Patent Application
20090035515
This invention deals with improvements in the production of absorbent items, like nappies, sanitary towels, incontinence pads and similar. More specifically, this invention deals with improvements in the production of the components used to coat absorbent and sanitary items externally.
In the production of sanitary towels, nappies and other sanitary items absorbent structures are usually used enclosed between a top sheet, which comes into contact with the epidermis of the user, and a lower back sheet, turned outwards in relation to the skin of who is wearing the absorbent item. The top and back sheets are obtained by cutting a continuous semi-finished product, produced in a preceding phase of production.
The coating layers, and in particular the top sheet must have a surface that is soft to touch. Moreover the back sheet must be impermeable to liquids, while the top sheet must have a structure to allow fast passage of the biological liquid (blood, urine or other) from the external side towards the internal side, that is towards the mass of absorbent material making up the core of the towel.
Usually the back sheet is produced in polymer film, which can be coated in textile material, to provide the required textile feeling to the finished product. The top sheet is often also produced in polymer film or in non-woven fabric. To allow the outflow of liquids, the substrate or support that constitutes the base of the top sheet (be it a film, or non-woven fabric) can have a perforation. The top sheet, above all if produced in polymer film, can also be coated in textile material.
Among the various methods suggested for the surface treatment and perforation of the polymer film, and among the various absorbent items which use polymer film or other coating material in various configurations by way of example those described in U.S. Pat. Nos. 3,484,835; 3,911,187; 3,950,480; 3,957,414; 4,151,240; 4,342,314; 4,463,045; 3,967,623; 3,665,921; 5,171,238; 3,945,386 are mentioned. Other techniques of perforation are described in WO 93/12749. The publication GB-A-2,171,016 describes a sanitary towel with an external structure characterized by the incorporation of fibers in an external coating layer.
EP-A-737,462 describes a weblike product, i.e. a sheet or ply product, composed of a base formed by a polymer film, on which is evenly distributed a resin or glue, which serves as an anchor to a flock fiber. In an embodiment of this product, it is foreseen that the resin is laid in longitudinal strips, so that bands coated in flock fiber and bands free of fiber can form on the film. The fiber free bands or zones usually correspond to a strip which, in the final absorbent item coated with this material, is arranged in correspondence to the central area where the biological liquid is collected. In this area the base film is also apertured to allow the fluid to pass into the absorbent core. The lateral surface bands of the top sheet are, on the other hand, entirely covered by flock fiber, that is of fiber applied by flocking.
JP-59-222330 describes an absorbent product in which flock fibers of great length are applied on the internal surface of a layer of coating of the absorbent item and form part of the absorbent core. They are not therefore, destined to come into contact with the body of the user who wears the absorbent item.
Further absorbent items coated in plastic material with a fiber coating applied by flocking are described in U.S. Pat. Nos. 6,497,688 and 6,365,794 and in European patent EP-B-1,070,492.
Flocking is a technique of fiber application in which the film, on which an anchor resin has been applied, is made pass under one or more fiber distribution heads, which fibers have been previously treated to become polarized. The fibers are entered into an electrostatic field, whose lines of force are essentially at right angles to the surface of the polymer film and are thus made fall onto the film itself in an essentially orthogonal way to the surface of the film. They are anchored to the film by the effect of resin reticulation.
The need to pre-treat or, what is technically called, “activate” the fibers to polarize them makes the fibers particularly expensive. They must, in fact, be immersed into a specific saline solution and absorb ionic groups, which distribute themselves appropriately in the fibers. This process of fiber activation directs them according to the lines of force of the electrostatic field in which they are inserted to be distributed on the film.
To reduce the cost of semi-finished products composed of the film coated by flocking, and therefore to reduce the costs of the absorbent items which make use of such a semi-finished product, it is necessary to reduce the quantity of flock fibers, i.e. the weight of fiber per unit of surface. Nevertheless, technological limits exist which prevent falling below a certain weight of flock fiber, due to the difficulty of controlling the distribution of the fibers on the film. In other words, when the quantity of flock fibers per unit of surface of polymer support film falls below a certain value, it is no longer possible to obtain an even distribution of the fibers, as the flocking machines do not allow effective control of the flocking process. Furthermore, when the weight is very low, the effect in terms of soft and pleasing touch of the flocking is lost or, in any case, drastically reduced.
An object of this invention is to realize a method to obtain a semi-finished flock product to use as specified above, which overcomes or reduces the limits of known methods and which drastically reduces the quantity of flock fibers per unit of surface.
