SYSTEM FOR TREATING MATERIALS FOR SEPARATION

Abstract: A system (10) is provided for treating a mixture (12) containing desired materials (14) and contaminating plastic materials (16) for separation at a subsequent material processing stage. The system (10) comprises a treatment station (18), guiding means (24, 25, 30) for guiding the mixture (12) into the treatment station (18), and heating means (20) for heating a fluid medium flowing in said treatment station (18). The heating means (20) is arranged so that the mixture (12) at said treatment station (18) is heated to a temperature within a predetermined temperature range below melting points of the plastic materials. When heated to that temperature and exposed in the treatment station (18) within a predetermined time period the contaminating plastic materials (16) change their physical characteristics to a form allowing separation a the subsequent material processing stage. The system is particularly useful for removing plastic fibers from natural fibers such as wool, cotton or silk.

Description: SYSTEM FOR TREATING MATERIALS FOR SEPARATION TECHNICAL FIELD OF THE INVENTION THIS INVENTION relates to a system for treating a mixture of desired materials and contaminating materials for separation at a subsequent material processing stage and in particular but not limited to a system for treating a mixture of natural fibres contaminated with polymer fibres for separating the treated polymer fibres at a subsequent fibre processing stage. BACKGROUND OF THE INVENTION Quality of many products depend to a large extent on purity of the materials used for them. In the case of natural fibre products, their expected prices can be greatly reduced if flaws due to contamination with foreign materials are present. Apart from reduced prices reputation and sales of the producers can also be affected. Accordingly maintaining or improving product quality is very important to manufactures of the products and suppliers of raw materials for the products. Attempts made to separate contaminating materials have been successful for certain types of contaminants. For example during wool processing carbonising using acids to turn grass seeds into carbon for separation and combing using fine combs to remove short fibres, coiled fibres and remaining vegetable matter have achieve certain success. Visual inspection followed by manually picking of contaminating foreign materials are also used to separate certain contaminating materials. However none of the above prior art attempts can successfully separate contaminating foreign materials which substantially resemble the desired materials in both colour and physical character. In the wool industry it is known that wool fibre is frequently contaminated with polymer fibres due to the wide spread use of wool packing and baling twines made of polymer fibre materials. Polymer fibre contamination cannot be separated from wool fibres by carbonising or combing as their physical characteristics are substantially similar. In addition as they may be white or in other colours, when the contaminating fibres are of the same or similar colour they are also difficult to detect visually especially when embedded in the wool fibres. United States patent no. 5,305,497 to Liverani et al. teaches a device for separating polypropylene fibres mixed with discontinuous silk fibres coming from waste silk. The mixture of fibres for feeding to the device must be in the form of a lap with fibres at least semicombed or at least made sufficiently straight. This device has a pair of endless steel belts with electrical resistors arranged thereon for heating the belts. In order to heat the polypropylene fibres mixed with the silk fibres the belts are moved onto each other to compress the mixture and at the same time heating and transferring the mixture along the belts. The polypropylene fibres form clusters when subject to heat and compressive force. The clusters of the polypropylene fibres will stick to the steel belts. To prevent the clusters from sticking thereto the belts are coated with a Teflon material, along This system thus applies heat directly and conductively to the silk material. The silk fibres are prone to damage when using this prior art device as it is difficult to control and maintain temperature on the belts. Electric resistance heating takes a considerable long time to heat the belts to a desired temperature. Any occurrence of overheating will also take a relatively long time to cool to the desired temperature. The quality of most natural fibre materials deteriorates when subject to prolonged contact with the heated belts while under compressive force. OBIECT OF THE INVENTION An object of the present invention is to alleviate or to at least reduce to a certain level one or more of the prior art disadvantages. OUTLINE OF THE INVENTION In one aspect therefore the present invention resides in a system for treating a mixture containing desired materials and contaminating plastic materials for separation at a subsequent material processing stage. The system comprises a treatment station, guiding means for guiding the mixture into the treatment station, heating means for heating a fluid medium flowing in said treatment station so that the mixture at said treatment station is heated to a temperature within a predetermined temperature range below melting points of the plastic materials, at which the contaminating plastic materials change their physical characteristics to a form allowing separation at the subsequent material processing stage when exposed in the treatment station within a predetermined time period. In another aspect therefore the present invention resides in a method for treating a mixture containing desired materials and