MXPA96006129A - Lyopellular fiber and a process for suffering - Google Patents

Abstract

The present invention relates to a process for the manufacture of lyocell fibers with a greater tendency to fibrillation, including the steps of: (1) dissolving cellulose in a solvent to form a solution, (2) extruding the solution through a matrix for forming a plurality of filaments, and (3) washing the filaments to remove the solvent, whereby the cell fiber is formed, characterized by the step of (4) subjecting the cell fiber to effective conditions to reduce the Degree of Polymerization of cellulose at least 200 unit

Description

* FIBER DE LIOCÉLÜLA AND A PROCESS FOR YOUR MANUFACTURE Field of the Invention This invention relates to a process for manufacturing lyocell fiber with an increased tendency to fibrillation and to the lyocell fiber which has an increased tendency to fibrillation. It is known that cellulose fiber can be made by extruding a cellulose solution in a suitable solvent in a coagulation bath. This process is referred to as "spinning with solvents" and the cellulose fiber produced by it is referred to as cellulose fiber "spun with solvents" or as a lyocell fiber. Lyocell fiber should be distinguished from cellulose fiber made by other known processes, which depend on the formation of a soluble chemical derivative of cellulose and its subsequent decomposition to regenerate cellulose, for example, the viscose process. Lyocell fibers are known for their impressive physical properties, such as tensile strength, compared to fibers such as viscose rayon fibers. An example of a solvent spinning process is described in U.S. Patent No. 4,246,221, the content of which is incorporated herein by reference. The cellulose is dissolved in a solvent such as an aqueous N-oxide of tertiary amine, for example N-methylmorpholine N-oxide. The resulting solution is then extruded through a suitable matrix in an aqueous bath to produce a set of filaments which is washed with water to remove the solvent and subsequently dried. The fibers may exhibit a tendency to fibrillation particularly when subjected to mechanical stress in the wet state. Fibrillation occurs when the structure of the fiber is broken down in the longitudinal direction so that fine fibrils of the fiber are partially detached, giving a hairy appearance to the fiber and the fabric containing it, for example woven cloth or knitted fabric. Said fibrillation is believed to be caused by the mechanical abrasion of the fibers during the treatment in a wet and expanded state. Higher temperatures and longer treatment times tend to produce higher degrees of fibrillation. Lyocell fiber appears to be particularly sensitive to such abrasion and consequently it is often found that it is more susceptible to fibrillation than other types of cellulose fiber. Intensive efforts have been made to reduce the fibrillation of lyocell fibers. The presence of fibrillated fibers is useful in certain end uses. For example, filter materials containing fibrillated fibers generally have high efficiency. Fibrillation is induced in papermaking processes by splitting the fibers, which is generally known to increase the strength and transparency of the paper.

Fibrillation can also be used in the manufacture of non-woven fabrics, for example hydroentangled fabrics, to provide improved cohesion, protection and strength. Although the tendency to fibrillation of lyocell fibers is higher than that of the other cellulose fibers, it is not always as great as may be desired for some end uses. It is an object of the present invention to provide lyocell fiber with a higher tendency to fibrillation. Disclosure of the Invention The present invention provides a process for the manufacture of lyocell fiber with a greater tendency to fibrillation, including the steps of: (1) dissolving cellulose in a solvent to form a solution, (2) extruding the solution to through a die to form a plurality of filaments, and (3) washing the filaments to remove the solvent, whereby the lyocell fiber is formed; and the characteristic step of (4) subjecting the cell fiber to effective conditions to reduce the Degree of Polymerization of the cellulose by at least about 200 units. The solvent preferably comprises a tertiary amine N-oxide, more preferably N-methylmorpholine N-oxide (NXMO), and generally contains a small proportion of water. When a water miscible solvent is used, such as NMMO, the filaments are generally washed in step (3) with an aqueous liquor to remove the solvent from the filaments. The lyocell fiber at the end of step (3) is in the form of never dried and generally requires drying. In one embodiment of the invention, the degradation step (4) is performed on the never dried fiber which is subsequently dried. In another embodiment of the invention, the fiber is dried between steps (3) and (4). The use of the degradation step (4) according to the invention in the previously dried fiber may be convenient if discontinuous processing times or longer treatment times are desired. The previously dried fiber can be treated in the form of fiber, yarn or fabric, including woven, knitted and non-woven fabric. Lyocell fiber is produced in the form of tow which is commonly converted into short length fiber for processing, either in the state of never dried or dried. A lyocell tow can be converted into staple fiber either before or after the degradation step (4) and before or after drying. The lyocell fiber manufactured by the process of the invention can be non-pigmented (bright or raw) or pigmented, for example by incorporating a matte pigment such as titanium dioxide.

The degree of polymerization (G.P.) of the cellulose is conveniently evaluated by viscosimetry of a dilute solution of cellulose in a solvent which is an aqueous solution of a metal / amine complex, for example, cuproammonium hydroxide solution. A suitable method, based on TAPPI Standard T206, is described below as Test Method 1. The G.P. of cellulose is a measure of the number of anhydroglucose units per molecule. It will be understood that the G.P. measured in this way is a G.P. of the average viscosity. The desired reduction in G.P. of the cellulose in the degradation step (4) can be achieved in different ways. In one embodiment of the invention, the G.P. is reduced by a bleaching treatment, preferably using a bleach liquor. The bleach liquor can be applied to the fiber by passing through a bath, padding, or spraying, for example, particularly by spraying the liquor onto a fiber tow coming out of a roller contact line. Bleaching of the never dried fiber may be performed using an aqueous solution comprising a hypochlorite such as sodium hypochlorite, for example a solution containing 0.1 to 10, preferably 0.25 to 4, more preferably 0.5 to 2, percent by weight of NxOCl ( expressed as available chlorine). The bleach liquor may optionally further contain an alkali such as sodium hydroxide, for example up to about 0.5 or up to about 1 weight percent sodium hydroxide.

