WO2012175815A1 - Procédé de blanchiment d'un matériau fibreux - Google Patents

Procédé de blanchiment d'un matériau fibreux Download PDF

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Publication number
WO2012175815A1
WO2012175815A1 PCT/FI2012/050653 FI2012050653W WO2012175815A1 WO 2012175815 A1 WO2012175815 A1 WO 2012175815A1 FI 2012050653 W FI2012050653 W FI 2012050653W WO 2012175815 A1 WO2012175815 A1 WO 2012175815A1
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Prior art keywords
bleaching
fibres
cellulose
fibre
carbamate
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PCT/FI2012/050653
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English (en)
Inventor
Sakari Siren
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Carbatec Oy
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Publication of WO2012175815A1 publication Critical patent/WO2012175815A1/fr

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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
    • D06L4/20—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen
    • D06L4/27—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using organic agents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B16/00—Regeneration of cellulose
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
    • D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/001—Modification of pulp properties
    • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/166—Bleaching ; Apparatus therefor with per compounds with peracids

Definitions

  • the invention relates to a method for bleaching fibre material that comprises cellulose based regenerated fibres and cellulose based regenerated compound fibres, as well as well as modified regenerated and regenerated compound fibres.
  • Regenerated fibres can be manufactured by a chemical process from natural raw materials consisting of large molecules, such as cellulose.
  • cellulose based regenerated fibres that is, regenerated cellulose fibres include, for example, viscose, modal, cupro, Biocelsol, lyocell fibres, and fibres regenerated from cellulose carbamate.
  • Regenerated cellulose compound fibres include, for example, cellulose carbamate fibres.
  • the regenerated fibres and regenerated compound fibres can also be modified further, for example by chemical treatments.
  • modification it is possible to obtain, for example, special fibres with various functional proper- ties, such as flame-retardant properties, electrical conductivity, or antimicrobi- city.
  • modified regenerated fibres include, for example, cellulose based hybrid fibres, such as silicate-containing viscose fibres, silicate-containing Biocelsol and cellulose carbamate fibres, as well as silicate- containing fibres regenerated from cellulose carbamate, which are poorly inflammable or non-inflammable, i.e. so-called flame-retardant fibres.
  • the silicate addition can also be made into the modal viscose before the step of spinning the modal viscose intermediate (or intermediate product), whereby the fibres made by this method are also provided with the flame retarding property.
  • the process of manufacturing viscose fibres also contains post-treatment steps, such as a bleaching step, for the purpose of, for example, increasing the brightness of the fibre or improving its stability.
  • the bleaching is performed either by removing colour-inducing chromophoric compounds or by chemically modifying the structure of said compounds with the bleaching process in such a way that the colour-inducing properties of the molecules weaken or disappear.
  • the bleaching process it is also possible to remove other impurities from the fibre material, for example to reduce the residual sulphur content of fibres made by the viscose method.
  • the bleaching process carried out on the fibre production line can be considered a necessary partial process in the production of fibre raw material meeting commercial quality requirements.
  • a generally known way of bleaching various cellulose based regenerated fibres is alkaline oxygen chemical bleaching with hydrogen peroxide (H2O2). Such a method is presented, for example, in document US 5,071 ,439.
  • Another well-known method for bleaching cellulose based regenerated fibres is chlorine bleaching by using sodium hypochlorite.
  • the sodium hypochlorite bleaching is also an alkaline bleaching process.
  • the aim of the present invention is to provide an improved method for bleaching material that comprises cellulose based regenerated fibres and regenerated compound fibres as well as modified regenerated fibres and regenerated compound fibres.
  • the aim of the invention is to improve the quality, such as the brightness level, of the fibre material after the bleaching, preserving the functional properties, such as strength and/or flame retarding properties, of the regenerated cellulose fibre at such a level that the fibre material is suitable for its use.
  • the method is primarily characterized in that the fibre material comprising cellulose-containing raw material is bleached by a method applying a bleaching solution that contains a peracid.
