EP3938570A1 - A method for bleaching cotton fabrics - Google Patents

A method for bleaching cotton fabrics

Info

Publication number
EP3938570A1
EP3938570A1 EP19920252.4A EP19920252A EP3938570A1 EP 3938570 A1 EP3938570 A1 EP 3938570A1 EP 19920252 A EP19920252 A EP 19920252A EP 3938570 A1 EP3938570 A1 EP 3938570A1
Authority
EP
European Patent Office
Prior art keywords
bleaching
cotton
weight
hot
hydrogen peroxide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19920252.4A
Other languages
German (de)
French (fr)
Other versions
EP3938570A4 (en
Inventor
Semih Durmus
Irem YALIN OKER
Derya AYDIN
Bahar SEZGIN
Ceren DOGAN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Akkim Kimya Sanayi Ve Ticaret AS
Original Assignee
Ak Kim Kimya Sanayi Ve Ticaret AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ak Kim Kimya Sanayi Ve Ticaret AS filed Critical Ak Kim Kimya Sanayi Ve Ticaret AS
Publication of EP3938570A1 publication Critical patent/EP3938570A1/en
Publication of EP3938570A4 publication Critical patent/EP3938570A4/en
Pending legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
    • D06L4/00—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs
    • D06L4/10—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which develop oxygen
    • D06L4/12—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which develop oxygen combined with specific additives

Definitions

  • the present invention relates to a method for bleaching raw cotton or cotton fabrics.
  • the present invention particularly relates to a hot bleaching method for bleaching raw cotton or cotton fabrics by using peroxide.
  • finishing is the process of cleaning the cotton for the dyeing process, after the cotton is processed as fiber, fabric or yarn. This process is based on removal of all of the dirts from fiber except cellulose.
  • Bleaching process is substantially important for removing oil, dirt and brown pigments existing in the nature of cotton and for obtaining a floor which has uniform characteristics before dyeing. There is no need for bleaching to be very good for dyeing except light and brilliant colors. However, it is important that the hydrophility (water absorption) is good, there remains no bleaching wastes (hydrogen peroxide, etc.) thereon and dyeing shall be realized with a light acidic bath. On the other hand, a good bleaching process is needed for dyeing of light colored fabrics.
  • Bleaching activators create peracid by reacting with perhydroxyl anion which occurs as a result of deterioration of hydrogen peroxide in the presence of alkali and hydrogen peroxide during the bleaching process.
  • Peracids provide more effective bleaching when compared with the bleaching process realized by only hydrogen peroxide at low temperature.
  • hydrogen peroxide bleaching realized by using bleaching activators a better whiteness level and higher polymerization degree are obtained at low temperature and in short time when compared with traditional peroxide bleaching.
  • TAED tetra-acetyl- ethylene-diamine
  • NOBS nano-benzoiloxy-benzene sulphonate
  • a liquid detergent comprising anhydrous bleaching activator together with surfactants.
  • the liquid matrix comprises TAED as the activator.
  • the amount of TAED is low and it can be stored in a stable manner only when it has high viscosity.
  • the document with number KR201301 13245 relates to an environment-friendly cotton fiber bleaching method, using an enzyme, which does not give harm to humans.
  • the cotton fiber is cleaned and bleached in a bath comprising cellulase, stabilizer, Na2CC>3, triacetine, hydrogen peroxide, water, bleaching agent and catalase.
  • the present invention relates to a method for bleaching raw cotton or cotton fabrics, for meeting the above mentioned requirements and for eliminating the above mentioned disadvantages and for bringing new advantages to the related technical field.
  • the primary object of the present invention is to obtain a hot bleaching method realized at lowered temperatures.
  • An object of the present invention is to obtain a bleaching method realized at lowered pH values and where neutralization process is not needed by means of addition of acid afterwards.
  • Another object of the present invention is to obtain a bleaching method which requires rinsing steps with reduced number.
  • Another object of the present invention is to obtain a bleaching method where water consumption is reduced.
  • Another object of the present invention is to obtain a bleaching method where the waste water load is reduced.
  • Another object of the present invention is to obtain an environment-friendly bleaching method.
  • Another object of the present invention is to obtain a bleaching method which eliminates problems like weight loss, decrease in break and tear strength in fabric.
  • a similar object of the present invention is to obtain a bleaching method which decreases energy and time loss.
  • the present invention describes a method for hot or cold bleaching of raw cotton or cotton fabrics in the presence of hydrogen peroxide, said method comprises the step of adding at least one glycol derived compound, which is in mixture form with X-COCH 3 dissolved in water, to the bleaching bath comprising hydrogen peroxide and caustic and which is in contact with raw cotton or cotton fabric, and X group in said X-COCH 3 structure is selected from at least one O-acetylated acetyl donor selected from salicylic acid (C 6 H 4 (OH)COOH), Acetic acid (CH 3 COOH), Diacetin (CH 3 COOCH 2 ) 2 CHOH), Cellulose ((C 6 H 10 O 5 )n), Glicose (C 6 H 12 O 6 ), Sucrose (C 1 2 H 22 O 1 1 ).
  • X group in said X-COCH 3 structure is selected from at least one O-acetylated acetyl donor selected from salicylic acid (C 6 H 4 (OH)COOH
  • X group in said X-COCH 3 structure is diacetin ((CH 3 COOCH 2 ) 2 CHOH) or salicylic acid (C 6 H 4 (OH)COOH).
  • said glycol derived compound is selected from ethylene glycol, polyethylene glycol derivatives and glycerol esters.
  • said glycol derived compound is propane-1 ,2,3 triol.
  • the bleaching bath moreover comprises peroxide stabilizer.
  • the bleaching bath moreover comprises wetting agent.
  • the hot bleaching process is realized between 60 and 80°C.
  • the hot bleaching process is realized at 75°C.
  • the hot bleaching process is realized between 30 and 90 minutes.
  • the hot bleaching process is realized between 30 and 60 minutes.
  • the hot bleaching bath comprises caustic between 0.1% and 1% by weight, hydrogen peroxide between 0.1% and 1 % by weight and O-acetylated acetyl donor (-O-COCH 3 ) between 0.1% and 1 % by weight.
