High-temperature-resistant in-situ polymerization coating degradable can packaging film and production process

Abstract

The application discloses a kind of high-temperature-resistant in-situ polymerization coating degradable can packaging film and production process, comprising: degradable substrate layer, the degradable substrate layer is made of biodegradable resin composition;High-temperature-resistant coating, the high-temperature-resistant coating is formed on the coating of at least one surface of degradable substrate layer by in-situ polymerization;Wherein, the high-temperature-resistant coating is formed by in-situ polymerization reaction of coating precursor solution on the surface of degradable substrate layer Dense coating, the beneficial effects of the present application are: by coating precursor solution of high-temperature-resistant polymer on the surface of degradable substrate, and directly initiate polymerization reaction to form coating on substrate surface, this in-situ polymerization makes coating polymer and substrate surface molecular chain form chemical bonding or strong interface interaction, significantly improve the adhesion of coating and substrate, realize no blistering, no peeling phenomenon after high-temperature cooking 30 minutes, solve the problem that coating is easily peeled off in traditional coating process.

Description

Technical Field

[0001] This invention relates to the field of biodegradable packaging materials technology, specifically to a high-temperature resistant in-situ polymerized coating biodegradable can packaging film and its production process. Background Technology

[0002] Canned food packaging is an important form of packaging in the food industry. Although traditional metal cans have good sealing and high temperature resistance, they have disadvantages such as being heavy, inconvenient to open, and not suitable for microwave heating. With the development of plastic packaging technology, more and more canned foods are beginning to use plastic packaging materials to replace traditional metal packaging. Currently, commonly used plastic can packaging materials mainly include polymer materials such as polypropylene (PP) and polyethylene terephthalate (PET).

[0003] However, traditional plastic packaging materials are difficult to degrade in the natural environment, and their disposal causes serious "white pollution" problems. With the increasing awareness of environmental protection and the implementation of plastic restriction policies in various countries, the development of degradable can packaging materials has become a research hotspot in the industry. Currently, the degradable packaging films available on the market mainly include biodegradable materials such as polylactic acid, poly(adipate-butyl terephthalate) copolymer, polycaprolactone, and polybutylene succinate. Although these materials can degrade in the natural environment, they have poor heat resistance and cannot meet the requirements of high-temperature cooking sterilization of canned food. Therefore, this application proposes a high-temperature resistant in-situ polymerized coating degradable can packaging film and its production process. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature resistant in-situ polymerized coating biodegradable can packaging film and its production process, in order to solve the problems mentioned in the background art, such as poor heat resistance and insufficient barrier properties of existing biodegradable packaging films, as well as the weak adhesion between the coating and the substrate and easy peeling in traditional coating processes.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-temperature resistant in-situ polymerized biodegradable can packaging film, comprising: A biodegradable substrate layer, said biodegradable substrate layer being made of a biodegradable resin composition; A high-temperature resistant coating, wherein the high-temperature resistant coating is formed on at least one surface of a biodegradable substrate layer by in-situ polymerization; The high-temperature resistant coating is formed by in-situ polymerization of a coating precursor solution on the surface of a degradable substrate layer to create a dense coating.

[0006] Preferably, the biodegradable resin composition is selected from one or more blends of PBAT, PLA, PCL, PBS, and PHA, and the blend further contains a reinforcing modifier selected from at least one of nanocellulose, nanomontmorillonite, and nanotitanium dioxide.

[0007] Preferably, the coating precursor solution comprises a polymerizable monomer or prepolymer, a crosslinking agent, and a solvent; the polymerizable monomer or prepolymer is selected from at least one of polyimide precursors, bio-based epoxy resin prepolymers, silicone precursors, and modified phenolic resin prepolymers.

[0008] A production process for a high-temperature resistant, in-situ polymerized, biodegradable can packaging film includes the following steps: S1. Preparation of biodegradable substrate layer: The biodegradable resin composition is melt-blended and then blown or cast to form a substrate film; S2. Preparation of coating precursor solution: Mix polymerizable monomers or prepolymers, crosslinking agents and solvents in proportion; S3. Coating and in-situ polymerization: The coating precursor solution prepared in step S2 is uniformly coated onto the surface of the substrate film obtained in step S1, and then heat-treated under specific temperature conditions to allow the coating precursor to undergo in-situ polymerization on the substrate surface to form a high-temperature resistant coating. S4. Post-processing: The coated film obtained in step S3 is cooled, drawn, and wound up to obtain the finished packaging film.

[0009] Preferably, the biodegradable resin composition in step S1 comprises: 50-80 parts by weight of PBAT, 10-30 parts by weight of PLA, 1-10 parts by weight of nanocellulose and 1-5 parts by weight of compatibilizer.

