The history of paper making derives from the ancient Egypt, the Egyptians made paper from reeds. Using cotton and linen fibers to make paper spreads to Europe in the 13th century, and people become more and more likely to make rag paper by using fabric, which is a factor contributes to the development of printing. Using wood to make pulp for paper began with the development of mechanical pulping in Germany by Friedrich Gottlob Keller in the 1840s. Then the chemical making process is followed.
How to Make Paper Pulp?
Chipping wood for the making of pulp, only the heartwood and sapwood can be used for making pulp, and they are usually chipped to the uniform sized chips. Mechanical pulping is paper making method by grinding fiber raw materials into the wood pulp, which plays key role in paper making industry. If the wood is steamed before grinding, it is called pressure ground wood pulp (PGW). The method of just ground up the chips with the plates, then the final pulp is refiner mechanical pulp (RMP). If the chips are steamed during the process of pulping, the final pulp is called thermomechanical pulp. (TMP).
Wood chips are firstly treated with sodium carbonate, sodium hydroxide, sodium sulfite and other chemicals before refining pulp in equipment similar to a mechanical mill. The environment of the chemical treatment is gentle (lower temperature, shorter time, less extreme pH) than in a chemical pulping process. It is easy to refine the fibres without removing the lignin. This kind of way to make pulp is called chemithermomechanical pulping (CTMP).
Chemical pulping refers to the method by combining wood chips and chemicals so that the lignin is broken down by the heat and the chemicals in the digest vessels. The working principle is by breaking down the lignin which binds the cellulose fibres, which is just the material we need to make pulp. The kraft process is the dominant chemical pulping method, with the sulfite process being second. Soda pulping was the first successful chemical pulping method in the history.
Recycled pulping is also called deinked pulping (DIP) or recycled paper pulping. Recycled paper is processed by chemicals to remove printing inks or other unwanted components. The finished recycled pulp can be as raw material to make newsprint, toilet paper and facial tissue, etc. This method can save the a lot of wood, it is a recycling process, and occupy a large portion in the paper pulp supplying industry.
This method refers to use organic solvents to break down lignin and hemicellulose into soluble fragments at temperatures above 140 °C. The pulping liquor is easily recovered by distillation. The using solvent is to make the lignin more soluble in the cooking liquor. The common used solvents are ethanol, methanol, formic acid and acetic acid, and they usually used with water.
There are many types of paper pulping, except the method in the above, methods such as biopulping is also under the research. After the pulping process, it needs to blench the pulp to make white paper.