HPMC Production Process and Manufacturing Process
Sep. 25, 2021
HPMC was first reported in 1905 and was produced by reacting cellulose with dimethyl sulphate, but it was not possible to isolate cellulose ethers at that time. 1912 saw the first patent for the preparation of cellulose ethers. 1927 saw the successful synthesis and isolation of HPMC. 1938 saw the industrial production of MC by Dow Chemical Company in the USA. The industrial production of HPMC was carried out in the USA in 1948 and the production process reached maturity in 1960~1970.
The production process of HPMC can be divided into two categories: gas-phase and liquid-phase.
Liquid Phase Method
At present, Chinese manufacturers mainly use the liquid phase method to produce HPMC. The raw material is usually refined cotton, which is crushed in a combination crusher, or refined cotton is directly alkalised and etherified with a binary mixture of organic solvents. The finished product is processed in batches and granulated at high temperatures. Most of the special treatments are only to delay hydration time products are not treated with anti-mould and compounding and are packed by hand.
1,Low internal pressure in the equipment during the reaction, low requirements for equipment pressure-bearing capacity and low risk.
2,After immersing the cellulose in the lye solution, a thoroughly dissolved and uniformly alkalised alkali cellulose is obtained. The alkali solution has good permeability and swelling of the cellulose.
3,The volume of the etherification reactor is small and the alkali cellulose is uniformly swollen.
4,The quality of the product can be easily controlled to give a more homogeneous product in terms of substitution and viscosity, and the variety can be easily varied.
1,The reactor is usually not too large and the production capacity is small due to statistical limitations.
2,The reaction control is less automated than the gas phase method and therefore less accurate.
3,The absence of mould and compound treatment affects the viscosity stability of the product and production costs.
4,The refining and purification of crude oil products requires a lot of equipment, complex operation and high labour intensity.
5,Packaging is manual and labour costs are high.
Vapour phase method
Developed countries such as Europe, America and Japan mostly use the gas phase process. Wood pulp is used as raw material and alkalisation and etherisation are carried out in the same reaction equipment. The reaction process is controlled by advanced automatic means, allowing accurate control of temperature and pressure. After completion of the reaction, the excess chloromethane and by-product dimethyl ether enter the recovery system in gaseous form and are recycled separately. Refining and purification processes are carried out in a continuous rotary filter press. Pulverisation is carried out in a high efficiency finished product pulveriser, together with drying to remove excess water. Auxiliary processes such as mixing and packaging are also carried out under an automatic control system.
1,Low reaction temperatures, short reaction times and more accurate reaction control than the liquid phase method.
2,Compact equipment and high single batch throughput.
3,No complex solvent recovery system is required and labour costs and labour intensity are low.
1,Large investment in equipment and automation, high technical content and considerable investment and construction costs.
2,Due to the high degree of automation, the quality of the operators is high.
3,In the event of a breakdown, major accidents can easily occur and one problem can lead to the shutdown of the entire line.
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