Developing agents general-purpose

Most general-purpose release agents have been developed for this market in part because of their low toxicity and chemical inertness and do not usually present health and safety problems. Some of the solvent dispersions require appropriate care in handling volatile solvents, and many supphers are offering water-based alternatives. Some of the sohds, particularly finely divided hydrophobic sohds, can also present inhalation problems. Some of the metallic soaps are toxic, although there is a trend away from the heavier, more toxic metals such as lead. The reactive type of release coating with monomers, prepolymers, and catalysts often presents specific handling difficulties. The potential user with health and safety questions is advised to consult the manufacturer directly. 

Most general-purpose developers in use today are metol-hydroquinone-based (MQ) rather than Phenidone-hydroquinone-based (PQ). This is in part because Phenidone has not been around that long as a developing agent, and also because Phenidone is more expensive. However, because of the allergic reaction to metol suffered by many photographers (Appendix 3 Pharmacopoeia), it is sometimes desirable to substitute Phenidone. 

Buffered organic/inorganic metallic blend. General purpose catalyst with minimal effect on physical properties. Will not contribute to odor development and does not discolor finished polyester/cellulose or all-cotton fabrics. Excellent agent for carbamate reactants. 

The most successful method developed for the production of a general-purpose synthetic rubber was the emulsion copolymerization of butadiene and styrene (SBR), which still represents the main process in use today [54,64-69]. The general principles of copolymerization will be discussed in a later section, but it is instructive at this point to examine the other main features of this system. The types of recipes used are seen in Table V [67]. The recipes shown are to be considered only as typical, as they are subject to many variations. It should be noted that the initiator in the SO C recipe (hot rubber) is the persulfate, whereas in the recipe (cold rubber) the initiator consists of a redox system comprising the hydroperoxide-iron(II)-sulfoxylate-EDTA. In the latter case, the initiating radicals are formed by the reaction of the hydroperoxide with the ferrous iron, whose concentration is controlled by the EDTA complexing agent the sulfoxylate is needed to convert the oxidized ferric(III) back to ferrous iron. The phosphate salt serves as a stabilizing electrolyte for the latex. 

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