Flame-retardant lyocell filament

Abstract

To provide a filament having flame retardancy, and moreover, a manufacturing method and use thereof.SOLUTION: A filament having flame retardancy is a flame-retardant filament (FR filament) containing a flame retardant and cellulose and is characterized by that the filament is a lyocell filament.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to flame retardant lyocell filaments, as well as to a method for producing same and to uses of said flame retardant filaments. [Background technology]

[0002] Flame retardant fibers are used in a wide variety of applications, from industrial fabrics to outer garments. Cellulosic fibers have been used in these applications for a long time, but cellulosic filaments have not yet received much attention and are not widely used in this field due to their reportedly poor dimensional stability and low wet strength. As used herein, the term filament refers to the specialized term used by, for example, BISFA (The International Bureau For The Standardization Of Man-Made Fibres). The term (further terminology used in the present specification and claims is also as defined in BISFA publications, see below) defines very long fibers that are considered continuous (endless), and are distinguished from filaments of shorter fiber types, such as staple fibers, flock, etc. For such shorter fiber types, dimensional stability and strength concerns are less important, and therefore cellulosic staple fibers, etc., have been widely used, even in versions containing additives, including flame retardants. For filaments, however, concerns regarding dimensional stability and strength properties, especially wet strength, are a greater issue. This is one of the reasons why cellulosic filaments, especially flame-retardant filaments, are still not widely used.

[0003] In the prior art, viscose staple fibers have been produced using flame retardants as additives. U.S. Patent Application Publication Nos. 2012 / 0156486(A1) and 2013 / 0149932(A1) are examples of specifications relating to such prior art staple fibers. However, cellulosic filaments such as viscose filaments, when produced with flame retardants, have not exhibited the required properties, such as dimensional stability and sufficient dry and wet strength, necessary to withstand demanding textile processes such as weaving, dyeing, and finishing, as well as achieving adequate textile performance with respect to shrinkage when washed or used in a broken state. Summary of the Invention [Problem to be solved by the invention]

[0004] In light of the above problems, the object of the present invention is to provide a flame-retardant filament (FR filament) that meets high-quality standards in terms of strength and dimensional stability. The term flame-retardant filament, as used herein, defines a filament that has a flame retardant agent incorporated into its matrix, rather than simply being coated with a flame-retardant material. [Means for solving the problem]

[0005] This problem can be solved in the following manner. <1> The problem is solved according to the present invention by a filament according to the invention. <2> ~ <5> The present invention further relates to the following aspects: <6> Also provided is a method for producing a medicament for use in a method according to the present invention, also in preferred embodiments of which are described below. <7> ~ <9> Finally, the present invention relates to the following aspects: <10> and the embodiments described below. <11> and preferred embodiments of the present invention are described in the following aspects. <12> ~ <15> Further extensions are provided in the following description. DETAILED DESCRIPTION OF THE INVENTION

[0006] It has been surprisingly discovered that flame-retardant lyocell filaments overcome the shortcomings of the prior art and the perceptions and concerns about flame-retardant cellulosic filaments, such as viscose filaments. The lyocell filaments described herein surprisingly exhibit a sufficiently high balance of properties to be reliably produced in the form of flame-retardant filaments. These FR filaments are highly promising for the production of various products, including filament yarns, and further fabrics for protective clothing, or fabrics or nonwovens for other industrial applications, made from the filaments and yarns according to the invention.

[0007] Lyocell fibers are known in the art, and general methods for their production are disclosed, for example, in U.S. Pat. No. 4,246,221 and the 2009 edition of the BISFA (International Bureau for Standardization of Man-Made Fibers) publication "Terminology of Man-Made Fibers," both references being incorporated herein in their entirety. Reference is also made to WO 02 / 18682 A1 and WO 02 / 72929 A1 relating to methods for producing cellulose filament yarns, the entire contents of which are also incorporated herein.

[0008] As indicated above, the FR filaments according to the present invention are lyocell filaments, i.e., filaments produced using the lyocell process. This process is known to those skilled in the art and therefore will not be described in further detail herein. The Examples and also the patent documents mentioned herein provide a description of this process. The filaments may have any desired linear density, with suitable values ​​ranging from 0.6 to 4 dtex, and preferred values ​​ranging from 0.8 to 2 dtex. The cellulosic raw material used to produce the FR filaments of the present invention is not critical; any type of raw material suitable for the lyocell process may be used.

