Filler Engineering for Energy Savings and Improved Paper Properties

Delong Song, Chunxu Dong, Art Ragauskas and Yulin Deng*Delong Song, Chunxu Dong, Art Ragauskas and Yulin Deng*

IPST at Georgia TechIPST at Georgia Tech

Georgia institute of Technology Georgia institute of Technology

TAPPI Con’09

June, 2009

Advantages of Using Filler in PaperAdvantages of Using Filler in Paper

• Increase filler content in paper will improve paper optical properties (brightness, opacity, printing quality)

• Increase filler content in paper will reduce the papermaking cost– pulp price: $350-600/ton– filler cost (clay or PCC): $130-150/ton

• Increase water drainage rate • Increase solid content of paper web• Substitution of fiber will reduce the carbon footprint

Problems of Using Filler in PaperProblems of Using Filler in Paper•• Reduces the paper strengthReduces the paper strength•• Reduce the bulkReduce the bulk•• Some effects on the wetSome effects on the wet--end operation end operation

–– retentionretention–– sizing reversion (PCC filler)sizing reversion (PCC filler)–– water clarificationwater clarification–– two two sidenesssideness–– dense paperdense paper–– LintingLinting and dustingand dusting

Filler Engineering: Past ResearchesFiller Engineering: Past Researches

•• New generation filersNew generation filers–– High aspect ratio fillers (PCC, Clay)High aspect ratio fillers (PCC, Clay)–– Low cost fillers (Gypsum fillers)Low cost fillers (Gypsum fillers)–– High quality fillers (TiOHigh quality fillers (TiO22, , nanofillersnanofillers) ) –– NanosilicateNanosilicate filersfilers

•• Filer modification and novel treatment techniquesFiler modification and novel treatment techniques–– Wood finesWood fines--filler compositesfiller composites–– Pretreatment of fillers (Pretreatment of fillers (preflocculationpreflocculation))– Polymer coating

Our Approach: Filler Treatment Using Starch

Filler

Starch adsorbed on filler Starch coated on filler aggregate

StarchIn traditional papermaking

Our approachfiber

Coated Filler

fiber

• Spray drying method• Wet slurry method• Polymer precipitation method

The best method depends on your paper grade, location (transportation cost), and fillers (PCC, Clay)

Filler Modification with Polymer Coating

Spray Drying MethodSpray Drying Method

Filler + starch + water

Cook

Filler + dissolved starch + water

Spray Dry

Starch-coated filler

CoatedCoatedFillerFiller

FillerFiller

Starch used is raw starch, which is ~$0.3/Lb, comparing with cationic starch of ~$1.3/lb

Both potato and corn starch can be used

2.5% starch based on clay is enough

One of our engineered fillers: raw starch (corn starch) coated clay: Spray dried method

Modifying the Spraying Dry Method by Adding Crosslinker

Starch Coated Clay for Linerboard Starch Coated Clay for Linerboard ApplicationApplication

• Why do we add filler in linerboard?– Energy saving– Machine running ability improvement – Printing quality– Raw material cost reduction

• Problems– Strength reduction– Filler retention

• Modified Clay – IMERYS (Atlanta, GA)– Modified clay coated with

precooked 2.5% corn starch via spray drying of 40% clay slurry

– Control: conventional clay with 3 lb/ton cationic starch

• Furnish– SW kraft pulp, kappa 105,

Inland– Pulp was beaten to C.S.F.

350 ml• Handsheets

– TAPPI method, 180 g/m2 ,

CPAM retention aid.

Spray – Dried Starch-Coated Clay – Handsheet ResultsTensile Index vs. Filler Content

30

35

40

45

50

55

0 5 10 15 20Filler Content (%)

Tens

ile In

dex

(Nm

/g)

Orig. Clay

2.5Corn

Ring Crush Index vs. Filler Content at Different CPAM Levels

11

12

13

14

15

16

17

0 2 4 6 8 10 12 14

Filler Content (%)

RIn

g C

rush

Inde

x (N

m/g

)

Orig. C lay (0-2 ppm C P A M )

Spray-D ried M o d. C lay, 2 .5C o rn (0-2 ppm C P A M )

R in g C r u s h I n d e x ( G M ) v s . C la y C o n t e n t

8

1 0

1 2

1 4

0 % 5 % 1 0 % 1 5 % 2 0 % 2 5 %

F i l le r C o n t e n t in S h e e t ( % )G

M R

ing

Cru

sh

Inde

x(N

m/g

)U n f i l le d L in e r C o n t r o l ( W i t h o u t S ta r c h ) U n m o d . C la y C o n t r o l w i t h C a t i

M o d i f ie d C la y ( U n m o d i f ie d S t a r c h ) M o d i f ie d C la y ( L o w V is c . S t a r c

