CN114752048A - Catalyst and application of preparation method thereof in preparation of biomedical polylactic acid - Google Patents
Catalyst and application of preparation method thereof in preparation of biomedical polylactic acid Download PDFInfo
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- CN114752048A CN114752048A CN202210374793.8A CN202210374793A CN114752048A CN 114752048 A CN114752048 A CN 114752048A CN 202210374793 A CN202210374793 A CN 202210374793A CN 114752048 A CN114752048 A CN 114752048A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/83—Alkali metals, alkaline earth metals, beryllium, magnesium, copper, silver, gold, zinc, cadmium, mercury, manganese, or compounds thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
- C08G63/08—Lactones or lactides
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/823—Preparation processes characterised by the catalyst used for the preparation of polylactones or polylactides
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/84—Boron, aluminium, gallium, indium, thallium, rare-earth metals, or compounds thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/87—Non-metals or inter-compounds thereof
Abstract
The invention discloses a catalyst and application of a preparation method thereof in preparation of biomedical polylactic acid, wherein the catalyst is prepared from the following raw materials: simple substance, polyether ester, carboxylic acid/carboxylic acid metal salt mixture, zinc oxide, kaolin and carrier; the catalyst is divided into two parts, namely a catalyst-1 and a catalyst-2; the catalyst-1 comprises a carboxylic acid/carboxylic acid metal salt mixture, zinc oxide and a carrier, and the catalyst-2 comprises a simple substance, polyether esters, zinc oxide, kaolin and a carrier. The invention provides a method for preparing polylactic acid by a melt polycondensation method of a catalyst system, which has simple process and low cost through technical improvement, and the prepared catalyst is used for preparing the polylactic acid, so that the polymerization activity can be effectively improved, and the metal residue can be reduced.
Description
Technical Field
The invention belongs to the technical field of medical materials, and particularly relates to a catalyst and an application of a preparation method of the catalyst in preparation of biomedical polylactic acid.
Background
Polylactic acid is an important bio-based degradable high polymer material. It has excellent physical and mechanical properties, biodegradability and biocompatibility, can be molded and processed by a traditional method, and has good application prospect in the fields of agriculture, packaging materials, daily life, clothing, biomedical materials and the like.
Polylactic acid can be synthesized by ring-opening polymerization of lactide, which is a dimer of lactic acid, and polycondensation of lactic acid. The ring-opening polymerization method is easy to prepare the high molecular weight polylactic acid, and has realized the industrial production, but the production cost is higher.
The existing preparation method of polylactic acid generally has metal residues, and the metal catalyst residues cause cytotoxicity, so that the application of the polylactic acid in the medical field is influenced. In the traditional melt polycondensation method, the reasons for causing metal residue leakage of the product and causing biotoxicity are manifold, on one hand, the metal residue leakage is caused by the loss of a reaction vessel and a pipeline, on the other hand, the main reason is caused by the catalyst adopted by the traditional melt polycondensation method, and the important technical problem for limiting the wide-range application of polylactic acid in medical and medical polylactic acid is also solved.
In addition, Chinese patent application Nos. CN1132868C and CN1616515A disclose solid phase polycondensation methods using a solid particle dehydrating agent under vacuum, but due to the problems of separation and the like, the process has low preparation yield, low product purity, is difficult to be widely applied in the medical field, is difficult to realize continuous production, has high crystallization temperature (90-140 ℃), overlong crystallization time (2-20 hours) and solid phase polycondensation (more than 20 hours), has low efficiency and correspondingly improved cost, and is not beneficial to commercial use. Chinese patent CN1865321A discloses a solid phase polycondensation method to prepare high molecular weight heat-resistant polylactic acid copolymer, but the method needs to be crystallized under reduced pressure, and the solid phase polycondensation time is as long as 25-60 hours, and the product purity is also existed.
In conclusion, no preparation method for commercial medical grade high molecular polylactic acid really suitable for large-scale production exists at present.
Disclosure of Invention
The invention mainly solves the technical problem of providing a catalyst and an application of a preparation method thereof in preparation of biomedical polylactic acid, and provides a method for preparing polylactic acid with higher molecular weight by a melt polycondensation method with simple process and low cost of a catalyst system through technical improvement. The specific scheme comprises the following steps:
a catalyst comprising the following components:
simple substance, polyether ester, carboxylic acid/carboxylic acid metal salt mixture, zinc oxide, kaolin and carrier.
Preferably, the catalyst is divided into two parts, catalyst-1 and catalyst-2, which are prepared, stored and used in equal parts.
