High-shrinkage BOPP printing film and preparation method thereof

Abstract

The invention belongs to the technical field of plastic films, and particularly provides a high-shrinkage BOPP printing film and a preparation method thereof. The preparation method of the high-shrinkage BOPP printing film comprises the following steps: carrying out corona and activation treatment on a BOPP base film, and then coating a layer of coating composition to obtain the high-shrinkage BOPP printing film, in the preparation process of the coating composition, a ductility agent prepared from polyvinyl alcohol and acrylamide and a stabilizer prepared from alkylamine and glycidyl ether are added, so that the prepared high-shrinkage BOPP printing film has the advantages of being easy to print and few in heated wrinkles.

Description

Technical Field

[0001] This application belongs to the field of plastic film technology, and in particular relates to a high-shrinkage BOPP printing film and its preparation method. Background Technology

[0002] Bis-directional polypropylene (BOPP) film, as a polymer film material with excellent mechanical properties, barrier properties, and processing adaptability, is widely used in food packaging, daily necessities packaging, and industrial packaging. Its lightweight, low cost, and good mechanical strength make it one of the core choices in the packaging material field. Furthermore, with the increasing demands of the packaging industry for product appearance and information transmission, the printability of BOPP film has become an important factor in expanding its application scenarios.

[0003] BOPP substrate is a non-polar polymer material with low surface energy, resulting in poor wetting and spreading properties between ink and the film surface, insufficient printing adhesion, and smudges, severely limiting its application in high-requirement printing and packaging scenarios. Therefore, improving the hydrophilic and printable properties of BOPP printing film has become one of the core directions of research and development for this type of material. To address the insufficient hydrophilicity and printability of BOPP substrate, a technical solution is to add a functional coating to the film surface. By coating the BOPP film with a certain degree of hydrophilicity, the surface energy of the film can be effectively increased, improving the interfacial interaction between ink and the film surface, enhancing printability, and resulting in clearer resolution and more durable adhesion stability of the printed pattern.

[0004] However, while coating technology improves the hydrophilicity and printability of BOPP printing films, significant technical challenges remain in practical applications. Due to differences in physical properties such as thermal expansion coefficients and shrinkage rates between the BOPP substrate and coating materials, stress mismatch occurs between the substrate and coating during heat shrinkage processing, leading to defects such as coating bulging, wrinkles, and surface roughness. These defects not only compromise the integrity and aesthetics of the printed pattern but may also affect the film's barrier properties and mechanical stability, reducing the overall quality of the packaged product. Furthermore, insufficient interfacial bonding strength between the coating and substrate, and inherent film-forming defects in the coating itself, exacerbate surface quality issues during shrinkage, thus hindering performance improvements in BOPP printing films.

[0005] In summary, optimizing the coating formulation and mitigating stress mismatch during the heat shrinkage process to prepare a shrinkable and printable BOPP film remains an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned issues, and in order to improve the printability of BOPP printing film while reducing wrinkles and bulging when the BOPP printing film is heated, this application provides a high-shrinkage BOPP printing film and its preparation method.

[0007] This application first provides a method for preparing a high-shrinkage BOPP printing film, comprising the following steps: a BOPP base film is subjected to corona treatment and activation, and then coated with a coating composition to obtain a high-shrinkage BOPP printing film; The preparation method of the coating composition includes the following steps: first, mixing the silicon source and solvent, adjusting the pH, then adding the titanium source, ductile agent, stabilizer, and sonicating. The ductile agent is prepared by mixing polyvinyl alcohol and acrylamide; The stabilizer is prepared by reacting alkylamines and glycidyl ethers together, followed by mixing with boric acid derivatives.

[0008] Furthermore, the process parameters for the corona treatment are: power 1-3W, time 15-30s.

[0009] Furthermore, the activation process involves grafting a silane coupling agent and acrylic acid onto the corona-treated BOPP base film.

[0010] Furthermore, the preparation method of the ductile agent includes the following steps: choline chloride and ethylene glycol are mixed, polyvinyl alcohol is added, stirred and dissolved, then acrylamide is added, cooled to room temperature, and then a polymerization reaction is carried out. The mixture is then pulverized and ball-milled to obtain the ductile agent.

