Pulp and paper are also known as paper and wood pulp. Both these products are obtained from the wood obtained from different parts of trees. The best quality of paper is obtained from the inner bark of a tree called bark or rags. The bark is peeled off by making a circular motion to remove it and then it is washed and bleached many times by mixing different chemicals like chlorine, caustic soda, sulphuric acid and chromium trioxide which makes it white in color. These chemicals also help in removing the impurities present in sugars, proteins, fats etc.
If these chemicals are not used for bleaching then papers get a yellowish look because common household bleach does not work on cellulose which is present in all natural paper materials. This process helps to develop characteristics of good quality paper called toning where the colors become muted with time. Following important processes take place during manufacture of paper products;
Bleaching process : After removing rags they are exposed to caustic soda (sodium hydroxide) solution which goes through them by absorbing water out of wood due to its chemical makeup that has a certain basicity property (pKa value). This action makes them lighter in color and gives a tan look to paper.
Sorting process : After bleaching, the chemicals and impurities in rags are removed by making use of pulp which is obtained from the inner part of the tree like bark, roots etc. The chemicals used for removing these impurities are chromium trioxide and sulphuric acid. Sorting is done to remove the ink and other chemicals present in rags. This helps in removing the colored pigments present in rags.
Reconditioning process : After drying, papers are given an additional treatment which makes them thin and smooth. This process is called reconditioning. Reconditioning consists of applying a coating of sizing on each side of the paper and then a coating of gum Arabic mixture. This mixture dries immediately to give a smooth and thin surface known as mat finish to paper.
Calendaring : Calendaring is a process in which friction provided by rubbing between two sheets of quartz sand causes them to become smooth and soft. This gives a shiny finish to papers since usually its back side has matte texture due to which they appear dull initially but when you rub it with a smooth surface it becomes shiny after a certain period of time. Calendaring also helps to remove roughness etc that gets caused due to burning or excessive rubbing during the manufacturing process itself as well as during the drying process.
Drying process : After smoothening, papers are dried under controlled temperature conditions so that they get perfectly flat after getting shiny after calendaring with fine sand applied using a machine like belt sander etc on both sides across their faces at same time so that the machine can move through both faces at a same time. This process also helps in removing water and ink impurities as well as in bonding the papers together.
The Asia Pulp and Paper Group is a multinational corporation based in Singapore. The company deals with the production of paper, pulp, tissue, packaging products as well as related services such as recycling and financial trading activities. It operates 37 manufacturing plants worldwide which are spread out across 17 countries-of-operations in the globe.
Andrea Parker is a reporter for Zobuz. She previously worked at Huffington Post and Vanity Fair. Andrea is based in NYC and covers issues affecting her city. In addition to her severe coffee addiction, she’s a Netflix enthusiast, a red wine drinker, and a voracious reader.