Method for producing lyocell staple fiber

Abstract

The present invention comprises the following steps in the following order: a) extruding filaments from a solution of cellulose in an organic solvent; b) precipitating cellulose to form continuous cellulose filaments; c) washing the cellulose filaments; d) contacting the cellulose filaments with a cross-linking agent; e) reacting the cellulose filaments with a cross-linking agent in a reaction chamber; f) washing the treated cellulose filaments; g) cutting the cleaned cellulose filaments to form staple fibers; h) forming a nonwoven fabric from the staple fibers and pressing the nonwoven fabric; i) applying a finishing touch to the nonwoven fabric and pressing the nonwoven fabric; The present invention relates to a method for producing lyocell staple fiber, comprising:

Description

[Technical Field]

[0001] The present invention relates to a method for producing lyocell staple fibers and to lyocell staple fibers obtainable by the method according to the invention. [Background technology]

[0002] In light of the environmental problems associated with the known viscose process for producing cellulose fibers, efforts have been made over the past few decades to provide more environmentally friendly alternatives. One possibility that has arisen, which has attracted particular attention in recent years, is to dissolve cellulose in an organic solvent without forming derivatives and extrude bodies from said solution. Fibers spun from such solutions have received the generic name lyocell from BISFA (The International Bureau for the Standardization of Man-made Fibers), where organic solvent is understood to mean a mixture of organic chemicals and water.

[0003] Furthermore, such fibers are also known by the term "solvent-spun fibers."

[0004] In particular, mixtures of tertiary amine oxides and water have proven to be perfectly suitable as organic solvents for producing lyocell fibers and other lyocell molded bodies, respectively. N-methylmorpholine-N-oxide (NMMO) is primarily used as the amine oxide. Other suitable amine oxides are disclosed in EP 0 553 070 A. Ionic liquids are also suitable as organic solvents. Methods for producing cellulose molded bodies from a solution of cellulose in a mixture of NMMO and water are disclosed, for example, in US Pat. No. 4,246,221 or WO 93 / 19230 A. According to these methods, the cellulose solution is extruded through a spinneret, stretched in an air gap, and precipitated from the solution in an aqueous precipitation tank. This process will hereinafter be referred to as the "amine oxide process" or "lyocell process," and the abbreviation "NMMO" will hereinafter refer to any tertiary amine oxide capable of dissolving cellulose. Fibers produced by the amine oxide process are characterized by high fiber strength in the conditioned as well as the wet state, high wet modulus, and high hook strength.

[0005] Commercially produced lyocell fiber is primarily in the form of staple fiber.

[0006] Continuous filaments are initially formed from the spinning solution as it is extruded through the spinneret. These are allowed to settle in the spinning tank, and continuous cellulose filaments remain. These cellulose filaments can be cut into discrete lengths to form staple fibers.

[0007] Extensive prior art is known regarding the processing of lyocell fibers after spinning.

[0008] The steps required in any case to process lyocell fibers are as follows (note that the following listing should not be interpreted as a chronological order of the process): - Washing it multiple times; - Applying finishes; - taking measures to induce crimp in the fibre; - Drying the fabric once or several times if necessary; - and cutting the fibers into staple fibers.

[0009] Furthermore, lyocell fibers are known to have a particular tendency to fibrillate, a property for which numerous remedies have already been proposed, and the treatment of lyocell fibers with crosslinking agents is a commercially important procedure.

[0010] Suitable crosslinking agents are described, for example, in EP 0 538 977 A, WO 97 / 49856 A, and WO 99 / 19555 A. Other crosslinking agents are known, for example, from WO 94 / 09191 A and WO 95 / 28516 A.

[0011] Particularly preferred crosslinkers are those of formula (I)

[0012] [ka] where X represents a halogen, R=H or an ionic moiety, and n=0 or 1. or a salt of this compound. Hereinafter, this substance will also be referred to as "NHDT."

[0013] Furthermore, the prior art offers different concepts regarding the question of when to cut the cellulose filaments into staple fibers and, consequently, in what form (continuous filaments or already cut staple fibers) the lyocell fibers are subjected to the various processing steps indicated above.

[0014] For example, WO 94 / 27903A and WO 95 / 24520A disclose methods for carrying out a washing step and a crimp-inducing step on uncut cellulose filaments, also called "post-tow treatment." In this method, crimp is induced in the fibers using a so-called "stuffer box." WO 98 / 28516A describes that, within the scope of post-tow treatment, lyocell fibers can be treated with a crosslinking agent.

[0015] On the other hand, from WO 97 / 14829 A a process is known in which the cellulose filaments are cut into staple fibres immediately after spinning and the first washing bath.

[0016] In the process of WO 97 / 14829A, a nonwoven fleece is formed from staple fibers, and the fibers are given a so-called "permanent crimp" by squeezing or pressing the nonwoven. Further processing steps up to the initial drying of the fibers are passed through in the form of staple fibers or in the form of this nonwoven. Hereinafter, this concept will be referred to as "fleece post-treatment".

[0017] Alternative methods for producing crosslinked fibers are known from US 5,562,739 A, GB 2373784 A, and WO 2004 / 007818 A1.

[0018] Further details regarding the processing of as-spun fibers are known from CN204265902(U), CN203960407(U), CN203904520(U), CN203403200(U), CN203402582(U), CN204000264(U), CN203999953(U), CN106757906(A), and CN108360182(A).