contaminating plastic materials for separation at a subsequent material processing stage. The method comprising the steps of: a. guiding the mixture into a treatment station; b. applying heat to a fluid medium flowing in said treatment station so that the mixture at said treatment station is heated to a temperature within a predetermined range below melting points of the plastic materials; and c. exposing the mixture in the treatment station for a predetermined time period so that the contaminating plastic materials change their physic characteristics to a form allowing separation at the subsequent material processing stage. Typically the forms of the changed characteristics include shrinking, curling, balling of the contaminating material, beads, denser mass or larger mass, so that the contaminating materials can be separated by beating, combing or be easily identified for picking. The desired material in the mixture may include one of natural fibres including wool, cotton, silk and the like. Said one natural fibres may be in the form of loose fibres, slivers or the like. The contaminating plastic materials may be any type of heat shrinkable plastic fibres including polyethylene (PE) fibres, polypropylene (PP) fibres, high- density polyethylene (HDPE) fibres, nylon and the like. PE and PP fibres are commonly used in baling twine and packagings for seeds and fertilisers. HDPE fibres are generally used in packagings for the desired materials. It is therefore unavoidable that some of the desired materials are contaminated with the PE, PP and/or HDPE materials. It is preferred that the heating means includes a heat source and a blower arranged to blow or draw said fluid medium over the heat source and into the treatment station. Examples of the heat source include fuel burners, electronic heaters, microwave, steam and the like. Said fluid medium may be any flowable material. Typically said fluid medium is air. The heat source may be arranged in any suitable location. In a preferred the heat source is located within feed rollers upstream of the treatment station. The predetermined temperature range is typically between 1 50-300 degree Centigrade and the predetermined time period is typically within 1 to 20 seconds. In a preferred application the treatment station is heated to 180-192 degrees Centigrade and the mixture is exposed to heat in the treatment station for about 3 seconds. The system for the present invention may be provided with guiding means for movably guiding the mixture into the treatment station at a speed of travel so that the mixture is exposed to heat within the predetermined time period. The guiding means may include one or more of a laminar air stream, a conveying arrangement, rollers or the like. In one form said guiding means includes a first pair of cooperating feed rollers arranged upstream of said treatment station for guiding said mixture into the treatment station. The guiding means may include a second pair of cooperating feed rollers arranged downstream of said treatment station for guiding treated mixture out of the treatment station. The rollers each have a hollow body with perforations and a baffle arranged in the body. The baffles of said first pair are so arranged that an air stream guiding said mixture towards the treatment station enters into said body through said perforations on one side of the baffles, and the heated fluid medium enters said treatment station through said perforations on opposite side of the baffles . One or more connection paths may be connected to the first pair of feed rollers. The connection path or paths are arranged for substantial of said guide air stream to bypass said treatment station. Typically the connection path or paths are arranged to join said first and second pairs of feed rollers so that said guide air stream can guide the treated mixture downstream of the treatment station. In preference one or more fluid medium return paths are connected to said first pair of feed rollers and are so arranged that the fluid medium flowing in said treatment station can return to the treatment station through the perforations in said first feed rollers. A pump may be included in one or each said return paths for pumping said fluid medium towards the first feed rollers. For wool processing the said processing stage may be any one of the stages for scouring, carding, gilling, combing and spinning or between any two stages. Desirably the treatment station is incorporated in the carding stage or the combing stage. More desirably the treatment station is arranged at the doffer in the carding stage. The treatment station may have means directing said mixture along a serpentine path. Said directing means may include rollers and/or conveyors and/or air stream. BRIEF DESCRIPTION OF THE DRAWINGS In order that the system of the present invention cam be readily understood and put in practically effect the description will now refer to the accompanying drawings which illustrate non-limiting embodiments of the present invention and wherein:- Figure 1 is a schematic drawing showing one embodiment of the system according to the present invention; Figure 2 is a schematic drawing showing a second embodiment of the system according to the present invention; Figure 3 is a schematic drawing showing a third embodiment of the system according to the present invention; Figure 4 is a schematic drawing showing a fourth embodiment of the system according to the present invention; Figure 5 is a schematic drawing showing a fifth embodiment of the system according to the present invention; Figure 6 is a schematic drawing showing a sixth embodiment of the system according to the present invention; Figures 6A to 6C are schematic drawings showing different serpentine