Propyl methyl cellulose (HPMC for short) is a high-tech fine chemical product in short supply in China, and is one of the most versatile and best performing varieties of cellulose. Due to its excellent thickening, emulsification, colloid protection and moisture retention properties, it is used in coatings, polymerisation, construction materials, oil drilling and extraction, textiles, food, pharmaceuticals, ceramics, electronic devices and agricultural seeds. In developed countries, HPMC is widely used in various industrial fields and daily life, and has become an indispensable chemical auxiliary, known as "industrial MSG".

1、Product overview

Cellulose ethers are an important class of water-soluble macromolecular compounds, which are a series of products made from natural cellulose (alpha-cellulose, including cotton staple or wood pulp) through alkylation and etherification reactions. Cellulose ethers are divided into ionic and non-ionic products, ionic products are mainly carboxymethyl cellulose (CMC), non-ionic products include methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC) and so on. 

HPMC is a white powder, tasteless, odourless, non-toxic, and completely unchanged in the human body and excreted. It is easily soluble in water, but insoluble in hot water. HPMC has excellent properties of thickening, emulsification, film formation, dispersion, colloid protection, moisture retention, adhesion, acid and alkali resistance, enzyme resistance, etc. It is widely used in construction, coating, medicine, food, textile, oil field, cosmetics, detergent, ceramics, ink and chemical polymerization process.

2、Domestic and foreign production status

2. 1 Foreign production status

Water-soluble cellulose ethers have been developed and put into production in foreign industrial countries since the mid-1930s and developed rapidly in the 1950s, and have formed a huge industry with ionic and non-ionic products as the main products.

At present, the world's total production capacity of cellulose ether has reached 500,000 t, of which ionic type accounts for 67%. 2000 world total production of 470,000 t, non-ionic cellulose ether is significantly less than ionic cellulose ether. This is due to the fact that the price of non-ionic cellulose ethers is generally higher, while ionic cellulose ethers are mostly used in the production of CMC because of their lower price. Only a few countries with advanced industries in the USA, Europe and Japan are able to achieve large-scale production. The table below shows the capacity and variety of water-soluble cellulose ethers produced in the world's leading countries.

The USA and Germany are the world's leading producers of water-soluble cellulose, with large scale production facilities and advanced production technology. South Korea and Japan in Asia have imported technology and equipment from Germany and the United States to organise production, with production capacity reaching or exceeding the level of 10,000 tonnes respectively, making them the world's leading producers. The MC series is mainly used in construction in the world, and its use in construction reaches more than 50% in Europe and the USA. Particular mention should be made of Korea, where the water-soluble cellulose industry, which started for the construction of the Olympic stadium in 1988, has reached a scale of 18,500t/a in the last 10 years or so.

2. 2 Domestic production situation

The industrial production of cellulose ether products in China started in the mid-1960s when the Wuxi Chemical Research and Design Institute, Luzhou Chemical Factory and Huian Chemical Factory started to research and develop HPMC, and in recent years HPMC technology has advanced considerably and its demand has been growing at a rate of 15 % per year. At present, the main manufacturers of HPMC in China are Feicheng Ruitai Fine Chemical Co. Ltd. and Luzhou Chemical Factory. Among them, Luzhou Chemical Factory Tianpu Fine Chemical Factory has been reformed and expanded to have a total production capacity of 1400t/a of HPMC and methyl cellulose (MC) in early 1999.

According to statistics, in 2002, the production capacity of HPMC in China was 3500t/a, but the actual output was only 2000 tons, and the main manufacturers were located in Hebei, Shandong, Hunan, Fujian, Sichuan, Zhejiang and Shaanxi provinces.

3. Production technology

3. 1 Domestic and foreign technology status

At present, the world's more advanced non-ionic cellulose ether production technology mainly has the United States Dow Chemical Co. Shinetsu Chemical Co. of Japan and Samsung Fine Chemical Co. of Korea have introduced technology from Dow Chemical Co. of the USA and Loedige Co. of Germany respectively.

The domestic HPMC production process generally adopts intermittent production, but the technology is relatively backward, and there are defects in the quality control of its products, and there are differences in the quality of each kettle product.

Compared with foreign technology, domestic technology is at an obvious disadvantage in terms of technology, equipment, scale, after-sales service, environmental protection and self-control, mainly in the following aspects (see Table 2).

3. 2 Introduction to the production process

The production process of cellulose ether has its commonality, that is, refined cotton or wood pulp is impregnated by liquid caustic soda, pressed to remove the excess lye, to obtain alkali cellulose, then add solvent, etherification agent, under a certain temperature and pressure for etherification reaction, the reaction end point is subject to the required degree of etherification, and then neutralized and washed, dried, crushed, etc. to obtain finished products.

The chemical reaction equation for the production of HPMC using chloromethane and propylene oxide as etherifying agents is:

Rcell - OH + NaOH + CH3Cl + CH2OCHCH3

　　　→Rcell - O - CH2OHCHCH3 + NaCl + H2O

The advanced foreign production technology all adopt the one-step method to produce HPMC, and its production process is shown in Figure 2:

 

Figure HPMC production process flow chart

The key equipment for the production of HPMC is the reactor, dryer, granulator, pulverizer, etc. At present, many foreign manufacturers are using the equipment produced in Germany. The equipment produced in China, whether in terms of production capacity or manufacturing quality, cannot meet the needs of high quality HPMC production.

