ENERGY CURABLE TECHNOLOGIES CHRIS ORILALL, PHD SARTOMER AMERICAS ARKEMA INC.
ENERGY CURABLE TECHNOLOGIES
CHRIS ORILALL, PHDSARTOMER AMERICAS
ARKEMA INC.
OUTLINE
Advantages of UV/EB Curing
Energy Sources (UV vs EB, Lamps, LED)
Photo-initiators
Monomers and Oligomers
Structure Property Relationships
WHAT IS ENERGY CURING?
Use of UV energy, visible light or high energy electrons to initiate polymerization to form a continuous coating, ink or adhesive film.
Alternative to thermal evaporation of solvents or water, oxidative (air) curing or two-part film forming methods.
“Energy Curing” or “UV/EB Curing” often used interchangeably with Radiation Curing
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PROCESS OVERVIEW OF UV/EB CURING
100% Solids System● No Solvent (less regulatory restrictions) or Water● Applied as a viscous liquid system● Eliminates the need for solvent extraction systems (no oven required)● Instant Cure● Tunable Properties by formulating approach
Equipment Advantages● Very high lines speed possible● Small equipment footprint● Reduced energy usage● Increased throughput/ lowered manufacturing cost● Retrofitting of existing lines possible
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UV/EB formulation
UV/EB Unit
COATING UNIT/INKJET
ENERGY CURING INDUSTRIAL APPLICATIONS
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Coatings
• Wood• Metal• Industrial• Optical fiber• Cosmetic• Flooring/roofing/road Marking
Developments
• Coil
Adhesives
• UV/EB• Optically clear adhesives• Anaerobic• Construction• PVC plastisol
GraphicArts
• OPV• Inkjet• Inks
Developments• Heat transfer
labels• Low-
extractable food applications
Adhesives
• UV/EB• Anaerobic• Construction• Laminating• PSA
Coatings
• Wood• Metal• Industrial• Optical fiber• Cosmetic• Flooring/
roofing/ road marking
Developments• Coil
Electronics
• Dry film• Display• Solar• Liquid resists• Photopolymer
plates
Advanced Materials
• Artificial marble
• Lenses• 3D printing
(stereo lithography)
• Dental• Composites• Electrical
insulation• Vacuum
impregnation
Chemical Intermediates
• SAP • Oil field• Leather/
textile• Dispersing
agents
Others
• Rubber• Epoxy
modification
UV (AND VISIBLE LIGHT) CURING
UV Lamp as source of energy
Requires Photoinitiator to absorb energy and initiate polymerization
Must match PI absorbance to lamp output
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hv (light) +
free radicalU
V La
mp
ELECTRON BEAM CURING
Electrons emitted from a filament and accelerated to high energies● Can cure thick sections or through opaque substratesRadicals formed by direct reaction of coating components with electrons ● No Photo-initiator required Cure method of choice for food packaging ● very high conversion/very low migratables
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Elec
tron
Bea
m
UV CURING - ELECTROMAGNETIC SPECTRUM
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Range for UV/Visible Curing
UV CURING LAMPS
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• Clears• Thin films• Surface cure
• Pigmented systems• Deep cure• Thick film
• White pigmented• Visible light cure• Gloss control
Visible light cure
NB: Some processes use more than one type to achieve desired results, e.g., V bulb + D bulb in series
UV-LED SPECTRAL DISTRIBUTION
UV-LED units provide a “single” wavelength (narrow distribution)High energy output in UVA range vs broad spectrumOutput is concentrated at long UV wavelengths
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phoseon.com
WHAT’S IN A TYPICAL FORMULATION?