  • the cellulose- containing raw material is advantageously dissolving pulp or cellulose- containing raw material equal to dissolving pulp.
  • the fibres in the material to be bleached may include: cellulose based regenerated fibres, such as regenerated cellulose fibres comprising an intermediary cellulose xanthogenation step and cellulose regeneration in their manufacturing process; cellulose based regenerated compound fibres, such as cellulose carbamate fibres; cellulose fibres regenerated from cellulose carbamate, or regenerated cellulose fibres comprising direct dissolution of enzyme-treated cellulose in their manufacturing process.
  • the fibres in the material to be bleached contain silicate and/or alkali hydrolyzable carbamate groups.
  • the fibres can be so-called alkali labile fibres, such as regenerated cellulose compound fibres, modified regenerated cellulose compound fibres, or modified regenerated cellulose fibres.
  • alkali labile fibres such as regenerated cellulose compound fibres, modified regenerated cellulose compound fibres, or modified regenerated cellulose fibres.
  • Such fibres include silicate-containing viscose fibres, silicate-containing Biocelsol fibres, silicate-containing cellulose carbamate fibres, silicate-containing fibres regenerated from silicate-containing cellulose carbamate fibres, and cellulose carbamate fibres.
  • the bleaching solution may contain, for example, one of the following perac- ids: peracetic acid, performic acid, or persulphuric acid (Caro's acid).
  • the peracid content of the bleaching solution may range from 0.06 to 2000 mmol/l.
  • the bleaching solution may also contain 2,2'-bipyridin.
  • the bleaching solution may also contain transition metal chelating agents and/or other stabilizers which are compatible with the peracids.
  • the pH of the bleaching solution may range from 1 to 11 , advantageously from 2 to 11 , and most advantageously from 5 to 7.
  • the temperature of the bleaching solution may range from 20 to 100*0, advantageously from 50 to 70 .
  • the final bleaching result to be achieved can be advantageously intensified, particularly in the case of other than silicate-containing fibre materials, by raising the pH value of the fibre material with an alkaline solution in a so-called post- bleaching step after the bleaching.
  • a so-called post- bleaching step after the bleaching.
  • the pH is increased from a pH level of 5 (buffer level) to a pH level of for example 6 to 8, to activate the bleaching chemical residues contained in the fibre material, this process step advantageously resulting in an enhanced final bleaching result.
  • the pH value of the fibre material to be treated before the bleaching may range from 1 to 14, advantageously from 7 to 14, and, when peracetic acid is used, preferably from 8 to 9.
  • the bleaching method according to the invention can be carried out in a continuous process.
  • Fig. 1 shows an embodiment of the method according to the invention in a chart.
  • the bleaching method according to the invention can be used for bleaching various fibre materials, particularly fibre material that contains regenerated cellulose fibres and regenerated cellulose compound fibres.
  • Such fibres include, for example, viscose and modal fibres, that is, fibres which comprise the intermediary step of cellulose xanthogenation and the regeneration of cellulose in their manufacturing process, as well as cellulose carbamate fibres spinned from cellulose carbamate, and fibres further regenerated from cellulose carbamate fibres.
  • the method is also suitable for the bleaching of fibres made by processes based on N-methylmorpholine oxide or other ionic solvents, or a process based on direct dissolution of enzyme treated cellulose (for example, the Biocelsol process).
  • Biocelsol refers in this text to the technology (direct dissolution of enzyme treated cellulose by means of sodium zincate solution (ZnO/NaOH)) which has been described, for example, in publication WO 2009/135875.
  • Carbamate fibres in general can be either cellulose carbamate fibres or cellulose fibres regenerated further from cellulose carbamate fibres and made by hydrolysing the carbamate groups contained in the cellulose carbamate fibres either partly or as completely as possible, typically by an alkaline hydrolysis step after the spinning of the cellulose carbamate fibre.
  • the bleaching method is also particularly suitable for the bleaching of modified regenerated fibres and modified regenerated compound fibres, such as alkali labile special fibres.
  • modified regenerated fibres and modified regenerated compound fibres such as alkali labile special fibres.
