Dimensional scaling of aqueous ink imbibition and inkjet printability on

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Dimensional Scaling of Aqueous Ink Imbibition and Inkjet Printability on Porous Pigment Coated Paper−A Revisit Agne Swerin*

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Bioscience and Materials − Surface, Process and Formulation, RISE Technical Research Institutes of Sweden, Stockholm SE-114 86, Sweden School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Chemistry, Surface and Corrosion Science, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden ABSTRACT: A recently published dimensional scaling of infiltration of water-based inkjet fluids was used to revisit published inkjet printability data on mineral-pigment-based, inkjet-receptive coated papers. The dimensional scaling was developed using simple fluids on homogeneous isotropic media and applied on uncoated papers using complex inkjet fluids but so far has not been related to printability. It is shown that the scaling can also work for coated papers using commercial dye- and pigment-based inks with a suggested relation to printability as given by the color gamut area, in which the primary factor is the product of permeability and capillary pressure. A successful scaling suggests that inkjet printability can be predicted from flow and materials parameters, namely, porosity, viscosity, imbibed volume, permeability, and capillary pressure, and would be of general applicability in other areas of inkjet printing. The results further imply the usefulness of the approach in other functional surface modification using waterborne procedures on hard or soft porous materials.

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INTRODUCTION Inkjet printing technologies have been used in many industrial fields ever since their first application for graphic print appearance on paper. Waterborne inks are formulated for a variety of other purposes, such as in fabrication, patterning, and layering on paper, textile, ceramics, devices, or biological tissue1−3 for functional properties such as wear resistance, friction, or flow control. Inkjet printing on paper is growing because of high-speed continuous equipment with good graphic quality. Many of the inkjet receptive coating developments since the early years have been aimed at achieving hydrophilic, highporosity surface without any macroscopic structure in order to absorb ink jet droplets quickly and with little spreading, wicking, or dye penetration.4 Silica coatings have been a strong candidate to fulfill the image quality requirements for ink jet printing with water-based inks. This is probably primarily due to the small void fraction available for liquid uptake and the narrow pore diameters for fluid flow. On the other hand, silica coatings are expensive, have high binder demand, and show poor rheology at high solid content. More recent studies5−7 and review have concerned other coating pigments,8 such as those based on kaolin and calcium carbonate modified for inkjet receptive coatings, whereas nanocellulose-containing coatings9 seem to offer new potential but are yet to be fully explored. Developments of alternatives for silica pigments have been spurred on by the availability of other types of pigments and the process rheology requirements for silica coatings, such © XXXX American Chemical Society

as the need to be able to perform coating operations in-line with paper production at higher machine speeds and at higher solids content of the mineral pigment slurries. The extent and rate of liquid penetration rate is of utmost importance for inkjet receptive coatings. A simple calculation for the liquid that the coating layer needs to take up can be made by assuming 1200 dots per inch printing resolution in full-tone and 5 picoliter droplet volume containing 90% w/w liquid. Further assuming a 10 μm coating layer of 50% porosity to absorb all the liquid, this requires liquid uptake of 2 cm3 inkjet liquid per cm3 of substrate. Development of inkjet receptive coating layers should thus involve how to accommodate for the liquid into the coating layer. Accurate prediction of the extent and rate of liquid flow in relation to materials properties is clearly needed. The classical approach to the problem of analysis and prediction is by assuming capillary flow according to LucasWashburn (LW), which when applied to porous pigment coating assumes a set of equally sized capillaries of unified wetting properties resulting in a square-root dependence of time for the unidirectional flow. Other geometries and flow situations have been analyzed, e.g., axial, spherical, and radial with time dependencies of t1/4 to t1/3 and, for example, a fast Received: Revised: Accepted: Published: A

August 13, 2018 November 13, 2018 November 18, 2018 November 19, 2018 DOI: 10.1021/acs.iecr.8b03868 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research Table 1. Properties of the Coating Pigments (As Given by Suppliers) coating material characteristics particle shape secondary particle size, μm surface area (m2g−1) pore volume (cm3g−1) internal pore diameter (nm)

P609

ED5

MPS

EXP1

EXP2

silica gel, amorphous irregular 9

silica gel, amorphous irregular 9

mesoporous silica spherical 3

amorphous silica mixed with kaolin, ca. 1:1 w/w (28% solids) spherical silica, kaolin platelets 4

amorphous silica mixed with kaolin, ca. 3:1 w/w (47% solids) spherical silica, kaolin platelets 3

400

400

380

65

65

1.2

1.8

0.52

n.a.

n.a.

