Development of water-based adhesives for oriented Polypropylene (OPP) lamination

Abstract

Eco-friendly laminating adhesive has been developed for flexible packaging industries due to urgent restriction of volatile organic compounds (VOCs) emissions from anthropogenic sources. The water-based polyurethane laminating adhesive was derived by a condensation polymerization of isophorone diisocyanate, polypropylene glycol and 2,2-bis(hydroxymethyl)propionic acid, while the water-based polyacrylate laminating adhesive was synthesized by an emulsion polymerization of 2-ethylhexyl acrylate, ethylene glycol methyl ether acrylate, styrene, 2-hydroxyethyl methacrylate and acrylic acid. The parameters influencing the adhesive’s performance consisted of chemical composition, reinforcing fillers and manufacturing processes. Among those parameters, the fabrication of waterborne core-shell polyacrylate laminating adhesive through a two-stage seeded semi-batch emulsion polymerization was desirable with a rigid core having a glass transition temperature (Tg) of -14.9 °C encapsulated by a soft shell having Tg ranging from -18.4 °C to -32.0 °C, depending on variables. The optimal formulation was accomplished using a core-to-shell ratio of 0.5 and 10 wt% of ethylene glycol methyl ether acrylate concentration in its shell, giving a bonded joint 180° peel strength 214.5 N/m with high cohesive strength and good adhesion to various substrates. This water-based laminating adhesive system has the possibility of replacing solventborne technology.