Preparation method of high-temperature-resistant degradable plastic and application of high-temperature-resistant degradable plastic in food packaging

Abstract

The invention belongs to the technical field of plastic, and particularly relates to a preparation method of high-temperature-resistant degradable plastic and application of the high-temperature-resistant degradable plastic in food packaging. The preparation method of the high-temperature-resistant degradable plastic comprises the following steps: (1) weighing the following raw materials in parts by mass: 65-70 parts of polylactic acid, 15-20 parts of polyethylene glycol terephthalate, 10-14 parts of polyglycolic acid, 4-8 parts of poly (butylene succinate), 3-6 parts of filler, 2-5 parts of compatilizer and 1-2 parts of plasticizer; and (2) mixing the raw materials, putting the mixture into a double-screw extruder, and carrying out melt extrusion to obtain the high-temperature-resistant degradable plastic. The high-temperature-resistant degradable plastic prepared by the preparation method disclosed by the invention is excellent in high temperature resistance, tensile property and impact resistance. The plastic material disclosed by the invention can be safely used for manufacturing food packaging products, is particularly suitable for food packaging, transportation and storage scenes needing to tolerate a certain temperature, and is beneficial to promoting the deep application of degradable materials in the food industry.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plastics, and particularly relates to a preparation method of high-temperature-resistant degradable plastic and application thereof in food packaging. BACKGROUND

[0002] Biodegradable plastics are considered as an important way to solve the problem of plastic pollution because raw materials thereof can be derived from renewable resources (such as corn starch, sugarcane, cellulose, etc.) and can be decomposed by microorganisms into harmless substances such as water, carbon dioxide and / or methane under specific conditions. Poly-lactic acid has good thermal stability and a wide processing window, and is widely used in various fields. However, the brittleness and poor high-temperature resistance of PLA limit its use in fields requiring high-temperature resistance and impact resistance, such as food packaging containers.

[0003] At present, the mainstream methods for improving the heat resistance and toughness of poly-lactic acid include: adding nucleating agents, introducing filler particles, implementing cross-linking or introducing elastic phases. However, practice shows that the improvement of the thermal deformation temperature by nucleating agents and fillers is small; cross-linking reaction significantly damages the melt flowability, which restricts the processing of thin-walled products; the elastomer can effectively toughen, but a large amount of addition will inhibit the biodegradation process; and the introduction of the elastic phase leads to a decrease in heat resistance.

[0004] Therefore, under the premise of ensuring the degradable property, it is still a technical bottleneck to be broken through for the PLA material system to simultaneously achieve high thermal stability, high rigidity and high impact resistance. SUMMARY

[0005] The application aims to provide a preparation method of high-temperature-resistant degradable plastic and application thereof in food packaging.

[0006] In order to achieve the above-mentioned purpose, the application provides the following technical scheme. A preparation method of high-temperature-resistant degradable plastic, comprising the following steps: (1) the following raw materials are weighed according to the mass fraction: 65-70 parts of poly-lactic acid, 15-20 parts of polyethylene terephthalate, 10-14 parts of polyglycolic acid, 4-8 parts of polybutylene succinate, 3-6 parts of filler, 2-5 parts of compatibilizer and 1-2 parts of plasticizer; (2) the raw materials are mixed and put into a double-screw extruder for melt extrusion to obtain the high-temperature-resistant degradable plastic.

[0007] Preferably, the melt index of the poly-lactic acid is 20-25 g / 10 min at 190 DEG C and 2.16 kg.

[0008] More preferably, the melt index of the poly-lactic acid is 22 g / 10 min at 190 DEG C and 2.16 kg. It can be selected from Anhui Fengyuan Group Co., Ltd., model PLA FY401.

[0009] Preferably, the polyethylene terephthalate is PET of model 4210G of South Asia Plastic.

[0010] Preferably, the notched impact strength of the polybutylene succinate is 7-10 kJ / m², and the heat distortion temperature is 210-220℃.

[0011] More preferably, the polybutylene succinate is VALOX™ PBT V4860HR of Saudi Basic, notched impact: 9.18kJ / m², heat distortion temperature: 221℃. Or the polybutylene succinate is VALOX™ PBT ENH4550 of Saudi Basic, notched impact: 7.14kJ / m², heat distortion temperature: 220℃.

