Additol P 791 Aliphatic polyanhydride Cytec Surface Specialties North America South and Central America Acrylic Resins Powder coating Additol™ P 791 is a solid aliphatic polyanhydride hardener for use with solid acrylic resins containing glycidyl groups to manufacture powder coatings. The binder ratio is dependent on the equivalent weight of the glycidyl functional resin employed. Solid aliphatic polyanhydride hardener. Used with solid acrylic resins containing glycidyl groups to manufacture powder coatings.