Polymeric schiff base metal compound, preparation method and application thereof

Abstract

The application relates to the technical field of organic synthesis, in particular to a polymeric Schiff base metal compound, a preparation method and application thereof, the polymeric Schiff base metal compound has structures shown in formula I to formula IV. The polycentered polymeric Schiff base metal compound provided by the application has the advantages of simple synthesis method, easy purification and high product purity. Since long-chain polyether glycol is introduced, the melting point of the Schiff base catalyst is low, and the Schiff base catalyst is better dispersed in glycolide. The polymeric Schiff base catalyst has a polycentered structure, and the catalytic activity of the original single-center catalyst can be improved through the synergistic coordination effect between the poly-metal centers. The polymeric Schiff base catalyst provided by the application has high catalytic activity, and when the polymeric Schiff base catalyst is used to catalyze the ring-opening polymerization of glycolide to generate polyglycolic acid, the polymerization reaction speed is high. Experimental results show that when the polyglycolic acid is prepared by using the catalyst provided by the application, the reaction yield can reach 97.2%.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a polymeric Schiff alkali metal compound, its preparation method, and its application. Background Technology

[0002] Polyglycolic acid (PEG) is a synthetic polymer material with good biodegradability and biocompatibility. It possesses excellent processing properties, mechanical strength and modulus, as well as high solvent resistance and high gas barrier properties, making it suitable for medical polymer materials (such as surgical sutures and artificial skin). PEG can be decomposed into environmentally friendly compounds by water, microorganisms, and enzymes, thus showing significant promise as a biodegradable plastic for applications in packaging materials and degradable films.

[0003] Currently, polyglycolic acid (PGA) is generally prepared using cyclic ester ring-opening polymerization, such as the ring-opening polymerization of glycolide. In this process, stannous octoate is typically used as the catalyst, exhibiting significantly higher catalytic activity than other metal catalysts. In the commercial production of aliphatic polyesters, increasing the polymerization rate helps improve production efficiency and reduce costs. Increasing the polymerization temperature is one solution to this problem. However, increasing the polymerization temperature disrupts the reaction equilibrium, increases the depolymerization rate of the product, and severely affects polymer chain growth. It also increases side reactions, leading to an increase in the yellowness index of the product. Another solution to increase the polymerization rate is to increase the amount of metal catalyst. However, in the ring-opening polymerization of cyclic esters, adding excessive metal catalyst to the reaction system can result in residual metal compounds in the product, reducing its thermal stability.

[0004] Therefore, there is a need to find catalysts with higher activity for the synthesis of cyclic ester polymers. In recent years, Schiff base catalysts have been widely used due to their high catalytic activity. However, their synthesis often requires multiple reaction steps, and each step requires a large amount of solvent purification, making the preparation process cumbersome, causing serious environmental pollution, and resulting in low yields. Moreover, current Schiff base catalysts have poor solubility and high melting points, making them difficult to disperse in monomers, which affects the catalytic activity of the catalysts. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a polymeric Schiff alkali metal compound, its preparation method and application, wherein the Schiff alkali metal compound has high catalytic activity.

[0006] To achieve the above objectives, the present invention provides a polymeric Schiff alkali metal compound having any one of the structures of formulas I to IV:

[0007]

[0008] Wherein, R1 is selected from substituted or unsubstituted alkyl, cycloalkyl, aryl or heteroaryl groups;

[0009] R2 is selected from the group remaining after removing two hydroxyl groups from polyether glycol;

[0010] R3 is selected from hydrogen, halogen, nitro, substituted or unsubstituted alkyl or alkoxy groups;

[0011] R4 is selected from halogen, substituted or unsubstituted alkoxy or ester groups;

[0012] M1 is selected from zinc, cobalt, nickel, or tin;

[0013] M2 is selected from aluminum, indium, chromium, iron, manganese, cerium, or yttrium;

[0014] n represents the degree of aggregation.

[0015] R1 is preferably a substituted or unsubstituted C2-C6 alkyl, C3-C12 cycloalkyl, C6-C12 aryl, or C4-C11 heteroaryl; more preferably a substituted or unsubstituted C2-C6 alkyl, C5-C6 cycloalkyl, C6 aryl, or C4-C5 heteroaryl. The aryl or heteroaryl group is preferably a monocyclic aryl or heteroaryl group. The heteroatom of the heteroaryl group includes, but is not limited to, one or more of N, O, and S. R1 is further preferably a substituted or unsubstituted C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, or phenyl group.

[0016] The substituent of R1 is preferably one or more selected from halogen, nitro, hydroxyl, amino, cyano, C1-C6 alkyl, C1-C6 alkoxy, C1-C6 haloalkyl, and C1-C6 haloalkoxy. More preferably, it is one or more selected from fluorine, chlorine, bromine, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, methoxy, ethoxy, propoxy, fluoromethyl, difluoromethyl, and trifluoromethyl.

[0017] In some specific embodiments of the present invention, R1 is selected from ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, 2-methyl-1,3-propanediamine, 2,2'-dimethylpropanediamine, 1,4-butanediamine, 1,2-cyclohexanediamine, o-phenylenediamine, 3-nitro-o-phenylenediamine, 4-nitro-o-phenylenediamine, 3-bromo-o-phenylenediamine, 4-bromo-o-phenylenediamine, 4,5-dibromo-o-phenylenediamine, 4-bromo-5-fluoro-o-phenylenediamine, 4-bromo-5-methyl-o-phenylenediamine, 4-chloro-5-bromo-o-phenylenediamine, 3-methyl-5-bromo-o-phenylenediamine, The group remaining after removing two amino groups from 4-methoxy-o-phenylenediamine, 4-chloro-5-fluoro-o-phenylenediamine, 4,5-dichloro-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-trifluoromethyl-o-phenylenediamine, 3-chloro-o-phenylenediamine, 3-chloro-5-trifluoromethyl-o-phenylenediamine, 4,5-difluoro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 3-fluoro-o-phenylenediamine, 3,4-difluoro-o-phenylenediamine, 3,5-difluoro-o-phenylenediamine, 4,5-dimethyl-o-phenylenediamine, 4-methyl-o-phenylenediamine, 3,5-dimethyl-o-phenylenediamine, or 4-chloro-5-methyl-o-phenylenediamine.

