Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
  • D01D5/30—Conjugate filaments; Spinnerette packs therefor
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/253—Formation of filaments, threads, or the like with a non-circular cross section; Spinnerette packs therefor
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
  • D01F8/06—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyolefin as constituent
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
  • D01F8/14—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyester as constituent
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
  • D04H3/016—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the fineness
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
  • D04H3/018—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the shape

Definitions

• the present invention relates to a method and apparatus for producing nonwoven fabrics and, in particular, to a spunbond process for manufacturing fabrics wherein individual constituent fiber components of extruded plural-component synthetic fibers are separated by differential heat shrinkage into microfibers in line with the extrusion of the plural-component fibers.
• nonwoven fabrics having improved characteristics such as greater bulkiness and softness, superior flexibility and drape, and better barrier and filtration properties for use in products such as disposable absorbent articles, medical garments and filtration materials. It has been found that nonwoven fabrics having desirable qualities can be manufactured from splittable plural- component fibers. Such plural-component fibers typically include at least two different polymers arranged as microfilaments or segments across the cross section of the fiber, which segments extend continuously along the length of the fiber. By separating these plural-component fibers into their constituent segments after extrusion, a fine denier fabric with desirable characteristics can be produced. A number of known techniques have been used to separate the individual segments of plural-component fibers.
• fiber segments can be separated by applying mechanical force to the fibers, such as high pressure water jets, beating, carding, calendering, or other mechanical working of the fibers.
• mechanical force such as high pressure water jets, beating, carding, calendering, or other mechanical working of the fibers.
• one of the components of the plural-component fibers can be dissolved by a solvent applied to the fiber, such that segments formed of the undissolved component remain.
• U.S. Patent No. 5,783,503 to Gillespie et al. discloses splitting plural-component fibers during free fall from a spinneret from which the fibers are extruded, and prior to deposition of the fibers onto a collection surface such as a forming table or belt.
• U.S. Patent No. 5,783,503 discloses a number of possible techniques for splitting the fibers, including: drawing and stretching or attenuating the fibers in a pressurized gaseous stream of air or steam; developing a triboelectric charge in at least one of the components; applying an external field to the fibers; and subjecting the falling fibers to air turbulence. These techniques rely on a number of properties of the different polymer components, including: miscibility, differences in melting points, crystallinity, viscosity, conductivity, and the ability to develop a triboelectric charge.
• U.S. Patent No. 5,759,926 has a number of significant limitations. Because separation of the fiber segments is caused by adsorption of water, it may be necessary to expose the fibers to the hot aqueous solution for a substantial period of time. Specifically, the separation process can take up to thirty seconds to complete, thereby significantly limiting the rate at which the web can be transported and formed. Moreover, because the process requires application of a hot aqueous solution to the web, a drum drier is required to dry the web prior to bonding, which adds a time consuming step and substantially increases the cost and complexity of the system.
• in-line fiber splitting in a spunbond process is achieved by differential heat shrinkage of two or more components of a plural- component fiber, such as a ribbon-shaped bicomponent fiber.
• Two or more polymers that shrink to substantially different degrees upon application of heat are extruded from an array of orifices of a spinneret as interleaved or alternating components of plural- component fibers.
• the array of plural-component fibers is drawn through an aspirator and attenuated prior to being deposited on a web-forming belt. Once on the belt, the fiber web is conveyed to a heater which heats the web to a temperature sufficient to cause differential heat shrinkage of the polymer components, thereby causing the fiber segments formed of the components to separate. After fiber separation, the web is bonded to form the nonwoven fabric.
• the polymer components of the plural-component fibers of the present invention preferably have a difference in heat shrinkage of at least approximately ten percent. It has been found by the present inventors that a bicomponent ribbon-shaped fiber having alternating first and second fiber segments respectively formed of two different polymer components results in superior component separation and produces a nonwoven fabric with exceptional qualities. Heating of the web to cause differential shrinkage is accomplished using blown hot air, blown steam, radiant heat, or other methods of applying heat and combinations thereof. The heating unit, disposed along the web transport path, heats the fibers to a temperature sufficient to effect differential shrinkage and fiber splitting, preferably in less that one second.
