Deproteinization of Nonammonia and Ammonia Natural Rubber Latices by Ethylenediaminetetraacetic Acid

Deproteinized natural rubber (DPNR) was made from sodium hydroxymethylglycinate latex (SH-latex) and ammonia latex (NH3-latex) by mixing with different forms of ethylenediaminetetraacetic acid (EDTA) in the presence of sodium dodecyl sulfate (SDS). The mixtures were stirred at room temperature followed by centrifugation to separate the denatured proteins. The optimized reaction contained 0.01 wt% ethylenediaminetetraacetic acid tetrasodium (EDTA-4Na) with 1% SDS. The nitrogen contents of the DPNR from SH-latex and NH3-latex were reduced to 0.005 wt% and 0.008 wt%, respectively, compared to 0.551 wt% in the starting SH-latex and 0.587 wt% in the NH3-latex. SDS-PAGE analysis and FT-IR spectroscopy showed decomposition of latex proteins to peptides of smaller molecular weight. Physical properties of the DPNR rubber were studied. The novel EDTA-4Na treatment is considered an effective deproteinization method with potential application on both ammonia and nonammonia preservative systems.