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Office papers stability during accelerated ageing.

1. Introduction

Almost all of the paper that is used today is made of wood fibres (Stenius, 2000). Besides fibres as main ingredients for paper manufacturing, pigments/dyes, adhesives, additives, fillers, starch and other chemicals are necessary. According to paper type these materials are added in bigger or smaller quantities (Neimo, 1999). Paper products are an important part of everyday life (households, offices and industry). Nearly all paper is eventually thrown away. The use of recycled fibres for paper manufacture is highly desirable.

The paper recycling process include wash, remove and bleach of unwanted particles from collected printed paper so that it can be sold as an alternative to virgin paper (Behin & Vahed, 2007). Because of their physical and chemical characteristics surfactants are widely used in some subprocesses of recycling. The type of surfactant employed depends on requirements like removal of dirt from fibres and surfaces, conditioning of fibres or structuring of products.

A surfactant is a molecule with two distinct regions--a water soluble polar head and a non polar hydrocarbon tale which is sparingly soluble in water. There are three types of polar heads: ionic (cationic and anionic), zwitterionic and non-ionic. However, anionic and nonionic surfactants are more commonly used (Zhao et al., 2004). Surfactants will be absorbed at an air-water or oil-water interface and at the surface of a solid. The long hydrocarbon tail interacts with fats and oils whilst the water soluble head group bonds with water. This action removes and captures dirt particles, and prevents their re-deposition.

Paper optical characteristics in graphic profession are extremely important. Because of different phases of recycling process, as well as paper ageing (Jaaskelainen & Liitia, 2007), optical characteristics are significantly changed. Surfactant as well plays an important role in the optical properties.

Only light, which is absorbed by a molecule may lead to chemical reaction. Pure cellulose absorbs visible light only to a small extent, while absorption in near UV spectral region is more pronounced. It is therefore light mainly in the spectral range 300--550 nm which induces most of the damage in cellulose during exposure to electromagnetic radiation (Strlic & Kolar, 2005).

Paper is widely used everyday, not just in photocopying purposes, but for handwriting and printing documents used for archiving during long period of time. In paper industry tendency is to use higher amount of recycled fibres. For secondary fibres production it is necessary to applied chemical treatments with different surface active agents.

The purpose of this paper was to examine the surfactants influence on the optical characteristics of office papers, one made from recycled fibres and two from mixed sources (IQ & Navigator) exposed to accelerated ageing. Extra research was made with filter paper at the same experimental conditions for better understanding the surface active agent influence on that chosen samples. Filter paper is made from virgin fibres only and doesn't contain other components which are necessary in office paper production and can interact with surfactants.

2. Experimental

Office paper made from recycled fibre, two office papers made from mixed sources (IQ & Navigator) and filter papers were used like experimental samples.

Quantity of most common used filler calcium carbonate in original office papers, were measured by alkalimetric titration. Ash amount was experimentally defined by burning dry paper samples at 920[degrees]C.

The samples have been separately soaking (10 minutes) in three different surfactants solution: i) sodium lauryl ether sulfate, SLES, (anionic), ii) cocamidopropyl betaine, CAPB, (zwitterionic) and iii) fatty alcohol etoksylate, FAE, (nonionic) for two surfactant mass fractions (1.0%, 2.5%).

The samples were dried naturally at room temperature and after that accelerating ageing by electric lamp that emits visible and near ultraviolet electromagnetic radiation was performed. Examined samples were exposed to radiation in time interval of 90 minutes.

Papers reflectance measurements were processed using X-rite Spectrophotometer, Digital Swatchbook in the interval of the wavelengths from 410 nm to 700 nm for every 10 nm. These measurements were supported by ColorShop 2.0 software and analysed by Technical Graphic Origin 6.0 Professional. The reflectance measured over white background was the basis for the evaluation of optical properties of experimental samples. In purpose of better evaluation, reflectance spectra of non soaked samples, called original sample, were measured also.

3. Results and discussion

Spectral reflectance data for non aged and aged filter papers soaked in surface active agent (SAA) solution are presented at Fig.1., [w.sub.SAA] = 1.0 % and Fig.2., [w.sub.SAA] = 2.5 %.

[FIGURE 1 OMITTED]

The results have shown higher reflectance values of non aged original filter paper in relation with aged original filter paper. Reflectance values of original filter paper exposed to UV radiation are significantly reduced. The highest reduction is noted for the wavelengths lower than 550 nm.

