MXPA97001501A - Leaf material that has a fibrous surface and method to make my - Google Patents

Abstract

The present invention relates to a process for forming a sheet material having a fibrous surface and the sheet material produced with this, the fibers are produced by deposition of a thermosensitive material, heated, on a substrate, which is a speed conveyor. approximately equal to the speed of the material that is deposited, manipulating the density and denier of the fiber, a sheet material can be made that is, either softer or tougher to the tac

Description

LEAF MATERIAL WHICH HAS A FIBROUS SURFACE AND METHOD TO DO THE SAME FIELD OF THE INVENTION The present invention relates to a sheet material having a fibrous surface and to a method for producing the same.

BACKGROUND OF THE INVENTION Absorbent, disposable garments such as diapers and adult incontinence products typically have a three-ply construction. The first layer, is the layer closest to the body of the user, is a layer permeable to liquid. The second layer, located between the first and third layers, acts to absorb the liquids flowing through the first layer. Finally, the third or outer layer is impermeable to the liquid to prevent liquids from leaving the garment. Typically, the outer layer or backsheet is comprised of a thin, thermoplastic film, such as polyethylene. Although the back sheet develops the function of not allowing liquids to come out of the diaper, it lacks an aesthetic appearance of clothes. This appearance similar to clothing is of interest to older children and users of adult incontinence products. Adults who use these products do not want to be perceived as wearing a "plastic-looking" diaper. This rational exposition also applies to children as they grow up. These children also do not want to be perceived as a "baby" who wears a "diaper". To make matters worse, parents of children who wear diapers have consistently requested products that are aesthetically clean and attractive. Previously, when a clothing-like appearance was desired, it was known in the art of making a sheet material in a rolling process. The United States Patent NO. 4,828,556 to Braun et al., Discloses a breathable, multi-layered clothing-like barrier that was used as an outer covering for an absorbent, disposable garment. Braun taught a breathable, that is, one that is permeable to water vapor, the outer covering comprising a nonwoven web, blown in a molten, porous state; a secondary layer, which is a continuous film of polyvinyl alcohol; a third layer comprising a nonwoven, porous web. The third layer is formed by spun bond, melt bond or by laminating a spin link to a bond in the molten state, or vice versa. The third layer is a thermoplastic polymer and preferably a polyolefin, with polypropylene and polyethylene being more preferred. The present invention is directed to a sheet material having a fibrous surface and to a method for producing this sheet material. The sheet material is manufactured by depositing a thermosensitive material on a substrate and is used in situations in which a sensation and appearance similar to clothing for a particular garment is required or desired. This invention also provides a means for manufacturing a sheet material having a fibrous surface that can be used to form disposable, absorbent garments. Accordingly, a sheet for disposable diapers and adult incontinence products is provided which offers the user the appearance and feel of an incontinence product or dress diaper.

BRIEF DESCRIPTION OF THE INVENTION The sheet material of the present invention has a fibrous surface and includes a substrate having a plurality of essentially straight fibers bonded thereto and projecting outwardly from the substrate. Fiber, as referred to throughout the description of the invention and in the claims, is defined as that portion of the structure that begins at the point where the change in diameter / change in length is less than 0.3 and continues until the termination of the structure. The process of the present invention involves a printing roller process that produces a rule of flexible fibers that have a distinctly clothing-like feel.

The sheet material of the invention can be manufactured according to a process comprising the steps of heating a thermosensitive material sufficiently to reduce its viscosity to process it, and preferably at least to its melting point, depositing the thermosensitive material on it. the substrate in discrete quantities, directing the deposited material out from the substrate to form a fiber, and finish the fiber. A similar process has been used for the manufacture of mechanical fastening hooks, as described in the commonly assigned United States Patent NO. 4,058,274 to Thomas et al. The patent discloses a modified gravure printing process used to deposit discrete amounts of heat-sensitive material on a substrate to create the hooks. The hooks are printed on the substrate at a density of approximately 81 hooks per cm2. The thermosensitive materials employed in U.S. Patent No. 4,058,274, hot melt adhesives of polyamide and polyester, produce rigid sets of hooks that have a non-distinct feel to clothing.

