Adhesion promotion to difficult substrates for hot melt adhesives

A process for forming a hot melt adhesive composition which comprises combining:

• a) 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;
• b) 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;
• c) an optional wax;
• and
• d) 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 wherein the hot melt adhesive composition demonstrates improved adhesiveness to a 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.