Patent Publication Number: US-2020277728-A1

Title: Polymer fibre having improved long-term dispersibility

Description:
The invention relates to a polymer fibre having improved long-term dispersibility, a method for production thereof, and use thereof. 
     Polymer fibres, i.e. fibres based on synthetic polymers, are produced industrially on a large scale. In this case the underlying synthetic polymer is produced by means of a melt spinning process. To this end, the thermoplastic polymer material is melted and is conducted in the liquid state into a spinning beam by means of an extruder. The molten material is fed from this spinning beam to what are known as spinnerets. The spinneret usually has a spinneret plate provided with a number of holes, from which the individual capillaries (filaments) of the fibres are extruded. Besides the melt spinning method, wet or solvent spinning methods are also used to produce staple fibres. In this case, instead of the melt, a highly viscous solution of a synthetic polymer is extruded through dies having fine holes. Both methods are referred to by a person skilled in the art as what are known as multi-position spinning methods. 
     The polymer fibres produced in this way are used for textile and/or technical applications. Here, it is advantageous if the polymer fibres have a good dispersibility in aqueous systems, for example for the production of wet-laid nonwovens. In addition, it is advantageous for textile applications if the polymer fibres have a good and soft grip. 
     The modification or finishing of polymer fibres for the particular end application or for the necessary intermediate treatment steps, e.g. stretching and/or crimping, is usually accomplished by applying suitable finishes or layers which are applied to the surface of the finished polymer fibre or polymer fibre to be treated. 
     Another possibility for chemical modification can be accomplished on the polymer basic structure itself, for example, by incorporating compounds having a flaming action into the polymer main and/or side chain. 
     Furthermore, additives, for example, antistatics or dye pigments can be introduced into the molten thermoplastic polymer or introduced into the polymer fibre during the multi-position spinning process. 
     The dispersion behaviour of a polymer fibre is influenced, inter alia, by the nature of the synthetic polymers. In particular in the case of fibres of thermoplastic polymer, the dispersibility in aqueous systems is therefore influenced and adjusted by the finishes or layers applied to the surface. 
     The dispersibility produced or improved by means of suitable finishes or layers is already sufficient for many textile applications. 
     For food-related applications, however, different requirements apply; the used substances and materials must be approved for contact with food pursuant to EU Reg. No. 231/2012. It is additionally desirable if the equipped polymer fibres are present in dispersed form for a relatively long time and/or under more extreme conditions, e.g. high pressure, strong shear forces and elevated temperature, in particular also in aggressive, acidic, aqueous systems, and if this dispersibility is retained even after a relatively long storage time. 
     It is therefore the object to provide a polymer fibre with improved dispersibility, in particular long-term dispersibility, which has a good dispersibility even after a relatively long period of storage and additionally is approved for contact with food pursuant to EU Reg. No. 231/2012. In addition, the polymer fibre should be readily dispersible also under extreme conditions, i.e. high pressure, severe shear forces and elevated temperature, in particular also in aggressive aqueous systems which optionally have a pH of &lt;7 and/or electrolytes, in particular saline-based electrolytes, and this good dispersibility should be retained, even after a relatively long period of storage. 
     The aforesaid object is solved by the polymer fibre according to the invention comprising at least one synthetic polymer, preferably at least one synthetic thermoplastic polymer, characterised in that the fibre on the surface has a preparation comprising at least one cellulose ether selected from the group carboxymethyl cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methylethyl cellulose (MEC), hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose (HPMC), ethylhydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose, and mixtures thereof. 
    
    
     Polymers 
     The synthetic polymers according to the invention which form the dispersion medium preferably comprise thermoplastic polymers, in particular thermoplastic polycondensates, particularly preferably what are known as synthetic biopolymers, particularly preferably thermoplastic polycondensates based on what are known as biopolymers. 
     The term “thermoplastic polymer” designates in the present invention a plastic which can be deformed (thermoplastically) in a specific temperature range, preferably in the range of 25° C. to 350° C. This process is reversible, that is, it can be repeated arbitrarily frequently by cooling and re-heating as far as into the molten state as long as the so-called thermal decomposition of the material is not initiated by overheating. This is the difference between thermoplastic polymers and thermosetting plastics and elastomers. 
