Dispersion Barrier Coating Mechanics under Crease Stresses in Flexo Converting
Flexographic dispersion barrier coatings retain water and grease resistance under crease stresses only when coating elongation capacity matches board strain.
Styrene-Acrylic Emulsion
Aqueous Dispersion
Synthetic copolymer dispersions synthesized from styrene and acrylic monomers function as binders and functional coatings in paper converting. A styrene-acrylic emulsion comprises sub-micron copolymer particles suspended in a water medium, stabilized by anionic or non-ionic surfactants. The hard styrene segments provide stiffness, water resistance, chemical resistance, and high gloss, while acrylic monomers impart flexibility and adhesion to cellulosic fibers.
Formulations apply this copolymer system to enhance print gloss and liquid barrier properties on coated board.
Barrier Performance
Paperboard substrates require protective barrier coatings when used in chilled or humid packaging environments. Applying a styrene-acrylic emulsion creates a continuous polymer film upon water evaporation and heat curing. This film resists water penetration, grease absorption, and mineral oil migration from recycled fiber layers.
Adjusting the monomer ratio alters the glass transition temperature, allowing formulators to optimize film toughness against blocking resistance in rewound rolls. Low glass transition temperatures promote seamless film formation without heating, but increase the risk of sheets sticking together inside warm storage reels. Coating formulations incorporate synthetic wax dispersions to lower slip coefficients while maintaining strong water-repellent properties.
Application Property
Rheology modifiers control viscosity under high shear conditions in metering blade coaters. Good mechanical stability prevents emulsion breakdown during intense pump circulation.