EP4698716A1

EP4698716A1 - Ozone treatment of cellulosic man-made fibres fabrics

Info

Publication number: EP4698716A1
Application number: EP24720195.7A
Authority: EP
Inventors: Begoña GARCIA VICTORIA; Ignasi OSET CÉSPEDES; Alejandro BAOS RUBIO; Michael Andrew Kininmonth; James Martin Taylor
Original assignee: Lenzing AG; Chemiefaser Lenzing AG; Jeanologia SL
Current assignee: Lenzing AG; Jeanologia SL
Priority date: 2023-04-21
Filing date: 2024-04-18
Publication date: 2026-02-25
Also published as: CN120958191A; WO2024218257A1

Abstract

The present invention discloses a process for producing a dyed and finished man-made cellulosic fibre fabric having a clean, soft touch finish, comprising subjecting the fabric to a wet processing treatment using mechanical action and giving the fabric a tumbling treatment, characterized in that the fabric is additionally treated with ozone. Furthermore, a fabric or garment finished using this process and which has a clean soft touch finish is disclosed.

Description

Ozone treatment of cellulosic man-made fibres fabrics

This invention relates to a process for the dyeing and finishing of a fabric, or a garment, made from cellulosic man-made fibres, in particular lyocell, modal or viscose fibres.

In this specification, the term “cellulosic wood-based fibre fabric”, “lyocell fabric”, “modal fabric” or “viscose fabric” means a fabric formed, particularly woven or knitted, from yams, particularly staple fibre yarns (but not exclusively), comprising cellulosic man-made fibers, lyocell, modal or viscose fibres respectively.

Such yams may comprise lyocell fibres alone or in a blend of lyocell fibres with fibres of one or more other cellulosic fibres alone such as cotton, viscose, linen or non-cellulosic types, such as polyester, elastane or nylon. Such yams may also comprise modal fibres alone or in a blend with one or more other cellulosic fibres or non-cellulosic types, such as cotton, viscose, linen, polyester, elastane or nylon. Furthermore, the fabric may additionally include yams that do not incorporate lyocell, modal or viscose fibres, for example yams of other fiber types referred to and blends thereof.

Lyocell fibers are produced by extrusion of a solution of cellulose through a spinning jet into a coagulation bath by a process known as solvent spinning. They are thus alternatively known as solvent spun cellulose fibers. Such a process is described in US-A-4,246,221 and uses as the solvent an aqueous tertiary amine N-oxide, particularly N-methylmorpholine N-oxide. Lyocell fibres are thereby distinguished from other man-made cellulose fibers, which themselves are produced by forming the cellulose into soluble chemical derivatives and then extruding a solution of this derivative into a bath that regenerates the extrudate as cellulose fibres; such as viscose fibers or modal fibers.

Modal fibre is a high wet modulus fibre produced using a modified version of the viscose process. In the viscose process fibre is produced by extruding a solution of a cellulose derivative through very small spinneret holes and then precipitating the cellulose derivative by changing the pH and by converting the derivative back to cellulose.

Cellulose in the form of wood pulp is usually used as the starting material, although other sources of cellulose such as bamboo, cotton linters and cellulose materials gained from recycling processes are also used. The wood pulp is steeped in sodium hydroxide and then reacted with carbon disulphide to convert it to cellulose xanthate. The xanthate is dissolved in a sodium hydroxide solution to yield a viscous, golden coloured liquid which is commonly called viscose. The viscose is de-aerated and filtered. It is then extruded through precious metal spinnerets into a spin-bath consisting of sulphuric acid, sodium sulphate and zinc sulphate. The acid reacts with the sodium hydroxide in the viscose to cause precipitation of the cellulose xanthate. The acid also reacts with the cellulose xanthate converting it back to cellulose.

While the newly formed fibre is still in a plastic state it is stretched to increase the orientation of the cellulose molecules with the axis of the fibre and encourage crystallisation. The fibre may then be cut into lengths to form staple fibre or it may be kept as continuous filament or tow depending on the design of the spinning machine and the product required.

In the remainder of the process the fibre is washed to remove non-cellulose products of the reaction such as sodium sulphate and hydrogen sulphide, then finished with lubricants and anti-stats to aid downstream processing and finally dried.