M o d i f ie d C la y ( P r o p r ie t a r y P o ly m e r )

T e n s i le I n d e x ( G e o m e t r ic M e a n ) v s . C la y C o n t e n t

3 5

4 5

5 5

6 5

0 % 5 % 1 0 % 1 5 % 2 0 % 2 5 %

F i l le r C o n t e n t in S h e e t ( % )

GM

Ten

sile

Inde

x (N

m/g

)

U n f i l le d L in e r C o n t r o l ( W i t h o u t S t a r c h )U n m o d . C la y C o n t r o l w i t h C a t io n ic S t a r c hM o d i f ie d C la y ( U n m o d i f ie d S t a r c h )M o d i f ie d C la y ( L o w V is c . S t a r c h )M o d i f ie d C la y ( P r o p r ie t a r y P o ly m e r )

Handsheet Properties Using different Starches(Lab Results)

Stiffness reduced only slightly at 10% modified clay content. Over 10% increase in tensile and ring crush with modified vs conventional clay

GM Ring Crush Index vs. Clay Content

7

8

9

10

11

12

13

0 5 10 15 20 25

Clay Content in Sheet (%)

GM

Rin

g C

rush

inde

x (N

m/g

)

Original ClayModified Clay

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25

Clay content (%)

Stiff

ness

(mN

m),

GM

Modified clayOriginal clay

HertyHerty TrialTrial

Herty Pilot TrialHerty Pilot Trial

Bulk maintained at 10% modified clay content

1.2

1.3

1.4

1.5

1.6

0 5 10 15 20 25

Clay content (%)

Bul

k (c

m3 /g

)

Modified clayOriginal clay

Effect of Clay on Sheet Dewatering

0

10

20

30

40

50

60

0 10 20 30 40 50 60Sheet Ash Content (%)

Solid

Conte

nt (%

)

Clay, Couch CMod. Clay, Couch CClay, Press CMod. Clay, Press C

Dryness off Couch

Dryness out of Press

Summary of Starch Coated Clay in Linerboard Application

(Spray Dry Method)• Raw Starch can be easily coated on clay surface• 2.5% starch (based on filler) is enough to

achieve highest strength benefit• Adding starch coated filler to linerboard can

reduce papermaking cost• Up to 8% of starch coated filler do not reduce

the strength properties • Adding filler can significantly improve the

drainage rate, solid content and drying rate • Several mill trials using starch coated filler have

been done

Starch-clay Composite by Fatty Acid Complexation

Unmodified corn starch and palmitic acid (or stearic acid sodium salt)

Starch

HCl (below pH 4)

NaOH (pH 11~12)Cooking

Neutralization

Clay Fatty acidStarch

HCl

NaOH (pH 11~12)Cooking

Neutralization

Clay Fatty acid

The mechanism of starch-filler composite is due to the formation of starch-fatty acid complex which is water insoluble at low pH

Wet methods

Starch-Clay Composite Aggregates Formation

Cooked raw starchClay slurry (2-25%)

Fatty acid

Low pH < 4

Starch-clay composite suspension

0

10

20

30

40

50

20 40 60 80 100Temperature, °C

%

Solubility

Swelling Power

Solubility: temperature and pH effects

0

10

20

30

40

50

2 4 6 8 10 12pH

%

SolubilitySwelling Power

Application of the technique

• Can be used for modifying both clay and PCC. For PCC, calcium ions can precipitate the starch and no acid is need to bring the pH down

• Can be applied to different paper grades

Physical properties

10

30

50

70

0% 10% 20%

Clay dosage, %

Tens

ile In

dex,

Nm

/g

starch(palmitic 10%) clay 1:1 starch(palmitic 30%) clay 1:1 clayconventional method

0

250

500

750

1000

0% 10% 20%

Clay dosage, %ZD

T, K

Pa

starch(palmitic 10%) clay 1:1 starch(palmitic 30%) clay 1:1 clayconventional method

~120% increase comparing to clay-fiber only

~ 60% increase comparing to cationic starch (conventional method) method

Copy paper

Physical properties (cont.)

