Yerabook 2010 fullcerig.pagora.grenoble-inp.fr/dossier/LGP2-yearbook... · in Figure 1.The polymer charge of PAE resin was determined from ... Yearbook 2010 FV 2010-06-10:Yerabook

Yearbook 2010 LGP2106

Éder José Siqueira+33 476 154 [email protected] : Pr. E.Mauret, Pr. N.Belgacem

The wet strengthening of papers is an important area inthe field of papermaking, even this grade of papers

represents only about 7% of the total production. In most cases, theseproducts correspond to a high added value segment of the paper market(banknote paper, filters, labels, etc) or to a segment that is growing rapidly(absorbing papers). In order to bring this wet-strength property to the paper,additives are generally introduced into the pulp suspension and adsorbedby the fibres. The adsorption occurs through attractive electrostaticinteractions. These chemicals must be well retained and react in order togive to the paper its end-use properties. However, the additives used todaymay impact environment; they are still used due to their efficiency and theirrelatively low costs compared to other possible treatments. Higherconstraints in environmental laws may impact this situation and newinnovative ways of treatments based on renewable resources have to beconsidered. On the other hand, the control of these phenomena still remainsdifficult mainly when part of the treated papers are re-pulped. Indeed, whenthe papers produced are no suitable, the papermakers recycled them backto the beginning of the process and high amount of chemicals andmechanical energy are necessary to disintegrate wet-strengthened papers.In this context, the project, will focus on the most important issues in thisarea. The first sub-project will be devoted to the recycling of wet-strengthpapers and the unit operation of disintegration as well as the use of properlychosen chemicals. In the second sub-project, the conditions for an optimaladsorption and reaction of the wet-strength additives will be investigatedand the third sub-project will be dedicated to the study of new alternativeand more environmentally friendly ways of treating papers.

Optimization of the manufacturingprocess of wet-strengthened papers

year

Background

Paper PhysicsConverting Biomaterial Packaging

2nd

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Wet strength is one of the most significant propertiesespecially for tissue paper, paper towel, banknote, liquid

packaging base paper and some printing grades. It is defined as the tensilestrength of cellulosic paper sheets re-wetted with water [1].Polyamideamine-epichlorohydrin resins (PAE) are commonly used wet-strength additive. The traditional PAE is synthesized from adipic acid anddiethylenetriamine by condensation followed by the addition reaction ofepichlorohydrin [1,5]. The obtained product contain: (i) the specific 3-hydroxy azetidinium groups which include quaternary ammonium structuresand are present at about 75% of the amideamine repeating units [1,3] and(ii) significant amounts of carboxylate groups as end groups ofpolyamideamine chains in PAE . The azetidinium rings (AZR) can react withcarboxylate groups to form esters especially at high temperatures. In thePAE aqueous solutions, partially cross-linked structures betweenpolyamideamine chains are present resulting in the formation of highly-dense PAE molecules [1,6], which are generally characterized by extremelylarge polydispersivity values [1,6]. The mechanisms of wet-strengthdevelopment of cellulose sheets prepared with PAE have been extensivelystudied, and reinforcement and protection mechanisms have beenproposed [1-5]. The former is the so-called reaction mechanism betweenAZR of PAE and carboxyl groups of cellulose fibers, which are present asminor functional groups. The latter is the formation of a second water-insoluble PAE network in the sheet, which may moreover inhibit, at leastpartially, hydrogen bond breakage in paper sheets re-wetted by water.Generally, 0.5-2% (of dry weight of pulp) PAE is added to pulp slurries asa wet-end additive in papermaking, and sufficient wet strength appears onthe PAE-treated paper after the drying process. Typically, paper treated withPAE resin retains at least 15% of the paper’s dry strength after completewetting with water.

A commercial aqueous PAEsolution (solid content 20 ± 0,5%)

was studied. The typical repeating unit in commercial solutions is showedin Figure 1. The polymer charge of PAE resin was determined frompolyelectrolyte titration using a particle charge detection apparatus Mütek

461 rue de la Papeterie BP65 - 38402 Saint Martin d'Hères Cedex - FranceTel 33 (0)4 76 82 69 00 - Fax 33 (0)4 76 82 69 33 107

Chemical processes

Paper physics

Printing processes

environment engineeering

Papermaking and

Converting Biomaterials

Packaging

Introduction

Resultsa.Characterization of PAE resin

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Yearbook 2010 LGP2108

PCD 3 (Mütek Analytic GmbH). PAE films were obtained by drying thePAE solution on a polyethylene plate for one week at 25oC and 50%humidity. The PAE films were then heated in an oven at 105oC fordifferent time intervals. FTIR spectra of PAE films heated and unheatedwere collected using a FTIR Spectrometer Paragon 1000 (Perkin Elmer)in ATR mode (Attenuated Total Reflection). Dynamic mechanicalproperties of PAE films were measured using a Rheometric System

Analyzer III (TA Instruments) intension cantilever mode (10 x 5 x 1mm) at 1Hz scanning at 2oC/min. Theglass temperature (Tg) was taken asthe temperature at the peak of the tanδ curve in the glass transition region.

