Tackified And Non-Tackified Nonwovens Of Controlled Stiffness And Retained Foldability
The present disclosure relates generally to a nonwoven filtration media comprising a bonded mix of different, discontinuous, thermoplastic resin fibers and optionally discontinuous cellulosic fibers. In some embodiments a tackifier is added to the nonwoven filtration media to provide a sticky or adhesive surface on the fibers. The nonwoven media has an advantageous combination of stiffness, foldability, efficiency and the ability to retain a fold. The nonwoven media can be thermally bonded during the production process. The advantageous combination of mechanical properties allow the disclosed nonwoven media to accept and retain folds and pleats better than some conventional filtration materials while the mix of different fibers provides desirable filtration properties.
This application is a continuation-in-part of International Application No. PCT/FI2007/050281, filed May 16, 2007, which claims the benefit of U.S. Provisional Application No. 60/866,820, filed Nov. 21, 2006 and from U.S. Provisional Application No. 60/800,613, filed May 16, 2006, the contents of each of which are incorporated herein by reference in their entirety.
FIELDThe present disclosure relates generally to a nonwoven web comprising a mix of discontinuous, thermoplastic resin fibers having a combination of high stiffness, foldability and filtration properties. In some embodiments the fibers of the web are coated with a tackifier. The nonwoven web can advantageously be used as a filtration media. The present disclosure also provides a method of making the filtration media. In some embodiments the nonwoven filtration media can advantageously be used as part of an air filter.
BACKGROUNDSome desirable filtration properties of nonwoven fabrics used as filtration media are that they be permeable to the fluid being filtered yet have high filtration efficiency. High permeability to the fluid being filtered is desirable as less energy is required to move the fluid through the filter media. High filtration efficiency is, of course, desirable as it allows the filtration media to more effectively remove contaminants in the fluid being filtered. Filtration properties can be quantified using tests such as Frazier Permeability, dP, PFE efficiency and Index.
In many applications, filtration media are required which have structural integrity by themselves for conversion into various shapes. For example, the filtration media can be folded into a pleated shape that gives far more surface area than a non-pleated shape in the same space.
Large fibers in a filtration media provide stiffness for pleating but undesirably degrade filtration efficiency. Further, some stiff filtration media are difficult to fold and may not “hold” the pleat, allowing the pleat to close and degrading filtration properties. Small fibers in a filtration media improve efficiency and foldability but reduce stiffness. A filtration media having an advantageous combination of stiffness, foldability, filtration properties and the ability to retain a fold is desirable.
SUMMARYThe present disclosure relates generally to a nonwoven filtration media comprising a bonded mix of different, discontinuous, thermoplastic resin fibers and optionally discontinuous cellulosic fibers. The nonwoven media has an advantageous combination of Gurley Stiffness and LED score foldability within a preselected range dependent on the Gurley Stiffness, filtration properties and the ability to retain a fold. The nonwoven filtration media can be thermally bonded during the production process. The advantageous combination of high stiffness and foldability properties allow the disclosed nonwoven media to accept and retain folds and pleats better than some conventional filtration materials while the mix of different fibers provides desirable filtration properties.
One embodiment of the nonwoven filtration media comprising a bonded mix of different, discontinuous, thermoplastic resin fibers and optionally discontinuous cellulosic fibers. The nonwoven filtration media can be thermally bonded during the production process. At least some of the fibers are coated with a tackiness agent. The tackified, nonwoven media has an advantageous combination of Gurley Stiffness, an LED score foldability within a preselected range dependent on the Gurley Stiffness, filtration properties and the ability to retain a fold. The advantageous combination of high stiffness and foldability properties allow the disclosed nonwoven media to accept and retain folds and pleats better than some conventional filtration materials while the tackiness agent and mix of different fibers provides desirable filtration properties.
One embodiment of a nonwoven filtration media comprises a mix of 0 percent to about 90 percent of staple length fibers having a denier of 10 or greater and about 10 percent to about 100 percent of the fibers having a denier of 4 or less. About 30 percent to about 85 percent of the fibers will be conjugate fibers. Preferably, the nonwoven filtration media will comprise a mixture of 0 percent to about 85 percent conjugate fibers having a denier of 15 or more and 0 percent to about 80 percent of conjugate fibers having a denier of 4 or less. The staple length fibers are carded and cross lapped to form a single layer with the different fibers homogeneously distributed through the thickness of the layer. The nonwoven filtration media is thermally bonded by contact with heated rollers. This nonwoven filtration media will have a basis weight between about 90 gsm to about 370 gsm, a Frazier Permeability between about 150 CFM/square foot/square foot and about 850 CFM/square foot, a PFE greater than or equal to 30 percent, a dP between about 0.03 inches water gauge at 110 fpm and about 0.22 inches water gauge at 110 fpm, an Index between about 300 and about 1600, a MD Gurley stiffness of more than 1400 and an LED score foldability within a preselected range dependent on the Gurley Stiffness
One embodiment of a nonwoven filtration media comprises a mix of staple length fibers all having a denier of 5 or less. Advantageously, about 30 percent to about 85 percent of the fibers in the nonwoven filtration media will be conjugate fibers having a denier of 5 or less. The staple length fibers are carded and cross lapped to form a single layer with the different fibers homogeneously distributed through the thickness of the layer. The nonwoven filtration media is thermally bonded by contact with heated rollers. This nonwoven filtration media will have a basis weight between about 90 gsm to about 370 gsm, a Frazier Permeability between about 150 CFM/square foot and about 850 CFM/square foot, a PFE greater than or equal to 30 percent, a dP between about 0.03 inches water gauge at 110 fpm and about 0.22 inches water gauge at 110 fpm, an Index between about 300 and about 1600 a MD Gurley stiffness of more than 1400 and an LED score foldability within a preselected range dependent on the Gurley Stiffness
The disclosed nonwoven filtration media may be used in a number of different applications. The media is advantageously used in air filtration for home or commercial heating, ventilating and air conditioning (HVAC) services. It may also be used in filtration of breathing air in transportation applications like automobile cabin air filtration, airplane cabin air filtration, and train and boat air filtration. While the nonwoven filtration media is preferably directed to air filtration, in different embodiments other gasses and other fluids may be filtered as well. Such other gasses may include, for example, nitrogen. Other fluids may include liquids like oil or water.
In general, unless otherwise explicitly stated the disclosed materials and processes may be alternately formulated to comprise, consist of, or consist essentially of, any appropriate components, moieties or steps herein disclosed. The disclosed materials and processes may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants, moieties, species and steps used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objective of the present disclosure.
When the word “about” is used herein it is meant that the amount or condition it modifies can vary some beyond the stated amount so long as the function and/or objective of the disclosure are realized. The skilled artisan understands that there is seldom time to fully explore the extent of any area and expects that the disclosed result might extend, at least somewhat, beyond one or more of the disclosed limits. Later, having the benefit of this disclosure and understanding the concept and embodiments disclosed herein, a person of ordinary skill can, without inventive effort, explore beyond the disclosed limits and, when embodiments are found to be without any unexpected characteristics, those embodiments are within the meaning of the term about as used herein.
DEFINITIONSBiconstituent fiber—A fiber that has been formed from a mixture of two or more polymers extruded from the same spinneret. Biconstituent fibers do not have the various polymer components arranged in relatively constantly positioned distinct zones across the cross-sectional area of the fiber and the various polymers are usually not continuous along the entire length of the fiber, instead usually forming fibrils which start and end at random. Biconstituent fibers are sometimes also referred to as multiconstituent fibers.
Binder—An adhesive material used to bind a web of fibers together or bond one web to another. The principal properties of a binder are adhesion and cohesion. The binder can be in solid form, for example a powder, film or fiber, in liquid form, for example a solution, dispersion or emulsion or in foam form.
Bonding—The process of securing fibers or filaments to each other in a nonwoven web. The fibers or filaments can be secured by thermal bonding such as in calendering or through air bonding; mechanical means such as in needlepunching; or jets of pressurized fluid such as water in hydroentangling.
Calendering—the process of moving a nonwoven material between opposing surfaces. The opposing surfaces include flat platens, rollers, rollers having projections and combinations thereof. Either or both of the opposing surfaces may be heated.
Card—A machine designed to separate fibers from impurities, to align the fibers and deliver the aligned fibers as a batt or web. The fibers in the web can be aligned randomly or parallel with each other predominantly in the machine direction. The card consists of a series of rolls and drums that are covered with a plurality of projecting wires or metal teeth.