  • Such fibres include cellulose based hybrid fibres, for example silicate-containing regenerated fibres and regenerated com- pound fibres, such as silicate containing viscose, modal, Biocelsol and carbamate fibres, if silicate has been added to the spinning solution before the spinning step.
  • Silicate-containing viscose fibres refer to cellulose/silica hybrid fibres made by the viscose process and to which waterglass ⁇ i.e.
  • Silicate-containing carbamate fibres refer to cellulose/silica hybrid fibres made by the so-called carbamate process, to which waterglass has been added in connection with the manufacture of the carbamate fibre to provide flame retarding properties.
  • Such fibres may also be called multicomponent products or fibres.
  • the content of silicon dioxide (S1O2) may be 5 to 50% and advantageously about 20 to 40%, calculated of the dry substance of the fibre.
  • the modification can be performed by adding substances, for example, before the regeneration of the fibres made by the viscose method, or before the step of spinning the fibres made by the carbamate method, for example by adding waterglass to provide the fibre with a flame retarding property.
  • the flame retarding property provided by the addition of silicate can also be added to modal viscose before the step of spinning the modal viscose intermediate (or the intermediate product), whereby such a process can be applied for manufacturing flame retardant fibres with a higher tensile strength, which can primarily also be called silicate-containing viscose fibres and not actually silicate-containing modal fibres, because the method does not give the quality level of modal fibre but instead it is possible to provide a silicate-containing viscose fibre with flame retarding properties, to be used in a yarn spinning application.
  • the method according to the invention can also be used for the bleaching of other cellulose-based products, such as films, granules or other solid substances. These products may also be chemically further modified, for example to provide flame retarding properties.
  • Dissolving pulp is primarily used as raw material for regenerated cellulose fibres and modified cellulose compound fibres. Also other cellulose-containing raw materials which are equal to dissolving pulp can be used as the raw material. For example, cotton linter pulp can be used as the raw material. In addition to those mentioned above, in some cases it is also possible to use cellulose raw materials which are atypical of conventional manufacturing processes of cellulose fibres and regenerated cellulose compound fibres.
  • dissolving pulp is characterized by a low viscosity level with low distribution (also from one pulp batch to another), a high brightness level (for example >88% (ISO)), and a low content of impurities, for example a low residual lignin content, a low hemicellulose content (R18: >93%), as well as low contents of alkaline earth metal ions ⁇ inter alia, Ca, Mg) and of pitch and resin compounds.
  • Dissolving pulp can be, for example, dissolving pulp made by the sulphite process or the prehydrolysis sulphate process from softwood or hardwood raw material or non-wood raw material.
  • the dissolving pulp can be TCF or ECF bleached, advantageously TCF bleached.
  • the raw material for fibre material that comprises regenerated cellulose fibre it is also possible to use mixtures consisting of two or more different cellulose-containing raw materials.
  • the method according to the invention it is possible to enhance the bleaching of fibre material made of typical cellulose raw materials, such as dissolving pulp or other cellulose-containing raw material equal to dissolving pulp, and to improve the brightness/whiteness level of the fibre material.
  • the brightness of the fibre material which can be measured, for example, as CIE whiteness according to the standard IS011475, or as ISO brightness according to the standard ISO3688/ISO2470, can increase by even 5 to 10 % units with respect to the brightness of fibre material obtained by conventional alkaline hydrogen peroxide bleaching or hypochlorite bleaching under conditions which are as optimal as possible.
  • peracid bleaching for example peracetic acid bleaching
  • peracetic acid bleaching has the result that less depolymeriza- tion of cellulose, which might lead to fibre damage, as manifested for example as impaired tensile strength of the fibre, takes place during the bleaching process.
  • peracetic acid is also an environmentally healthy bleaching chemical.
  • reaction time of bleaching can be less than 10 minutes, for example 3 to 6 minutes, or 4 minutes.