10−15

10−15

6

no measured internal pores

no measured internal pores

a

n.a., not available.

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initial linear t regime followed by t1/2 10 and inertia effects of flow when applied to paper-based substrates and printing situations.11 A thorough review with theoretical development and experiments12 used an energy balance model between simultaneous spreading and penetration and verification directly related to inkjet flow. If the geometry of a porous pigment coating is not known, or can be assumed to be so on good grounds, Darcian flow in porous media offers a physically correct alternative description, as has recently been used, for example, in edge wicking in liquid packaging board.13,14 We developed a dimensional scaling starting from fluid motion equations that when applied to inkjet flow conditions could neglect inertia and gravity for imbibing picoliter-size droplets and thus arrive at Darcian flow. This was used first on homogeneous isotropic porous media with simple fluids15,16 and second on paper substrates with inkjet ink fluids.17 The product of permeability k and capillary pressure pc was suggested as primary parameter governing ink imbibition and to be a predictor of printability but no relation to printability was given so far. We revisit an earlier investigation,18,19 in which laboratory prepared inkjet receptive mineral pigmented paper coatings were evaluated for their inkjet printability (color gamut area), however no physically correct treatment of flow and materials properties in relation to inkjet printability was offered. The validity of a Darcy flow evaluation needs to be concluded after comparing the magnitude of capillary flow with inertia and gravity effects, both of which can be of major significance if microliter-sized droplets are used for liquid imbibition18,19 instead of picoliter-size.15,16 There are many aspects of inkjet printing, for example, the several processes in parallel (precursor films, diffusion),8 effect of binder,20 and complex flow situation in real-type porous coatings,21 that the present study does not discuss. Similar approaches aiming at relating printability to ink imbibition start from LW assumptions but either are unfortunately not complete enough to allow the Darcian flow re-evaluation22 or lack printability results.23 A series of studies7,24 concern several aspects of inkjet printability and liquid imbibition but not on the very same set of samples or with complete printability results to allow re-evaluation. The Darcian flow approach15 enables such re-evaluation, which is aimed at further understanding of how flow and materials properties of inkjet receptive coatings are related to, and can help predict, inkjet printability. In this case, printability is given by the color appearance (gamut area). Some background is given but the focus is on results not published and evaluations not made when results from the earlier study was first reported.

