RU2471910C2 - Absorbent web comprising regenerated cellulose microfiber - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: absorbent paper web comprises cellulose paper-forming fiber and up to 75 wt % fibrillated regenerated cellulose microfiber which can be regenerated from the cellulose solution. As the solvent N-oxide of tertiary amine or a solvent selected from ionic liquids is used. Fibrillation of microfiber is controlled so that the fiber has a reduced graininess and a reduced degree of grinding in comparison with non-fibrillated regenerated cellulose microfiber.

EFFECT: addition of fibrillated fibers in the absorbent web provides the increased value measured by a simple measuring device of absorption capacity and increased value of stretchability in wet condition, increased ratio of stretchabilities in the transverse direction in the wet, dry condition, less geometric average modulus of rupture, increased specific volume.

17 cl, 13 tbl, 38 dwg

Description

FIELD OF THE INVENTION

The present invention generally relates to an absorbent fabric and, in particular, to an absorbent fabric made from paper-forming fibers, such as softwood and hardwood pulp containing regenerated cellulose microfiber.

BACKGROUND

Regenerated cellulose lyocell fiber is well known. Typically, lyocell fiber is made from reprecipitated cellulose formed from an aqueous solution of amine oxide. A common method is to form lyocell fibers from a solution of cellulose in aqueous tertiary amine N-oxide, for example from a solution in N-methylmorpholine N-oxide (NMMO). The solution is usually extruded through a suitable spinneret into an aqueous coagulating bath to obtain finished fibers. These fibers are widely used in textiles. Due to the fact that lyocell fiber includes highly crystalline alpha cellulose, it tends to fibrillate, which is undesirable in most textiles and is considered a disadvantage. In this regard, US Pat. No. 6,235,392 and US Patent Application Publication No. 2001/0028955, Luo et al ., Describe various methods for producing lyocell fibers with a reduced tendency to fibrillation.

On the other hand, fibrillation of cellulose fibers is desirable in some applications, such as filtration. For example, US Pat. No. 6,042,769 to Gannon et al . Describes a method for preparing lyocell fibers that are easy to fibrillate. The fibers thus obtained can be treated with a disintegrator, as noted in column 5 of the '769 patent (see lines 30 and further. See also US Pat. No. 5,725,821, Gannon et al) . Highly fibrillated lyocell fibers have been found to be suitable for filter media with a very high degree of productivity. In this regard, patent application US 2003/0168401 and publication US 2003/0177909, Koslow, should be noted.

As is known, lyocell fibers having fiber diameters and lengths similar to paper-forming fibers are used in the manufacture of an absorbent web. In this regard, US Pat. No. 6,841,038, Horenziak et al ., Describes a method and apparatus for preparing an absorbent web comprising lyocell fibers (see FIG. 2 of the '038 patent, which describes a conventional air drying method (TAD process) for preparing an absorbent canvases). US Pat. No. 5,935,880, Wang et al ., Also discloses nonwoven fiber nets including lyocell fibers (see also publication of US Patent Application US 2006/0019571). Such fibers tend to flocculate and are thus extremely inconvenient to use in the traditional wet spinning process in the manufacture of absorbent rolls.

While the use of lyocell fibers in absorbent materials is known, it has not been previously appreciated that very thin lyocell fibers or other regenerated cellulose fibers with extremely low grain sizes can provide unique combinations of properties such as wet strength, absorbency and softness , even when used in the composition of the paper-forming mass in limited quantities. Moreover, the fabric according to the invention is particularly applicable as a cleaning cloth, as it is highly effective in removing contaminants from the surface. According to the present invention, it has been found that regenerated cellulosic microfiber can be easily incorporated into a hardwood and softwood paper-forming fiber matrix to enhance network characteristics and provide higher quality characteristics even when using lower than higher quality paper-forming fibers.

SUMMARY OF THE INVENTION

The absorbent paper web includes pulp pulp-derived paper-forming fiber and up to about 75 wt.% Fibrillated regenerated cellulose microfiber having a CSF value of less than 175 ml. The fibrillated regenerated cellulose microfiber is present in amounts of from 40 wt.% And in some cases more, based on the weight of the fiber; more than about 35% is usually present, based on the weight of fiber in the web. The possibility of using more than 37.5% and even more will be obvious to specialists in this field. In the various web-based products, any fibrillated cellulose microfiber described herein can be used with a content of more than 25%, more than 30% or more than 35%, 40% or more by weight, depending on the desired properties for the intended application. In some embodiments, the regenerated cellulosic microfiber may be present with a content in the range of 10-75%, as described below; it will be understood that the weight ranges described herein can be replaced in any embodiment of the web according to the invention of the web, if necessary.

The paper-forming fiber is organized into a fiber matrix, and the lyocell microfiber is dosed and distributed in the fiber matrix to form a microfiber network in it, as can be seen from Figure 1 , which is a micrograph of creped fabric with 20% cellulose microfiber. The fibrillation of the regenerated cellulose microfiber is controlled so that the fiber has a reduced grain size and a reduced degree of grinding compared to the non-fibrillated regenerated cellulose fiber from which it is prepared, so that the microfiber provides increased absorbency, strength or softness, typically providing one or more of the following characteristics : (a) the absorbent web has an increased SAT and an increased wet elongation in comparison with a similar fabric obtained without regenerated cellulose microfiber; (b) the absorbent web has an increased wet / dry stretch ratio compared to a similar web obtained without regenerated cellulose microfiber; (c) the absorbent web has a smaller geometric mean (GM) tear modulus than a similar web having similar tensile values obtained without regenerated cellulose microfiber; or (d) the absorbent web has an increased volume compared to a similar web having similar tensile values obtained without regenerated cellulosic microfiber. Particularly suitable fibers are obtained from a solution of cellulose with dissolved cellulose, including a solvent selected from ionic liquids and N-oxides of tertiary amines.

The present invention also provides products with an unusually high wet / dry stretch ratio, which makes it possible to produce softer products due to the fact that the tensile strength in the dry state of the final towel, for example, is often determined by the requirements for tensile strength in the wet state. One embodiment of the invention includes a web prepared with fiber that has been pre-treated with a high concentration baking powder.

Additional features and advantages of the invention will be apparent from the discussion that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to the Figures, in which:

Figure 1 is a micrograph showing a creped tissue with 20% regenerated cellulose microfiber;

Figure 2 is a histogram showing the fiber size or “fine grain” of fibrillated lyocell fibers;

Figure 3 is a plot of the FDA measured fiber length for various samples of fibrillated lyocell fiber;

Figure 4 is a micrograph of unmilled regenerated cellulose fiber with a thickness of 1.5 denier, having a grain size of 16.7 mg / 100 m;

Figure 5 is a micrograph of the milled regenerated cellulose fiber with a sieve number of 14;

6 is a micrograph of milled regenerated cellulose fiber with a sieve number of 200;

7-11 are micrographs with increasing magnification of fibrillated regenerated cellulose microfiber, which is passed through a mesh with a number of sieves 200 according to the Bayer-MacNett classifier (Bauer-McNett);

Figures 12-17 are graphs of the physical properties of hand webs comprising regenerated cellulose microfiber, where Figure 12 is a graph of the volume of a hand cloth versus extensibility (breaking length), Figure 13 is a graph of roughness versus roughness extensibility, Fig.14 is a graph of the dependence of opacity on extensibility, Fig.15 is a graph of the dependence of the module on extensibility, Fig.16 is a graph of the dependence of the gap of the canvas for hands t elongation, and Fig is a graph of the dependence of the volume of the canvas for hands from ZDT-binding;

Fig. 18 is a photomicrograph at a magnification of 250 softwood handcloth without fibrillated regenerated cellulose fiber;

Fig. 19 is a photomicrograph at a magnification of 250 softwood hand webs including 20% fibrillated regenerated cellulose microfiber;

FIG. 20 is a schematic diagram of a wet pressing paper machine that can be applied using the present invention; FIG.

Fig is a graph of the dependence of softness (panel) from the two-layer GM-extensibility for the fabric base of the fabric 12 pounds / foot sheets (20 g / m ² ) with paper pulp of southern grades and regenerated cellulose microfiber obtained by the CWP method;

Figure 22 is a graph of panel softness versus extensibility for various fabric webs;

23 is a graph of volume versus extensibility for a creped CWP base web.

24 is a plot of MD elongation versus CD elongation for a CWP tissue base of a web;

Fig is a graph of the dependence of the GM-module of the gap from GM-extensibility for the fabric base of the canvas;

Fig is a graph of the dependence of the change of elongation from% microfiber for fabric and the base of the towel;

Fig is a graph of the dependence of the density of paper on elongation for the fabric base of the canvas;

Fig is a graph of the dependence of paper density on elongation for CWP-base canvas;

Fig is a graph of the dependence of the two-layer SAT from CD extensibility in the wet state;

30 is a plot of wet CD versus dry CD extensibility for a CWP base web;

Fig is a photomicrograph obtained on a scanning electron microscope (SEM) of a crepe tissue without microfiber;

Fig is a micrograph of creped fabric with 20% microfiber;

Fig is a graph of the dependence of the breaking length in the wet state of the breaking length in the dry state for various products, showing the effect of the regenerated cellulose microfiber and baking powder on the extensibility of the products;

Fig is a graph of the dependence of the GM module of the gap from the breaking length, showing the effect of regenerated cellulose microfiber and baking powder on the strength of the product;

Fig. 35 is a graph of volume versus breaking length showing the effect of regenerated cellulosic microfiber and baking powder on product volume;

Fig. 36 is a block diagram illustrating fiber pretreatment before feeding pulp to a paper machine;

Fig. 37 is a graph of TAPPI opacity versus paper density showing that regenerated cellulosic microfiber significantly increases the opacity of the fabric base of the web obtained using recycled paper pulp; and

Fig. 38 is a graph of panel softness (arbitrary scale) versus breaking length in meters.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described in detail below with reference to several embodiments and numerous examples. This discussion is for illustration purposes only. Modifications and particular examples within the scope of the present invention as claimed in the appended claims will be readily apparent to those skilled in the art.

The terms used herein are provided in their usual meaning consistent with the typical definitions given below; mil stands for thousandths of an inch; mg stands for milligrams, and m ² stands for square meters, percent stands for mass percent (dry matter), тон ton ’stands for short ton (2000 pounds), and so on. Unless explicitly stated otherwise, the version of the testing method used is equivalent to that which was valid as of January 1, 2007, and the tested samples were prepared in accordance with the standard of the Technical Association in the Pulp and Paper Industry (TAPPI); that is, kept in an atmosphere of 23 ° ± 1.0 ° C (73.4 ° ± 1.8 ° F) at 50% relative humidity for at least about 2 hours.

The absorbency of the products of the invention was measured with a simple absorbency meter. A simple absorbency meter is an apparatus suitable, in particular, for measuring hydrophilicity and absorbency characteristics of tissue samples, napkins or towels. In this test, a 2.0 inch (5.1 cm) diameter tissue, tissue, or towel sample was placed between the top flat plastic cover and the grooved bottom of the sample plate. A tissue, tissue, or towel sample disc is held in place by a 1/8-inch (0.32 cm) wide flange circumference. The sample was not compressed in the holder. Deionized water was added to the sample at 73 ° F (23 ° C) in the center of the bottom of the sample plate through a channel with a diameter of 1 mm. This water was at a height of hydrostatic pressure minus 5 mm. Spreading was initiated by pulsed introduction introduced at the beginning of the measurement by the device mechanism. Water was thus absorbed by a sample of cloth, napkin or towel from this central entry point, radially distributed under the action of capillary forces. When the absorption rate of water decreased below 0.005 g of water in 5 seconds, the test was completed. The amount of water withdrawn from the reservoir and absorbed by the sample was weighed and given as grams of water per square meter of sample or grams of water per gram of web. Practically applied Gravimetric Absorbency Testing System from M / K Systems Inc. This is a commercial system that can be obtained from M / K Systems Inc., 12 Garden Street, Danvers, Mass., 01923. The water absorption capacity (WAC), also referred to as SAT, is actually determined by the device itself. WAC is defined as the point on the graph where the time-mass curve has a “zero” slope, that is, the sample stops absorption. The completion criterion for the test is defined as the maximum change in the mass of water absorbed over a fixed period of time. Essentially, this is estimated as zero slope in the time-mass graph. The program uses a change of 0.005 g over a 5 second time interval as a termination criterion until a “slow SAT” is indicated, in which case the termination criterion is a 1 mg increase in 20 seconds.

Unless explicitly stated otherwise, the terms “paper weight”, BWT, bwt, and so on, refer to a stack weight of 3,000 square feet (278.7 m ² ) sheets of product. Concentration refers to the percent solids in the resulting web structure, for example, calculated on a completely dry mass. “Air drying” means incorporating residual moisture, typically up to about 10% moisture for pulp and up to about 6% for paper. The structure of the canvas, which is in the stage of formation, containing 50% water and 50% completely dry pulp, has a concentration of 50%.

The terms “cellulosic”, “cellulosic web” and the like are intended to mean any product including a paper-forming fiber containing cellulose as a main component. “Paper-forming fibers” include raw wood pulps or recycled (secondary) cellulosic fibers or fiber mixtures containing cellulosic fibers. Fibers suitable for the manufacture of web structures according to this invention include: non-wood fibers such as cotton fibers or derivatives of cotton, manila hemp, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed filament, pineapple foliage fibers; and wood fibers, for example, obtained from deciduous and coniferous trees, including softwood fibers, such as softwood unbleached sulfated fibers of the northern varieties and southern varieties; solid wood fibers such as eucalyptus, maple, birch, poplar, or the like. The paper-forming fibers used in connection with the invention are typically naturally occurring pulp-derived fibers (as opposed to fibers isolated from solution, such as lyocell or rayon) that are isolated from their source by any of a number of hydrofracturing methods close to the method, known in the prior art, including sulfate, sulfite, polysulfide, soda boiling, etc. The pulp can be bleached, if necessary, by chemical methods, including the use of chlorine, chlorine dioxide, oxygen, alkaline peroxide and so on. The naturally occurring pulp-derived fibers are here simply referred to as “pulp-derived” paper-forming fibers. The products of the present invention include a blend of conventional fibers (or those derived from primary pulp or secondary sources) and high-grain lignin-rich tubular fibers, such as bleached chemical thermomechanical pulp (BCTMP). The fibers obtained through the pulp thus also include finely divided fibers such as BCTMP, as well as thermomechanical pulp (TMP), chemical thermomechanical pulp (CTMP) and alkaline peroxide mechanical pulp (APMP). “Paper pulp” and similar terms refer to aqueous compositions, including paper-forming fibers, optionally wet strength resins, baking powder and the like, for the manufacture of paper products. In order to calculate the relative percentages of paper-forming fibers, the content of fibrillated lyocell was excluded, as described below.

