The document discusses formulations for UV curable inks. It states that formulations typically contain 20-35% oligomers, 10-25% monomers, 15-20% pigments, and 1-5% additives. Epoxy acrylate, urethane acrylate, and polyester acrylate are common oligomers that provide properties like adhesion and reactivity. Reactive diluents like mono-functional, di-functional, and tri-functional acrylates are added to reduce viscosity while maintaining reactivity. Photoinitiators are needed to initiate polymerization and are classified as type I or II depending on their mechanism of radical generation.

1. By ASHISH ZORE
11/22/12 1

2. Formulation
Oligomers 20-35%
Monomer 10-25%
Pigments 15-20%
Additives 1-5%
Photoinitiator s 5-10%
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3. Mostly ,Acrylate are used Epoxy acrylate
because of their reactivity. Urethane acrylate
Reactivity order is:
Polyester acrylate
Acrylate>Methacrylate>allyl>
styrenyl>vinyl

4. Epoxy acrylate
Improved pigment wetting and enhanced
substrate adhesion may be obtained from
resins with residual hydroxyl group

5. Epoxy acrylate (ctd)
Aromatic resin e.g. BPA epoxy acrylate
It is widely used in inks due to good adhesion and wetting
properties, chemical inertness.
To improve the lithographic performance the residual hydroxyl
are sometimes esterified with long chain fatty acids.
Acrylate of epoxydized oil
Unsaturated natural oils such as soyabean and linseed oil can be
readily epoxidised and subsequently reacted with acrylic acid to
yield radiation curable resin with good inkmaking
characteristics.
Draw back: low reactivity leading to retardation in cure speed.

6. Epoxy acrylate (ctd)

7. Urethane Acrylate
Prepared by reacting isocynate group from urethane with
hydroxyl functional acrylate e.g. hydroxyl ethyl acrylate.
ONC-R-NCO + 2 HO-R’ R’OCONHRNHOCOR’
where R is urethane backbone and can be TDI, HMDI,
IPDI, MDI.
In case where R is aromatic di isocynate e.g. toluene di
isocynate lack of flexibility leads to high viscosity.
Hence , they are chain extended by reaction with polyols
or with polyester or polyether which itself has residual
hydroxyl functionality.

8. Polyester Acrylate
Preparation :
1. Acrylic acid with residual hydroxyl group from polyester.
2. Hydroxyl acrylate e.g. hydroxyl ethyl acrylate with residual acid
from polyester.
ROH + CH2 = CH2 – COOH CH2 = CH2 – COOR + H2 O
Strong acid such as methane sulfonic acid is required for
complete esterification.
Permissible reaction temperature is under 100 degrees.
Azeotropic solvents such as benzene has to be used to remove
water & solvent itself has to be removed later.
Inhibitor such as nitrobenzene and phenothiazine are added to
prevent free radical polymerization.

9. Performance properties
Oligomer Performance effect
Advantages disadvantages
Epoxy Hardness , chemical resistance, high viscosity, limited flexibility,
acrylate high reactivity, high gloss, yellowness (for aromatic)
inexpensive, good adhesion slow cure (for oil epoxy acrylate)
Aliphatic Increase flexibility, toughness, expensive
Urethane weathering, hardness, chemical
Acrylate resistance
Aromatic Decrease cost(vs. aliphatic), tend to yellow on exposure to
Urethane better scratch resistance, light
Acrylate chemical resistance, toughness
Polyester Low viscosity, good pigment Inferior chemical resistance(esp.
acrylate wetting, good adhesion to non alkali), poor reactivity for low
porous substrate(plastic , mol. Wt.
tinplate)

10. • reduce viscosity
• solubilize solid prepolymer
• contribute pigment wetting
• reactivity
• improve adhesion, chemical resistance,etc

11. Diluents
Diluents are of 2 types: Reactive diluents and non reactive
plasticizing diluents.
In EB & UV curing , reactive diluents are mostly acrylates
functionality which can copolymerize with main resin and
form 100% solids formulation.
But problem is many acrylates with good viscosity
reducing properties have toxic hazards, odour, volatility
problems.

