A preparation method of polylactic acid mixed with phenylphosphonate

Abstract

The present invention discloses a preparation method of polylactic acid mixed with phenylphosphonate, and relates to the technical field of polylactic acid processing aids. Through S10, spraying phenylphosphonate slurry onto the surface of polylactic acid, setting the temperature to 70-90°C, stirring at low speed for 0.1-1h, and ending the spraying; S20, turning on high-speed stirring, setting the temperature to 100-120°C, mixing and drying for 15-90min; S30, obtaining polylactic acid mixed with phenylphosphonate; spraying the phenylphosphonate slurry onto the surface of polylactic acid by spraying through an atomizing nozzle. The phenylphosphonate nucleating agents involved in the present invention include calcium phenylphosphonate, magnesium phenylphosphonate, zinc phenylphosphonate, and sodium phenylphosphonate. The raw materials are widely available and are added to the matrix polylactic acid without affecting the heat resistance and degradation performance of the material, and the nucleating agent effect is significant. The hydrothermal method and the in-situ mixing method are used in combination. Compared with other hydrothermal methods for preparing polylactic acid nucleating agents, the synthesis time of the nucleating agent is greatly shortened, saving energy.

Description

Technical Field

[0001] The invention relates to the technical field of polylactic acid processing aids, in particular to a preparation method of polylactic acid mixed with phenylphosphonate. Background Art

[0002] Polylactic acid (PLA), a bio-based, fully biodegradable plastic, offers advantages such as abundant raw material resources, excellent material mechanics, and ease of processing and molding. Its production cost and overall performance are superior among fully biodegradable plastics. To reduce white pollution, conserve petroleum resources, and reduce carbon emissions, fully biodegradable plastics are gradually replacing non-biodegradable plastics in disposable items such as cutlery, shopping bags, courier bags, lunch boxes, and straws. In addition to these areas, PLA has the potential to replace non-biodegradable plastics, particularly petroleum-based plastics, in many other applications. However, PLA's slow crystallization rate results in long molding cycles for its products, and its low crystallinity leads to low heat deformation temperatures and poor impact resistance. These drawbacks significantly limit its application.

[0003] During the polylactic acid modification process, adding a small amount of nucleating agent can accelerate the crystallization rate of polylactic acid, which is an effective means to achieve crystallization of polylactic acid at high cooling rates. At present, the industrialized polylactic acid nucleating agents are divided into two categories: organic nucleating agents and inorganic nucleating agents. Organic nucleating agents for polylactic acid include hydrazides, amides, and low molecular weight aliphatic amines. The preparation process of organic nucleating agents is complex and the production cost is high. In particular, the synthesis process involves organic solvents, which have a significant negative impact on the environment. Commonly used inorganic nucleating agents for polylactic acid are generally nucleating agents used in traditional polyolefin materials, including talc, calcium carbonate, silica, and montmorillonite. This type of polylactic acid nucleating agent has a high dosage, is easy to agglomerate, has unsatisfactory effect, and has poor compatibility with polylactic acid, which ultimately affects the mechanical properties of the product.

[0004] As organic-inorganic hybrid substances, organic phosphonates have good compatibility with polylactic acid due to their unique chemical composition, molecular structure, and morphology, and have a significant nucleating effect on polylactic acid. Phenylphosphonates prepared in Chinese patents CN106220889 and CN104877172A have relatively simple preparation processes, minimal environmental pollution, and are effective nucleating agents in polylactic acid. However, these methods suffer from long preparation cycles, time-consuming drying of ultrafine powders, low production efficiency, and easy agglomeration during drying, which affects their nucleating effect in polylactic acid. Summary of the Invention

[0005] In view of the above-mentioned technical problems, the purpose of the present invention is to prepare a polylactic acid nucleating agent of organic phosphonate and its supporting use method. The polylactic acid nucleating agent is an organic phosphonate and exists in the form of slurry. The synthesis of the nucleating agent has the advantages of simple process, short preparation cycle, low pollution, and no need for crushing; the supporting use method is an in-situ mixing method, which makes the nucleating agent easy to disperse in the polylactic acid resin and has significant nucleation effect. Specifically, it includes the following

[0006] S10, spraying the phenylphosphonate slurry onto the surface of the polylactic acid, setting the temperature to 70-90°C, stirring at a low speed for 0.1-1h, and completing the spraying;

[0007] S20, start high-speed stirring, set the temperature to 100-120°C, and mix and dry for 15-90 minutes;

[0008] S30, obtaining polylactic acid blended with phenylphosphonate;

[0009] The phenylphosphonate slurry is sprayed onto the surface of the polylactic acid through an atomizing nozzle.

