Certain thermoplastic acrylics are compatible with medium and long oil alkyds, and can be used to improve the colour and colour retention of decorative alkyd paints, whilst shortening drying time and increasing hardness. This, however, is achieved at the expense of paint solids content.
Suitable alkyd compatible acrylics include :
Neocryl B731 Zeneca Resins
Plexigum P28 Rohm
Paraloid B67 Rohm + Haas