Mineral-based panel comprising grooves and a method for forming grooves

Abstract

A mineral-based panel including a mineral-based core and at least one groove. The at least one groove may be provided in a rear side of the panel. The mineral-based panels may be floor panel, a building panel, a wall panel, a ceiling panel or a furniture panel. A method for forming such grooves in a mineral-based panel. Furthermore, a mineral-based panel including a mineral-based core and polymer-based lower layer(s) attached to the core. A locking system of the panel includes a strip extending horizontally beyond an upper portion of the panel, and a horizontal portion of the strip is entirely formed in the polymer-based lower layer(s).

Claims

1. A mineral-based floor panel comprising a mineral-based core, wherein the mineral-based core comprises magnesium oxide, wherein the mineral-based core further comprises magnesium chloride and/or magnesium sulphate, wherein the panel comprises at least one groove, and wherein the at least one groove is provided in a rear side of the panel, between two coplanar lowermost surfaces of the floor panel.

2. The mineral-based panel according to claim 1, wherein the mineral-based core further comprises magnesium sulphate.

3. The mineral-based panel according to claim 1, wherein the at least one groove is provided in a lower side of the mineral-based core.

4. The mineral-based panel according to claim 1, further comprising a lower arrangement comprising at least one lower layer being attached to a lower side of the mineral-based core.

5. The mineral-based panel according to claim 4, wherein the at least one groove is at least partly provided in the lower arrangement between two opposing lowermost edges of the at least one lower layer.

6. The mineral-based panel according to claim 4, wherein the lower arrangement comprises at least one polymer-based layer.

7. The mineral-based panel according to claim 6, wherein said at least one polymer-based layer is at least one thermoplastic layer.

8. The mineral-based panel according to claim 6, wherein said at least one polymer-based layer is at least one thermosetting layer.

9. The mineral-based panel according to claim 1, further comprising an upper arrangement comprising at least one upper layer being attached to an upper side of the mineral-based core.

10. The mineral-based panel according to claim 9, wherein the upper arrangement comprises at least one polymer-based layer.

11. The mineral-based panel according to claim 10, wherein said at least one polymer-based layer is at least one thermoplastic layer.

12. The mineral-based panel according to claim 10, wherein said at least one polymer-based layer is at least one thermosetting layer.

13. The mineral-based panel according to claim 1, wherein the at least one groove is provided in the core, the core being provided between an upper and a lower arrangement.

14. The mineral-based panel according to claim 1, further comprising a cover layer at least partly covering the at least one groove.

15. The mineral-based panel according to claim 1, further comprising at least one reinforcement layer.

16. The mineral-based panel according to claim 1, comprising a plurality of grooves, wherein at least two grooves have different characteristics.

17. The mineral-based panel according to claim 1, wherein said at least one groove is provided in an interior of the rear side being spaced from a pair of opposite edge portions of the panel.

18. The mineral-based panel according to claim 1, wherein the at least one groove is continuous or discontinuous.

19. The mineral-based panel according to claim 1, comprising at least two groove arrangements.

20. The mineral-based panel according to claim 1, wherein the at least one groove is provided in a surface, and an area of the surface is less than 90% of an area of a front side of the panel.

21. A mineral-based panel comprising a mineral-based core, and a lower arrangement comprising at least one polymer-based lower layer, the lower arrangement being attached to a lower side of the mineral-based core, wherein the mineral-based panel further comprises a locking system for horizontal and/or vertical locking, said locking system comprising a strip extending horizontally beyond an upper portion of the mineral-based panel, wherein at least a horizontal portion of the strip is entirely formed in the lower arrangement, and wherein a horizontal and/or vertical locking surface is provided on the at least one polymer-based lower layer, the horizontal and/or vertical locking surface being configured, when locking the panel to a similar panel, to horizontally and/or vertically lock to a second locking system of the similar panel.

22. The mineral-based panel according to claim 21, wherein the strip comprises a locking element.

23. The mineral-based panel according to claim 21, wherein the horizontal portion comprises the entire strip, wherein the entire strip is formed in the at least one polymer-based lower layer.

24. The mineral-based panel according to claim 21, wherein the locking element comprises a portion of the mineral-based core.

25. The mineral-based panel according to claim 21, wherein the horizontal locking system comprises a locking element and a locking groove, and/or wherein the vertical locking system comprises a tongue and a tongue groove.

26. The mineral-based panel according to claim 21, wherein a horizontal extension of the tongue from a vertical plane (VP) is smaller than an extension of the strip from a vertical plane (VP).

27. The mineral-based panel according to claim 21, wherein said polymer-based lower layer is a thermoplastic layer.

28. The mineral-based panel according to claim 21, wherein said polymer-based lower layer is at least one a thermosetting layer.

29. The mineral-based panel according to claim 21, wherein the mineral-based core comprises magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate.

30. The mineral-based panel according to claim 21, wherein the mineral-based core comprises cement.

31. The mineral-based panel according to claim 21, further comprising an upper arrangement comprising at least one upper layer being attached to an upper side of the mineral-based core.

32. The mineral-based panel according to claim 31, wherein the upper arrangement comprises at least one polymer-based layer.

33. The mineral-based panel according to claim 21, further comprising at least one reinforcement layer.

34. The mineral-based panel according to claim 33, wherein the at least one reinforcement layer is provided in the mineral-based core.

35. The mineral-based panel according to claim 33, wherein at least one reinforcement layer is positioned in a top portion and/or a bottom portion of the mineral-based core.

36. The mineral-based panel according to claim 33, wherein the at least one reinforcement layer is provided in the upper and/or the lower arrangement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure will in the following be described in connection to exemplary embodiments and in greater detail with reference to the appended exemplary drawings, wherein:

(2) FIGS. 1a-1c illustrate embodiments of a panel in a top view and in bottom views.

(3) FIGS. 2a-2e illustrate embodiments of a panel in a cross-sectional side view and in bottom views.

(4) FIGS. 3a-3g illustrate embodiments of a panel in cross-sectional side views and zoomed-in cross-sectional side views of a panel.

(5) FIGS. 4a-4g illustrate embodiments of a panel in cross-sectional side views and zoomed-in cross-sectional side views of a panel.

(6) FIGS. 5a-5e illustrate in side views and in perspective views embodiments of methods for providing grooves in a panel and in a side view an embodiment of a panel or a board element before providing groove(s) and/or a locking system therein.

(7) FIGS. 6a-6d illustrate embodiments of a panel in cross-sectional side views and in a bottom view.