BRIEF DESCRIPTION OF THE DRAWINGS Although the description concludes with claims that point out particularly and differently claim the b matter that is considered to form the present invention, it is believed that the invention will be better understood from the following descriptions, which are taken in combination with the accompanying drawings, in which like elements are designated by the same reference number and: Figure 1 is a microgram by electronic scanning showing a mat of unbonded, long fibers of this invention. Figure 2 is a microgram by electronic scanning showing a long, thermally bonded fiber mat of this invention; Figure 3 is a microgram by electronic scanning showing a unbonded, short fiber mat of the present invention; Figure 4 is a schematic profile view of a fiber produced according to the present invention; and Figure 5 is a side elevation view of an apparatus that can be used to produce a sheet similar to clothing of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The material sheet of the present invention comprises a substrate 18 having a plurality of flexible fibers 10, bonded to at least one surface of the substrate 18. Each fiber 10 of the sheet may be attached to a substrate 18. in a predetermined pattern. Each of the fibers has a base 12 and a rod 14 as illustrated in Figure 4. The bases 12 of the fibers 10 contact and are bonded to the substrate 18, and support the rods of fibers 14 projecting outwardly. from the substrate 18 and bases 12. The rods 14 end at the far end 16 of the fiber 10. A fiber ruler 10 can be provided on the surface of a paper or film by any suitable method and apparatus, including methods that produce a free form fiber 10 as described and claimed herein below. As used herein, the term "free-form" means a structure that is not removed from a mold cavity or extrusion die in solid form or with a defined shape. The fibers 10 are deposited on a substrate in a molten state, preferably in a liquid state, and solidified by cooling, preferably by freezing to rigid, in the desired structure and shape as described hereinafter. The free form fiber 10 or the fiber assembly 10 can be produced by manufacturing processes that are similar to those processes commonly known as printing gravure printing, template-screen. Using the template-screen printing process, a generally healthy substrate 18 having opposite faces is passed between the jaw 50 of two generally cylindrical rollers., a printing roller 52 and a backing roller 54 as shown in Figure 5. The rollers 52 and 54 have "" '"generally parallel centerlines and are maintained in contact relation with the substrate 18 as it passes through. through the jaw 50. The first roller 52, referred to as the printing roller, has a screen 56 having the desired pattern for the fibers that are deposited on the substrate The second roller 54, referred to as the backing roller, provides support and reacts against the printing roller 52 to place the substrate 18 against the printing roller 52 as the substrate 18 passes through the jaw 50. The heat-sensitive materials, preferably thermoplastic material, from which the fibers 10 are formed, it is supplied from a heated source, such as a tundish (not shown). The thermosensitive material is heated, preferably to at least its melting point, and is It operates in the sieve 56 as the printing roller 52 is rotated about its center line. A blade 62 forces the thermosensitive material through the screen 56 onto the substrate 18 in the desired pattern. As the relative movement between the substrate 18 and the rollers 52 and 54 continues, the fibers 10 are stretched or directed in a direction having a vertical component, imparting a length to the fiber 10. When the fiber 10 reaches a desired length, the fiber 10 can be separated by a separating means 58, or the fiber 10 can be stretched until it breaks without the use of a dedicated separation means. Then the fiber 10 is cooled, and preferably frozen, in a solid structure. Upon the solidification of the fiber material, if desired, the fibers can then be formed into a non-woven matrix. For example, the fibers can be bonded together to the substrate using pressure rollers or other methods commonly used in the industry to form non-woven matrices. As used herein, the term "non-woven" means that the fibers 10 are not woven systematically. The fibers 10 are instead formed in a random network. The substrate 18 of the sheet material must be sufficiently formed to preclude tearing or separation between the individual fibers 10 to provide a surface to which the fibers will readily adhere, and preferably to be capable of being bonded to or formed into an article of wear. The substrate 18 must also be capable of being rolled to withstand conventional manufacturing processes, be flexible in such a way that it can be bent and flexed in a desired configuration, and be able to withstand the heat of the thermoplastic material deposited thereon without melt or incur deteriorating effects until the fibers solidify. Substrate 18 should also be available in a variety of widths. Suitable substrates 18 include fired fabrics, woven materials, nonwovens, rubber, vinyl, particularly polyolefilic films, and paper. Preferably, the polyolefin film is a polyethylene film having a thickness of 0.5 to 1.05 mils. A suitable polyethylene film is manufactured by Tredegar Film Products and marketed commercially as P8570. In addition, any of the backup movies Xt) previously used to make disposable absorbent garments would be suitable for use as a substrate, including porous film sheets. A suitable porous polyethylene film is manufactured by Tredegar Film Products and sold commercially as P5652. The base 12 of the fiber 10 is the generally flat portion of the fiber 10 which is attached to the substrate 18 and abuts the proximal end of the stem 14 of the fiber 10. As used herein the term "base" is refers to that potion of fiber 10 that is in direct contact with a substrate 18 and supports the shank 14 of the fiber 10. It is not necessary that a demarcation be apparent between the base 