Anti-sticking packaging film and method for manufacturing the same

Abstract

This invention discloses an anti-stick packaging film and its preparation method. The anti-stick packaging film includes a heat-sealing substrate and an anti-stick coating partially covering its inner surface, forming an anti-stick area and a heat-sealing area. The anti-stick coating consists of a base layer and a top layer. The base layer comprises hydrogenated styrene-butadiene block copolymer, aliphatic polyurethane acrylate, and γ-glycidyl etheroxypropyltrimethoxysilane. The top layer comprises branched polyvinyl butyral, polyamide-imide, and silica. The coating surface has a nanoscale texture and a water contact angle ≥150°. This invention, through a double-layer coating structure and a targeted coating process, achieves excellent and durable superhydrophobic anti-stick effects while maintaining good heat-sealing performance, effectively reducing residue and making it suitable for packaging highly viscous foods such as sauces and yogurt.

Description

Technical Field

[0001] This invention relates to the field of packaging film technology, specifically to an anti-stick packaging film and a method for preparing the anti-stick packaging film. Background Technology

[0002] In the current food packaging industry, sticky products such as sauces, yogurt, and coffee often use ordinary plastic film as packaging material. However, this type of material is prone to causing the contents to adhere to the inner wall of the packaging during use, resulting in residue. This not only affects the consumer experience but also leads to product waste to some extent, failing to meet modern consumers' demands for convenience and sustainability.

[0003] To achieve the anti-stick function of packaging materials, traditional methods typically employ surface modification or the application of special coatings. For example, some packaging films reduce surface energy and achieve a certain anti-stick effect by coating the substrate surface with fluorinated compounds or silicone oils. For instance, an oil-resistant food packaging film, as shown in Chinese patent application (CN120206917A), comprises, in sequence, an oil-resistant layer, an abrasion-resistant layer, an aluminum foil layer, a moisture-proof layer, a support layer, a sealing layer, and a printing layer. The abrasion-resistant layer is composed of plant fibers and low-density polyethylene resin, and a polytetrafluoroethylene coating is disposed within the abrasion-resistant layer. Nano-boron nitride is ultrasonically dispersed in a polyol, and then modified with silica nanofibers to improve oil resistance. However, the use of fluorinated materials may raise concerns about food safety and environmental impact. Furthermore, the multi-layered composite structure and complex modification process lead to increased production costs, reduced processing efficiency, and difficulties in maintaining strong adhesion between the coating and the substrate, thus limiting its application in actual production.

[0004] Furthermore, existing anti-stick coatings mostly rely on a single functional layer, making it difficult to achieve a durable and stable superhydrophobic effect while maintaining mechanical properties. Therefore, developing a packaging material that combines good anti-stick properties, strong processing adaptability, and compliance with food safety requirements remains a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an anti-stick packaging film that has a good, durable, and safe anti-stick effect.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides an anti-stick packaging film, comprising a heat-sealing substrate stacked thereon and an anti-stick coating partially covering the surface of the heat-sealing substrate. The anti-stick coating is applied to the inner surface of the heat-sealing substrate by positioning, such that the inner surface of the heat-sealing substrate forms an anti-stick area with the anti-stick coating and a heat-sealing area without the anti-stick coating. The anti-stick coating comprises a base coating and a top coating in sequence along the direction away from the heat-sealing substrate. Based on the total mass of the base coating, the base coating comprises, by mass percentage, 12.2%~22.5% hydrogenated styrene-butadiene block copolymer, 14.8%~25.3% aliphatic polyurethane acrylate, 0.2%~5.8% γ-glycidyl etheroxypropyltrimethoxysilane, with the balance being the first solvent; Based on the total mass of the topcoat, the topcoat comprises, by mass percentage, 25.2%~38.8% branched polyvinyl butyral, 12.4%~21.7% polyamide-imide, 2.5%~7.6% silica, with the balance being a second solvent; After the anti-stick coating is applied and cured by a textured roller, a texture with a width of 20nm~200nm and a depth of 5nm~50nm is formed on its surface.

[0007] As a preferred technical solution, the first solvent is one or a mixture of methyl isobutyl ketone, ethyl acetate, methyl ethyl ketone, and isopropanol.

