Kraftpapper

Kraftpapper, also known as kraft paper, is a strong, coarse paper produced from kraft pulp. It is typically unbleached and brown in color, though it can be bleached to a lighter shade. Its defining qualities are high tear resistance, good tensile strength, and stiffness relative to its weight, which make it well suited for packaging applications.

Production of kraftpaper relies on the kraft process, an alkaline pulping method that uses cooking liquor containing sodium hydroxide and sodium sulfide. This preserves long cellulose fibers, yielding a strong pulp with high strength and yield. The pulp can be bleached to produce lighter kraft papers, but most traditional kraft is brown. Byproducts from the process, such as tall oil and lignin, are often recovered for energy or chemical use. Modern mills also emphasize environmental controls, chlorine-free bleaching, and responsible energy consumption.

Kraftpaper comes in a range of grades. Unbleached kraft is common for sacks, bags, wrapping, and general packaging. Kraft linerboard, a high-strength grade, is used as the outer layers in corrugated cardboard. The surface texture can be smooth or rough, and coatings or surface treatments may be applied to improve printability or moisture resistance. Typical basis weights vary widely, from light wrapping grades to heavy-duty sacks and linerboard.

Environment and history: Kraft pulp’s high strength and yield have made it a staple of the packaging industry. Kraft paper is widely recyclable and biodegradable. The process originated in the late 19th century, with the name kraft meaning “strength” in German, reflecting the durable pulp it produces.