CN1108032A - Process for producing cellulose fibers with reduced tendency to fibrillate - Google Patents

Abstract

The invention relates to a method for producing cellulose fibres with a reduced tendency to fibrillation, comprising spinning a solution of cellulose in a tertiary amine oxide into fibres, bringing the freshly spun fibres into contact with a textile auxiliary having at least two reactive groups, and carrying out a heat treatment, characterised in that the heat treatment is carried out by means of electromagnetic radiation.

Description

Process for producing cellulose fibers with reduced tendency to fibrillate

The invention relates to a process for the production of cellulose fibers with a reduced tendency to fibrillate.

As an alternative to the viscose method, a series of methods have been described in recent years in which cellulose that has not been derivatized is dissolved in an organic solvent, a combination of an organic solvent and an inorganic salt, or a saline solution. The cellulose fibers produced from such solutions are given the generic name Lyocell by BISFA (International Bureau for the Standardization of Man-Made Fibres). BISFA defines a cellulose fiber as Lyocell, which is obtained by spinning in an organic solvent. The "organic solvent" is defined by BISFA as a mixture of organic chemicals and water. "Solvent spinning" means dissolving and spinning without forming derivatives.

However, so far, only one method of producing cellulose fibers under the generic name Lyocell has been industrially realized. In this method, tertiary amine-oxides, in particular N-methylmorpholine-N-oxide (NMMO), are used as solvents. Such a process is described eg in US-A-4,246,221 and provides fibers which are distinguished by high tenacity, high wet modulus and high loop strength.

However, the usability of shaped surfaces such as fabrics made from said fibers is greatly limited due to the extreme tendency of the fibers to fibrillate in the wet state. Fibrillation is to be understood as the splitting of wet fibers in the length direction due to mechanical stress in the wet state, thereby giving fibers a hair- or fur-like appearance. Fabrics made and dyed from such fibers can lose color intensity considerably after a few washes. In addition, light colored bands may appear along frayed and wrinkled edges. The presumed reason for the fibrillation is that the fibers consist of thin fibers aligned in the fiber direction with only small-scale transverse crosslinks between them.

WO 92/14871 discloses a method for the manufacture of fibers with a reduced tendency to fibrillate. All baths had a maximum pH of 8.5 and contacting the freshly spun fibers with the baths prior to first drying would result in the stated reduced tendency to fibrillate.

WO 92/07124 likewise discloses a method for the production of fibers with reduced tendency to fibrillate, according to which freshly spun, not yet dried fibers are treated with a cationic polymer. Polymers with imidazole groups and azetidinyl groups are proposed as such polymers. In addition, they can also be treated with emulsifiable polymers, such as polyethylene or polyester vinyl (ester), or can also be combined with glyoxal to cross-link.

At the CELLUCON Symposium in Lund, Sweden in 1993, S.Mortimer pointed out in a report that the fibrillation tendency increases with the gradual elongation of the fiber.

The task set forth by the present invention is to provide a process which can be carried out in a simple manner and which produces cellulose fibers of the generic name Lyocell with a reduced tendency to fibrillate.

According to the invention, the process for the production of cellulose fibers with a reduced tendency to fibrillation comprises contacting freshly spun, not yet dried fibers with a textile auxiliary (Textilhilfsmittel) with at least two reactive groups and washing with an aqueous buffer , provided that glyoxal cannot be used as a textile auxiliary.

Dyes having two reactive groups have proven to be particularly suitable as textile auxiliaries. According to the invention, however, it is also possible to use colorless textile auxiliaries, that is to say non-absorbing for visible light.

According to the invention, preference is given to using textile auxiliaries which carry one or two vinylsulfone groups as active groups.

A suitable embodiment of the method according to the invention is characterized in that the freshly spun fibers are brought into contact with a textile auxiliary in an alkaline medium.

It has been shown that the tendency to fibrillation is greatly reduced when an alkaline environment of alkali metal carbonates and alkali metal hydroxides is formed.

A further preferred variant of the method according to the invention consists in thermally treating the fibers which have come into contact with the textile auxiliary. This heat treatment significantly shortens the impregnation time.

