GENERATION OF A PU-RUBBER-POWDER FLOOR PANEL USING A THERMO-SELECTIVE CATALYST

Abstract

The invention relates to a method of producing a polyurethane floor panel, the method comprising mixing rubber powder, a polyol, an isocyanate component and a thermo-selective catalyst for creating a liquid two-component polyurethane reaction mixture, the thermo-selective catalyst being adapted to trigger the reaction of the polyols and the isocyanate into polyurethane selectively in case the temperature of the reaction mixture exceeds an activation temperature of the thermo-selective catalyst stirring the reaction mixture for at least 15 minutes filling the stirred liquid reaction mixture into a mold applying pressure under a temperature that exceeds the activation temperature on the mold and removing the hardened polyurethane floor panel from the mold.

Claims

1. A method of producing a polyurethane floor panel, the method comprising: mixing rubber powder, a polyol component, an isocyanate component and a thermo-selective catalyst for creating a liquid two-component polyurethane reaction mixture, the thermo-selective catalyst being adapted to trigger the reaction of the polyols and the isocyanate into polyurethane selectively in case the temperature of the reaction mixture exceeds an activation temperature of the thermo-selective catalyst; stirring the reaction mixture for at least 15 minutes, preferably for at least 30 minutes; filling the stirred liquid reaction mixture into a mold having the shape of the floor panel; applying pressure under a temperature that exceeds the activation temperature on the mold for letting the polyol and the isocyanate react within the mold into a solid polyurethane matrix, the matrix embedding the rubber powder particles and forming the polyurethane floor panel; and removing the hardened polyurethane floor panel from the mold.

2. The method of claim 1, the thermo-selective catalyst being an organic amine.

3. The method of claim 2, the organic amine being 1,8-diazabicyclo[5.4.0]undec-7-ene.

4. The method of claim 1, the reaction mixture comprising a curing catalyst, the curing catalyst being adapted to boost the curing of the polyurethane into the hardened polyurethane floor panel.

5. The method of claim 4, the curing catalyst being an organotin compound.

6. The method of claim 5, the organotin compound being a dioctyltin mercaptide catalyst.

7. The method of claim 1, the reaction mixture comprising the thermo-selective catalyst in an amount of 0.03-0.05% by weight of the reaction mixture; and/or the reaction mixture comprising the curing catalyst in an amount of 0.0020-0.0030% by weight of the reaction mixture.

8. The method of claim 1, the mixing further comprising: adding a zeolite to the polyol component and/or to the rubber powder for creating the liquid two-component polyurethane reaction mixture.

9. The method of claim 1, the reaction mixture being free of water.

10. The method of claim 1 used for generating a polyurethane floor panel having one or more of the following properties: bubble free; anti-slip surface with depressions and/or elevations; easily removable from the mold.

11. The method of claim 1, the reaction mixture comprising the rubber powder in an amount of 55-85%, preferably 65%-75% by weight of the reaction mixture; and/or the reaction mixture comprising the polyol component and the isocyanate component combined in an amount of 15-45%, preferably 25%-35% by weight of the reaction mixture.

12. The method of claim 1, the reaction mixture having an NCO/OH ratio in a range of 1.05 to 1.25, preferably 1.15 to 1.2.

13. The method of claim 1, the temperature exceeding the activation temperature being a temperature above 75° C., in particular above 80° C.

14. The method of claim 1, the pressure being in the range of 50-70 kg/cm.sup.2, in particular 55-65 kg/cm.sup.2.

15. The method of claim 1, the mold having dimensions adapted to form a polyurethane floor panel being 1 mm-6 mm, preferably 2-4 mm thick.

16. The method of claim 1, the mold comprising elevations and/or depressions for generating depressions and/or elevations on the surface of the polyurethane floor panel formed in the mold.

17. The method claim 1, the polyol component comprising polyethylene glycol with a molecular weight of 4.000-6.000 g/mol; and/or the isocyanate component comprising polyphenyl-methan-polyisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), and o-(p-isocyanatobenzyl)phenyl-isocyanat.

