BE1020739A3 - PANEL FOR FORMING A FLOOR COATING, METHOD FOR MANUFACTURING SUCH PANELS AND GRANULATE USED HEREIN. - Google Patents

Description

Panel for forming a floor covering, method for manufacturing such panels and granules used herein.

This invention relates to panels for forming a floor covering, to a method for manufacturing such panels and to a granulate used herein.

More specifically, the invention relates to panels comprising at least one layer, more particularly a substrate layer, of thermoplastic material. Furthermore, such panels may comprise at least one top layer with a printed decor and a transparent or transparent wear layer above the said layer.

In particular, the present invention relates to panels of the type comprising coupling means or coupling parts at two or more opposite edges, with which two such floor panels can be coupled to the relevant edges such that they are locked to each other both in a horizontal direction perpendicular to the edge and in the plane of the floor panels, as in a vertical direction perpendicular to the plane of the floor panels. Such floor panels can be used to assemble a so-called floating floor covering, wherein the floor panels are connected to each other at their edges, but lie freely on the substrate.

Such panels are known, for example, from EP 1 938 963 and WO 2010/023042. More specifically, vinyl-based floor panels are known from these documents for forming a floating floor covering. Such vinyl-based floor panels usually have a thickness of 3 to 5 millimeters and have a high material density. The core of the panels is in each case constructed from one or more layers of thermoplastic material, for example soft PVC, which can comprise fillers. A transparent thermoplastic layer and possibly a superficial lacquer layer have been applied above the printing.

The panels from the prior art have the disadvantage that they are highly subject to shrinking and expansion under the influence of temperature. Shrinking and expansion can lead to the floor covering or the individual panels being spun up and, for example, to the mutual release of the coupling parts or to the moving apart of the individual panel-shaped elements, whereby gaps can arise. The properties of the prior art panels are such that problems can already arise with heating due to incident sunlight, for example near a window in a room.

It is known from WO 2012/004701 to use a glass fiber layer or embedded profiles for increasing the dimensional stability of such panels. In particular, the bending stiffness of the panels is addressed here.

The present invention contemplates an alternative panel, which is primarily intended as a floor panel for forming a floating floor covering. According to various preferred embodiments of the invention, a solution is also provided for one or more problems with the panels from the prior art.

To this end, the invention according to its first independent aspect relates to a panel for forming a floor covering, said panel comprising at least one layer consisting of thermoplastic material, characterized in that said layer still comprises at least individual fibers, preferably with a length greater than 1 mm . By "separate fibers" is meant that they are not in themselves part of a layer or a prefabricated layer, such as a glass fiber cloth, but are, for example, freely dispersed in the thermoplastic material, whether or not uniform. The inventors have found that the use of such loose or separate fibers can greatly contribute to the dimensional stability of the panels, and in particular can limit the degree of expansion or shrinkage. Such individual fibers are generally found to be better embedded in the thermoplastic material than, for example, a glass fiber cloth. Moreover, they can be active over a greater thickness of the thermoplastic material than such glass fiber fleece (non-woven) or glass fiber cloth (woven), such that shrinking or expansion due to shearing over such glass fiber cloth can be avoided to a large extent.

The fibers in question preferably have an average length of 3 millimeters or more. Good results have been achieved with fibers with an average length of approximately 4.5 millimeters. Preferably, the average length is shorter than 10 millimeters, or even shorter than 6 millimeters.

The layer in question preferably comprises between 1 and 25 weight percent of the fibers in question, and more preferably between 5 and 15 weight percent, without any other fillers such as chalk being included.

Glass fibers are preferably used for the fibers. E-Glass is preferably chosen, for example as defined in DIN 1259. According to an alternative, steel fibers or other fibers such as carbon fibers, aramid fibers or polyethylene fibers can be used.

Moisture-resistant fibers are preferably used, and therefore no cellulose fibers, unless they are coated or treated, for example by acetylation, to make them moisture-resistant at least to some extent.

Preferably, the fibers, for example glass fibers, have an average diameter of between 1 and 100 micrometers or better between 3 and 30 micrometers, the range between 5 and 25 micrometers being the best in various experiments.

The fibers are preferably provided with a coating or treatment that improves the adhesion with the thermoplastic material. The surface of the fibers is preferably treated with Silane.

