Offset Ink Research Articles

Thermal and spectroscopic analyses on the molecular interaction between eucalyptus kraft pulp components and offset printing inks

Thermal and infrared spectroscopic analyzes were carried out in order to study the kind of interaction between the anatomical components of the bleached eucalyptus kraft pulp with offset inks. A Bauer-McNett fiber classifier was used in order to obtain the anatomical components of the pulp, separately. The determinations of the enthalpy of the processes occurring in the samples of inks and pulp, as well as the enthalpy of these components interactions were obtained by Differential Scanning Calorimetry. In the interaction between pulp and offset ink, the reduced enthalpy values of the endothermic peak were interpreted as due to the released energy for adhesion of the ink pigment to the substratum. The low enthalpy value, 58 to 121 cal.g -, ¹indicated that the settling of the ink occurs by physical interactions. The pulp fraction enriched with vessel elements caused a higher energy release during the adherence of the pigment into the pulp.

On estimation of complex refractive index and colour of dry black and cyan offset inks by a multi-function spectrophotometer

The optical properties of inks have much importance in quality inspection of prints. For instance, gloss and gloss mottling of a print depend not only on the surface roughness of the print but also on the spectral properties such as the wavelength-dependent complex refractive index of the ink. We have developed a device, the so-called multi-function spectrophotometer (MFS), that allows the measurement of reflectance and thereby assessment of the complex refractive index of the dry ink. Here, we report on the complex refractive index of dry black and cyan offset inks. Such information has importance in the study of gloss of prints. Furthermore, we show that the colour of these dry inks can be obtained with our apparatus by using light scattering data from the dry ink.

Some applications of viscometry from studies on the absorption of vegetable oils and solvents by paper substrates

In previous studies on the drying performance of oleoresinous and solvent-based offset lithographic printing inks, a test was devised to determine the rate of absorption of drops of vegetable oils and solvents deposited on the surface of a paper substrate. The influence of viscosity on the rate of horizontal capillary absorption indicated a potential use of the absorption data to predict viscosity in the oxidative polymerization of polyunsaturated vegetable oils. Volumes as low as 1.0 mL could be used in thermal oxidative polymerization studies and tested by the Drop Deposition method. The stain radii Rs of absorbed drops of the oil, e.g., on blotting paper or filter paper substrates, follow a linear relationship with the square root of time ( \( {\sqrt t } \) s) and the slopes m of the Rs vs \( {\sqrt t } \) graphs are converted to dynamic viscosity in dPa.s units using a modified form of the Lucas Washburn equation from which \( m \propto {\sqrt {1 \mathord{\left/ {\vphantom {1 {2\eta }}} \right. \kern-\nulldelimiterspace} {2\eta }} } \). The study has implications for assessing the stability of vegetable oils used in frying operations. The test method may also be used in the study of room temperature oxidative polymerization of polyunsaturated vegetable oils to evaluate drier catalysts used in surface coatings.

Lithographic offset ink rheology related to sensory descriptions of appearance and handling

Lithographic offset inks are pigment dispersions that behave as pseudoplastic, thixotropic fluids. Printers, who use these fluids in offset printing, judge some aspects of ink quality using a set of practiced visual and tactile perceptions that are referred to collectively as the “ink body.” Measurements of ink flow behavior are routinely performed to validate offset ink quality, but the measurements usually have been restricted to a small number of readings, such as a viscosity and a yield value. These measures, although suitable to provide some level of flow description of the ink, do not sufficiently represent perceptions of the fluid properties. A sequence of tests was developed to correspond more closely to an evaluation of ink body observable through sensory interaction with the fluid by sight and touch. Offset inks with a wide range of different body characteristics were rated by a sensory panel on a scorecard. Measurements in the test sequence were then used to predict the sensory panel ratings according to an algorithm obtained by partial least squares (PLS) regression analysis. Overall, the broader rheological description provides a better representation of the flow properties of offset printing ink. The test is suitable for practical use in a manufacturing environment for quality assurance.

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.

Mobility of Water in a Hydrophobic Polymeric Matrix as a Model System for an Offset Printing Ink

As a fundamental research for elucidation of effects of "dampening water", which is added during the usual offset printing, on the printing performance, 1H-PFGStE NMR and T2 measurements were carried out to investigate the mobility of water in model ink systems consisting of a phenol resin and oil components. Only for crosslinked systems with an aluminum chelate or abietic acid, some of the water showed a "restricted diffusion", meaning that the water is distributed in a limited region of some micron size in the polymer matrix and the water movement is confined within the region.

