US20240141570A1 - Process and apparatus for producing a voluminous nonwoven fabric - Google Patents

Process and apparatus for producing a voluminous nonwoven fabric Download PDF

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Publication number
US20240141570A1
US20240141570A1 US18/318,751 US202318318751A US2024141570A1 US 20240141570 A1 US20240141570 A1 US 20240141570A1 US 202318318751 A US202318318751 A US 202318318751A US 2024141570 A1 US2024141570 A1 US 2024141570A1
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Prior art keywords
filaments
nonwoven fabric
calendar
sub
process according
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Rosaldo Fare'
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Fare' SpA A Socio Unico
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Fare' SpA A Socio Unico
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    • 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
    • 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
    • D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
    • D04H3/16—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion
    • 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
    • D01D5/22—Formation of filaments, threads, or the like with a crimped or curled structure; with a special structure to simulate wool
    • 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
    • D01D5/32—Side-by-side structure; Spinnerette packs therefor
    • D—TEXTILES; PAPER
    • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
    • D02G—CRIMPING OR CURLING FIBRES, FILAMENTS, THREADS, OR YARNS; YARNS OR THREADS
    • D02G1/00—Producing crimped or curled fibres, filaments, yarns, or threads, giving them latent characteristics
    • D02G1/02—Producing crimped or curled fibres, filaments, yarns, or threads, giving them latent characteristics by twisting, fixing the twist and backtwisting, i.e. by imparting false twist
    • D02G1/04—Devices for imparting false twist
    • D02G1/06—Spindles
    • 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
    • D04H3/005—Synthetic yarns or filaments
    • 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
    • D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
    • D04H3/14—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with bonds between thermoplastic yarns or filaments produced by welding
    • D04H3/147—Composite yarns or filaments
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06C—FINISHING, DRESSING, TENTERING OR STRETCHING TEXTILE FABRICS
    • D06C15/00—Calendering, pressing, ironing, glossing or glazing textile fabrics
    • D06C15/02—Calendering, pressing, ironing, glossing or glazing textile fabrics between co-operating press or calender rolls
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06C—FINISHING, DRESSING, TENTERING OR STRETCHING TEXTILE FABRICS
    • D06C15/00—Calendering, pressing, ironing, glossing or glazing textile fabrics
    • D06C15/08—Rollers therefor
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06C—FINISHING, DRESSING, TENTERING OR STRETCHING TEXTILE FABRICS
    • D06C7/00—Heating or cooling textile fabrics
    • D06C7/02—Setting

Definitions

  • the present invention relates to a process and apparatus for producing a nonwoven fabric and, in particular, voluminous nonwoven fabrics obtained by spunbond process.
  • spunbond fabrics are obtained by extruding, drawing and depositing a plurality of filaments of plastic material on a conveyor belt.
  • the filaments deposited on the belt are then constrained or bonded together at a plurality of points, by means of different processes, such as for example calendaring, applying air or water jets, or welding, etc.
  • a typical plant for producing spunbond filaments comprises a spinning head fed by extruders, a drawing unit and a deposition unit for depositing the drawn filaments on a movable support (collecting surface) where the nonwoven fabric is formed.
  • the nonwoven fabrics of spunbond type are used in various fields such as for example medical and sanitary ones, but also in the geotechnical field, in civil engineering, in building construction. Depending on the application, the nonwoven fabric must have different mechanical characteristics in terms of finishing, resistance to particular agents, etc., so as to meet the different requirements of the sectors of use.
  • Nonwoven fabrics made from filaments formed by of two or more components, so as to be able to exploit the different characteristics of the materials used, are known in the art.
  • the two sub-filaments may be made of materials having different characteristics, whereby the multicomponent filament is initially extruded and drawn, thus forming a not-crimped continuous filament.
  • the multicomponent filament is deposited on the collector, the two sub-filaments behave in a different way, thus crimping the multicomponent filament.
  • the two sub-filaments may be made of materials having different coefficients of thermal expansion. If the multicomponent filament is subjected to thermal treatment, the two sub-filaments expand/shrink in a different way with respect to one another, thereby crimping the multicomponent filament.
