LOW-ODOUR DECORATIVE SURFACE COVERING

Field of the Invention

[0001 ] The invention generally relates to finishing work for buildings, in particular to decorative surface coverings (such as e.g. floorings or wallcoverings) exhibiting low odour release before and after installation. The invention more specifically relates to decorative floor or wall coverings comprising a core structure and at least two odour barrier layers. The invention is also related to a method for the production of such decorative surface coverings.

Background of the Invention

[0002] Decorative surface coverings are employed in residential, commercial and institutional applications where decorative effects, durability and ease of installation and maintenance are important considerations.

[0003] In order to improve properties like walking comfort as well as acoustical and thermal insulation, it is known to produce floor coverings including a base structure made of a thermoplastic material associated on its reverse face to a backing, for example a foam backing or a textile backing.

[0004] US 7,923,387 discloses a floor covering having a double rollable reinforcement, of the type comprising on the front a calendered sheet of predefined thickness, a first reinforcement, a layer of foam and a second reinforcement, made from polyester material comprising a grid and a non-woven layer on the back.

[0005] WO 03/100161 relates to a flooring comprising a base support, the visible surface of which consists of a surface covering providing decoration and wear resistance and the back surface of the base support consists of a textile web. The link between the textile web and the back surface of the support is made of a discontinuous primer ensuring their adherence with limited penetration into the thickness of the textile web so as to allow the textile web fibers to slide mutually in the folding zones of the flooring.

[0006] The decorative surface coverings may be designed to imitate other materials such as ceramic tile, wood, stone and brick, linen textiles, cork and the like, or they can be designed with unique combinations of color, particles and other decorative features which are not available in other types of surface coverings. Also, surface coverings with textural features, e.g., features that realistically mimic the textures of the imitated materials have been on the market for a long time.

[0007] However, an oftentimes neglected but critical parameter for a successful imitation is odour. For successful imitation, surface coverings are required to have low odour despite the presence of a PVC core layer, whether this is before installation, during installation or after installation on the floor.

[0008] In the prior art, several techniques for odour control can be found. For instance, one can add to a product a substance having an odour more pleasant or intense than the odour to mask, or add a substance specifically dedicated to neutralize the compound or class of compounds generating the unpleasant odour. However, these methods have many disadvantages such as limited durability, difficulty of mechanism identification and so on.

[0009] It is also known in the prior art to provide decorative surface coverings exhibiting a low volatile organic compound (VOC) release thanks to a top layer acting as barrier layer, to meet health and environmental requirements. However, low VOC and low odour are properties which are not necessarily directly correlated to each other.

[0010] WO2015/158596 relates to decorative surface coverings, in particular, floor or wall coverings, exhibiting low volatile organic compounds (VOC) emission, comprising one or more adjacent plasticized polyvinyl chloride layers and a polyurethane top-layer, said top-layer being obtained from radiation curing a 100% solids polyurethane formulation.

[0011 ] WO2015/158595 relates to decorative surface coverings, in particular floor or wall coverings, exhibiting low VOC emission, comprising one or more adjacent plasticized polyvinyl chloride layers and a polyurethane top-layer, said top-layer being obtained from the actinic irradiation of an aqueous ethylenically unsaturated polyurethane dispersion after evaporation of the water part.

[0012] However, as described in Revah S., Morgan-Sagastume J.M. (2005) Methods of Odor and VOC Control, in: Shareefdeen Z., Singh A. (eds) Biotechnology for Odor and Air Pollution Control. Springer, Berlin, Heidelberg, the odor is defined as a stimulus of olfactory cells in the presence of specific compounds including VOCs and VICs.

[0013] Consequently, having a product exhibiting a low-level of VOC does not guarantee that the product exhibits a low level of odour.

[0014] Thus, there is a need for decorative surface coverings, in particular floorcoverings or wallcoverings, exhibiting low odour.

