AU712681B2

AU712681B2 - Cellulose fibre

Info

Publication number: AU712681B2
Application number: AU66955/96A
Authority: AU
Inventors: Heinrich Firgo; Sigrid Seidl
Original assignee: Lenzing AG; Chemiefaser Lenzing AG
Current assignee: Lenzing AG
Priority date: 1995-08-18
Filing date: 1996-08-16
Publication date: 1999-11-11
Anticipated expiration: 2016-08-16
Also published as: ATE162858T1; NO971754D0; WO1997007267A1; CA2202141A1; EP0783602A1; DE59600086D1; EP0783602B1; AT402642B; NO971754L; CN1165544A; BR9606586A; JPH10507497A; ATA140295A; AU6695596A

Abstract

The invention relates to a process for producing cellulose fibres by the amine oxide process in which a solution of cellulose is spun in an aqueous tertiary amine oxide into fibres and the fibres are brought into contact with a cross-linking agent, in which said cross-linking agent is a sulphonium compound of formula (I) in which R1 is CH2CH2Z, alkyl, aryl, substituted alkyl or a heterocycle, Z is halogen, sulphato, thiosulphato, phosphato or hydroxy and Y<-> is an anion, and/or a sulphonium compound of formula (II) in which OW is the radical of a polybasic acid in salt or acid form and R2 is CH2CH2OW, alkyl, aryl, substituted alkyl or a heterocycle.

Description

WO 97/07267 PCT/AT96/00147 1 CELLULOSE FIBRE The present invention is concerned with a new cellulose fibre and a process for the production of this fibre.

As an alternative to the viscose process, in recent years there has been described a number of processes wherein cellulose, without forming a derivative, is dissolved in an organic solvent, a combination of an organic solvent and an inorganic salt, or in aqueous saline solutions. Cellulose fibres made from such solutions have received by BISFA (The International Bureau for the Standardisation of man made Fibres) the generic name Lyocell. As Lyocell, BISFA defines a cellulose fibre obtained by a spinning process from an organic solvent. By "organic solvent", BISFA understands a mixture of an organic chemical and water.

So far, however, only one process for the production of a cellulose fibre of the Lyocell type has achieved industrialscale realization. In this process, in the following referred to as amine-oxide process, a tertiary amine-oxide, particularly N-methylmorpholine-N-oxide (NMMO), is used as a solvent. Such a process is described for instance in US-A 4,246,221 and provides fibres which exhibit a high tensile strength, a high wet-modulus and a high loop strength.

A typical feature of the Lyocell fibres is their pronounced tendency to fibrillate when wet. Fibrillation means the breaking off of the fibre in longitudinal direction at mechanical stress in a wet condition, so that the fibre gets hairy, furry. The reason for fibrillation may be that the fibres consist of fibrils which are arranged in the longitudinal direction of the fibre axis and that there is only little crosslinking between these.

WO 92/14871 describes a process for the production of a fibre having a reduced tendency to fibrillation. The reduced tendency to fibrillation is attained by providing all the WO 97/07267 PCT/AT96/00147 -2baths with which the fibre is contacted before the first drying with a maximum pH value of WO 92/07124 also describes a process for the production of a fibre having a reduced tendency to fibrillation, according to which the freshly spun, i.e.not dried, fibre is treated with a polymer which can be cationized. As such a polymer, a polymer having imidazole and azetidine groups is mentioned.

Additionally, there may be carried out a treatment with an emulsifiable polymer, such as polyethylene or polyvinylacetate, or a crosslinking with glyoxal.

In a lecture given by S. Mortimer at the CELLUCON conference in 1993 in Lund, Sweden, it was mentioned that the tendency to fibrillation rises as drawing is increased.

Moreover, the following methods to reduce the tendency to fibrillation of Lyocell fibres have been published For instance, from WO 95/02082 of the applicant it is known that fibrillation may be reduced by certain combinations of spinning parameters.

Moreover, it is known that the fibrillation properties of Lyocell fibres may be improved by chemical crosslinking.

Thus, e.g. EP-A 0 538 977 describes crosslinking of Lyocell fibres with chemical reagents able to react with cellulose in a state before any drying, i.e. when the fibre is produced, as well as in a dried state, i.e. substantially during the textile finish of the plane fibre assemblies.

The crosslinking reagents exemplified in the above patent application EP-A 0 538 977 exhibit as groups capable of crosslinking halogen-substituted, nitrogen-containing ring structures able to react with the hydroxyl groups of the cellulose in alkaline conditions. Moreover, compounds comprising vinyl sulphone groups or their precursors are ;©cribed. These compounds substantially also react only when WO 97/07267 PCT/AT96/00147 -3alkali is added, or they require alkali as a neutralisation reagent for cleaved acids.