[0011] Furthermore, the preparation method of the stabilizer includes the following steps: mixing alkylamine and glycidyl ether, carrying out a ring-opening reaction, cooling to room temperature after the reaction is completed, adding boric acid derivative to form a mixture, solidifying, pulverizing, and grinding to obtain the stabilizer.

[0012] Furthermore, the mass ratio of polyvinyl alcohol to acrylamide is 1:(1.5-3).

[0013] Furthermore, the ball milling process is as follows: zirconium oxide with a particle size of 0.5-1 mm is selected as the ball milling medium, the ball milling time is 2-3 hours, and the speed is 450-500 rpm.

[0014] Furthermore, the silane coupling agent is an aminosilane coupling agent.

[0015] Furthermore, the reaction conditions for the ring-opening reaction are: under a nitrogen atmosphere, at 65-70°C, for 12-15 hours.

[0016] This application also provides a high-shrinkage BOPP printing film, which is prepared by the above-described preparation method.

[0017] Compared with the prior art, this application has the following beneficial effects: 1. By grafting acrylic polymer onto the surface of BOPP film and coating it with a coating composition mainly composed of silica and titanium dioxide, the hydrophilicity of BOPP film is improved, which is conducive to the printing of water-based inks.

[0018] 2. Adding ductile agents and stabilizers to the coating composition, during the encapsulation process, the BOPP film is heated, and the hydrogen bonds between polyvinyl alcohol and polyacrylamide in the ductile agent dissociate, which gives the coating a certain deformation ability. At the same time, after the stabilizer is heated, the amino and oxygen in it form borate ester bonds coordinated with boric acid (BN), causing the coating to shrink and reducing coating bulging and peeling from the BOPP film. Attached Figure Description

[0019] Figure 1 The surface roughness test data of the high-shrinkage BOPP films of Examples 1-3 and Comparative Examples 1-2 of this application after being heated are shown.

[0020] Figure 2 The water contact angle test data are for the high-shrinkage BOPP membranes of Examples 1-3 and Comparative Examples 1-2 of this application. Detailed Implementation

[0021] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments, clearly and completely describing the technical solutions in the embodiments of this application. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0024] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0025] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0026] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0027] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0029] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0030] In this application, room temperature refers to 0-40°C, including but not limited to 10-40°C, or further to 20-30°C.

[0031] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0032] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0033] Preparation Example Weigh out 0.5g of silica, 190g of copolymer polypropylene, and 0.15g of glyceryl monostearate, and mix them as the top layer material; weigh out 200g of homopolymer polypropylene, 8g of maleic anhydride-grafted polypropylene, 0.2g of erucamide, and 0.1g of EP548s nucleating agent, and mix them as the core layer material; weigh out 2g of silica, 200g of copolymer polypropylene, and 0.15g of glyceryl monostearate, and mix them as the bottom layer material; melt each layer using an extruder and co-extrude through a three-layer die. The melt extrusion temperature of the top layer is 220-245℃. The melt extrusion temperature of the lower surface layer is 210-225℃, and the melt extrusion temperature of the core layer is 235-255℃. After being cooled by rollers at 10-15℃, it is cast into a sheet with a thickness of 1mm. After preheating at 130℃, it is stretched longitudinally by 6 times, and then the temperature is adjusted to 150℃ for transverse stretching, with a transverse stretching ratio of 9. It is then shaped at 150℃, and finally trimmed and wound up to obtain the BOPP base film. The average thickness of the upper surface layer is 3.6μm, the average thickness of the lower surface layer is 3μm, and the average thickness of the BOPP base film is 38.9μm.

