Multi-ply forming of linerboard by successive twin-wire roll forming
Bengt Nordström, SCA R&D Centre, Sundsvall, Sweden
An analysis of the requirements for multi-ply forming of linerboard suggests successive twin-wire roll forming as a preferable method. This involves roll forming of the second and subsequent plies directly onto the previously formed web.
Successive two-ply forming in roll units was evaluated in a pilot machine investigation using a testliner furnish. In the first section of the investigation, Z-strength of the two-ply paper was shown to be insensitive to the dry solids content of the first ply when applying the second ply for dry solids contents up to at least 17%. The results moreover suggest that the ply adhesion did not limit the Z-strength of the two-ply paper.
The second section dealt with effects of the speed difference between fiber suspension and wire, as changed simultaneously for both plies by the wire speed. The possibility to obtain a low anisotropy was demonstrated by an MD/CD-ratio for tensile strength down to about 1.5 and an even lower ratio for compression strength.
The Ambertec formation, tensile strength, and burst strength that were obtained with the present two-ply forming correspond to the formation and strengths observed for single-ply roll forming at a lower grammage, with similar headbox consistency and furnish.
Nordic Pulp & Paper Research Journal (NPPRJ) is an international scientific magazine covering science and technology for the areas of wood or bio-mass constituents, pulp and paper and including new fiber-based materials, recovery and by-products from pulping processes, bio-refining and energy issues. Articles meeting required scientific standards are accepted from any continent. Open Access: Articles not available through Gold Open Access may be purchased by credit card as a pdf file, to be downloaded within 24 h after ordering, at a price of 22 EUR per article. (Value added tax may apply depending on your location, which you enter at payment logout.) Such articles have Green Open Access, i.e. authors may share articles on their personal non-commerical homepage immediately after publication on the website and download them to non-commercial hosting platforms one year after publication in a full issue of NPPRJ. ISSN: 0283-2631