RU2195962C2 - Structure and product of personal hygiene arranged to absorb viscoelastic liquid and containing a substance of viscoelastic properties to alter viscoelastic properties of such liquid and method for absorbing viscoelastic liquid - Google Patents

Abstract

FIELD: medicine. SUBSTANCE: the innovation deals with a structure designed to absorb viscoelastic liquid and containing a synthetic support including a substance of viscoelastic properties being placed at its surface to have contact with the mentioned viscoelastic liquid and, thus, considerably affect viscoelastic properties of viscoelastic liquid. Absorbing structure is very useful as a constituent of distributive layer of hygienic lining to absorb menstrual liquid and in other blood-adjacent products, as, for example, surgical sheets. Treated material at the contact with viscoelastic liquid, such as menstrual liquid, for example, changes viscoelastic properties of liquid and increases absorption degree and distribution along all absorbing structure. EFFECT: higher efficiency. 24 cl, 6 dwg, 1 ex, 6 tbl _

Description

BACKGROUND OF THE INVENTION
There are numerous applications for materials that can quickly absorb and / or transfer fluids, such as body excreta, etc. Examples are disposable personal care products, such as disposable diapers and training pants, feminine hygiene products, such as sanitary towels and tampons, and products for use in incontinence, such as liners and underwear. Other industrial products, such as napkins, oil-absorbing products and absorbent products, are subject to the same requirements as, for example, patient care items, such as dressings. Since these liquids have different properties, it is difficult to provide a material that would be able to satisfy many of these requirements and would be economically consistent with a single use, which is required in many applications. In particular, fluids, such as menstrual fluids, have, for example, viscoelastic properties that challenge traditional methods of absorption and distribution. The viscous and / or elastic components of such fluids tend to have unique requirements for absorption and / or distribution. These requirements are often incompatible with the best performance with respect to other fluid components that are less viscous or elastic, which usually requires a compromise in the overall performance. For example, the pore and capillary sizes in an ideal material for absorbing and distributing less viscoelastic components are different from that which is best suited for more viscoelastic components. To create the structure of non-woven materials, foams, films, etc. which would satisfy all these requirements, a lot of effort was expended, but without complete success. Another approach is to change the viscoelastic properties of the liquid itself. Numerous methods have been applied to change the bulk properties of viscoelastic fluids, including the use of substances that affect intermolecular bonds and the physical interweaving of macromolecules.

 Nonwoven fabrics and their manufacture are the subject of extensive development, the result of which is a wide variety of materials for numerous applications. For example, nonwovens with a low surface density and an open structure are used in personal care products, for example, disposable diapers, as lining fabrics that provide dry contact with the skin, but easily transfer liquids to more absorbent materials, which can also be nonwovens other composition and / or structure. For many applications, the ability to absorb and transmit viscous fluids, such as menstrual fluids, is important for the effective action of these products on the distribution of fluids in order to maximize the absorption properties of this or underlying materials. For other applications, non-woven materials with higher surface densities and porous structures can be designed to be suitable for use in filtering, absorbing and insulating, for example, as wrappers for sterilized objects, napkins or protective clothing for use in medicine, veterinary medicine or industry. Nonwoven materials with even higher surface density have been created for use in land reclamation, agriculture and construction. Of the almost unlimited number of examples of types of non-woven materials and cases of their use, only a few examples are known to specialists in this field, who also recognize that they are constantly discovering new non-woven materials and cases of their use. In addition, various methods and equipment have been developed for the manufacture of nonwoven materials having the desired structures and compositions suitable for their use. Examples of such methods are spinning, melt spinning, carding, and others, which will be described in detail below. The present invention is generally applicable to non-woven materials that are obvious to a person skilled in the art, and is not limited to reference to specific non-woven materials or examples thereof, which are only illustrative.

 It is not always possible to efficiently produce a nonwoven material that has all the desired properties in a molded form, and it is often necessary to process a nonwoven material to improve or change properties such as wettability of one or more liquids, absorption or distribution properties, repellent properties with respect to one or more liquids, electrostatic properties, conductivity and softness, mentioned here as a few examples. Conventional processing methods include steps such as dipping a nonwoven material into a treatment bath, coating a coating of the treatment composition or spraying it onto the nonwoven fabric, and printing the nonwoven fabric with the treatment composition. For economic and other reasons, it is usually desirable to use a minimum amount of the processing composition, which gives the desired effect with an acceptable degree of uniformity. It is known, for example, that the heat in the additional drying step in order to remove water deposited with the processing composition can adversely affect the strength properties of the nonwoven material , and also lead to an increase in production costs. Therefore, it is desirable to provide an improved processing method and / or composition for nonwoven materials that can be effectively and efficiently applied to the desired treatment without adversely affecting the desired properties of the nonwoven materials, while also achieving the desired results. More specifically, it is desirable to provide a treated non-woven material suitable for use with viscoelastic fluids and having the property of modifying characteristics, such as, for example, the viscosity and / or elasticity of the released viscoelastic fluid, in order to regulate the movement of the fluid, for example, the perception, distribution or absorption of fluid in objects personal hygiene such as sanitary napkins.

