Patent Application
20050198931
The prior art teaches numerous variations of and elements in addition to the basic absorbent core, topsheet and backsheet arrangement, with each variation or additional element being directed to improving a specific characteristic of the disposable absorbent article.
While there are a great many variations in the specific structural features of disposable absorbent articles, they are frequently presented to the consumer in the same manner. Essentially, the disposable absorbent article, irrespective of what specific structural features are used, is packaged in a box or bag from which the consumer withdraws the article as needed.
The problem of protecting the disposable absorbent article once it is removed from the package in which it is sold has been addressed in the prior art. Catamenial pads, for example, are commonly packaged individually and sold to the consumer in some sort of container, typically a bag or box, which holds a convenient number of the individually packaged articles. For example, in patent application WO 94/14396, entitled Fold and Wrap Package for Catamenial Pads Providing Convenient Disposal Means, an individual package for a catamenial pad is disclosed which provides containment prior to use and also convenient disposal of a soiled catamenial pad after use. The individual package comprises a wrapper configured to have a pouch and a closure flap. The pouch is designed so that an unused catamenial pad may be disposed within the pouch, typically in folded configuration, with the flap being positioned over the mouth of the pouch, and frangibly bonded thereto e.g. with an adhesive tape tab in order to close the pouch prior to use. The package is used by peeling the flap away from the pouch by breaking the frangible bonds between the flap and the pouch, removing the unused catamenial pad from the pouch, and finally completely opening the pouch such that the package is a flat wrapper. A soiled catamenial pad can be then secured to the flat wrapper typically by means of its panty fastening adhesive, the catamenial pad and the wrapper arranged into a disposal configuration, typically rolled and folded on themselves, and finally secured in this configuration by securing the adhesive tape tab to another portion of the wrapper.
U.S. Pat. No. 4,556,146 entitled Individually Packaged Disposable Absorbent Article discloses a disposable absorbent article, such as a catamenial pad, associated with a wrapper which overlays one major surface of the catamenial pad, and is releasably attached thereto, typically by means of the catamenial pad panty fastening adhesive. The wrapper is larger than the external perimeter of the disposable absorbent article, so that when the disposable absorbent article and the wrapper are folded as a unit, typically around two fold-axes, the respective longitudinal side flaps of the wrapper may be frangibly sealed together along common longitudinal edges, thereby providing the disposable absorbent article with an individual package. Preferably, the disposable absorbent article is releasably attached directly to the wrapper by means of its panty fastening adhesive element, thereby eliminating the need to provide a release paper.
Typically the panty fastening adhesive, as disclosed in U.S. Pat. No. 4,556,146, is provided as a coating of a known pressure sensitive adhesive in strips or other suitable patterns, such as for example as a single strip oriented longitudinally and substantially covering the centre of the catamenial pad backsheet.
From a process point of view, the adhesive coating can be actually applied to the release paper, and then transferred to the backsheet of the disposable absorbent article by joining the release paper in the desired position to the backsheet, before formation of the individual package, which can be performed either according to WO 94/14396, or according to U.S. Pat. No. 4,556,146, both documents as mentioned above. In the latter case, the release paper has to be permanently attached to the wrapper material before formation of the individual package. Alternatively, direct application of the adhesive coating onto the backsheet in the desired pattern can be provided, with subsequent joining of the absorbent article to the wrapper material, which eliminates the need of a separate release paper, simplifies the process and saves material. This method is particularly suitable for the individually packaged disposable absorbent article according to U.S. Pat. No. 4,556,146.
Direct adhesive application onto the backsheet usually occurs onto a continuous web-like layered structure from which the individual absorbent articles are subsequently formed by cutting them from said structure along a respective desired outer perimeter. The layered structure can already comprise all the elements, namely layers, which eventually form the disposable absorbent article, or some further elements can be added in a subsequent step after the cutting step.
