1. Overview
Polyethylene is the most important downstream product of ethylene. Polyethylene (PE) accounts for 70% of world polyolefin consumption, 44% of total thermoplastic consumption and 52% of world ethylene production. Polyethylene is basically divided into three categories, namely high-pressure low-density polyethylene (LDPE), high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). Film is its main processing product, followed by sheets and coatings, hollow containers such as bottles, cans and barrels, and other various injection and blow molding products, insulation and sheathing of pipes, wires and cables. Mainly used in packaging, agriculture and transportation sectors. Compared with other countries in the world, China uses more low-density polyethylene and LLDPE in agricultural films. China is the country with the largest output of agricultural film in the world, which is determined by the characteristics of China as a big agricultural country.
2. Production capacity and output
By the end of 1998, 26 sets of polyethylene plants have been built in China, with a total production capacity of 25 10000 tons.
3. Brief description of production method
HP-LDPE is produced by two high-pressure liquid phase methods, namely kettle method and tube method. The polymer produced by kettle process has narrow molecular weight distribution and many branches; However, the products produced by tubular process have wider molecular weight distribution and fewer branched chains.
Except for the polymerization reactor, the process steps of the kettle method and the tubular method are similar. The maximum single-line reactor capacity of the tubular process is 200,000 tons/year (for example, Exxon's factory in Belgium and DSM's factory in the Netherlands), and the maximum single-line reactor capacity of the kettle process is 6,543,800 tons/year (possibly reaching 200,000 tons/year), which is a device built by QGPC Company in Qatar using Orchem(CdF) technology.
Both kettle process and tubular process have their own advantages. Generally speaking, large equipment tends to use tubular process. Kettle method is the first choice to produce special brand equipment. The LDPE plant 1998 1 1 put into operation in June in Qilu Petrochemical Company adopted the high-pressure tubular process of DSM company in the Netherlands, which is the one with the largest product brand and single-line capacity among similar plants in China at present. Yanshan Petrochemical Company will also build a 200,000-ton/year low-density polyethylene plant with Exxon technology, and the contract has been signed.
Linear polyethylene (HDPE/LLDPE) is produced by low pressure liquid phase method and gas phase method. At present, the two liquid-phase methods in the world, namely slurry method and solution method, still dominate the total output. The important solution processes are medium pressure process of DuPont (now Novacor), low pressure cooling process of Dow and DSM process. These devices can alternately produce HDPE and LLDPE (called convertible devices in industry and full density polyethylene in China). The two most widely used slurry methods are loop reactor method using light diluent (Phillips and Solvay) and stirred tank method using heavy diluent (Hoechst, Nissan and Mitsui). The main product of slurry process is high density polyethylene, but some MDPE can also be produced as a by-product.
UCC and BP are the main holders of gas phase technology in polyethylene production line. Gas phase process equipment is generally convertible equipment, which can alternately produce LLDPE and HDPE, but it is limited by some patent agreements. Equipment licensed to produce two products must usually give priority to producing one product for a long time. Even for convertible devices, frequent interchange between HDPE and LLDPE products is uneconomical, and it is not actually done.
From 65438 to 0997, the world's peaceful polyethylene production capacity was about 50.7 million tons/year, and the production capacity of North America and Western Europe accounted for more than half of the world's total production capacity. Asian countries (including Japan) account for 1/4 of the world's total capacity. As far as technology is concerned, high-pressure polyethylene accounts for about 38%, and pipeline method and kettle method account for almost half each. Slurry method accounts for about half of the 62% share of bus polyethylene. In China, the proportion of kettle method, tube method, slurry method, gas phase method and solution method in the total polyethylene production capacity from 65438 to 0998 is 9%, 18%, 26%, 43% and 3.2% respectively. Compared with the average productivity ratios of various process methods in the world (19%, 19%, 30%, 24%, 8), the gas phase method is higher, the tubular method is similar, and other methods are lower.
