Breaking through the foreign technological restrictions in production processes, the EPDM production facility of Blue Ocean New Materials utilizes CNPC’s own proprietary technology
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On April 26, a public notice was issued regarding the acceptance of the environmental impact assessment report for Lanhai New Materials (Tongzhou Bay) Co., Ltd.’s high-end polyolefin new materials project (re-submitted for approval). According to the information in this notice, the environmental impact assessment for the aforementioned project had already received approval from the Nantong Data Bureau on August 30, 2024 (under reference number Tong Data Approval No. 40). The original project utilized the ethylene resources from coastal refining and chemical projects within the China National Petroleum Corporation’s system, and relied primarily on China National Petroleum’s own technologies to produce new material products such as POE, FDPE (solution-process octene copolymer), EPDM, and 1-heptene/1-octene. These products are intended to replace imported high-end materials such as POE, POP, and EPDM. The project involves the construction of 1 set of a 100,000 t/a POE production facility, 1 set of a 100,000 t/a 1-ene/1-octene production facility, 1 set of a 200,000 t/a FDPE production facility (using the solution process for octene copolymerization), 2 sets of 250,000 t/a EPDM production facilities, 2 sets of 1,000 Nm³/h hydrogen production facilities via electrolysis of water, along with the necessary utility systems and auxiliary facilities. The original project is currently carrying out pile foundation work. It is reported that during the construction of the original project, while keeping the overall process flow unchanged, Blue Ocean New Materials (Tongzhou Bay) Co., Ltd. made adjustments to the process for the EPDM rubber production unit; the production process was changed from Italian IPT technology to a technology developed by CNPC itself. The reason for this change is mainly the foreign restrictions on the production processes for high-end EPDM. The EPDM products manufactured using available technologies fall far short in terms of performance compared to those produced using CNPC’s own technologies. With the adjustments, the ML(1+4) at 125 degrees Celsius for CNPC’s proprietary products can reach a maximum of 90, while the corresponding value for the original IPT products is 80 at the same temperature ； CNPC’s proprietary technology employs a methanol washing inactivation process; the vanadium content in the product
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1. Structural characteristics of EPDM: EPDM is an amorphous, non-crystalline rubber in which the vinyl and propylene monomer units along its molecular backbone are arranged in a random manner, losing the regularity of the structure found in polyethylene or polypropylene, thus forming an elastic rubber. When the ethylene content is in the range of 20–40 mol%, the glass transition temperature (Tg) of EPDM is approximately –60°C. It exhibits good low-temperature properties such as low-temperature compressive deformation and low-temperature elasticity, but its heat resistance is poor. To prevent the formation of propylene chains and ensure a random distribution within the EPDM molecules, it is generally required that the ethylene content be greater than 50 mol%. However, when the ethylene content exceeds 70 mol%, ethylene chains crystallize, the glass transition temperature (Tg) rises, the cold resistance decreases, and the processability worsens. It is generally believed that an ethylene content of around 60 mol% yields good processability as well as favorable physical and mechanical properties for the vulcanized rubber. The molecular chains of ethylene-propylene rubber contain no polar groups, the chain segments are relatively flexible, and the intermolecular forces are weak. The third monomer used in ethylene propylene diene monomer rubber is a non-conjugated diene, and its type and amount have a direct impact on both the vulcanization rate and the physical and mechanical properties of the vulcanized rubber. The level of the third monomer content is expressed by the iodine value; a higher content corresponds to a higher iodine value, which leads to faster vulcanization. This improves the physical and mechanical properties of the vulcanized rubber, such as stress at fixed strain, heat generation, and compression set. However, the scorch time is shorter and the heat resistance decreases. The iodine value of ethylene-propylene rubber ranges from 6 to 30 g of iodine per 100 g of rubber, with most values being around 15 g of iodine per 100 g of rubber. Therefore, the choice should be made based on the performance requirements of the product when using it.
