Gloss oil glazing process for outer packing carton

Abstract

The invention relates to the technical field of outer packing carton gloss oil glazing, and discloses an outer packing carton gloss oil glazing process which comprises the following steps: removing dust, paper scraps and other impurities on the surface of an outer packing carton to be glazed through a high-voltage electrostatic dust collection device, controlling the electrostatic voltage to be 30-50kV, and ensuring that the surface of the carton is clean and free of foreign matters; through the synergistic effect of paper box pretreatment, precise coating and gradient curing, the problems of uneven coating thickness and multiple surface flaws of a traditional process are solved, the surface of the coating is flat and smooth, the glossiness can be regulated and controlled according to needs, the adhesive force, the wear resistance and the water resistance of the coating are remarkably improved, and the coating quality is improved. The appearance quality and the protection performance of the carton are greatly improved; and the automatic continuous production process is adopted, the gradient curing technology is combined, the gloss oil drying and curing time is greatly shortened, compared with a traditional technology, the production efficiency is improved by 30%-50%, and meanwhile the manual operation intensity is reduced.

Description

A varnishing process for outer packaging paper boxes Technical Field

[0001] This application relates to the technical field of varnishing outer packaging paper boxes, and in particular to a varnishing process for outer packaging paper boxes. Background Technology

[0002] In the packaging and printing industry, the surface finishing process of outer packaging boxes directly affects the product's appearance, texture, protective performance, and market competitiveness. Varnishing, as an important method of surface finishing, enhances the box's gloss, abrasion resistance, water resistance, and scratch resistance by applying a varnish coating, while also improving the color saturation and three-dimensionality of printed patterns.

[0003] However, in practical applications, most existing varnishes have uneven thickness, which easily leads to surface defects such as sagging, exposed substrate, and orange peel, affecting the appearance quality of the paper box. Secondly, the drying and curing efficiency of varnishes is low. Traditional natural air drying or hot air drying methods are time-consuming and easily lead to solvent residue inside the coating, reducing the coating's adhesion and weather resistance. Finally, the varnishing process has poor adaptability to paper boxes of different materials and weights, making it difficult to balance the stiffness protection of thin paper boxes with the coating penetration problem of thick paper boxes.

[0004] Therefore, those skilled in the art have provided a varnishing process for outer packaging paper boxes to solve the problems mentioned in the background art. Summary of the Invention

[0005] To address the issues raised in the background art, such as uneven coating thickness leading to surface defects like drips, exposed substrate, and orange peel texture, which affect the appearance quality of paper boxes; secondly, the low drying and curing efficiency of varnishes, with traditional natural air drying or hot air drying methods being time-consuming and prone to solvent residue inside the coating, reducing coating adhesion and weather resistance; and finally, the poor adaptability of varnishing processes to paper boxes of different materials and weights, making it difficult to simultaneously ensure the stiffness protection of thin paper boxes and address the coating penetration problem of thick paper boxes, this application provides a varnishing process for outer packaging paper boxes.

[0006] This application provides a varnishing process for outer packaging paper boxes, which employs the following technical solution: It includes the following steps:

[0007] Step 1: Cardboard box pretreatment;

[0008] Step 2: Varnish preparation;

[0009] Step 3: Precise coating;

[0010] Step 4: Gradient curing;

[0011] Step 5: Surface treatment;

[0012] Step Six: Quality Inspection.

[0013] Preferably, the pretreatment of the cardboard box includes:

[0014] Cleaning and dust removal: The outer packaging cardboard box to be varnished is passed through a high-voltage electrostatic dust removal device to remove dust, paper scraps and other impurities from the surface. The electrostatic voltage is controlled at 30-50kV to ensure that the surface of the cardboard box is clean and free of foreign objects, and to avoid pinholes and pits in the coating.

[0015] Preheating and humidification: Depending on the material of the cardboard box (e.g., white cardboard, kraft paper, corrugated paper) and its weight, place the box in a preheating and humidification device. Control the preheating temperature at 40-60℃ and the relative humidity at 50%-60%, for 10-20 minutes. This step ensures even moisture distribution on the box surface, reducing uneven shrinkage during varnish coating and improving the adhesion between the varnish and the box surface. For corrugated boxes, the preheating temperature should be appropriately reduced and the time extended to prevent deformation of the corrugated layer.