Unbleached sulphated mild wood fiber is a low-disperse fiber produced by the well-known sulphating (sulphate) pulping method from conifers and includes mild unbleached sulphated fiber of northern and southern varieties, unbleached sulphated fiber of Douglas fir and so on. Unbleached sulfated softwood fibers generally have a lignin content of less than 5 wt.%, A weighted average fiber length of more than 2 mm, as well as an arithmetic average fiber length of more than 0.6 mm.

Unbleached sulfated solid wood fiber is produced by a sulfate cooking method from solid wood sources, that is, eucalyptus, and also usually has a lignin content of less than 5 wt.%. Unbleached sulfated solid wood fibers are shorter than soft wood fibers, typically have a weight average fiber length of less than 1 mm and an arithmetic average length of less than 0.5 mm or less than 0.4 mm.

Recycled fiber can be added to the pulp in any quantity. While any suitable recycled fiber can be used, recycled fiber with relatively low levels of wood fiber is preferred in many cases, for example, recycled fiber with less than 15 wt.% Lignin or less than 10 wt. The% lignin content may be preferable depending on the composition of the mixture of paper pulp used and the application.

The thickness of the calipers and / or the volume given here can be measured as the thickness of the calipers on 8 or 16 paintings, as indicated. The caliper thickness and the volume of the hand blade are based on a thickness of 5 webs. The canvases were placed one above the other and the caliper thickness was measured near the central part of the stack. Preferably, test samples were aged in the atmosphere at 23 ° ± 1.0 ° C (73.4 ° ± 1.8 ° F) at 50% relative humidity for at least about 2 hours and then measured on a Thwing-Albert 89- model II-JR or Progage Electronic thickness gauge with fixed parts of 2-inch (50.8 mm) diameter, constant load of 539 ± 10 grams and a descent speed of 0.231 inch / s (0.587 cm / s). To test the final product, each product web tested must have the same number of layers as the commercial product. For preliminary testing, eight canvases are selected and stacked together. When testing napkins, napkins were unfolded before stacking. To test the base of the web without devices for winding the tape into a roll, each test fabric should have the same number of layers as it turns out without a device for winding the tape into a roll. Separate layers should be used to test the base of the web without the bobbin of the paper machine. The canvases were stacked, jointly aligned in a line in the longitudinal direction. On custom embossed or printed products, you must try to avoid measurements in these areas, if possible. Volume can also be expressed in units of volume / mass (specific volume) by dividing the caliper thickness by paper density .

The term “dewatering by densifying the web or paper pulp structure” refers to mechanical dehydration by wet pressing on a dewatering cloth, for example, in some embodiments, by applying mechanical pressure constantly to the surface of the web structure, as in the gap between the pressure roller and the pressing shoe, where the structure of the canvas is in contact with paper cloth. The term “sealing dehydration” is used to distinguish between methods in which the initial dehydration of the web structure was carried out mainly by thermal methods, as in the case of, for example, US Pat. No. 4,529,480, Trokhan, and US Pat. No. 5,607,551, Farrington et al. Dehydration by densifying the web structure, therefore, refers, for example, to removing water from the web structure that is being formed, having a concentration of less than 30% or about, by applying pressure to it and / or increasing the concentration in the web structure by about 15 % or more by applying pressure to it.

Creping can be expressed as a percentage, calculated by the formula:

Percentage of creping = [speed of the 1st reel / speed of the American dryer] × 100%

The web structure, creped at a surface speed of 100 fpm (feet per minute) (30.5 meters per minute) from the drying cylinder to the bobbin at a speed of 80 fpm (24.4 meters per minute), has a crepe creping of 20%.

The creping adhesive used to fix the structure of the web to the drying cylinder of the American drying apparatus is preferably hygroscopic, re-wettable, substantially non-crosslinked adhesive. Examples of preferred adhesives are those that contain the poly (vinyl alcohol) of the general type described in US Pat. No. 4,528,316, Soerens et al . Other acceptable adhesives are described in US Patent Application Serial Number 10/409042 (Patent Publication US 2005-0006040 A1), filed April 9, 2003, entitled “ Improved Creping Adhesive Modifier and Process for Producing Paper Products ”. The disclosures of the '316 patent and the' 042 patent are incorporated herein by reference. Suitable adhesives were optionally provided with modifiers and so on. It is preferable to use a cross-linking agent and / or modifier in the calculated amounts or not for the entire amount of glue.

“Baking powder”, “baking powder composition”, “plasticizer” and similar terms refer to compositions used to reduce extensibility or soften absorbent paper products. Typically, these compositions include surfactants as an active ingredient and are further discussed below.

The “degree of grinding” (CSF) was determined according to TAPPI T227 OM-94 (Canadian Standard Method). Any suitable method of preparing regenerated cellulose microfiber to check the degree of grinding can be used if the fiber is well dispersed. For example, if a fiber is pulverized at a concentration of 5% for several minutes or more, that is, 5-20 minutes before testing, the fiber is well dispersed for testing. Similarly, partially dried fibrillated regenerated cellulosic microfibers can be treated for 5 minutes in an English grinder at a concentration of 1.2% in order to ensure proper dispersion of the fibers. Both preparation and testing are carried out at room temperature and either distilled or deionized water is used.

The term “web made without regenerated cellulose microfibre” and the like refers to a web made in essentially the same way, having essentially the same composition as the web made with regenerated cellulosic microfibre, except that the paper pulp does not include regenerated cellulose microfiber, which replaces a paper-forming fiber having essentially the same composition as another paper-forming fiber in the web. Thus, with respect to a web having 60 wt.% Soft wood fiber of the northern grades, 20 wt.% Solid wood fiber of the northern grades and 20 wt.% Regenerated cellulose microfiber, which is produced by the CWP method, a similar web without regenerated cellulose microfiber is produced by the same CWP-method with 75 wt.% Soft wood fiber of northern varieties and 25 wt.% Solid wood fiber of northern varieties.

Lyocell fibers are solvent-formed cellulosic fibers obtained by extruding a cellulose solution into a coagulating bath. Lyocell fiber is thinner than cellulose fiber produced by other known methods, which are based on the formation of soluble chemical derivatives of cellulose and their subsequent decomposition to regenerate cellulose, for example, in a viscose process. Lyocell is a general term for fibers formed directly from a solution of cellulose in an amine-containing medium, usually in a tertiary amine N-oxide. The production of lyocell fiber is the subject of numerous patents. Examples of solvent spinning processes for producing lyocell fibers are described in US Pat. No. 6,235,392 to Luo et al .; US patents 6042769 and 5725821, Gannon et al ., which are included in this description as a reference material.

“MD” indicates the longitudinal direction and “CD” indicates the transverse direction relative to the axis of movement of the machine.

Opacity was measured using the TAPPI test method, T425-OM-91 or equivalent.

The term “predominant” and similar terminology means a content of greater than 50 wt.%. The fibrillated lyocell content in the web was calculated based on the total fiber mass in the web; where the relative amount of other paper-forming fibers was calculated excluding the content of fibrillated lyocell. So, if the web, which consists of 20% fibrillated lyocell, 35 wt.% Mild wood fiber and 45 wt.% Solid wood fiber contains solid wood fiber as the predominant paper-forming fiber due to the fact that 45/80 paper-forming fiber (excluding fibrillated lyocell) is solid wood fiber.

Dry tensile strengths (MD- and CD-), elongations, their ratios (modules), tensile modulus, load and tensile were measured using an Instron standard testing device or other suitable elongation tensile tester, which can be configured in various ways typically on strips of 3 inches or 15 mm wide of fabric, or towels, or hand sheets, held in the atmosphere at 23 ° ± 1 ° C (73.4 ° ± 1 ° F) at 50% relative humidity for 2 hours. The tensile test is carried out at a slide speed of 2 inches / min (5 cm / min). The tensile strength is sometimes referred to simply as “tensile” and is given in breaking length (km), g / 3 inches (g / 7.62 cm) or g / inch (g / cm).

The geometrically averaged (GM) fracture modulus is expressed in grams / 3 inches /% stress (grams / 7.62 cm /% stress) until other units are indicated. The percentage of tension is dimensionless, and there is no need to define units. The values of elongation refer to discontinuous values, unless explicitly stated otherwise. Tensile strengths were given in g / 3 inches or g / cm (grams / 7.62 cm) at break.

The GM break modulus is calculated using the following formula:

[(MD elongation / MD elongation at break) × (CD elongation / CD elongation at break)] ^1/2

The rupture module for hand webs can alternatively be measured on a 15 mm sample if necessary and expressed in kg / mm ² (see FIG. 15).

Relations of extensibility are simply relations of quantities determined by the above methods. Unless explicitly stated otherwise, the property of extensibility is a property of a dry web.

TEA is a measure of strength and is given by CD-TEA, MD-TEA or GM-TEA. Total Absorbed Energy (TEA) is calculated as the area under the load-elongation curve using a tensile meter, as previously described above. The area is based on the elongation achieved when the web extends to break and the load applied to the web drops to 65% of the peak tensile load. Since the thickness of the paper web is usually unknown and varies during the test, it is common practice to ignore the transverse width of the web and report a “load” on the web as a load per unit length or usually in units of grams per 3 inches of width (7.62 cm). To calculate TEA, the load was converted to grams per millimeter and the area was calculated by integration. Elongation units are millimeters per millimeter, so the final TEA units become g-mm / mm ² .

The wet stretch of the fabric according to the present invention was measured using a three-inch (7.62 cm) wide ribbon of fabric, which was folded into a loop, clamped in a special mount called the Finch Cup, then immersed in water. The Finch Cup, which is available from Thwing-Albert Instrument Company, Philadelphia, Pa., Was mounted on a tensile meter equipped with a 2.0 lb (0.91 kg) cage with a Finch Cup flange fixed between the lower cam of the meter and the ends of the fabric loop clamped in the upper cam of the tensile tester. The sample was immersed in water, which was brought to a pH of 7.0 ± 0.1 and the extensibility was tested 5 seconds after immersion. The values were divided by two, as required for the calculation for the loop.

The ratio of wet / dry extensibility was expressed as a percentage by multiplying the ratio by 100. For towel-type products, the ratio of wet / dry CD extensibility is most significant. Throughout this specification and claims, the term “wet / dry ratio” or similar terms refers to the ratio of CD-wet and dry stretch ratios unless otherwise indicated explicitly. In the case of hand canvases, the MD and CD values are approximately equivalent.

A plasticizer or additional baking powder was calculated as the mass “in the state immediately after delivery” of a commercial composition with a baking powder per ton of completely dry fiber, using a commercially available composition with a baking powder, without taking into account additional diluents or dispersants that can be added to the composition after receipt from the seller.

Baking powder compositions typically include cationic or anionic amphiphilic compounds or mixtures thereof (hereinafter referred to as surfactants) combined with other diluents and non-ionic amphiphilic compounds, where the usual surfactant content in the baking powder composition varies from about 10 wt.% To about 90 wt.%. Diluents include propylene glycol, ethanol, propanol, water, polyethylene glycols and non-ionic amphiphilic compounds. Diluents are often added to the surfactant composition in order to make the latter more easily processed (i.e., with reduced viscosity and melting point). Some diluents are artifacts of the synthesis of a surfactant in a package (e.g. propylene glycol). Non-ionic amphiphilic compounds, in addition to controlling the properties of the composition, can be added to enhance the wettability of the disintegrant, where both disintegration and preservation of the absorbency are necessary for the substrate to which the disintegrant is applied. Non-ionic amphiphilic compounds can be added to baking powder compositions to disperse water-immiscible surfactant packets in water streams, such as those found in papermaking. Alternatively, a non-ionic amphiphilic compound, or mixtures of various non-ionic amphiphilic compounds, as shown in US Pat. No. 6,969,443 to Kokko , can be carefully selected to predictably control the loosening properties of the final disintegrant composition.

When formulating a composition with a disintegrant directly from surfactants, the additional disintegrant includes amphiphilic additives such as a nonionic surfactant, i.e. polyethylene glycol fatty esters and diluents such as propylene glycol, respectively, up to about 90 wt.% Of the applied composition with baking powder; however, with the exception that the diluent content is more than about 30% by weight; non-amphiphilic diluent is excluded in order to calculate the composition with added baking powder per ton of fiber. Similarly, the water content is excluded when calculating the additional baking powder.

The term “Type C” quat refers to an imidazolium-based surfactant, while the term “Type C” disintegrant refers to a disintegrant composition that includes type C quat. A preferred type C disintegrant composition includes Type C quat and an anionic surfactant as described in US Pat. No. 6,245,197, mixed with nonionic amphiphilic components and other diluents as described in US Pat. No. 6,969,443. The disclosures of '197 and' 443 are incorporated herein by reference. woven material.

It has been found that, according to the present invention, increased ratios of wet / dry CD stretch ratios are detected when paper-forming fibers are pretreated with a loosening composition or a plasticizer composition before being incorporated into the web structure. In this regard, the present invention can use disintegrants, including amidoamine salts derived from amines partially acid neutralized. Such substances are described in US patent 4720383 and in the work, Evans, Chemistry and Industry , July 5, 1969, pp. 893-903; Egan, J. Am. Oil Chemist's Soc Vol. 55 (1978), pp. 118-121; and Trivedi et al., J. Am. Oil Chemist's Soc , June 1981, pp. 754-756, which are incorporated herein by reference; as shown, plasticizers are often available commercially as complex mixtures more often than as individual compounds. While the following discussion will focus on the predominant particles of a surfactant, it should be understood that commercially available mixtures and compositions should generally be used in practice.

Quasoft 202-JR is an acceptable substance that includes a surfactant obtained by alkylating a condensation product of oleic acid and diethylene triamine. Synthesis conditions with a lack of an alkylating agent (e.g. diethyl sulfate) and only one alkylation step, followed by pH adjustment for protonation of unleaded particles, result in a mixture consisting of cationic ethylated and cationic unleaded particles. A smaller fraction (for example, about 10%) of the obtained amidoamine is cyclized to imidazoline compounds. Since only the imidazoline moieties of these substances are quaternary ammonium compounds, the compositions as a whole are pH sensitive. Therefore, in the practical implementation of the present invention with this class of chemicals, the pH in the headbox should be about 6-8, more preferably 6-7, and most preferably 6.5-7.

