A bio-based indole acid zinc salt nucleating agent and its preparation method and application

Abstract

The invention discloses a bio-based indole acid zinc salt nucleating agent, which is prepared by reacting an indole acid compound with an acid zinc substance; the nucleating agent of the invention is mixed with polylactic acid by a melt blending method, and is extruded or injection molded into a polylactic acid product, which can provide good nucleation efficiency for polylactic acid during the preparation process, and the nucleation effect is very stable, and the obtained polylactic acid product has the characteristics of biodegradability, excellent mechanical properties and excellent antibacterial properties. This type of nucleating agent has a simple preparation method, and the raw materials are derived from bio-based materials, which has the potential for sustainable development. It is not only easy to achieve large-scale production, but also can provide excellent antibacterial properties for polylactic acid products, and can expand the application field of polylactic acid plastic products.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic additives, and particularly relates to a bio-based indole acid zinc salt nucleating agent and a preparation method and application thereof. Background Art

[0002] Polylactic acid (PLA) is a biodegradable polymer formed by the polymerization of lactic acid molecules. Lactic acid is an organic acid containing two carbon atoms and can be prepared from a variety of plant materials through a fermentation process, such as corn and sugarcane, which makes PLA a renewable resource. Compared with traditional plastics, its production process emits less carbon emissions, which helps reduce dependence on limited fossil fuels and reduce greenhouse gas emissions, which is in line with the development direction of a low-carbon economy. PLA has attracted much attention due to its biodegradability and renewability, and has a wide range of applications in many fields. First, as an environmentally friendly material, PLA is widely used in the field of food packaging. Due to its biodegradability, it can avoid the negative impact of plastic pollution on the environment, so it is considered to be a sustainable packaging material alternative. Secondly, PLA also has important applications in the field of medical devices, such as degradable sutures, stents, etc., because of its good biocompatibility and will not cause adverse effects on the human body. In addition, PLA can also be used in fiber products, 3D printing and other fields, showing a wide range of application prospects.

[0003] However, despite its many advantages, PLA still faces some challenges in industrial production and commercial applications. Among them, its slow crystallization speed and poor heat resistance limit its application in high temperature environments, which has become one of the key factors restricting its further development. At the same time, with the continuous development of society, consumers have an increasing demand for low-processing, preservative-free products, so people have higher and higher requirements for the antibacterial properties of packaging materials. However, in order to achieve the antibacterial properties of PLA at the same time, it is necessary to add multiple additives at the same time. The total amount of additives added will be too high, which will affect the processing performance of the product or repel each other, affecting the realization of the function. The existing commercial nucleating agents cannot provide crystallization properties for PLA products while providing antibacterial properties. Therefore, the development of high-performance nucleating agents that combine nucleating agents and antibacterial agents based on natural resources is of great significance for expanding and realizing the versatility of PLA. Summary of the invention

[0004] The object of the present invention is to overcome the above technical defects and provide an environmentally friendly bio-based indole acid zinc salt nucleating agent with biodegradability and biocompatibility, which can accelerate the crystallization rate of PLA during the molding process to improve the crystallinity, heat resistance and antibacterial properties of PLA.

[0005] The present invention is achieved through the following technical solutions:

[0006] A bio-based indole acid zinc salt nucleating agent, wherein the bio-based indole acid zinc salt nucleating agent has the following structure:

[0007]

[0008] Among them, n is a constant, n=0, 1, 2, 3.

