Moisture-curable polyurethane hot melt adhesive and multilayer sheet using the same
There are provided a moisture-curable polyurethane hot melt adhesive containing a urethane prepolymer obtained by reacting a polyol (A) with a polyisocyanate (B), wherein the polyol (A) contains 40 to 80 mass % of a polycarbonate polyol (a1), 5 to 40 mass % of polytetramethylene glycol (a2), and 5 to 40 mass % of a polyester polyol (a3) obtained by reacting a polycarboxylic acid containing an aliphatic polycarboxylic acid and an aromatic polycarboxylic acid with a polyether polyol obtained by adding an alkylene oxide to bisphenol A, based on the total amount of the polyol (A), and a multilayer sheet using this adhesive. This adhesive can maintain excellent adhesion strength even after washing is repeatedly performed under stringent washing conditions without impairing soft texture of a multilayer sheet.
1. A moisture-curable polyurethane hot melt adhesive containing a urethane prepolymer obtained by reacting a polyol (A) with a polyisocyanate (B), wherein the polyol (A) contains 40 to 80 mass % of a polycarbonate polyol (a1), 5 to 40 mass % of polytetramethylene glycol (a2), and 5 to 40 mass % of a polyester polyol (a3) obtained by reacting a polycarboxylic acid containing an aliphatic polycarboxylic acid and an aromatic polycarboxylic acid with a polyether polyol obtained by adding an alkylene oxide to bisphenol A, based on the total amount of the polyol (A).
2. The moisture-curable polyurethane hot melt adhesive according to claim 1 , wherein the polyester polyol (a3) is obtained by reacting sebacic acid and isophthalic acid with a polyether polyol obtained by adding an alkylene oxide to bisphenol A.
3. The moisture-curable polyurethane hot melt adhesive according to claim 1 , wherein the polyol (A) further contains 0.5 to 5.0 mass % of a polyether polyol (a4) having three or more hydroxyl groups.
4. The moisture-curable polyurethane hot melt adhesive according to claim 1 , wherein the equivalent ratio of isocyanate groups possessed by the polyisocyanate (B) and hydroxyl groups possessed by the polyol (A) (isocyanate groups/hydroxyl groups) is in the range of 1.1 to 5.0.
5. A multilayer sheet in which a first fibrous substrate and a second fibrous substrate or a resin film are adhered with an adhesive layer interposed therebetween, wherein the adhesive layer is a cured product of the moisture-curable polyurethane hot melt adhesive according to claim 1 .
6. The multilayer sheet according to claim 5 , wherein the first fibrous substrate is a substrate made of at least one of a polyester fiber and a nylon fiber and the second fibrous substrate or the resin film is a polyurethane resin film or a fluorine resin film.