Downstream applications and prospects of cracked C5

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01 Isoprene. The main uses of isoprene are in the rubber and fine chemical industries. In rubber applications, isoprene serves as an important monomer for synthetic rubbers, and it is primarily used in the production of synthetic isoprene rubber, styrene-isoprene-styrene (SIS) block copolymers, and butyl rubber. The rubber industry’s consumption of isoprene accounts for 77.4% of the annual production of isoprene. The application of isoprene in the fine chemicals industry is mainly reflected in two areas: one is the final synthesis of fragrances such as methyl heptenone, vitamin E, and linalool to produce linalyl acetate and other fragrance compounds ； The second is pinacol ester, an intermediate for synthesizing the highly effective and low-toxicity pyrethroid insecticides via isopentenol. According to the latest research, the application prospects of isoprene are such that isoprene and polybutadiene can be used to synthesize a random copolymer: butadiene/isoprene rubber ； This random copolymer possesses special properties that differ from those of homopolymers (isoprene rubber and butadiene rubber). Such rubber not only exhibits excellent fatigue resistance, cold resistance, and tear resistance, but also good dynamic mechanical properties, wear resistance, and anti-slip characteristics. Industrial production has not yet been achieved, but it holds great potential for application. 02 Mesitylene. The main uses of mesitylene are in the production of C5 petroleum resins and curing agents such as methyl hydrogenated phthalic anhydride (including methyl**phthalic anhydride and methyl hexahydrophthalic anhydride) ； In addition, the following can also be produced: isoprene concentrate resins, specific isoprene concentrate resins modified with high amounts of monoolefins, aromatic-modified isoprene concentrate resins, terpene-modified isoprene resins, aromatic and terpene-modified isoprene resins, and so on ； Pentane-based petroleum resins feature a low acid value, good miscibility, water resistance, ethanol resistance, and chemical resistance. They also have the ability to adjust viscosity and exhibit good thermal stability, which makes them widely used as thickeners in rubber and adhesive industries, as well as in coatings, road marker paints, inks, and the papermaking industry. Isopentadiene can also be used to produce methyl hydrogenated phthalic anhydride; methyl hydrogenated phthalic anhydride, as well as methyl hexahydrophthalic anhydride, are liquid organic anhydride curing agents for epoxy resins with excellent properties ； Hydrogenated anhydride curing agents, when used in combination with low-viscosity epoxy resins, can produce cured products that have low viscosity, good impregnation properties, a long service life, and excellent overall mechanical and electrical properties; they are thus the preferred raw materials for industries such as electronics, electrical machinery, and transformer casting applications ； Methyl hexahydrophthalic anhydride is particularly suitable for use in outdoor applications, such as in the curing of epoxy resins that offer good resistance to ultraviolet rays and moisture, for use in LEDs, special-purpose capacitors, ignition coils, sports equipment, and other similar applications. The application prospects of isopentadiene: Domestic companies produce C5 petroleum resins, which are usually mixed C5 petroleum resins obtained from the C5 fractions remaining after most of the cyclopentadiene has been removed. The quality of these resins differs significantly from that of isopentadiene-based petroleum resins. With the continuous development and upgrading of China’s automotive industry, there will be an increasing demand for high-quality C5 petroleum resins as well as for high-performance curing agents suitable for outdoor use. This will also lead to a higher demand for isopentadiene. Given that current domestic production cannot meet this demand, it is inevitable that imports will increase further. 03 Cyclopentadiene/Dicyclopentadiene: The main uses of cyclopentadiene/dicyclopentadiene are determined by the reactivity of cyclopentadiene itself as well as the characteristics of its production process. Industrially, cyclopentadiene is first dimerized to form dicyclopentadiene, and then through depolymerization or further dimerization, cyclopentadiene or dicyclopentadiene of various purities can be obtained. Based on their purity, dicyclopentadiene can be classified into polymer-grade (mass fraction ≥99%), EPDM-grade (95% ≤ mass fraction ≤99%), polyester-grade (80% ≤ mass fraction ≤85%), and low-purity grade (68% ≤ mass fraction ≤80%). Unsaturated resins are widely used thermosetting resins that are generally produced through the polycondensation reaction of diacids and diols. They are linear polymers containing ester bonds and unsaturated double bonds. Depending on their functional purposes, they can be used as matrix materials; when reinforced with glass fibers, they form composite materials that find application in fields such as wind energy, rail transport, green building, lightweight engineering, and medicine ； On the other hand, it can be mixed with inorganic fillers to create non-reinforced materials for use in areas such as artificial stones, coatings, and cast artworks. The application of dicyclopentadiene in unsaturated resins is mainly to partially replace phthalic anhydride-modified unsaturated polyester resins. Unsaturated polyester resins modified with DPCD use 10% less styrene than conventional unsaturated polyester resins, which not only reduces production costs but also improves the heat resistance and corrosion resistance of the resins; in particular, there is a significant increase in air-drying properties and flexural strength ； Compared with conventional petroleum resins, dicyclopentadiene (DCPD) hydrogenated resins have their unsaturated bonds eliminated after hydrogenation, resulting in increased chemical stability while retaining their cyclic structure. They can easily form molecular entanglements with the rubber phase in the matrix polymer, and exhibit relatively suitable adhesion to both polar and non-polar materials ； It is particularly suitable for the field of disposable sanitary materials, such as food packaging, disposable diapers, pressure-sensitive adhesives, and women’s sanitary pads. EPDM is one of the three major types of synthetic rubber in the world, and it is widely used in various rubber products such as wires and cables, automotive parts, and waterproof membranes. Future prospects for cyclopentadiene/dicyclopentadiene: In 2018, China’s capacity to produce dicyclopentadiene through the pyrolysis of C5 fractions was around 445,000 tons, with actual production amounting to about 268,000 tons ； Bicyclic unsaturated resins consume approximately 171,000 tons of dicyclopentadiene, accounting for about 64% of the total ； DPCD hydrogenated petroleum resin consumes approximately 84,000 tons of dicyclopentadiene, accounting for about 31% of the total ； The ethylidene norbornene (ENB) industry consumes approximately 7,700 tons of dicyclopentadiene, accounting for about 3% of the total consumption ； In addition, about 7,500 tons of dicyclopentadiene were produced from the export of pyrolyzed C5, accounting for approximately 3%. Currently, the domestic demand for DCPD-hydrogenated petroleum resins amounts to 400,000 tons per year. Before 2015, no domestic manufacturers were producing such resins; by 2018, the production capacity had reached 100,000 tons per year, with an average annual growth rate of around 3%. Driven by this annual demand of approximately 400,000 tons in China, it is expected that the production capacity of DCPD-hydrogenated petroleum resins will increase at a rate of 5% over the next three years, thereby further boosting the demand for dicyclopentadiene (DPCD).