1. Mechanical wood-pulp (mechanical wood-pulp) mechanical wood pulp, also known as groundwood pulp, is a kind of pulp made from fiber raw materials by mechanical method. It plays an important role in the paper industry. It has the advantages of low production cost, simple production process, strong ink absorption, high opacity, soft and smooth paper. Suitable for printing requirements. However, due to the short fiber and high content of noncellulose components, the paper strength is low. In addition, because most of the lignin and other noncellulose in the wood has not been removed, the paper produced with it is easy to turn yellow and brittle, and can not be preserved for a long time. Mechanical wood pulp usually refers to white mechanical wood pulp and brown mechanical wood pulp. White mechanical wood pulp is mainly used to produce newsprint, and can also be mixed with other pulps to make writing paper and printing paper; the brown mechanical wood pulp is mostly used to produce packaging paper and paperboard, especially industrial paperboard.
2. Sulphate wood pulp uses a mixture of sodium hydroxide and sodium sulfide as a cooking agent. In the cooking process, because of the mild action of the liquid, the fiber is not strongly eroded, so it is strong and tough. The paper made has excellent folding, bursting, and tearing strength. It can be divided into bleached and unbleached. Unbleached kraft wood pulp can be used to make kraft paper, bag paper, kraft liner paper, packaging paper, and paperboard. Bleached kraft wood pulp can be used to make high-grade printing paper, newspaper, offset paper, and writing paper.
3. Sulfite wood pulp is made from a mixture of sulfite and acid sulfite. The pulp has long fibers, soft properties, good toughness, high strength, easy bleaching, and excellent interlacing ability. According to the degree of refining, it can be divided into unbleached, semi bleached, and bleached. The unbleached pulp contains a small amount of lignin and colored impurities, so it is yellow and the fiber is hard. It is mostly used to make medium printing paper, thin packaging paper, translucent paper, and oil-proof paper. Semi bleached pulp contains a lot of pentoses, so transparent tracing paper and imitation parchment are made. The fiber of bleached pulp is white, pure, and soft, but its strength is lower than that of unbleached pulp. This kind of pulp is mostly used to make all kinds of high-grade paper.
4. Waste paper pulp (wastepaper pulp) waste paper pulp is made by using used waste paper or the edge of paper cut by the printing plant as raw materials, stirring by mechanical force, bleaching, or deinking. The fiber strength and properties of waste paper pulp are determined by the types of pulp used in waste paper. However, the properties of the fiber are worse than those of the original fiber because it is eroded by liquid medicine or damaged by mechanical force. According to the quality of waste paper pulp, it is used to make printing paper, writing paper, paperboard, and lower grade paper.