Investigation of the Interaction of Cationic Starch Derivatives with Cellulose Fibres with Respect to Paper Strength

Transcription

1 Investigation of the Interaction of Cationic Starch Derivatives with Cellulose Fibres with Respect to Paper Strength M. Ulbrich, S. Radosta, W. Vorwerg

2 Outline 1 Introduction 2 Method Determination of starch adsorption Adsorption isotherms Chromatograms and molar mass distributions 3 Results Statistical evaluation of the experimental design Adsorption behaviour of two starches and specific charge distribution Paper strength 4 Summary & Conclusion 2

3 1 Introduction cationic starch is one of the most important paper additives cationic starch generally improves the dry strength of the paper in paper industry the application in the wet-end end is limited to about 2-2.5% 2.5% cationic starch per pulp with a maximum degree of substitution (DS) of 0.1 cationic starch does not adsorb completely, a part is lost in process water it is necessary to investigate influence of starch adsorption on cellulose fibres to: make the starch input in the wet-end more economic fix more starch in the paper sheet enhance paper strength by means of cationic starch significantly 3

4 1 Introduction varied impacts Adsorption time Electrolyte content Pulp constant impacts Starch concentration Starch adsorption Anionic trash Additives DS Paper quality Starch source 4

5 1 Introduction investigated impacts constant factors DS 6 graded DS values from native to 0.13 Adsorption time 1 hour Pulp primary pulp Electrolyte content 5 different electrolyte compositions Anionic trash no anionic trash Starch concentration 4 graded initial starch concentrations between 1 6% Additives Source no additives potato starch 5

6 2 Method Determination of starch adsorption starch solution 0.5% filtration (5µm) water (different quality) dilution to initial concentration dried cellulose fibres shaking (1 hour) filtrate (with starch) filtration (5µm) cellulose fibres with adsorbed starch C 0 C e characterisation of starch by means of SEC-MALLS C 0 C e adsorbed amount waste 6

7 2 Method 25 Adsorption isotherm Adsorbed Starch [mg/g] c 0 = 200µg/ml (2% 2%) c 0 = 600µg/ml (6% 6%) c 0 = 400µg/ml (4% 4%) calculation of the adsorbed amount Γ = ((C 0 -C e ) x V ) / m [mg/g] 5 c 0 = 100µg/ml (1% starch/cellulose fibres) Γ C 0 C e V m adsorbed starch amount initial concentration [µg/ml] equilibrium concentration [µg/ml] volume of the starch solution [l] mass of cellulose fibre [g] Equilibrium concentration c e [µg/ml] 7

8 2 Method Concentration [rel.] µg/ml (1% starch/pulp) Initial starch 100µg/ml Adsorbed starch Concentration [rel.] µg/ml (2% starch/pulp) Initial starch 200µg/ml Adsorbed starch increased adsorption and changes in the molecular composition of the adsorbed starch by increasing initial starch concentration Volume [ml] Volume [ml] µg/ml (4% starch/pulp) Initial starch 400µg/ml Adsorbed starch µg/ml (6% starch/pulp) Initial starch 600µg/ml Adsorbed starch Concentration [rel.] Volume [ml] Concentration [rel.] Volume [ml] chromatograms of DS 0.10 in deionised water (DW) 8

9 2 Method Differential weight fraction dw/d(log M) Differential weight fraction dw/d(log M) DS 0.10 in DW (1% 1%) Initial starch 100µl/ml Adsorbed starch Molar mass [g/mol] DS 0.10 in DW (4%) Initial starch 400µg/ml Adsorbed starch Molar mass [g/mol] Differential weight fraction dw/d(log M) Differential weight fraction dw/d(log M) DS 0.10 in DW (2%) Initial starch 200µg/ml Adsorbed starch Molar mass [g/mol] DS 0.10 in DW (6%) Initial starch 600µg/ml Adsorbed starch Molar mass [g/mol] shift of the molar mass distribution curve of the adsorbed starch to lower molar mass with increasing initial starch concentration molar mass distribution curves of DS 0.10 in DW 9

10 2 Method 7 Paper strength DS 0.10 in DW 360 Tension length [km] Tension strength Bursting strength Bursting strength [kpa] 3 1% 2% 4% 6% 210 paper strength at different initial starch concentrations 10

11 3 Results Experimental design DS nativ e DW DW DW DW DW DW w ater of M NaCl M NaCl M NaCl M NaCl M NaCl M NaCl different 36 dgh 36 dgh 36 dgh 36 dgh 36 dgh 36 dgh quality 0.05 M NaCl 0.05 M NaCl 0.05 M NaCl 0.05 M NaCl 0.05 M NaCl 0.05 M NaCl increasing ionic strength of the water PW PW PW PW PW PW gradation of concentration: % starch per pulp DW deionised water + Na-Azid 0.05 M NaCl 0.05 M NaCl in DW + Na-Azid M NaCl M NaCl in DW + Na-Azid PW process water (Na 2 SO 4 und CaCl 2 ) + Na-Azid 36 dgh water of 36 dgh (MgCl 2 und CaCl 2 ) + Na-Azid (PTS Heidenau ) 11

12 3 Results Statistical evaluation 20 Influence of DS on adsorption Statistical evaluation of the experimental design with Statgraphics Plus 4.1 software Adsorbed starch amount [mg/g] native DS DS 0.03 DS 0.06 DS 0.10 DS 0.13 Mean diagrams and 95% confidence intervals: The target values (e.g. adsorbed amount at all 6 DS-values, each in all 5 water qualities and each at all 4 initial starch concentrations within the experimental design) were put together in categories (native starch, DS etc.) and the means are calculated. The confidence interval is the range, where the true value is located with a 95% confidence level. In case of no overlapping of the confidence intervals of the different means, there is a statistically significant difference between the means with a 95% confidence level. 12