     Within the scope of the present invention, the following polymers are preferably understood by the term “thermoplastic polymer”: 
     acrylonitrile ethylene propylene (diene) styrene copolymer, acrylonitrile methacrylate copolymer, acrylonitrile methyl methacrylate copolymer, acrylonitrile chlorinated polyethylene styrene copolymer, acrylonitrile butadiene styrene copolymer, acrylonitrile ethylene propylene styrene copolymer, aromatic polyester, acrylonitrile styrene acryloester copolymer, butadiene styrene copolymer, cellulose acetate, cellulose acetobutyrate, cellulose acetopropionate, hydrated cellulose, carboxymethyl cellulose, cellulose nitrate, cellulose propionate, cellulose triacetate, polyvinylchloride, ethylene acrylic acid copolymer, ethylene butylacrylate copolymer, ethylene chlorotrifluoroethylene copolymer, ethylene ethylacrylate copolymer, ethylene methacrylate copolymer, ethylene methacrylic acid copolymer, ethylene tetrafluoroethylene copolymer, ethylene vinylalcohol copolymer, ethylene butene copolymer, ethylcellulose, polystyrene, polyfluoroethylene propylene, methylmethacrylate acrylonitrile butadiene styrene copolymer, methylmethacrylate butadiene styrene copolymer, methylcellulose, polyamide 11, polyamide 12, polyamide 46, polyamide 6, polyamide 6-3-T, polyamide 6-terephthalic acid copolymer, polyamide 66, polyamide 69, polyamide 610, polyamide 612, polyamide 6I, polyamide MXD 6, polyamide PDA-T, polyamide, polyarylether, polyaryletherketone, polyamide imide, polyarylamide, polyamino-bis-maleimide, polyarylate, polybutene-1, polybutylacrylate, polybenzimidazole, poly-bis-maleimide, polyoxadiazobenzimidazole, polybutylene terephthalate, polycarbonate, polychiorotrifluoroethylene, polyethylene, polyestercarbonate, polyaryletherketone, polyetheretherketone, polyetherimide, polyetherketone, polyethylene oxide, polyarylethersulfone, polyethylene terephthalate, polyimide, polyisobutylene, polyisocyanurate, polyimide sulfone, polymethacrylimide, polymethacrylate, poly-4-methylpentene-1, polyacetal, polypropylene, polyphenylene oxide, polypropylene oxide, polyphenylene sulfide, polyphenylene sulfone, polystyrene, polysulfone, polytetrafluoroethylene, polyurethane, polyvinylacetate, polyvinylalcohol, polyvinylbutyral, polyvinylchloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinylfluoride, polyvinylmethylether, polyvinylpyrrolidone, styrene butadiene copolymer, styrene isoprene copolymer, styrene maleic acid anhydride copolymer, styrene maleic acid anhydride butadiene copolymer, styrene methylmethacrylate copolymer, styrene methylstyrene copolymer, styrene acrylonitrile copolymer, vinylchloride ethylene copolymer, vinyichioride methacrylate copolymer, vinyichioride maleic acid anhydride copolymer, vinylchloride maleimide copolymer, vinylchioride methylmethacrylate copolymer, vinylchloride octylacrylate copolymer, vinylchloride vinylacetate copolymer, vinylchioride vinylidene chloride copolymer and vinylchloride vinylidene chloride acrylonitrile copolymer. 
     Within the scope of the present invention, the term “thermoplastic polymer” is preferably understood to be a polymer that differs chemically and/or physically from the cellulose ethers used in the preparation. The thread-forming thermoplastic polymers preferably do not comprise any cellulose ethers. 
     Particularly well-suited are high-melting thermoplastic polymers (Mp 100° C.), which are very well suited for staple fibre production. 
     Suitable high-melting thermoplastic polymers are, for example, polyamides such as polyhexamethylene adipinamide, polycaprolactam, aromatic or partially aromatic polyamides (“aramide”), aliphatic polyamides such as Nylon, partially aromatic or fully aromatic polyesters, polyphenylene sulfide (PPS), polymers with ether and keto groups such as polyetherketone (PEK) and polyether etherketone (PEEK) or polyolefins such as polyethylene or polypropylene. 