Summary of the Invention

[0015] A first aspect of the invention pertains to a decorative surface covering, e.g., a decorative floor covering or a decorative wall covering. The decorative surface covering comprises a core structure comprising one or more thermoset or thermoplastic layers, a first odour barrier layer on the top of the core structure and a second odour barrier layer on the back of the core structure. The odour barrier layers are selected in such a way that, in a sample of the decorative surface covering having size A4 according to ISO standard 216 (corresponding to a surface of 623.7 cm ² and an aspect ratio of 1.414:1 ) and having 95% (±1 %) of the sample edges sealed in a gas-tight fashion, diffusion of odorants across the sample into a Nalophan® bag filled with a volume of 40 litres of N2 at 21 °C during 24 hours leads to an odour concentration of not more than 100 OllE/m ³ , i.e. 100 European odour units as defined in European standard EN 13725:2003. To carry out the test, 95(±1 )% of the sample edges (side surfaces) are sealed in such a way that no (or only a negligible part of the) odorants can reach the gas volume otherwise than by diffusion across the first and second odour barrier layers or through the exposed (unsealed) 5(±1 )% of the sample edges. The sealing could be effected by application of a gas-tight cover, e.g. aluminum foil or the like. Only 95% (±1 %) of the sample edges are sealed for the purpose of testing in order to take into account that in a realistic use case, the edges of the surface covering will not be perfectly sealed.

[0016] As will be appreciated, the provision of the first and second odour barrier layers significantly helps to reduce odour. The fact that a first odour barrier layer is present on the top side of the structure significantly reduces the emissions of odorant from the top side of the surface covering. The back side of the decorative surface covering, may have been neglected as a source of odorants in the prior art because it may have been considered to be sealed off by the underfloor or the wall. However, in order to achieve low levels of odorant emission into ambient air from decorative surface coverings even before or during installation of the product on the floor or the wall, e.g. during presentation of samples or removal of the product from packaging, appropriate measures may have to be taken. The fact that a second odour barrier layer is present on the back side of the core structure significantly reduces the emissions of odorant from the back side of the surface covering.

[0017] The qualifier “decorative” is used herein to indicate that the item so characterized remains visible when in use as intended and thus determines the outer appearance of the surface when the surface covering is installed.

[0018] The thermoset or thermoplastic layers could be based, e.g., on polyvinyl chloride (PVC), polypropylene (PP), rubber, or the like. The core structure could comprise a combination of (i) plural thermoset layers, (ii) plural thermoplastic layers, (iii) one or more thermoset layers and one or more thermoplastic layers. Preferably, the core layer comprises one or more PVC layers. The thermoset or thermoplastic layers may further include filler(s), pigment(s) and/or other additives (e.g. processing aids, etc.) The presence of further layers, e.g. reinforcement layers like a fibre veil or a grid, within the core structure is possible.

[0019] Optionally, the decorative surface covering could comprise a second core structure, including one or more thermoset or thermoplastic layers on the back of the second odour barrier layer.

[0020] The first odour barrier layer could comprise a polyurethane (Pll) layer, e.g. in the form of a Pll topcoat.

[0021 ] The abovementioned polyurethane (Pll) layer is preferably a coating layer, comprising a cured polymeric and/or oligomeric layer made of cured oligomers and/or polymers, the oligomers and polymers being selected from the group consisting of: (meth)acrylate copolymers, polyether (meth)acrylates, polyester (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, amino (meth)acrylates, melamine (meth)acrylates, silicone (meth)acrylates, and phosphazene (meth)acrylates.

[0022] The Pll layer could comprise acid functionalities and/or anionic or cationic salt groups.

[0023] The thickness of such a Pll layer would preferably be comprised between 4 pm and 30 pm and more preferably between 10 pm and 20 pm. [0024] The second odour barrier layer could comprise a PET (polyethylene terephthalate) film, a polyvinyl alcohol based layer or a Pll (polyurethane) layer. The second odour barrier layer may also consist of several individual layers of different polymers, e.g. any combination of the above-named ones.