[0018] R2 is preferably a group remaining after removing two hydroxyl groups from a polyether glycol, more preferably a group remaining after removing two hydroxyl groups from polyethylene glycol or polypropylene glycol. In some specific embodiments of the present invention, R2 is a group remaining after removing two hydroxyl groups from polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, polyethylene glycol 1500, polyethylene glycol 2000, polyethylene glycol 3000, polypropylene glycol 600, polypropylene glycol 1000, polypropylene glycol 1500, polypropylene glycol 2000, polypropylene glycol 3000, polytetrahydrofuran 650, polytetrahydrofuran 850, polytetrahydrofuran 1000, polytetrahydrofuran 2000, or polytetrahydrofuran 2900.

[0019] The R3 is preferably hydrogen, halogen, nitro, substituted or unsubstituted C1-C6 alkyl or C1-C6 alkoxy; more preferably hydrogen, halogen, nitro, substituted or unsubstituted C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C1 alkoxy, C2 alkoxy, C3 alkoxy, C4 alkoxy, C5 alkoxy, C6 alkoxy; even more preferably hydrogen, halogen, nitro, substituted or unsubstituted methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, methoxy, ethoxy, n-propoxy or isopropoxy.

[0020] The substituent of R3 is preferably one or more selected from halogen, nitro, hydroxyl, amino, cyano, C1-C6 alkyl, C1-C6 alkoxy, C1-C6 haloalkyl, and C1-C6 haloalkoxy. More preferably, it is one or more selected from fluorine, chlorine, bromine, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, methoxy, ethoxy, propoxy, fluoromethyl, difluoromethyl, and trifluoromethyl.

[0021] In some specific embodiments of the present invention, R3 is selected from hydrogen, -CH3, -CH2CH3, -CH(CH3)2, -OCH(CH3)2, -C(CH3)3, -OCH3 or -OCH2CH3.

[0022] The R4 is preferably a halogen, a substituted or unsubstituted C1-C6 alkoxy or ester group; more preferably a fluorine, chlorine, bromine, a substituted or unsubstituted methoxy, ethoxy, n-propoxy, isopropoxy, methyl ester or ethyl ester group.

[0023] The substituent of R4 is preferably one or more selected from halogen, nitro, hydroxyl, amino, cyano, C1-C6 alkyl, C1-C6 alkoxy, C1-C6 haloalkyl, and C1-C6 haloalkoxy. More preferably, it is one or more selected from fluorine, chlorine, bromine, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, methoxy, ethoxy, propoxy, fluoromethyl, difluoromethyl, and trifluoromethyl.

[0024] In some specific embodiments of the present invention, R4 is selected from -OCH3, -OCH2CH3, -OCH(CH3)2, -Cl or -OOCCH3.

[0025] The degree of aggregation is n, which is preferably any integer from 5 to 100.

[0026] This invention introduces a long-chain polyether glycol into the structure of the aforementioned polymeric Schiff alkali metal compound, resulting in higher solubility, a lower melting point, and better dispersibility in glycolide. This Schiff alkali metal compound exhibits high catalytic activity and a high reaction yield as a catalyst for the preparation of cyclic ester polymers.

[0027] This invention provides a method for preparing the above-mentioned polymeric Schiff alkali metal compound, comprising the following steps:

[0028] a) Reacting polyether glycol with an alkali metal to obtain a polyether glycol alkali metal salt;

[0029] b) The polyether diol alkali metal salt and chloromethyl salicylaldehyde were reacted to obtain the polyether diol bis-salicylaldehyde compound;

[0030] c) React the polyether diol bis(salicylaldehyde) compound and the diamino compound to obtain the Schiff base polymer;

[0031] d) React Schiff base polymers with metal compounds to obtain polymeric Schiff base metal compounds.

[0032] The polyether glycol in step a) above is preferably at least one of polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, polyethylene glycol 1500, polyethylene glycol 2000, polyethylene glycol 3000, polypropylene glycol 600, polypropylene glycol 1000, polypropylene glycol 1500, polypropylene glycol 2000, polypropylene glycol 3000, polytetrahydrofuran 650, polytetrahydrofuran 850, polytetrahydrofuran 1000, polytetrahydrofuran 2000, and polytetrahydrofuran 2900.

[0033] The preferred reaction temperature for the polyether glycol and the alkali metal is 25–100°C, and the preferred reaction time is 1–10 h. The preferred molar ratio of the polyether glycol to the alkali metal is 1:2.1–1:4. The preferred alkali metal includes one of lithium, sodium, and potassium.

[0034] The present invention does not specifically limit the source of the above-mentioned chloromethyl salicylic aldehyde, which can be commercially available or prepared according to methods known to those skilled in the art. Preferably, the synthesis of the chloromethyl salicylic aldehyde includes the following steps:

[0035] Salicylaldehyde compounds are reacted with formaldehyde compounds in the presence of a catalyst to produce chloromethylsalicylaldehyde.

[0036] The salicylaldehyde compounds preferably include at least one of salicylaldehyde, 3-methylsalicylaldehyde, 3-methoxysalicylaldehyde, 3-ethoxysalicylaldehyde, 3-tert-butylsalicylaldehyde, 3-bromosalicylaldehyde, 3-chlorosalicylaldehyde, 5-chlorosalicylaldehyde, 5-methylsalicylaldehyde, and 5-nitrosalicylaldehyde.

[0037] The formaldehyde compounds preferably include at least one of formaldehyde, trioxymethylene, or paraoxymethylene.

[0038] The preferred molar ratio of the salicylaldehyde compound to the formaldehyde compound is 1:1 to 1:2.

[0039] The preferred temperature for the reaction is 0–95°C, and the preferred reaction time is 2–60 h.

[0040] The catalyst is preferably at least one of HCl, concentrated sulfuric acid, phosphoric acid, acetic acid, aluminum trichloride, zinc chloride, and tin chloride.

[0041] In step b), the molar ratio of the chloromethyl salicylic aldehyde and the polyether diol alkali metal salt is preferably 2:1 to 3:1, the reaction temperature is preferably 20 to 120°C, and the reaction time is preferably 2 to 48 hours.

[0042] In some specific embodiments of the present invention, the reaction equation for step b) is as follows:

[0043]

[0044]

[0045] M is selected from lithium, sodium, or potassium.

[0046] In step c), the molar ratio of the polyether diol bisalicylic acid compound and the diamino compound is preferably 1:0.6 to 1.5, the reaction temperature is preferably 20 to 100°C, and the reaction time is preferably 2 to 48 hours.

