Published: April 2002
Superabsorbent polymers (SAPs) represent a class of organic chemicals defined primarily by the their functional capability rather than their chemical structure. SAPs are polymers that are capable of absorbing and retaining large quantities of water and other aqueous mixtures. They find attractive commercial applications in baby diapers, feminine hygiene products, and adult incontinence products. Other emerging applications include medical wound dressings, soil/water stabilization layers in farming and civil engineering structures, food packaging, fiber and metallic cable sealing, lubricants and sealants, and cosmetics.
Global production of SAP is approximately 1 million metric tons annually. The vast majority of the capacity to produce SAP is in the hands of 4 companies: BASF, Nippon Shokubai, Stockhausen and Dow. As the demand in industrialized countries for SAP in personal hygiene products slows to levels approaching GDP rates, attention by SAP producers has been focused on better market penetration in developing countries, and expanding the application of SAP into new end-uses.
Commercial superabsorbent polymers are made primarily via homopolymerization of glacial acrylic acid or acrylamide, copolymerization of acrylic acid with acrylamide, or vinyl alcohol, and graft copolymerization of polyacrylic acid with starch.
Grafting of starch to polyacrylic acid is done to enhance biodegradability. SAPs are fabricated primarily in the form of dry, white powders, but there are emerging applications of SAP in fiber and laminate form. Nearly all commercial polymerization to make SAP is conducted in batch reactors where aqueous polymerization forms a viscous gel that is subsequently cut, dried and milled to desired end property specifications. A small proportion of SAP is produced via inverse emulsion polymerization, and a small proportion of production is manufactured via continuous reaction in moving belts and possibly in plug flow reactors.
This report updates the 1990 original PEP190 report on superabsorbent polymers. We provide historical and forecast market data on supply and demand segmented geographically and by end use application, describe the competitor environment among producers, and describe andcommercial technology utilized to make SAPs.
We provide in this report preliminary process designs and the corresponding economics for making improved commercial specification SAP using batch, aqueous solution polymerization using processes and procedures documented by Dow Chemical. We also provide a design and the corresponding economics for a novel continuous polymerization reaction using a plug flow reactor design based upon patents by BASF.