12 and the stem 14 of the fiber 10. It is only important that the shank 14 not be separated from the base 12 and that the base 12 does not separate from the substrate 18 during use. The shape of the footprint of the base 12 on the substrate 18 is not critical and can be increased in any direction to provide greater structural integrity. As used herein the term "footprint" refers to the flat contact area of the base on the substrate 18. The aspect of relationship (length to width ratio) of the sides of the footprint should not be too large, otherwise The fiber 10 can be unstable when it is subjected to forces parallel to the shorter side of the tread. An aspect ratio of less than about 1.5: 1 is preferred, and a generally circular footprint is more preferred. For the embodiment described herein, a base having a generally circular footprint and approximately 0.02 mm to 0.32 mm in diameter, is suitable. The fibers 10 of the present invention vary in length from about 0.15 to about 65 mm in length. Preferably, their lengths will be from about 0.15 to about 0.5 mm. The set of fibers 10 can be provided in any configuration, spacing and density as desired. The configuration, separation and density of the fibers 10 are determined primarily by the screen mesh 56 of the printing roller 52. The printing roller screen 56 has a mesh ranging from about 50 to 200, and in the preferred embodiment, from about 100 to 200. Also, as the diameters of the base 12 of the fiber 10 decrease or the length of the fibers 10 increase, the sheet similar to clothes becomes softer to the touch. It is advantageous to arrange a set of fibers 10 in rows, such that each fiber 10 is generally equally spaced apart from the adjacent fiber. The rows are generally oriented in the direction of the machine and in the transverse direction of the machine according to the manufacturing process described and claimed herein. Generally, each row of fibers 10 with machine direction and transverse direction of the machine will be equally spaced from adjacent rows of fibers with machine direction and machine transverse direction, to provide a generally uniform feel to the touch. Of course, those skilled in the art will recognize that a variety of deposition patterns can be used. The separation of the fiber can vary from about 2 fibers per millimeter to about 8 fibers per millimeter and, in the preferred embodiment, about 6.1 fibers per millimeter. The density of the fibers, number of fibers per unit area on the sheet material is determined primarily by the size of the screen mesh 56 of the printing roller 52. As the mesh size of the screen 56 increases, the density of the fibers on the sheet material increases correspondingly. Generally, as the mesh increases, the clothing-like sheet becomes softer to the touch due to the corresponding increase in fiber density. However, a person skilled in the art will recognize that if the fibers 10 are too continuously separated, consolidation and entanglement of the fibers will occur. 10. Conversely, if the fibers are separated too far apart, the sheet will adopt a non-clothing-like feel. The fibers of this invention will have a density of about 4 to about 62 fibers / mm2 and preferably about 16 to about 49 fibers / mm2. Most preferably, it will be about 37 fibers / mm2. Because of the similar nature to clothing of this sheet, the fibers 10 can be measured in terms of Denier. The Denier for purposes of this invention is defined as the weight in grams per 9,000 meters of fiber. The fibers of this invention have a Denier ranging from 0.20 to 6.0 and, in the preferred embodiment from 0.5 to 1.5. The Denier of a fiber, results from the method of this invention, is calculated by measuring the diameter of the individual fiber, calculating the volume of a cylinder and multiplying the volume by the density of the material, in grams / cm3, used to make the fibers . The fibers of the present invention can be defined in terms of the shear strength. These will have a shear strength of less than 50 gr / m2, and preferably a shear strength of 0. A low resistance to shear stress is desirable because the user will not enjoy using an article that would interconnect with the clothing of the shear. user or body hair. In addition, if the article were to have a high shear strength, the fibers would be more rigid and would not have a clothing-like feel. As used herein, the term "shear strength" refers to the force required to initiate a slip of the fibers relative to the hook portion of a hook and loop fastener. To test the shear strength of these fibers, a sheet containing the fibers made by the method of this invention was placed on a sheet containing a hook portion of a hook and loop fastener. The two sheets were then pulled in opposite parallel directions and the force required to initiate a movement between the two sheets was then measured as the shear strength. The shear strength can be measured according to the description of the commonly assigned U.S. Patent No. 4,699,622, issued October 13, 1987 to Toussant et al. The description of this patent is hereby incorporated by reference for the purpose of showing how to measure the shear strength of the present invention. The fibers 10 of this invention can also be characterized in terms of the resistance to separation. The fibers 10 of this invention have a negligible separation resistance and, preferably, a separation strength of approximately 0 g / square inch. As used herein, "strength" in the separation refers to the force required to move a fiber sheet away from a sheet, which contains the curl portion of a curl hook fastener, in a direction perpendicular to the surface of the sheet that contains the curls. Accordingly, the extremely low, almost non-existent, separation resistance of the fibers 10 indicates the extent to which the fibers 10 would not link with the wearer's clothing or body hair. The resistance in the separation can be measured according to the test method ASTM D903-49 entitled "Resistance to Separation of Adhesive Bond Removal". This test method is hereby incorporated