[0008] As a preferred technical solution, the second solvent is a mixed solvent composed of ethanol and propylene glycol methyl ether in a mass ratio of (2~1):1.

[0009] As a preferred technical solution, the number-average molecular weight of the hydrogenated styrene-butadiene block copolymer is 40,000~80,000 g / mol.

[0010] As a preferred technical solution, the solution viscosity of the branched polyvinyl butyral, as determined by ASTM D1343 standard, is 40~55 mPa·s.

[0011] As a preferred technical solution, the silica is fumed silica with a BET specific surface area of ​​180~250m². 2 / g.

[0012] As a preferred technical solution, the dry film thickness of the top coating is 1.0~2.0μm, and the dry film thickness of the bottom coating is 1.5~3.0μm.

[0013] As a preferred technical solution, the contact angle between the anti-stick coating and water is ≥150°.

[0014] Secondly, the present invention provides a method for preparing an anti-stick packaging film having at least one of the above-mentioned technical features, comprising the following steps: S001. Hydrogenated styrene-butadiene block copolymer and aliphatic polyurethane acrylate are dissolved in the first solvent and stirred at 40℃~60℃ until completely dissolved. γ-glycidyl etheroxypropyltrimethoxysilane is added and stirred evenly to obtain the primer. S002. The primer liquid is selectively roller-coated onto the inner surface of the heat-sealing substrate using an anilox roller, followed by a drying process to form a primer coating layer. S003. The substrate with the base coating is cured once; S004. Dissolve branched polyvinyl butyral and polyamide-imide in a second solvent and stir until completely dissolved. Then add silica and stir to disperse evenly at 25℃~45℃ to obtain a topcoat liquid. S005. The topcoat liquid is selectively roller-coated onto the surface of the cured base coating by positioning coating, and then dried a second time to form the topcoat. S006. Before the topcoat has completely cooled, emboss it using an embossing roller, then rewind it and perform a second curing.

[0015] As a preferred technical solution, the conditions for the first curing are: curing at 35℃~50℃ for 12~24 hours; and the conditions for the second curing are: curing at room temperature for 24~48 hours.

[0016] As a preferred technical solution, the conditions for the first drying are: drying at a temperature of 60℃~90℃ for 1~3 minutes; the conditions for the second drying are: drying at a temperature of 70℃~110℃ for 2~5 minutes.

[0017] The advantages and beneficial effects of this invention are as follows: The anti-stick coating adopts a two-layer structure design combining a topcoat and a primer. The primer layer uses hydrogenated styrene-butadiene block copolymer and aliphatic polyurethane acrylate as the main resin matrix, providing excellent initial tack and flexibility, enhancing the adhesion between the coating and the heat-sealing substrate. γ-glycidyl etheroxypropyltrimethoxysilane further enhances the bonding force between the primer layer and the heat-sealing substrate. The topcoat layer uses branched polyvinyl butyral and polyamide-imide as the composite resin matrix, imparting excellent mechanical strength and scratch resistance to the surface layer. The polyamide-imide further provides heat resistance and surface hardness, and together with uniformly dispersed silica particles, it constructs a textured structure. This invention can form a long-term stable hydrophobic surface on the heat-sealing substrate.

[0018] This invention employs a positioning coating technique on the inner surface of a heat-sealing substrate to partially cover it with an anti-stick coating that has superhydrophobic properties. This creates a functional zone on the inner surface of the substrate that serves as both an anti-stick zone and a heat-sealing zone. The anti-stick zone has excellent hydrophobic properties, which can effectively reduce the adhesion between the contents and the packaging film, thereby reducing the residue when the contents flow out. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation process of the anti-stick packaging film shown in this invention. Detailed Implementation