Visualisation of the distribution of offset ink components printed onto coated paper

Abstract The design of minerals for coated papers to maximise ink hold out and printed colour density has been an area of much study over the years. It is desirable in terms of cost and press runnability to achieve the required colour density with the minimum amount of ink applied. In this work, a series of heatset offset ink components was printed separately onto a coated paper and then combined into a varnish and then a whole ink. The ink components were visualised by focused ion beam (FIB) to determine which of the ink components entered the coating layer. The ink varnish was also applied to modified thin layer chromatography (TLC) plates, which had been coated with the same coating formulation as the paper samples. The separation of the ink components on modified TLC plates was assessed using FTIR spectroscopy. The results show that ink components, which enter the coating layer after offset printing, can be visualised in the FIB instrument. An exception to this was the mineral oil, which did not remain in the coating layer after drying and placing under vacuum due to its volatile nature. It was noticed that the contrast of the FIB image increased significantly when the samples with wax dissolved in the oil were imaged, which also allowed for a very clear imaging of the porous structure of coating layer. This type of image would be excellent for fundamental studies of detailed pore structure within a coating layer. This work agrees with other published findings which show that the pigments and hard resins remain on the surface of the coating, whereas the mineral and vegetable oils are mobile and penetrate into the coating layer. Ester solvent and dissolved wax also penetrate into the coating layer.

Acoustic emission and tack of heat-set inks during setting on MWC-papers and fountain solution emulsification

This thesis claims a relationship between the film splitting sound emission from the printing press nip and the dynamic interaction occurring there between ink, fountain solution and substrate in offset lithography. The film splitting sound derives from the cavitation formed by the pressure drop in the second half of the print nip flow passage. As the ink film is strained, the cavities expand and eventually implode into breaking filaments at the nip exit, while emitting a partly audible, broadband, high frequency, noisy sound. A free-field microphone, A/D-converter and laptop computer were used to record pressure signals in the frequency range of 10 Hz to 50 kHz emitted by a variety of printing instruments and presses for a range of offset ink and paper types. After signal acquisition and filtering two signal averages of power and frequency were estimated. This average power increased with increasing loads of sheet-fed offset ink on an ink distributor, in accordance with a mass-conservation model developed. The behaviour of average frequency and power over different ink load ranges indicated transitions between different flow regimes. A glossy fine-coated paper gave higher average power than a corresponding matte paper during printing with such inks on a laboratory device, possibly due to an air sealing effect. The sound from tack measurements with the Deltack instrument during setting of heat-set offset inks printed on MWC papers showed a relation between the measured tack rise and average power, reflecting changes in splitting mechanism during the course of setting. With the Hydroscope instrument the interaction between these heat-set inks and fountain solution was studied, with the measured tack and sound emission displaying a clear, but non-linear, correlation. A heat-set offset pilot trial showed that the acoustic response from the printing nip sensitively and systematically detected changes in (LWC) paper type, optical density, ink-fount balance, and press stability. Pilot trials of cold-set offset inks on newsprint by sheet-fed presses indicated a strong correlation between evolution in average power, optical density and fountain solution consumption during the first thousand sheets normally needed for stabilisation. Acoustic measurements of ink film splitting have, aside from the laboratory studies performed by one Japanese group, previously received little attention, with the current study showing that a great deal of information useful to the printer can be accessed from this sound emission. Although the detailed mechanisms for ink film splitting have to be further studied and supported by mathematical simulation, the sensitivity of the acoustic method recommends its implementation for monitoring and control of offset printing.

Quantitative evaluation of europium in blue ballpoint pen inks/offset printing inks tagged with europium thenoyltrifluoroacetonate by spectrofluorometry and ICP-AES

Tagging of writing/printing inks with suitable inorganic taggants such as rare-earth chelates has the potential to help document examiners identify fraud in sensitive written/printed documents. Selection of rare-earth chelates as taggants primarily depends on the satisfactory sensitivity of analytical determination and the absence of the taggants in normal varieties of inks used for document writing/printing. Spectrofluorometric determination of trace amounts of europium in blue ballpoint pen inks and offset printing inks tagged with europium thenoyltrifluoroacetonate was carried out with sodium tungstate solution. Sodium tungstate acts as a specific reagent that enhances the fluorescence intensity of the Eu3+ ion. The excitation and emission wavelengths are 270 nm and 605 nm respectively. The results were compared with the data obtained with ICP-AES. Satisfactory recoveries were observed with precision better than 5% RSD and comparable accuracy. Under the optimized experimental conditions, detection limits and quantitation limits were determined. The detection limits obtained by spectrofluorometry and ICP-AES were 0.01 microg/mL and 0.006 microg/mL respectively whereas the limits of quantitation were about 0.03 microg/mL and 0.018 microg/mL respectively. The spectrofluorometric method is rapid, selective, sensitive and accurate for the determination of europium in blue ballpoint pen ink and offset printing inks and may be suitable for application in the examination of sensitive documents to aid in document related crime investigation. The advantages and limitations of the tagging approach and proposed analytical techniques are discussed.

