Heat-resistant biodegradable film-making material and production process thereof

Abstract

The invention discloses a heat-resistant biodegradable film-making material, which is prepared from the following ingredients in parts by mass: 30 to 60 parts of modified polylactic acid, 20 to 35 parts of toughening agents, 10 to 18 parts of multifunctional modifiers, 0.4 to 1.4 parts of nucleating agents, 3 to 5 parts of plasticizers and 0.3 to 0.8 part of bio-based chain extenders. 0.3-10 parts of a composite heat stabilizer and 4-15 parts of an antibacterial agent; the modified polylactic acid is prepared from the following components in parts by mass: 35 to 50 parts of polylactic acid, 5 to 25 parts of polypropylene carbonate, 1 to 6 parts of micromolecular compatilizer and 0.2 to 2 parts of initiator. And the modified polylactic acid improves the biodegradation rate. The heat-resistant biodegradable film-making material disclosed by the invention has excellent temperature resistance, degradability, mechanical strength and toughness, can be widely applied to various industries, and has good application and market prospects. The invention also discloses a production process of the heat-resistant biodegradable film-making material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of film-making materials, in particular to a heat-resistant biodegradable film-making material and a production process thereof. BACKGROUND

[0002] Vacuum packaging technology plays an irreplaceable role in the fields of food, clothing, medicine, electronics, etc. due to its excellent oxygen barrier, moisture-proof and fresh-keeping performance. As the core carrier of vacuum packaging, the performance of vacuum bag material directly determines the reliability and applicability of the packaging.

[0003] At present, the existing vacuum bag material is mostly based on polyethylene (PE), polypropylene (PP) or polyvinyl chloride (PVC) as the base resin. Although these materials have certain processing convenience and cost advantage, they have defects and limitations: insufficient heat resistance: the softening point of traditional materials (such as PE) is relatively low (usually < 120℃), and deformation or thermal decomposition easily occurs in high-temperature sterilization or heat sealing process; environmental protection and health risk: a large amount of plasticizer (such as phthalate) needs to be added in PVC processing, which has migration risk and does not meet the safety requirements of food contact materials.

[0004] In view of the above problems, the existing technology attempts to improve the material performance through blending modification, nano-filling or surface coating, etc. For example: heat-resistant modification: inorganic fillers or crosslinking agents are introduced to improve the thermal stability, but excessive addition will deteriorate the flexibility and transparency of the material; environmentally friendly alternative materials: biobased materials such as polylactic acid (PLA) are explored, but their heat resistance, moisture resistance and mechanical strength still cannot meet the stringent requirements of vacuum bags. In addition, the scheme of improving the sealing performance of the material by modifying with organosilicon in the existing technology often causes interface delamination due to poor compatibility of organosilicon with the substrate, or relies on high-cost chemical grafting process, which is difficult to realize large-scale application. Therefore, it is urgent to develop a vacuum bag film material with excellent heat resistance, strong mechanical properties and environmental protection, and to break through the bottleneck of simultaneous optimization of processability, cost and performance in the existing modification technology, in order to meet the urgent needs of diversified application scenarios for high-performance vacuum packaging.

[0005] In summary, the heat resistance of the existing PLA film material can be realized by mixing with biodegradable resins with a higher softening point such as PBS, and on the other hand, the crystallization process is combined. However, in the actual application process, there are also problems such as high price of PBS, high total migration amount of PBS food simulant, low efficiency of crystallization process and unstable product performance. Therefore, how to provide a low-cost, high-efficiency and degradable heat-resistant polylactic acid pipe material is a problem to be solved. SUMMARY

[0006] The present application aims to solve the problems raised in the background art and provide a heat-resistant biodegradable film-making material and a production process thereof.

[0007] To solve the above technical problems, the technical scheme of the present application is: a heat-resistant biodegradable film material, characterized in that it comprises the following components in parts by mass:

[0008] modified polylactic acid 30-60 parts, toughening agent 20-35 parts, multifunctional modifier 10-18 parts, nucleating agent 0.4-1.4 parts, plasticizer 3-5 parts, bio-based chain extender 0.3-0.8 parts, composite heat stabilizer 0.3-10 parts, antibacterial agent 4-15 parts;

[0009] The modified polylactic acid comprises the following components in parts by mass: polylactic acid 35-50 parts, polypropylene carbonate 5-25 parts, small molecule compatibility agent 1-6 parts, initiator 0.2-2 parts. The modified polylactic acid improves the biodegradation rate.