Preferably, the catalyst-1 comprises a carboxylic acid/carboxylic acid metal salt mixture, zinc oxide and a carrier, and the catalyst-2 comprises a simple substance, polyether esters, zinc oxide, kaolin and a carrier.
Preferably, the simple substance is one of magnesium, calcium and strontium.
Preferably, the polyether ester is tetrahydrofuran-caprolactone diol or polyethylene glycol-butylene adipate diol.
Preferably, the carboxylic acid in the carboxylic acid/carboxylic acid metal salt mixture comprises one or more of unsaturated medium chain fatty acids (2-12 carbons); the carboxylic acid in the metal carboxylate salt comprises one or more of unsaturated medium chain fatty acids (2-12 carbons), and the metal in the metal carboxylate salt comprises one or more of magnesium, calcium, aluminum and barium.
Preferably, the mass ratio of carboxylic acid to metal carboxylate in the carboxylic acid/metal carboxylate mixture is (80-90): (1-10).
Preferably, the kaolin is ultrafine calcined kaolin, having a particle size of less than 2 μm in an amount greater than 90%, and a whiteness of greater than 90%.
The carrier is one of coconut shell activated carbon, coal-based activated carbon and asphalt-based spherical activated carbon;
preferably, in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture to the zinc oxide to the carrier is (10-20): (1-5): (10-30).
Preferably, in the catalyst-2, the mass ratio of the simple substance, the polyether esters, the zinc oxide, the kaolin and the carrier is (20-30): (1-7): (3-10): (30-70).
The preparation method of the catalyst comprises the following steps:
(1) dispersing a carboxylic acid metal salt in a carboxylic acid to produce a carboxylic acid/carboxylic acid metal salt mixture;
(2) Dissolving zinc oxide and a mixture of carboxylic acid/metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving in a solvent, and stirring in an open container for 5-60min to prepare a steeping liquor-2;
(5) uniformly stirring zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
Preferably, the solvent includes one or both of methanol and ethanol.
Preferably, the amount of the solvent is 2 to 50 times of the mass of the dispersion in the current solvent, based on uniform dispersion of the dispersion. However, the volume of the impregnating solution-1 in the step 3 is not more than that of the carrier, and the volume of the impregnating solution-2 in the step 6 is not more than that of the mixed material.
Preferably, the drying comprises: drying the materials in an oven at 40-50 deg.C for 6-24 h.
Preferably, the low temperature firing comprises: raising the temperature to 45-60 ℃ at a heating rate of 1-5 ℃/min under the nitrogen atmosphere, keeping the temperature for more than 4h, and naturally cooling to room temperature.
Preferably, the firing comprises: heating to 80-90 deg.C at a heating rate of 1-15 deg.C/min under nitrogen atmosphere, maintaining for more than 4h, and naturally cooling to room temperature.
A method for preparing biomedical polylactic acid by adopting the catalyst comprises the following steps:
(1) under the normal pressure state, no catalyst is added, and the moisture in the raw material lactic acid is removed by blowing inert gas, wherein the dehydration temperature is 50-60 ℃, and the dehydration time is 1-5 hours;
(2) adding a catalyst-1 into the dehydrated lactic acid, reacting in a low vacuum state, and then continuing to perform pre-polycondensation in a high vacuum state, wherein the polymerization dehydration temperature is 120-;
(3) combining a catalyst-2 with isocyanate, and carrying out melt vacuum polycondensation on a lactic acid prepolymer obtained by a prepolymerization process, wherein the polymerization temperature is 140-155 ℃, and the polymerization time is 5-10 hours.
Preferably, in step (2), the amount of catalyst-1 is 0.05-0.2% wt based on the mass of lactic acid.
Preferably, in the step (3), the isocyanate comprises one or two of HDI or IPDI, and the ratio of the amount of the substance of the isocyanate to the sum of the amounts of the simple substance and the zinc oxide substance in the catalyst-2 is 1:1 to 10: 1. (HDI means hexamethylene diisocyanate, IPDI means isophorone diisocyanate)
Preferably, in step (3), catalyst-2 is used in an amount of 0.4 to 0.6% wt based on the mass of the lactic acid prepolymer.
Preferably, in step (1), the inert gas is replaced by nitrogen or carbon dioxide.
Preferably, in the step (2), the low vacuum degree is 2000-10000Pa, and the high vacuum degree is 20-1000 Pa.
Preferably, in step (3), the vacuum is 20 to 1000 Pa.