EP-A-0538977, published 28 April 1993, discloses the heat treatment of cellulose fibers impregnated with dyestuffs. However, it has been found that heating the fibers impregnated with textile auxiliaries with hot air shortens the impregnation time, but there is the risk that the fibers are heated irregularly. Therefore, before the fibers inside the fiber bundle to be dried have reached the required temperature, the fibers on the outside may already be partially dried. This will adversely affect the quality of the fibers produced.

It has been found that the disadvantages arising from this simple heat treatment can be overcome when the fibers are irradiated with electromagnetic waves, especially microwaves. Through microwave radiation, on the one hand, the fibers can be heated at the same time, and on the other hand, the premature drying of the fibers can be eliminated. The radiation of electromagnetic waves provides this possibility, such as welding fiber bundles into plastic sheaths and exposing them to electromagnetic fields in the welded state middle.

The above-mentioned advantages are also obtained when the fibers are conveyed through narrow channels, for example as planar objects on a conveyor belt, wherein the fibers are exposed to electromagnetic waves. The channel can be designed in such a way that there is only a small space above the fibers, whereby partial drying of the outer fibers can be avoided. At the same time, this method of fixation of textile auxiliaries also opens up the possibility of a simple process and large-scale production.

Accordingly, the present invention also relates to a process for the production of cellulose fibers with a reduced tendency to fibrillate, in which method a solution of cellulose in a tertiary amine oxide is spun into fibers and the freshly spun fibers are combined with at least two reactive fibers. The method is characterized in that the heat treatment is carried out by radiation of electromagnetic waves.

Also according to the arrangement of the method according to the invention, preference will be given to using a textile auxiliary which has vinylsulfone groups as reactive groups, and which is preferably a dye. However, it is also possible to use colorless textile auxiliaries which do not absorb visible light.

A more preferred arrangement of the method according to the invention consists in using microwaves for the heat treatment.

The present invention will be described in more detail in conjunction with the following examples. All % are understood as % by weight.

Manufacture of Cellulose Fibers

The method disclosed according to EP-A-0356419 provides a solution of cellulose formed in NMMO which is extruded through a spinneret. The filaments thus obtained are introduced via an air gap into an aqueous spinning bath in which the cellulose coagulates. The fibers obtained in the spinning bath were washed and had a titer of 1.7 dtex. The scoured fibers will be used in the examples described below and made into fibers as described in the specification and claims as freshly spun, not yet dried fibers.

1) Treatment with textile auxiliaries without subsequent heat treatment

A) General processing method

1 g of each fiber produced according to the above method was immersed in 190 ml of an aqueous solution (dye liquor) at 40° C. for 30 minutes; the aqueous solution contained textile auxiliaries with two reactive groups and Na ₂ SO ₄ . Next, NaOH (3%), Na ₂ CO ₃ (4%) or a mixture of NaOH, Na ₂ CO ₃ (4% Na ₂ CO ₃ and 0.2 g/l NaOH) were added to fix the textile auxiliary.

After a further 60 minutes at 40°C, the fibers were washed several times in order to remove any textile aids not fixed to the fibres. The washed fibers were then treated with an aqueous buffer for 30 minutes, then washed with water (15 minutes) and dried at 60°C. Next, the fiber's fibrillation tendency and other fiber data are checked.

Evaluation of fibrosis

During the washing process or rather the calendering process in the wet state, the friction between the fibers will be simulated by the following test: 8 fibers with a length of 20mm and 4ml of water are placed in a 20ml sample bottle, and Shaking was performed for 9 hours on stage 12 in a laboratory shaker RO-10 (Laborschüttelger Öt) of Fa. Gerhardt, Bonn (BRD). Thereafter the fibrillation properties of the fibers were evaluated by counting the number of fine fibers per 0.276 mm of fiber length under a microscope.

Other Fiber Data

Fiber strength and fiber elongation will be checked in accordance with the BISFA guidelines, 1993 edition, which is "For testing viscosity, modulus (modal), cuprous, Lyocell, acetate and triacetate commonly produced fibers and silk internationally recognized approach to the

B) Example

The fibers were treated with the dyes Remazol Black B and Remazol Red RB as textile auxiliaries (producer: Hoechst AG) according to the method described above.