[0012] The application can improve the high temperature resistance of degradable plastics by adding polyethylene terephthalate, polyglycolic acid and polybutylene succinate in PLA at the same time, and can improve the impact resistance of plastics when adding a specific amount of polyethylene terephthalate, polyglycolic acid and polybutylene succinate. Analysis is that the glass transition temperature and melting point of PET are much higher than those of PLA, PGA has a very high melting point and good crystallization ability, and its crystallization region can play a role of physical crosslinking point at high temperature, limiting the movement of PLA segment. PBS itself has a low Tg, but in the ternary blending system, it can play a role in improving the compatibility of PET / PGA and PLA, and its flexible segment allows the rigid structure of PET / PGA to better play the role of "support". However, the tensile strength at this time is not ideal, and analysis is that in this proportion, the system may form a co-continuous phase structure, although this structure is beneficial to the dissipation of impact energy, but it will limit the overall strength when stretching.

[0013] Preferably, the filler includes cellulose nanocrystals TL-003 and hydrophobically modified nanocellulose TL-017 in a mass ratio of 1: (2-3).

[0014] The application can improve the tensile strength of plastics by adding a specific ratio of cellulose nanocrystals TL-003 and hydrophobically modified nanocellulose TL-017 in the plastic system. Analysis is that the filler can form a three-dimensional network structure in the matrix, which can hinder the propagation of microcracks.

[0015] Preferably, the plasticizer is acetyl tri-butyl citrate.

[0016] Preferably, the total amount of polyethylene terephthalate, polyglycolic acid and polybutylene succinate accounts for less than 50% of the mass fraction of polylactic acid.

[0017] The total mass fraction of polyethylene terephthalate, polyglycolic acid and polybutylene succinate in the polylactic acid is less than 50%. The blending of PLA and polymers can be avoided due to excessive addition, which leads to difficult degradation of PLA.

[0018] Preferably, the compatibilizer is epoxy soybean oil.

[0019] Preferably, the conditions for melt extrusion in the twin-screw extruder are: Zone 1: 150-155 DEG C; Zone 2: 165-170 DEG C; Zone 3: 240-245 DEG C; Zone 4: 195-200 DEG C; Zone 5: 190-195 DEG C; Zone 6: 180-185 DEG C; Zone 7: 175-180 DEG C.

[0020] The second aspect of the present application provides a preparation method of a high-temperature-resistant degradable plastic and its application in food packaging.

[0021] Compared with the prior art, the present application has the following advantages and beneficial effects: 1. The high-temperature-resistant degradable plastic prepared by the present application has outstanding performance in heat resistance, tensile strength and impact resistance, can maintain the stability of structure and performance in a higher temperature environment, and effectively widens the application temperature range of degradable materials. The excellent mechanical properties ensure that the material is not easily damaged during processing and use, and is suitable for industrial and packaging fields with high requirements for strength and heat resistance, significantly improving the practical value and market competitiveness of biobased degradable plastics.

[0022] 2. The plastic material of the present application can be safely used for the manufacture of food packaging products, especially for food packaging, transportation and storage scenes that need to withstand a certain temperature, which helps to promote the deep application of degradable materials in the food industry. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0024] Embodiment 1 The present embodiment provides a preparation method of a high-temperature-resistant degradable plastic, comprising the following steps: (1) The following raw materials are weighed by mass fraction: polylactic acid (PLA) 68 parts, polyethylene terephthalate (PET) 16 parts, polyglycolic acid (PGA) 12 parts, polybutylene succinate (PBS) 5 parts, filler 5 parts, compatibilizer epoxy soybean oil (ESO) 3 parts, plasticizer acetyl tri-butyl citrate 1.5 parts; (2) The raw materials are mixed and put into a twin-screw extruder for melt extrusion. The conditions for melt extrusion in the twin-screw extruder are as follows: Zone 1 (feeding section): 152°C; low-temperature conveying of PLA / PET / PBS to prevent pre-degradation of PLA; Zone 2 (melting section): 170°C, melt of PLA / PBS, injection of ESO and plasticizer to improve flowability; Zone 3 (melting section): 245°C, forced melting of PET and high-temperature shearing to break up PET phase; Zone 4 (mixing section): 200°C, side feeding of PGA and bamboo fibers, moderate-temperature dispersion to protect heat-sensitive components; Zone 5 (mixing section): 190°C; Zone 6 (homogenization section): 185°C, melt homogenization to balance temperature gradient; Zone 7 (die): 175°C, low-temperature discharging, to obtain a high-temperature-resistant degradable plastic.

