Degradable food packaging film with heat sealing function and production process thereof

Abstract

The invention relates to the technical field of food packaging materials, in particular to a degradable food packaging film with a heat sealing function and a production process thereof, and the production process comprises the following steps: step I, supplying a base coiled material; step II, carrying out surface pretreatment for improving adhesive force on the printing surface of the base coiled material; thirdly, printing is conducted on the base body coiled material, and printing ink is primarily dried; step IV, conveying the primarily dried coiled material to a film surface steering mechanism, and selectively overturning the coiled material according to process requirements so as to carry out subsequent treatment or printing on the other surface; v, thoroughly drying or curing the printed pattern; according to the invention, through collaborative design of materials and processes, the packaging film has industrial degradability while ensuring printing performance and reliable heat sealing, the structure of the packaging film is simplified compared with that of a traditional multi-layer composite film, the production process is continuous, the packaging film is easy to transform on existing equipment to realize mass production, and the packaging film has remarkable environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of food packaging materials technology, specifically to a biodegradable food packaging film with built-in heat-sealing function and its production process. Background Technology

[0002] Currently, the food packaging industry widely uses multilayer composite films (such as PET / PAPER / PE / AL / PE, etc.) to balance printability, barrier properties, and heat-sealing functions.

[0003] However, the aforementioned multilayer composite membranes usually contain non-degradable polymer or metal layers, which makes recycling difficult and causes long-term environmental pollution. At the same time, the preparation process of multilayer composite structures is complex and costly.

[0004] To address the aforementioned issues, the industry urgently needs a packaging film material and corresponding production process that can degrade under industrial composting or biodegradation conditions while ensuring printing appearance and heat-sealing reliability. Based on this, the present invention proposes a degradable packaging film structure with built-in heat-sealing function and its roll-to-roll continuous production process. Through optimization of material formulation and process parameters, it balances printing quality, heat-sealing performance, and degradability. Summary of the Invention

[0005] The purpose of this invention is to provide a biodegradable food packaging film with built-in heat-sealing function and its production process, in order to solve the problems that multilayer composite films usually contain non-degradable polymer or metal layers, which leads to difficulties in recycling and long-term environmental pollution. At the same time, the preparation process of multilayer composite structures is complex and costly.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A biodegradable food packaging film with built-in heat-sealing function and its manufacturing process include the following steps:

[0008] Step 1: Supply the substrate roll material;

[0009] Step II: Perform surface pretreatment on the printed surface of the substrate roll to improve adhesion;

[0010] Step III: Print on the substrate roll and allow the printing ink to initially dry;

[0011] Step IV: The pre-dried roll material is conveyed to the film turning mechanism. Depending on the process requirements, the roll material can be flipped over to facilitate subsequent processing or printing on the other side.

[0012] Step V: Thoroughly dry or cure the printed pattern;

[0013] Step VI: Apply a heat-sealing layer to the side facing the seal by coating or co-extrusion.

[0014] Step VII: Perform online quality inspection on the processed roll material and roll it up as a finished roll material.

[0015] As a further optimization of the present invention, the substrate roll material is a biodegradable thermoplastic polymer or a blend thereof.

[0016] As a further optimization of the present invention, the substrate roll material is a blend of PLA and PBAT.

[0017] As a further optimization of the present invention, the thickness of the substrate roll is 20–80 μm.

[0018] As a further optimization of the present invention, the surface pretreatment is corona treatment or plasma treatment.

[0019] As a further optimization of the present invention, the printing uses water-based or low-solvent printing ink suitable for food contact, and at least two sets of ovens or equivalent partitioned drying / setting devices are used in the initial drying or setting steps.

[0020] As a further optimization of the present invention, the heat-sealing layer is obtained by coating PBAT or PBAT / PLA blended heat-sealing coating, or by co-extrusion to form an inner PBAT layer.

[0021] As a further optimization of the present invention, in step VI, when a coating method is used, the basis weight of the heat-sealing coating is 1–8 g / m². 2 When co-extrusion is used, the thickness of the PBAT inner layer is 2-20 μm; and the process includes online detection of the coating basis weight of the heat-sealing coating or the thickness of the co-extruded layer to ensure consistency.

[0022] As a further optimization of the present invention, the following components are included sequentially from the printing surface to the sealing surface: a substrate layer, a printing layer or a protective layer, and a heat-sealing layer facing the sealing surface; the substrate layer is made of a biodegradable thermoplastic polymer or a blend thereof; the heat-sealing layer is a biodegradable heat-sealing material or an inner sealing layer formed by co-extrusion.

[0023] As a further optimization of the present invention, the substrate layer is a blend of PLA and PBAT, with a mass ratio of PLA to PBAT of 60–80:20–40; the overall film thickness is 20–80 μm; and the heat-sealing strength measured under standard heat-sealing test conditions is not less than 4 N / 15 mm; the film meets the testing requirements for industrial compost degradability.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] In this invention, through the synergistic design of materials and processes, the packaging film is made industrially biodegradable while ensuring printability and reliable heat sealing. The structure is simpler than that of traditional multilayer composite films, the production process is continuous and easy to modify existing equipment to achieve mass production, and it has significant environmental and economic benefits. Attached Figure Description

[0026] Figure 1 This is a production process flow diagram of a biodegradable food packaging film with built-in heat-sealing function according to the present invention.