[0010] The mixing equipment used is a high-speed mixer.

[0011] Specifically, in an ordinary reactor, at normal pressure and temperature below 100°C, the raw materials are stirred and reacted to prepare a nucleating agent slurry, which is then sprayed directly onto the polylactic acid material in a high-speed mixer (generally a mixture of polylactic acid as the main raw material) using an atomizing nozzle. Then, the nucleating agent slurry undergoes hydrothermal action in an environment of 100-120°C to complete the crystal stabilization of the nucleating agent itself, and at the same time, it is fully mixed with the polylactic acid and dried, and finally granulated by screw extrusion.

[0012] This production process, which integrates the preparation, drying, and mixing of polylactic acid nucleating agents, can significantly shorten the preparation cycle and save energy. It also solves a series of problems encountered in the preparation of organic nucleating agents, such as environmental pollution and high costs, equipment requirements for hydrothermal reactions, and long drying cycles, easy agglomeration, difficulty in subsequent crushing, and dust pollution caused by crushing of ultrafine inorganic powder nucleating agents.

[0013] Preferably, the phenylphosphonate slurry accounts for 0.3-1% of the total mass of the polylactic acid.

[0014] Preferably, the atomizing nozzle sprays onto the surface of the polylactic acid through an exhaust port.

[0015] Preferably, the low-speed stirring in S10 is at a stirring speed of 100-300 r / min.

[0016] Preferably, the low-speed stirring in S10 is at a stirring speed of 700-900 r / min.

[0017] Preferably, the preparation of the phenylphosphonate slurry comprises the following:

[0018] S11, adding a suspension or aqueous solution of one or more chloride salts to an aqueous solution of phenylphosphonic acid to obtain a chloride salt phenylphosphonic acid mixed solution;

[0019] S12, stirring the chloride phenylphosphonic acid mixture at a constant temperature to react;

[0020] S13, adjusting the pH value of the chloride phenylphosphonic acid mixed solution to 6-7.

[0021] Preferably, the chloride salt is CaCl2, MgCl2, ZnCl2, or NaCl.

[0022] Preferably, the mass ratio of the chloride salt to the phenylphosphonic acid aqueous solution is 0.5:1 to 1:5.

[0023] Preferably, the reaction conditions of S12 are: temperature 30-90° C., time 2-10 h, and stirring speed 100-300 r / min.

[0024] Preferably, the pH value of the chloride salt-phenylphosphonic acid mixture is adjusted by adjusting the dosage ratio of the chloride salt and the aqueous solution of the phenylphosphonic acid.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The phenylphosphonate nucleating agents involved in the present invention include calcium phenylphosphonate, magnesium phenylphosphonate, zinc phenylphosphonate, and sodium phenylphosphonate. The raw materials are widely available and adding them to the matrix polylactic acid does not affect the heat resistance and degradation properties of the material. The nucleating agent effect is significant.

[0027] (2) The combined use of the hydrothermal method and the in-situ mixing method significantly shortens the synthesis time of the nucleating agent compared to other hydrothermal methods for preparing polylactic acid nucleating agents, saving energy. Generally, when preparing phenylphosphonate nucleating agents by the hydrothermal method, it is necessary to continuously stir at 100-150°C for 24-72 hours in a specific pressure-resistant reactor to obtain nucleating agent crystals with stable performance. In the present invention, the hydrothermal reaction occurs in a high-speed mixer: at 100-120°C, the water evaporates within 15-90 minutes, and the nucleating agent crystals themselves also reach a stable state. In addition, this combined method eliminates the powder dehydration-drying-particle agglomeration and subsequent refinement and crushing process and the corresponding equipment investment, significantly reducing production costs and saving energy. At the same time, it avoids the generation of a large amount of dust pollution during the centralized drying and crushing process of the nucleating agent powder, avoids the risk of dust explosion, and improves production safety.