[0009] As indicated above, the present invention is particularly characterized by the fact that the novel and inventive FR filaments exhibit a surprisingly high balance of mechanical (strength / tensile) properties in the dry and even wet state, as well as a very satisfactory dimensional stability. At the same time, the desired flame retardancy can be obtained even with filaments without excessively sacrificing mechanical properties. The strength properties obtainable with the filaments of the present invention are typically specified in the conditioned state, and for the FR filaments of the present invention, these properties are typically as follows: The average dry tensile strength (FFk) of the filaments is at least 22 cN / tex. The average dry breaking elongation (FDk) of the filaments is at least 6%, preferably 6% to 8%. These properties are evaluated using the following test equipment and parameters: Test equipment: USTER® Tensorapid 4 2.4.2 UTR4 / 500N: Test length: 500 mm Clamping speed: 60mm / min Clamping pressure: 30% Preload: 4.1cN

[0010] The filaments according to the invention therefore exhibit favorable high dimensional stability, which provides benefits to the yarns and fabrics produced therefrom. Thus, high-quality flame-retardant products can be produced using the FR filaments of the invention.

[0011] As mentioned above, the filaments of the present invention are FR filaments, i.e., filaments incorporating a flame retardant. The filaments of the present invention are lyocell filaments. Therefore, the incorporation of the flame retardant can be achieved by including the flame retardant in the spinning solution (or at least in the composition before the filaments are spun) in a suitable manner, as further shown in the examples contained herein. The type of flame retardant is not critical, and it is typically present in the form of a solution of the flame retardant, preferably an aqueous solution, in particular in the spinning solution or spinning composition. However, the flame retardant may also be present in the form of a finely divided powder or a dispersion of such a finely divided powder. If such a solid form of the flame retardant is to be used, it is preferred that the average particle size of the flame retardant be 50% or less of the filament diameter, more preferably 30% or less, and even more preferably 10% or less of the filament diameter.

[0012] The amount of flame retardant in the final filament is typically in the range of 2 to 50% by weight of the filament, preferably 10 to 40%, and even more preferably 15 to 30% by weight. This amount may be adjusted as needed (e.g., in relation to the desired degree of flame retardancy) and can be controlled by the ratio of cellulose to flame retardant in the spinning solution or spinning composition.

[0013] The type of flame retardant is not critical, as mentioned above. However, flame retardants based on nitrogen- and phosphorus-containing compounds are preferred, such as those commercially available under the trademark Aflammit®. Organophosphorus compounds, such as Aflammit KWB, are particularly preferred. Any flame retardant used may be subjected to a pretreatment, such as milling, to obtain a particle size suitable for the spinning process (if not soluble in the spinning composition), typically depending on the desired filament diameter. Such processes are known to those skilled in the art.

[0014] In one embodiment of the present invention, flame retardants that are oxidative condensation products of tetrakishydroxyalkylphosphonium salts and ammonia, and / or flame retardants that are nitrogen compounds containing one or more amine groups are excluded.

[0015] As outlined above, the FR filaments according to the present invention are lyocell filaments. Therefore, the process for producing the filaments according to the present invention includes providing a spinning solution containing at least cellulose, water, NMMO, and the flame retardant, spinning the solution, and recovering the filaments by a method known to those skilled in the art. According to the present invention, it has been specified that a spinning speed of about 250 to 750 m / min, such as 300 to 600 m / min, preferably 350 to 450 m / min, can be used. During the process, any further additives and stabilizers required, such as dyes and pigments, may be added as needed.

[0016] The filaments may, of course, be subjected to any conventional post-spinning treatment, such as coating, finishing, etc. Those skilled in the art will be able to select an appropriate process depending on the intended use of the FR filaments. However, a preferred exemplary spinning process, including a detailed overview of the various process steps, is outlined below.

[0017] The present invention provides a process for producing the lyocell filaments described herein, and also, for example, lyocell multifilament yarns. The process will now be described in detail with reference to individual process steps. It is understood that these process steps and corresponding preferred embodiments may be combined as appropriate, and that the present application encompasses and discloses these combinations, even if not explicitly described herein.

[0018] ·Spinning solution production It has been found preferable to use a cellulose starting material that meets the following requirements:

[0019] The rheological properties of known lyocell spinning solutions may not be compatible with the requirements for high-speed filament yarn production. For example, known spinning solution compositions used in staple fiber production result in an unacceptable number of filament breaks. It has been found that this problem can be overcome by using a cellulose raw material with a broader molecular weight distribution than previously disclosed, i.e., blending 5-30 wt. % of a cellulose having a scan viscosity in the range of 450-700 ml / g, preferably 10-25 wt. % of a cellulose having a scan viscosity in the range of 300-450 ml / g, preferably 75-90 wt. % of a cellulose having a scan viscosity in the range of 300-450 ml / g, provided that the difference in scan viscosity between these two fractions is at least 40 ml / g, preferably at least 100 ml / g. Scan viscosity is determined in caprylethylenediamine solution according to SCAN-CM 15:99, a technique known to those skilled in the art and which can be performed on commercially available equipment, such as the Auto PulpIVA PSLRheotek equipment.

