阅读说明：本技术 一种聚乳酸及其立构复合物膜材料和制备方法 (Polylactic acid and stereocomplex film material thereof and preparation method ) 是由 景占鑫 黄晓兰 廖梦玲 杜晓梅 刘幸琪 廖铭能 洪鹏志 李�泳 于 2021-07-30 设计创作，主要内容包括：本发明提出了一种聚乳酸及其立构复合物膜材料和制备方法,包括以下步骤：双羟基小分子有机化合物、内酯单体以及催化剂反应得到双羟基官能化共聚酯；双羟基官能化共聚酯、丙交酯及催化剂,反应得到双羟基官能化共聚酯/聚乳酸嵌段共聚物；将双羟基官能化共聚酯/聚乳酸嵌段共聚物、2(6-异氰酸酯已脲基)-6-甲基4[1H]-嘧啶酮加入甲苯中,加入催化剂,反应得到柔性多嵌段聚合物；将柔性多嵌段聚合物与左旋聚乳酸和/或右旋聚乳酸混合,通过流延法或共混造粒、注塑成型,得到聚乳酸或聚乳酸立构复合物膜材料。与常规聚乳酸及其立构复合物材料的增韧相比,本发明所制备的聚乳酸或聚乳酸立构复合物膜材料具有较高的力学强度和韧性,具有用作包装材料的潜力。(The invention provides a polylactic acid and a stereocomplex film material thereof and a preparation method, comprising the following steps: reacting a dihydroxyl micromolecule organic compound, a lactone monomer and a catalyst to obtain dihydroxyl functionalized copolyester; the dihydroxy functional copolyester, lactide and catalyst react to obtain dihydroxy functional copolyester/polylactic acid block copolymer; adding a dihydroxy functional copolyester/polylactic acid block copolymer and 2 (6-isocyanate-hexamethylene ureido) -6-methyl 4[1H ] -pyrimidone into toluene, adding a catalyst, and reacting to obtain a flexible multi-block polymer; mixing the flexible multi-block polymer with the levorotatory polylactic acid and/or the dextrorotatory polylactic acid, and obtaining the polylactic acid or polylactic acid stereocomplex film material through tape casting or blending granulation and injection molding. Compared with the toughening of the conventional polylactic acid and the stereocomplex material thereof, the polylactic acid or the stereocomplex material of the polylactic acid prepared by the invention has higher mechanical strength and toughness and has the potential of being used as a packaging material.)

1. A preparation method of polylactic acid and a stereocomplex film material thereof is characterized by comprising the following steps:

reacting a dihydroxyl micromolecule organic compound, a lactone monomer and a catalyst to obtain dihydroxyl functionalized copolyester;

the dihydroxy functional copolyester, lactide and catalyst react to obtain dihydroxy functional copolyester/polylactic acid block copolymer;

adding a dihydroxy functional copolyester/polylactic acid block copolymer and 2 (6-isocyanate-hexamethylene ureido) -6-methyl 4[1H ] -pyrimidone into toluene, adding a catalyst, and reacting to obtain a flexible multi-block polymer;

and carrying out tape casting or blending granulation and injection molding on the flexible multi-block polymer and the levorotatory polylactic acid and/or the dextrorotatory polylactic acid to obtain the polylactic acid or polylactic acid stereocomplex film material.

2. The method according to claim 1, wherein the dihydroxy small molecule organic compound is one of ethylene glycol, diethylene glycol, propylene glycol and 1, 4-butanediol, and the amount of dihydroxy small molecule organic compound added is 0.05-10% of the amount of lactone monomer material.

3. The method of claim 1, wherein the lactone monomer is one or more of epsilon-caprolactone, delta-valerolactone, and racemic lactide.

4. The method of claim 1, wherein the lactide is one or both of levorotatory lactide and dextrorotatory lactide.

5. The method of claim 1, wherein the product obtained in each step is purified by dissolving with dichloromethane or chloroform, and then precipitating with methanol.

6. The method of claim 1, wherein the catalyst is stannous octoate or dibutyltin dilaurate; the dosage of the catalyst is 0.05-1.0% of the total amount of lactone monomers or lactide substances, or 0.5-5.0% of the amount of the dihydroxyl functionalized copolyester/polylactic acid block copolymer.