(8) FIGS. 7a-7b illustrate embodiments of a wall panel and a ceiling panel in cross-sectional side views.

(9) FIGS. 7c-7e illustrate embodiments of a panel in zoomed-in cross-sectional side views and in a cross-sectional top view.

(10) FIGS. 8a-8e illustrate embodiments of a panel in side views.

DETAILED DESCRIPTION

(11) Next, various embodiments of a panel 1 is described with reference to the embodiments in FIGS. 1a-1c, 2a-2e, 3a-3g and 4a-4g.

(12) FIGS. 1a and 1c show in a top view and a bottom view an embodiment of a mineral-based panel 1, such as a floor panel. More specifically, FIG. 1a shows a front side 2 of the panel and FIG. 1c shows a rear side 4 of the panel comprising at least one groove 19 in a rear side of the panel, preferably a plurality of grooves. For reference, FIG. 1b illustrates in a bottom view a rear side 4 of the panel before grooves 19 is formed therein.

(13) Below, embodiments of the mineral-based panel 1 will mostly be described in the context of a floor panel, but it is understood that the panel also may be a building panel, a wall panel, a ceiling panel or a furniture panel.

(14) As shown in an embodiment in the cross-sectional side view in FIG. 2a, the panel 1, such as that in FIGS. 1a-1c, comprises a mineral-based core 3. In one example, the core comprises magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate. In one example, the core comprises cement. The core may further comprise least one selected from the group of a filler, additive(s) and a binding agent. In this embodiment, the at least one groove 19 is provided in a lower side 3a the core 3.

(15) A top structure 11 is provided on, such as attached to, an upper side 3b of the core 3. Various types of top structures are conceivable. The top structure 11 may comprise a décor layer 11a. In a first example, the décor layer 11a comprises a printed décor, such as a digitally printed décor. In a second example, the décor layer comprises a print film. The printed décor may be provided directly on the upper side of the core. Optionally, a primer may be provided on the core under the printed décor. Moreover, a coating layer 11b, such as a UV curable coating layer, a lacquer or a hot-melt coating layer, and/or a wear layer 11c may be provided on the décor layer. In some examples, the coating layer 11b may be provided on the wear layer 11c.

(16) In the embodiments in the cross-sectional side views in FIG. 3a-3g and 4a-4g, the panel may comprise a mineral-based core 3 in accordance with any of the embodiments and examples described in relation to FIGS. 1a-1c and 2a-2e, whereby reference is made thereto.

(17) As shown in FIGS. 3a-3b, the panel may further comprise a lower arrangement 5 which is attached to the lower side 3a of the core 3. The lower arrangement 5 may comprise at least one lower layer, such as one lower layer 5a as shown in FIGS. 3a and 3b. FIGS. 3d and 3f illustrate a zoomed-in view of the lower arrangement 5 in any of the embodiments in FIGS. 3a-3b comprising two lower layers 5a, 5b and three lower layers 5a, 5b, 5c, respectively.

(18) The at least one groove 19 may be at least partly provided in the lower arrangement 5 as shown in FIGS. 3a-3b, 3d and 3f. As shown in FIG. 3f and in FIG. 3a, indicating the groove(s) 19 by a dash-dotted line, the at least one groove may fully penetrate at least one lower layer 5a. As shown in FIG. 3a by the dash-dotted line, the at least one groove 19 may fully penetrate the lower arrangement 5, preferably extending into the core 3.

(19) As shown in FIGS. 3a and 3c, the panel may further comprise an upper arrangement 7 which is attached to the upper side 3b of the core 3. The upper arrangement 7 may comprise at least one upper layer, such as one upper layer 7a as shown in FIGS. 3a and 3c. FIGS. 3e and 3g illustrate a zoomed-in view of the upper arrangement 7 in any of the embodiments in FIGS. 3a and 3c comprising two upper layers 7a, 7b and three upper layers 7a, 7b, 7c, respectively.

(20) In any of the embodiments herein, such as in any of FIGS. 3a-3g, a density of the at least one lower layer, such as all lower layers, may be larger than a density of the core. Moreover, in any of the embodiments herein, a density of at least one upper layer, such as all upper layers, may be larger than a density of the mineral-based core.

(21) The panel in any of the FIGS. 3a-3c may comprise a top structure 11 provided on, such as attached to, the upper side 3b of the core in FIG. 3b or provided on, such as attached to, the upper arrangement 7 in FIGS. 3a and 3c. Embodiments and examples of the top structure 11 in FIGS. 3a-3c may be similar to any of the embodiments and examples described in relation to FIGS. 1a-1c and 2a-2e, whereby reference is made thereto.

(22) In some embodiments, the lower 5 and/or upper 7 arrangement(s), such as in any of FIGS. 3a-3g, may comprise at least one polymer-based layer.

(23) Any, or preferably both, of the lower 5 and upper 7 arrangements may comprise at least one thermoplastic layer 5a-c, 7a-c, for example comprising PVC, PE, TPU, PP, PET or ABS. The core 3 may comprise magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate.

(24) Any, or preferably both, of the lower 5 and upper 7 arrangements may comprise at least one thermosetting layer 5a-c, 7a-c, for example comprising a melamine-formaldehyde resin, epoxy resin, preferably crosslinked with an amine hardener, PU, polyurea or acrylate polymers.

(25) In some embodiments, the lower 5 and/or upper 7 arrangement(s), such as in FIGS. 3a-3g, may comprise at least one wood-based layer or cellulose-based layer, such as a veneer, paper, solid wood layer, MDF layer, HDF layer, DPL layer, HPL layer, or particle board layer.

(26) At least one lower layer, preferably all lower layers, may comprise magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate. Moreover, at least one upper layer, preferably all upper layers, may comprise magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate. Any of these embodiments may be particularly advantageous when the core comprises magnesium oxide.

(27) At least one lower layer, preferably all lower layers, may comprise cement, such as at least 30 wt % of cement. Moreover, at least one upper layer, preferably all upper layers, may comprise cement, such as at least 30 wt % of cement. Any of these embodiments may be particularly advantageous when the core comprises cement.

(28) Embodiments and examples of the panel 1 in the cross-sectional side views in FIGS. 4a-4g, such as the lower 5 and upper 7 arrangements and the top structure 11, may be largely analogous to the embodiments and examples described in relation to FIGS. 1a-1c, 2a-2e and 3a-3g, whereby reference is made thereto. In addition, FIG. 4a illustrates that the lower arrangement 5 may comprise a backing layer 5′, which the groove(s) 19 preferably fully penetrate.