[0034] Example 1 The preparation method of the high-shrinkage BOPP printed film in this embodiment is as follows: 1) Take a BOPP base film and subject it to single-sided corona treatment at a power of 1W for 30 seconds to obtain a BOPP corona-treated film. Then, take 6g of acrylic acid, 2g of 3-aminopropyltriethoxysilane, 0.03g of initiator 1173, 2g of polyvinyl alcohol, and 60g of deionized water and mix them evenly. Then, apply the solution at a concentration of 4g / m 2The wet film coating was applied to the BOPP corona film at a wavelength of 365nm and a power of 20W. It was then cured under UV light for 10 minutes, immersed in deionized water for 30 minutes, removed and dried to obtain the pretreated BOPP film. 2) Weigh 20.9g of choline chloride and 18.6g of ethylene glycol into a flask, stir at 70℃ for 50min, introduce nitrogen gas, add 3g of polyvinyl alcohol, adjust the temperature to 120℃, stir for 3h, then add 4.5g of acrylamide and 0.09g of initiator 1173, continue stirring for 30min, pour into a polytetrafluoroethylene container, cool to room temperature, and carry out polymerization reaction under ultraviolet light irradiation at wavelength 365nm, power 8W, time 2h. After the reaction is completed, take out the product, crush it, ball mill it, select zirconium oxide with a particle size of 0.5mm as the ball milling medium, ball milling time is 2h, speed is 500rpm, dry, and obtain the ductile agent; 3) Measure 50 mL of tetrahydrofuran into a flask, add 1.3 g of 3-butoxypropylamine and 2 g of 1,4-butanediol diglycidyl ether under a nitrogen atmosphere, heat to 65 °C, reflux for 15 h, cool to room temperature after the reaction, add 1 g of anthraquinone boric acid and mix well, pour into a petri dish, the liquid level is less than 0.2 mm, irradiate under 365 nm UV light for 50 min, then heat treat at 120 °C for 1 h, collect the solid component, crush and grind, then transfer to a constant temperature and humidity chamber (temperature 30 °C, relative humidity 90%) and place for 30 min to obtain the stabilizer; 4) Weigh 60g of deionized water, 100g of ethanol, 0.6g of KH-550, and 0.2g of polyvinyl alcohol into a beaker and sonicate to mix thoroughly. Then add 16g of tetraethyl orthosilicate and adjust the pH of the system to 3 using hydrochloric acid. After sonicating for 5 minutes, add a mixture of 24g of tetrabutyl titanate and 50g of ethanol at a rate of 10mL / min and continue sonicating for 1 hour. Subsequently, add 0.4g of ductile agent and 0.5g of stabilizer to obtain the coating composition. Apply the coating composition to a BOPP film with a dry coating weight of 5g / m². 2 Curing at room temperature for 8 hours, washing, and drying at 30°C yields a high-shrinkage BOPP printing film.

[0035] The BOPP base film in this embodiment was prepared using the preparation example.

[0036] Example 2 The preparation method of the high-shrinkage BOPP printed film in this embodiment is as follows: 1) Take a BOPP base film and subject it to single-sided corona treatment at 3W for 15s to obtain a BOPP corona-treated film. Then, take 6g of acrylic acid, 2g of 3-aminopropyltriethoxysilane, 0.03g of initiator 1173, 2g of polyvinyl alcohol, and 60g of deionized water and mix them evenly. Then, apply the solution at 4.5g / m2 The wet film coating was applied to the BOPP corona film at a wavelength of 365nm and a power of 20W. It was then cured under UV light for 20 minutes, immersed in deionized water for 30 minutes, removed and dried to obtain the pretreated BOPP film. 2) Weigh 20.9g of choline chloride and 18.6g of ethylene glycol into a flask, stir at 70℃ for 50min, introduce nitrogen gas, add 3g of polyvinyl alcohol, adjust the temperature to 120℃, stir for 3h, then add 9g of acrylamide and 0.2g of initiator 1173, continue stirring for 30min, pour into a polytetrafluoroethylene container, cool to room temperature, and carry out the polymerization reaction under ultraviolet light at a wavelength of 365nm, a power of 8W, and a time of 3h. After the reaction is completed, take out the product, crush it, and ball mill it. Select zirconium oxide with a particle size of 1mm as the ball milling medium, ball mill for 3h at a speed of 450rpm, and dry it to obtain the ductile agent. 3) Measure 50 mL of tetrahydrofuran into a flask, add 1.3 g of 3-butoxypropylamine and 2 g of 1,4-butanediol diglycidyl ether under a nitrogen atmosphere, heat to 70 °C, reflux for 12 h, cool to room temperature after the reaction, add 1 g of anthraquinone, mix well, pour into a petri dish, the liquid level is less than 0.2 mm, irradiate under 365 nm UV light for 50 min, then heat treat at 120 °C for 1.5 h, collect the solid component, crush, grind, and then transfer to a constant temperature and humidity chamber (temperature 30 °C, relative humidity 90%), place for 30 min to obtain the stabilizer; 4) Weigh 60g of deionized water, 90g of ethanol, 0.6g of KH-550, and 0.2g of polyvinyl alcohol into a beaker and sonicate to mix thoroughly. Then add 16g of tetraethyl orthosilicate and adjust the pH of the system to 3.5 using hydrochloric acid. After sonicating for 5 minutes, add a mixture of 24g of tetrabutyl titanate and 50g of ethanol at a rate of 10mL / min and continue sonicating for 1 hour. Subsequently, add 0.4g of ductile agent and 0.4g of stabilizer to obtain the coating composition. Coat the coating composition onto a BOPP film with a dry coating weight of 5g / m². 2 Curing at room temperature for 8 hours, washing, and drying at 30°C yields a high-shrinkage BOPP printing film.

