Pre-stretched film having improved edges

Abstract

Rolls of pre-stretched cling film are used to manually wrap and unitize bulky loads such as boxes on a pallet. Using film that has previously been plastically stretched simplifies the wrapping operation. Unfortunately, however, the pre-stretched rolls of film have edges which are prone to fail during use. The disclosed invention concerns rolls of pre-stretched cling wrap having improved edges that are less prone to fail, and the method and apparatus for producing such rolls.

I claim:  
     
         1 . A process for producing a roll of pre-stretched film have improved edges comprising; supplying a pre-stretched web of thermoplastic material to slitting and annealing station, slitting the pre-stretched web, thermally annealing the web along the slit line, and winding the slit and annealed material into rolls.  
     
     
         2 . A process according the  claim 1  wherein the slitting and annealing occurs by contacting the pre-stretched web with a heated slitting and annealing blade, whereby slitting and annealing are accomplished simultaneously.  
     
     
         3 . A process according to  claim 1  wherein the annealing step occurs independently of the slitting step and the annealing step comprises heating a narrow strip of web by means of a heating device.  
     
     
         4 . A process according to  claim 3 , wherein the heating device is adapted to conform closely to the surface of the pre-stretched web.  
     
     
         5 . A process according to  claim 4  wherein the heating device is arc-shaped and adapted to closely conform to the surface of the web as it passes over a roll.  
     
     
         6 . A process according to  claim 3  wherein slitting is accomplished by means of a heated blade.  
     
     
         7 . Apparatus for slitting and edge annealing a pre-stretched web of plastic film comprising: inlet guide means for directing a web of pre-stretched plastic into a slitting and annealing station, support means for said plastic web in said slitting and annealing station, slitting means for slitting said plastic web and producing a slit edge, annealing means for annealing said web adjacent said slit edge, and discharge guide means for directing said slit and edge annealed web away from said slitting and annealing station.  
     
     
         8 . Apparatus according to  claim 7  wherein said slitting means and said annealing means constitute a thermally heated blade means that contacts said plastic web.  
     
     
         9 . Apparatus according to  claim 8  wherein said support means comprises and arc-shaped shoe adapted to receive said slitting means and said annealing means.  
     
     
         10 . Apparatus according to  claim 7  wherein said annealing means comprises a narrow heating device adapted to closely conform to the web.  
     
     
         11 . Apparatus according to  claim 10  wherein said heating device is arc shaped and adapted to closely conform to the web as is passes over a roller.  
     
     
         12 . Apparatus according to  claim 11  wherein said heating device heats and anneals by applying hot air to the web.  
     
     
         13 . Apparatus according to  claim 7  further comprising a winder for forming a roll of edge slit and annealed web.  
     
     
         14 . A roll of pre-stretched film having slit and annealed edges.  
     
     
         15 . A roll of film according to  claim 14  wherein the film comprises a layer of material containing low density polyethylene or linear low density polyethylene.  
     
     
         16 . A roll of film according to  claim 15  wherein said roll of film is wound on a core.