Textile absorbent materials capable of expanding in one coordinate direction at least to create room for the increased volume due to imbibition of liquid to be absorbed are more particularly needed in connection with disposable articles such as baby diapers, incontinence products and femcare hygiene, and also in the sector of absorbent articles for packaging and food technology.
This function is traditionally performed by suitable combination products comprising pulp, superabsorbent granules or fibers and liquid-distributing layers comprising synthetic nonwovens, pulp or cotton.
In recognition of the responsibility toward sustainability of the Earth's natural resources and the conscious approach to the consequences of their use, it is industry's responsibility to minimize the consumption of raw materials and packaging materials and also the transportation energy for manufacture and sales as far as possible. As far as the production of hygiene articles is concerned, this means primarily a reduction in primary energy requirements, pulp, transportation volume, packaging films and cardboard and waste volume.
Numerous projects are known particularly in the field of baby diapers, not only from the literature but also from industrial design, seeking to partially or completely replace the absorbency of cellulose/pulp by using superabsorbent granules (superabsorbents) and succeeding. It is technically, economically and ecologically desirable for, for example, modern baby diapers or adult incontinence articles to be completely converted to pulp-free absorbent pads in order that the influence of using disposable articles on climate change may be kept as small as possible.
Two fundamentally different approaches are known in order to reduce/eliminate the pulp from baby diapers, incontinence products and femcare hygiene articles:
EP 724 418 describes the production of a laminate which consists of two outer plies, of which at least one ply is hydrophilic and which are glued to each other using a water-sensitive pressure-sensitive adhesive, so that isolated unglued sections can punctiformly incorporate superabsorbent which, in the swollen state, specifically breaks open the gluing and achieves the laminate volume increase needed for the swell volume. It has to be assumed that only limited integrity can be achieved for the laminate in the swollen state.
US 20020102392 proposes a method for producing an absorption-capable laminate with incorporated sections of superabsorbents and elastic properties. Sections of superabsorbents are positioned via a vacuum system, between two outer plies, of which one is shirred in the longitudinal direction using a profiled roller, and transversely to the manufacturing direction, to obtain a longitudinally extendable laminate, wherein the elasticity and shining can be increased by using elastic films or nonwovens.
US20020115969 discloses a method for the longitudinally continuous production of a laminate with individual sheetings of superabsorbents which have been installed with hot glue between two outer plies such that strips of superabsorbent-covered and superabsorbent-free regions in each case are formed transversely to the manufacturing direction.
The production of a laminate comprising two outer plies with punctiformly incorporated sections of superabsorbents is described in WO 2004071539 and WO 2004071363. A textured vacuum roller is used to cause a first outer layer to develop depressions, which are filled with superabsorbents and fibers and bonded to the second outer layer. Comparable products have long also been used as supports in surgery and patient care.
Superabsorbents undergo a weight increase of 2500-5000% as they imbibe liquid. The associated increase in volume has to be accommodated through suitable flexibility on the part of the surrounding carrier material. This is in principle not a problem in the case of conventional pulp/superabsorbent pads, since the pulp allows expansion in all three dimensions. In the case of so-called superabsorbent laminates, in which superabsorbent granules or superabsorbent/fiber mixtures are fixed using pressure-sensitive adhesive or thermally between two or more plies of nonwovens, film, tissue or the like, this function has to be made possible by the outer plies of the laminate, whether through stretching or through geometric flexibility. But at all times the containment of the superabsorbent has to be ensured without one of the outer plies breaking or the lamination tearing open. It is further desirable that this laminate be elastically extendable not just perpendicularly to its production plane but also within this plane itself in order not only to facilitate the volume enlargement on the part of the superabsorbent due to liquid imbibition but also to combine with other components of the above-identified hygiene articles in not impairing their flexibility and ability to conform to the particular body contour.
The invention accordingly has for its object to provide a production method enabling the continuous production of absorption-capable textile sheeting material with high manufacturing capacity and, as a result, cost-effectively, wherein the end product has not only area-elastic properties to optimally adapt to the body contour of the user but also volume-elastic properties to accommodate large amounts of liquid.