Preferably the fibers exhibit a coefficient of thermal expansion that is smaller than the thermoplastic material in which they are located and / or a Young's modulus that is larger than the thermoplastic material in which they are located.

Preferably, fibers are used with a Young's modulus of more than 40, more preferably more than 60 GPa.

Preferably, fibers are used with a thermal expansion coefficient of less than 30 µm / mK, and more preferably of less than 5 µm / mK.

The aforementioned thermoplastic material preferably relates to polyvinyl chloride, preferably semi-rigid or even soft polyvinyl chloride (PVC), namely PVC with plasticizers, for example with a proportion of plasticizers in the PVC of more than 20 or more than 30% by weight. It is clear that polypropylene (PP), polyethylene (PET) or polyurethane (PUR) can also be used instead of PVC.

The panel of the invention preferably comprises above the above-mentioned layer at least one further printed decor and a translucent or transparent wear layer arranged above it. The aforementioned decor may consist of a printing carried out on a plastic film, for example a printed PVC film, PU film, PP film, PET film. In the case of a PP film, it may, for example, be oriented polypropylene films. The wear layer preferably also comprises a thermoplastic material, such as PVC, PU, PP or PET. The transparent thermoplastic wear layer is preferably free of solid additives, such as ceramic particles to promote wear resistance, although this type of particles is not in itself excluded. However, the inventor has determined that they can be omitted for the purpose of achieving good transparency, while still maintaining an acceptable wear resistance, namely a wear resistance comparable or better than that of an AC2 or AC3 class laminate panel, measured according to EN 13329. The wear layer preferably has a thickness of at least 0.15 millimeters, and more preferably at least 0.3 millimeters, but preferably less than 1 millimeter, with 0.2 to 0.4 millimeters being a good value. With this good value, a sufficient wear resistance can already be obtained for residential applications on the basis of the thermoplastic material of the wear layer alone, that is without taking into account any solid additives. For example, it is possible to achieve an IP value (initial wear point) of 2000 or more with the tabertests, as described in EN 13329, annex E.

According to an alternative, it is not excluded that the printed decor or printing would be provided on the underside of the wear layer.

Preferably, the aforementioned thermoplastic layer further comprises at least one glass fiber cloth or glass fiber fleece. This is preferably a so-called "non-woven", namely a fiberglass fleece. The inventors have established that this can be achieved with a fiberglass fleece, a better embedding in the thermoplastic material and therefore a more efficient operation of the glass fibers.

The thermoplastic layer, which according to the invention comprises the individual fibers, preferably relates to a substrate layer, namely a layer which extends below a top layer. Such a layer is preferably at least halfway in the thickness of the panel. In this way the risk of a possible bending effect with changing temperature is limited or excluded.

The substrate of the panel can be constructed in various possible ways. A number of options are listed below without being exhaustive.

According to a first possibility, the panel comprises at least two such layers based on thermoplastic material. These layers can be directly on top of each other, or be separated by one or more intermediate layers, such as a glass fiber cloth or glass fiber fleece. According to this first possibility, the thickness of the panel is preferably 40 percent or more, or even half or more, formed by these layers. In other words, the substrate of the panel, that is to say the layers located below the decor, can be mainly formed by such layers with thermoplastic material and individual fibers. It is self-evident that in this way the degree of expansion or shrinkage with temperature variations can be effectively reduced.

According to a second possibility, the panel comprises only one such layer based on thermoplastic material and fibers. Such a layer is preferably at least in the middle of the thickness of the panel and / or the substrate. The layer in question preferably constitutes at least 10 percent, and more preferably at least 50 percent, of the thickness of the panel and / or the substrate. The remaining part of the thickness of the substrate can then be formed by layers of thermoplastic material, which then do not necessarily comprise fibers and / or by one or more glass fiber cloths or glass fiber webs. It is not excluded that the layer in question forms more than 80 percent or even the entire substrate.

The substrate preferably has a thickness of 1.3 to 10 millimeters. The entire floor panel preferably has a thickness between 2 and 6 millimeters. The substrate preferably forms at least half the thickness of the floor panel.

A back layer or bottom layer, preferably a vapor-tight layer, may be provided on the underside of the substrate. Such a back layer or bottom layer preferably consists of a thermoplastic plastic layer. The counter layer preferably has a thickness that corresponds to the thickness of the top layer, including any back layer, but is preferably made thinner. The counter layer preferably functions as a balancing layer, such that a balanced sandwich structure can be obtained, namely without or with only minimal plating of the panels.

