Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D39/00—Filtering material for liquid or gaseous fluids
  • B01D39/02—Loose filtering material, e.g. loose fibres
  • B01D39/04—Organic material, e.g. cellulose, cotton
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D—SEPARATION
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  • B01D39/08—Filter cloth, i.e. woven, knitted or interlaced material
  • B01D39/086—Filter cloth, i.e. woven, knitted or interlaced material of inorganic material
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D39/14—Other self-supporting filtering material ; Other filtering material
  • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
  • B01D39/1607—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous
  • B01D39/1623—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous of synthetic origin
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D39/14—Other self-supporting filtering material ; Other filtering material
  • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
  • B01D39/1607—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous
  • B01D39/1623—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous of synthetic origin
  • B01D39/163—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous of synthetic origin sintered or bonded
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D39/14—Other self-supporting filtering material ; Other filtering material
  • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
  • B01D39/18—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being cellulose or derivatives thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D46/0001—Making filtering elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D46/02—Particle separators, e.g. dust precipitators, having hollow filters made of flexible material
• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
  • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
  • B01D46/2411—Filter cartridges
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D46/521—Particle separators, e.g. dust precipitators, using filters embodying folded corrugated or wound sheet material using folded, pleated material
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D46/521—Particle separators, e.g. dust precipitators, using filters embodying folded corrugated or wound sheet material using folded, pleated material
  • B01D46/523—Particle separators, e.g. dust precipitators, using filters embodying folded corrugated or wound sheet material using folded, pleated material with means for maintaining spacing between the pleats or folds
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D46/546—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms using nano- or microfibres
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/0007—Electro-spinning
• • D—TEXTILES; PAPER
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  • D01D5/003—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion
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  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/0007—Electro-spinning
  • D01D5/0061—Electro-spinning characterised by the electro-spinning apparatus
  • D01D5/0076—Electro-spinning characterised by the electro-spinning apparatus characterised by the collecting device, e.g. drum, wheel, endless belt, plate or grid
  • D01D5/0084—Coating by electro-spinning, i.e. the electro-spun fibres are not removed from the collecting device but remain integral with it, e.g. coating of prostheses
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/10—Other agents for modifying properties
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  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/78—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products
  • D01F6/80—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products from copolyamides
• • D—TEXTILES; PAPER
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  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/88—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polycondensation products as major constituent with other polymers or low-molecular-weight compounds
  • D01F6/90—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polycondensation products as major constituent with other polymers or low-molecular-weight compounds of polyamides
• • D—TEXTILES; PAPER
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  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
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  • D01F6/92—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polycondensation products as major constituent with other polymers or low-molecular-weight compounds of polyesters
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
  • D04H3/02—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of forming fleeces or layers, e.g. reorientation of yarns or filaments
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  • Y10T428/2967—Synthetic resin or polymer
  • Y10T428/2969—Polyamide, polyimide or polyester
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2913—Rod, strand, filament or fiber
  • Y10T428/298—Physical dimension
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/10—Scrim [e.g., open net or mesh, gauze, loose or open weave or knit, etc.]
  • Y10T442/102—Woven scrim
  • Y10T442/159—Including a nonwoven fabric which is not a scrim
  • Y10T442/16—Two or more nonwoven layers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
  • Y10T442/608—Including strand or fiber material which is of specific structural definition
  • Y10T442/614—Strand or fiber material specified as having microdimensions [i.e., microfiber]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
  • Y10T442/608—Including strand or fiber material which is of specific structural definition
  • Y10T442/614—Strand or fiber material specified as having microdimensions [i.e., microfiber]
  • Y10T442/626—Microfiber is synthetic polymer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
  • Y10T442/659—Including an additional nonwoven fabric

Definitions

• the substrate can be positioned in the fluid stream upstream, downstream or in an internal layer.
• filtration media for filtration, i.e. the removal of unwanted particles from a fluid such as gas or liquid.
• the common filtration process removes particulate from fluids including an air stream or other gaseous stream or from a liquid stream such as a hydraulic fluid, lubricant oil, fuel, water stream or other fluids.
• Such filtration processes require the mechanical strength, chemical and physical stability of the microfiber and the substrate materials.