[0020] To obtain such cellulose raw materials (e.g., from wood pulp) to achieve the required molecular polydispersity, blends of different starting materials may be used. The optimal blend ratio will depend on the actual molecular weight of each blend component, the filament manufacturing conditions, and the specific product requirements of the filament yarn. Alternatively, the required cellulose polydispersity can be achieved, for example, by blending during the wood pulp manufacturing process before drying. This eliminates the need for careful monitoring and blending of pulp stock during lyocell production.

[0021] The total cellulose content in the spinning solution is typically 10-20% by weight, preferably 10-16% by weight, such as 12-14% by weight. Those skilled in the art will recognize the components required for a spinning solution for the lyocell process, and further details regarding said components and general manufacturing methods are not considered necessary here. See U.S. Pat. No. 5,589,125, WO 96 / 18760, WO 02 / 18682, and WO 93 / 19230, all of which are incorporated herein by reference.

[0022] To further control the process according to the present invention, a high level of process monitoring and control is preferably used to ensure uniformity of the composition of the spinning solution, which may include in-line measurement of spinning solution composition / pressure / temperature, in-line measurement of particle content, in-line measurement of spinning solution temperature distribution in the jet / nozzle, and periodic offline cross-checks.

[0023] It is further preferable to control and, if necessary, improve the quality of the lyocell spinning solution used in the present invention, because the presence of large particles can result in unacceptable breakage of individual filaments during the formation process. Examples of such particles are impurities, such as sand and gel particles containing insufficiently dissolved cellulose. One option for minimizing the content of such solid impurities is a filtration process. Multistage filtration of the spinning solution is the optimal method for minimizing solid impurities. Those skilled in the art will understand that higher filtration stringency is required for finer filament finenesses. Typically, for example, depth filtration with an absolute rejection power of about 20 microns has been found to be effective for 1.3 decitex filaments. For finer decitex filaments, an absolute rejection power of 15 microns is preferred. Equipment and process parameters for carrying out filtration are known to those skilled in the art. In addition, it was found that it was appropriate to adjust the viscosity of the spinning solution to a range of 500 to 1350 Pa·s, measured at 110° C. and a shear rate of 1.2 (1 / s).

[0024] The temperature of the spinning solution during its preparation is typically in the range of 105-120°C, preferably 105-115°C. Prior to the actual spinning / extrusion, the solution is heated, after filtration if desired, to a higher temperature, typically 115-135°C, preferably 120-130°C, using processes and equipment known to those skilled in the art. This process, together with the filtration step, increases the homogeneity of the spinning solution after its initial preparation in order to provide the spinning solution (sometimes referred to as the spin) suitable for extrusion through a spinning nozzle. Preferably, the spinning solution is then brought to a temperature of 110-135°C, preferably 115-135°C, prior to extrusion / spinning, a process which may include intermediate cooling and heating stages, as well as a tempering stage (where the spinning solution is maintained at a given temperature for a specific period of time). Such processes are known to those skilled in the art.

[0025] Filament extrusion It has been found that ensuring a uniform and consistent flow rate of the spinning solution through each spinneret nozzle hole further improves the process and helps meet the quality requirements for the individual cellulose filaments and, consequently, for the multifilament yarn. This is particularly relevant in view of the very high production speeds required for filament and filament yarn production, in the range of 200 m / min or higher. According to the present invention, production speeds of 200 m / min or higher can be achieved, such as 400 m / min or higher, preferably 700 m / min or higher, and even up to 1000 m / min or higher. Suitable ranges are 200-1500 m / min, such as 400-1000 m / min or 700-1000 m / min, including ranges such as 700-1500 m / min.

[0026] Each spinneret section used to extrude the lyocell spinning solution has a number of nozzle holes corresponding to the number of filaments required in the continuous filament yarn. Multiple spinneret sections can be combined into a single spinneret plate to extrude multiple yarns from a single jet, as disclosed, for example, in WO 03014429 A1, which is incorporated herein by reference.

[0027] The number of nozzle holes for each filament yarn may be selected depending on the type of yarn intended, but the number is typically in the range of 10 to 300, preferably 20 to 200, such as 30 to 150.