Alternatively, the pH of the bleach liquor can be controlled in the range of 5.5 to 8, preferably around 6 to 7. It has been found that degradation is relatively rapid in these pH ranges. A hypochlorite bleach liquor can be applied, if desired, to the fiber at elevated temperature, for example about 50 ° C. The less concentrated bleach liquors can be used in the discontinuous treatment of the previously dried lyocell fiber. For example, the bleach liquor may contain 0.1 to 1 weight percent of available chlorine and the bleaching may be carried out at a slightly elevated temperature, for example 30 to 60 ° C, from 1 to 3 hours. The bleaching can alternatively be performed using an aqueous solution comprising a peroxide, in particular hydrogen hydroxide, for example a solution containing 0.5 to 20, preferably 1 to 6, more preferably 1 to 4, percent by weight of hydrogen peroxide. A peroxide bleach liquor preferably also contains an alkali such as sodium hydroxide, for example about 0.05 to 1.0 weight percent sodium hydroxide. The pH of an alkaline peroxide bleach liquor is preferably in the range of 9 to 13, more preferably 10 to 12. Preferably, no peroxide stabilizer is used. Alkyl peroxide solutions (pH 1 or less) can alternatively be used. A peroxide bleach liquor is preferably applied to the fiber at room temperature or less to decrease the undesired decomposition of peroxide. It has been generally found that peroxide bleaching liquors are less effective in reducing G.P. of the cellulose that the hypochlorite bleach liquors and consequently the latter can be preferred if large reductions in the G.P. are desired. The effectiveness of a peroxide treatment can be increased by pretreating the lyocell fiber with a solution of a transition metal ion which catalyzes the decomposition of the peroxide ions, for example copper or iron cations. It will be appreciated that said pretreatment is preferably used in conjunction with a peroxide liquor application technique which does not include a circulation bath. The effectiveness of a bleaching treatment such as hypochlorite or peroxide bleach can alternatively be improved by exposure to ultraviolet variation. After the fiber has been moistened with a bleach liquor, preferably it is heated to induce and accelerate the degradation reaction during which the G.P. of cellulose is reduced. For example, a lyocell fiber tow moistened with bleach liquor can be passed through a heated steam tunnel or box J. Wet or superheated steam can be used. The temperature in a steam tunnel can be in the approximate range of 80 to 130 ° C and the residence time can be in the range of 10 to 200 or 20 to 60 seconds, although it will be understood that the temperature and time should be choose taking into consideration the degree of reduction in the GP of the desired cellulose. Other types of equipment can be used such as a J-box or a base steam machine if longer vaporization times are desired, for example in the range of 5 to 30 minutes. Alternatively, the fiber moistened with a hypochlorite bleach liquor can be treated with aqueous acid or an acid solution or particularly a neutral buffered solution to cause degradation. Alternatively, the previously dried lyocell fiber can be subjected to the degradation step (4) according to the invention using conventional bleaching equipment for cotton, for example bleaching autoclave. In addition, alternatively, the never-dried or previously dried lyocell fiber can be subjected in the form of tow or fiber cut from the degradation step (4) according to the invention using conventional equipment for the wet continuous treatment of the wet spun fibers. . For example, the lyocell fiber can be spread on a continuous woven wire belt and then be passed under a series of sprinklers or other liquor distribution apparatuses alternating with mangle rolls, using the type of equipment generally known for washing rayon of freshly spun viscose. Longer treatment times are more easily obtained using such alternative types of equipment than when a wetted tow is passed through a steam tunnel. Alternatively, other treatments may be used bleaching known in the art for cellulose, for example bleaching of chlorite. Aggressive conditions should generally be chosen to ensure a considerable reduction in the G.P. In another embodiment of the invention, the G.P. of the '"' ') Cellulose is reduced by treating the lyocell fiber with an aqueous acid The acid is preferably a mineral acid, more preferably hydrochloric acid, sulfuric acid or in particular nitric acid For example, the fiber can be moistened with a solution containing 0.2 to 4.5 percent weight of concentrated nitric acid in water. After wetting with acid, the fiber is preferably heated to cause the desired reduction in G.P., for example by passing through a steam tunnel as described above with respect to aqueous bleaching processes.

After treatment with a bleach or acid liquor to reduce the G.P. of cellulose, the lyocell fiber is usually washed to remove traces of the chemicals used to induce degradation and byproducts and is generally then dried in a manner known.

