BACKWASHING OF PARTIALLY PROCESSED WOOL

Abstract: A process for backwashing a travelling fibre assembly, subsequent to carding of the assembly, including directing one or more flows of a fluid at the fibre assembly to dislodge contaminants from the assembly and, if necessary, thereafter subjecting the fibre assembly to a drying step sufficient to remove a selected proportion of the fluid retained by the fibre assembly. The process as illustrated shows a sliver (10) being passed successively through the nips (11) of a series of spaced pairs (12) of opposed contra-rotating rollers (12a, 12b). The nips (11) are spaced at a distance R which is preferably less than the mean length of the fibres in the sliver (10). The sliver (10) is pre-wet at a pre-wetting station (14), e.g. a pad, prior to being sprayed by a jet or jets (16) of water and a cleaning medium. The sliver (10) then passes a jet or jets (18) of rinse water.

Description: BACKWASHING OF PARTIALLY PROCESSED WOOL Field of the Invention The present invention relates to the backwashing of partially processed wool and more particularly to an improved method for washing pre-comb wool in sliver form. Background Art Prior to the 1960's it was established practice in many wool combing plants to wash wools downstream of carding. Some combers re-washed after carding while others preferred to defer the process until after combing. This process was called backwashing and the wool was essentially subjected to a three-step scour. Typically, 24 slivers each having a linear density of 30 to 40g/m were fed to a first scouring bowl at a speed of about lOm min. The first scouring bowl normally contained warm water at 35 to 45°C and approximately 0.5% detergent. The slivers were then sent to a second bowl which either contained warm water and detergent in the same manner as the first bowl or acted as a warm rinse bowl. The slivers were then directed to a third bowl which was a warm rinse bowl. In some instances the slivers were then directed to a further rinse bowl. Each of the scouring and rinse bowls was fitted with guide rolls and squeeze rollers to aid in the scouring and rinsing processes. After leaving the rinse bowls the slivers passed through a drying machine and then entered a gill box. The object of backwashing was to remove any impurities still remaining after scouring and carding, thereby improving the colour and hence the commercial value of the top. Other subsidiary advantages of backwashing were small improvements in the yield and average fibre length of the top. During the 1960's wool scourers adopted the use of synthetic detergents rather than the traditional soap. Synthetic detergents were found to be much more efficient in cleaning wool at the initial scouring stage, and thus the relative value of backwashing diminished. This factor, coupled with the high cost of backwashing operations, resulted in the practice of backwashing being largely abandoned. Backwashing however remained in use for rinsing after dyeing, and as a preparation for applying resins to wool in some sliver shrinkproofing methods. In the last decade or so, the output production rate (ie kg/hr) in scouring operations has increased. As a consequence of this increase there has been an increase in the level of scourable residuals residing in commercial consignments of scoured wool. Irrespective of this trend, and until the present invention, the value of backwashing wool slivers for use in modern high speed spinning operations had not been re-evaluated. There has been a reluctance to re-introduce backwashing primarily because of its relatively high cost. Conventional backwashing machines have a high capital cost, require a large operational area, are labour intensive, have a high energy demand and a relatively poor running efficiency. As already noted, traditional backwashing practice amounted to a further scouring step. It has now been realised, in accordance with the invention, that the carding process modifies the adhesion of scourable residuals in the wool and that traditional backwashing to remove these residuals from carded wool is inefficient because it is unnecessary. It has been found that these residuals are located primarily on outer surfaces of the wool fibres in sliver, bound quite loosely to the structure, and that they can be dislodged without any need for immersion of the sliver as traditionally practised, and the consequent intensive drying. Backwashing can therefore be