EP2706133A1 - Method for manufacturing viscose fibres - Google Patents

Abstract

Producing viscose fibers, comprises: providing a viscose spinning dope; and spinning the viscose spinning dope through many round spinning orifices into a spin bath to form spun threads. The viscose spinning dope comprises a coagulation retardant, preferably polyethylene glycol, in a proportion of at least 2.5%, preferably 3.5-4.5%, based on cellulose. The spinning bath has sulfuric acid content of 110-140 g/l, preferably 120-130 g/l, sodium sulfate content of 250-400 g/l, preferably 350 g/l, and zinc sulfate content of 5-20 g/l, preferably 7 g/l. An independent claim is also included for viscose fibers obtainable by the above mentioned process.

Description

The present invention relates to a process for the production of viscose fibers and viscose fibers obtainable by the process according to the invention. The invention further relates to the use of the viscose fibers according to the invention in a nonwoven and to a nonwoven which contains viscose fibers according to the invention.

It is known that some properties of viscose fibers, e.g. their absorption capacity, are strongly influenced by the expression of the fiber cross-section.

The cross-section of conventional viscose fibers, that is fibers spun from a conventional viscose spinning composition through round-section spinning holes into a spinning bath of conventional composition, is irregular and lobed / corrugated due to various effects caused by coagulation and regeneration of the cellulose.

For modifying the cross-section of viscose fibers, it is known to pass the viscose spinning mase through spinning holes having specific cross-sections, e.g. to spin a flat cross-section or a multi-limb cross-section. Accordingly, fibers are obtained with e.g. flat or multi-legged cross section, wherein the cross sections of the fibers obtained from a plurality of exactly equal shaped holes of a nozzle are substantially equal.

It is also known to modify the cross-section of viscose fibers by adjusting parameters such as the composition of the viscose spinning composition, the addition of modifiers to the viscose spinning composition, the composition of the spinning bath, the distortion, etc. In this case, irregular cross sections can be obtained with pronounced legs up to practically round cross sections. Examples of such modifications are in Götze, "Chemiefasern nach den Viskoseverfahren", 1st edition (1940), pages 428-435 ; Herzog, Textile Research 8 (1926), 87-93 ; US 4,388,260 ; US 4,129,679 and WO 2004/005595 described.

The non-prepublished European patent application EP 11191093.1 describes the production of viscose flax fibers by spinning from jet holes of flat cross-section using a dope containing a coagulation retarder, especially polyethylene glycol (PEG).

A field of use of viscose fibers are nonwovens, e.g. hydroentangled nonwovens for use as wipes in the hygiene sector.

An important requirement of such nonwovens is that they can be used in disposal, e.g. Do not block the sewage system via toilet flushes. It is therefore necessary that the nonwovens on the one hand in the dry or wet state have sufficient strength and on the other hand dissolve as much as possible in the disposal of the sewage system, preferably in the individual fibers.

The WO 2006/134132 describes the use of Viskoseflachfasern in a fiber composite with the purpose to improve the solubility of the fiber composite in water.

It is still the object to provide new viscose fibers with a modified cross-section available, which have favorable properties over conventional viscose fibers. In particular, there is a need for modified viscose fibers suitable for use in nonwovens.

• Bereitstellen einer Viskosespinnmasse
• Verspinnen der Viskosespinnmasse durch eine Vielzahl von runden Spinnöffnungen in ein Spinnbad unter Bildung von Spinnfäden,
  wobei
• die Viskosespinnmasse einen Koagulationsverzögerer, insbesondere Polyethylenglykol, in einem Anteil von zumindest 2,5%, bevorzugt 3,5% bis 4,5%, jeweils bezogen auf Cellulose, enthält und
• das Spinnbad einen Gehalt an H₂SO₄ von 110-140 g/L, bevorzugt 120-130 g/L, einen Gehalt an Na₂SO₄ von 250-400 g/L, bevorzugt 300-400 g/L, besonders bevorzugt 350 g/L und einen Gehalt an ZnSO₄ von 5-20 g/L, bevorzugt 5-10 g/L, besonders bevorzugt 7 g/L aufweist.