  • the cold bleaching process is realized at room temperature and the cold bleaching bath comprises caustic between 5% and 10% by weight, peroxide between 6% and 10% by weight and O-acetylated acetyl donor between 0.5% and 2% by weight.
  • the molar proportion of glycol derived compound to O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
  • the present invention moreover describes a method for hot or cold bleaching of raw cotton or cotton fabrics in the presence of hydrogen peroxide, wherein the following steps are provided: heating a bleaching bath, comprising hydrogen peroxide between 0.1 % and 1% by weight, caustic between 0.1 % and 1% by weight, stabilizer and wetting agent and which is in contact with the raw cotton or cotton fabric to be bleached, to 75°C, afterwards adding O- acetylated diacetin or salicylic acid dissolved in water in mixture form with propane-1 ,2,3 triol to the bleaching bath, and subjecting raw cotton or cotton fabric to bleaching process for 30- 60 minutes at 75°C.
  • the present invention moreover describes the usage of acetyl donor, selected from at least one O-acetylated salicylic acid (C 6 H (OH)COOH), Acetic acid (CH 3 COOH), Diacetin (CH 3 COOCH 2 ) 2 CHOH), Cellulose ((C 6 H 10 O 5 )n), Glicose (C 6 H 12 O 6 ), Sucrose (C 1 2 H 22 O 1 1 ) dissolved in water in mixture form with at least one glycol derivative, as a peroxide activator for hot or cold bleaching of raw cotton or cotton fabrics.
  • acetyl donor selected from at least one O-acetylated salicylic acid (C 6 H (OH)COOH), Acetic acid (CH 3 COOH), Diacetin (CH 3 COOCH 2 ) 2 CHOH), Cellulose ((C 6 H 10 O 5 )n), Glicose (C 6 H 12 O 6 ), Sucrose (C 1 2 H 22 O 1 1 ) dissolved in water in mixture
  • said usage is for hot bleaching of raw cotton or cotton fabrics.
  • said glycol derived compound is selected from ethylene glycol, polyethylene glycol derivatives and glycerol esters.
  • said glycol derived compound is propane-1 ,2,3 triol.
  • the molar proportion of glycol derived compound to O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
  • a method for bleaching raw cotton or cotton fabrics by using peroxide.
  • at least one bleaching bath is used where raw cotton or cotton fabrics are bleached.
  • Said bleaching bath comprises hydrogen peroxide.
  • Hydrogen peroxide forms active oxygen and oxidizes the color components inside the fiber and decomposes them and thus, hydrogen peroxide makes them colorless.
  • the bleaching bath of the present invention moreover comprises peroxide stabilizer which supports decomposition of peroxide in a stepped manner during the bleaching process realized in hot medium and which supports formation of uniform/homogeneous whitening.
  • peroxide stabilizers which are preferred according to the performances of controlling peroxide decomposition, there are alkali metal salts, phosphinic acids and salts thereof. Other suitable stabilizers can also be used.
  • the bleaching bath moreover comprises caustic (sodium hydroxide).
  • caustic sodium hydroxide
  • Caustic cleans the impurities by saponifying the impurities and triggers decomposition of hydrogen peroxide into active oxygen.
  • caustic sponifies the oil derived impurities existing in the structure of cotton and directly affects water absorption and whiteness characteristics.
  • Potassium hydroxide can also be used for the same purpose instead of caustic.
  • peroxide activator peroxide activator (X- COCH3) comprising at least one acetyl group is used as the peroxide activator.
  • Peroxide activator enters into reaction with hydrogen peroxide in the bleaching bath and active oxygen occurs as a result of this reaction.
  • the chemical structure of the peroxide activator (X-COCH3) comprising at least one acetyl group is shown by Formula I.
  • acetyl group donor or donors are used as the peroxide activator.
  • Said acetyl group donor or donors is/are selected from N-acetylated and O-acetylated acetyl donor molecules.
  • N-acetylated acetyl donor or donors is/are selected from N,N,N'N'-tetra- acetyl-ethylene-diamine (TAED), N-acetyl glycine, N-acetyl-DL-metionine, N-acetyl-L-sistein and acetaminopheny (4-acetamidophenol).
  • TAED N,N,N'N'-tetra- acetyl-ethylene-diamine
  • N-acetyl glycine N-acetyl-DL-metionine
  • N-acetyl-L-sistein N-acetaminopheny (4-acetamidophenol
  • O-acetylated acetyl donor or donors is/are selected from sugar acetates like triacetine, penta-acetate-glicose and octa-acetate sucrose, acetate mannitole (acetate esters of sugars), acetic anhydride and acetyl salicylic acid.
  • triacetine or acetyl salicylic acid is used as the O- acetylated acetyl donor.
  • X one of the structures of salicylic acid (C 6 H (OH)COOH), Acetic acid (CH 3 COOH), N,N,N- triacetylethylenediamine (C 8 H 14 N 2 O 3 ), Diacetin (CH 3 COOCH 2 ) 2 CHOH), Glycine (C 2 H 5 NO 2 ), Cysteine (C 3 H7NO2S), Aminophenol (C 6 H7NO), Cellulose ((C 6 H 10 O 5 )n), Glicose (C 6 H12O 6 ), Sucrose (C 12 H 22 O 11 ), Methionine (C 5 H 11 NO 2 S) can be used.
  • salicylic acid C 6 H (OH)COOH
  • Acetic acid CH 3 COOH
  • N,N,N- triacetylethylenediamine C 8 H 14 N 2 O 3
  • Diacetin CH 3 COOCH 2 ) 2 CHOH
  • Glycine C 2 H 5 NO 2
  • Cysteine C 3 H7NO2S
  • salicylic acid C 6 H 4 (OH)COOH
  • Acetic acid CH 3 COOH
  • Diacetin CH 3 COOCH 2 ) 2 CHOH
  • Cellulose ((C 6 H 10 0 5 ) n )
  • Glicose C 6 H12O 6
  • Sucrose C 12 H 22 O 11
  • X for the X-COCH3 acetyl donor, diacetin (CH 3 COOCH 2 ) 2 CHOH) is used since it provides peracetic acid concentration to be higher.
  • salcylic acid C 6 H 4 (OH)COOH
  • peroxide activator acetyl donor enters into reaction with hydrogen peroxide in the bleaching bath and peracetic acid is formed which has a stronger bleaching effect.