• the filter media can be exposed to a broad range of temperature conditions, humidity, mechanical vibration and shock and both reactive and non- reactive, abrasive or non-abrasive particulates entrained in the fluid flow.
• the filtration media often require the self-cleaning ability of exposing the filter media to a reverse pressure pulse (a short reversal of fluid flow to remove surface coating of particulate) or other cleaning mechanism that can remove entrained particulate from the surface of the filter media.
• a reverse pressure pulse a short reversal of fluid flow to remove surface coating of particulate
• Such reverse cleaning can result in substantially improved (i.e.) reduced pressure drop after the pulse cleaning.
• Particle capture efficiency typically is not improved after pulse cleaning, however pulse cleaning will reduce pressure drop, saving energy for filtration operation.
• Such filters can be removed for service and cleaned in aqueous or non-aqueous cleaning compositions.
• a preferred mode of the invention is a polymer blend comprising a first polymer and a second, but different polymer (differing in polymer type, molecular weight or physical property) that is conditioned or treated at elevated temperature.
• the polymer blend can be reacted and formed into a single chemical specie or can be physically combined into a blended composition by an annealing process. Annealing implies a physical change, like crystallinity, stress relaxation or orientation.
• Preferred materials are chemically reacted into a single polymeric specie such that a Differential Scanning Calorimeter analysis reveals a single polymeric material.
• Such a material when combined with a preferred additive material, can form a surface coating of the additive on the microfiber that provides oleophobicity, hydrophobicity or other associated improved stability when contacted with high temperature, high humidity and difficult operating conditions.
• the fine fiber of the class of materials can have a diameter of 2 microns to less than 0.01 micron.
• Such microfibers can have a smooth surface comprising a discrete layer of the additive material or an outer coating of the additive material that is partly solubilized or alloyed in the polymer surface, or both.
• Preferred materials for use in the blended polymeric systems include nylon 6; nylon 66; nylon 6-10; nylon (6-66-610) copolymers and other linear generally aliphatic nylon compositions.
• a preferred nylon copolymer resin (SNP-651) was analyzed for molecular weight by the end group titration. (J.E. Walz and G.B. Taylor, determination of the molecular weight of nylon, Anal. Chem. Vol. 19, Number 7, pp 448-450 (1947). A number average molecular weight (W n ) was between 21,500 and 24,800. The composition was estimated by the phase diagram of melt temperature of three component nylon, nylon 6 about 45%, nylon 66 about 20% and nylon 610 about 25%. (Page 286, Nylon Plastics Handbook, Melvin Kohan ed. Hanser Publisher, New York (1995)).
• a polyvinylalcohol having a hydrolysis degree of from 87 to 99.9+% can be used in such polymer systems. These are preferably cross linked. And they are most preferably crosslinked and combined with substantial quantities of the oleophobic and hydrophobic additive materials.
• polymeric blends or alloys of differing polymers are also contemplated by the invention.
• compatible mixtures of polymers are useful in forming the microfiber materials of the invention.
• Additive composition such a fluoro-surfactant, a nonionic surfactant, low molecular weight resins (e.g.) tertiary butylphenol resin having a molecular weight of less than about 3000 can be used.
• the resin is characterized by oligomeric bonding between phenol nuclei in the absence of methylene bridging groups. The positions of the hydroxyl and the tertiary butyl group can be randomly positioned around the rings. Bonding between phenolic nuclei always occurs next to hydroxyl group, not randomly.
• the polymeric material can be combined with an alcohol soluble nonlinear polymerized resin formed from bis-phenol A.
• an alcohol soluble nonlinear polymerized resin formed from bis-phenol A.
• Such material is similar to the tertiary butylphenol resin described above in that it is formed using oligomeric bonds that directly connect aromatic ring to aromatic ring in the absence of any bridging groups such as alkylene or methylene groups.
• a particularly preferred material of the invention comprises a microfiber material having a dimension of about 2 to 0.01 microns. The most preferred fiber size range between 0.05 to 0.5 micron. Such fibers with the preferred size provide excellent filter activity, ease of back pulse cleaning and other aspects.
• the highly preferred polymer systems of the invention have adhering characteristic such that when contacted with a cellulosic substrate adheres to the substrate with sufficient strength such that it is securely bonded to the substrate and can resist the delaminating effects of a reverse pulse cleaning technique and other mechanical . stresses.
