Current Development Status of C-Aromatic Petroleum Resins

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The C-aromatics fraction produced as a by-product of the ethylene plant (referred to as cracked C) is the residual fraction remaining after the extraction of the C fraction and the C-C fraction from cracked naphtha, with the latter being used for the production of BTX via hydrogenation; this fraction accounts for approximately 10% to 20% of the total ethylene output. With the rapid development of China’s petrochemical industry, and in particular the increasing production capacity of ethylene year by year, the amount of cracking C is also on the rise. How to utilize this resource to develop downstream products is attracting growing attention. Currently, cracked C is mainly used to produce aromatic petroleum resins; the resins synthesized using appropriate processes can be widely applied in the coatings, paint, rubber, and light industry sectors. The remaining mixed aromatics can serve as solvents for producing coatings, thereby enabling a total utilization rate of C of 90%. I. Ethylene and C resources 1. Cracking of C resources The main raw materials for ethylene cracking include ethane, propane, butane, naphtha, diesel, etc.; aromatic hydrocarbons are produced as by-products in these processes, although their yield and composition vary depending on the raw materials used for cracking. In our country, the enterprises that currently produce ethylene include Yangzi Petrochemical, Shanghai Petrochemical, Tianjin Petrochemical, Liaoyang Petrochemical, Yanshan Petrochemical, Qilu Petrochemical, Xin* Dushanzi Petrochemical, Guangzhou Petrochemical, Daqing Petrochemical, Jilin Petrochemical, Lanzhou Petrochemical, Zhongyuan Petrochemical, and others ； In 2006, the ethylene production was 9.68 million tons; based on a yield of 11%, 1.06 million tons of C1 could be produced. 2. General characteristics of the cracking C fraction The composition of the cracking C fraction is extremely complex, comprising around 150 different components that are quite dispersed. From a synthetic perspective, they can be divided into two categories: active components that can undergo polymerization, such as styrene and vinyl toluenes, as well as dicyclopentadiene ； Another category of inactive components includes alkylbenzenes and polycyclic aromatics, which are used as polymerization solvents during the polymerization process ； Based on the chemical structure and reactivity of the active components in the pyrolysis fractions, the first category includes styrene and its derivatives, such as styrene and vinyl toluene ； The second category of indenes and their derivatives such as indene, methylindene, etc ； The third category consists of dicyclopentadiene and the cyclopentadiene produced upon its decomposition. 3. c-Aromatic petroleum resins: Due to the highly complex composition resulting from cracking, only components such as styrene, dicyclopentadiene, vinyl toluene, and indene can be separated ； A mature and suitable method of utilization is not to separate them, but to directly use their mixed components to produce aromatic petroleum resins. Aromatic petroleum resin is a functional resin in the form of a resinous substance, ranging in color from light yellow to dark brown. Its relative molecular mass is between 200 and 5000, with a softening point typically between 80 and 130°C, a density of 1.06 g/cm³, and a ignition point above 260°C. Due to the absence of polar groups in its structure, it exhibits good water resistance, acid and alkali resistance, weather resistance, and resistance to photo-aging. It has good solubility in organic solvents, especially petroleum-based solvents, and mixes well with other resins. It also possesses properties such as brittleness, viscosity-increasing effect, adhesiveness, and plasticity. II. Current status of foreign C-aromatic petroleum resins: The United States began research on C9 petroleum resins as early as 1930, and in the 1940s, the Picco company in the U.S. achieved industrial production of c-alkyl aromatic petroleum resins ； Japan was the first to build a plant for producing C-aromatic petroleum resins with a capacity of 4,000 tons per year in 1961. With the development of the petroleum industry, petroleum resins have seen rapid growth; their production technologies have become increasingly sophisticated, and production on a considerable scale is now possible. In recent years, with continuous improvements in production technology and increased market competition, new varieties have emerged and their areas of application have expanded; they have developed into functional synthetic resins available in a wide variety of types, grades, and for multiple uses. At present, the production of petroleum resins worldwide is largely monopolized by large companies in the United States, Western Europe, Japan, and other regions. The United States and Japan are the world’s largest consumers of petroleum resins, accounting for about two-thirds of the global total consumption. The main suppliers of petroleum resin raw materials are the American companies Lyondell, Exxon, Neville, Lawter, Hercules, Sunbelt, Resinall, Sartomer, and Dow ； In Western Europe: VFT, DSM, Hercules, CDF ； Mitsui Chemicals of Japan, Nippon Petrochemical, Tobon Chemical of Japan, Tosoh Corporation of Japan, etc. In the United States, the consumption proportions of C petroleum resin are 45% for rubber additives, 15% for adhesives and sealants, 20% for coatings, and 20% for other applications ； In Japan, the consumption proportions of C petroleum resin are: 35% for inks, 15% for adhesives and sealants, 10% for rubber additives, 10% for hot-melt adhesives, and 30% for other applications. III. Current status of domestic c-aromatic petroleum resins. C-petroleum resins are essential additives in the coating industry, ink industry, papermaking industry, and plastics industry. As a very promising composite material, they are widely used in rubber tires. Compared with other similar substances, c-petrol resin has the following advantages: ① Large output of raw materials at low cost; ② Complex product composition, allowing multiple uses of the same material and offering a wide range of properties; ③ Non-toxic, causing minimal environmental pollution, with only small amounts of wastewater that are easy to treat being discharged; ④ High demand for this product. Research on petroleum resins in our country started relatively late. The Qianjin Chemical Plant of Yanshan Petrochemical Company, Anshan Chemical Research Institute, Hangzhou Chemical Research Institute, Shanghai Coating Research Institute, Daqing Petroleum and Chemical Institute, and others have conducted research, and several thousand-ton-scale production facilities have been built. Representative manufacturers and product specifications include Anshan Yihua Chemical Co., Ltd., Daqing Huake Group Co., Ltd., etc ； At present, the production volume of C petroleum resin in our country is low and its quality is poor, which limits its applications; as a result, China’s C resources are not fully utilized. Currently, the price of c-petrol resin has risen to 8,000 yuan per ton, showing an upward trend year by year. Based on the main domestic manufacturers and their production capacities, two companies in the Northeast produce 35,000 tons per year, two companies in Hebei produce 27,000 tons per year, two companies in Henan also produce 27,000 tons per year, and two companies in Shandong produce 31,000 tons per year. There is one company in Tianjin and one in Nanjing, with production volumes of 15,000 tons per year and 8,000 tons per year respectively. In total, the annual production volume is 143,000 tons. With the development of China’s economy, the demand for C petroleum resin will continue to increase. Similar to other countries, in China this type of petroleum resin is primarily used in industries such as coatings, adhesives, rubber additives, and inks. In our country, there are few grades of C petroleum resin; they have a dark color, no unified quality standards, and their use is not yet widespread. In the paint industry, for example, the current production volume of industrial coatings is 4.1772 million tons, requiring 1.25 million tons of resins; if petroleum resin is used in an amount of 10%, then 125,000 tons or more are needed. However, there are few light-colored resin products available in the domestic market, which limits their use in high-end paints. Due to its dark color and poor solubility, it is used only by some small paint manufacturers; larger paint factories use it solely for the production of low-quality paints. It is also employed in tire additives, low-grade inks, and as adhesives in rubber shoe manufacturing. If further measures such as the introduction of polar groups, copolymerization, and hydrorefining are taken to improve product quality, c-petrol resin will have an even larger market. In the rubber industry, petroleum resin is primarily used as a rubber softener (or additive), replacing guayule resin in equal amounts. The raw material for gum rosin comes from the coking industry and cannot meet the needs of the rubber industry. C-petroleum resin can be used as a quality improver and functional additive for styrene-butadiene rubber; styrene-butadiene rubber lacks viscosity and is hard, while C-petroleum resin helps to separate the molecules of this rubber, thereby enhancing its bonding properties. In tape products, adhesives composed of rubber, thickeners, softeners, and petroleum resins along with solvents can be used. When c-resin is added to natural rubber and styrene-butadiene rubber, the vulcanization rate of the rubber is slower compared to when guma resin is used. The rubber compound obtained after processing is smooth and even, with good dispersibility. When c-resin replaces guma resin in bicycle tread compounds, the resulting materials exhibit excellent processability, are smooth and even, are easy to disperse, and also have improved strength. By using C resin in rubber products, it is possible to increase the amount of recycled rubber and filler used in the rubber formula while reducing the amount of natural rubber used. As a result, costs can be significantly reduced without compromising the quality of the rubber products. For example, the use of C resin in rubber shoes can save 700 yuan per 10,000 pairs of shoes. Furthermore, since resin C provides better high-temperature softening properties and dispersion for rubber, its use allows for the elimination of one rubber mixing step, thereby shortening the production cycle and improving efficiency. Taking advantage of its low acid value, high softening point, good water resistance and mildew resistance, as well as rapid solvent release, c-resin can be used as a glazing agent for cartons. Actual production has shown that the finishing agent for c-resin cartons is easy to apply, dries quickly, and offers excellent performance. It not only improves the quality of packaging and enhances the production efficiency of carton finishing but also reduces the costs associated with this process. Therefore, the widespread application of C-resin polishers in the packaging industry holds great promise. In recent years, China’s paint production has been increasing year by year. In 2003, it reached 2.415 million tons, of which 1.642 million tons were industrial paints. In 2004, the production amount rose to 2.982 million tons, with 1.848 million tons being industrial paints. In 2005, it reached 4.0409 million tons, of which 2.74 million tons were industrial paints. In 2006, it reached 5.0784 million tons, with 3.5238 million tons being industrial paints. By 2007, it reached 5.9728 million tons, of which 4.1772 million tons were industrial paints ； It is estimated that by 2010, the demand for C in our country will reach around 300,000 tons, and as its applications continue to expand, resins are evolving toward having lighter colors and greater thermal stability. Therefore, it is even more important to accelerate research on petroleum resins in our country, particularly the industrialization of hydrogenated petroleum resins.