Modern viscose plants are designed to recover as much of the by-products of the process as possible. This is essential to avoid environmental pollution and to ensure the safety of the workforce and surrounding community. Better recovery and recycling of by-products can also give a positive economic benefit.

The modal process is similar to the viscose process in most respects. It differs in that coagulation and stretching are achieved first using a spin-bath that consists of a lower concentration acid and no zinc sulphate. The newly coagulated fibre which consists mainly of cellulose xanthate is stretched by up to three times. This causes the cellulose xanthate molecules to align parallel to one another. The cellulose xanthate is then converted back to cellulose by further acid treatment. An additive may also be mixed with the spinning solution to slow down the regeneration of the cellulose during spinning. Together with modified spin-bath and viscose composition, the additive allows the fibre to be stretched to a much greater extent than normal viscose. This gives a fibre with a higher orientation which is stronger than viscose and has a modulus closer to that of cotton.

Modal fibre is often used in blend with cotton to give softer fabrics than would be made with cotton alone. It is used widely in knitted fabrics for lingerie and ladies apparel.

Prior Art

Lyocell fibres are known to have a tendency to fibril late under relaxed wet abrasive conditions such as those present during vigorous dyeing and finishing processes, and various methods of dealing with this phenomenon have been proposed.

When it is desirable to avoid developing surface fibrillation, then dyeing is carried out using relatively gentle processing, such as pad-dyeing of open width fabric, and applying a resin finishing treatment using a cross-linking agent is carried out on the dyed fabric to protect the fibres against fibrillation in subsequent laundering processes.

Another method of dealing with this fibrillation tendency is to treat the fabric so as 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 produces a gross hairy effect, often matted, on the surface of the fabric and thereby disfigures its appearance. On the other hand, the development of the shorter fibrils formed in the fibrillation process (so called “secondary fibrillation”) is encouraged. These shorter fibrils create a surface finish characterized 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 surface and referred to as a “soft touch finish”. When the shorter fibrils are sufficiently developed then the soft touch of the fabric is more pronounced and the soft touch finish is referred to as a “peach touch finish”.

An example of such a procedure is described in WO-A-95/30043, and involves removing the product of primary fibrillation, which is formed during a dyeing process, by a post treatment with an acid catalyst used in conjunction with an optional cross-linking agent such as an N-methylol resin. Another example is described in WO-A-97/30204, where the lyocell fabric before dyeing is given a pre-treatment with an aqueous solution of an oxidizing agent such as sodium hypochlorite or hydrogen peroxide at elevated temperatures. A further example is described in GB-A-2, 314,568 and involves the use of the dyeing machine itself, for example a jet dyeing machine, to subject the lyocell fabric to an extended treatment with a solution of a strong mineral acid such as sulphuric acid for 30 to 120 minutes before rinsing the fabric and then commencing the dyeing sequence in the same machine. Each of these processes has been difficult to control to produce consistent results and none of them has been taken through into full scale commercial operation.

One process used successfully in commercial processing involves a posttreatment of a lyocell fabric that has been subjected to a wet processing operation such as dyeing. The protruding ends produced in primary fibrillation are removed in this post treatment by applying to the fabric a solution of a cellulase enzyme. WO-A- 96/17994 discloses such a process. The desired secondary fibrillation is developed in subsequent processing for example, in the dyeing process itself (if later) or in subsequent washing and drying steps using rotary tumbling machines, to produce a soft-touch finish on the surface of the fabric.

Cellulase enzyme treatments are successful in removing the long fibre ends produced in primary fibrillation from the surface of the fabric, but they are expensive both in terms of material costs and in terms of processing time.

A process was also developed to overcome these deficiencies and is described in WO-A-02/103104. It comprises a pre-treatment of a lyocell fabric carried out before the normal fibrillation inducing steps of dyeing (such as jet dyeing), washing and drying, using vigorous action on the fabric in at least one of those steps so as to produce fibrillation on the surface of the fabric, and it involves evenly impregnating the fabric with an aqueous solution of an acid or acid donor before heat treating it in a gaseous atmosphere to activate the action of the acid or acid donor. The temperature ranges quoted for heat treatment are 120 - 220°C, preferably 140-200°C. This process is able to produce dyed and finished lyocell fabrics having a clean, soft touch finish, substantially free of visible crease marks.