Quaternary ammonium compounds, such as dialkyl dimethyl quaternary ammonium salts, are also acceptable, especially when the alkyl groups contain from about 10 to 24 carbon atoms. These compounds have the advantage of being relatively insensitive to pH.

Biodegradable plasticizers may be used. Representative biodegradable cationic plasticizers / disintegrants are described in US Pat. Nos. 5,312,522; 5,415,737; 5262007; 5264082 and 5223096, which are included in this description as a reference material. The compounds are biodegradable diesters of quaternary ammonium compounds, quaternized amino esters and esters based on biodegradable vegetable oil functionalized with quaternary ammonium chloride and dieruclide dimethylammonium diester chloride, and are representative biodegradable pliable representative.

Baking powder compositions may include dialkyl dimethyl ammonium salts of the formula:

bis-dialkylamidoammonium salts of the formula:

As well as dialkylmethylimidazolium salts (quads of type C) of the formula:

,

,

where each R may be the same or different and each R represents a hydrocarbon chain having a chain length of from about 12 to about 22 carbon atoms, and may be saturated or unsaturated; and wherein said compounds are associated with a suitable anion. One acceptable salt is a dialkylimidazolium compound, and the associated anion is methyl sulfate. Typical quaternary ammonium surfactants include hexamethonium bromide, tetraethylammonium bromide, lauryltrimethylammonium chloride, dihydrogenated fatty aliphatic dimethylammonium methyl sulfate, oleylimidazolium and so on.

A component of a nonionic surfactant, such as PEG diols, and PEG mono or fatty acid diesters, and PEG mono or fatty alcohol diesters, either individually or in combination with a quaternary surfactant, can also be used. ammonium Suitable compounds include the reaction product of a fatty acid or fatty alcohol with ethylene oxide, for example a polyethylene glycol fatty acid diester (PEG diols or PEG diesters). Examples of non-ionic surfactants that can be used are polyethylene glycol dioleate, polyethylene glycol dilaurate, polypropylene glycol dioleate, polypropylene glycol dilaurate, polyethylene glycol monooleate, polyethylene glycol mono-oleate and further polypropylene glycol monooleate and monolurate. Additional details can be found in US patent 6969443, Bruce Kokko , entitled " Method of Making Absorbent Sheet from Recycle Furnish ".

After treatment with a baking powder, the pulp is mixed with strength adjusting agents, such as a stable wet strength agent (WSR), optional dry strength agents, and so on, until a web is formed. Suitable stable wet strength agents are known to those skilled in the art. A complete but not exclusive list of useful strength improvers includes urea-formaldehyde resins, melamine-formaldehyde resins, glyoxylated polyacrylamide resins, polyamidamine-epihalohydrin resins and the like. Shrink polyacrylamides are prepared by reacting acrylamide with diallyldimethylammonium chloride (DADMAC) to form a cationic polyacrylamide copolymer, which is ultimately reacted with glyoxal to form a cationic crosslinked resin that increases the wet strength of glyoxylated polyacrylamide. These materials are generally described in US Pat. Nos. 3,556,932 to Coscia et al . and US 3,556,933, Williams et al ., which are incorporated herein by reference. Resins of this type are commercially available under the brand name PAREZ. Various acrylamide / -DADMAC / glyoxal molar ratios can be used to prepare cross-linked resins that are useful as wet strength reagents. In addition, other dialdehydes can replace glyoxal to obtain wet shrink strength characteristics. Particularly suitable are the wet-resistant polyamidamine-epichlorohydrin resins which are, for example, sold under the trademarks Kymene 557LX and Kymene 557H by Hercules Inc., Wilmington, Delaware and Amres® from Georgia-Pacific Resins, Inc. These resins and a method for preparing resins are described in US Pat. No. 3,700,623 and US Pat. No. 3,772,076, each of which is incorporated herein by reference. A detailed description of polymeric epihalohydrin resins is given in Chapter 2: “ Alkaline-Curing Polymeric Amine-Epichlorohydrin,” Espy in “ Wet Strength Resins and Their Application” (L. Chan, Editor, 1994), which is incorporated herein by reference . An acceptable list of wet strength resins is described by Westfelt in Cellulose Chemistry and Technology Volume 13, p. 813, 1979, which is incorporated herein by reference.

Suitable dry strength agents include starch, guar gum, polyacrylamides, carboxymethyl cellulose (CMC) and the like. Carboxymethyl cellulose is particularly applicable, an example of which is sold under the trademark Hercules CMC , Hercules Inc., Wilmington, Delaware.

According to the invention, the regenerated cellulosic fiber is obtained from a cellulose solution including cellulose dissolved in a solvent including tertiary amine N-oxides or ionic liquids. The solvent composition for dissolving cellulose and preparing unmodified cellulose solutions typically includes tertiary amine oxides such as N-methylmorpholine-N-oxide (NMMO) and similar compounds listed in US Pat. No. 4,246,221 , which is incorporated herein by reference material. Cellulose solutions may contain poor solvents for cellulose such as water, alkanols or other solvents, as will be apparent from the discussion that follows.

Suitable cellulose solvents are listed in table 1 below.

Table 1 Examples of tertiary amine N-oxide solvents Tertiary amine N-oxide % water % pulp N-methylmorpholine-N-oxide up to 22 up to 38 N, N-dimethyl-ethanol-amine-N-oxide up to 12.5 up to 31 N, N-dimethylcyclohexylamine-N-oxide up to 21 up to 44 N-methyl homopiperidine-N-oxide 5.5-20 1-22 N, N, N-triethylamine-N-oxide 7-29 5-15 2- (2-hydroxypropoxy) -N-ethyl-N, N, -dimethyl-amide-N-oxide 5-10 2-7.5 N-methylpiperidine-N-oxide up to 17.5 5-17.5 N, N-dimethylbenzylamine-N-oxide 5.5-17 1-20

See also patent US 3508945, Johnson , which is included in this description as a reference material.

Details regarding the preparation of cellulose solutions, including cellulose dissolved in suitable ionic liquids, and the regeneration of cellulose therefrom are given in US Pat. No. 6,824,599 to Swatloski et al , entitled “ Dissolution and Processing of Cellulose Using Ionic Liquids, ” which is included in this description as a reference. Here again acceptable levels of solvents that do not dissolve the cellulose can be included. This patent generally describes a method for dissolving cellulose in an ionic liquid without derivatization and regeneration of cellulose in various structural forms. It has been described that the solubility of cellulose and the properties of the solution can be controlled by the selection of components for an ionic liquid with small cations and halide or pseudo-halide anions that favor dissolution. Preferred ionic liquids for dissolving cellulose include liquids with cyclic cations, such as the following: imidazolium; pyridinium; pyridazinium; pyrimidinium; pyrazinia; pyrazolium; oxazolium; 1,2,3-triazolium; 1,2,4-triazolium; thiazolium; piperidinium; pyrrolidinium; quinolinium and isoquinolinium.

Processing techniques for ionic liquids / cellulose solutions are also discussed in US Pat. No. 6,808,557, Holbrey et al ., Entitled “ Cellulose Matrix Encapsulation and Method ”, which is incorporated herein by reference (see also US Patent Application US 11 / 087,496; patent US 2005/0288484, Holbrey et al., entitled “ Polymer Dissolution and Blend Formation in Ionic Liquids ”, and US Pat. No. 6808557, Holbrey et al., entitled “ Cellulose Matrix Encapsulation and Method ”, which are incorporated herein by reference as reference material). With respect to ionic liquids, the following documents generally provide additional details: patent application US 11 / 406,620, (patent publication US 2006/0241287, Hecht et al., Entitled “ Extracting Biopolymers From a Biomass Using Ionic Liquids ”); patent application US 11 / 472,724, (patent publication US 2006/0240727, Price et al., entitled “ Ionic Liquid Based Products and Method of Using the Same ”); patent application US 11 / 472,729; (Patent Publication US 2006/0240728, Price et al., entitled “ Ionic Liquid Based Products and Method of Using the Same ”); patent application US 11 / 263,391, (patent publication US 2006/0090271, Price et al., entitled “ Processes For Modifying Textiles Using Ionic Liquids ”); and patent application US 11/375963 by Amano et al. (publication US 2006/0207722), which are included in this description as a reference material. Some ionic liquids and pseudo-ionic liquids that can be used are first described by Konig et al., Chem. Commun. 2005, 1170-1172 , which is incorporated herein by reference.

The term “ionic liquid” refers to a molten composition comprising an ionic compound, which preferably is a stable liquid at temperatures lower than 100 ° C. under normal pressure. Typically, such liquids have a very low vapor pressure at 100 ° C, less than 75 mbar (7.5 kPa) or about and preferably less than 50 mbar (5.0 kPa) or less than 25 mbar (2.5 kPa) at 100 ° C. The most suitable liquids will have a vapor pressure of less than 10 mbar (1.0 kPa) at 100 ° C and often the vapor pressure is so low that it is negligible and not easily measurable as it is less than 1 mbar (0.1 kPa) at 100 ° C.

Suitable commercially available ionic liquids are Basionic ^™ ionic liquids available from BASF (Florham Park, NJ) and are listed in Table 2 below.

table 2 Typical ionic liquids STANDARD Name abbreviation Basionic ™ Class The product's name ChemAbstr Number EMIM Cl ST 80 1-ethyl-3-methylimidazolium chloride 65039-09-0 EMIM CH ₃ SO ₃ ST 35 1-ethyl-3-methylimidazolium methanesulfonate 145022-45-3 BMIM Cl ST 70 1-butyl-3-methylimidazolium chloride 79917-90-1 BMIM CH ₃ SO ₃ ST 78 1-butyl-3-methylimidazolium methanesulfonate 342789-81-5 MTBS ST 62 methyl tri-N-butylammonium methyl sulfate 13106-24-6 MMMPZ MeOSO ₃ ST 33 1,2,4-trimethylpyrazolium methyl sulfate EMMIM EtOSO ₃ ST 67 1-ethyl-2,3-dimethylimidazolium ethyl sulfate 516474-08-01 MMMIM MeOSO ₃ ST 99 1,2,3-trimethyl-imidazolium methyl sulfate 65086-12-6 ACID Name abbreviation Basionic ™ Class The product's name ChemAbstr Number HMIM Cl AC 75 methylimidazolium chloride 35487-17-3 HMIM HSO ₄ AC 39 methylimidazolium hydrosulfate 681281-87-8 EMIM HSO ₄ AC 25 1-ethyl-3-methylimidazolium hydrosulfate 412009-61-1 EMIM AlCl ₄ AC 09 1-ethyl-3-methylimidazolium tetrachloroaluminate 80432-05-9 BMIM HSO _{4 </} AC 28 1-butyl-3-methylimidazolium hydrosulfate 262297-13-2 BMIM AlCl ₄ AC 01 1-butyl-3-methylimidazolium tetrachloroaluminate 80432-09-3 BASIC Name abbreviation Basionic ™ Class The product's name ChemAbstr Number EMIM Acetate BC 01 1-ethyl-3-methylimidazolium acetate 143314-17-4 BMIM Acetate DC 02 1-butyl-3-methylimidazolium acetate 284049-75-8 LIQUID AT ROOM TEMPERATURE Name abbreviation Basionic ™ Class The product's name ChemAbstr Number EMIM EtOSO ₃ LQ 01 1-ethyl-3-methylimidazolium ethyl sulfate 342573-75-5 BMIM MeOSO ₃ LQ 02 1-butyl-3-methylimidazolium methyl sulfate 401788-98-5 LOW VISCOSITY Name abbreviation Basionic ™ Class The product's name ChemAbstr Number EMIM SCN VS 01 1-Ethyl-3-methylimidazolium thiocyanate 331717-63-6 BMIM SCN VS 02 1-Butyl-3-methylimidazolium thiocyanate 344790-87-0 FUNCTIONALIZED Name abbreviation Basionic ™ Class The product's name ChemAbstr Number Acetate COL FS 85 Choline Acetate 14586-35-7 Salicylate COL FS 65 Choline Salicylate 2016-36-6 MTEOA MeOSO ₃ FS 01 Tris (2-hydroxyethyl) methylammonium methyl sulfate 29463-06-7

Cellulose solutions including ionic liquids having here a solute content of about 5% by weight of unmodified cellulose are commercially available from Aldrich. These compositions use alkyl methyl imidazolium acetate as a solvent. It was found that choline-based ionic liquids are not particularly suitable for dissolving cellulose.

After receiving the cellulose solution, it is spun into fiber, fibrillated and incorporated into the absorbent web, as described below.

Synthetic cellulose, such as lyocell, is broken down into micro and nanofibers and added to traditional wood pulp. The fiber can be fibrillated in a disk mill, for example, or using any other suitable technique using a PFI mill. A relatively short fiber is preferably used, and the density is retained during fibrillation. Favorable properties of fibrillated lyocell include: biodegradability, the presence of hydrogen bonds, dispersion, the ability to re-boil and smaller microfibers than, for example, fibers that can be obtained by molding from a solvent.

Fibrillated lyocell or its equivalent has advantages over melt-splittable spunbond fibers. Synthetic fibers with a thickness of the order of microdeny are formed in various forms. For example, nylon / PET fiber with a thickness of 3 denier in a so-called wedge-shaped configuration can be split into 16 or 32 segments, usually in a method of hydrobinding. Each 16-segment fiber segment should have a grain size of about 2 mg / 100 m compared to eucalyptus pulp having about 7 mg / 100 m. Unfortunately, a number of drawbacks are associated with this approach in traditional wet application methods. Dispersion is less than optimal. Melt-formed fibers must be split before a web is formed, and there is no effective way to do this. The most affordable polymers for these fibers are not biodegradable. The granularity is smaller than that of wood pulp, but still high enough so that they must be used in significant quantities and constitute an expensive part of the paper pulp. Ultimately, the lack of hydrogen bonds requires other methods of retaining the fibers in the fabric.

Fibrillated lyocell has fibers that can be small, of the order of 0.1-0.25 microns (μm) in diameter, calculated on a grain size of 0.0013-0.0079 mg / 100 m. Provided that these fibers are available as individual fibers separated from the original fiber, the density of the pulp fibers can be impressively increased with a very low level of addition. Even fibers that are not separated from the original fiber can provide an advantage to the pulp. Product properties, such as dispersion, reboilability, hydrogen bonds and biodegradability, are preserved since the fibers are cellulose.

