阅读说明：本技术 一种医用丙交酯聚合物及其制备方法 (Medical lactide polymer and preparation method thereof ) 是由 李若云 吴侃 吴姗姗 李凌晨 蒋冠森 于 2021-09-15 设计创作，主要内容包括：本发明涉及一种医用丙交酯聚合物及其制备方法,将单体、催化剂和肌醇同时加入反应釜中,并进行丙交酯的开环聚合反应,待反应转化率达到60～70％时,降低反应温度至105～130℃,继续反应20～120h,结束反应,得到医用丙交酯聚合物；在所述开环聚合反应之前,所述反应釜中的水分含量占反应物总质量的100～1000ppm；所述肌醇的加入量占单体总质量的万分之一到千分之一。制得的医用丙交酯聚合物的数均分子量为15～25万g/mol,分子量分布指数为1.8～2.2；单体含量为0-2wt％；结晶度为30～65％。本发明的方法,以肌醇和水作为引发剂,一方面肌醇作为引发剂引发单体聚合,另一方面肌醇还可以作为成核剂在后面的反应过程中提高聚合物的结晶性,实现了在合成反应途中提高医用丙交酯聚合物结晶性的目的。(The invention relates to a medical lactide polymer and a preparation method thereof, wherein a monomer, a catalyst and inositol are simultaneously added into a reaction kettle, the ring-opening polymerization reaction of lactide is carried out, when the reaction conversion rate reaches 60-70%, the reaction temperature is reduced to 105-130 ℃, the reaction is continued for 20-120 h, and the reaction is finished to obtain the medical lactide polymer; before the ring-opening polymerization reaction, the water content in the reaction kettle accounts for 100-1000 ppm of the total mass of reactants; the addition amount of the inositol accounts for ten-thousandth to one thousandth of the total mass of the monomer. The number average molecular weight of the prepared medical lactide polymer is 15-25 ten thousand g/mol, and the molecular weight distribution index is 1.8-2.2; the monomer content is 0-2 wt%; the crystallinity is 30 to 65%. The method of the invention takes inositol and water as initiators, on one hand, the inositol is taken as the initiator to initiate the polymerization of the monomer, on the other hand, the inositol can also be taken as a nucleating agent to improve the crystallinity of the polymer in the following reaction process, and the purpose of improving the crystallinity of the medical lactide polymer in the synthesis reaction process is realized.)

1. A preparation method of medical lactide polymer is characterized by comprising the following steps: simultaneously adding a monomer, a catalyst and inositol into a reaction kettle, carrying out ring-opening polymerization reaction on lactide, reducing the reaction temperature to 105-130 ℃ when the reaction conversion rate reaches 60-70%, and finishing the reaction when the reaction is continued for 20-120 h to obtain a medical lactide polymer;

the monomer is lactide or a mixture of lactide and glycolide; the lactide is levorotatory lactide and/or dextrorotatory lactide; in the added monomers, the mole content of the levorotatory lactide monomer or the dextrorotatory lactide monomer is more than or equal to 60mol percent;

before the ring-opening polymerization reaction, the water content in the reaction kettle accounts for 100-1000 ppm of the total mass of reactants;

the addition amount of the inositol accounts for ten-thousandth to one thousandth of the total mass of the monomer.

2. The preparation method of the lactide polymer for medical use according to claim 1, wherein the preparation method comprises the following specific steps:

(1) uniformly mixing a catalyst, inositol and a completely melted monomer, and keeping the water content in a reaction system at 100-1000 ppm of the total mass of reactants and the micro-positive pressure of the reaction system at 0.01-0.1 Mpa;

(2) raising the temperature of the reaction system to 180-210 ℃ and reacting for 3-6 h;

(3) and (3) reducing the temperature of the reaction system to 105-130 ℃ and reacting for 20-120 h to obtain the medical lactide polymer.

3. The preparation method of the medical lactide polymer according to claim 1, wherein in the step (1), the catalyst is stannous octoate, and the dosage is one ten thousandth to one thousandth of the total mass of the monomers.

4. The preparation method of the lactide polymer for medical use according to claim 2, wherein the step (1) further comprises: firstly, putting a monomer, a catalyst and inositol into a reaction kettle at room temperature, and enabling the water content in the reaction kettle to account for 100-1000 ppm of the total mass of reactants and the micro-positive pressure in the reaction kettle to be 0.01-0.1 MPa; and then placing the closed reaction system at the temperature of 120-140 ℃, and continuously stirring to completely melt the monomers.

