Disposable diaper with longitudinal superabsorbent concentration gradient

Hygienic disposable article, configured for use as a diaper and accordingly, of the type having:

• linen-protecting sheet means,
• porous covering means composed of non-woven material and arranged to face the wearer's body,
• absorbent body means arranged between said linen-protecting sheet means, and said porous covering means, said absorbent body means extending from a crotch area into a waist area of said article, said absorbent body means being composed of a mixture of wood-pulp fibers and expandable material, said absorbent body means having a reinforcement region extending along a longitudinally center of the diaper, said reinforcement region being arranged along said crotch area homogeneously with said absorbent body means, said hygienic disposable article comprising:
• said expandable material including particles of a superabsorbent material, such as water-insoluble, highly waterabsorbent hydrogel, arranged along the direction of the longitudinal axis of said diaper, and applied in continuously decreasing quantity outwards from the portions of said reinforcement region proximate the crotch area, in such a way that the concentration of said particles of superabsorbent material in said absorbent body means, in said reinforcement region is 8% to 40% of the weight of said absorbent body means, while in the area of the waist, the concentration of said particles of superabsorbent material is 1% to 7% of the weight of said absorbent body means.