MULTI-LAYER MATERIAL FOR PRESS MOLDING, A DELIVERY SYSTEM AND A RESULTING FIBER PRODUCT

Abstract

The present invention relates to a multi-layer material for press molding, a delivery system and a resulting fiber product. Also, a method for recovery is disclosed.

Claims

1. A multilayer substrate comprising at least one layer providing tensile strength and one layer containing fibers with an internal strength low enough to be formed in a press forming operations, forming new bonds in, at least partly, new relative positions.

2. A multilayer substrate according to claim 1 wherein said layer providing tensile strength provides a tensile strength that is at least about 10%, preferably at least about 20%, most preferred at least about 50%, higher than the tensile strength of the other layer.

3. A multilayer substrate according to claim 1, wherein said substrate is at least a three-layer material.

4. A multilayer substrate according to claim 3, wherein said higher tensile strength is provided by at least one of the outer layers, preferably wherein the minimum tensile strength is about 75 N/m (CD).

5. A multilayer substrate according to claim 3, wherein said higher tensile strength is provided by the two outer layers, preferably wherein the total minimum tensile strength is about 150 N/m (MD).

6. A multilayer substrate according to claim 3, wherein the layer(s) with higher tensile strength is thinner than the central layer(s).

7. A multilayer substrate according to claim 1, wherein the material with low initial tensile strength provides one or more layers with better re-pulpability.

8. A multilayer substrate according to claim 3, wherein at least one of the outer layers has a higher hydrophobicity and/or oleophobicity, preferably by using a water and/or grease repellent, such as alkylketen dimer, alkenyl succinic anhydride or waxes or a combination thereof

9. A multilayer substrate according to claim 3, wherein at least one of the outer layers has a higher relative wet strength.

10. A multilayer substrate according to claim 3, wherein at least one of the outer layers has a higher density.

11. A multilayer substrate according to claim 1, wherein the density is below about 0.5 kg/dm.sup.3, preferably from about 0.1 to about 0.4 kg/dm.sup.3.

12. A multilayer substrate according to claim 1, wherein the grammage is from about 100 to about 2000 g/m.sup.2, preferably from about 300 to about 1500 g/m.sup.2.

13. A multilayer substrate according to claim 1, wherein the moisture content is from about 4 to about 25%, preferably from about 7 to about 15%.

14. A multilayer substrate according to claim 3, wherein at least one of the outer layers comprises one or more additives for extra strength and wet strength, preferably wherein at least one component of said additive(s) comprises fibers of man-made polymers.

15. A method for treating a multilayer substrate according to claim 1 for providing a multilayer product comprising the following steps: a) providing said multilayer substrate, b) subjecting said substrate to high pressure, and c) subjecting said substrate to high temperature, thus providing a multilayer product.

16. A method according to claim 15 wherein the high pressure and high temperature of step b and/or c) is provided by a press pad device and a stamp device.

17. A method according to claim 15 wherein the substrate emanates from ChemiThermo Mechanical Pulp, Thermo Mechanical Pulp, Kraft pulp, sulfate pulp, sulfite pulp, recycled pulp material, board or carton, or a combination thereof.

18. A method according to claim 15 wherein the substrate emanates from bleached or non-bleached pulp, or a combination thereof.

19. A method according to claim 15 wherein the substrate emanates from hardwood or softwood, bagasse, algae or straw or a combination thereof.

20. A method according to claim 15 wherein step a) is preceded by a delivery step comprising forming the substrate into a strip and subsequently folding said strip.

21. A multilayer product obtainable by a method according to claim 15.

22. A multilayer product according to claim 21 wherein said product is a moulded product, such as a screw cap, a container, a bread clip or a package, wherein said container may be a disposable drinking cup or dairy product carton or auto-clave package or a tray, or a plate for eating or keeping food, or a paper or paperboard, such as a folding boxboard.

23. A multilayer product according to claim 21 wherein said product is provided so that one of the outer layers form threads or click-on function for sealable packaging, for example a container, a closure or a part of container or closure.

24. Use of a multilayer product according to claim 21 wherein said product is/are a part(s) of a moulded product, such as a screw cap, a container, a bread clip or a package, wherein said container may be a disposable drinking cup or dairy product carton or auto-clave package or a tray, or a plate for eating or keeping food, or a paper or paperboard, such as a folding boxboard.

25. Method for re-cycling a multilayer product according to claim 21 for providing re-cycled pulp comprising the following steps: i) providing said multilayer product, preferably after usage thereof, ii) submerging said product into a liquid, preferably water, most preferred warm water, iii) optionally adding to said liquid one or more decoupling agents, iv) exposing said product in said liquid for shear forces thus providing a re-cycled pulp.

Description

FIGURES

[0055] FIG. 1 shows a schematic production of a multi-layer material according to the present invention where, typically one or both of the outer formed layers, are strong and carry the loose held together other layers.

[0056] FIG. 2 shows a schematic slitting operation where a bigger roll of the internally loose held together material is re-winded and slitted to several smaller rolls adopted thereby exposed to high tensile tension in the web and share forces from the slitting operations.

[0057] FIG. 3 shows a schematic forming operation where the partly loose held together fiber material are un-winded, cut, pulled, draped pressed and possible post cut into a multilayer structure with extra strong inside and/or outside surfaces.

[0058] FIG. 4 shows a schematic multilayer formed structure where one or both of the outer layers has a higher resistance towards the re-pulping operations while the central layer is more easily separated and through that delaminating the structure increasing re-pulpability and through that recyclability.

