In this specification, the term"modal fabric"means a fabric woven or knitted from staple fibre yarns comprising regenerated cellulose fibres of the modal type. Modal fibres are defined in International Standard ISO 2076: 1999 (E) and are high wet-modulus, high breaking- strength regenerated cellulose fibres produced using particular viscose and regeneration bath compositions which allow greater molecular orientation during stretch coagulation of the fibres. Another regenerated cellulose fibre of the modal type, again with high wet modulus and high breaking strength, is known as a polynosic fibre and was developed in Japan by the Tachikawa Company. Both modal and polynosic fibres are often referred to as high wet- modulus (HWM) fibres because that is their significant characteristic compared with ordinary viscose fibres.

The staple fibre yarns used may comprise just modal-type fibres or a blend of modal-type fibres with one or more other fibre types such as cotton, linen, polyester and nylon. Furthermore, the fabrics may additionally include yarns which do not incorporate modal-type fibres, for example yarns of the other fibre types referred to and blends thereof.

Regenerated cellulose fibres are produced by forming cellulose into a soluble chemical derivative and then extruding a solution of this derivative through a spinning jet into a bath which regenerates the extrudate as cellulose fibres. Viscose fibres are produced in this way.

Particular spinning conditions and formulations are used to

produce the high wet-modulus regenerated cellulose fibres known as modal and polynosic fibres and referred to herein as modal-type fibres.

Background Lyocell fibres, which are solvent-spun cellulose fibres, not regenerated cellulose fibres (see ISO 2076: 1999 (E)), were introduced commercially relatively recently. Lyocell fibres have a tendency to fibrillate during vigorous dyeing and finishing processes, and much effort has been put into controlling this phenomenon. In particular, treatments have been developed to remove the relatively long protruding fibre ends which are formed in the first stage of the fibrillation process (so-called"primary fibrillation") and which otherwise produce a hairy effect, often matted, on the surface of the fabric and thus disfigure its appearance. On the other hand, the development of the shorter fibrils which are formed in the fibrillation process (so-called"secondary fibrillation") is encouraged.

These shorter fibrils create a surface finish which is characterised as being"clean", in the sense of being substantially free from a hairy effect, and as having a soft touch imparted by the shorter fibrils on the fabric surface and which is referred to as a"soft-touch finish".

When the shorter fibrils are sufficiently developed, the soft touch of the fabric surface is more pronounced and the soft-touch finish is referred to as a"peach-touch finish".

Examples of such treatments for lyocell fabrics are described in WO 95/30043, WO 97/30204, and GB 2314568.

Of the modal-type regenerated cellulose fibres, modal fibres themselves are less susceptible to fibrillation than lyocell fibres. Although fibrillation can be induced in such modal fibres by vigorous processing, controlling the fibrillation to produce the desired clean, soft-touch finish to a commercially acceptable standard has proved difficult. Polynosic fibres fibrillate more easily than

modal fibres but, again, controlling the fibrillation to produce the desired surface finish is difficult. The present invention aims to provide modal fabrics as defined with a clean, soft-touch finish which is consistently reproducible to a commercial standard.

Disclosure of the Invention The present invention provides a process for producing a dyed and finished modal fabric having a clean, soft-touch surface finish by carrying out the steps of dyeing, washing and drying the fabric using vigorous action on the fabric in at least one of the steps, characterised in that, before the dyeing step is carried out, the fabric is evenly impregnated with an aqueous solution of an acid or acid donor and is then heat treated in a gaseous atmosphere to activate the action of the acid or acid donor, whereby the dyed and finished fabric has a clean, soft-touch surface finish. In particular, the soft-touch finish achieved may be a peach-touch finish.

The vigorous action required to cause fibrillation in modal fabrics is known to fabric processors; it involves flexing and abrading forces acting on the fabric during processing, usually through the combined action on the fabric of turbulent fluid flows and equipment surfaces moving at differential speed to the fabric. Turbulent liquid flows, such as are encountered in fabric jet dyeing machines and in rotary tumbling machines, are more effective in producing such fibrillation in a shorter processing time.

The ability of the process of the invention to deliver dyed modal fabrics having a clean, soft-touch finish after a vigorous processing step such as jet dyeing or rotary tumbling is of commercial importance. It means that the fabric can be processed on existing equipment using normal process routines without the need for extended processing times. For example, a dyeing cycle of six hours or less

may be used in a jet dyeing machine. Suitable jet dyeing machines include machines known as Thies Ecosoft, Thies Soft TRD, Gaston County Futura, and Hisaka Circular CUT-SL.

Conventional dyes and dye recipes for modal fabrics may be used in the process of the invention, including those based on direct dyes, vat dyes, sulphur dyes and reactive dyes.

In addition to its application to woven and knitted modal fabrics in the length, the process of the invention can also be used in respect of the dyeing and finishing of piece goods or garments made from modal fabrics. Garments made from modal fabrics can benefit by acquiring a desirable clean, soft-touch finish on the surface of the garment.

