A Gravure Printing Ink for Tipping Paper, Its Preparation Method and Printing Process

Abstract

This invention relates to the field of printing ink technology, specifically to a gravure printing ink for cork paper, its preparation method, and printing process. By weight, the components include: 7-10 parts PVB resin, 2-3 parts rosin resin, 20-30 parts powder, and 60-80 parts solvent; the solvent includes alcohol solvents; the ink has a viscosity of 15-18 seconds at 25°C and a fineness of 300-800 nm. By limiting the viscosity of the PVB resin to 5-8 seconds and the molecular weight of the rosin resin to 300-500, the leveling properties of the ink can be improved; by limiting the oil absorption of the powder to 25-35 g / 100 g, color difference problems in ink printing can be reduced; the ink prepared by this invention has a viscosity of 15-18 seconds at 25°C and a fineness of 300-800 nm, which is suitable for full-page gravure printing.

Description

Technical Field

[0001] This invention relates to the field of printing ink technology, specifically to a cork paper gravure printing ink and its preparation method and printing process. Background Technology

[0002] As the core outer packaging material for cigarette filters, the printing quality of tipping paper directly affects the appearance and safety of cigarette products. Gravure printing has become the mainstream process for tipping paper printing due to its high pattern reproduction and stable production efficiency. With the advancement of green printing policies and the upgrading of food safety standards, traditional solvent-based inks are gradually being phased out due to problems such as high VOC emissions and organic solvent residues. Water-based gravure printing inks, with their advantages of being environmentally friendly, non-toxic, and VOC-free, have become the inevitable direction for industry development. Existing water-based inks generally suffer from insufficient adhesion and poor gloss, leading to color fading and poor abrasion resistance after printing on tipping paper, making it difficult to meet the stringent packaging quality requirements of high-end cigarettes. At the same time, the traditional gravure printing process is difficult to control in terms of registration accuracy, and tension fluctuations can easily lead to misalignment of printed patterns, further limiting the improvement of product qualification rates. Therefore, developing a special ink for tipping paper with good dispersion stability, fast drying speed, strong adhesion, and compatibility with high-speed gravure printing, as well as optimizing the printing process, has become a technical pain point that the industry urgently needs to overcome.

[0003] Chinese invention patent application CN104875476A discloses a gravure printing machine and process with an oil brushing device. By adopting 28-38 micrometer shallow printing and integrated equipment design, it achieves a printing speed of 120m / min while meeting the environmental protection requirements of zero VOC emissions. However, the water-based ink system used in this solution uses conventional acrylic resin as the base material. Due to the high latent heat of vaporization of water, the drying speed is relatively slow. During high-speed printing, moisture residue is prone to occur, leading to problems such as print sticking, plate clogging, or color migration. The defect rate increases significantly, especially in humid environments. On the other hand, the patent does not optimize the ink dispersion stability. The pigments are prone to agglomeration and sedimentation in the system, and stratification occurs after long-term storage, affecting the uniformity of printing color and dot transfer effect. Summary of the Invention

[0004] The first aspect of this invention provides a gravure printing ink for cork paper, comprising, by weight: 7-10 parts of PVB (polyvinyl butyral) resin, 2-3 parts of rosin resin, 20-30 parts of powder, and 60-80 parts of solvent; wherein the solvent includes alcohol solvents; the ink has a viscosity of 15-18 seconds (2# cup, Zein cup) at 25°C and a fineness of 300-800 nm.

[0005] The components also include additives, including defoamers, leveling agents, and dispersants.

[0006] The alcohol solvents include ethanol and water.

[0007] The time for the PVB resin is 5-8 seconds.

[0008] Optionally, the time for the PVB resin is 5-7 seconds.

[0009] Optionally, the time for the PVB resin is 5-6 seconds.