• the polymer material In such a mode, the polymer material must stay attached to the substrate while undergoing a pulse clean input that is substantially equal to the typical filtration conditions except in a reverse direction across the filter structure.
• Such adhesion can arise from solvent effects of fiber formation as the fiber is contacted with the substrate or the post treatment of the fiber on the substrate with heat or pressure.
• a fine fiber filter structure includes a bi-layer or multi-layer structure wherein the filter contains one or more fine fiber layers combined with or separated by one or more synthetic, cellulosic or blended webs.
• Another preferred motif is a structure including fine fiber in a matrix or blend of other fibers.
• microfiber and filter material of the invention are deemed moisture resistant where the material can survive immersion at a temperature of greater than 160°F while maintaining efficiency for a time greater than about 5 minutes.
• solvent resistance in the microfiber material and the filter material of the invention is obtained from a material that can survive contact with a solvent such as ethanol, a hydrocarbon, a hydraulic fluid, or an aromatic solvent for a period of time greater than about 5 minutes at 70°F while maintaining 50% efficiency.
• FIGURE 1 depicts a typical electrostatic emitter driven apparatus for production of the fine fibers of the invention.
• the fine fibers that comprise the micro- or nanofiber containing layer of the invention can be fiber and can have a diameter of about 0.001 to 2 micron, preferably 0.05 to 0.5 micron.
• the thickness of the typical fine fiber filtration layer ranges from about 1 to 100 times the fiber diameter with a basis weight ranging from about 0.01 to 240 micrograms-cm "2 .
• production gases or off gases from industrial processes or engines may contain particulate material therein. Before such gases can be, or should be, discharged through various downstream equipment to the atmosphere, it may be desirable to obtain a substantial removal of particulate material from those streams.
• the "lifetime" of a filter is typically defined according to a selected limiting pressure drop across the filter.
• the pressure buildup across the filter defines the lifetime at a defined level for that application or design. Since this buildup of pressure is a result of load, for systems of equal efficiency a longer life is typically directly associated with higher capacity. Efficiency is the propensity of the media to trap, rather than pass, particulates. It should be apparent that typically the more efficient a filter media is at removing particulates from a gas flow stream, in general the more rapidly the filter media will approach the "lifetime" pressure differential (assuming other variables to be held constant). In this application the term “unchanged for filtration purposes” refers to maintaining sufficient efficiency to remove particulate from the fluid stream as is necessary for the selected application.
• a simple filter design such as that described above is subject to at least two types of problems.
• particulate material rapidly builds up on the upstream side of the filter, as a thin dust cake or layer, increasing the pressure drop.
• Various methods have been applied to increase the "lifetime" of surface-loaded filter systems, such as paper filters.
• One method is to provide the media in a pleated construction, so that the surface area of media encountered by the gas flow stream is increased relative to a flat, non-pleated construction. While this increases filter lifetime, it is still substantially limited.
• depth media In many applications, especially those involving relatively high flow rates, an alternative type of filter media, sometimes generally referred to as "depth” media, is used.
• a typical depth media comprises a relatively thick tangle of fibrous material.
• Depth media is generally defined in terms of its porosity, density or percent solids content. For example, a 2-3% solidity media would be a depth media mat of fibers arranged such that approximately 2-3% of the overall volume comprises fibrous materials (solids), the remainder being air or gas space.
• Another useful parameter for defining depth media is fiber diameter. If percent solidity is held constant, but fiber diameter (size) is reduced, pore size or interfiber space is reduced; i.e. the filter becomes more efficient and will more effectively trap smaller particles.
• a typical conventional depth media filter is a deep, relatively constant (or uniform) density, media, i.e. a system in which the solidity of the depth media remains substantially constant throughout its thickness.
• substantially constant in this context, it is meant that only relatively minor fluctuations in density, if any, are found throughout the depth of the media. Such fluctuations, for example, may result from a slight compression of an outer engaged surface, by a container in which the filter media is positioned.
• Gradient density depth media arrangements have been developed, some such arrangements are described, for example, in U.S. Patent Nos. 4,082,476; 5,238,474; and 5,364,456.
• a depth media arrangement can be designed to provide "loading" of particulate materials substantially throughout its volume or depth. Thus, such arrangements can be designed to load with a higher amount of particulate material, relative to surface loaded systems, when full filter lifetime is reached.
