Patent Application
20150211158
This invention relates to a process for forming a high loft, nonwoven web exhibiting excellent recovery.
Typically, polymeric fibers, formed by spunbonding, meltblowing or by some other extrusion process are collected downstream from an emitter, such as a die with a plurality of nozzles, on a horizontal oriented conveyor belt. Such processes tends to produce two-dimensional web where the fibers are oriented in the x and y directions since they are laid down in a horizontal plane. There are few if any fibers within the formed web that are oriented in the z-direction. Because of this, the finished web tends to lack recovery once it is compressed. This presents an issue when such finished webs need to be rolled up or stacked for transport by truck, or rail to a distant manufacturing, or distribution facility. If the webs are compacted or compressed during shipment, they lack the ability to recovery to their original thickness. In addition, once compacted or compressed, such webs tend to become hard and/or stiff and their pore structure may become less open. Furthermore, the drapeability of such webs can be diminished. Functionally, if a compacted or compressed web cannot recover to approximately its initial loft thickness after shipment, it can lose some of its thermal and/or acoustical insulation properties, thereby rendering the material less than desirable for this purpose.
Now, a high loft, nonwoven web, exhibiting excellent recovery, has been invented.
Briefly, this invention relates to a process for forming a high loft, nonwoven web exhibiting excellent recovery.
The high loft, nonwoven web is a three dimensional structure with fibers oriented in the x, y and z directions. The web can be constructed as a single layer or be formed with two or more layers. The web has a thickness of less than about 250 millimeters and a basis weight of from between about 50 g/m2 to about 3,000 g/m2. The web can be bonded using a thermal bonder, a chemical bonder, a hydro-mechanical bonder, a mechanical bonder, or be left unbonded. A vertical cross-section of the web, when taken parallel to its machine direction, exhibits a plurality of snugly stacked, approximately V, U, or C-shaped structures, with each approximately V, U, or C-shaped shaped structure having an apex facing in the machine direction. The web has a recovery value of from between about 20% to about 99% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes.
An apparatus for producing a high loft, nonwoven web having a three dimensional structure with fibers oriented in the x, y and z directions is also taught. The apparatus includes a die having a plurality of nozzles each emitting a filament, and each of the plurality of nozzles having a distal end. A pair of moving surfaces is located from between about 10 cm to about 150 cm of the distal end of each of the plurality of nozzles. The pair of moving surfaces forms a convergent passage having an entry and an exit. The apparatus also includes a mechanism for depositing the plurality of filaments onto and between the pair of moving surfaces. The plurality of filaments is routed through the convergent passage in descending travel from the entry to the exit to form a 3-dimensional structure. The apparatus further includes a bonder located downstream of and in vertically alignment with the pair of moving surfaces for bonding the 3-dimensional structure to create a high loft, nonwoven web with the filaments transformed into fibers oriented in the x, y and z directions. The web has a thickness of less than about 250 mm and a basis weight ranging from between about 50 g/m2 to about 3,000 g/m2. A vertical cross-section of the high loft, nonwoven web, when taken parallel to its machine direction, exhibits a plurality of snugly stacked, approximately V, U, or C-shaped structures, with each approximately V, U, or C-shaped structure having an apex facing in the machine direction. In other words, the approximately V or U shaped structure is rotated 90 degrees to a horizontal orientation with the apex of each facing to the right. The C-shaped structure is reversed in position so that the apex of each faces to the right. The high loft, nonwoven web has a recovery value ranging from between about 20% to about 99% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes.
A process for forming a high loft, nonwoven web includes the steps of introducing a molten polymer to a die having a plurality of nozzles. Emitting, ejecting or extruding the molten polymer through the plurality of nozzles to form a plurality of filaments. Air or gas streams are then used to facilitate downward movement of the plurality of filaments. The filaments are directed towards a pair of moving surfaces located at a distance of from between about 10 cm to about 150 cm from the plurality of nozzles. The pair of moving surfaces forms a convergent passage having an entry and an exit. The plurality of filaments is deposited into the entry of the convergent passage. The plurality of filaments is then routed through the convergent passage in descending travel from the entry to the exit and between the pair of moving surfaces in a machine direction to form a 3-dimensional structure with the filaments transformed into fibers which are oriented in the x, y and z directions. Lastly, the 3-dimensional structure is bonded to form a high loft, nonwoven web having a thickness of less than about 250 millimeters and a basis weight ranging from between about 50 g/m2 to about 3,000 g/m2. A vertical cross-section of the high loft, nonwoven web, when taken parallel to its machine direction, exhibits a plurality of snugly stacked, approximately V, U, or C-shaped structures, with each approximately V, U, or C-shaped structure having an apex facing in the machine direction. The high loft, nonwoven web has a recovery value ranging from between about 20% to about 99% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes.
