TW202110520A - Filter media comprising polyamide nanofiber layer - Google Patents

Abstract

Filter media comprising a polyamide nanofiber layer is disclosed. The polyamide may have a Relative Viscosity from 2 to 200. The polyamide nanofiber layer may have a melt point of 225°C or greater. The nanofibers may have an average fiber diameter of less than 1000 nanometers (1 micron). Methods for preparing the filter media are also disclosed. In general, the method includes: (a) providing a spinnable polyamide polymer composition, wherein the polyamide has a Relative Viscosity from 2 to 200; (b) melt spinning the polyamide polymer composition into a plurality of nanofibers having an average fiber diameter of less than 1 micron, followed by (c) forming the polyamide nanofiber layer.

Description

Filter media containing polyamide nanofiber layer

The present invention relates to a filter medium containing at least one polyamide nanofiber nonwoven fabric layer, and a method for manufacturing the at least one layer by a melt-blown process using polyamide having a relative viscosity of 2 to 200.

Common filtration methods remove particulates from fluids, including air streams or other gas streams, or from liquid streams, such as hydraulic oil, lubricating oil, fuel, water streams, or other fluids. Such a filtration method requires the mechanical strength, chemical stability, and physical stability of the microfibers and the base material. The filter media may be exposed to a wide range of temperature conditions, humidity, mechanical vibration and shock, and reactive and non-reactive, abrasive or non-abrasive particles entrained in the fluid stream. The filter can be stopped and cleaned in an aqueous or non-aqueous cleaning composition. Such media is usually manufactured by spinning or meltblowing into fine fibers and then forming an interlocking web of microfibers on a porous substrate. In the meltblown method, the fibers can form a physical bond between the fibers to interlock the fiber mat into an integrated layer. This material can then be processed into desired filter styles, such as cartridges, pans, cans, plates, bags, and pouches. Within these structures, the media can be significantly pleated, wound, or otherwise placed on the carrier structure.

Existing filter media are described in the art. For example, U.S. Patent No. 6,746,517 discloses the use of fine filters or fibers having a fiber diameter of about 0.0001 to 0.5 microns made by electrospinning into fine fibers using conventional techniques.

US Patent No. 7,115,150 discloses that a filter arrangement for defogging includes a barrier medium that is generally pleated and treated with fine fiber deposits. The filter arrangement can be in the form of a tubular radial sealing element; a tubular axial sealing element; a downstream air filter; a countercurrent air filter; and a plate filter and may have multiple layers of pleated media containing fine fibers.

U.S. Patent No. 6,716,274 discloses that a filter arrangement for industrial air filters includes a barrier medium that is generally pleated and treated with fine fiber deposits. This medium is particularly advantageous in high temperature (greater than 60°C) operating environments.

U.S. Patent Nos. 6,955,775; 7,070,640; 7,179,317; 7,270,693; 7,316,723; 8,366,797; 8,709,118; and 9,718,012 disclose improved polymer materials and fine fiber materials that can be made of improved polymer materials, which are microfiber and nanofiber structures form. The microfiber and nanofiber structures can be used for a variety of useful purposes, including forming filter materials.

U.S. Patent No. 8,512,432 discloses a composite filter media structure, which includes a base substrate including a non-woven synthetic fabric formed by a spunbond method from many fibers. The base substrate has a filtration efficiency of about 35% to less than 50% measured according to the EN 1822 (1998) test program. A nanofiber layer is deposited on one side of the base substrate. The composite filter media structure has a minimum filtration efficiency of approximately 70% measured according to the EN 1822 (1998) test program.

US20070074628 discloses coalescing filter media for removing liquid aerosols, oil and/or water from gas streams. The medium contains at least one nanofiber network of nanofiber layers composed of continuous polymer nanofibers substantially free of polyolefin, each nanofiber layer having an average fiber diameter of less than about 800 nm and having a matrix of ^{at least about 2.5 g/m 2} weight. The nanofiber layer of nanofiber layer is made by electroblowing a solution of nylon 6,6 polymer.

Various designs of filter media have also been described in the art. For example, US Patent No. 7,877,704 describes replaceable filter elements including multiple filter media and related filtration systems, techniques, and methods. As disclosed, the filter element includes an outer filter medium and an inner filter medium. The external filter media is operable to remove particulates present in the fluid stream and/or to coalesce the water contained in the fluid stream. The internal filter media is operable to remove particulates from the fluid stream, separate water from the fluid stream, and remove particulates from the fluid stream.

US Patent No. 8,784,542 discloses a ^{nanofiber membrane layer with a basis weight of 0.01-50 g/m 2} and a porosity of 60-95%, which contains polymer nanofibers with a number average fiber diameter of 50-600 nm. The polymer nanofibers consist of a polymer composition containing semi-crystalline polyamide with a C/N ratio of at most 5.5. The invention also relates to a water and air filtration device containing such a nanofiber membrane layer.

The multilayer structure has also been described. For example, US Patent No. 8,308,834 discloses a composite filter medium, which includes a base substrate including a non-woven synthetic fabric formed by a spunbond method from many fibers. The base substrate has a minimum filtration efficiency of approximately 50% measured according to the ASHRAE 52.2-1999 test program. A nanofiber layer is deposited on one side of the base substrate. The composite filter media structure has a minimum filtration efficiency of approximately 75% measured according to the ASHRAE 52.2-1999 test program.

European Patent No. 2321029 discloses a composite filter medium comprising a multi-component filter medium containing at least two different materials, at least one of which is a low melting point component; fine particles supported by the multi-component filter medium Fibers, the fine fibers are formed of a polymeric material and have an average fiber diameter of less than about 500 nm, wherein the fine fibers are thermally bonded to the multi-component filter media by the low melting point component.

U.S. Patent No. 8,679,218 discloses a filter media having multiple layers. As disclosed, the filter media includes a nanofiber layer attached to another layer. The layer to which the nanofiber layer is attached is formed of multiple fiber types (e.g., fibers that produce structures with different air permeability and/or pressure drop). The disclosed nanofiber layer can be attached to a single-phase or multi-phase layer. The disclosed nanofiber layer can be made by melt blowing. The filter media can be designed to have advantageous properties, including in some cases high dust particle capture efficiency and/or high dust holding capacity.

Various methods of preparing filter elements are disclosed in the art. For example, US Publication No. 2015/0157971 discloses a filter barrier including at least one barrier layer including polymer nanofibers interwoven with microfibers and at least one base layer including polymer microfibers. The filter barrier can be manufactured by electrospinning.

As indicated above, polymer membranes, including nanofibers and microfiber nonwovens, are known in the art and used for a variety of applications, including those associated with filter media and clothing. Known techniques for forming fine-pored polymer structures include xerogel and aerogel film formation, electrospinning, meltblowing, and centrifugal spinning with a rotary spinneret and two-phase use of propellant gas through fine channels. Polymer extrusion.

US Publication No. 2014/0097558 discloses a method of manufacturing filter media, such as personal protective equipment masks or breathing masks, which includes an electrospinning method to form nanofibers onto a convex mold that can, for example, be in the shape of a human face. See also U.S. Publication No. 2015/0145175. WO 2014/074818 discloses nanofiber webs and xerogels for selectively filtering target compounds or elements from liquids. Also described are methods for forming nanofiber webs and xerogels, methods for treating liquids using nanofiber webs and xerogels, and methods for analyzing target compounds or elements using nanofiber webs and xerogels.

Although various technologies and materials have been proposed, conventional filter media are still far from ideal in terms of manufacturing cost, processability, and product properties.

In some embodiments, the present disclosure relates to a filter medium comprising a nanofiber nonwoven fabric layer, wherein the nanofiber nonwoven fabric layer includes polyamide having a relative viscosity of 2 to 200, which is spun to have a relative viscosity of less than Nanofibers with an average fiber diameter of 1 micron (1000 nanometers) are formed into layers. The nanofiber nonwoven fabric layer may include polyamide spun into nanofibers having an average fiber diameter of less than 1 micrometer (1000 nanometers) and formed into a layer, wherein the layer has a melting point of 225° C. or higher. The filter may be an air filter, an oil filter, a bag filter, a liquid filter or a breathing filter, such as a face mask, surgical mask or personal protective equipment. In some aspects, the polyamide may be nylon 6,6. In a further aspect, the polyamide may be a derivative, copolymer, blend, or alloy of nylon 6,6 and nylon 6. In some aspects, the polyamide is high temperature nylon. In some aspects, the polyamide is a long-chain aliphatic nylon selected from N6, N6T/66, N612, N6/66, N11, and N12, where "N" refers to nylon, and "T" refers to Phthalic acid. The nanofiber nonwoven fabric layer may have an air permeability value of ^{less than 200 CFM/ft 2.} In some aspects, the nanofiber nonwoven fabric layer has an air permeability value of ^{50 to 200 CFM/ft 2.} The nanofibers may have an average fiber diameter of 100 to 907 nanometers, for example, 300 to 700 nanometers or 350 to 650 nanometers. The non-woven fabric product may have a basis weight of 150 grams per square meter (gsm) or less, for example, 5 to 150 gsm or 10 to 125 gsm. The filter media may further include a scrim layer. In some aspects, the nanofiber nonwoven layer can be spun onto the scrim layer. In a further aspect, the nanofiber nonwoven layer can be spun onto the layer of the non-scrim layer. In some aspects, the nanofiber nonwoven fabric layer is sandwiched between the scrim layer and at least one other layer. In a further aspect, the nanofiber nonwoven fabric layer is sandwiched between at least two non-scrim layers. In a still further aspect, the nanofiber nonwoven fabric layer is the outermost layer. The filter medium may further comprise at least one additional layer and may spun a nanofiber nonwoven fabric layer onto one of the at least one additional layer. The relative viscosity of the polyamide in the nanofiber nonwoven fabric layer can be reduced by at least 20% compared with the polyamide before spinning and layering.

In some embodiments, the present disclosure relates to a method of manufacturing a filter medium comprising a layer of polyamide nanofibers, the method comprising: (a) providing a spinnable polyamide polymer composition, wherein the polyamide Have a relative viscosity of 2 to 200; (b) melt-spun the polyamide polymer composition into many nanofibers having an average fiber diameter of less than 1 micrometer (1000 nanometers); and (c) melt the nanofibers Molded onto an existing filter media layer, wherein the polyamide nanofiber layer has an average nanofiber diameter less than 1000 nanometers.

In some embodiments, the present disclosure relates to a method of manufacturing a filter medium comprising a layer of polyamide nanofibers, the method comprising: (a) providing a spinnable polyamide polymer composition; (b) combining the The polyamide polymer composition is melt-spun into many nanofibers having an average fiber diameter of less than 1 micron (1000 nanometers); and (c) molding the nanofibers onto an existing filter media layer, wherein the polyamide The amine nanofiber layer has an average nanofiber diameter of less than 1000 nanometers and a melting point of 225°C or higher. The polyamide nanofiber layer can be melt-spun by melt-blowing into a high-speed gas stream through a die. The polyamide nanofiber layer can be melt-spun by a two-phase propellant gas spinning method, which includes using pressurized gas to extrude the polyamide polymer composition in liquid form through a fiber forming channel. The polyamide nanofiber layer can be formed by collecting the nanofibers on a moving belt. In some aspects, the polyamide composition comprises nylon 6,6. In a further aspect, the polyamide composition comprises a derivative, copolymer, blend or alloy of nylon 6,6 and nylon 6. In a still further aspect, the polyamide comprises HTN. In some aspects, the polyamide is a long-chain aliphatic nylon selected from N6, N6T/66, N612, N6/66, N11, and N12, where "N" refers to nylon, and "T" refers to Phthalic acid. The polyamide nanofiber layer may have a basis weight of 150 gsm or less. The filter media may further include a scrim layer. In some aspects, the polyamide nanofiber layer can be spun onto the scrim layer. In a further aspect, the polyamide nanofiber layer can be spun onto a layer that is not a scrim layer. In a still further aspect, the polyamide nanofiber layer can be sandwiched between the scrim layer and at least one other layer. In a still further aspect, the polyamide nanofiber layer can be sandwiched between at least two non-scrim layers. In some aspects, the polyamide nanofiber layer is the outermost layer. In some aspects, the filter media may further comprise at least one additional layer and the nanofiber nonwoven fabric layer may be spun onto one of the at least one additional layer. The relative viscosity of the polyamide in the polyamide nanofiber layer can be reduced by at least 20% compared with the polyamide before spinning and layering.

Priority statement

This application claims the priority of U.S. Provisional Application No. 62/841,485 filed on May 1, 2019, the entire content and disclosure of which are incorporated herein by reference.

Summary

The present invention relates in part to filter media comprising a nonwoven layer of polyamide nanofibers. The polyamide may have a melting point greater than 225°C. The polyamide may have a relative viscosity of 2 to 200, for example, 2 to 100, 2 to 60, 20 to 50, 20 to 13, 13 to 20, or 2 to 12. Polyamide can be spun or melt-blown into nanofibers with an average diameter of less than 1000 nanometers (1 micron) and formed into non-woven fabric products. The nanofiber nonwoven fabric layer containing polyamide is then incorporated into the filter. The layer can be manufactured as follows: (a) provide a spinnable polyamide polymer composition, which can be melt blown, wherein the polyamide has a relative viscosity of 2 to 200; (b) by involving a two-phase propellant gas spinning The silk method spun or melt-blown a polyamide polymer composition into many nanofibers with an average fiber diameter of less than 1 micron, including using pressurized gas to extrude the polyamide polymer composition in liquid form through a fiber forming channel Then (c) the nanofibers are formed into products. The general method of meltblown technology is shown in Figures 1 and 2.

以及尼龍6,6與尼龍6的共聚物、共混物和合金

Particularly preferred polyamides include: nylon 6,6

And nylon 6,6 and nylon 6 copolymers, blends and alloys

Other embodiments include nylon derivatives, copolymers, blends and alloys containing nylon 6,6 or nylon 6 or made from nylon 6,6 or nylon 6, or copolymers with the above repeating units, including but not limited to : N6T/66, N612, N6/66, N11 and N12, where "N" refers to nylon and "T" refers to terephthalic acid. Another preferred embodiment includes high temperature nylon ("HTN") and blends, derivatives or copolymers containing them. In addition, another preferred embodiment includes long-chain aliphatic polyamides made with long-chain diacids and blends, derivatives or copolymers containing them.

The present disclosure is understood with reference to Figures 1 and 2, which respectively illustrate a two-phase propellant gas spinning system and common meltblown technology that can be used to manufacture nanofibers. In particular, a method of manufacturing a nanofiber nonwoven product is disclosed herein, in which the nonwoven is melt-spun by melt-blowing into a high-speed gas stream through a spinneret. More specifically, the melt-spinning of the nonwoven fabric by the two-phase propellant gas spinning method includes the use of pressurized gas to extrude the polyamide polymer composition in liquid form through the fiber forming channel.

Definition and test method

The terms used herein are given their ordinary meanings consistent with the definitions given below; gsm means basis weight in grams per square meter, RV means relative viscosity and so on.

Unless otherwise specified, percentages, parts per million (ppm), etc. refer to weight percentages or parts by weight based on the weight of the composition.

Typical definitions and test methods are further listed in U.S. Publication Nos. 2015/0107457 and 2015/0111019. The term "nano-fiber nonwoven fabric product" refers to, for example, a network of many substantially randomly oriented fibers, in which the overall repetitive structure cannot be visually noticed in the arrangement of the fibers. The fibers can be bonded to each other, or can be entangled rather than bonded to impart strength and integrity to the web. The fibers may be chopped fibers or continuous fibers, and may include a single material or many materials, as a combination of different fibers or as a combination of similar fibers each composed of different materials. Nanofiber nonwoven products are mainly composed of nanofibers. "Mainly" means that more than 50% of the fibers in the web are nanofibers. The term "nanofiber" refers to a fiber having a number average fiber diameter of less than 1000 nanometers or 1 micrometer. In the case of non-circular cross-sectional nanofibers, the term "diameter" as used herein refers to the largest cross-sectional dimension.

The basis weight can be measured by ASTM D-3776 and ^{reported in gsm (g/m 2} ).

"Consisting essentially of" and similar terms refer to the listed components and exclude other ingredients that would substantially change the basic and novel characteristics of the composition or article. Unless otherwise specified or obvious, when a composition or article includes 90% by weight or more of the or listed components, the composition or article essentially consists of the or listed components. That is, the term excludes more than 10% of unlisted components.

Unless otherwise specified, the test method used to determine the average fiber diameter is as shown in Hassan et al., J of Membrane Sci., 427, 336-344, 2013, unless otherwise specified.

The air permeability is measured using an air permeability tester available from Precision Instrument Company, Hagerstown, MD. Air permeability is defined as the air flow through the material sheet at 23 ± 1°C under a specified pressure head. It is usually expressed in cubic feet/minute/square foot under a water pressure of 0.50 in. (12.7 mm), in cubic centimeters/second/square centimeter, or the elapsed time per unit area of a sheet of a given volume. The above-mentioned instrument is capable of measuring air permeability from 0 to about 5000 cubic feet per minute per square foot of test area. In order to compare air permeability, it is convenient to express a value normalized to a basis weight of 5 gsm. This is done by measuring the air permeability value and basis weight of the sample (usually @ 0.5" H ₂ O), and then multiplying the actual air permeability value by the ratio of the actual basis weight (in gsm) to 5. For example, if a 15 gsm basis The heavy sample has ^{a value of 10 CFM/ft 2} and its normalized 5 gsm air permeability value is 30 CFM/ft ² .

