MXPA00006476A - Nonwoven web of superabsorbent fiber and method - Google Patents

Abstract

A nonwoven web and method of preparing a novel nonwoven web of superabsorbent fiber are disclosed. An aqueous solution of superabsorbent precursor polymer is extruded under defined conditions through a plurality of die orifices to form a plurality of threadlines. The threadlines are attenuated with a defined primary gaseous source to form fiber under conditions of controlled macro scale turbulence and under conditions sufficient to permit the viscosity of each threadline, as it leaves a die orifice and for a distance of no more than about 8 cm, to increase incrementally with increasing distance from the die, while substantially maintaining uniformity of viscosity in the radial direction, at a rate sufficient to provide fiber having the desired attenuation and mean fiber diameter without significant fiber breakage. The attenuated threadlines are dried with a defined secondary gaseous source. The resulting fibers are deposited randomly on a moving foraminous surface to form a substantially uniform web. Moving foraminous surface is positioned about 10 to about 100 cm from the last gaseous source to contact the threadlines. The fibers have a mean fiber diameter in the range of about 0.1 to 30 mm and are substantially free of shot. The attenuating and drying steps are carried out under conditions of controlled macro scale turbulence.

Description

NON-WOVEN FABRIC OF SUPERABSORBENT FIBER AND METHOD 1. Technical Field This invention relates to a non-woven fabric of superabsorbent fiber. In one aspect, the invention relates to a method for preparing a non-woven fiber of super-absorbent end fiber.

Background Certain polymers are called superabsorbent polymer because of their ability to absorb and retain fluids. The poly (acrylic acid) copolymer is an example of a superabsorbent polymer.

Dry spinning can form a superabsorbent polymer in continuous filaments. The spinning in sec extrudes an aqueous solution of the polymer in the air. Using a highly concentrated polymer solution, the liquid filaments are extruded and then solidified, dried, pulled hot and treated with heat in a gaseous environment.

A non-woven superabsorbent fibrous web can be produced by first forming an aqueous fiber-forming polymer solution in filaments which are contacted with a primary air stream having a sufficient velocity to attenuate the filaments. The attenuated filaments are brought into contact in a fiber forming zone with a secondary air stream having an effective rate for attenuating the filaments further, for fragmenting the filaments into fibers, and for transporting the fibers to a tissue forming zone. . The "fragmented" fibers are collected in a cross-linked fabric formed in the tissue-forming zone, and the tissue is cured.

A non-woven fabric of water-soluble resin fibers may consist of fine fibers of water-soluble resin having an average fiber diameter of 30 μm or less and a basis weight of 5 to 500 g / m2. The fabric can be produced by extruding an aqueous solution of water-soluble resin or a resin soluble in molten water and plasticized with water through nozzles, stretching the extruded material to form fiber with a high velocity gas flow, heating the fibers to evaporate the water in the fibers and then collect the fibers Water-soluble resins can include poly (vinyl alcohol) when the application is primarily directed to the use of pullulan, a natural glucan. The high velocity gas flow may consist of air at a temperature of from 20 ° C to 60 ° C a linear velocity of 10 to 1,000 m / second. The fibers can be dried by banks of infrared heaters located on both sides and parallel to the fiber stream.

Some methods for forming fibrous fabrics or the products of a solution of a polymer or a molten polymer produce very short fibers, and consequently, differ significantly from meltblowing and spin-linked processes which can be used to prepare the fabrics non-woven of molten thermoplastic polymers.

Steam can be used in the process of fiber formation. A polymeric composition containing agu can be extruded under conditions using a supercritical fluid condition d, avoiding scintillation, and spraying gelled fibers embedded in water to form tissues. The melt blow can be used in the fiber forming process.

The coformation can be used in the process of fiber formation. The fibers or particles are crushed with the melt blown fibers as they are formed.

Spinning can be used in the fiber formation process.

Introduction to the Invention The superabsorbent precursor polymers having high molecular weights, for example, by way of example of molecular weights greater than 500,000 and a minimum crosslinking can provide an absorbency under high fluid load.

By superabsorbent polymer is meant a polymer which provides high fluid absorbency under load at a level of 10 grams of 0.9% by weight aqueous sodium chloride per gram of dry absorbent fiber or woven fabric.

The spinning fiber of higher molecular weight polymers is highly challenged, even in the case where the polymer is a linear chain polymer, particularly when the molecular chain is flexible.

The ultrasuperior module and the high strength fiber of the extremely high molecular weight polyethylene are prepared only by a slow gel spin.

The fiber spinning of a solution of a flexible linear chain polymer involves an unraveling and stretching of the polymer molecules entangled and rolled in the solution. When these molecules are large, the unraveling and stretching process becomes very difficult and slow if it is successful at all. The time of relaxation is long.

Therefore, it has been thought that preparing an essentially continuous fibr of a higher molecular weight polymer solution is particularly impossible with the high speed nonwoven spinning processes. The high-speed non-woven spinning process is operated at spin speeds of 10 times to 100 times higher than those of conventional textile fiber spinning. . At higher spinning speeds the higher molecular weight poly (vinyl alcohol) microfiber fabric (124,000 - 180,000) was observed to be flaked indicating fiber breakage.

It is another object of the present invention to provide a novel nonwoven fabric and a method for preparing a significantly improved nonwoven fabric which includes an essentially continuous superabsorbent microfiber having a mechanical strength, high fluid absorbency, and preferred handling properties.

It is an object of the present invention to provide a novel non-woven fabric and a method for preparing a novel significantly improved non-woven fabric including a super-absorbent and continuous fine fiber having mechanical strength, high fluid absorbency, and preferred handling properties.

Another object of the present invention is to provide a substantially improved continuous superabsorbent microfiber and a non-woven fabric which includes these microfibers which have a mechanical strength, high fluid absorbency and preferred handling properties.

A further object of the present invention is to provide a significantly improved continuous superabsorbent fiber and non-woven fabrics including these fine fibers having mechanical strength, high fluid absorbency and preferred handling properties.

Yet another object of the present invention is to provide a disposable absorbent product which includes a significantly improved nonwoven fabric that includes an essentially continuous superabsorbent microfiber.

Yet another object of the present invention is to provide a disposable absorbent product which includes a significantly improved nonwoven fabric that includes a continuous superabsorbent fine fiber.

These and other objects will be further apparent to a person with ordinary skill in the art of considering the detailed description of the description and the claims that follow.

