Manufacturing Process
Collection and Transportation
Often, a paper stock dealer or recycling center will collect recovered paper from home, schools or office. Then at the recycling center, the collected paper is wrapped in tight bales and transported our paper mill, where it is recycled into new paper.
Storage and Sorting
Our workers unload the recovered paper and store it into warehouses until needed . Successful recycling requires clean recovered paper, so we keep our paper free from contaminants, such as food, plastic, metal, wax and other trash, which make paper difficult to recycle. Morever, paper is sorted into different grades such as newspapers, duplex, white cutting, scan boards and old books, etc suitable for different layers of papers because we uses different grades of recovered paper to make different types of recycled paper products. Finally, forklifts move the paper from the warehouse to large conveyors.
Re-pulping and Screening
The paper moves by conveyor to a big vat called a pulper, which contains water and chemicals. The pulper chops the recovered paper into small pieces. Heating the mixture breaks the paper down more quickly into tiny strands of cellulose (organic plant material) called fibers. Eventually, the old paper turns into a mushy mixture called pulp. The pulp is forced through screens containing holes and slots of various shapes and sizes. The screens remove small contaminants such as bits of plastic and globs of glue. This process is called screening.
Cleaning
Mills also clean pulp by spinning it around in large cone-shaped cylinders. Heavy contaminants like staples are thrown to the outside of the cone and fall through the bottom of the cylinder. Lighter contaminants collect in the center of the cone and are removed. This process is called cleaning.
Deinking
Sometimes the pulp must undergo a “pulp laundering” operation called deinking (de-inking) to remove printing ink and “stickies” (sticky materials like glue residue and adhesives). Small particles of ink are rinsed from the pulp with water in a process called washing. Larger particles and stickies are removed with air bubbles in another process called floatation. During floatation, pulp is fed into a large vat called a floatation cell, where air and soaplike chemicals call surfactants are injected into the pulp. The surfactants cause ink and stickies to loosen from the pulp and stick to the air bubbles as they float to the top of the mixture. The inky air bubbles create foam or froth which is removed from the top, leaving the clean pulp behind.
Refining and Bleaching
During refining, the pulp is beaten to make the recycled fibers swell, making them ideal for papermaking. If the pulp contains any large bundles of fibers, refining separates them into individual fibers. If the recovered paper is colored, color stripping chemicals remove the dyes from the paper. The pulp used for bottom or filler layer genreally dont require bleaching.
Papermaking
Now the clean pulp is ready to be made into paper. The pulp is mixed with water and chemicals to make it 99.5% water. This watery pulp mixture enters the headbox, a giant metal box at the beginning of the paper machine, and then is sprayed in a continuous wide jet (with the help of moulds) onto a huge flat wire screen which is moving very quickly through the paper machine. On the screen, water starts to drain from the pulp, and the recycled fibers quickly begin to bond together to form a watery sheet. The sheet moves rapidly through a series of felt-covered press rollers which squeeze out more water. The sheet, which now resembles paper, passes through a series of heated metal rollers which dry the paper. Then, we undergo a layer of coating on the paper. Coating gives paper a smooth, glossy surface for printing. Finally, the finished paper is wound into a giant roll and removed from the paper machine. The roll of paper is cut into smaller rolls, or sometimes into sheets, before being shipped to a converting plant where it will be printed or made into products such as envelopes, paper bags, or boxes.