Polymerization continued copolymer latexes prepared

Svoboda et al. [160] investigated the emulsion copolymerization and ter-polymerization of VC with vinyl accetate, butyl acrylate and/or ethyl acrylate. The polymerizations proceeded under batch and continuous conditions and were initiated by peroxodisulfates. Anionic emulsifiers (sodium dodecyl sulfate, sodium dodecylbenzene sulfonate,..) and blends of anionic and non-ionic emulsifiers (mostly polyoxyethylene type) were used. Copolymer latexes prepared with emulsifier blends were much more stable than those with an anionic emulsifier. As expected, the copolymers prepared by continuous polymerization gave copolymers with homogeneous composition. In the batch copolymerizations, the shift in the copolymer composition with conversion was observed and particles with broader size distribution were prepared. For example, the batch VC/ethyl acrylate polymer latexes gave particles with a diameter from 180 nra to 320 nm. 

M ass Process. In the mass (or bulk) (83) ABS process the polymerization is conducted in a monomer medium rather than in water. This process usually consists of a series of two or more continuous reactors. The mbber used in this process is most commonly a solution-polymerized linear polybutadiene (or copolymer containing sytrene), although some mass processes utilize emulsion-polymerized ABS with a high mbber content for the mbber component (84). If a linear mbber is used, a solution of the mbber in the monomers is prepared for feeding to the reactor system. If emulsion ABS is used as the source of mbber, a dispersion of the ABS in the monomers is usually prepared after the water has been removed from the ABS latex. 

The polymerization of a mixture of more than one monomer leads to copolymers if two monomers are involved and to terpolymers in the case of three monomers. At low conversions, the composition of the polymer that forms from just two monomers depends on the reactivity of the free radical formed from one monomer toward the other monomer or the free radical chain of the second monomer as well as toward its own monomer and its free radical chain. As the process continues, the monomer composition changes continually and the nature of the monomer distribution in the polymer chains changes. It is beyond the scope of this laboratory manual to discuss the complexity of reactivity ratios in copolymerization. It should be pointed out that the formation of terpolymers is even more complex from the theoretical standpoint. This does not mean that such terpolymers cannot be prepared and applied to practical situations. In fact, Experiment 5 is an example of the preparation of a terpolymer latex that has been suggested for use as an exterior protective coating. 

Interest continues in the binding of heparin to polymers in an attempt to produce non-thrombogenic surfaces. This has been the aim in the use of glutaralde-hyde-protein complexes as coatings for latex rubber and polyurethanes. Glutaraldehyde has also been used to bind antibodies to partially hydrolysed polyamide surfaces for enzyme-linked radioassay techniques. One of the few examples of direct polymerization (as opposed to surface modification) in an attempt to produce polymers having improved compatibility involves the use of 2-methacryloyloxyethylphosphoryl choline in the formation of homopolymers and copolymers with methyl methacrylate. An isocyanato-urethane methacrylate has been synthesized from 2-hydroxyethyl methacrylate in connection with dental materials research in which the preparation of poly functional monomers for improvement of interfacial bonding with tooth tissue is a topic of some interest. 

The emulsion polymerization process (batch or continuous) is widely used for producing ABS because various grades of ABS resins can be manufactured. In a continuous process, two to six reactors are used in series with rubber latex feed added either to the first reactor or the first two reactors. In a typical ABS emulsion process, the styrene/acrylonitrile copolymer (SAN) and polybutadiene (PBL) are separately prepared by emulsion pro-... 

---