Times are changing in the world of consumer packaging. The modern consumer is more environmentally conscientious with their choices, and there is increased demand for products that are sustainably and efficiently packaged. Changes in consumer sentiment and increasingly regulatory pressures require renewed focus on waste reduction and sustainability in the packaging industry.
A good starting point for any sustainable initiative is to increase efficiency and reduce waste. One of the most effective ways of reducing waste is through a technique called source reduction. The U.S. EPA considers source reduction—the elimination of waste before it is created—to be at the top of their waste management hierarchy. In simple terms, less packaging material equals less packaging waste.
A key measure of efficiency in the consumer packaging industry is the product-to-package ratio. A high product-to-package ratio implies that a minimal amount of packaging material is capable of adequately protecting and delivering a product to market. Flexible packaging solutions are particularly efficient, and in the most optimal conditions such as flexible drink pouches, the product-to-package ratio may reach 97:3—i.e. only ~3% of the gross weight is contributed by the packaging material itself. Flexible packaging solutions provide additional benefits with regard to reduced transportation costs leading to lower fossil fuel consumption and greenhouse gas emissions.
Flexible packaging has enjoyed tremendous market growth in the last decade as it holds particular appeal to both retailers and consumers alike. Retailers know that modern customers make rapid purchasing decisions based on the visual appeal of the packaging material. Advances in printing and coatings have allowed for almost unlimited customizability. In particular, matte coatings, haptic coatings and metallic coating have brought a richness in appearance that was not previously possible with plastic and paper substrates.
Although flexible packaging is already an efficient means to bring consumer products to market and its high product-to-package ratio supports source reduction,there is room for improvement with regard to sustainability. In particular, its reliance on multi-layered, plastic structures derived from fossil-fuels along with its poor recyclability are big challenges.
The different layers of material used in flexible packaging serve different functional requirements such as barrier properties, heat sealability or aesthetic effects. Multi-layered structures often include laminated or extruded polymeric films or foils—at the end of the product’s life cycle, these materials cannot be separated from one another for reprocessing and instead the whole construction is often landfilled. Finding an alternative construction that meets the functional requirements yet is more easily recyclable, repulpable or compostable is critical to delivering a solution.
For a plastic packaging material to be recycled, it must be a mono-material—composed of a single recyclable component—that can be separated from other waste streams prior to being melted down and reprocessed. There is some exception to this as all commercial plastics are blends of resin with various additives, fillers and stabilizers. Common workhorse additives may not interfere with the recycling process, but if certain amounts of EVOH or other functional polymers are included in a waste stream above a threshold percentage, the recycling process may be compromised. Recyclers may also rely upon additives or compatibilizer agents to allow the use of less than ideal recycling feedstock, however this incurs additional cost and complexity to the process.
Packaging materials composed of paper must be assessed for repulpability and typically must not be laminated to continuous films or foils that inhibit the repulping process. Additionally, care must be taken to use coatings, adhesives, and inks that are friendly to repulping and recycling efforts. Paper is preferred from an environmental and sustainability standpoint when compared to fossil-fuel based plastics; however, plastic films are generally higher performance with regard to barrier properties and tear resistance.
Simple Packaging, Demanding Barrier Properties
In addition to providing graphics, brand messaging, labelling and other product info, a packaging material must adequately protect its contents. Key properties like moisture vapor transmission rate (MVTR), oxygen transmission rate (OTR), and other barrier properties like water absorptivity (Cobb), and oil / grease resistance (OGR) must be suitable to protect the product during its shelf-life. Meeting all of these requirements with a single material is challenging, and the industry has traditionally relied upon constructions made up of different layers of materials to meet the application demands.
For package materials that are primarily composed of paper, assuring that the package is resistant to moisture as well as oil and grease is especially critical. For paper-based packaging solutions, a coextruded or laminated polymeric film such as polyethylene may be used for heat sealing and to provide adequate resistance to moisture and grease. Alternatively, water-based coating (s) may be used to provide these properties.
The property of oxygen transmission rate (OTR) is especially important in food packaging; oxygen is a particularly reactive gas, and is capable of causing rancidity, oxidation, odor and other undesirable signs of aging. Standard materials used in flexible packaging like polyethylene (PE) and polypropylene (PP) do not provide adequate protection from oxygen ingress. To provide “high oxygen barrier” properties then requires the use of an additional functional layer wherein ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), or metallized oriented polyester terephthalate (mOPET) are used to provide the needed protection. Nylon is also commonly employed in multi-layered structures due to its high melting point, heat resistance and oxygen barrier properties.
