What Are the Raw Materials for Paper Pulp Making
What are the raw materials for paper pulp making
Papermaking raw material refers to the raw materials used in the paper making industry. Mainly divided into two categories including plant fiber and non-plant fiber (inorganic fiber, chemical fiber, metal fiber). At present, the main raw material in the world is plant fiber. There are many kinds of plant fiber raw materials, which can be divided into six categories:
- Coniferous wood, also known as cork, such as larch, Korean pine, Masson pine, Pinus yunnanensis, Pinus sylvestris var.mongolica, etc.
- Hardwood, such as poplar, birch, eucalyptus, etc.
- Grasses: reeds, bamboos, mango stalks, wheat straw, straw, alpine rush, sorghum stalks, bagasse, etc.
- Bast fiber, such as linen, jute, kenaf, sandalwood bark, mulberry bark, cotton stalk bark, etc.
- A variety of wool fibers, such as cotton, cotton fleece, cotton rags.
- Waste paper fiber, classified as first class waste paper (unprinted white paper edges selected from factories or related units, broken paper scraps. Second grade waste paper (printed waste books and periodicals). Third class waste paper (all but the above two kinds of waste paper, old cardboard, broken paper box) etc.
Among them, the first three categories are the main and important raw materials in the paper making industry. Below, we focus on the treatment of these three kinds of raw materials and the paper pulp made from this three kinds of raw materials and the paper products that suitable for manufacturing by these pulp.
Treatment process of different raw materials
The quality and use of paper pulp vary according to the type of raw material and pulping method. The modern paper and pulp technology is mainly composed of two links:
- Pulping section: pulping is the first step in papermaking. There are three methods to convert wood to pulp: mechanical pulping, chemical pulping and semi-chemical pulping. At present, the raw materials used in large paper and pulp mills are processed wood pulp and recycled paper.
- Papermaking section (paper-making section): the pulp is evenly interwoven and dehydrated, then dried, pressed, rolled, cut and packaged. "
- The pulping section is the most critical stage. What processes have been used for the first three types of raw materials in the pulping stage and what are the uses of their products?
For pulping, divided by raw materials: cork and hardwood pulp called wood pulp, grass pulp called straw pulp.
According to the paper and pulp technology: cork and hardwood pulp can be subdivided into mechanical pulp, chemical mechanical wood pulp, chemical wood pulp (can also be divided into Kraft pulp, sulfite wood pulp).
Mechanical wood pulp
Mechanical wood pulp, also known as grinding wood pulp, is a pulp made of mechanical method for grinding fiber raw material. Its production cost is low, production process is simple, paper has strong ink absorption, high opacity, soft and smooth paper, suitable for printing, but because of short fiber and high content of non cellulose components, it is low in paper strength. In addition, because of the wood in the wood. Most of lignin and other non cellulosic materials have not been removed, and the paper produced by them is yellow and crisp and can not be preserved for long.
Mechanical wood pulp usually refers to white mechanical wood pulp and brown mechanical wood. White mechanical wood pulp is mainly used to produce newsprint, but it can also be used in other pulps to copy writing paper and printing paper. Brown mechanical wood pulp is mainly used in the production of packaging paper and paperboard, especially industrial paperboard.
Kraft wood pulp
Kraft wood pulp is a mixture of sodium hydroxide and sodium sulfide as cooking agent. In the cooking process, because the action of the liquid is relatively mild, the fiber is not strongly eroded, so the paper is strong The paper has excellent resistance to breaking and tearing.
It can be divided into bleaching and unbleached generally.
Unbleached Kraft pulp can be used to make Kraft paper, sack paper. Kraft carton board and general wrapping paper and paper wrench, etc.
Bleached Kraft pulp can be used to produce high-grade printing paper, drawing newspaper, offset paper and writing paper. It is added to newsprint and magazine paper to provide sufficient strength for high-speed printing presses. Bleached pulp is also used in the production of tissues and food cardboard.
Sulfite wood pulp
Sulfite wood pulp is a mixture of sulfite and acid sulfite as cooking agent. The pulp has long fiber, soft properties, good toughness, high strength, easy bleaching and excellent interweaving ability.
According to its refining degree, it can be divided into three kinds: unbleached, semi-bleached and bleached.
Sulfite pulp has found an important market in the need for good evenness and medium strength securities paper, writing paper and photocopy paper. Usually hardwood Kraft or caustic soda pulp is added to improve evenness and opacity. Toilet paper and sheet paper are also heavily used with sulfite pulp to obtain the required softness, loose thickness and absorb ability.
Straw pulp, commonly used straw, straw, baleen grass and so on. Straw pulp is generally prepared by caustic soda, sulfate, neutral sulfite or chlorination. The method is called alkaline straw pulp, Kraft straw pulp, sulfite straw pulp, neutral sulfite straw pulp and chlorinated straw pulp respectively.
Grass pulp generally contains more hemicellulose, easy beating and sizing. However, there are significant differences among the grass species, such as the straw pulp fiber is short, the mixed cells are many, the filtration water is poor, the paper forming rate is large, the quality is brittle, the tear degree is low.
The straw pulp fiber length and the filtration water ability are better than the grass pulp, the paper is stronger, while the grass pulp fiber length is better than the straw pulp fiber length and the filtration water capacity is better than the straw pulp.
Transparency is also high; the pulp is clean and tough, the fiber is slender, has superior interweaving power, the paper is fine and smooth, and the mechanical strength is good. Bleached baleen straw pulp and other straw pulp in the processing process can be used in the manufacture of all kinds of high-medium and high-grade writing and typing paper. General grass pulp can be mixed with other pulp, making cultural paper. Unbleached grass pulp is used to make wrapping paper and cardboard.
To make wood pulp, you may need these equipment: wood chip hopper, desander, blender, Johnson screen, pressure knotter, fine sieve, digester, heat exchanger, blow tank, vacuum drum washer, reaction tower, bleaching tower, conditioner, vertical pipe, heater, commingler, pulp storage silo, condensate system, exhaust gas collection condensation system, recovery system, pulp board machine, pulp board cutting machine, packing machine, supporting tank, pump valve etc. CNBM offer all kinds of paper pulp related equipment, please leave us messages for details and quotation. Get in touch now!