hauser).

The composition of the electret paintings can be entered active particles for various purposes, for example, sorbent, catalyst, etc. for Example, in U.S. patent No. UAH 5,696, 199 (Senkus and others) described various types suitable for this active particles. Active particles having absorbing properties - for example, activated carbon or aluminum - can be entered in the cloth to absorb the vapors of organic substances during filtration. Typically, these active particles may be present in amounts up to 80% (by volume) of the composition of fabrics. Non-woven cloth containing active particles are described, for example, in U.S. patent No. 3,971,373 (Braun); No. 4,100,324 (Anderson) and No. 4,429,001 (Kolpin and others).

Among the polymers suitable for use in the manufacture useful for the purposes of the present invention the fibers are non-conductive thermoplastic organic polymers. Such polymers are typically able to hold large values of the trapped electric charge, and suitable for processing into fibers, for example, using devices pulling from the melt or spinning the disorders. The term "thermoplastic" refers to a polymer that softens under the action of heat. The term "organic" refers to a polymer structure which is formed by the carbon atoms. Among the preferred polymers are polyolefins, such as polypropylene and poly-4-methyl-1-penten; mixtures or copolymers containing one or more of these polymers; and mixtures of such polymers. Other polymers may include polyethylene and other polyolefins, polyvinylchloride, polystyrene, polycarbonates, polyethylenterephtalate, other polyesters, and combinations of these polymers, and other non-conductive polymers.

Fibers from these polymers may be made with an admixture of other suitable additives. Such fibers are to be composed of multiple polymer components can ekstrudirovaniya be molded or otherwise. See U.S. patent No. 4,729,371 (Krueger and Dyrud) and U.S. patent No. 4,795,668 and No. 4,547,420 (Krueger and Meuag). These different polymer components may be located along the length of the fibers in parallel or concentrically, forming, for example, two-component fiber. Fibers can be assembled in such a way as to obtain a macroscopically homogeneous fabric, i.e., the fabric formed from the fibers almost the same structure.

The fiber used for the purposes of the present invention, for the formation of suitable dsfilters fibrous product does not require use of ionomers, in particular, neutralized with metal ion copolymers of ethylene and acrylic or methacrylic acid (or both together). Fibrous electret nonwoven cloth can be made of the above polymers without the addition of from 5 to 25% (by weight) of (meth)acrylic acid partially neutralized with metal ions of the acid groups.

Characteristics of electret paintings can be improved by introducing additives in the composition from which the formed fibers, prior to contact with the polar liquid. In combination with the fibers or material from which they are formed, preferably using "improving additive against oil mist". This "improving additive against oil mist" is a component that, when added to the material from which is formed of fiber, or, for example, deposited on the finished fiber, can improve the ability of the fibrous electret nonwoven cloth filter oil aerosol particles.

To enhance the performance of electret to the polymeric material can be introduced Supplement containing fluorine. In U.S. patent No. 5,411,481 and No. 5,472,481 (Jones and others) described the application of permit processing by melting fluoride additive having a melting point of not less than 25°and a molecular weight of approximately from 500 to 2000. This forcode the containing additive can be used to improve resistance to oil mist. Known class of additives that improve the properties of the rechargeable water jet of electrets. Such additives represent a connection, which includes the solution of perforate containing not less than 18% of fluorine (of the total weight of the additive) - see U.S. patent No. 5,908,598 (Rousseau, and others). One of the additives of this type is introduced in an amount not less than 0.1% by weight of thermoplastic material fluorinated oxalide described in U.S. patent No. 5,411,576 as "Additive A".

Other possible additives are thermally stable compounds or oligomers based on triazine, which in addition to nitrogen atoms of the triazine containing at least one nitrogen atom. Another additive that has been proven that it improves the properties of electrets, charge jet of water is Chimasssorb™ 944 LF (poly[[6-(1,1,3,3,-TETRAMETHYLBUTYL)amino]-s-triazine-2,4-diyl][(2,2,6,6.-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6.-tetramethyl-4-piperidyl)imino])supplied by the company Ciba-Geigy Corp. Supplements Chimasssorb™ 944 and "Additive A" can be combined. Additive Chimasssorb™ and/or other aforementioned additives present in the polymer in amounts of, preferably, from about 0.1% to about 5% weight of the polymer, more preferably from about 0.2% to about 2%, and even more preferably from about 0.2% to about 1% weight of the polymer. It is also known that some other space is stenno employed amines resulting increase in leaf electric charge, which improves the filtering.

Such containing added fiber after forming of the heated molten mixture of polymer and additives - and post-operative vacation and charging - can be subjected to heat treatment during the formation of the electret web. The finished product can have improved characteristics of the filter, if electret made this way - look at the patent application U.S. Serial No. 08/941,864, corresponding to international publication WO 99/16533. Additives can be incorporated into the fabric and after molding, for example, using the method of surface fluorination described in filed July 2, 1998 the patent application U.S. Serial No. 09/109,497 (Jones and others).

