Fibre treatment

Description: TECHNICAL FIELD [Detailed description of the invention]

Field of invention The present invention relates to a method for reducing the tendency of lyocell fibers to become fibrilized. It is known that cellulose fibers can be produced by extrusion from a solution of cellulose in a suitable solvent into a coagulation bath. This method is called "solvent spinning", and the cellulose fibers produced thereby are called "solvent spinning" cellulose fibers or lyocell fibers. Lyocell fibers should be distinguished from cellulose fibers produced by other known methods, which are due to the production of soluble chemical derivatives of cellulose fibers and the subsequent decomposition to regenerate cellulose. For example, it is based on the viscose method. One example of a solvent spinning method is described in US Pat. No. 4,246,221, the contents of which are incorporated herein by reference. Cellulose is dissolved in an aqueous tertiary amine N-oxide, such as N-methylmorpholine N-oxide. The resulting solution is then extruded into an aqueous coagulation bath through a suitable die to form filaments, which are washed in water to remove solvent and then dried. Fibers tend to become fibril, especially when subjected to mechanical stresses in wet conditions. Fibrillation occurs when the fibrous structure breaks in the longitudinal direction, thereby allowing the fine fibrils to partially detach from the fibers, giving the fibers and fabrics containing the fibers, for example, woven and knitted fabrics a fluffy appearance. Give. Dyed fabrics containing fibrillated fibers tend to have a "frosted" appearance, which can be aesthetically unpleasant. It is believed that such fibrillation is caused by mechanical friction of the fibers during treatment of the fibers in wet and swollen conditions. Wetting processes, such as the dyeing process, always cause the fibers to undergo mechanical friction. In general, the higher the treatment temperature and the longer the treatment time, the higher the tendency for fibrillation to occur. Lyocell fibers are particularly sensitive to such friction, and as a result, they are often more prone to fibrillation than other types of cellulose fibers. The present invention relates to a method for treating lyocell fibers to reduce or prevent the tendency of lyocell fibers to become fibrilized. However, some of these treatment methods adversely affect the mechanical properties of the fiber, such as toughness and elongation, by making the fiber brittle, for example, or the processability of the fiber and fabric, especially dyeing. It has been found that it can adversely affect sexuality. It can be difficult to find a treatment method that sufficiently reduces the fibrillation tendency without such adverse effects. Background technology EP-A-538,977 describes a method of providing solvent-spun cellulose fibers with a reduced fibrillation tendency, wherein the chemistry has 2 to 6 functional groups that are reactive with cellulose. The fibers are treated with reagents. The chemical reagent can be a polyhalogenated polyazine, a compound containing a polyazine ring containing two or more vinyl sulfone groups, or a precursor thereof. The fibers can be treated with an aqueous solution of a chemical reagent in an undried or pre-dried state, and the aqueous reagent solution can be made weakly alkaline by the addition of sodium carbonate, sodium bicarbonate or sodium hydroxide. However, when the solvent-spun fibers are treated with a halogenated polyazine-type reagent, the reduction in fibrillation tendencies thus obtained is that the fabric containing the treated fibers is scoured and washed. It is known that it tends to be lost when it is used. It is believed that such reagents react with cellulose to produce multiple aromatic / aliphatic ether groups, which tend to be chemically hydrolyzed during fabric processing and washing. WO-A-94 / 24343, published on October 27, 1994, discloses a similar method. FR-A-2273091 describes a method for producing polynosic viscose rayon fibers having a reduced tendency to crosslink, where the fibers are at least two acrylamide groups in the primary gel state of polynosic viscose rayon production. It is treated at temperatures below 100 ° C with a cross-linking agent containing and an alkaline catalyst. 