According to a different aspect, an object of this invention is to provide a different type of superficial workmanship of the support or substrate, for example in polymer film or in non-woven fabric to obtain a pleasing surface effect, which prevents the uncomfortable feeling of plastic, that is the polymer film on direct contact with the skin when the support is destined to form the top sheet and/or which is aesthetically more appreciable.
According to another aspect, an object of this invention is to provide a new semi-finished product to coat sanitary towels as well as a new type of absorbent product or item using this semi-finished product.
Therefore, according to a possible embodiment the invention relates a method to produce a weblike material including a substrate or support, by way of example and in particular (but not exclusively) in polymer film or non-woven fabric, in which:
According to a preferred embodiment of the invention, the quantity of fibers which remains anchored to the film is between 0 and 20 g/m2 and preferably between 0 and 10 g/m2 and even more preferably between 0 and 5 g/m2.
The adhesive can be composed for example of a polymer and cross-linkable resin. Resins suited to this use can be polymer resin of various kind and specifically, but not exclusively, vinyl resins and in particular acrylic resins, without excluding other types of resins. Resins suited to this kind of use can be the following:
As an alternative to the polymer cross-linkable resins it is also possible to use other adhesives, like hot melt adhesives. They are thermoplastic rubber or polyolefin based adhesives. They are sold in granules, powder or rolls, fused before or after application on the substrate. After flocking the adhesive is hardened by cooling at ambient temperature. Possible hot melt adhesives used are the following:
The flocking method according to the invention achieves a series of advantages and functions. This, in particular:
implies a three dimensional effect which, as is known, is desirable for a top sheet because it is an indication of a soft touch (guaranteed in this case also with low quantities of flock fibers), and above all because it helps the outflow of the liquid towards the lower layer:
if the support is non-woven fabric or pierced film, distribution of the flock fiber with design implies minor coverage of the holes, increasing therefore the performance of the top sheet in terms of liquid acquisition;
in distribution of the flock fiber with design, the contact surface is smaller and therefore also the rewet value will be lower compared to the case in which the flock fiber is distributed over the entire surface;
using hot polymerizable and photo hardening resins, it is possible to crosslink by UV irradiation (or microwaves, radio frequency or any IR/UV combination): in this case, once flocked, the substrate (glued and flocked) is passed through a field of ultraviolet rays to allow crosslinking of the glue, where the UV rays must strike the largest possible surface of glue and flock fiber. A solution is opted for that distributes the glue and flock fiber according to geometric or ornamental design to create more or less thin areas but in any case separated one from the others, to allow the UV rays to strike the horizontal surface and the lateral sides of the glue which traps the flock fibers: therefore moving from a full surface coating to a coating in the form of a design, the surface exposed to radiation is enlarged and crosslinking improved.
To improve adhesion of the fibers to the resin, a plasma or corona treatment can be performed on the resin itself, before being flocked; such types of treatment involve an increase to the resin polarity, increasing the ability of cohesion of the flock fibers, which are also polar. Also in this case, a print distribution of the flock fiber, involves an improvement of crosslinking as the surface exposed to the treatment increases.
Below frequent reference will be made to an anchor resin. It must be understood that this is only one of the ways of anchoring the flock fibers, which can also be fixed to the support, for example, with a hot melt adhesive or other equivalent adhesive. In this context, the term adhesive means a hot melt adhesive, a resin, or any other product that is suitable to being applied according to the criteria described and compatible with the use to which the flock material is destined.
Furthermore, specific reference will be made below to the application to a polymer film, which can also be an elastic polymer film. This is a substrate or support which makes the most of the application of the present invention, as the application of the flock fibers avoids the contact of the skin with the polymer material forming the film. Flock films are particularly ideal in the production of the back sheet of the absorbent product. Apertured flocked films are unfoldable as top sheet. It is not excluded, to use other kinds of substrate on which flocking is preformed, for example a non-woven, which may be but not necessarily apertured, preferably for the production of the top sheet.
Substantially, the invention is based on the idea of reducing the total quantity of flock fibers which remain anchored to the film applying the anchor adhesive according to a design rather than in continuous mode. In this way the overall surface of the film or other substrate or support is only partially covered with adhesive and therefore with flock fibers, reducing the quantity of raw material consumed. The distribution of the zones on which the adhesive is applied and therefore on which the fiber is anchored is such that the film has ample areas with a discontinuous but substantially even distribution of flock fibers.