• the quick separation obtained using differential heat shrinkage of the fiber components makes it possible to produce a spunbonded fabric, wherein component separation takes place in-line with fiber extrusion in a spunbond process. Specifically, when fiber component separation is achieved in seconds or less than a second, the web bonding can be done in an in-line operation immediately following fiber extrusion, web formation and fiber component separation.
• the in-line spunbond process of the present invention produces a fine denier nonwoven fabric having desirable properties such as improved bulkiness, softness, flexibility, drape, and barrier and filtration properties.
• Fig. 1 is a diagrammatic view of an apparatus for performing a spunbond process employing fiber splitting in line with fiber extrusion to form a nonwoven fabric.
• Fig. 2 is a cross-sectional view of a bicomponent fiber having a circular cross section and wedge-shaped segments.
• Fig. 3 is a cross-sectional view of a hollow bicomponent fiber having a circular cross section.
• Fig. 4 is a cross-sectional view of a five-segment bicomponent fiber having a cross-shaped cross section.
• Fig. 5 is a cross-sectional view of a nine-segment bicomponent fiber having a cross-shaped cross section.
• Fig. 6 is a cross-sectional view of a ten-segment ribbon-shaped bicomponent fiber.
• in-line fiber splitting in a spunbond process is achieved by differential heat shrinkage of two or more components of a plural-component fiber, such as a ribbon-shaped fiber or a fiber with another suitable cross-sectional shape.
• spunbond refers to a process of forming a nonwoven fabric or web from small diameter fibers or filaments produced by extruding molten polymers from orifices of a spinneret. The filaments are drawn as they cool and are randomly laid on a forming surface, such that the filaments form a nonwoven web. The web is subsequently bonded using one of several known techniques to form the nonwoven fabric.
• Fig. 1 diagrammatically illustrates an apparatus 10 for producing a nonwoven fabric according to the spunbond process of the present invention.
• Apparatus 10 includes hoppers 12 and 14 into which pellets of two different polymers, polymers A and B described hereinbelow, are respectively placed. Polymers A and B are respectively fed from hoppers 12 and 14 to screw extruders 16 and 18 which melt the polymers.
• the molten polymers respectively flow through heated pipes 20 and 22 to metering pumps 24 and 26, which in turn feed the two polymer streams to a suitable spin pack 28 with internal parts for forming bicomponent fibers of a chosen cross-section and number of segments.
• segment and “microfiber” refer to a portion of a fiber having a composition that is distinct from the composition of another portion of the fiber
• bicomponent refers to a fiber having two or more segments, wherein at least one of the segments comprises one material or component (e.g., a polymer), and the remaining segments comprise another, different material or component.
• plurical-component refers to a fiber having two or more segments, wherein each segment comprises one of at least two different materials or components which make up the fiber (thus, a bicomponent fiber is a type of plural-component fiber).
• Spin pack 28 includes a spinneret 30 with orifices 32 which shape the bicomponent fibers extruded therethrough.
• orifices 32 may be arranged in a substantially horizontal, rectangular array, with each orifice extruding an individual plural-component fiber.
• Figs. 2-6 Various bicomponent fiber cross-sections that are suitable for use with the present invention are shown in Figs. 2-6.
• a fiber having a substantially round cross- section with eight wedge-shaped segments or "pieces of pie” is shown in Fig. 2.
• the wedge-shaped segments are alternately formed of two different polymers A and B, such that adjacent segments are formed of different polymers. Fibers having the cross- section shown in Fig. 2 and methods of making them are disclosed in U.S. Patent No.
• Fig. 3 illustrates a plural-component fiber having a cross-section similar to that shown in Fig. 2, except that the fiber is hollow, such that the wedge-shaped segments do not extend completely to the center. Because the segments made of like polymers cannot be connected to each other near the fiber center, the segments of the hollow fiber shown in Fig. 3 more readily and consistently separate than those of the solid plural-component fiber shown in Fig. 2.