Lyocell fiber has important differences from wood pulp fibers. The most important difference is the length of lyocell fibers. For wood pulp fibers, only a micron length is possible and, therefore, action in the area of direct fiber-to-fiber communication. Wood pulp fibrillation by pulverizing the pulp leads to stronger, denser canvases. Lyocell fibers, however, are potentially as long as the original fibers. These fibers can act as independent fibers and increase volume while maintaining or improving strength. Swamp pine and Southern mixed wood (MSHW) are two examples of fibers that are of lower quality relative to pulp of the highest level of softness. The term “pulp of the highest level of quality”, as used here, refers to pulps from softwoods of northern grades and eucalyptus, usually used in light industry to obtain products of the mildest class for a bath, for face and towels. Swamp pine is coarser than the unbleached sulfated softwood of the northern grades, and mixed hardwood of the southern grades is coarser and more finely chopped than the commercially available eucalyptus. A lower grain size and lower content of fine particles in the market pulp of the highest quality level leads to a higher fiber density, expressed as the number of fibers per gram (N or N _{i> 0.2} ) in table 1. Grit and length values in table 1 were obtained using the OpTest fiber quality analyzer. The results were obtained by the formulas below:

Northern Bleached Sulphated Softwoods (NBSK) and Eucalyptus have more fiber per gram than bog pine and hardwood. Smaller grit leads to higher fiber density and smoother webs.

Table 3 Fiber properties Sample Type of C, mg / 100 m Fine inclusion,% L _{n mm} N, MM / g L _n , _{> 0.2 mm} N _{> 0.2 mm} , MM / g Southern hardwood Pulp 10.1 21 0.28 35 0.91 eleven Solid wood of the southern grades and a small amount of fine inclusions Pulp 10.1 7 0.54 eighteen 0.94 eleven Eucalyptus Aracruz Pulp 6.9 5 0.50 29th 0.72 twenty Southern softwood Pulp 18.7 9 0.60 9 1,57 3 A mixture of southern varieties (30% softwood / 70% hardwood) Pulp 14.2 3 1.24 6 1.74 four A mixture of southern varieties (30% softwood / 70% hardwood) Canvas base 11.0 eighteen 0.31 29th 0.93 10 30% Southern softwood / 70% Eucalyptus Canvas base 8.3 7 0.47 26 0.77 16

For comparison, “unmodified” or “original” lyocell fibers have a grain size of 16.6 mg / 100 m before fibrillation and a diameter of about 11-12 microns. The fibers have a grain size of the order of 0.001-0.008 mg / 100 m. Thus, the fiber density can be impressively increased at relatively low levels of addition. The fiber length of the original fiber can be selected, and the fiber length of the fibrils can depend on the initial length and size when cut during the fibrillation process.

Fibrils of fibrillated lyocell have a grain size of the order of 0.001-0.008 mg / 100 m. Thus, the fiber density can be impressively increased at relatively low levels of addition. The fiber length of the original fiber can be selected, and the fiber length of the fibrils can depend on the initial length and the degree of cutting during the fibrillation process, as can be seen from figure 2 and 3.

The sizes of the fibers passing the mesh with a sieve number of 200 are of the order of magnitude of 0.2 microns per 100 microns. Using these sizes, fiber density can be calculated as 200 billion fibers per gram. In comparison, southern sorts of wood can have three million fibers per gram and eucalyptus can have twelve million fibers per gram (Table 3). Obviously, these fibers are fibrils, which are obtained by splitting from the original unmilled fibers. Different types of lyocell fibers designed for easy fibrillation can lead to fibers with a diameter of 0.2 microns, which may have a length of 1000 microns or more, instead of 100. As indicated above, fibrillated fibers of regenerated cellulose can be obtained by obtaining the “original” fibers having a diameter of 10-12 microns or so, followed by fibrillation of the starting fibers. Alternatively, lyocell fibrillated microfibres have recently become available from Engineered Fibers Technology (Shelton, Connecticut), which have acceptable properties. As can be seen from FIG. 2, series analyzes by the Bauer-MacNett classifier of fibrillated lyocell samples show different degrees of “fine grain”. Particularly preferred materials have more than 40% fiber, which is finer than the 14th sieve number, and have a very low grit (low degree of grinding). For obviousness, the sizes of the sieve numbers are presented in table 4 below.

Table 4 Sieve Number Size Sieve Number # Inches Microns fourteen .0555 1400 28 .028 700 60 .0098 250 one hundred .0059 150 200 .0029 74

Details on fractionation using the Bauer-McNett classifier can be found in Gooding et al., “Fractionation in a Bauer-McNett Classifier”, Journal of Pulp and Paper Science; Vol. 27, No. December 12 , 12, 2001, which is incorporated herein by reference.

Figure 3 is a graph showing the fiber length as measured by the FQA analyzer for various samples, including samples 17-20 shown in Figure 2. From these data it can be seen that most of the fine fiber is excluded by FQA analysis and the length before fibrillation has an effect on fineness.

Depending on the intended desired properties, webs can be used in various products with more than 35%, more than 40% or more than 45%, 50% or more, by weight of any fibrillated cellulose microfiber as defined herein. Typically, up to about 75% by weight of regenerated cellulose microfiber is used; although in some cases up to 90 or 95% by weight of regenerated cellulose microfiber may, for example, be used. The minimum amount of regenerated cellulose microfibre that is used can be more than 35% or 40% in any quantity to an acceptable maximum, i.e. 35 + X (%), where X is any positive number up to 50 or up to 70, if necessary. The following typical ranges of composition can be applied to an absorbent sheet:

% regenerated cellulose microfiber % obtained through pulp paper-forming fiber > 35 to and including 95 5 to less than 65 > 40 to and including 95 5 to less than 60 > 35 to and including 75 25 to less than 65 > 40 to and including 75 25 to less than 60 37.5-75 25-62.5 40-75 25-60

In some embodiments, the regenerated cellulosic microfiber may be present in the range of 10-75%, as described below; it is understood that the aforementioned weight ranges can be replaced in any embodiment of the invention, if desired for the web.

In its various aspects, the present invention relates, in part, to an absorbent paper web comprising from about 90 wt.% Or less, for example, less than 65 wt.% To about 25 wt.% Of pulp pulp-forming paper-forming fiber and from about 10 wt.% up to about 75 wt.% fibrillated regenerated cellulose microfiber having a CSF value of less than 175 ml, where the paper-forming fiber is organized into a fiber matrix and lyocell microfibre is metered and distributed into a fiber mat Itza to form therein microfiber network. Microfiber fibrillation is controlled in such a way that it has a reduced grain size and a reduced degree of grinding compared to the regenerated cellulose microfiber from which it is made, so that the microfiber network provides at least one of the following properties to the absorbent web:

(a) the absorbent web has an increased SAT and an increased wet elongation compared to a similar web obtained without regenerated cellulose microfiber;

(b) the absorbent web has a higher ratio of wet / dry CD extensibility compared to a similar web obtained without regenerated cellulose microfiber;

(c) the absorbent web has a smaller GM tear modulus than a similar web having similar tensile values obtained without regenerated cellulose microfiber; or

(d) the absorbent web has an increased volume compared to a similar web having similar tensile values and obtained without regenerated cellulosic microfiber. Typically, the absorbent web has a wet / dry stretch ratio of at least 25% higher than the ratio of a similar web obtained without regenerated cellulose microfiber; typically, the absorbent web has a wet / dry stretch ratio of at least 50% higher than the ratio of a similar web obtained without regenerated cellulose microfiber. In some cases, the absorbent web has a wet / dry stretch ratio of at least 100% higher than the ratio of a similar web obtained without regenerated cellulose microfiber.

In some embodiments, the absorbent web of the invention has a GM tear modulus of at least 20% less than a similar web having similar tensile values obtained without regenerated cellulose microfiber, and the absorbent web has a specific volume of at least 5% higher than a similar web having similar tensile values obtained without regenerated cellulose microfiber. A specific volume of at least 10% higher than that of a similar web having similar tensile values obtained without regenerated cellulosic microfiber is easily achieved.

One of a series of preferred embodiments comprises from about 5 wt.% To about 75 wt.% Regenerated cellulose microfiber, where the regenerated cellulose microfiber has a CSF value of less than 150 ml. More typically, the regenerated cellulosic microfiber has a CSF value of less than 100 ml; but a CSF value of less than 50 ml or 25 ml is preferred in many cases. Similarly, regenerated cellulose microfiber having a CSF value of 0 ml is used. While any suitable microfiber size can be used, the regenerated cellulosic microfiber typically has an average diameter of less than about 2.0 microns, for example from about 0.1 to about 2 microns. Regenerated cellulose microfiber may have a grain size of less than about 0.5 mg / 100 m; from about 0.001 mg / 100 m to about 0.2 mg / 100 m in many cases. Fibrillated regenerated cellulose may have a fiber density of more than 50 million fibers / gram. In one embodiment, the fibrillated regenerated cellulose has a weight average diameter of less than 2 microns, a weight average length of less than 500 microns, and a fiber density of more than 400 million fibers / gram. In another embodiment, the fibrillated regenerated cellulose has a weighted average diameter of less than 1 micron, a weighted average length of less than 400 microns, and a fiber density of more than 2 billion fibers / gram. In a further embodiment, the fibrillated regenerated cellulose has a weight average diameter of less than 0.5 microns, a weight average length of less than 300 microns, and a fiber density of more than 10 billion fibers / gram. In addition, fibrillated regenerated cellulose may have a weighted average diameter of less than 0.25 microns, a weighted average length of less than 200 microns, and a fiber density of more than 50 billion fibers / gram. In some cases, a fiber density of more than 200 billion fibers / gram is used.

In particular, as can be seen from FIG. 2, at least 50%, at least 60%, at least 70%, or at least 80% of the microfibre may be thinner than sieve number 14.

The product typically has a paper weight of from about 5 pounds (2.3 kg) per sheet of sheets at 3,000 square (278.7 m ² ) feet (8 g / m ² ) to about 40 pounds (18 kg) per sheet of sheet (278, 7 m ² ) at 3,000 square feet (65 g / m ² ). For a towel, the base of the web can have a paper weight of from about 15 pounds (6.8 kg) per foot sheet (278.7 m ² ) of 3000 square feet (24 g / m ² ) to about 35 pounds (16 kg) per foot sheet (278.7 m ² ) of 3000 square feet (57 g / m ² ), and pulp-derived paper-forming fiber includes predominantly softwood fiber, usually predominantly unbleached sulfated softwood fiber of southern varieties and at least 20 wt.% Obtained through solid wood fiber paper pulp.

In another aspect of the invention, there is provided an absorbent paper web for a fabric or towel comprising from about 90% to about 25% by weight pulp-forming paper fibers and from about 10% to about 75% by weight regenerated cellulose microfiber having CSF a value of less than 100 ml, where the absorbent web has an absorbency of at least about 4 g / g. Absorbency of at least about 4.5 g / g, at least about 5 g / g; or at least about 7.5 g / g is sometimes preferred. In numerous cases, the absorbent web has an absorbency of from about 6 g / g to about 9.5 g / g. In some cases, the web includes from about 80-30% obtained through pulp paper-forming fibers and from about 20% to about 70% fibrillated regenerated cellulose microfiber. From about 70-35% of the paper-forming fiber can be approximately together with from about 30 wt.% To about 65 wt.% Of the regenerated cellulose microfiber. From about 60-40% of the paper-forming fiber obtained through the pulp and from about 40% to about 60% by weight of fibrillated regenerated cellulose microfibre can be used in the web, especially if high efficiency wipes are desired.

Another product of the invention is an absorbent paper web for fabric or towel, comprising from about 90 wt.% To about 25 wt.% Obtained through pulp paper-forming fibers and from about 10 wt.% To about 75 wt.% Regenerated cellulose microfiber having a CSF value of less than 100 ml, where the regenerated cellulosic microfiber has a fiber density of greater than 50 million fibers / gram. The regenerated cellulosic microfiber may have a weight average diameter of less than 2 microns, a weight average length of less than 500 microns, and a fiber density of more than 400 million fibers / gram; or regenerated cellulosic microfiber has a weight average diameter of less than 1 micron, a weight average length of less than 400 microns, and a fiber density of more than 2 billion fibers / gram. In one embodiment, the regenerated cellulosic microfiber has a weighted average diameter of less than 0.5 microns, a weighted average length of less than 300 microns, and a fiber density of more than 10 billion fibers / gram, and in another embodiment, the regenerated cellulosic microfiber has a weighted average diameter less than 0.25 microns, a weighted average length of less than 200 microns, and a fiber density of more than 50 billion fibers / gram. A fiber density greater than 200 billion fibers / gram is available if necessary.

The canvas may include a resin that increases the strength in the dry state, such as carboxymethyl cellulose and a resin that increases the strength in the wet state, such as polyamidine-epihalohydrin resin. The ratio of CD-elongation in the wet / dry state can be in the range from about 35% and about 60%, for example, at least about 40% or at least about 45%.

A further aspect of the invention provides an absorbent cellulosic web comprising:

(a) cellulosic pulp-forming paper-forming fibers in an amount of from about 25 wt.% to about 90 wt.%; and

(b) fibrillated regenerated cellulose fibers in an amount of from about 75 wt.% to about 10 wt.%, where said regenerated cellulose fibers have an average fiber width of less than about 4 microns. The average fiber width may be less than about 2 microns; less than about 1 micron; or less than about 0.5 microns. The average fiber length of the regenerated cellulosic fibers may be less than about 500 micrometers; less than about 250 micrometers; less than about 150 micrometers; less than about 100 micrometers; or the average lyocell fiber length is less than about 75 micrometers, if necessary.

Another product of the invention is an absorbent cellulosic web, including:

(a) cellulosic pulp-forming paper-forming fibers in an amount of from about 25 wt.% to about 90 wt.%; and

(b) fibrillated regenerated cellulose fibers in an amount of from about 75 wt.% to about 10 wt.%, where said regenerated cellulose fibers have an average fiber length of less than about 500 microns.

The average fiber length of the fibrillated regenerated cellulose fiber may be less than about 250 microns, less than about 150 or 100 microns, or less than about 75 microns, if necessary.

In some embodiments, the web has a paper density of less than 8 pounds / foot of sheets per 3,000 square feet (13.0 g / m ² ) and normalized TAPPI opacity greater than 6 TAPPI opacity units per pound of paper density (2, 7 units of opacity according to TAPPI per kg). In other cases, such a web has a normalized paper density greater than 6.5 TAPPI opacity units per pound of paper density (2.9 TAPPI opacity units per kg). The gain in opacity is particularly useful in connection with the fiber returned to circulation, for example, where the web is basically a fiber returned to circulation. Fabric base webs that have a paper density of from about 9 pounds to about 11 pounds / foot of sheets (from about 15 to about 18 g / m ² ) made from recycled fiber typically have normalized opacity greater than 5 opacity TAPPI per pound of paper density (2.3 opacity units per TAPPI per kg). The products listed below optionally have the above opacity characteristics.