  • Pat. No. 3,458,390 teaches to make side-by-side multicomponent filaments in which the contact surface between the two filaments generates a shape coupling (by means of “undercuts”), so as to mechanically constrain or entangle the sub-filaments to one another. Therefore, the two sub-filaments are joined by such mechanical constraint and do not split during the required treatments (for example thermal treatments). It is difficult to obtain such a shape. Moreover, excessive stress may cause the multicomponent filament to undesirably split. Finally, it is not known how to make a nonwoven fabric by such multicomponent filament.
  • a process for producing a nonwoven fabric comprises the steps of:
  • steps (c) and (d) are performed substantially simultaneously by means of a heated calendar.
  • steps (c) and (d) at least part of the filaments of the nonwoven fabric are subjected to bonding, that is, at least part of the filaments are thermally constrained together so as to provide the nonwoven fabric with at least partial consolidation and stabilization of the nonwoven fabric.
  • the calendar provides enough space for the fibers of the nonwoven fabric (i.e., where the fibers are not subjected to bonding) that allows them to crimp so that, as a result, the thickness of the nonwoven fabric increases.
  • the use of a heated calendar allows at least a portion of the filaments to be entangled at some constraining points (or zones) of the nonwoven fabric and at least a portion of the filaments to crimp at points where they are not constrained to each other. Through such crimping, the volume (particularly the thickness) of the nonwoven fabric can then increase at the portions of the nonwoven fabric where the filaments are not constrained together, thus producing a voluminous nonwoven fabric.
  • the calendar allows a constraint between the filaments of the nonwoven fabric to be achieved.
  • both an increase in the volume of the nonwoven fabric and a partial consolidation thereof can be substantially simultaneously achieved.
  • the composition of the nonwoven fabric treated by the calendar is substantially homogeneous, that is, each portion of the nonwoven fabric has essentially the same filament composition compared with the other portions of the nonwoven fabric.
  • the preferred solution has a single type of filaments for the entire nonwoven fabric and they are configured to crimp due to heating.
  • the fabric is single-layered, so that the crimping of the filaments of a layer of nonwoven fabric is not limited by filaments (which do not crimp) of a different layer of fabric.
  • the nonwoven fabric treated by the calendar is preferably not-bonded (i.e., it typically has a bonding area between 0% and 1%) before treatment by means of the heated calendar.
  • the device for extruding filaments i.e., the device that forms the nonwoven fabric, comprising the aforementioned spinneret
  • the heated calendar is typically placed in the plant immediately downstream of the filament extruding device.
  • the filament extruding device there are no elements adapted to bond or heat the nonwoven fabric.
  • the calendar is configured to define on the nonwoven fabric a bonding area between 5% and 25%, more preferably between 7% and 18%.
  • the concept of bonding area is well-known in the art and is commonly expressed as the (percent) ratio of the constrained area of nonwoven fabric in a surface unit to the area of that surface unit.
  • the bonding area is the ratio of the sum of the constrained areas of nonwoven fabric in that portion to the area of the portion itself.
  • a 10% bonding area implies that, in a surface unit of the nonwoven fabric, 10% of the area of the nonwoven fabric portion is occupied by filaments constrained to each other, and 90% of the area of the nonwoven fabric is occupied by filaments not constrained to each other, i.e., not yet consolidated with each other.
  • the bonding area is low enough to provide free space in the nonwoven fabric for the filaments to crimp, while at the same time ensuring sufficient consolidation of the fabric at the constraining points, that is, at the points where the filaments are consolidated with each other.
  • the volume (particularly the thickness) of the nonwoven fabric increases at the portions that have not been constrained, i.e., entangled, to each other, while the thickness of the nonwoven fabric remains essentially unchanged at the bonding points or zones.
  • the calendar typically has protrusions, that is, there are protrusions on the surface of at least one of the rollers forming the calendar.
  • the calendar comprises a pair of rollers, in which a roller has protrusions whereas the remaining roller has a smooth surface, which therefore typically acts as a countering surface for the protrusions, i.e., the nonwoven fabric treated by the calendar is compressed into the space between the protrusions of the first roller and the substantially smooth surface of the second roller.
  • the calendar has less than 50 protrusions per cm 2 , preferably less than 40 protrusions per cm 2 , more preferably between 5 and 30 protrusions per cm 2 .
  • the number of protrusions per surface unit of the calendar contributes to define the bonding area that the calendar can provide to the nonwoven fabric.
  • the bonding area is typically proportional to the number of protrusions per surface unit of the heated calendar.
