Synthetic fibres such as polyester, NYLON (RTM) , KEVLAR (RTM) and acrylic fibres are in widespread use and have many attractive properties. Polyester fibres are particularly suitable for clothing and other applications because they have a degree of fire resistance, they are easily washable and they are strong. However, synthetic fibres suffer from the disadvantage that they are not very water absorbent. Water absorbency is a highly desirable property for synthetic fibres in very many applications such as towels, some items of clothing, surgical clothing and dressings and many other applications.

It is an object of the present invention to provide a process whereby synthetic fibres can be rendered more absorbent, and an absorbent synthetic fibre.

The invention provideds a method of treating synthetic fibres including the steps of treating the fibres with a swelling agent to cause them to swell and subsequently treating them with an alcohol to cause the alcohol to be incorporated on or in the fibre.

The swelling agent used can be any convenient substance which will effect swelling of the fibre concerned and which, preferably, causes a degree of alteration to a surface layer of the fibre. For use as a swelling agent many of the typical agents can be used which are classed as "carriers" in the dyeing process. Typical carriers are: INVALON PBN (manufactured by CIBA-GEIGY) DILATIN AUT (manufactured by SANDOZ) SETAVIN CAW (manufactured by ZIMMER & SCHWARZ) DILATIN NAN (manufactured by SANDOZ) DILATIN OM (manufactured by SANDOZ) DILATIN TPC (manufactured by SANDOZ) All the above as carriers are found to be satisfactory, however, we have found that DILATIN OM has less of a foaming problem than the others and therefore is preferred.

The swelling agent or carrier will normally be applied in the form of a solution. An application of 3% of the dry weight of the fibre being treated of the above carriers has been found satisfactory and gives a sufficient degree of surface treatment during a reasonable treatment period. However, it will be a appreciated that many variations in the strength of the carrier solution and the length of treatment are possible.

Conventional dyeing can be carried out at about 100°C "at the boil" using a carrier, or the carrier

can be eliminated and dyeing can be carried out at an elevated temperature, for example 130°C. In carrying this invention into effect, it has been found advantageous to treat the fibres with the carrier at a temperature above 100°C. Preferably the temperature is at least 110°C and desirably 130°C or more. The use of a strongly alkaline pH magnifies the effect of the carrier and is highly desirable. A treatment time at this temperature of 45 minutes has been found to be satisfactory for a 2 kg batch, but again, the period of time can be varied to suit different fibres and different temperatures.

As alkali, sodium hydroxide has found to be quite satisfactory because it is cheap and easily available. Potassium Hydroxide will probably be equally applicable, because it is the alkilinity more than the other component of the material which is important. Other hydroxides would probably also be useful, but in view of the ready availability and cheapness of sodium hydroxide it is unlikely that any other alkali would be commercially practical.

In carrying out the second step and treating the prepared fibres with an alcohol, the alcohol can conveniently be used in a solution, for example an aqueous solution.

Preferably the alcohol used is a glycol. Each molecule of the alcohol can be considered to have a carbon based core and one or more hydroxyl groups

connected thereto. As it has been empirically determined that it is the hydroxyl groups in the final product which increase the water absorption, it is desirable to use an alcohol in which the proportion of hydroxyl groups to the carbon based core is as high as possible. For this reason glycols have advantages over simple alcohols. Methyl and ethyl alcohol would be possible contenders for use in the second step but both are relatively expensive and methyl alcohol is poisonous. Simple alcohols which have been found useful are ethylene glycol and poly-ethylene glycol. Poly-ethylene glycol having a polymer chain of 3 to 5 units has been found satisfactory in so far as cost and performance is concerned.

