Multilayer films

Abstract

A multilayer film is disclosed in which an outer surface is coated with a first hot-seal adhesive and the opposite outer surface comprises a layer based on a polyolefin compound or polyvinyl compound, wherein the first hot-seal adhesive may A) contain cellulose nitrate and one or more acrylic polymers, and B) can be sealed to the layer based on a polyolefin or polyvinyl compound. A process for the production of this multilayer film is also disclosed. The multilayer film according to the invention is suitable for producing flexible packagings, in particular for packaging foodstuffs. The multilayer film according to the invention is characterized by low amounts of coating material and adhesive and thus by a low overall weight.

1 . A multilayer film having an outer surface having a coating of a first hot-seal adhesive and an opposite outer surface having a layer based on a polyolefin or polyvinyl compound, wherein the first hot-seal adhesive: 
 A) comprises cellulose nitrate and one or more acrylic polymers; and    B) can be sealed with the layer based on a polyolefin or polyvinyl compound.    
     
     
         2 . A multilayer film according to  claim 1 , wherein the first hot-seal adhesive is comprised of: 
 I) 45 to 60 wt. % of at least one cellulose nitrate (I);    II) 0.5 to 20 wt. % of at least one acrylic polymer (II);    III) 0.5 to 20 wt. % of at least one polyalkylene glycol (III);    IV) 0.5 to 15 wt. % of at least one chelate compound (IV) with titanium as central atom; and    V) 0 to 10 wt. % of at least one plasticizer; the sum of the components (I) to (V) totalling 100 wt. %.    
     
     
         3 . A multilayer film according to  claim 1 , wherein the first hot-seal adhesive is comprised of: 
 I) at least one cellulose nitrate (I);    II) at least one methyl methacrylate copolymer having an average molecular weight of 30,000 to 80,000;    III) at least one water-soluble polypropylene glycol; and    IV) at least one chelate compound with titanium as central atom (IV) comprising a chelating compound selected from the group consisting of ethyl acetonate, acetyl acetonate, lactic acid, lactic acid salts, and triethanolamine.    
     
     
         4 . A multilayer film according to  claim 2 , wherein the first hot-seal adhesive is additionally comprised of: 
 VI) 1 to 10 wt. % of at least one inorganic acid; and    VII) 1 to 10 wt. % of at least one organosilicon compound, the sum of the components (I) to (VII) totalling 100 wt. %.    
     
     
         5 . A multilayer film according to  claim 4 , wherein at least one inorganic acid (VI) is selected from the group consisting of phosphorus-containing and sulfur-containing acids.  
     
     
         6 . A multilayer film according to  claim 1 , wherein the first hot-seal adhesive comprises a compound of the general empirical formula (R 1 O) 3 Si-R 2 -X, wherein R 1 O is selected from the group consisting of methoxyl, ethoxyl and methoxylethoxyl groups; 
 R 2  is (CH 2 ) y  where y=1 to 10; and    X is selected from the group consisting of amino, hydroxy, vinyl, methacrylic and epoxide groups.    
     
     
         7 . A multilayer film according to  claim 1 , wherein the first hot-seal adhesive is a high gloss sealing lacquer.  
     
     
         8 . A multilayer film according to  claim 1 , wherein the first hot-seal adhesive covers substantially the whole area of the outer surface.  
     
     
         9 . A multilayer film according to  claim 1 , wherein the layer based on a polyolefin or polyvinyl compound contains a sealable polyacrylate composition.  
     
     
         10 . A multilayer film according to  claim 1 , wherein the outer surface additionally has a coating of a second hot-seal adhesive in such a way that the coating of the first hot-seal adhesive and the coating of the second hot-seal adhesive together substantially cover the whole area of the outer surface.  
     
     
         11 . A multilayer film according to  claim 10 , wherein the second hot-seal adhesive is comprised of: 
 i) 25 to 90 wt. % of at least one ethylene/vinyl acetate copolymer;    ii) 1 to 50 wt. % of at least one tackifying resin; and    iii) 1 to 40 wt. % of at least one wax-based lubricant; the sum of the components i) to iii) totalling 100 wt. %.    
     
     
         12 . A multilayer film according to  claim 10 , wherein the second hot-seal adhesive is comprised of: 
 (i) at least one ethylene-vinyl acetate copolymer i) having a vinyl acetate content of 30 to 40 wt. % and a melt index of 2 to 5 g/10 minutes (ASTM D 1238);    (ii) at least one tackifying resin ii) selected from the group consisting of functional hydrocarbon resins and hydrogenated hydrocarbon resins;    (iii)at least one wax iii) selected from the group consisting of carnauba wax, paraffin wax, and oxazoline wax.    
     
     
         13 . A multilayer film according to  claim 10 , wherein the second hot-seal adhesive can be sealed to the layer based on a polyolefin or polyvinyl compound situated on the opposite outer surface.  
     
     
         14 . A multilayer film according to  claim 13 , wherein the layer based on a polyolefin or polyvinyl compound contains one or more copolymers selected from the group consisting of ethylene-vinyl acetate copolymers and polypropylene copolymers.  
     
     
         15 . A multilayer film according to  claim 1 , wherein the first hot-seal adhesive is applied over a sealing region of the outer surface containing printing ink.  
     
     
         16 . A process for producing a multilayer film according to  claim 1 , said process comprising: 
 a) applying the first hot-seal adhesive in the form of a 20 to 30 wt. % solution or dispersion in one or more volatile organic solvents to the outside surface; and    b) evaporating the one or more organic solvents;    so that at least a portion of the area of the outer surface is covered by a layer of the first hot-seal adhesive.    
     
     
         17 . A flexible package comprising a multilayer film according to  claim 1 , wherein the layer of the first hot-seal adhesive on the outer surface is sealed to the layer based on the polyolefin or polyvinyl compound.  
     
     
         18 . A flexible package according to  claim 17 , wherein the sealing of the first hot-seal layer to the layer based on a polyolefin or polyvinyl compound is carried out at 100° to 160° C. and between 0.3 bar and 6 bar.  
     
     
         19 . A flexible package according to  claim 17 , wherein the outer surface additionally has a coating of a second hot-seal adhesive such that the coating of the first hot-seal adhesive and the coating of the second hot-seal adhesive together substantially cover the whole area of the outer surface and the layer of the second hot-seal adhesive is sealed to the layer based on the polyolefin or polyvinyl compound.  
     
     
         20 . A method of packaging a foodstuff, said method comprising packaging said foodstuff in a multilayer film according to  claim 1  and sealing the layer of the first hot-seal adhesive on the outer surface to the layer based on the polyolefin or polyvinyl compound.