18. The method claim 1, wherein at least the polyol component, the isocyanate component and the thermo-selective catalyst are mixed with each other in a single step before the stirring is started.

19. The method of claim 1, wherein the solid PU matrix is a non-foamed, bubble-free PU mass.

20. A polyurethane floor panel comprising a solid polyurethane matrix, wherein rubber powder particles are homogeneously embedded in the matrix, the floor panel comprising a thermo-selective catalyst, the thermo-selective catalyst being adapted to trigger the reaction of polyols and isocyanates into polyurethane selectively in case the temperature of the reaction mixture exceeds an activation temperature of the thermo-selective catalyst.

21. The polyurethane floor panel of claim 20 being bubble-free and/or comprising elevations and/or depressions on at least one of its surfaces adapted to provide an anti-slip effect.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

[0057] FIG. 1 is a flowchart of a method of producing a floor panel according to an embodiment of the invention,

[0058] FIG. 2 is a cross-sectional view of a reaction mixture within a mold,

[0059] FIG. 3 depicts a one-step process of generating a 2K reaction mixture that already comprises the thermo-selective catalyst, and

[0060] FIG. 4 shows a floor panel with anti-slip elevations.

DETAILED DESCRIPTION

[0061] FIG. 1 is a flowchart of a method of producing a floor panel according to an embodiment of the invention.

[0062] In a first step 102, at least the following components are mixed: rubber powder 308, a polyol component 302, an isocyanate component 304, and a thermo-selective catalyst 306.

[0063] For example, the rubber powder can be produced from rubber scraps obtained from used tires from motor vehicles and trucks. The scraps are granulated and then cryogenically milled into rubber powder. This may have the advantage of reusing rather than disposing resources. This approach represents an effective and inexpensive way of recycling discarded tires. The obtained rubber powder particles have good mechanical properties, in particular low specific weight, thermal and acoustic isolation properties, elasticity, compressive strength and good energy absorption capacity. The rubber powder completely consists of or comprises a significant proportion (e.g. at least 40%) of particles of a size of less than 100 μm. The rubber powder particle size distribution can range e.g. from 0.1 μm to 180 μm.

[0064] The polyol component can comprise polyethylene glycol (PEG) with a molecular weight of 4.000-6.000 g/mol.

[0065] According to one embodiment, the polyol component is a mixture of a diol and a triol. The diol is preferably a difunctional (preferably highly reactive) polyether polyol, which contains primary hydroxyl groups. It contains an antioxidant which is free from BHT (2,6-Di-t-butyl-hydroxytoluene). Typical properties: OH Number of about 29 mg KOH/g, a viscosity at 25° C. of about 778 mPa/s, a water content of about 0.05%, and a density at 25° C. of about 1.02 g/cm.sup.3 DIN 51 757.

[0066] The triol is preferably a trifunctional (preferably highly reactive) polyether polyol which contains primary hydroxyl groups. It is preferably free from BHT. Typical properties: OH Number of about 28 mg KOH/g, viscosity at 25° C. of about 100 mPa/s, water content of about 0.04%, and density at 25° C. of about 1.02 g/cm.sup.3.

[0067] The isocyanate component can comprise a mixture of polyphenyl-mehtan-polyisocyanate, 4,4′MDI and o-(p-isocyanatobenzyl)phenyl-isocyanate. For instance, the isocyanate component can have a molar mass of about 250 g/mol, an NCO-content of 33.5 g/100 g, an 4,4′-MDI isomer content of 48 g/100 g and a viscosity at 25° C. of about 12 mPa and a density at 25° C. of about 1.19 g/cm.sup.3.

[0068] Using the above described polyol component and isocyanate component may have the advantage that both components are poorly reactive compared to other polyols and isocyanates used for producing polyurethane. Thus, the time during which the reaction mixture can be thoroughly mixed may be increased.

