Patent ID: 6960627

Claim:
A water-soluble or water-swellable film consisting of a cross-linked polyvinyl alcohol obtained by mixing in water a polyvinyl alcohol with a polycarboxylic acid of formula (1) ROOC-A-COOR (1) where A represents one or more, identical or different groups of the formulae —(CH 2 ) m —; —(CH═CH) n —; —(C 6 H u X 4-u ) o —; —(C 5 H 3 ) p —; —(C 6 H 10 ) q —; —(CH(OH)) r —; —(CH(COOR)) s —; —(C(OH)(COOR)) t —, X is H, OH or COOR, R is H, C a H 2a-1 , an alkaline earth or alkali metal atom or NH 4 , a is from 1 to 10, m is from 0 to 20, n is from 0 to 6, o is from 0 to 3, p is from 0 to 3, q is from 0 to 3, r is from 0 to 10, s is from 0 to 5, t is from 0 to 5 and u is from 1 to 4 and heating the mixture to a temperature above 150° C. to cross-link said polyvinyl alcohol.