[0025] The melt index of polylactic acid is 22 g / 10 min at 190°C under a load of 2.16 kg. Anhui Fengyuan Group Co., Ltd., model PLA FY401.

[0026] Polyethylene terephthalate, South Asia Plastic Industry Co., Ltd., model 4210G.

[0027] Polyglycolic acid, Hubei Xingyan New Material Technology Co., Ltd.

[0028] Polybutylene succinate, model Saudi Basic VALOX™ PBT V4860HR, notched impact: 9.18 kJ / m², heat distortion temperature: 221°C.

[0029] The filler includes cellulose nanocrystals TL-003 and hydrophobically modified nanocellulose TL-017 in a mass ratio of 1:2. Hydrophobically modified nanocellulose TL-017, Nanjing Tianlu Nanotechnology Co., Ltd. Cellulose nanocrystals TL-003, Nanjing Tianlu Nanotechnology Co., Ltd.

[0030] Example 2 The present embodiment provides a method for preparing a high-temperature-resistant degradable plastic, including the following steps: (1) The following raw materials are weighed according to mass fraction: 70 parts of polylactic acid (PLA), 15 parts of polyethylene terephthalate (PET), 14 parts of polyglycolic acid (PGA), 4 parts of polybutylene succinate (PBS), 6 parts of filler, 2 parts of compatible agent epoxidized soybean oil (ESO), and 2 parts of plasticizer acetyl tri-butyl citrate; (2) The raw materials are mixed and put into a twin-screw extruder for melt extrusion. The conditions for melt extrusion in the twin-screw extruder are as follows: Zone 1 (feeding section): 152°C; low-temperature conveying of PLA / PET / PBS to prevent pre-degradation of PLA; Zone 2 (melting section): 170°C, melt of PLA / PBS, injection of ESO and plasticizer to improve flowability; Zone 3 (melting section): 245°C, forced melting of PET and high-temperature shearing to break up PET phase; Zone 4 (mixing section): 200°C, side feeding of PGA and bamboo fibers, moderate-temperature dispersion to protect heat-sensitive components; Zone 5 (mixing section): 190°C; Zone 6 (homogenization section): 185°C, melt homogenization to balance temperature gradient; Zone 7 (die): 175°C, low-temperature discharging, to obtain a high-temperature-resistant degradable plastic.

[0031] The melt index of polylactic acid is 22 g / 10 min at 190°C under a load of 2.16 kg. Anhui Fengyuan Group Co., Ltd., model PLA FY401.

[0032] Polyethylene terephthalate, South Asia Plastic Industry Co., Ltd., model 4210G.

[0033] Polyglycolic acid, Hubei Xingyan New Material Technology Co., Ltd.

[0034] Polybutylene succinate, model Saudi Basic VALOX™ PBT ENH4550, notched impact: 7.14 kJ / m², heat distortion temperature: 220°C.

[0035] The filler includes cellulose nanocrystals TL-003 and hydrophobically modified nanocellulose TL-017 in a mass ratio of 1:3. Hydrophobically modified nanocellulose TL-017, Nanjing Tianlu Nanotechnology Co., Ltd. Cellulose nanocrystals TL-003, Nanjing Tianlu Nanotechnology Co., Ltd.

[0036] Example 3 The present embodiment provides a method for preparing a high-temperature-resistant degradable plastic, including the following steps: (1) The following raw materials are weighed according to mass fraction: 65 parts of polylactic acid (PLA), 15 parts of polyethylene terephthalate (PET), 10 parts of polyglycolic acid (PGA), 4 parts of polybutylene succinate (PBS), 6 parts of filler, 5 parts of compatibilizer epoxidized soybean oil (ESO), and 1 part of plasticizer acetyl tri-butyl citrate. (2) The raw materials are mixed and put into a twin-screw extruder for melt extrusion. The conditions for melt extrusion in the twin-screw extruder are as follows: Zone 1 (feeding section): 152°C; low-temperature conveying of PLA / PET / PBS to prevent pre-degradation of PLA; Zone 2 (melting section): 170°C, melt of PLA / PBS, injection of ESO and plasticizer to improve fluidity; Zone 3 (melting section): 245°C, forced melting of PET and high-temperature shearing to break up the PET phase; Zone 4 (mixing section): 200°C, side feeding of PGA and bamboo fibers, moderate-temperature dispersion to protect the heat-sensitive components; Zone 5 (mixing section): 190°C; Zone 6 (homogenization section): 185°C, homogenization of the melt and balance of the temperature gradient; Zone 7 (die): 175°C, low-temperature discharging, to obtain a high-temperature-resistant degradable plastic.

