Flexographic Ink Research Articles

Flexographic Printing of Trametes versicolor Laccase for Indicator Applications

Trametes versicolor laccase papers were prepared, and their suitability was tested for anticounterfeiting and oxygen indicator concepts in packaging applications. Laccase was coated and printed onto paper with a flexographic ink base, a sulfo polyester resin, Hydro‐Rez 1100D (HZ1100D). Laccase remains active on paper with flexographic ink HZ1100D after printing with flexographic press. Colour change of papers was observed when 2,2‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS) solution was applied to the paper. A strong colour change to dark green was obtained on the papers prepared by coating or printing of laccase with HZ1100D onto EUCA paper. EUCA paper appeared to be well suited for laccase‐based indicator applications because it remained rough even after ink deposition, allowing rapid absorption of ABTS solution. Finally, the indicators demonstrated to work as oxygen indicators in a package. Indicator colour was changed when oxygen was leaked to the package. As a conclusion, the laccase papers described here would be well suited for various indicator applications and could be produced using flexographic printing, allowing large scale manufacturing. Copyright © 2014 John Wiley & Sons, Ltd.

Deinking flexographic-printed papers: Destabilization of flexographic ink dispersions with copper compounds

Flexographic printing inks form electrosterically stabilized colloidal dispersions in water that display extreme stability at the alkaline pH values of most wastepaper deinking systems. A significant amount of U.S. newspapers are now printed using water-based flexographic inks, and the residual inks from these sources are problematic to remove in deinking plants. A successful flocculant for flexographic ink particles used in deinking plant filtrate streams requires that both the electrostatic and steric components of colloidal stabilization be eliminated simultaneously. The present study shows the advantageous characteristics of cupric chloride in achieving rapid flocculation of flexographic inks. Flocculation experiments were performed with a model ink as well as a mixture of offset and flexographic inks from recycled newspapers. The critical coagulation concentration of cupric chloride has been compared to other chloride, nitrate, and copper salts. Copper(II) chloride has been found to be significantly more effective than other such salts in achieving destabilization and aggregation of flexographic ink particles. A possible flocculation mechanism of flexographic ink particles by cupric chloride is presented.

Study on Anti-Friction Performance of Water-Based Flexographic Ink

In order to improve the anti-friction performance of water-based flexographic ink, we made up different kinds of water-base flexographic ink by changing the kinds of film-forming resin or adding different kinds of friction resistant additives, and then evaluated the friction resistant performance of the ink by the rate of density decay. According to analysis the influencing factors of the anti-friction performance of ink, aiming at improving the cohesion of molecular systems and smooth degree of membrane surface, and reducing the friction coefficient as well. The result shows that different molecular structure of film-forming resin ink will cause different cohesion of molecules system in ink, which impacts the ink friction performance. Adding appropriate anti-friction performance additives can improve ink cohesion of molecular system, and improve the ink anti-friction performance as well.

Antibacterial flexographic ink containing silver nanoparticles

The current work deals with the effects of incorporation of silver nanoparticles on the antibacterial and the thermal properties of a flexographic ink. The stable and uniform dispersion of silver nanoparticles in the ink were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal properties of the pure and nanoparticle loaded ink films were also evaluated using TGA and DSC techniques. The results from this study proved acceptable dispersion characteristics, wherein, the flexographic ink showed a significant antibacterial activity against Gram-positive and Gram-negative bacteria

Flexographic printing ink modified with hyperbranched polymers: Boltorn™ P500 and Boltorn™ P1000

Abstract The flexographic printing ink Urania® was modified with commercially available hyperbranched polymers, Boltorn™ P500 and Boltorn™ P1000. The surface tension of the printing inks was measured and the rheology behaviour of pure polymers and printing inks is presented. The obtained flow curves (shear stress versus shear rate) for printing inks exhibited pseudoplastic behaviour. Modified flexographic inks were laboratory printed on three different plastic films: PE, oPP and PET. The impact of a small amount of hyperbranched polymers on printing ink colour was examined by optical density, total colour difference ΔE (L∗, a∗, b∗, CIE) and the gloss of the print film. In general, the addition of hyperbranched polymers improved the colour properties of the overprinted sample and colour fastness to rubbing. The influence of hyperbranched polymers on the rheological properties, optical density and L∗, a∗, b∗ coordinates and colour fastness is discussed.

