EP2231906B1 - Microfiber - Google Patents

Description

The present invention relates to a high strength cellulosic regenerate fiber having a single fiber titer of between 0.6 and 0.9 dtex, and yarns and sheets containing such regenerated fibers.

The cellulosic regenerated fibers today are mainly fibers known by the viscose process and are produced worldwide. For standard applications in the textile and nonwovens sector, fibers with a single fiber titer between 0.9 and 16 dtex are used. Fibers with a smaller single fiber titer are commonly referred to as microfibers, where the term "microfiber" generally refers to fibers having a denier of less than 1.0 dtex or, depending on the density of the material, a diameter of 9 to 10 μm (FIG. Lexikon der Textilveredlung ", HK Rouette, 1995, Volume 2, pp. 1250 ff; Laumann Verlag, Duelm s). It is also known that fabrics made of microfibers are fundamentally softer than those made of coarser fibers.

Consumers and the clothing industry today demand versatile comfort and a wide variety of design options for textiles. Among other things, it is also important that even thin, soft fabrics have a high strength, are resistant and dimensionally stable and that the appearance is still as unchanged as possible even after prolonged use. Therefore, it is nowadays no longer sufficient to process only fibers with a low titer, without paying attention to the fiber strength and above all to the fiber strength in the wet state.

At the same time, however, such fibers must also be easy to process in the textile chain. In particular, it must be ensured that the fibers have a high uniformity and uniformity in titer and cut length.

From the literature a variety of approaches for the production of cellulosic microfibers are known. Some of these approaches are based on the standard viscose process, based on a cellulose xanthate solution:
The Russian patent SU 759627 For the production of viscose microfibers, a spinning bath of organic acids in organic solvents instead of aqueous dilute sulfuric acid is proposed, whereby the production of fibers with up to 0.05 dtex should be possible. Information on the strength of the fibers thus produced are not recognizable.

FR 2764910 claims a method in which the delay should be hydraulic instead of mechanical. Viscose fibers are obtained with a linear density of 0.3 dtex. Details about the strength of these fibers are not included.

The US 6197230 and the references cited therein suggest the atomization of the cellulose dope by means of air, nitrogen or water jet to produce a mixture of fibers and microfibers. The fibers obtained are mainly ultrafine and have clearly uneven diameters. The product of this process is neither intended for textile applications nor does it appear suitable. Information about the strength of these fibers are not found.

The US 3785918 also discloses the preparation of a blend of viscose fibers and microfibers using a spinning device according to the ejector principle. The obtained microfibers should be used for papermaking. They are very uneven and therefore not suitable for textile applications.

The US 4468428 discloses the production of viscose fibers with a diameter of 8 microns using a spinneret with nozzle hole diameters of 20 microns. Such nozzle hole diameters are not sufficient for large-scale production operation Operational safety operable because it is both very quickly deposits on the spin bath side of the nozzle hole, including the uniformity of the fiber diameter and the spinning security suffers or the entire nozzle channel is clogged by dirt particles and therefore the fiber titer varies even more.

The CN 1418990 discloses the production of ultrafine viscose fibers by a special adjustment of the withdrawal forces and matched nozzle hole diameter. The fibers obtained in this way have a titer of 0.56 to 0.22 dtex. The achieved strength of these fibers can not be found in the document.

The JP 2005187959 proposes to use cellulose from California cedar for the production of viscose staple fibers. This is to obtain fibers over a wide titer range between 0.2 and 30 den, which would also include microfibers. However, the range between 1.5 and 10 μm, ie outside the microfiber range, is preferred. For fiber strength no information is given.

The JP 58089924 discloses nonwoven ultrafine fiber webs having a single fiber diameter of 0.05-2 μm. The fibers may be made by the viscose, cuprammonium or acetate process. It seems important that they can be burned. In particular, for textile applications such fine fibers are no longer suitable.