     Within the high-melting thermoplastic polymers, melt-spinnable polymers are particularly preferred. 
     Melt-spinnable polyesters consist predominantly of building blocks which are derived from aromatic dicarboxylic acids and aliphatic diols. Common aromatic dicarboxylic acid building blocks are the divalent radicals of benzene dicarboxylic acids, in particular terephthalic acid and isophthalic acid; common diols have 2 to 4 C atoms, with ethylene glycol and/or propane-1,3-diol being particularly suitable. 
     Particularly preferred are polyesters having at least 95 mol % polyethylene terephthalate (PET). 
     Such polyesters, in particular polyethylene terephthalate, usually have a molecular weight corresponding to an intrinsic viscosity (IV) of 0.4 to 1.4 (dl/g), measured for solutions in dichloroacetic acid at 25° C. 
     The term “synthetic biopolymer” designates in the present invention a material which consists of biogenic raw materials (renewable raw materials). A delimitation is thus made from the conventional petroleum-based materials or plastics such as, for example, polyethylene (PE), polypropylene (PP) and polyvinylchloride (PVC). 
     According to the invention, particularly preferred synthetic biopolymers are thermoplastic polycondensates based on what are known as biopolymers which comprise repeating units of lactic acid, hydroxybutyric acid and/or glycolic acid, preferably of lactic acid and/or glycolic acid, in particular of lactic acid. Polylactic acids are particularly preferred in this case. 
     “Polylactic acid” is understood here as polymers which are constructed of lactic acid units. Such polylactic acids are usually produced by condensation of lactic acids but are also obtained by ring-opening polymerisation of lactides under suitable conditions. 
     According to the invention, particularly suitable polylactic acids comprise poly(glycolide-co-L-lactide), poly(L-lactide), poly(L-lactide-co-ϵ-caprolactone), poly(L-lactide-co-glycolide), poly(L-lactide-co-D,L-lactide), poly(D,L-lactide-co-glycolide) as well as poly(dioxanone). Such polymers are available commercially for example from the company Boehringer Ingelheim Pharma KG (Germany) under the trade names Resomer® GL 903, Resomer® L 206 S, Resomer® L 207 S, Resomer® L 209 S, Resomer® L 210, Resomer® L 210 S, Resomer® LC 703 S, Resomer® LG 824 S, Resomer® LG 855 S, Resomer® LG 857 S, Resomer® LR 704 S, Resomer® LR 706 S, Resomer® LR 708, Resomer® LR 927 S, Resomer® RG 509 S and Resomer® X 206 S. 
     For the purposes of the present invention, particularly advantageous polylactic acids are in particular poly-D-, poly-L- or poly-D,L-lactic acids. 
     In a particularly preferred embodiment the synthetic polymer is a thermoplastic condensate based on lactic acids. 
     The polylactic acids used according to the invention have a number-average molecular weight (Mn), preferably determined by gel permeation chromatography against narrowly distributed polystyrene standards or by end-group titration, of at least 500 g/mol, preferably at least 1,000 g/mol, particularly preferably at least 5,000 g/mol, expediently at least 10,000 g/mol, in particular at least 25,000 g/mol. On the other hand, the number-average is preferably at most 1,000,000 g/mol, expediently at most 500,000 g/mol, more favourably at most 100,000 g/mol, in particular at most 50,000 g/mol. A number-average molecular weight in the range from at least 10,000 g/mol to 500,000 g/mol has proved quite particularly successful within the scope of the present invention. 
     The weight-average molecular weight (Mw) of preferred lactic acid polymers, in particular of poly-D-, poly-L- or poly-D,L-lactic acids, preferably determined by gel permeation chromatography against narrowly distributed polystyrene standards, lies preferably in the range from 750 g/mol to 5,000,000 g/mol, preferably in the range from 5,000 g/mol to 1,000,000 g/mol, particularly preferably in the range from 10,000 g/mol to 500,000 g/mol, in particular in the range from 30,000 g/mol to 500,000 g/mol, and the polydispersity of these polymers is more favourably in the range from 1.5 to 5. 