Synthesis of the Invention Briefly, the present invention provides a novel non-woven fabric and a method for preparing a woven fabric of an essentially continuous super-absorbent fine fiber. An aqueous polymer solution is prepared from about 10 to about 75% by weight of a polymer. linear superabsorbent precursor having a molecular weight d from about 300,000 to about 10,000,000. The polymer solution is extruded at a temperature in the range d about 20 ° C to about 180 ° C at a viscosity in the range of about 3 to about 1,000 Pa second, through a matrix having a plurality of holes to form a plurality of yarn lines. The matrix holes have diameters in the range of from around 0.20 to around d 1.2 millimeters. The resulting yarn lines are attenuated with a primary gaseous source under conditions sufficient to allow the viscosity of each line of yarn, when leaving or die hole and for a distance of no more than about 8 centimeters to increase incrementally with a distance of increase from the matrixwhile essentially maintaining the uniformity of the viscosity in the radial direction, at a rate sufficient to provide the fiber having the desired attenuation and fiber diameter without significant fiber breakage. The primary gas source has a relative humidity of from about 30 to about 100%, a temperature from about 20 ° C to about 100 ° C, a speed of from about 150 to about 400 m / s, a horizontal angle of incidence from about d 70 ° to about 110 °, and a vertical angle of incidence of n more than about 90 °. The yarn lines are dried to form fibers with a secondary gaseous source at a temperature of from about 140 ° C to about 320 ° C and at a speed of from about 60 to about 125 m / s. The secondary gaseous source has a horizontal angle d incidence of from about 70 ° to about 110 ° and a vertical angle of incidence of no more than about 90 °. The fibers are randomly deposited on a movable perforated surface to form an essentially uniform fabric on a scale of from about 0.4 to about 1.9 square centimeter. The movable perforated surface is placed about 10 to about 60 centimeters from the opening from which the last gas source emerges to make contact with the yarn lines. The fibers have a mean fiber diameter in the range from about 0.1 to about 10 μm and are essentially free of milkshake. The attenuation and drying steps are carried out under conditions of controlled-scale turbulence, and the fibers are of a length such that they can be seen as continuous in comparison with their diameters. The uniform tissue is exposed to a high-energy source selected from the group consisting of heat, microwave electron beam, and radio-frequency frequency irradiation to insolubilize the polymer and make an established cross-linkage in the superabsorbent precursor polymer. The stabilized fabric is subsequently treated for a certain structure of tissue attributes such as wetting, compaction, etching, bonding and laminating.

The present invention also provides a novel non-woven fabric and a method for preparing a non-woven cloth significantly. improved including the continuous superabsorbent end fiber in which the primary gas source has a relative humidity of from about 60 to 95%, a temperature of from about 20 ° C to about 100 ° C, a speed of from about 30 at about 150 m / s, or horizontal angle of incidence from about 70 ° around 110 °, and a vertical angle of incidence of no more than about 90 °. The yarn lines are dried to form fibers with a secondary gaseous source at a temperature d from about 140 ° C to about 320 ° C and at a rate of from about 30 to about 150 m / s at a horizontal incidence angle. from about 70 ° to around d 110 °, and a vertical angle of incidence of no more than about 90 °. The fibers are randomly deposited on a mobile foraminous surface to form an essentially uniform fabric on a scale of from about 1.9 to about 6. square centimeters, the mobile foraminous surface being from about 10 to about 100 centimeters. The opening from which the last gas source emerges to make contact with the yarn lines, whose fibers have a mean fiber diameter in the range of from about 10 to about 30 μm and are essentially uniform in diameter. The attenuation and drying steps are carried out under conditions of minimum macroscale turbulence.

The present invention also provides a novel non-woven fabric and a method for preparing continuous and significantly improved superabsorbent fibers and a non-woven fabric including these fibers in which the primary gas source has a relative humidity of from about 65 to 90. %, a temperature from about 20 ° C to about 100 ° C, a speed of less than about 30 m / s, or horizontal angle of incidence from about 70 ° around 110 °, and a vertical angle of incidence d around 90 °. The yarn lines are dried to form fibers with a secondary gaseous source at a temperature d from about 140 ° C to about 320 ° C and having a velocity of less than about 30 m / s, a horizontal angle of incidence from about 70 ° to about 110 °, and its vertical angle of incidence of about 90 °. The resulting fibers are attenuated with a tertiary gaseous source having a temperature in the range of about 10 ° C around 50 ° C, a speed in the range of about 3 to about 240 m / s, a horizontal angle of incidence d from around 70 ° to around 110 °, and a vertical incidence angle of no more than about 90 °. The fibers are randomly deposited on a movable perforated surface to form an essentially non-uniform fabric on a scale d from about 1.9 to about 6.5 square centimeters the movable perforated surface being positioned at about 1 to about 100 centimeters from the opening from which the last gas source emerges to make contact with the yarn lines, whose fibers have an average fiber diameter in the range of from about 10 to about 30 μm and are essentially uniform in diameter in which the d steps conditioning, drying and attenuation are carried out under conditions of minimum macroscale turbulence.

The present invention also provides a substantially improved substantially continuous superabsorbent microfiber and a non-woven fabric including these fibers in which the fibers have a mean fibr diameter in the range of from about 0.1 to about 10 μm, are essentially free of beaten, and they are of a length ta that these can be seen as continuous compared to their diameters. The fabric is essentially uniform on a scale of from about 0.4 to about 1.9 cm2, depending on the average fiber diameter.

The present invention further provides a significantly improved non-woven tel including a superabsorbent and continuous end fiber, in which the fibers have an average fiber diameter in the range of from about 10 to about 100 μm, are essentially free of milkshake and they are essentially uniform in diameter; and the fabric is essentially uniform on a scale of from about 1.9 to about 6.5 centimeters squared, depending on the diameter of the average fibr.

The present invention provides a disposable absorbent product having a significantly improved nonwoven fabric that includes a continuous or essentially continuous superabsorbent fiber.

The non-woven fabrics of superabsorbent fibers of the present invention are particularly useful in the production of such disposable absorbent products as diapers, underpants, catamenial devices such as sanitary napkins, plugs and the like; incontinence products, similar cleansing cloths.

Brief Description of the Drawings Figure 1 is a schematic perspective view partially illustrating the preparation of a knitted fabric according to an embodiment of the present invention and illustrating the horizontal angle of incidence.

Figure 2 shows a cross-sectional view of the lower part of the tip portion of the matrix of Figure 1, taken along line 2-2. The figure illustrates the vertical angle of incidence.

Fig. 3 is a perspective view of a part of a line of superabsorbent yarn produced according to the present invention.

Figure 4 is a perspective view of a part of the yarn line shown in Figure 3.

Figure 5 is a schematic representation d an embodiment of the present invention.

Detailed description of the invention It has been found through empirical development that non-woven fabrics of high absorbency including essentially continuous fiber, for example having very few "milkshakes" were obtained through a high-speed non-woven spinning process, with a process modification novel, superabsorbent precursor polymers of extremely high molecular weight such as 8,000,000.

The novel fiber forming mechanism believes that it involves a strong affinity of the water molecules to the carboxylic group of the polyacrylic acid copolymer which, for example, can make the long polymer chain stiffer, thereby facilitating the untangling and stretching. The mechanism may involve the ionic repair of the carboxyl group of the sodium polyacrylic acid copolymer An essentially improved nonwoven fabric has been prepared from the sodium polyacrylic acid copolymer under a novel process that includes a meticulous control of the gaseous ambient, within which the lines of solution yarn are extruded, in humidity and temperature, avoiding premature excessive evaporation. the solvent water before the wetted yarn lines are attenuated into a desirable fine size without breaking or "fragmentation". The fiber essentially continues to contain very little "churning" and the tissues were particularly uniform soft when the turbulences of the secondary hot dried airs and the primary steam were controlled.

"Fabric uniformity" is a term used here to refer to the extent to which any part of the nonwoven fabric produced according to the present invention having a given area is like any other part having the same. area. Tissue uniformity is a function of fiber diameter and the manner in which the fibers are deposited on the mobile foraminous surface Ideally, any given area of the tissue will be indistinguishable from any other area with respect to such parameters as the porosity, the volume hollow, the pore size, the thickness d tissue and the like. However, uniformity variations are evident in tissues as parts which are thinner than other parts. Such variations can be visually estimated to give a subjective determination of uniformity. Alternatively, tissue uniformity can be qualitatively estimated by measuring the thickness of the tissue or the transmission of use through the tissue.

