Modified melamine-formaldehyde resins, paper impregnated therewith, method for manufacturing floor panels and use of dicyandiamide as a modifier in melamine-formaldehyde resins

Abstract

Use of dicyandiamide as a modifying agent in melamine-formaldehyde resin (34) for a floor panel (10) comprising a substrate (24) and a top layer (26) defining an upper surface (18) of the floor panel (10). The floor panel (10) is provided with embossings (20, 21, 22) extending from the upper surface (18) such that a thickness (T) of the floor panel (10) varies along a cross-section of the floor panel (10). The top layer (26) comprises a modified melamine-formaldehyde resin (34) and at least one modifying agent, the modified melamine-formaldehyde resin (34) comprising formaldehyde and melamine in a F / M molar ratio in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75, thereby providing a floor panel (10) with improved transparency at the embossings (20, 21, 22).

Description

Technical Field

[0001] This invention relates to modified melamine-formaldehyde resin, which can be used, for example, in the manufacture of floor panels. The invention also relates to paper impregnated with modified melamine-formaldehyde resin, and a method for manufacturing floor panels.

[0002] More specifically, the present invention is based on the inventors’ discovery that the use of dicyandiamide as a modifier in melamine-formaldehyde resins provides benefits, particularly in the direct pressure lamination (DPL) process and in floor panels manufactured by that process. Background Technology

[0003] DPL flooring panels are well known, for example, from EP 2879885. Here, this can refer to, for example, flooring panels having a substrate, which is essentially composed of medium-density fiberboard (MDF) or high-density fiberboard (HDF) with a top layer directly pressed thereon. Typically, the top layer comprises a decorative layer in the form of printed paper sheets. The printing, also known as decoration, can form a representation of wood or stone patterns or any other pattern, such as stylized designs. The printed paper can be impregnated in melamine-formaldehyde resin, which is cured when the substrate and top layer are pressed together, causing the top layer to harden and adhere to the substrate.

[0004] It is also known to provide embossing on the upper surface of such floor panels, through which, for example, wood holes or joints in deeper areas of tile decoration can be imitated. As described in WO 2006 / 066776 and WO 2017 / 072657, embossing can be formed when the substrate and top layer are pressed together.

[0005] In some cases, it is desirable for the embossing to be quite deep, possibly extending down into the substrate. When deep embossing is applied to floor panels known in the prior art, embossing defects can occur. These may include, for example, cracks appearing in the decorative layer, tears or splits in the decorative layer, and / or the decorative layer not being sufficiently stretched to cover the entire floor panel.

[0006] Document WO 2006 / 066776 describes a DPL floor panel comprising deep embossing, which creates a so-called scraped wood imitation or achieves a plank effect. The pressing board used in the DPL process is designed such that most pressing defects appearing in the top layer are located on a portion of the floor panel to be removed. Therefore, this document proposes a method for handling pressing defects, but does not offer a solution for how to avoid them.

[0007] Document WO 2017 / 072657 relates to a DPL floor panel that includes deep embossing, for example, to achieve a slatted effect or to mimic the joints between tiles. The deep embossing (recesses) is created in the substrate, for example, by sawing, before the substrate and top layer are stacked and pressed together. Therefore, the method for manufacturing this floor panel requires additional equipment and further process steps compared to conventional DPL processes.

[0008] US 6001925 describes a modified melamine-formaldehyde resin prepared by reacting melamine with formaldehyde under alkaline conditions at an F / M molar ratio in the range of about 1.55 to 2.5, wherein the resin is prepared in the presence of about 1-10 wt% dicyandiamide and about 1-10 wt% sorbitol based on the total weight of the resin solids.

[0009] US 2336370 describes the production of dicyandiamide resin by modifying dicyandiamide resin with melamine.

[0010] WO 96 / 20230 describes a modified melamine-formaldehyde resin made from a condensate of formaldehyde, melamine, and a modifier, containing a) 5 to 25% by weight of dicyandiamide based on melamine; and b) 8 to 30% by weight of a water-soluble polyol having at least two hydroxyl alkyl groups based on melamine, wherein the molar ratio of formaldehyde to melamine is 1.2 to 2.5.

[0011] US 5346937 relates to a modifier for melamine-formaldehyde resin and a highly reactive thermosetting resin prepared using the modifier, wherein the highly reactive thermosetting resin comprises 1 mol melamine, 1.5 to 3.5 mol formaldehyde, 0.5 to 5% polyol based on melamine plus formaldehyde by weight, and 0.5 to 10% modifier based on liquid resin by weight.

[0012] The limited tensile strength and flexibility of the known resin are limiting factors during pressing and curing in the direct pressure lamination process. For example, if such a resin is used to impregnate paper, and the paper is used in the DPL process to form boards, a large number of boards will have pressing defects. Summary of the Invention

[0013] The main objective of this invention is to provide an alternative floor panel and / or a method for manufacturing said floor panel, wherein a solution is provided for one or more problems of floor panels and prior art methods.

[0014] Therefore, the present invention relates to a modified melamine-formaldehyde resin, paper impregnated with the modified melamine-formaldehyde resin, a method for manufacturing floor panels, and the use of dicyandiamide as a modifier in melamine-formaldehyde resin, as defined in the appended independent claims, wherein preferred embodiments are defined in the dependent claims.

[0015] This invention relates to modified melamine-formaldehyde resins comprising formaldehyde and melamine, wherein the resin contains dicyandiamide, wherein the dicyandiamide is preferably present in an amount suitable for increasing the flexibility and tensile strength of the melamine-formaldehyde resin during pressing and curing in a direct pressure lamination process. Dicyandiamide is thus used as a modifier in melamine-formaldehyde resins, preferably for increasing the flexibility and tensile strength of the melamine-formaldehyde resin during pressing and curing in a direct pressure lamination process.

[0016] As used herein, the term "flexibility and stretchability" refers to the ability of an uncured or semi-cured resin to conform to an embossed surface during the final curing step, such as on and / or impregnated with paper in a decorative layer. Thus, the term "flexibility and stretchability" indicates the ability of the resin to be deeply drawn into the embossed surface without exhibiting embossing defects. During pressing and curing in direct pressure lamination (DPL) processes, particularly when using a press plate that includes an embossing device, the effective area of ​​the upper surface of the floor panel increases, at least due to the embossing formed in the upper surface. Therefore, during the pressing and curing steps, the resin must be able to bend and stretch to cover the resulting larger effective area. The inventors have found that the resin's ability to do this can be quantified using a dry stretch test performed according to EN ISO 1924-2 / 3 or TAPPI T 494 on paper saturated with the corresponding resin and compared with other resins impregnated on the same type of paper under the same conditions. This is one possible way to quantify whether "flexibility and stretchability" is sufficient for the resin to be used in the DPL process, and this does not constitute a limiting factor. Preferably, the tensile test is performed on paper with a residual moisture content of 7 wt% or about 7 wt%, allowing for good comparison of test results. In the tensile test, the elongation at break can be recorded as a representative value of flexibility and tensile strength. The paper may be, for example, decorative paper, such as digitally printed decorative paper or similar printed decorative paper, with a basis weight of 40 to 135 g / m². 2 between.

