High-barrier polylactic acid packaging material and method for preparing the same
By optimizing the composition and preparation process of polylactic acid (PLA) materials, the compatibility and barrier properties of PLA materials in the food packaging field have been solved, resulting in PLA packaging materials with high barrier properties, high toughness, and transparency, suitable for high-temperature scenarios in food packaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WEIFANG ENG VOCATIONAL COLLEGE
- Filing Date
- 2026-04-22
- Publication Date
- 2026-06-23
Smart Images
Figure SMS_6
Abstract
Description
Technical Field
[0001] This invention discloses a high-barrier polylactic acid packaging material and its preparation method, belonging to the field of organic polymer materials technology. Background Technology
[0002] Polylactic acid (PLA), a biodegradable material derived from renewable plant resources, can be completely degraded into carbon dioxide and water by microorganisms in the natural environment after use, with low energy consumption and minimal pollution during its production process. Due to its excellent transparency, renewability, and food safety, its application in food packaging is increasingly widespread, and it is expected to become one of the core materials replacing traditional petroleum-based plastics. However, PLA's high molecular chain rigidity and slow crystallization rate result in high brittleness, which is detrimental to transportation and transshipment. The heat distortion temperature of PLA materials is typically below 60°C, making it difficult to meet the requirements of high-temperature scenarios such as hot beverage filling and microwave heating, severely limiting its large-scale application in food packaging. Furthermore, PLA has poor barrier properties against oxygen and water vapor; oxygen penetration accelerates food oxidation and spoilage, while moisture ingress causes dry foods to become damp, affecting their shelf life.
[0003] Prior art with publication number CN120118494A discloses a high-temperature resistant, high-toughness, controllable degradable polylactic acid material, the raw materials comprising, by mass percentage: 40% 60% polylactic acid, 10% 20% polylactic acid Polyurethane block copolymer, 20% 40% active talc and 1% The addition of 5% additives improves the heat resistance of the material, but its barrier properties are poor. Prior art, disclosed in CN103540111B, discloses a high-strength, high-temperature resistant, fully degradable polylactic acid (PLA) sheet and its preparation method. The sheet is prepared by combining 50%-78% PLA, 10%-30% toughening components, 10%-30% inorganic fillers, and 1%-3% other additives. The inorganic fillers consist of glass fiber, talc, wollastonite, and mica powder. However, the inorganic fillers have poor compatibility with the PLA matrix and are prone to agglomeration, leading to increased material haze.
[0004] In summary, existing polylactic acid (PLA) materials suffer from poor material compatibility and weak barrier properties. Therefore, developing a PLA material that simultaneously possesses high barrier properties, high toughness, and good transparency has become a pressing technical challenge in this field. Summary of the Invention
[0005] In order to solve the above-mentioned problems in the prior art, the present invention provides a high-barrier polylactic acid packaging material and its preparation method, and achieves the following objectives: to prepare a polylactic acid packaging material with strong barrier ability, good toughness and good transparency.
[0006] To achieve the above objectives, the following technical solution is adopted: A high-barrier polylactic acid packaging material, the raw materials comprising, by weight: 60-78 parts PLLA particles, 12-19.5 parts PDLA particles, 7-12 parts polycaprolactone, 4-8 parts lactic acid-lactide oligomer, 11-15 parts polylactic acid modified functional masterbatch, and 0.6-1 parts anti-hydrolysis agent.
[0007] The lactic acid-lactide oligomer comprises, by weight, 44-50 parts of L-lactic acid, 90-115 parts of D,L-lactide, and 0.1-0.3 parts of titanium-zinc catalyst.
[0008] The polylactic acid modified functional masterbatch comprises, by weight, 12-15 parts of zinc borate with low water content, 0.5-1 part of silane coupling agent, 10-15 parts of anhydrous ethanol, 22-28 parts of lactic acid oligomer, and 12-20 parts of ethylene-vinyl alcohol copolymer (EVOH).
[0009] The zinc borate with low water content is zinc borate with 3,5 water content, and its chemical formula is 2ZnO·3B2O3·3.5H2O.
