Moisture curable polyurethane hot melt adhesive composition having low levels of diisocyanate monomer

A process for preparing a moisture curable polyurethane hot melt adhesive composition, the process comprising:

• reacting
• at least one polyol having a number average molecular weight greater than 1000 g/mole,
• a monofunctional compound comprising one isocyanate-reactive group and having a molecular weight no greater than 400 g/mole,
• a multifunctional compound comprising at least two isocyanate-reactive groups and having a molecular weight no greater than 400 g/mole, and
• diisocyanate monomer component comprising
• at least 20% by weight asymmetrical diisocyanate monomer based on the weight of the diisocyanate monomer component, and
• symmetrical diisocyanate monomer,
• to form an isocyanate-terminated polyurethane prepolymer,
• the moisture curable hot melt adhesive composition comprising no greater than 0.1% by weight diisocyanate monomer.

A moisture curable hot melt adhesive composition comprising:

• an isocyanate-terminated polyurethane prepolymer comprising the reaction product of
• a diisocyanate monomer component comprising
• from 30% by weight to 65% by weight asymmetrical diisocyanate monomer based on the weight of the diisocyanate monomer component, and
• a symmetrical diisocyanate monomer,
• at least one polyol having a number average molecular weight greater than 1000 g/mole,
• a monofunctional compound comprising one isocyanate-reactive group and having a molecular weight no greater than 400 g/mole, and
• a multifunctional compound comprising at least two isocyanate-reactive groups and having a molecular weight no greater than 400 g/mole,
• the moisture curable hot melt adhesive composition comprising no greater than 0.1% by weight diisocyanate monomer.

A moisture curable hot melt adhesive composition comprising:

• an isocyanate-terminated polyurethane prepolymer comprising the reaction product of
• a diisocyanate monomer component comprising
• from 30% by weight to 65% by weight asymmetrical diisocyanate monomer based on the weight of the diisocyanate monomer component, and
• a symmetrical diisocyanate monomer,
• at least one polyol having a number average molecular weight greater than 1000 g/mole,
• a monofunctional compound comprising one isocyanate-reactive group and having a molecular weight no greater than 400 g/mole, and
• a multifunctional compound comprising at least two isocyanate-reactive groups and having a molecular weight no greater than 400 g/mole,
• the ratio of the weight of the monofunctional compound to the weight of the multifunctional compound being less than 0.5:1, and
• the sum of the monofunctional compound and the multifunctional compound being from 0.1% by weight to 10% by weight based on the weight of the moisture curable hot melt adhesive composition,
• the stoichiometric ratio of isocyanate groups to the sum of the hydroxyl groups present on the polyol, the isocyanate-reactive group of the monofunctional compound and the isocyanate-reactive groups of the multifunctional compound being from 1.15:1 to 1.35:1.