It has been found desirable to use an application of 3% polyethylene glycol by weight based on a 2kg batch for 60 minutes at a temperature above 100°C, preferably above 110°C and desirably at about 130°C. Of course, these temperature, the dwell time and the strength of solution can be varied widely from fibre to fibre and from fabric to fabric in order to achieve the desired degree of water absorbency. The process of the invention can be carried out on fibre per se in the hank, as sliver, or on cones or the like. However, the process can equally well be carried out on fabrics formed as by weaving or

knitting or otherwise.

After the second step it is advantageous to treat the fibre with a softener. This again gives a ^' significant increase to the water absorbency of the fibres and adds significance to the water absorbency already applied by the carrier/alcohol treatment. However, whilst the carrier/alcohol treatment is permanent, in that it is not significantly reduced by very many washings of the fibre or fabric, the effect imparted by the softener is reduced after washing and is therefore not permanent. It is envisaged that in relation to articles which are to be washed subsequently, the use of a softener in washing liquid would be recommended to maintain a very high level of absorbtivity.

The process of the invention can be carried out alone, but can very conveniently be carried out simultaneously with the dyeing of the fabric or fibre. Thus, the alcohol is conveniently added to the dye liquor and the dyeing step is carried out simultaneously with the application of the alcohol.

The invention includes of course fibres, filaments and yarns treated in accordance with the invention as well as fabrics and other fibrous formed structures treated in accordance with the method of the invention.

The invention further includes a synthetic fibre having a water absorption capacity (as measured by the

—fo¬

rest described herein) of ^ 250%. Preferably the capacity is ^ 400%.

The invention will be described further, by way of example, with reference to preferred methods thereof, it being understood that the following description is illustrative and not limitative of the scope of the invention.

Fig. 1 is a diagram essentially in the form of a time/temperature graph illustrating the process and its various components.

Table 1 is a selected group of results showing the improvement of the invention.

Table 2 shows the results of spot sinking and weight increase tests carried out at an early stage of experimentation on the first production batch. It will be seen that comparative figures are for the K81 sample as shown in Table 1.

Table 3 shows the results of the various tests after each of stages 1, 2 and 3 of the process in relation to a polyester terry towelling double sided of a weight 280g per square metre, processed in two kilogram batches on the HT80 machine.

Tables 4 and 5 show the result of the process when applied to over thirty samples of terry towelling each of 250kg weight and of material comparable to that described in relation to Table 3.

In carrying out a preferred method of the invention (see Fig. 2) a conventional dyeing machine

is used which has a pressure chamber capable of operating at temperatures above 100°C.

As a preliminary to the specific example to be described later, it should be stated, for the avoidance of doubt, that the method of the invention is not limited to a dyeing process nor to the treatment of fabric. The method of the invention is applicable to fibres in any raw or partly processed form or to any particular type of fabric. Further, the method can be carried out independently of any dyeing process and, indeed, can be carried out prior to or after any dyeing process if it should be necessary. However, as the carrier is a common part of a dyeing process, it is very convenient to carry out the method of the invention simultaneously with a reasonably conventional dyeing step.

The fibre of the invention can be fibre per se in bulk, as sliver, as filaments, as thread, or as fabric or other structure formed by weaving, knitting or other fabric forming processes.

The fibre of the invention can be made by the method of the invention or otherwise.

A preferred exemplary method of the invention is carried out in a conventional sample pressure dyeing machine having a tank with a capacity of 50 litres and manufactured by Roaches Limited. A two kilogram batch of a warp knitted terry polyester fabric having a weight of about 280gm sq/ ^m and a yarn count of 34