[0010] Existing water-based inks generally suffer from poor stability, making it difficult to meet the stringent packaging quality requirements of high-end cigarettes. This invention reveals that ink stability can be improved through the synergistic effect of limiting the viscosity of PVB resin to 5-8 seconds and the number-average molecular weight of rosin resin to 200-600. The limited viscosity of PVB resin ensures that it forms a uniform and stable resin matrix in the solvent, preventing both excessively high viscosity from hindering system flow and excessively low viscosity from causing uncontrolled spreading during film formation. Meanwhile, the specific number-average molecular weight of rosin resin combines good solubility and flowability, forming a complementary and compatible system with PVB resin: PVB resin provides the adhesion and structural stability required for film formation, while rosin resin reduces the surface tension of the system, promoting rapid ink spreading on the cork paper surface. The synergistic properties of both allow the ink to maintain a stable system state during printing, smoothly fill the printing cylinders, and be evenly transferred to the substrate, effectively avoiding leveling defects such as pinholes and sagging, and significantly improving the ink's leveling performance.

[0011] The number average molecular weight of the rosin resin is 300-500.

[0012] The oil absorption capacity of the powder is 15-40g / 100g.

[0013] Optionally, the oil absorption capacity of the powder is 25-35g / 100g.

[0014] This invention limits the oil absorption of the powder to 25-35g / 100g, reducing printing color difference through synergistic effects with the resin and solvent system. Powder with an oil absorption within this range can fully absorb the resin liquid formed by PVB and rosin resin, preventing powder agglomeration in the system due to insufficient absorption, which would cause uneven color distribution during printing. Conversely, excessive oil absorption will not over-consume resin, leading to insufficient resin during ink film formation and causing localized color variations. Simultaneously, this oil absorption is matched with the solvent's dissolving capacity and the resin's film-forming characteristics: the solvent ensures sufficient resin dissolution to meet the powder's adsorption requirements, while the resin, through close binding with the adsorbed powder, ensures consistent color transfer during ink transfer, thus fundamentally preventing color difference problems caused by uneven powder dispersion or resin adsorption imbalance.

[0015] The powder includes inorganic powder, which includes at least one of the following: iron yellow (iron oxide yellow), iron red (iron oxide red), titanium dioxide, iron oxide black, iron oxide brown, chrome yellow, chrome green, ultramarine, cobalt blue, cadmium red, cadmium yellow, nano zinc oxide, nano zirconium oxide, antimony white, and zinc sulfide.

[0016] The second aspect of the present invention provides a method for preparing ink, comprising the following steps: adding PVB resin and rosin resin to a solvent and mixing until the resin is completely dissolved to obtain a resin liquid; adding powder to the resin liquid to obtain a mixture; and grinding the mixture to obtain ink.

[0017] The availability of raw materials for the inks in this invention lays the foundation for large-scale production, while the synergistic effect of the ethanol-water mixed solvent with the resin and powder achieves the dual goals of VOC emission reduction and improved drying efficiency. Ethanol, as a volatile alcohol solvent, can rapidly dissolve PVB resin and rosin resin, providing the system with good solubility and flowability. Water, as an environmentally friendly solvent, not only has no VOC emissions but also regulates the evaporation rate of ethanol, preventing premature film formation on the ink surface and internal solvent residue due to excessively rapid evaporation, or excessively slow evaporation affecting drying efficiency. The mixed solvent works synergistically with the solubility of the resin and the dispersion stability of the powder: on the one hand, it ensures sufficient dispersion of each component, ensuring the stability of the ink system and reducing sedimentation and stratification; on the other hand, the rapid evaporation characteristics of ethanol combined with the rate-regulating effect of water significantly reduce VOC emissions from traditional solvent-based inks and improve the drying speed of the ink after printing, avoiding problems such as print sticking and plate clogging, thus balancing environmental protection and production efficiency.

