Polyester film for aluminum plating and preparation method thereof

Abstract

A polyester film for aluminum plating comprises a base material and a reinforced coating arranged on at least one side of the base material, the surface roughness Ra of the polyester film for aluminum plating is 0.02-0.03 [mu] m, and the surface energy gamma is 35-45 mJ / m < 2 >; the reinforced coating comprises the following components in percentage by weight: 10-25% of modified polyester resin; 0.1%-5% of a cross-linking agent; 0.01%-1% of an auxiliary agent; 0.5%-1% of silicon dioxide particles; and 68%-89.39% of deionized water. The modified polyester resin in the reinforced coating can be cross-linked to form a compact three-dimensional network, water vapor is blocked, and the initial adhesive force with the base material / aluminum layer is improved, so that the polyester film for aluminum plating can still keep good aluminum adhesive force under the extreme cooking conditions of 121 DEG C and 40 minutes.

Description

Technical Field

[0001] This invention relates to a polyester film for aluminum plating and its preparation method, belonging to the field of film technology. Background Technology

[0002] As people's living standards improve, they pay more attention to quality when shopping, especially in the food sector. Therefore, food products are generally packaged. The main purpose of food packaging is to slow down spoilage, and it is typically made of multiple layers of film. The barrier layer's function is to block external water and oxygen, thus delaying their spoilage.

[0003] Currently, there are many types of barrier layers on the market, the most common being aluminized film and nylon film. Aluminized film is opaque, making it difficult for customers to observe the condition of food when used for packaging; nylon film is transparent and has high strength and good barrier properties, but it is easily affected by ultraviolet light, limiting its application scenarios. Therefore, new materials are needed as barrier layers.

[0004] Alumina-coated film is a transparent film produced by evaporating high-purity aluminum wire into a gaseous state at high temperatures, introducing oxygen to obtain alumina, and then depositing the alumina onto a film substrate. It possesses excellent barrier properties. However, at higher temperatures (e.g., above 110°C), alumina-coated films exhibit poor structural stability and are prone to deformation and interlayer delamination. This is because existing polyester films have weak adhesion. Even with corona treatment to improve surface polarity, they still cannot meet the adhesion requirements of special coatings such as solvent-free coatings. Especially under high temperature and high humidity conditions, the surface tension of polyester films decreases drastically, making it difficult to ensure that the alumina layer will not detach during processing. Furthermore, although offline coating pretreatment agents are used to enhance the interlayer adhesion of the vapor-deposited layer, this pretreatment layer is relatively thick, making it difficult to fully meet the requirements for boiling resistance and anti-adhesion.

[0005] CN113912894A discloses a transparent, high-barrier polyester-coated alumina film and its preparation method. The film comprises a substrate, a polyurethane base layer, an alumina layer, and a polyurethane top layer, sequentially arranged. The thickness of the alumina layer is 80-140 μm, and the thicknesses of the polyurethane base layer and the polyurethane top layer are both 8-15 μm. This patent further improves the film's retort resistance and barrier properties by adding more modified silica sol to the polyurethane coating solution. However, this patent still suffers from insufficient optimization in substrate selection, resulting in the film's retort resistance still needing improvement. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a polyester film for aluminum plating and its preparation method. The modified polyester resin in the enhanced coating can crosslink to form a dense three-dimensional network, blocking moisture and improving the initial adhesion to the substrate / aluminum layer. Furthermore, the polyester film for aluminum plating can maintain good aluminum adhesion even under extreme boiling conditions of 121°C for 40 minutes.

[0007] The technical solution adopted by this invention to solve its technical problem is: A polyester film for aluminizing includes a substrate and a reinforcing coating disposed on at least one side of the substrate. The surface roughness Ra of the polyester film for aluminizing is 0.02 μm-0.03 μm, and the surface energy γ is 35 mJ / m. 2 -45mJ / m 2 The reinforcing coating comprises the following components in weight percentages: Modified polyester resin: 10%-25%; Crosslinking agent: 0.1%-5%; Additives: 0.01%-1%; Silica particles: 0.5%-1%; Deionized water: 68%-89.39%.

[0008] The modified polyester resin in the aforementioned aluminizing polyester film is polymerized from the following parts by weight of polyacid and polyol: 10-15 parts of 1,4-butanediol; 10-15 parts of 1,6-hexanediol; 5-10 parts of neopentyl glycol; 5-10 parts isophthalic acid; 5-10 parts terephthalic acid; 5-10 parts of dimethylolpropionic acid.

