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임완희(Wanhee Im),오규덕(Kyudeok Oh),Araz Rajabi Abhari,이지홍(Jee-Hong Lee),이학래(Hak Lae Lee) 한국펄프·종이공학회 2017 펄프.종이기술 Vol.49 No.5
To examine the most appropriate way for the evaluation of fold cracking of coated papers based on the image analysis method, various handsheets with different levels of ash contents were prepared and double coated. The effect of the ash level on handsheet properties was examined. Also the influence of ash level on fold cracking was tested to establish the most practical way to analyze the fold cracking of coated papers. Image analysis of the coating surface rather than coating cross section gave better results for fold crack evaluation. Fold angle of 30 degree and white and contrast values of 0/100 were found most appropriate for fold cracking evaluation.
충전물 선응집체 크기와 나노 바인더에 의한 도공지의 접힘터짐 변화
임완희(Wanhee Im),서동일(Dongil Seo),오규덕(Kyudeok Oh),정영빈(Young Bin Jeong),윤혜정(Hye Jung Youn),이학래(Hak Lae Lee) 한국펄프·종이공학회 2015 펄프.종이기술 Vol.47 No.5
Papermakers wish to increase the filler content of printing and writing grades because it allows saving in production cost through fiber replacement and improving the formation, and optical and printing properties of the paper. However, high filler loading in the base paper has negative side effects. It reduces the mechanical properties of paper and induces cracking at the fold after coating process. Fold cracking is one of the most frequent quality complaints for magazines, high quality books, etc. Two approaches were examined as methods to reduce fold cracking. One approach was to use preflocculated fillers, which was expected to reduce the fold cracking because it would decrease the interfiber bonding. The other approach was to use a new coating binder that gives greater binding power and thereby provides an opportunity of reducing the fold cracking of coated paper. When filler preflocculation was employed in producing the base paper, fold cracking becomes more severe than conventional filler loading condition. On the other hand, use of nano sized binder in coating improved the tensile properties of the coating layer and thereby decreased the crack area. It was shown that tensile properties of coating layer played an important role in fold cracking of coating.
고해와 카르복시메틸화의 복합 전처리가 펄프의 특성 및 셀룰로오스 나노피브릴 제조에 미치는 영향
임완희(Wanhee Im),이석호(Seakho Lee),이학래(Hak Lae Lee),윤혜정(Hye Jung Youn) 한국펄프·종이공학회 2017 펄프.종이기술 Vol.49 No.5
Cellulose nanofibrils have a big attraction because of unique properties such as high aspect ratio and specific surface area, high mechanical stiffness, biodegradability, and sustainability. One of limitations associated with the application of cellulose nanofibrils is the high energy demand during a nanofibrillation process. Various pretreatments have been proposed to reduce the energy consumption. In this study, a combined pretreatment of beating and carboxymethylation was investigated as a pretreatment to make the fibrillation easy and to reduce energy consumption. The sequence and severity of the pretreatment were controlled, and pulp properties and nanofibrillation degree were evaluated. The combined pretreatment of carboxymethylation and beating was more effective in terms of energy saving than the single carboxymethylation chemical treatment. However, economic feasibility of the combined pretreatment to produce cellulose nanofibrils should be evaluated in a mill scale.
카르복시메틸화 전처리에 따른 셀룰로오스 나노피브릴의 특성
임완희(Wanhee Im),이석호(Seakho Lee),박현지(Hyeonji Park),이학래(Hak Lae Lee),윤혜정(Hye Jung Youn) 한국펄프·종이공학회 2016 펄프.종이기술 Vol.48 No.6
Cellulose nanofibrils (CNF) are considered prospective material in a sustainable society due to its several technically attractive properties and renewable characteristics. However, the isolation of CNF by mechanical processes still requires high energy consumption. Chemical pretreatment of cellulose may provide an opportunity of decreasing energy consumption for CNF production. In this study, carboxymethylation which introduces carboxyl groups to hydroxyl groups was considered. The carboxyl contents of pulp fibers was greatly affected by chloroacetic acid amount and reaction temperature. Never-dried pulp fibers showed higher carboxyl content than once-dried pulp. The charge properties of pulp fiber such as carboxyl group contents had a strong influence on energy consumption to isolate CNF. As the carboxyl content of pulp fibers increased, the required grinding pass number for the production of cellulose nanofibrils was significantly reduced and the resultant cellulose nanofibrils had smaller and more uniform width.