EXPERIMENTAL SECTION Polymers. Poly(vinyl alcohol) (Mowiol 18−88, Kuraray Specialties Europe) was used as pigment binder. The molecular weight was 160 kg/mol and the degree of hydrolysis 88 mol % (partially hydrolyzed), as supplied by the manufacturer and was used as a 10% solution. Poly-DADMAC (Eka Chemicals) with molecular weight of 4 kg/mol was used as cationic additive in the coatings. Pigments. The pigments used were two commercial silica gels and three experimental products. Two silica gels were obtained from Grace Davison, Sylojet P609 and Syloid ED5, denoted P609 and ED5 respectively. Mesoporous silica (MPS) from an aerosol-assisted polymer-templating process25 was laboratory prepared and Eka Chemicals supplied the experimental products EXP1 and EXP2. Table 1 gives properties of the different pigments used. The experimental inkjet pigments from Eka Chemicals were supplied as water-based slurries, containing amorphous SiO2, kaolin and a cationic polymer in the case of EXP1. The approximate composition was 10−25% amorphous silica, 10− 25% kaolin and less than 5% cationic polymer for EXP1 (supplied at 28% solids) and 20−40% amorphous silica with 5−20% kaolin for EXP2 (supplied at 47% solids). The MPS material consists of polymer-templated, mesoporous silica. The dried powder possesses particles with a spherical particle shape, controlled internal pore structure and narrow pore size distribution. The synthesis process of the mesoporous silica powders is described in detail elsewhere.19,25 The internal pores, in this case with a diameter of approximately 6 nm, are too small for the binder molecules to enter, and therefore the binder demand for this material could be significantly reduced compared to other silica gels,26 still with good printability. Coating Formulation, Application, and Characterization. The poly(vinyl alcohol) (PVA) powder was dissolved in water at 10% solids during continuous stirring, the solution heated to 80 °C and held at that temperature for a few hours until the PVA was dissolved. The solution was cooled to room temperature before any addition of pigments or additive. The PVA solution was mixed with either the pure silica pigments or with a suspension of silica pigments and water in the case of the MPS silica. The cationic additive poly-DADMAC was mixed into the PVA solution before the addition of any pigment to minimize flocculation. Coatings formulations were optimized to achieve coatings with good pigment binding and minimum rub-off. Coatings were all formulated with 100 pph pigment and Table 2 gives composition of the coatings together with values from surface energy characterization. The EXP1 and EXP2 were used without additional binder or B

DOI: 10.1021/acs.iecr.8b03868 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research

The wet pore volume in the coatings was calculated from water retention measurements29,30 in which a coating formulation sample is pressure-filtrated and the retained water is taken as the gravimetric water retention value. Tenmilliliter samples of the coating formulations were used and values that are, according to the method, reported in grams of water retained in the coating/area of the pressure filtration cell (8 cm3) are here converted to wet pore volume in cm3 g−1. Surface Energy and Liquid Imbibition on Coated Papers. The interaction between a liquid droplet and the coating surface was analyzed using an optical contact angle device (FibroDAT, Fibro Systems AB, now part of TMI) with a temporal resolution of 20 ms. The same device was used to measure surface tension of the cyan inks with the pendant drop technique. For the purpose of this study the imbibition and spreading are the important parameters. We evaluate the penetrated depth for imbibing 4 μL droplets of water or inks with focus on the faster initial time period. We assume that the extent of spreading is low in comparison and that it starts to have significant influence only after the fast initial imbibition (the first 100−200 ms). The surface energies of coated papers were analyzed using two polar (water, ethylene glycol) and one apolar (diiodomethane) probe liquids, which allowed determination of polar and dispersive surface energies according to the van Oss− Chaudhury−Good method.31,32 The curve of the contact angle against time was extrapolated to zero time at the point in the measurement when the base of the drop stays constant for the first time. Inkjet Printers and Inks. Three different inkjet printers have been used with the matching inks, Canon Pixma iP4000 with Canon BCI-6 dye-based inks, Epson Stylus C86 with Epson T044 pigmented inks and Hewlett-Packard HP5850 with HP57 Vivera dye-based inks. Table 3 gives key properties of the inks (cyan color). The pendant drop technique was used to measure the surface tension.

Table 2. Coating Compositions and Surface Energy Propertiesa coating pigment 100 pph P609 ED5 MPS EXP1 EXP2

PVA (pph)

pDADMAC (pph)

80 100 15

1 5 2

surface energy total (mJ m−2)

surface energy polar (mJ m−2)

surface energy dispersive (mJ m−2)

67 n.a. 51 63 62

24 n.a. 11 21 18

43 n.a. 40 42 44

a

pph, parts per hundred; n.a., not analyzed.

