Starch ether forming

Hydroxylall l Starch Ethers. Starch hydroxyethyl ethers with a degree of substitution (DS) of 0.05—0.10 ate produced in various ways, but usually their preparation begins at the end of the wet-milling process, utilizing a high soHds-starch suspension. The ether modification of ungelatinized starch is filterable and can be produced economically in a pure form. 

Cationic Starches. The two general categories of commercial cationic starches are tertiary and quaternary aminoalkyl ethers. Tertiary aminoalkyl ethers are prepared by treating an alkaline starch dispersion with a tertiary amine containing a P-halogenated alkyl, 3-chloto-2-hydtoxyptopyl radical, or a 2,3-epoxypropyl group. Under these reaction conditions, starch ethers are formed that contain tertiary amine free bases. Treatment with acid easily produces the cationic form. Amines used in this reaction include 2-dimethylaminoethyl chloride, 2-diethylaminoethyl chloride, and A/-(2,3-epoxypropyl) diethylamine. Commercial preparation of low DS derivatives employ reaction times of 6—12 h at 40—45°C for complete reaction. The final product is filtered, washed, and dried. 

Commercially available cationic starches for wet end application are quaternary and tertiary products. These products have been available since about the mid 1950 s and no new basic chemistry has been developed since that time. The development in the late 1940 s and early 1950 s of starch ethers and esters made in the original granule form led to a torrent of starch derivatives for industrial use. Very few of these became commercial. This is possibly because the functions that were required by the industrial and food markets were far... 

The reaction proceeded through nucleophilic displacement of chloride and a starch ether was formed. The ether derivative was quaternized and made cationic by addition of a mineral acid. Teriary amino starches so made are used predominantly at acidic pH where the charge remains maximum. As neutral pH is approached, the charge is diminished until at weakly alkaline pH the charge is lost. 

Quaternary ammonium starch ethers are prepared by reacting the chlorohydrin form of... 

Maize Starch (Indian Corn Starch), (CeHioOs). mw (162.14)x, white amor powd, does not melt, decomposes when heated insol in cold w, ale, or ether, forms a jelly with hot w. Can be prepd from Indian corn by grinding with w and straining the resulting milky liq. On standing, starch settles out and can be sepd by decantation. Has been used as a binder in blasting expls to form NH4 nitrate agglomerates which when sieved had a bulk d of 0.65g/cc or less (Ref 2) Refs l)Hackh s (1944), 508 2) J. Taylor... 

If starch is present when an oilseed is extruded, the fat and starch will form a complex that is not soluble in ether, the normal method used for fat analysis. Studies have shown that fat will enter a complex with starch on the basis of a 1 to 10 ratio. An acid hydrolysis is necessary to measure the correct and actual fat level in such a case. 

In general, dehydration and depolymerization have been considered as the two main processes associated with the degradation mechanism of polysaccharides [22], In the case of starch, ether bonds and unsaturated stmctures are formed via thermal condensation between hydroxyl groups of starch chains, which eliminates water and other small molecnles, and by dehydration of hydroxyl groups in the glucose ring. It was observed that water was the main prodnct of decomposition of modified starch at a temperatnre below 300°C, formed by inter-molecnlar or intramolecular condensation of starch hydroxyls [23,24],... 

In addition, they are used in combination with casein solutions and synthetic resin emulsions. Whereas starch ethers and esters and also aldehyde starches are used to only a limited extent in the adhesives field, the thermal degradation products of starches, the water-soluble dextrins, are still important in quantitative terms as raw materials for adhesives. They are used on their own in aqueous form or as mixtures with synthetic resin emulsions. 

Other Aqueous Adhesive Solutions. Besides starches and dextrins, cellulose ethers, primarily methyl cellulose and carboxymethyl cellulose, and in some cases also starch ethers, are important as wallpaper pastes and poster glues. The products are generally marketed in the form of powders that are dissolved in water by the user. Aqueous... 

Wallpapers include those with a PVC or metal surface and rough-textured plain wallpapers. They are applied with pastes of pre-gelatinized starch, starch ethers, carboxymethyl or methyl cellulose in the form of 2-10% solutions. For rough-textured plain wallpapers and heavy wallpapers, moisture resistance and tack are increased by utilizing poly(vinyl acetate) redispersion powders. High solid, emulsion-based adhesives, optionally in conjunction with resin-enhanced pastes (special purpose pastes), are used preferably for heavy vinyl- and metal-faced wallpapers. 

The reaction will proceed in aqueous suspension, but the ether formed becomes swellable in cold water if DS becomes >0.1. Therefore, the process is mostly run in aqueous organic solvents such as methanol, ethanol, isopropanol, acetone. After the reaction, the unswollen and undissolved c. is filtered off, washed and dried. Usually DS is 0.2-0.6. Carboxymethylation enhances die hydrophilic character of - starch polysaccharides (- anionic starch). 

Dissolve 34 g. of o-nitroaniline in a warm mixture of 63 ml. of concentrated hydrochloric acid and 63 ml. of water contained in a 600 ml. beaker. Place the beaker in an ice - salt bath, and cool to 0-5° whilst stirring mechanically the o-nitroaniline hydrochloride will separate in a finely-divided crystalline form. Add a cold solution of 18 g. of sodium nitrite in 40 ml. of water slowly and with stirring to an end point with potassium iodide - starch paper do not allow the temperature to rise above 5-7 . Introduce, whilst stirring vigorously, a solution of 40 g. of sodium borofluoride in 80 ml. of water. Stir for a further 10 minutes, and filter the solid diazonium fluoborate with suction on a sintered glass funnel. Wash it immediately once with 25 ml. of cold 5 per cent, sodium borofluoride solution, then twice with 15 ml. portions of rectified (or methylated) spirit and several times with ether in each washing stir... 

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