[0028] (3) Compared with the traditional drying method, the in-situ mixing method of the present invention uses an atomizing nozzle to spray the nucleating agent slurry directly onto the substrate polylactic acid particles. The operation is simple. Under the stirring of the high-speed mixer, the polylactic acid particles have a large specific surface area. The nucleating agent slurry quickly forms a liquid layer with a thickness of less than 200 μm on the surface of the polylactic acid particles. Under the conditions of 100-120°C, the water in the thin layer evaporates and leaves the surface of the polylactic acid particles, leaving a thinner nucleating agent powder layer. Under the condition of rapid loss of water, not only will the nucleating agent coated on the surface of the polylactic acid particles not agglomerate, but the polylactic acid will not decompose and affect the mechanical properties of the material. The nucleating agent powder on the surface of the polylactic acid also plays a role in preventing the particles from softening and sticking under the environment of 100-120°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The DSC curves of the examples, blank samples, comparative examples, example 2, example 7, example 8, example 9, and example 10 were cooled at 20°C / min. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Below by specific embodiment, the present invention is further described, but protection scope of the present invention is not limited to following specific embodiment.It is CaCl that phenylphosphonate nucleating agent of the present invention comprises calcium phenylphosphonate, magnesium phenylphosphonate, zinc phenylphosphonate, phenylphosphine material , MgCl , ZnCl and one or more in the NaCl and phenylphosphonic acid.Above-mentioned phenylphosphonate nucleating agent all has the nucleation effect that accelerates polylactic acid crystallization in polylactic acid, therefore only with CaCl , MgCl , ZnCl Be that the phenylphosphonate slurries of raw material preparation add in the polylactic acid for embodiment to illustrate, but CaCl , MgCl , ZnCl With the mixture of any proportion between the NaCl be that raw material is still protected acid sodium of the present invention or their mixture, in original scope.

[0032] The polylactic acid material selected in this embodiment is the FY 601 polylactic acid product produced by Anhui Fengyuan Futailai Polylactic Acid Co., Ltd., with a melting point of 175°C, a glass transition temperature of 60°C, and a melt index of 9g / 10min. The reaction equipment used is a laboratory digital display constant temperature oil bath, the spray nozzle is a commercially available ordinary adjustable flow nozzle with 4 sizes, a working pressure of 1.5kg-3kg, and a nozzle diameter of 0.5mm-1mm. The extrusion equipment is a Berstorff ZE25A twin-screw extruder, the mixing equipment is a high-speed mixer SHR-50A from Zhangjiagang Tongsha Plastic Machinery Co., Ltd., the drying equipment is an electric constant temperature hot blast drying oven DHG-9923A from Shanghai Jinghong Experimental Equipment Co., Ltd., and the testing equipment is a TA differential scanning calorimeter Q2000 from the United States. Other raw materials are all commercially available.

[0033] Comparative Example

[0034] (1) Preparation of calcium phenylphosphonate slurry

[0035] Weigh 0.63 kg of CaCl₂ and add it to 1.0 L of deionized water. Weigh 0.90 kg of phenylphosphonic acid and dissolve it in 2 L of deionized water. Add the CaCl₂ solution to the phenylphosphonic acid aqueous solution, heat to 60-65°C, and stir at a constant temperature of 200 rpm for 5 hours. The resulting calcium phenylphosphonate slurry is centrifuged and dehydrated, then dried at 120°C to obtain calcium phenylphosphonate powder. The calcium phenylphosphonate powder is then pulverized in a jet mill to obtain ultrafine calcium phenylphosphonate powder.

[0036] (2) Calcium phenylphosphonate is mixed with polylactic acid, and calcium phenylphosphonate accounts for 0.5% of the total weight of the formula

[0037] 0.05 kg of ultrafine calcium phenylphosphonate powder and 10 kg of polylactic acid were added to a high-speed mixer. After high-speed mixing at room temperature for 30 minutes, the mixed materials were extruded into granules in a twin-screw extruder at an extrusion temperature of 170-190° C. and an extrusion screw speed of 250 rpm.