The polymeric material for forming fibers at room temperature has a specific resistance not less than 1014Ohm×see it is Preferable that the specific resistance was not less than 1016Ohm×see Specific resistance of the polymer material for the manufacture of fibers can be determined using the standard test ASTM D 257-93. The material for the fibers used for the manufacture of fibers by extrusion from the melt must be practically free from components such as antistatic agents, which can increase the conductivity of the material, or otherwise affect the ability of the fibers to hold the electrostatic damage to the module is practical charges.

Manufactured in accordance with the present invention, the nonwoven fabric can be used in the filtration masks, are made so as to protect at least the nose and mouth of the user.

Figure 2 shows the filtering face mask 40, which can be constructed with the use of an electrostatically charged nonwoven fabric made according to the present invention. Cup-shaped, in General, the portion of the mask frame 42 is made to encircle the nose and mouth of the user. Electret filter material designed to remove particle contaminants from the inhaled air, is placed in the body of the mask 42, as a rule, throughout its surface. A layer of electret filter material may be supported by other layers, for example, forming a layer made of thermally connected fibers, such as bicomponent fibers having outer thermoplastic layer, which gives them the ability to be welded to each other touch points when heated. Examples of other structures of the filtering face mask that can be used fibrous electret nonwoven fabric, to give the U.S. patent No. 4,536,440 (Berg), No. 4,807,619 (Dyrud and others), No. 4,883,547 (Japuntich), No. 5,307,796 (Kronzer) and No. 5,374,458 (Burgio). Electret filter material can also be applied, for example, the filter cartridge respirators, such as cartridges are described in U.S. patent No. Re. 35,062 (Brostrom and others) or No. 5,062,421 (Burns and Reishel). Therefore, the mask 40 shown here for illustrative purposes only, and the use of this electret filter material is not limited to the implementation described here. Part of the housing 42 is porous, so that the inhaled air could pass through it.

To hold the mask 40 on the face of the user may be provided with tape or a soft mount 44. Although figure 2 shows only one tape 46, a soft mount 44 may consist of more than one tape 46 and have many different constructions, for example, disclosed in U.S. patent No. 4,827,924 (Japuntich, and others), No. 5,237,986 (Seppalla and others) or No. 5,464,010 (Byram).

Applicants believe that the present method of charging creates the fibers of positive and negative charges so that these positive and negative charges are randomly distributed throughout the volume of the canvas. Random charge distribution ensures the absence of polarization of the canvas. Thus, fibrous electret nonwoven fabric made in accordance with the present invention, almost no is polarized in the direction perpendicular to the plane of the canvas. Fiber, charged by the above method, show a perfect match with the configuration of charges shown in Figure 5C is the patent application U.S. Serial No. 08/865,362. If fibrous fabric was subjected to the procedure of charging by corona discharge, the charge distribution it will be similar to the configuration shown in Figure 5B of the same application. Cloth made from fibers that have been charged exclusively as stated here by the way, as a rule, has captured unpolarized charge uniformly distributed throughout the volume of the canvas. The term "essentially unpolarized charge corresponds to a fibrous electret paintings, which in DRT-analysis detected discharge current, the magnitude of which is related to the area of the measuring electrode, does not exceed 1 µc/m2. This configuration charges can be detected by subjecting the fabric to the test mode, thermally stimulated discharge current (TSRT).

Analysis of thermally stimulated discharge current is heated electret cloths with the intention that captured and frozen charges was freed and was able to form a configuration with lower energy, creating a discharge current that can be detected in the external circuit. Thermally stimulated discharge currents are considered Lavergne and others in the article "Study of thermally stimulated currents" (A review of Thermo-Stimulated Current, IEEE Electrical Insulation Magazine, vol. 9, no. 2, 5-21, 1993, Chen et al in the book "Study of thermally stimulating avannah processes" (Analysis of Thermally Stimulated Process), Pergamon Press, 1981.

The polarization of the electric charges can be created in the canvas, which was charged in accordance with the present invention, by heating it to a certain temperature higher than the glass transition temperature (Tgof the polymer, i.e. the temperature at which the polymer changes from a hard and relatively brittle condition to a viscous or rubbery. The glass transition temperature (Tg) below the melting temperature of the polymer (Tm). After heating to a temperature exceeding (Tg), the sample is cooled at constant electrostatic field to "freeze" the polarization of the trapped charges. Now thermally stimulated discharge current can be measured, reheating electret material with a constant rate of increase of temperature and measuring generated in the external circuit current. For polarization and subsequent thermally stimulated discharge handy device Solomat TSC/RMA model 91000 rotating electrode manufactured by TherMold Partners, L.P., Thermal Analysis Instruments of Stamford, Connecticut.

