The hottest polypropylene production process 1

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Polypropylene production process

(3) Borstar process. Borstar process (North clamp sample (plus extended meter star bimodal) PP process of Borealis (Nordic chemical) is a new PP production process developed only in 1998. This process is derived from North Star bimodal polyethylene process. The process adopts the same ring tube and gas phase reactor as North Star bimodal polyethylene process. The design is based on Z-N catalyst, and can also use the single active center catalyst under pilot test. Its basic configuration is to use double reactors, namely, loop reactor in series with gas phase reactor to produce homopolymer and random copolymer, and then connect one or two gas phase reactors in series to produce impact copolymer, which depends on the rubber content in the final product. For example, the production of impact copolymer with high rubber content requires a second gas phase copolymerization reactor. In May, 2000, Borealis built the world's first bimodal PP production device with a production capacity of 20 ◆ medical materials in Schwechat, Austria, with a production capacity of 10000 tons/year now and in the future. In the traditional polypropylene process, the polymerization reaction is carried out below the critical point of propylene. In order to prevent light components (such as hydrogen and ethylene) and inert components from generating bubbles, the polymerization temperature is controlled at ℃. The loop reactor of Beixing bimodal polypropylene process can be operated at high temperature (℃) or above the supercritical point of propylene. The polymerization temperature and pressure are very high, which can prevent the formation of bubbles. This is the only polypropylene process polymerized under supercritical conditions. The main characteristics of Beixing bimodal polypropylene technology with bimodal high temperature process can be summarized as follows: advanced catalyst technology, wide polymerization conditions, wide product range and excellent product performance

(a) MgCl2 supported catalyst (BC1) with higher activity is used. The higher the reaction temperature is, the higher the activity is. The activity at 80 ℃ is 60000kg pp/kg cat, so the residual amount of catalyst in the product is very low. In addition, Borstar process can produce all types of products with one catalyst system

(b) by adopting the combined process route of loop reactor and gas-phase fluidized bed reactor, the MWD, isotactic index and comonomer content of products can be flexibly controlled. High temperature or supercritical operation of the loop reactor not only improves the catalyst activity, but also improves the heat transfer capacity of the reactor, reduces the liquid density, increases the solid concentration, and improves the production efficiency of the reactor. The discharge from the loop reactor is directly added to the gas-phase reactor, which does not need to gasify the monomer with steam. The liquid-phase monomer is gasified by the heat of gas-phase polymerization reaction, which reduces the steam consumption. The one-way conversion rate of the reaction is high, which can reach more than 80%, and the circulation amount of monomer is small

(c) since the loop reactor operates under supercritical conditions, the concentration of hydrogen that can be added is almost unlimited, and the gas phase reactor is also suitable for the operation of high hydrogen concentration. This reactor combination has the ability to directly produce products with high melt flow rate and high comonomer content in the reactor. At present, fiber grade products with MFR of more than 1000g/10min and random copolymers with ethylene content of 6% (mass fraction) have been developed

(d) it can produce single peak products with very narrow molecular weight distribution and double peak products with wide molecular weight distribution, which widens the molecular weight distribution of polymers and improves the processability of products. The molecular weight distribution of the polymer varies with the reactor temperature by 3 The cleaning of waste plastics increases and decreases, which can produce products with the required molecular weight distribution. Even for products with high MFR, MWD can also be controlled, making the products have some unique properties, such as low creep and high melt strength; (e) Due to the higher polymerization temperature, the produced polymer has higher crystallinity and isotactic index, and the xylene soluble matter is very low, about 1% (mass fraction). The rigidity under the same impact strength is 10% higher than that of traditional polypropylene products

(f) the distribution of comonomers in random copolymers is very uniform, so they have very good heat sealing and optical properties. Because the reaction condition is above the critical point, only a few polymers are dissolved in propylene, which reduces the cauldron sticking phenomenon when the content of random copolymer is high. The system can add a larger number of comonomers, and the ethylene content in random copolymer can reach up to 10% (mass fraction)

(g) impact copolymer with higher rubber phase content can be produced. One copolymerization reactor can produce impact copolymers with a maximum rubber phase content of 25% (ethylene content of 15%), and two copolymerization reactors can produce impact copolymers with a maximum rubber phase content of 50% (ethylene content of 30%). The comprehensive performance of impact resistance and rigidity of the product is better

(tegracore polyphenylsulfone (PPSU) foam can be used as the core material of various structural foam and sandwich technology h) Borealis developed and applied borapc technology in its Borstar process. The use of proprietary process controller can carry out process control in various ways, realize forward-looking control and edge clamping operation, improve the output by 2%-3%, improve the stability of reaction condition control and product quality, shorten the product transition time, and reduce the transition material

source: China's plastics industry

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