Super Absorbent Polymer Surface Crosslinking for Permeability

The patent applies local quality by creating a surface crosslinked layer with higher crosslinking density on the outer surface of the polymer particles, while maintaining lower overall crosslinking density in the bulk. This is achieved by treating the polymer particles with a crosslinking agent that preferentially reacts at the surface, forming a dense crosslinked network only at the surface region. This resolves the contradiction by allowing the surface to provide structural integrity for liquid permeability while the bulk maintains the porosity needed for centrifuge retention capacity.

The patent segments the polymer particle structure into two distinct regions: an inner bulk region with lower crosslinking density for absorption function, and an outer surface layer with higher crosslinking density for structural stability. This segmentation allows each region to independently optimize its properties - the bulk provides absorption capacity while the surface provides mechanical strength and liquid permeability control.

The patent employs preliminary action by using a specific surface treatment process that applies the crosslinking agent under controlled conditions (temperature, time, concentration) to ensure uniform penetration depth before the crosslinking reaction completes. This preliminary control of reaction conditions prevents over-penetration or uneven distribution, achieving consistent surface layer thickness across all particles.

The patent optimizes manufacturing precision by carefully controlling key parameters of the surface crosslinking process: the concentration of the crosslinking agent solution, the treatment temperature, and the treatment time. By adjusting these parameters within specific ranges, the patent achieves uniform surface crosslinked layer formation with controlled thickness, resolving the contradiction between improving absorption under pressure and maintaining manufacturing precision.