• Fibers of this type are disclosed in U.S. Patent Nos. 4,051 ,287 and 4,109,038, the disclosures of which are incorporated herein by reference in their entirety.
• Fig. 4 illustrates a five-segment plural-component fiber having a cross section in the shape of a cross, wherein four polymer A segments extend radially outward at four, 90°-spaced points from a central, polymer B segment.
• Fig. 5 illustrates another cross-shaped plural-component fiber cross section, having a central, polymer B segment, four, 90°-spaced polymer A segments extending radially from the central segment, and four additional polymer B segments extending radially further outward from the ends of the four polymer A segments, respectively, for a total of nine separable segments.
• a ten-segment bicomponent fiber having a ribbon-shaped cross-section with alternating polymer A and polymer B segments disposed side-by-side is shown in Fig. 6.
• Each segment adjoins adjacent segments along lines extending substantially perpendicular to the longer edge of the ribbon, such that the segments have a generally rectangular cross section. It has been experimentally found by the present inventors that, where splitting of the fiber segments is achieved using differential heat shrinkage of two different polymer components, the plural-component fiber having a ribbon- shaped cross-section provides faster and more complete segment separation relative to plural-component fibers having other cross sections.
• the ribbon-shaped fiber still results in a very soft fabric relative to other fiber cross-sections, because of the shape of the ribbon produces a very low bending modulus (i.e., the unseparated portions of the ribbon fibers can still twist and bend in three dimensions, and the adjoining separated portion of the fibers have a high degree of freedom to bend in different directions relative to each other).
• an array of bicomponent or plural-component fibers 34 exit the spinneret 30 of spin pack 28 and are pulled downward and attenuated by an aspirator 36 which is fed by compressed air or steam from pipe 38.
• Aspirator 36 can be, for example, of the gun type or of the slot type, extending across the full width of the fiber array, i.e., in the direction corresponding to the width of the web to be formed by the fibers.
• a typical spinneret and aspirator arrangement useful for this process is illustrated in U.S. Patent No. 3,802,817, the disclosure of which is incorporated herein by reference in its entirety.
• Aspirator 36 delivers attenuated fibers 40 onto a web-forming screen belt 42 which is supported and driven by rolls 44 and 46.
• a suction box 48 is connected to a fan (not shown) to pull room air (at the ambient temperature) through screen belt 42 and cause fibers 40 to form a nonwoven web on screen 42.
• the web is heated to cause differential heat shrinkage of the two component materials of the fibers. Specifically, when heated to a temperature below their melting points, one of polymers (e.g., polymer B) shrinks, relative to its unheated size, more than the other polymer (e.g., polymer A) shrinks relative to its unheated size.
• a difference in heat shrinkage between the two polymers can be measured as the percent shrinkage of polymer B minus the percent shrinkage of polymer A.
• the difference in heat shrinkage is significant, crimping and separation of the fiber segments occurs.
• a high degree of crimping and splitting (separation) of the plural-component fibers is desirable, since a lofty or bulky nonwoven fabric having good softness, flexibility and drape characteristics and barrier properties results. It has been experimentally found by the present inventors that two components of a plural-component fiber having a difference in heat shrinkage of at least approximately ten percent provide a high degree of rapid separation of the components of the fiber into individual segments under the heating conditions of the present invention, and higher heat shrinkage differences result in even more complete and rapid separation.
• the polymers of the extruded plural-component fibers preferably have a difference in heat shrinkage of at least approximately ten percent under the heating conditions applied in the system of the present invention (e.g., taking into account the velocity of the fibers exiting the aspirator, the fiber and microfiber deniers and the weight of the web per unit area, the speed of the belt, the temperature and duration of the heat applied and the type of heat). More preferably, the polymers of the extruded plural-component fibers have a difference in heat shrinkage of at least approximately twenty percent, and still more preferably greater than twenty-five percent.