[0069] The thermo-selective catalyst, e.g. 1,8-diazabicyclo[5.4.0]undec-7-ene, does not trigger the reaction of the polyols and the isocyanates into polyurethane at room temperature. Therefore, the mixture generated in step 102 can be thoroughly mixed and stirred in step 104 at room temperature for a long time period, e.g. more than 15 minutes, more than 30 minutes or even 60 minutes to ensure a homogeneous distribution of all components of the reaction mixture. However, if the reaction mixture is heated about the activation temperature of the thermo-selective catalyst, e.g. is heated to 80° C., the thermo-selective catalyst will trigger the reaction of the polyol component and the isocyanate component into a polyurethane matrix. The reaction mixture generated in step 102 corresponds to a so called “2K” reaction mixture.

[0070] A “2K” PU reaction mixture is APU reaction mixture that will not react and harden into PU unless it is mixed with a catalyst (or unless an already present but an active catalyst is activated). The use of a 2K reaction mixture may in addition have the advantage that the polyurethane panels produced from such a mixture is less susceptible to damage from chemicals, whether or UV rays compared to floor panels produced from a “1K” PU reaction mixture. A “1K” PU reaction mixture can be described as a “single-component” reaction mixture that does not require a particular catalyst as the moisture already contained in the 1K reaction mixture or the environment there it is applied is typically sufficient for causing the one K reaction mixture to harden into polyurethane.

[0071] A “catalyst” as used herein is a substance that causes or accelerates a chemical reaction without itself being affected. A curing catalyst as used herein is a catalyst capable of curing the reaction of the polyol component with the isocyanate component into PU and of completely hardening the generated PU mass. The curing catalyst is capable of catalyzing the PU generation reaction also at a late stage of the reaction at which the generated PU polymers are of high molecular mass.

[0072] After the 2K PU reaction mixture was thoroughly stirred for at least 30 minutes in step 104, the stirred liquid reaction mixture is filled in step 106 into a mold 202 (see e.g. FIGS. 2 and 3). The mold may have the shape of a rectangle or square or any other form. Depending on the type of floor panel to be produced, the sides of the mold forming the rectangle square can be several centimeters and even more than 40 cm long. The mold can be dimensioned such that the height of the floor panel is in the range of 0.5-3 cm. However, preferably, the mold is dimensioned such that the height of the floor panel is smaller than 7 mm.

[0073] In some embodiments, the mold is already heated to a temperature that is close to or above the activation temperature of the thermo-selective catalyst. In preferred embodiments, the temperature of the mold is still below the activation temperature of the thermo-selective catalyst when the liquid reaction mixture is filled into the mold to ensure that the polymerization reaction to form the polyurethane is not prematurely triggered. The liquid reaction mixture is allowed to fill the mold and any depressions formed by the mold, if any, completely. Then, the mold is closed and heated about the activation temperature of the thermo-selective catalyst. In addition, pressure is applied on the mold in step 108. Preferably, the pressure is applied for at least 3 minutes, more preferably for at least 5 minutes. A typical time period for applying the pressure is in the range of 5-10 minutes. The pressure ensures that the liquid 2K PU mixture penetrates also smaller depressions and cavities defined by the mold and in addition compacts the rubber powder particles to a defined degree in order to produce floor panels with a defined elasticity.

[0074] After a time period sufficient for a complete polymerization of the adults and to complete hardening of the PU floor panel, the hardened floor panel is removed in step 110 from the mold. Typically, the PU polymerization reaction and the complete hardening takes about 10 to 30 minutes, depending on the particular composition of the reaction mixture and the dimensions of the mold.

[0075] FIG. 2 is a cross-sectional view of a reaction mixture within a mold 202. FIG. 2 is only a schematic drawing: typically, the rubber powder particles 204 which are embedded in a cellular PU matrix 206 constitute about 70% by weight of the 2K PU reaction mixture 208 that is filled into the mold. FIG. 2 shows a cross-section of a region of a closed mold comprising an upper side and the lower side. The two sides of the mold are mechanically fixed to each other such that a leaking of the liquid reaction mixture 208 is prevented. After the complete hardening of the reaction mixture 208, the mold is opened and the hardened floor panel is removed.