  • the calendar is heated to a temperature higher than 100° C., more preferably higher than 130° C., even more preferably to a temperature of about 160° C.
  • the calendar temperature is typically chosen according to the type of polymer used in filament production, and in particular according to the melting and/or softening points of the polymers used in the production of the nonwoven filaments.
  • the calendar is heated to a temperature above the softening point of one of the materials that form the filaments of the nonwoven fabric, typically above the melting point of one of the materials that form the filaments.
  • the filaments before the treatment by the heated calendar, are in an essentially non-crimped condition, that is, the filaments begin to crimp at the heated calendar.
  • crimped and non-crimped condition of a filament is known to the field technician and, in particular, in a non-crimped condition the filaments are substantially devoid of crimps.
  • Some crimped filaments on the other hand, have a plurality of crimps and a wavy, irregular pattern such that the length of a crimped filament is significantly less than the length of the same filament in the non-crimped condition.
  • the filaments of the present invention are therefore deposited in a preferably non-crimped manner. Therefore, when the non-crimped filaments are deposited, they exhibit a “crimp percentage” typically greater than 50 percent, and preferably greater than 70 percent.
  • the “crimp percentage”, known in the art, can be for example measured by making two signs spaced from one another on a filament to be tested and measuring the distance between the two signs along a straight line. The same filament is then extended (i.e. made straight) and the distance between the two signs is measured again. The percentage ratio between the first value and the second value of the distance, as known, is the value of the “crimp percentage”.
  • crimped filaments are considered those having a radius of curvature less than 5 mm in the relaxed state.
  • step (d) in which by passing through a heated calendar the thickness of the nonwoven fabric increased, the nonwoven fabric undergoes a cooling step.
  • a cooling step can, for example, help to set the properties of the nonwoven fabric and also to prevent heated filaments from adhering to the device that moves the nonwoven fabric.
  • the cooling step is carried out by cooling means comprising at least one of: a cooling device configured to direct a gas flow against the nonwoven fabric at a temperature between 30° C. and 140° C., for example; a suction roller; a cooled conveyor belt.
  • a cooling device configured to direct a gas flow against the nonwoven fabric at a temperature between 30° C. and 140° C., for example; a suction roller; a cooled conveyor belt.
  • a cooling device configured to direct a flow of gas against the nonwoven fabric can be configured to direct a gas flow along a direction incident, preferably substantially perpendicular, to the nonwoven fabric.
  • a suction roller can be equipped with an air suction system, so as to simultaneously attract and cool the nonwoven fabric.
  • a cooled conveyor belt can be cooled by means known in the art and not described in detail herein, for example air suction means can be used.
  • step (e) of setting the nonwoven fabric comprises additional calendaring of the nonwoven fabric.
  • additional calendaring allows additional cohesion to be performed at several points in the nonwoven fabric.
  • the filaments extruded from the spinneret in step (a) are at least bicomponent filaments.
  • Such bicomponent filaments comprise two sub-filaments adhered to each other.
  • the two sub-filaments are extruded according to a side-by-side configuration so as to form, between the two sub-filaments, a contact surface which, in the filament cross-section, has at least one inflection point so as to provide a substantially wavy conformation.
  • the two sub-filaments are preferably made of materials having different melting temperature and/or different viscosity.
  • a further aspect of the present invention relates to a calendar for the treatment of nonwoven fabrics, comprising heating elements and configured to define, on a nonwoven fabric, a bonding area between 5% and 25%, more preferably between 7% and 18%, and characterized by having a number of protrusions lower than 50 protrusions per cm 2 , more preferably lower than 40 protrusions per cm 2 , even more preferably between 5 and 30 protrusions per cm 2 .
  • the heating elements allow heat treatment to be performed on the fabric, while the bonding area gives the filaments thereof enough space to crimp, so that the volume (thickness) of the nonwoven fabric can be increased.
  • Such heating elements preferably comprise a fluidic circuit inside the calendar in which a heated liquid, typically diathermal oil, flows.
  • calendars heated by electric means are known.
  • the protrusions on the calendar may have different shapes in different embodiments of the present invention.
  • the protrusions can be substantially shaped as a cylinder, truncated cone, truncated pyramid.
  • the density of protrusions on the outer surface of the calendar contributes to define the bonding area of the nonwoven fabric treated with the calendar itself.
