Investigation of the effect of Investigation of the effect of press and paper variables on press and paper variables on

linting during the offset printing linting during the offset printing of newsprintof newsprint

Afriana SudarnoAfriana Sudarno11, Warren Batchelor, Warren Batchelor11, , Paul BanhamPaul Banham22, Chamundi Gujjari, Chamundi Gujjari11

11APPI, Monash UniversityAPPI, Monash University22Norske Skog, Boyer, TasmaniaNorske Skog, Boyer, Tasmania

60th Annual Appita Conference, Appita, p 25 (2006).

IntroductionIntroductionOffsetOffset

Ink transfers to paper from printing plate with Ink transfers to paper from printing plate with separate transfer cylinder called offset or separate transfer cylinder called offset or blanket cylinderblanket cylinder

LithographyLithographyInk and water donInk and water don’’t mix. Image on the offset t mix. Image on the offset plate (hydrophobic) receives ink. Nonplate (hydrophobic) receives ink. Non--image image area (hydrophilic) repels ink, accepts water. area (hydrophilic) repels ink, accepts water.

LintingLintingRemoval of particles from surface of paper and Removal of particles from surface of paper and accumulation on blanket, ink, fountain solution accumulation on blanket, ink, fountain solution trainstrains

ObjectiveObjective

Identify and quantify effect of variables on Identify and quantify effect of variables on linting in offset printinglinting in offset printing

Heidelberg GTOHeidelberg GTO--52 and Man52 and Man--Roland UnisetRoland UnisetHeidelberg: Controlled Temperature and Humidity ExperimentHeidelberg: Controlled Temperature and Humidity Experiment

Man Roland: Controlled TemperatureMan Roland: Controlled Temperature

Sample CollectionSample CollectionTape pullsTape pulls

Adhesive tape used to Adhesive tape used to remove lint from printing remove lint from printing blanketblanketWeight measurementWeight measurement

Domtar Lint CollectorDomtar Lint Collector5% 5% isopropanolisopropanol used to used to clean lint from blanket clean lint from blanket Collected using Collected using domtardomtarframeframeFiltered with glass filterFiltered with glass filterWeight measurement to Weight measurement to confirm tape pull resultconfirm tape pull resultImage Analysis using Image Image Analysis using Image Pro Pro

Area and length distributionArea and length distribution

Prüfbau Deltack13.5BBlackHeidelberg GTO-52

13.5ABlackHeidelberg GTO-52Man-Roland Uniset

Man-Roland Uniset9ABlackHeidelberg GTO-526ABlackHeidelberg GTO-52

Man-Roland Uniset4ABlackHeidelberg GTO-52TackBrandColourTrial

Paper: Improved brightness (ISO Paper: Improved brightness (ISO brightness 74), 52 gsmbrightness 74), 52 gsm

ManMan--Roland Uniset TrialRoland Uniset TrialPrinting Press Variables:Printing Press Variables:

Ink Tack Ink Tack Tack 4, 9, 13.5Tack 4, 9, 13.5

Paper Side Paper Side T/S or B/ST/S or B/S

Print CouplePrint CoupleTop unit Top unit

Take off angles 78Take off angles 78ºº and 102and 102ºº

Bottom unitBottom unitTake off angles 27Take off angles 27ºº and 153and 153ºº

Printing Screen Printing Screen 0%, 25%, 50%, 75%, 100%0%, 25%, 50%, 75%, 100%

Bottom unit of Man-Roland Uniset

Top Unit of Man-Roland Uniset

TS

BS

TS

BS

102102ºº

153153ºº

Heidelberg GTOHeidelberg GTO--52 Trials52 Trials

7000 copies printed7000 copies printedTack Tack

4, 6, 13.54, 6, 13.5

Printing ScreenPrinting Screen0%, 25%, 50%, 75%, 0%, 25%, 50%, 75%, 100%100%

Results Part 1Results Part 1Effect of TakeEffect of Take--Off Angle and Paper SideOff Angle and Paper Side

0

1

2

3

4

5

6

7

0 20 40 60 80 100 120 140 160 180Angle

Lint

(gsm

)

Top sideBottom side

Highest average lint result (BS 153Highest average lint result (BS 153ºº taketake--off angle) is off angle) is ~ 5times~ 5timessmallest average lint result (TS 27smallest average lint result (TS 27ºº taketake--off angle )off angle )

Area Distribution Comparison of Tack 4 Ink: Area Distribution Comparison of Tack 4 Ink: Lowest Lint Result (TS, 27Lowest Lint Result (TS, 27ºº TakeTake--off Angle)off Angle)

0

10

20

30

40

50

60

70

80

0 5000 10000 15000 20000 25000Mean Area (µm2)

Are

a D

istri

butio

n (%

) .

0% 25% 50% 75% 100%

Tack 4 Highest Lint Result (BS, 153Tack 4 Highest Lint Result (BS, 153ºº TakeTake--Off Angle)Off Angle)

••2727ºº : nearly half of the total area of lint is in the : nearly half of the total area of lint is in the smallest size class, while smallest size class, while ••153153ºº : the largest area class contains the most lint : the largest area class contains the most lint except for 0%except for 0%

05

1015202530354045

0 5000 10000 15000 20000 25000 30000Mean Area (µm2)

Area

Dis

tribu

tion

(%)

.