[0009] When n=0, the bio-based indole acid zinc salt nucleating agent is 3-indolecarboxylic acid zinc salt, and its structure is as follows:

[0010]

[0011] When n=1, the bio-based indole acid zinc salt nucleating agent is 3-indoleacetic acid zinc salt, and its structure is as follows:

[0012]

[0013] When n=2, the bio-based indole acid zinc salt nucleating agent is 3-indolepropionic acid zinc salt, and its structure is as follows:

[0014]

[0015] When n=3, the bio-based indole acid zinc salt nucleating agent is 3-indolebutyric acid zinc salt, and its structure is as follows:

[0016]

[0017] The present invention provides a method for preparing a bio-based indole acid zinc salt nucleating agent, comprising the following steps:

[0018] S1: dissolving the indole acid compound in a solvent and dispersing it uniformly to obtain a mixed solution;

[0019] S2: adding an acid zinc substance to a solvent to obtain an acid zinc solution;

[0020] S3: The reaction temperature is 20-60°C, the mixed solution of S1 is added dropwise to the acid zinc solution of S2, and after the addition is completed, the mixture is kept warm under stirring, and then the temperature is raised to 60-100°C and the stirring reaction is continued, and the stirring is stopped to obtain a reaction solution;

[0021] S4: filtering the reaction solution of S3 to obtain a filter cake, washing the filter cake, filtering by suction, and drying to obtain a bio-based indole acid zinc salt nucleating agent.

[0022] Preferably, the indole acid compound in S1 is selected from any one of 3-indolecarboxylic acid, 3-indoleacetic acid, 3-indolepropionic acid or 3-indolebutyric acid, and the molar concentration of the indole acid compound in the mixed solution of S1 is 0.2-1.2 mol / L; the acid zinc substance in S2 is selected from any one or more of zinc acetate, zinc hydrochloride, zinc nitrate or zinc phosphate, and the molar concentration of the acid zinc substance in the acid zinc solution of S2 is 0.1-0.4 mol / L.

[0023] Preferably, the solvents described in S1 and S2 are selected from methanol, and the method for uniform dispersion in S1 is ultrasonic dispersion.

[0024] Preferably, the molar ratio of the indole acid compound to the zinc acid substance is 2-10:1.

[0025] Preferably, in S3, the total time for adding the mixed solution of S1 dropwise to the acid zinc solution of S2 is 1-3 hours, and the adding process is carried out in a nitrogen atmosphere.

[0026] Preferably, after the temperature in S3 is raised to 60-100° C., the stirring reaction time is continued for 12-36 hours.

[0027] Preferably, the detergent used for washing the filter cake in S4 is selected from any one or more of methanol or tetrahydrofuran, and the washing times are two or more.

[0028] The present invention provides application of the bio-based indole acid zinc salt nucleating agent for preparing a polylactic acid composition.

[0029] The present invention also provides a polylactic acid composition, comprising the bio-based indole acid zinc salt nucleating agent and polylactic acid.

[0030] The present invention has the following beneficial effects:

[0031] (1) The present invention uses indole acid compounds and acid zinc substances as raw materials to synthesize bio-based indole acid zinc salt nucleating agents, with a simple synthesis route, low processing cost, and a yield of more than 90%.

[0032] (2) The nucleating agent of the present invention belongs to the bio-based indole acid zinc salt nucleating agent. The raw materials are derived from bio-based materials. The obtained polylactic acid products are biodegradable and belong to environmentally friendly biomass nucleating agents. They have a significant effect of promoting PLA crystallization in polylactic acid, can provide good nucleation efficiency for polylactic acid during the preparation process, and the nucleation effect is very stable. After adding 0.1wt% of the nucleating agent of the present application, the crystallization temperature of the polylactic acid composition is increased to 119°C at the highest, and the crystallinity is increased to more than 46%.

[0033] (3) After adding the nucleating agent of the present application, the heat deformation temperature (HDT) of PLA is significantly increased, and increases with the extension of annealing time. After annealing for 60 seconds, the HDT of the polylactic acid composition with 0.1wt% of the nucleating agent of the present application can reach a maximum of 121°C, which is at least 45°C higher than that of pure PLA.

[0034] (4) After adding the nucleating agent of the present application, the impact strength of PLA is improved. This is because the addition of the nucleating agent increases the crystallinity of PLA, thereby increasing the impact strength. The polylactic acid composition prepared by the present application has excellent mechanical properties.

