Preparation process of laser printing coating of PET film

Abstract

The application provides a preparation process of a PET film laser printing coating and belongs to the technical field of laser printing coatings.The preparation process comprises the following steps: S1, according to the weight fraction, 72-75 parts of water-based acrylic resin emulsion, 2-2.5 parts of polydimethylsiloxane, 5-7 parts of silicon-doped titanium dioxide, 1-2 parts of silane coupling agent KH-570, 2-3 parts of crosslinking agent vinyltriethoxysilane, 2-4 parts of film-forming aid propylene glycol phenyl ether, 0.6-0.8 parts of photoinitiator and 0.3-0.5 parts of defoaming agent are put into a double-screw high-speed dispersion machine, are dispersed, are left to stand and a mixture is obtained; S2, after the PET film is subjected to corona treatment, pretreated PET film is obtained; S3, the mixture obtained in S1 is uniformly coated on the pretreated PET film obtained in S2, and curing treatment is carried out, and thus the PET film laser printing coating is obtained. The application can effectively improve the heat resistance of the prepared PET film laser printing coating and the adsorption capacity of the PET film laser printing coating to carbon powder.

Description

Technical Field

[0001] This invention belongs to the field of laser printing coating technology, and in particular relates to a preparation process for laser printing coating of PET film. Background Technology

[0002] Polyethylene terephthalate (PET) film boasts advantages such as high mechanical strength, high transparency, high heat resistance, and low cost, leading to its increasing application in medical films, advertising labels, and other fields. However, the regular molecular chain structure and high crystallinity of PET hinder direct adhesion of toner. To ensure optimal printing results for laser-printed toner on PET film, a coating is typically applied to the surface to optimize interfacial bonding. Water-based acrylic resins, using water as the dispersion medium, have extremely low VOC content, meeting international environmental standards. Furthermore, their high transparency allows for vibrant colors and clear patterns; therefore, existing coatings generally utilize water-based acrylic resins.

[0003] However, the polarity match between water-based acrylic resin and laser printing toner is insufficient. A significant difference in polarity between the toner and the coating weakens intermolecular forces, affecting the effective adhesion / adsorption of the toner and leading to image spots or trailing. Furthermore, laser printing toner is fixed onto the medium by heating, requiring the coating to withstand extremely short bursts of high temperature. Conventional water-based acrylic resins typically have a heat resistance below 120°C. During laser printing, the coating is prone to softening, discoloration, or blistering, affecting image quality. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a preparation process for a laser printing coating on PET film, which can effectively improve the heat resistance and toner adsorption capacity of the obtained laser printing coating on PET film.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a preparation process for a laser-printed coating on a PET film, comprising the following steps:

[0006] S1. By weight, add 72-75 parts of water-based acrylic resin emulsion, 2-2.5 parts of polydimethylsiloxane, 5-7 parts of silicon-doped titanium dioxide, 1-2 parts of silane coupling agent KH-570, 2-3 parts of crosslinking agent vinyltriethoxysilane, 2-4 parts of film-forming aid propylene glycol phenyl ether, 0.6-0.8 parts of photoinitiator and 0.3-0.5 parts of defoamer into a twin-screw high-speed disperser, disperse, and let stand to obtain a mixture;

[0007] S2. After corona treatment, the PET film is obtained as a pretreated PET film.

[0008] S3. The mixture obtained in S1 is evenly coated onto the pretreated PET film obtained in S2, and then cured to obtain the laser printing coating of the PET film.

[0009] Furthermore, in S1, the specific operation of dispersion is as follows: first disperse at a speed of 480-520 rpm for 4-5 minutes, then disperse at a speed of 1150-1200 rpm for 6-8 minutes, and then disperse at a speed of 1800-2000 rpm for 2.5-3.5 minutes.

[0010] Furthermore, in S3, the curing process includes thermal curing and photocuring.

[0011] Furthermore, the thickness of the laser-printed coating on the PET film is 5±0.5μm.

[0012] Furthermore, the preparation method of the silicon-doped titanium dioxide is as follows:

[0013] A1. At room temperature, ethanol is divided into two parts, namely the first part of ethanol and the second part of ethanol, and the molar amounts of the first part of ethanol and the second part of ethanol are equal; tetrabutyl titanate, tetraethyl orthosilicate and the first part of ethanol are mixed and stirred to obtain the first mixture; water, nitric acid and the second part of ethanol are mixed and stirred to obtain the second mixture.

