Deinking is an industrial process for removing printing ink from recycled paper paper to create a paper pulp that is not wrinkled.
The key in the deinking process is the ability to release ink from the fibers. This is achieved by a combination of mechanical action and chemical means. In Europe the most common process is flotation flotation.
Paper is one of the main targets for recycling. The concern about recycling wood pulp paper is that the fibers are degraded with each cycle and after recycling 4-6 times the fibers become too short and weak for use in paper making.
Video Deinking
Histori
Prior to the invention of the paper machine in 1799, the most common source of fiber was recycled fibers from used textiles, hence it was a name rag paper. The fabrics are from hemp, linen and cotton. New to the introduction of wood pulp in 1843 paper production does not depend on recycled materials.
Recycled waste paper prior to industrialization of paper production, fabric paper is recycled to make low level boards. A process for removing printing inks from recycled paper was discovered by German lawyer Justus Claproth in 1774. He trained together with German paper producer Johann Engelhard Schmid. Today this method is called deinking.
First in the 1950s and 1960s the use of recycled paper fibers made from pulp began to increase, and was mainly used in paper and paperboard packaging. In the 1950s the flotation technique of scum was adjusted for deinking recycled paper. The use of recovered paper increased in the 1970s primarily in graphic and hygienic paper, and accelerated in the 1980s. Annual growth in the use of recovered paper increased by 6% between 1980 and 1996. The use of virgin fiber only increased 2% in the same period. In 1997, the production of recoverable paper was 42% of total paper production.
Maps Deinking
Deinking Process
Sorting
Used paper may contain a mixture of different types of paper made from a mixture of different paper. It should be sorted before processing. Broken (waste paper from paper production) is usually used directly in paper machines.
- Office waste (OW)
- Old magazine paper (OMP)
- Old print (ONP)
- Cartes
- Corrugated fiberboard
Recycled paper can be used to make paper of the same or lower quality than the original. The sorted paper is copied and sent to cardboard. Pulpmill uses waste paper grade in accordance with the quality of paper you want to make.
Debaling
Bal opened and large foreign objects sorted on the conveyor belt to the pulper. Many foreign materials are ready to be removed. Yarn, binder, etc. Issued from hydropulper by "ragger". Metal straps and staples can be filtered or removed by magnets. The pressure sensitive bands supported by the film remain intact: the PSA adhesive and backing are both released together.
Pulping
Pulp is a batch, which uses a tub with a high shear rotor, or continuous, using a long, hollow drum. Drum pulpers are very expensive but have the advantage of not breaking down contaminants, thus providing a cleaner end product.
Pulper cut paper for smaller pieces; water and chemicals added. Normally, the pH is adjusted to 8.5 - 10.0. The normal deinking chemicals are:
- pH control: sodium silicate or sodium hydroxide
- Bleaching: hydrogen peroxide
- Source of calcium ion: hard water, lime or calcium chloride
- Collectors: fatty acids, fatty acid emulsions, organic fatty acids or siloxane modified
After pulping, the mixture is a slurry. The slurry goes to the filtration.
Cleaning and filtering
The centrifugal clearance rotates the pulp slurry in the cleanser, causing a denser material from the slurry fibers to move outward and rejected. Screens, with slots or holes, are used to remove contaminants that are larger than the slurry fibers.
Materials that are more difficult to remove include wax coatings on corrugated cartons and adhesives, soft rubber particles that can make precipitate and soil recycled paper. Adhesives can be derived from bookkeeping, hot melt adhesives, PSA adhesives from paper labels, laminated adhesives of reinforced adhesive tapes, etc. Decide step
In the deinking stage the goal is to remove and remove hydrophobic contaminants from recycled paper. Most contaminants print ink and adhesive. Some processes are used, most commonly flotation or washing.
Flotation ink removal
Flotation froth was adapted from the flotation process used in the mining industry in the 1960s. This is the most common deinking process in Europe that is used to recover recycled paper. Often most collectors are added to the flotation inlet. The process temperature is usually in the range of 45 - 55 ° C. The air is blown into pulp suspension. Collectors have a good affinity for ink particles and air bubbles, causing them to stick. The air bubbles lift the ink to the surface and form a thick foam that can be released. Usually the setup is a two-stage system with 3, 4 or 5 flotation cells in series. Flotation ink removal is very effective in removing ink particles larger than about 10 Âμm.
Wash deinking
Wash deinking consists of a washing stage in which a dispersant is added to wash the printing ink. When the pulp pulp is dried (thickened), the medium to fine particles are washed out. This process is particularly useful for removing particles smaller than about 30 Âμm, such as water-based inks, fillers, coating particles, fines and micro adhesives. This process is more common when making paper pulp for the network. Processing equipment are belt filters, pressure belt filters, disk filters, and static filters. This stage is much more efficient than normal washing/dewatering.
Combined leaching and flotation
High quality deinking of office waste and other printing paper often uses a combination of washing and flotation.
Enzymatic ink removal
This deinking method uses industrial or food grade enzymes in conjunction with the removal of ink to help remove ink at the recycling plant. More efficient ink removal improves fiber yield, reduces the amount of dirt, and increases the brightness of the paper. Often the use of enzymatic deinking helps manufacturers reduce the use of their bleach or use cheaper equipment.
Other ink removal processes
Dissolved air flotation (DAF) is used by some factories in the ink removal phase and will remove some ink and fillers (ash); However, this is mainly used to clarify the water process.
Washing/dewatering
Washing/dewatering (thickening) is the screening process. Small particles (& lt; 5 Âμm) are removed by passing water through the pulp.
Bleaching
If white paper is desired, bleaching uses peroxide or hydrosulfite to increase the brightness of the pulp. The bleaching method is the same for mechanical pulps, but the goal is to make the fibers brighter.
Papermaking
Deinked fibers are made into new paper products in the same way as virgin wood fibers, see papermaking.
Byproducts
The remaining unusable materials, especially inks, plastics, fillers and short fibers, are called sludge . Mud is buried in landfills, burned to produce energy in paper mills or used as fertilizer by local farmers.
Problems
Water-based flexographic printing inks with particle sizes below 5 Âμm and poor solubility under alkaline conditions can cause problems in deinking, especially in the flotation stage. The solution is to use an extra acid leaching stage.
Temperature control is important because it affects adhesive stickiness.
Additional problems arise when considering the amount of potentially present chemicals in the paper for recycling. Studies have shown that the paper may contain as many as 10,000 different chemicals, whose fate in the deinking process is still unknown.
See also
- Dissolved air flotation
- Environmental issues with paper
- Flot a flotation
- German inventor and inventor
- Recycle paper
- Pulp & amp; Paper chemicals
References
Further reading
- GÃÆ'¶ttsching, Lothar; Pakarinen, Heikki (2000). Papermaking Science and Technology: 7. Recycled Fiber and Deinking . Finland. ISBN: 952-5216-07-1.
Source of the article : Wikipedia
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