Carded web—A nonwoven web of discontinuous fibers produced by carding.
Carding—A process for making nonwoven webs on a card.
Cellulose fiber—A fiber comprised substantially of cellulose. Cellulosic fibers come from manmade sources (for example, regenerated cellulose fibers or lyocell fibers) or natural sources such as cellulose fibers or cellulose pulp from woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, kenaf, sisal, abaca, milkweed, straw, jute, hemp, and bagasse.
Cellulose material—A material comprised substantially of cellulose. The material may be a fiber or a film. Cellulosic materials come from manmade sources (for example, regenerated cellulose films and fibers) or natural sources such as fibers or pulp from woody and non-woody plants.
Conjugate fiber—A fiber comprising a first fiber portion extending substantially continuously along the length of the fiber and comprising a first thermoplastic polymeric material having a first melting point and a second fiber portion extending substantially continuously along the length of the fiber and defining at least a portion of a fiber exterior surface, the second fiber portion comprising a second thermoplastic polymeric material having a second melting point. Typically, the second melting point is lower than the first melting point. The fiber portions are arranged in substantially constantly positioned distinct zones across the cross-section of the fiber. A conjugate fiber includes fibers comprising two or more polymers or fiber portions. Conjugate fibers are formed by extruding polymer sources from separate extruders through a spinneret to form a single fiber. Typically, different polymeric materials are extruded from each extruder, although a conjugate fiber may encompass extrusion of the same polymeric material from separate extruders. The configuration of conjugate fibers can be symmetric (e.g., sheath:core or side:side) or they can be asymmetric (e.g., offset core within sheath; crescent moon configuration within a fiber having an overall round shape). The shape of the conjugate fiber can be any shape that is convenient to the producer for the intended end use, e.g., round, trilobal, triangular, dog-boned, flat or hollow.
Cross machine direction (CD)—The nonwoven web direction perpendicular to the machine direction.
Denier—A unit used to indicate the fineness of a filament given by the weight in grams for 9,000 meters of filament. A filament of 1 denier has a mass of 1 gram for 9,000 meters of length.
Entanglement—A method of bonding a web by interlocking or wrapping fibers in the web about each other. The method may use mechanical means such as in needlepunching or jets of pressurized fluid such as water in hydroentangling.
Fiber—A material form characterized by an extremely high ratio of length to diameter. As used herein, the terms fiber and filament are used interchangeably unless otherwise specifically indicated.
Filament—A substantially continuous fiber. As used herein, the terms fiber and filament are used interchangeably unless otherwise specifically indicated.
Foam application—A method of applying a material such as a binder or tackifier in a foam form to a fibrous web. The foam form contains less fluid than the same material in a liquid form and thus requires less energy and time to dry the foam and, if applicable, cure the material.
Lyocell—Manmade cellulose material obtained by the direct dissolution of cellulose in an organic solvent without the formation of an intermediate compound and subsequent extrusion of the solution of cellulose and organic solvent into a coagulating bath.
Machine direction (MD)—The long direction of a nonwoven web material that is parallel to and in the direction in which the nonwoven web material is finally accumulated.
Meltblown fiber—A fiber formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, die capillaries into a high velocity gas (e.g., air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. The meltblown process includes the melt spray process.
MERV—Minimum Efficiency Reporting Value which is defined in ASHRAE Standard 52.2-1999, Section 11.2.L and Section 12. As an example a MERV 6 filter will have the ability, as per the standard and under its specified conditions, to remove 35% to 50% of a 3-10 micron KCI particle insult. A MERV 7 filter will have the ability to remove 50% to 70% of a 3-10 micron KCI particle insult and a MERV 8 filter will have the ability to remove over 70% of a 3-10 micron KCI particle insult. The higher the MERV number, the higher the filtration performance of a filter.
Monocomponent fiber—A fiber formed from one or more extruders using only one polymer. This is not meant to exclude fibers formed from one polymer to which small amounts of additives have been added for coloration, anti-static properties, lubrication, hydrophilicity, etc. These additives, e.g. titanium dioxide for color, are generally present in low amounts such as less than 5 weight percent.
Needlepunching or Needling—A method of bonding a web by interlocking or wrapping fibers in the web about each other. The method uses a plurality of barbed needles to carry fiber portions in a vertical direction through the web.
Non-thermoplastic polymer—Any polymer material that does not fall within the definition of thermoplastic polymer.
Nonwoven fabric, sheet or web—A material having a structure of individual fibers that are interlaid, but not in an identifiable manner as in a woven or knitted fabric. Nonwoven materials have been formed from many processes such as, for example, meltblowing, spin laying, carding, air laying and water laying processes. The basis weight of nonwoven materials is usually expressed in weight per unit area, for example in grams per square meter (gsm) or ounces per square foot (osf) or ounces per square yard (osy). As used herein a nonwoven sheet includes a wetlaid paper sheet.
Polymer—A long chain of repeating, organic structural units. Generally includes, for example, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc, and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” includes all possible geometrical configurations. These configurations include, for example, isotactic, syndiotactic and random symmetries.
Regenerated cellulose—Manmade cellulose obtained by chemical treatment of natural cellulose to form a soluble chemical derivative or intermediate compound and subsequent decomposition of the derivative to regenerate the cellulose. Regenerated cellulose includes spun rayon and cellophane film. Regenerated cellulose processes include the viscose process, the cuprammonium process and saponification of cellulose acetate.
Short fiber—A fiber that has been formed at, or cut to, lengths of generally one quarter to one half inch (0.6 to 1.3 cm).
Spunlaid filament—A filament formed by extruding molten thermoplastic materials from a plurality of fine, usually circular, capillaries of a spinneret. The diameter of the extruded filaments is then rapidly reduced as by, for example, eductive drawing and/or other well-known mechanisms. Spunlaid fibers are generally continuous with deniers within the range of about 0.1 to 5 or more.
Spunbond nonwoven web—Webs formed (usually) in a single process by extruding at least one molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinneret. The filaments are partly quenched and then drawn out to reduce fiber denier and increase molecular orientation within the fiber. The filaments are generally continuous and not tacky when they are deposited onto a collecting surface as a fibrous batt. The spunlaid fibrous batt is then bonded by, for example, thermal bonding, calendering, chemical binders, mechanical needling, hydraulic entanglement or combinations thereof, to produce a nonwoven fabric.
Staple fiber—A fiber that has been formed at, or cut to, staple lengths of generally one quarter to eight inches (0.6 to 20 cm).
Synthetic fiber—a fiber comprised of manmade material, for example glass, polymer, combination of polymers, metal, carbon, regenerated cellulose or lyocell.
Substantially continuous—in reference to the polymeric filaments of a nonwoven web, it is meant that a majority of the filaments or fibers formed by extrusion through orifices remain continuous as they are drawn and then impacted on a collection device. Some filaments may be broken during the attenuation or drawing process, with a substantial majority of the filaments remaining continuous.
Tackifier or Tackiness Agent—a material such as a resin used to impart adhesive properties to otherwise nonadhesive materials such as a nonwoven web. A tackifier can coat the fibers in a nonwoven web to provide the web with adhesive fiber surfaces. Binder resins are typically not tackifiers as curing the binder resin substantially eliminates the ability of the binder to impart adhesive properties to the web.
Tex—A unit used to indicate the fineness of a filament given by the weight in grams for 1,000 meters of filament. A filament of 1 tex has a mass of 1 gram for 1,000 meters of length.
Thermal bonding—A calender process comprising passing a web of fibers to be bonded between a heated calender roll and an anvil roll. The anvil is usually flat. Filaments or fibers in the bonding area are joined by heat and pressure imparted by the rolls. Thermal bonding can also be used to join layers together in a composite material as well as to impart integrity to each individual layer by bonding filaments and/or fibers within each layer.
Thermal point bonding—A thermal bonding process comprising passing a web of fibers to be bonded between a heated calender roll and an anvil roll. The calender roll is patterned in some way so that the fabric is not bonded across its entire surface and the anvil is usually flat. Filaments or fibers in the bonding area are joined by heat and pressure imparted by the rolls. Typically, the percent bonding area varies from around 10% to around 30% of the web surface area. Thermal point bonding can also be used to join layers together in a composite material as well as to impart integrity to each individual layer by bonding filaments and/or fibers within each layer.