It has been discovered that in disposable absorbent articles, particularly of the thin type such as thin sanitary napkins and pantiliners, the coverage of the panty fastening adhesive onto the backsheet should be preferably extended substantially to the whole surface of the backsheet intended to get in contact with the undergarment in use, or at least to portions of the outer perimeter of the article, preferably those portions extending along the longitudinal edges of the disposable absorbent article. This is advantageous in terms of stability during use of the article, which in turn is capable of staying in place in the crotch area of the undergarment, where it has been applied by the user, more effectively withstanding the stresses and tensions induced by the user's movements.
However in an individually packaged disposable absorbent article, namely a catamenial pad or pantiliner, the preferred features of a panty fastening adhesive coverage at least partially extending up to the outer perimeter of the absorbent article, and the absence of the release paper, constitute in combination two contrasting, and so far antithetical needs from a process point of view. On one hand in fact the absence of a release paper necessarily implies direct adhesive coating onto the backsheet. On the other hand, according to the known technique, a patterned coating of adhesive which is exactly registered with at least part of the outer perimeter of a disposable absorbent article is not practically feasible, either when the coating is applied before or when is applied after the single disposable absorbent article has been formed from a continuous web-like structure by cutting it along the desired outer perimeter. The only theoretical alternative is to apply the adhesive coating to the continuous web-like structure in such a way that it overlaps the portions of the outer perimeter of the disposable absorbent articles along which the adhesive is meant to arrive, and that the subsequent cutting operation in order to form and separate the individual articles occurs directly through the adhesive layer. As it is known in the art, this leads to adhesive sticking to the knife implement, with obvious problems of adhesive build up on the knife and unreliability of the process.
It has been surprisingly discovered that the problem of providing in a reliable and simple way individually wrapped disposable absorbent articles where each article is releasably attached to the wrapper element without the need of a release paper, and moreover where the panty fastening adhesive extends along at least part of the outer perimeter of each individual disposable absorbent article, can be solved by combining in a process for providing release paper-free, individually wrapped disposable absorbent articles, the direct application of the adhesive for panty fastening onto the backsheet layer in a continuous web-like layered structure from which the individual disposable absorbent articles are to be formed, and the cutting of the individual disposable absorbent articles from the continuous web-like layered structure at least partially through the adhesive layer, at least along the portions of the outer perimeter where the adhesive must be present. Direct cut through the adhesive layer without adhesive sticking and build up on the cutting implement is done by applying the technique of cutting with a knife which is internally cooled.
According to the present invention, a method and an apparatus are described for providing individually wrapped, release paper-free disposable absorbent articles having the panty fastening adhesive extending along at least part of the respective outer perimeter.
The present invention relates to a process for manufacturing individually packaged disposable absorbent articles comprising the steps of:
The present invention also relates to an apparatus for performing the process above, comprising a cutting implement for the cutting of the individual disposable absorbent articles from the continuous web-like layered structure, which comprises at least one knife which is internally cooled.
The present invention refers to a process and to an apparatus for providing individually packaged disposable absorbent articles. As used herein the term “absorbent article” refers to those articles intended to absorb and retain liquid and in particular those articles which are placed against or in proximity to a wearer's body to absorb and contain the various liquids discharged from the body, e.g. perspiration, blood, menses, urine, vaginal secretions and the like. A “disposable absorbent article” is an absorbent article which is intended to be discarded after a single use, i.e. which is not intended to be laundered or otherwise restored and reused. Particularly, the disposable absorbent article is described below by reference to a sanitary napkin or pantiliner.
As shown in
In order to more fully assess the utility of the process and apparatus of the present invention a description of a typical disposable absorbent article follows.
Topsheet
The topsheet is compliant, soft feeling, and non-irritating to the wearer's skin. Useful topsheets are well known in the art and may be manufactured from either hydrophobic or hydrophilic fibres and may, for example, be cared, spun bonded, melt blown, or air laid. Alternatively, the topsheet may be a continuous film or sheet of, for example, thermoplastic material which is apertured. When referring to the topsheet a multi layer structure or a monolayer structure is contemplated.