The US 3539678 describes a modified viscose process obtained with fibers having a high wet modulus, so-called HWM fibers. These should be producible in a titer range of 0.7 to 5.0. The examples contain only fibers with a denier of 1.0 denier (corresponding to 1.1 dtex) with a dry strength of max. 2.93 g / den (corresponding to 25.9 cN / tex).

In addition to the viscose method, the prior art proposes further methods known per se for the production of cellulosic microfibers:
The GB 310944 discloses the production of filament yarns with a single fiber titer of at most 1 den by the Cuoxam method. For example, fibers of 0.7 denier and a dry strength of 2.64 g / den (corresponding to 23.3 cN / tex) can be achieved. The cuoxam process has significant environmental problems and is therefore no longer used worldwide with one or two exceptions.

The WO 98/58102 proposes a lyocell method for the production of cellulose microfibers. It should be emphasized at this point that a lyocell process does not lead to cellulose regenerated fibers in the context of this application, since in the lyocell process, the cellulose is only physically dissolved and reprecipitated, while in the production of cellulose regenerated first a cellulose derivative, such as cellulose xanthogenate or - as in the case of the Cuprammoniumverfahrens - a cellulose-metal complex is generated, which is regenerated in the course of the process back to pure, undissolved cellulose. By using special pulps with a specific molar mass distribution, which is achieved for example by electron irradiation of the pulp, can according to the WO 98/58102 Fibers are made with a Einzelfasertiter from 0.3 to 1.0 dtex, preferably 0.8 to 1.0 dtex. However, nothing is said about the fiber strengths achievable with this method and the production costs are increased by the particular pulp.

WO 2005/106085 . US 2005-056956 . US 2002-148050 . WO 01/86043 and the references cited therein describe various approaches to the preparation of cellulosic microfibers by modifying the lyocell method by meltblowing or centrifugal spinning. However, the fibers obtained herewith have uneven titer and fiber length distributions, so they are not suitable for high quality textile and fiber technical applications are suitable. The methods require at least one compared to the usual lyocell process completely new spinning apparatus.

DE 19622476 and DE 19632540 propose the mixing of an amine oxide cellulose solution with a viscous desolvation medium and the subsequent application of various shear fields to this mixture. However, this also uneven titer and fiber length distributions are achieved, so that these fibers are not suitable for high-quality textile and technical applications. About the achievable fiber strengths nothing is removable. In addition, the process is extremely complicated by the required handling of Desolvatationsmediums and not feasible in a conventional lyocell production plant.

US 6153136 and US 6511746 disclose the preparation of cellulosic microfibers by a modified lyocell process with special design of the spinneret geometry which effects a phase separation between cellulose and solvent. Nothing can be inferred about the fiber strengths achievable with this method.

In summary, therefore, the prior art discloses only fine to ultrafine cellulosic fibers which were either produced with economically and / or ecologically meaningless methods, have sufficient strength or have no information on this or are already unusable for textile purposes due to their preparation. In fact, some publications reveal nothing more than the intention of the authors to (also) want to make fine cellulosic fibers.

1. a) Das Rotorspinnverfahren benötigt eine signifikant höhere Faserzahl im Garnquerschnitt als das Ringspinnverfahren. In der Praxis kann davon ausgegangen werden, dass ein Rotorgarn zumindest 100 Fasern im Garnquerschnitt aufweisen muß.
2. b) Rotorgarne weisen signifikant geringere Garnfestigkeiten auf als Ringgarne gleicher Garnfeinheit
3. c) Analog zum Ringspinnverfahren wird die Produktivität der Garnherstellung durch die Drehzahl des Rotors und die Höhe der Garndrehung bestimmt.

