WO1997007267A1

WO1997007267A1 - Cellulose fibre

Info

Publication number: WO1997007267A1
Application number: PCT/AT1996/000147
Authority: WO
Inventors: Sigrid Seidl; Heinrich Firgo
Original assignee: Lenzing Aktiengesellschaft
Priority date: 1995-08-18
Filing date: 1996-08-16
Publication date: 1997-02-27
Also published as: AT402642B; ATE162858T1; CN1165544A; ATA140295A; CA2202141A1; EP0783602A1; NO971754D0; JPH10507497A; AU6695596A; EP0783602B1; BR9606586A; AU712681B2; DE59600086D1; NO971754L

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 R¿2? is CH2CH2OW, alkyl, aryl, substituted alkyl or a heterocycle.

Description

Cellulose fiber

The present invention relates to a new cellulose fiber and a method for producing this cellulose fiber.

As an alternative to the viscose process, a number of processes have been described in recent years in which cellulose is dissolved in an organic solvent, a combination of an organic solvent with an inorganic salt or in aqueous salt solutions without the formation of a derivative. Cellulose fibers made from such solutions were given the generic name Lyocell by BISFA (The International Bureau for the Standardization of man made Fibers). BISFA defines a cellulose fiber as Lyocell, which is obtained from an organic solvent by a spinning process. BISFA understands "organic solvent" as a mixture of an organic chemical and water.

To date, however, only a single process for the production of a cellulose fiber of the Lyocell type has prevailed until industrial implementation. In this process, hereinafter referred to as the amine oxide process, a tertiary amine oxide, in particular N-methylmorpholine-N-oxide (NMMO), is used as the solvent. Such a method is e.g. in US-A-4,246,221 and provides fibers which are characterized by high strength, a high wet modulus and by a high loop strength.

A characteristic property of Lyocell fibers is their pronounced tendency to fibrillate when wet. Fibrillation is understood to mean breaking open the wet fiber in the longitudinal direction under mechanical stress in the wet state, as a result of which the fiber is given a hairy, furry appearance. The reason for the fibrillation is believed to be the fiber consists of fibrils arranged in the direction of the fibers, between which there is only a small amount of crosslinking.

WO 92/14871 describes a method for producing a fiber with a reduced tendency to fibrillation. This is achieved in that all baths with which the freshly spun fiber comes into contact before the first drying have a pH of a maximum of 8.5.

WO 92/07124 also describes a method for producing a fiber with a reduced tendency to fibrillation, according to which the freshly spun, that is to say not yet dried, fiber is treated with a cationizable polymer. A polymer with imidazole and azetidine groups is mentioned as such a polymer. In addition, treatment with an emulsifiable polymer, e.g. Polyethylene or polyvinyl acetate, or crosslinking with glyoxal.

In a report from the 1993 CELLUCON conference in Lund, Sweden. Lecture given to Mortimer mentioned that the tendency to fibrillation increased with increasing stretching.

The following methods have also been published to reduce the tendency of Lyocell fibers to fibrillate:

From WO 95/02082 by the applicant it is known, for example, that the fibrillation can be reduced by certain combinations of spinning parameters.

It is also known that the fibrillation properties of Lyocell fibers can be improved by chemical crosslinking. For example, EP-A-0 538 977 describes the crosslinking of lyocell fibers with chemical reagents which can react with cellulose, both in the never-dried state, that is to say during fiber production, and also in the dried state, that is to say essentially during the textile finishing of the textile fabrics.

The crosslinking reagents cited as examples in the above-mentioned patent application EP-A - 0 538 977 have, as crosslinkable groups, halogen-substituted, nitrogen-containing ring structures which are capable of reacting with the hydroxyl groups of cellulose under alkaline conditions. Compounds with vinyl sulfone groups or their precursors are also described. These compounds also react essentially only when alkali is added or require alkali as neutralizing reagent for split off acids.