Values of the discharge current and temperature are deposited on the graph along the x (y) and y (abscissa). The peak value (peak current) and the waveform of the discharge current characterize the mechanism of retention of charges in the electret sheet. The electret paintings containing electrostatic for the poison, the maximum peak and the shape of the curve correlated with the configuration of charges captured electret material. The amount of charge protexia in the external circuit due to the movement of charges in the electret sheet configuration with lower energy can be determined by integrating the peak (or peaks) discharge curve.

Fibrous electret cloth according to the present invention show the measured charge density, which is a measure of the relative amount of unpolarized trapped charges. The measured charge density can be estimated using the considered procedure. Fibrous electret cloth according to the present invention preferably show the measured charge density not less than about 0.12 microcolor per square meter (µc/m2), more preferably the measured charge density is not less than approximately 0.2 µc/m2even more preferably more than 0.3 µc/m2. In some cases, the measured charge density can exceed 0.6 µc/m2.

Advantages and other features and details of the present invention is further illustrated below by examples. Although these examples are intended for this purpose, referred to the specific ingredients, quantities and other conditions are not n is in any case should not be construed as unduly limit the present invention. For example, even if the example shows a method of manufacturing a single product, the manufacturing process can be continuous. For further disclosure of the selected mainly examples showing how to implement the preferred implementation of the present invention and which properties can, as a rule, possess a finished product.

EXAMPLES

Sample preparation

Non-woven cloth was made generally as described in Wente, Van A. Indus. Engn. and Chem. 1342-46 (1956). As a thermoplastic resin was used, if not stated otherwise, polypropylene FINA 3860X supplied by the company Fina Oil and Chemical Co., Houston, Texas. Used extruder Berstoff 60 mm, 44:1, with eight heating zones and two together-rotating augers supplied by the company Berstoff of Charlotte, North Carolina. If the resin additives were introduced, they were prepared in the extruder Werner Pfleiderer 30 mm, 36:1, together with two rotating augers supplied by the company Corp. of Ramsey, New Jersey. The specific weight of the fabric was, unless otherwise indicated, approximately 54 to 60 g/m2.

Test DOP-permeability and pressure drop

Test DOP-permeability and pressure drop was carried out by passing an aerosol containing particles of dioctylphthalate (DOP) with a median diameter of 0.3 μm, a pattern non-woven cloth with a diameter of 11.45 cm (4.5 inches) with a flow rate of 42.5 DM3/min. flow Rate at the surface about what Azza was 6.9 cm/sec. Particles DOP was created using the company supplied TSI of St. Paul, Minnesota TSI atomizer No. 212 having four holes. Pressure clean air inlet of the spray was 270 kPa (30 psi), which ensured the generation of an aerosol concentration of DOP particles from about 70 to 110 mg per cubic meter. The samples were exposed to a stream containing particles DOP aerosol for 30 seconds. The permeability of the DOP particles through the sample was determined using optical storage chambers Percent Penetration Meter Model TRA-8F, the company supplied Air Techniques Inc. of Baltimore, Maryland. The pressure drop across the sample (PD) was measured by an electronic pressure gauge and recorded in inverse millimeters of water column (mm H2O).

The values of DOP-permeability (DOPP) and pressure drop are used to calculate the quality factor (QF) natural logarithm (In) DOFP in accordance with the following formula:

QF[(mm H2O)-1]=-(ln(DIP[%])/100)/ΔR[mm H2O].

The quality factor of the sample that have not been previously exposed to an aerosol, is called the initial quality factor (QFH). Higher values of the initial quality factor indicate the best initial filtering properties. On the contrary, lower values of the initial quality factor consistently correlate with the worst characteristics of the filter is for.

The measured charge density

Polarization electrostatic charges created in four samples paintings of each species by: 1) heating each sample to a temperature of 100°With; 2) the polarization of each of the samples in a constant electrostatic field with a strength of 2.5 kV/mm for 5, 10, 15 or 20 minutes; and 3) cooling each of the samples in the presence of an electrostatic field to a temperature of - 50°to "freeze" captured and induced in the leaf charges. Then each sample was heated again to "frozen" charges acquired mobility and could form a configuration with lower energy, creating a measurable discharge current in the external circuit. In particular, after the above-mentioned polarization of each of the samples was heated from a temperature - 50°With up to approximately 160°With a speed of about 3°in a minute. Generated by the external current was measured as a function of temperature. Unadjusted value of the measured charge density of each of the samples was determined by calculating the area under the curve peak and dividing the result by the area of the sample. For the unadjusted value of the measured charge density paintings were accepted most of the unadjusted values measured charge density of all four samples of this type of fabric. Polarization and after the respective thermally stimulated discharge was carried out by the device Solomat TSC/RMA model 91000 rotating electrode, produced by TherMold Partners, L.P., Thermal Analysis Instruments of Stamford, Connecticut. The measured charge density due to the captured non-polarized charges, can be determined by comparison with a cloth of the same composition and with the same physical characteristics, but not exposed to processing. The measured charge density of the treated cloth was determined by subtracting the unadjusted values measured charge density of the raw canvas of the unadjusted values measured charge density of the treated fabric.