[0010] The lactic acid oligomer is an L-lactic acid oligomer with a molecular weight of 2000~4000.
[0011] The ethylene-vinyl alcohol copolymer has an ethylene content of 30-32%.
[0012] The anti-hydrolysis agent is polycarbodiimide with a degree of polymerization of 2500-3000.
[0013] The polycaprolactone has a number-average molecular weight range of 80,000 to 120,000 and a water content of <0.05%.
[0014] The PLLA particles: The number average molecular weight of PLLA ranges from 150,000 to 200,000, and the water content is <0.05%.
[0015] The PDLA particles have a number-average molecular weight range of 120,000 to 180,000 and a water content of <0.05%.
[0016] The silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.
[0017] The titanium-zinc catalyst is obtained by compounding tetrabutyl titanate and zinc lactate, with a mass ratio of tetrabutyl titanate to zinc lactate of 1:(2~3).
[0018] A method for preparing a high-barrier polylactic acid packaging material includes the following steps: Step 1: Preparation of lactic acid-lactide oligomers L-lactic acid, D,L-lactide, and a titanium-zinc catalyst were added to a reactor, and nitrogen gas was introduced for protection. The temperature was raised to 145-160°C, and the reaction was stirred for 4-5 hours. The nitrogen gas was then stopped, and the reactor was evacuated to a pressure < -0.08 MPa. The reaction was carried out under reduced pressure for 2-3 hours. After the reaction was completed, the product was discharged while hot, cooled, and granulated to obtain a lactic acid-lactide oligomer with a number average molecular weight of 3000.
[0019] Step 2: Preparation of polylactic acid modified functional masterbatch A silane coupling agent is mixed evenly with anhydrous ethanol to obtain a silane coupling agent solution. Zinc borate with low water content is dried in a 100℃ oven for 4-6 hours to remove surface adsorbed water. After natural cooling, it is added to a high-speed mixer and stirred. The silane coupling agent solution is sprayed onto the zinc borate with low water content through the top of the mixer. The mixture is stirred at 300-550 r / min for 1.5-2 hours, then heated to 85-90℃ and stirred for another 0.5-1 hour to evaporate excess ethanol. The material is discharged after cooling to room temperature. After discharge, the material is pulverized and passed through a 2000-mesh sieve to obtain modified zinc borate with low water content.
[0020] Modified low-water zinc borate, lactic acid oligomer, and EVOH are added to a mixer. The mixer speed is controlled at 90~140 r / min, and the mixture is mixed at 180~190℃ for 8~20 min. The mixture is then extruded and granulated to obtain polylactic acid modified functional masterbatch.
[0021] Step 3: Mixing and extrusion PLLA granules, PDLA granules, polycaprolactone, lactic acid-lactide oligomer, anti-hydrolysis agent, and polylactic acid modified functional masterbatch are added to a mixer and premixed at 76-88℃ for 20-60 minutes to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion to obtain high-barrier polylactic acid packaging material. The temperature control of the twin-screw extruder during melt extrusion is as follows: feed section 150-160℃, melt section 180-195℃, and die head section 170-190℃.
[0022] The beneficial effects of this invention are as follows: 1. The high-barrier polylactic acid packaging material prepared by this invention has an oxygen permeability of 1.22~1.75 cm. 3 / (m 2 (24h), water vapor transmission rate is 0.88~1.16 g / (m²). 2(24h) It exhibits excellent barrier properties against water and oxygen; the polylactic acid modified functional masterbatch contains modified low-water zinc borate, which itself has good heat resistance and transparency. After surface modification with a silane coupling agent, the interfacial bonding force with the PLA matrix is enhanced, which can improve heat resistance through physical barrier effect while maintaining the transparency of the material. The modified low-water zinc borate, after dispersion, can prolong the penetration path of water and gas molecules in polylactic acid materials, and synergistically enhance the barrier properties of the material with EVOH.