As used herein, polyamide compositions and similar terms refer to compositions containing polyamides, including copolymers, terpolymers, polymer blends, alloys, and derivatives of polyamides. In addition, the "polyamide" as used herein refers to a polymer having as a component a polymer in which there is a link between an amine group in one molecule and a carboxylic acid group in another molecule. In some aspects, polyamide is the component present in the greatest amount. For example, polyamide containing 40% by weight nylon 6, 30% by weight polyethylene, and 30% by weight polypropylene is referred to herein as polyamide because the nylon 6 component is present in the largest amount. In addition, polyamide containing 20% by weight nylon 6, 20% by weight nylon 66, 30% by weight polyethylene, and 30% by weight polypropylene is also referred to herein as polyamide because the components of nylon 6 and nylon 66 total It is the component present in the largest amount. Suitable alloys may include, for example, 20% nylon 6, 60% nylon 6,6, and 20% by weight polyester.

Exemplary polyamides and polyamide compositions are described in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 18, page 328371 (Wiley 1982), the disclosure of which is incorporated herein by reference.

In short, polyamide is a product containing repeating amide groups as a component of the main polymer chain. Linear polyamides are of particular interest and can be formed by the condensation of difunctional monomers as is well known in the art. Polyamide is often referred to as nylon. Although they are generally regarded as condensation polymers, polyamides are also formed by addition polymerization. This method of preparation is especially important for some polymers in which the monomer is a cyclic endoamide (ie nylon 6). Specific polymers and copolymers and their preparation can be found in the following patents: U.S. Patent Nos. 4,760,129; 5,504,185; 5,543,495; 5,698,658; 6,011,134; 6,136,947; 6,169,162; 7,138,482; 7,381,788; and 8,759,475.

A class of polyamides that are particularly preferred for some uses include, for example, Glasscock et al., High Performance Polyamides Fulfill Demanding Requirements for Automotive Thermal Management Components, (DuPont), http://www2. High temperature nylon (HTN's) described in dupont.com/Automotive/en_US/assets/downloads/knowledg e%20center/HTN-whitepaper-R8.pdf. Such polymers usually include one or more of the following structures:

The relative viscosity (RV) of polyamide refers to the ratio of the solution or solvent viscosity measured in a capillary viscometer at 25°C (ASTM D 789). For this use, the solvent is formic acid containing 10% by weight of water and 90% by weight of formic acid. The solution is 8.4% by weight polymer dissolved in a solvent.

The relative viscosity (ηr) is the absolute viscosity ratio of the polymer solution to formic acid: ηr = (ηp/ηf) = (fr x dp x tp)/ ηf where: dp = the density of the formic acid-polymer solution at 25°C, tp = Average outflow time of formic acid-polymer solution, s, ηf = absolute viscosity of formic acid, kPa xs (E+6cP) and fr = viscometer tube coefficient, mm ² /s (cSt)/s = η _r /t ₃ .

A typical calculation for a 50 RV sample is: ηr = (fr x dp x tp)/ ηf where: fr = viscometer tube coefficient, usually 0.485675 cSt/s dp = density of the polymer-formic acid solution, usually 1.1900 g/ ml tp = the average outflow time of the polymer-formic acid solution, usually 135.00 s ηf = the absolute viscosity of the formic acid, usually 1.56 cP gives ηr = (0.485675 cSt/sx 1.1900 g/ml x 135.00 s)/ 1.56 cP = 50.0 RV . The term t ₃ is the outflow time of the S-3 calibration oil required to determine the absolute viscosity of formic acid as required in ASTM D789.

Another embodiment of the present invention relates to the production of a filter media layer comprising polyamide nanofibers having an average fiber diameter of less than 1 micron and having an RV of 2 to 200. In this alternative embodiment, preferred RV ranges include: 2 to 200, 2 to 100, 2 to 60, and 5 to 60. The nanofibers are then converted into nonwoven webs. As RV increases beyond approximately 20 to 30, operating temperature becomes a larger consideration parameter. At RV above the range of approximately 20 to 30, the temperature must be carefully controlled to melt the polymer for processing purposes. 8,777,599中。 Methods or examples of melting technology, and heating and cooling sources that can be used in the device to independently control the temperature of the fiber production device are described in US Patent No. 8,777,599. Non-limiting examples include resistance heaters, radiant heaters, cold or heated gases (air or nitrogen) or conduction, convection or radiation heat transfer mechanisms.

When spinning nylon 6,6, reducing RV is usually not an ideal approach, but in the production of nanofibers, this may actually be an advantage. In certain aspects of the invention, it has been found to be advantageous to melt-spun nylon 6,6 at the lowest possible RV to achieve the smallest filament diameter in the production of nanofiber filaments. Increasing the process temperature only slightly reduces the viscosity. Advantageously, the viscosity of nylon 6,6 can be reduced by depolymerizing the polymer under humidification. This is an advantage compared to addition polymers such as polypropylene. In some aspects, the RV of the polyamide nanofiber layer is at least 20% smaller than the RV of the polyamide before spinning or meltblown and layering, for example, at least 25%, at least 30%, at least 35%, or less. At least 40% or less than 45%.

Non-limiting examples of polymers include polyamide, polypropylene and copolymers, polyethylene and copolymers, polyester, polystyrene, polyurethane, and combinations thereof. Thermoplastic polymers and biodegradable polymers are also suitable for melt-blown or melt-spun nanofibers as disclosed. As discussed herein, the polymer can be melt-spun or melt-blown, preferably by two-phase propellant gas spinning, melt-spinning or melt-blowning, including the use of pressurized gas to extrude the polyamide in liquid form through the fiber forming channel Polymer composition.

Other polymer materials that can be used in the nanofibers of the present invention include addition polymer and condensation polymer materials, such as polyolefins, polyacetals, polyamides (as discussed previously), polyesters, cellulose ethers and esters, poly Alkylene sulfide, polyarylene oxide, polysulfide, modified polysulfide polymer and mixtures thereof. The preferred materials in these categories include polyamide, polyethylene, polybutylene terephthalate (PBT), polypropylene, poly(vinyl chloride), polymethylmethacrylate (and other acrylic resins) ), polystyrene and its copolymers (including ABA block copolymers), poly(vinylidene fluoride), poly(vinylidene chloride), crosslinked and non-crosslinked forms of various degrees of hydrolysis (87% to 99.5%) polyvinyl alcohol. Addition polymers tend to be glassy (Tg greater than room temperature). This is the case of polyvinyl chloride and polymethyl methacrylate, polystyrene polymer compositions or alloys, or low crystallinity in the case of polyvinylidene fluoride and polyvinyl alcohol materials. The nylon copolymer embodied herein can be formed by combining various diamine compounds, various diacid compounds, and various intracyclic amide structures in a reaction mixture, and then forming a monomer material having a monomer material randomly positioned in the polyamide structure Made of nylon. For example, nylon 6,6-6,10 material is nylon made from a blend of _{hexamethylene diamine and C 6} and C _{10 diacids. Nylon 6-6, 6-6, 10} are nylons made by copolymerization of ε-aminocaproic acid, hexamethylene diamine, and a _{blend of C 6} and C 10 diacid materials.

Block copolymers can also be used in the method of the present invention. For such copolymers, the choice of solvent swelling agent is important. The solvent is selected so that both blocks are soluble in the solvent. An example is ABA (styrene-EP-styrene) or AB (styrene-EP) polymers in dichloromethane solvent. If a component is insoluble in the solvent, it will form a gel. Examples of such block copolymers are Kraton® type styrene-b-butadiene and styrene-b-hydrogenated butadiene (ethylene propylene), Pebax® type ε-caprolactam-b-ethylene oxide Alkyl, Sympatex® polyester-b-ethylene oxide, and polyurethane of ethylene oxide and isocyanate.

Addition polymers, such as polyvinylidene fluoride, syndiotactic polystyrene, copolymers of vinylidene fluoride and hexafluoropropylene, polyvinyl alcohol, polyvinyl acetate, amorphous addition polymers, such as poly (Acrylonitrile) and its copolymers with acrylic acid and methacrylate, polystyrene, poly(vinyl chloride) and its various copolymers, poly(methyl methacrylate) and its various copolymers are known to be relatively easy to solution Spinning because they are soluble under low pressure and temperature. It is expected that these can be melt spun as a method of manufacturing nanofibers according to the present disclosure.

A polymer composition comprising two or more polymeric materials formed in a polymer admixture, an alloy format, or in a cross-linked chemical bonding structure has substantial advantages. We believe that such polymer compositions improve physical properties by changing polymer properties, such as improving polymer chain flexibility or chain mobility, increasing overall molecular weight, and providing reinforcement by forming a network of polymeric materials.

In one embodiment of this concept, for beneficial properties, two related polymer materials can be blended. For example, high molecular weight polyvinyl chloride can be blended with low molecular weight polyvinyl chloride. Similarly, high molecular weight nylon materials can be blended with low molecular weight nylon materials.

In some embodiments, such as those described in US Patent No. 5,913,993, a small amount of polyethylene polymer may be blended with a nylon compound used to form a nanofiber nonwoven with desired characteristics. Polyethylene is added to nylon to enhance specific properties, such as softness. The use of polyethylene also reduces production costs and facilitates further downstream processing, such as bonding to other fabrics or itself. Improved fabrics can be made by adding small amounts of polyethylene to the nylon feed used to produce nanofiber meltblown fabrics. More specifically, it can be achieved by forming a blend of polyethylene and nylon 66, extruding the blend in the form of many continuous filaments, guiding the filaments through a die to melt-blown the filaments, and depositing the filaments to the collection On the surface, the fabric is made by forming a net.

The polyethylene that can be used in the method of this embodiment of the present invention preferably has a melt index of about 5 g/10 min to about 200 g/10 min, more preferably about 17 g/10 min to about 150 g/10 min . The polyethylene should preferably have a density of about 0.85 g/cm3 to about 1.1 g/cm3, and most preferably about 0.93 g/cm3 to about 0.95 g/cm3. Optimally, the melt index of polyethylene is about 150 and the density is about 0.93.

The polyethylene used in the method of this embodiment of the invention may be added at a concentration of about 0.05% to about 20%. In a preferred embodiment, the concentration of polyethylene is from about 0.1% to about 1.2%. Optimally, polyethylene is present at about 0.5%. The polyethylene concentration in the fabric made according to the method is approximately equal to the percentage of polyethylene added during the manufacturing process. Therefore, the percentage of polyethylene in the fabric of this embodiment of the invention is generally from about 0.05% to about 20%, preferably about 0.5%. Therefore, the fabric generally contains about 80 to about 99.95% by weight nylon. The filament extrusion step can be performed between about 250°C and about 325°C. Preferably, the temperature range is about 280°C to about 315°C, but it may be lower if nylon 6 is used.

The blend or copolymer of polyethylene and nylon can be formed in any suitable manner. Generally, the nylon compound is nylon 6,6; however, other polyamides in the nylon family can be used. Mixtures of nylon can also be used. In a specific example, polyethylene is blended with a mixture of nylon 6 and nylon 6,6. Polyethylene and nylon polymers are usually supplied in the form of pellets, crumbs, flakes, etc. The required amount of polyethylene pellets or crumbs can be blended with nylon pellets or crumbs in a suitable mixing device, such as a rotating drum, and the resulting blend can be introduced into a conventional extruder or spunbond The feed hopper of the line. It is also possible to produce blends or copolymers by introducing an appropriate mixture into a continuous polymerization spinning system.

In addition, different types of polymers can be blended. For example, high-molecular-weight styrene materials can be blended with low-molecular-weight, high-impact polystyrene. Nylon-6 materials can be blended with nylon copolymers, such as nylon-6; 6,6; 6,10 copolymers. In addition, polyvinyl alcohol having a low degree of hydrolysis, such as 87% hydrolyzed polyvinyl alcohol, can be blended with fully or superhydrolyzed polyvinyl alcohol having a degree of hydrolysis of 98 to 99.9% and higher. All these materials mixed can be cross-linked using an appropriate cross-linking system. Nylon can be cross-linked using a cross-linking agent that can react with the nitrogen atom in the amide bond. Polyvinyl alcohol materials can use hydroxyl-reactive materials, such as monoaldehydes, such as formaldehyde, urea, melamine-formaldehyde resins and their analogs, boric acid and other inorganic compounds, dialdehydes, diacids, urethanes, epoxy resins Cross-link with other known cross-linking agents. Cross-linking technology is a well-known and well-understood phenomenon in which cross-linking agents react and form covalent bonds between polymer chains to significantly improve molecular weight, chemical resistance, overall strength, and resistance to mechanical degradation.

The nanofiber can be made of polymer material or polymer + additives. A preferred mode of the present invention is a polymer blend comprising a first polymer and a second but different polymer (different in polymer type, molecular weight or physical properties) adjusted or treated at elevated temperature. The polymer blend can be reacted and formed into a single chemical species or can be physically combined into a blend composition through an annealing process. Annealing means physical changes such as crystallinity, stress relaxation or orientation. Chemically reacting the preferred material into a single polymer species so that differential scanning calorimeter (DSC) analysis reveals that a single polymer material produces improved stability when exposed to high temperature, high humidity, and difficult operating conditions. The nanofibers of this type of material may have a diameter of approximately 0.01 to 5 microns. Preferred materials for blending polymer systems include nylon 6; nylon 66; nylon 6,10; nylon (6-66-6,10) copolymers and other linear, generally aliphatic nylon compositions.

One embodiment of manufacturing the nanofiber nonwoven fabric of the present invention is two-phase spinning or melt-blowing with a propellant gas through a spinning channel roughly as described in US Patent No. 8,668,854. This method involves a two-phase flow of polymer or polymer solution and pressurized propellant gas (usually air) into fine, better converging channels. The channel is usually and preferably in a ring configuration. It is believed that the polymer is sheared by the air flow in the fine, better converging channel to build up a polymer film on both sides of the channel. These polymer film layers are further sheared into fibers by the propellant gas stream. Here, a mobile collection belt can still be used and the basis weight of the nanofiber nonwoven fabric can be controlled by adjusting the speed of the belt. The distance of the collector can also be used to control the fineness of the nanofiber nonwoven fabric. Refer to Figure 1 for a better understanding of this method.

FIG. 1 schematically illustrates the operation of a system for spinning nanofiber nonwovens, which includes a polymer feed assembly 110, an air feed 1210, a spinning drum 130, a collection belt 140, and a take-up shaft 150. During operation, the polyamide melt or solution is fed into the spinning drum 130, where high-pressure air is used to flow through the fine channels in the drum to shear the polymer into nanofibers. Details are provided in the aforementioned U.S. Patent No. 8,668,854. The throughput and basis weight are controlled by the speed of the belt. If desired, functional additives such as charcoal, copper, etc. can be added with the air feed.

In another configuration of the spinneret used in the system of Figure 1, the particulate material can be added with a separate inlet as shown in U.S. Patent No. 8,808,594 to Marshall et al.

Another method that can be used is to melt-blown the polyamide nanofiber web of the present invention (Figure 2). Melt blowing involves extruding the polymer into a relatively high velocity, usually hot gas stream. In order to produce suitable nanofibers, such as Hassan et al., J Membrane Sci., 427, 336-344, 2013 and Ellison et al., Polymer, 48 (11), 3306-3316, 2007 and International Nonwoven Journal, Summer 2003, No. As shown on pages 21-28, careful selection of hole and capillary geometry and temperature are required.

In some aspects, the polyamide nanofibers are melt blown. Meltblowing is advantageously cheaper than electrospinning. Meltblown is a type of process developed to form fibers and nonwoven webs; fibers are formed by extruding molten thermoplastic polymer materials or polymers through multiple small holes. The resulting molten threads or filaments enter a converging high-speed gas stream, which thins or stretches the filaments of molten polymer to reduce their diameter. Thereafter, the high-speed gas stream carries the melt-blown fibers and deposits on a collecting surface or forming line to form a non-woven web of randomly distributed melt-blown fibers. The formation of fibers and nonwoven webs by melt blowing is well known in the art. See, for example, U.S. Patent Nos. 3,016,599; 3,704,198; 3,755,527; 3,849,241; 3,978,185; 4,100,324; 4,118,531; and 4,663,220.

US Patent No. 7,300,272 discloses a fiber extrusion pack for extruding molten material to form a series of fibers, which includes a plurality of split distribution plates arranged in a stack to form each split distribution plate The fiber extrudes a layer within the assembly, and the features on the distribution plate form a distribution network that conveys the molten material to the holes in the fiber extrusion element. Each distribution plate includes a set of plate segments, and gaps are set between adjacent plate segments. The adjacent edges of the plate segments are shaped to form reservoirs along the gaps, and sealing plugs are placed in the reservoirs to prevent molten material from leaking from the gaps. The sealing plug may be formed by molten material leaking into the gap and collected and solidified in the reservoir or by placing the plugging material in the reservoir during pack assembly. This element can be used to manufacture nanofibers together with the melt blown system described in the aforementioned patents.

Such melt blowing can form a polyamide nanofiber web with an oxidative degradation index ("ODI") of 214 to 4162 ppm. The ODI was measured with a fluorescence detector using gel permeation chromatography (GPC). The instrument is calibrated with quinine external standards. Dissolve 0.1 g of nylon in 10 ml of 90% formic acid. The solution was then analyzed by GPC with a fluorescence detector. The detector wavelength used for ODI is 340 nm for excitation and 415 nm for emission. In addition, such meltblown can bring a thermal degradation index ("TDI") of 26 – 1129 ppm. TDI is measured in the same way as ODI, except that the detector wavelength used for TDI is 300 nm for excitation and 338 nm for emission. Melt blowing can also bring about relative viscosities as described herein. TDI and ODI test methods are also disclosed in US Patent No. 3,525,124.

