The shift from fossil-based packaging materials to more sustainable alternatives is driven by evolving environmental regulations aiming for enhanced recyclability and biodegradability. Dispersion coatings, as opposed to extrusion-based approaches, offer significant advantages by reducing the coat weights, but generally, multiple coating layers are needed to meet functional performance requirements. This study explores the application of upscaled multilayer dispersion coatings comprising polylactic acid-based coating (PLAX) and hybrid nanomaterial lacquer (bioORMOCER^®) on commercial base papers for barrier packaging using semi-pilot reverse gravure and industrial-scale rod coaters. One multilayer structure demonstrated a low water vapour transmission rate (WVTR), achieving a WVTR of 12 g/(m²·day) under standard conditions and a 78% reduction of WVTR compared to the substrate under elevated humidity. The other multilayer structure exhibited an excellent oxygen transmission rate (OTR) of 2.3 cc/(m²·day·bar) at dry conditions, which is comparable to conventional high-performance alternatives. Both multilayer coatings enhanced the grease and mineral oil barriers significantly, as heptane vapour transmission rate (HVTR) reductions exceeded 97%. The multilayer coatings demonstrated strong potential for scalable production of sustainable, high-barrier packaging materials. These findings highlight the capability of dispersion coatings to replace traditional fossil-based barriers, advancing the development of environmentally friendly packaging solutions.

The growing demand for sustainable packaging materials highlights the need for bio-based alternatives to fossil-derived polymers, particularly in barrier applications where reduced environmental impact and recyclability are critical. Poly(lactic acid) is a promising candidate due to its renewable origin and biodegradability, yet its application in aqueous dispersion coatings remains underdeveloped. In this study, copolymers were synthesized from L-(+)-lactic acid, itaconic acid, and 1,4-/2,3-butanediol via polycondensation, and a solvent-free thermomechanical method was used to prepare aqueous dispersions from the produced copolymers. The main objective of this study was to identify an optimal composition for the copolymer and dispersion to achieve small and uniformly sized dispersion particles while also assessing the scalability of the process from laboratory to pilot production. The smallest dispersion particles and most uniform size distribution were achieved with a copolymer that had an M_n close to the average (10,180 g mol⁻¹) and a low T_g (−1.4 °C). The grade and dosage of the dispersion stabilizer significantly influenced the particle size and particle size distribution. The process scale-up, including polymer production at pilot scale and dispersion preparation at bench scale, was successfully demonstrated. The water vapor barrier properties of the coated dispersions were promising (<10 g/m² at 23 °C/50% RH), supporting the potential of aqueous PLA-based dispersions as sustainable barrier coatings.