The invention has at least the following advantages:
1) the invention adopts a melt direct polycondensation method, has high reactant concentration, does not adopt any organic solvent, has simple production equipment, is convenient to operate and is easy to realize industrial continuous production.
2) The invention is very suitable for the requirement of mild conditions in material engineering, the reaction time is short, the reaction conditions are easy to control, the molecular weight of the obtained product polylactic acid is 2-20 ten thousand, and the material can be widely applied to the industries of medicine and the like.
3) Compared with a single catalyst, the catalyst adopted in the invention has higher polymerization activity under the same condition, and the obtained product can meet the requirements on metal residue and biotoxicity in clinical application without special treatment;
4) the basis of the design idea of the invention is still that the polylactic acid is synthesized by a ring-opening polymerization method, the two-step reaction is carried out, in the first step, the lactic acid is subjected to dehydration and cyclization, and in the second step, the polylactic acid is prepared by ring-opening polymerization, a new composite catalyst is developed by means of years of research and production experience, and a large number of experiments verify that the components and properties are detected by sampling the system along with the reaction, after the lactic acid subjected to water removal in the reaction step (2) provided by the invention is added with the catalyst-1, the dehydration and cyclization reaction is carried out, and after the catalyst-2 is added in the step (3), the ring-opening polymerization reaction is carried out, so that the polylactic acid is generated. It was verified that a small amount of polylactic acid product may be present in step (2) without significant effect on the overall production yield and product properties.
5) The composite catalyst used in the present invention, which comprises a carboxylate metal salt, is known to be, in general, the catalyst can cause metal residue, has biotoxicity and influences the application range of materials, but the catalyst adopted by the invention can greatly reduce the metal residue (reaching the medical standard) on the basis of effectively improving the activity of the polymerization reaction by adopting the catalyst, this is probably due to the fact that on the one hand, specific metals, carboxylic acids and their proportions are used, and on the other hand, a composite catalyst system is used instead of a simple metal salt catalyst, the method is different from all the technical means for solving the problem of metal residue in the past (the former means does not adopt a metal-containing catalyst, and often causes a series of problems of low polymerization activity, poor controllability of a reaction process and the like), and has important significance for the application of polylactic acid in the medical field.
Detailed Description
The following detailed description of the preferred embodiments of the present invention is provided to enable those skilled in the art to more readily understand the advantages and features of the present invention, and to clearly and unequivocally define the scope of the present invention.
Unless otherwise stated, the separation and purification methods of the products obtained in the following examples and comparative examples are all conventional methods for preparing polylactic acid in the laboratory: chloroform dissolves the polymerization product and methanol is separated out.
Example 1 preparation of the catalyst:
(1) dispersing a carboxylic acid metal salt in a carboxylic acid to produce a carboxylic acid/carboxylic acid metal salt mixture;
(2) dissolving zinc oxide and a mixture of carboxylic acid/metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving the mixture in a solvent, and stirring the mixture in an open container for 5-60min to prepare an impregnation liquid-2;
(5) uniformly stirring and mixing zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The simple substance is magnesium.
The polyether ester is tetrahydrofuran-caprolactone diol.
The carboxylic acid in the carboxylic acid/metal carboxylate mixture comprises alpha-linolenic acid; the metal in the metal carboxylate salt comprises calcium.
The mass ratio of carboxylic acid to metal carboxylate salt in the carboxylic acid/metal carboxylate salt mixture is 80: 10.
The kaolin is superfine calcined kaolin, the amount of the kaolin with the particle size less than 2 mu m is more than 90%, and the whiteness is more than 90%.
The carrier is coconut shell activated carbon (purchased);
in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is 10:5: 30).
In the catalyst-2, the mass ratio of the simple substance, the polyether esters, the zinc oxide, the kaolin and the carrier is 30:20:2:5: 30.
The solvent includes methanol.
The dosage of the solvent is 50 times of the mass of the dispersion in the current solvent, and the dispersion is uniform. However, the volume of the impregnating solution-1 in the step 3 is not more than that of the carrier, and the volume of the impregnating solution-2 in the step 6 is not more than that of the mixed material.
The drying comprises the following steps: the material was placed in an oven at 40-50 ℃ for 24 h.
The low-temperature roasting comprises the following steps: under the nitrogen atmosphere, the temperature is raised to 60 ℃ at the heating rate of 5 ℃/min and kept for 9h, and the mixture is naturally cooled to the room temperature.