[0020] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0021] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly or implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This invention provides an anti-stick packaging film, comprising a heat-sealable substrate stacked in layers and an anti-stick coating partially covering the surface of the heat-sealable substrate. The anti-stick coating is applied to the inner surface of the heat-sealable substrate through a positioning coating, thereby forming an anti-stick area with the anti-stick coating and a heat-sealable area without the anti-stick coating on the inner surface of the heat-sealable substrate. The anti-stick coating sequentially comprises a base coating and a top coating in a direction away from the heat-sealable substrate. Based on the total mass of the base coating, the base coating comprises, by mass percentage, 12.2%~22.5% hydrogenated styrene-butadiene block copolymer and 14.8%~25.3% aliphatic polyurethane acrylate. The coating consists of 0.2-5.8% γ-glycidyl etheroxypropyltrimethoxysilane, with the remainder being the first solvent; based on the total mass of the topcoat, the topcoat comprises 25.2%-38.8% branched polyvinyl butyral, 12.4%-21.7% polyamide-imide, 2.5%-7.6% silica, with the remainder being the second solvent; after the anti-stick coating is applied and cured by an anilox roller, its surface forms a texture with a width of 20nm-200nm and a depth of 5nm-50nm; the retention of the heat-sealing zone ensures the reliability of the heat-sealing of the packaging film on the high-speed packaging line.

[0024] This invention constructs a composite structure with functional zones on the surface of a heat-sealing substrate through a double-layer coating structure and a positioning coating process. The anti-stick zone achieves excellent hydrophobic properties through the base coating and top coating structure. The nanoscale texture formed on its surface increases surface roughness and, combined with low surface energy materials, jointly constructs a stable Cassie-Baxter state, thereby preventing the adhesion of highly viscous contents (such as sauces and yogurt).

[0025] It should be noted that the so-called Cassie-Baxter state is a classic wetting model describing liquids on rough solid surfaces. Unlike the Wenzel state, where the liquid completely wets the microscopic grooves of the surface, in the Cassie-Baxter state, the droplet cannot penetrate into the gaps in the micro / nanostructure. Instead, it is supported by the protrusions on its top, causing a large amount of air to be trapped below the droplet, forming an air cushion effect. In this state, the droplet actually sits on a composite surface composed of solid protrusions and air. The apparent contact angle in this state is much larger than the intrinsic contact angle, and the droplet easily rolls under small external forces, thus achieving self-cleaning and anti-adhesion effects.

[0026] The hydrogenated styrene-butadiene block copolymer (SEBS) in the primer provides initial tack and flexibility, and its saturated carbon-carbon backbone structure enhances anti-aging properties. Aliphatic polyurethane acrylate contributes to good film-forming properties and adhesion. γ-glycidyl etheroxypropyltrimethoxysilane acts as an adhesion promoter, and its epoxy and methoxy groups can form chemical bonds (such as Si-OC, Si-O-Si) with the substrate surface and coating resin respectively during the curing process, enhancing the interfacial bonding between the primer and the heat-sealing substrate (usually polyolefin materials) and preventing the coating from peeling off during use.

[0027] In the topcoat, branched polyvinyl butyral (PVB) provides excellent mechanical strength and toughness, and its branched structure helps to form a denser network. Polyamide-imide (PAI) imparts excellent heat resistance, surface hardness, and dimensional stability to the coating. The carbonyl groups on its imide rings may form intermolecular hydrogen bonds with the hydroxyl groups of PVB, enhancing the cohesive strength of the composite resin matrix. Silica nanoparticles are uniformly dispersed in the topcoat, and during the curing process, they work with the resin matrix to construct a rough micro-nano composite structure. The size range of this nanotexture can be controlled to some extent by the silica content and drying process parameters. Textures that are too narrow or too shallow are insufficient to stably trap air, leading to a decrease in hydrophobicity; textures that are too wide or too deep may reduce the mechanical strength and transparency of the coating and increase the difficulty of production process control. The anilox roller coating process can, to a certain extent, ensure the uniformity and controllability of the coating thickness and texture morphology.

[0028] In some embodiments, the first solvent is one or a mixture of methyl isobutyl ketone, ethyl acetate, methyl ethyl ketone, and isopropanol. These solvents are chosen primarily based on their good solubility in the components of the base coating, suitable evaporation rates, and lack of adverse effects on heat-sealing substrates (such as PE, PP, and PET). Methyl isobutyl ketone has good solubility in SEBS and polyurethane acrylates, but its evaporation rate is relatively fast; ethyl acetate, methyl ethyl ketone, and isopropanol are low to medium boiling point solvents with moderate evaporation rates, which are beneficial for controlling leveling during coating and avoiding defects such as orange peel or pinholes.