[0019] In particular, with respect to the production of lyocell staple fibers treated with a crosslinking agent (hereinafter referred to as "crosslinked fibers"), known methods for processing as-spun fibers present problems both in terms of chemical consumption and process efficiency. Summary of the Invention [Problem to be solved by the invention]

[0020] It is an object of the present invention to provide an improved method for producing crosslinked lyocell staple fiber. [Means for solving the problem]

[0021] This goal involves the following steps in the following order: a) extruding filaments from a solution of cellulose in an organic solvent; b) precipitating cellulose to form continuous cellulose filaments; c) washing the cellulose filaments; d) contacting the cellulose filaments with a cross-linking agent; e) reacting the cellulose filaments with a cross-linking agent in a reaction chamber; f) washing the treated cellulose filaments; g) cutting the washed cellulose filaments into staple fibers; h) forming a nonwoven fleece from the staple fibers and pressing the nonwoven fleece; i) applying a finishing touch to the nonwoven fleece and pressing the nonwoven fleece; This is achieved by a method for producing lyocell staple fiber, including:

[0022] Preferred embodiments are set forth in the dependent claims. [Brief explanation of the drawings]

[0023] [Figure 1] 1 shows a block diagram illustrating the sequence of a preferred embodiment of the method according to the invention; [Figure 2] FIG. 2 shows an image of a Lyocell staple fiber according to the invention under an optical microscope in polarized light. [Figure 3]FIG. 1 shows a comparison of the Hoeller coefficient of prior art lyocell fibers and lyocell staple fibers according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Surprisingly, it has been found that elements of the two concepts, the tow post-treatment on the one hand and the fleece post-treatment on the other, can be combined in a novel manner, resulting in significant improvements in the fiber properties.

[0025] According to the invention, the initial washing of the fibers (to remove the solvent) and their contacting and reaction with the crosslinking agent are carried out while the fibers are still in the form of (continuous) cellulose filaments, i.e., in the form of a tow, which are only cut into staple fibers, formed into a nonwoven fleece, pressed and finished after a fresh washing (hereinafter also referred to as "crosslinking agent washing").

[0026] It has been found that, compared to so-called "fleece post-treatments", steps c) to f), and in particular step e), the treatment with a crosslinking agent, carried out on the fibers in tow form, leads to significant savings in terms of the energy applied and the chemicals used, which also means that milder conditions can be used for treating the fibers compared to "fleece post-treatments".

[0027] However, the final process steps h) and i) in nonwoven form give the fibers the additional valuable property of "residual crimp".

[0028] According to WO 97 / 14829, "residual crimp" is understood as the presence of an average of at least two squeeze points per millimeter of filament length, which squeeze points remain on the dry fiber and are visible as a color change when viewed under linearly polarized light. Preferably, this "residual crimp" is still detectable after the mechanical stresses that occur during carding and spinning.

[0029] Surprisingly, the crosslinked fibers obtainable by the method according to the invention have better fiber data than fibers treated with the same crosslinking agent according to the prior art (ie as fleece or tow).

[0030] A preferred embodiment of the method according to the invention is characterized in that the filaments or staple fibres are dried only after step i).

[0031] The reaction of the cellulose filaments with the crosslinking agent is usually carried out at elevated temperatures.

[0032] In particular, the reaction in step e) can be carried out with an energy input.

[0033] Furthermore, the reaction in step e) is preferably carried out in the presence of steam. Naturally, other options arise as well, such as treatment with electromagnetic waves, in particular with microwaves.

[0034] In a preferred embodiment, step e) of the method according to the invention is carried out in a steam chamber, for example a J-box can be used for this step.

[0035] The duration of step e) may be from 3 to 30 minutes, preferably from 10 to 25 minutes, particularly preferably from 15 to 20 minutes.

[0036] The crosslinking agent can be used in an amount that results in a content G (unit: moles) of crosslinking agent per kg of cellulose (atro), the content G being determined by the following formula: G×R=0.10 to 0.45, preferably 0.10 to 0.35, particularly preferably 0.20 to 0.35 (wherein R represents the number of reactive groups in the crosslinker). where R is at least 2, and in the case of the crosslinker NHDT having formula (I), R=2. In the case of other crosslinkers, R may be >2. For example, in the case of the sodium salt of p-[(4,6-dichloro-1,3,5-triazin-2-yl)amino]-benzenesulfonic acid ("SDTB"), which can be used as a crosslinker, the following applies: R=3.

[0037] For purposes of the present invention, it will be understood by those skilled in the art that the term "reactive group" refers to a group that is capable of covalently bonding with the OH groups of cellulose.

[0038] The amount required to achieve the desired content of crosslinking agent in the cellulose can be determined by a person skilled in the art within the scope of preliminary tests. It can usually be assumed that it will be found in the fiber in the range of 30% to 70% by weight, in particular 40% to 60% by weight, of the crosslinking agent originally used.

[0039] The amount of crosslinker available in the fiber can be determined by analyzing the properties that characterize the crosslinker, for example, in the case of a nitrogenous crosslinker, by using quantitative nitrogen analysis of the fiber.

[0040] In a preferred embodiment, the compound of formula (I)

[0041] [ka] where X represents a halogen, R=H or an ionic moiety, and n=0 or 1. or the respective salts of this compound, preferably the sodium salt of 2,4-dichloro-6-hydroxy-1.3.5-triazine, which will hereinafter be abbreviated as "NHDT", are used as crosslinking agents in the process according to the invention.

[0042] This compound has two reactive groups (two halogen moieties).