The general object of this invention is to provide a process for forming a high loft, nonwoven web exhibiting excellent recovery. A more specific object of this invention is to provide a process for forming a high loft, nonwoven web with good thermal insulation and/or acoustical insulation values.
Another object of this invention is to provide a process for forming a high loft, nonwoven web which can be used in the bedding, upholstery, filtration, foam replacement materials, and products utilizing cushioning materials.
A further object of this invention is to provide a process for forming a high loft, nonwoven web exhibiting from between about 20% to about 99% recovery after compression, and such web exhibits a high porosity.
Still another object of this invention is to provide a process for forming a high loft, nonwoven web exhibiting excellent recovery such that it can be compactly shipped without losing any material properties.
Still further, an object of this invention is to provide a process for forming a high loft, nonwoven web exhibiting from between about 40% to about 90% recovery after compression.
Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings.
Referring to
The high loft, nonwoven web 10 can be formed from a variety of materials. The high loft, nonwoven web 10 can be formed from man-made fibers. The fibers can be staple fibers. Typically, the high loft, nonwoven web 10 is formed from a polymer. The polymer can be selected from the group consisting of: polyolefins, polyesters, polyethylene terephthalates, polybutylene terephthalates, polycyclohexylene dimethylene terephthalates, polytrimethylene terephthalates, polymethyl methacrylates, polyamides, nylons, polyacrylics, polystyrenes, polyvinyls, polytetrafluoroethylenes, ultrahigh molecular weight polyethylenes, very high molecular weight polyethylenes, high molecular weight polyethylenes, polyether ether ketones, non-fibrous plasticized celluloses, polyethylenes, polypropylenes, polybutylenes, polymethylpentenes, low-density polyethylenes, linear low-density polyethylenes, high-density polyethylenes, polystyrenes, acrylonitrile-butadiene-styrenes, styrene-acrylonitriles, styrene-butadienes, styrene-maleic anhydrides, ethylene vinyl acetates, ethylene vinyl alcohols, polyvinyl chlorides, cellulose acetates, cellulose acetate butyrates, plasticized cellulosics, cellulose propionates, ethyl celluloses, natural fibers, any derivative thereof, any polymer blend thereof, any copolymer thereof or any combination thereof. Those skilled in the chemical arts may know of other polymers that can also be used to form the high loft, nonwoven web of this invention. It should be understood that the high loft, nonwoven web 10 of this invention is not limited to just those polymers identified above.
The high loft, nonwoven web 10 can be formed or manufactured using many different kinds and types of equipment and processes. Some commonly known technology which can be used to form the high loft, nonwoven web 10 include, but are not limited to: spinning processes such as meltblowing, spunbond, spunmelt, solution blowing, electrospinning. In addition, the high loft, nonwoven web 10 can be manufactured by a dry-laid process such as an air-lay process, a carding process or any combination of any two or more such processes where fibers are laid down at a nip between two moving surfaces. The manufactured high loft, nonwoven web 10 can be bonded or be unbounded. A bonding step adds strength and integrity to the finished web 10.
By “spunbond” it is meant a process for producing strong fibrous nonwovens webs directly from thermoplastic polymers by attenuating the spun filaments using low temperature, high speed air while quenching the fibers near the spinnerette face. Individual fibers are then laid down randomly on a collection belt and are then conveyed to a bonder. The bonder gives the web strength and integrity. Fiber size is usually below 250 μm, the average fiber size is in the range of from between about 10 microns to about 50 microns and the fibers are very strong compared to meltblown fibers because of the molecular chain alignment that is achieved during the attenuating of the crystallized (solidified) filaments. A typical spunbond die has multiple rows of polymer nozzle holes. A typical melt flow rate is below about 500 grams/10 minutes.