A drawback consists in that when the halogenated, nitrogencontaining rings or the vinyl sulphons and their precursor substances respectively are reacted, salts are formed which afterwards have to be washed out of the fibre. Moreover, also excess residual chemicals not reacted with the cellulose have to be washed out. This means that in a continuous fibre production process, another post-treatment step is necessary, causing further investment and operating costs and creating additional problems with contaminated waste water.

In WO 94/24343 of the applicant, similar processes for crosslinking Lyocell fibres to reduce fibrillation are proposed describing the use of alkali buffers and an exposure to electromagnetical waves as particularly advantageous.

WO 94/20656 describes a reduction of the fibrillation of Lyocell fibres by means of crosslinking using conventional crosslinking chemicals usually employed to improve crease angles of cellulose textiles, while a simultaneous reduction of the dye absorption does not occur, when the crosslinking is carried out in the simultaneous presence of flexible, linear polymers. Substantially, conventional N-methylol resins (containing a low formaldehyde level) and the usual acidic catalysts are used. This method is described as efficient for use on the dried as well as the never dried fibre.

From US-A- 3,251,642 it is known that treating the fibres of regenerated cellulose, such as viscose, or cotton, particularly treating the textiles made from these fibres, with sulphatoalkyl sulphonium salts leads to an improvement of the recuperative capacity of the wet and dry crease angles due to the crosslinking of the regenerated cellulose.

Therefore these salts are employed as so-called non-creasing finishing agents. Furthermore, it is known that in strong WO 97/07267 PCT/AT96/00147 -4alkaline conditions, the reaction of cotton with sulphatoalkyl sulphonium salts, particularly the inner salt of disodium-tris(p-sulphatoethyl)sulphonium (in the following, this inner salt will be abbreviated by trisSS), takes place already at room temperature.

Treatment of polymers containing reactive NH-, OH- or SH groups with a sulphonium salt such as trisSS and a base is described in the Belgian patent applications nos. 627 220 and no. 640 713, as well as in the British patent applications nos. 988,511, 1,047,323 and 1,059,568 and in US-A 3,251,642. The crosslinking of cellulose textile materials with trisSS is described in US-A 3,480,382 and in US-A 3,542,503. Further, it is known from GB-A 1,082,600 to use trisSS in combination with dyes to crosslink cellulose during a dyeing process.

In the literature cited above, dried substrates such as fibres, textiles, films and paper are impregnated with aqueous 5 25% solutions of the crosslinking agent and 4 aqueous solutions of alkali, either treating first with the crosslinking agent and afterwards with alkali or inversely treating first with alkali and thereafter with the crosslinking agent.

When potentially alkali compounds such as alkali metal bicarbonates are used, the crosslinking agent may be applied with the alkali from a bath, and afterwards a treatment for crosslinking may be carried out at an elevated temperature.

Moreover, between treatment with the crosslinking agent and treatment with alkali, an intermediate drying may be carried out. As alkali compounds, alkali metal hydroxides, alkali metal carbonates and bicarbonates and quaternary ammonium bases such as trimethylammonium hydroxide are used. As reaction times, 10 minutes at room temperature and shorter residence times at a higher temperature, e.g. 3 minutes at 150'C, are indicated. After the reaction, the alkali has to ,e washed out of the substrate.

WO 97/07267 PCT/AT96/00147 In the state of the art, no process is known whereby the tendency to fibrillation of fibres produced according to the amine-oxide process may be efficiently controlled. Thus it is the object of the present invention to provide a process for the production of Lyocell fibres whereby fibres having a predetermined tendency to fibrillation may be produced.

The process according to the invention for the production of cellulose fibres according to the amine-oxide process, wherein a solution of cellulose in an aqueous tertiary amineoxide is spun to fibres and the fibres are contacted with a crosslinking agent, is characterized in that as a crosslinking agent a sulphonium compound of the formula (I)

SCH

2

CH

2

Z

S--CH

2

CH

2 Z

(I)

R1 wherein R 1 is CH 2

CH

2 Z, alkyl, particularly C 1

-C

4 alkyl, aryl, substituted alkyl or a hetero ring, Z is halogen, sulphato, thiosulphato, phosphato or hydroxy, and Y- is an anion, and/or a sulphonium compound of the formula (II)

CH

2

CH

2 0W

S+--CH

2

CH

2 0W (II)

R

2 wherein OW is the residue of a polybasic acid in the form of salt or acid and R 2 is CH 2

CH

2 0W, alkyl, particularly C l

C

4 alkyl, aryl, substituted alkyl or a hetero ring, is used.