carried out prior to combing at much lower cost than before, offering, at an acceptable cost, the possibility of improvements in topmaking as well as a reduced frequency of roll laps, spinning breaks and winding faults. These advantages offer substantial economic benefits to wool spinners. Particular benefits may be incurred for superfine wools, and perhaps for wools that are difficult to scour. Any re-introduction of the backwashing concept as an integral part of modern practice rather than as a stand-alone unit must recognise that the present and foreseeable delivery speeds of modern carding and giUing machines are in the order of 60 to 150m/min. Summary of the Invention The present invention provides, in one aspect, a process for backwashing a travelling fibre assembly subsequent to carding of the assembly, preferably wool sliver immediately downstream of carding, including:- • directing one or more flows of a fluid at the fibre assembly to dislodge contaminants from the assembly; and, if necessary, • thereafter subjecting the fibre assembly to a drying step sufficient to remove a selected proportion of said fluid retained by the fibre assembly. The invention also provides, in another aspect, apparatus for backwashing a travelling fibre assembly, preferably sliver immediately downstream of carding, including means to direct one or more flows of a fluid at the fibre assembly to dislodge contaminants from the assembly. The apparatus may further include means to thereafter subject the fibre assembly to a drying step sufficient to remove a selected proportion of said fluid retained by the fibre assembly. In a still further aspect, the invention provides a process for backwashing a fibre assembly travelling at 60m/min or greater, subsequent to carding of the assembly, including passing the fibre assembly through a single bath of a cleaning fluid for a dwell time of 5 seconds or less. The process and apparatus is preferably integrated into wool processing plant, eg worsted processing plant, so that the backwashing is applied to the fabric assembly on the run between other stages, eg between carding and gilling. Said drying step may consist of or include directing a jet of air onto the fibre assembly to evaporate or knock away the fluid. The washed sliver may additionally be rinsed prior to drying. Preferably, control is maintained over the fibres during backwashing so that the fibres of the sliver are not disturbed during the process. This may be effected, eg, by gripping the sliver at spaced locations, at a separation approximately equal to or less than the mean fibre length in the sliver. This would typically be a spacing between contacts in the range 40-60mm. The fibre assembly may be pre-wet, eg with a pad, before being subjected to the directed flow(s) of fluid. These flows may include an initial jet of liquid and then a rinsing jet of liquid. Preferably, saturation of the fibres of the assembly is minimised or avoided, eg by confining the residence time in liquid streams to a maximum of a few seconds, eg 1 or 2 sees, and the degree of wetness is maintained at a level sufficient for contaminants to be dislodged while minimising the energy necessary to effect the drying step. The inventive method and apparatus may be advantageously applied to a multiple sliver feed and more particularly to a multiple sliver feed prior to entry into a gilling machine. The fluid utilised is preferably liquid water, most preferably warmed above ambient, and may include a cleaning medium, but may alternatively be steam, pastes, solvents or foams. The backwashing step is preferably incorporated in a high speed carding or combing operation, eg at a delivery speed in the range 60 to 120m/min. Advantageously, a force eg suction is applied to improve the penetration of the washing, rinsing and/or drying fluids among the fibres of the assembly. Brief Description of the Drawings Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a schematic side view of a first embodiment of the invention; Figure 2 is a schematic side view of a second embodiment of the invention; Figure 3 is a schematic side view of a third embodiment of the invention; Figure 4 is a schematic side view of a fourth embodiment of the invention; Figure 5 is a schematic side view of an alternative form of the embodiment shown in Figure 4; and Figure 6 is a cross-sectional diagram of a still further embodiment of the invention utilising suction drums in a liquor bath. Embodiments