By “spunmelt” it is meant a process where fibers are spun from molten polymers through a plurality of nozzles located in a die head connected to one or more extruders. A spunmelt process may include meltblowing and/or spunbonding.
By “meltblowing” it is meant a process where a plurality of molten polymer streams are attenuated using an elevated temperature, high speed gas stream. The gas can be air or other gases known to those skilled in the art. The attenuated fibers are then collected on a moving belt, conveyor or a dual drum collector. Typically, a meltblowing die has around 35 nozzles per inch, a row of spinnerettes and two inclined air or gas jets for attenuating the fiber streams. U.S. Pat. No. 4,380,570 and WO 2005/106,085 A1 teach meltblowing processes where multiple rows of polymer nozzles are surrounded by air nozzles and the streams flowing therefrom are aligned parallel to one another.
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In
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The high loft, nonwoven web 10 can be formed with different basis weights. Generally, the basis weight of the high loft, nonwoven web 10 ranges from between about 50 grams per square meter (g/m2) to about 3,000 g/m2. Desirably, the basis weight of the high loft, nonwoven web 10 ranges from between about 750 grams per square meter (g/m2) to about 2,500 g/m2. More desirably, the basis weight of the high loft, nonwoven web 10 ranges from between about 100 grams per square meter (g/m2) to about 1,000 g/m2. Even more desirably, the basis weight of the high loft, nonwoven web 10 is less than about 600 g/m2.
The high loft, nonwoven web 10 can also vary in density. Generally, the high loft, nonwoven web 10 has a density ranging from between about 10 kilograms per cubic meters (Kg/m3) to about 250 Kg/m3. Desirably, the high loft, nonwoven web 10 has a density ranging from between about 20 Kg/m3 to about 200 Kg/m3. More desirably, the high loft, nonwoven web 10 has a density ranging from between about 30 Kg/m3 to about 150 Kg/m3. Even more desirably, the high loft, nonwoven web 10 has a density ranging from between about 40 Kg/m3 to about 100 Kg/m3.
The high loft, nonwoven web 10 can be bonded or unbounded. Desirably, the high loft, nonwoven web 10 is bonded. Bonding generally imparts strength and integrity to the web 10. Bonding can be performed using different type of equipment and processes known to those skilled in the art. Various bonders include: mechanical bonders such as needle bonding, hydro-mechanical bonders, also known as wet bonding, thermal bonders, which include through air bonding and oven thermal bonding and chemical bonding. Whichever type of bonder is utilized, some of the fibers 12, 14, 16, 18, 20 and 22 are bonded together to make the high loft, nonwoven web 10, 10′ and 10″stronger.
Furthermore, the high loft, nonwoven web 10 can be formed from polypropylene having a melt flow rate ranging from between about 4 g/10 min. to about 6,000 g/10 min at a temperature of 230° C. and at a pressure of 2.16 kg according to the teachings of ASTM D 1238 testing method. Desirably, the high loft, nonwoven web 10 can be formed from polypropylene having a melt flow rate ranging from between about 35 g/10 min. to about 2,500 g/10 min at a temperature of 230° C. and at a pressure of 2.16 kg. More desirably, the high loft, nonwoven web 10 can be formed from polypropylene having a melt flow rate ranging from between about 500 g/10 min. to about 2,000 g/10 min at a temperature of 230° C. and at a pressure of 2.16 kg. Most desirably, the high loft, nonwoven web 10 can be formed from polypropylene having a melt flow rate ranging from between about 500 g/10 min. to about 1,500 g/10 min at a temperature of 230° C. and at a pressure of 2.16 kg.
Referring again to
It should be understood that each layer of the two layer web 10′, shown in
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It should be understood that the two layer web 10′ can be formed as two separate layersl4 and 16 from comingled fibrous materials where each layer has a different fiber size, is formed from a different material, has different fiber cross-sections, etc. Furthermore, the two layered web 10′ could be laminated to one or more layers. The additional layers could be a thermoplastic film, a film, another nonwoven material, paper, cardboard, etc.
