WO2013132021A1

WO2013132021A1 - Sheetlike material with reduced density

Info

Publication number: WO2013132021A1
Application number: PCT/EP2013/054634
Authority: WO
Inventors: Sergey LEDERMANN; Tiemo ARNDT; Klaus Erhard; Manuela FIEDLER
Original assignee: Philip Morris Products S.A.
Priority date: 2012-03-09
Filing date: 2013-03-07
Publication date: 2013-09-12
Also published as: WO2013132017A1

Abstract

A sheetlike material according to the present invention comprises the coarse fraction of fractionated cellulose fibres, and further at least one additional component selected from expandable microspheres, microfibrillated cellulose, and a cationic dry additive.

Description

Sheetlike material with reduced density

The invention relates to a sheetlike material comprising cellulose fibres. In the manufacturing of paper and cardboard, especially in the field of printing and packaging material, there is a need in reducing costs of such material. This can be achieved by reducing the costs of the raw materials used in the paper production. However, a substitution of individual components by cheaper components typically has unwanted effects on the properties of the sheetlike material, especially its mechanical or optical properties or its printability.

In the international Patent Application WO-A-2010/1 25247 the replacement of relatively expensive fibres by a cheaper filler material such as precipitated calcium carbonate (PCC) is disclosed. Since the filler material deteriorates the mechanical properties of the paper product by weakening an inter-fibre bonding, an amount of nanofibrillated cellulose, also named microfibrillated cellulose (MFC), and a cationic poly-electrolyte is added to the basic furnish used for the manufacturing of paper or the paper board product. By this, the surface of the filler and possibly also that of the fibres is modified and an improved tensile strength of a paper sheet may be achieved also with high filler content.

In the international Patent Application WO-A-01 /2931 1 a layered sheetlike material is disclosed where a coarse fraction of fractionated fibres is used to form a middle layer with high bulk and low density and a finer fraction of fractionated fibres with an improved surface quality is used for surface layers.

In the international Patent Application WO-A-2007/1 30690 discloses a method for reducing the density of a paperboard by adding expandable synthetic polymer microspheres in combination with polyacrylamide to the wet pulp. The expandable microspheres expand in the heating and drying process of the paperboard thereby reducing the density of the paper product by an otherwise constant weight. However, it is known that the addition of expandable microspheres reduces the internal strength of paper, which may have a negative impact on converting properties like creasing. The loss of internal strength thereby limits the application of expandable microspheres. There is a need for paper material or sheetlike material containing cellulose fibres overcoming drawbacks of state of the art paper material. Especially, there is a need for sheetlike material containing cellulose fibres having reduced manufacturing costs, but wherein the sheetlike material otherwise maintains or improves the properties of conventional paper or cardboard, in particular regarding bending stiffness and flexibility of the sheetlike material.

According to the present invention there is provided a sheetlike material comprising the coarse fraction of fractionated cellulose fibres, wherein the sheetlike material further comprises at least one additional component selected from expandable microspheres; microfibrillated cellulose; and a cationic dry additive.

Throughout the application, the term "sheetlike material" is used to refer to thin material that can be produced in a paper making process. According to the use herein, "sheetlike material" can be either in the form of a sheet of thin material or a web of thin material. In particular, the sheetlike material has a paper weight of between 20 grams per square meter (gsm) to about 2000 grams per square meter (gsm). In particular, sheetlike material has a thickness of between about 0.020 mm and about 3 mm

Sheetlike material as used in the printing and packaging industry, but also for use as for example wallpapers, is based on cellulose fibres. These are mainly obtained through processing of wood fibres but also of other plant fibres such as hemp or flax. The quality of the fibres is primarily given by the raw material and by the process for obtaining the fibres. Softwood is growing faster and has longer fibres, while hardwood is growing slower and has shorter fibres. To gain access to the fibres the plant is treated mechanically, chemically or mechanically and chemically. While a mechanical treatment generally reduces a fibre length, a chemical treatment is gentler to the fibres such that longer fibres can be obtained in chemical pulp. In addition, the pulp may be treated mechanically and chemically, so called mechanical chemical pulp.

According to the present invention the fractionated fibres are the coarse fraction of fractionated cellulose. The coarse fraction after fractionation comprises longer fibres and has a lower density and a lower internal binding strength. This is especially suitable for a high bulk, low density layer. The low density additionally supports the expansion of expandable microspheres by not exceeding a force needed to expand the sheetlike material which has to be overcome by the expandable microspheres upon expansion.

Fractionated fibres (FF) are obtained through fractionation of cellulose fibres as for example described in the international Patent Application WO-A- 01/2931 1 . Fractionation is a well-known process in paper manufacturing, wherein fibres are separated according to their length. Longer and shorter fibres are then placed in different locations along the thickness of a paper. With fractionation, the volume and bending stiffness of paper may be increased. The coarse fraction after fractionation comprises longer fibres at a lower density and a lower internal binding strength than the fine fraction, especially in the wet state of the pulp.

