Emulsion manufacturing process

Manufacturing processes have been improved by use of on-line computer control and statistical process control leading to more uniform final products. Production methods now include inverse (water-in-oil) suspension polymerization, inverse emulsion polymerization, and continuous aqueous solution polymerization on moving belts. Conventional azo, peroxy, redox, and gamma-ray initiators are used in batch and continuous processes. Recent patents describe processes for preparing transparent and stable microlatexes by inverse microemulsion polymerization. New methods have also been described for reducing residual acrylamide monomer in finished products. 

In addition to graft copolymer attached to the mbber particle surface, the formation of styrene—acrylonitrile copolymer occluded within the mbber particle may occur. The mechanism and extent of occluded polymer formation depends on the manufacturing process. The factors affecting occlusion formation in bulk (77) and emulsion processes (78) have been described. The use of block copolymers of styrene and butadiene in bulk systems can control particle size and give rise to unusual particle morphologies (eg, coil, rod, capsule, cellular) (77). 

Continuous polymerization systems offer the possibiUty of several advantages including better heat transfer and cooling capacity, reduction in downtime, more uniform products, and less raw material handling (59,60). In some continuous emulsion homopolymerization processes, materials are added continuously to a first ketde and partially polymerized, then passed into a second reactor where, with additional initiator, the reaction is concluded. Continuous emulsion copolymerizations of vinyl acetate with ethylene have been described (61—64). Recirculating loop reactors which have high heat-transfer rates have found use for the manufacture of latexes for paint appHcations (59). 

The original SBR process is carried out at. 50° C and is referred to as hot polymerization. It accounts for only about 5% of aU the mbber produced today. The dominant cold polymerization technology today employs more active initiators to effect polymerization at about 5°C. It accounts for about 85% of the products manufactured. Typical emulsion polymerization processes incorporate about 75% butadiene. The initiators are based on persulfate in conjunction with mercaptans (197), or organic hydroperoxide in conjunction with ferrous ion (198). The rest of SBR is produced by anionic solution polymerization. The density of unvulcanized SBR is 0.933 (199). The T ranges from —59" C to —64 C (199). 

Miller, W. G., Incidence of Microbial Contamination of Emulsion Paints During the Manufacturing Process, JOCCA, 1973, 56 (7) 307. 

Polystyrene is unusual among commodity polymers in that we can prepare it in a variety of forms by a diversity of polymerization methods in several types of reaction vessel. j Polystyrene may be atactic, isotactic, or syndiotactic. Polymerization methods include free radical, cationic, anionic, and coordination catalysis. Manufacturing processes include bulk, solution, suspension, and emulsion polymerization. We manufacture random copolymers ... 

Why are suspension and emulsion polymerization processes the primary methods by which polyvinyl chloride is manufactured How are these processes carried out ... 

Polymerisation of a monomer or mixture of monomers which have been emulsified with soap in water. SBR, neoprene and nitrile rubbers are manufactured by the emulsion polymerisation process. 

Manufacturing Processes. The three manufacturing processes already mentioned (continuous mass polymerization, batch suspension and emulsion polymerization) continued to compete with each other after 1945. Whereas the third one gradually decreased in importance, the other two were given preference in... 

The emulsion polymerization process is used by 17 production facilities to produce latex mbber products as well as solid cmmb mbber. Latex production follows the same processing steps as emulsion cmmb mbber production up to the finishing process. Between 5 and 10% of emulsion polymerized SBR and nearly 30% of nitrile mbber production (NBR) are sold as latex. Latex mbber is used to manufacture dipped goods, paper coatings, paints, carpet backing, and many other commodities. 

Commercial materials are copolymers manufactured by the emulsion polymerization process. Two main types of PVAs are used in construction ... 

Finally the purified, stabilized and filtered nitroglycerine is transported from the store to the departments where it is required for further manufacturing processes (to make dynamite or smokeless powder). When required for smokeless powder manufacture, nitroglycerine can be transported as an aqueous emulsion by means... 

Styrene-butadiene rubber, or E-SBR as it is known in manufacturing circles, was first developed in the 1930s. Known as Buna S, the compound was prepared by I.G. Farbenindustrie in Germany. Manufacturing styrene-butadiene rubber was through an emulsion polymerization process which produced a material that had a low reaction viscosity, yet had all the attributes of natural rubber. 

The goal of food emulsion manufacturers is to produce emulsions that meet or exceed the expectations of their clientele. As a first step, companies typically conduct market studies to determine what these expectations are. Sensory evaluations are then used to translate these expectations into product-specific criteria (e.g., emulsion color, texture, appearance) that serve as guidelines to design the emulsification process and verify the quality of the produced emulsion. If emulsion properties comply with the set standards (i.e., their values are within an acceptable range), manufacturers can be confident that their customer base will be satisfied with the product. 

This example demonstrates that storage stability tests are extremely useful as they allow emulsion manufacturers to accurately follow even small changes in emulsion properties. Plots of droplet size distribution and concentration as a function of time can be used to determine the kinetics of the instability process and to determine the shelf life of the product by setting upper and lower limits for both mean droplet size and concentration at each port. 

The ingredient composition and manufacturing process are important for the different types of whippable emulsions. In many industrially produced whippable emulsions, functional ingredients, such as food emulsifiers and hydrocolloids are used to improve functionality and product stability. 

The manufacturing process of emulsions is apparently more cumbersome and time-consuming than that for the conventional formulations. This adds to the cost of the product. 

Wenz and colleagues at Bayer Polymers Inc. describe the use of Raman spectroscopy to monitor the progress of a graft emulsion polymerization process, specifically the manufacture of ABS graft copolymer, in order to select the appropriate reaction termination point.40 Early termination reduces product yield and results in an extra product purification step termination too late reduces product quality. As Figure 5.5 illustrates, the reaction composition over time is not smooth and predictable, making it unlikely that off-line analysis would ever be fast enough to ensure correct control decisions. 

In conclusion, the approval of Restasis by the FDA is an important milestone in lipid emulsion research for ophthalmic application. This approval reflects the achievements of the last decade in terms of the availability of better ingredients, improved manufacturing processes, feasibility of sterilization, and better understanding of the optimization process. In all of the comparative studies done so far, positively charged SME achieved better ocular bioavailability regardless of the studied drug. Research efforts are underway to further explore the mechanism of interaction of positively charged SMEs with ocular tissues and to translate the results of this research into enhanced clinical performance. 

Sometimes the surfactants used for cleaning in manufacturing processes create undesirable O/W emulsions. This can be difficult to deal with since emulsification is usually an important aspect of a cleaning process. If the process or the detergent formulation cannot be adjusted to prevent the undesirable emulsion formation then a separate demulsification/separation step may be needed. In some cases these emulsions can be broken by separating out and concentrating the dispersed phase, such as by membrane ultrafiltration [454],... 

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