by reference with a method for determining the separation resistance of the present invention. As contrasted with the fibers of the present invention, U.S. Patent No. 5,180,534 to Thomas et al. Discloses a fastening system employing a hook-like member composed of a thermoplastic material. Patent 5,184,534 describes a method in which the clamping system must withstand a separation force of at least 200 gr., and must withstand a shearing stress of at least 500 gr. The hook described in said patent would create a garment that would adhere to the wearer's clothing and body hair, in this way, creating a reasonably uncomfortable garment. The thermosensitive material must have a sufficiently low melting point to provide a relatively high viscosity and easy to process to provide a peel and temperature resistant consistency close to the melting point of the material, such that the fibers 10 can be stret and formed according to the manufacturing method cited herein. As used herein, "heat sensitive" refers to the property of a material that gradually changes from the solid state to the liquid state upon the application of heat. Typically, the melting points vary from 85 degrees Celsius to 150 degrees Celsius. It is also important that the fibers 10 be visco-elastic, to allow greater variation in the parameters that affect the structure of the fibers. As used herein, the phrase "visco-elastic" describes the mechanical behavior of a material that exhibits a delayed and viscous elastic response to also resist instantaneous elasticity. Convenient is the material having a complex viscosity ranging from about 50 to about 130 pascals-seconds at a substrate application temperature. The fibers 10 are preferably comprised of a thermoplastic material. The term "thermoplastic" refers to uncrosslinked polymers of a thermosensitive material that flows under the application of heat or pressure. The hot-melt adhesive thermoplastics are well suited for the manufacture of the clothing-like fibers of the present invention, particularly in accordance with the process described and claimed below. As used herein, the phrase "hot melt adhesive" refers to a viscoelastic thermoplastic material that maintains the residual strength upon solidification of the liquid state. Hot melt adhesives are particularly suitable and preferred, including adhesives based on ethylene vinyl acetate and polyethylene. An adhesive having a complex viscosity of about 90 plus minus 40 pascals-seconds at about 100 degrees centigrade has been found to work well. Some commercially available examples of useful hot melt adhesives include PRIMACOR® and EASTOBOND® A3 available from Dow ical and Eastman ical, respectively.

MANUFACTURING PROCESS The clothing-like sheet described above, can be manufactured according to the process comprising the steps of depositing discrete quantities of thermosensitive material, heated, on a substrate that is transported in relation to the means selected to deposit the thermosensitive material, heated. More particularly the process comprises the steps of providing a thermosensitive material, as described above, and heating it to at least the melting point in such a manner that the heated thermosensitive material is in a fluid, fluidic state. Substrate 18 is provided and transported relative to the means for depositing 52 of this heated material. A means is also provided for depositing 52 discrete quantities of the thermosensitive, heated material. Discrete amounts of the heated, thermosensitive material are deposited on the substrate 18 from the reservoir means 52. It will be apparent to one skilled in the art that the reservoir means 52 for depositing discrete quantities of heat-sensitive material can be transported and the substrate 18 maintained. fixed or, preferably, the substrate 18 transported and the deposit means held fixed, to provide relative movement between the substrate 18 and the deposit means 52. The phrase "storage means" refers to any apparatus that transfers thermosensitive material in liquid form from a quantity of volume towards the substrate in discrete quantities corresponding to the individual fibers. The term "deposit" means melting the thermosensitive material from a volume form and dosing said material on the substrate in units corresponding to the individual fibers. Two directions are defined during the transport of the substrate 18 and the deposition of the discrete quantities of the thermosensitive material forming the fiber 10. The first direction is the transport direction of the substrate 18 in relation to the means for depositing 52 of the thermosensitive material. The second direction is the direction of deposition of said material on the transported substrate 18 at the time of deposition. During the process for the deposition of the thermosensitive material, heated, on the substrate 18, a differential speed can be incurred between the transported substrate 18 and the thermosensitive material that is deposited. Said differential velocity is considered "positive", if the velocity of the substrate 18 in the first direction is greater than the velocity of the deposit means at the deposition point of said material on the substrate. Conversely, a differential speed is considered "negative", if the speed of the transported substrate is less than the speed of the deposit means. It will be apparent to a person skilled in the art that if the means for depositing the thermosensitive, heated material are kept fixed and the substrate is transported, a positive differential velocity results. The viscoelastic biological properties of a thermosensitive material can provide lateral stretching of the material when there is a differential velocity. This lateral stretching will result in a fiber 10 having a degree of curl that is dependent on the differential speed. When there is no differential velocity, the thermosensitive materials will experience only a horizontal stretch and not a lateral stretch. In this way, a straight fiber 10 would result. The present invention preferably does not employ differential speeds between