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SCOURING SYSTEM FOR WOOL

The invention relates to continuous washing processes, including greasy wool scouring and yarn scouring (by tape scour or by package-to- package wet processing machinery). For example, the invention relates to an improvement to the scour described and claimed in New Zealand Patent specification No. 168134 the content of which is incorporated by way of reference. The invention is actually applicable to any scour including a WRONZ™ comprehensive scouring system with mini-bowls as described in WRONZ Report No. 49. 1978. 9p. by P.E. Chisnall and R.G. Stewart entitled Studies in Woolscouring.IV. Commercial Scouring with mini-bowls.

An example is a comprehensive scouring system with mini-bowls which is an aqueous woolscouring train which removes wool grease, suint and dirt from wool in a succession of mini-bowls, each separated from the next by a high pressure squeeze press. Typically, as shown in the attached Figure 1 , there are six bowls, although seven-bowl scours do exist. The wool passes firstly through three (or four) scouring bowls, at about 60°C and containing detergent, then through two (usually) cold rinsing bowls, and finally a heated (about 60°C) rinse bowl. The wool is then squeezed and dried.

Within each bowl there is a circulation of liquor (flowround) from under the squeeze press (sidetank) to a jet box at the front of the bowl. From here the liquor is jetted to wet the incoming wool.

The first bowl is continuously depleted of liquor by two mechanisms: 1 . by the movement of entrained liquor in the wool mat into bowl two; and

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2. by the controlled flow of liquor, after various solids and grease removal processes, to drain (flowdown) to prevent an unacceptable build-up of contaminants.

To make up the volume of the first bowl to the required level, liquor from bowl 2 is pumped into bowl 1 . Bowl 2 is then made up in turn from the bowl 3 liquor, which in turn is made up from the final hot rinse bowl. This overall flow of liquor is counter to the flow of wool (usually 1-2 litres/kg greasy wool) and is called flowback. This serves to concentrate the con¬ taminants in the first part of the scour train.

Three mechanisms operate to remove contaminants from the wool as it moves down the scouring train i.e.:

1 . contaminants which are part of the entrained liquor from the previous bowl are removed by dilution as the wool mat moves through successively cleaner bowls;

2. contaminants still attached to the fibre surface are removed because they have had longer immersion in the hot liquors and have been subjected to more prolonged agitation; and

3. contaminants still attached to the fibre surface are removed because they encounter greater concentrations of free detergent.

In conventional scouring, detergent is only added to the second and third bowls. The amount of detergent added depends on the type of wool being scoured. For good quality crossbred fleece, the minimum addition would seldom be less than 3 kg detergent/tonne greasy wool. Wools that are finer, dirtier or are from lambs or the sliping process would require more

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detergent. The detergent addition is usually into the sidetank, in a region where there is some turbulence to ensure satisfactory mixing.

Thus both detergent and hot rinse water from the final bowl of the scour are separately added to the somewhat contaminated liquor in the final scouring bowl.

It is an object of the present invention to provide a wool scouring process which goes some way to producing wool with less residual woolgrease and/or wool with a brighter colour than wool produced by conventional processes or which at least provides the public with a useful choice.

Broadly, the invention provides a wool scouring process in which wool is squeezed then sprayed with a detergent solution then squeezed again, after it has been treated in a final scouring bowl.

Particularly the invention provides a wool scouring process in which wool is squeezed then sprayed with a detergent solution or fresh water then squeezed again prior to rinsing.

The invention is preferably intended for use with a mini-bowl scouring system of the type designed by the applicants and known as a WRONZ™ wool scour.

The wool is sprayed with fresh water or flowback liquor from a final hot rinse bowl, in which is dissolved most or all of the detergent used in the scouring process.

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The invention also provides scoured wool when produced by the inventive process.

Broadly the invention involves replacing in a wool scour the squeeze- press after the last scouring bowl with a squeeze-spray-squeeze system.

In particular, after removal of the wool from the last scouring bowl an initial squeeze is applied to the wool which is then sprayed with fresh water or a flowback liquor from the final hot rinse bowl of the wool scour. All or most of the detergent used in the scouring process is mixed with the fresh water or flowback liquor so the wool is treated with a detergent solution which is relatively clean and concentrated. Then the wool is squeezed again to thereby improve the colour of the scoured wool and reduce the residual grease content before it enters the first rinse bowl of the wool scour.

In the scouring process according to the present invention, the detergent is added as a solution to the wool after most of the contaminants have been removed. This is done by replacing the squeeze press which normally follows the last scouring bowl (usually the third bowl) of a wool scour with a squeeze-spray-squeeze system. This can comprise a conventional squeeze press, followed by a conveyor or some other transport mechanism on which the wool is carried beneath a spray. The spray is made up of flowback liquor (from the last [hot] rinse bowl of the wool scour) in which all or most of the detergent used in the scouring process has been dissolved. Alternatively the spray can be fresh water in which all or most of the detergent used in the scouring process has been dissolved. The wool then passes through another conventional squeeze press and into the rinse bowls as usual.

