Production of moistureproof sheet wrapping materials coated with copolymers applied from aqueous dispersions

Claim 1

A PROCESS FOR THE PRODUCTION OF MOISTURE-PROOF SHEET WRAPPING MATERIAL CONSISTING OF A FLEXIBLE BASE FILM OF A WATER-SENSITIVE, ORGANIC, NON-FIBROUS MATRIAL HAVING A SMOOTH ADHERENT COATING OF A NORMALLY CRYSTALLINE, SYNTHETIC ORGANIC POLYMER SELECTED FROM THE GROUP CONSISTING OF VINYLIDENE CHLORIDE POLYMERS AND COPOLYMERS WHICH PROCESS COMPRISES PREPARING AN AQUEIOS COLLOIDAL DISPERSION OF THE POLYMER WHEREIN THE POLYMER IS IN A PREDOMINATELY AMORPHOUS STATE, AGING SAID DISPERSION TO CONVERT THE POLYMER FROM SAID PREDOMINANTLY AMORPHOUS STATE TO A PARTIALLY CRYSTALLINE STATE IN WHICH THE PARTICLES OF POLYMER EXHIBIT AN X-RAY DIFFRACTION PATTERN HAVING AT LEAST ON E BUT NOT MORE THAN THREE DISTINCT RINGS; APPLYING THE AGED COLLOIDAL DISPERSION TO AT LEAST ONE SIDE OF THE BASE FILM IN A LAYER OF SUCH THINNESS THAT THE WATER COMPONENT IS ADSORBED BY THE BASE FILM WHEN THE POLYMER PARTICLES FROM A SMOTH, TRANSPARENT, IMPERFECTLY COALESCED NON-MOISTUREPROOFING SURFACE COATING ON THE BASE FILM; REMOVING THE ADSORBED WATER FROM THE BASE FILM BY EVAPORATION AT A TEMPERATURE SUCH THAT THE PERMEABILITY VALUE OF THE COATED FILM IS AT LEAST 500; AND THEREAFTER SUBJECTING THE COATED FILM TO A TEMPERATURE SUFFICIENTLY ELEVATED TO COMPLETE THE COALESCENCE OF THE POLYMER PARTICLES AND REDUCE THE PERMEABILITY VALUE OF THE COATED FILM BELOW TO RENDER HE FILM MOISTURE PROOF.