Referring again to
It should also be recognized that an additive can be incorporated into the high loft, nonwoven web 10, 10′ or 10″. The additive (not shown) can be applied to the high loft, nonwoven web 10, 10′ or 10″during manufacture. The additive can be applied in various ways, including but not limited to: being sprayed on, being sprinkled on, being extruded, being combined with, being painted on, being immersed, etc. The additive can be a gas, a liquid, a solid or a semi-solid. The additive can be selected from the group consisting of: a superabsorbent, absorbent particles, pulp fibers, polymers, nanoparticles, abrasive particulars, active particles, active compounds, ion exchange resins, zeolites, softening agents, plasticizers, ceramic particles pigments, dyes, flavorants, aromas, controlled release vesicles, binders, adhesives, tackifiers, surface modification agents, lubricating agents, emulsifiers, vitamins, peroxides, antimicrobials, deodorizers, fire retardants, flame retardants, antifoaming agents, anti-static agents, biocides, antifungals, degradation agents, stabilizing agents, conductivity modifying agents, or any combination thereof.
Referring now to
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When the pair of moving surfaces, 44 and 46, consists of a first rotatable drum 48 and a second rotatable drum 50, the first rotatable drum 48 will have a diameter d1 and the second rotatable drum 50 will have a diameter d2 Desirably, the diameter d1 is approximately equal to the diameter d2. More desirably, the diameters d1 and d2 are identical. The first and second rotatable drums, 48 and 50 respectively, will be aligned parallel to one another on the same plane X1-X1. It should be understood that the apparatus 34 is horizontally oriented so that the filaments 40 will move from left to right in a machine direction (MD) between the first and second rotatable drums, 48 and 50 respectively.
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The first and second rotatable drums, 48 and 50 respectively, can be operated at room temperature. Alternatively, the first and second rotatable drums, 48 and 50 respectively, could be operated at an elevated temperature or at a temperature below room temperature. Desirably, the first and second rotatable drums, 48 and 50 respectively, are operated at room temperature.
The first and second rotatable drums, 48 and 50 respectively, can be hollow cylinders with their outer peripheries covered with a forming wire or screen. The forming wire or screen can be produced from a variety of different materials known to those skilled in the art. For example, the forming wire or screen could be made from a synthetic material, such as polyethylene terephthalate (PET). Alternatively, the forming wire or screen could be made from: metal, steel, aluminum, a plastic, a thermoplastics, etc. The first and second rotatable drums, 48 and 50 respectively, could also be constructed out of various materials, such as wood, steel, cast iron, aluminum, etc. Another option is to cover the outer peripheries of the first and second rotatable drums, 48 and 50 respectively, with metal belts. The metal belts could be ferrous or non-ferrous. The metal belts could contain a plurality of apertures, openings or holes arranged in a predetermined pattern or could be randomly arranged. The size and shape of the apertures, openings or holes can vary. As is known to those skilled in the art, each of the first and second rotatable drums, 48 and 50 respectively, can be equipped with adjustable vacuum chamber, if desired. Sometimes, it is advantageous to slightly heat the outer peripheries of the first and second rotatable drums, 48 and 50 respectively; so that the incoming filaments 40 will more readily form onto them. The reason for this is that the open mesh design of a wire, screen or a metal belt containing apertures, openings or holes can form a specific texture or pattern onto the outer surfaces of the high loft, nonwoven web 10, 10′, 10″ or 11 that is being produced. Such texture or pattern may enhance the sound insulation and/or thermal absorption properties of the finished web 10, 10′, 10″ or 11. This is an important attribute when the finished high loft, nonwoven web 10, 10′, 10′ or 11 is to be used for sound and/or thermal insulation purposes.
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The outer peripheries of the first and second rotatable drums, 48 and 50 respectively, are spaced apart from one another thereby creating a convergence passage 60. By “convergent passage” it is meant a point of converging, to approach a point. This converging passage 60 narrows down to a dimension equal to a nip 62 established between the first and second rotatable drums, 48 and 50 respectively. The nip 62 can vary in dimension. The first and second rotating drums, 48 and 50 respectively, should be mounted such that the dimension of the nip 62 established therebetween can be easily adjusted. Generally, the nip 62 can range from between about 0.5 cm to about 25 cm. Desirably, the nip 62 is greater than about 0.5 cm. More desirably, the nip 62 ranges from between about 0.5 cm to about 10 cm. Even more desirably, the nip 62 ranges from between about 0.5 cm to about 8 cm. Most desirably, the nip 62 is less than about 5 cm.
