High-performance polytetrafluoroethylene (PTFE) fiber materials have been obtained in various fields of the national economy due to their excellent high and low temperature stability, chemical stability, electrical insulation, non-adhesion, weather resistance, flame retardant, self-lubricating properties, etc. Extensive applications have become the preferred material for environmental protection, filtration, construction, aerospace and other fields.
Due to the nature of PTFE itself, the production of PTFE fibers cannot be simply used for the molding process of thermoplastic polymers (such as extrusion molding). This technical bottleneck is also an important reason why China cannot produce PTFE fibers for a long time. The research and development staff of the project independently developed the membrane-splitting method to produce PTFE fibers, that is, a three-dimensional three-dimensional stretching method was used to prepare expanded PTFE films that meet certain conditions. After the PTFE film was cut, a certain tension and heat treatment process was passed. , make it into the desired PTFE fiber.
Break the technology of developed countries**
According to Dr. Hao Xinmin, senior engineer of the Institute of Military Equipment Research and Development who participated in the research and development, because PTFE is insoluble in any solvent, and the macromolecular chains are arranged in a straight line, the rigidity is high, and the viscosity is high above the melting point, and it cannot be spun by traditional solution method or melting method. Silk, which has become a major technical problem in the field of deep processing of PTFE materials, has also become a technical bottleneck for the application of PTFE materials in China.
At present, only a few companies in the world have mastered the production technology of PTFE fibers. The main production processes include carrier spinning and paste extrusion. However, these companies have long implemented technology in China and the price of the products is very high. The application cost of PTFE fibers has been increased, which has severely restricted the development and application development of PTFE fibers.
From the analysis of only a few foreign production samples, a process of difficult exploration and hard work started several years ago. It is reported that a group of companies, research institutes, and users researched and designed the production process of PTFE membrane split length and length fiber, and developed a temperature gradient controlled non-equal, wide-amplitude, multi-stretch PTFE fiber production process. High-strength and special-shaped PTFE filaments and short fibers were developed to solve the problem of "filament" of PTFE staple fibers. A multi-angular-type membrane split long fiber cutter, a wear-resistant diamond short fiber slitting needle roller, and a dental floss film cutting were developed. Key equipment, such as screw extruder, two-roller calender, non-equal-speed stretcher, gradient temperature controlled variable width stretcher, slit length fiber slitter, staple fiber slitter, fiber Extruded series of production equipment such as drafting machines and crimpers, and established large-scale production lines; R&D and production of “ひ”-shaped PTFE floss, high-strength pure PTFE gradient coating filter materials, all of these process technologies, series products and production Equipment, no similar or identical literature reports at home and abroad, is novel and innovative. Product inspections further prove that the PTFE fiber produced has filled the domestic gap, and the performance of PTFE fiber is at the leading international level. The PTFE fiber application products are all at the international advanced and domestic leading level.
The expert appraisal committee that has already formed a production capacity of 10,000 tons is a strong lineup. The director and deputy director of the Appraisal Committee are respectively Sun Jinliang, Jiang Shicheng and Zhang Yaoming. They are from chemical fiber materials, industrial textiles, environmental protection, chemical industry, etc. The 11 famous experts in the field unanimously agreed that the project is a major integrated innovation in the processing technology, production equipment, and product development of high-performance fibers in China. It has a demonstration effect and the overall technology has reached the international advanced level.
In the opinion of the experts, the experts believed that the project invented the PTFE uniform three-dimensional processing and filming process technology, and independently developed and integrated innovative PTFE membrane and fiber-specific complete sets of production equipment. The operation was stable and a thousand-ton production capacity had been formed. This scientific research achievement has independent intellectual property rights. It has applied for 10 invention patents and has authorized 4 items. The social and economic benefits are significant, and the market has a broad application prospect.
Ye Yongmao, a consultant and professor-level senior engineer of the China Chemical Fiber Industry Association, told the reporter: “The National Development and Reform Commission has clearly listed the development and production of PTFE fibers and products as one of the focal points in the “Twelve Five-year Plan” in this year’s “Guidance Catalog for Industrial Structure Adjustment”. In the beginning of the year, we can see the fruitful results of the serialization of the project's completion units.” PTFE fiber is an excellent skeleton material, and its mass production can promote aramid 1313, aryl sulfone, polyphenyl ether fiber, etc. The application of high-performance fiber to filter media can speed up the transformation of China's chemical fiber industry's economic development mode, promote the structural adjustment and optimization of chemical fiber industry, and improve and develop modern industrial systems.
