WO1999002767A1

WO1999002767A1 - A method for pre-fibrillation of lyocell

Info

Publication number: WO1999002767A1
Application number: PCT/DK1998/000284
Authority: WO
Inventors: Alexander Nikolov
Original assignee: Novo Nordisk A/S
Priority date: 1997-07-07
Filing date: 1998-06-29
Publication date: 1999-01-21
Also published as: AU7908198A

Abstract

A method for primary fibrillation of lyocell or lyocell blends comprising the step of immersing lyocell fibres in an aqueous solution at a pH in the range of 2-10 and subjecting the fibres to mechanical stress.

Description

A METHOD FOR PRE-FIBRILLATION OF LYOCELL

The present invention relates to an improved method for pre-fibrillation of lyocell fibres, including fibres present in yarn, woven, non-woven or knitted fabric, and garment sown of such fabric.

BACKGROUND OF THE INVENTION

Lyocell (CLY) is a generic name for a regenerated cellulosic fibre obtained by spinning of dissolved wood pulp in the organic solvent NMMO (methyl-morpholine-N-oxide) . Examples of registered brand names of lyocell fibre are NewCell^® (from Akzo Nobel), Tencel^® (from Courtaulds Fibres) and LenzingLyocell^® (from Lenzing) ; of these is NewCell a filament whereas the other two branded products are staple fibers.

Today, essentially all lyocell fibres produced are used in the textile and garment industries.

At the present stage of development, lyocell fibres possess a unique property, namely the tendency to fibrillate. Fibrillation is a longitudinal splitting of a single wet fibre into microfibres of typically less than 1 to 4 microns in diameter, caused by mechanical stress. It could be illustrated as a peeling of a banana.

The fibrillation can only be prevented by minimizing the effect of mechanical stress when processing a fabric in an open width. However, in order to protect against fibrillation during domestic machine washing of the garments produced, it is necessary to apply an additional chemical finishing treatment with a resin (resination) . Protection from fibrillation can be obtained by applying a chemical coating on the fabric e.g. with "AXIS", a chemical product marketed by Courtaulds Fibres Ltd. This chemical keeps the fabric surface clean, but when such a chemical coating is applied on the fabric, it is impossible to obtain a "secondary" and sometimes highly desirable fibrillation which may result in for example a soft feel and/or look, the socalled "peach skin" effect.

Fibrils can be cleaned or removed from the lyocell fibres or fabric or garment by an enzymatic treatment known as Bio- Polishing™ in which a cellulolytic enzyme, preferably an endo- beta-1, 4-glucanase (EC 3.2.1.4) under controlled conditions hydrolyses the cellulosic fibres in order to remove or clean the surface from fibrills (hairs) .

After the Bio-Polishing™ treatment step the lyocell fibres may be subjected to further conventional abrading wet process steps which will generate some fibrillation. Accordingly, it is very important to initially fibrillate the fabric to a maximum extent in order to clean (defibrillate) the surface from all fibrils (hairs) that otherwise may appear in later process steps. This fibrillation process is known as a "primary fibrillation" or "pre-fibrillation" . The most important parameters of the pre-fibrillation process step are wet conditions and mechanical stress.

The wet conditions causes the fibre to swell. It is known that the rate of fibrillation increases with increased pH and increased temperature of the swelling process bath. Therefore, to obtain a high pH, addition of caustic soda or soda ash of concentrations up to 5 g/1 is conventionally recommended, resulting in very strongly alkaline conditions.

Process conditions for a conventional pre-fibrillation method for 100% lyocell fabric or garments, as well as blends of lyocell with other cellulosic fibres, is as follows: 1:5 - 1:20 Liquor Ratio (LR) 2.0 - 5.0 g/1 of Caustic Soda or Soda Ash (resulting in a pH of at least 13-14)

2.0 - 4.0 g/1 of Lubricant

Temperature: 80-120°C. Process holding time: 15-90 min.

The lubricant acts like a softening coating or film on the fibres/fabric which prevents crease-marks.

The main disadvantage of the conventional pre-fibrillation method is the high loss of strength of the fabric/garment after pre-fibrillation. Also, change of colour shade may occur when treating dyed fabric or garment (approximately 90% of all treated garment is dyed; approximately 20% of all treated fabric is dyed) due to instability of certain dyes at the highly alkaline pH and the high temperature conditions. Further, the conventional method is time-consuming and costly, primarily due to the high temperatures applied and the necessity for rinsing and pH adjustment after the treatment.