Thermoplastic polymer—A polymer that softens and is fusible when exposed to heat, returning generally to its unsoftened state when cooled to room temperature. Thermoplastic materials include, for example, polyvinyl chlorides, some polyesters, polyamides, polyfluorocarbons, polyolefins, some polyurethanes, polystyrenes, polyvinyl alcohol, copolymers of ethylene and at least one vinyl monomer (e.g., poly (ethylene vinyl acetates), and acrylic resins.
Triboelectrically charged fibers—Two yarns of dissimilar polymers that can be rubbed together and exchange charges in such a consistent manner that one fiber forms a positive charge and the other a negative charge.
Referring now to the drawings wherein like elements are numbered alike in the several Figures:
In one embodiment, a thermally bonded nonwoven filtration media comprising a mixture of discontinuous, fibers is disclosed. The different fibers are substantially homogeneously distributed throughout the thickness of the media. The nonwoven filtration media has an advantageous combination of Gurley Stiffness, foldability within a predetermined range dependent on the Gurley Stiffness and filtration efficiency.
The nonwoven filtration media can be comprised of many different staple length fibers, including synthetic fibers and cellulose fibers. Advantageously, the synthetic fibers include thermoplastic polymer fibers such as one or more of polyester, polyolefin and polyamide. Typically, at least some of the polymer fibers will be conjugate fibers. Advantageously, about 30 percent to about 85 percent of the polymer fibers will be conjugate fibers. As used in this disclosure fiber percentages are by weight of total fibers in the final nonwoven filtration media. Some suitable synthetic fibers are listed below.
Advantageously the cellulosic fibers include one or more of cotton fibers, rayon fibers, lyocell fibers and kenaf bast fibers. Other cellulosic fibers may be useful in the disclosed nonwoven filtration media. It is believed that the cost of some cellulosic fiber materials, for example lyocell, may limit their use in some applications.
Some suitable cellulosic fibers are listed below.
The chosen fiber denier for each fiber type of the nonwoven filtration media will be in the range of about 0.1 to about 45. Commercially available nonwoven, higher efficiency (MERV 7 and above), self supporting media, for example pleated air filtration media, use fibers having deniers of 6 and less. Use of fibers having these lower deniers was thought necessary to achieve the desired efficiency (MERV 7 or above). Using fibers with deniers higher than 6 in a self supporting media was not thought desirable as the larger fibers were not thought to provide as efficient a barrier to contamination as smaller fibers and would not allow the media to achieve the desired higher efficiency. Surprisingly and contrary to conventional practice, some of the disclosed embodiments provide a nonwoven, self supporting media having higher efficiency that is formed using a combination of fiber types having small denier fibers in the range of about 6 or less and fiber types having large denier fibers in the range of about 8 to about 45. Advantageously, at least one fiber type is a conjugate fiber. Further, large denier fibers can provide a nonwoven, self supporting, high efficiency media with increased pleat holding ability when compared to a higher efficiency media comprising only small denier fibers. Some disclosed embodiments comprise a nonwoven, self supporting filtration media having an efficiency of MERV 7 or above and including both fiber types having a denier of 6 or less and fiber types having a denier of 8 and above, including a conjugate fiber type. Presently, nonwoven materials comprising 6 denier fibers, for example 6 denier polyester fibers, are excluded from some disclosed embodiments.
Some exemplary staple fibers for use in the disclosed nonwoven filtration media are 0.9 denier monocomponent polyester fibers; 2.25 denier monocomponent polyester fibers; 3 denier monocomponent polyester fibers; 3 denier monocomponent polypropylene fibers; 4 denier polyester core/polyester sheath conjugate fibers; 10 denier polyester core/polyester sheath conjugate fibers; 15 denier monocomponent polyester fibers; 15 denier polyester core/polyester sheath conjugate fibers; 45 denier monocomponent polyester fibers; 2 to 4 decitex low finish or scoured polypropylene fibers; 2 to 4 denier scoured modacrylic fibers; kenaf fibers; and rayon fibers. Naturally, fibers of other deniers, other polymers and other configurations may prove useful in the disclosed nonwoven filtration media.
The nonwoven filtration media will have a basis weight (weight per unit area) of about 0.3 ounces per square foot (osf) (about 90 gsm) and up. The high limit for basis weight will depend on the end use application. Advantageously, the nonwoven filtration media will have a basis weight of about 0.3 osf (about 90 gsm) to about 1.2 osf (about 370 gsm).
The nonwoven filtration media will have a thickness of about 0.04 inches (about 1 mm) to about 0.25 inches (about 6.4 mm) or more depending on the end use application. Advantageously, the nonwoven filtration media will have a thickness of about 0.08 inches (about 2.0 mm) to about 0.12 inches (about 3 mm).
There are numerous known technologies for forming a nonwoven filtration media from staple length fibers, including air laying, wet laying and carding. Presently, carding is considered an advantageous method for making the nonwoven filtration media. Preselected types of staple length fibers are mixed in preselected proportions and the mixture is fed to a card machine. The card machine forms the mixed fibers into a matt. Fibers in the carded matt will be homogeneously distributed, although the majority of fibers will typically be aligned in the machine direction. The matt may optionally be layered using, for example, a cross lapper machine. The cross lapper machine layers the lighter web leaving the card. The carded web enters the cross lapper machine in one direction and the layered matt leaves the cross lapper machine in a direction perpendicular to the entry direction. The layered matt will typically have an increased basis weight as compared to the carded matt. The layered maft may have a cross direction fiber orientation, although fibers in the layered maft are typically more randomly oriented than in the carded matt.
Many technologies can be employed to join or bond the fibers in the matt. Some useful bonding technologies include, for example, one or more of entangling, thermal calendering of the matt to fuse thermoplastic fibers therein, application of ultrasonic energy to the matt and/or application of resin materials to the matt. Presently, mechanical entanglement such as needlepunching is considered advantageous forjoining fibers of the matt.
Heat can be applied to the entangled matt to at least partially melt the thermoplastic fibers therein. Upon cooling, the melted thermoplastic fibers harden and fuse the fibers in the entangled matt. One advantageous method of thermal bonding is running the entangled matt over one or more heated rolls. The media can be threaded through the system utilizing additional rolls, which may not be shown, to heat one or both sides of the entangled matt.
Resin binders can be added to the nonwoven filtration media after carding or bonding. Some suitable resin binders are ethylene vinyl chloride, ethylene vinyl acetates, acrylics and acrylates. Resin binders are typically applied as a solution and are dried and/or cured by heating. The resin binder solution can be added using conventional processes, for example, by spraying, dipping or foaming the matt. Resin binders are typically non-adhesive after curing.
The nonwoven filtration media can be coupled to a second nonwoven web to form a composite filtration media. The second nonwoven web can be comprised of continuous filaments, for example a spunbonded web, or discontinuous fiber, for example a carded web or a wet laid web. Typically, the coupled media and web will be in continuous face to face contact. The coupled webs can be joined by adhesive bonding; thermal bonding; mechanical entanglement or ultrasonic bonding. Alternately, the nonwoven filtration media can be used as a base over which charged fibers, such as triboelectrically charged fibers, can be laid and mechanically entangled. Additionally, different layers comprising cotton and polyester-cotton mixtures layers can be layered between the nonwoven filtration media and the triboelectrically charged fibers. See Table 5, Examples 208 to 210.
After formation and bonding, the filtration media material may be charged or corona treated. Corona treatment further increases filtration efficiency by drawing particles to be filtered toward the nonwoven filtration media by virtue of its electrical charge. Corona treatment can be carried out by a number of different techniques. One technique is described in U.S. Pat. No. 5,401,446 to Tsai et al. assigned to the University of Tennessee Research Corporation and incorporated herein by reference in its entirety. Other methods of corona treatment are known in the art.
The disclosed nonwoven filtration media may be made into a filter by any suitable means known in the art, for example by rotary pleating. Rotary pleating, while faster than many other pleating methods, is indicated to be quite dependent upon the stiffness of the filter medium. Gurley Stiffness values of at least 600 mg are required to allow pleating on high speed rotary pleating equipment. Other methods of pleating are not as sensitive to filtration media stiffness but are slower. Rotary pleating is discussed in, for example, U.S. Pat. No. 5,709,735 to Midkiff and Neely.
