Harry Joseph Spinelli

Group transfer polymerization and its use in water based pigment dispersants and emulsion stabilizers

Abstract Group transfer polymerization (GTP) can be used to make AB diblock acrylic polymers. It provides excellent control of the structure of these polymers. With a hydrophilic B block, these polymers have been used to prepare water based emulsions, pigment dispersions, and slurries. These systems have property advantages over emulsions and dispersions made with conventional stabilizers. These advantages include increased stability, smaller particle sizes, lower viscosities, and less moisture sensitivity. The structure of the AB diblock polymer affects the properties of both the pigment dispersion and the emulsion particle. The composition, size and ratio of each block affect the overall quality. For aqueous systems, a balance of hydrophobic ‘A’ blocks and very hydrophilic ‘B’ blocks is needed for optimum properties. The hydrophobic ‘A’ blocks, which are homo or copolymers of methacrylate monomers (such as butyl or ethylhexyl methacrylate), are surface active and can associate with either pigment or emulsion polymer surfaces. The hydrophilic ‘B’ blocks, which are neutralized acid or amine containing copolymers, provide both ionic as well as steric stabilization in water-borne systems.

Methacrylate Star Polymers via Group Transfer Polymerization

Star polymers are highly branched polymers with linear arms radiating out from a central core. Methacrylate stars can be easily made by using Group Transfer Polymerization technology. They are made by synthesizing blocks of monofunctional (e.g. MMA) and polyfunctional methacrylates (e.g. ethyleneglycol dimethacrylate EGDM). The monofunctional monomer forms the arm of the star. The polyfunctional monomer forms a highly crosslinked core. The polyfunctional monomer is added at a higher level than the moles of initiator or living ends. A variety of compositions and sizes can be obtained by controlling both the process and the raw materials used to make them.