5. The method for preparing the medical lactide polymer according to claim 4, wherein the specific operations of making the water content in the reaction kettle account for 100-1000 ppm of the total mass of the reactants and making the micro-positive pressure in the reaction kettle be 0.01-0.1 MPa are as follows: firstly, vacuumizing a reaction kettle containing a monomer, a catalyst and inositol to be below 100Pa, then introducing high-purity nitrogen to be 0.01-0.1 MPa, repeating the replacement for 3 times, then opening a moisture test interface, continuously introducing the high-purity nitrogen into the reaction kettle, closing the moisture test interface when the moisture in a reaction system reaches 100-1000 ppm, continuously introducing the high-purity nitrogen to enable the micro-positive pressure in the reaction kettle to be 0.01-0.1 MPa, and finally closing the high-purity nitrogen and nitrogen introduction interface.

6. The process for preparing lactide polymer for medical use according to claim 5, wherein the temperature of the reaction system is adjusted by heating with an oil bath.

7. The method for preparing the medical lactide polymer according to any one of claims 1 to 6, wherein the medical lactide polymer has a number average molecular weight of 15 to 25 ten thousand g/mol and a molecular weight distribution index of 1.8 to 2.2; the monomer content is 0-2 wt%; the crystallinity is 30 to 65%.

Technical Field

The invention belongs to the technical field of lactide polymers, and relates to a medical lactide polymer and a preparation method thereof.

Background

Compared with industrial lactide polymers, medical lactide polymers have higher requirements, such as medical lactide polymers, and for medical lactide polymers for bone fixation, on one hand, the material should have sufficiently high strength, and on the other hand, the material should meet the requirement of biocompatibility. Therefore, the medical lactide polymer should have a high molecular weight and a low residual monomer content in order to reduce the processing-induced molecular weight reduction, so that the final product still has a sufficiently high molecular weight, and a low residual monomer content is also advantageous for the material to meet the biocompatibility requirements.

The ring-opening polymerization is the main method for obtaining high molecular weight medical lactide polymer at present, but the experimental result shows that the conversion rate of the reaction is about 85% when the reaction reaches the highest molecular weight, about 15% of monomer is bound to remain in the product, and the residue is far higher than the requirement of YY/T0510 or YY/T0661, so a proper method is required to be found for removing the monomer. CN103819658A discloses a production method of a medical lactide polymer with low lactide content, wherein a medical lactide polymer with a conversion rate of 10-30% is obtained firstly in the patent, then the product is further polymerized to obtain the medical lactide polymer with the conversion rate of more than 90%, then the monomer is reduced to below 5 wt% through pressure reduction, and then the lactide monomer is reduced to below 0.1 wt% through reverse inert gas, but the method needs to transfer the polymer, the whole reaction process involves a plurality of devices, and the device cost is high. Patent CN101353417A designs a multistage continuous polymerization device, lactide monomer passes through a prepolymerization reactor, twin-screw extrusion, melt pump delivery, a static mixer and a tubular reactor in sequence, to improve the conversion rate of lactide, but the lactide content in the finally obtained medical lactide polymer is within 5%, and the medical grade requirement cannot be met.

Therefore, it is very important to develop a simple and feasible method for preparing medical lactide polymer with high enough molecular weight and low monomer residue.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a low-monomer-residue high-molecular-weight lactide polymer and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following scheme:

a preparation method of a medical lactide polymer comprises the steps of adding a monomer, a catalyst and inositol into a reaction kettle at the same time, carrying out ring-opening polymerization reaction on lactide, reducing the reaction temperature to 105-130 ℃ when the reaction conversion rate reaches 60-70%, and finishing the reaction when the reaction continues for 20-120 hours to obtain the medical lactide polymer;

the monomer is lactide or a mixture of lactide and glycolide; the lactide is levorotatory lactide and/or dextrorotatory lactide; in the added monomers, the mole content of the levorotatory lactide monomer or the dextrorotatory lactide monomer is more than or equal to 60mol percent; the molar content is controlled to ensure crystallinity of the resulting lactide polymer.

Before the ring-opening polymerization reaction, the water content in the reaction kettle accounts for 100-1000 ppm of the total mass of reactants;

the addition amount of the inositol accounts for ten-thousandth to one thousandth of the total mass of the monomer.