Assessment of the complex refractive index of an optically very dense solid layer: Case study offset magenta ink

A recently built multifunction spectrophotometer is used to measure reflectance from a dried liquid layer of optically very dense medium applied as a liquid onto the probe window in the form of a face of a prism. The measurement consists of scanning across of the wavelength range 400–800 nm and recording the s- and p-polarized light reflection. Complex refractive data is extracted using Azzam’s theory for light reflection. As an example, data for the case of dry magenta offset ink are shown, an application where the complex refractive index of the solidified ink layer is important in the evaluation of the print quality. The present method is not restricted to the case of inks but is proposed to be applicable across a broad range of applications, such as assessment of the optical properties of paints and biomedical samples.

Energy required for detachment of inks from printed newsprint in fibre slurries—Effects of vehicles and aging

Different vehicles in offset ink formulation were found to give different resistance to detachment shear force. Our results show that during the early stage after printing, it is more difficult to detach mineral oil based ink than vegetable oil based ink. However, after ageing the energy required for ink detachment is similar for both types of ink. This paper provides explanation on how the vehicles in ink formulation can affect the energy required for ink detachment.

Development of Mineral Oil Free Offset Printing Ink Using Vegetable Oil Esters

Until the middle of this century, fats and oils are the major raw material source for paints, coating and lubricating applications. These markets are completely taken over by petroleum based stocks due to their abundance and versatility. However, recent public awareness to use environmentally acceptable products that minimize pollution, are compatible to human health and readily biodegradable created opportunities for vegetable oils for application in paints and printing inks. The formulation of vegetable oil methyl ester based 'green' offset printing ink that reduces the volatile organic compounds (VOC) has been discussed in the present study. Methyl esters of rapeseed, soybean, rice bran and palm oil have been prepared and their physical properties have been measured and compared with standard petroleum feed stock. Varnishes were prepared with these esters and their properties are also compared with that of the petroleum based products. Rheological properties of the inks are also evaluated and compared with standard printing ink using petroleum based solvent. In general performance of the ester-based printing inks are comparable with that of the mineral oil based product. On the basis of tack stability and gloss, ester based inks are much superior than the mineral oil based products. In conclusion, a new non-volatile diluent for printing ink has been developed. The diluent is made from common vegetable oils like rapeseed, soybean, rice bran and palm oil, a renewable source that is environmental friendly. Vegetable oil esters offer a cost effective solution for mineral oil based printing ink to meet VOCs regulations.

CHARACTERIZATION OF OFFSET PRINTING INK TAGGED WITH RARE-EARTH TAGGANTS BY X-RAY EMISSION TECHNIQUES

Proton Induced X-ray Emission (PIXE) and Energy Dispersive X-ray Fluorescence (EDXRF) techniques have been used for elemental characterization of offset printing ink tagged with rare-earth taggants. The offset printing ink was tagged with rare-earth ( La , Pr , Nd , Sm , Eu and Gd ) thenoyltrifluoroacetonate chelates at about 1000-ppm level for each element separately. Small aliquots (approximately 20 mg) of tagged inks were coated on paper supports in the form of small circles having diameter 10–15 mm each and then analyzed. In the case of PIXE, a proton beam of energy 4 MeV and in the case of EDXRF a radioisotope source of 241 Am (100 mCi ) was used to excite the samples. The PIXE analysis showed well-resolved rare-earth L X-rays and EDXRF analysis showed the K X-rays of rare earths. Satisfactory results to identify and quantify the taggants were achieved.