Other methods known in the art which reduce the G.P. cellulose can also be used, for example exposure to cellulolytic enzymes, electron beam radiation, ozone, ultrasonic vibrations or treatment with peroxy compounds such as peracetic acid, or salts of persulfate and perborate. Combinations of two or more methods can be used. The ultrasonic treatment also serves to induce fibrillation in the fiber. The step of reduction of G.P. (4) generally degrades "*" the tensile properties of the lyocell fibers It would normally be thought that this is very undesirable, however it has been found that the fiber produced according to the process of the invention generally has satisfactory tensile properties for use in the end uses in which fiber with high fibrillation is desired, eg the manufacture of paper and non-woven articles The GP of the cellulose used in the manufacture of known lyocell fiber is commonly in the range of 400 to 1000, often 400 to 700. The cellulose GP in the cellulose fiber 0 produced by the process of the invention may be below 150, more preferably below 200, below 150 or about 100. The GP of the Cellulose in the cellulose fiber produced by the process of the invention is preferably at least 75, because in values lower than this, the fiber tends to disintegrate. although a negative G.P. is a physical impossibility, the cited values of G.P. they are obtained by applying the standard conversion to the viscosity measurements of the solution in the manner described above and not by direct measurement.) The G.P. of the cellulose in the lyocell fiber produced by the process of the invention is preferably in the range of 0 to 350, more preferably 150 to 250, particularly if the G.P. of the lyocell fiber before treatment in the degradation step (4) is in the range of 500 to 600. The G.P. of the cellulose can be reduced by at least 300 units in the degradation step. The G.P. of cellulose can be reduced from 200 to 500 units, often from 300 to 400 units in the degradation step. Surprisingly it has been found that the tendency to fibrillation of the lyocell fiber produced by the process of the invention is markedly higher than that of the lyocell fiber of the same G.P. manufactured using cellulose with G.P. low as the starting material and omitting the step of reducing G.P. of the invention, for example if the G.P. of the fiber is 400. The concentration of the fiber subjected to the degradation step (4) according to the invention can generally be in the range of 0.5 to 30 dtex. It has been found that the process of the invention is more effective in increasing the fibrillation tendency of fibers of relatively low concentration, for example 1 to 5 dtex or 1 to 30 dtex, perhaps due to its higher surface to volume ratio. It has been observed that the tendency to fibrillation of the lyocell fiber is directly related to the cellulose concentration of the solution from which it is made. 5 It will be understood that the elevation of the cellulose concentration generally needs a reduction G.P. of cellulose to maintain the viscosity of the solution below the maximum possible working viscosity. The increase in the tendency to fibrillation feasible by using the process of the invention is generally greater than the feasible increase by raising the cellulose concentration of the solution. The lyocell fiber produced by the process of the invention is useful for example in the manufacture of paper and non-woven articles, either alone or in blends with other types of fiber, including standard lyocell fiber. A slurry for the manufacture of paper containing lyocell fiber produced by the process of the invention requires significantly less mechanical work, for example shaking, refining, disintegration or hydrodisintegration, to reach a chosen grade of refining than the slurry containing lyocell fiber. standard. This is a particular advantage of the invention. The process of the invention can reduce the working time required by a high shear apparatus in the resulting fiber to 50% or less, preferably 20% or 5 less, more preferably 10 percent or less, of the time required to achieve a certain refining using standard fiber. Methods that reduce working time to a value in the range of 20 to 50 percent, or 20 to 33 percent, of the time required for standard fiber can be preferred. The lyocell fiber produced according to the invention can be fibrillated in high constant effort devices as hydrodisintegrators, which induce little fibrillation, or no fibrillation, in conventional fibers under usual operating conditions. The lyocell fiber produced from According to the process of the invention, it can have improved absorbency and wick properties compared to conventional lyocell fiber, making it useful in the manufacture of absorbent articles. The susceptibility of a fiber to fibrillation in mechanical work can be evaluated in a It is convenient to subject a diluted slurry of the fiber to mechanical work under standard conditions and by measuring the drainage (refining) properties of the slurry after various degrees of work. The refining of the grout falls as the degree of fibrillation increases. Lyocell fiber of the prior art is typically capable of being beaten at Refined 400 Canadian Standard, using the decay test defined below as Test Method 3, by a disintegrator number in the range of 200,000 to 250,000 and 200 Refined Standard of Canada by a number of revolutions of disintegrator in the range of 250,000 to 350,000, although sometimes a higher number of revolutions may be required. The invention further provides lyocell fiber capable of being whipped at Refinado 400 Standard of Canada in the decay test by no more than 150,000 5 disintegrator revolutions, in particular by a disintegrator number of revolutions within the range of 30,000 to 150,000 a often within the range of 50,000 to 100,000. The invention further provides lyocell fiber capable of being beaten at Refined 200 Standard of Canada in the Test * ^ D Disintegration for no more than 200,000 disintegrator revolutions, in particular for a number of disintegrator revolutions within the range of 50,000 to 150,000 or 200,000, often within the range of 75,000 to 125,000. It can be considered that the paper made of fiber of The cell in accordance with the invention has a variety of useful properties. It has generally been found that the opacity of the paper containing lyocell fiber increases as the degree of beating is increased. This is contrary to the general experience with paper made from wood pulp. He paper can have high air permeability compared to paper made from 100% wood pulp; this is believed to be a consequence of the generally round cross-section of the fibrous and lyocell fibers. Paper can have good particle retention when used as a filter. The The mixtures of lyocell fiber of the invention and wood pulp provide papers with higher opacity, tear strength and air permeability compared to 100% wood pulp papers. The relatively long lyocell fiber, for example 6 mm long, can be used in papermaking compared to conventional wood pulp fiber, producing paper with good tear strength. Examples of applications for lyocell fiber containing paper according to the invention rj include, but are not limited to, paper for dielectric capacitors, battery separators, stencil paper, paper for filtration including gas, air and smoke filtration and the filtration of liquids such as milk, coffee and other beverages, fuel, oil and blood plasma, security paper, photo paper, washable paper and wrapping paper, special printing paper and tea bags. It is an advantage of the invention that the hydroentangled fabrics can be made of lyocell fiber provided according to the invention at pressures of tangles lower than those required for untreated lyocell fiber for similar fabric properties, at least for short lengths of staple fiber (up to 5 or 10 mm). This reduces the cost of hydroentanglement. Alternatively, a larger degree of hydroentanglement can be obtained at a pressure determined that with lyocell fibers of the prior art. A hydroentangled fabric made of lyocell fiber provided in accordance with the invention may have better tensile properties than a cloth made of untreated lyocell fiber., although it will be understood that the hydroenredo conditions will need to be optimized by trial and error for the best results in any particular case. A hydroentangled fabric containing lyocell fiber provided according to the invention can exhibit high opacity, high particle retention in filtration applications, increased insulating and wetting properties and excellent properties such as a cloth. Examples of applications for hydroentangled fabrics containing lyocell fiber provided according to the invention include, but are not limited to, artificial leather and suede, disposable wipes (including wipes, lint-free, for room and lens cleaning), gauzes including medical gauzes, garment fabrics, filter fabrics, floppy liners, rubber filler sheets, liquid dispensing layers or absorbent covers in absorbent pads, for example diapers, incontinence pads and fillings, surgical and medical insulating fabrics , battery separators, substrates for coated fabrics and interlinings. The lyocell fiber is provided according to the invention can fibrillate to a certain extent during dry processes for the manufacture of non-woven fabric, for example needle drilling. These non-woven fabrics can exhibit improved filtration efficiency compared to fabrics containing conventional lyocell fiber. The fiber provided by the invention is useful in the manufacture of textile articles such as woven or knitted articles, alone or in combination with other types of fiber including lyocell fiber of the prior art. The presence of the lyocell fiber provided by the invention can "^ used to provide desirable aesthetic effects such as a peach skin effect Fibrillation can be induced in such fabrics by known processes such as brushing and agamuzado in addition to the fibrillation generated in the wet processing steps normally found in the manufacture of fabrics. The fiber provided according to the invention is useful in the manufacture of tea bags, coffee filters and similar articles. The fiber can be mixed with other fibers in the manufacture of paper and hydroentangled fabrics. The fiber can be mixed as a protective hair with microglass fiber to improve the strength of the glass fiber paper made therefrom. The fiber can be felted in mixture with wool. Fiber can be used in the manufacture of coarse filter paper for filtration of liquids, such as fruit and vegetable juices, wine and beer. The fiber can be used in the manufacture of coarse filter paper for the filtration of viscous liquids, for example viscose. The fiber can be used in tampons and other absorbent articles with improved absorbency. The lyocell fiber can be usefully fibrillated during dry processing, as well as during wet processing, for example during processes such as grinding, crushing, crushing, brushing and sanding. The fibrils of the fibrillated lyocell fiber can be removed by enzymatic finishing techniques, for example cellulose treatment. «^^ 0 The following procedures identified as Test Methods 1 to 4 were used to evaluate fiber performance: - Method d Test 1 - Measurement of Viscosity v G.P. (the G.P. Test) of Cuproamonic Solution 15 This test is based on Standard TAPPI T206 os-63. The cellulose is dissolved in cuproammonium hydroxide solution containing 15 ± 0.1 g / l of copper and 200 ± 5 g / l of ammonia, with nitrous acid content < 0.5 g / l, (Shirley Institute standard) to give a cellulose concentration solution known accurately (approximately 1% by weight). The flow time of the solution through a Shirley viscometer at 20 ° C is measured, from which the viscosity can be calculated in a standard manner. The G.P. of the average viscosity is determined using the empirical equation: 25 G.P. - 412.4285 ln [100 (tk / t) / nC] = 348 where t is the flow time in seconds, k the constate of gravity, C the tube constant, and n the water density in g / ml at the temperature of the test (0.9982 at 20 ° C). Test Method 2 - Measurement of the Tendency to Fibrillation (Sonication) Ten lyocell fibers (20 ± 1 mm long) are placed in distilled water (10 ml) contained within a glass bottle (50 mm long x 25 mm in diameter). An ultrasonic probe is inserted into the bottle, taking care that the tip of the probe is well centered and placed 5 ± 0.5 mm from the bottom of the bottle. This distance is critical for reproducibility. The bottle is surrounded with an ice bath and the ultrasonic probe is connected. After a set time, the probe is disconnected and the fibers are transferred to two drops of water placed on a microscope slide. A photomicrograph is taken under x20 magnification of an area representative of the sample. The fibrillation index (Cf) is evaluated by comparison with a set of photographic standards classified from 0 (without fibrillation) to 30 (high fibrillation). Alternatively, Cf can be measured from the photomicrograph using the following formula: Cf = nx / L where n is the number of fibrils counted, x is the average length of the fibrils in mm, and L is the length in mm of the fiber at along which the fibrils are counted. The ultrasonic energy level and sonication time (5-15 minutes, standard 8 minutes) required may vary. Equipment calibration must be verified using a fiber sample of known fibrillation tendency (Cf 4-5 by Test Method 2) before use and between each group of five samples. Test Method 3 - Measurement of the Fibrillation Tendency (The Disintegration Test) "" * "*? The lyocell fiber (6 g, cut fiber length of 5 mm) and demineralized water (2 1) are placed in the standard blaster rate described in TAPPI Standard T-205 om-88, and disintegrate (simulating valley batter) until the fiber is well dispersed. available from Mess er Instruments Limited, Gravesend, Kent, ed Kingdom and from Büchel van de Korput BV, Veemendaal, The Netherlands. The Canada Standard Refining (REC) of the fiber in the resulting slurry or paste is measured in accordance with Standard TAPPI T227 om-94 and recorded in ml. In general, the pasta is divided into two 1 1 portions for the REC measurement and the two results are averaged. The REC curves can then be developed against the disintegrator revolutions or decay time and the relative degree of disintegration can be required to achieve a given REC evaluated by interpolation. The zero point is defined as the one that is recorded after 2500 disintegrator revolutions, which serve to ensure the dispersion of the fiber in the pulp before the REC measurement. Test Method 2 is quick to perform, but 5 can provide variable results due to the small sample of fiber. Test Method 3 provides very reproducible results. These factors must be taken into account during the evaluation of the tendency to fibrillation. Test Method 4 - Measurement of the Trend to Fibrillation r ~ > (Vallevi shake Lyocell fiber is tested by shake in accordance with TAPPI T 200 om-85 data sheet except that a paste consistency of 0.9% is used.The beater used is preferably a special one for the lyocell fiber test .