[0016] Preferably, the varnish preparation includes:

[0017] Base Varnish Selection: Choose water-based, UV, or alcohol-based varnishes based on the intended use of the cardboard box. Water-based varnishes are suitable for food packaging boxes with high environmental protection requirements, UV varnishes are suitable for gift packaging boxes with high requirements for gloss and abrasion resistance, and alcohol-based varnishes are suitable for general packaging boxes that require fast drying.

[0018] Functional additives: Functional additives are added to the base varnish, including leveling agents (0.5% - 1% of the total varnish mass), defoamers (0.3% - 0.8%), abrasion resistant agents (2% - 5%), and gloss modifiers (1% - 3%). By adjusting the type and amount of gloss modifiers, high-gloss (gloss ≥ 80°), matte (gloss ≤ 30°), or semi-matte (gloss 40° - 60°) effects can be achieved on the surface of the paper box.

[0019] Mixing: Place the base varnish and functional additives into a high-speed mixer, controlling the mixing speed at 800-1200 rpm for 15-20 minutes to ensure the varnish system is uniform and stable, without clumping or layering. After mixing, test the viscosity of the varnish and adjust it to 15-25s (Ford Cup 4) to meet the coating process requirements.

[0020] Preferably, the precise coating includes:

[0021] Coating equipment selection: A combined coating equipment is adopted, integrating gravure coating, flexographic coating, and spray coating, which can be flexibly switched according to the surface pattern and coating requirements of the cardboard box. For overall surface coating of the cardboard box, gravure coating or flexographic coating is used; for targeted varnishing of local patterns, spray coating is used for precise positioning coating.

[0022] Coating parameter control: Gravure coating: control the gravure roller's anilox depth to 20-60μm, coating speed to 10-30m / min, and coating pressure to 0.2-0.5MPa to ensure uniform coating thickness, controlled at 5-15μm; Flexographic coating: select a flexographic printing plate with a hardness of 60-80 Shore, coating speed to 15-35m / min, anilox roller line count to 200-400 lines / inch, suitable for thin coatings and fine patterns; Spray coating: use high-pressure airless spraying equipment, spraying pressure to 10-15MPa, nozzle diameter to 0.3-0.5mm, spraying distance to 15-25cm, and control the nozzle movement trajectory through a CNC system to achieve precise positioning for local varnishing, with coating thickness controllable at 8-20μm.

[0023] Coating deviation correction: A vision inspection system is installed on the coating equipment to monitor the thickness and position deviation of the coating in real time. When the deviation exceeds ±0.5μm, the system automatically adjusts the pressure and speed of the coating roller or the parameters of the spray nozzle to ensure coating accuracy.

[0024] Preferably, the gradient curing includes:

[0025] Preliminary Drying: For cardboard boxes coated with water-based or alcohol-based varnishes, they are first placed in a hot air drying tunnel for preliminary drying. The hot air temperature is controlled at 60-80℃, the air velocity at 2-3m / s, and the drying time is 5-10 minutes. This removes most of the solvent from the varnish, allowing the coating to initially form a film. For cardboard boxes coated with UV varnishes, they directly enter the UV pre-curing stage. Low-power UV lamps (80-120W / cm) are used for irradiation for 2-3 seconds to allow the coating surface to initially cure, preventing scratches during subsequent processing.

[0026] Deep Curing: Water-based / Alcohol-based Varnish: After initial drying, the cardboard box is placed in an infrared drying device. The infrared wavelength is controlled at 2-5μm, the drying temperature at 80-100℃, and the drying time at 8-12 minutes to achieve deep curing of the coating and ensure that the solvent residue is ≤0.5%. UV Varnish: The pre-cured cardboard box is placed in a high-power UV curing device. A UV lamp with a wavelength of 365nm (power of 200-300W / cm) is used, along with nitrogen protection (nitrogen concentration ≥95%), and the irradiation time is 3-5 seconds to prevent oxidation and yellowing of the coating during the curing process, while improving the curing degree and adhesion of the coating.

[0027] Cooling and setting: The cured cardboard box is sent into the cooling channel and cooled to room temperature (20-25℃) with cold air for 3-5 minutes to set the coating and enhance its hardness and wear resistance.