7. The method of claim 1, wherein the molar ratio of lactide to dihydroxy functional copolyester building blocks is (10-1) to (1-2).

8. The method of claim 1, wherein the mass ratio of the dihydroxy functional copolyester/polylactic acid block copolymer to 2 (6-isocyanatoureyl) -6-methyl 4[1H ] -pyrimidinone is (0.5-2): 1.

9. The method according to claim 1, wherein the used L-polylactic acid has a molecular weight of 10-20 ten thousand and the used D-polylactic acid has a molecular weight of 6-15 ten thousand;

the mass ratio of the levorotatory polylactic acid to the dextrorotatory polylactic acid is (10-0) to (0-10);

the mass ratio of the flexible multi-block polymer to the levorotatory polylactic acid and/or the dextrorotatory polylactic acid is (3-50): 100.

10. Polylactic acid and a stereocomplex film material thereof, characterized by being prepared by the method of any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of biodegradable high polymer material modification, and more particularly relates to polylactic acid and a stereocomplex film material thereof and a preparation method thereof.

Background

With the increasing environmental problems caused by petrochemical-based polymer materials, biomass-based polymer materials based on renewable resources such as starch, straw and the like have been rapidly developed. Among many biomass-based polymers, polylactic acid is known as the most promising species for development. However, polylactic acid and stereocomplex materials thereof still have the defect of poor toughness, so that the application of the polylactic acid and stereocomplex materials is limited.

In recent years, with the increasing awareness of environmental protection, the importance of polylactic acid and its stereocomplex materials is becoming more apparent, and various methods for toughening polylactic acid and its stereocomplex materials are being developed, wherein polylactic acid or its stereocomplex materials and flexible polymers are mainly blended and modified, and some patents disclose modified polylactic acid materials and polylactic acid toughening materials, but these materials use a large amount of plasticizers or generate significant phase separation during the preparation process, so that the melt strength is reduced or the toughening effect is limited. The other is that in the blending modification processing process of polylactic acid or a stereocomplex material thereof, molecules with functional groups are introduced, and the molecules and the polylactic acid or the stereocomplex thereof generate chemical reaction to form an interface layer at a two-phase interface so as to improve the phase interface adhesive force. This will introduce chemical cross-linking structure in polylactic acid or its stereo composite material, reduce the degradation performance of polylactic acid or its stereo composite material, and also affect its recovery thermoplastic reprocessing performance.

The modified polylactic acid and the stereo composite material thereof have obviously reduced mechanical strength, influence on the processing technology, degradation performance, recycled thermoplastic reprocessing performance and the like, and seriously limit the large-scale application of the polylactic acid and the stereo composite material thereof in more fields.

Disclosure of Invention

In order to overcome the defects of the existing toughening method of polylactic acid and stereocomplex materials thereof in material processing conditions and performance, the invention provides polylactic acid and stereocomplex film materials thereof and a preparation method thereof.

The technical scheme adopted by the invention is that,

a preparation method of polylactic acid and a stereocomplex film material thereof comprises the following steps:

reacting a dihydroxyl micromolecule organic compound, a lactone monomer and a catalyst to obtain dihydroxyl copolyester;

the dihydroxy functional copolyester, lactide and catalyst react to obtain dihydroxy functional copolyester/polylactic acid block copolymer;

adding a dihydroxy functional copolyester/polylactic acid block copolymer and 2 (6-isocyanate-hexamethylene ureido) -6-methyl 4[1H ] -pyrimidone into toluene, adding a catalyst, and reacting to obtain a flexible multi-block polymer;

and carrying out tape casting or blending granulation and injection molding on the flexible multi-block polymer and the levorotatory polylactic acid and/or the dextrorotatory polylactic acid to obtain the polylactic acid or polylactic acid stereocomplex film material.

As a further improvement of the invention, the dihydroxy small molecule organic compound is one of ethylene glycol, diethylene glycol, propylene glycol and 1, 4-butanediol, and the addition amount of the dihydroxy small molecule organic compound is 0.05-10% of the amount of the lactone monomer substance.

As a further improvement of the invention, the lactone monomer is one or more of epsilon-caprolactone, delta-valerolactone and racemic lactide.

As a further improvement of the invention, the lactide is one or two of levorotatory lactide and dextrorotatory lactide.