The results are better considered as comparative within each series of experiments. Brief Description of the Drawings Figures 1 and 2 are graphs of the Canada Standard Refined expressed in ml, (y axis) against the beating time, expressed in minutes, (x axis) for the samples in Examples 1 and 2, respectively. Figures 3, 4 and 5 are graphs of the Canadian Standard Refining, expressed in ml, (y axis) against the number of disintegrator revolutions, expressed in thousands of revolutions, (x-axis) for the samples in Examples 3, 4 and 5, respectively. Figures 6 and 7 are graphs of the Canada Standard Refining, expressed in ml, (y axis) against the beating time, expressed in minutes, (x axis) for the samples in Examples 7 and 8, respectively. Figure 8 is a graph of the beating time required to achieve the Canada Standard Refining 200, expressed in minutes, (y axis) against the G.P. of the Fiber (x-axis) for the samples in Example 9. The invention is illustrated by the following examples, in which lyocell fiber was prepared in a known manner by spinning a solution of wood pulp fiber in N-methylmorpholine N -watery oxide: - Example 1 The lyocell fiber tow never dried (samples of 1.7 dtex raw, 300 g) was saturated with an aqueous solution containing hydrogen peroxide (1% by volume) or sodium hypochlorite (1% by weight of available chlorine), and in both cases sodium hydroxide (0.5%) in weight) and placed in a steam engine. The steaming cycle was heated for 7 minutes, 110 ° C for 1 minute and cooled under vacuum for 4 minutes. The vaporized fiber was washed and dried and presented the properties shown in Table 1: Table 1 Ref. G.P. dtex TSA ESA 'TH EH% cN / tex cN / tex No reaction YA 563 0-2 1.76 40.6 13.5 36.7 16.0 Peroxide IB 299 5-15 1.76 34.8 11.1 23.7 11.6 Hypochlorite IC 92 20-30 1.78 23.8 6.8 18.0 8.8 (The G.P. was measured by Test Method 1. The tendency to Fibrillation (Cf) was measured by Test Method 2. TSA = dry traction in air, ESA - dry extensibility in air, TH = traction in wet, EH = wet extensibility.) The fiber was manually cut to 5%. mm, a mesh was formed with it (nominally 60 g / ma), and underwent hydroentanglement using several jet pressures (measured in several). The hydroentangled non woven lyocell fabric thus obtained presented the properties shown in Table 2: Table 2 Ref. Jet Burst load (daN) General drive < * barios D.M. D.M. D.C. D.C. (daN / g) dry humid dry humid dry humid No reaction AI 100 3.56 2-54 4.63 2.75 4.13 2.65 160 3.84 125 3.74 4.01 3.79 3.65 200 3.48 3.16 - - - - Peroxide IB 75 2.77 1-07 2.63 1.51 3.60 1.75 100 5.00 3132 3.51 3.55 5.76 4.56 Hypochlorite IC 75 4.77 IJ2 3.34. 5.49 _ 100 5.06 1.96 4.44 1.92 4.76 1.94 160 4.24 1.46 2.40 1.08 3.45 1.28 5 (DM = machine direction, DC = cross direction) The treated fiber could become a hydroentangled nonwoven fabric stronger than the untreated control fiber under adequate conditions. Notably, several fabrics made from untreated fiber exhibited general dry traction plus 5 high than any of the control fibers. This is remarkable without the treated fiber having inferior tensile properties to the untreated fiber. The lyocell fiber cut was watered to a paste consistency of 0.9% and subjected to valley / * "*" batter using Test Method 4. The relationship between the REC of the pasta and the beating time is shown in Figure 1 and Table 3. It can be seen that much shorter beating times were required to reach the same degree of refining with treated fiber as with untreated fiber. 15 Table 3 Ref. Minimum beat time to reach Sample 200 REC 400 REC Not treated IA 226 155 Peroxide IB 110 85 _, t 'Hypochlorite I C 46 29 Example 2 The never-dried lyocell tow (crude 1.7 dtex) was treated as follows: 2A. Control untreated. 2B. In-line bleaching, sodium hypochlorite solution (1% by weight of available chlorine) at 50 ° C, residence time in a bath of 4 seconds, followed by steaming in a tunnel (100 ° C of steam) for 25 seconds. 2 C. Like 2B, but the residence time in the bathroom of 7 seconds and the time of vaporization of 50 seconds. 2D As 2B, but off line, the residence time in the bath of 60 seconds and vaporized as described in Example 1. 2E. As 2D, but 2% by weight of available chlorine. 2F. As 2D, but using hydrogen peroxide solution (1% by weight). The treated fiber was washed and dried and cut to 5 mm. The lyocell fiber cut was watered to a paste consistency of 0.9% and beaten valley using Test Method 4. The relationship between the REC of the pulp and the whipping time is shown in Figure 2 and the Table 4. It can be seen that much shorter beating times were required to reach the same degree of refining with treated fiber as with untreated fiber. Table 4 Minimum beating time to reach Sample 200 REC 400 REC 2A 248 197 2B 98 75 2C - 61 2D - 50 2E 27 14 2F 109 83 The aqueous suspensions whipped from samples 2A-2E were converted into paper. The physical properties of all the samples (tear strength, burst index, tensile strength and thickness) were very similar. The cut fiber was converted into meshes and hydroentangled as described in Example 1 (jet pressure of 100 bar). The fabric samples thus obtained had the properties shown in Table 5: Table 5 G.P. Tractor Resistance Fiber Fiber CN / tex 2A 524 43.2 18.6 27.9 2B 227 40.9 41.7 62.4 2C 206 36.1 35.2 69.9 2D 159 34.7 45.5 79.6 2E 40 23.3 18.5 49.3 Example 2 was repeated, except that the following treatment conditions were used: 3A As 2A. 3B Online, nitric acid solution (0.72% by weight of concentrated nitric acid) at 50 ° C, residence time in the bath for 4 seconds, followed by vaporization (25 seconds). 3C As 3B, but 2.8% nitric acid. 3D Like 3B, but 4.25% of nitric acid. The treated fiber was washed and dried and cut to 5 mm.

