Classifications

• • 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
  • D04H3/10—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 yarns or filaments made mechanically
  • D04H3/105—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 yarns or filaments made mechanically by needling
• • 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
  • D01D5/08—Melt spinning methods
  • D01D5/098—Melt spinning methods with simultaneous stretching
  • D01D5/0985—Melt spinning methods with simultaneous stretching by means of a flowing gas (e.g. melt-blowing)
• • 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
  • D01D5/23—Formation of filaments, threads, or the like with a crimped or curled structure; with a special structure to simulate wool by asymmetrical cooling of filaments, threads, or the like, leaving the spinnerettes
• • 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
  • 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

Definitions

• This invention relates to a method of and apparatus for producing fabrics of or including crimped polymeric filaments.
• the filaments are of polypropylene.
• this invention relates to the production of so-called "spun bonded" fabrics, which require a pre-determined resilience, as they are used in the manufacture of carpets or floor coverings, filters and wipes, and hygiene and healthcare textile products, and the like.
• Spun bonded fabrics are also used to produce clothing products which are required to provide warmth to a wearer, and which are required to have good draping qualities and /or flexibility. In some other cases, the fabric has to provide good acoustic qualities .
• spun bonded fabrics can be used in a wide variety and almost infinite number of applications.
• the fabrics according to this invention can be used in any of these applications.
• the filaments issuing from the spinneret orifices are drawn away at high speed traditionally by air jets spaced apart from the spinneret and typically incorporating a venturi nozzle for accelerating the air, and thus the filaments, which also pas s through the venturi device, to the desired velocities.
• This process is known as "draw down", and it is important to note that although air jets incorporating venturi nozzles are typically used, any high speed drawing device could be used, such as high speed rollers which could drag the filaments at high speed away from the spinneret orifices through which the filaments emerge.
• the filaments are solidified by means of a wide, slow moving flow of air which may be directed from one or both sides of the filament.
• the cross current of air provides a cooling air environment which solidifies the molten polymer constituting the filaments, and in general this cross-current o f air extends from the spinneret plate to the drawing device to ensure the complete solidification of polymer.
• this cooling of the filaments occurs over a vertical depth beneath the spinneret plate of between 2-4m and air flows through the vertically drawn filament bunch at a speed in the region of 0.5 m/ s . ,
• the spinneret has a large number of apertures and it is usual to use a plurality of spinnerets arranged relative to one another such that filament bundles issuing from each of the spinnerets overlap to such an extent that a uniform filament web results .
• the drawing device deposits the cooled filaments onto a moving conveyor, for example in the form of a mesh screen.
• the drawing device may be caused to oscillate which results in the laying down of a lapped mat of filaments on the conveyor.
• the thickness of the filament mat may be controlled.
• the denier of the filaments may be controlled by various means including controlling the rate at which the polymer is forced through the spinneret and the rate of drawing off of the filaments from the spinneret..
• a number of methods are known to connect the randomly aligned filaments deposited on the conveyor into a stable textile-like fabric.
• the mat of filaments is passed under pressure continuously between two or more calendar rolls.
• the calendar rolls is heated and has an embossed surface pattern consisting of raised diamond shapes in staggered rows.
• the filaments are not only connected, but the mat of filaments is compressed into a sheet material of thickness set by the gap, which is adjustable, between the calendar rolls.
• the heated calendar roll with the embossed surface pattern co-operates against a cold calendar roller causing the filaments to be spot welded together at the pressure points created between the two calendar rollers creating the spun bonded fabric.
• the second known method of connecting the filaments laid down on the conveyor is to pass the web of filaments through a barbed needle felting machine in order that the filaments in the web become entangled together such that they do not easily separate and thus define the spun bonded fabric .
• spun bonded fabrics Uses to which spun bonded fabrics have been successfully put include: surgical dressings , cover stock material for babies disposable nappies, hygienic products, geotextile re-enforcing materials, surgical gowns and hospital operating theatre sheets, agricultural sun screen fabrics, motorway, landfill, and drainage liner fabrics, air filtration fabrics, and hygiene textile products in general.
• the spun bonded fabric process as described hereinabove has reached a very advanced state of development, there are some serious disadvantages in the material produced by the known methods.
• the materials lack the aesthetics of traditional woven or knitted textile materials such as drape, three dimensional flexibility, softness and resilience (springiness) .
• they are often are stiff and in this respect they often have a flexibility feel similar to a sheet of thick cardboard, which has a limiting effect on the use of the spun bonded fabrics.
