PLA laminated film composite material, preparation method and application thereof

Abstract

This invention discloses a PLA coating composite material, its preparation method, and its application, belonging to the field of coated paper technology. The composite material comprises the following raw materials in parts by weight: 70-80 parts of polylactic acid; 20-30 parts of bio-based toughening component; 15-25 parts of cationic filler; 2-4 parts of heat-resistant compatibilizer; and 1 part of nucleating agent TMC-3001. The heat-resistant compatibilizer is a terpolymer formed by norbornene imide, 1,6-hexanediol diacrylate, and glycidyl methacrylate. The PLA coating composite material provided in this application constructs an "organic-inorganic" dual reinforcement system through the synergistic effect of the heat-resistant compatibilizer and the cationic filler, which not only strengthens the material's intrinsic properties but also improves the interfacial bonding strength between the coating layer and the paper. Ultimately, a fully biodegradable coating material with high heat resistance, excellent flexibility, and strong interlayer bonding is obtained. This fully biodegradable coating material is suitable for preparing heat-resistant coated paper products.

Description

Technical Field

[0001] This invention belongs to the field of coated paper technology, specifically relating to a PLA coated composite material, its preparation method, and its application. Background Technology

[0002] Paper packaging holds a place in the packaging industry due to its advantages such as low plastic usage, low cost, high stiffness, and good printability. However, paper has poor water resistance, making pure paper packaging unsuitable for packaging containing moisture. To improve the performance of paper packaging, one or two layers of plastic film are usually coated on the paper surface to create paper-plastic composite materials, also known as coated paper.

[0003] Coated paper can be used in paper cups, instant noodle bowls, coffee cups, paper bags, etc. These products are usually discarded after a single use, greatly increasing the burden on the environment. Therefore, using fully biodegradable plastic instead of polyethylene as the coating material in the production of disposable coated paper products results in coated paper products that can be decomposed and absorbed by microorganisms in the environment, converting into carbon dioxide and water without polluting the environment.

[0004] Fully biodegradable plastics include polylactic acid (PLA), polybutylene succinate (PBS), copolymers of butylene adipate and butylene terephthalate (PBAT), and polycaprolactone (PCL). Among these, PLA can be obtained from sugar fermentation to produce lactic acid, which serves as a polymerization raw material. Furthermore, under composting conditions, it can be converted back into lactic acid, which is then absorbed and decomposed into water and carbon dioxide. It is a fully bio-based and biodegradable plastic, and currently the most widely used and successful biodegradable plastic. However, PLA has poor heat resistance and is soft. With a melting point of only around 60℃, the coated paper product made of pure PLA or ordinary PLA composite material is prone to softening and deformation when filled with hot drinks or food or microwaved. This not only affects the user experience and structural integrity of the product, but also causes a sharp drop in film strength, leading to problems such as film damage or failure of adhesion to the paper base. This poses a safety hazard of scalding users and fails to meet the basic performance requirements of hot beverage packaging in the market. Therefore, providing a heat-resistant PLA coated composite material is a technical problem that needs to be solved. Summary of the Invention

[0005] One of the objectives of this invention is to provide a PLA coating composite material to solve the problem of poor heat resistance of current PLA coating composite materials.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned PLA coating composite material.

[0007] The third objective of this invention is to provide applications of the aforementioned PLA coating composite material.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A PLA coating composite material comprises the following raw materials in parts by weight:

[0010] 70-80 parts of polylactic acid;

[0011] 20-30 parts of bio-based toughening component;

[0012] 15-25 parts of cationized filler;

[0013] 2-4 parts of heat-resistant compatibilizer;

[0014] 0.3-1 part lubricant.

[0015] The heat-resistant compatibilizer is a terpolymer formed by norbornene imide, 1,6-hexanediol diacrylate and glycidyl methacrylate.

[0016] The bio-based toughening components are polybutylene terephthalate (PBAT) and / or polycaprolactone (PCL).

