阅读说明：本技术 多层纸板 (Multilayer paperboard ) 是由 F.彭 A.莫伯格 于 2014-12-15 设计创作，主要内容包括：本发明涉及多层纸板。具体而言,本发明涉及具有高的松厚度和维持的强度的高品质多层纸板。所述纸板包括至少三层：表面层、中间层和背层,其中所述中间层包括至少50重量％、优选至少80重量％、更优选至少90重量％的来自阔叶木纤维的高温化学热磨机械浆(HT-CTMP),所有的百分比都基于所述中间层的总纤维重量计算。所述纸板具有高强度、良好的保护性以及高质量的外观,适合用作例如液体包装纸板、食品服务板、绘画纸板或者香烟纸板。(The present invention relates to a multi-ply paperboard. In particular, the present invention relates to high quality multi-ply paperboard having high bulk and maintained strength. The paperboard comprises at least three layers: a surface layer, an intermediate layer and a backing layer, wherein the intermediate layer comprises at least 50 wt.%, preferably at least 80 wt.%, more preferably at least 90 wt.% of high temperature chemical thermomechanical pulp (HT-CTMP) from hardwood fibers, all percentages being calculated on the total fiber weight of the intermediate layer. The paperboard has high strength, good protection and a high quality appearance and is suitable for use as, for example, liquid packaging board, food service board, drawing board or cigarette board.)

1. High quality paperboard comprising at least three layers: a surface layer, an intermediate layer and a backing layer, wherein the intermediate layer comprises at least 50 wt% of high temperature chemical thermomechanical pulp (HT-CTMP) from hardwood fibers, all percentages being calculated on the total fiber weight of the intermediate layer, wherein the intermediate layer comprises as dry strength additives at least one cationic polymer, such as cationic starch, and at least one anionic polymer, such as anionic CMC (carboxymethylcellulose), or anionic polyacrylamide (a-PAM).

2. Paperboard according to claim 1, wherein the middle layer exhibits less than 400kg/m³And a z-strength of at least 150 kPa.

3. Paperboard according to any of claims 1 to 2, wherein the middle layer exhibits at least 100J/m²ScottBond value of (a).

4. Paperboard according to any one of claims 1 to 3, wherein the hardwood pulp in the intermediate pulp has a bulk density of less than 300kg/m³Is the density of a pulp sheet according to ISO 534: 2005.

5. Paperboard according to claim 1, wherein the middle ply further comprises a dry strength additive selected from the group consisting of: nano-fibrillated cellulose, polyvinylamine, chitosan, primary and secondary amines, polyethylene diamine, modified polyacrylamide, and combinations thereof.

6. Paperboard according to any one of claims 1 to 5, wherein the intermediate layer comprises cationic starch in an amount of at least 20 kg/ton, and/or anionic polymer in an amount of at least 0.1 kg/ton.

7. Paperboard according to any one of claims 1 to 5, wherein the intermediate layer comprises CMC in an amount of at least 1 kg/ton.

8. Paperboard according to any one of claims 1 to 5, wherein the intermediate layer comprises A-PAM in an amount of at least 0.1 kg/ton.

9. Paperboard according to claim 1, wherein the middle layer comprises at least 80 wt.% of high temperature chemical thermomechanical pulp (HT-CTMP) from hardwood fibers.

10. Paperboard according to claim 1, wherein the intermediate layer comprises at least 90 wt.% of high temperature chemical thermomechanical pulp (HT-CTMP) from hardwood fibers.

11. Paperboard according to claim 2, wherein the middle layer exhibits less than 350kg/m³The density of (c).

12. Paperboard according to claim 2, wherein the middle layer exhibits less than 300kg/m³The density of (c).

13. Paperboard according to claim 2, wherein the middle ply exhibits a z-strength of at least 250 kPa.

14. Paperboard according to claim 2, wherein the middle layer exhibits a z-strength of at least 350 kPa.

15. Paperboard according to claim 3, wherein the middle layer exhibits at least 150J/m²Scott Bond value of (a).

16. Paperboard according to claim 4, wherein the hardwood pulp in the intermediate pulp has a bulk density of less than 250kg/m³Is the density of a pulp sheet according to ISO 534: 2005.

