Printed Cardboard Containers

What is Cartonboard?

Cartonboard is a multilayered material, typically incorporating three or more layers or plies, derived from wood. The main variants of printed cardboard containers are solid bleached board, solid unbleached board, folding boxboard and white lined chipboard. Cartonboard usually has a white, pigmented coating on one or both surfaces.

Product Specifications

Product specifications vary with respect to the pulp composition of the various layers and by the grammage (weight per sq. metre in grammes) and thickness. It can be combined with other materials to vary the visual appearance and to extend the protective properties. Typical additions would include laminations, coatings and impregnations. The various layers of the printed cardboard containers are combined in a wet state on the board making machine, and might consist of one or several different types of pulp. The top layer of the board generally has a smooth white pigmented coating based on china clay or calcium carbonate. The reverse side may also be coated or it may be white, brown, cream or gray in colour depending on the grade of fibre used.

Papers and cardboards are classified by their fibre composition, the processing, manufacture and treatment at the mill, by grammage and thickness. Grammage is the weight of a square metre in grammes (g/m²), whilst thickness is measured in microns (µm), equivalent to 1000ths of a millimetre. The crossover point between paper and cardboard is normally considered to be around 160g/m² as it is only at this level that a fibrous material is likely to be stiff and rigid enough to make a container. Most folding cartons are in the range 200-600g/m² for grammage and 350-800µm for thickness.

Multilayering

Multilayering provides important technical features and gives flexibility in the choice of fibres (pulp) for each layer. It gives the printed cardboard good stiffness, creasing, folding, and gluing properties. It also assists grammage and thickness control. It is particularly important to use good quality fibre in the two surface layers as these experience the greatest effect of externally applied stresses which can extend or compress them in printing, conversion and in use.

Cartonboard possesses stiffness, rigidity and a toughness that provides compression strength to protect products in distribution and use. It can be cut, creased, folded and glued, offering scope to the designer to produce functional and creative food packaging. The surface is usually white and smooth and can be printed by all the main printing processes. Printing cardboard containers will typically combine important and legal product information with attractive promotional designs.

The product is suitable for embossing and hot foil stamping, and can also be laminated to other materials, such as aluminium foil, or plastics, such as PE, PP and PET, and given treatments which extend its range of appearance and performance properties.

Producing printed cardboard containers

Cartonboard is produced on the board machine in several stages. Firstly, a dilute suspension of cellulose fibre (pulp) in water is formed into a thin layer of entangled fibres on a moving plastic mesh, known as the wire. Some of the water is removed by drainage and further layers of pulp are added to complete the grammage, thickness and composition of the cartonboard. The rest of the water is removed by pressing and drying, during which process inter-fibre bonding develops.

The board is usually coated to improve the whiteness, smoothness and surface finish for printing, varnishing and the general appearance. Finally, there are a number of finishing operations that take place such as slitting, reeling, sheeting, labelling, palletising and wrapping with moisture resistant material for storage and distribution.