BG99236A - Method for the production of cellulose fibres having reduced capability of fibrillation - Google Patents

Abstract

The invention relates to a method according to which cellulose solution in tertiary aminoxide is spinned in fibres which are immediately treated with textile auxiliary agent which has at least two reactive groups. The fibres are then subjected to heat treatment by electromagneic waves.

Description

The invention relates to a method for the production of fibers has a reduced tendency to fibrillation.

As an alternative to the process for the production of viscose, a number of methods have been described in recent years in which cellulose is dissolved in an organic solvent, a combination of an organic solvent and an inorganic salt, or in an aqueous salt-free solution. The cellulosic fibers produced from such solutions have been given the name Lyocell (BISFA (International Bureau of Artificial Fiber Standardization)). Cellulose fiber obtained from an organic solvent by a spinning method is defined as BISFA lyocel. An organic solvent of BISFA means a mixture of an organic reagent and water. Solvent spinning should mean dissolving and spinning without derivatives.

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To date, a single industrial method for the production of cellulose fiber - lyocell, has been established. In this process, tertiary amino oxide, especially Nmethylmorpholine-N-oxide (NMMO), is used as the solvent. Such a method is described e.g. in US-A patent 4,246,221 and results in fibers characterized by high strength, high wetting modulus and high tensile strength.

The suitability of flat products, e.g. however, the fabric obtained from said fibers is strongly limited by the pronounced tendency of these fibers to fibrillate in the wet w state. Fibrillation refers to the separation of wet fibers along the length of elementary fibers under mechanical loading in the wet state, whereby the fibers receive a fuzzy and rough appearance. The fabric made from these fibers and dyed, after a few washes, loses the intensity of staining. Adding to this is the formation of light streaks along the creased folds and rubbing edges. The reason for the fibrillation is that the fibers are composed of elementary fibers arranged in the direction of the fiber, of which there is only a slight cross-linking.

^w WO 92/14871 describes a method for producing fibers with a reduced tendency to fibrate. This is achieved by treating all baths with which the freshly spun fibers are treated before the first drying with a maximum pH of 8.5.

WO 92/07124 also discloses a method of producing a fiber is a reduced tendency to fibrate, according to which freshly spun, still-dried fibers are treated with a cationic polymer. Such a polymer is one that contains imidazole and acetidine groups. Additionally, an emulsifiable polymer treatment, such as e.g. polyethylene or polyvinyl acetate or glyoxal crosslinking.

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In a report presented by Om S. Mortimer at the 1993 CELLUCON conference in Lund, Sweden, it was mentioned that the tendency to fibrate increased with increasing fiber orientation.

The invention is intended to provide a method which is carried out in the usual way and allows the production of cellulose fibers of the type lyocell with a reduced tendency to fibration.

The method of producing cellulose fibers with a reduced tendency to fibrate according to the invention consists in the fact that the newly spun, not yet dried fibers are treated with one textile auxiliary containing at least two reactive groups and washed with water buffer provided that glyoxal is not used as a textile aid.

Dyes that have two reactive groups have proven to be particularly useful textile aids. According to the invention, textile auxiliaries that are colorless can also be used, i.e. they do not absorb visible light.

According to the invention, textile auxiliaries are preferred which, as reactive groups, contain one or two vinylsulfone groups.

An advantageous embodiment of the method according to the invention is characterized in that the newly spun fibers are treated with the textile auxiliary in an alkaline medium.

The tendency to fibrillation has been shown to decrease significantly when the alkaline medium is formed by an alkali metal carbonate and an alkali metal hydroxide.

Another preferred embodiment of the process according to the invention is that the fibers that have been in contact with the textile auxiliary are subjected to heat treatment. Heat treatment dramatically reduces the duration of impregnation.

EP-A - 0 538 977, published April 28, 1993 describes the thermal treatment of dye-impregnated cellulose fibers. However, it turns out that hot air heating of the fibers impregnated with the textile aid shortens the impregnation time, but there is a risk of uneven heating of the fibers. For example, The outer fibers of a bundle of fibers to be dried may already be partially dried until the fibers inside have reached the required temperature. This adversely affects the quality of the fibers produced.

It has been found that this disadvantage arising from ordinary heat treatment can be overcome if the fibers are exposed to electromagnetic waves, especially microwaves. When irradiated with microwaves, the fibers are heated uniformly on the one hand, and premature drying can be prevented on the one hand, since an irradiation with electromagnetic waves offers the possibility of a bundle of fibers, e.g. to be welded in a plastic sheath and in this condition to be exposed to the electromagnetic field.

The aforementioned advantages are also present when fibers located e.g. in one plane on the conveyor belt, are passed through a narrow channel in which they are subjected to electromagnetic waves. This groove may be so constructed that there is a small clearance above the fibers, which may prevent partial drying of the exterior fibers. At the same time, this variant of fixing the textile auxiliary also reveals a technically easy-to-realize production opportunity.

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Accordingly, the invention further relates to a method for the preparation of cellulose fibers, a reduced tendency for fibrillation, in which a solution of cellulose in tertiary aminoxide is spun into fibers and the newly spun fibers are treated with a textile aid containing at least two reactive groups, and subjected to heat treatment, which method is characterized in that the heat treatment is carried out by irradiation with electromagnetic waves.