  • the area of the calendar surface without protrusions allows the thickness of the nonwoven fabric to be increased because crimping of at least part of the nonwoven fabric filaments is allowed in that area.
  • a further aspect of the present invention relates to an apparatus for making a nonwoven fabric, comprising a spinneret for extruding a plurality of filaments and collecting means to collect the filaments and form a nonwoven fabric, a calendar heated according to one or more of the aspects discussed above and a device for thermal treatment and at least one setting device.
  • the spinneret of the apparatus is configured so as to extrude a bicomponent filament comprising two sub-filaments arranged in a side-by-side configuration in which, in cross section, the contact surface between the two sub-filaments has at least one inflection, so as to define a substantially wave-like shape.
  • the collecting means to collect filaments are typically in the form of a conveyor belt or the like, are typically perforated or otherwise gas permeable.
  • Appropriate means can be provided below the filament collecting means so that a depression is created at the zone in which the filaments are deposited on the filament collecting means.
  • the heated calendar for nonwoven fabrics is characterized by having heating elements that allow the calendar to be heated.
  • Such a calendar is also characterized by protrusions that allow the bonding of the nonwoven fabric to be performed. In areas where no bonding of the nonwoven fabric occurs, the action of the heated calendar allows an increase in thickness of the nonwoven fabric by crimping at least part of the filaments of the nonwoven fabric.
  • various setting or bonding devices are known in the art and can be used in the present invention so as to consolidate the bulked layer of the nonwoven fabric.
  • the setting device may comprise an additional calendar equipped with reliefs so as to impart additional embossing to the nonwoven fabric.
  • An additional aspect of the present invention further relates to a nonwoven fabric as obtainable by a process according to one or more of the aspects discussed above, wherein the nonwoven fabric comprises a number of constrained areas between 4 and 50 per cm 2 , preferably between 4 and 40 per cm 2 , more preferably between 5 and 30 per cm 2 , so as to preferably define a bonding area between 5% and 25%, more preferably between 7% and 18%.
  • FIG. 1 is a schematic view of an apparatus for producing a nonwoven fabric according to a first embodiment
  • FIG. 2 shows a top schematic view of a nonwoven fabric of FIG. 1 ;
  • FIGS. 3 A, 3 B are sectional views of possible filaments that can be used to form a nonwoven fabric with an apparatus according to the present invention.
  • An apparatus 10 for producing a nonwoven fabric 150 comprises, in a known manner, a device 1 for extruding continuous filaments 100 and collecting means 2 for depositing and moving continuous filaments 100 in a forward direction D.
  • a device 1 for extruding continuous filaments 100 and collecting means 2 for depositing and moving continuous filaments 100 in a forward direction D.
  • Various devices 1 known in the art can be used for the purpose.
  • the devices described in Patent Applications WO2008/072278 and WO2008/075176 can be used.
  • such devices have a spinneret 1 a for extruding a plurality of filaments 100 , typically followed by a drawing unit 1 b .
  • a cooling zone is arranged upstream of the drawing unit to direct air flows toward the filaments 100 after the extrusion from the spinneret 1 a , so that they are cooled appropriately.
  • Patent EP1939334 describes a possible cooling chamber that can be used in the present invention; this Patent describes also a device for extruding and collecting filaments which is adapted to be used in the present invention.
  • the device 1 At its outlet (i.e., the portion from which the nonwoven fabric exits the device 1 ), the device 1 comprises a pair of rollers 9 , wherein the rollers are typically provided with a smooth outer surface. Passing the filament layer through the two rollers 9 allows the filaments of the nonwoven fabric to be compacted. At least one of the rollers 9 can be heated, so as to carry out a first step of crimping at least one portion of the filaments 100 , thereby allowing an initial increase in the volume (thickness) of the nonwoven fabric 150 . Typically, the rollers 9 are configured so as to avoid forming a bonding between the filaments 100 .
  • the heating temperature of the rollers 9 is preferably lower than the heating temperature of the calendar 20 , which is better described below.
  • Preferred temperatures for the rollers 9 are between 50° C. and 140° C., typically around 90° C. and in any case chosen according to the nature of the polymers used, i.e., typically lower than at least the melting temperature of the materials forming the filaments 100 .