The roasting comprises the following steps: under the nitrogen atmosphere, the temperature is raised to 90 ℃ at the heating rate of 15 ℃/min and kept for 8h, and the mixture is naturally cooled to the room temperature.
Example 2 preparation of catalyst:
(1) dispersing a metal carboxylate salt in a carboxylic acid to produce a carboxylic acid/metal carboxylate salt mixture;
(2) dissolving zinc oxide and a mixture of carboxylic acid and metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) Stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving the mixture in a solvent, and stirring the mixture in an open container for 5-60min to prepare an impregnation liquid-2;
(5) uniformly stirring and mixing zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The simple substance is calcium.
The polyether ester is polyethylene glycol-butanediol adipate glycol.
The carboxylic acid in the carboxylic acid/metal carboxylate mixture comprises alpha-linolenic acid and the metal in the metal carboxylate comprises magnesium.
The mass ratio of carboxylic acid to metal carboxylate salt in the carboxylic acid/metal carboxylate salt mixture is 90: 5.
The kaolin is superfine calcined kaolin, the amount of the kaolin with the particle size less than 2 mu m is more than 90%, and the whiteness is more than 90%.
The carrier is coal-based activated carbon (purchased);
in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is 20:1: 10.
In the catalyst-2, the mass ratio of the simple substance to the polyether esters to the zinc oxide to the kaolin to the carrier is 20:30:7:10: 50.
The solvent comprises ethanol.
The dosage of the solvent is 20 times of the mass of the dispersion in the current solvent, and the dispersion is uniform. However, the volume of the impregnating solution-1 in the step 3 is not more than that of the carrier, and the volume of the impregnating solution-2 in the step 6 is not more than that of the mixed material.
The drying comprises the following steps: the material was placed in an oven at 40-50 ℃ for 6 h.
The low-temperature roasting comprises the following steps: under the nitrogen atmosphere, the temperature is raised to 45 ℃ at the heating rate of 5 ℃/min and kept for 4h, and the mixture is naturally cooled to the room temperature.
The roasting comprises the following steps: under the nitrogen atmosphere, the temperature is increased to 80 ℃ at the heating rate of 10 ℃/min and kept for 5h, and the mixture is naturally cooled to the room temperature.
Example 3 preparation of catalyst:
(1) dispersing a metal carboxylate salt in a carboxylic acid to produce a carboxylic acid/metal carboxylate salt mixture;
(2) dissolving zinc oxide and a mixture of carboxylic acid and metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving in a solvent, and stirring in an open container for 5-60min to prepare a steeping liquor-2;
(5) Uniformly stirring and mixing zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The simple substance is strontium.
The polyether ester is tetrahydrofuran-caprolactone diol.
The carboxylic acid in the carboxylic acid/metal carboxylate mixture comprises alpha-linolenic acid; the metal in the metal carboxylate salt comprises aluminum.
The mass ratio of carboxylic acid to metal carboxylate salt in the carboxylic acid/metal carboxylate salt mixture is 60: 5.
The kaolin is superfine calcined kaolin, the amount of the kaolin with the particle size less than 2 mu m is more than 90%, and the whiteness is more than 90%.
The carrier is pitch-based spherical activated carbon (purchased);
in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is 5:3: 20.
In the catalyst-2, the mass ratio of the simple substance, the polyether esters, the zinc oxide, the kaolin and the carrier is 25:27:4:7: 55.
The obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The solvent comprises a mixed solvent prepared by the volume ratio of methanol to ethanol of 1: 1.
The dosage of the solvent is 35 times of the mass of the dispersion in the current solvent, and the dispersion is uniform. However, the volume of the impregnation liquid-1 in the step 3 is not more than that of the carrier, and the volume of the impregnation liquid-2 in the step 6 is not more than that of the mixed material.
The drying comprises the following steps: the material was placed in an oven at 40-50 ℃ for 18h to dry.
The low-temperature roasting comprises the following steps: raising the temperature to 50 ℃ at a heating rate of 3 ℃/min for 7h in a nitrogen atmosphere, and naturally cooling to room temperature.
The roasting comprises the following steps: raising the temperature to 790 ℃ at a heating rate of 8 ℃/min for 6h in a nitrogen atmosphere, and naturally cooling to room temperature.
Preparation of catalyst of comparative example 1 (zinc oxide was not included in catalyst-1):
(1) dispersing a metal carboxylate salt in a carboxylic acid to produce a carboxylic acid/metal carboxylate salt mixture;
(2) dissolving zinc oxide and a mixture of carboxylic acid and metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving in a solvent, and stirring in an open container for 5-60min to prepare a steeping liquor-2;
(5) Uniformly stirring and mixing zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The simple substance is strontium.