[0025] Preferably, the second odour barrier layer is directly laminated to the lowermost of the one or more thermoset or thermoplastic layers. The core structure could comprise one or more PVC plastisol layers and/or one or more calendered PVC layers. The core structure could also consist of a hybrid stack of PVC layers comprising one or more calendered PVC layers and at least one PVC plastisol layer. In such a hybrid stack, the backmost layer is preferably a PVC plastisol layer.

[0026] In order to ascertain satisfactory adherence with the core structure, the second odour barrier layer could include a tie layer and/or a tie agent rendering the second odour barrier layer compatible with the (lowermost layer of) the core structure. For instance, the second odour barrier layer could include a PVC-compatible tie layer and/or a PVC compatible tie agent when the backmost layer of the core structure is a PVC layer.

[0027] When the second odour barrier layer comprises a Pll layer, the latter is preferably a coating layer, comprising a cured polymeric and/or oligomeric layer made of cured oligomers and/or polymers, the oligomers and polymers being selected from the group consisting of: (meth)acrylate copolymers, polyether (meth)acrylates, polyester (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, amino (meth)acrylates, melamine (meth)acrylates, silicone (meth)acrylates, and phosphazene (meth)acrylates.

[0028] The Pll layer of the second odour barrier layer could comprise acid functionalities and/or anionic or cationic salt groups.

[0029] The thickness of the Pll layer second odour barrier layer would preferably be comprised between 4 pm and 30 pm and more preferably between 10 pm and 20 pm.

[0030] If the odour barrier layer comprises a polyvinyl alcohol based layer, it preferably includes polyvinyl alcohol and a silane compound, the silane compound comprising at least one amine. The silane compound is chosen from the group formed by (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane, aminoethylamino- propylsilanetriol, aminoethylaminopropyl-trimethoxysilane, N-(2-aminoethyl)-(3- aminopropyl)trimethoxysilane, N-(2-aminoethyl)-(3-aminopropyl)methyldimethoxy- silane, N-[2-(benzylamino)ethyl]-(3-aminopropyl)trimethoxysilane, N-[2-(vinylbenzyl- amino)ethyl]-(3-aminopropyl)-trimethoxysilane, (N-cyclohexylaminomethyl)methyl- diethoxysilane, (N-cyclohexylaminomethyl)tri-ethoxysilane, N-cyclohexyl-(3-amino- propyl)tri-methoxysilane, (N-phenylaminomethyl)trimethoxysilane, (3-ureidopropyl)tri- methoxysilane and vinylbenzylaminoethylaminopropyltrimethoxysilane.

[0031 ] The thickness of such a polyvinyl alcohol based layer is preferably comprised between 6 pm and 22 pm and more preferably between 8 pm and 20 pm.

[0032] If the second odour barrier layer comprises a PET film, it preferably comprises a tie layer of a PVC-compatible copolyester. The PET film, including any tie layer, preferably has a thickness of at least 12 pm.

[0033] The decorative surface covering could include a backing for contacting the subfloor or wall (or other surface) to be covered. In this case, the second odour barrier layer is preferably sandwiched between the backmost of the one or more PVC layer and the backing. Advantageously, the backing may comprise or consist of a textile backing, e.g. a polyester non-woven textile, or of a polyolefin backing. The textile backing preferably comprises or consists of a polyester non-woven textile.

[0034] If the product has a backing underneath or behind the core structure, the second odour barrier is preferably sandwiched between the core structure and the backing. The second odour barrier layer could be tied to the backing with adhesive. The adhesive used to tie the backing to the second odour barrier layer is preferably selected such that a sample consisting of a PET film in A4 format (21 cm x 29.7 cm) sealed with aluminum foil on the back side (i.e. the side not carrying the adhesive), on which 3.7 g of adhesive had been dispersed, melted and solidified, generates an odour concentration of not more than 800 OU /m ³ , preferably of not more than 700 OllE/m ³ , and more preferably of not more than 500 OllE/m ³ , after 48 hours in an N2 atmosphere at 20°C and a pressure of 1013 hPa. Preferably, the adhesive is a hot melt copolyester or polyurethane adhesive. Particularly preferably, the hot melt copolyester or polyurethane adhesive has a melt flow index (MFI) comprised in the range from 10 to 50 g/(10 min), measured with a load of 2.16 kg at 160°C, in accordance with ISO standard 1133-1 . [0035] The decorative floor or wall covering also preferably comprises a wear layer on top of the core structure and below the first odour barrier layer. The wear layer could, e.g., be a PVC layer or a PET layer.