[0047] The diamino compound preferably includes ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, 2-methyl-1,3-propanediamine, 2,2'-dimethylpropanediamine, 1,4-butanediamine, 1,2-cyclohexanediamine, o-phenylenediamine, 3-nitro-o-phenylenediamine, 4-nitro-o-phenylenediamine, 3-bromo-o-phenylenediamine, 4-bromo-o-phenylenediamine, 4,5-dibromo-o-phenylenediamine, 4-bromo-5-fluoro-o-phenylenediamine, 4-bromo-5-methyl-o-phenylenediamine, 4-chloro-5-bromo-o-phenylenediamine, 3-methyl-5-bromo-o-phenylenediamine, 4- At least one of methoxy-o-phenylenediamine, 4-chloro-5-fluoro-o-phenylenediamine, 4,5-dichloro-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-trifluoromethyl-o-phenylenediamine, 3-chloro-o-phenylenediamine, 3-chloro-5-trifluoromethyl-o-phenylenediamine, 4,5-difluoro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 3-fluoro-o-phenylenediamine, 3,4-difluoro-o-phenylenediamine, 3,5-difluoro-o-phenylenediamine, 4,5-dimethyl-o-phenylenediamine, 4-methyl-o-phenylenediamine, 3,5-dimethyl-o-phenylenediamine, and 4-chloro-5-methyl-o-phenylenediamine.

[0048] In some specific embodiments of the present invention, the reaction equation for step c) is as follows:

[0049]

[0050] In step d), the metal compound preferably includes at least one of zinc chloride, zinc acetate, ethyl zinc, stannous chloride, ferric chloride, indium chloride, cobalt acetate, aluminum isopropoxide, aluminum ethoxylate, nickel acetate, and triethylaluminum.

[0051] Preferably, the molar ratio of the diamino compound residues to the metal compound in the Schiff base polymer is 1:1 to 1:1.2, the reaction temperature is preferably 20 to 120°C, and the reaction time is preferably 2 to 100 h.

[0052] In some specific embodiments of the present invention, the reaction equations for steps c) and d) are as follows:

[0053]

[0054] This invention provides the application of the above-mentioned polymeric Schiff base metal compound or the polymeric Schiff base metal compound prepared by the above-mentioned preparation method as a catalyst in the preparation of cyclic ester polymers.

[0055] Preferably, the cyclic ester polymer is polyglycolic acid.

[0056] Based on this, the present invention provides a method for preparing polyglycolic acid, comprising the following steps:

[0057] Under an inert atmosphere, glycolide or a mixture of glycolide and an epoxy compound is reacted in the presence of a catalyst and an initiator to obtain polyglycolic acid.

[0058] The catalyst is the above-mentioned polymeric Schiff alkali metal compound or the polymeric Schiff alkali metal compound prepared by the above preparation method.

[0059] The initiator is preferably an alcohol.

[0060] The preferred mass ratio of the catalyst to the glycolide is 1:(20-2000).

[0061] The preferred molar ratio of the initiator to glycolide is 1:(100-2000).

[0062] The preferred ratio of the number of moles of the epoxy compound to the number of moles of the glycolide is (0-10):(90-100).

[0063] The preferred temperature for the reaction is 120–240°C, and the preferred reaction time is 2–24 h.

[0064] The epoxy compound is preferably any one or more of the following: propylene oxide, butane oxide, 1,2-epoxycyclopentane, 1,2-epoxycyclohexane, 1,2-epoxyoctane, 1,2-epoxydodecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, allyl glycidyl ether, styrene oxide, isopropyl glycidyl ether, tert-butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether, 2-toluene glycidyl ether, or benzyl glycidyl ether.

[0065] In the above reaction, the epoxy compound may or may not be added. Whether it is added depends on the metal element in the catalyst. When the metal element is aluminum, tin or indium, the amount of epoxy compound added is 0; when the metal element is zinc, iron, cobalt, nickel, manganese, chromium, cerium or yttrium, the amount of epoxy compound added is not 0.

[0066] The above preparation method has mild reaction conditions, high product yield, and reduces the production cost of the catalyst.

[0067] Compared with the prior art, the present invention provides a polymeric Schiff alkali metal compound having the structures shown in Formulas I to IV.

[0068] The method for synthesizing multi-center polymerizable Schiff base metal compounds provided by this invention is simple, easy to purify, and yields products with high purity. Due to the introduction of long-chain polyether diols, this Schiff base catalyst has a lower melting point and disperses better in glycolide. The polymerizable Schiff base catalyst has a multi-center structure, and through the synergistic coordination between the multiple metal centers, it can improve the catalytic activity of the original single-center catalyst. The polymerizable Schiff base catalyst provided by this invention exhibits high catalytic activity. When used to catalyze the ring-opening polymerization of glycolide to produce polyglycolic acid, it shows a high polymerization rate. Experimental results show that the yield of polyglycolic acid prepared using the catalyst of this invention can reach 97.2%. Detailed Implementation

[0069] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, illustrates the polymeric Schiff alkali metal compounds, their preparation methods, and applications. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention and are not intended to limit the scope of the claims.

[0070] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0071] Example 1

[0072] 0.1 mol polyethylene glycol 600, 0.3 mol metallic sodium, and 200 mL anhydrous toluene were added to a 1 L round-bottom flask, mixed and stirred, and heated to 65 °C. After the metallic sodium stopped decreasing, the unreacted metallic sodium was removed, and then the toluene was removed under vacuum to obtain sodium polyethylene glycol.

[0073] In the following embodiments of the present invention, the sodium polyethylene glycol (polyethylene glycol 800), sodium polyethylene glycol (polyethylene glycol 1000), and sodium polypropylene glycol (polypropylene glycol 1000) used were all prepared according to the above method, except that polyethylene glycol 600 was replaced with polyethylene glycol 800, polyethylene glycol 1000, and polypropylene glycol 1000.

[0074] Example 2

[0075] 2.1 178 g of 3-tert-butylsalicylaldehyde, 97.3 g of formaldehyde solution (37 wt%), and 1000 mL of concentrated hydrochloric acid (37 wt%) were added to a 2 L round-bottom flask. The mixture was stirred and continuously purged with concentrated sulfuric acid-dried HCl gas at 10 °C for 12 h. The round-bottom flask was then sealed, and the mixture was stirred at 30 °C for 36 h. The temperature was then raised to 70 °C and stirred for another 36 h. The mixture was then cooled to 25 °C, and the crude product was dissolved in diethyl ether and transferred to a separatory funnel. The aqueous solution was allowed to stand and the solution was separated. The diethyl ether solution was washed with saturated sodium bicarbonate solution until neutral, and then washed three times with saturated NaCl solution. The diethyl ether solution was dried with anhydrous magnesium sulfate for 24 h, filtered, and the solvent was removed under normal pressure. The resulting solid was then recrystallized with petroleum ether and dried under vacuum at 35 °C for 24 h to obtain 209.1 g of 5-chloromethyl-3-tert-butylsalicylaldehyde with a purity of 99.5%.

