Nucleating agent, its preparation method and application

Abstract

The application discloses a nucleating agent and a preparation method and application thereof, and belongs to the technical field of material engineering, and solves the problem of unsatisfactory nucleation effect of inorganic nucleating agents on polylactic acid in the prior art. The nucleating agent has a core-shell structure, the core layer is hydroxyapatite, and the shell layer is zinc citrate; the particle size of the nucleating agent is 1-2 mu m, and the particle size of the zinc citrate is 100-200 nm. The nucleating agent provided by the application loads zinc citrate on the surface of hydroxyapatite, significantly improves the compatibility and dispersibility of the nucleating agent and polylactic acid, and effectively improves the crystallization rate and crystallinity of the polylactic acid system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material engineering, and more particularly to a nucleating agent and a preparation method and application thereof. BACKGROUND

[0002] Poly lactic acid (PLA) is a new type of bio-based polymer, which is made from renewable plant resources (such as corn) as raw material. Starch is saccharified to obtain glucose, and a specific strain is used to ferment glucose to produce high-purity lactic acid, which is then synthesized into poly lactic acid. Poly lactic acid is a new type of bio-based material with good biodegradability, biocompatibility and processing performance.

[0003] Poly lactic acid is a semi-crystalline polymer with slow crystallization rate, so the heat resistance of the products made from it is poor, with a heat distortion temperature (HDT) of about 58℃, which seriously hinders the application of poly lactic acid in a wider field. After the complete crystallization of amorphous poly lactic acid, the bending modulus and strength increase by 25%, and the impact resistance increases. In order to improve the heat resistance of poly lactic acid, researchers have done a lot of research. Patent CN103146163A discloses a sepiolite and diisocyanate, maleimide organic-inorganic hybrid high-efficiency nucleating agent, which can increase the crystallinity of the product to 55%, shorten the molding time of the poly lactic acid product, and increase the heat resistance of the product to above 120℃. Patent CN115044069A discloses a preparation method of blending phenyl phosphonate poly lactic acid, which has good compatibility with the poly lactic acid matrix and can shorten the synthesis time of the poly lactic acid nucleating agent. Patent CN110713583A discloses a preparation method for in-situ synthesis of poly lactic acid nucleating agent, which adds diisocyanate and hydrazide to the poly lactic acid melt for in-situ reaction grafting, significantly improving the heat resistance and toughness of poly lactic acid. Patent CN108384210A discloses a method for improving poly lactic acid using pyruvate as a poly lactic acid nucleating agent, which can effectively improve the crystallization rate and crystallinity of poly lactic acid, and also has potential biocompatibility and biodegradability.

[0004] Adding nucleating agents for heterogeneous nucleation is the most effective and economical method for modifying the crystallization and heat resistance of polymers. Organic nucleating agents have good nucleation effect, but many of them contain aromatic hydrocarbon structures, even heavy metal ions, which can cause harm to the human body and the environment. Inorganic nucleating agents, such as talc, montmorillonite, carbon black, and apatite, are widely available and low in price, so they are widely used in the field of poly lactic acid nucleation. However, such nucleating agents have poor nucleation effect, and a small amount of addition has no obvious nucleation effect, and a high content can easily make the product brittle, affecting the use effect, so how to improve the compatibility of inorganic nucleating agents with the poly lactic acid matrix and improve the nucleation effect is a problem to be solved. SUMMARY

[0005] The present application provides a nucleating agent and a preparation method and application thereof, to solve the problem of unsatisfactory nucleation effect of inorganic nucleating agent on polylactic acid in the prior art.

[0006] In a first aspect, the present application provides a nucleating agent with a core-shell structure, wherein the core layer is hydroxyapatite and the shell layer is zinc citrate; the particle size of the nucleating agent is 1-2 μm, and the particle size of the zinc citrate is 100-200 nm.

