Flexibilized polyurethanes for flexible packaging adhesive without aromatic amine migration

Abstract

Provided is an adhesive comprising a reaction product of (A1) an aliphatic isocyanate having an NCO group content of 18 to 64 and (A2) a polyol or polyamine having a molecular weight of from 400 to 4000; and (B) a polyaspartate compound, wherein viscosity of the adhesive, as measured @ 23° C. according to ASTM D4212-16, remains below 60 seconds for after four hours, and wherein the adhesive develops an acceptable bond strength to a substrate, defined as having a minimum of 150 g/in. measured @ 23° C. according to ASTM D 1876-01 or substrate tear, in less than or equal to five days after the substrate is laminated with the adhesive. The adhesives are free of aromatic amines and may find use in multi-layered laminated films for the production of flexible packaging useful in a variety of industries, including the food processing, cosmetics, and detergents industries.

1 . An adhesive comprising a reaction product of
 (A) an isocyanate-terminated prepolymer having an NCO group content of from 3% to 25% and an average functionality of 2 to 6, comprising a reaction product of
 (A1) an aliphatic isocyanate having an NCO group content of 18 to 64, and 
 (A2) a polyol or polyamine having a molecular weight of from 400 to 4000; and 
   (B) a polyaspartate compound according to formula (I)   
       
         
           
           
               
               
           
         
         wherein, 
         X represents a linear or branched aliphatic group obtained by removing amino groups from a linear or branched aliphatic polyamine, 
         R 1  and R 2  are identical or different and represent organic groups which are inert towards isocyanate groups at a temperature of 100° C. or less, 
         R 3  and R 4  are identical or different and represent hydrogen or organic groups which are inert towards isocyanate groups at a temperature of 100° C. or less, 
         n represents an integer with a value of at least 2, 
         wherein viscosity of the adhesive, as measured @ 23° C. according to ASTM D4212-16, remains below 60 seconds after four hours, and 
         wherein the adhesive develops an acceptable bond strength to a substrate, defined as having a minimum of 150 g/in. measured @ 23° C. according to ASTM D 1876-01 or substrate tear, in less than or equal to five days after the substrate is laminated with the adhesive. 
       
     
     
         2 . The adhesive according to  claim 1  further including (C), a polyol having a molecular weight of from 400 to 4000. 
     
     
         3 . The adhesive according to  claim 1 , wherein (A2), the polyol or the polyamine is based on one of a polyether, a polyester, a polycarbonate, a polycarbonate ester, a polycaprolactone, and a polybutadiene. 
     
     
         4 . The adhesive according to  claim 1 , wherein polyol (C) is based on one of a polyether, a polyester, a polycarbonate, a polycarbonate ester, a polycaprolactone, and a polybutadiene. 
     
     
         5 . The adhesive according to  claim 1 , wherein the adhesive develops an acceptable bond strength to a substrate, defined as having a minimum of 150 g/in. measured @ 23° C. according to ASTM D 1876-01 or substrate tear, in less than or equal to one day after the substrate is laminated with the adhesive. 
     
     
         6 . The adhesive according to  claim 1 , wherein the aliphatic polyisocyanate (A1) is selected from the group consisting of 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, dodecamethylene diisocyanate, 2-methyl-1,5-diisocyanatopentane, 1,4-diisocyanatocyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane, 2,4-diisocyanato-dicyclohexyl-methane, 4,4′-diisocyanato-dicyclohexyl-methane, 1,3-bis (isocyanatomethyl)-cyclohexane, 1,4-bis (isocyanatomethyl)-cyclohexane, 1-isocyanato-1-methyl-3(4)-isocyanatomethyl-cyclohexane, bis(4-isocyanato-3-methyl-cyclohexyl)-methane, 1,4-cyclohexane diisocyanate, trimers, isocyanurates, uretdiones, biurets, allophanates, iminooxadiazine diones, carbodiimides, oxadiazine triones, and prepolymers of any of these, and mixtures thereof. 
     