[0037] The melt index of the polylactic acid is 22 g / 10 min at 190°C under a load of 2.16 kg. Anhui Fengyuan Group Co., Ltd., model PLA FY401.

[0038] The polyethylene terephthalate is of model 4210G from Nan Ya Plastics Corporation.

[0039] The polyglycolic acid is from Hubei Xingyan New Material Technology Co., Ltd.

[0040] The polybutylene succinate is of model VALOX™ PBT V4860HR from Saudi Basic, with a notched impact of 9.18 kJ / m² and a heat distortion temperature of 221°C.

[0041] The filler includes cellulose nanocrystals TL-003 and hydrophobically modified nanocellulose TL-017 in a mass ratio of 1:2. The hydrophobically modified nanocellulose TL-017 is from Nanjing Tianlu Nanotechnology Co., Ltd. The cellulose nanocrystals TL-003 are from Nanjing Tianlu Nanotechnology Co., Ltd.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that the polylactic acid is of model PLA REVODE110, with a melt index of 7 g / 10 min at 190°C under a load of 2.16 kg, from Zhejiang Haizheng Group Co., Ltd.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that the polyethylene terephthalate is of model 4410G from Nan Ya Plastics Corporation.

[0044] Comparative Example 3 The difference between this comparative example and Example 1 is that the polybutylene succinate is of model VALOX™ PBTK4530 from Saudi Basic, with a notched impact of 5.91 kJ / m² and a heat distortion temperature of 194°C.

[0045] Comparative Example 4 The difference between this comparative example and Example 1 is that the filler comprises cellulose nanocrystals TL-003 and hydrophobically modified nanocellulose TL-017 in a mass ratio of 2:1.

[0046] Comparative Example 5 The difference between this comparative example and Example 1 is that the total amount of polyethylene terephthalate (PET), polyglycolic acid (PGA), and polybutylene succinate (PBS) is unchanged, but the ratio is changed.

[0047] The following raw materials were weighed out in parts by mass: polylactic acid (PLA) 68 parts, polyethylene terephthalate (PET) 11 parts, polyglycolic acid (PGA) 11 parts, polybutylene succinate (PBS) 11 parts, filler 5 parts, compatibilizer epoxidized soybean oil (ESO) 3 parts, plasticizer acetyl tributyl citrate 1.5 parts.

[0048] Comparative Example 6 The difference between this comparative example and Example 1 is that the total amount of polyethylene terephthalate (PET), polyglycolic acid (PGA), and polybutylene succinate (PBS) is unchanged, but the ratio is changed.

[0049] The following raw materials were weighed out in parts by mass: polylactic acid (PLA) 68 parts, polyethylene terephthalate (PET) 5 parts, polyglycolic acid (PGA) 16 parts, polybutylene succinate (PBS) 12 parts, filler 5 parts, compatibilizer epoxidized soybean oil (ESO) 3 parts, plasticizer acetyl tributyl citrate 1.5 parts.

[0050] Comparative Example 7 The total amount of polyethylene terephthalate (PET), polyglycolic acid (PGA), and polybutylene succinate (PBS) is unchanged, but the ratio is changed.

[0051] The following raw materials were weighed out in parts by mass: polylactic acid (PLA) 68 parts, polyethylene terephthalate (PET) 12 parts, polyglycolic acid (PGA) 5 parts, polybutylene succinate (PBS) 16 parts, filler 5 parts, compatibilizer epoxidized soybean oil (ESO) 3 parts, plasticizer acetyl tributyl citrate 1.5 parts.

[0052] Performance Test The high-temperature-resistant degradable plastics prepared in Examples 1-2 and Comparative Examples 1-7 were subjected to performance testing.

[0053] (1) Heat distortion temperature: The heat distortion temperature was tested according to the standard ISO 75, with a load of 0.45 MPa, a sample size of 80 mm x 10 mm x 4 mm, and a temperature rise rate of 120℃ / h; (2) Impact strength: impact strength was tested according to standard ISO 179, Izod, sample size 80mm x 10mm x 4mm, A type notch; (3) Tensile strength: tensile strength was tested according to standard ISO 527, sample size 170mm x 10mm x 4mm, tensile rate 500mm / min.

