Modified polylactic acid material and preparation method thereof
By modifying polysulfide with polylactic acid, the problem of insufficient strength and toughness of polylactic acid materials was solved, the material performance was improved and controlled degradation was achieved, and the application scenarios were broadened.
Patent Information
- Application Number
- CN202511964187.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-02-24
AI Technical Summary
There is a need for improvement in the mechanical tensile properties and processing methods of polylactic acid materials, especially the problems of low strength and poor toughness, which limit their application scenarios.
Modified polylactic acid materials are prepared by blending polysulfide with polylactic acid in a specific ratio and through molding treatment. This process avoids phase separation, improves the crystallinity and glass transition temperature of the material, and introduces dynamic covalent bonds to enhance performance.
It improves the mechanical tensile properties and processing methods of polylactic acid, enhances the strength and toughness of the material, and has controllable degradation properties, avoiding the phase separation problem of traditional modifiers and enabling low-temperature processing.
Smart Images
Figure CN121554926A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a modified polylactic acid material and its preparation method, belonging to the field of polymer materials and their preparation technology. Background Technology
[0002] Polylactic acid (PLA), a representative biodegradable polymer, is an excellent alternative to petroleum-based plastics. Its safety, non-toxicity, and biocompatibility make it suitable as a substrate for surgical sutures and drug carriers. PLA is a linear thermoplastic polyester obtained from lactic acid through direct polycondensation or ring-opening polymerization of lactide. Its glass transition temperature (GLT) is... T g ) and melting point T m (Approximately 60) o C and 175 o C. Compared to other biodegradable plastics, polylactic acid (PLA) has higher strength and modulus, but its heat resistance is poor, and it is prone to brittle fracture at room temperature. Therefore, modification is usually required to broaden its application scenarios. Furthermore, PLA's low elongation at break, poor impact resistance, and high brittleness limit its application and development in specific environments. Therefore, providing a method to modify PLA materials to improve its mechanical tensile properties and processing methods is essential for effectively expanding its application scenarios. Summary of the Invention
[0003] This invention addresses the problems of existing polylactic acid (PLA) in terms of mechanical tensile properties and processing methods by providing a modified PLA material and its preparation method.
[0004] The technical solution of the present invention: One of the objectives of this invention is to provide a modified polylactic acid material, which is made by blending and molding polysulfide and polylactic acid; The structure of the polythiolactone is as follows: or
[0005] Polydithiolactide and polymonothiolactide In the formula, R is benzyl alcohol, dibenzyl alcohol, benzyl mercaptan or dibenzyl mercaptan, and n is an integer from 10 to 8000.
[0006] Further specified, the blending molar ratio of polythiolactide to polylactic acid is (0~100):(100~0), and the amount of both polythiolactide and polylactic acid is not 0.
[0007] Further specifying, the blending molar ratio of polythiolactide to polylactic acid is (40~70):(30~60).
[0008] Further specified, the molding temperature is 50~100℃.
[0009] A second objective of this invention is to provide a method for preparing the above-mentioned modified polylactic acid material, the method comprising the following steps: (1) Dissolve polysulfide in an organic solvent, stir until homogeneous, add polylactic acid, and stir until homogeneous to obtain a blend solution; (2) Remove the organic solvent from the blending solution to obtain the blended polymer; (3) The blended polymer is subjected to molding treatment to obtain modified polylactic acid material.
[0010] Further specifying, the organic solvent is dichloromethane.
[0011] Further specified, the stirring temperature in (1) is 30~60℃.
[0012] Further specifying, in (2), the organic solvent is removed by vacuum drying.
[0013] Further specifying, (3) the molding process is compression molding.
[0014] Further specified, (3) the elongation at break of the modified polylactic acid material is ≥100%.
[0015] Beneficial effects: This invention modifies polysulfide and polylactic acid by blending, improving the mechanical tensile properties and processing characteristics of polylactic acid. Compared with existing technologies, it has the following advantages: (1) The polysulfide used in this invention is obtained by replacing oxygen atoms in the polylactic acid (PLA) structure with sulfur atoms. The structural similarity of the polysulfide to PLA is over 95%, allowing for complete blending without phase separation. The crystallinity and glass transition temperature of the blended material are altered, resulting in a significant improvement in the strength and toughness of the final material, effectively solving the problems of low strength and poor toughness in PLA. Compared to traditional PLA blend modification methods that mainly rely on modifying agents such as small organic molecules (e.g., plasticizers, coupling agents), large organic molecules (e.g., elastomers, polymer blends), small inorganic molecules (e.g., nanoparticle precursors, inorganic acid salts), and large inorganic molecules (e.g., nanocomposite materials, inorganic polymers), this invention avoids the phase separation problem between the modifying agents and PLA. The enhancement method of this invention is a phase-separation-free modification method, which can maximize the enhancement of PLA material properties.