  • Advantages can also be achieved in a batch bleaching process of fibres and fibre material containing them (such as drawing stock and roving strings as well as textiles, such as knitwear and woven fabrics). It is typical of the batch bleaching process that the reaction time is significantly longer than in bleaching on a fibre production line, for example 30 to 60 minutes or even several hours.
  • a problem in the bleaching of, for example, textiles and drawing stock is the randomly concentrated transition metal ion impurities contained in the material, or even metal particles remaining as impurities in connection with the processing of the fibre material.
  • said impurities catalyze the chemical decomposition of hydrogen peroxide, resulting in e.g.
  • Regenerated cellulose fibres for example viscose fibres, are characterized by colour affinity differences discernible in textiles (knitwear and woven fabrics) after the dying process when blends are made from different viscose fibre batches by the same manufacturer, viscose fibres by different manufacturers, or blends of viscose fibres with other fibres, such as cotton.
  • the dyeing properties of viscose textile fibre bleached with peracetic acid do not differ substantially from, for example, the final result obtained with a typical alkaline hydrogen peroxide bleaching process.
  • the peracid bleaching may have a property that improves the dyeing property of the fibres.
  • alkali lability refers to the dissolution of silicate contained in the fibre and/or hydrolyzation of the carbamate group contained in the fibre, caused by alkaline conditions.
  • Alkali labile special fibres include, for example, a) silicate containing viscose fibre, which may be made either in a viscose process or via a modal viscose intermediate product, b) silicate containing Biocelsol fibre, c) silicate containing cellulose carbamate fibre, which may be silicate containing cellulose carbamate fibre or silicate containing cellulose fibre regenerated from silicate containing cellulose carbamate fibre, and d) cellulose carbamate fibre (which does not contain silicate).
  • the method according to the invention it is possible to achieve the following advantages in the bleaching process of silicate containing viscose fibres and silicate containing carbamate fibres, in view of the silicic acid polymer contained in the fibre and in view of the cellulose structure: Less silicate is dissolved in the peracid bleaching process according to the invention than in alkaline bleaching processes, for example alkaline hydrogen peroxide bleaching and hypochlorite bleaching.
  • the cellulose structure is also depolymerized less in the peracid bleaching according to the invention than in alkaline hydrogen peroxide bleaching or hypochlorite bleaching.
  • silicate containing viscose fibre made via a modal viscose type intermediate product or silicate-containing carbamate fibre is bleached in such a fibre manufacturing process where the aim is to manufacture silicate containing cellulose fibre suitable for yarn spinning applications.
  • Silicate containing cellulose fibres with functional flame retarding properties can be used for manufacturing, for example, non-woven fabrics or yarn (which is further used for making textiles). Manufacturing yarn from silicate-containing cellulose fibres sets significant technical challenges for achieving sufficient fibre strength properties, and the utilization of peracid bleaching in the process is a partial factor in solving these challenges.
  • Peracid bleaching for example peracetic acid bleaching, when carried out under the bleaching conditions according to the invention, does not involve the harmful phenomena presented under points (a) and (b) above. The longer the reaction time of the bleaching, the more significant the management of the harmful phenomena.
  • a bright- ness level higher by even 5 to 10% can be achieved by peracetic acid bleaching (in a continuous bleaching process according to the invention) than by alkaline hydrogen peroxide bleaching, the tensile strength level of the fibre remaining on a level that is at least equal. Thanks to the peracetic acid bleaching, it is also possible to achieve a strength level that is improved by even 5 to 20%, depending on the fibre type.
  • the pH value of the bleached fibre material typically shifts to the pH range of 5 to 6.
  • silicate containing cellulose fibre not treated with aluminate
  • it is advantageous, particularly to prevent strong yellowing in the heat treatment of the fibre that the fibre set to a pH value ⁇ 7 in peracetic bleaching is washed with water, followed by avivage of the fibre.
  • the fibre typically has to be neutralized with an acid, for example a weak acid, such as acetic acid, when an alkaline bleaching process (alkaline hydrogen peroxide bleaching, hypochlorite bleaching) is used.