[0076] 2.2 Dissolve 52.2g of sodium polypropylene glycol (polypropylene glycol 1000) prepared in Example 1 in 300mL of toluene, and then add it dropwise at a rate of 2mL / min to a 300mL toluene solution of 22.7g of 5-chloromethyl-3-tert-butylsalicylaldehyde. After the addition is complete, heat to 70℃ and react for 3h. Stop heating, add 100mL of water, mix well, and transfer the material to a separatory funnel. Let it stand to separate the salt solution. Wash the oil phase with deionized water several times until the aqueous phase is neutral. Add 40g of anhydrous sodium sulfate and dry for 24h. After filtration, remove the solvent under vacuum to obtain 65.5g of disalicylaldehyde compound.

[0077] The obtained disalicylaldehyde compound was analyzed by nuclear magnetic resonance (NMR), and its proton NMR spectra were as follows: δ = 10.09-10.31 ppm corresponds to the characteristic chemical shift of hydrogen on the aldehyde group in salicylaldehyde; δ = 7.02-7.38 ppm corresponds to the characteristic chemical shift of hydrogen on the benzene ring in salicylaldehyde; δ = 4.75-4.86 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group attached to the benzene ring in salicylaldehyde; δ = 3.29-3.41 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group adjacent to oxygen in polypropylene glycol; δ = 1.71-1.82 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group not adjacent to oxygen in polypropylene glycol; and δ = 1.33-1.46 ppm corresponds to the characteristic chemical shift of hydrogen on the tert-butyl group in salicylaldehyde.

[0078] This proves the successful synthesis of disalicylaldehyde compounds.

[0079] Example 3

[0080] 3.1 136 g of 3-methylsalicylaldehyde, 89.2 g of formaldehyde solution (37 wt%), and 800 mL of concentrated hydrochloric acid (37 wt%) were added to a 2 L round-bottom flask. The mixture was stirred and continuously purged with concentrated sulfuric acid-dried HCl gas at 15 °C for 10 h. The round-bottom flask was then sealed, and the mixture was stirred at 25 °C for 30 h. The temperature was then raised to 60 °C and stirred for another 30 h. The mixture was then cooled to 25 °C, and the crude product was dissolved in diethyl ether and transferred to a separatory funnel. The aqueous solution was allowed to stand and the solution was separated. The diethyl ether solution was washed with saturated sodium bicarbonate solution until neutral, and then washed three times with saturated NaCl solution. The diethyl ether solution was dried with anhydrous magnesium sulfate for 24 h, filtered, and the solvent was removed under normal pressure. The resulting solid was then recrystallized with petroleum ether and dried under vacuum at 30 °C for 24 h to obtain 170 g of 5-chloromethyl-3-methylsalicylaldehyde with a purity of 99.8%.

[0081] 3.2 Dissolve 32.2g of sodium polyethylene glycol (polyethylene glycol 600) prepared in Example 1 in 400mL of toluene, and then add it dropwise at a rate of 2mL / min to a 250mL toluene solution of 18.4g of 5-chloromethyl-3-methylsalicylaldehyde. After the addition is complete, heat to 65℃ and react for 6h. Stop heating, add 150mL of water, mix well, and transfer the material to a separatory funnel. Let it stand to separate the salt solution. Wash the oil phase with deionized water several times until the aqueous phase is neutral. Add 60g of anhydrous sodium sulfate and dry for 24h. After filtration, remove the solvent under vacuum to obtain 42.5g of disalicylaldehyde compound.

[0082] The obtained disalicylaldehyde compound was analyzed by nuclear magnetic resonance (NMR), and its proton NMR spectrum results are as follows: δ = 10.11-10.29 ppm corresponds to the characteristic chemical shift of hydrogen on the aldehyde group in salicylaldehyde; δ = 7.03-7.41 ppm corresponds to the characteristic chemical shift of hydrogen on the benzene ring in salicylaldehyde; δ = 4.76-4.85 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group attached to the benzene ring in salicylaldehyde; δ = 3.41-3.62 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group in polyethylene glycol; and δ = 2.09-2.21 ppm corresponds to the characteristic chemical shift of hydrogen on the methyl group in salicylaldehyde.

[0083] This proves the successful synthesis of disalicylaldehyde compounds.

[0084] Example 4

[0085] 4.1 76 g of 3-methoxysalicylaldehyde, 48.6 g of formaldehyde solution (37 wt%), and 600 mL of concentrated hydrochloric acid (37 wt%) were added to a 2 L round-bottom flask. The mixture was stirred and continuously purged with concentrated sulfuric acid-dried HCl gas at 5 °C for 15 h. The round-bottom flask was then sealed, and the mixture was stirred at 35 °C for 33 h. The temperature was then raised to 50 °C and stirred for 24 h. The mixture was cooled to 25 °C, and the crude product was dissolved in diethyl ether and transferred to a separatory funnel. The aqueous solution was allowed to stand and the solution was separated. The diethyl ether solution was washed with saturated sodium bicarbonate solution until neutral, and then washed three times with saturated NaCl solution. The diethyl ether solution was dried with anhydrous magnesium sulfate for 24 h, filtered, and the solvent was removed under normal pressure. The resulting solid was recrystallized with petroleum ether and dried under vacuum at 25 °C for 24 h to obtain 91.2 g of 5-chloromethyl-3-methoxysalicylaldehyde with a purity of 99.6%.

[0086] 4.2 Dissolve 42.2g of sodium polyethylene glycol (polyethylene glycol 800) prepared in Example 1 in 500mL of toluene, and then add it dropwise at a rate of 3mL / min to a 400mL toluene solution of 20g of 5-chloromethyl-3-methoxysalicylaldehyde. After the addition is complete, heat to 60℃ and react for 10h. Stop heating, add 200mL of water to dissolve, mix well, transfer the material to a separatory funnel, let stand to separate the salt solution, wash the oil phase with deionized water several times until the aqueous phase is neutral, add 80g of anhydrous sodium sulfate and dry for 24h, filter and remove the solvent under vacuum to obtain 50.2g of disalicylaldehyde compound.