A disadvantage is that in the reaction of the halogenated, nitrogen-containing rings or the vinyl sulfones or their precursors, salts are formed which then have to be washed out of the fiber, and excess chemicals which have not reacted with the cellulose fiber must also be washed out. This means that a further post-treatment step is necessary in a continuous fiber production process, which causes further investment costs and operating costs and additionally brings with it problems with contaminated wastewater.

WO 94/24343 by the applicant proposes similar procedures for crosslinking the Lyσcell fiber against fibrillation, where the use of alkaline buffers and radiation with electromagnetic waves are described as being particularly advantageous.

WO 94/20656 describes that the fibrillation of Lyocell fibers by crosslinking with conventional crosslinking chemicals, which is usually used to improve the Crease angle of cellulose textiles are used without reducing the dyeability of the fibers if the crosslinking is carried out in the presence of flexible, linear polymers. Essentially, conventional N-methylol resins (low in formaldehyde) and the usual acidic catalysts are used. The method is described as leading to success for both the dried and the never dried fiber.

It is known from US-A-3,251,642 that the treatment of fibers from regenerated cellulose, e.g. Viscose, or cotton, especially the treatment of fabrics made from these fibers, with sulfatoalkyl sulfonium salts as a result of the crosslinking of the regenerated cellulose to improve the wet and dry crease angle recovery ability. These salts are therefore used as so-called crease-free finishing agents. It is also known that under strongly alkaline conditions, the reaction of cotton with sulfatoalkyl sulfonium salts, in particular the inner salt of disodium tris (β-sulfatoethyl) sulfonium (this inner salt is abbreviated below with trisSS), already takes place at room temperature.

The treatment of polymers containing reactive NH, OH or SH groups with a sulfonium salt such as trisSS and a base is described in Belgian patent applications no. 627 220 and no. 640 713 and in British patent applications no. 988,511, 1,047,323 and 1,059,568 and in US-A-3,251,642. The crosslinking of cellulosic textile materials with trisSS is described in US Pat. No. 3,480,382 and in US Pat. No. 3,542,503. Furthermore, it is known from GB-A-1,082,600 to use trisSS in combination with dyes for crosslinking the cellulose during a dyeing process. In the patent literature cited above, dried substrates, such as fibers, fabrics, films and paper, are impregnated with aqueous, 5-25% strength solutions of the crosslinking agent and 4-35% strength aqueous solutions of alkali, either first with crosslinking agent and then with alkali , or vice versa, first with alkali and then with crosslinker.

When using potentially alkaline compounds, such as, for example, alkali metal bicarbonates, the crosslinker with the alkali can be applied from a bath and a treatment at high temperature can then be carried out for the crosslinking. In addition, intermediate drying can be carried out between the treatment with crosslinking agent and the treatment with alkali. Alkaline metal hydroxides, alkali metal carbonates and bicarbonates, and quaternary ammonium bases such as trimethylammonium hydroxide are used as alkaline compounds. The reaction times given are 10 minutes at room temperature or shorter residence times at a higher temperature, for example 3 minutes at 150 ^° C. After the reaction, the substrate must be washed free of alkali.

No method is known in the prior art with which the fibrillation tendency of fibers which have been produced by the amine oxide method can be controlled in a targeted manner. The present invention thus aims to provide a process for the production of Lyocell fibers with which fibers can be produced which have a predetermined tendency to fibrillate.

The process according to the invention for the production of cellulose fibers by the amine oxide process, in which process a solution of cellulose in an aqueous tertiary amine oxide is spun into fibers and the fibers are brought into contact with a crosslinking agent, is characterized in that a sulfonium compound of the formula (I ) CH-CH-.Z, y 2 2

S - CH-CH-.Z. Y ~ (I)

\ 2 2

^R l

wherein R. CH_CH ₂ Z, alkyl, in particular c ₁ -C ₄ alkyl, aryl, substituted alkyl or a heterocycle, Z is halogen, sulfato, thiosulfato, phosphato or hydroxy, and Y ~ is an anion, and / or a sulfonium compound of the formula (II)

CH ₂ CH ₂ OW

S ⁺ v—. CH2-CH2-OW ( ^x II) '

^R 2

where OW is the residue of a polybasic acid in salt or acid form, and R. CH-CH-OW, alkyl, in particular C ₁ -C.alkyl, aryl, substituted alkyl or a heterocycle, is used.