[0007] In a second aspect, the present application provides a preparation method of a nucleating agent, comprising the following steps: adding a metal chelating agent to a uniform hydroxyapatite slurry, heating to 70-90 ℃; adding a zinc ion solution, maintaining the temperature for 50-90 min, adding an alkali solution and reacting for 20-40 min; adding a citric acid solution, reacting for 1.5-2.5 h to obtain a crude product; and purifying to obtain the nucleating agent.

[0008] As a possible implementation manner, the purification comprises the following steps: standing the crude product for 10-15 h, centrifuging and drying to obtain the nucleating agent.

[0009] As a possible implementation manner, the centrifuging is performed at a speed of 6000-10000 r / m for 5-10 min; and / or the drying is performed at 50-80 ℃ for 20-30 h under vacuum.

[0010] As a possible implementation manner, the uniform hydroxyapatite slurry is obtained by ultrasonic dispersion of hydroxyapatite in deionized water; and / or the alkali solution is added dropwise; and / or the citric acid solution is added dropwise.

[0011] As a possible implementation manner, the mass ratio of the metal chelating agent to the hydroxyapatite is 0.3-0.4:1; and / or the concentration of the alkali solution is 1-2 mol / L, and the molar ratio of the alkali to the zinc ion is 1:0.2-1; and / or the concentration of the citric acid solution is 1.5-2.5 mol / L, and the molar ratio of the citric acid to the zinc ion is 1:0.3-0.7.

[0012] As a possible implementation manner, the metal chelating agent is any one of ethylenediaminetetraacetic acid, amino triacetic acid and diethylene triamine pentaacetic acid; and / or, the zinc ion is any one of a zinc sulfate solution and a zinc nitrate solution; and / or, the alkali solution is any one of a sodium hydroxide solution and a potassium hydroxide solution.

[0013] In a third aspect, the application provides application of the nucleating agent of any possible implementation manner of the first aspect or the nucleating agent prepared by the preparation method of any possible implementation manner of the second aspect in preparation of a polylactic acid product.

[0014] As a possible implementation manner, the nucleating agent is used in combination with a chain extender.

[0015] As a possible implementation manner, the polylactic acid product is applied in a specific environment; the specific environment is a temperature of 25-130 DEG C and a humidity of 65%-100%; or the specific environment is a temperature of 25-130 DEG C and immersion in water.

[0016] The nucleating agent provided by the application loads zinc citrate on the surface of hydroxyapatite, and a large number of hydroxyl groups exist on the surface of hydroxyapatite, which has hydrophilicity, while polylactic acid is a hydrophobic polymer. After the surface of hydroxyapatite is loaded with zinc citrate, the hydrophilicity is reduced, and meanwhile, the lattice matching relationship between zinc citrate and polylactic acid can induce the stacking of polylactic acid molecular chains, so as to improve the compatibility and dispersibility of the two and increase the crystallinity. The nucleating agent provided by the application significantly improves the compatibility and dispersibility of the nucleating agent and polylactic acid, and effectively increases the crystallization rate and crystallinity of the polylactic acid system.

[0017] The preparation method of the nucleating agent provided by the application has the advantages of simple operation, small dosage and low cost.

[0018] In the application of the nucleating agent as a polylactic acid nucleating agent, when the nucleating agent is used in combination with a chain extender, the nucleating agent has the effects of simultaneously improving the heat resistance of polylactic acid and increasing the solvent strength of polylactic acid. The injection-molded sample can be used without deformation under high-temperature and high-humidity conditions, and has excellent stability under extreme conditions. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0020] Figure 1The synthesis route map of the nucleating agent provided by the embodiment of the present application, wherein, chelating represents chelation, absorption represents absorption, complexation represents complexation, HAP represents hydroxyapatite, and ZnCC@HAP represents zinc citrate loaded on hydroxyapatite, i.e., the nucleating agent prepared by the present application.