• the disadvantages mentioned hereinabove we believe are predominantly due to the fact that in the methods described hereinabove, the resulting filaments are basically straight or in other words have little or no crimp (which improves the bulk of the filament and hence many qualities such as flexibility and drape of fabrics using such filaments) .
• this invention seeks to provide a method and apparatus by which self crimp may be induced into the filaments, so that an improved spun bonded fabric will result.
• the two polymers used obviously are required to have dissimilar properties, and by careful choice of the two polymers, a self- crimping filament may result.
• a further disadvantage of this known method of producing self- crimped fibres is the very high up keep costs of the specialised apparatus required to form the filaments.
• the filaments are drawn from the spinneret so that at the drawing device, the filaments are travelling at a speed of at least 400 metres per minute, (ii) the apertures in the spinneret are of a cross section which comprises or approximates a C-shape to extrude, at the spinneret plate, filaments of the same cross sectional shape, and (iii) the cooling air flow is towards the open mouth of the C shape of the filament cross section.
• the air flow is at a rate in the order of between 3m/s and 30m/s, and most preferably between 3 and 10 m/s and the depth of the sheet is preferably les s than 500mm, but this will to some extend depend upon the filament bundle being extruded and sheet depths of more than 500mm may be required.
• the air knife is preferably disposed immediately below the exit face of the spinneret from which the filaments exit the apertures.
• the air flow is of a depth of 50mm.
• C- shape or substantial C-shape any shape which has a majour peripheral portion between the ends of which is an inwardly directe mouth.
• a square, rectangular or circular shape with a quadrant or any regular or irregular shape with a single portion removed to define a mouth would approximate a C-shape in accordance with this invention.
• the at least one orifice comprises: a first portion having a first transverse cross-section defining a discontinuous loop, wherein the loop substantially surrounds a solid portion of a spinneret plate; and a second portion having a second transverse cross-section defining a continuous loop corresponding substantially the discontinuous loop of the first portion, wherein molten thermoplastic plastics material is passed in use through the at least one orifice in a direction from the first portion to the second portion.
• fabrics of highly crimped, specifically helical three-dimensionally crimped filaments have been produced without having to resort to the use of bi-polymer filaments or additional mechanical treatments such as stretching or mechanical crimping.
• the fabric has draping properties rather than being stiff, and is flexible.
• the fabric has greater warmth through air entrapment within the crimped filament structure.
• the loft, resiliency and springiness of the fabric is also be greatly improved.
• the filaments must be drawn from the spinneret plate (where they are moving quite slowly) so as to reach a speed at least in the order of 400 metres per minute. Any less draw down results in little or no self crimping of the filaments.
• the upper limit of draw down speed is a practical one in that if the speed of draw down is too high then the filaments simply break, which of course is unacceptable.
• the method further comprises a step of heat setting the self-crimped filaments. This ensures that the helical crimp in the filaments is made substantially permanent.
• the heat treatment takes place immediately after the spinning step, which is after the filaments have passed through the drawing device.
• an air suction means disposed at the opposite side of the spinneret plate to that on which the air knife is disposed.
• the addition of a suction means helps to maintain the uniformity of the air flow through the filaments and to restrict the depth of air flow to the depth of the air knife outlet from which the flow emerges. Additionally, the suction means assists in the drawing of the air through the filaments, and ensures that the velocity of air through the filaments does not decrease significantly.
• apparatus for making spun bonded fabrics from or including filaments of polymeric material comprising g) a spinneret plate for extruding the polymer in molten form out of the apertures in the spinneret plate to produce filaments
• an air knife arranged to blow a flow of cooling air in the form of a sheet transverse to the filaments as they pass from the spinneret to the drawing device
• k means for effecting treatment on the mat to connect the individual filaments together to form a fabric, characterised in that
• the drawing device is such at to cause the filaments to be travelling at a speed of at least 400 metres per minute at the drawing device,
• the apertures in the spinneret are of a cross section which comprises or approximates a C-shape to extrude, at the spinneret plate, filaments of the same cross sectional shape, and
• the air knife is arranged to direct the cooling air flow towards the open mouth of the C shape of the filament cross section
• Figure 1 is a schematic representation of an apparatus for forming spun-bonded fabrics according to a first embodiment of the invention
• Figure 2 is a schematic representation of an apparatus for forming spun-bonded fabrics according to another embodiment of the invention.
• Figure 3 is a schematic representation of a preferred shape cross section for the apertures in the spinneret plates of the embodiments of the invention shown in Figs . 1 and 2;
• Figure 4 is a schematic representation showing various examples of spinneret aperture shape which may be adopted for this invention to show how different these shapes might be.
• an apparatus for forming spun bonded fabric according to the invention is designated generally by the reference numeral 1.