The dye Remazol Black B carries two vinylsulfone groups, while the dye Remazol Red B carries one vinylsulfone group and one monochlorotriazine group.

The staining solution contained 3% Remazol Black B or 0.5% Remazol Red RB. In each example, the pH of the dyeing solution was 4.6. The aqueous buffer used was an aqueous solution containing 3% acetic acid and 7% sodium acetate. The pH of the solution was 4.6. After treatment with the buffer, the fibers were washed with water for 15 minutes prior to detection. Table 1a gives the fixative used for each and gives the fibrillation (number of fine fibers), denier (dtex), fiber tenacity (cN/tex) and fiber elongation (%). Examples 1, 2 and 3 were carried out with the dye Remazol Black B, while Example 4 was carried out with the dye Remazol Red RB.

Table 1b lists the results of a comparative test without dye.

Table 1a (textile auxiliaries) Examples Fixing agent Fine fiber Denier Strength Elongation 1 NaOH 22 1,82 28,81 11,142 Na ₂ CO ₃ 2 2,07 26,39 10,673 NaOH+Na ₂ CO ₃ 0 2,34 24,94 10,044 NaOH + Na ₂ CO ₃ 5 2,34 30,00 11,74

Table 1b (Comparative) Example Fixing agent Fine fiber Denier Strength Elongation 5 NaOH >60 1,80 33,76 12,716 Na ₂ CO ₃ 60 1,56 33,78 12,157 NaOH+Na ₂ CO ₃ > 60 1, 72 30, 18 12, 148 NaOH + Na ₂ CO ₃ > 60 1, 72 32, 00 12, 70

A comparison of the results in Tables 1a and 1b shows that in the case of the aforementioned dyes Remazol Black B and Remazol Red RB, the textile auxiliaries will greatly reduce the fiber's tendency to fibrillate, and for the NaOH+Na used for the fixation of the textile auxiliaries The combination of ₂ CO ₃ also greatly reduces the tendency to fibrillation.

It turns out that the above results can also be achieved using other textile auxiliaries with two reactive groups. Thus, Remazol Black B and Remazol Red RB may represent other textile auxiliaries which likewise carry at least two reactive groups.

2) Treatment with textile auxiliaries with subsequent heat treatment

Immerse 1 g of various fibers prepared according to the above method in 190 ml dyeing solution (containing 0.2% Remazol black B, 2% Na ₂ CO ₃ , 0.2% NaOH, pH=11.5) for 3 times, each time for 30 seconds. The fibers are pressed after each dip. Each sample was then heat-treated twice for 40 seconds in a circulating air oven at 180°C. Each heat-treated sample was then treated with the above-mentioned acetate buffer (pH=4.6) for 30 minutes, washed with water for 15 minutes, dried at 60° C. and tested. The results are listed in Table 2, wherein Example 10 is a comparative example of preparation (Example 10 repeats Example 9, however no textile auxiliaries are used therein).

Table 2

Example Fine Fiber Denier Strength Strength Elongation

9 24 1,56 33,78 12,15

10 ＞57 1,80 33,76 12,71

As can be seen from Table 2, heat treatment of fibers impregnated with textile auxiliaries greatly reduces the impregnation time and also reduces the tendency to fibrillate.

Similar good results were obtained using the dye Remazol red RB.

3. Treatment with textile auxiliaries with subsequent microwave irradiation

10 g of fibers prepared according to the above _method were immersed in 900 ml of dye liquor (10% Remazol Black B, 10% _Na2SO4 , 8% _Na2CO3 ; pH adjusted to _11.5 with NaOH) for 9 minutes. The fiber was then pressed and divided into two equal portions (Examples 12, 13). Example 11 serves as a comparative example and gives the properties of fibers not treated with textile auxiliaries. For Examples 12 and 13, after impregnation with the dye liquor, the fibers were pressed and heated to 180° C. and maintained at this temperature for 180 seconds (Example 12), or irradiated with 90 watts of microwaves for 50 seconds (Example 12). 13). The fibers were then treated in the above acetate buffer at pH 4.6 for 30 minutes, washed with water for 15 minutes and dried at 60°C. The test results are listed in Table 3.