Staple fibers can be made into yarns by various spinning techniques. These spinning processes have different advantages and disadvantages. The "classic" ring spinning process is known for its flexibility to process fibers of different fineness and fiber length. Depending on the respective raw material ring spinning machines or modified ring spinning process such. For example, the COMPACT and SIRO processes are able to produce yarns of the highest fineness. In practice, it can be assumed that ring yarns must have at least 50 fibers in the yarn cross section. However, a significant disadvantage of the ring spinning process is its low productivity, which is due to the technology of the ring spinning process. Due to the technological fundamentals of the ring spinning process - the productivity of this spinning process is determined by the amount of yarn twist and the spindle speed - the costs of yarn production increase significantly with increasing yarn count. The production of fine or finest yarns after the ring spinning process is therefore extremely expensive. The fineness of yarns is expressed as a yarn number. The higher the yarn count of a yarn, the finer it is. In the metric measurement system, the yarn count is given as Nm ("number metric"), internationally also as Ne ("number English").
The rotor spinning process known since about 1970 is characterized by a significantly higher productivity compared to the ring spinning process. With yarns of fineness 200 dtex (Ne 30 (Nm 50)) it can be assumed that the productivity of modern rotor spinning machines exceeds the productivity of ring spinning machines by a factor of approximately six. Compared to the ring spinning process, however, the rotor spinning process has the following disadvantages due to the technological principles of yarn production:

1. a) The rotor spinning process requires a significantly higher number of fibers in the yarn cross section than the ring spinning process. In practice, it can be assumed that a rotor yarn must have at least 100 fibers in the yarn cross section.
2. b) Rotor yarns have significantly lower yarn strengths than ring yarns of the same yarn count
3. c) Similar to the ring spinning process, the productivity of yarn production is determined by the speed of the rotor and the amount of yarn twist.

However, due to the above-mentioned technological principles, rotor spinning machines are not able to produce fine yarns with the same fineness and strength as ring spinning machines.

In the Murata vortex spinning (MVS) process developed by Murata, which belongs to the category of airjet spinning processes, the productivity of the spinning process is significantly higher than the productivity of the ring and rotor spinning processes. For yarns of fineness 200 dtex (Ne 30 (Nm 50)), the productivity of this spinning process is about 2.5 times higher compared to rotor spinning. Compared to the ring spinning process, the productivity of this process is even higher by about a factor of 15. Spun processes based on the Murata vortex principle require about 75-80 fibers in the yarn cross-section. This means that this spinning system is able to spin much finer yarns than the rotor spinning process. The strength of yarns produced on the basis of the MVS process is at a significantly higher level compared to rotor yarns.
Like the rotor spinning process, the MVS spinning process requires fibers whose fiber strength makes it possible to produce yarns with yarn strengths which ensure high productivity during further processing into knitted or woven fabrics.
The cellulosic microfibers described above are not suitable for processing in high-performance spinning processes because of their relatively low absolute strength. High-fine yarns made of these fibers, which are needed to produce the increasingly demanded from the market lightweight textiles made of cellulosic fibers, could therefore not be produced with modern high-performance spinning process.
Compared to this prior art, the object was to provide a cellulosic fiber available, the current requirements for an economically and environmentally responsible manufacturing process as well as increased wearing comfort and improved appearance of the garment made from it is sufficient. In addition, this fiber should be producible on existing production facilities. In addition, there has been a demand for inexpensive high-performance yarns made of such fibers.

The solution to this problem is a high-strength cellulosic regenerated fiber, which has a single fiber titer T (dtex) between 0.6 and 0.9, preferably between 0.6 and 0.8, a strength (B _c ) in the conditioned state of B _c (cN ) ≥ 1.3√T + 2T and a wet modulus (B _m ) at an elongation of 5% in the wet state of B _m (cN) ≥ 0.5 * √T. The fiber according to the invention preferably has a fineness-related strength in the conditioned state of at least 34.5 cN / tex. The fineness-related wet modulus of this fiber is preferably at least 5.6 cN / tex.

As upper limits of the properties according to the invention, a strength of 50.0 cN / tex and a wet modulus of 10.0 cN / tex are preferred.

The fiber according to the invention can analogously to in AT 287905 be prepared described methods. However, the spinning parameters such as spinning mass output per nozzle hole and take-off speed must be adjusted according to the desired single-fiber titer. Surprisingly, it has been found that the strength and modulus of the fibers according to the invention are substantially higher than those given in the US Pat AT 287905 was to be expected.