[0010] In the above-mentioned heat-resistant biodegradable film material, the polylactic acid is at least two of left-handed polylactic acid (PLLA), right-handed polylactic acid (PDLA), and stereocomplex polylactic acid (SC-PLA).

[0011] In the above-mentioned heat-resistant biodegradable film material, the toughening agent is polybutylene adipate / terephthalate (PBAT). It provides excellent flexibility and impact resistance, ensuring that the film material does not crack when vacuumized as a bag.

[0012] In the above-mentioned heat-resistant biodegradable film material, the multifunctional modifier is polyhydroxyalkanoate (PHBV). It improves the compatibility of modified polylactic acid and PBAT. PHBV itself has better heat resistance than polylactic acid (thermal deformation temperature can reach more than 120℃), which can improve the overall heat resistance. It significantly promotes the start-up speed of biodegradation in natural / soil environment.

[0013] In the above-mentioned heat-resistant biodegradable film material, the nucleating agent is talc. It can greatly improve the crystallinity and crystallization rate of modified polylactic acid, greatly improve its thermal deformation temperature, and enable the film material to withstand the instantaneous high temperature of a vacuum sealer.

[0014] In the above-mentioned heat-resistant biodegradable film material, the plasticizer is at least one of acetyl tri-butyl citrate (ATBC) and polyethylene glycol (PEG). It improves processing fluidity and low-temperature toughness.

[0015] In the above-mentioned heat-resistant biodegradable film material, the composite heat stabilizer is at least two of 2,6-di-tert-butyl-4-methylphenol, octylated diphenylamine, polycarbodiimide, N-phenyl-N'-isopropyl-p-phenylenediamine, distearyl thiodipropionate, dilauryl thiodipropionate, and tris(nonylphenyl) phosphite.

[0016] In the heat-resistant biodegradable film material, the antibacterial agent is at least one of artemisinin, lignin, catechol, acetylated chitin, chlorogenic acid, dihydromyricetin, baicalin, lotus leaf base, pyrroloquinoline quinone.

[0017] In the heat-resistant biodegradable film material, the bio-based chain extender is at least one of bio-based isocyanate and bio-based diol / amine. The bio-based chain extender repairs and modifies the molecular chain rupture of the modified polylactic acid and the toughening agent caused by trace moisture during processing, improves the melt strength and mechanical properties of the film, and indirectly benefits the heat resistance.

[0018] The application also provides a production process of the heat-resistant biodegradable film material, comprising the following steps:

[0019] (1) drying the modified polylactic acid at 60-100 DEG C for 8-24h;

[0020] (2) weighing the components of the modified polylactic acid and the toughening agent according to the mass fraction, and mixing them in a high-speed mixer at room temperature for 5-8 minutes;

[0021] (3) weighing the components of the multifunctional modifier, the nucleating agent, the plasticizer, the compatibilizer, the bio-based chain extender, the composite heat stabilizer and the antibacterial agent according to the mass fraction, and then mixing them in the high-speed mixer at room temperature for 10-15 minutes;

[0022] (4) melting and blending the uniformly mixed raw materials in the step (3) in a screw extruder with a length-diameter ratio of 60:1, the operating temperature of each temperature zone of the extruder is 160-180 DEG C, the screw rotation speed is 300-600 Hz, and the modified resin for preparing the heat-resistant biodegradable film material is obtained by cooling, drawing and granulating;

[0023] (5) vacuum drying the modified resin obtained in the step (4) at 60-80 DEG C for 5-10h;

[0024] (6) melting and processing the modified resin after the drying treatment in the step (5) as a master batch in an extruder with a compression ratio of (30-50):1, and then film forming through a die;

[0025] (7) pre-setting the extruded film by a rapid cooling system and a traction machine for cooling, stretching and orientation, the temperature of the cooling medium is 15-25 DEG C, the cooling time is 5-15s, and the drawing speed is 1-5m / s;

[0026] (8) After the stretching, the film material is fixed on the microwave heating device for annealing and recrystallization. The original molecular chain segment is disoriented by the microwave effect, the non-uniform crystal is disintegrated and rearranged to form more dense alpha crystal, which can significantly improve the mechanical strength and temperature resistance of the film material. The microwave heating temperature is 40-60 DEG C, and the heating time is 5-15 s;

[0027] (9) After the microwave annealing and recrystallization, the film material is again subjected to the secondary shaping after crystallization by the rapid cooling system and the stretching system in step (6). The cooling medium temperature is 10-20 DEG C, the cooling time is 5-15 s, and the stretching rate is 1-5 m / s.