13 3 Results Statistical evaluation Relation of DS and water quality Relation of water quality and concentration Adsorbed starch amount [mg/g] DW M NaCl 36 dgh 0.05 M NaCl PW Adsorbed starch amount [mg/g] % 2% 4% 6% native DS DS 0.03 DS 0.06 DS 0.10 DS 0.13 DW M NaCl 36 dgh 0.05 M NaCl PW with increasing DS the impact of water quality on adsorption decreases at higher salt content an increasing initial starch concentration results no significant increase in adsorption 13

14 3 Results Adsorption and molecular composition Adsorbed starch amount [mg/g] Adsorption isotherms DS 0.03 DW 36 dgh DRI [rel.] Chromatograms DS 0.03 (6% starch/pulp) Initial starch DS 0.03 (600µg/ml) Adsorbed starch in DW Adsorbed starch in 36 dgh amylose Equilibrium concentration c e [µg/ml] Volume [ml] amylopectin DS 0.03 (6%): in DW more starch adsorbed, in 36 dgh primarily amylopectin adsorbed 14

15 3 Results Adsorption and molecular composition Molar mass distribution curves of DS 0.03 Differential weight fraction dw/d(log M) DS 0.03 in DW Before adsorption Adsorbed starch M W (10 6 ) [g/mol] Molar mass [g/mol] Differential weight fraction dw/d(log M) DS 0.03 in 36 dgh M W (10 6 ) [g/mol] Before adsorption Adsorbed starch Molar mass [g/mol] 15

16 3 Results Distribution of substituents C h ro mato g ram DS 0.03 fro m semi-p rep arative SEC Specif. charge distribution DS 0.03 C o n c en trati o n [rel. ] F raction 1 F r. 2 F raction El ution tim e [m in.] S p e c i f. c h a r g e ( x ) [ g - 1 ] Specif. charge Average molar mass amylopectin amylose F raction 1 F raction 2 F raction M o l a r m a s s ( x ) [ g / m o l ] amylopectin amylose DS 0.03: amylopectin significant higher substituted than amylose 16

17 3 Results Water quality and paper properties 6.5 Paper strength DS Tension length [km] Tension strength Bursting strength Bursting strength [kpa] 3.5 DW 36 dgh 200 DS 0.03 (6%): in DW higher paper strength at notedly higher adsorption (both amylose and amylopectin) 17

18 3 Results Adsorption and molecular composition Adsorbed starch amount [mg/g] Adsorption isotherms DS 0.10 DW 36 dgh DRI [rel.] Chromatograms DS 0.10 Initial starch DS 0.10 Adsorbed starch in DW Adsorbed starch in 36 dgh Equilibrium concentration c e [µg/ml] Volume [ml] DS 0.10 (6%): in 36 dgh slightly more starch adsorbed, in DW mainly amylose adsorbed 18

19 3 Results Adsorption and molecular composition Molar mass distribution curves of DS 0.10 DS 0.10 in DW DS 0.10 in 36 dgh Differential weight fraction M W (10 6 ) [g/mol] Before adsorption Adsorbed starch 7.07 Differential weight fraction M W (10 6 ) [g/mol] Before adsorption Adsorbed starch Molar mass [g/mol] Molar mass [g/mol] 19

20 3 Results Distribution of substituents Chromatogram D S 0.10 from semi-preparativ e S EC Specif. charge distribution DS 0.10 C o n ce n tra tio n [ re l.] Fraction 1 Fr. 2 Fraction 3 Specif. charge (x )[g -1 ] amylopectin amylose Molar mass (x10 6 ) [g/mol] Fraction 1 Fraction 2 Fraction 3 0 Elu tio n time [min.] amylopectin amylose DS 0.10: amylopectin higher substituted than amylose 20

21 3 Results Water quality and paper properties 6 Paper strength DS 0.10 Tension strength Bursting strength 350 Tension length [km] Bursting strength [kpa] 2 DW 36 dgh 150 DS 0.10 (6%): in 36 dgh higher paper strength at slightly higher adsorption (both amylose and amylopectin) 21

22 3 Results Relation between DS, water quality and paper properties Tension strength 8 Tension length [km] tension length average deviation about km 1 D W M N a Cl 3 6 dg H M N a Cl Electrolyte content P W Native DS paper quality at 4% starch/pulp 22

23 4 Summary & Conclusion adsorption method is a suitable tool for investigation of polymer paper additives (under processing conditions) correlation between adsorption behaviour of cationic starch and paper quality interacting impact of DS and electrolyte content on adsorption and paper quality interacting impact of electrolyte content and initial starch concentration on adsorption probably there is an optimal amylopectin/amylose ratio of adsorbed starch for highest paper strength in low ionic strength derivatives with DS values between and 0.06 had best performance in terms of paper quality at higher ionic strength DS values between 0.03 and 0.10 were best for high paper strength (4% starch/pulp) investigations can contribute to improving efficiency of papermaking by optimisation of cationic starch in combination with other additives the research work will be continued with consideration of the common use of several additives 23

24 Acknowledgement FNR Fachagentur Nachwachsende Rohstoffe (Gülzow) Südzucker AG and Agrana (Mannheim/Ochsenfurt) and ZFT (Tulln) PTS (Heidenau) and all colleagues from department starch and molecular characterisation from Fraunhofer IAP (Potsdam-Golm) 24

25 Thank you for your attention 25