2. Properties of EPDM Rubber Due to its highly saturated structure, the arrangement of atoms and groups along the molecular chains of EPDM rubber is similar to that of natural rubber. The relatively flexible molecular chains endow EPDM with many excellent properties. (1) It has excellent ozone resistance. It far exceeds butyl rubber and neoprene. In a medium containing 100 PPm of ozone, EPDM did not crack after 2430 hours. It is generally believed that butyl rubber, which is considered to have good resistance to ozone aging, develops significant cracks after only 534 hours ； Neoprene, on the other hand, has only 46 hours. At a 30% ozone concentration, neoprene developed cracks after only 7 minutes, whereas EPDM showed no changes even after 1 hour. Adding a small amount of EPDM to butyl rubber can significantly improve its ozone resistance. The ozone resistance can be significantly improved when ethylene propylene diene monomer rubber is used in combination with natural rubber (35/65) or styrene-butadiene rubber (30/70). (2) It has excellent weather resistance and color stability, preventing the products from cracking and ensuring that their color remains unchanged over time. SBR showed no cracks after being exposed to sunlight for 3 years, while SBS developed cracks after just 5 days and broke after 70 days ； Large cracks appeared in the natural rubber after 150 days. (3) It exhibits excellent heat aging resistance, surpassing butyl rubber. Ethylene-propylene rubber ages easily, but can be used for long periods in conditions of 85°C to 90°C. The short-term operating temperature can reach 150°C. (4) It has good cold tolerance. It still maintains good flexibility at -55°C. It begins to harden at -57°C and becomes brittle at -77°C. (5) High elasticity and low compressive deformation. It has good impact elasticity, with a rebound rate of 50%–60%, second only to styrene-butadiene rubber and natural rubber. Moreover, it maintains good elasticity at low temperatures. (6) It has excellent electrical insulation properties, surpassing those of butyl rubber. In particular, its corona resistance is very outstanding. The corona resistance of butyl rubber does not exceed 2 hours, whereas that of EPDM can last for more than two months. The dielectric constant of EPDM is 2.27 ； The dielectric loss tangent is below 0.0023. The volume resistivity is above 1016~1017 ohm·cm ； Under alternating voltage, the breakdown strength is 32–35 kV/mm, and its electrical insulation properties remain very stable even after being immersed in water. When used for insulating high-voltage cables, ethylene-propylene rubber has the outstanding advantage of not developing treeing. (7) Good resistance to chemical corrosion. It exhibits particularly good stability toward inorganic acids and bases as well as polar solvents. (8) It has a low specific gravity (0.87), making it the variety with the lowest specific gravity among synthetic rubbers. The main drawback of EPDM is its slow vulcanization speed, as well as poor co-vulcanization properties when used in combination with other rubbers. It is not flame-resistant, has relatively poor oil resistance, and exhibits weak self-adhesion as well as inter-adhesion (since the molecules contain neither reactive groups nor polar groups, the adhesive strength is low); it is difficult to bond, which poses challenges to the manufacturing process.
II. Applications of EPDM in Cables EPDM possesses excellent properties such as heat resistance, ozone resistance, aging resistance, chemical resistance (except for non-polar solvents), electrical insulation properties, impact elasticity, and performance at low temperatures (a wide operating range of –57 to 150°C). It also features low density and high fillability (allowing for the incorporation of large amounts of plasticizers and fillers), as well as resistance to hot water and steam. Additionally, it is easy to blend and modify with polyolefin plastics, which enables its widespread use in industries such as automotive sealing components, wires and cables, heat-resistant hoses and tapes, fireproofing materials, oil additives, and plastic modification. Its development has been rapid in recent years, and its production capacity and consumption rank fourth among the seven major synthetic rubbers, behind styrene-butadiene rubber, cis-butadiene rubber, and isoprene rubber. EPDM is primarily used as an insulating layer in wires and cables, especially in those that require high temperature resistance and voltage tolerance. Its excellent insulating properties, water resistance, and aging resistance make it an ideal material for insulating wires and cables; it is particularly suitable for medium and high-voltage cables. Examples of its formulations are shown in Table 1.
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