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In the third quarter of 2026, the domestic high-end segment of basic organosilicon downstream sectors achieved a landmark industrial breakthrough: a continuous production unit for low-volatility high-hydroxyl linear hydroxyl silicone oil with a designed annual capacity of 41,000 tons officially completed a 168-hour full-load steady-state operation assessment. For the series of products produced by this unit, the mass fraction of hydroxyl groups can be precisely customized in the range of 0.5% to 12%. Among them, for the high-activity grades with a hydroxyl mass fraction above 8%, the kinematic viscosity deviation at 25°C is controlled within ±1.5%, the total volatile content after constant-temperature baking at 200°C for 3 hours is stably below 0.06%, and the end-capping rate of hydroxyl groups on the molecular chain reaches 99.2%. All core performance indicators have reached the international leading level. This achievement marks that China has completely ended the history of long-term dependence on imports for high-purity low-volatility linear hydroxyl silicone oil, providing fully independent and controllable core basic raw material support for key fields such as high-end addition-cured silicone rubber, organic silicone potting adhesives for electronic components, photovoltaic module encapsulants, and fabric waterproof and oil-repellent finishing agents.
Hydroxyl silicone oil is the most core functional intermediate category in the methyl silicone oil sequence. By introducing active hydroxyl groups at both ends of the polysiloxane molecular chain, the material not only retains the excellent weather resistance, electrical insulation and low surface tension characteristics of methyl silicone oil, but also has active sites that can undergo cross-linking reactions with functional groups such as siloxane and isocyanate. It is the key hub material connecting basic organosilicon monomers and downstream high-end organosilicon products. Different from the widely circulated ordinary hydrolyzed hydroxyl silicone oil in the market, the molecular chain of high-purity low-volatility linear hydroxyl silicone oil presents a regular straight-chain structure without side-chain active group interference. The hydroxyl end-capping rate exceeds 99%, and no small-molecule ring body precipitates during long-term use at 200°C. It is the core raw material for preparing high-transparency, high-aging-resistance, low-modulus high-end organosilicon products. For nearly 28 years, the domestic industry has long adopted the traditional cyclic siloxane intermittent ring-opening hydrolysis process to produce hydroxyl silicone oil, and has been unable to break through three common industry technical bottlenecks for a long time. First, a large number of D3~D10 small-molecule cyclic siloxanes are inevitably generated during the ring-opening polymerization process, which are extremely difficult to remove in subsequent steps. The total volatile content of products has long been higher than 1.5%, and downstream products are prone to small-molecule migration and performance degradation during high-temperature service. Second, the distribution of hydroxyl groups on the molecular chain is highly random, and the presence of a large amount of side hydroxyl groups will cause local gelation in the downstream cross-linking reaction, resulting in a significant drop in the mechanical properties and transparency of the products. Third, the hydroxyl content deviation of products from different batches has long been higher than 6%, which completely cannot meet the application scenarios that have extremely high requirements for cross-linking density consistency, such as electronic packaging and photovoltaic packaging. Previously, more than 93% of the market share of low-volatility high-hydroxyl linear hydroxyl silicone oil used in domestic high-end electronics and photovoltaic fields was monopolized by leading overseas enterprises. For special specification products involving semiconductor packaging and aerospace-grade silicone rubber, the procurement price is 10 to 16 times that of domestic ordinary hydroxyl silicone oil, and the delivery cycle of some controlled grades can be as long as 20 months, which has seriously restricted the technological iteration speed of the domestic high-end organosilicon product industry.
