Emulsion polymer resins are made from methacrylate monomers that are not miscible with water and thus form discrete droplets. Droplet diameter and dispersion can be controlled through agitation speed, emulsifier and stabilizer. Methacrylate monomers are then typically polymerized to resin particles at ambient temperature, and are 'ready to use' for various applications. Protective, adhesive and decorative properties are achieved with specialty monomers, pigments and dyes.
Due to low-VOC regulations, emulsion polymers typically hold a strong position in coatings for automotive, wood and construction applications. Resins with superior chemical resistance are obtained with hydroxy-group containing methacrylates that can be crosslinked, e.g. with diisocyanates. All methacrylate resins demonstrate superior weatherability, for instance in architectural applications. Emulsion polymers are convenient to handle and easily applied to any substrate. Specialty monomers, such as VISIOMER® MEEU, help solve adhesion problems, e.g. between old alkyd paints and waterborne trim coatings. For more detailed information, please also refer to the paints and coatings.
Core-shell emulsion polymers
Emulsion polymers with a crosslinked core are used in a wide variety of applications. The crosslinkers selected and the applied process have an influence on the final polymer properties. VISIOMER® AMA is an asymmetric crosslinker featuring one methacrylate and one allyl group, or two different polymerizable groups of different reactivities. It is used to covalently crosslink the shell with the core of an emulsion polymer. The crosslinking efficiency also depends on the polymerization process.
In standard batch processes, symmetric crosslinkers like VISIOMER® EGDMA are most efficient. In a semibatch process, the efficient primary incorporation of the methacrylic group of VISIOMER® AMA combined with delayed crosslinking of the less reactive allyl group results in a high crosslinking efficiency. One major application of core-shell emulsion polymers are impact modifiers.