The lyocell fiber cut was subjected to disintegration using Test Method 3. The relationship between the REC of the pulp and the beating time is shown in Figure 3 and Table 6. It can be seen that more beating times were required short to reach the same degree of refining with treated fiber as with untreated fiber. Table 6 Disintegration speed xlOOO to reach Sample 200 REC 400 REC 3A 262 205 3B 221 179 3C 170 138 3D 149 119 Example 4 Example 2 was repeated, except that the following treatment conditions were used: 4A Untreated control. 4B Offline, sodium hypochlorite solution (0.5% by weight of available chlorine) at 50 ° C, residence time in the bathroom for 60 seconds, without vaporization. 4C As 4B, except that the treatment bath also contains 15 g / l of sodium bicarbonate (pH 8.5). No vaporizing was used. 4D As 4B, except that the treatment bath also contains 15 g / l of sodium dihydrogen phosphate (pH 6.8). No vaporizing was used. 4E As 4B, except that the treatment bath also contains 7.5 g / l of citric acid and 7.5 g / l of sodium dihydrogen citrate (pH 5.5). No vaporizing was used. 4F As 2D. The treated fiber was washed and dried and cut to 5 mm. The lyocell fiber cut was evaluated using Test Method 3. The relationship between the REC of the pulp and the whipping time is shown in Figure 4 and Table 7. It can be seen that the addition of bicarbonate or phosphate buffer reduced The beating time required to reach any particular degree of refining. Table 7 XlOOO disintegration revolutions to reach Sample 200 REC 400 REC 4A 315 261 4B 254 221 4C 176 133 4D 86 65 4E 280 230 4F 43 32 Example 2 was repeated, except that the following treatment conditions were used: 5A Untreated control. 5B Hydrogen peroxide solution (1.0% by weight) at 50 ° C, in line at the line speed of 6 m / min (residence in the bath for 7 seconds), followed by steaming for 50 seconds. 5C As 5B, except that the treatment bath also contains 0.5% by weight of sodium hydroxide. 5D As 5C, except that the treatment bath containing sodium hypochlorite (1% by weight of available chlorine) instead of hydrogen peroxide. The treated fiber was washed and dried and cut to 5 mm. The lyocell fiber cut was evaluated using Test Method 3. The relationship between the REC of the pulp and the disintegrator revolutions is shown in Figure 5 and Table 8. It can be seen that the addition of sodium hydroxide reduced the time of whipping required to reach any particular degree of refining when the hydrogen peroxide was cooled as the bleaching agent. Table 8 Disintegration speed x 1000 pair to reach Sample 200 REC 400 REC 5A 246 211 5B 246 214 SC 189 135 5D 121 80 EXAMPLE 6 The lyocell fiber was bleached using the liquors from the treatment bath described in Example 4 under the reference codes 4B, 4C, 4D and 4E at 25 and 50 ° C. The results obtained are shown in Table 9: Table 9 Ucor Temperature ° C PH G.P. dtex Traction Extension cN / tex% inguno - - 548 2.0 37.7 15 4B 25 11.46 524 1.9 37.7 15 4B 50 10.71 406 1.9 37.1 14 4C 25 8.65 489 1.8 35.9 14 4C 50 8.64 376 1.8 33.4 13 4D 25 6.73 298 2.0 28.7 10 4D 50 6.69 308 1.9 24.7 7 4E 25 5.67 526 1.9 37.8 14 The samples treated at 50 ° C were those of Example 4. Hem o_7 A non-pigmented cellulose solution in N-methylmorpholine aqueous N-oxide was extruded through a plurality of spinning nozzles (spinning speed 37 m / min) and It was washed with water. The concentration of the individual filaments was 1.7 dtex and the concentration of the combined tow was 64 ktex. The tow was then first passed through a bath containing aqueous sodium hypochlorite solution (temperature 76-80 ° C, steam spray, residence time of 60 seconds) and then through a circulating bath to which was added continuously sulfuric acid (temperature 67 ° C, pH 8, residence time approximately 5 seconds). The tow was then washed with cold water and dried. The fibrillation tendency of the fiber was evaluated by Test Method 4. The concentration of hypochlorite in the treatment bath and the experimental results are shown in Figure 6 and Table 10.