Preferably, the fiber according to the invention is present as staple fiber, ie it is cut to a uniform length in the course of the production process. Usual cutting lengths for staple fibers for the textile sector are between about 25 and 90 mm. Only such a uniform length of all fibers allows easy processing on the today in the textile chain usual machines with high productivity.

The present invention also provides a yarn of the fibers according to the invention. Such a yarn is characterized by a higher softness compared to yarns of coarser denier fibers. Compared to yarns of the cellulosic microfibers known from the prior art, the yarns according to the invention have a higher strength. In order to have suitable properties for the particular application, such an inventive yarn in addition to the fibers of the invention also fibers of other origin, such as synthetic microfibers of polyester, polyamide or polyacrylic, other cellulosic fibers (eg cotton, especially combed cotton, lyocell, cupro, linen , Ramie, Kapok ....), fine fibers of animal origin such as alpaca, angora, cashmere, mohair and various silks. This type of mixture of different types of fibers is commonly referred to as intimate mixing.
In particular, it was surprising that yarns according to the invention could be produced with very high fineness by means of airjet spinning processes. With the fibers according to the invention, it is possible for the first time to exceed previously known spin-off limits of high-performance spinning processes. This applies equally to rotor and airjet spinning processes such as the Murata Vortex spinning process. In the MVS spinning process, it is now possible to produce fine 74 dtex yarns (Ne 80 (Nm 135)), whose yarn strength enables easy further processing into textile surfaces. In the rotor spinning process, by using fibers according to the patent application, it becomes possible for the first time to spin out yarns finer than 91 dtex (Ne 65).
These higher-denier yarns also always have a smaller number of thin spots and higher yarn uniformity than yarns of coarser-denier fibers.

Preferred embodiments of the present invention are yarns prepared by means of air spinning processes with a fineness of more than 200 dtex, preferably less than 118 dtex, more preferably less than 100 dtex.

The yarn of the invention may consist of 100% of the regenerated cellulosic fibers or additionally contain at least one or a mixture of several other fine fiber types of the above types.

Since it has been found that the fibers according to the invention are particularly suitable for producing high-quality, finer, softer textile surfaces with particularly pleasant wearing properties, blends with further fiber types, such as synthetic microfibers of polyester, polyamide or polyacrylic, other cellulosic fibers ( eg cotton, especially combed cotton, lyocell, cupro, linen, ramie, kapok ....), fine fibers of animal origin such as alpaca, angora, cashmere, mohair, various silks, into consideration.

With the MVS process also so-called core yarns can be produced whose inner "core" consists of a different type of fiber than the outer "shell". It is for example possible to produce a yarn with a core of continuous filament of polyamide, polyester or elastane and a sheath of the fiber according to the invention and thus to combine mechanical and comfort properties of the two types of fibers.

Likewise an object of the present invention is a textile fabric containing the fibers according to the invention. In addition to the fibers according to the invention, the fabric as well as the yarn according to the invention may also contain other fibers. The sheet is preferably a woven or knitted fabric, but may in principle also be a nonwoven. For high-quality nonwovens, the use of fibers of uniform length and diameter as well as high strength can be of crucial importance.

Since it has been shown that the fibers according to the invention are particularly suitable for producing high-quality, finer, softer textile surfaces with particularly pleasant wearing properties, fabrics are involved a basis weight of less than 150 g / m ² , but in particular less than 115 g / m ^2, a preferred embodiment of the present invention. These may consist of 100% of the cellulosic regenerated fibers or additionally contain at least one other fine type of fiber. For example, with the fibers according to the invention woven shirt and blouse fabrics with a weight per unit area of less than 100 g / m ² from yarns of high-performance spinning processes such as rotor or airjet spinning processes are possible.

For the above reasons, for example, synthetic microfibers of polyester, polyamide or polyacrylic, other cellulosic fibers (eg cotton, especially combed cotton, lyocell, cupro, linen, ramie, kapok ....), fine fibers of animal origin such as alpaca, Angora, cashmere, mohair, various silks, preferred mixing partners for the production of finest yarns and light-weight textiles.