In one advantageous embodiment one or more tackifiers are coated over fibers of the nonwoven media. A tackifier is a natural or synthetic material that adheres to, and provides a long lasting sticky or adhesive surface on, the fibers of the nonwoven filtration media. Some suitable tackifiers include elastomeric polymeric emulsions such as HYSTRETCH® elastomeric emulsions available from Lubrizol Advanced materials of Pittsburgh, Pa.; FLEXCRYL® adhesive emulsions available from Air Products Polymers L.P. of Allentown, Pa.; and SPAR CRYL materials available from Spartan Chemical Laboratories, Inc. of Spartanburg, S.C. The amount of tackifier added to the nonwoven filtration media can typically be in the range of about 0.5 percent by weight of the nonwoven filtration media to about 30 percent by weight of the nonwoven filtration media. Advantageously, the amount of tackifier added to the nonwoven filtration media can be in the range of about 1.5 percent by weight of the nonwoven filtration media to about 15 percent by weight of the nonwoven filtration media. The preferred amount of tackifier in some embodiments can be in the range of about 1.5% to about 6% while in other embodiments the amount of tackifier can be in the range of about 1.5% to about 3%.
Tackifiers are typically applied as an emulsion, solution or foam and excess fluid removed, for example by heating. The tackifier emulsion or solution can be added using conventional processes, for example, by foaming, spraying brushing or dipping the nonwoven filtration media.
In one presently preferred method, preselected types of staple length fibers are mixed in preselected proportions. The staple length fiber mixture is fed to a card machine. The card machine forms the mixed, staple length fibers into a matt. The matt is cross lapped to increase basis weight and rearrange fiber orientation. The carded and lapped matt is needle punched to mechanically entangle the fibers therein. The entangled matt is thermally bonded by running the matt over one or more heated rolls. The matt can also be optionally compressed by rolls during thermal bonding. Liquid resin binders are optionally applied to the thermal bonded matt. The binder comprising matt is heated to dry the matt and/or to cure the binder. A nonwoven web can optionally be superimposed on the carded matt prior to needle punching so that the carded matt and nonwoven web are mechanically entangled into a composite filtration media.
A tackifier, typically in solution, can be added to the nonwoven filtration media at any convenient point during manufacturing. Application of a tackifier solution to the fibers before carding or to the carded matt before thermal bonding can lead to problems with formation of the desired nonwoven filtration media. It is advantageous to apply the tackifier to the nonwoven filtration media after thermal bonding of the fibers.
As discussed above the nonwoven filtration media has an advantageous combination of Gurley Stiffness, foldability within a predetermined range dependent on the Gurley Stiffness and filtration properties. Filtration properties can be quantified using tests such as Frazier Permeability, dP, PFE efficiency and Index. Test methods are discussed below.
Frazier Air Permeability
Frazier air permeability test is a measure of the permeability of a filtration media to air. The Frazier test is performed in accordance with ASTM D461-72, D737-75, F778-82, TAPPI T251 and ISO 9237, and is reported as an average of 4 sample readings. The test reports the amount of air that flows in cubic feet per minute per square foot at a resistance of 0.5″ water gauge. CFM/square foot results can be converted to liters per square meter per minute (LSM) by multiplying CFM/square foot by 304.8. It is believed advantageous that the disclosed nonwoven filtration media have a Frazier Permeability in the range of about 150 CFM/square foot to about 850 CFM/square foot.
dP and PFE Efficiency
dP and PFE are test results from ASHRAE standard ASHRAE 52.2-1999. dP is pressure drop or resistance as measured in inches of water gauge at 110 feet per minute air velocity. PFE is the particle fraction efficiency percentage removal efficiency at 110 feet per minute air velocity. One reportable PFE range averages the efficiency between 3 to 10 micron particle sizes and another reportable range averages the efficiency between the 1 to 3 micron particle sizes. It is believed advantageous that the disclosed nonwoven filtration media have a dP in the range of about 0.03 to about 0.22. inches water gauge and a 3 to 10 micron range particle fraction efficiency of between 17.8% and 93.3% and/or a 1 to 3 micron range particle fraction efficiency of between 1.5% and 71.4%.
Index
Index is calculated using the PFE result for 3 to 10 micron efficiency divided by dP. Index is unitless. It is believed advantageous that the disclosed nonwoven filtration media have an Index in the range of about 300 to about 1600.
Gurley Stiffness
Gurley Stiffness measures nonwoven filtration media stiffness. The Gurley Stiffness test method, discussed in more detail below, generally follows TAPPI Method T 543 om-94. Gurley stiffness is measured in the machine direction (MD) and results are reported in milligrams.
-
- 1) Level the tester using the bubble level on front/top.
- 2) Obtain a square foot sample of media with the MD marked on it, ensuring the product has not been excessively handled or bent.
- 3) With reference to
FIG. 4 , cut three specimens across the width that are 1″×2″ with 2″ side being parallel to the CD. Mark samples “CD”. These samples reflect flexure in the MD plane and are used to obtain MD Gurley stiffness values. - 4) Cut three specimens across the width that are 2″×1″ with 2″ side being parallel to the MD. Mark samples “CD”. These samples reflect flexure in the CD plane and are used to obtain CD Gurley stiffness values.
- 5) Set up tester as in table below.
- 6) Orient the specimen in Gurley holder with 2″ side in jaws and fuzzy (AIR ENTERING) side facing right, position sample to the right.
- 7) Always start first arm movement from right to left.
- 8) Once media releases from vane stop all movement. Wait one minute to allow arm movement to slow and stop it (+/−¼″) gently.
- 9) Start arm movement to left until media releases from vane.
- 10) Push the converter button and record the record values.
- 11) Average the three tests for both MD and CD separately and report average of three for each.
The stiffer the nonwoven, the higher the Gurley stiffness reading. A Gurley Bending Resistance Tester model 4171D available from Gurley Precision Instruments of Troy, N.Y. has been found suitable for the above testing.
LED Foldability Score
The “LED score” test measures the ability of a nonwoven media to accept and retain a fold. The “LED score” test is similar to a Shirley Crease Retention Test, (American Association of Textile and Color Chemists (AATCC)-66-2003 et al). Briefly, the “LED score” test is performed using the following procedure:
-
- 1) Obtain specimen.
- 2) With reference to
FIG. 5 , cut specimen into a ½″ wide×4″ long test sample with long direction parallel to CD. - 3) Place test sample on flat metal surface.
- 4) Place angle iron in contact with test sample with apex against sample.
- 5) Strike angle iron once with 1170 gram hammer.
- 6) Fold test sample at score and place in file folder type cardboard sleeve. See
FIG. 1 . - 7) Place folded test sample and sleeve under 1800 gram weight for 30 seconds. See
FIG. 2 . - 8) Remove weight from folded test sample and sleeve and remove test sample from sleeve keeping it closed.
- 9) Position test sample vertically immediately in front of measuring apparatus.
- 10) Release and slip vertical leg of test sample into measuring apparatus.
- 11) Within 3 to 5 seconds align bottom of protractor portion with free leg of test sample.
- 12) Read “LED Score” test result. See
FIG. 3 . - 13) Repeat three times for each specimen.
- 14) Average results.
The measured angle is related to the nonwoven filtration media's resistance to opening, e.g. the ability to retain a fold or pleat. The more foldable a nonwoven, the higher the LED score angle.
The right combination or range of Gurley stiffness and retained foldability properties allows a nonwoven filtration media material to accept and hold a better fold or pleat with a straighter line between the fold peak and valley than other nonwoven filtration medias having properties outside of this range. Such combinations of Gurley stiffness and retained foldability properties are desirable in the manufacture of filter products. Naturally, not every nonwoven will have the advantageous combinations of Gurley stiffness and retained foldability properties disclosed herein. Further, even nonwoven media having similar combinations of Gurley stiffness and retained foldability properties to those disclosed herein will not have the presently disclosed filtration properties.
Filters used in heating, ventilation and air conditioning (HVAC) systems can comprise a peripheral housing defining an open center with nonwoven filtration media sealed to the housing and spanning the open center. The housing allows the filter to be handled and sealed to the HVAC system. Air to be filtered is moved through the media. Thus, during use the nonwoven filtration media is subjected to a pressure drop caused by air movement through that media. The filter and nonwoven filtration media are also subjected to varying temperature and humidity conditions depending on geographic location and time of year.
Some nonwoven media cannot maintain their shape, for example pleats, when subjected to the pressure drop and varying temperature and humidity conditions of a HVAC system unless one or both faces of the nonwoven media is supported by an open mesh framework spanning the edges of the housing.
In some embodiments the disclosed nonwoven filtration media is self supporting, that is the media has a combination of MD Gurley stiffness and retained (LED) foldability to allow it to maintain its shape when used in a HVAC system without requiring face support by an open mesh framework spanning the edges of the housing.