As a result of the above, efficiently recycling the multi-layered materials that comprise flexible packaging is not possible. For example, if a multi-layered construction includes layers of oriented PET, polyethylene, and EVOH, then it is not feasible to recycle and instead it must be landfilled. In the above construction, PET provides stiffness and temperature resistance, EVOH enhances oxygen barrier properties and polyethylene enables heat sealing. Functional and performance coatings may provide an alternative to the use of coextruded or laminated multi-layers.
Enhancing Sustainability and Recyclability with Coatings
One strategy toimprove the sustainability of packaging constructions is to remove additional material layers and replace them with coatings that minimize material usage or reduce interference with the recycling, repulping, or composting processes. Replacing extruded or laminated films with functional coatings may also offer further improvements in converting efficiency; the material usage of coatings is often significantly less than those of extrusions or laminations. Compared with an extruded polyolefin heat seal layer, a heat sealable coating made from a water-based dispersion may allow for a thinner coating, less capital investment, and reduced material usage. If the goal is to minimize the use of plastics, paper or boardstock coated with well-engineered coatings may provide a viable alternative and increase the proportion of bio-based materials used in the construction.
Coatings can be applied at minimal coat weights using multiple passes to provide a continuous film. In some cases, coatings can be engineered to make the final construction more recyclable, repulpable or otherwise improve the ability to reclaim value from the packaging material after its lifecycle is complete. To refer to a previous example, polyethylene and polypropylene perform well as moisture barriers; however, they do not provide an adequate barrier to oxygen. Rather than laminating a different material layer with enhanced oxygen barrier properties, a well-engineered barrier coating that is more compatible with the recycling process could instead be used.
Barrier coatings may also be employed with paper or board stock to improve MVTR, OTR, moisture, or oil / grease resistance. When very high barrier properties are not required, switching from plastic to a well-engineered, paper-based flexible packaging is a viable means to increase sustainability and reduce the use of materials based on fossil-fuels.
Heat sealing is an important and efficient method for manufacturing packages and pouches from filmic or paper roll stock and can also be accomplished with coatings. Heat seals are thermoplastic layers that when heated to an activation temperature begin to soften—with heat, pressure and dwell time, the polymer is able to flow and wet-out the substrate to form a reliable bond after cooling. Common materials employed are polyolefins and other thermoplastics like ethylene vinyl acetate (EVA). In multi-layer constructions, one of the required laminated or co-extruded layers may be a heat sealable polymer. As reliable extrusion often requires a caliper thicker than that needed for heat seal strength, the use of a thinner, water-based heat seal coating may reduce material usage providing enhanced sustainability through source reduction.
As reliable extrusion often requires a caliper thicker than that needed for heat seal strength, the use of a thinner, water-based heat seal coating may reduce material usage providing enhanced sustainability through source reduction.
High Performance Requires a Continuous, Pin-Hole Free Coating
If a coating is to replace a laminated or extruded polymeric film, it is critical that the coating be well-adhered, continuous and free of pin-holes. In the case of filmic substrates, a primer may be required to provide suitable anchorage. In the case of paper, which often has porosity and surface irregularities, a double coat or double bump enhances the coating’s continuity. Compared to a single coated pass, a double bump or second coating pass often enables less coated material to be used which saves material resources. Multiple passes or bumps seeks to assure that the final coated film is continuous and free of pin-holes.
To improve runnability and to eliminate defects due to transfer issues, foaming or other method specific aspects, coatings can be formulated for various coating methods such as rod, rotogravure, and flexo to provide effective coverage and runnability.
Various tests such as Cobb moisture resistance, dye stain, oil / grease resistance and MVTR can provide insights into the integrity of the coating. Careful trial work can determine the number of coating passes required as well as the optimal total coatweight. It is critical to perform these determinations for each substrate as differences in smoothness, porosity, surface energy and holdout will affect the dynamics of the coating process.
