Method of bonding plastic sheets

Claim 1

IN A METHOD OF PACKAGING FOODSTUFFS SENSITIVE TO SOLVENT VAPORS IN PLASTIC SHEET WRAPPING MATERIAL ESSENTIALLY CONSISTING OF AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ESTERS, POLYVINYL RESINS AND MIXED POLYMERISATES OF POLYVINYL RESINS AND ADAPTED TO BE MADE ADHESIVE BY APPLICATION THERETO OF A SOFTENER, THE SEALING OF SAID PACKAGE, COMPRISING THE STEPS OF COATING AT LEAST ONE SURFACE PORTION OF SAID PLASTIC SHEET WRAPPING MATERIAL WITH A SOFTENER ADAPTED TO MAKE SAID PLASTIC SURFACE PORTION ADHESIVE, SAID SOFTENER CONSISTING ESSENTIALLY OF A MEMBER OF THE GROUP CONSISTING OF GLYCEROL TRIACETATE AND GLYCEROL DIACETATE, SAID SOFTENER PRIOR TO APPLICATION THEREOF BEING DILUTED WITH A SOLVENT BELONGING TO THE GROUP CONSISTING OF METHANOL AND ETHANOL; ALLOWING SAID SURFACE PORTION WITH SAID DILUTED PREDETERMINED SOFTENER APPLIED THERETO STAND UNTIL SAID SOLVENT HAS SUBSTANTIALLY EVAPORATED SO AS TO FORM AN ADHESIVE SURFACE PORTION CONSISTING ESSENTIALLY OF SAID COMPOUND AND SAID SOFTENER AND BEING FREE OF SAID SOLVENT; AND THEREAFTER PRESSING THE THUS FORMED ADHESIVE SURFACE PORTION AGAINST ANOTHER SURFACE PORTION OF SAID SHEET WRAPPING MATERIAL WHEREBY SAID SURFACE PORTIONS ARE BONDED TO EACH OTHER WITHOUT FORMING SOLVENT VAPORS.