0%25%50%75%100%

Printing Screen Area Distribution Printing Screen Area Distribution Heidelberg GTOHeidelberg GTO--52 Tack 452 Tack 4

Results is between 27Results is between 27ºº and 153and 153ºº ManMan--Roland Uniset DistributionsRoland Uniset Distributions

0

10

20

30

40

50

60

0 5000 10000 15000 20000 25000 30000Mean Area (mm2)

Are

a D

istri

butio

n (%

)

0%25%50%75%100%

HypothesisHypothesis

Higher take off angle, Higher take off angle, higher force, larger higher force, larger and more lint and more lint Use Use PrufbauPrufbau Deltack Deltack to testto test

Ink film splitting forceInk film splitting forceVaried printing speedsVaried printing speeds0.1 0.1 mLmL black tack 13.5 black tack 13.5

0.000.200.400.600.801.001.201.40

0 1 2 3

Printing Speed (m/s)

Tack

For

ce (N

)

Results Part 2Results Part 2Effect of Ink Tack : B/SEffect of Ink Tack : B/S

0

1

2

3

4

5

6

0 2 4 6 8 10 12 14 16

Ink Tack

Lint

Res

ults

(g/s

qm)

Man-Roland 50%, 25,000 copies

Man-Roland 100%, 25,000 copies

Heidelberg 50%, 7000 copies

Heidelberg 100%, 7000 copies

Effect of TackEffect of TackLint Area Distribution of 50%, 27Lint Area Distribution of 50%, 27ºº TakeTake--Off AngleOff Angle

05

101520253035404550

0 5000 10000 15000 20000 25000 30000Mean Area (µm2)

Area

Dis

tribu

tion

(%)

Tack4 T/S

Tack9 T/S

Tack13.5 T/S

Lint Area Distribution of 50% Lint Area Distribution of 50% Screen and 153Screen and 153ºº TakeTake--off Angleoff Angle

0

10

20

30

40

50

60

70

80

0 10000 20000 30000 40000

Mean Area (µm2)

Are

a D

istri

butio

n (%

)

Tack4 B/S

Tack9 B/S

Tack13.5B/S

Ink Tack and LintInk Tack and LintTack : Measured using InkometerTack : Measured using Inkometer

800 rpm800 rpmInk weight: 1.67 gramsInk weight: 1.67 grams

PrintingPrintingInk Thickness 1Ink Thickness 1--2 2 µµm m

Assuming ink film splits in the middleAssuming ink film splits in the middle

~1071040Man-Roland ~106130Heidelberg3x1053.37.9Inkometer

s-1m/scmShear RateSpeedDiameter

Inks Inks Shear thinningShear thinningApparent viscosity falls with apparent shear Apparent viscosity falls with apparent shear raterate

Measurements need to be performed at Measurements need to be performed at shear rate relevant to press under shear rate relevant to press under investigationinvestigationInkometer tack not a good predictor of Inkometer tack not a good predictor of lintinglinting

Results Part 3Results Part 3Effect of Printing ScreenEffect of Printing Screen

ManMan--Roland: Average of Tack 4, 9, 13.5Roland: Average of Tack 4, 9, 13.5Heidelberg: Tack4Heidelberg: Tack4

0

1

2

3

4

5

6

0 20 40 60 80 100

Screen Coverage (%)

Ave

rage

Lin

t (g/

sqm

)

B/S Average Lint Man-Roland T/S Average Lint Man-Roland B/S Lint Heidelberg

ConclusionsConclusionsSignificant printing parameters related to Significant printing parameters related to

lint:lint:TakeTake--off angleoff angle

Lint Increased greatly with takeLint Increased greatly with take--off off angleangleHigher take off angle, higher force, Higher take off angle, higher force, larger and more lintlarger and more lint

Printing screenPrinting screenMaximum at 25% screen toneMaximum at 25% screen tone

Ink TackInk TackNo large difference in tack 4,6, and 9No large difference in tack 4,6, and 9Tack 13.5 gave somewhat higher resultTack 13.5 gave somewhat higher result

Inkometer measures tack at a much Inkometer measures tack at a much lower shear rates compared to the shear lower shear rates compared to the shear rate in commercial printing pressrate in commercial printing press

Conclusions Cont.Conclusions Cont.

AcknowledgementsAcknowledgementsDr Wei Dr Wei ShenShenJohn Pollard, Grant Brennan John Pollard, Grant Brennan Shaun Jenkins, Elaine Filliponi, Herman Shaun Jenkins, Elaine Filliponi, Herman MulyadiMulyadi, Robert , Robert VukasinovicVukasinovicThe financial support of the MGS, The financial support of the MGS, Smartprint CRC, Norske Skog and the Smartprint CRC, Norske Skog and the Australian Research Council, through the Australian Research Council, through the SPIRT grant scheme, are gratefully SPIRT grant scheme, are gratefully acknowledgedacknowledged