raw materials for radiation curing inks
TRANSCRIPT
By ASHISH ZORE
23年 4月 12日 1
Formulation
Oligomers 20-35%
Monomer 10-25%
Pigments 15-20%
Additives 1-5%
Photoinitiator s
5-10%
23年 4月 12日 2
Mostly ,Acrylate are used because of their reactivity.Reactivity order is: Acrylate>Methacrylate>allyl> styrenyl>vinyl
Epoxy acrylateUrethane acrylatePolyester acrylate
Epoxy acrylate
Improved pigment wetting and enhanced substrate adhesion may be obtained from resins with residual hydroxyl group
Epoxy acrylate (ctd)Aromatic resin e.g. BPA epoxy acrylateIt 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.
Epoxy acrylate (ctd)
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.
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.
Performance propertiesOligomer Performance effect
Advantages disadvantages
Epoxy acrylate
Hardness , chemical resistance, high reactivity, high gloss, inexpensive, good adhesion
high viscosity, limited flexibility, yellowness (for aromatic)slow cure (for oil epoxy acrylate)
Aliphatic Urethane Acrylate
Increase flexibility, toughness, weathering, hardness, chemical resistance
expensive
Aromatic Urethane Acrylate
Decrease cost(vs. aliphatic), better scratch resistance, chemical resistance, toughness
tend to yellow on exposure to light
Polyester acrylate
Low viscosity, good pigment wetting, good adhesion to non porous substrate(plastic , tinplate)
Inferior chemical resistance(esp. alkali), poor reactivity for low mol. Wt.
• reduce viscosity• solubilize solid prepolymer• contribute pigment wetting• reactivity• improve adhesion, chemical resistance,etc
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.
Reactive Diluents Reactive Diluents used are divided in:Monofunctional monomers.Di functional acrylatesTri functional acrylatesHigh functionality monomers
Monofunctional monomersGood viscosity reducersLack ability to crosslinkImpart 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
Di functional acrylatesReaction 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
Di functional acrylatesLimited 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 lowGood pigment wetting and ink making
properties
Trifunctional acrylatesAcrylation of polyols Three most important polyols are:
Pentaerythritol, Trimetehylolpropane, glycerol.
Pentaerythritol triacrylate (PETA)
Trimetehylolpropane triacrylate(TMPTA)
Trifunctional acrylatesGood viscosity reduction with fast cureAbility for extensive crosslinkingPETA – severe irritantTMPTA – moderate irritant
Trifunctional acrylates
Viscosity – 0.1 to 1 paReasonable viscosity
cutting powerHigh crosslink density Good cure speedVery low skin irritancy
propoxylated glycerol triacrylate
To over come this irritation, the hydroxyl functionality have been ethoxylated or propoxylated prior to Acrylation.
Nonreactive plasticizing diluentsImprove flow outImpart flexibility to cured filmMust have good compatibility with vehicleHigh 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.
Photo initiators for radical polymerization are classified as :1. Cleavage (type I) and 2. H-abstraction type (type II) initiators
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.
Type I Photo initiatorCOMMERCIAL NAME
DEAP
Irgacure 184
Darocur 1173
Irgacure 907
CHEMICAL NAME
2,2Diethoxyacetophenone
1-hydroxycyclohexyl Benzophenone
2-Hydroxy-2-methyl-1-phenyl-propan-1-one
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one
STRUCTURE
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
Type II Photo-initiator CHEMICAL NAME
Benzophenone
4-Phenyl Benzophenone
2-Isopropyl thioxanthone
COMMERCIAL NAME
-
Trigonal 12
Quantacure ITX
STRUCTURE
H-donorCHEMICAL NAME
Triethanolamine
Methyl diethanolamine
Ethyl-4-dimethyl aminobenzoate
2-ethylhexyl 4-(dimethylamino)benzoate
COMMERCIAL NAME
TEA
MDEA
Quantacure EPD
Escalol 507
STRUCTURE
AdvantagesUV Ink does not dry in the screenNo volatile solventVery Rapid curingUV Ink has excellent color valueNo heatOne pack systemSpace savingEnergy saving
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