GB2258189A

GB2258189A - Lightweight laminated paperboard

Info

Publication number: GB2258189A
Application number: GB9216325A
Authority: GB
Inventors: Fargas Francisca Cobo
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-08-01
Filing date: 1992-07-31
Publication date: 1993-02-03
Also published as: IT1256889B; FR2682133A1; NL9201374A; DE4225229A1; ES2033582A1; ITTO920629A1; ES2033582B1; DE4225229C2; GB9216325D0; ITTO920629A0

Description

2238139 1 - LIGHTWEIGHT LAMINATED PAPERBOARD This invention relates to

laminated paperboard and, more particularly, to laminated paperboard with a centre ply having alternating grooves and ridges, which has characteristics of strength and rigidity equivalent to solid laminated paperboard, but is 30% to 45% lighter in weight.

Laminated paperboard or pasted chipboard, which has two or more flat plies glued together, is normally used for covers in books, loose-leaf binders and as panels in boards for tabletop games and the like, which require the characteristics of rigidity, strength, stability, smooth outer surfaces, and resistance to bending and folding. In order to provide these characteristics, the laminated paperboard or pasted chipboard is made of flat layers glued together to form a solid mass which is relatively heavy and is costly to produce because of the amount of paperboard required.

To overcome these problems, corrugated paperboard including an internal corrugated layer of paperboard to replace one or more of the flat layers and having internal spaces has been utilized. However, such corrugated paperboard does not have the rigidity and strength required to replace solid laminated paperboard which is typically used for covers in looseleaf binders, books, gameboards and the like. In particular, such corrugated paperboard, although light in weight, is - 2 easily folded and bent. It is also unsatisfactory in providing a smooth outer surface, as the ridges of the fluted or corrugated ply are transferred through the thin outer plies or liners commonly used in corrugated paperboard. Thus, corrugated paperboard is not satisfactory in replacing solid laminated paperboard to reduce its weight and cost for such purposes.

In addition, it has also been known to use a form of corrugated paperboard, referred to in the industry as E flute corrugated, which has approximately 295 corrugations per metre run of paperboard. This relatively high number of flutes, compared to other commonly used corrugations, is not sufficiently resistant to bending and folding and does not have sufficiently smooth outer surfaces and, therefore, cannot be used to satisfactorily replace solid laminated paperboard typically used in loose-leaf binders, books, gameboards and the like.

It has also been known to use heavier weight outer plies with an E flute type corrugated centre ply to add rigidity and smoothness. Such paperboard is still not sufficiently resistant to bending and folding, and the ridges of the corrugated centre ply still transfer their form through the outer ply to create an uneven outer surface.

Accordingly, it is an object of the present invention to overcome the aforesaid drawbacks.

The present invention provides laminated paperboard, comprising:

a first layer of paperboard having a thickness in the range 0.3 mm to 1.5 mm inclusive; a second layer of paperboard having a thickness in the range 0.3 mm to 1. 5 mm inclusive; the outer surfaces of said first and second layers being substantially flat and smooth; and a first internal layer of contoured paperboard, having a thickness in the range 0.23 mm to 0.5 mm inclusive and having grooves and ridges, disposed between and glued to the inner surfaces of each of said first and second layers of paperboard, and wherein:

the grooves and ridges have a height in the range 0.90 mm to 1.2 mm inclusive; the number of grooves and ridges of the said first internal layer of contoured paperboard is in the range 350 to 400, inclusive, sets of grooves and ridges per metre run of paperboard; and one side of said first internal layer of contoured paperboard is inset within the inner surface of said second layer of paperboard by at least 0. 1 mm, the said curved surfaces on the curved one side increasing the contact area and gluing region between said layers thereby to increase the rigidity and strength of said laminated paperboard.

Such laminated paperboard with a centre ply having alternating grooves and ridges is light in weight and therefore less costly to produce, yet notwithstanding has characteristics of rigidity, strength, resistance to bending, and a smooth outer surface equivalent to those of solid laminated paperboard having flat plies.

Such laminated paperboard has increased rigidity and strength as a result of the large number of grooves and ridges utilized and as a result of increasing the area of the glued surfaces between the various layers by insetting the surfaces of adjacent layers.

Such laminated paperboard can provide greater parallelism and moisture stability as a result of specially-designed contours of grooves and ridges and their reduced interaction as compared to solid laminated paperboard.

In accordance with embodiments of the present invention illustrated in the accompanying drawings, there is provided laminated paperboard having spaced-apart first and second layers of paperboard, and an internal layer of contoured paperboard disposed between and glued to each of the first and second outer layers of the paperboard. The internal layer of contoured paperboard consists of specially-designed contours of curved grooves and ridges in an alternating pattern.