EXAMPLES

1. Exemplary Description

[0059] A. Forming of a first outer or inner layer [0060] B. Forming of a second central layer [0061] C. Forming of a third layer outer or inner layer [0062] D. Additional manufacturing processes where the material is exposed to mechanical or chemical stress. Mechanical stress is typically enforced through compression (calendaring) and tensile stress in mechanical or drying operations. Chemical stress are typically enforced trough moisture or water for example from an operation adding a water solvable or dispersible additive. [0063] E. Winding operation where the material is exposed to tensile forces in order to create a stable enough roll. If the tension in the winding operation are not high enough the tension inside the roll will not be sufficient to prevent so called telescoping in handling. [0064] F. Rewinding operation where the web tension is needed to pull the material from the larger original roll and high enough to create sufficient web tension in the smaller resulting roll in order to enable safe handling. The tension is typically achieved through that the smaller roll is driven and that the rotation of the bigger roll is held back or braked. [0065] G. Unwinding in the converting operation. The web tension creating tensile forces of the material is needed to create a flat and controlled web. This is typically achieved through that the material is pulled by a feeding unit and that the roll is held back through a braking mechanism. Unwinding means that the layers of the roll where the inside material rests towards the outside of the material needs to be separated creating tensile forces but also out of plane or share forces risking the material to break, dust or that part of once surface resides on the other if the surface strength of the material is not high enough. [0066] H. In some operations the material is cut into blanks prior to the feeding operation creating tensile and share forces on the material. [0067] I. The material, as a web or as sheets (or blanks) are typically fed into the pressing operation (J.) through a pushing operation by the feeder in order to avoid tensile forces then the material later is punched or draped into the mould (see FIGS. 1 and 2 press pad device). The pushing operation create compressive and buckling forces on the material demanding that the material is strong and stiff enough not to be compressed, folded or buckled when fed. [0068] J. Pressing device (reference also to FIGS. 1 and 2 below). The material is typically pushed flat into the pressing area and then pushed or draped into the press pad device with the stamp or with a dedicated tool. The material needs to be strong enough not to brake from tensile or share forces crated from the pressing device and the walls of the pad and the same times a significant amount of fibers need to be loose enough to be relocated under the pressing operation. During the pressing operation the material will be formed and with new bonds formed. The nature of the material and the additives added will determine the properties of the new laminate structure. Typically, materials will contain strength, wet-strength and hydrophobic properties and may be stronger and/or more resistant to water while materials without these additives will create properties enabling better re-pulping properties. Where the material is folded in the pushing down or draping operation it will for folds where the inside or outside material will come in direct contact with itself forming, typically stronger, re-enforcement structures. [0069] K. The forming and pressing operation results in a multilayer structure typically with the outer and/or inner layers are given extra strength from the additives originally added to create a or several strong layers in the manufacturing and converting operations. If the item formed is to be cut after forming, the strength of outer(s) aid the cutting operation through better share and bending resistance.

[0070] The formed product would benefit from extra strength.

[0071] As a non-limiting example, the minimum tensile strength could be 150 N/m (MD) in total, where there would be essentially no strength in the middle layer. Thus, in each outer layer there would be a tensile strength of about 75 N/m (CD). [0072] L. After use the fibers in the item need to be recycled enable new use as packaging or other products. This is typically done trough that the item is collected, transported and, tougher with other fiber and paper products re-pulped. The re-pulping, which constitutes the fifth aspect of the present invention, is typically done in an operation where the items are submerged into warm water, with or without decoupling, agents and exposed to share forces causing fibers bonds to separate. Typically, stronger bonds, bonds that are aided with additives and thick structures are harder to re-pulp. [0073] M. The multilayer where one or several layers are easier will delaminate or partly delaminate causing the easier to re-pulp layers to separate into single fibers. The harder to separate layers will end up as thinner layers or flakes and through that geometrical transformation they separate to single fibers easier than if they were kept in a thicker structure. If all or part of the stronger layer would not separate totally these will be screened of enabling the major part of the structure to be recycled into new paper or fiber products.

2. Measurements

[0074] If air-laid trial material (carrier sheet), that is a multi-layered material according to the present invention, has been treated during a trial and is subsequently measured with regard to e.g. tensile strength conducted on the full material (including tissue), data (testing results) can be collected and may be represented as follows:

TABLE-US-00001 Parameter Test Method Unit Targ LSL USL Basis Weight EN 12625-6 (g/m.sup.2) 16.5 15 17.5 Thickness EN 12625-3 (m) 1300 Tensile Strength MD dry EN 12625-4 (N/m) 150 120 Elongation MD EN 12625-4 (%) 25 20 Air permeability Internal Method (l/m2/s) 2400 1870 DPMK 001 Moisture EN 287 % 5.5 6

[0075] Elongation and air permeability of the tissue carrier are two important parameters for converting on the air-laid machine.

[0076] Additional measurements on an exemplary thermobonded air-laid, tissue carrier, gave the following values:

TABLE-US-00002 Property Value/Unit Test method Basis weight 700 g/m.sup.2 NWSP 130.1.R0 (15) Thickness (2.0 kPa) 5.6 mm NWSP 120.6.R0 (15) Density 0.13 g/cm.sup.3 Calculated Tensile strength (dry) MD 49 N/50 mm NWSP 110.4.R0 (15) Tensile strength (dry) CD 46 N/50 mm NWSP 110.4.R0 (15) Elongation (dry) MD 1.02% NWSP 110.4.R0 (15) Elongation (dry) CD 1.31% NWSP 110.4.R0 (15) Bond Strength 0.2 N/50 mm

[0077] Various embodiments of the present invention have been described above but a person skilled in the art realizes further minor alterations that would fall into the scope of the present invention. The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments but should be defined only in accordance with the following claims and their equivalents. For example, any of the above-noted layered configurations or methods may be combined with other known methods. Other aspects, advantages and modifications within the scope of the invention will be apparent to those skilled in the art to which the invention pertains.