the transported substrate 18 and the thermosensitive material that is deposited, such that it results in a substantially straight fiber. As used herein, the phrase "essentially straight" means that the fiber does not include the hook portion of the restrainable mechanical fastening system as taught in commonly assigned United States Patent No. 5,180,534 to Thomas et al. This definition, however, it does not preclude the fibers from having a degree of curvature as found in other synthetic fibers. The fiber may be curved, for example, and not by way of limitation, to such a range that the internal angles between any two points in the fiber and a straight line, which divides the fiber into two points, is less than 70 degrees to preferably less than 50 degrees. In operation, the substrate is transported in a first direction relative to the reservoir means 52. More particularly, the substrate 18 is conveyed through the jaw 50, and preferably guided by an intake roller (not shown). This provides a clean substrate area 18 for the continuous deposition of fibers 10, and the removal of portions of the substrate 18 having fibers 10 deposited thereon. The direction generally parallel to the conveying direction of the substrate 18 as it passes through the jaw 50, is referred to as the "machine direction". The machine direction is generally orthogonal to the center lines of the printing roller 52 and the backing roller 54. The direction generally orthogonal to the machine direction and parallel to the plane of the substrate, is referred to as the "transverse direction of the machine". " The "jaw plane" is the plane that has a line coincident with the jaw 50 and straight to both the print roller 52, and the backing roller 54. With reference to Figure 5, the sheet similar to clothing according to FIG. The present invention can be manufactured using a printing roller printing process. The substrate 18 can be passed through the jaw 50 formed between two juxtaposed rollers, a printing roller 52 and a backing roller 54. The rolls have substantially parallel, mutual central lines, generally arranged parallel to the plane of the substrate 18. Each one of the rollers 52 and 54, is rotated about its respective centerline such that the rollers have substantially the same surface direction, in the jaw 50. Typically, the impression roller 52 will have a diameter of about 195 to 220 mm during laboratory practice, but can vary up to 350 mm in an industrial setting. Usually, the printing roller 52 will be rotated at about 6 to 100 rpm to provide a tangential surface velocity of about 1798 to 30.175 mm / sec. If desired, both the printing roller 52 and the backing roller 54 can be driven by an external matrix force (not shown), or a roller can be driven by an external matrix force and the second roller driven by frictional engagement with the first roller. It has been found that an AC electric motor that has an output of approximately 1,500 watts provides the proper matrix force. By rotating, the rollers 52 and 54 act as a reservoir means for depositing the thermosensitive material, heated on the substrate 18 to form the fibers. The reservoir means must be able to adjust the temperature of the thermosensitive material in the liquid state, provide substantially uniform separation in both machine and transverse directions of the machine and produce the desired density of fibers within the assembly. Also, the reservoir means is preferably adjustable to produce fibers having various diameters of the base and height of the rod. The printing roller 52, specifically, maintains the reservoir means for depositing the fibers in the substrate 18 in the desired assembly, as discussed above, (or other configuration) according to the present manufacturing process. A suitable reservoir means for depositing fiber material on the substrate 18 is the printing roller 56 of the printing roller 52. For the embodiment described herein, the printing roller 52 having a mesh that produces approximately 2 to approximately 8 fibers per linear millimeter is useful. A printing roller 52 having a mesh that produces from about 4 fibers to about 7 fibers per millimeter is preferred., and a printing roller having mesh that produces about 6 fibers per millimeter is more preferred. The printing roller 52 and the backing roller 54 should be compressed, coincident with the plane connecting the center lines of the rollers 52 and 54, to start the adhesive of the cells 56 on a roller on the substrate 18 and, provide enough frictional coupling to drive the opposite roller if it is not driven externally. Generally, a pressure of about 5.0 to 60.0 psi is useful. The backing roll 54 may be a little softer and non-deformable than the print roller 52, to provide cushioning of the fiber material as it is deposited on the substrate 18 from the print roller 52. A roller is suitable. backing 54 having a rubber coating with a hardness of Shora A durometer of about 40 to 60. The temperature of the printing roller 52 is not critical, however the printing roller 52 must be heated to prevent the solidification of the fibers. during the transfer and deposition on the substrate 18. Generally, a surface temperature of the printing roll 52 close to the temperature of the source material is desired. It has been found that a temperature of the printing roller 52 of approximately 100 degrees centigrade works well. It should be recognized that a cooling roll may be necessary if the substrate 18 is adversely affected by the heat transferred from the fiber material. If a cooling roller is desired, it can be incorporated into the backup roller 54 using means well known to one skilled in the art. This arrangement is often necessary if a substrate of polypropylene, polyethylene or other polyolefin substrate is used. The thermosensitive material used to form the individual fibers 10 must be maintained in a supply tank that maintains the appropriate temperature to apply the fibers to the substrate. Typically, a temperature slightly above the melting point of the material is desired. The material is