GB941399A - Oxidised starch products - Google Patents

Abstract

941,399. Dialdehyde starch hydrazones. MILES LABORATORIES Inc. May 25, 1962 (July 10, 1961), No. 20252/62. Heading C3U. A cationic oxidised starch hydrazone is obtained by reacting under essentially non- degradative conditions in an aqueous acidic medium, a water-insoluble oxidised starch containing at least 5 % of theory of carbonyl groups with a nitrogen-containing compound which is a water-soluble hydrazine or hydrazide containing a tertiary or a quaternary nitrogen atom, said nitrogen-containing compound corresponding to the formula R 1 -N-NH 2 where not more R 2 than one of R 1 and R 2 is a hydrogen atom, each of R 1 and R 2 may be alkyl, quaternary nitrogen- or tertiary nitrogen-substituted akyl or acyl radicals and R 1 and R 2 together contain not more than 10 carbon atoms. The oxidised starch hydrazone is in the original granule form, is insoluble in cold water and is readily gelatinisable in hot water. "Oxidised starch" is defined as starch in which from 0À5% to at least 95 % of the anhydroglucose units have been oxidised to contain reactive carbonyl groups while the polymer remains in high polymeric form and in the original granular state. Oxidising agents include periodic acid and soluble salts thereof, soluble dichromates, chlorine and hydrogen peroxide. The starch may be obtained from e.g. corn, wheat, potato, tapioca, waxy maize and high amylose corn. Specified nitrogen-containing compounds are unsymmetrical dimethylhydrazine, #-triethylaminoethyl hydrazine hydrochloride, betaine hydrazide hydrochloride and N-dimethyl-glycine hydrazide hydrochloride. Preferably, when the oxidised starch contains up to about 10% of theory of carbonyl groups, all the carbonyl groups are reacted, while when the oxidised starch contains about 90 % of theory of carbonyl groups i.e. commercial dialdehyde starch, only up to 10% of the carbonyl groups are reacted with the nitrogen-containing compound. The introduction of cationic groups adds a positive charge to the oxidised starch molecule and increases its affinity for anionic materials such as pigments and paper pulp. The hydrazones of low-oxidised starch are of value as retention agents for pigments, dyes and wet-strength resins, and as agents for flocculating finelydivided anionic materials. The hydrazones of highly-oxidised starch are of value as wet-end additives in paper manufacture and for increasing the dry and wet strengths of the finished paper.