[0038] Example 1:

[0039] (1) Preparation of calcium phenylphosphonate slurry

[0040] Weigh 0.63 kg of CaCl₂ and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the CaCl₂ solution to the aqueous phenylphosphonic acid solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a calcium phenylphosphonate slurry.

[0041] (2) Calcium phenylphosphonate is mixed with polylactic acid in situ, and calcium phenylphosphonate accounts for 0.3% of the total weight of the formula

[0042] 68g of calcium phenylphosphonate slurry was weighed and added to a liquid tank. 10kg of polylactic acid was added to a high-speed mixer. An atomizing nozzle was aligned with the vent on the high-speed mixer. The high-speed mixing dryer was turned on at a low speed and set at 80°C for spraying. After a spraying time of 10 min, the high-speed mixing dryer was turned on at a high speed and set at 110°C for drying for 30 min. The evenly mixed material was extruded and granulated in a twin-screw extruder at an extrusion temperature of 170-190°C and an extrusion screw speed of 250 rpm.

[0043] Example 2:

[0044] (1) Preparation of calcium phenylphosphonate slurry

[0045] Weigh 0.63 kg of CaCl₂ and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the CaCl₂ solution to the aqueous phenylphosphonic acid solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a calcium phenylphosphonate slurry.

[0046] (2) Calcium phenylphosphonate is mixed with polylactic acid in situ, and calcium phenylphosphonate accounts for 0.5% of the total weight of the formula

[0047] 113g of calcium phenylphosphonate slurry was weighed and added to a liquid tank. 10kg of polylactic acid was added to a high-speed mixer. An atomizing nozzle was aligned with the vent on the high-speed mixer, and the high-speed mixing dryer was turned on at a low speed and set at 80°C for spraying. After a spraying time of 10 minutes, the high-speed mixing dryer was turned on at a high speed and set at 110°C for drying for 30 minutes. The evenly mixed material was extruded and granulated in a twin-screw extruder at an extrusion temperature of 170-190°C and an extrusion screw speed of 250rpm.

[0048] Example 3:

[0049] (1) Preparation of calcium phenylphosphonate slurry

[0050] Weigh 0.63 kg of CaCl₂ and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the CaCl₂ solution to the aqueous phenylphosphonic acid solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a calcium phenylphosphonate slurry.

[0051] (2) Calcium phenylphosphonate is mixed with polylactic acid in situ, and calcium phenylphosphonate accounts for 1.0% of the total weight of the formula

[0052] 226g of calcium phenylphosphonate slurry was weighed and added to a liquid tank. 10kg of polylactic acid was added to a high-speed mixer. An atomizing nozzle was aligned with the vent on the high-speed mixer. The high-speed mixing dryer was switched on at a low speed and set at 80°C for spraying. After a spraying time of 10 min, the high-speed mixing dryer was switched on at a high speed and set at 110°C for drying for 30 min. The evenly mixed material was extruded and granulated in a twin-screw extruder at a temperature of 170-190°C and a screw speed of 250 rpm.

[0053] Example 4:

[0054] (1) Preparation of calcium phenylphosphonate slurry

[0055] Weigh 0.63 kg of CaCl₂ and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the CaCl₂ solution to the aqueous phenylphosphonic acid solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a calcium phenylphosphonate slurry.

[0056] (2) Calcium phenylphosphonate is mixed with polylactic acid in situ, and calcium phenylphosphonate accounts for 0.5% of the total weight of the formula

[0057] 113g of calcium phenylphosphonate slurry was weighed and added to a liquid tank. 10kg of polylactic acid was added to a high-speed mixer. An atomizing nozzle was aligned with the vent on the high-speed mixer, and the high-speed mixing dryer was turned on at a low speed and set at 70°C for spraying. After a spraying time of 10 minutes, the high-speed mixing dryer was turned on at a high speed and set at 110°C for drying for 30 minutes. The evenly mixed material was extruded and granulated in a twin-screw extruder at an extrusion temperature of 170-190°C and an extrusion screw speed of 250rpm.