metric was prepared. The fabric was preset by heat setting to discourage later shrinking. In the tank of the machine a solution was prepared based on 3% INVALON PBN on the weight of the sample being dyed in water at 40°C. Caustic Soda was added to achieve a pH of 12. About 20 kg of solution was used. The fabric unsudded and the temperature of the solution was raised from 40°C up to 130°C at a rate of 2°C per minute. When the temperature of 130°C had been reached the solution was kept at this temperature for 45 minutes and thereafter allowed to cool to 40°C. At this stage the bath was emptied and a new bath was prepared also at 40°C which consisted of approximately 20Kg of solution. This solution included 3% of polyethylene glycol having from 3 to 5 carbon atoms in its chain based on the 2kg of fabric being processed. The solution also contained 0.2% ^w /w of TERASIL PINK 4BL (manufactured by Ciba) plus lg per litre of solution of a dispersing agent. The batch and the solution were heated from 40°C up to 130°C at a rate of 1°C per minute. Having reached 130°C the solution was maintained at this temperature for 60 minutes and then allowed to cool to 60°C and the bath emptied. The bath was then refilled with 20kg of water with 3% (by weight of the batch) CASSAPRET SRH-X (a suitable softener) . The bath was then heated gradually up to 60°C maintained at that temperature for 15 minutes and allowed to

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cool to 40°C, the bath was dropped and the batch of fabric dried on a stenter in air at a 150°C.

A control sample was used which was dyed in a conventional manner using the same dye to give precisely the same shade but without the glycol in the dye bath.

The difference between the treated fabric and the control fabric were quite startling as is evidenced by the following test for absorbency. Whilst these tests are non-standard, they are repeatable

Test Procedure for Absorbent Polyester

The unique process of the invention for improving the absorption properties of polyester is permanent to normal washing. It significantly improves the following properties:

ABSORBTION

WICKABILITY

WETTABILITY The following is a description of the testing techniques used.

The process, which imparts the absorbant properties to synthetic fibres is permanent to normal washing. Prior to testing for these special absorbent properties it is necessary to remove any "temporary finishes" which may be present on a "washing-off" procedure.

The washing off procedure is as follows:

(a) Cut out a 30cm x 30cm sample, which should be sufficient in size to cover the few special tests. (b) Wash the material to be tested for 15 minutes in hard water only at 50°C with no detergents, (c) Rinse the washed material very thoroughly under cold hard water to ensure that all detergents are removed. ( --) D y fabric thoroughly in an oven with air circulation at about 120°C.

2. PREPARATION OF TEST SAMPLES

Cut the pretreated sample measuring 30cm x 30cm in the following shapes: (a) Sinking test 1.5cm x 1.5cm square (Two samples)

(b) Spot absorbtion test..10cm x 10cm square (One sample)

(c) Wicking test 50mm x 200mm (Warp direction) x 50mm (weft direction and 50mm (warp direction) x 200mm (Weft direction)

(d) Weight absorbtion 100cm square (usually) or circle (One)

3. SINKING TEST

Fill a glass laboratory beaker with cold hard water. With tweezers, lay a 1.5cm x 1.5cm sample of the fabric to be tested face side down, on the surface of the water. From the time the fabric is laid on the surface of the water, count the number of seconds for

the square sample being tested to sink below the surface of the water.

Repeat the test face side up, and record both results.

4. SPOT ABSORBTION TEST Lay the 10cm x 10cm sample to be tested on a non-absorbent material (e.g. glass or plastics) . Take a glass pipette, and lay drops of cold hard water on the surface of the face of the fabric. Observe the number of seconds that each of 5 drops takes to fully sink into the fabric.

Record the worst result.

Repeat the test on the back of the fabric.

5. WICKING TEST

Take a glass beaker containing a coloured dye, in a contrasting colour to the colour of the fabric to be tested.

Place a yellow laundry marker 2cm from the bottom of the 50mm x 200mm sample to be tested.

Put the test sample into the beaker of dye, so the yellow marker is just level with the dye solution.

Leave the sample immersed for 60 seconds. Remove the sample from the beaker and immediately mark the height to which the dyestuff has risen. Record this height in mm.

Repeat the test in the other direction (warp or weft) .

6. WEIGHT ABSORBTION TEST

Take the 100cm square or circle of sample to be tested with tweezers, and lay on the surface of cold

hard water in a glass beaker. Leave the sample for 30 seconds. After 30 seconds, remove the sample from the glass beaker with tweezers, and allow to drip for 15 seconds to remove excess water. Weigh the tested material immediately, on a balance.