(29) Generally herein, the panel may extend in a first horizontal direction x and in a perpendicular second horizontal direction y. Moreover, the panel may extend in a vertical direction z which may be perpendicular to the first and second horizontal directions. The panel 1 may comprise a first pair of opposite edge portions 1a, 1b, which may be long edge portions, and a second pair of opposite edge portions 1c, 1d, which may be short edge portions. The long edge portions may extend along the first horizontal direction x and the short edge portions may extend along the second horizontal direction y.

(30) Preferably, and as shown in e.g. FIGS. 1c, 2a-2e, 3a-3c, 3d, 3f and 4a-4d, the at least one groove 19 extends along the first horizontal direction x, which may be parallel with the long edge portions. However, as illustrated in a bottom view in the embodiment in FIG. 6d, it is equally conceivable that the at least one groove extends along the second horizontal direction y, which may be parallel with the short edge portions. In some embodiments, the panels may be essentially square and the at least one groove 19 may extend along one pair of opposite edge portions.

(31) The panel in any of the embodiments in FIGS. 1a-1c, 2a-2e, 3a-3g and 4a-4g may comprise a locking system 50a on the first pair 1a, 1b of opposite edge portions. The locking system may comprise a tongue 10 and a tongue groove 9 on the respective edge portion for vertical locking. For example, the tongue and tongue groove may be integrally formed with the panel. The locking system may further comprise a locking groove 14 and a locking element 8 on the respective edge portion for horizontal locking. The locking element is preferably provided on a strip 6 extending horizontally beyond an upper portion of the panel 1.

(32) Alternatively, or additionally, any of the panels in FIGS. 1a-1c, 2a-2e, 3a-3g and 4a-4g may comprise a locking system 50b on the second pair 1c, 1d of opposite edge portions. The locking system may comprise a tongue 10′ and a tongue groove 9′ on the respective edge portion for vertical locking. For example, and as shown in FIGS. 3a-3c, the tongue 10′ may be a separate locking tongue 10″ provided in a displacement groove 10a, preferably providing a fold down locking system. A non-limiting embodiment of a separate locking tongue 10″ is illustrated in FIG. 7e in a cross-sectional top view. This so-called bristle tongue is preferably formed in one-piece and comprises flexible protrusions 28. The locking system may further comprise a locking groove 14′ and a locking element 8′ on the respective edge portion for horizontal locking. The locking element is preferably provided on a strip 6′ extending horizontally beyond an upper portion of the panel 1.

(33) FIGS. 2b-2e show various geometries and patterns of the grooves 19 in top views. At least some grooves 19 may have different groove widths GW as shown in FIG. 2b.

(34) Preferably, the grooves 19 are formed in an interior of the rear side 4 and are spaced from the first 1a, 1b and/or second 1c, 1d pair of opposite edge portions, preferably both of them. For example, the entire parts of the at least one groove may be provided inside a vertical plane VP at all edge portions 1a-d. The vertical plane VP may be defined by immediately juxtaposed upper portions of two neighboring joint edge portions of two joined panels, such as floor panels, and may be perpendicular to a horizontal plane HF and/or HR, respectively, provided along the front side 2 and rear side 4. A groove length GL of at least some grooves 19, preferably all grooves, may be smaller than a length BL, preferably a maximal length, of the rear side. The length BL may be a length which is parallel with the long edge portions of the panel.

(35) The at least one groove 19 in any of FIGS. 1a, 1c, 2a-2e, 3a-3g and 4a-4g etc. may be provided inwardly of the locking system on the first 1a, 1b and/or second 1c, 1d pair of opposite edges. The groove length GL of the at least one groove, preferably all grooves, may be smaller than a distance DL between the locking systems at opposite short edge portions 1c, 1d.

(36) In some embodiments, however, and as shown in the side view in FIGS. 3b-3c and in FIG. 2e, the at least one groove 19 may extend to at least one edge portion 1c of a pair of opposite edge portions, such as opposite short edge portions 1c, 1d, of the panel. In FIG. 3b, the at least one groove 19 extends to one edge portion 1c, which is illustrated as a short edge portion. In FIG. 3c, the at least one groove 19 extends to both edge portions 1c, 1d of the pair, which are illustrated as short edge portions 1c, 1d. When the groove(s) 19 extend to a locking groove 14 or 14′, they may be provided below an underside 4a or 4c, respectively, of the corresponding edge portion. The underside 4a, 4c may be a lowermost portion of the edge portion.

(37) FIGS. 3a-3b also illustrate that a shape of one or both end portions 16 of the at least one groove 19 along their longitudinal direction may be curved, such as at one or both short edges 1c, 1d. For example, this shape may be obtained when the grooves are formed by a rotating cutting device, such as a jumping tool. In FIG. 3a both end portions 16 are curved. In FIG. 3b one end portion 16 is curved and one end portion is parallel with the front side 2, preferably such that it intersects a portion of the locking groove 14′.

(38) FIG. 3c shows that the at least one groove 19, in particular its end portion(s) 16, may be parallel with the front side 2, preferably such that they intersect at least a portion of the strip 6′ and/or at least a portion of the locking groove 14′.

(39) The at least one groove may be continuous as shown in e.g. FIGS. 1c, 2b, 2e, and 3a-c, preferably along the first horizontal direction x, or along the second horizontal direction y as shown in FIG. 6d.

(40) The at least one groove may be discontinuous as shown in e.g. FIGS. 2c-2d. Preferably, the at least one groove is discontinuous along the first horizontal direction x. The panel 1 may comprise at least two groove arrangements 40, such as a plurality of them. A longitudinal extension of the grooves 19 in each groove arrangement may be parallel to each other. Preferably, a longitudinal extension of each groove arrangement, such as along the first horizontal direction x, may be parallel to each other and preferably extends in parallel with an edge portion 1a, 1b of the panel, preferably a long edge portion, which may be an edge portion of the first pair.

(41) As illustrated in FIG. 2c, the grooves in a pair of adjacent groove arrangements 40, preferably all of them, may be aligned along the second horizontal direction y. As illustrated in FIG. 2d, the grooves in a pair of adjacent groove arrangements 40, preferably all of them, may be offset along the second horizontal direction y.

(42) The groove arrangements 40 may be discontinuous, such as along the first horizontal direction x. The groove arrangements 40 may be separated by a separation portion 30.