[0010] Preferably, the coating method in step S3 is selected from gravure coating, roller coating, spray coating, and dip coating, and the coating thickness is controlled to be 2-20μm.

[0011] Preferably, the gradient heating includes: S31, First temperature range: Treat at 80-120℃ for 5-15 minutes to allow partial evaporation of the solvent and initiate prepolymerization; S32, Second temperature zone: Treat at 120-160℃ for 10-20 minutes to allow the polymerization reaction to proceed fully; S33, Third temperature range: Treat at 160-200℃ for 5-10 minutes to allow the coating to fully cure and form a chemical bond with the substrate.

[0012] Preferably, in step S3, the surface of the substrate film is subjected to corona treatment or plasma treatment before coating, and humidity control is introduced during the coating process. By adjusting the ambient humidity to 40-80%RH, the sol-gel reaction of the coating precursor is induced.

[0013] Compared with the prior art, the beneficial effects of the present invention are: By coating a precursor solution of a high-temperature resistant polymer onto the surface of a biodegradable substrate and directly initiating a polymerization reaction on the substrate surface to form a coating, this in-situ polymerization method enables chemical bonding or strong interfacial interaction between the polymer in the coating and the molecular chains on the substrate surface, which significantly improves the adhesion between the coating and the substrate. This results in no bubbling or peeling after 30 minutes of high-temperature cooking, solving the problem of easy coating peeling in traditional coating processes. The gradient heating heat treatment process allows the coating precursor to gradually complete the polymerization reaction on the substrate surface, avoiding thermal damage to the biodegradable substrate caused by high-temperature instantaneous treatment. At the same time, the dense coating structure formed during the gradient heating process has excellent oxygen and water vapor barrier properties. By adding reinforcing modifiers such as nanocellulose, the mechanical properties and heat resistance of the biodegradable substrate itself are improved; by selecting appropriate coating materials and polymerization reaction types, the coating has excellent high-temperature resistance. Detailed Implementation

[0014] Exemplary embodiments will be described in detail below. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] This invention provides a technical solution: a high-temperature resistant in-situ polymerized biodegradable can packaging film, comprising: A biodegradable substrate layer, said biodegradable substrate layer being made of a biodegradable resin composition; A high-temperature resistant coating, wherein the high-temperature resistant coating is formed on at least one surface of a biodegradable substrate layer by in-situ polymerization; The high-temperature resistant coating is formed by in-situ polymerization of a coating precursor solution on the surface of a degradable substrate layer to create a dense coating.

[0016] A production process for a high-temperature resistant, in-situ polymerized, biodegradable can packaging film includes the following steps: S1. Preparation of biodegradable substrate layer: The biodegradable resin composition is melt-blended and then blown or cast to form a substrate film; S2. Preparation of coating precursor solution: Mix polymerizable monomers or prepolymers, crosslinking agents and solvents in proportion; S3. Coating and in-situ polymerization: The coating precursor solution prepared in step S2 is uniformly coated onto the surface of the substrate film obtained in step S1, and then heat-treated under specific temperature conditions to allow the coating precursor to undergo in-situ polymerization on the substrate surface to form a high-temperature resistant coating. S4. Post-processing: The coated film obtained in step S3 is cooled, drawn, and wound up to obtain the finished packaging film. Example

[0017] This embodiment provides a high-temperature resistant in-situ polymerized biodegradable can packaging film and its production process, as detailed below: Weigh out 70 parts PBAT, 20 parts PLA, 5 parts nanocellulose, and 3 parts compatibilizer (epoxidized soybean oil) by weight. Add the above raw materials to a high-speed mixer and mix evenly. Then place them in a twin-screw extruder for melt blending and extrusion. Control the extrusion temperature at 150-170℃ and the screw speed at 200rpm. After extrusion granulation, pass the granules through a casting machine at 170℃ to form a substrate film with a thickness of 80μm. Pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) were added to N-methylpyrrolidone (NMP) at a molar ratio of 1.02:1. The mixture was stirred and reacted at 0-5°C for 4 hours under nitrogen protection to obtain a polyamic acid solution with a solid content of 15%, which is a polyimide precursor solution. The surface of the prepared substrate film was subjected to corona treatment at a power of 3kW and a speed of 20m / min. The prepared polyamic acid solution was uniformly coated onto the corona-treated substrate film surface using a gravure coating method, with the coating thickness controlled at 8μm. The coated substrate film was then placed in a gradient temperature oven for heat treatment. First, it was treated at 100℃ for 10 minutes to allow partial evaporation of the NMP solvent and initiate prepolymerization. Then, it was treated at 150℃ for 15 minutes to allow the polyamic acid to undergo a thermal imidization reaction to generate polyimide. Finally, it was treated at 180℃ for 8 minutes to allow the polyimide to completely cure and form a chemical bond with the substrate. The obtained coated film is cooled to room temperature by a cooling roller, then pulled by a traction device, and finally wound up to obtain the finished packaging film with a total thickness of approximately 88 μm.

