WO1995025195A1

WO1995025195A1 - Textile bleaching process

Info

Publication number: WO1995025195A1
Application number: PCT/GB1995/000414
Authority: WO
Inventors: Richard Garfield Jones; Gwenda Mcintyre; William Stuart Hickman; Michael Anthony Parry
Original assignee: Solvay Interox Limited
Priority date: 1994-03-16
Filing date: 1995-02-28
Publication date: 1995-09-21
Also published as: AU1816795A; TNSN95020A1; TR28689A; GB9405114D0

Abstract

A process for the bleaching of dyed textiles with peroxygen compounds is provided. The process comprises contacting the textiles with an aqueous solution of an iron salt, an aqueous solution of a peroxygen compound and subsequently an aqueous solution of a sequestrant for iron. The peroxygen compound can include Caro's acid, hydrogen peroxide, sources of hydrogen peroxide including sodium percarbonate and sodium perborate mono and tetrahydrates, low molecular weight alipathic peracids such as C1 to C6 alipathic peracids, especially performic, peracetic or perpropionic acid, and persulphate salts, including sodium, potassium and ammonium perdisulphates and potassium permonosulphate, and is preferably Caro's acid, hydrogen peroxide, peracetic acid or a persulphate salt. The process is particularly suitable for the bleaching of denim.

Description

Textile Bleaching Process

This invention concerns a process for the bleaching of textiles. More specifically, this invention concerns a process for the bleaching of dyed textiles with peroxygen compounds. Modern textiles are available in a wide range of colours, commonly produced by dying process. The clothing industry, however, often requires that the textiles undergo further physical and/or chemical treatment to reduce the intensity of the colour, and to produce a worn, washed down or "distressed styling" effect. Such treatments are particularly common for cotton denim, which, although widely available in a variety of colours, is most commonly blue, the blue colour normally being produced by dyeing the denim with an indigo dye.

The worn effect of textiles can be produced by tumbling the textiles with abrasive stones, in so-called stone-washing processes. The physical action of the stones abrades the textiles causing a reduction in the intensity of the colour. Such stone-washing processes suffer from a number of drawbacks, not the least of which are necessity for costly, reinforced machinery to withstand the pounding of the stones, and problems with solid residues from the stones damaging the machinery and coating the textiles. Alternative methods of producing a worn effect on textiles employ chemical bleaching agents to reduce the intensity of the coloration of textiles. Many processes have been proposed, particularly for cotton denims, but generally the bleaching agents employed fall into one of four groups. The first of these groups employ chlorine-derived bleaching agents, such as sodium hypochlorite or chlorinated cyanurates. Examples of such processes are disclosed in US Patent Nos. 4,900,323 and 4,997,450. The effectiveness of chlorine-based bleaches in this application is undoubted, but, particularly in recent years, manufacturers and the general public have become increasingly conscious of the possible environmental impact of the use of chlorine-based systems.

The second _, group employ potassium permanganate as bleaching agent. Examples of such processes are disclosed in International Patent Application Nos. WO92/1 3987 and WO91 /091 71 and also in US Patent No. 4,900,323. The use of potassium permanganate is effective at bleaching the textiles, but has come under scrutiny in recent years on account of the risks of discharge of toxic heavy metals into the environment.

The third group employs an enzyme system such as a cellulase as bleaching agent to digest the surface of dyed cotton fibres, for example as disclosed in European Patent Application Nos. 0 307 564 and 0 435 876. The action of cellulase enzymes removes sections of the dyed fibres without reducing the intensity of the dye. When operating with a cellulase system, it has been found necessary to exercise strict process control to prevent the sections being redeposited on the fibres, because such redeposition would negate or reduce the desired bleaching effect.

The fourth group employ peroxygen compounds as bleaching agent. US Patent No. 4,900,323 contemplates, but does not exemplify, the use of ammonium persulphate amongst other bleaching agents as a component together with abrasive insoluble carrier materials in a solid powder. This process suffers from the disadvantage that powder can abrade the equipment being used to effect the bleaching, and also from accumulation of the powder in eg sumps or filters of the equipment and also on the textiles being bleached. US Patent No. 5, 1 1 4,426 contemplates, but does not exemplify, the use of perborates and percarbonates as components in the production of abrasive stones which are stated to avoid the problems associated with solid accumulation by gradually dissolving to leave no residue, and which can be used in place of conventional pumice stones. The process employs at least in part the physical action of the stones on the textiles to achieve bleaching which can cause physical damage to the apparatus used, or necessitate the use of reinforced apparatus. International Patent Application No. WO92/1 8683 teaches the use of hydrogen peroxide, or a precursor thereto, in combination with a peroxidase enzyme.

The impregnation with a solution of a ferrous salt, followed by a peroxygen bleaching stage has been proposed in the ferrous mordant process for the bleaching of naturally pigmented fibres containing melanin, see for example Handbook of Fiber Science and Technology, edited by Lewin and Sello, Vol 1 , part B, p325. The ferrous mordant process requires that a solution of iron (II) is employed, and to ensure this, the solution comprises a reducing agent. Additionally, the fibres are often rinsed with a solution of a sequestrant to remove from the fibre those excess ferrous ions that are not associated with the melanin on the fibre. The ferrous mordant process also conventionally employs an alkaline bleaching stage. Chesner and Woodford, J. Soc. Dyers and Colourists, 1 958, 74, p532 teach that the ferrous mordant process requires the formation of an iron-melanin-protein complex. In the course of the studies leading to the present invention, it was found that the ferrous mordant process was not effective at bleaching dyed textiles. It is a first object of the present invention to provide an alternative process for bleaching dyed textiles employing a peroxygen bleaching system.

It is a second object of further aspects of the present invention to provide a multi-stage process for bleaching dyed textiles employing a peroxygen bleaching system. According to a first aspect of the present invention, there is provided a process for the bleaching of dyed textiles, characterised in that the process comprises: contacting the textiles with an aqueous dispersion of an iron salt, contacting the textiles with an aqueous acidic solution of a peroxygen.

According to a second aspect of the present invention, there is provided a multi-stage process for the bleaching of dyed textiles, characterised in that the process comprises: in stage 1 , contacting the textiles with an aqueous dispersion of an iron salt, and in stage 2, contacting the textiles with an aqueous acidic solution of a peroxygen .