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Simpie trial experiments have been carried out by the applicants on a pilot wool scouring plant to examine the effect of making these changes to the scouring process, without changing the scouring temperature or the amount of detergent used.

An example of the invention will be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a diagram of a Wool Research Organisation of New Zealand (WRONZ) comprehensive scouring system with mini-bowls; and

Figure 2 shows a diagrammatic view from the side of modifications incorporated to a pilot WRONZ mini-bowl wool scouring plant.

The example of the invention will now be described with reference to a WRONZ mini-bowl scouring system as shown in Figure 1 . It is to be appreciated that with minor modification the technology is applicable to any scouring system.

The pilot plant is based on a WRONZ mini-bowl scouring system incorporating a train of six bowls 1 ,2,3,4,5 and 6 in which the bowls normally have dunkers and rakes (not shown) which slowly move wool along the train in the direction of arrow 7. Squeeze rollers 8 are normally situated between each bowl. The addition of detergent is shown by arrows 9 and cold rinse water by arrows 10. Flowback from the final rinse bowl is indicated by arrow 1 1 . The recycling of liquids is indicated by the arrows. The other ancillary scour equipment is indicated only by way of example.

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The system indicated in Figure 1 was modified by adding another squeeze press at 12 between the last scour bowl 3 and the first cold rinse bowl 4.

As shown in Figure 2 a laboratory squeeze press 14 was inserted into the scouring train. The detergent, which is normally added to the scouring bowls, was instead mixed with flowback from the final hot rinse bowl 6.

The woolscour was modified by removal of a rotary dunker from bowl 4 and in its place a small, 300mm wide laboratory squeeze press 14 (roller diameter 100mm) was inserted (Figure 2). A chute 1 5, constructed of light stainless steel, conducted a woolmat (arrow 1 6) from the conveyor 1 3 to the laboratory squeeze press 14, and another chute 17 from the press 14 into bowl 4. When the scour was operating in conventional mode the top roller 18 of the laboratory squeeze press 14 was removed, so the rotating bottom roller 1 9 served only to convey the wool mat from the conveyor 13 to bowl 4.

When the scour was operating in modified mode the wool passed through the small squeeze press 14, at a pressure approximately equivalent to that found in the squeeze press of a commercial wool scour.

In conventional mode, the flowback from bowl 6 was led into a side tank 3a of bowl 3. In modified mode, the flowback from bowl 6 was diverted to a 60 litre fibreglass tank and its flow (measured by timed flow into a measuring cylinder) was manually controlled by a valve to give a flow of 1 .5 litres/kg greasy wool scoured (i.e. equal to the flowdown from bowl 1 ).

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ln conventional mode the detergent was added to the sidetanks of bowls 2 and 3. In modified mode the detergent was added to the 60 litre fibreglass tank as a 10% (m/m) solution to ensure good mixing and at the same rate (as 100% detergent) as it had been added to the scour during conventional scouring. The flowback-detergent mixture in the fibreglass tank was pumped to a spraybar 20 attached to the frame of the bowl 3 squeeze press, at a rate such that the level remained constant at the midpoint of the fibreglass mixing tank. The spraybar consisted of two B1 /4HH-10SQ Fuiljet jets (Spraying Systems NZ Limited) mounted 1 50mm apart on a 25mm diameter pipe, arranged to give a spray which effectively covered the width of the wool mat.

The scouring procedure set out below was followed for each of the three trials.

The scour was set up in conventional scouring mode i.e. 3 hot (60°C) scouring bowls, 2 cold and 1 hot (60°C) rinse bowls. The wool throughput was set at approximately 1 50kg/h greasy and total detergent usage was 3.0kg/tonne greasy wool.

Three trials were carried out using:

1 . a good fleece wool;

2. a poorly coloured fleece wool; and

3. an oddment/dagwool blend.

Trial 1. Good Fleece Wool

Four bales (773kg) of a single lot of greasy crossbred wool were processed.

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Relevant wool properties are given in Table

Table I. Some properties of the good fleece wool used in scouring Trial 1

Fibre diameter 37.0 μm

Yield 75.4% dry

Colour Y 63.5 (Y-Z) 3.0

Two bales of the wool were blended by layering in a large pile and then making vertical cuts when feeding the scour. The wool passed through a mechanical opener before scouring.

Trial 2. Poorly Coloured Fleece Wool

Five bales (800kg) of a single farm lot of poorly coloured greasy crossbred wool (type BC, 3-5") were processed.

Relevant wool properties are given in Table II.

Table II. Some properties of the poorly coloured fleece wool used in scouring Trial 2.

Fibre diameter 37.0 μm

Yield 85.4% dry

Colour Y 56.2 (Y-Z) 6.0

The wool was blended by layering in a large pile, and then making vertical cuts when feeding the scour. The wool passed through a mechanical opener before scouring.