Filter media

The polyamide nanofibers described herein are advantageously used in various filter media applications, including air filters, oil filters, bag filters, liquid filters, breathing filters, fuel filters, hydraulic oil filters, etc. Wait. Polyamide nanofibers are generally not conceived as the only layer in a filter, they are conceived as being used with or replacing one or more layers in a traditional filter. The polyamide nanofiber layer is also referred to as a polyamide-containing nanofiber nonwoven fabric layer.

Filter parameter

A common parameter peculiar to filter media is the "efficiency" of the filter media. Efficiency is the tendency of the medium to trap particles rather than allowing them to pass through the medium unfiltered. Another common feature is the pressure drop across the medium, which has traditionally been related to the porosity of the medium. The pressure drop is related to how much the filter media restricts fluid flow. Larger pores generally allow greater fluid flow, but unfortunately also usually result in more particles being passed through. Therefore, efficiency often goes against the pressure drop. In particular, although it is generally desirable to trap large amounts of particles, providing such high efficiency often has the undesirable effect of increasing the restrictiveness of the medium and therefore the pressure drop across the medium. This shortens the life of the filter.

Efficiency usually refers to or refers to the initial efficiency, that is, the efficiency of the filter media after it is made but before it is used and loaded with particles. During use, the filter media traps particulates and thereby occludes and traps particulates in the media in the form of dust cake and/or other forms. These filtered particles block the larger pores in the medium, thereby preventing smaller particles from passing through the pores and thereby increasing the efficiency of the medium over time to a working efficiency greater than the initial efficiency. However, by blocking the fluid flow path, these filtered particles also eliminate or partially block the fluid path and thereby increase the pressure drop across the medium so that it more restricts the fluid flow.

Generally, filter life depends on the pressure drop across the filter (delta P). In one embodiment, delta P may be 0.5 to 10 mm H ₂ O, such as 0.5 to 5 mm H ₂ O or 0.5 to 3 mm H ₂ O. As more and more particles are filtered out of the fluid flow and captured by the filter media, the filter media becomes more restrictive of the fluid flow. Therefore, the pressure drop across the filter medium becomes higher. Eventually, the media becomes too restrictive, so that the fluid flow rate is insufficient to meet the fluid requirements of a given application. Calculate the filter replacement interval to roughly coincide with this event (e.g., before reaching an insufficient fluid flow condition). The filter replacement interval can also be measured by a sensor that measures the pressure drop load across the medium.

Generally, electrospun nanofiber media is expected to provide excellent filtration efficiency. This is because considering the fact that smaller fibers occupy less volume than larger fibers, nanofibers with smaller diameters can be stacked together without increasing the overall solidity of the media. Therefore, the electrospun nanofiber media can effectively capture the filter media formed by thick fibers, such as the fine particles that the meltblown fiber filter media cannot capture. However, larger-sized particles can quickly block the pores on the upstream surface of the electrospun nanofiber media, thereby increasing the pressure drop of the filter media to an unacceptable level, thereby shortening the filter life. Multi-layer filter media containing polyamide nanofiber layers are improved on the basis of these filter media, which can trap smaller particles in the depth of the melt-spun polyamide nanofiber layer, thereby improving the filter Maintain high filtration efficiency while maintaining longevity.

Polyamide nanofibers offer several advantages over traditional filter materials, including filters containing polypropylene layers. Surprisingly and unexpectedly, it has been found that the formation of polyamide nanofiber layer by melt-blowing brings improved strength, higher melting point, and increased compared with traditional filter materials, including filters containing polypropylene layers. Chemical resistance, smaller pore size and lower melt flow index in certain liquids. By incorporating polyamide nanofibers into the filter, due to the melt spinning method, the production cost of the filter can be reduced compared with other methods, such as electrospinning. Compared with traditional filter materials, polyamide nanofibers also improve filtration efficiency due to their small pore size. A filter with a polyamide nanofiber layer can also have a reduced weight compared to a conventional filter, and due to the improved efficiency seen with the use of polyamide nanofibers, even the layer of the filter structure can be simplified. Another advantage of using polyamide nanofibers is that for filters with pleats, as described below, polyamide nanofibers can be combined with scrims or substrates for use in the pleating process compared to traditional filters. Less time and lower temperature allow less energy to be used in the pleating process. Finally, the addition of the polyamide nanofiber layer usually does not require changes in equipment made specifically for use with the filter, such as the size of the tank surrounding the filter.

Filter media layer

The filter media usually contains several layers, each layer providing different filtering characteristics. One such layer is a scrim layer, such as a reinforcement layer. In some aspects, the scrim layer is selected to have considerable filtering capacity and efficiency. However, in other respects, the scrim layer has almost no filtering capacity and efficiency. The scrim layer may have a thickness of 0.1 to 0.81 mm, for example 0.2 to 0.3 mm, or about 0.25 mm. The basis weight of the scrim layer can be 5 to 203 gsm, such as 5 to 60 gsm, 15 to 45 gsm, or any value in between. The fibers of the scrim layer may have a median fiber diameter of 1 to 1000 microns, for example, 1 to 500 microns, 1 to 100 microns, or any value in between. The thickness, basis weight, and median fiber diameter can be selected based on the type of filter media in which the scrim is used. Generally, the scrim may have a Frazier air permeability between 111 CFM and 1675 CFM at a pressure difference of 0.5 inches of water, such as 450 to 650 CFM, 500 to 600 CFM, 550 to 1675, or any value in between . The filtration efficiency of the scrim layer can be characterized by comparing the number of fine dust particles on the upstream and downstream sides of the scrim measured with the PALAS MFP-2000 (Germany) equipment of 0.3 μm to 10 μm. In one embodiment, ISO fine dust with a dust concentration of ^{70 mg/m 3 , a sample test size of 100 2} cm, and a face velocity of 20 cm/s are used to measure the scrim selected as the scrim layer Filtration efficiency. Suitable scrims may be selected from generally commercially available scrims, or may be formed by spunbonding, carding, or batting or another method using a suitable polymer. Suitable polymers for scrims include, but are not limited to, polyester, polypropylene, polyethylene, and polyamide, such as nylon or a combination of two or more of these polymers. Scrims suitable for the scrim layer are available from suppliers in various thicknesses, including in particular Berry Plastics, formerly Fiberweb Inc, of Old Hickory, Tennessee or Cerex Advanced Fabrics, Inc. of Cantonment, Florida. More than one scrim layer can be incorporated into the filter media.

The other layer in the filter media is the polyamide nanofiber layer. In some aspects, the layer is spun or meltblown directly onto one or more scrim layers. In some embodiments, the polyamide nanofiber layer has a thickness of at least 1 mm, usually 1.0 mm to 6.0 mm, preferably 0.07 mm to 3 mm, and in one embodiment about 0.13 mm; and less than 150 gsm (grams Per square meter), such as a basis weight less than 120 gsm or a basis weight less than 100 gsm. In terms of ranges, the basis weight can be 5 to 150 gsm, for example 10 to 150 gsm, 10 to 120 gsm, or 10 to 100 gsm. The fibers of the polyamide nanofiber layer have a median fiber diameter of 1 nanometer to 1,000 nanometers as described herein, and may be less than 1,000 nanometers, such as less than 907 nanometers, less than 900 nanometers, less than 800 nanometers, less than 700 nanometers, less than 600 nanometers. Nanometers or less than 500 nanometers. In terms of the lower limit, the average fiber diameter of the nanofibers in the fiber layer of the nonwoven fabric may have at least 100 nanometers, at least 110 nanometers, at least 115 nanometers, at least 120 nanometers, at least 125 nanometers, at least 130 nanometers, at least 150 nanometers, at least An average fiber diameter of 300 nanometers or at least 350 nanometers. In one embodiment, the polyamide nanometer can be characterized by comparing the number of fine dust particles on the upstream side and the downstream side of the medium measured with the PALAS MFP-2000 (Germany) equipment of 0.3 μm to 10 μm. The filtration efficiency of the fiber layer.

The term "layer" as used herein does not require that the polyamide nanofibers completely cover the surface on which they are spun. This layer may completely cover the surface area of the underlying layer or may cover less than 99% of the surface area, such as less than 90%, less than 80%, less than 70%, or less than 60%. In some aspects, the polyamide nanofiber layer can cover at least 5% of the surface area of the underlying layer, such as at least 10%, at least 20%, at least 30%, or at least 40%. In terms of scope, the polyamide nanofiber layer may cover 5 to 100% of the layer spun thereon, such as 5 to 99%, 10 to 90%, 20 to 80%, 30 to 70%, or 40%. To 60%. The same applies to the layer spun onto the polyamide layer.

In addition to the scrim layer and the polyamide nanofiber layer, a conventional layer may also be included. These conventional layers can be formed by melt spinning or electrospinning.

Further descriptions of conventional filter media layers are disclosed in several references disclosed in the background of this application. In some aspects, the additional layer may include, for example, polyvinyl chloride (PVC), polyolefin, polyacetal, polyester, cellulose ether, polyalkylene sulfide, polyarylene oxide, polyarylene, modified Polyvinyl alcohol, polyamide, polystyrene, polyacrylonitrile, polyvinylidene chloride, polymethyl methacrylate, and polyvinylidene fluoride polymers such as polyvinyl alcohol, polyamide, polystyrene, polyacrylonitrile.

The solvent used in the polymer solution for the electrospinning of fine fibers may include acetic acid, formic acid, m-cresol, trifluoroethanol, hexafluoroisopropanol, chlorinated solvents, alcohol, water, ethanol, isopropanol, Acetone and N-methylpyrrolidone and methanol. The solvent is appropriately selected according to the solubility of the polymer and the required fine fiber size. For example, a mixture of formic acid and acetic acid can be used for polyamide (which is also often referred to as nylon) to produce nylon fine fibers that can have an average fine fiber diameter of less than 100 nanometers.

As mentioned above, in some aspects, the polyamide nanofiber layer is melt spun directly onto the scrim layer. In a specific embodiment, no solvent is used when manufacturing the nanofiber filament layer. One or more additional layers can then be deposited on the polyamide nanofiber layer, such as two additional layers, three additional layers, four additional layers, or five or more layers. In a further aspect, an additional layer may be deposited on the side of the scrim layer opposite the polyamide nanofiber layer. In a still further aspect, one or more additional scrim layers may be included in the filter. More than one polyamide nanofiber layer can also be included. In a further aspect, the polyamide nanofiber layer is not melt spun directly onto the scrim layer, but melt spun onto a different layer. In a further embodiment, the scrim layer is omitted and the filter consists of a polyamide nanofiber layer and the other layers described herein. In the above aspects, the polyamide nanofiber layer can be sandwiched between other melt-spun layers, between electrospun layers, or between melt-spun and electrospun layers.

In another aspect of the invention, one or more layers can be combined to create a filter media having a higher thickness. The additional layer also increases the dust holding capacity of the medium. Interestingly, when more layers are added, the efficiency of the fabric does not increase much. This is because with the addition of layers, the mean flow pore size does not change significantly and smaller particles that pass through the first layer continue to pass through other layers. The laminated fabric will provide a thicker medium to increase the dust holding capacity of the medium without significantly increasing the filtration efficiency. A gradient filter can be created by adding another layer with higher filtration efficiency. This gradient filter will provide higher filtration efficiency.

Although the above description is generally applicable to various uses of filter media, further descriptions of specific types of filters are provided below. air filter

As described herein, polyamide nanofiber layers can be used in air filters. The air filter can be used for applications including air circulation systems in buildings, vehicles, vacuum cleaners, face masks, breathing filters, and other applications that need to filter air. Fluid streams such as air and gas streams often carry particulate matter in them. Some or all particulates need to be removed from the fluid stream. For example, the intake air flow in the passenger cabin of a motor vehicle, the air in a computer disk drive, HVAC air, clean room ventilation and the use of filter bags, barrier fabrics, the use of woven materials, the air intake of motor vehicle engines or power generation equipment; The gas stream of a gas turbine; and the intake stream of various combustion furnaces often include particulate matter in it. In the case of cabin air filters, it is desirable to remove particulate matter for passenger comfort and/or for aesthetics. Regarding the intake streams of engines, gas turbines, and combustion furnaces, particulate matter needs to be removed, because particulates can cause substantial damage to the internal operations of the various institutions involved. In other cases, the generated gas or exhaust from industrial processes or engines may contain particulate matter. It may be desirable to remove particulate matter significantly from these streams before these gases can or should be discharged into the atmosphere through various downstream equipment. .

A general understanding of some basic principles and problems of air filter design can be understood by considering the following types of filter media: surface load media; and depth media. Each of these types of media has been thoroughly studied, and each has been widely used. Some of their principles are described in, for example, U.S. Patent Nos. 5,082,476; 5,238,474; and 5,364,456. The complete disclosures of these three patents are incorporated herein by reference.

In some aspects, polyamide nanofibers can be shaped and attached to the filter substrate. Natural fiber and synthetic fiber substrates can be used, such as spunbonded fabrics, synthetic fiber nonwoven fabrics and nonwoven fabrics made of blends of cellulose plastic, synthetic fibers and glass fibers, nonwoven and woven glass cloth, extruded Out and punching plastic mesh materials, organic polymer UF and MF membranes. The sheet-like substrate or cellulosic nonwoven web can then be formed into a filter structure and placed in a fluid stream (including an air stream or a liquid stream) to remove suspended or entrained particles from the stream. The shape and structure of the filter material depends on the design engineer. An important parameter of the formed filter element is its resistance to the effects of heat, humidity, or both. An important aspect of the filter media of the present invention is the ability of the filter media to withstand contact with hot and humid air. When in contact with such a stream of hot and humid air, the polyamide nanofibers should be exposed to air with a temperature of 60°C and 100% relative humidity for 16 hours, and more than 50% of the fibers should remain unchanged for filtration purposes. One aspect of the filter media of the present invention is a test of the ability of the filter media to withstand warm water immersion for a significant time. The immersion test can provide valuable information about the ability of the polyamide nanofibers to withstand damp and heat conditions and to withstand the cleaning of the filter element in an aqueous solution containing a significant proportion of strong cleaning surfactants and strong alkaline materials. Preferably, the polyamide nanofibers of the present invention can withstand hot water immersion while keeping at least 50% or even at least 75% of the fine fibers formed on the surface of the substrate as active filter components. The retention rate of at least 50% of polyamide nanofibers can maintain substantial filtration efficiency () without loss of filtration capacity or increased back pressure. With a polyamide nanofiber basis weight of about 0.01 to 240 micrograms/cm², the thickness of a typical polyamide nanofiber filter layer is 0.001 to 5 microns, such as 0.01 to 3 microns. The polyamide nanofiber layer formed on the substrate in the filter should be substantially uniform in terms of filtration performance and fiber position. Substantial uniformity means that the fibers sufficiently cover the substrate to have at least some measurable filtration efficiency throughout the covered substrate. Can achieve sufficient filtration under a wide range of fiber weight changes. Correspondingly, the polyamide nanofiber layer can be changed in terms of fiber coverage, basis weight, layer thickness, or other measures of fiber weight and still remain well within the limits of the present invention. Even the relatively small weight of fine fibers can increase the efficiency of the overall filter structure.

The "life" of the filter is usually defined by the selected ultimate pressure drop across the filter. The accumulation of pressure across the filter limits the lifetime to the level defined for the application or design. Since this accumulation of pressure is the result of loading, for an iso-efficiency system, a longer life is usually directly related to a higher capacity. Efficiency is the tendency of the medium to trap particles instead of letting them pass. Generally, the more efficiently the filter media removes particulates from the gas stream, the faster the filter media generally reaches the "lifetime" pressure difference (assuming other variables remain constant). In this application, the term "constantly used for filtration purposes" refers to maintaining sufficient efficiency in removing particulates from the fluid stream necessary for the selected application.

Paper filter elements are a widely used form of surface load media. Generally speaking, paper elements comprise a dense mat of cellulose, synthetic fibers, or other fibers oriented across a gas stream carrying particulate matter. The paper is usually constructed to be permeable to airflow, and also has a sufficiently fine pore size and appropriate porosity to prevent particles larger than the selected fineness from passing through. When the gas (fluid) passes through the filter paper, the upstream side of the filter paper works by diffusion and interception to capture and retain selected fine particles in the gas (fluid) stream. These particles are collected as dust cake on the upstream side of the filter paper. In due course, the dust cake also began to act as a filter to improve efficiency. This is sometimes referred to as "seasoning", that is, the development of efficiency that is greater than the initial efficiency.

The simple filter design as described above has at least two types of problems. First, a relatively simple defect, namely the rupture of the paper, causes the system to fail. Secondly, particulate matter quickly accumulates into a thin dust cake or layer on the upstream side of the filter to increase the pressure drop. Various methods have been used to increase the "life" of surface-loaded filter systems, such as paper filters. One method is to provide the medium in a corrugated configuration to increase the surface area of the medium encountered by the air stream relative to a flat, unfolded configuration. Although this increases the filter life, it is still quite limited. Therefore, the surface load medium is mainly used for the purpose of passing through the filter medium at a relatively low speed, which is usually no higher than about 20-30 feet per minute and usually about 10 feet per minute or lower. The term "velocity" in this case is the average velocity through the medium (i.e. the flow rate per unit area of the medium).