[0028] (10) After the film material is cut to a fixed length and air dried, the heat-resistant biodegradable film material is obtained.

[0029] The present application has the following advantages:

[0030] (1) The heat-resistant biodegradable film material has excellent temperature resistance, degradation, good mechanical strength, toughness and processing characteristics, and can be widely used in various industries, and has good application and market prospect.

[0031] (2) The present application solves the problems of poor temperature resistance and low mechanical strength of polylactic acid by combining functional modification, rapid cooling, microwave annealing and recrystallization, and stretching orientation of polylactic acid, and the process is simple and the production efficiency is high.

[0032] (3) The main raw material of the present application is derived from natural renewable resources, which is widely available and green and environmentally friendly. The heat-resistant biodegradable film material can be directly composted into biomass after the use period, and carbon dioxide and water, which has no pressure on the environment. BRIEF DESCRIPTION OF DRAWINGS

[0033] Table 1 shows the composition of the heat-resistant biodegradable film material of examples 1-5.

[0034] Table 2 shows the temperature resistance, crystallinity, biodegradation rate, notched impact strength and tensile strength of the film material. DETAILED DESCRIPTION

[0035] The present application will be described in detail by specific embodiments. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. The composition of the heat-resistant biodegradable film material in examples 1-5 is shown in Table 1.

[0036] Table 1 shows the composition of the heat-resistant biodegradable film material of examples 1-5.

[0037]

[0038] Example 1:

[0039] A heat-resistant biodegradable film material, the raw material comprises the following components in mass fraction: modified polylactic acid 45.5 parts, toughening agent 20 parts, multifunctional modifier 12 parts, nucleating agent 0.5 parts, plasticizer 3 parts, bio-based chain extender 0.5 parts; composite heat stabilizer 4 parts, antibacterial agent 3 parts.

[0040] The modified polylactic acid is a cylindrical particle with an average particle size of 1.5 mm, and an intrinsic viscosity ([η]) of 2.5 dL / g.

[0041] The modified polylactic acid comprises PLLA 25 parts, SC-PLA 10 parts, polypropylene carbonate 8 parts, β-cyclodextrin 2 parts, and diisopropyl peroxydicarbonate 0.5 parts.

[0042] The preparation steps of the modified polylactic acid are as follows:

[0043] The PLLA, SC-PLA, polypropylene carbonate, β-cyclodextrin, and diisopropyl peroxydicarbonate are uniformly mixed in a mixer, and then added to a twin-screw extruder for melt grafting reaction, with an extrusion temperature of 160-180°C and a rotation speed of 300 rpm / min. After cooling, stretching, granulation and screening, the modified polylactic acid is obtained.

[0044] The auxiliary materials specifically include polybutylene adipate terephthalate (PBAT) 20 parts, polyhydroxyalkanoate (PHBV) 12 parts, talc 0.5 parts, acetyl tri-butyl citrate (ATBC) 3 parts, and bio-based isocyanate 0.5 parts; 2,6-di-tert-butyl-4-methylphenol 4 parts, and artemisinin 3 parts

[0045] The production process of the heat-resistant biodegradable film material is as follows:

[0046] (1) The modified polylactic acid is dried at 60°C for 12h.

[0047] (2) The components of the modified polylactic acid, the toughening agent, and the selection of the mass fraction are weighed, and placed in a high-speed mixer at room temperature for 6 minutes;

[0048] (3) The components of the multifunctional modifier, the nucleating agent, the plasticizer, the compatibilizer, the bio-based chain extender, the composite heat stabilizer, and the antibacterial agent are weighed according to the mass fraction, and then placed in a high-speed mixer with the materials in step (2) at room temperature for 12 minutes;

[0049] (4) The uniformly mixed raw materials in step (3) are added to a screw extruder with a length-diameter ratio of 60:1 for melt blending, with an operating temperature of 160-180°C in each temperature zone of the extruder, and a screw rotation speed of 400 Hz. After cooling, stretching, and granulation, the modified resin for making heat-resistant biodegradable film material is obtained;

[0050] (5) The modified resin obtained in step (4) is vacuum dried at 70°C for 6 hours.

[0051] (6) The modified resin after drying in step (5) is used as the masterbatch and melted in an extruder with a compression ratio of 30:1. Then, the film is extruded through the die.

[0052] (7) The extruded film is cooled and stretched and pre-oriented by a rapid cooling system and a traction machine, so that the internal molecular orientation of the film is arranged and shaped. The cooling medium temperature is 18℃, the cooling time is 10s, and the stretching rate is 3m / s.