[0018] The synergistic matching of the ink's viscosity of 15-18 seconds at 25°C and its fineness of 300-800nm ​​in this invention provides crucial process adaptability for gravure full-page printing. Regarding viscosity, the 15-18 second range ensures smooth ink filling of the gravure printing roller cells, preventing insufficient cell filling and printing gaps due to excessive viscosity, while also avoiding excessive diffusion and ink smearing during transfer due to excessively low viscosity. Regarding fineness, the 300-800nm ​​particle size ensures uniform dispersion of the powder in the resin solution, preventing clogged printing roller cells due to excessively large particles, thus maintaining printing continuity, while also ensuring a smooth surface and uniform color after ink film formation. This synergistic effect allows the ink to achieve both full filling and efficient transfer of ink within the cells during high-speed gravure full-page printing, while also enabling rapid film formation, perfectly adapting to the process characteristics of gravure printing and ensuring stable and controllable printing quality.

[0019] A third aspect of the present invention provides a printing process using the ink described above, wherein the printing process is gravure full-page printing and the printing roller is engraved using an electro-engraving process.

[0020] The mesh count of the printing roller is 180-200 mesh, and the depth is 34-41 μm.

[0021] This invention achieves a 20-30% reduction in ink consumption through deep synergy between the ink characteristics, gravure printing process, and the parameters of the electro-engraved roller (180-200 mesh, 34-41μm), while simultaneously reducing VOC emissions and production costs. This is likely due to the precise matching of the ink's viscosity, fineness, and other characteristics with the cell parameters of the electro-engraved roller: a cell count of 180-200 mesh and a depth of 34-41μm. Compared to deeper printing, this reduces the ink load per square meter, while the ink's excellent flowability and filling properties ensure that the ink in shallow cells is fully transferred to the tipping paper surface, preventing a decline in printing quality due to shallower cells. Furthermore, the high-precision cell shape and distribution of the electro-engraved roller, combined with the gravure printing process, enables uniform ink transfer; and the ink's rapid film-forming properties and strong adhesion further ensure that the clarity and durability of the printed pattern remain unaffected despite the reduced ink consumption. This synergistic effect of ink, process, and printing roller not only reduces ink consumption and directly lowers production costs, but also further reduces VOC emissions due to the reduced ink usage, achieving a win-win situation for printing quality, environmental protection, and economy.

[0022] Optionally, the mesh count of the printing roller is 190-200 mesh, and the depth is 34-37 μm.

[0023] The printing process is carried out at a temperature of 90-110℃ and a printing speed of 250-300m / min.

[0024] Beneficial effects 1. By limiting the time of PVB resin to 5-8 seconds and the molecular weight of rosin resin to 200-600, the stability of the ink can be improved.

[0025] 2. By limiting the oil absorption of the powder to 25-35g / 100g, the color difference problem in ink printing can be reduced.

[0026] 3. The ink prepared by this invention has a viscosity of 15-18 seconds at 25°C and a fineness of 300-800 nm, which can be matched with gravure full-page printing.

[0027] 4. The raw materials for preparing the ink of this invention are readily available, and the solvent is a mixture of ethanol and water, which effectively reduces VOC emissions and improves drying efficiency.

[0028] 5. The ink of this invention is used in conjunction with gravure full-page printing. The printing roller adopts an electro-engraving process. The mesh count of the printing roller is 180-200 mesh and the depth is 34-41μm. Compared with deep plate printing, while maintaining the printing effect, the amount of ink used in the printing process can be reduced by 10-20%, further reducing VOC emissions and production costs. Detailed Implementation

[0029] Example 1 A type of gravure printing ink for cork paper, by weight, comprises: 7 parts of PVB resin (5 seconds), 3 parts of rosin resin (molecular weight 400-500), 20 parts of powder (iron yellow, manufacturer: Rongju, oil absorption: 28g / 100g), and 60 parts of solvent (ethanol aqueous solution, ethanol:water volume ratio = 100:10).

