RU2399708C2 - Method of preparing mercerised fibre - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of preparing mercerised fibre involves treatment of cellulose fibre with a mercerising agent with large concentration of dissolved hemicellulose accumulated after continuous recycling of alkaline solutions or through addition of soluble carbohydrates, with concentration of alkali of approximately 5-15% of the total weight of the mixture. Temperature and period of time must be sufficient for preparation of mercerised cellulose fibres which form fibre fabric having air porosity equal to or greater than approximately 100 cubic feet in a minute per square foot, determined using the TAPPI T251 cm-85 at pressure of 125 Pa on hand moulding sheets 60 gcm.

EFFECT: high porosity of material.

8 cl, 4 dwg, 2 tbl, 3 ex

Description

FIELD OF TECHNOLOGY

The present invention relates to a method for the production of mercerized cellulosic fibers and fibrous products prepared from them. The invention also relates to cellulosic fibers, cellulosic sheet materials containing fibers, and articles made therefrom, such as automobile oil, air filters and tobacco products.

BACKGROUND

Mercerized fibers and articles made therefrom are known and described in US Pat. Nos. 5,766,159 and 6,063,982, incorporated herein by reference in their entirety.

SUMMARY OF THE INVENTION

One feature of the present invention relates to mercerized cellulose fibers that form a fibrous web having an air permeability equal to or greater than about 100 cubic meters. feet per minute per sq. ft as determined by TAPPI T251 st-85 on 60 gsm hand-cast sheets at a pressure of 125 Pa, and preferably having a bend index equal to or greater than 2.5 and a curl index equal to or greater than 0.28, measured by a fiber quality analyzer (FQA), manufactured by the Canadian company Optest. Another feature of the present invention relates to a porous fibrous web or paper or paperboard containing mercerized fibers of the present invention. The porosity characteristics of the web make it suitable for use where porosity of the web is desired.

Another feature of the present invention relates to a porous or non-porous paper or cardboard base containing mercerized fibers of the present invention. Another embodiment of the present invention relates to a manufacturing product, the whole body or part of which is made of a fibrous web containing mercerized fibers of the present invention. There are also other products that are not limited to an absorbent liquid absorbent product, such as personal care products, sanitary napkins, tampons, diapers, incontinence pads, surgical sponges, compresses, bandages and handkerchiefs that are disclosed and described in US Pat. 5766159 and 6063982, as well as filter products, such as air filters, which are disclosed and described in US patent No. 6797044 and 6767391, and oil filters, which are disclosed and described in US patent No. 6706181 and 6379537. Another feature of the present invention eniya relates to a manufacturing method of the present invention, mercerized fibers, which comprises treating cellulosic fibers using merserizuyuschego agent at a concentration and temperature and for a time sufficient for the manufacture of mercerized cellulosic fibers present invention. To obtain the planned results, it is important that this operation is carried out using a mercerizing liquid with a high concentration of dissolved carbohydrates, such as a reverse mercerizing solution "as is" in its fully alkaline state.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will be further described with the accompanying drawings, in which:

figure 1 shows non-mercerized fiber;

figure 2 shows the mercerized form of the fiber of figure 1;

figure 3 shows the contour length of the fiber; and

Fig. 4 is a graph illustrating the air permeability of various samples of mercerized fiber when tested according to TAPPI T251 cm-85 on 60 gsm manual casting sheets at a pressure of 125 Pa.

DESCRIPTION OF BEST OPTIONS FOR CARRYING OUT THE INVENTION

Mercerized cellulose fibers formed into a fiber web have an air permeability equal to or greater than about 100 cubic meters. feet per minute per sq. ft as determined by TAPPI T251 cm-85 on 60 gsm manual casting sheets at a test pressure of 125 Pa. Preferably, the air permeability is equal to or greater than about 110 cubic meters. feet per minute per sq. foot. In more preferred embodiments, the fibrous web has an air permeability equal to or greater than about 115 cubic meters. feet per minute per sq. ft and most preferably equal to or greater than 120 cubic meters. ft per sq. foot.

Preferably, the mercerized fibers of the present invention have a curl index of equal to or greater than about 0.26, determined by a fiber quality analyzer manufactured and sold by Canadian company OpTest. The curl index and methods for measuring it are well known in the art. In better embodiments of the present invention, the fibers have a curl index of from about 0.275. The fiber curl index is most preferably from about 0.275 to 0.370, and most preferably from about 0.285 to 0.360.