[0028] Preferably, the surface treatment includes:

[0029] Polishing: For cardboard boxes requiring high gloss, a mechanical polishing machine is used to polish the surface of the cured coating. The polishing wheel speed is 800-1000 r / min, the polishing pressure is 0.1-0.3 MPa, and the polishing time is 1-2 minutes to further improve the gloss and smoothness of the cardboard box surface.

[0030] Lamination protection (optional): For special purpose cartons (such as transport packaging cartons), a lamination treatment can be applied to the coated surface using BOPP film or PET film, which is bonded to the coating through hot pressing at a temperature of 80-100℃ and a pressure of 0.3-0.5MPa, to enhance the carton's water resistance and tear resistance.

[0031] Preferably, the quality inspection includes:

[0032] Appearance inspection: Visual inspection and magnification (10-20x) are used to check for defects such as drips, exposed substrate, pinholes, and orange peel on the surface coating of the cardboard box. At the same time, the color uniformity and pattern clarity of the coating are also checked.

[0033] Performance testing: The coating's gloss (using a gloss meter, test angle 60°), abrasion resistance (using an abrasion tester, 500g load, 500 rub cycles), adhesion (using the cross-cut adhesion test, adhesion grade ≥4B), and water resistance (using a water droplet test, water droplets on the coating surface for 30 minutes without penetration) are tested.

[0034] Acceptance criteria: Paper boxes with no obvious defects in appearance and whose performance indicators meet the preset standards are considered qualified. Unqualified products are reworked or scrapped.

[0035] In summary, this application includes the following beneficial technical effects:

[0036] 1. Improved coating quality: Through the synergistic effect of carton pretreatment, precise coating and gradient curing, the problems of uneven coating thickness and many surface defects in traditional processes are solved. The coating surface is smooth and flat, and the gloss can be adjusted as needed. In addition, the adhesion, wear resistance and water resistance of the coating are significantly improved, and the appearance quality and protective performance of the carton are greatly improved.

[0037] 2. Improved production efficiency: The automated continuous production process, combined with gradient curing technology, significantly shortens the drying and curing time of the varnish. Compared with traditional processes, production efficiency is increased by 30% - 50%, while reducing the intensity of manual operation.

[0038] 3. Enhanced adaptability: The varnish formula, coating method and curing parameters can be flexibly adjusted according to the material, weight and usage requirements of the cardboard box to adapt to different types of outer packaging cardboard boxes and meet diverse surface finishing needs.

[0039] 4. Green and environmentally friendly: Prioritize the use of environmentally friendly varnishes such as water-based and alcohol-soluble varnishes to reduce the use of organic solvents. The solvent residue in the process is low, which meets the environmental protection standards of food packaging and other fields. At the same time, the UV curing process has low energy consumption and no waste gas emissions, further reducing environmental pollution in the production process. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0041] This application discloses a varnishing process for outer packaging paper boxes, including the following steps:

[0042] Step 1: Cardboard box pretreatment;

[0043] Step 2: Varnish preparation;

[0044] Step 3: Precise coating;

[0045] Step 4: Gradient curing;

[0046] Step 5: Surface treatment;

[0047] Step Six: Quality Inspection.

[0048] In this application, the pretreatment of the cardboard box includes:

[0049] Cleaning and dust removal: The outer packaging cardboard box to be varnished is passed through a high-voltage electrostatic dust removal device to remove dust, paper scraps and other impurities from the surface. The electrostatic voltage is controlled at 30-50kV to ensure that the surface of the cardboard box is clean and free of foreign objects, and to avoid pinholes and pits in the coating.

[0050] Preheating and humidification: Depending on the material of the cardboard box (e.g., white cardboard, kraft paper, corrugated paper) and its weight, place the box in a preheating and humidification device. Control the preheating temperature at 40-60℃ and the relative humidity at 50%-60%, for 10-20 minutes. This step ensures even moisture distribution on the box surface, reducing uneven shrinkage during varnish coating and improving the adhesion between the varnish and the box surface. For corrugated boxes, the preheating temperature should be appropriately reduced and the time extended to prevent deformation of the corrugated layer.

[0051] In this application, the formulation of the varnish includes:

[0052] Base Varnish Selection: Choose water-based, UV, or alcohol-based varnishes based on the intended use of the cardboard box. Water-based varnishes are suitable for food packaging boxes with high environmental protection requirements, UV varnishes are suitable for gift packaging boxes with high requirements for gloss and abrasion resistance, and alcohol-based varnishes are suitable for general packaging boxes that require fast drying.

