In a device for the melting and measured discharge of a thermoplastic adhesive, a sealing sleeve conveys the solid thermoplastic adhesive into the inlet end of a melting chamber. The sealing sleeve is formed of a temperature resistant, poor heat conductive material with good sliding properties, such as polytetrafluoroethylene. Further, the sealing sleeve is provided with slots extending in the axial direction of the sleeve from the end more remote from the melting chamber toward the melting chamber.