The term "textiles" is used herein in the wide context of the term, for example as defined in "Textile Terms and Definitions", 9th Edition, 1 991 published by The Textiles Institute. The processes according to the present invention can be employed for textiles comprising, for example, cotton, silk, wool, jute, linen, nylon, polyester, polyacrylonitrile and mixtures thereof. The textiles can be dyed with a wide range of dyes, including reactive dyes, dispersed dyes, sulphur dyes/ particularly sulphur black dyes and vat dyes, particularly indigo dyes. The processes are particularly suitable for the bleaching of cotton denim, and especially suitable for the bleaching of indigo-dyed cotton denim. Sources of iron that can be employed in the preparation of the aqueous iron dispersions comprise iron salts. The iron can be in either the (II) or (III) oxidation states. It is desirable that the iron should be evenly distributed throughout the dispersion to reduce variability in the process. The dispersion can employ water-insoluble iron salts, for example, in the form of a suspension or colloid, but preferably water soluble iron salts are employed . Examples of suitable iron salts include ferrous and ferric hydroxides, halides, sulphates, nitrates, oxides, phosphates, carbonates, hydrogencarbonates, borates, acetates, ferrous and ferric alums and sequestered iron salts. The concentration of iron salt in the aqueous iron solutions is commonly less than 20 g/l and usually less than 1 5 g/l with concentrations of from about 0.5 g/l to about 1 2 g/l, particularly from about 2 g/l to about 9 g/l being preferred . The dispersions of iron preferably do not comprise significant concentrations of additional components which can cause excessive and wasteful decomposition of peroxygen compounds under the conditions employed for the contact of the textiles with peroxygen solution. Examples of such undesirable additional components include, in particular, reducing agents commonly employed in ferrous mordant processes, such as sodium dithionite. Peroxygen compounds that can be employed in the processes according to the present invention include Caro's acid (an equilibrium mixture of hydrogen peroxide, sulphuric acid, water and peroxymoπosulphuric acid), hydrogen peroxide, sources of hydrogen peroxide including sodium percarbonate and sodium perborate mono and tetrahydrates, low molecular weight aliphatic peracids such as C 1 to C6 aliphatic peracids, especially performic, peracetic or perpropionic acid and persulphate salts, including sodium, potassium and ammonium perdisulphates and potassium permonosulphate. Preferably, the peroxygen compound is selected from the group consisting of Caro's acid, hydrogen peroxide, peracetic acid and persulphate salts, and is particularly preferably Caro's acid or hydrogen peroxide.

When Caro's acid is employed, the Caro's acid can be prepared in a number of ways, but is most conveniently prepared by reaction of hydrogen peroxide solution with sulphuric acid solution . The resulting Caro's acid solution comprises unreacted sulphuric acid and hydrogen peroxide, and permonosulphuric acid, H2SO5. The quantities and concentrations of reagents employed can be selected so as to produce the desired concentration of permonosulphuric acid directly, but in many cases, it is preferred to employ reagent quantities and concentrations to produce a Caro's acid solution comprising a higher concentration of permonosulphuric acid than is actually desired, and to employ a subsequent dilution stage. The use of the latter process generates permonosulphuric acid particularly efficiently, and also reduces the concentration of unreacted sulphuric acid, resulting in a more stable Caro's acid solution. Preferably, the reagent concentrations of both sulphuric acid and hydrogen peroxide are greater than 50% w/w, with concentrations of hydrogen peroxide greater than 65 % w/w, and sulphuric acid greater than 90% w/w being particularly preferred . Although it is possible to add the sulphuric acid to the hydrogen peroxide, it is preferable that the hydrogen peroxide is added to the sulphuric acid. The reaction between hydrogen peroxide and sulphuric acid is highly exothermic, and therefore it is often desirable that both controlled reagent additions and cooling be employed . In some embodiments, the temperature is controlled to a temperature of preferably less than about 30 ° C and more preferably less than about 25 °C. In some embodiments of the present invention, and particularly where large scale production of Caro's acid is desired, the Caro's acid solution is preferably prepared by the use of a Caro's acid generator such as that described in International Patent Application No. WO 92/07791 . In certain embodiments of the present invention, the Caro's acid is employed as a partially neutralised Caro's acid solution, produced by adding alkali to Caro's acid solutions in an amount which is less than the amount which would be required to completely neutralise both the sulphuric acid and permonosulphuric acid . Such a solution therefore comprises at least some permonosulphate ions, HSO5 . Preferably, the amount of alkali added is sufficient to produce a Caro's acid solution having a pH, prior to its employment in the production of a peroxygen solution in the present invention, of from about 0.75 to 2.5, preferably from about 1 to 2 and particularly preferably about 1 .5. When Caro's acid is employed as peroxygen in the processes according to the present invention, the concentration of permonosulphate (as H2SO5) in the peroxygen solution is commonly less than 30 g/l and usually less than 25g/l. In many embodiments, the concentration of permonosulphate in the solution is from about 1 g/l to about 20 g/l and preferably from about 2g/l to about 1 5 g/l.

It will be recognised that in addition to permonosulphate, Caro's acid normally comprises hydrogen peroxide and sulphuric acid . The concentrations of these components can vary widely for a given permonosulphate concentration . In the process according to the present invention, the weight ratio of hydrogen peroxide to permonosulphate (as H2SO5) in the peroxygen solution is commonly from about 5 : 1 to 1 : 50, usually from about 1 : 1 to 1 :40 and the weight ratio of sulphuric acid to permonosulphate (as H2SO5) in the solutions is commonly from about 5 : 1 to 1 : 1 0, usually from about 3 : 1 to 1 : 5.

In certain embodiments of the present invention, good results have been achieved employing a peroxygen solution comprising from about 2g/l to about 1 5 g/l permonosulphate (as H2SO5), from about 0. 1 g/l to about 3 g/l hydrogen peroxide and from about 1 0 g/l to about 20 g/l sulphuric acid.

When hydrogen peroxide is employed as the only peroxygen, the concentration of hydrogen peroxide in the peroxygen solution is commonly less than 20g/l and usually less than 1 5g/l, with concentrations from about

0.1 g/l to about 1 0 g/l, particularly from about 0.3 g/l to about 5 g/l, being preferred .

When a low molecular weight aliphatic peracid is employed as peroxygen, the concentration of peracid in the peroxygen solution is commonly less than 10g/l and usually less than 7.5g/l, with concentrations from about 0.1 g/l to about 5 g/l, particularly from about 0.5 g/l to about 3 g/l, being preferred . When the low molecular weight aliphatic peracid comprises peracetic acid, it is conveniently supplied in the form of an equilibrium solution comprising acetic acid, hydrogen peroxide and water in addition to peracetic acid. The concentrations of these additional components can vary widely for a given peracetic acid concentration. In many embodiments, the weight ratio of peracetic acid to hydrogen peroxide will be from about 1 5 : 1 to about 1 : 1 0, preferably from about 3 : 1 to about 1 : 7, and the weight ratio of peracetic acid to acetic acid will be from about 2 : 1 to about 1 : 20, preferably from about 1 : 1 to about 1 : 4. It will be recognised that the comments above regarding peracetic acid compositions can also apply correspondingly to other aliphatic peracids, notably performic and perpropionic acid .

