Best Practices in Paperboad Selection and Paper Converting
The process from packaging concept to finished product involves several strategic choices. In this article, we will analyze some of these steps. The substrate onto which the design will be printed is carefully matched to the characteristics of the product it will contain. Depending on the design and target market, specific paperboard grades are preferred. Selection of substrate will also influence the ability of the printed piece to fold in the tray former or converting equipment and withstand the product's weight and compression forces against it.
According to the paperboard grade and grammage, die cutting and creasing are planned, designed and implemented. The die depth and width is precisely adjusted to cut and crease effectively, neither insufficiently - which would require rework -
nor excessively which would wear out the elements too quickly.
Having reviewed these principles, we will review some major paperboard grades and their applications used tray forming and folding carton manufacturing. We will then focus more on paperboard packaging for food products.
Die Cutting for Paperboard Packaging
One the main principles in die cutting is that the cut should precise and should not leave loose fibers or debris behind. When tuning the die cutting process, the paperboard's tensile strength and tear resistance must be factored in. The moisture content also affects runnability and cutting properties - the higher it is, the more difficult to cut. On the contrary, low levels would make it too fragile, generating dust particles.
The premises should maintain constant temperature and humidity to prevent the material from contracting or expanding, making register harder to achieve.
Paperboard Creasing Best Practices for Tray Formers and Folding Carton Converting
Folding cartons and paperboard trays require creases to be marked on the substrate so that the tray former and other converting equipment can adequately fold the blanks. An incorrect crease may cause it to crack open, or make the material spring back preventing effective glue bonding. The crease parameters such as width and depth must be carefully gauged considering the paperboard thickness and properties, and grain direction.
The crease is effected by a sharp steel ruler with smoothed edges, which pushes the paperboard into the counter plate. A thicker material would require a wider groover. Paperboard coating in all cases should be flexible to prevent cracking.
Of course, creasing causes the different layers in the paperboard to delaminate, but that is natural. It is an expected and controlled effect for the intended purposes.
Folding Carton and Paperboard Tray Glueing Methods
Hot-melt and water-based and the most prevalent types of glue used in the packaging industry. The surfaces bond when the glue undergoes a chemical reaction with the substrate, it cools down, and the solvent evaporates.
Hot-melt glues are applied with a nozzle system. Water-based can use nozzles or a glue wheel system. Glue adherence should be able to rip the fiber, rather than just the coating of the paperboard. How much glue, applied with how much force for how long, are some of the main parameters that affect the result. The quantity of adhesive utilized varies based on both the paperboard grade and the glue type. As a rule of thumb, glue should penetrate up to a depth of 1 to 3 times the fiber diameter.
Special Focus on Paperboard Packaging for Food Products
Paper and paperboard are made of interweaved cellulose fibers obtained from wood by using sulfite and sulfate. The fibers are then pulped and / or bleached and treated with chemicals and strengthening agents.
Functional Properties of Paperboard
Packaging technology must balance food protection with other issues, including energy and material costs, social and environmental impacts such as pollutants and disposal of municipal solid waste.
Paperboard packaging for food products should retard product deterioration, preserve its qualities and ensure shelf-life. It does so by protecting the product from chemical, biological, and physical harm.
The informational and branding dimensions impact packaging design and material usage and may involve unique finishes like lamination and varnishing. The image and style of the product can make a difference, both on the shelves and in the online environment.
Folding cartons and food trays must also offer conveniences like easy handling and resealability, and in many cases, microwavability. Consumers prefer lightweight materials, which are easy to open and integrates with the next step - consumption. Packaging is expected to save time in food preparation.
Main Paper and Board Grades used in Packaging
Plain paper does not offer reasonable protection as primary packaging, unless it is coated, impregnated or laminated to improve its functional performance, and only for shorter periods of time.
Paperboard has a higher density and is made of several layers and is ideal to manufacture cartons and trays, though rarely in direct contact with food. It can be further classified into:
White board: Composed of multiple layers of bleached chemical pulp. It is the only paperboard type suitable for direct contact with food.
Solid board: Characterized by higher strength, it is made of several plies of bleached sulfate board. Combined with polyethylene lamination, it is apt to form liquid cartons, used for milk, soft drinks, and juice.
Chipboard: Sourced from recycled paper, it is not appropriate for direct contact with food. It is added as the outer layer of cereal boxes, for example.
Fiberboard: there is a solid kind that has high strength, and it can be used in milk powder or coffee packages if a plastic or aluminum laminate is applied to it. A second kind is manufactured in corrugated format, with high resistance to damage, making a light, cost-effective case packing for retail food products.
The following are not suitable for folding cartons or food trays:
Kraft paper is available in different types such as bleached white, heavy duty, unbleached and of course the natural brown. The latter is the sturdiest of all and is utilized for wrapping and bags.
Sulfite paper has a glaze coating that gives it a better appearance and provides higher resistance to moisture and oils. It is usually employed in bakery or confectionery products.
Greaseproof paper undergoes a particular treatment that provides resistance to fatty matter but not against moisture. It is used to wrap oily foods like snacks or cookies.
Glassine has a highly glossy finish and the most extreme anti-grease process, used as a liner for cooking fats, baked goods, and fast food.
Parchment paper is utilized to package butter and lard.
Environmental impact of paperboard packaging
A thorough analysis of the material from manufacture to disposal is critical in assessing the environmental footprint of the package. We should consider material use, energy consumption, and waste generation.
This is difficult to achieve, as the package must balance all dimensions: safekeeping the quality of food, supporting a visually appealing message, being made from renewable material, generating minimum waste, at a cost-effective relationship.
Commercial Paperboard Grades for Package Printing
Iggesund in their paperboard product manual recommends the following usage:
Solid Bleached Board (SBB, GZ): With a grammage ranging from 180 to 380 g/m2, it is best Perfumes, Cosmetics, Chocolates, Pharmaceuticals, Wines and Spirits.
Folding Box Board (FBB, GC1): Ranging from 220 to 350g/m2, it is best suited for Cosmetics, Chocolates, Medical and Healthcare.
Folding Box Board (FBB, GC2): With a grammage from 200 to 325g/m2, it is utilized for Confectionery, Frozen and chilled food, Wines and spirits, Biscuits and other foods, Beverages, Pharma and Healthcare, and Microwaveable products.
New Paperboard Grades for Folding Cartons - 2018
Metsä Board, a European producer of fresh fiber paperboard, launched a new eco-barrier paperboard. It is bio-based, biodegradable, and recyclable - especially suited for food service. It is also very versatile in printing and converting.
The new bio-based special barrier is fluorochemicals-free. It can be used with foods demanding grease resistance, and the barrier can be further enhanced with extra varnish layers.
A Finnish converter, OffsetKolmio Oy, tested the new paperboard grade, reducing print machine time for barrier treatment by 50%, and requiring 65% less varnish. This FSB substrate is a lightweight paperboard, available in basis weights of 195–290 g/m2. It is also safe for food contact.
Commitment with High-Performance Paper Converting
Heiber + Schröder interacts with customers worldwide, gathering their experiences using window patchers and tray formers for paperboard packaging.
It also partners with the foremost companies in the package printing industry to deliver time-saving, cost-saving solutions for paper converters.
New consumer trends, new package printing technologies, and new materials demand that tray formers, and window patchers take advantage of their functionality. Heiber + Schröder prides in quickly identifying these factors and developing innovative paper converting equipment.