[0014] A2. Add the second mixture obtained in A1 dropwise to the first mixture and continue stirring to obtain a uniform and transparent sol;

[0015] A3. After allowing the sol obtained in A2 to stand at room temperature for 24 hours, dry it at 55-75℃ for 12 hours to obtain a dry gel.

[0016] A4. Place the dry gel obtained in A3 into a muffle furnace, heat it, and after heat treatment, allow it to cool naturally to room temperature to obtain silicon-doped titanium dioxide powder.

[0017] Furthermore, in A1, the molar ratio of tetrabutyl titanate, tetraethyl orthosilicate, ethanol, water, and nitric acid is 1:(0.3-0.4):25:4:0.2.

[0018] Furthermore, in A2, the second mixture is added dropwise to the first mixture at a rate of 1-1.5 mL / min.

[0019] Furthermore, in A4, the heating rate is 3-5℃ / min, the heat treatment temperature is 490-510℃, and the heat treatment time is 68-80min.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention utilizes silicon-doped titanium dioxide to form micron-sized composite protrusions in the coating through controlled aggregation or interaction with the resin matrix, thereby enhancing the mechanical anchoring of the toner through physical embedding. The high specific surface area and residual hydroxyl groups (-OH) on the surface of silicon-doped titanium dioxide form hydrogen bonds or covalent bonds with the carboxyl groups (-COOH) in the toner, improving the chemisorption strength. Silicon-doped titanium dioxide exhibits a reflectivity ≥75% in the near-infrared band (700-2500nm), reflecting external thermal radiation, reducing the internal temperature gradient of the coating, minimizing molecular chain breakage caused by heat accumulation, and improving the coating's heat resistance.

[0022] Polydimethylsiloxane (PDS) forms Si-O-Ti bonds through a condensation reaction between silanol groups (-Si-OH) and hydroxyl groups (-OH) on the surface of silicon-doped titanium dioxide at a high temperature of 150°C (operation temperature). This creates a continuous three-dimensional cross-linked network that synergistically suppresses the thermal motion of resin molecular chains and improves interfacial compatibility, reducing defects caused by phase separation. Furthermore, this structure increases the nanoscale roughness of the coating surface, increasing the physical contact area between the toner and the coating. By increasing the specific surface area, it enhances van der Waals forces, synergistically improving adhesion. The highly polar surface of silicon-doped titanium dioxide partially compensates for the polarity loss in the low surface energy regions of PDS, alleviating overall phase separation through localized chemical bonding (Si-O-Ti). Simultaneously, the low surface energy regions of PDS and the highly polar surface of silicon-doped titanium dioxide form a gradient distribution, balancing the polarity differences of the toner and improving adsorption uniformity. Attached Figure Description

[0023] Figure 1 This is a comparative trend chart showing the peel strength test data of the laser-printed coatings of PET films prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention after being kept at a constant temperature of 150°C for 10 minutes.

[0024] Figure 2 This is a comparative trend chart showing the adhesion test data of laser printing toner (images and text) for PET film laser printing coatings prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0026] Example 1: (1) The preparation method of silicon-doped titanium dioxide is as follows:

[0027] A1. At room temperature, ethanol is divided into two portions, namely, a first portion and a second portion, with the same molar amount. Tetrabutyl titanate, tetraethyl orthosilicate, and the first portion of ethanol are mixed and stirred to obtain a first mixture. Water, nitric acid, and the second portion of ethanol are mixed and stirred to obtain a second mixture. The molar ratio of tetrabutyl titanate, tetraethyl orthosilicate, ethanol, water, and nitric acid is 1:0.35:25:4:0.2.

[0028] A2. Add the second mixture obtained in A1 dropwise to the first mixture at a rate of 1.2 mL / min, and continue stirring (magnetic stirring at 800 rpm) to obtain a uniform and transparent sol.

[0029] A3. After the sol obtained in A2 is allowed to stand at room temperature for 24 hours, it is dried at 50°C for 6 hours and then dried at 70°C for 6 hours to obtain a dry gel.

[0030] A4. Place the dry gel obtained in A3 into a muffle furnace and heat it to 500°C at a heating rate of 4°C / min. After heat treatment at this temperature for 75 minutes, allow it to cool naturally to room temperature to obtain silicon-doped titanium dioxide powder.