[0058] Example 5:

[0059] (1) Preparation of calcium phenylphosphonate slurry

[0060] Weigh 0.63 kg of CaCl₂ and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the CaCl₂ solution to the aqueous phenylphosphonic acid solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a calcium phenylphosphonate slurry.

[0061] (2) Calcium phenylphosphonate is mixed with polylactic acid in situ, and calcium phenylphosphonate accounts for 0.5% of the total weight of the formula

[0062] 113g of calcium phenylphosphonate slurry was weighed and added to a liquid tank. 10kg of polylactic acid was added to a high-speed mixer. An atomizing nozzle was aligned with the vent on the high-speed mixer, and the high-speed mixing dryer was turned on at a low speed and a setting temperature of 90°C. The mixture was sprayed for 10 minutes. The high-speed mixing dryer was turned on at a high speed and a setting temperature of 110°C. The mixture was dried for 30 minutes. The mixed material was then extruded and granulated in a twin-screw extruder at an extrusion temperature of 170-190°C and a screw speed of 250rpm.

[0063] Example 6:

[0064] (1) Preparation of calcium phenylphosphonate slurry

[0065] Weigh 0.63 kg of CaCl₂ and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the CaCl₂ solution to the aqueous phenylphosphonic acid solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a calcium phenylphosphonate slurry.

[0066] (2) Calcium phenylphosphonate is mixed with polylactic acid in situ, and calcium phenylphosphonate accounts for 0.5% of the total weight of the formula

[0067] 113g of calcium phenylphosphonate slurry was weighed and added to a liquid tank. 10kg of polylactic acid was added to a high-speed mixer. An atomizing nozzle was aligned with the vent on the high-speed mixer, and the high-speed mixing dryer was turned on at a low speed and set at 80°C for spraying. After a spraying time of 10 minutes, the high-speed mixing dryer was turned on at a high speed and set at 100°C for drying for 30 minutes. The evenly mixed material was extruded and granulated in a twin-screw extruder at an extrusion temperature of 170-190°C and an extrusion screw speed of 250rpm.

[0068] Example 7:

[0069] (1) Preparation of calcium phenylphosphonate slurry

[0070] Weigh CaCl2 and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the CaCl2 solution to the aqueous phenylphosphonic acid solution. Heat to 60-65°C and stir at 200 rpm for 5 hours to obtain a calcium phenylphosphonate slurry.

[0071] (2) Calcium phenylphosphonate is mixed with polylactic acid in situ, and calcium phenylphosphonate accounts for 0.5% of the total weight of the formula

[0072] 113g of calcium phenylphosphonate slurry was weighed and added to a liquid tank. 10kg of polylactic acid was added to a high-speed mixer. An atomizing nozzle was aligned with the vent on the high-speed mixer, and the high-speed mixing dryer was turned on at a low speed and set at 80°C for spraying. After a spraying time of 10 minutes, the high-speed mixing dryer was turned on at a high speed and set at 120°C for drying for 30 minutes. The evenly mixed material was extruded and granulated in a twin-screw extruder at an extrusion temperature of 170-190°C and an extrusion screw speed of 250rpm.

[0073] Example 8:

[0074] (1) Preparation of magnesium phenylphosphonate slurry

[0075] Weigh 0.81 kg of MgCl₂ and add it to 1.0 L of deionized water. Dissolve 1.35 kg of phenylphosphonic acid in 2 L of deionized water. Add the MgCl₂ solution to the aqueous phenylphosphonic acid solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a magnesium phenylphosphonate slurry.

[0076] (2) Magnesium phenylphosphonate is mixed with the formula poly in situ, and magnesium phenylphosphonate accounts for 0.5% of the total weight of the formula

[0077] Weigh 99g of magnesium phenylphosphonate slurry and add it to a liquid tank. Add 10kg of polylactic acid to a high-speed mixing dryer. Align the atomizing nozzle with the exhaust hole on the high-speed mixer. Turn on the low speed gear of the high-speed mixing dryer and set the temperature to 80°C. Then spray. After the spraying time is 10 minutes, turn on the high speed gear of the high-speed mixing dryer and set the temperature to 110°C. Dry for 30 minutes. The mixed material is extruded and granulated in a twin-screw extruder at an extrusion temperature of 170-190°C and an extrusion screw speed of 250rpm.

