The hottest polypropylene production process

  • Detail

Polypropylene production process

bulk bamboo powder water evaporation gas phase combined process

bulk gas phase combined process mainly includes Spheripol process of Basel company, Hypol process of Mitsui chemical company of Japan, Borstar process of Nordic chemical company, etc

(1) Spheripol process. Spheripol process was successfully developed by Basell polyolefin company. Since its first industrialization in 1982, this technology is by far the most successful and widely used polypropylene production process. Spheripol process is a polymerization process combining liquid-phase prepolymerization with liquid-phase homopolymerization and gas-phase copolymerization. The process uses high-efficiency catalyst. The particle size of PP powder produced by the catalyst is spherical, with large and uniform particles, adjustable distribution, which can be both wide and narrow. It can produce all kinds of products with full range and multi-purpose. Its homopolymer and random copolymerization products are characterized by high clarity, good optical properties and no odor. The liquid phase loop reactor used in Spheripol process has the following advantages:

(a) it has a high reactor time-space yield (up to 400kgpp/h.m3), small reactor volume and low investment

(b) the reactor has simple structure and low material requirements. Low temperature carbon steel can be used. The design and manufacture are simple. Due to the small pipe diameter (DN500 or DN600), the pipe wall is thin even if the pressure is high

(c) the straight leg part of the reactor with jacket can be used as the pillar of the reactor frame, which reduces the investment

(d) due to the small volume of the reactor, short residence time, fast product switching and less transition materials

(E) polymer particles are suspended in propylene liquid, and there is good heat transfer between polymer and propylene. Using cooling jacket to withdraw the reaction heat, the heat transfer area per unit volume is large, the heat transfer coefficient is large, and the overall heat transfer coefficient of the loop reactor is as high as 1600w/(m2. ℃)

(f) the slurry in the loop reactor is circulated at a high speed by an axial flow pump, and the fluid flow rate is as high as 7m/s. therefore, the polymer slurry can be stirred evenly, the catalyst system can be evenly distributed, the polymerization reaction conditions can be easily and accurately controlled, the product quality is uniform, it is not easy to produce hot spots, it is not easy to stick to the wall, and the energy consumption of the axial flow pump is also low

(g) the concentration of polymer slurry in the reactor is high (mass fraction is greater than 50%), and the one-way conversion rate of the reactor is high, and the one-way conversion rate of homopolymer propylene is 50%-60%. These characteristics make the loop reactor very suitable for the production of homopolymers and random copolymers. At the beginning of Spheripol process, gf-2a, ft-4s, ucd-104 and other high-efficiency catalysts are used. The catalyst activity reaches 40kgpp/gcat, and the isotacticity of the product is 90%-99%, which can not remove ash and random substances

at present, this technology has developed to the second generation. Compared with the first generation technology using single loop reactor, the second generation technology using double loop reactor can significantly improve the operating pressure and temperature, and can produce bimodal polypropylene. The catalyst system adopts the fourth or fifth generation Z-N high-efficiency catalyst, increases the hydrogen separation and recovery unit, improves the high-pressure and low-pressure degassing equipment of polymer, improves the steam, drying and propylene accident discharge unit, increases the operational flexibility, improves the efficiency, and significantly reduces the consumption of raw material monomer and various utilities. The obtained product has a more uniform particle size and a wider range of melt flow index (from 0..0g/10min), which can produce a new PP brand with high rigidity, high crystallinity and low heat sealing temperature. The impact copolymerization of Spheripol process is produced by gas phase method, and the reactor is one or two dense phase fluidized bed reactors in series. The reactor adopts gas-phase dense phase fluidized bed. One gas-phase reactor system can be used to produce impact copolymers with ethylene content of 8% - 12% (mass fraction). If it is necessary to produce special impact copolymers with higher rubber phase content and more than one dispersed phase (such as low stress whitening products), two gas-phase reactor systems need to be designed to maintain the independence of gas-phase composition and operating conditions in the two gas-phase reactor systems, Two different copolymers can be obtained and added to the homopolymer

