Reflections on the Development of High Strength Corrugated Paper (2)

On the contrary, in 1998, the domestic consumption of corrugated materials was 9.56 million tons, and the corrugated material recovery rate in the United States was 68.9%. If our recovery rate can reach 50%, the domestic waste corrugated box material can be recycled by nearly 5 million tons, which is very Considerable numbers. Although the quality of domestic OCC is not as good as that of AOCC, this part of raw materials should not be ignored in any case. Domestic OCC is still dominated by grass fibers. In the past, people were prejudiced against the recovery of waste paper from grass fibers. The results of the study showed that the quality of paper can be improved to a certain extent in the recycling process, such as the proper use of additives. , should be able to produce better quality corrugated paper.
Lack of timber resources in China, we should pay attention to the use of wheat straw half chemical pulp production of corrugated paper. The experience of producing the high-strength corrugated base paper by using the semi-chemical wheat straw mixed with a certain proportion of OCC in Spanish SAICA paper mill is worth learning from. The reason why the plant uses semi-chemical wheat straw pulp is that there is a shortage of European OCC supply, and the second is that wheat straw is relatively cheap. The factory uses self-developed continuous steaming equipment and processes to produce semi-chemical wheat straw pulp at a constant liquid-to-liquid ratio under atmospheric pressure, and mixes 50% to 75% of OCC to produce high-quality, high-strength corrugated base paper.
The quality of semi-chemical wheat straw pulp is not a problem. The problem is to solve the waste water treatment. The wheat straw half chemical pulp wastewater treatment has no successful experience. The above-mentioned Spanish SAICA paper mill began to mix Nissan's 300t straw liquor with the white water of the paper machine, and anaerobic fermentation was carried out in three 15,000m3 tanks. The biogas produced was sent to the boiler for power generation. Wastewater can be discharged after being subjected to aerobic treatment. In the mid-1980s, the local pollutant discharge standard was COD 10000mg/L, and the wastewater COD of the plant was 5700-7500mg/L, which could meet the discharge standards. Many articles were reported as successful waste water treatment; the discharge standard was set to 5000mg in the late 1980s. / L, factories can only use straw pulp production to meet the standard requirements. However, with the increasingly stringent control of local government's emission standards, the requirement for COD emissions was less than 500mg/L by 1998. Although the plant spent 2 million US dollars for two years of research, it did not find a good way to reach the standard, and finally had to temporarily Chemical wheat straw production line closed. According to Mr. Escudero at the TAPPI Paper Technology Seminar at the 99' China International Paper Exhibition in November 1999, they are developing new processes for lignin precipitation and wet oxidation, and believe that the waste liquid undergoes lignin precipitation and wet oxidation. After anaerobic-aerobic treatment, it can meet the emission standards. By 2003, it plans to reconstruct a semi-chemical wheat straw pulp production line with a daily output of 400-600 tons (200-300 t/d for each continuous steamer). The above-mentioned lignin precipitation and wet oxidation processes are currently undergoing pilot tests. In fact, the SAICA paper mill has so far failed to solve the problem of semi-chemical wheat straw waste liquid pollution.
In the past, some NSSC plants discharged pulp slurry into the river. Due to the presence of hemicellulose and acetate, the BOD content of the waste fluid was very high, causing serious pollution to the water body; some plants concentrated the waste fluid on the fluidized bed. Combustion gives a mixture of sodium carbonate and sodium sulfide but cannot be used directly in NSSC mills. Another relatively mature method is cross recovery. When the semi-chemical pulp and the sulphate pulp plant are together, the former's waste can be sent to the sulphate pulp mill recovery system for recycling. The semi-chemical wheat straw black liquor has a high content of organic matter, and the calorific value is not a problem; the problem is that the semi-chemical pulp black liquor evaporates and when evaporating to a higher concentration, the black liquor has a great viscosity and thixotropy. In the past, the Paper Research Institute of the Ministry of Light Industry studied the black liquor performance of straw half-chemical pulp. The results showed that the black liquor viscosity of straw half-chemical pulp is much higher than that of chemical pulp black liquor, and the highest concentration that can be evaporated is also much lower, but It is proposed that increasing the residual black liquor can solve the problem of evaporation. However, there is still a lack of systematic research on the properties of wheat straw semi-chemical pulp black liquor, and the chemical recovery of wheat straw half chemical pulp is even more inexperienced. The use of wheat straw to produce semi-chemical pulp is an aspect of making full use of China's fiber resources. Government departments and industry should pay attention to and support the research and development of semi-chemical wheat straw waste liquid recovery and treatment process technology.
