Sack paper
Encyclopedia
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.
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. Machine direction elongation can be further improved by pressing between very elastic cylinders causing more microcrepping. 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.
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.
, and multiwall paper bags for cement, food, chemicals, consumer goods,flour bags etc.
plastic hazard free
Kraft paper
Kraft paper or kraft is paper or paperboard produced from chemical pulp produced in the kraft process.Pulp produced by the kraft process is stronger than that made by other pulping processes; acidic sulfite processes degrade cellulose more, leading to weaker fibers, and mechanical pulping...
with high elasticity
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....
and high tear resistance, designed for packaging products with high demands for strength and durability.
Manufacturing
Wood pulpWood pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...
for sack paper is made from softwood
Softwood
The term softwood is used to describe wood from trees that are known as gymnosperms.Conifers are an example. It may also be used to describe trees, which tend to be evergreen, notable exceptions being bald cypress and the larches....
by the kraft process
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...
. The long fibers provides the paper its strength and is added wet strength chemicals
Wet strength
Wet strength of paper is a measure of how well the fibreweb is holding together upon a force of rupture. Wet strength is routinely expressed as the ratio of wet to dry tensile force at break.-Mechanism:...
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
Crêpe paper
Crêpe paper is tissue paper that has been coated with sizing and then creped to create gathers.-Production:Paper that is creped is produced on a paper machine that has a single large steam-heated drying cylinder fitted with a hot-air hood. The raw material is paper pulp. The Yankee cylinder is...
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. Machine direction elongation can be further improved by pressing between very elastic cylinders causing more microcrepping. The paper may be coated with polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
(PE) to ensure an effective barrier against moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
, grease
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
and bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. A paper sack can be made of several layers of sack paper depending on the toughness needed.
Properties
Kraft paperKraft paper
Kraft paper or kraft is paper or paperboard produced from chemical pulp produced in the kraft process.Pulp produced by the kraft process is stronger than that made by other pulping processes; acidic sulfite processes degrade cellulose more, leading to weaker fibers, and mechanical pulping...
based sacks
Paper bag
A paper bag or paper sack is a preformed container made of paper, usually with an opening on one side. It can be one layer of paper or multiple layers of paper and other flexible materials. A bag is used for packaging and/or carrying items....
have the advantage of being soft and strong at the same time. The stretch or elongation
Elongation
In astronomy, a planet's elongation is the angle between the Sun and the planet, as viewed from Earth. Elongations occur when an inner planet’s position, in its orbital path, is at tangent to the view from Earth. Because these inner planets are inside the Earth’s orbits their positions as viewed...
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.
Applications
Sack paper is used in paper bags, such as shopping bagShopping bag
Shopping bags are medium sized bags, typically around 10-20 litres in volume , that are often used by grocery shoppers to carry home their purchases...
, and multiwall paper bags for cement, food, chemicals, consumer goods,flour bags etc.
plastic hazard free
External links
- European Kraft Paper Producers for the Flexible Packaging Industry
- European federation of multiwall paper sack manufactures
- Paper Shipping Sack Manufactureres Assn http://www.pssma.org/index.php?id=1