[0029] In some embodiments, the second solvent is a mixed solvent composed of ethanol and propylene glycol methyl ether in a mass ratio of (2~1):1. This mixed solvent system exhibits good solubility and volatility gradient for branched PVB and PAI, while also being environmentally friendly. Ethanol, as the main solvent, has good solubility for PVB and evaporates quickly, which helps in the initial shaping of the coating; propylene glycol methyl ether, as a high-boiling-point solvent, evaporates slowly, maintaining a certain fluidity of the coating during the drying process, promoting uniform distribution of silica particles and leveling of the coating, and preventing silica agglomeration or coating cracking due to excessively rapid solvent evaporation.

[0030] In some embodiments, the number-average molecular weight of the hydrogenated styrene-butadiene block copolymer is 40,000 to 80,000 g / mol. SEBS within this molecular weight range provides the optimal balance of mechanical properties in the undercoat. Too low a molecular weight may result in insufficient cohesive strength and reduced flexibility of the coating, affecting its adhesion as a transition layer; too high a molecular weight will increase solution viscosity, making coating processes (especially anilox roller transfer) difficult and potentially leading to uneven coating. Within this range, the styrene hard segments of SEBS provide physical crosslinking points, imparting a certain strength to the coating, while the hydrogenated butadiene soft segments provide good flexibility and compatibility with the substrate for the anti-stick coating.

[0031] In some embodiments, the solution viscosity of branched polyvinyl butyral, as determined according to ASTM D1343, is 40–55 mPa·s. This viscosity range reflects the suitable molecular chain length and degree of branching of the branched PVB. Viscosity affects the rheology of the topcoat solution, coating uniformity, and the final coating density. Too low a viscosity may lead to excessive shrinkage of the coating during drying, making it difficult to achieve the required film thickness and resulting in insufficient mechanical strength; too high a viscosity makes coating difficult, easily causing streaks, and worsening the uniformity of silica dispersion, thus affecting surface texture formation and superhydrophobic properties.

[0032] In some embodiments, the silica is fumed silica with a BET specific surface area of ​​180~250 m². 2 / g. High specific surface area fumed silica is chosen because of its small primary particle size (typically in the nanometer range), abundant surface silanol groups, ease of dispersion in resin systems, and ability to aid in the construction of the required micro / nano rough structures. If the specific surface area is too low, the number of particles per unit mass is small, resulting in low efficiency in roughness construction and potentially making it difficult to achieve the required contact angle for superhydrophobicity; if the specific surface area is too high, the van der Waals forces between particles are strong, leading to agglomeration and difficulty in uniform dispersion in the topcoat liquid. This could result in uneven coating surface, decreased transparency, and even deterioration of mechanical properties.

[0033] In some embodiments, the dry film thickness of the topcoat is 1.0–2.0 μm, and the dry film thickness of the basecoat is 1.5–3.0 μm. The basecoat thickness needs to be sufficient to cover microscopic irregularities on the substrate surface, providing a continuous and well-adhered transition layer. Too thin a layer may result in insufficient adhesion or incomplete coverage; too thick a layer increases cost and the risk of curling due to increased internal stress. The topcoat thickness needs to ensure complete encapsulation of silica particles and the formation of a stable surface texture. Too thin a layer may result in incomplete texture or poor abrasion resistance; too thick a layer may bury texture features, affecting superhydrophobicity, while also increasing coating difficulty and cost.

[0034] Also, it should be noted that the base coat is slightly thicker than the top coat, which helps to buffer stress and enhance overall adhesion.

[0035] In some embodiments, the contact angle between the anti-stick coating and water is ≥150°. A contact angle ≥150° indicates that the coating surface has reached a superhydrophobic state, exhibiting extremely low adhesion to common sticky foods (such as mayonnaise, honey, and yogurt). This is mainly attributed to the interaction between the low surface energy resin components (PVB, PAI) in the topcoat and the nanoscale textured structure constructed from silica, which significantly reduces the actual contact area between droplets and the solid surface, making the droplets roll off easily and thus achieving excellent anti-stick properties.