• Polymeric materials have been fabricated in non- woven and woven fabrics, fibers and microfibers.
• the polymeric material provides the physical properties required for product stability. These materials should not change significantly in dimension, suffer reduced molecular weight, become less flexible or subject to stress cracking or physically deteriorate in the presence of sunlight, humidity, high temperatures or other negative environmental effects.
• the invention relates to an improved polymeric material that can maintain physical properties in the face of incident electromagnetic radiation such as environmental light, heat, humidity and other physical challenges.
• Polymer materials that can be used in the polymeric compositions of the invention include both addition polymer and condensation polymer materials such as polyolefin, polyacetal, polyamide, polyester, cellulose ether and ester, polyalkylene sulfide, polyarylene oxide, polysulfone, modified polysulfone polymers and mixtures thereof.
• Preferred materials that fall within these generic classes include polyethylene, polypropylene, poly(vinylchloride), polymethylmethacrylate (and other acrylic resins), polystyrene, and copolymers thereof (including ABA type block copolymers), poly(vinylidene fluoride), poly(vinylidene chloride), polyvinylalcohol in various degrees of hydrolysis (87% to 99.5%) in crosslinked and non-crosslinked forms.
• Preferred addition polymers tend to be glassy (a Tg greater than room temperature).
• nylon condensation polymers are nylon materials.
• nylon is a generic name for all long chain synthetic polyamides.
• nylon nomenclature includes a series of numbers such as in nylon-6,6 which indicates that the starting materials are a C 6 diamine and a C 6 diacid (the first digit indicating a C 6 diamine and the second digit indicating a C 6 dicarboxylic acid compound).
• nylon-6 made by the polycondensation of epsilon caprolactam in the presence of a small amount of water. This reaction forms a nylon-6 (made from a cyclic lactam - also known as episilon-aminocaproic acid) that is a linear polyamide.
• nylon copolymers are also contemplated. Copolymers can be made by combining various diamine compounds, various diacid compounds and various cyclic lactam structures in a reaction mixture and then forming the nylon with randomly positioned monomeric materials in a polyamide structure.
• a nylon 6,6-6,10 material is a nylon manufactured from hexamethylene diamine and a C 6 and a C 10 blend of diacids.
• a nylon 6-6,6-6,10 is a nylon manufactured by copolymerization of epsilonaminocaproic acid, hexamethylene diamine and a blend of a C 6 and a C 10 diacid material.
• Block copolymers are also useful in the process of this invention. With such copolymers the choice of solvent swelling agent is important.
• the selected solvent is such that both blocks were soluble in the solvent.
• One example is a ABA (styrene-EP-styrene) or AB (styrene-EP) polymer in methylene chloride solvent. If one component is not soluble in the solvent, it will form a gel.
• block copolymers examples include Kraton ® type of styrene-b-butadiene and styrene-b- hydrogenated butadiene(ethylene propylene), Pebax ® type of e-caprolactam-b- ethylene oxide, Sympatex ® polyester-b-ethylene oxide and polyurethanes of ethylene oxide and isocyanates.
• highly crystalline polymer like polyethylene and polypropylene require high temperature, high pressure solvent if they are to be solution spun. Therefore, solution spinning of the polyethylene and polypropylene is very difficult. Electrostatic solution spinning is one method of making nanofibers and microfiber.
• polymeric compositions comprising two or more polymeric materials in polymer admixture, alloy format or in a crosslinked chemically bonded structure.
• polymer compositions improve physical properties by changing polymer attributes such as improving polymer chain flexibility or chain mobility, increasing overall molecular weight and providing reinforcement through the formation of networks of polymeric materials.
• two related polymer materials can be blended for beneficial properties.
• a high molecular weight polyvinylchloride can be blended with a low molecular weight polyvinylchloride.
• a high molecular weight nylon material can be blended with a low molecular weight nylon material.
• differing species of a general polymeric genus can be blended.
• a high molecular weight styrene material can be blended with a low molecular weight, high impact polystyrene.
• a Nylon-6 material can be blended with a nylon copolymer such as a Nylon-6; 6,6; 6,10 copolymer.
