Application of rare earth complex and preparation method of polylactide

Abstract

The invention discloses application of a rare earth complex and a preparation method of polylactide. The rare earth complex is formed by complexing rare earth ions and organic acid, the organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid and ferulic acid, and the rare earth complex can be used as a catalyst for ring-opening polymerization of lactide.

Description

Technical Field

[0001] The invention relates to the use of a rare earth complex and a method for preparing polylactide. Background Art

[0002] Polylactide is a widely used biodegradable polymer material with good processability, biocompatibility and degradability. It has broad application prospects in industries such as biomedicine, packaging, textiles and agriculture. Polylactide is usually prepared by ring-opening polymerization of lactide, generally using metal-based catalysts such as tin, aluminum, zinc, lithium, calcium and iron. Most of these catalysts are sensitive to air and moisture, and are not easy to prepare and use.

[0003] CN116925110A discloses a rare earth complex having the chemical formula [Ce(L) 3 (A)] 2 , wherein L is an organic ligand anion formed by benzoic acid and its derivatives, and A is a derivative of 1,10-phenanthroline. The rare earth complex has good antibacterial properties.

[0004] CN107602377A discloses a method for preparing a p-hydroxybenzoic acid rare earth complex nano-microsphere, wherein lanthanum nitrate hexahydrate and p-hydroxybenzoic acid are dissolved in anhydrous ethanol, stirred and mixed evenly, and then polyvinyl pyrrolidone and fatty alcohol polyoxyethylene ether are added, dissolved completely, and sodium sulfate is added to obtain a mixed solution. The mixed solution is allowed to stand and then filtered, and then the pH is adjusted to 7 with ammonia water. The mixed solution after pH adjustment is condensed and refluxed at 80-90° C., and then centrifuged to obtain p-hydroxybenzoic acid rare earth complex nano-microsphere.

[0005] CN115491003A discloses the use of a rare earth amino acid complex in improving the softening temperature of polylactic acid, wherein the rare earth amino acid complex is formed by complexing rare earth ions and amino acids, the rare earth element of the rare earth metal ions is selected from one or more of lanthanum, cerium and samarium, and the amino acid is selected from at least one of proline, L-phenylalanine, tyrosine and tryptophan.

[0006] Therefore, currently, there is no report on the use of a complex formed by a rare earth ion and an organic acid (eg, mandelic acid, etc.) as a catalyst for the ring-opening polymerization of lactide. Summary of the invention

[0007] In view of this, one object of the present invention is to provide a rare earth complex as a catalyst for the ring-opening polymerization of lactide. Another object of the present invention is to provide a method for preparing polylactide, which can successfully prepare polylactide. Further, the preparation method does not require the use of a solvent, and the biological toxicity of the obtained product is low. Furthermore, the polylactide obtained by the preparation method has a higher molecular weight and a narrower molecular weight distribution.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0009] On the one hand, the present invention provides a use of a rare earth complex as a catalyst for the ring-opening polymerization of lactide, characterized in that the rare earth complex is formed by complexing rare earth ions and organic acids; the organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid, and ferulic acid.

[0010] According to the use of the present invention, preferably, the rare earth ion is selected from one or more of lanthanum and cerium, and the organic acid is mandelic acid.

[0011] According to the use of the present invention, preferably, the rare earth complex is prepared by the following method: reacting an organic acid and a rare earth inorganic salt in the presence of alcohol and / or water to obtain a rare earth complex;

[0012] The organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid and ferulic acid.

[0013] According to the use of the present invention, preferably, the molar ratio of the rare earth element in the organic acid and the rare earth inorganic salt is (0.6-1):0.2;

[0014] The rare earth inorganic salt is selected from one or more of rare earth nitrates, rare earth chlorides, rare earth acetates, and rare earth carbonates.

[0015] According to the use of the present invention, preferably, the alcohol is selected from one or more of methanol, ethanol, ethylene glycol, glycerol, isopropanol, pentaerythritol and benzyl alcohol;

[0016] The reaction temperature is 100-180° C., the reaction time is 12-95 hours, and the reaction is carried out in a reactor.

[0017] According to the use of the present invention, preferably, a reaction solution II containing a rare earth inorganic salt and an alcohol is added dropwise to a reaction solution I containing an organic acid and an alcohol, and then stirred at 20 to 35° C. for 0.5 to 3 hours to obtain a mixed solution; the mixed solution is reacted to obtain a rare earth complex;

[0018] The pH of the reaction solution I is 6.5-7.5.

[0019] According to the use of the present invention, preferably, the reaction product obtained by the reaction is washed and then dried to obtain the rare earth complex.

