Pellets are produced in a mixing vessel. In this process, the material to be pelletized is passed through a propeller-like mixer with a helical centrifugal motion and sprayed with a finely nebulized wetting agent until pellets of the desired size have been formed. High yields of well-rounded pellets can be obtained in this way. The pellets can be coated for the purpose of controlled release of the active ingredient.

An apparatus for layering powder onto particles has a vessel in which a rotor is mounted rotatable therein around a vertical axis. The rotor is a disc with a supporting surface for supporting particles. The apparatus also has a feeder with a substantially horizontal introducing member protruding slightly into the vessel above the disc. The introducing member limits a liquid outlet and an annular powder outlet encompassing the liquid outlet. During a layering operation, the introducing member protrudes into a bed of particles lying on the rotating disc and moved by the latter. There can then be sprayed liquid and powder simultaneously onto the particles passing in proximity of the outlets. This enables layering powder onto particles to produce thereby pellets having sizes lying in a narrow range.

Sterically hindered phenol antioxidant additive granules are formed from a paste comprising an organic processing agent comprising a friability reduction agent. The friability reduction agent preferably is an alcohol, more preferably an alkanol having up to about 8 carbon atoms, most preferably methanol, ethanol, and/or isopranol. After drying, the granules consist essentially of the sterically hindered phenol antioxidant additive system. The granules have a balanced hardness that provides sufficient abrasion resistance while permitting ready dispersion into a polymer host.

A compacted particulate polymer additive composition in a dry granular form formed from a substantially uniform mixture of the following components: (a) at least one particulate sterically-hindered phenolic compound, and (b) one or more particulate polymer additives other than a sterically-hindered phenolic compound; wherein the particles of said composition are held together in compacted dry granular form exclusively or substantially exclusively by contact with dried surfaces of in situ desolvated particles from particles of one or more at least partially solvated components of (a), and optionally by contact with dried surfaces of in situ desolvated particles from particles of one or more at least partially solvated components of (b). Compositions of this type except that there is no component (b) are also described.

A pelleted stabilizer additive system and a method of making same with a good pellet yield, preferably at least about 90 wt. %. The stabilizer additive system comprises at least a stabilizer and a processing aid, preferably a mold release agent. The processing aid has a lower melting temperature than the stabilizer. The stabilizer comprises less than 50 wt. % the combined total weight of the stabilizer and the mold release agent.