[0009] The silicon dioxide particles in the aforementioned aluminized polyester film have a particle size of 80nm to 150nm.

[0010] The above-mentioned polyester film for aluminum plating has a dry film thickness of 10nm to 80nm for the reinforcing coating.

[0011] The crosslinking agent in the above-mentioned aluminized polyester film is one or more of isocyanate, oxazoline, and melamine in any weight ratio.

[0012] The above-mentioned polyester film for metallization uses acetylation diols and organosilicon additives as additives.

[0013] The aforementioned aluminized polyester film uses a PET substrate with a thickness of 12~25μm.

[0014] A method for preparing a polyester film for metallization, the method comprising the following steps: a. The base material is fed into the extrusion system to melt and extrude the base material melt; b. Forming the substrate melt into an amorphous cast sheet on a cooling roller; c. After the cooled cast plastic sheet is preheated, it is stretched longitudinally by 3.0 to 5.0 times to obtain a film; d. The membrane is subjected to corona treatment on one or both sides, with a surface roughness Ra of 0.03 μm-0.04 μm and a surface energy γ of 35 mJ / m. 2 -45mJ / m 2 The reinforcing coating solution is applied to one or both sides of the corona-treated film to obtain a coated film. e. After preheating, the coated film is stretched laterally by 3.0 to 5.0 times to obtain a thin film, which is then heat-set to obtain a polyester film for metallization.

[0015] In the above-mentioned method for preparing aluminized polyester film, the preheating temperature in step c is 60℃-80℃; the preheating temperature in step e is 100℃-120℃; and the heat setting temperature in step f is 220℃-240℃.

[0016] The beneficial effects of this invention are: 1. The present invention coats an adhesion-enhancing coating on the surface of a 12-25μm thick PET substrate. The optimized selection of modified polyester resin polymer monomers in the reinforcement coating significantly improves the adhesion of PET film to aluminum, especially to vacuum metallization, effectively solving the problem of insufficient adhesion of polyester film in the prior art.

[0017] 2. The surface roughness of the prepared polyester film for metallization is controlled to be 0.02μm-0.03μm, and the surface energy γ is 35mJ / m. 2 -45mJ / m 2 By combining the application of reinforced coatings, the initial formation and long-term durability of the aluminum-plated layer can be optimized from both physical and chemical dimensions. This ensures that the polyester film can still maintain good aluminum adhesion under extreme boiling conditions of 121°C for 40 minutes, exhibiting excellent boiling resistance and anti-blocking properties, thus meeting the requirements of special application scenarios such as high-end packaging.

[0018] 3. This invention employs an online coating surface treatment process and corona treatment to improve the surface roughness and affinity of the PET film. The online coating process allows the coating to be stretched laterally by 3-5 times simultaneously with the PET substrate, forming a good interfacial bond with the substrate and avoiding the problems of thick coatings and easy peeling in traditional pretreatment layers. 4. The coating of the present invention adopts a water-based system formula, which has good environmental protection and non-toxicity, and meets the requirements of green environmental protection. Detailed Implementation

[0019] This invention involves coating a reinforcing coating onto a PET substrate. The reinforcing coating is made of a modified polyester resin as the film material. The modified polyester resin is polymerized from the following parts by weight of polyacids and polyols: 10-15 parts of 1,4-butanediol; 10-15 parts of 1,6-hexanediol; 5-10 parts of neopentyl glycol; 5-10 parts isophthalic acid; 5-10 parts terephthalic acid; 5-10 parts of dimethylolpropionic acid.

[0020] Among them, 1,4-butanediol and 1,6-hexanediol have long and flexible chain segments—methylene structures, which act like "springs" and can effectively absorb and release stress through their own deformation, preventing coating cracking or peeling from the substrate / aluminum layer due to stress concentration. The use of 1,4-butanediol and 1,6-hexanediol together controls the length and distribution of the polyester soft chain segments, achieving an optimal balance of flexibility between "brittleness" and "excessive softness." If only 1,4-butanediol is used, its short carbon chain provides limited flexibility and easily forms highly regular crystalline regions, resulting in a hard and brittle coating; if only 1,6-hexanediol is used, the excessively long aliphatic chains may lead to an overly soft resin, high initial tack, and insufficient hardness and heat resistance.