Accordingly, the object of the present invention is to provide an improved method for pre-fibrillation of lyocell which do not have these known disadvantages.

DESCRIPTION OF THE INVENTION

The applicant has found that, in order to obtain a high level of pre-fibrillation without any significant loss of fabric or fibre strength, the conventional method for primary fibrillation of lyocell or lyocell blends is advantageously modified by: a. replacing Na-carbonate with another salt which does not impart alkaline conditions; b. carrying out the method at a neutral or acidic pH or slightly alkaline pH; and c. carrying out the method for a shorter time.

Accordingly, in a first aspect the present invention relates to a method for primary fibrillation of lyocell or lyocell blends wherein the lyocell fibres are immersed in an aqueous solution at a pH in the range of 2-10, preferably in the range of 3-9, even more preferably in the range of 4-7, and subjecting the fibres to mechanical stress.

Preferably, the aqueous solution comprises one or more conventional builder components which may also act as a buffer capable of maintaining pH of the aqueous solution within the desired range. For economical reasons such a builder is usually selected from the group consisting of alkali metal or alkanolamine salts of organic or inorganic salts but it is contemplated that any conventional builder or buffer (pH 2-10) is useful.

Examples of useful salts are alkali metal salts and alkanolamine salts of phosphates, phosphonates, phosphonocarboxylates, carboxylic acids, amino acids, dicarboxylic acids, diglycolic acids, hydroxycarboxylic acids and inorganic acids; especially sodium, potassium, ethanolamine and triethanolamine salts of orthophosphate, pyrophosphate, tripolyphosphate, metaphosphate, hexametaphosphate and phytic acid; or of ethane-1, 1-diphosphonate, ethane-1, 1, 2- triphosphonate, ethane-l-hydroxy-1, 1-diphosphonate and derivatives thereof, ethanehydroxy-1, 1, 2-triphosphonate, ethane, 1, 2-dicarboxy-l, 2-diphosphonate and methanehydroxyphosphonate; or of 2-phosphonobutane-l, 2- dicarboxylate, l-phosphonobutane-2, 3, 4-tricarboxylate and alpha- methylphosphonosuccinate; or of acetic acid, formic acid, benzoic acid, salicylic acid; or of aspartic acid, glutamic acid and glycine; or of oxalic acid, malonic acid, succinic acid, glutaric acid, phtalic acid, sebacic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, itaconic acid, methylsuccinic acid, 3-methylglutaic acid, 2, 2-dimethylmalonic acid, maleic acid, fumaric acid, glutamic acid, and decane-1, 10-dicarboxylic acid; or of diglycolic acid, thioglycolic acid, oxalacetic acid, hydroxydisuccinic acid, carboxymethylhydroxysuccinic acid and carboxymethyltartronic acid; or of glycolic acid, malic acid, hydroxypivalic acid, tartaric acid, citric acid, lactic acid, gluconic acid, mucic acid, glucuronic acid and dialdehydrostarch oxide; or of inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid. Further, it is contemplated that any combination of these conventional builders and/or buffers is useful in the method of the present invention. In a preferred embodiment of the invention, the builder or buffer salt is a sodium salt. For economical reasons it may be advantageous to use sodium acetate, sodium phosphate, sodium chloride, sodium citrate, sodium sulfate or any combination thereof. It has been found that, in particular, sodium chloride is very useful in the present invention.

Typically, the amount of builder or buffer salt in the aqueous solution is in the range of 0.1 to 50 g/1, preferably 0.5 to 6 g/1.

The aqueous solution may further comprise a lubricant, preferably in the range of 0.5 to 6 g/1, more preferably in the range of 2 to 4 g/1. The method of the present invention is carried out at a temperature of between 20°C and 120°C, preferably between 50°C and 70°C, and the lyocell fibres are maintained in the solution, with or without being subjected to mechanical stress, for between 10 and 90 minutes. In a preferred embodiment, the method of the invention is carried out under the following conditions: • 0.5 - 5.0 g/1 of builder/buffer (sodium acetate, sodium phosphate, sodium chloride, sodium sulfate, sodium citrate)

• 0.5 - 4.0 g/1 of Lubricant

• pH 4.0 - 7.0 • Temperature: 40-120°C

• Process time: 15-90 min.

