Disposable underpants and method of continuously producing the same

Abstract

Disposable underpants 1 according to the invention has an improved sealability at the crotch of user by providing a fitting elastic member 55 and has an absorbent core 7 having an improved shape retention by providing a first nonwoven fabric 73 as an intermediate layer inside the absorbent core 7 and adhering it to the upper and lower layers thereof. Since the absorbent core needs not be heated, inexpensive disposable underpants can be produced. Further, according to an inventive production method, a step of adhering elastic members to an outer sheet 2 and a step of producing inner absorbent members 6 are separately performed, and no heating treatment is performed in the absorbent core production step. Accordingly, the disposable underpants can be produced at a remarkably higher speed.

What is claimed is:  
     
         1 . Disposable underpants having one waist-opening and a pair of leg-openings, having elastic members provided near the edges of the waist- and leg-openings and having the opposite sides thereof bonded, comprising: 
 an outer sheet and an inner absorbent member, wherein:    the outer sheet is provided with a waist elastic member, leg elastic members and a fitting elastic member provided between the waist elastic member and the leg elastic members, the fitting elastic member being comprised of a plurality of thread-like elastic materials in parallel with the waist elastic member,    the inner absorbent member includes a permeable top sheet, an impermeable back sheet and an absorbent core accommodated between the top and back sheets, and    the absorbent core includes an upper layer made of a mixture of pulp fibers and super absorbent polymer particles, an intermediate layer provided with a first nonwoven fabric, and a lower layer made of a mixture of pulp fibers and super absorbent polymer particles, the intermediate layers being adhered to the upper and lower layers by an adhesive.    
     
     
         2 . Disposable underpants according to  claim 1 , wherein the absorbent core further includes a second nonwoven fabric located below the lower layer thereof, and a tissue located above the upper layer thereof, the second nonwoven fabric being adhered to the lower layer and a portion of the second nonwoven fabric projecting out from the outer periphery of the lower layer is turned up onto the lower layer and adhered while being placed to the first nonwoven fabric.  
     
     
         3 . Disposable underpants according to  claim 2 , wherein the upper layer of the absorbent core is formed larger than the lower layer thereof, the upper layer is formed to have a substantially sandglass-shape having narrowed portions at the left and right sides of a middle portion with respect to its longitudinal direction in its plan view while the lower layer is formed to have a rectangular shape in its plan view, and the upper and lower layers are laid such that a center line of the upper layer with respect to its widthwise direction and that of the lower layer correspond with each other.  
     
     
         4 . Disposable underpants according to  claim 2 , wherein the first nonwoven fabric of the intermediate layer of the adhesive unapplied portion, and the adhesive applied portion forms an aggregate of a multitude of lines.  
     
     
         5 . Disposable underpants according to  claim 2 , wherein the outer sheet includes an outermost nonwoven fabric and an inner nonwoven fabric, and at least the leg elastic members and the fitting elastic member are provided between these two nonwoven fabrics.  
     
     
         6 . Disposable underpants according to  claim 5 , wherein the waist elastic member is provided between a turned portion formed by turning the outermost nonwoven fabric onto the inner nonwoven fabric at the waist-opening edge and the inner nonwoven fabric.  
     
     
         7 . Disposable underpants according to  claim 1 , wherein the fitting elastic member is provided more toward the waistopening edge than a longitudinal end of the absorbent core of the inner absorbent member, so that the fitting elastic member and the absorbent core do not overlap.  
     
     
         8 . Disposable underpants according to  claim 1 , wherein the fitting elastic member partly overlaps the absorbent .core of the inner absorbent member, a portion thereof located in the overlapping portion being provided in non-stretched state so as not to contract.  
     
     
         9 . Disposable underpants according to  claim 1 , wherein the stretching force of the fitting elastic member differs in the front and rear parts of the disposable underpants.  
     
     
         10 . Disposable underpants according to  claim 1 , wherein each leg elastic member is made of a plurality of thread-like elastic materials, that thread-like elastic materials are, at the front part of the disposal underpants, comprised of left and right side portions extending along the leg-opening edges of the front part of disposable underpants and connecting portions connecting the leading ends of the side portions, thereby forming substantially U-shaped lines, while being, at the rear part of the disposable underpants, likewise comprised of left and right side portions extending along the leg-opening edges of rear part of the disposable underpants and connecting portions connecting the leading ends of the side portions, thereby forming substantially u-shaped lines, and the connecting portions of the front and rear lines do not intersect with each other at the crotch of the disposable underpants.  
     
     
         11 . Disposable underpants according to  claim 10 , wherein the spacing between the respective thread-like elastic materials of each leg elastic member is narrowest at intermediate positions between the side ends of the side portions and the middle of the connecting portions and gradually widens toward the side ends of the side portions and toward the middle of the connecting portions.  
     
     
         12 . Disposable underpants according to  claim 10 , wherein the stretching force of the thread-like elastic materials of the leg elastic members are weakest at intermediate positions between the side ends of the side portions and the middle of the connecting portions and gradually becomes stronger toward the side ends of the side portions and toward the middle of the connecting portions.  
     
     
         13 . Disposable underpants according to  claim 1 , wherein the left and right side ends of the impermeable back sheet of the inner absorbent member are turned up onto the upper surface of the permeable top sheet, and raised gathers made of a nonwoven fabric and provided with a stretchable member are adhered onto the upper surfaces of the turned portions.  
     
     
         14 . Disposable underpants according to  claim 1 , wherein the left and right sides of the disposable underpants are bonded by putting the outer sheet together and applying heating to melt it.  
     
     
         15 . A method for continuously producing disposable underpants according to  claim 1 , comprises the steps of: 
 adhering a waist elastic member, leg elastic members and a fitting elastic members to a continuous web of an outer sheet,    producing an absorbent core by adhering an upper layer made of a mixture of pulp fibers and super absorbent polymer particles and an lower layer made of a mixture of pulp fibers and super absorbent polymer particles to the upper and lower surfaces of first nonwoven fabric of an intermediate layer by an adhesive,    producing inner absorbent members using the absorbent core,    forming a laminated assembly by adhering the inner absorbent members at specified intervals onto the continuous web of the outer sheet having the respective elastic members adhered thereto,    folding the laminated assembly in two with the inner absorbent members faced inward,    providing cut-away portions for the leg-openings in the laminated assembly folded in two,    bonding the opposite sides on the laminated assembly folded in two, and    separating the laminated assembly having its opposite sides adhered at specified intervals to form the individual disposable underpants.    
     
     
         16 . A method according to  claim 15 , wherein disposable underpants having different sizes are produced in the same production line by adjusting the bonding intervals on continuous laminated assembly folded or intervals at which the opposite sides of the disposable underpants are bonded.