considered to be at or above the "melting point" if the material is partially or completely in a liquid state. If the temperature of the thermosensitive material is too hot, the thermosensitive material will flow in a sediment in a somewhat hemispherical, small form, and will not be stretched to a fiber. Conversely, if the source temperature is too low, the thermosensitive material will not transfer from the supply to the means for depositing the material, or, subsequently will not transfer properly from the deposit means 52 to the substrate in the set or configuration. desired. In addition, this can cause obstruction and obstruction of the deposit means. The source of the material should also impart a temperature profile in the transverse direction of the machine, generally uniform, to the material, which is in communication with the means - to deposit the adhesive material on the substrate 18, and easily be like the fiber material The supply is heated externally by known means (not shown) to maintain the fiber material in a liquid state, and at the appropriate temperature. The preferred temperature is above the melting point but below that at which a significant loss of the discoelastic capacity occurs. As illustrated in Figure 5, the printing roller 52 of the present invention includes a heated pressure bar and a printing screen 56. The heat-sensitive material is fed from a storage trough (not shown) to the inlet port 65. of the heated pressure bar 60. The pressure bar 60 is heated to keep the thermosensitive material at its melting point. The heated thermosensitive material is fed from the pressure bar 60 onto the inner surface of the printing roller 52. The heat-sensitive material is fed through a slot (not shown) in the lower part of the pressure bar 60 to create uniform distribution of the material through the printing roller 52. A knife 62 is juxtaposed with the inner surface of the printing roller 52, which controls the amount of thermosensitive material applied to the printing roller 54. The blade 62 and the heated pressure bar 60 are held fixed as the print roller 52 is rotated, allowing the knife 62 to clean the inner circumference of the roller 52 for forcing the fiber through the printing roller 52 onto the substrate 18. This arrangement allows the fiber material to be deposited from the printing roller 52 towards the substrate 18 in the desired assembly, in accordance with the geometry of the sieve 56 on the circumference of the printing roller 52. As seen in Figure 5, the blade 62 is preferably arranged perpendicular to the inner surface of the printing roller 52. After the fiber material deposited from the sieve 56 on the substrate 18, the rollers 52 and 54 continue to rotate, in the directions indicated by the arrows in Figure 5. This results in a period of Relative behavior between the transported substrate 18 and the sieve 56 during which period (before separation), the fiber material connects the substrate 18 and the printing roller 52. As the relative displacement continues, the fiber material is stretched until the separation occurs, and the fiber 10 is separated from the screen 56 of the printing roller 52. As used herein, the term "stretch" means the increase in the linear dimensions, at least a part of which increase arrives to be permanent in a substantial way for the life of the sheet material. The length of the resulting fibers 10 will vary with the application of the sheet material, and the nature of the thermosensitive material. After it has been deposited on the substrate 18, the fibers 10 can be separated from the printing roller 52. If desired, the separation can be achieved as a separate, intended step, in the process using a separating means to separate the tips towards the means of linking the sheet similar to clothing. However, depending on the adjustment of various parameters, such as the angle between the substrate, and the reservoir means, the differential speed, the velocity of the thermosensitive, heated material, the cell, etc., a separate separation stage and intended not to it may be necessary Separation can occur naturally as a function of the substrate that is transported away from the point of deposition. If used, the separation means 58 must be adjustable to suit the various fiber sizes 10 and also provide uniformity throughout the transverse direction of the assembly machine. The term "separation means" refers to any component apparatus that longitudinally separates the fiber 10. The separation means 58 should also be clean and non-dusty, oxidized or impart corrosion and contaminating materials to the fiber. A suitable separation means 58 is a wire arranged generally parallel to the center line of the rollers 52 and 54, and spaced from the substrate 18 at a distance that is a little greater than the perpendicular distance of the highest elevation of the solidified fiber at substrate 18. Preferably, the wire 58 is electrically heated to prevent the formation of the molten fiber material on the separation means 58, and to accommodate any cooling of the fibers that occur between the time that the fiber material leaves the fiber. heated fountain. The heating of the separation medium 58 must also maintain a uniform temperature distribution in the transverse direction of the machine, so as to produce a set of fibers 10 having a substantially uniform geometry. Generally, as the temperature of the fiber material increases, a relatively cooler hot wire temperature separation means 58 can be adapted. Also, as the speed of the substrate 18 is decreased, it happens that cooling of the hot wire 58 is less frequent as each fiber is separated., making a hot wire of power in watts relatively lower more feasible at the same temperatures. It should be recognized that as the temperature of the hot wire increases, a fiber 10 having a generally shorter stem length results. Conversely, the length of the rod will be increased in inverse proportion as the temperature of the hot wire 58 decreases. It is not necessary that the separation means 58 make contact with the fiber 10 so that