Views:4 Author:Site Editor Publish Time: 2020-09-28 Origin:Site
Regarding HPMC questions and answers
6. What is the proper viscosity of hydroxypropyl methylcellulose (HPMC)?
——Answer: Generally 100000cps is enough for putty powder, and the requirement for mortar is higher, and 100000-200000cps is better. Moreover, the most important role of HPMC is water retention, followed by thickening. In putty powder, as long as the water retention is good, the viscosity is lower (30,000-80,000), it is also possible, of course, the viscosity is higher, the relative water retention is better.
7. What are the main raw materials of hydroxypropyl methyl cellulose (HPMC)?
—— A: The main raw materials of hydroxypropyl methylcellulose (HPMC): refined cotton, methyl chloride, and propylene oxide.
8. What is the main function of the application of HPMC in putty powder? Does chemistry occur? ——Answer: HPMC plays three roles of thickening, water retention and construction in the putty powder. Thickening: Cellulose can be thickened to suspend, keep the solution uniform, and resist sagging. Water retention: make the putty powder dry slowly, and assist the gray calcium to react under the action of water. Construction: Cellulose has a lubricating effect, which can make the putty powder have good workability. HPMC does not participate in any chemical reaction, only plays a supporting role. Putty powder is added with water and applied to the wall. It is a chemical reaction. Because of the formation of new substances, the putty powder on the wall is removed from the wall and ground into powder. Then it will not work, because a new substance (calcium carbonate) ) Again. The main components of gray calcium powder are: a mixture of Ca(OH)2, CaO and a small amount of CaCO3, CaO+H2O=Ca(OH)2-Ca(OH)2+CO2=CaCO3↓+H2O Gray calcium in water and air Under the action of CO2, calcium carbonate is formed, while HPMC only retains water and assists the better reaction of gray calcium. It does not participate in any reaction.
9. What is the gel temperature of hydroxypropyl methylcellulose related to?
——Answer: The gel temperature of HPMC is related to its methoxy group content. The lower the methoxy group content, the higher the gel temperature ↑ .
10. Is there any relationship between the drop of putty powder and HPMC?
——Answer: The drop of putty powder is mainly related to the quality of ash calcium, but not to HPMC. Low calcium content of gray calcium and inappropriate ratio of CaO and Ca(OH)2 in gray calcium will cause powder loss. If it has something to do with HPMC, then the poor water retention of HPMC will also cause powder drop. For specific reasons, please refer to question 9.
11. What is the difference between the cold water instant type and the hot melt type of hydroxypropyl methylcellulose in the production process?
——Answer: The cold water quick-dissolving type of HPMC is surface-treated with glyoxal, and it is quickly dispersed in cold water, but it is not really dissolved. When the viscosity rises, it is dissolved. The hot melt type has no surface treatment of glyoxal. If the amount of glyoxal is large, the dispersion will be faster, but the viscosity will rise slowly, and if the amount is small, the opposite is true.
12. What is the odor of hydroxypropyl methylcellulose (HPMC)?
——Answer: The HPMC produced by the solvent method uses toluene and isopropanol as the solvent. If it is not washed well, it will have some residual smell.
13. How to choose the right hydroxypropyl methylcellulose (HPMC) for different purposes?
——Answer: The application of putty powder: the requirement is lower, the viscosity is 100,000, it is enough, the important thing is to keep the water better. Application of mortar: high requirements, high viscosity, 150,000-200,000 is better. Glue application: instant products are required, with high viscosity.
14. The application of HPMC in putty powder, why the putty powder produces bubbles?
——Answer: HPMC plays three roles in the putty powder: thickening, water retention and construction. Do not participate in any reaction. Reasons for bubbles: 1. Too much water was put in. 2. If the bottom layer is not dry, just scrape another layer on it, which will also cause bubbles.
15. What should be paid attention to in the actual application of the relationship between the viscosity of HPMC and temperature?
——Answer: The viscosity of HPMC is inversely proportional to temperature, that is, the viscosity increases as the temperature decreases. We usually say that the viscosity of a product refers to the result of testing its 2% aqueous solution at a temperature of 20 degrees Celsius. In practical applications, in areas with large temperature differences between summer and winter, it should be noted that it is recommended to use a relatively low viscosity in winter, which is more conducive to construction. Otherwise, when the temperature is low, the viscosity of the cellulose will increase, and the hand will feel heavy when scraped.
Hydroxypropyl methyl cellulose is divided into two kinds of ordinary hot soluble cold water instantly soluble. Hydroxypropyl methyl cellulose uses are 1, Gypsum series In the gypsum series of products, cellulose ethers are mainly used to retain water and increase smoothness. Together they play a cer