[0036] Please see Figure 1 The present invention also provides a method for preparing an anti-stick packaging film, comprising the following steps: S001. Hydrogenated styrene-butadiene block copolymer and aliphatic polyurethane acrylate are dissolved in the first solvent and stirred at 40℃~60℃ until completely dissolved. γ-glycidyl etheroxypropyltrimethoxysilane is added and stirred evenly to obtain the primer. S002. Use an anilox roller to selectively apply the primer liquid to the inner surface of the heat-sealing substrate, and then perform a drying process to form the primer coating. S003. The substrate with the base coating is cured once; S004. Dissolve branched polyvinyl butyral and polyamide-imide in a second solvent and stir until completely dissolved. Then add silica and stir to disperse evenly at 25℃~45℃ to obtain a topcoat liquid. S005. Selectively roll-coating the topcoat liquid onto the surface of the cured base coating layer by positioning coating, followed by secondary drying to form the topcoat layer; S006. Before the topcoat has completely cooled, emboss it using an embossing roller, then rewind it and perform a second curing.

[0037] In step S001, moderate heating helps the polymer chains such as SEBS to expand and dissolve, shortening the dissolution time. However, excessively high temperatures may cause the solvent to evaporate too quickly or trigger polymer degradation. In step S002, selective roller coating ensures that the primer is applied only to the pre-defined anti-stick zone by precisely controlling the dot distribution and engraving depth of the anilox roller. Parameters such as the anilox roller's line count and volume directly affect the thickness and uniformity of the primer coating. The purpose of primary drying is to remove most of the solvent, allowing the primer coating to initially cure. Temperature and time must be balanced to ensure drying efficiency and prevent substrate deformation due to overheating. Step S003, primary curing, is a mild physicochemical process. Under these conditions, polymer chains gain sufficient mobility for rearrangement and relaxation, helping to eliminate internal stress. Simultaneously, γ-glycidoxypropyltrimethoxysilane has more time to undergo hydrolysis-condensation reactions with the substrate surface and the coating polymer, forming stronger chemical bonds and thus improving adhesion. In step S004, the addition and dispersion of silica are crucial. Controlling the stirring temperature and using high-shear dispersion equipment (such as a high-speed disperser) helps break up silica agglomerates and achieve nanoscale uniform dispersion in the resin solution. Excessive temperature may cause the solvent to evaporate too quickly. Step S005, the positioning coating, also employs anilox roller technology to ensure the topcoat precisely covers the basecoat. The secondary drying temperature is higher than the primary drying temperature to thoroughly remove the topcoat solvent and may trigger further imidization of PAI, improving the coating's heat resistance and hardness. In step S006, embossing is performed before the topcoat has completely cooled (typically above its glass transition temperature Tg). At this stage, the coating still possesses a certain degree of plasticity, allowing the embossing roller (whose surface may have micron or nanoscale structures) to more effectively replicate or induce the formation of the final nanotexture on its surface.

[0038] The method described in this invention not only shapes the surface morphology but also allows for the directional alignment of the surface polymer and silica particles, optimizing hydrophobic properties. Subsequent secondary curing allows the coating system to reach final thermodynamic equilibrium, releasing residual stress and promoting the stabilization of the coating's internal structure and the full expression of its properties.

[0039] In some embodiments, the conditions for primary curing are: curing at 35°C to 50°C for 12 to 24 hours; the conditions for secondary curing are: curing at room temperature for 24 to 48 hours; the conditions for primary drying are: drying at 60°C to 90°C for 1 to 3 minutes; and the conditions for secondary drying are: drying at 70°C to 110°C for 2 to 5 minutes. The primary curing temperature and time directly affect adhesion. If the temperature is too low or the time is too short, the silane coupling agent will not react sufficiently; if the temperature is too high, the base coat may soften excessively. Secondary curing, performed at room temperature, is an economical and effective process for stress relaxation and performance stabilization. The drying temperature is set in a gradient; primary drying focuses on safely removing solvent without damaging the substrate, while secondary drying ensures complete curing of the topcoat and achieves optimal mechanical properties.

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer; raw materials and reagents used, unless otherwise specified, are products obtainable through legitimate market channels. Peel strength was tested according to GB / T 1040.3 standard.

[0041] Example 1 This embodiment provides an anti-stick packaging film and its preparation method.

