The Gas Phrase Method of Producing Hydroxypropyl Methyl Cellulose (HPMC)
The crushed cellulose fine powder is added to a horizontal reactor with a strong agitating device. Under the condition that no additional organic solvent is needed, a certain amount of alkaline liquid, etherifying agent, and a small amount of recovered low boiling point by-products are directly added, and the etherification reaction is completed in the semi-dry state. After the etherification reaction is completed, the finished product is obtained through hot water washing, drying, crushing, and sieving.
The flowchart of the production method is shown in the following figure:
The main equipment of the gas-phase production method:
EQUIPMENT NAME | REMARKS | EQUIPMENT NAME | REMARKS |
Cellulose Mill |
| Pelletizer |
|
Horizontal Reactor | From Germany | Drying Machine |
|
Compressor |
| Ultrafine Mill | From Germany |
Washing Filter | From Germany |
The main parameters of the gas–phase production method:
Item | Reference of Consumption Quota | Item | Reference of Consumption Quota | ||
Raw materials | Cellulose/t | 0.80 – 0.85 | Power | Water/t | 5.00-8.00 |
50% Alkaline liquid/t | 0.96 – 1.00 | Electricity/kWh | 3300-3800 | ||
Methyl chloride/t | 0.63 – 0.75 | Steam/t | 4.0-6.0 | ||
Propylene oxide/t | 0.18 – 0.23 | ||||
In a production method based on this technology, no other solvent is needed. After the synthesis reaction is completed, the etherifying agent added for completing the reaction can be completely recovered. Therefore, the technology has an obvious cost and environmental advantages. However, due to the large investment, a high degree of automation, under the condition that the equipment does not meet the full production standards, it can easily lead to high consumption of propylene oxide and chloroform, poor uniformity of products and the like. As a result, the production process has not been accepted by most manufacturers. With the development and rectification of the industry, the gas-solid-phase production technology will be the development trend of construction-grade hydroxypropyl methyl cellulose (HPMC).