The term "relatively small scale" is used throughout this description in relation to tissue uniformity and defines the approximate area of each of the various parts of the fabric which are to be compared. In general, the scale will typically be in the range of from around d 0. 4 to about 6.5 square centimeters, depending on average fiber diameter. When the average fiber diameter is d μm or less, the appropriate area in square centimeters to evaluate the uniformity of the tissue, for example the scale is 0.19 times the diameter of main fiber in μm or 0.4 square centimeter, whichever is greater. The scale is determined by multiplying the main fiber diameter by 0.1 when the average fiber diameter is in the range of about 2.1 to about 10 μm. For the average fiber diameters of about 2.1 μm or less, however, the scale is 0.4 cm2. When the average fiber diameter is greater than 10 μm, the appropriate multiplier is 0.215. The phrase "on a scale from about 0.4 to about 6.5 cm2 means that the area of a non-woven fabric which is to be compared with other parts of the same fabric, each of whose parts has essentially the same area will be In the given range, the selected area in square centimeters will be (1) approximately 0.19 times the average fiber diameter in μ when the average fiber diameter is 10 μm or less or 0. square centimeters, whichever is greater or (2) approximately 0.215 times the average fiber diameter when the average fiber diameter is greater than 10 μm.

As used herein, the term "shot" refers to polymer particles which are generally larger in diameter than the average diameter of the fibers produced by the extrusion process. The production of the shot is typically associated with the breaking of filaments and the accompanying accumulation of the polymer solution on the tip of the matrix.

The term "molecular weight" refers to the average weight molecular weight, unless otherwise indicated.

The term "turbulence" is used herein to refer to the starting in a fluid, typically a gas, from a smooth or aerodynamic flow. The term is intended to apply to the extent or degree to which the fluid flow varies erratically in magnitude and direction with time and is essentially variable in the pattern. The term "macro-scale turbulence" means only that the turbulence is on a scale such that it affects the orientation and spacing of the fibers or the fiber segments relative to each other as they approach the fiber-forming surface, in the which length of such fiber segments is equal to or smaller than the scale d. Turbulence is "controlled" when its magnitude is maintained below a certain level empirically. The minimum turbulence can be achieved by selecting the appropriate process variables and allowing it to increase only to an extent necessary to achieve a given objective.

Due to the difficulty of measuring turbulence, indirect means must be used to determine when turbulence is being controlled to a sufficient degree. Tale indirect means are tissue uniformity. The uniformity of the fabric is defined as a function of both the area of fabric to be evaluated and the average diameter of the fibers of which the fabric is composed. For example, producing non-woven fabrics will give a very uniform product if the scale, for example, the area of the fabric used for comparative purposes is large, for example, on the order of several square meters. On the other hand, the uniformity of the same fabric will be very poor if the scale is going to be very small so that it is on the order of the average diameter of the fibers. The scale selected for the evaluation of the tissues prepared according to the present invention, therefore, is based on the production of non-woven fabrics by various processes for a variety of applications.

The term "yarn line" is used throughout the description and claims to refer to the article forced and shaped as the polymer solution is forced through the die hole but before such shaped article has solidified or become drying A yarn line is essentially liquid or semi-solid. The term "fibers" is used to designate the line of solidified or dried yarn.The transition from a line of yarn to a fiber is gradual.

With respect to the "back side" and the "front side" of the wire line curtain, the rear side of the curtain is the side toward which the movable perforated surface approaches. The perforated surface then passes under the yarn line curtain and moves out of it with a non-woven fabric that has been formed thereon. The side e where the tissue has been formed is the front side of the curtain line of threads.

When possible, all units are SI unit (International System of Units); whether they are basic derivatives. Therefore, the unit for viscosity is Pascal seconds, abbreviated here as Pa s. The pascal-second is equal to 10 poises, the most common unit of viscosity.

Turning first to the method of the present invention for preparing an essentially improved nonwoven fabric including the superabsorbent fibers, such method generally includes the following steps: A. Prepare an aqueous polymer solution of a linear superabsorbent precursor polymer; B. Extrude the resulting polymer solution through a die having a plurality of holes to form a plurality of yarn lines; C. Attenuate the resulting wire lines with a primary gas source; D. Dry the attenuated yarn lines with a secondary gaseous source to form fibers; E. Deposit the resulting fibers at random on a movable perforated surface to form an essentially uniform fabric; Y F. Insolubilizar the fiber in a tissue insolubl in water but inflatable in water.

In general, the first two steps are independent of the device or the details of the process used. As will be evident from here on, however, this is not the case for the remaining steps. That is, some of the limitations of the attenuation, drying and deposition steps will depend on whether the superabsorbent precursor fibers produced are essentially continuous or continuous.

The first step (step A) of the method involves preparing an aqueous superabsorbent precursor polymer solution which includes from about 10 to about 75% by weight of the polymer. Because the solubility of polymer in water is inversely proportional to the molecular weight of the polymer, higher concentrations, for example, concentrations above 40% by weight are practical only when the molecular weights of the polymer are below 100,000. The preferred concentration range It is from around 2 to around 60% by weight. More preferably, the concentration of the superabsorbent precursor polymer in the solution is in the range of from about 25 to about 40% by weight.

In general, the superabsorbent precursor polymer of the present invention has a molecular weight of from about 300,000 to about 10,000,000. Preferred ranges are from about 3,000,000 to about 8,000,000, more preferably from about 500,000 to about 4,000,000.

The superabsorbent precursor polymer solution may also contain, in addition to a cross-linked linkage moiety in the polymer column and / or the crosslinking agents, minor amounts of other materials, eg, amounts of other materials which together constitute less than 50% by weight of the total solids content of the solution. Such other materials include, by way of illustration only, plasticizers, such as polyethylene glycols, glycerin and the like; dyes or dyes; spreaders, such as clay, starch and the like; other functional substances; and similar.

In the second step (step B), the polymer solution is extruded at a temperature of from about 20 ° to about 180 ° C and has a viscosity at the extrusion temperature of from about 3 to about 1,000 pascal seconds through a die having a plurality of orifices to form a plurality of yarn lines, whose orifices have diameters in the range of from about 0.2 to about 1.2 millimeters. The extrusion temperature will preferably be in the range of from about 70 ° C to about 95 ° C. The viscosity of the preferred polymer solution will be from about 5 to about 30 pascal seconds. The holes in the matrix will preferably have diameters of from about 0.3 to about 0. millimeters. The holes are arranged in as many rows as around 7 rows. Such rows are perpendicular to the direction of travel of the movable perforated surface on which the non-woven fabric is formed. The length of such rows defines the width of the fabric which is formed. Such arrangement of the holes results in a "sheet" "curtain" of lines of threads. The thickness of such a curtain is determined by the number of rows of crafts, but it is very small by comparison in the width of the curtain. For convenience, such a curtain of thread lines is occasionally mentioned here as the "thread line plane". Such plane and perpendicular to the movable perforated surface on which the tissue is formed, even when such orientation is not essential is not required.

Even though the viscosity of the solution is a function of temperature, it is also a function of the molecular weight of the polymer and the concentration of the polymer in the solution. Consequently, all these variables require that they be taken into consideration to maintain the viscosity of the solution at the extrusion temperature in the appropriate range.

The resulting yarn lines are then attenuated in step C with the primary gas source to form fibers under sufficient conditions to allow the viscosity of each yarn line to leave a matrix hole and a distance of no more than about 8 centimeters, to increase incrementally with an increasing distance from the matrix, while maintaining the uniformity of the viscosity in the radial direction. The line attenuation rate of yarn should be sufficient to provide fibers having the desired strength and the desired average fiber diameter without significant fiber breakage. The primary gas source has a relative humidity of from about 40 to 100% and a temperature of from about 20 ° C to about 100 ° C, or horizontal angle of incidence of about 70 ° C about 110 ° and a vertical angle of incidence of no more d around 90 °.