[0021] Neopentyl glycol provides a large number of side groups and steric hindrance. It can protect the adjacent ester bonds, greatly enhancing the polyester chain's resistance to hydrolysis. In a high-temperature steam environment of 121°C, ordinary ester bonds are easily attacked and broken by water molecules, but the structure of neopentyl glycol can effectively prevent this process and maintain the integrity of the coating network.

[0022] Terephthalic acid shares the same main monomer structure as the PET substrate, which endows the coating with excellent compatibility, allowing it to adhere firmly to the substrate like a "native" component. Simultaneously, the symmetrical benzene ring structure provides the coating with a high glass transition temperature and mechanical strength, enabling it to maintain sufficient rigidity and resist deformation even under high cooking temperatures, preserving the coating's shape. Isophthalic acid provides an asymmetrical benzene ring structure. This asymmetrical structure makes the molecular chains more prone to rotation under stress, absorbing some energy. Working synergistically with terephthalic acid, it achieves a balance of rigidity and flexibility.

[0023] Dimethylolpropionic acid can react with the crosslinking agent in the coating solution to connect the linear polyester chains into a dense three-dimensional network structure, thereby effectively blocking moisture, improving boiling resistance, and providing initial adhesion to the substrate / aluminum layer.

[0024] This invention controls the surface roughness Ra of the polyester film for aluminizing to 0.02μm-0.03μm by adding nano-sized silica particles with an average particle size (D50) between 80nm and 200nm to the coating solution. Excessive roughness leads to overly sharp and steep peaks and valleys in the film. At these sharp "peaks," the aluminized layer may become thinner due to uneven thickness, becoming mechanically weak points. Conversely, an overly smooth surface loses its mechanical anchoring effect, causing adhesion to revert to a weaker state relying solely on chemical bonds and van der Waals forces, making it difficult to withstand rigorous boiling tests. Under the thermal stress of boiling, stress easily concentrates at these points, inducing microcracks, ultimately causing the aluminized layer to fail from these defects. Therefore, this invention controls the surface roughness of the polyester film to 0.02μm-0.03μm to ensure its resistance to boiling after aluminizing. The surface energy (γ) of the polyester film for aluminizing is also controlled to be 35mJ / m. 2 -45mJ / m 2 The modified polyester resin in the coating contains polar groups such as carboxyl groups, which react with the crosslinking agent to form a network. The surface chemistry of this network determines the final surface energy. Excessively high surface energy usually means the surface is too hydrophilic. Under boiling conditions, such a coating will easily adsorb water molecules, which will accumulate at the interface between the coating and the aluminum layer, acting as a "de-adhesive" agent, disrupting interfacial bonds and leading to decreased adhesion. Conversely, excessively low surface energy will result in uneven aluminum plating and insufficient initial adhesion. Therefore, this invention controls the surface layer energy to 35 mJ / m². 2 -45mJ / m 2 It can ensure both adhesion and resistance to boiling.

[0025] The modified polyester resin in the reinforcing coating of this invention is obtained by polymerizing flexible segments (butanediol, hexanediol), hydrolysis-resistant units (neopentyl glycol), crosslinking centers (DMPA), and a rigid / asymmetric skeleton (terephthalic acid / isophthalic acid) in a reasonable ratio, making the prepared polyester film more resistant to retorting after aluminizing. This modified polyester enables the reinforcing coating to form a strong "anchoring" bond with the PET substrate during the longitudinal / transverse biaxial stretching process of the polyester film, ultimately forming a coating network with high crosslinking density, high hydrolytic stability, and excellent "rigid-flexible balance". At the same time, the surface roughness of the reinforced aluminized polyester film is controlled to 0.02μm-0.04μm, and the surface energy γ is 35mJ / m. 2 -45mJ / m 2This technology optimizes both the initial formation and long-term durability of the aluminum coating from both physical and chemical perspectives. It ensures that the polyester film maintains good aluminum adhesion even under extreme retorting conditions of 121°C for 40 minutes, exhibiting excellent retort resistance and anti-blocking properties, thus meeting the requirements of special applications such as high-end packaging.

[0026] The substrate of this invention is a PET substrate with a thickness of 12~25μm.