Preferably, the aforementioned thermoplastic material of the layer comprising the individual fibers according to the invention, furthermore comprises fillers, such as limestone.

A lacquer layer can be used as the top layer of the panel. This can be a UV or an electron beam curing lacquer layer or a PU lacquer layer.

The invention is preferably applied to floor panels which are provided on the relevant edges with mechanical coupling means that allow two of such floor panels to be coupled to each other such that a locking is obtained both in a vertical direction perpendicular to the plane of the coupled panels, and in a horizontal direction perpendicular to the coupled edge and in the plane of the panels. The coupling means preferably have one or a combination of two or more of the following properties: the property that the mechanical coupling means or coupling parts are essentially designed as a tooth and a groove bounded by an upper lip and a lower lip, said tongue and groove mainly are responsible for the locking in the said vertical direction, and wherein the tongue and the groove are provided with additional locking parts, mainly responsible for the locking in the said horizontal direction. The locking parts preferably comprise a protrusion on the underside of the tooth and a recess in the lower groove lip. Such coupling means and locking parts are known, for example, from WO 97/47834; the property that the mechanical coupling means or coupling parts press the coupled floor panels against each other, for example in that these mechanical coupling means are designed with so-called pre-stress, as is known per se from EP 1 026 341. The tension force with which the floor panels touch each other or towards each other pressed, for example, in combination with the above characteristic, can be obtained by means of a lower lip bent in coupled position which presses against the underside of the tooth in an attempt to spring back; - the property that the mechanical coupling means allow coupling on the basis of a horizontal, or almost horizontal, sliding movement of the panels towards each other; the property that the mechanical coupling means allow a coupling on the basis of a turning movement W along the relevant edges; the property that the mechanical coupling means permit a coupling on the basis of a downwardly directed movement of a male coupling part, for example with a tooth, into a female coupling part, for example with a groove. With this type of panels there is a high risk of the connection coming loose when the panels are expanded or swung up, since in such a case the locking in the vertical direction can be weak; - the property that the mechanical coupling means, or at least the associated upper edge, is realized on the basis of a milling operation with rotary milling.

Preferably, said coupling means are mainly implemented in said substrate, more particularly at least in the layer which according to the invention comprises the loose fibers. Preferably said coupling means are provided on the basis of a milling operation with rotating milling tools. The floor panel of the invention preferably relates to a rectangular, either elongated or square, panel which is provided with mechanical coupling means on both pairs of opposite edges.

Panels provided with coupling means preferably have a thickness of at least 2.5, more preferably at least 3 millimeters.

It is not excluded that the invention is applied to panels which are free of coupling means at their edges, wherein these panels are then intended to be glued with their underside against the substrate. Such panels preferably have a thickness of less than 4 millimeters, but preferably of more than 1.5 millimeters.

The panels of the invention preferably have a width of 8 centimeters or more. Particularly preferred dimensions are a width between 14 and 22 centimeters and a length between 118 and 220 centimeters. It is clear that this concerns panel-shaped elements and therefore not room-wide floor coverings. However, the panel-shaped elements do not necessarily have to be rigid, but can be rolled up. In particular, the invention relates to so-called LVT (luxury vinyl tile) in plank format or in tile format.

According to an independent second aspect, the invention further relates to a method that can be used for the manufacture of panels with the characteristics of the first aspect or the preferred embodiments thereof, but which can also be used more broadly. To this end, the invention relates to a method for manufacturing panels, wherein this method comprises at least the step of forming a layer of thermoplastic material, characterized in that the layer formed comprises individual fibers, preferably with a length greater than 1 millimeter.

According to a particularly preferred embodiment, said layer is formed on the basis of a granulate of the aforementioned thermoplastic material. This granulate can for instance be initially scattered or, on the other hand, deposited on a substrate, after which this granulate is consolidated into a thermoplastic layer by means of a, preferably heated, pressing operation. According to the most preferred embodiment, the granulate is deposited, or optionally scattered, on a transport device, and passed between the belts of a continuous pressing device where the consolidation takes place, or at least is at least initiated. According to the present particularly preferred embodiment, a device can be used for this purpose, such as the one known per se from WO 2012/016916.