[0028] Uniformity of spinning solution flow rate can be improved by providing good temperature control within the spinneret and the individual nozzles. Temperature variations within and between the nozzles during spinning should be as small as possible, preferably within ±2°C. This can be achieved by directly heating the spinneret and the individual nozzles in a series of different zones, allowing any local differences in spinning solution temperature to be offset and precisely controlling the temperature of the spinning solution as it exits each spinneret nozzle. Examples of such temperature control means are disclosed in WO 02 / 072929 and WO 01 / 81662, which are incorporated herein by reference.

[0029] The spinneret nozzle profile is preferably designed to maximize smooth acceleration of the spinning solution through the nozzle while minimizing pressure loss. Important design features of the nozzle include, but are not limited to, a smooth entrance surface and a sharp edge at the nozzle exit.

[0030] ·Initial cooling After exiting the spinning nozzle, the individual filaments are typically subjected to a cooling process, typically using an air stream. Cooling is achieved by ventilation, preferably controlled cross draft with an air gap. Preferably, this is done by using a ventilation system. The ventilation should have a controlled humidity to achieve the desired cooling effect without adversely affecting the fiber quality. Suitable humidity values ​​are known to those skilled in the art. However, direct application of known Lyocell staple fiber procedures to this process would not work well because it would require a very long air gap (more than 200 mm) to take into account the high filament production speed. However, such an air gap is not feasible because the individual filaments would move and come into contact, leading to filament fusion and poor product quality. For the same reasons, it has been found that high-speed cross ventilation disclosed for staple fiber production can also present problems. In addition, for filament products, greater uniformity and consistency of drawing is required compared to staple fibers.

[0031] The present invention therefore provides a novel means of adjusting the filament manufacturing process to meet the quality requirements of filament yarn production.

[0032] Suitable cross-ventilation mechanisms are disclosed, for example, in WO 03014436 A1, which is incorporated herein by reference.Uniform filament cooling over the length of the air gap is preferred.

[0033] As outlined above, the long air gaps considered necessary according to general spinning process understanding are not feasible, especially when considering high production speeds. However, it has been found that air gap lengths longer than those typically used in staple fiber production, such as about 40-130 mm, can be successfully used. Preferably, the air gap is in the range of 40-120 mm, such as 50-100 mm. In embodiments, this can be combined with increased filament spacing at the spinneret face (about twice the nozzle spacing used in lyocell staple fiber production). Such a mechanism has been found to be beneficial for filament production. Increasing filament spacing in this manner reduces the likelihood of filament contact and allows for the required uniform filament cooling.

[0034] The cross-ventilation speed is preferably much lower than that used in lyocell staple fiber production. Suitable values ​​are 0.5 to 3 m / s, preferably 1 to 2 m / s. The humidity value may be in the range of 0.5 to 10 g of water per kg of air, such as 2 to 5 g of water per kg of air. The air temperature is preferably controlled to a value below 25°C, such as below 20°C.

[0035] Initial solidification of the filament After exiting the spinneret nozzle and cooling in the air gap, the produced filaments must be further processed for initial solidification. This is achieved by placing the individual filaments in a coagulation bath, also called a spin bath. It has been found that, in order to achieve a high degree of uniformity in product quality, it is preferable for this further initial solidification of the filaments to occur within narrow tolerances, i.e., with only slight variations, and preferably at precisely the same location. It has been found that conventional spin bath designs are often not suitable for this purpose because fluid forces resulting from high filament speeds (greater than about 400 m / min) disrupt the bath surface, resulting in uneven initial solidification (and variable air gap size), as well as the possibility of filament fusion and other damage. To address such issues, it has been determined that it is preferable to use a shallow spin bath having a depth of less than 50 mm.

[0036] Such spin baths are described, for example, in WO 03014, which is incorporated herein by reference. 432(A1), which discloses a shallow spin bath depth in the range of 5 to 40 mm, preferably 5 to 30 mm, and more preferably 10 to 20 mm. The use of such a shallow spin bath makes it possible to control the contact position of the spun filaments with the coagulation solution in the spin bath, thereby avoiding the problems that can occur when using conventional spin bath depths.

[0037] Additionally, it has been found that filament quality can also be improved if the amine oxide concentration in the spin bath is controlled to a value lower than that typically used in lyocell fiber production. Spin bath concentrations of less than 25 wt. %, more preferably less than 20 wt. %, and even more preferably less than 15 wt. % amine oxide have been found to improve filament quality. A preferred range for the amine oxide concentration is 5-25 wt. %, such as 8-20 wt. % or 10-15 wt. %, which is significantly lower than the ranges disclosed for lyocell staple fiber production. To be able to maintain such low amine oxide concentrations, continuous monitoring of the spin bath composition is preferred, whereby adjustment of the concentration can be achieved, for example, by water replenishment and / or selective removal of excess amine oxide. The temperature of the spin bath is typically in the range of 5 to 30°C, preferably 8 to 16°C.