[0053] (8) After stretching, the membrane material is fixed on a microwave heating device for annealing and recrystallization. The microwave action causes the original molecular chain segments to deorient, and the non-uniform crystals to disintegrate and rearrange to form a denser α crystal, which can significantly improve the mechanical strength and temperature resistance of the membrane material. The microwave heating temperature is 60℃ and the heating time is 20s.

[0054] (9) After microwave annealing and recrystallization, the film material is subjected to secondary shaping after crystallization by passing it through the rapid cooling system and stretching system in step (6). The cooling medium temperature is 15℃, the cooling time is 8s, and the stretching rate is 2m / s.

[0055] (10) After cutting the membrane material to a fixed length and air-drying it, the heat-resistant biodegradable membrane material is obtained.

[0056] Example 2:

[0057] A heat-resistant biodegradable film-forming material, the raw materials of which include the following components in parts by weight: 46.5 parts modified polylactic acid, 30 parts toughening agent, 15 parts multifunctional modifier, 0.5 parts nucleating agent, 3 parts plasticizer, 1.5 parts bio-based chain extender; 6 parts composite heat stabilizer, and 3 parts antibacterial agent.

[0058] The modified polylactic acid is cylindrical particles with an average particle size of 1.5 mm and an intrinsic viscosity ([η]) of 3 dL / g.

[0059] The modified polylactic acid comprises 25 parts of PLLA, 10 parts of SC-PLA, 9 parts of polypropylene carbonate, 2 parts of β-cyclodextrin, and 0.5 parts of diisopropyl peroxide.

[0060] The preparation steps of the modified polylactic acid are as follows:

[0061] The PLLA, SC-PLA, polypropylene carbonate, β-cyclodextrin, and diisopropyl peroxydicarbonate are mixed uniformly in a mixer, and then added to a twin-screw extruder for melt grafting reaction. The extrusion temperature is 160-180°C, and the rotation speed is 300 rpm / min. After cooling, stretching, granulation, and screening, the modified polylactic acid is obtained.

[0062] The auxiliary materials specifically include polybutylene adipate terephthalate (PBAT) 30 parts, polyhydroxyalkanoate (PHBV) 15 parts, talc 0.5 part, acetyl tri-butyl citrate (ATBC) 3 parts, and bio-based isocyanate 1.5 parts; 2,6-di-tert-butyl-4-methylphenol 5 parts, and artemisinin 3 parts.

[0063] The production process of the heat-resistant biodegradable film material is as follows:

[0064] (1) The modified polylactic acid is dried at 60°C for 12 hours.

[0065] (2) The components of the modified polylactic acid, the toughening agent, and the selection of the components are weighed according to the mass fraction, and are mixed in a high-speed mixer at room temperature for 6 minutes;

[0066] (3) The components of the multifunctional modifier, the nucleating agent, the plasticizer, the compatibilizer, the bio-based chain extender, the composite heat stabilizer, and the antibacterial agent are weighed according to the mass fraction, and then are placed in a high-speed mixer with the materials in step (2) at room temperature for 12 minutes;

[0067] (4) The uniformly mixed raw materials in step (3) are added to a screw extruder with a length-diameter ratio of 60:1 for melt blending. The operating temperature of each temperature zone of the extruder is 160-180°C, and the screw rotation speed is 400 Hz. After cooling, stretching, and granulation, the modified resin for making heat-resistant biodegradable film material is obtained;

[0068] (5) The modified resin obtained in step (4) is vacuum dried at 70°C for 6 hours;

[0069] (6) The modified resin after drying treatment in step (5) is used as a master batch and is fed into an extruder with a compression ratio of 30:1 for melt processing. Then, the film material is extruded through a die.

[0070] (7) The extruded film material is cooled, stretched, and oriented by a rapid cooling system and a traction machine to make the molecules in the film material orient and arrange, and the cooling medium temperature is 18°C, the cooling time is 10 seconds, and the stretching rate is 3 m / s.

[0071] (8) After the stretching is completed, the film material is fixed on the microwave heating device for annealing and recrystallization. The original molecular chain segment is disoriented by the microwave action, the non-uniform crystal is disintegrated and rearranged to form a more dense alpha crystal, which can significantly improve the mechanical strength and temperature resistance of the film material. The microwave heating temperature is 60°C, and the heating time is 20s;

[0072] (9) After the microwave annealing and recrystallization are completed, the film material is again subjected to the secondary shaping after crystallization by the rapid cooling system and the stretching system in step (6). The cooling medium temperature is 15°C, the cooling time is 8s, and the stretching rate is 2m / s.