While in known methods only the possibility of forming ample strip-like zones, which are completely coated with fibers, are envisaged, separated from one another by large strip-like zones which are completely free of fibers, for example in correspondence of the apertures for draining the body liquids, according to the invention the zones coated by flocked fibers have, in reality, a non continuous distribution of resin or other adhesive and therefore of fibers, i.e. a microdistribution of areas fitted with resin and fibers alternated with resin-free (and therefore fibreless) micro-surfaces.
This can be obtained for example by applying the adhesive according to a lined design or motif, i.e. including substantially parallel lines, for example in machine direction or in transversal direction or again in a direction, which is inclined by an angle different from 90° compared to the machine direction. Alternatively, the adhesive can be distributed in dots or spots or circular, ring-shaped, quadrangular, polygonal areas or similar of small size and according to a dense pitch.
The overall area of the fibreless zones can vary from 1 to 99% and preferably between 10 and 90% of the overall useful area of the substrate. According to a possible embodiment, the fibreless area is equal or lower to the 50% of the useful overall area of the surface of the substrate or support. For example, it can be envisaged that the maximum distance between two fiber-coated zones is equal to or lower than 10 mm and preferably between 1 and 10 mm. It is not excluded to use different distances. In particular, when the flocking has a mainly aesthetic function, the distance between flocked areas can be 5 cm. For example this can occur when flocking is used to decorate a back sheet with a logo or other way, which is a part of the finished product not destined to the direct contact with the skin of the person wearing it.
When the resin or other adhesive is applied in parallel lines, the distance between the lines can be for example equal to or lower than 10 mm. The lines can have a width of between 1 and 10 mm and preferably between 1 and 5 mm and even more preferably between 1 and 2 mm. Between adjacent lines an adhesive-free strip can be defined. The width of such adhesive-free strips being between 1 and 10, and preferably between 1 and 5 mm and even more preferably between 2 and 3 mm.
According to a possible embodiment, the adhesive is distributed in a simple and repetitive motif, with a distance of between 1 and 10 mm. For example the resin is distributed according to discrete areas, separated by resin-free areas. This distribution can be made according to a lined design, or also in circular or similar areas. The possibility of distributing the adhesive and therefore the flock fibers in the form of a complex ornamental design, for example a floral or other design, composed by a group of areas of various form, linear or also non-linear, is also possible. In this case no distance is defined between the glued areas.
According to a different embodiment of the method according to the invention, the resin or other adhesive is distributed according to an ornamental or decorative motif, for example to define a logo or brand of the producer of the finished absorbent item on which the weblike material in flock film is applied as an external coating.
To give greater prestige and higher quality to the product, according to a possible embodiment of the method according to the invention a colored resin or other adhesive is used. Alternatively, or in combination, colored fibers can be used. For example, colored resins, in particular and preferably of a single color, and colored fibers, of a color different to that of the resin, can be applied on a white base polymer film. Or, the resin or other adhesive can be colorless or the same color of the base film, while the fibers are colored. Or, the fibers are colorless or the same color of the base film and the resin is colored. Or the film can be colored and the glue and/or the fiber can be white or colored in colors different to those of the film.
According to an advantageous embodiment of the method of this invention, the resin is applied to the film by a patterned roller. This can be a roller with a pattern realized by recesses or depressions, in which the resin is collected which is then yielded to the film. Alternatively, the resin can be applied to raised zones of the roller, and from these yielded to the film.
The fibers can have a length of between 0.35 and 2 mm and preferably between 0.4 and 0.8 mm and even more preferably between 0.5 and 0.6 mm. Alternatively, also for cost reasons, milled flock fibers can be used. In this kind of product the fiber lengths are distributed over a large area, between a minimum limit and a maximum limit, for example defined by the values indicated above.
The flock fibers can also measure between 0.3 and 3.3 dtex, and preferably between 0.3 and 1.7 dtex, and even more preferably between 0.3 and 0.95 dtex.
The fibers can be viscose, polyester, Nylon®, acrylic fibers or other materials suitable and compatible with the use to which the flocked substrate is destined.
According to a possible embodiment of the invention, when a resin is used as adhesive, it can be an expandable resin. Using this kind of resin, during the crosslinking and/or polymerisation phase it expands increasing in volume, giving way to an effect of a relief design on the surface of the film. In this way a combined effect is achieved from the relief pattern, defined by the expanded resin and the flock fiber anchored by the same resin.
The expandable resin can be any resin available on the market, compatible with the type of application to which the semi-finished product obtained by flocking is destined. For example, a resin called EXPANCEL, produced by Schonox GmbH Expancel, Germany can be used.