Examples 1-8 and comparative example C1

The canvas of the extruded from the melt microfibers were produced as described above, polypropylene FINA 3860X supplied by the company Fina Oil and Chemical Co. The specific weight of the fabric was about 50-60 grams per square meter (g/m2) when the effective diameter of the fibers is about 8-9 microns. This fabric were cut individual samples about the size of 22×11 inches (55,9×27.9 cm). These individual samples were saturated non-aqueous liquid, for which they were immersed into the liquid, squeezed and not removing from the liquid, and allowed to expand. Then, the samples were removed from the liquid and dried in air. Of these samples cut out circles with a diameter of about 5.25 inches (13.3 cm), which have been subjected to the above test, DOP-bronzemist and the pressure drop in the Central part of each of the circles with a diameter of about 4.5 " (11,4 cm). For each of the samples by the method described above was determined initial quality factor (QFH). For each of the samples was cut and tested a sample duplicate. Were cut and tested the same samples and the raw canvas. Average results of duplicate tests are given in table 1.

The data in table 1 show that soaking fiber fabric selected liquid and subsequent drying has provided the canvas with a good initial value of the quality factor. The data in table 1 also show that, as a rule, the higher the value of the dielectric constant of the liquid, the more noticeable the improvement of the filtering performance it provides.

Table 1
The influence of the non-aqueous processing on the quality of filtering
Example No.LiquidDipole moment (Debye)The dielectric constant (ε)QFh(mm H2O)-1
1Acetone2,8820,70,25
2Acetonitrile3,9237,50,19
3Dimethylformamide3,82 36,710,38
4The sulfoxide3,9646,60,22
5Ethylene glycol2,2837,00,28
6Isopropanol1,6618,30,09
7Methanol1,7032,60,30
8Acetic acid1,776,150,14
C1nonono0,09

Examples 9-16 and comparative example C2

The canvas of the extruded from the melt of the microfibers was made as well as for examples 1-8 and comparative example C1, except that it was introduced additive "Additive A" according to U.S. patent No. 5,411,576 in an amount of about 1% by weight of polypropylene resin, and the samples were subjected to tempering at a temperature of 160°C for 10 minutes.

Additive "Additive a" has the following structure:

The resulting canvas either by weight or by the effective diameter of the fibers was not different from cloth produced without additives. From canvases were cut, moist and dried separate samples of the same was made the but in examples 1-8. Of these samples were cut circles subjected to the above tests. Average results of duplicate tests are given in table 2.

Table 2
The influence of the non-aqueous processing on the quality of filtration in the presence of fluoride supplements "Additive A"
Sample # LiquidDipole moment (Debye)The dielectric constant (ε)QFh(mm H2O)-1
9Acetone2,8820,70,23
10Acetonitrile3,9237,50,30
11Dimethylformamide3,8236,710,22
12The sulfoxide3,9646,60,38
13Ethylene glycol2,2837,00,62
14Isopropanol1,6618,30,20
15Methanol1,7032,60,40
16Acetic acid1,776,1 0,12
C2nonono0,11

The data in table 2 show that, as a rule, the higher the value of the dielectric constant of the liquid, the more noticeable the improvement of the filtering performance it provides. All the samples tested showed improved filtering performance relative to the comparative sample which was not subjected to processing in accordance with the present invention.

Examples 17 to 24 and comparative examples C3-C6

Examples 17 to 20 and comparative examples C3-C5 were made of canvas from extruded from a melt of polypropylene microfibers in the same way that was described with reference to examples 1-8 and C1, but for the manufacture of fibers was used polypropylene ESCOPRENE 3505G (supplied by Exxon Corp.). Examples 21-24 and C6 were made as examples 17-20 and C3-C5, but unlike the latter, their composition was introduced fluorine-containing additive "Additive A" according to U.S. patent No. 5,411,576. All the paintings had a specific weight of about 50-60 g/m2and the effective diameter of the fibers is about 8-9 microns. The additive was injected in an amount of about 1% by weight of the polypropylene resin, the samples were subjected to tempering at a temperature of 140°C for 10 minutes. All examples 17-24 and C3-C6 were processed by the same method as examples 18 and C1. For each of the examples was determined initial quality factor (QFH).

Then all of the paintings by the method described above was determined as the measured charge density.

The data of table 3 show that the fabric treated with fluids with higher values of the dielectric constant, tend to show higher values of the measured charge density and a more marked improvement in filtering performance. Examples 21 and C6 drawn from the General trend (negative value and high value, respectively), probably due to the interaction of the additive and solvent.

