Polyvalent metal-substituted starch products
View Patent ↗Improved starch-metal derivatives are provided which have excellent dry flow characteristics and ready dispersability in hot or cold water. The preferred derivatives comprise granules of starch which have been expanded or preswelled and cross-linked, followed by reaction with a polyvalent metal salt, especially salts of Ca, Mg, Zn Cu and Al.
1. A starch-polyvalent metal derivative comprising starch granules selected from the group consisting of wheat, waxy wheat, corn, waxy corn, high amylose corn, oat, rice, tapioca, mung bean, and potato starches and mixtures thereof which are prepared by initially expanding starch granules in water, reacting the expanded granules first with a cross-linking agent selected from the group consisting of sodium trimetaphosphate, sodium tripolyphosphate, phosphoryl chloride, eplchiorohydrin and mixtures thereof, and then with an agent to bond or attach hydrophobic moieties to the surface of the granules, said moieties derived from hydrophobic acids and acid anhydrides, and thereafter reacting the reacted granules with a polyvalent metal, selected from the group consisting of Groups 2–13, inclusive, of the Periodic Table, said starch derivative being rapidly dispersible in both hot and cold water.
2. The derivative of claim 1 , said metal being selected from the group consisting of the Group 2 metals of the Periodic Table.
3. The derivative of claim 1 , said hydrophobic moieties being bridged by said polyvalent metal.
4. The derivative of claim 3 , said hydrophobic moieties being present at a level of from about 0.1–50% by weight, based upon the total weight of the starch taken as 100% by weight.
5. The derivative of claim 4 , said level-being from about 1–30%.
6. The derivative of claim 5 , said level being from about 5–25%.
7. The derivative of claim 1 , said moieties derived from acid anhydrides of the formula
wherein R is a di- or trimethylene group and R' is a straight or branched chain hydrocarbon group having from about 2–20 carbon atoms therein.
8. The derivative of claim 7 , wherein R' is a straight or branched chain alkyl, alkenyl or alkynl group.
9. The derivative of claim 7 , wherein R' has from about 6–12 carbon atoms therein.
10. The derivative of claim 3 , said moieties derived from octenyl succinic anhydride.
11. The derivative of claim 1 , said metal selected from the group consisting of the alkaline earth metals, zinc and aluminum.