EP0647281A1

EP0647281A1 - Method of producing cellulose fibres with a decreased tendency to fibrillation

Info

Publication number: EP0647281A1
Application number: EP94912409A
Authority: EP
Inventors: Heinrich Firgo; Markus Eibl; Johann Schickermüller
Original assignee: Lenzing AG; Chemiefaser Lenzing AG
Current assignee: Lenzing AG
Priority date: 1993-04-21
Filing date: 1994-04-20
Publication date: 1995-04-12
Also published as: GB9424722D0; HU9403717D0; DE4492198D2; HRP940261A2; AU684274B2; CA2137232A1; BR9405150A; CN1108032A; CN1041948C; GB2284177A; PL306801A1; UA32560C2; JP2753396B2; RO112768B1; ZA942727B; SK152994A3; CZ303094A3; GB2284177B; BG99236A; RU2127775C1

Abstract

Described is a method of producing cellulose fibres with a decreased tendency to fibrillation, in which method a solution of cellulose in a tertiary-amine oxide is spun into fibres and the freshly spun fibres brought into contact with a textile auxiliary carrying at least two reactive groups and then subjected to heat treatment, the method being characterized in that the heat treatment is carried out by irradiating the fibres with electromagnetic radiation.

Description

Process for the production of cellulose fibers with reduced

Fibrillation tendency

The invention relates to a method for producing cellulose fibers with a reduced tendency to fibrillation.

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. "Solvent spinning" is intended to mean dissolving and spinning without derivatization.

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, 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.

The usability of fabrics, for example fabrics made from the fibers mentioned, is severely restricted by the pronounced tendency of these fibers 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. One made from these fibers and dyed fabric loses color intensity over the course of a few washes. In addition, there are bright stripes on the scuffed and crease edges. The reason for the fibrillation is assumed to be that 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 cationic 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 lecture given by S. Mortimer at the 1993 CELLUCON conference in Lund, Sweden, it was mentioned that the tendency to fibrillation increased with increasing stretching.

The object of the invention is to provide a method which can be carried out in a simple manner and which allows cellulose fibers of the Lyocell genus to be produced with a reduced tendency to fibrillation.

The process according to the invention for the production of cellulose fibers with reduced tendency to fibrillation consists in that the freshly spun, not yet dried fibers are brought into contact with a textile auxiliary which carries at least two reactive groups and are washed with an aqueous buffer, with the proviso that as Auxiliary textile Glyoxal is not used.

Dyes which have two reactive groups have proven particularly useful as textile auxiliaries. However, textile auxiliaries which are colorless, i.e. do not absorb visible light.

Textile auxiliaries which carry one or two vinylsulfone groups as reactive groups are preferably used according to the invention.

An expedient embodiment of the method according to the invention is characterized in that the freshly spun fibers are brought into contact with the textile auxiliary in an alkaline environment.

It has been shown that the tendency to fibrillation is particularly reduced when the alkaline medium is formed by an alkali carbonate and an alkali hydroxide.

Another preferred variant of the method according to the invention is that the fibers brought into contact with the textile auxiliary are heat-treated. The heat treatment drastically shortens the impregnation time.

EP-A-0 538 977, published on April 28, 1993, describes a heat treatment of cellulose fibers impregnated with a dye. However, it has been shown that heating the fibers impregnated with the textile auxiliary with hot air can shorten the impregnation time, but there is a risk that the fibers will be heated irregularly. For example, the outer fibers of a fiber bundle to be dried may already have partially dried, while the fibers inside have not yet reached the required temperature. This has an adverse effect on the quality of the fibers produced. It has been found that this disadvantage, which occurs in simple heat treatment, can be overcome if the fibers are irradiated with electromagnetic waves, in particular with microwaves. When irradiated with microwaves, the fibers are heated uniformly on the one hand, and on the other hand premature drying of the fibers can be prevented, since irradiation with electromagnetic waves offers the possibility of, for example, welding the fiber bundle into a plastic covering and exposing it to the electromagnetic field in the welded state .

The above advantages are also given when the fibers, e.g. as a flat fabric lying on a conveyor belt, transported through a narrow channel in which they are exposed to electromagnetic waves. This channel can be designed in such a way that there is little air space above the fibers, which can prevent the external fibers from drying partially. At the same time, this variant of fixing the textile auxiliary also opens up a large-scale production possibility that is technically simple to implement.

Accordingly, the invention further relates to a process for the production of cellulose fibers with reduced tendency to fibrillation, in which process a solution of cellulose in a tertiary amine oxide is spun into fibers and the freshly spun fibers are brought into contact with a textile auxiliary which carries at least two reactive groups and are heat-treated, which method is characterized in that the heat treatment is carried out by irradiation with electromagnetic waves.

According to this embodiment of the process according to the invention, a textile auxiliary is preferably used which carries vinyl sulfone groups as reactive groups and is preferably a dye. However, textile auxiliaries can also be used are used that are colorless, i.e. do not absorb visible light.

