In a horizontal mixer, the adhesion of composite particles to the inner wall lowers the productivity of the composite particles. In this study, we thermodynamically evaluated the influence on the production yield of the surface free energy, which is related to the adhesion of processing materials to the inner wall. The surface free energy was calculated from the measured contact angles by taking into account acid-base interactions and surface roughness, and then the change in free energy of interaction Delta G when the processing materials adhere to the inner wall was estimated. A good correlation was found between the weight of silica particles adhering to the treated wall surface and Delta G. By contrast, on addition of a polymer with low softening point, the weight of adhering silica particles was almost constant regardless of Delta G, because the surface of the inner wall was coated with polymer. Furthermore, the yield loss of composite particles varied according to sequence in which the polymer was added. In conclusion, Delta G was shown to be an important factor in suppressing the adhesion of composite particles to the inner wall.