     The inherent viscosity of particularly suitable lactic acid polymers, in particular poly-D-, poly-L- or poly-D,L-lactic acids, measured in chloroform at 25° C., 0.1% polymer concentration, lies in the range of 0.5 dl/g to 8.0 dl/g, preferably in the range of 0.8 dl/g to 7.0 dl/g, in particular in the range of 1.5 dl/g to 3.2 dl/g. 
     Furthermore, the inherent viscosity of particularly suitable lactic acid polymers, in particular poly-D-, poly-L- or poly-D,L-lactic acids, measured in hexafluoro-2-propanol at 30° C., 0.1% polymer concentration, is in the range of 1.0 dl/g to 2.6 dl/g, in particular in the range of 1.3 dl/g to 2.3 dl/g. 
     Within the scope of the present invention, furthermore polymers, in particular thermoplastic polymers, having a glass transition temperature higher than 20° C., more favourably higher than 25° C., preferably higher than 30° C., particularly preferably higher than 35° C., in particular higher than 40° C., are extremely advantageous. Within the scope of a quite particularly preferred embodiment of the present invention, the glass transition temperature of the polymer lies in the range of 35° C. to 55° C., in particular in the range of 40° C. to 50° C. 
     Furthermore, polymers having a melting point higher than 50° C., more favourably of at least 60° C., preferably higher than 150° C., particularly preferably in the range of 160° C. to 210° C., in particular in the range of 175° C. to 195° C., are particularly suitable. 
     In this case, the glass temperature and the melting point of the polymer are preferably determined by means of Differential Scanning calorimetry; or DSC for short. In this connection, the following procedure has proved quite particularly successful: 
     Performing the DSC measurement under nitrogen on a Mettler-Toledo DSC 30S. The calibration is preferably made with indium. The measurements are preferably made under dry oxygen-free nitrogen (flow rate: preferably 40 ml/min). The sample weight is preferably selected between 15 mg and 20 mg. The samples are initially heated from 0° C. to preferably a temperature above the melting point of the polymer to be studied, then cooled to 0° C. and heated a second time from 0° C. to the said temperature at a heating rate of 10° C./min. 
     Polyesters, in particular lactic acid polymers, are quite particularly preferred as thermoplastic polymers. 
     Polymer Fibre 
     The polymer fibre according to the invention can be present as a finite fibre, e.g. as what is known as a staple fibre or as an infinite fibre (filament). For better dispersibility the fibre is preferably present as a staple fibre. The length of the aforesaid staple fibres is not subject to any fundamental restriction but is generally 1 to 200 mm, preferably 2 to 120 mm, particularly preferably 2 to 60 mm. In particular short fibres can be well cut from the fibres according to the invention. These are understood to be fibre lengths of 5 mm and less, in particular of 4 mm and less. 
     The individual titre of the polymer fibres according to the invention, preferably stable fibres, is between 0.3 and 30 dtex, preferably 0.5 to 13 dtex. For some applications titres between 0.3 and 3 dtex and fibre lengths of &lt;10 mm, in particular &lt;8 mm, particularly preferably &lt;6 mm, in particular preferably &lt;4 mm, are particularly well suited. 
     The polymer fibres according to the invention are preferably produced from thermoplastic polymers, in particular thermoplastic organic polymers, particularly preferably from thermoplastic organic polycondensates, by means of melt spinning methods. In this case the polymer material is melted in an extruder and processed by means of spinnerets to form the polymer fibres. The polymer fibres according to the invention usually do not comprise any fibres that were produced by spinning from solution, in particular by means of electrospinning. 
     The polymer fibre can also be present as a bicomponent fibre, where the fibre consists of a component A (core) and a component B (shell). In a further embodiment the melting point of the thermoplastic polymer in component A is at least 5° C., preferably at least 10° C., particularly preferably at least 20° C. higher than the melting point of the thermoplastic polymer in component B. Preferably the melting point of the thermoplastic polymer in component A is at least 100° C., preferably at least 140° C., particularly preferably at least 150° C. 