• a polyvinylalcohol having a low degree of hydrolysis such as a 87% hydrolyzed polyvinylalcohol can be blended with a fully or superhydrolyzed polyvinylalcohol having a degree of hydrolysis between 98 and 99.9% and higher. All of these materials in admixture can be crosslinked using appropriate crosslinking mechanisms. Nylons can be crosslinked using crosslinking agents that are reactive with the nitrogen atom in the amide linkage.
• Polyvinylalcohol materials can be crosslinked using hydroxyl reactive materials such as monoaldehydes, such as formaldehyde, ureas, melamine-formaldebyde resin and its analogues, boric acids and other inorganic compounds, dialdehydes, diacids, urethanes, epoxies and other known crosslinking agents.
• Crosslinking technology is a well known and understood phenomenon in which a crosslinking reagent reacts and forms covalent bonds between polymer chains to substantially improve molecular weight, chemical resistance, overall strength and resistance to mechanical degradation. We have found that additive materials can significantly improve the properties of the polymer materials in the form of a fine fiber.
• Fluoro-organic wetting agents useful in this invention are organic molecules represented by the formula R G wherein R/is a fluoroaliphatic radical and G is a group which contains at least one hydrophilic group such as cationic, anionic, nonionic, or amphoteric groups. Nonionic materials are preferred.
• hydrogen or chlorine atoms can be present as substituents on the skeletal chain.
• radicals containing a large number of carbon atoms may function adequately, compounds containing not more than about 20 carbon atoms are preferred since large radicals usually represent a less efficient utilization of fluorine than is possible with shorter skeletal chains.
• R/ contains about 2 to 8 carbon atoms.
• R is H or C 1-18 alkyl group, and each R can be the same as or different
• amphoteric groups which are usable in the fluoro-organic wetting agent employed in this invention include groups which contain at least one cationic group as defined above and at least one anionic group as defined above.
• Fibers described in this invention address these limitations and will therefore be usable in a very wide variety of filtration, textile, membrane and other diverse applications.
• a filter media construction according to the present invention includes a first layer of permeable coarse fibrous media or substrate having a first surface.
• a first layer of fine fiber media is secured to the first surface of the first layer of permeable coarse fibrous media.
• the first layer of permeable coarse fibrous material comprises fibers having an average diameter of at least 10 microns, typically and preferably about 12 (or 14) to 30 microns.
• the first layer of permeable coarse fibrous material comprises a media having a basis weight of no greater than about 200 grams/meter 2 , preferably about 0.50 to 150 g/m 2 , and most preferably at least 8 g/m 2 .
• the first layer of permeable coarse fibrous media is at least 0.0005 inch (12 microns) thick, and typically and preferably is about 0.001 to 0.030 inch (25-800 microns) thick.
• the filter media formed into the pleated Z shaped format can contain the fine fiber media of the invention.
• Glen et al., U.S. Patent No. 5,853,442 disclose a bag house structure having filter elements that can contain the fine fiber structures of the invention.
• Berkhoel et al., U.S. Patent No. 5,954,849 show a dust collector structure useful in processing typically air having large dust loads to filter dust from an air stream after processing a workpiece generates a significant dust load in an environmental air.
• Gillingham U.S. Design Patent No. 425,189, discloses a panel filter using the Z filter design.
• a substantially planar grid 60 Facing the emitter 40, but spaced apart therefrom, is a substantially planar grid 60 upon which the collecting media 70 (i.e. substrate or combined substrate is positioned. Air can be drawn through the grid.
• the collecting media 70 is passed around rollers 71 and 72 which are positioned adjacent opposite ends of grid 60.
• a high voltage electrostatic potential is maintained between emitter 40 and grid 60 by means of a suitable electrostatic voltage source 61 and connections 62 and 63 which connect respectively to the grid 60 and emitter 40.
• the polymer solution is pumped to the rotating union 41 or reservoir from reservoir 80.
• the forward facing portion 42 rotates while liquid exits from holes 44, or is picked up from a reservoir, and moves from the outer edge of the emitter toward collecting media 70 positioned on grid 60.
• FIG. 3 is a scanning electron micrograph image showing the relationship of typical dust particles having a diameter of about 2 and about 5 microns with respect to the sizes of pores in typical cellulose media and in the typical fine fiber structures.
• the 2 micron particle 31 and the 5 micron particle 32 is shown in a cellulosic media 33 with pore sizes that are shown to be quite a bit larger than the typical particle diameters.
