Method for continuously producing polypropylene carbonate by preheating liquid phase method in channelization manner

Abstract

The invention discloses a method for continuously producing polypropylene carbonate by a preheating liquid phase method in a channelization manner, which comprises the following steps: (1) feeding rawmaterials including propylene oxide and a catalyst into a premixing tank according to a certain proportion, uniformly mixing, and pumping into a channelization reactor; (2) preheating carbon dioxideto 40-150 DEG C, pumping into a channelization reactor, and pressurizing to 1-15 MPa; (3) heating to 70-150 DEG C to enable epoxypropane and carbon dioxide to be in contact in a pipelined reactor in the presence of a catalyst, and carrying out a polymerization reaction; (4) after part or all of the polymerization reaction product material flow flows through a cooling section group, separating outpart of the polypropylene carbonate from the polymerization reaction product material flow, and circulating the rest of the polymerization reaction product material flow to the step (1); wherein the catalyst is modified by mixed acid, and the zinc-cobalt double metal cyanide complex catalyst is obtained by reacting water-soluble metal salts of zinc and cobalt in a water-soluble solvent.

Description

technical field [0001] The invention relates to a pipelined and continuous production method of polypropylene carbonate by a preheating liquid phase method. Background technique [0002] Carbon dioxide, one of the main greenhouse gases, has attracted attention as a carbon-resource that can replace traditional fossil fuels for the synthesis of many important chemicals due to its cheap, easy-to-obtain, non-toxic and non-flammable advantages. Polycarbonate materials have great performance advantages, including: high strength, high light transmission, high durability, high light transmission, heat resistance and electrical insulation. In addition, this material is easier to process and dye. Polycarbonate (referred to as PC) is a high molecular polymer containing carbonate groups (-OC(=O)O-) in the molecular chain. carbon dioxide (CO 2 ) can be alternately copolymerized with alkylene oxide to obtain a polypropylene carbonate green material with biodegradable properties. [000...

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Problems solved by technology

[0005] From the perspective of the catalyst used, the prior art adopts zinc-cobalt DMC catalyst in the production of polypropylene carbonate, and the problem of existence is that, in industry, the epoxy monomer mass ratio of adding catalyst and adding will be at least ≤ 1 / 1000 ( That is, when the catalyst dosage is ≤1000ppm, that is, 0.1wt%, the overall production cost and the cost of catalyst residue are relatively low, and have economic value

Since the viscosity of polypropylene carbonate increases with the proportion of carbonate units (F CO2 ) and molecular weight (Mn) increased; this in turn produced two difficult problems, one is F CO2 In contradiction with Mn, since the viscosity of polypropylene carbonate increases with the increase of the number average molecular weight, polypropylene carbonate with large molecular weight hinders CO 2 The insertion reaction, so that the increase in the molecular weight of polypropylene carbonate generally means a lower F CO2

Second, with the F CO2 The increase of polypropylene carbonate also increases the viscosity of polypropylene carbonate, which makes the molecular weight distribution range of polypropylene carbonate products broaden, so there is also polypropylene carbonate polymer molecular weight distribution (PDI) and high F CO2 Contradictory, polypropylene carbonates with low PDI values ​​often cannot simultaneously have high F CO2 , it is more difficult to aggregate into a low PDI value, high F CO2 and high molecular weight polycarbonate

If the temperature is too high, the content of carbonate chains will be low, the molecular weight distribution will be broadened, and the proportion of by-product cyclic carbonate will increase, which will reduce the quality of the product

[0011] Although a small number of continuous flow processes have been developed, there are problems: there is inevitably an amplification effect, which brings many uncertainties to further industrial applications; some continuous flow processes are not fully reacted in a short period of time, and need to increase The reaction time is used to increase the conversion rate, resulting in a decrease in production efficiency

[0012] Another disadvantage of the semi-batch or batch process is that the process has to be stopped in order to remove the product, thus resulting in a loss of time

[0013] Compared with the conventional copolymerization reaction, the particularity of the polycarbonate copolymerization reaction is that increasing the content of carbonate units in polycarbonate is related to optimizing the molecular weight distribution of polypropylene carbonate products. As the molecular weight of propylene ester increases, the viscosity increases accordingly. The high-viscosity copolymerization reaction system restricts the polymerization of carbon dioxide into the polypropylene carbonate molecule. The aggregation of oxides leads to violent polymerization of epoxides, and a large number of polyether chain links are generated in a short period of time, resulting in tailing, which further increases the viscosity of the copolymerization reaction system. Therefore, under the existing technical conditions, high molecular weight polyether Propylene carbonate often means that the content of carbonate units in polypropylene carbonate is low. Correspondingly, polypropylene carbonate with high content of carbonate units often means low molecular weight, or the molecular weight distribution range of polypropylene carbonate products is wide. Polymer molecular weight distribution (PDI) has a higher value, and even has obvious tailing phenomenon; the amplification effect of producing polypropylene carbonate does not exist in isolation, and is also related to increasing the content of carbonate units in polypropylene carbonate and optimizing polycarbonate. The molecular weight distribution of the product of propylene carbonate is related, as the molecular weight of polypropylene carbonate increases, the viscosity increases thereupon, and the heat and mass transfer efficiency of the copolymerization reaction system with high viscosity decreases, and it is easy to form a dead zone in the reaction device, making The amplification effect becomes larger, which also leads to a wide range of molecular weight distribution of polypropylene carbonate products, with a larger PDI value

[0014] In summary, how to increase the content of carbonate units, reduce the proportion of by-product cyclic carbonates in the crude product, increase the molecular weight of the polymerization product polypropylene carbonate while reducing the relative molecular mass distribution coefficient, and solve the amplification effect of large-scale production are Those skilled in the art urgently need to solve the problem, those skilled in the art especially need a kind of technical solution that can solve the above three problems at the same time, but there is no disclosure of this kind of technical solution at present

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