[0017] By using dicyandiamide as a modifier in melamine-formaldehyde resin, the resin becomes more flexible and stretchable in the press and can better withstand deep embossing, resulting in fewer pressing defects, such as cracks.

[0018] The direct pressure lamination (DPL) process preferably uses a temperature of at least 150°C, such as 180°C to 220°C or 150°C to 200°C, a pressing duration of 12 to 60 seconds, and a pressure of more than 20 bar, such as 35 to 40 bar or 20 to 80 bar.

[0019] Preferably, the modified melamine-formaldehyde resin in which dicyandiamide is used as a modifier comprises formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, preferably 1.70 to 1.80, and more preferably 1.73 to 1.75. Within these ranges, optimal ratios between methylene and ether bridge formations, as well as their respective properties, can be obtained in the cured resin. Methylene bridges are thermodynamically advantageous, while ether bridges are kinetically advantageous. A good ratio between the two crosslinking bridges results in an optimal combination of flexibility, such as the wet and dry strength of the impregnated paper, the obtained stiffness, and the required reaction time in the DPL process. The reaction time should not be too fast to allow sufficient elongation before the resin cures, nor should it be too slow to allow for an economical approach. Within such a range, undesirable resin yellowing will not occur in the DPL process.

[0020] Based on the total weight of melamine and dicyandiamide, dicyandiamide is preferably present in an amount ranging from 25% to 45% by weight, more preferably 30% to 40% by weight, even more preferably 32% to 38% by weight, and most preferably 34% to 36% by weight. The amount of dicyandiamide presented herein imparts optimal performance to the modified melamine-formaldehyde resin for the DPL process. It has been found that if the amount is above 25%, the flexibility and tensile strength are sufficient. In lesser to more preferred embodiments, the amount is at least 27%, at least 29%, at least 31%, at least 33%, and at least 35%, and in lesser to more preferred embodiments, the amount is at most 41%, at most 39%, and at most 37%. It is best when the amount is between 34% and 36%. When the amount is above 45%, the resin becomes brittle, making it less suitable for the DPL process. If the amount is above 38%, the solubility of dicyandiamide is a limiting factor in the manufacture of modified melamine-formaldehyde resin.

[0021] In a preferred embodiment, based on the total weight of melamine and dicyandiamide, the amount of dicyandiamide is in the range of 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight, and formaldehyde and melamine are present in a formaldehyde / melamine (F / M) molar ratio in the range of 1.60 to 1.80, preferably 1.70 to 1.80, and more preferably 1.73 to 1.75. It has been found that the combination of the amount of dicyandiamide as presented herein and the F / M molar ratio as presented herein imparts optimal performance to the modified melamine-formaldehyde resin for the DPL process. For example, if a board comprising the paper is formed in the DPL process using paper impregnated with the resin according to this preferred embodiment, there are no visible pressing defects or almost no visible pressing defects caused by the paper and / or at the height of the paper. The paper may be, for example, decorative paper.

[0022] Optionally, the direct pressure lamination process includes the step of impregnating a carrier with melamine-formaldehyde resin prior to lamination with a substrate, thereby forming a floor panel. The carrier forms the top layer portion, preferably forming the top decorative layer.

[0023] By providing modified melamine-formaldehyde in the decorative layer of the floor paneling, the decorative layer is less prone to pressing defects.

[0024] The present invention also relates to paper impregnated with the aforementioned modified melamine-formaldehyde resin. Preferably, the paper is printing paper, such as printed decorative paper. This paper can be used to produce floor paneling and can, for example, form a decorative layer for floor paneling. The printing paper can be digital printing paper or similar printing paper. The basis weight of the paper can be from 40 to 135 g / m². 2 For example, 60 to 90 g / m 2 .

[0025] The present invention also relates to the use of dicyandiamide as a modifier in melamine-formaldehyde resins for use in flooring panels. In a preferred embodiment, the flooring panel preferably comprises a substrate and a top layer, the top layer defining an upper surface of the flooring panel, the flooring panel being provided with embossing extending from the upper surface such that the thickness of the flooring panel varies along its cross-section, and the top layer comprising a modified melamine-formaldehyde resin comprising formaldehyde and melamine in an F / M molar ratio in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75; and at least one modifier. Thus, a flooring panel with improved transparency at the embossed areas is provided.

[0026] As is common in the art, if cracks appear at the embossing, the resin's transparency deteriorates, and the floor paneling will have a less attractive appearance. By using dicyandiamide, embossing defects such as cracks at the embossing can be mitigated and preferably avoided.

[0027] This invention also relates to a modified melamine-formaldehyde resin, comprising: - Formaldehyde and melamine; - Based on the total weight of melamine and dicyandiamide, a dicyandiamide content ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight; and - Preferred polyols, most preferably glycerol, are used in an amount of 1 to 5% by weight, preferably 2 to 4% by weight, and more preferably 3 to 4% by weight, based on the total liquid weight of the resin.

[0028] The use of polyols can increase the scratch and / or abrasion resistance of fully cured resins, while maintaining the desired flexibility and tensile strength introduced by dicyandiamide during storage.

[0029] In a preferred embodiment, the modified melamine-formaldehyde resin comprises formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, preferably from 1.70 to 1.80, and more preferably from 1.73 to 1.75.

[0030] Finally, the present invention also relates to a method for manufacturing a floor panel. The floor panel includes a substrate and a top layer defining an upper surface of the floor panel. Furthermore, the floor panel is provided with an embossed pattern extending from the upper surface, such that the thickness of the floor panel varies along its cross-section. The method includes the following steps: a) Provide a substrate.

[0031] (b) Provide a top layer comprising a modified melamine-formaldehyde resin and at least one modifier, wherein the modified melamine-formaldehyde resin comprises formaldehyde and melamine with an F / M molar ratio preferably in the range of 1.60 to 1.80, more preferably 1.70 to 1.80, and more preferably 1.73 to 1.75. The at least one modifier is dicyandiamide.

[0032] c) It constitutes a stack consisting of a substrate and a top layer.

[0033] d) The stack is pressed using a pressure plate that includes an embossing device and a heating device. During the pressing process, the embossing device provides embossing to the floor panel, and the heating device hardens the modified melamine-formaldehyde resin and adheres the top layer to the substrate.