The percent increase in weight is recorded as follows:

2 2

Wet qm/m - Dry qm/m = % increase in weight Dry gm/m

TABLE 1

7. SPECIFICATION AND RESULTS FOR K60

K81

This was the first production batch processed on the HT-80

TABLE III

TABLE III Continued A B S O R P T I O N

S P O T S I K I N G W I C K I N G Tests Face Back Face Back Length Weight Increase

CONTROL 10mins+ 10mins+ 10nιins+ 10mins+ Omm 8.4% ^"

30mm 261%

44mm 535% 51mm 479%

Omm 240% 50mm 499% 61mm 447%

43mm 461%

54mm 476% 53mm 476%

TABLE IV ABSORPTION DATA ON POLYESTER TOWELLING

Quality: K108 Customers :Marks & Spencer

SINKING TEST WICKING WEIGHT ABSORPTION

Colour Job No, Loop Pile

Green 8174 Osec Osec RF 609 Osec Osec

RF 610 Osec Osec RF 611 Osec Osec 8175 Osec Osec

8153 Osec Osec 8164 Osec Osec a

I 8156 Osec Osec 8157 lsec lsec 8162 Osec Osec 8221 Osec Osec

Control Sample I80sec+ I80sec+ I80sec+ I80sec+ Untreated

TABLE ABSORPTION DATA ON POLYESTER TOWELLING QUALITY:. K108 Customer: Marks & Spencer.

SINKING TEST SPOT TEST Loop Pile Loop Pile

I 80sec+ 180sec+

In a second preferred method the polyethylene glycol was replaced in an equivalent amount by ethylene glycol. The results were virtually identical to those obtained in the first preferred method mentioned above.

In a third exemplary method, processes comparable to the aforesaid processes were carried out in relation to a flat polyester single jersey. Details of the fabric are as follows: Fibre Denier 1.7 denier per filament. Yarn Count 1/30 English Cotton Count

2

Fabric Weight I55gm/m

(or comparable figures if the fabric is knitted.

It is important that we give enough identifying data to enable a third party to purchase the identical fabric so that he can carry out identical tests. Please also mention whether or not the fabric was dyed or was it in a natural colour.

The process of the invention was carried out on on one sample, weighing 2k.g and consisting of some

10 metres of the fabric. The fabric was pretreated, and then treated in accordance with the previous method. After treating, samples were cut from the treated and tested in accordance with the procedures previously used.

One test was carried out per result. Control samples were cut from the untreated fabric.

The results of the aforesaid treatment and tests are as set out in Table VI

Absorption Data on Polyester Single Jersey. Finished weight 160qm/m—

TEST CONTROL TREATED

Sinking Loop 5mins + lOsec. to Sink Test absorbed immediately Pile 5mins + lOsec. to sink absorbed immediately

Spot Loop lOmins + Osecs Test Pile lO ins + Osecs

Wicking Omins 52secs

Weight Absorption +2% +262%

The mechanis (s) by which the process of the invention works are not, at present, fully understood. Even though carriers are very well known for use as swelling agents in the dyeing industry, even their operation in that field is not fully understood. It is believed, however, that the carrier attacks the surfaces of the fibre and either allows a certain amount of water to enter into the

body of the fibres thereby swelling them, or alters the molecular configuration of the fibres in some way as to cause the individual polymer molecules to become less tightly packed, thus leaving rather larger sites or cavities on the surface of the fibre which can hold water or other molecules. It is also believed that the carrier has a roughening effect on the fibre surface which causes the surface area of the fibre to be increased. In dyeing these factors are instrumental in allowing the dye to adhere to the surface of the fibres and also to diffuse into the body of the fibres.