1,3,5-Triacryloylhexahydro-1,3,5-triazine and N, N'-methylenebisacrylamide are preferred examples of cross-linking agents. The dye affinity of the fiber is not changed by this treatment. The method described in FR-A-2273091 suffers from the drawback of requiring a processing time of 5 to 15 minutes. Such times are unacceptably long in the fiber manufacturing process, where line speeds are generally in the range of 10-100 m / min, especially if the fibers are processed in an uncut form as tow. .. Disclosure of the present invention An object of the present invention is to provide a method for reducing the fibrilization tendency of lyocell fibers, which can be rapidly implemented under fiber manufacturing conditions. A further object of the present invention is a method of reducing the tendency of lyocell fibers to become fibrilized, in which the treated fibers retain resistance to fibrilization during the next wetting process such as scouring, dyeing and washing. Is to provide. A further object of the present invention is to provide lyocell fibers with improved dyeability. According to the present invention, an aqueous solution containing (1) an inorganic alkali and a chemical reagent having a plurality of acrylamide groups dissolved therein is applied to undried fibers by a method for reducing the fibrillation tendency of Riocel fibers. Here, the average number of acrylamide groups per molecule of the chemical reagent in solution is at least 2.1, and (2) the fibers after application of the chemical reagents are heated between the fibers and the chemical reagents. A method is provided that is characterized by causing the reaction of. Examples of suitable inorganic alkalis include sodium hydroxide, sodium silicate and trisodium phosphate, (trisodium orthophosphate), which would be preferred. A mixture of alkalis, such as a mixture of both sodium hydroxide and trisodium phosphate, can be used. The chemical reagent is preferably 3 acrylamide groups (-NHCOCH = CH).₂Group), and preferably 1,3,5-triacryloylhexahydro-1,3,5-triazine. The hydroxyl group in the cellulose molecule reacts with the acrylamide group in the chemical reagent by Michael addition, thereby cross-linking the cellulose molecule. The solution can generally contain 5 to 50, preferably 10 to 20 g / liter of chemical reagents. It has been found that this type of chemical reagent tends to hydrolyze in aqueous alkaline solutions, especially at high pH, during long storage times, or when long coating times are used. If the degree of hydrolysis is excessive, for example, if the average number of acrylamide groups per molecule in the solution is less than about 2 when the solution is applied to the fibers, it was imparted by treatment with chemical reagents. , It turns out that protection against fibril is reduced or eliminated. The average number of acrylamide groups per molecule in solution can also be referred to as the functional value of the reagent. It is preferably at least 2.2, and even more preferably at least 2.5. For reagents with 3 acrylamide groups, the functional value of the reagent is preferably close to 3, but in practice, hydrolysis in solution results in a functional value of 2.9 or 2.7 or less. It was further found that chemical reagents initially containing only two acrylamide groups exhibited an unsatisfactory reduction in fibrillation tendencies than chemical reagents initially containing three or more acrylamide groups. The pH of the solution containing the alkali and chemical reagents is preferably in the range of 11-14, more preferably in the range of 11.5-12.5. It was found that if the pH was below the preferred range, the reaction rate would be undesirably slow. It was further found that if the pH was above the preferred range, the rate of hydrolysis of the functional groups in the chemical reagents would be undesirably rapid. The concentration of inorganic alkali in the solution is selected to set the pH to the desired value. The concentration of inorganic alkali in solution is generally about 1-100 g / liter, preferably about 20-about 50 g / liter for weak alkalis such as trisodium phosphate, or caustic soda such as sodium hydroxide. Then, it is about 2 to about 10 g / liter. Fibers treated by the methods of the invention often contain 0.25 to 3% by weight of cellulose-bound (immobilized) chemical reagents relative to air-dried fibers. The amount of immobilized reagent can be evaluated, for example, by measuring the nitrogen content of the fiber. It was surprisingly found that useful protection against fibrillation can also be obtained with fixed reagent amounts as low as 0.25 to 1%. This is advantageous because reagents suitable for use in the present invention are often expensive and therefore it is desired to minimize the amount used. Fixed reagent amounts in the range of 0.4-0.8% have been found to provide a useful balance between protection against fibrillation and expense. It has been found that the fibers treated by the method of the present invention generally have at least the same dye affinity as the dye affinity of the untreated fibers. This is noteworthy because the cross-linking treatment generally reduces the dyeability of the cellulose fibers. It was also found to be even more surprising that fibers containing 1-3% immobilized reagents exhibited advantageous dyeability with certain dyes, such as certain directly reactive dyes, than untreated fibers. .. Therefore, the