Modified PLA and preparation method thereof

Abstract

The invention discloses modified polylactic acid (PLA), which belongs to the technical field of biodegradable polymers and comprises the following components in parts by weight: 100 parts of polylactic acid (PLA), 20 parts of poly (butylene adipate-co-terephthalate) (PBAT), 1 part of lignin and 0.5-2 parts of porous hollow microspheres. The invention further discloses a preparation method of the modified PLA, the technical problems that PLA is poor in toughness and low in hydrolysis speed are solved, and the modified PLA is widely applied to production of biodegradable polymers.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer technology, and particularly relates to a modified PLA and its preparation method. Background Technology

[0003] Polylactic acid (PLA) is one of the most widely used biodegradable materials, boasting numerous advantages such as excellent degradability, good biocompatibility, and sustainable sourcing. It finds wide application in medical, agricultural, and everyday packaging materials. However, PLA also has significant performance disadvantages, including poor mechanical properties and a slow degradation rate.

[0004] To address the disadvantages of polylactic acid (PLA), such as poor mechanical properties, slow degradation rate, and long degradation cycle, current research mainly focuses on modifying PLA by using tough biodegradable polymers in conjunction with chain extenders / compatibility agents. However, this approach often faces drawbacks such as poor compatibility between the two polymers and high toxicity of the chain extenders.

[0005] Therefore, in the field of biodegradable polymer equipment technology, there is still a need for research and improvement on modified PLA and its preparation methods. This is a current research hotspot and focus in the field of biodegradable polymer technology, and it is also the starting point for the completion of this invention. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a modified PLA to solve the technical problems of poor toughness and slow hydrolysis rate of PLA.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is: a modified PLA, comprising the following components: 100 parts by weight of polylactic acid (PLA), 20 parts by weight of polybutylene adipate terephthalate (PBAT), 1 part by weight of lignin, and 0.5 to 2 parts by weight of porous hollow microspheres.

[0008] As an improvement, the porous hollow microspheres are hollow mesoporous silica microspheres.

[0009] Another technical problem to be solved by the present invention is to provide a method for preparing modified PLA, so as to solve the technical problems of poor toughness and slow hydrolysis rate of PLA.

[0010] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for preparing modified PLA, comprising the following steps: S1. Drying PLA, PBAT, lignin, and porous hollow microspheres at 80°C for 4 hours; S2. Weighing 1 part by weight of lignin and 0.5-2 parts by weight of porous hollow microspheres and adding them to a reaction vessel containing 400 parts by weight of dichloromethane solvent and stirring for dispersion treatment; S3. Mixing 20 parts by weight of PBAT and 100 parts by weight of PLA evenly and dividing it into several equal parts, adding 1 part to the reaction vessel every half hour, and stirring at 400 rpm for 30 minutes; S4. After all the solvent has been added, stirring is continued for 5 hours, and then the mixture is heated to 80°C in the reaction vessel for 24 hours to allow the solvent in the mixture to fully evaporate; S5. After the solvent has evaporated, a quaternary composite material is obtained.

[0011] After adopting the above technical solution, the beneficial effects of the present invention are:

[0012] The invention uses PBAT as a toughening agent for PLA material, and selects pure natural materials lignin and porous hollow microspheres to compatibilize PLA / PBAT, thus preparing a quaternary composite material of PLA / PBAT / lignin / porous hollow microspheres. It achieves good mechanical properties, and the entire material system is of green and sustainable origin, with good biocompatibility and low cost. The hollow environment of the porous hollow microspheres can serve as a closed environment for the degradation of composite material, accelerating the degradation of PLA and PBAT within the microspheres and improving the degradation rate of composite material. Attached Figure Description

[0013] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0014] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0015] Figure 1 This is a diagram showing the surface morphology and dimensions of the porous hollow microspheres in an embodiment of the present invention;

[0016] Figure 2This is a topographic image of the porous hollow microspheres under the tensile cross-section in an embodiment of the present invention;

[0017] Figure 3 These are graphs showing the elongation at break and tensile strength of composite materials with different proportions in embodiments of the present invention.

[0018] Figure 4 This is a graph showing the degradation performance of composite materials with different ratios of porous hollow microspheres under acidic degradation conditions. Detailed Implementation

[0019] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The terms used in this specification, such as "front," "back," "left," "right," "inner," "outer," and "middle," are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of the invention.

