Abstract: Flexographic printing on corrugated cardboard boxes is one of the most widely used and industrialized printing processes in the packaging printing industry. It has the advantages of low plate making cost, low printing pressure, wide substrate adaptability, and high production efficiency. It is widely used in paper substrate printing scenarios such as express packaging, food cartons, and industrial outer packaging. The water-based ink suitable for corrugated paper high-speed flexographic printing production line puts forward special working condition requirements different from film flexographic printing for the binder lotion: high solid content can improve the ink dyeing density and drying efficiency, and it is suitable for high-speed machine continuous production; The low viscosity characteristic can ensure precise ink transfer of the mesh roller, reduce dot blockage and ink flying defects; Excellent rheological stability and compatibility with additives can significantly reduce process issues such as foaming, delamination, and precipitation during high-speed printing. The traditional styrene acrylic lotion has low solid content, high viscosity and poor rheological adaptability, which cannot meet the production requirements of modern corrugated box high-speed flexographic printing. The formulation synthesis and process optimization of high solid and low viscosity styrene acrylic lotion were carried out in a targeted manner, and the regulation laws of emulsifier compound system, seed monomer feeding ratio, and polymerization process parameters on the particle size distribution, system viscosity, and storage stability of the lotion were systematically explored. The self-made high solid and low viscosity styrene acrylic lotion was used as the ink binder to prepare corrugated special flexographic ink, and the ink transfer performance, field color density, dot reproduction accuracy, drying rate, and storage stability were comprehensively evaluated. The compatibility mechanism of the lotion and various ink additives was analyzed to solve the engineering problems of traditional ink high-speed printing, such as blistering, ink flying, blocking, delamination and sedimentation, and finally optimized to obtain a suitable corrugated box high-speed flexographic ink. The optimal lotion synthesis formula and preparation process of printing provide experimental basis and technical reference for the industrial upgrading of high-performance carton flexographic ink wash.
1. Research background and significance of topic selection
With the green, high-speed, and intelligent upgrading of the packaging printing industry, water-based flexographic printing ink has become the mainstream consumable for corrugated box printing due to its advantages of no VOC emissions, low toxicity, environmental protection, safety and flame retardancy, and low cost, fully replacing traditional solvent based inks. Flexographic printing relies on quantitative ink transfer using a mesh roller and light pressure contact to complete graphic and text transfer, with strict requirements for ink viscosity, fluidity, solid content, and thixotropy. At present, the solid content of most commercial ordinary styrene acrylic lotion is low. In order to meet the coloring concentration, it is necessary to improve the viscosity of ink preparation, which is very easy to cause defects such as heavy ink hanging on the anilox roll, delayed drying of the ink layer, dot paste, rough edges of the image and text, etc. during high-speed printing; At the same time, the conventional lotion has wide particle size distribution, poor rheological properties of the system, and is prone to foaming, demulsification, pigment agglomeration and sedimentation under high-speed shear conditions, which seriously restricts the production efficiency and printing quality of corrugated box printing.
In view of the above industry pain points, this paper focuses on the exclusive working conditions of corrugated box flexographic printing, and proposes to develop a modified styrene acrylic lotion with high solid content, low viscosity, narrow particle size distribution, and excellent rheological adaptability, so as to improve the solid content without increasing the viscosity of the ink system, take into account the high tinting power, fast drying and high-speed printing liquidity of the ink, and adapt to the high-speed continuous production needs of modern corrugated printing equipment. It has important engineering application value for improving the printing clarity of the carton, reducing the rate of defective production, and promoting the upgrading of green process of packaging and printing.
2 Experimental System and Synthesis Process Design
In this paper, a semi continuous seed lotion polymerization process was used to prepare a high solid and low viscosity styrene acrylic lotion. The styrene and acrylate soft and hard monomers were used as the main copolymers, and the anionic and non-ionic composite emulsion system was used. By adjusting the feed ratio of the seed lotion, the monomer drop acceleration rate, the reaction temperature, and the amount of initiator, the lotion particle size was controllable, the viscosity was reduced, and the solid content was increased. The experiment focuses on the two core variables of emulsifier compounding mechanism and seed polymerization ratio, and explores the influence of different process parameters on the macro viscosity, micro particle size distribution and system stability of lotion. Different from conventional lotion polymerization, this research uses narrow distribution particle size control technology to improve the solid content of the system while avoiding the viscosity surge caused by molecular chain entanglement, breaking through the performance balance problem of traditional lotion that “high solid must be high viscosity”.
In the experiment, styrene acrylic lotion prepared with different formulas was used as the only film forming binder, and mixed with pigments, dispersants, defoamers, thickeners and wetting agents to prepare special flexographic ink for corrugated boxes. The rheological curve, storage stability, foam performance, drying performance, field density and dot gain rate of the ink were systematically tested, and the impact of lotion structure on the printability of the ink was comprehensively evaluated.