As a further improvement of the invention, the product obtained in each step of the reaction is purified by dissolving with dichloromethane or chloroform, and then precipitating and separating with methanol.

As a further improvement of the present invention, the catalyst is stannous octoate or dibutyltin dilaurate; the dosage of the catalyst is 0.05-1.0% of the total amount of lactone monomers or lactide substances, or 0.5-5.0% of the amount of the dihydroxyl functionalized copolyester/polylactic acid block copolymer.

As a further improvement of the invention, the molar ratio of the lactide to the dihydroxyl functionalized copolyester basic unit is (10-1) to (1-2).

As a further improvement of the invention, the mass ratio of the dihydroxyl-functionalized copolyester/polylactic acid block copolymer to the 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidinone is (0.5-2): 1.

As further modification of the invention, the used levorotatory polylactic acid has the molecular weight of 10-20 ten thousand, and the used dextrorotatory polylactic acid has the molecular weight of 6-15 ten thousand.

As a further modification of the invention, the mass ratio of the levorotatory polylactic acid to the dextrorotatory polylactic acid is (10-0): 0-10.

As a further modification of the invention, the mass ratio of the flexible multi-block polymer to the L-polylactic acid and/or the D-polylactic acid is (3-50): 100.

Polylactic acid and a stereocomplex film material thereof are prepared by the method.

Compared with the prior art, the invention has the following advantages:

the invention provides a polylactic acid and a stereocomplex film material thereof and a preparation method thereof, which synthesizes a plurality of flexible multi-block polymers by adopting a method of combining ring-opening polymerization and supermolecule assembly, and then mixes the flexible multi-block polymers with the polylactic acid or the stereocomplex thereof to prepare the toughened polylactic acid or the stereocomplex film material thereof. Because the synthesized flexible multi-block polymer contains the polylactic acid block, the polylactic acid block has good compatibility with the polylactic acid or the polylactic acid stereocomplex, and is beneficial to improving the mechanical properties of the polylactic acid and the stereocomplex material thereof. The polylactic acid or the stereo composite membrane material prepared by the method has high mechanical strength and good toughness, the tensile strength of the polylactic acid or the stereo composite membrane material is about 30-75 MPa, the elongation at break is 15-630%, and the polylactic acid or the stereo composite membrane material has wide application prospect in the field of modification of the polylactic acid and the stereo composite membrane material.

Drawings

FIG. 1 is an optical photograph of the polylactic acid film material obtained in example 1.

Fig. 2 is a tensile stress-strain curve of the polylactic acid film material obtained in example 2.

FIG. 3 is an X-ray diffractometer test curve of the polylactic acid stereocomplex film material prepared in example 3.

FIG. 4 is a tensile stress-strain curve of the polylactic acid stereocomplex film material prepared in example 4.

FIG. 5 is a differential scanning calorimeter test curve of polylactic acid stereocomplex film material prepared in example 5.

Detailed Description

The polylactic acid comprises L-polylactic acid, D-polylactic acid and meso-polylactic acid. The levorotatory polylactic acid and the dextrorotatory polylactic acid are semi-crystalline polyester, the glass transition temperature is about 60 ℃, the melting temperature is about 160-180 ℃, and the tensile strength is about 40-60 MPa; however, the meso-polylactic acid is amorphous. At present, all the commercial polylactic acid is levorotatory polylactic acid, and the insufficient toughness limits the application of the polylactic acid in many fields. When the levorotatory polylactic acid and the dextrorotatory polylactic acid are mixed, a large number of hydrogen bonds are formed among molecular chains to form a polylactic acid stereocomplex material with a structure different from that of the levorotatory polylactic acid and the dextrorotatory polylactic acid, and the polylactic acid stereocomplex material has high melting temperature, high crystallization rate, hydrolysis resistance and the like.

The present invention will be further described with reference to specific embodiments, but the present invention is not limited to the examples in any way. The starting reagents employed in the examples of the present invention are, unless otherwise specified, those that are conventionally purchased.