Table 3
The measured charge density after polarization
SampleNonaqueous polar liquidQFh(mm H2O)-1Unadjusted measured charge density (µc/m2)The measured charge density (µc/m2)
C3no0,090,050,00
17acetone0,170,710,66
18the sulfoxide0,661,611,56/td>
C4n-hexane0,080,110,07
19isopropanol0,090,070,02
20morpholine0,170,660,61
C5no0,148,950,00
21acetone0,188,65-0,35
22the sulfoxide0,6514,55,55
C6n-hexane0,1211,32,35
23isopropanol0,17of 10.581,63
24morpholine0,299,780,83

Examples 25-26

Examples 25-26 were studied to determine the influence of the surface tension of the liquid on the charge of cloths made from microfibers obtained by the method of extrusion from the melt. To study the inuence of the surface tension of a liquid by the amount of electric charge cut from two different paintings from extruded from the melt fibers samples of size 11×21 inches (55,9×27.9 cm) were immersed in a mixture of ethanol with water. Issledovanlyafauny consisted of fibers:

Table 4
SampleDescriptionThe surface energy (units)
25Polypropylene FINA 3860 with fluoride additive (1% by weight of the polypropylene) 
26Polypropylene FINA 3860 

Examples 25-26 were made from the following table 4 materials on the technology used for the manufacture of example 1. Each of the first samples were processed in approximately 200 ml of ethanol, poured into a plastic or aluminum container. Each of the samples in addition was rumpled, to ensure complete wetting and almost complete removal of entrapped air. Then the vessel was added the amount of water needed to obtain one of the eight preset calculated values of the coefficient of surface tension- 24, 26, 28, 30, 35, 40, 50 or 60 Dyne/see the Required amount of added water was calculated by the Szyszkowski equation given in the book "the properties of gases and liquids, their estimation and correlation" ("The Properties of Gases and Liquids, their Estimation and Correlation" Reid, Prausnitz and Sherwood, pp. 622-624, 3-th edition, McGraw-Hill, Inc., New York, 1977). The investigated values of the coefficient of surface tension, the corresponding values of ethanol content and the number of added water are shown below in table 5.

Table 5
Estimated value of the coefficient of surface tension (Dyne/cm)The volume fraction of ethanolThe amount of water added to 200 ml of ethanol (ml)
240,88326,3
26determined as 0.72077,8
280,587140
30to 0.480217
350,294480
400,184889
500,0742510
600,0277200

After adding water to the vessel, submerged in the liquid, the painting was male for about 30 seconds, and then left free. The sample remained in the water-alcohol mixture for about 5 minutes and then again 30 seconds Mali and again was released. Again, after waiting five minutes, the sample is again 30 seconds Mali and was released. Then the sample to remove excess fluid was twice passed through the rolls and at night and hung them on the clothesline to dry. From each sample cut out circles, and a pair of such groups were subjected to the above test, DOP-permeability and pressure drop. Averaged (two tests) the results of tests for each condition are presented below in table 6.

Table 6
Estimated value of the coefficient of surfaceThe average value of the quality factor (MM H2O)-1
tension (Dyne/cm)Sample 25Sample 26
240,747(0,088)0,194(0,033)
260,936(0,006)0,214(being 0.036)
280,952(0,124)0,452(0,008)
300,807(0,239)0,669(0,023)
351,161(0.079 in)0,742(0,056)
401,169(0,042)0,682(0,064)
500,873(0,053)0,703(0,043)
600,609(0,008)0,580(0,020)

Values in parentheses are standard deviations.

Examples 25, which comprised about 1% of fluoride supplements and subjected to heat treatment for 10 minutes at 140°With demonstrated sufficiently smooth curve with a flat maximum quality factor when the value of the coefficient of surface tension of the water-alcohol mixture in the range of from about 35 to 40 Dyne/see Examples 26, not containing such additives, showed a sharp increase in the coefficient of the quality coefficient of the surface tension of the water-alcohol mixture in the range of from about 24 to 28 Dyne/see

Indicated a sharp increase in the quality factor, apparently, due to the surface energy of the canvas. The surface energy is made without additives polypropylene is about 30 Dyne/cm of Liquid surface tension coefficient of less than a specified value, moisten the fibers of the fabric in a continuous film, whereas a liquid with surface tension coefficient exceeding a specified surface energy, tend to form when pressing or drying drops. Examples 25 made of a fluoride additive, obviously due to the influence of additives, have lower surface energy than the examples 26. It can be assumed that the magnitude of the surface energy of the examples 25 is in the range of about 20 Dyne/cm or less. In other words, it seems, least of all coefficients of surface tension, studied for tests on these samples than probably explains the absence of a jump in quality factor with the change of the coefficient of surface tension.

The above-cited patents and patent applications, including those cited in the section "Background of invention"included in the text as reference.