[0036] More preferably, a decorative layer, e.g., a printing substrate carrying a printed decorative motif, can be added between the top of the core structure and the wear layer.

[0037] It will be appreciated that the decorative surface covering is especially well suited for being conditioned in the form of a roll (“sheet flooring” or “sheet wallcovering”). Such a roll would preferably have a width of 1 .5 m or more. Flooring or wall covering sheets with large widths may be regarded as preferred embodiments of the invention because the installed product has a low number or low length of joints per unit area, from which odorants can diffuse into the ambient air.

[0038] A further aspect of the invention concerns a method for manufacturing a decorative surface covering as disclosed herein, wherein hot melt copolyester or polyurethane adhesive is applied in powder or non-woven form between the second odour barrier layer and a backing (e.g. a textile backing). Bonding of the second odour barrier layer to the backing is preferably achieved by application of heat and pressure, e.g. by calendaring or by activation of the hot melt copolyester or polyurethane adhesive with infrared heaters, followed by lamination between two rolls.

[0039] In the present document, the verb “to comprise” and the expression “to be comprised of” are used as open transitional phrases meaning “to consist at least of” or “to include”. The term “layer” designates one among plural sheets or thicknesses of material that make up the floor covering. Plural similar sheets or thicknesses assembled on top of one another could be considered constituting a complex layer, provided that the assembly forms a functional unit. For instance, the wear layer or the odour barrier layers could consist of a single sheet or a stack of sublayers.

[0040] When the present document uses expressions relating to the position of one element of the surface covering to another, like the words “top”, “bottom”, “above”, “upper”, below”, “front”, “back”, etc., alone or in combination with another word, reference is made to an orientation of the surface covering when used with the decorative (exposed) side facing away from the surface being covered. The words “front”, “above”, “upper”, “top”, etc. mean “closer to the exposed surface” while “back”, “below”, “lower”, “bottom”, etc. mean “farther away from the exposed surface”. However, this is only to be taken as a naming convention in the context of the present document and must not be understood as implying that the invention be limited to the surface covering with that particular orientation.

Brief Description of the Drawings

[0041 ] By way of example, preferred, non-limiting embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 : is a schematic cross-sectional view of a decorative surface covering according to an embodiment of the invention;

Fig. 2: is a perspective schematic view of the installation of sheet flooring in accordance with the invention;

Fig. 3: is a schematic illustration of hot melt adhesive sprinkled or sprayed on the second odour barrier layer.

Detailed Description of Preferred Embodiments

[0042] It will be understood that the following description and drawings describe embodiments of the invention by way of example and for illustration purposes. They shall not limit the scope or nature of the claimed subject matter. It is worthwhile noting that the drawings are schematic illustrations and, as such, are not to scale. Furthermore, for the sake of clarity, they do not necessarily show element dimensions that are proportional to one another.

[0043] Fig. 1 shows a resilient decorative floor covering 10 made up of different layers. Decorative floor covering 10 includes a core structure 12 made (exclusively or principally) from PVC and providing the main structural support to the entire construction. The core structure 12 may itself be comprised of plural sublayers, such as PVC plastisol layers or calendered PVC layers and, optionally, one or more reinforcement layers, e.g. glass veils, fibre grids or the like. On its upper side, the core structure 12 supports a decorative layer 14, e.g., a printing substrate carrying a printed decorative motif. The decorative layer 14 is protected by a transparent (or at least translucent) wear layer 16. On top of the wear layer 16, a first odour barrier layer 18. On its back side, the core structure 12 supports a textile backing 20. A second odour barrier layer 22 is sandwiched between the core structure 12 and the textile backing 20. Each layer is firmly attached to its respective adjacent layer(s) in such a way that all relevant normative requirements regarding peel strength and/or resistance to delamination of floor coverings are met.

