IMPRESIÓN DIGITAL DE LA BALDOSA CERÁMICA:

EVOLUCIÓN Y DESAFÍOS

Davide Gardini & Michele DondiCNR-ISTEC, Istituto di Scienza e Tecnologia dei Materiali

Ceramici, Faenza, Italy

A story of success …

>7000

~200

number of printers

Advantages of digital decoration:• high quality, non-contact printing

• decoration line simplified and shortened

• improved logistic and management

• value added

Major market of inkjet

installation of new printers per year in the World

Contents

Evolution of the digital decorationof ceramic tiles:

• Colorant types and manufacturing

• Ink properties and formulation

• Inkjet printers and components

Challenges for digitaldecoration:

• Print quality

• Sustainability

development of micronized inks

number of inkjet printers worldwide

Turning points

4

5

2016 2018

Evolution of the technology of colorants for inks

Pigmentos micronizados

gris

azul claro

amarillo claro

azul

rosa

marron

ocrabeige

CIANO

MAGENTA

AMARILLO

NEGRO

C

M

Y

K

CoAl2O4

Co2SiO4

(Co,Mn,Fe) (Fe,Cr,Mn)2O4

CaSnSiO5:Cr

(Fe,Cr,Mn)3O4

ZrSiO4:PrTiO2:Cr,Sb(Zn,Fe,Cr,Al)3O4

TEÓRICO INDUSTRIAL FÓRMULA

What

may

hap

pen

duri

ng

inkj

et p

rinting

Dondi et al., cfi/DKG, 89 [8-9] (2012) E59-E64.

GE

LIF

ICATIO

N

Paradigm shift: from pigment to ink

Phenomenon Ink property

Nozzle clogging particle size

Ink dripping

surfacetension

Ink spreading overthe nozzle

Ink spreading overthe tile

Ink drop sizeand shape

viscosityInk penetrationinto the tile

Ink addressability density

Corrosion of nozzles pH

Pigment sedimentation

Zeta potential

Dondi et al., cfi/DKG, 89 [8-9] (2012) E59-E64.

Field of ceramic inks(depending on the print head characteristics)

Gardini et al., J. Nanosci. Nanotechnol. 15 (2015) 3552

Evolution of carrierswater-glycol

inks (total output, tons)

inks

(fr

action o

f th

e glo

bal

pro

duct

ion)

9

Emissions and bad smell during printingUnsuitable with micronized pigments

Not perfectly Newtonian rheological behavior Some paraffinic oils will have soon «Risk Phrases» (EU)

Industrial production capacity saturated

Cheap and safeSmell during firing

Environmental advantagesexpected

water-glycol

10

Evolution of carriers (why)

Ink rheological features

Rheological properties:Newtonian fluids with low viscosity

0.010

0.100

1.000

0.1 1 10 100 1000

Shear rate (s-1)

Sh

ear

visc

osity

(P

a s)

62-01-a163-01-a164-01-a165-01-a166-01-a167-01-a168-01-a175-01-a1

Window of physical properties :ever narrower target

paraffinic oil

TPnB

glycol ethers

measurements at 20°C

target at theoperating temperature

40-45 °Cviscosity 4-10 mPa ssurf. tens. 25-30 mN/m

11

Ink shelf life

No sedimentationStability over time

steric stabilization

electrostaticstabilization block co-polymers

consisting of two or more polymer subunits joined by covalent bond

“unsoluble block” strong affinity with pigment’s surface “soluble block”

strong affinity with carrier

12

electrostericstabilization

+

+

++

+

+

+++

+

++

-

-

-

--

- -

--

-

Manufacturers ofinkjet printer for ceramic tiles

+ 5 Chinese manufacturers >>>

���� 2001

2014 ����

development of micronized inks

2

17

number of inkjet printers worldwide

number of inkjet printer manufacturers

Reliable printing systems

Recognized added value

Turning points

14

The Inkjet Printing System

Introduction to Digital Decoration, IIEA e-learning course (2013).

