Synthesis of terephthaloyl chloride_Kain Industrial Additive

Background and overview^【1】

In the “Twelfth Five-Year Plan” development concept of the high-tech fiber industry, the “Twelfth Five-Year Plan” is listed as the “pilot research to industrial production stage” of aramid 1414, and the simultaneous research of “equipment, raw materials, and fibers” will be strengthened. Shandong Province’s 2009 Major Special Project Guidelines for the Transformation of Independent Innovation Achievements lists “thousand-ton aramid II, aramid fiber and raw materials, aramid paper and applications, and aramid fiber products” as one of the 14 key high-tech industrial chains to be supported. important content.

The “State Council’s Decision on Accelerating the Cultivation and Development of Strategic Emerging Industries” issued on October 18, 2010 pointed out that by 2020, new materials will become the leading industry of China’s national economy. High-performance fibers and their composite materials such as carbon fiber, aramid fiber, and ultra-high molecular weight polyethylene fiber are among the strategic materials for the national economy and national defense construction. By developing the high-performance fiber industry and breaking foreign blockades and monopolies, my country’s Military equipment strength and industrial upgrading of the national economy.

In recent years, China has made continuous breakthroughs in the field of high-performance fibers. After nearly 20 years of scientific research and trial production, although the output is still small, my country’s high-tech enterprises have made breakthroughs in the field of high-performance fibers such as aramid. From the trial production stage to the early stage of industrial large-scale production. Terephthaloyl chloride is an important polymer monomer in the production of aramid 1414. Relevant national departments should guide and support the development of the terephthaloyl chloride industry from a policy perspective and give it sufficient attention and support to promote the industrialization of aramid 1414. process.

Terephthaloyl chloride decomposes in water and alcohol and is an acidic corrosive product. Terephthaloyl chloride is a derivative of the chlorine-consuming intermediate thionyl chloride and the aromatic carboxylic acid-terephthalic acid. It is generally referred to as para-acyl chloride or TPC or TCL. It is a homologous isomer with isophthaloyl chloride. It is mainly used as the polymerization monomer of aramid 1414 and aramid sulfone fiber. It is also widely used in the synthesis of permeable membrane materials, polymer materials, pesticides, etc.

Application

Terephthaloyl chloride is mainly used to polymerize with p-phenylenediamine to produce high-performance fiber aramid 1414 (PPTA) and aramid sulfone (PSA). It can also be used in the preparation of plastic additives, polymer materials, permeable membrane materials, and Pharmaceutical and pesticide industries, etc. The rapid development of high-performance fibers in China has brought rare development opportunities to the application and market of terephthaloyl chloride.

Synthesis^{【2】【3】}

1. Thionyl chloride method

Use terephthalic acid as raw material, react with sulfoxide chloride under the action of a small amount of catalyst N, N-dimethylformamide or pyridine, and distill to obtain terephthaloyl chloride. The reaction process is as follows:

The production process of the thionyl chloride method is simple. Thionyl chloride is an acidic corrosive product. Thionyl chloride is used to replace highly toxic raw materials such as phosphorus pentachloride, chlorine, and phosgene used in traditional processes. Thionyl chloride It is used both as a raw material and as a solvent to react with solid raw materials under normal pressure. It is easy to feed and choose an effective catalyst. The reaction time is short, the yield is increased to more than 98%, and the product purity is more than 99.9%. The by-products produced in the process are all Gaseous substances are easy to separate, and the risk and labor intensity for workers are greatly reduced compared with traditional processes.

2. Phosphorus pentachloride method

Terephthalic acid and phosphorus pentachloride are mixed, heated and melted, and the reaction is completed by refluxing until all the acid is dissolved.

<img id="ProductImg_News" src="https://www.xrhhg.com/upfile/2021/0827/201812141316268564.png" style="-webkit-text-stroke- background-color:transparent; border- bottom-color:rgb(51, 51, 51); border-bottom-style:none; border-bottom- border-image-outset:0; border-image-repeat:stretch; border-image-slice:100%; border-image-source:none; border-image- border-left-color:rgb(51, 51, 51); border-left-style:none; border-left- border-right-color:rgb(51, 51 , 51); border-right-style:none; border-right- border-top-color:rgb(51, 51, 51); border-top-style:none; border-top- box-sizing:border-box ; color:rgb(51, 51, 51); font-family:& font-size:13px; font-style:normal; font-variant:normal; font-weight:400; letter-spacing:normal; list-style -image:none; list-style-positionThe molecular weight, color, mechanical properties, etc. of the product will have a serious impact. The quality of aramid fiber is highly dependent on its raw materials. However, most of the domestic upstream raw material manufacturers of aramid fiber are small in scale. The enterprises have poor technical and financial strength and unstable production, resulting in unstable raw material quality and affecting the quality of the raw materials. Stability in aramid production.

2. Packaging and transportation methods cannot meet production, safety and storage requirements

At present, the packaging barrels used by domestic terephthaloyl chloride manufacturers are generally plastic barrels of various specifications or 200 L steel-plastic composite barrels. Plastic barrel packaging is easy for domestic enterprises to cut and use, but during storage, it is easily affected by sunlight conditions, The quality of products is reduced due to the influence of humid air in the environment. Steel-plastic composite barrels have good sealing conditions, which can reduce the impact of storage conditions on product quality. However, the material temperature during filling is often above 90°C, which is higher than the melting point of terephthaloyl chloride products, and the user unit uses melt feeding. method, the barrel must be heated again when adding materials. If an ordinary steel-plastic composite barrel is used instead of a high-temperature-resistant and corrosion-resistant steel-plastic composite barrel, the liner of the steel-plastic composite barrel will easily fall off under high temperature conditions. , causing safety accidents.

3. Unified quality standards and testing methods have not yet been established in China

At present, domestic production enterprises have not yet established unified product quality standards and testing methods, and mainly conduct quality control based on corporate standards. There are still doubts about some quality standards, such as melting point. There is no unified and exact melting point value in domestic reports. Generally, pure organic compounds should have a fixed melting point, but actual substances can only measure the melting range. In actual practice, capillary melting points are used. When measuring the melting range with a differential scanning calorimeter (DSC), the melting range is 81-83°C. The melting range is wide and has a large impact. Analysis of the influencing factors is mainly that terephthaloyl chloride easily decomposes when exposed to water in the air. It is difficult to completely isolate it from the air during sample preparation and testing, so different results will appear during testing.

References

[1]Wang Ronghai, Li Yunlong, Li Wenjuan, Guo Qiang, Domestic terephthaloyl chloride production, application status and development considerations, China Chlor-Alkali, 2011.05, page 22

[2] Sheng Qingquan, Xiao Jianmou, Luan Weili, Liu Taize, Research progress on the synthesis of terephthaloyl chloride, Jiangxi Chemical Industry, 2007.04, page 15

[3] Wang Dengkui, a method for preparing terephthaloyl chloride, Chinese patent: 01139192.8, 2001-12-25

[4] Sun Maojian, Song Xiquan, Development status and prospects of my country’s meta-aramid industry, Textile Herald, 2007.12, page 68

[5] Ye Yongmao, “Twelfth Five-Year Plan” Development Concept of High-tech Fiber Industry, The 16th China International Chemical Fiber Conference (Wujiang 2010), 2010.09.