paths within the treatment station of the system according to the present invention; Figure 7 is a schematic drawing showing a seventh embodiment of the system according to the present invention, in which the treatment station is incorporated into a carding stage for wool processing; Figure 8 is a schematic drawing showing an eight embodiment of the system according to the present invention; and Figures 9 to 1 1 show contaminated wool before, during and after being subject to treatment in the system according to the present invention. DETAILED DESCRIPTION OF THE DRAWINGS Referring initially to Figure 1 there is shown a system 10 for treating a mixture 12 of wool fibres 14 and polymer fibres 16 which represent contamination of the wool fibres 14. The system 10 has a treatment station 18 which in this case has a hot air blower 20 for blowing hot air at about 180°C onto the mixture 12. The mixture 12 as can be seen is guided into the treatment station 18 by guiding means in the form of a perforated conveyor 22 movably controlled by spaced rollers 24. The rollers 24 are controlled so that the mixture 12 is exposed to heat in the treatment 18 for about 3 seconds. Figure 1 shows that the treated contaminating fibres 1 6 change shape and a fine reticulating comb 26 separates the treated fibres 16 from the wool fibres 14. Clean wool fibre 28 is thereby obtained following combing. In the embodiment shown in Figure 2, the mixture 12 is guided into the treatment station 18 and then guided through the station 18 under tension by rollers 30. Figure 3 shows an embodiment of the system 10 which is similar to the Figure 2 embodiment except for the addition of a conveyor 24. The embodiment of the system 10 shown in Figure 4 has a further conveyor 25. The embodiments shown in Figures 1 to 4 have hot air applied from one side of the mixture 12. In the Figure 5 embodiment the treatment station 18 has air openings 32 positioned just downstream of the rollers 30 at the inlet end of the station 18. The openings 32 allow hot air to be applied to either sides of the mixture 12. In this manner contaminating plastic materials 16 on or near both surfaces of the mixture 12 are equally treated. Figure 6 shows an embodiment of the system 10 which guides the wool mixture 12 from the doffer 34 of the carding stage into the treatment station 18 for heat treatment before being collected in the coil head 36. As can be seen the treatment station 18 shown in Figure 6 has a serpentine path which helps to reduce the length of the station 18. Another form of the serpentine path is shown in Figure 6A. As for the previous embodiments the treatment station 18 has feed rollers 30 at inlet and outlet thereof. The feed rollers 30 at the inlet guide the mixture 12 into the station 18. Thereafter various rollers and conveyors arranged as shown move the mixture 12 in a three loop serpentine path before being guided by the feed rollers 30 at the outlet out of the station 18. In Figure 6B there is shown a further form of the serpentine path. In this form a pulley arrangement is used to train the mixture 12 along a serpentine path. The form of the serpentine path for the mixture 12 in Figure 6C is guided by a series a rollers arranged as shown. In Figure 7 the system 10 is incorporated into the carding stage of wool processing. In this embodiment, the treatment station has an oven 38 shaped to fit over the lower part of the doffer 40. The wall of the oven which embraces the doffer 40 is spaced from the outer perimeter of the doffer 40 so that the mixture 12 can enter the space in which it is subject to heat treatment. The mixture 12 is guided by the doffer 40 to the doffer comb 42 which removes the mixture 12 from the doffer 40. Col lander rollers 44 guide the mixture 12 out of the carding stage and the station 18. Figure 8 shows an embodiment of the system 10 according to the present invention in which both heated air and a guide air stream are reused. In this embodiment the feed rollers 30 have a hollow body with perforations, and a baffle plate 52 separating the perforations so that half of the perforations are exposed to the guide air stream 54 shown in solid arrows and half are exposed to heated air 56 shown in hollow arrows. A conduit 58 provides a bypass path for the air stream 52 through said perforations of the rollers 30 at the inlet of said treatment station 18 to flow to said rollers 30 at the outlet of the station 18. The air stream 54 then flows through perforations of the rollers at said outlet to guide treated mixture 12 to a subsequent process station (not shown). The heated air 56 is recirculated by a pump 60 in a conduit 62 which joins the rollers 30 at the inlet and the outlet. The perforations and the baffle plate 52 in the rollers 30 allow substantially all of the guide air stream to bypass the station 18 and to be reused for guiding treated mixture 12. The same also allow substantially all of the heated air 56 to recirculate in and out of the station 18 so that heating costs are minimised. Figure 9 shows a sample of wool 14 contaminated with polymer fibres 16. As can be seen in Figure 10 the fibres 16 shrunk following heat treatment at the station 18. They become shorter but with denser mass and larger cross-section. In Figure 1 1 the treated fibres 16 have been removed in a combing processing step. It should be noted that the treated fibres 16 do not adhere to the wool fibres 14 as the hot air in the treatment station 18 does not reach melting point of the fibres 16. This allows removal of the fibres 16 without significant loss in wool fibres 14. Whilst the above has been given by way of illustrative example of the present invention many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as herein set forth.