[0023] 2. The high-barrier polylactic acid packaging material prepared by this invention has a heat distortion temperature of 109~118℃, a haze of 5.1~6.4%, and a cantilever beam impact strength of 10.5~11.7kJ / m². 2 It is said to possess high transparency, high toughness, and excellent high-temperature resistance. Lactic acid-lactide oligomers have a structure similar to PLA and good compatibility. Adding lactic acid-lactide oligomers to polylactic acid helps induce PLLA and PDLA to form SC crystals, improving material strength and heat resistance; the addition of anti-hydrolysis agents can inhibit hydrolytic degradation and prevent material performance degradation at high temperatures. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.
[0025] Example 1: A high-barrier polylactic acid packaging material A high-barrier polylactic acid packaging material, the raw materials comprising, by weight: 65 parts PLLA particles, 15 parts PDLA particles, 10 parts polycaprolactone, 4 parts lactic acid-lactide oligomer, 11 parts polylactic acid modified functional masterbatch, and 0.6 parts anti-hydrolysis agent.
[0026] The lactic acid-lactide oligomer comprises, by weight, 44 parts of L-lactic acid, 90 parts of D,L-lactide, and 0.1 parts of titanium-zinc catalyst.
[0027] The polylactic acid modified functional masterbatch comprises, by weight, 15 parts of zinc borate with low water content, 0.5 parts of silane coupling agent KH-550, 10 parts of anhydrous ethanol, 30 parts of lactic acid oligomer, and 15 parts of ethylene-vinyl alcohol copolymer (EVOH).
[0028] A method for preparing a high-barrier polylactic acid packaging material includes the following steps: Step 1: Preparation of lactic acid-lactide oligomers L-lactic acid, D,L-lactide, and a titanium-zinc catalyst were added to a reactor, protected by nitrogen gas, and the temperature was raised to 150°C. The reactor was stirred for 5 hours. The reactor was then evacuated to a pressure < -0.08 MPa and the reaction was carried out under reduced pressure for 2 hours. After the reaction was completed, the product was discharged while hot, cooled, and granulated to obtain a lactic acid-lactide oligomer with a number average molecular weight of 2000.
[0029] Step 2: Preparation of polylactic acid modified functional masterbatch A solution of silane coupling agent was prepared by dropwise addition to anhydrous ethanol and thorough mixing. Zinc borate with low water content was dried in a 100℃ oven for 4-6 hours to remove surface adsorbed water. After natural cooling, it was added to a high-speed mixer and stirred. The solution was sprayed through the top of the mixer, and the mixture was stirred at 300-550 rpm for 1.5 hours. The temperature was then raised to 85℃ and stirring continued for 1 hour to evaporate excess ethanol. After the material in the system cooled to room temperature, it was discharged, pulverized, and passed through a 2000-mesh sieve to obtain modified zinc borate with low water content. Modified zinc borate with low water content, lactic acid oligomer, and EVOH were added to a Banbury mixer. The Banbury mixer speed was controlled at 100 rpm, and the mixture was stirred at 180℃ for 20 minutes. The mixture was then extruded and granulated to obtain polylactic acid modified functional masterbatch.
[0030] The silane coupling agent used in this step is γ-aminopropyltriethoxysilane.
[0031] Step 3: Mixing and extrusion PLLA granules, PDLA granules, polycaprolactone, lactic acid-lactide oligomer, anti-hydrolysis agent, and polylactic acid modified functional masterbatch were added to a mixer and premixed at 80°C for 30 minutes. The mixture was then melt-extruded into a twin-screw extruder to obtain high-barrier polylactic acid packaging material. The temperature control of the twin-screw extruder during melt extrusion was as follows: feed section 150°C, melt section 190°C, and die head section 180°C.
[0032] Example 2: A high-barrier polylactic acid packaging material A high-barrier polylactic acid packaging material, the raw materials comprising, by weight: 70 parts PLLA particles, 18 parts PDLA particles, 10 parts polycaprolactone, 6 parts lactic acid-lactide oligomer, 12 parts polylactic acid modified functional masterbatch, and 0.6 parts anti-hydrolysis agent.
[0033] The lactic acid-lactide oligomer comprises, by weight, 48 parts of L-lactic acid, 100 parts of D,L-lactide, and 0.24 parts of titanium-zinc catalyst.
