Method of coating linear polyester with aqueous latex

Claim 1

In a method of preparing film base material consisting of biaxially oriented synthetic linear polyester of highly hydrophobic character which comprises coating as a layer on to a layer-respective film of linear polyester an aqueous latex of a copolymer which has been prepared by copolymerizing vinylidene chloride, an alkyl acrylate or methacrylate and optionally a copolymerizable acid and/or at least one allyl, methallyl or vinyl monomer which comprises either an active halogen group or an active methylene group, the improvement which comprises adding to said latex, a mixture of an anionic surfactant which is either an alkyl aryl polyether sulfate or sulfonate of the formula ##STR17## or an alkyl aryl polyether phosphate of the formula ##STR18## wherein R is alkyl having 6 to 10 carbon atoms, R 1 is hydrogen or alkyl having 1 to 5 carbon atoms, M is hydrogen, an alkali metal or ammonium, R 2 is hydrogen, an alkali metal, ammonium or alkyl having 1 to 5 carbon atoms, m is 0 or 1 and n is 3 to 15, and a nonionic surfactant which is an alkyl aryl polyalkylene oxide containing at least some hydroxypropylene oxide derived units of the formula ##STR19## or of the formula ##STR20## wherein R, R 1 and n have the meanings assigned to them above, x is 1 to 4, and y is 3 to 10, the proportions of nonionic to anionic surfactant being from 1 to 50 by weight up to 50 to 50 by weight, the total amount of surfactant present in the aqueous medium being up to 3%W/V of the monomers used, and then drying the coated layer and completing the orientation if it has not already been biaxially oriented.