[0053] Functional additives: Functional additives are added to the base varnish, including leveling agents (0.5% - 1% of the total varnish mass), defoamers (0.3% - 0.8%), abrasion resistant agents (2% - 5%), and gloss modifiers (1% - 3%). By adjusting the type and amount of gloss modifiers, high-gloss (gloss ≥ 80°), matte (gloss ≤ 30°), or semi-matte (gloss 40° - 60°) effects can be achieved on the surface of the paper box.

[0054] Mixing: Place the base varnish and functional additives into a high-speed mixer, controlling the mixing speed at 800-1200 rpm for 15-20 minutes to ensure the varnish system is uniform and stable, without clumping or layering. After mixing, test the viscosity of the varnish and adjust it to 15-25s (Ford Cup 4) to meet the coating process requirements.

[0055] In this application, precision coating includes:

[0056] Coating equipment selection: A combined coating equipment is adopted, integrating gravure coating, flexographic coating, and spray coating, which can be flexibly switched according to the surface pattern and coating requirements of the cardboard box. For overall surface coating of the cardboard box, gravure coating or flexographic coating is used; for targeted varnishing of local patterns, spray coating is used for precise positioning coating.

[0057] Coating parameter control: Gravure coating: control the gravure roller's anilox depth to 20-60μm, coating speed to 10-30m / min, and coating pressure to 0.2-0.5MPa to ensure uniform coating thickness, controlled at 5-15μm; Flexographic coating: select a flexographic printing plate with a hardness of 60-80 Shore, coating speed to 15-35m / min, anilox roller line count to 200-400 lines / inch, suitable for thin coatings and fine patterns; Spray coating: use high-pressure airless spraying equipment, spraying pressure to 10-15MPa, nozzle diameter to 0.3-0.5mm, spraying distance to 15-25cm, and control the nozzle movement trajectory through a CNC system to achieve precise positioning for local varnishing, with coating thickness controllable at 8-20μm.

[0058] Coating deviation correction: A vision inspection system is installed on the coating equipment to monitor the thickness and position deviation of the coating in real time. When the deviation exceeds ±0.5μm, the system automatically adjusts the pressure and speed of the coating roller or the parameters of the spray nozzle to ensure coating accuracy.

[0059] In this application, gradient curing includes:

[0060] Preliminary Drying: For cardboard boxes coated with water-based or alcohol-based varnishes, they are first placed in a hot air drying tunnel for preliminary drying. The hot air temperature is controlled at 60-80℃, the air velocity at 2-3m / s, and the drying time is 5-10 minutes. This removes most of the solvent from the varnish, allowing the coating to initially form a film. For cardboard boxes coated with UV varnishes, they directly enter the UV pre-curing stage. Low-power UV lamps (80-120W / cm) are used for irradiation for 2-3 seconds to allow the coating surface to initially cure, preventing scratches during subsequent processing.

[0061] Deep Curing: Water-based / Alcohol-based Varnish: After initial drying, the cardboard box is placed in an infrared drying device. The infrared wavelength is controlled at 2-5μm, the drying temperature at 80-100℃, and the drying time at 8-12 minutes to achieve deep curing of the coating and ensure that the solvent residue is ≤0.5%. UV Varnish: The pre-cured cardboard box is placed in a high-power UV curing device. A UV lamp with a wavelength of 365nm (power of 200-300W / cm) is used, along with nitrogen protection (nitrogen concentration ≥95%), and the irradiation time is 3-5 seconds to prevent oxidation and yellowing of the coating during the curing process, while improving the curing degree and adhesion of the coating.

[0062] Cooling and setting: The cured cardboard box is sent into the cooling channel and cooled to room temperature (20-25℃) with cold air for 3-5 minutes to set the coating and enhance its hardness and wear resistance.

[0063] In this application, the surface treatment includes:

[0064] Polishing: For cardboard boxes requiring high gloss, a mechanical polishing machine is used to polish the surface of the cured coating. The polishing wheel speed is 800-1000 r / min, the polishing pressure is 0.1-0.3 MPa, and the polishing time is 1-2 minutes to further improve the gloss and smoothness of the cardboard box surface.