According to this variant of the process according to the invention, a textile auxiliary is preferred which, as reactive groups, contains vinylsulfone groups and is preferably a dye. However, textile auxiliaries that are colorless may also be used. they do not absorb visible light.

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

The invention is more clearly explained by the following examples. Understand all percentages by weight.

Preparation of cellulose fibers

According to the method described in EP-A-0 356 419, a cellulose solution in NMMO is obtained which is extruded through a spinning nozzle. The resulting filaments, passing through an air section, are introduced into a water precipitate bath in which the cellulose coagulates. The fibers obtained in the precipitate bath were washed and showed a titer of 1.7 dtex. The washed fibers are used in the examples described below and are those fibers which in the present description and in the present claims are referred to as freshly spun, not yet dried fibers.

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1) Textile polishing treatment without further heat treatment

(a) A general description of the method

1 g of the fibers obtained by the above method were impregnated for 30 minutes at 40 ° C with 190 ml of an aqueous solution containing a textile auxiliary having two reactive groups and Na- SO ₄ . NaOH (3%), Na.CO ₃ (4%) or a mixture of NaOH, Na ₂ CO ₃ (4% Na ₂ CO ₃ and 0.2 g / l NaOH) was then added to fix the textile auxiliary. for another 60 minutes at 40 ° C, the fibers are washed several times to remove the textile auxiliary that is not fixed to the fiber, then the washed fibers are treated with water buffer for 30 minutes and then washed again with water (15 minutes). and dried at 60 [deg.] C. The tendency of the fibers to fibril as well as other parameters of the fiber is then examined.

Assessment of fibrillation

The rubbing of the fibers into each other when washing, respectively. on wet testing, simulate with the following test: 8 fibers of 20 mm length are placed together with 4 ml of water in a 20 ml test bottle and shaken for 9 hours in a laboratory shaker, type RO-10 Gerhardt, Bonn (BRD), Grade 12, fibrillation was evaluated under a microscope, establishing the number of elementary fibers at 0.276 mm of fiber length.

Other fiber data

The strength and elongation of the fiber are tested according to the BISFA Internationally agreed methods for testing viscose, modal, cupro, lyocell, acetate and triacetate staple fibers and tows, 1993 edition.

b) examples

The Remasol Schwarz dye (black) B and Remasol Rot (red) RB fibers are treated as textile auxiliaries according to the method described above (manufacturer: Hoechst AG). The Remasol Schwarz B dye contains two vinylsulfone groups and the Remasol Rot B dye contains one vinylsulfone and one monochlorothiazine group.

The solution contains 3% Remasol Schwarz B, resp. 0.5% Remasol Rot RB. The pH of the dye solution was 4.6 in each example. The aqueous buffer used is an aqueous solution containing 3% acetic acid and 7% sodium acetate. The pH of this solution is 4.6. After treatment, the buffer is washed, the fibers are washed for 15 minutes with water and then tested. Table 1a lists the retainer used, fibrillation (number of elementary fibers), titer (dtex), fiber strength (cN / tex) and fiber elongation (%). Examples 1, 2 and 3 were made with Remasol Schwarz B dye and Example 4 with Remasol Rot RB dye.

Table 16 shows the results of comparative trials performed without dye.

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Table 1a (Textile Aid)

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approx. retainer ele. fiber titer strength extension ¹ 1. | NaOH ; 22 and 1.82 28,81 11.14 2. Na, C (C 1 2! 2.07 26.39 10,67 and 3.: NaOH + Na, CO, 1 0; 2,34 24,94 10.04 ! i 4 'XT L \ TT 1 XT if 1 17 1

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Table 16 (comparison)

approx. retainer ele. fibers titer strength extension 5. NaOH > 60 1.80 33.76 12,71, 6. 7. To -> ('O- 60 1.56 33.78 12.15 ...... ........... · <NaOH + Na _? CO ₄ > 60 1.72 30.18 12.14 I 8. NaOH + Na _? CO ₄ > 60 1.72 32,00 12.70

A comparison of the results in Tables 1a and 16 shows that the textile auxiliary, in this case Remasol Schwarz B and Remasol Rot RB dyes, dramatically reduces the tendency of the fibers to fibrillate and that the combination of NaOH + Na _? CO ₃ , which is used to fix the textile auxiliary, also significantly reduces the tendency to fibrillate.

It has also been found that the above results can be obtained by using other textile auxiliaries containing two reactive groups. Thus, Remasol Schwarz B and Remasol Rot RB also represent other textile auxiliaries, which also contain at least two reactive groups.

2) Treatment with textile auxiliaries with subsequent heat treatment

Impregnate 1 g of the fibers obtained by the above method into a 190 ml dye solution (containing 0.2% Remdzol Schwarz B, 2% Na _? CO ₃ , 0.2% NaOH, pH = 11.5) for 3 times in 30 seconds by squeezing the fibers after each impregnation. Thereafter, each sample is subjected to a heat treatment of 40 times each. The sample is heat treated twice. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Then, each heat-treated sample was treated for 30 minutes with the aforementioned acetate buffer (pH = 4.6), washed with water for 15 minutes, dried at 60 ° C and examined. The results are presented in Table 6, Example 10 being the control (Example 9 was repeated Example 9, with no textile auxiliary used).