SUMMARY OF THE INVENTION
The present invention relates to structures especially adapted for the perception of fluids with viscoelastic properties, namely menstrual fluid, mucus, blood products, bowel movements, etc., which are obvious to specialists in this field. The structures of the invention are useful as, for example, feminine hygiene products such as menstrual fluid absorbers such as sanitary napkins and tampons, care products for infants and children, such as disposable diapers and training pants, dressings, urinary incontinence products and products for wiping and absorbing oils. According to the invention, the structure contains a synthetic, often normally hydrophobic, substrate including a substance for changing viscoelastic properties, placed with the possibility of contact with a viscoelastic fluid. The substrate is successfully a nonwoven material, which can be, for example, fibers obtained by spinning, melt spinning, co-molding or carding. Additional substrates that can be used include foams and films that can be fibrillated, perforated, or otherwise processed to give them the properties of fibers, as well as laminated materials thereof and / or non-woven materials. Depending on the specific application, the structure can be used as a body contacting body, a distribution layer between the body and the absorbent layer, an absorbent layer or more than one of these layers. Upon contact, the structure according to the invention changes the viscoelastic properties of the liquid so as to improve the properties of perception, distribution and absorption of the liquid. It is desirable that the substance that changes the viscoelastic properties is harmless to use and does not pollute the environment when removed. Examples of useful substances are alkyl polyglycosides having 8-10 carbon atoms in the alkyl chain. These alkyl polyglycosides alter the viscoelastic properties of viscoelastic fluids, and also increase the wettability of the surfaces of synthetic materials. Other examples of viscoelastic modifiers include a bovine lipid surfactant (Survant. Ross Laboretories), a drug used to treat acute respiratory distress syndrome and mycoviscidosis, and enzymes such as papain or pepsin that break down protein structures. Some dextrins and dextrans can also be used as viscoelastic modifiers. Dextrans (macrosa) are glucose polymers with chain structures and molecular weights up to, for example, 200,000, derived from sucrose, often through bacterial action. As is known, dextrins are usually solid derivatives of starch, often formed when the starch is heated either individually or with nitric acid, for example, 4000 molecular weight dextran manufactured by Polydex Pharmaceuticals, Ltd., Scarborough, Canada. If desired, a normally hydrophobic substrate can be additionally or simultaneously treated with a surfactant to increase its wettability. Adding a viscoelastic modifying agent to the substrate can be carried out by conventional methods, for example by spraying, coating, dipping, etc., although it is useful to use a strong jet of powder particles in cases where it is desirable to minimize drying and / or spin. On the other hand, in some cases it may be useful to introduce a substance that modifies the viscoelastic properties as an internal additive in the polymer melt. The amount of viscoelastic modifying agent used will depend on the particular end use, as well as factors such as surface density and porosity of the substrate.

Brief Description of the Drawings
FIG. 1 is a schematic illustration of a processing method according to the present invention, useful when applied to one or both sides of a nonwoven material.

 FIG. 2 is an exemplary personal care product in the form of a sanitary napkin including a treated fabric lining according to the present invention.

 FIG. 3 is a graph of the dependence of the measured values of elastic stresses in a viscoelastic composition on the amount of the introduced substance, which changes the viscoelastic properties.

 FIG. 4 is a graph of the dependence of the measured viscosity values of the viscoelastic composition on the amount of the introduced substance that changes the viscoelastic properties.

 FIG. 5 is a diagram comparing the results of testing the absorption distance into the material according to the invention and to materials treated with other substances.

 FIG. 6 is a graph of further comparison of materials with respect to absorption distance.

Test methods
Viscoelastic properties were determined by the method described in the instruction manual for the viscoelastic analyzer VILASTIK 3 (VILASTIK SCIENTIFIC, INC. Mailbox 160261, Austin, TX 78716, USA). The device was calibrated by the manufacturer, and this calibration was checked before measuring the samples. An immunosol (VWR Scientific) was used as a connective fluid. The measurements were carried out under the "Tension" mode, at a frequency of 0.05 Hz, with an integration time of 39 seconds, under ambient conditions, when installed on a medium drive and with a medium-sized tube for samples (stainless steel, internal radius 0.0916 cm and length 6.561 cm).

 The absorption results were determined by the method described in US patent 5314582 in the name of Nguyen and Vargas. Absorption occurred in a horizontal manner, under ambient conditions and without using any load to limit the samples. Five samples of 25 x 203 mm in size were used (203 mm in the direction of movement during the test). The results are presented as the distance (in inches) of absorption in twenty minutes.

The following test procedure was used to evaluate the perceptive ability of female pads. Using a Harvard Epereytes syringe pump, 250 μl of drops of a menstrual fluid simulator were dispensed from a 30 cm ³ syringe at a rate of 3 ml / min. The fluid was supplied through a tube with an inner diameter of 1.6 mm attached to the syringe. A Plexiglass plate was used to control the placement of the end of the tube slightly above the top surface of the test material. The pump was adjusted to deliver one drop, followed by a pause of thirty seconds before feeding the next drop. To record the time spent by the drop for complete penetration through the top layer into the product, a stopwatch was used. A total of three drops (750 μl) were applied to one test site on the product. Then the product was rearranged and the second test place was wetted in the same way. Processed the results of five repetitions of each test mode.

In the study of rheological properties and absorption as a viscoelastic fluid, either homogenized chicken egg white was used, obtained by drawing 50 cm ^{3 of} egg white into a 60 cm ³ disposable syringe and squeezing it out with a flow rate of 100 cm ² / min and repeating this process as a whole for five cycles (fluid A), or a synthetic menstrual fluid simulator described in co-assigned provisional patent application SN 60/046702, filed May 14, 1997, entitled "Artificial fluid" the body spine ", the contents of which are incorporated herein by reference (liquid B). Fluid B contained a fluid designed to simulate viscoelastic and other properties of menstrual fluid. In order to prepare this liquid, blood (in this case, defibrinated pig blood) was separated by centrifugation at 3000 rpm for 30 minutes, although other methods or speeds and time periods could be used if they were effective. Plasma was separated and stored separately, and in addition to this, the leukocyte film was removed and discarded, and the erythrocyte mass was separately stored. The eggs were divided (in this case, the eggs of large individuals), the yolk and brisket were discarded and egg white was kept. Separate the egg white into thick and liquid parts by filtering through a 1000 micron nylon mesh for about 3 minutes and discard the more liquid part. Note that it is possible to use a grid with other cell sizes, and the duration or method of separation may be different, provided that at least the necessary viscosity is provided. The thick part of the egg white that remained on the grid was collected and drawn into a 60 cm ³ syringe, which was then placed on a programmable syringe pump and homogenized by extruding its contents five times and re-filling it. In this example, the degree of homogenization was controlled using a syringe pump with a capacity of about 100 ml / min and a tube with an inner diameter of about 3 mm. After homogenization, thick egg white had a viscosity of about 20 centipoise at 150 ^-1 sec; then it was placed in a centrifuge and rotated for about 10 minutes at about 3000 rpm to remove foreign substances and air bubbles, although any effective method can be used to remove foreign substances and bubbles.