• the 2 micron particle 31 appears to be approximately equal to or greater than the typical openings between the fibers in the fiber web 35 while the 5 micron particle 32 appears to be larger than any of the openings in the fine fiber web 35.
• filters are made of composites of substrate and thin layer of micro- and nanofibers
• such composite makes an excellent filter medium for self-cleaning application. Cleaning the surface by back pulsing repeatedly rejuvenates the filter medium.
• fine fiber with poor adhesion to substrates can delaminate upon a back pulse that passes from the interior of a filter through a substrate to the micro fiber. Therefore, good cohesion between micro fibers and adhesion between substrate fibers and electrospun fibers is critical for successful use.
• Products that meet the above requirements can be obtained using fibers made from different polymer materials.
• Small fibers with good adhesion properties can be made from such polymers like polyvinylidene chloride, poly vinyl alcohol and polymers and copolymers comprising various nylons such as nylon 6, nylon 4,6; nylon 6,6; nylon 6,10 and copolymers thereof.
• Excellent fibers can be made from PVDF, but to make sufficiently small fiber diameters requires chlorinated solvents.
• Nylon 6, Nylon 66 and Nylon 6,10 can be electrospun. But, solvents such as formic acid, m-cresol, tri-fluoro ethanol, hexafluoro isopropanol are either difficult to handle or very expensive.
• Fine fiber samples were prepared from a copolymer of nylon 6, 66, 610 nylon copolymer resin (SNP-651) was analyzed for molecular weight by the end group titration. (J.E. Walz and G.B. Taylor, determination of the molecular weight of nylon, Anal. Chem. Vol. 19, Number 7, pp 448-450 (1947). Number average molecular weight was between 21,500 and 24,800.
• the composition was estimated by the phase diagram of melt temperature of three component nylon, nylon 6 about
• Example 2 Cross-linking of nylon fibers with phenolic resin and epoxy resin
• Copolyamide nylon 6, 66, 610 described earlier is mixed with phenolic resin, identified as Georgia Pacific 5137 and spun into fiber. Nylo Phenolic Resin ratio and its melt temperature of blends are shown here;
• Blends of polyamide with epoxy resin, such Epon 828 from Shell and Epi-Rez 510 can be used.
• Scotchgard ® FC-430 and 431 from 3M Company were added to polyamide before spinning. Add-on amount was 10% of solids. Addition of Scotchgard did not hinder fiber formation. THC bench shows that Scotchgard-like high molecular weight repellant finish did not improve water resistance. Scotchgard added samples were heated at 300 F° for 10 minutes as suggested by manufacturer.
• Polymeric films were cast from polyamides with tinanate coupling agents from Kenrich Petrochemicals, Inc. They include isopropyl triisostearoyl titanate (KR TTS), neopentyl (diallyl) oxytri (dioctyl) phosphato titanate (LICA12), neopentyl (dially) oxy, tri (N-ethylene diamino) ethyl zirconate (NZ44). Cast films were soaked in boiling water. Control sample without coupling agent loses its strength immediately, while coupling agent added samples maintained its form for up to ten minutes. These coupling agents added samples were spun into fiber (0.2 micron fiber).
• Example 5 Modification with Low Molecular Weight p-tert-butyl phenol polymer Oligomers of para-tert-butyl phenol, molecular weight range 400 to 1100, was purchased from Enzymol International, Columbus, Ohio. These low molecular weight polymers are soluble in low alcohols, such as ethanol, isopropanol and butanol. These polymers were added to co-polyamide described earlier and electrospun into 0.2 micron fibers without adverse consequences. Some polymers and additives hinder the electrospinning process. Unlike the conventional phenolic resin described in Example 2, we have found that this group of polymers does not interfere with fiber forming process.
• Type 8 Nylon was originally developed to prepare soluble and crosslinkable resin for coating and adhesive application.
• This type of polymer is made by the reaction of polyamide 66 with formaldehyde and alcohol in the presence of acid. (Ref. Cairns, T.L.; Foster, H.D.; Larcher, A.W.; Schneider, A.K.; Schreiber, R.S. J. Am. Chem. Soc. 1949, 71, 651).
• This type of polymer can be elctrospun and can be cross-linked.