The role of surface hydrophobicity in offset ink setting

The role of surface hydrophobicity in offset ink setting

Surface Modification of Pyrolytic Carbon Black from Waste Tires and Its Use as Pigment for Offset Printing Ink

Pyrolysis has the potential of transforming waste into valuable products. Pyrolytic carbon black (PCB) is one of the most important products resulting from the pyrolysis of used tires. One of the most significant applications of modified pyrolytic carbon black is its use as pigment for offset printing ink to obtain high added values. Inverse gas chromatography (IGC) results show that a large quantity of inorganic matters and carbonaceous deposit are removed by treating the pyrolytic carbon black with nitric acid solution. Plenty of active sites originally occupied by inorganic ash and coke are recovered. The surface energy of pyrolytic carbon black (TWPC) modified by titanate-coupling agent-especially the specific interaction γ sp s, determined by the specific probe molecule, toluene-shows the strong interaction between the TWPC and the synthetic resins. The offset printing ink performance confirms the IGC prediction. And TWPC has the great potential of applications in printing ink industry as pigment.

Acoustic investigation of cavitation noise from offset ink film splitting

The acoustic signal from the nip during film splitting between inked rollers and on ink transfer to paper was investigated on laboratory scale, using two sheet-fed offset inks (based on mineral o ...

Directives COV et alternative lipochimique : peintures, encres, nettoyage, dégraissage…

European Union has just established two Directives with the target to reduce VOC emission in the atmosphere. Directive 99/13/CE concerns the emissions from industrial equipments and Directive 2004/42/CE concerns the content of VOC from solvent used to dilute architectural paints and varnishes and car refinishing paints. Regarding these directives, positions are different depending of the industrial activity category. Some are looking for substitution of VOC by no volatile compounds. Lipochemistry provides such compounds with some added values like biodegradability, renewability, no toxicity. Some industrial activities already use this substitution. That’s the case for roads bituminous coatings, agrochemical treatment, offset inks, cleaning and degreasing, and coatings. This has been possible because volatility is not a deciding factor for these applications. Some developments are still possible if we find solution for volatility when this characteristic is necessary for the application.

Trend of Environmentally Friendly Offset Ink.

Trend of Environmentally Friendly Offset Ink.

The evaluation of printability and non-enzymatic NADH reduction of 4′-chlorophenylazo-2-naphthol for use as a printing pigment

The printability of 4′-chlorophenylazo-2-naphthol (CPAN) was evaluated on gloss-coated paper. The preliminary results indicated that the proposed pigment could be used in offset and oil-based ink production. The pigment and its potential reduction product, 4-chloroaniline, were then separated by a reverse phase high-pressure liquid chromatography system. The pigment was incubated with NADH at 37°C for half an hour at different pH values to investigate its possible reduction into the corresponding primary amines (ie 4-chloroaniline and 2-amino-1-naphthol). However, no reduction was observed. This finding indicates a desirable evidence for the pigment in terms of its stability against NADH (nicotinamide adenine dinucleotide), a known biochemical reducing agent in living organisms when the potential toxicity from aromatic primary amines is considered.

Absorption Properties of Coatings: A Selected Overview of Absorption Criteria Derived from Recent Pore Network Modelling

Absorption of fluids into porous media controls the printability characteristics of coated papers in respect to ink setting rate and phenomena such as wicking and bleeding. The dynamic of absorption is related to the runnability on printing presses. Pore structure, size distribution, and surface chemistry are the parameters which can be used to design structures for optimal absorption. To achieve a working understanding it has been necessary to develop the theory of absorption to encompass the short timescale fast absorption occurring during wetting of the fluid ink onto the surface of the paper. The phenomena of fluid spread and absorption are studied and shown to depend on the observed pore size distribution rather than porosity alone. This finding calls into question the traditional acceptance of the Lucas–Washburn relationship for such porous networks as the hydraulic absorption radius determined from experimental absorption rate measurements fails to follow the actual measured pore size trend. It is necessary to invoke the concept of a preferred pathway of absorption in which only selected groups within the finest connecting pores or throats of the network in combination with intermediate pore reservoirs contribute maximally to the transmission of fluid through the coating structure as porosity increases. By defining the pore size range involved in this mechanism using an inertial wetting term, found in the short time solution to the Bosanquet equation, it is possible for the first time to identify the connective structures responsible for the important time dependent absorption properties of coatings and their relationship to the ink tackification and/or setting rates for a range of printing ink solvents and diluents, including offset, rotogravure, flexographic, and ink jet inks. Additionally, the differential chromatographic effect of coatings and associated binder systems results in further time dependent offset ink setting phenomena in which miscible ink oils of different natures separate within the coating pores and between the pores and synthetic latex binders. In situ determination of the viscosity and solids content of an offset ink via static ink tack measurements allows the dynamic of ink setting to be studied on real coating systems. Combining these criteria, the necessary steps can be followed to design the coating pigment structures required for optimising existing and future fluid‐based printing technologies.