After centrifugation, a thick homogenized egg white containing ovomucin was injected with a syringe into a 300 cm ³ fenvel portable vessel (registered name). Then 60 cm ^{3 of} pork plasma was added to the portable vessel. A portable vessel was squeezed to remove all air bubbles from it and placed in a Stomacher laboratory mixer, where its contents were mixed at normal (or medium) speed for about 2 minutes. Then a portable vessel was removed from the mixer, 60 cm ^{3 of} erythrocyte mass was added and mixed by hand kneading for about 2 minutes or until the contents looked homogeneous. The hematocrit of the final mixture showed an erythrocyte content of about 30 wt.%, Which usually should be at least between 28 and 32 wt.% For the artificial menstrual fluid prepared according to this example. The amount of egg white was about 40 wt.%
The components and equipment used in the preparation of this artificial menstrual fluid are commercially available. The sources for obtaining the components and equipment used in this example are listed below, although, of course, other sources can be used, provided that they are approximately equivalent.

 Blood (pork): Kokaliko Bayelogical, Inc., 449 Stevens Road, Rimstone, Pensilvania, 17567, (717) 336-1990, USA.

 Fenwell portable vessel (registered name), 300 ml, with connector, code 4R2014: Baxter Helfke Corporation, Fenwell Division, Deerfield, Illinois, USA.

 Programmable syringe pump "Harvard Epereites" model 55-4143; Harvard Epereites, Southnetics, Minnesota, USA.

 Laboratory stirrer "Stomacher 400" VA 7021 modules, serial number 31968. Syoward Medical, London, England, UK.

 1000 micron mesh product CMN-1000-B: Resin Parte, Inc., Mailbox 4650, Miami Lake, Florida 33014-0650, USA.

 Hemat Stat-11 device for measuring hematocrit, serial number 1194Z03127: Separation Technology, Inc., 1096 Reiner Drive, Altamon Springs, Florida 32714, USA.

DETAILED DESCRIPTION OF THE INVENTION
Definitions
As used herein, the term “viscoelastic” refers to a composition having at least one significant component that is moderately viscous and / or has elastic properties. “Moderately viscous” means that the component has a viscosity at least equal to that of ordinary human blood plasma. "Elastic" means that the component has an elasticity equal to or greater than the elasticity of the plasma of human blood.

As used herein, the term “viscoelastic modifier” means an organic substance which, when contacted in an effective amount with a viscoelastic composition, substantially modifies the properties of this viscoelastic composition, for example, reducing its viscosity and / or weakening its elastic nature. “Significantly changes” means that the property, measured as described, changes by at least a statistically significant value, and it is useful if this change in many applications will be at least about 30%. As used herein, the term “nonwoven fabric or material” means a material having a structure of individual fibers or threads that are intertwined but not in an orderly or recognizable manner, such as in a knitted fabric. This term also encompasses elementary fibers and strands of fibers, yarn or tows, as well as foams and films that are fibrillated, perforated, or otherwise processed to give them properties similar to those of fabric. Non-woven fabrics or materials are made in many ways, such as, for example, spinning melt fibers, spinning and carding. The surface density of non-woven fabrics is usually expressed in ounces per square yard (ounce / sq. Yard) or grams per square meter (g / m ² ), and effective fiber diameters are usually expressed in microns. (Note that to convert from ounce / sq. Yards to g / m ² multiply by 33.91).

As used herein, the term “microfibers” refers to small diameter fibers having an average diameter of not more than about 75 microns, for example having an average diameter of from about 0.5 microns to about 50 microns or more. In particular, microfibers can have an average diameter of from about 2 microns to about 40 microns. Another frequently used expression for fiber diameter is denier, which is expressed in grams per 9000 meters of fiber and can be calculated by squaring the fiber diameter in microns, multiplying by the density in g / cm ³ and multiplying by 0.00707. A smaller denier means a thinner fiber, and a larger denier means a thicker or heavier fiber. For example, a diameter of polypropylene fiber equal to 15 microns can be converted in denier by squaring, multiplying the result by 0.89 g / cm ³ and multiplying by 0.00707. Thus, a polypropylene fiber with a diameter of 15 microns has a denier of about 1.42 (15 ² • 0.69 • 0.00707 = 1.415). Outside the United States, the most common unit of measure is tex, which is defined in grams per kilometer of fiber. Tex can be calculated as denier / 9.

 As used herein, the term "spun fibers" refers to fibers of small diameter that are formed by extruding molten thermoplastic material in the form of elementary fibers from a plurality of small, usually round, openings of a spinneret, followed by a rapid reduction in the diameter of the formed fiber fibers as described, for example, in US Pat. No. 4,340,563 in the name of Appel and others, US patent N 3692618 in the name of Dorschner and others, US patent 3802817 in the name of Matsuki and others, US patents 3338992 and 3341394 in the name of Kinney, US patent 3502763 in the name of Hartman, patent US 3502538 in the name of Levy and US patent 3542615 in the name of Dobo et al. When the spun fibers are deposited on a prefabricated surface, they are chilled and usually non-tacky. Spun fibers are typically continuous and often have average diameters greater than 7 microns, more specifically, between about 10 and 20 microns.

 As used herein, the term “meltblown fibers with extrusion of a gas stream” means fibers formed by extruding molten thermoplastic material through a plurality of small, usually circular, openings of a spinneret in the form of molten filaments or filaments into converging at one point high-speed flows of typically heated gas (e.g. air), which pull the elementary fibers from the molten thermoplastic material to reduce their diameter, which can be up to the diameter of a microwave . After that, the fibers formed in this way are carried away by a high-speed gas flow and are deposited on the collecting surface, often still sticky, with the formation of a canvas with a random arrangement of such fibers. Such a method is described, for example, in US Pat. No. 3,849,241 to Byutin. The fibers obtained by melt spinning with a gas stream are microfibers that may be continuous or non-continuous and typically have an average diameter of less than 10 microns.