The term "coarse fraction" of fractionated cellulose fibres is used throughout the present application to indicate the part of the fractionate fibres that does not pass through a mesh 50 screen. On the other hand, the term "fine fraction" as is used throughout the present application to indicate the part of the fractionate fibres that does pass through a mesh 50 screen. It is clear to the person skilled in the art that there may be an overlap of fibre lengths of fibres passing through the mesh and fibres not passing through the mesh 50 screen. For example, due to the longitudinal extension of the fibres, some longer fibres may pass through the screen. In general, the longer the fibres, the more pronounced is their effect when used in the coarse fraction of the cellulose fibres. In general, the shorter the fibres, the more pronounced is their effect when used in the fine fraction of the cellulose fibres.

Microfibrillated cellulose (MFC) is a material composed of nano-sized cellulose fibrils with a high length to width ratio. Typical lateral dimensions are 5 to 20 nanometres and longitudinal dimension is in a wide range from tenths of nanometres to several microns. Microfibrillated cellulose is obtained by special treatment of any cellulose containing source including wood-based fibres. Microfibrillated cellulose is commercially available and its properties are as such known. A cationic dry additive is a retention polymer used in paper manufacturing. Preferably, the cationic dry additive is cationic starch. However, also other cationic polyelectrolytes such as for example cationic polyacrylamide, cationic polyvinylamine, polyamidoamine-epichlorohydrin or combinations of different cationic polyelectrolytes may be used. A cationic dry additive also facilitates the dewatering of the pulp during a manufacturing process. This additionally supports a compensation of the effect of microfibrillated cellulose that has the tendency to bind water in the pulp.

Expandable microspheres (EM) are small spherical plastic particles, typically thermally expandable microspheres (TEMs) consisting of a copolymer shell, for example a gastight thermoplastic shell encapsulating a small amount of hydrocarbon. The shell of the expandable microsphere softens upon heat, whereas the enclosed hydrocarbon increases its pressure. Thus the volume of the microspheres increases and the expandable microsphere expands irreversibly to many times its original volume on heating. Preferably, the expandable microspheres are added to the pulp in an unexpanded state. The expandable microspheres are expanded in the fabrication process of the paper, typically upon heat in the drying process of the paper. However, expandable microspheres may also be added to the pulp in an already expanded state. Expandable microspheres may be used in boards and papers primarily to make the board or paper thicker to save raw material or to improve bending stiffness of the board at a given basis weight. Expandable microspheres are commercially available, for example under the trade name Expancel® from Akzo Nobel.

In order to improve the paper or cardboard properties the sheetlike material according to the invention comprises individual components that are combined in specific combinations. All of the combinations have the common inventive concept that a given bending stiffness of the sheetlike material may be maintained or improved through a selective combination of components that individually influence the bending stiffness of the paper or board either through a strong influence of the E-Modulus or a strong influence on the thickness of the sheetlike material.

The bending stiffness is given by the formula below, s _{= jB x i}3 _L

b 12

wherein S*_> corresponds to the bending stiffness, E corresponds to the E-modulus and t corresponds to the thickness of the sheetlike material. Since the bending stiffness is proportional to the thickness to the power of three, a component responsible for the thickness of the sheetlike material, like for example expandable microspheres or the coarse fraction of fractionated fibres can significantly contribute to the bending stiffness of the sheetlike material. On the other hand, the increasing fragility of thick paper or board can be compensated by components with a high E-Modulus, like for example microfibrillated cellulose or a cationic dry additive like, for example, cationic starch.

The combination of components is in advantageously selected such that the sheetlike material according to the invention provides for a reduction of fibres per unit area, while at the same time maintaining the mechanical properties of the sheetlike material. Therefore, the sheetlike material according to the invention may be produced at a comparatively low price and while maintaining the physical properties that allow the use as printing and packaging material.

In an embodiment of the invention the sheetlike material further comprises microfibrillated cellulose or a cationic dry additive such as, for example, cationic starch combined with expandable microspheres or the fine fraction of fractionated fibres. Preferably, the fine fraction of fractionated fibres is located in an outer layer or towards the outside of a single layer of the sheetlike material. This has the advantage of improving the elasticity and firmness of the sheetlike material. In addition, advantageously, the shorter fibres of the fine fraction of fractionated fibres allow for a smoother surface than the longer fibres of the coarse fraction of fractionated fibres. Therefore, according to the invention, it is advantageous to arrange the fine fraction closer towards the outer surface of the sheetlike material. This improves the smoothness of the surface and thus reduces the need for calandering the sheetlike material during production of the sheetlike material. This has in turn the advantage, that a compression of the expandable microspheres and the bulkier coarse fraction in a middle or bulk layer of the sheetlike material is avoided. Such a compression would be otherwise counterproductive in the aim to increase the thickness of the sheetlike material.