According to yet another particularly preferred embodiment, said layer is formed on the basis of an extruded thermoplastic material. This may, for example, be material obtained by means of a so-called bambari mixer (Kobe Steel Ltd.), in which granules of the relevant thermoplastic material are kneaded, wherein the kneaded material is extruded into a layer at least between a set of rollers.

Still according to the above two particularly preferred embodiments, said granules preferably comprise at least a portion of the aforementioned individual fibers, preferably glass fibers.

It goes without saying that the layer obtained in the aforementioned step must then be processed with other material, whether or not in layers, to form the final panel. It is also possible that in the first instance plates or sheets are obtained from which several of such panels are obtained by division.

The processing of the relevant layer can generally take place in various ways. According to a first possibility, the layer in question is fused at least on the surface by means of heat and pressure with one or more further thermoplastic layers, such as a printed decorative film and / or a wear layer and / or a further substrate layer. According to a second possibility, the material of one or more further layers, in particular one or more further substrate layers, is applied in liquid form or in paste form by calendering them or, alternatively, applying them to the layer already formed. According to a third possibility, the layer containing the fibers according to the invention is applied to other layers already formed, for example on a glass fiber fleece or on a glass fiber cloth and / or on a further substrate layer already formed.

The method of the invention preferably comprises the step of arranging a glass fiber layer in the relevant layer, preferably a glass fiber fleece or non-woven.

According to a third independent aspect, the present invention further relates to a material that can be used in the method of the second aspect and / or the preferred embodiments thereof. To this end the invention relates to a granulate for forming thermoplastic material, wherein this granulate comprises, in addition to the relevant thermoplastic material, glass fibers, preferably with an average length greater than 1 mm, and more preferably with an average length of 3 millimeters or more.

It goes without saying that the thermoplastic material may furthermore exhibit the compositions cited in the context of the first aspect. The thermoplastic material preferably relates to a starting material for forming semi-rigid or soft PVC.

It is clear that, according to the invention, by "substrate" is meant an internal layer of the floor panel itself, which may per se be of one or more layers, but wherein the layer or layers in question preferably have a joint thickness that is greater than half the thickness of the entire panel in question and / or wherein the layer or layers in question have a combined weight that is preferably greater than half the weight of the entire panel in question. The contour of the optional coupling parts is preferably mainly or completely embodied in the substrate.

Furthermore, it is clear that "fibers" means elongated particles. Preferably, the length of such fiber is at least one hundred times its average diameter. It is preferably fibers with a circular or substantially circular cross-section.

With the insight to better demonstrate the features of the invention, a few preferred embodiments are described below as an example without any limiting character, with reference to the accompanying drawings, in which: Figure 1 shows a panel with the features of the invention; figure 2 represents a cross-section on a larger scale along the line II-II in figure 1; figure 3 schematically shows a few steps in a method with the features of the second aspect.

Figure 1 shows a rectangular and elongated floor panel 1 with a pair of long sides 2-3 and a pair of short sides 4-5.

Figure 2 shows that the relevant floor panel 1 is made up of different layers 6-7-8-9-10.

The substrate 11 is formed by a layer 9 of thermoplastic material, in this case soft PVC, which comprises individual fibers, such as glass fibers. The respective substrate layer 9 further comprises an embedded glass fiber fleece 12. Above the relevant layer 9 a top layer 13 is provided, which in itself comprises a printed decorative film 7 and a transparent wear layer 6 based on thermoplastic material. The top layer 13 furthermore comprises a back layer 8 located under the decorative film 7. In the example, both the back layer 8, the decorative film 7 and the wear layer 6 are made on the basis of polyvinyl chloride.

In the example, the decorative foil 7 is provided with a print with a wood pattern 14, wherein for each panel 1 the image is each provided with a single wooden board.

On the underside 15 of the substrate 11 a counter layer 10, also based on soft PVC, is applied.

Figure 2 shows that the layer 9 comprising the fibers is present at least in the middle of the thickness T of the substrate 11. In this case the relevant layer 9 forms the entire substrate 11.

Figure 2 furthermore shows that the respective layer 9 comprising the individual fibers makes up at least 40 percent, and here even more than half the thickness T1 of the panel 1.

