Patent Publication Number: US-2013247492-A1

Title: Floor panel and method for manufacturing floor panels

Description:
This invention relates to floor panels and to a method for manufacturing such floor panels. 
     From DE 10 2006 030 852 A1 floor panels are known, which, on their bottom side, are provided with factory-applied glue strips. By means of these glue strips, a gluing of the panels on an underlying surface can be obtained. The use of glue strips may lead to undesired footfall sound when using a floor covering composed of such floor panels. 
     The present invention aims at an optimum realization of floor panels which are provided with glue at the factory. To this aim, the invention relates to a floor panel having the characteristic that this floor panel on its bottom side is provided with a factory-applied glue, said glue substantially consisting of synthetic rubber. 
     The inventors have found that such glue can have interesting features. It can show a high resistance against peeling off (English: peel strength) at room temperature. When installing the floor panels, it can allow a rearrangement of the installed panel for a certain period of time. This type of glues is strongly resistant against ageing, which is of interest when the panels have to remain in their package for a long time, and of course when the panels are intended for a floor covering which must remain installed for a long time. Ageing of this type of glues is also limited when they are exposed to a warm and humid climate. This latter is of interest when transporting the panels, for example, in containers, and also for installation in tropical countries. Moreover, such glue remains stable under the influence of water. 
     Preferably, said glue substantially consists of butyl rubber. Preferably, the glue relates to an isobutylene isoprene rubber (IIR) or a polyisobutylene rubber. 
     Preferably, glue is applied having a density, as measured according to DIN EN ISO 2811-1, of more than 1 gram per milliliter, or still better of 1.5 grams per milliliter or more. It is noted that densities between 1 and 1.2 or 1.3 grams per milliliter are very interesting for applying such glues in an industrial manner, as they can easily be applied via roller applications and can be pumped. 
     Preferably, the glue has a softening point (English: softening point), as measured according to DIN EN 1238, of higher than 80° C. or still better of higher than 120° C. 
     For the present invention, for example, the glues Prestik® 3321 of Bostik and Terostat-6813 of Henkel can be applied. 
     Preferably, said glue is covered at the factory by means of a foil, such as a paper sheet or a synthetic material foil. 
     Preferably, said glue forms a layer on the back side of the respective panel. This means that the thickness of the glue layer is at least 5 times smaller than the width of the glue layer. Preferably, the glue layer covers at least 50% of the surface of the bottom side of the floor panel and still better at least 85% thereof, or essentially the entire bottom side of the floor panel. 
     Preferably, said glue has a maximum thickness of 1 millimeter or less in a condition in which the floor panel is not yet installed, for example, in the package. In this manner, a pre-glued floor panel can be realized in an economic manner; moreover, a thin glue layer leads to a more comfortable application feeling during installation and/or when using a floor covering consisting of a plurality of such floor panels. 
     Preferably, the floor panel of the invention has a thickness of 5 millimeters or less, the glue layer excluded. In the case that the thickness of the floor panel is situated between 3 and 5 millimeters, said floor panel, preferably on at least two opposite edges thereof, for example, on the long edges in the case of elongate floor panels, and possibly on both pairs of opposite edges, comprises profiles allowing an alignment of the edges of two such floor panels in mutual respect. Herein, this may relate to an alignment in the direction perpendicular to the plane of the floor panels, wherein thus possible height differences between adjoining edges of adjacent floor panels can be kept under control, and/or to achieving an alignment in the direction perpendicular to the adjoining edges of adjacent floor panels and in the plane of the floor panels, wherein thus possible gaps between the adjoining edges of adjacent floor panels can be kept under control. It is not excluded that floor panels of lesser or greater thickness also show such profiles on one or both pairs of opposite edges. In the case that the floor panel has a thickness of less than 3 millimeters, it is preferably made without such profiles, or, in other words, it comprises substantially vertical walls. In this last case, possibly in fact use can be made of a clearance angle underneath the surface of the panels, wherein the edge, in other words, in the direction of the floor panel itself, deviates from the vertical. Preferably, this deviation is 30° or less, 
     Preferably, the floor panel of the invention substantially consists of synthetic material, either thermo-hardening synthetic material or thermoplastic synthetic material. In the case of thermo-hardening synthetic material, this can be chosen from the list consisting of melamine, melamine formaldehyde, urea formaldehyde, phenol formaldehyde and combinations of those. For example, the respective floor panel can substantially consist of so-called compact laminate. Herein, this relates to a floor panel wherein at least the core thereof is composed of paper sheets provided with thermo-hardening synthetic material, which are consolidated, for example, by means of a press treatment. In the case of thermoplastic synthetic material, it can be chosen from the list consisting of polyvinyl chloride, polyurethane, polypropylene, polyethylene and combinations of those. For example, the respective floor panel may consist substantially of soft polyvinyl chloride, which usually also comprises more than 10 percent by weight of plasticizer. 
     Preferably, the floor panel of the invention is made waterproof, or the floor panel shows a possible edge swelling, as measured according to EN 13329, of less than 12 percent or even of 5 percent or less. 
     The invention further also relates to a method which is highly suitable for manufacturing the floor panels of the invention. To this aim, the present invention also relates to a method for manufacturing floor panels, with the characteristic that said glue is applied by means of a roller device. As already explained, the glues applied within the scope of the invention are highly suitable for being pumped and for being applied by means of a roller device. These methods are very convenient within the frame of a continuous production process. Preferably, the method further also comprises the step wherein the glue is pumped from a reservoir. Preferably, the glue is provided in liquid condition on the bottom side of the floor panel in a continuous manner by means of said roller device. 
    
