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The Origin and Generation Mechanism of GlcA during Alkaline Peroxide Bleaching of Aspen CTMP

Author: HuoDan
Tutor: QinMengHua
School: Shandong Institute of Light Industry
Course: Pulp and Paper Engineering
Keywords: aspen CTMP alkaline peroxide bleaching uronic acid glucuronic acid
CLC: TS745
Type: Master's thesis
Year: 2011
Downloads: 30
Quote: 0
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Abstract


More high yield pulp was used for the production of value-added paper, due to its less investment, high yield and low water consumption in recent years. Aspen is one of the most suitable hardwood for mechanical pulp production, The chemical thermomechanical pulp （CTMP） was one of the most popular high yield pulping, while there was more dissolved and colloidal substances （DCS） released into the process water. The accumulation of anionic groups （AGs） in the process water systems can lead to various problems for the papermaking process and properties of final paper. Uronic acids included glucuronic acid （GlcA） and galacturonic acid （GalA） are the most important AGs in high-yield pulps. However, few studies on GlcA, in particular, about the generation mechanism and behavior of GlcA in alkaline peroxide bleaching of CTMP were reported. Therefore it is important to study systematically the uronic acid especially GlcA in aspen chemimechanical pulp, for the optimization of pulping and papermaking process.The origin and generation mechanism of GlcA during alkaline peroxide bleaching of apsen were studied in the paper. The effects of various factors on the release of uronic acids during bleaching process were evaluated. The effects of uronic acids on the physical properties of final pulp were also discussed.The result showed that a large amount of GlcA existed in the fibres of bleached aspen CTMP, as well as DCS. The increase of GlcA in pulp fibres may be due to the following reasons: a small amount of the glucose in the long chains of fibres was oxidized to GlcA during alkaline peroxide bleaching, GlcA in LCC was exposed during alkaline peroxide bleaching. The origin of GlcA in DCS may result from that the degradation and release of 4-O-methylglucuronic acid in hemicelluloses and glucuronic acid in LCC. The glucose monomer in DCS can not futher oxidized into GlcA.The release of uronic acids was mainly affected by the system alkalinity. The effect of H2O2 on the release of uronic acids is not obvious. But more H2O2 will further oxidize uronic acids to low molecular carboxylic acid derivatives, resulted in slightly decreasing the content of uronic acids in DCS is lower. A majority of uronic acid could release into the pulp system at the initial stages of bleaching. High bleaching temperature could promote the release of uronic acids. The influence of different model compounds of uronic acid, including GlcA, GalA and Poly-GalA, on the paper properties was also discussed. The result showed that adding uronic acid in the pulp will lead to decrease the breaking length and burst index, and increase the bulk index of final paper. Mono-GalA will lead to the increase of tearing resistance, while the poly-GalA will decrease the tearing index of final paper.

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CLC: > Industrial Technology > Light industry,handicrafts > Paper Industry > Pulping process > Bleach
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