In some advantageous embodiments of the disclosed nonwoven filtration media the MD Gurley stiffness is above about 2400 milligrams and the retained (LED) foldability is maintained between about 39.3 degrees and about 134 degrees. In some other advantageous embodiments of the disclosed nonwoven filtration media the MD Gurley stiffness is below 2400 milligrams and retained (LED) foldability is maintained between about 40 degrees and about 108 degrees.
Especially advantageous combinations of Gurley stiffness and retained (LED) foldability (wherein ranges are indicated by letters A to H) are shown in Table 1.
Having generally described the invention, the following examples and those on the attached Tables are included for purposes of illustration so that the invention may be more readily understood and are in no way intended to limit the scope of the invention unless otherwise specifically indicated. The Examples were comprised of staple fibers in the combinations shown on the Tables and were prepared using conventional carding and cross lapping equipment and conditions. Unless otherwise noted the examples were bonded using heated rollers, sometimes in combination with oven heating unless otherwise indicated. Some examples were bonded using ultrasonic energy. Table 5 lists bonding conditions for some examples.
Nonwoven Filtration Media Comprising a Mix of Staple Length Fibers Having a Denier of 4 or Less and 10 or More.
Example 2 in range A was prepared by carding and fibers to form a nonwoven matt. The matt was thermally bonded over heated rollers. This filtration media comprises 85% staple length fibers having a denier of 4 or less and 15% staple length fibers having a denier of 10 or more. 70% of the fibers of Example 2 are staple length conjugate fibers having a denier less than 4 and a lower melting point polyester sheath, higher melting point polyester core. The fibers are homogeneously distributed throughout the single layer media. This nonwoven filtration media has a basis weight of about 177 gsm, a Frazier permeability of about 321 CFM/square foot, a dP of about 0.18, a PFE efficiency of about 58, a MD Gurley stiffness of about 3266 milligrams and a LED score test result of about 62 degrees.
Example 17 in range C was prepared by carding and fibers to form a nonwoven matt. The matt was thermally bonded over heated rollers. This filtration media comprises 75% staple length fibers having a denier of 4 or less and 25% staple length fibers having a denier of 10 or more. 50% of the fibers of Example 17 are staple length conjugate fibers having a denier less than 4 and a lower melting point polyester sheath, higher melting point polyester core. The fibers are homogeneously distributed throughout the single layer media. This nonwoven filtration media has a basis weight of about 180 gsm, a Frazier permeability of about 615 CFM/square foot, a MD Gurley stiffness of about 2630 milligrams and a LED score test result of about 66 degrees.
Example 50 in range E was prepared by carding and fibers to form a nonwoven matt. The matt was thermally bonded over heated rollers. This filtration media comprises 75% staple length fibers having a denier of 4 or less and 25% staple length fibers having a denier of 10 or more. 75% of the fibers of Example 50 are staple length conjugate fibers having a denier less than 4 and a lower melting point polyester sheath, higher melting point polyester core. The fibers are homogeneously distributed throughout the single layer media. This nonwoven filtration media has a basis weight of about 131 gsm, a Frazier permeability of about 580 CFM/square foot, a dP of about 0.076, a PFE efficiency of about 44, a MD Gurley stiffness of about 1770 milligrams and a LED score test result of about 85 degrees.
Nonwoven Filtration Media Comprising Staple Length Fibers all Having a Denier of 5 or Less.
Example 8 in range B was prepared by carding and fibers to form a nonwoven matt. The matt was thermally bonded over heated rollers. This filtration media comprises 80% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 10% 0.9 denier staple length polyester fibers; and 10% 2.25 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. This nonwoven filtration media has a basis weight of about 150 gsm, a Frazier permeability of about 409 CFM/square foot, a dP of about 0.12, a PFE efficiency of about 50, a MD Gurley stiffness of about 2900 milligrams and a LED score test result of about 91 degrees.
Example 38 in range D was prepared by carding and fibers to form a nonwoven matt. The matt was thermally bonded over heated rollers. This filtration media comprises 52% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 5% 0.9 denier staple length polyester fibers; and 43% 2.25 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. This nonwoven filtration media has a basis weight of about 180 gsm, a Frazier permeability of about 340 CFM/square foot, a dP of about 0.16, a PFE efficiency of about 62, a MD Gurley stiffness of about 2000 milligrams and a LED score test result of about 40 degrees.
Nonwoven Filtration Media Comprising Staple Length Kenaf Fibers.
Example 18 in range C was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 50% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 25% 4 denier staple length polyester fibers; and 25% staple length kenaf fibers. The fibers are homogeneously distributed throughout the single layer media. This nonwoven filtration media has a basis weight of about 165 gsm, a Frazier permeability of about 460, a dP of about 0.1, a PFE efficiency of about 52, a MD Gurley stiffness of about 2585 milligrams and a LED score test result of about 64.5 degrees.
Example 21 in range C was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 70% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 15% 4 denier staple length polyester fibers; and 15% staple length kenaf fibers. The fibers are homogeneously distributed throughout the single layer media. This filtration media has a basis weight of about 168 gsm, a Frazier permeability of about 430, a dP of about 0.1, a PFE efficiency of about 48, a MD Gurley stiffness of about 2515 and a LED score test result of about 69.7 degrees.
Example 61 in range E was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 40% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 35% 4 denier staple length polyester fibers; and 25% staple length kenaf fibers. The fibers are homogeneously distributed throughout the single layer media. This filtration media has a basis weight of about 160 gsm, a Frazier permeability of about 525, a dP of about 0.08, a PFE efficiency of about 54, a MD Gurley stiffness of about 1650 milligrams and an LED score test result of about 64.5 degrees.
Example 82 in range F was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 30% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 35% 4 denier staple length polyester fibers; and 35% staple length kenaf fibers. The fibers are homogeneously distributed throughout the single layer media. This filtration media has a basis weight of about 160 gsm, a Frazier permeability of about 530, a dP of about 0.08, a PFE efficiency of about 48, a MD Gurley stiffness of about 1297 milligrams and an LED score test result of about 63.5 degrees.
Nonwoven Filtration Media Comprising a Blend of Recycled, Staple Length, Polyester Fibers and Cotton Fibers.
Example 29 in range D was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 70% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 15% 0.9 denier staple length polyester fibers; and 15% of a blend of recycled, staple length, polyester fibers and cotton fibers. The fibers are homogeneously distributed throughout the single layer media. One side of the media was run over a roller heated to 380° F. to partially melt and fuse the fibers. This filtration media has a basis weight of about 190 gsm, a Frazier permeability of about 290, a dP of about 0.2, a PFE efficiency of about 66, a MD Gurley stiffness of about 2209 milligrams and a LED score test result of about 63.3 degrees.
Example 30 in range D was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 70% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; and 30% of a blend of recycled, staple length, polyester fibers and cotton fibers. The fibers are homogeneously distributed throughout the single layer media. One side of the media was run over a roller heated to 400° F. to partially melt and fuse the fibers. This filtration media has a basis weight of about 200 gsm, a Frazier permeability of about 330, a dP of about 0.16, a PFE efficiency of about 73, a MD Gurley stiffness of about 2195 milligrams and a LED score test result in the range of about 53.0 degrees.
Nonwoven Filtration Media Comprising Staple Length Polypropylene Fibers.
Example 75 in range E was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises about 65% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 15% 3 denier staple length uncharged polypropylene fibers; and 20% 0.9 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. This filtration media has a basis weight of about 116 gsm, a Frazier permeability of about 418, a MD Gurley stiffness of between about 1411 milligrams and a LED score test result in the range of about 66.5 degrees.
Example 77 in range F was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises about 40% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; about 30% 3 denier staple length uncharged polypropylene fibers; and about 30% 15 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. One side of the media was run over a roller heated to about 352° F. to partially melt and fuse the fibers. This filtration media has a basis weight of about 160 gsm, a Frazier permeability of about 514, a dP of about 0.08, a PFE efficiency of about 41, a MD Gurley stiffness of about 1371 milligrams and a LED score test result of about 50.8 degrees.
Example 105 in range G was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises about 60% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 25% 3 denier staple length uncharged polypropylene fibers; and about 15% 15 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. One side of the media was run over a roller heated to about 352° F. to partially melt and fuse the fibers. This filtration media has a basis weight of about 113 gsm, a Frazier permeability of about 613, a MD Gurley stiffness of about 955 milligrams and a LED score test result in the range of about 65.0 degrees.