  • Peracetic acid formation from hydrogen peroxide by means of N,N,N'N'-tetra-acetyl-ethylene-diamine (TAED), which is an N-acetylated acetyl donor, is realized according to the reaction schema given below.
  • Such reactions are realized by means of attacking of the acetyl group in basic pH to the carbonyl carbon atom in a nucleophilic manner.
  • N-acetylated or O-acetylated groups have electrophilic chemical characteristics and therefore, they are prone to nucleophilic attack.
  • amide or ester bond is broken and acetyl group is formed from the donor molecule.
  • bleaching method X-COCH3, which is dissolved in water, is added to a bleaching bath, comprising hydrogen peroxide, caustic and preferably peroxide stabilizer, as peroxide activator.
  • X-COCH3 is added to the bleaching bath by mixing with a glycol derived compound which will support the solubility in water.
  • X-COCH3 is mixed with one or more compounds selected from the compounds like preferably ethylene glycol, polyethylene glycol derivatives and glycerol esters and is added to the bleaching bath.
  • cleaning function is also provided.
  • said compounds also have effects like water absorption and whiteness performance.
  • the molar proportion of the glycol derived compound to the acetyl donor is between 1 :1 and 1 :10.
  • glycol derived compounds there are compounds like ethylene glycol, polyethylene glycol derivatives and glycerol esters. At least one of said glycol derived compounds is added to the bleaching bath by mixing one or more selected from the subject matter N-acetylated and/or O-acetylated acetyl donor dissolved in water. There is also the cleaning function besides the function of supporting solubility of glycol derived compounds. Thus, said compounds also have favorable effects on water absorption and whiteness performance.
  • the bleaching process is preferably realized between 60°C and 80°C.
  • the mixture of at least one of said glycol derived compounds and the subject matter N-acetylated and/or O-acetylated acetyl donor or donors dissolved in water is added to the bleaching bath at temperatures between 60°C and 80°C which is the process temperature.
  • the solubility of the subject matter acetyl donor inside hydrogen peroxide is substantially high.
  • peracetic acid is formed in situ and the formed peracetic acid can be used in a more effective manner in the system.
  • the obtained peracetic acid is decomposed as a result of the effect of temperature and bleaching is realized.
  • the mixture comprising at least one of the glycol derived compounds and the subject matter N-acetylated and/or O-acetylated acetyl donor or donors dissolved in water, is added to the bleaching bath comprising hydrogen peroxide, caustic and preferably peroxide stabilizer, peracetic acid formation is realized in a stable manner and in sufficient amount.
  • peracetic formation in the bleaching bath is repeatable.
  • the molar proportion of the subject matter glycol derived compound to the N- acetylated and/or O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
  • propane-1 ,2,3 triol is used as the glycol derivative.
  • the subject matter bleaching method is suitable for hot bleaching of raw cotton or cotton fabrics. Accordingly, in the subject matter hot bleaching method, the bleaching process is preferably realized at temperatures between 60 and 80°C. The hot bleaching process is preferably realized between 30 and 90 minutes.
  • the hot bleaching bath preferably comprises caustic between 0.1% and 1% by weight.
  • the hot bleaching bath preferably comprises hydrogen peroxide between 0.1% and 1 % by weight.
  • the hot bleaching bath preferably comprises the subject matter N-acetylated and/or O-acetylated acetyl donor between 0.1% and 1 % by weight.
  • the hot bleaching bath preferably comprises stabilizer between 15% and 80% by weight.
  • the subject matter bleaching method moreover can be adapted in order to be applied in cold bleaching of raw cotton or cotton fabrics.
  • the fabric is impregnated in the bleaching bath prepared in medium temperature, and after the impregnated fabric is compressed at a specific pressure, it is wrapped onto the ducks and the contact thereof to the air is broken and it is rotated for between 12 and 24 hours and waited.
  • caustic, peroxide, ion holder, wetting agent and stabilizer are used.
  • acetyl donor mixture dissolved in water, is added to the bleaching bath.
  • the acetyl donor is mixed with a glycol derived compound which will support the solubility in water and is added to the bleaching bath.
  • the beginning pH is near 1 1 ; however, pH decreases gradually due to peracetic formation.
  • the cold bleaching bath preferably caustic between 5% and 10% by weight, peroxide between 6% and 10% by weight and peroxide activator between 0.5% and 2% by weight.
  • the cold bleaching bath preferably caustic between 5% and 10% by weight, peroxide between 6% and 10% by weight, at least one subject matter N-acetylated and/or at least one subject matter O- acetylated acetyl donor between 0.5% and 2% by weight.
  • the bleaching bath can also comprise a wetting agent.
  • Said wetting agent comprises the mixture of anionic and non-ionic surfactants which facilitate removing of the saponified impurity from the surface.
  • the wetting agent must be resistant to bath conditions (pH, temperature). There shall be no affinity of the wetting agent to the fibers.
  • the preferred wetting agents there are the etoxylates and propoxylates of the oil alcohols and sodium salt of the sulphonic acid and sodium salt of the aromatic sulphonic acid.
  • Other suitable wetting agents can also be used.
  • the bleaching bath can comprise wetting agent between 12% and 50% by weight.
  • the bleaching bath can also comprise ion holder.
  • ion holder Another factor which leads to rapid decomposition of hydrogen peroxide is the catalyst effect of some metal ions. Iron, manganese, copper, cobalt and the oxides thereof increase the decomposition speed of hydrogen peroxide in an important manner. If there are metal ions in the bleaching medium, hydrogen peroxide molecules begin to decompose in a very rapid manner when compared with radical chain mechanism and meanwhile, they oxidize cellulose fibers and damage them.
  • ion holder can also be added, which will form complex, together with stabilizers to the bleaching bath.
  • acrylic acid polymers, phosphonic acid derivatives, phosphonic acid salts, various metal salts and the mixtures thereof are provided. Other suitable ion holders can also be used.
  • the solution comprising caustic with proportion of 0.25% by weight, hydrogen peroxide with proportion of 0.3% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.02% by weight and ethylene diamine tetra (methylene phosphonic acid) as stabilizer with proportion of 0.02% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with the cotton towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Afterwards, 0.5% triacetine solution in mixture form with the propane-1 ,2,3 triol has been added to the bleaching bath. The towel fabric is subjected to the process for 45 minutes at 75°C.