present invention provides a method for improving the dyeability of riocell fibers, wherein the present invention does not contain (1) a solution containing an inorganic alkali and a chemical reagent containing a plurality of acrylamide groups dissolved therein. Applying to dry fibers and (2) heating the fibers coated with chemical reagents to cause a reaction between the fibers and the chemical reagents, thereby based on the weight of the air-dried fibers. In addition, it is characterized in that 1 to 3% by weight of a chemical reagent is immobilized on the fiber. The aqueous solution used in the method of the present invention can further contain sodium sulphate, preferably at a concentration in the range of 10-50 g / liter, calculated as an anhydrous salt. It has been found that the addition of sodium sulphate can improve the efficiency and / or rate of reaction of chemical reagents with cellulose. The method of the present invention can be carried out by passing lyocell fibers through an aqueous circulating bath containing both inorganic alkali and chemical reagents. Chemical reagents are susceptible to hydrolysis in such a circulating bath, and the volume of the bath is therefore preferably as small as possible. Alternatively, separate solutions of inorganic alkali and chemical reagents can be mixed immediately prior to application to the fibers and applied to the fibers, for example by padding or spray application. Yet another, such separate solutions can also be applied individually to the fibers. In this procedure, which can be preferred, the first solution is applied to the fibers, for example in a circulating bath or by padding or spraying, and if necessary, then squeezed to squeeze the excess solution. And then the second solution can be applied to the fibers, for example by padding or spray application. The separate solutions may be applied to the fibers in any order. If sodium sulphate is used, sodium sulphate may be included in any separate solution. The temperature of the solution is generally chosen with care for the criteria required for the chemical reagent to be applied in a dissolved state in the fiber, and is often in the range of 60 ° C from the ambient temperature. After application of the chemical reagent solution to the fiber, the pH of the solution in contact with the fiber will generally be lower than the solution of the coating agent. This is due to the buffering effect of the carboxyl groups commonly present in the cellulose molecule. Therefore, when separate solutions of inorganic alkali and chemical reagents are applied to the fibers, the pH of the solution in contact with the fibers does not necessarily have to be in the preferred range for a single solution prior to application to the fibers. Absent. If this procedure is used, the pH of the aqueous solution containing the inorganic alkali and the chemical reagent containing multiple acrylamide groups described above is the pH of the mixture of the separate solutions at the ratio at which the separate solutions are applied. It is defined as being. After applying the inorganic alkali and chemical reagents to the fibers in aqueous solution, the wet fibers undergo an immobilization step to cause the fibers to react with the chemical reagents. The temperature of the heat treatment is considered to be the maximum temperature that can be reached during the immobilization step. It is usually at least about 50 ° C, can be at least 80 ° C, and can be up to about 100 ° C, or up to about 140 ° C. The fibers coated with the solution are preferably heated to a temperature higher than the coating step, for example by steaming or microwaves, to cause a reaction between the cellulose and the chemical reagents. Dry heating is generally less preferred. The total processing time (application and immobilization) is generally less than 3 minutes, preferably less than 2 minutes, more preferably less than 1 minute. This short processing time is a special advantage of the present invention. A further advantage of the present invention is the effective use of chemical reagents. After treatment of the chemical reagents with an alkaline solution according to the method of the invention, the fibers are washed and dried. This washing step preferably comprises washing with a dilute aqueous acid solution such that the pH of the dried fibers is in the range of about 4.5 to about 6.5. The present invention further provides a method for the production of lyocell fibers with reduced fibrillation tendencies, the method of which is: (a) A step of dissolving cellulose in a solvent to form a solution, wherein the solvent is miscible with water. (b) A step of extruding the solution through a die to form a fiber precursor. (c) A step of passing the fiber precursor into at least one aqueous bath to form fibers. (d) A step of applying an aqueous solution containing an