[0035] (5) After adding the nucleating agent of the present application, PLA has a significant inhibitory effect on the growth of Escherichia coli and Staphylococcus aureus, with an inhibition rate of more than 90%. The polylactic acid composition prepared by the present application has excellent antibacterial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a typical reaction formula of 3-indole acid and zinc acetate of the present invention.

[0037] Figure 2 This is the H NMR spectrum of the nucleating agent 3-indolecarboxylic acid zinc salt.

[0038] Figure 3 This is the H NMR spectrum of the nucleating agent 3-indoleacetic acid zinc salt.

[0039] Figure 4 This is the H NMR spectrum of the nucleating agent 3-indolepropionic acid zinc salt.

[0040] Figure 5 This is the H NMR spectrum of the nucleating agent 3-indolebutyric acid zinc salt.

[0041] Figure 6 This is the DSC spectrum of 3-indolecarboxylic acid zinc salt nucleating agent added to PLA.

[0042] Figure 7 This is the DSC spectrum of the nucleating agent zinc salt of 3-indoleacetic acid added to PLA.

[0043] Figure 8 This is the DSC spectrum of 3-indolepropionic acid zinc salt nucleating agent added to PLA.

[0044] Fig. 9 This is the DSC spectrum of 3-indolebutyric acid zinc salt nucleating agent added to PLA.

[0045] Fig.10 The graph shows the antibacterial effects of pure PLA, PLA containing indole acid zinc salt nucleating agent, and PLA containing zinc citrate nucleating agent on Escherichia coli and Staphylococcus aureus. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0047] The raw materials used in the present invention are all commercially available.

[0048] Various performance test methods:

[0049] (1) DSC test: According to the determination method of GB1662-81, the non-isothermal crystallization and melting behavior of polylactic acid was studied on a differential scanning calorimeter. The sample amount was 5-10 mg in a nitrogen atmosphere. The temperature was raised from room temperature to 200°C at 20°C / min and kept at that temperature for 5 min; then the temperature was lowered from 200°C to room temperature at a rate of 10°C / min, and the crystallization temperature was recorded; finally, the temperature was raised from room temperature to 200°C at a rate of 10°C / min, and the degree of crystallinity was calculated using the DSC program.

[0050] (2) Heat deformation temperature test: According to GB1634-79 plastic bending load heat deformation temperature test method, a SWB-300D Vicat softening tester was used to test the sample in a three-point simply supported beam mode. The length / width / thickness of the test specimen was 80 / 10 / 4 mm, respectively.

[0051] (3) Impact strength test: The impact test strips obtained by injection molding were subjected to impact test according to GB / T 1843-2008 standard.

[0052] (4) Antibacterial performance test:

[0053] 1) Before the experiment, all experimental items, including liquid culture medium, LB culture medium, centrifuge tubes, etc., must be sterilized under high temperature and high pressure conditions.

[0054] 2) Escherichia coli and Staphylococcus aureus were mixed evenly in LB liquid medium, inoculated with an inoculation loop, immersed in 10ul LB liquid medium, blown evenly 30 times with a pipette, and the resulting bacterial suspension was diluted to an initial concentration of 107. Subsequently, the diluted bacterial solution was added to a 12-well plate containing a polylactic acid composition sample added with a bio-based indole acid zinc salt nucleating agent, and the volume ratio was in accordance with 20mL / cm 2 Finally, the 12-well plate was placed in a 37°C incubator for 3 hours.

[0055] 3) Inoculation and counting: After 3 hours of immersion culture, the extract was taken out and implanted into LB solid medium and cultured in an incubator at 37°C for 24 hours. After 24 hours, the number of colonies was counted for screening.

[0056] Example 1

[0057] 20 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0058] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0059] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 20°C for 1 hour; then the mixture was transferred to 60°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80° C. to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 92.4%.

