Application of the hottest BCTMP in high-grade coa

Application of BCTMP in high-grade coated printing paper

bctmp is the English abbreviation of blended chemithermomechanicalpulp. At present, many paper researchers at home and abroad are actively exploring its application in all kinds of paper. The application research of BCTMP has far-reaching social benefits, which is particularly important for China, which is relatively short of wood resources. In the past, people have been very controversial about the application of high yield mechanical pulp in printing/writing paper, mainly because the paper produced by mechanical pulp is easy to turn yellow, and lignin is considered to be the reason for the reduction of durability. However, recent studies have shown that the main reason for the aging and degradation of paper is the acidity of paper, not lignin. In terms of mechanical properties, the stability of lignin containing paper made under alkaline conditions is as good as that of non lignin containing paper, but light induced yellowing is still a problem. Light induced yellowing is related to the lignin content in the pulp, but when the dosage is 10% - 25%, the yellowing is not obvious in most cases, which is acceptable, and the degree of yellowing in coated paper will be smaller. 2. We attach great importance to the construction of new material industry system

in the past, BCTMP was mainly used in paper, light offset paper, whiteboard and white cardboard in China, but it was rarely used in high-grade coated printing paper. However, with the increasingly fierce market competition, coated printing paper manufacturers are facing huge cost pressure. In the past two years, some paper-making enterprises in China have also begun to try to add 0~30% BCTMP pulp to coated paper, thus opening the prelude to the application of BCTMP in high-end coated printing paper

1 introduction to coated printing paper in developed countries in Europe and the United States

Europe is the main production area of BCTMP, and it is also an advocate for the use of BCTMP. The research on BCTMP has a long history of application and has been successfully applied in coated printing paper. The classification of coated paper in Europe is shown in Table 1. The United States is a major consumer of coated paper in the world, accounting for 30% of the world's coated paper consumption. Its demand trend affects the direction of the global coated paper market. In 2003, a total of 11.5 million tons of coated printing paper were consumed, of which more than half were coated paper containing mechanical pulp, and the coated paper containing mechanical pulp was mainly low weight coated paper. Some experts predict that with the improvement of whiteness of mechanical pulp, the market share of coated paper containing mechanical pulp will further increase

2 current situation of coated printing paper in China

the national output of coated paper in 2004 was about 3million tons, of which 2.5 million tons were coated paper. CGW coated paper with a quantitative range of 80~150g/m2 is relatively scarce in China's paper consumption market, and the demand for this paper in the market will increase year by year

3 B application practice of CTMP in high-grade coated paper on the 120th anniversary of the Sino Japanese War of 1894-1895

3.1 selection of BCTMP pulp types

bctmp pulp types, materials, manufacturers are different, their physical properties are also different. First of all, the purpose of using the pulp should be clear, and the selection of pulp species and the determination of usage should be carried out in combination with its own equipment characteristics. For example, Hb type (high loose thickness) can be selected to increase the thickness in order to install a ruler on the bending table; In order to reduce the cost and replace more chemical pulp as much as possible, HT type (high strength) BCTMP can be selected

3.2 precautions for the application of BCTMP

at present, BCTMP has two types: broad-leaved pulp and coniferous pulp. In high-grade coated printing paper, broad-leaved ground wood pulp is mainly used. Its BCTMP fiber is short and coarse, the content of fine fiber is relatively large, and the fiber contains more negative charges. These characteristics determine some problems in its production and application

3.2.1 water filtration problem

due to the high content of BCTMP fine fibers, when making high weight paper, the pulp layer is thick, and water filtration becomes difficult. Therefore, it is better to treat the pulp alone or adopt particle retention system when beating

3.2.2 paper strength

when a small amount of BCTMP is added, the strength does not change much, and there is a slight upward trend. When the dosage exceeds 15%, the strength decreases significantly, especially the folding resistance. Therefore, the proportion of coniferous pulp should be appropriately increased

3.2.3 smoothness

due to the short and thick BCTMP fiber, the smoothness of the paper surface is low. Therefore, to affect the coating quality, it is necessary to increase the pressure of the press and calender roll, and the ash content of the paper can be appropriately increased on the premise of ensuring the strength of the paper

3.2.4 coating performance

due to the addition of excessive BCTMP, the fibers are easy to be pulled out during surface sizing or scraper coating, resulting in difficulties in the operation of the coater. Therefore, special attention should be paid to the fiber bundle content of BCTMP, choose BCTMP with low fiber bundle content, add dry strength agent in the pulp or increase the penetration of surface sizing solution in the paper to improve the bonding strength in the base paper

4 application prospect of BCTMP

because BCTMP has many advantages, such as low cost, high loose thickness, high paper opacity, good coating of paper fillers, many paper workers are actively studying to expand its application scope and dosage. With the application of paper gripper and stacker, the reduction of the difference between the two sides of the paper and the improvement of the coating method, it is believed that the pulp has a broad application prospect in high-end coated printing paper

information source: Hunan papermaking Author: Wu Baoyu

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