[0027] The preparation method of polyester film for metallization includes the following steps: a. The base material is fed into the extrusion system to melt and extrude the base material melt; b. Forming the substrate melt into an amorphous cast sheet on a cooling roller; c. After the cooled cast plastic sheet is preheated to 60℃-80℃, it is stretched longitudinally by 3.0 to 5.0 times to obtain a film; d. The membrane is subjected to corona treatment on one or both sides, with a surface roughness Ra of 0.02 μm-0.04 μm and a surface energy γ of 48 mJ / m. 2 -58mJ / m 2 The reinforcing coating solution is applied to one or both sides of the corona-treated film to obtain a coated film. e. After preheating the coated film at 100℃-120℃, stretch it laterally by 3.0 to 5.0 times to obtain a thin film, and heat-set it at 220℃-240℃ to obtain a polyester film for metallization.

[0028] The present invention will be further described below with reference to the embodiments. Example 1

[0029] A method for preparing reinforced polyester film for metallization includes the following steps: (1) Online surface treatment was performed on a 12μm thick PET substrate using corona treatment with a corona intensity of 2KW, which increased the surface roughness Ra of the PET substrate to 0.03μm; the surface energy (γ) was controlled at 48mJ / m 2 ; (2) The treated PET substrate is coated with an adhesion-enhancing coating on the surface of the PET substrate by online coating, and the coating thickness is 10nm; (3) The adhesion-enhancing coating (enhancing coating) is made from the following raw materials in parts by weight: Modified polyester resin: 10%; Isocyanate: 0.1%; Acrylene diol: 0.01%; Silica particles: 0.5%; Deionized water: 89.39%; The modified polyester resin is copolymerized from the following monomers: 10 parts of 1,4-butanediol; 10 parts of 1,6-hexanediol; 5 parts of neopentyl glycol; 5 parts isophthalic acid; 5 parts terephthalic acid; 5 parts of dimethylolpropionic acid; The silica particles have a particle size of 80 nm.

[0030] (4) The coating was dried at 100℃, stretched 3 times laterally, and cured at 220℃ for 30 seconds to form a dense and uniform coating structure. The surface roughness Ra of the cured coating was 0.02μm, and the surface energy (γ) was 35mJ / m. 2 .

[0031] (5) The prepared reinforced aluminized polyester film is placed in a vacuum aluminizing equipment, heated and melted at 1300℃ and evaporated into gaseous aluminum, so that aluminum atoms adhere to the coating surface to form an extremely thin aluminized layer. The treated film has excellent aluminum adhesion, and the aluminum layer adhesion reaches 10N / 25mm.

[0032] (6) After the prepared reinforced aluminized polyester film was boiled at 121°C for 40 minutes, the adhesion rate of the aluminum layer was 100%, indicating that the film has excellent boiling resistance. Example 2

[0033] A method for preparing a reinforced polyester film for metallization includes the following steps: (1) Online surface treatment was performed on a 25μm thick PET substrate using corona treatment with a corona intensity of 8KW, which increased the surface roughness Ra of the PET substrate to 0.04μm; the surface energy (γ) was controlled at 58mJ / m 2 ; (2) The treated PET substrate is coated with an adhesion-enhancing coating on the surface of the PET substrate by online coating, and the coating thickness is 80nm; (3) The adhesion-enhancing coating is made from the following raw materials in parts by weight: Modified polyester resin: 25%; Oxazoline: 5%; Organosilicon wetting agent: 1%; Silica particles: 1%; Deionized water: 68%; The modified polyester resin is copolymerized from the following monomers under an initiator: 15 parts of 1,4-butanediol; 15 parts of 1,6-hexanediol; 10 parts of neopentyl glycol; 10 parts of isophthalic acid; 10 parts terephthalic acid; 10 parts of dimethylolpropionic acid; The silica particles have a particle size of 150 nm.

[0034] (4) The coating was dried at 120℃, stretched 5 times laterally, and cured at 240℃ for 60s to form a dense and uniform coating structure. The surface roughness Ra of the cured coating was 0.03μm, and the surface energy (γ) was 45mJ / m. 2 .

[0035] (5) The prepared reinforced aluminized polyester film is placed in a vacuum aluminizing equipment, heated and melted at 1300℃ and evaporated into gaseous aluminum, so that aluminum atoms adhere to the coating surface to form an extremely thin aluminized layer. The treated film has excellent aluminum adhesion, and the aluminum layer adhesion reaches 9N / 25mm.