In general the expandable resin will be a so-called self-expanding resin, that is composed of micro-spheres of thermoplastic polymers, which contain a gas (for example isobutene) or a liquid. With the temperature the fluid contained in the micro-spheres expands and the sides of it soften and deform by yielding with consequent increase in the permanent volume of the structure.
According to an improved embodiment of the invention, a perfumed-substance can be applied to the material obtained. The perfumed substance can be:
1) applied by spray, immediately after flocking, before passing the film into the furnace where crosslinking and/or polymerisation of the resin occurs, or after hardening of an adhesive for example of the hot melt kind;
2) added to the adhesive before its application to the film;
3) added in the phase of activating the fibers, that is in the saline solution in which the fibers are immersed to make them polar; according to the features and the nature of the substances used.
The perfumed substances can be of various kind and typically essential oil based, like for example the essences distributed with the commercial name HS 29 by NEARCHIMICA (Italy). Alternatively perfumed micro-encapsulated substances can be used, composed of lipo-soluble micro-encapsulated perfumes dispersed in water. Such microencapsulated products are activated by rubbing, after which the capsules break and release the perfume. These products include for example:
VERAROMA sold by EIGENMANN&VERONELLI SpA (Italy);
PROFUMO MICROINCAPSULATO, sold by TILLMANNS SPA (Italia).
The fragrances can be varied; fruit-flowers, but also emollients (calendula-officinal sage-aloe).
The fragrances can be combined to cyclodextrins, to increase the release time. Cyclodextrins are cyclic oligosaccharides, used as agents for the slow release of the fragrance. In fact the perfume molecules are encapsulated in the cavities of the cyclodextrins and do not evaporate. These are held for a long period and water is necessary for the release of the perfume molecules. Practically, even small quantities of water are enough to free the perfume molecules and simultaneously the organic molecules creating the bad odors join together, going to fill the cavities previously occupied by the perfume. The cyclodextrins, therefore increase the duration of the fragrance, allowing the controlled release at the moment of real need, and at the same time act as odor-eating substances. The cyclodextrins can be applied as above by addition to the resin or other adhesive, or by spray after flocking.
The invention also concerns a semi-finished material including a base substrate, for example a nonwoven, or preferably a base polymer film, an anchoring pattern-distributed adhesive and a layer of flock fibers anchored by said adhesive to the substrate or base support.
According to a possible embodiment of the invention, perfumes or curative substances can be applied to the product, known for their beneficial effects on the skin, like substances containing aloe, bees wax, calendula, ginseng, etc. These substances can be added directly during preparation of the resin, or sprayed on the flocked product, before it is passed to the furnace. Natural essences or extracts of plants or animal or vegetal secretions can be used. They can be soluble in water or made soluble by using tensio-active agents.
These substances, essences, extracts or active ingredients can be microencapsulated, to obtain a gradual release. During the resin preparation phase microcapsules can be added containing fragrances or active principle ingredients of the kind indicated above, with dimensions of the microcapsules of about 1 micron and resistances to temperature greater than 300° C. The process of micro-encapsulation protects the particles of substances added within the microcapsules in invisible resin which release the active substance only by light rubbing guaranteeing duration over time, when the product is packaged, while during use breakage of the micro-capsules is obtained and the consequent emission of the substances in it contained. These microcapsules are compatible with water, solvent, acrylic systems and are applicable by the most common ways of print, coating, spray and/or foulard. The microcapsules mentioned can also contain odor-eating anti-bacterial solutions or curative ingredients of various kind.
Further advantageous characteristics of the method and product according to the invention are indicated in the claims attached.
The invention is better understood following the description and the drawing, which shows a practical non-limiting embodiment of the invention. More specifically the drawing shows:
B1 indicates a spool of polymer film F (or other substrate or support, for example a non-woven) to treat, which is unwound according to arrow f and fed to a flocking machine 1. Upstream of flocking machine 1 is a print application station 3 of an anchor resin, in which a polymerizable and/or cross-linkable resin R is distributed on the upper side of film F. Station 3 includes, in the example shown, a counter-roller 101 around which the polymer film F is guided. A recessed print roller 103, that is with surface recesses or depressions in which the polymerizable and/or cross-linkable resin is collected cooperates with counter-roller 101. The recesses or depressions are realized according to a preset pattern, as described below, so that resin R is applied to film F according to a corresponding pattern.
Resin R is distributed on roller 103 by a distributor roller 105, which is in surface contact with roller 103, and which picks up the polymerizable and/or cross-linkable resin R from a container, here schematically represented as a tub 109.
