Dr. A. Lehmann COST FP1205 Training School, Jena 2015 · 2017-04-26 · Global fiber production –historical development CIRFS; International Rayon and Synthetic Fibres Committee;

© Fraunhofer

DISSOLUTION AND PROCESSING OF CELLULOSE

FROM ALKALINE MEDIA - CARBAMATE AND VISCOSE

SYSTEM

Dr. A. Lehmann

COST FP1205 Training School, Jena 2015

© Fraunhofer

Introduction – Global fiber market

Viscose Process

Carbamte Process

Summary

DISSOLUTION AND PROCESSING OF CELLULOSE

FROM ALKALINE MEDIA - CARBAMATE AND VISCOSE

SYSTEM

© Fraunhofer

IntroductionGlobal fiber production – historical development

CIRFS; International Rayon and Synthetic Fibres Committee; “World Man-Made Fibres Production”, 2011.

Cotton [Mio. t]

Wool [Mio. t]

Synthetics [Mio. t]

Cellulosic [Mio. t]

2,7

0,7

1,5

10

total

: 15.2 Mio t

19603,1

15,3

1,9

19

Cotton [Mio. t]

Wool [Mio. t]

Synthetics [Mio. t]

Cellulosic [Mio. t]

1990

total

: 39.3 Mio t

4,9

53,6

1,1

26,3

Cotton [Mio. t]

Wool [Mio. t]

Synthetics [Mio. t]

Cellulosic [Mio. t]

total

: 86 Mio t

2012

© Fraunhofer


Global textile market

Cotton stagnant at ~27 Mio t/a

High cotton prices

~35% minimum share of cellulosics in textiles

GAP of 15 Mio t/a of cellulosic fiber in 2030

Grow rates

Viscose, Lyocell > 9%/a

Acetate 1.5%/a

The Fiber Year 2013: World Survey on Textiles & Nonwovens, April 2013; H. Sixta, PapSaT Course, 2014, Helsinki

© Fraunhofer

Man-Made Fiber Year Book 2013, 4.

19

70

19

90

19

94

19

98

20

02

20

03

20

04

20

05

20

06

20

07

20

08

20

09

20

10

20

11

20

12

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0x1

06 t/a

Year

Lyocell and viscose based staple fiber production


© Fraunhofer IAP

Viscose technology

Carbamate technology

alkalization

derivatization

spinning

regeneration

regenerated

cellulose fibre

dissolution of

cell.-derivative

+ R

- R

Lyocell (NMMO) technology

Ionic Liquid technology

direct

dissolution of

cellulose

spinning &

regeneration

regenerated

cellulose fibre

dissolving pulp dissolving pulp

IntroductionShaping of cellulose into filaments

© Fraunhofer

Overview production of man-made cellulosic fibers via

cellulose carbamate route

Similarity between the Viscose

and the CarbaCell® process

allows “revamp” of viscose

plants

Spinning process is performed

at room temperature

Reduced sulphur and heavy

metal emissions

Textile character was adressed

in this development

© Fraunhofer IAP

THE VISCOSE PROCESS

© Fraunhofer IAP

AlkalizationPre-

ripeningXan-

thationDis-

solvingMaturity Spinning

Introduction

© Fraunhofer IAP

AlkalizationPre-

ripeningXan-

thationDis-

solvingMaturity Spinning

4 Main steps:

Manufacture of dissolving pulp

Production of the polymer solution, the viscose

Spinning of fibers, filaments, films, casings, …

Aftertreatment of the extrudet products

Each of these steps includes many influencing parameters on the

structure and the properties of the resulting products.

Introduction

© Fraunhofer IAP

ALKALIZATIONThe viscose process

© Fraunhofer IAP

Treatment of pulp (sheet) with aqueous sodium hydroxide („alkali lye“)

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-

solvingMaturity Shaping

© Fraunhofer IAP

0 5 10 15 20 25 30 35 40

0

5

10

15

20

25

NaO

H/1

00g

Cell

ulo

se [

g]

NaOHaq [%]

Chemical constitution

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


13 g NaOH per 100 g Cellulose

=

2 mol AGU bind/interact with 1 mol NaOH

© Fraunhofer IAP

The crystalline structure of AC - WAXS qualitative phase analysis

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Dissolving pulp Alkali cellulose (AC I)

0 20 40 60 80 1000

10

20

30

40

50

60

70

rel.