12. Reactive Diluents
Reactive Diluents used are divided in:
Monofunctional monomers.
Di functional acrylates
Tri functional acrylates
High functionality monomers

13. Monofunctional monomers
Good viscosity reducers
Lack ability to crosslink
Impart flexibility to print film(reactive plasticizer)
Excessive may lead poor film properties
Example :
Isodecyl acrylate (IDA)
Phenoxy ethyl acrylate (PEEA)
2-hydroxy ethyl acrylate (2EHA)
Isobornyl acrylate
N-Vinyl pyrrolidone

14. Di functional acrylates
Reaction of diol with acrylic acid.
Chemical name Viscosity at 25 (cps)
1,4- butane diol diacrylate (BDDA) 6
1,6- hexane diol diacrylate (HDDA) 7
Neopentyl glycol diacrylate (NPGDA) 7
Diethylene glycol diacrylate (DEGDA) 8
Triethylene glycol diacrylate (TEGDA) 25
Polyethylene glycol diacrylate (PEGDA) 10-30
Tripropylene glycol diacrylate (TPGDA) 16
2,2- Dionol diacrylate (DDA) ca. 1000
Bisphenol A diacrylate (ABPE2) ca. 1000-1500

15. Di functional acrylates
Limited use due to toxicity factor, in particular
skin irritation and potential sensitization
Except TPGDA & DDA , all other mentioned are
severe irritants.
PEGDA – mol wt 500 – moderate irritant –
comparatively high viscosity.
Viscosity is not particularly low
Good pigment wetting and ink making properties

16. Trifunctional acrylates
Acrylation of polyols
Three most important polyols are: Pentaerythritol,
Trimetehylolpropane, glycerol.
Pentaerythritol triacrylate (PETA) Trimetehylolpropane triacrylate(TMPTA)

17. Trifunctional acrylates
Good viscosity reduction with fast cure
Ability for extensive crosslinking
PETA – severe irritant
TMPTA – moderate irritant

18. Trifunctional acrylates
To over come this irritation, the hydroxyl
functionality have been ethoxylated or
propoxylated prior to Acrylation.
Viscosity – 0.1 to 1 pa
Reasonable viscosity cutting
power
High crosslink density
Good cure speed
Very low skin irritancy
propoxylated glycerol triacrylate

19. Nonreactive plasticizing
diluents
Improve flow out
Impart flexibility to cured film
Must have good compatibility with vehicle
High boiling esters, highly branched alcohols and
alkyl phosphates are used
Benzophenone – used as photo initiator can
reduce viscosity , aid pigment wetting and is
powerful solvent.

20. Photo initiators for radical polymerization are classified as :
1. Cleavage (type I) and
2. H-abstraction type (type II) initiators

21. Type I Photo initiator
They simply undergo fragmentation into reactive
species under UV light.
Example: Benzoin and derivatives, benzil ketals,
acetophenones derivatives
Breakdown of some of these have odour problem but
less severe.

22. Type I Photo initiator
CHEMICAL NAME STRUCTURE
COMMERCIAL NAME
2,2Diethoxyaceto DEAP
phenone
1-hydroxycyclohexyl Irgacure 184
Benzophenone
Darocur 1173
2-Hydroxy-2-methyl-
1-phenyl-propan-1-one
2-Methyl-1[4- Irgacure 907
(methylthio)phenyl]-
2-morpholinopropan-
1-one

23. Type II Photo-initiator
Photolysis in the presence of hydrogen donors leads
to the formation of a radical (Here, ketyl radical)
produced from the carbonyl compound and another
radical derived from the hydrogen donor.
Co-initiator (H-donor) - Tertiary amines(mostly
used),
ethers, alcohols,thiols

24. Type II Photo-initiator
CHEMICAL NAME STRUCTURE COMMERCIAL NAME
Benzophenone -
4-Phenyl
Trigonal 12
Benzophenone
2-Isopropyl Quantacure ITX
thioxanthone

25. H-donor
CHEMICAL NAME STRUCTURE COMMERCIAL NAME
TEA
Triethanolamine
MDEA
Methyl
diethanolamine
Ethyl-4-dimethyl Quantacure EPD
aminobenzoate
2-ethylhexyl Escalol 507
4-(dimethylamino)
benzoate

26. Advantages
UV Ink does not dry in the screen
No volatile solvent
Very Rapid curing
UV Ink has excellent color value
No heat
One pack system
Space saving
Energy saving
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