The conventional pre-fibrillation method will, according to the following data provided by Courtaulds Fibres Ltd. on 100% Tencel (2x1 Twill, 220 g) , typically result in a loss of tensile strength and tear strength: Tensile Strength (64 trousers and 50 blouses)

* Before pre-fibrillation = 190 kg

* After pre-fibrillation = 171 kg (= 10% loss) Tear Strength (1800 trousers and 1400 blouses)

* Before pre-fibrillation = 6.4 kg

* After pre-fibrillation = 4.1 kg (= 34% loss)

By using the method of the present invention, it is possible to obtain a reduction of the bursting strength of about 2-5%. This is shown in the Example below disclosing trials of the inventive method carried out on 100% Tencel (knitted) after (see results listed below for tear/bursting strength of 100% Tencel (knitted) for trials "a)", "d) " and "e)" in TABLE 1) (Note: The bursting strength is considered as less (or least) affected by any kind of treatment) .

Conventionally, pre-fibrillation of blends of lyocell with other cellulosic fibres is more complicated. As mentioned above, a fibrillation to its maximum extent is intended, while the harsh conditions applied are unacceptable for the non-lyocell part of the blend. Besides, the cellulosic fibres possess quite different characteristics as to resistance to mechanical stress. Laboratory scale tests on blends of Tencel with cotton, linen and ramie showed loss of tear strength of around 10-30% (see results of trials "a)", "b)", "d) " and "e)" in TABLE 1). Industrial scale test on a blend of Tencel/Linen 60/40 in high speed jet (ICBT Alizee) resulted in around 70% loss of tear strength.

Cellulase Treatment

By using the primary fibrillation method of the invention it is possible, in the same aqueous solution, to carry out a Bio- Polishing™ treatment (a cellulase treatment) as known in the art .

In the present context, the term "cellulase" refers to an enzyme which catalyses the degradation of cellulose to glucose, cellobiose, triose and other cello-oligosaccharides .

In the present context the term "cellulase" is understood to include a mature protein or a precursor form thereof or a functional fragment thereof which essentially has the activity of the full-length enzyme. Furthermore, the term "cellulase" is intended to include homologues or analogues of said enzyme. Such homologues comprise an amino acid sequence exhibiting a degree of identity of at least 60% with the amino acid sequence of the parent enzyme, i.e. the parent cellulase. The degree of identity may be determined by conventional methods, see for instance, Altshul et al., Bull. Math. Bio. 48_, 1986, pp. 603-616, and Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA 8J9, 1992, pp. 10915-10919.

The cellulase to be used in the present invention may be a monocomponent (recombinant) cellulase, i.e. a cellulase essen- tially free from other proteins or cellulase proteins. A recombinant cellulase component may be cloned and expressed according to standard techniques conventional to the skilled person. In a preferred embodiment of the invention, the cellulase to be used in the method is an endoglucanase (EC 3.2.1.4), preferably a monocomponent (recombinant) endoglucanase.

Preferably, the cellulase is a microbial cellulase, more preferably a bacterial or fungal cellulase.

Examples of bacterial cellulases are cellulases derived from or producible by bacteria from the group of genera consisting of Pseudomonas or Bacillus, in particular Bacillus lautus .

The cellulase or endoglucanase may be an acid, a neutral or an alkaline cellulase or endoglucanase, i.e. exhibiting maximum cellulolytic activity in the acid, neutral or alkaline range, respectively.

As the primary fibrillation according to the invention is carried out at a slightly acidic or at a neutral pH, a useful cellulase is an acid cellulase, preferably a fungal acid cellulase, which is derived from or producible by fungi from the group of genera consisting of Trichoderma, Actinomyces, Myrothecium, Aspergillus, and Botrytis .

A preferred useful acid cellulase is derived from or produ- cible by fungi from the group of species consisting of Trichoderma viride, Trichoderma reesei, Trichoderma longibrachiatum, Myrothecium verrucaria, Aspergillus niger, Aspergillus oryzae, and Botrytis cinerea.

Another useful cellulase or endoglucanase is a neutral or alkaline cellulase, preferably a fungal neutral or alkaline cellulase, which is derived from or producible by fungi from the group of genera consisting of Aspergillus, Penicillium, Myceliophthora, Humicola, Irpex, Fusarium, Stachybotrys, Scopu- lariopsis, Chaetomium, Mycogone, Verticillium, Myrothecium, Papulospora, Gliocladium, Cephalosporium and Acremonium.

A preferred alkaline cellulase is derived from or producible by fungi from the group of species consisting of Humicola insolens, Fusarium oxysporum, Myceliopthora thermophila, or Cephalosporium sp. , preferably from the group of species consisting of Humicola insolens, DSM 1800, Fusarium oxysporum, DSM 2672, Myceliopthora thermophila, CBS 117.65, or Cephalosporium s_^, RYM-202.