[0087] The obtained disalicylaldehyde compound was analyzed by nuclear magnetic resonance (NMR), and its proton NMR spectrum results are as follows: δ = 10.13-10.31 ppm corresponds to the characteristic chemical shift of hydrogen on the aldehyde group in salicylaldehyde; δ = 7.05-7.36 ppm corresponds to the characteristic chemical shift of hydrogen on the benzene ring in salicylaldehyde; δ = 4.76-4.88 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group attached to the benzene ring in salicylaldehyde; δ = 3.75-3.91 ppm corresponds to the characteristic chemical shift of hydrogen on the methoxy group in salicylaldehyde; and δ = 3.45-3.65 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group in polyethylene glycol.

[0088] This proves the successful synthesis of disalicylaldehyde compounds.

[0089] Example 5

[0090] 5.1 68 g of 5-methylsalicylaldehyde, 56.8 g of formaldehyde solution (37 wt%), and 400 mL of concentrated hydrochloric acid (37 wt%) were added to a 2 L round-bottom flask. The mixture was stirred and continuously purged with concentrated sulfuric acid-dried HCl gas at 10 °C for 10 h. The round-bottom flask was then sealed, and the mixture was stirred at 40 °C for 24 h. The temperature was then raised to 70 °C and stirred for 20 h. The mixture was cooled to 25 °C, and the crude product was dissolved in diethyl ether and transferred to a separatory funnel. The aqueous solution was allowed to stand and the solution was separated. The diethyl ether solution was washed with saturated sodium bicarbonate solution until neutral, and then washed three times with saturated NaCl solution. The diethyl ether solution was dried with anhydrous magnesium sulfate for 24 h, filtered, and the solvent was removed under normal pressure. The resulting solid was recrystallized with petroleum ether and dried under vacuum at 25 °C for 24 h to obtain 83.3 g of 3-chloromethyl-5-methylsalicylaldehyde with a purity of 99.7%.

[0091] 5.2 Dissolve 52.2g of sodium polyethylene glycol (polyethylene glycol 1000) prepared in Example 1 in 600mL of toluene, and then add it dropwise at a rate of 3mL / min to a 300mL toluene solution of 18.4g of 3-chloromethyl-5-methylsalicylaldehyde. After the addition is complete, heat to 70℃ and react for 10h. Stop heating, add 250mL of water, mix well, and transfer the material to a separatory funnel. Let it stand to separate the salt solution. Wash the oil phase with deionized water several times until the aqueous phase is neutral. Add 100g of anhydrous sodium sulfate and dry for 24h. After filtration, remove the solvent under vacuum to obtain 62g of disalicylaldehyde compound.

[0092] The obtained disalicylaldehyde compound was analyzed by nuclear magnetic resonance (NMR), and its proton NMR spectrum results are as follows: δ = 10.11-10.28 ppm corresponds to the characteristic chemical shift of hydrogen on the aldehyde group in salicylaldehyde; δ = 7.21-7.59 ppm corresponds to the characteristic chemical shift of hydrogen on the benzene ring in salicylaldehyde; δ = 4.76-4.88 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group attached to the benzene ring in salicylaldehyde; δ = 3.45-3.65 ppm corresponds to the characteristic chemical shift of hydrogen on the methylene group in polyethylene glycol; and δ = 2.28-2.44 ppm corresponds to the characteristic chemical shift of hydrogen on the methyl group in salicylaldehyde.

[0093] This proves the successful synthesis of disalicylaldehyde compounds.

[0094] Example 6

[0095] 6.1 Dissolve 30.4g of the disalicylaldehyde compound prepared in Example 2 in 300mL of toluene, mix with 1.2g of ethylenediamine and stir, and heat to 65°C. After 10h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 28.9g of polymeric Schiff base.

[0096] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 20100 g / mol.

[0097] 6.2 Dissolve 15g of the polymeric Schiff base prepared in 6.1 above in 200mL of toluene, mix with 20mL of a toluene solution containing 1.1g of triethylaluminum, heat to 80℃, and after 24h, add 10mL of ethanol. After 3h, remove toluene and ethanol by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 14.4g of polymeric Schiff base aluminum catalyst.

[0098] 6.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 116g of glycolide, 0.1g of benzyl alcohol and 1.6g of the Schiff base aluminum catalyst prepared in 6.2 were added to the reaction flask in sequence, mixed and stirred and rapidly heated to 180℃. After 7h, 112.7g of polyglycolic acid was obtained, with a yield of 97.2%.

[0099] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 96,000 g / mol.

[0100] Example 7

[0101] 7.1 Dissolve 30.1g of the disalicylaldehyde compound prepared in Example 2 in 300mL of toluene, mix with 1.5g of 1,3-propanediamine, stir and heat to 70°C. After 8h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 100mL of ethanol to wash, filter and dry to obtain 29g of polymeric Schiff base.

[0102] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 23300 g / mol.

[0103] 7.2 Dissolve 15g of the polymeric Schiff base prepared in 7.1 above in 150mL of tetrahydrofuran, mix with 1.4g of zinc chloride in 30mL of ethanol solution, heat to 60℃, and after 48h, remove tetrahydrofuran and ethanol by vacuuming at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 14.1g of polymeric Schiff base zinc catalyst.

[0104] 7.3 The reaction flask was repeatedly evacuated and purged with nitrogen. 232g of glycolide, 0.2g of benzyl alcohol, 2.6g of tert-butyl glycidyl ether and 3g of the Schiff base zinc catalyst prepared in 7.2 were added to the reaction flask in sequence. The mixture was stirred and the temperature was rapidly raised to 185℃. After 6 hours, 222.9g of polyglycolic acid was obtained, with a yield of 96.1%.

[0105] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 83000 g / mol.

[0106] Example 8

[0107] 8.1 Dissolve 29.8g of the disalicylaldehyde compound prepared in Example 2 in 200mL of toluene, mix with 2.3g of 1,2-cyclohexanediamine, stir and heat to 75°C. After 6h, remove toluene under vacuum of 300Pa. When no more liquid distills out, add 100mL of ethanol to wash, filter, and dry to obtain 29.5g of polymeric Schiff base.

[0108] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 26900 g / mol.

[0109] 8.2 Dissolve 16g of the polymeric Schiff base prepared in 8.1 above in 250mL of toluene, mix with 2g of aluminum isopropoxide in 30mL of toluene solution, heat to 85℃, and after 30h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 15.9g of polymeric Schiff base aluminum catalyst.

[0110] 8.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 116g of glycolide, 0.1g of benzyl alcohol and 1.7g of the above Schiff base aluminum catalyst were added to the reaction flask in sequence, mixed and stirred and rapidly heated to 190℃. After 5h, 112.4g of polyglycolic acid was obtained, with a yield of 96.9%.