(43) Preferably, the separation portion extends continuously between a pair of opposite edge portions 1a, 1b, such as long edge portions, along the second horizontal direction y. For example, the separation portion may be rectangular.

(44) In some embodiments, there may be a middle area MA without any grooves as shown in FIG. 2e. The grooves 19 may be located mainly at the outer parts of the panel 1, such as rear side 4, preferably along the second horizontal direction y. This may be used to increase the stability of the panel.

(45) Before grooves are formed in the panel 1, an area A′ of the front side 2 may be essentially the same as an area A of the rear side 4, cf. FIGS. 1a-1b. The area of the front side and rear side may be an area in a horizontal plane HF and HR, respectively, provided along the front side and rear side.

(46) The at least one groove reduces the area A of the rear side. The area A of the rear side may be less than 90% of the area A′ of the front side, such as 60-85%. In some embodiments the area A may be less than 80% of the area A′, such as less than 70%. Alternatively, or additionally, a volume VG of the groove(s) may be at least 5 vol %, such as at least 10 vol %, preferably 5-30 vol %, such as 10-20 vol %.

(47) A plurality of grooves 19 may have the same characteristics, such as groove depths GD and/or groove widths GW. Alternatively, or additionally, a cross-sectional shape of at least two grooves may be the same. As shown e.g. in the embodiments in FIGS. 2a and 4a-4c, the groove depths GD and the groove widths GW of a plurality of grooves may be the same. The groove depth may be a length along the vertical direction z.

(48) At least two grooves of a plurality of grooves 19 may have different characteristics, such as groove depths GD and/or groove widths GW. Alternatively, or additionally, a cross-sectional shape CS of at least two grooves may be different. FIG. 4d shows in an embodiment a cross-sectional side view of a panel 1 wherein a groove depth GD of at least two grooves 19 may be different. For example, inner grooves 19b along the second horizontal direction y may be formed with a different groove depth GD than outer grooves 19a. For example, grooves of each groove arrangement 40 may have the same characteristics while the characteristics of at least two different groove arrangements 40 may differ.

(49) FIG. 4d also shows that a groove width GW of at least two grooves 19 may be different. Moreover, at least one groove 19c may comprise an opening having a groove width GW that is larger than a groove width of an inner part of the at least one groove.

(50) FIG. 4d also shows that a cross-sectional shape CS of at least two grooves 19 may be different.

(51) In non-limiting examples, any groove depth GD herein may be at least 0.2, such as at least 0.3, preferably at least 0.4, times a thickness T of the panel 1. The groove depth GD may be for example 0.1-0.6 times the panel thickness T. When the thickness is 2-40 mm, a groove depth of any of the grooves may be at least 0.2-24 mm, such as 0.5-10 mm. For example, a floor panel having a thickness of 2-10 mm may have groove depth which is at least 0.2-1.0 mm, such as 1.2-6.0 mm.

(52) In any of the embodiments described above, the groove width GW may be 0.2-1.5, such as 0.5-1.0, times the panel thickness T. Moreover, there may be a space S extending between the grooves along the second horizontal direction y. For example, the space S may be at least 0.2-1.0 times the panel thickness T.

(53) In any of the embodiments herein, such as in FIGS. 1a-1c, 2a-2e, 3a-3g and 4a-4g the mineral-based panel may comprise at least one reinforcement layer, such as a glass-fibre layer.

(54) As shown in FIG. 2a, the at least one reinforcement layer 13 may be provided in the core 3. In a first example, a single reinforcement layer 13 may be provided in a centre portion of the core. In a second example, and as shown in FIG. 4e, the at least one reinforcement layer 13 may be positioned in a top portion and/or a bottom portion of the core 3. For example, at least one, preferably a single, reinforcement layer may be positioned essentially at the upper 3b and/or lower 3a side of the core.

(55) Generally, and as shown in FIGS. 4f-4g, at least one reinforcement layer 15, 17 may be positioned in a top portion and/or a bottom portion of any lower layer 5a and/or upper layer 7a.

(56) Alternatively, or additionally, and as shown in e.g. FIGS. 3a-3c, the at least one reinforcement layer 18a, 18b may optionally be provided between the core 3 and the upper arrangement 7 and/or between the core 3 and the lower arrangement 5.

(57) The at least one reinforcement layer 17, 15 may be provided in any upper layer 7a, 7b, 7c and/or any lower layer 5a, 5b, 5c, as illustrated in FIGS. 3d-3f.

(58) The at least one groove may be provided below the at least one reinforcement layer, such as below any, some or all of the at least one reinforcement layer selected from the group of the reinforcement layers 13, 15, 17 and 18a-b described above. In some embodiments, however, and as shown in e.g. FIG. 3f, the at least one groove may be provided through at least one reinforcement layer 15. This is also illustrated in FIG. 3a where the groove(s) 19 indicated by a dash-dotted line may be provided through a reinforcement layer 18a.

(59) Alternatively, or additionally, to the reinforcement layers, the core 3, and optionally any lower 5a, 5b, 5c and/or upper 7a, 7b, 7c layer, may comprise separate reinforcement particles 26, such as fibres. In some embodiments, and as illustrated in FIG. 4c, a lower layer 5a, 5b, 5c, such as a bottommost layer 5a, of the lower arrangement 5 or the core 3 may comprise separate reinforcement particles 26. The at least one groove 19 may be provided in the lower layer 5a only, in the core 3 only, or, as illustrated by the dash-dotted line in FIG. 4c, may extend into the core 3. Optionally, the core 3 or the upper arrangement may in the either scenario comprise intact reinforcement layer(s).

(60) FIGS. 4b-4c illustrate that the at least one groove 19 may be covered with a cover layer 12, which preferably is separately formed. Generally, the cover layer may be attached to the lower side 3a of the core or the lower arrangement 5. For example, the cover layer may be a flexible layer, such as a foam layer. The cover layer may be a foam rubber, cork, a natural material. This may be used to hide the grooves, such as an opening 25 of the grooves, for example for providing a moisture sealing or to improve the sound properties of the panel.

(61) In some embodiments, the at least one groove may be at least partially filled, such as completely filled, with a separate material 27. Preferably, the separate material may impact the properties of the panel, such as its sound properties. This may be particularly advantageous when a cover layer 12 is provided on the rear side 4, such as in FIG. 4c.