The invention relates to a preparation method of polylactic acid and a stereocomplex film material thereof, which comprises the following steps: firstly, initiating a lactone monomer by using a dihydroxyl small-molecule organic compound to generate dihydroxyl functionalized copolyester; then the dihydroxyl functionalized copolyester initiates lactide polymerization to generate dihydroxyl functionalized copolyester/polylactic acid segmented copolymer; reacting a dihydroxy functional copolyester/polylactic acid block copolymer with 2 (6-isocyanatoureyl) -6-methyl 4[1H ] -pyrimidinone to produce a flexible multi-block polymer; the flexible multi-block polymer and the commercial levorotatory polylactic acid or the mixture of the commercial levorotatory polylactic acid and the commercial dextrorotatory polylactic acid are molded by tape casting method or granulation and injection molding, and the toughened polylactic acid or polylactic acid stereocomplex film material can be obtained.

The scheme of the invention specifically provides a preparation method of polylactic acid and a stereocomplex film material thereof, which is specifically carried out according to the following steps:

(1) under the protection of inert gas, adding a dihydroxyl small-molecule organic compound, a lactone monomer and a catalyst into a reaction container, heating to 120-130 ℃, heating, refluxing, stirring, reacting for 12-72 hours, cooling after the reaction is finished, and purifying and drying to obtain dihydroxyl functionalized copolyester;

(2) mixing the synthesized dihydroxyl functionalized copolyester with lactide, heating to 120-150 ℃ in an inert gas atmosphere, adding a catalyst, refluxing, stirring and reacting for 24-72 hours, cooling after the reaction is finished, and purifying and drying to obtain a dihydroxyl functionalized copolyester/polylactic acid block copolymer;

(3) adding a dihydroxy functional copolyester/polylactic acid segmented copolymer and 2 (6-isocyanate-ureido) -6-methyl 4[1H ] -pyrimidone into toluene, heating to 110-130 ℃, refluxing and stirring until the materials are dissolved, adding a catalyst, continuously reacting for 16-48 hours, and after the reaction is finished, separating, purifying and drying to obtain a flexible multi-segmented polymer;

(4) and further mixing the synthesized flexible multi-block polymer with the levorotatory polylactic acid or the blend of the levorotatory polylactic acid and the dextrorotatory polylactic acid, and finally obtaining the polylactic acid or the polylactic acid stereo-composite membrane material by tape casting or injection molding.

The invention is also characterized in that:

wherein the dihydroxy small molecule organic compound in the step (1) is one of ethylene glycol, diethylene glycol, propylene glycol and 1, 4-butanediol, and the addition amount of the dihydroxy small molecule organic compound is 0.05-10% of the amount of the lactone monomer substance. The lactone monomer is one or two or all of epsilon-caprolactone, delta-valerolactone and racemic lactide.

Wherein, the lactide in the step (2) is one of levorotatory lactide and dextrorotatory lactide. The molar ratio of the lactide to the dihydroxyl functionalized copolyester basic unit is (10-1) to (1-2).

Wherein the mass ratio of the dihydroxy functional copolyester/polylactic acid block copolymer to the 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone in the step (3) is (0.5-2): 1.

The present invention will now be described in further detail with reference to the accompanying drawings and specific examples, which are given by way of illustration and not of limitation.

Compared with the toughening of the conventional polylactic acid and the stereocomplex material thereof, the polylactic acid or the stereocomplex material of the polylactic acid prepared by the invention has higher mechanical strength and toughness and has the potential of being used as a packaging material.

Example 1

(1) Adding ethylene glycol, delta-valerolactone and racemic lactide into a three-neck flask, heating to 120 ℃ under the nitrogen atmosphere, adding stannous octoate, refluxing for 24 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxy functional copolyester, wherein the mass ratio of the total mass of the delta-valerolactone and the racemic lactide to the mass of the initiator is 100:1, and the mass ratio of the delta-valerolactone and the racemic lactide is 3: 7; the using amount of the stannous octoate is 0.1 percent of the total amount of delta-valerolactone and racemic lactide;

(2) adding dihydroxyl functionalized copolyester and levorotatory lactide into a three-neck flask, removing water and residual solvent, heating to 120 ℃ in nitrogen atmosphere, adding stannous octoate, refluxing and reacting for 24 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxyl functionalized copolyester/polylactic acid segmented copolymer, wherein the molar ratio of the levorotatory lactide to the dihydroxyl functionalized copolyester basic unit is 1: 1; the dosage of the stannous octoate is 0.2 percent of the amount of the levorotatory lactide substance;

