World Polypropylene Technology Development Trend

Polypropylene process technology in the 1990s was basically developed along the main line of improving the economics of the device. There was no major change in the basic process design of polypropylene, but by making major improvements to the catalyst and using larger equipment, the polypropylene device The single-line production capacity is improved and the economy is improved. In terms of products, a large number of high-value-added products such as high melt flow homopolymers, high transparency, low heat-sealing random copolymers, and high-impact copolymers have been developed.

In the new century, polypropylene technology will still have remarkable development 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 develop and will continue to grow steadily for at least the next 10 years. The metallocene/single-site catalyst will expand its product and market scope and begin to develop into the general product market. In terms of process technology, already industrialized technologies will further improve and reduce costs, the average single-line production capacity of new installations will continue to increase, advanced control and forecasting models will be developed, and the integration of production devices and enterprise information technology systems will become even closer.

(l) Catalyst development is still 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 constantly developing new products with better performance, and the performance gap with metallocene catalysts is continuously narrowing.

The recent major progress of the polypropylene Ziegler-Natta catalyst is to broaden the product range of the Ziegler-Natta catalyst system and to develop an electronic system. The product range is continuously expanding, and the product performance is further developed in the following aspects: It is possible to obtain products with high melt flow rate without visbreaking in the reactor (for example, for the fiber market, with a melt flow rate of up to 1800 g/10 min. Product); improve the crystallinity and isotacticity of the polymer by improving the catalyst, producing a more rigid product; reducing the heat sealing temperature of the product; improving the optical performance; using two-stage polymerization bimodal resin production technology to make the polypropylene resin The broadening of the molecular weight distribution enables the product to have a combination of optimized rigidity and impact resistance properties; a product with a polydispersity of 3.2-10 can be produced using a reactor system consisting of two homopolymerization reactors; deflection of the product Modulus can reach more than 2300 MPa.

In addition, in the future, a mixed catalyst system of metallocene and traditional Ziegler-Natta catalysts will also be developed. This mixed catalyst system can use dual reactors or dual processes. Both 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 progress is the production of bimodal polypropylene resins in a single reactor. The Star Corporation claims that the use of mixed catalysts to produce bimodal or multimodal resins, the process is easier to control, the molecular weight distribution is more stable, and the copolymer products are more flexible. Big.

(b) Metallocene catalysts. Metallocene catalysts are the most interesting olefin polymerization catalysts since the 1990s. 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-strength isotactic polypropylene, highly transparent syndiotactic polypropylene, isotactic polypropylene and syndiotactic polypropylene. Blends and ultra-high-performance polypropylene impact copolymers.

The current developments in metallocene polypropylene resins mainly include: (1) development of products with lower melt flow rates; (2) improvement of productivity; (3) development of products with higher melting points; (4) use of mixed catalysts Production of products with broad molecular weight distribution; (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 many patents on chromium, molybdenum and tungsten metallocenes and bridged metallocene catalysts for cycloolefin polymerization. Some patent applications disclose methods for preparing ethylene/CO copolymers using a Group V11l metallocene catalyst system. The metallocene catalysts developed have high yields at high temperatures and pressures. The Finnner uses bi-catalyst systems (two metallocene catalysts or Ziegler-Natta/metallocene mixed catalysts), multi-stage reaction or multi-reactor methods to prepare bimodal or broad molecular weight distribution polyolefins. Reactor-blended isotactic and syndiotactic polypropylenes were prepared using a special dual metallocene reminder system. Japan Polymer Chemical Co., Ltd. (a joint venture between Mitsubishi Chemical and Tosoh Corporation) manufactures isotactic polypropylene resin with high bulk density using a styrene copolymer-supported metallocene catalyst system; and uses a modified support metallocene catalyst system. A wide molecular weight distribution polyolefin resin was prepared. Hearst develops metallocene catalyst systems for cycloolefins and palladium catalyst systems. A cocatalyst system that forms a covalent bond with a support such as silicon, and a novel metallocene catalyst that forms a ligand with a boronic acid benzene compound are disclosed.

DSM can be produced by polymerization of zirconocene catalyst at high temperature to produce polypropylene resin with a wide molecular weight distribution. Copolymers of propylene and 1,2-butadiene can be prepared using metallocene catalysts. A series of unimodal and bimodal copolymers, EPDMs, and copolymers of propylene and some functional groups with a wide range of molecular weight distributions using special transition metal compounds are disclosed. Dow polymer-supported metallocene catalysts have very high yields when used in gas phase polymerizations. Monomers with functional groups can be introduced into the propylene polymer using a single-site catalyst of controlled geometry with a borane compound as a cocatalyst. A carrier-controlled geometry single-site catalyst has strong binding ability to comonomer and can produce copolymers with a high percentage of comonomer. The use of special metallocene catalyst systems and activators allows the copolymer to have a broad molecular weight distribution (3-10). The mercapto-substituted metallocene catalyst system can produce a bimodal, narrow molecular weight distribution, high ethylene content polyolefin resin. The use of a mixture of a metallocene/borane catalyst and a controlled geometry titanium catalyst in a solution polymerization reaction can have a very high yield.