(62) FIGS. 5a-5b show embodiments of a method of forming the at least one groove 19 in a rear side 4 of a panel 1, such as in a mineral-based core 3 and/or in a lower arrangement 5 of the panel. For example, the lower arrangement may comprise any of the polymer-based layer(s) described herein. Alternatively, and as described herein, the lower arrangement may comprise wood-based layer(s) or cellulose-based layer(s) or it may comprise magnesium oxide. The panel is arranged on a support member 60. The grooves may be formed by a rotating operation. A rotating cutting device 20, for example comprising at least one saw blade 20a-20d, may be used. The rotating cutting device may comprise at least one tooth element 24a-24d. The saw blades 20a-20d may be arranged side-by-side as shown in FIG. 5a. Preferably, the rotating cutting device displaceably mounted in a frame member (not shown) and may be a jumping tool. The panel may be displaced in a feeding direction and may pass by the rotating cutting device. The front side 2 may point downwards during forming of the grooves. The rotating cutting device, such as the at least one saw blade, and the panel may be displaced relative to each other for forming the grooves. For example, the rotating cutting device may be displaced along a displacement axis D towards the panel and away from the panel, such as from above, or, alternatively, from below if the front side 2 is pointing upwards. Thereby, a plurality of grooves 19 may be formed in accordance with any embodiment described herein, such as in any of FIGS. 1a-1c, 2a-2e, 3a-3g, 4a-4g, 6a-6d or 7a-7b. Preferably, the grooves are formed in an interior of the rear side 4 and being spaced from the first and/or second pair of opposite edge portions 1a, 1b and 1c, 1d, preferably both of them. For example, the grooves may be formed such that they do not intersect any part of the locking systems on the long and/or short edge portions.

(63) In some embodiments, the grooves 19 may be formed by a non-rotating operation, such as by carving. A non-rotating tool may be utilized, for example a carving tool 22 comprising at least one tooth element 23a-23d. FIG. 5c shows a carving tool 22 comprising a plurality of tooth elements 23a-23d. The tooth elements may be located after each other along a carving axis CA. In operation of the carving tool 22, the carving axis may be parallel with a feeding direction FD. The tooth elements may be offset in a direction which is perpendicular to the feeding direction, such as horizontally and/or vertically offset. The tooth elements may be configured to consecutively remove material from the panel.

(64) Preferably, the carving tool 22 is fixedly mounted in a frame member (not shown), at least in a direction along the carving axis CA. In operation of the carving tool, the panel may be displaced with respect to the frame member in the feeding direction. The panel may be displaced against the carving tool 22 in the feeding direction FD. Each tooth may carve at least 0.05 mm, such as at least 0.1 mm, for example 0.05-0.5 mm, e.g. in a mineral-based material, such as in the core 3 and/or in the lower arrangement 5.

(65) In some embodiments, however, the carving tool may be displaceably mounted in the frame member. For example, carving tool may be a jumping carving tool.

(66) The material 21 removed from the panel when forming the grooves, such as chips, may be recycled. Magnesium oxide may be recycled, such as fully recycled, for example by heating the removed material above a critical temperature so that it assumes powder form.

(67) The method described above is equally conceivable for a mineral-based board element 80. The mineral-based board element may be dividable or may be divided into at least two panels 1, such as by sawing, cutting or breaking. In a first example, the grooves are formed before dividing the board element. In a second example, the grooves are formed after dividing the board element. In the second example, the grooves may be formed before or after forming of the locking system on opposite edge portions 1a, 1b and/or 1c, 1d.

(68) FIGS. 6a-6c illustrate in cross-sectional side views embodiments of various locations of the at least one groove 19 in a panel 1. In FIG. 6a, the at least one groove 19 is provided in an upper side 3b of the core 3. Moreover, FIG. 6b illustrates the at least one groove 19 being provided in a lower side 3a and an upper side 3b of the core 3. Finally, FIG. 6c illustrates that the groove(s) may be provided in the core (3), wherein the core is provided between an upper 7 and a lower 5 arrangement. Thereby, the groove(s) become internal groove(s). For example, the at least one groove 19 may be provided in an upper side 3b of the core 3 and, optionally, at least partly provided in a lower arrangement 5. For example, the at least one groove may fully penetrate at least one lower layer 5a of the lower arrangement. Optionally, the groove(s) may extend into the lower side 3a of the core 3. Alternatively, or additionally, to the embodiment in FIG. 6c, the groove(s) 19 may be provided in the lower side 3a.

(69) Preferably, an upper arrangement 7 comprising at least one upper layer 7a, 7b, 7c is attached to the upper side 3b of the core 3 in any of FIGS. 6a-6c. Embodiments and examples of the core 3, the lower layer 5, the upper layer 7, an optional top structure 11, an optional at least one reinforcement layer 13, 15, 17, 18a, 18b, a locking system 50a, 50b etc. have been described elsewhere, such as in relation to FIGS. 1a-1c, 2a-2e, 3a-3g and 4a-4g, whereby reference is made thereto.

(70) The bottom view in FIGS. 1c and 2b-2e illustrate embodiments of a rectangular panel 1 comprising at least one groove 19 which is parallel with the long edge portions. FIG. 6d illustrates in a bottom view an embodiment of a rectangular panel 1 comprising at least one groove 19 which is parallel with the short edge portions.

(71) FIGS. 7a-7b illustrate in cross-sectional side views embodiments of a wall panel 1 and a ceiling panel 1, respectively. Embodiments and examples thereof may be similar to any of the embodiments and examples herein, such as described in relation to FIGS. 1a-1c, 2a-2e, 3a-3g, 4a-4g, 5a-5d and 6a-6d, whereby reference is made thereto.

(72) Optionally, as shown in FIG. 7a, the wall panel 1 may comprise a locking system 50a, 50b for interlocking wall panels of a similar type. The wall panel may be attached to a subwall member 70 in accordance with known principles in the art, such as by clips. In a first example, the wall panel comprises a mineral-based core 3 without any lower 5 and upper 7 arrangements. In a second example, the wall panel comprises a mineral-based core 3 and an upper arrangement 7 and, optionally, a lower arrangement 5.

(73) As shown in FIG. 7b, the ceiling panel 1 may comprise engagement portions 72 for installing it in a grid of profiles 71 in accordance with known principles in the art. The groove(s) 19 may face upwards towards a subroof. The ceiling panel may comprise a mineral-based core 3, preferably without any upper 7 and/or lower 5 arrangement(s). For example, the mineral-based core may comprise magnesium oxide or gypsum.

(74) FIGS. 2a, 4a-4d, 6a-6c, 7c and 8a-8b and FIGS. 3a-3c, 7d and 8c-8e show embodiments of long edge portions 1a, 1b and short edge portions 1c, 1d of a panel configured to be locked by angling A and by a vertical displacement V, respectively.

