MXPA97003817A - Method to produce elastic film strips, and an absorbent product that incorporates these it - Google Patents

Abstract

The present invention relates to a method for producing a plurality of strips from a single canvas (1) of elastic film, wherein the single canvas (1) is fed in a direction of longitudinal advance (X) to an area of cut (b), wherein the canvas is cut longitudinally into a plurality of strips (2-6) the plurality of strips is then further fed in the direction of advance while simultaneously lengthening in the longitudinal direction to thereby reduce its width (e) and thickness. The invention also relates to an absorbent product that makes use of a plurality of strips that are thin and rectangular flat in one or more elasticized areas of the product, in order to provide good and uniform breathing capacity along the elastified area (s).

Description

"METHOD TO PRODUCE ELASTIC FILM STRIPS, AND AN ABSORBENT PRODUCT THAT INCORPORATES THESE STRIPS" FIELD OF THE INVENTION The present invention relates to a method for producing a plurality of elastic film strips from a single elastic film canvas and with an absorbent article for absorbing human exudate, wherein the strips are fixed in an area to be elastified. .

PREVIOUS TECHNIQUE In some absorbent articles of the prior art, e.g., US Patent Number A-3 860 003, a strip of rubber material is applied in an area of the article to be elastified so as to provide a better fit for the user and that provides increased comfort as well as to help prevent leakage. These elasticized zones, however, give rise to many problems such as the pressure in the leg of the user because the strip that is kept as narrow as possible to save material, is still wide enough to provide a tension enough in order to provide a good fit in all movement positions. An additional problem arises because the strip itself is made of rubber and therefore does not provide a "breathable" material, that is, a material constructed to allow the moisture of human skin to escape. Since the strip is relatively wide, this can frequently result in certain areas of the body that are still frequently wet which can result in injuries, loss of skin resistance, abrasion and infection. In order to solve this problem of moisture release, it is known in the art, however, to use films of elastic material which are capable of "breathing". These films, however, are more expensive and often only have limited respirability at best. Even when relatively thin strips are available (v. Gr, up to about 6 mm wide), they result in handling problems when it comes to using these small strips which makes them impractical for this object. In addition, when supplied, each individual roll of thin strip must be packaged separately which results in waste as well as increased expense.

As a solution to the pressure zones of the user's thighs and to improve the release of moisture, US Patent Number A-4 687 477 proposes a solution that replaces the individual wide strips in the elasticized leg areas of the user. an absorbent garment, by means of series of between three and forty five rubber filaments placed side by side along the areas to be elasticized. Even though these rubber strips allow good breathability due to the spaces between them, rubber, however, has the disadvantage of being a rather heavy material. In addition, rubber is a molded product and therefore a certain thickness must be maintained in order to have a level of uniformity in the rubber filament that provides adequate strength against breakage. This thickness in turn increases the weight even more. However, more importantly, since the rubber strips must subsequently be divided into separate filaments and moved laterally apart from one another for the application of the product, the molded parts are formed as individual molded rubber filaments which are held together so that it is intrinsically separable. This intrinsic separability is effected by a weak rubber fusion between the adjacent filaments, for example, by spraying talcum powder into the individual filaments and then allowing a slight contact between them. This requirement for separability however is very problematic, since the weakness of the bond between the filaments is difficult to control exactly. If the resistance is too low (ie, a very weak bond) this may result in premature separation of the joint between the filaments and, if too strong, one of the filaments may break during the proposed separation from the adjacent filament. In any case, the resulting loose filaments become difficult to treat and, when this happens, during the operation in the machine, the resulting arrest is very costly, especially in the field of manufacturing an absorbent article wherein the production speed is very high (e.g., a belt speed of about 200 meters per minute.) The present invention therefore seeks to provide a means for elastification that provides good breathability in the area of elasticization, which is thin and light and can be handled without the risk of premature separation of the filaments.Thus, when the strips are applied to an absorbent article, the article can be produced more lightly and more economically than hitherto.