17. Paperboard according to claim 4, wherein the hardwood pulp in the intermediate pulp has a bulk density of less than 200kg/m³Is the density of a pulp sheet according to ISO 534: 2005.

18. Paperboard according to claim 6, wherein the middle layer comprises cationic starch in an amount of at least 40 kg/ton.

19. Paperboard according to claim 7, wherein the intermediate layer comprises CMC in an amount of at least 1.5 kg/ton.

20. Paperboard according to claim 8, wherein the middle layer comprises a-PAM in an amount of at least 0.2 kg/ton.

21. Cardboard according to any of claims 1 to 20, wherein the hardwood fibers are from birch and/or eucalyptus.

22. A paperboard for containing liquids, characterized in that it is made from the paperboard according to any one of claims 1-21.

23. A board for holding food, characterized in that it is made from a board according to any one of claims 1-21.

Technical Field

The present invention relates to high quality multi-ply paperboard (paperboard) having a high bulk (bulk) and a maintained strength (main drawn paperboard).

Background

There are a number of applications where paperboard is used. All these applications have their own specific requirements for the board, and therefore the properties of the board must be different depending on the intended end use.

The paperboard to be converted (e.g., coated, printed, cut, creased, and folded) into packaging articles on fast-running automated machines must have the required strength to resist the strains and stresses generated during the conversion process. The board must also have a high resistance to bending, not only to obtain good runnability during converting, but also to be critical for the desired packaging properties. For long shelf life products, the package must also have good barrier properties to light, oxygen and moisture. Properties such as smoothness and dimensional stability are also important in the conversion process.

The bulk (inverse density) of the board is an important property because it contributes to the thickness of the donor board. The increased thickness improves the bending stiffness of the plate. The high bulk further enables the papermaker to reduce the amount of fibers in the board, which involves cost savings. However, high bulk often results in a reduction in internal strength. One challenge for papermakers is to increase the bulk of the paperboard while maintaining strength.

Paperboard typically comprises 1-5 plies. The board to be converted often comprises more than one layer. Multi-ply paperboard often exhibits a higher flex resistance index than single ply paperboard. Paperboard consisting of three or more plies comprises a top ply and a back ply (back ply) and one or more intermediate plies.

Chemical pastes are often used in the top and back layers of the board to provide strength and good printing properties to the board. The middle layer of the panel may contain both mechanical and/or chemical pulp. Mechanical pulp, such as CTMP, is a desirable raw material because it has a rather low density and can be produced at a lower cost than chemical pulp. Furthermore, mechanical pulp has a higher yield and therefore a higher efficiency of raw material use. In high-quality boards, softwood CTMP is the most common mechanical pulp for the interlayer, because softwood CTMP, in addition to having a high bulk, also has long fibers that provide good internal bonding (binding). Due to its high strength properties, chemical pulp is also used in the intermediate layer, usually in combination with mechanical pulp, as reinforcement.

Patent specification WO2006084883 discloses a high quality paperboard with an intermediate layer containing a high amount of hardwood CTMP. However, in the production of paperboard disclosed in WO2006084883, there is an upper limit on how high a bulk can be obtained at a maintained strength. Thus, there remains a need for high quality paperboard having high bulk and maintained strength.

Disclosure of Invention

The present invention discloses a high quality paperboard comprising at least three layers; a surface layer, an intermediate layer and a backing layer, wherein the intermediate layer comprises at least 50%, preferably at least 80%, more preferably at least 90% of high temperature chemical thermomechanical pulp (HT-CTMP) from hardwood fibers, calculated to the total fiber weight of the intermediate layer.