  • the coupling between the rollers 9 and the nonwoven fabric preferably prevents, or at least limits, the inflow of ambient air into the device 1 at the collecting means 2 .
  • the continuous filaments 100 can have different shapes.
  • the continuous filaments 100 are bicomponent filaments, i.e. they have two sub-filaments 100 a , 100 b coupled to one another.
  • the bicomponent filament 100 can take different configurations, such as core-sheath or, more preferably, side-by-side.
  • the filaments 100 comprise two sub-filaments 100 a , 100 b made by coextruding two materials, typically polymers.
  • the sub-filaments 100 a , 100 b are arranged in side-by-side configuration.
  • a particular configuration of the filaments 100 is described in detail in the co-pending Application EP16198713.
  • the materials for the two sub-filaments 100 a , 100 b are preferably selected among PP, coPP, PE, CoPE, PET, CoPET, PA, PLA. Preferred combinations are: PP/PE, PP/CoPP, PP/PP, PET/PP, PET/CoPET, PA/PP, PLA/PP, PLA/PE.
  • the materials of the sub-filaments 100 a , 100 b are selected so as to allow them to crimp during a heat treatment.
  • the difference between the melting temperature of the sub-filaments 100 a and the melting temperature of the sub-filaments 100 b is different by at least 10° C., and preferably by at least 20° C.; the two materials of the sub-filaments 100 a , 100 b have different viscosity, preferably with a difference of more than 20%, when measured by the same method and under the same conditions.
  • the two materials can be tested with the same viscometer (e.g., rotational or capillary viscometer) or, more generally, the viscosity can be determined by a common method defined in a recognized standard (e.g., ASTM D3835).
  • the preferred configuration of the two sub-filaments 100 a , 100 b is the side-by-side one in which the two sub-filaments are provided next to each other so that, in section, the two sub-filaments 100 a , 100 b are divided by a line representing the contact surface 105 .
  • the contact surface 105 has at least one inflection so as to define a wavy shape.
  • the contact surface has a shape that shows at least one peak 3 , 32 alternating with at least one trough 33 .
  • “peaks” and “troughs” are the crests 3 , 32 , 33 formed by the wave, i.e. the maxima and the minima.
  • the peaks 3 , 32 are directed in the opposite direction with respect to the troughs 33 . It should be noted that, typically, the difference between the troughs 33 and the peaks 3 , 32 is given only by the orientation chosen for the section of the filament.
  • the section of the contact surface 105 forms a wave with at least two crests 3 , 32 , 33 ; in particular, in preferred embodiments there are exactly three crests 3 , 32 , 33 .
  • the period T of the wave is between 40% and 100% of the length of the diameter of the multicomponent filament 100 .
  • the “diameter” of the multicomponent filament 100 it should be noted that for convenience's sake, reference will be made to the “diameter” of the multicomponent filament 100 . However, the following description can be applied also to the case of a not-circular filament section. In this case, the “diameter” should be considered as the greatest dimension of the section. If the troughs 33 and the peaks 3 , 32 have the same length, then as a result the length of each trough and peak is preferably between 20% and 50% of the diameter (or between 1 ⁇ 5 and 1 ⁇ 2 of the diameter).
  • the period “T” of the wave is the sum of the lengths of a tough and a peak.
  • the period T may also be measured as the distance between two subsequent peaks (or toughs).
  • the contact surface 105 changes at least once its curvature, i.e. has at least one inflection.
  • the section of the contact surface covers at least one period of the waveform. More preferably, the contact surface has at least two peaks and one trough, thus covering at least 1.5 periods of the waveform.
  • the waveform meets the edge of the filament section at a middle point between trough and peak, i.e. far from the trough and/or the peak adjacent to the edge.
  • the wave shape is substantially sinusoidal. Note that, given the small size of the filament section, the waveform will actually approximate to a sinusoid. Specifically, the ideal shape of the section of the filament 100 , having a length of 1.5 periods and a strictly sinusoidal shape, is shown in FIG. 3 A .
  • FIG. 3 B shows a possible real pattern of the section of the contact surface 105 , with the wavelength of the contact surface slightly longer than the period T, the peaks cut off at the edge of the section and the wave shape approximating a sinusoid without strictly complying with its geometrical parameters.
  • collecting means 2 typically in the form of a conveyor belt or the like, that allows the filaments 100 to be transported in a forward direction D.