[0021] Example 1:

[0022] This invention provides a modified PLA, comprising the following components: 100 parts by weight of polylactic acid (PLA), 20 parts by weight of polybutylene adipate terephthalate (PBAT), 1 part by weight of lignin, and 1 part by weight of porous hollow microspheres, wherein the porous hollow microspheres are hollow mesoporous silica microspheres, and detailed parameters of the porous hollow microspheres are shown in the table below:

[0023]

[0024]

[0025] Scanning electron microscope image of porous hollow microspheres as shown below Figure 1 and Figure 2 As shown, from Figure 1 The SEM surface morphology test results show that the porous hollow microspheres are in the tens of micrometers in size and have a large number of random pores on the surface. Figure 2The results of tensile cross-section SEM show that the surface pores of the blended porous hollow microspheres contain a large number of filamentous polymers. This is because PLA and PBAT molecular chains are extensively interwoven into the pores of the porous hollow microspheres, proving that the porous hollow microspheres can physically crosslink the polymers, thereby achieving good biocompatibility and a faster degradation rate.

[0026] Example 2:

[0027] The present invention provides a modified PLA, which is basically the same as that in Example 1, except that it includes the following components: 100 parts by weight of polylactic acid (PLA), 20 parts by weight of polybutylene adipate terephthalate (PBAT), 1 part by weight of lignin, and 0.5 parts by weight of porous hollow microspheres.

[0028] Example 3:

[0029] The present invention provides a modified PLA, which is basically the same as that in Example 1, except that it includes the following components: 100 parts by weight of polylactic acid (PLA), 20 parts by weight of polybutylene adipate terephthalate (PBAT), 1 part by weight of lignin, and 2 parts by weight of porous hollow microspheres.

[0030] Example 4:

[0031] This invention provides a method for preparing modified PLA, comprising the following steps: S1. Drying PLA, PBAT, lignin, and porous hollow microspheres at 80°C for 4 hours; S2. Weighing 1 part by weight of lignin and 1 part by weight of porous hollow microspheres and adding them to a reaction vessel containing 400 parts by weight of dichloromethane solvent and stirring for dispersion treatment, wherein the reaction vessel is a mechanically stirred reaction vessel; S3. Mixing 20 parts by weight of PBAT and 100 parts by weight of PLA evenly and dividing it into 3 or more equal parts, adding 1 part to the reaction vessel every half hour, and stirring at 400 rpm for 30 minutes; S4. After all the PBAT is added, stirring is continued for 5 hours, and then the mixture is heated to 80°C in the reaction vessel for 24 hours to allow the solvent in the mixture to fully evaporate; S5. After the solvent has evaporated, a quaternary composite material is obtained.

[0032] Example 5:

[0033] This invention provides a method for preparing modified PLA, comprising the following steps: S1. Drying PLA, PBAT, lignin, and porous hollow microspheres at 80°C for 4 hours; S2. Weighing 1 part by weight of lignin and 0.5 parts by weight of porous hollow microspheres and adding them to a reaction vessel containing 400 parts by weight of dichloromethane solvent and stirring for dispersion treatment; S3. Mixing 20 parts by weight of PBAT and 100 parts by weight of PLA evenly and dividing it into 3 or more equal parts, adding 1 part to the reaction vessel every half hour, and stirring at 400 rpm for 30 minutes; S4. After all the mixture is added, stirring is continued for 5 hours, and then the mixture is heated to 80°C in the reaction vessel for 24 hours to allow the solvent in the internal mixture to fully evaporate; S5. After the solvent has evaporated, a quaternary composite material is obtained.

[0034] Example 6:

[0035] This invention provides a method for preparing modified PLA, comprising the following steps: S1. Drying PLA, PBAT, lignin, and porous hollow microspheres at 80°C for 4 hours; S2. Weighing 1 part by weight of lignin and 2 parts by weight of porous hollow microspheres and adding them to a reaction vessel containing 400 parts by weight of dichloromethane solvent and stirring for dispersion treatment; S3. Mixing 20 parts by weight of PBAT and 100 parts by weight of PLA evenly and dividing it into 3 or more equal parts, adding 1 part to the reaction vessel every half hour, and stirring at 400 rpm for 30 minutes; S4. After all the mixture is added, stirring is continued for 5 hours, and then the mixture is heated to 80°C in the reaction vessel for 24 hours to allow the solvent in the internal mixture to fully evaporate; S5. After the solvent has evaporated, a quaternary composite material is obtained.

