Prevention of Vessel Picking Trouble by the Stratified Sheet Formation
- Resource Type
- Journal Article
- Authors
- Hiroki Nanko; Junji Ohsawa; Shun-ichiro Mukoyoshi
- Source
- JAPAN TAPPI JOURNAL. 1987, 41(9):823
- Subject
- JPRI Multi-head
Multi-layered handsheet
Stratified sheet formation
Vessel picking
- Language
- English
- ISSN
- 0022-815X
1881-1000
Vessel picking troubles of printing papers made from tropical hardwood pulps can be easily prevented by covering vessel elements with several fibers. This paper deals with the effect of covering layer on vessel picking.Using multi-layered handsheet forming device (JPRI Multi-head) two-layered sheets consisted of a thin surface layer and a thick bottom layer were prepared. Non-vessel picking pulps such as Buna (beech) or softwood BKP were used for the surface layer. Lauan BKP which contains large vessel elements was used for the bottom layer. Vessel pick tendency was evaluated by IGT printing test.The extremely thin surface layer of 2g/m2 of Buna BKP can effectively prevent picking, where single vessel element is covered only by 4 to 7 fibers. Softwood BKP also has the same effect as Buna BKP. This means that vessel pick phenomenon is controlled by small amount of fibers covering vessels. These fibers play the roll of fixing vessels on the sheet surface and of preventing initial lifting of vessels which leads to complete destruction of vessel-to-under layer bonding.Stratified sheet formation with single hydraulic headbox appears to be the most promising technology for vessel pick prevention, because it can perfectly prevent vessel picking without limitation of pulp woods used for the mid layer of the sheet.