[0111] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was found to be 95,000 g / mol.

[0112] Example 9

[0113] 9.1 Dissolve 19.2g of the disalicylaldehyde compound prepared in Example 3 in 250mL of toluene, mix with 3.1g of 4-nitro-o-phenylenediamine, stir and heat to 60°C. After 12h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 150mL of ethanol to wash, filter and dry to obtain 20.2g of polymeric Schiff base.

[0114] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 23000 g / mol.

[0115] 9.2 Dissolve 11g of the polymeric Schiff base prepared in 9.1 above in 200mL of tetrahydrofuran, mix with 1.8g of cobalt acetate in 30mL of ethanol solution, heat to 55℃, and after 60h, remove tetrahydrofuran and ethanol by vacuuming at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 10.5g of polymeric Schiff base cobalt catalyst.

[0116] 9.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 232g of glycolide, 0.22g of benzyl alcohol, 3g of phenyl glycidyl ether and 2.3g of the Schiff base cobalt catalyst prepared in 9.2 above were added to the reaction flask in sequence. The mixture was stirred and the temperature was rapidly raised to 195℃. After 4h, 223.4g of polyglycolic acid was obtained, with a yield of 96.3%.

[0117] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 88,000 g / mol.

[0118] Example 10

[0119] 10.1 Dissolve 20g of the disalicylaldehyde compound prepared in Example 3 in 300mL of tetrahydrofuran, mix with 3.74g of 4-bromo-o-phenylenediamine, stir and heat to 55°C. After 15h, remove the tetrahydrofuran under vacuum of 300Pa. When no more liquid distills out, add 200mL of ethanol to wash, filter and dry to obtain 21.5g of polymeric Schiff base.

[0120] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 13000 g / mol.

[0121] 10.2 Dissolve 11.5g of the polymeric Schiff base prepared in 10.1 in 150mL of toluene, mix with 20mL of toluene solution containing 1.62g of aluminum ethoxy, heat to 80℃, and after 36h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 11.4g of polymeric Schiff base aluminum catalyst.

[0122] 10.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 232g of glycolide, 0.2g of benzyl alcohol and 2.4g of the Schiff base aluminum catalyst prepared in 10.2 were added to the reaction flask in sequence. The mixture was stirred and the temperature was rapidly raised to 190℃. After 8h, 223.9g of polyglycolic acid was obtained, with a yield of 96.5%.

[0123] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 99,000 g / mol.

[0124] Example 11

[0125] 11.1 Dissolve 20.6g of the disalicylaldehyde compound prepared in Example 3 in 350mL of toluene, mix and stir with 2.16g of o-phenylenediamine and heat to 50°C. After 18h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 250mL of ethanol to wash, filter and dry to obtain 20.5g of polymeric Schiff base.

[0126] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 10000 g / mol.

[0127] 11.2 Dissolve 11g of the polymeric Schiff base prepared in 11.1 above in 150mL of tetrahydrofuran, mix with 1.83g of zinc acetate in 40mL of ethanol solution, heat to 65℃, and after 36h, remove tetrahydrofuran and ethanol by vacuuming at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 10.6g of polymeric Schiff base zinc catalyst.

[0128] 11.3 The reaction flask was repeatedly evacuated and purged with nitrogen. 232g of glycolide, 0.2g of benzyl alcohol, 1.16g of isopropyl glycidyl ether and 2.2g of the Schiff base zinc catalyst prepared in 11.2 were added to the reaction flask in sequence. The mixture was stirred and the temperature was rapidly raised to 185℃. After 12h, 220.6g of polyglycolic acid was obtained, with a yield of 95.1%.

[0129] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 85,000 g / mol.

[0130] Example 12

[0131] 12.1 Dissolve 27.1g of the disalicylaldehyde compound prepared in Example 4 in 400mL of toluene, mix and stir with 2.83g of 4-chloro-o-phenylenediamine and heat to 55°C. After 10h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 200mL of ethanol to wash, filter and dry to obtain 27g of polymeric Schiff base.

[0132] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 10200 g / mol.

[0133] 12.2 Dissolve 14g of the polymeric Schiff base prepared in 12.1 above in 200mL of tetrahydrofuran, mix with 2.21g of indium chloride in 30mL of ethanol solution, heat to 50℃, and after 72h, remove tetrahydrofuran and ethanol by vacuuming at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 14.1g of polymeric Schiff base indium catalyst.

[0134] 12.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 116g of glycolide, 0.1g of benzyl alcohol and 1.6g of the Schiff base indium catalyst prepared in 12.2 were added to the reaction flask in sequence, mixed and stirred and rapidly heated to 175℃. After 9h, 110.5g of polyglycolic acid was obtained, with a yield of 95.3%.

[0135] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 92000 g / mol.

[0136] Example 13

[0137] 13.1 Dissolve 25.94 g of the disalicylaldehyde compound prepared in Example 4 in 450 mL of toluene, mix with 1.48 g of 1,2-propanediamine, stir and heat to 60 °C. After 8 h, remove toluene by vacuum at a vacuum degree of 300 Pa. When no more liquid distills out, add 150 mL of ethanol to wash, filter and dry to obtain 24.9 g of polymeric Schiff base.

[0138] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 13200 g / mol.

[0139] 13.2 Dissolve 13.5g of the polymeric Schiff base prepared in 13.1 above in 250mL of tetrahydrofuran, mix with 1.76g of nickel acetate in 40mL of ethanol solution, heat to 55℃, and after 84h, remove tetrahydrofuran and ethanol by vacuuming at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 12.9g of polymeric Schiff base nickel catalyst.

[0140] 13.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 232g of glycolide, 0.25g of benzyl alcohol, 1.5g of phenyl glycidyl ether and 2.8g of the Schiff base nickel catalyst prepared in 13.2 were added to the reaction flask in sequence. The mixture was stirred and the temperature was rapidly raised to 170℃. After 12h, 221.8g of polyglycolic acid was obtained, with a yield of 95.6%.

[0141] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 78,000 g / mol.

[0142] Example 14

[0143] 14.1 Dissolve 25.3g of the disalicylaldehyde compound prepared in Example 4 in 400mL of toluene, mix with 1.76g of 2-methyl-1,3-propanediamine, stir and heat to 55°C. After 20h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 100mL of ethanol to wash, filter and dry to obtain 24.6g of polymeric Schiff base.

[0144] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 15800 g / mol.

[0145] 14.2 Dissolve 13g of the polymeric Schiff base prepared in 14.1 above in 200mL of toluene, mix with 30mL of toluene solution containing 2.04g of aluminum isopropoxide, heat to 85℃, and after 48h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 13g of polymeric Schiff base aluminum catalyst.