Another preferred embodiment of the method according to the invention is that the heat treatment is carried out by means of microwaves.

The invention is explained in more detail with the following examples. All% figures are to be understood as mass%.

Manufacture of cellulose fibers

According to the process described in EP-A-0 356 419, a solution of cellulose in NMMO was produced, which was extruded through a spinneret. The filaments obtained were passed through an air gap into an aqueous precipitation bath in which the cellulose coagulated. The fibers obtained in the precipitation bath were washed and had a titer of 1.7 dtex. The washed fibers were used for the examples described below and represent those fibers which are referred to in the present description and in the present patent claims as freshly spun, not yet dried fibers.

1) Treatment with textile auxiliaries without subsequent heat treatment

A) General procedure

1 g each of fibers produced by the above process was placed in 190 ml of an aqueous solution (liquor) which had a textile auxiliary which had two reactive groups and Na_S0. contained, impregnated at 40 ° C for 30 minutes. NaOH (3%), Na ₂ CO ₃ (4%) or a mixture of NaOH, Na_CO ₃ (4% a ₂ CO 3 and 0.2 g / 1 NaOH) was then added to fix the textile auxiliary. After a further 60 minutes at 40 ° C, the fibers were washed a few times to remove the textile aid not attached to the fiber. The washed fibers were then treated with an aqueous buffer for 30 minutes and then washed again with water (15 minutes) and dried at 60 ° C. The fibers were then examined for their tendency to fibrillate and for other fiber data.

Fibrillation assessment

The friction of the fibers against one another during washing processes or during finishing processes when wet was simulated by the following test: 8 fibers with a length of 20 mm were placed in a 20 ml sample vial with 4 ml of water and were held in a laboratory shaker of the type RO for 9 hours. 10 from Gerhardt, Bonn (FRG) shaken at level 12. The fibrillation behavior of the fibers was then assessed under the microscope by counting the number of fibrils per 0.276 mm fiber length.

More fiber data

Fiber strength and fiber elongation were tested according to the BISFA regulation "Internationally agreed methods for testing viscose, modal, cupro, lyocell, acetate and triacetate staple fibers and tows", edition 1993.

B) Examples

Fibers were treated with the dye Remazol Black B and Remazol Red RB as textile auxiliaries (manufacturer: Hoechst AG) in accordance with the process described above. The dye Remazol Black B carries two vinyl sulfone groups and the dye Remazol Red B carries a vinyl sulfone group and a monochlorotriazine group. The fleet contained 3% Remazol Black B and 0.5% Remazol Red RB. The pH of the liquor was 4.6 in each example. The aqueous buffer used was an aqueous solution containing 3% acetic acid and 7% sodium acetate. The pH of this solution was 4.6. After the treatment with the buffer, the fibers were washed with water for 15 minutes and then examined. Table la shows the fixing agent used in each case, the fibrillation (number of fibrils), the titer (dtex), the fiber strength (cN / tex) and the fiber elongation (%). Examples 1, 2 and 3 were carried out with the dye Remazol Black B and Example 4 with the dye Remazol Red RB.

Table 1b shows the results of comparative tests which were carried out without dye.

Table la (textile auxiliaries)

E.g. fixative fibrils titer fix. strain

1 NaOH ⁽ 22 1.82 28.81 11.14

2 Na ₂ CO ₃ 2 2.07 26.39 10.67

3 NaOH + Na ₂ CO ₃ 0 2.34 24.94 10.04

4 NaOH + Na ₂ CO ₃ 5 2.34 30.00 11.74

Table lb (comparison)

E.g. fixative fibrils titer fix. strain

5 NaOH> 60 1.80 33.76 12.71

6 Na ₂ CO ₃ 60 1.56 33.78 12.15

7 NaOH + Na ₂ CO ₃ > 60 1.72 30.18 12.14

8 NaOH + Na ₂ CO ₃ > 60 1.72 32.00 12.70 A comparison of the results of Tables la and lb shows that the textile auxiliary, in the present case the dyes Remazol Black B, and Remazol Red RB, drastically reduces the tendency of the fibers to fibrillate and that the combination of NaOH + Na ^ CO-, which is used for fixation of the textile auxiliary is used, the tendency to fibrillation is also further reduced significantly.

It has been shown that the above results are also obtained when using other textile auxiliaries which have two reactive groups. Remazol Black B and Remazol Red RB are therefore representative of other textile auxiliaries that also carry at least two reactive groups.

2) Treatment with textile auxiliaries with subsequent heat treatment

In each case 1 g of the fibers produced according to the above method was impregnated in 190 ml of liquor (containing 0.2% Remazol Black B, 2% Na _^ CO-, 0.2% NaOH, pH = 11.5) for 3 times 30 seconds, the Fibers were pressed after each impregnation. Each sample was then heat treated 2 times 40 seconds in a forced 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 examined. The results are given in Table 2, Example 10 being a control (Example 9 was repeated for Example 10, but no textile auxiliary was used).