Preferably, the mercerized fibers of the present invention have a bend of equal to or greater than about 2.5, determined by a fiber quality analyzer manufactured and sold by Canadian company OpTest. The bend index and methods for measuring it are well known in the art. In the best embodiments of the present invention, the fibers have a bend of about 2.50 to 2.80. The fiber bending rate is more preferably from about 2.55 to 2.75, and most preferably from about 2.60 to 2.70.

Mercerized fibers of the present invention can be made from cellulose fibers obtained from deciduous wood, softwood, or a combination of hardwood and softwood, prepared for use in a paper production composition by any known cooking, refinement and bleaching methods, such as, for example, known mechanical , thermomechanical, chemical and semi-chemical, etc. cellulose production methods. In some embodiments, at least a portion of the cellulose fibers can be obtained from non-woody herbaceous plants and / or agricultural waste, including without limitation kenaf, sugarcane, hemp, jute, flax, sisal or abacus, although legislative restrictions and other considerations may make the use of hemp or other fiber sources is impractical or impossible. Recycled or recycled fibers or any cellulose-based textile waste can also be a fiber source. Bleached or unbleached pulp fibers may be used in the method of the present invention. In the best embodiments of the invention, mixtures of cellulose fibers obtained from deciduous and coniferous wood are used. In more preferred embodiments, the majority of the fibers (greater than 50% by weight, preferably greater than 60% by weight and most preferably greater than approximately 80% by weight) are obtained from bleached softwood pulp and, in most preferred embodiments, all or substantially all of the fibers obtained from coniferous wood.

Mercerized cellulosic fibers of the present invention are prepared by treating suitable cellulosic fibers with a suitable mercerizing agent at a concentration, over time and at a temperature sufficient to produce mercerized cellulosic fibers having the desired characteristics. For example, pulp fibers selected from the group consisting of bleached and unbleached hardwood pulp, coniferous wood and squeezed pulp, preferably bleached softwood pulp fibers, can be combined with some water to form slurry. The amount of water added to the wood fibers should be sufficient to form a slurry, preferably having a consistency in the range of about 0.1 to 88% by weight, and preferably in the range of about 8 to 40% by weight. Consistency is defined as the mass of wood fibers of kiln drying kiln divided by the total mass of slurry. To achieve high porosity, it is important to carry out the mercerization step using mercerizing solutions with a high content of dissolved hemicelluloses (continuously reused and / or artificially enriched by adding soluble carbohydrates), because only carbohydrates with a high molecular weight can be re-deposited from the solution onto the fiber surface during mercerization.

After the slurry is obtained, it is treated with a mercerizing solution obtained by combining a suitable mercerizing agent or combining two or more such agents with a polar solvent such as water. Suitable mercerizing agents include inorganic bases such as alkali metal and alkaline earth metal hydroxides such as potassium hydroxide, lithium hydroxide and sodium hydroxide, sodium carbonate and ammonium hydroxide, as well as various amines and amides used in the mercerization of cellulose fibers, white liquor (for example, a caustic solution containing Na ₂ S and Na ₂ CO ₃ ) or a combination of two or more of the above substances or mixtures with some amount of a polar solvent, such as water. Preferred mercerizing agents are alkali metal hydroxides and more preferred mercerizing agents are potassium hydroxide and sodium hydroxide.

The processing efficiency depends both on the concentration of the mercerizing agent and the temperature, and on the use of alkaline mercerizing solutions "as is" after continuous circulation or enriched by the addition of carbohydrates. At lower temperatures, weaker solutions may be used to obtain a similar effect. The concentrations of mercerizing agents may vary, provided that the desired results are achieved. When using preferred sodium hydroxide-based mercerizing agents, the concentrations are usually greater than about 12%, more preferably greater than about 14%, and most preferably greater than about 15-20%. Mercerization temperatures may vary, provided that the desired results are achieved. When using preferred sodium hydroxide-based mercerizing agents, temperatures are usually above about 20 ° C, more preferably above about 23 ° C, and most preferably from about 20 to about 80 ° C.

Although the treatment of cellulose with a mercerizing solution is relatively independent of the slurry consistency, a lower consistency may require a more alkaline mercerizing solution in order to maintain the desired concentration. In addition, slurry consistencies of about 30 wt.% And higher may require more sophisticated mixing techniques in order to ensure sufficient contact between the slurry wood fibers and strong alkali.