0.0

0.2

0.4

0.6

0.8

0% 10% 20% 30%

Composite dosage, %

Burs

t Ind

ex, k

Pa●

m2/

g

starch(palmitic 10%) clay 1:1 starch(palmitic 30%) clay 1:1 clay

0

2

4

6

0% 10% 20% 30%

Composite dosage, %Fo

ldin

g In

dex,

tim

es●m

2/g

starch(palmitic 10%) clay 1:1 starch(palmitic 30%) clay 1:1 clay

Copy paper

Optical properties

10

30

50

70

90

87 88 89 90

Brightness

Tens

ile In

dex,

Nm

/g

starch(palmitic 30%) clay 1:1 starch(palmitic 10%) clay 1:1 clay

10

30

50

70

90

70 75 80 85 90 95

Opacity. %

Tens

ile In

dex,

Nm

/g

starch(palmitic 30%) clay 1:1 starch(palmitic 10%) clay 1:1 clay

Copy paper

fatty acid

10%

fatty acid

30%

fatty acid

10%

fatty acid

30%

Distribution and Bonding (SEM)Copy paper

Additional advantage (sizing)

0

0.2

0.4

0.6

0.8

1

0% 10% 20% 30% 40%Compostite Dosage, %

Wet

tabi

lity (R

)

Pamitic 10% to starchPalmitic 30% to starch

Rate of change of wettability (R) = Change of contact angle / change of time

5s 60s

30%

10%

• The pulp with various amounts of clay-starch composites was diluted to 1L of 0.5 wt% respectively.

• Percol-175 was added at 0.1wt% based on solid weight for clay retention.

• Drainage time was measured by a Dynamic drainage analyzer (DDA).

Drainage test

Energy saving and machine runnabilityimprovement by adding fillers

Vacuum vessel (0.2 bar)

Stirrer (800rpm)DDA drainage unit

Drainage is measured as the time from the start of run until air start being sucked though the sheet.

Effect of filler content on the drainage rate

6

6.5

7

7.5

8

8.5

9

9.5

10

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35filler content

time

of d

rain

age/

s

Clay filler; C-PAM retention aid at 2lb/ton; linerboard

Drainage rate was increased (or drainage time decreased) >20% byadding 20% fillers

• Unbleached kraft pulp (60% hardwood and 40% softwood) was refined in a Valley beater to a freeness of 400 CSF.

• Starch modified clay (spray-dry method) was provided by Imerys as the filler.

• Percol-175 (high molecular weight, low charge density polyacrylamideretention aid) was obtained from Ciba specialty Chemicals.

• The filler content was determined by ashing the paper in a muffler oven according to the standard TAPPI method T211.

• After a slightly wet pressing (50psi,5min, no heating), handsheets with a target basis weight of 200g/m2 were prepared and ready for pressing and drying test

Water removal tests (press and drying sections)

Wet pressing test• The testing system used was

the MTS Testing Machine controlled by a MTS 458.20 Micro Console.

• Handsheets were cut to a suitable size for the MTS press. The weights of the samples before and after press (600psi) were both measured immediately. •MTS 458.20 Micro Console.

Drying test• After wet pressing test, the

sheets were dried at 105°C by a Mettler Toledo® LJ16 moisture analyzer.

• The percent of solids content was measured every 30 seconds, and the lost water weight was

obtained.Mettler Toledo® LJ16 moisture analyzer

Effect of filler addition on the solid content after press

0.2

0.24

0.28

0.32

0.36

0.4

0 5 10 15 20 25 30

Fille r Content (%)

Solid

Con

tent

aft

er P

ress

ing

(%)

Test-1 and Test-2 were two independent tests with the same pressure

Solid content increased from 30% to 36% under 600 psi pressing

Test-10.20

0.24

0.28

0.32

0.36

0.40

0% 5% 10% 15% 20% 25% 30%filler content, %

Solid

con

tent

afte

r pre

ssin

g (%

)

Test-2

Solid content increased 6 absolute points by adding 23% filler.

Effect of filler addition on the solid content after press

1

1.5

2

2.5

3

0 0.05 0.1 0.15 0.2 0.25 0.3

filler content

wat

er/d

ry w

eigh

t aft

er p

ress

Relative water content (water/dry paper) after press decreased from 2.3 to 1.65 by adding 25% filler, witch corresponding to 26% reduction in the water content

1

1.5

2

2.5

3

0 5 10 15 20 25 30filler content, %

wat

er w

eigh

t /dr

y w

eigh

t afte

r pre

ss

Two figures were generated from two independent tests

Web solid content as a function of press cycles at 600psi

25

30

35

40

45

50

0 1 2 3 4 5 6press cycles

solid

con

tent

, %

0% filler 6% filler11% filler 18% filler23% filler

Solid content increased by 5 weight percents by adding 23% filler.

For every 1% increase in exiting press solids, an approximate 4% increase in machine speed can be projected on a dryer-limited machine. 5% increase in solid content will result in 20% improvement in the machine speed.

20

25

30

35

40

45

0 5 10 15 20 25

filler content, %

solid

con

tent

, %

1150psi610psi

Solid content as a function of filler content

25

30

35

40

45

50

0 5 10 15 20 25filler content, %

solid

con

tent

, %

5 4 32 1

Different pressure (single cycle) Different cycles at 600 psi

Effect of filler addition on the drying rate

The water drying time decreased from 10 minutes to 8 minutes, which saving drying energy by 20%.