Table 2

E.g. fibril titer strength strain

9 24 1.56 33.78 12.15

10> 57 1.80 33.76 12.71 Table 2 shows that heat treatment of the fibers impregnated with the textile auxiliary agent drastically reduces the impregnation time and that the tendency to fibrillation is nevertheless reduced.

Similarly good results were achieved with the dye Remazol Red RB.

3. Treatment with textile auxiliaries with subsequent irradiation with microwaves

10 g of the fibers produced according to the above process were impregnated in 900 ml of liquor (10% Remazol Black B, 10% a ₂ SO, 8% Na ₂ CO ₃ ; pH was adjusted to 11.5 with NaOH) for 9 minutes. The fibers were then squeezed out and divided into two equal parts (Examples 12, 13). Example 11 served as a control and gives the properties of the fibers not treated with a textile auxiliary. For Examples 12 and 13, the fibers were pressed off after impregnation with the liquor and either heated to 180 ° C. for 180 seconds (Example 12) or irradiated with 90 watt microwaves for 50 seconds (Example 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 results of the tests are shown in Table 3.

Table 3 Ex. Heating Fibrils Titer Festigk. strain

11 56 1.83 31.98 11.52

12 180s; 180 ° C 11 1.91 23.70 9.77

13 50s; 90 W 7 1.92 31.23 11.34

It can be seen from Table 3 that microwave exposure further shortens the heating time and that the tendency to fibrillation is further reduced. Similar good results regarding the reduced tendency to fibrillation were obtained than other textile auxiliaries with at least two reactive groups were used instead of Remazol Schwarz B. It has been shown in particular that the beneficial effect on the tendency to fibrillation is similarly pronounced as in the case of glyoxal. Furthermore, it has been shown that the above, favorable effect which a radiation with microwaves brings with it can also be observed with glyoxal and other dialdehydes, as can be seen from the following example.

2 g of fibers, which were produced according to the method described in section 1, were washed twice for 3 minutes with 140 ml of a liquor containing 2% glyoxal and 0.66% cross-linking catalyst (e.g. Condensol FB, a mixture of ZnCl_ and MgCl_, manufacturer: BASF) impregnated. The liquor was then squeezed out, the fibers into 2 parts (Examples 15, 16). Example 14 served as a control, for example 15 the fibers were treated in a forced air oven at 100 ° C for 10 minutes and for example 16 the fibers were exposed to a power of 500 watts twice for 60 seconds with a microwave. The fibrillation results are given in Table 4 below.

The above procedure was repeated using glutardialdehyde (3.4%) instead of glyoxal. The fibrillation results of the fibers obtained are also shown in Table 4 (Examples 17, 18 and 19 correspond to Examples 14, 15 and 16, respectively).

Table 1

Example textile aids treatment fibrils

14 35.5

15 glyoxal 10 min; 100 '' C 24.0

16 glyoxal 60 sec; 500 W 8.5

17 -, -___ 35.5

18 glutardialdehyde 10 min; 100 '' C 10.5

19 glutardialdehyde 60 sec; 500 W 21.0

Claims

Claims:

1. A process for the production of cellulose fibers with reduced tendency to fibrillation, in which process a solution of cellulose in a tertiary amine oxide is spun into fibers and the freshly spun fibers are brought into contact with a textile auxiliary which carries at least two reactive groups and washed with an aqueous buffer with the proviso 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 a textile auxiliary.

3. The method according to claim 1 or 2, characterized in that a textile auxiliary is used which carries at least one vinyl sulfone group as a reactive group.

4. The method according to any one of claims 1 to 3, characterized in that the freshly spun fibers are brought into contact with the textile auxiliary in an alkaline environment.

5. The method according to claim 3, characterized in that the alkaline medium is formed by an alkali carbonate and an alkali hydroxide.

6. The method according to one or more of claims 1 to 5, characterized in that the fibers brought into contact with the textile auxiliary are heat-treated.

7. A process for the production of cellulose fibers with reduced tendency to fibrillation, in which process a solution of cellulose in a tertiary amine oxide is spun into fibers and the freshly spun fibers with a textile auxiliary which has at least two reactive groups carries, brought into contact and heat treated, characterized in that the heat treatment is carried out by irradiation with electromagnetic waves.

8. The method according to claim 7, characterized in that a dye or a colorless substance is used as a textile auxiliary.

9. The method according to claim 7 or 8, characterized in that a textile auxiliary is used which carries at least one vinyl sulfone group as a reactive group.

10. The method according to any one of claims 7 to 9, characterized in that the freshly spun fibers are brought into contact with the textile auxiliary in an alkaline environment.

11. The method according to claim 10, characterized in that the alkaline medium is formed by an alkali carbonate and an alkali hydroxide.

12. The method according to one or more of claims 7 to 11, characterized in that the heat treatment is carried out by means of microwaves.