Surprisingly, it has been shown that by treating fibres produced according to the amine-oxide process with the above sulphonium compounds, it becomes possible not only to reduce the tendency to fibrillation of the fibres, but to efficiently control it.

WO 97/07267 PCT/AT96/00147 -6- In the process according to the invention, an inner salt of dialkali-tris-(p-sulphatoethyl)sulphonium, particularly the inner salt of disodium-tris-(p-sulphatoethyl)sulphonium, is preferably used as the sulphonium compound of formula (II).

According to the process according to the invention, the fibres may be contacted with the crosslinking agent in a never dried state as well as in a dried state. It is preferred however to contact the fibres with the crosslinking agent in a never dried state, e.g. when they are freshly spun.

Preferably, the fibres are treated with a base after having been contacted with the crosslinking agent. The fibres may be dried before treatment with the base.

A particularly advantageous embodiment of the process according to the invention consists in that the fibres are treated with a base and simultaneously are contacted with the crosslinking agent, base and crosslinking agent being present in a mol ratio of substantially 3 1 (base:crosslinking agent). Subsequently, the fibres are dried. It has been shown that in this embodiment of the process according to the invention, no washing of the fibres is required. This is advantageous insofar as it allows to eliminate a step in the production process.

The fibres are best contacted with an aqueous solution containing trisSS in a concentration of from 0,3 to 25% by mass, preferably 0,5 to 5% by mass. The base is contained in the aqueous solution in 0,8 to 100 molar amounts, preferably in 2,5 to 3,5 molar amounts, based on trisSS. As bases, particularly alkali metal hydroxides, alkali metal carbonates and bicarbonates, quaternary ammonium bases and polymer amines are used. Further it was found that according to the invention, also buffer solutions having a pH in the range of rom 5 to 12, preferably of from 7 to 9, may be employed.

M WO 97/07267 PCT/AT96/00147 -7- Washing also will not be necessary when a potentially alkaline compound such as a hydrogen carbonate is used as a base.

The invention is also concerned with cellulose fibres having a predetermined tendency to fibrillation which may be obtained according to the process according to the invention.

Further, the invention is concerned with the use of a sulphonium compound of the formula (I)

CH

2

CH

2

Z

S+ CH 2

CH

2 Z Y-

(I)

R1 wherein R 1 Z and Y- have the meaning indicated above, and/or a sulphonium compound of the formula (II)

CH

2

CH

2 0W

S+-CH

2

CH

2 OW

(II)

R

2 wherein OW and R 2 have the meaning indicated in Claim 1, for treating fibres produced according to the amine-oxide process and threads and textiles of fibres produced according to the amine-oxide process.

The invention is further concerned with the use of an inner salt of dialkali-tris(p-sulphatoethyl)sulphonium for treating fibres produced according to the amine-oxide process and threads and textiles of fibres produced according to the amine-oxide process.

It is particularly appropriate to use an aqueous solution containing a base and an inner salt of dialkali-tris(psulphatoethyl)sulphonium, base and crosslinking agent being WO 97/07267 PCT/AT96/00147 -8present in a mol ratio of substantially 3:1 (base:crosslinking agent) for treating fibres produced according to the amine-oxide process and threads and textiles of fibres produced according to the amine-oxide process.

The freshly spun, never dried fibre strand or the never dried fleeze (staple fibre) may first be impregnated with a solution of trisSS and after squeezing to a moisture content of 100 to 150% be impregnated with the base solution. The order of the treatment may also be reversed. After a residence time of approximately 10 minutes at room temperature, it may be washed and dried.

Furthermore it is possible to first impregnate the fibre with a solution of trisSS and after squeezing to a moisture content of 100 to 150% dry the fibre and carry out the treatment with the base immediately afterwards or later.

Moreover, the process according to the invention may be carried out in a single step, treating the fibre simultaneously with the solution of trisSS and small amounts of base in a single-step process. Surprisingly, it has been found that for the single-step process not only potentially alkaline compounds such as alkali metal bicarbonates may be used, but also alkali in an appropriately low concentration may be used.

After the single-step process, a temperature treatment of the impregnated fibre is necessary. The temperature treatment may be attained by drying at temperatures of at least 60°C. When the mol ratio of base to trisSS is not higher than 3 1, a subsequent washing will not be necessary.

It has been shown that when the above sulphonium compounds are used, an efficient reduction or even elimination of fibrillation may be obtained by means of the reaction conditions (concentration of crosslinking agent, amount and type of the bases used).