[0038] Similar to the preferred embodiment disclosed above for the spinning solution, high stringency spin bath solution filtration is contemplated to minimize the possibility of damage to the delicate freshly formed filaments by undesirable solid impurities in the spin bath, which is especially important for very high production speeds above 700 m / min.

[0039] Within the spin bath, the individual filaments of the desired final yarn are brought together into an initial multifilament bundle by an outlet from the spin bath, typically a ring-shaped outlet, which serves to bring the filaments together and also to control the amount of spin bath solution that leaves the bath with the filament bundle. Suitable mechanisms are known to those skilled in the art. Because at least some of the filaments come into contact with the ring-shaped outlet, the shape and even the choice of material for the ring-shaped outlet influence the tension on the filament bundle. Those skilled in the art will know suitable materials and shapes for these outlets from the spin bath to minimize any negative effects on the filament bundle.

[0040] Thus, in a preferred embodiment of the process according to the present invention, the process comprises the step of preparing a spinning solution suitable for the Lyocell process containing 10 to 15% by weight of cellulose, preferably 12 to 14% by weight, the cellulose being the aforementioned blend of celluloses with different scan viscosities. The process further comprises the step of extruding the spinning solution through an extrusion nozzle while maintaining a temperature fluctuation of ±2°C or less as it passes through the extrusion nozzle. The filaments thus produced are subjected to initial cooling as described above, followed by the initial solidification of the filaments thus obtained in a coagulation bath (spin bath) having a depth of less than 50 mm, preferably 5 to 40 mm, more preferably 10 to 20 mm.

[0041] The composition of the coagulation liquid used in this coagulation bath exhibits an amine oxide concentration of 23 wt.% or less, more preferably less than 20 wt.%, and even more preferably less than 15 wt.%. Control of this amine oxide content can be achieved by adjusting the concentration within the preferred range by selective removal of amine oxide and / or by replenishment with fresh water.

[0042] Such a process ensures the production of high quality and particularly uniform filaments. The filaments may be introduced into the coagulation bath in a manner that ensures, in particular, uniform coagulation and therefore uniform filament properties. Additionally, in the process embodiments described above, it is preferred to adjust the distance between the individual filaments during extrusion, for example by using wider nozzle spacing, compared to standard lyocell staple fiber production processes, as described further below. These preferred process parameters and conditions allow for the production of lyocell filaments with high uniformity, as described herein, while also allowing for the desired high process speeds (spinning speeds of 200 m / min or more, more preferably 400 m / min or more, and in embodiments, 700 m / min or more). In this regard, the present invention further allows for the continuous, long-term production of cellulose lyocell filaments and corresponding yarns, since the process parameters and conditions described above avoid filament breakage and the like, which would require the production of filaments and yarns to be stopped.

[0043] Filament drawing After leaving the spin bath, the multifilament bundle is typically taken up by guide rollers that direct the bundle to the next processing stage, such as washing, drying, and winding, resulting in the final yarn. Preferably, no stretching of the filament bundle occurs during this process. The distance from the exit of the spin bath to the point of contact with the guide rollers may be selected as needed, with distances of 40 to 750 mm, such as 100 to 400 mm, being shown to be suitable. It has been found that this process step can provide additional options for controlling and influencing product quality. For example, this process step allows for the adjustment of the crystalline structure of the filaments, thereby achieving the desired properties of the lyocell continuous filament yarn. As mentioned above and in the following aspects, <1> As can be derived from the wording, success in this process step has been found to be closely related to the rheology of the spinning solution and the consistency of extrusion from the nozzle, as discussed above.

[0044] As mentioned above, a means such as a guide roller takes the filaments and gathers them to form an initial yarn, which is then guided towards further processing steps. According to the present invention, the maximum tension applied to the filament bundle (yarn) at the contact point between the filament bundle and the guide roller is (4.2 x number of filaments / filament fineness). 0.69 Preferably, the tension is equal to or less than 4.2 × 60 = 1.33. This tension refers to the tension applied to the filaments / filament bundle from the position where they leave the spinning nozzle to the position of first contact, for example, to the position of first contact with the guide roller provided after the coagulation step. From the formula provided above, for example, the maximum tension for a filament bundle having 60 filaments and a yarn fineness of 80 dtex (each filament has a fineness of 1.33 dtex) is determined, and the maximum tension is (4.2 × 60:1.33) 0.69 , and therefore 37.3cN.