The application of the solution of the acid or acid donor and the subsequent heat treatment step may be applied to the modal fabric prior to its being converted into piece goods or garments. However, it may also be applied to the piece goods or garments after conversion.

It has been found that the clean, soft-touch finish produced on the modal fabric is protected against deterioration in subsequent processing. In particular, articles comprising the dyed fabric, such as garments or other piece goods, retain their clean, soft-touch finish through repeated laundering cycles.

The solution of the acid or acid donor is preferably an aqueous solution. The fabric may be evenly impregnated with this solution using any of the conventional techniques for applying liquids to fabric. Fabric in the length may be passed in open width through a pad bath of the aqueous solution, usually with a wet pick-up of the solution in the range 65 to'80 per cent by weight on weight of fabric.

Piece goods such as garments may be immersed in the solution in a vessel such as a drum washing machine.

The acid or acid donor is preferably a weak acid of the type used as a catalyst for resins used in textile finishing processes. Usually, these have a pH of greater than about 3. Suitable acids or acid donors include organic acids such as citric acid and tartaric acid, and Lewis acids. Magnesium chloride, ammonium chloride, zinc chloride, zinc fluoroborate and zinc nitrate are suitable weak acids or acid donors. Mixtures of two or more of these compounds may also be used and, indeed, manufacturers of acid catalysts for resin finishing sometimes use mixtures in their catalyst formulations. An example of a commercial product which can be used in the process of the invention is Condensol FB (trade mark of BASF AG), an acid catalyst comprising a mixture of magnesium chloride and zinc fluoroborate.

Preferred solution concentrations of the acid or acid donor depend upon the particular acid or acid donor used, lower concentrations with highly active materials to avoid unwanted acid damage to the fabric and higher concentrations with less active materials. For commercial products, the manufacturers recommend concentrations for resin-finishing processes and, in general, such concentrations may be used in the process of the invention.

Organic acids can be used in the concentration range of about 2 to 20 g/l, for example about 4 to 6 g/l in the case of citric acid. Citric acid applied at a concentration of 4 g/1 has a pH of 3.2. Less active acids or acid donors may use greater concentrations, for example up to about 40 g/1.

Magnesium chloride applied at a concentration of 20 g/1 has a pH of 7.5. Unnecessarily large concentrations are preferably to be avoided in all cases to prevent unwanted acid damage to the fabric and to minimise chemical usage.

The impregnated fabric is then heat-treated in a gaseous atmosphere, for example in a hot air oven. It may previously be dried in a separate step but preferably the

drying is just the initial stage of the heating step. The modal fabric preferably is treated in open width, for example on a stenter passing through a heating oven or chamber. The temperature of the gaseous atmosphere used in the heat treatment is chosen to be effective in initiating the action of the particular acid or acid donor used. In general, a range of 120°C to 220°C is suitable, more preferably a range of 140°C to 200°C. Again, preferred processing times depend upon the particular acid or acid donor used but are usually in the range 30 seconds to 5 minutes. Any residual acid may be removed by washing or scouring the heat-treated fabric and then re-drying it.

If yarns of the modal fabric have been sized or lubricated to facilitate weaving or knitting, then the fabric preferably is subjected to a desizing or scouring operation, usually carried out prior to the impregnation with the acid or acid donor. This may be a conventional operation in which the fabric is passed through a scouring bath to remove the size or lubricant. If pre-bleaching of the fabric is required, then it is preferred that this is carried out prior to the impregnation with the acid or acid donor.

Another possible treatment of the fabric is a so-called causticising treatment with an aqueous sodium hydroxide solution. This should be carried out after the impregnation with the acid or acid donor and the subsequent heat treatment but before the dyeing step. Causticising is carried out to improve the flexibility of the fabric in the wet state. Causticising also enhances dyeability of the fabric, which may be depressed by the acid treatment, and has the further effect that the fabric is tightened in structure, which helps to reduce any propensity for shrinkage in later wet processing. After causticising, the fabric should be thoroughly rinsed with hot and then cold water to remove residual caustic soda.

After being washed to remove any unfixed dye, the dyed fabric may be given one or more conventional finishing treatments, including application of a soft-finish by a conventional padding operation. This may be carried out after the dyeing and washing processes without the need for any intermediate drying of the fabric. If a wet tumbling treatment is required to develop a soft-touch finish, this may be carried out in a rotary tumbling machine after dyeing, either together with or after any soft finish treatment. The finished fabric may then be given a final drying, for example in a tumble-drying machine.

The invention is illustrated by the following Examples:- Example 1 A modal fabric comprised a woven fabric of basis weight 180 gsm (grams per square metre) constructed in a 2 by 1 twill weave from yarns of count 1/20s Ne comprising 100 per cent high wet-modulus modal fibres of 1.3 dtex (HWM Modal fibres ex Lenzing AG).