In recent years, China's polyethylene industry has also made gratifying achievements in catalyst development, localization of process equipment and new product development.
Remarkable progress has been made in the localization of catalysts. Yanshan Petrochemical Company has built a 30-ton/year domestic HDPE catalyst production plant, and the catalyst produced has been used in large industrial plants. At present, the coverage rate of domestic catalyst in slurry HDPE plant has exceeded 80%.
The research of metallocene catalysts in China has made gratifying progress. By the middle of 1996, * * had developed five model tests or patented technologies and obtained five China patent application numbers. Metallocene -LLDPE with bimodal molecular weight distribution was prepared by Beijing Institute of Petrochemical Technology, Lanzhou Chemical Company and Shanghai Institute of Chemical Technology in a gas-phase fluidized bed model test device, and the Institute of Stone Science also synthesized products with high density, low density, ultra-low density and long chain. The metallocene catalyst APE- 1S developed by the institute successfully passed the pilot test in Liao Hua, and completed the pilot test of loop slurry continuous reactor in cooperation with Phillips Company of the United States. The results show that the catalyst has high activity and good catalytic ability for the polymerization of 1- hexene, and the polymer product has good particle size distribution and high bulk density. 1March, 1999, the catalyst passed the appraisal organized by Sinopec Group and China Petroleum and Natural Gas Group Company.
The process development has achieved fruitful results. Shanghai Institute of Pharmaceutical Industry, Design Institute of Yangzi Petrochemical Company and Yanshan Petrochemical Company have developed slurry high density polyethylene. The 65,438+400,000 tons/year HDPE plant of Yanhua Company was designed and built by our country. From 1 June 1992 1 scheme determination to1September 26, 19941completion and production, it only took 27 months and 25 days, saving 47.43 million yuan in foreign exchange compared with imported technology and equipment construction. After that, a 70,000-ton/year production line was built in Lanzhou Chemical Company.
Yangzi Petrochemical Company has completed the "Complete Technical Package of Slurry HDPE with an annual output of 200,000 tons" and passed the appraisal of sinopec group 1997. This technology can greatly reduce the project cost of newly-built polyethylene plant and effectively guide the expansion and transformation of existing plants.
The new technology of producing full density polyethylene by slurry method and horizontal gas-phase kettle jointly developed by Shanghai Pharmaceutical Industry Design Institute and Yanshan Petrochemical Company has applied for China patent and will be implemented in Yanshan industrial plant soon.
Some achievements have been made in the development of new products. The high-strength membranes, pipes and large hollow containers produced by Qilu Petrochemical Company have become the company's fist products. After the successful application of HDPE-coated pipeline special material in Shaanxi-Beijing natural gas gathering and transportation project, it recently defeated many well-known foreign companies in international bidding, realized the export to Egypt pipeline anticorrosion plant, and broke the situation that European and American companies completely controlled the synthetic resin special material in the Middle East. Yanshan Petrochemical Company trial-produced 6000M high molecular weight, wide molecular weight distribution and good ESCR performance. Beijing Research Institute of Chemical Technology has successfully developed HDPE material which can be used in automobile fuel tanks. The institute simulated the two-kettle series polymerization of ethylene in a 2-liter polymerization kettle, and prepared high molecular weight butene * * * HDPE resin with bimodal molecular weight distribution. Its performance index is equivalent to that of foreign basic resin for single-layer automobile fuel tank.
4. Demand
198 China produced 2.3 million tons of polyethylene, including 740,000 tons of HDPE, 5965438+10,000 tons of LDPE and 9765438+10,000 tons of LLDPE (including HDPE produced by full-density polyethylene plant). From 65438 to 0998, China imported 2.42 million tons of polyethylene, with an apparent consumption of 4.72 million tons. 1998 the polyethylene production capacity in China is about 4.5% of the world production capacity (55.23 million tons), and the apparent consumption is 10.8% of the world consumption (43.7 million tons). Because a considerable part of polyethylene imported from China is used for feed processing, half of the resin used for feed processing is often left at home. When calculating the demand, it is calculated that 60% of the imported resin is imported and processed, and half of the imported polyethylene stays at home, that is, 70% of the imported resin meets the domestic demand.
