Development status of HPMC production technology and process of hydroxypropyl methyl cellulose in China

Hydroxypropyl methyl cellulose HPMC to the current domestic production is given priority to with liquid phase method technology, this technology is represented by wuxi chemical industry research and design institute in China research unit in the 1970 s, research achievements on the basis of the promotion, the original is the gas phase method etherification reaction, because the equipment is not adapt to our country, then worked out the liquid phase method etherification reaction, So far high bath ratio liquid phase etherification reaction process route is still the main production process of some well-known cellulose ether manufacturers.

Domestic hydroxypropyl methyl cellulose HPMC production generally uses refined cotton as raw material (some manufacturers also began to try to use wood pulp), and domestic grinder grinding or directly use refined cotton alkalization, etherification using binary mixed organic solvent, reaction in the vertical reactor. The purification process uses an intermittent process in which the organic solvent is removed in a reactor and the crude product is purified through several washes and dehydrations through scrubbers and centrifuges. Finished product processing with intermittent granulation, under heating condition (there is also a manufacturer without granulation), drying and crushing the conventional manner, most of the special processing is just delay hydration time of product (quickly dissolve) processing without mildew prevent and distribution processing, packaging use manual way.

The liquid phase method has the following advantages: the reaction process equipment internal pressure is small, the equipment pressure capacity requirements are low, small risk; After impregnating in lye, cellulose can be fully expanded and evenly alkalized. Lye has better infiltration and swelling of cellulose. The etherification reactor is small, coupled with the uniform swelling of alkali cellulose, so the quality of the product is easy to control, the substitution degree and viscosity can be obtained more uniform products, varieties are also easy to replace.

However, this process also has the following disadvantages: the reactor is usually not too large, the statistical limitations lead to a small production capacity, in order to improve the output, it is necessary to increase the number of reactors; Refined and purified crude products need more equipment, complex operation, labor intensity; Because there is no anti-mildew and compound treatment, resulting in product viscosity stability and production costs are affected; Packaging by manual way, labor intensity, high labor cost; The automation degree of reaction control is lower than that of gas phase process, so the control accuracy is relatively low. Compared with the gas phase process, complex solvent recovery systems are required.

With the improvement of domestic hydroxypropyl methyl cellulose HPMC production technology, some enterprises through continuous independent innovation, large kettle liquid phase method has been developed by leaps and means, and has its own technical characteristics. Anxin chemistry uses the original HPMC production process, not only the production process is reasonable, the operation control parameters are accurate and reliable, the full and reasonable use of raw materials and other characteristics, and the product replacement degree is uniform, the reaction is completely thorough, the solution transparency is good, and at the same time to ensure the stability of product quality. HPMC production line of some enterprises has been automated transformation, to achieve the device’s DCS automation control requirements, materials including liquid, solid raw materials can be used to accurately measure and add DCS system, temperature and pressure control in the reaction process are all realized DCS automatic control and remote monitoring, In terms of feasibility, reliability, stability and safety of production, it is obviously improved compared with the traditional production mode, which not only saves manpower, reduces labor intensity, but also improves the operating environment on site.