Feed additives, polymeric

During the development of these criteria the Semenov analysis was extended to systems with heat-exchanger reservoir temperatures different from feed temperatures (Tr < Tq) and with delayed runaway (larger value of e), which resulted In significant concentration drift prior to runaway. Since values of e for chain-addition polymerizations are not nearly as small as those for the gaseous explosions Investigated by Semenov, R-A Is not as sensitive nor Is It as early In terms of extent of reaction. 

Figure 6, Ejfect of solvent concentration on the molecular weight-conversion rehtionships of a tubular-addition polymerization reactor of fix size using a specified initiator type. Each point along the curves represents an optimum initiator feed concentrationr-reactor jacket temperature combination, (kinetic parameters of the initiator Ea = 24,948 Kcal/mol In k/ = 26,494 In sec f = 0.5)...

The composition of llie copolymer formed from n monomers in addition polymerization can be expressed in terms of the monomer feed composition and n n — 1) binary reactivity ratios. Thus, for terpolymerization [16],... 

The product may be of more complex structure if more than two monomers are utilized. For example, if nonhomopolymerizable monomers as described above402 are included at the beginning of the polymerization, the final product would have them on the periphery of the branched structure. Feeding the polymerization with different monomers would provide additional flexibility to this arms-first approach of making hyperbranched polymers. 

The composition of a copolymer formed in an addition-polymerization reaction will not simply be the composition of the feed M1/M2 since the reactivity of the two monomers to the initiating and propagating species (whether free radical, anion or cation) may differ. The kinetics of copolymerization is a suitable route for the introduction of the concepts since this then allows the composition of the copolymers to be described systematically. Free-radical reactions are those mostly encountered in reactive processing and are considered below. 

Uses Inks paint and varnish driers catalyst anodizing mineral supplement in feed additives foam stabilizer in food-pkg. adhesives polymerization catalyst in mfg. of paper/paperboard in contact with aq./ fatty foods catalyst for curing urethanes, epoxies additive in fuels, lubricants crosslinking reflective and conductive coatings on glass or other substrates... 

Uses Antioxidant for lubricants, rubber, waxes monomer stabilizer insecticide mfg. of dyes polymerization inhibitor for acrylic ester monomers chain transfer agent in rubber prod. polymerization control agent in food-pkg. adhesives food and feed additive treatment of food-producing animals mfg. of chlorpromazine and related antipsychotic drugs anthelmintic drug antioxidant in dry rosin size in mfg. of paper/paper-board in contact with aq./fatty foods in food-contact rubber articles for repeated use... 

Chapter 5 describes the use of polymeric food additives such as colorants, antioxidants, nonnutritive sweeteners, nonnutritive hydrocolloids, animal feed additives, as well as indicators and biosensors in foods. Polymeric food additives are to enhance food quality, to preserve and enhance food flavor, taste, and appearance without affecting food nutritional value. They are substances other than basic foodstuffs, which exhibit their functions prior to consumption of the food products, either acting as aids in the manufacture, preservation, coloration, and stabilization of food products, or serving to improve the biological value of certain foods. 

The preceding discussion of free-radical addition polymerization has considered only homogeneous reactions. Considerable polymer is produced commercially by a complex heterogeneous free-radical addition process known as emulsion polymerization. This process was developed in the United States during World War II to manufacture synthetic rubber. A rational explanation of the mechanism of emulsion polymerization was proposed by Harkins [4] and quantified by Smith and Ewart [5] after the war, when information gathered at various locations could be freely exchanged. Perhaps the best way to introduce the subject is to list the feed sent to a typical reactor. 

Since acrylic polymerizations liberate considerable heat, violent or mnaway reactions are avoided by gradual addition of the reactants to the kettie. Usually the monomers are added by a gravity feed from weighing or measuring tanks situated close to the kettie. The rate of monomer addition is adjusted to permit removal of heat with full flow of water in the condenser and a partial flow in the cooling jacket. Flow in the jacket can be increased to control the polymerization in cases of erroneous feed rates or other unexpected circumstances. A supply of inhibitor is kept on hand to stop the polymerization if the cooling becomes inadequate. 

---