Hyperbranched polymers – their application in printing inks

Urania® flexographic printing ink was modified with the commercially available hyperbranched polymer Boltorn H2004. The surface tension of the printing inks was measured and the rheology behaviour of the printing inks was assessed. The flow curves (shear stress vs. shear rate) for the printing inks exhibited pseudoplastic behaviour. Modified flexographic inks were laboratory printed on three different plastic films: polyethylene, polypropylene and polyethylene terephthalate. The impact of a small amount of hyperbranched polymer on printing ink colour was examined by optical density, total colour difference ΔE ∗ (CIE L ∗, a ∗, b ∗) and the gloss of the printed film. In general, the addition of the hyperbranched polymer improved the colour fastness and hardness resistance. The influence of the hyperbranched polymer on the rheological properties, optical density, CIE LAB coordinates and colour fastness is discussed.

Development of printable bioactive paper containing laccase

Compatibility of Trametes versicolor and Trametes hirsuta laccases was studied with polymers used for flexographic inks. The aim was to produce bioactive paper with ability to change color. Optimum pH for the stability of Trametes versicolor and Trametes hirsuta laccases was determined during storage at room temperature for 60 days. The optimum pH for the stability of both laccases was 8–9. The stabilization effect of flexo printing inks on the enzymes was tested in liquid form and when coated on paper. Sulfo polyester resin HZ1100D stabilized the two laccases both in solution and on paper. For example, Trametes versicolor laccase remained stable for at least 8 weeks when coated with HZ1100D polymer. Furthermore, the adsorption of the flexo inks to cellulose was studied with quartz crystal microbalance with dissipation monitoring (QCM-D). It was observed that HZ1100D also adsorbs well on cellulose over a wide pH range. The results suggested that laccases are well suited to bioactive paper applications. Large scale manufacturing of bioactive paper products by flexo printing would be possible because of the compatibility of laccases with flexo inks.

Biodeinking of flexographic inks by fungal laccases using synthetic and natural mediators

The use of new printing technologies based on flexographic inks hampers ink elimination during paper recycling, making necessary the development of alternative methods. Decolorization of four flexographic inks has been evaluated by using fungal laccases, three of them from basidiomycetes (Trametes villosa, Coriolopsis rigida, and Pycnoporus coccineus), and one from the ascomycete Myceliophthora thermophila in the presence of synthetic and natural mediators.The results obtained showed a higher capacity of the three basidiomycete laccases to decolorize flexographic inks as compared with M. thermophila laccase, a low redox potential laccase. Basidiomycete laccases decolorized inks without mediators at long reaction times, although the presence of natural or synthetic mediators (above all HBT) accelerated the process. On the other hand, M. thermophila laccase was unable to decolorize the inks assayed. The addition of syringyl-type mediators led to medium levels of decolorization except for R48 ink, which was almost completely decolorized.Most decolorization was obtained during the first hours of treatment, when all the basidiomycete laccases were fully active in the presence of mediators. As opposed to other basidiomycete laccases, which become inactive in the presence of HBT after 24h, the enzyme of P. coccineus was not deactivated by this mediator even after 48h. A complete loss of M. thermophila laccase activity was observed at short times with acetosyringone and methyl syringate, the only two mediators able to promote ink decolorization with this enzyme.

Сучасний стан розвитку флексографічних фарб для паковань

The realized research of current range and trends in the development of flexographic inks for packing allows correctly choose the best printing inks for packaging of the highest quality, which would be safe to the environment in the same time. Thus, the development of environmentally friendly inks for printing on packaging materials capable of biodegradable in vivo, is an actual scientific and applied problem whose solution will improve the production processes of manufacture and packing design and environmental utilization.

