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

23年 4月 12日 26