As a preferred technical scheme:

the preparation method of the medical lactide polymer comprises the following specific steps:

(1) uniformly mixing a catalyst, inositol and a completely melted monomer, wherein the water content in a reaction system accounts for 100-1000 ppm of the total mass of reactants (the water content is enough to initiate monomer polymerization, but not too much to cause excessive later degradation), and the micro-positive pressure of the reaction system is kept at 0.01-0.1 MPa (gas leaks to the outside under micro-positive pressure, and external air cannot enter the reaction system to cause polymer degradation or reaction termination (the positive pressure already indicates that the pressure is greater than the atmospheric pressure, and the positive pressure of 0.01-0.1 MPa is 0.01-0.1 MPa greater than the atmospheric pressure), the pressure of 0.1MPa is enough, and the requirement of excessive pressure on the pressure resistance of equipment is also high);

(2) heating the temperature of the reaction system to 180-210 ℃ and reacting for 3-6 h (prepolymerization, aiming at controlling the reaction conversion rate to reach 60-70%);

(3) and (3) reducing the temperature of the reaction system to 105-130 ℃, and reacting for 20-120 h (crystallizing the polymer to promote the monomer to gather in an amorphous region and promote the consumption of the monomer, wherein the polymer cannot be crystallized when the temperature is too low or too high), so as to obtain the medical lactide polymer.

According to the preparation method of the medical lactide polymer, the catalyst is stannous octoate, and the using amount is one ten thousandth to one thousandth of the total mass of the monomers.

The preparation method of the medical lactide polymer as described above, step (1) may further include: firstly, putting a monomer, a catalyst and inositol into a reaction kettle at room temperature, and enabling the water content in the reaction kettle to account for 100-1000 ppm of the total mass of reactants and the micro-positive pressure in the reaction kettle to be 0.01-0.1 MPa; and then placing the closed reaction system at the temperature of 120-140 ℃, and continuously stirring to completely melt the monomers.

The preparation method of the medical lactide polymer enables the water content in the reaction kettle to account for 100-1000 ppm of the total mass of reactants and the micro-positive pressure in the reaction kettle to be 0.01-0.1 MPa, and comprises the following specific operations: firstly, vacuumizing a reaction kettle containing a monomer, a catalyst and inositol to be below 100Pa, then introducing high-purity nitrogen to be 0.01-0.1 MPa, repeating the replacement for 3 times, then opening a moisture test interface, continuously introducing the high-purity nitrogen into the reaction kettle, closing the moisture test interface when the moisture in a reaction system reaches 100-1000 ppm, continuously introducing the high-purity nitrogen to enable the micro-positive pressure in the reaction kettle to be 0.01-0.1 MPa, and finally closing the high-purity nitrogen and nitrogen introduction interface.

After 3 times of replacement, the system is not closed, the moisture test interface is opened once, and the moisture test interface is closed after the moisture obtained by the test is 100-1000 ppm, so that the moisture content requirement can be met. And closing the moisture test interface, and continuously filling nitrogen to increase the pressure in the system, wherein the moisture content in the high-purity nitrogen is very low, so that the moisture content in the system is stabilized at 100-1000 ppm.

In the preparation method of the medical lactide polymer, the temperature of the reaction system is adjusted by heating in an oil bath.

According to the preparation method of the medical lactide polymer, the number average molecular weight of the medical lactide polymer is 15-25 ten thousand g/mol, and the molecular weight distribution index is 1.8-2.2; the monomer content is 0-2 wt%; the crystallinity is 30 to 65%.

The mechanism of the invention is as follows:

for the ring-opening polymerization of lactide, if the polymer is gradually crystallized by the reaction to the late stage, the monomer is aggregated from the crystalline region to the amorphous region, thereby continuing the reaction. However, the crystallinity of the lactide polymer for medical use is poor, and the crystallization rate is slow and the crystallinity is low without artificially adding an auxiliary agent, so that most of the monomers are difficult to aggregate in an amorphous region. If the crystallinity of the lactide polymer for medical use is improved during the reaction, the monomers can be allowed to continue to react and the molecular weight of the polymer can be further increased.

In order to improve the crystallinity of the medical lactide polymer, the prior art mainly adopts a mode of adding an external substance, namely a crystallization nucleating agent, and for example, talcum powder, trimesic acid triamide, N' -diphenyl fatty acid dihydrazide and the like can effectively improve the crystallinity of the medical lactide polymer. However, these nucleating agents are added by blending after the synthesis of the lactide polymer for medical use is completed, and if the nucleating agents are added at the beginning of the ring-opening polymerization of lactide, the molecular weight increase is affected, and if the nucleating agents are added during the polymerization, moisture and air are easily introduced into the reaction, resulting in the degradation of the lactide polymer for medical use.