[0021] Figure 2 The TEM images of different stages in the preparation process of the nucleating agent B provided by the embodiment of the present application, wherein, a) represents zinc citrate, i.e., the nucleating agent A (ZnCC); (b), (c), and (d) represent hydroxyapatite loaded with zinc citrate, i.e., the nucleating agent B (ZnCC@HAP-1.0), the nucleating agent C (ZnCC@HAP-1.5), and the nucleating agent D (ZnCC@HAP-2.0), respectively.

[0022] Figure 3 The thermogravimetric curve provided by the embodiment of the present application, wherein, HAP represents hydroxyapatite (nucleating agent E), and ZnCC@HAP-1.0, ZnCC@HAP-1.5, and ZnCC@HAP-2.0 represent the nucleating agent B, the nucleating agent C, and the nucleating agent D, respectively.

[0023] Figure 4 The XPS provided by the embodiment of the present application, wherein, HAP represents hydroxyapatite (nucleating agent E), and ZnCC@HAP-1.0, ZnCC@HAP-1.5, and ZnCC@HAP-2.0 represent the nucleating agent B, the nucleating agent C, and the nucleating agent D, respectively.

[0024] Figure 5 The FTIR provided by the embodiment of the present application, wherein, HAP represents hydroxyapatite (nucleating agent E), and ZnCC, ZnCC@HAP-1.0, ZnCC@HAP-1.5, and ZnCC@HAP-2.0 represent the nucleating agent A, the nucleating agent B, the nucleating agent C, and the nucleating agent D, respectively.

[0025] Figure 6 The XRD image provided by the embodiment of the present application, wherein, HAP represents hydroxyapatite (nucleating agent E), and ZnCC, ZnCC@HAP-1.0, ZnCC@HAP-1.5, and ZnCC@HAP-2.0 represent the nucleating agent A, the nucleating agent B, the nucleating agent C, and the nucleating agent D, respectively.

[0026] Figure 7A chloroform dispersion solution schematic diagram provided by the embodiment of the present application is shown from left to right as chloroform, HAP / chloroform (chloroform solution of nucleating agent E), ZnCC@HAP-1.0 / chloroform (chloroform solution of nucleating agent B), ZnCC@HAP-1.5 / chloroform (chloroform solution of nucleating agent C), ZnCC@HAP-2.0 / chloroform (chloroform solution of nucleating agent D) and ZnCC / chloroform (chloroform solution of nucleating agent A). DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0028] To solve the problem that the inorganic nucleating agent in the prior art has an unsatisfactory nucleation effect on polylactic acid, the embodiment of the present application provides a preparation experiment of a nucleating agent. It can be known that the product prepared by the present application has rod-like morphological characteristics, which is beneficial to inducing the crystallization and orientation of the polymer in the spinning process and improving the performance of the fiber.

[0029] Further, the embodiment of the present application provides an application effect test experiment of a nucleating agent. It can be known that the polylactic acid product prepared by the product prepared by the present application has high stability in extreme environment and can adapt to high temperature and high humidity environment.

[0030] The technical solutions of the present application will be further described below with reference to specific embodiments.

[0031] Embodiment 1

[0032] The embodiment provides a preparation experiment of a nucleating agent.

[0033] The nucleating agent B to the nucleating agent D in the embodiment are prepared according to the synthesis route shown in the following formula. Figure 1

[0034] 3g of zinc acetate is dissolved in 90mL of ethanol, and then 3mL of distilled water is added. The solution is heated to 80℃, and stirred and refluxed for 2h. After stirring, an equimolar (2.6257g) of citric acid (dissolved in ethanol, 2mol / L) is added, and the reaction is carried out for 5h. The solution is naturally cooled to room temperature and left overnight to improve the crystallinity. The precipitate is suction filtered, and the filter cake is repeatedly washed with ethanol and distilled water for three times. After vacuum drying, a white powder is obtained. The white powder is dried at 120℃ for 5h to obtain zinc citrate (ZnCC) as the nucleating agent A.