Generally speaking, as the air flow rate through the pleated paper medium increases, the filter life decreases by a factor proportional to the square of the velocity. Therefore, when a pleated paper surface load type filter system is used as a particulate filter of a system that requires a considerable air flow, a relatively large surface area of the filter medium is required. For example, a typical cylindrical pleated paper filter element for highway diesel trucks is approximately 9-15 inches in diameter and approximately 12-24 inches in length, with pleats approximately 1-2 inches deep. Therefore, the filtration surface area of the media (one side) is usually 30 to 300 square feet.

In many applications, especially those involving relatively high flow rates, another type of filter media is used, sometimes commonly referred to as "deep" media. A typical depth medium contains relatively thick clumps of fibrous material. Depth media is usually defined by its porosity, density, or solid content percentage. For example, 2-3% solidity media is a deep media fiber mat arranged so that approximately 2-3% of the total volume contains fibrous material (solids) and the rest is air or gas space.

Another useful parameter for defining depth media is fiber diameter. If the solidity percentage remains constant, but the fiber diameter (size) decreases, the pore size or inter-fiber voids decrease, that is, the filter becomes more efficient and traps smaller particles more effectively.

A typical conventional depth media filter is a deep relatively constant (or uniform) density media, that is, a system in which the solidity of the depth media remains substantially constant throughout its thickness. "Substantially constant" in this case means that only relatively slight density fluctuations (if any) are found throughout the depth of the medium. These fluctuations may be caused by, for example, slight compression of the outer joint surface of the container in which the filter medium is placed.

Gradient density depth media layouts have been developed. Some such arrangements are described in, for example, U.S. Patent Nos. 4,082,476; 5,238,474; and 5,364,456. The depth media arrangement can generally be designed to provide a "load" of particulate matter substantially throughout its volume or depth. Therefore, such an arrangement can be designed to load a higher amount of particulate matter when compared to a surface loading system when the full filter life is reached. However, these arrangements usually sacrifice efficiency because a relatively low solidity medium is required for large loads. Gradient density systems, such as those in the above-mentioned patents, have been designed to provide considerable efficiency and longer life. In some cases, surface loading media is used as the "polish" filter in these arrangements.

The filter media construction according to the present invention includes a first layer or substrate permeable to coarse fiber media having a first surface. The first layer of polyamide nanofiber medium is fixed to the first surface of the first layer of permeable coarse fiber medium and the second layer of polyamide nanofiber medium is fixed to the substrate. The first layer of permeable coarse fiber material preferably comprises fibers having an average fiber diameter of at least 10 microns, usually and preferably about 12 (or 14) to 30 microns. The first and second layers of the permeable coarse fiber material also preferably include those having ^{a basis weight of at most about 200 gsm (grams per square meter or g/m 2} ), preferably about 0.50 to 150 gsm, and most preferably at least 8 gsm medium. The first layer of the permeable coarse fiber medium is preferably at least 0.0005 inches (12 microns) thick, and is generally and preferably about 0.001 to 0.030 inches (25-800 microns) thick.

In some arrangements, the first layer of permeable coarse fiber material contains at least 1 m/min, usually and preferably about 2 to 900 m/min when assessed by the Frazier air permeability test separately from the rest of the structure. (Approximately 0.03-15 m-sec ⁻¹ ) breathable material. When referring to efficiency in this document, unless otherwise specified, it means the efficiency when measured with 0.78μ monodisperse polystyrene spherical particles at 20 fpm (6.1 meters per minute) in accordance with ASTM-1215-89 as described herein.

In some aspects, the polyamide nanofiber layer affixed to the first surface of the permeable coarse fiber medium layer is a layer of nanofiber and microfiber medium, wherein the fibers have a maximum of about 2 microns, usually and preferably a maximum of about 1. An average fiber diameter of micrometers, and generally and preferably has a fiber diameter of less than 0.5 micrometers and in the range of about 0.05 to 0.5 micrometers. The first layer of fine fiber material fixed to the first surface of the first layer of permeable coarse fiber material also preferably has a total thickness of at most about 30 microns, more preferably at most 20 microns, and most preferably at most about 10 microns, usually And preferably within a thickness of about 1-8 times (more preferably at most 5 times) the average fiber diameter of the fine fibers of the layer.

Certain aspects include filter media generally defined in the overall filter construction. Some preferred arrangements for this use include media arranged in a cylindrical pleat configuration, the pleats generally being longitudinal, i.e. extending in the same direction as the longitudinal axis of the cylinder. For such an arrangement, the media can be embedded in the end cap as a conventional filter. If desired, for typical conventional applications, such an arrangement may include upstream and downstream liners.

In some applications, the media according to the present invention can be used in combination with other types of media, such as conventional media, to improve overall filtration performance or life. For example, the media according to the present invention can be laminated to conventional media, used in a stacked arrangement; or incorporated (integrated feature) into a media structure that includes one or more conventional media zones. For good loading, it can be used upstream of these media; and/or it can be used as a high-efficiency polishing filter downstream of conventional media.

Certain arrangements according to the invention can also be used in liquid filter systems, i.e. in which the particles to be filtered are carried in the liquid. In specific applications, such as thermal fluids, the melting point of nylon nanofiber fabrics provides advantages. The melting point of the nylon nanofiber fabric may be 223°C to 360°C, for example, 225°C to 350°C. Certain arrangements according to the invention can also be used for mist collectors, for example arrangements for filtering fine mist from the air.

Various filter designs are shown in patents disclosing and claiming various aspects of filter structures for use with filter materials. US Patent No. 4,720,292 discloses a radial sealing design of a filter assembly with a substantially cylindrical filter element design, the filter is sealed by a relatively soft rubber end cap with a cylindrical radially inward surface element. US Patent No. 5,082,476 discloses a filter design using depth media, which includes a foam base and a pleated element combined with the microfiber material of the present invention. US Patent No. 5,104,537 relates to a filter structure that can be used to filter liquid media. The liquid is carried into the filter housing, passes through the outside of the filter into the inner annular core, and then returns to effective use in the structure. Such filters are very useful for filtering hydraulic oil. US Patent No. 5,613,992 shows a typical diesel engine intake filter structure. The structure obtains air that may or may not contain entrained moisture from the external aspect of the housing. The air passes through the filter, and at the same time, moisture can pass to the bottom of the housing and can be discharged from the housing. US Patent No. 5,820,646 discloses a Z filter structure, which uses a specific pleated filter design containing blocked channels, which requires the fluid stream to pass through at least one filter media layer in a "Z"-shaped path to obtain proper filtration performance . The filter media formed in a pleated Z-shaped pattern may contain the fine fiber media of the present invention. U.S. Patent No. 5,853,442 discloses a baghouse structure having a filter element that can contain the fine fiber structure of the present invention. U.S. Patent No. 5,954,849 shows a dust collector structure that can be used to process air that usually has a large dust content to filter dust from the air stream after the workpiece is processed to generate a large amount of dust load in the ambient air. Finally, U.S. Design Patent No. 425,189 discloses a plate filter designed using a Z filter.

The medium may be a polyester synthetic medium, a medium made of cellulose, or a blend of these types of materials. An example of a usable cellulosic medium is: approximately 45-55 lbs./3000 ft ² (84.7 g/m ² ), such as ^{a basis weight of 48-54 lbs./3000 ft 2} ; approximately 0.005-0.015 in, such as approximately 0.010 in. (0.25 mm) thickness; about 20-25 ft/min, such as about 22 ft/min (6.7 m/min) frazier air permeability; about 55-65 microns, such as about 62 microns pore size; at least about 7 lbs/in, such as 8.5 lbs./in (3.9 kg/in) wet tensile strength; about 15-25 psi, such as about 23 psi (159 kPa) longitudinal wet off rupture strength (burst strength wet off of the machine). The cellulosic medium can be treated with fine fibers, such as fibers having a size (diameter) of 5 microns or less, and in some cases sub-micrometers. If fine fibers need to be used, various methods can be used to apply fine fibers to the media. For example, some such methods are characterized in U.S. Patent No. 5,423,892, column 32, lines 48-60. More specifically, such methods are described in U.S. Patent Nos. 3,878,014; 3,676,242; 3,841,953; and 3,849,241, which are incorporated herein by reference. Enough fine fibers are generally applied until the resulting media construction has an individual test between 50 and 90% using the SAE fine dust test according to SAE J726C, and an overall efficiency greater than 90%.

Examples of useful filter configurations are described in US Patent No. 5,820,646. In another exemplary embodiment, the groove pattern (not shown) includes a tapered groove. "Tapered" means that the groove expands along its length so that the downstream opening of the groove is larger than the upstream opening. Such filter construction is described in U.S. Application Serial No. 08/639,220, which is incorporated herein by reference in its entirety. Details regarding fine fibers and their materials and manufacture are disclosed in U.S. Application Serial No. 09/871,583, which is incorporated herein by reference.

Various filter designs are shown in patents disclosing and claiming various aspects of filter structures for use with filter materials. US Patent No. 7,008,465 discloses a filter design that can be used in a wet-dry vacuum. US Patent No. 4,720,292 discloses a radial sealing design of a filter assembly with a substantially cylindrical filter element design, the filter is sealed by a relatively soft rubber end cap with a cylindrical radially inward surface element. US Patent No. 5,082,476 discloses a filter design using depth media, which includes a foam base and a pleated element combined with the microfiber material of the present invention. US Patent No. 5,104,537 relates to a filter structure that can be used to filter liquid media. The liquid is carried into the filter housing, passes through the outside of the filter into the inner annular core, and then returns to effective use in the structure. Such filters are very useful for filtering hydraulic oil. US Patent No. 5,613,992 shows a typical diesel engine intake filter structure. The structure obtains air that may or may not contain entrained moisture from the external aspect of the housing. The air passes through the filter, and at the same time, moisture can pass to the bottom of the housing and can be discharged from the housing. US Patent No. 5,820,646 discloses a Z filter structure, which uses a specific pleated filter design containing blocked channels, which requires the fluid stream to pass through at least one filter media layer in a "Z"-shaped path to obtain proper filtration performance . The filter media formed in a pleated Z-shaped pattern may contain the fine fiber media of the present invention. U.S. Patent No. 5,853,442 discloses a baghouse structure having a filter element that can contain the fine fiber structure of the present invention. Berkhoel et al., U.S. Patent No. 5,954,849 shows a dust collector structure that can be used to process air that usually has a large dust content to filter dust from the air stream after the workpiece is processed to generate a large dust load in the ambient air. Finally, Gillingham, US Design Patent No. 425,189 discloses a plate filter designed using a Z filter. Oil filter

Oil filters intended for internal combustion engines conventionally contain filter media with fibers obtained from wood pulp. Such wood pulp fibers are generally 1 to 7 mm long and 15 to 45 microns in diameter. Due to its relatively low cost, processability, various mechanical and chemical properties, and durability in the final application, natural wood pulp is to a large extent a better raw material for the production of filter media. The filter media is pleated to increase the filter surface area across the direction of oil flow.

US Patent No. 3,288,299 discloses a dual-type oil filter cartridge, in which part of the flow passes through a surface-type filter element, such as pleated paper, and the remaining flow passes through a depth-type filter element, such as a thick fiber block. The oil filter and adapter are disclosed in US Patent No. 3,912,631.

A typical oil filter includes a pleated filter medium (or filter medium) and a backing structure. Conventional filter media exhibit low rigidity and have poor mechanical strength in terms of tensile strength and burst strength. The filter media is therefore used with metal mesh or other types of pleated shapes when used in the final application.

Nevertheless, considering the low mechanical strength, the filter medium is liable to rupture over time at temperatures encountered in internal combustion engines when exposed to engine oil, such as 125 to 135°C.

Although filter media products made of wood pulp are still excellent choices for most automotive and heavy oil power applications, they exhibit improved strength when the media is exposed to various chemical, thermal and mechanical stresses in the final application environment And the market demand for durable oil filtration products continues to grow over time. This demand stems from the more demanding end-use conditions that the media is subjected to and the ever-increasing demand for filter media that can be used safely for longer periods of time in the end-application without breaking or failing.

The long-standing and widely used solution to this need is to incorporate a small amount of synthetic fiber, usually PET polyester, in an amount of about 5-20%. The result of this reinforcing fiber supply is higher media strength and enhanced chemical and mechanical durability when the media is exposed to the final application environment due to the excellent chemical, thermal and mechanical durability of the synthetic fiber itself.

For air filters, alternative technical solutions based mainly on non-natural fibers have been described in the art. U.S. Patent No. 7,608,125 discloses a wet-laid fiber mat composed of about 20-60% by weight of glass fibers, about 15-60% by weight of polymer fibers, and about 15-40% by weight of binders for binding the fibers MERV filter. The disclosed adhesive is a latex modified with melamine formaldehyde.

U.S. Publication No. 2012/0175298 discloses a HEPA filter containing a nonwoven web of two different fiber components. The first fiber component is formed by fibers of polyester, polyamide, polyolefin, polylactide, cellulose ester, and polycaprolactone, and is at least 20% of the weight of the web. The second fiber can be composed of cellulose fiber (Lyocell) or glass or a combination of both. In addition, there are adhesive components formed of acrylic polymers, styrenic polymers, vinyl polymers, polyurethanes, and combinations thereof.

U.S. Publication No. 2013/0233789 discloses a glass-free nonwoven fuel filter media composed of a blend of chopped synthetic fibers and fibrillated cellulose fibers.

U.S. Patent Nos. 7,488,365, 8,236,082, and 8,778,047 disclose additional filter media that contain 50 to 100% of synthetic fibers by weight of the fiber web. In fact, known filter media containing a high percentage of synthetic fibers cannot be pleated or self-supported by themselves. They must be co-pleated or used with some additional mechanical support layer, such as a plastic or wire mesh backing. Enhanced.

Media made with high amounts of synthetic fibers generally tend to exhibit drape and they lack sufficient stiffness and rigidity to cause folds to collapse without additional support. Due to the thermal and mechanical properties of synthetic fibers, 100% synthetic media as disclosed in the art cannot maintain groove patterns, such as corrugated or pleated structures. The fibrous medium according to the present invention is easily grooveable, that is, corrugated and pleated, and the material can maintain its original groove even after a long exposure time in hot engine oil having a temperature of, for example, 140°C Most of the deep (or corrugation depth). This feature also helps to extend the working life of the fiber media.

Some oil filters can eliminate expensive backing materials to provide a filter that is easier to flute (or corrugate) and pleated. The final result is that the fiber media can be used to manufacture filters without supporting backing materials, and at the same time, it can achieve significantly higher rupture strength than conventional oil filter media containing wood pulp, and excellent glycol assisted disintegration (glycol assisted disintegration). ) Tolerance and excellent dust filtering capacity and particle removal efficiency.

By incorporating the polyamide nanofiber layer into the oil filter, due to the above-mentioned benefits of the polyamide nanofiber layer, several of the above-mentioned problems may be alleviated.

Like the other filter media described herein, oil filters are usually multilayer filters. Exemplary thermoplastic fibers suitable for additional layers in oil filters include polyester (e.g., polyethylene terephthalate, such as polyethylene terephthalate (PET), polyethylene terephthalate). Butylene glycol ester (PBT), etc.), polyolefin (such as polyethylene, polypropylene, etc.), polyacrylonitrile (PAN) and additional polyamide layers (nylon, such as nylon-6, nylon 6,6, nylon-6 , 12, etc.). Preferable are PET fibers that exhibit good chemical resistance and heat resistance, which are important properties for the use of the medium as an oil filter.

In one embodiment, the thermoplastic synthetic fiber is selected from fibers having an average fiber diameter of 0.1 μm to 15 μm, such as 0.1 μm to 10 μm, and an average length of 1 to 50 mm, such as 1 to 20 mm. Generally speaking, fibers having a length greater than 5 mm, especially greater than 10 mm, are preferred due to good breaking strength. In this article, "silicacious fibers" mainly represents "glass" fibers, such as microglass fibers.

These fibers generally have an aspect ratio (length-to-diameter ratio) of 1,000 to 1. In one embodiment, the glass fiber has an average fiber diameter of 0.1 μm to 5 μm and an aspect ratio of 1,000 to 1. In particular, the glass fiber may have an average fiber diameter of 0.4 to 2.6 μm. It is preferable to include a sufficient amount of glass fibers to improve the efficiency of the fibrous media as a filter. In one embodiment, the synthetic fiber contains up to 30% by weight, preferably up to 20% by weight of glass fiber based on the total weight of the fiber. Although synthetic fibers contain only up to 30% by weight or up to 20% by weight of glass fibers based on the total weight of the fibers, this amount is sufficient to prepare the fibrous media used in the filter example. Generally, the prior art synthetic filter media includes a high amount of glass fiber to achieve sufficient filtration efficiency for gas or liquid even under high temperature conditions, such as 150°C. However, by using less glass fibers in the fibrous medium as described in the scope of the patent application, it is possible to provide a fibrous medium with excellent filtering properties in terms of particle removal efficiency and hot oil breaking strength. In a particularly preferred embodiment, there are at least two types of glass fibers, namely a first type of fiber having an average fiber diameter of less than 1 μm and a second type of fiber having an average fiber diameter of 2 μm or more. The weight ratio of these two types of fibers is usually 1:100 to 100:1, especially about 1:10 to 10:1. Synthetic fibers may also include up to 40% by weight, preferably up to 30% by weight, based on the total weight of the fiber, of regenerated cellulose materials, such as Lyocell or viscose or a combination thereof.

