Paper pulp or pulp is a fibrous material that is made from plant fiber with different pulp processing. The major ingredient of pulp includes cellulose, hemicellulose, lignin, pigment, resin, pectin, and ash, etc. In general, cellulose fiber is separated chemically or mechanically from raw materials like wood, straw, bomb, sugarcane, wastepaper, and so on. According to different ways, the paper pulp can be classified into various types. For applications, paper pulp is one of the most abundant raw materials around the world. The widest application of pulp is paper making, besides, artificial fiber, plastic, paint, interlayer and other fields.
Paper pulp processing
There is no doubt that paper pulp is the raw material of paper. Paper pulp is made from the plant with long and high percent fiber, the wood fiber is the most common kind of plant fiber. Paper pulp processing usually mean crushing, cooking washing, screening, bleaching, cleaning, and drying of plant fiber.
There are many types of paper pulp processing, chemical pulping, mechanical pulping and chemi-mechanical pulping are three typical types among them. Take chemical pulping as an example, it has three basic procedures like pulp cooking processing, pulp washing processing, and pulp bleaching processing. The whole set of chemical processing requires many paper pulp machines, such as pulp digester, vacuum drum washer, disc filter, twin roll press and other related equipment.
Paper pulp category
Paper pulp have too many categories according to different methods. Specific categories are as follows:
- By processing, chemical pulp, mechanical pulp and chemi-mechanical pulp.
- By raw material, wood pulp, straw pulp, bomb pulp and waste paper pulp, etc.
- By pulp yield, chemical pulp(40~50%), high-yield chemical pulp(50～65%), semi-chemical pulp(65～84%), chemi-mechanical pulp(85～94%) and mechanical pulp(94~98%).
- By applications, paper pulp for own use and market pulp.
- By Comprehensive name, bleached sulphate softwood pulp, unbleached sulfite reed pulp, poplar ground wood pulp, etc.
Among all kinds of paper pulp, chemical pulp has biggest share. In 1987, the world’s total output of chemical pulp reached 11.135 million tons, accounting for 71% of the total pulp production (155.86 million tons), mechanical pulp accounted for 21%, and chemical mechanical pulp has fewer yields because it develops relatively late, but its growth is fast.
Paper pulp applications
As for the paper pulp applications, different kind of paper pulp has individual applications.
- Mechanical wood pulp has two types: white mechanical wood pulp and brown mechanical wood pulp. The White mechanical wood pulp is mainly used to manufacture newsprint, or writing paper and printing paper with other pulp together. Brown mechanical wood pulp is mostly manufacturing wrapping paper and paperboard, especially industrial paperboard.
- Sulphate Wood Pulp has two types: bleached pulp and unbleached pulp. The unbleached sulphate wood pulp is used for processing kraft paper, sack paper, Kraft Liner Board, general wrapping paper, and boards. The bleached sulphate wood pulp is used for processing text paper, pictorial paper, offset paper and writing paper, etc.
- Sulphite Wood Pulp can be divided into three types: bleached pulp unbleached and partly bleached pulp. Unbleached pulp has small amounts of lignin and colored impurities, so it is yellow and has hard fiber. It is mainly applied in making medium fine printing paper, tissue paper, translucent paper and greaseproof paper. The partly bleached paper is applied for making tracing paper and parchmyn, etc. The bleached paper has white fiber, soft texture, and lower fiber strength. It mainly used for making all kind of fin paper.
- The waste paper pulp is made from waste paper or useless deckle edge. It can be used to make printing paper, writing paper, paper board and coarse paper.