  • the silicate containing cellulose fibre is utilized in a further application, in which the wash resistance proper- ties of the fibre should be maximized in view of the stability of the silicate, for example an aluminate treatment of the silicate-containing cellulose fibre is feasible, for example a treatment with a sodium aluminate solution.
  • the aluminate treatment can be advantageously combined with the peracid bleaching process in such a way that in a so-called post-bleaching step following the peracid bleaching, the pH of the fibre material is raised by a base, for example sodium hydroxide or sodium carbonate, to a pH level of 8 to 10, followed by an aluminate treatment of the peracid-bleached silicate- containing cellulose fibre.
  • a base for example sodium hydroxide or sodium carbonate
  • the peracid bleaching process for example peracetic acid bleaching, does not, in practice, cause hydrolysis of the carbamate group in the fibre or in the fibre material comprising them.
  • the non-hydrolyzing bleaching process has a particular importance in, for example, a production process, in which the aim is to manufacture cellulose carbamate fibres or to maintain the carbamate functionality of the fibre.
  • the bleaching process maintaining the carbamate functionality of the cellulose carbamate fibre has, for example, the following advantages: a) the bleaching process does not cause significant nitrogen emissions or a problem of industrial hygiene in view of released ammonia; b) the tensile strength of the fibre is not decreased significantly, also for the reason that no hydrolysis of the carbamate group takes place; non-optimized hydrolysis of the carbamate group could result in an impairment of the tensile strength of the fibre; and c) by the effect of the carbamate group, the cellulose carbamate fibre also has intrinsic antibacterial properties which can be maintained in the peracid bleaching process. Consequently, the silicate containing carbamate fibre can have both flame retarding properties and antibacterial properties.
  • the antibacterial properties of cellulose carbamate fibre have been verified by carrying out a test on antimicrobial activity according to the standard AATCC 100, by applying the bacterial strains S. aureus ATCC 43300 and K. pneumoniae ATCC 27736. According to the tests, for example a sample with a total nitrogen content of 1 .0% was antibacterially active, the bacterial reduction being >99% and logarithmically expressed a reduction of >2 log.
  • Table 1 below shows, by way of example, changes in ISO brightness and CIE whiteness as well as total nitrogen content of cellulose carbamate fibre bleached with peracetic acid, in measurement units or percentage units com- pared with untreated reference fibre.
  • the carbamate cellulose fibres were bleached by using an equilibrium peracetic acid solution whose peracetic acid content was 1 3 mmol/l, the bleaching temperature of ⁇ ' ⁇ , the bleaching reaction time of 180 seconds, and the pH value of the bleaching solution was adjusted and maintained by a sodium hydroxide solution to the value given in the table.
  • the total nitrogen contents were determined by the Kjeldahl method, the nitrogen analyses by an accredited method.
  • the standard ISO 3188 describes an embodiment of the total nitrogen content on the basis of the Kjeldahl method.
  • the method according to the invention is also advantageous in bleaching such regenerated cellulose fibres which contain non-alkali labile substituents, in whose manufacture it is a significant challenge to achieve a sufficient ten- sile strength level for the fibre.
  • cellulose fibres include, for example, Biocelsol fibres and cellulose fibres regenerated from cellulose carbamate fibres.
  • the fibre strength properties obtained in spinning and the immediately following steps should be kept at least unchanged also after the bleaching process. It is thus possi- ble by the method according to the invention to obtain a benefit also in the bleaching of, for example, cellulose fibre regenerated from cellulose carbamate fibre, and in the bleaching of fibre made by the Biocelsol process.
  • the issue is that peracid bleaching according to the invention causes less depolymerisation of the cellulose structure during the bleaching process than, for example, alkaline hydrogen peroxide bleaching or hypochlorite bleaching.
  • the method can be used for reducing residual sulphur content of the fibres, for example in connection with the manufacture of viscose fibres.
  • the significance of the management of the residual sulphur content is pronounced particularly in the case of silicate-containing viscose fibres, because it is typical of the manufacturing process of these fibres that the residual sulphur contents of the fibres are on a clearly higher level than in the case of silicate-free viscose fibres.