The curved surfaces on one side of the internal layer of contoured paperboard are inset in one of the first and second outer layers of paperboard by at least 0.1 mm to increase the contact area and gluing area between the layers so as to increase the strength and rigidity of the laminated paperboard.

The grooves and ridges in the internal layer of contoured paperboard are of a relatively low height, whereas the number of grooves and ridges per metre run is relatively high. These features combine with the feature of increasing the contact area and gluing area between the layers to offer a substantially improved laminated paperboard.which is lighter in weight and less costly to produce than solid laminated paperboard, since it utilizes less material, but yet is substantially equivalent, in rigidity, strength and resistance to bending, to heavier solid laminated paperboard which has flat layers glued together to form a solid mass.

The present invention also includes an embodiment having two or more internal layers of contoured paperboard with each disposed between and glued to adjacent outer layers of the paperboard material. Such laminated paperboard with additional internal contoured layers is useful when thicker and more rigid paperboard is required for particular uses, such as heavy bookcovers, loose-leaf covers, and the like.

In a third illustrated embodiment in accordance with the present invention, the grooves and ridges of the first internal layer of contoured paperboard extend in a first direction, and the grooves and ridges of the second 6 - internal layer of contoured paperboard extend in a second direction, which is disposed at 900 to the first direction, to form a laminated paperboard having grooves and ridges which are offset from each other by 900 (referred to herein as cross-ridges) further to increase the strength and rigidity of the laminated paperboard of the present invention. All of this offers a device wherein the grain direction of both layers is balanced.

Advantageously, as a result of the present invention, there is offered a laminated paperboard which is light in weight and is less costly to produce, but yet has substantially equivalent characteristics of strength, rigidity, and resistance to bending as heavier solid laminated paperboard having flat plies.

Laminated paperboard constructed in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view, partially in section, of a first embodiment of the invention; Figure 2 is a cross-sectional view of the embodiment of Figure 1 and shows thelayer of contoured paperboard disposed between and glued to the outer layers of the paperboard; Figure 3 is a cross-sectional view of the layer of contoured paperboard and the degree to which it is inset in the outer layers of the paperboard; Figure 4 is a cross-sectional view of a modified embodiment of the present invention which includes a second layer of the contoured paperboard; and Figure 5 is a perspective view of a third embodiment of the present invention wherein one layer of the contoured paperboard is disposed at 90 with respect to a second layer of the contoured paperboard.

Referring to the accompanying drawings, the first embodiment shown in Figures I and 2 consists of laminated paperboard 10 comprising three layers 12, 14 and 16. The outer layers 12 and 14 are flat on their outer surfaces and are formed of paperboard, and each has a thickness in the range of 0.3 mm to 1.5 mm (0.01211 to 0.06011).

The internal layer 16 of contoured or profiled paperboard consists of specially-designed contours defined by curved grooves 16a and ridges l6b in an alternating pattern and has a thickness in the range of 0.23 mm to 0.5 mm (0.00911 to 0.02011). The layer 16 is disposed between and glued to the inner surfaces of each of the outer layers 12 and 14 along the upper and lower curved surfaces 16a and 16b. one curved surface 16a and an adjacent curved surface 16b make up one set of curved surfaces designated 18. Each set of curved surfaces 18 has a height in the range of 0.90 mm to 1.2 mm (0.03511 to 0.047"), and the number of sets 18 is in the range of 350 to 400 per metre run of paperboard. In a preferred example, there are 375 sets of curved surfaces 18 per metre run, and the curved surfaces have a preferred height of 1.0 mm (0. 03911).

In forming the laminated paperboard 10, the layer 16 has glue applied thereto, and the layers 12 and 16 are passed through rollers under a sufficient pressure to press the two layers together to adhere them. As a result, the curved surfaces 16a adhere to the inner surface 12a of layer 12, and the pressure causes the curved surfaces 16a to imbed and become inset or "indented" into the surface 12a by at least 0.1 mm (0.00411) and up to as much as 0.25 mm (0.01011).

In a preferred example, the amount of inset is 0.2 mm (0.00811). That increases the contact area between surfaces 16a and 12a, so that the gluing area between the layers 12 and 16 is increased. As a result, the rigidity and strength of the laminated paperboard 10 is substantially increased.

As the layer 16 has glue applied thereto, the composite of layers 12 and 16 can then be adhered to the layer 14 by passing said layers through equipment to supply sufficient pressure to cause a bond and to slightly imbed curved surfaces 16b into the inner surface 14a of layer 14.