(3) adding a dihydroxy functional copolyester/polylactic acid block copolymer, 2 (6-isocyanate-uretonide) -6-methyl 4[1H ] -pyrimidone and toluene into a three-neck flask, heating to 110 ℃, adding stannous octoate to react for 24H, removing unreacted 2 (6-isocyanate-uretonide) -6-methyl 4[1H ] -pyrimidone and a solvent after the reaction is finished, and drying to obtain a flexible multi-block polymer, wherein the mass ratio of the 2 (6-isocyanate-uretonide) -6-methyl 4[1H ] -pyrimidone to the dihydroxy functional copolyester/polylactic acid block copolymer is 1:1, and the solution concentration is 30 mg/mL; the using amount of the stannous octoate is 2.0 percent of the mass of the dihydroxy functional copolyester/polylactic acid block copolymer;

(4) adding a flexible multi-block polymer, commercially available levorotatory polylactic acid and chloroform into a beaker, stirring at room temperature for 1h, placing the mixed solution into a polytetrafluoroethylene mold, then placing at room temperature for 24h, placing the mold into a vacuum oven at 30 ℃ for drying for 24h, and finally obtaining the toughened polylactic acid membrane material, wherein the mass ratio of the flexible multi-block polymer to the commercially available levorotatory polylactic acid is 1:10, and the solution concentration is 20 mg/mL.

The obtained polylactic acid film material has the tensile strength of 48MPa and the elongation at break of 68 percent. FIG. 1 is an optical photograph of the polylactic acid film material prepared in this example. The prepared polylactic acid film material has better light transmission.

Example 2

(1) Adding diethylene glycol, epsilon-caprolactone and racemic lactide into a three-neck flask, heating to 130 ℃ in a nitrogen atmosphere, adding stannous octoate, carrying out reflux reaction for 36 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxy functional copolyester, wherein the mass ratio of the total mass of the epsilon-caprolactone and the racemic lactide to the mass of the initiator is 100:1, and the mass ratio of the epsilon-caprolactone to the racemic lactide is 5: 5; the using amount of the stannous octoate is 0.1 percent of the total amount of epsilon-caprolactone and racemic lactide;

(2) adding dihydroxyl functionalized copolyester and D-lactide into a three-neck flask, removing water and residual solvent, heating to 150 ℃ in nitrogen atmosphere, adding stannous octoate, refluxing for 36 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxyl functionalized copolyester/polylactic acid segmented copolymer, wherein the molar ratio of the basic units of the D-lactide to the dihydroxyl functionalized copolyester is 1: 2; the using amount of the stannous octoate is 0.1 percent of the amount of the D-lactide substance;

(3) adding a dihydroxy functional copolyester/polylactic acid block copolymer, 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and toluene into a three-neck flask, heating to 110 ℃, adding dibutyltin dilaurate, reacting for 24 hours, removing unreacted 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and a solvent after the reaction is finished, and drying to obtain a flexible multi-block polymer, wherein the mass ratio of the 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone to the dihydroxy functional copolyester/polylactic acid block copolymer is 2:1, and the solution concentration is 40 mg/mL; the using amount of the dibutyltin dilaurate is 2.0 percent of the mass of the dihydroxy functionalized copolyester/polylactic acid block copolymer;

(4) adding a flexible multi-block polymer, commercially available levorotatory polylactic acid and chloroform into a beaker, stirring at room temperature for 1h, placing the mixed solution into a polytetrafluoroethylene mold, standing at room temperature for 24h, and placing the mold in a vacuum oven at 40 ℃ for drying for 24h to finally obtain the toughened polylactic acid membrane material, wherein the mass ratio of the flexible multi-block polymer to the commercially available levorotatory polylactic acid is 0.5:10, and the solution concentration is 50 mg/mL.

The tensile strength of the obtained polylactic acid film material is 43MPa, and the elongation at break is 520%. Fig. 2 is a tensile stress-strain curve of the polylactic acid film material prepared in this example. The breaking elongation of the prepared polylactic acid film material is obviously improved, which shows that the brittleness of the polylactic acid is obviously improved, and the polylactic acid film material shows good toughness.