[0017] Bio-based toughening components are flexible and biodegradable polymers. Blending them can improve the toughness of polylactic acid (PLA), but their compatibility is poor. Therefore, this invention employs a heat-resistant compatibilizer to perform in-situ compatibilization modification of PLA and the bio-based toughening component. The epoxy groups carried on the compatibilizer's molecular chain can undergo ring-opening reactions with the terminal carboxyl or hydroxyl groups of PLA and the bio-based toughening component during processing, effectively improving their interfacial compatibility and promoting stress transfer. This allows the composite material to maintain biodegradability while achieving improved flexibility and mechanical properties. Furthermore, the heat-resistant compatibilizer of this invention carries an imide ring with a rigid phenolic group. The imide ring structure effectively enhances the heat resistance of the composite material; while the phenolic hydroxyl groups can bond with oxygen-containing groups (such as cellulose hydroxyl groups) on the surface of the base paper through hydrogen bonds and van der Waals forces, which helps to enhance the adhesion strength between the coating layer and the paper substrate. Ultimately, a fully bio-based coating material with good flexibility, high heat resistance, and excellent interlayer bonding is obtained.

[0018] Furthermore, the raw materials for preparing norbornene imide include norbornene adienoic anhydride and aminophenol compounds, with a molar ratio of norbornene adienoic anhydride to aminophenol compounds of 1:1.

[0019] Further, the aminophenolic compound is at least one of p-aminophenol, 4-amino-3-ethylphenol, 3-amino-5-fluorophenol, and 2-(3,4-dihydroxyphenyl)ethylamine, preferably 2-(3,4-dihydroxyphenyl)ethylamine.

[0020] Furthermore, the preparation steps of the norbornene imide are as follows:

[0021] Add norbornyl olefinic anhydride and glacial acetic acid to a flask, stir well, then add an aminophenol compound. Stir at room temperature for 2 hours, then heat to 120°C and react for 6-8 hours. Collect the water produced by the reaction using a water separator. After the reaction is complete, remove the glacial acetic acid by rotary evaporation to obtain norbornyl imide.

[0022] Furthermore, the preparation steps of the heat-resistant compatibilizer are as follows:

[0023] Toluene was added to a flask, and the temperature was raised to 75°C under nitrogen protection. Azobisisobutyronitrile, α-methylstyrene dimer, norbornene imide, 1,6-hexanediol diacrylate, and glycidyl methacrylate were mixed evenly to obtain mixture a. Mixture a was added dropwise to the flask while stirring. After the addition was complete, the reaction was kept at the temperature for 6-8 hours. After the reaction was completed, the reaction product was poured into anhydrous ethanol to precipitate flocculent material. The mixture was filtered, and the filter cake was washed three times with anhydrous ethanol and acetone, and then dried under vacuum at 50°C for 12 hours to obtain a heat-resistant compatibilizer.

[0024] Furthermore, the ratio of norbornene imide, 1,6-hexanediol diacrylate, and glycidyl methacrylate is 3-6 g: 0.004-0.005 mol: 0.015-0.018 mol, the amount of azobisisobutyronitrile is 4-5% of the total mass of norbornene imide, 1,6-hexanediol diacrylate, and glycidyl methacrylate, and the amount of α-methylstyrene dimer is 20% of the mass of azobisisobutyronitrile.

[0025] Furthermore, the cationized filler is an inorganic filler modified with a cationic surfactant, and the amount of cationic surfactant used is 2-5% of the mass of the inorganic filler.

[0026] Introducing appropriate amounts of inorganic fillers into polylactic acid (PLA) material systems is an effective way to improve their heat resistance. However, due to the poor interfacial compatibility between inorganic fillers and the PLA matrix, the fillers are prone to agglomeration and are difficult to disperse uniformly. This not only fails to fully exert their reinforcing and heat-resistant effects but may also become stress concentration points, leading to a decline in the mechanical properties of the material. To address this, this invention uses cationic surfactants to modify inorganic fillers. This modification treatment brings dual benefits: firstly, by reducing the surface energy of the fillers, it effectively inhibits their agglomeration, promotes their uniform dispersion in the PLA matrix, and enhances the reinforcing and heat-resistant performance of the fillers; secondly, in subsequent coating processes, the cationically modified fillers can form electrostatic adsorption with the paper substrate surface rich in oxygen-containing functional groups due to their positive surface charge, thereby enhancing the interfacial adhesion strength between the coating layer and the paper layer.

[0027] Furthermore, the cationic surfactant is at least one selected from dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

[0028] Furthermore, the inorganic filler has a particle size range of 1-10 μm.

[0029] Furthermore, the inorganic filler is at least one of talc, calcium carbonate, calcium sulfate, mica, and silicon dioxide, preferably talc.

