Barrier coating - from laboratory to machine trial

摘要

Laboratory studies conducted at Scion and CMSE have led to the development of a formulation that has shown particular promise as a barrier coating for fibreboard as judged by specific tests such as area coverage and water vapour transmission rate (WVTR). Ongoing investigations into process and other variables have optimised the barrier coating to a level where data obtained are highly reproducible and indicative of good performance when the product is used for food packaging applications In this paper, we report on the further development of the Scion/CMSE formulation together with its successful application in two barrier coating trials carried out on a commercial scale. No difficulties were encountered in scale-up of the formulation. Multiple half-tonne batches were mixed and stored in Schutz containers for several days prior to the machine trials. The barrier formulations ran well in multiple-stage coating trials conducted under normal machine operating conditions, whether applied with a rod or air-knife. Single and double coated products from the trials were evaluated for area coverage, WVTR and creep performance using an edgewise compressive creep test (ECCTX). Best results were obtained for a single coat application. All coatings gave improvements in ECCTX creep behaviour, which equates to longer box lifetime, of greater than 50 percent when compared with uncoated board. Microscopic (SEM) examination of the coated board surface indicated the presence of either pin holes or craters, but not at an excessive level. While regarded as successful, the trials showed that further improvements are possible. The work also demonstrated the Dow coater to be a useful laboratory device in the development of barrier coating formulations.