    
     
       With the intention of better showing the characteristics of the invention, hereafter, as an example without any limitative character, some preferred embodiments are described, with reference to the accompanying drawings, wherein: 
         FIG. 1  schematically and in perspective represents a panel having the characteristics of the invention; 
         FIG. 2 , at a larger scale, represents a cross-section according to the line II-II indicated in  FIG. 1 ; 
         FIG. 3 , in a view on the area indicated by F3in  FIG. 2 , represents a variant; and 
         FIG. 4  in cross-section represents adjoining edges of adjacent panels, for a variant. 
     
    
    
       FIG. 1  schematically represents a floor panel  1  in accordance with the present invention. In this case, this relates to a rectangular and oblong panel  1  with a first pair of opposite edges  2 - 3 , namely the long edges, and a second pair of opposite edges  4 - 5 , namely the short edges. Both pairs of edges  2 - 3 ,  4 - 5  comprise profiles  6 , which allow an alignment between adjoining edges of floor panels which are adjacent in a floor covering. 
       FIG. 2  clearly shows that the profiles  6  on the long edges  2 - 3  form a first alignment system, resulting in an alignment in the plane of the floor panels and perpendicular to the respective edges  2 - 3 , namely an alignment in the horizontal direction R 2 , and form a second alignment system, resulting in an alignment perpendicular to the plane of the floor panels, namely an alignment in the vertical direction R 1 . The profiles  6  illustrated here are substantially formed as a tongue  7  and groove  8  connection, which provide for said alignment in vertical direction R 1 , wherein the tongue  7 , at least one of the groove lips  9 - 10 , respectively, in this case the lowermost groove lip  9  only, is provided with additional alignment elements  11 - 12 , which provide for said alignment in said horizontal direction R 2 . The respective alignment elements  11 - 12  are formed by a recess on the underside of the tongue  7 , which cooperates with a protruding part on the upper surface of the lowermost groove lip  9 . 
     The profiles  6  are of the type which allows coupling two of such panels or floor panels  1  to each other by bringing these profiles  6 , at user&#39;s option, into each other by means of a turning movement W around the respective edge, or by a horizontal shifting movement S towards each other. In this case, the profiles  6  are realized entirely in the core material  13 . 
       FIG. 2  further illustrates that the core material  13  in the panel  1  of the example is at least composed of a plurality of paper sheets  14 , which are provided with thermo-hardening synthetic material  15 . 
     The panel  1  of  FIG. 2  further comprises a print  16 , a wear-resistant layer  17  and a backing layer  18  or balancing layer. The print  16  is provided on a paper sheet  19 , and its pattern  20  represents a wood motif, more particularly the motif of only a single wooden plank. The wear-resistant layer  17  of the example comprises a paper layer  21 , in this case provided with thermo-hardening synthetic material  15  and possibly hard particles, such as aluminum oxide. The backing layer  18  or balancing layer, too, comprises a paper sheet  22  provided with thermo-hardening synthetic material  15 . 
     The panel  1  illustrated in  FIG. 2  is free from one-piece board materials, such as MDF or HDF (Medium or High Density Fiberboard). 