[0045] Maintaining such a specific maximum tension ensures that filament breakage is prevented so that high-quality yarn can be obtained. Additionally, this helps ensure that the filament production process can continue for the required time without failure. Those skilled in the art will understand that the tensions referred to herein are tensions measured using samples taken from the entire process by using a three-roll testing apparatus, Schmidt-Zugspan-nungsmessgerat ETB-100. The tensions measured on the filaments and filament bundles at the specified contact locations referred to herein are determined by adjusting the process parameters disclosed herein for the present invention, in particular the composition of the spinning solution, the spin bath depth and the spin bath liquid (coagulation bath) composition, the cross-draft, and spinneret design, such as nozzle design and nozzle spacing, in order to adjust the tension value to a value according to the formula provided above. By adjusting it, it can be used to control product quality and process stability.

[0046] Cleaning the filament Since the filaments after initial solidification and cooling still contain amine oxide, the resulting filaments and / or yarn are typically subjected to washing. The amine oxide can be removed from the newly formed yarn via countercurrent flow of demineralized water or other suitable liquid, typically at 70-80°C. As with the previous process steps, conventional washing methods, such as the use of troughs, are not suitable for high production speeds exceeding about 400 m / min. It has been found that this can present problems in terms of speed. Additionally, uniform application of the wash solution to each individual filament is preferred to obtain a high-quality product. At the same time, it is also preferred that there is minimal contact between the sensitive filaments and the washing surface in order to maintain the integrity of the filaments to achieve the desired yarn properties. Furthermore, individual filament yarns need to be washed in close proximity to each other, and line length should be minimized to make the process economically viable. In view of the above, it has been found that a preferred washing process includes the following, either alone or in combination:

[0047] Washing is preferably carried out using a series of driven rollers, with each yarn being individually subjected to a series of wash impregnation / wash removal steps.

[0048] It has been found beneficial to provide a means for uniformly removing or dewatering liquid from each yarn filament after each wash-impregnation step without damaging the sensitive filaments. This can be achieved, for example, through appropriately designed and positioned pin guides. The pin guides may be constructed, for example, of a matte chrome finish. The guides allow for close spacing of the filament yarns (approximately 3 mm), good contact with the filaments, and provide uniform liquid removal and low tension to minimize filament damage.

[0049] If desired, an alkaline wash step may be included to enhance the efficiency of removing residual solvent from the filaments.

[0050] The spent wash solution (after the first pin guide) typically has an amine oxide concentration of 10-30%, preferably 18-20%, before being returned to solvent recovery.

[0051] "Fabric softeners" may be applied to aid in further processing. Types and methods of application are known to those skilled in the art. For example, a "lick-roller" mechanism may be used to Applying about 1% of the finish onto the filaments followed by nip rollers to control the tension of the yarn going into the dryer has been found to be effective.

[0052] Drying the yarn Again, good control of this process helps develop optimal yarn properties and minimize the possibility of filament damage. Drying means as well as drying parameters are known to those skilled in the art. Preferred embodiments are defined below.

[0053] The dryer may consist of, for example, 12 to 30 heated drums, each about 1 m in diameter. The individual speeds are preferably controlled to ensure that the filament tension remains low and constant, preferably less than 10 cN, and preferably less than 6 cN. The spacing of the yarns throughout the drying process may be about 2 to 6 mm.

[0054] The initial temperature of the dryer is about 150° C. In later stages of the drying process, the temperature may be lower as drying progresses.

[0055] After drying, antistatic agents and / or fabric softeners may be applied to the filament yarn by means known to those skilled in the art.

[0056] Further processing steps, such as blending, bulking, and interweaving of the yarns, may be applied after drying and before collection using processes known to those skilled in the art. If desired, fabric softeners may be applied to the yarns prior to the steps indicated above.

[0057] - Thread collection The yarn may be collected using standard winding equipment; a suitable example is a single-row winder. The winder speed is used to fine-tune the upstream process speed to maintain a low and constant yarn tension.

[0058] Those skilled in the art will understand that various modifiers, such as dyes, antimicrobial products, ion exchange products, activated carbon, nanoparticles, lotions, flame retardant products, superabsorbents, impregnating agents, dyes, finishing agents, crosslinking agents, grafting agents, binders, and mixtures thereof, may be added during the preparation of the spinning solution or in the washing zone, provided that the addition does not interfere with the spinning process. This allows the produced filaments and yarns to be modified to meet individual product requirements. Those skilled in the art will be familiar with how to add such above-mentioned substances during the lyocell filament yarn production process. In this regard, it has been found that many desirable modifiers that would normally be added in the washing stage are not effective in the filament yarn path due to the high line speed and therefore short residence time. Another alternative approach for introducing these modifiers is to recover the thoroughly washed but "not dried" filament yarns and subject them to further batch-wise processing, where residence time is not a limiting factor.