 The term “bonded carded fiber nonwoven fabric” or “BCW” as used herein refers to nonwoven fabrics formed by carding methods known to those skilled in the art and further described, for example, in co-assigned U.S. Patent No. 4,488,928 to Alikhan and Schmidt, which is given here for reference. In short, carding methods include converting a mixture, for example staple fibers, with bonding fibers or other bonding components into a bulky cotton that is combed or otherwise treated to provide a substantially uniform surface density. This non-woven material is heated or otherwise treated to activate the adhesive component, resulting in a single, usually loose, non-woven material.

 As used herein, the term “polymer” generally covers, but is not limited to, homopolymers, copolymers, such as, for example, grafted copolymers, block copolymers, random and alternating copolymers, terpolymers, etc. and mixtures and modifications thereof. In addition, unless otherwise specified, the term "polymer" will cover all possible geometric configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and disordered symmetries.

 As used herein, the term “single component” fiber refers to a fiber formed from one or more extruders using only one polymer. This does not mean the exclusion of fibers formed from a single polymer, in which additives are added in small quantities for dyeing, imparting antistatic properties, oiling, ensuring hydrophilicity, etc. These additives, for example titanium dioxide for coloring, are usually present in an amount of less than 5 wt.%, And most often in an amount of about 2 wt.%.

 As used herein, the term “combined fibers” refers to fibers that are formed from at least two polymers extruded from separate extruders but formed together to form one fiber. Combined fibers are sometimes also called multicomponent or bicomponent fibers. The polymers are usually different from each other, although the combined fibers can be single-component fibers. The polymers are located on essentially permanently located distinct sections of the cross-sectional area of the combined fibers and continuously extend along the length of the combined fibers. The structure of such a combined fiber can be, for example, in the form of a sheath and a core or in the form of “islands in the sea”. Combined fibers are described in US Pat. No. 5,108,820 to Kaneko et al., US Pat. No. 5,336,552 to Streck et al. And US Pat. No. 5,382,400 to Pike et al. In bicomponent fibers, polymers may be present in 75/25, 50/50, 25 ratios. / 75 or in any other desirable respects.

 As used herein, the term “bicomponent fibers” refers to fibers that are formed from at least two polymers extruded as a mixture from the same extruder. The term “mixture” is defined below. In bicomponent fibers, various polymer components are not located on relatively distinct distinct sections of the fiber cross-sectional area, and different polymers are usually not continuous along the entire length of the fiber, but instead usually form fibrils or protofibrils that randomly start and end. Bi-ingredient fibers are sometimes also called multi-ingredient fibers. Fibers of this general type are discussed, for example, in US Pat. No. 5,108,827 to Gessner. Bicomponent and bicomponent fibers are also discussed in the textbook Polymer Blends and Composites by Jhon A. Manson and Leslie H. Sperling, copyright 1976 by Plenum Press, a division of Plenum Publishing Corporation of New York, IBSN 0-306-30831-2, on pages 273-277.

 As used herein, the term “mixture” as applied to polymers means a mixture of two or more polymers, while the term “alloy” means a subclass of mixtures in which the components are not miscible but compatible. "Miscibility" and "immiscibility" are defined as the properties of mixtures, respectively having negative and positive values for the free energy of mixing. In addition, “alignment” is defined as the process of changing the boundary properties of an immiscible polymer mixture in order to make an alloy.

 As used herein, the term “bonding by passing hot air” or “LHBH” means a method of bonding a non-woven material, for example a non-woven material of bicomponent fibers, by which air is forced through the non-woven material hot enough to melt one of the polymers from which the fibers are made. The air flow rate is often in the range of 30-150 m / min, and the residence time of the material can be up to 6 seconds. Melting and re-hardening of the polymer provide bonding. The bonding method by passing hot air has limited adjustability and is often regarded as the second stage of the bonding process. Since at least one component is required to be bonded using the “SPHV” method, the application of this method is limited to non-woven materials with two components, such as non-woven materials from two-component fibers or non-woven materials containing adhesive fibers, powder, etc. P. The “SPHV” method is often used for bonding non-woven materials such as “BCW”.

As used herein, the term "thermal dot bonding" means the passage of a fabric or non-woven material of bonded fibers between a heated calender roll and a back roll. The calender roll is usually, although not always, in some way embossed so that the entire fabric is not fastened over its entire surface. As a result of this, for functional as well as aesthetic reasons, various relief designs for calender rolls have been developed. In one example, the pattern has sharp protrusions and is a Hansen-Pennings or “X and P” pattern with an almost 30% bond area at about 30 bonds / cm ² , as described in US Pat. No. 3,855,046 to Hansen and Pennings. The relief pattern of type "X and P" has bonding areas with square sharp protrusions or pins, with the lateral size of each pin being 0.965 mm, the distance between the pins being 1.778 mm and the bond depth 0.584 mm. In the resulting figure, the bonding area is about 29.5%. Another typical pattern for pin bonding is the stretched bonding pattern of Hansen and Pennings or "EXP", which provides a bonding area of 15% with square pins having a lateral size of 0.94 mm, the distance between the pins is 2.464 mm and the depth of bonding is 0.991 mm. Another typical point bonding pattern, designated “714”, has square pin bonding portions in which each pin has a lateral dimension of 0.584 mm with a pin spacing of 1.575 mm and a bond depth of 0.838 mm. The resulting pattern has a bond area of about 15%. Another common pattern is the "S-Star" pattern, which has a bond area of about 16.9%. The drawing "S-Star" has the form of transversely directed stripes or "velveteen" interrupted by asterisks. Other common patterns include a diamond-shaped pattern with repeating and slightly offset diamonds and a wire mesh pattern that looks like its name shows, such as a window net. Typically, the bonding area varies from about 10% to about 30% of the area of the layered non-woven material. As is well known in the art, pin bonding allows you to hold together layers of layered material, as well as to give integrity to each individual layer by bonding threads and / or fibers to each other.

 As used herein, the term “personal care product” refers to diapers, training pants, absorbent underwear, adult urinary incontinence products, sanitary napkins and feminine hygiene products such as sanitary napkins and tampons.