[0031] (2) A process for preparing a laser-printed coating on a PET film, comprising the following steps:

[0032] S1. By weight, 74 parts of waterborne acrylic resin emulsion, 2.2 parts of polydimethylsiloxane, 6 parts of silicon-doped titanium dioxide, 1.5 parts of silane coupling agent KH-570, 2.5 parts of crosslinking agent vinyltriethoxysilane, 3 parts of film-forming aid propylene glycol phenyl ether, 0.7 parts of photoinitiator Irgacure 819, and 0.4 parts of defoamer BYK-024 are added into a twin-screw high-speed disperser. First, disperse at 500 rpm for 4.5 min (temperature < 30℃), then disperse at 1180 rpm for 7 min (circulating water cooling to maintain 35±2℃), and then disperse at 1900 rpm for 3 min (nitrogen protection, temperature < 40℃). Let stand for 35 min at 25℃ and humidity ≤ 30% to eliminate internal stress and stabilize viscosity, thus obtaining the mixture.

[0033] S2. After corona treatment, the PET film is pretreated to obtain a pretreated PET film. Corona treatment parameters: corona power is set to 42kW, and the treatment speed is 12m / min linear speed; after corona treatment, it is cleaned with 0.5% fluorocarbon surfactant (Capstone FS-63) aerosol to remove impurities while maintaining surface energy.

[0034] S3. Using a micro-gravure coating head (150 lines / cm ceramic anilox roller + 65 Shore A rubber roller), at a coating speed of 10m / min, the mixture obtained in S1 is uniformly coated onto the pretreated PET film obtained in S2, followed by curing. The curing process includes thermal curing and photocuring. The thermal curing operation is as follows: first, pre-baking at approximately 80℃ for 2.5min (pre-crosslinking), then curing at approximately 120℃ for 2min (main crosslinking), and then curing at approximately 135℃ for 1min (post-curing). Simultaneously, the photocuring operation is as follows: UV-LED irradiation (395nm, 600mJ / cm²). 2 After curing, the film is naturally cooled to below 40℃, and the winding tension is ≤5N / m to prevent the coating from cracking due to thermal shrinkage. This yields a PET film laser-printed coating with a thickness of 4.9μm.

[0035] Example 2: The difference between this example and Example 1 is that: a preparation process for a laser-printed coating on a PET film includes the following steps:

[0036] S1. By weight, 72 parts of water-based acrylic resin emulsion, 2 parts of polydimethylsiloxane, 5 parts of silicon-doped titanium dioxide, 1 part of silane coupling agent KH-570, 2 parts of crosslinking agent vinyltriethoxysilane, 2 parts of film-forming aid propylene glycol phenyl ether, 0.6 parts of photoinitiator Irgacure 819, and 0.3 parts of defoamer BYK-024 are added into a twin-screw high-speed disperser. The mixture is first dispersed at 480 rpm for 5 minutes, then at 1150 rpm for 8 minutes, and then at 1800 rpm for 3.5 minutes. After standing, the mixture is obtained.

[0037] S2. After corona treatment, the PET film is obtained as a pretreated PET film.

[0038] S3. The mixture obtained in S1 is uniformly coated onto the pretreated PET film obtained in S2 and cured to obtain a PET film laser printing coating with a thickness of 4.8μm.

[0039] Example 3: The difference between this example and Example 1 is that: a preparation process for a laser-printed coating on a PET film includes the following steps:

[0040] S1. By weight, 75 parts of water-based acrylic resin emulsion, 2.5 parts of polydimethylsiloxane, 7 parts of silicon-doped titanium dioxide, 2 parts of silane coupling agent KH-570, 3 parts of crosslinking agent vinyltriethoxysilane, 4 parts of film-forming aid propylene glycol phenyl ether, 0.8 parts of photoinitiator Irgacure 819, and 0.5 parts of defoamer BYK-024 are added into a twin-screw high-speed disperser. The mixture is first dispersed at 520 rpm for 4 minutes, then at 1200 rpm for 6 minutes, and then at 2000 rpm for 2.5 minutes. After standing, the mixture is obtained.

[0041] S2. After corona treatment, the PET film is obtained as a pretreated PET film.

[0042] S3. The mixture obtained in S1 is uniformly coated onto the pretreated PET film obtained in S2 and cured to obtain a PET film laser printing coating with a thickness of 5.2μm.