cationic additive. The solids content of the coating formulations was 19−21% except for EXP1 and EXP2 which were used as received at 28% and 47% respectively. The coatings were applied using a laboratory rod coater (K Control Coater 202, RK Print-Coat Instruments Ltd.) with metering bars no. 2 (groove 0.15 mm, wet film 12 μm), no. 3 (groove 0.31 mm, wet film 24 μm) and no. 4 (groove 0.51 mm, wet film 40 μm) at a coating speed of 4−6 m min−1. The rod size, pressure and coating speed was optimized for each coating in order to achieve the best coating result. The target coat weight was 10 g m−2 to gain full coverage of the substrate, which gives a dry coat of 6−8 μm. Two different substrates were used, highly sized standard commercial copy paper (80 g m−2) and a nonporous PET substrate (Melinex 752, DuPont, 50 g m−2), used mainly to prepare coatings for the NMR porosity measurement. The coated sheets were dried using IR on an air permeable plastic substrate that gave no adherence. The paper sheets were fixed with magnet strips to avoid cockling during drying. The distance to the lamp was 30 cm, temperature 60−70 °C and drying time 1−2 min. Before printing the coating quality of the sheets were evaluated under UV-light to guarantee full coverage and an even surface. Surface Roughness and SEM. Surface roughness was measured for coated papers using white-light optical profilometry (Zygo NewView 5010, Zygo Instruments) and values for rms (Rq) and peak-to-valley (Ra) averages are given. SEM was performed with and without gold sputtering using a Philips FEI XL30 ESEM. Samples without gold coating were measured in ESEM mode at a low vacuum of 70−80 Pa. NMR Cryoporometry and Water Retention. Cryoporometry was used to characterize the pore volume and the pore size distribution of a coating in the range of 1−100 nm and details are given elsewhere.27 NMR cryoporometry has been compared with other pore volume measurement techniques28 and offers the advantage of covering nm to μm pore ranges in one measurement. The technique is based on the principle of the freezing and melting temperature suppression of fluids entrapped within the pores (phase transition). Samples of dried coatings were saturated with a wetting liquid (in this case octamethylcyclotetrasiloxane to minimize swelling of polymers) and the NMR cryo procedure was used. The results given here are total pore volume (cm3 g−1) and divided into small pores with radius 10 nm but 50 nm. The porosity was calculated from total pore volumes and densities of the coatings. The specific surface area was calculated from pore volumes for the P609, ED5, and MPS coatings for which maximum or predominant values of pore radii could be obtained.

Table 3. Characterization of Cyan Inks cyan ink

HP57

Canon BCI-6

Epson T0442

colorant density (g cm−3) pH surface tension (mN m−1) viscosity (mPa s)a

dye 1.08 6.4 32 ≥2

dye 1.11 9.1 35 1−5

pigment 1.10 8.6 31.5 10 and 50 nm density ρs (g cm−3) porosity ε (cm3cm−3) (1) surface area s (m2 g−1) (2) surface area s (m2 g−1) (3) wet pore volume (cm3 g−1) (4)

4.3 and 3.4 3.09

n.a. 1.31

3.0 and 2.4 0.83

2.8 and 2.2 0.14

1.6 and 1.3 0.49

0.21 0.25

0.12 0.18

0.02 0.07

0 0.01

0 0.05

2.63 1.54 0.83

1.01 0.876 0.53

0.74 1.45 0.54

0.13 0.813 0.10

0.44 1.69 0.46

400

400

380

65

65

660

260

140

n.a.

n.a.

1.11

1.09

1.04

1.23

1.01

In which ∇* is a dimensionless form of the tensor. The dimensionless prefactors

ρk , tcμϵ

kpc wclcμ

and

ρϵgk wcμ

describe the

influence of inertia, pressure and gravity, respectively. The characteristic time tc, length lc, and velocity wc are defined and discussed elsewhere.15 In order to calculate the respective prefactors we need to measure or estimate the permeability and pressure terms k and pc, which we do not know separately but the product kpc can be calculated from the maximum penetrated depth h and corresponding time t⊥ according to17 kpc =

h2μϵ 2t⊥

(4)