It was found that the products according to the invention exhibit unusually high ratios of CD-elongations in the wet / dry state when the paper-forming fibers obtained through pulp are pre-treated with a baking powder composition. Wet / dry ratios of more than 30%, i.e., about 35% or large, are easily achieved; usually in the range of about 35% to 60%. Ratios of at least about 40% or at least about 45% can be seen in the examples below. The pulp is preferably processed at a high concentration, that is, greater than 2%, preferably greater than 3% or 4% and usually between 3-8% in the inlet stream of the machine pool, in a pulper, for example. The paper-forming fibers obtained through the pulp, or at least a part of the paper-forming fibers obtained through the pulp, can, for example, be pretreated with a baking powder during pulping. All or some of the fibers may be pretreated; 50 wt.%, 75 wt.%, And up to 100 wt.% Obtained through the pulp of the fiber can be pretreated, including or excluding the content of regenerated cellulose, where pretreatment may not be critical. Then the fiber can be ground, as you know, in a disk mill. Thus, a resin that improves dry strength and / or a resin that increases wet strength can also be used. Processing of the fiber obtained through the pulp can be carried out from about 1 to about 50 pounds of the baking powder composition per ton of fiber obtained through the pulp (dry base) (from 0.5 to 23 kg). From about 5-30 or 10-20 pounds of disintegrant per ton of fiber obtained through the pulp (approximately 2.0-12 or 4.1-8.2 kg per metric ton) is suitable in most cases.

Pretreatment can be carried out for any acceptable length of time, for example at least 20 minutes, at least 45 minutes, or at least 2 hours. In general, pre-processing will be in the time range from 20 minutes to 48 hours. The pre-treatment time is calculated as the amount of time during which the aqueous paper-forming fiber obtained through the pulp is in contact with the aqueous baking powder before the formation of the fabric structure, which is in the formation stage. In acceptable amounts, a wet strength resin and a dry strength resin were added; for example, either one or both can be added to the web in amounts from 2.5 to 40 pounds per ton of paper-forming fiber obtained through the pulp (1.0 to 16 kg per metric ton).

The present invention also includes methods of obtaining, such as a method of obtaining an absorbent cellulosic fabric, including:

(a) obtaining an aqueous pulp with a fiber mixture containing from about 90% to about 25% pulp-derived paper-forming fibers, where the fiber mixture also includes from about 10 wt.% to 75 wt.% regenerated cellulose microfibers having a CSF value less than 175 ml; (b) placing the aqueous paper pulp on a perforated base to form a structure of the web in the process of formation and at least partially dehydrating the resulting web structure; and

(c) drying the web structure to obtain an absorbent web. Typically, aqueous paper pulp has a concentration of 2% or less; even more typically, aqueous pulp has a concentration of 1% or less. In some cases, the aqueous paper pulp has a concentration of 5% or less, and in other cases, the concentration is 3% or less. The resulting structure of the canvas can be dehydrated by compaction with paper-forming cloth and transferred to the American drying apparatus and creped on it. Alternatively, a web-dehydrated web structure is applied to a rotating cylinder and fabric fastened thereon, or a web-fabric that is in the process of formation is at least partially dehydrated by air drying, or a web-fabric that is in the process of formation is at least partially dehydrated by forced air drying. In many cases, the fiber blend includes unbleached sulfated softwood and unbleached sulfated hardwood. The ratios of the various components of the fiber can be changed as described above.

Another method of obtaining the base of the fabric web according to the invention includes:

(a) preparing an aqueous paper pulp comprising solid wood fiber or soft wood fiber and a fibrillated regenerated cellulose microfiber having a CSF value of less than 100 ml and a fiber density of more than 400 million fibers per gram;

(b) placing the aqueous paper pulp on a perforated base to form an emerging web structure and at least partially dehydrating the resulting web structure; and

(c) drying the web structure to obtain an absorbent web. A fibrillated regenerated cellulose fiber can have a fiber density of more than 1 billion fibers per gram, or a fibrillated regenerated cellulose fiber has a fiber density greater than 100 billion fibers per gram, if necessary.

The invention is further illustrated in the following Examples.

EXAMPLES

Example 1

The study of the canvas for hands was carried out with soft wood of southern grades and fibrillated fiber lyocell. The original lyocell fiber had a thickness of 1.5 denier (16.6 mg / 100 m) with a length of 4 mm (see Figure 4), which was then fibrillated to achieve a degree of milling <50 CSF. As can be seen from FIGS. 5 and 6, the fibrillated fiber has a much lower grain size than the original fiber. 7-11 are microphotographs of fibrillated lyocell material that was passed through a 200 mesh sieve mesh according to the Bauer McNett classifier. This material is commonly referred to as “finely divided inclusions”. In wood pulp, finely divided inclusions are mainly particles, not fibers. The fibrous nature of this material should allow it to interweave among many fibers and, therefore, increase the strength of the network. This material makes up a significant amount (16-29%) of fibrillated lyocell with a CSF value of 40.

The sizes of the fibers passing through the mesh with a sieve number of 200 are about 0.2 microns in size with a length of 100 microns. Using these dimensions, fiber density can be calculated as 200 billion fibers per gram. In comparison, swamp pine may have three million fibers per gram and eucalyptus may have twenty million fibers per gram (Table 1). Comparing the finely divided fraction with the images of sieve number 14, it is obvious that these fibers are fibers that are split from the original unmilled fibers. Various forms of lyocell fiber designed for rapid fibrillation can lead to fibers with a diameter of 0.2 microns, which may have a length of 1000 microns or more instead of 100 microns.

One aspect of the invention is to improve the performance of southern pulp, but other uses are obvious: to further increase the softness of the highest quality fabric at a given strength, increase the softness of the secondary fiber, improve the hand feel of the towel, increase the strength of the towel when wet, and increase the SAT .

12-17 show the strong influence of fibrillated lyocell on the properties of the canvas for hands. Volume, opacity, smoothness, modulus and tear are improved at a given level of elongation. The results were compared as a function of extensibility, since strength is always an important variable in tissue products. In addition, unbleached sulfated wood pulp tends to fall on similar curves for a given variable, so it is advisable to shift to a new curve for a strong change in the properties of the final product. The fibrillated lyocell favorably changes the volume / strength curve (FIG. 12). Some of the microfibers can be incorporated into the pores between much larger softwood fibers, but the overall result is that lyocell dissipates between the softwood fibers with an increase in network volume.

Fibrillated lyocell promotes smoothness, which is measured as Bendtsen roughness (Fig. 13). Bendtsen roughness is obtained by measuring the air flow between a weighted plate and a paper sample. Smoother webs allow less air flow. Small fibers can fill some surface pores, which should in other circumstances take place on a sheet of 100% soft wood. The strong effect of smoothness on an uncreped hand cloth should be maintained even after the creping process.

Opacity is another variable improved by lyocell (Fig. 14). A large number of microfibers creates a huge surface area for light scattering. Below 80 opacity units is equivalent to canvases with eucalyptus content up to 100%, thus achieving this opacity in case of 80% softwood of southern varieties is significant.

The hand canvas module is lower at a given extensibility with lyocell (Fig. 15). As a result, drapability should improve. A large number of fibers gets into the network better and allows a more even distribution of the load. One of the drawbacks of southern softwood is its tendency to achieve less elongation in creped fabric than northern softwood. Obviously, lyocell can help overcome this shortcoming. The fibrillated lyocell improves the tear properties of the hand sheet (FIG. 16). Southern softwood often attracts attention due to its tensile strength relative to other unbleached sulfated pulps, so it is noticeable that fibrillated lyocell increases the tensile characteristics of softwood hand paintings. Rupture is usually considered an important property for tissue, but it shows a different way in which lyocell can enhance network properties.

The role of soft wood fibers can generally be described as ensuring the strength of the network, while solid wood fibers provide smoothness and opacity. Fibrillated lyocell has a length sufficient to improve network properties, while its low grain size provides the benefits of hardwood.

From the above, it is obvious that lyocell fibers are more different than wood pulp fibers. Wood pulp fiber is a complex structure comprising several layers (P, S1, S2, S3), each with single strands of cellulose arranged in a spiral around the fiber axis. During mechanical grinding, parts of the layers P and S1 are separated in the form of a finely divided product and fibers. These fibers are generally very short, possibly no longer than 20 microns. Fibers tend to act in close proximity to fibers when crossing with other fibers. Thus, wood pulp fibers tend to increase bond strength, web strength, web density and web elongation. The multilayer structure of the fiber wall with spiral fibers makes it impossible to split the wood fiber along its axis using commercial methods. In contrast, lyocell fiber has a much simpler structure, which allows the fibers to split along its axis. The resulting fibers are small, about 0.1-0.25 microns in diameter, and as long as the original fiber. The length of the fibers is likely to be shorter than the “original” fiber, and the decay of multiple fibers may be insufficient. However, if a sufficient number of fibers can work as individual fibers, the properties of the paper can have a significant effect with a relatively low level of addition.

The relative grain sizes of pulp and paper pulp and lyocell can be discussed. Northern softwood (NBSK) has a grain size of about 14 mg / 100 m compared to marsh pine, 20 mg / 100 m. Southern mixed hardwood (MSHW) has a grain size of 10 mg / 100 m compared to 6.5 eucalyptus mg / 100 m. Lyocell fibers with diameters in the range of 0.1-0.25 microns should have grain sizes in the range of 0.0013-0.0079 mg / 100 m. One way to characterize the difference between the highest quality paper pulp and paper pulp southern varieties is the fiber density, expressed as the number of fibers per gram of paper masses (N). N is inversely proportional to grain size, thus, pulp of the highest quality level has a higher fiber density than pulp of southern varieties. Southern grades of pulp fiber density can be increased to equal or superior pulp fiber density of the highest quality level by adding fibrillated lyocell.

Lyocell microfibres have many attractive features, including biodegradability, dispersibility, reboilability, low graininess and extremely low grain to length ratio (C / L). A low C / L ratio means that the strength of the web can be obtained with a lower level of binding, which makes the web more flexible (smaller modulus, as shown in FIG. 15).

Table 5 summarizes effects that are significant at a 99% confidence level (excluding where noted). The purpose of the various treatments was to measure the relative effects on strength. Southern softwood is less effective in increasing the strength of the net than northern softwood, so it is one subject of interest to investigate whether lyocell can strengthen southern softwood. Pulp with 20% lyocell and 80% southern softwood is significantly better than 100% southern softwood. Volume, opacity and tear are higher at a given extensibility, while the roughness and modulus are smaller. These trends are directionally favorable for fabric properties.

Hand cloths for table 5 were obtained according to the TAPPI method T-205. Volumetric thickness in cubic centimeters per gram is obtained by dividing the caliper thickness by the density of the paper. Bendtsen roughness is obtained by measuring the air flow between a solid plate and a paper sample. “L” refers to the labeled side of the hand sheet that adheres to the metal plate during drying, while “U” refers to the unlabeled side. ZDT refers to lateral extensibility of the canvas for hands.

Table 5 The main effects on the properties of the canvas for hands Test Average value The effect of grinding the mass of soft wood Lyocell fibrillation effect Mutual effect of pulverization of lyocell mass Caliper thickness 5 cloths (cm ³ / g) 1.76 -0.19 0.15 Bendtsen roughness, side L-1kg (ml / min) 466 -235 -101 28 (95%) Bendtsen roughness, U-1kg side (ml / min) 1482 137 (95%) ZDT fiber binding (psi, bar) 49 (340) 36 (250) -11 (-76) -13 (-90) HS-gap, g 120 20 (95%) TAPPI Opacity 77 -four 13 Breaking length, km 3,5 1.8 -0.6 (95%) Hand canvas extension,% 2,4 0.9 -0.4 (95%) Hand stretch energy, kg-mm 6.7 5.3 -1.9 (95%) The tensile modulus of the canvas for hands, kg / mm ² 98 28 -eighteen

Table 5 repeats the advantages of fibrillated lyocell shown graphically in FIGS. 12-17: higher volume, better smoothness, higher tear, better opacity and lower modulus.

Table 6 compares the morphology of lyocell and softwood fibers, as measured by OpTest Optical Fiber Quality Analyzer (FQA). The "source" lyocell fibers (Figure 4) have a grain size of 16.7 mg / 100 m, similar to the grain size of southern varieties of softwood (20 mg / 100 m). After fibrillation, the grain size measured by FQA dropped to 11.9, similarly to the soft wood of the northern varieties. Apparently, the resolution of the FQA is unable to accurately measure either the length and width, or the grain size of very thin fibers. The smallest fine particle measured by FQA is 41 microns. The narrowest width measured by FQA is 7 microns. Thus, a grain size of 11.9 mg / 100 m is not representative of fibrillated lyocell. Based on the calculations, a fiber with a diameter of one micron has a grain size of 0.17 mg / 100 m, and 0.1 micron fiber has a grain size of 0.0017 mg / 100 m. The average grain size of the lyocell is obviously less than 11.9 mg / 100 m FQA measurements. The differences in fiber size are more apparent when comparing Figs. 18 and 19. Fig. 18 is a micrograph taken with only unbleached sulfated softwood of southern varieties, milled by 1000 calls in a PFI mill, while Fig. 19 is a canvas. for hands, produced with 80% of the same softwood of southern varieties and 20% of ground lyocell fiber. The exceptionally low graininess of fibrillated lyocell relative to traditional wood pulp is evident.

Table 6 The morphology of fibrillated lyocell compared to whole lyocell and softwood FQA OpTest parameter Fibrillated lyocell Lyocell, 1.5 denier Southern softwood Ln mm 0.38 2.87 0.68 Lw mm 1,64 3.09 2.40 Lz mm 2,58 3.18 3.26 Fine inclusions (n),% 67.4 2.9 64.0 Fine inclusions (w),% 16.3 0.1 8.5 Curl indicator (mass.) 0.36 0,03 0.19 Width, microns 16.5 20.1 29.9 Granularity, mg / 100 m 11.9 16.7 20.5 CSF-degree of grinding, ml 22 746

Combined softwood and southern hardwood are cheaper than pulp of the highest quality level, but the softwood pulp's ability to produce soft tissue is less than desirable for some applications. Mills producing products of the highest quality may require the purchase of fibers of the highest quality, such as northern softwood and eucalyptus for the highest quality of softness, which increases the price and adversely affects the balance of the ground fiber. According to the present invention, milled lyocell fibers were added to improve the quality of the pulp.

