Adhesion promotion to difficult substrates for hot melt adhesives

Abstract

Hot melt adhesive compositions which have enhanced adhesion to difficult substrates, particularly at refrigerator/freezer temperatures or at elevated temperatures. The inventive compositions require a base polymer comprising at least one metallocene ethylene-containing polymer or at least one non-metallocene, amorphous, propylene containing polymer; a tackifier; an optional wax; and an adhesion promoting additive comprising at least one semi-crystalline polymer having a weight average molecular weight of about 30,000 daltons or less. It has been found that the adhesion promoting additive of this invention enhances the adhesion properties of a hot melt adhesive composition having a metallocene ethylene-containing base polymer or non-metallocene, amorphous, propylene containing base polymer, particularly at elevated temperatures or at low refrigerator and freezer temperatures where other conventional adhesives have been unsuccessful.

1 - 30 . (canceled) 
     
     
         31 . An article comprising:
 one or more substrate materials; and   a hot melt adhesive composition comprising:   i) a base polymer comprising at least one metallocene ethylene-containing polymer or at least one non-metallocene, amorphous, propylene containing polymer wherein the metallocene ethylene-containing polymer comprises at least one polymer selected from the group consisting of a metallocene ethylene-octene polymer, a metallocene ethylene-butene polymer, and a metallocene ethylene-hexene copolymer; and wherein the non-metallocene, amorphous, propylene containing polymer comprises at least one polymer selected from the group consisting of a non-metallocene amorphous propylene-butene copolymer, a non-metallocene amorphous propylene-ethylene copolymer, and a non-metallocene amorphous propylene-butene-ethylene terpolymer, wherein the base polymer is provided in an amount of from about 20% to about 80% by weight of the hot melt adhesive composition;   ii) a tackifier which comprises an aliphatic or aromatic modified cycloaliphatic hydrocarbon resin or a polyterpene, wherein the tackifier is provided in an amount of from about 15% to about 70% by weight of the hot melt adhesive composition;   iii) an optional wax; and   iv) an adhesion promoting additive provided in an amount of from about 1% to about 17% by weight of the hot melt adhesive composition comprising at least one semi-crystalline polymer having an average weight average molecular weight of about 30,000 daltons or less and, which is selected from the group consisting of a polypropylene polymer, a maleated polypropylene polymer, a maleated polyethylene polymer, and copolymers thereof.   
     
     
         32 . The article of  claim 31 , wherein the substrate material comprises a packaging material. 
     
     
         33 . The article of  claim 31 , wherein the substrate material is selected from the group consisting of plastic films, plastic sheets, metal sheets, lacquer coated papers, polypropylene, wood, paper, cellulosics, corrugated cardboard, coated board, coated carton stock composites, aluminum, glass, steel, rebar, and combinations thereof 
     
     
         34 . The article of  claim 31 , wherein the substrate material comprises a polyolefin film. 
     
     
         35 . The article of  claim 31 , wherein the substrate material comprises a vinyl film. 
     
     
         36 . The article of  claim 31 , wherein the substrate material comprises a metal sheet. 
     
     
         37 . The article of  claim 31 , wherein the substrate material is selected from the group consisting of a plastic film, a metal sheet, and combinations thereof. 
     
     
         38 . The article of  claim 31 , wherein the substrate material comprises a plastic film. 
     
     
         39 . The article of  claim 31 , wherein the substrate material comprises acrylic coated paperboard and the base polymer comprises at least one metallocene ethylene-containing polymer. 
     
     
         40 . The article of  claim 31 , wherein the substrate material is selected from the group consisting of steel, wood, plastic films, plastic sheets, and combinations thereof and the base polymer comprises at least one amorphous, propylene containing polymer. 
     
     
         41 . The article of  claim 31 , wherein the hot melt adhesive composition demonstrates improved adhesiveness to the substrate at temperatures of greater than or equal to 60° C., as compared to a composition lacking the adhesion promoting additive, when the base polymer includes at least one non-metallocene, amorphous, propylene containing polymer, and the hot melt adhesive composition demonstrates improved adhesiveness to a substrate at temperatures of less than or equal to 5° C., as compared to a composition lacking the adhesion promoting additive, when the base polymer includes at least one metallocene ethylene-containing polymer. 
     
     
         42 . The article of  claim 31 , wherein the adhesion promoting additive comprises a maleated polymer having a percent bound of about 50% or greater. 
     
     
         43 . The article of  claim 31 , wherein the adhesion promoting additive has a Mettler drop point of from about 100° C. to about 170° C. 
     
     
         44 . The article of  claim 31 , wherein the adhesion promoting additive has a viscosity, based on Brookfield viscometer measurement at 190° C., of from about 100 cps to about 5000 cps. 
     
     
         45 . The article of  claim 31 , wherein the metallocene ethylene-containing polymer has a melt index of from about 200 to about 2000. 
     
     
         46 . The article of  claim 31 , wherein the metallocene ethylene-containing polymer has a melt index of from about 400 to about 1200. 
     
     
         47 . The article of  claim 31 , wherein the metallocene ethylene-containing polymer has a specific gravity of about 0.90 or below. 
     
     
         48 . The article of  claim 31 , wherein the base polymer comprises at least one metallocene-ethylene containing polymer, and wherein the optional wax is present. 
     
     
         49 . The article of  claim 31 , wherein the base polymer comprises at least one non-metallocene amorphous propylene containing polymer, and wherein the optional wax is not present. 
     
     
         50 . The article of  claim 31 , wherein the base polymer comprises a metallocene ethylene-octene copolymer. 
     
     
         51 . The article of  claim 31 , wherein the base polymer comprises a metallocene ethylene-hexene copolymer. 
     
     
         52 . The article of  claim 31 , wherein the base polymer comprises a non-metallocene amorphous poly-alpha-olefin.