The fabric was scoured in open width using an aqueous scour bath containing a non-ionic detergent and sodium carbonate and at a temperature of 90°C, and it was then dried on a stenter at a temperature of 100°C.

Half of the scoured fabric was reserved as a control and the other half was impregnated by padding with an aqueous solution of 14 g/1 of magnesium chloride hexahydrate and 1.0 g/1 of a wetting agent, Kieralon JET (Kieralon is a trademark of BASF AG), at 80 per cent wet pick-up. The impregnated fabric was stentered and dried at a temperature of 110° C and then heat treated in air at a temperature of 190° C for 50 seconds. The treated fabric and the control fabric were then each dyed and finished using the same regime. Dyeing was carried out on a Gaston County Futura

jet dyeing machine over a period of 6 hours using an aqueous dyebath containing:- Procion H-EXL dye at 4.0 per cent owf (on weight of fabric) (Procion is a trademark of Dystar AG), Sodium sulphate at 60g/1, Soda ash at 20 g/1.

The dyed fabrics were rinsed with water to remove unfixed dye, softened using Edunine CSA (Edunine is a trademark of Uniqema) at 2.0 per cent owf applied from an aqueous bath at a temperature of 40°C, and then tumble-dried in a Thies Rototumbler fabric tumbling machine.

The control fabric was unfibrillated and had a normal smooth surface. The treated fabric had developed a clean, soft-touch finish.

Example 2 A modal fabric comprised a woven fabric of basis weight 180 gsm constructed in a 2 by 1 twill weave from yarns of count 1/20s Ne comprising 100 per cent high wet-modulus fibres of the modal type of 1.3 dtex (HWM Modal fibres ex Lenzing AG) The fabric was scoured in open width using an aqueous scour bath containing a non-ionic detergent and sodium carbonate and at a temperature of 90°C, and then it was dried on a stenter at a temperature of 100°C.

The desized fabric was then evenly impregnated with an aqueous solution of citric acid at a concentration of 4.0 g/l by uniformly squeezing the solution into the fabric using a pad mangle at an expression of 75 per cent wet pick-up. The impregnated fabric was dried and heat- treated on a stenter frame in air at a temperature of 160°C for 5.0 minutes. After thorough rinsing with water and drying, the treated fabric was ready for dyeing.

Dyeing was carried out in a Thies Ecosoft Plus jet dyeing machine. In addition to the treated fabric, an untreated but desized control fabric of the same specification was also dyed and finished as hereinafter set out.

The dyeing method used was a hot-exhaust migration dyeing method carried out over a period of 6 hours using an aqueous dyebath containing:- Procion Navy H-EXL dye at 4.0 per cent owf, Sodium sulphate at 60g/l, Soda ash at 20g/l.

After rinsing with water, the dyed fabrics were treated with a soft finish, Edunine CSA, at 20 per cent owf applied from an aqueous bath at a temperature of 40°C, before being tumble-dried in a fabric rope tumbler (Biancalani Aero 1000). The dyed control fabric was unfibrillated and had a normal smooth surface. The treated fabric had developed a degree of fibrillation of the short, secondary fibrillation type, which gave it a clean, soft-touch surface having the characteristic of a peach-touch finish.

Example 3 A modal fabric comprised a double jersey interlock fabric knitted from yarn of count 1/20s Ne. The yarn comprised a 70: 30 blend by weight of polynosic fibres and polyester fibres of which the polynosic fibres were of 1.7 dtex and 38mm staple length (Junalon fibres ex Fujibo) and the polyester fibres were of 1.5 dtex and 38mm staple length (Trevira type 140 fibres ex Hoechst AG).

The fabric was slit to open width and divided, with part being kept as an untreated control and part being impregnated in a pad bath at 80 per cent wet pick-up with an aqueous solution containing 14 g/1 magnesium chloride

and 1.0 per cent Kieralon JET. The impregnated fabric was then placed on a stenter and dried in air at a temperature of 110°C before being heat treated in air at a temperature of 190°C for 45 seconds.

The treated fabric and the control fabric were then individually subjected to the following scouring, dyeing, softening and drying regime. Scouring was carried out using an aqueous solution of a nonionic detergent and sodium carbonate at a temperature of 90°C for 30 minutes.

The fabrics were then rinsed in water before being dyed over a period of 6 hours in a jet dyeing machine as described in Example 1 using the same dyebath recipe but with the dye at 3.0 per cent owf.

After rinsing with water, the dyed fabrics were treated with a soft finish, Sandoperm MEJ (Sandoperm is a trademark of Clariant AG), at 2.0 per cent owf from an aqueous bath at a temperature of 40°C and were then tumble- dried in a Biancalani Aero 1000 fabric rope tumbler.

The dyed control fabric had a somewhat matted surface appearance created by uncontrolled fibrillation. The fabric treated according to the invention had a soft peach-touch finish and a uniform, clean appearance free from long fibrils and visible crease marks.