Two figures were generated from two independent tests

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14time,min

wat

er re

mov

ed/to

tal w

ater

,%

24%

21%

16%

11%

6%

0%

0

20

40

60

80

100

120

0 2 4 6 8 10 12

time  (min)water removed/total w

ater 

(%)

0%

4.98%

9.39%

16.41%

21.70%

25.90%

Test-1Test-2

Drying time (8min) with 24% filler Drying time (10min) with 0% filler

Mill Trials

• 5 mill trials have been done by Imerys at different mills (4 at Interstate Paper and 1 at Stora Enso).

• Linerboard and starch coated filler made by spray drying was used

Impact of Traditional Filler in Linerboard

20

21

22

23

24

25

26

27

28

29

30

Control (0) 2.5 5% Filler in board

STF

I (N

m/g

)

4.8% loss from

unfilled9.5% loss from

unfilled

6

6.57

7.58

8.5

99.5

1010.5

11

Control (0) 2.5 5% Filler in board

Rin

g C

rush

(Nm

/g) 7% loss

from unfilled 14% loss

from unfilled

Most suitable for mills making heavy weight linerboard with some strength to give.Probably not applicable across the grade range for any mill.Probably won’t allow incremental production gains (machine speed gains not possible due to strength loss)

- improved drying rates recouped as energy savings, or if machine can refine more will gain back some strength whilst reducing CSF

37

Commercial Trial HistoryMarch 2007: 8 hour trial on 55lb (268 g/m2) High Performance Liner

Speed kept constant10% reduction in steam demand seen at 4% in base ply

October 2007: 24 hour trial on same grade as previousMachine speed gains of 10-13 m/min were achievedOld Corrugated Containerboard (OCC/recycled) flow was interrupted, which allowed an unexpected evaluation of OCC versus SEKSEK appeared to have more impact on machine speed at lower levels than OCC

March 2008: 72 hour trial encompassing a range of gradesAddition rates up to 5.5% were run successfullySignificant gains in productivity (up to 6%) were achieved relative to typical run rates (speed increases >30 m/min on some grades)

**Interstate Paper was member of a state funded project, and is aware that this information has beenshared with other paperboard producers.

In all trials:- No paper was lost to breaks- Strength levels were within specification- Runnability was excellent

Commercial Trial 3: Productivity Summary

5.8%5.3%3.9%Max Productivity Boost (%)

47.451.345.6Max Trial Production Rate (stph)

342829Max Speed Gain (m/min)

618534779Max Speed (m/min)

2.9%3.3%3.2%Trial Productivity Boost (%)

46.150.345.3Trial Production Rate (stph)

44.848.743.9Target Production Rate (stph)

171624Trial Speed Gain (m/min)

601522774Trial Speed (m/min)

584506750Target Speed (m/min)

4.80%4.50%3.90%Average SEK addition

55# STFI(268g/m2 High Performance)

69# Mullen(336g/m2

Standard)

42# Mullen (205g/m2

Standard)Grade

Commercial Trial 3: Impact on Strength

25

27

29

31

33

35

37

39

0 1 2 3 4 5 6

SEK Flow (% of Primary Ply)

STFI

(lbf

/in)

Target

Minimum

90.0

100.0

110.0

120.0

130.0

140.0

150.0

160.0

0 1 2 3 4 5 6SEK Flow (% of Primary Ply)

Mul

len

42# Mullen 69# Mullen

Target

Target

Minimum

Minimum

No correlation between critical strength tests and SEK dosage rates.

40

Value Proposition for SEK in Linerboard

4 -5% SEK in linerboard results in the following benefits:

• Fiber replacement or extender • Can substitute or extend OCC and Virgin fiber• No statistical impact on strength and slide angle• Faster drainage and drying • Reduced steam demand - 10% • Potential for speed increase - ~ 100 fpm • Production rate increase of up to 3tph on 55lb liner

Overall Conclusions• Adding our starch coated clay to linerboards

– improve water drainage rate– increase machine runnability– increase solid content by 3-5 absolute point– Saving drying energy by >10%

• Starch coated filler does not detrimentally impact linerboard sheet strength up to filler content of 8%

• The starch modified filler can also be used to improve newsprint properties• The starch coated filler shows higher strength properties than adding filler and starch

separately in wet end.• Two modification methods (wet and spray drying) are developed• Our techniques can be used for both PCC and clay• Several mill trials have been done, and the longest trial was last three weeks. The

trail was very success. • Intellectual Property

– A patent of filler modification use starch and starch-fatty acid composite has been filed at US Patent Agent in September 2007

• Publication number: US 2008/0087396 A1