In a preferred example of laminated board 10, the area of contact surface between surfaces 12a and 16a is at least twice the area of contact surface between surfaces 14a and 16b. In addition, the total thickness of the laminated paperboard 10 is in the range of 1.5 mm to 4.70 mm or 0. 06011 to 0.18511, and in a preferred example it is in the range of 2.0 mm to 3.0 mm or 0.07911 to 0.118".

Figure 3 is a detailed view of Figure 2 to illustrate more clearly the amount of inset between curved surfaces 16a and inner surface 12a wherein the range of inset is between 0.1 ram and 0.25 mm, with the preferred amount being 0.2 mm. As shown, the amount of inset of 0.1 mm or 0.2 mm is represented by arrow 30 and is the maximum inset along arc 32 of curved surface 16a, with arc 32 defining a chord 34. For purposes of illustration, measurements of the chord 34 have been taken for different insets 30. For example, when inset 30 is 0.1 mm, chord 34 is at least 0. 52 mm in width. If this width is multiplied by the length of curved surface 16a (shown by arrow 36), the area of contact surface between surfaces 16a and 12a can be calculated to determine the increased gluing area between layers 12 and 16. In another example, when inset 30 is 0.2 mm, chord 34 will be at least 0.67 mm in width, and when inset 30 is 0.25 ram, chord 34 will be at least 0.73 mm in width. Accordingly, the amount of gluing area between the layers 12 and 16 is significantly wider than in other situations of only point contact in the gluing area, such as in corrugated board, so that in the present invention, this contributes to the increased strength and rigidity of the laminated paperboard.

The second embodiment, shown in Figure 4, is a laminated paperboard 100 comprising five layers 120, 140, 160, 180 and 200. Layers 120, 140, and 180, similar to layers 12 and 14, are formed of paperboard, and each has a thickness in the range of 0.3 mm to 1.5 mm (0.01211 to 0.06011).

The same as the layer 16 of the contoured paperboard, layers 160 and 200 are also formed of contoured paperboard, and each has a thickness in the range of 0.23 mm to 0.5 mm (0.00911 to 0.02011). Layer 160 is disposed between and glued to each of the layers 120 and 140 along the curved surfaces 160a and 160b, and layer 200 is disposed between and glued to each of the layers 140 and 180 along the curved surfaces 200a and 200b. Each set of curved surfaces in layer 160 includes one curved surface 160a and an adjacent curved surface 160b while each set of curved surfaces in the layer 200 includes a curved surface 200a and an adjacent curved surface 200b. In addition, each set of curved surfaces in each of the layers 160 and 200 has a height in the range of 0.90 mm to 1.2 mm (0. 03511 to 0.047"), and the number of sets in each layer is in the range of 350 to 400 sets of curved surfaces per metre run of paperboard.-. In a preferred example, there are 375 sets of curved surfaces per metre run in the layers 160 and 200, and the curved surfaces have a preferred height of 1.0 mm (0.03911).

In forming laminated paperboard 100, the layer 160 has glue applied thereto, and layers 120 and 160 are processed through equipment under a sufficient pressure to press the two layers together to adhere them. As a result, the curved surfaces 160a are adhered to the inner surface 120a of layer 120, and the pressure causes curved surfaces 160a to imbed and become inset into surface 120a by at least 0.1 mm (0.00411) and up to as much as 0.25 mm. (0.01011). In a preferred example, the amount of inset is 0.2 mm (0.00811). That increases the area of the contact surface between surfaces 120a and 160a, so that the gluing area between the layers 120 and 160 is increased, which increases also the rigidity and strength of the product. Furthermore, the correlation between the amount of inset 30 and chord 34, as explained above with respect to Figure 3, is also applicable to this embodiment. The composite of layers 120 and 160 is then adhered to layer 140 in the same manner as explained with regard to layers 12, 14 and 16. In completing the formation of paperboard 100, layer 200 has glue applied thereto, and layers 180 and 200 are passed through rollers under sufficient pressure to press the two layers- together to adhere them. As a result, curved surfaces 200b are adhered to the inner surface 180a of layer 180, and the pressure causes curved surfaces 200b to imbed and become inset into surface 180a by at least 0.1 mm. (0.00411) and up to now at - 12 least 0.25 mm (0.01011). In a preferred example, the amount of inset is 0. 2 mm (0.00811). Again, the correlations given in Figure 3 are applicable also to this embodiment. Therewith the contact area or surface between surfaces 200b and 180a is increased, so that the gluing area between the layers 180 and 200 is increased, and therefore the rigidity and strength of the laminated paperboard is increased.