the two-step process of steaming and drying is used to treat polymers, which can easily condense the steam in the steam tail gas, while the manipulator increases automation in the plastic production workshop and laboratory to separate pure hydrocarbon monomers, which can completely recycle the hydrocarbons in the tail gas and reduce the consumption of monomers. The closed-circuit nitrogen drying system also reduces the nitrogen consumption of the unit. In addition, Spheripol process adopts the modular design method, which can meet the requirements of different users. It is easy to build step by step (such as putting on the homopolymer production system first and adding the gas-phase reaction system at the right time), and the production capacity of the device is also easy to expand. Spheripol process has strict and perfect safety system design, so that the device has high operational stability and safety. The new generation Spheripol process uses pure additives to join the system, which makes the product quality more uniform and stable, and facilitates product switching. Spheripol process technology can provide a full range of products, including homopolymers, random copolymers, impact copolymers, terpolymers (ethylene propylene butene copolymers). The MFR range of its homopolymer products is 0 G/10min, MFR of industrial products reaches 1860g/10min (special non granulated products), and bending modulus of high rigid products reaches 2300mpa. The ethylene content in the industrial random copolymer products is as high as 4.5% (mass fraction), and there are ethylene propylene butene terpolymer products. The initial temperature of film sealing is as low as 110 ℃, which can compete with the random copolymerization with high ethylene content produced by gas-phase process. Impact copolymer products have good comprehensive properties of rigidity and impact resistance. The ethylene content of the product can be as high as 25% (40% rubber phase), and has the ability to reach 40% ethylene content (60% rubber phase). In addition, Spheripol process can flexibly increase the polymer dispersion index (PI) by adding peroxide and double loop reactor according to the needs of products By adjusting the molecular weight distribution of products, products with MFR up to 1800g/10min and large particles without granulation can be directly produced in the reactor, making the Spheripol process highly competitive. Another feature of Spheripol process is advanced catalyst technology. Basell has a variety of catalyst systems that can be used in Spheripol process to produce different types of products. For example, mc-gf2a catalyst is used to produce homopolymers, otherwise it is easy to cause dangerous situations such as machine failure and personal injury. Mc-m1 is used to produce large spherical impact copolymers, homopolymers and random copolymers, while some high modulus homopolymers use d-electron donors (dicyclopenyl dimethoxy silane, referred to as dcpmc), Some special impact copolymers with high ethylene content also need to use special catalysts. Basell company has registered a number of patents for diethyl catalysts and has also commercialized products, such as mc-126 and mc-127. Diethyl catalysts have high polymerization activity (up to 100tpp/kg cat) and long life, good isotactic index control, high hydrogen sensitivity, and narrow molecular weight distribution of products. At present, there are nearly 100 polypropylene units produced by Spheripol process in the world, with a total production capacity of about 14.6 million tons/year, accounting for 36.8% of the total production capacity of polypropylene in the world. Among them, the production capacity of North America is 4.03 million tons/year, that of Asia is 4.19 million tons/year, that of Western Europe is 4.015 million tons/year, that of central and Eastern Europe is 620000 tons/year, and that of the Middle East and Africa is 1.315 million tons/year

(2) Hypol process. Hypol process was successfully developed by Mitsui chemical company in the early 1980s. This process uses hy-hs-ii catalyst (tk-ii), which is a multi-stage polymerization process. It integrates the advantages of bulk propylene polymerization process with the advantages of gas-phase polymerization process. It is a combined process technology that can produce polypropylene products of various brands without deashing and removing random substances. The technology of this process is basically the same as that of Spheripol process. The main difference is that homopolymer in the Hypol process cannot be discharged from the bypass of the gas phase reactor, and part of the flash steam from the high-pressure degassing tank is pumped back to the gas phase reactor. In the production of homopolymer, the first gas-phase reactor actually plays a flashing role. The gas phase reactor is based on the special design of fluidized bed and stirring (scraper) vessel. When producing impact copolymer, the reactor has no dirt and does not need cleaning. During the production of homopolymer, the gas-phase reactor can be used as the final polymerization kettle, which improves the production capacity. Moreover, the gas-phase reactor is flexible and can produce impact resistant copolymers with 25% ethylene content

based on the technology provided by diethyl ether, Mitsui has produced the 5th generation rk-rh catalyst, whose activity is times higher than that of the 4th generation catalyst. Hypol process can produce PP products with homopolymer, random and impact resistance, and MFR range is 0 Kg/10min, the product has high stereoregularity and rigidity, and the film has good optical properties (transparency and gloss); Directional varieties such as monofilament, strip and fiber have good processability (directivity), which can make the finished products have good properties, and the melt flow rate is very high. Varieties used for high-speed injection molding can be directly polymerized without heat treatment and other measures. At present, there are 22 polypropylene units produced by Hypol process in the world, with a total production capacity of about 2.51 million tons/year, accounting for about 6.3% of the total production capacity of polypropylene in the world

Copyright © 2011 JIN SHI