[0037] The BOPP base film in this embodiment was prepared using the preparation example.

[0038] Example 3 The preparation method of the high-shrinkage BOPP printed film in this embodiment is as follows: 1) Take a BOPP base film and subject it to single-sided corona treatment at a power of 1.5W for 25 seconds to obtain a BOPP corona-treated film. Then, take 6g of acrylic acid, 2g of 3-aminopropyltriethoxysilane, 0.03g of initiator 1173, 1.5g of polyvinyl alcohol, and 60g of deionized water and mix them evenly. Then, apply the solution at a concentration of 4g / m 2 The wet film coating was applied to the BOPP corona film at a wavelength of 365nm and a power of 20W. It was then cured under UV light for 10 minutes, immersed in deionized water for 30 minutes, removed and dried to obtain the pretreated BOPP film. 2) Weigh 21g of choline chloride and 18.5g of ethylene glycol into a flask, stir at 70℃ for 50min, introduce nitrogen gas, add 3g of polyvinyl alcohol, adjust the temperature to 120℃, stir for 3h, then add 6g of acrylamide and 0.09g of initiator 1173, continue stirring for 30min, pour into a polytetrafluoroethylene container, cool to room temperature, and carry out polymerization reaction under ultraviolet light at a wavelength of 365nm, power of 8W, and time of 2.5h. After the reaction is completed, take out the product, crush it, and ball mill it. Select zirconium oxide with a particle size of 0.5mm as the ball milling medium, ball mill for 2h at a speed of 500rpm, and dry it to obtain the ductile agent. 3) Measure 50 mL of tetrahydrofuran into a flask, add 1.4 g of 3-butoxypropylamine and 2 g of 1,4-butanediol diglycidyl ether under a nitrogen atmosphere, heat to 68 °C, reflux for 14 h, cool to room temperature after the reaction, add 1 g of anthraquinone boric acid and mix well, pour into a petri dish, the liquid level is less than 0.2 mm, irradiate under 365 nm UV light for 50 min, then heat treat at 120 °C for 1 h, collect the solid component, crush and grind, then transfer to a constant temperature and humidity chamber (temperature 30 °C, relative humidity 90%) and place for 30 min to obtain the stabilizer; 4) Weigh 60g of deionized water, 100g of ethanol, 0.6g of KH-550, and 0.2g of polyvinyl alcohol into a beaker and sonicate to mix thoroughly. Then add 16g of tetraethyl orthosilicate and adjust the pH of the system to 3 using hydrochloric acid. After sonicating for 5 minutes, add a mixture of 24g of tetrabutyl titanate and 50g of ethanol at a rate of 10mL / min and continue sonicating for 1 hour. Subsequently, add 0.4g of ductile agent and 0.5g of stabilizer to obtain the coating composition. Apply the coating composition to a BOPP film with a dry coating weight of 4.8g / m². 2 Curing at room temperature for 8 hours, washing, and drying at 30°C yields a high-shrinkage BOPP printing film.

[0039] The BOPP base film in this embodiment was prepared using the preparation example.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that no ductile agent was added to the coating composition, while the remaining steps are the same as in Example 1.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that no stabilizer was added to the coating composition, while the remaining steps are the same as in Example 1.

