A method for improving the quality of polycarbonate-polyether polyol produced by liquid phase method

Abstract

The invention discloses a method for improving the quality of polycarbonate-polyether polyol produced by a liquid phase method. The method comprises the following steps: (1) pumping raw materials including a chain transfer agent, an epoxy compound, a catalyst and carbon dioxide from an inlet of a straight pipe type reactor, and contacting the chain transfer agent, the epoxy compound and carbon dioxide in a first heating section set to carry out polymerization reactions; (2) making the reaction liquid flow to a second heating section set until the content of polycarbonate-polyether polyol in the reaction liquid is not lower than 70%; (3) making part or all of the polymerization reaction product material flow to flow through a cooling section set to separate out part of polycarbonate-polyether polyol, and circulating the rest of the polymerization reaction product material flow back to the step (1); wherein the catalyst is a zinc-cobalt double-metal cyanide complex catalyst obtained by reacting water-soluble metal salts of zinc and cobalt in a water-soluble solvent; the catalyst is modified by a mixed acid during synthesis, and the mixed acid comprises at least one organic acid and at least one water-soluble inorganic acid.

Description

technical field [0001] The invention relates to a method for improving the quality of polycarbonate-polyether polyol produced by liquid phase method. Background technique [0002] Polycarbonate-polyether polyol is a kind of polyol with carbonate group in the molecule and hydroxyl group at the end of the molecular chain. carbon dioxide (CO 2 ) and epoxy compound regulation copolymerization method is CO 2 A chain transfer agent is added during the copolymerization with epoxide, and the molecular weight of the product is controlled by controlling the chain transfer of the reaction. Studies have shown that 20wt% CO 2 CO 2 Compared with the preparation process of traditional polyether polyols, the preparation process of polycarbonate-polyether polyols can reduce 11-19% of greenhouse gas emissions and 13-16% of energy consumption. Therefore, CO 2 The method of regulating copolymerization with epoxy oxide has broad application prospects and high industrial value. [0003] At ...

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Problems solved by technology

[0005] When adopting zinc-cobalt DMC catalyzer to synthesize polycarbonate-polyether polyol, the problem of existence is, in industry, add catalyzer and the epoxy monomer mass ratio of adding will at least ≤ 1 / 1000 (that is catalyst charging ≤ 1000ppm, Promptly 0.1wt%), the overall production cost and the cost of catalyst residues are relatively low, and have economic value

Otherwise, the catalyst has no application value due to the increase in production cost due to the excessive addition of the catalyst

An important means of controlling the molecular weight of polycarbonate-polyether polyols with smaller molecular weights is to add a higher proportion of initiators, generally 1 / 50 to 1 / 90 of the molar number of epoxy monomers. Under such conditions, Most of the catalysts will lose activity; or although a very small number of catalysts still maintain weak activity, the reaction time is greatly prolonged (more than 12 hours) to obtain polymers, which is due to the fact that the reaction time is actually caused by a higher proportion of the initiator Catalyst deactivation, which prolongs the activation process of the catalyst for the reactants (by hours)

It takes longer reaction time and more energy consumption, which increases the production cost

[0006] In addition, under the conditions of the above-mentioned higher ratio of initiator addition, the structural ratio of polycarbonate in the polycarbonate-polyether polyol structure obtained by synthesis will be reduced (<50%), that is, the fixation of carbon dioxide rate reduction

Because the addition of a higher proportion of initiator will cause a large number of catalyst active sites to be quenched or occupied, the macroscopic manifestation is that the catalyst activity is reduced or even deactivated

The reduction of the carbon dioxide fixation rate indicates that the proportion of the low-cost carbon dioxide raw material in the polymer is reduced, which means that the proportion of the higher-cost epoxide is increased, which leads to an increase in the production cost of the polymer on the one hand, and on the other hand, is beneficial to energy saving and emission reduction. (Consumption of CO2) is also less effective

Correspondingly, polycarbonate-polyether polyols with high carbonate unit content are often accompanied by low molecular weight, or the molecular weight distribution range of polycarbonate-polyether polyol products is wide, and the polymer molecular weight polydispersity index (PDI ) has a higher value, and even has obvious tailing phenomenon; the amplification effect of producing polycarbonate-polyether polyol does not exist in isolation, and it is also related to the increase in the content of carbonate units in polycarbonate-polyether polyol and Improving the molecular weight distribution of the product is related. As the molecular weight of polycarbonate-polyether polyol increases, the viscosity increases. The heat and mass transfer efficiency of the high-viscosity copolymerization reaction system decreases, and it is easy to form a dead zone in the reaction device. make the amplification effect bigger

[0022] Therefore, improving the carbonate unit content of polycarbonate-polyether polyol, optimizing the molecular weight distribution of the product of polycarbonate-polyether polyol and solving the amplification effect of large-scale production of polycarbonate-polyether polyol When, it is necessary to optimize and improve from multiple aspects such as the catalyst of polycarbonate-polyether polyol, polycarbonate-polyether polyol copolymerization reaction process and polycarbonate-polyether polyol synthesis equipment, those skilled in the art There is an urgent need for a technical solution that can solve the above three problems at the same time, but there is no solution yet

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