[0078] Example 9:

[0079] (1) Preparation of zinc phenylphosphonate slurry

[0080] Weigh 0.65 kg of ZnCl2 and add it to 1.0 L of deionized water. Dissolve 0.75 kg of phenylphosphonic acid in 2 L of deionized water. Add the ZnCl2 suspension to the phenylphosphonic acid aqueous solution. Heat to 60-65°C and stir at 200 rpm for 5 hours to obtain a zinc phenylphosphonate slurry.

[0081] (2) Zinc phenylphosphonate is mixed with the formulated polylactic acid in situ, and the zinc phenylphosphonate accounts for 0.5% of the total mass of the formulation

[0082] 136g of zinc phenylphosphonate slurry was added to a liquid tank, and 10kg of polylactic acid was added to a high-speed mixer. The atomizing nozzle was aligned with the exhaust hole on the high-speed mixer, and the high-speed mixer dryer was turned on the low speed gear and set to 80°C for spraying. After the spraying time was completed for 10 minutes, the high-speed mixer dryer was turned on the high speed gear and set to 110°C for drying for 30 minutes. The homogeneously mixed material was extruded into pellets in a twin-screw extruder at an extrusion temperature of 170-190°C and a screw speed of 250 rpm.

[0083] Example 10:

[0084] (1) Preparation of sodium phenylphosphonate slurry

[0085] Weigh 0.33 kg of NaCl and add it to 1.0 L of deionized water. Dissolve 0.90 kg of phenylphosphonic acid in 2 L of deionized water. Add the NaCl solution to the phenylphosphonic acid aqueous solution, heat to 60-65°C, and stir at 200 rpm for 5 hours to obtain a sodium phenylphosphonate slurry.

[0086] (2) Sodium phenylphosphonate slurry is mixed with polylactic acid in situ, and sodium phenylphosphonate accounts for 0.5% of the total mass of the formula

[0087] Add 120g of sodium phenylphosphonate slurry to a liquid tank and 10kg of polylactic acid to a high-speed mixer. Align the atomizing nozzle with the exhaust port on the high-speed mixer and turn on the low speed gear of the high-speed mixer dryer, set the temperature to 80°C, and spray. After spraying for 10 minutes, turn on the high speed gear of the high-speed mixer dryer and set the temperature to 110°C. Dry for 30 minutes. Extrude the mixed material into pellets in a twin-screw extruder at an extrusion temperature of 170-190°C and a screw speed of 250rpm.

[0088] Example Characterization Test

[0089] The polylactic acid pellets uniformly mixed in the high-speed mixing dryer were pelletized by a twin-screw extruder. The extrusion temperature was set at 170-190°C and the extrusion screw speed was 250 rpm. The extruded material strips were cooled in a water trough and cut into pellets by a pelletizer. The polylactic acid pellets Examples 1-4 and the comparative example were dried in a hot air dehumidification dryer at 80°C for 5 hours and then used for subsequent testing.

[0090] Table 1 shows the melt index test results of the blank sample (unprocessed polylactic acid), the comparative example and Example 2. The test results show that, compared with the blank sample, the melt index of the polylactic acid modified material of the comparative example and Example 2 increases slightly, which is due to the degradation caused by the heat resistance of polylactic acid processing. The melt index of Example 2 and the comparative example is basically the same, indicating that the in-situ mixing method of directly spraying the slurry on the material and using a high-speed mixer to dry the material does not cause serious degradation of the material due to the high water content in the slurry. The main reason is that the slurry is sprayed on the surface of the material to form a very thin liquid film under the stirring action of the high-speed mixer. When the temperature is at or above the boiling point of water, the water in the slurry film will evaporate rapidly and detach from the surface of the polylactic acid particles, and the polylactic acid cannot be hydrolyzed. Therefore, the in-situ mixing method will not affect the performance of the polylactic acid.