[0020] On the other hand, the present invention provides a method for preparing polylactide, comprising the following steps: subjecting lactide to a ring-opening polymerization reaction in the presence of a rare earth complex and an initiator to obtain polylactide;

[0021] The rare earth complex is formed by the complexation of rare earth ions and organic acids; the organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid, and ferulic acid;

[0022] The initiator is selected from one or more of aliphatic monoalcohols or phenyl monoalcohols containing 1 to 10 carbon atoms.

[0023] According to the preparation method of the present invention, preferably, the mass ratio of lactide to rare earth complex is 10000:(1-15); based on 10 g of lactide, the amount of initiator used is 7-25 μL.

[0024] According to the preparation method of the present invention, preferably, the reaction temperature of the ring-opening polymerization reaction is 50-200° C., the reaction time of the ring-opening polymerization reaction is 0.5-24 h, and the ring-opening polymerization reaction is carried out under a pressure of ≤1 Pa.

[0025] The present invention finds that the rare earth complex of the present invention can be used as a catalyst for the ring-opening polymerization reaction of lactide. The preparation method of the present invention can successfully prepare polylactide. Furthermore, the preparation method does not require the use of a solvent, and the biological toxicity of the obtained product is low. Furthermore, the polylactide obtained by the preparation method has a higher molecular weight and a narrower molecular weight distribution. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] <Application of rare earth complexes>

[0028] The rare earth complex of the present invention can be used as a catalyst for the ring-opening polymerization of lactide. The rare earth complex of the present invention is formed by the complexation of rare earth ions and organic acids.

[0029] The lactide may be selected from one or more of L-lactide, D-lactide, meso-lactide and racemic-lactide. According to one embodiment of the present invention, the lactide is L-lactide.

[0030] The rare earth element of the rare earth ion is selected from one or more of lanthanum or cerium. In some embodiments, the rare earth element of the rare earth ion is lanthanum. In other embodiments, the rare earth element of the rare earth ion is cerium.

[0031] The organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid and ferulic acid. Preferably, the organic acid is mandelic acid.

[0032] According to one specific embodiment of the present invention, the rare earth complex is a cerium mandelate complex. According to another specific embodiment of the present invention, the rare earth complex is a lanthanum mandelate complex.

[0033] The rare earth complex of the present invention can be prepared by the following method: reacting an organic acid with a rare earth inorganic salt in the presence of alcohol and / or water to obtain the rare earth complex.

[0034] The organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid and ferulic acid. Preferably, the organic acid is mandelic acid.

[0035] The rare earth inorganic salt is selected from one or more of rare earth nitrates, rare earth chlorides, rare earth acetates, and rare earth carbonates. In some embodiments, the rare earth inorganic salt is a rare earth nitrate. In other embodiments, the rare earth inorganic salt is a rare earth chloride.

[0036] Preferably, the rare earth element in the rare earth inorganic salt is selected from one or more of lanthanum and cerium. In some embodiments, the rare earth element in the rare earth inorganic salt is lanthanum. In some embodiments, the rare earth element in the rare earth inorganic salt is cerium.

[0037] In some embodiments, the rare earth inorganic salt is lanthanum chloride. In other embodiments, the rare earth inorganic salt is cerium nitrate. The rare earth inorganic salt can be used in the form of its hydrate.

[0038] The molar ratio of the organic acid to the rare earth element in the rare earth inorganic salt is (0.6-1):0.2. In some embodiments, it is (0.7-0.9):0.2. In other embodiments, it is (0.75-0.85):0.2.

[0039] The alcohol is selected from one or more of methanol, ethanol, ethylene glycol, glycerol, isopropanol, pentaerythritol and benzyl alcohol. Preferably, the alcohol is selected from one or more of methanol, ethanol and ethylene glycol.

[0040] Based on 122 mg of the organic acid, the amount of alcohol used can be 10 to 40 mL, preferably 15 to 30 mL, and more preferably 20 to 25 mL.

[0041] The reaction temperature may be 100 to 180°C; preferably 120 to 170°C; more preferably 130 to 150°C.

[0042] The reaction time may be 12 to 95 hours, preferably 40 to 90 hours, and more preferably 60 to 80 hours.

[0043] The reaction can be carried out in a reactor.

[0044] In certain embodiments, a reaction solution II containing a rare earth inorganic salt and an alcohol is added dropwise to a reaction solution I containing an organic acid and an alcohol, and then stirred to obtain a mixed solution; and the mixed solution is reacted to obtain a rare earth complex.

[0045] In the reaction solution II, the molar volume ratio of the rare earth element in the rare earth inorganic salt to the alcohol is (0.05-0.4) mol:5 mL; preferably (0.1-0.3) mol:5 mL; more preferably (0.15-0.25) mol:5 mL.