Other examples of useful cellulases are variants having, as a parent cellulase, a cellulase of fungal origin, e.g. a cellulase derivable from a strain of the fungal genus Humicola, Trichoderma or Fusarium. Useful commercial cellulases according to the invention are Cellusoft™ L, Cellusoft™ Plus L, and Cellusoft™ Ultra L (available from Novo Nordisk A/S) .

The needed cellulase dosage greatly depends on the enzyme reaction time, i.e. a relatively short enzymatic reaction time necessitates a relatively increased enzyme dosage, and vice versa. In general, enzyme dosage may be stipulated in accordance with the reaction time available.

A cellulase dosage/time ratio similar to what is known from conventional biopolishing may be used. According to the invention the concentration of the cellulase enzyme in the aqueous medium may typically be 0.01-250 mg of enzyme protein per g of lyocell fibre, in particular 0.1- 50 mg of enzyme protein per g of lyocell fibre.

Typically, the cellulase reaction time is from about 10 minutes to about 4 hours, preferably from about 20 minutes to about 2 hours .

The method of the invention may be carried out in the presence of certain components which can be added to the cellulase, i.e. the formulated cellulase composition, or se- parately to the wash liquor wherein the enzyme treatment takes place. Examples of such components include a stabilizer, a wetting agent, a buffer and a dispersing agent. The stabilizer may be an agent stabilizing the cellulolytic enzyme.

Dyeing of lyocell fibres It is possible, after the primary fibrillation according to the invention and after the cellulase treatment, in the same aqueous solution, to carry out the dyeing of the lyocell fibres (see Example 23) . By using this combined process approximately half of the normal process time can be saved, because no rinse steps are needed after the primary fibrillation and after the cellulase treatment, and the dyeing procedure acts as an inactivation procedure for the cellulase.

The dyeing of the lyocell fibres is carried out as known in the art, typically by using the instructions of the manufacturers of the dyes/colorants.

The invention is illustrated in the following non-limiting examples .

MATERIALS AND METHODS

Buffer/pH: Na-carbonate was replaced by e.g. Na-acetate (see "Trial c)") or Na-phosphate (see "Trial g)"). The effect of pH-value was tested by comparing results of "Trial c) " and "Trial h)". The results of the tests were evaluated the level of pre- fibrillation (or Pilling Note) obtained and by the final tear strength of the fabric.

The level of pre-fibrillation (Pilling Note) of the samples was evaluated by applying Martindale test (after 500 revolutions), where the lower the Pilling Note value (lowest value = 1, highest value = 5) , the higher (the better) the pre- fibrillation level. For comparison, a Reference sample was used, treated only with water.

The tear strength was measured according to Standard Method: ASTM D 1424, where 5 measurements on each sample were made .

The effect of different treatments was evaluated as a loss of tear strength against a reference.

The bursting strength on the knitted fabrics was measured according to Standard Method: ISO 2960.

EXAMPLES 1 - 19

Fabric swatches of the following types : No. 1 - Tencel/Cotton 55/45 No. 2 - 100% Tencel (knitted) No. 3 - Tencel/Linen 60/40 No. 4 - Tencel/Ramie No. 5 - Tencel/NewCell No. 6 - 100% Tencel (woven) No. 7 - 100% LenzingLyocell were desized with amylase (50 ml of Aquazym Ultra 250L from Novo Nordisk A/S) for 15 minutes at 60°C. After a rinse with cold water, the swatches were treated for pre-fibrillation in a washing machine (type: ascator FLE 120 MP, Electrolux, Sweden) at a liquor ratio of 1:10, and with a lubricant (LYOPREP EXTRA, T. S. Chemicals, U.K.) under the process conditions listed below (trial A)-S)). After treatment, the samples were dried under open air and evaluated for tear strength and pilling grade. The results are summarized in TABLE 1.

Trial A) 2 g/1 Na₂C03; 4 g/1 lubricant; 90°C; 90 min. Trial B) 0.5 g/1 Na2C0₃; 4 g/1 lubricant; 90°C; 90 min.

Trial C) 0.5 g/1 Na-acetate (pH 6.5); 4 g/1 lubricant; 90°C;

90 min.

Trial D) 2 g/1 Na2Cθ3; 0.5 g/1 lubricant; 90°C; 90 min.

5 Trial E) 2 g/1 Na2Cθ3,- 4 g/1 lubricant; 90°C; 60 min.

Trial F) Reference (only water) (fabric: 1,2,3,4)

Trial G) 0.5 g/1 Na-phosphate (pH 6.5); 4 g/1 lubricant;

90°C; 90 min.