 As used herein, the term "hydrophilic" means that the polymer material has free surface energy, so that the polymer material has the ability to be wetted by an aqueous medium, i.e. liquid medium in which water is the main component. The term "hydrophobic" refers to those materials that are not hydrophilic by definition. The expression "hydrophobic in nature" refers to those materials that are hydrophobic in their chemical composition without additives or treatments affecting hydrophobicity. As is known, hydrophobic materials can be treated internally or externally with surfactants and the like. to give them hydrophilicity.

 In addition, other substances, such as pigments, can be mixed with the polymer used to make the nonwoven fabric of this invention, to give each layer the same or a different color. The pigments used as internal additives for thermoplastic polymers for the manufacture of spun fibers and fibers formed from a melt by drawing a stream of gas are known in the art. The pigment used is usually present in an amount of less than about 5 wt.%. by weight of the layer, although other additives may be present in a total amount of less than about 25 wt.%.

 The fibers from which the fabric is made according to this invention can be produced, for example, by melt spinning or spinning with a gas stream, including those that produce bicomponent, bicomponent, or polymeric mixed fibers that are well known in the art. These methods typically use an extruder to feed the molten thermoplastic polymer into dies, where the polymer is converted into fibers, which may have a staple length or more. The fibers are then stretched (usually pneumatically) and deposited on a moving permeable mat or tape to form a non-woven fabric. Fibers produced by melt spinning and spinning with a gas stream are microfibers as defined above.

 The manufacture of nonwoven materials from fibers molded from a melt by drawing a stream of gas, in General, are discussed above and in the links.

 As mentioned, the non-woven material may also be material of bonded carded fibers. Non-woven materials from bonded carded fibers are made from staple fibers, which are usually purchased in bales. Bales are placed in a bobbin machine that separates the fibers. The fibers are then sent to a comb or carding machine, which further separates the staple fibers and aligns them along the machine to form a fibrous nonwoven material substantially oriented in the direction along the machine. After the formation of the nonwoven material, it is then bonded using one or more known bonding methods. One such method is powder bonding, in which the powdered adhesive is distributed over the nonwoven material and then activated, usually by heating the nonwoven material and the adhesive with hot air. Another suitable bonding method is pattern bonding, using heated calender rolls or ultrasonic equipment for bonding fibers, usually a localized bonding pattern, although, if desired, the nonwoven fabric can be bonded over its entire surface. Another suitable bonding method, especially when using bicomponent staple fibers, is bonding with transmitted hot air.

The fabric used in this invention may be a multilayer laminate. An example of a multilayer layered material is a material in which some layers are made of spun fibers and meltblown by a gas stream, such as, for example, laminated fibers / fibers formed by melt by a gas flow / spun fibers described in US Pat. No. 4,041,203 to Brock et al., US Pat. No. 5,169,706 to Collier et al. and US Pat. No. 4,374,888 to Bornslager. Such a layered material can be made by sequentially depositing on a moving forming tape a first layer of spun fibers, then a layer of fibers molded from the melt with a gas stream, and finally another layer of spun fibers and then bonding the layered material in the manner described below. On the other hand, the layers can be manufactured separately, assembled on rolls and combined at a separate bonding stage. Such fabrics typically have a surface density of from about 6 to 400 g / m ² or, more specifically, from about 25 to about 100 g / m ² . Processing in accordance with the invention can be carried out in the process of manufacturing a nonwoven material or outside it on previously produced substrates or nonwoven materials.

 Non-woven materials from spun fibers are usually bonded in some way during their manufacture in order to give them sufficient structural integrity to withstand harsh conditions during further processing into a finished product. Bonding can be carried out in a number of ways, namely, hydro-entangling, needle-piercing, ultrasonic bonding, adhesive bonding, stitch bonding, bonding by passing hot air and thermal bonding.

 For some applications, it may be desirable to treat the nonwoven material in a corona discharge or otherwise expose it to an active agent before applying a viscoelastic modifier. Such processing methods are described in a jointly assigned US application Serial No. 08/665172 to Yahiaoui, Ning, Bolyan, Jac Dowall, Potts and Van Howte, filed June 14, 1996 and incorporated herein by reference.

 The effect of the active agent is aimed at increasing the affinity of the hydrophilic polymer material to a porous hydrophobic polymer substrate. It can be, for example, in the form of a corona discharge. Another example of exposure to an active agent may be plasma treatment.

 Not wishing to be bound by theory, we believe that the action of an active agent on a porous hydrophobic polymer substrate leads to changes in the surface of the substrate, due to which the surface energy of the substrate temporarily increases. This, in turn, allows the treatment solution to penetrate the porous substrate; thus, the porous substrate can be saturated with the treatment solution.

 Although the action of the active agent on the porous substrate is a desirable method of temporarily increasing the surface energy of the substrate, other methods may also be used. For example, a porous substrate can be treated with ozone or by passing an oxidizing solution through it, such as, for example, an aqueous medium containing chromium trioxide and sulfuric acid. However, with such other methods, attention should be paid to preventing or minimizing the destruction of the porous substrate.

 The intensity of exposure to the active agent can be controlled in a controlled manner, at least one size of fibrous nonwoven material. When a porous substrate is coated with a hydrophilic polymer material, the size or degree of hydrophilicity of the coating is directly proportional to the intensity of this effect. Thus, the hydrophilicity of the coating of the polymeric material will change in a controlled manner, at least one size of the fibrous non-woven material.

Using known methods, it is possible to easily change in a controlled manner the intensity of exposure to the active agent. For example, an apparatus for creating a corona discharge can be used, which has an electrode divided into segments, and in which it is possible to independently measure the distance of each segment from the sample being processed. As another example, it is possible to use an apparatus for creating a corona discharge having a system of electrodes with a gradient of the spark gap; in this case, one electrode can be rotated around an axis that is perpendicular to the length of the electrode. Other methods may be used; see, for example, Fabrication of a Continuous Wettability Gradient by Radio Frequency Plasma Discharge, WGPitt J. Colloid Interface Sci., 133, 1, 223 (1989); and "Wettability Gradient Surface Prepared by Corona Discharge Treatment", JHLee, et al., Transactions of 17 ^th Annual Meeting of the Society for Biomaterials, May 1-5, 1991, page 133, Scottdate, Arizona.