Microfibrillated cellulose and cationic starch are binders that improve the inter-fibre bonding. By adding one or both of these components less cellulose fibres may be used or short cellulose fibres or cellulose fibres with a low quality may be used without losing mechanical strength, especially with regard to the bending stiffness of the sheetlike material. Depending on the fibres used, an enhancement of the bending stiffness compared to conventional sheetlike material containing cellulose fibres may be achieved.

Expandable microspheres and the coarse fraction of fractionated fibres are both capable of reducing the density of the paper, thereby reducing the grammage or basis weight of the sheetlike material. With expandable microspheres or the coarse fraction of fractionated fibres preferably a low density bulk may be manufactured that is mainly responsible for the thickness of the sheetlike material.

With the combination of microfibrillated cellulose or cationic starch and expandable microspheres or the coarse fraction of fractionated fibres, expensive fibres may at least partially be replaced by cheaper fibres. The expandable microspheres or the coarse fraction of fractionated fibres may lead to a weak structure with low mechanical quality which is, according to the invention, compensated by the addition of microfibrillated cellulose or a cationic dry additive, such as cationic starch, providing a high E-Modulus.

Since microfibrillated cellulose or cationic starch, and in particular the combination of microfibrillated cellulose and cationic starch, may significantly enhance the mechanical stiffness of the sheetlike material, only small amounts of these components need to be added, thus saving material costs.

In another embodiment the sheetlike material comprises microfibrillated cellulose combined with expandable microspheres and the coarse fraction of fractionated fibres. In this combination the expandable microspheres enhance the thickness of the sheetlike material, and with that, the binding stiffness. Nevertheless, at higher amounts of expandable microspheres the bending stiffness decreases as the sheetlike material becomes brittle. Microfibrillated cellulose on the other hand enhances the flexibility of the sheetlike material through a high E-Modulus. Hence, the bending stiffness loss resulting from the addition of higher amounts of expandable microspheres can be advantageously compensated.

In yet another embodiment the sheetlike material comprises a cationic dry additive like for example cationic starch, expandable microspheres and the coarse fraction of fractionated fibres. This combination also has the advantage to enhance the bending stiffness of the sheetlike material or to compensate a loss in bending stiffness due to the presence of high amounts of expandable microspheres. In addition, cationic starch is a low cost component such that such sheetlike material may be produced cost effectively.

In a further embodiment, the sheetlike material comprises microfibrillated cellulose and cationic starch combined with expandable microspheres and the coarse fraction of fractionated fibres. Such a combination has the advantage to significantly increase the effects of the expandable microspheres and the microfibrillated cellulose. The cationic starch influences the binding characteristics of a layer. The addition of expandable microspheres may lead to a reduction of the inner strength of the sheetlike material. Generally, the inter-fibre bonding is stronger than the bonding of a fibre/microsphere mixture. Also, lesser fibres per unit area are present, which additionally weakens the bonding in the sheetlike material. By adding cationic starch the bonding characteristics and therefore the bending stiffness of the sheetlike material is enhanced. In addition, cationic starch or another cationic polyelectrolyte such as cationic polyacrylamide helps to retain the expandable microspheres in the pulp such that lower amounts of expandable microspheres and microfibrillated cellulose are required. Otherwise, the expandable microspheres tend to be washed out during the early stages of the formation of the sheetlike material, where the pulp still has a very high water content.

In yet a further embodiment, the sheetlike material comprises microfibrillated cellulose combined with the coarse fraction of fractionated fibres. Again, this combination has the advantage of combining a material with low density (fractionated fibres) that strongly contributes to the thickness of the sheetlike material with a material with high E-modulus (microfibrillated cellulose). Thereby, the sheetlike material may be made thinner and thus saving material cost and lowering the weight of the sheetlike material. Or, maintaining the same thickness of the sheetlike material, its bending stiffness may be increased.

In another embodiment the sheetlike material comprises a cationic dry additive such as, for example, cationic starch combined with the coarse fraction of fractionated fibres, in particular the coarse fraction of fractionated fibres. This combination also has the advantage of combining a material with low density (the coarse fraction of fractionated fibres) that strongly contributes to the thickness of the sheetlike material with a material with high E-modulus (cationic starch). Possibly, the effects of the combination of cationic starch with the coarse fraction of fractionated fibres are not as prominent as those with the combination of microfibrillated cellulose and expandable microspheres, however a sheetlike material with the coarse fraction of fractionated fibres and a cationic dry additive such as, for example, cationic starch may be produced cost effectively.