[0043] The crosslinking agent of the compound of formula (I) is preferably used in an amount of 30 to 80 g, preferably 45 to 60 g, per kg of cellulose (atro).

[0044] The object of the present invention is to provide a polyester fiber having residual crimp and a low coefficient of variation (CV) of wet abrasion resistance (NSF). NSF The problem is solved by the Lyocell staple fiber obtainable by the above-described method according to the present invention using the crosslinking agent NHDT, in which the crosslinking ratio (%) is 50% or less.

[0045] In a preferred embodiment variant, the Lyocell staple fibers according to the invention have a CV of less than or equal to 45%, particularly preferably less than or equal to 40%. NSF It has.

[0046] NSF fiber This is a key value for the resistance of the fiber to fibrillation during washing and is determined by the test method shown in the examples. Due to the good wet abrasion resistance of the fibers according to the invention, this requirement, which is essential for crosslinked fibers, is also fulfilled.

[0047] Fiber coefficient of variation CV NSF is determined by the measurement method described in the Examples section below.

[0048] The low CV of the fibers according to the invention, as specified above, NSF The value represents a very important distinguishing feature compared to fibers produced by fleece crosslinking with NHDT. As mentioned above, conventional fleece post-treatments cause fiber damage during the crosslinking reaction, which not only reduces strength but also increases the variability of the (reduced) strength, since not all cellulose chains are damaged to the same extent. This ultimately leads to the coefficient of variation of wet abrasion resistance, CV NSF becomes higher.

[0049] As shown in Tables 4 and 5 below, according to Examples 1 to 8, the fibers according to the present invention all had a CV of less than 45%. NSF values, with CVs below 40% in most cases NSFSuch a low CV NSF This is not expected from fibers crosslinked with NHDT by fleece post-treatment. Evaluation of numerous examples of fleece crosslinked fibers (e.g., commercial Lyocell staple fibers, LENZING™ Lyocell LF type with a fineness of 1.7 dtex from Lenzing Aktiengesellschaft, Werkstrasse 2, A-4860 Lenzing) shows that they all have a CV in the range between 60% and 80%. NSF It is shown to have a value.

[0050] The object of the present invention can also be obtained by the process according to the invention using the crosslinking agent NHDT, which in addition has the following properties: the fibers have a fineness in the range of 1.2 dtex to 1.5 dtex, preferably 1.25 dtex to 1.45 dtex; - the fibers have a residual crimp, - the fibers have a fiber strength in the normal weight state of at least 36 cN / tex, preferably in the range of 38 cN / tex to 42 cN / tex; the fibers have a Hoeller coefficient F1 ≥ 2.1, preferably ≥ 2.4, particularly preferably in the range from 2.5 to 3.2, and the fibers have a Hoeller coefficient F2 ≥ 3.0, preferably ≥ 3.5, particularly preferably in the range from 4.0 to 5.5; This is achieved by Lyocell staple fiber, which is characterized by a combination of:

[0051] Furthermore, the object of the present invention can also be obtained by the process according to the invention using the crosslinking agent NHDT, which further has the following properties: The fibers have a fineness in the range of 0.6 dtex to 1.2 dtex, preferably 0.7 dtex to 1.15 dtex, particularly preferably 0.8 dtex to 1.1 dtex. - the fibers have a residual crimp, the fibers have a fiber strength in the normal weight state of at least 40 cN / tex, preferably in the range of 42 cN / tex to 49 cN / tex, particularly preferably in the range of 43.5 cN / tex to 46 cN / tex; the fibers have a Hoeller coefficient F1 ≥ 2.8, preferably ≥ 3.0, particularly preferably in the range from 3.2 to 3.5, and the fibers have a Hoeller coefficient F2 ≥ 3.0, preferably ≥ 3.6, particularly preferably in the range from 3.9 to 5.5; This is achieved by Lyocell staple fiber, which is characterized by a combination of:

[0052] In a preferred embodiment variant, these fibers having a fineness of 0.6 dtex to 1.2 dtex and 1.2 dtex to 1.5 dtex as described above each have a coefficient of variation CV of wet abrasion resistance of 50% or less, in particular 45% or less. NSF It has.

[0053] In commercially produced fibers, there are usually multiple fibers, and those skilled in the art will understand that the term "fiber fineness" as used herein refers to the average of several measurements, preferably 20 measurements, on several fibers.

[0054] The fibers of the present invention differ primarily from commercially available crosslinked lyocell fibers produced by conventional post-tow treatments in the residual crimp characteristics described above.

[0055] Compared to NHDT-crosslinked lyocell fibers produced in fleece post-treatment, the fibers according to the invention are distinguished by their increased fiber strength, especially in the positive weight state.

[0056] Furthermore, the fibers according to the present invention have a significantly lower CV, as explained above. NSF In this case, it differs from Lyocell fibers crosslinked with NHDT by fleece post-treatment.

[0057] In 1984, Holler and Puchegger (Melliand Textilberichte 1984, 65, 573-574) introduced a "new method to characterize regenerated cellulose fibers."

[0058] The authors provide a graph reflecting the properties of the fiber based on the two calculated coefficients, which are plotted on two axes to generate the so-called "Hoeller graph," in which different fiber types have different regions.

[0059] The mechanical properties that generate these two coefficients Fiber Fiber properties are well known to experts and can be found in BISFA "Testing methods for viscose, modal, lyocell and acetate staple fibers and tows" ["Test methods for viscose, modal, lyocell and acetate staple fibers and tows"] 2004 edition, Chapter 7, and can be tested accordingly.