[0027] Figure 2 This is a schematic diagram of a biodegradable food packaging film with built-in heat-sealing function according to the present invention;

[0028] Figure 3 This is a schematic diagram of a biodegradable food packaging film with built-in heat-sealing function according to the present invention. Detailed Implementation

[0029] Please see Figures 1-3 The present invention provides a technical solution:

[0030] Regarding product structure:

[0031] A biodegradable food packaging film with built-in heat-sealing function, comprising, from the printed surface to the sealing surface: a base layer, (optional) a printed layer / protective layer, and a heat-sealing layer; the base layer is composed of a biodegradable thermoplastic polymer or a blend thereof; the heat-sealing layer is a biodegradable heat-sealing material or an inner sealing layer formed by co-extrusion.

[0032] In terms of technology:

[0033] A manufacturing process for a biodegradable food packaging film with built-in heat-sealing function includes the following steps:

[0034] Supply of base roll material;

[0035] Surface pretreatment (e.g., corona or plasma treatment) of the printed surface of the substrate roll material can improve adhesion.

[0036] The printing is performed on the substrate roll using water-based or low-solvent printing inks suitable for food contact, and the printing inks are pre-dried in the first set of ovens.

[0037] The pre-dried roll is conveyed to a reverse or directional conveying device and flipped over as needed for back-side processing or secondary printing;

[0038] The printed pattern is then subjected to a deep drying / setting process using a second set of ovens;

[0039] On the side facing the seal, a biodegradable heat-sealing coating is applied by coating (using a scraper, gravure, etc.) and then shaped, or a heat-sealing layer is formed in the inner layer by co-extrusion to replace the coating step.

[0040] The processed roll material undergoes online quality inspection (e.g., printing quality, coating weight, layer thickness, tension, etc.) and is then wound into finished roll material.

[0041] Example 1:

[0042] Printed type with heat-sealable coating (preferred embodiment):

[0043] Materials and formulations (e.g.) Figure 1 As shown):

[0044] Matrix material: PLA / PBAT blend, mass ratio PLA:PBAT = 70:30 (preferred range PLA 60–80wt%, PBAT 20–40wt%);

[0045] Substrate film thickness: 30 μm (preferred range 20–80 μm);

[0046] Surface pretreatment: Corona treatment, with a treatment intensity of approximately 40 mN / m (preferably 30–60 mN / m);

[0047] Printing ink: Water-based dispersion printing ink that complies with food contact regulations (specific grades and formulations are listed in the engineering test records);

[0048] Heat-sealing coating: PBAT-based biodegradable heat-sealing coating, with a coating weight of 3 g / m². 2 (Preferred range 1–8 g / m³) 2 );

[0049] Oven parameters (example): Pre-drying (initial drying) zone temperature 60–80℃; Post-drying (setting) zone temperature 90–120℃ (zone control to avoid PLA substrate degradation);

[0050] Heat sealing parameters (for sealing equipment reference): sealing temperature 120℃, sealing pressure 0.8MPa, sealing time 1.0s (preferred sealing temperature range 100–150℃, sealing pressure 0.2–2.0MPa, sealing time 0.5–2.0s).

[0051] Process steps:

[0052] The aforementioned substrate roll is supplied to a roll-to-roll printing press;

[0053] The printed surface of the roll material is subjected to corona treatment (approximately 40 mN / m);

[0054] Water-based dispersion ink is used for rotary printing (or flexographic or gravure printing) on ​​a printing press. After printing, the ink enters the first set of ovens for initial drying (example temperature range 60–80℃).

[0055] After initial drying, the roll material is conveyed to a reverse-loading flipping device, which can flip the film surface as needed for post-processing or secondary printing on the back side;

[0056] After being flipped or oriented, the roll material enters the second set of ovens for deep drying / setting (example temperature 90–120°C);

[0057] Apply PBAT-based heat-sealing coating to the side facing the seal using a scraper, with a coating weight of approximately 3 g / m². 2 After coating, it is cured in a low-temperature setting zone (example 80–120℃);

[0058] Online inspection (printing quality, coating weight, layer thickness, tension, etc.) is conducted, and the qualified products are rolled up into finished rolls.

[0059] Example of test results (to be actually measured and recorded in engineering tests):

[0060] Heat seal strength (according to ASTM F88 or corresponding GB standard, 15mm wide strip): ≥6N / 15mm;

[0061] Printing color difference (compared with standard sample): ΔE≤5;

[0062] The product has no layering and the seal is complete and flat.

