所属分类：常见问题 发布时间：2020-12-03 15:19:33 来源：http://www.lcnmb500.com 浏览量：
1. Raw material factor
Due to the high sulfate content in urea, when urea is added at the later stage of resin polycondensation reaction, it is equivalent to adding curing agent to promote the rapid crosslinking of resin into network structure. If the treatment is not timely, the resin will be solidified in the reactor. Therefore, standard industrial urea raw materials should be selected in production to limit the sulfate content in urea to less than 0.01%.
2. Balance of operation
When the temperature and pressure are not stable or fluctuate too much, the process of resin polycondensation is uneven, which is easy to cause wall sticking. Therefore, in the production operation, it should be slowly pressurized and heated. 3 MPa, then slowly raise the temperature and keep the pressure for about 2-15 min. 1 MPa per minute.
3. Temperature difference of kettle wall
When the temperature of cooling medium is too low or the temperature drops suddenly, the temperature difference between the reactor wall and the material is too large, resulting in the glue sticking on the wall of the reactor in contact with hardox500 wear-resistant plate. Therefore, both heating and cooling should be carried out within the reasonable temperature difference range. Generally, the steam service temperature should be less than 180 ℃, the temperature difference thermal shock should be less than 120 ℃, and the cooling shock should be less than 90 ℃. At the same time, attention should be paid to determine the appropriate inlet and outlet temperature of the cooling medium to maintain balanced operation.
4. Reaction temperature and time
When the reaction temperature is below 80 C, if ammonia chloride is used as catalyst, the pH value will not show up due to the rapid reaction of ammonia chloride. When the temperature rises, pH will decrease rapidly, the reaction speed will accelerate, and the condensation reaction will be too intense, resulting in sticky walls. In addition, if the polycondensation reaction time is too long, the molecular weight of the resin is large and the viscosity is too high. Therefore, the temperature and time of polycondensation should be controlled correctly and the reaction should be terminated in time. Generally, the temperature of reaction solution should be controlled within 0 ~ 95 ℃.