Cartonboard is made from cellulose fibres that are produced either from timber or by reusing recovered fibre or waste paper. A combination of the two can be used and there are various types of fibre that produce different characteristics.
Pulp is manufactured either mechanically or chemically using forest thinnings and saw mill waste so leaving the larger trees to mature for sawn timber for such uses as building and furniture. All pulp used by Pro Carton member companies is made using timber from certified forests and in managed forests more trees are planted than cut so ensuring an increasing and infinitely renewable raw material base.
Recovered fibre or waste paper is collected across Europe as close to the point of use as possible to reduce transport. All types of paper, board and packaging can be used and after sorting bales of recovered fibre are delivered to cartonboard mills for use. It is estimated that paper and board fibres can be used up to seven times. In Europe about 46% of cartonboard is manufactured from pulp with the balance of 54% being produced using recovered fibre or waste paper.
The start of the production process is the preparation area. Here, the fibre, either in the form of pulp or recovered paper, is mixed with water in large hydrapulpers until a very fine suspension is achieved. This is then cleaned to remove any contraries, refined to enhance strength and then pumped to the Cartonboard machine where the cartonboard is manufactured.
The fibre and water mixture from the preparation plant, is pumped to the Cartonboard machine and this very thin mixture is put onto several continuously moving wire meshs. As the water drains away through the mesh the fibres begin to 'set' and then each of the sheets are brought together to form a continuous sheet of Cartonboard. This is then pressed by large rollers to squeeze more water out and then passed over steam heated cylinders to evaporate more water.
When the cartonboard has reached the required moisture content, up to three layers of coating -made of clay and chalk predominantly- are added to the surface of the board. These coatings improve smoothness and gloss and are required to achieve the high quality printing that is needed on cartons.
The whole process is computer controlled within very narrow tolerances to ensure consistency of quality. Once the cartonboard has been made it is then moved to the finishing area where it is cut to suit individual customer needs either into smaller reels or, more often into sheets on pallets.
After the cartonboard has been wound up into huge reels at the end of the machine, it has to be converted into a format that printers and otter customers can use. The majority of cartonboard is sold in sheets on pallets but it is also wound into smaller reels that are then despatched to the customers who print directly from the reels.