Surprisingly, it has been found that treating fibers which have been produced by the amine oxide process with the above-mentioned sulfonium compounds opens up a way of not only reducing the tendency of the fibers to fibrillate, but even of controlling them in a targeted manner.

An internal salt of dialkali-tris (β-sulfatoethyl) sulfonium, in particular the inner salt of disodium tris (β-sulfatoethyl) sulfonium, is preferably used as the sulfonium compound of the formula (II) in the process according to the invention.

According to the method according to the invention, the fibers can be brought into contact with the crosslinking agent both in the never-dried state and in the dried state, although it is preferred to use the fibers in the never-dried state, for example freshly spun, to be brought into contact with the crosslinking agent.

The fibers are preferably treated with a base after they have been brought into contact with the crosslinking agent, and the fibers can be dried before treatment with the base.

A particularly advantageous embodiment of the process according to the invention consists in treating the fibers with a base and simultaneously bringing them into contact with the crosslinking agent, the base and crosslinking agent being in a molar ratio of essentially 3: 1 (base: crosslinking agent). The fibers are then dried. It has been found that no washing of the fibers is required in this embodiment of the method according to the invention. This is advantageous in that one step in the manufacturing process can be saved.

The fibers are best brought into contact with an aqueous solution which contains trisSS in a concentration of 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, preferably in 2.5 to 3.5 molar amount, based on trisSS. In particular, alkali metal hydroxides, alkali metal carbonates and bicarbonates, quaternary ammonium bases and polymeric amines are used as the base. It has also been found that buffer solutions with a pH in the range from 5 to 12, preferably from 7 to 9, can also be used according to the invention.

Washing is also unnecessary if a potentially alkaline compound, for example a bicarbonate, is used as the base. The invention also relates to cellulose fibers with a predetermined tendency to fibrillation, which are obtainable by the process according to the invention.

The invention further relates to the use of a sulfonium compound of the formula (I)

wherein R_, Z and Y ~ have the meaning given above, and / or a sulfonium compound of the formula (II)

CH ₂ CH ₂ OW CH ₂ CH ₂ OW (II)

^R 2

wherein OW and R_ have the meaning given in claim 1, for the treatment of fibers which have been produced by the amine oxide process and of yarns and fabrics made of fibers which have been produced by the amine oxide process.

The invention also relates to the use of an inner salt of dialkali tris (β-sulfatoethyl) sulfonium for the treatment of fibers which have been produced by the amine oxide process and of yarns and woven fabrics made of fibers which have been produced by the amine oxide process.

It is particularly useful to use an aqueous solution which contains a base and an inner salt of

Dialkali-Tris (ß-sulfatoethyl) sulfoniums, wherein base and crosslinking agent are in a molar ratio of essentially 3: 1 (base: crosslinking agent), for the treatment of fibers by the amine oxide process and yarns and fabrics made from fibers made by the amine oxide process.

The freshly spun, never-dried fiber strand or the never-dried fiber flake can first be impregnated with the solution of trisSS and, after being squeezed to a moisture content of 100 to 150%, impregnated with the base solution, whereby the order of treatment can also be reversed. After a residence time of about 10 minutes at room temperature, washing and drying can be carried out.

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

In addition, the process according to the invention can be carried out in one step, the fiber being treated simultaneously with the solution of trisSS and small amounts of base in a one-step process. Surprisingly, it was found that not only potentially alkaline compounds, such as alkali metal bicarbonates, can be used for the single-step process, but also alkali can be used in a correspondingly low concentration.

In the one-step process, heat treatment of the impregnated fiber is then required. The temperature treatment can be achieved by drying at temperatures of at least 60 ° C. If the molar ratio of base to triSS is not greater than 3: 1, subsequent washing is not necessary.