     
         7 . The adhesive according to  claim 1 , wherein X represents a group obtained by removing the amino groups from 1,4-diaminobutane, 1,6-diaminohexane, 2-methyl-1,5-pentane diamine, 2,2,4- and 2,4,4-trimethyl-1,6-diamino-hexane, 1,3-cyclohexane diamine, 1,4-cyclohexane diamine, 3-(aminomethyl)-3,5,5-trimethylcyclohexan-1-amine, 2,4-hexahydrotoluylene diamine, 2,6-hexahydrotoluylene diamine, 4,4′-diamino-dicyclohexyl methane, 3,3′-dimethyl-4,4′-diamino-dicyclohexyl-methane, and 3,3′-diethyl-4,4′-diamino-dicyclohexyl methane. 
     
     
         8 . The adhesive according to  claim 1 , wherein R 1  and R 2  represent a methyl, ethyl, propyl, or butyl group, wherein R 3  and R 4  represent hydrogen, and wherein n is 2. 
     
     
         9 . A process comprising reacting and curing the adhesive according to  claim 1 . 
     
     
         10 . A substrate having applied thereto the adhesive according to  claim 1 . 
     
     
         11 . The substrate according to  claim 10 , wherein the substrate is selected from the group consisting of aluminum, copper, and steel, thermoplastic polymers, wood, cement, concrete, and glass. 
     
     
         12 . A multi-layered laminated film comprising a layer of the adhesive according to  claim 1  applied to one or more substrate layers, each layer independently having a thickness of from 5 μm to 250 μm, wherein the multi-layered laminated film has a total thickness of from 20 μm to 750 μm. 
     
     
         13 . The multi-layered laminated film according to  claim 12 , wherein the one or more substrate layers are independently selected from the group consisting of paper, metal and thermoplastic polymers. 
     
     
         14 . The multi-layered laminated film according to  claim 13 , wherein the metal is selected from the group consisting of aluminum, copper, and steel. 
     
     
         15 . The multi-layered laminated film according to  claim 13 , wherein the thermoplastic polymer is independently selected from the group consisting of polyethylene, polyethylene terephthalate, corona-treated polyethylene terephthalate, metalized polyethylene terephthalate, and corona-treated polypropylene. 
     
     
         16 . A flexible packaging material comprising the multi-layered laminated film according to  claim 12 . 
     
     
         17 . A process of minimizing aromatic amine migration in a packaging material, the process comprising: applying the adhesive according to  claim 1  to a packaging material substrate, and curing the adhesive. 
     
     
         18 . The process according to  claim 17 , wherein the packaging material substrate comprises one or more layers selected from the group consisting of paper, metal and thermoplastic polymers. 
     
     
         19 . The process according to  claim 18 , wherein the thermoplastic polymers are independently selected from the group consisting of polyethylene, polyethylene terephthalate, corona-treated polyethylene, corona-treated polyethylene terephthalate, metalized polyethylene terephthalate, polypropylene, and corona-treated polypropylene. 
     
     
         20 . An adhesive comprising a reaction product of
 (A1) an aliphatic isocyanate having an NCO group content of 18 to 64;   (A2) a polyol or polyamine having a molecular weight of from 400 to 4000; and   (B) a polyaspartate compound according to formula (I)   
       
         
           
           
               
               
           
         
         wherein, 
         X represents a linear or branched aliphatic group obtained by removing amino groups from a linear or branched aliphatic polyamine, 
         R 1  and R 2  are identical or different and represent organic groups which are inert towards isocyanate groups at a temperature of 100° C. or less, 
         R 3  and R 4  are identical or different and represent hydrogen or organic groups which are inert towards isocyanate groups at a temperature of 100° C. or less, 
         n represents an integer with a value of at least 2, 
         wherein viscosity of the adhesive, as measured @ 23° C. according to ASTM D4212-16, remains below 60 seconds after four hours, and 
         wherein the adhesive develops an acceptable bond strength to a substrate, defined as having a minimum of 150 g/in. measured @ 23° C. according to ASTM D 1876-01 or substrate tear, in less than or equal to five days after the substrate is laminated with the adhesive. 
       
     
     
         21 - 22 . (canceled)