Production Technology and Development Prospect of Hydroxypropyl Methyl Cellulose

Abstract: Hydroxypropyl methylcellulose (HPMC for short) is a high-tech fine chemical product that is in short supply in China, and is widely used in many industrial fields and daily life. In our country, the production technology and application development of such products are still in their infancy. Therefore, it is particularly important to master the latest production technology and put forward ideas for its application technology and market development.

Key words:hydroxypropyl methylcellulose; process technology; application development

Hydroxypropyl methylcellulose (HPMC for short) is a high-tech fine chemical product that is in short supply in China. It is the variety with the widest application and the best performance among all kinds of cellulose. Due to the excellent properties of thickening, emulsification, protective colloid, and moisture retention, the product is widely used in coatings, polymerization, building materials, oil drilling and mining, textiles, food, medicine, daily ceramics, electronic devices, and agricultural seeds, etc. department. In developed countries, HPMC is widely used in various industrial fields and daily life. It is called "industrial monosodium glutamate" and has become an indispensable chemical additive.

1. Product overview

Cellulose ether is an important class of water-soluble polymer compounds. It is a general term for a series of products produced by alkalization and etherification of natural cellulose (α-cellulose, including cotton linters or wood pulp). Cellulose ethers are divided into two types: ionic and non-ionic. The ionic products are mainly carboxymethyl cellulose (CMC), and the non-ionic products include methyl cellulose (MC), hydroxypropyl methyl cellulose ( HPMC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), etc.

HPMC is a water-soluble non-ionic cellulose ether, which is the product obtained when some of the methoxy groups in methyl cellulose (MC) are replaced by hydroxypropoxy groups.

HPMC is a white powder, tasteless, odorless, non-toxic, completely unchanged in the human body and excreted from the body. The product is soluble in water, but insoluble in hot water. The aqueous solution is a colorless transparent viscous substance. HPMC has excellent thickening, emulsifying, film-forming, dispersing, protective colloid, moisture retention, adhesion, acid and alkali resistance, enzyme resistance and other properties, and is widely used in construction, coatings, medicine, food, textiles, oil fields, cosmetics, washing Agents, ceramics, inks and chemical polymerization processes.

2. Production status at home and abroad

2.1 Production status abroad

Since the mid-1930s, water-soluble cellulose ethers have been successively developed and put into production in industrially developed countries abroad, and have developed rapidly in the 1950s. Up to now, a huge industry of two major types of products, ionic and non-ionic, has been formed. CMC, MC, and HEC are the most important varieties of ionic and nonionic cellulose ethers, respectively.

At present, the total production capacity of cellulose ether in the world has reached 500,000 tons, of which ionic type accounts for 67%. In 2000, the world's total output was 470,000 tons, and the non-ionic cellulose ether was significantly less than the ionic cellulose ether. This is because the price of non-ionic cellulose ethers is generally higher, while the price of ionic cellulose ethers is lower, so most of the general applications choose CMC. Since the production of MC and HEC uses methyl chloride and ethylene oxide as etherification agents, a complete set of process systems for handling these low-boiling dangerous substances is required, and there are high requirements for safety and environmental protection. So far, only the United States and Europe Large-scale production can only be achieved in a few industrially developed countries such as Japan and Japan.

The United States and Germany are the most important producers of water-soluble cellulose in the world, with relatively large-scale production equipment and advanced production technology. South Korea and Japan in Asia have introduced technology and equipment from Germany and the United States to organize production, and their production capacity has reached or exceeded the level of 10,000 tons respectively, becoming the world's major producers. MC series are mainly used in construction in the world, and its use in construction has reached more than 50% in European and American countries. In particular, South Korea needs to be mentioned. The water-soluble cellulose industry that emerged for the construction of Olympic venues in 1988 has reached a scale of 18,500t/a in the past 10 years.

2.2 Domestic Production Status

The industrial production of cellulose ether products in my country began in the mid-1960s, when Wuxi Chemical Research and Design Institute, Luzhou Chemical Plant and Hui'an Chemical Plant began to research and develop HPMC. In recent years, HPMC technology has made great progress, and its demand has been growing at a rate of 15% per year. At present, the main manufacturers of HPMC in my country are Feicheng Ruitai Fine Chemical Co., Ltd. and Luzhou Chemical Plant. Among them, Tianpu Fine Chemical Plant of Luzhou Chemical Plant has been rebuilt and expanded, and at the beginning of 1999, it has formed a total production capacity of 1400t/a HPMC and methyl cellulose (MC).

According to statistics, my country's HPMC production capacity was 3500t/a in 2002, but the actual output was only over 2000 tons. The main manufacturers are located in Hebei, Shandong, Hunan, Fujian, Sichuan, Zhejiang and Shaanxi provinces.

3. Production technology

3.1 Current status of technology at home and abroad

At present, the more advanced non-ionic cellulose ether production technologies in the world mainly include the production technologies of Dow Chemical Company of the United States, Hercules Company, and Clarite Company of Germany. Japan's Shin-Etsu Chemical and South Korea's Samsung Fine Chemicals introduced technologies from the US Dow Chemical Company and the German Ludigo Company respectively.

The domestic HPMC production process generally adopts intermittent production, but the technology is relatively backward, and its products have defects in quality control, and there are differences in the quality of each kettle product. Products can only be sold by reducing the index, which cannot meet the requirements in many fields. At the same time, due to the generally small scale of domestic production, there are great risks in the expansion of scale.

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.