In

ten

sit

y [

e.u

.]

Scattering angle 2

Dissolving Pulp

AC I

© Fraunhofer IAP

The crystalline structure of AC - WAXS qualitative phase analysis

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Cell I AC I AC II AC III AC IV

Volume per AGU [Å³] 165,5 278,8 227,0 261,2 196,2

Increase in contrast to Cell I [Å³] - 113,3 61,5 95,7 3,7

© Fraunhofer IAP

Chemical constitution of AC

The viscose process

R - O H + N a O H + H 2 O

R - O - N a +

R - O H + N a + O H -

a l c o x i d e

o r

a d d i t i o n c o m p o u n d

Anhydrous acetic acid

Alcoxide : AcO-Na+ + R-OH

Addition compound: AcO-Na+ + H2O

By knowing the total alkali content

in the steeping liquor the ratio of

the two chemical constitutions can

be calculated

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

0 1 2 3 4 5 6

0,0

0,5

1,0

1,5

2,0

2,5

3,0

alc

oxid

e g

rou

ps p

er

AG

U

NaOH per AGU [mol]

Chemical constitution of AC

The viscose process

AC for technical use always a

mixture of alcoxide as well as

addition compound exists

Whereas in AC

H2O alcoxide

NaOH alcoxide Technical used for AC prepartation

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

PRE-RIPENINGThe viscose process

© Fraunhofer IAP

DP-Reduction – Viscosity measurement

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Same effects as by alkalization induced continue during pre-ripening

O2-adsorption of AC leads to degradation of the DP

By this aldehyde as well as carboxyl groups are formed

0 20 40 60 800

50

100

150

200

250

vis

co

sity [

cP

]

time [h]

18°C

25 °C

35°C

OO

OOH

OH

OH

OH

OO

O

OH

OHOH

OH

OH

OH

© Fraunhofer IAP

DP-Reduction – Molecular weight distribution

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


In dependence on concentration of alkali lye fractionation can be observed

Alkalization conditions typical for viscose remove low molecular weight

compounds during already alkalization

P. Strunk, phD-Thesis, Umea University, Sweden 2012

© Fraunhofer IAP

DP-Reduction – Molecular weight distribution

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Pulp

AC 15 min

AC 30 min

End of pre-

ripening

Mw x103

[g/mol]

Mn x103

[g/mol]

Mw/Mn

Pulp 505 243 2,1

AC 15 min 494 233 2,1

AC 30 min 436 214 2,0

End of pre-

ripening

205 128 1,6

© Fraunhofer IAP

XANTHATIONThe viscose process

© Fraunhofer IAP

Main Reaction

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

Main Reaction

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


CS2 reacts with AC and lye

Amorphous regions will be

modified first

© Fraunhofer IAP

Main Reaction Side Reaction

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


CS2 reacts with AC and lye

Amorphous regions will be

modified first

Caused by instability of cellulose

xanthate (CX) and reaction with lye

mainly NaCS3 is formed (yellow)

© Fraunhofer IAP

Reaction

„Pre-reaction“ of carbon disulfide with

NaOH to form NaHCS2O

Reaction pathway II ~5x faster

than III

Ratio II : III

75% : 25%

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

Structural changes during xanthation

AC I structure can be considered as

typical layer lattice

CS2 can penetrate between layer

lattice and expanding the crystal

structure

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


AC I CX

a [Å] 12,8 18

c [Å] 13,2 19

b[°] 40 28

© Fraunhofer IAP

DISSOLVINGThe viscose process

© Fraunhofer IAP

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

Dope preparation

CX (!!which contains NaOHaq!!) will be dissolved with diluted alkali lye to

realize between 4,5% and 8% alkali in the dope

Solubility differs from:

Structural point: kind and amount of amorphous and crystalline regions in

the CX

Chemical point: Number and distribution of the xanthate groups

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

Dope preparation – influence xanthation pattern

Equal distribution of xanthate groups along the

chains improves dope quality

During dissolution (normal 90 – 150 min) trans-

xanthation (mainly) between the chains occurs

By this trans-xanthation CS2 is lost and g-value

decreases

To minimize this applied dissolution temperature

is < 10 °C

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

MATURITYThe viscose process

© Fraunhofer IAP

The maturity

Maturity (keeping temperature controlled certain time) has to be applied

Viscose, as it is dissolved, can not be spun into filaments

Chemical as well as colloidal chemical processes happen

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

The maturity – chemical processes

Main process is the elimination of xanthate groups (see Dissolving)

Splitting off xanthate groups via hydrolysis (reversible, bp: Na2CS3) and

saponification (non-reversible, bp: Na2S) possible

Alkali content determine way of splitting off increasing alkali content

increases saponification reaction

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

The maturity – Degree Hottenroth °H

Determination of capability for coagulation of viscose

Principle: Amount of Electrolytes which is necessary to coagulate viscose

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Degree Hottenroth °H

• NH4Cl as electrolyte

• Addition of 10% NH4Claq to Viscose up to the coagulation point

• Used ml NH4Claq is °H

© Fraunhofer IAP

The maturity – Degree Hottenroth °H

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


A. Schwaighofer et al. Anal. Bioanal. Chem, 400, 2011, 2449

During Ripening (°H decreases)

loss of g-value as well as increasing

Na2CS3-content

© Fraunhofer IAP

SHAPINGThe viscose process

© Fraunhofer IAP

Shaping of viscose

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Liquid viscose ray from nozzle has to be transferred into a gel fiber by

coagulation and decomposite the xanthate into hydrate cellulose

Colloidal chemical as well as chemical processes in quick succession

© Fraunhofer IAP

Shaping of viscose – General considerations

Viscose = aqueous solution of an anionic electrolyte with ionic groups (xanthate)

as well as hydrophilic non-ionic groups (OH-groups)

!!!xOH > xxanthate Stabilization of colloidal system mainly by solvatation of

hydroxyl groups instead electrostatic repulsion of ionic xanthate groups!!!

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

Shaping of viscose – General considerations

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Precipitation

Drawing

Decomposition

Drying

Influence acid/salt on structure formation(Diffusion, by-product formation, swelling, shrinkage, …)

Single bath / multi bath drawing(Skin/Core structure, influence of Zn2+, cross-section …)

Formation of hydrocellulose(Regeneration)

© Fraunhofer IAP

COAGULATIONPrecipitation

© Fraunhofer IAP

Shaping of viscose – Coagulation

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP


The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


Prim. Structure Formation

Coagulation

Second. Structure Formation

Dehydratation, densification

Decomposition

Orientation, crystallization

© Fraunhofer IAP


3 types of coagulation possible

1) by acid

2) by salt (electrolyte´s)

3) combination of acid and salt

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

Shaping of viscose – Coagulation by acid

Sulphuric acid in spin bath neutralize alkali in viscose ray

Na2SO4 is formed and act´s as desolvatation agent

In strong acid, such as the Lilienfeld-type spin-bath,

the xanthic acid is protonated and stabilized, leading

to slower regeneration of the cellulose.

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


CellO

S

S-Na+Cell

O

S

SHCell OH + CS2

fast slow

H2SO4

+ NaHSO4

Picture from F. F. Morehead, W. A. Sisson; Skin Effect in Viscose Rayon; Textile Research Journal; December 1945; 15; 443-450

© Fraunhofer IAP

Shaping of viscose – Coagulation by salt´s

colloidal disperse phase in viscose is kept in solution by SOLVATATION

Coagulation can be started by Additives, which causes DESOLVTATION

e.g. hydrophilic salt´s

Hydrophilic forces of salt ions overcome those of colloidal disperse phase

Solvatation shell of salt ions is formed with water from colloidal disperse

phase cellulose xanthate become unsoluble COAGULATION

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


© Fraunhofer IAP

Shaping of viscose – Coagulation by salt´s

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


M. Horio, Textile Research Journal, 1950, 20, 373

O S

SCell M e

M e = M et al l ic elem ent

The S-Me bond controls the solubility of cellulose xanthate in water.

