Polysaccharide derivatives containing aldehyde groups for use as paper additives

Polysaccharide aldehydes having the general structure +TR such as starch, cellulose and gum aldehydes, are useful for imparting wet, dry, or temporary wet strength to paper. They are prepared by a non-oxidative method which involves reacting the polysaccharide base, in the presence of alkali, with a derivatizing acetal reagent having the general structure and then hydrolyzing the acetal by adjusting the pH to less than 7, preferably 2-4. R is (CH2)n or a divalent aromatic group and n os 0 or greater; R1, R6, and R7 are hydrogen or an organic group; R2, R5, and R8 are (CH2)m with m being 1-6; R3 and R4 are hydrogen or a lower alkyl; Y is an anion; Z is an organic group capable of reacting with the polysaccharide base to form an ether derivative and selected from the group consisting of an epoxide, ethylenically unsaturated group, halohydrin, and halogen; R11, if present, is a divalent organic group containing no reactive substiuents; and A and A' are lower alkyls or together form at least a 5-membered cyclic acetal.