[0065] Lamination protection (optional): For special purpose cartons (such as transport packaging cartons), a lamination treatment can be applied to the coated surface using BOPP film or PET film, which is bonded to the coating through hot pressing at a temperature of 80-100℃ and a pressure of 0.3-0.5MPa, to enhance the carton's water resistance and tear resistance.

[0066] In this application, quality inspection includes:

[0067] Appearance inspection: Visual inspection and magnification (10-20x) are used to check for defects such as drips, exposed substrate, pinholes, and orange peel on the surface coating of the cardboard box. At the same time, the color uniformity and pattern clarity of the coating are also checked.

[0068] Performance testing: The coating's gloss (using a gloss meter, test angle 60°), abrasion resistance (using an abrasion tester, 500g load, 500 rub cycles), adhesion (using the cross-cut adhesion test, adhesion grade ≥4B), and water resistance (using a water droplet test, water droplets on the coating surface for 30 minutes without penetration) are tested.

[0069] Acceptance criteria: Paper boxes with no obvious defects in appearance and whose performance indicators meet the preset standards are considered qualified. Unqualified products are reworked or scrapped.

[0070] All standard parts used in this invention can be purchased from the market, and irregular parts can be customized according to the description in the specification. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here.

[0071] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0072] Secondly: In the embodiments disclosed in this invention, only the structures involved in the embodiments disclosed in this invention are involved. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

Claims

1. A varnishing process for outer packaging paper boxes, characterized in that, Includes the following steps: Step 1: Cardboard box pretreatment; Step 2: Varnish preparation; Step 3: Precision coating; Step 4: Gradient curing; Step 5: Surface treatment; Step 6: Quality inspection.

2. The varnishing process for outer packaging paper boxes according to claim 1, characterized in that: The pretreatment of the cardboard boxes includes: Cleaning and dust removal: The outer packaging cardboard boxes to be varnished are passed through a high-voltage electrostatic dust removal device to remove surface dust, paper scraps, and other impurities. The electrostatic voltage is controlled at 30-50kV to ensure that the cardboard box surface is clean and free of foreign objects, avoiding pinholes and pitting in the coating. Preheating and humidity conditioning: Depending on the material of the cardboard box (such as white cardboard, kraft paper, corrugated paper) and its basis weight, the cardboard box is placed in a preheating and humidity conditioning device, controlling the preheating temperature at 40-60℃ and the relative humidity at 50%-60%, for 10-20 minutes. This step ensures uniform moisture distribution on the cardboard box surface, reduces uneven shrinkage during varnish coating, and improves the adhesion between the varnish and the cardboard box surface. For corrugated cardboard boxes, the preheating temperature should be appropriately reduced and the time extended to prevent deformation of the corrugated layer.

3. The varnishing process for outer packaging paper boxes according to claim 1, characterized in that: The preparation of the varnish includes: Base varnish selection: Based on the usage requirements of the cardboard box, select water-based varnish, UV varnish, or alcohol-soluble varnish as the base varnish. Water-based varnish is suitable for food packaging cardboard boxes with high environmental protection requirements; UV varnish is suitable for gift packaging cardboard boxes with high requirements for gloss and abrasion resistance; and alcohol-soluble varnish is suitable for ordinary packaging cardboard boxes that require rapid drying. Functional additives: Add functional additives to the base varnish, including leveling agents (0.5% - 1% of the total varnish mass), defoamers (0.3% - 0.8%), abrasion resistant agents (2% - 5%), and gloss modifiers (1% - 3%). By adjusting the type and amount of gloss modifiers, high-gloss (gloss ≥ 80°), matte (gloss ≤ 30°), or semi-matte (gloss 40° - 60°) effects can be achieved on the cardboard box surface. Mixing: Place the base varnish and functional additives into a high-speed mixer, controlling the mixing speed at 800-1200 rpm for 15-20 minutes to ensure the varnish system is uniform and stable, without clumping or layering. After mixing, test the viscosity of the varnish and adjust it to 15-25s (Ford Cup 4) to meet the coating process requirements.