• the apparatus comprises an extruder 2 for extruding polymer which is introduced into the apparatus via hopper 3 and fed into the spinneret via filter 4, gear pump 5 and spin beam 6.
• the extruded polymer is forced through apertures (also referred to herein as orifices) in the spinneret 7 and is then subject to a cross current of air in the form of a sheet of air flow produced by air knife 8.
• the cross current of air provides a rapid cooling air environment.
• an air suction means 8A for example in the form of a duct in which a vacuum is created, disposed at the opposite side of the spinneret plate to that on which the air knife is disposed.
• the addition of a suction means helps to maintain the uniformity of the air flow through the filaments and to restrict the depth of air flow to the depth of the air knife outlet from which the flow emerges. Additionally, the suction means 8A assists in the drawing of the air through the filaments, and ensures that the velocity of air through the filaments does not decrease significantly.
• the filaments issuing from the spinneret orifices are drawn away at high speed by a drawing device in the form of air jet 9 positioned some distance away from the spinneret.
• the air jet 9 blows the cool filament onto a moving conveyor in the from of mesh belt 10 where the filaments 1 1 are collected.
• the drawing speed is such that the filaments as they travel through the air jet 9 are moving at least at a speed of 400 metres per minute.
• the filaments are deposited onto the moving mesh belt 10 in a randomly aligned mat or web 1 1.
• the filaments are consolidated into a stable textile-like fabric by passing the randomly aligned web through two or more calendar rolls 12 which form a bonder.
• One but preferably each of the calendar rolls is heated and has an embossed surface pattern.
• the web of filaments 1 1 is compressed in thickness into a sheet material 13.
• the thickness of the sheet material is related to the thickness of the mat entering the bonder and the bond area of the patterned roll and preferably the gap between the calendar rolls 12, 14 is fixed to maintain a fixed bonding pressure..
• the mat, before it enters the bonder is preferably subjected to pre heating at station S to effect pre-shrink of the fibres if necessary.
• the randomly aligned web of filaments 11 is consolidated by passing the web through a barbed needle felting machine 20 in order that the filaments 1 1 in the web become entangled together such that they do not easily separate and thus become useful as a textile-like material 22.
• the filaments as they leave the air jet 9 show a propensity to self crimp to a high degree, and as a result the fabric 13 or 22 which results from the process, has excellent qualities of bulk, drape and flexibility, and is excellent for the various uses of spun bonded fabric as described herein.
• FIG. 3 a typical orifice having a non-circular cross- section which comprises a full circular cross-section with one quarter of a circle removed is shown.
• a spinneret with orifices with this shape is particularly effective in the method of the invention.
• the air flow should be into the mouth M of the cross section of the filaments. This flow can be in the direction of middle of the mouth, but best results have been obtained by blowing the air into the edge of the mouth as indicated bv arrows A, where the air flow is tangential to the face 33.
• the filament is drawn down, so its cross sectional shape will change, and so it is best if the air flow is applied as soon after the filaments emerge from the spinneret plate as possible.
• This particular orifice shape can be described in more general terms as having an arcuate peripheral portion 31 and two rectilinear portions 32, 33.
• An orifice shape being a full circle would have a geometric centre at 34, but in the case of the orifice shape shown in Figure 3, the geometric centre will move to a position approximately at 35.
• the rectilinear portions 32, 33 of the shape 30 therefore approach and recede from the geometric centre 35 in a particular angular sector defined by the dotted lines 36, 37.
• the base angle ⁇ ° of this sector is 90°, but different angles may be selected.
• the orifice cross section in any event approximates a C shape, and the invention requires that the orifice has a C shape or an approximate C-shape, again for reasons given below.
• the C shape can be an exact shape as shown in Fig. 4 (a) , or it may be of quite a different form to approximate a C shape as indicated in the other parts of Fig. 4. In each case, the approximate shape of the C is indicated by the dotted line X, and the mouth is indicated by the letter M.
• the spinneret orifice extends through the spinneret plate at right angles to the plate exit face, but this is not necessary and the orifice could pass through the plate at an angle.
• the spun bonded fabric may be produced without being calendared or needled as described above.
• a cross-lapping machine (not shown) may additionally be provided immediately after the air jets 9. Said machine oscillates laterally of a translating belt, such as the mesh belt 10 shown in the Figures and thus a web of gossamer-like crimped filaments may be laid on such a belt from side to side at a uniform thickness and subsequently needled, calendared or otherwise processed to connect the filaments into a fabric.
• the spun bonded fabrics produced according to the invention can be effectively needled whereas the needling of filaments crimped by more conventional methods often results in the tearing and breakage of the filaments . This results from the improved resiliency and elasticity properties possessed by the self-crimping filaments.
• MFI Melt Flow Index
• the extruder was set with a temperature profile of 190-220°C and the spinneret and head were maintained at a temperature of 205°C.
• Some distance away but directly in line with the spinneret was a suction device of the type sold on the UK market under the trade name "Airmover” .