Table 3 Example heating fine fiber fibrous fiber strength extension 11 --- 56 1,83 31,98 11,5212 180s; 180 ° C 11 1,91 23,70 9,7713 50s; 90W 7 1,92 31,23 11,34

It can be seen from Table 3 that the heating time is further greatly shortened by microwave radiation, and the tendency of fibrillation is also further greatly reduced. Equally good results in reducing the tendency to fibrillation are obtained when other textile auxiliaries with at least two reactive groups are used instead of Remazol Black B. In particular, they show a similarly strong beneficial effect on fibrillation propensity as glyoxal. It has also been shown that the aforementioned beneficial effects of irradiation with microwaves are also observed with glyoxal and other dialdehydes, as will be understood from the examples hereinafter.

2 g of fibers produced according to the method described in the first part above were treated with 140 ml of a dye liquor containing 2% glyoxal and 0.66% crosslinking catalyst (for example, Condensol FB, a mixture of _ZnCl2 and _MgCl2 , producer: BASF) Two dips of 3 minutes each were performed. The dye liquor was then squeezed out and the fibers were split into two parts (Examples 15, 16). Example 14 As a comparative example, for Example 15, the fiber will be treated in a circulating air oven at 100°C for 10 minutes, while for Example 16, the fiber will be exposed twice for 60 seconds to a microwave with a power of 500W . The results of fibrillation are listed in Table 4 below.

The above procedure was repeated except that the glyoxal was replaced with glutaraldehyde (3.4%). The results of the fibrillation of the fibers obtained are also listed in Table 4 (Examples 17, 18 and 19 correspond to Examples 14, 15 or 16).

Table 4

Example Textile Auxiliary Treatment Fine Fiber

14 ---- - - - - 35,5

15 Glyoxal 10 minutes; 100°C 24,0

16 Glyoxal 60 seconds; 500W 8,5

17 ---- - - - - 35,5

18 Glutaraldehyde 10 minutes; 100℃ 10,5

19 glutaraldehyde 60 seconds; 500W 21,0

Claims (12)

1. A method for the manufacture of cellulose fibers with reduced tendency to fibrillation, the method comprising spinning a cellulose solution in a tertiary amine oxide into fibers, and mixing the freshly spun fibers with at least two textile auxiliaries with active groups contact, followed by washing with an aqueous buffer, provided that glyoxal is not used as a textile auxiliary. 2. The method according to claim 1, characterized in that a dye or a colorless substance is used as textile auxiliary. 3. The method according to claim 1 or 2, characterized in that textile auxiliaries are used which carry at least one vinylsulfone group as reactive group. 4. A method according to any one of claims 1-3, characterized in that the freshly spun fibers are brought into contact with a textile auxiliary in an alkaline medium. 5. The method according to claim 3, characterized in that the alkaline medium consists of alkali metal carbonates and alkali metal hydroxides. 6. Process according to one or more of claims 1-5, characterized in that the fibers which have been in contact with the textile auxiliary are subjected to a heat treatment. 7. A method for the manufacture of cellulose fibers with reduced fibrillation tendency, which method comprises spinning a cellulose solution in a tertiary amine oxide into fibers, and mixing the freshly spun fibers with a textile auxiliary agent with at least two reactive groups contact, and perform heat treatment, characterized in that the heat treatment is performed by electromagnetic wave radiation. 8. The method according to claim 7, characterized in that a dye or a colorless substance is used as textile auxiliary. 9. The method according to claim 7 or 8, characterized in that textile auxiliaries are used which carry at least one vinylsulfone group as reactive group. 10. A method according to any one of claims 7-9, characterized in that the freshly spun fibers are brought into contact with a textile auxiliary in an alkaline medium. 11. The method according to claim 10, characterized in that the alkaline medium consists of alkali metal carbonates and alkali metal hydroxides. 12. Process according to one or more of claims 7-11, characterized in that the heat treatment is carried out using microwaves.