Greaseproof and Barrier Stocks for Fills That Defeat Plain Kraft
High-density refining and fluorine-free dispersion coatings block lipid migration and moisture breakdown where unrefined kraft papers fail under aggressive fills.
Styrene-Butadiene Emulsion
Coating Binder
Aqueous polymer dispersion provides the internal cohesion required for high speed paperboard converting operations. Styrene-butadiene emulsion functions as a synthetic latex binder within pigment coatings applied to folding boxboard and graphic grades. The colloidal suspension consists of rigid thermoplastic polymer particles dispersed stably in water through surfactant action.
During drying on the machine cylinder, water evaporates and the discrete polymer spheres deform under capillary forces. Coalescence creates a continuous elastomeric film that binds mineral pigments tightly to the cellulose base paper. Shear viscosity remains low at high application speeds despite high solids content, which prevents blade scratching on modern trailing blade coaters.
Surface Mechanics
Pigment binding strength depends entirely on polymer film continuity across the porous substrate surface. Styrene-butadiene emulsion delivers high dry and wet pick resistance during offset lithography printing runs. Print gloss improves because the thermoplastic binder flows slightly under calendering nip pressure, smoothing micro pores in the coating layer.
Stiffness is maintained through the butadiene rubber segment, which imparts sufficient flexibility to prevent cracking during creasing and folding carton conversion. Blister resistance under heat set web offset drying conditions is governed by latex Tg values and pigment volume concentration limits. Crosslinking agents can be added to the formulation when higher solvent resistance is demanded by specialized packaging end uses.
Barrier Property
Moisture vapor transmission rates decrease because the hydrophobic polymer matrix blocks interstitial pathways between inorganic pigment platelets. Styrene-butadiene emulsion contributes indirectly to liquid barrier performance when formulated into functional top coats for food service packaging. Cohesive strength of the coated layer prevents picking when high tack adhesives are applied during carton side seam gluing.
The migration of mineral oils from recycled paperboard substrates is retarded by the tight film structure formed during latex coalescence. Regulatory compliance for direct food contact applications requires careful selection of residual monomers and emulsifying surfactants present in the dispersion.