The convergent passage 60 has an entry 64 and an exit 66 established by the circumference of the first and second rotatable drums, 48 and 50 respectively. As the plurality of filaments 40 are deposited at the entry 64 of the convergent passage 60 they are directed and routed onto and between the pair of moving surfaces 44 and 46. The routing is facilitated by the rotation of the first and second rotatable drums, 48 and 50 respectively. The routing causes the plurality of filaments 40 to pass through the convergent passage 60 in descending travel from the entry 64 to the exit 66. The rotational movement of the first and second rotatable drums, 48 and 50 respectively, will cause some of the plurality of filaments 40 to temporarily contact the outer peripheries of the first and second rotatable drums, 48 and 50 respectively. These filaments 40 will be compressed against the remaining filaments 40 passing through the nip 62 to create a 3-dimensional structure 68. The plurality of filaments 40 will be compressed at the nip 62 and this confined space helps the filaments 40, which are transformed into fibers 12 as they cool, to be aligned in the x, y and z directions. By “transformed” it is meant to change markedly the appearance or form of; to change the nature, function, or condition of; convert. Thus a 3-dimensional structure 68 is produced instead of a 2-dimensional structure. The 3-dimensional structure 68 usually will not have a very good recovery value unless fiber-to-fiber bonds are created using some known bonding process to stabilize the formed 3-dimensional structure 68.
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It should be understood that some high loft, nonwoven webs 10 can be formed from certain materials and for certain uses, wherein bonding is not necessary. However, for most high loft, nonwoven webs 10, it is advantageous to subject the 3-dimensional structure 68 to a bonding process. Bonding generally imparts strength and integrity into the finished web 10. Various bonding techniques can be utilized. A single bonder or a pair of oppositely aligned bonders can be utilized.
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The heat from a thermal bonder will lock some of the fibers 12 to one another in the x, y and z directions. All the fibers 12 do not have to be bonded together, just enough to create the high loft, nonwoven web 10. The fibers 12 are created as the plurality of filaments 40 solidify in the 3-dimensional structure 68. By bonding some of the plurality of fibers 12 together, a high loft, nonwoven web 10 is create having a thickness of less than about 250 mm, desirably, less than about 200 mm, and more desirably, less than about 100 mm. The high loft, nonwoven web 10 also has a basis weight ranging from between about 50 g/m2 to about 3,000 g/m2, desirably, from between about 100 g/m2 to about 2,000 g/m2, and more desirably, from between about 100 g/m2 to about 600 g/m2. Furthermore, a vertical cross-section of the web 10, when taken parallel to its machine direction, exhibits a plurality of snugly stacked, approximately V, U, or C-shaped structures 24. Each of the approximately V, U or C-shaped structures 24 has an apex 26 facing in the machine direction. In other words, the approximately V or U shaped structure is rotated 90 degrees to a horizontal orientation with the apex of each facing to the right. The C-shaped structure is reversed in position so that the apex of each faces to the right. This high loft, nonwoven web 10 has a recovery value ranging from between about 20% to about 99% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes, according to IST 120.2 (01). The IST 120.2 (01) test requires the material to be compressed under a pressure of 0.25 psi for a time period of 30 minutes. Desirably, the high loft, nonwoven web 10 has a recovery value ranging from between about 30% to about 95% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes, according to IST 120.2 (01). More desirably, the high loft, nonwoven web 10 has a recovery value ranging from between about 40% to about 90% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes, according to IST 120.2 (01). Most desirably, the high loft, nonwoven web 10 has a recovery value ranging from between about 50% to about 80% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes, according to IST 120.2 (01).
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It should be understood that the high loft, nonwoven web 10 could also be partially or fully immersed in a liquid solution containing an additive 80. The liquid solution could be chemically or electrically charged so as to cause the additive 80 to better adhere to the high loft, nonwoven web 10.