In another embodiment the sheetlike material comprises expandable microspheres combined with the coarse fraction of fractionated fibres. This combination has the advantage that both components add to the thickness and low density of the sheetlike material and to some extent also add to its bending stiffness. In addition, especially the coarse fraction of fractionated cellulose comprises longer fibres and has a lower density and a lower internal binding strength. The low density of the fractionated fibres and low internal binding strength additionally supports the expansion of the expandable microspheres. On the other hand, the fine fraction of fractionated fibres may advantageously contribute to the flexibility of the sheetlike material.

In a further embodiment the sheetlike material comprises microfibrillated cellulose combined with expandable microspheres and the coarse fraction of fractionated fibres. This combination has the advantage of enabling the production of a sheetlike material having low density and increased bending stiffness. While the coarse fraction of fractionated fibres positively work in combination with expandable microspheres (see above), the microfibrillated cellulose enhances the binding stiffness. Thus a sheetlike material having lower basis weight and improved mechanical properties compared to conventional sheetlike material containing cellulose fibres may be manufactured.

In another embodiment the sheetlike material comprises a cationic dry additive such as, for example, cationic starch combined with expandable microspheres and the coarse fraction of fractionated fibres. This combination also has the advantage of enabling the production of a sheetlike material having low density and increased bending stiffness. Although the increase in bending stiffness using cationic starch may not be as expressed as with microfibrillated cellulose, cationic starch also helps to retain the expandable microspheres in the pulp such that lower amounts of expandable microspheres may be required.

In a preferred embodiment the sheetlike material according to the invention comprises a combination of microfibrillated cellulose, cationic starch, expandable microspheres and the coarse fraction of fractionated fibres. By the combination of these four components, the advantages of the individual combinations as mentioned above are combined and will not be discussed again. In addition, more flexibility is provided in adapting the amounts of the individual components for the requirements of the sheetlike material and its future use.

The sheetlike material according to the present invention has an identical or an enhanced bending stiffness compared to conventional fibrous sheetlike material containing cellulose fibres, and preferably has a paper weight which is reduced by between about 5 percent and about 70 percent, most preferably reduced by between about 10 percent and about 30 percent, compared to conventional fibrous sheetlike material containing cellulose fibres.

According to an aspect of the sheetlike material of the present invention, the sheetlike material comprises between about 70 percent and about 99.5 percent pulp. Pulp is the basic material in paper manufacturing and is basically defined by its fibre content. A cost reduction may be achieved by reducing the amount of expensive cellulose fibres in the pulp or by reducing the amount of pulp or by a combination thereof. A lower percentage of pulp, for example in the range of between about 70 percent and about 90 percent, is preferably used with a combination of microfibrillated cellulose and expandable microspheres. Remaining percentage of the pulp may be organic or inorganic filler. According to another aspect of the sheetlike material according to the present invention the pulp is at least one of mechanical or chemical pulp. Mechanical pulp typically has a lower density than chemical pulp. Also, the internal bonding strength is lower in the mechanical pulp than in the chemical pulp. Different treatments of the pulp also influence further mechanical or optical properties of the final product. Depending on the desired characteristics of the sheetlike material mechanical pulp, chemical pulp or a combination thereof is used.

Preferably, the pulp contains paper broke. Paper broke is a waste material that is created before the paper is dried during the paper manufacturing process and may be reused in the pulp. Paper broke is a cheap raw material containing cellulose fibres, generally short fibres due to the previous fabrication process. Reusing paper broke as pulp material can advantageously reduce the costs of the pulp.

In a preferred embodiment of the sheetlike material according to the present invention, the chemical pulp contains an inorganic filler. By adding filler the internal bonding strength in the chemical pulp is reduced. Especially, if a chemical pulp contains expandable microspheres a bonding strength is lowered by the addition of a filler in order for the microspheres to be fully expandable. Another advantage of adding filler is that filler may replace cellulose fibres and hence reduces cost. The amount of inorganic filler preferably is between about 10 percent and about 30 percent of the dry paper weight. Inorganic filler preferably is precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), clay or kaolin but may also be another inorganic filler as known for the use in paper production. Coated paper broke often contains inorganic fillers such that upon reusing coated paper broke, paper broke as well as inorganic fillers are recycled.

According to a further aspect of the sheetlike material according to the present invention, the amount of microfibrillated cellulose ranges between about 0.5 percent and about 6 percent of the dry paper weight. Preferably, between about 2 percent and about 4 percent, more preferably 3 percent of microfibrillated cellulose is added to the pulp. Due to the relatively high costs of microfibrillated cellulose a small amount thereof is preferred. According to a further aspect of the sheetlike material according to the present invention, the amount of expandable microspheres ranges between about 0.5 percent and about 6 percent of a dry paper weight. Preferably, between about 2 percent and about 4 percent, more preferably about 3 percent of expandable microspheres are added to the pulp. Due to the relatively high costs of expandable microspheres a small amount thereof is preferred. In addition, although expandable microspheres enhance the thickness of the layer and with that its bending stiffness to a certain point, the addition of larger amounts of expandable microspheres reduces the bending stiffness as the sheetlike material becomes brittle.