Flexographic ink film's resistance to inkjet ink's solvent flow in Hybrid Printing

Flexographic ink film's resistance to inkjet ink's solvent flow in Hybrid Printing

Nanofibrillated cellulose as a coating agent to improve print quality of synthetic fiber sheets

To determine the potential of nanofibrillated cellulose (NFC) for use as a coating material, we studied the characteristics of several NFC-coated samples on a synthetic fiber sheet. We used two water-based printing methods to characterize the change in print quality and prepared two types of NFC by two different physical treatment methods. Various coat weights were applied onto synthetic fiber sheets, and the printability of the coated sheets was evaluated by ink absorption rates and print density. Ink pigment penetration was characterized with a confocal laser scanning microscope and a scanning electron microscope, with chemical analysis of samples using focused ion beam. The contact angle and the ink penetration rates decreased with increased coat weight of NFC. This result is the opposite of what the Lucas-Washburn equation would predict. For pigment-based flexographic inks, ink pigments were captured at the NFC layer. For dye-based inks, the ink components penetrated and moved through the NFC-coated layer. For ink-jet printing, the print quality improved with the NFC coating.

Effect of substrate properties on conductive traces printed with silver-based flexographic ink

Article Effect of substrate properties on conductive traces printed with silver-based flexographic ink was published on January 1, 2009 in the journal Nordic Pulp & Paper Research Journal (volume 24, issue 1).

Opportunities and challenges of using ultrafiltration for the concentration of diluted coating materials

The use of cross-flow ultrafiltration for the recovery of coating material from aqueous streams started about 30 years ago with electro-deposition paint in the automotive industry. This early success can be related to both environmental and economical advantages of using ultrafiltration. Ultrafiltration recovers and concentrates electro-deposition paint on the retentate side and produces purified water on the permeate side. Based on this success, the focus more recently moved to other coating materials, such as paper coatings, latex and flexographic ink. Similar to electro-deposition paint, the concept is to recover the diluted coating materials with ultrafiltration to obtain a solid-free permeate stream, which can be either recycled or easily treated, and a retentate stream, which contains the coating materials preferably at concentrations suitable for recycling or disposal. The advantages can be directly translated into very short payback times for ultrafiltration systems of typically less than two years. Application studies focusing on the coating recovery in a paper mill, the concentration of latex from the tank wash at a latex producer and the recovery of flexographic ink at a producer of printed cartons will highlight these benefits.

A method for evaluating ink mileage in gravure printing

Researchers have studied ink mileage curves for many years, and they have reported several models for curve fitting. Regression coefficients derived from curve fitting have been found to be very useful for comparing different inks and have been related to various properties of ink and paper. However, these models were based on experimental data from prints made on IGT and Prüfbau printability testers using offset inks. The quantity of ink transferred, and hence the amount of ink on paper, was determined by the weight difference of the printing disk before and after printing. These models have not been tested on other ink types or on commercial printing presses. The challenge has been that it is difficult to accurately measure the coat weight of gravure or flexographic ink film. In this study, eight coated rotogravure papers were printed on a Cerutti rotogravure web press. The ink film coat weights at different tonal values were calculated from the copper (Cu) concentrations in both liquid ink and printed paper samples, which we analyzed using an atomic absorption (AA) spectrometer after digestion. The ink film coat weight and relative reflection density data were fitted by different models using OriginPro® 7.5 software. The degree of fit was determined by the sum of the squares of residuals and the distribution of residuals around zero. Both the Oittinen and Calabro-Savagnone models fitted the experimental data equally well. The regression coefficients derived from curve fitting could be related to paper properties such as surface roughness, air permeability, and pore size. We found that the saturation density Ds had higher correlations with air permeability and with pore size than with surface roughness. The parameter m, which determines the steepness of the density curve in the region of very thin film (also called density smoothness), was highly correlated with paper roughness as measured by the profilometer and at a less significant level with air permeability. The parameter n was well correlated with both profilometer roughness and air permeability.

