Moisture resistance coating of packaging paper from biobased silylated soybean oil

Abstract

• A one component cure system derived from reactive silylated soybean oil provided good moisture resistant coatings to Kraft papers. • Successful coating of Kraft papers in the lab was followed by a pilot scale-up coating using industrial gravure roll coaters. • The effects of catalyst concentration and water content on the cure rate of the oil have been studied. • Critical properties including Cobb values, WVTR and contact angle were evaluated as well as the morphology of the coated surfaces using SEM. The moisture resistance of Kraft paper was greatly improved when it was coated with silylated soybean oil that was cured via silanol condensation. This moisture barrier coating was prepared from LowSat ® Soybean oil that was grafted with vinyltrimethoxysilane (VTMS) using a relatively simple process based on the “Ene reaction”. The viscosity of the resulting oil was unaffected by the silylation reaction and remained low (32 cPs). Thus, the paper coating process required no solvent, additional diluent or the need to emulsify the oil which provided a convenient one-component cure system. Dibutyltin dilaurate (DBTDL) was found to be an effective condensation catalyst and under optimal conditions complete cure was achieved in a short period of time. The cure rate was a function of the catalyst concentration, available water and the temperature. Initially, Kraft papers were coated with the silylated soybean oil in the lab and this process was followed by a pilot scale-up using a commercial gravure roll coater. Cobb values and water vapor transmission rate indicated the cured coating provided a good barrier coating. Scanning electron microscopy (SEM) images of the coated paper confirmed a uniform coating with good adhesion of the coating material to the paper.