Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1998-06-25
2001-05-15
Lewis, Aaron J. (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S385010, C604S385230, C604S385101, C604S358000
Reexamination Certificate
active
06232521
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to absorbent article in particular sanitary napkins having a breathable backsheet which exhibit reduced wet through onto the users garments.
BACKGROUND OF THE INVENTION
The primary consumer needs which underlie development in the absorbent article field, in particular catamenials is a high protection and comfort level.
One highly desirable means of improving the comfort of absorbent articles is the use of so called ‘breathable backsheets’. Breathable backsheets may comprise an apertured formed film having directional fluid transfer as disclosed in for example U.S. Pat. No. 4,591,523. Such apertured breathable backsheets are typically vapour and air permeable allowing gaseous exchange with the environment. This thereby allows for the evaporation of a portion of the fluid stored in the core and increases the circulation of air within the absorbent article. This is particularly beneficial as it reduces the sticky feeling experienced by many wearers during use, particularly over extended periods of time.
However, the main drawback associated with the use of breathable backsheets in absorbent article is the increased probability of leakage, commonly referred to as wet through onto the users garment. Although such breathable backsheets in principle only allow the transfer of materials in the gaseous state and only one directional fluid transfer, physical mechanisms such as extrusion, diffusion and capillary action may still occur and result in the transfer of the fluids in the opposing direction through the backsheet and onto the users garments. In particular, these mechanisms become more dominant if the product is utilised during physical exertion, for heavy discharge loads or over extended periods of time. In effect, while breathable backsheets provide excellent comfort improvements they result in an unacceptable level of failure with regard to protection, especially under stressed conditions.
The problem of wet through onto users garments due to the incorporation of such breathable backsheets in absorbent articles has been recognized in the art. Attempts to solve the problem have mainly resided in the use of multiple layer backsheets such as those illustrated in U.S. Pat. No. 4,341,216. Similarly unpublished European patent application no. 94203230 discloses breathable absorbent articles comprising a breathable backsheet consisting of at least two breathable layers which are unattached to one another over the core area. Also unpublished European patent application no. 94203228 discloses a breathable backsheet for disposable absorbent articles comprising an outer layer of a gas permeable, hydrophobic, polymeric fibrous fabric and an inner layer comprising an apertured formed film having directional fluid transport.
Alternatively, another proposed solution to the problem has been to increase the thickness of the absorbent articles, which is usually achieved by increasing the core thickness in order to ensure the desired protection level.
However, none of the above solutions have proved fully satisfactory. This is particularly the case for thin products, as thickness is also considered as a key variable affecting product comfort. Thus, there exists a dichotomy in the methods available to provide increased comfort absorbent products, such that thin breathable products cannot provide the desired level of protection.
As a result, there exists a need to provide an absorbent article which offers improved comfort by the employment of a breathable backsheet and having a reduced thickness which maintains the required level of protection.
It has now been found that breathable backsheets may be utilised in thin sanitary napkins, thereby providing both a high level of protection and comfort by creating a hydrophobicity gradient between the backsheet and the core, achieved by the utilisation of a low surface energy material such as silicone and chlorofluorocarbons or a low surface energy treatment. In this manner it is believed that the physical mechanisms such as diffusion and capillary action are hindered and wet through is considerably reduced if not completely eliminated
A further advantage of the present invention is that, since it allows to provide breathable backsheets coated with the hydrophobic material, it is no longer necessary that this layer be entirely synthetic and it may be at least partially naturally derived. This provides an important consumer noticeable benefit as the product imparts a more natural feel to the touch.
The use of surface energy gradients as such is discussed in unpublished U.S. application Ser. No. 08/442,935. It discloses fluid transport webs, e.g. topsheets, which exhibit surface energy gradients. The web facilitates fluid transport in one direction and resists transport in the opposite direction. The web comprises first and second surfaces, which are separated from one another by an intermediate portion. The first surface of the web has a lower surface energy than the surface energy of the intermediate, thereby creating a surface energy gradient. Suitable low surface energy materials include silicone, fluoropolymers and paraffins. The web is particularly suited as a topsheet for absorbent articles in order to transport fluid away from the wearer-contacting surface into the absorbent structure.
SUMMARY OF THE INVENTION
The first aspect of the present invention relates to a disposable absorbent article comprising, a liquid pervious topsheet, an absorbent core and a backsheet. The core is intermediate the topsheet and the backsheet. The backsheet comprises a liquid permeable polymeric film having uni-directional fluid transfer towards the core, and the core comprises a fluid storage layer and the backsheet comprises an outer layer. The core and the backsheet each comprise at least one layer, wherein each layer has a wearer facing surface and a garment facing surface and each surface of these layers has a fluid contact angle. The absorbent article has a lower portion extending from and including the garment facing surface of the fluid storage layer to and including the garment facing surface of the outer layer. The present invention is characterized in that the wearer facing surface of at least one of the layers in the lower portion has a fluid contact angle greater than the fluid contact angle of the adjacent garment facing surface of an adjacent layer.
A second aspect of the present invention relates to the situation wherein the garment facing surface of at least one of the layers in the lower portion has a fluid contact angle greater than the fluid contact angle of the wearer facing surface of the same layer.
A further aspect of the present invention relates to a process for the production of an absorbent article described above comprising the step of applying a low surface energy material to the surface of at least one of the layers in the lower portion.
Another aspect of the present invention relates to a process for the production of an absorbent article described above comprising the step of incorporating a low surface energy material within one of the layers in the lower portion.
REFERENCES:
patent: 3881489 (1975-05-01), Hartwell
patent: 4591523 (1986-05-01), Thompson
patent: 4704107 (1987-11-01), Coates
patent: 4842596 (1989-06-01), Kielpikowski et al.
patent: 5006187 (1991-04-01), Cook et al.
patent: 5334177 (1994-08-01), Cohen
patent: 5525407 (1996-06-01), Yang
patent: 5603707 (1997-02-01), Trombetta et al.
patent: 5643239 (1997-07-01), Bodford et al.
patent: 5762643 (1998-06-01), Ray et al.
patent: 5830555 (1998-11-01), Srinivasan et al.
patent: 5928209 (1999-07-01), Bodford et al.
patent: 5990376 (1999-11-01), Inoue et al.
patent: B1 6177607 (2001-01-01), Blaney et al.
Bewick-Sonntag Christopher Philip
Divo Michael
Veglio Paolo
Bogart Michael
Cummings Theodore P.
Fitzpatrick Matthew P.
Johnson Kevin C.
Lewis Aaron J.
LandOfFree
Absorbent articles having fluid contact angle gradients does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Absorbent articles having fluid contact angle gradients, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Absorbent articles having fluid contact angle gradients will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2551073