Claims: CLAIMS 1 . A system for treating a mixture containing desired materials and contaminating plastic materials for separation at a subsequent material processing stage, the system comprises a treatment station, guiding means for guiding the mixture into the treatment station, heating means for heating a fluid medium flowing in said treatment station so that the mixture at said treatment station is heated to a temperature within a predetermined temperature range below melting points of the plastic materials, at which the contaminating plastic materials change their physical characteristics to a form allowing separation at the subsequent material processing stage when exposed in the treatment station within a predetermined time period. 2. A method for treating a mixture containing desired materials and contaminating plastic materials for separation at a subsequent material processing stage, the method comprises the steps of: a. guiding the mixture into a treatment station; b. applying heat to a fluid medium flowing in said treatment station so that the mixture at said treatment station is heated to a temperature within a predetermined range below melting points of the plastic materials; and c. exposing the mixture in the treatment station for a predetermined time period so that the contaminating plastic materials change their physic characteristics to a form al lowing separation at the subsequent material processing stage. 3. The invention according to claim 1 or 2 wherein the changed characteristics include shrinking, curling, balling of the contaminating material, beads, denser mass or larger mass, so that the contaminating materials can be separated by beating, combing or be easily identified for picking. 4. The invention according to claim 1 or 2 wherein the desired material in the mixture includes one of natural fibres including wool, cotton, silk and the like. 5. The invention according to claim 1 or 2 wherein the contaminating plastic materials is any type of heat shrinkable plastic fibres including polyethylene (PE) fibres, polypropylene (PP) fibres, high-density polyethylene (HDPE) fibres and the like. 6. The invention according to claim 1 or 2 wherein the heating means includes a heat source and a blower arranged to blow or draw said fluid medium over the heat source and into the treatment station. Examples of the heat source include fuel burners, electronic heaters, microwave, steam and the like. 7. The invention according to claim 1 or 2 wherein the predetermined temperature range is between 150-300 degree Centigrade and the predetermined time period is within 1 to 20 seconds. 8. The invention according to claim 7 wherein the treatment station is heated to 180-192 degrees Centigrade and the mixture is exposed to heat in the treatment station for about 3 seconds. 9. The invention according to claim 7 or 8 wherein the system is provided with guiding means for movably guiding the mixture into the treatment station at a speed of travel so that the mixture is exposed to heat within the predetermined time period. 10. The invention according to claim 9 wherein the guiding means includes one or more of a laminar air stream, a conveying arrangement, rollers or the like. 1 1 . The invention according to claim 9 or 10 wherein said guiding means includes a first pair of cooperating feed rollers arranged upstream of said treatment station for guiding said mixture into the treatment station, the rollers each having a hollow body with perforations and a baffle arranged in the body, the baffles of said first pair are so arranged that an air stream guiding said mixture towards the treatment station enters into said body through said perforations on one side of the baffles, and the heated fluid medium enters said treatment station through said perforations on opposite side of the baffles . 12. The invention according to claim 1 1 wherein the guiding means include a second pair of cooperating feed rollers arranged downstream of said treatment station for guiding treated mixture out of the treatment station. 13. The invention according to claim 1 1 or 12 wherein one or more connection paths are connected to the first pair of feed rollers, the connection path or paths are arranged for substantial of said guide air stream to bypass said treatment station. 14. The invention according to claim 12 wherein the connection path or paths are arranged to join said first and second pairs of feed rollers so that said guide air stream can flow to guide the treated mixture downstream of the treatment station. 1 5. The invention according to any one of claims 1 1 to 14 wherein one or more fluid medium return paths are connected to said first pair of feed rollers and are so arranged that the fluid medium flowing in said treatment station can return to the treatment station through the perforations in said first feed rollers. 16. The invention according to claim 1 5 wherein a pump is included in one or each said return paths for pumping said fluid medium towards the first feed rollers. 1 7. The invention according to any one of the preceding claims wherein the system/method is for wool processing and the said processing stage is one of the stages for scouring, carding, gilling, combing and spinning. 18. The invention according to claim 1 7 wherein the treatment station is incorporated in the carding stage or the combing stage. 19. The invention according to claim 1 7 or 18 wherein the treatment station is arranged at the doffer in the carding stage. 20. The invention according to any one of the preceding claims wherein the treatment station having means directing said mixture along a serpentine path. 21 . The invention according to claim 20 wherein said directing means includes rollers and/or conveyors and/or air stream.

Inventors: ARMSTRONG PETER ELLIOTT SCOTT, ARMSTRONG, PETER, ELLIOTT, SCOTT
Applicants: ARMSTRONG PETER ELLIOTT SCOTT, POLYGON PTY LTD AS TRUSTEE FOR, ARMSTRONG, PETER, ELLIOTT, SCOTT, POLYGON PTY LTD AS TRUSTEE FOR POLYGON UNIT TRUST
Application year: 1999
Main classification: B07B13
IPC codes: B03B1, B07B13, B29B17, D01B3, D01B9, D01G9, D01G13, D01G15, D01G31, D01G37, D06B3, D06L1