[0054] The results are shown in Table 1.

[0055] Table 1 Test results Thermal distortion temperature °C Izod notched impact strength 23°C, KJ / m 2 ]] Tensile strength MPa Elongation at break % Example 1 119 34 98 142 Example 2 113 32 97 137 Example 3 117 33 95 133 Comparative Example 1 95 28 96 117 Comparative Example 2 104 26 100 126 Comparative Example 3 91 24 94 103 Comparative Example 4 106 26 103 128 Comparative Example 5 97 37 74 144 Comparative Example 6 78 30 77 131 Comparative Example 7 88 38 68 147 As can be seen from Table 1, the high-temperature-resistant plastics of Examples 1-3 have excellent high-temperature resistance, impact resistance and tensile strength performance.

[0056] In Comparative Example 1, the high molecular weight PLA has a slow crystallization speed and a significantly decreased heat resistance.

[0057] In Comparative Example 2, different types of polyethylene terephthalate are used, and the impact resistance is decreased.

[0058] In Comparative Example 3, the notched impact of K4530 is only 5.91 kJ / m2, and the interfacial compatibility is deteriorated, resulting in a decrease in impact resistance.

[0059] In Comparative Example 4, TL-017 is halved, resulting in an increase in interfacial stress concentration and a decrease in impact resistance.

[0060] In Comparative Examples 5 and 7, the proportion of PBS is increased, resulting in dilution of the flexible phase and a decrease in heat resistance.

[0061] In Comparative Example 6, the content of PET is decreased, the core heat-resistant phase is missing, and the heat resistance is significantly decreased.

[0062] As can be seen from the results, any deviation of the components in the system of the present application will destroy the "rigid-flexible-heat-resistant" triangular balance of the plastic: Comparative Examples 1, 2 and 3 show that the key polymer types in the system of the present application cannot be replaced, and the molecular weight / crystallinity / impact strength needs to be strictly matched to achieve the improvement of comprehensive performance. Comparative Example 4 proves that the filler needs to maintain TL-017 as the dominant interface, otherwise it will be brittle. Comparative Examples 5, 6 and 7 show that polyethylene terephthalate (PET), polyglycolic acid (PGA) and polybutylene succinate (PBS) can achieve balanced improvement of heat resistance and strength when compounded in a specific ratio.

[0063] The above describes the preferred embodiments of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered within the scope of protection of the present application.

Claims

1. A method for preparing a high temperature resistant degradable plastic, characterized in that, The method comprises the following steps: (1) the following raw materials are weighed according to the mass fraction: polylactic acid 65-70 parts, polyethylene terephthalate 15-20 parts, polyglycolic acid 10-14 parts, polybutylene succinate 4-8 parts, filler 3-6 parts, compatibilizer 2-5 parts, plasticizer 1-2 parts; (2) the raw materials are mixed and put into a double screw extruder for melt extrusion to obtain the high-temperature-resistant degradable plastic.

2. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The melt index of polylactic acid is 20-25 g / 10 min at 190℃ under a load of 2.16 kg.

3. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The filler includes cellulose nanocrystals TL-003 and hydrophobically modified nanocellulose TL-017 in a mass ratio of 1: (2-3).

4. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The polyethylene terephthalate is of model Nanya Plastic 4210G.

5. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The notched impact strength of polybutylene succinate is 7-10 kJ / m², and the heat distortion temperature is 210-220℃.

6. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The plasticizer is acetyl tri-butyl citrate.

7. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The total mass fraction of polyethylene terephthalate, polyglycolic acid and polybutylene succinate in polylactic acid is less than 50%.

8. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The compatibilizer is epoxy soybean oil.

9. The method for preparing high-temperature resistant biodegradable plastic according to claim 1, characterized in that, The melt extrusion conditions in the double screw extruder are as follows: Zone 1: 150-155℃; Zone 2: 165-170℃; Zone 3: 240-245℃; Zone 4: 195-200℃; Zone 5: 190-195℃; Zone 6: 180-185℃; Zone 7: 175-180℃.

10. Use of the high-temperature-resistant degradable plastic according to any one of claims 1-9 in food packaging. ​ ​