Patent GB-999809-A (GB)
Title: Non-fogging film and process
IPC: C08J5/18
Filed: 1963-08-29
Abstract: A non-fogging polyolefin film is made by admixing a polyolefin resin from at least one olefin having up to three carbon atoms with between 0.05% and 2% by weight, especially 0.1-0.3% based on the weight of said polyolefin, of at least one surface active agent having the formula <FORM:0999809/C3/1> in which R is an alkyl group having 1-17 carbon atoms and R1 is an alkyl group containing from 1 to 4 carbon atoms, said surface active agent at the temperature of melt-extrusion being resistant to thermal degradation and being sufficiently incompatible with the polyolefin resin at ambient temperature conditions whereby during cooling of the extruded film said agent concentrates at the surface of said film, and thereafter melt-extruding said polymeric material into the shape of a film, and cooling said film whereby to produce a non-fogging, transparent film having said surface active agent concentrated at the surface thereof. Preferably the polyolefin resin is a blend of an ethylene polymer having a density below 0.925 g./cc. at 25 DEG  C. and an ethylene polymer having a density of at least 0.935 g./cc. at 25 DEG  C. Specified surface active agents include N-lauroyl-sarcosine, N-myristoyl-sarcosine, N-palmitoylsarcosine, N-capryloylsarcosine, N - stearoylsarcosine, N - myristoyl - N ethyl - aminoacetic acid, and N - lauroyl-N-butylaminoacetic acid. Mixtures of these agents may also be used, e.g. a mixture of 0.1% by weight of N-lauroylsarcosine and 0.1% by weight of palmitoylsarcosine and there may also be added to the resin fillers, pigments, siliceous materials, anti-blocking agents and ultra-violet light absorbers.  After extrusion the film may be biaxially oriented.  Such films do not fog an exposure to moisture, and so are useful in wrapping products of high moisture content.ALSO:Foods are wrapped in a polyolefin film which does not fog on exposure to moisture.  Such film is made by admixing a polyolefin resin from at least one olefin having up to three carbon atoms with between 0.05% and 2% by weight, especially 0.1-0.3%, based on the weight of said polyolefin, of at least one surface active agent having the formula: <FORM:0999809/A1-A3/1> in which R is an alkyl group having 7-17 carbon atoms and R1 is an alkyl group containing from 1 to 4 carbon atoms, said surface active agent at the temperature of melt-extrusion being resistant to thermal degradation and being sufficiently incompatible with the polyolefin resin at ambient temperature conditions whereby during cooling of the extruded film said agent concentrates at the surface of said film, and thereafter melt-extruding said polymeric material into the shape of a film, and cooling said film whereby to produce a nonfogging, transparent film having said surface active agent concentrated at the surface thereof.  Preferably the polyolefin resin is a blend of an ethylene polymer having a density below 0.925g./cc. at 25 DEG C. and an ethylene polymer having a density of at least 0.935g./cc. at 25 DEG C.  Specified surface active agents include N-lauroylsarcosine, N-myristoylsarcosine, N-palmitoyl sarcosine, N-capryloylsarcosine, N-stearoyl-sarcosine, N-myristoyl-N-ethyl-aminoacetic acid, and N-lauroyl-N-butyl-aminoacetic acid.  Mixtures of these agents may also be used e.g. a mixture of 0.1% by weight of N-lauroylsarcosine and 0.1% by weight of palmitoylsarcosine, and there may also be added to the resin fillers, pigments, siliceous materials, anti-blocking agents and ultra-violet light absorbers. After extrusion the film may be biaxially oriented.  In an example, a melt is extruded at 215 DEG C. at 2.5 ft. per min. through an annular die to form a tubular film, which is passed over an internal quenching mandrel at 25 DEG C., then through a first external heating zone at 100 DEG C., and a second heating zone at 115 DEG C. in which the tube is expanded circumferentially by gas pressure, stretched longitudinally, cooled and slit to form a flat film, stretched 4.6 times in the longitudinal direction and 5 times in the transverse direction.  Such films do not fog on exposure to moisture, and so are useful in wrapping products of high moisture content.  In an example, such a film is formed into a bag, a head of lettuce inserted, the bag sealed and passed through a heating tunnel to shrink the film to a tight fit over the head of lettuce. When the package was refrigerated at 40 DEG F., there was no indication of fogging on the interior of the bag.