The polypropylene process technology of the 1990s was basically developed along the main line of improving the economics of the plant. The basic process design of polypropylene did not change much, but through the significant improvement of the catalyst and the use of larger equipment, the polypropylene plant The production capacity of single lines has increased and the economy has improved. In terms of products, it is mainly to develop a large number of high value-added products such as: high melt flow homopolymer, high transparency, low heat seal random copolymer, high impact copolymer and so on. In the new century, polypropylene technology will continue to develop with remarkable interest and will remain one of the most active areas in the development of synthetic resin technology in the future. The Ziegler-Natta catalyst will continue to grow and will continue to grow steadily for at least 10 years. The metallocene/single-site catalyst will expand its product and market range and begin to develop into the general product market. In terms of process technology, the already industrialized technology will be further improved and reduced, the average single-line production capacity of new devices will continue to increase, and advanced control and prediction models will be developed. The combination of production equipment and enterprise information technology systems will be closer. (l ) Catalyst development remains the focus. (a) Conventional catalysts. Conventional polypropylene catalysts such as Ziegler-Natta catalysts (ZN) and chromium catalysts have been continuously developed. Ziegler-Natta catalysts are continually developing new products with better performance, and the performance gap between them and metallocene catalysts is shrinking. A recent major advance in polypropylene Ziegler-Natta catalysts has been to broaden the product range of the Ziegler-Natta catalyst system and to develop electronic systems. The product range is continuously broadened, and the further development of product performance is reflected in the ability to obtain high melt flow rate products without visbreaking in the reactor (eg, for fiber market, melt flow rate up to 1800 g/10 min) Product); by improving the catalyst, improving the crystallinity and isotacticity of the polymer, producing a product with better rigidity; lowering the heat sealing temperature of the product; improving the optical properties; using a two-stage polymerization bimodal resin production technology to make the polypropylene resin The molecular weight distribution is broadened, so that the product has the comprehensive properties of optimized rigidity and impact resistance; the product with a polydispersity of 3.2-10 can be produced by a reactor system consisting of two homopolymerization reactors; The modulus can reach more than 2300 MPa. In addition, in the future, mixed catalyst systems of metallocene and traditional Ziegler-Natta catalysts will also be developed. This mixed catalyst system can be used in a dual reactor or a dual process. The two catalysts can be used in one reactor or used in In different reactors connected in series or in parallel, it is expected that blending after production is also feasible. The current major development is the production of bimodal polypropylene resin in a single reactor. The company says that it uses a mixed catalyst to produce bimodal or multimodal resins. The process is easier to control, the molecular weight distribution is more stable, and the flexibility of the copolymer product is more. Big. (b) a metallocene catalyst. Metallocene catalysts are the most attractive olefin polymerization catalysts since the 1990s. The industrialization of metallocene catalysts has created conditions for the production of polypropylene resins with significantly improved physical and mechanical properties, such as the production of ultra-high-rigidity isotactic polypropylene, highly transparent syndiotactic polypropylene, isotactic polypropylene and syndiotactic polypropylene. Blends and ultra-high performance polypropylene impact copolymers. At present, the development work on metallocene polypropylene resin mainly includes: (1) development of products with lower melt flow rate; (2) improvement of yield; (3) development of products with higher melting point; (4) use of mixed catalysts Production of broad molecular weight distribution products; (5) development of random and impact copolymers; (6) development of metallocene catalysts more suitable for existing devices. Many companies have patents related to this: BASF has a number of patents on chromium, molybdenum and tungsten metallocene and bridge metallocene catalysts for the polymerization of cyclic olefins. Some patent applications disclose a process for the preparation of ethylene/CO copolymers using a V11l metallocene catalyst system. The metallocene catalysts developed have high yields at high temperatures and pressures. Finner produces bimodal or broad molecular weight distribution polyolefins using a dual catalyst system (two metallocene catalysts or a Ziegler-Natta/metallocene mixed catalyst), a multi-stage reaction or a multi-reactor process. The reactor blended isotactic and syndiotactic polypropylene was prepared using a special dual metallocene catalyst system. Japan Polymer Chemical Company (a joint venture between Mitsubishi Chemical and Toki Chemical Co., Ltd.) uses a metallocene catalyst system with a styrene copolymer as a carrier to prepare an isotactic polypropylene resin with a high bulk density; a modified support metallocene catalyst system A polyolefin resin having a broad molecular weight distribution is prepared. Hearst develops metallocene catalyst systems for cyclic olefins and palladium catalyst systems. A cocatalyst system that forms a covalent bond with a support such as silicon is disclosed; a new metallocene catalyst that forms a ligand with a boronic acid benzene compound. The DSM can be polymerized by a zirconocene catalyst at a high temperature to produce a polypropylene resin having a broad molecular weight distribution. Copolymers of propylene and 1,2-butadiene can be prepared using a metallocene catalyst. A series of monomodal and bimodal copolymers, EPDMs, and copolymers of propylene with some functional groups using a wide range of transition metal compounds to prepare broad molecular weight distributions are disclosed. Dow's polymer-supported metallocene catalysts have very high yields when used in gas phase polymerization. A monomer having a functional group can be introduced into the propylene polymer using a single-site catalyst having a controlled geometry of a borane compound as a cocatalyst. A carrier-type controlled geometry single-site catalyst has a strong binding ability to a comonomer, and a copolymer having a high percentage of comonomer can be prepared. The use of a special metallocene catalyst system and an activator allows the copolymer to have a broad molecular weight distribution (3-10). The fluorenyl-substituted metallocene catalyst system can produce a bimodal narrow molecular weight distribution of high ethylene content polyolefin resin. The use of a combination of a morocene/borane catalyst and a controlled geometry titanium catalyst in a solution polymerization reaction can have a high yield. |
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