US Patent 7201959 Absorbent polymeric composition

A moisture-absorbing polymeric material is disclosed which comprises a combination of a thermoplastic material with an absorbent. The thermoplastic material is chosen such that when the absorbent is added to the thermoplastic material in the molten state, the absorbent will tend to migrate towards the surface of the moisture-absorbing polymeric material. This results in a concentration gradient for the absorbent wherein the desiccant is more highly concentrated in an outer layer of the polymer material than towards the center. In this way, more absorbent is pushed towards the surface where it can more easily absorb moisture from the surrounding atmosphere.