of the Invention For simplicity of explanation, the various embodiments of the invention illustrate a single carded sliver being individually washed. However, it should be appreciated that the embodiments could be modified so as to enable multiple sliver feed, and indeed multiple feed would be the usual practice. Figure 1 illustrates a sliver 10 being passed successively through the nips 11 of a series of spaced pairs 12 of opposed contra-rotating rollers 12a, 12b. The nips 11 are spaced at a distance R which is preferably less than the mean length of the fibres in the sliver 10. The sliver 10 is pre-wet at a pre-wetting station 14, eg a pad, prior to being sprayed by a jet or jets 16 of warm water and a cleaning medium. The sliver 10 then passes a jet or jets 18 of rinse water. Residual contaminants in the sliver have been found to be primarily loosely bound at the outer more exposed surfaces of the fibres, having been encouraged to those locations in the carding process. In many applications, there is no need to immerse the sliver in the traditional way in a scouring bowl, and it has proven sufficient in a preferred embodiment to wash away the contaminants with an initial jet of warm cleaning water and a follow up rinse jet. Furthermore, because there is no immersion, saturation of the fibres is reduced by an appropriate level of liquid flow. The energy required to achieve drying is minimised. In some cases, a separate on-line drying facility 19 will be necessary, in others no drying operation will be required. A jet of air will typically be sufficient. It may be appropriate to cuttle or fold the sliver 10 in the drying facility. Figure 2 illustrates an alternative arrangement to that illustrated in Figure 1, wherein rather than passing through the nips of opposed pairs of rollers 12a, 12b, the sliver 110 traverses about a series of spaced rollers 112a, 112b, 112c. The sliver 1 10 is still pre- wetted, sprayed with jets 116 of warm water and cleaning medium, and then rinsed (112). Figure 3 illustrates an alternative arrangement which allows the cleaning medium, which typically comprises warm water and detergent, to be forced through the sliver 210 to improve penetration among the fibres. It may be necessary to force the cleaning fluid through the sliver 210 because of the physical properties of the wool. As illustrated in Figure 3 , the sliver 210 would pass through the nips 211 of a series of pairs 212 of opposed rollers 212a, 212b, which adopt a similar arrangement to that shown in Figure 1. However, at the point where the sliver 210 is sprayed with jets 216 of warm water and cleaning medium, suction 215 would be applied to draw the warm water and cleaning medium now containing the contaminants through the slivers 210 and thus wash all of the fibres in the sliver. Figure 4 illustrates an alternative arrangement to that shown in Figure 3 wherein the wool sliver 310 passes between a guide roll 320 and a suction drum 322, travels across the suction drum 322, and then passes between the suction drum 322 and a second guide roll 324. As the sliver 310 passes over the suction drum 322 a spray of cleaning medium would be applied by the jets 316 onto the sliver 310. Suction would then be applied (315) so as to draw the cleaning medium through the sliver 310 and into the suction drum. Figure 5 illustrates an arrangement wherein two suction drums 422 are combined. Multiple suction drums 422 could be used to enable multiple washing stages and/or rinsing stages or to simply enable consecutive washing and rinsing stages. Furthermore, additional guide rolls (not shown) may be included in between each of the suction drums. Figures 2 to 5 do not include drying facilities but these would be provided where necessary as preferred. Although all the embodiments include a pre-wetting step, this may be not required and is not essential. Conversely, in some applications, a more positive pre-wetting step may be needed. For example, the sliver may be drawn briefly through a single bath of cleaning fluid for pre-wetting purposes. It may be desirable in some applications for the last or exit nip in the embodiments of Figures 1 and 3 (and possibly the centre nip in Figure 1) to be a pressurized nip, and for the embodiments of Figures 2, 4 or 5 to include one or more pressurized downstream and/or exit nips. These may facilitate optimum downstream fluid content in the sliver. In one embodiment of the invention it is envisaged that the