This object is achieved according to the invention by virtue of the fact that owing to the incorporation of superabsorbents and one or more elastic interplies, consisting of individual threads, strands or bands between two outer plies of a thusly produced laminate, this laminate is made extendable essentially transversely to the production direction and shirred in the relaxed state to the extent that the elastic interplies contain individual sections of superabsorbent in the manner of a quilted blanket and create room for the expansion of the laminate on fluid imbibition perpendicularly to and within the manufacturing plane. For use within the context of modern ultra-thin and elastic hygiene articles, it is important that the laminate thus produced is completely elastic and extendable and conforms perfectly to the body contour in both the dry and the moist state.
As a result of the shining and texturing thus achieved on the skin-sided surface of the laminate, or to be more precise on that side from where the liquid to be imbibed comes into contact with the laminate and advantageously in association with an appropriately hydrophilic and transportation-capable outer layer, an excellent conductance of liquid not only in the dry but also in the moist state is ensured. Furthermore, a laminate produced in this way is always permeable perpendicularly to its manufacturing plane in the region of the gluing of the elastic plies even in the swollen state without being hindered by the swelling of the superabsorbent, so that the texture of the surface and the choice of appropriate outer layer ensure transportation performance even on the skin-remote side and the skin-sided outer layer can be optimized in respect of back-wetting/skin moisture.
According to the invention, first the front end of the first outer textile layer 20 is applied to the end portion of an elongate rod- or tube-shaped core 5 and, by imposing an advancement movement around the core, folded into a shape which is closed in a hoselike form.
In the further course of the advancement movement on the core, through tapering of the cross section of the core, the circumference of this hose is shortened to the effect that excess material is ducted through ducting rails or rods 8 outside the hose into suitable cutouts in the core 5; subsequently, two or more driven feed devices 11, 14 which ring the mold and are contrarotatory in pairs loosely withdraw groups of elastic threads or strands 50, 53 from circumferentially spaced-apart individual guides 17 and place them with friction-caused low pre-tensioning around the first outer material layer in the course of the advancement on the core. Areal pattern 32 of elastic threads or strands which surrounds the tube of the first outer sheeting of material in a cruciformly symmetrical manner has a pressure-sensitive adhesive 29 applied to it in thread form, which wets and enfolds the essentially bare elastic threads. In the continued course of the forward feed movement, the cross section of the core is enlarged to tauten the hose of the first outer sheeting of material and thereby cause it to come into contact with the elastic threads and finally be brought into a flat shape. On both sides of this flat hose, a pair of advancement or contact rollers 38 is used to bond two individual sheets of the second outer material layer 32 onto the free surface of the first outer material sheeting 20 and the elastic threads 17 provided with the pressure-sensitive adhesive 29. As this bond is being formed, individual tracks of superabsorbent 47 are introduced on both sides of the hose of the first outer sheeting of material, between it and the supplied second outer sheeting of material. Finally, the hose thus produced is severed lengthwise into individual sheetings and these are traversingly wound onto individual rolls or deposited in boxes.
As a result of the folding-in of the hose of the first sheeting of material and producing the circumferential elasticity of the hose by spreading apart the first outer sheeting of material by expanding the elastic thread pattern 32, with respect to comparable winding processes for elastic hoses based on pre-tensioned threads or bands (for example WO 03041627, DE 102004026070) an appreciable reduction in complexity by eliminating the drive for individual guides of the threads and increased productivity in proportion with the transverse extensibility of the laminate are produced since, according to experience, the manufacturing speed is limited by the limiting speed of the ring-shaped feed devices. The width of the applicator system for the pressure-sensitive adhesive 29 is furthermore reduced to the same degree.
Since, following application of the elastic threads or bands to the hose of the first outer sheeting of material, these threads or bands only touch punctiformly and are otherwise bare, a pressure-sensitive adhesive applied spirally or meanderingly is forced through the areal pattern of the elastic threads, preferably in order that these elastic threads are enfolded and are oriented essentially around the threads after spreading apart of the hose of the first outer sheeting of material, as a result of which a glue pattern which corresponds to the areal pattern 32 (
It has proven to be advantageous to form the core 5, in accordance with
The first outer material layer, once it has been pressed into the storage struts, can easily be maintained by negative pressure, introduction of compressed air or by electrostatic charging in a position closely bearing against the guiding and storage struts of the core, and be pulled with low friction over the core.