Example 111 in range H was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 40% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 30% 3 denier staple length uncharged polypropylene fibers; and about 30% 15 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. One side of the media was run over a roller heated to about 352° F. to partially melt and fuse the fibers. This filtration media has a basis weight of about 120 gsm, a Frazier permeability of about 630, a MD Gurley stiffness of about 637 milligrams and a LED score test result of about 56.7 degrees.
Nonwoven Filtration Media Comprising 10 Denier, Staple Length, Conjugate Polyester Fibers.
Example 85 in range F was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises about 35% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; about 35% 10 denier, staple length conjugate polyester fibers; and about 30% 0.9 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. This filtration media has a basis weight of about 116 gsm, a Frazier permeability of about 500, a dP of about 0.1, a PFE efficiency of about 48, a MD Gurley stiffness of about 1258 milligrams and a LED score test result in the range of about 59.5 degrees.
Example 104 in range G was prepared by carding and heat bonding fibers to form a nonwoven filtration media. This filtration media comprises 55% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; 10% 10 denier, staple length conjugate polyester fibers; and 35% 3 denier staple length polyester fibers. The fibers are homogeneously distributed throughout the single layer media. This filtration media has a basis weight of about 120 gsm, a Frazier permeability of about 560, a dP of about 0.08, a PFE efficiency of about 38, a MD Gurley stiffness of about 960 milligrams and a LED score test result of about 68.2 degrees.
Nonwoven Filtration Media Comprising More than One Layer.
Example 19 in range C was prepared by carding and heat bonding fibers to form a first nonwoven filtration media. This first nonwoven media includes about 70% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and about 30% 15 denier polyester fibers. The first filtration media was needled onto a second spunbond nonwoven filtration media comprising 0.5 osy polypropylene filaments to form the nonwoven composite material. One side of the composite material was run over a roller heated to about 320° F. to partially melt and fuse the fibers. This nonwoven composite material has a basis weight of about 168 gsm, a Frazier permeability of about 530, a MD Gurley stiffness of about 2583 milligrams and a LED score test result of about 74.0 degrees.
Example 26 in range D was prepared by carding and heat bonding fibers to form a first nonwoven filtration media. This first nonwoven media includes about 70% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and about 30% 15 denier staple length polyester fibers. The first filtration media was needled onto a second spunbond nonwoven filtration media comprising 0.5 osy polypropylene filaments to form the nonwoven composite material. One side of the material was run over a roller heated to about 335° F. to partially melt and fuse the fibers. This nonwoven composite material has a basis weight of about 153 gsm, a Frazier permeability of about 540, a dP of about 0.07, a PFE efficiency of about 44, a MD Gurley stiffness of about 2298 milligrams and a LED score test result of about 86.7 degrees.
Example 169 in range D is a 2 layer nonwoven filtration media. Each layer was an independently carded matt formed using a different card machine. One carded matt comprised 50% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and 50% 3 denier, staple length polyester fibers. The other carded matt comprised 50% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and 50% 45 denier, staple length polyester fibers. Each carded matt was cross lapped using a separate cross lapper. The cross lapped matts were overlaid, mechanically entangled by needling and thermally bonded using a heated roller. Each carded matt contributed one half to the weight of this 2 layer nonwoven filtration media. This nonwoven composite material has a basis weight of about 150 gsm, a Frazier permeability of about 500, a dP of about 0.075, a PFE efficiency of about 45, a MD Gurley stiffness of about 2300 milligrams and a LED score test result of about 73 degrees.
Resin and Thermal Bonded Nonwoven Filtration Media.
Nonwoven filtration medias can be bonded using liquid resins or binders.
Example 180 in range D was prepared by carding fibers to form a matt. This matt comprises about 15% 2.25 denier staple length, monocomponent polyester fibers; about 50% 15 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and about 35% 45 denier staple length, monocomponent polyester fibers. The fibers are homogeneously distributed throughout the single layer media. One side of the matt was heated over a heated roller to partially melt and fuse the fibers. A solution of resin binder was applied to the heat bonded matt. The impregnated matt was run through an oven having multiple heating zones with each zone heated to between 241 and 298° F. This filtration media has a resin content of about 15 percent by weight of the media, a basis weight of about 140 gsm, a Frazier permeability of about 580, a dP of about 0.04, a PFE efficiency of about 30, a and a MD Gurley stiffness of about 1965 milligrams and a LED score test result of about 94 degrees.
Example 194 in range F was prepared by carding fibers to form a matt. This matt comprises about 35% 3 denier staple length, monocomponent polyester fibers; about 50% 15 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and about 15% 45 denier staple length, monocomponent polyester fibers. The fibers are homogeneously distributed throughout the single layer media. A solution of resin binder was applied to the heat bonded matt. One side of the matt was heated over a heated roller to partially melt and fuse the fibers and dry the resin binder. This filtration media has a resin content of about 15 percent by weight of the media, a basis weight of about 150 gsm, a Frazier permeability of about 614, a MD Gurley stiffness of about 1371 milligrams and a LED score test result of about 72 degrees.
Example 211 in range C was prepared by carding fibers to form a matt. This matt comprises about 10% 4 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers; about 65% 15 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and about 25% 45 denier staple length, monocomponent polyester fibers. The fibers are homogeneously distributed throughout the single layer media. One side of the matt was heated over a heated roller to partially melt and fuse the fibers. A solution of resin binder was applied to the heat bonded matt. The impregnated matt was run through an oven having multiple heating zones with each zone heated to between 186 and 220° F. This filtration media has a resin content of about 15 percent by weight of the media, a basis weight of about 165 gsm, a Frazier permeability of about 671, a dP of about 0.033, a PFE efficiency of about 18, a MD Gurley stiffness of about 2615 milligrams and a LED score test result of about 101.5 degrees.
Ultrasonic Bonded Nonwoven Filtration Media.
Nonwoven filtration medias can be bonded using ultrasonic energy. Ultrasonic bonding is generally performed using a specifically tuned horn vibrating at a high frequency in close proximity to an anvil roll. The anvil roll can either be flat or have a pattern engraved into the roll.
Example 116 in range H was prepared by carding and ultrasonic bonding fibers to form a nonwoven filtration media. This filtration media comprises about 25% 15 denier polyester fibers; about 25% 45 denier polyester fibers and about 50% 3 denier polypropylene fibers. The fibers are homogeneously distributed throughout the single layer media. This nonwoven filtration media was ultrasonically bonded using a flat anvil roll, a horn and a frequency of 20 kHz, a step position of 7378 with a target force of 800 Newtons on a Hermann Ultrasonics laboratory scale unit (Schaumberg, Ill.). This filtration media has a basis weight of about 170 gsm, a Frazier permeability of about 413, a MD Gurley stiffness of about 140 milligrams and a LED score test result of about 73.3 degrees.
Tackified Nonwoven Filtration Media 1
Examples 218 and 219 and Example 220 were prepared by carding and cross lapping fibers to form a matt. This matt comprises about 63% 4 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers, about 17% 15 denier staple length, monocomponent polyester fibers and about 20% 3 denier staple length, monocomponent polyester fibers. The fibers are substantially homogeneously distributed throughout the single layer media.
One side of the matt was heated over a heated roller to partially melt and fuse the fibers. No tackifier or tack agent was applied to the media of Examples 218, 219 and 220.
This filtration media has a basis weight of about 157 gsm, a Frazier permeability of about 496, a dP of about 0.073, a PFE efficiency of about 51.8, an index of about 710, a and a MD Gurley stiffness of about 2493 milligrams and a LED score test result of about 66.1 degrees.
Examples 221, 222 and 223 used the media of examples 218 to 220. An aqueous emulsion of Hystretch V-60 tack agent was sprayed against one side of the media to provide the add-ons shown in Table 6. Examples 221 and 222 were dried by running through a three zone forced air dryer with zone temperatures of about 280° F., 320° F. and 350° F. Example 223 was dried in still air at ambient temperatures (about 78° F.) for about 14 hours so as to dry the media to the touch. Physical properties of these Examples are illustrated on Table 6.
