2. It is a giant in the acrylic fiber industry, and the precursor preparation technology originated from the acrylic fiber industry. In recent years, due to the competition of other chemical fibers, the acrylic fiber market is shrinking year by year, while the polyacrylonitrile-based carbon fiber is booming. In the next decade, with the development of wind turbine blades, pressure vessels, automobile rail transit, solar energy and other industrial applications, a low-cost carbon fiber industrial revolution will be triggered. Judging from the current international carbon fiber technology, "lifting bundles to speed up" is an effective way to reduce costs, and the idea of lifting bundles will bring precursor production closer to acrylic fiber industry. Internationally, Zaltertek has formed a successful experience in manufacturing precursor with acrylic fiber device. On the basis of its acrylic fiber factory, Montefibre Carbon Company of Spain has started to produce 80-480K precursor. In the history of carbon fiber development in China, precursor and acrylic fiber used to be two skins. Precursor despises the "rough technology" of acrylic fiber, and acrylic fiber despises the "small pot frying" of precursor. With the gradual development, the main acrylic fiber factories enter the mass production of precursors, while the "small pot" is expanding year by year, and technical integration is an inevitable trend. At present, China is still a big country in acrylic fiber production and consumption, and still has a relatively complete independent industrial system and experienced technical production team, which is undoubtedly a strong foundation for the sustainable development and growth of China's carbon fiber industry application. We put forward the "development strategy of acrylic fiber precursor merging", mainly aiming at the decline of acrylic fiber and the rapid development of carbon fiber, and exploring a way of "old chefs cooking new dishes" for China's acrylic fiber industry. Among them, to what extent do kitchen equipment, recipes and cooking temperatures need to be updated or innovated? I hope to get the voice and discussion from domestic experts on acrylic fiber and precursor.
character introduction
12
Mi Lin Kun
Born in the new society (49 years after the national liberation), I grew up under the red flag. 1966 graduated from junior high school and went to Chongming farm for exercise; 1974 joined Shanghai Petrochemical Company and worked as an intern in the spinning floor of Lanzhou Chemical Fiber Factory (302). After returning to Jinshan, he served as the monitor of spinning operation in Class B. 1979, dispatching office served as chief dispatcher, deputy stationmaster and section chief; 1992 as production director; 1994 was rated as a model worker of Sinopec; 1997 Head of the merger research group of Zhejiang Acrylic Fiber Factory; /kloc-since 0/998, he has been the general manager of Jinyong Company and the secretary of the Party branch; 1988 passed the self-study exam and obtained the college diploma; MBA in 2000.
After retirement, I worked in Ningbo Zhongxin Acrylic Fiber Company and Shen Heng Co., Ltd. successively, and experienced the one-step and two-step methods of NaSCN, trained the technical routes of DMF, DMSO and DMAc, and had rich practical experience in acrylic fiber production.
In the first phase of this seminar, I will introduce some research and thinking of Guo, an old expert:
Teacher Mi has prepared a series of articles, which will be published on the official WeChat account one after another:
What is the development status of acrylic fiber industry in China?
Solution of Acrylic Fiber Industry in China —— Blending and Development of Acrylic Fiber and Precursor
Operation mode of acrylic fiber production and large tow precursor production (dispatching operation mode)
Design practice of polyacrylonitrile carbon fiber tow precursor process
Welcome domestic dormant acrylic fiber experts and precursor experts standing in the center of the stage to actively participate in the discussion of "the integrated development strategy of acrylic fiber precursor".
The outlet of acrylic fiber industry in China.
-The integration and development of acrylic fiber and precursor.
China acrylic fiber faces new development opportunities and challenges. When establishing the future development goal of acrylic fiber in China and planning the coexistence of acrylic fiber and precursor production, the overall situation of acrylic fiber industry in China is briefly analyzed to evaluate the necessity of making the overall goal plan of acrylic fiber industry and the feasibility of concrete implementation.
The development of acrylic fiber industry in China: Japanese acrylic fiber is recognized as the highest level in the world in terms of functionality and quality. The gap between American and foreign acrylic fibers is mainly in technology, quality and product variety. China acrylic fiber from scratch, from less to more, from small to large, the production capacity is considerable. The total amount of main products has been in the forefront of the world, and the process of acrylic fiber capacity expansion has been basically completed on 20 10. However, with the shrinking of the world acrylic fiber industry, the main performance is the shrinking demand. In recent ten years, the demand for acrylic fiber products in the downstream market has been saturated and shrinking. As the world acrylic fiber production and consumption center, China acrylic fiber has excess capacity and low capacity utilization rate. The main problem is to improve the performance of chemical fiber products such as energy and environment to replace acrylic fiber. At the same time, on the other hand, the polyacrylonitrile-based carbon fiber industry has entered a new round of development, especially the large tow precursor. According to the industry forecast, the total demand for industrial-grade carbon fiber will exceed 6,543,800,000 tons in 2030, and the demand for large tow precursor will be considerable in the near 654,38,000 years. At the beginning of the year, I predicted that the ratio of acrylic fiber to precursor in China would be 50:50 in the next decade. I think the acrylic fiber industry in China should take the development road of coexistence of acrylic fiber and precursor production.
