Starch carbamates

Phenyl- and other aryl-carbamates of starch appeared to be nontoxic to Aspergillus oryzae, Aspergillus niger, and Penicillium expansum.2550 2-(Hydroxypropyl)starch carbamate was also tested without any particular success in enzyme-immobilizaton studies.2553 Improvements in the weight gain of ruminants upon feeding with fodder supplemented with carbamates was reported.2554... 

A convenient route to the production of starch carbamates was presented2386,2590-2593 in which starch reacted with acrylonitrile and, subse-quendy, partly hydrolyzed into carbamates. 

Soluble carbamates have been considered for applications that include adhesives, pigmented coatings, paper coatings, and surfactants.2551,2555 Starch carbamates having double bonds in the side chains are UV-curable and have been reported as... 

Starch carbamate block copolymers are biodegradable.2643 During production, the reaction mixture can be supplemented with vegetable derivatives, molasses,... 

The determination of the carbamoyl group in starch carbamates is based on cleavage of the carboxyamido group from the carbamate in alkaline hydrolysis. For this determination, the ammonia liberated is steam-distilled into boric acid followed by titration with 0.05 M aqueous sulfuric acid.2665 Additional information on starch carbamates can be found in the article by Roberts.2666... 

Starch is subject to fermentation by many microorganisms and, unless the mud is saturated with salt or the pH is >11.5, a preservative or biocide must be added if the mud is to be used for an extended period of time. The most common biocide until the mid-1980s was paraformaldehyde [9002-81-7]. This material has been largely replaced by isothia2olones (at 5—10 ppm cone) (74), carbamates, and glutaraldehyde [111-30-8]. Alternatively, the biocide may be incorporated during the processing of the starch and is present in the commercial product. 

Cellulose carbamate and its derivatives are able to immobilize enzymes easily with the help of dialdehydes such as dialdehyde starch, glutaraldehyde, and glyoxal [62]. Since cellulose triphenylcarbamate or tricarbanilate prepared... 

Conjugated chromophores develop from the PBT and these will screen the photoinduced decomposition of the hydroperoxides in PP. This effect results in an accumulation of hydroperoxides from the PP. Iron diethyldithio-carbamate has been shown to exhibit an initial stabilisation effect on polyethylene followed by sensitisation as does anthraquinone . Trace volatiles have been measured during the photooxidation of polyethylenes while ferric stearate/cerium(III) mixtures and starch materials are good degradants . ... 

Starch reacts with isocyanates to produce carbamates (urethanes), which are esters of carbamic acid. Several reactions of starch with phenyl-, various aryl-, 1-naphthyl-isocyanates or 1,6-hexamethylene- and 2,4-tolyl-diisocyanates were conducted either in pyridine or morpholine below the boiling point of these solvents.2546-2548 In each case all three hydroxyl groups of the glucose units reacted to give tricarbanilates, provided a sufficient amount of the isocyanate reagent was used. 

Cationization of carbamates is possible by reacting starch with amides in the presence of mineral or carboxylic acids2618 or by utilizing the Mannich reaction.2619... 

Chemical modifications may also include the derivatization of starch by reaction of its hydroxyl groups with alkylene oxides. Other suitable substances are such that form ether linkages, ester linkages, urethane linkages, carbamate linkages, or isocyanate linkages. The degree of substitution of the chemically modified starch varies from 0.05 to 0.2. 

MBT 2-mercaptobenzothiazole and related thiazoles TH tetramethylthiurams and related thiurams CAR carbamates TUthioureas CS corn starch LAC lactose... 

For these and a variety of special non-food purposes esters with higher fatty acids, succinic, adipic and citric acids and carbamates (reaction products with urea), have also been prepared. Examples of starch ethers are 2-hydroxyethyl and 2-hydroxypropyl starches prepared by reaction of starch with oxirane (ethylene oxide) and methyloxirane (propylene-l,2-oxide). The reaction occurs preferentially at the secondary hydroxyl groups at C-2, with less on the C-3 and C-6 hydroxyl groups. The most common products are those shown in Figure 4.15. The degree of substitution tends to be <0.2. According to the reaction conditions, polyoxaalkyl starches ... 

Recently, ecotoxic tests performed on several materials showed that biomaterials (starch, cellulose, polylactic acid, etc.) in soil conditions had a toxic effect at the beginning of the process, and became non toxic after 60 days. On the contrary, polyethylene materials with pro oxidant additives showed a toxic response after 60 days (Fritz, 2004). Similarly, inhibition effects occur during Sturm tests with this material. One explanation could be the release in the environment of poisonous substances contained in the pro-oxidant additive (di thio carbamates) or in other unknown additives. These harmful substanees accumulate in soils. For the above reasons and for agricultural requirements (no accumulation of toxic substances in soils), ecotoxic tests should be performed after a lag phase of three or six months. 

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