  • peracetic acid bleaching of silicate-containing viscose fibre it is possible to achieve an even 25% lower residual sulphur level of the fibre than by alkaline hydrogen peroxide bleaching at optimum conditions.
  • a high residual sulphur content at chemically favourable conditions results in the formation of strongly odourous sulphur compounds, for example in a fibre bale or in final products processed from the fibres.
  • FIG. 1 shows an exemplary chart on the spinning and manufacture of viscose and modal type fibres as well as carbamate fibre and Biocelsol fibre.
  • Solution 2 entering the spinning step that is, a) spinning viscose or modal viscose, that is, cellulose xanthogenate solution as such, advantageously post-aged and filtered, or a multicomponent solution that contains cellulose xanthogenate solution and an alkaline solution of silicon dioxide, or b) an alkaline solution of cellulose carbamate as such filtered, or a multicomponent solution that contains an alkaline solution of cellulose carbamate and an alkaline solution of silicon dioxide, or c) a Biocelsol solution as such filtered, or a multicomponent solution that contains Biocelsol solution and an alkaline solution of silicon dioxide.
  • the manufacture continues either on route A to filaments, i.e.
  • the spinning solution or the multicomponent solution 2 made of it can be, for example, pressed through a nozzle to one or more fibres in a spinning bath 4,25, in a regeneration or coagulation solution suitable for each fibre type, i.e. in a spinning solution used as a spinning bath, in which, depending on the nature of the spinning solution, solid cellulose fibres or solid cellulose carbamate fibres are formed, for example, or in the case of spinning a multicomponent solution, cellulose fibres or cellulose carbamate fibres which contain silicon dioxide in the form of silicic acid are formed.
  • the nozzle can be selected so that the manufacture of films or other multicomponent products is also possible.
  • the solidification of the fibres or other products thus takes place automatically so that the regeneration or coagulation solution is immediately on the outlet side of the nozzle.
  • the products formed in the spinning bath preferably filament fibres, are collected through the nozzle around draw rollers and are drawn 27. By stretching, it is possible to increase the strength of the fibers.
  • the fibres can also be washed in connection with or after the drawing 6.
  • the fibres are cut 29 to a desired length after the drawing.
  • the fibres are bleached 8,31 by applying the bleaching method according to the invention. If regenerated cellulose fibre is made of cellulose carbamate fibre (not from a multicomponent solution), optimized hydrolysis of the carbamate can be carried out alternatively before or after the bleaching step.
  • the pH of the fibre material is adjusted to a desired value.
  • the fibres can also be treated with various finishing agents 33, after which they are dried 10,35 and collected, for example as filaments 12 or staple fibres 37.
  • the bleaching chemical used in the bleaching solution is a peracid, such as peracetic acid (CH 3 COOOH).
  • a corresponding final result can also be achieved with other peracids, such as performic acid or persulphuric acid (Caro's acid).
  • the content of the peracid, such as peracetic acid, in the bleaching solution may range, for example, from 0.06 to 2000 mmol/l.
  • the bleaching solution may contain distilled peracetic acid, or an equilibrium mixture of peracetic acid containing hydrogen peroxide and acetic acid.
  • the peracetic acid used as the bleaching chemical can also be made enzymati- cally or by means of activator chemicals, such as tetraacetylethylenediamine (TAED) or pentaacetyl glucose, or from hydrogen peroxide and acetanhy- drice in the process in situ.
  • the bleaching can also be performed, for example, as peracetic acid bleaching catalyzed by 2,2'-bipyridin.
  • the bleaching solution may, for example, contain a preparate that contains, for example, chelating agents of transition metal ions which catalyze the decomposition of peracetic acid and hydrogen peroxide, and/or other stabilizers, such as tetrasodium pyrophosphate or aspartic acid diethoxy succinate (AES) or a derivative thereof.
  • chelating agents can also be added in a separate pre-chelating step before the actual bleaching treatment.
  • the pH of the bleaching solution can range from 1 to 11.
  • the pH of the solution is between 2 and 11.