Spreading the core apart after the elastic interlayers and the pressure-sensitive adhesive have been applied is advantageously achieved when guiding struts, which are mutually opposite pairwise, gradually widen in the further course of the core in their expansion direction transversely to the longitudinal axis of the core and a further pair of guiding struts is decreased in its width to the same degree, so that the hose of the first outer layer is continuously pulled out of the storage struts and pulled taut over the tips of the guiding struts and is thus brought into sheetlike contact with the pressure-sensitively glued elastic plies (
Advantageously, the core 5 for this process is disposed to be perpendicular in its longitudinal direction such that the advancement rolls 56 are situated at the lower end of core 5 (
The superabsorbent 47 is advantageously supplied in separate volumetrically or weight-dosed continuous individual lines or tracks which are either introduced into the glue-free regions of the areal pattern in an intermittent manner by pulsating compressed air or pistons, or are intermittently deflected in line with the areal pattern 32 in a direction transversely to the centrifugal direction of the hose of the first outer sheeting of material. For simplicity of use, it can be sufficient to allow these individual tracks to trickle down continuously, in which case it is advantageous to supply two individual tracks per cassette of the areal pattern.
It may be useful and advantageous for the hose of the first outer material sheeting 20 to be relaxed in the transverse direction by reducing the width of the guiding struts before being supplied into the tensile rolls 56, so that it has a slight degree of waviness at the time the second outer sheeting 44 is supplied, as a result of which small pockets are formed in the region of the nonglued zones of areal pattern 26, which facilitate the laydown of superabsorbent 33.
In a further development of the invention, this waviness can be suitably policed to control the ratio of the widths of the first and second outer sheetings of material relative to each other to the extent that the laminate thus produced has a higher degree of waviness on the side of the first outer layer than on the side of the second outer layer. This makes it possible to minimize the particular costly material of the outer layers 20 and 44 while keeping the swell volume of individual cassettes the same.
In the description which follows the present invention is explained in more detail in connection with the drawings which schematically illustrate how the method according to the invention is carried out in the production of area-elastic absorption-capable sheeting material. In the drawings
a shows the construction of the core comprising guiding and storage struts;
b shows the construction of the core comprising guiding and storage struts and guiding rails in the region of the tapering of the core;
c shows the construction of the core in the region of the spreading apart of the core;
d shows the construction of the core after spreading apart is complete;
a shows the areal pattern, obtained on using two oppositely driven feed means as per
b shows the areal pattern, obtained on using two oppositely driven feed means as per
c shows the areal pattern, obtained on using two oppositely driven feed means as per
a shows a schematic depiction of a detail from the cross section of the core on using two storage struts between respectively two guiding struts and policing the sectionwise intake of the first outer layer by positioning the guiding rails; and
b shows areal patterns of elastic threads of the elastic sheeting material produced according to
The device 2 depicted in a simplified and highly schematicized manner in
From a rotatably mounted and driven material roller 26, a first textile layer 20 is preferably conveyed under sheeting tension control, folded via a forming shoulder 6 into a hose of rectangular cross section and laid onto the front end of core 5 formed by multiple struts 35, 38 in this example (
This hose thus formed is subsequently guided over the cross-sectionally tapered core, so that the hose merely guides the core on the ends of the guiding struts 35, which shorten in their width, and inbetween material of the hose is guided using guiding rails or wires 8 in vacant spaces formed by storage struts 38 disposed between the guiding struts (
This hose, thus shortened in its circumference, is subsequently guided by two contrarotatingly turning feed means 11, 14. In the feed means, individual elastic threads, bands or strands 50, 53 are each withdrawn by circumferentially spaced-apart individual guides 17 of stationary packages or rolls and laid down onto the hose of the first outer material layer 20. The superposition of the rotary motions of the two feed means 11, 14 by the advancement of the first material layer 20 results in an oppositely diagonal pattern of the elastic elements 50, 53, which only contacts the first layer material layer on the tips of the guiding rails 35 of core 5, but is otherwise bare,
In the continued course of advancement on the core, the elastic threads 50, 53 have pressure-sensitive adhesive applied to them, preferably as a curtain of spiraling or meandering threads, which on impingement on the bare oppositely diagonal pattern of elastic threads 50, 53 is diverted by these and preferentially wets and enfolds the elastic threads, but specifically cross-over points between threads 50 and 53,
In the continued course of advancement on the core 5, the latter is spread in its cross section such that any two opposite guiding struts are expanded in their width, and a complementary pair of guiding struts is reduced in its width, to the effect that initially the material of the first layer 20 remaining in the storage struts 38 of the core 5 is continuously detached and the hose of the first material layer 20 is tensioned taut over the ends of the guiding rails 35 (
In a further step in the course of the advancement, this hose thus formed into a flat shape is introduced into a device of two driven opposite advancement elements, here two rolls or rollers 56, which supply in the last instance the advancement for withdrawing the first outer layer 20 of the material roll 26 and the transportation of all materials over the core.