[0016] (2) The random polysulfide used in this invention is gel-like and viscous. Blending it with polylactic acid can change the properties of the blended polymer, effectively reduce the processing temperature of polylactic acid, and allow for molding at low temperatures.
[0017] (3) The thioester bond in the polysulfide used in this invention has a longer bond length and lower polarity, which makes the main chain more flexible and the chain segment movement ability better. When subjected to tensile force or external impact, the molecular chain can absorb energy by rotating or elongating, which makes it tough and enhances the toughness of the modified polylactic acid.
[0018] (4) This invention utilizes the dynamic characteristics of sulfur in polysulfide lactide to introduce a variety of sulfur-containing dynamic covalent bonds sulfide ester bonds into the main chain of the polymer. Compared with traditional oxygen ester bonds, these bonds have lower bond energies and exhibit higher kinetic instability, enabling controllable degradation of the material. Therefore, the modified polylactic acid also has good recyclability. Attached Figure Description
[0019] Figure 1 The image shows the tensile test results of the modified polylactic acid material prepared in Example 1. Figure 2 The image shows the tensile test results of the modified polylactic acid material prepared in Example 2. Figure 3 The image shows the tensile test results of the modified polylactic acid material prepared in Example 3. Figure 4 The image shows the tensile test results of the modified polylactic acid material prepared in Example 4. Figure 5 The image shows a comparison of the tensile test results of the modified polylactic acid materials prepared in Examples 1-4. Detailed Implementation
[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.
[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art may make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.
[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.
[0024] The preparation method of poly(monothiolactide) used in the following examples is as follows: Thiolactide monomer (172 mg, 1.0 mmol, 100 equivalents) was added to a 4 mL reaction flask, followed by the addition of catalyst DMAP (1.4 mg, 10 μmol, 1 equivalent), and a toluene solution of benzyl alcohol as initiator (20 μL, 10 μmol, 1 equivalent). The mixture was stirred and reacted at room temperature. After 3.0 h, the reaction was completed, quenched with 5% dilute hydrochloric acid aqueous solution, and the polymer was precipitated in cold methanol at -20 °C. The conversion rate was 33%, indicating that the reaction had reached equilibrium, and the molecular weight was obtained. M n >5.2 kDa, molecular weight distribution Đ = 1.62 Polyester product polythiolactide, the polymer is a colorless, transparent, viscous gel-like solid.
[0025] Example 1: The process for preparing a poly(monothiolactide) / polylactic acid blend with a molar ratio of 70:30 in this embodiment is as follows: The specific operating steps are as follows: The first step involved dissolving poly(monothiolactide) (480 mg, 3 mmol) in 10 mL of dichloromethane. o Stirring at C for 1.0 h yields a colorless and transparent solution.
[0026] The second step involves dissolving commercially available polylactic acid (48.0 mg, 0.33 mmol) in the solution obtained in the first step, at a concentration of 50 mg / L. o Stirring at C for 1.0 h yielded a colorless and transparent blend solution.
[0027] The third step is at 50 o The solvent evaporated in a forced-air drying oven at C for 2.0 h, 50 o The polymer was vacuum dried at 70°C for 16.0 h, then molded using a small flat vulcanizing apparatus at a molding temperature of 70°C. o C, with a pressure of 200 MPa. The obtained modified polylactic acid material was cut into dumbbell-shaped samples (35 mm × 2 mm × 0.2 mm) using a standard No. 4 cutter, and subjected to mechanical tensile testing. The test results are as follows. Figure 1 As shown.
[0028] Example 2: The process for preparing a poly(monothiolactide) / polylactic acid blend with a molar ratio of 60:40 in this embodiment is as follows: The specific operating steps are as follows: The first step involved dissolving poly(monothiolactide) (480 mg, 3 mmol) in 15 mL of dichloromethane. o Stirring at C for 1.0 h yields a colorless and transparent solution.
[0029] The second step involves dissolving commercially available polylactic acid (288 mg, 2 mmol) in the solution obtained in the first step, at 50... o Stirring at C for 1.0 h yielded a colorless and transparent blend solution.
[0030] The third step is at 50 o The solvent evaporated in a forced-air drying oven at C for 2.0 h, 50 o The polymer was vacuum dried at 70°C for 16.0 h, then molded using a small flat vulcanizing apparatus at a molding temperature of 70°C. o C, with a pressure of 200 MPa. The obtained modified polylactic acid material was cut into dumbbell-shaped samples (35 mm × 2 mm × 0.2 mm) using a standard No. 4 cutter, and subjected to mechanical tensile testing. The test results are as follows. Figure 2 As shown.
