MICROWAVE PROCESSING OF COMPRESSED WOOL FIBER MASS

Abstract: Compressed wool fiber mass, e.g. wool bales (26) containing raw wool fleeces, is subjected to microwave radiation (20) (typically with power levels in the range of 3 kW to 100 kW). The controlled heating process typically achieves temperatures in the range 30 DEG C to 50 DEG C. This avoids deleterious effects of the wool fiber and achieves generally uniform relaxation effect in the wool fibers. It causes a large expansion of the wool mass after release of the mass from the bale, whereby subsequent conventional scouring process may be implemented in a beneficial manner.

Description: TITLE MICROWAVE PROCESSING OF COMPRESSED WOOL FIBER MASS FIELD OF THE INVENTION The present invention relates to processing wool bales. BACKGROUND OF THE INVENTION A wool bale is formed by pressing a multiplicity of fleeces from sheep into a compact mass which usually is then contained in a hessian or other bag or container for the purpose of transportation and storage. Frequently straps such as steel straps are applied around one or more bales to compress and hold the mass tightly. Frequently long term storage is required before the processing of the fleece prior to manufacturing various products. The first stage in the processing of wool from bales in a conventional method is to scour the wool. This step comprises combing out the mass of fibres so they are no longer compacted and as far as practicable aligned in a common direction so that subsequent steps such as spinning into yarn can occur. Higher quality wool fibres especially are very fine and have great value and must be carefully handled to maintain fibre length, a commercially very important quality. The scouring process is also aimed at removing foreign matter and dirt particles so that a high quality product can emerge. One known preliminary step to aid the scouring process is to heat the compressed wool bale before the scouring step typically by injecting steam or hot air into the compressed wool bale through suitable pipework at temperatures of about 80°C or more . It is believed that this elevated temperature causes a physical relaxation in the wool fibres and there is then less resistance in the scouring process. Frequently higher temperatures occur with deleterious hot spots as high as 100°C in the wool mass. In a paper entitled "Radio-Frequency Heating of Jumbo Wool Bales", Ainsworth and Winston (Journal of the Textile Institute - (1985) No. 3 pp 171-184) have published the results of experiments using high frequency radio waves e.g. at 13.56 MHz to process greasy wool in high density bale form prior to scouring. The report concludes that radio- frequency heating is a method of rapidly heating large bales but that there would always be a large variation of temperatures within a bale. With a bale of 450kg, the authors report obtaining a temperature increase of 20°C in about 15 minutes with a consumption of 36MJ or lOkWh of energy. To the best of the present inventors knowledge, such radio-frequency heating has not been implemented on any commercial scale or further developed, probably due to a complex range of factors. Accordingly, there has been a long-standing need for practicable and cost effective processing of wool prior to scouring yet a commercially acceptable method and apparatus has not previously been identified or developed. However, despite the long-standing and commercially significant issue of facilitating the scouring of wool fibres, the effectiveness of techniques used to date have been limited. The present invention involves the surprising realisation that a simple, cost-effective and practicable development can be implemented to enhance this process with important economic significances. SUMMARY OF THE INVENTION Broadly, the present invention consists in a method of processing a compressed wool fibre mass comprising subjecting the mass to microwave radiation in a dose related to the mass to achieve a relaxation effect in the wool fibres to facilitate subsequent scouring operations, the dose being such that an elevated temperature relative to ambient conditions is established relatively speedily but at a temperature significantly less than that which would cause significant damage to wool fibres and in a manner such that the volume of the mass is permitted to increase significantly. A typical mass would be a whole wool bale or a part of such a bale. Often wool bales are highly compressed into a "tripack" which will weigh about 200kg and be of a cube form of approximately 700mm side. Sometimes a double or triple bale is formed with steel straps holding together a mass of length around 1.5m and sides of 700mm. The present invention can conveniently be implemented by taking one bale from such a tripack and processing it in a microwave oven established to operate at suitable frequency, power level and time conditions whereby a 200% increase in volume is typically found. However, with appropriate microwave ovens processing of larger masses can be effected. Further inventive aspects associated with the present subject matter consist in establishing particularly beneficial processing conditions and singly or in any combination these inventive aspects comprise: * controlling temperature throughout the wool bale to be sufficiently uniform for efficient securing and approximately 40°C and typically in the range 30°C to 50°C. * controlling time of treatment of each wool bale to be approximately three minutes and preferably in the range of two minutes to ten minutes. * controlling microwave transmissions to be energy in the range of 300MHz to 30GHz and preferably about 902 to 928 MHz or 2400 to 2500 MHz. * Using power levels in the range 3kW to lOOkW. Satisfactory results have been obtained both with the use and without the use of mode stirrers for the microwave oven and both with and without the use of a turntable for the microwave oven. Especially when it is possible to allow the treated bale to stand for some time before subsequent scouring, relative hot spots in the bale are believed to dissipate to achieve