At high levels of pulverization, the masses of fibers can be separated from the original fiber and work as independent micro- or possibly even nano-fibers. The degree of fibrillation was measured according to the Canadian Standard of Grinding Degree (CSF). Unmilled lyocell has a milling degree of about 800 ml, and test quantities are prepared at about 400, 200 and 40 ml. It was hypothetically hypothesized that a high level of pulverization would produce the greatest effect at the lowest rate of addition. Larger grinding creates a higher content of very low-grain fibers, but can also reduce the average fiber length. It is preferable to maximize the production of fine-grained fibers while minimizing fiber cutting. In the present study, 4 mm hand webs were milled to 22 ml with an average fiber length (Lw) of 1.6 mm. As discussed previously, a value of 1.6 mm, according to FQA measurements, is not considered a true average value, but is only intended to show the direction of decreasing length when grinding the mass. The fibrillated lyocell obtained for the latter examples starts from 6 mm fibers with a grain size of 16.7 mg / 100 m before pulverization. Ideal fibers are significantly smaller than eucalyptus, while maintaining a sufficient length. In fact, pulverization significantly reduces the length of the fiber, however, they have a length sufficient to strengthen the fiber network.

Lyocell microfiber makes it possible to significantly increase the number of fibers / gram of paper pulp by adding only moderate amounts of microfiber. We can discuss the calculation results in table 7, from which we can see that fibrillated lyocell easily reaches a fiber density of more than a billion fibers per gram.

Table 7 Dimensions of fibrillated lyocell fiber D, microns C mg / 100 m Length mm N, million fibers / g 0.1 0.0013 0.1 795775 0.25 0.0079 0.2 63662 0.5 0,031 0.3 10610 one 0,126 0.4 1989 2 0.50 0.5 398 11.5 16.6 6 one

In comparison, eucalyptus fiber, which has a relatively large number of fibers, has only up to about 20 million fibers per gram.

Example 2

This example of a hand canvas demonstrates that the advantage of fibrillated lyocell arises mainly from short, low-grain fibers to a greater extent than from partially milled original fibers that inadvertently survived the mass grinding process. Lyocell with a size of 6 mm on 1.5 denier was ground to a grinding degree of 40 and separated into fractions in the Bauer McNett classifier using a mesh with mesh numbers 14, 28, 48, 100 and 200. The fiber length is the primary factor, which determines the passage of fibers through each mesh. Fractions with mesh numbers 14 and 28 were combined to create one fraction, subsequently referred to as “long fibers”. The fractions with sieve numbers 48, 100, 200 and the part passing through the sieve number 200 were pooled to form a second fraction, subsequently referred to as “short fibers”. Southern softwood was obtained by grinding its mass by 1000 revolutions in a PFI mill. Hand sheets were made at a paper density of 15 pounds / foot of sheets (24 g / m ² ), pressed at 15 psi (100 kPa) for five minutes, and dried on a steam-heated drum. Table 8 compares hand canvases made with various combinations of softwood and fibrillated lyocell. Softwood alone (Sample 1) has low opacity, low elongation and low elongation. 20% of long fibers (Sample 2) moderately improve opacity and elongation, but not extensibility. 20% of short fibers (Sample 3) significantly increase opacity, elongation, and extensibility, more significantly than non-ground lyocell (Sample 4). Sample 5 uses re-combined long fibers and short fibers to approximate the initial fibrillated lyocell. From this example, it may be obvious that the contribution of short fibers to the present invention is predominant.

Table 8 Hand towels with a density of 15 pounds / foot sheets (24 g / m ² ) with various components
fibrillated lyocell Sample Description Opacity TAPPI (Opacity Units) Hand canvas extension (%) Breaking length (km) Specific Volume (cm ³ / g) Paper Weight (lbs / ream sheets, g / m ²⁾ one 100% southern softwood 46 0.7 0.75 2.92 14.3 (23.3) 2 80% Southern softwood / 20% fibrillated long fiber lyocell 52 0.9 0.73 3.09 15.4 (25.1) 3 80% Southern softwood / 20% fibrillated short fiber lyocell 65 1.4 0.98 2.98 15.0 (24.4) four 80% Southern softwood / 20% fibrillated unfractionated lyocell 61 1.3 0.95 2.81 15.7 (25.6) 5 80% Southern softwood / 20% fibrillated long fiber lyocell / 10% fibrillated short fiber lyocell 59 1.3 0.92 2.97 14.9 (24.2) Long = fractions sieve number 14 and sieve number 28
Short - mixture sieve number 48 + sieve number 100 + sieve number 200+ material passed through a mesh with sieve number 200

FIG. 20 illustrates one embodiment of the present invention in which a machine pool 50 , which can be divided into sections, is used to prepare paper pulps that are treated with chemicals that have different uses depending on the nature of the different fibers used. In this embodiment, a split headbox is shown, thereby allowing the layered product to be obtained. The product of the present invention can be obtained from one or more pressure boxes 20 , 20 ', and, regardless of the number of pressure boxes, they can be layered or non-layered. The treated paper pulp is transported through various channels 40 and 41, through which it enters the headbox of the sickle forming machine 10 , which is well known, although any suitable configuration can be applied.

Fig. 20 shows a part forming a web structure, or a wet part, with a liquid permeable element of a perforated substrate 11 , which may be of any suitable configuration. The perforated base element 11 can be made of any of several known materials, including photopolymer fabric, cloth, woven or synthetic fiber mesh, with a very thin synthetic fiber insulating mat attached to the mesh. The element of the perforated base 11 is supported in a standard way on the rollers, including the remote roller 15 and the pressing roller 16 .

The resulting fabric 12 is supported on rollers 18 and 19, which are mounted relative to the outer roll 15 to guide the forming wire 12 until converging on the element of the perforated base 11 on the cylindrical remote roller 15 at an acute angle with respect to the element of the perforated base 11. The element of the perforated base 11 and the wire 12 move at the same speed and in the same direction, which is the direction of rotation of the outrigger roller 15. The forming wire 12 and the element of the perforated base 11 converge the surface of the forming roll 15 to form a wedge-shaped space or gap in which one or more jets of water or a foamed liquid dispersion of the fiber can be injected and captured between the forming wire 12 and the element of the perforated base 11 to enhance the flow through the wire 12 into the tray 22, where it collected for reuse in the process (returned to circulation through line 24).

The structure of the fabric W, which is in the process of formation, formed in the process, is carried out along the longitudinal direction 30 by the action of the element of the perforated base 11 to the pressing roller 16, where the wet structure of the fabric W, which is in the stage of formation, is transferred to the American dryer 26. The liquid is removed by pressing from the wet of the web structure W by the pressing roller 16, while the web structure is moved to the American drying apparatus 26, where it is dried and fixed by means of a creping knife 27. End Single web structure is collected on the tension roller 28.

A container 44 is provided for collecting water squeezed out of the paper pulp by a pressing roller 16, as well as collected water removed from the fabric by a Ule 29 cloth-washing machine. Water collected in the container 44 can be collected in a production line 45 for separate processing in order to remove surface-active substances and fibers from the water and returning the recycled water back to the paper machine 10.

With CWP-applying apparatus of the type shown in Figure 20, a series of absorbent webs were prepared from the pulp, from mixed hardwood / softwood pulp and comprising floured lyocell fiber. The general approach was to crush softwood to the required level and obtain a softwood / solidwood mixture in the mixing tank. After making a control sample from 100% pulp of paper pulp, additional samples were obtained by measuring microfiber in a mixture. Elongation was optionally corrected either by the action of baking powder or starch. The applied pulps of the southern grades are softwood and hardwood. Paper pulp of the “highest level of quality” was obtained from northern varieties of soft wood and eucalyptus. Tissue creping was kept constant to reduce the number of variables. 1.8 lb / T (0.9 kg / ton) 1145 PAE was used and 15 degree knives were used, except for towel samples, for which 8 degree knives were used. The temperature of the dryer was constant, 248 ° F (120 ° C). Paper density, MDDT, CDDT and caliper thickness were measured on all rollers. CDWT and two-layer SAT were measured for some test samples and softness was examined using a panel of prepared testers using two-layer samples, 4 inches × 28 inches (10.2 cm × 71.1 cm), obtained from the base of the web on the outer side surface of the American dryer. Details and results are shown in tables 9-10 and Fig.21-32.

Table 9 Materials for testing CWP samples Wood pulp Microfibre The degree of grinding of soft wood [ml] 40% Southern softwood /
60% Southern hardwood 0 570 32% softwood southern varieties /
48% Southern Hardwood 20 (217 csf) 570 20% softwood southern varieties /
30% Southern Hardwood 50 (217 csf) 570 0 100 (217 csf) 40% Southern softwood /
60% Southern hardwood 0 570 32% softwood southern varieties /
48% Southern Hardwood 20 (40 csf) 570 36% southern softwood /
54% Southern Hardwood 10 (40 csf) 570 38% softwood southern varieties /
57% Southern hardwood 5 (40 csf) 570 40% Northern softwood / 60% Southern hardwood 0 580 38% Northern softwood / 57% Southern hardwood 5 (40 csf) 580 32% Northern softwood / 48% Southern hardwood 20 (40 csf) 580 70% softwood southern varieties /
30% Southern Hardwood 0 580 56% softwood southern varieties /
24% Southern Hardwood 20 (40 csf) 580 40% Southern softwood /
60% Southern hardwood 0 680 36% southern softwood /
54% Southern Hardwood 10 (40 csf) 680 38% softwood southern varieties /
57% Southern hardwood 5 (40 csf) 680 39% Southern softwood /
59% Southern Hardwood 2 (40 csf) 680 40% northern softwood / 60% eucalyptus 0 580 32% northern softwood / 48% eucalyptus 20 (40 csf) 580 50% northern softwood / 50% eucalyptus 0 580 40% northern softwood / 40% eucalyptus 20 (40 csf) 580 (Differences in the degree of grinding of soft wood arising from the grinding of the mass)

Bath fabric produced with paper pulp of southern varieties and 10% microfibre was 21% stronger than the control sample with the same softness (Fig.21). Based on the latter result, the microfibre web should be softer than the control sample if extensibility is reduced by stiffer creping, calendaring, embossing, and so on. From FIG. 22, it can be seen that the microfibre lyocell has exceptional ability to achieve low paper density at acceptable levels of elongation and softness.

From Fig.23 it can be seen that the addition of microfibre lyocells in the CWP method increases the volume at different paper densities and tensile strengths. This is an unexpected result due to the fact that the specialist cannot expect an increase in volume from finely divided inclusions. This result is not observed in other methods, for example, a fabric creping method, where the fabric structure is formed in vacuum before applying an American drying apparatus to the drying cylinder.

Microfiber provides advantages to both the paper pulp of the southern grades and the paper pulp of the highest level of quality (soft wood of the northern grades and eucalyptus), but the paper pulp of the southern grades to a greater extent.

Microfiber significantly increases the strength and elongation of fabrics with low paper density. The high fiber density provided by microfiber creates a very uniform network. Although most of the trends characteristic of microfibre observed in the study of handwraps were confirmed for creped fabric, the great influence of microfibre on elongation and modulus was unexpected (see Fig. 24-28).

The volume, strength and opacity provided by microfibre makes it possible to reduce paper density, which is not achieved in the case of wood pulp. Stretchability increases from 250 g / 3 in. (250 g / 7.62 cm) at 10 pounds / foot of sheets (16 g / m ² ) to 400 g / 3 in. (400 g / 7.62 cm) at 8 pounds / foot of sheets ( 13.0 g / m ² ) by adding 20% microfibre and CMC / WSR composition. A web with a density of 5.2 lbs / stack of sheets (8.5 g / m ² ) was obtained at the same extensibility as a control web with a density of 10 lbs / stack of sheets (16 g / m ² ) with the same combination of 20% microfibre and CMC / WSR, and more durable wood pulp is provided.

Microfibre in the towel increased wet tensile, wet / dry ratio and SAT absorption capacity. This had consequences in the form of a higher level of softness of the towel or rag. The wet / dry ratio for one sample increased from about 20% to 39% with the addition of 20% microfibre. Microfiber modified the SAT / wet strength curve.

Lyocell 217 CSF had an unacceptable level of flocculants and nucleoli. Therefore, 400 CSF fiber was not used, and 40 CSF microfibre was used in the remaining tests. The 40 CSF microfibers were dispersed uniformly, and it was found that the 217 CSF microfibers could be dispersed after re-passing through a conical mill which was unloaded for 20 minutes. In the 217 CSF process, microfiber was reduced to 20 CSF.

Micrographs of Bauer McNett fractions (see FIGS. 5, 6 and 7-11) suggest that half of the fibers in 40 CSF lyocells are not disintegrated. The consequence of this observation is that the results obtained in this test can possibly be obtained with half levels of addition, if the method continues until the fibrillation of 100% fibers.

The adhesion of the American dryer is slightly less in the case of microfiber paper pulp. The height of the dam in the headbox is increased due to less possibility for drainage, but can be controlled by the action of increased vacuum.

Strong effect on elongation / modulus.

24, 25, and 26 show noticeable microfiber effects. Microfiber increases the elongation and elongation of the web. For example, the fabric base of a bath sheet with a density of 12 pounds / foot of sheets (20 g / m ² ), produced with 100% wood pulp, includes 40% softwood of southern varieties and 60% of hardwood of southern varieties. If 20% microfibre is added, the elongation increases by 48%, but the modulus increases by only 13%. A slight increase in module results from a significant increase in elongation of the web. MD elongation increases from 24.2% to 30.5%, and CD elongation increases from 4.2% to 6.0%. Microfibers give an advantage to the paper pulp of the southern grades and paper pulp of the highest level of quality (soft wood of the northern grades and eucalyptus), but a greater advantage is given to the paper pulp of the southern grades. This was demonstrated by comparing the “theoretical” elongation, defined as (speed of the American dryer / bobbin speed - 1) * 100. The theoretical MD elongation in this study was (100/80 -1) * 100 = 25%. Here, the definition is the amount of stress required for easy exit creped canvas. It is possible to obtain an actual elongation higher than theoretical elongation, since an uncreated web also has a small elongation. Southern pulp in this example has an elongation of 24.2%, slightly below theoretical. In southern paper pulp or paper pulp of the highest quality level, MD elongation is high, 31-32%. The advantages provided to the paper pulp of the southern grades are greater, since its initial characteristics are much lower.

Fig. 26 shows a change in elongation obtained by microfibre. Microfibre increases the extensibility in slightly ground tissue paper pulps, but the extensibility decreases in the paper pulp for a towel, where a larger percentage of the pulp is ground. The latter result is consistent with hand webs, but a large increase in extensibility in low-density fabrics is unexpected and not observed in hand webs. Note that 20% of microfibre in hand sheets with non-ground soft wood of the southern grades does not lead to higher extensibility.

