Hydroxyethyl methyl cellulose HEMC can be used as colloid protective agent, emulsifier and dispersant due to its surface active function in aqueous solution. An example of its application is as follows: The effect of hydroxyethyl methyl cellulose on the properties of cement. Hydroxyethyl methylcellulose is an odorless, tasteless, nontoxic white powder that dissolves in cold water to form a clear, viscous solution. It has the properties of thickening, binding, dispersing, emulsifying, film-forming, suspending, adsorbing, gelling, surface-active, retaining moisture and protecting colloids. Due to the surface active function of the aqueous solution, it can be used as a colloid protective agent, an emulsifier and a dispersant. Hydroxyethyl methyl cellulose aqueous solution has good hydrophilicity and is a high-efficiency water-retaining agent.

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A method for preparing hydroxyethyl methyl cellulose, the method comprises using refined cotton as a raw material and ethylene oxide as an etherifying agent to prepare hydroxyethyl methyl cellulose. The raw materials for preparing hydroxyethyl methyl cellulose are prepared in parts by weight: 700-800 parts of a mixture of toluene and isopropanol as a solvent, 30-40 parts of water, 70-80 parts of sodium hydroxide, 80-85 parts of refined cotton, 20-28 parts of oxyethane, 80-90 parts of methyl chloride, and 16-19 parts of glacial acetic acid; the specific steps are:

The first step, in the reactor, add toluene and isopropanol mixture, water, and sodium hydroxide, be warming up to 60～80 ℃, be incubated 20～40 minutes;

The second step, alkalization: cool the above materials to 30～50℃, add refined cotton, spray the mixture of toluene and isopropanol with solvent, evacuate to 0.006Mpa, fill with nitrogen for 3 replacements, and carry out alkali after replacement The alkalization conditions are as follows: the alkalization time is 2 hours, and the alkalization temperature is 30°C to 50°C;

The third step, etherification: the alkalization is completed, the reactor is evacuated to 0.05～0.07MPa, ethylene oxide and methyl chloride are added, and kept for 30～50 minutes; the first stage of etherification: 40～60℃, 1.0～2.0 hour, the pressure is controlled between 0.150.3Mpa; the second stage of etherification: 60～90℃, 2.0～2.5 hours, the pressure is controlled between 0.40.8Mpa;

The 4th step, neutralization: add metered glacial acetic acid in advance to the precipitation kettle, press into the etherified material for neutralization, heat up 75～80 ℃ to carry out precipitation, the temperature rises to 102 ℃, and the detection pH value is 68 When the precipitation is completed, the precipitation tank is filled with tap water treated by the reverse osmosis device at 90℃～100℃;

The fifth step, centrifugal washing: the material in the fourth step is centrifuged by a horizontal screw centrifuge, and the separated material is transferred to a washing kettle filled with hot water in advance, and the material is washed;

The sixth step, centrifugal drying: the washed material is transported into the dryer through a horizontal screw centrifuge, the material is dried at 150-170°C, and the dried material is pulverized and packaged.

Compared with the existing cellulose ether production technology, the present invention adopts ethylene oxide as the etherifying agent to prepare hydroxyethyl methyl cellulose, and has good anti-mildew ability because it contains hydroxyethyl group, Good viscosity stability and mildew resistance during long-term storage. Can be used instead of other cellulose ethers.