Effect of Compression Granulation and Sieving Conditions on Compressed Pellet Strength in Wet Process Granulation Pressing

In the wet granule compression method using a polymer-binder, the factors influencing the tensile strength of compressed powder bed were experimentally investigated. It was revealed that there was a binder concentration at which the strength of compressed powder bed was maximized when the powder contains moisture during crushing. It was also found that the strength did not increase monotonically with the binder concentration when the ball diameter in crushing operation and the sieve opening in sieving operation were changed. In any cases examined, particle size distribution of the agglomeration had a bimodal distribution and the fractions of agglomerations under 100 μm were varied by the conditions. The adhesion force calculated from the tensile strengths had a maximum value near the fraction of 0.7. This fact shows that the particle size distribution of agglomeration is one of the governing factor for the strength, and there exists a size distribution which maximizes the strength.