Absorbent Structure
When referring to the absorbent structure a multi layer structure or a mono layer structure are contemplated. Useful absorbent structures are well-known in the art and may be manufactured from a wide variety of materials which are capable of absorbing and retaining liquids. For example, a batt of absorbent fibres, a multiplicity of plies of creped cellulose wadding, or any equivalent material may be used. Known absorbent gelling materials are also typically comprised in the absorbent structure. The absorbent capacity of the material used must be sufficient to absorb and retain the expected liquid loading in the intended use of the article without undue bulk. In a preferred embodiment the absorbent structure is a thin layered structure comprising two or more fibrous layers and particles of absorbent gelling materials comprised therebetween.
Backsheet
The backsheet primarily prevents the exudates absorbed and contained in the absorbent structure from wetting articles that contact the absorbent product such as underpants, pants, pajamas and undergarments. The backsheet may be manufactured from any flexible, liquid impermeable material which is non irritating to the wearer. Typically, the backsheet is a sheet of polyethylene film. Preferably the backsheet is also water vapour or gas permeable. When referring to the backsheet a multi layer structure or a mono layer structure is contemplated.
The Panty-Fastening Adhesive
The backsheet typically forms the garment-facing surface of the absorbent article on which the panty fastening adhesive is placed. Panty-fastening adhesives can comprise any adhesive or glue used in the art for such purposes. These adhesives typically are pressure sensitive and remain tacky well below their application temperature. Suitable adhesives are for example Savare LA203 and Savare LA303 made by Savare I.C. of Milan in Italy, Coramelt 867 by Koemmerling in Pirmasens in Germany, Fuller D3964ZP and Fuller H-2238ZP manufactured by the H.B. Fuller Co. in Lueneburg, in Germany, NS34-2823 as manufactured by National Starch and Chemical of Bridgewater, N.J.
In accordance with the teaching of this invention, and with specific reference to
The continuous web-like layered structure 34 of
An adhesive application unit 36 applies a layer of pressure sensitive adhesive 38 in a preferably continuous stripe onto the liquid impervious outer layer 14 of the continuous web-like layered structure 34. Typically the adhesive application unit 30 is a hot melt coating unit, for example preferably a known bar coating apparatus, for the application of a layer of the preferred hot melt pressure sensitive adhesive onto the liquid impervious outer layer 14 in the desired thickness. Alternatively other known methods of adhesive application can be used, for example non-contact methods such as hot melt spraying. According to a preferred embodiment of the present invention, the pressure sensitive adhesive 38 is applied in a continuous stripe which is slightly narrower than the continuous web-like layered structure 34, as indicated in
The continuous web-like layered structure 34 with the layer of pressure sensitive adhesive 38 applied thereon is conveyed to the cutting unit 44 comprising a cutting implement with at least one knife. Typically, as illustrated in
The trimmed material 52, 52′ resulting from the cutting step is then withdrawn and disposed of after cut. Typically, as shown in
For example, if the individual disposable absorbent articles are not cut from the continuous web-like layered structure 34 being adjacent to one another, but instead with a small gap between each pair of subsequent articles, the amount of trimmed material will be slightly increased, but it will consist in a continuous, ladder-shaped element which can be easily withdrawn altogether from the cutting unit 44 and suitably disposed of, without the need of a separate device, e.g. a vacuum system, for withdrawal of the discrete trim material elements 52′ as shown in
After the cutting step, the continuous layer of pressure sensitive adhesive 38 provides the adhesive elements 24 on the backsheet layer 14 of the individual disposable absorbent articles 10 cut from the continuous web-like layered structure 34. The adhesive element 24 extends along substantially the entire length of the longitudinal perimeter segments 20, as shown in
A distinct system, typically a vacuum system as well, is also provided in the counter roll 48 in order to keep after the cutting step the newly formed individual disposable absorbent articles 10 onto the outer surface of the counter roll 48 until they are transferred onto a continuous band of wrapper material 54 and releasably adhered thereto by means of the respective adhesive elements 24 at a coupling unit 56 comprising a pressing roll or bump roll 58 which presses the individual disposable absorbent articles 10 onto the wrapper material 54. The bump roll 58 can be pitched, as shown in
As it is known in the art, the speed of the band of wrapper material 54, registered with the peripheral speed of the bump roll 58, can be suitably selected and is typically higher than the peripheral speed of the counter roll 48, such that subsequent individual disposable absorbent articles 10 are coupled with the desired spacing (pitch) onto the band of wrapper material 54.