[0034] By providing a top layer comprising a modified melamine-formaldehyde resin, which includes dicyandiamide as a modifier, the stack including this top layer can be embossed and laminated without the top layer exhibiting many embossing defects, such as cracks at the embossing points, or the top layer not being sufficiently stretched to completely cover the substrate. Therefore, there will be less waste in manufacturing.

[0035] Preferably, based on the total weight of melamine and dicyandiamide, dicyandiamide is present in the modified melamine-formaldehyde resin in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight. In lesser to more preferred embodiments, the amount is at least 27%, at least 29%, at least 31%, at least 33%, and at least 35%, and in lesser to more preferred embodiments, the amount is at most 41%, at most 39%, and at most 37%.

[0036] The amount of dicyandiamide presented in this article gives the modified melamine-formaldehyde resin the best performance of the above-described method for manufacturing floor panels.

[0037] Optionally, the modified melamine-formaldehyde resin further comprises a polyol in an amount ranging from 1 to 5% by weight, preferably 2 to 4% by weight, and most preferably 3 to 4% by weight, based on the total liquid weight of the resin.

[0038] A polyol can be a single polyol, such as glycerol, monoethylene glycol (MEG), diethylene glycol (DEG), or polyethylene glycol (PEG), such as, for example, polyethylene glycol 400. Alternatively, a polyol can be a mixture of different polyols, such as two or more polyols.

[0039] Optionally, the polyol is glycerol.

[0040] Optionally, the substrate includes medium-density fiberboard (MDF) or high-density fiberboard (HDF).

[0041] By providing a substrate including MDF or HDF, embossing, and more specifically deep embossing extending into the substrate, will be dimensionally stable.

[0042] Optionally, the top layer includes a decorative layer. The decorative layer includes a printing substrate, more specifically, printing paper.

[0043] Optionally, the decorative layer is impregnated with modified melamine-formaldehyde resin.

[0044] By impregnating the decorative layer with modified melamine-formaldehyde resin, the decorative layer exhibits improved flexibility and stretchability. Therefore, the decorative layer is flexible and stretchable enough to withstand pressure without causing undue cracking or movement relative to the substrate.

[0045] Preferably, in step d), the pressure plate applies a pressure of 20 to 80 bar to the stack, the temperature during pressing is 150 to 200°C, and the pressing duration is 12 to 60 seconds. These are common pressing conditions for the DPL process.

[0046] The present invention also relates to a floor panel comprising a substrate and a top layer, the top layer defining an upper surface of the floor panel. Furthermore, the floor panel is provided with an embossed pattern extending from the upper surface, such that the thickness of the floor panel varies along its cross-section. The top layer comprises a modified melamine-formaldehyde resin and at least one modifier, the modified melamine-formaldehyde resin comprising formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75, wherein the at least one modifier is dicyandiamide.

[0047] Preferably, based on the total weight of melamine and dicyandiamide, dicyandiamide is present in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight.

[0048] Optionally, based on the total liquid weight of the resin, the modified melamine-formaldehyde resin further includes a polyol in an amount ranging from 1 to 5% by weight, preferably 2 to 4% by weight, and most preferably 3 to 4% by weight.

[0049] Optionally, the polyol is glycerol.

[0050] Optionally, the substrate may include medium-density fiberboard or high-density fiberboard.

[0051] By using MDF or HDF in the substrate, floor panels will exhibit good stiffness and sound absorption properties, for example.

[0052] Optionally, the top layer includes a decorative layer. The decorative layer includes a printing substrate, more specifically, printing paper.

[0053] Optionally, the decorative layer comprises a modified melamine-formaldehyde resin.

[0054] To protect the decorative layer, the top layer may also include an overlay. The overlay may include a carrier, more specifically, a carrier primarily composed of paper.

[0055] To improve the durability and abrasion resistance of floor panels, a protective resin layer may also be included as the top layer.

[0056] Optionally, the variation in the thickness of the floor panel is at least a variation in the thickness of the substrate.

[0057] By using embossing that extends into the substrate, the thickness of the substrate is varied, resulting in floor panels with an improved natural look and feel.

[0058] For example, to achieve a slatted effect or mimic the seams between tiles, at least some of the embossing can take the form of bevels or other chamfers set on one or more edges of the floor panel.

[0059] To give floor paneling an improved, more natural look, at least some of the embossing can be in the form of structure-imitating embossing set in the upper surface of the floor paneling. Preferably, the structure-imitating embossing can mimic the structure of wood.

[0060] Optionally, the floor paneling is direct pressure laminated floor paneling. Attached Figure Description

[0061] To better illustrate the features of the invention, some preferred embodiments are described below with reference to the accompanying drawings, as examples without any limiting features, wherein...

[0062] Figure 1 This refers to a floor panel manufactured according to the present invention; Figure 2 Indicates along Figure 1 The cross section of line II-II in the middle; Figure 3 Representing it in a magnified manner Figure 2 As shown by F3, and Figure 4 This refers to a portion of the method according to the invention that can be used to manufacture the floor panels of the present invention. Detailed Implementation

[0063] In the accompanying drawings, reference numeral 10 generally indicates a floor panel manufactured according to the present invention.

[0064] The floor panel 10 is typically rectangular and has a first pair of opposite sides 12, 13 and a second pair of opposite sides 14, 15. Figure 1 In the first pair of opposite sides 12, 13, the lengths are longer than those of the second pair 14, 15. However, it should be understood that the principles of the invention can be applied to slabs and tiles of any shape, including slabs and tiles with sides of the same length. Such slabs and tiles include square or polygonal slabs and tiles.

[0065] In order to allow multiple floor panels 10 to be laid to form a floating floor, each floor panel 10 may have at least one pair of opposite sides 12, 13 provided with an integral coupling part 16, 17 that allows mechanical coupling between adjacent floor panels 10. (See reference...) Figure 2 Examples of such connecting parts 16 and 17 are described in more detail.

[0066] The floor panel 10 also includes an upper surface 18 that forms the surface of the floor panel 10 and is visible when the floor panel is installed on the underlying surface or subfloor.

[0067] from Figure 2 As can be seen, the floor panel 10 is provided with embossings 20, 21, and 22 extending from the upper surface 18, such that the thickness T of the floor panel 10 varies along its cross-section. The embossings 20, 21, and 22 are provided to give the floor panel 10 a natural look and feel. For this purpose, characteristics such as depth, length, width, and orientation of each respective embossing 20, 21, and 22 of the floor panel 10 can be varied.

[0068] To achieve a slatted effect or mimic the joints between tiles, at least some of the embossing 20, 21, 22 may be in the form of bevels 22 or other chamfers set on one or more edges of the floor panel 10.

[0069] In one variation, at least some of the embossings 20, 21, 22 are in the form of imitation structure embossings 20, 21 provided on the upper surface 18 of the floor panel 10. By way of example only, the imitation structure embossings 20, 21 can imitate wood structures, such as wood pores.