[0046] The pH of the reaction solution I is 6.5 to 7.5; preferably, the pH of the reaction solution I is 6.8 to 7.2; more preferably, the pH of the reaction solution I is 7. The pH of the reaction solution I can be adjusted using an alkaline aqueous solution. The alkaline aqueous solution can be an alkali metal hydroxide aqueous solution. Examples of alkali metal hydroxides include, but are not limited to, sodium hydroxide, potassium hydroxide,

[0047] In the reaction solution I, the mass volume ratio of the organic acid to the alcohol may be (100-150) mg:15 mL; preferably (120-130) mg:15 mL.

[0048] The stirring may be performed at a temperature of 20 to 35°C, preferably 25 to 30°C.

[0049] The stirring time may be 0.5 to 3 hours, preferably 1 to 2 hours.

[0050] In certain embodiments, the method further comprises the following steps: mixing an organic acid with an alcohol, and then adjusting the pH to 6.5 to 7.5, preferably 6.8 to 7.2, and more preferably 7, with an alkaline aqueous solution to obtain a reaction solution I.

[0051] The alkaline aqueous solution can be an alkali metal hydroxide aqueous solution. Examples of alkali metal hydroxides include, but are not limited to, sodium hydroxide and potassium hydroxide.

[0052] In certain embodiments, the method further comprises the following steps: washing the reaction product obtained by the reaction, and then drying the product to obtain a rare earth complex.

[0053] The reaction product can be washed with ethanol and water.

[0054] The drying temperature may be 60 to 95° C., preferably 70 to 90° C., and more preferably 75 to 85° C. The drying may be performed under vacuum.

[0055] <Method for producing polylactide>

[0056] The preparation method of polylactide of the present invention comprises the following steps: subjecting lactide to a ring-opening polymerization reaction in the presence of a rare earth complex and an initiator to obtain polylactide.

[0057] The lactide may be selected from one or more of L-lactide, D-lactide, meso-lactide and racemic-lactide. According to one embodiment of the present invention, the lactide is L-lactide.

[0058] The rare earth complex is formed by the complexation of rare earth ions and organic acids. The rare earth complex is specifically described above and will not be described in detail here.

[0059] The mass ratio of lactide to the rare earth complex may be 10000:(1-15); preferably 10000:(2-12); more preferably 10000:(3-10).

[0060] The initiator is selected from aliphatic monoalcohols or phenyl monoalcohols containing 1 to 10 carbon atoms. In some embodiments, the initiator is selected from aliphatic monoalcohols containing 1 to 5 carbon atoms; preferably, the initiator is selected from aliphatic monoalcohols containing 2 to 3 carbon atoms. In other embodiments, the initiator is selected from phenyl monoalcohols containing 6 to 8 carbon atoms; preferably, the initiator is selected from phenyl monoalcohols containing 6 to 7 carbon atoms. Examples of initiators include, but are not limited to, benzyl alcohol and isopropanol.

[0061] Based on 10 g of lactide, the amount of the initiator used is 7 to 25 μL, preferably 10 to 20 μL. In certain embodiments, based on 10 g of lactide, the amount of the initiator used is 13 to 15 μL.

[0062] The reaction temperature of the ring-opening polymerization reaction is 50 to 200°C, preferably 100 to 180°C, and more preferably 150 to 170°C.

[0063] The reaction time of the ring-opening polymerization reaction is 0.5 to 24 hours, preferably 5 to 20 hours, and more preferably 10 to 15 hours.

[0064] The ring-opening polymerization reaction can be carried out at a pressure of ≤1 Pa; preferably, at a pressure of ≤0.1 Pa; more preferably, at a pressure of ≤10 -2 Pause and proceed.

[0065] After the reaction time is reached, the reaction can be terminated by cooling.

[0066] In some embodiments, the following steps are further included: purifying and drying the reaction product obtained by the ring-opening polymerization reaction to obtain polylactide. Specifically, the reaction product obtained by the ring-opening polymerization reaction is mixed with a solvent to obtain a mixed solution. The polylactide in the mixed solution is precipitated to obtain a precipitate. The precipitate is dried to obtain polylactide. In some embodiments, the solvent is chloroform. Cold methanol can be used to precipitate the polylactide in the mixed solution. The drying temperature can be 40 to 90°C; preferably 50 to 70°C. The drying time can be 5 to 20 hours; preferably 7 to 18 hours; more preferably 10 to 15 hours. Drying can be performed under vacuum conditions.

[0067] In some embodiments, the method further comprises the step of preparing a rare earth complex. The method for preparing the rare earth complex is as described above and will not be repeated here.

[0068] Here is the test method:

[0069] Conversion rate of L-lactide: detected by using Swiss Bruker Avance 500 nuclear magnetic resonance spectrometer. The test solvent was deuterated chloroform and the test temperature was 25°C.

[0070] Polylactide molecular weight: detected by Agilent gel permeation chromatography; the test solvent is chloroform, the test temperature is 25°C, and the flow rate is 1 mL / min.