When a persulphate salt is employed as peroxygen, the concentration of persulphate salt in the peroxygen solution is commonly less than 35 g/l and usually less than 30 g/l, with concentrations from about 1 g/l to about 25g/l, particularly from about 5g/l to about 20g/l, being preferred. Many of the peroxygen solutions that can be employed in the processes according to the present invention can be so employed without any pH adjustment. However, in many embodiments, the pH is adjusted to a desired value by the addition of acid or alkali. The pH of the peroxygen solution is commonly adjusted to be in the range of from about 0.5 to about 5, usually from about 0.75 to about 4. In many embodiments, the pH of the peroxygen solution, particularly where hydrogen peroxide, peracetic acid or persulphate salts are employed, will require acidification to reach the desired pH value. Where this is the case, acids employable include inorganic acids, such as sulphuric, nitric, phosphoric and hydrochloric acids and low molecular weight organic acids, such as formic and acetic acids. In certain embodiments, particularly good results have been achieved with sulphuric, hydrochloric and formic acids.

Prior to contact with the solutions according to the present invention, the textiles may be de-sized to remove sizing compounds from the textile, and hence to permit more rapid wetting of the textile by the solutions. Methods conventional in the de-sizing art can be employed, including particularly enzymatic de-sizing and oxidative de-sizing. However, if no prior de-sizing stage is employed, it is believed that the process according to the present invention will serve to de-size the textiles, thus achieving combined decolourisation and de-sizing. Combined decolourisation and de- sizing therefore offers the possibility of reducing the processing time, and hence the process costs.

In the processes according to the present invention, the textiles are contacted with an aqueous acidic solution of a peroxygen compound in the presence of an effective amount of iron to enhance the bleaching effect of the peroxygen compound . This differs from the typical ferrous mordant process which employs an intervening washing stage between an iron contact and the melanin-removing stage. The contact between the textiles to be bleached and both the iron dispersion and the peroxygen solution can be achieved by employing a single solution comprising both components. However, the use of such a process is likely to be less favoured in many embodiments on account of the likelihood of the iron causing unacceptable decomposition of the peroxygen. In most embodiments of the present invention, the contact between the textiles and the iron dispersion will be a separate stage preceding contact with the peroxygen solution.

Contact between, the textiles and the iron dispersion can be effected at a wide range of solution temperatures. In many embodiments, the temperature is likely to be below about 50°C, and will usually be selected in the range of from about 1 0°C to about 40°C, preferably from about ambient temperature (normally about 1 8 - 25 °C) to about 35 °C. However, in some embodiments, the contact between the textiles and the iron dispersion is carried out at a more elevated temperature, such as that employed for the contact between the textiles and the peroxygen solution. The use of such a more elevated temperature can be advantageous as it may avoid or ameliorate the need for the textiles to heat up in the peroxygen solution. The contact between the textiles and the iron dispersion is maintained until the required degree of solution is absorbed by the textiles. This can be varied at the discretion of the process user, but commonly contact is maintained until the textiles are substantially saturated with dispersion. Contact times can vary according to the desired degree of absorption, amongst other process variable such as whether the textiles are de-sized or not, and the method employed to effect contact. In certain embodiments, contact times are likely to be up to 1 hour, commonly up to 30 minutes, with contact times in the range of from 1 0 seconds to 1 5 minutes, preferably from 30 seconds to 1 0 minutes being particularly suitable. However, in other embodiments, longer contact times, such as overnight soaking, can be employed if desired .

After contact with the iron dispersion, the textiles to be bleached can be contacted with the peroxygen solution without undergoing intermediate treatment. In certain embodiments, the textiles are at least partially dried to remove any excess iron dispersion prior to contact with the peroxygen solution. This drying can be achieved by one of a number of methods well known in the art, for example the application of hot air to the textiles, or by mechanical means, such as contacting the textiles with an absorbent material or subjecting the textiles to compression, for example between drying rollers. When the textiles comprise garments, the drying can be achieved by use of an appropriate hydroextractive technique such as spin- drying. Preferably, no intermediate rinse treatment, or contact with a sequestrant, is employed, because it is believed that such a treatment may reduce the concentration of iron on the textiles.

Contact between the textiles and the peroxygen solution can be effected employing a solution at a wide range of temperatures up to the boiling point of the solution. In many embodiments, the temperature is likely to be above about 50 °C, and will usually be less than 1 00°C. Preferably, the temperature is selected to be greater than about 60°C, particularly preferably greater than about 70°C. In certain embodiments of the present invention, good results have been achieved employing a temperature of from 75 °C to 99°C. The contact between the textiles and the peroxygen solution, is maintained until the required degree of bleaching is achieved and will also vary according to other process variables such as the concentration of peroxygen in the solution, the solution temperature and whether the textiles are de-sized or not. All other things being equal, it will be recognised that a longer contact time will be employed when it is desired to produce a greater decolourised effect. In certain embodiments, contact times are likely to be up to 1 hour, commonly up to 30 minutes, with contact times in the range of from 1 minute to 20 minutes, with from 3 minutes to 1 5 minutes being particularly suitable. However, in other embodiments, longer contact times, such as overnight soaking, can be employed if desired .

In many embodiments of the present invention, after contact with the peroxygen solution, the textiles are contacted with an aqueous solution of a sequestrant for iron. Sequestrants for iron that can be employed in the process according to the present invention are well known for this purpose in the art. These are often organic chelating compounds, many suitable examples being classified in the literature as carboxylic acid, hydroxycarboxylic or aminocarboxyiic acid complexing agents or as organic amino- or hydroxy-polyphosphonic acid complexing agents, either in acid or soluble salt forms. Representative sequestrants expressed in acid form include picolinic acid, dipicoiinic acid, quinolinic acid, gluconic acid, hydroxyethylene di phosphonic acid, and any compound satisfying the general formula:

I I I ! z z

in which Z represents either -CH2CO2H or -CH2 O3H2, x represents an integer selected from 1 to 6, and preferably is 2, and y represents an integer selected from 0, 1 , 2 or 3. Within this general formula especially preferred sequestrants include ethyleπediamine tetra acetic acid (EDTA) , dieτhylenetriamine penta acetic acid, ethylenediamine tetrakis (methylenephosphonic acid) (EDTMP) , and diethylenetriamine pentakis (methylenephosphonic acid) (DTPMP) . A further sequestrant comprises cyclohexane-1 ,2-diamine tetrakis (methylenephosphonic acid), CDTMP. The concentration of sequestrant employed is commonly less than 1 50 g/l and usually less than 1 00 g/l with concentrations of from about 5 g/l to about 75 g/l, particularly from about 1 0 g/l to about 50 g/l being preferred .