[0073] (10) After the film material is cut to a fixed length and air-dried, the heat-resistant biodegradable film material is obtained.

[0074] Example 3:

[0075] A heat-resistant biodegradable film material, the raw materials comprising the following components in mass fraction: modified polylactic acid 51.5 parts, toughening agent 25 parts, multifunctional modifier 10 parts, nucleating agent 0.4 parts, plasticizer 5 parts, bio-based chain extender 1.2 parts; composite heat stabilizer 4 parts, antibacterial agent 2 parts.

[0076] The modified polylactic acid is a cylindrical particle with an average particle size of 2mm, and a characteristic viscosity ([η]) of 3dL / g.

[0077] The modified polylactic acid comprises PLLA 25 parts, PDLA 15 parts, polypropylene carbonate 8 parts, triethyl citrate 0.5 parts, β-cyclodextrin 2.5 parts, azobiscyclohexyl nitrile 0.2 parts, and diisopropyl peroxydicarbonate 0.3 parts.

[0078] The preparation steps of the modified polylactic acid are as follows:

[0079] The PLLA, PDLA, polypropylene carbonate, triethyl citrate, β-cyclodextrin, azobiscyclohexyl nitrile, and diisopropyl peroxydicarbonate are uniformly mixed in a mixer, and then added to a twin-screw extruder for melt grafting reaction. The extrusion temperature is 160-180°C, and the rotation speed is 300rpm / min. After cooling, stretching, granulation and screening, the modified polylactic acid is obtained.

[0080] The auxiliary materials specifically include polybutylene adipate / terephthalate (PBAT) 25 parts, polyhydroxyalkanoate (PHBV) 10 parts, talc 0.4 parts, acetyl triethyl citrate (ATBC) 2 parts, polyethylene glycol (PEG) 2 parts, bio-based isocyanate 0.4 parts, bio-based diol / amine 0.2 parts, 2,6-di-tert-butyl-4-methylphenol 4 parts, and artemisinin 2 parts.

[0081] The production process of the heat-resistant biodegradable film material is as follows:

[0082] (1) The modified polylactic acid is dried at 60°C for 12h.

[0083] (2) The components of the modified polylactic acid, the toughening agent, and the component composition selection are weighed according to the mass fraction, and placed in a high-speed mixer at room temperature for 6 minutes;

[0084] (3) The components of the multifunctional modifier, the nucleating agent, the plasticizer, the compatibilizer, the bio-based chain extender, the composite heat stabilizer, and the antibacterial agent are weighed according to the mass fraction, and then placed in a high-speed mixer at room temperature for 12 minutes with the materials in step (2);

[0085] (4) The uniformly mixed raw materials in step (3) are added to a screw extruder with a length-diameter ratio of 60:1 for melt blending, the operating temperature of each temperature zone of the extruder is 160-180°C, the screw rotation speed is 400Hz, and the modified resin for making heat-resistant biodegradable film materials is obtained after cooling, drawing, and granulating;

[0086] (5) The modified resin obtained in step (4) is vacuum dried at 70°C for 6h;

[0087] (6) The modified resin after drying treatment in step (5) is used as a master batch and is fed into an extruder with a compression ratio of 30:1 for melt processing, and then a film material is extruded through a die.

[0088] (7) The extruded film material is cooled, stretched, and oriented by a rapid cooling system and a traction machine to make the molecules in the film material orient and arrange, the cooling medium temperature is 18°C, the cooling time is 10s, and the stretching rate is 3m / s;

[0089] (8) After the stretching is completed, the film material is fixed on a microwave heating device for annealing and recrystallization, the microwave action makes the original molecular chain segments de-orient, the non-uniform crystals disintegrate and rearrange to form more dense α crystals, which can significantly improve the mechanical strength and temperature resistance of the film material, the microwave heating temperature is 60°C, and the heating time is 20s;

[0090] (9) After the microwave annealing and recrystallization are completed, the film material is again subjected to secondary setting after crystallization by the rapid cooling system and the stretching system in step (6). The cooling medium temperature is 15°C, the cooling time is 8s, and the stretching rate is 2m / s.

[0091] (10) After the film material is cut to a fixed length and air dried, the heat-resistant biodegradable film material is obtained.