[0034] The polylactic acid modified functional masterbatch comprises, by weight, 12 parts of zinc borate with low water content, 0.5 parts of silane coupling agent, 10 parts of anhydrous ethanol, 35 parts of lactic acid oligomer, and 20 parts of ethylene-vinyl alcohol copolymer (EVOH).
[0035] A method for preparing a high-barrier polylactic acid packaging material includes the following steps: Step 1: Preparation of lactic acid-lactide oligomers L-lactic acid, D,L-lactide, and a titanium-zinc catalyst were added to a reactor, protected by nitrogen gas, and the temperature was raised to 145°C. The reactor was stirred for 5 hours. The reactor was then evacuated to a pressure < -0.08 MPa and the reaction was carried out under reduced pressure for 3 hours. After the reaction was completed, the product was discharged while hot, cooled, and granulated to obtain a lactic acid-lactide oligomer with a number average molecular weight of 4000.
[0036] Step 2: Preparation of polylactic acid modified functional masterbatch A solution of silane coupling agent was prepared by dropwise addition to anhydrous ethanol and thorough mixing. Zinc borate with low water content was dried in a 100℃ oven for 4-6 hours to remove surface adsorbed water. After natural cooling, it was added to a high-speed mixer and stirred. The solution was sprayed through the top of the mixer, and the mixture was stirred at 300-550 rpm for 1.5 hours. The temperature was then raised to 90℃ and stirring continued for 0.5 hours to evaporate excess ethanol. After the material in the system cooled to room temperature, it was discharged, pulverized, and passed through a 2000-mesh sieve to obtain modified zinc borate with low water content. Modified zinc borate with low water content, lactic acid oligomer, and EVOH were added to a Banbury mixer. The Banbury mixer speed was controlled at 140 rpm, and the mixture was stirred at 190℃ for 8 minutes. The mixture was then extruded and granulated to obtain polylactic acid modified functional masterbatch.
[0037] The silane coupling agent used in this step is γ-glycidoxypropyltrimethoxysilane.
[0038] Step 3: Mixing and extrusion PLLA granules, PDLA granules, polycaprolactone, lactic acid-lactide oligomer, anti-hydrolysis agent, and polylactic acid modified functional masterbatch were added to a mixer and premixed at 88°C for 20 minutes. The mixture was then melt-extruded into a twin-screw extruder to obtain high-barrier polylactic acid packaging material. The temperature control of the twin-screw extruder during melt extrusion was as follows: feed section 150°C, melt section 190°C, and die head section 170°C.
[0039] Example 3: A high-barrier polylactic acid packaging material A high-barrier polylactic acid packaging material, the raw materials comprising, by weight: 78 parts PLLA particles, 19.5 parts PDLA particles, 12 parts polycaprolactone, 8 parts lactic acid-lactide oligomer, 15 parts polylactic acid modified functional masterbatch, and 1 part anti-hydrolysis agent.
[0040] The lactic acid-lactide oligomer comprises, by weight, 50 parts of L-lactic acid, 110 parts of D,L-lactide, and 0.18 parts of titanium-zinc catalyst.
[0041] The polylactic acid modified functional masterbatch comprises, by weight, 15 parts of zinc borate with low water content, 1 part of silane coupling agent, 15 parts of anhydrous ethanol, 28 parts of lactic acid oligomer, and 12 parts of ethylene-vinyl alcohol copolymer.
[0042] A method for preparing a high-barrier polylactic acid packaging material includes the following steps: Step 1: Preparation of lactic acid-lactide oligomers L-lactic acid, D,L-lactide, and a titanium-zinc catalyst were added to a reactor, and nitrogen gas was introduced for protection. The temperature was raised to 160°C, and the reaction was stirred for 4 hours. The reactor was then evacuated to a pressure < -0.08 MPa, and the reaction was carried out under reduced pressure for 3 hours. After the reaction was completed, the product was discharged while hot, cooled, and granulated to obtain a lactic acid-lactide oligomer with a number average molecular weight of 3000.