[0146] 14.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 232g of glycolide, 0.2g of benzyl alcohol and 2.8g of the Schiff base aluminum catalyst prepared in 14.2 were added to the reaction flask in sequence. The mixture was stirred and the temperature was rapidly raised to 165℃. After 15h, 224.1g of polyglycolic acid was obtained, with a yield of 96.6%.

[0147] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 91000 g / mol.

[0148] Example 15

[0149] 15.1 Dissolve 28.5g of the disalicylaldehyde compound prepared in Example 5 in 350mL of tetrahydrofuran, mix with 1.48g of 1,3-propanediamine, stir and heat to 50°C. After 24h, remove the tetrahydrofuran under vacuum of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter and dry to obtain 27.1g of polymeric Schiff base.

[0150] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 20500 g / mol.

[0151] 15.2 Dissolve 14.5g of the polymeric Schiff base prepared in 15.1 above in 200mL of tetrahydrofuran, mix with 1.77g of cobalt acetate in 30mL of methanol solution, heat to 60℃, and after 36h, remove tetrahydrofuran and methanol by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 13.8g of polymeric Schiff base cobalt catalyst.

[0152] 15.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 232g of glycolide, 0.25g of benzyl alcohol, 1.3g of tert-butyl glycidyl ether, and 3.1g of the Schiff base cobalt catalyst prepared in 15.2 were added to the reaction flask in sequence. The mixture was stirred and the temperature was rapidly raised to 160℃. After 18h, 222.7g of polyglycolic acid was obtained, with a yield of 96%.

[0153] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 76000 g / mol.

[0154] Example 16

[0155] 16.1 Dissolve 28.2g of the disalicylaldehyde compound prepared in Example 5 in 300mL of tetrahydrofuran, mix with 3.54g of 4,5-dichloro-o-phenylenediamine, stir and heat to 45°C. After 30h, remove the tetrahydrofuran under vacuum of 300Pa. When no more liquid distills out, add 100mL of ethanol to wash, filter and dry to obtain 28.7g of polymeric Schiff base.

[0156] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was found to be 25000 g / mol.

[0157] 16.2 Dissolve 15.5g of the polymeric Schiff base prepared in 16.1 above in 250mL of toluene, mix with 20mL of toluene solution containing 1.62g of aluminum ethoxy, heat to 90℃, and after 24h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 15g of polymeric Schiff base aluminum catalyst.

[0158] 16.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 232g of glycolide, 0.2g of benzyl alcohol and 3.2g of the above Schiff base aluminum catalyst were added to the reaction flask in sequence, mixed and stirred and rapidly heated to 155℃. After 20h, 222.0g of polyglycolic acid was obtained, with a yield of 95.7%.

[0159] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 96,000 g / mol.

[0160] Example 17

[0161] 17.1 Dissolve 28g of the disalicylaldehyde compound prepared in Example 5 in 250mL of toluene, mix with 2.44g of 4-methyl-o-phenylenediamine, stir and heat to 40°C. After 36h, remove toluene by vacuum at a vacuum degree of 300Pa. When no more liquid distills out, add 150mL of ethanol to wash, filter, dry and obtain 27.4g of polymeric Schiff base.

[0162] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 28300 g / mol.

[0163] 17.2 Dissolve 15g of the polymeric Schiff base prepared in 17.1 above in 300mL of tetrahydrofuran, mix with 50mL of ethanol solution containing 1.9g of stannous chloride, heat to 65℃, and after 48h, remove tetrahydrofuran and ethanol by vacuuming at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 14.8g of polymeric Schiff base tin catalyst.

[0164] 17.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 232g of glycolide, 0.22g of benzyl alcohol and 3.23g of the above Schiff base tin catalyst were added to the reaction flask in sequence, mixed and stirred and rapidly heated to 150℃. After 24h, 221.3g of polyglycolic acid was obtained, with a yield of 95.4%.

[0165] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was determined to be 88,000 g / mol.

[0166] Comparative Example 1

[0167] 1.1 Dissolve 0.42 g of 2,4-diacetyl-resorcinol in 100 mL of toluene, mix with 0.22 g of 4-methyl-o-phenylenediamine, stir and heat to 40 °C. After 36 h, remove toluene under vacuum of 300 Pa. When no more liquid distills out, add 150 mL of ethanol to wash, filter and dry to obtain 0.59 g of polymeric Schiff base.

[0168] The obtained polymeric Schiff base was analyzed by gel permeation chromatography, and the number average molecular weight of the polymeric Schiff base was determined to be 7600 g / mol.

[0169] 1.2 Dissolve 0.33g of the polymeric Schiff base prepared in 1.1 above in 100mL of tetrahydrofuran, mix with 0.2g of stannous chloride in 30mL of ethanol solution, heat to 65℃, and after 48h, remove tetrahydrofuran and ethanol by vacuuming at a vacuum degree of 300Pa. When no more liquid distills out, add 50mL of ethanol to wash, filter, and dry to obtain 0.43g of polymeric Schiff base tin catalyst.

[0170] 1.3 The reaction flask was repeatedly evacuated and filled with nitrogen. 23.2g of glycolide, 0.022g of benzyl alcohol and 0.32g of the above Schiff base tin catalyst were added to the reaction flask in sequence, mixed and stirred and rapidly heated to 150℃. After 24h, 21.8g of polyglycolic acid was obtained, with a yield of 94.1%.

[0171] The polyglycolic acid obtained in this example was analyzed by gel permeation chromatography, and the number average molecular weight of polyglycolic acid was found to be 67,000 g / mol. Compared with Example 17, both the molecular weight and yield were reduced.

[0172] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A polymeric Schiff alkali metal compound having the structures shown in Formulas I to IV: Formula I; Formula II; Formula III; Formula IV; in, R1 is selected from substituted or unsubstituted alkyl, cycloalkyl, aryl or heteroaryl groups; R2 is selected from the group remaining after removing two hydroxyl groups from polyether glycol; R3 is selected from hydrogen, halogen, nitro, substituted or unsubstituted alkyl or alkoxy groups; R4 is selected from halogens, substituted or unsubstituted alkoxy groups, or -OOCCH3; M1 is selected from zinc, cobalt, nickel, or tin; M2 is selected from aluminum, indium, chromium, iron, manganese, cerium, or yttrium; n represents the degree of aggregation.