[0092] Example 4:

[0093] A heat-resistant biodegradable film forming material, the raw material comprises the following components in mass fraction: modified polylactic acid 37.5 parts, toughening agent 20 parts, multifunctional modifier 12 parts, nucleating agent 0.5 parts, plasticizer 3 parts, composite thermal stabilizer 4 parts, antibacterial agent 5 parts.

[0094] The modified polylactic acid is a cylindrical particle with an average particle size of 1 mm and an intrinsic viscosity ([eta]) of 1.5 dL / g.

[0095] The modified polylactic acid comprises PLLA 20 parts, SC-PLA 8 parts, polypropylene carbonate 6 parts, beta-cyclodextrin 2 parts, and diisopropyl peroxydicarbonate 0.5 parts.

[0096] The preparation steps of the modified polylactic acid are as follows:

[0097] The PLLA, SC-PLA, polypropylene carbonate, beta-cyclodextrin, and diisopropyl peroxydicarbonate are uniformly mixed in a mixer, and then added to a twin-screw extruder for melt grafting reaction, with an extrusion temperature of 160-180°C and a rotation speed of 300 rpm / min. After cooling, stretching, granulation and screening, the modified polylactic acid is obtained.

[0098] The auxiliary materials specifically include polybutylene adipate terephthalate (PBAT) 20 parts, polyhydroxyalkanoate (PHBV) 12 parts, talc 0.5 parts, acetyl tri-butyl citrate (ATBC) 3 parts, 2,6-di-tert-butyl-4-methylphenol 4 parts, and artemisinin 5 parts.

[0099] The production process of the heat-resistant biodegradable film forming material is as follows:

[0100] (1) The modified polylactic acid is dried at 60°C for 12 hours.

[0101] (2) The components of the modified polylactic acid and the toughening agent are weighed according to the mass fraction, and mixed in a high-speed mixer at room temperature for 6 minutes;

[0102] (3) The components of the multifunctional modifier, nucleating agent, plasticizer, compatibilizer, bio-based chain extender, composite thermal stabilizer, and antibacterial agent are weighed according to the mass fraction, and then mixed with the materials in step (2) in a high-speed mixer at room temperature for 12 minutes;

[0103] (4) The uniformly mixed raw materials in step (3) are added to a screw extruder with a length-diameter ratio of 60:1 for melt blending, with an operating temperature of 160-180°C in each temperature zone of the extruder and a screw rotation speed of 400 Hz. After cooling, stretching, and granulation, the modified resin for making heat-resistant biodegradable film forming material is obtained;

[0104] (5) The modified resin obtained in step (4) is vacuum dried at 70°C for 6h;

[0105] (6) The modified resin after drying treatment in step (5) is used as a master batch and fed into an extruder with a compression ratio of 30:1 for melt processing, and then a film material is extruded through a die.

[0106] (7) The extruded film material is cooled and stretched by a rapid cooling system and a traction machine to orient and arrange the molecules in the film material, the cooling medium temperature is 18°C, the cooling time is 10s, and the stretching rate is 3m / s.

[0107] (8) After the stretching is completed, the film material is fixed on a microwave heating device for annealing and recrystallization, the original molecular chain segments are disoriented by the microwave action, the non-uniform crystals are disintegrated and rearranged to form more compact α crystals, which can significantly improve the mechanical strength and temperature resistance of the film material, the microwave heating temperature is 60°C, and the heating time is 20s.

[0108] (9) After the microwave annealing and recrystallization are completed, the film material is again subjected to secondary setting after crystallization by the rapid cooling system and the stretching system in step (6). The cooling medium temperature is 15°C, the cooling time is 8s, and the stretching rate is 2m / s.

[0109] (10) After the film material is cut to a fixed length and air dried, the heat-resistant biodegradable film material is obtained.

[0110] Example 5:

[0111] A heat-resistant biodegradable film material, the raw materials comprising the following components in mass fraction: modified polylactic acid 35 parts, multifunctional modifier 12 parts, nucleating agent 0.5 parts, plasticizer 3 parts, composite thermal stabilizer 4 parts, and antibacterial agent 5 parts.

[0112] The modified polylactic acid is a cylindrical particle with an average particle size of 0.8mm and a characteristic viscosity ([η]) of 1dL / g.

[0113] The modified polylactic acid comprises PLLA 25 parts and SC-PLA 10 parts.

[0114] The preparation steps of the modified polylactic acid are as follows:

[0115] The PLLA and SC-PLA are uniformly mixed in a mixer, and then fed into a twin-screw extruder for melt grafting reaction, the extrusion temperature is 160-180°C, and the rotation speed is 300rpm / min. After cooling, stretching, granulation and screening, the modified polylactic acid is obtained.