According to another aspect of the sheetlike material of the present invention, the amount of a combination of expandable microspheres and microfibrillated fibres ranges between about 2 percent and about 6 percent of a dry paper weight. Due to the positive combined effect of expandable microspheres and microfibrillated fibres an amount of these components added to the pulp may be kept in a low range. Preferably, in this combination, the amount of microfibrillated cellulose is in the range between about 50 percent and about 600 percent of expandable microspheres, more preferably in the range between about 100 percent and about 400 percent of expandable microspheres.

According to a further aspect of the sheetlike material according to the present invention, the amount of cationic starch is between about 0.5 percent and about 2 percent of the dry paper weight. The advantages of the addition of cationic starch have been described above. A low amount of starch improves the tensile strength, while higher amounts may complicate the manufacturing process due to the stickiness of cationic starch.

According to another aspect of the sheetlike material according to the present invention, the sheetlike material comprises a first and a second layer, wherein the first layer comprises the at least one of microfibrillated cellulose or a cationic dry additive such as, for example, cationic starch and the second layer comprises the at least one of expandable microspheres or the coarse fraction of fractionated fibres. In order to enhance the characteristics of the sheetlike material according to the present invention, the sheetlike material may be layered, with a first layer comprising microfibrillated cellulose or cationic starch or a combination thereof. These components may be regarded as binders, improving an inter-fibre bonding with the advantages as described above.

Preferably, the second layer comprises expandable microspheres or the coarse fraction of fractionated fibres or a combination thereof. Both components are capable of reducing the density of the paper, thereby reducing the grammage or basis weight of the sheetlike material.

Preferably, the second layer is a low density bulk layer mainly responsible for the thickness of the sheetlike material and the first layer is preferably a thin layer with high bending stiffness. This combination is preferably such that the sheetlike material according to the invention provides for a reduction of fibres per unit area, while at the same time keeping the mechanical properties. Instead of using expensive fibres, the second layer may comprise cheaper or less quality fibres and only provide a weak structure, which is covered by the first layer provided with a high E-Modulus. The thick second layer can significantly contribute to the bending stiffness of the sheetlike material.

Since the microfibrillated cellulose or the cationic starch, in particular the combination thereof, significantly enhance the mechanical stiffness of the first layer, the first layer may be a thin layer thus saving material. In addition, a thin layer may also have a higher density, which does not significantly influence the overall density of the sheetlike material due to its limited thickness.

By the provision of two layers, each layer may be directed to or optimised with regard to one desired characteristic, for example density, while the other layer may be directed to and optimised with regard to another desired characteristic, for example bending stiffness. While such an individual layer as such would not serve the demands of for example packaging material, the combination does. In addition, should one layer have a negative effect on a property, such an effect may be compensated by the other layer.

According to an aspect of the sheetlike material according to the present invention, the sheetlike material comprises a third layer. Preferably, the first and the third layers are arranged on opposite sides of the second layer and the third layer comprises at least one of microfibrillated cellulose or a cationic dry additive such as, for example, cationic starch.

By this so called "l-Beam" arrangement a high bending stiffness can be achieved with a rather bulky second inner layer and two flexible first and third outer layers. In general, the first and third outer layers are provided with high E- Modulus through the microfibrillated cellulose, a cationic dry additive such as, for example, cationic starch or the combination thereof. These outer layers are combined with the second inner layer with a high thickness or low density achieved through the expandable microspheres, the coarse fraction of fractionated fibres or the combination thereof. Since the second inner layer is covered on both sides with a thin layer having a high bending stiffness, the inner layer may be optimized to low density and low cost. For example, few and cheap fibres or waste or recycled material accumulated in a former paper manufacturing process may be used essentially regardless of the mechanical properties of the second layer. The mechanical properties are compensated by the outer layers.

According to another aspect of the sheetlike material according to the invention, also the second layer comprises a cationic dry additive such as, for example, cationic starch.

According to a further aspect of the sheetlike material according to the present invention, the first or third layer comprises expandable microspheres or the fine fraction of fractionated fibres.

By mixing expandable microspheres or fractionated fibres directly with microfibrillated cellulose or starch, the mechanical properties of the individual layers may further be optimised in each layer. In addition, it may be fully taken advantage of an interaction of the individual components. For example, cationic starch may directly work in combination with the expandable microspheres and the microfibrillated cellulose in the first or third layer such that the second layer may be provided with no starch or a lesser amount of other components in general.