Sodium ions of NaCX can be interchanged with cations of the coagulants.

The stability of the newly produced colloidal system is closely correlated with

the CV of the precipitation agent.

© Fraunhofer IAP

Shaping of viscose – Coagulation by acid/salt

The viscose process

AlkalizationPre-

ripeningXan-

thationDis-



0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

cH

2S

O4 [

mm

ol

/l]

cNa2SO4 [mol/l]

When acid co-exist´s with

metal sulfates in coagulation

media it´s coagulation power is

remarkably depressed.

H2SO4/Na2SO4

© Fraunhofer IAP


The viscose process

AlkalizationPre-

ripeningXan-

thationDis-



0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

cH

2S

O4 [

mm

ol

/l]

cNa2SO4 [mol/l]

When acid co-exist´s with

metal sulfates in coagulation

media it´s coagulation power is

remarkably depressed.

Hard precipitaion becomes soft

precipitation

H2SO4/Na2SO4Na+ H+ Na+ H+, Na+

© Fraunhofer IAP


The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


S

S-N a+OC ell

S

S HOC ell

S

S-M e+OC ell

O HC ell

H + M e+fas t rap id /

fast

s low

fast

© Fraunhofer IAP


The viscose process

AlkalizationPre-

ripeningXan-

thationDis-


H2SO4 [g/l] Na2SO4 [g/l] ZnSO4 [g/l]

Textile Rayon 100 - 125 230 - 250 5 – 10

Cord Rayon 120 - 130 ~250 20 – 30

Staple Fiber 110 - 120 330 - 340 5 – 10

Lilienfeld Rayon 550 - 680 / /

Man-made cellulosic fibers based on

carbamate process

Viscose Lyocell CarbaCell

© Fraunhofer

Overview production of man-made cellulosic fibers via

cellulose carbamate route

Similarity between the Viscose

and the CarbaCell® process

allows “revamp” of viscose

plants

Spinning process is performed

at room temperature

Reduced sulphur and heavy

metal emissions

Textile character was adressed

in this development

© Fraunhofer IAP

Synthesis routes for cellulose carbamate

Basic principle Decomposition of urea at 130°C … 140°C

to ammonia and isocyanic acid reacting with cellulose

Different ways of cellulose activation

liquid ammonia (-35°C) + 10 % urea (Ekman et al., Neste OY)

alkalization and partial removal of alkali, pre-ripening (CarbaCell)

alkoholic (MeOH) alkalization with reduced NaOH input (DITF)

aqueous NaOH of low concentration plus urea (Fraunhofer IAP)

Synthesis routes A. CarbaCell (DE 19635 473)

alkalization – intercalation with urea – reaction with urea in xylene

B. Fraunhofer IAP (EP 1509548 B1)

activation (aqueous NaOH + urea), reaction in a kneader, no washing

C. DITF Denkendorf (DE 196 35 707)

alcoholic alkalization - reaction with urea in a melt of urea

© Fraunhofer IAP

Effects of NaOH-urea solutions on celluloseThe basic effect: synergy of NaOH and urea

cellulose I

© Fraunhofer IAP

Effects of NaOH-urea solutions on celluloseThe basic effect: synergy of NaOH and urea

6 wt. % NaOH const. 30 wt. % urea const.

J. Kunze, H.-P. Fink: Macromol. Symp. (2005)

© Fraunhofer IAP

Structural changes of cellulose in the carbamate

process demonstrated by 13C-CP/MAS-NMR

C-6

C-2,3,5

C-4

C-1

dissolving pulp (cell. I)

cellulose carbamate (cell. IV)

cellulose carbamate (cell. II)

carbacell-fibre (cell. II)

Na-cellulose ICNH2

O

3,2% N

route A, B

route A, B

route C

route A, B, C

© Fraunhofer IAP

X-ray diffraction patterns of cellulose modifications

in the cellulose carbamate processing route

diss. pulp (cell I) CC route A,B (cell II) CC route C (cell IV) final fibre (cell II)

© Fraunhofer IAP

Distribution of carbamate substituents by 13C-NMR

Distribution of substituents depends on type & conditions of the synthesis

cellulose II - type carbamate with block-like substitution (amorphous regions)

cellulose IV - type carbamate with homogeneous distribution along the chains

DS = 0,54ch

DS = 0ch

Probe CC 3/1

4

2

2s2(?)