The German All-In-One Reactor can be used to complete multiple process steps in one machine, with automatic control, stable product quality and safe and reliable operation.

The main raw materials for the production of HPMC are refined cotton, sodium hydroxide, chloromethane and propylene oxide. The consumption quotas are shown in the table below (according to foreign technology).

4. Suggestions for the development of HPMC projects

4. 1 Good development opportunities for the construction of HPMC projects in China

In 2001 and 2003, the State Economic and Trade Commission issued the second and third batches of national key technical transformation "double high and one excellent" project orientation plan (i.e. industrialization of high-tech technology, transformation of traditional industries by university technology and advanced and applicable technology, and optimization of key products and technology structure), which clearly pointed out that the special fine chemical products, especially those with a large gap in the domestic market and the main products and technologies, should be developed in China. It is also clearly pointed out that the transformation of special fine chemical products, especially those with a large shortage in the domestic market and mainly dependent on imports, such as hydroxypropyl methyl cellulose, should be focused on improving the grade and processing depth of existing products and increasing product specifications. This policy direction not only clarifies that HPMC is a product with a large shortage in the domestic market and mainly relies on imports, but also indicates the national policy of encouraging the development of special fine chemical products.

In 2000, the China Cellulose Ether Industry Association proposed to vigorously develop cellulose derivatives and other fine chemical products, and in the industrial structure adjustment plan, it was proposed to focus on the development of non-ionic cellulose ethers, especially MC/HPMC products; the China Chlor-alkali Industry Association proposed the idea of developing MC/HPMC products in the plan of developing downstream products of chlorine products; the Investment Research Institute of the State Planning Commission and the China

The Institute of Investment of the State Planning Commission and the China Engineering Consulting Association as well as local governments have listed MC/HPMC as a key development project.

According to overseas experience in developing cellulose products, the national demand for HPMC products is increasing with the development of the economy. China is one of the fastest growing economies in the world, therefore, the application of HPMC in China is very promising, and it is a favorable time to develop this project.

4. 2 There is a huge market potential for HPMC products in China

At present, China's cellulose ether market is still dominated by ionic products (CMC), which account for more than 95 % of the total consumption, while non-ionic cellulose ethers (MC, HPMC, HEC, etc.) only account for 5 % of the total consumption, while in developed countries in Europe and America, the consumption of these two types of products each accounts for 50 %. CMC still has a large market only because of its ease of manufacture and low price, but some parts of the traditional market may have been replaced by non-ionic ethers. It is expected that as the manufacturing process of non-ionic ethers is further improved and perfected, the cost will be reduced and the consumption of non-ionic ethers will be on a general upward trend. According to the Chinese cellulose industry and foreign manufacturers, in the next few years, China's MC/HPMC demand can reach an annual growth rate of 15 %, mainly based on the following reasons: First, with the success of Beijing's bid for the 2008 Olympic Games, the construction of Olympic venues and urban infrastructure will gradually reach the international advanced level. As an excellent additive for construction and coating, MC/HPMC will be widely used, and this will serve as a demonstration effect to drive the construction and coating industry to use MC/HPMC products in large quantities nationwide. Secondly, with the popularisation of urban commercial concrete and the reduction of the price of cellulose products, a large number of commercial concrete can be added with MC/HPMC products to enhance the rheological properties and water retention performance, gradually replacing the existing cement additives, MC/HPMC will have a broad application prospect. Third, the development of the domestic PVC industry will drive the demand for MC/HPMC. 2005, China's PVC production is expected to reach 4 million tons, the amount of HPMC required for 1200t ~ 1400t. Fourthly, in the field of medicine and food, with people's health and environmental awareness, MC/HPMC, which is harmless to physiology and does not pollute the environment, will gradually replace CMC, and will be developed rapidly.

According to the above analysis, by 2006, China's MC/HPMC market demand is expected to be 4000t~5000t. For this reason, major foreign manufacturers have taken China as the largest potential market and have expanded their production capacity to squeeze out the Chinese market.

4. 3 The construction of HPMC projects has good economic benefits

According to the preliminary estimation, according to the current market demand in China, the total investment for the construction of an HPMC plant with an annual production capacity of 6000t at the world production level is about RMB 400 million (including working capital), and after the plant is put into operation, the average selling price of the product will be RMB 65,000/t, the average annual sales revenue will be RMB 390 million, the average annual profit will be RMB 150 million, and the average annual income tax will be RMB 46.77 million. The average annual income tax is 46.77 million yuan. According to the economic benefit assessment, the project investment profit rate is as high as 36%, the investment profit and tax rate is 46%, and the financial internal rate of return is 30%, so the economic benefit is very significant. After the project is put into operation, it will only take 3 years to recover the entire investment.

It can be seen that, at the current favorable time, the vigorous development of HPMC project is not only in line with the national and industry industrial development policy, to meet the expanding domestic market needs, but also can shorten the gap between China's cellulose industry and foreign advanced countries, promote national economic development, and create huge economic benefits for enterprises.