When essentially continuous fibers are being formed, the velocity of the primary gas source is in the range of from about 150 to about 400 m / sec. The most preferred primary gas source velocity is from about 60 to about 300 m / s. The most preferable primary gas-fueled speed is in the range from about 70 to about 200 m / s. For the production of continuous fibers, however, the velocity of the primary gas source is in the range of from about 30 to about 150 m / s.

The attenuation step involves a balance between the attenuating aspects and the drying aspects since and inevitably some water loss from the hil lines usually occurs. However, optimum attenuation conditions can not always coincide with optimal dry conditions. Consequently, a conflict may arise between the two parameters which requires against a set of commitment conditions.

It is important that the yarn lines be attenuated to the desired level without breaking. An excessive attenuation rate creates excessive tension on the yarn lines which leads to a frequent yarn line or fiber breaks and increases in shot formation particularly with microfibers having diameters in the range from about 0.1 to around 10 μm. Very slow attenuation rates, however, fails to give fiber sufficiently strong. On the other hand, a drying of the yarn line too fast, especially during the step d attenuation, results in increased breaks and in an increased draft production. If the drying of the hilum line is very slow during the drying step, a fusion or binding of excessive interfiber occurs as a result of fibers that are too wet when placed on the mobile foraminous surface. As a result, ideal drying conditions are typically not optimal for the production of highly attenuated strong fibers. Therefore, somewhat opposite requirements are achieved to attenuate and dry the yarn lines by controlling the humidity and the relative temperature of the primary gas source, as well as its speed. The attenuation step results in no more than partial drying of the yarn lines to provide the incremental increase in the yarn line viscosity.

The drying of partially dried attenuated yarn lines is achieved in step D by means of a secondary gas source. The secondary gas source has a temperature of from about 140 ° C to about 320 ° C.

The vertical and horizontal angles of the incidence requirements are the same as those for the primary gas source. For the production of essentially continuous fiber, the secondary gas source has a velocity of from about 60 to about 125 m / s. Continuous fiber production requires a secondary gaseous source having a velocity d from about 30 to about 150 m / s.

As used herein, the term "primary gaseous source" means a gaseous source which is the first and contact the lines of threads as they emerge from the matrix. The term "secondary gas source" refers to a gaseous source which makes contact with the lines of threads or fiber after the lines of threads have been contacted by the primary gas source. Therefore, "primary" and "secondary" s refer to the order in which the two gas sources make contact with the thread lines after they have emerged from the matrix. Subsequent gaseous sources, if used, will be referred to as "tertiary" "quaternary" and others. Although they fall within the spirit and scope of the present invention, the use of such subsequent gaseous sources is usually neither practical nor necessary, and consequently, is not preferred, with the two exceptions described below.

Each of the gaseous sources required by steps C and D, and each additional gaseous source, if used preferably, will comprise at least two gas streams with the two streams being more preferred. When the currents are used, they are located on the opposite side of the wire line curtain. The current that sticks to the filaments from the front side of the curtain line of threads has a positive vertical angle of incidence, while the current that sticks to the strands from the back side of the curtain line of threads has an angle d negative vertical incidence. However, the absolute value of vertical angle of incidence for each current must be within the limitations described here, even though both currents do not need to have the same absolute value for their vertical angles of incidence. Consequently, it should be understood that the requirement with respect to the vertical angle of incidence refers to an absolute value when a gas source involves more than a gaseous current.

In the first step of the method of the present invention, step E, the fibers resulting from the previous step are randomly deposited on a movable perforated surface. In the case of the production of essentially continuous fibers, the movable perforated surface is from about 10 about 60 cm from the opening from which the last gaseous source that contacts the wire lines emerges. The distance between the movable perforated surface and such an aperture is occasionally mentioned here as the forming distance. The average fiber diameter is in the range of from about d 0.1 to about 10 μm. The fibers are essentially uniform in diameter and are essentially draft-free.

When the continuous fibers are produced, the forming distance is preferably from about 1 to about 100 cm, and the average fiber diameter is in the range of from about 10 to about 100 μm. The continuous fibers produce an essentially uniform fabric.

The area or scale used for purposes of comparison in evaluating the uniformity of the fabric is a function of fiber diameter. The scale for a fabric that includes essentially continuous fibers is in the range of about 0.4 to about 1.9 cm2, while the scale for a fabric that includes continuous fibers is in the range d from about 1.9 to about 6.5. cm2.

Step C requires macroscale-controlled turbulence and sufficient conditions to allow the viscosity of each line of yarns, as this leaves a matrix hole, increases incrementally with increasing distance from the matrix, while maintaining the uniformity of the matrix. viscosity in the radial direction, at a rate sufficient to provide fibers having the desired attenuation and average fiber diameter without a significant fiber breakage. The means to melt both requirements involves controlling four parameters or variables associated with the gaseous source, including moisture relative, the temperature, l speed, and the orientation in relation to the curtain line d threads. The macroscale turbulence is primarily a function of the gaseous stream velocity and the orientation of the gaseous source when it is glued to the wireline curtain. The viscosity of the line of threads, even though it is affected by the speed of the gas source, is a function of the relative humidity and the temperature of the primary gas source. Such parameters or variables are discussed below with respect to the "turbulence a macro-scale "and the" viscosity of the thread line ".

Referring now to macroscale turbulence, attenuation and drying are carried out under controlled macroscale turbulence conditions in a preferred embodiment, attenuation and drying are carried out under conditions of "minimum macroscale turbulence thus helping the formation The term "minimum macroscale turbulence" means only that the turbulence grad which allows the formation of a desired uniform tissue occurs which is partly dependent on the spacing and orientation of the uniform fiber.

Some turbulence is unavoidable, in fact necessary, given the fact that the attenuation results from entrapment of the wire lines in a mobile gas stream. A minimum gas stream velocity is determined empirically. The minimum gas source velocity is much higher than the extrusion rate.

In certain cases, macro-scale turbulence is greater than the minimum, even when it is still controlled. For example, when the fibers or particles to be ground with the yarn lines as they are formed, a greater degree of turbulence is required to achieve a degree of crushing which is sufficient to provide uniform coherent fabric.

The macroscale turbulence is also a function of the nature of the gaseous source and its orientation by sticking it to the curtain of the thread line. Furthermore, the efficiency of the yarn line attenuation is, at least in part, dependent on the orientation of the gas source. The orientation of the gas source is defined by the horizontal angle of incidence and the vertical angle of incidence.

The horizontal angle of incidence is better defined with reference to Figure 1. Figure 1 is a diagrammatic perspective view partially illustrating the preparation of a nonwoven according to an embodiment of the present invention. The polymer solution is extruded through a plurality of holes in the face 11 of the die 10 to form a curtain of wires 12. Upon finding the line curtain d yarns 12 the perforated band 13 moving in the direction of arrow 14, the non-woven fabric 15 is formed. Line 16 lies in the plane of the curtain of the line of threads 12 and is parallel with the face 11 of the matrix 10. The arrow 17 represents the orientation of a gaseous stream in relationship to line 16 with the direction of flow being in the same direction as arrow 17. The angle 18 formed by line 16 and arrow 1 are in the horizontal angle of incidence. The angle 18 e determined in relation to the part of the right side of the line 16 with respect to a matrix facing the observer 10, towards which the perforated band 13 is moving. The horizontal angle of incidence of each gas source is in the rang from around 70 ° to around 110 °, with an angle d around 90 ° being preferred.

