Paper Technology International 2024 - Journal - Page 69
PAPERTECHNOLOGYINTERNATIONAL
The BIM Barrier Standard helps us identify which properties are required. To meet the requirements up to three different barriers
can then be applied in up to three layers.
polymeric latexes and pigments have high surface energy (lower
hydrophobicity) and are widely used as a primary layer to even
out paper surfaces and facilitate deposition of a second overlaying
coating layer.
Barrier coatings based on thermoplastic polymers are often
heat sealable with technologies such hot-bar welding, impulse
welding and ultrasonic. Effective sealing can be achieved at approx.
100-150 °C depending on contact pressure and dwell time. Heat
sealing are typically used in food packaging applications including
昀氀exible pouches and bags, as well as tray and bowl sealing for food
packaging.
The increased focus on recycling and sustainable packaging
has driven the trend to replace fossil raw materials in water based
coatings with renewable analogues. Alternative biopolymers, like
polysaccharides and lignins, along with bio based waxes can be
used for fully or partially biobased coatings. Today, the higher cost,
more dif昀椀cult processing and lower performance in comparison to
fossil based, hinders exploitation in many industrial applications.
For applications with high sustainability demands, biobased barrier
coatings are still interesting alternatives to consider. Introducing
viable fully or partly bio based barriers is a focus area in the industry.
Application of barrier coatings on paper surfaces can be
achieved with conventional coating methods in-line or off-line such
as Bar or Blade, Roll, Air-knife, Flexographic and Spraying. Drying
can be achieved with Infrared, Contact drying or hot air ovens.
These method provides a controlled and precise application of
the additives to the paper surface. The deposited of respective
layer have a large effect on barrier resistance depending on paper
substrate and demand and typically varies between 2-15 g/m2 (dry).
Barrier coatings represent a complex technology with
thousands different types of waxes, polymers, and pigments.
Formulating modern, highly ef昀椀cient, and sustainable products
demands speci昀椀c scienti昀椀c skills and expertise. BIM Kemi has
developed an extensive barrier coating program that is intended for
昀椀bre based packaging, BIM Barrier™. Functional barrier concepts
has been a focus area in the company for over 40 years.
BIM Barrier™ is applied on the surface of paper or board
in order to add functions like oil and grease resistance, moist and
water resistance. Depending on the end-use and desired properties
of the packaging materials, different types of barrier coatings, or
even a combination of barriers, can be necessary. Therefore, we at
BIM Kemi have de昀椀ned the BIM Barrier Standards. This is a tool to
help eliminate over-packaging and achieve optimal use of resources
by identifying the requirements for each product.
The Barrier Standards required for a packaging material
are de昀椀ned by the demand placed on the barrier and the expected
packaging life term. Depending on requirements we can tailor a
solution with one layer, two layer or combination of two layers or
even three layer to create the perfect mix of properties. A typical
multilayer concept intended for food packaging is shown in image
4 and consist of a pigment based pre-coating with one or two over
layers to provide oxygen and OGR/water/moist resistance.
Example multilayer concept for food packaging that consists of
primer layer and WOGR barrier deposited on paper substrate
towards the inside and a printable (pigment based) outer layer.
Combination system
Combining wet end additives and surface coatings in
paper and board manufacturing can offer enhanced oil and grease
resistance to the 昀椀nal product. The combination allows for a
comprehensive approach to enhance resistance throughout the
entire paper structure. Combining wet end additives and surface
coatings allows for customization without compromising other
essential characteristics of the paper and is advantageous for high
demand barriers.
Barrier coatings can only provide OGR to the surface of the
substrate and offer no internal protection, i.e., protection from the
migration or “wicking” of oils and fats through contact with any cut
edges inside the packaging. Here, an internal treatment to the pulp
is necessary to give wicking protection. Additionally, adding a wet
end additive to the pulp, can enable low grammage weight surface
barrier coatings while achieving desired OGR properties. For high
demand barriers, a combination of wet-end additive and surface
coating is advantageous.
BIM Kemi has developed a new technological innovation
signi昀椀cantly improving oil and grease resistance of 昀椀bre based paper
and board packaging products by combining wet-end treatment, BIM
Oilguard™ with barrier coatings, BIM Barrier™.
BIM Dual Barrier is especially advantageous for packaging
types where it is hard to achieve an even coating, such as
3D-shaped products and low-weight surfaces but can be used for all
types of 昀椀bre based packaging with higher demands.
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