Example 3

(1) Adding diethylene glycol, delta-valerolactone and epsilon-caprolactone into a three-neck flask, heating to 120 ℃ under the nitrogen atmosphere, adding stannous octoate for reflux reaction for 24 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxy functional copolyester, wherein the mass ratio of the total mass of the delta-valerolactone and the epsilon-caprolactone to the mass of the initiator is 100:1, and the mass ratio of the delta-valerolactone and the epsilon-caprolactone is 5: 5; the using amount of the stannous octoate is 0.3 percent of the total amount of delta-valerolactone and epsilon-caprolactone;

(2) adding dihydroxyl functionalized copolyester and levorotatory lactide into a three-neck flask, removing water and residual solvent, heating to 120 ℃ in nitrogen atmosphere, adding stannous octoate, refluxing and reacting for 24 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxyl functionalized copolyester/polylactic acid segmented copolymer, wherein the basic units of the levorotatory lactide and the dihydroxyl functionalized copolyester are 2: 1; the dosage of the stannous octoate is 0.1 percent of that of the levorotatory lactide substance;

(3) adding a dihydroxy functional copolyester/polylactic acid block copolymer, 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and toluene into a three-neck flask, heating to 110 ℃, adding dibutyltin dilaurate, reacting for 24 hours, removing unreacted 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and a solvent after the reaction is finished, and drying to obtain a flexible multi-block polymer, wherein the mass ratio of the 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone to the dihydroxy functional copolyester/polylactic acid block copolymer is 2:1, and the solution concentration is 20 mg/mL; the using amount of the dibutyltin dilaurate is 3.0 percent of the mass of the dihydroxy functionalized copolyester/polylactic acid block copolymer;

(4) adding a flexible multi-block polymer, commercially available levorotatory polylactic acid, commercially available dextrorotatory polylactic acid and chloroform into a beaker, stirring for 1h at room temperature, placing the mixed solution into a polytetrafluoroethylene mold, standing for 24h at room temperature, and placing the mold in a vacuum oven at 40 ℃ for drying for 24h to finally obtain the toughened polylactic acid stereocomplex film material, wherein the mass ratio of the flexible multi-block polymer to the commercially available levorotatory polylactic acid and dextrorotatory polylactic acid is 0.5:10, the mass ratio of the commercially available levorotatory polylactic acid to the commercially available dextrorotatory polylactic acid is 5:5, and the solution concentration is 50 mg/mL.

The tensile strength of the polylactic acid stereocomplex film material is 52MPa, and the elongation at break is 45%. FIG. 3 is an X-ray diffractometer test curve of the polylactic acid stereocomplex film material prepared in this example. The prepared polylactic acid stereocomplex film material has obvious diffraction peaks of (110), (300)/(030) and (220) planes of beta crystals formed by polylactic acid stereocomplex crystals at 2 theta (12.0), 20.9 and 24.0.

Example 4

(1) Adding 1, 4-butanediol, delta-valerolactone and epsilon-caprolactone into a three-neck flask, heating to 120 ℃ under the argon atmosphere, adding dibutyltin dilaurate, carrying out reflux reaction for 24 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxy functional copolyester, wherein the mass ratio of the total mass of the delta-valerolactone and the epsilon-caprolactone to an initiator is 100:1, and the mass ratio of the delta-valerolactone to the epsilon-caprolactone is 1: 10; the using amount of the stannous octoate is 0.2 percent of the total amount of delta-valerolactone and epsilon-caprolactone;

(2) adding dihydroxy functional copolyester and levorotatory lactide into a three-neck flask, mixing, removing water and residual solvent, heating to 120 ℃ under argon atmosphere, adding dibutyltin dilaurate, performing reflux reaction for 30 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxy functional copolyester/polylactic acid block copolymer, wherein the basic units of the levorotatory lactide and the dihydroxy functional copolyester are 1: 4; the dosage of the stannous octoate is 0.1 percent of that of the levorotatory lactide substance;

(3) adding a dihydroxy functional copolyester/polylactic acid block copolymer, 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and toluene into a three-neck flask, heating to 110 ℃, adding dibutyltin dilaurate for reaction for 24 hours, removing unreacted 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and a solvent after the reaction is finished, and drying to obtain a flexible multi-block polymer, wherein the mass ratio of the 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone to the dihydroxy functional copolyester/polylactic acid block copolymer is 2:1, and the solution concentration is 30 mg/mL; the using amount of the dibutyltin dilaurate is 2.0 percent of the mass of the dihydroxy functionalized copolyester/polylactic acid block copolymer;