COMPENDIUM OF THE INVENTION The aforementioned problems are solved by the features of the invention as defined in the method of claim 1 and in the product of claim 7. Preferred features of the invention are defined in the dependent claims. Adopting the method of the invention, the individual strips produced remain combined as a single sheet of film of uniform thickness having no seams formed in the material before being cut into individual strips. This allows easier handling and avoids any of the measures related to the control of joint strength between the individual strips. The film canvas and the resulting strips can therefore be very thin, (e.g., between 5 and 120 micrometers) since there are no separable joints. Furthermore, only by lengthening the film after passing through the cutting zone, each of the resulting strips becomes narrower and simultaneously forms an intermediate free zone between the strips without lateral movement. This zone will allow moisture to escape in an elasticized area of an article, where the strips are applied subsequently.

The finished absorbent item equipped with these strips will therefore have elasticized portions "breathable" that in this way can be produced very light compared to articles of the prior art.

BRIEF DESCRIPTION OF THE DRAWING A preferred embodiment of the invention will now be described in greater detail with reference to the accompanying figure, wherein an enlarged schematic plan view of an elastic film canvas is illustrated during processing from being an individual elastic film to a plurality thereof. of separate and elongated strips for subsequent attachment to an absorbent article.

DETAILED DESCRIPTION OF A PREFERRED MODALITY A single canvas 1 or continuous ribbon of an air impermeable elastic film is continually passed from its supply roll (not shown) through the "a" to "d" areas which will be described in greater detail below.