[0036] (6) After the prepared reinforced aluminized polyester film was boiled at 121°C for 40 minutes, the adhesion rate of the aluminum layer was 100%, indicating that the film has excellent boiling resistance. Example 3

[0037] A method for preparing a reinforced polyester film for metallization includes the following steps: (1) Online surface treatment was performed on an 18μm thick PET substrate using corona treatment with a corona intensity of 5KW, which increased the surface roughness Ra of the PET substrate to 0.035μm; the surface energy (γ) was controlled at 53mJ / m 2 ; (2) The treated PET substrate is coated with an adhesion-enhancing coating on the surface of the PET substrate by online coating, and the coating thickness is 45nm; (3) The adhesion-enhancing coating is made from the following raw materials in parts by weight: Modified polyester resin: 17%; Isocyanate: 2.5%; Acetylene diol: 0.5%; Silica particles: 0.75%; Deionized water: 79.25%; The modified polyester resin is copolymerized from the following monomers under an initiator: 12.5 parts of 1,4-butanediol; 12.5 parts of 1,6-hexanediol; 7.5 parts of neopentyl glycol; 7.5 parts of isophthalic acid; 7.5 parts terephthalic acid; 7.5 parts of dimethylolpropionic acid; The silica particles have a diameter of 120 nm.

[0038] (4) The coating was dried at 110℃, stretched 4 times laterally, and cured at 230℃ for 45s to form a dense and uniform coating structure. The surface roughness Ra of the cured coating was 0.025μm, and the surface energy (γ) was 40mJ / m. 2 .

[0039] (5) The prepared reinforced aluminized polyester film is placed in a vacuum aluminizing equipment, heated and melted at 1300℃ and evaporated into gaseous aluminum, so that aluminum atoms adhere to the coating surface to form an extremely thin aluminized layer. The treated film has excellent aluminum adhesion, and the aluminum layer adhesion reaches 12N / 25mm.

[0040] (6) After the prepared reinforced aluminized polyester film was boiled at 121°C for 40 minutes, the adhesion rate of the aluminum layer was 100%, indicating that the film has excellent boiling resistance. Example 4

[0041] A method for preparing a reinforced polyester film for metallization includes the following steps: (1) Online surface treatment was performed on a 15μm thick PET substrate using corona treatment with a corona intensity of 3.5KW, which increased the surface roughness Ra of the PET substrate to 0.032μm; the surface energy (γ) was controlled at 50mJ / m 2 ; (2) The treated PET substrate is coated with an adhesion-enhancing coating on the surface of the PET substrate by online coating, and the coating thickness is 30nm; (3) The adhesion-enhancing coating is made from the following raw materials in parts by weight: Modified polyester resin: 13%; Oxazoline: 1.5%; Organosilicon wetting agent: 0.25%; Silica particles: 0.6%; Deionized water: 84.65%; The modified polyester resin is copolymerized from the following monomers under an initiator: 11 parts of 1,4-butanediol; 11 parts of 1,6-hexanediol; 6 parts of neopentyl glycol; 6 parts isophthalic acid; 6 parts terephthalic acid; 6 parts of dimethylolpropionic acid; The silica particles have a diameter of 100 nm.

[0042] (4) The coating was dried at 105℃, stretched 3.5 times laterally, and cured at 225℃ for 37s to form a dense and uniform coating structure. The surface roughness Ra of the cured coating was 0.023μm, and the surface energy (γ) was 38mJ / m. 2 .

[0043] (5) The prepared reinforced aluminized polyester film is placed in a vacuum aluminizing equipment, heated and melted at 1300℃ and evaporated into gaseous aluminum, so that aluminum atoms adhere to the coating surface to form an extremely thin aluminized layer. The treated film has excellent aluminum adhesion, and the aluminum layer adhesion reaches 10N / 25mm.

[0044] (6) After the prepared reinforced aluminized polyester film was boiled at 121°C for 40 minutes, the adhesion rate of the aluminum layer was 100%, indicating that the film has excellent boiling resistance. Example 5

[0045] A method for preparing a reinforced aluminized polyester film includes the following steps: (1) Online surface treatment was performed on a 21μm thick PET substrate using corona treatment with a corona intensity of 6.5KW, which increased the surface roughness Ra of the PET substrate to 0.038μm; the surface energy (γ) was controlled at 42.5mJ / m 2 ; (2) The treated PET substrate is coated with an adhesion-enhancing coating on the surface of the PET substrate by online coating, and the coating thickness is 65nm; (3) The adhesion-enhancing coating is made from the following raw materials in parts by weight: Modified polyester resin: 20%; Isocyanate: 4%; Acrylene diol: 0.7%; Silica particles: 0.8%; Deionized water: 74.5%; The modified polyester resin is copolymerized from the following monomers under an initiator: 14 parts of 1,4-butanediol; 14 parts of 1,6-hexanediol; 9 parts of neopentyl glycol; 9 parts of isophthalic acid; 9 parts terephthalic acid; 9 parts of dimethylolpropionic acid; The silica particles have a diameter of 135 nm.