The vertical angle of incidence is better defined with reference to Figure 2, Figure 2 shows a cross-sectional view of a small part of the matrix 20 which has a hole 21, taken along the line 2-2 of the Figure 1. The arrow 22 represents the centerline of the line of threads (not shown) arising from the hole 21, with the flow direction being the same as the direction of the arrow 22. The arrow 23 represents the orientation of a stream. gaseous in relation to arrow 22, with the direction of flow being in the same direction as arrow 23. The angle 2 formed by arrows 21 and 22 is the vertical angle d incidence. The vertical angle of incidence of any gaseous source will generally be no more than about 90 °. Preferably, the vertical angle of incidence will not be more than about 60 °, and more preferably will not be more than about 45 °. The preferred values for the vertical angle of incidence refer to the absolute values when any given gas source involves more than one gaseous current.

The macroscale turbulence is partly a function of the orientation of the gas source. From a consideration of FIGS. 1 and 2, the horizontal angle of the incidence has the ultimate effect on macroscale turbulence (eg, tissue uniformity) when the angle is around 90 °. In a similar way, the vertical angle of incidence has the last effect on the macroscale turbulence when it is around 0 ° C. If the 90 ° horizontal angle of incidence is deviated and / or the vertical angle of incidence increases above 0 °, the macroscale turbulence is reduced to some extent by decreasing the velocity of the gas source.

The macroscale turbulence of any gaseous fuent requires to be carefully controlled along the full width of the curtain of the yarn line. Such control is partly achieved through the use of multiple designs. For example, a manifold is used which has a gradually reduced cross section. In addition, a combination of the honeycomb sections with metal pores and sintered grates or separators effectively destroys the large scale turbulent swirl currents which may otherwise be formed.

Upon leaving the controlled high velocity gas source from the opening of a multiple duct, it carries surrounding ambient air, and its speed is decreased as the distance from said opening is increased. Such a transfer moment between the high-velocity gas source and the ambient air increases the size of the turbulent eddies. Turbulent swirls on a smaller scale help to entangle the fibers in an initial phase near the opening from which the gas source emerges, but eddies which grow at a distance of about 50 centimeters or more from such an opening adversely affect uniformity. of the tissue by forming light weight and heavy weight areas in the tissue. And it is important that the training distances remain within the limits specified here. In addition, some entrapment of ambient air is essentially to keep the large-scale eddy currents to a minimum.

Referring now to the Thread Line Speed, the primary gas source has a relative humidity of from about 30 to 100 percent. More preferably, the gaseous source will have a relative humidity of from about d 60 to about 95 percent. More preferably, the relative humidity of the primary gas source will be in the range d from about 60 to about 90 percent.

It has been found that the presence of water droplets in the moistened gas source has adverse effects on the yarn line and fiber formation, particularly with respect to shot formation. Consequently, it is preferred that any droplets of water which may be present in the moistened gaseous source have diameters smaller than the diameters of the yarn lines. More preferably, the moistened gas stream is essentially free of water droplets.

In practice, water droplets are successfully removed from the moistened gaseous source through the use of a blow separator. Additionally, it is useful to heat all ducts through which the humidified gaseous source passes before striking the wire lines. However, the temperatures of the duct should be such that the temperature of the humidified gas source remains within acceptable limits as already described.

The temperature of the primary gas source is in the range of from about 20 ° C to about 100 ° C. The temperature most preferably is in the range from about 40 ° C to about 100 ° C, and more preferably d from about 60 ° C to about 90 ° C.

The viscosity requirements are understood with reference to Figures 3 and 4. Figure 3 is a perspective view of a part of the line of threads 30 having a longitudinal ej 31 as it emerges from the hole 32 in the matrix 3 (shown in a partial cross section) that has the car 34. The plane 35 is perpendicular to the axis 31 and is at a distance dx from the face of matrix 34. The plane 36 is also perpendicular to the axis 31 and is at a distance d2 from the car of the matrix 34, with d2 being greater than dx (for example, D2 > dx). The section 37 of the line of threads 30 lies between the planes 36. Because the line of threads 30 is being attenuated, the diameter of the line of threads decreases with the distance e increasing from the matrix. Consequently, the section 37 of the line of threads 30 approaches an inverted truncated cone or more adequately to an inverted frustum of a cone.

The section 37 of the line of threads 30 of FIG. 3 which is located between the planes 35 and 36 of FIG. 3 is shown in a perspective view in FIG. 4. In said FIG. 4, the wire line section is shown in FIG. 40 has an axis 4 and is defined by the upper plane 42 (for example, the plane 35 in FIG. 3), and the lower plane 43 (for example, the plane 36 in FIG. 3). Both planes are perpendicular to the axis 41 and are parallel to each other. Additional planes 44 and 45 are shown, whose planes are also perpendicular to axis 41 (parallel to planes 42 and 43), and are at distances d3 and d4 respectively, from the face of the array which is not shown (e.g. , the face 34 of the die 33 in FIG. 3). The upper plane 42 and the lower plane 43 are at distances dx and d2, respectively, from the face of the matrix. Thus, d1 < d3 < d4 < d2. The points 42A, 42B, 42C and 42D lie in an upper plane 42. Similarly, the points 43A, 43B and 43 lie in a lower plane 43; points 44A, 44B or 44C lie in plane 44; and the points 45A, 45B and 45C lie in the plane 45.

With reference to Figure 4, the uniformity viscosity in the radial direction provides that the viscosity of the yarn line at any point lying in a plan perpendicular to the axis 41 is approximately the same. This is the viscosity of the yarn line at the points 42A, 42B, 42C 42D is essentially the same. However, the viscosity at points 43A, 43 and 43C is essentially the same; the viscosity at points 44A, 44B and 44C is essentially the same; and the viscosity at points 45A, 45B and 45C is essentially the same.

However, the viscosity of the yarn line increases incrementally with increasing distance from the array. That is, the viscosity of the yarn line e any of the points 44A, 44B and 44C, again referenced to Figure 4, is greater than the viscosity d of any of the points 42A, 42B, 42C and 42D. The viscosity e any of the points 45A, 45B and 45C in turn is greater than the viscosity at any of the points 44A, 44B and 44C Finally, the viscosity at any of the points 43A, 43 and 43C is greater than the viscosity of any of the points 45A, 45B and 45C.

All viscosity ratios above can be expressed mathematically as follows, where hp is the viscosity at point n: • fr 3A >; -fr 3B >; -fr-43C > - ^ 45 A ^ -fr 45B ^ - ^ 45C > p44 p. 44B »L.A4í4C h 4.2A» h L. 2 '»h p. 42C »h. p42D The extension of the viscosity increase with the increasing distance from the matrix is critical over the distance from the matrix specified here. However, the increase should not be large enough to contribute to fiber breakage or so small that the yarn line does not sufficiently solidify before reaching the movable perforated surface on which the non-woven fabric is formed. The term "incrementally" is associated with the increase in viscosity to lead to the concept that such an increase is an imperceptible or slight increase from a given plane having a very small thickness to the next plane or adjacent to the matrix. Therefore, such a change in viscosity can be considered to be the derivative of dy / dx, where dy is the increase in viscosity that results from a dx increasing distance from the matrix when such increases in distance approach zero. .