First of all, China carbon fiber industry should focus on developing large tow carbon fiber! China carbon fiber enterprises should pay attention to large tow carbon fiber and its industrial application. The most potential market is energy, automobile and other industrial applications, which is bound to be a broad market for low-cost large tow carbon fiber applications. Because the traditional market of small tow carbon fiber, such as aerospace market, is a slow and limited development process, the expansion space of sports equipment market is limited. Moreover, with the maturity of technology and the popularization of market application, the mechanical properties of large tow are not only T300 grade, but also T700 strength grade and medium-high modulus. Nowadays, low-cost carbon fiber and its composites are the global development trend. Almost all the carbon fiber giants in the world are supported by the powerful acrylic fiber industry. In the process of carbon fiber industrialization and commercialization, the technical foundation of acrylic fiber industry plays an important role.
Second, maintain an appropriate capacity scale. Mainly based on two reasons, one is that the commercial production of acrylic fiber will continue as long as the performance and appearance of wool are needed in the market, and some characteristics of acrylic fiber products can not be replaced by other synthetic fiber products, such as its unique practical properties such as dyeability, resilience, climate adaptability and some antibacterial properties, acrylic fiber products still have certain market competitiveness; Secondly, make full use of the existing polymerization and solvent recovery production capacity of acrylic fiber factory and the supporting capacity of public works, and at the same time, use the existing waste rubber and waste silk treatment system to digest and treat the waste silk and waste rubber produced after precursor production, which not only reduces the investment, but also ensures and supports the low-cost precursor production. I always think that the technological basis of acrylic fiber is an important evaluation index for developing the potential of large tow carbon fiber. Unless there is a revolutionary breakthrough in technology and acrylic fiber has a strong industrial foundation, there is no basis for developing large tow carbon fiber.
The total acrylic fiber production capacity in China is maintained at 500,000 tons/year, which basically meets the domestic processing demand. According to the change of market demand, import some acrylic varieties appropriately. According to the market change and demand, acrylic fiber production still needs to adhere to the idea of variety development and form differentiated products with high added value, which is also the need of enterprise transformation and upgrading. It is suggested that the steam setting process of acrylic fiber production line should be reformed, and the intermittent setting should be changed into continuous setting, so that the energy consumption and operating cost can be further reduced by selecting mature processes and equipment.
Developing large tow precursor is the best choice for China acrylic fiber.
Reforming and adopting the experience of large-scale acrylic fiber production and engineering system to produce industrial-grade large-scale low-cost large tow precursor is an important development direction of acrylic fiber enterprises in China at the critical stage, and it is also the best choice for acrylic fiber industry to get rid of the predicament.
Make full use of the existing public works and waste rubber and waste silk treatment system in acrylic fiber plant to reduce investment;
Make full use of skilled technical workers and the management experience of acrylic fiber factory to ensure the continuity of production technology and product quality;
Fully learn from the profound understanding and strict requirements of acrylic fiber enterprises on production cost and economic ability to ensure the lowest cost;
The technicians and operators of acrylic fiber factory should fully respect and deeply understand the technical characteristics of precursor production and organically integrate precursor technology into acrylic fiber industrial system.
To sum up, it is a wise and pragmatic choice for China Acrylic Fiber to develop the production of large tow carbon fiber precursor, which fully conforms to the global development trend of low-cost carbon fiber and its composites. Moreover, Japan's Mitsubishi, Turkey's AKSA, China's Jilin Chemical Fiber, Shanghai Petrochemical, Japan's Toray's Zoltak acrylic fiber factory in Mexico and Hungary, and Germany's SGL's acquisition of Portuguese acrylic fiber factory are all worthy of learning and reference.
On the basis of analyzing the characteristics of acrylic fiber production process, the technical problems existing in the production of large tow carbon fiber precursor by using existing production equipment are as follows:
The material structure determines the performance, and the structure of polyacrylonitrile-based carbon fiber is evolved from the precursor structure through pre-oxidation and carbonization. The structural characteristics of precursors, such as * * * poly composition, compactness, fineness, crystal orientation and structural uniformity, as well as various defects, largely determine the properties of the finally prepared carbon fiber.
Structure of polyacrylonitrile precursor and its influence on properties;
The arrangement and stacking structure between polymer chains is called supramolecular structure, which is the main factor that determines the properties of fibers, including crystal structure and orientation structure.
* * * The "two-phase quasicrystal structure model" refers to relatively ordered quasicrystal regions and disordered amorphous regions, and the "two-phase model" theory is the theoretical basis for determining the crystallinity of polymers.
* * The crystalline structure of polymer is closely related to its properties, and the crystallinity and grain size increase with the increase of molecular weight.
* * * Orientation process is an ordered process of molecules under the action of external field. The higher the axial crystallinity of PAN precursor, the denser the fiber and the higher the tensile strength of carbon fiber.