This object is achieved by the process according to the invention for producing viscose fibers, which comprises the steps:

• Providing a Viskosepinnmasse
• Spinning the viscose spinning mass through a plurality of round spinning orifices into a spinning bath to form filaments,
  in which
• the Viskosepinnmasse a Koagulationsverzögerer, in particular polyethylene glycol, in a proportion of at least 2.5%, preferably 3.5% to 4.5%, each based on cellulose, and contains
• the spinning bath has a content of H ₂ SO ₄ of 110-140 g / L, preferably 120-130 g / L, a content of Na ₂ SO ₄ of 250-400 g / L, preferably 300-400 g / L, particularly preferred 350 g / L and has a content of ZnSO ₄ of 5-20 g / L, preferably 5-10 g / L, particularly preferably 7 g / L.

Brief description of the figures

• FIG. 1 shows the photomicrographically recorded cross-sections of viscose fibers, which were spun from a Viskosepinnmasse without the addition of PEG.
• FIG. 2 Figure 4 shows the cross-sections of viscose fibers spun from a viscose gum with addition of 1.3% PEG based on cellulose.
• FIG. 3 shows the cross-sections of viscose fibers according to the invention, which were spun from a Viskosepinnmasse with the addition of 2.6% PEG, based on cellulose.
• FIG. 4 shows the cross sections of viscose fibers according to the invention, which were spun from a viscose spinning composition with the addition of 3.9% PEG, based on cellulose.

Detailed description of the invention

It has surprisingly been found that novel viscose fibers with a special cross-sectional modification can be produced by a combination of certain process parameters in the viscose process.

The presence of a coagulation retarder, in particular PEG, in certain concentration ranges in the viscose spinning mass is obviously important.

Further suitable coagulation inhibitors are N-free polyoxyalkylene derivatives, N-free oxyethylated and N-containing oxyethylated compounds and N-containing compounds (amines, quaternary ammonium salts).

The coagulation retardant is preferably added to the viscose spinning composition immediately before spinning.

Furthermore, the filaments are spun into a spinning bath with a relatively high acid concentration (H ₂ SO ₄ ). This supports the coagulation of the fiber from the outside and thus causes a fixation of the geometry. Also important is the content of zinc sulfate in the spinning bath.

The remaining process parameters can be kept in the usual ranges for the viscose process. Apart from the presence of the coagulation retarder, it is possible to use a customary viscose spinning material. A typical standard spinning viscose has while a content of cellulose of 8-10 wt.% And a content of NaOH of 5-9 wt.%. The nozzle delay can be 1.0 to 3.0. The stretching of the filaments after leaving the spinning bath can be from 10% to more than 40%.

The viscose fibers obtainable by the process according to the invention are standard viscose fibers, i. no modal fibers (as defined by the BISFA - Bureau for the International Standardization of Man-Made Fibers).

Surprisingly, the viscose fibers according to the invention have very different, irregular multi-limbed and / or curved fiber cross-sections.

In particular, the viscose fibers according to the invention are characterized in that at least 50% of the fibers have a letter-shaped cross-section. Although not all cross sections of the fibers are directly attributable to a letter form, the cross sections convey the overall impression of a letter soup or alphabet pasta.

The fibers have multi-limbed cross sections in the form of letters such as E, F, H, L, I, J, L, C, U, V, S, N, M, W, Y and Z.

It was found that the expression of the letter form depends on the amount of coagulation inhibitor used, in particular PEG.

With too low amounts of PEG (below 2.5% based on cellulose), the cross-section of the spun fibers differs only slightly from conventional viscose fibers. Such fibers are in the FIG. 2 shown.

With amounts of Koagulationsverzögerer in the lower range of the invention, for example in the case of PEG 2.5% to 3.5%, pronounced legs of the fibers and in particular a higher proportion of "multi-limbed" letters such as E, F or H. Such fibers are in the FIG. 3 shown.

