Superabsorbent polymers (SAPs) are synthetic polymers that are able to absorb about 500 to 1000 times their own weight in water. Such superabsorbent polymers have begun to be used in real-world applications for sanitary items, and are currently being widely utilized not only in hygiene products, such as disposable baby diapers, sanitary pads and the like, but also in gardening soil repair agents, water stop materials for civil construction, seeding sheets, freshness retaining agents in the field of food distribution, and fomentation materials.
In the preparation of the superabsorbent polymer, water, which is the polymerization medium, is used in various applications, including facilitating the dispersion of the crosslinking agent during the surface crosslinking process, etc. Also, residual moisture in the final product functions as an anti-static agent and a plasticizer for resin, and plays a role in suppressing the generation of very fine superabsorbent polymer dust in the course of application, and additionally preventing the grinding of the superabsorbent polymer particles. Generally, however, when even a small amount of water is added to the superabsorbent polymer, the surface stickiness of the polymer may be increased by the water absorbed thereto, and irreversible agglomeration of the superabsorbent polymer particles may take place. This increase in stickiness and agglomeration may result in poor processability, such as a high burden on the preparation and application processes, consequently increasing the particle size of the superabsorbent polymer, deteriorating the properties thereof, and decreasing productivity. Superabsorbent polymers have been mainly studied to date for polymerization processes and improved absorption performance, and for surface crosslinkage to realize surface properties thereof or increased absorption under pressure, and research leading to changes in the surface properties of superabsorbent polymers has been carried out to increase transmittance or to prevent caking when the superabsorbent polymers are stored.
In this regard, Korean Patent Application Publication No. 2012-0081113 discloses a method of preparing an absorbent polymer containing water-insoluble inorganic particles.
However, this conventional technique is problematic because the surface stickiness of the superabsorbent polymer increases with an increase in moisture content on the surface thereof, undesirably resulting in agglomeration, poor processability, and low productivity, as in the above case. Hence, there is a requirement to develop a superabsorbent polymer that may satisfy both high moisture content and high processability.