[0060] The two Hoeller coefficients F1 and F2 are calculated as described below: F1=-1.109+0.03992*FFk-0.06502*FDk+0.04634*FFn-0.04048*FDn+0.08936*BISFA elastic modulus+0.02748*SFk+0.02559*KFk, and F2=-7.070+0.02771*FFk+0.04335*FDk+0.02541*FFn+0.03885*FDn-0.01542*BISFA modulus+0.2891*SFk+0.1640*KFk, During the ceremony, FFk is the fiber strength in the normal state, FDk is the elongation of the fiber in the normal state, FFn is the fiber strength in the wet state, FDn is the elongation of the fiber in wet condition; BISFA modulus is the wet modulus at 5% elongation, SFk is the hook strength in the correct state, SDk is the hook elongation in the correct state, KFk is the nodal strength in the normal state, is.

[0061] According to Lenzinger Berichte 2013, 91, 07-12, fibers from different production processes (e.g., direct dissolution vs. derivatization) can be clearly distinguished from each other on the Hoeller graph. Even within the direct dissolution fiber type, fibers produced from different direct solvents (e.g., fibers spun from solution in ionic liquids vs. from solution in NMMO) have different regions.

[0062] Commercially available lyocell fibers (uncrosslinked) exhibit Hoeller F1 values ​​between 2 and 3 and Hoeller F2 values ​​between 2 and 8 (WO 2015 / 101543 and Lenzinger Berichte 2013, 91, 07-12). Fibers produced from direct solution in ionic liquids range from Hoeller F1 values ​​between 3 and 5.5 and Hoeller F2 values ​​between 7 and 10.5 (Lenzinger Berichte 2013, 91, 07-12). WO 2015 / 101543 discloses a new lyocell fiber type with a lower range of Hoeller F2 values ​​between 1 and 6 and Hoeller F1 values ​​between -0.6 and the upper right boundary, defined by F2-4.5*F1 ≥ 3, especially ≥ 1.

[0063] Thus, WO 2015 / 101543 describes (uncrosslinked) lyocell fibers with a specific position on the Hoeller graph. The claimed lyocell fibers were produced using a mixture of high-quality wood pulp with a high alpha content and a low content of non-celluloses, such as hemicellulose, to achieve a specific molecular weight distribution and optimized spinning parameters. This involves reducing the effect of air gaps, carrying out spinning at high temperatures, and using lower draw ratios. Despite not being crosslinked, the fibers are characterized by increased wet abrasion resistance.

[0064] Further forms of non-crosslinked lyocell fibers in other regions of the Hoeller graph are disclosed in WO2019 / 170670A1.

[0065] The fibers according to the invention have Hoeller coefficients F1 ≥ 2.1 and F2 ≥ 3.0 for finenesses in the range of 1.2 dtex to 1.5 dtex, and F1 ≥ 2.8 and F2 ≥ 3.0 for finenesses in the range of 0.6 dtex to 1.2 dtex. Crosslinked lyocell fibers with such high Hoeller coefficients F1 and F2 for the respective finenesses have not yet been described.

[0066] The table below shows the parameters relevant to the determination of the Hoeller coefficient for some example Lyocell fibers A to H. fiber Summarizes the parameter values.

[0067] [Table 1]

[0068] Fiber A is a commercially available crosslinked fiber having mechanical crimps, produced according to conventional post-tow treatment, and was treated with a crosslinking agent different from the crosslinking agent used to produce fibers according to the present invention.

[0069] Fiber B is a commercially available crosslinked lyocell fiber that has been treated with the same crosslinking agent as the fiber according to the invention, but Fiber B has also been produced by a post-tow treatment.

[0070] Fiber C is a commercially available fiber produced by fleece post-treatment and treated with the same crosslinking agent as the fiber according to the invention.

[0071] Fiber D, like fiber C, is an ultra-fine fiber produced by fleece post-treatment and treated with the same crosslinking agent as the fiber according to the invention, and differs significantly from fiber C in its low fineness.

[0072] Another comparison was made with Fiber E, a standard non-crosslinked Lyocell fiber. This comparison allowed us to see the effect of the crosslinking process. fiber It is possible to estimate the effect on the parameters.

[0073] Also shown is fiber F, a non-crosslinked lyocell microfiber. This fiber is used to compare crosslinked microfibers or to evaluate the crosslinking process of microfibers. fiber It is also suitable for determining the effect on parameters.

[0074] Table 1 above shows the Hoeller coefficients of fibers G and H according to the present invention. According to this, fiber G is a fiber having a fineness within the range of fibers A, B, C, and E, which are not according to the present invention. Fiber H is an ultrafine fiber having a fineness within the range of fibers D and F, which are not according to the present invention. Table 1 shows that the Hoeller coefficients of the fibers according to the present invention are significantly different from the Hoeller coefficients of the other crosslinked lyocell fibers A to D, and also from the Hoeller coefficients of non-crosslinked lyocell fibers E and F, especially when compared with fibers within the same fineness range.

[0075] In FIG. 3, which shows the results of a number of measurements on fibers of types A to H, the difference between the Hoeller coefficients F1 and F2 can be seen even more clearly graphically.

[0076] Thus, the fibers according to the invention exhibit extremely high strength.