5. Growth rate
1983- 1998 The average annual growth rate of polyethylene consumption in China is 15.2%, which is 1.5 times the GDP growth rate (10.3%). From 1993 to 1997, the average operating rate of polyethylene plants in China is 90.5%.
6. Application allocation
The largest amount of LDPE is film and sheet, followed by extrusion coating, injection molding and wire and cable. These four applications account for 90% of LDPE applications.
Film is the largest market for low density polyethylene, with packaging and non-packaging applications accounting for 50% and 50% respectively. Extrusion coating is the second largest market of LDPE in the world, and it is a rapidly growing application field of LDPE, which is mainly conducive to the development of packaging technology and the continuous innovation of packaging style.
The application of film and sheet accounts for 75% of LLDPE consumption in the world. Injection molding and wire and cable are the second and third largest application fields of LLDPE respectively, but they only account for 7% ~ 65% of the total consumption of LLDPE. Stretched film is the fastest growing market of LLDPE in the global packaging field, which is replacing packaging tape, corrugated board, wrapping paper and shrink packaging.
Packaging accounts for 75% of HDPE resin consumption, construction accounts for 10%~ 15%, and the rest 10%~ 15% is used for other consumer goods and industrial supplies. Blow molding and injection molding are the main application fields in the United States and western Europe, accounting for about 60%~50% of the total consumption. However, in Japan and other Asian countries, the consumption of HDPE in these areas only accounts for 65,438+0/3 of the total consumption. According to the proportion of consumption, the proportion of film consumption in Asian countries is twice that of the United States and Western Europe.
Taking the American market as an example, the departments with the largest consumption of HDPE are all kinds of bottles, barrels, cans and packaging bags, followed by sheets, pipes, packaging boxes, trays, wires and cables. However, the applications with the highest annual growth rate are expected to be automobile fuel tanks, barrels and tanks, followed by linings, water supply and irrigation pipes and geotechnical films.
Film accounts for almost 60% of polyethylene consumption in China (see table), of which agricultural film accounts for 20.4%. From 65438 to 0998, China consumed more than 700,000 tons of polyethylene resin for agricultural film. China is the country with the highest output of agricultural film in the world, which is determined by the characteristics of China as a big agricultural country. Other applications of polyethylene include pipes, plates, hollow containers, monofilaments, woven products, injection molded parts, wires and cables. Domestic pipes are mainly agricultural pipes, followed by drinking water pipes and gas pipes; Hollow containers are mainly used for packaging beverages, cosmetics, edible oil and medicines. 1997 About 60,000 tons of resin is consumed for containers with a capacity of 100 liter; Monofilament and woven products are mainly used for ropes, fishing nets and colored striped cloth; Cable materials are mainly used for insulation materials, cross-linked cable materials and sheath materials; Injection molding is mainly used to produce turnover boxes, plastic trays, plastic bottle caps and other products; Others include polyethylene coatings and chlorinated polyethylene.
7. Development prospects
For many years, China's polyethylene production has been unable to meet the market demand, and the import volume accounts for about half of the apparent demand. 1983- 1997 The average apparent demand satisfaction rate of polyethylene in China is 46%, and the average satisfaction rate is 54%. If China's large and medium-sized ethylene can be reformed in 2002, it is estimated that the polyethylene production capacity will reach 3.7 million tons, and the output will be 3.3 million tons according to the operating rate of 90%. According to the historical demand change and the forecast of China's national economic development, it is predicted that the polyethylene demand in China will be 5.86 million tons in 2002, 7.9 million tons in 2005 and 1.220( 1.480) tons in 2065. It is estimated that the satisfaction rate and apparent satisfaction rate of polyethylene in China in 2002 are 56% and 47% respectively. It is equivalent to the average level of 1983- 1997. Polyethylene has considerable market potential in China, and it is a petrochemical product with great development prospects.