  • the solution comprising caustic with proportion of 0.5% by weight, hydrogen peroxide with proportion of 0.7% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.02% by weight and ethylene diamine tetra (methylene phosphonic acid) as stabilizer with proportion of 0.02% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with the cotton towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Afterwards, 1 .5% triacetine solution in mixture form with the propane-1 ,2,3 triol has been added to the bleaching bath. Towel fabric has been subjected to process for 45 minutes at 75°C.
  • the solution comprising caustic with proportion of 0.3% by weight, hydrogen peroxide with proportion of 0.7% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.02% by weight and ethylene diamine tetra (methylene phosphonic acid) as stabilizer with proportion of 0.02% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Afterwards, 1% acetyl salcylic acid solution in mixture form with the propane-1 ,2,3 triol has been added to the bleaching bath. Towel fabric has been subjected to process for 45 minutes at 75°C.
  • the solution comprising caustic with proportion of 0.07% by weight, hydrogen peroxide with proportion of 0.1% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.5% by weight and the solution, comprising N,N,N'N'-tetra- acetyl-ethylene-diamine (TAED), as activator with proportion of 8% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Towel fabric has been subjected to process for 45 minutes at 75°C. While the pH was near 11 at the beginning, pH value has decreased to 5.5-6 at the end of the process. After the bleaching process, the towel fabric has been rinsed three times with boiling water and once with cool water and dried and conditioned. 61 berger whiteness value has been obtained.
  • TAED N,N,N'N'-tetra- acetyl-ethylene-diamine
  • the solution comprising caustic with proportion of 0.07% by weight, hydrogen peroxide with proportion of 0.1% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.5% by weight and TAED as activator with proportion of 6% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with towel fabric, and the system has been heated to 75°C at speed of 5°C/minute.
  • Towel fabric has been subjected to process for 45 minutes at 75°C. While the pH was near 11 at the beginning, pH value has decreased to 5.5-6 at the end of the process.
  • the towel fabric has been rinsed three times with boiling water and once with cool water and dried and conditioned. 45 berger whiteness value has been obtained.

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Abstract

The present invention relates to a method for hot or cold bleaching of raw cotton or cotton fabrics in the presence of hydrogen peroxide. The method is characterized in that said method comprises the step of adding at least one glycol derived compound, which is in mixture form with X-COCH3 dissolved in water, to the bleaching bath comprising hydrogen peroxide and caustic and which is in contact with raw cotton or cotton fabric and X group in said X-COCH3 structure is selected from at least one O-acetylated acetyl donor selected from salicylic acid (C6H4(OH)COOH), Acetic acid (CH3COOH), Diacetin (CH3COOCH2)2 CHOH), Cellulose ((C6H10O5)n), Glicose (C6H12O6), Sucrose (C12H22O11).

Description

A METHOD FOR BLEACHING COTTON FABRICS
TECHNICAL FIELD
The present invention relates to a method for bleaching raw cotton or cotton fabrics.
The present invention particularly relates to a hot bleaching method for bleaching raw cotton or cotton fabrics by using peroxide.
KNOWN STATE OF THE ART
In order to dye natural raw cotton, natural raw cotton shall be subjected to cleaning and bleaching processes named as finishing. Finishing is the process of cleaning the cotton for the dyeing process, after the cotton is processed as fiber, fabric or yarn. This process is based on removal of all of the dirts from fiber except cellulose.
Bleaching process is substantially important for removing oil, dirt and brown pigments existing in the nature of cotton and for obtaining a floor which has uniform characteristics before dyeing. There is no need for bleaching to be very good for dyeing except light and brilliant colors. However, it is important that the hydrophility (water absorption) is good, there remains no bleaching wastes (hydrogen peroxide, etc.) thereon and dyeing shall be realized with a light acidic bath. On the other hand, a good bleaching process is needed for dyeing of light colored fabrics.
Hydrogen peroxide is frequently used for bleaching cotton and other cellulosic fibers. Hydrogen peroxide bleaching provides satisfying whiteness and it is environment-friendly. However, there are also disadvantages like high level of energy requirement and the fiber is damaged due to heavy bleaching conditions at high temperature. For instance, the process of bleaching of cotton fabrics by means of hot bleaching method is realized at high temperatures (95-100°C) and at high pH values (pH=11). As the main component in the system, caustic and peroxide are used. The bleaching is realized by means of forming perhydroxyl anion from peroxide in the presence of caustic. Whitening in the fabric does not begin before 80°C, and during the process, pH value of the bleaching bath shall be near 11. Since the pH value on the surface of the fabric stays within these values, acid must be added for the neutralization process for passing to the following processes after bleaching. There are pluralities of rinsing steps for removing caustic, peroxide and impurity from the fabric. Moreover, realization of process at high pH value leads to weight loss and decrease in the tear and breakage strength in the fabric. The energy and time loss due to operation of the system at high temperatures like 95-100°C and water consumption which occurs due to rinsing steps and the waste water load lead to a harmful condition for the environment and high cost for textile companies.
In order to be able to overcome these problems, in the known state of the art, there are studies realized on bleaching activators.
Bleaching activators create peracid by reacting with perhydroxyl anion which occurs as a result of deterioration of hydrogen peroxide in the presence of alkali and hydrogen peroxide during the bleaching process. Peracids provide more effective bleaching when compared with the bleaching process realized by only hydrogen peroxide at low temperature. In hydrogen peroxide bleaching realized by using bleaching activators, a better whiteness level and higher polymerization degree are obtained at low temperature and in short time when compared with traditional peroxide bleaching. In the recent periods, TAED (tetra-acetyl- ethylene-diamine) and NOBS (nananoiloxy-benzene sulphonate) are frequently used as the peracid bleaching activators.
In the literature, one of the related documents is the patent with number US 3,687,803. In this document, a bleaching composition is described comprising benzoyl chloride as activator together with hydrogen peroxide in order to be used in textile field.
In the patent application with number DE 40 24 531 A1 , a liquid detergent is described comprising anhydrous bleaching activator together with surfactants. The liquid matrix comprises TAED as the activator. However, the amount of TAED is low and it can be stored in a stable manner only when it has high viscosity.