[0077] In particular, conventional fleece post-treatments result in a significant loss of fiber strength as a result of damage during the crosslinking reaction, as shown for fibers C and D. The damage occurs due to hydrolysis of the cellulose chains. The chains become shorter, which results in a decrease in fiber strength.

[0078] Conversely, fibers produced by post-tow treatment, in addition to a lack of residual crimp, exhibit the drawback of extremely brittle fibers, regardless of crosslinker chemistry. This is evident from the low snag and knot strengths of fibers A and B. In this case, fibers G and H according to the invention yield excellent values, meaning that embrittlement problems did not occur, resulting in significantly higher Hoeller coefficients F2.

[0079] Most notably, the Hoeller coefficient F1 also increases compared to the standard fibers (fibers E and F), because the weighting of the fiber elongation in the dry and wet states (FDk, FDn) is negative in it. In particular, the wet elongation (FDn) is significantly reduced due to cross-linking of the fibers.

[0080] Additionally, the yarn length (SDk) is also important. Similarly, low yarn length equals brittle fibers. Brittle fibers lead to poor processability, which is due, among other things, to the formation of dust during the spinning process.

[0081] The fibers according to the invention are also superior to commercially available lyocell fibers crosslinked with NHDT in terms of their fiber elongation in the normalized state (FDk), which is preferably 10% or more, particularly preferably 10% to 11%.

[0082] As a result of such properties, the fibers according to the invention preferably have a working capacity of 380%*cN / tex or more. The working capacity as shown in Table 2 is obtained from the product of the fiber strength FFn [cN / tex] and the elongation FDk [%].

[0083] [Table 2]

[0084] Compared to commercially produced fibers crosslinked with NHDT, the fibers according to the invention also have an increased nitrogen content at the same amount of crosslinking agent, i.e. a higher efficiency of the crosslinking reaction.

[0085] Furthermore, the fibers according to the invention are preferably characterized by a wet abrasion resistance (NSF) of at least 300 revolutions per dtex (r / dtex), preferably at least 400 r / dtex, particularly preferably at least 450 r / dtex. Non-crosslinked lyocell fibers have an NSF of approximately 40 to 80 r / dtex.

[0086] The content G (in moles) of crosslinking agent per kg of cellulose (atro) in the fibers according to the invention preferably corresponds to the following formula: G×R=0.10 to 0.45, preferably 0.10 to 0.35, particularly preferably 0.20 to 0.35 where R represents the number of reactive groups in the crosslinker, as previously defined above. Follow.

[0087] Particularly preferably, the content of the crosslinking agent of the compound of formula (I) is 2.0 to 3.0% by weight based on the cellulose (atro).

[0088] The present invention also relates to a fiber bundle containing at least 20 kg of lyocell staple fiber according to the invention. The present invention thus provides commercial quantities of fiber according to the invention.

[0089] Such quantities of lyocell staple fiber would not be producible in laboratory systems with one or only a few spinnerets, especially those with only a few spinholes, such as those used for scientific research.

[0090] On the flip side, of course, there are certain differences between such laboratory systems and commercial production. fiber There are significant differences regarding the issue of fiber manufacturability with parameters.

[0091] The present invention also provides a method for producing a lyocell staple fiber according to the present invention. fiber Regarding goods.

[0092] fiber The article is preferably provided in the form of a yarn. In either case, the production of the yarn also requires a certain amount of fiber, in other words, at least several kg of fiber, which would not be possible to produce in a laboratory system such as the one described above.

[0093] In Table 3 below, yarn data for two fiber bales (Comparative Bales 1 and 2) of commercially produced fiber C are illustrated in comparison with one bale of each of inventive fiber G produced according to Examples 2 and 5 as further shown below.

[0094] [Table 3]

[0095] In addition to high yarn strength and yarn elongation, bales made from the fibers according to the invention have improved product quality due to the reduced thickness and fineness variations and the number of nits. The dust value is also reduced due to the mentioned reduced fiber brittleness. This improves the processability of the fibers on the spinning machine.

[0096] Detailed Description of the Drawings Figure 1 is a block diagram of the process steps as they are carried out to produce a preferred embodiment of the fiber according to the invention. The initial washing of the fiber (to remove the solvent) and the contacting and reaction of the fiber with the cross-linking agent are carried out while the fiber is still in the form of (continuous) cellulose filaments, i.e. in the form of a tow. The cellulose filaments are only cut into staple fibers after washing away the cross-linking agent. The individual steps are listed below in chronological order: 1) Generation of spinning solution; 2) fiber spinning, which involves extrusion of filaments from a solution of cellulose in an organic solvent and precipitation of the cellulose to form continuous cellulose filaments; 3) Cleaning of cellulose filaments, utilizing tow cleaning; 4) Impregnation by contacting the cellulose filaments with a cross-linking agent; 5) Reaction of cellulose filaments with cross-linking agent in a reaction chamber; 6) Washing the treated cellulose filaments to remove the cross-linking agent; 7) Cutting of the washed cellulose filaments into staple fibers; 8) Formation of nonwoven fleece from staple fibers; 9) Dewatering by pressing the nonwoven fleece; 10) Finishing the nonwoven fleece and pressing the nonwoven fleece again; 11) Drying; 12) Fiber bale production.

[0097] Figure 2 shows a polarized light micrograph of a preferred embodiment of a lyocell staple fiber according to the invention (Example 1 from Table 4 below). With the aid of linearly polarized light, the irregular squeeze points maintained on the dry fiber during spinning are visualized. According to WO 97 / 14829, "residual crimp" is understood to mean the presence of an average of at least two squeeze points per millimeter of filament length. The fiber of Figure 2 has the valuable property of "residual crimp", which results from the final process steps h) and i) of the method according to the invention (process steps 9 to 11 in Figure 1, respectively). The microcrimp of the lyocell staple fiber of Figure 2 amounts to 107 / 2 cm.

[0098] FIG. 3 shows a Hoeller diagram 50 with a comparison of Hoeller coefficients F1 and F2 of prior art lyocell fibers and preferred embodiments of lyocell staple fibers according to the present invention.

[0099] Figure 50 shows the results of measurements on fibers of type A to type H. See Table 1 and the explanations related to fibers A to H. Axes 51 and 52 correspond to the Hoeller coefficients F1 and F2, respectively. Figure 50 can then be divided into several regions 53 to 58, where region 53 contains the points of fibers A and B, region 54 contains the points of fibers C and D, region 55 contains the points of fiber E, and region 56 contains the points of fiber F. Fibers G (region 57) and H (region 58) according to the invention are clearly separated from the other regions 53 to 56. [Example]

[0100] Examples 1 to 5 Continuous cellulose filaments were spun in a semi-commercial pilot plant in a manner known per se to form fiber tows, which were continuously washed to render them free of NMMO. After washing the tows, the fiber tows were pressed to minimize carryover of wash water to subsequent impregnation baths. The impregnation bath contained a cross-linking agent (NHDT) and was continuously enriched with cross-linking agent from a strong bath. Immediately after contact with the cross-linking agent, a sodium hydroxide solution was applied in a further bath. The sodium hydroxide bath was also continuously enriched with sodium hydroxide solution to maintain a suitable constant concentration over time.

[0101] To reduce side reactions, the vessel was cooled to 10° C. The fiber tow thus modified was then introduced into a steam chamber designed in the form of a J-box.

[0102] The residence time could be measured using the corresponding markings on the tow and a stopwatch.

[0103] The fiber tow was drawn from the J-box and subjected to a crosslinker wash to remove excess chemicals. Immediately thereafter, the tow was fed to a cutting tower to form staple fibers. The fiber staple was rinsed with water and subjected to the formation of a nonwoven fleece. After the nonwoven fleece was formed, the nonwoven fleece was pressed and subjected to finishing. The finished nonwoven fleece was pressed again, opened by a nonwoven fleece separator, and dried in a suitable dryer to form finished fibers, which were then fed to a baler.

[0104] Table 4 below summarizes the test parameters of several tests (Examples 1-5) for the production of fibers according to the present invention having a fineness in the range of approximately 1.35 dtex. The experiments demonstrate the effect of various important production parameters, namely NHDT dosage, alkaline bath concentration, and residence time.

[0105] [Table 4]

[0106] In Example 2, the increased production rate resulted in a decreased residence time, demonstrating that crosslinked fibers can be similarly produced, but at a lower nitrogen loading.

[0107] Table 5 below further shows the test parameters of several tests (Examples 6-8) for the production of ultrafine fibers according to the present invention having a fineness in the range of approximately 0.9 dtex. The production parameters NHDT dosage, alkaline bath concentration, and residence time were kept essentially constant throughout the tests. The test data therefore represent the results of the tests for fibers produced by the method according to the present invention. fiber It shows the natural, production-related variation of the parameters.

[0108] [Table 5]

[0109] All Examples 1 to 8 show a coefficient of variation of wet abrasion resistance, CV, regardless of the fineness of the produced fibers. NSF is below 45% in each case, or even below 40% in the majority of examples.

[0110] In principle, the technique according to the invention is also suitable for various other modifications on fiber strands, such as, for example, the application of reactive dyes which are then crosslinked.

[0111] However, the technology according to the invention is also generally suitable for the application of other modifiers than crosslinkers, such as, for example, chitosan (WO2010 / 031091A1).

[0112] In addition to the above-mentioned crosslinking agent NHDT, other crosslinking agents, such as those described in the above-mentioned documents, or other reactive resins that cure under the influence of atmospheric humidity, oxygen, or temperature, such as single- or multi-component systems, especially epoxies, acrylates, polyurethanes, and similar compounds, can also be used. In particular, the conditions required for applying the chemicals can be very easily adjusted. For example, the impregnation bath can be heated. The reaction chamber can also be adapted to the required temperature or residence time, respectively.

[0113] Test Method Determination of wet abrasion resistance (NSF) Wet abrasion resistance (NSF) is a key value for the resistance of a fiber to fibrillation. This key value was determined using the wet abrasion method described in "Zur Fasernassscheuerung von Viskosefasern", Faserforschung und Textiltechnik 19 (1968), No. 10, pp. 447-452. In this process, the fiber is rolled over a moist roller and rubbed off. The number of revolutions until the fiber breaks in half is determined.

[0114] The abrasion resistance of a single fiber, preloaded in the wet state by a preload weight, is determined using a steel rotating shaft covered with a filament hose (viscose filament stocking). The number of revolutions until the fiber wears and breaks is counted and related to the fineness of the respective fiber.

[0115] To calibrate the measurement or to ensure that wear of the filament stocking does not affect the measurement, the wet abrasion resistance of the calibration fiber is determined at regular intervals, in particular at least daily. The calibration measurement value should preferably not deviate by more than 20% from the long-term average value of all calibration measurements using a new filament stocking; otherwise, the filament stocking must be replaced. Within the scope of the present invention, TAHT-crosslinked Lyocell staple fiber of the type LENZING® Lyocell A100 from Lenzing AG (Werkstrasse 2, A-4860 Lenzing) with a fineness of 1.3 dtex (e.g., produced by the process described in WO 95 / 28516) was used for calibration. The long-term average wet abrasion resistance NSF of all calibration measurements for this fiber was 471 r / dtex.

[0116] The wet abrasion resistance was determined by utilizing a Lenzing Instruments device "Delta 100." The steel shaft was continuously moved longitudinally during the measurement to avoid grooves in the filament hose.

[0117] The source of the filament hose (viscose filament stocking) was VOM BAUR GmbH & KG. (Markstrasse 34, D-42369 Wuppertal).

[0118] From the 20 strands of fiber, one fiber with a length of 38 mm is placed on a steel shaft with a thickness of 1 cm in each case and loaded with a preload weight. The steel shaft, covered with a filament hose, is continuously moistened during rotation. During the measurement, the steel shaft is rotated at a speed of 500 revolutions per minute and simultaneously moved back and forth diagonally to the axis of the fiber, resulting in a pendulum movement of approximately 1 cm.

[0119] The number of revolutions was determined until the fiber was abraded and the preload weight touched the contact. After 5000 revolutions, the measurement should be stopped in any case to avoid erroneous readings. The measured wet abrasion resistance NSF is obtained by dividing the average of all 20 measurements of the number of revolutions by the fineness of the respective fiber [r / dtex].

[0120] Test parameters: Water flow rate: 8.2 mL / min Rotation speed: 500 rpm Wear angle: 40° Preload weight: 50mg

[0121] 200 r / dtex and above, especially 400 r / dtex and above, constitute low fibrillation (LF) fibers, or fibers that are resistant to fibrillation in conventional wet processes.

[0122] Coefficient of variation of wet abrasion resistance CV NSF Decision CV of Lyocell staple fiber according to the present invention NSF is the standard deviation of wet abrasion resistance (NSF) σ NSF and the expected value μ NSF is the ratio of: CV NSF =σ NSF / μ NSF . Since it is only possible to determine wet abrasion resistance using measurements from samples with limited sample size, the average NSF value across measurements from random samples is used. * The expected value μ NSF Therefore, the approximated CV * NSF is the standard deviation s NSF The average value of NSF * This is obtained by normalizing with: CV * NSF =s NSF / NSF * . CV determined from random samples as sample size n → ∞ * NSFis the CV determined from the expected value NSF converges to.

[0123] If the sample size is insufficiently small or the sample is inappropriate, for example, if fibers are taken from only a portion of the sample, the determined CV * NSF is thereby CV NSF There is a possibility of significant deviation from

[0124] Therefore, the coefficient of variation, CV, of Lyocell staple fiber NSF To determine a meaningful value of NSF, a sufficiently large sample of fibers from a sufficiently large sample (e.g., a fiber bale) should be used to determine each NSF. For this purpose, it is preferable to take fiber tufts from different locations in the sample and determine the NSF of each fiber from the fiber tuft as described above. Thus, at least 20 fiber tufts from different locations in the bale should be used to determine the average NSF * and the coefficient of variation, CV * NSF is determined from these 20 measurements.

[0125] As a check, additional samples of fibers from at least 20 different fiber tufts are again taken and examined independently of the previously selected fiber tufts. The average NSF value is then calculated from all the predetermined NSF values ​​of all the samples. * and the coefficient of variation, CV * NSF The average NSF thus obtained is calculated. * or coefficient of variation CV * NSF If differs by more than 10% from the previously determined value for the first sample, and especially if it differs by more than 5%, the above procedure must be repeated until sufficient convergence of the determined values ​​is obtained.

[0126] Depending on the homogeneity of the sample to be tested, a total random sample of more than 100 fibers, and in some cases more than 1000 fibers, may be required in this manner to determine the coefficient of variation.

[0127] Nitrogen analyzer for determining nitrogen loading by combusting a sample The nitrogen loading for the fiber is determined by measuring the N content by burning the sample (for example, using a LECO FP 328 nitrogen analyzer), from which the amount of crosslinker can be determined.

[0128] Counting microcrimps To obtain a composite sample, fibers were removed from a fiber sample taken from a fiber bale at various positions. A drop of glycerin was placed on a slide, and several individual fibers from the composite sample were placed as straight as possible in it. A cover glass was placed on top of the drop of glycerin containing several individual fibers. The slide was placed under a polarizing microscope. The number of microcrimps within an area (2 × 2 cm) of the cover glass was counted.

[0129] Dust test (yarn) Dust formation in the spinning process is induced, for example, by brittle fibers and their poor processability. Dust formation was measured in a pilot plant. The fiber to be tested was wound. Approximately 500 g of yarn was wound at a bobbin speed of 1000 m / min. The amount of wound yarn was determined to the nearest 1 mg. The fiber dust generated in this process was collected and weighed to the nearest 0.1 mg using an analytical balance. The amount of fiber dust is a clear indication of the degree of mechanical damage done to the fiber during processing in the spinning mill. The higher the amount of dust [ppm], the more sensitive the fiber is during processing.

[0130] The following formula was used for the calculation: Dust (unit: ppm) = (measured fiber dust [g] * 1,000,000) / amount of wound yarn [g] For example: 97.83 ppm = (0.0520 g * 1,000,000) / 531.512 g

[0131] Thin / thick patches and knits Yarns have various surface irregularities, such as thinness variations, thickness variations, and knits. Testing for thinness variations, thickness variations, and knits was performed using the following steps: The yarn to be tested was checked using a USTER® Tester. The tester uses a capacitance method to determine the weight variation of fiber strands, thereby inferring surface irregularities. The average yarn weight was determined based on the first 100 meters of the yarn. The subsequent 1000 meters of yarn were measured to the nearest 1 cm. The deviation from the initial measured average was recorded. The number of deviations (-50% for thinness variations, +50% for thickness variations, and +>100% for knits) was counted. Knits are thickness variations shorter than 1 cm and exhibit a yarn weight deviation from the average yarn weight of >100%. The USTER® Tester usually indicates how many knits occurred with a deviation of >140% or >200% (see Table 3).

Claims

1. Steps in the following order: a) extruding filaments from a solution of cellulose in an organic solvent; b) precipitating cellulose to form continuous cellulose filaments; c) washing the cellulose filaments; d) contacting the cellulose filaments with a cross-linking agent; e) reacting the cellulose filaments with a cross-linking agent in a reaction chamber; f) washing the treated cellulose filaments; g) cutting the washed cellulose filaments into staple fibers; h) forming a nonwoven fleece from the staple fibers and pressing the nonwoven fleece; i) applying a finishing touch to the nonwoven fleece and pressing the nonwoven fleece; 1. A method for producing lyocell staple fiber, comprising:

2. 2. The method according to claim 1, wherein the nonwoven fleece is dried only after step i).

3. 3. The method according to claim 1 or 2, characterized in that the reaction in step e) is carried out with an energy input.

4. 4. The process according to claim 3, characterized in that the reaction in step e) is carried out in the presence of steam.

5. 5. The method of claim 4, wherein step e) is carried out in a steam chamber.

6. 6. The method according to claim 1, wherein the duration of step e) is between 3 and 30 minutes.

7. The crosslinking agent is used in an amount such that there is a content G (in moles) of crosslinking agent per kg of cellulose (atro), said content G being in accordance with the following formula: G x R = 0.10 to 0.45 where R represents the number of reactive groups in the crosslinker.

7. The method according to claim 1, wherein the first and second electrodes are connected to a first electrode.

8. Compounds of formula (I) 【Chemical 1】 where X represents a halogen, R=H or an ionic moiety, and n=0 or 1.

8. The method according to claim 1, wherein a salt of this compound is used as a crosslinking agent.

9. 9. The method of claim 8, wherein the salt of the compound is a sodium salt.

10. 10. The method according to claim 8 or 9, characterized in that the crosslinking agent of the compound of formula (I) is used in an amount of 30 to 80 g per kg of cellulose (atro).

11. The fiber, It has residual crimp and the coefficient of variation (CV) of wet abrasion resistance ＮＳＦ ) is 50% or less, particularly 45% or less, and Compounds of formula (I) 【Chemistry 2】 1. A lyocell staple fiber crosslinked with a compound of formula (I) wherein X represents a halogen, R=H or an ionic moiety, and n=0 or 1, or a salt of this compound.

12. The following characteristics: - the fibres have a fineness ranging from 1.2 dtex to 1.5 dtex; - the fibers have residual crimp; - the fibers have a fiber strength of at least 36 cN / tex in the normal weight state; - the fibers have a Hoeller coefficient in the range F1 ≥ 2.1; - the fibers have a Hoeller coefficient in the range of F2 ≥ 3.0; - the fibres are made of a compound of formula (I) 【Chemistry 3】 wherein X represents a halogen, R=H or an ionic moiety, and n=0 or 1, or a salt of this compound; Lyocell staple fiber is characterized by a combination of:

13. The following characteristics: - the fibres have a fineness ranging from 0.6 dtex to 1.2 dtex; - the fibers have residual crimp; - the fibers have a fiber strength of at least 40 cN / tex in the normal weight state; - the fibers have a Hoeller coefficient in the range of F1 ≥ 2.8; - the fibers have a Hoeller coefficient in the range of F2 ≥ 3.0; - the fibres are made of a compound of formula (I) 【Chemistry 4】 wherein X represents a halogen, R=H or an ionic moiety, and n=0 or 1, or a salt of this compound; Lyocell staple fiber is characterized by a combination of:

14. 14. Lyocell staple fiber according to claim 12 or 13, characterized in that the fiber has a wet abrasion coefficient of variation (NSF CV) of 50% or less.

15. 15. Lyocell staple fiber according to any one of claims 11 to 14, characterized by a fiber elongation of 10% or more in the normal weight state.

16. 16. Lyocell staple fiber according to any one of claims 11 to 15, characterized by a wet abrasion resistance (NSF) of 300 r / dtex (revolutions / dtex) or more.

17. The following formula: G x R = 0.10 to 0.45 where R represents the number of reactive groups in the crosslinker.

17. Lyocell staple fiber according to any one of claims 11 to 16, characterized in that it has a content G (in moles) of crosslinking agent per kg of cellulose (atro) according to:

18. 18. Lyocell staple fiber according to claim 17, characterized in that the content of crosslinking agent of compound of formula (I) amounts to 1.8 to 4.5% by weight, based on cellulose (atro).

19. A fiber bundle containing at least 20 kg of lyocell staple fiber according to any one of claims 11 to 18.

20. A textile article comprising the lyocell staple fiber according to any one of claims 11 to 18.

21. 21. The fibrous article of claim 20 in the form of a yarn.

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