The polyether ester is tetrahydrofuran-caprolactone diol.
The carboxylic acid in the carboxylic acid/metal carboxylate mixture comprises alpha-linolenic acid; the metal in the metal carboxylate salt comprises aluminum.
The mass ratio of carboxylic acid to metal carboxylate salt in the carboxylic acid/metal carboxylate salt mixture is 60: 5.
The kaolin is superfine calcined kaolin, the amount of the kaolin with the particle size less than 2 mu m is more than 90%, and the whiteness is more than 90%.
The carrier is pitch-based spherical activated carbon (purchased);
in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is 5:3: 20.
In the catalyst-2, the mass ratio of the simple substance, the polyether esters, the zinc oxide, the kaolin and the carrier is 25:27:4:7: 55.
The obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The solvent comprises a mixed solvent prepared by the volume ratio of methanol to ethanol of 1: 1.
The dosage of the solvent is 35 times of the mass of the dispersion in the current solvent, and the dispersion is uniform. However, the volume of the impregnation liquid-1 in the step 3 is not more than that of the carrier, and the volume of the impregnation liquid-2 in the step 6 is not more than that of the mixed material.
The drying comprises the following steps: the material was placed in an oven at 40-50 ℃ for 18h to dry.
The low-temperature roasting comprises the following steps: raising the temperature to 50 ℃ at a heating rate of 3 ℃/min for 7h in a nitrogen atmosphere, and naturally cooling to room temperature.
The roasting comprises the following steps: raising the temperature to 790 ℃ at a heating rate of 8 ℃/min for 6h under the nitrogen atmosphere, and naturally cooling to room temperature.
Comparative example 2 preparation of catalyst (zinc oxide was not included in catalyst-2):
(1) dispersing a metal carboxylate salt in a carboxylic acid to produce a carboxylic acid/metal carboxylate salt mixture;
(2) dissolving zinc oxide and a mixture of carboxylic acid and metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving in a solvent, and stirring in an open container for 5-60min to prepare a steeping liquor-2;
(5) Uniformly stirring and mixing zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The simple substance is strontium.
The polyether ester is tetrahydrofuran-caprolactone diol.
The carboxylic acid in the carboxylic acid/metal carboxylate mixture comprises alpha-linolenic acid; the metal in the metal carboxylate salt comprises aluminum.
The mass ratio of carboxylic acid to metal carboxylate salt in the carboxylic acid/metal carboxylate salt mixture is 60: 5.
The kaolin is superfine calcined kaolin, the amount of the kaolin with the particle size less than 2 mu m is more than 90%, and the whiteness is more than 90%.
The carrier is pitch-based spherical activated carbon (purchased);
in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is 5:3: 20.
In the catalyst-2, the mass ratio of the simple substance, the polyether esters, the zinc oxide, the kaolin and the carrier is 25:27:4:7: 55.
The obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The solvent comprises a mixed solvent prepared by the volume ratio of methanol to ethanol of 1: 1.
The dosage of the solvent is 35 times of the mass of the dispersion in the current solvent, and the dispersion is uniform. However, the volume of the impregnating solution-1 in the step 3 is not more than that of the carrier, and the volume of the impregnating solution-2 in the step 6 is not more than that of the mixed material.
The drying comprises the following steps: the material was placed in an oven at 40-50 ℃ for 18 h.
The low-temperature roasting comprises the following steps: under the nitrogen atmosphere, heating to 50 ℃ at the heating rate of 3 ℃/min, keeping for 7h, and naturally cooling to room temperature.
The roasting comprises the following steps: raising the temperature to 790 ℃ at a heating rate of 8 ℃/min for 6h under the nitrogen atmosphere, and naturally cooling to room temperature.
Comparative example 3 preparation of catalyst (different metal, carboxylic acid ratios):
(1) dispersing a metal carboxylate salt in a carboxylic acid to produce a carboxylic acid/metal carboxylate salt mixture;
(2) dissolving zinc oxide and a mixture of carboxylic acid and metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving in a solvent, and stirring in an open container for 5-60min to prepare a steeping liquor-2;
(5) Uniformly stirring and mixing zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The simple substance is strontium.
The polyether ester is tetrahydrofuran-caprolactone diol.