The present invention can be successfully implemented in the absence of any element, if it was not specifically listed asintegral.

1. A method of making a fibrous electret fabric, consisting of the steps: soaking consisting of non-conductive fibers of the fabric a sufficient number of non-aqueous polar liquid, not giving the fibers conductive properties; and thorough drying of the moistened cloth for the formation of a fibrous electret web.

2. The method according to claim 1, characterized in that the fibrous electret fabric has long-lasting electrostatic charge.

3. The method according to claim 2, characterized in that the fibrous electret fabric is a nonwoven, which contains microfiber.

4. The method according to claim 1, characterized in that the fibrous electret sheet can be demonstrated in the test results DOP-permeability and pressure drop of the quality factor is not less than 0.2 (mm H2O)-1.

5. The method according to claim 1, characterized in that the fibers on their surfaces contain fluorine atoms.

6. The method according to claim 1, characterized in that it includes a step of hardening fiber fabric, prior to the step of soaking the cloth.

7. The method according to claim 1, characterized in that the cloth is soaked: by pushing the cloth, immersed in a nonaqueous polar liquid, and providing him the opportunity to return in the not-compressed state, while remaining immersed in the liquid; by direction of the flow of the river is Noah polar liquid on the cloth; by transmission of sound energy through the polar liquid to the cloth; by increasing pressure nonaqueous polar liquid in contact with the fabric; and/or by immersing the fabric in a nonaqueous polar liquid.

8. The method according to claim 1, characterized in that the nonaqueous polar liquid selected from the group consisting of methanol, isopropanol, ethylene glycol, dimethyl sulfoxide, dimethylformamide, acetonitrile and acetone.

9. The method according to claim 1, characterized in that the cloth dries: on the air; the effect of heat source on canvas; static vacuum on the canvas; the influence of the flow of heated dry gas onto the canvas; and/or mechanical removal of non-aqueous polar liquid.

10. The method according to claim 1, wherein the fibers include polypropylene, poly-4-methyl-1-penten or both of the polymer.

11. The method according to claim 1, characterized in that the nonaqueous polar liquid has a dipole moment, which constitutes at least about 0.5 Debye, and the fact that the nonaqueous polar liquid has a dielectric constant of at least about 10.

12. The method according to claim 1, characterized in that the nonaqueous polar liquid leaves no conductive non-volatile residues, which could mask or destroy the electrical charge of the canvas.



 

Same patents:

FIELD: methods of production of electret items, electret filters and respirators.

SUBSTANCE: the invention presents a method of production of electret items, electret filters and respirators with heightened resistivity to the oil mist. The invention falls into production processes of electret items, electret packed beds and respirators, and may be used for removal of corpuscles from gases, especially for removal of aerosols from air. The method provides for: formation of a melted material consisting of a mixture of a polymer composed of a mixture of a polymer representing a non-current-conducting thermoplastic resin with a specific resistivity exceeding 1014 Ohms·cm with a fluorine compound as an additive compound; shaping it to the required form and quenching it up to the temperature lower than the melting point of the polymer. The material is calcined and treated with an electric charge to give it electret properties. The invention improves the capability of filtering oily aerosols.

EFFECT: the invention improves the capability of filtering oily aerosols.

19 cl, 16 tbl, 19 dwg, 23 ex

The invention relates to the production of filter materials intended for the manufacture of filter used for the purification of gas and air from dust and liquid droplets

The invention relates to a filter material for air purification from harmful substances such as harmful aerosols (dust, smoke, fog), vapours of organic compounds with a boiling point above 60oWith (benzene, toluene, ethanol, gasoline, kerosene, acetone, etc., and acid gases (chlorine, fluorine, sulfur-containing compounds)

The invention relates to materials for liquidation of emergency floods of oil and petroleum products to surface water and land
The invention relates to filtration materials, mainly used for plastic dispersions type, such as dispersion cataphoretic primer used for painting surfaces in automotive production

The invention relates to filtration materials used for cleaning hot gases with temperatures up to 260oWith

The invention relates to the development of polymer fine-fibrous filtering materials, exhibiting a stable electret effect

FIELD: methods of production of electret items, electret filters and respirators.

SUBSTANCE: the invention presents a method of production of electret items, electret filters and respirators with heightened resistivity to the oil mist. The invention falls into production processes of electret items, electret packed beds and respirators, and may be used for removal of corpuscles from gases, especially for removal of aerosols from air. The method provides for: formation of a melted material consisting of a mixture of a polymer composed of a mixture of a polymer representing a non-current-conducting thermoplastic resin with a specific resistivity exceeding 1014 Ohms·cm with a fluorine compound as an additive compound; shaping it to the required form and quenching it up to the temperature lower than the melting point of the polymer. The material is calcined and treated with an electric charge to give it electret properties. The invention improves the capability of filtering oily aerosols.