The document with number KR201301 13245 relates to an environment-friendly cotton fiber bleaching method, using an enzyme, which does not give harm to humans. In said method, the cotton fiber is cleaned and bleached in a bath comprising cellulase, stabilizer, Na2CC>3, triacetine, hydrogen peroxide, water, bleaching agent and catalase.
In said documents, peroxide activators cannot realize the bleaching process in a sufficient and effective and simple manner. As a result, because of all of the abovementioned problems and because of the insufficiency of the present solutions about the subject, an improvement is required in the related technical field.
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates to a method for bleaching raw cotton or cotton fabrics, for meeting the above mentioned requirements and for eliminating the above mentioned disadvantages and for bringing new advantages to the related technical field.
The primary object of the present invention is to obtain a hot bleaching method realized at lowered temperatures.
An object of the present invention is to obtain a bleaching method realized at lowered pH values and where neutralization process is not needed by means of addition of acid afterwards.
Another object of the present invention is to obtain a bleaching method which requires rinsing steps with reduced number.
Another object of the present invention is to obtain a bleaching method where water consumption is reduced.
Another object of the present invention is to obtain a bleaching method where the waste water load is reduced.
Another object of the present invention is to obtain an environment-friendly bleaching method.
Another object of the present invention is to obtain a bleaching method which eliminates problems like weight loss, decrease in break and tear strength in fabric.
A similar object of the present invention is to obtain a bleaching method which decreases energy and time loss.
In order to realize the above mentioned objects, the present invention describes a method for hot or cold bleaching of raw cotton or cotton fabrics in the presence of hydrogen peroxide, said method comprises the step of adding at least one glycol derived compound, which is in mixture form with X-COCH3 dissolved in water, to the bleaching bath comprising hydrogen peroxide and caustic and which is in contact with raw cotton or cotton fabric, and X group in said X-COCH3 structure is selected from at least one O-acetylated acetyl donor selected from salicylic acid (C6H4(OH)COOH), Acetic acid (CH3COOH), Diacetin (CH3COOCH2)2 CHOH), Cellulose ((C6H10O5)n), Glicose (C6H12O6), Sucrose (C1 2H22O1 1).
In another preferred embodiment of the present invention, X group in said X-COCH3 structure is diacetin ((CH3COOCH2)2CHOH) or salicylic acid (C6H4(OH)COOH).
In another preferred embodiment of the present invention, said glycol derived compound is selected from ethylene glycol, polyethylene glycol derivatives and glycerol esters.
In another preferred embodiment of the present invention, said glycol derived compound is propane-1 ,2,3 triol.
In another preferred embodiment of the present invention, the bleaching bath moreover comprises peroxide stabilizer.
In another preferred embodiment of the present invention, the bleaching bath moreover comprises wetting agent.
In another preferred embodiment of the present invention, the hot bleaching process is realized between 60 and 80°C.
In another preferred embodiment of the present invention, the hot bleaching process is realized at 75°C.
In another preferred embodiment of the present invention, the hot bleaching process is realized between 30 and 90 minutes.
In another preferred embodiment of the present invention, the hot bleaching process is realized between 30 and 60 minutes.
In another preferred embodiment of the present invention, the hot bleaching bath comprises caustic between 0.1% and 1% by weight, hydrogen peroxide between 0.1% and 1 % by weight and O-acetylated acetyl donor (-O-COCH3) between 0.1% and 1 % by weight. In another preferred embodiment of the present invention, the cold bleaching process is realized at room temperature and the cold bleaching bath comprises caustic between 5% and 10% by weight, peroxide between 6% and 10% by weight and O-acetylated acetyl donor between 0.5% and 2% by weight.
In another preferred embodiment of the present invention, the molar proportion of glycol derived compound to O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
The present invention moreover describes a method for hot or cold bleaching of raw cotton or cotton fabrics in the presence of hydrogen peroxide, wherein the following steps are provided: heating a bleaching bath, comprising hydrogen peroxide between 0.1 % and 1% by weight, caustic between 0.1 % and 1% by weight, stabilizer and wetting agent and which is in contact with the raw cotton or cotton fabric to be bleached, to 75°C, afterwards adding O- acetylated diacetin or salicylic acid dissolved in water in mixture form with propane-1 ,2,3 triol to the bleaching bath, and subjecting raw cotton or cotton fabric to bleaching process for 30- 60 minutes at 75°C.
The present invention moreover describes the usage of acetyl donor, selected from at least one O-acetylated salicylic acid (C6H (OH)COOH), Acetic acid (CH3COOH), Diacetin (CH3COOCH2)2CHOH), Cellulose ((C6H10O5)n), Glicose (C6H12O6), Sucrose (C1 2H22O1 1) dissolved in water in mixture form with at least one glycol derivative, as a peroxide activator for hot or cold bleaching of raw cotton or cotton fabrics.
In a preferred embodiment of the present invention, said usage is for hot bleaching of raw cotton or cotton fabrics.
In another preferred embodiment of the present invention, said glycol derived compound is selected from ethylene glycol, polyethylene glycol derivatives and glycerol esters.
In another preferred embodiment of the present invention, said glycol derived compound is propane-1 ,2,3 triol.
In another preferred embodiment of the present invention, the molar proportion of glycol derived compound to O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
The structural and characteristic properties and all advantages of the present invention will be understood in a more clear manner by means of the below mentioned detailed description and therefore, evaluation shall be made by taking into consideration the below mentioned detailed description.
DETAILED DESCRIPTION OF THE INVENTION
In this detailed description, the subject matter relates to a bleaching method and is explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.
By means of the present invention, a method is described for bleaching raw cotton or cotton fabrics by using peroxide. In the method of the present invention, at least one bleaching bath is used where raw cotton or cotton fabrics are bleached. Said bleaching bath comprises hydrogen peroxide. Hydrogen peroxide forms active oxygen and oxidizes the color components inside the fiber and decomposes them and thus, hydrogen peroxide makes them colorless.