Examples 224, 225, 226, 227 and 228 used the media of examples 218 to 220. An aqueous emulsion of Hystretch V-60 tack agent, available from Lubrizol of Pittsburgh, Pa., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Examples 224 and 225 were dried by running through a three zone forced air dryer with zone temperatures of about 280° F., 320° F. and 350° F. Examples 226, 227 and 228 were dried in still air at ambient temperatures (about 65° F. to about 78° F.) for about 14 hours so as to dry the media to the touch. Physical properties of these Examples are illustrated on Table 6.
Example 229 used the media of examples 218 to 220. An aqueous emulsion of Flexacryl 1625 tack agent, available from Air Products Polymers of Allentown, Pa., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Example 229 was dried in still air at ambient temperatures (about 65° F.) for about 14 hours so as to dry the media to the touch. Physical properties of these Examples are illustrated on Table 6.
Examples 230 and 231 used the media of examples 218 to 220. An aqueous emulsion of Spar Cryl 102 tack agent, available from Spartan Chemical Laboratories, Inc of Spartanburg, S.C., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Examples 230 and 231 were dried in still air at ambient temperatures (about 65° F.) for about 14 hours so as to dry the media to the touch. Physical properties of these Examples are illustrated on Table 6.
Tackified Nonwoven Filtration Media 2
Examples 232 and 233 were prepared by carding and cross lapping fibers to form a matt. This matt comprises about 50% 15 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers, about 15% 2.25 denier staple length, monocomponent polyester fibers and about 35% 45 denier staple length, monocomponent polyester fibers. The fibers are substantially homogeneously distributed throughout the single layer media.
One side of the matt was heated over a heated roller to partially melt and fuse the fibers. No tackifier or tack agent was applied to the media of Examples 232 and 233.
This filtration media has a basis weight of about 159 gsm, a Frazier permeability of about 621, a dP of about 0.051, a PFE efficiency of about 43.3, an index of about 847, a MD Gurley stiffness of about 1872 milligrams and a LED score test result of about 78.6 degrees.
Examples 234 and 235 used the media of examples 232 to 233. An aqueous emulsion of Hystretch V-60 tack agent was sprayed against one side of the media to provide the add-ons shown in Table 6. Examples 234 and 235 were dried in still air at ambient temperatures (about 78° F.) for about 14 hours so as to dry the media to the touch. Physical properties of these Examples are illustrated on Table 6.
Examples 236, 237 and 238 used the media of Examples 232 and 233. An aqueous emulsion of Hystretch V-60 tack agent, available from Lubrizol of Pittsburgh, Pa., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Examples 236 and 237 were dried in still air at ambient temperatures (about 78° F.) for about 14 hours so as to dry the media to the touch. Example 238 was dried by running through a three zone forced air dryer with zone temperatures of about 280° F., 320° F. and 350° F. Physical properties of these Examples are illustrated on Table 6.
Tackified Nonwoven Filtration Media 3
Example 239 comprises about 38% 15 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers, about 11.4% 2.25 denier staple length, monocomponent polyester fibers, about 26% 45 denier staple length, monocomponent polyester fibers, about 12% 3.3 denier staple length, triboelectrically chargeable polypropylene fibers and about 12% 3 denier staple length, triboelectrically chargeable modacrylic fibers. Example 239 was prepared by carding and cross lapping a combination of 50% 15 denier conjugate fibers, 15% 2.25 denier polyester fibers and 35% 45 denier polyester fibers to form a matt. The malt was entangled by needling and heated over a heated roller to partially melt and fuse the fibers. The tribocharged fibers (about 12% 3.3 denier staple length, triboelectrically chargeable polypropylene fibers and about 12% 3 denier staple length, triboelectrically chargeable modacrylic fibers) were homogeneously blended, applied over the matt and entangled into the matt using needling. The matt and entangled, tribocharged fibers were heated over a heated roller to partially melt and fuse the fibers. No tackifier or tack agent was applied to the media of Examples 239.
This filtration media has a basis weight of about 159 gsm, a Frazier permeability of about 505, a dP of about 0.077, a PFE efficiency of about 77.9, an index of about 1012, a MD Gurley stiffness of about 1731 milligrams and a LED score test result of about 65.3 degrees.
Example 240 used the media of example 239. An aqueous emulsion of Hystretch V-60 tack agent, available from Lubrizol of Pittsburgh, Pa., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Example 240 was dried in still air at ambient temperatures (about 65° F.) for about 14 hours so as to dry the media to the touch.
Example 241 used the media of example 239. An aqueous emulsion of Flexacryl 1625 tack agent, available from Air Products Polymers of Allentown, Pa., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Example 241 was dried in still air at ambient temperatures (about 78° F.) for about 14 hours so as to dry the media to the touch.
Example 242 used the media of examples 239. An aqueous emulsion of Spar Cryl 102 tack agent, available from Spartan Chemical Laboratories, Inc of Spartanburg, S.C., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Example 242 was dried in still air at ambient temperatures (about 78° F.) for about 14 hours so as to dry the media to the touch.
Physical properties of these Examples are illustrated on Table 6.
Tackified, Two Layer, Nonwoven Filtration Media 4
Example 243 is a 2 layer nonwoven filtration media. Each layer was an independently carded matt formed using a different card machine. One carded matt comprised 50% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and 50% 3 denier, staple length polyester fibers. The other carded matt comprised 50% 4 denier, staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and 50% 3 denier, staple length polyester fibers. Each carded matt was cross lapped using a separate cross lapper.
The cross lapped matts were overlaid, mechanically entangled by needling. One side of the entangled matts was run over a heated roller to partially melt and fuse the fibers in the media. Each carded matt contributed one half to the weight of this 2 layer nonwoven filtration media. No tackifier or tack agent was applied to the media of Examples 243.
This filtration media has a basis weight of about 150 gsm, a Frazier permeability of about 500, a dP of about 0.075, a PFE efficiency of about 45.4, an index of about 605, a MD Gurley stiffness of about 2300 milligrams and a LED score test result of about 71.6 degrees.
Example 244 used the media of example 243. An aqueous emulsion of Hystretch V-60 tack agent, available from Lubrizol of Pittsburgh, Pa., was sprayed against both sides of the media to provide the add-ons shown in Table 6. Example 244 was dried by running through a three zone forced air dryer with zone temperatures of about 280° F., 320° F. and 350° F. Physical properties of this Example are illustrated on Table 6.
Tackified Nonwoven Filtration Media 5
Example 245 was prepared by carding and cross lapping fibers to form a matt. This matt comprises about 50% 4 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers, about 8% 0.9 denier staple length, monocomponent polyester fibers and about 43% 2.25 denier staple length, monocomponent polyester fibers. The fibers are substantially homogeneously distributed throughout the single layer media.
One side of the matt was heated over a heated roller to partially melt and fuse the fibers. No tackifier or tack agent was applied to the media of Example 245.
This filtration media has a basis weight of about 174 gsm, a Frazier permeability of about 230, a dP of about 0.169, a PFE efficiency of about 88.3, an index of about 522, a MD Gurley stiffness of about 1965 milligrams and a LED score test result of about 51 degrees.
Examples 246 and 247 used the media of example 245. An aqueous emulsion of Hystretch V-60 tack agent was sprayed against both sides of the media to provide the add-ons shown in Table 6. Examples 246 and 247 were dried by running through a three zone forced air dryer with zone temperatures of about 280° F., 320° F. and 350° F. Physical properties of these Examples are illustrated on Table 6.
Tackified Nonwoven Filtration Media 6
Examples 248 to 252 were prepared by carding and cross lapping fibers to form a matt. This matt comprises about 80% 4 denier staple length, lower melting point polyester sheath, higher melting point polyester core conjugate fibers and about 20% 3 denier staple length, monocomponent polyester fibers. The fibers are substantially homogeneously distributed throughout the single layer media. One side of the matt was heated over a heated roller to partially melt and fuse the fibers.
Foams were prepared by mixing the reported amounts of tackifier and water. The tackifier and water mixture was wisked forcefully for about 60 seconds to entrain air into the mixture and form a foam. The foam was applied to the media in a uniform fashion using a flat blade applicator.
The aqueous based foam of Hystretch V-60 tack agent was applied to one side of Examples 248 to 252 to provide the add-ons shown in Table 6 in percentage by weight. Examples 248 to 252 were dried for about four hours at a temperature in the range of about 60° F. to about 80° F. Physical properties of these Examples are illustrated on Table 6.