Table 10 Ref. Chlorine available Minimum beating time to reach% by weight 400 REC 200 REC 7A Control 187 240 7B 0.2 153 204 7C 0.3 120 170 7D 4.47 109 Example 8 Example 7 was repeated except that matte fiber (pigmented with titanium dioxide) was used. The concentration of hypochlorite in the treatment bath and the experimental results are shown in Figure 7 and Table 11. Table 11 Ref. Chlorine available Minimum churning time to reach% by weight 400 RI 200 REC 8A Control 143 197 8B 0.2 122 174 8C 0.45 114 167 8D 0.65 87 126 Example 9 The lyocell fiber was degraded according to the invention under various conditions and its G.P. and shake performance were evaluated using Test Methods 1 and 4 respectively. The relationship between the beat time at 200 REC and the G.P. of the fiber is shown in Figure 8. (The data plotted with a cross are factory tests and the data plotted with a square fill are laboratory tests.) The three samples with G.P. Above 500 are untreated controls. EXAMPLE 10 The lyocell fiber was spun from a solution in N-methylmorpholine aqueous N-oxide of pulp "Viscokraft" (Trade Mark of International Paper Co., USA) of G.P. nominal of 600 with nominal cellulose concentration of 15%, washed, saturated with solutions of various reagents (bath temperature of 50 ° C, residence time of 60 seconds), vaporized in the manner of Example 1 for 60 seconds and dried. The inG.P. and Fibrillation index (Cf) of the fiber were evaluated by Test Methods 1 and 2. Table 12 shows the results obtained: Table 12 Reagents Tempe-atura Vapor ° C GJ ». Cf 15 Control not treated 565 1.3 Series 1 0.5% NaOH 110 567 0.7 0.05% NaOCI 110 548 2.1 0.25% NaOCl 110 427 1.8 0.5% NaOCl 110 306 3.7 1.0% NaOCl 110 178 11.0 2.0% NaOCl 110 44 30.0 Series 2 25 1.0% NaOCI + 0.5% NaOH 508 1.1 Series 3 1.0% NaOCl + 0.5% NaOH 100-120 169 -176 8.7-11.0 1.0% NaOCl + 0.5% NaOH 110 109 20.3 1.0% NaOCl + 0.25% NaOH 110 139 18.4 1.0% NaOCl + 0.5% NaOH 110 155 20.0 1.0% NaOCl + 1.0% NaOH no 168 15.1 1.0% NaOCi + 2.0% NaOH 110 194 7.3 The concentration of NaOCl is expressed in terms of percentage by weight of available chlorine. The concentration of NaOH is expressed in terms of percentage by weight. It will be noted that the bleached samples of G.P. The low fibrillation rates were significantly higher than any of the unbleached samples. It will also be recognized that cellulose solutions whose G.P. is below 200 can not be easily spun to the fiber through the processes of spinning with solvents. Example 11 The never dried lyocell tow was passed through a bleaching bath containing 0.5% by weight of NaOH and a bleaching agent, vaporized (steam temperature 100 ° C), washed and dried. The G.P. of Fibrillation index (Cf) of the dried fiber were evaluated. The experimental conditions and the results are shown in Table 13, Cf being cited as the range observed between different photographs. Table 13 Whitening Bath Time of Steaming G.P. Agent Temperature ° C Time in sec, 'uunnddooss seconds Control. 532 1-2 1.0% H202 60 50 25 426 3-5 l.ll% NaOCI 40 50 50 205 4-12 1.11% NaOC! 40 25 25 249 2-8 1.10% NaOCI 60 50 50 203 4-16 1.10% NaOCl 60 25 25 227 7-14 0.98% NaOCl 70 50 50 221 4-10 0.98% NaOCI 70 25 25 251 2-10 1.00% NaOCI 60 50 25 235 6-8 (The percentage of NaOCl is the percentage by weight of available chlorine, the percentage of H202 is the percentage by weight).