Like many other fabrics, modal and viscose fabrics pill during use and care. This is undesirable and reductions in the pilling propensity of a fabric can increase its attractiveness and utility.

Pilling is a surface defect of textiles due to abrasion and wear. It is caused by the ends of fibres from which the fabric is constructed working loose at the surface of the fabric. If one end of the fibre is gripped in the fabric, then the loose end has a tendency to roll up into a tangled ball. It may also combine with other nearby loose fibre ends to form larger tangled balls. These balls of fibre attached to the surface of the fabric are known as pills and their formation is known as pilling.

Pilling happens during washing and wearing of fabrics when loose fiber ends work out of the surface of the fabric. Then abrasion of the surface of the fabric in washing and when rubbed against other surfaces during wear causes the loose fiber ends to roll up into small bundles which are anchored to the surface of the fabric by fibers that are still forming part of the fabric. It is generally recognized that pilling occurs in four distinct stages which are fuzz formation, entanglement, growth, and wear-off.

All fabrics pill to some extent and modal tends to be somewhat more than viscose. Pilling is a problem if the pills become large enough to be visible and remain attached to the fabric by fibers that are still anchored in its structure. Pilling is affected by the design and construction of the fabric, the fibers used to make it, the way in which it is processed during manufacturing, the behavior of the wearer, and the environment where it is used. Stronger fibers are more likely to pill in use because the fibers holding the pills in place do not break easily to release the pills from the fabric surface. Fabrics made from synthetic fibres such as polyester, nylon and acrylic tend to pill the most, but natural fiber fabrics such as wool and cotton also pill to some extent.

A fabric is more likely to pill if it consists of shorter fibers because there are more fiber ends than in a fabric made using longer fibers and because shorter fibers are less well anchored in the fabric and hence more likely to work loose. The more loose fibers there are in a fabric, the more likely it is that pills will form.

Pilling can be avoided by preventing the movement of fibres out of the surface of the fabric. This can be done by singeing the surface of the fabric to remove fibre ends protruding from the surface and by increasing the twist in the yarn to more firmly lock fibres into the fabric. Proprietary finishes and chemical treatments are available which can prevent or reduce pilling. Polymeric coatings can be used to bind fibers into the fabric surface and prevent the fibres from entangling at the surface of the fabric. Weak points are sometimes created in fibres so that when pills do form they are less likely to remain attached. The anchoring fibres break at the weak points releasing the pill. Cotton fabrics can be treated with cellulase enzymes to remove surface fibres and hence prevent pilling.

Modal and viscose fabrics may pill during dyeing and finishing and during subsequent wearing and care of garments made from them. Pilling may be controlled using the methods described above. Using higher twist yams and weaving or knitting tighter fabrics will reduce pilling. Anti-pill finishes may be applied to prevent pilling.

Pilling of these fabrics can be minimized during dyeing and finishing by using relatively gentle processing, such as pad dyeing of open width fabric and resin finishing with a crosslinking agent, usually carried out on a dyed fabric, to set the fibres and hence prevent them moving out of the fabric during subsequent laundering processes.

Removing surface hairs from a modal and viscose fabric will also reduce the tendency to pill. One way this can be done is by singeing the surface of the fabric by passing the fabric through a flame.

In the case of modal and viscose, like many other fabrics, they pill during use and care. This is undesirable and reductions in the pilling propensity of a fabric can increase its attractiveness and utility.

Pilling of the fabrics can be minimized during dyeing and finishing by using relatively gentle processing, such as pad dyeing of open width fabric and resin finishing with a crosslinking agent, usually carried out on a dyed fabric, to set the fibres and hence prevent them moving out of the fabric during subsequent laundering processes.

Removing surface hairs from a modal or viscose fabric will also reduce the tendency to pill. One way this can be done is by singeing the surface of the fabric by passing the fabric through a flame.

Another way to remove surface hairs on cellulosic fabrics is by enzyme treatment using a cellulase enzyme. Cellulase enzyme treatment can be successful in removing the long fibre ends from the surface, but tend to be ineffective on both modal or viscose fabrics, plus they are expensive both in terms of material cost and in terms of processing time.