Ye Yongmao introduced the production of PTFE fiber and its application products using the membrane splitting method, which mainly includes PTFE long fiber and PTFE short fiber. The products developed by PTFE long fiber include: Long fiber yarn, Poly IV PTFE sewing thread, PTFE floss, PTFE-based PTFE long fiber reinforced mesh, PTFE-based PTFE vinyl cloth, Teflon-coated needled felt filter, etc. . The PTFE long and short fiber product technology produced by this project is at the international advanced level. The price of the product is about 35% of that of similar foreign products, which greatly reduces the production cost of domestic users and lays a foundation for the application of high-performance PTFE fibers for environmental protection in China. The foundation.
The ideal material for dust-removing filter material Fang Aimin, director of the Dust Removal and Ash Removal Research Institute of the State Power Environmental Protection Research Institute, said: “The major breakthrough in domestic PTFE fiber production technology has successfully broken the monopoly and technology of our products abroad for many years. **, will lead to the upgrading of environmental protection technology and materials, in the 'second five' countries to promote the 'blue sky project' of the key stage, has great social significance, and achieved important economic benefits."
According to Fang Aimin, the important application of PTFE fiber in this project is the preparation of PTFE filter media for high temperature corrosive flue gas dust removal. Nowadays, domestic PTFE filter media has been widely used in waste incineration, coal-fired power plants, steel industry and other industries. It is one of the key materials for energy conservation and emission reduction in China. At the same time, PTFE filter media can also be used in corrosive high-temperature environments. Gas-solid two-phase separation as a filter separation material.
At present, there are about 40 sets of municipal solid waste incinerators and hazardous solid waste incinerators in China, all of which use PTFE long- and short-fiber products produced by this project as raw materials to produce PTFE dust-removing filter materials, with a total filtration area of more than 700,000. Above the square meter, the total amount of PTFE fibers used is approximately 595.31 tons. For example, in 2009, the length of PTFE long fiber used in the bag filter used in the production of waste incinerators was 40 tons, and the amount of short fibers used was 240 tons, accounting for more than 91% of the total waste incineration industry.
In the power industry, nine power plants have used the PTFE long fiber filter bag base fabric produced by this project, with a total area of 245,000 square meters and a total weight of about 36.75 tons using PTFE fibers. Teflon-based vinyl cloth provides a key support for the 30,000-hour service life of filter materials in China's power industry. Its current market share exceeds 50%. Pure PTFE fiber membrane filter continuous use temperature up to 250 °C, instantaneous operating temperature of 280 °C, acid and alkali resistant, not be hydrolyzed, not oxidized. The service life is up to 4 years and far exceeds the ordinary coated filter media.
According to reports, PM2.5 refers to particulates with a diameter less than or equal to 2.5 microns in the atmosphere, also known as lung-injectable particulates, and has important effects on air quality and visibility. Compared with coarser airborne particles, PM2.5 has a small particle size, is rich in toxic and hazardous substances, has a long residence time in the atmosphere, and has a long transportation distance, and thus has a greater impact on human health and atmospheric environmental quality.
In most parts of China, especially in North China where industry is concentrated, PM2.5 accounts for the majority of airborne particulate matter. PM2.5 is also the main cause of hazy weather. In the past, there was no PM2.5 in China's air quality standards.
The Ministry of Environmental Protection has recently issued the "Ambient Weight Measurement Method for Ambient Air PM10 and PM2.5," which for the first time regulates the measurement of particulate matter PM2.5 suspended in the air and having a diameter of 2.5 μm or less. The dedusting products using polytetrafluoroethylene cloth and its covered filter media have a filtration efficiency of 99.99% for PM2.5.
All these have made great contributions to our country's implementation of energy conservation and emission reduction policies and policies, making our country no longer subject to control in the key area of PTFE filter materials, and saving the country the cost of environmental protection investment.