The inositol and the water in the reaction system added in the invention both play the role of an initiator and can initiate the polymerization of the lactide monomer. Wherein 100ppm to 1000ppm of moisture enables lactide to be polymerized to obtain a polymer having a high molecular weight and avoids a large decrease in molecular weight during polymerization (too small a moisture content results in too few reactive sites and a molecular weight that cannot be brought to a sufficient height; and when the moisture content is too high, degradation increases during polymerization resulting in a decrease in molecular weight). The added inositol has a huge molecular structure, the activity is lower than that of water molecules, and the dosage of the inositol is equivalent to the water content and is in the same order of magnitude, so that only part of the inositol initiates lactide to obtain a lactide polymer with inositol at the molecular chain head, and the head end of the lactide polymer is compatible with the inositol and can be used as a compatilizer of the lactide polymer obtained by initiating unreacted inositol and water.

In addition, the invention controls the temperature to be reduced when the reaction conversion rate reaches 60-70 percent, because the viscosity of the polymer is high, the unreacted monomer is difficult to continue the diffusion reaction, in addition, the invention reduces the reaction temperature to 105-130 ℃, the molten lactide polymer gradually crystallizes and changes from transparent to opaque, in the crystallization process, the residual unexcited inositol can be used as a nucleating agent to promote the rapid crystallization of the medical lactide polymer chain segment and drive the monomer to diffuse to the amorphous region, thereby being further reacted and consumed, finally obtaining the medical lactide polymer with the monomer residual quantity of less than 2 percent and promoting the further increase of the molecular weight of the lactide polymer, therefore, the lactide polymer with enough high molecular weight is obtained, and in addition, the lactide polymer has good crystallinity, thereby laying a good foundation for later molding processing.

Advantageous effects

(1) The preparation method of the medical lactide polymer takes inositol and water as initiators, on one hand, the inositol is used as the initiator to initiate monomer polymerization, on the other hand, the inositol can also be used as a nucleating agent to improve the crystallinity of the polymer in the following reaction process, and the purpose of improving the crystallinity of the medical lactide polymer in the synthesis reaction process is realized;

(2) according to the preparation method of the medical lactide polymer, when the reaction conversion rate reaches 60-70%, the polymerization temperature is reduced to 105-130 ℃ of the crystallization temperature of the medical lactide polymer, and the structure of the molecular chain head end of the medical lactide polymer has good crystallinity and can be used as a crystallization nucleating agent to promote the crystallization of the medical lactide polymer chain segment, so that unreacted monomers are discharged to an amorphous region, the concentration of the unreacted monomers is increased, the reaction is further carried out, and the reduction of the concentration of the monomers is realized;

(3) according to the preparation method of the medical lactide polymer, the synthesis of the whole reaction and the removal of the monomers are completed in one reaction kettle, the occupied area is small, and the equipment is relatively simple.

Detailed Description

The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

In the method, the specific operation that the water content in the reaction kettle accounts for 100-1000 ppm of the total mass of reactants and the micro-positive pressure in the reaction kettle is 0.01-0.1 MPa is as follows: firstly, vacuumizing a reaction kettle containing a monomer, a catalyst and inositol to be below 100Pa, introducing nitrogen to 0.01-0.1 MPa, repeatedly replacing for 3 times, then opening a moisture test interface, continuously introducing nitrogen into the reaction kettle, closing the moisture test interface when the moisture in a reaction system reaches 100-1000 ppm, continuously introducing the nitrogen to enable the micro-positive pressure in the reaction kettle to be 0.01-0.1 MPa, and finally closing the nitrogen and the nitrogen introduction interface.

Example 1

A preparation method of a medical lactide polymer comprises the following specific steps:

(1) adding stannous octoate, inositol and a completely melted monomer (levorotatory lactide) into a reaction kettle simultaneously, uniformly mixing, and keeping the water content in the reaction system to be 100ppm of the total mass of reactants and the micro-positive pressure of the reaction system to be 0.01 MPa;

wherein the addition amount of inositol accounts for ten-thousandth of the total mass of the monomers; the dosage of the stannous octoate is one ten-thousandth of the total mass of the monomer.

(2) And (3) adopting an oil bath heating mode, raising the temperature of the reaction system to 180 ℃, carrying out ring-opening polymerization reaction for 6h (the reaction conversion rate is up to 60-70%), reducing the temperature of the reaction system to 105 ℃, reacting for 120h, and finishing the reaction to obtain the medical lactide polymer.