According to another aspect of the sheetlike material according to the present invention, any one of the layers each comprises between about 70 percent and about 99.5 percent pulp. A high amount of pulp, for example in the range of between about 90 percent and about 99 percent, more preferably between about 94 percent and about 99 percent, is used for the first and third layers containing microfibrillated cellulose or cationic starch, where the first and third layers preferably are only formed as thin layers. A lower percentage of pulp, for example in the range between about 70 percent and about 90 percent, is preferably used in the second layer comprising the expandable microspheres, more preferably if the second layer comprises a combination of microfibrillated cellulose and expandable microspheres. Second layers or more generally layers that are formed as bulk or thick layers in addition to pulp typically also comprise a certain amount of filler or ash.

According to a further aspect of the sheetlike material according to the present invention the amount of microfibrillated cellulose per layer ranges between about 0.5 percent and about 6 percent of the dry paper weight, and the amount of expandable microspheres ranges between about 0.5 percent and about 6 percent of a dry paper weight. Preferably, in this combination, the amount of microfibrillated cellulose is in the range between about 50 percent and about 600 percent of expandable microspheres, more preferably in the range between about 100 percent and about 400 percent of expandable microspheres

According to another aspect of the sheetlike material according to the present invention, the second layer contains paper broke. Paper broke, as already outlined above is a waste material in the paper manufacturing process. Paper broke is a cheap raw material and its reuse may reduce cost and prevent waste.

According to a further aspect of the sheetlike material according to the present invention, the sheetlike material comprises one or several further layers. Each of the one or several further layers comprises at least one of the following components: microfibrillated cellulose, a cationic dry additive such a for example cationic starch, expandable microspheres, fractionated fibres, inorganic filler or paper broke.

Paperboard and especially cardboard or packaging material based on fibrous material, comprises several layers in order to achieve a required thickness, stability, insulation property and other physical or chemical properties. These further layers may also comprise one or several of the components of the layers described for the sheetlike material according to the invention. By these means mechanical properties of the final product may further be optimised according to a user's need or to the requirements of a production or paper treatment apparatus.

According to a further aspect of the sheetlike material according to the present invention, the sheetlike material forms a part of paper, paperboard or cardboard, especially forms a part of solid bleached board, solid unbleached board, folding boxboard or white lined chipboard. The sheetlike material according to the invention is especially suited for the production of paper, paperboard or cardboard, where costs or the reduction of costs play an important role, but where otherwise the (mechanical) properties of conventional paper, paperboard or cardboard have to be maintained or improved.

According to another aspect of the invention, the invention is related to a container, wherein the container comprises sheetlike material comprising the coarse fraction of fractionated cellulose fibres, wherein the sheetlike material further comprises at least one additional component selected from expandable microspheres microfibrillated cellulose and a cationic dry additive. The same advantages apply as already discussed with regard to the sheetlike material above.

Preferably, the amount of inorganic filler in the sheetlike material of the container is between about 10 percent and about 30 percent of the dry paper and wherein the filler is a component selected from the group consisting of: precipitated calcium carbonate, ground calcium carbonate, clay and kaolin. The same advantages apply as already discussed with regard to the sheetlike material above.

Preferably, the amount of microfibrillated cellulose in the sheetlike material of the container ranges between about 0.5 percent and about 6 percent of the dry paper weight. The same advantages apply as already discussed with regard to the sheetlike material above.

Preferably, the amount of expandable microspheres in the sheetlike material of the container ranges between about 0.5 percent and about 6 percent of a dry paper weight. The same advantages apply as already discussed with regard to the sheetlike material above. Preferably, the amount of a combination of expandable microspheres and microfibrillated fibres in the sheetlike material of the container ranges between about 0.5 percent about 6 percent of a dry paper weight. The same advantages apply as already discussed with regard to the sheetlike material above.

Preferably, the amount of the cationic dry additive in the sheetlike material of the container ranges between about 0.5 percent and about 2 percent of the dry paper weight. The same advantages apply as already discussed with regard to the sheetlike material above.

Preferably, the sheetlike material of the container comprises paper broke. The same advantages apply as already discussed with regard to the sheetlike material above.

Preferably, the sheetlike material of the container is one of solid bleached board, solid unbleached board, folding boxboard or white lined chipboard. The same advantages apply as already discussed with regard to the sheetlike material above.

According to a further aspect of the sheetlike material according to the present invention, the sheetlike material is used as packaging material for consumer goods, in particular for smoking articles. Conventional packaging material may be replaced by the sheetlike material according to the invention or by paper, paperboard or cardboard comprising the sheetlike material according to the invention, respectively.