1

C=O

6s

6

* *

*

*3

Kettenende

5

13C-NMR-Spektren von gelöster Cellulose

und gelöstem Cellulose-Carbamat in ZnCl /H O2 2

13C-NMR spectra of cellulose and

cellulose carbamate dissolved in ZnCl2/H2O

sample CC 3/1

CC3/1 CC3/2 CC1/4 CC1/1 CC1/3 CC2/2 CC2/3

0,0

0,1

0,2

0,3

0,4

DS

(i)

Carbamat-Probe

DS2

DS3

DS6

carbamate samples

© Fraunhofer IAP

Set-up spinning line for CCA

drying

spinning pump

nozzleCoagulation bath

(H2SO4, Na2SO4)

fiber

Drawing

washing

Finishing

decomposition

storage tank

H2O > 90°C Alkaliaq >

90°C

© Fraunhofer IAP

Fiber propertiesMorphology

CarbaCell Lyocell Viscose

Viscose Lyocell CarbaCell

© Fraunhofer

Comparison of cellulose carbamate and textile viscose

© Fraunhofer

Comparison of cellulose carbamate and textile viscose

Cellulose carbamate Textile viscose

Spinning bath low H2SO4/low Na2SO4

single spinning and regeneration

bath

mid H2SO4/low Na2SO4

single spinning and regeneration bath

spinning temp. ~ 25 °C ~25 °C – 40 °C

DP 230 - 300 320 - 400

Degree of

crystallinity

~ 35 – 40 % ~ 25 – 30 %

Orientation factor high for crystalline region

low for amorphous region

high for crystalline region

middle for amorphous region

cross-section circular to oval lobulated shape

Mechanical

properties

s: ~ 20 cN/tex

e: ~5-20%

EMod: ~1500 cN/tex

s: ~ 20 cN/tex

e: ~5-20%

EMod: ~600 - 1200 cN/tex

© Fraunhofer IAP

Fiber propertiesDegree of crystallinity and crystallite dimensions

Carbamate filaments own relative dense homogeneous round to oval cross-section morphology

(similar Lyocell)

Cryo-fracture reveals no fibrillation effects (different to Lyocell)

Degree of crystallinity is relative high compared to textile viscose (similar to Lyocell)

Crystallite dimensions along and transvers to fiber direction vary in a range typical for man-made

cellulosics

© Fraunhofer IAP

Tensile properties of different cellulosic fibers

Egypt ian cot ton Viscose f iber CARBACELL

(typical) f ilament yarn

Tit re [tex] 0.17 0.28

Tenacity, dry [cN/tex] 24-26 22-26 13-26

Tenacity, wet [cN/tex] 30-34 10-15 4-9

Elongat ion, dry [%] 7-9 20-25 8-27

Elongat ion, wet [%] 12-14 25-30 10-27

Wet modulus [cN/tex] 200 40-60 30-200

Water retent ion [%] 50 90 110

Industrial spinning trial at PREFIL Premnitz, Germany

© Fraunhofer IAP

Thanks for your attention

Prof. Fink

Dr. Ebeling

Dr. Kunze

Dr. Ebert

Mrs. Schindel

Mr. Weidel

Mr. Doß

Dr. André Lehmann

Fraunhofer IAP

Dpt. Fibertechnology

Geiselbergstr. 69

14476 Potsdam OT Golm

phone.: 0331 568 1510

Fax.: 0331 568 3000

Mail: [email protected]

Dr. A. Lehmann COST FP1205 Training School, Jena 2015 · 2017-04-26 · Global fiber production –historical development CIRFS; International Rayon and Synthetic Fibres Committee;

Documents