Historically there are several ways to achieve a wash-down effect on readymade indigo denim garments in a commercial fashion laundry. These include detergents, pumice stones, enzymes and chemical bleaching agents or a combination of two or more of these. Those bleaching agents are used to accelerate the process time of indigo colour loss. Bleaching is primarily carried out in order to lighten the indigo colour to achieve the final desired shade. Sodium Hypochlorite, Potassium Permanganate and to a lesser extent, Hydrogen Peroxide and Laccase enzymes are the main bleaching chemicals employed for the so-called “wash-down effect”.

Due to cost and availability, in the majority of cases sodium hypochlorite is used for bleaching. However due to AOX (adsorbable halogenated organic compounds) being released into the wastewater effluent, chlorine-free bleaching technologies have become an object of intense interest for the denim finishing industry.

Alternative bleaching agents, such as laccase enzyme, sulfinic acid derivatives or glucose have a better environmental acceptability, but come with some practical application issues. Therefore the main development activity has focused on the use of advanced oxidation processes (AOPs) particularly ozonation.

Ozone has a powerful oxidizing capacity, and has been found to have strong potential for decolourisation of textile dyes. Commercial machines (both garment processing machines and fabric preparation machines) are now available in order to fade indigo-dyed garments by ozonation. Problem

In view of the state of the art described above there was a need for a process which allows new and unique effects to be achieved with greater flexibility of process and better control to produce the desired clean, soft touch finish of fabrics in the form of garments or piece goods for both lyocell, modal or viscose.

Disclosure of the Invention

The present invention provides for a process for producing a dyed and finished man-made cellulosic fibre fabric or garment made from man-made cellulosic fibre fabric having a clean soft touch finish.

The invention comprises subjecting that man-made cellulosic fibre fabric to a wet processing treatment using mechanical action to induce fibrillation on the surface of the fabric and subsequently giving the fabric a tumbling treatment to develop the clean, soft touch finish wherein at a stage prior to the tumbling treatment, the fabric is additionally treated with ozone, i.e. subjected to impregnation with either a solution of ozone, or gaseous ozone, under controlled conditions. Surprisingly, it has been found that the use of ozone in the process makes removal of surface hairs from the fabric much quicker resulting in a reduction in process time and chemical consumption. The mechanical treatment action will induce fibrillation on the surface of the fabric in the case of lyocell or loosen surface fibers on modal and viscose. The tumbling treatment will develop the clean, desired soft touch finish. The ozone treatment may take place before, during or after the wet processing treatment.

According to a preferred embodiment of the invention the fabric is in an undyed state prior to the ozone treatment.

It is a major subject of the new process according to the invention for woodbased cellulosic based textiles to deal with or avoid inherent issues such as gross fibrillation with lyocell or pilling with viscose and modal. The clean soft touch finish comprises in short lyocell fibrils on the fibre surface that are not sufficiently long to entangle or shortened hairs on the viscose/modal fabric surface that are not sufficiently long to entangle to form pills.. This is shown in the figures attached.

It has also been found that the ozone can be effective if generated in situ, for instance by impregnating the fabric in hydrogen peroxide and subsequent exposure of the impregnated fabric with high intensity UV light.

The process of invention may be applied to woven and knitted lyocell or modal or viscose fabrics in the length. It may also be applied to manufactured garments and piece goods made from lyocell, modal or viscose fabrics, for which it is especially useful. The effect of the ozone treatment seems to be one of weakening the surface fibres of the lyocell fabric so that the relatively long fibres formed during the intensive wet processing phase are more easily removed in the normal course of later processing steps.

As a secondary effect of the ozone treatment on man-made cellulosic fibre fabrics or garments, there appears to be a reduction in the cellulose degree of polymerization (DP). This loss of tensile strength appears to be significant enough to be used as a processing technique to more easily remove surface fibres from the surface of the fabric.

Preferably the ozone treatment is done by introducing ozone enriched air into a closed mechanical treatment chamber containing the fabric and in which the fabric is then mechanically treated during the ozone treatment time. Afterwards the ozone is purged from the chamber prior to removing the fabric. Preferably, for the purposes of the present invention the mechanical treatment shall be either tumbling or an open-width treatment. Hence the mechanical treatment chamber may be either a tumbling chamber or a chamber wherein the fabric will be treated open-width.