(75) FIGS. 3a-3b, 4a-4c, 6c, 7c-7d and 8a-8e illustrate embodiments of a mineral-based panel 1, such as a floor panel, comprising a mineral-based core 3 and wherein the lower arrangement 5 may comprise at least one polymer-based lower layer 5a, 5b, 5c. The panel comprises a locking system 50a, 50b for horizontal and/or vertical locking comprising a strip 6, 6′ extending horizontally beyond an upper portion 2a, 2a′ of the panel. At least a horizontal portion 51 of the strip is entirely formed in the lower arrangement 5. Thereby, an upper surface of the strip may be exposed and, provided that there is no cover layer 12 attached to a lower side of the lower arrangement (cf. FIG. 4c), a lower surface provided vertically below the upper surface may be exposed.

(76) In any embodiment herein, the lower arrangement 5 may comprise a single lower layer 5a, and optionally a second 5b and/or a third 5c lower layer, cf. FIGS. 3d and 3f. As shown in e.g. FIGS. 3a, 6c, 7c-7d, 8a-8c and 8e, the panel 1 may further comprise an upper arrangement 7 comprising at least one upper layer 7a. In any embodiment herein, the upper arrangement 7 may comprise a single upper layer 7a, and optionally a second 7b and/or a third 7c upper layer, cf. FIGS. 3e and 3g. Embodiments of reinforcement layers 13, 15, 17, 18a, 18b and/or reinforcement particles 26, which are conceivable for any of the panels in e.g. FIGS. 7c-7e and 8a-8e, have been described elsewhere herein, such as in relation to FIGS. 2a, 3a-3f, 4c and 4e-4g, whereby reference is made thereto. Alternatively, additionally, the panel may comprise a top structure 11 as described elsewhere herein.

(77) In any embodiment herein, such as in FIGS. 1a-1c, 2a-2e, 3a-3g, 4a-4g, 5a-5e, 6a-6d, 7a-7e and 8a-8e, the core 3 may comprise at least 30 wt % magnesium oxide, and, optionally, magnesium chloride and/or magnesium sulphate. For example, the core 3 may comprise 35-55 wt % magnesium oxide and, optionally, 15-35 wt % magnesium chloride and/or magnesium sulphate. Optionally, the core may further comprise a filler, such as fly ash or calcium carbonate, preferably in an amount of 0-40 wt %, and/or a binding agent, such as wood shavings or wood dust, preferably in an amount of 0-10 wt %. More generally, the core 3 may comprise an inorganic matrix material, preferably with at least 20 wt % of an inorganic matrix material, such as cement, such as hydraulic or non-hydraulic cement, or gypsum.

(78) The polymer-based lower layer(s) 5a, 5b, 5c may be thermoplastic layer(s), for example comprising PVC, PE, TPU, PP, PET or ABS, preferably being provided on the magnesium oxide core 3 described in the previous paragraph. The panel 1 may further comprise thermoplastic upper layer(s) 7a, 7b, 7c, for example comprising PVC, PE, TPU, PP, PET or ABS. In a first example, the panel comprises a lower layer 5a and an upper layer 7a, each comprising PVC in an amount of 40-60 wt %, a filler, such as calcium carbonate or talc, in an amount of 40-60 wt %, a plasticizer, such as dioctyl terephthalate (DOTP), in an amount of 0-10 wt %, and additive(s), such as pigments, a lubricant, a stabilizer, or an acrylic processing aid, in an amount of 0-5 wt %. In a second example, the panel comprises a lower layer 5a and an upper layer 7a, each comprising PE, PP, PET, TPU or polyolefin copolymers in an amount of 30-60 wt %, a filler, such as calcium carbonate or talc, in an amount of 40-70 wt %, and additive(s), such as pigments, a coupling agent, a lubricant, or an antioxidant, in an amount of 0-5 wt %. A thickness of the panel may be 5-10 mm, such as 4-7 mm, and a thickness of each of the upper and lower arrangements may be 15-35%, such as 20-40%, of the thickness of the panel.

(79) In some embodiments, the polymer-based lower layer(s) 5a, 5b, 5c may be thermosetting layer(s), for example comprising a melamine resin, epoxy resin, preferably crosslinked with an amine hardener, PU, polyurea or acrylate polymers, preferably being provided on the magnesium oxide core 3 described in the penultimate paragraph above. The panel 1 may further comprise thermoplastic upper layer(s) 7a, 7b, 7c, for example comprising a melamine resin, epoxy resin, preferably crosslinked with an amine hardener, PU, polyurea or acrylate polymers. In a third example, the panel comprises a lower layer 5a and an upper layer 7a, each comprising an epoxy resin and an amino hardener or polyols and isocyanates in an amount of 40-60 wt %, a filler, such as calcium carbonate, barium sulphate, sand or talc, in an amount of 20-50 wt %, and additive(s), such as pigments, a catalyst, a defoaming agent, a dispersing agent, or a chain extender, in an amount of 0-5 wt %. A thickness of the panel may be 4-7 mm, and a thickness of each of the upper and lower arrangements may be 15-35%, such as 20-40%, of the thickness of the panel.

(80) In any of the first, second and third examples above, the upper and lower arrangements may comprise the same polymer-based material compositions, such as being provided with the core in an ABA layered structure, or different polymer-based material compositions, such as being provided with the core in an ABC layered structure.

(81) FIGS. 4a-4c, 7c and 8a-8b illustrate a locking system 50a around long edge portions 1a, 1b. The locking system 50b in FIGS. 3a-3b, 7c-7d and 8c-8e are shown around their short edge portions 1c, 1d. Alternatively, or additionally, however, it is equally conceivable to use a locking system 50a as in any of FIGS. 8c-8e on the long edge portions 1a, 1b of the panels.

(82) In FIGS. 3a-3b, 4a-4c, 6c, 7c-7d and 8a-8e the strip 6, 6′ comprises a locking element 8, 8′ and the horizontal portion 51 is provided at least horizontally inwardly of the locking element 8, 8′. In FIGS. 3a-3b, 4a-4c, 6c, 8b and 8d, the horizontal portion 51 comprises the entire strip including the locking element.