From the above description of the relationship between structure and properties, it can be clearly seen that the production process conditions and equipment of polyacrylonitrile-based carbon fiber precursor must be designed according to the requirements of carbon fiber materials.
1, chemical composition-* * poly composition and proportion:
1. 1 required properties of fiber-grade polyacrylonitrile;
Molecular weight and its distribution are the main characteristics of polymers, and polymers with higher molecular weight play a very important role in the strength and modulus of fibers. The molecular weight range of spinnable polymers is very wide. From the point of view of processing cost, it is reasonable that the polymer concentration in spinning dope should be as high as possible, because it means that there is relatively little solvent to be recovered per unit fiber, thus reducing the energy consumption of recovery. However, under the specified stock solution viscosity, because the polymer concentration is inversely proportional to viscosity-average molecular weight, the lower molecular weight is definitely ideal, so the performance of the polymer in the existing production equipment obviously cannot meet the requirements for producing precursors. To improve the molecular weight of polymer, improve the viscosity of stock solution and appropriately reduce the concentration of stock solution, it is necessary to comprehensively balance and find the best match.
The molecular weight of 1.2 polymer is influenced by many variables.
Among them, there have been many literature reports on the types and concentrations of * * * monomers, that is, the composition ratio. In the early research and development process of PAN-based carbon fiber, especially in the years when Japanese patents were published, from 1979 to 1990, precursor technology began to get rid of acrylic fiber technology, which has been leading the development of carbon fiber technology in the world in many aspects such as * * * polymer composition and * * * monomer selection. In the production of acrylonitrile fiber, polyacrylonitrile fiber is prepared from acrylonitrile and usually at least one other monomer, and monomer MA, MMA or VA is used to improve the spinnability of acrylonitrile polymer and improve fiber characteristics. We must note that the two most common * * * monomers in commercial polyacrylonitrile fiber are MA and VA. Although the low reactivity ratio of VA is not conducive to polymer control and chain transfer in polymerization, it is precisely because of its superior low cost that VA is often selected as the * * * monomer in the manufacturing process of wet spinning polyacrylonitrile fiber, that is, VA has a price advantage. Combined with the changes in monomer selection and monomer ratio of Mitsubishi Corporation of Japan since 1985, it is pointed out that the polymerization monomer and composition of acrylic fiber are not suitable for producing carbon fiber precursor and should be adjusted. Under the same technological conditions, the fiber spun with VA as the second monomer is slightly less rigid and soft to the touch. This is because the side group OCOCOCOCH 3 of VA is connected to the main chain carbon with oxygen atoms, while the side group COOCH 3 of MA is connected to the main chain carbon with carbon atoms. This is the biggest microscopic difference between VA and MA, so using VA as the second monomer of ordinary acrylic fiber can increase the flexibility of macromolecular chain. When preparing high performance carbon fiber, polyacrylonitrile seems to be the most ideal from the perspective of structural uniformity and carbon yield. However, when polyacrylonitrile is pre-oxidized, the exothermic peak is narrow and concentrated, and it is easy to break wires, so it is difficult to prepare carbon fibers with excellent properties. Adding a certain amount of poly (* * *) into the polymer can reduce the activation energy of the reaction when preparing carbon fiber, which is beneficial to promoting cyclization and crosslinking, alleviating the exothermic reaction of pre-oxidation, improving the density and uniformity of fiber and ensuring the strength of carbon fiber. We often say that the structure and properties of the initial polymer determine the structure and properties of the final carbon fiber. As carbon fiber precursor, these functional requirements should be met when selecting monomers.
Most domestic acrylic fiber enterprises choose VA as the second monomer, that is, most enterprises that produce polyacrylonitrile-based carbon fibers use AN, MA and IA ternary poly * * *, while many patents of foreign companies involve using AN-based polymers to provide carbon fibers suitable for pre-oxidation reaction characteristics and excellent viscosity stability of spinning dope, and some companies use other polymers to improve the properties of carbon fibers. Therefore, it is very important to choose the composition and content of * * * monomer.
Due to the different chemical structures of different monomers, their reactivity is also different, and the composition and ratio of monomers prepared are also different. From the existing research and comparative analysis, the results show that four different monomers, methyl methacrylate (MMA), methyl ester (MA), itaconic acid (IA) and acrylamide (AM), react with acrylonitrile (AN). When the content of IA increased, the total conversion rate of polymerization decreased. At the same concentration and temperature, different monomers have the least influence on the falling ball viscosity of spinning dope. Under the ratio of 98:2, AM has the best effect of reducing pre-oxidation temperature and relieving heat release, followed by IA.
The distribution of poly components in the polymerization process is of great significance for the synthesis of stable spinning dope. * * * poly components have different functions in spinning process and pre-oxidation of precursors, and also have different effects on the sequence distribution of * * * polymers. Generally, the monomer content of * * * is controlled below 5%, that is, total amount control. Toray Company of Japan uses binary polymer precursors of an and IA with relative contents of 98: 2, 99: 1, 99.5: 0.5, etc. Japan's Mitsubishi Corporation prefers acrylic acid (AA).