the separation occurs. The fiber 10 can be separated by radiant heat emitted from separation means 58. For the embodiment described herein, a nickel chrome wire of round cross section, having a diameter of about 0.51 mm heated to a temperature of about 343 degrees centigrade to about 416 degrees centigrade. It will be apparent that a blade, laser cutter or other separation means 58 can be replaced by the hot wire 58 described above. It is important that the separation means 58 be disposed in a position that allows the stretching of the fiber material that occurs before the fiber 10 is separated. In the separation means 58 are disposed too far from the plane of the substrate 18, the fiber material will pass below the separation means and will not be intercepted by it, forming a very long fiber 10 which will not be properly separated from the substrate or from the substrate. the adjacent fibers. Conversely, if the separation means 58 are arranged too close to the plane of the substrate 18, the separation means will truncate the rod 14 to form an abrasive or abrasive. A hot wire separation means 58 disposed about 12.6 mm to 38.0 mm, preferably about 9.5 mm in the machine direction from the jaw point, about 5.0 mm to 9.5 mm. radially outwardly from the backing roll 54 and about 2.0 mm to about 7.0 mm radially outwardly of the print roller 52, is suitably positioned for the manufacturing process described herein. It may also be necessary to separate the individual fibers from the printing roller 52, as part of the process that forms the clothing-like sheet. When separated, a fiber 10 is divided longitudinally into two parts, a base 12 and a distal end 16 that remain with the clothing-like sheet and a jig (not shown) that remains with the printing roller 52 and that can be recycled as desired. After the fibers 10 are separated from the bar, the fibers 10 are allowed to solidify before contacting the fibers with other objects. After the fibers 10 have solidified, the substrate can be wound onto a roll for storage as desired. The substrate 18 can be transported through the jaw 50 in the machine direction at about 3 to about 31 meters per minute. The substrate 18 is preferably stretched through the jaw at a speed equal to the tangential speed of the printing roller 52, producing little or no differential speed. However, with the present invention, a differential velocity of plus minus 2% will acceptably produce the fibers of this invention. As the differential velocity decreases, the fiber 10 obtains an orthogonal position relative to the substrate 18. For this reason, the substrate 18 and the printing roller 52 preferably do not have differential velocities they have no movement and differential speed at a ratio of 1: 1 One skilled in the art should consider the radius of curvature and a printing roller 52 and its relation to the differential speed and the angle between the substrate 18 and the plane of the jaw 50. As the radius of the curvature of the printing roller 52, jimmy and rod 14 of fiber 10 which is formed, they are stretched away from the substrate 18 at an angle which, the proximity of the jaw 50 is more orthogonal to the plane of the jaw. Upon solidification, said fiber 10 will typically be relatively more straight than a fiber 10 manufactured under conditions that are similar, except for the use of a greater radius of curvature of the printing roller 52. In this way, to provide an improved sheet According to the present invention, it is important to provide the apparatus used to manufacture the sheet a means for imparting a vector orientation that is close to orthogonal (no more than about 10 degrees off the axis in any direction), the plane of the substrate 18 in the base 12 of fiber 10 for discrete quantities of the thermosensitive material, deposited. Once the thermosensitive material is deposited on the substrate 18 and separated, the sheet can then be subjected to a bonding process to form a non-woven matrix as described above. This process includes thermally discrete, pressure, ultrasonic, or other well-known fiber link techniques. The sheet of material, if bonded or unraveled can then be used to form a topsheet, a core wrap, a backsheet or cuff for a disposable absorbent article. Although it is preferred that the bonding fibers be connected in either direction, the fibers 10 may be interconnected laterally in the machine direction. To achieve this interconnection, the source of the thermosensitive material is heated to a temperature that exceeds the melting point of the material, and that causes a reduction in the viscosity of the material. The material becomes "soft" and, as applied, the distal end 16 of a fiber will become laterally connected in the machine direction to the fiber 10 in the next row. Although this description discloses a substrate 18 having a thermosensitive material coated on one side, those skilled in the art will recognize that the same process can be used to provide the substrate 18 that is coated or coated on both sides with a heat-sensitive material. Various modifications of the apparatus and method described are feasible and within the scope of the claimed invention. If desired, by providing a relatively rigid substrate A and sufficient tension, the backing roller 54 of the apparatus of Figure 5 can be omitted. On the other hand, as is well known to one skilled in the art, the substrate 18 can wrap roller printing through the use of drag rollers that produce an S-shaped arc around the print roller. In this configuration, the jaw 50 does not exist as described in figure 5, but, instead, the tension of the substrate is responsible for the deposition of the thermosensitive material, heated, from the cells of the printing roller 52. However, one must recognize that if this variant configuration is selected for the apparatus and means for depositing the heated thermosensitive material on the substrate 18, the substrate 18 must have sufficient tensile strength to prevent tearing and maintain the tension necessary for proper deposition of the thermosensitive material, heated.