After contact with the peroxygen solution, the textiles can then be contacted with the solution of sequestrant for iron without intervening treatment, but preferably the textiles are water rinsed to remove substantially all of the peroxygen solution from the textiles before contact with the sequestrant solution. However, in certain embodiments of the present invention, it has been found that an increased decolourisation of the textiles can be achieved if, in place of, or in addition to, the water rinse, the textiles are contacted with an alkaline solution, commonly sodium hydroxide, at elevated temperature, commoniy from 70°C to the 1 00°C, and preferably greater than 80°C. The contact time of the textiles with such an alkaline solution is often in the range of from 30 seconds to about 30 minutes, with contact times in the range of from 1 minute to 1 5 minutes being particularly common . The concentration of alkali employed in the solution is usually in the range of from 25g/l to 1 50g/l, preferably from 80g/l to 1 20g/l.

In many embodiments, the temperature of the sequestrant solution is likely to be below about 50°C, and will usually be selected in the range of from about 1 0°C to about 40° C, and is preferably about ambient temperature (normally about 1 8 - 25 °C) . The purpose of the contact between the textiles and the sequestrant solution is to reduce the amount of iron remaining on the textiles resulting from the contact with the iron solution, preferably substantially all of the iron being removed . Accordingly, contact is usually maintained until the required degree of iron removal has occurred . Contact times can vary widely, for example according to the degree of iron absorbed onto the textiles, amongst other process variable such as the method employed to effect contact. In certain embodiments, contact times are likely to be less than 1 hour, commonly less than 30 minutes, with contact times in the range of from 1 0 seconds to 1 5 minutes, preferably from 30 seconds to 10 minutes being particularly suitable. However, in other embodiments, longer contact times, such as overnight soaking, can be employed if desired .

After contact with the sequestrant solution, the textiles are normally treated to remove the sequestrant solution from the textiles. This treatment often comprises rinsing the textiles with water, with a plurality of rinses, such as 2 to 4, being preferred. When Caro's acid is employed as the peroxygen, the textiles are preferably treated to remove any residual acidity with an aqueous solution of an alkali, commonly sodium hydroxide solution, followed by one or more, such as 2 to 4, water rinses. The concentration of alkali employed in the solution is usually in the range of from 25g/l to 1 50g/l, preferably from 80g/l to 1 20g/l. In many embodiments, the contact times and temperatures employed for the contact with the alkali solution and water rinses are in the same ranges as those employed for the contact of the textiles with the sequestrant solution.

Methods and apparatus for contacting the textiles with the iron dispersion and peroxygen, sequestrant and alkali solutions, and water rinses are well known in the art, and include baths and sprays of the solutions. Where baths are employed, the arrangement can be such that the textiles are passed through the bath, with the dimensions of the bath and the rate of textiles passage being selected so as to achieve the desired residence time. In many embodiments, however, a batch process is employed, with the textiles commonly being in the form of garments or other articles. In certain embodiments, it may be desirable for the textiles to be contacted with the iron dispersion and peroxygen, sequestrant and alkali solutions using a bath of each, and with the water rinse(s) using a spray. When baths are employed for achieving contact between the textiles and the iron dispersion and peroxygen solutions, the liquor ratios of the baths, i.e. the ratio of the volume of liquid to the mass of textiles, are commonly selected in the range of from 1 : 1 to 50 : 1 , preferably 5 : 1 or greater and particularly preferably from 1 5 : 1 to 40 : 1 . When baths are employed for achieving contact between the textiles and the sequestrant and alkali solutions and for the water rinses, the liquor ratios of the baths are commonly selected in the range of from 5 : 1 to 75 : 1 , and preferably from 40 : 1 to 60 : 1 . Examples of suitable apparatus that can be employed in the process according to the present invention include washer-extractors and continuous batch washers, for example tunnel washers. It will be recognised that in general terms, the more efficient the apparatus employed, the lower the liquor ratio that may be employed .

In many embodiments, it is desirable to employ a wetting agent to facilitate wetting of the textiles by the solutions with which the textiles are contacted . This is particularly the case for the peroxygen solution and iron dispersion. The wetting agents can be chosen from those conventionally used in the art, including anionic, nonionic, amphoteric and cationic surfactants. The wetting agent should be compatible with the other constituents of solution in which it is employed, and this is particularly important in the case of the peroxygen solution . For example, where the peroxygen solution comprises Caro's acid or peracetic acid, the presence of chloride and/or bromide ions in the surfactant can be undesirable as their presence may reduce the chemical stability of the peroxygen. Particularly suitable wetting agents are selected from one or more of alkylbenzenesulphonates, alkylsulphonates, alkylether sulphates, alkyl sulphosucciπates, alcohol ethoxyiates, alkylphenol ethoxylates, propoxylated alcohol ethoxylates, amine oxides, alkyl glucosides and alkyl quaternary ammonium phosphate esters. When the peroxygen solution comprises hydrogen peroxide, it is preferred that an alkyl sulphosuccinate wetting agent is employed. It is believed that, in addition to improving the wetting of the textiles, the use of an alkyl sulphosuccinate stabilises the hydrogen peroxide solution sufficiently to prolong its presence in the peroxygen solution, and thus increase its bleaching performance, but does not over-stabilise the hydrogen peroxide to the extent that it is so stable that its bleaching performance is impaired.

In certain embodiments of the present invention, it may be advantageous for stoning of the textiles with an abrasive agent, such as pumice stones, to be employed during the contact with either or both of the peroxygen solution and the iron dispersion. This may allow a combined decolourising effect on the textiles of both the peroxygen bleaching action and the abrasive action.

According to a further aspect of the present invention, there is provided a multi-stage process for the bleaching of dyed textiles, characterised in that the process comprises: in stage 1 , contacting the textiles with an aqueous solution of an acid, in stage 2, contacting the textiles with an aqueous dispersion of an iron salt, and in stage 3, contacting the textiles with an aqueous acidic solution of a peroxygen.

When the textiles are contacted with an aqueous solution of an acid in stage 1 , the solution commonly has a pH in the range of from 0.2 to 2.5, and preferably from 0.5 to 1 . The contact times and temperatures employed for the contact with the acid solution are usually in the same ranges as those employed for the contact of the textiles with the sequestrant solution.