The required processing time may vary, provided that the desired mercerized fiber results are achieved. The processing time is preferably short, although the treatment of wood fibers with a strong alkaline mercerizing agent can be carried out for 10 hours or more, if desired. Typically, wood fibers are processed for about 10 seconds to 1 hour, more preferably 30 seconds to 30 minutes, and most preferably 1 minute to 5 minutes. During processing, the wood fibers and the mercerizing solution are intensively mixed to ensure sufficient contact and reaction between the fibers and the alkaline solution.

The processing of wood fibers can be carried out at atmospheric pressure, pressure below or above atmospheric. To facilitate equipment designs and operations used, atmospheric pressure is most preferred.

Mercerized fibers of the present invention can be used for any purpose using mercerized and conventional cellulosic fibers. For example, these fibers, either alone or in physical admixture with conventional cellulosic fibers, or crosslinked with such conventional cellulosic fibers, described in more detail in published US patent application 2004/0177935, can be used to make fibrous webs using known methods and devices. See, for example, the methods and devices described in the Handbook For Pulp & Paper Technologies, 2nd Edition, G. A. Smook, Angus Wilde Publications (1992) and the references therein. Preferably, these fibrous webs are made by a process comprising: a) preparing an aqueous suspension of cellulose and b) forming the web and drying the aqueous suspension of cellulose to produce a paper or cardboard web or fibrous base.

In step (a) of a better embodiment of the present invention, an aqueous suspension of cellulose is used. Methods for preparing aqueous pulp suspensions are well known in the art of paper and paperboard and will not be described in detail. See, for example, the G.A.Smook publication cited above and the references therein. The cellulosic fiber component in the composition can be any chemical pulp, such as bleached kraft pulp, although it is not believed that the invention is limited to kraft pulps, which can also be used to give good results with other chemical pulps, such as sulfite pulps, mechanical pulps, for example cellulose from wood pulp, and other types of cellulose and mixtures thereof, such as chemical-mechanical and thermomechanical cellulose. Recycled fibers and / or textile waste are also suitable fiber sources.

Although not essential for the present invention, the pulp is preferably bleached to remove lignins and achieve the desired degree of whiteness using one or more processing methods known in the art, including, for example, bleaching sequences with atomic chlorine, bleaching sequences using chlorine dioxide, sequences bleaching without the use of chlorine, the sequence of bleaching without using atomic chlorine, as well as combinations or variations of the steps of any of the above and other sequences and steps related to bleaching. After bleaching, washing and passing the pulp through sieves, it is usually subjected to refinement at one or several stages.

In step (b) of the method of the present invention, the cellulose suspension from step (a) is formed into a web and dried to obtain a dry paper or cardboard web. Methods and devices for forming the web and drying the cellulose suspension are well known in the field of paper and paperboard manufacturing. See, for example, the G.A.Smook publication cited above and the references therein. Any known methods of forming the web and drying may be used. Therefore, these methods will not be described herein in detail. For example, an aqueous paper feed composition containing cellulose and other additives is laid out from the loading tank of a suitable papermaking machine to form a single or multilayer web on a papermaking machine, such as a long mesh machine, or any other suitable papermaking machine known in the art, as well as those that may become famous in the future. For example, the so-called “slice” of a composition consisting of water pulp of a relatively low concentration of cellulose fibers, together with microspheres and various additives and fillers dispersed in it, is pushed out of the loading tank onto a porous endless moving belt or mesh on which the mass is dehydrated by gradual draining through small openings in the mesh under vacuum in the molding section until a web of cellulose fibers and other materials is formed on the mesh . The dehydrated wet sheet is transferred from the forming section to the pressing section on special shaft structures, where it passes through several contact areas of the presses in which water is removed and the wet sheet of paper is compacted. The web is then passed into the initial drying section to remove most of the remaining moisture and further densify the web fibers to obtain a predetermined thickness, density and base weight.

Wet or aerial sheets can be used for a variety of purposes. For example, the webs of the present invention can be used for purposes where the porosity of the web is an advantage. For example, the fibers and webs of the present invention can be used for the manufacture of cigarette paper by known methods, such as, for example, methods described in more detail in US patent No. 6722889, 6202650 and 5540242.

