Hot melt adhesive with functionalized metallocene catalyzed polyolefins

Abstract

A hot melt adhesive composition containing a functionalized polymer, namely, a metallocene catalyzed polyolefin elastomer grafted with maleic anhydride, together with a non-functionalized secondary polymer, namely, a metallocene catalyzed random or block polyolefin elastomer having a melt index equal to or greater than 15, a first tackifying resin having a softening point of at least 95° C., and a wax. The composition may optionally include an aromatic reinforcing resin having a softening point equal to or higher than 115° C., and a plasticizer. These hot melts provide superior hot tack, excellent adhesion, flexibility, and heat resistance above 150° F. in applications such as rigid packaging, hot fill packaging, and bottle labeling.

We claim: 
     
         1 . A hot melt adhesive composition, comprising:
 about 5% to about 50% by weight of a functionalized polymer comprising a metallocene catalyzed random polyolefin elastomer grafted with maleic anhydride;   about 5% to about 70% by weight of a non-functionalized polymer comprising a metallocene catalyzed random or block polyolefin elastomer as a secondary polymer with melt index equal or greater than 15 MI;   a solid or liquid plasticizer in an amount up about 30%;   about 5% to about 30% by weight of a wax;   about 20% to about 70% by weight of a first tackifying resin having a softening point of at least about 95° C.;   about 0% to about 20% by weight of an aromatic reinforcing resin having a softening point equal to or higher than 115° C.;   about 0.1% to about 5% by weight of a stabilizer; and   about 0% to about 3% by weight of auxiliary additives;   wherein the viscosity of the composition is equal to or less than about 20,000 centipoise at 163° C. and the composition has an initial average peel force equal to or greater than 200 grams at room temperature using hard to bond clear label films selected from the group consisting of clear polypropylene, polyethylene, polypropylene/polyethylene, and metalized oriented polypropylene label films.   
     
     
         2 . The composition of  claim 1  further including about 1% to about 25% by weight of an auxiliary polymer selected from the group consisting of metallocene catalyzed polyolefin elastomers, propylene based copolymers, ethylene-based copolymers, ethylene/alpha-olefin copolymers, olefin block copolymers, ethylene vinyl acetate (EVA), ethylene n-butyl acrylate copolymers, and styrenic block copolymers. 
     
     
         3 . The composition of  claim 1  wherein said wax is selected from the group consisting of paraffin wax, microcrystalline wax, and synthetic waxes, specifically but not limited to chemically modified waxes, polymerized alpha olefin, Fisher-Tropsch, and other Polyethylene (PE) wax. 
     
     
         4 . The composition of  claim 1  wherein said first tackifying resin has a softening point of from about 95° C. to about 140° C. 
     
     
         5 . The composition of  claim 1  wherein said composition has a viscosity equal to or less than 10,000 centipoise at 1.63° C. 
     
     
         6 . The composition of  claim 1  comprising about 1% to about 10% of said aromatic reinforcing resin, wherein the said aromatic reinforcing resin is a product from pure monomer polymerization and has a softening point of from about 115° C. to about 140° C. 
     
     
         7 . The composition of  claim 1  wherein said aromatic reinforcing resin has a softening point of from about 115° C. to about 160° C. 
     
     
         8 . The composition of  claim 1  wherein said composition passed the Standard IOPP Test after 24 Hours at 140° F., under stress at 250 grams. 
     
     
         9 . The composition of  claim 1  wherein said composition passed the bond retention test after 24 hours using the Mandrel Test Method at a temperature equal to or higher than 160° F. 
     
     
         10 . The composition of  claim 1 , wherein the plasticizer is a solid. 
     
     
         11 . The composition of  claim 1 , wherein the plasticizer is a liquid 
     
     
         12 . The composition of  claim 11 , wherein the liquid plasticizer comprises mineral oil. 
     
     
         13 . The composition of  claim 11 , wherein the liquid plasticizer comprises polybutene. 
     
     
         14 . The composition of  claim 1 , wherein the amount of plastizicer is up to about 10%. 
     
     
         15 . The composition of  claim 1 , wherein the amount of plastizicer is up to about 5%. 
     
     
         16 . A method for adhering a label to a plastic bottle comprising applying an adhesive formulation of  claim 1  to the bottle and bonding the label to the adhesive. 
     
     
         17 . The method of  claim 16 , wherein the label is a plastic label. 
     
     
         18 . The method of  claim 16 , wherein the label is selected from the group consisting of polypropylene, polyethylene, polypropylene/polyethylene, and metalized oriented polypropylene.