Examples of parameters of the second middle layer and the first and possibly also the third outer layer are given in the following table in comparison to conventional papers:

Middle Layer

Current Invention

grammage [g/m²] 100 100 DIN EN ISO 536

MFC [ percent] 0 0.5 to 5

Cationic starch [ percent] 0 to 1 .0 0.5 to 2.0

EM (Eg.Expancel®) [ percent] 0 0.5 to 6

Cationic polyacrylamide [ percent] 0 0.01 to 0.05

Fillers [ percent] 0 to 3 12 to 30

Broke [ percent] 0..100 0 to 100

ash level [ percent] O to 10 12 to 30

Mechanical Pulps

Bulk percent 100 105 to 132 EN 20 534

Bending stiffness percent 100 1 10 to 150 DIN 53 121 /L&W °5

Scott Bond percent 100 80 to 90 TAPPI T 833 pm-94

E-Modulus percent 100 90 to 1 10 DIN EN ISO 1924-2

Chemical Pulps

Bulk percent 100 103 to 1 10 EN 20 534

Bending stiffness percent 100 1 10 to 130 DIN 53 121 /L&W °5

Scott Bond percent 100 100 to 160 TAPPI T 833 pm-94

E-Modulus percent 100 100 to 120 DIN EN ISO 1924-2

Outer Layer(s)

Current Invention

Grammage [g/m²] 60 60 DIN EN ISO 536

MFC [ percent] 0 1 .5 to 5

Cationic starch [ percent] 0 to 1 .0 0.5 to 2.0

Fillers [ percent] O to 3 12 to 30

Broke [ percent] 0 to100 0 to 100

ash level [ percent] O to 10 O to 10

Chemical Pulps

Bulk percent 100 100 EN 20 534

Stiffness index percent 100 105 to 120

roughness percent 100 70 to 90

Table 1 : Parameters In this table, grammage corresponds to the basis weight of the layer. Scott

Bond is a parameter reflecting the delamination strength of the paper or cardboard, that is, the tendency of the board to delaminate when pulled in a direction perpendicular to its plane. The last row indicates the standards according to which the individual data were measured. Examples of sheetlike materials according to the present invention are given in the following tables 2 to 4: In these tables, F, C and R stands for Front (or top) layer, Center (or middle) layer and Reverse (or back) layer. Percentages are given in percent of dry paper weight.

Table 2: Solid bleached board (SBB)

- Solid bleached board (SBB) containing bleached Kraft pulp (BKP) or solid unbleached board (SUB) containing unbleached Kraft pulp. The boards comprise a one or a three layer structure.

Any one of the structures may contain a centre layer or the one layer if only one layer is present, where the centre layer comprises between about 70 percent and about 89.5 percent pulp and between about 0.5 percent and about 3 percent Expancel® and between about 10 percent and about 30 percent filler/ash.

Any one of the structures may as an alternative contain a centre layer or the one layer if only one layer is present, where the centre layer comprises between about 70 percent and about 84 percent pulp, possibly also between about 70 percent and about 89.5 percent pulp, and between about 2 percent and about 6 percent Expancel®/microfibrillated cellulose mixture and between about 10 percent and about 30 percent filler/ash.

A three layer structure may contain two outer layers comprising between about 94 percent and about 99 percent pulp and between about 1 percent and about 6 percent microfibrillated cellulose. Percent Percent EM &

Percent Filler / ash

Pulp Percent EM Microfibril. Microfibril.

No. F C R pulp in level in type in layer Cellulose in Cellulose in

layer percent layer layer

BKP • •

4

MP • 70-99.5 0.5-3 >0<30

BKP • •

5

MP • 70-98 2-6 >0<30

BKP • • 94-99 1-6

6

MP • 70-99.5 0.5-3 >0<30

BKP • • 94-99 1-6

7

MP • 70-99.5 2-6 >0<30

BKP/

MP-FF • •

8

MP-CF • 70-99.5 0.5-3 >0<30

BKP/

MP-FF • •

9

MP-CF • 70-98 2-6 >0<30

BKP/

94-99 1-6

MP-FF • •

10

MP-CF • 70-99.5 0.5-3 >0<30

BKP/ • • 94-99 1-6

11 MP-FF

MP-CF • 70-99.5 2-6 >0<30

Table 3: Folding boxboard (FBB)

- Folding boxboard (FBB) comprising a single or central layer of mechanical pulp or mechanical chemical pulp. In structures where the centre layer comprises Expancel® or an Expancel®/microfibrillated mixture, mechanical pulp or a coarse fraction of fractionated mechanical pulp is used. In structures where two outer layers comprise microfibrillated cellulose, bleached Kraft pulp or a combination of bleached Kraft pulp and the fine fraction of fractionated mechanical pulp is used. Typically, where the centre layer comprises the coarse fraction of the mechanical pulp, the outer layers comprise the fine fraction of the mechanical pulp.