Rows of print heads

Print head

Print head plate

Nozzle

Problems and Technological Solutions

moisture

dust

aspiration (between color bars, etc)protective boxcleaning of the nozzle plate

standardrecommendedrecommended

nozzle cloggingproduction stop

ink recirculation and filtrationoverpressure in the print headstand-by proceduresolvents to clean print heads

standardon requeststandardrecommended

high temperatureon the line

blast chilling before the printerrearrangement of the glazing line

on requestrecommended

vibrations conveyor beltvibrations absorbers

standardstandard

high speed of the line

high resolution (transversal)high jetting frequency larger amount of ink

standardrecommendedrecommended

firing ink colorimetric calibrationkiln curve frozen

standardrecommended

17

Potential of print heads

print heads for inks

001

SBX

drop

vol

ume

(pL)

load capacity (g/m2)

property inks SBX 001

transversal resolution (dpi)

360 180 28

drop volume (pL)

5-60 80 50-200

max load (g/m 2) <20 100700-3000

nozzle diameter(μm)

20-40 70 400

Digital glazing

19

Challenges

Print quality image resolutionhigh loadcolor saturation

Sustainability economicenvironmental

100 µm

extremely irregular outline

many small imprints

Satellite dropsSpray due to splashingGrayscale side-effect

Print quality

Ink-support interactions

Tile wetting and ink spreading

WATER-BASED INK

OIL-BASED INK

OB on engobeOB on glazeWB on engobeWB on glaze

Ink spreading over the green tile

Ink imprint area on unfired tiles versus the nominal imprint area of a spherical drop (different volumes)

Spreading index :unfired versus fired glazed tiles

High load printing

Ink behavior at high regimes

usual measurement

range for ceramic inks ink-jet

stress regime

More detail into the printing behavior

Viscosity at high regimesDynamic surface tensionYield stressRelaxation timeTime-dependence (thixotropy)Temperature-dependence (gelification)Mechanical moduli (viscous and elastic)Sedimentation test (dynamic)

Color saturation

Pigment formulation

Pigment-glaze interactions

Pigment resistance to micronization

Color loss (pigment amorphisation)

Pigment size reduction during micronization

Zanelli et al. Ceramics International, 41 (2015) 6507Güngör et al., Ceramics International, 41 (2015) 6498

Color loss(pigment-glazeinteractions)

conventional pigment

micronized pigment

Zanelli et al. Ceramics Int., 41 (2015) 6507Güngör et al., Ceramics Int., 41 (2015) 6498

Pigment design for inks

Novel pigment formulations to improve the behavior during micronisation, printing and firing

From best yield and ideal pigment stoichiometryto batches based on ink color development

Unbalanced stoichiometriesMultiphase inksSacrificial componentsPrimer and buffer effects

C Y M K

Co-Al Pr-Zr-Si Cr-Sn-Si Co-Me

Co-Si Zn-Cr-Al Cr-Fe-Mn Co-Cr-Fe

Zn-Cr-Fe Cr-Sn

~5% ~50% ~40% ~5%

Co-Si Co-Al Co-Cr Co-Me Pr-Zr-Si

<5% <10%

Challenge: long-term sustainability

Pr+400%

Co+100%

CONVENTIONAL DECORATION DIGITAL DECORATION

Falling price of ceramic inks

32

-80% in 10 years

Decomposición de veículos y aditivosTINTA DIGITAL

TINTA ROTOCOLOR

Dependencia muy fuerte del gradiente térmico

Diferencia de comportamiento térmico en relacion a las tintas

convencionales

5 °C/min

40 °C/min

Ferrari & Zannini, Thermochim. Acta 639 (2016)

Glicol éteres Alcoholes Ácidos Ésteres Alcanos CetonasHidrocarburos aromáticos Aldehídos

Emisiones en la cocción (laboratório)

Ferrari & Zannini, Thermochim. Acta 639 (2016)

60°C ~250°C ~350°C ~450°C

strippingevaporation in current

of water vapor

pyrolisisthermochemical decomposition

combustionburning

Emissions in the roller kiln

CO2 H2OCO2 H2O

(organic C)

organic molecules(organic C)

CONCLUSIONES

Aparentemente, la impresión digital está en su estadio de maturidad :la taja de variación (en materiales, maquinárias y precios) bajó mucho,así como el número de nuevas instalaciones.

Sin embargo, hay cuestiones abiertas :

• calidad y resolución de la impresión,

• eficiencia en el uso de las tintas,

• alta descarga y esmaltación digital,

• temperatura de trabajo (impresora),

• emisiones de los hornos,

• reducción/revisión de los aditivos,

• eficiencia del proceso productivo (tintas),

• sostenibilidad a largo prazo.