For higher amounts of coagulation retardants, for example in the case of PEG 3.5 to 6.0%, the proportion of curved, kidney-shaped cross sections and letter forms such as I; J, C, U or V larger. Such fibers are in the FIG. 4 shown.

The proportion of fibers with a cavity in cross-section is less than 10%, preferably less than 5%, in the viscose fibers according to the invention. The fibers are massive viscose fibers, not so about hollow fibers or collapsed hollow fibers such as from the US 4,129,679 known.

The viscose fibers of the invention are preferably also characterized in that the surface of the fibers is substantially smooth. By "substantially smooth" is meant, in particular, that the fiber has substantially no grooves in the longitudinal direction, which have a groove depth of more than 10%, in particular more than 5% of the fiber thickness. As "grooves" are to be understood that typical for standard viscose fibers, in relation to the width of the fiber small indentations in the longitudinal direction.

The viscose fibers according to the invention preferably have a titer of less than 5 dtex, preferably 1.3 to 3.3 dtex.

Most preferably, the viscose fibers of the present invention are in the form of staple fibers, i. as a multiplicity of cut fibers. The cutting length can be 0.3 to 150 mm.

It has been found that the viscose fibers according to the invention are outstandingly suitable for use in a nonwoven, in particular a hydroentangled nonwoven. In particular for nonwovens with a good dispersibility in water (flushability), fibers with a cutting length of 3 to 20 mm, in particular 3 to 12 mm are suitable. For nonwovens for use in textiles, cutting lengths of 30 mm to 60 mm, in particular 30 mm to 40 mm are of interest.

Accordingly, the present invention also relates to a nonwoven comprising viscose fibers according to the invention.

The viscose fibers according to the invention may be present in the nonwoven in a proportion of up to 100%, preferably 50-100%.

The nonwovens can be produced by wet-laying processes as well as dry-laying processes such as airlaid and carding / carding. The solidification can be carried out with the aid of binders and / or mechanical consolidation processes, preferably with needling and hydroentanglement.

It has been found that nonwovens of viscose fibers according to the invention dissolve very quickly in water and do not clog wastewater pumps.

Therefore, nonwovens according to the invention are preferably suitable for wipes and / or wet wipes, in particular in the hygiene sector.

However, the viscose fibers according to the invention are also outstandingly suitable for the production of yarns and nonwovens for textiles and clothing with comfort and thermo-regulating properties (insulation against cold and heat) and for the production of filter media. In particular, fibers with a cut length of 30 to 150 mm, in particular 40 to 110 mm, particularly preferably 40 mm (cotton type) and 70 mm (wool type) are suitable for textile applications. For filter media, in particular wet-laid nonwovens containing fibers with a cut length of 3 to 12 mm are suitable.

Examples:

• Düsenverzug:    2,0
• Verstreckung (nach Verlassen des Spinnbades):    15%
• Viskose:    Standardspinnviskose
• Spinnbadzusammensetzung: 130 g/l H₂SO₄, 350 g/l Na₂SO₄, 7,0 g/l ZnSO₄
• Nachbehandlung: Aufschwemmen, Waschen, Nachbehandlung, Schnitt

Each viscose spinning composition was spun and further treated through a spinneret having round orifices with a diameter of 60 μm as follows:

• Nozzle delay: 2.0
• Drawing (after leaving the spinning bath): 15%
• Viscose: standard spinning viscose
• Spin bath composition: 130 g / l H ₂ SO ₄ , 350 g / l Na ₂ SO ₄ , 7.0 g / l ZnSO ₄
• After treatment: flooding, washing, after treatment, cut

Beispiel 1:

Keine Zugabe von PEG zur Viskosespinnmasse

Beispiel 2:

Zugabe von 1,3 % PEG bezogen auf Cellulose zur Viskosespinnmasse unmittelbar vor dem Verspinnen.

Beispiel 3:

Zugabe von 2,6% PEG bezogen auf Cellulose zur Viskosespinnmasse unmittelbar vor dem Verspinnen.