  • the collecting means 2 are typically perforated or otherwise gas permeable.
  • Appropriate means can be provided below the collecting means 2 so that a depression is created at the zone in which the filaments 100 are deposited on the collecting means 2 themselves.
  • the apparatus 10 is configured so as to form a substantially homogeneous nonwoven fabric in which the composition of filaments is substantially constant throughout the entire volume of the nonwoven fabric.
  • the entire volume of the nonwoven fabric is formed by a single type of filament.
  • the nonwoven fabric is therefore preferably single-layered, or otherwise formed by several layers having composition identical to one another.
  • the apparatus 10 further comprises a heated calendar 20 downstream of the device 1 for extruding filaments 100 .
  • the heated calendar 20 is typically arranged immediately downstream of the device 1 for extruding filaments 100 .
  • the apparatus does not have any devices adapted to thermally treat, specifically heat, and/or bond, the nonwoven fabric arranged between the device 1 for extruding filaments 100 and the heated calendar 20 .
  • This heated calendar 20 comprises a plurality of rollers 20 a , 20 b , preferably a pair of rollers 20 a , 20 b , and heating elements 200 .
  • the heating elements 200 preferably comprise a fluidic circuit which is arranged inside the heated calendar 20 and in which a heated liquid, typically diathermal oil, flows.
  • a heated liquid typically diathermal oil
  • alternative heating elements are possible, such as electric means adapted to heat the calendar 20 .
  • Protrusions 21 extend on the outer surface 60 of at least one of the rollers 20 b .
  • the heated calendar 20 has a pair of rollers 20 a , 20 b , in which a first roller 20 b has protrusions on its surface, while the second roller 20 a has a substantially smooth surface.
  • the smooth surface acts as a countering element for the protrusions 21 of the other roller.
  • the roller with the protrusions 21 is the one arranged, in use, above the nonwoven fabric 150 .
  • This heated calendar 20 is configured to define a bonding area between 5% and 25%.
  • the bonding area is a concept known in the art as the ratio (typically expressed as a percentage) of the sum of the constrained areas 2011 (i.e., the areas of the nonwoven fabric where the filaments are subject to constraints) in a surface unit to the area of the surface unit 202 of the nonwoven fabric 150 .
  • the bonding area is between 5% and 25%, more preferably between 7% and 18%.
  • the surface unit can be chosen as any area, preferably square shaped, whose dimensions may contain a significant number of constrained areas 2011 .
  • a preferred surface unit for calculating the bonding area is an area on the surface of the nonwoven fabric having dimensions D 1 equal to 10 cm and D 2 equal to 10 cm.
  • the bonding area can be calculated as the ratio of the sum of the constrained areas 2011 in the surface unit to the area of the surface unit 202 of the nonwoven fabric 150 itself, which is calculated, in the case of a square unit, as D 1 multiplied by D 2 .
  • the bonding area can be expressed as a percentage by multiplying by a factor of 100 said ratio of the sum of the constrained areas 2011 to the area of the surface unit 202 of the nonwoven fabric 150 .
  • the heated calendar 20 comprises a plurality of rollers, preferably a pair of rollers 20 a , 20 b .
  • the outer surface 60 of at least one of the rollers 20 a , 20 b is provided with protrusions 21 .
  • the ratio of the number of protrusions 21 on the outer surface 60 of a roller 20 a , 20 b to the outer surface 60 of the same roller defines the amount of protrusions 21 per surface unit.
  • the number of protrusions 21 per cm 2 is between 4 and 50 protrusions per cm 2 , preferably between 4 and 40 protrusions per cm 2 , more preferably between 5 and 30 protrusions per cm 2 .
  • the number of protrusions 21 per cm 2 i.e. the density of protrusions 21 , contributes to define the bonding area since the greater the number of protrusions 21 , the greater the number of constrained areas 2011 , i.e. the greater the numerator of the formula discussed above to calculate the bonding area.
  • the number of protrusions 21 per cm 2 of the calendar corresponds to the density of the constrained areas 2011 formed on the nonwoven fabric 150 by means of the heated calendar 20 itself.
  • the nonwoven fabric 150 comprises a number of constrained areas 2011 between 4 and 50 per cm 2 , preferably between 4 and 40 per cm 2 , more preferably between 5 and 30 per cm 2 .