     The thermoplastic polymers used in the bicomponent fibres are the polymers already mentioned previously. 
     Preparation 
     The polymer fibre according to the invention has, on the surface, between 0.1 and 20 wt. %, preferably 0.5 to 3 wt. %, of a preparation which comprises at least one cellulose ether selected from the group carboxymethyl cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methylethyl cellulose (MEC), hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose (HPMC), ethylhydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose, and mixtures thereof. 
     In a preferred embodiment the preparation comprises at least two cellulose ethers selected from the group carboxymethyl cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methylethyl cellulose (MEC), hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose (HPMC), ethylhydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose, particularly preferred are preparations from methyl cellulose (MC) and hydroxypropylmethyl cellulose (HPMC), these being present in amounts of from 0.1 and 20 wt. %, preferably 0.5 to 3 wt. %, on the surface of the polymer fibres according to the invention. 
     The preparation according to the invention covers at least 99% of the total surface of the fibre, preferably at least 99.5%, in particular at least 99.9%, particularly preferably 100% of the total surface of the fibre. The coverage of the surface is determined by means of microscopic methods. The preparation according to the invention is preferably applied exclusively to the fibres, and not subsequently to the textile fabrics produced from the fibres. 
     The preparation according to the invention usually has a thickness of 5-10 nm on the fibres. The thickness is determined by means of microscopic methods. 
     The cellulose ether(s) used in accordance with the invention are substances approved in accordance with EU Reg. No. 231/2012 as additives. Substances of this kind are commercially obtainable, for example under the name VIVAPUR® or Methocel™. 
     In a preferred embodiment the preparation comprises cellulose ether, but in particular carboxymethyl cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methylethyl cellulose (MEC), hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose (HPMC), ethylhydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose, particularly preferred are preparations of methyl cellulose (MC) and hydroxypropylmethyl cellulose (HPMC), which have a gelling temperature in the range of 35° C. to 90° C., preferably in the range of 40° C. to 70° C., in particular in the range of 45° C. to 60° C., particularly preferably in the range of 45° C. to 55° C. 
     The cellulose ether(s) used in accordance with the invention usually have a degree of substitution (number of the substituted hydroxy groups per glucose molecule) in the range of from 1.3 to 2.6, preferably from 1.6 to 2.0. The degree of substitution is usually determined by means of gas chromatography. 
     The cellulose ether(s) used in accordance with the invention, but in particular the methyl celluloses, preferably have a methoxy group fraction of from 26% to 33%, in particular of from 27% to 32%. 
     The hydroxypropyl celluloses used in accordance with the invention preferably have a hydroxypropyl group fraction of at most 5%. 
     The hydroxypropyl celluloses used in accordance with the invention preferably have a hydroxypropyl group fraction of from 7% to 12%. 
     The cellulose ether(s) used in accordance with the invention, but in particular the methyl celluloses, preferably have a methoxy group fraction of from 26% to 33%, in particular of from 27% to 32%, and a hydroxypropyl group fraction of at most 5%. 
     The cellulose ether(s) used in accordance with the invention, but in particular the hydroxypropyl celluloses, preferably have a methoxy group fraction of from 26% to 33%, in particular of from 27% to 32%, and a hydroxypropyl group fraction of from 7% to 12%. 
     The cellulose ether(s) used in accordance with the invention usually have a mean molecular weight Mn between 10,000 and 380,000 g/mol, preferably between 10,000 and 200,000 g/mol, in particular between 10,000 and 100,000 g/mol, in particular preferably between 12,000 and 60,000 g/mol, particularly preferably between 12,000 and 40,000 g/mol. The mean molecular weight Mn is usually determined by means of gel permeation chromatography (GPC). 
     The cellulose ether(s) used in accordance with the invention usually have a degree of polymerisation of from 50 to 1000. 
     The cellulose ether(s) used in accordance with the invention usually have a viscosity of from 10 to 40 mPas, measured as 2 wt. % solution in demineralised water (demineralised water according to DIN standard EN50272-2:2001) at 20° C. (30 seconds after activation of the solution (rest phase), measurements are taken over a further 30 seconds and the measured value is thus obtained after one minute), for example by means of Brookfield LVT. 