[0018] The packaging film prepared in this embodiment was subjected to performance testing, and the results are as follows: Coating adhesion (cross-cut adhesion test): Grade 0, no cross-cut adhesion. High temperature resistance (121℃ / 30min boiling): No blistering, peeling, or deformation in appearance; tensile strength retention rate of 92%; Oxygen permeability: 3.2 cm³ / (m²·24h·0.1MPa); Water vapor transmission rate: 2.1 g / (m²·24h); Tensile strength: 32.5 MPa; Elongation at break: 185%. Example

[0019] This embodiment provides a high-temperature resistant in-situ polymerized biodegradable can packaging film and its production process. The difference between this embodiment and Embodiment 1 lies in the coating material and the type of polymerization reaction, as detailed below: Weigh out 60 parts PCL (polycaprolactone), 30 parts PBS (polybutylene succinate), 6 parts nano montmorillonite, and 4 parts compatibilizer (titanium ester coupling agent) by weight. Mix the above raw materials evenly and then melt-blend and extrude them through a twin-screw extruder. The extrusion temperature is controlled at 130-150℃ and the screw speed is 180rpm. After granulation, the substrate film with a thickness of 70μm is produced by blow molding at 140℃. Bio-based epoxy resin (Bio-EPX100) and bio-based amine curing agent (Bio-Amine200) were mixed at a mass ratio of 100:35, and an appropriate amount of anhydrous ethanol was added to dilute to a solid content of 20%. After stirring evenly, an epoxy-amine coating precursor solution was obtained. The substrate film surface was subjected to plasma treatment at a power of 500W for 30 seconds. An epoxy-amine coating precursor solution was then applied to the treated substrate film surface by roller coating, with the coating thickness controlled at 5μm. The coated substrate film was then placed in an oven for gradient temperature heat treatment. First, it was treated at 80°C for 12 minutes to allow ethanol to evaporate and initiate pre-crosslinking; then it was treated at 110°C for 20 minutes to allow the epoxy-amine crosslinking reaction to proceed fully; finally, it was treated at 130°C for 10 minutes to allow the coating to fully cure (this step was at a lower temperature than in Example 1 to accommodate the heat resistance of the PCL / PBS substrate). Finally, post-treatment was performed: cooling, traction, and winding to obtain the finished packaging film.

[0020] The performance test results of the packaging film prepared in this embodiment are as follows: Coating adhesion: Grade 0; High temperature resistance (121℃ / 30min boiling): No blistering or peeling on the surface, slight deformation (due to softening of the substrate), tensile strength retention rate of 86%; Oxygen permeability: 4.5 cm³ / (m²·24h·0.1 MPa); Water vapor transmission rate: 2.8 g / (m²·24h); Tensile strength: 28.7 MPa; Elongation at break: 210%. Example

[0021] This embodiment provides a high-temperature resistant in-situ polymerized biodegradable can packaging film and its production process. The difference from Embodiment 1 is the introduction of an organic-inorganic hybrid gradient structure, as detailed below: First, the biodegradable substrate layer was prepared: as in Example 1, the thickness of the substrate film was adjusted to 60 μm; Next, the coating precursor solution was prepared: 5 parts of tetraethyl orthosilicate (TEOS), 15 parts of phenolic resin prepolymer modified with titanate coupling agent, 30 parts of anhydrous ethanol, 1 part of deionized water, and 0.5 parts of hydrochloric acid (0.1 mol / L) were mixed and stirred at room temperature for 2 hours to obtain an organic-inorganic hybrid coating precursor solution. Then, coating and in-situ polymerization treatment were carried out: the substrate film surface was corona treated with a power of 3kW and a speed of 20m / min. The hybrid coating precursor solution was sprayed onto the treated substrate film surface, with the coating thickness controlled at 12μm. The coated substrate film was then placed in a temperature and humidity controlled oven for heat treatment, while the relative humidity inside the oven was adjusted to 60%RH. First, it was treated at 90℃ for 15 minutes to induce a sol-gel reaction of TEOS under humidity-induced conditions, generating nano-SiO2 particles. Then, it was treated at 130℃ for 15 minutes to induce thermal polymerization of the phenolic resin prepolymer. Finally, it was treated at 170℃ for 8 minutes to completely cure the organic-inorganic hybrid coating, forming a gradient structure with gradually increasing inorganic content from the inside to the outside. Finally, post-processing is performed: the obtained coated film is cooled, drawn, and wound up, and then stretched 2.0 times in both the longitudinal and transverse directions at 80°C to perform biaxial stretching treatment, so that the molecular chains are oriented, further improving the mechanical properties and barrier properties.