[0071] Preparation Example 1

[0072] 122 mg of mandelic acid was dissolved in 15 mL of methanol, and then the pH was adjusted to 7 with a 1 mol / L sodium hydroxide aqueous solution to obtain a reaction solution I. 71 mg of lanthanum chloride hexahydrate was dissolved in 5 mL of methanol and stirred at 25° C. until dissolved to obtain a reaction solution II.

[0073] The reaction solution II was added dropwise to the reaction solution I, and the mixture was stirred at 25° C. for 1 h to obtain a mixed solution.

[0074] The mixed solution was reacted in a reactor at 130° C. for 72 hours to obtain a reaction product. The reaction product was washed with ethanol and hot water three times respectively, and then vacuum dried at 80° C. to obtain a rare earth complex.

[0075] Elemental analysis of the rare earth complex (measured values): C: 51.4 (52.06), H: 4.3 (4.25), O: 25.7 (25.88).

[0076] Preparation Example 2

[0077] The same preparation method as in Preparation Example 1 was used except that 71 mg of lanthanum chloride hexahydrate was replaced by 87 mg of cerium nitrate hexahydrate.

[0078] Elemental analysis (measured values) of the obtained rare earth complex: C: 51.3 (51.79), H: 4.26 (4.34), O: 25.6 (25.31).

[0079] Embodiments 1 to 4

[0080] 10 g of L-lactide was placed in a Schlenk tube, and the rare earth complex and initiator prepared by the method of Preparation Example 2 were added to the Schlenk tube. Then, the Schlenk tube was evacuated to a pressure of ≤10 -2 Pa. The reaction system was heated to 160°C for 12 hours, and then the temperature was rapidly lowered to terminate the reaction, thereby obtaining a reaction product. The reaction product was dissolved in chloroform, and then cold methanol was added to obtain a precipitate. The precipitate was vacuum dried at 60°C for 12 hours to obtain polylactide. The amount of rare earth complex, the type and amount of initiator are shown in Table 1.

[0081] Table 1

[0082]

[0083] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be thought of by those skilled in the art shall fall within the scope of the present invention.

Claims

1. Use of a rare earth complex as a catalyst for the ring-opening polymerization of lactide, characterized in that: The rare earth complex is formed by complexing rare earth ions and organic acids; the organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid and ferulic acid.

2. The use according to claim 1, characterized in that The rare earth ion is selected from one or more of lanthanum and cerium, and the organic acid is mandelic acid.

3. The use according to claim 1, characterized in that The rare earth complex is prepared by the following method: reacting an organic acid and a rare earth inorganic salt in the presence of alcohol and / or water to obtain a rare earth complex; The organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid and ferulic acid.

4. The use according to claim 3, characterized in that The molar ratio of the rare earth element in the organic acid and the rare earth inorganic salt is (0.6-1):0.2; The rare earth inorganic salt is selected from one or more of rare earth nitrates, rare earth chlorides, rare earth acetates, and rare earth carbonates.

5. The use according to claim 3, characterized in that: The alcohol is selected from one or more of methanol, ethanol, ethylene glycol, glycerol, isopropanol, pentaerythritol and benzyl alcohol; The reaction temperature is 100-180° C., the reaction time is 12-95 hours, and the reaction is carried out in a reactor.

6. The use according to claim 3, characterized in that: The reaction solution II containing a rare earth inorganic salt and an alcohol is added dropwise to the reaction solution I containing an organic acid and an alcohol, and then stirred at 20 to 35° C. for 0.5 to 3 hours to obtain a mixed solution; the mixed solution is reacted to obtain a rare earth complex; The pH of the reaction solution I is 6.5-7.

5.

7. The use according to claim 3, characterized in that: The reaction product obtained by the reaction is washed and then dried to obtain a rare earth complex.

8. A method for preparing polylactide, characterized in that: The method comprises the following steps: subjecting lactide to a ring-opening polymerization reaction in the presence of a rare earth complex and an initiator to obtain polylactide; The rare earth complex is formed by the complexation of rare earth ions and organic acids; the organic acid is selected from one or more of benzoic acid, mandelic acid, salicylic acid, cinnamic acid, caffeic acid, and ferulic acid; The initiator is selected from one or more of aliphatic monoalcohols or phenyl monoalcohols containing 1 to 10 carbon atoms.

9. The preparation method according to claim 8, characterized in that: The mass ratio of lactide to the rare earth complex is 10000:(1-15); based on 10 g of lactide, the amount of the initiator is 7-25 μL.

10. The preparation method according to any one of claims 8 to 9, characterized in that: The reaction temperature of the ring-opening polymerization reaction is 50-200° C., the reaction time of the ring-opening polymerization reaction is 0.5-24 hours, and the ring-opening polymerization reaction is carried out under a pressure of ≤1Pa.

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