Coextruded plastic film label for in-mold labeling

Abstract

A label particularly adapted for use in in-mold labeling of blow-molded polyethylene containers comprising a heat activatable ethylene polymer adhesive layer and a surface printable layer with optional intermediate layers to provide interlayer adhesion and recycle of reground labels.

What is claimed is:  
     
       1. A polymeric adhesive label particularly adapted for use in the in-mold labeling of blow-molded polyethylene containers comprising: (1) a heat activatable adhesive substrate layer of a polymer selected from the group consisting of (a) homopolymers of ethylene (b) copolymers of ethylene with one or more α-olefins having from 4 to 8 carbons (c) mixtures of (a) and (b) and (d) mixtures of either (a), (b) or (c) with up to 50 percent by weight of a copolymer comprising ethylene and from about 1 percent to about 30 percent by weight of a copolymerizable ethylenically unsaturated carboxylic acid or ester containing comonomer; (2) when the heat activatable adhesive substrate layer comprises (a), (b) or (c) an interlayer of a copolymer of ethylene and from about 1 percent to about 30 percent by weight of a copolymerizable ethylenically unsaturated carboxylic acid or ester containing comonomer; and (3) a surface printable layer comprising polystyrene. 
     
     
       2. A label according to claim  1  having a 1 percent secant modulus of from about 150,000 to about 600,000 lbs/in 2  (1.034×10 9  to 4.136×10 9  Pa) and a thickness of from about 0.001 to about 0.010 inch (0.025 to about 0.25 mm). 
     
     
       3. A label according to claim  1  having a 1 percent secant modulus from about 200,000 to about 400,000 lb/in 2  (1.378×10 9  to 2.758×10 9  Pa). 
     
     
       4. A label according to claim  1  having a thickness from about 0.002 to about 0.005 inches (0.05 to about 0.127 mm). 
     
     
       5. A label according to claim  1 , wherein the heat activatable adhesive substrate comprises low density polyethylene. 
     
     
       6. A label according to claim  1 , wherein the carboxylic acid or ester containing comonomer is vinyl acetate. 
     
     
       7. A label according to claim  1  additionally containing a recycle layer of ground remelted label interposed between the heat activatable adhesive substrate and the surface printable layer. 
     
     
       8. A label according to claim  1 , wherein the surface printable layer additionally comprises from about 30 percent to about 2 percent by weight of a pigment or filler. 
     
     
       9. A polymeric adhesive label particularly adapted for use in the in-mold labeling of blow-molded polyethylene containers comprising: (1) a heat activatable adhesive substrate layer of a polymer selected from the group consisting of (a) homopolymers of ethylene (b) copolymers of ethylene with one or more α-olefins having from 4 to 8 carbons (c) mixtures of (a) and (b) and (d) mixtures of either (a), (b) or (c) with up to 95 percent by weight of a copolymer comprising ethylene and from about 1 percent to about 30 percent by weight of a copolymerizable ethylenically unsaturated carboxylic acid or ester containing comonomer; (2) when the heat activatable adhesive substrate layer comprises (a), (b), or (c) and interlayer of a copolymer of ethylene and from about 1 percent to about 30 percent by weight of a copolymerizable ethylenically unsaturated carboxylic acid or ester containing comonomer, and (3) a surface printable layer comprising polystyrene. 
     
     
       10. A method of making polymeric labels adapted for use in the in- mold labeling of blow - molded polyethylene containers, comprising the steps of:    
         a )  coextruding a film comprised of a heat activatable adhesive substrate layer and a surface printable layer, by either  ( i )  extruding resins to be used in the layers through a multi - feedblock die in the form of a film; or  ( ii )  extruding a tube which is later expanded by use of compressed air or an expansion mandrel to provide a film comprising the layers;    
         b )  slitting the film to a suitable width;    
         c )  printing on the surface printable layer; and    
         d )  die cutting labels from the printed film,    
         wherein materials for the coextruded film are selected so that the labels therefrom are unaffected by water or high humidity; are sufficiently stiff that wrinkling or folding does not occur during handling of the labels by in - mold labeling equipment; and are sufficiently elastic or flexible that upon attachment to the container the labels remain adhered thereto without splitting or separating despite bending, flexing, or squeezing of the container.   
     
     
       11. A method according to claim  10 , wherein the heat activatable adhesive substrate layer comprises a polymer selected from the group consisting of ( a )  homopolymers of ethylene;  ( b )  copolymers of ethylene with one or more α - olefins having from  4  to  8  carbons;  ( c )  mixtures of  ( a )  and  ( b ) ; and  ( d )  mixtures of either  ( a ), ( b ) , or  ( c )  with up to  50  percent by weight of a copolymer comprising ethylene and from about  1  percent to about  30  percent by weight of a copolymerizable ethylenically unsaturated carboxylic acid or ester containing comonomer.   
     
     
       12. A method according to claim  10 , further comprising collecting scrap label stock, regrinding the scrap, and coextruding the reground scrap as a recycle layer between the heat activatable adhesive substrate layer and surface printable layer. 
     
     
       13. A method according to claim  10 , wherein materials for the coextruded film are selected so that the labels therefrom have a  1  percent secant modulus of from about  150 , 000  to about  600 , 000  lbs/in 2 . 
     
     
       14. A method according to claim  10 , wherein materials for the coextruded film are selected so that the labels therefrom have a  1  percent secant modulus of from about  200 , 000  to about  400 , 000  lbs/in 2 . 
     
     
       15. A method according to claim  10 , wherein the labels have an overall thickness of from about  0 . 001  to about  0 . 010  inches.