[0035] ​2 g of hydroxyapatite was placed in 100 mL of deionized water and ultrasonically dispersed and stirred for 30 min; 0.68 g of a metal chelator was added, the mixture was heated to 80°C in a water bath, and stirred for 3 hours; 0.04 mol of zinc sulfate was added while maintaining the temperature at 80°C, and the mixture was reacted for 1 hour; 16 mL of a 1.5 mol / L sodium hydroxide solution was added dropwise, and the mixture was reacted for 0.5 hour after the addition was complete; 40 mL of a 2 mol / L citric acid solution was added dropwise, and the mixture was reacted for 2 hours; the mixture was allowed to stand for 12 hours; differential centrifugation was performed at a speed of 8000 r / m for 8 minutes; the supernatant was removed, and the mixture was dried in a vacuum oven at 60°C for 24 hours to obtain ZnCC@HAP-1.0, i.e., nucleating agent B.

[0036] 2 g of hydroxyapatite was placed in 100 mL of deionized water and ultrasonically dispersed and stirred for 30 min; 0.68 g of a metal chelator was added, the mixture was heated to 80°C in a water bath, and stirred for 3 hours; 0.06 mol of zinc sulfate was added while maintaining the temperature at 80°C, and the mixture was reacted for 1 hour; 24 mL of a 1.5 mol / L sodium hydroxide solution was added dropwise, and the mixture was reacted for 0.5 hour after the addition was complete; 60 mL of a 2 mol / L citric acid solution was added dropwise, and the mixture was reacted for 2 hours; the mixture was allowed to stand for 12 hours; differential centrifugation was performed at a speed of 8000 r / m for 8 minutes; the supernatant was removed, and the mixture was dried in a vacuum oven at 60°C for 24 hours to obtain ZnCC@HAP-1.5, i.e., nucleating agent C.

[0037] 2 g of hydroxyapatite was placed in 100 mL of deionized water and ultrasonically dispersed and stirred for 30 min; 0.68 g of a metal chelator was added, the mixture was heated to 80°C in a water bath, and stirred for 3 hours; 0.08 mol of zinc sulfate was added while maintaining the temperature at 80°C, and the mixture was reacted for 1 hour; 32 mL of a 1.5 mol / L sodium hydroxide solution was added dropwise, and the mixture was reacted for 0.5 hour after the addition was complete; 80 mL of a 2 mol / L citric acid solution was added dropwise, and the mixture was reacted for 2 hours; the mixture was allowed to stand for 12 hours; differential centrifugation was performed at 8000 rpm for 8 minutes; the supernatant was removed, and the mixture was dried in a vacuum oven at 60°C for 24 hours to obtain ZnCC@HAP-2.0, i.e., nucleating agent D.

[0038] 2 g of hydroxyapatite was used as the nucleating agent E.

[0039] Example 2

[0040] This example provides a performance characterization experiment of a nucleating agent.

[0041] The nucleating agents B to E prepared in Example 1 were observed by TEM, and the following results were obtained: Figure 2 The results shown, Figure 2 Comparing (b), (c), and (d) with (a), the large rod-shaped object is hydroxyapatite, and the small black-gray particles on the surface are zinc citrate. It can be seen that the target product was successfully prepared.

[0042] The nucleating agents B to E prepared in Example 1 were subjected to thermogravimetric analysis. The analysis conditions were as follows: 3 to 5 mg of sample was weighed in an Al2O3 crucible under a nitrogen atmosphere and heated from 30°C to 600°C at a heating rate of 10°C to obtain the following: Figure 3 The results shown by Figure 3 It can be seen that with the increase of zinc citrate in the synthesis ratio, the thermal weight loss of the material becomes obvious. Combined with the thermogravimetric curve of zinc citrate, it can be concluded that the loading amount of zinc citrate increases and the material is successfully loaded on the surface of hydroxyapatite.