[0042] The anti-stick packaging film includes a heat-sealable substrate stacked on top of each other and an anti-stick coating partially covering the surface of the heat-sealable substrate. The heat-sealable substrate is a biaxially oriented polypropylene (BOPP) film. The anti-stick coating is applied to the inner surface of the BOPP film by positioning, such that the inner surface forms an anti-stick area with the anti-stick coating and a heat-sealable area without the anti-stick coating. The anti-stick coating includes a base coating and a top coating sequentially in the direction away from the heat-sealable substrate.

[0043] Based on the total mass of the base coating, the base coating comprises, by mass percentage, 15.0% hydrogenated styrene-butadiene block copolymer, 20.0% aliphatic polyurethane acrylate, 3.0% γ-glycidyl etheroxypropyltrimethoxysilane, and the balance being a first solvent. The first solvent is a mixture of toluene and ethyl acetate in a mass ratio of 1:1.

[0044] Based on the total mass of the topcoat, the topcoat comprises, by mass percentage, 30.0% branched polyvinyl butyral, 17.0% polyamide-imide, 5.0% silica, with the balance being a second solvent. The second solvent is a mixture of ethanol and propylene glycol methyl ether in a mass ratio of 1.5:1.

[0045] Its preparation method includes the following steps: S001. Hydrogenated styrene-butadiene block copolymer and aliphatic polyurethane acrylate are dissolved in the first solvent and stirred at 50°C until completely dissolved. γ-glycidyl etheroxypropyltrimethoxysilane is added and stirred evenly to obtain the primer. S002. The primer liquid is selectively roller-coated onto the inner surface of the BOPP heat-sealing substrate using an anilox roller, and then dried at 75°C for 2 minutes to form the primer coating. S003. The substrate with the base coating is cured at 40°C for 18 hours. S004. Dissolve branched polyvinyl butyral and polyamide-imide in a second solvent and stir until completely dissolved. Then add silica and stir to disperse evenly at 35°C to obtain a topcoat liquid. S005. The topcoat liquid is selectively roller-coated onto the surface of the cured base coating by positioning coating, and then dried again at 90°C for 3 minutes to form the topcoat. S006. Before the topcoat has completely cooled, emboss it using an embossing roller, then roll it up and allow it to cure again at room temperature for 36 hours. After the anti-stick coating is applied and cured by the anilox roller, a texture with a width of 100 nm and a depth of 25 nm is formed on its surface.

[0046] The anti-stick packaging film prepared in this embodiment has a contact angle of 152° with water in the anti-stick area. The peel strength is 4.5 N / cm. After undergoing an accelerated aging test at 85°C and 85% relative humidity for 7 days, the contact angle remained at 148°, and the coating showed no peeling or wrinkling.

[0047] Example 2 This embodiment provides an anti-stick packaging film and its preparation method.

[0048] Compared to Example 1, the only difference is that the first solvent is butanone (methyl ethyl ketone). The second solvent is a mixture of ethanol and propylene glycol methyl ether in a mass ratio of 2:1. The primer preparation temperature is 45°C; the first drying condition is 65°C for 3 minutes; the first curing condition is 45°C for 15 hours; the topcoat dispersion temperature is 40°C; the second drying condition is 100°C for 2.5 minutes; and the second curing condition is 48 hours at room temperature.

[0049] The anti-stick packaging film prepared in this embodiment has a water contact angle of 154° in the anti-stick area. The peel strength is 4.2 N / cm. After 7 days of accelerated aging testing, the contact angle is 150°.

[0050] Example 3 This embodiment provides an anti-stick packaging film and its preparation method.

[0051] Compared to Example 1, the only difference is that the number-average molecular weight of the hydrogenated styrene-butadiene block copolymer is 50,000 g / mol. The solution viscosity of the branched polyvinyl butyral, as determined by ASTM D1343, is 45 mPa·s. The dry film thickness of the topcoat is 1.5 μm, and the dry film thickness of the bottomcoat is 2.0 μm.

[0052] The anti-stick packaging film prepared in this embodiment has a water contact angle of 153° in its anti-stick area. Due to the optimization of molecular weight and viscosity, the peel strength between the coating and the substrate is improved to 5.0 N / cm. After 7 days of accelerated aging test, the contact angle is 149°.