There are various factors which prevent the bleaching reactions from being realized in the desired manner. When the reaction conditions are not taken into consideration carefully, for instance, when excessive hydrogen peroxide is put into the bath, if the bleaching process is continued even if the oxidization of all foreign substances is finished, cellulose macro molecules begin to enter into reaction as the organic substance and oxy-cellulose occurs. This means that the fibers are damaged. During the bleaching process, the foreign substances in the cotton decrease the strength of the hydrogen peroxide bath and accelerate the automatic decomposition, and as a result of this, the fibers are damaged. In such cases, besides the main reaction mentioned above, some hydrogen peroxide automatically decomposes. The hydrogen peroxide, which decomposes in this manner, does not contribute to bleaching and is lost and the fibers are damaged since the decomposition is rapid. For the optimization of the bleaching process, this reaction must be substantially prevented and decelerated. Therefore, the bleaching bath of the present invention moreover comprises peroxide stabilizer which supports decomposition of peroxide in a stepped manner during the bleaching process realized in hot medium and which supports formation of uniform/homogeneous whitening. Among the peroxide stabilizers which are preferred according to the performances of controlling peroxide decomposition, there are alkali metal salts, phosphinic acids and salts thereof. Other suitable stabilizers can also be used.
In the method of the present invention, the bleaching bath moreover comprises caustic (sodium hydroxide). Caustic cleans the impurities by saponifying the impurities and triggers decomposition of hydrogen peroxide into active oxygen. Besides, caustic sponifies the oil derived impurities existing in the structure of cotton and directly affects water absorption and whiteness characteristics. Potassium hydroxide can also be used for the same purpose instead of caustic.
In the method of the present invention, as the peroxide activator, peroxide activator (X- COCH3) comprising at least one acetyl group is used. Peroxide activator enters into reaction with hydrogen peroxide in the bleaching bath and active oxygen occurs as a result of this reaction. The chemical structure of the peroxide activator (X-COCH3) comprising at least one acetyl group is shown by Formula I.
In the method of the present invention, as the peroxide activator, at least one acetyl group donor or donors (acetyl donor or donors) are used. Said acetyl group donor or donors is/are selected from N-acetylated and O-acetylated acetyl donor molecules.
The subject matter N-acetylated acetyl donor or donors is/are selected from N,N,N'N'-tetra- acetyl-ethylene-diamine (TAED), N-acetyl glycine, N-acetyl-DL-metionine, N-acetyl-L-sistein and acetaminopheny (4-acetamidophenol).
The subject matter O-acetylated acetyl donor or donors is/are selected from sugar acetates like triacetine, penta-acetate-glicose and octa-acetate sucrose, acetate mannitole (acetate esters of sugars), acetic anhydride and acetyl salicylic acid. In another particularly preferred embodiment of the present invention, triacetine or acetyl salicylic acid is used as the O- acetylated acetyl donor.
In the literature, it has been observed that the usage of acetyl salicylic acid as the O- acetylated acetyl donor forms peracetic acid (200 mg/ml) with high concentration as a result of a reaction which is not in balance and shown in Figure 1 . In the present invention, berger whiteness value is obtained which is above 50 depending on high peracetic acid formation in the usage of triacetine or acetyl salicylic acid as the O-acetylated acetyl donor.
In order to provide formation of peracetic acid for said X-COCH3 acetyl donor; as X, one of the structures of salicylic acid (C6H (OH)COOH), Acetic acid (CH3COOH), N,N,N- triacetylethylenediamine (C8H14N2O3), Diacetin (CH3COOCH2)2CHOH), Glycine (C2H5NO2), Cysteine (C3H7NO2S), Aminophenol (C6H7NO), Cellulose ((C6H10O5)n), Glicose (C6H12O6), Sucrose (C12H22O11), Methionine (C5H11NO2S) can be used. Preferably salicylic acid (C6H4(OH)COOH), Acetic acid (CH3COOH), Diacetin (CH3COOCH2)2CHOH), Cellulose ((C6H1005)n), Glicose (C6H12O6), Sucrose (C12H22O11) can be used. Most preferably, as X for the X-COCH3 acetyl donor, diacetin (CH3COOCH2)2CHOH) is used since it provides peracetic acid concentration to be higher. In another preferred application, as X for the X- COCH3 acetyl donor, salcylic acid (C6H4(OH)COOH) is used since it provides the peracetic acid concentration to be higher. As peroxide activator, acetyl donor enters into reaction with hydrogen peroxide in the bleaching bath and peracetic acid is formed which has a stronger bleaching effect. Peracetic acid formation from hydrogen peroxide by means of N,N,N'N'-tetra-acetyl-ethylene-diamine (TAED), which is an N-acetylated acetyl donor, is realized according to the reaction schema given below.
Such reactions are realized by means of attacking of the acetyl group in basic pH to the carbonyl carbon atom in a nucleophilic manner. N-acetylated or O-acetylated groups have electrophilic chemical characteristics and therefore, they are prone to nucleophilic attack. Thus, amide or ester bond is broken and acetyl group is formed from the donor molecule. In the subject matter bleaching method, X-COCH3, which is dissolved in water, is added to a bleaching bath, comprising hydrogen peroxide, caustic and preferably peroxide stabilizer, as peroxide activator. Since the solubility in water is limited, X-COCH3 is added to the bleaching bath by mixing with a glycol derived compound which will support the solubility in water. In a preferred embodiment of the present invention, X-COCH3 is mixed with one or more compounds selected from the compounds like preferably ethylene glycol, polyethylene glycol derivatives and glycerol esters and is added to the bleaching bath. Besides supporting the solubility of the preferred compounds, cleaning function is also provided. Thus, said compounds also have effects like water absorption and whiteness performance. The molar proportion of the glycol derived compound to the acetyl donor is between 1 :1 and 1 :10.
Among the preferred glycol derived compounds, there are compounds like ethylene glycol, polyethylene glycol derivatives and glycerol esters. At least one of said glycol derived compounds is added to the bleaching bath by mixing one or more selected from the subject matter N-acetylated and/or O-acetylated acetyl donor dissolved in water. There is also the cleaning function besides the function of supporting solubility of glycol derived compounds. Thus, said compounds also have favorable effects on water absorption and whiteness performance.