[0031] Example 3: The process for preparing the poly(monothiolactide) / polylactic acid blend polymer with a molar ratio of 40:60 in this embodiment is as follows: The specific operating steps are as follows: The first step involved dissolving poly(monothiolactide) (480 mg, 3 mmol) in 10 mL of dichloromethane. o Stirring at C for 1.0 h yields a colorless and transparent solution.
[0032] The second step involves dissolving commercially available polylactic acid (648 mg, 4.5 mmol) in the solution obtained in the first step, at a concentration of 50 mg / L. o Stirring at C for 1.0 h yielded a colorless and transparent blend solution.
[0033] The third step is at 50 o The solvent evaporated in a forced-air drying oven at C for 2.0 h, 50 o The polymer was vacuum dried at 70°C for 16.0 h, then molded using a small flat vulcanizing apparatus at a molding temperature of 70°C. o C, with a pressure of 200 MPa. The obtained modified polylactic acid material was cut into dumbbell-shaped samples (35 mm × 2 mm × 0.2 mm) using a standard No. 4 cutter, and subjected to mechanical tensile testing. The test results are as follows. Figure 3 As shown.
[0034] Example 4: The process for preparing the poly(monothiolactide) / polylactic acid blend polymer with a molar ratio of 20:80 in this embodiment is as follows: The specific operating steps are as follows: The first step involved dissolving poly(monothiolactide) (480 mg, 3 mmol) in 10 mL of dichloromethane. o Stirring at C for 1.0 h yields a colorless and transparent solution.
[0035] The second step involves dissolving commercially available polylactic acid (1920 mg, 12 mmol) in the solution obtained in the first step, at a concentration of 50 mg / mL. o Stirring at C for 1.0 h yielded a colorless and transparent blend solution.
[0036] The third step is at 50 o The solvent evaporated in a forced-air drying oven at C for 2.0 h, 50 o The polymer was vacuum dried at 70°C for 16.0 h, then molded using a small flat vulcanizing apparatus at a molding temperature of 70°C. o C, with a pressure of 200 MPa. The obtained modified polylactic acid material was cut into dumbbell-shaped samples (35 mm × 2 mm × 0.2 mm) using a standard No. 4 cutter, and subjected to mechanical tensile testing. The test results are as follows. Figure 4 As shown.
[0037] Figure 5 The figures show a comparison of the tensile test results of the modified polylactic acid materials prepared in Examples 1-4. As can be seen from the figures, the mechanical tensile properties of the modified polylactic acid materials are related to the ratio of poly(monothiolactide) and polylactic acid. The tensile strength increases with the decrease of poly(monothiolactide) and the increase of polylactic acid, but the elongation at break is similar, all around 100% or above. When the ratio is less than a certain value, the blending modification of poly(monothiolactide) is not obvious, and the polymer properties are similar to those of pure polylactic acid, as shown in the figure at 20:80.
[0038] The above description is only a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.
Claims
1. A modified polylactic acid material, characterized in that, It is made by blending and molding polysulfide and polylactic acid; The structure of the polythiolactone is as follows: or In the formula, R is benzyl alcohol, dibenzyl alcohol, benzyl mercaptan or dibenzyl mercaptan, and n is an integer from 10 to 8000.
2. The modified polylactic acid material according to claim 1, characterized in that, The blending molar ratio of polythiolactide to polylactic acid is (0~100):(100~0), and the amount of both polythiolactide and polylactic acid is not 0.
3. The modified polylactic acid material according to claim 1, characterized in that, The molar ratio of polythiolactide to polylactic acid is (40~70):(30~60).
4. The modified polylactic acid material according to claim 1, characterized in that, The molding temperature is 50~100℃.
5. A method for preparing the modified polylactic acid material according to any one of claims 1 to 4, characterized in that, include: (1) Dissolve polysulfide in an organic solvent, stir until homogeneous, add polylactic acid, and stir until homogeneous to obtain a blend solution; (2) Remove the organic solvent from the blending solution to obtain the blended polymer; (3) The blended polymer is subjected to molding treatment to obtain modified polylactic acid material.
6. The preparation method according to claim 5, characterized in that, The organic solvent is dichloromethane.
7. The preparation method according to claim 5, characterized in that, (1) The stirring temperature is 30~60℃.
8. The preparation method according to claim 5, characterized in that, (2) The organic solvent is removed by vacuum drying.
9. The preparation method according to claim 5, characterized in that, (3) The molding process is compression molding.
10. The preparation method according to claim 5, characterized in that, (3) The elongation at break of the modified polylactic acid material obtained is ≥100%.