Water retention of flexographic inks and its influence on final print gloss

Flexographic printing is a process that employs a flexible printing form and low viscous ink, often water-based. The flexible printing form is favourable for printing on rough surfaces, but the high surface tension of the ink may cause printability problems.This work has focused on the interaction between paper/paperboard coating and water-based flexographic ink, aimed at increasing the knowledge about the printing process in form of physical/chemical parameters that are important for ink setting. The effects of printing conditions on print quality, such as printing pressure and temperature, have also been in focus.The work has shown that fluids of different polarities, i.e. different dipole moments, behave differently when being absorbed by a coating layer. Due to their chemical compatibility to the coating layer, fluids with large dipole moment fill the pore matrix of the coating to a lesser extent but penetrate further into the coating than fluids with small dipole moments. On the other hand, polarity of the coating layer also affects the print. When printing on coatings with different polarities, higher print densities was obtained on the more polar substrates. As a tentative explanation, it is proposed that the ink builds different layer structures during drying depending on the coating polarity.Print gloss is related to the ink setting which, in turn, is affected by the solvent retaining capacity of the ink. Large water holding capacity allows the ink components to smoothen out before the structure is set, resulting in a higher print gloss. The rheology of inks is affected by temperature; at a higher temperature the viscosity is reduced. The reduction in ink viscosity at higher temperature has been shown to affect the print quality, e.g., print density and dot gain. It is suggested that a thicker layer is immobilised during impression due to the lower viscosity and that it is an explanation of the higher print density at a higher printing temperature.The influence of impression pressure on dot gain has been experimentally evaluated and mathematically modelled with good agreement. The dot gain is shown to respond non-linearly to the applied printing pressure.Studies based on pilot coated and printed paperboards is also reported, and it is shown that the print quality, e.g. print density, print gloss and dot gain, is largely dependent on the type of ink chosen and on the coating characteristics. Higher clay content in the coating resulted in increased dot gain and a decreased mottling.

Transfer characterization of UV flexographic ink: Relationships between printability and rheological properties

Transfer characterization of UV flexographic ink: Relationships between printability and rheological properties

Print quality and resistance for water-based flexography on polymer-coated boards: Dependence on ink formulation and substrate pretreatment

The performance of water-based acrylic flexographic inks laboratory printed on three different polymer-coated boards, namely coated with LDPE, OPP and PP, have been analysed and interpreted. The print quality and resistance properties obtained were related to varying ink formulation, in particular choice of emulsion polymer and presence of silicone additive in the vehicle, as well as varying levels of corona pretreatment. Print mottle and adhesion were worst on PP, while wet (water) rub and scratch resistance were worst on OPP and PE, respectively. However, these properties could be greatly influenced by the ink formulation, more so than corona level. In general addition of silicone improved scratch resistance, due to reduction in polar energy component of the print surface, but at the expense of worsened wet rub resistance. The emulsion polymer giving best resistance performance was generally found to give poorest optical properties, presumably due to more limited resolubility on press.

Correlations between properties of water-based flexographic inks and their print uniformity on PE-coated board

Uniformity of fulltone flexographic prints on PE-coated board was investigated for a large matrix of aqueous inks with varying acrylic-based vehicles and pigment concentrations, and with their a ...

Influence of formulation and properties of water-based flexographic inks on printing performance for PE-coated board

In this study the flexographic printing of lowdensity polyethylene- (LDPE-) coated liquid packaging board is analysed for a range of water-based inks, varying in type of pigment and acrylate-poly ...

Rheology and surface tension of water-based flexographic inks and implications for wetting of PE-coated board

Article Rheology and surface tension of water-based flexographic inks and implications for wetting of PE-coated board was published on December 1, 2005 in the journal Nordic Pulp & Paper Research Journal (volume 20, issue 4).