In the textile industry, the newly approved National Advanced Printing and Dyeing Technology Innovation Center, the National Advanced Functional Fiber Innovation Center established last year, and the National High Performance Medical Device Innovation Center, the National Integrated Circuit Characteristic Process and Packaging Test Innovation Center, and the National Rare Earth Functional Material Innovation Center approved by the Ministry of Industry and Information Technology this year are all areas that are urgently needed by the country and need to focus on achieving technological breakthroughs, It concerns the foundation of manufacturing power.

Implementing the "innovation driven development strategy", grasping the key points and complementing the weak points are the needs of national development, specifically, the need to remove the risk of some core technologies being "stuck". For example, the strategic industry represented by carbon fiber must be independent and controllable, and give play to the national strength to plan and develop step by step.

Wet spinning process for carbon fiber preparation with important strategic significance

High performance polyacrylonitrile (PAN) based carbon fiber is a new dual-use material related to national strategic security. It has been strictly prohibited by the international community for a long time, and the research and development of key equipment fields are severely restricted. The wet spinning process, as an important technical basis for carbon fiber for national defense equipment, is a key technical weakness in the research and tackling of domestic carbon fiber.

Due to the influence of carbon fiber precursor preparation technology, until the end of the last century, the development of domestic carbon fiber technology has been hovering at a low level that can not achieve industrialization. Carbon fiber for structural composite materials of national defense equipment is completely dependent on imports, which brings great risks to national security and development. It is urgent to develop carbon fiber localization technology that meets the needs of high-end equipment in key areas of our country, so as to achieve the independent guarantee of key materials.

The preparation of PAN based carbon fiber has the longest process flow in the material field, including polymerization, spinning, pre oxidation, carbonization (graphitization), surface treatment and other process links. The carbon fiber prepared by PAN solution wet spinning process has a unique surface groove structure, which is conducive to improving the interface performance of carbon fiber resin matrix composites as structural materials. China's national defense field, represented by aerospace, has long used the wet spinning process to prepare carbon fibers. Therefore, the development of wet spinning process for carbon fiber preparation has important strategic significance and market value in China.

"An original carbon fiber variety", forming a series of products based on wet spinning process

Taking the preparation of carbon fiber composites as the technical and industrial basis, Weihai Expanding Fiber Co., Ltd., based on its commitment to the localization of key national strategic materials and the pursuit of achieving autonomy and controllability of key raw materials in the industrial chain, is committed to the technical breakthrough and industrialization construction of PAN based carbon fiber localization.

Supported by the science and technology and industrialization plan of many ministries and commissions, such as the Ministry of Science and Technology, the Bureau of Science and Industry, the National Development and Reform Commission, and the Ministry of Industry and Information Technology, and under the guidance of the application and development of key models, aiming at the problems such as fiber defect control, fiber surface section morphology control, multi position/multi tow process state consistency control of traditional DMSO wet spinning technology, and carbon fiber performance/specification serialization technology research to meet high-end application needs, Weihai Expanding, together with Beijing University of Chemical Technology, Fudan University and other scientific research institutions, based on the independent innovation and original innovation of process technology, achieved a number of key technological breakthroughs through the independent innovation of new technologies and industrialization technologies for preparing carbon fiber precursor through the dimethyl sulfoxide wet spinning process, combined with the re innovation of key equipment——

Break through the key technology of efficient preparation of high-quality spinning solution, and solve the problem of de monomer and de foaming of high solid content and high viscosity polymer solution;

The development of washing/drawing integrated combined drafting process and equipment, independent innovation of new multi position spinning technology, effectively improved the quality consistency and stability of multi position precursor;

We have developed efficient spinning process and equipment with temperature gradient characteristics to achieve effective regulation of carbon fiber modulus and meet the needs of the aviation field;

The new technology of hot air interactive conveying pre oxidation furnace has been successfully developed, breaking the traditional four temperature zone mode, establishing a new process with six temperature zones, and breaking the bottleneck of efficient and long-term stable operation of the pre oxidation production equipment with a width of 3m;

A new spinning technology of low fiber PAN precursor has been developed to realize the structure optimization of low fiber PAN precursor with radial homogeneity and axial high orientation;

The fiber pre oxidation technology with controllable structure combination has been developed to solve the technical problem of preparing carbon fiber with medium and high modulus;

We have developed domestic key equipment technology integrating simulation design, manufacturing and operation management, and solved the problem of quality consistency of carbon fiber industrialization with different moduli.

Through systematic technical breakthrough, we have developed a series of technologies and products based on tensile strength, a series of technologies and products based on tensile modulus, and a series of technologies and products based on tow specifications, realizing large-scale production and large-scale application of high-performance carbon fibers, and establishing a complete technology research and development and kiloton industrialization system for preparing high-strength carbon fibers based on the wet spinning process.

The mechanical property indexes of T300 and T800 carbon fiber products developed and produced in this project exceed the level of similar products of Toray Company of Japan, and their performance stability is equivalent; The breakthrough 300 m/min spinning speed in the multi position state has increased the industrial wet spinning speed by more than 1.5 times, establishing innovation confidence for the industry. However, the original innovative new high-strength carbon fiber product has the tensile strength and modulus up to the Japanese Toray T700S carbon fiber level, and the composite interface performance is superior to this product (Toray only has the dry wet T700 grade, not the wet T700 grade). Experts identified that "Toray has created a carbon fiber variety with the high strength of T700 grade carbon fiber and excellent surface structural performance of T300 grade carbon fiber".

Practice the development strategy of domestic carbon fiber with strong strength

Weihai expands the stabilized carbon fiber products based on the wet spinning process, which have been widely used in national defense construction such as aviation, aerospace, weapons, electronics, high-end industrial equipment such as wind power, civil engineering and other fields. It is a major supplier of carbon fiber for national defense in China, and the first and largest supplier in the aviation field. It not only solves the "availability", "availability" and "ease of use" problems of the localization of carbon fiber for structural purposes, It has broken the foreign monopoly in this field, realized the independent guarantee of domestic key strategic materials, and has become the largest carbon beam supplier of Vestas, an international leading wind power enterprise, in China. With its unremitting efforts, Weihai Expanding has implemented the principle that "key technologies cannot be obtained, bought or acquired. Only by holding key core technologies in their own hands can we fundamentally safeguard national economic security, national defense security and other security", and adhere to the path of independent and controllable development of key technologies.

For "Industrialized preparation technology of high-strength PAN based carbon fiber based on wet spinning process", Experts identified that: "Based on original innovation and independent innovation, the project realized independent innovation based on DMSO intermittent polymerization and wet spinning, and stably prepared high-strength/high-strength medium modulus PAN based carbon fibers in a large scale, covering GQ3522 (T300), GQ4522 (T700) and QZ5526 (T800) series products, supporting the application of composite materials for key national defense batch production models. The overall achievements reached the international advanced level". The project won the first prize of Science and Technology Progress Award of China Textile Industry Federation in 2019.