[0043] Comparative Example 1: The difference between this comparative example and Example 1 is that polydimethylsiloxane and silicon-doped titanium dioxide are removed.

[0044] Specifically, a process for preparing a laser-printed coating on a PET film includes the following steps:

[0045] S1. By weight, 74 parts of water-based acrylic resin emulsion, 1.5 parts of silane coupling agent KH-570, 2.5 parts of crosslinking agent vinyltriethoxysilane, 3 parts of film-forming aid propylene glycol phenyl ether, 0.7 parts of photoinitiator Irgacure 819 and 0.4 parts of defoamer BYK-024 are added into a twin-screw high-speed disperser. First, disperse at 500 rpm for 4.5 min (temperature < 30℃), then disperse at 1180 rpm for 7 min (circulating water cooling to maintain 35±2℃), then disperse at 1900 rpm for 3 min (nitrogen protection, temperature < 40℃). Let stand for 35 min at 25℃ and humidity ≤ 30% to eliminate internal stress and stabilize viscosity, thus obtaining the mixture.

[0046] S2. After corona treatment, the PET film is pretreated to obtain a pretreated PET film. Corona treatment parameters: corona power is set to 42kW, and the treatment speed is 12m / min linear speed; after corona treatment, it is cleaned with 0.5% fluorocarbon surfactant (Capstone FS-63) aerosol to remove impurities while maintaining surface energy.

[0047] S3. Using a micro-gravure coating head (150 lines / cm ceramic anilox roller + 65 Shore A rubber roller), at a coating speed of 10m / min, the mixture obtained in S1 is uniformly coated onto the pretreated PET film obtained in S2, followed by curing. The curing process includes thermal curing and photocuring. The thermal curing operation is as follows: first, pre-baking at approximately 80℃ for 2.5min (pre-crosslinking), then curing at approximately 120℃ for 2min (main crosslinking), and then curing at approximately 135℃ for 1min (post-curing). Simultaneously, the photocuring operation is as follows: UV-LED irradiation (395nm, 600mJ / cm²). 2 After curing, the film is naturally cooled to below 40℃, and the winding tension is ≤5N / m to prevent the coating from cracking due to thermal shrinkage. This yields a PET film laser-printed coating with a thickness of 4.9μm.

[0048] Comparative Example 2: The difference between this comparative example and Example 1 is that silicon-doped titanium dioxide was removed.

[0049] Comparative Example 3: The difference between this comparative example and Example 1 is that polydimethylsiloxane is removed.

[0050] Test Example: Test Items and Methods: 1. The samples prepared in Examples 1-3 and Comparative Examples 1-3 were placed in a high-temperature chamber and heated to 150°C at a rate of 5°C / min. The temperature was maintained for 10 min to ensure that the coating and the PET film substrate were fully heated. The peel strength was then tested according to the standard ASTM D3330. The unit is N / mm.

[0051] 2. Laser printing was performed on the surfaces of the PET film laser printing coatings prepared in Examples 1-3 and Comparative Examples 1-3, respectively. After the toner was fixed to the medium (coating) by instantaneous heating (150-180℃), the adhesion was tested according to standard ASTM D3359 (cross-cut test). Adhesion (%) = (Total number of squares - Number of squares detached) / Total number of squares × 100%.

[0052] Experimental results: see Table 1.

[0053] Table 1. Test data for the experimental cases

[0054] Peel strength (N / mm) Adhesion (%) Example 1 5.2 99.1 Example 2 5.2 99.3 Example 3 5.4 99.4 Comparative Example 1 3.8 96.9 Comparative Example 2 3.3 96.0 Comparative Example 3 4.7 98.3

[0055] Results Analysis: Analysis of Examples 1-3 combined with the data in Table 1 and... Figures 1-2 As can be seen, the peel strength of the PET film laser printing coating of the present invention (Examples 1-3) reaches more than 5.2 N / mm after being kept at a constant temperature of 150°C for 10 min, and the adhesion of the laser printing toner (images) reaches more than 99.0%.

