Starve-fed

Abstract: It is well known that the amount of surfactant must be carefully controlled during starve-fed emulsion polymerization processes. Too little surfactant leads to emulsion instability and coagulation, while too much surfactant leads to secondary particle formation. Although these relationships are qualitatively understood in the art, there is little quantitative basis to guide the synthetic chemist, especially in multistep starve-fed emulsion polymerization processes to make larger supermicron particles. We have developed a method, which will be described in a companion article, to control the surfactant level by monitoring the surface tension during polymerization. In order to quantitatively predict how much surfactant to add at any given time, one needs to know in advance the adsorption characteristics of the soap. Further complicating the matter is the formation of “in situ” or oligomeric surfactant during polymerization with aqueous initiators such as ammonium persulfate. This work demonstrates how to prepare surface-active oligomers and how to make latex particles using them as surfactant. First, we established the mass balance for the initiator-derived sulfate groups in seed latexes by conductometric, potentiometric, and iodometric titrations. Based on the characterization of seed latexes, a method for determining the effective sulfate concentration has been developed. When surface-active oligomers were used as the only surfactant, we obtained a series of monodisperse, supermicron copolymer latex particles with diameters up to 3.22 μm. This is a similar result to that obtained with a commercially made anionic surfactant. © 1995 John Wiley & Sons, Inc.

Abstract: Simultaneous control of the molecular weight and the molecular weight distribution in the production of toner resins can be accomplished by using a starve fed emulsion polymerization process, which includes: selecting a desired molecular weight and molecular weight distribution of the polymer resin; determining a starve fed fraction to achieve the desired molecular weight and molecular weight distribution; and charging a reaction vessel with a chain transfer agent and a first monomer emulsion, and polymerizing monomer in the first monomer emulsion while simultaneously adding to the reaction vessel additional monomer, in the form of a second monomer emulsion, and additional chain transfer agent. The resins thus produced may be used in dry toners, liquid developers and inks suitable, for example, for ink jet applications.

Abstract: Telechelic oligomers with dialdehyde end groups and 2,3-dihydroxypropan-1-methacrylate acetonide repeat units were prepared by the ozonolytic cleavage of poly(2,3-dihydroxypropan-1-methacrylate acetonide-stat-butadiene) copolymers. The latter were prepared by monomer starve-fed emulsion polymerization at elevated temperatures and at atmospheric pressure. In contrast to similar copolymerizations of methyl and butyl methacrylate these polymerizations generated a gel fraction as well as the usual soluble copolymer. However, following ozonolysis and work up with dimethyl sulphide the whole reaction mixture became soluble. Impurities derived from oligomers with carboxylic acid end groups were removed by preparative ion exchange with a strong base ion exchange resin. The oligomers have potential applications as components of amphiphilic networks.