Abstract: An anhydride-containing thermoplastic resin such as a styrene maleic anhydride copolymer is processed in a vented extruder in the present of a nitrogenous chemical blowing agent to both imidize at least a portion of the anhydride groups and remove volatile residues such as unreacted styrene monomer from the resin.

Abstract: A thermoplastic resin such as a styrene/maleic anhydride copolymer is treated to remove volatile impurities such as unreacted styrene by admixing with a chemical blowing agent and extruding under a vacuum. The chemical blowing agent is converted into an inert gas such as carbon dioxide during extrusion; the gas evolved is removed, together with the volatile impurities, through one or more vents in the extruder. The use of a chemical blowing agent, rather than the inert gas itself, permits the facile distribution of the CO.sub.2 stripping agent throughout the molten thermoplastic resin using commonly available extruders without the need for elaborate gas injection means.

Abstract: A broaching tool includes a holder and a plurality of broaching inserts mounted therein. Spacers are situated between successive pairs of inserts and are formed of a tougher material than the inserts. Each spacer includes a reinforcing web which abuts against a rear surface of its respective leading insert. The reinforcing web extends higher than a lower level of the cutting edge of that respective leading insert, so as to reinforce that insert. The web terminates short of its respective trailing insert, whereby a space is formed between the reinforcing web and the trailing insert for receiving chips formed by the latter.