The filter media can be contained in tanks, including single tanks or double tanks. Each tank may have an inlet and an outlet for introducing oil flow and discharging filtered oil, respectively. The filter media in each tank may be different to achieve different filtering capabilities. For example, the first tank contains a filter housing for full flow path filtration, while the second tank contains a filter housing for reduced-flow path filtering. U.S. Publication No. 2008/0116125 describes such a double tank in detail. Bag filter

Bag filters have been described in the art, including in U.S. Patent No. 7,318,852 and U.S. Publication No. 2009/2055226. Dust collectors, also known as baghouses, are commonly used to filter particulate matter from industrial wastewater or exhaust gas. Once filtered, the purified exhaust gas can be discharged into the atmosphere or recirculated. Such a baghouse dust collector structure usually includes one or more flexible filter banks supported in a box or similar structure. In such a filter box and bank, the filter bag is usually fixed in the box and held in a position where the effluent efficiently passes through the bag and thereby removes entrained particles. The filter bag fixed in the box is usually supported by a structure that separates upstream and downstream air and supports the filter bag to maintain efficient operation.

More specifically, in so-called "baghouse filters", particulate matter is removed from the gas stream as the stream is passed through the filter media. In a typical application, the filter media has a substantially sleeve-like tubular configuration, and the air flow is arranged to deposit filtered particles on the outside of the sleeve. In this type of application, the filter media is periodically cleaned by applying a pulsed reverse flow to the media. The pulsed reverse flow is used to remove the filtered particulates from the outside of the sleeve to collect in the baghouse filter structure. Lower part. U.S. Patent No. 4,983,434 explains the baghouse filter structure and prior art filter laminates.

Separation of particulate impurities from industrial fluid streams is usually achieved using fabric filters. These fabric-based filter media remove particulates from fluids. When the flow resistance or pressure drop across the fabric caused by the accumulation of particulates on the filter becomes significant, the filter must be cleaned and the particulate cake removed.

It is common in the industrial filtration market to characterize the type of filter bag by cleaning methods. The most common types of cleaning techniques are reverse air, vibrator and pulse jet. Reverse air and vibrator technology is considered a low-energy cleaning technology.

The reverse air technology is a gentle air backwash that collects dust on the inner filter bag. Backwashing collapses the bag and ruptures the dust cake, which is discharged from the bottom of the bag to the hopper. The vibrator mechanism also removes the filter cake collected on the inside of the bag. Connect the top of the bag to the swing arm, which creates a sine wave in the bag to remove the dust cake. Pulse jet cleaning technology uses short pulses of compressed air, which enter the inner top of the filter tube. As the pulsed clean air passes through the tube venturi, it inhales secondary air and the resulting air mass causes the bag to violently expand and throw off the collected dust cake. The bag usually quickly retracts into the cage and resumes the work of collecting particles.

Among the three cleaning technologies, pulse jets exert the greatest stress on the filter media. However, in recent years, industrial process engineers have increasingly chosen pulse jet bag chambers.

The need for high temperature (up to 200°C) thermally stable, chemically resistant filter media in the baghouse narrows the selection of filter media for pulse jet applications to only a few viable candidates. Common high-temperature fabrics include polytetrafluoroethylene (PTFE), glass fiber, or polyimide (polyimide is used stably and continuously up to 260°C). When the effects of high temperature are combined with the effects of oxidizers, acids, or sulphur, glass fibers and polyimide media tend to fail prematurely. Therefore, PTFE is preferably used. Commercially available PTFE fabric is a supported needle felt of PTFE fibers. These felts usually weigh 20-26 oz/yd ² and are reinforced with multifilament scrims (4-6 oz/yd 2). The mat is composed of short fibers (usually 6.7 denier/filament or 7.4 dtex/filament, and 2-6 inches long). This product works similarly to many other felt media, namely the primary dust cake "seasons" the bag. This seasoning, sometimes called deep penetration, results in more efficient filtration of the media, but the disadvantage is that the pressure drop across the media increases during use. Eventually, the bag will be blinded or clogged and the bag must be washed or replaced. Generally, the media suffers from low filtration efficiency, blinding, and dimensional instability (shrinkage) at high temperatures.

Another type of structure designed for high temperatures is described in US Patent No. 5,171,339. A bag filter is disclosed, which includes a bag retainer clothed in a filter bag. The cloth of the filter bag comprises poly(meta-phenylene diamine), polyester or polyphenylene having a thin non-woven fabric of poly (p-phenylene diamine) fiber needled into it A laminate of thioether fiber felt, the poly(p-phenylene diamine) cloth is placed on the surface of the filter bag that is first exposed to the particle-laden hot gas stream. The poly(p-xylylenediamine) cloth may have a basis weight of 1 to 2 oz/yd2.

A two-layer product of a porous expanded PTFE (ePTFE) membrane laminated to a woven porous expanded PTFE fiber fabric has also been used. Due to several reasons, but mainly because the woven fiber fabric backing is not easy to install on the pulse jet cage stent, the commercial success of this product has not yet been achieved. The woven yarn slides on its own and generates excessive stress on the film, causing the film to rupture.

Non-woven fabrics have been advantageously used in the manufacture of filter media. Generally, the nonwovens used for this type of application have been entangled and integrated by mechanical needle punching (sometimes called "needle-felting"), which requires barb needles to penetrate the fiber web structure Insert and extract repeatedly.

US Patent No. 4,556,601 discloses a spunlace nonwoven fabric that can be used as a heavy-duty gas filter.

US Patent No. 6,740,142 discloses nanofibers for baghouse filters. The flexible bag is at least partially covered by a layer having a basis weight of 0.005 to 2.0 grams per square meter (gsm) and a thickness of 0.1 to 3 microns. This layer contains polymer fine fibers with a diameter of about 0.01 to about 0.5 microns, but is limited in basis weight due to the limitation of its production method.

In some aspects, the filter may comprise a thermally stabilized nanomesh layer having a basis weight greater than about 0.1 gsm, or greater than about 0.5 gsm, or greater than about 5 gsm, or even greater than about 10 gsm and up to about 90 gsm Filter media. The filter media further includes a substrate to which the nanomesh is bonded in face-to-face relationship. Advantageously, the nanomesh layer is arranged on the upstream surface or the upstream side of the filter bag, that is, on the surface that is first exposed to the particle-laden hot gas stream.

In a further embodiment, the filter comprises a composite material having a first base layer of thermally stabilized nanomesh bonded to it in a face-to-face relationship and a second base layer bonded to the nanomesh layer, the The nanomesh is arranged on the upstream side of the filter bag, that is, on the surface of the filter bag that is first exposed to the particle-laden hot gas stream, wherein the nanomesh has a basis weight greater than about 0.1 gsm. In some cases it is advantageous to arrange the second base layer between the nanomesh and the first base layer, while in other cases it is better to arrange the nanomesh layer between the first and second base layer.

The polymer that can be used for electroblown or meltblown the nanofiber web of the present invention is polyamide (PA), preferably selected from polyamide 6, polyamide 6,6, polyamide 6,12, polyamide 11. Polyamide 12, polyamide 4,6, semi-aromatic polyamide, high-temperature polyamide, and polyamide of any combination or blend thereof. The polyamide (PA) used to prepare the blend composition of the present invention is well known in the art. Representative polyamides include semi-crystalline and amorphous polyamide resins having a molecular weight of at least 5,000 as described in, for example, U.S. Patent Nos. 4,410,661; 4,478,978; 4,554,320; and 4,174,358.

According to the present invention, it is also possible to use polyamides obtained by copolymerization of two of the above-mentioned polymers, by ternary copolymerization of the above-mentioned polymers or their constituent monomers, such as those of adipic acid, isophthalic acid and hexamethylene diamine. Copolymers, or blends of polyamides, such as blends of PA 6, 6 and PA 6. Preferably, the polyamide is linear and has a melting point or softening point higher than 200°C.

In addition to the polyamide nanofiber layer of the present invention formed by melt spinning, such polyamide formed by electrospinning can also be used. The polyamide used for spinning fibers contains thermally stable additives such as antioxidants. If the polyamide is spun from a solution, a suitable antioxidant for use in the present invention is any material that can be dissolved in the spinning solvent along with the polyamide. Examples of such materials are copper halides and hindered phenols. "Hindered phenol" refers to a compound whose molecular structure contains a phenol ring, in which one of the carbon atoms in the cis position of the hydroxyl moiety bears an alkyl group or both of them bear an alkyl group. The alkyl group is preferably a tert-butyl moiety and both adjacent carbon atoms have a tert-butyl moiety.

Antioxidants include, but are not limited to: phenolic amides, such as N,N'-hexamethylene bis(3,5-di-(tert)-butyl-4-hydroxyhydrocinnamamide) (Irganox 1098); Amines, such as various modified anilines (such as Irganox 5057); phenolic esters, such as ethylenebis(oxyethylene)bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)-propionic acid Esters (Irganox 245) (all available from Ciba Specialty Chemicals Corp., Tarrytown, NY); organic or inorganic salts, such as cuprous iodide available as Polyad 201 (from Ciba Specialty Chemicals Corp., Tarrytown, NY), A mixture of potassium iodide and zinc salt of octadecanoic acid, and a mixture of copper acetate, potassium bromide and calcium salt of octadecanoic acid available as Polyad 1932-41 (from Polyad Services Inc., Earth City, Mo.) ; Hindered amines, such as 1,3,5-triazine-2,4,6-triamine, N,N′″-[1,2-ethylenediyl-bis[[[4,6-bis-[butyl (1,2,2,6,6-pentamethyl-4-pyridinyl)amino]-1,3,5-triazin-2-yl)imino]-3,1-propane基]]bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-pyridinyl) (Chimassorb 119 FL), 1 ,6-Hexanediamine, N,N′-bis(2,2,6,6-tetramethyl-4-pyridinyl) containing 2,4,6-trichloro-1,3,5-triazine )-Polymer, the reaction product of N-butyl-2,2,6,6-tetramethyl-4-pyrimidinamine and N-butyl-1-butylamine (Chimassorb 2020) and poly((6- [(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][2,2,6,6-tetramethyl-4 -Pyridinyl]imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-pyridinyl)imino]]) (Chimassorb 944) (both Obtained from Ciba Specialty Chemicals Corp., Tarrytown, NY); polymerized hindered phenols, such as 2,2,4 trimethyl-1,2 dihydroxyquinoline (Ultranox 254, from Crompton Corporation, a subsidiary of Chemtura Corporation, Middlebury, Conn., 06749); hindered phosphites, such as bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite (Ultranox 626, from Crompton Corporati on, a subsidiary of Chemtura Corporation, Middlebury, Conn., 06749); and tris(2,4-di-tert-butyl-phenyl) phosphite (Irgafos 168, from Ciba Specialty Chemicals Corp., Tarrytown, NY) ; 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid (Fiberstab PA6, available from Ciba Specialty Chemicals Corp., Tarrytown, NY) and their combinations and blends.

The antioxidant used as the stabilizer may be 0.01 to 10% by weight, especially 0.05 to 5% by weight, of the polyamide layer formed by electrospinning.

The base layer of the bag filter can be formed from various conventional fibers, including cellulose fibers, such as cotton, hemp or other natural fibers, inorganic fibers, including glass fibers, carbon fibers, or organic fibers, such as polyester, polyimide, and polyimide. Amide, polyolefin or other conventional fibers or polymeric materials and mixtures thereof.

The base layer of the filter bag of the present invention may be woven or non-woven. In woven bags, the fibers are usually formed into an interlocking web in a typical weave pattern. Nonwovens are usually manufactured by loosely forming fibers without a specific orientation, and then bonding the fibers into a filter fabric. One mode of constructing the elements of the present invention includes the use of felted media as a substrate. Felt is a compressed porous nonwoven fabric made by laying discrete natural or synthetic fibers and compressing these fibers into a felt layer using commonly available felt bonding techniques known to those skilled in the art.

Fibers that produce fabrics that exhibit excellent resilience and are resistant to the effects of air travel and particle retention are generally used. The fabric is stable to chemical particles and can be stable to the different temperatures of the air passing through the bag house and the temperature of the particles trapped on the surface of the filter.

The filter structure of the present invention usually maintains their useful open shape by supporting the substrate + nano mesh layer composite material on a suitable support structure, such as a retainer on the neck of the bag, or the support structure can be located inside the bag. Such a support may be formed by a linear member in the form of a winding or a cage structure. Alternatively, the support may comprise a porous ceramic or metal structure that mimics the shape of a bag. If the support structure contacts the filter substrate over a large portion of its surface area, the support structure should be permeable to allow air to pass through the structure and should not provide a gradual increase in pressure drop across the filter bag. Such supporting structures can be formed so that they contact the entire interior of the filter bag and maintain the filter bag with a high-efficiency filter shape or confirmation.

The method of combining the nanomesh layer and the substrate to manufacture the present composite structure is not specifically limited. The nanofibers of the nanomesh layer can be physically interwoven in the base layer, or they can be combined by the fusion of the fibers of the nanomesh layer and the fibers of the base, such as by heat, adhesive or ultrasonic lamination or bonding.

The thermal method for bonding the base layer to the nano mesh layer or nano mesh + base layer includes calendering. "Calendar" is a method of passing a web through a nip between two rolls. The rollers may be in contact with each other, or there may be a fixed or variable gap between the surfaces of the rollers.

Advantageously, in the calendering method, a nip is formed between the soft roll and the hard roll. A "soft roll" is a roll that deforms under pressure applied to hold the two rolls together in a calender. A "hard roll" is a roll having a surface that does not undergo deformation that has a significant effect on the method or product under the pressure of the method. "Unpatterned" rolls are rolls that have a smooth surface within the capabilities of the method used to make them. Unlike a point bonding roll, there are no dots or patterns to intentionally create a pattern on the web as it passes through the nip. The hard roll in the calendering method used in the present invention may be patterned or unpatterned.

Adhesive lamination can be carried out in conjunction with calendering or in the presence of a solvent-based adhesive at low temperatures, such as room temperature, to apply pressure to the laminate by other means. Alternatively, hot melt adhesives can be used at elevated temperatures. Those skilled in the art will readily recognize suitable adhesives that can be used in the method of the present invention.

Examples of methods of interweaving fibers according to such physical bonding are needle punching and water jet processing, also called hydroentangling or spun lacing. As disclosed in U.S. Patent Nos. 3,431,611 and 4,955,116, needle punching (or needling) is basically composed of a small bundle of single fibers rolled down through a carded fiber batt, which has such a large number of punches. To form a cohesive textile structure.

In order to manufacture the filter of the present invention, it is desirable to perform needling processing (or water jet processing) on the high-density layer (substrate) side of the nonwoven fabric. Compared with the case where the needling processing is performed on the low-density layer (nano mesh) side, the needling processing on the high-density layer side can suppress the collapse or deformation of pores associated with interweaving, and undesirable widening of the pore size, by This suppresses the reduction in the initial cleaning efficiency of smaller particles. It is preferable to set the number of needles per unit area (the number of punctures) in the range of about 40 to about 100 penetrations/cm2 to suppress undesirable widening of the pore size and to perform sufficient interweaving operations. In addition, it should penetrate up to about 25% of the surface area of the low density layer.

The as-spun nanoweb may mainly or completely contain nanofibers, advantageously made by electrospinning, such as classical electrospinning or electroblowing, and in some cases by meltblowing or other such suitable methods. Classic electrospinning is a technique set forth in US Patent No. 4,127,706, in which a high voltage is applied to a polymer in a solution to produce nanofibers and nonwoven mats. However, the total transport volume in the electrospinning method is too low to be commercially viable for forming larger basis weight nanowebs.

The "electrospray" method is disclosed in WO 03/080905. The polymer solution stream containing the polymer and the solvent is fed from a storage tank to a series of spinning nozzles in the spinneret, a high voltage is applied to it and the polymer solution is discharged through it. At the same time, compressed air heated as needed is discharged from an air nozzle arranged on the side or periphery of the spinning nozzle. The air is conveyed roughly downward as a jet stream, which surrounds and conveys the newly discharged polymer solution and helps to form a fibrous web, which is collected on a grounded porous collection belt above the vacuum chamber. The electrospray method can form a commercial size and amount of nanonets in a relatively short period of time with a basis weight of more than about 1 gsm, and even as high as about 40 gsm or higher.

The substrate can be arranged on a collector to collect and combine the nanofiber web spun on the substrate. Examples of the substrate may include various non-woven fabrics, such as melt-blown non-woven fabrics, needle punched or spunlaced non-woven fabrics, woven fabrics, knitted fabrics, paper, etc., and may be used without limitation, as long as nanometers can be added to the substrate. Fibre layer. The nonwoven fabric may include spunbond fibers, dry-laid or wet-laid fibers, cellulose fibers, meltblown fibers, glass fibers, or blends thereof. Alternatively, the nanomesh layer can be deposited directly onto the felt substrate.

