Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Reexamination Certificate
1997-05-02
2001-06-05
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
C428S138000, C428S297700, C428S297400
Reexamination Certificate
active
06242074
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for melt bonding fibers onto formed films to achieve a cloth-like texture. The resulting product is useful in a disposable product, for example, as topsheets in diapers and hygiene products.
BACKGROUND OF THE INVENTION
Absorbent articles such as sanitary napkins, incontinent devices, diapers, wound dressings and other products are well known. These articles absorb liquid and retain the liquid within a core. The interior or topsheet of the absorbent article is made of a flexible plastic film material. Many attempts have been made to overcome the negative characteristics of the glossy or “plastic” look and sticky tactile feel to the plastic films. It is therefore desirable to produce absorbent devices which have a cloth-like look and feel to a user's skin.
Many types of films have been proposed to overcome these tactile problems, including the use of microapertured polymeric webs. Various types of formed or perforated films and processes for making formed films are disclosed in: U.S. Pat. Nos. 3,871,378; 3,929,135; 4,041,951; 4,259,286; 4,323,069; 4,324,246; 4,327,730; 4,342,314; 4,351,784; 4,463,045; 4,508,256; 4,541,794; 4,552,709; 4,629,643; 4,741,877; 4,772,444; 4,878,825; 5,158,819 and Des. 268,962 which depict a variety of absorbent articles using cell shapes and surface texturing or aperturing techniques aimed at providing a film having the desired aesthetic characteristics.
While these films allow fluid passage therethrough, there is a considerable top surface area which does not allow passage of fluid through the film onto an absorbent core below. Thus, the areas of film between the apertures still adhere to the wearer's skin, especially when there is liquid present. This adherence also results in a sticky or plastic perception against the wearer's skin.
Another attempt to overcome the disadvantages of plastic films involves the use of flocked films, where adhesives are used to bond fibrils and/or fibers to a plastic film. However, the application and handling of the adhesive material onto a formed perforated film has many disadvantages. It is difficult to uniformly apply the adhesive to the formed film layer such that the fibers adequately adhere to the film. The fibers tend to rub off and produce “lint” on the wearer. Further, the adhesive materials, whether aqueous or solvent-based, bring additional chemicals into direct contact with the wearer's skin. These adhesives sometimes result in allergic and/or sensitive reactions, such as diaper rash. In addition, the environmental concerns of handling, application and recovery of the volatile materials in the adhesive materials must be addressed.
Another attempt to overcome the disadvantages of plastic films involved a process wherein thick layers of fibers are laminated to plastic films by pulling the fibrous webs under tension, for example, U.S. Pat. No.4,995,930 and German DE 40-16-348-A1. However, these processes have drawbacks in that only thick layers of fibrous material can withstand the applied tension and maintain their web integrity while being laminated to a plastic film. However, in many end uses it is undesirable to have thick layers of fibers on the plastic film. Thick layers of fibrous webs will retard the flow rate of fluid into the absorptive device. They will also, by their dense mass of fibers, retain fluids within themselves by capillary retention. This will yield a sensation of wetness to the user. Both of these negative attributes of prior art are overcome by the present invention.
Accordingly, it is one object of the present invention to provide a formed film having a thin layer of fibers adhered thereto, which film has an aesthetically desirable cloth-like look and tactile feel.
It is another object of the present invention to provide a cloth-like three-dimensional fibrous coated polymeric material which does not produce perceptible noise typically associated with plastics when worn by a user.
Another object of the present invention is to provide a three-dimensional fibrous coated polymeric material which is suitable for use disposable absorbent product, such as diapers, catamenial pads and adult incontinent products and wound dressings.
Another object of the present invention is to provide a method and apparatus for producing three-dimensional polymeric webs coated with a fibrous material that is so light and thin that it cannot maintain its own integrity under tension.
DISCLOSURE OF THE INVENTION
The present invention relates to surface-modified perforated or formed polymeric films, wherein a fibrous material is applied to a formed or three-dimensional polymeric film without the use of adhesive materials. The fibrous material can comprise loose fibers, fibrous webs, woven or non-woven materials. In one embodiment, a thin layer of the fibrous material is melt bonded to a top surface of the molten or semi-molten film material at a point in time prior to forming the three-dimensional structure of the film.
The fibrous coated film of the present invention combines the advantages of increased fluid acquisition and dryness, as well as the cloth-like surface feel of cloth or non-woven materials. The resulting surface-modified formed film has a suede or cloth-like texture and surprisingly provides increased fluid acquisition to a product incorporating such formed film. The film of the present invention is especially useful as an absorbent product topsheet material.
The use of hydrophobic fibers results in a soft feel and a dull, fibrous look without capillary wetting at the liquid acquisition surface of the fibrous coated formed film. The fibrous surface on the formed film can be achieved using one or a combination of fiber transfer processes, including fiber air laying, fiber carding, melt blowing, fiber dusting, flocking or a spun bond process.
According to the present invention, a predetermined amount of a fibrous material is introduced onto a top surface of a film material just prior to or directly at the point of forming the three-dimensional structure of the film. In preferred embodiments, the film is formed into a three-dimensional structure using a vacuum or pressure differential process. The fibrous material covers a predetermined area of the film surface and embeds or fuses onto the top surface of the film. One embodiment of the present invention uses an air-layed or carding process such that the fibrous material is transferred to the surface of the film by a conveyor belt system. Another embodiment uses a melt blown process such that the fibrous material is directly applied to a top surface of the film at the point in time prior to the formation of the three-dimensional structure of the film.
The fibrous material can comprise either loose fibers or lightweight webs of fibrous material. One advantage of the present invention is that a uniformly thin layer of fibrous material can be applied to a film during the film making process. Until the present invention, it has not been possible to supply a thin layer of fibrous material under low to minimal tension (and in certain embodiments, at near zero tension) onto a film being formed. In particular, attempts to supply lightweight webs onto films were unsuccessful since the lightweight fibrous webs break under tension and lose their web integrity. Until the present invention, it has not been possible to simultaneously supply a lightweight fibrous material onto a film during a process for making a formed or three-dimensional film.
The lightweight material is supplied under zero or near zero tension applied to the fibrous material. There are sufficient forces present to keep a continuous supply of fibrous material being continuously applied onto the film material. These forces are such that the integrity of the fibrous material is not destroyed during the application of the lightweight fibrous material onto the film.
The resulting film has the aesthetic appeal of cloth-like fabrics. Further, the film has the dryness aspect of three-dimensional formed films and allows ready f
Cole Elizabeth M.
Jenkens & Gilchrist PC
Tredegar Film Products Corporation
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