The film can be of any suitable material as long as it is deformable in a sufficiently elastic manner without the risk of breaking. However, the film of preference is very thin, e.g., with a thickness of between 10 and 150 micrometers in the relaxed state. Examples of suitable films can be those produced from elastomers based on polystyrene / elastomer block copolymers such as S-B-S, S-EB-S and S-I-S. Other suitable films can be produced eg, EVA, EBA or EPDM. Preferably, the film can also have an elastic extension capacity of more than 100 percent (ie, it can be elastically extended by 100 percent or more, with respect to its relaxed dimension). Zone "a" ends in line "A" which is aligned with the upper part of the plurality of dotted lines 7. A second zone "b", ending in the line B, is an area in which the elastic canvas is separated into a plurality of strips of an "e" width by cutting the single canvas lengthwise in one or more places across the width of the canvas. These locations are represented by the lines 7 dotted in the figure. The cut of the canvas 1 can occur in several ways. For example, a plurality of rotating circular discs may be placed on one side of the canvas, each of the discs having a cutting edge placed in the plane of the canvas 1 and resting against an underlying support surface. These cutting discs can be eg, of a width of one millimeter and therefore can be conveniently used side by side. As an alternative, an ultrasonic cutter can be used as it is known per se. Other appropriate cutting methods will be apparent to a person skilled in the art. Even though four separate cutting locations have been illustrated by each of the four lines 7 and therefore, producing five strips 2, 3, 4, 5 and 6, the number of locations may vary according to the requirements. Each of the "e" widths will preferably be the same and therefore, in the example shown, each strip will have an "e" width of approximately 6 millimeters when starting from a canvas of a width of approximately 30 millimeters. The feeding of the canvas can occur in any appropriate way, the pairs of driven rollers that hold the canvas between them can be an appropriate example. This feeding means, however, must be placed in an appropriate manner so that the canvas 1 is fed in its longitudinal direction of advance (see arrow X) in a given condition, however, an essentially non-elongated condition through zones "a" and "b", applying only low tension to the canvas. In this way, the film canvas 1 will therefore have an essentially uniform thickness and width through these areas. Zone "c" starts on line "B". An appropriate means such as a roller that is operated at a lower speed than the other driven roller pairs is provided in line with the line "B" and serves to provide a resistive force to the movement of the strips 2-6 in downstream of line "B". The cut strips are fed in the X direction and their front edge by an appropriate means such as a pair of rollers or by fixing the strips to the products in a movable production line, for example. Due to the feeding that is found by the resistive force, each of the strips is lengthened in the longitudinal direction so that its width will change from an "e" width to a width "f" through the length of the zone " c ". Each of the strips while in zone "c" will have its two edges 8 and 9 converging until the width "f" is reached. The width "f" then is the final width of each of the individual strips 2 to 6 that will be applied to the absorbent product. As can be seen in the figure, the contraction of the width of the strips in the area "c" causes the strips to separate between the adjacent edges so that a gap g 'is formed between the two strips 2 and 3, for example. Similarly, a space of g1 ', g' '' and g "" is formed between the strips 3, 4, 5 and 6 as shown. The spacing between the strips preferably is constant across the area "d" in such a way that each strip is rectangular. In a preferred embodiment, the width of the strips 2 to 6 is also constant. The final width of the canvas of the film 1 after stretching and including the separation between each strip, is provided by the formula: Final width = M (1- ((1-k) / N)) where k = the coefficient of contraction M = original width of the film not elongated N = the number of strips after separating. It should also be noted that not only the width but also the thickness of each strip will decrease during elongation. It will therefore be appreciated that the resulting strips can be very thin (e.g., up to 5 micrometers) and very narrow (e.g., as low as 1 or 2 millimeters) but the safe production of the strips Individuals is possible due to the fact that the strips started as a single canvas. For current requirements, a strip width of 3 millimeters in elongated condition is appropriate, even when the width of the strip can be varied within large limits. With the individual strips 2 to 6 in an extended condition (zone "d") and spaced apart by a distance "g", the plurality of strips is applied to a product in an area designated for elasticizing, and is properly fixed. In addition, due to the spacing between the strips, a breathability space has been provided between each strip without any lateral movement being made. The invention also relates to absorbent articles such as diapers or sanitary pads which per se are well known. These items usually comprise a waterproof backing layer as well as a permeable top sheet designated for body contact, between which an absorbent (e.g., a core of cellulose pulp with a superabsorbent polymer) is placed. In order to provide a good fit during movement, the elasticized zones are provided, eg, in the portions designed to be around the leg or waist of the wearer. In order to provide an elasticized zone, the strips in the area "d" (see above) are thus fixed to the article in a collected or uncollected condition (in a per se way) and, due to its inherent elasticity, provide an elastic zone. Due to the separation "g" between the strips, no lateral movement of the strips is required to obtain a product that therefore has a breathable elastic zone which is also made of a particularly light elastic film. Since the strips can be of constant width along their length if the elongation is constant, they will therefore have a spacing that is constant between the adjacent strips which provides a uniform breathability throughout the entire length of the strip. Elasticized area. When a certain number of strips are provided on opposite sides of the absorbent product, two canvases 1, normals will be used for either side in order to avoid any of the forces of lateral movement in the thin strips. However, the strips for example can be divided into sections in a non-elongated zone (or of low elongation) and then directed to either side of the product before being cut and lengthened. In the less opferred mode, the canvas can be cut and lengthened into strips that are led to respective groups on either side of the product, while maintaining the separation between the strips of each group. The final thickness of the strips can be as low as 5 micrometers to about 100 micrometers, even when a thickness between 10 micrometers and 40 micrometers is appropriate. Similarly, an appropriate width would be between 2 and 16 millimeters in the elongated condition and preferably between 3 and 8 millimeters. The elasticized zone can also be a belt or belt area of an absorbent article. In a further embodiment, the strips can be provided which have a fibrous material surface on one side (which has advantages per se). To achieve this, the non-porous elastic sheet can also be attached to a fibrous cover material to provide a combined canvas before the cutting zone and therefore the fibrous material will be maintained essentially intact by each of the continuous strips still in the web. elongated condition. A further advantageous embodiment of the invention is its application to provide a divided band which provides good breathing capacity in relation to the absorbent products manufactured in the "longitudinal" direction. As is known in the art, absorbent garments can be produced by placing the upper end (the end of the belt) towards the lower end in the direction of the path of the conveyor belt which is called longitudinal production, or they can be transverse to the longitudinal direction that is called cross production. When producing absorbent products in the longitudinal production, the manufacture of eg, of seams and the application of eg, the elastic of the leg in the longitudinal direction is a relatively simple matter since the synchronization is not complicated . However, when a layer is applied or a seam is formed that is required in the transverse direction, specific difficulties result. A specific example is related to the application of the elastic of the waist in the form of a foam canvas or similar. In order to achieve elasticization and application of the strip in this condition, the strip has to be cut in the form of a similar patch and then elongated before being applied and fixed to the waist area. The Patent Number EP-A-0 338 662 shows an example of an apparatus that is designed to carry out this operation. The apparatus comprises two circular discs placed at an angle towards the verticalhaving each of the pin discs therein to receive one end of a pre-cut strip at the position of the closest spacing of the discs, and, by rotating the discs to a further spaced apart position, then the strip is It lengthens and can then be applied in this elongated condition to an absorbent product. To provide an elasticized waistband in this area consisting of a plurality of thin strips (in the manner defined above with respect to the method of the invention), in order to provide a waistband having a good waist area. Breathing capacity, this is difficult since the lengthening and application of many individual strips leads to many difficulties. Consequently, when longitudinal production is used, waist bands are often produced using a wide strip of material instead. With the method of the invention, however, a solution to this problem is provided since the elastic parts of the separated waistband can be provided with ends that are not cut to allow the application to e.g. of pins of the discs (see e.g., pins 15 in Patent Number EP 0 338 662), but nevertheless the intermediate part of the elastic portion between the ends (e.g., from 1 or 2 centimeters from each end) they will be cut in one or more places (ie, joining lines 7 in the figure). In this way, the patch can be applied as above, to the disc pins or the like without difficulty and, by lengthening the individual strip portions of the patch will contract in width and thickness in order to provide an appearance as in the "d" zone. of the figure. In this way, an elongated patch will be produced in the disks having two uncut ends (such as in the "a" zone) joined by a plurality of strips (such as in the "d" zone). This strip will then be applied in the elongated condition to the waist region and will be fixed to it. Since the patches are discrete entities that are to be applied to the waist portion of the article, these patches can be produced using a method as shown in only the "a" and "b" areas of the figure, but when the cutting means they are operated intermittently to cut only the required areas, leaving the uncut ends forward and back in sequence. This method then allows the continuous tape of the fixed patches to be wound onto an additional reel for later use if this is required. When the patches are applied in longitudinal production, the reel is unwound and, by appropriate means, cut into separate patches which are then rotated through 90 ° and individually fixed to the pins in the rotating discs (as in Patent Number EP-A 0 338 662) for elongation and application. To avoid the requirement of a 90 ° rotation, the patches can be cut alternately between their ends (leaving two ends still uncut) by using multiple cutters that are synchronized with the motion of the film. Although the invention has been described above in relation to a preferred embodiment thereof, the invention is not limited thereto and it will be appreciated that many variations of the invention are possible within the scope of the appended claims. For example, other materials and applications are possible.