In all cases, there was a considerable increase in the tendency to fibrillation. Example 12 The previously dried bright lyocell fiber of 1.7 dtex and 5 mm (200 kg) was bleached in aqueous sodium hypochlorite (3 g / l of available chlorine) at 40 ° C for 75 minutes, soaked in aqueous sodium metabisulfite ( 1 g / l) as anticloro for 30 minutes, washed with dilute acetic acid to return the pH of the fiber to neutral and dried. The G.P. The nominal cellulose of which the fiber was made was 600 and the G.P. The average fiber treated was 217 (range 177-230, six samples). The results of the Disintegration Test for the treated test and for an untreated control sample are shown in Table 14. Table 14 Disintegrator revolutions 0 100,000 150,000 REC of control sample 650 620 510 Treated sample REC 656 400 80 Example 13 A tow of 8 ktex of never-dried shiny lyocell fiber of 1.7 dtex was passed through a first aqueous bath containing sulfate copper (II) (0.1% p / h) and a second aqueous bath containing hydrogen peroxide (4% p / h) and sodium hydroxide (0.5% p / h). The temperature of each bath was 20-25 ° C and the residence times in the baths were 10 and 131 seconds respectively. The tow was then passed through a steam tunnel at 100 ° C with a residence time of 120 seconds, rinsed and dried. A sample treated as above was also prepared, but with the omission of the copper sulfate bath and an untreated control sample. The results of the decay test are given in Table 15. Table 15 Disintegrator speed x 1000 0 50 75 100 175 200 REC of control sample untreated 697 - - 672 - 611 Sample treated (without CuSCH) 715 - - 491 66 - Sample treated (with CuS04) 702 335 124 - - _ The line indicates that no measurement was made. Example 14 A tow of 5.3 ktex bright lyocell fiber of 1.7 dtex was passed through an aqueous bath containing sodium hypochlorite (17-20 ° C, residence time of 42 seconds), then through a steam tunnel (100 ° C, residence time 120 seconds), rinsed and dried. The tendency to fibrillation was measured by Test Method 3 in fiber cut to 5 mm and the number of disintegrator revolutions (in thousands, krev) required to reach 200 REC was estimated by graphic interpellation. Table 16 shows other experimental details and results Table 16 Bathroom G.P. dtex Traction Extension krev to cN / tex% 200 REC None (control) 533 1.88 36.2 11 307 0. 1% C1.D 429 1.85 36.7 11 228 0. 3% C1.D 341 1.69 37.3 11 190 1. 0% C1.D 154 1.68 34.1 1 100 2. 0% C1.D 49 1-91 22.0 6 61 1. 0% O.D + 0.5% Na? H 242 1.80 37.0 12 140 (Cl.D = available chlorine,% = percentage by weight) Example 15 A tow of 10.6 ktex bright lyocell fiber of 1.7 dtex was passed through an aqueous bath containing sodium hypochlorite (16-18 ° C, residence time of 32 seconds), then through a steam tunnel (100 ° C, residence time of 120 seconds), rinsed and dried. The tendency to fibrillation was measured as described in Example 14. Other details and results of the experiment are shown in Table 17. Table 17 Bathroom G.P. krev to 200 REC None (control) 501 341 0.5% H202 + 0.5% NaOH 180 123 1.0% H202 + 0.5% NaOH 158 113 2.0% H202 + 0.5% NaOH 156 117 3.0% H202 + 0.5% NaOH 147 113 4.0% H202 + 0.5% NaOH 120 87 (% = percentage by weight) EXAMPLE 16 Glossy lyocell tow never dried (various concentrations of fiber, ie dtex) was soaked in an aqueous solution containing sodium hypochlorite (1% by weight of available chlorine) and sodium hydroxide (0.5% by weight), vaporized for 1 minute as described in Example 1, washed, dried and cut to 5 mm in length. The G.P. and tendency to fibrillation (Test Method 3) of the treated fiber and untreated control samples are reported in Table 18. Table 18 Control Fiber treated dtex G.P. REC G.P. REC 0 rev 100 rev 0 rev 100 rev 1. 7 530 685 656 136 658 179 2. 4 540 698 673 140 695 413 3. 4 557 705 696 136 705 560 Example 17 Glossy lyocell tow never dried (1.7 dtex / filament, total 15.4 ktex) was passed at 6.4 m / min through an application bath containing 4 wt% hydrogen peroxide and 0.5 wt% hydroxide of sodium (temperature 17-19 ° C, residence time of 125-130 seconds), then through a steam tunnel (100 ° C, residence time of 120 seconds), washed and dried. The washing step optionally included a wash with 2% by weight hydrochloric acid. The fibrillation properties of the fiber and of an untreated control (measured by the Disintegration Test) are reported in Table 19. Table 19 krev to 400 REC of krev to 200 REC Control 185 235 Treated (12 samples) 75-100 95-120

