Graduate Thesis Or Dissertation

 

Understanding the chemistry of rosin sizing and developing new sizing technologies Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9593v046x

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  • First, a thermodynamic analysis was carried out upon a sizing-desizing process. The energetic analysis shows that rosin soap size should be bound to fibers through primary chemical forces such as covalent bonds to effect sizing. Secondary chemical forces are all thermodynamically unstable to the attack of water molecules. It is also shown that the stronger the bonding between size and fibers is, the higher the degree of sizing of paper can be. Then ferric and ferrous ions were investigated as mordants for rosin soap size. While ferric ion at pH 3.0 to 4.0 and ferrous ion at pH around 5.5 are able to induce a very high level of sizing to unbleached Douglas-fir kraft pulp, they have virtually no effect on bleached Douglas-fir kraft pulp and bleached hardwood chemical pulp. The reason is believed to be due to the difference in lignin content of the unbleached and bleached pulps. Two possible structures of the complex formed between these transition metal ions and lignin are postulated. The excellent sizing results induced by iron ions in mechanical pulp strongly support this hypothesis. Finally, metal ions Mg²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Cu²⁺ and Zn²⁺ are used with polyamines as mordants of rosin soap size. While Mg²⁺/PEI and Mn²⁺/PEI shows no effect and Fe³⁺/PEI is very effective in an acidic pH range, Zn²⁺/PEI can induce moderate sizing and Fe²⁺/PEI and Cu²⁺/PEI can induce very high levels of sizing under neutral to alkaline conditions (up to pH 10 with Cu²⁺ /PEI) in various pulps. The incorporation of polyamines can also greatly improve the sizing efficiency when alum is the mordant. The tensile and bursting strength of the handsheets can also be improved by 20-30% with these mordants. It is observed that the pH of maximum sizing efficacy of these metal ions is in the vicinity of their pK₁ values. In addition, their performances as mordants of rosin soap sizing coincide with the Irving-Williams Effect which describes the general trends in the stability of metal complexes.
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