|Willett, Julious - J L|
Submitted to: Journal of Biobased Materials and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2007
Publication Date: 8/1/2007
Citation: Shogren, R.L., Gonzalez, S.O., Willett, J.L., Graiver, D., Swift, G. 2007. Preparation of sorbitol citrate polyesters by reactive extrusion and application as inhibitiors of calcium carbonate precipitation. Journal of Biobased Materials and Bioenergy. 1(2):229-237. Interpretive Summary: Synthetic water-soluble polymers made from petroleum such as polyacrylic acid (PAA) are commonly used to prevent hard water deposits in laundry and dishwater detergents, industrial cooling systems, reverse osmosis systems, pools, etc. It would be desirable to find an alternative to PAA which is made from renewable materials such as corn and is non-toxic. Through cooperative research between USDA/ARS and Folia, Inc., it has been found that a polymer made from sorbitol and citric acid (both made from corn) has similar activity as PAA in controlling hard water scaling. An efficient method of preparing the sorbitol/citric polymer using a heated auger called an extruder was also developed. Unlike previous work, this method requires no added water or solvent so the process is clean and relatively low cost. These results should be useful to companies involved in formulating detergents and water treatment chemicals, especially where a low-toxicity, degradable product is desired.
Technical Abstract: Sorbitol citrates were prepared using a vented ZSK-30-twin-screw extruder as part of a program to develop bio-based, water soluble polycarboxylates. A Box-Behnken experimental design was used and included the variables sorbitol, citric acid, sodium citrate, temperature and feed rate. Extent of ester formation increased with increasing sorbitol, temperature and with decreasing feed rate. Weight average molecular weights by light scattering ranged from 1000 to 26,000 and increased with lower sodium, lower feed rates and higher temperatures. Sorbitol citrates inhibited crystallization of supersaturated CaCO3 and this activity increased with increasing citric acid content and increasing extent of reaction/molecular weight. This work suggests that reactive extrusion is an efficient and practical method to prepare low molecular weight, water soluble sorbitol citrate polyesters and that these could function as antiscalants in detergents and other applications.