The plasticizers known in the prior art can be advantageously added to the above-mentioned various polymers to reduce the Tg of the fiber polymer. The appropriate plasticizer depends on the polymer to be electrospun or electroblown, and the specific end use of the nanomesh. For example, nylon polymers can be plasticized with water or even residual solvents left over from electro-spinning or electro-blowing processes. Other plasticizers known in the prior art that can be used to reduce the Tg of polymers include, but are not limited to, aliphatic diols, aromatic sulphanomides, phthalates, including but not limited to those selected from ortho Dibutyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dioctyl phthalate, diisodecyl phthalate, diundecyl phthalate Esters, didodecyl phthalate and diphenyl phthalate, and so on. The Handbook of Plasticizers, edited by George Wypych, 2004 Chemtec Publishing, which is incorporated herein by reference, discloses other polymer/plasticizer combinations that can be used in the present invention. Liquid filter

Liquid filter media are often used to filter microorganisms. Biopharmaceutical manufacturing is constantly looking for ways to streamline operations, combine and eliminate steps, and reduce the time it takes to process each batch of drug substance. At the same time, market and regulatory pressures are driving biopharmaceuticals to reduce their costs. Since the removal of bacteria, mycoplasma, and viruses accounts for a large percentage of the total cost of drug raw material purification, there is a great need for methods to increase the filtration throughput of the porous membrane and reduce the purification processing time.

With the introduction of new pre-filter media and the corresponding increase in the throughput of bacteria, mycoplasma and virus retention filters, the filtration of feed streams has become flux-limited. Therefore, a significant improvement in the permeability of the bacteria, mycoplasma, and virus retention filters has a direct beneficial effect on the cost of the bacteria, mycoplasma, and virus filtration steps.

Filters used for liquid filtration can generally be classified as fibrous non-woven media filters or porous film membrane filters.

Porous membrane membrane liquid filters or other types of filter media can be used unsupported or in combination with porous substrates or carriers. The porous membrane liquid filtration membrane, which generally has a pore size smaller than that of the porous fibrous nonwoven media, can be used for: (a) Microfiltration (MF), in which the particles filtered out of the liquid are usually in the range of about 0.1 micrometer (μm) to about 10 μm (B) Ultrafiltration (UF), in which the particles filtered out of the liquid are generally in the range of about 2 nanometers (nm) to about 0.1 μm; and (c) Reverse Osmosis (RO), in which the liquid is filtered The particles are usually in the range of about 1 Å to about 1 nm.

The retroviral retention membrane is generally considered to be on the open end of the ultrafiltration membrane.

High permeability and highly reliable retention are two parameters desired in liquid filtration membranes. However, there is a trade-off between these two parameters, and for the same type of liquid filtration membrane, greater retention can be achieved by sacrificing permeability. The inherent limitations of conventional methods for making liquid filtration membranes prevent the porosity of the membrane from exceeding a certain threshold, thus limiting the magnitude of the permeability that can be achieved at any given pore size.

Fiber nonwoven liquid filter media include, but are not limited to, nonwoven media formed by spunbond, meltblown or spunlaced continuous fibers; hydroentangled nonwoven media formed by carded staple fibers, etc., and/or combinations thereof . Generally, fibrous nonwoven media filters used for liquid filtration have pore sizes generally greater than about 1 μm.

Non-woven materials are widely used in the manufacture of filtration products. The pleated membrane filter cartridge usually includes a nonwoven material as a drainage layer (see, for example, U.S. Patent Nos. 6,074,869, 5,846,438, and 5,652,050, each assigned to Pall Corporation; and U.S. Patent No. 6,598,749, which is assigned to Cuno Inc, now Is 3M Purification Inc.).

The non-woven microporous material can also be used as the adjacent porous membrane layer on it, such as the support mesh of the Biomax® ultrafiltration membrane produced by EMD Millipore Corporation, of Billerica, Mass.

The nonwoven microporous material can also be used as a support framework to increase the strength of the porous membrane on the nonwoven microporous structure, such as the Milligard™ filter also available from EMD Millipore Corporation.

The nonwoven microporous material can also be used for "coarse pre-filtration" to increase the capacity of the porous membrane placed downstream of the nonwoven microporous material by removing suspended particles having a diameter generally greater than about 1 μm. The porous membrane usually provides a critical biosafety barrier or structure with a well-defined pore size or molecular weight cut-off. Critical filtration is characterized by a high degree of removal (usually >99.99%, as determined by specified tests) of microorganisms and virus particles as expected and verifiable. Critical filtration is often used in multiple manufacturing stages and at the point of use to ensure the sterility of liquid medicines and liquid biopharmaceuticals.

Meltblown and spunbond fiber media are often referred to as "traditional" or "conventional" nonwovens. The fibers in these traditional nonwovens are usually at least about 1,000 nm in diameter, so the effective pore size in the traditional nonwovens is greater than about 1 micron. The methods of making traditional nonwovens often produce very uneven fiber mats.

In the past, the random nature of conventional nonwoven mat formation processes (such as by meltblown and spunbond) has led to the general assumption that nonwoven mats are not suitable for any critical filtration of liquid streams. Therefore, filtration devices containing conventional nonwoven mats are usually only pre-processed. These pads are used for filtration purposes to increase the capacity of porous critical filtration membranes placed downstream of conventional nonwoven pads.

Another type of nonwovens includes electrospun nanofiber nonwoven mats, which are similar to "traditional" or "conventional" nonwovens, which are generally assumed to be unsuitable for critical filtration of liquid streams. (See, for example, Bjorge et al., Performance assessment of electrospun nanofibers for filter applications, Desalination, 249, (2009), 942-948).

The electrospun polymer nanofiber mat is very porous, where the "pore" size is roughly linearly proportional to the fiber diameter, and the porosity is relatively independent of the fiber diameter. The porosity of electrospun nanofiber mats is typically in the range of approximately 85% to 90% to produce nanofiber mats that exhibit significantly improved permeability compared to dip-cast membranes of similar thickness and pore size ratings. Due to the reduced porosity of the UF membrane discussed above, the porosity advantage of electrospun polymer nanofiber mats over porous membranes is amplified in the smaller pore size range typically required for virus filtration.

The electrospun nanofiber nonwoven mat is manufactured by using electric potential to spin a polymer solution or melt, rather than by the meltblown, wet-laid or extrusion manufacturing methods used to manufacture conventional or traditional nonwovens. The diameter of fibers usually obtained by electrospinning is in the range of 10 nm to 1,000 nm, and is 1 to 3 orders of magnitude smaller than conventional or traditional nonwovens.

The electrospun nanofiber mat is formed by placing the dissolved or molten polymer material near the first electrode and applying a potential to pull the dissolved or molten polymer material in the form of fibers from the first electrode to the second electrode. In the method of manufacturing the electrospun nanofiber mat, the fibers are not forced to lay in the mat by hot air jets or other mechanical means that can lead to an extremely wide pore size distribution. On the contrary, due to the mutual electric repulsion between the electrospun nanofibers, the electrospun nanofibers form a very uniform mat.

WO 2010/107503 assigned to EMD Millipore Corporation teaches that nanofiber mats of specific thickness and fiber diameter provide an improved combination of liquid permeability and microbial retention. The thinnest sample taught is 55 μm thick and has a permeability of 4,960 lmh/psi. However, it does not describe the method for determining retention assurance or the assurance level achieved. Generally, nanofiber mats provide 2-10 times better permeability than porous membrane counterparts with similar retention, which is believed to be due to the higher porosity of nanofiber mats (~90% vs. 70% for typical wet-cast porous membranes). -80%).

Electrospun nanofiber mats can be manufactured by depositing fibers on conventional spunbond nonwovens (examples of face-to-face interfaces of nonwovens and nanofiber layers are taught in WO 2009/010020 assigned to Elmarco sro; and assigned to Clarcor Inc. .'S U.S. Published Application No. 200910199717, each of which is incorporated herein by reference in its entirety). In each of these methods, the surface roughness of the supporting nonwoven fabric may propagate into the nanofiber layer to cause potential inhomogeneities in the nanofiber structure, thereby potentially compromising the retention characteristics.

U.S. Patent No. 7,585,437 to Jirsak et al. teaches a nozzleless method for producing nanofibers from a polymer solution using electrospinning and a device for implementing the method.

WO 2003/080905 assigned to Nano Technics Co. LTD., which is incorporated herein by reference in its entirety, teaches an electrospray method in which a polymer solution stream containing polymer and solvent is fed from a storage tank to a spinneret A series of spinning nozzles inside apply high voltage to it and discharge the polymer solution through it. The compressed air heated as needed is released from the air nozzles arranged on the side or periphery of the spinning nozzle. The compressed air is conveyed roughly downward as a jet stream, which surrounds and conveys the newly discharged polymer solution, thus helping to form a nanofiber web, which is collected on a grounded porous collection belt located above the vacuum chamber.

US Publication No. 2004/0038014 to Schaefer et al. teaches a non-woven filter mat for filtering contaminants, which contains one or more thick collections of fine polymer microfibers and nanofibers formed by electrospinning Floor.

U.S. Publication No. 2009/0199717 to Green teaches a method of forming an electrospun fiber layer on a substrate layer, a significant amount of electrospun fibers having fibers with a diameter of less than 100 nanometers (nm).

Bjorge et al. taught in Desalination 249 (2009) 942-948 an electrospun nylon nanofiber mat having a nanofiber diameter of about 50 nm to 100 nm and a thickness of about 120 μm. The measured bacterial LRV of the unsurface-treated fiber is 1.6-2.2. Bjorge et al. allegedly concluded that the bacteria removal efficiency of nanofiber electrospun mats is not satisfactory.

Gopal et al. taught in the Journal of Membrane Science 289 (2007) 210-219 electrospun polyether turpentine nanofiber mats, where the nanofibers have a diameter of approximately 470 nm. In the liquid filtration process, the nanofiber mat acts as a filter screen to filter out particles larger than 1 micron (μm) and as a depth filter (such as a pre-filter) for particles smaller than 1 micron.

Aussawasathien et al. in Journal of Membrane Science, 315 (2008) 11-19 taught electrospun nanofibers with a diameter of about 30 nm to 110 nm for removing polystyrene particles with a diameter of about 0.5 μm to 10 μm .

One reason for the research work to study the properties of the collector electrode is to control the orientation of the nanofibers collected on the electrode. In Nano Letters, vol. 5, no. 5 (2005) 913-916, Li et al. described the introduction of an insulating gap in the collecting electrode and the influence of the area and geometry of the introduced insulating gap. They proved that the assembly and alignment of nanofibers can be controlled by changing the collector electrode pattern.

Many methods focusing on geometric surface properties, such as roughness, have been published. For example, US Publication No. 2011/0305872 describes changing the surface roughness of a substrate by inserting a polymer layer to change the binding properties of biological products on the substrate. Describes the optical profilometry to measure the surface roughness on the substrate using the Olympus LEXT OLS4000 laser confocal microscope.

For critical filtration applications, achieving high microbial retention is not enough in itself, but it is required to achieve this with high assurance in a reliable manner. In order to predict retention assurance, statistical methods, such as censored data regression, are usually used to analyze life data for reliability, in which life is truncated. (Blanchard, (2007), Quantifying Sterilizing Membrane Retention Assurance, BioProcess International, v.5, No. 5, pages 44-51).

U.S. Publication No. 2014/0166945 discloses a liquid filter comprising a porous polymer nanofiber layer on a carrier, wherein at least on the surface of the carrier facing the polymer nanofiber layer, the root mean square height of the surface is less than about 70 microns. This publication number discloses various polymers that can be used for the nanofiber layer and for the carrier.

Electrospun nanofibers can be prepared from a wide range of polymers and polymer compounds, including thermoplastic and thermoset polymers. Suitable polymers include, but are not limited to, nylon, polyimide, aliphatic polyamide, aromatic polyamide, polyimide, cellulose, cellulose acetate, polyether sulfide, polyurethane, poly(ureaurethane), Polybenzimidazole (PBI), polyetherimide, polyacrylonitrile (PAN), poly(ethylene terephthalate), polypropylene, polyaniline, poly(ethylene oxide), poly(naphthalene) Ethylene dicarboxylate), poly(butylene terephthalate), styrene butadiene rubber, polystyrene, poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidene fluoride) , Poly(vinyl butene), polymethyl methacrylate (PMMA), their copolymers, derivative compounds and blends and/or combinations.

Non-limiting examples of single or multilayer porous substrates or supports include smooth nonwoven fabrics. In other non-limiting examples, the smooth nonwoven fabric carrier has a substantially uniform thickness. Smooth non-woven fabrics are made of various thermoplastic polymers, including polyolefins, polyesters, polyamides, etc.

The uniformity of the nonwoven substrate of the composite filter media that captures or collects electrospun nanofibers can at least partially determine the properties in the resulting nanofiber layer of the final composite filter structure. For example, the smoother the surface of the substrate used to collect electrospun nanofibers, the more uniform the resulting nanofiber layer structure.

The smoothness of the supporting non-woven fabric belongs to geometric smoothness, or lacks rough surface features larger than a fiber diameter of the non-woven fabric, and low hairiness, that is, the number of fibers and/or loops protruding from the surface is small. Geometric smoothness is easily measured by many common techniques, such as mechanical and optical profilometry, visible light reflectance (gloss meter) and other techniques known to those skilled in the art.

In some aspects, the electrospun nanofiber layer is bonded to a smooth nonwoven support. The bonding can be achieved by methods well known in the art, including but not limited to thermal calendering between heated smooth rolls, ultrasonic bonding, and bonding by gas. Bonding the electrospun nanofiber layer to the nonwoven carrier improves the strength of the composite material and the compression resistance of the composite material, so that the resulting composite filter media can withstand and shape the composite filter platform into a useful filter shape and Size-related or force when installing the composite filter platform into the filter device.

In other embodiments of the composite liquid filtration platform, the physical properties of the porous electrospun nanofiber layer, such as thickness, density, and pore size and shape, can be affected according to the bonding method used between the nanofiber layer and the smooth nonwoven carrier . For example, hot calendering can be used to reduce the thickness and increase the density and reduce the porosity of the electrospun nanofiber layer, and reduce the size of the pores. This in turn reduces the flow rate through the composite filter medium under a given external pressure difference.

Generally speaking, ultrasonic bonding will bond to a smaller area of the electrospun nanofiber layer than thermal calendering, so it has less influence on the thickness, density and pore size of the electrospun nanofiber layer.

Hot gas or hot air bonding usually has the least effect on the thickness, density, and pore size of the electrospun nanofiber layer, so this bonding method is better in applications that need to maintain a higher fluid flow rate.

When using thermal calendering, care must be taken not to over-bond the electrospun nanofiber layers so that the nanofibers melt and no longer maintain their structure as single fibers. In extreme cases, excessive bonding will cause the nanofibers to melt completely to form a film. One or both of the rolls used are heated to about ambient temperature, for example a temperature of about 25°C to about 300°C. The porous nanofiber media and/or porous support or substrate may be compressed between the rolls at a pressure of about 0 lb/in to about 1000 lb/in (178 kg/cm).

The calendering conditions, such as roll temperature, nip pressure and line speed, can be adjusted to achieve the desired degree of solidity. Generally speaking, the application of higher temperature, pressure, and/or residence time at elevated temperature and/or pressure results in increased solidity.

In the entire process of forming, forming and manufacturing composite filter media, if desired, other mechanical steps may be included, such as stretching, cooling, heating, sintering, annealing, reeling, and unreeling. )Wait. Breathing filter

US Publication No. 2014/0097558 discloses that various types of breathing filters are known in the art. Personal protective equipment (PPE), especially disposable masks, may need to comply with certain regulations during the design and manufacturing process. It may consider the ability and smoothness of the user to breathe while wearing the mask, as well as the fit and comfort of the user wearing the mask. Due to the disposable nature of the mask, low-cost manufacturing methods may be required. It may be necessary to meet certain regulatory standards, such as EN149:2001 for Europe or 42 CFR part 84 for US or ISO 17420. The PPE under these regulations is a Class III product in accordance with the PPE Directives in Europe or other parts of the world. PPE, such as disposable masks or reusable cartridges can contain filter media, which can be made of melt blown fiber and/or microglass materials. When the particles in the air are trapped in the fibrous matrix contained in the filter medium of the mask, filtering by the mask is realized.

The nanofibers formed by the electrospinning of the polymer solution can be functionalized by adding another material to the polymer solution. The additional functionalized material is operable to remove the gas and may contain one or more chemicals that can capture the gas (where the gas may be volatile organic chemicals (VOCs), acid vapor, carbon dioxide (CO ₂ ), nitric oxide ( NO), nitrogen dioxide (NO ₂ ), ozone (O ₃ ), hydrogen cyanide (HCN), arsine (AsH ₃ ), hydrogen fluoride (HF), chlorine dioxide (ClOC ₂ ), ethylene oxide (C ₂ H ₄ O), formaldehyde (CH ₂ O), bromomethane (CH ₃ Br) and/or phosphine (PH3)). In one embodiment, the functionalized material may include biocides (that is, chemicals or microorganisms that contain, harmless or control any harmful organisms by chemical or biological means), virucides (that is, inactivate Or one of physical or chemical agents that destroy viruses) and/or bactericides (that is, substances that kill bacteria, such as disinfectants, preservatives, or antibiotics). In other embodiments, the functionalized nanofibers are operable to dehumidify, control temperature, indicate the end of service life, indicate clogging materials, and/or provide fresh odors in the mask.