The carboxylic acid in the carboxylic acid/metal carboxylate mixture comprises alpha-linolenic acid; the metal in the metal carboxylate salt comprises aluminum.
The mass ratio of carboxylic acid to metal carboxylate salt in the carboxylic acid/metal carboxylate salt mixture is 80: 13.
The kaolin is superfine calcined kaolin, the amount of the kaolin with the particle size less than 2 mu m is more than 90%, and the whiteness is more than 90%.
The carrier is pitch-based spherical activated carbon (purchased);
in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is 5:3: 20.
In the catalyst-2, the mass ratio of the simple substance, the polyether esters, the zinc oxide, the kaolin and the carrier is 25:27:4:7: 55.
The obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The solvent comprises a mixed solvent prepared by the volume ratio of methanol to ethanol of 1: 1.
The dosage of the solvent is 35 times of the mass of the dispersion in the current solvent, and the dispersion is uniform. However, the volume of the impregnation liquid-1 in the step 3 is not more than that of the carrier, and the volume of the impregnation liquid-2 in the step 6 is not more than that of the mixed material.
The drying comprises the following steps: the material was placed in an oven at 40-50 ℃ for 18h to dry.
The low-temperature roasting comprises the following steps: raising the temperature to 50 ℃ at a heating rate of 3 ℃/min for 7h in a nitrogen atmosphere, and naturally cooling to room temperature.
The roasting comprises the following steps: raising the temperature to 790 ℃ at a heating rate of 8 ℃/min for 6h in a nitrogen atmosphere, and naturally cooling to room temperature.
Comparative example 4 preparation of catalyst (different metal, carboxylic acid ratios):
(1) dispersing a carboxylic acid metal salt in a carboxylic acid to produce a carboxylic acid/carboxylic acid metal salt mixture;
(2) dissolving zinc oxide and a mixture of carboxylic acid and metal carboxylate in a solvent, and stirring in an open container to prepare an impregnation liquid-1;
(3) stirring the impregnation liquid-1 and a carrier in an open container, drying the obtained mixture at normal temperature, and roasting at low temperature to obtain a catalyst-1;
(4) under the condition of water bath at 30-40 ℃, mixing a simple substance and polyether esters, dissolving in a solvent, and stirring in an open container for 5-60min to prepare a steeping liquor-2;
(5) Uniformly stirring and mixing zinc oxide, kaolin and a carrier in an open container to obtain a mixed material;
(6) adding the impregnation liquid-2 obtained in the step 4 into the mixed material obtained in the step 5, and continuously stirring and uniformly mixing in an open container;
(7) drying and roasting the mixture obtained in the step 6 to obtain a catalyst-2;
the obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The simple substance is strontium.
The polyether ester is tetrahydrofuran-caprolactone diol.
The carboxylic acid in the carboxylic acid/metal carboxylate mixture comprises alpha-linolenic acid; the metal in the metal carboxylate salt comprises aluminum.
The mass ratio of carboxylic acid to metal carboxylate in the carboxylic acid/metal carboxylate mixture is 95: 1.
The kaolin is superfine calcined kaolin, the amount of the particle size of the kaolin smaller than 2 mu m is more than 90%, and the whiteness is more than 90%.
The carrier is pitch-based spherical activated carbon (purchased);
in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is 5:3: 20.
In the catalyst-2, the mass ratio of the simple substance, the polyether esters, the zinc oxide, the kaolin and the carrier is 25:27:4:7: 55.
The obtained catalyst-1 and catalyst-2 are packaged and stored respectively, and are used according to requirements.
The solvent comprises a mixed solvent prepared by the volume ratio of methanol to ethanol of 1: 1.
The dosage of the solvent is 35 times of the mass of the dispersion in the current solvent, and the dispersion is uniform. However, the volume of the impregnation liquid-1 in the step 3 is not more than that of the carrier, and the volume of the impregnation liquid-2 in the step 6 is not more than that of the mixed material.
The drying comprises the following steps: the material was placed in an oven at 40-50 ℃ for 18h to dry.
The low-temperature roasting comprises the following steps: under the nitrogen atmosphere, heating to 50 ℃ at the heating rate of 3 ℃/min, keeping for 7h, and naturally cooling to room temperature.
The roasting comprises the following steps: raising the temperature to 790 ℃ at a heating rate of 8 ℃/min for 6h under the nitrogen atmosphere, and naturally cooling to room temperature.