(83) In FIGS. 7c-7d, 8a, 8c and 8e, the locking element 8, 8′ comprises a portion of the core 3, such as at a distal end portion 8b, 8b′ of the locking element. For example, before forming the locking system 50a, 50b in the panel 1, the core 3, the lower arrangement 5, and optionally the upper arrangement 7, may extend into the edge portion(s) 1a-1d of the panel, cf. the embodiment of a mineral-based board element 80 in FIG. 5e. The locking system may be formed by removing material from the edge portion(s) 1a-1d. As shown in FIG. 5e, a portion 3′ of the core 3 may remain in the edge portion after the forming of the locking system, such as at the distal end portion 8b, 8b′ of the locking element. In particular, a portion 3′ of the core may remain at substantially the same vertical position as that of an inner portion 3″ of the core.

(84) As shown in e.g. FIGS. 3a-3b, 4a-4c, 6c, 7c-7d and 8a-8e, a horizontal locking system may comprise a locking element 8, 8′ and a locking groove 14, 14′. A vertical locking system may comprise a tongue 10, 10′, 10″ and a tongue groove 9, 9′. Alternatively, or additionally, and as shown in e.g. FIGS. 8c-8e, the locking element 8, 8′ and locking groove 14, 14′ may comprise vertical locking surfaces 6b, 6b′ configured to cooperate for vertical locking. In FIG. 8e there are no vertical locking surfaces situated at the vertical plane.

(85) FIGS. 8a-8e illustrate that the lower arrangement 5 may comprise a horizontal 6a, 6a′ and/or a vertical 6b, 6b′ locking surface. Horizontal locking surfaces 6a, 6a′ may be provided on the locking element 8, 8′ and locking groove 14, 14′ and/or vertical locking surfaces 6b, 6b′ may be provided on the tongue 10, 10′ and tongue groove 9, 9′. Moreover, a vertical locking surface 6b may be provided in an inner 8a and/or an outer surface 8c of the locking element 8, 8′ and may be configured to cooperate with a vertical locking surface 6b′ provided in an outer 14c and/or an inner surface 14a of the locking groove, respectively.

(86) In some embodiments, and as shown in e.g. FIGS. 8c-8e, the horizontal 6a, 6a′ and vertical 6b, 6b′ locking surfaces may be provided by a common, preferably inclined, surface, for example the inner surface 8a and the outer surface 14c and/or the outer surface 8c and the inner surface 14a. The common surface may also be situated at the juxtaposed upper portions of the panels 1, 1′ as shown in FIG. 8d.

(87) Alternatively, or additionally, and as shown e.g. in FIGS. 8a-8c, a vertical locking surface 6b, 6b′ may be provided in the upper arrangement 7. Yet alternatively, or additionally, and as shown e.g. in FIGS. 8a-8c and 8e, a horizontal locking surface 6a, 6a′ may be provided in the upper arrangement 7.

(88) It is clear that in some embodiments herein, at least one vertical locking surface 6b, 6b′ may be at least partially provided in the core 3 as shown in e.g. FIGS. 4b, 4d and 8d. Moreover, the tongue 10, 10′ and/or the tongue groove 9, 9′ may be formed at least partially, such as entirely, in the core 3 as shown in e.g. FIGS. 2a, 3a-3c, 4b-4d, 6a-6c, 7c-7d and 8a-8d. For example, an outer and/or lower portion of the tongue 10, 10′ may comprise a portion of the core 3. Similarly, the displacement groove 10a may be formed at least partially, preferably entirely, in the core 3 as shown in e.g. FIG. 3a-3c. In some embodiments, the tongue 10, 10′ and/or the tongue groove 9, 9′ may be formed at least partially, such as entirely, in the upper arrangement 7 as shown in e.g. FIGS. 6a-6c, 7c-7d and 8a-8c. Similarly, the displacement groove 10a may be formed at least partially, such as entirely, in the upper arrangement 7 as shown in e.g. FIG. 7d.

(89) It is understood that embodiments may include a set of panels comprising a plurality of panels 1 in accordance with any of the embodiments and examples herein, such as in FIGS. 1a-1c, 2a-2e, 3a-3g, 4a-4g, 5a-5d, 6a-6d, 7a-7e and 8a-8e. Each panel may comprise a locking system 50a, 50b suitable for interlocking the panels.

(90) The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims and items in an embodiment section below. In addition, it is noted that the locking system 50a, 50b described in relation to e.g. FIGS. 8a-8e are equally conceivable for the first aspect.

Embodiments

(91) Further aspects of the inventive concept are provided below. Embodiments and examples of these aspects are largely analogous to the embodiments and examples as described above, whereby reference is made to the above for a detailed description.

(92) Item 1. A mineral-based panel (1), such as a floor panel, comprising a mineral-based core (3), wherein the panel comprises at least one groove (19), preferably a plurality of grooves.

(93) Item 2. The mineral-based panel according to item 1, wherein the at least one groove (19) is provided in a rear side (4) of the panel.

(94) Item 3. The mineral-based panel according to item 1 or 2, wherein the at least one groove is provided in a lower side (3a) of the mineral-based core.

(95) Item 4. The mineral-based panel according to any of the preceding items, wherein the at least one groove is provided in an upper side (3b) of the mineral-based core.

(96) Item 5. The mineral-based panel according to any of the preceding items, wherein the mineral-based core comprises magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate.

(97) Item 6. The mineral-based panel according to any of the preceding items, wherein the mineral-based core comprises cement.

(98) Item 7. The mineral-based panel according to any of the preceding items, further comprising a lower arrangement (5) comprising at least one lower layer (5a) being attached to a lower side (3a) of the mineral-based core.

(99) Item 8. The mineral-based panel according to item 7, wherein the at least one groove is at least partly provided in the lower arrangement, such as the at least one groove fully penetrating at least one lower layer (5a) of the lower arrangement.

(100) Item 9. The mineral-based panel according to item 7 or 8, wherein at least one lower layer (5a, 5b, 5c) in the lower arrangement, preferably all lower layers, comprises magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate.

(101) Item 10. The mineral-based panel according to any of the preceding items 7-9, wherein at least one lower layer (5a, 5b, 5c) in the lower arrangement, preferably all lower layers, comprises cement.

(102) Item 11. The mineral-based panel according to any of the preceding items 7-10, wherein the lower arrangement (5) comprises at least one polymer-based layer, such as at least one thermoplastic layer, for example comprising PVC, PE, TPU, PP, PET or ABS, or at least one thermosetting layer, for example comprising a melamine-formaldehyde resin, epoxy resin, preferably crosslinked with an amine hardener, PU, polyurea or acrylate polymers.

