Starch xanthates production

Suggested industrial uses of carbohydrate xanthates, apart from the cellulose Viscose process, include the flotation of minerals and the production of plastics. Two patents by Brown and his associate claim an effective purification of both iron ore and silvinite ore by froth-flotation processes employing, for example, sodium starch xanthate, pine oil, and a suitable amine. Silberstein obtained plastic masses from mixtures of sodium dextrin xanthate with urea, formaldehyde, or glyceritol. Starch xanthate has been suggested as a dispersing, wetting, and adhesive ma-... 

WI Starch Xanthate. Research by Wing and others (22, 27-29) has shown that water-soluble (WS) starch xanthates, in combination with cationic polymers to form polyelectrolyte complexes, can effectively remove heavy metals from waste water. To eliminate the expensive cationic polymer and give a more economical method of heavy metal removal, further research by Wing and others (12,30-33) showed that xanthation of a highly crosslinked starch yields a water-insoluble (WI) product that is effective in removing heavy metals from waste water without the need for a cationic polymer. In more recent work, Tare and Chaudhari (34) evaluated the effectiveness of the starch xanthate (WS and WI) process for removal of hexavalent chromium from synthetic waste waters. 

Starch xanthate can be methylated as well as acetylated.45 The first reaction is base-catalyzed and the second acid-catalyzed. Neither procedure decreases the DS of the modified xanthate. Cationization of starch xanthate occurs on reaction with the water-soluble poly(vinylbenzyltrimethylammonium) chloride.2157 Xanthates have been cyanoethylated to produce rubber mixes.2158 2159 Sulfonated products were made by reaction with sultones.2160... 

The modification of cellulose with alkaline carbon disulfide to introduce xanthate groups has been extensively exploited in the industrial production of viscose. Early work on the preparation and properties of starch xanthate has been discussed. Xanthate derivatives of cellulose and starch have been discussed with respect to general xanthate chemistry, and the xanthation of cellulose in homogeneous medium is known to be a second-order reaction. Cellulose xanthate shows some potential as a matrix for enzyme insolubilization, " and stable derivatives of this xanthate may be prepared by transesterification. Thermal decomposition of cellulose allyl- and benzyl-xanthates gives 5,6-cellulosene. Some thiocarbonyl derivatives of polysaccharides have been prepared. "... 

The chemical nature of starch xanthate-poly(ethylenimine) has been studied in view of its efficacy as a wet-end additive for improving the mechanical strength of paper. Model systems suggested that small amounts of starch xanthide and poly(ethylenimine)thiuram disulphide, possible products of atmospheric oxidation, might be present these compounds would react rapidly with poly(ethyl-enimine) to yield thionocarbamates and thioureas, respectively. 

The latter method has the advantage of recycling the natural or waste product. Significant examples are cotton modified with amines [3, 4], starch utilized in xanthate form [5, 6, 7], thiol type keratine gel prepared from the wool [8, 9,10], wool simply reduced [11] or modified with amine groups [12, 13, 14] and finally polysaccharides such as cellulose [15, 16, 17], glucose [18] or polyosides [19] modified with thiol or amine groups. 

Limitations in possibility of chemical modifications of starch result from steric hindrance of reaction sites, solubility, viscosity of reaction medium, and susceptibility to side reactions among them, depolymerization almost always accompanies intended modification. As a rule, polysaccharides are soluble, although frequently only sparingly, in water and dimethyl sulfoxide. Polysaccharides solubilize on xanthation, i.e., on reaction with CS2 in alkaline medium, to form syrups of xanthates. On acidification polysaccharides could be recovered. Such procedure was utilized for several decades for production of artificial silk from cellulose. 

---