Comparative example 5 preparation of a medical polylactic acid (using stannous catalyst, one-step synthesis):
(1) under the anhydrous and anaerobic condition, 5kg of L-lactide (L-lactide) with the purity of 99.8 percent is added into a polymerization reaction bottle. 1.40ml of stannous octoate and 1.98ml of dodecanol, L-lactide, stannous octoate and dodecanol are added successively according to the molar ratio of 8000: 1: 2. vacuumizing to remove water and oxygen.
(2) Dissolving a monomer at 130 ℃, sealing a pipe by using a high-temperature spray gun under the high vacuum of 500-1000 Pa, ensuring the vacuum degree of a system, reacting for 48 hours, and stirring along with magnetons in the reaction process.
(3) Chloroform dissolves the polymerization product, and methanol is separated out to obtain the polylactic acid with the weight-average molecular weight of 320 KDa.
Comparative example 6 preparation of a medical polylactic acid (two-step synthesis using bicyclic guanidine catalyst):
80g of L-lactic acid (90% by mass) was charged into the reaction vessel, and the vacuum-argon filling operation was repeated three times. Heating to 120 ℃ under 200Torr, and carrying out dehydration reaction for 1 h. The reaction vessel was then depressurized to 100Torr and the reaction was continued at 150 ℃ for 1 hour. Then, the reaction kettle is decompressed to 30Torr, and the reaction is continued for 1h at 170 ℃ to obtain the OLLA.
11.1mg of bicyclic guanidine as a catalyst was added to the reaction vessel, and the pressure in the reaction vessel was reduced to 10Torr, and the temperature was raised to 210 ℃ to react for 20 hours. After the reaction is stopped, the reaction kettle is cooled to room temperature, the polymer is dissolved by acetone, then the solution is poured into ethanol with the temperature of 0 ℃, the pressure is reduced and filtered, and the solid is dried for 36 hours at the temperature of 50 ℃ under vacuum to obtain white solid, namely high biological safetyThe yield of the medicinal polylactic acid is 71.7 percent, and the molecular weight of the polymer is 4.2 multiplied by 104，PDI 1.88。
And (3) performance detection: the catalysts obtained in the above examples 1-3 and comparative examples 1-5 are used for preparing polylactic acid, and the preparation method comprises the following steps:
(1) under the normal pressure state, no catalyst is added, and the moisture in the raw material lactic acid is removed by blowing inert gas, wherein the dehydration temperature is 60 ℃, and the dehydration time is 5 hours;
(2) Adding a catalyst-1 into the dehydrated lactic acid, reacting in a low vacuum state, and then continuing to perform pre-polycondensation in a high vacuum state, wherein the polymerization dehydration temperature is 130 ℃, and the total polymerization dehydration time is 4 hours;
(3) combining a catalyst-2 with isocyanate, and carrying out melt vacuum polycondensation on a lactic acid prepolymer obtained by a prepolymerization process, wherein the polymerization temperature is 155 ℃, and the polymerization time is 5 hours.
In the step (2), the dosage of the catalyst-1 is 0.2 wt% of the mass of the lactic acid.
In the step (3), the isocyanate includes HDI, and the ratio of the amount of the substance of the isocyanate to the sum of the amounts of the simple substance and the zinc oxide substance in the catalyst-2 is 10: 1. .
In the step (3), the amount of the catalyst-2 is 0.6 wt% of the mass of the lactic acid prepolymer.
In the step (1), the inert gas is nitrogen.
In the step (2), the low vacuum degree is 10000Pa, and the high vacuum degree is 1000 Pa.
In the step (3), the vacuum degree is 1000 Pa.