  • the pH of the solution is preferably between 5 and 7.
  • the pH of the solution can be, for example, between 5.0 and 5.5.
  • the pH of the bleaching solution refers to the pH of the solution prepared for the bleaching process.
  • the temperature of the bleaching solution may be, for example, between 20 and 100 ⁇ , advantageously betwe en 50 and 70 .
  • the final bleaching result to be achieved can be advantageously intensified, particularly in the case of other than silicate-containing fibre materials, by raising the pH value of the fibre material with an alkaline solution in a so- called post-bleaching step after the bleaching.
  • the pH is increased from a pH level of 5 (buffer level) to a pH level of for example 6 to 8, to activate the bleaching chemical residues contained in the fibre material, this process step advantageously resulting in an enhanced final bleaching result.
  • a press roll for adjusting the content of the bleaching solution absorbed in the fibre material carried to the latter step, in the case of a continuous bleaching process.
  • the final bleaching result of the fibres can also be influenced by one or more of the following parameters: the pH value of the fibre material, such as a fibre mat formed of several single fibres, for example the fibre/water suspension or filament rope moving on a wire, before the bleaching; the peracid content or the joint effect of the contents of hydrogen peroxide and peracid in the bleaching solution; the temperature of the fibre material before the bleaching; the retention time of the bleaching; the circulating solution flow rate of the bleaching; the content of chelating agent and/or stabilizer in the bleaching solution.
  • the pH value of the fibres to be treated, such as a fibre mat of filament tow formed of fibres, before the bleaching may be, for example, between 1 and 14, advantageously between 7 and 14.
  • the pH of the fibre material to be treated can be adjusted to a target value, for example, with sodium hydroxide or sodium carbonate.
  • the peracetic acid content of the bleaching solution may be, for example, about 6 mmol/l.
  • the temperature of the fibre mat or filament tow may be, for example, about 80 .
  • the fibre mat can thus also be washed more efficiently after the bleaching process.
  • the bleaching process according to the invention can be implemented with few changes in the existing bleaching apparatuses. It can also be easily applied in already existing plants for manufacturing regenerated fibre, applying an alkaline hydrogen peroxide bleaching process.
  • the bleaching can also be performed in a continuous process.
  • the reaction time of bleaching can be less than 10 minutes, for example 3 to 6 minutes, or 4 minutes.
  • atypical cellulose refers to biomasses and/or pulps which contain natural fibres, such as so-called paper pulp. Such raw materials can also be called raw materials which are atypical of viscose processes. Bleaching according to the examples 1 to 12 can also be carried out on regenerated cellulose fibres made of other cellulose containing raw materials, such as fibre made of dissolving pulp or cotton linter pulp.
  • Example 1 A method for bleaching fibre material comprising regenerated cellulose fibre made of atypical cellulose-containing raw material, characterized in that the fibre material is treated with a bleaching solution containing a peracid.
  • Example 2 A method for bleaching fibre material comprising regenerated cellulose fibre made of atypical cellulose-containing raw material, characterized in that the fibre material is treated with a bleaching solution containing a peracid.
  • the atypical cellulose-containing raw material is a raw material having a high con- tent of hemicellulose and/or containing other impurities, having been treated by an alkali solution treatment and/or with enzymes.
  • Example 3 The method according to example 1 or 2, characterized in that the regenerated cellulose fibres are fibres based on ionic solvents, fibres made by an enzyme treatment process, viscose, modal or carbamate fibres.
  • Example 4 The method according to any of the preceding examples, characterized in that the regenerated cellulose fibres contain silicate.
  • Example 5 The method according to any of the preceding examples, characterized in that the bleaching solution contains at least one of the following peracids: peracetic acid, performic acid, or persulphuric acid.
  • Example 6 The method according to any of the preceding examples, characterized in that the bleaching solution contains 2,2'-bipyridin.
  • Example 7 The method according to any of the preceding examples, characterized in that the bleaching solution contains chelating agents of transition metals and/or other stabilizers compatible with peracetic acids.
