Cellulose ether is a widely used polymer fine chemical material made from natural polymer cellulose through chemical treatment. After the manufacture of cellulose nitrate and cellulose acetate in the 19th century, chemists have developed a series of cellulose derivatives of many cellulose ethers, and new application fields have been discovered continuously, involving many industrial sectors. Cellulose ether products such as sodium carboxymethyl cellulose (CMC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methyl hydroxyethyl cellulose (MHEC)and methyl hydroxypropyl cellulose (MHPC) and other cellulose ethers are known as “industrial monosodium glutamate” and have been widely used in oil drilling, construction, coatings, food, medicine and daily chemicals.
Hydroxyethylmethylcellulose (MHEC) is an odorless, tasteless, non-toxic white powder that can be dissolved in cold water to form a transparent viscous solution. It has the characteristics of thickening, binding, dispersing, emulsifying, film-forming, suspending, adsorbing, gelling, surface active, maintaining moisture and protecting colloid. Due to the surface active function of the aqueous solution, it can be used as a colloidal protective agent, emulsifier and dispersant. Hydroxyethyl methylcellulose aqueous solution has good hydrophilicity and is an efficient water retention agent. Because hydroxyethyl methylcellulose contains hydroxyethyl groups, it has good anti-mildew ability, good viscosity stability and mildew resistance during long-term storage.
Hydroxyethyl methylcellulose (HEMC) is prepared by introducing ethylene oxide substituents (MS 0.3~0.4) into methylcellulose (MC), and its salt resistance is better than that of unmodified polymers. The gelation temperature of methylcellulose is also higher than that of MC.
Structure:
Feature:
The main characteristics of hydroxyethyl methylcellulose (HEMC) are:
Application:
Hydroxyethyl methylcellulose can be used as a colloidal protective agent, emulsifier and dispersant due to its surface-active function in aqueous solution. Its application examples are as follows:
Preparation:
A preparation method of hydroxyethyl methylcellulose, the method is to use refined cotton as a raw material and ethylene oxide as an etherification agent to prepare hydroxyethyl methylcellulose. The weight parts of raw materials for preparing hydroxyethyl methyl cellulose are as follows: 700-800 parts of toluene and isopropanol mixture as solvent, 30-40 parts of water, 70-80 parts of sodium hydroxide, 80-85 parts of refined cotton, ring 20-28 parts of oxyethane, 80-90 parts of methyl chloride, 16-19 parts of glacial acetic acid; the specific steps are:
The first step, in the reaction kettle, add toluene and isopropanol mixture, water, and sodium hydroxide, heat up to 60-80 ° C, keep warm for 20-40 minutes;
The second step, alkalization: cool the above materials to 30-50°C, add refined cotton, spray the toluene and isopropanol mixture solvent, pump it to 0.006Mpa, fill nitrogen for 3 replacements, and carry out after the replacement Alkalinization, the alkalization conditions are: the alkalization time is 2 hours, and the alkalization temperature is 30°C to 50°C;
The third step, etherification: after the alkalization is completed, the reactor is evacuated to 0.05-0.07MPa, and ethylene oxide and methyl chloride are added for 30-50 minutes; the first stage of etherification: 40-60°C, 1.0-2.0 Hours, the pressure is controlled between 0.15 and 0.3Mpa; the second stage of etherification: 60～90℃, 2.0～2.5 hours, the pressure is controlled between 0.4 and 0.8Mpa;
The fourth step, neutralization: Add the measured glacial acetic acid in advance to the precipitation kettle, press into the etherified material for neutralization, raise the temperature to 75-80°C for precipitation, the temperature rises to 102°C, and the pH value is 6 At 8 o’clock, the desolventization is completed; the desolventization tank is filled with tap water treated by a reverse osmosis device at 90 ° C to 100 ° C;
The fifth step, centrifugal washing: the material in the fourth step is centrifuged through a horizontal screw centrifuge, and the separated material is transferred to a washing tank filled with hot water in advance for washing of the material;
The sixth step, centrifugal drying: the washed material is conveyed into the dryer through a horizontal screw centrifuge, and the material is dried at 150-170°C, and the dried material is crushed and packaged.
Compared with the existing cellulose ether production technology, the present invention uses ethylene oxide as the etherification agent to prepare hydroxyethyl methyl cellulose, which has good anti-mold ability due to containing hydroxyethyl groups. It has good viscosity stability and mildew resistance during long-term storage. It can be used instead of other cellulose ethers.