 As mentioned above, an important parameter of processed nonwovens for many applications with viscoelastic fluids, for example as distribution layers for sanitary napkins, is absorbency or the ability to quickly distribute menstrual fluid during use to ensure maximum absorbent ability of the product.

 As has been shown, surfactants known from the prior art, such as ethoxylated hydrocarbons, siloxanes and ionic surfactants, promote absorption, but not by the mechanism of the present invention. Such conventional surfactants increase wettability, but are not able to effectively weaken the viscoelastic properties of the menstrual fluid in such a way as to enhance absorption to the extent consistent with the present invention. According to the invention, the use of substances that change the viscoelastic properties, such as, for example, certain alkyl glycosides, leads, as it has been established, not only to weaken the viscoelastic properties of the released fluid, but also to provide surface-active properties for the rapid distribution of the viscoelastic fluid. For best results, alkylpolyglycosides should have 8-10 carbon atoms in the alkyl chain and be present in an amount of from about 0.2% to about 5% based on the total weight of the material and the weight of the alkpolyglycoside composition, which may be aqueous with, for example, about 40% of water. Other viscoelastic properties will be apparent to those skilled in the art, for example, a surfactant from bovine lipid extract (Survanta, Ross Laboratorium) and proteolytic enzymes such as papain and pepsin, as well as certain dextrins and dextrans.

Table 1 below shows the effect on the rheological properties of an egg white viscoelastic fluid (described above in the Test Methods section as “fluid A”) of the addition of a viscoelastic modifying agent, Glucopon 220 UP, obtained as 60% (by weight) a solution of alkylpolyglycoside in water, commercially available from Henkel Corporation. The rheological properties of the viscoelastic fluid based on egg protein (fluid A) were measured with and without Glucopone 220. Glucopon was directly injected into a viscoelastic fluid and intermittently mixed for at least 24 hours to ensure complete mixing. The final concentration of "Glucopone 220" mixed with a viscoelastic fluid,
was 1.0%. A viscoelastic fluid without Glucopon 220 was also intermittently mixed for at least 24 hours to duplicate the same shear pattern as in a fluid containing Glucopon. Measurements were performed as described in the Test Methods section. Elastic stress at a strain of approximately 1 decreased by 36%, while viscosity at a shear rate of approximately 0.1 sec ^-1 decreased by 30%. Percentages were obtained using the difference between the values for the control sample and the sample with a substance that changes the viscoelastic properties divided by the value for the control sample, and multiplying the result by 100.

Table 2 and FIGS. 3 and 4 show the results of a similar example (experiment 1 in FIGS. 3 and 4) using a second viscoelastic fluid (fluid B). In this example, a viscoelastic modifier and a viscoelastic fluid were mixed with either a 10-fold inversion and leaving for 1 hour, or using a glass stirrer for 1 minute and leaving at least 30 minutes. The differences in preparation, apparently, only slightly affected the results of the experiments, if at all influenced them. In this case, the amount of Glucopon 220, which changes the viscoelastic properties and is mixed with a viscoelastic fluid, was at least about 1.0%. The elastic stress during deformation of about 1 decreased in the range of 60-100% (taking into account the limitations of the equipment for sensitivity), while the viscosity at a shear rate of about 0.1 sec ^-1 decreased by almost 77%, which indicates the possibility of applying the invention to various viscoelastic fluids .

 Figures 3 and 4 show these results as a function of the amount of added viscoelastic modifying agent. As is clearly shown, the amount of a substance that changes viscoelastic properties radically affects the decrease in both elastic stress and viscosity of a viscoelastic fluid (fluid B).

 The present invention is believed to be useful for reducing viscoelasticity and improving fluid movement with respect to a variety of viscoelastic fluid compositions, although use in sanitary napkins is a highly desirable application.

 Table 3 below shows the results of absorbing non-woven material from bonded carded fibers, which can be used as a distribution layer in the structure of the sanitary napkin. Bonded carded nonwoven fabric made for the purpose of these tests was carded fiber nonwoven bonded with hot air, or TABCW fabricated as described below. Washed fabrics or identical fabrics prepared using four different surface treatments were tested. Absorption studies were carried out with a viscoelastic fluid based on egg white (described in the Test Methods section as fluid A); measured the distance over which absorption took place within 20 minutes of exposure of the liquid to the tissue. Glucopon-treated TABCW fabrics showed the greatest absorption distances.

100% by weight non-woven fabric consisted of two-component staple fibers with a polyethylene sheath and a polypropylene core, having a weight number of 3 denier and a length of 38 millimeters. Bicomponent fibers were obtained from Chisso Corporation and were delivered with a sizing applied by the seller. Staple fibers were passed through a baking powder and uniformly mixed before combing into a cotton wool at a linear speed of 15.24 m / min. After the formation of the nonwoven material, it was sent through a device for fastening by passing hot air (drum type) at an air temperature of 131 ^o C. The residence time in this device was between 3 and 4.5 seconds. The resulting nonwoven material had a surface density of 100 g / m ² and a specific gravity of 0.06 g / cm ³ . The nonwoven fabric was then wound onto a roll.

 Material A is the above-described nonwoven material, which was washed to remove the sizing applied by the seller and then treated with 2.0% Glucopon 220, as described below. Material B is the non-woven material described above, which was washed to remove the sizing applied by the seller, and then treated with 0.45% calcium alginate, as described below. Material C is the above-described nonwoven fabric with a sizing applied by the seller. Material D is the above-described nonwoven material, which was washed to remove the sizing applied by the seller.