• a particularly advantageous combination of polymers has been found by the present inventors to be the combination of polypropylene (polymer A) and polyethylene terepthalate (PET) modified with 20 mole percent purified isopthalic acid and a powdered transesterification inhibitor (GE Ultranox 626) (polymer B), which have a difference in heat shrinkage of approximately thirty percent under the heating conditions of the present invention.
• the web formed on web-forming belt 42 passes in close proximity to (e.g., directly under or over) a heating unit 50 which causes the temperature of the fibers of the web to increase to a temperature at which differential heat shrinkage of polymers A and B occurs, thereby causing the plural-component fibers to separate into their constituent segments. That is, the temperature of the web is raised to a temperature below the melting points of polymer A and polymer B but high enough to sufficiently shrink at least one of the two polymers to cause separation between adjacent segments of the fibers.
• the terms “separation” and “separate” connote substantial detachment of segments from adjacent segments along at least a substantial portion of the longitudinal extent of the segments, but do not require total separation (although total separation or nearly total separation is desirable and can be achieved with certain polymer and process combinations).
• some crimping of the fibers may occur in addition to fiber splitting to further increase the softness and bulkiness of the fabric.
• some degree of crimping of the fiber segments typically occurs at the time of initial shrinkage, the segments of the unseparated portions of the fibers experience significant crimping due to the shrinkage difference between the unseparated segments, and the segments of the separated portions of the fibers may also experience some degree of crimping, depending on the particular polymer components and the process conditions.
• Heating unit 50 can supply any type of heat suitable for causing differential heat shrinkage and separation of the fiber components, including, but not limited to: hot air blown through the web (convection heating); steam blown through the web; radiant heat; and combinations thereof.
• the terms “heater” and “heating unit” may include a single heater element or device or multiple heaters arranged serially along the web-conveying belt. It should be understood that, while the heat applied may be in the form of steam, separation of the components is caused by the heating of the fiber and not as a result of adsorption of moisture or because the heat is conveyed in the form of moisture.
• the polymer components of the plural-component fibers of the present invention need not be hydrophilic; in fact, the polymer components of the fibers of the present invention preferably are not hydrophilic.
• the use of heat to separate fiber segments by differential heat shrinkage in accordance with the present invention results in much faster separation than prior art systems relying on adsorption of water by a hydrophilic polymer to separate plural- component fibers.
• use of heat to separate the above-described polypropylene and modified PET polymers results in rapid and nearly total separation of the segments formed of these polymers when heat is applied to a portion of a moving web for less than approximately one second.
• the modified PET begins to experience significant heat shrinkage when the fibers are heated to temperatures above approximately 200 °F, which can be reached very quickly with blown hot air or steam or even radiant heat.
• the temperature of the web was rapidly raised to 250 °F ⁇ 15 °F, immediately causing a high degree shrinkage of the modified PET and, consequently, fiber segment separation (under these conditions, polypropylene does not experience significant shrinkage).
• the time required to heat a portion of the web in order to substantially complete the shrinkage process and cause separation of the fibers is a function of the fabric thickness or weight per unit area, with heating time increasing generally linearly with unit thickness or weight. Further, within the range of temperatures which cause differential heat shrinkage, higher temperatures reduce the time required to substantially complete the shrinkage process.
• the heating time can be controlled by the speed of the belt conveying the web and/or the length of the portion of the web directly receiving heat from the heater (i.e., the length of the heater in the belt moving direction).
• the heating parameters are such that differential shrinkage can be completed in less than approximately one second so that the heating unit is of a reasonable length at the belt speeds typically used in to manufacture nonwoven fabrics in an in-line spunbond process (e.g., hundreds of meters/minute).
• the web passes through an optional compaction roll 52 and then leaves the screen and passes through a nip formed by heated calender rolls 54 and 56.
• One of the calender rolls is embossed to have raised nodules which fuse the fibers together only at the points where the nodules contact the web, leaving the fibers between the bond points still bulky and giving the resultant bonded nonwoven fabric good flexibility and drape.