[0056] Analyze Example 1 and Comparative Examples 1-3 and combine the data in Table 1 and Figures 1-2 As shown in the comparison between Comparative Examples 1 and 2, adding polydimethylsiloxane alone leads to a decrease in the peel strength of the laser-printed PET film coating after being kept at 150°C for 10 minutes, resulting in a decrease in the adhesion of the laser-printed toner (images). This is because polydimethylsiloxane migrates to the coating surface, forming a low surface energy region, which increases the polarity difference with the toner, weakening electrostatic adsorption and van der Waals forces. Simultaneously, polydimethylsiloxane covers the carboxyl groups (-COOH) and hydroxyl groups (-OH) in the waterborne acrylic resin, reducing the hydrogen bonding sites with the toner, thus reducing the physical adsorption strength of the coating on the toner. Waterborne acrylic resin is a polar system, while polydimethylsiloxane is a non-polar organosilicon material; when the two are mixed, phase separation easily occurs, forming interface defects, which accelerates coating cracking or peeling at 150°C.

[0057] Comparisons of Comparative Examples 1 and 3 show that adding silicon-doped titanium dioxide alone improves the peel strength of the laser-printed PET film coating after being held at 150°C for 10 minutes, thus enhancing the adhesion of the laser-printed toner (images). Further comparison with Example 1 shows that the simultaneous addition of polydimethylsiloxane and silicon-doped titanium dioxide produces a synergistic effect, synergistically improving the peel strength of the laser-printed PET film coating after being held at 150°C for 10 minutes, and synergistically enhancing the adhesion of the laser-printed toner (images).

[0058] Although the present invention 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 the present invention should be included within the protection scope of the present invention.

Claims

1. A process for preparing a laser-printed coating on a PET film, characterized in that, Includes the following steps: S1. By weight, add 72-75 parts of water-based acrylic resin emulsion, 2-2.5 parts of polydimethylsiloxane, 5-7 parts of silicon-doped titanium dioxide, 1-2 parts of silane coupling agent KH-570, 2-3 parts of crosslinking agent vinyltriethoxysilane, 2-4 parts of film-forming aid propylene glycol phenyl ether, 0.6-0.8 parts of photoinitiator and 0.3-0.5 parts of defoamer into a twin-screw high-speed disperser, disperse, and let stand to obtain a mixture; S2. After corona treatment, the PET film is obtained as a pretreated PET film. S3. The mixture obtained in S1 is evenly coated onto the pretreated PET film obtained in S2, and cured to obtain the laser printing coating of PET film. The method for preparing the silicon-doped titanium dioxide is as follows: A1. At room temperature, ethanol is divided into two parts, namely the first part of ethanol and the second part of ethanol, and the molar amounts of the first part of ethanol and the second part of ethanol are equal; tetrabutyl titanate, tetraethyl orthosilicate and the first part of ethanol are mixed and stirred to obtain the first mixture; water, nitric acid and the second part of ethanol are mixed and stirred to obtain the second mixture. A2. Add the second mixture obtained in A1 dropwise to the first mixture and continue stirring to obtain a uniform and transparent sol; A3. After allowing the sol obtained in A2 to stand at room temperature for 24 hours, dry it at 55-75℃ for 12 hours to obtain a dry gel; A4. Place the dry gel obtained in A3 into a muffle furnace, heat it, and after heat treatment, allow it to cool naturally to room temperature to obtain silicon-doped titanium dioxide powder.

2. The preparation process of the PET film laser printing coating according to claim 1, characterized in that, In S1, the specific dispersion operation is as follows: first disperse at a speed of 480-520 rpm for 4-5 minutes, then disperse at a speed of 1150-1200 rpm for 6-8 minutes, and then disperse at a speed of 1800-2000 rpm for 2.5-3.5 minutes.

3. The preparation process of the PET film laser printing coating according to claim 1, characterized in that, In S3, the curing process includes thermal curing and photocuring.

4. The preparation process of the PET film laser printing coating according to claim 1, characterized in that, The thickness of the laser-printed coating on the PET film is 5±0.5μm.

5. The preparation process of the PET film laser printing coating according to claim 1, characterized in that, In A1, the molar ratio of tetrabutyl titanate, tetraethyl orthosilicate, ethanol, water and nitric acid is 1:(0.3-0.4):25:4:0.

2.

6. The preparation process of the PET film laser printing coating according to claim 1, characterized in that, In A2, the second mixture is added dropwise to the first mixture at a rate of 1-1.5 mL / min.

7. The preparation process of the PET film laser printing coating according to claim 1, characterized in that, In A4, the heating rate is 3-5℃ / min, the heat treatment temperature is 490-510℃, and the heat treatment time is 68-80min.

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