It is problematic to measure the viscosity of the yarn line at a given point, or to measure or estimate the concentration and temperature from which a viscosity can be calculated estimated. Notwithstanding this, it has been empirically determined that the above conditions for viscosity should come off when the fibers have the required characteristics, including the absence of draft, the desired fiber diameters, and the desired molecular orientation attenuation are achieved. Significant deviations from such viscosity requirements produce draft, broken fibers, uneven tissue formation, and / fibers having irregular and highly variable diameters.

It has been found that the fibers or particle can be mixed with the yarn lines. The primary and secondary gaseous sources are used with the particle fibers that are being introduced into the secondary gas source. When two secondary gas streams are employed, which is preferred, the fibers or particles may be included in either or both of the secondary gas sources.

Alternatively, they may be employed between gas sources in the preparation of a coform fabric including a primary gas source, a secondary gas source, and a tertiary gas source. In a first exception to the general avoidance of the use of a subsequent gaseous source, for example, a gaseous source in addition to the primary and secondary gaseous sources, the fibers or particle are included in the tertiary gaseous source, in which case a sufficient only tertiary gas stream usually When the tertiary gaseous source carrying particles or fiber carrier is used, the tertiary gaseous source will be at room temperature and will have a velocity of about 5 to about 15 meters per second. While a heated gas source can be used, care must be taken to avoid softening the fibers to an extent that causes excessive bonding of the superabsorbent precursor fibers with one another and / or the fibers or particles with which they are intermixed.

A second exception relates to the formation of a non-woven fabric of continuous fibers. In this case, three gas sources contribute to the control of the turbulence, consequently, to improve the uniformity of the tissue. The characteristics of the three gas sources are briefly described below.

The primary gas source has a relative humidity of from about 40 to 100 percent, a temperature of from about 20 ° C to about 100 ° C, or horizontal angle of incidence from about 70 ° around 110 ° C , and a vertical angle of incidence of no more than about 90 °. The viscosity of the primary gas source is no more than about 45 meters per second. The speed will preferably be in the range of from about 5 to about 15 meters per second. The function of the primary gaseous source is to provide the necessary conditions to allow the required viscosity increases of the yarn line as described above. The primary gas source in this case functions as a source of conditioning.

The secondary gas source has a temperature from about 20 ° C to about 100 ° C, a horizontal angle of incidence from about 70 ° to about 100 °, and a vertical angle of incidence of no more than about 100 ° C. 90 °. The velocity of the secondary gaseous source is typically no more than about 45 meters per second. The velocity of the secondary gas source is in the range of about 5 to about 15 meters per second. The secondary gas furnace serves to partially dry the yarn lines partially, even though a small attenuation grad may also take place.

Finally, the tertiary gas source has a lower temperature and a higher velocity than any primary gaseous source or secondary gaseous source. The tertiary gaseous source functions to attenuate and completely dry the fibers. The tertiary gaseous source has a temperature in the range of from about 10 ° C to about 50 ° C. The velocity of the tertiary gas source varies from about 30 to about 245 meters per second. In addition such a gaseous source has a horizontal angle of incidence d from about 70 ° to about 110 ° and a vertical angle of incidence of no more than about 90 °.

The present invention is further illustrated by the actual examples that follow. Such examples, however, should not be considered in any way as limiting the spirit or scope of the present invention.

Example 1 . 9 kilograms of acrylic acid, 2.29 kilograms of sodium hydroxide, 143 grams of 3-amino-1-propanol vini ether, and 11.97 grams of potassium persulfate, all available from the Aldrich Chemical Company, were added to a 10-gallon coated reactor containing 21.78 kilograms of distilled water and equipped with an agitator. The aggregate components were mixed at room temperature to form a completely dissolved solution. The reactor was heated at 60 ° for four hours. The agitator was placed continuously. The sodium salt solution of polyacrylic acid formed included 73.8% by weight of sodium acrylate, 24.2% by weight of acrylic acid and 2% by weight of 3-amino-1-propanol vinyl ether.

Example 2 The polymer solution prepared in the Example was used to prepare the non-woven fabrics on an apparatus having a matrix 6 inches wide (15.2 centimeters) which has 120 holes (20 holes per inch or about 11.8 holes per centimeter) . Each hole has a diameter of 0.46 millimeters. The matrix was constructed essentially as described in the United States Patent Nos. 3,755,527, 3,795,571 and 3,849,241, each of which is incorporated herein by reference. The primary gaseous source was divided into two streams, the outlets of which were located parallel to and closely adjacent to the extrusion holes. Each primary ga current output was around 0.86 millimeters wide. The ducts led to the primary gaseous current outlets at an angle of 30 ° from the vertical, for example, the plane at which the centers of the extrusion holes were located. Thus, the vertical incidence angles for the primary gas streams they were 30 ° and -30 °, respectively. The absolute value of the vertical angle d incidence for each of the two primary gas streams is 30 °. The horizontal angle of incidence for the primary gaseous stream was 90 °.

The secondary gaseous source was also divided into two secondary gas streams. The first secondary gas stream was introduced on the back side of the wire line curtain. The vertical angle of incidence for the first secondary gas stream was -30 °. The horizontal angle of incidence was 90 °. The output of the first secondary gas stream was located about centimeters below the tip of the array and about 2 centimeters from the line curtain of threads.

The second secondary gaseous stream was introduced on the front side of the wire line curtain. The vertical angle of incidence for the second gas stream segund was around 0o and the horizontal angle of incidence was 90 °. Therefore, the second secondary gas stream exited the secondary gaseous secondary conduit approximately parallel with the curtain line of threads. The output of the second secondary gas stream was located about 5 centimeters below the die tip and about 10 centimeters from the yarn curtain. The mobile perforated surface was located approximately 22-76 centimeters below the secondary gaseous source exits which were approximately equal distances below the die tip. A vacuum of 2-6 inches of water (0.005-0.015 atm) remained low. the wire.

The polyacrylic acid copolymer solution of Example 1 (26% solid) was heated in a two-liter Buchi autoclave at 50 ° C under an air pressure of 80 pounds per square inch over atmospheric pressure (5.4 atm).

The solution was pumped by means of a Zenith bomb, to the matrix through a transfer pipe heated to around 82 ° C. The solution was extruded at around 82 ° C. The gaseous primary source is hot moistened air at a temperature of approximately 93 ° C, 79 ° relative humidity and a pressure of 6 pounds per square inch above atmospheric pressure (0.41 atm) before the primary air separation outlet . The secondary gas source was compressed air heated to a temperature of 260 ° -316 ° C; the flow rate was 300-400 cfm (42.5-61.4 liters per second). The temperature of the die tip was maintained at 82 ° C, and the extrusion rate was 0.33-0.83 grams per minut per hole.

Four extrusion rates of different solutions of 0.33, 0.55, 0.67 and 0.83 grams per minute were used to form the non-woven fabrics. The basis weight for each cloth produced varied from 34 to 38 grams per square meter. Measurements of fiber size distribution were made on these four tissues. Measurements of the fiber size distribution involved measuring the diameter of each fibr which crossed an arbitrary straight line drawn on an electron scanning micrograph and typically required measuring the diameters of 50 fibers. The results of such measurements are summarized in Tables 2-1.

Table 2-1 Fiber Diameter Distribution The data in Table 2-1 were established as frequency against fiber diameter in μm to aid in visualization of the fiber diameter frequencies.

The tensile properties of the non-woven fabrics obtained were measured according to standard test procedures, Method 5102, Federal Standard 191A. The strip tension procedure gave results for maximum load, percent elongation and energy.

