By Yang Ruiying, Zhong Weike, Wei Zhihua, China National Chemical Economic and Technical Development Centre (CNCET)

Output largely for captive use

As a colorless, non-toxic and combustible gas at normal temperature and pressure, vinylidene fluoride (VDF) is one of the important monomers in the production of fluorine-containing polymer materials. It can be used to produce polyvinylidene fluoride (PVDF), fluororubber and fluoroplastics.
   There are many production routes to VDF monomer, including HCFC-142b pyrolysis, HFC-152a decomposition, one-step vinylidene chloride (VDC), HF removal by HCFC-143a, tetrachloroethane and co-pyrolysis. Apart from the first two processes, the other processes have been hardly put into industrial use due to the low yield and harsh reaction conditions. At present, the majority of domestic VDF production is made by HCFC-142b pyrolysis.
   There were 17 VDF producers in China in 2018, with a total capacity of 88 000 t/a. Among them, four producers, Inner Mongolia 3F Wanhao Fluorochemical Co., Ltd. (15 000 t/a), Shandong Huaxia Shenzhou New Material Co., Ltd. (13 000 t/a), ARKEMA (Changshu) Fluorochemical Co., Ltd. (12 000 t/a) and SOLVAY Specialty Polymer (Changshu) Co., Ltd. (10 000 t/a), reported capacity above 10 000 t/a each, and their aggregate capacity accounted for 56.8% of the domestic total. At the same time, Shandong Deyi New Material Co., Ltd., Changshu 3F Zhenfu New Material Co., Ltd., DAIKIN Fluorochemical (China) Co., Ltd. and Zhejiang Juhua Co., Ltd. recorded capacity of 5 000 t/a each. Jiangsu Sanmei Chemical Co., Ltd’s VDF unit has not been put into operation since the completion of construction in 2014, and Sinochem Blue Sky Fluorine Material Co., Ltd’s VDF unit has been idled since 2017. As such, China's VDF output was about 54 000 tons, and the average operating rate was at 61.5% in 2018.
   VDF is generally not sold in the market, but mainly for captive use. A small number of producers pipe their output to other producers. It is mostly used to produce PVDF and fluororubber through polymerization. In addition, a copolymer of VDF and chlorotrifluoroethylene as well as a copolymer of VDF and tetrafluoroethylene and perfluoroethylene are elastomers with good heat resistance.

Two key application fields

   At present, domestic VDF goods are mainly used in the production of fluororesin PVDF, fluororubber 26 and fluororubber 246. In 2018, China's VDF consumption was about 47 000 tons, nearly 80% of which was used to produce PVDF and 20% to produce fluororubber.
   1. PVDF
   PVDF is a crystalline polymer with low melting point at 160-170℃. It has high mechanical strength, wear resistance, cutting resistance, high-temperature resistance, corrosion resistance, good electrical performance, as well as excellent weather resistance, ultraviolet resistance, radiation resistance and processing performance. At the same time, it has merits such as low processing temperature and good melting flow. Therefore, it can be made into tubes, plates, rods, films and fibers to be mainly used as anticorrosive materials for chemical engineering sector; double casing for wires and cables of electronics and aviation; coating for optical fiber, and capacitor film and electric heat tape for high-permittivity materials.
   At present, there are 12 PVDF production producers in China. In 2018, the total capacity was 49 000 t/a and the output was about 34 000 tons, reflecting that the overall operating rate was about 70%. The average annual growth rates of China's PVDF capacity and output were 9.4% and 19.2%, respectively, from 2014 to 2018. The top five PVDF producers in China are ARKEMA (Changshu) Fluorochemical Co., Ltd., Shandong Huaxia Shenzhou New Material Co., Ltd., Inner Mongolia 3F Wanhao Fluorochemical Co., Ltd., Shandong Deyi New Material Co., Ltd. and SOLVAY Specialty Polymer (Changshu) Co., Ltd. Their total PVDF capacity and output accounted for 73% and 86% of the domestic total, which indicated that the industrial concentration was high.
   2. Fluororubber
   Fluororubber can be divided into three categories: fluorocarbon rubber (olefin fluororubber, nitroso fluororubber, fluorinated acrylate, perfluoroether rubber), fluorosilicone rubber and fluorinated phosphazene rubber (fluoroalkoxyphosphazene elastomer). The main derivatives of VDF are poly (VDF-HFP) and poly (VDF-TFE-HFP), referred to as fluororubber 26 and 246 respectively.
   At present, there are nine fluororubber producers in China. In 2018, the capacity totaled 22 000 t/a and the output about 18 000 tons, reflecting that the overall operating rate was about 85%. The operating rate has been increasing year by year. From 2014 to 2018, the domestic output grew fast at an average annual growth rate of 13.6%. Shandong Huaxia Shenzhou New Material Co., Ltd. is the biggest producer, with the capacity taking up 1/4 of the domestic total.
   Despite a lot of excellent properties, its processability is worse than ordinary rubber, as the high processing viscosity makes it difficult to be mixed and shaped.

Growth rate of supply and demand to slow down in the future

   Fluoropolymer is an indispensable new material for the development of national strategic emerging industries and cutting-edge technology fields, such as aerospace, electronic and electrical, environmental protection, and new energy. PVDF and fluororubber 246 (with high fluorine content) were listed in the encouraged category of Industrial Structure Adjustment Guidance Catalogue (revised in 2019), signaling that there is still big room for development in the future. The supply and demand growth of VDF and downstream polymers in China will slow down in the next few years. It is estimated that the annual growth rate of domestic VDF production and demand will be averaged at 5-6% from 2020 to 2023.
   PVDF is mainly used in three fields - petrochemical, electronic and electrical, as well as fluorocarbon coating. Among them, coating is still the biggest application field, as solar energy back plate membrane and lithium battery binder are growing at the fastest pace, and water treatment membrane field also has growth potential in the future. It is expected that the average annual growth rate of China's PVDF output will be about 6% and that of demand will be 8% from 2020 to 2023.
   Fluororubber and related products are mainly used in automobile manufacturing industry, chemical industry, petrochemical industry, aerospace, light industry, machinery manufacturing industry and home appliances industry. The demand for fluororubber will be relatively stable in the future. It is expected that the average annual growth rate of China's fluororubber output will be 5% and that of consumption will be slightly higher from 2020 to 2023.