Enhanced Dry and Wet Web Runnability by

Spray Application of Different Polymers –

Laboratory and Pilot Scale Studies

Event: EFPRO-CEPI early stage researchers workshop 2012

VTT: Kristian Salminen, Janne Kataja-aho, Elias Retulainen & Timo Rantanen

Åbo Akademi: Hanna Lindqvist & Anna Sundberg

2 10/8/2012

Background: Wet web properties and paper machine runnability

• Paper machines have reached

their practical maximum width (~11

m). To increase production,

higher speed and less downtime is

required

•Increase of production speed is

often limited by mechanical

properties of wet web

• The fact remains that paper mills

do not typically add chemicals to

improve mechanical properties of

wet web

Pakarinen et al 1995

Hokkanen 1996

3 10/8/2012

Background: Interactions between fibers in the wet state

Hubbe 2006

“ …molecular segments already tend to mix with each other

already at wet state, before the start of drying process. A random

process of molecular motions would be expected to result in

interpenetration and tangling, i.e. a three-dimensional zone of

contact” (Hubbe 2006)

4 10/8/2012

Background: Modification of the fiber surface with polymers

Myllytie 2010

The dispersion of fibrils and interdiffusion between fiber

surfaces can be tailored by adsorbing different polymers onto

fibers Modified from Myllytie 2010

5 10/8/2012

…was to clarify the effects of spraying some

commercial polymers on mechanical

properties of dry and wet paper

The objective of this study…

6 10/8/2012

Methods: Spraying tests at laboratory

CMC

Chitosan

Starch

guar gum

Wet

pressing

50 kPa

350 kPa

Preparation of samples

Measurements

7 10/8/2012

Higher retention of polymers (with no cationic charge)

No effect on formation

To avoid adsorption of polymers mainly to fines fraction

Methods: Why to add polymers by spraying?

8 10/8/2012

Spraying of guar gum increased the wet web tensile strength

significantly, the increase was dependent on MW of guar gum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

45 50 55 60 65

We

t w

eb

te

ns

ile

s

tre

ng

th[

kN

/m ]

Dryness [ % ]

Reference (water spray) Cationic starch 1 g/m2

CMC 1 g/m2 Chitosan 1 g/m2

Guar gum 1 g/m2 Hyd. guar gum 1 g/m2

Reference

ChitosanCMC

Guar gum

Hydrolyzed guar gum

Cationic starch

+130%

Laboratory scale tests: SW kraft pulp

9 10/8/2012

Spraying of guar gum was a significantly more efficient (6

times) way to improve the wet web tensile strength than

addition of guar gum to pulp suspension

0

20

40

60

80

100

120

140

0.0 0.5 1.0 1.5 2.0

Inc

rea

se

in

we

t w

eb

s

tre

ng

th [

% ]

Guar gum addition [ % ]

Spray addition Addition to pulp suspension

Laboratory scale tests: SW kraft pulp

10 10/8/2012

14 3 2

Tasoimulaatikot

1-4

HiVac

3 2 1

Rintapöytä

Kuormitus-

Listat 1-5

MB Imut

1 3 2

MB suction

1 2 3

Forming boardVacuum flatboxes

1-4

Load lists

1-5

Chemicaladdition by

spraying

Pilot trials with CTMP furnish

CTMP furnish for board mid-ply

Running speed 300 m/min

11 10/8/2012

23.8 24.2 24.4 24.0 23.4

0

5

10

15

20

25

We

b d

ryn

es

s a

fte

r fo

rme

r s

ec

tio

n [

% ]

Spraying of guar gum had little effect on dryness after former

or press section

Addition of cationic starch to pulp suspension decreased,

while addition of guar gum increased the wet web tensile

strength at a given dryness level

0.00

0.05

0.10

0.15

0.20

0.25

0.30

35 40 45 50

We

t w

eb

te

ns

ile

s

tre

ng

th [

kN

/m ]

Dryness [ % ]

Starch 10 kg/t Starch 20 kg/tReference Guar Gum 0.1 g/m2Guar Gum 0.3 g/m2

Nip load 500 kN/m

Nip load 1000 kN/m

Pilot trials: CTMP (board mid-ply)

10

kg/t

20

kg/t 1

kg/t

3

kg/t

Ref

12 10/8/2012

88111

127100 109 116

0

20

40

60

80

100

120

140

Inte

rna

l b

on

d

str

en

gth

[ J

/m2

]Addition of 20% guar gum of the corresponding amount of cationic

starch was needed to obtain similar increase in int. bond strength

Pilot trials: CTMP (board mid-ply)

10

kg/t

20

kg/t

1

kg/t

2

kg/t

3

kg/t

Ref

3.1 2.9 2.9 3.1 3.2 3.1

0

0.5

1

1.5

2

2.5

3

3.5

Bu

lk [

cm

3/g

]

13 10/8/2012

Adding cationic starch improved strength properties of dry paper, but had no positive effects on wet web strength

Spraying of non-ionic guar gum appeared to be an interesting possibility to improve strength properties of wet paper

The increase in wet web tensile strength with guar gum was higher for chemical pulp than for chemimechanical pulp

Spraying of guar gum on former section had no effect on dryness after the former or press section

Guar gum spraying improved internal bond strength of CTMP furnish interesting also for board manufacturing

Summary

14 10/8/2012

Thank you for your attention!!!

The support of Kemira, Metso Paper, Stora Enso, UPM and

TEKES to this study is gratefully acknowledged