[0059] The FR filaments according to the present invention can be used to produce further products, such as yarns, fabrics, and nonwovens. The yarns may contain various numbers of the filaments of the present invention, with suitable examples being 10 to 200 filaments, such as 15 to 150, and in embodiments, 25 to 100. The fineness of the yarns may cover a wide range depending on the intended field of use, for example, finenesses in the range of 30 to 150 denier, such as 50 to 120 denier. Due to their unique balance of properties, such as high mechanical strength and relatively low elongation at break, high-quality products with high dimensional stability can be produced using the filaments of the present invention.

[0060] The FR filaments of the present invention may be used alone to produce further (textile) products, but they may also be blended with other types of fibers to create filament mixtures with the desired property profile. In particular, blending the FR filaments of the present invention with other fibers may be an option when the intended product does not require a high degree of flame retardancy. Another option is to blend the FR filaments with high-strength filaments when a high-strength fabric is desired. In either case, the FR filaments of the present invention have therefore been shown to provide good properties even when blended with other types of fibers, as explained above.

[0061] The following examples illustrate the invention. [Example]

[0062] The following examples demonstrate the superior properties of the FR lyocell filaments of the present invention compared to non-flame retardant viscose, cupro, and lyocell filaments. Example 1 shows the properties of FR lyocell filaments according to the invention. Comparative Examples 1 to 3 are made of viscose filaments, cupra filaments, and ribs, respectively. These exhibit the properties of yossel filaments, all of which do not contain flame-retardant ingredients.

[0063] The filament according to the present invention in Example 1 was produced as follows. Pulp (cellulose) was impregnated with a 78% aqueous solution of N-methylmorpholine N-oxide (NMMO) and a small amount of stabilizer. The resulting suspension contained 11.6% cellulose, 68% NMMO, 20.4% water, and the stabilizer GPE. The pulp consisted of a mixture of cellulose sulfite and cellulose sulfate. A flame retardant (Aflammit KWB, a suspension of 20% ground Aflammit KWB in 50% aqueous NMMO) was added to prepare the final spinning solution. Excess water was removed from the slurry under shear and heat to yield a fiber-free spinning solution containing 12.7% cellulose, 73.8% NMMO, 10.7% water, and 2.8% flame retardant (all percentages by weight of the total composition). The spinning solution was filtered and extruded through a nozzle into an air gap by a wet-dry process at 114° C. An air flow was provided in the air gap to stabilize the extrusion process. The spinning speed was 400 m / min. After passing through the air gap, the cellulose was precipitated in a spin bath containing 10% NMMO, the remainder water. The endless filaments thus obtained were washed with water, impregnated with a finish, dried and wound onto bobbins. Washing was carried out in countercurrent with completely demineralized water. Drying was carried out in a contact dryer, reducing the humidity to 10.5%. These filaments were used to produce a multifilament consisting of a single filament. A non-twisted filament yarn was produced from the multifilament. A fabric can be produced from the filament yarn. The linear density of the produced yarn was 20 to 200 dtex, preferably 50 to 150 dtex.

[0064] For further details of the manufacturing process, reference is made to US Pat. No. 4,246,221, WO 02 / 18682 A1, and WO 02 / 72929 A1.

[0065] Filament Comparative Examples 1-3 were produced using a conventional process, and the lyocell filaments were produced using the experimental setup described in Example 1, except that no flame retardant component was used. The properties of each are reported below.

[0066] [Table 1]

[0067] [Table 2]

[0068] Comparative Examples 1 and 2 show that viscose and cupra filaments exhibit completely insufficient properties even without the addition of flame retardants. On the other hand, FR lyocell filaments exhibit very satisfactory mechanical properties, although slightly lower than those of Comparative Example 3, i.e., non-FR lyocell filaments. However, the properties of the FR lyocell filaments according to the present invention are significantly improved compared to the non-FR viscose and cupra filaments. The comparative examples using other types of cellulose filaments suffer from a significant imbalance in mechanical properties, making it impossible to produce dimensionally stable products from these filaments. At the same time, the flame-retardant filaments of the present invention exhibit not only very satisfactory flame retardancy but also an excellent balance of mechanical properties.