The world is moving towards a future that is focused on green, sustainable initiatives. Flexible packaging, while providing an efficient, high product-to-package ratio, has a limited ability to be recycled due to its reliance on multi-layered, plastic constructions. It is then essential to develop manufacturing strategies that reduce material use through source reduction and improve the ability of flexible packaging to be recycled rather than landfilled.
The use of well-engineered barrier and heat seal coatings may reduce material use and help to provide a more recyclable or repulpable construction while delivering the barrier and protective properties required. Additionally, paper and boardstock may be enhanced with suitable barrier coatings to provide moisture or oil / grease resistance comparable to polymeric films; this provides a means to limit the amount of fossil-fuel based materials used in the construction. There is greater consumer demand and regulatory pressure to limit or ban the use of single-use plastic containers and / or packaging. It is then critical to explore new and innovative means to enhance the sustainability and recyclability of flexible packaging to benefit the environment, consumers and manufacturers today and well into the future.
Cattie Adhesives—40 Years of Industrial Experience in Adhesives & Coatings
Cattie Adhesives is a leading USA based manufacturer and value-added supplier of water-based and hotmelt adhesives, heat seals and coatings. With 40 years of industrial experience, our trained application chemists are well equipped to serve you and your challenging applications.
Our barrier coatings are formulated to provide enhanced moisture vapor transmission rate (MVTR), oxygen transmission rate (OTR), moisture resistance (Cobb), and oil / grease resistance (OGR) to coated and non-coated paper and board substrates. Coatings may also be used on filmic substrates after appropriate treatment or application of primers. Select grades are compliant with FDA regulations for food contact including 21 CFR 176.170 and 176.180 as well as EU regulations. Coatings are formulated for a variety of coating methods including rod coating and printing press applications.
We offer a wide range of heat seal coatings that are compliant with FDA requirements for direct food contact and direct skin contact. Our heat seals bond well to a variety of substrates including paper, films, glass, metal and wood; additionally, a range of heat seal temperatures and bond strengths are available. Please reach out to discuss your particular application requirements as heat seals are particularly sensitive to substrates and sealing conditions.
In addition to providing a wide range of barrier coatings, heat seals and adhesives, Cattie Adhesives can serve as your trusted advisor and consultative partner. We will work with you to understand your applications, manufacturing processes and requirements so as to provide you with the best adhesive and coating solutions.
Reach out and schedule a technical consultation with one of our representatives today!
Cattie Barrier Coatings
8244D: A Balanced Barrier Coating An industry workhorse designed for an excellent balance of water, vapor and oil resistance. Its rheological and film-forming properties provide for exceptional coater runnability even in highly pigmented systems.
8244E: Enhanced Block Resistance & Repulpability A firmer version of 8244D providing improved block resistance and good repulpability. Water resistance is greater than 8244D but lower with regard to oil resistance.
8861: Cost Effective with Good Water Resistance Primarily used when good water resistance is required. For many applications, it is most cost effective especially when high oil resistance is not required.
8768: Balanced Oil, Grease and Water Resistance A styrene-acrylic resin supported emulsion developed for a balance of MVTR, Cobb, and oil / grease resistance. Good block resistance and high gloss.
8769: Acrylic with Excellent Oil & Grease Resistance An acrylic resin supported emulsion (RSE) developed for excellent oil and grease resistance. Water resistance is also good with excellent Cobb values. Good block resistance and high gloss.
8242: Enhanced Oxygen Transmission Rate (OTR) When protected or sandwiched between a suitable water vapor barrier coating like 8244E, 8242 provides good oxygen barrier properties. Halogen-free.
8437: Primer for Bonding Polypropylene Films When applied to treated polypropylene at low coatweights, 8437 serves as a primer to allow the use of Cattie barrier coatings on filmic, polyolefin substrates.
Cattie Adhesive Product Categories
- Hotmelt Adhesives and PSAs
- Water-based Adhesives and PSAs
- Flooring Adhesives
- Heat Seals
- Cohesives and Cold Seals
- Barrier Coatings for Paper & Board
- Specialty Adhesives
Industries Served by Cattie Adhesives
- Packaging and Bottling
- Graphic Arts and Bookbinding
- Paper and Converting
- Industrial Tapes and Adhesives
Services Provided by Cattie Adhesives
- Custom Formulated Adhesives
- Adhesive Toll Manufacturing Services
- Lab Testing Services
- Lab Prototyping
- Application Consulting