Tension characteristics of the woven fabrics were obtained. All reported values were normalized to allow differences in base weights.

To assist in the visualization of the characteristic voltage data, the data were drawn bar graphs, with separate bars for the data in the machine direction, the data in the transverse direction, and the average of the address data. of the machine and the transversal direction, respectively.

Example 3 In order to prepare a coformmed tissue, the procedure of Example 2 was essentially repeated. A leaf of soft wood pulp mainly (Coosa CR-54 manufactured by Kimberly-Clark Corporation, in its Coosa Mill Pines Alabama) was fibrized with a hammer mill and then s sped with air at a speed of 83 meters per second to through a rectangular duct that has a depth of 2. centimeters. The dilution rate, defined as grams of fiberized pulp per cubic meter of carrier air volume, s kept in the range of from around 2.8 to around 8. to minimize flocculation. The resulting airborne fiber stream was then injected into the first secondary gaseous stream carrying yarn line in the region where the first secondary gaseous stream carrying the yarn line and the second secondary gaseous stream meet. Both vertical and horizontal angles of incidence of the airborne fiber current were around d 90 °. The current left the rectangular duct to about 1 centimeter from the region where the two secondary gas streams meet.

In each case, the resulting coformed fabric was highly integrated and strong, but it was soft, voluminous and absorbent. The fabric was composed of 50-70 percent by weight of pulp fiber and had a basis weight of around 500 grams / m2. Even after the heat treatment in a convection oven to cross-link the polyacrylic acid copolymer, these fabrics were very soft, absorbent and of reasonable mechanical strength, as shown in Table 3.1. Such coformmed fabrics are useful as wipers or components of other absorbent products.

Peak Tension Property Example 4 In this example, in addition to the Coosa pulp, the superabsorbent powder (Favor 880 of Stockhausen Inc.) was introduced into the pulp stream before its encounter with the first secondary gaseous stream carrying the yarn line. The composition was about 33. % superabsorbent fiber, 33% pulp, and 34% superabsorbent powder. The total base weight was measured. This material was very soft after being manufactured. In 30 minutes, this one transmitted 0.95 of water solution of NaCl to around 23 centimeters.

Example 5 This example is similar to that of Example 4, with the exception of the composition of the material. A woven coform fabric was successfully made with about 3% superabsorbent fiber, 3% Coosa pulp, and about 94% superabsorbent polv (Favor 880 from Stockhausen, Inc.). The material had an excellent superabsorbent material holding capacity SA since a fair amount of superabsorbent powder particles were adhered to the superabsorbent fibers.

Example 6 This is similar to Example 2, with the exception that the relative humidity of the primary gas stream is varied. As determined from the SEM, satisfactory results were achieved only when the relative humidity level is in the range of 30% to 100%.

Having thus described the invention numerous changes and modifications thereof will be readily apparent to those experts who have ordinary skill in the art without departing from the spirit or scope of the invention.

Claims (30)

R E I V I N D I C A C I O N S

1. A method for preparing a non-woven fabric having substantially continuous superabsorbent fine fiber, which comprises the steps of: to. preparing an aqueous polymer solution of about 10 to about 75 weight percent of a linear superabsorbent precursor polymer having a molecular weight of from about 300,000 to about 10,000,000; b. extruding said polymer solution at a temperature of from about 20 ° C to about 180 ° C and a viscosity of from about 3 to about 100 passages per second through a matrix having a plurality of holes to form a plurality of yarn lines, said holes have diameters in the range of from about 0.20 to about 1.2 millimeters; c. to attenuate said yarn lines with a primary gaseous source under sufficient conditions to allow the viscosity of each line of yarn, by leaving a matrix hole and by a distance of no more than about centimeters, increasing incrementally with increasing distance. from the die, while maintaining essentially uniformity of viscosity in the radial direction, at a sufficient rate to provide fibers having a desired attenuation and a mean fiber diameter without a significant fibr disruption.

2. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 1, characterized in that the primary gas source has a relative humidity of from about 30 to 100%.

3. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 2, characterized in that the primary gas source has a temperature of from about 20 ° C to about 100 ° C. , a speed of from about d 150 to about 400 meters per second, a horizontal angle of incidence from about 70 ° to about 110 °, and its vertical angle of incidence of no more than about 90 °.

4. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 1, characterized in that the primary gas source has a relative humidity of from about 60 to 95%.

5. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 4, characterized in that the primary gas source has a temperature of from about 20 ° C to about 100 ° C, a speed from about d 30 to about 150 meters per second, a horizontal angle d incidence from about 70 ° to about 110 °, and its vertical angle of incidence of no more than about 90 °.

6. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 1, characterized in that the primary gas source has a relative humidity of about 65% to 90%.

7. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 6, characterized in that the primary gas source has a temperature of from about 20 ° C to about 100 ° C. , a speed of less than about 30 meters per second, a horizontal angle of incidence d from about 70 ° to about 110 °, and a vertical angle of incidence of about 90 °.

8. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, ta and as claimed in clause 3, characterized in that it further comprises: d. drying said yarn lines to form fiber with a secondary gas source at a temperature of from about 140 ° C to about 320 ° C and having a velocity of from about 60 to about 125 meters per second of which secondary gaseous source has a horizontal angle d incidence from about 70 ° to about 110 °, and its vertical angle of incidence of no more than about 90 °.

9. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, ta and as claimed in clause 8, characterized in that it further comprises: and. depositing the random fibers on a movable perforated surface to form an essentially uniform fabric on a scale of from about 0.4 to about 1.9 cm2, said movable perforated surface being from about 1 to about 60 centimeters from the opening from which the last gaseous source emerges to make contact with the yarn lines, whose fibers have a mean fiber diameter in the range of from about 0.1 to about 10 μm and are essentially draft-free; wherein said d attenuation and drying steps are carried out under conditions of controlled macroscale turbulence and said fibers are d such that they can be viewed as continuous and compared with their diameters.

10. A method for preparing a non-woven fabric having an essentially continuous super-absorbent fine fiber, ta and as claimed in clause 9, characterized in that it further comprises: F. Expose said uniform fabric to a high energy source selected from the group consisting of heat, electron ray, microwave, and a radiofrequency irradiation to make a stable cross-link in the superabsorbent precursor polymer.

11. A method for preparing a non-woven fabric having an essentially continuous super-absorbent fine fiber, ta and as claimed in clause 9, characterized in that it further comprises: g. Treat the stabilized fabric later by wetting, compacting, etching, bonding lamination or a combination thereof.

12. A method for preparing a non-woven fabric having an essentially continuous super-absorbent fine fiber, as claimed in clause 5, characterized in that it comprises: d. drying said yarn lines to form fibers with a secondary gaseous source at a temperature d from about 140 ° C to about 320 ° C and having a velocity of from about 30 to about 150 meters per second, whose gaseous source Secondary has a horizontal angle of incidence from about 70 ° to about 110 °, and a vertical angle of incidence of no more than about 90 °.

13. A method for preparing a non-woven fabric having a substantially continuous superabsorbent fine fiber, ta and as claimed in clause 12, characterized in that it further comprises: and. Depositing the fibers at random on a movable perforated surface to form an essentially uniform fabric on a scale of from about 1.9 to about 6.5 cm2, said movable perforated surface being from about 10 to about 100 centimeters from the aperture from the which emerges the last gas source to make contact with the yarn lines, whose fibers have a mean fibr diameter in the range of from about 10 to about 30 μ and are essentially uniform in diameter; in which the attenuation and drying steps are carried out under conditions d of a minimum macroscale turbulence.