inorganic alkali and a chemical reagent having a plurality of acrylamide groups to the fiber, wherein the average number of acrylamide groups per molecule of the chemical reagent in the solution is at least 2.1. (e) A step of heating the fiber at at least 50 ° C, thereby causing a reaction between the chemical reagent and the fiber. (f) The step of washing the fibers and (g) Step of drying the fiber, Including. The fibers are undried fibers at the end of step (c) and at steps (d) and (e) and generally have a moisture absorption rate of 120-150%. The present invention further provides a method of reducing the fibrilization tendency of riocell fibers, the method of which is an inorganic alkali and at least three in aqueous solution at a temperature of at least about 50 ° C in the undried state of the fibers. It is treated with a chemical reagent having an acrylamide group, wherein the pH of the solution before application to the fiber is in the range of 11.5 to 14, preferably in the range of 11.75 to 12.5. The advantage of the present invention is that it can be carried out at various line speeds, i.e. in a manufacturing plant for producing lyocell fibers in stretched form fiber tow. The fibers are protected against fibrillation in the early stages, especially before the wetting process of dried fibers or fabrics made from them, such as woven or knitted fabrics. Such wet processing operations include scouring, dyeing and washing. The present invention is illustrated by the following examples. The material is evaluated for the degree of fibrillation using the method described below as Test Method 1 and the tendency for fibrillation using the technique described as Test Method 2 or 2A. Test method 1 (evaluation of fibrillation) There is no internationally accepted standard for evaluating fibrillation, and the following method was used to evaluate the fibrillation index (FI). We identified a series of fibers, from non-fibrillated fibers to highly fibrillated fibers. Then, the standard length of the fiber of each sample was measured, and the number of fibrils (fine fluff extending from the body of the fiber) was calculated along the standard length. The length of each fibril was measured, and the number of fibrils x any number of average lengths of each fibril was determined for each fiber. The fiber with the highest arbitrary number was identified as the most fibrillated and the arbitrary fibrillation index was set to 10. Fibers that were not fibrillated at all were given a fibrillation index of 0, and the remaining fibers were graded from 0 to 10 relative to any number measured under a microscope. The fibers measured were then used to form a standardized scale. Five to ten fibers were visually compared to microscopic standardized samples to determine the fibrillation index of all other fiber samples. The visually determined number for each fiber was then averaged to provide a fibrillation index of the tested sample. It will be appreciated that visual decisions and averaging are many times faster than measurements. And those skilled in the art of textiles have found to be coherent with respect to textile grading. In general, fabrics containing fibers with a FI of 2 or greater can have a "blurred" appearance. The desired target for fiber FI is 1 or less, preferably 0.5 or less in fabrics, including washed fabrics. Test method 2 (induction of fibrillation) A) Refining process. 1 g of fiber was placed in a stainless steel cylinder about 25 cm long x 4 cm in diameter and having a capacity of 250 ml. Add 50 ml of a regular refining solution containing 2 g / l Detergyl FS955 (anionic cleaner available from ICI plc) and 2 g / l sodium carbonate, screw cap and cap cylinder at 95 ° C. 60. It mixed upside down at 60 rpm for 1 minute. The smelted fibers were then rinsed with hot and cold water. B) Blender processing. 0.5 g of scoured fiber was cut to a length of 5-6 mm and dispersed in 500 ml of water at ambient temperature, placed in a household blender (liquefaction machine), and the blender was run at about 12000 rpm for 2 minutes. .. The fibers were then harvested, dried and evaluated for fibrillation using Test Method 1. Test method 2A (induction of fibrillation) This is the same as in Test 2, but the smelting process (A) was omitted. Test method 3 (fiber treatment) The following general procedure was used to evaluate the fiber treatment status. A solution of cellulose in aqueous N-methylmorpholine N-oxide (NMMO) was extruded into an aqueous coagulation bath to form 1.7 decitex riocell filaments, washed with water until it was substantially free of NMMO. These undried Riocel filaments or fibers are swirled in a hot aqueous bath containing 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAHT) and the following alkalis to 0.5 ml / Rinse with an aqueous acetic acid solution of l and dry. Test method 4 (fiber treatment) The