[0043] Step 2: Preparation of polylactic acid modified functional masterbatch A solution was prepared by adding silane coupling agent dropwise to anhydrous ethanol and mixing thoroughly. Zinc borate with low water content was dried in a 100℃ oven for 4-6 hours to remove surface adsorbed water. After natural cooling, it was added to a high-speed mixer and stirred. The solution was sprayed through the top of the mixer, and the mixture was stirred at 300 rpm for 1.5 hours. The temperature was then raised to 85℃ and stirring continued for 1 hour to evaporate excess ethanol. After the material in the system cooled to room temperature, it was discharged, pulverized, and passed through a 2000-mesh sieve to obtain modified zinc borate with low water content. Modified zinc borate with low water content, lactic acid oligomer, and EVOH were added to a Banbury mixer. The Banbury mixer speed was controlled at 140 rpm, and the mixture was stirred at 185℃ for 10 minutes. The mixture was then extruded and granulated to obtain polylactic acid modified functional masterbatch.
[0044] The silane coupling agent used in this step is γ-glycidoxypropyltrimethoxysilane.
[0045] Step 3: Mixing and extrusion PLLA granules, PDLA granules, polycaprolactone, lactic acid-lactide oligomer, anti-hydrolysis agent, and polylactic acid modified functional masterbatch were added to a mixer and premixed at 80°C for 30 minutes. The mixture was then melt-extruded into a twin-screw extruder to obtain high-barrier polylactic acid packaging material. The temperature control of the twin-screw extruder during melt extrusion was as follows: feed section 160°C, melt section 195°C, and die head section 180°C.
[0046] Example 4: A high-barrier polylactic acid packaging material A high-barrier polylactic acid packaging material, the raw materials comprising, by weight: 60 parts PLLA particles, 12 parts PDLA particles, 7 parts polycaprolactone, 4 parts lactic acid-lactide oligomer, 12 parts polylactic acid modified functional masterbatch, and 0.6 parts anti-hydrolysis agent.
[0047] The lactic acid-lactide oligomer comprises, by weight, 50 parts of L-lactic acid, 115 parts of D,L-lactide, and 0.3 parts of titanium-zinc catalyst.
[0048] The polylactic acid modified functional masterbatch comprises, by weight, 12 parts of zinc borate with low water content, 1 part of silane coupling agent, 10 parts of anhydrous ethanol, 30 parts of lactic acid oligomer, and 12 parts of ethylene-vinyl alcohol copolymer.
[0049] A method for preparing a high-barrier polylactic acid packaging material includes the following steps: Step 1: Preparation of lactic acid-lactide oligomers L-lactic acid, D,L-lactide, and a titanium-zinc catalyst were added to a reactor, protected by nitrogen gas, and the temperature was raised to 150°C. The reactor was stirred for 4 hours. The reactor was then evacuated to a pressure < -0.08 MPa and the reaction was carried out under reduced pressure for 2 hours. After the reaction was completed, the product was discharged while hot, cooled, and granulated to obtain a lactic acid-lactide oligomer with a number average molecular weight of 5000.
[0050] Step 2: Preparation of polylactic acid modified functional masterbatch A solution of silane coupling agent was prepared by dropwise addition to anhydrous ethanol and thorough mixing. Zinc borate with low water content was dried in a 100℃ oven for 4-6 hours to remove surface adsorbed water. After natural cooling, it was added to a high-speed mixer and stirred. The solution was sprayed through the top of the mixer, and the mixture was stirred at 400 rpm for 2 hours. The temperature was then raised to 85℃ and stirring continued for 1 hour to evaporate excess ethanol. After the material in the system cooled to room temperature, it was discharged, pulverized, and passed through a 2000-mesh sieve to obtain modified zinc borate with low water content. Modified zinc borate with low water content, lactic acid oligomer, and EVOH were added to a Banbury mixer. The Banbury mixer speed was controlled at 120 rpm, and the mixture was stirred at 185℃ for 15 minutes. The mixture was then extruded and granulated to obtain polylactic acid modified functional masterbatch.
[0051] The silane coupling agent used in this step is γ-methacryloyloxypropyltrimethoxysilane.