[0030] A method for preparing a gravure printing ink for cork paper comprises the following steps: S1: Add the solvent to the container, and add PVB resin and rosin resin while stirring at 250 rpm. After the addition is complete, increase the speed to 900 rpm and stir for 1.5 hours until the resin is completely dissolved to obtain the resin solution. S2: Add powder while stirring at 200-300 rpm. After the addition is complete, increase the speed to 900 rpm and stir for 1.5 hours to obtain a mixture. S3: Transfer the mixture to a sand mill and grind it until the fineness is qualified; add the remaining materials of the additives (defoamer, leveling agent, dispersant) and stir evenly to obtain ink (2# cup, Zein cup, 25℃, viscosity: 16 seconds, fineness: D50=500nm).

[0031] A printing process using the ink prepared above, wherein the printing process is gravure full-page printing and the printing roller is engraved using an electro-engraving process.

[0032] The screen holes on the printing roller have a mesh count of 190 and a depth of 37 μm.

[0033] The printing process is carried out at a temperature of 100℃ and a printing speed of 275m / min.

[0034] Example 2 A type of gravure printing ink for cork paper, by weight, comprises: 8 parts of PVB resin (6 seconds), 3 parts of rosin resin, 25 parts of powder (iron oxide red, manufacturer: Rongju, oil absorption: 25g / 100g), and 70 parts of solvent (ethanol aqueous solution).

[0035] A method for preparing a gravure printing ink for cork paper, the specific implementation method is the same as in Example 1, the ink parameters are: (2# cup, Zein cup, 25℃, viscosity: 17 seconds, fineness: D50=500nm).

[0036] A printing process, specifically implemented in the same way as in Example 1, except that the mesh count of the printing roller is 200 mesh and the depth is 34 μm.

[0037] A printing process, the specific implementation method of which is the same as in Example 2.

[0038] Comparative Example 1 A type of gravure printing ink for cork paper, by weight, comprises: 8 parts of PVB resin (6 seconds), 3 parts of rosin resin, 25 parts of powder (iron yellow, manufacturer: Rongju, oil absorption: 28g / 100g), and 70 parts of solvent (ethanol aqueous solution).

[0039] A method for preparing a gravure printing ink for cork paper, the specific implementation method is the same as in Example 1, the ink parameters are: (2# cup, Zein cup, 25℃, viscosity: 17 seconds, fineness: D50=500nm).

[0040] A printing process, specifically implemented in the same way as in Example 1, except that the mesh count of the printing roller is 210 mesh and the depth is 34 μm.

[0041] Comparative Example 2 A type of gravure printing ink for cork paper, comprising: 8 parts of PVB resin (6 seconds), 2 parts of rosin resin, 20 parts of powder (iron yellow, manufacturer: Lanxess, oil absorption: 38g / 100g), and 100 parts of solvent (ethanol aqueous solution).

[0042] A method for preparing a gravure printing ink for cork paper, the specific implementation method is the same as in Example 1, the ink parameters are: (2# cup, Zein cup, 25℃, viscosity: 16 seconds, fineness: D50=500nm).

[0043] A printing process, specifically implemented in the same way as in Example 1, except that the mesh count of the printing roller is 200 mesh and the depth is 34 μm.

[0044] Comparative Example 3 A type of gravure printing ink for cork paper, by weight, comprises: 10 parts of PVB resin (viscosity of 8 seconds at 25°C), 3 parts of rosin resin, 25 parts of powder (iron oxide red, manufacturer: Lanxess, oil absorption: 38g / 100g), and 130 parts of solvent (ethanol aqueous solution).

[0045] A method for preparing a gravure printing ink for cork paper, the specific implementation method is the same as in Example 1, the ink parameters are: (2# cup, Zein cup, 25℃, viscosity: 17 seconds, fineness: D50=500nm).

[0046] A printing process, specifically implemented in the same way as in Example 1, except that the mesh count of the printing roller is 200 mesh and the depth is 34 μm.