following general procedure was used to assess the fiber treatment status. A solution of cellulose in aqueous N-methylmorpholine N-oxide (NMMO) was extruded into an aqueous coagulation bath to form 1.7 decitex riocell filaments, which were washed until substantially free of NMMO. These undried filaments are then passed through a coating unit containing 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAHT) and alkali, and in some cases sodium sulfate. It was. It was then squeezed with a nip before passing through the steam environment for immobilization of TAHT on the fibers. The steaming time was 1-2 minutes unless otherwise instructed. The filaments were then washed with water or dilute acid and then with water to remove all unwanted treatment chemicals. Test method 5 (Measurement of TAHT concentration and functional value) The following test method was used to evaluate the average number (functionality) of acrylamide machines per molecule in aqueous solution containing TAHT and its hydrolysis products, and the concentration of TAHT in such solutions. It has been found that the UV spectrum of TAHT shows absorption peaks at 195 and 230 nm, and the UV spectrum of its hydrolysis products shows a peak at 195 nm. Absorption measurements can be conveniently performed using a solution containing 5-20 mg / l TAHT with a 10 mm pass length. The concentration of TAHT in aqueous solution can be determined by comparing the absorption peaks measured at 230 nm to the calibration curve obtained using a solution in pure water of known concentration. It has been found that the average functional value in a solution containing TAHT and its hydrolysis products can be evaluated by the following equation. F = (A₂₃₀/ A₁₉₅-0.057) /0.1423 (In the formula, F is the functional value, and A₂₃₀And A₁₉₅Are absorptions measured at 230 nm and 195 nm, respectively. ) Concentrations and functional values of other chemical reagents containing multiple acrylamide groups can be determined by similarly designed, experimentally confirmed methods. Example 1 The undried Riocel filament (1.7 decitex) was treated by Test Method 4. Aqueous filament (134 g / min) containing 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAHT), sodium sulfate (usually 20 g / l) and trisodium phosphate (TSP) Passed through the bath. Add solid TAHT (3.4 gl / min) and TSP (5.8 g / min) and sodium hydroxide solution (5% solution) into the circulating solution using an in-line high shear mixer / pump. This bath was maintained in a constant state (TAHT concentration, 10.8 to 16.0 g / l, TSP concentration, 15.8 to 20.5 g / l, temperature, 46 to 51 ° C, and pH, 11.6 to 12.0). (The functional value of TAHT was evaluated by Test Method 5.). The fibers were then niped before being exposed to saturated steam for 2 minutes. The fibers were then washed and dried and the fibrillation tendencies were assessed by Test Methods 1 and 2. The amount of immobilized TAHT was evaluated by Kjuldahl nitrogen analysis. The results are provided in Table 1.<img file="JPP3479079B2_D0001.tif" />Example 2 Another alkali Test method 4 was performed using an aqueous bath containing TAHT (15 g / l) and various alkalis. Full details are provided in Table 2.<img file="JPP3479079B2_D0002.tif" /> This indicates that various alkalis can be used in the methods of the present invention. Immobilization efficiency is the ratio of the amount of chemical reagent bound to the air-dried fiber to the amount present on the fiber after the coating process. Example 3 Test Method 3 was performed using a bath containing 40 g / l TAHT and 30 g / l TSP (trisodium orthophosphate) for 30 seconds at 80 ° C. In a series of experiments, the bath further contained 50 g / l sodium sulphate decahydrate (Glauber salt). The fibers were then treated by various methods for an additional 30 seconds, as shown in Table 3. Fibrilization occurred by Test Method 2 and was evaluated by Test 1. The results are shown in Table 3.<img file="JPP3479079B2_D0003.tif" /> Zero fibrillation was observed when TAHT was used with or without sodium sulphate. Addition of sodium sulfate increased the degree of immobilization of TAHT. Example 4 An aqueous solution containing 40 g / l TAHT and inorganic alkali was padded on undried lyocell fibers at 80 ° C. and the fibers were steamed at 98% / 100% relative humidity for 1 minute to 0.5 m / l acetic acid. Rinse with aqueous solution and dry. Fibrilization occurred by Test Method 2 and was evaluated by Test Method 1. The results are shown in Table 4.<img file="JPP3479079B2_D0004.tif" /> A significant decrease in fibrillation tendency was observed in all cases. Example 5 Use of sodium hydroxide. Test Method 4 was performed using a solution at 50 ° C containing TAHT (15 g / l) and various concentrations (shown in Table 5) of sodium hydroxide.