The building block of small cardboard boxes is containerboard. It is a thick, heavy paper which is essential for the internal and external liners as well as the corrugated wavy flutes in the middle of the cardboard sandwich. Before containerboard is manufactured, it all starts with wood fibers and paper pulp.
Pulp is manufactured from softwood trees such as fir, spruce or the hardwood aspen and birch trees. It is a material made by splitting fibers off of trees, fiber crops or recycled material (deinked pulp). The separation of fibers can be done mechanically or by a chemical reaction (kraft process). Some examples of fiber rich crops are flax, jute, hemp, linen and cotton. Currently chemical pulp represents over ninety percent of the market pulp available, with US and Canada being the largest manufacturers and contributing to over a third of the world’s output. Mechanical pulping was first done in Germany in the 1800s and shortly after followed by chemical wood pulping which is now the prevailing technique.
Wood pulping is continuous during the year and commercially significant. Yet trees have to be grown for many years. Reforestation and sustainable forestry management allow tree harvesting to not be deadly to our forest biodiversity. The Forest Stewardship Council is a body which certifies paper products made from renewable sources or following the principles of sustainable forestry management. When trees are used for fiber and paper pulp production, only the wood core (sap-wood and heart-wood) is used. Bark is chipped off and used as fuel or with limited application in the furniture industry.
Harvesting fibers from crops is another method. It is sometimes viewed as a more reliable source since it only takes one season for the crops to be ready to harvest. A lot shorter cycle, yet very seasonable and weather dependent which makes it hard to guarantee year-round supply.
Wood chips and crop fibers are turned into heavy fiberboards which are then transported to a paper mill for further processing. Wood and crops utilized into pulp manufacturing contain four ingredients – water, lignin, cellulose and some other carbohydrate polymers. The objective of pulping is to decompose the large fiber structure of the chips or crops into a consistent fiber mass. Chemical pulping mixes the ingredients with chemicals and decomposes lignin which makes the cellulose fibers stick together without damaging them. Chemical pulping is used to make stronger paper which is popular in the packaging industry and relevant to small cardboard boxes. Mechanical pulping is the more efficient method yet less popular. By mechanical pulping more paper can be produced from less trees, yet the final outcome is softer paper which is used in production of newsprint stock. A combination of the two is also popular with regards to compliance with product requirements.
Bleaching is a natural next step in the manufacture of corrugated fiberboard. Bleaching agents such as chlorine, oxygen etc. are used and often raise environmental concerns. Bleaching improves printing qualities of paper and there is a variety of industries, packaging and shipping for instance, which do not need all cardboard boxes to be white. Such uses of paper, in combination with deinked or recycled pulp is an example of environmentally friendly packaging. Large and small cardboard boxes manufactured without pulping agents are such representatives.
Back home to small cardboard boxes
Filed Under Small Cardboard Boxes | Comments Off on Cardboard Boxes, Fibers and Paper Pulp