PAE molecules, owing to the presence ofAZR, are cationic, thus facilitating adsorption

onto anionic pulp fibres, usually by an ion-exchange mechanism [3]. Thecharges of the PAE in aqueous solutions were determined bypolyelectrolyte titration and 0,001 N PES-Na polyelectrolyte solution wasused as an anionic standard polyelectrolyte. The titrant solution wasinjected until the PAE molecules in solution were neutralized to theisoelectric point. The measurements were carried out with dilutedsolution and at 20oC under different pH values. The calculated valueswere 3,164 meq/g at pH 3 and 1,633 meq/g at pH 7.

The heated and unheated PAE films weresubjected to FTIR analysis to detect whether

any structural changes of PAE molecules in the films occurred after theheating treatment. Figure 2 shows the spectra of a sample heated at105oC for 12 h and an unheated sample. Both heated and unheatedPAE films had typical amide I and II absorption bands at 1643 and 1550cm-1 respectively [8]. The decreased absorption band around 1060cm-1 for the heated film may be due to the opening of the azetidinium ring[7]. The increased absorption band around 1260 cm-1 for the heated PAEfilm may be due to amide linkages, which were formed between carboxylgroups at the end of polyamideamine chains and azetidinium groups in

b.Colloidal Titration

Éder José Siqueira

Figure 1: Typical chemical structure ofpolyamideamine epichlorohydrin.

c.FTIR analyses

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PAE films. Theabsorption band at1728 cm-1 may beattributed to C=Ostretching vibrationsof ester bonds [1].

The heated and unheatedPAE films were

characterized by DMA. These tests provide accurate assessment of thermaltransitions in the material. Figure 3 shows the dynamic mechanical analysisof two PAE films heated at 105oC for 10 min and 2 h, respectively. The PAEfilms present two relaxations next the glass transitions referred in theliterature to the polyamide and to the polyepichlorohydrin, thus confirmingthe formation of a copolymer during PAE synthesis. The films heated at105oC even 2 h show a shoulder near to first relaxation, which is believedto reflect the presence of different network phases in the microstructure ofPAE films. One can also observe an increase of the storage modulusattributed to the crosslinking process. Moreover, after two hours heating,the films showed a shift in the transitions and, at the same time, a decreaseless pronounced of the storage modulus that can be attributed to anincrease in the crosslinking density during thermal post-treatment at 105oCin the oven.

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Chemical processes

Paper physics

Printing processes

environment engineeering

Papermaking and

Converting Biomaterials

Packaging

d.Dynamic Mechanical Analysis (DMA)

Figure 2: FTIR spectra of heated and unheated PAE films preparedby casting of a PAE solution on polyethylene plates.

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Yearbook 2010 LGP2110

[1] Obokata, T., Isogai, A., The mechanism of wet-strength developmentof cellulose sheets prepared with polyamideamine-epichlorohydrin (PAE)resin, Colloids and Surfaces A : Physicochem. Eng. Aspects, 2007, 320,p.525.

[2] Bates, N. A., Polyamide-epichlorohydrin wet-strength resin II : astudy of the mechanism of wet-strength development in paper, TappiJournal, 1969, 52, p.1162.

[3] Espy, H. H., The mechanism of wet-strength development in paper :a review, Tappi Journal, 1995, 78, p.90.

[4] Wagberg, L., Björklund, M., On the mechanism behind wet strengthdevelopment in papers containing wet strength resins, Nord Pulp PaperRes. J., 1993, 8, p.53.

[5] Fisher, S. A., Structure and wet-strength activity of polyaminoamideepichlorohydrin resin having azetidinium functionality, Tappi J., 1996,79, p.179.

[6] Obokata, T., Isogai, A., Wet-strength development sheets withpolyamideamine epichlorohydrin (PAE) resin by physical interactions,

References

Éder José Siqueira

Figure 3: Log E’ vs. T and tan δ vs. T of thePAE films heated at 105oC for (A) 10 min and (B) 2 h.

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Nord Pulp Paper Res. J., 2009, 24, p.135.

[7] Russel, T. P., Piermarini, G. J., Miller, P. J., Pressure/Temperaturereaction phase diagram for dinitro azetidinium dinitramide, Journal ofphysical chemistry B, 1997, 101, p.3566.

[8] Cooper, S. J., Coogan, M., Everall, Neil, Priestnall, I., A polarized µ- FTIRstudy on a model system for nylon 66: implications for the nylon Brillstructure, Polymer, 2001, 42, p.10119.

461 rue de la Papeterie BP65 - 38402 Saint Martin d'Hères Cedex - FranceTel 33 (0)4 76 82 69 00 - Fax 33 (0)4 76 82 69 33 111

Chemical processes

Paper physics

Printing processes

environment engineeering

Papermaking and

Converting Biomaterials

Packaging

Yearbook 2010 FV 2010-06-10:Yerabook 2010 full 30/08/10 16:31 Page 111