(2) Polypropylene
1. Overview
Polypropylene is a common resin closely related to our daily life and the most important downstream product of propylene. 50% of the world's propylene and 65% of China's propylene are used to make polypropylene. Polypropylene is the fastest growing general thermoplastic resin in the world, and its total amount is second only to polyethylene and polyvinyl chloride. 198, the world polypropylene production capacity was 29.25 million tons,197, the world polypropylene production was about 23.9 million tons, and the output value was about 2 100 billion dollars. Since 199 1, the world output has increased by about 9% every year, second only to LLDPE in general resin.
Like other general-purpose resins, the Asian financial crisis has also had a great impact on the demand for polypropylene. Even at a low forecast level, compared with other resins, polypropylene still maintains a relatively strong growth rate. The new forecast shows that from 1997 to 2002, the average annual growth rate of world polypropylene demand is 7. 1%, while the average annual growth rates of polyethylene, PVC and polystyrene are 5.2%, 5.0% and 4. 1% respectively. The reasons for the rapid growth of polypropylene demand can be simply summarized as: cheap, light weight, good processability and wide use. The development of catalysts and new processes has further promoted the expansion of application fields, such as the development of new uses such as automobiles and food packaging, and further promoted the growth of demand. In the past, the automobile industry did not use so much polypropylene, and polypropylene was rarely used in blow molding and thermoforming. Some people say: "As long as the material of a product is changed into plastic, then this product has the potential to use polypropylene".
2. Brief description of production process-gas phase method and bulk method are gradually replacing slurry method.
According to the configuration of reaction medium and reactor, the polymerization process can be roughly divided into three basic types:
(1) bulk polymerization was carried out in liquid propylene. The reactor can be a liquid kettle reactor, such as Exxon, Mitsui (now Hongwei Polymer Company), Sumitomo, etc. It can also be a loop reactor, such as Montell, Hoechst (now part of Targor), Phillips and Solvay processes.
(2) Slurry process, in which propylene is dissolved in hydrocarbon diluents such as butane, pentane, hexane, heptane or nonane, and the reactor can be a continuous stirred tank reactor, such as Amoco, Montell, Hoechst (now Tagore) and Mitsui (now magnificent polymer); Reactions in batch stirred tank reactors (such as Mitsui), loop reactors (such as Solvay) and boiling butane (this process was used by Huntsman in Woodbury, and the device belonged to Shell before 1987).
(3) Gas phase method, in which propylene is directly polymerized to produce solid polymer, and the reactors used are: fluidized bed (such as UCC and Sumitomo); Horizontal stirred bed (such as Amoco/Su Zhi) and vertical stirred bed (such as BASF, now Tagarl).
Technically, bulk polymerization is also a kind of slurry polymerization, but the word "bulk" is used in any process with propylene as diluent in industry, and the process with non-propylene as diluent is called slurry polymerization.
At present, about 55% of the factory capacity in the world is based on bulk method, 25% is based on gas phase method, and the rest is based on slurry method. Since 1990, the number of slurry production equipment in the world has been declining, giving way to bulk method and gas phase method technology. This situation is particularly evident in North America, Western Europe and Japan. This trend is expected to continue because the gas phase method and the ontology method are basically used in the global new capacity and expansion capacity.
According to the special issue of CW 1998 1 1, the capabilities of various polypropylene technologies and their proportion in the total production capacity are: Sphere line1/10,000 tons of Montell company (accounting for 37% of the global total production capacity); Uccshak process is 5 million tons (17%); 3,800,000 tons (13%) of the Tagalovolin process; Mitsui Haibo is 200 million tons (7%); Amoco 200 million tons (7%); Shell's early technology is 800,000 tons (3%); El paso1100,000 tons (3%); Sumitomo 350,000 tons (1%). The remaining 12% includes equipment manufactured by China technology. Borealis is using its Borstar technology to build a new 200,000-ton polypropylene plant.