Additional components that can be present in one or more of the solutions include corrosion inhibitors and fibre protection agents. Corrosion inhibitors can be desirable to prevent or ameliorate corrosion of metal fittings which may be present on the textiles being bleached or of the equipment being used in the process. Corrosion inhibitors for this purpose will vary^' according to the nature of the bleaching agent and the metal fitting it is desired to protect, and many examples are known in the art.

Particularly suitable examples include triazoles and alkali metal phosphates, particularly dipotassium hydrogenphosphate. Fibre protection agents that may be employed in the process according to the present invention include those that are well known in related field , such as wool treatment, and include protein hydrolysates, highly sulphated oils, sulphonate and ammonium salts, for example lignin sulphonates. Particularly preferred fibre protecting agents comprise cross-linking agents, particularly nitrogen- containing cellulose cross linking agents, including formaldehyde derivatives, urea derivatives, urea-formaldehyde derivatives, furan derivatives and guanidine derivatives.

According to a particularly preferred aspect of the present invention, there is provided a process for bleaching indigo-dyed textiles, characterised in- that the process comprises: i. contacting the textiles with an aqueous solution of ferrous or ferric sulphate, and ii. contacting the textiles with an aqueous solution of hydrogen peroxide at a pH of from 0.5 to 5, the concentration of hydrogen peroxide being from 0. 1 to 1 0 g/l, the aqueous solution of hydrogen peroxide additionally comprising an alkyl sulphosuccinate wetting agent, and a nitrogen containing cellulose cross-linking agent.

Having described the invention in general terms, specific embodiments thereof are described in greater detail by way of example only.

In the Examples, the following general procedure was followed . The denim fabric to be bleached was immersed in a specified iron solution at the desired temperature and liquor ratio for the desired time. The fabric was then removed from the solution and excess liquor removed by contact with absorbent material. The fabric was then contacted with the specified peroxygen solution in a Jeffries Dyemaster at the desired temperature and liquor ratio for the desired time. The fabric was removed from the Dyemaster and rinsed with demineralised water for 5 seconds before immersion in a specified sequestrant solution at the desired temperature and liquor ratio for the desired time. In Examples when Caro's acid was employed as peroxygen, the fabric was then immersed in an aqueous solution of sodium hydroxide (1 OOg/l) at ambient temperature at a liquor ratio of 50 : 1 for 3 minutes and then rinsed in two demineraiised baths (liquor ratio of 50 : 1, ambient temperature for 3 minutes). The fabric was spin-dried to remove excess water and then dried on a rotary glazer. The reflectance of the fabric was measured using a Carl Zeiss "Elrepho" Electric Reflectance Photometer. The untreated denim fabric had a reflectance of 8%, unless otherwise specified.

Examples 1 to 12

In Examples 1 to 12, two Caro's acid solutions were employed, solution A comprising 34% w/w H2SO5, 11.1% w/w H2O2 and 30.9% H2SO4; solution B comprising 27.5% w/w H2SO5, 0.9% w/w H2O2 and 57.6% H2SO4. The concentration (Cone Caro, Cone Fe, both g/l), the liquor ratio (LR Caro, LR Fe), the contact time (Time Caro, Time Fe, both minutes) and the temperature (Temp Caro, Temp Fe, both °C) of the Caro's acid and iron solutions were as detailed in Table 1 below. The source of iron for the iron solution was FeSO₄.7H₂0. The iron solution and the Caro's acid solutions each contained 10 g/l of a combined nonionic/anionic wetting agent available from BASF under the trade name Leophen EA302. The sequestrant solution employed was 10Og/l of a 40% w/w solution of sodium diethylenetriaminepenta acetic acid (Na₅DTPA) available from Allied Colloids under the trade name Tetralon B, at a liquor ratio of 50 : 1 for 3 minutes at ambient temperature. The reflectances (%) achieved are given in Table 1 below.

Table 1

Example No: 1 2. 3 4 5 6 7 8 9 10 11 12

Cone Fe 8 8 4 8 8 8 4 4 4 8 4 4 LR Fe 20 35 35 20 35 35 35 20 20 20 35 20

Temp Fe 35 25 25 25 35 25 35 35 25 35 35 25

Time Fe 3 3- 6 3 6 6 3 6 6 6 3 3

Caro's soln B B B A A A B A B B A A

Cone Caro 25 20 25 25 20 25 25 25 20 20 20 20 LR Caro 20 35 20 35 35 20 35 35 35 20 20 20

Temp Caro 90 90 75 75 75 90 75 90 90 75 90 75

Time Caro 6 6 6 12 6 12 12 6 12 12 12 6

Reflectance 41 44 23 24 20 44 21 37 51 25 45 16 Examples 1 3 to 22

In Examples 1 3 to 22, the procedure of Example 1 was followed, except that the Caro's acid solution contact time was 3 minutes and the temperature of the iron solution was 25 ° C, and that the concentration and temperature of Caro's acid and the concentration of iron were varied as in Table 2 below. The resulting reflectances of the fabric are also given in Table 2.

Table 2 Example No: 1 3 14 1 5 1 6 1 7 1 8 1 9 20 21 22

Cone Fe 6 8 6 8 8 7 5.3 7 7 7

Cone Caro 30 20 20 20 30 1 6.6 25 25 25 25

Temp Caro 86 86 96 96 96 91 91 82.6 98 91 Reflectance 25 33 41 46 48 39 34 27 48 41

The results in Tables 1 and 2 demonstrated the use of Caro's acid as peroxygen in the process according to the present invention. The results also demonstrated that denim having a wide range of reflectances can be produced by varying the conditions of the process.

Examples 23 - 32

In Examples 23 - 32 the procedure of Example 1 2 was followed, except that hydrogen peroxide acidified to the desired pH with 50% w/w sulphuric acid solution was employed as peroxygen, the wetting agent employed in the iron solution and the bleach solution was a sodium alkyl sulphosuccinate available from Allied Colloids under the trade name Alcopol 070PG, the hydrogen peroxide concentration and temperature of the hydrogen peroxide solution being varied as in Table 3 below, no sodium hydroxide rinse was employed and the liquor ratios of the sequestrant bath and both water rinses were 40 : 1 and 100 : 1 respectively. The reflectances achieved are given in Table 3 below. In this Table, the concentration of hydrogen peroxide (cone O) is expressed as g/l of active oxygen. Table 3

Example No: 23 24 25 26 27 28 29 30 31 32

pH 1 2 1 2 2.34 1 .5 1 .5 1 .5 1 .5 1 .5

Cone 0 0.5 0.5 0.5 0.5 0.75 0.33 1 .1 7 0.75 0.75 0.75

Temp H2O2 85 85 95 95 90 90 90 81 .6 98.4 90

Reflectance 23 30 24 32 1 9 20 34 27 39 34

The results in Table 3 demonstrated the use of hydrogen peroxide as peroxygen in the process according to the present invention, and also that denim having a wide range of reflectances can be produced by varying the conditions of the process.