[0052] Step 3: Mixing and extrusion PLLA granules, PDLA granules, polycaprolactone, lactic acid-lactide oligomer, anti-hydrolysis agent, and polylactic acid modified functional masterbatch were added to a mixer and premixed at 76°C for 60 minutes. The mixture was then melt-extruded into a twin-screw extruder to obtain high-barrier polylactic acid packaging material. The temperature control of the twin-screw extruder during melt extrusion was as follows: feed section 160°C, melt section 180°C, and die head section 170°C.
[0053] Comparative Example 1: A polylactic acid packaging material The difference between this comparative example and Example 1 is that this comparative example does not involve the preparation of lactic acid-lactide oligomers, and the raw materials in the final compounding and extrusion step do not include lactic acid-lactide oligomers. Apart from this, the remaining operations and control conditions in this comparative example are consistent with those in Example 1.
[0054] Comparative Example 2: A polylactic acid packaging material The difference between this comparative example and Example 1 is that the preparation of modified low-water zinc borate is not involved in the step of preparing polylactic acid modified functional masterbatch in this comparative example. Apart from this, the remaining operations and control conditions in this comparative example are consistent with the steps in Example 1.
[0055] Performance testing The high-barrier polylactic acid packaging materials of Examples 1, 2, 3, and 4, and the polylactic acid packaging materials of Comparative Examples 1 and 2 were subjected to performance tests. The test methods are as follows; the test results are shown in Table 1.
[0056] Oxygen permeability (OTR): The high-barrier polylactic acid packaging material was processed into a 0.1 mm thick sample for testing according to the method provided in GB / T 1038.1-2022 "Test method for gas permeability of plastic films and sheets - Part 1: Differential pressure method".
[0057] Water vapor transmission rate (WVTR): The high-barrier polylactic acid packaging material was processed into a 0.1 mm thick sample for testing according to the method provided in GB / T 26253-2010 "Determination of water vapor transmission rate of plastic films and sheets by infrared detector".
[0058] Haze: The high-barrier polylactic acid packaging material was processed into a 50mm*50mm*0.15mm sample for testing according to the method provided in GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics".
[0059] Heat distortion temperature: According to the method provided in GB / T 1634.2-2019 "Determination of load distortion temperature of plastics - Part 2: Plastics and hard rubber", the high-barrier polylactic acid packaging material was processed into a sample of 80mm*10mm*4mm for testing. The applied bending stress was 1.8MPa and the heating rate was 120℃ / h.
[0060] Toughness test: According to the test method in GB / T 1843-2008 "Determination of impact strength of plastic cantilever beam", the high-barrier polylactic acid packaging material was processed into a 2mm thick sample and its cantilever beam impact strength was tested.
[0061] Table 1 Performance test results of Examples 1, 2, 3, and 4 and Comparative Examples 1 and 2 The test results show that the oxygen permeability of the high-barrier polylactic acid packaging material prepared by this invention is 1.22~1.75 cm. 3 / (m 2 (24h), water vapor transmission rate is 0.88~1.16 g / (m²). 2 The temperature range is 24h, indicating excellent barrier properties against water and oxygen; the heat distortion temperature is 109~118℃, indicating good high-temperature resistance; the haze is 5.1~6.4%, and the cantilever beam impact strength is 10.5~11.7kJ / m. 2 This demonstrates that the high-barrier polylactic acid packaging material prepared by this invention has both high transparency and high toughness.
[0062] Comparative Example 1 did not involve lactic acid-lactide oligomers, and its heat distortion temperature and cantilever beam impact strength were significantly lower than those of Examples 1-4. Comparative Example 2 did not use modified low-water zinc borate, and its barrier properties were significantly affected compared to Examples 1-4.
[0063] Obviously, there are many other possible implementation methods under the concept of this invention. It should be stated here that any changes made under the inventive concept of this invention will fall within the protection scope of this invention.