By the end of 1998, China's continuous polypropylene production capacity was about10.8 million tons, of which the bulk process accounted for 80%, the gas phase process accounted for 1 1%, and the slurry process accounted for 9%. In addition, there are batch process units with a total capacity of about 700,000 tons, ranging from 2,000 tons to 10000 tons.
In recent two years, China has made remarkable progress in polypropylene technology. The most important achievement is to develop an efficient propylene polymerization catalyst and a complete set of polypropylene production technology. In addition, the development of new products has also made remarkable achievements.
N-type efficient propylene polymerization catalyst developed by Beijing Institute of Chemical Technology has been patented in China, the United States, Germany, Britain, France, Italy and the Netherlands. The catalyst has achieved long-term stable operation in large-scale industrial devices and produced various brands of large-tonnage qualified products. Compared with imported catalysts, the 70,000-ton/year plant can save nearly 8.3 million yuan per year. Phillips, which cooperates with the Institute, has built a 60-ton/year N catalyst production facility in Houston, USA, and its products are sold all over the world.
The DQ- 1 spherical high-efficiency catalyst successfully developed by Beijing Institute of Chemical Technology passed the pilot test, and carried out industrial tests in three stages: homopolymerization, random * * * polymerization and block * * * polymerization in an industrial plant with a capacity of 70,000 tons/year. Seven brands of qualified products were produced in batches, and the output exceeded 6,543,800 tons. The catalyst has passed the appraisal organized by petrochemical group company, and the production device has been completed and put into operation.
CS-ⅰ catalyst and CS-2 catalyst successfully developed by Institute of Chemistry, Chinese Academy of Sciences have also been used in many polypropylene industrial plants in China and exported abroad.
At present, the domestic coverage of polypropylene catalyst in China has exceeded 2/3. Organic Plant of Dalian Petrochemical Company, No.2 Chemical Plant of Yanhua Company, Lanlian Chemical General Factory and Guo Qian Refinery respectively built a set of 40,000 tons/year polypropylene plant with domestic kettle-type bulk technology, and all of them were put into operation successfully.
China has developed a polypropylene process with liquid phase loop reactor, using N-type high efficiency catalyst. The 70,000-ton/year polypropylene plants in Changling, Wuhan, Jiujiang, Fujian, Jinan, Dalian and Jingmen, and the 6,543.8+10,000-ton/year polypropylene plant in the anniversary celebration have all been successfully put into operation, and the performance indexes of the plants have reached the level of similar plants introduced in China in the 1990s.
The localization rate of polypropylene loop reactor equipment built in China reaches 80.4%, and the total investment of imported 70,000 tons/year polypropylene plant is about 90-65.438+0 billion yuan, while the total investment of the same scale plant in China is below 500 million yuan.
In terms of new product development, Yanshan Petrochemical Company has developed a special material for polypropylene washing machine barrels, which has been recognized by many washing machine manufacturers in China. Shanghai Petrochemical Company has developed a series of special materials for polypropylene casting film, washing machine and paintable automobile bumper. The polypropylene special material produced by Maoming Petrochemical Company replaced imported products and was recognized by Guangdong Midea Group Household Appliances Co., Ltd.; In cooperation with Beijing Research Institute of Chemical Technology, most of the plastics used in Li Xia automobiles are products of China Petrochemical Group, and the research and development of special materials for automobiles is continuing, so as to be applied to other vehicles.
3. Domestic demand and growth rate in recent years
1998 China's polypropylene output was 2.07 million tons, the net import was/kloc-0.52 million tons, and the apparent demand was 3.59 million tons. 1998 About 7 1% of the imported resin belongs to non-general trade imports such as import, feed processing, bonded warehouses, etc. However, all the resins imported from this channel may not be converted into products for re-export, and about half of them remain in China. It is estimated that the domestic demand for polypropylene is about 3 million tons. The average annual growth rates of output, net import, apparent demand and demand of 1983-1998 and 15 are 22.2%, 2 1.7%, 22.2% and 2 1.3% respectively. During the period of 1993-1998, the domestic demand growth rate of polypropylene in China was about 2. 1 times of the GDP growth rate (10.3%) in the same period, which exceeded the average growth rate of synthetic resin (16.7% and1..