[0070] If possible Figure 2 As can be further seen, the floor panel 10 of the present invention comprises multiple layers, including at least a substrate 24 and a top layer 26. It is conceivable that the floor panel 10 may also include additional layers, such as a backing layer 28, a sound insulation layer, and / or layers with other uses.

[0071] As described above, the depths of embossings 20, 21, and 22 can vary. In one exemplary embodiment, embossings 20, 22, or at least some thereof, may extend into the substrate 24 such that a change in the thickness T of the floor panel 10 is at least a change in the thickness t of the substrate 24. In another exemplary embodiment, embossing 21, or at least some thereof, extends only into the top layer 26. By way of example only, the embossing can be at least 200 μm deep.

[0072] exist Figure 2 In this embodiment, substrate 24 forms the actual core of floor panel 10. However, it is not excluded that substrate 24 consists of several layers or portions. Substrate 24 preferably comprises a wood-based product, more preferably wood fiberboard. According to a preferred embodiment, substrate 24 comprises medium-density fiberboard (MDF) or high-density fiberboard (HDF).

[0073] As mentioned above, Figure 2A floor panel 10 manufactured according to the invention is shown, which also has connecting portions 16, 17 on at least a first pair of opposing sides 12, 13. The connecting portions 16, 17 allow locking between two such floor panels 10 in the vertical direction V and the horizontal direction H perpendicular to the connecting sides. The connecting portions 16, 17 shown are of the type that allow two such floor panels 10 to be connected together by rotational movement. Here, this relates to a specific type of connecting portion because they also allow the floor panels 10 to be connected by substantially horizontal movement of the floor panels 10 relative to each other, while performing a snap-fit ​​action. This last mentioned connection method is not shown.

[0074] The connecting portions 16 and 17 may be in the form of a tongue 16 and a recess 17, each of which may be provided with complementary locking elements 30 and 32. Preferably, the tongue 16 includes a protrusion 30 on its underside. The protrusion 30 is adapted to interact with a locking surface 32 located at the recess 17.

[0075] The connecting portions 16 and 17 are substantially, and preferably even entirely, integrally formed with and made of the material of the floor panel 10. More specifically, the connecting portions 16 and 17 are integrally formed in the substrate 24. However, it should be understood that the connecting portions 16 and 17 may alternatively be configured to be integrally connected to separate portions of the floor panel 10.

[0076] Of course, other types of connectors can also be used. For example, connectors that allow connection solely through rotational movement can be provided. Another type is the so-called "push-lock" connector, which allows connection of floor panels through downward and substantially vertical movement.

[0077] It is not excluded that the second pair of opposite sides 14, 15 may also be provided with an integral mechanical connection. These can be of the same type as the connections on the first pair of opposite sides, but this is not mandatory. A particular embodiment is one in which a rotating connection is applied on a pair of long sides, and a push-lock connection is applied on a pair of short sides. In this way, when the two floor panels 10 are engaged by rotating along their adjacent long sides, the short side of the rotated panel will engage with the push-lock connection on the short side of the third panel 10.

[0078] exist Figure 3An embodiment of the top layer 26 defining the upper surface 18 of the floor panel 10 is shown in more detail. The top layer 26 comprises a modified melamine-formaldehyde resin 34, which includes formaldehyde and melamine, wherein the molar ratio of formaldehyde to melamine (F / M) is in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75. By way of example only, the F / M molar ratio may be about 1.74. The modified melamine-formaldehyde resin 34 also includes at least one modifier, wherein the at least one modifier is dicyandiamide.

[0079] Advantageously, based on the total weight of melamine and dicyandiamide, dicyandiamide is present in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight. By way of example only, based on the total weight of melamine and dicyandiamide, the amount of dicyandiamide may be about 35% by weight.

[0080] In one embodiment, the modified melamine-formaldehyde resin 34 further includes a polyol, the amount of which is in the range of 1 to 5% by weight, preferably 2 to 4% by weight, and most preferably 3 to 4% by weight, based on the total liquid weight of the resin. The polyol can be, for example, any of monoethylene glycol (MEG) or diethylene glycol (DEG). By way of example only, the amount of polyol can be about 3.40% by weight based on the total liquid weight of the resin.

[0081] In one specific implementation, the polyol can be glycerol.

[0082] Preferably, the top layer 26 includes a decorative layer 36. In this document, decorative layer 36 refers to a layer that provides a visual appearance (such as a wood or stone pattern) to the floor panel 10. In one variation, decorative layer 36 includes a printing carrier 38, more specifically, printed paper. The printing on the printing carrier 38 preferably depicts a natural product, such as wood, stone, or ceramic, but may also depict decorative patterns. This printing can be achieved using any of the following printing techniques: offset printing, gravure printing, or digital printing, where, for example, a digital printing press or inkjet printing press is used. However, other printing techniques are not excluded.

[0083] Advantageously, the decorative layer 36 comprises a modified melamine-formaldehyde resin 34. In one variant, the printing carrier 38 may be impregnated with the modified melamine-formaldehyde resin 34.

[0084] In an exemplary embodiment, the top layer 26 may also include a cover layer 40. Preferably, the cover layer 40 includes a carrier 42, more specifically, a carrier 42 primarily composed of paper. The cover layer 40 may also include a resin 44, particularly melamine-formaldehyde resin 44. The cover layer 40 is configured as a transparent layer, which sits above the decorative layer 36, advantageously directly above the decorative layer 36. Preferably, although not essential, the cover layer 40 includes abrasion-resistant particles, such as corundum.

[0085] Although not shown in the figures, the top layer 26 may include a protective resin layer. In one variation, the protective resin layer may replace the cover layer 40 and thus may be placed directly above the decorative layer 36. In another variation, the top layer 26 includes both the cover layer 40 and the protective resin layer. The protective resin layer may then be placed on top of the cover layer 40. However, another location is not excluded. Preferably, the protective resin layer is composed of melamine-formaldehyde resin, which may include abrasion-resistant particles such as corundum.

[0086] In one embodiment of the invention, the floor panel 10 is a direct pressure laminate (DPL) floor panel 10. Preferably, the DPL floor panel is manufactured by the method according to the invention.

[0087] Furthermore, the present invention relates to a method for manufacturing a floor panel 10 having the above-described features. Figure 4 A portion of this method is illustrated schematically.

[0088] In one step of the method, referred to as step a), substrate 24 is provided. Although the fabrication of substrate 24 or any layers or portions thereof that may be included is not shown, it should be understood that any suitable technique may be used to achieve this purpose.

[0089] The method further includes step b), wherein a top layer 26 is provided. The top layer 26 comprises a modified melamine-formaldehyde resin 34 comprising formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, preferably from 1.70 to 1.80, more preferably from 1.73 to 1.75; and at least one modifier. The at least one modifier is dicyandiamide.

