HEMC hydroxyethyl methyl cellulose production process
Hydroxyethyl methyl cellulose HEMC can be used as a colloidal protective agent, emulsifier and dispersant due to its surface activity in aqueous solution. Effect of hydroxyethyl methyl cellulose on cement properties. Hydroxyethyl methyl cellulose is a odorless, tasteless, non-toxic white powder that dissolves in cold water to form a transparent, sticky solution. With thickening, adhesion, dispersion, emulsification, film formation, suspension, adsorption, gelling, surface activity, water retention and colloid protection, etc. Water solution can be used as colloid protectant, emulsifier and dispersant because of its surface active function. Hydroxyethyl methyl cellulose aqueous solution has good hydrophilicity and is an efficient water retaining agent.
HEMC production process
The invention discloses a preparation method for hydroxyethyl methyl cellulose, which uses refined cotton as raw material and ethylene oxide as etherifying agent to prepare hydroxyethyl methyl cellulose. The raw materials for the preparation of hydroxyethyl methyl cellulose by weight are: toluene and isopropanol mixture 700 ~ 800 parts as solvent, 30 ~ 40 parts water, sodium hydroxide 70 ~ 80 parts, refined cotton 80 ~ 85 parts, ethylene oxide 20 ~ 28 parts, methane chloride 80 ~ 90 parts, glacial acetic acid 16 ~ 19 parts; The specific steps are as follows:
The first step is to add toluene and isopropyl alcohol mixture, water, and sodium hydroxide in the reaction kettle, heat up to 60 ~ 80℃, hold for 20 ~ 40 minutes;
The second step, alkalization: the material is cooled to 30 ~ 50℃, refined cotton, toluene and isopropyl alcohol mixture solvent spray, vacuum to – 0.006mpa, filled with nitrogen for 3 times replacement, replacement of alkalization, alkalization conditions: alkalization time is 2 hours, alkalization temperature is 30℃-50℃;
The third step, etherification: after the alkalization, the reactor was vacuumized to 0.05-0.07mpa, and ethylene oxide and methane chloride were added for 30-50 minutes. First stage of etherification: 40 ~ 60℃, 1.0 ~ 2.0Hour, the pressure is controlled between 0.15 0.3mpa; The second stage of etherification: 60 ~ 90℃, 2.0 ~ 2.5 hours, pressure control between 0.4- 0.8mpa;
The fourth step, neutralization: add measured glacial acetic acid in the desolvation reactor in advance, press into the etherized material for neutralization, temperature rise to 75 ~ 80℃ for desolvation, temperature rise to 102℃, PH detection 6-8 Is the completion of dissolution; Fill 90℃ ~ 100℃ reverse osmosis installed treated tap water in the dessolubilization kettle;
The fifth step, centrifugal washing: the fourth step of the material through the horizontal spiral centrifuge centrifugal separation, separation of materials transferred to the pre-filled hot water washing kettle, material washing;
The sixth step, centrifugal drying: the material after washing is conveyed into the dryer through the horizontal spiral centrifuge, and the material is dried at 150 ~ 170℃. The dried material is crushed and packaged.
Compared with the existing production technology of cellulose ether, the invention uses ethylene oxide as etherification agent to prepare hydroxyethyl methyl cellulose, which contains hydroxyethyl group, has good mildew resistance, good viscosity stability and mildew resistance when stored for a long time. Can be used instead of other cellulose ether.