[0116] Auxiliary materials specifically, polyhydroxyalkanoate (PHBV) 12 parts, talc 0.5 parts, acetyl tri-butyl citrate (ATBC) 3 parts, 2,6-di-tert-butyl-4-methylphenol 4 parts, artemisinin 5 parts.

[0117] The production process of the heat-resistant biodegradable film material comprises the following steps:

[0118] (1) The modified polylactic acid is dried at 60℃ for 12h.

[0119] (2) The components of the modified polylactic acid, the toughening agent, and the components of the selection by mass are weighed, and then placed in a high-speed mixer at room temperature for 6 minutes;

[0120] (3) The components of the multifunctional modifier, the nucleating agent, the plasticizer, the compatibilizer, the bio-based chain extender, the composite heat stabilizer, and the antibacterial agent are selected by mass, and then placed in a high-speed mixer at room temperature for 12 minutes;

[0121] (4) The uniformly mixed raw materials in step (3) are added to a screw extruder with a length-diameter ratio of 60:1 for melt blending, the operating temperature of each temperature zone of the extruder is 160-180℃, the screw rotation speed is 400Hz, and the modified resin for making heat-resistant biodegradable film material is obtained after cooling, drawing, and granulating;

[0122] (5) The modified resin obtained in step (4) is vacuum dried at 70℃ for 6h;

[0123] (6) The modified resin after drying treatment in step (5) is used as a master batch and is fed into an extruder with a compression ratio of 30:1 for melt processing, and then a film material is extruded through a die.

[0124] (7) The extruded film material is cooled, stretched, and oriented by a rapid cooling system and a traction machine, the internal molecular orientation and arrangement of the film material are preset and fixed, the cooling medium temperature is 18℃, the cooling time is 10s, and the drawing rate is 3m / s;

[0125] (8) After the drawing is completed, the film material is fixed on a microwave heating device for annealing and recrystallization, the original molecular chain segments are disoriented by microwave action, the non-uniform crystals are disintegrated and rearranged to form more dense α crystals, which can significantly improve the mechanical strength and temperature resistance of the film material, the microwave heating temperature is 60℃, and the heating time is 20s;

[0126] (9) After the microwave annealing and recrystallization are completed, the film material is again subjected to secondary setting after crystallization by the rapid cooling system and the stretching system in step (6). The cooling medium temperature is 15℃, the cooling time is 8s, and the drawing rate is 2m / s.

[0127] (10) The film material is cut to a fixed length and air-dried to obtain the heat-resistant biodegradable film material.

[0128] The biodegradable film material was prepared according to the materials and methods of Examples 1-5, and then the film material was subjected to a compost degradation test under laboratory simulation conditions, a deformation test in hot water to measure the temperature resistance of the film material, a differential scanning calorimeter test and calculation of the crystallinity of the film material, and a tensile strength test and a notched impact strength test of the pressed sheet sample according to GB / T 1040.2-2006 "Determination of the tensile properties of plastics - Part 2: test conditions for moulded and extruded plastics" and GB / T 1843-2008 "Plastics: Determination of Charpy Impact Strength". The results of the temperature resistance, crystallinity, biodegradation rate, notched impact strength and tensile strength tests are shown in Table 2.

[0129] Table 2 Temperature resistance, crystallinity, biodegradation rate, notched impact strength and tensile strength of the film material

[0130]

[0131] The relative biodegradation rate of the film material in Examples 1-5 within six months was more than 90%, the film material in Examples 1-3 was subjected to a drawing and microwave high-efficiency crystallization process, and the crystallinity was more than 35%, the film material could be stirred in hot water at a temperature of at least 75°C without deformation, the heat resistance temperature was as high as 85°C, and the notched impact strength and tensile strength were relatively high, which could meet the requirements. Among them, the amount of toughening agent, multifunctional modifier and bio-based chain extender in Example 2 was relatively high, and compared with Examples 1 and 2, the notched impact strength and tensile strength of the film material and the temperature resistance effect were better. In Example 4, no polypropylene carbonate and bio-based chain extender was added to the modified polylactic acid in Example 1, and the crystallinity of the film material was relatively low, the temperature resistance, biodegradation rate, notched impact strength and tensile strength were all decreased. In Example 5, no small molecule compatibilizer, initiator and toughening agent was added, the crystallinity of the film material was relatively low, the temperature resistance, notched impact strength and tensile strength were all lower.