In examples with a three layer structure with bleached Kraft pulp in the outer layers, the centre layer may comprise between about 70 percent and about 99.5 percent of mechanical pulp and between about 0.5 percent and about 3 percent Expancel® and between about 0 percent and about 30 percent filler/ash. As an alternative the centre layer contains between about 2 and about 6 percent Expancel®/microfibrillated cellulose mixture and between about 0 percent and about 30 percent filler/ash. This layer may also contain a maximum amount of mechanical pulp of about 98 percent.

Such a three layer structure with a centre structure containing Expancel® is combined with two outer layers comprising between about 94 percent and about 99 percent mechanical pulp and between about 1 percent and about 6 percent microfibrillated cellulose.

In examples with a three layer structures with added fine and coarse fractions of fractionated mechanical pulp, the centre layer comprises between about 70 percent and about 99.5 percent of pulp and either between about 0.5 percent and about 3 percent Expancel® or between about 2 percent and about 6 percent Expancel®/microfibrillated cellulose mixture, as well as between about 0 percent and about 30 percent filler/ash. This structure is combined into a three layer structure containing two outer layers comprising between about 94 percent and about 99 percent pulp and between about 1 percent and about 6 percent microfibrillated cellulose. The centre layer of the three layer structure may also contain a maximum amount of mechanical pulp of about 98 percent including coarse fraction.

Percent Percent EM &

Percent Filler / ash

Pulp Percent EM Microfibril. Microfibril.

No. pulp in level in type in layer Cellulose in Cellulose in

layer percent layer layer

Table 4: White lined chipboard (WLC)

- For white lined chipboard (WLC) comprising three layer structures recovered fibres (RCF) as pulp or bleached Kraft pulp is used. The three layer structure contains a centre layer comprising between about 70 percent and about 99.5 percent pulp and between about 0.5 percent and about 3 percent Expancel® or between about 2 percent and about 6 percent Expancel®/microfibrillated cellulose mixture, as well as between about 0 percent and about 30 percent filler/ash.

These centre layers are combined with two outer layers comprising between about 94 percent and about 99 percent pulp and between about 1 percent and about 6 percent microfibrillated cellulose.

With three layer structures the pulp used is preferably identical for the two outer layers. However, also different pulp may be used, which may in particular be applicable if the sheetlike material according to the invention is provided with further layers such that an outer layer of the three layer structure becomes an intermediate layer.

Claims

1 . Sheetlike material comprising the coarse fraction of fractionated cellulose fibres, wherein the sheetlike material further comprises at least one additional component selected from

a. expandable microspheres;

b. microfibrillated cellulose; and

c. a cationic dry additive.

2. Sheetlike material according to claim 1 , comprising microfibrillated cellulose, a cationic dry additive, expandable microspheres and the fine fraction of fractionated fibres.

3. Sheetlike material according to claim 1 or 2, comprising between about 70 percent and about 99.5 percent pulp.

4. Sheetlike material according claim 2 or 3, wherein the pulp comprises chemical pulp, the chemical pulp comprising an inorganic filler and comprises paper broke.

5. Container, wherein the container comprises sheetlike material comprising the coarse fraction of fractionated cellulose fibres, wherein the sheetlike material further comprises at least one additional component selected from a. expandable microspheres;

b. microfibrillated cellulose; and

c. a cationic dry additive.

6. Container according to claim 5, wherein the amount of inorganic filler in the sheetlike material is between about 10 percent and about 30 percent of the dry paper and wherein the filler is a component selected from the group consisting of: precipitated calcium carbonate, ground calcium carbonate, clay and kaolin.

7. Container according to any one of claims 5 to 6, wherein the amount of microfibrillated cellulose in the sheetlike material ranges between about 0.5 percent and about 6 percent of the dry paper weight.

8. Container according to any one of claims 5 to 7, wherein the amount of expandable microspheres in the sheetlike material ranges between about 0.5 percent and about 6 percent of a dry paper weight.

9. Container according to any one of claims 5 to 8, wherein the amount of a combination of expandable microspheres and microfibrillated fibres in the sheetlike material ranges between about 0.5 percent about 6 percent of a dry paper weight.

10. Container according to any one of claims 5 to 9, wherein the amount of the cationic dry additive in the sheetlike material ranges between about 0.5 percent and about 2 percent of the dry paper weight.

1 1 . Container according to any one of the preceding claims wherein the sheetlike material comprises paper broke.

12. Container according to any one of the preceding claims wherein the sheetlike material is one of solid bleached board, solid unbleached board, folding boxboard or white lined chipboard.

13. Sheet material according to claims 1 to 4, used as packaging material for consumer goods, in particular for smoking articles.

14. Container for consumer goods, wherein the container is made from a sheetlike material according to any of the claims 1 to 4. Use of a sheetlike material according to claims 1 to 4, to manufacture container for consumer goods, in particular for smoking articles.