During the bleaching process, while the beginning pH is near 1 1 , pH decreases to the range between 5 and 6 because of peracetic formation. The raw cotton or the cotton fabric which is to be whitened exists in the bleaching bath. By means of addition of peroxide activator comprising at least one acetyl group, the bleaching process is preferably realized between 60°C and 80°C. The mixture of at least one of said glycol derived compounds and the subject matter N-acetylated and/or O-acetylated acetyl donor or donors dissolved in water is added to the bleaching bath at temperatures between 60°C and 80°C which is the process temperature. The solubility of the subject matter acetyl donor inside hydrogen peroxide is substantially high. Thus, in the bleaching bath comprising hydrogen peroxide and caustic, peracetic acid is formed in situ and the formed peracetic acid can be used in a more effective manner in the system. The obtained peracetic acid is decomposed as a result of the effect of temperature and bleaching is realized. When the mixture, comprising at least one of the glycol derived compounds and the subject matter N-acetylated and/or O-acetylated acetyl donor or donors dissolved in water, is added to the bleaching bath comprising hydrogen peroxide, caustic and preferably peroxide stabilizer, peracetic acid formation is realized in a stable manner and in sufficient amount. Moreover, peracetic formation in the bleaching bath is repeatable. Since there is no need to use an additional tank, it is also suitable for operation application. Preferably, the molar proportion of the subject matter glycol derived compound to the N- acetylated and/or O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
In a particularly preferred embodiment of the present invention, propane-1 ,2,3 triol is used as the glycol derivative.
The subject matter bleaching method is suitable for hot bleaching of raw cotton or cotton fabrics. Accordingly, in the subject matter hot bleaching method, the bleaching process is preferably realized at temperatures between 60 and 80°C. The hot bleaching process is preferably realized between 30 and 90 minutes. The hot bleaching bath preferably comprises caustic between 0.1% and 1% by weight. The hot bleaching bath preferably comprises hydrogen peroxide between 0.1% and 1 % by weight. The hot bleaching bath preferably comprises the subject matter N-acetylated and/or O-acetylated acetyl donor between 0.1% and 1 % by weight. The hot bleaching bath preferably comprises stabilizer between 15% and 80% by weight.
The subject matter bleaching method moreover can be adapted in order to be applied in cold bleaching of raw cotton or cotton fabrics. In the known cold bleaching methods, the fabric is impregnated in the bleaching bath prepared in medium temperature, and after the impregnated fabric is compressed at a specific pressure, it is wrapped onto the ducks and the contact thereof to the air is broken and it is rotated for between 12 and 24 hours and waited. In the cold bleaching bath; caustic, peroxide, ion holder, wetting agent and stabilizer are used. In a subject matter cold bleaching method, acetyl donor mixture, dissolved in water, is added to the bleaching bath. Since the solubility thereof in water is limited, the acetyl donor is mixed with a glycol derived compound which will support the solubility in water and is added to the bleaching bath. During the process, the beginning pH is near 1 1 ; however, pH decreases gradually due to peracetic formation. In a subject matter cold bleaching method, the cold bleaching bath preferably caustic between 5% and 10% by weight, peroxide between 6% and 10% by weight and peroxide activator between 0.5% and 2% by weight.
Since the dissolvabilities of these in water are delimited, these are mixed with a glycol derived compound which will support water solubility thereof and are added to the bleaching bath. During the process, the beginning pH is near 1 1 ; however, pH decreases gradually due to peracetic formation. In a subject matter cold bleaching method, the cold bleaching bath preferably caustic between 5% and 10% by weight, peroxide between 6% and 10% by weight, at least one subject matter N-acetylated and/or at least one subject matter O- acetylated acetyl donor between 0.5% and 2% by weight.
By means of the subject matter bleaching method, a bleaching system has been obtained which is more environment-friendly when compared with the traditional methods and which is improved in terms of pH, temperature and duration. Moreover, the strength value of the bleached fabrics also increases.
In the bleaching method of the present invention, the bleaching bath can also comprise a wetting agent. Said wetting agent comprises the mixture of anionic and non-ionic surfactants which facilitate removing of the saponified impurity from the surface. In the bath, the raw cotton or the fabric comprising cotton is wetted in the best manner and the removed foreign substances stay in the bath in the form of dispersion. The wetting agent must be resistant to bath conditions (pH, temperature). There shall be no affinity of the wetting agent to the fibers. Among the preferred wetting agents, there are the etoxylates and propoxylates of the oil alcohols and sodium salt of the sulphonic acid and sodium salt of the aromatic sulphonic acid. Other suitable wetting agents can also be used. The bleaching bath can comprise wetting agent between 12% and 50% by weight.
In the method of the present invention, the bleaching bath can also comprise ion holder. Another factor which leads to rapid decomposition of hydrogen peroxide is the catalyst effect of some metal ions. Iron, manganese, copper, cobalt and the oxides thereof increase the decomposition speed of hydrogen peroxide in an important manner. If there are metal ions in the bleaching medium, hydrogen peroxide molecules begin to decompose in a very rapid manner when compared with radical chain mechanism and meanwhile, they oxidize cellulose fibers and damage them. In order to prevent such side reactions and in order to guarantee slow and regular decomposition of peroxide, ion holder can also be added, which will form complex, together with stabilizers to the bleaching bath. Among the preferred ion holders, acrylic acid polymers, phosphonic acid derivatives, phosphonic acid salts, various metal salts and the mixtures thereof are provided. Other suitable ion holders can also be used.
EXAMPLES
Example 1
The solution, comprising caustic with proportion of 0.25% by weight, hydrogen peroxide with proportion of 0.3% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.02% by weight and ethylene diamine tetra (methylene phosphonic acid) as stabilizer with proportion of 0.02% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with the cotton towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Afterwards, 0.5% triacetine solution in mixture form with the propane-1 ,2,3 triol has been added to the bleaching bath. The towel fabric is subjected to the process for 45 minutes at 75°C. While the pH was near 1 1 at the beginning, pH value has decreased to 5.5-6 at the end of the process. After the bleaching process, the towel fabric has been rinsed three times with boiling water and once with cool water and dried and conditioned. 44 berger whiteness value has been obtained.
Example 2
The solution, comprising caustic with proportion of 0.5% by weight, hydrogen peroxide with proportion of 0.7% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.02% by weight and ethylene diamine tetra (methylene phosphonic acid) as stabilizer with proportion of 0.02% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with the cotton towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Afterwards, 1 .5% triacetine solution in mixture form with the propane-1 ,2,3 triol has been added to the bleaching bath. Towel fabric has been subjected to process for 45 minutes at 75°C. While the pH was near 1 1 at the beginning, pH value has decreased to 5-6 at the end of the process. After the bleaching process, the towel fabric has been rinsed three times with boiling water and once with cool water and dried and conditioned. 68 berger whiteness value has been obtained.