Trial H) 0.5 g/1 Na-acetate (pH 4.0); 4 g/1 lubricant;

10 90°C; 90 min.

Trial I) 0.5 g/1 Na2C0₃; 4 g/1 lubricant; 90°C; 90 min.

(same as Trial b) )

Trial J) 2 g/1 Na₂C03; 4 g/1 lubricant; 60°C; 90 min

Trial K) 2 g/1 Na-acetate (pH 6.5); 4 g/1 lubricant; 60°C; 15 90 min

Trial L) 2 g/1 Na-acetate (pH 6.5); 4 g/1 lubricant; 60°C;

40 min.

Trial M) 2 g/1 Na-phosphate (pH 6.5); 4 g/1 lubricant; 60°C;

40 min.

20 Trial N) 5 g/1 Na-acetate (pH 6.5); 4 g/1 lubricant; 60°C; 15 min.

Trial 0) 5 g/1 Na-phosphate (pH 6.5); 4 g/1 lubricant; 60°C;

15 min.

Trial P) 2 g/1 Na2C0₃; 4 g/1 lubricant; 90°C; 80 min.

25 Trial Q) 5 g/1 Na-acetate (pH 6.5); 4 g/1 lubricant; 60°C;

15 min.

Trial R) 5 g/1 Na-phosphate (pH 6.5); 4 g/1 lubricant; 60°C;

15 min.

Trial S) 2 g/1 Na-acetate (pH 6.5); 4 g/1 lubricant; 60°C; 30 40 min. TABLE 1

Pilling grade 5 = no pilling Pilling grade 1= heavy pilling

Selected fabric swatches from the trials above were further treated for de-fibrillation with an enzyme, dyed with a reactive dyestuff and washed 5-times, applying a typical home- washing procedure. The fabric samples were evaluated for pilling grade and the results show a retention of the pilling grade as that obtained just after the enzymatic de-fibrillation.

EXAMPLES 20 - 22

Pieces of approx. 10 meters of fabric:

• 100% Tencel-woven(280 g/m) • Tencel/Linen 50/50 (290 g/m)

• Tencel/Cotton 60/40 (320 g/m) were desized with amylase (Aquazym Ultra 250L from Novo Nordisk A/S) for 15 minutes at 60°C on a jet-dyer, type "Mini-soft" (Thies, Germany) . After a rinse with cold water, each of the fabrics were cut in 3 parts and one part of each fabric was treated for pre-fibrillation in the same machine (liquor ratio of 1:10, fabric speed = 75 m/min) by one of the methods described below (The lubricant used is PERILAN VF, Dr. Petry GmbH, Germany) : Trial A) 2 g/1 Na2C0₃; 4 g/1 lubricant; 90°C; 90 min.

Trial B) 5 g/1 Na-phosphate (pH 6.5); 4g/l lubricant ; 60°C; 15min. Trial C) 5 g/1 Na-acetate (pH 4.2); 4 g/1 lubricant; 60°C;15min. After treatment, the samples were dried under open air and evaluated for tear strength and pilling grade. The results are summarized in TABLE 2:

Pilling note 5 = no pilling Pilling note 1= heavy pilling

EXAMPLE 23

Pre-fibrillation, de-fibrillation and dyeing in the same bath.

Piece of approx. 25 meters of 100% Tencel-woven (280 g/m) fabric was placed in on a jet-dyer, type "Colora-Jet", France. Desizing: The fabric was desized with amylase (Aquazym Ultra 250L from Novo Nordisk A/S) for 15 minutes at 60°C. Pre-fibrilla tion : After desizing, the bath was drained and a cold water was added to establish a liquor ratio of around 1:15. At a fabric rotation (fabric speed = 75 m/min) to the bath were added 5.0 g/1 of Sodium chloride, 1.0 g/1 of Sodium acetate and 4.0 g/1 of lubricant (PERILAN VF, Dr. Petry GmbH, Germany). The bath was heated to 55°C and the pH was adjusted to 5.5 by addition of acetic acid. The fabric was rotated at these conditions for 25 min. Bio-Polishing (de-fibrilla tion) : Keeping the conditions described above, to the bath were added 2.0 g/1 of Cellusoft Plus L (a cellulase from Novo Nordisk A/S) and it was run for further 45 min. Dyeing: The dyeing was applied in the same bath, following the instructions of the dyestuff manufacturer - Zeneca, U.K. The procedure consists of: addition of 60 g/1 of Sodium chloride; 5 min rotation for salt dissolving; addition of 2.0% (on weight of fabric) PROCION Royal H-EXL within 15 min; slow (within approx. 40 min) heating to 80°C; keeping at this temperature for 30 min; addition of 20 g/1 of Sodium carbonate within 15 min; rotation at these conditions for another 45 min; drain; afterwash.