4 The development trend of corrugated paper The reduction of costs and the reduction in quantification are still the trends in the development of corrugated board. Based on the requirements of environmental protection and cost, the quantitative quantification of corrugated board, including boxboard and corrugated paper, must be reduced. The reason why the production of low-quantity cardboard is the market needs, followed by the progress of the aniline printing technology in recent years and the emergence of new corrugated types. The traditional corrugated type is A, C, B, and D. It is mainly used in cartons that require high strength. In recent years, new types of 楞-type E, F, and N have been designed. The main feature is that the corrugated height is much lower than that of traditional corrugated files. For low-volume corrugated paper. In the past, corrugated medium was generally 127-140 g/m2, and production of 90-115 g/m2 has been started. It is estimated that even 60-90 g/m2 corrugated paper will be produced in the future. Due to the quantitative reduction of the cardboard and corrugated base paper, the quantification of the entire corrugated board is also significantly reduced. In the past, generally 1000 to 1100 g/m2, and now a large quantitative amount of 600 g/m2, in some countries, the corrugated cardboard has a basis weight of only 500 g/m2, which highlights the high strength/weight characteristics of the corrugated carton. However, China's corrugated base paper is generally high-quantitative, and its strength can reach the national product standard A, and so on, so it has to import a considerable number of high-strength corrugated paper. Table 3 compares the lateral pressure index of several kinds of domestic and foreign corrugated base papers. The strength of several domestic products is significantly lower than that of several foreign products.
Table 3 Several domestic and foreign corrugated paper ring pressure index

The stiffness and compressive strength of the corrugated base paper play an important role in the overall strength of the carton. The cardboard stiffness D = Eh3 / 12, E is the elastic modulus, h is the thickness, visible thickness is very important for cardboard stiffness. How to make the cardboard in the quantitative reduction will not affect the stiffness due to a significant drop in thickness will be the key to the production of low basis weight corrugated paper. If conditions permit the use of a multilayer forming device, not only will it contribute to the stiffness of the product, but it will also contribute to the burst resistance. It is reported that the bursting resistance of two-layered products is 10% to 20% higher than that of one-layer products.
Although corrugated paper is not a high value-added product, many production lines abroad are equipped with advanced paper machines. Australia's Visy Paper Group Coolaroo paper mill has two board machines. No. 4 is a Voith-Toschi triple wire machine, producing corrugated base paper and linerboard of 112 to 260 g/m2, with a width of 2.5m and a speed of 700m/min. With an annual output of 120,000 tons, the No. 5 machine is a double long net with a width of 2.8m, a speed of 700m/min and an annual output of 95,000 tons. Indonesian Golden Group's No. 2 machine at Serang Paper Mill is BeloitGapFormer. In April 1996, it produced low-yield corrugated base paper, which was widened by 6.6m and the speed was 850 to 950m/min. When AOCC was used as raw material, 105g/m2 corrugated base paper was produced. EOCC and local OCC produce 150 g/m2 corrugated paper with an annual output of 340,000 t. A corrugated paper machine to be put into production at the Spanish SAICA paper mill is Voith's Duoformerbase GapFormer, which has a width of 8.1m, a speed of 1450m/min, a corrugated base paper quantity of 75 to 110g/m2, and an annual output of 500,000 tons. OTOR is one of the most important companies in Europe to produce corrugated paper from waste paper. It uses 1/3 scrap magazine paper, 2/3 OCC as raw material, and a Duoformer paper machine to produce 100 g/m2 at the Efienne du Rouvrag paper mill near Paris. Corrugated paper. The paper machine has a width of 7m, a speed of 600m/min and a daily output of 600t. It is interesting to note that the original paper machine was to produce low-quantity coated paper. After OTOR acquired the plant, it believed that the production of low-quantity coated paper was uncompetitive. It changed to use waste paper to produce corrugated paper and cardboard. Are the above examples inspiring us to reflect on whether it is necessary to devalue various investment concepts of corrugated paper production? (China Pulp and Paper Industry Research Institute Yan Shijun)