To allow relevant evaluation of penetrated depth, we assume that flow inside the coating is unidirectional transversal and not radial. For the present case using microliter size droplets, unlike previous15,17 cases using picoliter size droplets, it may be so that neither inertia or gravity terms can be neglected. We therefore need to estimate the dimensionless prefactors but realize the complication that we do not know pc and k separately but only the product from eq 4. For the purpose of analyses, we assume that although kpc is in the 1 × 10−10 N range (see below), isotropic porous materials15 showed a linear relation between pc and k for a range of pore sizes and simple liquids. Using these relations, we estimate pc to 50 MPa and k

n.a., not analyzed. (1) ε = Vp/(Vp+ρ−1 s ). (2) From suppliers for dry pigments. (3) Calculated from Vp divided by the maximum pore radius from NMR (values for EXP1 and EXP2 cannot be given because of no predominant or maximum pore radii). (4) From water retention measurements of wet coatings. a

E

DOI: 10.1021/acs.iecr.8b03868 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research to 2 × 10−18 m2. Another alternative is by calculation of k and pc separately15 according to k=

s(1 − ϵ)σ cosθ C ϵ3 ;p = ϵ s 2(1 − ϵ)2 c

dependence is not an assumption needed in the Darcian dimensional scaling and is not the result in these experiments. We observe that all the V and T curves do not collapse into one common curve, as for simple liquids on porous glass membranes15 but that the three coatings of high pore volume and larger amount of small pores (P609, ED5 and MPS) show the same scaling while the coatings having low pore volume and no small pores (EXP1 and EXP2) show different scaling. A closer look, however, shows that EXP1 scales similar to the high pore volume coatings although at much smaller V and T (see inset and linear slope values), whereas the EXP2 coating shows much slower imbibition compared to the other coatings. The dimensional scaling seems to be a valid approach to generalize inkjet ink imbibition on paper coatings for a set of quite different types of pigment coating materials. Ink Imbibition and Printability. We have established dimensional scaling of ink imbibition and now make the attempt to relate to inkjet printability. In the previous work,18,19 the rate of imbibition divided by pore volume was correlated to printability, however, such relation is not physically correct and would not be a suitable predictor of printability. Figure 4 gives the color gamut area as a function of kpc.

(5)

In which C is the Kozeny−Carman coefficient and set to 0.5 as for isotropic porous materials.36 The calculation requires knowing ε, which was given from the pore volume Vp from porometry and the density ρs of the coatings and in which s values used were supplied from manufacturers for the neat pigments. Calculations gave values of k ranging from 1 × 10−13 to 1 × 10−11 m2 and pc ranging from 103 to 104 Pa, yielding kpc ranging 1 × 10−9 to 1 × 10−7 N. The considerably larger kpc values using eq 5 compared to eq 4 can be due to the assumption of transversal flow, whereas interconnected pores allow radial and faster liquid fronts.15 We can now estimate the inertia and gravity prefactors in eq 3 to be 1 × 106 to 1 × 103 times less than the pressure term for the first and second way to estimate, respectively, and conclude that inertia and gravity terms can be neglected and eq 3 simplifies to the Darcy equation, according to eq 1. We define the dimensionless groups that describe the drop imbibition, a v(t ) dimensionless volume V = l 3 , where v(t) is the average c

imbibed volume at a time t calculated according to one set of t experiments, and dimensionless time T = t . V and T can be c

written as

tkp ij ϵ yz v (t )ϵ ; T = c jjj zzz vtot μ jk vtot z{ (6) We now apply the scaling to the only study that we know of in which both v(t) and inkjet printability has been given18 on the same set of samples. Figure 3 shows V as a function of T for 2/3

V=

Figure 4. Inkjet printability (color gamut area) versus the product of permeability k and capillary pressure pc for the different coatings on paper and different inkjet inks. The factor kpc is determined from eq 4, i.e., liquid imbibition distance, time, porosity, and viscosity.