• formation of fiber from this polymer is inferior to copolyamides and crosslinking can be tricky.
• this blend generates fibers efficiently, producing about 50 % more mass of fiber compared to Polymer A recipe.
• resultant polymeric microfibers produce a more chemically resistant fiber.
• a filter made from these fibers maintained more than 90 % filtration efficiency and unchanged fiber diameter even though inherently crosslinkable polymer is only 44% of the solid composition.
• This three-polymer composition of co-polyamide, alkoxy alkyl modified Nylon 66 and Bisphenol A creates excellent fiber forming, chemically resistant material.
• DSC of the polymer made with Nylon 46 and Nylon 66 shows broad single melt temperature, which are lower than the melting temperature of modified Nylon 46 (241 C°) or modified Nylon 66 (210 C°). This is an indication that during the reaction, both components are randomly distributed along the polymer chain. Thus, we believe that we have achieved random copolymer of Nylon 46 and Nylon 66 with alkoxy alkyl modification. These polymers are soluble in alcohols and mixtures of alcohol and water.
• PVA powders were purchased from Aldrich Chemicals. They were dissolved either in water or 50/50 mixture of methanol and water. They were mixed with crosslinking agent and toluene sulfonic acid catalyst before electrospinning. The resulting fiber mat was crosslinked in an oven at 150°C for 10 minutes before exposing to THC bench.
• a conventional cellulose air filter media was used as the substrate.
• This substrate had a basis weight of 67 pounds per 3000 square feet , a Frazier permeability of 16 feet per minute at 0.5 inches of water pressure drop, a thickness of 0.012 inches, and a LEFS efficiency of 41.6% .
• a fine fiber layer of Example 1 was added to the surface using the process described with a nominal fiber diameter of 0.2 microns. The resulting composite had a LEFS efficiency of 63.7%. After exposure to 140F air at 100% relative humidity for 1 hour the substrate only sample was allowed to cool and dry, it then had a LEFS efficiency of 36.5%. After exposure to 140F air at 100% relative humidity for 1 hour the composite sample was allowed to cool and dry, it then had a LEFS efficiency of 39.7%. Using the mathematical formulas described, the fine fiber layer efficiency retained after 1 hour of exposure was 13%, the number of effective fine fibers retained was 11%.
• a conventional cellulose air filter media was used as the substrate.
• This substrate had a basis weight of 67 pounds per 3000 square feet , a Frazier permeability of 16 feet per minute at 0.5 inches of water pressure drop, a thickness of 0.012 inches, and a LEFS efficiency of 41.6% .
• a fine fiber layer of Example 5 was added to the surface using the process described with a nominal fiber diameter of 0.2 microns. The resulting composite had a LEFS efficiency of 96.0%. After exposure to 160F air at 100% relative humidity for 3 hours the substrate only sample was allowed to cool and dry, it then had a LEFS efficiency of 35.3%. After exposure to 160F air at 100% relative humidity for 3 hours the composite sample was allowed to cool and dry, it then had a LEFS efficiency of 68.0%. Using the mathematical formulas described, the fine fiber layer efficiency retained after 3 hours of exposure was 58%, the number of effective fine fibers retained was 29%.
• a conventional cellulose air filter media was used as the substrate.
• This substrate had a basis weight of 67 pounds per 3000 square feet , a Frazier permeability of 16 feet per minute at 0.5 inches of water pressure drop, a thickness of 0.012 inches, and a LEFS efficiency of 41.6% .
• a fine fiber layer of a blend of Polymer A and Polymer B as described in Example 6 was added to the surface using the process described with a nominal fiber diameter of 0.2 microns. The resulting composite had a LEFS efficiency of 92.9%. After exposure to 160F air at 100% relative humidity for 3 hours the substrate only sample was allowed to cool and dry, it then had a LEFS efficiency of 35.3%.
• a conventional cellulose air filter media was used as the substrate.
• This substrate had a basis weight of 67 pounds per 3000 square feet , a Frazier permeability of 16 feet per minute at 0.5 inches of water pressure drop, a thickness of 0.012 inches, and a LEFS efficiency of 41.6% .
• a fine fiber layer of Polymer A, Polymer B, t-butyl phenol oligomer as described in Example 6 was added to the surface using the process described with a nominal fiber diameter of 0.2 microns. The resulting composite had a LEFS efficiency of 90.4%. After exposure to 160F air at 100% relative humidity for 3 hours the substrate only sample was allowed to cool and dry, it then had a LEFS efficiency of 35.3%.
