Oxidized starches applications

An interesting possible application in our society is in super absorbers, which are currently made with polyacrylates, but these suffer from poor biodegradability. Since the demand for short-use super absorbers is growing, a product with a short lifetime and therefore a quick and safe disposal is required. Carboxylated starch can be such a product, but first, an efficient method to oxidize starch needs to be developed. Currently used methods produce stoichiometric amounts of waste products, so the search for a catalytic process is ongoing. 

Converted starches, also called thin-boiling starches, are produced by degradation of the starch chains into small segments. They can be cooked in water at higher concentrations than native starches. Low-viscosity starches are needed in applications where a high solid starch paste with a pumpable and workable viscosity is required. There are four classes of commercial converted starches dextrins (hydrolysis in solid-state) acid-modified starches (hydrolysis in a slurry) oxidized starches and enzymically depolymerized starches. 

Anionic starches are obtained by reaction with phosphoric acid and alkali metal phosphates or by derivatization with carboxymethyl groups.30,31 This modification is primarily used to introduce amphoteric properties into cationic com starch for application on the wet end of the paper machine. Anionic starches with carboxymethyl substitution are used as thickeners in coating colors or as binders in coatings for specialty paper grades. Oxidized starches are inherently anionic but without thickening action. Potato starch already carries sufficient natural anionic charge to provide amphoteric properties after cationization.32... 

An alternative method to apply starch to paper, especially to paperboard grades, is to use a water box at the calender. Water boxes are used for wet-finishing of paper-board prior to coating application. Use of starch in the water box will increase surface strength and lessen fiber reswelling after coating application. Dilute dispersions of oxidized starch are used, frequently in conjunction with a lubricant to prevent calender roll picking. 

Application of Oxidized Starch-Containing Reagents (OSR) as Binding Agents in Production of Resin-Bonded Chipboard and Cane Fiber Board... 

Oxidized starch reagents may be used in washing powders as substituents of polyphosphates [11]. As investigations show OSR possess the number of unique physical-chemical properties allowing hoping on their application as one of the main components of detergents. 

The considerable amounts of glyoxylic and n-erythronic acid isolated after hydrolysis of hypochlorite-oxidized starch by Whistler and co-workers " " and by Eisenbraun and Purves indicate the significant introduction of keto groups by the oxidation, those keto-D- glucose residues being intermediates in the formation of 2,3-dicarboxyl units. Finally, it should be mentioned that the information obtained from studies of the oxidation of model compounds and of the chemistry of the carbonyl compounds so produced, previously discussed in the text, should be largely applicable to polysaccharides. ... 

Applications of oxidized starches have been reviewed.442,541-543... 

The applications of these techniques is illustrated by data on a variety of polymers, although the bulk of the discussion concerns a typical amorphous polymer, atactic polystyrene and a crystalline polymer, polyethylene oxide. A number of results are quoted which seem to indicate that phenyl group rotations or oscillations are not an important mechanism in the relaxation of polystyrene. Other materials mentioned are polypropylene oxide, starch and ionized copoly-... 

In conclusion, the selective oxidation of native starch by hydrogen peroxide in the presence of metallophthalocyanine catalysts provided hydrophilic materials which, from primary tests, look promising for their incorporation in paints and cosmetics. These catalysts are not expensive, readily available at industrial scale and employed in very low amounts. The catalytic system was very flexible because by simple modifications of the reaction conditions it was possible to prepare oxidized starches with the desired level of carboxyl and carbonyl functions that are suitable for different applications. No wastes were formed because the process did not involve any acids, bases or buffer solutions. 

Starch is added at the calender stack for curl control, surface strength, laying of surface fuzz, clay coating holdout, printing characteristics, and grease or oil resistance. Solids vary from 2 to 24%, depending on the starch type used and on the paper requirements. Low viscosity starches, hydroxy ethylated converted starches, and oxidized starches are used in this application. 

Starches have been oxidized with numerous oxidizing reagents mainly to reduce molecular weight and to increase solubility, for paper and food applications. Commercial oxidized starches are batch prepared utilizing room temperature conditions and low oxidant concentration (<3%) such as hypochlorite, permanganate, hydrogen peroxide, persulfate, periodate, and dichromate [60, 82-84]. Starch oxides have found a large application in adhesive production. 

Starch, cooked in the paper mill or supplied as - pregelatinized starch, is used also. Modified starches (- oxidized starch, - cationic starch or - starch ethers) are common in that application. Sodium - carboxymethyl cellulose is also effective, but as an anionic polymer, it requires a retention aid such as alum. 

For practical uses see - anionic starches, car-boxymethyl starch, - cationic starches, - cross-linked starches, - hydrophobic starches, - oxidized starches, - starch industrial applications. 

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