[0043] The nucleating agents B to E prepared in Example 1 were subjected to X-ray photoelectric spectroscopy analysis, and the XPS spectra were collected using a monochromatic Al Kα source, as shown in the following figure: Figure 4 The spectrum shown by Figure 4 It can be seen that with the increase of zinc citrate in the synthesis ratio, the signal peak of Zn element also increases accordingly, indicating that ZnCC is successfully loaded on the surface of hydroxyapatite.

[0044] The nucleating agents A to E prepared in Example 1 were subjected to infrared spectroscopy analysis. The test conditions were as follows: the corresponding nucleating agents were ground with potassium bromide and then tested. The transmission mode was selected and the scanning wave number range was 4000-600 cm -1 , with a resolution of 4cm -1 , the number of scans is 32, and the result is Figure 5 The results shown by Figure 5 It can be seen that the corresponding Zn-O bond can be observed on the surfaces of nucleating agents B, C, and D at 637 cm -1 The absorption peak near the -COO bond is at 1559 cm -1 The absorption peak near 370 nm demonstrated that zinc citrate nanoparticles were successfully loaded on the hydroxyapatite surface.

[0045] The nucleating agents A to E prepared in Example 1 were subjected to X-ray diffraction (XRD) testing. The testing conditions were as follows: a Cu-Kα target was used and the X-ray wavelength was The test voltage and current were 40 kV and 40 mA respectively, the scanning angle range was 5° to 70°, the step size was 0.02°, and the scanning rate was 0.25° / s. Figure 6 The results are shown, where ZnCC represents zinc citrate (nucleating agent A); HAP represents hydroxyapatite (nucleating agent E); ZnCC@HAP-1.0, ZnCC@HAP-1.5, and ZnCC@HAP-2.0 represent nucleating agents B, C, and D, respectively. Figure 6It can be seen that the diffraction peak of ZnCC appears in nucleating agent B, nucleating agent C and nucleating agent D, wherein the absorption peak at 2θ = 12.1 corresponds to the 020 crystal face of ZnCC, and the peak intensity at this position of nucleating agent B, nucleating agent C and nucleating agent D gradually increases with the increase of the feeding ratio, indicating that the amount of zinc citrate grafted on the surface of hydroxyapatite gradually increases.

[0046] The dispersibility of the nucleating agent A to nucleating agent E prepared in Example 1 was detected, and the detection condition was that 0.1 g of the nucleating agent was dissolved in 10 mL of chloroform solution and ultrasonically dispersed for 1 h to obtain the results as shown in Figure 7 Figure 7 It can be seen that the dispersibility of hydroxyapatite in chloroform is poor, and the solution is very turbid, and with the loading of zinc citrate, it can be seen that the solution becomes clear relative to the hydroxyapatite solution, indicating that the dispersibility of the material in chloroform is good, and indicating that the compatibility of polylactic acid and the nucleating agent is improved.

[0047] Example 3

[0048] The present embodiment provides an application effect test experiment of a nucleating agent.

[0049] 10 g of the nucleating agent to be tested was added to 1000 g of polylactic acid (PLA), and the initial solid-phase mixing was carried out, and then the melt mixing granulation was carried out through a double-screw extruder, and after drying, injection molding method was used to form (the mold temperature was 90℃), and the polylactic acid product was obtained, and the product was soaked in water at 95℃ and 110℃ for 30 min, respectively, and was heated in an oven at 60℃, 100℃ and 130℃, respectively, and the morphological difference was recorded to test the stability.

[0050] In the present embodiment, the nucleating agent B to nucleating agent E prepared in Example 1 were respectively used as the nucleating agent to be tested, and the stability of each was detected, and the results as shown in Table 1 were obtained.