Ageing of filter paper which is made from virgin fibres only and doesn't contain other components (additives like fillers and pigments) is a good example of breaking bonds in paper. Ageing is accelerated with paper exposure to direct sunlight or UV-light. The cause of that appearance is breaking a C-C or glycoside bond in paper. The respective wavelengths are 346 and 478 nm. Thus UV-light with wavelength lower than 300 nm will split covalent and hydrogen bonds in paper quite efficiently (Neimo, 1999). The reflectance values of filter paper soaked in surfactants solution are increased for the wavelengths lower then 460 nm and decreased for the wavelengths higher then 460 nm in comparison with original filter paper. Filter paper reflectance values, soaked in surfactant solution ([w.sub.SAA] = 1.0 %), are reduced in comparison with original for the wavelengths higher then 450 nm, while the reflectance values of aged soaked filter paper are extra reduced for the same wavelengths. In the visible part of spectra by wavelength lower than 550 nm soaked filter paper reflectance differences before and after ageing are significantly lower than original reflectance differences (Mikac Dadic et al., 2003).

Increasing the surfactant mass fractions leads to soaked filter paper reflectance values increase for wavelength lower than 460 nm and to reduce reflectance values at wavelength higher than 460 nm in comparison with non aged original (Fig. 2.).

[FIGURE 2 OMITTED]

Reflectance of soaked filter paper is slightly changed by ageing. Reflectance differences of soaked filter paper before and after ageing are reduced with increasing of surfactant mass fractions (Fig. 1. and Fig. 2.).

It could be assumed that by soaking filter paper in surface active agent solutions adsorption of surfactant molecules on fibres is achieved. Adsorbed molecules of surfactants, whatever their constitution (ionic, non-ionic or zwitterionic) is, slightly decrease reflectance of non aged original filter paper (expect in the blue part of spectrum, from 410 to 460 nm) and increase reflection of aged original filter paper (especially in the blue green part of spectrum, from 410 to 550nm). It is observed that all examined surfactants stabilized chemical-physical processes in the filter paper structure.

Spectral reflectance data for office paper made from recycled fibres soaked in surface active agent solutions are presented at Fig. 3., [w.sub.SAA] = 1.0 % and Fig. 4., [w.sub.SAA] = 2.5 %). reflectance of aged original office paper made from recycled fibres is slightly reduced for wavelength lower than 550 nm, and increased for wavelength higher than 500 nm (Fig. 3.) in comparison with non aged original. It is interesting that reflectance differences for aged and non aged original photocopy paper made from recycled fibres are significantly smaller then for original filter paper (Fig. 1. and Fig. 3.).

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

Reflectance differences of soaked office paper made from recycled fibres before and after ageing are higher with increase of surfactant mass fractions (Fig. 3., Fig. 4.), especially at wavelength lower than 500 nm.

The same chemical treatment for filter paper and office paper made from recycled fibres in used solutions of surface active agents has shown approximately the same reflectance variance in comparison with original non aged samples of those papers. Molecules of used surface active agents stabilise those samples during accelerated ageing.

Spectral reflectance data for IQ office paper are presented at Fig. 5. and for Navigator office paper at Fig. 6.

Reflectance values of original IQ paper exposed to near UV radiation are reduced in comparison with non aged original IQ paper (Fig. 5.). The highest reduction is noted for the wavelengths lower than 500 nm (aprox. 10% at 450 nm). The reflectance values of non aged IQ paper soaked in all surfactants solution ([w.sub.SAA] = 1.0 %) are more or less the same as for non aged IQ original.

[FIGURE 5 OMITTED]

With ageing reflectance of soaked IQ office paper is significantly changed after soaking in all surface active agent solutions. For the wavelengths lower than 500 nm reflectance values for samples soaked in fatty alcohol etoksylate solution are decreased, but for samples soaked in sodium lauryl ether sulfate and cocamidopropyl betaine solutions reflectances are increased in relation with aged original IQ office paper.

UV radiation influence on original Navigator paper is venial what indicate on quality of that office paper (Fig. 6.). Nonaged and aged original Navigator papers have the same reflectance spectra. Chemical treatment of Navigator paper in cocamidopropyl betaine solution had caused slightly increasing of reflection values for non aged sample in comparison with original and Navigator samples soaked in sodium lauryl ether sulfate and fatty alcohol etoksylate solution. On the other hand, reflectance value for Navigator sample soaked in sodium lauryl ether sulfate and fatty alcohol etoksylate solution are significantly decreased but for samples soaked in cocamidopropyl betaine solution there is not reflectance value change in comparison with aged original Navigator office paper.

In a whole measured wavelengths interval spectral reflectance data for original IQ and Navigator papers are totally different from ones for original filter paper and office paper made from recycled fibres. The reflectance spectra of both of examined office papers are very similar, so it is possible to conclude that they have similar chemical composition. High values of brightness ([R.sub.457] = 1.10) is consequence of fluorescent whitening agent (organic material) and low reflectance values from 520 to 620 nm is caused by blue-lilac dye.

