Starch soluble, oxidation

Class A. Water-soluble synthetic and natural organic polymers, which increase the viscosity of the mixing water. They include cellulose ethers, pregelatinized starches, polyethylene oxides, alginates, carrageenans, polyacrylamide, carboxyvinyl polymers and polyvinyl alcohol. 

Graft copolymers were also produced by bubbling alkylene oxides through starch solutions in dimethyl sulfoxide in the presence of potassium naphthenate.2888,2889 Another approach involved grafting polyethylene oxide) to starch. Polyethylene oxide) was converted into a chloroformate derivative and subjected to a reaction with starch alkoxide 2890 Poly(alkylene glycol) could be grafted onto starch by means of cyclic aliphatic acid anhydride in the presence of 4-toluenesulfonic acid 2891 The products were water soluble. 

Wing, R. E., and Willett, J.L. (1997) Water Soluble Oxidized Starches by Peroxide Reactive Extrusion, Ind. Crop. Prod. 1, 45-52. 

Wing RE, Willett JL. 1997. Water soluble oxidized starches by peroxide reactive extrusion. Ind Crops Prod 7 45-52. 

Desizing is carried out by means of enzymatic insertion (at the starch sizing), oxidation, or hydrolysis (water soluble and synthetic sizing). 

A few substances indicate the presence of a specific oxidized or reduced species. Starch, for example, forms a dark blue complex with 13 and can be used to signal the presence of excess 13 (color change colorless to blue), or the completion of a reaction in which 13 is consumed (color change blue to colorless). Another example of a specific indicator is thiocyanate, which forms a soluble red-colored complex, Fe(SCN) +, with Fe +. 

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

Water-Soluble Films. Water-soluble films can be produced from such polymers as poly(vinyl alcohol) (PVOH), methylceUulose, poly(ethylene oxide), or starch (qv) (see Cellulose ethers Polyethers Vinyl polymers). Water-soluble films are used for packaging and dispensing portions of detergents, bleaches, and dyes. A principal market is disposable laundry bags for hospital use. Disposal packaging for herbicides and insecticides is an emerging use. 

Catalytic oxidation ia the presence of metals is claimed as both nonspecific and specific for the 6-hydoxyl depending on the metals used and the conditions employed for the oxidation. Nonspecific oxidation is achieved with silver or copper and oxygen (243), and noble metals with bismuth and oxygen (244). Specific oxidation is claimed with platinum at pH 6—10 ia water ia the presence of oxygen (245). Related patents to water-soluble carboxylated derivatives of starch are Hoechst s on the oxidation of ethoxylated starch and another on the oxidation of sucrose to a tricarboxyhc acid. AH the oxidations are specific to primary hydroxyls and are with a platinum catalyst at pH near neutraUty ia the presence of oxygen (246,247). Polysaccharides as raw materials ia the detergent iadustry have been reviewed (248). 

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

Within the gut, oxidative damage may be prevented by phytic acid, obtained from cereals and vegetables (Graf et al., 1987), and by soluble non-starch polysaccharides like pectin (Kohen et al., 1993). The use of antioxidant vitamins in the treatment of inflammatory bowel disease has also been su ested (Evans et al., 1990). 

The oxidative cleavage of v/c-diols to give two carbonyl functions (Eq. 5.3) by periodates was first observed by Malaprade and has since been widely applied to the carbohydrate area.50 Since both the reagent sodium periodate and the carbohydrate substrate are water soluble, the reaction is usually carried out in aqueous media.51 The reaction has been applied to polysaccharides such as starch.52 The periodate oxidations of sodium alginate in water as well as a dispersion in 1 1 ethanol-water mixture have been compared.53 Because sodium alginate forms a highly viscous solution, the oxidation was observed to be more extensive in ethanol-water. 

Desizing by chemical decomposition is applicable to starch-based sizes. Since starch and its hydrophilic derivatives are soluble in water, it might be assumed that a simple alkaline rinse with surfactant would be sufficient to effect removal from the fibre. As is also the case with some other size polymers, however, once the starch solution has dried to a film on the fibre surface it is much more difficult to effect rehydration and dissolution. Thus controlled chemical degradation is required to disintegrate and solubilise the size film without damaging the cellulosic fibre. Enzymatic, oxidative and hydrolytic degradation methods can be used. 