• the present invention is not limited to above-described bonding process, and other conventional bonding techniques can be employed, including, but not limited to: through-air bonding (particularly useful with the low melt temperature normally seen with high shrinkage components); needle punching; and hydroentangling (i.e., use of high-pressure water jets).
• through-air bonding particularly useful with the low melt temperature normally seen with high shrinkage components
• needle punching i.e., use of high-pressure water jets
• hydroentangling i.e., use of high-pressure water jets.
• through-air bonding technique as heat is applied to the web, the temperature of the web rises to a point at which differential shrinkage of the high-shrinkage polymer component occurs. As heat continues to be applied, the temperature of the web rises to a temperature to a point at which the high-shrinkage polymer becomes tacky and begins to melt, allowing the segments formed of high-shrinkage polymer to bond to adjacent polymers.
• differential heat shrinkage technique of the present invention can be applied to web or fabric forming processes that do not require bonding of the fibers.
• the differential heat shrinkage technique can be applied in spunlaid processes.
• one or more godets may be used prior to the aspirator for drawing and/or relaxing the fibers.
• a downstream godet may be operated at higher speed than an upstream godet to stretch the fibers, or a downstream godet may be operated at a lower speed than an upstream godet to relax the fibers.
• the above-described embodiment of the present invention relies principally on differential heat shrinkage of the web after deposition of the plural-component fibers on the web-forming surface
• measures may be taken to effect differential heat shrinkage and fiber splitting prior to deposition of the fibers onto the web-forming surface.
• Techniques which result in splitting or partial splitting of the fibers before laydown on the web-forming belt may result in a fabric with better coverage (free of open areas in the web) as well as the other advantageous fabric qualities described herein, as the fiber segments are able to lay down on the belt independently of each other, in a manner as if the segments had been actually spun with low deniers on the order of 0.1 denier/filament.
• the aforementioned godet(s) may be heated to assist the differential heat shrinkage of the fibers to facilitate splitting, and/or another conductive heating device, such as a hot plate, can be employed for this purpose.
• Hot air and/or steam can be applied to the fibers in the aspirator to cause the differential heat shrinkage fiber components to split before reaching the belt.
• a similar result can be achieved by direct heating of the aspirator to a temperature warm enough to induce differential shrinkage (but not warm enough to melt either component).
• splitting aids can also be employed, including, but not limited to: fluoropolymer or silicone compounds in one or more of the polymer components to make the components slippery and more prone to split; foaming agents in one or more of the components which induce swelling of one component relative to the other component; and use of ultrasonics in addition to heat to excite the two polymer components to enhance relative movement and splitting.
• the fine fiber segments separated by the system of the present invention produce a desirably softer fabric with greater loftiness and bulkiness than nonwoven fabrics made from known spunbond processes.
• Various additional improved fabric properties such as good fabric drape, high filtration, barrier properties, and coverage at low weight are also achieved with the ultra-low denier per filament resulting from the split fibers of the present invention.
• the nonwoven fabric formed by the process of the present invention is useful in any product where a fluffy nonwoven fabric is useful, such a thin sheets of padding.
• the nonwoven fabric of the present invention can be used in a variety of other commercial products including, but not limited to: softer diaper liners or other disposable absorbent articles; medical fabrics having barrier properties; and filtration media.
• a spinpack was utilized which produced 198 self-crimping fibers in a rectangular array, each fiber having a ten-segment, ribbon cross-section, with alternating polymer A and polymer B segments, as shown in Fig. 6.
• Polymers A and B were pumped at equal rates of 0.20 grams/minute/spinneret orifice, totaling 0.41 grams/minute/spinneret orifice.
• Each spinneret orifice was 0.8 mm long and had a 0.2 mm x 2.0 mm cross- section to produce the ribbon-shaped fibers.
• Polymer A was 12 MFR polypropylene.
• Polymer B was a high shrinkage type of co-polyester obtained from Amoco Chemical Company, specifically, polyethylene terepthalate modified with 20 mole percent purified isopthalic acid and a powdered transesterification inhibitor (GE Ultranox 626).