It is believed that the carrier treated fibres are receptive to the alcohol/glycol molecules in a manner comparable to the molecules of dye. It is believed that the core of the alcohol/glycol molecules, being essentially carbon based and therefore oleophilic is attracted to the essentially oleophilic surfaces of the polymer molecules making up the fibre. The molecules probably form a surface coating on the fibre, particularly over the enlarged surface created by the carrier and perhaps diffuse somewhat into the surface of the fibres. The hydroxyl molecules, being essential hydrophylic create the water absorbency which is observed in the test illustrated above in relation to the preferred embodiments. When water contacts the fibres which have been treated water molecules can rapidly adhere to the hydroxyl groups

on the surfaces of the fibres and migrate into the fibres to become attached to any hydroxyl groups on any alcohol which has penetrated into a surface layer of fibres. This adherence and possibly migration into the fibres manifests itself as a much increased absorbency. Of course, in relation to fibres which are not monofilament fibres, i.e. having been spun from staple fibre and in connection with fabrics formed from either sort of yarn, the hydrophylic surfaces on the fibres and fibre components of yarn greatly increase the capillary action of water within the fibres and fabrics, leading to much enhanced water absorption.

It should be stressed here that this mechanism is only postulated to explain the success of the process of the invention. Much testing and research will be needed before we can be sure whether or not this is actually correct.

As mentioned earlier, the scope of the invention is not limited to the precise examples shown above and variations can be made thereto.

For example, the process is equally applicable to fibres in any condition and to any type of fabric formed from such synthetic fibres . The process can be carried out independently of the dyeing process. Very many different fibres are treatable in addition to those listed above. The carrier and alcohols can also be varied from those used in the preferred

method. In the third step (the addition of the softener) any suitable softener can be used.

The alkalinity of the solution in which the carrier is used can vary from 8 to 14, or other values, but 11 is preferred.

Alkalies other than caustic soda can be used.

As carriers, swelling agents many substances can be used including:

INVALON PBN (manufactured by CIBA-GEIGY) DILATIN AUT (manufactured by SANDOZ)

ΞETAVIN CAW (manufactured by ZIMMER & SCHWARZ)

DILATIN NAN (manufactured by SANDOZ)

DILATIN OM (manufactured by SANDOZ)

DILATIN TPC (manufactured by SANDOZ) Many alcohols (which term is used to include glycols) can be used including:

ETHYLENE GLYCOL

POLYETHYLENE GLYCOL Grade 200

POLYETHYLENE GLYCOL Grade 300 Many softening agents can be used, including but not limited to the following:

CASSAPRET SRH-X (Hoechst)

LEOMIN Nl-X (Hoechst)

CERRANINE NC (Sandoz) TINEGAL SH (C.H.T.)

SOFTENING AGENTS LNS (ALLIED Colloids) .

Of course, fibres such as polyester, nylon, kevlar, nomex and acrylics can be treated using the

process of the invention.

It should be mentioned of course, that the first step of the invention, i.e. treatment with swelling agents, does not necessarily have to be carried out in an alkaline environment. A very prolonged treatment with the "carrier" can be used without the alkaline. However, it is -expected that treatment times could be increased by a factor of 10 or more, and the use of the alkali is much to be desired.

The fibres of the invention can be made by methods other than the method of the invention. Whilst the method of the invention is described as batch process, the invention can be carried out in a continuous or semi-continuous process, fibre/fabric being transferred by conveyor means via a series of baths, or being fed as a continous fabric sliver or the like via a series of baths, or via a single, changing bath.

The work described in the examples has been carried out in relation to fibres of a denier per filament of around 1.7. However, recent tentative but essentially non-quantitative experiments in relation to fibres of a denier per filament below 1.00 and even below 0.5 have suggested that even greater absorbtivity can be achieved. As smaller diameter fibres have a greater surface area to weight ratio, and as the effect of the method is a surface effect, this is to be expected.

Many other variations are possible within the

scope of the invention,