Table 2

approx. ele. fibers titer | : strength j extension ι 9. 24 1.56 33.78 12.15 10. > 57 1.80 33,76 | 12,71

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From Table 2 it is understood that a heat treatment of fibers impregnated with a textile auxiliary drastically reduces the impregnation time, and yet the tendency for fibrillation is reduced.

Remasol Rot RB dye can produce similar good results.

3. Treatment with textile afterburners with microwave g fiber irradiation obtained by the above method is impregnated in 900 ml of dye solution (10% Remasol Schwarz B, 10% Na ₉ SO ₄ , 8% Na 2 CO 4; pH adjusted with NaOH at 11.5) for 9 minutes. The fibers are then squeezed by compression and split into two equally large portions (Examples 12, 13). Example 11 serves as a control and shows the properties of fibers untreated with a textile auxiliary. In Examples 12 and 13, the fibers after impregnation with the dye solution are compressed by compression or heated 180 seconds at 180 ° C (Example 12) or irradiated for 50 seconds is 90 W microwaves (Example 13). the fibers were then treated for 30 minutes in the above acetate buffer at pH 4.6, washed with water for 15 minutes and dried at 60 ° C. The test results are shown in Table 3.

Table 3

j adj. ' warming up ele. fibers titer strength extension and 11.> - 56 1.83 31.98 ' i 11,52! D2. J 180s; 180 ° C 11 1.91 23.70 9.77 1 13. ί 50s; 90 W 7 1.92 31,23 i 114 §

Table 3 shows that microwave irradiation shortens the heating time further and that the tendency for fibrillation decreases further. Similar good results in reducing the tendency to fibrillation are obtained by using other textile auxiliaries with at least two reactive groups instead of Remasol Schwarz B. In particular, the beneficial effect on the tendency to fibrillation was as pronounced as for glyoxal. In addition, the above beneficial effect of microwave irradiation was also observed with glyoxal and other dialdehydes, as can be seen from the following example.

g fibers prepared as described in item 1 method are impregnated twice 3 minutes with 140 ml of a dyeing solution containing 2% glyoxal and 0.66% crosslinking catalyst (eg. Condensol FB, a mixture of _ZnCl? and _MgCl?, then the solution is squeezed by compression, the fibers are separated into 2 parts (Examples 15, 16) Example 14 serves as a control, for example 15 fibers are treated for 10 minutes in a convection oven at 100 ° C, and for example The 16 fibers are irradiated for 60 seconds with 50 W microwaves. The fibrillation results are shown in the following Table 4.

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

Table 4

I · »· ---- r- ^ t ·. _....... ..... example text, memo. remedy processing ele. fibers 14. 35.5 Ί-- - 15. glyoxal 10 min; 100 ° C ' 24,0 16. glyoxal 60 sec; 500 W 1 8.5 17. - 35.5 18. glutardialdehyde 10 min; 100 ° C 10.5 19. G '- glutardialdehyde 60 sec; 500 W 21.0

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Claims (12)

• · · 4 · · · · · · · · · · Patent Claims 1. A method for the preparation of cellulose fibers is a reduced tendency to fibrillation, in which a solution of cellulose in tertiary aminoxide is spun on fibers and the spinning fibers are treated with a textile auxiliary having at least two reactive groups and washed with water buffer provided that no glyoxal is used as a textile aid. 2. Method according to claim 1, characterized in that ** as a textile auxiliary agent is used a dye or Xi * · ^{1 1} a colorless solid. A method according to claim 1 or 2, characterized in that a textile auxiliary having at least one vinylsulfone group as a reactive group is used. Method according to one of Claims 1 to 3, characterized in that the newly spun fibers are treated with a textile aid in an alkaline medium. 5. The method according to claim 3, wherein the alkaline medium is formed from an alkali metal carbonate and an alkali metal hydroxide. Method according to one or more of Claims 1 to 5, characterized in that the fibers treated with the textile aid are subjected to heat treatment. 7. A method of producing cellulose fibers with a reduced tendency to fibrillation, in which a solution of cellulose in tertiary aminoxide is spun up to fibers and freshly spun fibers are treated with a textile aid containing at least two reactive groups and subjected to heat treatment, characterized in that the heat treatment is carried out by irradiation with electromagnetic waves. The method of claim 7, wherein a dye or colorless substance is used as a textile aid. A method according to claim 7 or 8, characterized in that a textile auxiliary containing at least one vinylsulfone group as a reactive group is used. A method according to one of claims 7 to 9, characterized in that the newly spun fibers are treated with a textile aid in an alkaline medium. A method according to claim 10, characterized in that the alkaline medium is formed from an alkali metal carbonate and an alkali metal hydroxide. A method according to one or more of claims 7 to 11, characterized in that the heat treatment is carried out with microwaves.