       FIG. 3  shows an example, wherein the floor panel  1  is provided with a relief  23 . In this case, the panel, at least on one edge  3 , however, preferably on both edges of a pair of opposite edges  2 - 3 , comprises a portion  24  which is impressed for forming a lower edge region, for example, as illustrated here, having the form of a chamfer or bevel. Preferably, such portion  24  is impressed over a depth D of more than 0.5 or more than 1 millimeter in respect to the global surface  25  of the panel  1 . Herein, the two uppermost layers  14 A- 14 B of the panel, at the location of the portion  24 , deviate from the horizontal plane H. The back side  26  of the panel  1  is flat. It is clear that such impressed portions  24  do not necessarily have to be available at the edge  3  of such panel  1 , nor does such portion  24  necessarily have to imitate or form chamfers. Other relief characteristics can be introduced into the surface  25  of the floor panels  1 , such as scraping traces, wood knots, wood pores, wood nerves, stone relief and so on. 
     In accordance with the present invention, the panels  1  of the examples on their bottom side are provided with factory-applied glue  27  on the basis of synthetic rubber, in this case on the basis of butyl rubber. In the examples, the glue  27  respectively forms a layer which essentially covers the entire bottom side of the panel  1 . Moreover, in the examples it is covered or protected by a paper foil  28 . Of course, this foil  28  has to be removed during installation in order to obtain an adherence to the underlying surface by means of the glue  27 . 
       FIG. 4  represents another example, wherein the edges  2 - 3  of the floor panels  1  of the invention are made substantially vertical. In this case, a clearance  29  is provided in that the edges deviate from the vertical towards the inner side of the panels  1 . Hereby, a space is formed underneath the surface  25  of the panels  1 , at the location of the adjoining edges  2 - 3  of the adjacent floor panels  1  This space can offer room for dust or dirt or glue or the like. In such embodiment, no alignment is provided between the adjacent floor panels  1 . 
     Further, it is also noted that for achieving an alignment in vertical direction only, use can be made of a traditional tongue  7  in groove  8  coupling, free from additional alignment elements  11 - 12 , which might have any alignment in horizontal direction, and, reciprocally, that for achieving an alignment in horizontal direction only, use can be made of profiles  6  with hook-shaped elements which engage one behind the other, as known, for example, from DE 200 17 461 U1. Other forms of profiles  6 , such as purely overlapping edges, for example, as known, amongst others, from JP 2001-288880, are not excluded. 
     Although the invention primarily is intended for floor panels  1 , it is also possible that such glue is applied for wall panels or ceiling panels. 
     It is clear that within the scope of the invention, the factory-applied glue is intended for obtaining an adherence to the underlying surface when installing the panels. Preferably, such glue forms the only connection with the underlying surface. This means that no other attachment means, such as nails or the like, are applied. Of course, the panels still can be mutually connected to each other, for example, by means of the also above-mentioned profiles. 
     The present invention is in no way limited to the herein above-described embodiments; on the contrary, such methods and panels can be realized according to various variants, without leaving the scope of the present invention.