Examples 33 - 42 In Examples 33 - 42 the procedure of Example 23 was followed, except that the pH of the hydrogen peroxide was adjusted by the addition of varying amounts of 98% w/w formic acid (Cone Formic, g/l), the hydrogen peroxide concentration and temperature of the hydrogen peroxide solution being varied as in Table 4 below. The reflectances achieved are given in Table 4 below. In this Table, the concentration of hydrogen peroxide (cone 0) is expressed as g/l of active oxygen.

Table 4

Example No: 33 34 35 36 37 38 39 40 41 42

Cone Formic 5 1 0 1 0 5 1 0 5 3.3 1 1 .7 7.5 7.5 pH 2.3 2.2 2.2 2.4 2.2 2.3 2.5 2.1 2.4 2.3

Cone O 0.5 0.5 1 .0 0.5 0.5 1 .0 0.75 0.75 0.75 0.75

Temp H2O2 85 85- 85 95 95 95 90 90 98.4 90

Reflectance 23 27 34 28 38 36 25 29 32 32

The results in Table 4 demonstrated the successful use of formic acid to acidify hydrogen peroxide solutions in the process according to the present invention.

Examples 43 - 46 .. .

In Examples 43 - 46, the procedure of Example 23 was followed except that the bleach employed was a solution of peracetic acid comprising 1 5% w/w peracetic acid and 1 4% w/w hydrogen peroxide available from Solvay Interox Limited under the Trademark Proxitane 1 507. The peracetic acid concentration (Cone O, g/l) and pH and temperature of the peroxygen solution (Temp Bleach) being varied as in Table 5 below. The reflectances achieved are given in Table 5 below. In this Table, the concentration of peracetic acid (Cone O) is expressed as g/l of active oxygen .

Table 5

Example No: 43 44 45 46

PH 1 .5 1 .5 0.75 1 .5

Cone O 0.5 0.5 1 .0 1 .0

Temp Bleach 85 95 95 95

Reflectance 29 40 1 8 21

The results in Table 5 demonstrated the use of peracetic acid as peroxygen in the process according to the present invention, and also that denim having a wide range of reflectances can be produced by varying the conditions of the process.

Examples 47 - 54

In Examples 47 - 54, the procedure of Example 1 3 was followed, except that Fe2(SO >3.5H2O was used as the source of iron, the concentration of iron, temperature and concentration of the Caro's acid solution were varied as in Table 6 below.

Table 6

Example No: 47 48 49 50 51 52 53 54

Cone Fe 5.3 7 5.3 7 5.3 7 5.3 7

Cone Caro 20 20 30 30 20 20 30 30

Temp Caro 86 86 86 86 96 96 96 96

Reflectance 34 33 26 28 44 46 42 44

The results in Table 6 demonstrated that an iron (III) salt could successfully be employed as source of iron in the process according to the present invention when Caro's acid was employed as the peroxygen. Examples 55 - 62

In Examples 55 - 62, the procedure of Example 1 3 was followed, except that FeCl2 was used as the source of iron, the concentration of iron, temperature and concentration of the Caro's acid solution were varied as in Table 7 below.

Table 7

Example No: 55 56 57 58 59 60 61 62

Cone Fe 2.7 3.6 2.7 3.6 2.7 3.6 2.7 3.6 Cone Caro 20 20 30 30 20 20 30 30

Temp Caro 86 86 86 86 96 96 96 96

Reflectance 34 34 29 29 45 48 42 42

The results in Table 7 demonstrated that iron (II ) chloride could successfully be employed as source of iron in the process according to the present invention when Caro's acid was employed as the peroxygen.

Examples 63 - 65

In Examples 63 - 65, the procedure of Example 24 was followed, except that Fe2(SO4)3.5H2O was used as the source of iron, the concentration of iron, temperature and concentration of the hydrogen peroxide solution were varied as in Table 8 below. The. concentration of hydrogen peroxide (Cone O) is expressed as g/l of active oxygen.

Table 8

Example No: 63 64 65

Cone O 1 .0 0.5 1 .0

Temp H2O2 85 95 95 Reflectance 21 24 27

The results in Table 8 demonstrated that an iron (III) salt could successfully be employed as source of iron in the process according to the present invention when hydrogen peroxide was employed as the peroxygen.

Examples 66 and 67

In Example 66, the procedure of Example 25 was followed, except that: 1 . Prior to contact with the iron solution, the fabric was contacted with an acid solution comprising 1 0 g/l Leophen EA302, adjusted to pH 0.7 with 50% sulphuric acid solution, at a liquor ratio of 20 : 1 for 3 minutes at ambient temperature, and subsequently washed in demineralised water (liquor ratio 100 : 1 ) for 3 minutes at ambient temperature, and

2. The acid was omitted from the oxidant bath. A hydrogen peroxide solution comprising 1 g/l Leophen EA302 and 1 .0 g/l active oxygen was employed.

Example 67 followed the same procedure as Example 66, but omitted the contact with the acid solution prior to contact with the iron solution.

The reflectances obtained were:

Example 66 25 % Example 67 14%

The results of Examples 66 and 67 demonstrated that the reflectance of the denim can be varied significantly by employing an acidic pre-wash compared with when such a wash is not employed .

Examples 68 - 71

In Examples 68 - 71 , the procedure of Example 25 was followed, except that the wetting agent employed in the iron solution was Leophen EA302, the bleaching bath comprised 1 .0 g/l hydrogen peroxide and 10 g/l Leophen EA302, and the pH of the bleach solution and the acid employed was varied as in Table 9 below.

Table 9

Example No: 68 69 70 71

Acid 50% H₂SO Acetic acid 36% HCI Formic acid

PH 0.75 2.05 0.93 1 .94

Reflectance 22 20 26 32

The results in Table 9 demonstrated that a range of different acids can be employed to acidify peroxygen solutions in the process according to the present invention. Example 72

In this example, the procedure of Example 31 was followed , except that the bleaching agent employed was ammonium persulphate. A reflectance of 1 9.4% was achieved . This result demonstrated that ammonium persulphate could be employed as peroxygen in the process according to the present invention.