Paper weight reduction

Microfiber has the potential to significantly reduce paper density. Figs. 27 and 28 show two examples in which paper density is reduced by 25% and 40-50%, respectively. In the first case, the base of the web with a density of 10 pounds / foot of sheets (16 g / m ² ) at 255 g / 3 inches (33.5 g / cm) of GM stretchability was reduced to a density of 8 pounds / foot of sheets (13 g / m ² ) at 403 g / 3 in. (52.9 g / cm) GM-extensibility with the introduction of 20% microfibre and a mixture of CMC / additive, increasing the strength in the wet state. The wet / dry ratio was 32%. A sample with a density of 8 pounds / foot of sheets (13 g / m ² ) and 403 g / 3 inches (52.9 g / m ² ) was 58% stronger than a control sample with a density of 10 pounds / foot of sheets (16 g / m ² ), however, the fracture modulus increased by only 23%. Opacity and molding were good. In the second case, the base of the web with a density of 10 pounds / foot of sheets (16 g / m ² ) at about 400 g / 3 inches (52.5 g / cm) was reduced to 5.2 pounds / foot of sheets (8.5 g / m ² ) with the same extensibility, using the same method as in the first case. Canvases with a density of 8 lbs / foot sheets (13 g / m ² ) have good uniformity. A web with a density of 5.2 pounds / foot of sheets (8.5 g / m ² ) had some openings, but the openings were caused by the limitations of the inclined template on PM 1 than by the fiber's ability to achieve good fiber distribution. A web with a density of 6 pounds / foot of sheets (9.8 g / m ² ) with good uniformity and extensibility is a significant achievement on the current prototype machine. A sickle shaped cutter can be suitable for even lower densities that cannot be achieved with 100% wood pulp. While such low densities may ultimately not be applied, this demonstrates the extent to which microfiber greatly affects the integrity of the fabric structure of the fabric.

Towel Properties.

Microfiber can improve towel strength when wet, wet / dry ratio, and SAT absorption capacity. The base of the canvas with a density of 15 pounds / foot of sheets (24 g / m ² ) was obtained from 100% pulp of paper pulp, including 70% of soft wood of southern varieties and 30% of hard wood of southern varieties. A traditional wet strength kit of 4 lbs / ton (2 kg / ton) CMC and 20 lbs / ton (10 kg / ton) Amres 25HP was used. Two control rolls had dry elongation of 2374 and 2400 g / 3 inches (311.5 and 315.0 g / cm) of GM extensibility and wet CD ratio of 303/1705 = 18% and 378/1664 = 23 % The composition of the pulp was changed to 80% of wood pulp and 20% of cellulose microfibers and the paper density of the product was maintained at 15 pounds / foot of sheets (24 g / m ² ). The volume increased, the opacity increased, the fracture modulus decreased 19%, and the tensile strengths in the dry state decreased to 2013 and 2171 g / 3 inches (264.2 and 284.9 g / cm). The wet / dry CD ratio on these two rolls increased to 506/1305 = 39% and 443/1545 = 29%. The absorption capacity of the SAT increased by 15%. The SAT absorption capacity and wet strength are usually inversely related, so the fact that microfiber increases both values means that the SAT / wet strength curve shifts positively. The selected results are presented graphically in figures 29 and 30 .

Without intending to be associated with any theory, it is assumed that the above results are the result of a microfiber network formed by microfiber. Fig. 31 is a micrograph of a creped web without microfiber; Fig. 32 is a micrograph of the corresponding web with 20% milled lyocell. From Figure 32 it can be seen that the microfiber greatly enhances the formation of a fiber network in the web even at low masses because of its extremely high density of fibers.

Table 11 presents the FQA measurement data for various lyocell pulps. Even though it is likely that many microfibers are not visible, some trends can be seen on the fibers that are observed. Unmilled lyocell has a very uniform length, a very small number of fine-grained particles and is very linear. Pulverization reduces the fiber length, generates “fine particles” (which are different from the fine particles of traditional wood pulp) and makes the fibers curly. A comparison of milled to 4 mm with milled to 6 mm suggests that the initial fiber length within a certain range may not be essential for the final fiber length, since most of the original fibers will be split into shorter fibers. A length of 6 mm is preferred over 4 mm, since the fiber should avoid the additional processing step of cut short fibers from tow. Typical conditions for fibrillated lyocell are low concentration (0.5% -1%), low intensity (which is determined by traditional pulverization technology) and high energy (possibly 20 HPday / ton (1400 MJ / ton)). High energy is desirable if regenerated cellulose is fibrillated, as it may take a long time at low energy. A concentration of up to 6% or greater may optionally be applied, and a high energy input of perhaps 20 HPD / ton (1400 MJ / ton) or more may be used.

Another result of Table 11 is that CSF lyocell 217 readily degrades to 20 CSF after passing through a conical mill unloaded for 20 minutes. The CSF pulp 20 is uniformly dispersed in contrast to the CSF pulp 217.

Table 11 OpTest Fiber Quality Analyzer Data for Lyocell Fiber Description Arithmetic average length, Ln, mm Weighted average length, Lw, mm Length in average weight, Lz, mm Fine inclusions, Fw,% Index Curl, Lw FQA fiber width, microns 6 mm-Lyocell ground to 40 CSF Sample 1 0.34 1.77 3.19 19.0 0.55 16.1 Sample 2 0.33 1.74 3.23 19.8 0.57 17.0 Sample 3 0.36 1.91 3.20 18.0 0.52 16.6 Bauer-MacNett Fractions
(Bauer McNett), 40 CSF Fraction 14 0.86 2.79 3,58 5,4 0.60 18.2 Faction 28 1,69 2,58 2.94 1,0 0.66 18.2 Faction 48 0.39 1.00 1,64 12.7 0.62 15,5 Fraction 100 0.21 0.36 0.54 29.4 0.57 14.7 Faction 200 0.11 0.22 1.48 70.0 0.70 12,4 6 mm lyocell, ground to 217 CSF 0.8 3.34 4.69 11.2 0.70 18.9 217 CSF lyocell, ground to 20 CSF 0.26 1,08 2,36 26.7 0.33 13.7 Unmilled 3 mm lyocell 2.87 3.09 3.18 0.1 0,03 20.1 4 mm lyocell, ground to 22 CSF 0.39 1,64 2,58 16.3 0.36 16.5

Mechanism

Without the intention of being connected with any theory, the mechanism of microfiber operation, as it seems, is its ability to significantly improve the uniformity of the network with an extremely high surface area. Several observations can be linked together to support this hypothesis: lyocell weakness, excellent durability leading to hand and tissue webs, and interactions with ground and ground wood pulp.

Unmilled lyocell is very weak in itself, and even highly milled lyocell approaches close to the strength potential of wood pulp (8-10 km). Alpha cellulose in lyocell and fiber morphology appear to increase strength through a very high number of weak bonds. A high fiber concentration provides more bonds between wood fibers when added to the fabric. Pulp of southern varieties, in general, and pine, in particular, has a low fiber density, which requires higher bond strength than pulp of the highest quality level for a given strength. Southern softwood can also be difficult to form, leading to islands of unbound flocculants. Microfiber can weave flocculants to improve network uniformity. This microfiber ability becomes more pronounced as paper density decreases. A strong effect on the strength is not observed in hand webs with a high paper density, since there is a sufficient amount of wood fibers to fill the canvas.

INDUSTRIAL APPLICABILITY

Fibrillated lyocell is expensive relative to the paper pulp of southern varieties, but it offers potential opportunities that cannot be obtained by another method. Fibrillated lyocell fibers at relatively low levels of addition can enhance southern pulp at a competitive price relative to top-quality pulp.

Additional examples

Additional typical configurations include a three-layer product for the face, which includes two outer layers with exceptional softness, and an inner layer with strength in the wet state and, possibly, with a higher level of strength in the dry state than the outer layers. The product is made by combining cellulose microfibers and appropriate reagents to impart desired properties. It may be possible to achieve exceptionally low paper weights when obtaining a product with good strength.

Microfibers provide a huge surface area and network uniformity due to the extremely high fiber density. Network quality leads to higher wet / dry tensile properties.

Absorbency characteristics (speed and capacity) are attributed to the structure with smaller pores created by microfibers. There may be a more optimal addition rate, where capacity and other benefits are realized without speed reduction.

Southern fabric pulp bath fabric

The fabric base of the bath sheet was produced with a density of 12 pounds / foot of sheets (20 g / m ² ) with 100% wood pulp, which included 40% soft wood of southern varieties and 60% of hard wood of southern varieties. Two rolls with tensile strengths of 384 and 385 g / 3 inches GM-extensibility (50.4 and 50.5 g / cm) and tear modules of 37.2 and 38.2 g /% were produced. The composition of the pulp was changed to 80% of wood pulp and 20% of cellulose microfibers. Two rolls were produced with extensibilities of 584 and 551 g / 3 inches of GM-extensibility (76.6 and 72.3 g / cm) and tensile modules of 42.7 and 42.9 g /%. Elongation increased by 48%, but the modulus increased only by 13%. Low module growth arose from a significant increase in blade elongation. MD elongation increased from 24.2% to 30.5%, and CD elongation increased from 4.2% to 6.0%. Southern pulp in this example had a 24.2% elongation, slightly below theoretical. The pulp of the highest quality level in Example 1 yielded about 27% MD elongation. In southern paper pulp or paper pulp of the highest level of quality, the MD elongation is high, 31-32%. The advantages provided by the pulp of southern varieties are great, since its initial characteristics are much lower.

Microfibers may be more favorable in fabric creped processes than in conventional air drying processes that require high permeability. The reason is that microfibers may tend to block the pore structure of the web, so that the air flow should be reduced in the traditional TAD method of air drying, but this is not a problem with wet pressing / creping methods in which the web is dehydrated by densification. One way to enhance the benefits of microfiber is to reduce paper density, but volume can then be a problem for certain products. Microfibre in combination with papermaking processes that form the web can be particularly beneficial for products with low paper weight with adequate volume. It should be noted that microfibers favorably alter the volume / strength relationship for CWP webs. The cellulosic substrate can be obtained by traditional methods (including TAD, CWP and their variants), known to specialists in this field. In many cases, the fabric creping techniques described in the following pending applications will be particularly suitable: US Patent Application Serial No. 11/804246 (Patent Publication US 2008-0029235), filed May 16, 2007, entitled “ Fabric Creped Absorbent Sheet with Variable Local Basis Weight ”, US Patent Application Serial Number 11/678669 (Patent Publication US 2007-0204966), entitled“ Method of Controlling Adhesive Build-Up on a Yankee Dryer ”; US Patent Application Serial Number 11/451112 (Patent Publication US 2006-0289133), filed June 12, 2006, entitled “ Fabric-Creped Sheet for Dispensers ”; US patent application serial number 11/451111, filed June 12, 2006 (patent publication US 2006-0289134), entitled " Method of Making Fabric-creped Sheet for Dispensers "; US Patent Application Serial Number 11/402609 (Patent Publication US 2006-0237154), filed April 12, 2006, entitled “ Multi-Ply Paper Towel With Absorbent Core ”; US patent application serial number 11/151761, filed June 14, 2005 (patent publication US 2005/0279471), entitled " High Solids Fabric-crepe Process for Producing Absorbent Sheet with In-Fabric Drying "; US patent application serial number 11/108458, filed April 18, 2005 (patent publication US 2005-0241787), entitled “ Fabric-Crepe and In Fabric Drying Process for Producing Absorbent Sheet ”; US patent application serial number 11/108375, filed April 18, 2005 (patent publication US 2005-0217814), entitled “ Fabric-crepe / Draw Process for Producing Absorbent Sheet ”; US Patent Application Serial Number 11/104014 filed April 12, 2005 (Patent Publication US 2005-0241786) entitled “ Wet-Pressed Tissue and Towel Products With Elevated CD Stretch and Low Tensile Ratios Made With a High Solids Fabric-Crepe Process ” ; (see also US Patent 7,399,378, issued July 15, 2008, entitled “ Fabric-crepe Process for Making Absorbent Sheet ”; US Patent Application Serial Number 12/033207, filed February 19, 2008, entitled “ Fabric Crepe Process With Prolonged Production Cycle ” The applications and patents indicated immediately above are especially important for the selection of equipment, materials, processing conditions, and so on, for creped products of the present invention, and these applications are incorporated herein by reference.

The wet structure of the web can also be dried either at the beginning of thermal dehydration, air drying or forced air drying. Suitable rotary air drying equipment is described in US Pat. No. 6,432,267 to Watson and US Pat. No. 6,447,640 to Watson et al.

Examples 78-89 for a towel.

Hand towels such as towels were obtained from paper pulp from soft wood / lyocell and tested for physical properties and to determine the effect of additives on the ratio of CD-extensibility in the wet / dry state. It has also been found that pretreatment of the pulp with a baking powder composition is surprisingly effective in increasing the ratio of CD extensibility in the wet / dry state of the product, making even softer products possible. Details are given below and are presented in table 12.

The wood pulp used in Examples 78-89, was a softwood unbleached sulfated pulp of southern varieties. CMC is the abbreviation for carboxymethyl cellulose, a dry strength improver that is added to 5 pounds / ton (2.5 kg / short ton) of fiber. Also in these examples, a wet strength improver (WSR) was added; Amres 25 HP (Georgia Pacific) added 20 pounds / ton (10 kg / short ton) of fiber (including lyocell content in the fiber weight). The baking powder composition (Db) used was of type C; the ion-pair baking powder composition as described above was applied as 10% active and added based on the weight of the paper-forming fiber obtained through the pulp, excluding the lyocell content.

The CMF used was a lyocell fiber with dimensions of 6 mm × 1.5 denier, which was ground to 40 ml of CSF before adding it to the pulp.

Next, the procedure was carried out as described below:

1. The pulp was pre-soaked in water before disintegration.

2. The pulp for samples 79, 81, 83, 85 and 86-89 was obtained by adding a disintegrant in the amounts indicated for the British disintegrator, and then adding a pre-soaked dry preform to approximately 3% concentration and disintegration.

3. If the grinding of the mass is indicated in table 11, the pulp was divided in half; half of the pulp was concentrated to grind the mass, washed for 1000 rpm and re-diluted to 3% with filtrate.