(4) adding a multi-block flexible polymer, commercially available levorotatory polylactic acid, commercially available dextrorotatory polylactic acid and chloroform into a beaker, stirring for 2 hours at room temperature, placing the mixed solution into a polytetrafluoroethylene mold, standing for 24 hours at room temperature, and placing the mold in a vacuum oven at 40 ℃ for drying for 24 hours to finally obtain the toughened polylactic acid stereocomplex film material, wherein the mass ratio of the flexible multi-block polymer to the commercially available levorotatory polylactic acid and dextrorotatory polylactic acid is 1:10, the mass ratio of the commercially available levorotatory polylactic acid to the dextrorotatory polylactic acid is 5:5, and the solution concentration is 20 mg/mL.

The tensile strength of the polylactic acid stereocomplex film material is 72MPa, and the elongation at break is 52%. FIG. 4 is a tensile stress-strain curve of the polylactic acid stereocomplex film material prepared in this example. The prepared polylactic acid stereocomplex film material has larger elongation at break, and the tensile strength is equivalent to that of pure polylactic acid or polylactic acid stereocomplex, and is not reduced by toughening.

Example 5

(1) Adding 1, 4-butanediol, delta-valerolactone and epsilon-caprolactone into a three-neck flask, heating to 130 ℃ under the argon atmosphere, adding dibutyltin dilaurate, carrying out reflux reaction for 48 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxy functional copolyester, wherein the mass ratio of the total mass of the delta-valerolactone and the epsilon-caprolactone to an initiator is 50:1, and the mass ratio of the delta-valerolactone to the epsilon-caprolactone is 5: 5; the using amount of the stannous octoate is 0.2 percent of the total amount of delta-valerolactone and epsilon-caprolactone;

(2) adding dihydroxy functional copolyester and levorotatory lactide into a three-neck flask, mixing, removing water and residual solvent, heating to 150 ℃ under argon atmosphere, adding dibutyltin dilaurate, carrying out reflux reaction for 24 hours, cooling, dissolving in dichloromethane, precipitating with methanol, and drying to obtain dihydroxy functional copolyester/polylactic acid block copolymer, wherein the basic units of the levorotatory lactide and the dihydroxy functional copolyester are 1: 4; the amount of dibutyltin dilaurate was 0.1% of the amount of the levo-lactide material;

(3) adding a dihydroxy functional copolyester/polylactic acid block copolymer, 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and toluene into a three-neck flask, heating to 110 ℃, adding dibutyltin dilaurate for reaction for 24 hours, removing unreacted 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone and a solvent after the reaction is finished, and drying to obtain a flexible multi-block polymer, wherein the mass ratio of the 2 (6-isocyanateureyl) -6-methyl 4[1H ] -pyrimidone to the dihydroxy functional copolyester/polylactic acid block copolymer is 1:1, and the solution concentration is 30 mg/mL; the using amount of the dibutyltin dilaurate is 1.0 percent of the mass of the dihydroxy functionalized copolyester/polylactic acid block copolymer;

(4) adding a multi-block flexible polymer, commercially available levorotatory polylactic acid, commercially available dextrorotatory polylactic acid and chloroform into a beaker, stirring for 2 hours at room temperature, placing the mixed solution into a polytetrafluoroethylene mold, standing for 24 hours at room temperature, and placing the mold in a vacuum oven at 40 ℃ for drying for 24 hours to finally obtain the toughened polylactic acid stereocomplex material, wherein the mass ratio of the flexible multi-block polymer to the commercially available levorotatory polylactic acid and dextrorotatory polylactic acid is 1.5:10, the mass ratio of the commercially available levorotatory polylactic acid to the commercially available dextrorotatory polylactic acid is 5:5, and the solution concentration is 20 mg/mL.

The tensile strength of the polylactic acid stereocomplex film material is 68MPa, and the elongation at break is 180 percent. FIG. 5 is a differential scanning calorimeter test curve of polylactic acid stereocomplex film material prepared in this example. The crystallization temperature of the prepared polylactic acid stereocomplex film material is about 118 ℃, and the melting temperature is 208 ℃.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.