 In FIG. 5 compares the absorption distances into the nonwoven material when treated with several other known substances. The main nonwoven material was the above material A, and the viscoelastic fluid was a mimic fluid simulator (fluid B). Triton X-102 is an alkyl phenol ethoxylate surfactant commercially available from Union Carbide. Y12488 is ethoxylated polydimethylsiloxane commercially available from Axis. Akhkovel N-62 is a mixture of ethoxylated hydrogenated castor oil and sorbitan monooleate, commercially available from ICC. Each of them was applied to a nonwoven material in an amount of 0.6 wt.% Of a substance that changes the viscoelastic properties (calculated on the active components), 0.5 wt. % "Triton 102", 1 wt.% Y12488 and 1.5 wt.% "Akhkovel". As shown, the results of measurements taken after 15 minutes indicate that substances that change the viscoelastic properties and are used according to the invention significantly increase the absorption distance.

 In order to demonstrate the effectiveness of other viscoelastic modifying agents, such as dextran (an oligosaccharide with a molecular weight of 4000, commercially available from Polydex Pharmaceuticals, Ltd., Scarborough, Toronto, Canada), a sample of nonwoven fabric such as BGW from the above-described two-component fibers Chisso Corporation’s production was oxidized in air plasma for 5 minutes using a Branson / IPC plasma processing machine model PM 119 at a power of 100 watts and a pressure of 80 Pa. The tissue that becomes wettable by plasma is then immediately immersed in an aqueous solution of the processing substance. Table 4 presents data on the concentration of processing substances.

Excess solution was removed from the saturated tissue by extraction under vacuum (by passing the saturated tissue over the gap to which the rarefaction was applied). After this extraction of the excess solution under the influence of tissue rarefaction due to wetting with the treatment solution, a weight gain of about 100% by weight was achieved. The treated tissues were dried at 80 ^° C for 8 hours or to constant weight and then tested for absorbency.

 The surfactants tested were treated as above, except that the oxidation step was omitted. Data on the concentrations of the solutions are presented in table 5.

 6 shows the results of a liquid absorption test B in connection with these substances, as well as with substance C ("HR6"). As shown, surfactants alone, such as sodium alginate and Triton X-102, cause reduced absorption. However, the use of substances according to the invention, changing viscoelastic properties, provides improved absorption over a wide range, which allows you to adapt this property to a specific application.

Table 6 shows that a selection of a specific substance that modifies the viscoelastic properties can be made to provide a predominant effect on either the viscosity or elasticity of the viscoelastic fluid. The tests were carried out with samples of liquid B after mixing 1 gram of the test solution (0.9% saline in the case of the control test) with 9 grams of the simulator by slow inversion for 15 minutes. As shown, Glucopon 220 has a dramatic effect on both viscosity and elasticity, while Dextran has a greater effect on elasticity than viscosity.
Material A was prepared by cutting out a sample of about 25 cm by about 30 cm from non-woven material. The sample was carefully washed for 5 minutes in tap water at a temperature of 27 ^° C and then for one minute in deionized water to remove essentially all of the dressing , applied by the seller to the fibers, and dried overnight in a thermostat with air circulation at a temperature of 35 ^° C. The sample was then dipped for about 5 seconds in a solution consisting of 200 g of Glucopon 220 UP (Henkel Corporation) in the delivery state, koto th has 60% activity in water, and 30 g hexanol (Catalog HI.330-3, Aldrich Chemical Company, Milwaukee, Wis., USA) in 6000 g deionized water at ambient temperature (20-25 ^o C). The solution contained 2.0% by weight of the active “Glucopon 220 UP.” The excess solution was removed from the wetted tissue by extraction under vacuum (i.e., by passing the wetted tissue over the gap to which the vacuum was applied). After that, the excess solution was removed under due to rarefaction, the sample, due to wetting with a solution, had a gain of about 100 wt.% based on the dry weight of the sample. The sample was then dried overnight in a thermostat at a temperature of 35 ^o C. Hexanol was completely removed during drying.

Material B was prepared in a plasma manner similar to that described in the jointly assigned patent application US SN 08/665172, filed June 14, 1996. The nonwoven material was washed and dried to remove the sizing as described for material A. Sample for 4 minutes, they were oxidized in air plasma using a Branson / IPC plasma treatment unit model PM119 at a power of 80 watts and a pressure of 80 Pa. Then, the sample was immersed for approximately 30 seconds in a solution consisting of 23.8 g of calcium chloride dihydrate (catalog 22.350-6, Aldic Cam Company, Milwaukee, Wisconsin, USA) and 6000 g of deionized water. The solution contained 0.3 wt.%. calcium chloride. From the wetted tissue, excess solution was removed by extraction under vacuum (i.e., by passing the wetted tissue over the gap to which the vacuum was applied). After this extraction of the excess solution under the action of rarefaction, the sample due to wetting with a solution of calcium chloride had a gain of about 150 wt.% (Calculated on the dry weight of the sample). A still wet sample was dipped for approximately 30 seconds into a solution consisting of 18.0 g or 0.3 wt.% High viscosity sodium alginate (catalog number A-7128, Sigma Camicile Company, St. Louis, Missouri, USA) in 6000 g of deionized water. Excess solution was removed from the wet sample by extraction under vacuum. The sample contained a total of about 300% solutions of both calcium chloride and sodium alginate, which led to the formation of a gel of sodium alginate on the fibers of the sample. The sample was then dried overnight in a thermostat at a temperature of 35 ^o C.

 Material D was prepared by washing the non-woven material to remove essentially all of the sizing applied by the seller, and dried as described for materials A and B.