The lactide polymer obtained by polymerizing 100 percent of levorotatory lactide monomer has crystallinity, but the crystallinity is weaker, the crystallization of the lactide polymer can be promoted under the action of inositol, and the finally prepared medical lactide polymer has the number average molecular weight of 20 ten thousand g/mol and the molecular weight distribution index of 2.2; the monomer content was 2 wt%; the crystallinity was 50%.

Comparative example 1

A method for preparing a lactide polymer, the specific steps are basically the same as those of example 1, except that inositol is not added in the step (1), and the prepared lactide polymer has the following indexes: the number average molecular weight is 10 ten thousand g/mol, and the molecular weight distribution index is 2.0; the monomer content was 10.9 wt%; the crystallinity is 12%;

comparing comparative example 1 with example 1, it can be seen that the lactide polymer in example 1 has a higher number average molecular weight, a lower monomer content and a higher crystallinity, because inositol is added as an initiator in example 1, and at a reaction stage corresponding to 105 ℃ during the reaction, at a constant temperature crystallization stage, inositol as a nucleating agent promotes the crystallization of the lactide polymer, unreacted monomers gradually aggregate to an amorphous region, the monomers gradually react to consume, and further increase of the molecular weight of the lactide polymer is promoted, whereas inositol is not added in comparative example 1, the crystallinity of the lactide polymer is not effectively improved, and the monomers cannot be further reacted to consume, so that example 1 has a higher molecular weight and crystallinity, and a lower residual monomer amount.

Comparative example 2

A method for producing a lactide polymer, substantially the same as in example 1 except that inositol in step (1) is replaced with dodecanol, wherein the lactide polymer is produced according to the following criteria: the number average molecular weight is 11 ten thousand g/mol, and the molecular weight distribution index is 2.1; the monomer content was 13 wt%; the crystallinity was 7.2%;

comparing comparative example 2 with example 1, it can be seen that the lactide polymer in example 1 has a higher number average molecular weight, a lower monomer content and a higher crystallinity, because dodecanol has a low melting point and cannot act as a nucleating agent to promote the crystallization of the lactide polymer, and therefore cannot effectively promote the consumption of monomers during the constant temperature process at 105 ℃, so that the molecular weight of the product is lower than that of example 1 and the residual amount of monomers is higher.

Comparative example 3

The preparation method of the lactide polymer basically comprises the same specific steps as example 1, except that in the step (1), the moisture content in a reaction kettle accounts for 20ppm of the total mass of reactants, and the prepared lactide polymer has the following indexes: the number average molecular weight is 20 ten thousand g/mol, and the molecular weight distribution index is 2.0; the monomer content was 30 wt%; the crystallinity was 14%. Comparative example 3 has a very high residual monomer content compared to example 1, because the low water content, less monomer to initiate the reaction, plus the large inositol molecular volume, the low ability to initiate the monomer ring opening, the final reactant available for the monomer reaction active sites are few, difficult to complete reaction, with a large amount of monomer residues.

Example 2

A preparation method of a medical lactide polymer comprises the following specific steps:

(1) firstly, monomers (a mixture of levorotatory lactide and glycolide with a molar ratio of 8: 2), stannous octoate and inositol are put into a reaction kettle at 24 ℃, and the water content in the reaction kettle accounts for 100ppm of the total mass of reactants and the micro-positive pressure in the reaction kettle is 0.01 MPa; then the closed reaction system is placed at 120 ℃ (adopting an oil bath heating mode) and is continuously stirred to completely melt the monomers.

Wherein the addition amount of inositol accounts for five ten-thousandth of the total mass of the monomers; the dosage of the stannous octoate is five ten-thousandth of the total mass of the monomer.

(2) And (3) adopting an oil bath heating mode, raising the temperature of the reaction system to 190 ℃ to perform ring-opening polymerization reaction for 3h (the reaction conversion rate is up to 60-70%), reducing the temperature of the reaction system to 110 ℃ to perform reaction for 108h, and finishing the reaction to obtain the medical lactide polymer.

The lactide polymer obtained by polymerizing levorotatory lactide and glycolide with the molar ratio of 8:2 has a large proportion of levorotatory lactide chain segments, the crystallinity of the levorotatory lactide chain segments is not completely interfered by glycolide chain segments, the levorotatory lactide chain segments still have crystallinity, but the crystallinity is weak, the crystallinity can be promoted under the action of inositol, the number average molecular weight of the finally prepared medical lactide polymer is 20 ten thousand g/mol, and the molecular weight distribution index is 2.1; the monomer content was 1.8 wt%; the crystallinity was 36%.

