DE4446491C2 - Process for the production of cellulose fibers and cellulose fibers with reduced tendency to fibrillate - Google Patents

Description

The invention relates to a method for manufacturing of cellulose fibers according to the preamble of the patent Claim 1, in which the spinning solution after leakage from the spinneret through at least two precipitation baths is carried out, the precipitation baths being selected in this way are opposite that at least in the first precipitation bath slower coagulation in the last precipitation bath the cellulose takes place. The invention further relates down cellulose fibers with a core jacket structure, the have a reduced tendency to fibrillation.

Because of high investment costs and especially because of The high environmental impact is considerable Interested in alternatives to the viscose process, according to which the vast majority of Cellu  Loose regenerate fibers are found. To Verspin is one of the most promising processes NEN solutions of cellulose in amine oxides preferably in N-methyl-morpholine-N-oxide (NMMNO), not last because it is the cumbersome way to go a derivatization of the cellulose is avoided. It it is known that cellulose in an NMMNO water system stem is soluble and by spinning in a mostly water NMMNO solution to textile fibers can (DE 28 30 685 C3, DD 142 898, EP 0 490 870 A2).

For the fibers produced by the NMMNO process are high strength compared to viscose fibers and characteristic of moduli. This is how the tear resistance lies generally in an approximate range of approx. 20 to 50 cN / tex and the initial moduli in one Range over approx.1,500 cN / tex. That means that Strengths pleasantly high, but often higher than him required and the moduli clearly too high for some Applications in the field of textile fibers with good tex Til use properties are in the z. B. the usual, for textile use in clothing proven viscose fibers with initial moduli clearly below 1,500 cN / tex.

Although the NMMNO process is already on an industrial scale is turned, and the fibers produced with it for some textile applications proved successful the latter show a number of differences compared to those produced by the viscose process Fibers and are therefore not in the textile area Usable in the usual way. They show u. a. Brittle and fibrillation tendency when wet. Also can achieve the values for the elongation at break not satisfy. It also proves to be disadvantageous  that the range of variation of textile-physical Characteristic values when the manufacturing conditions change is low.

The gradual coagulation in several successive following coagulation baths is made of viscose spinning process known. DE 31 00 368 A1 is provided beat the coagulation started in the first precipitation bath in two further coagulation baths to the full continue coagulation. This should make him considerable increase in processing speed can be achieved.

Processes for the production of cellulose fibers are white in Khim. volokna, 1989 (4), pp. 33-35 and in WO 96/07779 A1, US Pat. No. 4,261,943 and in Fiber Chemistry, Vol. 20, No. 1, September 1988, pp. 38/39 called.

One way of influencing strength and Chanzy u. a. (Polymer 31 (1990), 400-405) by adding inorganic Salts such as B. ammonium chloride or calcium chloride to the NMMNO spinning solution of the cellulose. So that will but a significant increase in strength and modulus reached. The fibers therefore tend to be even stronger Brittleness and fibrillation. Such fibers that the typical behavior of high-strength, high-modulus show for many technical purposes, especially in the form of solid matrix compounds, excellently suitable, however in the textile area cannot be used in the usual width.

One way to manufacture the module to a limited extent discontinue and thus the brittleness of the fibers decrease, is instead of mostly turned on set precipitation bath from an aqueous NMMNO solution a solution of NMMNO in isopropanol or amyl alcohol to use (SU 1 224 362) or both the spinning solution solution as well as the precipitation bath certain hydrophilic additives tive to add. The entering ge slight reduction in strength can be tolerated because the fibers are still strong sen, which correspond to those of viscose fibers. Total seen all together, however, these procedures always leave still wish openly, both in terms of grit of the fibers as well as with regard to the possible speed, the physical properties of the fibers too tax by changing the manufacturing conditions ern.  

The special properties of after the amine oxide Process fibers are made by structural Special features marked (Lenzinger reports 7/94 pp. 5-9 and 31-36) with one opposite textile viscose fibers more compact precipitation structure with increased crystallinity and chain orientation as well as changed crystallite form can be determined (J. Schurz et al., Lenzinger reports 9/94, p. 37, H.- P. Fink u. a., Proceedings of the Akzo-Nobel Viscose Chemistry Seminar "Challenges in Cellulosic Man-made Fibers ", Stockholm 1994). The above-mentioned possible read about the changes in module and brittleness change the fiber accordingly return structures (M. Dubé, R. H. Blackwell, TAPPI Proceedings 1983 "International Dissolving and Specialty Pulps ", p. 111, P. Weigel et al., Lenzinger Reports 9/94, p. 31). It has to be considered further that the one set in the manufacturing process Cavity structure of the thread, its coloring behavior co-determined.

In summary, it can therefore be stated that after As before, a key problem is flexible cellulo sea fibers with low brittleness and splinterliness to manufacture and influence the spinning process so that fibers that cover the entire area of application cover textile viscose fibers can.