Polymer film F passes into the nip between rollers 101 and 103 and on its surface turned towards print roller 103 is applied resin R according to a pattern corresponding to the pattern defined by the recesses or by the depressions in roller 103. The film on which resin R has been distributed is fed to the flocking machine 1.
The flocking machine 1 shown in
As resin R has been distributed on the surface of polymer film F according to a preset pattern, defined by the recesses of print roller 103, fibers 13 anchor on the film according to the same pattern, while the resin-free zones are also free of flocked fibers 13.
In strips or bands 25 or on the surface of the film which is flocked resin R is distributed according to a pattern which can be for example that represented schematically in one of the
In the example of
In
In the example of realization shown schematically in the enlargement of
As indicated in the introduction of this description the pattern according to which the resin is distributed is chosen so that the flocked areas have a sufficiently even distribution of fibers though with an extremely low weight, variable from between 0 and 30 g/m2, or from 0 to 20 g/m2 and preferably from 0 to 15 g/m2 and even more preferably from 0 to 10 g/m2 and even lower than for example to between 0 and 5 g/m2. According to an advantageous embodiment, the fiber is anyhow distributed with a weight greater than 0.5 g/m2 and preferably greater than 1 g/m2.
Distribution of the resin by way of print roller 103 allows to realize on film F, instead of a distribution of the flock fibers 13 according to geometric patterns, also a distribution according to a decorative or ornamental pattern, writing, a logo or other to personalize the product which is obtained from this kind of production.
Resin R can be an expandable resin, which during the passage in the furnace for polymerisation and/or crosslinking (as described below) expands increasing in volume, providing a further tactile feature to the finished product. The latter will have not only superficial flocking but also an effect of superficial irregularity with more or less marked swelling in correspondence of the zones in which resin R has been applied and has subsequently expanded in phase of crosslinking.
Downstream from flocking machine 1 the film is passed into furnace 23, where resin R is crosslinked. The outgoing film is rewound in spool B2.
Film F on spool B1 can be a previously apertured, optionally three-dimensional film, or station 3, flocking machine 1 and furnace 23 can be positioned downstream of a production line section, in which a film F is apertured in continuous. In the latter case production occurs in a single line.
The possibility to aperture the film after flocking is not excluded. Nevertheless this can be problematic as the heat or the pressure applied to the film to cause the aperturing can damage the flocked fibers.
The film can be apertured on the entire surface or apertured in zones, as described in EP-A-0 598 970. If the flocked film is used to produce the back sheet of the absorbent item it is not apertured.
An apertured film flocked according to bands 25,27 as shown in
In this way the plastic surface of film F is in contact with the body of the user only in the central area, while the sides have the layer of flocked fibers and therefore the skin is in contact with the fiber.
If the flock fiber is treated to be hydrophobic, this encourages the outflow of the liquid along the surface of the film towards the central zone, where it passes through the holes of the film and is quickly absorbed by the internal absorbent material. As clearly shown in
The hydrophobic treatment of the flock fiber can be advantageous also in cases where it is distributed on the entire surface or in any case also on the apertured zones of the film. In fact, as the distribution of the fibers according to the invention occurs in a discrete and discontinuous manner, that is in a pattern, with small fiber-free areas alternating with or surrounding the flocked surfaces, i.e. areas with fibers, the hydrophobic quality of the fiber encourages the outflow from the flocked zones to the unflocked zones and therefore fast drainage. For example, if the fibers are distributed in rows, with transversal dimensions of the flocked and unflocked rows in the range of 1-2 mm, the hydrophobic fibers encourage the flow of the liquids in the fiber free zones, which separate adjacent flocked rows.
The treatment to make the fibers hydrophobic generally occurs after the application on film F or other substrate or support, in a purposely provided station in combination with other stations, like a finishing station.
The back sheet 31 of towel 30 does not come into contact with the skin and so can be made in normal polymer film (
The polymer film can be an elastic and/or breathable film, i.e. micro-pierced, of a type known to the experts of the field.
In the schematic example shown in
The same kind of screen printing device can be also be used to perform the application of a cross-linkable resin.
Other kinds of devices for application of the cross-linkable resin and hot melt adhesive or other suitable adhesive are known and can be used as an alternative. For example, in the case of hot melt adhesive this can be distributed according to a pattern when it is still at its solid state, in granules or in powder and later fused when it is already on the substrate. Alternatively relief rollers can be used on whose projections is applied the fused adhesive which is then transferred to substrate F.
| Number | Date | Country | Kind |
|---|---|---|---|
| FI2005A000172 | Aug 2005 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IT06/00590 | 7/28/2006 | WO | 00 | 1/31/2008 |
