Research history
Polypropylene is another class of olefin polymer developed on the basis of polyethylene research work. Natta (Italy) In 1954, Ziegler (Germany) used TiCl3/A1(C2H5)2C1 catalyst for catalyzing ethylene polymerization for the polymerization of propylene, and isotactic polypropylene was first synthesized. The subsequent research on the synthesis of polypropylene mainly focused on two directions: one was the catalyst research, and the other was the polymerization process research.
The catalyst research direction of propylene polymerization has gone through five stages. The first used TiCl3/Al(C2H5)2C1 is called the first generation of propylene polymerization catalyst; in the mid-1960s, a complex catalyst of complexing TiCl3 with ether was known as the second generation of propylene polymerization catalyst; it appeared in the late 1960s. The supported catalyst supports TiCl3 with MgCl2 crystallites with a large specific surface area, thereby increasing the number of Ti atoms that are effectively used for catalysis and increasing the catalyst activity by more than 50 times. This is called third generation propylene polymerization catalyst; In the 1980s, the porous spherical MgCl2 alkoxide was used as the carrier, and the MgCl2-TiCl4 electron donor catalyst prepared by the de-alcoholation of TiCl4 was used as the fourth-generation propylene polymerization catalyst. The fourth-generation catalyst was characterized by its catalytic activity. Up to 50KgPP/g catalyst, the polymer is highly regular, and the product polypropylene is a spherical particle with a uniform particle size and can be directly processed without granulation. The fourth generation of catalysts was further developed by increasing the limit use temperature of these catalysts from 80°C to 170°C in the mid-1990s, further increasing the catalytic activity of propylene polymerization and increasing the productivity of the equipment; A new generation of catalysts, metallocene catalysts. The advantages of metallocene catalysts are higher activity, precise control of the molecular structure of the polypropylene molecule, and narrow molecular weight distribution of the polymer. Our research work on propylene polymerization catalysts began in the 1960s and various catalysts have been developed. In the 1980s, it began to produce complex 2 type catalysts. In the direction of high-efficiency carrier catalysts, YS-841, CS-1, CS-2, N-type, DQ-type, HDC-type, and STP-type were successively developed.
In the research of propylene polymerization process, since the industrialization of polypropylene in the 50's, the solvent method (or slurry method) was used initially. In the 1960s, the liquid-phase bulk process appeared. In the late 1960s, the gas-phase production process appeared. The reactors used in the equipment are tank reactors, loop reactors, stirred reactors, stirred bed reactors, fluidized bed reactors and the like. At present, 55% of the world's polypropylene production capacity uses the bulk process, 25% uses the gas phase process, and 20% the slurry process. China's polypropylene production mainly adopts the domesticized cauldron body technology and the ring tube body technology. At present, the localization rate of equipment reaches 80%, and the total production capacity is about 600KT/a.
Production scale
In the world's general-purpose resins, polypropylene has exceeded polyvinyl chloride in both production capacity and output, making it the second largest category after polyethylene. From 1994 to 1999, the global polypropylene production capacity increased by 52%, with an average annual growth of 10%, and the production capacity reached 31Mt. In 2000, the global polypropylene production capacity was close to 35Mt. In 2002, China's polypropylene production capacity was approximately 3. 74MT/a.
Production technology
From the late 1950s to the early 1960s, the polypropylene production process adopted the solvent method (or the slurry method). With the increase of the activity of the catalyst, the liquid phase bulk production process of polypropylene was realized in the mid-1960s, simplifying the process. The process has reduced production costs; in the late 1960s, a more simplified polypropylene gas phase production process was unveiled and further developed in the 1970s and 1980s; in the 1980s, the fourth generation of catalysts was able to effectively control polypropylene. The relative molecular mass, relative molecular mass distribution, particle size and morphology can be directly applied without granulation.
Polypropylene catalysts, advances in production process technology and the expansion of product applications are the main driving forces for the rapid development of the polypropylene industry. As the core of polypropylene production process technology, catalysts have been continuously researched and developed over the past decades and continuously updated. The catalyst activity has evolved from the first generation of 1 to 2 kg PP/g catalyst to the fourth generation of 30 to 60 kg PP. /g Catalyst, isotacticity increased from less than 90% to more than 98%. Polypropylene metallocene catalysts currently being industrialized are more active (2000 kg/g Zr). The continuous progress of the catalyst has promoted the continuous improvement, development and maturation of the polypropylene production process technology. The production process has achieved a simple process flow and "three nos" (no deashing, no off random matter, no solvent recovery). It is even possible to achieve a non-granulation process; economical, simplified bulk processes and gas phase processes have replaced earlier cumbersome and costly slurry processes and become the most used production technology in the polypropylene industry.
The evolution and development of polypropylene production process is as follows:
Applications
Since the industrialization of polypropylene in 1957, it has become the fastest-growing, fastest-growing and fastest-growing variety of general-purpose thermoplastic resins. Polypropylene production process is simple, raw material source is rich, product transparency, non-toxic, low density, easy processing, toughness, flexibility, chemical resistance, electrical insulation, and easy to copolymerize, blend, fill, Reinforced modification and alloying have been widely used in industries such as chemical, chemical fiber, construction, light industry, household appliances, automobiles, packaging, and medical fields.
Gift Box Socks,Winter Kids Socks,Womens Tube Socks,Kids Cotton Socks
Shaoxing Evergreen Knitting Co., Ltd. , https://www.egsock.com