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Referring now to
The first and second conveyor belts, 52 and 54 respectively, converge toward one another at a point located farthest away from the distal end 42 of each of said plurality of nozzles 38. An opening 55, equivalent to the nip 62, is present between the first and second conveyor belts 52 and 54 respectively. The opening 55 occurs and is situated at a plane X2-X2. The plane X2-X2 is equivalent to the plane X1-X1, shown in
As clearly shown in
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The conveyor belt 84 is mounted on a plurality of rollers 86. Four rollers 86 are depicted in
It should be understood that some high loft, nonwoven webs 10 can be formed from certain materials and for certain uses, wherein bonding is not necessary. However, it is advantageous when producing most nonwoven webs 10 to subject the 3-dimensional structure 68 to a bonding process. Bonding generally imparts strength and integrity into the finished web 10. Various bonding techniques can be utilized. In
Referring now to
It should be understood that various combinations can be obtained using one or more spunbond dies, meltblown dies, spunmelt dies, etc. When one wishes to manufacture a two layer web 10′, as shown in
A 3-dimensional structure 68 emerges from the exit 66 of the convergent passage 60. As explained above, it may be advantageous to bond the fibers 12 of the 3-dimensional web 10″together to increase the strength and improve the integrity of the web 10″. A bonder 74 is positioned downstream of the first and second rotatable drums 48 and 50 respectively. The bonder 74 can be any of the various kinds of bonders explained above. Desirably, the bonder 74 is a thermal or chemical bonder.
It should be understood that in any of the three apparatuses 34, 34′ or 34″described above, that one could add one or more features to them. For example, one could introduce natural or synthetic man-made fibers into the high loft, nonwoven web 10, 10′, 10″ or 11 during the manufacturing process. Likewise, non-thermoplastic materials could also be added to the webs 10, 10′, 10″ or 11 during manufacture.
Furthermore, one could spin or extrude multi-component fibers, fibers having different cross-sectional diameters, use curly fibers within the webs 10, 10′, 10′ or 11, or otherwise treat the fibers 12 is a particular way to obtain a unique finished high loft, nonwoven web 10, 10″, 10″ or 11.
It should also be recognized that the various processes, such as meltblown, spunbond, spunmelt, etc. may require that the filaments be attenuated at different temperatures, pressures, flow rates, etc. For example, the process air could be colder or hotter than the polymer melt.
The process of forming the high loft, nonwoven web 10, 10′, 10″ or 11 will be explains with reference to
The pair of moving surfaces 44 and 46 forms a convergent passage 60 having an entry 64 and an exit 66. The plurality of filaments 40 are deposited into the entry 64 of the convergent passage 60. The plurality of filaments 40 are then routed through the convergent passage 60 in descending travel from the entry 64 to the exit 66 and between the pair of moving surfaces 44 and 46 in a machine direction to form a 3-dimensional structure 68. In the 3-dimensional structure 68, the filaments 40 are transformed upon cooling into fibers 12 oriented in the x, y and z directions. The process further includes bonding the 3-dimensional structure 68 to form a high loft, nonwoven web 10, 10′, 10″ or 11 having a thickness t, t1 or t2 of less than about 250 millimeters and a basis weight ranging from between about 50 g/m2 to about 3,000 g/m2. The 3-dimensional structure 68 can be bonded using a variety of different bonders. Some bonders which can be used include but are not limited to: thermal bonding, through air bonding, oven bonding, chemical bonding, wet bonding, mechanical bonding or hydro-mechanical bonding.
A vertical cross-section of the high loft, nonwoven web 10, 10′, 10″ or 11, when taken parallel to the machine direction (MD), exhibits a plurality of snugly stacked, approximately V, U or C-shaped structures 24. Each of the approximately V, U or C-shaped structure 24 has an apex 26 facing in the machine direction (MD). In other words, the approximately V or U shaped structure is rotated 90 degrees to a horizontal orientation with the apex of each facing to the right. The C-shaped structure is reversed in position so that the apex of each faces to the right. The high loft, nonwoven web 10, 10′, 10″ or 11 has a recovery value ranging from between about 20% to about 99% after being compressed under a pressure of 0.25 psi for a time period of 30 minutes.
Referring again to
It should be understood that an additive 80 can be added to the high loft, nonwoven web 10, 10′, 10″ or 11 downstream of the bonder 74. The additive 80 can be any of those mentioned above. The additive 80 can be deposited onto the high loft, nonwoven web 10, 10′, 10″ or 11, or it could be sprayed thereon. Alternatively, the high loft, nonwoven web 10, 10′, 10″ or 11 could be immersed in a liquid solution containing an additive 80.
It should also be understood that the high loft, nonwoven web 10, 10′, 10″ or 11 can be dried downstream of the bonder 74. Likewise, the high loft, nonwoven web 10, 10′, 10″ or 11 could be cooled downstream of the bonder 74. Such cooling could reduce the temperature of the high loft, nonwoven web 10, 10′, 10″ or 11 to room temperature or thereabout.
