Directly compressible granular mannitol and method for its manufacture

Method to prepare directly compressible granular mannitol free from granulation binder, of friability less than 65% in a test A consisting in subjecting a given amount of mannitol granules whose granulometry is comprised between 400 and 500 .mu.m to crushing in a friabilimeter, the thus crushed mannitol granules being passed through a sieve having a mesh width of 351 .mu.m leaving, retained on the sieve, a residue representing a proportion in percent by weight of the given amount of granules subjected to crushing, the proportion in percent by weight of the given amount not retained on the sieve representing the friability, said method being characterized by the fact that into an open vessel, of horizontal axis or inclined to the horizontal, rotated around said axis at a speed of 2 to 10 rpm, containing a mass of mannitol granules at a temperature 145.degree. to 165.degree. C., kept in motion by the rotation of the vessel, there is introduced simultaneously and continuously

• on the one hand, crystalline mannitol of granulometry less than 5 mm, preferably less than 1.5 mm, and of a temperature from 5.degree. to 150.degree. C., preferably from 50.degree. to 150.degree. C.,
• on the other hand, mannitol essentially in the liquid state, divided or not into droplets of dry matter content higher than 99% and of a temperature comprised between 164.degree. and 180.degree. C.,
• the crystalline mannitol and the liquid mannitol being brought to the surface of the mass of granules in motion in a ratio of 6 to 1.5 parts by weight of liquid mannitol per 1 part by weight of crystalline mannitol, these parameters being selected within the limits indicated so that total fusion at the surface of the mass in motion does not occur where the mannitol essentially in the liquid state and the crystalline mannitol meet, the granules of large size which have a tendency to rise to the surface of the mass in motion by a segregation phenomenon being collected preferably by overflow to the outside of the rotary vessel.