Monolithic films having zoned breathability

#The present invention relates to monolithic films. More particularly, the present invention relates to monolithic films having zoned breathability and methods of making the same.

#Various types of garments are presently available for absorbing human discharge. Examples of these garments include baby diapers, feminine care products, incontinence garments and the like. Generally speaking, the basic structure of this class of garments requires an aqueous liquid pervious body-side liner, an absorbent pad containing one or more layers for receiving and absorbing the discharge, and an aqueous liquid impervious backing member for containing the discharge. Such garments usually include a film material that serves as an aqueous liquid impervious outer cover. However, such film material lacks breathability, causing the absorbent garments to be hot and uncomfortable.

#Monolithic films are “breathable” barriers in the sense that the film acts as a barrier to aqueous liquids and particulate matter but allows water vapor and air to pass therethrough. By achieving and maintaining high breathability, it is possible to provide an article that is more comfortable to wear since the migration of water vapor through the fabric helps reduce and/or limit discomfort resulting from excess moisture trapped against the skin. Thus, such an article can potentially contribute to an overall improved skin wellness.

#FIG. 1a is a schematic representation of an exemplary adhesive applicator assembly suitable for use in practicing the present invention and a zone treated monolithic film made therefrom;

#FIG. 1b is a schematic representation of an exemplary adhesive applicator assembly suitable for use in practicing the present invention and a zone treated monolithic film made therefrom;

#FIG. 2a is a plan view of a zone treated monolithic film suitable for use in practicing the present invention;

#Monolithic film is a non-porous film. Rather than holes produced by a physical processing of the monolithic film, the film has passages with cross-sectional sizes on a molecular scale formed by a polymerization process. The passages serve as conduits by which water (or other liquid) molecules can disseminate through the film. Vapor transmission occurs through a monolithic film as a result of a concentration gradient across the monolithic film. This process is referred to as activated diffusion. As water (or other liquid) evaporates on the body side of the film, the concentration of water vapor increases. The water vapor condenses and solubilizes on the surface of the body side of the film. As a liquid, the water molecules dissolve into the film. The water molecules then diffuse through the monolithic film and re-evaporate into the air on the side having a lower water vapor concentration.

#As this is mainly a diffusion-rate limited phenomenon, the water vapor transmission rate (WVTR) is a function of the type of polymer used in the monolithic film and the thickness of the monolithic film. As such, the permeability is selective in monolithic films. Permeability can be increased or decreased by changing the chemical or structural characteristics of the polymers used in the construction of the film.

#A monolithic film provides an absolute barrier to liquids, bacteria, and viruses as no pores are present in the film. However, distortion of the passages within a monolithic structure can cause elongation or deformation enabling viral pathogens to pass through the elongated opening of such passages. The liquid barrier properties of monolithic films are the result of the density of each type of monolithic film which prevents the passage of condensed liquids regardless of the viscosity or surface tension of the liquids. The liquid barrier properties are defined by burst strength, tensile properties, and abrasion resistance of each type of monolithic film as no liquid flow is possible unless the film ruptures.