Method of making molded cellulosic webs for use in absorbent articles

Abstract

Methods are disclosed for producing absorbent articles comprising molded airlaid webs and other molded fibrous webs. The molded webs can offer improved body fit and/or improved fluid handling. Molded airlaid webs, for example, can be formed having a central longitudinal hump and flexure zones longitudinally removed from the central hump to provide good contact with the body and improved fit when the article is squeezed from the sides. Molding can be achieved when a binder material is activated by an energy source and the web is held against a molding substrate. Energy sources can include microwaves, heated air, heated metal surfaces, ultraviolet radiation, ultrasonic energy, and the like.

We claim:  
     
         1 . A method of preparing an absorbent article, the method comprising: 
 providing an absorbent web comprising cellulosic fibers and binder material selected from at least one of a solid, an emulsion, a slurry, a dispersion, and a liquid;    applying radiofrequency energy to the binder material to activate the binder material;    reducing application of radiofrequency energy to the binder material;    deforming the absorbent web against a molding surface before the binder material becomes solidified to impart a three-dimensional shape to the absorbent web;    disposing the absorbent web above a backsheet;    disposing a topsheet above the absorbent web; and    attaching the topsheet to the backsheet.    
     
     
         2 . The method of  Claim 1 , wherein the binder material comprises one of a thermosetting material, a thermoplastic material, and combinations thereof.  
     
     
         3 . The method of  Claim 2 , wherein the binder material comprises a bicomponent fiber.  
     
     
         4 . The method of  Claim 1 , wherein the binder material comprises a latex.  
     
     
         5 . The method of  Claim 4 , wherein the binder material either is non-crosslinking or comprises a crosslinking inhibitor.  
     
     
         6 . The method of  Claim 1 , wherein the radiofrequency energy is microwave energy applied within a tunable microwave resonance chamber.  
     
     
         7 . The method of  Claim 6 , wherein the microwave energy is provided in the resonance chamber in a TM 010  or TM 020  mode.  
     
     
         8 . The method of  Claim 1 , wherein the binder material includes a water-soluble, non-colloidal, cationic thermosetting material.  
     
     
         9 . The method of  Claim 1 , further comprising adding moisture to the web prior to application of the radiofrequency energy.  
     
     
         10 . The method of  Claim 1 , wherein the maximum temperature of the web does not exceed 140° C. during activation of the binder.  
     
     
         11 . A method of making a molded absorbent web in an automated machine, the method comprising: 
 providing an absorbent web including cellulosic fibers and a binder material;    conveying the absorbent web into an automated molding device including a molding substrate;    heating the binder material in the absorbent web by applying radiofrequency energy;    deforming the absorbent web against the molding substrate to impose a shape to the absorbent web;    cooling the binder material; and    removing the web from the molding substrate;    wherein the shape imposed by the molding substrate is maintained by the binder material.    
     
     
         12 . The method of  Claim 11 , wherein the radiofrequency energy comprises microwaves and the binder material is microwave-sensitive.  
     
     
         13 . The method of  Claim 12 , wherein heating the binder material comprises passing the web through a microwave resonance chamber.  
     
     
         14 . The method of  Claim 11 , wherein the absorbent web additionally includes a microwave-sensitive component.  
     
     
         15 . The method of  Claim 14 , wherein the microwave-sensitive component is selected from a group consisting of water, an ionic aqueous solution, microwave-sensitive polymers, and combinations thereof.  
     
     
         16 . The method of  Claim 11 , wherein the binder material includes a dielectric loss constant substantially greater than that of cellulose.  
     
     
         17 . The method of  Claim 11 , wherein the binder material comprises a bicomponent fiber including a microwave-sensitive core component.  
     
     
         18 . The method of  Claim 11 , wherein the binder material comprises one of a thermosetting material, a thermoplastic material, and combinations thereof.  
     
     
         19 . The method of  Claim 12 , wherein heating the binder material and deforming the absorbent web occur simultaneously.  
     
     
         20 . The method of  Claim 19 , wherein the molding substrate comprises a microwave-transparent solid material.  
     
     
         21 . The method of  Claim 11 , wherein heating the binder material occurs prior to deforming the absorbent web.  
     
     
         22  The method of  Claim 11 , wherein the shape of the absorbent web imposed by the molding substrate comprises a central hump.  
     
     
         23 . The method of  Claim 11 , additionally comprising deforming the absorbent web against the molding substrate to impose to the absorbent web a three-dimensional shape having an overall surface depth of at least 2 mm.  
     
     
         24 . The method of  claim 11 , additionally comprising cutting the absorbent web before or after deforming the absorbent web to form more than one discrete absorbent web section.