The EXP1 coating falls out of the trend, most likely because it has very different properties (e.g., no small pores and low surface area), whereas the other data (here divided for the different inks) seem to fall on a linear trend. However, even after excluding the EXP1 series and two potential outliers, the rate of determination r2 for a linear relation is not more than 0.91. The reasoning for using kpc as a parameter is that this parameter can be measured from capillary rise or suction measurements and could thus allow screening or development of best candidate substrates for best inkjet printability. It is realized that the data set is limited but conclude having a relationship between ink imbibition and the functional property inkjet printability. We welcome other similar revisits to existing data or to include in new studies on ink imbibition in relation to inkjet printability or for use in other areas of aqueous-based inkjet printing on porous materials in relation to other end-use properties than color appearance.

Figure 3. Dimensionless volume V versus dimensionless time T for inkjet ink imbibition on different inkjet receptive paper coatings. The data for the different coating substrates are averages of the data for the different inkjet inks, except for the EXP1 (see inset), in which two inks behaved similarly but the third was significantly different.

inkjet inks’ imbibition into the coatings. In the case of the EXP1 coating, two of the inks behaved similarly but one differed. For the other coatings, averages of the three inks could be used with small scatter. The linear slopes of the curvilinear V(T) relations were 0.8, 0.6, 0.4, 0.9, and 0.1 for the P609, ED5, MPS, EXP1, and EXP2 coatings, respectively. The square-root (such as in LW) F

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(10) Quere, D. Inertial capillarity. Europhys. Lett. 1997, 39 (5), 533− 538. (11) Schoelkopf, J.; Gane, P. A. C.; Ridgway, C. J.; Matthews, G. P. Influence of inertia on liquid absorption into paper coating structures. Nord. Pulp Pap. Res. J. 2000, 15 (5), 422−430. (12) Daniel, R. C.; Berg, J. C. Spreading on and penetration into thin, permeable print media: Application to ink-jet printing. Adv. Colloid Interface Sci. 2006, 123−126, 439. (13) Mark, A.; Berce, A.; Sandboge, R.; Edelvik, F.; Glatt, E.; Rief, S.; Wiegmann, A.; Fredlund, M.; Amini, J.; Rentzhog, M.; Lai, R.; Martinsson, L.; Nyman, U.; Tryding, J. Multi-scale simulation of paperboard edge wicking using a fiber-resolving virtual paper model. Tappi J. 2012, 11 (6), 9−16. (14) Mark, A.; Tryding, J.; Amini, J.; Edelvik, F.; Fredlund, M.; Glatt, E.; Lai, R.; Martinsson, L.; Nyman, U.; Rentzhog, M.; Rief, S.; Wiegmann, A. Modeling and simulation of paperboard edge wicking. Nord. Pulp Pap. Res. J. 2012, 27 (2), 397−402. (15) Oko, A.; Martinez, D. M.; Swerin, A. Infiltration and dimensional scaling of inkjet droplets on thick isotropic porous materials. Microfluid. Nanofluid. 2014, 17 (2), 413−422. (16) Oko, A.; Martinez, D. M.; Swerin, A. Infiltration and dimensional scaling of inkjet droplets on thick isotropic porous materials (vol 17, pg 413, 2013). Microfluid. Nanofluid. 2014, 17 (2), 423−423. (17) Oko, A.; Claesson, P. M.; Niga, P.; Swerin, A. Measurements and dimensional scaling of spontaneous imbibition of inkjet droplets on paper. Nord. Pulp Pap. Res. J. 2016, 31 (1), 156−169. (18) Swerin, A.; König, A.; Brandner, B.; Andersson, K.; Lindgren, E. In The use of silica pigments in coated media for inkjet printing: Effects of absorption and porosity on printing performance and depthprofiling using confocal Raman spectroscopy. 8th Tappi Advanced Coating Fundamentals Symposium; TAPPI Press, 2008; pp 178−203. (19) Swerin, A.; König, A.; Andersson, K.; Lindgren, E. The Use of Silica Pigments in Coated Media for Inkjet Printing: Effects of Absorption and Porosity on Printing Performance. In 23rd PTS Coating Symposium; Baden-Baden, Germany, September 18−21, 2007; PTS: Munich, Germany, 2007. (20) Lamminmaki, T.; Kettle, J.; Puukko, P.; Ketoja, J.; Gane, P. The role of binder type in determining inkjet print quality. Nord. Pulp Pap. Res. J. 2010, 25 (3), 380−390. (21) Senden, T. J.; Knackstedt, M. A.; Lyne, M. B. Droplet penetration into porous networks: Role of pore morphology. Nord. Pulp Pap. Res. J. 2000, 15 (5), 554−563. (22) Wei, L.; Danio, J. In Fundamentals in the Development of High Performance Inkjet Receptive Coatings; TAPPI Press: 2008; pp 165− 177. (23) Lundberg, A.; Ortegren, J.; Alfthan, E.; Strom, G. Microscale droplet absorption into paper for inkjet printing. Nord. Pulp Pap. Res. J. 2011, 26 (1), 142−150. (24) Svanholm, E. Printability and Ink-Coating Interactions in Inkjet Printing. PhD Thesis; Karlstad University: Karlstad, Sweden, 2007. (25) Andersson, N.; Alberius, P. C. A.; Skov Pedersen, J.; Bergstrom, L. Structural features and adsorption behaviour of mesoporous silica particles formed from droplets generated in a spraying chamber. Microporous Mesoporous Mater. 2004, 72 (1−3), 175−183. (26) Wedin, P.; Svanholm, E.; Alberius, P. C. A.; Fogden, A. Surfactant-templated mesoporous silica as a pigment in inkjet paper coatings. J. Pulp Pap. Sci. 2006, 32 (1), 32−37. (27) Furó, I.; Daicic, J. NMR cryoporometry: A novel method for the investigation of the pore structure of paper and paper coatings. Nord. Pulp Pap. Res. J. 1999, 14 (3), 221−225. (28) Gane, P. A. C.; Ridgway, C. J.; Lehtinen, E.; Valiullin, R.; Furó, I.; Schoelkopf, J.; Paulapuro, H.; Daicic, J. Comparison of NMR cryoporometry, mercury intrusion porosimetry, and DSC thermoporosimetry in characterizing pore size distributions of compressed finely ground calcium carbonate structures. Ind. Eng. Chem. Res. 2004, 43 (24), 7920−7927. (29) Sandas, S. E.; Salminen, P. J.; Eklund, D. E. Measuring the Water-Retention of Coating Colors. Tappi J. 1989, 72 (12), 207−210.