In a preferred embodiment of the invention the ozone treatment is done using gaseous ozone at a concentration of 5 g ozone/Nm³ to 200 g ozone/Nm³ in atmospheric air, or more preferably at a concentration of 20 g ozone/Nm³ to 150 g ozone/Nm³, and at a temperature between 5°C and 40°C for a minimum time of 5 minutes and a maximum time of 75 minutes.

Preferably, the fabric is moist at the start of and during the ozone treatment having a moisture content in the range 40% to 90% (w/w), preferably in the range 40% to 75% (w/w).

There are two different machine options with which to expose the products to gaseous ozone.

In garment form, the machine takes the form of a large commercial washing machine. The garments are placed in a horizontal metal drum called a tumbler. Because of its relatively short half-life, ozone is always generated onsite by an ozone generator. In this case ozone is generated by coronadischarge, the advantage being greater sustainability, higher ozone production and higher cost affectivity. The tumbling machine is equipped with an ozone generator which uses electric power to charge the oxygen molecules to the incoming air and thus generate ozone. This coronadischarge ruptures the stable oxygen molecule and forms two oxygen radicals. These radicals can combine with oxygen molecules to form ozone. The resulting ozone is injected into the closed tumbler drum containing the garments made from lyocell fabrics. Exposure time to the ozone depends upon the weight of garments in the drum. At the end of the process cycle, the remaining ozone is exhausted from the machine to be decomposed into oxygen. There are different ways for this to happen, among others by sending the remaining gas from the drum to a heater and decomposing at a temperature of around 300°C Or by passing the gas through a catalytic ozone decomposition system such as a “carulite®” filter. In this case, the ozone will be decomposed by a chemical reaction happening in the filter.

In the fabric application route, the ozone generation is exactly the same as in the garment route. The fabric is treated open-width with the fabric travelling over numerous rollers within a closed compartment. The unit can be a “standalone” with the fabric travelling from A-frame to A-frame through the sealed compartment, or it can be part of an open-width fabric preparation line.

The treatment conditions for gaseous ozone take account of fabric weight, processing time and ozone concentration.

In another preferred embodiment of the invention the ozone treatment is done by impregnating the fabric with an aqueous solution of ozone and then subjected to the mechanical treatment.

In still another preferred embodiment of the ozone treatment according to the invention the ozone is going to be generated in situ. The fabric may be evenly impregnated with a solution of hydrogen peroxide 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 65-80% by weight of fabric. The ozone is then generated by exposing the impregnated fabric to high intensity UV light with gaseous extraction and thereafter subjected to the mechanical treatment.

If the yarns of the man-made cellulosic fibre fabric have been sized or lubricated to facilitate weaving or knitting, then the fabric is preferably subjected to a desizing or scouring operation prior to the ozone application. This desizing or scouring may be a conventional operation in which the fabric is passed through a scouring bath to remove the size or lubricant.

In one preferred embodiment of the invention the ozone treatment is carried out as a pre-treatment before further wet processing steps. If the ozone treatment is carried out on fabric prior to the normal wet processes such as jet dyeing it has surprisingly been found that much less mechanical and chemical action is needed to generate the desired clean soft touch finish. It is no longer necessary to utilize cellulase enzymes for instance. The ozone treatment is preferably carried out as a pre-treatment before the fibrillation inducing step on lyocell. The latter step is a wet processing step in which mechanical action exerted on the wet fabric causes fibrillation to occur on the fabric surface. This fibrillation is of the so-called primary fibrillation type in which relatively long protruding fibre ends are produced to give what would be an unsightly, hairy effect on the fabric surface if the fibre ends were to remain in place. The effect of the ozone treatment is to reduce the strength of these fibre ends, so that they are removed from the fabric surface during processing.

It appears that many of the fibre ends are removed during the subsequent wet processing steps, with any remaining ones being rubbed off the fabric surface during the later processing stages.

These subsequent wet processing steps where abrasion treatments take place may be the dyeing step, where the dyeing process exerts the requisite mechanical action on the fabric. In a preferred embodiment of the invention the wet processing treatment include a dyeing step. In the case of the treatment in fabrics in the length, this may be a jet dyeing operation using commercial water driven jet dyeing machines or air jet dyeing machines. In the case of treatment of garments this may be a rotary drum dyeing operation.