WO 97/07267 PCT/AT96/00147 -9- It has also been shown that the treatment with the crosslinking agent according to the invention may be carried out before, simultaneously with or after a dyeing process.

For instance, the indicated sulphonium compounds may be added to an alkaline dyeing bath.

By means of the following Examples, the invention will be explained in more detail. For the production of trisSS, reference to the Belgian patent applications nos. 627 204 and no. 620 775 is made.

Evaluation of fibrillation To evaluate the tendency to fibrillation, 8 fibres each having a length of 20 mm were put into a 20 ml test bottle with 4 ml of water and shaken during 9 hours at stage 12 in a laboratory mechanical shaker of the RO-10 type, made by the company Gerhardt, Bonn (Germany). Afterwards, the fibrillation behaviour of the fibres was evaluated under the microscope by means of counting the fibrils per 0,276 mm of fibre length.

According to this test, a conventional cellulose fibre of the Lyocell type exhibits approximately 50 fibrils per 0,276 mm of fibre length. A conventional cellulose fibre of the Modal type which has no tendency to fibrillation as is known was used as a comparative Example exhibited 1 to 2 fibrils.

Example 1 procedure A 1 g of freshly spun, not yet dried Lyocell fibres as a staple fleeze were impregnated with 100 ml of an aqueous solution of trisSS for 3 minutes at room temperature, squeezed to a water content of 140% and afterwards impregnated with 100 ml of an aqueous sodium hydroxide, i.e. an aqueous solution of sodium hydroxide, for 10 minutes at room temperature. Afterwards the WO 97/07267 PCT/AT96/00147 alkali was washed out of the fibres by means of 3% acetic acid and water, and the fibres were dried over night at Thereafter, the tendency to fibrillation of the fibres was analyzed according to the test described above. The results are shown below in Table 1.

Example 1 procedure B 1 g of freshly spun, not yet dried Lyocell fibres as a staple fleeze were impregnated with 100 ml of an aqueous solution of trisSS for 3 minutes at room temperature, dried for 2 hours at 60°C and afterwards impregnated with 100 ml of an aqueous sodium hydroxide for 10 minutes at room temperature.

Afterwards the alkali was washed out of the fibres by means of 3% acetic acid and water, and the fibres were dried over night at Thereafter, the tendency to fibrillation of the fibres was analyzed according to the test described above. The results are shown below in Table 1.

In Table 1, the concentration of trisSS is indicated in g/l.

The concentration of the aqueous sodium hydroxide is indicated in g of NaOH/1.

Table 1 Example trisSS Aqueous sodium Procedure Number of no. concentration hydroxide fibrils concentration 1 2 1 0,16 A 3 50 11,6 A 4 50 11,6 B 10 2,22 B 6 10 4,44 B 7 10 44,4 B 17 8 10 88,8 B 6 WO 97/07267 PCT/AT96/00147 -11- Examples 5 to 8 show that as the aqueous sodium hydroxide concentration increases, the number of fibrils decreases, i.e. that the fibre produced has a reduced tendency to fibrillation. Thus, when trisSS is used according to the invention, it is possible to control the tendency to fibrillation of the Lyocell fibre via the alkali concentration. Naturally, when bigger amounts of alkali are employed it is necessary to wash out the alkali of the fibres.

Identical results were obtained with a fibre strand.

Example 2 procedures Cl, C2, D1 and D2 1 g of freshly spun, not yet dried Lyocell fibres as a staple fleeze were impregnated with 100 ml of an aqueous solution of trisSS and a base (TBAH (tetrabutylammonium hydroxide), NaOH or KHCO 3 for 5 minutes at room temperature and squeezed to a water content of 140%. Afterwards, the fibre was either: dried at 60°C over night, washed and dried again procedure Cl); or dried at 60°C over night and not washed procedure C2); or dried at 100 C for 10 minutes, washed and dried again (procedure DI); or dried at 100'C for 10 minutes and not washed (=procedure D2).

Then the tendency to fibrillation of the fibres was analyzed according to the test described above. The results are shown below in Table 2. In Table 2, the trisSS concentration is indicated in g/l. The concentration of the base is indicated in g/l.