substantially uniform heating and thus relaxation effects. Furthermore it has been found that satisfactory results are obtained irrespective of whether the conventional securing straps, usual of steel around bales, are removed or not before the microwave treatment. It is believed use of the present invention offers the following advantageous features: * Deleterious effects on wool fibre caused by direct injection of steam or any other gaseous material is avoided as the microwave energy generates heat substantially uniformly and generally throughout the wool bale. * The invention can be applied using a single frequency or perhaps a combination of different frequency sources so that a desired temperature profile throughout the bale can be achieved and appropriate control is available. * The process can be arranged to be either semi- continuous or batch. * The process can be applied to regular sized bales as produced from shearing sheds or by using larger combinations such as tri-bales or parts thereof. * Use of the invention can permit substantially uniform heating and treatment of wool particularly after a bale has been allowed to stand for some time after microwave heating. The wool fibre has high insulating properties and it has been found that use of the invention can achieve uniformity and retention of heat for a considerably longer period after exposure to the microwaves and this residual time at elevated temperature leads to continued beneficial effects on the wool fibre, yet the process permits high plant utilisation. The process can be integrated with the stock piling of farm bales on the one hand and the stockpiling of processed bales or part bales on the other ready for a scouring operation. * The method can be applied with a suitably engineered processing system utilising well established technology in the microwave field. * The invention reliably achieves softening of the wool fibres thereby facilitating subsequent processes such as carding, cleaning and scouring with less maintenance demand on the machinery to be used for these subsequent operations since the wool fibres softened by use of the present invention yield up associated dirt and vegetable matter relatively easily. * Improved productivity is possible since wool fibres from bales processed according to the present invention provides raw wool product which is easier to handle by either mechanical or manual means. * The embodiments of the invention can be highly energy efficient and far more so than existing methods such as steaming. * Most importantly the present invention can be implemented with lower fibre damage than prior proposals and methods. The effective softening of the wool fibres results in a higher pliability and thereby longer fibre lengths on average can be preserved. This is important to the quality of the processed product. * Raw wool products resulting from the use of the present invention are less liable to tangle and this leads to reduced "noilage" which is loss due to fracturing of the wool fibre. Thus in general the present invention permits improved yields. * It is believed the present invention provides product with an improved colour compared with prior art proposals as a result of the processing techniques used. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 of the accompanying drawings is a schematic illustration of implementing the invention in a batch process; and Figure 2 is a schematic illustration of implementing the invention in a continuous process. Referring first to figure 1, a microwave oven 10 is connected through a wave guide 11 to a power supply 12. The oven 10 is arranged to be loaded and unloaded in a batch process utilising a conventional bale lifting truck 13, the oven 10 having a front door structure 14. As shown in figure 1 a tri-pack wool bale 15 is placed on a platform 16 within the oven, the tri-pack being shown with typical dimensions before heating is effected. Figure 1 also shows a tri-pack 16 with typical dimensions after the microwave treatment process and during removal by the truck 13. Referring now to figure 2, a continuous process is illustrated with a modified microwave oven 20 having an entry door structure 21 and an exit door structure 22. The oven 20 is connected through a wave guide 23 to a power supply 24. In this example the loading truck 25 loads tri-pack compressed wool bales 26 onto a roller conveyer 27, the tri- packs being sequentially passed through the microwave oven for a few minutes of heating before being discharged, a discharged tri-pack 28 illustrating the expansion being disposed on a receiving conveyor 29 for lateral discharge to subsequent storage or processing. In either figure 1 or figure 2 the wool bale can be supported on a turntable which is driven during the microwaving operation to facilitate even heating or alternatively the wool bale can be fixed in space. Example of the Invention Part of a tri-bale of wool was processed in a microwave facility in accordance with the schematic arrangement of Fig. 1. The wool sample comprised a 200kg cube and the processing conditions were as follows: Power level: 25kw Frequency: 922MHz Time : 5 minutes It was found that good penetration of the microwave energy occurred and substantial uniformity of treatment was achievable. After processing, the wool fibres were easily separated and expansion by about 200% of the body of the bale was observed. Relatively uniform heating is achieved to temperatures of about 50 °C. Comparative Results. A comparison was made by splitting sample tri-pack pieces so that part was processed according to the example set out above and part was processed using known steam heating technology. The wool was from bales of tripack fleeces (19 micron, 65 millimetre) . It was found that a 6-6% increase in production in the scouring step after treatment of wool was achieved with use of the present invention without making any adjustments to the scouring line. Improvements in quality were also noted with a better fibre length (average 1 • lmm longer using the invention), a better noilage (-0-9%) and one point better colour.