• Airmover By connecting a supply of high pressure compressed air to this device a venturi effect is created which enables the filaments issuing from the spinneret face to be sucked away at a high speed.
• By adjusting the volume and pressure of compressed air supplied to this "Airmover" the spinning speed of the filaments could be adjusted.
• a filament porcelain guide was positioned so that the filament bundle could be collected together and lead away to a precision filament take up winder which was situated nearby.
• the take up winder was fitted with an askew filament advancing roller so that several wraps of the filament bundle could be taken around it to give a positive traction to the filaments .
• the askew rollers were fitted with a tachometer calibrated in metres per minute so that the precise speed of spinning or draw off could be ascertained.
• the charged extruder was started and molten filaments soon emerged from the face of the spinneret which was of the type that creates a stress differential across the diameter of the orifice.
• the filaments were cooled by applying a stream of cooling air provided by a fan arrangement. The air was at a temperature of 14°C.
• the cooling filaments were drawn away by the air mover and then passed via the ceramic thread guide to the askew rollers of the precision take up winder, maintained at a speed of 250 metres per minute and collected as a bundle.
• the extruder was adjusted for output so that the final filaments had a denier of 5 per filament (9000 metres of a single filament weighed 5 grams) .
• the filaments which had not undergone any stretching or drawing process, other than melt draw down were unwound from the collecting bobbin of the winder and were measured in an Instron tensiometer and found to have a tenacity of 2.6 grams per denier with an elongation at break of 60%. Such filament properties are ideal for many textile applications . As the filaments were unwound from the collecting bobbin where they were under a high tension they were seen to have a straight appearance with no crimp present. However, within a few seconds of the winding tension being removed the filaments formed into tight helical crimps . A 90 metre hank of the 60 filament yarn was wound off the take up bobbin on a textile hank winder.
• the arms of the hank winder swift were collapsed to allow the removal of the hank and immediately the filaments self crimped into a helical crimp formation. These crimped filaments were stressed by hand to virtually their breaking point and then the tension was released. The degree of crimp in the filaments increased and could not be removed by applying high tension. Next a group of filaments were stressed to breaking point but when the broken filaments were examined none of the crimps had been removed and were measured to have increased in frequency.
• a further 90 metres length hank of filaments was prepared on the swift of the hank winder and removed, on removal, the filaments again reverted into a helical crimp formation.
• This hank of filaments was then placed in a hot air circulating oven maintained at a temperature of 130°C for a period of three minutes , on removal from the oven the helical crimp of the filaments had not been removed but was even more pronounced.
• the length of the hank was again measured and found to be 80 metres i.e. the hank had shrunk in length by 10 metres due to the heat setting step.
• the crimp percent of the heat set filaments was determined to be 60%. Crimp % is defined as :
• a stream of heated air (130°C) was blown onto the filaments resting on the perforated plate to heat set the filaments and further develop the helical crimp .
• the batt of highly crimped filaments was a very suitable material to convert into a textile product either by needling with felting needles, or by consolidating by means of an embossed heated calendar rolls.
• Example No. 1 was repeated, but the spinneret plate in the extruder was changed for one in which the orifices were arranged to pass through the spinneret plate and an angle, in this case at 45 degees.
• This spinneret plate had the same number of holes and shape as that shown in Fig 3 with the except that the holes were drilled at an angle of 45° to the exit surface of the spinneret.
• Example No. 1 was again repeated in all respects with the exception that the polypropylene resin was changed to a grade type XS 6500 made by Montell. This grade is narrow molecular weight distribution polymer with a melt flow index of 35. The resulting filaments crimped spontaneously on become tensionless after exiting from the Airmover used to draw the filaments away from the spinneret.
• Example No. 1 was again repeated in all respects with the exception that the polypropylene resin was changed to a grade type VS 6100 made by Montell. This grade is a narrow molecular weight distribution polymer with a melt flow index of 25.
• the helical crimp further increased and was of a permanent nature which could only be removed by heat setting under high tension at a temperature which was substantially higher than the 130°C used to heat set the crimps into the filaments .

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Mechanical Engineering (AREA)
• Nonwoven Fabrics (AREA)
• Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Inorganic Fibers (AREA)

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Publications (2)

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• 1999
  • 1999-08-05 GB GBGB9918376.6A patent/GB9918376D0/en not_active Ceased
• 2000
  • 2000-08-03 WO PCT/GB2000/002998 patent/WO2001011119A1/fr active IP Right Grant
  • 2000-08-03 EP EP00949790A patent/EP1313899B1/fr not_active Expired - Lifetime
  • 2000-08-03 AT AT00949790T patent/ATE325208T1/de not_active IP Right Cessation
  • 2000-08-03 DE DE60027790T patent/DE60027790D1/de not_active Expired - Lifetime
  • 2000-08-03 AU AU63058/00A patent/AU6305800A/en not_active Abandoned

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