[0042] Performance testing 1. Various performance tests were conducted on the high-shrinkage BOPP printing films of Examples 1-3 and Comparative Examples 1-2. The test methods and data are shown in Table 1.

[0043] 2. Surface roughness tests were performed on the high-shrinkage BOPP printed films of Examples 1-3 and Comparative Examples 1-2. Samples were first cut to a width of 15 mm and a length of 150 mm. The samples were then subjected to high-temperature treatment using a heat shrink apparatus at 130°C for 2 seconds. After the high-temperature treatment, the surface roughness of the samples was tested according to standard GB / T 31227-2014. The test results are as follows: Figure 1 As shown.

[0044] 3. Water Contact Angle Test: The water contact angle of the high-shrinkage BOPP printed films of Examples 1-3 and Comparative Examples 1-2 was tested using a contact angle tester. The water droplet volume was 5 μL. The test results are as follows: Figure 2 As shown.

[0045] Table 1 Performance test methods and data of high-shrinkage BOPP printed films in Examples 1-3 and Comparative Examples 1-2 Analysis of Examples 1-3 and Comparative Examples 1-2, in conjunction with Table 1, Figure 1 and Figure 2 It can be seen that the BOPP printing film prepared in the example has a certain heat shrinkage rate, and the surface roughness is significantly reduced after heating compared with the comparative example. This also indicates that the ductile agent and stabilizer added in the example effectively reduce the phenomenon of blistering and wrinkling of BOPP printing film after heating. At the same time, the BOPP film has good hydrophilicity and is suitable for printing with water-based inks.

[0046] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a high-shrinkage BOPP printing film, characterized in that: The process includes the following steps: the BOPP base film is subjected to corona treatment and activation, and then coated with a coating composition to obtain a high-shrinkage BOPP printing film; The preparation method of the coating composition includes the following steps: first, mixing the silicon source and solvent, adjusting the pH, then adding the titanium source, ductile agent, stabilizer, and sonicating. The ductile agent is prepared by mixing polyvinyl alcohol and acrylamide; The stabilizer is prepared by reacting alkylamines and glycidyl ethers together, followed by mixing with boric acid derivatives.

2. The method for preparing a high-shrinkage BOPP printing film according to claim 1, characterized in that: The process parameters for the corona discharge are: power 1-3W, time 15-30s.

3. The method for preparing a high-shrinkage BOPP printing film according to claim 1, characterized in that: The activation process involves grafting a silane coupling agent and acrylic acid onto a BOPP base film after corona treatment.

4. The method for preparing a high-shrinkage BOPP printing film according to claim 1, characterized in that: The preparation method of the ductile agent includes the following steps: choline chloride and ethylene glycol are mixed, polyvinyl alcohol is added, and the mixture is stirred to dissolve. Acrylamide is then added, the mixture is cooled to room temperature, and a polymerization reaction is carried out. The mixture is then pulverized and ball-milled to obtain the ductile agent.

5. The method for preparing a high-shrinkage BOPP printing film according to claim 1, characterized in that: The method for preparing the stabilizer includes the following steps: mixing alkylamine and glycidyl ether, performing a ring-opening reaction, cooling to room temperature after the reaction, adding boric acid derivative to form a mixture, solidifying, pulverizing, and grinding to obtain the stabilizer.

6. A method for preparing a high-shrinkage BOPP printing film according to claim 1 or 4, characterized in that: The mass ratio of polyvinyl alcohol to acrylamide is 1:(1.5-3).

7. The method for preparing a high-shrinkage BOPP printing film according to claim 4, characterized in that: The ball milling process is as follows: zirconium oxide with a particle size of 0.5-1mm is selected as the ball milling medium, the ball milling time is 2-3 hours, and the speed is 450-500 rpm.

8. The method for preparing a high-shrinkage BOPP printing film according to claim 3, characterized in that: The silane coupling agent is an aminosilane coupling agent.

9. The method for preparing a high-shrinkage BOPP printing film according to claim 5, characterized in that: The reaction conditions for the ring-opening reaction are: under a nitrogen atmosphere, at 65-70°C, for 12-15 hours.

10. A high-shrinkage BOPP printing film, characterized in that: It is prepared by any one of the preparation methods described in claims 1-9.

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