Experiments:
A number of high loft, nonwovens sample webs were produced using a meltblowing pilot line that had a 381 mm meltblowing die with multi-row spinnerettes known as the Biax meltblowing (MB) die. This die is commercially available from Biax-Fiberfilm Corporation having an office at N992 Quality Drive, Suite B, Greenville, Wis. 54942. The meltblowing spinnerettes had 242 polymer nozzles. The inside diameter of each spinnerette was 0.508 millimeters (mm) while the outside diameter of each spinnerette was 0.711 mm. Each polymer nozzle was surrounded by an air nozzle where the blowing air was coming from the annular space between the polymer nozzle and the air nozzle. The diameter of each of the air nozzles was 1.4 mm. The Biax meltblowing (MB) die design is taught in U.S. Pat. No. 5,476,616 and U.S. Patent Publication 2005/0056956 A1. Typical commercial Biax meltblowing (MB) dies have from between about 6,000 to about 11,000 nozzles per meter.
Several examples of high loft, nonwoven webs were made using the pilot meltblowing line to prove the concept of this invention. It should be understood that the high loft, nonwoven webs could also have been made using spunbond equipment. Furthermore, it should be understood that the exact process conditions used to make these samples could be changed. Any variation of the process conditions, such as air temperature, polymer chemistry or type, polymer melt temperature, polymer throughput, air throughput, etc. could be changed.
The first seven (7) nonwoven web samples were made of polypropylene that was provided by Exxon-Mobil under the trade name: ACHIEVE 6936G1. This polypropylene had a typical melt flow rate of 1,550 grams per 10 minutes (according to ASTM test D 1238, 230° C., 2.16 kg). The last two (2) nonwoven web samples (samples 8 and 9) were made of polylactic acid that was provided by Natureworks under the trade name: INGEO PLA 6202D. The polylactic acid had a melt flow rate of 15 grams (g) to 30 g per 10 minutes (according to ASTM test D 1238, 210° C., 2.16 kg).
Polypropylene samples were fabricated at the following process conditions:
Polymer melt temperature: 190° C.
Air temperature: 170° C.
Polymer throughput: 0.26 g/hole/minute
Air pressure: 35 KPa
The basis weight of these samples varied from between about 150 g/m2 to 500 g/m2 by varying the speed of the first and second rotatable drums or by varying the speed of the first and second conveyor belts. The Die to Collector Distance (DCD) varied between about 30 centimeters (cm) to about 45 cm.
Polylactic acid samples were made at the following process conditions;
Polymer melt temperature: 260° C.
Air temperature: 260° C.
Polymer throughput: 1 g/hole/minute
Air pressure: 35 KPa
The basis weight was around 500 g/m2 and the Die-to-Collector Distance (DCD) was around 75 cm.
Some of the samples were thermally bonded using an infra-red oven at a temperature of 120° C. and the dwell time (contact time) was about 3 seconds to about 5 seconds.
Basis weight is defined as the mass per unit area and it can be measured in grams per meter squared (g/m2). The basis weight test is done according the INDA standard IST 130.1 which is equivalent to the ASTM standard ASTM D3776. Ten (10) different samples were die cut from different locations in a larger sample web and each one had an individual area equal to 100 cm2. The weight of each replicate was measured using a sensitive balance within ±0.1% of weight on the balance. The basis weight in grams/m2 was measured by multiplying the average weight by 100.
Thickness is defined as the distance between one surface and an opposite surface of a single web measured under a specified pressure. For high loft, nonwoven webs, the thickness was measured according the INDA standard IST 120.2 (01). The apparatus include a thickness testing instrument that had: an anvil, a presser foot, and a scale indicating the distance between these two parallel plates. The foot presser was 305 mm×305 mm (12 inches×12 inches) in size and had a weight of 288 grams. Five representative specimens of the fabric were die cut and tested in the standard atmosphere for testing as prescribed in ASTM D1776. Samples were handled carefully to avoid altering the natural state of the fabric. Each specimen was placed on the bottom plate and the presser foot was placed with care on the top of the sample. The average thickness of these specimens is reported along with a standard deviation.