The new continuous production process that has achieved full production this time has corely overcome three technical problems that have plagued the global organosilicon industry for nearly half a century. First, a controllable gradient ring-opening polymerization system with active water was pioneered. The R&D team abandoned the traditional idea of directly mixing cyclic siloxane and water for ring-opening, and independently developed a new supported anionic catalyst. In 17 series-connected plug flow reaction units, the step-by-step controllable ring-opening of cyclic siloxane was realized. By precisely controlling the molar ratio of water in the reaction system, the generation ratio of side hydroxyl groups was controlled below 0.3% from the polymerization source, and the proportion of straight-chain molecules was increased to 99.7%, which completely solved the long-standing industry pain points of uneven hydroxyl distribution and excessive side hydroxyl content in traditional processes. Second, the world's first 9-stage coupled purification system for high-hydroxyl silicone oil systems has been built. Aiming at the industry problem that small-molecule cyclic siloxanes and linear hydroxyl silicone oil have similar boiling points and are extremely difficult to separate, the team innovatively adopted a combined purification process of "4-stage multi-stage vacuum distillation + 3-stage high-vacuum thin-film devolatilization + molecular sieve ultra-deep adsorption + inert gas bubbling replacement". The operating temperature throughout the process is strictly controlled below 175°C, which completely avoids the dehydration and condensation of hydroxyl groups at high temperatures. The total residual amount of D3~D10 ring bodies in the final product is less than 8ppm, and the total volatile content after constant-temperature baking at 200°C for 3 hours is only 0.057%, far lower than the average level of 1.8% of traditional process products, fully meeting the low-precipitation requirements of semiconductor electronic packaging materials for long-term service of more than 25 years. Third, a full-process in-situ real-time closed-loop quality control system has been built. The entire production unit, covering monomer pretreatment, ring-opening polymerization, purification and separation, and finished product blending, is equipped with online gel permeation chromatography and online near-infrared spectroscopy detection modules. The system samples and analyzes the hydroxyl content, molecular chain distribution, and ring residual amount of the reaction system in real time every 4 seconds. Once the parameters have a tiny deviation at the 0.04% level, the system automatically completes dynamic parameter adjustment, completely eliminating the performance difference between products from different batches in the traditional intermittent process, and realizing that the hydroxyl content deviation of products from different batches across 52 months is less than 0.7% with zero performance drift.
At present, this independently developed ultra-high-purity low-volatility linear hydroxyl silicone oil has completed long-term industrial application verification for more than 48 months in multiple national strategic core fields. In the field of high-end addition-cured silicone rubber, the high-transparency silicone rubber prepared with this product has a tensile strength of 6.2MPa and an elongation at break of more than 800%. After 2000 hours of thermal aging at 200°C, the performance retention rate reaches 94%. Related products have been batch applied in the packaging buffer layer of the new generation of flexible display screens. In the field of semiconductor electronic packaging, the organosilicon potting adhesive prepared with this product as the basic raw material has a volume resistivity greater than 1.8×10Ω·cm and a breakdown voltage greater than 38kV/mm. After 1000 temperature cycles from -65°C to 180°C, there is no cracking or small-molecule precipitation, and it has been fully applied in the packaging process of domestic third-generation semiconductor power devices. In the field of photovoltaic module packaging, the organosilicon sealant for photovoltaic modules prepared with this product has a yellowing index of only 0.6 after 3000 hours of UV aging and salt spray test, and the power generation efficiency attenuation rate of the module is less than 1.2%. It has been widely used in the frame sealing and junction box potting processes of domestic N-type TOPCon photovoltaic modules. In the field of high-end fabric functional finishing, the waterproof and oil-repellent finishing agent prepared with this product as the active ingredient has a waterproof rating of ISO level 5 after 80 times of industrial washing for the cross-linked protective film formed on the fabric surface, fully meeting the long-term use requirements of high-end outdoor functional fabrics.
According to the latest industry operation monitoring data, the market demand for domestic high-end low-volatility hydroxyl silicone oil in 2026 increased by 327% year-on-year compared with the same period in 2025. With the official launch of this domestic continuous production line, the market pattern where overseas products have long monopolized the market has been completely broken. The market procurement price of high-end low-volatility hydroxyl silicone oil has dropped by 78% year-on-year, and the delivery cycle for core downstream users has been greatly shortened from the original 20 months to less than 7 days. With the subsequent start of construction of the second production line of the same scale, it is expected that by 2029, the global market share of domestically produced high-end hydroxyl silicone oil will exceed 85%. It will not only fully meet the upgrading needs of domestic downstream industries such as electronics, photovoltaics and high-end manufacturing, but also greatly enhance the core voice of China's basic organosilicon high-end intermediates in the global new material industrial chain.