Conventional dyes and dye recipes for cellulosic fibres may be used in the process of the invention, including those based on direct, vat, sulphur and reactive dyes. Furthermore indigo dyed yarns may be used as the base for the fabric in a denim type application.

After being washed to remove any unfixed dye, the dyed fabric may be given one or more conventional finishing treatments including application of a softening finish. These may be carried out after the dyeing and washing processes without the need for intermediate dyeing of the fabric.

At this stage, the surface of the dyed fabric does not yet have the desired clean, soft touch finish. It may remain flat and slightly uneven in appearance, possibly with some adherent lint. In order to develop the desired finish, the fabric is given a tumbling treatment, sometimes referred to as a beating treatment, which raises the secondary fibrillation in an even nap over the fabric surface. This treatment preferably is carried out as a dry treatment i.e. without added liquid - however with the fabric in humid state - and may be the step in which the fabric is given its final drying.

In order to impart a peach touch finish, fabrics, but in particular garments and piece goods may be given an extended tumbling treatment in a rotary tumbling machine such as a tumble drier. Tumble driers usually operate at temperatures of between 70 and 100°C, often between 70 and 85°C. Fabric in rope form may be given a tumbling treatment in a fabric rope tumbler such as a Biancalani Airo. Tumbling times for a fabric rope should be 30-60 minutes, preferably 40-50 minutes. The air temperature to be used shall be 50-150°C. A shorter duration will result in incomplete removal of the fibrils; a longer duration is not needed to obtain the desired results and would not be feasible economically (a waste of time and money... ). In another preferred embodiment of the invention surprisingly it is also possible to achieve effective results by carrying out these ozone treatment steps after the wet processing step on the man-made cellulosic fibre fabric. The wet processing step may be a dyeing process involving mechanical action on the fabric, one example being jet dyeing in which the fabric, in rope form, is propelled through a dyeing machine under the influence of jets of liquor and is thereby subjected to vigorous action, as by bending and twisting forces and impact and abrasive forces against machine surfaces.

The dry lyocell fabric produced by the process of the invention is a dyed fabric having a clean, soft touch finish. The uniform, soft nap on the fabric surface imparts an attractive handle to the fabric and a subtle lustrous appearance, sometimes referred to as a frosted effect. When the nap is developed to a higher level, then the fabric surface may be characterized as having a peach touch finish.

The dry modal or viscose fabric produced by the process of the invention is a dyed fabric having a clean, soft touch finish characterised in that it has a low propensity to pill during subsequent wearing of garments made from it and during laundering of said garments. The uniform clean finish of the fabric surface imparts an attractive appearance to the fabric which is maintained throughout the life of garments made from it.

Therefore, another aspect of the present invention is fabric or garment finished using a process as described above according to the invention and which has a clean soft touch finish. A peach touch finish and a frosted effect both can be considered specific embodiments of a clean soft touch finish.

In the following typical embodiments of both processing routes are described in order to illustrate the invention. However, these embodiments are not limiting the scope of the invention in any way. The invention includes also any other embodiments which are based on the same inventive concept.

Embodiment 1 : Garment Process Route:

The process is applied to fabric in the form of garments prior to the garment dyeing. Application of this process prior to dyeing I washing avoids any negative fibrillation issues.

1 . Wet the garment with a simple wetting detergent (1 g/l), liquor to goods ratio of 6:1 , 30°C, 5 minutes.

2. Hydro extract to ~60% residual moisture.

3. Treat with ozone in a G2 ozone machine (the G2 ozone treatment machines are a development by Jeanologia S.L of Paterna, Spain.) between 20 and 60 minutes, at an ozone concentration of 100g ozone/Nm³, machine volume 3500 litres, garment load 50kgs, rotation speed 20 rpm

4. Rinse in water at 40°C (5 minutes, liquor to goods ration of 6:1 )

5. Traditional garment dyeing application.

6. Softening to give desired aesthetic (typical polyethylene softener or micro-silicone or blends of, for example)

7. Tumbler drying in a rotative tumbler at a temperature of 70°C during 45 minutes

Embodiment 2: Fabric Process Route:

Ozone can be used in combination with a number of fabric preparation systems (herein referred to as systems A - D) as indicated below in the table 1.

Table 1 :

Singeing and desizing are already described above in the description of the invention.