4. Domestic price
On June 5438- 10, 2000, the price of ordinary grade polypropylene (tensile grade) in Yuyao, China was about 6 100 yuan/ton. Historically, the price of polypropylene, like other general resins, fluctuated greatly. During the period of 1995, affected by various international emergencies, the supply of polypropylene was tight, the price rose, and artificial bargain-hunting intensified. 1995 in the second and third quarters, the brand price of generic drugs rose to more than 1 10,000 yuan/ton. 1997 After the fourth quarter, prices fell sharply due to the Asian financial crisis. In the first half of 1999, this downward trend has not been reversed, and the brand price of generic drugs has dropped to about 4,800 yuan. Although there has been a slow recovery since then, the current price level is at most equivalent to the level of 1997 in the fourth quarter, far from reaching the historical high price. 5. Application
The consumption pattern of polypropylene is influenced by the industrial structure in different regions and varies from region to region. Generally speaking, in industrialized countries, especially countries and regions with developed automobile industry, injection molding applications account for the main share of consumption. In the early stage of industrialization in agricultural countries, fibers accounted for a large proportion, mainly used as woven bags, tarpaulins and so on. In industrialized countries, durable consumer goods, such as automobiles, household appliances and carpets, account for about 50% of the final use of polypropylene. Consumption in these markets is greatly influenced by the periodicity of economic development and consumption level. Polypropylene also competes with other thermoplastics according to the specific requirements of various applications. These plastics are: (1) ABS; Used in vehicles and household appliances; (2) Nylon used for traffic, carpet veils and nonwovens; (3) Polyethylene used for household goods, consumer goods, hard packaging, films and wires and cables; (4) Polystyrene for hard packaging and household appliances; (5) pets; Veil for movies, hard package and carpets; (6) PVC used in films and medical supplies. Polypropylene has a wide range of applications and many fields, and almost no application can exceed 25% of the total market share of polypropylene.
Among the polypropylene produced in China, flat yarns for woven bags account for more than 50% of the polypropylene produced in China. Judging from the supply and demand structure of various polypropylene products in China from 65438 to 0997, flat wire materials basically meet the demand (the satisfaction rate of domestic products is 87%), but the satisfaction rate of domestic film materials is only 30%; The satisfaction rate of domestic injection molding is less than 10%. Most injection plastics produced in China are homopolymers (the ratio of polymer to homopolymer in the United States is about 2: 1), which can only be used in products with low performance requirements such as daily necessities. From the proportion of special materials of domestic materials and imported materials listed in Table 5, the proportion of special materials of imported materials is obviously higher than that of domestic materials. Judging from the performance of imported brands, a considerable number of imported polypropylene brands are thin-walled injection molding brands with high MI and fibers and non-woven fabrics.
Compared with the application in developed countries, China's polypropylene for injection molding (especially for automobiles) and polypropylene for fiber (especially for non-woven fabrics) still has great potential market space.
6. Development prospects
According to the historical law of polypropylene demand growth in China and the development trend of national economy in China, we predict that the growth rate of polypropylene demand will still be higher than that of national economy in the future. It is estimated that the apparent demand for polypropylene in China is 5.25 million tons in 2002, 7.3 million tons in 2005 and165438+800,000 tons in 2006 (see table). If China's large and medium-sized ethylene transformation can be completed by 2002, it is estimated that China's polypropylene production capacity will reach 3.48 million tons by then, and the output will be 310.3 million tons based on the operating rate of 90%. By then, the apparent satisfaction rate will reach 60%, and 40% of polypropylene still needs to be imported.