In this test, one measures the compression and recovery performance of the high loft, nonwoven web samples by observing the linear distance that a movable plane is displaced from a parallel surface by the high loft, nonwoven web samples while under a specified pressure. After a specified time interval, the pressure is removed and the recovery of the linear distance is measured. The performance of the high loft, nonwoven webs for use in furniture, clothing, and insulation applications (acoustic or thermal) may be estimated from these compression and recovery values. The original thickness T1, measured in millimeters (mm), was measured according to the IST 120.2 (01). The presser foot was raised and the 288 gram weight was replaced with 16.33 Kg (36 pounds) to provide a pressure of 1720 Pa (0.25 psi). The presser foot with the new weight was placed on top of the high loft, nonwoven webs samples for 30 minutes and then the compressed thickness T2 was measured. Finally, the presser foot was raised and replaced by the 36 pound weight with the 288 gram weight. After five (5) minutes, the presser foot was lowered to measure the thickness recovered, T3.
Percent compression=[(T1−T2)/T]×100
Percent Recovery=[T3/T1]×100
In this example, the effects of the collector type on the high loft, nonwoven web properties were looked at. Sample 1 and 2 showed a big difference in thickness or caliper of the nonwoven web. The big difference is mainly due to collecting the spun fibers on a flat belt versus collecting them between two rotating drums having a nip gap of 2.5 cm. The dual drum collection system increased the thickness by 1,500% although both samples have the same mass per unit area. Sample 3 showed that by thermally bonding the high loft, nonwoven sample #2, one could enhance the recovery properties by 26%. Such enhancement will greatly increase the thermal insulation and acoustical properties of a web. With the proper tuning of the fiber formation conditions and the bonding conditions, the compression and recovery properties can be greatly enhanced, see Table 1 below.
In this example, the effect of the Die-to-Collector Distance (DCD) on the compression-recovery properties of the high loft nonwoven web samples were looked at. The meltblown filaments were collected at a distance close to the die, where they are very tacky. This action created fiber to fiber bonding in the high loft, nonwoven web samples between the first and second rotatable drums and avoided the need for additional downstream bonding. This might work on equipment operating at a low polymer throughput to produce a high loft, nonwoven web with a basis weight of less than about 150 g/m2. However, when the polymer throughput and the basis weight increases, the blowing air causes the filaments to fly around and they prevent being captured on the first and second rotatable drums because of the difficult air management at a closer Die-to-Collector Distance (DCD). Samples 2 and 3 were collector at a DCD distance of 45 cm from the die face. Samples 4 and 5 were collected at a DCD distance of 30 cm from the die face. As shown in Table 2, collecting the fibers at a closer DCD distance, as in sample 4, enhanced the fiber to fiber bonding and achieved similar recovery performance to sample 3, which was thermally bonded. Sample 5 was obtained by oven bonding sample #4. However, it was found that this additional bonding actually decreased the recovery properties of sample 5 by 28% because the additional bonding actually caused the fibers to become brittle.
In this example, the effect that basis weight had on the compression-recovery properties of the high loft, nonwoven web samples were looked at. As shown in Table 3, by increasing the mass per unit area, the compressibility decreased which is obvious because of the larger nonwoven mass passing between the nip of the first and second rotatable drums. It was also noticed that by increasing the basis weight, the percent recovery after compression also increased, which may be due to the larger number of fiber-to-fiber bonds that were created. Collecting the fibers of samples 6 and 7 at a closer Die-to-Collector Distance (DCD) was not successful on the pilot scale because of the difficult air management and the larger mass of filaments that blocked the way in front the blowing attenuation air.
In this example, the concept of collecting spunmelt fibers at the nip formed between two rotating drums, for different polymers, were looked at. Sample 8 and 9 were produced using polylactic acid resin. Despite the spinning difficulty of such polymer and the shrinkage effect that accompanied the web formation, two high loft, nonwoven samples were collected. As shown in Table 4, sample 8, which was not thermally bonded, had higher compressibility but lower recovery properties than sample 9 which was thermally bonded using the infra-red thermal oven. Sample 9 was also stronger than sample 8 during handling and had a better structure integrity as sample 9 was not falling apart because of the fiber-to-fiber bonds that were created during the post heat treatment. It is well known that structural integrity of the loose fibers can be enhanced by using other bonding techniques, such as through air bonding or chemical bonding.
While the invention has been described in conjunction with several specific embodiments, it is to be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.