[0090] Advantageously, based on the total weight of melamine and dicyandiamide, dicyandiamide is present in the modified melamine-formaldehyde resin 34 in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight.

[0091] In one embodiment, the modified melamine-formaldehyde resin 34 further includes a polyol, the amount of which is in the range of 1 to 5% by weight, preferably 2 to 4% by weight, and most preferably 3 to 4% by weight, based on the total liquid weight of the resin.

[0092] In a specific implementation, the polyol can be glycerol.

[0093] In step c) of the method, a stack comprising a substrate 24 and a top layer 26 is formed. The stack may also include additional layers, such as a backing layer 28, a sound insulation layer, and / or layers with other uses.

[0094] In another step, referred to as step d), the stack formed in step c) is pressed. Pressing is performed by a pressure plate 46 comprising embossing devices 48, 50 and a heating device (not shown). Preferably, the pressure plate 46 is part of a hot press 52 in a manner known in the art.

[0095] During the pressing process, embossing devices 48 and 50 provide embossing patterns 20, 21, and 22 to the floor panel 10, and a heating device hardens the modified melamine-formaldehyde resin 34 and adheres the top layer 26 to the substrate 24. Thus, the floor panel 10 is formed, laminated, and cured in a single step.

[0096] In an exemplary embodiment, in step d), the pressure plate 46 applies a pressure of 20 bar to 80 bar to the stack, the temperature during pressing is 150°C to 200°C, and the pressing duration is 12 seconds to 60 seconds.

[0097] Preferably, the embossing devices 48, 50 are adapted to provide the desired structure for the floor panel 10. Thus, the embossing devices 48, 50 can be designed to form embossings 20, 22 extending into the substrate 24 and / or embossings extending only into the top layer 26. In a particularly advantageous variant, all embossings 20, 21, 22 can be formed in a single pressing operation. Therefore, it is evident that the pressing plate 46 includes all the embossing devices 48, 50 required to form the desired structure. In another variant, embossings 20, 21, 22 are formed in more than one step. For example, it is conceivable to form some embossings 20, 21, 22 prior to step b) of the method.

[0098] To enhance the visual appearance of the floor panel 10, the top layer 26 may include a decorative layer 36. In a preferred embodiment, the decorative layer 36 includes a printing carrier 38, more specifically, printed paper. Preferably, the printed paper has a weight of 60-100 g / m³. 2 More preferably 70-90 g / m 2 The optimal value is 74-84 g / m³. 2 .

[0099] Optionally, decorative layer 36 is impregnated with modified melamine-formaldehyde resin 34.

[0100] Alternatively, the top layer 26 may also include a cover layer 40. Preferably, the cover layer 40 includes a carrier 42 in a manner known in the art, more specifically a carrier 42 primarily composed of paper. The cover layer 40 may also include a resin 44, particularly a melamine-formaldehyde resin 44.

[0101] although Figure 4 Not shown, but top layer 26 may include additional layers, such as, for example, a protective resin layer. Preferably, the additional layer (if any) comprises a resin, more preferably a melamine-formaldehyde resin.

[0102] In one variant, all the resin in the top layer 26 is fully or at least partially cured in step d).

[0103] The present invention also relates to the use of dicyandiamide as a modifier in melamine-formaldehyde resin to increase the flexibility and tensile strength of melamine-formaldehyde resin during pressing and curing in a direct pressure lamination process.

[0104] Preferably, the modified melamine-formaldehyde resin 34 in which dicyandiamide is used as a modifier comprises formaldehyde and melamine in an F / M molar ratio in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75.

[0105] In one embodiment, based on the total weight of melamine and dicyandiamide, dicyandiamide may be present in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight.

[0106] In the most preferred embodiment, the modified melamine-formaldehyde resin 34 comprises formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75, and dicyandiamide is present in an amount ranging from 30% to 40%, preferably 32% to 38%, more preferably 34% to 36%. Preferably, the direct pressure lamination process includes the step of impregnating the carrier 38 with melamine-formaldehyde resin 34 prior to lamination with the substrate 24, thereby forming the floor panel 10. In one variant, the carrier 38 forms a portion of the top layer 26, preferably forming a decorative layer 36 of the top layer 26.

[0107] Furthermore, the present invention also relates to the use of dicyandiamide as a modifier in melamine-formaldehyde resin 34 for use in floor panel 10. Floor panel 10 includes a substrate 24 and a top layer 26, the top layer 26 defining an upper surface 18 of floor panel 10. Floor panel 10 is provided with embossings 20, 21, 22 extending from the upper surface 18, such that the thickness T of floor panel 10 varies along its cross-section. Top layer 26 comprises modified melamine-formaldehyde resin 34 and at least one modifier, the modified melamine-formaldehyde resin 34 comprising formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75. Thus, floor panel 10 with improved transparency at the embossings 20, 21, 22 is provided.

[0108] Preferably, the floor paneling is as described above regarding Figure 1-3 Floor paneling.

[0109] The present invention also relates to modified melamine-formaldehyde resin 34, which comprises: - Formaldehyde and melamine; - Based on the total weight of melamine and dicyandiamide, a dicyandiamide content ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight; and - Preferred polyols, most preferably glycerol, are used, and the amount is in the range of 1 to 5% by weight, preferably 2 to 4% by weight, and more preferably 3 to 4% by weight, based on the total liquid weight of the resin.

[0110] Preferably, the modified melamine-formaldehyde resin 34 comprises formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, more preferably from 1.70 to 1.80, and more preferably from 1.73 to 1.75.

[0111] Example

[0112] Example 1

[0113] This is a comparative study of the flexibility of decorative paper layers immersed in melamine-formaldehyde resin with and without dicyandiamide (DCDA).

[0114] Flexibility is measured in the form of elongation at break, which is the ratio between the increased length of a test sample and its initial length at a controlled temperature. It relates to the ability of a plastic sample to resist changes in shape without breaking. Elongation at break is measured as a percentage (elongation relative to the initial length at break).

[0115] Two resins were prepared. Dicyandiamide was present in the resin designated as the test resin. Dicyandiamide was not present in the resin designated as the reference resin. The composition and amounts of the resins are shown in Table 1 below.

[0116] Table 1

[0117]

[0118] The resins in Table 1 were prepared according to standard preparation methods using an automated IFA system capable of impregnation on the VITS impregnation line. DCDA, present in the test resin, was added to formaldehyde along with melamine. The dry content of the reference resin formulation was 48%, and the dry content of the test resin formulation was 42%. Sucrose was used as the sugar in the reference resin.