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Trial 3. Oddments/Dag Wool Blend

Four bales (700kg) of an oddments/dag wool blend were processed.

Relevant wool properties are given in Table III.

Table III. Some properties of the oddments/dag wool blend used in scouring Trial 3.

Composition

Oddments 55%

Fleece 25%

Second Oddments 10%

Dag wool 10%

Fibre diameter 35.1 μm

Yield 66.0% dry

Colour Y 50.0 (Y-Z) 7.9

The wool was obtained in an opened and blended state but was passed through a mechanical opener before scouring.

Scouring System for Wool

In each trial, conventional scouring was carried out for 3-4 hours to bring the contaminant levels in the bowls to near equilibrium values. This was done by removing the top roller from the laboratory squeeze press (1 8, Figure 2) so the wool was only squeezed once between bowls 3 and 4, and by separately adding the detergent and the hot rinse flowback (from the final rinse bowl) to the side tank of bowl 3. After the equilibration period, a small test bale (75 kg) of conventionally scoured wool was collected for testing.

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The scour was then modified by replacing the top squeeze roller on the laboratory squeeze press (18, Figure 2), and by diverting the hot rinse flowback into the fibreglass mixing tank where the detergent was added prior to spraying the mixture onto the woolmat after the first bowl 3 squeeze press. A small test bale (75 kg) of the modified scoured wool was then collected for testing.

After processing, the two test bales of scoured wool (conventional and modified) were each opened and sampled as follows.

The wool in the bale was divided into four parts. Each part was placed in a sampling bin, and ten 100g samples taken from it. The ten samples were combined, and the resulting 1 kg sample was cored to give approximately 100g wool cores.

Both 'as-is' and base colour were measured on the same sub-sample of cores. 'As-is' colour is the colour of the scoured wool, measured with minimal disturbance, while base colour is the colour of the wool after all surface contamination is removed by intensive cleaning. The base colour preparation technique is described in NZ standard NZS 8707: 1 984, while both 'as-is' and base colour are measured using a HunterLab reflectance spectrometer, recording the X, Y and Z tristimulus values, using the procedure in NZS 8707: 1 984. The Δ values, which measure the dirtiness of the wool, are calculated from the Y tristimulus values:

ΔY = Ybase ^~ Y'as-is'

The larger the ΔY value, the dirtier the wool.

The ΛY values from the four parts of the bale were averaged to give a final

ΔY value.

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Dichloromethane (DCM) extractabies of the cores were measured using IWS Test Method 136.

The scouring trials were relatively uneventful, except that the moisture meter on the dryer ceased to function during the first trial, and so the dryer operating parameters were set manually. It is not expected that this would have had any effect on the results of the trial.

In the modified mode there was some difficulty in getting the woolmat to run smoothly.

The detergent spray wet the wool quite effectively, but some liquor drained through to the solid plastic Flextrak™ conveyor, giving a small liquor flow down the conveyor. This made the grip of the woolmat on the conveyor less tenacious than usual, and mechanical intervention was required to ensure that the woolmat kept moving properly. It is expected that the conveyor could be easily modified to overcome this problem, perhaps by drilling holes in it, or by the use of some other material with a more textured surface.

There was also some difficulty in getting the woolmat to run smoothly through the laboratory squeeze press, which appeared to be caused by the small ( 10cm) diameter rollers having a very short nip region. Manual intervention was again required. A full size squeeze press would not exhibit this problem.

Contrary to expectations, there was little foam formed during the spraying of the liquors.

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The results of the scouring experiments are given in Tables IV-VI.

Table IV. ΔY values and dichloromethane extractabies for good fleece wool after conventional and modified scouring.

Test Conventional Scouring Modified Scouring

ΔY 4.8 2.1

DCM extractabies 0.50 0.27

Table V. ΔY values and dichloromethane extractable for poorly coloured fleece wool after conventional and modified scouring.

Test Conventional Scouring Modified Scouring

ΔY 6.0 4.0

DCM extractabies 0.40 0.31

Table VI. ΔY values and dichloromethane extractable for oddments/dag wool blend after conventional and modified scouring.

Test Conventional Scouring Modified Scouring

ΔY 5.5 4.0

DCM extractabies 0.36 0.28

The average improvement in wool colour (ΔY) for the three wools was 2.1 ΔY units, or, on a relative basis, about 40%.

The average decrease in residual grease concentration was about 0.1 3% (as % woolgrease on the scoured wool), or, in relative terms, a 30% decrease. Again this is a most significant improvement.

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Although there were slight difficulties in processing the wool through a temporarily modified system, there would appear to be simple engineering solutions.

The wool scoured by the modified system was significantly better (in terms of reduced DCM extractabies and better colour) than wool scoured by conventional means.

Thus by this invention there is provided a modified wool scour which improves the colour of the scoured wool and reduces the residual grease content.

A particular example of the invention has been described and it is envisaged that improvements and modifications can take place without departing from the scope of the appended claims.

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