Everyone is using paper in his daily life like water but ever think of it how is paper made? Many of us know that it is made from trees and that’s why we students made slogans like “Say No to Exam, Save trees“(Just kidding). But ever think about the nos. of processes it has gone through?
How is the paper made? Let’s get in the details of manufacturing process
1. Cutting Trees
Good quality paper is manufactured from wood grown in sustainably managed forests and plantations. The timber used for production comes either from deciduous trees such as birch, poplar, birch, and eucalyptus, or conifer trees like spruce-fir and pine.
2. Removed bark & chipped
When the logs arrive at the wood yard, they are fed into a rotating drum which removes the bark. Then the logs are chipped. The largest source of wood chips for papermaking is the recycled off-cuts from the industrials sawmills.
3. Pulp Generation
The wood chips are transported to the pulp mill on a conveyor belt. As they enter the pulp mill, the wood chips are fed into a digester. When they are cooked in an acid solution to dissolve the lignin and separate the plant fibers. We call the pulp obtained from this process wood-free because the lignin has been dissolved.
4. Removing Fibers
The fibers are washed to remove the acid solution, and the pulp is now soft and fibrous. Before it can be used to make white paper, the pulp is bleached, and any residual lignin, which would cause it to yellow with the age is filtered out.
To protect the environment, this bleaching can be chlorine-free, using oxygen and peroxide. The yellow-brown wood chips that entered the pulp mill have now been turned into white pulp, the principal raw ingredient for making it.
This treated pulp can be dried, baled, and transported to other paper mills, which may either not have their own pulp mill, or require a specific type of pulp to give it particular characteristics.
Whether produced on-site or bought on the market, the pulp enters the paper mill and is mixed with water.
6. Making Paper Web
The pulp solution is refined by passing it through a series of rotating and stationary blades. These give the fibres a variable degree of clean-cut or fibrillated ends. Fibrillated fibres are bind more tightly with adjacent fibres, creating a stronger paper.
Wood fibers alone produce rough textured and unevenly dense paper, and filler such as calcium carbonate and clay are mixed in to make it more opaque and give it more controlled density.
By far the most important process material is water. About 100 liters of fresh water needed to make 1kg of paper. Sophisticated wastewater treatment plants and closed water circulation systems on the paper line allow over 90% of this water to be recycled.
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The pulp solution is now a carefully controlled mix of fibers, fillers and coloring agents suspended in water, ready to enter the paper machine
The paper machine is the heart of the mill- a continuous running series of the manufacturing processes that will convert the pulp solution into the perfect grade for each market application.
The pulp solution is injected at high pressure directly into space and water is extracted resulting in the continuous web of paper.
7. Pressing & Drying
The delicate paper web is now carried into the press section. It is pressed against a hydraulically actuated metal pad which squeezes out the water in the paper. The drying cylinders dry it giving it the strength to become self-supporting.
Remember the drying process and techniques play a vital role in giving the quality of the paper.
The sheet passes along the papermaking machine at up to 1400 meters per minute. Coating colors are sprayed onto the rollers which then transfers the coating film to the paper web.
8. Rolling & Cutting
Then the surface of the paper web is dried by infrared heating panels and drying cylinders. Then the final paper web is rolled into a big roller up to 80km of length depending on the capacity rollers.
Papers are continuously passed through rollers applying the equal pressure to give the maximum surface finished quality. Then the big rolled sheets are cut into several narrow roller sheets. And these papers are then cut into smaller rectangular size for end-use.
Now the papers are ready for printing and binding and to be sold into the market.
So did you ever thought that the paper you are using for your rough work has gone through these numbers of the process?
Also read : How Glass is made from the sand?