Sack Kraft Paper, or just sack paper is a porous kraft paper with high elasticity and high tear resistance, designed for packaging products with high demands for strength and durability.[1]
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Wood pulp for sack paper is made from softwood by the kraft process. The long fibers provides the paper its strength and is added wet strength chemicals to even further improve the strength. Both white and brown grades are made. Sack paper is then produced on a paper machine from the wood pulp. The paper is microcrepped to give porosity and elastisity. Microcrepping is done by drying with loose draws allowing it to shrink. This is causing the paper to elongate 4% in machine direction and 10% in cross direction before busting.[1] Machine direction elongation can be further improved by pressing between very elastic cylinders causing more microcrepping.[1] The paper may be coated with polyethylene (PE) to ensure an effective barrier against moisture, grease and bacteria. A paper sack can be made of several layers of sack paper depending on the toughness needed.
Kraft paper based sacks have the advantage of being soft and strong at the same time. The stretch or elongation increases the energy required to break the material. They easily carry and protect products up to 50 kg, and adapt easily to the nature of their contents and to handling constraints. At the same time sacks are provide an excellent media for promotional messages and sophisticated printing designs.
Sack paper comes in a variety of calipers, basis weights, and treatments.
Sack paper is used in paper bags, such as shopping bag, and multiwall paper bags for cement, food, chemicals, consumer goods,flour bags etc. plastic hazard free