Furthermore, in forming laminated paperboard 100, the composite of layers 180 and 200 is glued to surface 140b by passing the composite device of layers through the rollers and the equipment to supply sufficient pressure to cause the bond and slightly to imbed the curved surfaces 200a into layer 140.

In a preferred example of the laminated paperboard 100, the contact region between surfaces 160a and 120a is at least twice the region of the contact surface between surfaces 160b and 140a, while the region of the contact area between surfaces 200b and 180a is at least twice the region of the contact area between surfaces 200a and 140b. Furthermore, the total thickness of the laminated paperboard 100 is in the range of 2.80 mm to 7.60 mm (0.11011 to 0.300"), and in a preferred example is in the range of 3.0 mm to 4.6 mm (0.11811 to 0.18111).

The third embodiment, shown in Figure 5, consists of laminated paperboard 300 comprising five layers 310, 320, 330, 340 and 350.Layers 310, 320 and 330 are formed of paperboard, and each has a thickness in the range of 0.3 mm to 1.5 mm. (0. 01211 to 0.060"), as in the first two embodiments.

The layers 340 and 350 are of contoured paperboard, and each has a thickness in the range of 0.23 mm. to 0.5 mm (0.00911 to 0.02011). Layers 340 and 350 are disposed between and glued to each of the layers 310, 320, and 330 along their curved surfaces, in a manner similar to that explained in the embodiment of Figure 4. Furthermore, the curved surfaces of the layers 340 and 350 have the same characteristics as those described in the embodiment of Figure 4 and, in all respects, are the same except for the direction of the curved surfaces in the layer. That is, in the Figure 5 embodiment, the curved surfaces in the layer 340 extend in a first direction, and the curved surfaces in the second layer 350 extend in a second direction to form laminated paperboard having cross ridges, whereby the resultant laminated paperboard is lighter in weight and has smooth outer surfaces. Furthermore, since the grain direction of layers 340 and 350 is different, the overall grain direction is more uniform and balanced.

Although the present invention has illustrated embodiments with one and two internal layers, it should be understood that the scope of the present invention is intended to include also three or more internal layers arranged in the manner described above.

In order more clearly to illustrate the degree to which the laminated paperboard of the present invention is lighter in weight than solid laminated paperboard, we shall provide two examples. In the first example we shall compare 100 point solid laminated paperboard with the embodiment of Figures I and 2 of the present invention. In the solid 100 point board, each of the three layers has a thickness of 0.85 mm and a weight of 551. 4 grams per square meter (M2) or a weight of 1,654.3 grams per R12. In accordance with the present invention, the 100 point board has outer layers 12 and 16, which can each have a thickness of 0.71 mm and a weight of 463 grams per M2. The internal layer 16 has a height of 1.12 mm, but a thickness of only 0.30 mm and a weight of approximately 209.8 grams/M2. Thus, the laminated board of the present invention weighs only 1,137.0 gramS/m2 compared with the 1,654.3 grams/M2 for solid laminated paperboard, with a savings of over 31% in the amount of paperboard utilized to obtain substantially the same characteristics of strength and rigidity as solid laminated paperboard.

Another example illustrates an even greater saving. For example, 172 point solid laminated paperboard can be compared with the embodiment of Figure 4. Typically, 172 point solid laminated paperboard, regardless of the number of plies, has a weight of 2,854.8 grams/M2. In accordance with the present invention, the 172 point - is - board has layers 120, 140, and 180, which can each have a thickness of 0. 71 mm and a weight of 463 grams/M2. The internal layers 160 and 200 each have a height of 1.12 mm, but a thickness of only 0.30 mm and a weight of approximately 209.8 grams/M2. Thus, the laminated board embodying the present invention weighs only 1,810.5 grams/M2 compared with the 2,854.8 grams/m2 of the solid laminated paperboard, for a savings of over 37% in the amount of paperboard utilized. It should be understood that internal layer 140 can even be made thinner than 0.71 mm, so that the savings in weight would even be greater.

A whole range of modifications, changes, and substitutions for what has been described in the foregoing description is possible within the scope of the appended claims. In some instances, some features will be employed without a corresponding use of the remaining ones.

- 16

Claims

C L A I M S

1. Laminated paperboard, comprising:

the grooves and ridges have a height in the range 0.90 mm to 1.2 mm inclusive; the number of grooves and ridges of the said first internal layer of contoured paperboard is in the range 350 to 400, inclusive, sets of grooves and ridges per metre run of paperboard; and one side of said first internal layer of contoured paperboard is inset within the inner surface of said second layer of paperboard by at least 0. 1 mm, the saidcurved surfaces on the curved one side increasing the contact area and gluing region between said layers thereby to increase the rigidity and strength of said laminated paperboard.