[0044] The second odour barrier layer 22 is firmly attached with its top surface to the core structure 12 and with its bottom surface to the textile backing 20. Turning specifically to the attachment of the textile backing 20 to the second odour barrier layer 22, a hot melt copolyester or polyurethane adhesive is used to tie both layers 20 and 22 together. It is worthwhile noting that the hot melt adhesive can, but need not, form an allover layer. The hot melt adhesive could, for instance, form a more or less patchy layer, provided that the spots of adhesive (or the gaps in the adhesive layer) are distributed substantially uniformly over the surface of the second odour barrier layer or the textile backing. Fig. 3 illustrates a distribution of hot melt adhesive particles 26 obtained by spraying them on a second odour barrier layer 22. As an alternative not illustrated here, the hot melt can be in a non-woven form.

[0045] The hot melt adhesive is selected such that a sample consisting of a PET film in A4 format (21 cm x 29.7 cm) sealed with aluminum foil on the back side (i.e. the side not carrying the adhesive), on which 3.7 g of adhesive had been dispersed, melted and solidified, generates an odour concentration of not more than 800 OllE/m ³ , preferably of not more than 700 OllE/m ³ , and more preferably of not more than 500 OllE/m ³ , after 48 hours in an N2 atmosphere at 20°C and a pressure of 1013 hPa. After the gas sample has been prepared, the odour concentration determination is preferably carried out according to European standard EN 13725:2003. If an alternative testing procedure should be used, the obtained results should be converted into European odour units. Samples may be preparated by spreading the hot melt adhesive on a suitable carrier (e.g. a PET film, such as a Lumirror™ film), melting it and letting it cool down again so that it solidifies. The adhesive on the carrier is then placed in a bag approved by European standard EN 13725:2003 for being in contact with the odorant sample, e.g. a Nalophan™ bag, and the bag is filled with N2. The odorants then diffuse into the gas phase in the bag interior for 48 hours. The necessary time for this was determined by monitoring the concentration of volatile organic compounds (VOCs): when that concentration approaches its maximum and levels out, thermodynamical equilibrium is approximately reached, for the VOCs. It should be noted, however, that the concentration of VOCs does not directly correlate with odour concentration. Accordingly, when the VOC concentration levels out, the odorant concentration may still be increasing. It is thus necessary to specify, in particular, the duration of the gas sample preparation. The gas sample, i.e. , the mixture of N2 and odorant, may then be used for the olfactometric analysis, taking into account the dilution of the odorant in the volume of N2.

[0046] The use of a second odour barrier layer on the back side of the core structure results in an effective reduction of the odorant emissions from the back side of the floor or wall covering into the ambient air, before, during and after pose. This in turn allows achieving better air quality in rooms where this type of flooring or wall covering is laid.

[0047] Fig. 2 is an illustration of a resilient decorative floor covering 10 conditioned for commercialization in the form of a roll 24. The roll 24 has a width W of at least 1.5 m, preferably of at least 1.7 m and still more preferably of at least 1.9 m. Increasing the width of the flooring has the advantage of reducing the number or length of joints per unit area. Therefore, the pathways available for odorants to diffuse from the edges (lateral sides) into ambient air are much more limited than for flooring made up of smaller flooring elements (e.g. tiles, planks, etc.)

[0048] It will also be appreciated that in a flooring structure such as the one shown in Fig. 1 , odorants emanating from the core structure are substantially prevented by, the first odour barrier layer 18 from diffusing into ambient air through the front side of the core structure 12, and by the second odour barrier layer 22 from diffusing into ambient air through the back side of the core structure 12. Due to the presence of the first and second odour barrier layers, the core structure 12 is practically sealed off from the ambient air, except at the edges of the individual floor covering elements. In order to further reduce odorant emissions via the joints, one may additionally seal the joints with an odour-barrier sealant.