The band of wrapper material 54 with attached individual disposable absorbent articles 10 subsequently proceeds to folding/cutting/sealing units, not illustrated in
According to a preferred embodiment of the present invention, the counter roll 48 of the cutting unit 44 can also be cooled to prevent possible adhesive buildup onto the counter roll as well. The cooling of the knife, typically of the entire knife roll 46, and of the counter roll 48 can be achieved with known means, for example by means of circulation of a known cooling fluid, such as a water-glycol solution. Typically, and preferably, the whole knife roll 46, and optionally the whole counter roll 48 are uniformly cooled, although it is also possible that only selected portions of the rolls are cooled, for example the knives in the knife roll 46, or the areas corresponding to the individual disposable absorbent articles in the counter roll 48.
Actual temperatures at which the knife roll 46 and optionally the counter roll 48 shall be cooled can depend on the environmental conditions at which the cutting step occurs. Typically the room temperature is between 20° C. and 30° C., preferably at about 25° C. The relative humidity is at least 40%, preferably between 40% and 60%, more preferably between 45% and 55%, most preferably about 50%. In such typical preferred process conditions, the temperature of the knife roll 46 is preferably kept between 0° C. and 6° C., more preferably between 2° C. and 4° C., most preferably at about 3° C. When the counter roll 48 is also preferably cooled, its temperature is kept between 5° C. and 20° C., preferably between 7° C. and 15° C., more preferably at about 10° C. It is particularly preferred, in order to prevent or limit formation of water condensate on areas of the counter roll 48 contacting the individual disposable absorbent articles 10 during their transport to the coupling unit 56, that the temperature of the counter roll, preferably also cooled as described above, be kept lower than the temperature of the knife roll 46, with a difference (ΔT) between 2° C. and 20° C., preferably between 5° C. and 10° C.
In a particularly preferred embodiment of the present invention, with typical room conditions of 24° C. and 50% relative humidity, the temperature of the knife roll 46 is about 3° C., and the temperature of the counter roll 48 is about 10° C., with a difference ΔT of about 7° C.
According to a further preferred embodiment of the present invention, the areas 60 of the knife roll 46 comprised within the perimeters defined by each knife 50 can be recessed with respect to the outer surface of the knife roll 46, in order to avoid accidental contact of the roll in said areas 60 with the adhesive 38, and to further reduce the risk of jamming of the apparatus, especially at the high speed which is typical of this type of processes. The depth of these recessed areas is preferably constant, and can be suitably tailored according to the thickness of the formed individual disposable absorbent articles 10, as can be readily determined by the skilled man.
The method and the apparatus of the present invention has been so far described in the arrangement where the individual disposable absorbent articles are cut from the continuous web-like layered structure 34 oriented in cross direction (CD), i.e. with the respective longitudinal axes perpendicular to the direction of travel of the web structure. Alternatively, the individual disposable absorbent articles can also be cut from the continuous web-like layered structure arranged in a machine direction (MD) orientation, and the respective changes and adjustments in the process and in the apparatus are readily at hand of the skilled man.
The adhesive layer applied in a preferably continuous stripe can have any preferred width or pattern, with a constant of variable basis weight. Preferably the application is in a continuous stripe having constant width and constant basis weight, as illustrated in the appended drawings. Preferred application method is hot melt bar coating, also known as slot coating. The adhesive layer can be applied preferably with a basis weight from 10 g/m2 to 40 g/m2, more preferably from 15 g/m2 and 30 g/m2, even more preferably from 20 g/m2 and 25 g/m2.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04005733.3 | Mar 2004 | EP | regional |