3.2 Brief introduction of production process

The production process of cellulose ethers has its common features, that is, the refined cotton or wood pulp is impregnated with liquid caustic soda, and the excess lye is removed by pressing to obtain alkali cellulose, and then added with solvent and etherifying agent, etherification is carried out under a certain temperature and pressure Reaction, the end point of the reaction is subject to the required degree of etherification, and then the finished product is obtained through neutralization, washing, drying, and crushing.

The production of HPMC uses methyl chloride and propylene oxide as etherification agents, and foreign advanced production technologies all use one-step method to produce HPMC.

The key equipment for producing HPMC is reactor, dryer, granulator, pulverizer, etc. At present, many foreign manufacturers use equipment produced in Germany. Domestically produced equipment cannot meet the needs of high-quality HPMC production in terms of production capacity and manufacturing quality.

The all-round reactor produced in Germany can realize multiple process steps with one device, realize automatic control, stable product quality, and safe and reliable production operation.

The main raw materials for producing HPMC are refined cotton, sodium hydroxide, methyl chloride, propylene oxide, etc.

4. Suggestions for developing HPMC projects

4.1 The construction of HPMC projects in China faces good development opportunities

In 2001 and 2003, the State Economic and Trade Commission issued the second batch and the third batch of national key technological transformation "double high and one excellent" project-oriented plans (i.e. high-tech industrialization, university technology and advanced and applicable technology to transform traditional industries, Optimizing key products and technology structure), clearly pointing out that special fine chemical products, especially those with a large gap in the domestic market, mainly rely on imported products such as hydroxypropyl methylcellulose, etc., to carry out key transformation, improve the grade and processing depth of existing products, Added product specifications. This policy orientation not only clarifies that HPMC is a product with a large gap in the domestic market and mainly relies on imports, but also shows the country's policy of encouraging the development of special fine chemical products.

In 2000, the China Fiber Ether Industry Association proposed to vigorously develop fine chemical products such as cellulose derivatives. In the industrial structure adjustment plan, it proposed to focus on the development of non-ionic cellulose ether, especially MC/HPMC products; China Chlor-Alkali Industry Association is developing In the downstream product planning of chlorine products, the idea of developing MC/HPMC products was put forward; the Investment Research Institute of the State Planning Commission, the China Engineering Consulting Association and local governments listed MC/HPMC as a key development project.

According to the experience of developing cellulose products abroad, the country's demand for products such as HPMC is increasing with the development of the economy. China is one of the countries with the fastest economic development in the world today. Therefore, the application prospect of HPMC in our country is very broad, and it is a favorable opportunity to develop this project at present.

4.2 my country's HPMC products have huge market potential

At present, the Chinese cellulose ether market is still dominated by ionic products (CMC), accounting for more than 95% of the total consumption, and non-ionic cellulose ethers (MC/HPMC/HEC, etc.) only account for 5% of the total consumption. In developed countries in Europe and the United States, the consumption of these two types of products each accounts for 50%. Due to the good salt resistance, heat resistance and appropriate surface activity of non-ionic cellulose ether, it is very suitable for modern advocating trends and is developing very rapidly. CMC still has a large market because of its ease of manufacture and low price, but some parts of the traditional market have been replaced by non-ionic ethers. It is expected that with the further improvement and perfection of the non-ionic ether manufacturing process, the cost will be reduced, and the consumption of non-ionic ether will show an overall upward trend. According to the estimates of China's cellulose industry and foreign manufacturers, in the next few years, the demand for MC/HPMC in my country can reach an annual growth rate of 15%, mainly based on the following reasons:

First, with the success of Beijing's bid to host the 2008 Olympic Games, the construction of Olympic venues and urban infrastructure will gradually reach the international advanced level. MC/HPMC, as an excellent additive for construction and coatings, will be widely used, and this will be used as a demonstration effect to drive the national construction and coatings industry to use MC/HPMC products in large quantities.

Second, with the popularization 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 rheological properties and water retention properties, and gradually replace the existing cement admixtures. MC/HPMC will have a broad market application prospects.

Third, the development of the domestic PVC industry will drive the demand for MC/HPMC. In 2005, my country's PVC output is expected to reach 4 million tons, and the required amount of HPMC is 1200t~1400t.

Fourth, in the fields of medicine and food, with the improvement of people's health and environmental awareness, non-ionic cellulose products such as MC/HPMC, which are harmless to physiology and do not pollute the environment, will gradually replace cmc and develop rapidly.

According to the above analysis, by 2006, my country's MC/HPMC market demand is expected to be 4000t~5000t. For this reason, major foreign manufacturers all regard China as the largest potential market, expand production capacity one after another, and occupy the Chinese market.

4.3 The construction of HPMC project has good economic benefits

According to preliminary estimates, according to the current market needs in China, foreign production technology will be introduced to build a HPMC plant with a world production level and an annual output of 6,000 tons. The total investment of the project is about 400 million yuan (including working capital). The price is calculated at 65,000 yuan/t, the average annual sales revenue is 390 million yuan, the average annual total profit is 150 million yuan, and the average annual income tax is 46.77 million yuan. According to the economic benefit evaluation, the project investment profit rate is as high as 36%, the investment profit tax rate is 46%, and the financial internal rate of return of the project is 30%. The economic benefits are very significant. After the project is completed and put into operation, it only takes 5 years to recover all the investment.

It can be seen that under the current favorable opportunity, vigorously developing HPMC projects not only conforms to the industrial development policies of the country and the industry, meets the needs of the domestic market, but also shortens the gap between my country's cellulose industry and foreign advanced countries, and promotes the development of national cellulose industry. Economic development creates huge economic benefits for enterprises.