EFFECT: the invention improves the capability of filtering oily aerosols.

19 cl, 16 tbl, 19 dwg, 23 ex

FIELD: methods for imparting charge to fibrous webs by means of non-aqueous liquid for usage of said webs as filters in filtering face masks for protection of user's mouth and nose.

SUBSTANCE: method involves wetting web formed from non-conductive fibers with non-aqueous polar liquid; substantially drying web for producing fibrous electronic web. Method differs from known methods of imparting charge to web in that it requires less energy for drying of web than methods using aqueous liquids. Also, many kinds of filaments poorly wetted with aqueous liquids are immediately wetted with non-aqueous liquids.

EFFECT: increased efficiency and simplified method.

12 cl, 2 dwg, 6 tbl, 26 ex

FIELD: fine-fiber filtering materials.

SUBSTANCE: the invention is pertinent to fine-fiber filtering materials used for individual means of protection of respiratory organs. The invention offers a protection material, a means of protection containing the offered material and a method of production of the fibrous material providing for electrostatic forming of the fibrous material from a solution of styrene copolymer with acrylonitrile in an organic solvent at the presence of electrostatic additives of bromide or iodide salts of tetraethyl- or tetrabutyl-ammonium. At that a solution containing an additive of a high-molecular methylmethacrylate in amount of 0.001-0.01 mass % in the capacity of dissolvent is used a mixture of ethyl acetate with butyl acetate at their mass ratio in the solution from 1/9 up to 9/1 accordingly. The invention allows to produce a material with improved mechanical characteristics and to provide stability of the production process.

EFFECT: the invention ensures production of the material with improved mechanical characteristics and stability of the production process.

5 cl, 2 tbl, 1 ex

FIELD: fine filtration of air; cleaning ventilation emissions from oil mist; cleaning air in venting pipe lines of gas-transfer unit oil tanks.

SUBSTANCE: proposed filter includes filter element with filter medium made from coarse and fine fibers laid in between outer and inner cylinders, cover and bottom. Filter medium is made from longitudinal and transversal oil-resistant synthetic (polypropylene) fibers; ratio of mass of longitudinal and transversal fibers is equal to (6-8) : 1 and ratio of diameters of thin and coarse fibers is equal to (0.5-1) : 10.

EFFECT: enhanced efficiency of cleaning at considerable increase of service life, oil return coefficient; enhanced ecological safety around compressor stations.

2 cl, 2 dwg

FIELD: filtering materials for liquid and gaseous fluids.

SUBSTANCE: filtering material is made of thermoplastic polymeric fibers. The density of material increases downstream, whereas the diameter of fibers decreases downstream. The inner layer of the material has areas the density of fibers in which is lower than the averaged density of upper layers by a factor of 2-6.

EFFECT: enhanced strength.

1 dwg, 1 tbl

FIELD: polymer materials and gas treatment.

SUBSTANCE: invention relates to polymeric fibrous filter materials designed for effective cleaning of air stream due to realization of mechanical and electrostatic filtration. Material suitable for use in respiratory masks contains (i) a layer in the form of cloth 1 mm thick made from polypropylene fibers with diameter 0.5-1.5 μm, packaging density 0.25-0.30 g/cm3, and electric charge with surface density 17-21 nCl/cm2, the layer being made by aerodynamic atomization of melt and electrization of fibers in corona discharge field during their formation, and (ii) an additional layer in the form of non-electrized cloth 1 mm thick made from polypropylene fibers with diameter 10-20 μm and packaging density 0.25-0.30 g/cm3, which is placed on the side directly facing air stream to be cleaned, the two layers being attached to each other by spot weld. Presence of two layers results in separate but complementary realization of mechanical and electrostatic filtration.

EFFECT: enhanced air cleaning efficiency and prolonged lifetime of filter material.

1 tbl

FIELD: methods and devices used for production of fibrous electret linen.

SUBSTANCE: the invention is pertaining to methods and devices used for production of fibrous electret linen. The method of giving of an electrostatic charge to the fibrous non-woven linen provides that the fibrous linen is soaked with a wetting liquid, then it is saturated with a water polar liquid and dried. The gained dry product represents an electret, which may be efficiently used in the air filters, for example, in respirators.

EFFECT: the invention ensures production of a fibrous electret linen, which may be efficiently used in the air filters, for example, in respirators.

13 cl, 3 ex, 5 tbl, 4 dwg

FIELD: chemical industry; oil refining industry and other industries.