<img file="JPP3479079B2_D0005.tif" />Example 6 Undried lyocell fiber (1.7 decitex), 1,3,5-triacrylloylhexahydro-1,3,5-triazine (TAHT) (initially 17 g / l), sodium sulfate (initially 17 g / l) ) And sodium hydroxide (initially 3.5 g / l) and passed through an aqueous bath (temperature 52-56 ° C, pH 12.0-12.4) (134 g / min). During the test, solid reagents and sodium hydroxide solution were added to the circulating solution in an attempt to maintain constant conditions during the test, except when due to hydrolysis of TAHT. The functional value of TAHT in the solution was measured by Test Method 5. The fibers were then squeezed with a nip and then exposed to saturated steam for 2 minutes. The fibers were then washed, dried and evaluated for fibrillation by Test Methods 1 and 2. TAHT immobilization levels were evaluated by Kjeldahl nitrogen analysis. The results are provided in Table 6.<img file="JPP3479079B2_D0006.tif" /> Under these conditions, TAHT suffers from transient hydrolysis in the treatment bath after the first few minutes, so samples with longer test times represent comparative examples. The protection against fibrillation imparted by the treatment decreased with increasing test time. The fibrillation index of this sample was unacceptably high, with an evaluable amount of TAHT immobilized on the fibers. It would be assessed that a lower TAHT immobilization level (less than 1%) desired for commercial reasons would provide even lower protection. Example 7 This experiment was designed to evaluate the effect of steaming time. Test method 4 was followed using a treatment solution containing TAHT (15 g / l) and trisodium phosphate (20 g / l). The results are shown in Table 7.<img file="JPP3479079B2_D0007.tif" /> The results show that under the conditions used for this treatment, the immobilization efficiency flattens with a steaming time of about 90 seconds or longer. Shorter immobilization times can be obtained by quickly preheating the toe prior to steaming or by using microwaves. Example 8 Immobilization using microwaves. Test method 4 was performed using TAHT (15 g / l) and trisodium phosphate (20 g / l) at 50 ° C. Samples were processed in batches and fixed for various times using a 700 W microwave oven instead of steaming. The results are provided in Table 8.<img file="JPP3479079B2_D0008.tif" />Example 9 Using an aqueous solution of TAHT and trisodium phosphate, constant conditions with respect to concentration and pH (12.8 to 13.9 g / l TAHT, 20.3 to 26.0 g / l, under conditions selected to minimize hydrolysis of TAHT. Test method 4 was performed using a feed of TAHT, trisodium phosphate and sodium hydroxide to maintain TSP, pH 11.79-11.95). The excess solution was squeezed out by passing the solution-coated fibers through the nip, crimped by passing it through the stuffer box, and folds were removed in the steaming box (J-box). 7.5 minutes after the start of the test, the first steam hose was connected to the steaming box (J-box), and 14 minutes after the start of the test, the second steam hose was connected. After a test time of 20 minutes, the temperature inside the steaming box was consistently about 100 ° C, measured by thermocouples at various locations. The residence time of the fibers in the steaming box was about 10 to 15 minutes. Table 9 shows the results of the fibers taken at various test times after the device was stabilized.<img file="JPP3479079B2_D0009.tif" />Example 10 Test Method 3 using different TAHT solution concentrations provided undried fibers with TAHT to provide different TAHT levels immobilized on the fibers. Use 20 g / l TSP at a temperature of 80 ° C. It was then treated with John Jeffries Hank Dyer for 30 minutes at a solution / product ratio of 20: 1. Table 10 shows the physical characteristics of the treated fibers.<img file="JPP3479079B2_D0010.tif" />The results show that with increasing TAHT, toughness and elongation decrease slightly. This reduction is considered acceptable for textile applications. Notably, the water absorption rate increased with increasing TAHT immobilization levels. This would indicate that cross-linking of the fibers in the swollen state increases the ability of the dried fibers to absorb water when re-wetted. The ability to control the rate of water absorption is an advantage of the present invention. Example 11 Undried lyocell fibers treated with TAHT by Test Method 4 (2.1-1.5 g / l TAHT, nominal 20 g / l TSP, pH 11.84-11.49) and contain 1.6-2.0% immobilized TAHT. Fiber samples were provided. These samples were spun into yarn and the yarn was woven into fabric. These fiber samples and untreated controls were dyed directly with dye under the following conditions: 10: 1 solution / product ratio, solution temperature 50 ° C, dye amount 3% owf. The fabric was immersed in a dyeing bath and operated for 10 minutes. NaCl was added to 4 g / l and the mixture was run for 10 minutes. The temperature was raised to 95 ° C. for 30 minutes, NaCl was added to a total of 20 g / l, and the mixture was operated for 30 minutes. It was cooled to 80 ° C for 10 minutes and operated for 15 minutes. The fabric was rinsed with hot and cold water, spin dried and dried. During the dyeing process, the solution in the dye bath was sampled and analyzed by visible spectrum to determine the rate of dye absorption. The results are expressed as% of dye depletion in the dyeing bath in comparison with the amount initially present, and are shown in Table 11.