  • Example 8 The method according to any of the preceding examples, characterized in that the peracid content is 0.06 to 2000 mmol/l.
  • Example 9 The method according to any of the preceding examples, characterized in that the pH of the bleaching solution is between 1 and 1 , advantageously between 2 and 11 , most advantageously between 5 and 7.
  • Example 10 The method according to any of the preceding examples, characterized in that the pH value of the fibre material to be treated, before bleaching, is between 1 and 14, advantageously between 7 and 14, preferably between 8 and 9.
  • Example 11 The method according to any of the preceding examples, characterized in that the temperature of the bleaching solution is 20 to 10 ⁇ , advantageously 50 to 70*0.
  • Example 12 The method according to any of the preceding examples, characterized in that the bleaching is performed in a continuous process.
  • the invention is not intended to be limited to the embodiments or uses presented above, but the invention is intended to be applied widely within the scope of the inventive idea as defined in the claims.

Abstract

La présente invention concerne un procédé de blanchiment d'un matériau comprenant des fibres composées d'une matière première contenant de la cellulose, procédé au cours duquel les fibres sont traitées avec une solution blanchissante contenant un peracide.
PCT/FI2012/050653 2011-06-23 2012-06-21 Procédé de blanchiment d'un matériau fibreux WO2012175815A1 (fr)

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FI20115668A FI123344B (fi) 2011-06-23 2011-06-23 Menetelmä kuitumateriaalin valkaisemiseksi
FI20115668 2011-06-23

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WO2016189205A1 (fr) * 2015-05-27 2016-12-01 Kemira Oyj Procédé pour réduire la viscosité de la pâte dans la production de pâte pour transformation chimique
CN112981577A (zh) * 2019-12-12 2021-06-18 连津格股份公司 完全不含氯地制造莫代尔纤维的方法
WO2023238458A1 (fr) * 2022-06-10 2023-12-14 大王製紙株式会社 Procédé de production de fibres de cellulose carbamatées et procédé de production de fibres fines de cellulose carbamatée

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GB845063A (en) * 1957-09-06 1960-08-17 Degussa Bleaching bath
GB926639A (en) * 1960-05-31 1963-05-22 Courtaulds Ltd Improvements relating to the treatment of cellulosic fabrics
WO1993013249A1 (fr) * 1991-12-31 1993-07-08 Kemira Oy Produit contenant du dioxyde de silicium et son procede de preparation

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GB845063A (en) * 1957-09-06 1960-08-17 Degussa Bleaching bath
GB926639A (en) * 1960-05-31 1963-05-22 Courtaulds Ltd Improvements relating to the treatment of cellulosic fabrics
WO1993013249A1 (fr) * 1991-12-31 1993-07-08 Kemira Oy Produit contenant du dioxyde de silicium et son procede de preparation

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RUCKER, J.W.: "Low Temperature Bleaching of Cotton with Peracetic acid", TEXTILE CHEMIST & COLORIST, vol. 21, no. 5, 1989, pages 19 - 25 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016189205A1 (fr) * 2015-05-27 2016-12-01 Kemira Oyj Procédé pour réduire la viscosité de la pâte dans la production de pâte pour transformation chimique
CN107690496A (zh) * 2015-05-27 2018-02-13 凯米罗总公司 溶解纸浆制造中降低纸浆粘度的方法
RU2703467C2 (ru) * 2015-05-27 2019-10-17 Кемира Ойй Способ снижения вязкости целлюлозы при производстве растворимой целлюлозы
US10513824B2 (en) 2015-05-27 2019-12-24 Kemira Oyj Method for reducing pulp viscosity in production of dissolving pulp
CN112981577A (zh) * 2019-12-12 2021-06-18 连津格股份公司 完全不含氯地制造莫代尔纤维的方法
WO2023238458A1 (fr) * 2022-06-10 2023-12-14 大王製紙株式会社 Procédé de production de fibres de cellulose carbamatées et procédé de production de fibres fines de cellulose carbamatée

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FI20115668A (fi) 2012-12-24
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