Claims (17)

1. CLAIMS 1. A process for the manufacture of lyocell fibers with a greater tendency to fibrillation, including the steps of: 5 (1) dissolving cellulose in a solvent to form a solution, (2) extruding the solution through a matrix to form a plurality of filaments, and (3) to wash the filaments to remove the solvent, * "<" whereby the lyocell fiber is formed, characterized by the passage of (4) subjecting the lyocell fiber to conditions effective to reduce the Degree of 15 Polymerization of cellulose at least 200 units.
2. 2. A process according to claim 1, characterized in that the solvent comprises a tertiary amine N-oxide.
3. 3. A process according to claim 2, characterized in that the tertiary amine N-oxide is N-methylmorpholine N-oxide.
4. 4. A process according to any preceding claim, characterized in that the Degree of The cellulose polymerization is reduced in step (4) by at least about 300 units.
5. 5. A process according to any preceding claim, characterized in that the Degree of Polymerization of the cellulose after step (4) is below 5 of approximately 250 units.
6. 6. A process according to any preceding claim, characterized in that the Degree of Polymerization is reduced in step (4) by a bleaching treatment. r * H 1.
7. A process according to claim 6, characterized in that the bleaching treatment comprises the application to the fiber of a bleaching liquor which is an aqueous solution comprising sodium hypochlorite.
8. 8. A process according to claim 7, characterized in that the concentration of sodium hypochlorite in the bleach liquor expressed as available chlorine is in the range of 0.5 to 2.0 weight percent.
9. 9. A process according to claim 6, characterized in that the bleaching treatment comprises the Application to the fiber of a bleach liquor which is an aqueous solution comprising hydrogen peroxide.
10. 10. A process according to any preceding claim, characterized in that the step (4) is made in lyocell fiber never dried.
11. 11. A process according to any of claims 1 to 9, characterized in that the step (4) is made in previously dried lyocell fiber.
12. Paper comprising lyocell fiber, characterized in that at least a part of the fiber of The lyocell has been manufactured by the process of any of claims 1 to 11.
13. 13. Hydro-entangled fabric comprising lyocell fiber, characterized in that at least a part of the lyocell fiber has been manufactured by the process of any * "* -, of claims 1 to 11.
14. 14. Lyocell fiber, characterized in that it is capable of being beaten at Refined 400 Canadian Standard in the Disintegration Test by a number of revolutions of disintegrator in the range from approximately 30,000 to 150,000.
15. 15. The cell fiber according to claim 14, characterized in that it is capable of being beaten at Refined 400 Canadian Standard in the Disintegration Test for a number of disintegrator revolutions in the range of 50,000 to 100,000.
16. 16. Lyocell fiber, characterized in that it is capable of being beaten at Refined 200 Canadian Standard in the Disintegration Test for a number of disintegrator revolutions in the range of 50,000 to 200,000.
17. 17. Lyocell fiber according to the 25 claim 16, characterized in that it is capable of being beaten at Refined 200 Canada Standard in the Disintegration Test by a disintegrator number in the range of about 75,000 to 125,000.