[0046] (4) The coating was dried at 115℃, stretched 4.5 times laterally, and cured at 235℃ for 52 seconds to form a dense and uniform coating structure. The surface roughness Ra of the cured coating was 0.027 μm, and the surface energy (γ) was 42 mJ / m. 2 .

[0047] (5) The prepared reinforced aluminized polyester film is placed in a vacuum aluminizing equipment, heated and melted at 1300℃ and evaporated into gaseous aluminum, so that aluminum atoms adhere to the coating surface to form an extremely thin aluminized layer. The treated film has excellent aluminum adhesion, and the aluminum layer adhesion reaches 12N / 25mm.

[0048] (6) After the prepared reinforced aluminized polyester film was boiled at 121°C for 40 minutes, the adhesion rate of the aluminum layer was 100%, indicating that the film has excellent boiling resistance. Comparative Example 1

[0049] A method for preparing a reinforced aluminized polyester film includes the following steps: (1) The 12μm thick PET substrate was not treated; (2) The untreated PET substrate is coated with an adhesion-enhancing coating on the film surface by online coating, and the coating thickness is 10 nm; (3) The adhesion-enhancing coating (enhancing coating) is made from the following raw materials in parts by weight: Modified polyester resin: 10%; Isocyanate: 0.1%; Acrylene diol: 0.01%; Silica particles: 0.8%; Deionized water: 88.59%; The modified polyester resin is copolymerized from the following monomers under an initiator: 10 parts of 1,4-butanediol; 10 parts of 1,6-hexanediol; 5 parts of neopentyl glycol; 5 parts isophthalic acid; 5 parts terephthalic acid; 5 parts of dimethylolpropionic acid; The silica particles have a particle size of 80 nm.

[0050] (4) The coating is dried at 100℃, stretched 3 times laterally, and shaped and cured at 220℃ for 30s to form a dense and uniform coating structure.

[0051] (5) The prepared reinforced aluminized polyester film is placed in a vacuum aluminizing equipment, heated and melted at 1300℃ and evaporated into gaseous aluminum, so that aluminum atoms adhere to the coating surface to form an extremely thin aluminized layer. The treated film has excellent aluminum adhesion, and the aluminum layer adhesion reaches 6N / 25mm.

[0052] (6) After the prepared reinforced aluminized polyester film was boiled at 121°C for 40 minutes, the aluminum layer adhesion retention rate was 82%, and the film had slightly poor boiling resistance. Comparative Example 2

[0053] A method for preparing a reinforced polyester film for metallization includes the following steps: (1) Online surface treatment was performed on a 21μm thick PET substrate using corona treatment with a corona intensity of 6.5KW, which increased the surface roughness Ra of the PET substrate to 0.035μm; the surface energy (γ) was controlled at 42.5mJ / m 2 ; (2) The treated PET substrate is coated with an adhesion-enhancing coating on the surface of the PET substrate by online coating, and the coating thickness is 65nm; (3) The adhesion-enhancing coating is made from the following raw materials in parts by weight: Waterborne polyester resin (unmodified, Toyobo, MD1245): 20%; Isocyanate: 4%; Acrylene diol: 0.7%; Silica particles: 0.8%; Deionized water: 74.5%; The silica particles have a diameter of 135 nm.

[0054] (4) The coating was dried at 115℃, stretched 4.5 times laterally, and cured at 235℃ for 52 seconds to form a dense and uniform coating structure. The surface roughness Ra of the cured coating was controlled at 0.035μm, and the surface energy (γ) was controlled at 42mJ / m. 2 .

[0055] (5) The prepared reinforced aluminized polyester film is placed in a vacuum aluminizing equipment, heated and melted at 1300℃ and evaporated into gaseous aluminum, so that aluminum atoms adhere to the coating surface to form an extremely thin aluminized layer. The treated film has excellent aluminum adhesion, and the aluminum layer adhesion reaches 3N / 25mm.