<img file="JPP3479079B2_D0011.tif" /> In these and other experiments, the dye absorption rates of untreated and treated lyocell fibers were similar. The main difference was the depth of the shade. In many cases, treated lyocell fibers are dyed in a deeper shade than untreated lyocell (absorbing more dye). This is advantageous because of both the potential for cost savings and the potential for dyeing deeper shades. Deeper shades can be described quantitatively using relative color depth values (Q-values). The Q-value is the relative color depth of a sample with respect to a particular standard sample that has a color depth given a value of 100. The surface color depth can be expressed as a solution of K / S over the range of 400-700 nm, where K is the absorption coefficient and S is the scattering coefficient. K / S can be calculated from the reflection value of the surface at a specific wavelength. The K / S solution is proportional to the amount of dye in the fabric. In a color comparison of fabrics dyed with one dye, a difference in Q-value of 5% or more will generally be visually different with the naked eye. Q-values are provided in Table 12 and TAHT-treated samples are shown in comparison to the corresponding untreated samples. The dye absorption rate indicates the ratio of the dye on the fiber compared to the amount initially present in the dye bath.<img file="JPP3479079B2_D0012.tif" /> Lyocell fibers treated by the methods of the invention have been found to be dyed in a deeper shade than untreated fibers in some cases, which corresponds substantially to the absorption of higher dyes. Example 12 Undried lyocell fibers in the form of tow were treated with TAHT by Test Method 3 to provide samples with varying amounts of TAHT immobilized on the fibers. Dried lyocell fibers were treated with TAHT in a similar manner. Treatment was performed using John Jeffries Hank Dyer for 30 minutes at 20 g / l TSP at a temperature of 80 ° C and a 22: 1 solution / product ratio. Samples were then stained with Direct Green 26 (1% owf) and the Q-value of the stained samples was evaluated against pretreated pre-dried Riocerto as standard. The results are shown in Table 13.<img file="JPP3479079B2_D0013.tif" /> All TAHT-treated dry fibers were dyed with a lighter shade than TAHT-treated undried fibers. In addition, all the fibers in the undried state treated with TAHT were deeply stained as compared with the untreated control sample. Example 13 Fibers containing undried lyocell fibers treated with TAHT according to Test Method 4 (2.1 to 1.5 g / l TAHT, nominal 20 g / l TSP, pH 11.84 to 11.49) and containing 1.6 to 2.0% immobilized TAHT. Samples were provided. These samples were spun into yarn and the yarn was woven into fabric. Fabrics made from these fabrics and untreated lyocell fibers were dyed with a range of reactive dyes. The staining history is shown below. Start with 25 ° C dye (1.1% by weight dye on fiber) Run for 10 minutes Sample 1 Raise to 80 ° C for 30 minutes, subdivide and Na₂SO₄Add sample 2 Run for 20 minutes, Na for 10 minutes₂SO₄Add sample 3 Run for 15 minutes Sample 4 Run for 45 minutes Sample 5 Fabric samples were removed at various times, rinsed with cold water and washed with soap. The amount of dye in various solutions was evaluated by a visible spectroscope. The% absorption of the dye from the dye bath to the fibers was evaluated from the amount of dye remaining in the dye solution. It is also called exhaustion. The percentage of dye on the fiber after rinsing the dye remaining in the fiber after washing with soap was evaluated by relative color intensity measurement using a visible spectroscope. The results are shown in Table 14.<img file="JPP3479079B2_D0014.tif" /> Results using Procion Yellow HE4R and Procion Red HE7B are typical (Procion is a trademark of ICI plc). Absorption rates were faster on TAHT-treated fabrics, and exhaustion continued to higher levels. The dye immobilization rate was similar for the two fabrics, but the final immobilization level of the TAHT treated fabric was higher than that of the control lyocell fabric. As described above, the TAHT-treated fabric showed higher dye use efficiency than the control. In addition, the TAHT treated fabrics were dyed with a deeper shade than the controls. Shorter dyeing cycles are possible given the faster exhaustion of TAHT treated fabrics.