Claims: CLAIMS : 1. A method of processing a compressed wool fibre mass comprising subjecting the mass to microwave radiation in a dose related to the mass to achieve a relaxation effect in the wool fibres to facilitate subsequent scouring operations, the dose being such that an elevated temperature relative to ambient conditions is established relatively speedily but at a temperature significantly less than that which would cause significant damage to wool fibres and in a manner such that the volume of the mass is permitted to increase significantly. 2. A method as claimed in claim 1 and wherein the method includes controlling temperature throughout the wool bale to be in the range of approximately 30°C to 50°C by selecting the radiation dose and time of application. 3. A method as claimed in claim 1 or claim 2 and wherein the method includes controlling the time of treatment for each wool bale to be approximately two minutes to ten minutes. 4. A method as claimed in any one of the preceding claims and wherein the method includes controlling the microwave energy dose to be in the frequency range of 300MHz to 30GHz. 5. A method as claimed in claim 4 and wherein the method includes controlling the microwave energy dose to be in the frequency range 902 to 928 MHz or in the frequency range 2400 to 2500 MHz. 6. A method as claimed in any one of the preceding claims and wherein the method includes controlling the microwave dose to have a power level in the range 3kW to lOOkW. 7. A method of processing wool comprising: (a) taking a compressed wool fibre mass and locating it in a microwave oven adapted to receive the mass and, when operated with a selected dose of microwave radiation, to establish a similar degree of heat-induced effects on the wool throughout the bale, (b) applying the selected dose of microwave radiation, the dose being applied for several minutes at a selected frequency and energy level to achieve throughout the wool bale temperatures in the range 30°C to 50°C. 8. A method as claimed in claim 8 and wherein the time for application of the selected dose is the range two minutes to ten minutes. 9. A method as claimed in claim 9 and including selecting the microwave energy dose to have a power level in the frequency range 3kW to lOOkW and an energy in the frequency range 902 to 928 MHz or 2400 to 2500 MHz. 10. A method of processing wool comprising processing a compressed wool fibre mass by a method as claimed in any one of the preceding claims while the mass is retained in a compressed form in means to restrain expansion, removing the means to restrain expansion to allow expansion of the wool fibre mass and effecting a wool scouring operation. 11. Wool fibre produced by the method as claimed in any one of the preceding claims.

Inventors: BRADHURST DOUGLAS HARDIE, MCLEAN DAVID WILLIAM, BRADHURST, DOUGLAS, HARDIE, MCLEAN, DAVID, WILLIAM
Applicants: BRADHURST DOUGLAS HARDIE, ILLAWARRA TECH CORP LTD, MCLEAN DAVID WILLIAM, BRADHURST, DOUGLAS, HARDIE, ILLAWARRA TECHNOLOGY CORPORATION LIMITED, MCLEAN, DAVID, WILLIAM
Application year: 1997
Main classification: D01B9
IPC codes: D01B3, D01B9, D01C3, D06M10