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Energy Cured FormulationConventional Liquid Coating
Binder
Diluent
Additives
Initiator Photoinitiator (for UV)
Pigments, Fillers Leveling, Flow, Wetting AidsDefoamer, Biocide, etc
Monomer reactive diluents
Reactive Oligomers
Pigments, Fillers Leveling, Flow, Wetting AidsDefoamer, Biocide, etc
N/A
Water or Solvents
Thermoplastic Polymers
O
O
O
O
O
OSR351 - TMPTA
O OOO
OHOH
O O
RADICAL PHOTOINITIATORS – TWO TYPES
Norrish Type I – Unimolecular Cleavage
Norrish Type II – Bimolecular H* Abstraction● Requires a Curing Synergist – Amine or Ether containing monomer
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Irgacure® 184 or PL-CPK (α-hydroxy ketone)
Benzophenone
OOH
hυ
O
+
OH
initiation
O
hυ
R2N R"
H H
OH
+R2N R"
Hinactive
initiating
PI SELECTION FOR THROUGH AND SURFACE CURE
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SUBSTRATE
Monomer Oligomer
FillersAdditives
PigmentsStabilizers
Shorter UV wavelength
SUBSTRATE
Monomer Oligomer
FillersAdditives
PigmentsStabilizers
Longer UV wavelength
200-350 nm PI Absorption 350-440 nm
Applications Pigmented coatings/inksThick coatings (>4 mil)Through cure
ClearcoatsThin coatingsSurface cure
Use PI Cocktail for best results
MATCHING EMISSION SPECTRUM OF LAMPS TO PHOTOINITIATOR
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0
20
40
60
80
100
0
50
100
150
200
280 310 330 350 370 390 410 430 450
V-Bulb
TPO
Emis
sion
V-bu
lb (3
00w
/in)
% Absorption
C
O
P
O
Irgacure® TPO, PL-TPO
Good match with V-bulb –through cure
Absorbance in LED range 385-405 nm
V-Bulb
RAW MATERIALS FOR FREE RADICAL UV/EB CURING
Acrylates: Fast cure, good properties balance, huge range of options
Methacrylates: Slower cure, can improve heat resistance and strength
Other classes such as vinyl ether, unsaturated polyester, allylics much less used
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RO
O
RO
O
(METH)ACRYLATE MONOMER ROLE IN FORMULATION
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Reactive Diluent – Replaces Volatile Solvents Used in Conventional Formulations –Becomes Part of Final Product
Property Effect Result
Viscosity Diluency Formulation Viscosity
Surface Tension Wetting Flowout, Adhesion
Refractive Index Light Bending Gloss, Brightness
Solubility Parameter Compatibility Filler/Pigment Dispersion, Adhesion
Equivalent Weight Crosslink Density Hardness, Shrinkage
(METH)ACRYLATE FUNCTIONALITY & PROPERTIES
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Property Mono Di Tri Tetra Penta
Cure Speed Slow Fast
Flexibility Flexible Brittle
Hardness Soft Hard
Solvent Resistance Less Best
Shrinkage Low High
OLIGOMER ROLE AND TYPES
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Binder – Replaces Resin/Polymer from Conventional Formulation. Provides Most of the Properties of the Cured Film
• BPA Types most common. Hard, brittle, fast cure, yellowing • Aliphatics and modified types more flexibleEpoxy Acrylates• Very flexible to very hard (functionality), tough and strong• Excellent weathering for aliphaticsUrethane Acrylates• Relatively low viscosity, good adhesion and pigment wetting• Cost/Performance balance vs epoxies and urethanesPolyester Acrylates• Curing synergists – increase surface cure• Polyether/ester amines – adhesion, fast cureAmino Acrylates• Adhesion promoters – acidic, polyester or acrylic for plastics,
metal, glassSpecialty
URETHANE ACRYLATE STRUCTURE & PROPERTIES
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EFFECT OF BACKBONE STRUCTURE ON MVTR
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0
20
40
60
80
100
120
HHP HHPUA
MVT
R (g
*mil/
m2*
day)
Neat Oligomer20% HDDA20% TCDMDA50% TCDMDA
CONTROLLING DIELECTRIC CONSTANT OF FORMULATIONS
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Oligomer Description
Average Dielectric Constant
(D150)
PRO 13832Polybutadiene Backbone
Aliphatic Urethane Acrylate1.93
PRO 13833Polyester Backbone
Aliphatic Urethane Acrylate2.19
PRO 13834
Polyether BackboneAliphatic Urethane Acrylate
2.21
PRO 13835 2.48
PRO 13836 2.54
PRO 13837 2.23
PRO 13838 2.06
PRO 13839Polycarbonate
Aliphatic Urethane Acrylate2.27
Monomer effect
APPLICATIONS FOR PRINTED/ FLEXIBLE ELECTRONICS
Moisture and Oxygen Barrier Layer Coatings
Resins for Liquid Optically Clear Adhesives (LOCA)
(Pressure Sensitive / Laminating/ Assembly) Adhesives
3D Printing Resins
Dispersion medium for Quantum Dots
Optically Clear Hard Coats
Scratch Resistant Coatings
Hepatic Coatings (e.g., Soft Touch)
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CORE COMPETENCE: (METH)ACRYLATE CHEMISTRY
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Monomers: Low molecular weightLow viscosity/ reactive diluentsUnique building blocks
Oligomers: High molecular weight; Backbone of the formulations; Provides the key properties
nO
O
H or CH3
R
Backbone
Functionality(Allylic,
Carboxylic & Hydroxyl)
Acrylate or Methacrylate