Paper

PAPER , sheet or roll of pressed cellulose fibers . It has a wide range of uses: used for packaging , writing , wall covering and as cladding . The first material that was used for writing in antiquity was papyrus ( the name of the paper later came from this word ). , adopted in many European languages \u200b\ u200b- “ papier ”, “ paper ” , etc. e .). It was made from the plant of the same name 5500 years ago . Papyrus stems were soaked , cut into narrow strips , laid out in several layers at right angles to one another , beaten until a sticky juice is released and then pressed into webs . The modern paper making process originated about 2,000 years ago in China . It consists of grinding wood fibers , straw , waste paper , cotton rags and some herbs to a state of pulp under the action of ALKALINE , e.g. SODIUM HYDROXIDE ( caustic soda ) . The lignin and other non - cellulosic substances are then removed and the resulting residue bleached . After washing and adding filler to provide a smooth and even surface , the pulp is dewatered on a wire mesh where a thin layer is formed. canvas and dry . _ The best grades of paper are made from chemical pulp prepared in the manner described above , while newsprint and other cheap grades of paper are made from mechanically produced wood pulp without chemical treatment and consist of wood fibres .

Modern ways of making paper differ little from those that were used 2000 years ago . The slurry of cellulose fibers is produced by whipping the mixture of fibers in water , after which they strain the fibers . Wet webs are pressed and heated to remove water and then subjected to further cleaning . The figure shows the modern papermaking process in schematic form . The raw logs go to the paper mill . Then they are sent to the debarker , which has chisels that strip the bark without damaging the wood . _ Then the wood can go straight to the crusher . This machine has rotating blades that cut the wood into pieces about 3 mm thick . _ _ From there the wood shavings go to the digester ( Kamira autoclave ) . Here , in the process of treatment with boiling chemicals , a pulp is obtained (" chemical cellulose "), after which the chemicals are extracted in a special device - extractor . An alternative is to feed the bark -free wood into a mechanical pulper , a type of grinder . These two streams are then mixed in the bleaching apparatus , pass into the stage pulper , and from there for further processing in a Jordan refiner . The deinked and bleached waste paper , ready for shredding , is also converted into pulp in a pulper equipped with a rotating multi -blade impeller and then added to the bulk in the refiner . The whole pulp is then fed into the separator , which is a filter , where non -fibrous inclusions are separated , and from there to the headbox . There , the required consistency of the pulp is established , after which it is fed at a controlled speed through the inlet device onto a flat surface moving at a high speed . speed phosphor bronze wire mesh . _ Here the vacuum boxes remove most of the water and a thin web is formed . The extracted water is filtered . The water and the screened pulp can be put back into circulation . _ The canvas is pressed to the required thickness by press rollers . and then dried on drying cylinders . _ This procedure ends with calendering . Paper waste is fed back to the pulper . And finally get a finished roll of paper .