For air-laid webs, mercerized cellulose can be pulverized to form friable cellulose using known methods such as, for example, the methods described in more detail in US Pat. Nos. 5,536,369, 4,667,786 and 4,269,188. The friable cellulose can then be used for various applications. The fibers and loose cellulose of the present invention can be molded into absorbent webs using known methods, such as, for example, methods used to form air-laid, wet-laid, carded cotton, non-woven fabrics, needle-punched non-woven fabrics, hydroconnection, etc.

For example, these absorbent webs can be used to make products for which the absorption / porosity of the webs and fibers of the present invention is an advantage, for example, personal care products such as diapers, tampons, sanitary napkins, baby bibs and incontinence pads, surgical sponges , compresses, bandages, handkerchiefs. These products and methods for their manufacture are described in more detail in US patent No. 5019063, 6063982 and 5766159. For example, absorbent products of the present invention in the form of personal care products contain at least one top layer, permeable to liquid, at least one back layer, impermeable for liquid adjacent to the upper layer, and at least one absorbent intermediate layer between the upper layer and the back layer. The absorbent intermediate layer of the present invention has an air porosity equal to or greater than about 100 cubic meters. feet per minute per sq. ft as determined by TAPPI T251 cm-85 on 60 gsm manual casting sheets at a test pressure of 125 Pa. Preferably, the air porosity of the intermediate layer is equal to or greater than about 110 cubic meters. feet per minute per sq. foot. In better embodiments of the present invention, the fibrous web has an air porosity equal to or greater than about 125 cubic meters. feet per minute per sq. foot.

The absorbent intermediate layer typically contains from about 10 to 100% by weight of the loose wood pulp of the present invention. This absorbent layer preferably contains from about 20 to 100 wt.% Loose wood pulp and most preferably about 50 wt.% Loose wood pulp and about 50 wt.% Untreated fiber. Alternatively, the absorbent intermediate layer may consist of about 10-90 wt.% Loose wood pulp and about 10-90 wt.% Superabsorbent polymers in the form of grains, powders, small threads or other forms. Super absorbent polymers can be mixed with loose wood pulp or can be placed in a separate absorbent layer above or below a layer of loose wood pulp to form a composite absorbent intermediate layer.

Both liquid permeable material and liquid impermeable material, when used, are well known to those skilled in the art. Accordingly, the top layer can be made of various materials, such as porous foams, cellular foams, plastic films with holes, natural (e.g. wood or cotton) fibers, synthetic fibers (e.g. polyester or polypropylene), or from combinations of natural and synthetic fibers. Preferably, the liquid permeable material is hydrophobic, which will effectively separate the human skin from the liquid with an absorbent intermediate layer. The liquid permeable material on the top layer can be processed in order to facilitate the passage of fluid through this layer, while recognizing, of course, that the top layer should remain relatively hydrophobic compared to the absorbent intermediate layer. When an upper layer is applied to it from a flexible, liquid-permeable material, an article is formed - a personal hygiene item. In one of the best embodiments, the second surface of the intermediate layer is covered with a back sheet of liquid impervious material, so that the absorbent intermediate layer is located between the upper layer and the back layer. The backing layer is preferably made of a thin plastic polyolefin film that is relatively impervious to liquids. Accordingly, the material of the back layer is selected so as to effectively impede the liquid absorbed by the absorbent intermediate layer, to wet the garments and other things in contact with the personal care product. Preferably, the backing layer is a polyethylene film of a thickness of about 0.012 mm to 0.051 cm. However, any commercially available liquid impermeable material having suitable flexibility can be used to make the backing layer.

The fibers and loose cellulose of the present invention can be made in the form of filter sheets using methods well known in the art. For example, such filter webs can be used to manufacture products for which the porosity characteristics of the webs and fibers of the present invention will be an advantage, for example, air filters and oil filters. Such filters are well known in the art and will not be described in detail herein.

The present invention will now be described with reference to the following examples. These examples are illustrative only, and the present invention is not limited to the materials, conditions or parameters of the methods set forth in the examples.