Bleach is typically a cold pad batch treatment carried out at 20-25°C with the following concentrations in the bleaching liquid: 60g/l Hydrogen Peroxide (35%), 40g/l Caustic Soda (100%), 4g/l Wetting detergent, 4g/l Peroxide stabilizer.

Causticisation refers to treatment of the fabric in open width form in 6° Baume NaOH with the sequence: Padding, dwelling and washing in open width.

Mercerization refers to treatment of fabric in 30° Baume NaOH, with the sequence: Padding, dwelling, and washing in open width.

In this embodiment the ozone treatment may be carried out on a G2 Dynamic ozone machine after all the fabric treatments listed in Table 1 : Running Speed is 10-30m/minute, ozone power 30g ozone/Nm³.

The fabric thus treated can now be dyed as fabric and made up into garments for washing or made up into garments in the undyed form and dyed as a garment. Fabrics and garments processed according to this invention show the same visual appearance as fabrics and garments treated by normal commercial routes for obtaining a clear, soft touch finish. However, the method according to this invention has less environmental impact than the well-known normal commercial routes (such as caustic, mercerization and enzyme treatments).

Description of the Figures:

Fig. 1 shows the lyocell fabric before ozone modification - note the surface hairs.

Fig. 2 shows the lyocell fabric after washing without ozone modification - note the high level of fibrillation and subsequent entanglement of the fibrils and hairs.

Fig. 3 shows the fabric after washing having been pre-treated in ozone according to the invention. Note the absence of pilled fibres and the presence only of short fibrils on the fabric surface.

The photographs (Fig. 4 and 5) demonstrate the effect achieved on viscose. Because there is no propensity to fibril late the effect of the ozone treatment (applied according to the invention) is to prevent the formation of pills created from entanglement of hairs on the fabric surface. Fig. 4 and 5 demonstrate a viscose fabric after repeated washing:

Fig.4 shows a viscose fabric without an ozone treatment - note the untidy pilled appearance of the fabric surface. Fig. 4a shows the fabric face view and Fig. 4b shows an edge view.

Fig.5 is the same fabric, washed in an identical manner, but having had a pretreatment in ozone. Note the cleaner surface appearance. Fig. 5a shows the fabric face view and Fig. 5b shows an edge view.

Claims

1 . A process for producing a dyed and finished man-made cellulosic fibre fabric having a clean, soft touch finish, comprising subjecting the fabric to a wet processing treatment using mechanical action, treating the fabric with ozone and additionally giving the fabric a tumbling treatment after the ozone treatment.

2. A process according to claim 1 , wherein the fabric is in an undyed state prior to the ozone treatment.

3. A process according to claim 1 in which the ozone treatment is done by introducing ozone enriched air into a closed mechanical treatment chamber containing the fabric and in which the fabric is then mechanically treated during the ozone treatment time.

4. A process according to claim 3, in which the ozone treatment is done using gaseous ozone at a concentration of 5 g ozone/Nm³ to 200 g ozone/Nm³ in atmospheric air, or more preferably at a concentration of 20 g ozone/Nm³ to 150 g ozone/Nm³, and at a temperature between 5°C and 40°C for a minimum time of 5 minutes and a maximum time of 75 minutes.

5. A process according to claim 3 in which the fabric is moist at the start of and during the ozone treatment having a moisture content in the range 40% to 90% (w/w), preferably in the range 40% to 75% (w/w).

6. A process according to claim 1 , in which the ozone treatment is done by impregnating the fabric with an aqueous solution of ozone and then subjecting it to the mechanical treatment.

7. A process according to claim 1 in which the ozone treatment is done by impregnating the fabric with a solution of hydrogen peroxide and exposing the impregnated fabric to high intensity UV light and then subjecting it to the mechanical treatment.

8. A process according to claim 1 in which the wet processing treatment includes a dyeing step.

9. A process according to claim 1 in which the ozone treatment is carried out as a pre-treatment before further wet processing steps.

10. A process according to claim 1 in which the fabric is in the form of a manufactured garment or a piece good.

11. A process according to claim 1 in which the tumbling treatment is a tumbling treatment for 30 - 60 minutes, preferably 40 -50 minutes, in a rotary tumbling machine to impart a peach touch finish.

12. A fabric or garment finished using a process according to claim 1 and which has a clean soft touch finish.