[0069] Flame-retardant lining From the yarn obtained using the FR lyocell filament of the present invention (den90 / 40 (multifilament having a total fineness of 90 denier with 40 filaments), yarn fineness dtex 100f40), 75 g / m 2 This lining was used to fabricate a moisture barrier (laminate, 148 g / m 2, 50% meta-aramid / 50% Lenzing FR (flame-retardant viscose staple fiber) / PU membrane), outer fabric (260g / m 2 A three-layer assembly comprising a 100% FR lyocell filament (50% Lenzing FR, 38% para-aramid, 12% PA) and a lining (100% FR lyocell filament) as identified above was evaluated for flame retardancy. The three-layer assembly passed the flame spread test according to EN ISO 15025:2002 Method A (outer fabric ignition test plus lining ignition test) and met all requirements according to EN 469 (EN 533 Index 3). The present invention includes the following aspects. <1> A flame-retardant filament (FR filament) comprising a flame retardant and cellulose, characterized in that the filament is a lyocell filament. <2> Average dry tensile strength of 22cN / tex or more <1> The FR filament described in <3> having an average wet tensile strength of 11 cN / tex or more; <1> or <2> The FR filament described in <4> The amount of the flame retardant is 2 to 50% by weight. <1> ~ <4> The FR filament according to any one of claims 1 to 4. <5> providing a composition comprising pulp, N-methylmorpholine N-oxide, water, and a flame retardant; and spinning the solution to produce filaments. <1> ~ <4> A method for producing the FR filament described in any one of claims 1 to 4. <6> The amount of the flame retardant and pulp in the spinning solution is within the range of 12 to 25% of the spinning solution. <5> The method described below. <7> The spinning speed is in the range of 250 to 750 m / min. <5> or <6> The method described below. <8> The pulp comprises cellulose sulfite and cellulose sulfate. <5> ~ <7> 10. The method according to any one of the preceding claims. <9> For the production of yarns, fabrics, and textile products, <1> ~ <4> FR filament according to any one of <5> ~ <8> Use of FR filaments manufactured according to any one of claims 1 to 4. <10> <1> ~ <4> FR filament according to any one of <5> ~ <8> 1. A yarn, fabric, or textile product comprising FR filaments produced according to any one of claims 1 to 9. <11> The FR filaments are blended with other types of fibers; <9> or <10> The use or product described in <12> Meets the requirements according to EN ISO 14 116 classification "Flame spread index 3" when tested according to EN ISO 15025:2002 Method B - Bottom ignition, <9> ~ <11> 10. The use or product according to any one of claims 1 to 9. <13> It is a multifilament yarn, <9> ~ <12> 10. The use or product according to any one of claims 1 to 9. <14> The FR filaments include a resin finish. <9> ~ <13> 10. The use or product according to any one of claims 1 to 9.

Claims

1. A flame-retardant filament (FR filament) comprising a flame retardant and cellulose, characterized in that the filament is a lyocell filament.

2. FR filament according to claim 1, having an average dry tensile strength of 22 cN / tex or more.

3. 3. The FR filament according to claim 1 or claim 2, having an average wet tensile strength of 11 cN / tex or more.

4. The FR filament according to any one of claims 1 to 3, wherein the amount of the flame retardant is 2 to 50% by weight.

5. A method for producing the FR filament according to any one of claims 1 to 4, comprising providing a composition comprising pulp, N-methylmorpholine N-oxide, water, and a flame retardant, and spinning the solution to produce a filament.

6. The method of claim 5, wherein the amount of flame retardant and pulp in the spinning solution is in the range of 12 to 25% of the spinning solution.

7. The method according to claim 5 or claim 6, wherein the spinning speed is in the range of 250 to 750 m / min.

8. The method according to any one of claims 5 to 7, wherein the pulp comprises cellulose sulfite and cellulose sulfate.

9. Use of the FR filaments according to any one of claims 1 to 4 or produced according to any one of claims 5 to 8 for the production of yarns, fabrics and textile products.

10. A yarn, fabric or textile product comprising the FR filament according to any one of claims 1 to 4 or the FR filament produced according to any one of claims 5 to 8.

11. 11. Use or product according to claim 9 or claim 10, wherein the FR filaments are blended with other types of fibres.

12. 12. Use or product according to any one of claims 9 to 11, which meets the requirements according to EN ISO 14 116 classification "Flame spread index 3" when tested according to EN ISO 15025:2002 Method B - Bottom end ignition.

13. The use or product according to any one of claims 9 to 12, which is a multifilament yarn.

14. The use or product of any one of claims 9 to 13, wherein the FR filaments comprise a resin finish.

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