Claims
1. A high-barrier polylactic acid packaging material, characterized in that: The raw materials for preparation include, by weight: 60-78 parts of PLLA particles, 12-19.5 parts of PDLA particles, 7-12 parts of polycaprolactone, 4-8 parts of lactic acid-lactide oligomer, 11-15 parts of polylactic acid modified functional masterbatch, and 0.6-1 parts of anti-hydrolysis agent. The lactic acid-lactide oligomer is prepared by means of the following raw materials in parts by weight: 44-50 parts of L-lactic acid, 90-115 parts of D,L-lactide, and 0.1-0.3 parts of titanium-zinc catalyst. The polylactic acid modified functional masterbatch comprises, by weight, 12-15 parts of zinc borate with low water content, 0.5-1 part of silane coupling agent, 10-15 parts of anhydrous ethanol, 22-28 parts of lactic acid oligomer, and 12-20 parts of ethylene-vinyl alcohol copolymer.
2. The high-barrier polylactic acid packaging material according to claim 1, characterized in that: The zinc borate with low water content is zinc borate with 3.5 water content; the lactic acid oligomer is L-lactic acid oligomer with a molecular weight of 2000~4000; the ethylene-vinyl alcohol copolymer has an ethylene content of 30~32%; the anti-hydrolysis agent is polycarbodiimide with a degree of polymerization of 2500~3000.
3. The high-barrier polylactic acid packaging material according to claim 1, characterized in that: The silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; the titanium-zinc catalyst is obtained by compounding tetrabutyl titanate and zinc lactate, and the mass ratio of tetrabutyl titanate to zinc lactate is 1:(2~3).
4. A method for preparing a high-barrier polylactic acid packaging material, characterized in that: The preparation method includes preparing lactic acid-lactide oligomers, preparing polylactic acid modified functional masterbatches, and compounding and extrusion steps; the preparation of lactic acid-lactide oligomers involves adding L-lactic acid, D,L-lactide, and titanium-zinc catalyst to a reactor, purging with nitrogen for protection, stirring and reacting for 5 hours, stopping the nitrogen purging, and then reacting under reduced pressure for 2 hours; after the reaction is completed, the material is discharged and granulated to obtain lactic acid-lactide oligomers.
5. The method for preparing a high-barrier polylactic acid packaging material according to claim 4, characterized in that: The stirring reaction is carried out at a temperature of 145~160℃; the depressurization reaction is carried out at a pressure of <-0.08MPa; the lactic acid-lactide oligomer has a number average molecular weight of 2000~5000.
6. The method for preparing a high-barrier polylactic acid packaging material according to claim 4, characterized in that: The preparation of polylactic acid modified functional masterbatch involves: adding dried zinc borate (low water content) to a high-speed mixer, spraying a silane coupling agent solution onto the zinc borate, stirring and reacting for 1.5-2 hours, then heating to 85-90°C and continuing stirring for 0.5-1 hour. After the system cools, the material is discharged to obtain modified zinc borate (low water content); adding the modified zinc borate (low water content), lactic acid oligomer, and ethylene-vinyl alcohol copolymer to a mixer and mixing for 8-20 minutes to obtain polylactic acid modified functional masterbatch.
7. The method for preparing a high-barrier polylactic acid packaging material according to claim 6, characterized in that: The silane coupling agent solution is prepared by mixing silane coupling agent with anhydrous ethanol.
8. The method for preparing a high-barrier polylactic acid packaging material according to claim 6, characterized in that: The mixing process is carried out at a temperature of 180~190℃ and a speed of 90~140r / min.
9. The method for preparing a high-barrier polylactic acid packaging material according to claim 4, characterized in that: The compounding and extrusion process involves adding PLLA particles, PDLA particles, polycaprolactone, lactic acid-lactide oligomer, anti-hydrolysis agent, and polylactic acid modified functional masterbatch to a mixer and premixing for 20-60 minutes to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion to obtain high-barrier polylactic acid packaging material.
10. The method for preparing a high-barrier polylactic acid packaging material according to claim 9, characterized in that: The stirring and premixing process: the premixing temperature is 76~88℃; the melt extrusion process: the temperature control of the twin-screw extruder is 150~160℃ in the feeding section, 180~195℃ in the melting section, and 170~190℃ in the die head section.