[0036] Comparative example:

[0037] I. Material Preparation

[0038] PLA, PBAT, porous hollow microspheres, and lignin were placed in a vacuum oven and dried at 80°C under vacuum for 12 hours to remove moisture before use. Separately, the dried 4A-grade molecular sieve was added to dichloromethane solvent and stirred for 4 hours to remove moisture from the dichloromethane before use. The PLA used was Nature Works 4032D, the PBAT was BASF ecoflex F Blend B1100, the porous hollow microspheres were Huaqi Technology K990, the lignin was Huamaike 890115, and the dichloromethane was from Sinopharm Group.

[0039] II. Preparation of PLA / 20% PBAT composite material

[0040] Measure 100 mL of the dried dichloromethane solvent from the molecular sieve and add it to a three-necked flask. Stir magnetically at 400 rpm. Weigh 10 g of dried PLA and 2 g of PBAT. First, add 2 g of PLA and 0.4 g of PBAT to the three-necked flask and stir magnetically for 30 minutes. Repeat the above steps until all PLA and PBAT are added, then continue stirring magnetically for 5 hours. After stirring, pour the mixture into a 12 cm diameter petri dish and place the dish in a fume hood at a controlled temperature of 25°C for 24 hours to allow the solvent to evaporate. After evaporation, press the film into dumbbell-shaped strips using a dumbbell mold for testing.

[0041] III. Preparation of PLA / 20% PBAT / 1% lignin / 0.5% porous hollow microsphere composite material

[0042] Measure 100 mL of the dried molecular sieve in dichloromethane solvent and add it to a three-necked flask. Next, weigh 0.1 g of dried lignin and 0.05 g of porous hollow microspheres and add them to the three-necked flask containing dichloromethane. Sonicate for 30 minutes. Then weigh 10 g of dried PLA and 2 g of PBAT. First, add 2 g of PLA and 0.4 g of PBAT to the three-necked flask and stir magnetically for 30 minutes. Repeat the above steps until all PLA and PBAT are added, then continue stirring magnetically for 5 hours. After magnetic stirring, pour the mixture into a 12 cm diameter petri dish and place the petri dish in a fume hood at a controlled temperature of 25°C for 24 hours to evaporate the solvent. After evaporation, use a dumbbell-shaped mold to press the film into dumbbell-shaped strips for testing.

[0043] IV. Preparation of PLA / 20% PBAT / 1% lignin / 1% porous hollow microsphere composite material

[0044] Measure 100 mL of the dried molecular sieve in dichloromethane solvent and add it to a three-necked flask. Next, weigh 0.1 g of dried lignin and 0.1 g of porous hollow microspheres and add them to the three-necked flask containing dichloromethane. Sonicate for 30 minutes. Then weigh 10 g of dried PLA and 2 g of PBAT. First, add 2 g of PLA and 0.4 g of PBAT to the three-necked flask and stir magnetically for 30 minutes. Repeat the above steps until all PLA and PBAT are added, then continue stirring magnetically for 5 hours. After magnetic stirring, pour the mixture into a 12 cm diameter petri dish and place the petri dish in a fume hood at a controlled temperature of 25°C for 24 hours to evaporate the solvent. After evaporation, use a dumbbell-shaped mold to press the film into dumbbell-shaped strips for testing.

[0045] V. Preparation of PLA / 20% PBAT / 1% lignin / 2% porous hollow microsphere composite material

[0046] Measure 100 mL of the dried molecular sieve in dichloromethane solvent and add it to a three-necked flask. Next, weigh 0.1 g of dried lignin and 0.2 g of porous hollow microspheres and add them to the three-necked flask containing dichloromethane. Sonicate for 30 minutes. Then weigh 10 g of dried PLA and 2 g of PBAT. First, add 2 g of PLA and 0.4 g of PBAT to the three-necked flask and stir magnetically for 30 minutes. Repeat the above steps until all PLA and PBAT are added, then continue stirring magnetically for 5 hours. After magnetic stirring, pour the mixture into a 12 cm diameter petri dish and place the petri dish in a fume hood at a controlled temperature of 25°C for 24 hours to evaporate the solvent. After evaporation, use a dumbbell-shaped mold to press the film into dumbbell-shaped strips for testing.