re-washing apparatus would be designed for re-washing a single sliver as it exits the card or as it feeds to a gilling machine. It is also envisaged that the apparatus may be used to wash the sliver feed to a gilling machine. In each of these arrangements it is envisaged that the sliver would be wetted, washed, possibly rinsed and then dried to an appropriate moisture content so that the sliver can then be subsequently processed without delay, ie the process is integrated into existing processing plant. In a still further embodiment illustrated in Figure 6, application of cleaning medium is by passage about and under a series of suction drums 522a, 522b,522c through a bath 530 of warm water and cleaning medium. The bath is held within a bowl 532 in a configuration similar to a single station of a traditional multiple bowl scouring or backwashing installation. The first suction drum 522a co-acts with a complementary contra-rotating roller 534 to define a delivery nip 511a. A pair of exit pressurized nips 51 lb,51 lc are associated with the final suction drum 522c and adjacent exit rollers 536,537. Effluent is collected at 538 at the intake from roller 534 and excess liquor is collected at 540 from nips 51 lb,51 lc for filtering and recycling. Spray jets 516 of further cleaning medium and warm water may be applied to the wetted sliver downstream of suction drum 522c. It should also be noted that the suction drums can be replaced by solid dip rollers or by a single, larger diameter suction drum or solid dip roller without any significant deterioration of the process outcome. The backwashing effected by the embodiment of Figure 6 is quite different from traditional backwashing in that there is only one bowl and that the dwell time in the bath is much less than the conventional dwell time in each of the two to four baths of traditional backwashing, e.g. preferably 5 sees or less, more preferably less than V 3 of the conventional dwell time. This difference arises from the different travel speeds of the sliver, e.g. 60 m/min or more in the embodiment of Figure 6 compared with 15 to 20 m/min in traditional backwashing practices. The cleaning medium may by simply liquid water or may comprise an aqueous detergent which may be mixed with water, steam, cleaning paste, foam, or other appropriate cleaning medium. It may be necessary to raise the temperature of the cleaning medium above those typically used to aid the cleaning process. Instead of warm water, steam may be employed as the washing jet. It is envisaged that apparatus and methods according to embodiments of the present invention would provide all of the advantages of prior art backwashing apparatus and methods without substantially delaying the processing time required to prepare the wool ready for spinning. Whereas prior art backwashing apparatus and methods required the slivers to dwell and soak in each of two to four scouring bowls for up to 8 to 15 seconds, washing of the sliver in accordance with embodiments of the present invention would ideally be achieved in 1 to 2 seconds or less. Forced liquid traversed, eg using a vacuum, can improve penetration of the sliver and washing contact with all or most fibres. Embodiments of the invention seek to wash contaminants from the surface of the fibres and preferably avoid saturation of the fibres. This will reduce both washing and drying times and drying energy. Accordingly, embodiments of the present invention are able to be incorporated into current high speed carding and combing processes (eg up to 120 m/min) without the need to reduce the delivery speed. It will be appreciated that the process of the invention might be utilised, in certain applications, to control the moisture content of the sliver within a desired range. This might be effected by setting the liquid flow and drying parameters, relative to sliver delivery speed, to produce a selected moisture content. The process may also be additionally used for traditional backwashing purposes, eg for rinsing after dyeing or as a preparation for applying resins to wool in some shrinkproofing methods. Embodiments of the invention have been described by way of example only and modifications are possible within the scope of the invention. It will also be understood that where the term "comprises" or its grammatical variants is employed herein, it is equivalent to the term "includes" and is not to be taken as excluding the presence of other elements or features.

