Optimized Drying and Curing Processes for New Functional Products Dr. Kai K. O. Bär adphos Digital Printing GmbH Optimized Drying and Curing Processes for New Functional Products NIR is a trademark of adphos. adphos owns more than 200 patents- or patent applications on the NIR-technology InPrint Show, November 10th, 2015 – Munich/Germany

Thin Layer Film Applications Functional Coatings and Treatment On  1 µm to 0.1 mm one/more Wet/dry or gaseous or organic or non-organic coatings InkJet Roll coating (flexo, gravure, offset) Screen Curtain Powder coat PVD, CVD … and Treatment On Substrates in combination with Drying Heating (melting, sintering, deposition) Curing (heat/radiation) only on surfaces Flat/cured/3D Continuous/sheet/batch

Dry – What is it?

H2O/solvent based UV coating? What is Dry at Drinks? 100 % UV-based coatings? H2O/solvent based UV coating? Thermal curable power?

Dry(ness) is not a proper quantified physical parameter! Quelle: www.ClipProject.info

Drying and Curing (Heating) Processes (1) Starts with Wetting and spreading at the surface porous non-porous Dehydration Suction into substrate Unforced drying by ambient evaporation over time Removal of moisture/viscosity increase

Drying and Curing (Heating) Processes (2) Fixing coating to substrate Mechanical adhesion Bonding Over coating Final coating treatment for functional properties Curing Sintering

Typical Todays Drying Technologies Hot air driers Hot drum/hot plate + hot air (m)IR and hot air (adphos)NIR®-dryer (with integrated high airflow rate, warm impingement air, air ventilation and removal)

Working Principles (1) Hot Air – heat transfer by heat convection Complete surface is heated relying on conduction through the ink/substrate Dries non-printed areas before all of ink pattern has been dried Circulating air can help remove the water molecules from the surface Air is generally heated outside of the drying system Very slow drying process Substrate Hot air Drying heating by conduction

Required Power for Hot Air Dryers Drying Power: ≙ Energy to heat up substrate mass + Energy to evaporate water (from ink pattern and removal of ambient moisture in the paper)

Working Principles (2) Hot plate/heated drum – heat transfer by hot contact area (conduction) From backside up approach Heats the substrate before the ink film Relies on conduction Drives water up to the surface High amounts of residual heat

Required Power for Heated Drum Drying Power: ≙ Energy to heat up substrate mass + Energy to evaporate water (from ink pattern and removal of ambient moisture of paper)

Working Principles (3) IR (Infra Red – Short, Medium To Long Wave) – only heat transfer to the surface by radiation Top down approach Heat absorption at complete substrate surface Dries non-printed surface before ink patterns are properly dried Relatively slow drying process

mIR is “color blind” for printed pattern Midwave IR Heats Both the Substrate and Printed Pattern – Nearly Equal Absorption mIR is “color blind” for printed pattern

Required Power of IR-Dryer Drying Power: ≙ Energy to heat up substrate mass + Energy to evaporate water (from ink pattern and removal of ambient moisture of paper)

Working Principles (4) NIR (adphosNIR) – heat transfer/process by Near Infra Read radiation High energy density penetrates ink film drying from the bottom up High energy density excites water molecules instantaneously Paper substrates are highly transparent to NIR producing limited substrate heating Emitters can be controlled across the web drying only areas being printed NIR has a high energy density (ultra fast drying process)

NIR-Drying Shows High Absorption in the Printed Pattern

Required Power for adphosNIR®-Dryer Drying Power: ≙ Majority Energy to remove (evaporate) the water from the ink pattern Remark: Substrate temperature rise results from heat conducted from the ink pattern and by minor direct absorption of NIR.

adphosNIR® allows Instantaneous setting of coating stops spreading and penetration Instantaneous evaporation of water and solvents water removal and disruption of high boiling temperature humectants (e.g. Glycol) Low thermal stress on the non-printed substrate no dry out  no remoistening needs applicable for thermal sensitive substrates (e.g. thermal paper, plastics, …) no afterwards web cooling required High dryer efficiency, enhanced print quality (higher color density, higher crisp) and improved speed range

Application Example (1) Enhanced Drying in Digital Printing Press Speed: 120 m/min for all applicable substrates Uncoated Coated esp. regular offset Up to 120 m/min only uncoated substrates Up to 80 m/min limited to some coated substrates only Energy consumption: Depending on paper width, ink coverage, paper type 40 kW to max. total 70 kW 80 – 100 kW Flat products no remoistening Wavy, strong dry out (needed 5 g/m² remoistening) Drying length: Total 300 mm Total 1,200 mm

Application Example (2) Process Color Printing on Corrugated Boards Speed: 200 m/min Width: 1,300 mm Total drying length: 1,500 mm Alternative driers get “banana shape” boards Low temperature (60 °C) air driers would require > 10 m Requires extreme more drying energy (2.5 – 3 times!) compared to NIR A = Pre-Treatment Driers B = InkJet Driers

Application Example (3) Process Color Printing on Plastics Speed: 50 m/min Width: 2,500 mm Substrate: PP, vinyl and other plastics Interstation dryer configuration Only final dryer configuration results in intercolor bleeding Here for no alternative driers with thermal inks are applicable

Application Example (4) Ink Jet Printing of nano silver inks on PET/Paper Hot air oven: 10 min @ 70 °C + 20 min @ 150 °C Midwave IR: 1 min @ up to 150 °C adphosNIR®: 1-4 s @ up to 250 °C (coating) and < 120 °C at substrates Xe-Flash: 2 - 15 s depending on coating thickness

Application Example (5) Additive Manufacturing – 3D Printing Speed: Up to 30 – (60) m/min Width: Up to 2,000 mm Materials: Plastics, metals! Special unique benefits with adphosNIR®-processing Preheating of plastics only up to crystallization point Metals can be processed from ambient Instantaneous melting of “printed/coated” area Width adjustable heating power Powder reusable due to low thermal treatments Quelle: http://www.lboro.ac.uk

Conclusions Drying starts immediately with the coating drop down Drying technology and configuration can strongly effect coating process performance and coating process quality and coating process applicability (is do-able or not!) and energy consumption and mandatorily drives the costs of coated product coating process costs substrate costs (due to required type of substrate) coating costs (consumption) Coating process preparation and standby total energy costs (startup, standby and print production, eventual cooling, remoistening, …) adphosNIR® allows application optimized systems design and is already widely proven in coating processing

adphosNIR® shows large benefits and wide range applicability Even though none of the today´s post processing technologies does fit for all – adphosNIR® shows large benefits and wide range applicability See us at our booth A6/G42 or at www.adphos.de