[0132] The above describes in detail a heat-resistant biodegradable film material and its production process provided by the embodiments of the present application. In this paper, specific examples are applied to describe the principles and implementation methods of the present application. The above examples are only used to help understand the technical solutions disclosed by the present application. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation methods and application scope will be changed, and the above description should not be understood as a limitation of the present application.

Claims

1. A heat-resistant biodegradable film-forming material, characterized by: The modified polylactic acid comprises the following components by mass fraction: The modified polylactic acid comprises the following components by mass fraction: polylactic acid 35-50 parts, polypropylene carbonate 5-25 parts, small molecule compatibilizer 1-6 parts, and initiator 0.2-2 parts. The poly-lactic acid is at least two of left-handed poly-lactic acid (PLLA), right-handed poly-lactic acid (PDLA), and stereocomplex poly-lactic acid (SC-PLA).

2. The heat resistant biodegradable film forming material according to claim 1, wherein: The toughening agent is polybutylene adipate terephthalate (PBAT).

3. The heat resistant biodegradable film forming material according to claim 1, wherein: The multifunctional modifier is polyhydroxyalkanoate (PHBV).

4. The heat resistant biodegradable film forming material according to claim 1, wherein: The nucleating agent is talc.

5. The heat resistant biodegradable film forming material according to claim 1, wherein The plasticizer is at least one of acetyl tri-butyl citrate (ATBC) and polyethylene glycol (PEG).

6. The heat resistant biodegradable film forming material according to claim 1, wherein: The composite heat stabilizer is at least two of 2,6-di-tert-butyl-4-methylphenol, octylated diphenylamine, polycarbodiimide, N-phenyl-N'-isopropyl-p-phenylenediamine, distearyl thiodipropionate, dilauryl thiodipropionate, and tris-nonylphenyl phosphite.

7. The heat resistant biodegradable film forming material according to claim 1, wherein: The antibacterial agent is at least one of artemisinin, lignin, catechol, acetylated chitin, chlorogenic acid, dihydro-myricetin, baicalin, lotus leaf base, and pyrroloquinoline quinone.

8. The heat resistant biodegradable film forming material according to claim 1, wherein: The bio-based chain extender is at least one of bio-based isocyanate and bio-based diol / amine.

9. The heat resistant biodegradable film forming material according to claim 1, wherein: The method comprises the following steps:

10. A production process of a heat-resistant biodegradable film forming material using any one of claims 1 to 8, characterized by: (1) drying the modified polylactic acid at 60-100°C for 8-24h; (2) weighing the components of the modified polylactic acid and the toughening agent according to the mass fraction, and mixing them in a high-speed mixer at room temperature for 5-8 minutes; (3) weighing the components of the multifunctional modifier, the nucleating agent, the plasticizer, the compatibilizer, the bio-based chain extender, the composite heat stabilizer, and the antibacterial agent according to the mass fraction, and then mixing them with the materials in step (2) in a high-speed mixer at room temperature for 10-15 minutes; (4) melting and blending the uniformly mixed raw materials in step (3) in a screw extruder with a length-diameter ratio of 60:1, the operating temperature of each temperature zone of the extruder is 160-180°C, the screw rotation speed is 300-600Hz, and the modified resin for making heat-resistant biodegradable film materials is obtained after cooling, drawing, and granulating; (5) vacuum drying the modified resin obtained in step (4) at 60-80°C for 5-10h; (6) melting and processing the modified resin after drying treatment in step (5) as a master batch in an extruder with a compression ratio of (30-50):1, and then film forming through a die; (7) pre-setting the extruded film by a rapid cooling system and a traction machine for cooling, stretching, and orientation, the cooling medium temperature is 15-25°C, the cooling time is 5-15s, and the drawing rate is 1-5m / s. ​ (8) After stretching, the membrane material is fixed on a microwave heating device for annealing and recrystallization. The microwave action causes the original molecular chain segments to deorient, and the non-uniform crystals to disintegrate and rearrange to form a denser α crystal, which can significantly improve the mechanical strength and temperature resistance of the membrane material. The microwave heating temperature is 40-60℃ and the heating time is 5-15s. (9) After microwave annealing and recrystallization, the film material is subjected to secondary shaping after crystallization by passing it through the rapid cooling system and stretching system in step (6). The cooling medium temperature is 10-20℃, the cooling time is 5-15s, and the stretching rate is 1-5m / s; (10) After cutting the membrane material to a fixed length and air drying, the heat-resistant biodegradable membrane material is obtained.

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