Views:7 Author:Site Editor Publish Time: 2021-05-17 Origin:Site
Hemc can be used as a colloid protector, emulsifier and dispersant due to its surface active function in aqueous solution.Examples of its applications are as follows:
1. Effect of hydroxyethyl methyl cellulose on cement performance.Hydroxyethyl methyl cellulose is an odorless, tasteless, non-toxic white powder that dissolves in cold water to form a clear, viscous solution.It has the properties of thickening, bonding, dispersing, emulsifying, film-forming, suspension, adsorption, gelling, surface activity, moisture retention and colloid protection.Because of the surface active function of water solution, it can be used as a colloid protector, emulsifier and dispersant.Hydroxyethyl methyl cellulose aqueous solution has good hydrophilicity and is a kind of efficient water-retaining agent.
The invention relates to a preparation method of hydroxyethyl methyl cellulose, which takes refined cotton as raw material and uses ethylene oxide as etherification agent to prepare hydroxyethyl methyl cellulose.The raw materials for the preparation of hydroxyethyl methyl cellulose by weight are as follows: toluene and isopropanol mixture 700 ~ 800 as solvent, water 30 ~ 40, sodium hydroxide 70 ~ 80, refined cotton 80 ~ 85, ethylene oxide 20 ~ 28, methane chloride 80 ~ 90, glacial acetic acid 16 ~ 19;Specific steps are as follows:
1, in the reaction kettle, add toluene and isopropanol mixture, water, and sodium hydroxide, temperature to 60 ~ 80℃, heat preservation 20 ~ 40 minutes;
2, alkalization: the material cooling to 30 ~ 50℃, add refined cotton, toluene and isopropanol mixture of solvent spray, vacuum to- 0.006MPa, filled with nitrogen for 3 times of replacement, after the replacement of alkalization, alkalization conditions: alkalization time for 2 hours, alkalization temperature of 30℃ 50℃;
3, etherification: alkalization is over, the reaction kettle is vacuumed to 0.05 ~ 0.07MPa, and ethylene oxide and chloromethane are added for 30 ~ 50 minutes.The first stage of etherification: 40 ~ 60℃, 1.0 ~ 2.0 hours, the pressure is controlled between 0.15-0.3MPa;The second stage of etherification: 60 ~ 90℃, 2.0 ~ 2.5 hours, the pressure is controlled between 0.4-0.8 MPa;
4, neutralization: add the measured glacial acetic acid in the desolution kettle in advance, press into the etherized material for neutralization, temperature rise 75 ~ 80℃ for desolution, the temperature rises to 102℃, pH value is 6-8 for the desolution is completed;In the desolvation kettle filled with 90℃ ~ 100℃ after the reverse osmosis treatment of tap water;
5, centrifugal washing: the material in the fourth step is centrifuged through the horizontal spiral centrifuge, and the separated material is transferred to the washing kettle filled with hot water in advance for material washing;
6, centrifugal drying: the material after washing is transported into the dryer through the horizontal spiral centrifuge, and the material is dried at 150 ~ 170℃. The dry material is crushed and packaged.
Compared with the existing cellulosic ether production technology, the invention uses ethylene oxide as etherifying agent to prepare hydroxyethyl methyl cellulose, which has good mildew resistance because of containing hydroxyethyl group, and good viscosity stability and mildew resistance when stored for a long time.It can be used as a substitute for other cellulose ether.