[0047] VI. The elongation at break and tensile strength of the composite materials with different proportions were tested respectively to obtain... Figure 3 The graphs show that: 1. Tensile test results indicate that pure PLA is brittle, which is not conducive to product use; the addition of PBAT to PLA improves toughness, but the effect is not significant. With the addition of porous hollow microspheres and lignin, the elongation at break and tensile strength of the composite material are enhanced. Among them, the modification effect is best with 1 part porous hollow microspheres. The modification effect is relatively poor with 0.5 parts porous hollow microspheres because the addition content is too low, resulting in fewer physical cross-linking sites and thus no significant improvement in mechanical properties. When 2 parts porous hollow microspheres are added, the high content leads to stress concentration and agglomeration, causing the mechanical properties to decline.

[0048] VII. The degradation of composite materials with different porous hollow microsphere ratios under acidic degradation environment was tested to obtain... Figure 4 The line graph comparison shows that: 1. The addition of porous hollow microspheres is beneficial to the degradation of the composite material because the hollow environment of the porous hollow microspheres can serve as a closed environment for the degradation of the composite material, accelerating the degradation of PLA and PBAT within the microspheres; 2. With the increase of the content of porous hollow microspheres, the degradation rate decreased at the 2-part addition content. This is because the large number and aggregation of porous hollow microspheres affect the transfer of hydrogen ions in the environment, which is not conducive to the attack of hydrogen ions on the ester groups on PLA and PBAT.

[0049] Conclusion: Magnetic stirring was used during sample preparation. To improve the stirring effect, 100 ml of dichloromethane was selected as the solvent. Since the solvent does not participate in the reaction, it does not affect the experimental results. Under laboratory conditions, the solvent was evaporated completely in a fume hood at a maintained temperature of 25°C for 24 hours, consistent with the evaporation effect at 80°C in industrial production, and this also did not affect the experimental results. PBAT was selected to toughen PLA, and lignin and porous hollow microspheres were used as compatibilizers for PBAT and PLA. The large number of hydroxyl and phenolic hydroxyl groups in lignin can form numerous hydrogen bonds with the surfaces of PBAT and PLA, increasing their compatibility. The numerous pores in the porous hollow microspheres allow PLA and PBAT molecular chains to form numerous entanglements within the pores, further improving their compatibility and matrix strength. Finally, the PLA / PBAT / lignin / porous hollow microsphere quaternary composite material showed significantly improved toughness and strength compared to PLA / PBAT alone. Aquatic environment is one of the necessary conditions for the degradation of biodegradable polyester. Since lignin has good water solubility, when the material is discarded, it can be soaked in water for a short time to remove some lignin, thus giving the entire material system a larger contact area with the aquatic environment, accelerating the degradation rate of PLA and shortening the degradation cycle.

[0050] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A modified PLA, characterized in that, It includes the following components: 100 parts by weight of polylactic acid (PLA), 20 parts by weight of polybutylene adipate terephthalate (PBAT), 1 part by weight of lignin, and 0.5 to 2 parts by weight of porous hollow microspheres.

2. The modified PLA according to claim 1, characterized in that, The porous hollow microspheres are hollow mesoporous silica microspheres.

3. A method for preparing modified PLA, characterized in that, Includes the following steps: S1. Dry PLA, PBAT, lignin, and porous hollow microspheres at 80℃ for 4 hours; S2. Weigh 1 part by weight of lignin and 0.5 to 2 parts by weight of porous hollow microspheres and add them to a reaction vessel containing 400 parts by weight of dichloromethane solvent and stir to disperse them; S3. Mix 20 parts by weight of PBAT and 100 parts by weight of PLA evenly and divide them into several equal parts. Add 1 part to the reaction vessel every half hour and stir at 400 rpm for 30 minutes. S4. After adding all the ingredients, stir continuously for 5 hours, then heat the mixture in the reactor to 80°C for 24 hours to allow the solvent in the mixture to fully evaporate; S5. After the solvent has evaporated, a quaternary composite material is obtained.

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