     The preparation according to the invention is usually applied as aqueous preparation, the solids content of cellulose ether(s) being 0.1 to 5.0 g/l. The aqueous preparation may also contain further constituents, for example anti-foaming agents, etc. 
     The polymer fibres finished in accordance with the invention demonstrate very good dispersibility of the fibres in water. On the one hand the fibres according to the invention disperse very quickly and remain dispersed over a relatively long period of time, and on the other hand polymer fibres finished in accordance with the invention also demonstrate good storage stability, i.e. even after storage of the fibres prepared in accordance with the invention of at least 1 month (at room temperature of 25° C. and a relative moisture in the range of from 20 to 70%), the fibres can disperse readily and are present very uniformly distributed in the form of dispersed fibres. The polymer fibres finished in accordance with the invention are also suitable for stabilisation of aqueous dispersions, in which, besides the fibres according to the invention, solid particulate particles, for example mineral particles, are additionally present. Polymer fibres with a titre between 0.3 and 3 dtex and a fibre length of &lt;10 mm, in particular &lt;8 mm, particularly preferably &lt;6 mm, in particular preferably &lt;4 mm, are suitable for this embodiment. 
     The polymer fibres finished in accordance with the invention furthermore also stabilise aqueous dispersions with other polymer fibres which are not finished in accordance with the invention. The other polymer fibres may differ in respect of the fibre-forming polymers or may also be identical, these other polymer fibres not being finished in accordance with the invention. The fibres according to the invention may thus be well-suited for used in the production of wet-laid textile fabrics. The addition of the polymer fibres finished in accordance with the invention may be performed in the pulper or sheet former. 
     Polymer fibres with a titre between 0.3 and 3 dtex and a fibre length of &lt;10 mm, in particular &lt;8 mm, particularly preferably &lt;6 mm, in particular preferably &lt;4 mm, are suitable for this embodiment. 
     The synthetic polymer fibres according to the invention are produced by conventional methods. The synthetic polymer is firstly dried if necessary and fed to an extruder. The molten material is then spun by means of conventional apparatuses having corresponding dies. The exit speed at the die outlet area is matched to the spinning speed, such that a fibre having the desired titre is created. The spinning speed is understood to be the speed at which the solidified threads are removed. The threads removed in this way may be fed either directly to stretching or may also be wound and stored and stretched at a later moment in time. The fibres and filaments stretched in the usual manner may then be fixed by generally conventional methods and cut to the desired length to form staple fibres. In this case, the fibres may be uncrimped or crimped, and in the crimped version the crimping must be configured for the wet-laying method (low crimping). 
     The formed fibres may have round, oval and other suitable cross sections, or also other shapes, such as dumbbell-shaped, kidney-shaped, triangular, or tri- or multi-lobal cross sections. Hollow fibres are also possible. Fibres formed from two or more polymers may also be used. 
     The fibre filaments thus produced are combined to form yarns and these in turn to form tows. The tows are initially laid down in cans for further processing. The tows stored intermediately in the cans are taken up and a large tow is produced. 
     Then, the large tow, these usually have 10-600 ktex, can be stretched using conventional methods on a conveyor line, preferably at 10 to 110 m/min entry speed Here preparations can be applied which promote the stretching but do not disadvantageously influence the subsequent properties. 
     The stretching ratios preferably extend from 1.25 to 4, particular from 2.5 to 3.5. The temperature during the stretching lies in the range of the glass transition temperature of the tow to be stretched and for polyester, for example, is between 40° C. and 80° C. 
     The stretching can be executed as single-stage or if desired using a two-stage stretching process (in this regard see for example U.S. Pat. No. 3,816,486). Before and during the stretching one or more dressings can be applied using conventional methods. 
