Process for coating polyolefin films

A process for coating a surface-activated polyolefin film with a vinylidene copolymer material, which comprises (a) applying to the surface of said film a solution in an organic solvent, of a vinylidene copolymer material containing in copolymerized form from 35 to 60 wt. % of vinylidene chloride, from 30 to 50 wt.% of one or more alkyl esters of acrylic and/or methacrylic acid, from 1 to 10 wt.% of acrylic and/or methacrylic acids and from 1 to 10 wt.% of one or more hydroxyalkyl esters of acrylic and/or methacrylic acid, a ratio of from 0.5:1 to 5:1 being maintained in said material between the number of carboxyl groups and the number of hydroxyl groups, said material consisting of one or more copolymers each comprising moieties of said vinylidene chloride and said alkyl esters, any copolymer which does not include moieties of said hydroxyalkyl esters containing moieties of said acrylic and/or methacrylic acids, said solution containing a latent catalyst to initiate a cross-linking interaction between the carboxyl and hydroxyl groups of the vinylidene copolymer material, said latent catalyst consisting of a substance liberating acid at a temperature of at least 70.degree. C., and said latent catalyst being the salt of an organic or inorganic acid with a tertiary amine, or an acid ester of a polybasic inorganic acid or polycarboxylic organic acid with an aliphatic alcohol and (b) heat-treating the thus coated film at a temperature of from 70.degree. C. to 130.degree. C., to dry said film and provoke said cross-linking.