Examples 73 and 74

In these Examples, the procedure of Example 24 was followed, except that the concentration of hydrogen peroxide used was 0.5 g/l active oxygen, and that after treatment in the oxidising bath, the fabric was divided , half being treated with a 40% w/w solution of sodium diethylenetriaminepenta acetic acid available from Allied Colloids under the trade name Tetralon B (Example 73), and half being treated with a 40% w/w solution of sodium ethylene diamine tetraacetate, commercially available from Ciba-Geigy under the trade name Irgalon BT (Example 74) .

The reflectances achieved were:

Example 73 21 %

Example 74 20%

The results of Examples 73 and 74 demonstrated that different sequestrants for iron could be employed in the process according to the present invention.

Examples 75 - 81

In Examples 75 - 81 , the denim employed was from a different batch from that employed in the previous Examples, and had a reflectance of 7.2%. The sample of denim was enzymatically desized by padding to 1 00% pick up of a 5 g/l solution of an amylase enzyme available from Novo-Nordisk under the Trade Name "Aquazyme 1 20L" at room temperature. The denim was stored for 1 7 hours in a polythene bag at 30°C. The procedure of Example 24 was then followed, except that the concentration of hydrogen peroxide (Cone 0, expressed as g/l active oxygen) and the temperature of the hydrogen peroxide (Temp H2O2, °C) were varied as detailed in Table 1 0 below. Additionally, a fibre protecting agent available from Sandoz under the Trade Name "Lanasan PW" was added to the hydrogen peroxide solution at the concentrations detailed in Table 1 0 (Cone Lan, g/l) . The reflectances achieved are also given in Table 1 0.

Table 1 0 Example No: 75 76 77 78 79 80 81

Cone Lan 5 5 10 10 7.5 7.5 7.5 Cone O 0.5 0.5 0.5 1.0 0.75 0.75 0.75 Temp H2O2 80 90 90 90 77 93 85 Reflectance 20 29 26 40 22 33 30

The results in Table 1 0 demonstrated that a fibre protecting agent could be employed in the process according to the present invention .

Examples 82 and 83

In Examples 82, the procedure of Example 24 was followed, except that the temperature of the hydrogen peroxide solution was 90°C and that the fabric was contacted with a 10% w/w solution of NaOH at a liquor ratio of 20 : 1 for 3 minutes at 95 °C prior to the contact with the sequestrant solution. In Example 83, the procedure of Example 82 was followed except that the temperature of the NaOH solution was 20°C. Samples of denim from the same batch as Examples 75 to 81 were employed . The reflectances achieved were as follows:

Reflectance Example 82 36%

Example 83 21 %

The results of Examples 82 and 83 demonstrated that the reflectance of the denim could be increased by employing a treatment with alkali at elevated temperature prior to contact with the sequestrant solution.

Examples 84 to 87 and Comparison C88

In Examples 84 - 87 and Comparison C88, the procedure of Example 24 was followed except that the concentration of hydrogen peroxide was 1 g/l as active oxygen. Samples of denim from the same batch as Examples 75 to 81 were employed. Additionally, the following variations were employed . In Example 85, a separate contact with iron solution was not employed, instead, 5ml of 4 g/l FeSθ4-7H2θ solution were added to the hydrogen peroxide solution. In Example 86, 2 mis of 1 0% w/w NaOH solution was added to the iron solution to form a colloidal dispersion of iron hydroxide prior to the addition of the denim. In Example 87, 1 0 g of 10% w/w sodium diethylenetriaminepenta acetic acid solution was added to the iron solution 5 minutes before addition of the denim. In Comparison C88, the denim solution was contacted with water containing no iron salts in place of the contact with the iron solution. The reflectances achieved are given below.

Reflectance Example 84 20%

Example 85 1 6%

Example 86 1 3%

Example 87 1 5 %

Comparison C88 1 0%

The results of Examples 85 to 87 demonstrated that the variations employed in these Examples can be used to increase the reflectance of denim, but that in each case, the reflectances were not as high as that achieved by the method of Example 84. The result of Comparison 88 demonstrated that the absence of the contact with a source of iron significantly impairs the increase in reflectance that is achieved by a peroxygen bleach.

Examples 89 and Comparisons C90 to C93

In the Example 89, 5g swatches of 10.5 oz undesized indigo-dyed cotton denim having a reflectance of 6% were employed . Liquor ratios of 20 : 1 were employed for all immersions unless otherwise specified. The swatches were immersed for 3 minutes at ambient temperature (ca 20°C) in an iron solution prepared by dissolving 4 g/l FeS0₄.7H,O an 1 0 g/l Alcopol 070PG in demineralised water, and then excess iron solution removed by draining and blotting with absorptive material. The swatches were then bleached for 10 minutes at 80°C in a Jeffries Dyemaster with a hydrogen peroxide solution comprising 1 .7 g/l active oxygen and 1 0 g/l Alcopol 070PG, the pH of the hydrogen peroxide solution being adjusted to pH 2 with sulphuric acid solution. After the hydrogen peroxide treatment, the swatches were rinsed with water, and treated with sequestrant solution (0.4% w/w Na₅DTPA solution), rinsed with water to remove traces of sequestrant solution, spun dry and then air dried. In comparison C90, the general method of Example 89 was employed, except that the iron solution also comprised 1 g/l of a stabilised sodium dithionite solution commercially available in the UK from Ciba-Geigy under the Trade Name "Clarite PS ", and the swatches were rinsed with 0.4% w/w Na ₅DTPA solution after the contact with the iron solution. In comparison C91 , the general method of Example 89 was employed, except that the swatches were rinsed with 0.4% w/w Na₅DTPA solution after the contact with the iron solution. In comparison C92, the general method of comparison 90 was employed, except that no sequestrant rinse was employed after the contact with the iron solution. In comparison C93, the general method of comparison 90 was employed, except that the swatches were rinsed with water in place of the sequestrant rinse after the contact with the iron solution. The reflectances ( %) achieved are given below.

Example/

Comparison No: 89 C90 C91 C92 C93

Reflectance 21 7 1 0 8 9

The results of comparisons C90 - C93 clearly demonstrate that the use of conditions analogous to the ferrous mordant process gave significantly inferior results compared with a process according to the present invention in Example 89.

Claims

1 . A process for the bleaching of dyed textiles, characterised in that the process comprises: i. contacting the textiles with an aqueous solution of an iron salt, and ii. contacting the textiles with an aqueous acidic solution of a peroxygen.

2. A multi-stage process for the bleaching of dyed textiles, characterised in that the process comprises: in stage 1 , contacting the textiles with an aqueous solution of an iron salt, and in stage 2, contacting the textiles with an aqueous acidic solution of a peroxygen.