Based on this, it is the task of the present the invention to propose new cellulose fibers, who have low brittleness and splinterliness, d. H. a reduced tendency to fiberation compared to the be known fibers. Another job is it, a process for making flexible cel to propose loose fibers with which it is possible  to produce the properties mentioned and influence them in a targeted manner.

The invention is accomplished with respect to the method the characterizing features of claim 1 and in refer to the cellulose fibers by the solved the features of claim 10. The Unteran sayings show advantageous developments.

The inventive method (claim 1) is distinguished is characterized in that the spinning solution contained in amine contains oxides dissolved cellulose after the leak from the spinneret through at least two precipitation baths to be led. It is essential that the precipitation baths are selected so that, at least in the first precipitation bath, compared to the last felling bath, a slower koagu cellulose. Because of that it is now Surprisingly possible that fibers with a so-called core-shell structure can, with the inside of the fiber (core) made of good ordered high-strength and high-modulus areas exists while the outer shell of the fiber (sheath) from little ordered flexible parts with relative low strength and low modulus. There a fiber is now available whose high solid core the desired basic properties ensures, while the flexible jacket opens Prevents splintering of the fibers and for good flexibility quality and low tendency to breakage. Crucial in the proposed method of manufacturing the Fiber is that the spinning solution after exiting the Spinneret successively by several, preferably by two, coagulation baths that increase the solubility of Cellu loosely reduced in amine oxide in different ways zen, is led. Here is the length of stay in the  Most precipitation bath so short that only an outer layer of the nascent fiber coagulates while the inside of the thread only in the second or in the following coagulation baths. The different Effect of the precipitation baths on the dissolving behavior of the NMMNO compared to cellulose has the effect that cross-section of different cellulose structures with different mechanical characteristics hen and thus according to the invention to reduce fibers lead to a tendency to fibrillation. According to the invention you have fibers with a solid core and flexible sheath if the first coagulation bath is a much slower koagu the cellulose dissolved in NMMNO acts as the following precipitation baths.

It is preferred in the process according to the invention proceeded so that a spinning solution containing in Amine oxide cellulose dissolved in and of itself concentrations. In general with a 5 to 20% amine oxide solution worked. A 7.5 to 15% solution is preferred used. Preferably with N-methyl-morpholine N-oxide (NMMNO) worked as an amine oxide.

As precipitation baths compared to at least the last one Precipitation bath of slowed coagulation are fundamental Lich suitable for all amine oxide-dissolving substances possibly also as mixtures and with other additives sets. Relatively slow-acting precipitants for the cellulose dissolved in amine oxide and thus for the first Precipitation bath are suitable, in particular alcohols and Alkanols as well as higher quality, preferably alipha tables, alcohols, ketones, carboxylic acids, amines and other nitrogen compounds, electrolyte solutions and mixtures of these Ver  bonds. However, alkanols such as buta are preferred nol, pentanol, hexanol and other higher molecular weight Alcohols or mixtures thereof. For the last fall bad that essentially the structure inside the fiber is determined, preferably water or an aqueous Amine oxide solution used.

The procedure is basically with several of the above felling baths described above can be carried out, wherein however, it is always assumed that at least the first precipitation baths compared to the last precipitation bath exhibit slowed down coagulation so that the front fibers described standing result.

Experiments have shown that it is sufficient Is when working with two felling baths.

Is the density of the solvent of the first fall bath lower than the density of the second precipitation bath and are neither precipitation baths or only very little miscible with one another, so according to the invention be gone that both precipitation baths in one container ter be stacked. This applies e.g. B. for alkanols with increasing molecular weight from hexa nol or a mixture thereof as the first precipitation bath and water or an aqueous amine oxide solution as second precipitation bath. In this way, the length of stay in the first coagulation bath very easily through the trigger speed of the thread and the layer thickness of the Upper precipitation bath can be set. According to the invention can thus by the choice of solvent in the he Most precipitation bath the structure of the outer part of the fiber (Coat) and by the solvent in the last case bad affects the structure of the fiber interior (core) be, while the thickness of the jacket by the Ver  because time is determined in the first precipitation bath. This enables light an extensive variation of the textile physics properties of the amine oxide process rens produced cellulose threads.

The invention further relates to cellulose fibers a core-shell structure (claim 10) produced by the method described above. This company are distinguished in that the structure of the Cellulose close to the fiber surface (coat) different from the structure inside the fiber (core) differentiates and the fibers thus a reduced Have a tendency to fibrillate. The invention Fibers have a much higher core area ordered structure than in the jacket area. This leads to the cellulose areas in the core of the Fibers have a high strength and a high start have module, while the jacket areas at ge lower strength and lower initial modulus have high flexibility and low brittleness. The high-strength core of the fiber thus ensures a high strength, while the flexible sheath Reduced tendency to break and brittleness of the fibers and ensures good flexibility. The invention ß fibers have a tear resistance in the troc No condition from 15 to 50 cN / tex and in wet condition rose from 10 to 30 cN / tex. The initial module lies in the range from 1,000 to 2,500 cN / tex (dry) or 60 to 300 cN / tex (wet). The stability in Water jet with a pre-load of 80% of the Wet tensile strength is greater than 6,000 s.