SUBSTANCE: the invention is pertaining to production of materials for the filtering water-separating elements used in devices for purification of organic fluids, predominantly, hydrocarbon fuels, oils, oil products from the emulsified water and mechanical impurities, and may be used for purification of aircraft and car fuels in chemical industry, oil refining industry and other industries. The porous reinforced material is produced out of a permeable in all directions polymeric material with a side-porous deep structure having a total porosity of no less than 50 % with the sizes of the elementary pores, predominantly, of 10 - 200 microns. At that the porous reinforced material is formed out of a framed material having filaments or fibers with a diameter, predominantly, of 5 - 400 microns, and an arranged between the above mentioned filaments or fibers filler manufactured out of a porous polyvinyl formal produced by the method of a dew-point structurization with the thermal treatment of a homogenized in water composition containing at least polyvinyl alcohol and aldehyde. The element for the screen-water-separator contains a filtering-coagulating septum embraced by a perforated shell rings and limiting from above and from below covers. At that the septum is made multilayered out of a sheet manufactured out of the above porous reinforced material. The technical result consists in an increased effectiveness of purification of fuels (jet engine fuels and diesel fuels) and the gaseous oil products from water, and also asphalt-resinous and sulfur-containing materials, an increased service life and productivity of the filtering screens based on the indicated filtering-coagulating material.

EFFECT: the invention ensures an increased effectiveness of purification of jet engine fuels, diesel fuels, gaseous oil products from water and also asphalt-resinous and sulfur-containing materials, service life and productivity of the filtering screens based on the filtering-coagulating material.

13 cl, 3 dwg

FIELD: methods of production of filtering materials.

SUBSTANCE: the invention is pertaining to the methods of production of filtering materials, in particular, to the method of production of the filtering fibrous materials, which may be used in a means of individual protection. The filtering fibrous material is produced by an electrostatic formation of a non-woven fibrous material from a working polymeric fiber-forming solution with dynamic viscosity of 1-30P, electrical conduction of 10-4-10-7 ohm-1 cm-1 in an electrostatic field at a potential difference from 10 up to 150 kV. The solution contains in the capacity of the polymer from 8.9 up to 24.6 mass % of styrene copolymer with 5.2-30.4 mass of acrylonitrile or triple styrene copolymer with 5.2-30.4 mass of acrylonitrile and 3.7-42.1 mass % of methyl methacrylate. As a dissolvent they use ethyl acetate, or butyl acetate either their mixture. The solution in addition contains high-molecular polymethyl methacrylate, a distilled water, the lowest alcohol taken from the group ethyl alcohol, methyl alcohol or isopropyl alcohol, at the following contents of ingredients of the polymeric fiber-forming solution, in mass %: polymeric compound - 8.9-24.6; high-molecular polymethyl methacrylate - 0.011-0.02; distilled water - 0.01-0.1; the lowest alcohol - 17-28; dissolvent - the rest. The efflux of the working polymeric fiber-forming solution is exercised at the volumetric speed of 0.1 up to 6 cm3 /minute. Feeding of the working polymeric fiber-forming solution is conducted from the space interval of 12-42 cm beginning from the point of its coming out from the batching device up to the settling surface. The produced filtering fibrous material contains a technological and a working layers made out of the polymeric fibrous material produced by the above described method. The technological layer material has the surface density of 1-3 g/m2 and is made out of fibers of 3-5 microns diameter. The working layer material is made out of fibers of 1.5-3 microns diameter. The double-layer material has the surface density of 32-38 g/m2, the standard resistance of 0.8-1.2 mm of the water column and the skip coefficient of no less than 95 %. The invention ensures an improved quality of the filtering material due to an increase of efficiency of penetration of fragments with a diameter of 0.3 microns at the standard resistance of 1.0 mm of the water column.

EFFECT: the invention ensures an improved quality of the filtering material, an increased efficiency of penetration of fragments with a diameter of parts of microns at the standard resistance of 1 mm of the water column.

4 cl, 2 ex

FIELD: natural gas industry; petrochemical industry; oil-producing industry; other branches of industry; methods of production of filtering materials and the filters for purification of gases and aerosols.

SUBSTANCE: the invention offers the filtering material made out of the polysulfone fibers with different diameter of the fibers produced by electromolding from the solution in the organic solvent with addition of an electrolyte; and the frame design filter supplied with the produced material having the density of 30 - 50 g/m2. The invention ensures the effective filtration of the aerosol particles at the high thermostability of the filter.

EFFECT: the invention ensures the effective filtration of the aerosol particles at the high thermostability of the filter.

5 cl, 1 tbl, 1 dwg

FIELD: methods for imparting charge to fibrous webs by means of non-aqueous liquid for usage of said webs as filters in filtering face masks for protection of user's mouth and nose.

SUBSTANCE: method involves wetting web formed from non-conductive fibers with non-aqueous polar liquid; substantially drying web for producing fibrous electronic web. Method differs from known methods of imparting charge to web in that it requires less energy for drying of web than methods using aqueous liquids. Also, many kinds of filaments poorly wetted with aqueous liquids are immediately wetted with non-aqueous liquids.

EFFECT: increased efficiency and simplified method.

12 cl, 2 dwg, 6 tbl, 26 ex

Up!