EXAMPLES Below are illustrative, non-limiting examples of the various fibers produced by the method of this invention.

EXAMPLE 1 Referring to Figure 3, the fibrous sheet produced by the method of this invention has a separation of 6.1 fibers / mm, resulting in a fiber density of 37.2 fibers / mm2. Each fiber has a base of approximately 0.04 mm and a fiber denier that varies from 0.2 to 0.3. The fibers produced vary in length from approximately 0.15 to 0.40 mm. The material used was a film cast as the substrate, and a low density polyethylene type resin for the fibers. Such material would be useful for applications in absorbent articles where a barrier against fluid is desired, such as the backsheet or cuffs of a disposable absorbent garment.

EXAMPLE 2 A fibrous sheet produced by the method of this invention has a separation of 6.1 fibers / mm, also resulting in a fiber density of 37.2 fibers / mm2. Each fiber has a base of approximately 0.04 mm and a fiber denier that varies from 0.2 to 0.3. The fibers produced vary in length from approximately 0.15 to 0.40 mm. The substrate being a perforated film sheet and the fibers made using any suitable thermoplastic olefin resin, such as low density polyethylene. Such material would be used in absorbent articles where fluid permeability is desired, such as a top sheet or a fabric. It will be apparent to a person skilled in the art that various other modifications and combinations of the parameters described above can be used. For example, multiple parameters can be adjusted, including different temperatures of the hot wire, different positions of the hot wire, other differential speeds, and different means for depositing the heated thermosensitive material on the transported substrate, are feasible. All of said combinations and permutations are within the scope of the following claims.

Claims (10)

1. CLAIMS 1. A method for manufacturing a sheet material having at least one surface that exhibits an appearance in texture similar to fibrous clothing, said method comprising the steps of: heating a thermosensitive polymeric material to at least the melting point of said thermosensitive polymeric material, such that said thermosensitive polymeric material is flowable and can be deposited on a substrate; depositing discrete quantities of said thermosensitive, flowable polymeric material on a surface of said substrate in a set; stretching said discrete deposits of said thermosensitive polymeric material from said surface of said substrate to form a set of essentially straight fibers, said assembly preferably having a density of 4 to 62 fibers / mm 2; and finish said fibers.
2. 2. The method for manufacturing a sheet material, according to claim 1, characterized in that it further comprises the steps of: providing a printing roller, said printing roller juxtaposed with a surface of said substrate and adapted to rotate around its central line, said central line being generally parallel to the plane of said substrate and generally perpendicular to a transport direction of the substrate; providing a backup roll juxtaposed with the other surface of said substrate and having a central line generally parallel to said center line of said printing roller; applying said thermosensitive polymeric material to the screen of said printing roller; rotating said printing roller and said backup roller at a peripheral differential speed of ± 2%; wherein said substrate is transported through said jaw; and depositing said discrete quantities of said thermosensitive, heated polymeric material through said screen on said substrate.
3. 3. The method for manufacturing a sheet material, according to claim 1 or 2, further characterized in that said substrate has a melting point higher than the melting point of said thermosensitive polymeric material.
4. 4. A sheet material having at least one fibrous surface that exhibits the appearance and texture similar to a fibrous clothing comprising: a substrate; and a set of free-form fibers, essentially straight, extending from at least one surface of said substrate, said set of fibers preferably having a density of 4 to 62 fibers / mm 2. The method for manufacturing a sheet material, according to claim 1 or 2, or the sheet material of claim 4, further characterized in that said set of essentially straight fibers has a density of 16 fibers / mm2 to 49 fibers / mm2. The method for manufacturing a sheet material, according to claim 1 or 2, or the sheet material of claim 4, further characterized in that said thermosensitive material is a hot melt adhesive of ethylene vinyl acetate or an adhesive hot melt polyethylene, which has a melting point of 85 ° C to 150 ° C. The method for manufacturing a sheet material, according to claim 1 or 2, or the sheet material of claim 4, further characterized in that said fibers are stretched to a length of 0.15 to 65 mm. The method for manufacturing a sheet material, according to claim 1 or 2, or the sheet material of claim 4, further characterized in that said fibers have a denier of 0.20 to 6.0. The method for manufacturing a sheet material, according to claim 1 or 2, or the sheet material of claim 4, further characterized in that said sheet material exhibits negligible separation resistance and shear strength less than 50 gr / m2. The method for manufacturing a sheet material, according to claim 9, further characterized in that said sheet material exhibits a separation resistance of 0 gr / 6.5mm2.