• the extruded ribbon fibers were drawn through an aspirator having a six inch wide slot with a 0.015 inch gap. Room temperature compressed air at 20 psig was used to feed the aspirator, producing a fiber velocity through the six inch wide slot aspirator of approximately 3000 meters/minute. No appreciable splitting of the ribbon fibers exiting the aspirator was observed.
• the attenuated fibers exiting the aspirator were delivered onto a screen belt, forming a web four inches wide.
• the belt speed was set to 30 meters/minute to yield a fabric weight of 1.6 ounces/square yard.
• the fiber denier was 1.6, giving 0.16 denier for each of the 10 segments in each ribbon fiber.
• a radiant heater was positioned one inch above the web lying on the belt. The heating area was approximately 20 inches in the belt running direction and six inches in the width direction. Twelve hundred (1200) watts of radiant heat (approximately 10 watts/sq.
• heating the web to 250°F ⁇ 15°F for approximately 1 second) from the heater was used to differentially shrink the fibers, thereby crimping and separating the individual fiber segments to yield a very soft, bulky web.
• the web was passed through a compaction roll having a compaction roll pressure of 40 pounds per inch of width.
• the web was hot pattern calendered, with a calender roll temperature of 220°F, yielding a fabric with good softness and drape as well as exceptional coverage, filtration and barrier properties.
• Example 1 was repeated with the same setup, except that the pump speeds were reduced equally so that each spinning orifice delivered 0.18 grams/minute (0.09 grams/minute for each polymer), and the aspirator air pressure was reduced to 15 psig, resulting in a fiber exit velocity from the aspirator of 1900 meters/minute.
• the fiber denier was 1.1 (0.11 denier per segment).
• the belt speed of 30 meters/minute yielded a fabric weight of 0.5 ounce/square yard of fabric. Again, a desirable fabric with exceptional softness and other properties was produced.
• Example 1 was repeated with the same setup, except that the pump speeds were increased equally so that each spinning orifice delivered 0.7 grams/minute (0.35 grams/minute for each polymer), and the aspirator air pressure was increased to 25 psig, resulting in a fiber exit velocity from the aspirator of 5000 meters/minute, and the fiber denier was 2.5 (0.25 denier per segment).
• the belt speed of 30 meters/minute yielded a fabric weight of 0.5 ounce/square yard of fabric. Again, a desirable fabric with exceptional softness and other properties was produced.
• the above example can be repeated with ribbon fibers having 20 or 40 segments of alternating A and B polymers.
• a 20 segment fiber results in a 0.12 denier per segment fabric
• a 40 segment fiber results in a 0.06 denier per segment fabric.
• the belt speed is preferably an order of magnitude higher than the belt speed used in the above experiment (e.g., up to approximately 600 mpm).
• the rapid (e.g., a fraction of a second) separation of the plural-component fibers achieved by the differential heat shrinkage technique of the present invention allows nonwoven fabrics formed from split, plural-component fibers to be manufactured in an in-line spunbond process at these high belt speeds with a heating unit and belt of a modest length, thereby making in-line spunbond processing of splittable plural- component fibers more economically attractive.
• a fine denier nonwoven fabric having desirable properties such improved bulkiness, softness, drape, and barrier properties can be produced from the in-line spunbond process of the present invention employing differential heat shrinkage of ribbon-shaped plural-component fibers to cause a high degree of fiber segment separation.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Nonwoven Fabrics (AREA)
• Filtering Materials (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Multicomponent Fibers (AREA)

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• 1998
  • 1998-10-09 JP JP2000515740A patent/JP2001519488A/ja active Pending
  • 1998-10-09 AU AU10763/99A patent/AU1076399A/en not_active Abandoned
  • 1998-10-09 EP EP98953364A patent/EP1024940A4/de not_active Withdrawn
  • 1998-10-09 WO PCT/US1998/021378 patent/WO1999019131A1/en not_active Application Discontinuation

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