Example 3
The solution, comprising caustic with proportion of 0.3% by weight, hydrogen peroxide with proportion of 0.7% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.02% by weight and ethylene diamine tetra (methylene phosphonic acid) as stabilizer with proportion of 0.02% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Afterwards, 1% acetyl salcylic acid solution in mixture form with the propane-1 ,2,3 triol has been added to the bleaching bath. Towel fabric has been subjected to process for 45 minutes at 75°C. While the pH was near 11 at the beginning, pH value has decreased to 5.5-6 at the end of the process. After the bleaching process, the towel fabric has been rinsed three times with boiling water and once with cool water and dried and conditioned. 59 berger whiteness value has been obtained. Example 4
The solution, comprising caustic with proportion of 0.07% by weight, hydrogen peroxide with proportion of 0.1% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.5% by weight and the solution, comprising N,N,N'N'-tetra- acetyl-ethylene-diamine (TAED), as activator with proportion of 8% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Towel fabric has been subjected to process for 45 minutes at 75°C. While the pH was near 11 at the beginning, pH value has decreased to 5.5-6 at the end of the process. After the bleaching process, the towel fabric has been rinsed three times with boiling water and once with cool water and dried and conditioned. 61 berger whiteness value has been obtained.
Example 5
The solution, comprising caustic with proportion of 0.07% by weight, hydrogen peroxide with proportion of 0.1% by weight, oil alcohol etoxilate mixture as wetting agent having 12 and 14 carbon chains with proportion of 0.5% by weight and TAED as activator with proportion of 6% by weight, has been loaded to the bleaching bath, where bleaching will be realized, together with towel fabric, and the system has been heated to 75°C at speed of 5°C/minute. Towel fabric has been subjected to process for 45 minutes at 75°C. While the pH was near 11 at the beginning, pH value has decreased to 5.5-6 at the end of the process. After the bleaching process, the towel fabric has been rinsed three times with boiling water and once with cool water and dried and conditioned. 45 berger whiteness value has been obtained.

Claims

1. A method for hot or cold bleaching of raw cotton or cotton fabrics in the presence of hydrogen peroxide, wherein said method comprises the step of adding at least one glycol derived compound, which is in mixture form with X-COCH3 dissolved in water, to the bleaching bath comprising hydrogen peroxide and caustic and which is in contact with raw cotton or cotton fabric, and X group in said X-COCH3 structure is selected from at least one O-acetylated acetyl donor selected from salicylic acid (C6H4(OH)COOH), Acetic acid (CH3COOH), Diacetin (CH3COOCH2)2 CHOH), Cellulose ((C6H10O5)n), Glicose (C6H12O6), Sucrose (C12H22O11).
2. The method according to claim 1 , wherein X group in said X-COCH3 structure is diacetin ( (CH3COOCH2)2CHOH) or salicylic acid (C6H4(OH)COOH).
3. The method according to any one of the preceding claims, wherein said glycol derived compound is selected from ethylene glycol, polyethylene glycol derivatives and glycerol esters.
4. The method according to claim 3, wherein said glycol derived compound is propane- 1 ,2,3 triol.
5. The method according to any one of the preceding claims, wherein the bleaching bath moreover comprises peroxide stabilizer.
6. The method according to any one of the preceding claims, wherein the bleaching bath moreover comprises wetting agent.
7. The method according to any one of the preceding claims, wherein the hot bleaching process is realized between 60 and 80°C.
8. The method according to any one of the preceding claims, wherein the hot bleaching process is realized at 75°C.
9. The method according to any one of the preceding claims, wherein the hot bleaching process is realized between 30 and 90 minutes.
10. The method according to claim 9, wherein the hot bleaching process is realized between 30 and 60 minutes.
11. The method according to any one of the preceding claims, wherein the hot bleaching bath comprises caustic between 0.1% and 1% by weight, hydrogen peroxide between 0.1 % and 1% by weight and O-acetylated acetyl donor (-O-COCH3) between 0.1% and 1 % by weight.
12. The method according to any one of the claims between 1 and 6, wherein the cold bleaching process is realized at room temperature and the cold bleaching bath comprises caustic between 5% and 10% by weight, peroxide between 6% and 10% by weight and O-acetylated acetyl donor between 0.5% and 2% by weight.
13. The method according to any one of the preceding claims, wherein the molar proportion of glycol derived compound to O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
14. A method for hot or cold bleaching of raw cotton or cotton fabrics in the presence of hydrogen peroxide, wherein the following steps are provided: heating a bleaching bath, comprising hydrogen peroxide between 0.1 % and 1% by weight, caustic between 0.1% and 1% by weight, stabilizer and wetting agent and which is in contact with the raw cotton or cotton fabric to be bleached, to 75°C, afterwards adding O- acetylated diacetin or salicylic acid dissolved in water in mixture form with propane- 1 ,2,3 triol to the bleaching bath and subjecting raw cotton or cotton fabric to bleaching process for 30-60 minutes at 75°C.
15. The usage of acetyl donor, selected from at least one O-acetylated salicylic acid (C6H4(OH)COOH), Acetic acid (CH3COOH), Diacetin (CH3COOCH2)2CHOH), Cellulose ((C6H10O5)n), Glicose (C6H12O6), Sucrose (C12H22O11) dissolved in water in mixture form with at least one glycol derivative, as a peroxide activator for hot or cold bleaching of raw cotton or cotton fabrics.
16. The usage according to claim 15, wherein said usage is for hot bleaching of raw cotton or cotton fabrics.
17. The usage according to claim 15 or 16, wherein said glycol derived compound is selected from ethylene glycol, polyethylene glycol derivatives and glycerol esters.
18. The usage according to claim 17, wherein said glycol derived compound is propane- 1 ,2,3 triol.
19. The usage according to any of the claims between 15 and 18, wherein the molar proportion of glycol derived compound to O-acetylated acetyl donor or donors is between 1 :1 and 1 :10.
20. A bleacher obtained in a compliant manner to the method given in claim 1.
EP19920252.4A 2019-03-15 2019-12-12 A method for bleaching cotton fabrics Pending EP3938570A4 (en)

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