It has been unexpectedly shown that the use of HT-CTMP from hardwood fibers in the middle layer enables the production of paperboard with very high bulk and with maintained strength properties. Furthermore, the use of HT-CTMP from hardwood fibers significantly improves the brightness properties and formation of paperboard. The middle layer of the board showed less than 400kg/m³Preferably less than 350kg/m³Even more preferably less than 300kg/m³A z-strength of at least 150kPa, preferably at least 250kPa, most preferably at least 350kPa, and at least 100J/m²Preferably at least 150J/m²Scott Bond value of (a).

Hardwood pulp in the intermediate pulpHaving a density of less than 300kg/m³Preferably less than 250kg/m³And even more preferably 200kg/m³(iii) density of (C) (pulp sheet density, ISO 534: 2005).

At least one of the layers of the paperboard of the invention, preferably the middle layer, may comprise a dry strength additive. The strength additive may be selected from the group consisting of cationic starch, anionic polymers, nanofibrillated cellulose, polyvinylamine, chitosan, primary and secondary amines, polyethylene diamine and modified polyacrylamides, and combinations thereof. The anionic polymer may for example be carboxymethylcellulose (CMC) and/or anionic polyacrylamide (a-PAM). The addition of such dry strength additives improves the strength properties of the paperboard and enables the use of high levels of HTCTMP from hardwood fibers in the middle layer. In a preferred embodiment, at least one layer comprises at least one cationic polymer (e.g. cationic starch) and at least one anionic polymer (e.g. anionic CMC (carboxymethyl cellulose), or anionic polyacrylamide (a-PAM)). The cationic and anionic polymers may be added in successive (successive) steps to the furnish forming the layer (furnish). This improves the strength of the resulting board product. Alternatively, the polymer may be added to the mixed ingredients simultaneously, or the polymer may be pre-mixed with the mixed ingredients.

Hardwood pulps used according to the present invention may be derived, for example, from eucalyptus, aspen (aspen), acacia (acacia), maple, beech, poplar (poptar) and/or birch.

Detailed Description

The paperboard of the present invention is a high quality paperboard suitable for use as, for example, a liquid packaging paperboard, a food service board, a drawing paperboard, or a cigarette paperboard.

High quality paperboard is paperboard with high strength (to be able to withstand conversion), good protection, and a high quality appearance.

Preferably, the multilayer paperboard of the present invention comprises three layers; a top layer, a back layer and at least one intermediate layer. The paperboard may further include a layer disposed between the outer layer and the intermediate layer. These intermediate layers may have the same or different fiber composition as the intermediate layers. The cardboard may for example comprise a total of four or five layers.

According to the invention, the middle ply comprises at least 50%, preferably at least 80%, and more preferably at least 90% hardwood HT-CTMP, which provides the paperboard with a high bulk without any significant reduction in the strength of the final paperboard product. The middle layer may also include a small amount of bleached or unbleached chemical pulp, such as 10, 15, or 20 weight percent, based on the total fiber weight of the middle layer. The top layer preferably comprises hardwood and/or softwood chemical pulp, which provides good strength and printing properties to the product. The backing layer may comprise hardwood and/or softwood chemical pulp.

The term "high temperature chemithermomechanical pulp (HT-CTMP)" as used herein refers to a pulp that has been preheated to a temperature of at least 140 ℃, preferably at least 150 ℃, or even more preferably at least 160 ℃ prior to the refining step.

Surprisingly, it has been shown that it is possible to produce a paperboard containing such a high content of HT-CTPMP from hardwood fibers in the middle layer, and still maintaining a high strength.