[0047] Comparative Example 4 A type of gravure printing ink for cork paper, by weight, comprises: 9 parts of PVB resin (viscosity of 6 seconds at 25℃), 2 parts of rosin resin, 18 parts of powder (iron yellow, manufacturer: Rongju, oil absorption: 28g / 100g), and 70 parts of solvent (ethanol aqueous solution).

[0048] A method for preparing a gravure printing ink for cork paper, the specific implementation method is the same as in Example 1, the ink parameters are: (2# cup, Zein cup, 25℃, viscosity: 17 seconds, fineness: D50=500nm).

[0049] A printing process, specifically implemented in the same way as in Example 1, except that the mesh count of the printing roller is 150 mesh and the depth is 54 μm.

[0050] Performance testing methods Performance tests were conducted using the inks and printing processes described in the examples and comparative examples, and the test data are listed in Table 1.

[0051] 1. Printing effect: Test method 7.10 in YC171-2014.

[0052] 2. Ink usage: Record the amount of ink used during the printing process.

[0053] 3. Color difference: Color difference meter, △E≤1 is OK.

[0054] Performance test data Table 1

[0055] As shown in Table 1, the ink formulations and printing processes used in Examples 1-2 exhibit excellent overall performance: both achieved satisfactory printing results, demonstrated good color difference control, and maintained a stable ink consumption of 4.5-4.7 g / m³. 2 The ink usage was at a relatively low level, demonstrating the effectiveness of the synergistic effect between the formulation and the process. However, the comparative example showed a clear weakness: while the printing effect of Comparative Example 1 met the standards, the ink usage was slightly low (4.3 g / m²). 2 However, Comparative Example 1 exhibited a color difference issue, resulting in a lighter shade. Comparative Examples 2 and 3 both suffered from poor leveling performance and a lighter color, failing to meet printing quality requirements even with ink usage comparable to some examples. Comparative Example 4, while meeting printing quality and color difference standards, had an ink usage as high as 5.5 g / m³. 2 The ink usage was significantly higher than in the comparative examples, increasing production costs and VOC emission risks. Overall, the ink formulation and printing process combination of the present invention effectively controls ink usage while ensuring printing quality and acceptable color difference, resulting in superior overall performance compared to the comparative examples.

Claims

1. A gravure printing ink for tipping paper, characterized in that, By weight, the components include: 7-10 parts PVB resin, 2-3 parts rosin resin, 20-30 parts powder, and 60-80 parts solvent; the solvent includes alcohol solvents; the viscosity of the PVB resin at 25°C is 5-8 seconds; the number average molecular weight of the rosin resin is 200-600; the viscosity of the ink tested with a #2 Zein cup at 25°C is 15-18 seconds, and the fineness is 300-800 nm.

2. The ink according to claim 1, characterized in that, The alcohol solvents include ethanol and water.

3. The ink according to claim 2, characterized in that, The time for the PVB resin is 5-8 seconds.

4. The ink according to claim 3, characterized in that, The number average molecular weight of the rosin resin is 300-500.

5. The ink according to claim 4, characterized in that, The oil absorption capacity of the powder is 25-35g / 100g.

6. A method for preparing the ink according to any one of claims 1-5, characterized in that, Includes the following steps: PVB resin and rosin resin are added to a solvent and mixed until the resin is completely dissolved to obtain a resin solution. The powder is added to the resin solution to prepare a mixture. The mixture is then ground to obtain the ink.

7. A printing process, characterized in that, The ink described in any one of claims 1-5 is used, and the printing process is gravure full-page printing, with the printing roller employing an electro-engraving process.

8. The printing process according to claim 7, characterized in that, The mesh count of the printing roller is 180-200 mesh, and the depth is 34-41 μm.

9. The printing process according to claim 7, characterized in that, The mesh count of the printing roller is 190-200 mesh, and the depth is 34-37μm.

10. The printing process according to claim 7, characterized in that, The printing process is carried out at a temperature of 90-110℃ and a printing speed of 250-300m / min.

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