[0022] The performance test results of the packaging film prepared in this embodiment are as follows: Coating adhesion: Grade 0; High temperature resistance (121℃ / 30min boiling): No blistering, peeling, or deformation in appearance; tensile strength retention rate of 95%; High temperature resistance (135℃ / 20min boiling): No blistering, no peeling, slight discoloration, and 89% retention of tensile strength; Oxygen permeability: 1.8 cm³ / (m²·24h·0.1 MPa); Water vapor transmission rate: 1.2 g / (m²·24h); Tensile strength: 38.2 MPa; Elongation at break: 165%.

[0023] 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 high-temperature resistant, in-situ polymerized, biodegradable canning film, characterized in that, include: A biodegradable substrate layer, said biodegradable substrate layer being made of a biodegradable resin composition; A high-temperature resistant coating, wherein the high-temperature resistant coating is formed on at least one surface of a biodegradable substrate layer by in-situ polymerization; The high-temperature resistant coating is formed by in-situ polymerization of a coating precursor solution on the surface of a degradable substrate layer to create a dense coating.

2. The high-temperature resistant in-situ polymerized biodegradable canning film according to claim 1, characterized in that: The biodegradable resin composition is selected from one or more blends of PBAT, PLA, PCL, PBS, and PHA. The blend also contains a reinforcing modifier selected from at least one of nanocellulose, nanomontmorillonite, and nanotitanium dioxide.

3. The high-temperature resistant in-situ polymerized biodegradable canning film according to claim 1, characterized in that: The coating precursor solution comprises a polymerizable monomer or prepolymer, a crosslinking agent, and a solvent; the polymerizable monomer or prepolymer is selected from at least one of polyimide precursors, bio-based epoxy resin prepolymers, silicone precursors, and modified phenolic resin prepolymers.

4. A production process for a high-temperature resistant in-situ polymerized biodegradable can packaging film, characterized in that: Includes the following steps: S1. Preparation of biodegradable substrate layer: The biodegradable resin composition is melt-blended and then blown or cast to form a substrate film; S2. Preparation of coating precursor solution: Mix polymerizable monomers or prepolymers, crosslinking agents and solvents in proportion; S3. Coating and in-situ polymerization: The coating precursor solution prepared in step S2 is uniformly coated onto the surface of the substrate film obtained in step S1, and then heat-treated under specific temperature conditions to allow the coating precursor to undergo in-situ polymerization on the substrate surface to form a high-temperature resistant coating. S4. Post-processing: The coated film obtained in step S3 is cooled, drawn, and wound up to obtain the finished packaging film.

5. The production process of the high-temperature resistant in-situ polymerized coating biodegradable can packaging film according to claim 4, characterized in that: The biodegradable resin composition in step S1 comprises: 50-80 parts by weight of PBAT, 10-30 parts by weight of PLA, 1-10 parts by weight of nanocellulose, and 1-5 parts by weight of compatibilizer.

6. The production process of the high-temperature resistant in-situ polymerized coating biodegradable can packaging film according to claim 4, characterized in that: The coating method in step S3 is selected from gravure coating, roller coating, spray coating, and dip coating, and the coating thickness is controlled to be 2-20μm.

7. The production process of the high-temperature resistant in-situ polymerized coating biodegradable can packaging film according to claim 4, characterized in that: The gradient heating includes: S31, First temperature range: Treat at 80-120℃ for 5-15 minutes to allow partial evaporation of the solvent and initiate prepolymerization; S32, Second temperature zone: Treat at 120-160℃ for 10-20 minutes to allow the polymerization reaction to proceed fully; S33, Third temperature range: Treat at 160-200℃ for 5-10 minutes to allow the coating to fully cure and form a chemical bond with the substrate.

8. The production process of the high-temperature resistant in-situ polymerized coating biodegradable can packaging film according to claim 4, characterized in that: In step S3, the substrate film surface is subjected to corona treatment or plasma treatment before coating, and humidity control is introduced during the coating process. By adjusting the ambient humidity to 40-80%RH, the sol-gel reaction of the coating precursor is induced.