2. The polymeric Schiff alkali metal compound according to claim 1, characterized in that, R1 is selected from substituted or unsubstituted C2-C6 alkyl, C3-C12 cycloalkyl, C6-C12 aryl or C4-C11 heteroaryl; R2 is selected from the group remaining after removing two hydroxyl groups from polyether glycol; The R3 is selected from hydrogen, halogen, nitro, substituted or unsubstituted C1-C6 alkyl or C1-C6 alkoxy; The R4 is selected from halogens, substituted or unsubstituted C1-C6 alkoxy groups, or -OOCCH3; n is any integer from 5 to 100.

3. The polymeric Schiff alkali metal compound according to claim 2, characterized in that, R1 is selected from substituted or unsubstituted C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and phenyl. R2 is selected from the group remaining after removing two hydroxyl groups from polyether glycol; The R3 is selected from hydrogen, halogen, nitro, substituted or unsubstituted methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, methoxy, ethoxy, n-propoxy, and isopropoxy. The R4 is selected from halogens, substituted or unsubstituted methoxy, ethoxy, n-propoxy, isopropoxy, or -OOCCH3.

4. The polymeric Schiff alkali metal compound according to claim 3, characterized in that, R1 is selected from ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, 2-methyl-1,3-propanediamine, 2,2'-dimethylpropanediamine, 1,4-butanediamine, 1,2-cyclohexanediamine, o-phenylenediamine, 3-nitro-o-phenylenediamine, 4-nitro-o-phenylenediamine, 3-bromo-o-phenylenediamine, 4-bromo-o-phenylenediamine, 4,5-dibromo-o-phenylenediamine, 4-bromo-5-fluoro-o-phenylenediamine, 4-bromo-5-methyl-o-phenylenediamine, 4-chloro-5-bromo-o-phenylenediamine, 3-methyl-5-bromo-o-phenylenediamine, 4-methoxy-o-phenylenediamine. The groups remaining after removing two amino groups from diamines, 4-chloro-5-fluoro-o-phenylenediamine, 4,5-dichloro-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-trifluoromethyl-o-phenylenediamine, 3-chloro-o-phenylenediamine, 3-chloro-5-trifluoromethyl-o-phenylenediamine, 4,5-difluoro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 3-fluoro-o-phenylenediamine, 3,4-difluoro-o-phenylenediamine, 3,5-difluoro-o-phenylenediamine, 4,5-dimethyl-o-phenylenediamine, 4-methyl-o-phenylenediamine, 3,5-dimethyl-o-phenylenediamine, or 4-chloro-5-methyl-o-phenylenediamine; R2 is selected from polyethylene glycol, polypropylene glycol, or polytetrahydrofuran after removing two hydroxyl groups; The R3 is selected from hydrogen, -CH3, -CH2CH3, -CH(CH3)2, -OCH(CH3)2, -C(CH3)3, -OCH3 or -OCH2CH3; The R4 is selected from -OCH3, -OCH2CH3, -OCH(CH3)2, -Cl or -OOCCH3.

5. A method for preparing the polymeric Schiff alkali metal compound according to any one of claims 1 to 4, comprising the following steps: a) Reaction of polyether glycol with an alkali metal yields polyether glycol alkali metal salts; b) The polyether diol alkali metal salt and chloromethyl salicylaldehyde were reacted to obtain the polyether diol bis-salicylaldehyde compound; c) React the polyether diol bis(salicylaldehyde) compound and the diamino compound to obtain the Schiff base polymer; d) React Schiff base polymers with metal compounds to obtain polymeric Schiff base metal compounds.

6. The preparation method according to claim 5, characterized in that, The synthesis of the chloromethyl salicylic aldehyde includes the following steps: Salicylaldehyde compounds are reacted with formaldehyde compounds in the presence of a catalyst to produce chloromethylsalicylaldehyde; The salicylaldehyde compounds include at least one of salicylaldehyde, 3-methylsalicylaldehyde, 3-methoxysalicylaldehyde, 3-ethoxysalicylaldehyde, 3-tert-butylsalicylaldehyde, 3-bromosalicylaldehyde, 3-chlorosalicylaldehyde, 5-chlorosalicylaldehyde, 5-methylsalicylaldehyde, and 5-nitrosalicylicylaldehyde. The formaldehyde compounds include at least one of formaldehyde, trioxymethylene, or paraoxymethylene; The molar ratio of the salicylaldehyde compound to the formaldehyde compound is 1:1 to 1:2; The reaction temperature is 0 ~ 95℃, and the reaction time is 2 ~ 60h; The catalyst is at least one of HCl, concentrated sulfuric acid, phosphoric acid, acetic acid, aluminum trichloride, zinc chloride, and tin chloride.

7. The preparation method according to claim 5, characterized in that, The reaction temperature of the polyether diol and the alkali metal is 25~100℃, and the reaction time is 1~10h; The molar ratio of the polyether diol to the alkali metal is 1:2.1 to 1:4; The alkali metal includes one of lithium, sodium, and potassium; In step b), the molar ratio of the chloromethyl salicylic aldehyde to the polyether diol alkali metal salt is 2:1 to 3:1; the reaction temperature is 20 to 120°C; and the reaction time is 2 to 48 hours. In step c), the molar ratio of the polyether diol bisalicylic acid compound to the diamino compound is 1:0.6~1.5; the reaction temperature is 20~100℃; and the reaction time is 2~48h. In step d), the metal compound includes at least one of zinc chloride, zinc acetate, ethyl zinc, stannous chloride, ferric chloride, indium chloride, cobalt acetate, aluminum isopropoxide, aluminum ethoxylate, nickel acetate, and triethylaluminum; the molar ratio of the diamino compound residue in the Schiff base polymer to the metal compound is 1:1 to 1:1.2; the reaction temperature is 20 to 120°C, and the reaction time is 2 to 100 h.

8. The use of the polymeric Schiff base metal compound according to any one of claims 1 to 4 or the polymeric Schiff base metal compound prepared by the preparation method according to any one of claims 5 to 7 as a catalyst in the preparation of cyclic ester polymers.

9. A method for preparing polyglycolic acid, comprising the following steps: Polyglycolic acid is obtained by reacting glycolide or a mixture of glycolide and an epoxy compound under an inert atmosphere with the aid of a catalyst and an initiator. The catalyst is a polymeric Schiff alkali metal compound as described in any one of claims 1 to 4 or a polymeric Schiff alkali metal compound prepared by the preparation method described in any one of claims 5 to 7.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the catalyst to the glycolide is 1:(20~2000); The reaction temperature is 120~240℃, and the reaction time is 2~24 h.

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