AU2011100702A4

AU2011100702A4 - Textile fibre separation by gravity and electrostatic forces

Info

Publication number: AU2011100702A4
Application number: AU2011100702A
Authority: AU
Inventors: Andrew Lewis
Original assignee: AUSTRALIAN FIBRE TECHNOLOGY
Current assignee: AUSTRALIAN FIBRE TECHNOLOGY; Lewis, Andrew Dr
Priority date: 2011-06-12
Filing date: 2011-06-12
Publication date: 2011-07-21
Anticipated expiration: 2019-06-12

Abstract

Abstract Many bulk fibres have a range of diameters. The coarse fibres reduce the market value of bulk fibre intended for apparel textiles. Silk and cashmere wool are considered to be exclusive, as they have a pleasant soft touch. This is a result of small fibre diameter. Raw cashmere normally under goes manual dehairing to remove the coarse guard hairs prior to apparel manufacture. Mechanisation has had limited success and to date only an extended carder is available for cashmere and other wool products, but it damages some of the fibres and only partially reduces the number of guard hairs. The operator is unable to choose the diameter of the two streams. The described invention utilises gravity and electrostatic forces to divide the bulk fibre into multiple streams of specific diameters, as required. The invention can be used for any clean and free fibres including animal, plant and blast fibres. E x Cx 30- X X 20 30 40 50 60 70 80 90 100 Fibre diameter (microns)

Description

1 Description The nature & feel of textiles is partly dependent upon the diameter of the fibre used. For some fibre there is an inverse correlation between market price and the fibre diameter. The Australian Wool Exchange regularly publishes quotes for Merino Wool at different average micron sizes. For 9-15 June 2011, 17 micron wool for the Southern Market was AUD 23.45/kg and 32 microns was AUD 560/kg. All wool producing animals have coarse guard hairs protruding through the softer down hairs. Dehairing is frequently carried out by hand. Mechanisation has had limited success and only with some fibres, specifically cashmere, and less so for alpaca (TJTI 2008 Vol. 99 No. 6 pp. 539aE"544). The present invention addresses this problem of dehairing fibre products such as cashmere, alpaca wool and any type of clean carded fibre, including plant fibre. Multiple streams of specific fibre diameter can be removed. In air, the rate of fall, due to gravity, is dependant on the surface area to mass ratio. Therefore it follows fibres with a larger diameter fall faster than small diameter fibres. Figure 1 is a plot of individual fibres (alpaca) that were inserted into a fast horizontal air stream and then allowed to settle from the air stream due to gravity. Large diameter fibres fall from the stream sooner than small diameter fibres. Fibre length was between 2 and 10cm. Electrostatic neutralisation A major problem is fibres cluster together as a result of electrostatic attraction. Neutralisation can be achieved with a high voltage (HT) alternating current (AC), as opposed to electrostatic precipitation/collection which uses direct current (DC). The neutralising effect of AC is well known in the discipline of electrochemistry. Horizontal air stream 2 Textile fibres are accelerated in an air stream. The fibres continue into a large volume where the air and fibres de-accelerate. As a result of gravity, the larger fibres drop from the stream sooner than the small diameter fibres, allowing collection by diameter. Neutralisation of electrostatic attraction can be maintained throughout the system (accelerating & de-accelerating chamber), by using opposing conducting electrodes, with HT AC. Vertical air stream Fibres rising in a column are separated based on fibre diameter, where small diameter rises faster than large diameter. Collection of the segregated fibres can be by electrostatic collection (HT DC). Prior to collection fibre-fibre interaction is eliminated by HT AC. Electrostatic and gravity separation Fibres pass into an electrostatic collector (HT DC) and settle on the charged electrode or plate. The charge is rapidly reversed. This causes the small diameter fibres to be ejected quicker than the larger ones. This is because electrostatic force between individual particles is inversely proportional to surface area, also small fibres can accelerate faster than large ones. The electrodes or plates are then earthed (neutralised) or go into HT AC (augmented neutralisation) and a vertical air stream passes over the plates collecting the small diameter fibres. These fibres are collected faster as a result of the fore mentioned process and as a result of gravity-airflow interaction. The process of collection followed by rejection can be repeated many times before the fibres are completely carried out of the electrostatic collector by the air stream. Timed air valves or electrostatic collectors collect the different fibre fractions.

Claims

1. Electrostatic neutralisation by high voltage alternating current separates the fibre clusters. A fast horizontal air stream carries the separated fibres into a large volume where de-acceleration occurs. Large diameter fibres fall from the air stream earlier than small diameter fibres as a result of gravitational forces.

2. The device as described in claim 1 wherein electrostatic neutralisation is maintained throughout the process, both in the accelerating and de-accelerating chambers.

3. The device as described in claim 1-2 wherein the air stream is vertical.

4. The device as described in claim 3 wherein the fibre is introduced to the air stream in batches. At any point in time the small diameter fibres have travelled further than the large diameter fibres

5. The device as described in claim 3-4 wherein electrostatic fibre collection, using direct current, is utilised at different points along the air stream.

6. Direct current (electrostatic collector) collects the UNSORTED fibre on one of two opposing charged plates. Rapid reversal, for a short duration, of the direct current causes rejection of the small diameter fibres faster than the larger diameter fibres. An air stream picks up the small diameter fibres and moves them away quicker than the large diameter fibres.

7. The device as described in claim 6 wherein an additional electrode or electrodes of negative charge is/are placed between or near the opposing charged plates to create a corona.

8. The device as described in claim 6-7 wherein the fibres after rejection and carrying a little up stream, are then attracted and collected to the opposite plate by maintaining a second reversal of the direct current. A third reversal of direct current occurs of short duration causes rejection of the small diameter fibres faster than the larger diameter fibres. An air stream picks up the small diameter fibres and moves them further upstream from the larger diameter fibres. 4

9. The device as described in claim 6-7 wherein the polarity of the plates are repeatedly reversed.

10. The device as described in claim 6-9 wherein a high voltage alternating current is applied to neutralise electrostatic attraction BETWEEN the fibres, during the short duration when rejection of fibres occurs, allowing more effective separation.

11. The device as described in claim 6-10 wherein the first fibres (small diameter) which leave the electrostatic plate region are directed by an air valve to a storage bin, the valves direct the later larger diameter fibres to different storage bins.

12. The device as described in claim 6-10 wherein electrostatic fibre collection using direct current is utilised at different points along the air stream.

13. The device as described in claim 1-12 wherein separation of different fibre diameters of all animal wools and plant fibres including but not limited to: sheep wool, goat wool, camel wool, rabbit hair, hemp, flax, pineapple leaf, banana, coir, New Zealand flax, manila hemp, kenaf, and algave fibres.