[0060] The NMR spectrum of the nucleating agent 3-indolecarboxylic acid zinc salt is as follows Figure 2 As shown. Among them, the chemical shift at 11.4 ppm is the -NH- proton signal peak on the indole ring, the chemical shift at 8.1 ppm is the proton signal peak on CH=C on the indole ring, and the chemical shifts at 7.8, 7.4 and 7.1 ppm are the proton signal peaks of the benzene ring on the indole ring.

[0061] Example 2

[0062] 20 mmol of 3-indoleacetic acid was dissolved in 100 ml of methanol, and ultrasonicated until the mixture was evenly dispersed to obtain a mixed solution.

[0063] 5 mmol of zinc hydrochloride was added to 50 ml of methanol solvent, and ultrasonicated to disperse the zinc hydrochloride uniformly to obtain a zinc hydrochloride solution.

[0064] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc hydrochloride solution, the system temperature was maintained at 20°C, and the reaction time was 2 hours; then the mixture was transferred to 60°C and stirred for 12 hours. After the reaction was completed, the solid product was filtered out, and the solid product was washed twice with methanol. The white solid product was then filtered out and dried in a vacuum oven set at 80°C to obtain a 3-indoleacetic acid zinc salt nucleating agent with a yield of 92.9%.

[0065] The NMR spectrum of the nucleating agent 3-indoleacetic acid zinc salt is as follows Figure 3As shown. Among them, the chemical shift at 10.7ppm is the -NH- proton signal peak on the indole ring, the chemical shifts at 7.5, 7.3, 7.0 and 6.9ppm are the proton signal peaks of the benzene ring on the indole ring, the chemical shift at 7.1ppm is the proton signal peak on CH=C on the indole ring, and the chemical shift at 3.5ppm is the proton signal peak on the methylene CH2.

[0066] Example 3

[0067] 20 mmol of 3-indolepropionic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0068] 10 mmol of zinc nitrate was added to 50 ml of methanol solvent, and ultrasonicated to disperse it uniformly to obtain a zinc nitrate solution.

[0069] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc nitrate solution, the system temperature was maintained at 20°C, and the reaction time was 3 hours; then the mixture was transferred to 60°C and stirred for 36 hours. After the reaction was completed, the solid product was filtered off, and the solid product was washed twice with tetrahydrofuran. The white solid product was then filtered off and dried in a vacuum oven set at 80°C to obtain a 3-indoleacetic acid zinc salt nucleating agent with a yield of 91.1%.

[0070] The NMR spectrum of the nucleating agent 3-indolepropionic acid zinc salt is as follows Figure 4 As shown. Among them, the chemical shift at 10.7ppm is the -NH- proton signal peak on the indole ring, the chemical shifts at 7.5, 7.3 and 6.9ppm are the proton signal peaks of the benzene ring on the indole ring, the chemical shift at 7.1ppm is the proton signal peak on CH=C on the indole ring, and the chemical shifts at 2.6, 2.1 and 1.8ppm are the proton signal peaks on the methylene CH2.

[0071] Example 4

[0072] 120 mmol of 3-indolebutyric acid was dissolved in 100 ml of methanol, and ultrasonicated until the mixture was evenly dispersed to obtain a mixed solution.

[0073] 20 mmol of zinc phosphate was added to 50 ml of methanol solvent, and the mixture was dispersed evenly by ultrasonication to obtain a zinc phosphate solution.

[0074] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc phosphate solution, the system temperature was maintained at 20°C, and the reaction time was 1 hour; then the mixture was transferred to 60°C and stirred for 12 hours. After the reaction was completed, the solid product was filtered out, and the solid product was washed twice with methanol. The white solid product was then filtered out and dried in a vacuum oven set at 80°C to obtain a 3-indoleacetic acid zinc salt nucleating agent with a yield of 93.5%.

[0075] The NMR spectrum of the nucleating agent 3-indolebutyric acid zinc salt is as follows Figure 5 As shown. Among them, the chemical shift at 10.7ppm is the -NH- proton signal peak on the indole ring, the chemical shifts at 7.5, 7.3 and 6.9ppm are the proton signal peaks of the benzene ring on the indole ring, the chemical shift at 7.1ppm is the proton signal peak on CH=C on the indole ring, and the chemical shifts at 2.6, 2.1 and 1.8ppm are the proton signal peaks on the methylene CH2.

[0076] Example 5

[0077] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0078] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0079] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 20°C for 1 hour; then the mixture was transferred to 60°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80° C. to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 93.3%.

[0080] Example 6

[0081] 60 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0082] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0083] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 20°C for 1 hour; then the mixture was transferred to 60°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. The white solid product was then filtered and dried in a vacuum oven set at 80°C to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 94.5%.

[0084] Example 7

[0085] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0086] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0087] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 40°C for 1 hour; then the mixture was transferred to 60°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80° C. to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 94.1%.

[0088] Example 8

[0089] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0090] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0091] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 60°C for 1 hour; then the mixture was transferred to 60°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80°C to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 94.7%.

[0092] Example 9

[0093] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0094] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0095] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 60°C for 1 hour; then the mixture was transferred to 70°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80° C. to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 94.9%.

[0096] Example 10

[0097] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0098] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0099] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 60°C for 1 hour; then the mixture was transferred to 85°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80° C. to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 91.9%.

[0100] Embodiment 11

[0101] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0102] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0103] Under nitrogen atmosphere, the mixed solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 60°C for 1 hour; then the mixture was transferred to 95°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, the solid product was filtered off and washed twice with methanol. The white solid product was then filtered off and dried in a vacuum oven at 80°C to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 90.1%.

[0104] Example 12

[0105] The polylactic acid and the nucleating agent obtained in Example 1 were dried in a 60°C oven for 6 hours, and the PLA and the nucleating agent were fully mixed in a mass ratio of 100:0.03. The temperature zone of the extruder was set to 150, 155, 160, 165, 170, and 180°C. The extruder speed was set to 300r / min. The material was then fed into a twin-screw extruder to obtain a polylactic acid composition with a weight percentage of 0.05wt% of 3-indolecarboxylic acid zinc salt, named PLA / ICA-0.03wt%.

[0106] Example 13

[0107] The polylactic acid and the nucleating agent obtained in Example 1 were dried in a 60°C oven for 6 hours, and the PLA and the nucleating agent were fully mixed in a mass ratio of 100:0.05, and the temperature zone of the extruder was set to 150, 155, 160, 165, 170, and 180°C. The extruder speed was set to 300r / min. The material was then fed into a twin-screw extruder to obtain a polylactic acid composition with a weight percentage of 0.05wt% of 3-indolecarboxylic acid zinc salt, named PLA / ICA-0.05wt%.

[0108] Embodiment 14

[0109] The polylactic acid and the nucleating agent obtained in Example 1 were dried in an oven at 60°C for 6 hours, and the PLA and the nucleating agent were fully mixed at a mass ratio of 100:0.1. The temperature zones of the extruder were set to 150, 155, 160, 165, 170, and 180°C. The extruder speed was set to 300r / min. The materials were then fed into a twin-screw extruder to obtain a polylactic acid composition with a weight percentage of 0.1wt% of 3-indolecarboxylic acid zinc salt, named PLA / ICA-0.1wt%. The DSC of 3-indolecarboxylic acid zinc salt added to PLA was as follows: Figure 6 shown.

[0110] Embodiment 15

[0111] The polylactic acid and the nucleating agent obtained in Example 2 were dried in an oven at 60°C for 6 hours, and the PLA and the nucleating agent were fully mixed at a mass ratio of 100:0.1. The temperature zones of the extruder were set to 150, 155, 160, 165, 170, and 180°C. The extruder speed was set to 300r / min. The materials were then fed into a twin-screw extruder to obtain a polylactic acid composition with a weight percentage of 0.1wt% of 3-indoleacetic acid zinc salt, named PLA / IAA-0.1wt%. The DSC of 3-indoleacetic acid zinc salt added to PLA was as follows: Figure 7 shown.

[0112] Example 16

[0113] The polylactic acid and the nucleating agent obtained in Example 3 were dried in an oven at 60°C for 6 hours, and the PLA and the nucleating agent were fully mixed at a mass ratio of 100:0.1. The temperature zones of the extruder were set to 150, 155, 160, 165, 170, and 180°C. The extruder speed was set to 300r / min. The materials were then fed into a twin-screw extruder to obtain a polylactic acid composition with a weight percentage of 0.1wt% of 3-indolepropionic acid zinc salt, named PLA / IPA-0.1wt%. The DSC of 3-indolepropionic acid zinc salt added to PLA was as follows: Figure 8 shown.

[0114] Embodiment 17

[0115] The polylactic acid and the nucleating agent obtained in Example 4 were dried in an oven at 60°C for 6 hours, and the PLA and the nucleating agent were fully mixed at a mass ratio of 100:0.1. The temperature zones of the extruder were set to 150, 155, 160, 165, 170, and 180°C. The extruder speed was set to 300r / min. The materials were then fed into a twin-screw extruder to obtain a polylactic acid composition with a weight percentage of 0.1wt% of 3-indolebutyric acid zinc salt, named PLA / IBA-0.1wt%. The DSC of 3-indolebutyric acid zinc salt added to PLA was as follows: Fig. 9 shown.

[0116] Comparative Example 1

[0117] 20 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of anhydrous ethanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0118] 10 mmol of zinc acetate was added to 50 ml of anhydrous ethanol as a solvent, and the mixture was dispersed evenly by ultrasonication to obtain a zinc acetate solution.

[0119] In a nitrogen atmosphere, the 3-indolecarboxylic acid solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 20°C for 1 hour; then the temperature was transferred to 60°C and the reaction was continued with stirring for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80° C. to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 77.8%.

[0120] Comparative Example 2

[0121] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0122] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0123] In a nitrogen atmosphere, the 3-indolecarboxylic acid solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 0°C for 1 hour; then the mixture was transferred to 60°C and stirred for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80°C to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 81.5%.

[0124] Comparative Example 3

[0125] 40 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0126] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0127] In a nitrogen atmosphere, the 3-indolecarboxylic acid solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 75°C for 1 hour; then the reaction was continued at 60°C with stirring for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. The white solid product was then filtered and dried in a vacuum oven set at 80°C to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 70.7%.

[0128] Comparative Example 4

[0129] 120 mmol of 3-indolecarboxylic acid was dissolved in 100 ml of methanol, and ultrasonicated to disperse the mixture uniformly to obtain a mixed solution.

[0130] 10 mmol of zinc acetate was added to 50 ml of methanol solvent, and the mixture was evenly dispersed by ultrasonication to obtain a zinc acetate solution.

[0131] In a nitrogen atmosphere, the 3-indolecarboxylic acid solution was slowly added dropwise to the zinc acetate solution, maintaining the system temperature at 20°C for 1 hour; then the temperature was transferred to 60°C and the reaction was continued with stirring for 24 hours. The reaction formula is as follows: Figure 1 After the reaction was completed, a solid product was obtained by filtration, and the solid product was washed twice with methanol. Then, the white solid product was obtained by filtration and dried in a vacuum oven set at 80°C to obtain a 3-indolecarboxylic acid zinc salt nucleating agent with a yield of 73.2%.

[0132] Comparative Example 5

[0133] The polylactic acid and the nucleating agent zinc citrate were dried in an oven at 60°C for 6 hours, and the PLA and the nucleating agent were fully mixed at a mass ratio of 100:0.1. The temperature zones of the extruder were set to 150, 155, 160, 165, 170, and 180°C. The speed of the extruder was set to 300r / min. The material was then fed into a twin-screw extruder to obtain a polylactic acid composition with a weight percentage of zinc citrate of 0.1wt%, named PLA / CA-0.1wt%.