4. The varnishing process for outer packaging paper boxes according to claim 1, characterized in that: The precision coating process includes: Coating equipment selection: A combined coating equipment is used, integrating gravure coating, flexographic coating, and spray coating, which can be flexibly switched according to the surface pattern of the cardboard box and coating requirements. For overall surface coating of the cardboard box, gravure coating or flexographic coating is used; for targeted varnishing of local patterns, spray coating is used for precise positioning coating. Coating parameter control: Gravure coating: control the gravure roller's anilox depth to 20-60μm, coating speed to 10-30m / min, and coating pressure to 0.2-0.5MPa to ensure uniform coating thickness, controlled at 5-15μm; Flexographic coating: select a flexographic printing plate with a hardness of 60-80 Shore, coating speed to 15-35m / min, anilox roller line count to 200-400 lines / inch, suitable for thin coatings and fine patterns; Spray coating: use high-pressure airless spraying equipment, spraying pressure to 10-15MPa, nozzle diameter to 0.3-0.5mm, spraying distance to 15-25cm, and control the nozzle movement trajectory through a CNC system to achieve precise positioning for local varnishing, with coating thickness controllable at 8-20μm. Coating deviation correction: A vision inspection system is installed on the coating equipment to monitor the thickness and position deviation of the coating in real time. When the deviation exceeds ±0.5μm, the system automatically adjusts the pressure and speed of the coating roller or the parameters of the spray nozzle to ensure coating accuracy.

5. The varnishing process for outer packaging paper boxes according to claim 1, characterized in that: The gradient curing process includes: Preliminary drying: For paper boxes coated with water-based or alcohol-based varnishes, they are first sent to a hot air drying channel for preliminary drying. The hot air temperature is controlled at 60-80℃, the air velocity at 2-3m / s, and the drying time is 5-10 minutes to remove most of the solvent in the varnish and allow the coating to initially form a film. For paper boxes coated with UV varnishes, they directly enter the UV pre-curing stage, using a low-power UV lamp (power 80-120W / cm) for 2-3 seconds to allow the coating surface to initially cure and prevent the coating from being scratched during subsequent processing. Deep Curing: Water-based / Alcohol-based Varnish: After initial drying, the cardboard box is placed in an infrared drying device. The infrared wavelength is controlled at 2-5μm, the drying temperature at 80-100℃, and the drying time at 8-12 minutes to achieve deep curing of the coating, ensuring that the solvent residue is ≤0.5%. UV Varnish: The pre-cured cardboard box is placed in a high-power UV curing device using a 365nm UV lamp (power 200-300W / cm) with nitrogen protection (nitrogen concentration ≥95%). The irradiation time is 3-5 seconds to prevent oxidation and yellowing of the coating during curing, while improving the curing degree and adhesion of the coating. Cooling and Shaping: The cured cardboard box is placed in a cooling channel and cooled to room temperature (20-25℃) with cold air for 3-5 minutes to set the coating and enhance its hardness and abrasion resistance.

6. The varnishing process for outer packaging paper boxes according to claim 1, characterized in that: The surface treatment includes: Polishing: For cardboard boxes requiring high gloss, a mechanical polishing machine is used to polish the cured coating surface. The polishing wheel speed is 800-1000 r / min, the polishing pressure is 0.1-0.3 MPa, and the polishing time is 1-2 minutes, further improving the gloss and smoothness of the cardboard box surface. Film lamination (optional): For cardboard boxes for special purposes (such as transport packaging boxes), a film lamination treatment can be applied to the coating surface using BOPP film or PET film. This film is bonded to the coating through hot pressing at a temperature of 80-100℃ and a pressure of 0.3-0.5 MPa, enhancing the cardboard box's water resistance and tear resistance.

7. The varnishing process for outer packaging paper boxes according to claim 1, characterized in that: The quality inspection includes: Appearance inspection: Check whether there are defects such as sagging, uncovering the base, pinholes, orange peel, etc. on the surface coating of the paper box through visual inspection and a magnifying glass (with a magnification of 10 - 20 times), and at the same time detect the color uniformity and pattern clarity of the coating. Performance inspection: Detect the glossiness of the coating (using a glossmeter, the test angle is 60°), abrasion resistance (using an abrasion tester, with a load of 500 g and 500 friction times), adhesion (using the cross-cut test method, the adhesion grade ≥ 4B), and waterproofness (using the water drop test, no penetration occurs when water drops are on the coating surface for 30 minutes). Qualification determination: The paper box with no obvious defects in appearance and the performance indicators meeting the preset standards is determined to be qualified, and the unqualified products are reworked or scrapped.