[0119] The test resin was observed to be significantly slower in its final reactivity than the reference resin; specifically, the turbidity time for the test resin was 15 minutes, compared to 5 minutes for the reference resin. Furthermore, during impregnation, the test resin was observed to have a turbidity time approximately two minutes slower than the reference resin.

[0120] Four different decorative papers (papers 1-4) were used in the experiment, each with a paper weight of 70 g / m². 2 75 g / m 2 and 110g / m 2 : Paper 1 - 70 g beige printing base paper Paper 2 - 70 g white printing base paper Paper 3 - 75 g monochrome base paper black Paper 4 - 110 g monochrome base paper white Each paper was immersed in its respective resin and then dried in an oven until its residual moisture content was about 7 wt%.

[0121] Oven temperature for drying paper: Paper immersed in reference resin - all oven zones at 130°C Paper immersed in test resin - all oven zones at 110°C Subsequently, samples of each decorative paper were cut into 6 cm x 18 cm pieces. Samples were cut from industrially manufactured impregnated paper. Samples were cut from the left (L) / middle (M) / right (R) side of the corresponding paper. These samples were then tested on a Zwick stretching table used to measure elongation at break using a constant elongation of 3 mm / min.

[0122] Before testing, the sample is wrapped in plastic to avoid interference with temperature and air humidity, as extreme humidity can affect the results.

[0123] The test was conducted at 20.9°C and 31% relative humidity.

[0124] The elongation at break was measured in both the longitudinal and transverse directions of the sample.

[0125] The results are shown in Table 2 below.

[0126] Table 2

[0127]

[0128] Unexpectedly, an increase in elongation at break was observed in all papers impregnated with melamine-formaldehyde resins containing DCDA. Compared to paper impregnated with resins without DCDA, an increase in longitudinal elongation of 35%–70% and transverse elongation of 80–235% was observed in paper impregnated with resins containing DCDA.

[0129] Therefore, it can be concluded that the presence of dicyandiamide in melamine-formaldehyde resin leads to an improvement in the resin's tensile strength / flexibility. The inventors have noted that the absence of sugar also has beneficial effects on the resin's flexibility and tensile properties, although to a much lower, even marginal, degree than the presence of DCDA according to the invention.

[0130] Example 2

[0131] In this embodiment, based on the total weight of the liquid resin, a resin comprising 8% DCDA by weight and 32.94% melamine by weight (i.e., a lower concentration of DCDA than that used in Example 1) was used to impregnate the decorative paper layer, and its feasibility for pressing was then examined.

[0132] Surprisingly, it was observed that, based on the total weight of the liquid resin, resin including 8% DCDA was unsuitable for pressing with a press plate containing an embossing device.

[0133] Example 3

[0134] To further evaluate the effect of DCDA present at different concentrations in melamine-formaldehyde resin on the flexibility of decorative paper layers, such as printed decorative paper, impregnated with it, the following experiments were conducted.

[0135] Samples 1, 2, and 3 were prepared using 0 wt.%, 17.50 wt.%, and 30.37 wt.% DCDA, respectively, based on the total weight of melamine and DCDA. The compositions of test samples 1, 2, and 3 are shown in Table 3.

[0136] Table 3. Composition of test resins 1, 2 and 3.

[0137]

[0138] Three samples of paper were impregnated using test resins 1, 2, and 3, and the flexural angle at break, elongation at maximum force, and elongation at maximum strain were tested. These tests were selected to evaluate the flexibility and / or elongated tear resistance of test resins 1, 2, and 3. The paper was digitally printed at 75 g / m². 2 Decorative paper.

[0139] Test samples 1, 2, and 3 were used for bending angle testing. The bending angle test was performed by attaching a 200 x 38 mm sheet of paper to the surface and then bending the sheet (on the short side) until it broke. For elongation testing, a general-purpose testing machine and a 200 x 30 mm sheet of paper were used to determine the "maximum elongation force" and "maximum elongation strain." The testing machine has a lower grip and an upper grip to hold the workpiece. The upper grip moves upward, causing the paper to elongate.

[0140] The test results are shown in Table 4.

[0141] Table 4. Results of tests on samples 1, 2 and 3.

[0142]

[0143] Table 4 shows that test sample 3, with 30.37 wt.% DCDA (calculated based on the total weight of melamine and DCDA), exhibited the best results, i.e., the highest flexibility, as determined by tests such as the bending angle test or under applied force and / or strain. Test sample 1, excluding DCDA, showed the worst resistance to breakage and / or tearing, while test sample 2, including only 17.50 wt.% DCDA, showed better resistance than sample 1, but significantly lower performance than test sample 3.

[0144] Example 4

[0145] Resin test samples 1, 2, and 3 were prepared using 0 wt.%, 17.50 wt.%, and 30.37 wt.% DCDA, respectively, based on the total weight of melamine and DCDA. The complete composition of test samples 1, 2, and 3 is shown in Table 3.

[0146] At a temperature of 195°C and 80 kg / cm² 2 Under pressure, paper samples impregnated with resin from test samples 1, 2, and 3 were pressed against an inclined plane for 20 seconds. These pressing conditions are those that can occur in the DPL process.

[0147] Inspect the pressing bevel for any tearing or damage that may have occurred during the pressing process. Only the paper impregnated with test sample 3 passed the test and showed no visible tears at the bevel, while the paper impregnated with test samples 1 and 2 did not show satisfactory results.

[0148] Preferred embodiments and variations of the present invention are defined in the following numbered items: 1. The use of dicyandiamide as a modifier in melamine-formaldehyde resin to increase the flexibility and tensile strength of the melamine-formaldehyde resin during pressing and curing in a direct pressure lamination process.

[0149] 2. The use of dicyandiamide according to item 1, wherein the modified melamine-formaldehyde resin comprises formaldehyde and melamine in an F / M molar ratio ranging from 1.60 to 1.80, preferably from 1.70 to 1.80, more preferably from 1.73 to 1.75.

[0150] 3. The use of dicyandiamide according to item 1 or 2, wherein, based on the total weight of melamine and dicyandiamide, dicyandiamide is present in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, more preferably 32% to 38% by weight, and most preferably 34% to 36% by weight.

[0151] 4. The use of dicyandiamide according to any one of items 1 to 3, wherein the direct pressure lamination process includes the step of impregnating a carrier with the melamine-formaldehyde resin, the carrier forming a portion of the top layer, preferably forming a decorative layer of the top layer before lamination with a substrate, thereby forming a floor panel.

[0152] 5. The use of dicyandiamide as a modifier in melamine-formaldehyde resin for flooring panels, the flooring panels comprising a substrate and a top layer, the top layer defining an upper surface of the flooring panel, wherein the flooring panel is provided with embossing extending from the upper surface such that the thickness T of the flooring panel varies along the cross-section of the flooring panel, the top layer comprising modified melamine-formaldehyde resin and at least one modifier, the modified melamine-formaldehyde resin comprising formaldehyde and melamine in an F / M molar ratio in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75, thereby providing a flooring panel with improved transparency at the embossing.

