Paper making and fiber liberation – Processes and products – Multi-layer waterlaid webs or sheets
Patent
1992-12-16
1995-04-04
Zirker, Daniel R.
Paper making and fiber liberation
Processes and products
Multi-layer waterlaid webs or sheets
162123, 428247, 428481, D21F 1100, D21F 1108
Patent
active
054034434
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention deals with a cardboard having a high resistance to tearing and a method to manufacture such a cardboard.
BACKGROUND OF THE INVENTION
For any type of packaging suitable for load-carrying functions of the packaged material, it is nowadays customary to utilize so-called Kraft liners from carton. These Kraft liners are distinguished by a high tearing resistance and preferably consist of long fiber cellulose. In order to manufacture such Kraft liners it is therefore necessary to use long-fibered wood, for instance pine or fir. These long-fibered types of timber have however the property of growing very slowly, so that the steadily increasing requirement for such packaging always results in irreparable damage being done to the woodlands or forest stands.
The above disadvantages occur not only in the manufacture of tear-resistant cartons, rather in other types of cardboard or carton, since it is always necessary to use pure natural timber for achieving adequate strength, wherein in each application case appropriately dimensioned cartons with a sufficient wall thickness must be used, which correspondingly increases the consumption of wood or timber. Another disadvantage in the know carton manufacture lies in that very large quantities of water are required in its manufacture, which is not justifiable from the environmental effect point of view and from the foreseeable development of the water reserve.
SUMMARY OF THE INVENTION
It is a task of the invention to create a solution by means of which cardboard or paper board can be made available maintaining the necessary strength standards, which require considerably less natural timber or even none at all for its fabrication and whose fabrication overall is much more environment friendly.
This task is solved in the invention by cardboard having high resistance to tearing incorporating at least two layers from cellulose, in between which a woven-fabric layer or scrim from natural or synthetic fibers is disposed, wherein the cellulose layers and the scrim are configured as composite members formed in the moist state.
The invention enables to make a tear-resistant carton or cardboard available, which, with the same or better strength properties compared to conventional cardboard, requires a considerably lower share of cellulose, meaning the cardboard can be fabricated with considerably lower material consumption and with a considerably smaller carton thickness, which however has the same strength properties. Herein there is formed a composite member by the interconnection of moist viscous cellulose layers with the interposed scrim from natural or synthetic fibers and subsequent pressing, meaning the fibers of the two layers interengage and engage into the scrim, so that a completely uniform member is formed in a single manufacturing step. Herein because of the deposition of the textile layer or scrim, the resistance to tearing of the cardboard is approximately the same in all directions. Because of the considerably lower cellulose share compared to known cardboard (Kraft liners) the energy- and water consumption can also be decisively reduced.
It is particularly advantageous if the cellulose layers consist of waste paper. Compared to the known such cartons, where waste paper cannot be used, since the cellulose fibers of waste paper are comparatively short fibers and therefore do not exhibit the required strength properties, it is possible in the invention to utilize only waste paper, since the strength of the carton is provided solely by the intimate connection between the cellulose fibers and the enclosed netting. At the same time the consumption of energy and water in manufacture can be still additionally reduced by using waste paper. For the scrim it was shown to be particularly advantageous to utilize a natural fiber from cotton, wool or silk or synthetic fibers from polyacrylonitrile, which is generally known as DRALON.TM., or polyester.
It is advantageously provided for increasing the strength and improving the formation o
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1004 Abstract Bulletin 59(1988) Jul., No. 1, Appleton, Wis., "Strength Properties of Filament Reinforced Paperboard Packaging".
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