EXAMPLE 1

According to this method, standard bleached pine kraft pulp (unbleached, produced at Georgetown paper mill) is treated with 15% sodium hydroxide at room temperature for 5-7 minutes. The loose wood pulp is washed and thickened. Sheets are made with a mass of approximately 750 g per square meter. meter, dried to a moisture content of approximately 7% and are tested. The use of this method for the production of wood pulp for the manufacture of absorbent products is disclosed in US patent No. 5,766,159 and 6,063,983, incorporated herein in full by reference. Previously, pulp quality checks did not cover porosity or other properties such as bending and curl, as these methods were not known. Three concentrations of caustic (5, 10, and 15%) were selected for fiber treatment. Microscopic examination of the fibers revealed that treating the fiber with 15% caustic yielded differences in fiber shape with respect to curl and tangling.

An analysis of fiber quality was used to obtain confusion values.

Fiber Quality Analysis - Bending and Curl *

Fiber Quality Analysis (FQA) measures the length, width, bending, and curl of fibers in suspension. This analysis is performed using a fiber analyzer that contains a cytometric flow cell through which fibers are passed. The entire sample is taken from a laboratory vessel, and one high-resolution camera takes pictures of individual fibers. In the measurements described below, circular polarized light is used.

a) Fiber length: characterized as contour length (L) or projected length from end to end (I). See FIG. 3.

b) Curl: is the gradual and continuous curvature of the fiber and is determined by the curl index:

Curl Index = (L / I) -1

c) Bending: A sharp change in the curvature of the fiber, as measured by the Kibblewhite bend. The modified bending index is a weighted sum of the number N (x) of bends in the range of "x" bending angles.

Bending index = [2N _(21-45) + 3N _(46-90) + 4N _(91-180) / L total]

The sample was compared with untreated pulp, as well as with commercially available cellulose (HBA “curved fiber” from Weyer-haeuser) and showed the following differences:

Sample Number Fiber length mm Fiber length mm Curl rate Bend index Weighted length Weighted mass Control 2,37 3.08 0.142 1.41 HBA 2,35 3.04 0.257 2,31 Mercerized 1.91 2,51 0.340 2.68

On the basis of the FQA analysis data and microscopic examination, absorption tests for friable cellulose were carried out. However, these tests were supplemented by physical measurements, and it was found that mercerized cellulose was too porous and went beyond the scale of a conventional Tappi Gurley porosity meter.

Cellulose porosity was determined using the following equipment:

a) capillary flow permeameter - gives constant permeability of Darcy and Gurley unit; b) permeameter "Cerulan PPM 100" - the results are expressed in units of Coresta.

Capillary flow permeameter

In this equipment, a sheet of paper or cellulose is inserted into the sample chamber and sealed using the upper and lower o-rings to prevent leakage on the sides of the sample. The diameter of the sample, its thickness and the desired control values (e.g. pressure drop, flow rate) are entered into the intuitive software, and the tests begin. After testing, the report generated by the software is used to pre-process the data and calculate the permeability values. Various permeameter models can be used to measure sample permeability in Rayls, Gurley, Frazier and Darcy units, as well as in other units. The Darcy permeability constant is calculated by the equation

Where

C = Darcy Constant Permeability,

F = Flow

T = sample thickness

V = Viscosity of gas (see table below),

D = Diameter of the sample

P = Pressure (atmospheres).

Viscosity Table

Gas / liquid Air Argon Helium Nitrogen Water Viscosity 0.0185 0.221 0.000198 0.0185 one

Our sample was compared with commercially available cellulose samples and showed the following differences:

Sample Number Darcy Permeability Commodity pulp 1,0258 Mercerized 7.2525

The Gurley number refers to the number of seconds required to allow 100 ml of air to enter the cylinder’s working volume. Our sample showed the following results:

Sample Number Gurley Average Commodity pulp 1 2,3628 Commodity pulp 2 1.6318 Mercerized 0.61522

Cerulean PPM 100 Permeameter - Coresta Porosity Test

This equipment provides accurate air permeability testing for most types of paper in the range of 10-40000 Coresta units. Coresta is the abbreviation of Center de Cooperation pour les Recherches Scienti-fiques Relatives au Tabac, an international organization of representatives of the tobacco industry that exchanges scientific and technical information related to tobacco factories and tobacco products.

The porosity of cigarette paper can be expressed in ml / min / cm ² , the volume of air in milliliters (at 20 ° C, 760 torr, relative humidity 55-65%), which passes through 1 cm ^{2 of a} flat sample of paper in 1 minute when creating a negative pressure 100 mm aq. Art. on one side of the sample. When analyzed using a Cerulean PPM 100 permeameter, the sample showed the following results:

Sample Number Coresta Units Commercial 1 461 Commercial 2 503 Mercerized 2705

Verification has shown that this material with high porosity can be used in the manufacture of cigarette paper to allow nicotine to be diluted by air suction. High porosity materials can also improve the performance of automotive filters or other filters in general. This superporous material could also be used in acoustics, for example as a sound-absorbing material. Our mercerized cellulose can be used alone or together with other types of fibers (synthetic or not) to improve filtering ability.