3. A multi-stage process for the bleaching of dyed textiles, characterised in that the process comprises: in stage 1 , contacting the textiles with an aqueous solution of an acid, in stage 2, contacting the textiles with an aqueous dispersion of an iron salt, and in stage 3, contacting the textiles with an aqueous acidic solution of a peroxygen.

4. A process according to any preceding claim, characterised in that the peroxygen compound is selected from the group consisting of Caro's acid, hydrogen peroxide, sources of hydrogen peroxide, low molecular weight aliphatic peracids and persulphate salts.

5. A process according to claim 4, characterised in that the peroxygen compound is selected from the group consisting of Caro's acid, hydrogen peroxide, peracetic acid and persulphate salts.

6. A process according to claim 5, characterised in that the peroxygen compound is Caro's acid or hydrogen peroxide.

7. A process according to claim 6, characterised in that the concentration of permonosulphate (as H2SO5) is less than 30 g/l.

8. A process according to claim 7, characterised in that the concentration of permonosulphate (as H2SO5) is from about 1 g/l to about 20 g/l.

9. A process according to claim 8, characterised in that the peroxygen solution comprises from about 2g/l to about 1 5 g/l permonosulphate (as H2SO5), from about 0.1 g/l to about 3 g/l hydrogen peroxide and from about 10 g/l to about 20 g/l sulphuric acid .

1 0. A process according to any one of claims 1 to 5, characterised in that the peroxygen is hydrogen peroxide, and that the concentration of hydrogen peroxide is less than 20 g/l.

1 1 . A process according to claim 1 0, characterised in that the concentration of hydrogen peroxide is from about 0.1 g/l to about 1 0 g/l.

1 2. A process according to claim 1 1 , characterised in that the concentration of hydrogen peroxide is from about 0.3 g/l to about 5 g/l.

1 3. A process according to any one of claims 1 to 5, characterised in that the peroxygen is peracetic acid , and that the concentration of peracetic acid is less than 10g/I.

1 4. A process according to claim 1 3, characterised in that the concentration of peracetic acid is from about 0. 1 g/l to about 5 g/l.

1 5. A process according to any one of claims 1 to 5, characterised in that the peroxygen is a persulphate salt, and that the concentration of persulphate salt is less than 35 g/l.

1 6. A process according to any preceding claim, characterised in that the iron salt is selected from the group consisting of iron (II) or iron (III) hydroxides, halides, sulphates, nitrates, oxides, phosphates, carbonates, hydrogencarbonates, borates, acetates, ferrous and ferric alums and sequestered iron salts.

1 7. A process according to any preceding claim, characterised in that the concentration of iron salt in the aqueous iron solutions is less than 20 g/l.

1 8. A process according to claim 1 7, characterised in that the concentration of iron salt in the aqueous iron solutions is from about 2 g/l to about 9 g/l.

1 9. A process according to any preceding claim, characterised in that after the contact with the peroxygen solution, the textiles are contacted with an aqueous solution of a sequestrant for iron.

20. A process according to claim 1 9, characterised in that the sequestrant for iron is selected from the group consisting of picolinic acid, dipicolinic acid, quinolinic acid, glucoπic acid, hydroxyethylene di phosphonic acid, cyclohexane- 1 , 2-diamine tetrakis (methylenephosphonic acid), and any compound satisfying the general formula:

Z---N -[-(CH₂)_x-N-)_y-Z

in which Z represents either -CH2CO2H or -CH2PO3H2, x represents an integer selected from 1 to 6, and preferably is 2, and y represents an integer selected from 0, 1 , 2 or 3, or water soluble salts thereof.

21 . A process according to claim 20, characterised in that the sequestrant for iron is selected from the group consisting of ethylenediamine tetra acetic acid, diethylenetriamine penta acetic acid, ethylenediamine tetrakis (methylenephosphonic acid), diethylenetriamine pentakis (methylenephosphonic acid), or salts thereof.

22. A process according to claim 20 or 21 , characterised in that the concentration of sequestrant is from 10 g/l to 50 g/l.

23. A process according to any preceding claim, characterised in that the temperature if the iron solution is from ambient temperature (normally from 1 8 - 25 °C) to 35 °C.

24 A process according to any one of claims 1 to 23, characterised in that the temperature if the iron solution is from 50°C to 100°C.

25. A process according to any preceding claim, characterised in that the temperature of the peroxygen solution is from 50°C to 1 00°C.

26. A process according to claim 25, characterised in that the temperature of the peroxygen solution is from 75 °C to 99 °C

27. A process according to any one of claims 1 9 to 22, characterised in that the temperature of the sequestrant solution is about ambient temperature.

28. A process according to any preceding claim, characterised in that the liquor ratios of the iron solution and peroxygen solution are, independently, from 1 : 1 to 50 : 1 .

29. A process according to claim 28, characterised in that the liquor ratios of the iron solution and peroxygen solution are, independently, from 1 5 : 1 to 40 : 1 .

30. A process according to any one of claims 1 9 to 22 or 27, characterised in that the liquor ratio of the sequestrant solution is from

25 : 1 to 75 : 1 .

31 . A process according to any preceding claim, characterised in that the textiles are pre-treated with an acid solution, prior to contact with the iron solution.

32. A process according to any preceding claim, characterised in that the textiles are contacted with an alkali solution at a temperature of from 70°C to the 1 00°C after contact with the peroxygen solution.

33. A process according to any preceding claim, characterised in that a wetting agent is employed in one or more of the solutions with which the textiles are contacted .

34. A process according to claim 33, characterised in that the wetting agent is an alkyl sulphosuccinate.

35. A process according to any preceding claim, characterised in that one or more of the solutions comprise a corrosion inhibitor and/or a fibre protection agent.

36. A process according to claim 35, characterised in that the fibre-protecting agent is a nitrogen containing cellulose cross linking agent.

37. A process for bleaching indigo-dyed textiles, characterised in that the process comprises: i. contacting the textiles with an aqueous solution of ferrous or ferric sulphate, and ii. contacting the textiles with an aqueous solution of hydrogen peroxide at a pH of from 0.5 to 5, the concentration of hydrogen peroxide being from 0.1 to 10 g/l, the aqueous solution of hydrogen peroxide additionally comprising an alkyl sulphosuccinate wetting agent, and a nitrogen containing cellulose cross-linking agent.

38. A process according to any preceding claim, characterised in that the textiles comprise indigo-dyed cotton denim.

39. A process for bleaching textiles, substantially as described herein with reference to any one of the Examples.

40. A process for bleaching textiles, substantially as described herein with reference to any novel feature or combination of features.

41 . Textiles, whenever bleached by a process according to any preceding claim.