     For the crimping/texturing of the stretched fibres which is to be carried out optionally, conventional methods of mechanical crimping using crimping machines known per se can be used. Preferred is a mechanical device for steam-assisted fibre crimping, such as a stuffer box. However, fibres crimped by other methods can also be used, thus for example three-dimensionally crimped fibres. In order to perform the crimping the tow is initially usually tempered to a temperature in the range of 50° to 100° C., preferably 70° to 85° C., particularly preferably to about 78° C. and treated with a pressure of the tow run-in rollers of 1.0 to 6.0 bar, particularly preferably at about 2.0 bar, a pressure in the stuffer box of 0.5 to 6.0 bar, particularly preferably 1.5-3.0 bar, with steam between 1.0 and 2.0 kg/min., particularly preferably 1.5 kg/min. 
     The preparation according to the invention is applied after the stretching, and a second time before the crimping machine, if a crimping is provided. The preparation according to the invention is usually heated and is applied to the fibre at an application temperature in the range of from 30 to 110° C. and is dried. 
     It has been found that the drying of the preparation according to the invention and all post-treatments of the fibres equipped with the preparation according to the invention are performed at a temperature of at most 120° C., since higher temperatures have an adverse effect on the dispersibility of the fibre. At temperatures of at most 120° C., very homogeneous and uniform preparation applications are achieved, and practically no settling is observed. Such an application is advantageous for the dispersibility according to the invention. 
     If the smooth or optionally crimped fibres are relaxed and/or fixed in the furnace or hot air stream, this occurs at temperatures of at most 130° C., since higher temperatures have an adverse effect on the dispersibility of the fibres. At temperatures above 130° C., the previously obtained homogeneous and uniform preparation applications are damaged and the dispersibility according to the invention is reduced. 
     In order to produce staple fibres, the smooth or optionally crimped fibres are taken up, followed by cutting and optionally hardening and depositing in pressed bales as flock. The staple fibres of the present invention are preferably cut on a mechanical cutting device downstream of the relaxation. In order to produce tow types, the cutting can be dispensed with. These tow types are deposited in bales in uncut form and pressed. 
     The fibres produced according to the invention in the crimped embodiment preferably have a degree of crimping of at least 2, preferably at least 3 crimps (crimp arcs) per cm, preferably 3 arcs per cm to 9.8 arcs per cm and particularly preferably 3.9 arcs per cm to 8.9 arcs per cm. In applications to produce textile surfaces, values for the degree of crimping of about 5 to 5.5 arcs per cm are particularly preferred. In order to produce textile surfaces by means of wet-laying methods, the degree of crimping must be adjusted individually. 
     The aforesaid parameters spinning speed, stretching, stretching ratios, stretching temperatures, fixing, fixing temperature, run-in speeds, crimping/texturing etc., are determined according to the particular polymer. These are parameters which the person skilled in the art selects in the usual range. 
     Textile fabrics can be produced from the fibres according to the invention, which are also the subject of the invention. As a result of the good dispersibility of the fibres according to the invention, such textile fabrics are preferably produced by wet-laid methods. 
     In addition to the improved dispersibility of the fibres in water, the polymer fibre according to the invention also exhibits a good pumpability of the dispersed fibres in water so that the polymer fibre according to the invention is particularly well suited for the production of textile fabrics using the wet-laying method. Since the fibres according to the invention promote the dispersibility of solid particulate particles, for example, mineral particles, textile fabrics with a mineral finish can also be produced. Polymer fibres with a titre between 0.3 and 3 dtex and a fibre length of &lt;10 mm, in particular &lt;8 mm, particularly preferably &lt;6 mm, in particular preferably &lt;4 mm, are suitable for this embodiment. 
     In addition to these wet-laying methods, what are known as melt-blowing methods (for example, as described in “Complete Textile Glossary, Celanese Acetate LLC, from 2000 or in “Chemiefaser-Lexikon, Robert Bauer, 10th edition, 1993) are also suitable. Such melt-blowing methods are suitable for producing fine-titre fibres or nonwovens, e.g. for applications in the hygiene sector. 
     The term “textile fabric” is therefore to be understood within the scope of this description in its broadest meaning. This can comprise all structures containing the fibres according to the invention which have been produced by a surface-forming technique. Examples of such textile fabrics are nonwovens, in particular wet-laid nonwovens, preferably based on staple fibres or nonwovens produced by the melt-blowing method. 