Substances that modify viscoelastic properties, such as, for example, an alkylpolyglycoside treatment composition, may contain other additives that correspond to the desired result and do not have a large detrimental effect on the activity of a modifier, for example, an alkylpolyglycoside. Examples of such additives are additional conventional surfactants, such as, for example, ethoxylated hydrocarbons or ionic surfactants or additives to improve joint wetting such as low molecular weight alcohols. As mentioned, it is desirable to apply the composition at a high dry matter content, preferably at a solvent or water content of 80% or less, in order to minimize drying and the associated costs and harmful effects. The processing composition can be applied in various quantities, depending on the desired results and application. In cases where sanitary pads are used in the distribution layers, impressive results are achieved by adding dry matter in the range of about 0.1% to about 5.0% based on the dry weight of the fabric, with an interval of about 0.2% to 3.0% useful in terms of both cost and performance. In addition, as will be understood by specialists in this field, in accordance with the invention, many substrate materials can be processed, including non-woven materials, such as materials from spun fibers, from fibers formed from a melt with drawing by a stream of gas, from carded and other fibers, as well as woven materials and even films, etc., in cases where an improved liquid distribution is desired. Specialists in this field will also be clear that some substances that change the viscoelastic properties can be used in the form of internal additives, i.e., being added directly or in concentrated form to the polymer melt. After forming the fibers, such additives will migrate to the surface of the fibers and give the desired result. For further consideration of the internal administration of supplements, see co-assigned US Pat. No. 5,540,979 to Yahiaoui, Potts, Perkins, Powers, and Jescombe, issued July 30, 1996, the contents of which are incorporated herein by reference in their entirety. The surface density of the substrate is not critical and can vary widely depending on the application. In cases where sanitary pads are used in the distribution layers, nonwovens made from woven or bonded carded fibers are often used with a surface density of, in general, from about 7 g / m ² to about 175 g / m ² .

 Examples of an viscoelastic modifying alkyl polyglycoside substance are Glucopon 225 or 22G, both of which are alkyl polyglycosides with 8-10 carbon atoms in the alkyl chain and are commercially available from Henkel Corporation, as well as Crodesta SL-40 (sucrose cocoate) from Creda, TL 2141 (analogue of "Glucopon 220") from ICC.

 With reference to FIG. 1, a method for applying a treatment fluid to one or both sides of a moving web will be described. As will be appreciated by those skilled in the art, the invention is equally applicable both to processing on the production line itself and to a separate processing step outside the processing line. The blade 12, for example, non-woven material of spun fibers or fibers formed from a melt with drawing by a gas stream, is guided along the backup rolls 15, 16 to a treatment area containing rotating spray heads 22 for applying the processing fluid to one side 14 of the sheet 12. For applying the processing liquid on the opposite side 22 of the fabric 12 can also be used optional processing section (shown by a dashed line), which may contain rotating spray heads 18. For each section about the processing fluid 30 is supplied from a reservoir (not shown). Subsequently, the treated web, if necessary, can be dried by passing over a drying drum 25 or other drying means and then wound into a roll or otherwise converted for the application for which it is intended. Other drying products include hot air dryers, infrared dryers, fans, etc.

 FIG. 2 illustrates an exemplary personal care product in the form of a sanitary napkin containing a distribution layer according to the present invention. As shown, the sanitary napkin 30 comprises an impermeable liner 40, an absorbent 38, a distribution layer 36, and a casing or a layer 34 in contact with the body. To improve the protection against lateral leakage, the absorbent 38 can also be wrapped 32 at the bottom and sides. According to the invention, a viscoelastic property modifying agent can be treated with any of the liner, distribution or absorbent layers, or all layers.

 Thus, the invention provides an improved processing method and the resulting processed nonwoven materials and articles containing them, which have the above advantages. Although the invention is illustrated in specific embodiments, it is not limited to them and is intended to encompass all equivalents that are broadly within the scope of the claims.

Claims (24)

 1. The structure used as feminine hygiene products, configured to receive a fluid having viscoelastic properties, containing a synthetic substrate selected from nonwoven materials and films, including a substance having viscoelastic properties and placed with the possibility of contact with the specified viscoelastic fluid .  2. The structure of claim 1, wherein said synthetic substrate is made of a hydrophobic in nature nonwoven material.  3. The structure of claim 2, having a fast rate of menstrual fluid intake, and wherein said substance having viscoelastic properties is an alkyl polyglycoside having 8-10 carbon atoms in the alkyl chain.  4. A personal care product containing a structure according to claim 3.  5. A personal care product according to claim 4, characterized in that it is made in the form of a means for receiving menstrual fluid.  6. The personal care product according to claim 5, wherein the means for receiving menstrual fluid is in the form of a sanitary towel, wherein said structure comprises a distribution layer of the sanitary towel.  7. The structure of claim 3, wherein said non-woven material comprises a non-woven material of woven fibers.  8. The structure according to claim 2, in which the substrate containing a substance having viscoelastic properties includes an oligosaccharide.  9. The structure of claim 3, wherein said substance having viscoelastic properties is present in an amount of from about 0.1 to about 5.0% of the added dry matter based on the dry weight of the nonwoven material.  10. A personal care product containing a structure according to claim 9.  11. A personal care product according to claim 10, characterized in that it is made in the form of means for absorbing menstrual fluid.  12. The personal care product of claim 11, wherein the means for absorbing menstrual fluid is in the form of a sanitary towel, wherein said structure comprises a distribution layer of the sanitary towel.  13. A personal care product according to claim 4, characterized in that it is made in the form of a means for holding stool.  14. A personal hygiene product according to claim 10, characterized in that it is made in the form of a stool retention aid.  15. A personal care product according to claim 13, characterized in that it is made in the form of a disposable diaper, wherein said structure contains a diaper lining.  16. A personal care product according to claim 14, characterized in that it is made in the form of a disposable diaper, wherein said structure contains a diaper lining.  17. A personal care product according to claim 13, characterized in that it is made in the form of a product for use in urinary incontinence.  18. A personal care product according to claim 14, characterized in that it is made in the form of a product for use in urinary incontinence.  19. The structure of claim 2, wherein said nonwoven fabric comprises polypropylene spun fibers.  20. The structure of claim 3, wherein said nonwoven fabric comprises polypropylene spun fibers.  21. A sanitary napkin comprising a lining, a lining and an absorbent disposed between said lining and said lining, in which a distribution layer containing an effective amount of a substance having viscoelastic properties is disposed on a substrate selected from nonwoven materials and films between said lining and said absorbent in the position of ensuring contact with it menstrual fluid during use.  22. A method of absorbing a viscoelastic fluid containing a step of contacting said viscoelastic fluid with a substrate selected from nonwoven materials and films containing an effective amount of a substance having viscoelastic properties.  23. A processing agent containing a substance for changing the properties of viscosity and / or elasticity of a viscoelastic fluid.  24. The structure of claim 1, wherein said synthetic substrate comprises a film.

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