A novel method of studying the ability of a coating layer to retard the photo-yellowing of the base paper

Fjellström, Helena; Höglund, Hans; Forsberg, Sven; Rolfson, Ola; Rundlöf, Mats

doi:10.3183/npprj-2007-22-03-p343-349

Cited by 2 publications

(6 citation statements)

References 15 publications

(20 reference statements)

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“…Fig 2 shows the transmittance factor, T F , as a function of coat weight for a kaolin clay pigment (Astra-Plus) and a ground calcium carbonate pigment (Carbital 90) before and after bleaching. As known from earlier work (Fossum et al 1976;Fjellström et al 2007a;Fjellström et al 2007b) Table1. Data for the kaolin and calcium carbonate (GCC, PCC) pigments used in this work as obtained from Imerys.…”

Section: Transmittance In the Uv-region (300-385 Nm)supporting

confidence: 54%

“…A novel method for studying the reflectance and transmittance of thin coating layers has been used to determine the UV-screening properties of the consisting components. The methodology has been thoroughly described in Fjellström et al (2007a), for instance the significance of transmittance measurements at low coat weights and the possibility to determine light scattering and light absorption characteristics of coating layers. Table 1 shows some characteristic properties (brightness, particle size and distribution and surface area) of the kaolin and calcium carbonate pigments used in this work.…”

Section: Resultsmentioning

confidence: 99%

“…To account for the specific conditions set by the instrument and the procedures, the optical values are referred to as transmittance factors or reflectance factors. For detailed information of the UV-VIS diffuse reflectance spectroscopy measurements, see Fjellström et al (2007a).…”

Section: Uv-vis Diffuse Reflectance Spectroscopymentioning

confidence: 99%

“…The coating layer was dried at room temperature before UV-VIS spectroscopic analysis. The basis weight (g/m 2 ) of the coating layer was determined as previously reported in Fjellström et al (2007a).…”

Section: Coating Proceduresmentioning

confidence: 99%

“…kaolin clay, calcium carbonate, talc) to synthetic inorganic or organic products (e.g., plastic and silica type products). Kaolin clay has been reported to be somewhat more effective in retarding the accelerated light-induced yellowing compared to a coating layer containing calcium carbonate pigments (Fossum et al 1976;Reinhardt, Arneberg 1988;Fjellström et al 2007a;Fjellström et al 2007b). Luo and Göttsching (1991) reported that kaolin was somewhat more effective in retarding the photo-yellowing of a base paper intended for light weight coated paper grades than a brighter calcium carbonate pigment.…”

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Coating

Fjellström

Höglund

Paulsson

et al. 2009

Nordic Pulp &Amp; Paper Research Journal

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SUMMARY:The ability of coating colours to obstruct ultraviolet (UV) radiation in the 300-385 nm region was examined with the aim of finding the best photo-stabilising formulation to inhibit discoloration of high-yield pulps. The influence of pigment type, bleaching of the pigments, pigment size, pigment size distribution, type of binder and addition of UV-absorbing compounds were examined using a newly developed method for studying the reflectance and transmittance properties of thin coating layers.The pigment type and coat weight was found to be the most important factors for reducing the transmittance of UV-radiation. Kaolin clays were more effective than calcium carbonate pigments and are therefore a better coating pigment for photostability reasons. Bleaching of the pigments, resulted in an overall minor decrease in transmittance for both kaolin and ground calcium carbonate (GCC) pigments, especially at low coat weights. Bleaching of the pigments changed the particle size distribution somewhat, which probably alters the structure in the coating layer. Precipitated calcium carbonate (PCC) pigments have a higher UV-screening potential compared to GCC pigments and should therefore be a better choice among the calcium carbonates. It was further concluded that a narrow pigment size distribution was beneficial for reducing the amount of transmitted UV-radiation that reaches the base paper. Styrene butadiene latex and polyvinylpyrrolidone were better in reducing the transmittance in the UV-region than polyvinyl alcohol.Adding a fluorescent whitening agent to a coating colour decreased the transmittance in the UV-region when the pigment was of the GCC type, and increased the transmittance when kaolin pigment was used. Addition of titanium dioxide (3 parts) to a coating colour containing kaolin pigment blocked about 90% of the UV-radiation at a coat weight of 10 g/m 2 , which is a common coat weight for a single coated paper. Another possibility is to double coat to increase the coat weight, which turns the transmittance factor closed to zero.

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Section: Transmittance In the Uv-region (300-385 Nm)supporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Section: Uv-vis Diffuse Reflectance Spectroscopymentioning

confidence: 99%

Section: Coating Proceduresmentioning

confidence: 99%

mentioning

confidence: 99%

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