[0053] Example 4 This embodiment provides an anti-stick packaging film and its preparation method.

[0054] Compared to Example 1, the only difference is that the number-average molecular weight of the hydrogenated styrene-butadiene block copolymer is 70,000 g / mol. The solution viscosity of the branched polyvinyl butyral, as determined by ASTM D1343, is 52 mPa·s. The dry film thickness of the topcoat is 1.2 μm, and the dry film thickness of the bottomcoat is 2.5 μm.

[0055] The anti-stick packaging film prepared in this embodiment has a water contact angle of 151° in the anti-stick area. The peel strength is 4.8 N / cm. After 7 days of accelerated aging testing, the contact angle is 147°.

[0056] Example 5 This embodiment provides an anti-stick packaging film and its preparation method.

[0057] Compared with Example 1, the only difference is that the dry film thickness of the top coating is 1.0 μm and the dry film thickness of the bottom coating is 3.0 μm.

[0058] The anti-stick packaging film prepared in this embodiment has a water contact angle of 155° in its anti-stick area. The thinner topcoat makes the surface texture effect more pronounced, but the peel strength between the coating and the substrate is slightly reduced to 4.0 N / cm. After 7 days of accelerated aging test, the contact angle is 150°.

[0059] Example 6 This embodiment provides an anti-stick packaging film and its preparation method.

[0060] Compared with Example 1, the only difference is that the dry film thickness of the top coating is 2.0 μm and the dry film thickness of the bottom coating is 1.5 μm.

[0061] The anti-stick packaging film prepared in this embodiment has a water contact angle of 150° in the anti-stick area. The peel strength between the coating and the substrate is 4.3 N / cm. After 7 days of accelerated aging test, the contact angle is 146°.

[0062] Example 7 This embodiment provides an anti-stick packaging film and its preparation method.

[0063] The only difference from Example 1 is that the silica is fumed silica with a BET specific surface area of ​​200 m². 2 / g.

[0064] The anti-stick packaging film prepared in this embodiment has a water contact angle of 156° in the anti-stick area. The peel strength between the coating and the substrate is 4.6 N / cm. After 7 days of accelerated aging test, the contact angle is 151°.

[0065] Example 8 This embodiment provides an anti-stick packaging film and its preparation method.

[0066] The only difference from Example 1 is that the silica is fumed silica with a BET specific surface area of ​​180 m². 2 / g.

[0067] The anti-stick packaging film prepared in this embodiment has a water contact angle of 153° in the anti-stick area. The peel strength is 4.4 N / cm. After 7 days of accelerated aging testing, the contact angle is 148°.

[0068] Example 9 This embodiment provides an anti-stick packaging film and its preparation method.

[0069] The only difference from Example 1 is that the silica is fumed silica with a BET specific surface area of ​​250 m². 2 / g.

[0070] The anti-stick packaging film prepared in this embodiment has a water contact angle of 157° in its anti-stick area. The extremely high specific surface area provides optimal hydrophobicity. The peel strength is 4.7 N / cm. After 7 days of accelerated aging testing, the contact angle is 152°.

[0071] Comparative Example 1 This comparative example uses commercially available ordinary polyethylene (PE) packaging film. The film surface has no functional anti-stick coating.

[0072] The PE film has a water contact angle of 85°. Its peel strength from the substrate was not tested. After 7 days of accelerated aging testing, the contact angle showed no significant change. It leaves significant residues in sauce-type products.

[0073] Comparative Example 2 This comparative example uses commercially available packaging film with a fluorinated non-stick coating.

[0074] The contact angle between the anti-stick film and water is 145°. Its peel strength from the substrate is 3.0 N / cm. After 7 days of accelerated aging testing, the contact angle decreased to 135°, and localized coating cracking occurred.

[0075] Comparative Example 3 This comparative example uses commercially available silicone oil-based anti-stick packaging film.

[0076] The anti-stick membrane initially exhibits a water contact angle of up to 110°, but it is not a durable coating. Its peel strength from the substrate is extremely low, only 1.5 N / cm, making it prone to migration and detachment. After 3 days of accelerated aging testing, the contact angle drops below 90°.