Claims: Claims 1. A process for backwashing a travelling fibre assembly, subsequent to carding of the assembly, including: - • directing one or more flows of a fluid at the fibre assembly to dislodge contaminants from the assembly; and, if necessary, • thereafter subjecting the fibre assembly to a drying step sufficient to remove a selected proportion of said fluid retained by the fibre assembly. 2. A process according to claim 1 wherein the fibre assembly is wool sliver immediately downstream of carding. 3. A process according to claim 1 or 2 wherein said drying step consist of or includes directing a jet of air onto the fibre assembly to evaporate or knock away the fluid. 4. A process according to claim 1, 2 or 3 wherein the washed fibre assembly is additionally rinsed prior to drying. 5. A process according to any preceding claim including maintaining control over the fibres during backwashing so that the fibres of the sliver are not materially disturbed during the process. 6. A process according to claim 5 wherein control is maintained by gripping the sliver at spaced locations, at a separation approximately equal to or less than the mean fibre length in the sliver. 7. A process according to any preceding claim wherein the fibre assembly is pre- wetted before being subjected to the directed flow of fluid. 8. A process according to any preceding wherein said flow(s) include an initial jet of liquid and then a rinsing jet of liquid. 9. A process according to any preceding claim wherein the degree of wetness is maintained at a level sufficient for contaminants to be dislodged while minimising the energy necessary to effect the drying step. 10. A process according to any preceding claim, integrated into wool processing e.g. worsted processing, so that the backwashing is applied to the fabric assembly on the run between other stages. 11. A process according to claim 10 wherein the backwashing is applied to the fibre assembly between carding & gilling. 12. A process according to claim 10 or 11 wherein the delivery speed of the fibre assembly is in the range 60 to 120m/min. 13. A process according to any preceding claim wherein a force e.g. suction is applied to improve the penetration of the washing, rinsing and/or drying fluids among the fibres of the assembly. 14. A process for backwashing a fibre assembly travelling at 60m/min or greater, subsequent to carding of the assembly, including passing the fibre assembly through a single bath of a cleaning fluid for a dwell time of 5 seconds or less. 15. A process according to claim 14 wherein the fibre assembly is wool sliver immediately downstream of carding. 16. A process according to claim 14 or 15 including maintaining control over the fibres during backwashing so that the fibres of the sliver are not materially disturbed during the process. 17. A process according to claim 14, 15 or 16 wherein integrated into wool processing e.g. wo irrsstteedd pprroocceessssiinngg, so that the backwashing is applied to the fabric assembly on the run between other stages 18. A process according to claim 17 wherein the backwashing is applied to the fibre assembly between carding & gilling. 19. A process according to any one of claims 14 or 18 wherein the delivery speed of the fibre assembly is in the range 60 to 120m/min. 20. A process according to any one of claims 12 to 16 wherein a force e.g. suction is applied to improve the penetration of the washing, rinsing and/or drying fluids among the fibres of the assembly. 21. Apparatus for backwashing a travelling fibre assembly, preferably sliver immediately downstream of carding, including means to direct one or more flows of a fluid at the fibre assembly to dislodge contaminants from the assembly. 22. Apparatus according to claim 21, further including means to thereafter subject the fibre assembly to a drying step sufficient to remove a selected proportion of said fluid retained by the fibre assembly. 23. Apparatus according to claim 22 wherein said drying step means consists of or includes means to direct a jet of air onto the fibre assembly to evaporate or knock away the fluid. 24. Apparatus according to claim 21, 22 or 23 integrated into a wool processing line, e.g. a worsted processing line, so that the backwashing is applied to the fabric assembly on the run between other stages. 25. Apparatus according to claim 24 wherein said backwashing apparatus is disposed immediately downstream of the carding stage, whereby the fibre assembly is wool sliver. 26. Apparatus according to any one of claims 21 to 25 further including means to rinse the fibre assembly prior to said drying. 27. Apparatus according to any one of claims 21 to 26 arranged to maintain control over the fibres during backwashing so that the fibres of the sliver are not materially disturbed therein. 28. Apparatus according to any one of claims 21 to 27 wherein said flow(s) include an initial jet of liquid and then a rinsing jet of liquid. 29. Apparatus according to any one of claims 21 to 28, further including means to apply a force e.g. suction to improve the penetration of the washing, rinsing and/or drying fluids among the fibres of the assembly. 30. Apparatus according to any one of claims 21 to 29, further including pressurized nip means to engage the fibre assembly downstream of said flow directing means.

Inventors: ROBINSON GARY ALFRED, ROBINSON, GARY, ALFRED
Applicants: COMMW SCIENT IND RES ORG, ROBINSON GARY ALFRED, COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH OR, ROBINSON, GARY, ALFRED
Application year: 1997
Main classification: D01B3
IPC codes: D01B3