Laminating adhesives based on primary hydroxyl-containing curatives

Abstract

A curative containing two or more primary hydroxyl groups per molecule and one or more moieties derived from a secondary hydroxyl-containing polyol such as polypropylene glycol is prepared in a multistage process wherein the secondary hydroxyl-containing polyol is end-capped with an excess of a reactant such as a polybasic acid and the resulting functionalized intermediate is then reacted with a polyol such as glycerin or diethylene glycol containing primary hydroxyl groups. Such curatives may be used in combination with isocyanate-functionalized polyurethane prepolymers to provide two component adhesives useful for laminating thin films and/or foils.

1 . A two component laminating adhesive comprising Component A and Component B, wherein Component A comprises at least one isocyanate-functionalized compound and Component B comprises a curative containing at least about two primary hydroxyl groups per molecule, said curative having been obtained by a process comprising reacting a first polyol containing predominately secondary hydroxyl groups with a stoichiometric excess of a reactant selected from the group consisting of polybasic acids, polybasic acid anhydrides, polybasic acid esters, and polyisocyanates to form an intermediate containing at least about two terminal functional groups per molecule selected from the group consisting of isocyanate, carboxylic acid and carboxylic acid ester and reacting said intermediate with a stoichiometric excess of a second polyol containing predominately primary hydroxyl groups. 
     
     
         2 . The two component laminating adhesive of  claim 1  wherein said first polyol is a polyalkylene glycol containing secondary hydroxyl groups. 
     
     
         3 . The two component laminating adhesive of  claim 1  wherein said first polyol is a polypropylene glycol. 
     
     
         4 . The two component laminating adhesive of  claim 1 , wherein Component A comprises an isocyanate-functionalized polyurethane prepolymer. 
     
     
         5 . The two component laminating adhesive of  claim 1 , wherein said reactant is selected from the group consisting of aliphatic linear saturated dicarboxylic acids containing from 4 to 12 carbon atoms, phthalic acids, orthophthalic acid anhydride, and mixtures thereof. 
     
     
         6 . The two component laminating adhesive of  claim 1 , wherein said second polyol is an aliphatic compound containing 2 to 5 hydroxyl groups per molecule and the ratio of primary hydroxyl groups to secondary hydroxyl groups in the second polyol is at least 2:1. 
     
     
         7 . The two component laminating adhesive of  claim 1 , wherein said second polyol is selected from the group consisting of ethylene glycol, ethylene glycol oligomers, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, and mixtures thereof. 
     
     
         8 . The two component laminating adhesive of  claim 1 , wherein said curative contains an average of about two to about four hydroxyl groups per molecule. 
     
     
         9 . The two component laminating adhesive of  claim 1 , wherein said reactant is selected from the group consisting of adipic acid, orthophthalic acid anhydride, and mixtures thereof. 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . (canceled) 
     
     
         13 . (canceled) 
     
     
         14 . (canceled) 
     
     
         15 . (canceled) 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . (canceled) 
     
     
         19 . (canceled) 
     
     
         20 . (canceled) 
     
     
         21 . A method of making a curative comprising:
 providing a first polyol containing predominately secondary hydroxyl groups;   providing a reactant selected from the group consisting of polybasic acids, polybasic acid anhydrides, polybasic acid esters, and polyisocyanates;   reacting the first polyol containing predominately secondary hydroxyl groups with a stoichiometric excess of the reactant selected from the group consisting of polybasic acids, polybasic acid anhydrides, polybasic acid esters, and polyisocyanates to form an intermediate containing at least about two terminal functional groups per molecule selected from the group consisting of isocyanate, carboxylic acid and carboxylic acid ester;   providing a second polyol containing predominately primary hydroxyl groups;   adding a stoichiometric excess of the second polyol containing predominately primary hydroxyl groups to the already formed intermediate; and   reacting the intermediate with the stoichiometric excess of the second polyol containing predominately primary hydroxyl groups to form the curative, the curative having at least about two primary hydroxyl groups per molecule;   wherein the curative will not separate and will react with an isocyanate-functionalized compound to provide a curable laminating adhesive.   
     
     
         22 . The method of  claim 21  wherein the reactant is reacted with the first polyol at a molar ratio of at least about 2:1. 
     
     
         23 . The method of  claim 21  wherein the intermediate is reacted with the second polyol for a time and at a temperature effective to convert essentially all of the terminal functional groups on the intermediate to either urethane or ester groups. 
     
     
         24 . The method of  claim 21  wherein the curative has the structure: Y—O—C(═O)—Z—C(═O)—O—CH(CH 3 )—CH 2 —O—(C 3 H 6 O) n —CH 2 —CH(CH 3 )—O—C(═O)—Z′—C(═O)—O—Y′
 wherein Y and Y′ are the same or different and are selected from the group consisting of HO—CH 2 —CH(OH)—CH 2 — and HO—(CH 2 —CH 2 —O—) p —CH 2 —CH 2 —; Z and Z′ are the same or different and are selected from the group consisting of —C 6 H 4 —, —(CH 2 ) o — and combinations thereof; p is 0 or an integer of 1 to 3; m and o are the same or different and are integers of from 2 to 10; and n is 0 or an integer of from 1 to 100. 
 
     
     
         25 . The method of  claim 24  wherein n is an integer of from 4 to 50. 
     
     
         26 . A laminating adhesive including:
 Component A comprising an isocyanate-functionalized compound; and   Component B comprising the curative of  claim 21 .   
     
     
         27 . The laminating adhesive of  claim 26 , including:
 Component A comprising a compound having two or more isocyanate groups per molecule; and   Component B comprising the curative of  claim 21  and a hydroxy-functional natural oil or fat.   
     
     
         28 . The laminating adhesive of  claim 26 , including:
 Component A comprising a compound having two or more isocyanate groups per molecule; and   Component B comprising 1% to 100% by weight of the curative of  claim 21 .   
     
     
         29 . The laminating adhesive of  claim 26 , including:
 Component A comprising a compound having two or more isocyanate groups per molecule; and   Component B comprising 1% to 100% by weight of the curative of  claim 21 .   
     
     
         30 . The laminating adhesive of  claim 26 , including:
 Component A comprising a compound having two or more isocyanate groups per molecule; and   Component B comprising 40% to 70% by weight of the curative of  claim 21 .   
     
     
         31 . A flexible film laminate comprising:
 (a) a first layer comprised of a first polyolefin film or first polyester film;   (b) a second layer comprised of a second polyolefin film, which may be the same or different from the first polyolefin film, a second polyester film, which may be the same as or different from the first polyester film, or a metal foil;   
       (c) an adhesive layer bonding the first layer to the second layer, said adhesive layer being a mixture of Component A comprising a compound having two or more isocyanate groups per molecule and Component B comprising 1% to 100% by weight of the curative of  claim 21 .