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 . 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 having the structure: Y—O—C(═O)—Z—C(═O)—O—CH(CH˜)—CH˜—O—(C˜H—O)˜—CH˜—CH(CH˜)—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—CH2—CH(OH)—CH2— and HO—(CH2—CH2—O—), —CH2—CH2—, Z and Z′ are the same or different and are selected from the group consisting of —C6H4—, —(CH2),,— and combinations thereof, p is 0 or an integer of 1 to 3, o is an integer of from 2 to 10, and n is 0 or an integer of from 1 to 100. 
 
     
     
         11 . The two component laminating adhesive of  claim 10  wherein n is an integer of from 4 to 50. 
     
     
         12 . (canceled) 
     
     
         13 . A process for making a curative containing at least about two primary hydroxyl groups per molecule 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 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. 
     
     
         14 . A laminate comprised of at least one polymeric film and the two component laminating adhesive of  claim 1  in cured form. 
     
     
         15 . The laminate of  claim 14  comprised of at least two polymeric films, wherein the two component laminating adhesive is located between two of said polymeric films and adheres said polymeric films to each other. 
     
     
         16 . The laminate of  claim 14  wherein at least one polymeric film is comprised of a thermoplastic selected from the group consisting of polyethylene terephthalate, polyethylene, polypropylene, and polyvinylidene chloride. 
     
     
         17 . The laminate of  claim 14  additionally comprising a metal foil, wherein the two component laminating adhesive is located between the metal foil and at least one polymeric film. 
     
     
         18 . The laminate of  claim 14  wherein at least one polymeric film is metallized or has a coating comprised of an inorganic oxide deposited thereon. 
     
     
         19 . A flexible film laminate comprising (a) a first layer comprised of a first polyolefin or first polyester; (b) a second layer comprised of a second polyolefin, which may be the same or different from the first polyolefin, a second polyester, which may be the same as or different from the first polyester, or a metal foil; (c) an adhesive layer bonding the first layer to the second layer, said adhesive layer being obtained by combining and reacting Component A and Component B in accordance with the two component laminating adhesive of  claim 1 . 
     
     
         20 . A method of making a flexible film laminate, said method comprising a) combining Component A and Component B in accordance with the two component laminating adhesive of  claim 1  to form an adhesive mixture, b) joining a first flexible film and a second flexible film using the adhesive mixture interposed between the first flexible film and the second flexible film, and c) curing the adhesive mixture.