Example 3

A preparation method of a medical lactide polymer comprises the following specific steps:

(1) firstly, monomer (D-lactide), stannous octoate and inositol are put into a reaction kettle at 25 ℃, the water content in the reaction kettle accounts for 200ppm of the total mass of reactants, and the micro-positive pressure in the reaction kettle is 0.1 MPa; the closed reaction system is placed at 130 ℃ (heating by oil bath) and is continuously stirred to completely melt the monomers.

Wherein the addition of the inositol accounts for one thousandth of the total mass of the monomers; the dosage of the stannous octoate is three ten-thousandth of the total mass of the monomer.

(2) And (3) adopting an oil bath heating mode, raising the temperature of the reaction system to 180 ℃, carrying out ring-opening polymerization reaction for 5 hours (the reaction conversion rate is up to 60-70%), reducing the temperature of the reaction system to 120 ℃, reacting for 72 hours, and finishing the reaction to obtain the medical lactide polymer.

The lactide polymer obtained by polymerizing 100 percent of dextro-lactide monomer has crystallinity, but the crystallinity is weaker, the crystallization of the lactide polymer can be promoted under the action of inositol, and the finally prepared medical lactide polymer has the number average molecular weight of 22 ten thousand g/mol and the molecular weight distribution index of 2.2; the monomer content was 1.1 wt%; the crystallinity was 55%.

Example 4

A preparation method of a medical lactide polymer comprises the following specific steps:

(1) firstly, monomers (a mixture of levorotatory lactide and dextrorotatory lactide with a molar ratio of 6: 4), stannous octoate and inositol are put into a reaction kettle at 24 ℃, and the water content in the reaction kettle accounts for 1000ppm of the total mass of reactants and the micro-positive pressure in the reaction kettle is 0.01 MPa; then the closed reaction system is placed at 140 ℃ (heating by adopting an oil bath), and is continuously stirred to completely melt the monomers.

Wherein the addition of the inositol accounts for one thousandth of the total mass of the monomers; the dosage of the stannous octoate is one ten-thousandth of the total mass of the monomer.

(2) And (3) adopting an oil bath heating mode, raising the temperature of the reaction system to 200 ℃ to perform ring-opening polymerization for 4h (the reaction conversion rate is up to 60-70%), reducing the temperature of the reaction system to 110 ℃ to perform reaction for 108h, and finishing the reaction to obtain the medical lactide polymer.

The lactide polymer obtained by polymerizing levorotatory lactide and dextrorotatory lactide with the molar ratio of 6:4 is interfered by a dextrorotatory lactide chain segment, the crystallinity of the levorotatory lactide chain segment is weakened, but the levorotatory lactide chain segment still has crystallinity, but the crystallinity is weak, the crystallization can be promoted under the action of inositol, and the finally prepared medical lactide polymer has the number average molecular weight of 16 ten thousand g/mol and the molecular weight distribution index of 2.4; the monomer content was 0.9 wt%; the crystallinity was 30%.

Example 5

A preparation method of a medical lactide polymer comprises the following specific steps:

(1) firstly, putting a monomer (levorotatory lactide), stannous octoate and inositol into a reaction kettle at 25 ℃, and enabling the water content in the reaction kettle to account for 400ppm of the total mass of reactants and the micro-positive pressure in the reaction kettle to be 0.04 MPa; the closed reaction system is placed at 130 ℃ (heating by oil bath) and is continuously stirred to completely melt the monomers.

Wherein the addition amount of inositol accounts for ten-thousandth of the total mass of the monomers; the dosage of the stannous octoate is one thousandth of the total mass of the monomer.

(2) And (2) adopting an oil bath heating mode, raising the temperature of the reaction system to 180 ℃, carrying out ring-opening polymerization reaction for 6h (the reaction conversion rate is up to 60-70%), reducing the temperature of the reaction system to 115 ℃, reacting for 100h, and finishing the reaction to obtain the medical lactide polymer.

The lactide polymer obtained by polymerizing 100 percent of levorotatory lactide monomer has crystallinity, but the crystallinity is weaker, the crystallization of the lactide polymer can be promoted under the action of inositol, and the finally prepared medical lactide polymer has the number average molecular weight of 25 ten thousand g/mol and the molecular weight distribution index of 2.1; the monomer content was 1.8 wt%; the crystallinity was 58%.