The paperboard of the present invention may also include dry strength additives. Dry strength additives that may be used include, but are not limited to: starch, polyacrylamide, carboxymethyl cellulose (CMC), nanofibrillated polysaccharide. In the context of the present invention, the nanofibrillated polysaccharide should comprise nanocellulose or bacterial (bacterial) cellulose spun with conventional spinning techniques or using electrospinning. Likewise, microfibrillated cellulose (MFC), also known as nanocellulose (nanocellulose), cellulose whiskers (whisskers), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC) or regenerated cellulose fibers and particles are included in the definition of nanofibrillated polysaccharide herein.

In one embodiment, one of the layers, preferably the middle layer, comprises cationic starch and anionic CMC. Cationic starch and anionic CMC may be added to one of the layers, preferably the intermediate layer, in successive steps. This can be done, for example, according to the methods disclosed in WO2006120235 or WO 2006041401. This has been shown to further increase the strength properties of the resulting paperboard product. Preferably, the intermediate layer comprises cationic starch in an amount of at least 20 kg/ton, or preferably at least 30 kg/ton, and CMC in an amount of at least 1 kg/ton or at least 2 kg/ton.

The present invention includes the following embodiments:

1. high quality paperboard comprising at least three layers: a surface layer, an intermediate layer and a backing layer, wherein the intermediate layer comprises at least 50 wt.%, preferably at least 80 wt.%, more preferably at least 90 wt.% of high temperature chemical thermomechanical pulp (HT-CTMP) from hardwood fibers, all percentages being calculated on the total fiber weight of the intermediate layer.

2. The paperboard according to item 1, wherein said middle layer exhibits less than 400kg/m³Preferably less than 350kg/m³Even more preferably less than 300kg/m³And a z-strength of at least 150kPa, preferably at least 250kPa, most preferably at least 350 kPa.

3. Paperboard according to any of items 1 to 2, wherein the middle layer exhibits at least 100J/m²Preferably at least 150J/m²Scott Bond value of (a).

4. Paperboard according to any of items 1 to 3, wherein the hardwood pulp in the intermediate pulp has a bulk density of less than 300kg/m³Preferably less than 250kg/m³And even more preferably 200kg/m³(iii) density of (C) (pulp sheet density, ISO 534: 2005).

5. The paperboard according to any of items 1 to 4, wherein the middle layer comprises a dry strength additive.

6. The paperboard according to item 5, wherein the dry strength additive is selected from the group consisting of cationic starch, anionic polymers, nanofibrillated cellulose, polyvinylamine, chitosan, primary and secondary amines, polyethylene diamine, modified polyacrylamides, and combinations thereof.

7. The paperboard according to any of items 1 to 6, wherein the middle layer comprises cationic starch in an amount of at least 20 kg/ton, preferably at least 40 kg/ton, and/or anionic polymer in an amount of at least 0.1 kg/ton.

8. The paperboard according to any of items 1 to 6, wherein the intermediate layer comprises CMC in an amount of at least 1 kg/ton, preferably at least 1.5 kg/ton.

9. The paperboard according to any of items 1 to 6, wherein the middle layer comprises A-PAM in an amount of at least 0.1 kg/ton, preferably at least 0.2 kg/ton.

10. The paperboard according to any one of items 1 to 9, wherein the hardwood fibers are from birch and/or eucalyptus.

11 paperboard for containing liquids, characterized in that it is made of a paperboard according to any one of claims 1-10.

12. A board for holding food, characterized in that it is made of a board according to any one of the claims 1-10.

Measuring and evaluating method

The following methods and standards apply both to the definitions of the appended claims and to the measurements made in the examples below.

Tensile index ISO 1924-3:2005

Scott Bond:TAPPI UM-403

Z-Strength SCAN-P80: 98

Density (cardboard, samples 1-2, Table 4) ISO 534:2011

Dehydration resistance (Draainage resistance) SCAN M3:65

Strain at failure ISO 1924-3:2005

Absolute Tensile energy index (Tensile energy abs. index): ISO 1924-3:2005

Tensile stiffness index (Tensile stiffness index): ISO 1924-3:2005

Density (pulp sheet Density, Table 1) ISO 534:2005