CONCLUSIONS Dimensional scaling of inkjet ink imbibition was related to inkjet printability of laboratory prepared porous mineral pigment coatings on paper. The revisit to earlier experimental data allowed us to evaluate the product of permeability and capillary pressure, as was suggested in earlier work, as a determining and predicting parameter for printability. Although the specific examples here are for inkjet color printing on coated paper, the approach is applicabile to other areas of inkjet printing and in general for liquid imbibition in porous materials.

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AUTHOR INFORMATION

Corresponding Author

*Email: [email protected]. Tel. +46 768 640031. ORCID

Agne Swerin: 0000-0002-6394-6990 Notes

The author declares no competing financial interest.

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ACKNOWLEDGMENTS Thanks to Amelie König, Kjell Andersson, and Erik Lindgren, coauthors of the original work from which results are reevaluated in the present work, and to Asaf Oko for valuable suggestions on data analyses. István Furó at KTH is thanked for the NMR cryoporometry characterization and interpretation. The investigation was part of the NextJet research project, funded by industry, the Kempe Foundations, and VINNOVA (Swedish Government Agency for Innovation Systems, grants 2007-02402 and 2011-03362) in the forestry-based industry sector research program 2007−2012. The Nils and Dorthi Troëdsson Foundation for Scientific Research supports an adjunct professorship for A.S. at KTH Royal Institute of Technology.

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REFERENCES

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DOI: 10.1021/acs.iecr.8b03868 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.iecr.8b03868 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX