A small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid, and a preparation method and application thereof

Abstract

The application belongs to the technical field of biodegradable polyester nucleating agent synthesis, and discloses a small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid, and a preparation method and application thereof.A novel polylactic acid nucleating agent designed and synthesized by the application is prepared by adding terephthaloyl chloride, methoxybenzoyl hydrazine and a bundling agent into a solvent and synthesizing at 60 DEG C.The nucleating agent is mixed with polylactic acid by a melt blending method, and is extruded or injection molded into a polylactic acid product, so that good nucleation efficiency is provided for polylactic acid during preparation, the nucleation effect is stable, the polylactic acid product obtained has a high crystallization peak temperature, excellent mechanical properties and other characteristics.The preparation method of the nucleating agent is simple, mass production can be realized, and the nucleating agent can be widely applied to the preparation of industrial polylactic acid plastic products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic materials, and particularly relates to a small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid as well as a preparation method and application thereof. BACKGROUND

[0002] In the past two decades, polylactic acid (PLA) has become one of the most commercially produced and consumed biodegradable polymers. It is widely used in many fields, such as disposable products, biomedical materials, food packaging, automobile parts and adhesives. The global annual consumption of PLA exceeds 200,000 tons, and the planned production capacity is close to 1,000,000 tons. Polylactic acid has good biodegradability, biocompatibility and mechanical properties, and has the potential to replace traditional plastics.

[0003] However, its consumption and application are still far behind traditional plastics, largely because of its slow crystallization speed, low crystallinity and unsuitability for blow molding. In addition, its brittleness and low elongation at break not only limit its application in fields with high requirements for heat resistance, such as engineering plastics and hot food packaging boxes, but also have plagued the academic and industrial communities for many years. Therefore, improving the crystallization ability of PLA is the key to expanding its application range.

[0004] In order to solve this problem, some nucleating agents have been used to improve the crystallinity of polylactic acid. For example, montmorillonite, calcium carbonate, hydrotalcite, titanium dioxide and silicon dioxide, but the biggest problem is that they have poor compatibility with polylactic acid and are prone to agglomeration, which ultimately leads to a decrease in the mechanical properties and transparency of polylactic acid products, limiting the application and sales of the products. Organic nucleating agents can solve this problem. The compatibility of polylactic acid and organic nucleating agents is excellent, and the crystallization performance of polylactic acid can be greatly improved, thereby improving the nucleation effect. Organic nucleating agents commonly used for polylactic acid include benzoate, amide compounds, sorbitol, organic phosphate and hydrazide compounds. SUMMARY

[0005] In order to overcome the slow crystallization of polylactic acid in the prior art, the primary purpose of the present application is to provide a small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid.

[0006] Another purpose of the present application is to provide a preparation method of the small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid.

[0007] Another purpose of the present application is to provide an application of the small-molecule hydrazide nucleating agent. Adding a small amount of the nucleating agent to polylactic acid can help polylactic acid crystallize at a high cooling rate and improve the crystallinity of polylactic acid products.

[0008] The purposes of the present application are achieved by the following technical solutions:

[0009] A small molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid, the small molecule hydrazide nucleating agent has the following structure:

[0010]

[0011] Wherein, R is a methoxy functional group on the ortho, meta or para of the benzene ring.

[0012] When R is a methoxy functional group on the ortho of the benzene ring, the small molecule hydrazide nucleating agent is named as BTAD-O; when R is a methoxy functional group on the meta of the benzene ring, the small molecule hydrazide nucleating agent is named as BTAD-M; when R is a methoxy functional group on the para of the benzene ring, the small molecule hydrazide nucleating agent is named as BTAD-P.

[0013] The small molecule hydrazide nucleating agent of the above type has the following structure:

[0014]

[0015] The preparation method of the above small molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid is according to the following operation steps:

[0016] The methoxybenzoyl hydrazine is dissolved in a solvent, ultrasonic dispersion is uniform, then a bundle of acid agents is added dropwise to obtain a mixed solution; the terephthaloyl chloride is added to the solvent to obtain a terephthaloyl chloride solution; the terephthaloyl chloride solution is added dropwise to the mixed solution under a nitrogen atmosphere and at a low reaction temperature of 0-10℃, after the dropwise addition is completed, the reaction is carried out under stirring and heat preservation, and then the reaction is continued under stirring at 60℃; the obtained reaction solution is washed with deionized water, filtered to obtain a filter cake, then washed with methanol, and after suction filtration and drying, the small molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid is obtained.

[0017] The molar ratio of the methoxybenzoyl hydrazine and the terephthaloyl chloride is 1:2-2.5.

[0018] The total dropwise addition time is 1-3h.

[0019] The total dropwise addition time is 1h; and the low reaction temperature is 0℃.

[0020] The time for transferring to continue the stirring reaction at 60℃ is 24-36h.

[0021] The time for transferring to continue the stirring reaction at 60℃ is 24h.

[0022] The concentration of methoxybenzoyl hydrazine in the mixed solution is 0.2-0.8 mol / L, and the concentration of the acid bundling agent is 0.5-1.5 mol / L; the concentration of the terephthaloyl chloride solution is 0.2-0.8 mol / L.

[0023] The application of the above-mentioned small-molecule hydrazide nucleating agent in improving the crystallization ability of polylactic acid is as follows: polylactic acid is dried at 60 DEG C for 4h, then the small-molecule hydrazide nucleating agent is melt-blended with polylactic acid at a mass ratio of 0.5-5:100 at a temperature of 200 DEG C and a rotation speed of 30-50 r / min for 10 min; then it is added into a double-screw extruder, the temperature of the extruder is set to 150, 155, 160, 165, 170, 180 DEG C, and the rotation speed is 300 r / min, to obtain polylactic acid granules with improved crystallization ability and different nucleating agent contents.

[0024] The present application has the following advantages and effects compared with the prior art:

[0025] (1) The present application uses benzoyl hydrazine and terephthaloyl chloride as raw materials to synthesize a small-molecule hydrazide nucleating agent, and the synthesis circuit is simple, the operation process is simple, the processing cost is low, and the yield is high, up to 90%.

[0026] (2) The nucleating agent of the present application belongs to an organic small-molecule nucleating agent, has good compatibility in polylactic acid, can be uniformly dispersed in a polylactic acid matrix, and a small amount of the nucleating agent can improve the crystallization rate of polylactic acid, and has excellent nucleation effect; after adding the nucleating agent, the crystallization temperature of polylactic acid resin is increased to 129.5 DEG C, and the crystallinity is increased from 14.6% to 63.7%. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The reaction formula of terephthaloyl chloride and benzoyl hydrazine in the present application.

[0028] Figure 2 The nuclear magnetic resonance spectrum of a series of nucleating agents.

[0029] Figure 3 The DSC spectrum of the nucleating agent added in PLA. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below in combination with examples and drawings, but the embodiments of the present application are not limited thereto.

[0031] Example 1

[0032] The small-molecule hydrazide nucleating agent is prepared by the following steps:

[0033] The 20 mmol 4-methoxybenzoyl hydrazine was dissolved in 100 ml solvent N-methyl pyrrolidone (NMP) and ultrasonically dispersed until uniform, then 5 ml of pyridine was added to obtain a mixed solution; next, 10 mmol of terephthaloyl chloride was added to 40 ml of solvent NMP and stirred until uniform to obtain a terephthaloyl chloride solution; under a nitrogen atmosphere, the terephthaloyl chloride solution was slowly added to the mixed solution, keeping the system temperature at 0°C, and taking 1 h. Subsequently, it was transferred to continue stirring at 60°C for 24 h. After the reaction was completed, it was first washed once with deionized water, and the solid product was obtained by suction filtration. The solid product was washed twice with methanol, and then the white solid product obtained by suction filtration was dried in a vacuum oven with a temperature setting of 80°C to obtain a small molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid. The nuclear magnetic resonance hydrogen spectrum of the nucleating agent BTAD-P is shown in (c) of FIG. 1. Figure 2

[0034] Example 2

[0035] The 20 mmol 4-methoxybenzoyl hydrazine was dissolved in 100 ml solvent N-methyl pyrrolidone (NMP) and ultrasonically dispersed until uniform, then 5 ml of pyridine was added to obtain a mixed solution; next, 10 mmol of terephthaloyl chloride was added to 40 ml of solvent NMP and stirred until uniform to obtain a terephthaloyl chloride solution; under a nitrogen atmosphere, the terephthaloyl chloride solution was slowly added to the mixed solution, keeping the system temperature at 0°C, and taking 1 h. Subsequently, it was transferred to continue stirring at 60°C for 24 h. After the reaction was completed, it was first washed once with deionized water, and the solid product was obtained by suction filtration. The solid product was washed twice with methanol, and then the white solid product obtained by suction filtration was dried in a vacuum oven with a temperature setting of 80°C to obtain a small molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid. The nuclear magnetic resonance hydrogen spectrum of the nucleating agent BTAD-P is shown in (c) of FIG. 1. Figure 2

[0036] Example 3

[0037] The 20 mmol 4-methoxybenzoyl hydrazine was dissolved in 100 ml solvent N-methyl pyrrolidone (NMP) and ultrasonically dispersed until uniform, then 5 ml of pyridine was added to obtain a mixed solution; next, 10 mmol of terephthaloyl chloride was added to 40 ml of solvent NMP and stirred until uniform to obtain a terephthaloyl chloride solution; under a nitrogen atmosphere, the terephthaloyl chloride solution was slowly added to the mixed solution, keeping the system temperature at 0°C, and taking 1 h. Subsequently, it was transferred to continue stirring at 60°C for 24 h. After the reaction was completed, it was first washed once with deionized water, and the solid product was obtained by suction filtration. The solid product was washed twice with methanol, and then the white solid product obtained by suction filtration was dried in a vacuum oven with a temperature setting of 80°C to obtain a small molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid. The nuclear magnetic resonance hydrogen spectrum of the nucleating agent BTAD-P is shown in (c) of FIG. 1.​​Figure 2 (a) in the presence of (b).

[0038] Example 4

[0039] Dissolve 25 mmol of 4-methoxybenzohydrazide in 100 ml of solvent N-methyl pyrrolidone (NMP), and sonicate until it is uniformly dispersed, then add 5 ml of pyridine to obtain a mixed solution. Next, add 10 mmol of terephthaloyl chloride to 40 ml of solvent NMP, and stir until it is uniformly dispersed to obtain a terephthaloyl chloride solution; slowly add the terephthaloyl chloride solution dropwise to the mixed solution under a nitrogen atmosphere, and maintain the system temperature at 0°C for 1 h. Subsequently, transfer to 60°C and continue stirring for 24 h. After the reaction is complete, wash once with deionized water, and filter to obtain a solid product. Wash the solid product twice with methanol, then filter the white solid product obtained, and dry in a vacuum oven with a temperature setting of 80°C to obtain a small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid.

[0040] Example 5

[0041] Dissolve 25 mmol of 3-methoxybenzohydrazide in 100 ml of solvent N-methyl pyrrolidone (NMP), and sonicate until it is uniformly dispersed, then add 5 ml of pyridine to obtain a mixed solution; next, add 10 mmol of terephthaloyl chloride to 40 ml of solvent NMP, and stir until it is uniformly dispersed to obtain a terephthaloyl chloride solution; slowly add the terephthaloyl chloride solution dropwise to the mixed solution under a nitrogen atmosphere, and maintain the system temperature at 0°C for 1 h. Subsequently, transfer to 60°C and continue stirring for 24 h. After the reaction is complete, wash once with deionized water, and filter to obtain a solid product. Wash the solid product twice with methanol, then filter the white solid product obtained, and dry in a vacuum oven with a temperature setting of 80°C to obtain a small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid.

[0042] Example 6

[0043] Dissolve 25 mmol of 2-methoxybenzohydrazide in 100 ml of solvent N-methyl pyrrolidone (NMP), and sonicate until it is uniformly dispersed, then add 5 ml of pyridine to obtain a mixed solution; next, add 10 mmol of terephthaloyl chloride to 40 ml of solvent NMP, and stir until it is uniformly dispersed to obtain a terephthaloyl chloride solution; slowly add the terephthaloyl chloride solution dropwise to the mixed solution under a nitrogen atmosphere, and maintain the system temperature at 0°C for 1 h. Subsequently, transfer to 60°C and continue stirring for 24 h. After the reaction is complete, wash once with deionized water, and filter to obtain a solid product. Wash the solid product twice with methanol, then filter the white solid product obtained, and dry in a vacuum oven with a temperature setting of 80°C to obtain a small-molecule hydrazide nucleating agent for improving the crystallization ability of polylactic acid.

[0044] Example 7

[0045] The polylactic acid and nucleating agent obtained in Example 3 were dried in an oven at 60°C for 6h, and the PLA and nucleating agent were mixed uniformly at a mass ratio of 100:0.5, and the temperature zones of the extruder were set at 160°C, 165°C, 170°C, 180°C, and 190°C. The rotation speed of the extruder was set at 300r / min. Then the mixture was fed into a twin-screw extruder to obtain the blended PLA-O 0.5 Sample.

[0046] Example 8

[0047] The polylactic acid and nucleating agent obtained in Example 2 were dried in an oven at 60°C for 6h, and the PLA and nucleating agent were mixed uniformly at a mass ratio of 100:0.5, and the temperature zones of the extruder were set at 160°C, 165°C, 170°C, 180°C, and 190°C. The rotation speed of the extruder was set at 300r / min. Then the mixture was fed into a twin-screw extruder to obtain the blended PLA-M 0.5 Sample.

[0048] Example 9

[0049] The polylactic acid and nucleating agent obtained in Example 1 were dried in an oven at 60°C for 6h, and the PLA and nucleating agent were mixed uniformly at a mass ratio of 100:0.5, and the temperature zones of the extruder were set at 160°C, 165°C, 170°C, 180°C, and 190°C. The rotation speed of the extruder was set at 300r / min. Then the mixture was fed into a twin-screw extruder to obtain the blended PLA-P 0.5 Sample.

[0050] Test 1

[0051] DSC test: The non-isothermal crystallization and melting behavior of polylactic acid was studied on a differential scanning calorimeter, and the atmosphere was nitrogen, and the PLA-O 0.5 The sample amount was 5-10mg. The temperature was raised from room temperature to 200°C at a rate of 20°C / min, and held for 5min; 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 crystallinity was calculated by the program of the DSC.

[0052] Test 2

[0053] DSC test: The non-isothermal crystallization and melting behavior of polylactic acid was studied on a differential scanning calorimeter, and the atmosphere was nitrogen, and the PLA-M 0.5The sample dosage is 5-10 mg. The temperature is increased from room temperature to 200℃ at a rate of 20℃ / min and held for 5 min. Then, the temperature is decreased from 200℃ to room temperature at a rate of 10℃ / min, and the crystallization temperature is recorded. Finally, the temperature is increased from room temperature to 200℃ at a rate of 10℃ / min, and the degree of crystallinity is calculated using the built-in DSC program.

[0054] Experiment 3

[0055] DSC testing: The non-isothermal crystallization melting behavior of polylactic acid (PLA-P) was studied using a differential scanning calorimeter under a nitrogen atmosphere. 0.5 The sample dosage is 5-10 mg. The temperature is increased from room temperature to 200℃ at a rate of 20℃ / min and held for 5 min. Then, the temperature is decreased from 200℃ to room temperature at a rate of 10℃ / min, and the crystallization temperature is recorded. Finally, the temperature is increased from room temperature to 200℃ at a rate of 10℃ / min, and the degree of crystallinity is calculated using the built-in DSC program.

[0056] Test Data and Analysis

[0057] The above experiments yielded the following results. Figure 3 As shown in the figure, all three types of small-molecule nucleating agents significantly improved the crystallization rate and crystallinity of polylactic acid (PLA). In the examples, adding only 0.5% of the small-molecule nucleating agent increased the crystallization temperatures of PLA to 102°C, 125.1°C, and 129.5°C, respectively, and the crystallinities reached 54.0%, 60.5%, and 63.7%, respectively. The dosage of this type of nucleating agent is the same as that of conventional nucleating agents, indicating that it is a highly efficient novel hydrazide nucleating agent.

[0058] The inventors also conducted the above-mentioned experiments on other embodiments, and the results were basically the same. Due to space limitations, they are not listed one by one.

[0059] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. The application of a small molecule acylhydrazine nucleating agent in improving the crystallization ability of polylactic acid, characterized in that: The small molecule amide nucleating agent has the following structure: Wherein, R is a methoxy functional group at the ortho, meta, or para position of the benzene ring; The application follows these steps: Polylactic acid was dried at 60℃ for 4 hours. Then, a small molecule hydrazide nucleating agent was melt-blended with polylactic acid at a mass ratio of 0.5:100 at 200℃ and a rotation speed of 30-50 r / min for 10 minutes. The mixture was then fed into a twin-screw extruder with extruder temperatures set to 150, 155, 160, 165, 170, and 180℃ and a rotation speed of 300 r / min to obtain polylactic acid granules with improved crystallinity.

2. The application according to claim 1, characterized in that: The preparation method of the small molecule acyl hydrazine nucleating agent is as follows: methoxybenzoyl hydrazine is dissolved in a solvent, ultrasonically dispersed evenly, and then an acid-binding agent is added dropwise to obtain a mixed solution; terephthaloyl chloride is added to the solvent to obtain a terephthaloyl chloride solution; under a nitrogen atmosphere and at a low reaction temperature of 0-10℃, the terephthaloyl chloride solution is added dropwise to the mixed solution, and after the addition is complete, the reaction is carried out under stirring conditions, and then transferred to 60℃ for continued stirring; the resulting reaction solution is washed with deionized water, filtered to obtain a filter cake, then washed with methanol, filtered, and dried to obtain a small molecule acyl hydrazine nucleating agent for improving the crystallization ability of polylactic acid.

3. The application according to claim 2, characterized in that: The molar ratio of methoxybenzoyl hydrazine and terephthaloyl chloride is 1:2-2.

5.

4. The application according to claim 2, characterized in that: The total dripping time is 1-3 hours.

5. The application according to claim 2, characterized in that: The total dripping time is 1 hour; the low reaction temperature is 0°C.

6. The application according to claim 2, characterized in that: The reaction was continued at 60°C for 24-36 hours.

7. The application according to claim 2, characterized in that: The reaction was continued at 60°C for 24 hours.

8. The application according to claim 2, characterized in that: The concentration of methoxybenzoyl hydrazine in the mixed solution is 0.22-0.8 mol / L, and the concentration of the acid-binding agent is 0.5-1.5 mol / L; the concentration of the terephthaloyl chloride solution is 0.2-0.8 mol / L.

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