[0056] (6) After the prepared reinforced aluminized polyester film was boiled at 121°C for 40 minutes, the aluminum layer adhesion retention rate was 42%, indicating that the film had poor boiling resistance.

[0057] The performance testing methods are as follows: (1) Peel strength: Refer to QB / T 2358-1998 "Test method for heat sealing strength of plastic film packaging bags", heat seal the heat sealing layer of EAA film with the aluminized layer, heat sealing temperature 125℃, pressure 0.25MPa, heat sealing time 1.8s, and then use a tensile testing machine to peel the aluminized layer off the aluminized film to obtain peel strength data.

[0058] (2) Coating appearance quality: visually inspected under a strong flashlight. The coating appearance evaluation level is divided into 3 categories: ○ is judged as having no defects such as mottled appearance, longitudinal lines or bubble spots; △ is judged as having slight mottled appearance, longitudinal lines or bubble spots; and × is judged as having severe mottled appearance, longitudinal lines or bubble spots.

[0059] The test results are shown in Table 1:

[0060] As can be seen from the comparison between Comparative Example 1 and Example 1, Example 1, which uses modified polyester resin and corona treatment simultaneously, has a better peel strength and better coating appearance after online coating compared to the untreated polyester film.

[0061] As can be seen from the comparison between Comparative Example 2 and Example 5, the coating of Comparative Example 2 did not use modified polyester resin, and its peel strength and coating appearance were poor.

[0062] As can be seen from Table 1, the reinforced coating prepared in the embodiments of the present invention has significantly improved peel strength and coating appearance compared with the reinforced coating prepared in the comparative example. This indicates that the reinforced aluminized polyester film of the present invention not only has excellent peel strength performance, but also excellent boiling resistance performance, and has good application prospects.

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A polyester film for aluminizing, comprising a substrate (1) and a reinforcing coating (2) disposed on at least one side of the substrate (1), characterized in that: The surface roughness Ra of the polyester film used for aluminizing is 0.02 μm-0.03 μm, and the surface energy γ is 35 mJ / m. 2 -45mJ / m 2 The coating liquid for the enhanced coating comprises the following components by weight percentage: Modified polyester resin: 10%-25%; Crosslinking agent: 0.1%-5%; Additives: 0.01%-1%; Silica particles: 0.5%-1%; Deionized water: 68%-89.39%.

2. The polyester film for aluminizing according to claim 1, characterized in that: The modified polyester resin is polymerized from the following parts by weight of polyacids and polyols: 10-15 parts of 1,4-butanediol; 10-15 parts of 1,6-hexanediol; 5-10 parts of neopentyl glycol; 5-10 parts isophthalic acid; 5-10 parts terephthalic acid; 5-10 parts of dimethylolpropionic acid.

3. The polyester film for aluminizing according to claim 1, characterized in that: The silica particles have a particle size of 80nm to 150nm.

4. The polyester film for aluminizing according to claim 1, characterized in that: The dry film thickness of the enhanced coating (2) is 10 nm to 80 nm.

5. The polyester film for aluminizing according to claim 1, characterized in that: The crosslinking agent is one or more of isocyanate, oxazoline, and melamine in any weight ratio.

6. The polyester film for aluminizing according to claim 1, characterized in that: The additives are acetylenic diols and organosilicon additives.

7. The polyester film for aluminizing according to claim 1, characterized in that: The substrate (1) is a PET substrate with a thickness of 12μm~25μm.

8. A method for preparing a polyester film for metallization as described in any one of claims 1-7, characterized in that: The preparation method includes the following steps: a. The base material is fed into the extrusion system to melt and extrude the base material melt; b. Forming the substrate melt into an amorphous cast sheet on a cooling roller; c. After the cooled cast plastic sheet is preheated, it is stretched longitudinally by 3.0 to 5.0 times to obtain a film; d. The membrane is subjected to corona treatment on one or both sides, with a surface roughness Ra of 0.03 μm-0.04 μm and a surface energy γ of 48 mJ / m. 2 -58mJ / m 2 The reinforcing coating solution is applied to one or both sides of the corona-treated film to obtain a coated film. e. After preheating, the coated film is stretched laterally by 3.0 to 5.0 times to obtain a thin film, which is then heat-set to obtain a polyester film for metallization.

9. The method for preparing aluminized polyester film according to claim 8, characterized in that: In step c, the preheating temperature is 60℃-80℃; in step e, the preheating temperature is 100℃-120℃; and in step f, the heat setting temperature is 220℃-240℃.

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