Beispiel 4:

Zugabe von 3,9% PEG bezogen auf Cellulose zur Viskosespinnmasse unmittelbar vor dem Verspinnen.

The following experiments were carried out:

Example 1:

No addition of PEG to Viscose Gum

Example 2:

Addition of 1.3% PEG based on cellulose to Viskosepinnmasse immediately before spinning.

Example 3:

Addition of 2.6% PEG based on cellulose to Viskosepinnmasse immediately before spinning.

Example 4:

Addition of 3.9% PEG based on cellulose to Viskosepinnmasse immediately before spinning.

The denier of the spun fibers was 1.7 dtex in each case, the cut length 40 mm.

The cross sections of the spun fibers are in the FIGS. 1 to 4 (according to Examples 1 to 4).

FIG. 1 shows the typical irregular lobed cross sections of a conventional viscose fiber.

FIG. 2 shows hardly any changes in the cross sections compared to FIG. 1 ,

Out FIG. 3 is the clear expression of thighs and the formation of very different, especially letter-shaped cross sections (especially of "multi-legged" letter shapes such as E, F and H) can be seen. The entirety of the cross sections gives the impression of a letter soup or of pasta noodles. It is also clear that the surface of the fibers compared to those of the Figures 1 and 2 is smoother.

In the fiber cross sections of the FIG. 4 the "multi-limbed" letterforms recede, the thighs are less pronounced, shapes such as I, J, C, U, or V are increasingly appearing, and the surface of the fibers are even smoother than those of the FIG. 3 , It remains the overall impression of a alphabet soup or of pasta noodles.

Dissolution properties of nonwovens of fibers according to the invention

Fibers having a basis weight of 50 g / l and having a titre of 1.7 dtex and cutting lengths of 12, 16 and 20 mm were produced from fibers according to the invention which had been produced in the viscose spinning composition using 3.9% PEG based on cellulose. m ² produced.

The dissolution properties of these nonwovens in water were determined by means of a tube test and a pump test and compared with the dissolution property of nonwovens of other viscose fibers. The tube test was based on the " Guidance Document for Assessing the Fluxability of Nonwoven Consumer Products, EDANA and INDA, 2nd Edition, 2009 ", the pump test is carried out completely according to this document.

The nonwovens of the fibers according to the invention showed excellent dissolution properties and behaved better, in particular, than nonwovens made of viscose flat fibers.

Claims (10)

Process for the production of viscose fibers, comprising the steps: - Providing a Viskosepinnmasse Spinning the viscose spinning mass through a plurality of round spinning openings into a spinning bath to form filaments,
in which the viscose spinning mass contains a coagulation retardant, in particular polyethylene glycol, in a proportion of at least 2.5%, preferably 3.5% to 4.5%, in each case based on cellulose, and the spinning bath has a content of H ₂ SO ₄ of 110-140 g / L, preferably 120-130 g / L, a content of Na ₂ SO ₄ of 250-400 g / L, preferably 300-400 g / L, especially preferably 350 g / L and has a content of ZnSO ₄ of 5-20 g / L, preferably 5-10 g / L, particularly preferably 7 g / L. Viscose fibers obtainable by a process according to claim 1. Viscose fibers according to claim 2, characterized in that the fibers have irregular multi-limb and / or curved fiber cross-sections. Viscose fibers according to claim 2 or 3, characterized in that at least 50% of the fibers have a letter-shaped cross section. Viscose fibers according to any one of claims 2 to 4, characterized in that the surface of the fibers is substantially smooth. Viscose fibers according to one of claims 2 to 5, characterized in that the fibers have a titer of less than 5 dtex, preferably 1.3 to 3.3 dtex. Viscose fibers, characterized in that they are in the form of staple fiber. Use of viscose fibers according to one of Claims 2 to 7 in a nonwoven. Nonwoven comprising viscose fibers according to one of claims 2 to 7. Yarns and textile articles containing viscose fibers according to one of Claims 2 to 7.

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