[0077] The comparison between the above embodiments and comparative examples shows that the anti-stick packaging film provided by the present invention successfully achieves an initial superhydrophobic performance far exceeding that of the comparative examples, while also possessing excellent adhesion and a long service life, and avoiding the safety and environmental problems that may be caused by fluorine-containing and silicone-containing materials.

[0078] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An anti-stick packaging film, comprising a heat-sealable substrate stacked on top of each other and an anti-stick coating partially covering the surface of the heat-sealable substrate, wherein the anti-stick coating is applied to the inner surface of the heat-sealable substrate by a positioning coating, such that the inner surface of the heat-sealable substrate forms an anti-stick area with the anti-stick coating and a heat-sealable area without the anti-stick coating, characterized in that, The anti-stick coating comprises, in sequence, a base coat and a top coat along the direction away from the heat-sealing substrate; Based on the total mass of the base coating, the base coating comprises, by mass percentage, 12.2% to 22.5% hydrogenated styrene-butadiene block copolymer, 14.8% to 25.3% aliphatic polyurethane acrylate, 0.2% to 5.8% γ-glycidyl etheroxypropyltrimethoxysilane, with the balance being the first solvent; Based on the total mass of the topcoat, the topcoat comprises, by mass percentage, 25.2%~38.8% branched polyvinyl butyral, 12.4%~21.7% polyamide-imide, 2.5%~7.6% silica, with the balance being a second solvent; After the anti-stick coating is applied and cured by a textured roller, a texture with a width of 20nm~200nm and a depth of 5nm~50nm is formed on its surface.

2. The anti-stick packaging film according to claim 1, characterized in that, The first solvent is one or a mixture of methyl isobutyl ketone, ethyl acetate, methyl ethyl ketone, and isopropanol.

3. The anti-stick packaging film according to claim 2, characterized in that, The second solvent is a mixed solvent composed of ethanol and propylene glycol methyl ether in a mass ratio of (2~1):

1.

4. The anti-stick packaging film according to claim 1, characterized in that, The number-average molecular weight of the hydrogenated styrene-butadiene block copolymer is 40,000 to 80,000 g / mol.

5. The anti-stick packaging film according to claim 4, characterized in that, The solution viscosity of the branched polyvinyl butyral, as determined by ASTM D1343, is 40-55 mPa·s.

6. The anti-stick packaging film according to claim 5, characterized in that, The dry film thickness of the topcoat is 1.0~2.0μm, and the dry film thickness of the bottomcoat is 1.5~3.0μm.

7. The anti-stick packaging film according to claim 3, characterized in that, The silica is fumed silica with a BET specific surface area of ​​180~250m². 2 / g.

8. The anti-stick packaging film according to claim 1, characterized in that, The contact angle between the anti-stick coating and water is ≥150°.

9. A method for preparing an anti-stick packaging film, characterized in that, Includes the following steps: S001. Hydrogenated styrene-butadiene block copolymer and aliphatic polyurethane acrylate are dissolved in the first solvent and stirred at 40℃~60℃ until completely dissolved. γ-glycidyl etheroxypropyltrimethoxysilane is added and stirred evenly to obtain the primer. S002. The primer liquid is selectively roller-coated onto the inner surface of the heat-sealing substrate using an anilox roller, followed by a drying process to form a primer coating layer. S003. The substrate with the base coating is cured once; S004. Dissolve branched polyvinyl butyral and polyamide-imide in a second solvent and stir until completely dissolved. Then add silica and stir to disperse evenly at 25℃~45℃ to obtain a topcoat liquid. S005. The topcoat liquid is selectively roller-coated onto the surface of the cured base coating by positioning coating, and then dried a second time to form the topcoat. S006. Before the topcoat has completely cooled, emboss it using an embossing roller, then rewind it and perform a second curing.

10. The preparation method according to claim 9, characterized in that, The conditions for the first curing are: curing at 35℃~50℃ for 12~24 hours; the conditions for the second curing are: curing at room temperature for 24~48 hours; the conditions for the first drying are: drying at 60℃~90℃ for 1~3 minutes; the conditions for the second drying are: drying at 70℃~110℃ for 2~5 minutes.

Images