2. Laminated paperboard in accordance with claim 1, further including:

a third layer of paperboard having a flat outer surface and a thickness in the range 0.3 mm to 1.5 mm inclusive; a second internal layer of contoured paperboard having a thickness in the range 0.23 mm to 0.5 mm inclusive and having grooves and ridges, disposed between and glued to the inner surfaces of each of said second and third layers of paperboard and having a height in the range of 0.90 mm to 1.2 mm inclusive; and wherein:

the number of grooves and ridges of said second internal layer of contoured paperboard is in the range 350 to 400, inclusive, sets of grooves and ridges per metre run of paperboard; and the curved surfaces on one side of said second internal layer of contoured paperboard are inset within the inner surface of said third layer of paperboard by at least 0.1 mm to increase the region of the contact area and gluing region between said layers to increase therefore the rigidity and strength of said laminated paperboard.

3. Laminated paperboard in accordance with claim 2, wherein the grooves and ridges of said first internal layer of contoured paperboard extend in a first direction and the grooves and ridges of said second internal layer of contoured paperboard extend in a second direction disposed at substantially 90 to said first direction to form a laminated paperboard having cross ridges to balance the grain directions of said first and second internal layers which are at 900 relative to each other.

4. Laminated paperboard in accordance with claim 1, wherein said first internal layer of contoured paperboard has 375 sets of grooves and ridges per metre run of paperboard.

5. Laminated paperboard in accordance with claim 2, wherein said first and second internal layers of contoured paperboard each have 375 grooves and ridges per metre run of paperboard.

6. Laminated paperboard in accordance with claim 1, wherein the extent of the contact area between said first internal layer of the contoured paperboard and said second layer of paperboard is greater than the extent of the contact area between said first internal layer of the contoured paperboard and said first layer of paperboard.

7. Laminated paperboard in accordance with claim 1, wherein the extent of the contact area between said first internal layer of contoured paperboard and said second layer of paperboard is at least double the extent of contact area between said first layer of paperboard.

8. Laminated paperboard in accordance with claim 1, wherein the total thickness of said laminated paperboard is in the range 1.5 mm (0.060 inch) to 4.70 mm (0.185 inch) inclusive.

9. Laminated paperboard in accordance with claim 1, wherein the total thickness of said laminated paperboard is in the range 2.0 mm (0.080 inch) to 3.0 mm (0.120 inch) inclusive.

10. Laminated paperboard in accordance with claim 2, wherein the total thickness of said laminated paperboard is in the range 2.80 mm (0.110 inch) to 7.60 mm (0.300 inch) inclusive.

11. Laminated paperboard in accordance with claim 2, wherein the total thickness of said laminated paperboard is in the range 3.0 mm (0.120 inch) to 4.6 mm (0.180 inch) inclusive.

12. Laminated paperboard in accordance with claim 1, wherein said laminated paperboard is suited or used to make cover boards for looseleaf binders and books which are light in weight and have required strength and rigidity as well as smooth outer surfaces.

13. Laminated paperboard in accordance with claim 1, wherein the grooves and ridges of said first internal layer of the contoured paperboard have a height of approximately 1.0 mm (0.03911).

14. Laminated paperboard in accordance with claim 2, wherein the grooves and ridges of said second internal layer of contoured paperboard have a height of approximately 1.0 mm (0.03911).

15. Laminated paperboard in accordance with claim 1, wherein the curved surfaces on one side of said first internal layer of contoured paperboard are inset within - 20 said second layer of paperboard by approximately 0.2 mm (0.00811).

16. Laminated paperboard in accordance with claim 2, wherein the curved surfaces on one side of said second internal layer of contoured paperboard are inset within said said third layer of paperboard by approximately 0.2 mm (0.00811).

17. Laminated paperboard in accordance with claim 1, wherein the curved surfaces on one side of said first internal layer of contoured paperboard are inset within said second layer of paperboard by no more than 0.25 mm (0.010").

18. Laminated paperboard in accordance with claim 2, wherein the curved surfaces on one side of said second internal layer of contoured paperboard are inset within said third layer of paperboard by no more than 0.25 mm. (0.01011).

19. Laminated paperboard substantially as herein described with reference to, and as illustrated by, Figures 1, 2 and 3 of the accompanying drawings.

20. Laminated paperboard in accordance with claim 19 but modified substantially as herein described with reference to, and as illustrated by, Figure 4 of the accompanying drawings.

21. Laminated paperboard in accordance with claim 19 but modified substantially as herein described with reference to, and as illustrated by, Figure 5 of the accompanying drawings.