Abstract: The thermally reversible cross-linked hot-melt adhesive has good handling properties and storage stability, can be repeatedly melted by heating and solidified by cooling, and has high adhesiveness and good pot life. It is obtained b melting and mixing a maleimide compound, having a maleimide group at a plurality of ends thereof, with a mixture of a star-branched-structure polyurethane resin having a furan ring at a plurality of ends thereof and a straight-chain polyurethane resin having a furan ring at both ends thereof. It has a low viscosity when being melted by heating, and, after being solidified by cooling, forms a high molecular weight body having a three-thmensionally cross-linked structure, and therefore, is a resin having high cohesive force and high adhesiveness. It does not react with moisture in the air and therefore can be stored in air, and is suitable as a hot-melt adhesive for bookbinding.

Abstract: Provided is a moisture-curable polyurethane hot-melt adhesive (PUR) that, when heated, produces less hazardous isocyanate gas, and is safe and easy for a user to handle. This moisture-curable polyurethane hot-melt adhesive comprises 100 parts by weight of a urethane pre-polymer which is a product obtained from a reaction between an excessive amount of diphenylmethane diisocyanate and a mixture of a crystalline polyester polyol and a non-crystalline polyester polyol and/or a non-crystalline polyether polyol, and 5-20 parts by weight of a surface-modified silica gel containing an amino group. Preferable as the surface-modified silica gel is a silica gel to which a residual group of a silane oligomer, which is a hydrolytic product of aminoalkyl(di or tri)alkoxysilane, is linked.