Metsä Board has been developing the boardmaking process for decades. The continuous evolution has resulted in lightweight paperboards that not only provide a better yield but also help minimize environmental impacts as they require less raw material and reduce transport weight and waste.
The long process of making high-performance board begins with pure, strong primary wood fibre, a completely renewable and recyclable raw material. Metsä Board sources wood only from sustainably managed commercial forests and supports independently verified forest certification.
The raw material is pulped, i.e. the fibres are extracted by grinding the wood mechanically or cooking it with chemicals. Metsä Board uses CMTP or mechanical pulp in the middle layer to make the board bulky yet light and chemical pulp in the outer layers to maximize strength.
As the pulp enters the folding boxboard machine, each section of the machine plays its part in shaping the properties that are desirable in a packaging board:
- strength for a dependable performance in the logistic chain and on the shelves
- stiffness and consistency for smooth runnability in converting
- brightness and smoothness for visually appealing printing results
Laying down the foundation
In the wire section, with separate units for the top, middle and reverse layers of the board, fibres become interwoven, forming a web.
High pressure in the press section increases fibre bonding, the basis of the compression resistance and durability of the end product.
Machine glazing makes the fibre surface smoother without loss of thickness.
In the size press, a starch-based solution is added to the board web to improve surface strength and stiffness.
The drying sections make the board remain flat, which ensures good runnability in printing and converting.
Adding the finishing touches
In the coating section, the board gets its final appearance, smoothness, gloss, brightness and absorption characteristics according to the specified coating recipe. The elastic-surfaced calender adds further surface smoothness and gloss to the board.
Throughout the machine, the automatic process control of properties such as grammage, moisture content and coating helps produce a consistent broad that enables trouble-free conversion.
The finished paperboard is wound onto jumbo reels, then cut into either reels or sheets to the customer’s specifications and packed in moisture-proof wrapping for transportation and storage.
In addition to strict quality standards, Metsä Board’s production units are committed to continuously improving their environmental performance. The mills’ ongoing drive for better energy efficiency has already significantly decreased Metsä Board’s CO2 emissions. Metsä Board will also keep increasing the already high share of biofuels in its production.