  • the apparatus 10 comprises a cooling device 5 arranged downstream of the heated calendar 20 .
  • a cooling device 5 may be equipped with means 55 to direct a gas flow G 3 , preferably air, against the nonwoven fabric.
  • a gas flow G 3 preferably air
  • the temperature of the gas flow G 3 is between 30 and 140° C.
  • a cooling device may comprise a surface 51 , 52 , and preferably two surfaces 51 , 52 , arranged parallel to the forward direction D of the nonwoven fabric 150 , and preferably movable.
  • the cooling device 5 can be configured so as to emit or suction gas G 3 from at least one of these surfaces.
  • the direction of the gas flow G 3 can be incident to the nonwoven fabric 150 and preferably substantially perpendicular to the nonwoven fabric 150 .
  • the gas flow G 3 is typically oriented so as to pass through the nonwoven fabric in the opposite direction with respect to the gravity, that is, from bottom to top, although the possibility of directing the gas flow G 3 from top to bottom is not excluded.
  • the apparatus 10 comprises a suction roller, not shown in the figures, equipped with an air suction system, so as to simultaneously attract and cool the nonwoven fabric 150 .
  • the apparatus 10 may comprise a cooled conveyor belt 8 to cool the nonwoven fabric 150 by means known in the art and not described in detail herein, such as by air suction means.
  • the apparatus 10 Downstream of the heated calendar 20 , considering the forward direction D of the nonwoven fabric 150 , and possibly also downstream of the at least one cooling device 5 , if any, the apparatus 10 typically comprises an additional setting device 7 .
  • Various setting devices are known in the art and can be used in the present invention so as to further consolidate the nonwoven fabric 150 .
  • the setting device 7 comprises a second calendar.
  • This second calendar may have reliefs so that additional embossing can be imparted to the nonwoven fabric 150 in order to perform further cohesion at different points of the nonwoven fabric 150 .
  • Some filaments 100 in use, are extruded from the spinneret 1 a and deposited on the collecting means 2 , typically after being passed through a drawing unit 1 b.
  • the filaments 100 are deposited in a non-crimped condition on the collecting means 2 , that is, they are essentially devoid of crimps when deposited on the collecting means 2 .
  • the thickness H 1 of the nonwoven fabric 150 deposited on the collecting means 2 is typically comparable to that of standard spunbond nonwoven fabrics made from single-component or bicomponent filaments.
  • the filaments 100 are bicomponent filaments typically comprising two sub-filaments 100 a , 100 b next to each other in a side-by-side configuration, with the contact surface preferably wave-shaped when viewed in cross section.
  • the first sub-filament 100 a is extruded under a constant pressure P 1 .
  • the extrusion pressure, i.e. the spinning pressure, of the second sub-filament varies, for example in a sinusoidal way, between to values P 0 and P 2 .
  • P 0 is less than P 1
  • P 2 is greater than P 1 .
  • the second sub-filament 100 b forms a protrusion within the first sub-filament P 1 , where the second sub-filament is extruded under pressure P 2 (or under a pressure higher than the pressure of the first sub-filament 100 a ).
  • the first sub-filament forms a protrusion within the second sub-filament 100 b , where the second sub-filament 100 b is extruded under a pressure P 0 (or a pressure lower than the pressure of the first filament).
  • the extrusion pressure can be varied at different areas of both the sub-filaments 100 a , 100 b .
  • the second sub-filament forms a protrusion within the first sub-filament and vice versa, where the pressure of the second sub-filament is greater than the pressure of the first sub-filament.
  • the filaments 100 When deposited on the collecting means, the filaments 100 form a nonwoven fabric 150 with thickness H 1 .
  • the filaments 100 are deposited on the belt in a random manner that results in a disordered distribution but substantially uniform density of the filaments.
  • the nonwoven fabric exits the device 1 it passes between two rollers 9 typically provided with smooth outer surfaces. This allows the filaments of the nonwoven fabric to be compacted.
  • a first step of crimping at least one portion of the filaments 100 can be further carried out, thereby allowing an initial increase in the volume (thickness) of the nonwoven fabric 150 .
  • the temperature of the rollers 9 is typically chosen so as to avoid forming a bonding between the filaments 100 .
