Paper making and fiber liberation – Processes and products
Patent
1991-07-09
1993-11-16
Jones, W. Gary
Paper making and fiber liberation
Processes and products
162142, 162158, D21H 2300
Patent
active
052620050
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a paper product of the kind being dry-defibered and converted to fluffed state for manufacturing thereof, for example, sanitary articles, such as napkins and sanitary towels.
BACKGROUND OF THE INVENTION
Materials of this kind have long been used for the manufacture of products of the kind in question, and are produced and marketed in the form of sheets or rolls. As fibre material, sulphite or sulphate pulp and also chemimechanical pulp, so-called CTMP, are used.
These products conventionally are produced in the wet way in that a fibre suspension is dewatered on a wire, pressed and dried. The dried web is reeled up or cut to sheets. As a starting material sulphate or sulphite pulp or chemimechanical pulp (CTMP) are used. The pulps made in this way are sold as so-called roll or sheet pulp.
The pulps alternatively can be sold in web shape after flash drying of the fibres. At flash drying the pulp fibres are dried in a fan drier. A pulp web is hereby pressed to about 50% dry solids content and torn so that individual fibres or fibre flocks are detached and thereafter dried when passing through the piping of the fan drier. The flash dried pulp then is pressed to bales. The resulting product has a high density, which offers transport-technical advantages compared with reel or sheet pulp. The transport economy of reel pulp, moreover, is made worse by the fact that cylindrical rolls have a low packing degree.
The chain of manufacture for soft absorption materials, such as napkins and towels, starts with the dry defibering or tearing of sheet, reel or bale pulp in order to detach the individual fibres bound in the sheet, web or bale. Due to their low moisture content, the pulp fibres then are relatively brittle. When there is a high bonding strength between the fibres in sheet, reel or bale pulp, the risk is great that the fibres will be damaged at the dry tearing and that much undesirable so-called fine material or dust will be formed. This is due to the fact, that a high bonding strength between the fibres implies high defibering energy. The producers of reel and flash dried pulp, therefore, are required to try to produce a product which can be torn as easily as possible, with weak fibre bonds in the product, which, however, must meet certain strength requirements for having good runnability in the defibering equipment. In order to obtain a product easy to tear, the roll or sheet manufacture in the commercial processes of to-day must increase the bulk of the product, which then also deteriorates its transport economy.
These problems are solved by the present invention.
SUMMARY OF THE INVENTION
The invention, thus, relates to a produce easy to defiber which substantially contains cellulose-containing fibre material, which at defibering can easily be converted to fluffed state and used in the manufacture, for example, of products for sanitary purposes, such as napkins and towels, and filters. This web-shaped product has such a strength that it can be reeled up or handled in sheet shape for storing and transport, without the addition of chemicals for increasing the bonding strength between the fibres.
According to the invention, the product has a density of 550-1000 kg/m.sup.3, preferably 550-700 kg/m.sup.3, a bursting index of 0.15-0.50 MN/kg, preferably 3.20-0.40 MN/kg and a grammage of 300-1500 g/m.sup.2, preferably 500-1000 g/m.sup.2, the product having a dry solids content of 70-95%.
The values are determined according to the following standards issued by the Scandinavian Pulp, Paper and Board, Testing Committee.
______________________________________ Density SCAN-P 7:75
Bursting strength SCAN-P 24:77
Grammage SCAN-P 6:75
Dry solids content SCAN-P 4:63
______________________________________
According to an important embodiment of the product according to the invention, the cellulose-containing fibre material is a lignocellulose high yield pulp, i.e. a pulp manufactured in a yield exceeding 90%.
According to an espicially important embodiment, t
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Eriksson Lennart
Hagglund Tjell-Ake
Hoglund Hans
Kolar Milan
Jones W. Gary
Lamb Brenda
SCA Pulp AB
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