[0091] Table 1 Example 1, comparative example and polylactic acid melt index test results.

[0092]

[0093] The polylactic acid pellets of Examples 1 to 10 and the comparative example were subjected to DSC testing, and the test steps and parameters were as follows:

[0094] The non-isothermal crystallization properties of polylactic acid composites were tested using a differential scanning calorimeter: under a nitrogen atmosphere, the sample was heated to 200°C at a constant rate of 20°C / min and kept warm for 5 minutes to eliminate the thermal history; then the temperature was cooled from 200°C to 30°C at a constant rate of 20°C / min; and then the temperature was heated from 30°C to 200°C at a constant rate of 20°C / min.

[0095] Figure 1 The non-isothermal DSC cooling curves of the polylactic acid blank sample, comparative example, example 2, example 7, example 8, example 9 and example 10 polylactic acid modified materials with different phenylphosphonates added are given. Table 2 shows the non-isothermal crystallization test results of polylactic acid, comparative example and examples 1 to 10 polylactic acid modified materials with different phenylphosphonates added. The larger the crystallization peak temperature, melting enthalpy and crystallinity, the faster the sample crystallization rate, the higher the crystallinity, and the better the effect of the added nucleating agent. From the DSC test results, it was found that under the test conditions, polylactic acid basically had no crystallization peak and low crystallinity, and the crystallization ability of polylactic acid was poor. However, after adding the phenylphosphonate nucleating agent prepared by the present invention, the crystallization rate of polylactic acid was significantly improved. The test results of the comparative example and example 2 show that the combined use of the hydrothermal method and the in-situ mixing method proposed in the present invention is practical.

[0096] Table 2 Non-isothermal crystallization performance test results of the embodiment, blank sample and comparative example.

[0097]

[0098]

[0099] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing polylactic acid blended with phenylphosphonate, characterized in that: These include: S10, spraying the phenylphosphonate slurry onto the surface of the polylactic acid, setting the temperature to 70-90°C, stirring at a low speed for 0.1-1h, and completing the spraying; S20, start high-speed stirring, set the temperature to 100~120℃, and mix and dry for 15min~90min; S30, obtaining polylactic acid blended with phenylphosphonate; The phenylphosphonate slurry is sprayed onto the surface of the polylactic acid through an atomizing nozzle; The phenylphosphonate slurry accounts for 0.5-1% of the total mass of the polylactic acid; The preparation of the phenylphosphonate slurry includes the following: S11, adding a suspension or aqueous solution of one or more chloride salts to an aqueous solution of phenylphosphonic acid to obtain a chloride salt phenylphosphonic acid mixed solution; S12, stirring the chloride phenylphosphonic acid mixture at a constant temperature to react; S13, adjusting the pH value of the chloride phenylphosphonic acid mixture to 6-7; The reaction conditions of S12 are temperature 30-90° C. and time 2-10 h.

2. The method for preparing polylactic acid blended with phenylphosphonate according to claim 1, wherein: The atomizing nozzle sprays onto the surface of the polylactic acid through the exhaust port.

3. The method for preparing polylactic acid blended with phenylphosphonate according to claim 1, wherein: The low-speed stirring in S10 has a stirring speed of 100-300 r / min.

4. The method for preparing polylactic acid blended with phenylphosphonate according to claim 1, wherein: The low-speed stirring in S10 has a stirring speed of 700-900 r / min.

5. The method for preparing polylactic acid blended with phenylphosphonate according to claim 1, wherein: The chloride salts are CaCl2, MgCl2, ZnCl2, and NaCl.

6. The method for preparing polylactic acid blended with phenylphosphonate according to claim 1, wherein: The mass ratio of the chloride salt to the phenylphosphonic acid aqueous solution is 0.5:1 to 1:

5.

7. The method for preparing polylactic acid blended with phenylphosphonate according to claim 1, wherein: The pH value of the chloride salt-phenylphosphonic acid mixed solution is adjusted by adjusting the dosage ratio of the chloride salt and the aqueous solution of phenylphosphonic acid.

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