[0051] Table 1 Product stability under different test environments

[0052] 95 °C water 110 °C water 60 °C oven 100 °C oven 130 °C oven Nucleating agent B No deformation No deformation No deformation No deformation No deformation Nucleating agent C No deformation No deformation No deformation No deformation No deformation Nucleating agent D No deformation No deformation No deformation No deformation No deformation Nucleating agent E Slight deformation Slight deformation Slight deformation Slight deformation Moderate deformation

[0053] As shown in Table 1, the polylactic acid product prepared by using the nucleating agent B to nucleating agent D prepared by the present application has high stability in extreme environments. After the polylactic acid is added with the nucleating agent, a large number of crystal nuclei of the polylactic acid are induced, and the crystallization rate is accelerated, so that the crystallinity of the material is greatly improved, the amorphous region is reduced, and the movement of the chain is hindered, so that the heat resistance of the material is improved.

[0054] ​While the preferred embodiments of the application have been described, additional variations and modifications can be made to these embodiments by those skilled in the art once they have the benefit of the present disclosure without departing from the spirit and scope of the application. Accordingly, it is intended that the appended claims include all such modifications and variations as fall within the scope of the present application.

[0055] It is apparent that those skilled in the art can make various changes and modifications to the application without departing from the spirit and scope of the application. It is therefore intended that the present application cover all such changes and modifications that are within its scope.

Claims

1. A nucleating agent, characterized in that It is a core-shell structure, in which the core layer is hydroxyapatite and the shell layer is zinc citrate; The particle size of the nucleating agent is 1-2 μm, and the particle size of the zinc citrate is 100-200 nm.

2. A method for preparing a nucleating agent, characterized in that: The following steps are involved: Add the metal chelating agent to the uniform turbid solution of hydroxyapatite and heat it to 70-90°C; Add zinc ion solution, maintain the temperature for 50 to 90 minutes, add alkali solution and react for 20 to 40 minutes; Add citric acid solution and react for 1.5 to 2.5 hours to obtain a crude product; The nucleating agent is obtained after purification.

3. The preparation method according to claim 2, characterized in that The purification comprises the following steps: The crude product is allowed to stand for 10 to 15 hours, centrifuged, and dried to obtain the nucleating agent.

4. The preparation method according to claim 3, characterized in that The centrifugal conditions are: a rotation speed of 6000 to 10000 r / m and a duration of 5 to 10 min; And / or, the drying condition is: vacuum drying at 50-80° C. for 20-30 hours.

5. The preparation method according to claim 2, characterized in that The uniform turbid solution of hydroxyapatite is obtained by uniformly dispersing hydroxyapatite in deionized water by ultrasonication; And / or, the adding of the alkaline solution is done dropwise; And / or, the citric acid solution is added dropwise.

6. The preparation method according to claim 2, characterized in that The molar ratio of the hydroxyapatite, the zinc ion and the citric acid is 1:5-20:10-40; and / or, the mass ratio of the metal chelating agent to the hydroxyapatite is 0.3-0.4:1; and / or, the concentration of the alkaline solution is 1 to 2 mol / L, and the molar ratio of the alkaline solution to the zinc ion is 1:0.2 to 1; And / or, the concentration of the citric acid solution is 1.5 to 2.5 mol / L, and the molar ratio of the citric acid to the zinc ions is 1:0.3 to 0.

7.

7. The preparation method according to claim 2, characterized in that The metal chelating agent is any one of ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriaminepentaacetic acid; And / or, the zinc ion is any one of zinc sulfate solution and zinc nitrate solution; And / or, the alkaline solution is any one of a sodium hydroxide solution and a potassium hydroxide solution.

8. Use of the nucleating agent according to claim 1 or the nucleating agent prepared by the preparation method according to any one of claims 2 to 7 in the preparation of polylactic acid products.

9. The use according to claim 8, characterized in that The nucleating agent is used in combination with a chain extender.

10. The use according to claim 8, characterized in that The polylactic acid product is used in a specific environment; The specific environment is a temperature of 25 to 130° C. and a humidity of 65% to 100%; or the specific environment is a temperature of 25 to 130° C. and soaking in water.

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