Thus, the absorbent articles of the present invention contain cellulose treated with chemicals commonly used in the industry. In addition, the chemicals used to create loose pulp can be easily removed by simple washing with water. Another advantage of the present invention is that cellulose with enhanced absorption capacity can be made using inexpensive chemicals with a relatively short reaction time. The resulting loose wood pulp can be used without additives as an absorbent intermediate layer or can be combined with other superabsorbent compounds and fibers to increase the absorbent capacity.

Although specific embodiments of the present invention are disclosed herein, these examples are used merely to illustrate the invention. Specialists in this field can identify numerous changes, modifications and substitutions for the invention in the essence and scope of the attached claims.

EXAMPLE 2

The air permeability characterization of several different commercial mercerized celluloses against mercerized bleached pine marsh kraft pulps according to the present invention was evaluated using the TAPPI T251 cm-85 procedure. The results are shown in the following table 1.

TABLE 1 Air permeability, cubic feet per minute per sq. foot Standard deviation Commercial A (1) 95.3 4.4 Commercial A (2) 108 5,6 Commercial In (1) 108 10.9 Commercial In (2) 105 13,2 Cellulose 1 of the present invention 127 3.8 Cellulose 2 of the present invention 150 11.6 Cellulose 3 of the present invention 125 6.2

The air permeability test was carried out using an FX 3300 device according to the TAPPI T251 cm-85 standard (samples 60 gsm, at a pressure of 125 Pa).

These results with corresponding standard deviations are shown in graph form in FIG. 4.

EXAMPLE 3

Samples of bleached unrefined kraft pulps from bog pine were mercerized under the above conditions using fresh alkaline solution or reused alkaline solutions. After a standard reaction time, the cellulose was washed with water, dried and tested for air permeability. Table 2 below shows data on the improvement of porosity from the initial conditions (fresh alkaline solution depleted by dissolving hemicelluloses) and for the same fibers after mercerization of alkaline solutions, which were reused 2 or 3 times.

TABLE 2 Reuse Air permeability Standard deviation 0 108 5,6 2 121 5.3 3 129 3.8

The test was carried out by IPS (Appleton-WI) using an FX 3300 device according to the TAPPI T251 cm-85 standard (samples 60 gsm, at a pressure of 125 Pa).

Claims (8)

1. A method of manufacturing mercerized fibers, comprising essentially treating cellulosic fibers with a mercerizing agent with a high concentration of dissolved hemicelluloses accumulated after continuous recycling of alkaline solutions or by adding soluble carbohydrates, with an alkali concentration of about 5 to 15 wt.% Of the total mixture at temperature and for a period of time sufficient to produce mercerized cellulose fibers forming fibrous webs having air porosity, equal to or greater than about 100 cubic meters. feet per minute per sq. ft, determined according to the TAPPI T251 st-85 procedure at a pressure of 125 Pa on 60 gsm manual casting sheets. 2. The method according to claim 1, where the air porosity of the mercerized fibers is equal to or greater than about 120 cubic feet per minute per square foot, determined according to the TAPPI T251 st-85 procedure at a pressure of 125 Pa on 60 gsm manual casting sheets. 3. The method according to claim 1, where the mercerized fibers have a curl index equal to or greater than approximately 0.26. 4. The method according to claim 1, where the mercerized fibers have a curl index in the range from about 0.275 to about 0.370. 5. The method according to claim 1, where the mercerized fibers have a bending index equal to or greater than about 2.5. 6. The method according to claim 1, where the mercerized fibers have a bending index in the range from about 2.50 to about 2.80. 7. The method according to claim 1, where mercerized fibers are prepared using mercerizing solutions enriched with dissolved hemicelluloses by continuously recycling reused and / or additional artificially enriched solutions with added soluble carbohydrates so that high molecular weight carbohydrates can be re-deposited from the solution onto the surface of the fibers during the mercerization. 8. The method according to claim 7, where the mercerizing solutions are used at a temperature of from about 20 ° to about 80 ° C.

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