Paper Technology International 2024 - Journal - Page 68
PAPERTECHNOLOGYINTERNATIONAL
Plastic 昀椀lms are typically applied to 昀椀bre based packaging by
extrusion or lamination technology. However, plastic 昀椀lms can cause
issues with repulpability and compostability of the 昀椀nal product. The
non-recyclable and non-biodegradable characteristics of plastic raise
signi昀椀cant concerns about environmental impact, contributing to
pollution in both land昀椀lls and aquatic ecosystems. The degradation
process of plastic is a lengthy one, ranging from tens to hundreds of
years, in昀氀uenced by environmental variables such as sunlight, heat,
and pH conditions. Compounding this issue, the effects of global
warming and acid rain, resulting from climate change, further slow
down the degradation of plastic. Consequently, plastic pollution in
the oceans in昀氀icts harm on organisms, and sea life. EU rules on
single-use plastic products (SUPD) aim to prevent and reduce the
impact of certain plastic products on the environment, in particular
the marine environment, and on human health.
PFAS are a diverse group of synthetic chemicals with strong
carbon-昀氀uorine bonds that are chemically inert and resistant to high
temperatures. PFAS based chemicals are commonly applied in
the wet end or as a surface sizing together with starch. However,
they are often referred to as “forever chemicals” due to their bio
persistence, leading to irreversible environmental exposure and
accumulation. Furthermore, exposure to PFAS has been linked to
carcinogenic effects and potential disruption of the human endocrine
and reproductive systems. This has led to a number of proposed
bans and restrictions in several countries, including a restriction
proposed by 昀椀ve EU-countries and submitted to ECHA on January
13, 2023.
To enhance sustainability and diminish the environmental
impact of plastics and PFAS, it is imperative to seek alternative
chemistries for 昀椀bre based packaging.
PFAS and plastic free chemistry adapted to end-use
requirements
There are various application methods employed to impart
PFAS and plastic free oil and grease resistance to 昀椀bre based
packaging. The choice of application method depends on various
factors, including the properties of the additives, the desired level of
resistance, the type of packaging being produced, and the speci昀椀c
requirements of the end-use applications. Each method offers a
unique approach to achieving effective oil and grease resistance.
Manufacturers may choose the method that best suits their
production processes and the characteristics they want to impart to
the 昀椀nal paper product.
At BIM Kemi, we have developed different chemical
concepts adapted to speci昀椀c customer requirements; wet end
additives, barrier coatings and combination systems for high
demand barrier properties.
Wet-end additives
The oil and grease resistant additives can be added directly
to the pulp slurry at different stages of pulp preparation. This allows
for uniform distribution of the additives among the paper 昀椀bres. By
incorporating these additives into the wet end of the papermaking
process, it enables paper manufacturers to produce grease resistant
paper or board, such as food wrapping paper, pizza cartoons etc,
without the need for barrier surface applications on- or of昀氀ine while
maintaining high speed production. It also enables the production
of grease resistant 3D moulded 昀椀bre products for fast food/food on
the go applications, without the use of a plastic lamination on the
surface or PFAS in the wet end.
BIM Kemi has developed a novel wet end additive that
provides grease and oil resistance, BIM Oilguard™ (European
patent pending). The additive is based on cationic micro dispersions
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with excellent attraction to the cellulose 昀椀bre enabling a good
distribution in the pulp suspension and adsorption to the cellulose
昀椀bre before forming the paper, board or moulded 昀椀bre product.
Studies have shown that no retention aids are needed and oil
uptake can be reduced by 80 % on bleached kraft virgin pulp sheets
and by 75 % on recycled kraft paperboard, see image below.
Oil and grease hold out comparing untreated paper with paper
treated with BIM Oilguard™
The additive also gives water resistance but is favourably
combined with a traditional sizing agent for optimal water sizing.
Performance testing of sheets made from different pulp source
treated with the wet end additive show that different pulp types
have different optimum dosage levels and give rise to different
OGR properties. It is well established that unbleached pulp
demonstrate better inherent water sizing ability and in general,
requires lower amount of sizing additive. This is also observed when
昀椀nding the optimum dosage level for BIM Oilguard™. Fine tuning
combinations of pulp types and level of re昀椀ning in combination with
BIM Oilguard™, excellent oil and grease resistant properties can be
achieved. Additionally, high density and good formation are other
important parameters when producing oil and grease resistant 昀椀bre
based food packages using a PFAS free wet end additive.
Barrier coatings
Barrier coatings are made from water based dispersions
that are laid on the surface of paper- or board to provide a protective
layer against water, moist, oils/fat (OGR) and oxygen. Barrier
formulations typically consist of aqueous polymer dispersions
(Latex) that forms a non-porous 昀椀lm after evaporation of water.
Latex is a stable aqueous dispersion of organic polymer particles.
Typically used polymers are modi昀椀ed ordinary styrene-butadienes,
different acrylates and methacrylates, polyole昀椀ns, vinylene
acetates, copolymers of these or natural biopolymers. Chemical
composition of barriers chemistry can be tailor made depending on
the demand placed on the barrier and expected packaging life term
requirements.
Different additives, such as waxes and pigments, can
be added to improve functional properties including oil, grease,
water- and moist resistance. Choice of additive is dependent on
desired property of the end product. Waxes are typically added to
boost hydrophobicity and oil/grease resistance. Pigment (昀椀llers)
may be added to increase properties such as runnability and
cost-effectiveness. Barrier coatings that are made of a blend of