The panel 1 of the example is further provided on both opposite edges 2-3 with mechanical coupling means or coupling parts 16. Figure 2 shows that at least the mechanical coupling means 16 on the long pair of sides 2-3 allow two of such floor panels 1 to be connected to each other be coupled such that a locking is obtained both in a vertical direction V1 perpendicular to the plane of the coupled panels 1, and in a horizontal direction H1 perpendicular to the coupled edges 2-3 and in the plane of the panels 1. The illustrated coupling means 16 have the property that they are essentially designed as a tooth 17 and a groove 18 bounded by an upper lip 19 and a lower lip 20, said tooth 17 and groove 18 being primarily responsible for locking in the aforementioned vertical direction VI, and wherein the tooth 17 and the groove 18 of additional locking members 21-22, primarily responsible for locking in said horizontal direction H1. In this case the locking parts comprise a protrusion 21 on the underside of the tooth 17 and a recess 22 in the lower lip 20 cooperating therewith.

The coupling means 16 shown here permit at least one coupling on the basis of a turning movement W along the relevant edges 2-3.

The mechanical coupling means 16 are mainly made in the layer 9, which according to the invention comprises the individual fibers. In the example, they are provided on the basis of a milling operation, for example with rotating tools.

Figure 3 shows some steps from a method for manufacturing the panel from figures 1 and 2. More in particular, the step of forming the layer 9 with thermoplastic material which, according to the invention, comprises the individual fibers is shown. .

In the example of Figure 3, the relevant layer 9 is formed on the basis of a granulate 23 of the relevant thermoplastic material. This is a granulate 23 with the characteristics of the third aspect, wherein the granules also comprise glass fibers.

Figure 3 shows that the granulate 23 is initially deposited on a conveyor device 25 on the basis of a spreading device 24, whereafter it is consolidated between the belts 26 of a continuous pressing device 27. The granulate 23 is herein passed past one or more heating devices 28, and it can optionally be cooled down again after the pressing operation or at the end of the pressing operation. Cooling ensures that the pressed plates, sheets or layers can be handled relatively quickly for further processing.

Figure 3 furthermore shows that simultaneously with the pressing, a further layer, in this case the glass fiber layer 12, can be applied or introduced by imparting this in the pressing operation on or between the granulate 23. For example, it may be a glass fiber layer 12 or a backing layer 8, a decorative film 7 or a wear layer 6. It may also be an assembly of layers that are already laminated together, such as a top layer 3 that is already fully or partially composed, which for example comprises at least one decorative film 7 and a wear layer 6, or at least one backing layer 8 and a decorative film 7, or both the backing layer 8, decorative film 7 and the wear layer 6. Any superficial lacquer layer is preferably applied after the pressing operation. This is not shown here.

The present invention is by no means limited to the embodiments described above, but such panels, methods and granules can be realized according to different variants without departing from the scope of the present invention. Moreover, instead of being floor panels, the panels can also be designed as wall panels or ceiling panels or even as furniture panels.

Claims (13)

A panel for forming a floor covering, said panel (1) comprising at least one layer (9) of thermoplastic material, characterized in that said layer (9) still comprises at least individual fibers with a length greater than 1 millimeter. Panel according to claim 1, characterized in that said panel (1) above said layer (9) further comprises at least one printed decor and a transparent or transparent wear layer (6). Panel according to claim 1 or 2, characterized in that the aforementioned layer (9) further comprises at least one glass fiber cloth or glass fiber fleece (12). Panel according to one of the preceding claims, characterized in that this panel comprises at least two such layers (9) based on thermoplastic material. Panel according to one of the preceding claims, characterized in that the aforementioned thermoplastic material is soft polyvinyl chloride. Panel according to one of the preceding claims, characterized in that the aforementioned thermoplastic material further comprises fillers. Panel according to one of the preceding claims, characterized in that the aforementioned individual fibers are glass fibers. Panel according to one of the preceding claims, characterized in that the aforementioned individual fibers have an average length of more than 3 mm. 9. Method for manufacturing panels, wherein this method comprises at least the step of forming a layer (9) of thermoplastic material, characterized in that the formed layer (9) comprises individual fibers with a length greater than 1 mm. The method according to claim 9, characterized in that said layer (9) is formed on the basis of a granulate (23) of said thermoplastic material. The method according to claim 10, characterized in that said granules (23) comprise at least a portion of said individual glass fibers. Method according to claim 9, characterized in that said layer (9) is formed on the basis of an extruded thermoplastic material. A granulate for forming thermoplastic material, wherein this granulate (23) comprises, in addition to the relevant thermoplastic material, also glass fibers with a length greater than 1 mm.