The filter layer can be formed directly on the carrier layer instead of being formed independently. The filter layer may contain one or more types of fibers, made of the same or different polymer fiber-forming materials. Most of the fibers in the filter layer are formed of fibrous materials that can receive satisfactory electret charges and maintain sufficient charge separation. A preferred polymer fiber-forming material is a non-conductive resin having a volume resistivity of ^{10 14 ohm-cm or higher at room temperature (22°C).} The resin may have ^{a volume resistivity of about 10 16} ohm-cm or higher. The electrical resistivity of polymer fibrous materials can be measured according to the standardized test ASTM D 257-93. Some examples of useful polymers include thermoplastic polymers containing polyolefins, such as polyethylene, polypropylene, polybutene, poly(4-methyl-1-pentene), and cycloolefin copolymers, and combination. Other polymers that are available but may be difficult to charge or may lose charge quickly include polycarbonate, block copolymers such as styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers, polycarbonate Esters such as polyethylene terephthalate, polyamide, polyurethane, and other polymers familiar to those of ordinary skill in the art. If desired, some or all of the filter layer fibers may be made of multi-component fibers, including splittable fibers. Suitable multicomponent (e.g., bicomponent) fibers include side-by-side, sheath-core, segmented pie, island-in-the-sea, tipped, and segmented ribbon fibers. If splittable fibers are used, various techniques familiar to those of ordinary skill in the art can be used to perform or promote splitting, including combing, air jet, embossing, calendering, hydroentangling or needle punching. The filter layer is preferably made of poly-4-methyl-1-pentene or polypropylene monocomponent fibers or poly-4-methyl-1-pentene and polypropylene in a layered or sheath-core configuration ( For example, poly-4-methyl-1-pentene or polypropylene on the outer surface) in the bicomponent fiber preparation. Optimally, the filter layer is made of polypropylene homopolymer monocomponent fibers due to the ability of polypropylene to retain electric charge particularly in humid environments. Additives can be added to the polymer to enhance filtration performance, electret charging ability, mechanical properties, aging properties, coloring, surface properties, or other related properties. Representative additives include fillers, nucleating agents (such as MILLAD™ 3988 dibenzylidene sorbitol, available from Milliken Chemical), electret charging enhancing additives (such as tristearyl melamine and various light stabilizers, such as CHIMASSORB™ 119 and CHIMASSORB 944 from Ciba Specialty Chemicals), curing initiators, stiffeners (e.g. poly(4-methyl-1-pentene)), surfactants and surface treatment agents (e.g., as given to Jones et al. US Patent Nos. 6,398,847 B1, 6,397,458 B1, and 6,409,806 B1 described in US Patent Nos. 6,398,847 B1, and 6,409,806 B1, fluorine atom treatment to improve the filtering performance in the oil mist environment). The types and amounts of these additives are familiar to those of ordinary skill in the art. For example, electret charge enhancing additives are generally present in an amount of less than about 5% by weight, and more usually less than about 2% by weight. The polymer fiber-forming material is also preferably substantially free of components such as antistatic agents, which may significantly increase electrical conductivity or otherwise interfere with the fiber's ability to receive and retain static charges.

The filter layer can have a variety of basis weights, fiber sizes, thicknesses, pressure drops, and other characteristics, and may be brittle enough in itself to not be rolled-to-roll processing. The filter layer may have a basis weight of, for example, about 0.5 to about 300 g/m ² (gsm), about 0.5 to about 100 gsm, about 1 to about 50 gsm, or about 2 to about 40 gsm. For example, a relatively low basis weight of about 2, 5, 15, 25, or 40 gsm is preferable for the filter layer. The fibers in the filter layer may have a median fiber size of, for example, less than about 10 μm, less than about 5 μm, or less than about 1 μm. The thickness of the filter layer may be, for example, about 0.1 to about 20 mm, about 0.2 to about 10 mm, or about 0.5 to about 5 mm. The nanofiber filter layer applied to some carrier layers (such as rough-textured carrier layers) at very low basis weights may not change the total media thickness. The basis weight and thickness of the filter layer can be controlled or adjusted, for example, by changing the collector speed or polymer delivery volume.

The carrier layer is strong enough to form a filter layer on the carrier layer and the resulting media can be further converted using roll-to-roll processing equipment as needed. The carrier layer can be formed of various materials, and can have various basis weights, thicknesses, pressure drops, and other characteristics. For example, the carrier layer can be a nonwoven mesh, woven fabric, knitted fabric, open cell foam, or perforated film. Nonwoven webs are the preferred carrier layer. Suitable fiber precursors for making such nonwoven webs include the polymer fiber-forming materials discussed above and other polymer fiber-forming materials that do not readily receive or retain static charges. The carrier layer can also be formed from natural fibers or from a blend of synthetic and natural fibers. If made of a nonwoven web, the carrier layer can be formed, for example, from a molten thermoplastic polymer using meltblown, melt spinning or other suitable web processing techniques, from natural fibers or from a blend of synthetic and natural fibers using carding or from Rando -Webber machine deposition formation, or formation using other techniques familiar to those of ordinary skill in the art. If made of a woven mesh or knitted fabric, the carrier layer can be formed, for example, of micro-denier continuous filaments or staple fiber yarns (ie yarns with a denier per filament (dpf) less than about 1) and use those familiar to those of ordinary skill in the art. Suitable processing techniques are processed into woven or knitted carrier fabrics. The carrier layer may, for example, have a basis weight of about 5 to about 300 gsm, more preferably about 40 to about 150 gsm. The thickness of the carrier layer may be, for example, about 0.2 to about 40 mm, about 0.2 to about 20 mm, about 0.5 to about 5 mm, or about 0.5 to about 1.5 mm.

In addition to the polyamide nanofiber layer, if necessary, additional layers can be added to the disclosed medium. Representative additional layers are familiar to those of ordinary skill in the art and include protective layers (e.g., anti-peeling layer, anti-irritation layer, and other covering layers), reinforcement layer, and absorbent layer. The adsorbent particles (for example, activated carbon particles or alumina particles) can also be introduced into the medium using methods familiar to those of ordinary skill in the art.

Various techniques can be used to perform the hydrocharging of the disclosed multilayer media, including impacting, immersing or condensing a polar fluid onto the media, followed by drying to charge the media. Representative patents describing hydraulic charging include the aforementioned U.S. Patent Nos. 5,496,507 and U.S. Patent Nos. 5,908,598; 6,375,886; 6,406,657; 6,454,986; and 6,743,464. It is preferable to use water as the polar hydraulic charging liquid, and it is preferable to use a liquid jet or a stream of droplets provided by any suitable spray means to expose the medium to the polar hydraulic charging liquid. Devices that can be used for hydroentanglement of fibers can generally be used to perform hydraulic charging, although the hydraulic charging is operated at a lower pressure than that normally used in hydroentanglement. U.S. Patent No. 5,496,507 describes an exemplary device in which a water jet or stream of water droplets is impinged on a medium at a pressure sufficient to provide an electret charge that enhances penetration for subsequent drying of the graft. The pressure required to achieve the best results may vary depending on the type of sprayer used, the type of polymer used to form the permeable layer, the thickness and density of the medium, and whether pre-treatment such as corona charging is performed before hydraulic charging. Generally, a pressure of about 69 to about 3450 kPa is suitable. Preferably, the water used to provide the water droplets is relatively pure. Distilled water or deionized water is better than tap water.

The disclosed medium can be subjected to other charging techniques before or after hydraulic charging, including electrostatic charging (for example, as described in U.S. Patent Nos. 4,215,682, 5,401,446 and 6,119,691), friction charging (for example, as described in U.S. Patent No. 4,798,850) Or plasma fluorination (for example, as described in U.S. Patent No. 6,397,458 B1). Corona charging followed by hydraulic charging, and plasma fluorination followed by hydraulic charging are the preferred combined charging techniques.

Additional breathing filters are described in, for example, U.S. Patent Nos. 4,011,067; 4,215,682; 4,592,815; 4,729,371; 4,798,850; 5,401,466; 5,496,507; 6,119,691; 6,183,670; 6,315,806; Tsai et al., Electrospinning Theory and Techniques, 14th Annual International TANDEC Nonwovens Conference, November 9-11, 2004. For example, other fiber webs are described in U.S. Patent Nos. 4,536,361 and 5,993,943. implementation plan

The present disclosure includes the following embodiments:

Embodiment 1: A filter medium containing a nanofiber nonwoven fabric layer, wherein the nanofiber nonwoven fabric layer includes polyamide having a relative viscosity of 2 to 200, which is spun into a filter medium having a relative viscosity of less than 1 micron (1000 nanometers). ) The average fiber diameter of the nanofibers is formed into a layer.

Embodiment 2: The embodiment according to Embodiment 1, wherein the nanofiber nonwoven fabric layer comprises polyamide spun into nanofibers having an average fiber diameter of less than 1 micrometer (1000 nanometers) and formed into a layer, wherein The layer has a melting point of 225°C or higher.

Embodiment 3: The embodiment according to embodiment 1 or 2, wherein the filter is an air filter, an oil filter, a bag filter, a liquid filter or a breathing filter.

Embodiment 4: An embodiment according to embodiment 1 or 2, wherein the polyamide is nylon 6,6.

Embodiment 5: The embodiment according to embodiment 1 or 2, wherein the polyamide is a derivative, copolymer, blend or alloy of nylon 6,6 and nylon 6.

Embodiment 6: The embodiment according to embodiment 1 or 2, wherein the polyamide is high temperature nylon.

Embodiment 7: The embodiment according to embodiment 1 or 2, wherein the polyamide is a long-chain aliphatic nylon selected from the group consisting of N6, N6T/66, N612, N6/66, N11 and N12, wherein "N" is Refers to nylon, and "T" refers to terephthalic acid.

Embodiment 8: The embodiment according to any one of embodiments 1-7, wherein the nanofiber nonwoven fabric layer has an air permeability value of less than 200 CFM/ft2.

Embodiment 9: The embodiment according to any one of the embodiments 1-8, wherein the nanofiber nonwoven fabric layer has an air permeability value of 50 to 200 CFM/ft2.

Embodiment 10: The embodiment according to any one of the embodiments 1-9, wherein the nanofibers have an average fiber diameter of 100 to 907 nanometers, such as 300 to 700 nanometers or 350 to 650 nanometers.

Embodiment 11: The embodiment according to any one of embodiments 1-10, wherein the nonwoven product has a basis weight of 150 GSM or less.

Embodiment 12: The embodiment according to any one of embodiments 1-11, wherein the filter media further comprises a scrim layer.

Embodiment 13: An embodiment according to embodiment 12, wherein the nanofiber nonwoven fabric layer is spun onto the scrim layer.

Embodiment 14: An embodiment according to embodiment 12, wherein the nanofiber nonwoven fabric layer is spun onto a layer of a non-scrim layer.

Embodiment 15: An embodiment according to embodiment 12, wherein the nanofiber nonwoven fabric layer is sandwiched between the scrim layer and at least one other layer.

Embodiment 16: An embodiment according to embodiment 12, wherein the nanofiber nonwoven fabric layer is sandwiched between at least two non-scrim layers.

Embodiment 17: An embodiment according to embodiment 12, wherein the nanofiber nonwoven fabric layer is the outermost layer.

Embodiment 18: The embodiment according to any one of embodiments 1-11, wherein the filter medium further comprises at least one additional layer and wherein the nanofiber nonwoven fabric layer is spun to one of the at least one additional layer on.

Embodiment 19: The embodiment according to any one of the embodiments 1-18, wherein the relative viscosity of the polyamide in the nanofiber nonwoven fabric layer is reduced by at least 20% compared with the polyamide before spinning and layering .

Embodiment 20: A method of manufacturing a filter medium containing a polyamide nanofiber layer, the method comprising: (a) providing a spinnable polyamide polymer composition, wherein the polyamide has a thickness of 2 to 200 Relative viscosity; (b) melt-spun the polyamide polymer composition into many nanofibers having an average fiber diameter of less than 1 micron (1000 nanometers); and (c) shape the nanofibers into existing filters On the dielectric layer, wherein the polyamide nanofiber layer has an average nanofiber diameter less than 1000 nanometers.

Embodiment 21: A method of manufacturing a filter medium containing a polyamide nanofiber layer, the method comprising: (a) providing a spinnable polyamide polymer composition; (b) combining the polyamide polymer The composition is melt-spun into many nanofibers having an average fiber diameter of less than 1 micron (1000 nanometers); and (c) molding the nanofibers onto an existing filter media layer, wherein the polyamide nanofiber layer has An average nanofiber diameter of less than 1000 nanometers and a melting point of 225°C or higher.

Embodiment 22: An embodiment according to embodiment 20 or 21, wherein the polyamide nanofiber layer is melt-spun by melt-blowing into a high-speed gas stream through a die.

Embodiment 23: The embodiment according to embodiment 20 or 21, wherein the polyamide nanofiber layer is melt-spinned by a two-phase propellant gas spinning method, which includes extruding liquid form of the polyamide nanofiber layer through a fiber forming channel with pressurized gas Polyamide polymer composition.

Embodiment 24: An embodiment according to any one of embodiments 20-23, wherein the polyamide nanofiber layer is formed by collecting nanofibers on a moving belt.

Embodiment 25: An embodiment according to any one of embodiments 20-24, wherein the polyamide composition comprises nylon 6,6.

Embodiment 26: The embodiment according to any one of embodiments 20-24, wherein the polyamide composition comprises a derivative, copolymer, blend or alloy of nylon 6,6 and nylon 6.

Embodiment 27: An embodiment according to any one of embodiments 20-24, wherein the polyamide comprises HTN.

Embodiment 28: The embodiment according to any one of embodiments 20-24, wherein the polyamide is a long-chain aliphatic nylon selected from the group consisting of N6, N6T/66, N612, N6/66, N11 and N12, wherein " N" refers to nylon, and "T" refers to terephthalic acid.

Embodiment 29: An embodiment according to any one of embodiments 20-28, wherein the polyamide nanofiber layer has a basis weight of 150 GSM or less.

Embodiment 30: An embodiment according to any one of embodiments 20-29, wherein the filter media further comprises a scrim layer.

Embodiment 31: The embodiment according to any one of embodiments 20-30, wherein the polyamide nanofiber layer is spun onto the scrim layer.

Embodiment 32: An embodiment according to embodiment 31, wherein the polyamide nanofiber layer is spun onto a layer that is not a scrim layer.

Embodiment 33: An embodiment according to embodiment 31, wherein the polyamide nanofiber layer is sandwiched between the scrim layer and at least one other layer.

Embodiment 34: An embodiment according to embodiment 31, wherein the polyamide nanofiber layer is sandwiched between at least two layers of non-scrim layers.

Embodiment 35: An embodiment according to embodiment 31, wherein the polyamide nanofiber layer is the outermost layer.

Embodiment 36: The embodiment according to any one of embodiments 20-31, wherein the filter medium further comprises at least one additional layer and wherein the nanofiber nonwoven fabric layer is spun to one of the at least one additional layer on.

Embodiment 37: The embodiment according to any one of embodiments 20-36, wherein the relative viscosity of the polyamide in the polyamide nanofiber layer is reduced by at least 20% compared to the polyamide before spinning and layering .

The present disclosure is further understood with the following non-limiting examples. Example Example 1

Using the program and device described in US 8,668,854 (roughly shown in Figure 1), nylon 6,6 is spun into a non-woven fabric of two basis weights by melt spinning onto a moving drum. An extruder with a high compression screw running at 20 RPM, with a temperature distribution of 245°C, 255°C, 265°C, and 265°C, is used. The polymer temperature was 252°C and air was used as the gas. A sample with a higher basis weight was made by the same method, but the nanofibers were spun onto the scrim. Here, the scrim is the neutral product of the present invention only used to increase the integrity of the nanofiber web of the present invention. The resin has a relative viscosity of 7.3. To ensure that the viscosity of the low RV resin remains constant, an approximately 5% excess of adipic acid is used to make the polymer.

According to the above article by Hassan et al., J Membrane Sci., 427, 336-344, 2013 characterizes the average fiber diameter, basis weight, and air permeability of the nonwoven fabric. The water vapor transmission rate (g/m ² /24hr) is also measured.

The results and details are shown in Table 1, and the finished non-woven fabric is shown in the photomicrographs of FIGS. 3 and 4. The nonwoven fabric has an average fiber diameter of 470 nm to 680 nm (average 575 nm). Table 1 Product properties of polyamide nanofiber nonwovens sample Resin RV Fiber diameter, nm Basis weight, gsm Air permeability (CFM/ft ² ) Water vapor transmission rate g/m ² /24 hr 1 7.3 470 118 182.8 1056 2 7.3 680 68 182.8 1140

It is recognized from Table 1 that the melt-spun nanofiber nonwoven fabric of the present invention has an average fiber diameter of 570 at an RV of 7.3. The air permeability is about 182.8 CFM/ft ² , and the water vapor transmission rate is about 1100 g/m ² /24 hrs on average.

Polyamides made into nanofibers with RVs higher than about 20-30 have higher molecular weights than those with lower RV values. The resulting polymer properties may be different from those having an RV value of less than 20, especially in terms of elasticity, strength, thermal or chemical stability, appearance and or surface properties. It may be necessary to use a mixture of lower and higher molecular weight polymers in nonwoven webs. Lower molecular weight polymers are easier to fibrillate, which may produce fibers with different diameters. If these polymers are not blended, separate nozzles can be used for polymers of different molecular weights.

In the case of polyamides having a RV higher than 20-30 and less than 200, the average fiber diameter of a considerable number of fibers in the fiber layer of the nonwoven fabric may be less than 1 micron, more preferably about 0.1 to 1 micron, or more Preferably 0.1 to about 0.6 microns. The resulting nonwoven fabric has an average fiber diameter of less than 1 micron.

