Method for preparing aliphatic polycarbonates by catalyzing by metal cyanide coordination catalyst

Abstract

The invention discloses a method for preparing aliphatic polycarbonates by catalyzing by the metal cyanide coordination catalyst. In a high pressure reactor, the metal cyanide coordination catalyst is utilized to catalyze epoxide and carbon dioxide body or solution copolymerization, wherein, the copolymerization temperature is 20-150 DEG C; the carbon dioxide pressure is 0.5-10MPa; the reaction time is 1-48h; the catalyst concentration is 1-100kg epoxide / g catalyst; the polymerization activity is more than 1.0kg of polymer / g catalyst; the weight-average molecular weight of the copolymer is more than 80 thousand; the molecular weight distribution is 1.5-4; the alternation degree of the copolymer is more than 90%; the cyclic carbonate by-product is less than 5wt%; the CO2 fixed rate of CO2 / epoxypropane copolymer is more than 40wt%; and the CO2 fixed rate of CO2 / cyclohexene oxide copolymer is more than 30wt%.

Description

Technical field [0001] The invention belongs to the field of polymer material synthesis, and specifically relates to a method for preparing aliphatic polycarbonate catalyzed by a metal cyanide coordination catalyst. Background technique [0002] Degradable polymer materials are one of the promising polymer materials. Among them, from CO 2 The direct synthesis of degradable aliphatic polycarbonate is due to the use of very cheap non-toxic CO 2 It has become a hot issue in the research field of degradable polymer materials. The key to its degradability is to obtain completely alternating CO 2 Copolymer. [0003] In the prior art, double metal cyanide (DMC) is used to catalyze epoxide and CO 2 Copolymerization to CO 2 The main problems of copolymers are: a considerable proportion of polyether exists in the structure of the resulting product and the content of cyclic carbonate in the product is relatively high. The DMC catalyst disclosed in the prior art catalyzes propylene oxide (PO...

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Problems solved by technology

[0003] In the prior art, double metal cyanide (DMC) is used to catalyze epoxide and CO 2 Copolymerization into CO 2 The main problems of the copolymer are: there is a considerable proportion of polyether in the structure of the obtained product and the content of cyclic carbonate in the product is relatively high

[0006] Another example: Early U.S. Patent US4500704 adopts ethylene glycol monomethyl ether as the cobalt-zinc bimetallic catalyst of the external ligand to catalyze propylene oxide (PO) and CO 2 Copolymerization, polymerization at 35°C for 48h under a polymerization pressure of 700psi, a copolymer with a number average molecular weight of 23,000 was obtained, and the glass transition temperature of the product was T g Only 8°C, indicating that its content of carbonate chains is low (full alternating PO / CO 2 Copolymer T g >35°C); In addition, the double metal cyanide catalysts disclosed in US patents US6713599, US6762278 and US4826053 etc. catalyze CO 2 The technology of copolymerization also has the same problem, that is, the molecular weight of the product is low, and the weight fraction of polycarbonate in the polymer is generally also lower than 20wt%, while the content of cyclic products is high, and the catalytic activity is low

[0007] The inventor's research group once adopted the Zn disclosed in Chinese patent ZL 200710066763.6 3 [Co(CN) 6 ] 2 (ZHCC)-based series of double metal cyanide catalysts (including supported double metal cyanide catalysts) catalyze epoxides such as PO, cyclohexene oxide (CHO) and CO 2 Copolymerization (Polymer, 2004, 45, 6519; J.Polym.Sci.Part A: Polym.Chem., 2004, 42, 5284; J.Polym.Sci.Part A: Polym.Chem., 2008, 46, 3128; Acta Catalytica Sinica, 2006, 27(4), 355), obtained PO / CO 2 Copolymers and CHO / CO 2 Copolymer, showing extremely high catalytic activity (>1kg polymer / g catalyst), the catalytic efficiency is 5 to 100 times that of traditional catalysts, but the degree of alternation of the obtained polymerization products is not ideal, such as for PO / CO 2 Copolymer, the degree of alternation is generally lower than 60%, the weight fraction of cyclic product by-products in the product can be controlled at 20wt% or less, and the weight average molecular weight is usually <40000

[0008] In summary, in the prior art, DMC is used to catalyze epoxide / CO 2 Copolymerization to obtain aliphatic polycarbonate cannot achieve catalytic epoxide and CO under the premise of high activity 2 The copolymerization is PO / CO 2 Alternate copolymerization, so the biodegradability of the obtained product becomes poor; a large amount of cyclic by-products are produced during the polymerization process, which not only consumes epoxy monomer, but also causes the separation problem of the product

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