| Sizing is an important process for most kinds of paper. The conventional method of sizing used soaped rosin and aluminum sulfate at acid condition , pH 4 to 5, which is so called acid sizing. The aluminum sulfate accelerates the decomposition of the cellulose and decreaces the quality and durability of paper .It is reported that 85 to 90 percent of decomposition of book paper is due to the acid matter in the paper and the folding endurance of such paper decreases 50 percent per seven years. Much more important is that such sizing method has more drawbacks such as can t use recycled white water, can t use CaCO3 as filler instead of part of wood fiber, it also corrodes machine and pollutes environment badly.The neutral sizing or neutral papermaking is put forward in 1950s , which means papermaking's pH value in the whole process is kept at 7 or higher. Compared with the acid sizing , neutral sizing can not only improve the performance of papermaking and wet end environment, improve the quality of paper, but also decrease the pollution to the environment, use the cheaper CaCO3 as filler, employ secondary fiber in great amount, etc..Although AKD and ASA , etc., can be used as neutral size ,in terms of production cost and performance, dispersed rosin size has supreme advantage. For many years, papermakers have been working hard in modifying rosin size, precipitating agent and sizing process so that sizing can be practiced under neutral or weakly basic condition.In this experiment, a new kind of rosin size is developed, presenting no difficulty in preparing, with PAC as precipitating agent and SB as retention agent, the effect of the size is good under acid and weakly basic condition (pH less than 8). In this experiment, the preparation of rosin size and the effect of each component on the effect of sizing are studied. The results of experiments detail as follows:1.The preparation of highmolecular emulsifying agent: the monomers used are unsaturated Benzene derivative, acrylester and a,p-unsaturated dibasic acids, unsaturated Benzene derivative 25%, initiator 0.8% (for the amount of monomers), water is 1.5 times of monomers , the temperature 80 C and reaction time 3h, the force of emulsifying agent gotten is 60s.2.The preparation of lowmolecular surfactant : the aliphatic alcohol poly(oxyethylene ether) sulfate and nonyl hydroxybenzene poly(oxyethylene eher) sulfate are prepared with the force of emulsifying 120s and 140s respectively.3.Two kinds of modified rosin, 115-type and 105-type, are prepared. The acid value and softening point of modified rosin is higher than natural rosin, with the 115-type' s the highest, so it is used to prepare rosin size.4. Using high-temperature-antiphase method, two kinds of rosin size are prepared. 95# size is made by using 10% highmloecular emulsifying agent and 3% nonyl hydroxybenzene poly (oxyethylene ether) sulfate and 101" size by using 3% aliphatic alcohol poly(oxy ethylene ether) sulfate and 5% nonyl hydroxybenzene poly(oxyethylene ether ) sulfate. The content of free rosin acid and solid in is higher than 101 "size, the former also has good mechanical and heat stability.5.The results of sizing test: the degree of sizing of 95# size is higher than that of 101# size from acid to basic condition. Much more important is that the 95# size also has good sizing effect at pH 7-8 .6.The effect of additives and conditions of process are tested.The best sizing effect are gotten under the following conditions: size 1%, PAC 0.8%, SB 0.6%, CaCO3 15% (for the amount of absolutely dry pulp), 7 pH value, the press O.SMPa, the drying temperature 85-90C, direct sizing.7. The effect of the two important components, size and PAC, on the physical property of paper is tested. The physical property of paper decreases with the increase of size, while PAC acts otherwise.
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