[FIGURE 6 OMITTED]

IQ and Navigator office papers are made from mixed sources fibres. Unlike office paper made from recycled fibres, they contain higher amount of calcium carbonate as filler. Percentage of calcium carbonate in Navigator is 23.8%, IQ 17.9% while in office paper made from recycled fibres is only 8.2%. Fillers are used to the largest extent in various printing and writing paper grades. Typical values for calcium carbonate as filler in different uncoated fine papers like copy, ink-jet and laser print are about 20 to 25% (Neimo, 1999).

One of the most common used filler type in paper is clay, alkaline aluminium silicate. IQ ash amount is 36.42% (27.53% calcium oxide) and Navigator is 13.37% (99.74% calcium oxide), so IQ paper contains some other inorganic filler (most probably clay). As we can see from our results amount of inorganic and organic compound of paper have great influence on changes in optical characteristics which are caused by accelerated ageing.

4. Conclusion

Near UV and visible electromagnetic radiation have significant influence on filter paper made only from virgin fibres without any additives (calcium carbonate, clay, dye, starch, pigment) decrease reflectance value of those papers, especially in blue part spectra. After chemical treatment with examined surface active agents these samples become optical stabile. Adsorbed molecules of surface active agents act like virgin fibre conservators and protect virgin fibre network from accelerated ageing.

Office paper made from recycled fibres has low brightness value ([R.sub.457] [approximately or equal to] 0.72). The recycled fibres are chemically saturated by previously done recycled process and adsorption of surface active agents is low. chemical treatment of those samples has no influence on their reflectance spectra and accelerated ageing has no influence on their optical properties either (reflectance values are even slightly higher after ageing).

Chemical treatment of Navigtor and IQ office papers shows different behaviour caused by different amount of calcium carbonate and other inorganic compounds. From all used surfactants zwitterionic cocamidopropyl betaine stabilize degradation of both office papers made from mixed sources under accelerated ageing.

It is obvious that chemical composition of paper fillers and surface active agents has important influence on stabilisation possibility of office paper during accelerated ageing. For our futhure work we planed to analyse more office paper available on global market to compare there optical stability and then to create longlife paper data base accessiable for paper industry.

DOI: 10.2507/daaam.scibook.2009.35

5. References

Behin J. & Vahed Sh. (2007). Effect of alkyl chain in alcohol deinking of recycled fibres in flotation process. Colloids and Surfaces A, Physicochemical and engineering aspects, Vol. 297, No. 1-3, (2007) (131.-141.), ISSN 0927-7757

Jaaskelainen, A-S. & Liitia (2007). UV/vis reflectance spectroscopy reveals the changes in fibre chemistry during ageing. SpectroscopyEurope, Vol. 19, No. 5, (October / November 2007) (11.-13.), ISSN 0966-0941

Mikac Dadic V.; Dzimbeg-Malcic V.; BolanCa I. & BolanCa Z. (2003). Optical characteristic of prints exposed to natural and accelerated ageing. DAAAM International Scientific Book, ISBN 3-901509-30-5, (July 2003) (401.-414.), ISSN 1726-9687

Neimo L. (1999). Papermaking Chemistry, Fapet Oy, ISBN 952-5216-04-7, Helsinki, Finland

Stenius, P. (2000). Forest Products Chemistry, Fapet Oy, ISBN 952-5216-03-9, Helsinki, Finland

Strlic, M. & Kolar J. (2005). Ageing and stabilisation of paper, ISBN 961-6551-03-5, Ljubljana, Slovenia

Zhao, Y.; Deng, Y. & Zhu, J.Y. (2004). Roles of Surfactants in Flotation Deinking. Progress in Paper Recycling, Vol. 14, No. 1, (November 2004) (41.-45.), ISSN 1061-1452

This Publication has to be referred as: Plazonic, I[vana]; Barbaric-Mikocevic, Z[eljka] & Dzimbeg-Malcic, V[esna] (2009). Office Papers Stability During Accelerated Ageing, Chapter 35 in DAAAM International Scientific Book 2009, pp. 333-340, B. Katalinic (Ed.), Published by DAAAM International, ISBN 978-3901509-69-8, ISSN 1726-9687, Vienna, Austria

Authors' data: B. Sc. Plazonic, I[vana]; Dr.Sc. Barbaric-Mikocevic, Z[eljka]; Dr. Sc. Dzimbeg-Malcic, V[esna], Faculty of Graphic Arts, University of Zagreb, Getaldiceva 2, 10000 Zagreb, Croatia, ivana.plazonic@grf.hr, barbaric@grf.hr, vesna.dzimbeg.malcic@grf.hr
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Title Annotation:Chapter 35
Author:Plazonic, I.; Barbaric-Mikocevic, Z.; Dzimbeg-Malcic, V.
Publication:DAAAM International Scientific Book
Article Type:Report
Geographic Code:4EXCR
Date:Jan 1, 2009
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