Claims (10)

CLAIMS t

1. The method for producing a flexible absorbent article having an elasticized area, from a single canvas (1) of film, wherein the single canvas (1) is fed in a direction of longitudinal advance (X) to an area (b) ) of cutting, where the canvas is cut longitudinally into a plurality of strips (2-6), the plurality of strips is then further fed in a direction of advancement simultaneously while lengthening in the longitudinal direction to thereby reduce its width (e) and thickness, characterized in that the film is an elastic film, and in that the plurality of strips (2-6) is applied to a canvas of an absorbent article in an area to be elastified, the strips are fixed firmly to an absorbent article simultaneously with its application, or shortly thereafter. The method according to claim 1, wherein the width of the strips (2-6) is reduced to a constant width (f) after being passed through an initial elongation zone (c). The method according to claim 1, or claim 2, wherein each of the strips has essentially the same constant width (f) after the initial elongation zone (c). The method according to claim 3, wherein the last three strips are produced having a gap (g ', g'1, g'11, g''11) between the opposite edges of the adjacent strips, and in where the separation is constant along the length of the strips. 5. The method according to any of the preceding claims, wherein all the strips (2-6) are applied to the absorbent article canvas while they are still attached to the single canvas (1). 6. The flexible absorbent article for the absorption of human exudate, the article having one or more elasticized zones wherein a plurality of elongate elastic members have been fixed, characterized in that each of the elastic members comprises a thin flat strip (2-6). ) of elastic film, each strip has an essentially constant width along its entire length and is separated from an adjacent strip by a distance (g ', g11, g' '', g'11 ') which is essentially constant to along the length of each strip. 7. The flexible absorbent article according to claim 6, characterized in that the strips have a thickness between 5 micrometers and 10 micrometers, preferably between 20 micrometers and 40 micrometers when applied to the product. The flexible absorbent article according to any of claims 6 or 7, characterized in that the strips have a width of between 2 millimeters and 16 millimeters and preferably between 3 millimeters and 8 millimeters when applied to the product. 9. The flexible absorbent article according to any of claims 6 to 8, characterized in that the absorbent article is an absorbent garment and in which the strips (2-6) are applied to the waist portion of the garment to be worn. absorbent. The flexible absorbent article according to any of claims 6 to 9, characterized in that the absorbent article is an absorbent garment, and in that the strips (2-6) are applied to the designated portions of the absorbent garment. to surround the legs or thighs of the user.