It has been found that when using the above sulfonium compounds over the reaction conditions (concentration of crosslinking agent, amount and type of used Base) a targeted reduction until elimination of fibrillation can be obtained.

It has also been shown that the treatment according to the invention with the crosslinking agent can be carried out before, simultaneously with or after a dyeing process. The sulfonium compounds mentioned can, for example, be added to the alkaline dyebath.

The invention is explained in more detail with the following examples. For the manufacture of the trisSS, reference is made to Belgian patent applications No. 627 204 and No. 620 775.

Fibrillation assessment

To assess the tendency to fibrillation, 8 fibers with a length of 20 mm each were placed in a 20 ml glass vial with 4 ml of water and shaken at level 12 for 9 hours with a laboratory shaker type RO-10 from Gerhardt, Bonn (DE). The fibrillation behavior of the fibers was then assessed under the microscope by counting the fibrils per 0.276 mm fiber length.

According to this test, a conventional cellulose fiber of the Lyocell genus has about 50 fibrils per 0.276 mm fiber length. A conventional cellulose fiber of the genus Modal, which is known to have no tendency to fibrillate and was used as a comparison, shows 1 to 2 fibrils.

Example 1 - Variant A

1 g of freshly spun and not yet dried lyocell fibers in flake form were impregnated at room temperature in 100 ml of an aqueous solution of trisSS for 3 minutes, squeezed to a water content of 140% and then impregnated for 10 minutes at room temperature in 100 ml of an aqueous sodium hydroxide solution. Then the fibers were 3% Washed acetic acid and water free of alkali and dried at 60 "C overnight.

The fibers were then tested for their tendency to fibrillate according to the test described above. The results are shown in Table 1 below.

Example 1 - Variant B

1 g of freshly spun and not yet dried lyocell fibers in flake form were impregnated at room temperature in 100 ml of an aqueous solution of trisSS for 3 minutes, dried for 2 hours at 60 ° C. and then impregnated for 10 minutes at room temperature in 100 ml of an aqueous sodium hydroxide solution. The fibers were then washed free of alkali with 3% acetic acid and water and dried at 60 ^* C overnight.

Table 1 shows the concentrations of trisSS in g / 1. The concentration of the sodium hydroxide solution is given in g NaOH / 1.

Table 1

Eg concentration concentration variant fibril number

No trisSS caustic soda

1 - - - 50

2 1 0.16 A 50

3 50 11.6 A 20

4 50 11.6 B 10

5 10 2.22 B 45

6 10 4.44 B 45

7 10 44.4 B 17 8 10 88, 8 B 6

Examples 5 to 8 show that the fibril count decreases with increasing concentration of sodium hydroxide solution, so that the fiber produced fibrillates less. When using trisSS according to the invention, it is thus possible to control the tendency of the lyocell fiber to fibrillate via the concentration of alkali. When using large amounts of alkali, it is of course necessary to wash the fibers free of alkali.

The same results were obtained with fibers in strand form.

Example 2 - Variants Cl, C2, Dl and D2

1 g of freshly spun and not yet dried lyocell fibers in flake form were impregnated at room temperature in 100 ml of an aqueous solution of trisSS and a base (TBAH (tetrabutylammonium hydroxide), NaOH or KHCO-) for 5 minutes and squeezed to a water content of 140%. The fiber was then either: dried at 60 ° C. overnight, washed and dried again (= variant Cl); or dried at 60 ° C. overnight and not washed

(= Variant C2); or dried at 100 ° C for 10 minutes, washed and dried again (= variant Dl); or dried at 100 ^* C for 10 minutes and not washed

(^ Variant D2).

