TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): The polymer component (C) is heat-processed in acidic condition. Dehydration polyene is formed, and vinylene-type monomer unit (B) is introduced, in order to obtain the copolymer (P). Preferred Composition: The polar group is ionic group which is anionic group and/or cationic group.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The vinyl-type copolymer is of formulae (I) and (II). The monomer unit is of formulae (III)-(V). An acetal modified region by mono aldehyde process or crosslinked by dialdehyde process is introduced into the copolymer (P). The ion-exchange membrane further contains reinforcing material. The reinforcing material is continuous support component containing porous film, mesh or nonwoven fabric.(o+p)/(n+o+p)=0.5-0.9;p/(n+o+p)=0.1-0.9;m/(m+n+o+p)=0.01-0.5;M=monomer unit containing polar group other than hydroxyl group;q/(q+m+n+o+p)=0.001-0.05;q.m/(q.m+m+n+o+p)=0.01-0.5;R1=H or carboxy;R2=H, methyl, carboxy or carboxymethyl;L=1-20C bivalent aliphatic hydrocarbyl optionally containing N and/or O;R1+R2=ring;andR3=H or alkali-metal atom.    TECHNOLOGY FOCUS - TEXTILES AND PAPER - Preferred Material: The nonwoven fabric is wet-laid nonwoven fabric of polyvinyl-alcohol-type short fiber. EXAMPLE - 115 mg Water, 25 g terminal mercapto group-containing polyvinyl alcohol and 6.2 g 2-acrylamide-2-methylpropanesulfonic acid were mixed together in nitrogen atmosphere and heated to 90 degrees C. 5.6 ml 2% Aqueous solution of 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)-2-propionamide) was added to the obtained solution, and polymerization was carried out for 4 hours. The reaction mixture was cooled, to obtain aqueous solution of block copolymer of polyvinyl alcohol and 2-acrylamido-2-methylpropane sulfonic acid. The pH of the solution was 9. After drying portion of aqueous solution, the mixture was dissolved in heavy water, in order to obtain block copolymer of polyvinyl alcohol and 2-acrylamide-2-methylpropanesulfonic acid. The obtained block copolymer had membrane resistance of 92.3 ( Omega ).cm2, dynamic transport number of 99% and polyene-ized rate of 77.1%.