     The fibres according to the invention are characterised by significantly improved permanence of the dispersibility as compared with fibres without the additive according to the invention. The fibres according to the invention have very good dispersibility, even after a relatively long period of storage, for example a number of weeks or months, in the form of bales or comparable structures. 
     In addition, the fibres according to the invention have an improved long-term dispersion, i.e. with dispersion of the fibres according to the invention in liquid media, for example in water, the fibres remain dispersed for longer and only start to settle after a relatively long period of time. 
     In addition, the fibres according to the invention demonstrate a reduced fibre fly, which results in an improvement in occupational safety, since the preparation ensures a significantly increased grip in the fibre composite. The reduced fibre fly is of great importance in particular for the formation of textile fabrics, for example nonwovens. 
     The textile fabrics produced by means of the fibres according to the invention are in particular wet-laid textile fabrics, in particular wet-laid nonwovens. 
     The textile fabrics produced by means of the fibres according to the invention contain the polymers according to the invention, to the surface of which between 0.1 and 20 wt. %, preferably 0.5 to 3 wt. % of a preparation is applied, which preparation comprises at least one cellulose ether selected from the group carboxymethyl cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methylethyl cellulose (MEC), hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose (HPMC), ethylhydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose, and mixtures thereof. The proportion of polymer fibres according to the invention in the textile fabric is usually at least 10 wt. %, in relation to the total weight of the textile fabric, preferably at least 20 wt. %, in particular at least 30 wt., %, particularly preferably at least 50 wt. %. In a particularly preferred embodiment, the textile fabric consists exclusively of the polymer fibres according to the invention. 
     Test methods: 
     Insofar as not already stated in the description above, the following measurement and test methods are used: 
     Titre: 
     The titre was determined in accordance with DIN EN IS01973. 
     Dispersibility: 
     In order to assess the dispersibility, the following test method has been developed and is used in accordance with the invention. 
     The fibres according to the invention are cut to a length of 2-12 mm. The cut fibres are introduced at room temperature (25° C.) into a glass vessel (dimensions: length 150 mm; width 200 mm; height 200 mm), which is filled with demineralised water (demineralised=completely desalinated). The amount of fibres is 0.25 g per litre demineralised water. For improved assessment, 1 g fibres and 4 litres demineralised water are usually used. 
     The fibre/demineralised water mixture is then stirred by means of a conventional laboratory magnetic stirrer (for example IKAMAG RCT) and a magnetic stirrer bar (80 mm) for at least three minutes (rotational speed in the range of 750-1500 rpm) and the stirring unit is switched off. It is then assessed whether all fibres are dispersed. 
     The dispersing behaviour of the fibres was assessed as follows: 
     not dispersed (−) 
     partially dispersed (○) 
     fully dispersed (+) 
     The above assessment was performed after defined time intervals. 
     A fibre not comprising the preparation according to the invention, but otherwise identical was used as a comparison. 
     Gelling temperature: 
     The gelling temperature was determined by means of an oscillation rheometer, model Physica MCR 301 from the company Anton Paar. 
     Insofar as not already specified in the above description, the following other parameters were determined by means of the measurement or test methods according to the publication “Methylcellulose, a Cellulose Derivative with Original Physical Properties and Extended Applications” in Polymers 2015, 7(5), 777-803. 
     The invention is explained by the following example without its scope being limited thereby. 
     EXAMPLES 
     Methyl cellulose solution was applied to melt-spun PLA fibres during processing on the conveyor line and was then dried. The produced PLA fibres thus have a preparation on the surface comprising at least one methyl cellulose (MC). 
     The produced PLA fibres comprise the preparation according to the invention on at least 99% of the total surface of the fibres. 
     The PLA fibres according to the invention were cut to a length of 6 mm, and 1 gram of the cut PLA fibres was dispersed and examined at room temperature (25° C.) as described beforehand. 
     For comparison, 1 gram PLA fibres without the additive according to the invention, but otherwise identical, was dispersed and examined at room temperature (25° C.) as described above. 
     The fibres according to the invention, in contrast to the comparison fibres (without the finish according to the invention), demonstrate a much improved long-term dispersion, and a much improved permanence of the dispersibility following a few weeks storage.