[0153] 6. The use of dicyandiamide according to item 5, wherein the floor panel is a floor panel according to any one of items 17 to 30.

[0154] 7. A modified melamine-formaldehyde resin 34, comprising: - Formaldehyde and melamine; - Based on the total weight of melamine and dicyandiamide, a dicyandiamide content ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight; and - Preferably, the polyol, most preferably, glycerol, is in the range of 1 to 5% by weight, more preferably 2 to 4% by weight, and more preferably 3 to 4% by weight, based on the total liquid weight of the resin.

[0155] 8. The modified melamine-formaldehyde resin 34 according to item 7, comprising formaldehyde and melamine in an F / M molar ratio in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75.

[0156] 9. A method for manufacturing a floor panel 10, the floor panel 10 including a substrate 24 and a top layer 26, the top layer 26 defining an upper surface 18 of the floor panel 10, wherein the floor panel 10 is provided with embossings 20, 21, 22 extending from the upper surface 18, such that the thickness T of the floor panel 10 varies along the cross-section of the floor panel 10, wherein the method includes the following steps: a) Provide the substrate 24; b) Providing the top layer 26, the top layer 26 comprising modified melamine-formaldehyde resin 34 and at least one modifier, wherein the modified melamine-formaldehyde resin 34 comprises formaldehyde and melamine with an F / M molar ratio preferably in the range of 1.60 to 1.80, more preferably 1.70 to 1.80, and more preferably 1.73 to 1.75, wherein the at least one modifier is dicyandiamide; c) Constructing a stack including the substrate 24 and the top layer 26; d) The stack is pressed by a pressure plate 46, which includes embossing devices 48 and 50 and a heating device, wherein the embossing devices 48 and 50 provide the embossing 20, 21, and 22 to the floor panel 10 during pressing, and wherein the heating device hardens the modified melamine-formaldehyde resin 34 and adheres the top layer 26 to the substrate 24 during pressing.

[0157] 10. The method according to item 9, wherein, based on the total weight of melamine and dicyandiamide, dicyandiamide is present in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight.

[0158] 11. The method according to item 9 or 10, wherein the modified melamine-formaldehyde resin 34 further comprises a polyol in an amount ranging from 1 to 5% by weight, preferably 2 to 4% by weight, and most preferably 3 to 4% by weight, based on the total liquid weight of the resin.

[0159] 12. The method according to item 11, wherein the polyol is glycerol.

[0160] 13. The method according to any one of items 9 to 12, wherein the substrate 24 comprises medium-density fiberboard or high-density fiberboard.

[0161] 14. The method according to any one of items 9 to 13, wherein the top layer 26 includes a decorative layer 36, the decorative layer 36 including a printing carrier 38, more specifically, printing paper.

[0162] 15. The method of item 14, wherein the decorative layer 36 is impregnated with the modified melamine-formaldehyde resin 34.

[0163] 16. The method according to any one of items 9 to 15, wherein in step d), the pressure plate 46 applies a pressure of 20 bar to 80 bar to the stack, the temperature during pressing is 150°C to 200°C, and the duration of pressing is 12 seconds to 60 seconds.

[0164] 17. A floor panel 10 comprising a substrate 24 and a top layer 26, the top layer 26 defining an upper surface 18 of the floor panel 10, wherein the floor panel 10 is provided with embossings 20, 21, 22 extending from the upper surface 18, such that the thickness T of the floor panel 10 varies along the cross-section of the floor panel 10. The top layer 26 comprises a modified melamine-formaldehyde resin 34 and at least one modifier, the modified melamine-formaldehyde resin 34 comprising formaldehyde and melamine in an F / M molar ratio in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75, wherein the at least one modifier is dicyandiamide.

[0165] 18. The floor panel 10 according to item 17, wherein, based on the total weight of melamine and dicyandiamide, dicyandiamide is present in an amount ranging from 25% to 45% by weight, preferably 30% to 40% by weight, and more preferably 34% to 36% by weight.

[0166] 19. The floor panel 10 according to item 17 or 18, wherein the modified melamine-formaldehyde resin 34 further comprises a polyol in an amount of 1 to 5% by weight, preferably 2 to 4% by weight, and most preferably 3 to 4% by weight, based on the total liquid weight of the resin.

[0167] 20. Floor panel 10 according to item 19, wherein the polyol is glycerol.

[0168] 21. The floor panel 10 according to any one of items 17 to 20, wherein the substrate 24 comprises medium-density fiberboard or high-density fiberboard.

[0169] 22. The floor panel 10 according to any one of items 17 to 21, wherein the top layer 26 includes a decorative layer 36, the decorative layer 36 including a printing carrier 38, more specifically, printed paper.

[0170] 23. The floor panel 10 according to item 22, wherein the decorative layer 36 comprises the modified melamine-formaldehyde resin 34.

[0171] 24. The floor panel 10 according to item 23, wherein the top layer 26 further includes a cover layer 40, the cover layer 40 including a carrier 42, more specifically, a carrier mainly composed of paper.

[0172] 25. The floor panel 10 according to any one of items 22 or 23, wherein the top layer 26 further comprises a protective resin layer.

[0173] 26. The floor panel 10 according to any one of items 17 to 25, wherein the variation in thickness T is at least a variation in thickness t of substrate 24.

[0174] 27. The floor panel 10 according to item 26, wherein at least some of the embossings 20, 21, 22 are in the form of bevels 22 or other chamfers provided on one or more edges of the floor panel 10.

[0175] 28. The floor panel 10 according to item 26 or 27, wherein at least some of the embossings 20, 21, 22 are in the form of imitation structure embossings 20, 21 disposed on the upper surface 18 of the floor panel 10, the imitation structure embossings 20, 21 preferably imitating the wood structure.

[0176] 29. The floor panel 10 according to any one of items 17-28, wherein the floor panel 10 is a direct pressure laminated floor panel 10.

[0177] 30. A paper (38) impregnated with a modified melamine-formaldehyde resin (34), said modified melamine-formaldehyde resin (34) comprising formaldehyde, melamine and dicyandiamide, wherein preferably, the amount of dicyandiamide is in the range of 25 to 45% by weight based on the total weight of melamine and dicyandiamide, preferably 30 to 40% by weight, more preferably 34 to 36% by weight, and / or wherein preferably, the formaldehyde / melamine molar ratio is in the range of 1.60 to 1.80, preferably 1.70 to 1.80, more preferably 1.73 to 1.75.

[0178] 31. The paper according to item 30, wherein, based on the total liquid weight of the resin, the resin (34) includes a polyol in an amount ranging from 1 to 5% by weight, preferably 2 to 4% by weight, more preferably 3 to 4% by weight, and most preferably glycerol.