Not all modified starches are suitable for removal by aqueous dissolution alone. Such modifications of natural starches are carried out to reduce solution viscosity, to improve adhesion and ostensibly to enhance aqueous solubility. Commercial brands vary [169], however, from readily soluble types to those of limited solubility. Indeed, some may be as difficult to dissolve as potato starch if they have been overdried. It is thus very important to be sure of the properties of any modified starch present. If there are any doubts about aqueous dissolution, desizing should be carried out by enzymatic or oxidative treatment. Even if the size polymer is sufficiently soluble, it is important to ensure that the washing-off range is adequate. Whilst the above comments relate to modified starches, other size polymers such as poly(vinyl acetate/alcohol) and acrylic acid copolymers vary from brand to brand with regard to ease of dissolution. 

The desizing of water-soluble size polymers can be summarised as follows. Batchwise or continuous methods can be used in both cases an adequate supply of hot water is needed during the washing-off. Hot water and detergent are needed to remove polyfvinyl alcohol) or carboxymethylcellulose. The addition of alkali may be beneficial with carboxymethylcellulose. Alkali is essential with modified starches and acrylic acid copolymers. Polyfvinyl alcohol) can be degraded effectively by alkaline oxidation. 

Instead, native starch has been oxidized with H202 in the presence of soluble organometallic complexes to meet specific hydrophilic/hydrophobic properties needed for end-products to be used in paper, paint and cosmetic industries [79-... 

The water-soluble iron tetrasulfophthalocyanine (FePcS) complex, which is cheap and available on an industrial scale, was also a very active and selective catalyst for the oxidation reaction. Starches of different origin (potatoes, rice, wheat, com) were oxidized by H202 following two operating modes, viz. oxidation in aqueous suspension and oxidation by incipient wetness. 

This catalytic system was very flexible because by simple modification of the reaction conditions it was possible to prepare oxidized polymers with the desired level of carboxyl and carbonyl functions. No waste was formed because the process did not involve any acids, bases or buffer solutions. The incipient wetness process is very easy to scale up. Hydrophilic starch was prepared in batches of 150 L and incorporated successfully in paint formulations. Good results were also obtained with in vitro and in vivo tests for cosmetic formulation. Interestingly, this is a rather unique example of a heterogeneous catalytic process involving a soluble catalyst and a solid substrate. 

The etherified starch was further transformed by hydrogenation of the double bonds to yield the corresponding linear octyl groups using [RhCl(TPPTS)3] catalyst soluble in EtOH-H20 mixtures. Complete hydrogenation was obtained at 40 °C under 30 bar of H2 after 12 h using 0.8-wt.% Rh-catalyst [84]. Other catalytic transformations such as double bond oxidation and olefin metathesis could possibly be used to prepare other modified starches for various applications. 

Carbonyl groups contribute to cross-linking reactions where hemiacetals are formed. These are the greatest influence on viscosity build-up when low oxidized starches are used at neutral to acidic pH. When highly oxidized starches are used, the influence of the carbonyl group is much less because the molecular weight has been lowered and solubility is increased. The complexity of the reaction is shown in Figure 1. 

Vigneshwaran, N., Kumar, S., Kathe, A. A., Varadarajan, P. V, Prasad, V. (2006). Functional finishing of cotton fabricsusing zinc oxide-soluble starch nanocomposites. Nanotechnology, 17, 5087-5095. 

The purpose of this procedure is to determine the acid-soluble constituents of commercial Blasting Explosives. To this group of constituents belong starch and antacid Ca carbonate. Infrequently Zn oxide is present, but it appears... 

Proteins suffer due to cost and chemical reactivity, malto-dextrins and corn syrup solids due to a dearth of interfacial function, lipophilic starches due to labelling constraints (a marketing decision), and gum arabic due to cost, as well as intermittent supply deficiencies. An inexpensive, "natural", strongly surface active polymer with excellent water solubility and chemical inertness clearly has vast economic potential. Oxidized, hydrolyzed and/or glycoamine starch-based derivatives were examined as possible avenues for delivering this polymer. 

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