[0063] Example 2:

[0064] Co-extruded self-sealing type (e.g.) Figure 2 (As shown): Structure and formulation:

[0065] Three-layer co-extruded film structure: outer layer PLA (for printing, thin), middle layer PBAT (for inner sealing layer, thick), inner layer PLA modified layer (or for protective layer); overall thickness 30–60μm (adjustable from 20–80μm).

[0066] Key points of the process:

[0067] The inner PBAT layer is formed by co-extrusion, so that heat sealing can be achieved without applying a heat-sealing coating during bag making / sealing;

[0068] Printing is carried out on the outer PLA layer, using two sets of ovens and a reverse-mounted device to ensure the color and setting quality of the printed pattern;

[0069] During co-extrusion, it is necessary to control the melt rheological properties and layer thickness of each layer to ensure the sealing window and film surface quality.

[0070] Testing: Heat sealing performance, printability and overall mechanical properties of the film were determined according to the testing method in Example 1.

[0071] Example 3:

[0072] Barrier Enhancement / Gloss Protection Type: Formulation and Process:

[0073] Add nano-clay (≤3wt%) to the matrix formulation as needed to improve barrier properties; or apply a water-based gloss / protective layer (1–2 g / m²) after printing. 2 To enhance surface gloss and abrasion resistance;

[0074] Other process steps are performed as in Example 1.

[0075] By selecting a biodegradable polymer system (e.g., PLA / PBAT blend) and a coordinated roll-to-roll printing / coating process (including corona / plasma pretreatment, two sets of drying ovens, and a reverse-mounted flipping device), high-quality printing effects and reliable heat-sealing performance of the packaging film are achieved, while ensuring the biodegradability of the materials and structure and the feasibility of industrial production. This invention is applicable to food packaging, daily-use packaging, and other packaging applications that require both printed appearance and heat sealing, and is easy to scale up after modification of existing production lines.

[0076] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A production process for a biodegradable food packaging film with built-in heat-sealing function, characterized in that, Includes the following steps: Step 1: Supply the substrate roll material; Step II: Perform surface pretreatment on the printed surface of the substrate roll to improve adhesion; Step III: Print on the substrate roll and allow the printing ink to initially dry; Step IV: The pre-dried roll material is conveyed to the film turning mechanism. Depending on the process requirements, the roll material can be flipped over to facilitate subsequent processing or printing on the other side. Step V: Thoroughly dry or cure the printed pattern; Step VI: Apply a heat-sealing layer to the side facing the seal by coating or co-extrusion. Step VII: Perform online quality inspection on the processed roll material and roll it up as a finished roll material.

2. The production process of a biodegradable food packaging film with built-in heat-sealing function according to claim 1, characterized in that: The substrate roll material is a biodegradable thermoplastic polymer or a blend thereof.

3. The production process of a biodegradable food packaging film with built-in heat-sealing function according to claim 1, characterized in that: The substrate roll material is a blend of PLA and PBAT.

4. The production process of a biodegradable food packaging film with built-in heat-sealing function according to claim 1, characterized in that: The thickness of the substrate roll is 20–80 μm.

5. The production process of a biodegradable food packaging film with built-in heat-sealing function according to claim 1, characterized in that: The surface pretreatment is corona treatment or plasma treatment.

6. The production process of a biodegradable food packaging film with built-in heat-sealing function according to claim 1, characterized in that: The printing uses water-based or low-solvent printing inks suitable for food contact, and employs at least two separate drying / setting units, either front or rear, or equivalent, during the initial drying or setting steps.

7. The production process of a biodegradable food packaging film with built-in heat-sealing function according to claim 1, characterized in that: The heat-sealing layer is obtained by coating with PBAT or PBAT / PLA blended heat-sealing coating, or by co-extrusion to form an inner PBAT layer.

8. The production process of a biodegradable food packaging film with built-in heat-sealing function according to claim 1, characterized in that: In step VI, when a coating method is used, the basis weight of the heat-sealing coating is 1–8 g / m². 2 When co-extrusion is used, the thickness of the PBAT inner layer is 2-20 μm; and the process includes online detection of the coating basis weight of the heat-sealing coating or the thickness of the co-extruded layer to ensure consistency.

9. A biodegradable food packaging film with built-in heat-sealing function according to any one of claims 1-8, characterized in that: The structure, from the printed surface to the sealing surface, comprises: a substrate layer, a printed layer or a protective layer, and a heat-sealing layer on the side facing the seal; the substrate layer is made of a biodegradable thermoplastic polymer or a blend thereof; the heat-sealing layer is a biodegradable heat-sealing material or an inner sealing layer formed by co-extrusion.

10. A biodegradable food packaging film with built-in heat-sealing function according to claim 9, characterized in that: The substrate layer is a blend of PLA and PBAT, with a mass ratio of PLA to PBAT of 60–80:20–40; the overall film thickness is 20–80 μm; and the heat-sealing strength measured under standard heat-sealing test conditions is not less than 4 N / 15 mm; the film meets the testing requirements for industrial compostability.

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