[0049] The second odour barrier layer 22 is preferably laminated directly to the lowermost layer of the core structure. The second odour barrier layer 22 preferably comprises a PET film and a copolyester tie layer coextruded therewith. The copolyester preferably comprises functional groups, such as, e.g., acetate or acrylate, that ascertain strong adhesion to the core structure. Examples of possible odour barrier films include Lumirror™ 10.91 and Lumirror™ 60.28, commercialized by Toray Plastics. [0050] Examples of hot melt adhesives include Abifor AC-2072 (co-polyester powder) and Abifor AC-2033 (thermoplastic Pll powder), commercialized by Abifor.

[0051 ] An example of hot melt adhesive in non-woven form is JCC-PES W125, commercialized by Shanghai TianYang hot melt adhesives Co, LTD.

Test results

[0052] A first olfactometric test was carried out on five samples.

[0053] The first sample (“sample A”) was a floor covering element as schematically illustrated in Fig. 1 , except that it did not comprise any second odour barrier layer between the core structure and the textile backing. The second sample (“sample B”) was a floor covering element as schematically illustrated in Fig. 1 , including the second odour barrier layer. The third sample (“sample C”), the fourth sample (“sample D”) and fifth sample (“sample E”) are commercially available floor covering elements as schematically illustrated in Fig. 1 , except that they did not comprise any second odour barrier layer between the core structure and the textile backing. The commercial name of sample C is “GREEN LINE” from IVC. The commercial name of sample D is “FORUM” from JUTEKS. The commercial name of sample E is “ULTRA” from IDEAL. 95% of the sample edges were sealed with aluminum foil in order to determine the odour concentration resulting from odorants originating from the back and top side of the samples, and not or almost not from the edges. The samples were placed into respective Nalophan™ bags, which were then filled with 40 litres of N2. All tests were carried out in a temperature-controlled room (T = 21 °C), at ambient pressure. The Nalophan™ bags were pressurized essentially at atmospheric pressure after filling with N2. Each sample are in A4 format (21 cm x 29.7 cm), i.e. with a size of 623.7 cm ² .

[0054] The VOCs concentration emitted by materials was regularly measured, until thermodynamic equilibrium was deemed reached, using a portable photoionization analyzer (RAE Systems/ppb RAE). This was the case 24 hours after closing the bags. The gas mixtures contained in the bags of samples A, B, C, D and E were then subjected to olfactometric analysis in accordance with European standard EN 13725. To apply different dilutions of the gas samples, an Odile™ olfactormeter was used.

[0055] The test results are shown in the table below:

[0056] The samples A, C, D and E are more emissive in terms of odour than the sample B. Consequently, the effect of the presence of two odour barrier layers, instead of only the first odour barrier layer, can be clearly seen when one compares the results of sample B with the other samples in terms of odour concentration.

[0057] An additional olfactometric test was carried out in order to characterize the adhesive used in sample B.

[0058] The sixth sample (“sample F”) consisted of a PET film in A4 format (21 cm x 29.7 cm), on which 3.7g of thermoplastic copolyester adhesive had been dispersed, melted and solidified. The adhesive of sample F was the same as the one used in sample B for bonding the textile backing to the second odour barrier layer. The back side of the PET film from sample F (i.e. the side not carrying the adhesive) was sealed with aluminum foil. Sample F was placed into Nalophan™ bag, which was then filled with 40 litres of N2. The test was carried out in a temperature-controlled room (T = 21 °C), at ambient pressure. The Nalophan™ bag was pressurized essentially at atmospheric pressure after filling with N2.

[0059] The VOCs concentration emitted by materials was regularly measured, until thermodynamic equilibrium was deemed reached, using a portable photoionization analyzer (RAE Systems/ppb RAE). This was the case 48 hours after closing the bag. The gas mixtures contained in the bag of sample F was then subjected to olfactometric analysis in accordance with European standard EN 13725. To apply different dilutions of the gas samples, an Odile™ olfactormeter was used.

[0060] The test result is shown in the table below:

[0061 ] While specific embodiments have been described herein in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.