These cellulose fibers can preferably be used with a like method described above who manufactured the.  

Further details and features of the invention from the following description of the Aus examples of leadership and based on the figures. Here demonstrate:

Fig. 1 is an electron microscopic (TEM) image of the fiber cross section (section) of a cellulose regenerated fiber precipitated in water from amine oxide solution.

Fig. 2 is a TEM image of the fiber cross-section (from section) of a cellulose regenerated in hexanol rat fiber from amine oxide solution

Fig. 3 is a TEM image of the fiber cross section (from section) of a cellulose precipitated in hexanol / water regenerated fiber from amine oxide solution.

example 1 (1st comparative example according to the prior art)

A spinning solution of 9% cellulose in NMMNO monohydrate with 0.1% by mass, based on cellulose propyl gallate as the stabilizing agent, was spun in a laboratory extruder with a 60-hole nozzle at a temperature of 90 ° C., a 10% solution of NMMNO in water was used. The fiber has the following parameters:

Resistance in the water jet when preloaded in 80% of the wet tensile strength: 55 s

The TEM image of the fiber cross section ( FIG. 1) shows a precipitation structure with high super-molecular order and finely dispersed pores.

Example 2 (2nd comparative example according to the prior art)

As example 1, but using hexanol as the precipitation bath has been.

Resistance in the water jet when exposed to 80% of the wet tensile strength: 8350 s

The TEM image of the fiber cross-section ( FIG. 2) shows a precipitation structure with a low supermolecular order and large heterogeneous cavities.

Example 3

As example 1, but with a 10% solution as the precipitation bath of NMMNO in water, over which a 100 mm thick Layer of hexanol was used.  

Resistance in the water jet when preloaded in 80% of the wet tensile strength: 8140 s

The TEM image of the fiber cross-section ( Fig. 2) shows a core-shell structure: in the edge region (2) low super-molecular order with large heterogeneous cavities and in the core (1) high super-molecular order with small, finely dispersed pores.

Example 4

As example 3, but instead of hexanol in the top layer of the precipitation bath a mixture of 90% Hexanol and 10% isopropanol was used.

Resistance in the water jet when preloaded in 80% of the wet tensile strength: 6320 s.

Claims (12)

1. A process for the production of cellulose fibers by spinning a spinning solution containing cellulose dissolved in amine oxides in concentrations known per se, through spinning nozzles over an air gap into a precipitation bath, characterized in that the spinning solution after it emerges from the spinning nozzle in succession by at least two Fällbä which is performed, the precipitating baths are selected so that at least in the first precipitating bath there is a slower coagulation of the cellulose compared to the last precipitating bath, the length of time in the precipitating baths with slowed down compared to the last precipitating bath is selected so that only the outer layer of the nascent thread coagulates. 2. The method according to claim 1, characterized in that for the precipitation baths with slowed down compared to the last felling bath Coagulation a solvent for amine oxides is set. 3. The method according to claim 2, characterized in that solvent, from selected from alkanols, such as hexanol or heptanol or octanol, higher alcohols such as Pro pandiol, butanediol or glycerin, carboxylic acids, Amines or other nitrogen compounds,  Electrolyte solutions or mixtures thereof be set. 4. The method according to claim 3, characterized in that as a solvent not miscible or only very slightly miscible with water Alkanols are used. 5. The method according to at least one of claims 1 to 4, characterized in that at least as the last t felling bath a felling bath, the water or a contains aqueous amine oxide solution is used. 6. The method according to at least one of claims 1 until 5, characterized in that as the amine oxide N-Me thyl-morpholine-N-oxide (NMMNO) is used. 7. The method according to at least one of claims 1 until 6, characterized in that with two precipitation baths is worked. 8. The method according to claim 7, characterized in that an insoluble in water first or only slightly soluble Precipitation bath over the second aqueous precipitation bath is layered. 9. The method according to claim 7 or 8, characterized in that by changing the Layer height of the first precipitation bath the ver  residence time of the fiber in the first precipitation bath is posed. 10. Cellulose fibers, produced by a method according to at least one of claims 1 to 9, characterized in that the cellulose fiber has a core-shell structure, the core region ( 1 ) having a higher strength and a higher initial modulus than the shell region ( 2 ). 11. Cellulose fiber according to claim 10, characterized in that the core region ( 1 ) has a high super-molecular order with small finely dispersed pores and the cladding region ( 2 ) has a low super-molecular order with larger than the core region ( 1 ) larger heterogeneous cavities. 12. cellulose fiber according to claim 10 or 11, characterized in that the initial module of dry fiber in the range of 1,000 to 2,500 cN / tex and the wet fiber in the range of 60 to 300 cN / tex.