The Category, Application and Property Index of Paper Pulp
Paper pulp is the basic raw material of paper making. It is processed and manufactured by paper pulper. The materials used for paper pulp making can be divided into four kinds: stem fiber, bast fiber, hull fiber and wood fiber, in which wood fiber is the most important one. Currently, the wood fiber resources is no longer sufficient for the rapidly developing paper and paper pulp industry all over the world. In order to make up for the lack of raw materials of paper making, a considerable amount of paper pulp are imported to China from abroad every year.
I. What is pulping
Pulping refers to the production process that the paper making industry uses chemical methods, mechanical methods or the combination of two methods to make the plant fiber materials dissociate into unbleached or bleached pulp.
II. The category and application of paper pulp
- Mechanical wood pulp
Mechanical wood pulp is also known as ground wood pulp. It is the paper pulp made from the fiber raw materials by mechanical grinding method, occupying an important position in the papermaking industry. The paper made of mechanical wood pulp has the advantages of low cost, simple production process, strong ink absorption, high opacity, soft and smooth. So it is suitable for printing. But because of the shorter fiber, higher non-cellulose components content, the strength of this kind of paper is lower.
In addition, because most of the lignin and other non-cellulose are not removed, the products of paper get easily yellowed and brittle and are not suitable for keeping long-term preservation. Mechanical pulp usually refers to white or brown mechanical wood pulps. The white mechanical wood pulp is mainly for newsprint paper, also can be added other paper pulps for producing copy writing and printing paper. The brown mechanical wood pulp is used for the production of packaging paper and paperboard, especially for industrial paperboard.
- Sulphate wood pulp
Sulphate wood pulp adopts the mixture of sodium hydroxide and sodium sulfide as cooking agent. During the cooking, because the liquid effect is less, the fiber is without strong erosion. Thus, the produced paper has the characteristics of strong strength, good folding endurance, good breaking resistance and tearing strength. It can be divided into the bleached type and unbleached type. The unbleached sulphate wood pulp can be used for making kraft paper, bag paper, kraft paperboard and general packaging paper and paperboard. The bleached sulphate wood pulp can be used for the high-grade printing paper, drawing paper, offset paper and writing paper.
- Sulfite wood pulp
Sulfite wood pulp adopts the mixed liquor of sulfurous acid and acid sulfite as the cooking agent. The fiber of the pulp is long and soft. So the pulp has the properties of good toughness, high strength, easy bleaching and excellent felt ability. Sulfite wood pulp can be divided into the unbleached type, the half bleached type and the bleached type. Because of that the pulp contains a small amount of lignin and colored impurities, the unbleached type is yellow and the fiber of it is hard. Paper made from unbleached sulfite wood pulp is mainly used as medium printing paper, thin packaging paper, translucent paper and greaseproof paper. The half bleached pulp contains a lot of pentosan, so it can be used for making transparent tracing paper and parchment. As for the bleached pulp, the fiber is white and the texture is soft. Because of the bleaching, the fiber strength of the bleached pulp is lower than the unbleached pulp. Generally speaking, the sulfite wood pulp is mainly used for making all kinds of advanced papers.
- Waste paper pulp
Waste paper pulp is made from the used waste paper or the paper trimming cut by the printing plants. Mixing the used paper with mechanical stress and bleaching or deinking the mixture, we can get the waste paper pulp. The fiber strength and performance of the waste paper pulp depends on the type of the waste paper.
Although, the fiber may be weaker compared with the original fiber because of the liquid erosion or mechanical stress. According to the quality of the paper pulp, it can be used to make printing paper, writing paper, paperboard and other kind of low-grade paper.
In addition, straw pulp, reed pulp, bagasse pulp, bamboo pulp, cotton pulp, hemp pulp and synthetic pulp have the same category and application as the wood pulp we talked about above.
III. Composition of the pulp
The fiber of paper pulp is mainly composed of cellulose, different degrees of hemi-cellulose, lignin, resin, pigment, pectin, ash and other substances. In which, the cellulose and hemi-cellulose are basic components of the paper pulp while the others components can be removed.
IV. Main property index of the paper pulp
There are many property index of the pulp. Generally speaking, there are two types of property index: physical index and chemical index. The physical index is the criterion for judging the value of the pulp. The tensile strength, breaking strength and tearing strength are main indicators of the imported pulp.
V. Inspection standard
The imported pulp inspection mainly includes weight inspection and physical property inspection. The inspection standards include American Standard (TAPPI), International standard (ISO), Nordic standard (SCAN), Australian standard (APPITA), Canada standard (CPPA), etc.
Anyang Machinery Co., Ltd. (AM) is affiliated to China National United Equipment Group Corp. China National Building Materials Group Corporation (CNBM), the wholly state-owned key mainstay enterprise, belongs to China National United Equipment Group Corp, which is under China’s State-owned Assets Supervision and Administration Commission of the State Council now .
AM has its own R&D center and provincial technical center. AM’s leading products include large chemical vessel, tower, reaction kettle, heat exchanger, complete pulp production line, batch cooking equipment, complete pulping equipment for large chemical pulp production line, APMP poplar CMP equipment, multi-disc vacuum filter and complete equipment for hollow brick, fly ash brick and aerated concrete block production line.
Meanwhile, AM is also dedicated in design, manufacture and installation of pressure vessel and machinery equipment of the metallurgy industry, building materials, power and environment protection, etc. in recent years.