The fibers were then tested for their tendency to fibrillate according to the test described above. The results are shown in Table 2 below. Table 2 shows the trisSS concentrations in g / 1. The concentration of the base is given in g / 1. Table 2

Eg concentration concentration variant fibril number

No trisSS base

1 - - 50

9 15 0, 34. TBAH Dl 50

10 15 0.34. TBAH D2 50

11 15 25.7 TBAH Cl 20

12 15 25.7 TBAH C2 20

13 15 25.7 TBAH Dl 20

14 15 25.7 TBAH D2 25

15 15 4.5 NaOH Cl isolated

16 15 4.5 NaOH C2 0

17 15 4.4 NaOH Cl isolated

18 15 4.4 NaOH C2 isolated

19 15 3.5 NaOH Cl 33

20 15 3.5 NaOH C2 35

21 15 3.5 NaOH Dl 32

22 15 3.5 NaOH D2 30

23 10 2.7 NaOH Dl 0

24 10 2.7 NaOH D2 0

25 15 79.0 KHC0 ₃ Cl 20

26 15 79.0 KHC0 ₃ C2 35

27 15 79.0 KHC0 ₃ Dl 20

28 15 79.0 KHCO_ D2 35

Examples 9 to 24 show the influence of the base concentration on the reduction in fibrillation. Even with a molar 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).

With a molar ratio of 2.7: 1 (Examples 10-22) the fibrillation is reduced by 40%. When using TBAOH in a ratio of 3: 1 to the crosslinker, fibrillation is reduced by 50%.

Furthermore, it can be seen from the examples that it is not necessary to wash out when using small amounts of alkali (e.g. 2.5 to 3.5 mol of base per 1 mol of crosslinking agent).

The same results were obtained with fibers in strand form.

It has also been shown that the treatment of the fibers according to the invention with the sulfonium compounds mentioned above practically does not impair their textile data, such as strength, elongation, etc.

Claims

Claims:

A process for the production of cellulose fibers by the amine oxide process, in which process a solution of cellulose in an aqueous tertiary amine oxide is spun into fibers and the fibers are brought into contact with a crosslinking agent, characterized in that a sulfonium compound of the formula (I)

wherein R., CH ₂ CH, Z, alkyl, aryl, substituted alkyl or a heterocycle, Z is halogen, sulfato, thiosulfato, phosphato or hydroxy, and Y ~ is an anion, and / or a sulfonium compound of the formula (II)

wherein OW is the residue of a polybasic acid in salt or acid form, and R ₂ CH ₂ CH ₂ OW, alkyl, aryl, substituted alkyl or a heterocycle is used.

Process according to Claim 1, characterized in that an inner salt of dialkali-tris (β-sulfatoethyl) sulfonium is used as the sulfonium compound of the formula (II). 3. The method according to claim 2, characterized in that the crosslinking agent is the inner salt of disodium tris (ß-sulfatoethyl) sulfonium.

Method according to one of claims 1 to 3, characterized in that the fibers are brought into contact with the crosslinking agent in a never-dried state.

Process according to one of Claims 1 to 4, characterized in that the fibers are treated with a base after they have been brought into contact with the crosslinking agent.

6. The method according to claim 5, characterized in that the fibers are dried before treatment with the base,

Process according to one of Claims 1 to 4, characterized in that the fibers are treated with a base and at the same time brought into contact with the crosslinking agent, the base and crosslinking agent being present in a molar ratio of essentially 3: 1 (base: crosslinking agent).

8. The method according to claim 7, characterized in that the fibers are dried.

9. cellulose fibers with a predetermined tendency to fibrillation, obtainable by a process according to one or more of claims 1 to 8. 10. Use of a sulfonium compound of the formula (I)

wherein R., Z and Y ~ have the meaning given in claim 1, and / or a sulfonium compound of the formula (II)

11. Use of an inner salt of dialkali tris (β-sulfatoethyl) sulfonium for the treatment of fibers which have been produced by the amine oxide process and of yarns and woven fabrics made of fibers which have been produced by the amine oxide process.

12. Use of an aqueous solution which contains a base and an inner salt of dialkali tris (β-sulfatoethyl) sulfonium, the base and crosslinking agent being present in a molar ratio of essentially 3: 1 (base: crosslinking agent) for the treatment of fibers made by the amine oxide process and of yarns and fabrics made of fibers made by the amine oxide process.