• the composite sample After exposure to 160F air at 100% relative humidity for 3 hours the composite sample was allowed to cool and dry, it then had a LEFS efficiency of 87.3%. Using the mathematical formulas described, the fine fiber layer efficiency retained after 3 hours of exposure was 97%, the number of effective fine fibers retained was 92%.
• a conventional cellulose air filter media was used as the substrate.
• This substrate had a basis weight of 67 pounds per 3000 square feet , a Frazier permeability of 16 feet per minute at 0.5 inches of water pressure drop, a thickness of 0.012 inches, and a LEFS efficiency of 41.6% .
• a fine fiber layer of crosslinked PNA with polyacrylic acid of Example 12 was added to the surface using the process described with a nominal fiber diameter of 0.2 microns. The resulting composite had a LEFS efficiency of 92.9%. After exposure to 160F air at 100% relative humidity for 2 hours the substrate only sample was allowed to cool and dry, it then had a LEFS efficiency of 35.3%.
• filtration efficiency as the measure of the number of fine fibers effectively and functionally retained in structure has a number of advantages over other possible methods such as SEM evaluation.
• the filtration measure evaluates several square inches of media yielding a better average than the tiny area seen in SEM photomicrographs (usually less than 0.0001 square inch
• the filtration measurement quantifies the number of fibers remaining functional in the structure. Those fibers that remain, but are clumped together or otherwise existing in an altered structure are only included by their measured effectiveness and functionality.
• This test is an accelerated indicator of filter media moisture resistance.
• the test uses the LEFS test bench to measure filter media performance changes upon immersion in water.
• Water temperature is a critical parameter and is chosen based on the survivability history of the media under investigation, the desire to minimize the test time and the ability of the test to discriminate between media types. Typical water temperatures re 70°F, 140°F or 160°F.
• Procedure A 4" diameter sample is cut from the media. Particle capture efficiency of the test specimen is calculated using 0.8 ⁇ m latex spheres as a test challenge contaminant in the LEFS (for a description of the LEFS test, see ASTM Standard F1215-89) bench operating at 20 FPM. The sample is then submerged in (typically 140°F) distilled water for 5 minutes. The sample is then placed on a drying rack and dried at room temperature (typically overnight). Once it is dry the sample is then retested for efficiency on the LEFS bench using the same conditions for the initial calculation.
• the purpose of this bench is to evaluate fine fiber media resistance to the affects of elevated temperature and high humidity under dynamic flow conditions.
• the test is intended to simulate extreme operating conditions of either an industrial filtration application, gas turbine inlet application, or heavy duty engine air intake environments. Samples are taken out, dried and LEFS tested at intervals.
• This system is mostly used to simulate hot humid conditions but can also be used to simulate hot/cold dry situations. Temperature -31 to 390°F
• Particle capture efficiency of the test specimen is calculated using 0.8 ⁇ m latex spheres as a test challenge contaminant in the LEFS bench operating at 20 FPM. The sample is then inserted into the THC media chuck. Test times can be from minutes to days depending on testing conditions.
• the sample is then placed on a drying rack and dried at room temperature (typically overnight). Once it is dry the sample is then retested for efficiency on the LEFS bench using the same conditions for the initial calculation. The previous steps are repeated for the fine fiber supporting substrate without fine fiber.
• the test uses the LEFS test bench to measure filter media performance changes upon immersion in room temperature ethanol.
• a 4" diameter sample is cut from the media. Particle capture efficiency of the test specimen is calculated using 0.8 ⁇ m latex spheres as a test challenge contaminant in the LEFS bench operating at 20 FPM. The sample is then submerged in alcohol for 1 minute.
• the sample is then placed on a drying rack and dried at room temperature (typically overnight). Once it is dry the sample is then retested for efficiency on the LEFS bench using the same conditions for the initial calculation. The previous steps are repeated for the fine fiber supporting substrate without fine fiber. From the above information one can calculate the efficiency component due only to the fine fiber and the resulting loss in efficiency due to alcohol damage. Once the loss in efficiency due to the fine fiber is determined one can calculate the amount of efficiency retained.

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