[0030] Furthermore, the preparation steps of the cationized filler are as follows:

[0031] Inorganic filler was ultrasonically dispersed in deionized water, then cationic surfactant was added, the temperature was raised to 60-80℃, and the reaction was stirred for 8-12 hours. After the reaction was completed, the mixture was filtered, and the filter cake was washed and dried to obtain cationic filler.

[0032] Furthermore, the PLA coating composite material also includes 1 part by weight of nucleating agent TMC-300 and 0.3-1 part by weight of lubricant.

[0033] Furthermore, the polylactic acid melt flow rate is 5-7 g / 10 min (210℃ / 2.16 kg), and the preferred polylactic acid resin is model 2002D and branded by NatureWorks, USA.

[0034] Furthermore, the polycaprolactone (PCL) is PCL6500 or PCL6800.

[0035] Furthermore, the lubricant is butyl stearate and / or calcium stearate.

[0036] The preparation method of the above-mentioned PLA coating composite material includes the following steps:

[0037] Polylactic acid, bio-based toughening components, and heat-resistant compatibilizers were dried at 60°C for 12 hours. After drying, they were mixed evenly and added to a twin-screw extruder. Nucleating agent TMC-300, cationic filler, and lubricant were added to the twin-screw extruder. The mixture was then blended, extruded, and granulated to obtain PLA coating composite material.

[0038] Furthermore, the temperatures of sections 1-6 of the twin-screw extruder are 140-150℃, 155-165℃, 170-175℃, 180-185℃, 185-190℃, and 180-185℃, respectively, and the rotation speeds of the main machine and the feeder are 10-30 rpm and 5-15 rpm, respectively.

[0039] The application of the above-mentioned PLA coated composite material or the PLA coated composite material prepared by the above-mentioned method in the preparation of heat-resistant coated paper products.

[0040] The beneficial effects of this invention are:

[0041] The PLA coating composite material provided by this invention achieves a comprehensive improvement in heat resistance, mechanical properties and adhesion properties through the synergistic effect of heat-resistant compatibilizer and cationic filler.

[0042] Among them, the heat-resistant compatibilizer not only reacts in situ with PLA and bio-based toughening components through epoxy groups, effectively improving interfacial compatibility and giving the material good flexibility, but also the imide ring it carries improves the heat resistance of the composite material, while the phenolic hydroxyl groups enhance the bonding force between the coating layer and the paper base.

[0043] Cationic fillers achieve uniform dispersion of inorganic fillers through surface modification, allowing them to fully exert their reinforcing and heat-resistant properties. Furthermore, they enhance interfacial adhesion by electrostatically adsorbing the paper base with their positive surface charge.

[0044] The two work together to construct an "organic-inorganic" dual reinforcement system, which not only strengthens the material's intrinsic properties but also improves the interfacial bonding strength between the coating layer and the paper, ultimately producing a fully biodegradable coating material that combines high heat resistance, excellent flexibility, and strong interlayer bonding. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] The following is a detailed description with reference to specific examples.

[0047] Preparation Example 1

[0048] A heat-resistant compatibilizer is prepared by the following steps:

[0049] 100 mL of toluene was added to a flask. Under nitrogen protection, the temperature was raised to 75 °C. 0.3 g of azobisisobutyronitrile, 0.06 g of α-methylstyrene dimer, 3 g of norbornene imide, 0.9 g of 1,6-hexanediol diacrylate, and 2.1 g of glycidyl methacrylate were mixed evenly to obtain mixture a. Mixture a was added dropwise to the flask while stirring. After the addition was complete, the mixture was kept at the temperature for 6 h. After the reaction was completed, the reaction product was poured into anhydrous ethanol to precipitate flocculent material. The mixture was filtered, and the filter cake was washed three times with anhydrous ethanol and acetone, respectively. The filter cake was then dried under vacuum at 50 °C for 12 h to obtain a heat-resistant compatibilizer.

[0050] The preparation steps of norborneol imide are as follows:

[0051] Add 0.1 mol norbornadipic anhydride and 60 mL glacial acetic acid to a flask, stir well, then add 0.1 mol p-aminophenol, stir at room temperature for 2 h, then heat to 120 °C and react for 6 h. Collect the water produced by the reaction using a water separator. After the reaction is complete, remove the glacial acetic acid by rotary evaporation to obtain norbornadipic imide.

[0052] Preparation Example 2

[0053] A heat-resistant compatibilizer is prepared by the following steps:

[0054] 100 mL of toluene was added to a flask. Under nitrogen protection, the temperature was raised to 75 °C. 0.4 g of azobisisobutyronitrile, 0.08 g of α-methylstyrene dimer, 4.5 g of norbornene imide, 1.0 g of 1,6-hexanediol diacrylate, and 2.4 g of glycidyl methacrylate were mixed evenly to obtain mixture a. Mixture a was added dropwise to the flask while stirring. After the addition was complete, the mixture was kept at the temperature for 7 h. After the reaction was completed, the reaction product was poured into anhydrous ethanol to precipitate flocculent material. The mixture was filtered, and the filter cake was washed three times with anhydrous ethanol and acetone, respectively. The filter cake was then dried under vacuum at 50 °C for 12 h to obtain a heat-resistant compatibilizer.

[0055] The preparation steps of norborneol imide are as follows:

[0056] Add 0.1 mol norbornadipic anhydride and 100 mL glacial acetic acid to a flask, stir well, then add 0.1 mol 2-(3,4-dihydroxyphenyl)ethylamine. Stir at room temperature for 2 h, then heat to 120 °C and react for 7 h. Collect the water produced by the reaction using a water separator. After the reaction is complete, remove the glacial acetic acid by rotary evaporation to obtain norbornadipic imide.

[0057] Preparation Example 3

[0058] A heat-resistant compatibilizer is prepared by the following steps:

[0059] 100 mL of toluene was added to a flask. Under nitrogen protection, the temperature was raised to 75 °C. 0.39 g of azobisisobutyronitrile, 0.08 g of α-methylstyrene dimer, 6 g of norbornene imide, 1.1 g of 1,6-hexanediol diacrylate, and 2.6 g of glycidyl methacrylate were mixed evenly to obtain mixture a. Mixture a was added dropwise to the flask while stirring. After the addition was complete, the mixture was kept at the temperature for 8 h. After the reaction was completed, the reaction product was poured into anhydrous ethanol to precipitate flocculent material. The mixture was filtered, and the filter cake was washed three times with anhydrous ethanol and acetone, and then dried under vacuum at 50 °C for 12 h to obtain a heat-resistant compatibilizer.

[0060] The preparation steps of norborneol imide are as follows:

[0061] Add 0.1 mol norbornadipic anhydride and 100 mL glacial acetic acid to a flask, stir well, then add 0.1 mol 2-(3,4-dihydroxyphenyl)ethylamine. Stir at room temperature for 2 h, then heat to 120 °C and react for 8 h. Collect the water produced by the reaction using a water separator. After the reaction is complete, remove the glacial acetic acid by rotary evaporation to obtain norbornadipic imide.

[0062] Compare with Example 1

[0063] A heat-resistant compatibilizer, which differs from Preparation Example 1 only in that norbornene imide in Preparation Example 1 is replaced with an equal mass of styrene.

[0064] Compare with Example 2

[0065] A heat-resistant compatibilizer, which differs from Preparation Example 2 only in that norbornene imide in Preparation Example 2 is replaced with an equal mass of styrene.

[0066] Compare with Example 3

[0067] A heat-resistant compatibilizer, which differs from Preparation Example 3 only in that norbornene imide in Preparation Example 3 is replaced with an equal mass of styrene.

[0068] Example 1

[0069] A PLA coating composite material comprises the following raw materials in parts by weight:

[0070] 70 parts of polylactic acid;

[0071] 30 parts of polybutylene terephthalate-adipate;

[0072] 15 parts of cationized filler;

[0073] Two parts of the heat-resistant compatibilizer of Preparation Example 1 were prepared.

[0074] Nucleating agent TMC-300 1 part;

[0075] 0.3 parts calcium stearate.

[0076] The preparation steps of the cationized filler are as follows:

[0077] 10g of talc powder was ultrasonically dispersed in 100mL of deionized water, and then 0.2g of hexadecyltrimethylammonium bromide was added. The mixture was heated to 60℃ and stirred for 8 hours. After the reaction was completed, the mixture was filtered, and the filter cake was washed and dried to obtain the cationized packing material.

[0078] The polylactic acid is model 2002D, brand name is NatureWorks (USA), the polybutylene terephthalate is PBATTH801T, and the talc particle size is 1-10μm.

[0079] The preparation method of the above-mentioned PLA coating composite material includes the following steps:

[0080] Polylactic acid, bio-based toughening components, and heat-resistant compatibilizers were dried at 60°C for 12 hours. After drying, they were mixed evenly and added to a twin-screw extruder. Nucleating agent TMC-300, cationic filler, and lubricant were added to the twin-screw extruder. The mixture was then blended, extruded, and granulated to obtain PLA coating composite material.

[0081] The temperatures of sections 1-6 of the twin-screw extruder are 140℃, 155℃, 170℃, 180℃, 185℃, and 180℃, respectively, and the rotation speeds of the main extruder and the feeder are 10 rpm and 5 rpm, respectively.

[0082] Example 2

[0083] A PLA coating composite material comprises the following raw materials in parts by weight:

[0084] 75 parts of polylactic acid;

[0085] 25 parts of polybutylene terephthalate-adipate;

[0086] 20 parts of cationized filler;

[0087] Three parts of the heat-resistant compatibilizer of Preparation Example 1 were prepared.

[0088] Nucleating agent TMC-300 1 part;

[0089] 0.5 parts calcium stearate.

[0090] The preparation steps of the cationized filler are as follows:

[0091] 10g of talc powder was ultrasonically dispersed in 100mL of deionized water, and then 0.3g of dodecyltrimethylammonium bromide was added. The mixture was heated to 70℃ and stirred for 10h. After the reaction was completed, the mixture was filtered, and the filter cake was washed and dried to obtain the cationized packing material.

[0092] The polylactic acid is model 2002D, brand name is NatureWorks (USA), the polybutylene terephthalate is PBATTH801T, and the talc particle size is 1-10μm.

[0093] The preparation method of the above-mentioned PLA coating composite material includes the following steps:

[0094] Polylactic acid, bio-based toughening components, and heat-resistant compatibilizers were dried at 60°C for 12 hours. After drying, they were mixed evenly and added to a twin-screw extruder. Nucleating agent TMC-300, cationic filler, and lubricant were added to the twin-screw extruder. The mixture was then blended, extruded, and granulated to obtain PLA coating composite material.

[0095] The temperatures of sections 1-6 of the twin-screw extruder are 145℃, 160℃, 170℃, 182℃, 188℃, and 180℃, respectively, and the rotation speeds of the main extruder and the feeder are 20 rpm and 10 rpm, respectively.

[0096] Example 3

[0097] A PLA coating composite material comprises the following raw materials in parts by weight:

[0098] 80 parts of polylactic acid;

[0099] 20 parts of polybutylene terephthalate-adipate;

[0100] 25 parts of cationized filler;

[0101] Four parts of the heat-resistant compatibilizer of Preparation Example 1;

[0102] Nucleating agent TMC-300 1 part;

[0103] 1 part calcium stearate. Copper.

[0104] The preparation steps of the cationized filler are as follows:

[0105] 10g of talc powder was ultrasonically dispersed in 100mL of deionized water, and then 0.5g of octadecyltrimethylammonium bromide was added. The mixture was heated to 80℃ and stirred for 12h. After the reaction was completed, the mixture was filtered, and the filter cake was washed and dried to obtain the cationized packing material.

[0106] The polylactic acid is model 2002D, brand name is NatureWorks (USA), the polybutylene terephthalate is PBATTH801T, and the talc particle size is 1-10μm.

[0107] The preparation method of the above-mentioned PLA coating composite material includes the following steps:

[0108] Polylactic acid, bio-based toughening components, and heat-resistant compatibilizers were dried at 60°C for 12 hours. After drying, they were mixed evenly and added to a twin-screw extruder. Nucleating agent TMC-300, cationic filler, and lubricant were added to the twin-screw extruder. The mixture was then blended, extruded, and granulated to obtain PLA coating composite material.

[0109] The temperatures of sections 1-6 of the twin-screw extruder are 150℃, 165℃, 175℃, 185℃, 190℃, and 185℃, respectively, and the rotation speeds of the main extruder and the feeder are 30 rpm and 15 rpm, respectively.

[0110] Example 4

[0111] A PLA coating composite material, compared with Example 1, differs only in that the heat-resistant compatibilizer in Example 1 is replaced with an equal weight of the product obtained in Example 2.

[0112] Example 5

[0113] A PLA coating composite material, compared with Example 1, differs only in that the heat-resistant compatibilizer in Example 1 is replaced with an equal weight of the product obtained in Preparation Example 3.

[0114] Example 6

[0115] A PLA coating composite material, compared with Example 2, differs only in that the heat-resistant compatibilizer in Example 2 is replaced with an equal weight of the product obtained in Example 2.

[0116] Example 7

[0117] A PLA coating composite material, compared with Example 2, differs only in that the heat-resistant compatibilizer in Example 2 is replaced with an equal weight of the product obtained in Example 3.

[0118] Example 8

[0119] A PLA coating composite material, compared with Example 3, differs only in that the heat-resistant compatibilizer in Example 2 is replaced with an equal weight of the product obtained in Example 2.

[0120] Example 9

[0121] A PLA coating composite material, compared with Example 3, differs only in that the heat-resistant compatibilizer in Example 2 is replaced with an equal weight of the product obtained in Example 3.

[0122] Comparative Example 1

[0123] A PLA coating composite material, compared with Example 1, differs only in that the heat-resistant compatibilizer in Example 1 is replaced with an equal weight of the product obtained in Comparative Example 1.

[0124] Comparative Example 2

[0125] A PLA coating composite material, compared with Example 1, differs only in that the heat-resistant compatibilizer in Example 1 is replaced with an equal weight of the product obtained from Comparative Example 2.

[0126] Comparative Example 3

[0127] A PLA coating composite material, compared with Example 1, differs only in that the heat-resistant compatibilizer in Example 1 is replaced with an equal weight of the product obtained from Comparative Example 3.

[0128] Comparative Example 4

[0129] A PLA coating composite material, which differs from Example 1 only in that the heat-resistant compatibilizer in Example 1 is removed.

[0130] Comparative Example 5

[0131] A PLA coating composite material, which differs from Example 1 only in that the cationized filler in Example 1 is removed.

[0132] Comparative Example 6

[0133] A PLA coating composite material, compared with Example 1, differs only in that the cationic filler in Example 1 is removed and the heat-resistant compatibilizer is replaced with an equal weight of the product obtained in Comparative Example 3.

[0134] Performance testing:

[0135] (1) The PLA coating composite materials obtained in Examples 1-9 and Comparative Examples 1-6 were subjected to microcalorie softening point test. The sample size was 10×10×4mm. The heating medium was phenylmethyl silicone oil. According to GB / T1633-2000 standard, the heating rate was 120℃ / h, the load was 10N, and the deformation was 1.00mm.

[0136] (2) The PLA coating composite materials obtained in Examples 1-9 and Comparative Examples 1-6 were added to a casting machine for coating experiments. Wood pulp paper (pure wood pulp cup paper, basis weight 200 g / m²) was used. 2 Guangzhou Juchen Trading Co., Ltd. uses the base paper to obtain coated paper through extrusion casting. The set temperature of the casting machine is as follows: the temperature of the first to fifth zones of the main machine is 80℃, 120℃, 160℃, 190℃, and 190℃, the temperature of the first to fifth zones of the die head is 200℃, the main machine screw speed is 200rpm, the traction rate is 8m / min, and the coating thickness is controlled at 50μm.

[0137] The tensile strength and elongation at break of the coated paper were tested according to GB / T1010.3-2006 standard.

[0138] The peel strength between the coating layer and the base paper was tested using an MK-90X electric peel strength tester, referring to GB / T8808-1988 "Peel Test Method for Flexible Composite Plastic Materials" (Method A). Each sample was tested three times, and the average value was recorded as 1.

[0139] The results are shown in Table 1:

[0140] Table 1. Statistical table of relevant performance tests of PLA coated composite materials and coated paper in the examples and comparative examples.

[0141]

[0142] As can be seen from the data recorded in Table 1, the Vicat softening temperature of the PLA coated composite materials obtained in Examples 1-9 is 118.7-120.6℃. Compared with Comparative Examples 1-6, the heat resistance is significantly improved. The tensile strength, elongation at break and peel strength of the obtained coated paper are also better than those of the comparative examples, indicating that the PLA coated composite material provided by the present invention has good temperature resistance, mechanical properties and bonding properties.

[0143] Specifically, the test results of Examples 1, 4, 5 and Comparative Examples 1, 2 and 3 show that, compared with using the products prepared in Comparative Examples 1-3 as compatibilizers, the products prepared in Examples 1-3 are more conducive to obtaining PLA film composite materials with heat resistance, high mechanical properties and bonding properties.

[0144] As can be seen from the test results of Examples 1, 4, 5 and 6, omitting the heat-resistant compatibilizer or cationic filler in this application, or using conventional compatibilizer, is not conducive to obtaining high-performance PLA coating composite materials.

[0145] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0146] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PLA coating composite material, characterized in that, Including the following parts by weight of raw materials: 70-80 parts of polylactic acid; 20-30 parts of bio-based toughening component; 15-25 parts of cationized filler; 2-4 parts of heat-resistant compatibilizer; The heat-resistant compatibilizer is a terpolymer formed by norbornene imide, 1,6-hexanediol diacrylate and glycidyl methacrylate. The ratio of norborneol imide, 1,6-hexanediol diacrylate, and glycidyl methacrylate is 3-6 g: 0.004-0.005 mol: 0.015-0.018 mol; The raw materials for preparing norbornyl imide include norbornyl anhydride and aminophenol compounds, with a molar ratio of norbornyl anhydride to aminophenol compounds of 1:1; The bio-based toughening component is polybutylene terephthalate and / or polycaprolactone.

2. The PLA coating composite material according to claim 1, characterized in that, The PLA coating composite material also includes 1 part by weight of nucleating agent TMC-300 and 0.3-1 part by weight of lubricant.

3. The PLA coating composite material according to claim 1, characterized in that, The aminophenolic compound is at least one of p-aminophenol, 4-amino-3-ethylphenol, 3-amino-5-fluorophenol, and 2-(3,4-dihydroxyphenyl)ethylamine.

4. The PLA coating composite material according to claim 3, characterized in that, The preparation steps of the norborneol imide are as follows: Add norbornyl olefinic anhydride and glacial acetic acid to a flask, stir well, then add an aminophenol compound. Stir at room temperature for 2 hours, then heat to 120°C and react for 6-8 hours. Collect the water produced by the reaction using a water separator. After the reaction is complete, remove the glacial acetic acid by rotary evaporation to obtain norbornyl imide.

5. The PLA coating composite material according to claim 1, characterized in that, The preparation steps for the heat-resistant compatibilizer are as follows: Toluene was added to a flask, and the temperature was raised to 75°C under nitrogen protection. Azobisisobutyronitrile, α-methylstyrene dimer, norbornene imide, 1,6-hexanediol diacrylate, and glycidyl methacrylate were mixed evenly to obtain mixture a. Mixture a was added dropwise to the flask while stirring. After the addition was complete, the reaction was kept at the temperature for 6-8 hours. After the reaction was completed, the reaction product was poured into anhydrous ethanol to precipitate flocculent material. The mixture was filtered, and the filter cake was washed three times with anhydrous ethanol and acetone, and then dried under vacuum at 50°C for 12 hours to obtain a heat-resistant compatibilizer.

6. The PLA coating composite material according to claim 5, characterized in that, The amount of azobisisobutyronitrile used is 4-5% of the total mass of norbornene imide, 1,6-hexanediol diacrylate and glycidyl methacrylate, and the amount of α-methylstyrene dimer is 20% of the mass of azobisisobutyronitrile.

7. The PLA coating composite material according to claim 1, characterized in that, The cationic filler is an inorganic filler modified with a cationic surfactant, and the amount of cationic surfactant used is 2-5% of the mass of the inorganic filler.

8. The PLA coating composite material according to claim 7, characterized in that, The cationic surfactant is at least one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

9. A method for preparing a PLA coating composite material, characterized in that, The method for preparing the PLA coating composite material according to claim 2 includes the following steps: Polylactic acid, bio-based toughening components, and heat-resistant compatibilizers were dried at 60°C for 12 hours. After drying, they were mixed evenly and added to a twin-screw extruder. Nucleating agent TMC-300, cationic filler, and lubricant were added to the twin-screw extruder. The mixture was then blended, extruded, and granulated to obtain PLA coating composite material.

10. The use of the PLA coating composite material as described in any one of claims 1-8 in the preparation of heat-resistant coated paper products.

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