  • the upper cylinder can be provided with means to heat it to a temperature preferably between 50° C. and 140° C., usually around 90° C. and in any case chosen according to the nature of the polymers used and able to provide a first cohesion of the filaments.
  • the coupling between the rollers 9 and the nonwoven fabric preferably prevents, or at least limits, the inflow of ambient air into the device 1 at the collecting means 2 .
  • the nonwoven fabric 150 is treated so that its volume (thickness) is increased by means of a heated calendar 20 equipped with protrusions 21 .
  • a plurality of constrained areas 2011 can be obtained on the nonwoven fabric, i.e. areas in which the filaments 100 are constrained to each other.
  • the spaces between these constrained areas 2011 allow the filaments to crimp in these spaces.
  • the nonwoven fabric increases its volume and in particular achieves a thickness H 2 that is greater than the thickness H 1 of the nonwoven fabric 150 before the calendaring process.
  • the thickness H 2 of the nonwoven fabric 150 increases, as described above, at the zones that have not been constrained, i.e., entangled by the protrusions 21 of the heated calendar 20 .
  • the increase in thickness H 2 is therefore “driven” by defining the constrained areas 2011 .
  • the composition of the filaments 100 in the nonwoven fabric is basically uniform.
  • all filaments 100 of the nonwoven fabric have the same composition, so they can be all crimped by the heated calendar 20 .
  • the final layout of the nonwoven fabric can be determined by appropriately selecting the distribution of the protrusions 21 , as this actually helps to define the bonding area and, accordingly, the possibility of increasing the thickness H 2 .
  • the nonwoven fabric 150 is cooled, for example by one or more of the above-described cooling devices 5 , vacuum roller and cooled conveyor belt 8 .
  • the cooling device 5 is configured to direct a gas flow G 3 against the nonwoven fabric 150 in which said gas flow G 3 is directed along a direction incident, preferably substantially perpendicular, to the forward direction of the nonwoven fabric 150 .
  • a suction roller not shown in figure, can be equipped with an air suction system, so as to simultaneously attract and cool the nonwoven fabric 150 by suction.
  • a cooled conveyor belt 8 can be cooled by means known in the art and not described in detail herein, for example air suction means can be used.
  • the nonwoven fabric 150 exiting the heated calendar 20 can be treated by an additional setting device 7 such as a calendar, where the nonwoven fabric 150 is consolidated.

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Nonwoven Fabrics (AREA)
US18/318,751 2022-05-17 2023-05-17 Process and apparatus for producing a voluminous nonwoven fabric Pending US20240141570A1 (en)

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IT102022000010262 2022-05-17

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Publication number Priority date Publication date Assignee Title
NL133639C (fr) 1964-09-26
US5382400A (en) 1992-08-21 1995-01-17 Kimberly-Clark Corporation Nonwoven multicomponent polymeric fabric and method for making same
AU2002361896A1 (en) * 2001-12-21 2003-07-15 Invista Technologies S.A.R.L. Stretchable composite sheets and processes for making
US7258758B2 (en) * 2001-12-21 2007-08-21 Kimberly-Clark Worldwide, Inc. Strong high loft low density nonwoven webs and laminates thereof
EP1726700B1 (fr) 2005-05-25 2013-02-27 Reifenhäuser GmbH & Co. KG Maschinenfabrik Procédé et dispositif pour la fabrication d'un non-tissé
DK1930492T3 (da) 2006-12-06 2011-01-10 Reifenhaeuser Gmbh & Co Kg Fremgangsmåde og indretning til fremstilling af en spinde-fiberdug
DE602006012527D1 (de) 2006-12-15 2010-04-08 Fare Spa Vorrichtung und Prozess zur Herstellung einer Spinnvliesmatte
WO2008072278A2 (fr) 2006-12-15 2008-06-19 Fare' S.P.A. Processus et appareil destiné à produire des tissus non tissés à partir de filaments extrudés
US9863067B2 (en) 2010-04-16 2018-01-09 Mitsui Chemicals, Inc. Crimped conjugated fiber and non-woven fabric comprising the fiber
EP3385423A1 (fr) * 2017-04-06 2018-10-10 FARE' S.p.A. Procédé et appareil pour la production d'un tissu non tissé volumineux
EP4223920A3 (fr) * 2016-11-14 2023-09-13 Fare' S.p.A. a Socio Unico Filament pour tissu non tissé filé-lié

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