Analysis of Key Research Results and Performance Patterns
3.1 Control mechanism of emulsifier compounding for lotion viscosity and particle size
The research shows that the lotion prepared by a single emulsion system has a wide particle size distribution, large and small particles are mixed and piled up, the internal friction resistance of the system is large, the overall viscosity is high, and the characteristics of high solid and low viscosity cannot be achieved. The use of anionic/nonionic emulsifier compound system can synergistically optimize the nucleation effect of lotion to form sufficient, uniform and stable latex particles. The narrow particle size distribution structure can effectively reduce the particle bulk density and fluid resistance, and significantly reduce the bulk viscosity of lotion while significantly increasing the solid content. At the same time, the composite emulsion system can enhance the surface charge density of latex particles, improve the stability of Zeta potential, effectively restrain the problems of particle agglomeration, sedimentation and stratification during the storage of lotion, and provide structural guarantee for the long-term storage and stability of ink wash. This study has determined the optimal compounding ratio of emulsifier suitable for high solid and low viscosity lotion, and provided core parameters for the formulation design of low viscosity lotion.
3.2 Effect of seed monomer ratio on stability of lotion polymerization
The proportion of seed monomer directly determines the nucleation amount and particle growth uniformity of lotion, and is a key process parameter for the synthesis of high solid and low viscosity lotion. The experimental results indicate that a reasonable increase in the proportion of seed monomers can form sufficient stable crystal nuclei, followed by uniform coverage and growth of monomers. The regularity of latex particles is significantly improved, and the viscosity of the system is controllable; A low seed ratio can cause secondary nucleation, uneven particle size, and large fluctuations in system viscosity; If the seed proportion is too high, it is easy to cause local overheating of the polymerization system, gel caking, and reduce the yield and stability of lotion. In this paper, through multiple sets of gradient tests, the optimal feeding range of seed monomer was determined, and high-quality styrene acrylic lotion with high solid content, low viscosity, transparent appearance and no gel was successfully prepared.
3.3 Improvement effect of high solid and low viscosity lotion on ink printability
The flexographic ink based on self-made high solid and low viscosity styrene acrylic lotion has significantly better rheological properties than ordinary lotion ink. Under high-speed shear printing conditions, ink exhibits excellent shear thinning characteristics, with a rapid decrease in viscosity and a significant improvement in flowability. This enables fast and uniform ink transfer by the web roller, completely improving defects such as ink flying, ink dragging, and uneven ink layer thickness during high-speed printing; Under static standing conditions, the viscosity of ink increases, effectively preventing pigment settling and layering, and improving ink storage stability. At the same time, the high solid content characteristics enable the ink to achieve high color density in a single ink transfer, with a full and uniform ink layer, strong graphic and text coverage, clear dots, and low expansion rate, greatly improving the precision and aesthetics of corrugated cardboard box printing graphics and text.
3.4 Compatibility of lotion and auxiliary system and process defect solving mechanism
The compatibility of styrene acrylic lotion with dispersant, defoamer, thickener and other conventional ink auxiliaries is mainly studied in this paper. The traditional high viscosity lotion system is easy to be out of balance with additives, resulting in ink foaming, thickening failure, layered flocculation and other problems. The low viscosity lotion prepared in this study has uniform particle size, stable interfacial activity, and excellent compatibility with various additives. It can effectively cooperate with defoamer to quickly eliminate micro foam generated by high-speed mixing and printing, and eliminate pinholes, sand holes, missing prints and other defects caused by foam; At the same time, it can be accurately matched with the thickening system, achieving adjustable and controllable ink viscosity, adapting to the production needs of different line numbers of mesh rollers and different printing speeds, effectively solving the industry’s shortcomings of poor adaptability and low yield of traditional corrugated flexographic ink printing technology.
4 Existing Problems and Formula Optimization Ideas
At the same time, the study pointed out the performance shortcomings of the high solid and low viscosity styrene acrylic lotion system: the surface tension of the low viscosity lotion system is relatively high, and the wettability and spread of the rough corrugated paper surface is slightly insufficient; The film-forming shrinkage rate of high solid systems is relatively high, and the friction resistance of ink films slightly decreases under extreme temperature and humidity conditions. In view of the above problems, the paper proposes an optimization scheme: improve the surface wettability of lotion through micro functional monomer modification, and match with appropriate wetting additives to improve the spreading effect of substrate; Fine tune the ratio of soft and hard monomers, optimize the balance between the hardness and toughness of the ink film, improve the resistance to friction and lamination of printed products, and further improve the comprehensive application performance of high solid and low viscosity lotion.
5 Research Conclusions and Engineering Application Value
Based on the actual production conditions of corrugated box high-speed flexographic printing, the dissertation successfully developed the synthesis process of high solid and low viscosity styrene acrylic lotion suitable for industrial production, clarified the regulation mechanism of emulsifier compounding and seed polymerization ratio on the particle size, viscosity and stability of lotion, and revealed the internal relationship between lotion structure and the rheological properties of ink, printing suitability, and storage stability. The research has proved that the high solid and low viscosity styrene acrylic lotion can effectively improve the ink transfer uniformity, image and text clarity and drying rate of flexo printing ink, solve the common process problems such as blistering, flying ink, blocking, delamination and sedimentation in the high-speed printing process, and greatly improve the printing quality and production efficiency of corrugated boxes. This study has improved the formula design theory of water-based connectors for cardboard boxes, providing solid experimental data and process support for the industrial research and mass production of high-performance, low-cost, and high-speed printing flexographic ink printing. It has important practical significance for promoting the green and efficient upgrading of corrugated packaging flexographic printing technology.
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Post time: Sep-18-2026