Oil and grease barrier properties of converted dispersion-coated paperboards
Ovaska, Sami-Seppo (2016-11-25)
Väitöskirja
Ovaska, Sami-Seppo
25.11.2016
Lappeenranta University of Technology
Acta Universitatis Lappeenrantaensis
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-009-0
https://urn.fi/URN:ISBN:978-952-335-009-0
Tiivistelmä
Changes in consumer habits and the replacement of solid trans fats in foodstuffs with
unsaturated fats have increased the demand for low-cost grease-resistant packaging materials
worldwide. Taking into account the global aim to reduce our dependence on oil-based plastics,
new bio-based solutions are needed to meet the demand for sustainable packaging solutions,
and the development of such materials was the focus of the work reported in this thesis.
Pigmented dispersion barrier coatings were prepared using a blade-coating technique on
commercial solid bleached sulphate paperboard. The coatings consisted of a bio-based
component, hydroxypropylated starch or hydroxypropyl cellulose, a styrene-butadiene latex
binder, and talc. The grease resistance in terms of time taken for a model grease to penetrate
the coated paperboard varied between a few hours and several days, depending on the coating
composition and on the ambient temperature during the test. Particular attention was given to
coatings that prevented oil to penetrate the whole 24 h test period described in ISO 16532-1.
The feasibility of producing barrier-coated boards was studied from the viewpoints of the
finishing and converting processes and their end-use applications. The findings suggested that
corona treatment should be used with caution if the board is to be printed, since it may cause a
drastic decrease in oil penetration time due to strike through that occur if the voltage of the
discharge is sufficiently high to change the electrical conductivity of the sample. The oil barrier
was impaired regardless of whether the uncoated or the coated side of the board was treated
with corona. Moreover, the coatings did not prevent the occurrence of reverse side effects.
Unexpectedly, contact angle determinations suggested that exposure to heat in converting
processes may even improve the oil repellency of dispersion coatings containing pigments due
to the migration of latex towards the outer surface. Migrated latex also induced self-healing of
the coating, according to scanning electron microscope (SEM) images that indicated the
disappearance of pinholes. The oil and grease resistance (OGR) was, however, dependent on
the oil viscosity and fatty acid composition. Particularly with moderately grease-resistant
samples, the penetration time of pure coconut and rapeseed oils was considerably longer than
that of their mixtures. Finally, press forming of paperboard led to a decrease in oil penetration
time, but none of the studied coating compositions completely lost their barrier properties.
The developed coating formulations seem to have a potential in many commercial sustainable
packaging applications in a transitional period before implementation of completely bio-based
coatings on an industrial scale. Potential uses may include e.g. instant meal trays and fast food
packages, but particular attention should be paid to the effects of converting and finishing
processes on the physical and barrier properties of the materials.
unsaturated fats have increased the demand for low-cost grease-resistant packaging materials
worldwide. Taking into account the global aim to reduce our dependence on oil-based plastics,
new bio-based solutions are needed to meet the demand for sustainable packaging solutions,
and the development of such materials was the focus of the work reported in this thesis.
Pigmented dispersion barrier coatings were prepared using a blade-coating technique on
commercial solid bleached sulphate paperboard. The coatings consisted of a bio-based
component, hydroxypropylated starch or hydroxypropyl cellulose, a styrene-butadiene latex
binder, and talc. The grease resistance in terms of time taken for a model grease to penetrate
the coated paperboard varied between a few hours and several days, depending on the coating
composition and on the ambient temperature during the test. Particular attention was given to
coatings that prevented oil to penetrate the whole 24 h test period described in ISO 16532-1.
The feasibility of producing barrier-coated boards was studied from the viewpoints of the
finishing and converting processes and their end-use applications. The findings suggested that
corona treatment should be used with caution if the board is to be printed, since it may cause a
drastic decrease in oil penetration time due to strike through that occur if the voltage of the
discharge is sufficiently high to change the electrical conductivity of the sample. The oil barrier
was impaired regardless of whether the uncoated or the coated side of the board was treated
with corona. Moreover, the coatings did not prevent the occurrence of reverse side effects.
Unexpectedly, contact angle determinations suggested that exposure to heat in converting
processes may even improve the oil repellency of dispersion coatings containing pigments due
to the migration of latex towards the outer surface. Migrated latex also induced self-healing of
the coating, according to scanning electron microscope (SEM) images that indicated the
disappearance of pinholes. The oil and grease resistance (OGR) was, however, dependent on
the oil viscosity and fatty acid composition. Particularly with moderately grease-resistant
samples, the penetration time of pure coconut and rapeseed oils was considerably longer than
that of their mixtures. Finally, press forming of paperboard led to a decrease in oil penetration
time, but none of the studied coating compositions completely lost their barrier properties.
The developed coating formulations seem to have a potential in many commercial sustainable
packaging applications in a transitional period before implementation of completely bio-based
coatings on an industrial scale. Potential uses may include e.g. instant meal trays and fast food
packages, but particular attention should be paid to the effects of converting and finishing
processes on the physical and barrier properties of the materials.
Kokoelmat
- Väitöskirjat [1099]