[0076] FIG. 3 depicts a one-step process 300 of generating a 2K reaction mixture 208. The reaction mixture does not only comprise a polyol component 302, an isocyanate component 304 and the rubber powder particles 308, but also comprises a thermo-selective catalyst 306. In addition, the reaction mixture may comprise one or more additional substances such as a zeolite 316 for removing any residual water from the reaction mixture or a curing catalyst 314 adapted to harden the polyurethane matrix at the end of the polymerization reaction between the polyol and the isocyanate component. The generation of the reaction mixture and the mixing of the substances contained therein can be directly performed in a container that comprises means, e.g. a stirrer, for homogeneously mixing all components of the reaction mixture. After a homogeneous 2K PU reaction mixture is generated, the mixture is drained through an outlet of the container and transfer it into one or more floor panel molds 202. At the bottom of FIG. 3A, a cross-sectional view of a closed floor panel mold comprising a hardened PU mass with embedded rubber particles 318 is shown. The floor panel may have a width of 400 mm and a height of 3 mm. The above described approach for generating PU-based floor panels comprising a PU matrix with embedded rubber powder particles may ensure that the floor panel mass 318 is free of bubbles, mechanically stable and shows homogeneous physicochemical properties. FIG. 3B shows the hardened floor panel having been removed from the mold without any damages to its surface.

[0077] Floor panels produced according to embodiments of the invention may be used for many different kinds of outdoor sports grounds and indoor sports halls in need of pavement with defined qualities depending on the type of sports or other form of activities that will be practiced. Sports floor surfaces should be soft enough for the various sports to protect the players from injuries and should have less running costs.

[0078] In a test series, various combinations of physicochemical parameters were tested. Some of these combinations resulted in the production of bubble free, dimensionally stable floor panels. The following parameter combination was observed to provide a floor plate having particularly desirable properties (bubble free, dimensionally stable):

TABLE-US-00001 Polyol Catalyst Time of Rubber Component Isocyanate Mixture Stirring applying Mould Powder (4600 PEG) Component [%] by duration pressure temperature [g] [g] [g] weight [min] [min] [° C.] 1130 370 130 2% 30 6 90

[0079] The catalyst mixture was added to an amount of 2% by weight to the reaction mixture. The catalyst mixture comprised the thermo-selective catalyst in an amount of 3% by weight of the catalyst mixture and the curing catalyst in an amount of 2% by weight of the catalyst mixture, so the overall amount of the catalysts in the reaction mixture was low. At first, the polyol component, the isocyanate component and the catalyst mixture was homogeneously mixed. Then, this mixture was mixed with the rubber powder until all components of the mixture were homogeneously distributed. The resulting mixture was put into a mold at 90° C. and pressure was applied on the mold. The reaction mixture was kept in the mold under pressure and 90° C. for 10 minutes and then the resulting floor panel was removed.

[0080] FIG. 4 shows a floor panel with several elevations 402 on the upper surface of the floor panel. Those elevated structures are beneficial in several use case scenarios as they may provide an anti-slip effect. Embodiments of the invention may allow generating floor panels with a complex 3D surface structure. The 3D surface structure may have a structure chosen in order to achieve a desired design effect, e.g. a particular way of reflecting or scattering light, or may have a 3D structure chosen in order to achieve a desired physical effect, e.g. providing an anti-slip surface.

LIST OF REFERENCE NUMERALS

[0081] 102-110 steps [0082] 200 cross-section of composite PU reaction mixture within mold [0083] 202 upper and lower side of the mold [0084] 204 rubber powder particles [0085] 206 polyurethane matrix [0086] 208 polyurethane/rubber powder reaction mixture [0087] 300 process of manufacturing a floor panel [0088] 302 first component [0089] 304 second component [0090] 306 thermo-selective catalyst [0091] 308 rubber powder [0092] 314 curing catalyst [0093] 316 zeolite [0094] 318 hardened floor panel within mold [0095] 320 floor panel removed from mold [0096] 402 anti-slip elevation on the upper surface of a PU floor panel 320