For a nonwoven, self supporting media a minimum basis weight is required to achieve a desired efficiency. A nonwoven, self supporting, non-tackified MERV 6 efficiency filtration media will typically require a basis weight of about 0.4 osf. To increase the efficiency of that media to MERV 8, the basis weight will have to be increased to about 0.6 osf. Surprisingly, if a tackifier is added to a nonwoven, self supporting, MERV 6 efficiency filtration media having a basis weight of about 0.4 osf the resulting tackified filtration media can achieve a MERV 8 efficiency. Further surprisingly, adding a tackifier to a self supporting filtration media appears to increase stiffness of the resulting tackified media. Thus, adding a tackifier to a self supporting media provides surprising increases to efficiency and stiffness without increasing base media weight.
While preferred embodiments of the foregoing invention have been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present invention.
Claims
1. A tackified air filtration media comprising a thermally bonded nonwoven web comprising a generally homogeneous mixture of fiber types, the web comprising about 10% to about 90% by weight of a first type of fibers having a length of about 0.6 cm to about 20 cm, the fibers including a first fiber portion extending substantially continuously along the length of each fiber and comprising a first thermoplastic polymeric material having a first melting point and a second fiber portion extending substantially continuously along the length of each fiber and defining at least a portion of a fiber exterior surface, the second fiber portion comprising a second thermoplastic polymeric material having a second melting point lower than the first melting point, and about 10% to about 90% by weight of a second type of fibers having a length of about 0.6 cm to about 20 cm; the media having a basis weight in the range of about 90 gsm to about 370 gsm; a thickness of about 1.0 mm to about 6.4 mm; a Frazier permeability of about 150 CFM/square foot to about 1000 CFM/square foot; and a combination of MD Gurley stiffness and LED score results selected from one of the following ranges: range Gurley Stiffness (mg) LED score (degrees) A Over 3000 60.2 to 101.7 B 2800 to 3000 55.0 to 104.2 C 2400 to 2800 53.3 to 101.5 D 1800 to 2400 39.7 to 108.2 E 1400 to 1800 41.2 to 98.3 F 1200 to 1400 77.0 to 86.0 G 800 to 1200 39.3 to 68.2 H Under 800 42.7 to 68.8 and;
- 0.5 percent by weight of nonwoven web to about 30 percent by weight of nonwoven web of a tackifier on fibers of the air filtration media.
2. The tackified air filtration media of claim 1, wherein the first thermoplastic polymeric material is polyester.
3. The tackified air filtration media of claim 1 being a single layer.
4. The tackified air filtration media of claim 1, wherein the first thermoplastic polymeric material is polyester and the second thermoplastic polymeric material is polyester.
5. The tackified air filtration media of claim 1, further comprising kenaf fibers having a length of about 0.6 cm to about 20 cm.
6. The tackified air filtration media of claim 1, comprising about 1.5% to about 15% of the tackifier on fibers of the air filtration media.
7. The tackified air filtration media of claim 1, wherein one fiber type has a denier in the range of about 0.9 to about 6 and the other fiber type has a denier in the range of about 8 to about 45.
8. The tackified air filtration media of claim 1, further being a self supporting media.
9. The tackified air filtration media of claim 1, having a MD Gurley stiffness over 1700.
10. The tackified air filtration media of claim 1, wherein:
- the first fiber type is selected from at least one of about 10% to about 85% 4 denier conjugate fibers comprising polyester first and second fiber portions or about 10% to about 85% 15 denier conjugate fibers comprising polyester first and second fiber portions;
- the second fiber type is selected from at least one of about 5% to about 30% monocomponent polyester fibers having a denier in the range of about 0.9 to about 45; about 15% to about 50% 3 denier chargeable polypropylene fibers; about 15% to about 30% polyester/cotton blend fibers; or about 15% to about 35% cellulosic fibers;
- at least one fiber type has a denier greater than 10; and
- about 1.5% to about 6% tackifier.
11. The tackified air filtration media of claim 1 further comprising a cured, non-fibrous binder resin between the fiber types.
12. The tackified air filtration media of claim 1 having a combination of Gurley stiffness and LED score results selected from one of the following ranges: range Gurley Stiffness (mg) LED score (degrees) A over 3,000 60.2 to 85.8; B 2,800 to 3,000 60.2 to 90.8; C 2,400 to 2,800 58.2 to 79.0; D 1,800 to 2,400 40.0 to 94.7; E 1,400 to 1,800 42.5 to 94.0; F 1,200 to 1,400 43.3 to 64.8; G 800 to 1,200 39.3 to 63.3; H under 800 42.7 to 68.8.
13. A method of making a tackified air filtration media comprising: range Gurley Stiffness (mg) LED score (degrees) A Over 3000 60.2 to 101.7 B 2800 to 3000 60.2 to 104.2 C 2400 to 2800 53.3 to 101.5 D 1800 to 2400 39.7 to 105.3 E 1400 to 1800 41.2 to 94.5 F 1200 to 1400 42.0 to 86.0 G 800 to 1200 39.3 to 68.2 H Under 800 42.7 to 68.8 and;
- forming a fiber mixture, comprising about 10% to about 90% by weight of a first type of fibers having a length of about 0.6 cm to about 20 cm, the fibers including a first fiber portion extending substantially continuously along the length of each fiber and comprising a first thermoplastic polymeric material having a first melting point and a second fiber portion extending substantially continuously along the length of each fiber and defining at least a portion of a fiber exterior surface, the second fiber portion comprising a second thermoplastic polymeric material having a second melting point lower than the first melting point, and about 10% to about 90% by weight of a second type of fibers having a length of about 0.6 cm to about 20 cm;
- forming the fiber mixture into a nonwoven matt;
- bonding the fibers in the nonwoven matt, the bonded nonwoven matt having a basis weight in the range of about 90 gsm to about 370 gsm; a thickness of about 1.0 mm to about 6.4 mm; a Frazier permeability of about 150 CFM/square foot to about 1000 CFM/square foot; and a combination of MD Gurley stiffness and LED score results selected from one of the following ranges:
- applying 0.5 percent by weight of nonwoven web to about 30 percent by weight of nonwoven matt of a tackifier to fibers of the bonded nonwoven matt to form the tackified air filtration media.
14. The method of claim 13 wherein the step of forming comprises carding the fiber mixture to form the nonwoven matt.
15. The method of claim 13 wherein the step of forming comprises carding the fiber mixture to form a web and cross lapping the web to form the nonwoven matt.
16. The method of claim 13 wherein the step of bonding comprises thermal bonding of the fibers in the nonwoven matt.
17. The method of claim 13 wherein the step of applying comprises spraying a tackifier on a surface of the bonded nonwoven matt.
18. The method of claim 13 further comprising the step of folding the media to form a self supporting structure.
19. A non-tackified air filtration media comprising a thermally bonded nonwoven web comprising a generally homogeneous mixture of fiber types, the web comprising about 30% to about 90% by weight of a first type of fibers having a length of about 0.6 cm to about 20 cm, the fibers including a first fiber portion extending substantially continuously along the length of each fiber and comprising a first thermoplastic polymeric material having a first melting point and a second fiber portion extending substantially continuously along the length of each fiber and defining at least a portion of a fiber exterior surface, the second fiber portion comprising a second thermoplastic polymeric material having a second melting point lower than the first melting point, and about 5% to about 70% by weight of a second type of fibers having a length of about 0.6 cm to about 20 cm; the media having a basis weight in the range of about 90 gsm to about 370 gsm; a thickness of about 1.0 mm to about 6.4 mm; a Frazier permeability of about 45,000 LSM to about 260,000 LSM; and a combination of Gurley stiffness and LED score results selected from one of the following ranges: range Gurley Stiffness (mg) LED score (degrees) A Over 3000 60.2 to 101.7 B 2800 to 3000 60.2 to 104.2 C 2400 to 2800 53.3 to 101.5 D 1800 to 2400 39.7 to 105.3 E 1400 to 1800 41.2 to 94.5 F 1200 to 1400 42.0 to 86.0 G 800 to 1200 39.3 to 68.2 H Under 800 42.7 to 68.8
20. The non-tackified air filtration media of claim 19, wherein one fiber type has a denier less than about 6 and the other fiber type has a denier greater than about 8.
Type: Application
Filed: Nov 8, 2007
Publication Date: May 29, 2008
Inventors: Leonard E. DUELLO (Hewitt, TX), Thomas D. Hawkins (Waco, TX), Christopher B. Peart (Madisonville, KY), Nathaniel J. Nance (Mexia, TX)
Application Number: 11/937,245
International Classification: B01D 39/16 (20060101); B29C 65/00 (20060101);