Claims

1. A method for primary fibrillation of lyocell or lyocell blends comprising the step of immersing the lyocell fibre in an aqueous solution at a pH in the range of 2-10 and subjecting the fibre to mechanical stress.

2. The method according to claim 1, wherein the solution comprises at least one builder or buffer compound selected from the group consisting of alkali metal salts and alkanolamine salts of phosphates, phosphonates, phosphonocarboxylates, carboxylic acids, amino acids, dicarboxylic acids, diglycolic acids, hydroxycarboxylic acids and inorganic acids.

3. The method according to claim 2, wherein the phosphate is selected from the group consisting of orthophosphate, pyrophosphate, tripolyphosphate, metaphosphate, hexametaphosphate and phytic acid.

4. The method according to claim 2, wherein the phosphonate is selected from the group consisting of ethane-1, 1-diphosphonate, ethane-1, 1, 2-triphosphonate, ethane-l-hydroxy-1, 1-diphosphonate and derivatives thereof, ethanehydroxy-1, 1, 2-triphosphonate, ethane, 1, 2-dicarboxy-l, 2-diphosphonate and methanehydroxyphosphonate.

5. The method according to claim 2, wherein the phosphonocarboxylate is selected from the group consisting of 2- phosphonobutane-1, 2-dicarboxylate, l-phosphonobutane-2, 3, - tricarboxylate and alpha-methylphosphonosuccinate .

6. The method according to claim 2, wherein the carboxylic acid is selected from the group consisting of acetic acid, formic acid, benzoic acid and salicylic acid.

7. The method according to claim 2, wherein the amino acid is selected from the group consisting of aspartic acid, glutamic acid and glycine.

8. The method according to claim 2, wherein the dicarboxylic acid is selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, phtalic acid, sebacic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, itaconic acid, methylsuccinic acid, 3-methylglutaic acid, 2,2- dimethylmalonic acid, maleic acid, fumaric acid, glutamic acid, and decane-1, 10-dicarboxylic acid.

9. The method according to claim 2, wherein the diglycolic acid is selected from the group consisting of diglycolic acid, thioglycolic acid, oxalacetic acid, hydroxydisuccinic acid, carboxymethylhydroxysuccinic acid and carboxymethyltartronic acid.

10. The method according to claim 2, wherein the hydroxycarboxylic acid is selected from the group consisting of glycolic acid, malic acid, hydroxypivalic acid, tartaric acid, citric acid, lactic acid, gluconic acid, mucic acid, glucuronic acid and dialdehydrostarch oxide.

11. The method according to claim 2, wherein the inorganic acid is selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

12. The method according to claim 2, wherein the alkali metal is selected from the group consisting of sodium and potassium.

5 13. The method according to claim 2, wherein the alkanolamine is selected from the group consisting of ethanolamine and triethanolamine .

14. The method according to any of the claims 2-13, wherein the 0 amount of builder or buffer is in the range of 0.01 to 50 g/1, preferably 0.5 to 6 g/1.

15. The method according to any of the claims 1-14, wherein the solution further comprises a lubricant, preferably in the range 5 of 0.5 to 6 g/1, preferably in the range of 2 to 4 g/1.

16. The method according to any of the claims 1-15, wherein the temperature of the solution is between 20┬░C and 120┬░C, preferably between 50┬░C and 70┬░C.

20

17. The method according to any of the claims 1-16, wherein the fibre is maintained in the solution, with or without being subjected to mechanical stress, for between 10 and 90 minutes.

25 18. The method according to claim 1, wherein the solution comprises at least sodium chloride.

19. The method according to claim 1, wherein the solution comprises at least sodium chloride and sodium acetate.

30

20. The method according to claim 1, wherein the solution has a pH in the range of 3-9.

21. The method according to claim 1, wherein the solution has a pH in the range of 4-7.

22. The method according to claim 1, wherein the lyocell fibre, simultaneously or subsequently to the primary fibrillation but in the same aqueous solution, is treated with a cellulase.

23. The method according to claim 22, wherein the lyocell fibre subsequently to the cellulase treatment, in the same aqueous solution, is dyed.