14. A method for preparing a non-woven fabric having a substantially continuous superabsorbent fine fiber, ta and as claimed in clause 13, characterized in that it further comprises: f. Expose said uniform tissue to a high energy source selected from the group consisting of heat, electron ray, microwave, and a radiofrequency irradiation to make a stable cross-link in the superabsorbent precursor polymer.

15. A method for preparing a non-woven fabric having a substantially continuous superabsorbent fine fiber, ta and as claimed in clause 14, characterized in that it further comprises: g. Treat the stabilized fabric later by wetting, compacting, etching, bonding lamination or a combination thereof.

16. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 7, characterized in that it comprises: d. drying said yarn lines to form fiber with a secondary gaseous source at a temperature of from about 140 ° C to about 320 ° C and having a velocity of less than about 30 meters per second, whose secondary gas source has a horizontal incidence angle d from about 70 ° to about 110 °, and a vertical incidence angle of no more than about 90 °.

17. A method for preparing a nonwoven fabric having an essentially continuous super absorbent fine fiber, as claimed in clause 16, characterized in that it further comprises: and. Attenuate said fibers with a tertiary gas source having a temperature of from about 10 ° C around 50 ° C, a speed from about 30 about 240 meters per second, a horizontal angle d incidence from about 70 ° at about 110 ° and its vertical angle of incidence of no more than about 90 °.

18. A method for preparing a non-woven fabric having a substantially continuous superabsorbent fine fiber, as claimed in clause 17, characterized in that it comprises: F. Depositing the fibers at random on a perforated surface to form an essentially uniform fabric on a scale of from about 1.9 to about 6. cm2, said movable perforated surface being from about 10 to about 100 centimeters from the aperture from the The last gas source for contacting the yarn lines emerges, whose fibers have a fiber diameter in the range of from about 10 to about 30 μm and are essentially uniform in diameter, in which said d steps and drying are carried out under conditions of minimum macroscale turbulence.

19. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, ta and as claimed in clause 18, characterized in that it further comprises: g. Expose said uniform tissue to a high energy source selected from the group consisting of heat, electronic ray, microwave, and a radiofrequency irradiation to make a stable cross-link in the superabsorbent precursor polymer.

20. A method for preparing a non-woven fabric having an essentially continuous super absorbent fine fiber, ta and as claimed in clause 19, characterized in that it further comprises: h. Treat the stabilized fabric later by wetting, compacting, etching, bonding lamination or a combination thereof.

21. A non-woven fabric of essentially continuous superabsorbent microfibr, comprising: to. A non-woven fabric containing an essentially continuous superabsorbent microfibr, said superabsorbent microfibr has an absorbency under fluid load at a level of 10 grams of 0.9% by weight of aqueous sodium chloride per gram of dry absorbent fiber; Y b. Said fibers have a mean fibr diameter in the range from about 0.1 to about 10 μm, being essentially free of draft, and being of a length such that they can be seen as continuous in comparison with their diameters.

22. A non-woven fabric of essentially continuous superabsorbent microfibr, as claimed in clause 21, characterized in that it is formed by preparing an aqueous polymer solution of about 10 about 75% by weight of a linear superabsorbent precursor polymer. it has a molecular weight of from about 300,000 to about 10,000,000; extruding a polymer solution at a temperature of from about 20 ° to about 180 ° C and at a viscosity of from about to about 1,000 pass-seconds through a matrix having a plurality of orifices to form a plurality of d lines of threadssaid orifices have diameters in the range d from about 0.20 to about 1.2 millimeters, and attenuate said yarn lines with a primary gas source under sufficient conditions to allow the viscosity of each yarn line, by leaving a hole therein. The matrix increases incrementally with the increasing distance from the matrix while essentially maintaining the uniformity of the viscosity in the radial direction, at a rate sufficient to provide fibers having desired attenuation and a medium fiber diameter without significant fiber breakage. .

23. A non-woven fabric of essentially continuous superabsorbent microfibr, as claimed in clause 22, characterized in that said fabric is essentially uniform on a scale from about 0. to about 1.9 cm2 depending on the average fiber diameter.

24. A non-woven fabric of essentially continuous superabsorbent microfibr, comprising: to. A non-woven fabric containing an essentially continuous superabsorbent microfibr, said superabsorbent microfibr has an absorbency under fluid load at a level of 10 grams of 0.9% by weight of aqueous sodium chloride per gram of dry absorbent fiber; Y b. Said fibers have an average fibr diameter in the range of from about 10 to about 100 μm being essentially free of draft, and being essentially uniform in diameter.

25. A non-woven fabric of essentially continuous superabsorbent microfibr, as claimed in clause 24, characterized in that it is formed by preparing an aqueous polymer solution of about 10 about 75% by weight of a linear superabsorbent precursor polymer having a molecular weight of from about 300,000 to about 10,000,000; extruding a polymer solution at a temperature of from about 20 ° to about 180 ° C and at a viscosity of from about to about 1,000 pass-seconds through a matrix having a plurality of orifices to form a plurality of d yarn lines, said holes have diameters in the range d from about 0.20 to about 1.2 millimeters; and attenuates said yarn lines with a primary gaseous source under sufficient conditions to allow the viscosity of each yarn line, upon leaving a matrix orifice, increases incrementally with increasing distance from the die, while maintaining essentially the uniformity of the viscosity in the radial direction, at a rate sufficient to provide fibers having desired attenuation and a mean fiber diameter without a significant fiber breakage.

26. A non-woven fabric of essentially continuous superabsorbent microfibr, as claimed in clause 25, characterized in that said fabric is essentially uniform on a scale of from about 1. to about 6.5 cm2 depending on the average fiber diameter.

27. A disposable absorbent product incorporating a non-woven fabric of an essentially continuous superabsorbent microfiber, as claimed in clause 23.

28. A disposable absorbent product, as claimed in clause 27, characterized in that it is formed to provide a disposable absorbent article selected from the group consisting of diapers, underpants, catamenial devices, sanitary napkins, incontinent products and cleansing wipes. .

29. A disposable absorbent product incorporating a non-woven fabric of an essentially continuous superabsorbent microfiber, as claimed in Clause 26.

30. A disposable absorbent product, as claimed in clause 29, characterized in that it is formed to provide a disposable absorbent article selected from the group consisting of diapers, training pants, catamenial devices, sanitary napkins, incontinent products and cleansing wipes. . R E S U E N A non-woven fabric and a method for preparing a novel non-woven fabric of superabsorbent fibr are described. An aqueous solution of the superabsorbent precursor polymer is extruded under defined conditions through a plurality of matrix holes to form a plurality of yarn lines. The yarn lines are attenuated with a primary gaseous source defined to form a fibr under conditions of controlled macroscale turbulence and under sufficient conditions to allow the viscosity of each yarn line, by leaving a matrix hole and a distance of no more than about 8 centimeters increase incrementally with the increasing distance from the die while maintaining essentially the uniformity of the viscosity in the radial direction, at a rate sufficient to provide a fiber having a desired attenuation and average fiber diameter without a significant fiber breakage. The lines of attenuated yarns are dried with a defined secondary gas source. The resulting fibers are randomly deposited on an on a movable perforated surface to form an essentially uniform fabric. The movable perforated surface is placed at about 10 to about 100 centimeters from the last gas source to make contact with the lines of threads, the fibers have an average fiber diameter in the range from about 0.1 to about 30 μm and are essentially free to shoot. The steps of attenuation and drying are carried out under controlled macro-scale turbulence conditions.