(103) Item 12. The mineral-based panel according to any of the preceding items 7-11, wherein the lower arrangement (5) comprises at least one wood-based layer or cellulose-based layer, such as a veneer, paper, solid wood layer, MDF layer, HDF layer, DPL layer, HPL layer or particle board layer.

(104) Item 13. The mineral-based panel according to any of the preceding items, further comprising an upper arrangement (7) comprising at least one upper layer (7a) being attached to an upper side (3b) of the mineral-based core.

(105) Item 14. The mineral-based panel according to item 13, wherein at least one upper layer (7a, 7b, 7c) in the upper arrangement, preferably all upper layers, comprises magnesium oxide and, optionally, magnesium chloride and/or magnesium sulphate.

(106) Item 15. The mineral-based panel according to item 13 or 14, wherein at least one upper layer (7a, 7b, 7c) in the upper arrangement, preferably all upper layers, comprises cement.

(107) Item 16. The mineral-based panel according to any of the preceding items 13-15, wherein the upper arrangement (7) comprises at least one polymer-based layer, such as at least one thermoplastic layer, for example comprising PVC, PE, TPU, PP, PET or ABS, or at least one thermosetting layer, for example comprising a melamine-formaldehyde resin, epoxy resin, preferably crosslinked with an amine hardener, PU, polyurea or acrylate polymers.

(108) Item 17. The mineral-based panel according to any of the preceding items 13-16, wherein the upper arrangement (7) comprises at least one wood-based layer or cellulose-based layer, such as a veneer, paper, solid wood layer, MDF layer, HDF layer, DPL layer, HPL layer or particle board layer.

(109) Item 18. The mineral-based panel according to any of the preceding items, further comprising a top structure (11) provided on, such as attached to, an upper side of the mineral-based core or provided on, such as attached to, an upper arrangement (7) of the mineral-based panel, said top structure preferably comprising a décor layer (11a).

(110) Item 19. The mineral-based panel according to item 18, wherein the top structure (11) comprises a coating layer (11b), such as a UV curable coating layer, a lacquer or a hot-melt coating layer, and/or a wear layer (11c), such as comprising aluminium oxide, a thermoplastic film, or a thermosetting resin.

(111) Item 20. The mineral-based panel according to any of the preceding items, further comprising a cover layer (12) at least partly covering the grooves.

(112) Item 21. The mineral-based panel according to any of the preceding items, further comprising at least one reinforcement layer (13; 15; 17; 18a, 18b), such as a glass-fibre layer.

(113) Item 22. The mineral-based panel according to item 21, wherein the at least one reinforcement layer (13) is provided in the mineral-based core.

(114) Item 23. The mineral-based panel according to item 21 or 22, wherein at least one reinforcement layer (13) is positioned in a top portion and/or a bottom portion of the mineral-based core.

(115) Item 24. The mineral-based panel according to any of the preceding items, wherein the at least one reinforcement layer (17; 15) is provided in an upper (7) and/or a lower (5) arrangement.

(116) Item 25. The mineral-based panel according to any of the preceding items, further comprising a locking system (50a; 50b), such as a mechanical locking system, for horizontal and/or vertical locking.

(117) Item 26. The mineral-based panel according to item 25, wherein the horizontal locking system comprises a locking element (8; 8′) and a locking groove (14; 14′), and/or wherein the vertical locking system comprises a tongue (10; 10′; 10″) and a tongue groove (9; 9′).

(118) Item 27. The mineral-based panel according to any of the preceding items, comprising a plurality of grooves, wherein at least two grooves (19) have different characteristics, such as groove depths (GD) and/or groove widths (GW).

(119) Item 28. The mineral-based panel according to any of the preceding items, wherein said at least one groove is provided in an interior of the panel, such as in the rear side (4) of the panel, being spaced from a pair of opposite edge portions (1c, 1d), such as opposite short edge portions, of the panel, preferably being spaced from all edge portions (1a-1d) of the panel.

(120) Item 29. The mineral-based panel according to any of the preceding items, wherein the at least one groove (19) extends to at least one edge portion, such as two edge portions, of a pair of opposite edge portions (1c, 1d), such as opposite short edge portions, of the panel.

(121) Item 30. The mineral-based panel according to any of the preceding items, wherein the at least one groove (19) is provided below an underside (4a, 4c) of an edge portion (1a, 1c) comprising a locking groove (14, 14′).

(122) Item 31. The mineral-based panel according to any of the preceding items, wherein a shape of one or both end portions (16) of the at least one groove (19) along its longitudinal direction is curved.

(123) Item 32. The mineral-based panel according to any of the preceding items, wherein one end portion (16) is, or both end portions (16), are parallel with a front side (2) of the panel, preferably such that they intersect at least a portion of the strip (6′) and/or at least a portion of the locking groove (14′).

(124) Item 33. The mineral-based panel according to any of the preceding items, wherein the panel is rectangular with long edge portions (1a, 1b) and short edge portions (1c, 1d) and wherein the at least one groove is parallel with the long edge portions.

(125) Item 34. The mineral-based panel according to any of the preceding items, wherein the at least one groove is continuous or discontinuous, preferably being parallel with long edge portions of the panel.

(126) Item 35. The mineral-based panel according to any of the preceding items, comprising at least two groove arrangements (40), such as a plurality of groove arrangements, wherein adjacent pairs of groove arrangements preferably are separated by a separation portion (30).

(127) Item 36. The mineral-based panel according to any of the preceding items, wherein an area (A) of a surface in which the at least one groove is provided, such as the rear side or the lower and/or upper side of the core, is less than 90%, such as less than 80%, of an area (A′) of a front side (2) of the panel.

(128) Item 37. A method for forming at least one groove (19) in a mineral-based panel (1), such as a floor panel, comprising: arranging the panel on a support member (60), and forming at least one groove (19) in the panel by removing material (21), such as chips, from the panel.

(129) Item 38. The method according to item 37, wherein the at least one groove (19) is provided in a rear side (4) of the panel.

(130) Item 39. The method according to item 37 or 38, wherein the at least one groove (19) is formed by rotational processing with at least one tooth element (24a-24d), such as by a rotating cutting device (20).

(131) Item 40. The method according to any of the preceding items 37-39, wherein the at least one groove (19) is formed by non-rotational processing with at least one tooth element (23a-23d), such as by carving, preferably using a carving tool (22).

(132) Item 41. The method according to any of the preceding items 37-40, further comprising forming a locking system (50a; 50b), such as a mechanical locking system, for horizontal and/or vertical locking of the mineral-based panel.