Example 1:

One according to AT 287905 cellulosic staple fiber produced in a commercial production plant with a titer of 0.8 dtex, measured in accordance with the BISFA regulations, in the conditioned state has a strength of 36.3 cN / tex and a modulus (5% elongation) of 5.9 cN / tex on.
From 100% of this fiber, yarns with Nm 100 (Ne 60), Nm 135 (Ne 80) and Nm 180 (Ne 100) were produced using the AirJet technology on an MVS spinning machine. They consistently had a significantly higher softness than a yarn made from commercially available Lenzing Modal® fiber.

In addition, the fiber according to the invention from Example 1 was spun into fine yarns with Nm 180 (Ne 100) for comparison with the known ring spinning and Siro processes (Table 1). It could be clearly stated that the AirJet yarns have an approximately comparable strength (Breaking Tenacity) and elongation (Breaking Elongation) showed as the ring or Siro yarns, which are known for high quality, but significantly lower productivity. Table 1 spinning process MVS ring Siro yarn count nm 100 135 180 180 180 ne 60 80 100 100 100 Breaking Tenacity cN / Tex 18.3 17.3 16.4 18.3 18.7 Breaking elongation EF (%) 7.3 6.3 5.6 7.0 6.6 The MVS yarns in Nm 100 and Nm 135, respectively, were used to produce knitted fabrics having basis weights in the range between 100 and 125 g / m ² . These knits were easy to produce and had excellent performance properties. Remark: 1 tex = 1000 / Nm.

Example 2:

One in a pilot plant also according to AT 287905 prepared staple cellulosic fiber with a titer of 0.65 dtex, measured in accordance with the BISFA regulations, in the conditioned state, a strength of 36.4 cN / tex and a modulus (5% elongation) of 6.3 cN / tex.
A yarn made from this fiber also had a significantly higher softness than a yarn made from commercially available Lenzing Modal® fiber.

Claims (12)

1. High-tenacity cellulosic regenerated fibre with an individual fibre titre T between 0.6 and 0.9 dtex, preferably between 0.6 and 0.8 dtex, characterised in that this reveals a tenacity (B_c) in the conditioned state of B_c(cN) ≥1.3√T+2T and a wet modulus (B_m) with an elongation of 5% of B_m (cN) ≥ 0.5* √T.
2. Regenerated fibre according to claim 1 whereby the regenerated fibre is a staple fibre.
3. Yarn which contains cellulosic regenerated fibres in accordance with claim 1.
4. Yarn according to claim 3, produced using the air spinning process with a fineness of less than 200 dtex (50 Nm), preferably less than 118 dtex(85 Nm), and most preferably less than 100 dtex (100 Nm).
5. Yarn according to claim 3 which comprises 100% cellulosic regenerated fibres.
6. Yarn according to claim 3 which contains in addition at least one other fine fibre type.
7. Yarn according to claim 6 whereby each other type of fibre is selected from the group comprising synthetic microfibers like polyester, polyamide or polyacrylic, other cellulosic fibres (e.g. cotton, in particular combed cottons, lyocell, cupro, linen, ramie, kapok) and fine fibres of animal origin such as alpaca, angora, cashmere, mohair and other silks.
8. Planar textile structure which contains cellulosic regenerated fibres in accordance with claim 1.
9. Planar textile structures according to claim 8 with a weight per surface area of less than 150 g/m2, and most preferably less than 115 g/m2.
10. Planar textile structure according to claim 8 comprising 100% cellulosic regenerated fibres.
11. Planar textile structure according to claim 8 which contains at least one other fine fibre type.
12. Planar textile structure according to claim 11 whereby each other fibre type is selected from the group containing synthetic micro fibres such as polyester, polyamide or polyacrylic, other cellulosic fibres (e.g. cotton, in particular combed cottons, Lyocell, cupro, linen, ramie, kapok) and fine fibres of animal origin such as alpaca, angora, cashmere, mohair and various silks.