[0179] 32. The paper (38) according to item 30 or 31, wherein the paper (38) is printing paper.

Claims

1. A modified melamine-formaldehyde resin (34) comprising formaldehyde and melamine, wherein, The resin (34) contains dicyandiamide, and wherein the formaldehyde / melamine molar ratio is in the range of 1.60 to 1.80, characterized in that the amount of dicyandiamide is in the range of 30 to 40% by weight based on the total weight of melamine and dicyandiamide, and the resin contains glycerol in the range of 1 to 5% by weight based on the total liquid weight of the resin.

2. The modified melamine-formaldehyde resin (34) according to claim 1, wherein, Based on the total weight of melamine and dicyandiamide, the amount of dicyandiamide is in the range of 32% to 38% by weight.

3. The modified melamine-formaldehyde resin (34) according to claim 1 or 2, comprising formaldehyde and melamine in a formaldehyde / melamine molar ratio in the range of 1.70 to 1.

80.

4. The modified melamine-formaldehyde resin (34) according to claim 1 or 2, wherein, Based on the total liquid weight of the resin, the resin contains glycerin in an amount ranging from 2% to 4% by weight.

5. The modified melamine-formaldehyde resin (34) according to claim 1, wherein, Based on the total weight of melamine and dicyandiamide, the amount of dicyandiamide is in the range of 34% to 36% by weight.

6. The modified melamine-formaldehyde resin (34) according to claim 1 or 2, comprising formaldehyde and melamine in a formaldehyde / melamine molar ratio in the range of 1.73 to 1.

75.

7. The modified melamine-formaldehyde resin (34) according to claim 1 or 2, wherein, Based on the total liquid weight of the resin, the resin contains glycerin in an amount ranging from 3% to 4% by weight.

8. A paper (38) impregnated with modified melamine-formaldehyde resin (34), characterized in that, The modified melamine-formaldehyde resin (34) is the modified melamine-formaldehyde resin (34) according to any one of claims 1 to 7.

9. The paper (38) impregnated with modified melamine-formaldehyde resin (34) according to claim 8, wherein, The paper (38) is printing paper.

10. A method for manufacturing a floor panel (10) comprising a substrate (24) and a top layer (26), the top layer (26) defining an upper surface (18) of the floor panel (10), wherein, The floor panel (10) is provided with embossing (20, 21, 22) extending from the upper surface (18), such that the thickness T of the floor panel (10) varies along the cross-section of the floor panel (10), wherein the method includes the following steps: a) Provide the substrate (24); b) Providing the top layer (26), the top layer (26) comprising a modified melamine-formaldehyde resin (34) and at least one modifier, the modified melamine-formaldehyde resin (34) comprising formaldehyde and melamine in a formaldehyde / melamine molar ratio in the range of 1.60 to 1.80, wherein the at least one modifier is dicyandiamide, and wherein, based on the total weight of melamine and dicyandiamide, the dicyandiamide is present in an amount in the range of 30 to 40% by weight, and based on the total liquid weight of the resin, the resin comprises glycerol in an amount in the range of 1 to 5% by weight; c) Constructing a stack comprising the substrate (24) and the top layer (26); d) The stack is pressed by a pressure plate (46) comprising an embossing device (48, 50) and a heating device, wherein the embossing device (48, 50) provides the embossing (20, 21, 22) to the floor panel (10) during pressing, and wherein the heating device hardens the modified melamine-formaldehyde resin (34) and causes the top layer (26) to adhere to the substrate (24) during pressing.

11. The method according to claim 10, wherein, Based on the total weight of melamine and dicyandiamide, dicyandiamide is present in an amount ranging from 32% to 38% by weight.

12. The method according to claim 10 or 11, wherein, Based on the total liquid weight of the resin, the resin contains glycerin in an amount ranging from 2% to 4% by weight.

13. The method according to claim 10 or 11, wherein, The substrate (24) includes medium-density fiberboard or high-density fiberboard.

14. The method according to claim 10 or 11, wherein, The top layer (26) includes a decorative layer (36), which includes a printing carrier (38).

15. The method according to claim 14, wherein, The decorative layer (36) is impregnated with the modified melamine-formaldehyde resin (34).

16. The method according to claim 10 or 11, wherein, In step d), the pressure plate (46) applies a pressure of 20 to 80 bar to the stack, the temperature during pressing is 150 to 200°C, and the pressing lasts for 12 to 60 seconds.

17. The method according to claim 10, wherein, The modified melamine-formaldehyde resin (34) contains formaldehyde and melamine in a formaldehyde / melamine molar ratio in the range of 1.70 to 1.

80.

18. The method according to claim 10, wherein, The modified melamine-formaldehyde resin (34) contains formaldehyde and melamine in a formaldehyde / melamine molar ratio in the range of 1.73 to 1.

75.

19. The method according to claim 10, wherein, Based on the total weight of melamine and dicyandiamide, dicyandiamide is present in an amount ranging from 34% to 36% by weight.

20. The method according to claim 10 or 11, wherein, Based on the total liquid weight of the resin, the resin contains glycerin in an amount ranging from 3% to 4% by weight.

21. The method according to claim 14, wherein, The printing carrier (38) is printing paper.

22. Use of dicyandiamide as a modifier in melamine-formaldehyde resin for increasing the flexibility and tensile strength of the melamine-formaldehyde resin during pressing and curing in a direct pressure lamination process, for use in a floor panel comprising a substrate and a top layer, the top layer defining the upper surface of the floor panel, wherein, The floor panel is provided with an embossed pattern extending from the upper surface, such that the thickness T of the floor panel varies along the cross-section of the floor panel. The top layer comprises the melamine-formaldehyde resin, in which dicyandiamide is used as a modifier. The resin contains formaldehyde and melamine at a formaldehyde / melamine molar ratio in the range of 1.60 to 1.

80. The dicyandiamide is present in an amount in the range of 30% to 40% by weight, based on the total weight of melamine and dicyandiamide. The resin contains glycerin in an amount in the range of 1% to 5% by weight, based on the total liquid weight of the resin.

23. The use according to claim 22, wherein, The resin contains formaldehyde and melamine in a formaldehyde / melamine molar ratio in the range of 1.70 to 1.

80.

24. The use according to claim 22, wherein, The resin contains formaldehyde and melamine in a formaldehyde / melamine molar ratio in the range of 1.73 to 1.

75.

25. The use according to claim 22, wherein, Based on the total weight of melamine and dicyandiamide, the dicyandiamide is present in an amount ranging from 32% to 38% by weight.

26. The use according to claim 22, wherein, Based on the total weight of melamine and dicyandiamide, the dicyandiamide is present in an amount ranging from 34% to 36% by weight.

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