How does Flexo water-based pre-printing ink solve the problem of fastness on non-absorbent materials?
Release Time : 2025-10-01
In the packaging printing industry, Flexo water-based pre-printing ink, thanks to its high brightness, strong visual impact, and environmentally friendly properties, is widely used in products such as corrugated boxes, labels, shopping bags, and children's books. However, when the printing substrate shifts from traditional absorbent paper to non-absorbent plastic films such as polyethylene, polypropylene, and polyester, poor ink adhesion, easy rub-off, and weak interlayer bonding become technical bottlenecks that restrict its application. The low surface energy and lack of porosity of non-absorbent materials make it difficult for water-based inks to effectively wet and anchor. In recent years, through the collaborative innovation of materials science and printing technology, Flexo water-based pre-printing ink has achieved significant breakthroughs in improving the adhesion of non-absorbent materials.
1. Resin System Optimization: Building a Strong Adhesion Foundation
The ink's binder is crucial to adhesion. Traditional water-based acrylic resins have poor adhesion to non-polar plastic surfaces. Modern flexo water-based pre-printing inks use modified acrylic resins or acrylic-polyurethane hybrid resins as the main binder. These resins incorporate structural units with lipophilic groups into their molecular chains, enhancing wetting on low-surface-energy plastic substrates. Furthermore, by adjusting the resin's glass transition temperature and molecular weight distribution, the ink forms a dense, flexible film with high cohesive strength during drying, strengthening the physical anchoring effect on the substrate. Some high-end products also incorporate crosslinkers to form a three-dimensional network structure after drying, further enhancing friction and scratch resistance.
2. Surface Treatment Technology Synergy: Improving Substrate Printability
Even with excellent ink properties, untreated plastic film surfaces can still struggle to adhere well. Therefore, corona treatment or plasma treatment of the substrate before printing is essential. Corona treatment modifies the physical and chemical properties of the plastic surface through high-voltage discharge, increasing surface roughness and polar groups, significantly increasing surface tension and making it easier for water-based inks to spread and penetrate.
3. Precise Addition of Functional Additives: Strengthening Interfacial Bonding
Scientifically adding functional additives to ink formulations is another key approach to addressing adhesion issues. For example, wetting and dispersing agents can reduce ink surface tension and improve wetting and spreading on low-energy surfaces. Adhesion promoters can form "molecular bridges" between the ink and the plastic substrate, strengthening interfacial bonding through chemical or physical interactions. Furthermore, the judicious use of anti-friction additives such as waxes or silicone oils can improve surface slip while avoiding adhesion loss caused by excessive lubrication, achieving a balanced performance.
4. Drying Process Optimization: Ensuring Film Integrity
Water-based inks primarily rely on evaporation to dry on non-absorbent substrates. Inadequate drying can result in residual moisture, leading to a loose film and reduced adhesion. Flexographic printing lines must be equipped with efficient hot air drying systems with optimally controlled drying temperature and air speed to ensure complete drying and film formation within a short period of time. Excessively high temperatures can cause film deformation, while insufficient temperatures can lead to poor drying. Modern flexographic printing equipment often utilizes multi-stage temperature control technology to achieve gradient drying, ensuring efficient drying while preventing blistering or cracking in the film layer, resulting in a dense, uniform fluorescent ink layer.
5. Surface Modification and Stable Dispersion of Fluorescent Pigments
Fluorescent pigments are mostly organic dyes or pigments, which are prone to migration, have poor lightfastness, and are not very compatible with water-based systems. Surface coating can improve the weather resistance and stability of fluorescent pigments in aqueous media. Furthermore, the use of high-efficiency dispersants and grinding processes ensures uniform and stable dispersion of fluorescent pigments in the ink, preventing agglomeration or precipitation. This not only ensures color vividness but also prevents localized adhesion weakness caused by uneven pigment distribution.
In summary, Flexo water-based pre-printing ink systematically addresses the challenge of strong adhesion on non-absorbent substrates through a multi-faceted approach encompassing resin modification, substrate pretreatment, the synergy of functional additives, drying process optimization, and pigment surface engineering.
1. Resin System Optimization: Building a Strong Adhesion Foundation
The ink's binder is crucial to adhesion. Traditional water-based acrylic resins have poor adhesion to non-polar plastic surfaces. Modern flexo water-based pre-printing inks use modified acrylic resins or acrylic-polyurethane hybrid resins as the main binder. These resins incorporate structural units with lipophilic groups into their molecular chains, enhancing wetting on low-surface-energy plastic substrates. Furthermore, by adjusting the resin's glass transition temperature and molecular weight distribution, the ink forms a dense, flexible film with high cohesive strength during drying, strengthening the physical anchoring effect on the substrate. Some high-end products also incorporate crosslinkers to form a three-dimensional network structure after drying, further enhancing friction and scratch resistance.
2. Surface Treatment Technology Synergy: Improving Substrate Printability
Even with excellent ink properties, untreated plastic film surfaces can still struggle to adhere well. Therefore, corona treatment or plasma treatment of the substrate before printing is essential. Corona treatment modifies the physical and chemical properties of the plastic surface through high-voltage discharge, increasing surface roughness and polar groups, significantly increasing surface tension and making it easier for water-based inks to spread and penetrate.
3. Precise Addition of Functional Additives: Strengthening Interfacial Bonding
Scientifically adding functional additives to ink formulations is another key approach to addressing adhesion issues. For example, wetting and dispersing agents can reduce ink surface tension and improve wetting and spreading on low-energy surfaces. Adhesion promoters can form "molecular bridges" between the ink and the plastic substrate, strengthening interfacial bonding through chemical or physical interactions. Furthermore, the judicious use of anti-friction additives such as waxes or silicone oils can improve surface slip while avoiding adhesion loss caused by excessive lubrication, achieving a balanced performance.
4. Drying Process Optimization: Ensuring Film Integrity
Water-based inks primarily rely on evaporation to dry on non-absorbent substrates. Inadequate drying can result in residual moisture, leading to a loose film and reduced adhesion. Flexographic printing lines must be equipped with efficient hot air drying systems with optimally controlled drying temperature and air speed to ensure complete drying and film formation within a short period of time. Excessively high temperatures can cause film deformation, while insufficient temperatures can lead to poor drying. Modern flexographic printing equipment often utilizes multi-stage temperature control technology to achieve gradient drying, ensuring efficient drying while preventing blistering or cracking in the film layer, resulting in a dense, uniform fluorescent ink layer.
5. Surface Modification and Stable Dispersion of Fluorescent Pigments
Fluorescent pigments are mostly organic dyes or pigments, which are prone to migration, have poor lightfastness, and are not very compatible with water-based systems. Surface coating can improve the weather resistance and stability of fluorescent pigments in aqueous media. Furthermore, the use of high-efficiency dispersants and grinding processes ensures uniform and stable dispersion of fluorescent pigments in the ink, preventing agglomeration or precipitation. This not only ensures color vividness but also prevents localized adhesion weakness caused by uneven pigment distribution.
In summary, Flexo water-based pre-printing ink systematically addresses the challenge of strong adhesion on non-absorbent substrates through a multi-faceted approach encompassing resin modification, substrate pretreatment, the synergy of functional additives, drying process optimization, and pigment surface engineering.