In one embodiment of the present invention, the advantage of blending two related polymers with different RV values (both less than 200 and having an average fiber diameter of less than 1 micron) for the desired properties is envisaged. Example 2

The nanofibers in the present invention are manufactured using the melt-blown method with the aid of the pack described in US Patent No. 7,300,272. Nylon 6,6 with 36 RV was melt spun and pumped to the meltblowing die. The moisture content of this resin is about 0.2% to about 1.0%. An extruder with four zones was used, and the temperature was in the range of 233 to 310°C. Use a die temperature of 286°C to 318°C. Use heated air as the gas in the melt blown method. The nanofibers were deposited on a 10 grams per square meter (gsm) thermally bonded nylon spunbond scrim available from Cerex Advanced Fabrics, Inc. under the trademark PBN-II®. Other spunbond fabrics can be used. Other fabrics can be used, such as polyester spunbond fabric, polypropylene spunbond fabric, nylon meltblown fabric or other woven, knitted, needle punched or other non-woven fabrics. No solvents or adhesives are used. Use nanofiber layers to make various fabrics. The basis weight of the nanofiber layer is between about 0.7 gsm and about 23 gsm. The average fiber diameter of these nanofiber layers is between about 0.36 microns to about 0.908 microns. The relative viscosity of these nanofiber layers is about 22 to about 31. The starting RV is 34 to 37 and approximately 36. The efficiency of these fabrics measured using TSI 8130 with a 0.3 micron challenge fluid is between about 2.71% to about 76.7%. The average pore size of these fabrics ranges from about 4.5 microns to about 84.1 microns. The air permeability of these fabrics is 21 to 1002 cfm/ft ² . Example 3

A resin having an RV of 34 to 37 is used together with the pack described in US Patent No. 7,300,272 to produce a nanofiber having an RV of about 16.8. This is a reduction in RV from resin to fabric of approximately 17.2 to 20.2 RV units. The resin contains approximately 1% by weight of moisture and runs on a small extruder with four zones with temperatures ranging from 233 to 310°C. A die temperature of approximately 308°C is used. Example 4

A resin having an RV of 34 to 37 is used together with the pack described in US Patent 7,300,272 to produce a nanofiber having an RV of about 19.7. This is a reduction in RV from resin to fabric of approximately 14.3 to 17.3 RV units. The resin contains approximately 1% by weight of moisture and runs on a small extruder with four zones with temperatures ranging from 233 to 310°C. A die temperature of approximately 277°C is used. Example 5

A resin with an RV of 34 to 37 is used with 2% nylon 6 blended in. The pack described in US Patent 7,300,272 was used to produce nanofibers with an RV of approximately 17.1. This is a reduction in RV from resin to fabric of approximately 16.9 to 19.9 RV units. The resin contains approximately 1% by weight of moisture and runs on a small extruder with four zones with temperatures ranging from 233 to 310°C. A die temperature of approximately 308°C is used. Other blends or copolymers of nylon can be used. In a preferred embodiment, a blend of nylon 6 and nylon 6,6 can be used. These nylon 6 and nylon 6,6 blends have a melting point between the melting point of nylon 6 at about 220°C and the melting point of nylon 6,6 at about 260°C. Example 6

Combine 3 to 6 nanofiber nonwoven layers to create a medium with higher basis weight and thickness. Each layer includes a nylon 6,6 nanofiber mesh on a 10 gsm nylon release scrim available under the trade name "PBN-II" from Cerex Advanced Fabrics, Inc. in Cantonment, Florida. Four different nets with different basis weights (13.3, 21.2, 13.2, and 20.2) as reported in Table 2 were used. Table 2 shows the basis weight, the filtration efficiency as measured with a 0.3 micron challenge fluid using TSI 8130, the medium flow pore size, and the average pressure drop (PD) as measured by TSI 8130. Measure two samples to report the average of the flow aperture, efficiency and pressure drop.

The fabric has a basis weight of 13.2 gsm to 127.2 gsm and a medium flow pore size of 3.9 to 5.8 microns and a filtration efficiency of 63.5% to 80.2% as measured by a TSI instrument as described above. Table 2 Floor Basis weight (gsm) Medium flow aperture ( micron ) Efficiency (%) Pressure drop (Pa) Average permeability (%) Ave. sample Ave. sample Ave. sample 1 2 1 2 1 2 1 13.3 5.8 63.5 37.7 36.5 3 39.9 4.7 4.5 4.8 69 72.2 65.8 47.3 49.6 45.1 31 4 53.2 5.1 5.1 5.1 67.5 68.9 66.1 47.9 51.4 44.5 32.5 5 66.5 5.1 5.4 4.7 66.7 65.8 67.5 46.9 43.5 50.3 33.3 6 79.8 5.2 4.8 5.6 65 67.6 62.3 45.1 49.1 41.2 35 1 21.2 5 76.7 56.1 23.3 3 63.6 3.9 3.8 4 79.5 81.1 77.8 75.9 82.2 69.6 20.5 4 84.8 4.1 4.2 4 79.4 77.7 81.2 70 63.6 76.4 20.6 5 106 4.3 4 4.6 76.1 78.3 73.8 46.4 66.6 26.2 23.9 6 127.2 4.3 4.3 4.4 80.2 81.1 79.3 74.5 80.3 68.7 19.8 1 13.2 5.4 66 41.4 34 3 39.6 4.8 4.6 5 65.6 64.7 66.6 45.7 49.9 41.6 34.4 4 52.8 5 4.5 5.5 65.7 65.7 65.8 46.1 51.7 40.5 34.3 5 66 4.6 4.4 4.7 65.2 65 65.5 46 51.1 40.9 34.8 6 79.2 4.8 5.1 4.4 65.9 65.8 66 46.9 41.3 52.6 34.1 1 20.2 5 73.8 52.1 26.2 4 80.8 5.2 4.2 6.3 76.9 74.3 79.5 74.3 66.9 81.7 23.1 5 101 4.6 4.8 4.5 76.4 78.2 74.6 74.3 81.3 67.4 23.6 6 121.2 4.9 4.5 5.3 79.1 80.4 77.8 76 71.8 80.1 20.9 Example 7- Bacteria and particle filtration efficiency test

Two sample filters were prepared using polyamide 66 nanofiber mesh. Filter 1 has a basis weight of 8.2 gsm and its nanofibers have an average fiber diameter of 612 nm and a median fiber diameter of 440 nm. The air permeability is 72.1 cfm/ft ² , the medium flow pore size is 7.2, and the bubble point is 28.1 microns. Filter 2 has a basis weight of 11.1 gsm and its nanofibers have an average fiber diameter of 612 nm and a median fiber diameter of 469 nm. The air permeability is 39.2 cfm/ft ² , the medium flow pore size is 5.9, and the bubble point is 25.7 microns. The thickness of each filter is approximately 20 mm. Each filter has a size of approximately 174 mm x approximately 178 mm.

Test the bacterial filtration efficiency (BFE) and particle filtration efficiency (PFE) of filter 1 and filter 2. Compare Filter 1 and Filter 2 with a standard filter made of three polypropylene layers (spunbond/meltblown/spunbond).

A BFE test was performed to determine the filtration efficiency of the test filter by comparing the bacterial control count upstream of the test filter with the bacterial count downstream. A sprayer was used to atomize the suspension of Staphylococcus aureus and delivered to the test product (2.8 x 10 ³ CFU) at a constant flow rate (28.3 L/m) and a fixed air pressure. The conditioning parameters are 85% ± 5% relative humidity and 21°C ± 5°C for a minimum of 4 hours. The challenge delivery is maintained at 1.7-3.0 x 10 ³ colony forming units (CFU) with an average fineness (MPS) of 3.0 ± 0.3 μm. The aerosol is extracted by the Anderson sampler of six-stage live particles for collection. This test method complies with ASTM F2101-19 and EN 14683:2019, Appendix B.

A pressure drop (delta P) test was performed to determine the air permeability of the test filter article by measuring the air pressure difference on both sides of the test article at a constant flow rate using a pressure gauge. The delta P test complies with EN 14683:2019, Appendix C and ASTM F2100-19.

A PFE test was performed to evaluate the non-living particle filtration efficiency (PFE) of the tested filter products (11.1 gsm, 8.2 gsm and standard samples). The monodisperse polystyrene latex spheres (PSL) were sprayed (atomized), dried and passed through the test filter product. A laser particle counter was used to count the particles passing through the filter product under test.

In the case where the test filter is present in the system, counting is performed for 1 minute. When there is no test filter product in the system, a 1-minute control count is performed before and after each test product, and these counts are averaged. A control count is performed to determine the average number of particles delivered to the test filter article. The filtration efficiency is calculated using the number of particles passing through the test filter article compared to the average of the control value.

This program uses the elementary particle filtration method described in ASTM F2299, with some exceptions; the program especially contains challenges of non-neutralization. In actual use, particles are charged, so this challenge represents a more natural state. Non-neutralized aerosols are also specified in the FDA guidance document on surgical masks.

The results of the BFE and PFE tests are shown in Table 3. The results shown in Table 3 are average results. For the 8.2 gsm meltblown polyamide and polypropylene standards, an average of 5 samples. For 11.1 and 11.1 gsm meltblown polyamides, an average of 4 samples.

Both 11.1 gsm and 8.2 gsm meltblown polyamide 66 nanofibers showed favorable PFE similar to the standard. Advantageously, the BFE of 11.1 gsm is also excellent, while improving (decreasing) delta P compared to the standard. This is a significant and unexpected improvement. Similarly, although the BFE is slightly lower, the 8.2 gsm meltblown polyamide 66 nanofiber exhibits a significantly lower delta P. The meltblown nanofibers of the present invention can provide functional efficiency with improved properties compared to polypropylene standards. table 3 Melt-blown polyamide 66 nanofiber Polypropylene standard 11.1 gsm 8.2 gsm BFE 97.2% 86.4% 97.3% PFE 97.5% 94.5% 98.1% delta P (mm H ₂ O/cm ² ) 2.95 1.22 3.82

Although the present invention has been described in detail, those skilled in the art will readily perceive modifications within the spirit and scope of the present invention. Such modifications are also regarded as part of the present invention. Based on the above discussion, relevant knowledge in the art, and the references discussed above in connection with the background of the invention (their disclosures are all incorporated herein by reference), further description is deemed unnecessary. In addition, it should be understood from the above discussion that aspects of the present invention and parts of various embodiments may be combined or interchanged in whole or in part. In addition, those of ordinary skill in the art will recognize that the above description is merely illustrative and is not intended to limit the present invention. Finally, all patents, publications and applications mentioned in this article are hereby incorporated by reference in their entirety.

110: Polymer feed assembly 1210: Air feed 130: Spinning cylinder 140: collection belt 150: take-up shaft

The present invention will be described in detail below with reference to the accompanying drawings, where similar signs refer to similar components and where:

Figures 1 and 2 are independent schematic diagrams of a two-phase propellant gas spinning system that can be used in the present invention;

Figure 3 is a photomicrograph at 50X magnification of nanofiber nylon 66 melt-spun into a nonwoven fabric with an RV of 7.3; and

Figure 4 is a photomicrograph at 8000X magnification of nylon 66 graded nanofibers from Figure 3 melt-spun into a nonwoven fabric with an RV of 7.3.

110: Polymer feed assembly

1210: Air feed

130: Spinning cylinder

140: collection belt

150: take-up shaft

Claims (37)

A filter medium containing a nanofiber nonwoven fabric layer, wherein the nanofiber nonwoven fabric layer includes polyamide having a relative viscosity of 2 to 200, and the system is spun into an average fiber having an average fiber size of less than 1 micron (1000 nanometers) Diameter of nanofibers and formed into layers. A filter medium comprising a nanofiber nonwoven fabric layer, wherein the nanofiber nonwoven fabric layer comprises polyamide spun into nanofibers having an average fiber diameter of less than 1 micrometer (1000 nanometers) and formed into a layer, wherein The layer has a melting point of 225°C or higher. The filter medium of claim 1 or 2, wherein the filter is an air filter, an oil filter, a bag filter, a liquid filter, or a breathing filter. The filter medium of claim 1 or 2, wherein the polyamide is nylon 6,6. The filter medium of claim 1 or 2, wherein the polyamide is a derivative, copolymer, blend, or alloy of nylon 6,6 and nylon 6. The filter medium of claim 1 or 2, wherein the polyamide is high temperature nylon. The filter medium of claim 1 or 2, wherein the polyamide is a long-chain aliphatic nylon selected from the group consisting of N6, N6T/66, N612, N6/66, N11 and N12, wherein "N" refers to nylon, And "T" means terephthalic acid. The filter medium according to any one of the preceding claims, wherein the nanofiber nonwoven fabric layer has an air permeability value of ^{less than 200 CFM/ft 2.} The filter medium according to any one of the preceding claims, wherein the nanofiber nonwoven fabric layer has an air permeability value of ^{50 to 200 CFM/ft 2.} The filter medium according to any one of the preceding claims, wherein the nanofibers have an average fiber diameter of 100 to 907 nanometers. The filter medium according to any one of the preceding claims, wherein the non-woven fabric product has a basis weight of 150 GSM or less. The filter medium according to any one of the preceding claims, wherein the filter medium further comprises a scrim layer. The filter medium of claim 12, wherein the nanofiber nonwoven fabric layer is spun onto the scrim layer. The filter medium of claim 12, wherein the nanofiber nonwoven fabric layer is spun onto the non-scrim layer. The filter medium of claim 12, wherein the nanofiber nonwoven fabric layer is sandwiched between the scrim layer and at least one other layer. The filter medium of claim 12, wherein the nanofiber nonwoven fabric layer is sandwiched between at least two non-scrim layers. The filter medium of claim 12, wherein the nanofiber nonwoven fabric layer is the outermost layer. The filter medium of any one of claims 1-11, wherein the filter medium further comprises at least one additional layer and wherein the nanofiber nonwoven fabric layer is spun onto one of the at least one additional layer. The filter medium according to any one of the preceding claims, wherein the relative viscosity of the polyamide in the nanofiber nonwoven fabric layer is reduced by at least 20% compared with the polyamide before spinning and layering. A method of manufacturing a filter medium containing a polyamide nanofiber layer, the method comprising: (a) Provide a spinnable polyamide polymer composition, wherein the polyamide has a relative viscosity of 2 to 200; (b) Melt-spun the polyamide polymer composition into many nanofibers having an average fiber diameter of less than 1 micrometer (1000 nanometers); and (c) Molding the nanofibers on an existing filter media layer, wherein the polyamide nanofiber layer has an average nanofiber diameter of less than 1000 nanometers. A method of manufacturing a filter medium containing a polyamide nanofiber layer, the method comprising: (a) Provide spinnable polyamide polymer compositions; (b) Melt-spun the polyamide polymer composition into many nanofibers having an average fiber diameter of less than 1 micrometer (1000 nanometers); and (c) Molding the nanofibers on an existing filter media layer, wherein the polyamide nanofiber layer has an average nanofiber diameter of less than 1000 nanometers and a melting point of 225°C or higher. (a) Provide spinnable polyamide polymer compositions; (b) Melt-spun the polyamide polymer composition into many nanofibers having an average fiber diameter of less than 1 micrometer (1000 nanometers); and (c) Molding the nanofibers on an existing filter media layer, wherein the polyamide nanofiber layer has an average nanofiber diameter of less than 1000 nanometers and a melting point of 225°C or higher. The method of manufacturing a filter medium according to claim 20 or 21, wherein the polyamide nanofiber layer is melt-spun by melt-blowing into a high-speed gas stream through a die. The method for manufacturing a filter medium according to claim 20 or 21, wherein the melt-spinning of the polyamide nanofiber layer by a two-phase propellant gas spinning method includes using pressurized gas to extrude a liquid form through a fiber forming channel Polyamide polymer composition. The method for manufacturing a filter medium according to any one of claims 20-23, wherein the polyamide nanofiber layer is formed by collecting nanofibers on a moving belt. The method for manufacturing a filter medium according to any one of claims 20-24, wherein the polyamide composition comprises nylon 6,6. The method for manufacturing a filter medium according to any one of claims 20-24, wherein the polyamide composition comprises a derivative, copolymer, blend or alloy of nylon 6,6 and nylon 6. The method for manufacturing a filter medium according to any one of claims 20-24, wherein the polyamide contains HTN. The method for manufacturing a filter medium according to any one of claims 20-24, wherein the polyamide is a long-chain aliphatic nylon selected from the group consisting of N6, N6T/66, N612, N6/66, N11 and N12, wherein " N" refers to nylon, and "T" refers to terephthalic acid. The method for manufacturing a filter medium according to any one of claims 20-28, wherein the polyamide nanofiber layer has a basis weight of 150 GSM or less. The method for manufacturing a filter medium according to any one of claims 20-29, wherein the filter medium further comprises a scrim layer. The method for manufacturing a filter medium according to any one of claims 20-30, wherein the polyamide nanofiber layer is spun onto the scrim layer. The method of manufacturing a filter medium according to claim 31, wherein the polyamide nanofiber layer is spun onto a layer of a non-scrim layer. The method of manufacturing a filter medium according to claim 31, wherein the polyamide nanofiber layer is sandwiched between a scrim layer and at least one other layer. The method of manufacturing a filter medium according to claim 31, wherein the polyamide nanofiber layer is sandwiched between at least two layers of non-scrim layers. The method of manufacturing a filter medium according to claim 31, wherein the polyamide nanofiber layer is the outermost layer. The method for manufacturing a filter medium according to any one of claims 20-31, wherein the filter medium further comprises at least one additional layer and wherein the nanofiber nonwoven fabric layer is spun to one of the at least one additional layer on. The method for manufacturing a filter medium according to any one of claims 20-36, wherein the relative viscosity of the polyamide in the polyamide nanofiber layer is reduced by at least 20% compared with the polyamide before spinning and layering .

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