[0134] Table 1 Test results of polylactic acid compositions of Examples 12-17 adding indole acid zinc salt nucleating agent and Comparative Example 5 adding zinc citrate nucleating agent

[0135]

[0136] It can be seen from the results in Table 1 that, by comparing Examples 14-17 with Comparative Example 5, the samples to which the bio-based indole acid zinc salt nucleating agent of the present application is added are superior to the samples to which the conventional nucleating agent zinc citrate is added in terms of crystallization temperature, crystallinity, heat deformation temperature, and impact strength, especially in terms of heat deformation temperature (HDT). At a content of 0.1 wt%, the heat deformation temperature is increased by more than 27°C compared with the samples to which the conventional nucleating agent zinc citrate is added.

[0137] In particular, when the addition amount of the bio-based indole acid zinc salt nucleating agent reaches 0.1 wt %, the inhibition rate of the obtained polylactic acid composition on Escherichia coli and Staphylococcus aureus can reach more than 90%.

Claims

1. A bio-based indole acid zinc salt nucleating agent, characterized in that: The bio-based indole acid zinc salt nucleating agent has the following structure: Wherein, n is a constant, n=0, 3.

2. The method for preparing a bio-based indole acid zinc salt nucleating agent according to claim 1, characterized in that: The following steps are involved: S1: dissolving the indole acid compound in a solvent and dispersing it uniformly to obtain a mixed solution; S2: adding an acid zinc substance to a solvent to obtain an acid zinc solution; S3: The reaction temperature is 20-60°C, the mixed solution of S1 is added dropwise to the acid zinc solution of S2, and after the addition is completed, the mixture is kept warm under stirring, and then the temperature is raised to 60-100°C and the stirring reaction is continued, and the stirring is stopped to obtain a reaction solution; S4: filtering the reaction solution of S3 to obtain a filter cake, washing the filter cake, filtering by suction, and drying to obtain a bio-based indole acid zinc salt nucleating agent.

3. The method for preparing a bio-based indole acid zinc salt nucleating agent according to claim 2, characterized in that: The indole acid compound in S1 is selected from any one of 3-indolecarboxylic acid or 3-indolebutyric acid, and the molar concentration of the indole acid compound in the mixed solution of S1 is 0.2-1.2 mol / L; the acid zinc substance in S2 is selected from any one or more of zinc acetate, zinc hydrochloride, zinc nitrate, zinc sulfate or zinc phosphate, and the molar concentration of the acid zinc substance in the acid zinc solution of S2 is 0.1-0.4 mol / L.

4. The method for preparing a bio-based indole acid zinc salt nucleating agent according to claim 2, characterized in that: The solvent described in S1 and S2 is selected from methanol, and the method for uniform dispersion in S1 is ultrasonic dispersion.

5. The method for preparing a bio-based indole acid zinc salt nucleating agent according to claim 2, characterized in that: The molar ratio of the indole acid compound to the acid zinc substance is 2-10:

1.

6. The method for preparing a bio-based indole acid zinc salt nucleating agent according to claim 2, characterized in that: In S3, the total time for adding the mixed solution of S1 dropwise to the zinc acid solution of S2 is 1-3 hours, and the dropping process is carried out in a nitrogen atmosphere.

7. The method for preparing a bio-based indole acid zinc salt nucleating agent according to claim 2, characterized in that: After the temperature in S3 is raised to 60-100°C, the stirring reaction time is continued for 12-36 hours.

8. The method for preparing a bio-based indole acid zinc salt nucleating agent according to claim 2, characterized in that: The detergent used for washing the filter cake in S4 is selected from any one or more of methanol or tetrahydrofuran, and the washing times are two or more.

9. The use of a bio-based indole acid zinc salt nucleating agent according to claim 1, characterized in that: Used for preparing polylactic acid composition.

10. A polylactic acid composition, characterized in that: It comprises the bio-based indole acid zinc salt nucleating agent as described in claim 1 and polylactic acid.

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