The advancement rollers 56 provide withdrawal and feeding, preferably under sheeting tension control, of an individual sheeting each of the second outer layer 44 of two mutually spaced-apart, rotatingly driven devices of material rolls 41, on both sides of the material sheeting 20, and sheetlike bonding thereof to the first material layer 20 and the elastic areal pattern 32 via the pressure-sensitive adhesive 29.
As the flattened hose of the first material sheeting 20 is brought together with the supplied planar lengths of the second material sheeting 44 by the advancement unit 56, a superabsorbent 47 is introduced on both sides of the hose in a perpendicular manner such that, in line with the areal pattern 32, individual lines or tracks adapted individually volumetrically or grammetrically to the advancement speed of the hose of the first material sheeting 20 are continuously trickled in, resulting in a product pattern as per
After the pressure-sensitive adhesive is set, advantageously by the contact pressure of the advancement rolls 56, and after bonding the two outer layers 20 and 44 among themselves to the incorporated elastic elements 50, 53 therebetween with inclusion of the superabsorbent introduced, this multi-ply hose thus formed is severed longitudinally into individual sheetings in the course of the continued advancement movement, which sheetings can selectively be transversingly wound up on rolls movement or deposited in boxes or coiled up.
In a further development of the inventive method described here, the width of the flat hose comprising a first textile layer 20 and areal pattern of elastic elements 32, having been spread apart into the flat state,
In a further development of the inventive method it can be desirable and advantageous for the planar sheeting material produced in this way to be endowed transversely to its production direction with sections of differing shirring for the external plies and thus differing swell volume, leading by controlling the superabsorbent distribution transversely to the production direction of the sheeting material to an advantageous transverse distribution of absorbency.
It can be advantageous to achieve the function of pressing the first textile layer into the vacant spaces of the storage struts instead of the guiding rails 8 by negative-pressure from the guiding core, by static charge build-up on the first material sheeting 20 versus the struts 35, 38 of the core, or by applying compressed air to the outside surface of the hose of the first material layer 20.
It can further be sensible and advantageous to achieve the functions of the respectively four guiding and storage struts from
Even if the isolation of individual sections of superabsorbents in glue-free regions of an otherwise mutually glued-together sheeting material comprising two outer layers 20, 44 and incorporating elastic plies 50, 53 is advantageous for the swelling effect and volume enlargement on the part of superabsorbent 47 in the liquid imbibition in accordance with the intended use, it can be sensible to wet the second outer layer 44 with an additional slight layer of pressure-sensitive adhesive before combining with the first outer layer 20 in a sheetlike manner or in longitudinal strips in order that the superabsorbent may be fixed as sheetlike as possible to thereby preempt any possible clumping of this material before commencement of liquid imbibition and to improve the haptics of the sheeting material thus produced.
Number | Date | Country | Kind |
---|---|---|---|
10 2010 013 288.8 | Mar 2010 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/DE2011/000339 | 3/27/2011 | WO | 00 | 9/21/2012 |