Carboxymethylation of starches

Cationization and carboxymethylation of starch in an extruder has been reported.45 17 Cationization of potato starch in a twin-screw extruder had an optimum reaction efficiency of 71%. Further work yielded 80% efficiency and products with 0.03-0.10 DS.44 Additional heat treatment of extruded products (made via reaction with quaternary ammonium reagents) with sodium trimetaphosphate or citric acid has improved reaction efficiencies and/or viscosities.48 Dry cationization in the presence of methanol and isopropanol49 or combined with microwave irradiation has also been done.50... 

Fig. 9. Plot of -In(l - x,) against -In for carboxymethylation of starch for determination of relative rate constants ki (slope) Co is the molar fiaction of unsubstituted AGU and x,- the partial DS values in position i. 0-2, 0-3, A 0-6. Rqrrinted from Ref 167 with permission from John Wiley Sons, Ltd, Copyright 2002.

The preparation of benzoylated car boxy met hylstarches has been reported. The relation between the conditions for carboxymethylation of starch and the properties of the resulting carboxymethylstarches has been investigated. The sodium salt of carboxymethylstarch is readily converted into the free-acid form, which could not be washed effectively because of swelling. The sodium salt of starch glycolate has been used as the substrate in an assay of a-amylase. ... 

Starch is a natural plant product and it has been modified to the carboxymethyl-ated form (CMS—carboxymethyl starch). Carboxymethylation of starch occurs in two steps involving sodium salt of CMS. 

Thomas, D.C. "Thermal Stability of Starch and Carboxymethyl Cellulose Polymers Used in Drilling Fluids," SPE Paper 8463, 1979 SPE Annual Technical Conference and Exhibition Las Vegas, September 23-26. 

Anionic starches, obtained by carboxymethylation of corn starch, provide improvements in film strength, pick resistance, opacity and air-leak density. They are used... 

The USPNF 23 states that sodium starch glycolate is the sodium salt of a carboxymethyl ether of starch, containing 2.8-4.2% sodium. 

The PhEur 2005 describes three types of material Types A and B occur as the sodium salt of a cross-linked partly O-carboxymethylated potato starch, containing 2.8-4.2% and 2.0-3.4% of sodium respectively. Type C is the sodium salt of a cross-linked by physical dehydration, partly O-carboxymethy-lated starch containing 2.8-5.0% sodium. 

A complete list of semi-synthetic heparinoids is outside the scope of this article. Products of sulfation of neutral polysaccharides include sulfates of starch, cellulose, - - xylan, dextran, " guaran, and synthetic polymers of o-glucose. A somewhat closer simulation of the structure of heparin was attempted by sulfating polysaccharides containing amino sugars or uronic acids or both, such as chitin and chitosan, " and the corresponding N-formyl, N-(car-boxymethyl), O-(carboxymethyl), and 5-carboxylated - deriva-... 

Investigation into the formation of carboxymethyl ethers of polysaccharides has continued, on account of the great utility of these derivatives as ion-exchange materials and polyelectrolytes. As expected, a whole series of polysaccharide derivatives of different degrees of substitution can be prepared by variation of the reaction conditions and molar proportions of monochloroacetic acid. " Published reports include the preparation of various carboxymethyl ethers of starches, amyloses, lichenan, pachymans, and chitin and introduction of the carboxymethyl group into polysaccharide derivatives constitutes a useful way of raising their solubility in water. By combining the introduction of alkyl and carboxy-... 

The TGA of CMS 4 (Figure 5.8b) has another (3 ) zone of weight loss (apart from the two zones of weight loss as in the case of starch) at 580 C, which is due to the degradation of the incorporated carboxymethyl groups. 

---