HPMC manufacturing is mainly completed by three reactions, namely choline treatment, hydroxypropylation and methylation.In recent years. The various technical parties have only focused on improving and improving the operation of each unit. Generally use cotton wool as raw material, with 50% sodium hydroxide water solution for alkaline treatment. Get sodium cellulose salt, in the hydroxypropyylation and methylation operation.The most commonly used hydroxyproylation reagent is propylene oxide. In the early stage also useful bromide, sulfate two, methyl ester reported.
Cellulose ether production process has its common, namely refined cotton or wood pulp by liquid caustic soda immersion. Pressing to remove excess alkali solution, alkali cellulose, add solvent, etherification agent, at a certain temperature, pressure for etherification reaction, reaction end is subject to the required ether degree, and then by neutralization washing, drying, crushing and other finished products.
One step ether method:
- Example 1: The powder staple is mixed with 50% water of sodium hydroxide solution at 60’C. And the propylene epoxy is fed continuously,when the reactor pressure is 2.26X 10 MPa. The reaction product hydroxypropyl methyl cellulose had 20.2% methyl substitution, 25% hydroxypropyl substitution. 4% and insoluble
- Example 2: Spray 50% sodium hydroxide solution on linwool and heat to 85C, add oxidized propylene, gas methane, and continue to heat until the reaction is complete.The results contains hydroxypropyl methyl cellulose of 17.0% and 24.8%.In the reaction, methyl conversion was 37.8% and oxidized propylene 26.2%.
Separate ether method:
- Example 3: First, the cellulose powder and propylene oxide are reflected in the nitrogen flow for 3h, and the reaction temperature is 30-60 C. Then, chloromethane is treated for 5h, and the reaction temperature is 35-80 C. Hydroxypropyl methylcellulose of 23.5% was obtained
- Example 4: The alkaline cellulose powder reacts with oxidized propylene in the presence of halogenated hydrocarbon, and then reacts with chlorthane in the presence of sodium hydroxide to obtain hydroxypropyl methyl cellulose with sodium hydroxide.In this reaction, the conversion rate of oxidized propylene and chloromechloride was 42.6% and 41.0%, respectively.