Table 2 Example trisSS Base Procedure Number of no. concentration concentration fibrils 1 9 15 0,34 TBAH D1 WO 97/07267 PCT/AT96/00147 -12- 15 0,34 TBAH D2 11 15 25,7 TBAH C1 12 15 25,7 TBAH C2 13 15 25,7 TBAH D1 14 15 25,7 TBAH D2 15 4,5 NaOH Cl occasional 16 15 4,5 NaOH C2 0 17 15 4,4 NaOH C1 occasional 18 15 4,4 NaOH C2 occasional 19 15 3,5 NaOH C1 33 15 3,5 NaOH C2 21 15 3,5 NaOH D1 32 22 15 3,5 NaOH D2 23 10 2,7 NaOH D1 0 24 10 2,7 NaOH D2 0 15 79,0 KHCO 3 C1 26 15 79,0 KHCO 3 C2 27 15 79,0 KHC0 3 D1 28 15 79,0 KHCO 3 D2 From Examples 9 to 24, the influence of the base concentration on the reduction of fibrillation can be seen.

Already at a mol ratio of base to crosslinking agent of 3 1, fibrillation is eliminated when NaOH is used as the alkali component (see Examples 23, 24), and it is not necessary to use higher amounts of NaOH (see Examples 15-18).

At a mol ratio of 2,7 1 (Examples 10-22), fibrillation is reduced by When TBAOH is used in a ratio of 3 1 to the crosslinking agent, fibrillation is reduced by Moreover, it can be seen from the Examples that when reduced amounts of alkali 2,5 to 3,5 mol of base per 1 mol of crosslinking agent) are used, washing out is not necessary.

The same results were obtained with a fibre strand.

WO 97/07267 PCT/AT96/00147 -13- Furthermore, it has been shown that the treatment of the fibres with the above sulphonium compounds according to the invention actually has no negative effect on its textile parameters such as strength, elongation etc.

Claims

1. A process for the production of cellulose fibres according to the amine-oxide process, wherein a solution of cellulose in an aqueous tertiary amine-oxide is spun to fibres and said fibres are contacted with a crosslinking agent, characterized in that as a crosslinking agent a sulphonium compound of the formula (I) CH 2 CH 2 Z S -CH 2 CH 2 Z Y- (I) R 1 wherein R 1 is CH 2 CH 2 Z, alkyl, aryl, substituted alkyl or a hetero ring, Z is halogen, sulphato, thiosulphato, phosphato or hydroxy, and Y- is an anion, and/or a sulphonium compound of the formula (II) CH 2 CH 2 0W S+--CH 2 CH20W (II) R 2 wherein OW is the residue of a polybasic acid in the form of salt or acid and R 2 is CH 2 CH 2 0W, alkyl, aryl, substituted alkyl or a hetero ring, is used.

2. A process according to Claim 1, characterized in that as said sulphonium compound of the formula (II) an inner salt of dialkali-tris(p-sulphatoethyl)sulphonium is used.

3. A process according to Claim 2, characterized in that as said crosslinking agent the inner salt of disodium-tris( p-sulphatoethyl)sulphonium is used. WO 97/07267 PCT/AT96/00147

4. A process according to one of the Claims 1 to 3, characterized in that said fibres are contacted with said crosslinking agent in a never dried state. A process according to one of the Claims 1 to 4, characterized in that said fibres are treated with a base after having been contacted with said crosslinking agent.

6. A process according to Claim 5, characterized in that said fibres are dried before being treated with said base.

7. A process according to one of the Claims 1 to 4, characterized in that said fibres are treated with a base and simultaneously contacted with said crosslinking agent, said base and said crosslinking agent being present in a mol ratio of substantially 3 1 (base: crosslinking agent).

8. A process according to Claim 7, characterized in that said fibres are dried.

9. Cellulose fibres having a predetermined tendency to fibrillation, obtainable according to a process according to one or more of the Claims 1 to 8. Use of a sulphonium compound of the formula (I) CH 2 CH 2 Z S+ CH 2 CH 2 Z Y- (I) R 1 wherein R 1 Z and Y have the meaning indicated in Claim 1, and/or a sulphonium compound of the formula (II) WO 97/07267 PCT/AT96/00147 -16- CH 2 CH 2 0W S -CH 2 CH 2 OW (II) R2 wherein OW and R 2 have the meaning indicated in Claim 1, for treating fibres produced according to the amine- oxide process, and threads and textiles of fibres produced according to the amine-oxide process.

11. Use of an inner salt of dialkali-tris(p- sulphatoethyl)sulphonium for treating fibres produced according to the amine-oxide process and threads and textiles of fibres produced according to the amine-oxide process.

12. Use of an aqueous solution containing a base and an inner salt of dialkali-tris(p-sulphatoethyl)sulphonium, said base and said crosslinking agent being present in a mol ratio of substantially 3 1 (base:crosslinking agent) for treating fibres produced according to the amine-oxide process, and threads and textiles of fibres produced according to the amine-oxide process.