In the preparation process, an online real-time viscosity monitoring system is adopted for a polymerization reaction system to carry out real-time viscosity monitoring; and (3) sampling the obtained product for metal residue detection: the method comprises the following steps of (1) digesting a polylactic acid sample by using a Multiwave 5000 microwave digestion instrument in cooperation with a 20SVT50 rotor, detecting residual metals (including metal ions of adopted carboxylic acid, metals related in simple substances, metals such as heavy metal and the like caused by pollution of pipelines and the like) in a product by using a digestion temperature of 240 ℃ at most, converting metal ions (not calculating anions) into the mass of the metal simple substances, and finally calculating the mass percentage of the metal simple substances in the mass of the carboxylic acid sample, wherein the results are as follows:
Firstly, in the aspect of real-time viscosity change, the viscosity of the system is detected before the pre-polycondensation reaction is started as the initial viscosity, the ratio (%) of the viscosity of the system detected in real time to the initial viscosity after the pre-polycondensation reaction is started is recorded as the viscosity ratio (see table 1 specifically), and the inventor finds that the viscosity of the system is increased to 141% -166% of the initial viscosity 0.5h after the pre-polycondensation reaction is started by adopting the catalyst prepared in the embodiment 1-3, which is obviously higher than that of the comparative example 1-6, and the catalyst adopted in the invention has a more prominent contribution to improving the polymerization activity no matter in the aspect of the adopted composite catalytic system or in the aspect of the adopted specific ratio, especially. Secondly, in terms of metal residue, as can be seen from detection results, the catalyst component provided by the invention reduces the metal residue to a certain extent, and on the other hand, the proportional relationship between reagents also reduces the metal residue to a certain extent, and in addition, we find that the heavy metal pollution residue caused by pipeline pollution is also remarkably reduced (relative to comparative example 5) by adopting our catalyst, and we guess that the influence of a reaction system on pipelines, reaction vessels and the like can be reduced probably due to the composite catalyst adopted by the invention; furthermore, the reduction in the amount of residual metal may be attributed to the fact that, after the use of the composite catalyst, the metal can be efficiently separated out in the subsequent purification step after the polymerization is completed, which is the main reason we guess. In addition, the preparation of polylactic acid with different molecular weights is tested, the molecular weight of the obtained product polylactic acid can be controlled to be 2-20 ten thousand by controlling the polymerization time (sum of the time of the prepolymerization reaction and the polycondensation reaction) to be 2-15h, and the metal residues are controlled to be below 0.0060% by weight. In addition, the weight average molecular weights of the products prepared in examples 1 to 3 of the present application were 18 ten thousand, 19 ten thousand and 19 ten thousand, respectively, and the polylactic acid prepared by the same method had a relatively stable molecular weight and a molecular weight distribution of 1.10 or less. In conclusion, the composite catalyst prepared by adopting the specific reagent and the specific proportion can obtain higher polymerization activity, reduce metal residue, and easily control the molecular weight of the product within a larger range, thereby being suitable for large-scale production and application.
TABLE 1 test results
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification, or any other related technical fields directly or indirectly, are included in the scope of the present invention.
Claims (10)
1. The catalyst is characterized by comprising the following components:
simple substance, polyether ester, carboxylic acid/carboxylic acid metal salt mixture, zinc oxide, kaolin and carrier.
2. The catalyst of claim 1, wherein: the catalyst is divided into two parts, namely a catalyst-1 and a catalyst-2; the catalyst-1 comprises a carboxylic acid/carboxylic acid metal salt mixture, zinc oxide and a carrier, and the catalyst-2 comprises a simple substance, polyether esters, zinc oxide, kaolin and a carrier.
3. The catalyst of claim 1, wherein: the simple substance is one of magnesium, calcium and strontium.
4. The catalyst of claim 1, wherein: the polyether ester is tetrahydrofuran-caprolactone diol or polyethylene glycol-butanediol adipate diol.
5. The catalyst of claim 1, wherein: the carboxylic acid in the carboxylic acid/carboxylic acid metal salt mixture comprises one or more of unsaturated medium chain fatty acids (2-12 carbons).
6. The catalyst of claim 1, wherein: the carboxylic acid in the carboxylic acid metal salt in the carboxylic acid/carboxylic acid metal salt mixture comprises one or more than two of unsaturated medium chain fatty acids (2-12 carbons), and the metal in the carboxylic acid metal salt comprises one or more than two of magnesium, calcium, aluminum and barium.
7. The catalyst of claim 1, wherein: the mass ratio of the carboxylic acid to the metal carboxylate in the carboxylic acid/metal carboxylate mixture is (80-90) to (1-10).
8. The catalyst of claim 1, wherein: the kaolin is superfine calcined kaolin, the amount of the kaolin with the particle size less than 2 mu m is more than 90 percent, and the whiteness is more than 90 percent; the carrier is one of coconut shell activated carbon, coal-based activated carbon and pitch-based spherical activated carbon.
9. The catalyst of claim 1, wherein: in the catalyst-1, the mass ratio of the carboxylic acid/carboxylic acid metal salt mixture, the zinc oxide and the carrier is (10-20): 1-5): 10-30; in the catalyst-2, the mass ratio of the simple substance, the polyether ester, the zinc oxide, the kaolin and the carrier is (20-30): (20-30): 1-7): 3-10): 30-70.
10. Use of a catalyst according to any one of claims 1 to 9 in the preparation of biomedical grade polylactic acid.
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