4. The pulp halves were re-combined in a beaker and, with vigorous stirring, AMRES resin was added to increase wet strength. After 5 min, CMC was added. Then, after another 5 minutes, the pulp was diluted to obtain hand canvases; 0.5 g hand canvas, pressed at 15 psi / 5 min (10 kPa), dried on a drum dryer and cured in an air oven with forced drying at 105 ° C / 5 min.

5. The pulp for samples 78, 80, 82, 84 was obtained through the stages indicated above, passing the baking powder and sometimes not grinding mass, as indicated in table 12.

6. For examples containing 20% CMF, CMF was added to softwood before adding WSR / CMC.

The effect of pretreatment of softwood pulp with baking powder can be seen in Fig . 33 . The wet / dry stretch ratio is significantly increased both by the addition of CMF and by pre-treatment with baking powder. In some cases, the wet strength remains substantially constant, while the dry strength decreases. The dry strength of towels is often determined by the required wet strength, which leads to products that are relatively inflexible. For example, a towel with a 25% wet / dry stretch ratio may have a dry strength substantially greater than desired in order to satisfy wet strength requirements. Grinding the mass is usually required to increase the strength, which reduces the volume and absorbency. An increase in the wet / dry stretch ratio from 24 to 47% makes it possible to reduce dry stretch by almost half. The smaller modulus at a given extensibility provided by CMF also contributes to a better sensation for the hand (Fig. 34). The baking powder to some extent reduces the volume in the tested samples (Fig. 35).

In industrial processes, it is preferable to pre-process the incoming stream of pulp-forming paper-forming fibers of the machine pool with the aim of increasing efficiency, as noted in the patent application US 11/867113 (patent publication US 2008-0083519), filed October 4, 2007, entitled “ Method of Producing Absorbent Sheet with Increased Wet / Dry CD Tensile Ratio ”, which is included in this description above; what can be seen in Fig. 36. In a typical application of the present invention, a baking powder was added to the pulp in a pulper 60, as shown in FIG. 36, which is a block diagram schematically illustrating the pulp feeding into a paper machine. Baking powder was added to the pulper 60, while the fiber at any concentration from about 3% to about 10%. The mixture was then pulped after adding a disintegrant for 10 minutes or more before adding a wet strength resin or a dry strength resin. The fiber in the pulp was usually diluted to a concentration of about 1 percent or so and then fed into the machine pool 50, where other additives could be added, including a stable resin that increases wet strength and a resin that increases dry strength. If necessary, a resin that increases the strength in the wet state and a resin that increases the strength in the dry state, in the pulper, or the inlet stream or the outlet stream of the machine pool, that is, 64 or 66, can be added; however, they must be added after the baking powder, as noted above; and the dry strength resin is preferably added after the wet strength resin. The pulp can be pulverized and / or enriched before or after it enters the machine pool, as is known in the art.

From the machine pool 50, the pulp was then diluted to a concentration of 0.1% or about and further fed into a headbox, such as headbox 20, through a mixing pump 68.

The opacity of the fabric base of the canvas

Using a paper machine of the type shown in FIG. 20, fabric web bases of various paper densities were obtained using fibrillated regenerated cellulose microfibre and recycled paper-forming fiber obtained through pulp. TAPPI opacity was measured and correlated with paper density as shown in FIG. 37 , which is a graph of TAPPI opacity versus paper density for 7 and 10 pound web webs (3 and 5 kg) having the formulations shown.

From FIG. 37, it can be seen that large increases in opacity, typically in the range of about 30% -40% or more, are easily achieved using fibrillated regenerated cellulose microfiber. Paired with the strength gain observed in the present invention, it is thus possible, according to the invention, to provide high quality fabric products using much less fiber than in the case of traditional products.

Additional examples of CWP samples .

Using a CWP apparatus of the class shown in FIG. 20, a series of adsorbent webs with softwood pulps were prepared, including ground microfibre lyocell fiber. The general method was to obtain a mixture of unbleached sulfated softwood and microfiber in a mixing tank and dilute the pulp to a concentration of less than 1% in the headbox. Elongation was changed using a resin that increases the strength in the wet state, and a resin that increases the strength in the dry state.

Details and results are shown in table 13.

Table 13 Crepe CWP Cloths CWP Number Pulp Percentage Percent Micro
fiber Additives Caliper thickness for 8 sheets, mils / 8 sheets (μm / 8 sheets) Paper Weight, lbs / 3000 square feet (g / m ² ) Tensile MD, g / 3 inches (g / cm) Elongation MD,% CD extensibility,
g / 3 inches (g / cm) Elongation CD,% CD-Finch Cured wet tensile g / 3 inches (g / cm) CD rupture modulus, g / m ² /% Tear modulus MD, g / m ² /% SAT g / g Specific Volume, cc / g 12-1 one hundred 0 No 29.6 (752) 9.6 (16) 686 (90.0) 23.9 500 (65.6) 5,4 83 29th 9,4 4.9 13-1 75 25 No 34.3 (871) 11.2 (18.2) 1405 (184.4) 31.6 1000 (131.2) 5.8 178 44 6.8 4,5 14-1 fifty fifty No 37.8 (960) 10.8 (17.6) 1264 (195.9) 31.5 790 (103.7) 8.5 94 40 7.9 5.3 15-1 fifty fifty 4 lb / ton (2 kg / short ton) cmc and 20 lb / ton (10 kg / short ton) Amres 31.4 (798) 11.0 (17.9) 1633 (214.3) 31,2 1093 (143.4) 9.1 396 (52.0) 122 53 6.6 4.2 16-1 75 25 4 lb / ton (2 kg / short ton) cmc and 20 lb / ton (10 kg / short ton) Amres 30.9 (785) 10.8 (17.6) 1205 (158.1) 29.5 956 (125) 6.2 323 (42.4) 166 35 7.1 4,5 17-1 75 25 4 lb / ton (2 kg / short ton) cmc and 20 lb / ton (10 kg / short ton) Amres 32.0 (813) 10.5 (17.1) 1452 (190.6) 32.6 1,080 (141.7) 5.7 284 (37.3) 186 46 7.0 4.0 18-1 one hundred 0 4 lb / ton (2 kg / short ton) cmc and 20 lb / ton (10 kg / short ton) Amres 28.4 (721) 10.8 (17.6) 1931 (253.4) 28.5 1540 (202.1) 4.9 501 (65.7) 297 70 8.6 3.4 19-1 one hundred 0 4 lb / ton (2 kg / short ton) cmc and 20 lb / ton (10 kg / short ton) Amres 26.2 (665) 10.2 (16.6) 1742 (228.6) 27.6 1499 (196.7) 5.1 364 (47.8) 305 66 7.6 3.8

Fig. 38 shows softness results on bilayer CWP samples. Control samples were prepared from a mixture of 40% southern timber and 60% hard southern timber from Naheola. Control samples included server-grade bleached softwood and eucalyptus. Cmf was added in amounts ranging from 2% to 20% of the pulp, the pulp components maintained the same 40/60 ratio of softwood and hardwood. For comparison, samples were prepared with soft wood of the northern varieties and eucalyptus. In addition, samples prepared with soft wood of the northern grades and hard wood of the southern grades showed a relative improvement with respect to 100% of the paper pulp of the southern grades. As can be seen from FIG. 38 , the cmf-containing material had increased softness and extensibility.

While the invention has been described in detail, modifications within the scope of the invention will be readily apparent to those skilled in the art. In view of the above discussion of the relevant prior art and references, including those discussed above in connection with the prior art and a detailed description of pending applications, all of which are incorporated by reference in their entirety, further description is deemed unnecessary.

Claims (17)

1. An absorbent paper web comprising pulp-forming paper-forming fiber and up to 75% by weight of regenerated cellulosic microfiber, where the absorbent web has an absorbency of at least 4 g / g, and the regenerated cellulose is obtained from a pulp solution with dissolved cellulose comprising a solvent selected from: N-oxides of tertiary amines; cellulose-soluble imidazolium salts; pyridinium salts dissolving cellulose; pyridazinium salts dissolving cellulose; pyrimidinium salts dissolving cellulose; pyrazinium salts dissolving cellulose; pyrazolium salts dissolving cellulose; cellulose dissolving oxazolium salts; cellulose dissolving 1,2,3-triazolium salts; cellulose dissolving 1,2,4-triazolium salts; cellulose-dissolving thiazolium salts; piperidinium salts dissolving cellulose; cellulose-dissolving pyrrolidinium salts; quinolinium salts dissolving cellulose; and cellulose-dissolving isoquinoline salts,
characterized in that the regenerated cellulose in the web includes more than 25 wt.% fibrillated regenerated cellulose microfiber having
a Canadian Standard of Grind (CSF) value of less than 100 ml, preferably less than 50 ml, more preferably less than 25 ml, and even more preferably a CSF value of 0 ml;
a weighted average diameter of less than 1 μm, preferably less than 0.5 μm, more preferably less than 0.25 μm;
a weighted average length of less than 400 microns, preferably less than 300 microns, more preferably less than 200 microns;
and a fiber density of more than 2 billion fibers / g, preferably more than 10 billion fibers / g, more preferably more than 50 billion fibers / g, and most preferably more than 200 billion fibers / g. 2. The absorbent fabric according to claim 1, having:
a value measured by a simple absorbency meter (SAT), at least 15% higher; and
an increased wet stretch is at least 40% higher compared to a similar web obtained without fibrillated regenerated cellulose microfiber. 3. The absorbent fabric according to claim 1, having a ratio of stretchability in the transverse (CD) direction in the wet / dry state is at least 25% higher, preferably at least 50% higher, more preferably at least 100% higher than the ratio for a similar web obtained without fibrillated regenerated cellulose microfiber. 4. The absorbent web according to claim 1, having a geometrically averaged (GM) tear modulus of at least 20% less than a similar web having similar tensile values obtained without fibrillated regenerated cellulose microfiber. 5. The absorbent web according to claim 1, having a specific volume of at least 5% higher, more preferably 10% higher than a similar web having similar tensile values obtained without fibrillated regenerated cellulose microfiber. 6. The absorbent fabric according to claim 1, in which the fabric includes more than 30 wt.%, Preferably more than 35 wt.%, More preferably from 40 wt.% To 75 wt.% And most preferably from 40 wt.% up to 60 wt.%, fibrillated regenerated cellulose microfiber, which has a CSF value of less than 100 ml. 7. The absorbent fabric according to claim 1, in which
fibrillated regenerated cellulose microfiber has a grain size of less than 0.5 mg / 100 m, preferably from 0.001 mg / 100 m to 0.2 mg / 100 m 8. The absorbent cellulosic fabric according to claim 1, in which the average fiber length of the fibrillated regenerated cellulose fibers is less than 250 microns, preferably less than 150 microns, more preferably less than 100 microns and most preferably less than 75 microns. 9. The absorbent fabric according to any one of claims 1 to 8, having
basis weight of from 5 pounds per ream of sheets of 3000 square feet (8 g / ^m2) to 40 pounds per ream of sheets of 3000 square feet (65 g / m ^2), preferably from 15 pounds per ream of sheets of 3,000 square feet (24 g / ^m2) to 35 pounds per ream of sheets in 3000 square feet (57 g / m ^2);
an absorbency of at least 4.5 g / g, preferably at least 5 g / g, more preferably from 6 g / g to 9.5 g / g, and most preferably at least 7.5 g / g;
a ratio of lateral extensibility (CD) in the wet / dry state of 35-60%, preferably at least 40% and more preferably at least 45%; and an average fiber width of less than 2 μm, preferably less than 1 μm, and more preferably less than 0.5 μm. 10. The absorbent cellulosic fabric according to any one of claims 1 to 8, having an increased opacity value compared to a fabric obtained without fibrillated regenerated cellulose microfiber, and preferably having an opacity normalized according to the standard of the Technical Association in the pulp and paper industry (TAPPI), more less than 5 opacity units per TAPPI / lb / foot sheets per 3000 square feet (3.1 opacity units per TAPPI / g / m ² ), more preferably more than 6.5 units opacity per TAPPI / pound / foot sheets of 3000 square feet (4.0 opacity at TAPPI / g / m ² ) with a paper weight of less than 8 pounds / foot of sheets of 3000 square feet (13.0 g / m ² ). 11. The absorbent fabric of claim 10, having
basis weight of from 5 pounds per ream of sheets of 3000 square feet (8 g / ^m2) to 40 pounds per ream of sheets of 3000 square feet (65 g / m ^2), preferably from 15 pounds per ream of sheets of 3000 square feet (24 g / m ² ) up to 35 pounds per foot of sheets of 3,000 square feet (57 g / m ² ); an absorbency of at least 4.5 g / g, preferably at least 5.0 g / g, more preferably from 6 g / g to 9.5 g / g, and most preferably at least 7.5 g / g;
a ratio of lateral extensibility (CD) in the wet / dry state, comprising 35% -60%, preferably at least 40% and more preferably at least 45%; and an average fiber width of less than 2 μm, preferably less than 1 μm, and more preferably less than 0.5 μm. 12. An absorbent sheet according to any one of claims 1 to 8, having a paper density of 5 pounds per foot of sheets of 3000 square feet (8 g / m ² ) to 40 pounds per foot of sheets of 3000 square feet (65 g / m ² ), preferably from 15 pounds per foot of sheets of 3,000 square feet (24 g / m ² ) to 35 pounds per foot of sheets of 3,000 square feet (57 g / m ² ). 13. An absorbent sheet according to any one of claims 1 to 8, having a paper density of 9 pounds per foot of sheets of 3000 square feet (15 g / m ² ) to 11 pounds per foot of sheets of 3000 square feet (18 g / m ² ). 14. The absorbent fabric according to item 13, having
an absorbency of at least 4.5 g / g, preferably at least 5 g / g, more preferably from 6 g / g to 9.5 g / g, and most preferably at least 7.5 g / g;
a ratio of lateral extensibility (CD) in the wet / dry state of 35-60%, preferably at least 40% and more preferably at least 45%; and an average fiber width of less than 2 μm, preferably less than 1 μm, and more preferably less than 0.5 μm. 15. The absorbent web according to any one of claims 1 to 8, in which the absorbent web has an absorbent capacity of at least 4.5 g / g, preferably at least 5 g / g, more preferably from 6 g / g to 9 5 g / g and most preferably at least 7.5 g / g. 16. The absorbent fabric according to any one of claims 1 to 8, in which the sheet has a ratio of extensibility in the transverse direction (CD) in the wet / dry state, comprising 35-60%, preferably at least 40% and more preferably at least 45 % 17. The absorbent fabric according to any one of claims 1 to 8, in which the average fiber width is less than 2 μm, preferably less than 1 μm and more preferably less than 0.5 μm.

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